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Sample records for rapid kinetic investigation

  1. Microfluidic mixers for the investigation of rapid protein folding kinetics using synchrotron radiation circular dichroism spectroscopy.

    PubMed

    Kane, Avinash S; Hoffmann, Armin; Baumgärtel, Peter; Seckler, Robert; Reichardt, Gerd; Horsley, David A; Schuler, Benjamin; Bakajin, Olgica

    2008-12-15

    We have developed a microfluidic mixer optimized for rapid measurements of protein folding kinetics using synchrotron radiation circular dichroism (SRCD) spectroscopy. The combination of fabrication in fused silica and synchrotron radiation allows measurements at wavelengths below 220 nm, the typical limit of commercial instrumentation. At these wavelengths, the discrimination between the different types of protein secondary structure increases sharply. The device was optimized for rapid mixing at moderate sample consumption by employing a serpentine channel design, resulting in a dead time of less than 200 micros. Here, we discuss the design and fabrication of the mixer and quantify the mixing efficiency using wide-field and confocal epi-fluorescence microscopy. We demonstrate the performance of the device in SRCD measurements of the folding kinetics of cytochrome c, a small, fast-folding protein. Our results show that the combination of SRCD with microfluidic mixing opens new possibilities for investigating rapid conformational changes in biological macromolecules that have previously been inaccessible.

  2. Kinetics of rapid covalent bond formation of aniline with humic acid: ESR investigations with nitroxide spin labels

    NASA Astrophysics Data System (ADS)

    Glinka, Kevin; Matthies, Michael; Theiling, Marius; Hideg, Kalman; Steinhoff, Heinz-Jürgen

    2016-04-01

    Sulfonamide antibiotics used in livestock farming are distributed to farmland by application of slurry as fertilizer. Previous work suggests rapid covalent binding of the aniline moiety to humic acids found in soil. In the current work, kinetics of this binding were measured in X-band EPR spectroscopy by incubating Leonardite humic acid (LHA) with a paramagnetic aniline spin label (anilino-NO (2,5,5-Trimethyl-2-(3-aminophenyl)pyrrolidin-1-oxyl)). Binding was detected by a pronounced broadening of the spectral lines after incubation of LHA with anilino-NO. The time evolution of the amplitude of this feature was used for determining the reaction kinetics. Single- and double-exponential models were fitted to the data obtained for modelling one or two first-order reactions. Reaction rates of 0.16 min-1 and 0.012 min-1, were found respectively. Addition of laccase peroxidase did not change the kinetics but significantly enhanced the reacting fraction of anilino-NO. This EPR-based method provides a technically simple and effective method for following rapid binding processes of a xenobiotic substance to humic acids.

  3. Rapid-Equilibrium Enzyme Kinetics

    ERIC Educational Resources Information Center

    Alberty, Robert A.

    2008-01-01

    Rapid-equilibrium rate equations for enzyme-catalyzed reactions are especially useful because if experimental data can be fit by these simpler rate equations, the Michaelis constants can be interpreted as equilibrium constants. However, for some reactions it is necessary to use the more complicated steady-state rate equations. Thermodynamics is…

  4. Rapid-Equilibrium Enzyme Kinetics

    ERIC Educational Resources Information Center

    Alberty, Robert A.

    2008-01-01

    Rapid-equilibrium rate equations for enzyme-catalyzed reactions are especially useful because if experimental data can be fit by these simpler rate equations, the Michaelis constants can be interpreted as equilibrium constants. However, for some reactions it is necessary to use the more complicated steady-state rate equations. Thermodynamics is…

  5. Kinetic investigation of wood pyrolysis

    SciTech Connect

    Thurner, F.; Mann, U.; Beck, S. R.

    1980-06-01

    The objective of this investigation was to determine the kinetics of the primary reactions of wood pyrolysis. A new experimental method was developed which enabled us to measure the rate of gas, tar, and char production while taking into account the temperature variations during the wood heating up. The experimental method developed did not require any sophisticated instruments. It facilitated the collection of gas, tar and residue (unreacted wood and char) as well as accurate measurement of the temperature inside the wood sample. Expressions relating the kinetic parameters to the measured variables were derived. The pyrolysis kinetics was investigated in the range of 300 to 400/sup 0/C at atmospheric pressure and under nitrogen atmosphere. Reaction temperature and mass fractions of gas, tar, and residue were measured as a function of time. Assuming first-order reactions, the kinetic parameters were determined using differential method. The measured activation energies of wood pyrolysis to gas, tar, and char were 88.6, 112.7, and 106.5 kJ/mole, respectively. These kinetic data were then used to predict the yield of the various pyrolysis products. It was found that the best prediction was obtained when an integral-mean temperature obtained from the temperature-time curve was used as reaction temperature. The pyrolysis products were analyzed to investigate the influence of the pyrolysis conditions on the composition. The gas consisted mainly of carbon dioxide, carbon monoxide, oxygen, and C/sub 3//sup +/-compounds. The gas composition depended on reaction time as well as reactor temperature. The tar analysis indicated that the tar consisted of about seven compounds. Its major compound was believed to be levoglucosan. Elemental analysis for the char showed that the carbon content increased with increasing temperature.

  6. An Introductory Level Kinetics Investigation.

    ERIC Educational Resources Information Center

    McGarvey, J. E. B.; Knipe, A. C.

    1980-01-01

    Provides a list of the reactions commonly used for introductory kinetics studies. These reactions illustrate the kinetics concepts of rate law, rate constant, and reaction order. Describes a kinetic study of the hydrolysis of 3-bromo-3-phenylpropanoic acid which offers many educational advantages. (CS)

  7. An Introductory Level Kinetics Investigation.

    ERIC Educational Resources Information Center

    McGarvey, J. E. B.; Knipe, A. C.

    1980-01-01

    Provides a list of the reactions commonly used for introductory kinetics studies. These reactions illustrate the kinetics concepts of rate law, rate constant, and reaction order. Describes a kinetic study of the hydrolysis of 3-bromo-3-phenylpropanoic acid which offers many educational advantages. (CS)

  8. Kinetic investigation of wood pyrolysis

    SciTech Connect

    Thurner, F.; Mann, U.

    1981-07-01

    The kinetics of wood pyrolysis into gas, tar, and char was investigated in the range of 300 to 400 degrees Celcius at atmospheric pressure. An experimental system which facilitates the monitoring of the actual sample temperature, collection of gas and tar, and measurement of the sample weight loss as a function of time was developed. It has been found that, in the range investigated, wood decomposition into gas, tar, and char can be described by three parallel first-order reactions as suggested by Shafizadeh and Chin (1977). The activation energies for these reactions are 88.6, 112.7 and 106.5 kJ/mol, respectively, and their frequency factors defined on a mass basis are 8.61 x 10 to the power of 5, 2.47 x 10 to the power of 8, and 4.43 x 10 to the power of 7 min-1. The composition of the pyrolysis products was also analyzed. It was found that the gas consists mainly of carbon dioxide, carbon monoxide, oxygen, and C3 + compounds with trace amounts of methane, ethylene, and acetylene. The tar consists of seven compounds with levoglucosan accounting for more than half. The char was analyzed by elemental analysis and it was found that its carbon content increases with increasing reactor temperature. (Refs. 12).

  9. Portable centrifugal analyzer for the determination of rapid reaction kinetics

    SciTech Connect

    Bostick, W.D.; Bauer, M.L.; McCracken, R.; Mrochek, J.E.

    1980-02-01

    A portable centrifugal analyzer prototype is capable of rapidly initiating reactions and monitoring 17 optical channels as they rotate past a stationary photodetector. An advanced rotor drive permits transfer of discretely loaded sample and reagent into a cuvette within 60 ms. Various rotor designs have been employed to ensure effieicnt mixing concurrent with solution transfer, thus permitting absorbance or luminescence measurements to be made almost immediately after solution contract. Dye-dillution studies have been used to investigate transfer and mixing efficiencies. Rotor designs with parallel access for sample and reagent into the cuvette were found to promote efficient mixing during liquid transfer. The hypochlorite-luminol chemiluminescent reaction served to demonstrate the utility of the system for performing rapid kinetic analyses. Appropriate adjustment of reaction conditions allows first-order reaction half-lives as short as 0.04 s to be measured. 13 figures, 3 tables.

  10. Rapid Microtubule Self-assembly Kinetics

    PubMed Central

    Gardner, Melissa K.; Charlebois, Blake D.; Jánosi, Imre M.; Howard, Jonathon; Hunt, Alan J.; Odde, David J.

    2011-01-01

    Microtubule assembly is vital for many fundamental cellular processes. Current models for microtubule assembly kinetics assume that the subunit disassociation rate from a microtubule tip is independent of free subunit concentration. Using Total-Internal-Reflection-Fluorescence (TIRF) microscopy and a laser tweezers assay to measure in vitro microtubule assembly with nanometer resolution, we find that the subunit dissociation rate from a microtubule tip increases as the free subunit concentration increases. These data are consistent with a two-dimensional model for microtubule assembly, and are explained by a shift in microtubule tip structure from a relatively blunt shape at low free concentrations to relatively tapered at high free concentrations. Because both the association and the dissociation rates increase at higher free subunit concentrations, we find that the kinetics of microtubule assembly are an order-of-magnitude higher than currently estimated in the literature. PMID:21854983

  11. Rapid microtubule self-assembly kinetics.

    PubMed

    Gardner, Melissa K; Charlebois, Blake D; Jánosi, Imre M; Howard, Jonathon; Hunt, Alan J; Odde, David J

    2011-08-19

    Microtubule assembly is vital for many fundamental cellular processes. Current models for microtubule assembly kinetics assume that the subunit dissociation rate from a microtubule tip is independent of free subunit concentration. Total-Internal-Reflection-Fluorescence (TIRF) microscopy experiments and data from a laser tweezers assay that measures in vitro microtubule assembly with nanometer resolution, provides evidence that the subunit dissociation rate from a microtubule tip increases as the free subunit concentration increases. These data are consistent with a two-dimensional model for microtubule assembly, and are explained by a shift in microtubule tip structure from a relatively blunt shape at low free concentrations to relatively tapered at high free concentrations. We find that because both the association and the dissociation rates increase at higher free subunit concentrations, the kinetics of microtubule assembly are an order-of-magnitude higher than currently estimated in the literature. Copyright © 2011 Elsevier Inc. All rights reserved.

  12. Investigating broadband acoustic adsorption using rapid manufacturing

    NASA Astrophysics Data System (ADS)

    Godbold, O.

    The reduction of nuisance noise and the removal of unwanted sound modes within a room or component enclosure-area can be accomplished through the use of acoustic absorbers. Sound absorption can be achieved through conversion of the kinetic energy associated with pressure waves, into heat energy via viscous dissipation. This occurs within open porous materials, or by utilising resonant effects produced using simple cavity and orifice configurations. The manufacture of traditional porous and resonant absorbers is commonly realised using basic manufacturing techniques. These techniques restrict the geometry of a given resonant construction, and limit the configuration of porous absorbers. The aim of this work is to exploit new and emerging capabilities of Rapid Manufacturing (RM) to produce components with geometrical freedom, and apply it to the development of broadband acoustic absorption. New and novel absorber geometric configurations are identified and their absorption performance is determined. The capabilities and limitations of RM processes in reproducing these configurations are demonstrated. The geometric configuration of RM resonant absorbers is investigated. Cavity modifications aimed at damping the resonant effect by restricting the motion of cavity air, and adding increased viscous resistance are explored. Modifications relating to cavity shape, the addition of internal perforations and increased cavity surface area have all been shown to add acoustic resistance, thereby increasing the bandwidth of absorption. Decreasing the hydraulic radius of the cavity cross section and reducing internal feature dimensions provide improved resistance over conventional configurations..

  13. Determination of rapid chlorination rate constants by a stopped-flow spectrophotometric competition kinetics method.

    PubMed

    Song, Dean; Liu, Huijuan; Qiang, Zhimin; Qu, Jiuhui

    2014-05-15

    Free chlorine is extensively used for water and wastewater disinfection nowadays. However, it still remains a big challenge to determine the rate constants of rapid chlorination reactions although competition kinetics and stopped-flow spectrophotometric (SFS) methods have been employed individually to investigate fast reaction kinetics. In this work, we proposed an SFS competition kinetics method to determine the rapid chlorination rate constants by using a common colorimetric reagent, N,N-diethyl-p-phenylenediamine (DPD), as a reference probe. A kinetic equation was first derived to estimate the reaction rate constant of DPD towards chlorine under a given pH and temperature condition. Then, on that basis, an SFS competition kinetics method was proposed to determine directly the chlorination rate constants of several representative compounds including tetracycline, ammonia, and four α-amino acids. Although Cl2O is more reactive than HOCl, its contribution to the overall chlorination kinetics of the test compounds could be neglected in this study. Finally, the developed method was validated through comparing the experimentally measured chlorination rate constants of the selected compounds with those obtained or calculated from literature and analyzing with Taft's correlation as well. This study demonstrates that the SFS competition kinetics method can measure the chlorination rate constants of a test compound rapidly and accurately.

  14. On the Nonequilibrium Interface Kinetics of Rapid Coupled Eutectic Growth

    NASA Astrophysics Data System (ADS)

    Dong, H.; Chen, Y. Z.; Shan, G. B.; Zhang, Z. R.; Liu, F.

    2017-08-01

    Nonequilibrium interface kinetics (NEIK) is expected to play an important role in coupled growth of eutectic alloys, when solidification velocity is high and intermetallic compound or topologically complex phases form in the crystallized product. In order to quantitatively evaluate the effect of NEIK on the rapid coupled eutectic growth, in this work, two nonequilibrium interface kinetic effects, i.e., atom attachment and solute trapping at the solid-liquid interface, were incorporated into the analyses of the coupled eutectic growth under the rapid solidification condition. First, a coupled growth model incorporating the preceding two nonequilibrium kinetic effects was derived. On this basis, an expression of kinetic undercooling (∆ T k), which is used to characterize the NEIK, was defined. The calculations based on the as-derived couple growth model show good agreement with the reported experimental results achieved in rapidly solidified eutectic Al-Sm alloys consisting of a solid solution phase ( α-Al) and an intermetallic compound phase (Al11Sm3). In terms of the definition of ∆ T k defined in this work, the role of NEIK in the coupled growth of the Al-Sm eutectic system was analyzed. The results show that with increasing the coupled growth velocity, ∆ T k increases continuously, and its ratio to the total undercooling reaches 0.32 at the maximum growth velocity for coupled eutectic growth. Parametric analyses on two key alloy parameters that influence ∆ T k, i.e., interface kinetic parameter ( μ i ) and solute distribution coefficient ( k e ), indicate that both μ i and k e influence the NEIK significantly and the decrease of either these two parameters enhances the NEIK effect.

  15. Biochemical thermodynamics and rapid-equilibrium enzyme kinetics.

    PubMed

    Alberty, Robert A

    2010-12-30

    Biochemical thermodynamics is based on the chemical thermodynamics of aqueous solutions, but it is quite different because pH is used as an independent variable. A transformed Gibbs energy G' is used, and that leads to transformed enthalpies H' and transformed entropies S'. Equilibrium constants for enzyme-catalyzed reactions are referred to as apparent equilibrium constants K' to indicate that they are functions of pH in addition to temperature and ionic strength. Despite this, the most useful way to store basic thermodynamic data on enzyme-catalyzed reactions is to give standard Gibbs energies of formation, standard enthalpies of formation, electric charges, and numbers of hydrogen atoms in species of biochemical reactants like ATP. This makes it possible to calculate standard transformed Gibbs energies of formation, standard transformed enthalpies of formation of reactants (sums of species), and apparent equilibrium constants at desired temperatures, pHs, and ionic strengths. These calculations are complicated, and therefore, a mathematical application in a computer is needed. Rapid-equilibrium enzyme kinetics is based on biochemical thermodynamics because all reactions in the mechanism prior to the rate-determining reaction are at equilibrium. The expression for the equilibrium concentration of the enzyme-substrate complex that yields products can be derived by applying Solve in a computer to the expressions for the equilibrium constants in the mechanism and the conservation equation for enzymatic sites. In 1979, Duggleby pointed out that the minimum number of velocities of enzyme-catalyzed reactions required to estimate the values of the kinetic parameters is equal to the number of kinetic parameters. Solve can be used to do this with steady-state rate equations as well as rapid-equilibrium rate equations, provided that the rate equation is a polynomial. Rapid-equilibrium rate equations can be derived for complicated mechanisms that involve several reactants

  16. Investigation of the kinetic model equations.

    PubMed

    Liu, Sha; Zhong, Chengwen

    2014-03-01

    Currently the Boltzmann equation and its model equations are widely used in numerical predictions for dilute gas flows. The nonlinear integro-differential Boltzmann equation is the fundamental equation in the kinetic theory of dilute monatomic gases. By replacing the nonlinear fivefold collision integral term by a nonlinear relaxation term, its model equations such as the famous Bhatnagar-Gross-Krook (BGK) equation are mathematically simple. Since the computational cost of solving model equations is much less than that of solving the full Boltzmann equation, the model equations are widely used in predicting rarefied flows, multiphase flows, chemical flows, and turbulent flows although their predictions are only qualitatively right for highly nonequilibrium flows in transitional regime. In this paper the differences between the Boltzmann equation and its model equations are investigated aiming at giving guidelines for the further development of kinetic models. By comparing the Boltzmann equation and its model equations using test cases with different nonequilibrium types, two factors (the information held by nonequilibrium moments and the different relaxation rates of high- and low-speed molecules) are found useful for adjusting the behaviors of modeled collision terms in kinetic regime. The usefulness of these two factors are confirmed by a generalized model collision term derived from a mathematical relation between the Boltzmann equation and BGK equation that is also derived in this paper. After the analysis of the difference between the Boltzmann equation and the BGK equation, an attempt at approximating the collision term is proposed.

  17. An experimental investigation of rapid boiling of

    NASA Astrophysics Data System (ADS)

    Tosse, S.; Vaagsaether, K.; Bjerketvedt, D.

    2015-05-01

    Storage of pressurized liquified gases is a growing safety concern in many industries. Knowledge of the thermodynamics and kinetics involved in the rapid depressurization and evaporation of such substances is key to the design and implementation of effective safety measures in storage and transportation situations. In the present study, experiments on the rapid depressurization of liquid are conducted in a vertical transparent shock tube which enables the observation of evaporation waves and other structures. The depressurization was initiated by puncturing a membrane in one end of the tube. The thermodynamic mechanisms that govern the evaporation process are not unique to , and the same principles can be applied to any liquified gas. The experiments were photographed by a high-speed camera. Evaporation waves propagating into the liquid were observed, traveling at a near constant velocity on the order of 20-30 m/s. A contact surface between the vapor and the liquid-vapor mixture was also observed, accelerating out of the tube. Pressure readings in the tube suggest that the evaporation wave could be similar to a spinodal decomposition wave, but further experiments are needed to confirm this. When the membrane was in direct contact with the liquified , some indications of homogeneous nucleation were observed.

  18. Probing fast ribozyme reactions under biological conditions with rapid quench-flow kinetics.

    PubMed

    Bingaman, Jamie L; Messina, Kyle J; Bevilacqua, Philip C

    2017-03-14

    Reaction kinetics on the millisecond timescale pervade the protein and RNA fields. To study such reactions, investigators often perturb the system with abiological solution conditions or substrates in order to slow the rate to timescales accessible by hand mixing; however, such perturbations can change the rate-limiting step and obscure key folding and chemical steps that are found under biological conditions. Mechanical methods for collecting data on the millisecond timescale, which allow these perturbations to be avoided, have been developed over the last few decades. These methods are relatively simple and can be conducted on affordable and commercially available instruments. Here, we focus on using the rapid quench-flow technique to study the fast reaction kinetics of RNA enzymes, or ribozymes, which often react on the millisecond timescale under biological conditions. Rapid quench of ribozymes is completely parallel to the familiar hand-mixing approach, including the use of radiolabeled RNAs and fractionation of reactions on polyacrylamide gels. We provide tips on addressing and preventing common problems that can arise with the rapid-quench technique. Guidance is also offered on ensuring the ribozyme is properly folded and fast-reacting. We hope that this article will facilitate the broader use of rapid-quench instrumentation to study fast-reacting ribozymes under biological reaction conditions.

  19. The nonextensive gas: a kinetic approach [rapid communication

    NASA Astrophysics Data System (ADS)

    Lima, J. A. S.; Silva, R.

    2005-05-01

    We discuss a kinetic nonextensive generalization of the Maxwellian ideal gas. The analysis rests on two basic assumptions: (i) instead of the standard Gaussian form, the q-gas is described by a power-law velocity distribution as suggested in the nonextensive Tsallis' framework (ii) the q-nonextensive generalization of the Boltzmann entropy formula governs the behavior of the q-gas. In this context, we show that the pressure and the internal energy are kinetically modified, but the general equation of state, PV=2U/3, remains valid. The adiabatic index is now a function of the nonextensive parameter, γ=Cp/CV=5/3q. However, the standard expression relating the specific heats (at constant pressure and volume) with the coefficient of expansion and the isothermal compressibility, CP-CV=TVα2/κT, is not modified.

  20. Investigation of Kinetics of MOCVD Systems

    DTIC Science & Technology

    1991-12-01

    growth rate was also observed by other investigators [81,95,96] when a threshold amount of HCI was exceeded. Jurgensen et al. [95] demonstrated that...Electrochem. Soc., 126, 1400 (1979). 94. Weyburne, D.W. and Quinlan, K.P., Report RADC-TR-85-238 (1985). 95. Jurgensen , H., Schmitz, D., Heyen, M. and

  1. Wound infection kinetics probed by MALDI-MS: rapid profiling of Staphylococcus aureus in mice.

    PubMed

    Narayana, Jayaram Lakshmaiah; Gopal, Judy; Wu, Hui-Fen

    2012-07-21

    Using direct matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS), we were able to investigate the role of the clinically important bacteria, Staphylococcus aureus, in wound infections using mice. The infection kinetics of S. aureus at the wound site and the host immune response has been investigated using MALDI-MS. In this study, for the first time, we report the growth pattern of S. aureus infection at a wound site. Using mice wound infection models; the following study fingerprints the bacterial-host (mice) response at the wound site as a function of increasing wound infection in order to establish the infection pattern of Staphylococcus aureus in wounds. The current approach is extremely simple, rapid, highly selective, sensitive and established MALDI-MS as a versatile tool for detecting bacteria in clinical samples, such as those collected from wound sites.

  2. Microbial pesticide removal in rapid sand filters for drinking water treatment--potential and kinetics.

    PubMed

    Hedegaard, Mathilde J; Albrechtsen, Hans-Jørgen

    2014-01-01

    Filter sand samples, taken from aerobic rapid sand filters used for treating groundwater at three Danish waterworks, were investigated for their pesticide removal potential and to assess the kinetics of the removal process. Microcosms were set up with filter sand, treated water, and the pesticides or metabolites mecoprop (MCPP), bentazone, glyphosate and p-nitrophenol were applied in initial concentrations of 0.03-2.4 μg/L. In all the investigated waterworks the concentration of pesticides in the water decreased - MCPP decreased to 42-85%, bentazone to 15-35%, glyphosate to 7-14% and p-nitrophenol 1-3% - from the initial concentration over a period of 6-13 days. Mineralisation of three out of four investigated pesticides was observed at Sjælsø waterworks Plant II - up to 43% of the initial glyphosate was mineralised within six days. At Sjælsø waterworks Plant II the removal kinetics of bentazone revealed that less than 30 min was needed to remove 50% of the bentazone at all the tested initial concentrations (0.1-2.4 μg/L). Increased oxygen availability led to greater and faster removal of bentazone in the microcosms. After 1 h, bentazone removal (an initial bentazone concentration of 0.1 μg/L) increased from 0.21%/g filter sand to 0.75%/g filter sand, when oxygen availability was increased from 0.28 mg O2/g filter sand to 1.09 mg O2/g filter sand. Bentazone was initially cleaved in the removal process. A metabolite, which contained the carbonyl group, was removed rapidly from the water phase and slowly mineralised after 24 h, while a metabolite which contained the benzene-ring was still present in the water phase. However, the microbial removal of this metabolite was initiated over seven days.

  3. A rapid quenched-flow device for the study of homogeneous polymerization kinetics

    NASA Astrophysics Data System (ADS)

    White, Curtis B.; Rosaaen, Kimberly A.; Landis, Clark R.

    2002-02-01

    We have designed and constructed a device, the rapid flow mixer (RFM), for investigating the kinetics of metallocene-catalyzed alkene polymerization reactions. The RFM operates over a wide range of reaction conditions (temperatures from -40 to 150 °C and pressures up to 500 psi) and has wetted components constructed from inert materials (stainless steel, Kalrez™, Teflon™). The closed system design and interface to an inert atmosphere glove box facilitates the handling of air and moisture sensitive reagents. Total reaction volumes per run may range from 750 μL to 15 mL. The drive assembly is interfaced to a personal computer that provides user control of reaction times and flow rates. Total reaction times span a range of ˜10 ms to >10 min.

  4. Austenite Formation Kinetics During Rapid Heating in a Microalloyed Steel

    SciTech Connect

    BURNETT,M.E.; DYKHUIZEN,RONALD C.; KELLEY,J. BRUCE; PUSKAR,JOSEPH D.; ROBINO,CHARLES V.

    1999-09-07

    The model parameters for the normalized 1054V1 material were compared to parameters previously generated for 1026 steel, and the transformation behavior was relatively consistent. Validation of the model predictions by heating into the austenite plus undissolved ferrite phase field and rapidly quenching resulted in reasonable predictions when compared to the measured volume fractions from optical metallography. The hot rolled 1054V1 material, which had a much coarser grain size and a non-equilibrium volume fraction of pearlite, had significantly different model parameters and the on heating transformation behavior of this material was less predictable with the established model. The differences in behavior is consistent with conventional wisdom that normalized micro-structure produce a more consistent response to processing, and it reinforces the need for additional work in this area.

  5. Kinetic Controls on Formation of Textures in Rapidly Cooled Rocks

    NASA Technical Reports Server (NTRS)

    Lofgren, Gary E.

    2006-01-01

    The crystallization of silicate melts is a complex process involving melts usually produced by partial melting and cooling environments that are rapid in volcanic lavas or so slow as to be auto-metamorphic in plutonic regimes. The volcanic lavas are amenable to laboratory study as are chondrules that comprise the bulk of chondritic meteorites. Dynamic crystallization studies of basalt and chondrule melts have shown that nucleation has a more profound effect on the final texture than the cooling or crystal growth rates. The sequence of crystal shapes grown at increasing degrees of supercooling (DELTA T) or cooling rate demonstrates the effect of increasing growth rate. Equant or euhedral crystals become skeletal, then dendritic and ultimately spherulitic indicating the nucleation temperature and the DELTA T when growth began. Because crystals cannot grow until they nucleate, cooling rate does not always correlate with crystal growth rate and thus crystal shape. Silicate melts cooled at the same rate can have drastically different textures depending on the temperature of nucleation. A dynamic crystallization study of basaltic rocks shows that basaltic lavas must erupt with sufficient crystals present in the melt to act as nuclei and foster growth. With nuclei present, growth will begin when the temperature drops below the liquidus temperature and typical basaltic textures such as intersertal, intergranular or subophitic will form. If nuclei are not present, crystallization will not begin immediately and the DELTA T will increase until embryos in the melts become nuclei. The DELTA T present when grow begins dictates the growth rate and the crystal shapes and thus the rock texture. If nucleation is delayed, growth will take place at high DELTA T and the crystals will favor skeletal or dendritic shapes. Chondrules are usually considered crystallized melt droplets and clearly some are, but most are not. Most chondrules have porphyritic textures that cannot develop from

  6. Kinetic Controls on Formation of Textures in Rapidly Cooled Rocks

    NASA Technical Reports Server (NTRS)

    Lofgren, Gary E.

    2006-01-01

    The crystallization of silicate melts is a complex process involving melts usually produced by partial melting and cooling environments that are rapid in volcanic lavas or so slow as to be auto-metamorphic in plutonic regimes. The volcanic lavas are amenable to laboratory study as are chondrules that comprise the bulk of chondritic meteorites. Dynamic crystallization studies of basalt and chondrule melts have shown that nucleation has a more profound effect on the final texture than the cooling or crystal growth rates. The sequence of crystal shapes grown at increasing degrees of supercooling (DELTA T) or cooling rate demonstrates the effect of increasing growth rate. Equant or euhedral crystals become skeletal, then dendritic and ultimately spherulitic indicating the nucleation temperature and the DELTA T when growth began. Because crystals cannot grow until they nucleate, cooling rate does not always correlate with crystal growth rate and thus crystal shape. Silicate melts cooled at the same rate can have drastically different textures depending on the temperature of nucleation. A dynamic crystallization study of basaltic rocks shows that basaltic lavas must erupt with sufficient crystals present in the melt to act as nuclei and foster growth. With nuclei present, growth will begin when the temperature drops below the liquidus temperature and typical basaltic textures such as intersertal, intergranular or subophitic will form. If nuclei are not present, crystallization will not begin immediately and the DELTA T will increase until embryos in the melts become nuclei. The DELTA T present when grow begins dictates the growth rate and the crystal shapes and thus the rock texture. If nucleation is delayed, growth will take place at high DELTA T and the crystals will favor skeletal or dendritic shapes. Chondrules are usually considered crystallized melt droplets and clearly some are, but most are not. Most chondrules have porphyritic textures that cannot develop from

  7. H-Atom Reaction Kinetics in Solid Parahydrogen Followed by Rapid Scan FTIR

    NASA Astrophysics Data System (ADS)

    Anderson, David T.

    2014-06-01

    Reactions of migrating H-atoms in parahydrogen (pH2) matrices with trapped molecular species provide a relatively unexplored yet well-established experimental method to study the kinetics and mechanisms of atom tunneling reactions in the 1.5 to 5 K temperature range. My group has now completed a series of experimental studies on the kinetics of reactions of H-atoms with HCOOH, CH3OH, and N2O which all show a pronounced inverse temperature dependence over this small temperature range. Conversely, the analogous H-atom reaction with NO displays a more standard Arrhenius behavior. In this talk, I will present a brief summary of these results with the objective of developing a predictive understanding of the kinetics of these H-atom tunneling reactions. I will also emphasize the advantages of following the kinetics using rapid scan FTIR. Fredrick M. Mutunga, Shelby E. Follett, and David T. Anderson, J. Chem. Phys. 139, 151104 (2013).

  8. Kinetic evidence for rapid oxidation of (-)-epicatechin by human myeloperoxidase

    SciTech Connect

    Spalteholz, Holger; Furtmueller, Paul Georg; Jakopitsch, Christa; Obinger, Christian; Schewe, Tankred; Sies, Helmut; Arnhold, Juergen

    2008-07-11

    Apocynin has been reported to require dimerization by myeloperoxidase (MPO) to inhibit leukocyte NADPH oxidase. (-)-Epicatechin, a dietary flavan-3-ol, has been identified as a 'prodrug' of apocynin-like metabolites that inhibit endothelial NADPH oxidase activity and elevate the cellular level of nitric oxide. Since (-)-epicatechin has tentatively been identified as substrate of MPO, we studied the one-electron oxidation of (-)-epicatechin by MPO. By using multi-mixing stopped-flow technique, we demonstrate that (-)-epicatechin is one of the most efficient electron donors for heme peroxidases investigated so far. Second order rate constants for the (-)-epicatechin-mediated conversion of MPO-compound I to compound II and compound II to resting enzyme were estimated to be 1.9 x 10{sup 7} and 4.5 x 10{sup 6} M{sup -1} s{sup -1}, respectively (pH 7, 25 deg. C). The data indicate that (-)-epicatechin is capable of undergoing fast MPO-mediated one-electron oxidation.

  9. Purification and characterization of Fab fragments with rapid reaction kinetics against myoglobin.

    PubMed

    Song, Hyung-Nam; Kim, Dong-Hyung; Park, Sung-Goo; Lee, Myung Kyu; Paek, Se-Hwan; Woo, Eui-Jeon

    2015-01-01

    Myoglobin is an early biomarker for acute myocardial infarction. Recently, we isolated the antibody IgG-Myo2-7ds, which exhibits unique rapid reaction kinetics toward human myoglobin antigen. Antibodies with rapid dissociation kinetics are thought to be premature IgG forms that are produced during the early stage of in vivo immunization. In the present study, we identified the epitope region of the IgG-Myo2-7ds antibody to be the C-terminal region of myoglobin, which corresponds to 144-154 aa. The Fab fragment was directly purified by papain cleavage and protein G affinity chromatography and demonstrated kinetics of an association constant of 4.02 × 10(4) M(-1) s(-1) and a dissociation constant of 2.28 × 10(-2) s(-1), which retained the unique reaction kinetics of intact IgG-Myo2-7ds antibodies. Because a rapid dissociation antibody can be utilized for antibody recycling, the results from this study would provide a platform for the development of antibody engineering in potential diagnostic areas such as a continuous monitoring system for heart disease.

  10. Construction of an antimyoglobin single-chain variable fragment with rapid reaction kinetics.

    PubMed

    Jang, Jun-Hyuck; Kim, Dong-Hyung; Paek, Se-Hwan; Woo, Eui-Jeon; Kim, Young-Wan

    2016-01-01

    Antibodies with rapid reaction kinetics (high association and dissociation rates), named reversible antibodies, are used to perform continuous monitoring of sensitive disease biomarkers. In cases of acute myocardial infarction (AMI), continuous monitoring and early diagnosis are important. Human myoglobin (Myo) is a useful biomarker for AMI during the early stage after the onset of symptoms. In this study, a single-chain variable fragment (scFv) specific to Myo was derived from an IgG antibody that has rapid reaction kinetics. Enzyme-linked immunosorbent assay revealed that recombinant scFv exhibited 3.8-fold reduced affinity compared with the parent IgG antibody based on the antibody concentration necessary for 50% of the maximum signal. The scFv retained the rapid reaction kinetic mode with average kon and koff of 2.63 × 10(5) M(-1) Sec(-1) and 3.25 × 10(-3) Sec(-1) , respectively, which were reduced to 10- and 2.3-fold compared with those of the parent antibody. The equilibrium constant for the association of the scFv (KA = 8.09 × 10(7) M(-1) ) was 4.6-fold lower than that of its parent IgG antibody. This scFv may be a starting point for further mutagenesis/kinetic and structural analyses providing valuable insight into the mechanism of reversible antibodies.

  11. Kinetics of the B1-B2 phase transition in KCl under rapid compression

    NASA Astrophysics Data System (ADS)

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Park, Changyong; Kono, Yoshio; Kenney-Benson, Curtis; Rod, Eric; Shen, Guoyin

    2016-01-01

    Kinetics of the B1-B2 phase transition in KCl has been investigated under various compression rates (0.03-13.5 GPa/s) in a dynamic diamond anvil cell using time-resolved x-ray diffraction and fast imaging. Our experimental data show that the volume fraction across the transition generally gives sigmoidal curves as a function of pressure during rapid compression. Based upon classical nucleation and growth theories (Johnson-Mehl-Avrami-Kolmogorov theories), we propose a model that is applicable for studying kinetics for the compression rates studied. The fit of the experimental volume fraction as a function of pressure provides information on effective activation energy and average activation volume at a given compression rate. The resulting parameters are successfully used for interpreting several experimental observables that are compression-rate dependent, such as the transition time, grain size, and over-pressurization. The effective activation energy (Qeff) is found to decrease linearly with the logarithm of compression rate. When Qeff is applied to the Arrhenius equation, this relationship can be used to interpret the experimentally observed linear relationship between the logarithm of the transition time and logarithm of the compression rates. The decrease of Qeff with increasing compression rate results in the decrease of the nucleation rate, which is qualitatively in agreement with the observed change of the grain size with compression rate. The observed over-pressurization is also well explained by the model when an exponential relationship between the average activation volume and the compression rate is assumed.

  12. Kinetics of the B1-B2 phase transition in KCl under rapid compression

    SciTech Connect

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Park, Changyong; Kono, Yoshio; Kenney-Benson, Curtis; Rod, Eric; Shen, Guoyin

    2016-01-28

    Kinetics of the B1-B2 phase transition in KCl has been investigated under various compression rates (0.03–13.5 GPa/s) in a dynamic diamond anvil cell using time-resolved x-ray diffraction and fast imaging. Our experimental data show that the volume fraction across the transition generally gives sigmoidal curves as a function of pressure during rapid compression. Based upon classical nucleation and growth theories (Johnson-Mehl-Avrami-Kolmogorov theories), we propose a model that is applicable for studying kinetics for the compression rates studied. The fit of the experimental volume fraction as a function of pressure provides information on effective activation energy and average activation volume at a given compression rate. The resulting parameters are successfully used for interpreting several experimental observables that are compression-rate dependent, such as the transition time, grain size, and over-pressurization. The effective activation energy (Q{sub eff}) is found to decrease linearly with the logarithm of compression rate. When Q{sub eff} is applied to the Arrhenius equation, this relationship can be used to interpret the experimentally observed linear relationship between the logarithm of the transition time and logarithm of the compression rates. The decrease of Q{sub eff} with increasing compression rate results in the decrease of the nucleation rate, which is qualitatively in agreement with the observed change of the grain size with compression rate. The observed over-pressurization is also well explained by the model when an exponential relationship between the average activation volume and the compression rate is assumed.

  13. Kinetic investigation of indium-palladium alloy electrodeposition

    SciTech Connect

    Vinogradov, S.N.; Perelygin, Yu.P.; Efimov, E.A.

    1988-01-01

    The kinetics of alloy deposition of ammonium-citrate electrolyte used to produce alloys with indium content were studied. The electrolytes were composed of palladium, indium, ammonium sulfate, monosodium citrate, ammonium chloride, and saccharin at pH 9.5. Stationary and rotating disk electrodes and a potentiostat were used for the investigation. Spectrophotometry determined the mixed formation of citrate-ammonia palladium complexes. It was found that the considerable depolarization of indium ion discharge into the alloy occurred when saccharin was present in the electrolyte, and its direct electroreduction occurs from hydroxide compounds.

  14. Refolded scFv Antibody Fragment against Myoglobin Shows Rapid Reaction Kinetics

    PubMed Central

    Song, Hyung-Nam; Jang, Jun-Hyuck; Kim, Young-Wan; Kim, Dong-Hyung; Park, Sung-Goo; Lee, Myung Kyu; Paek, Se-Hwan; Woo, Eui-Jeon

    2014-01-01

    Myoglobin is one of the early biomarkers for acute myocardial infarction. Recently, we have screened an antibody with unique rapid reaction kinetics toward human myoglobin antigen. Antibodies with rapid reaction kinetics are thought to be an early IgG form produced during early stage of in vivo immunization. We produced a recombinant scFv fragment for the premature antibody from Escherichia coli using refolding technology. The scFv gene was constructed by connection of the VH–VL sequence with a (Gly4Ser)3 linker. The scFv fragment without the pelB leader sequence was expressed at a high level, but the solubility was extremely low. A high concentration of 8 M urea was used for denaturation. The dilution refolding process in the presence of arginine and the redox reagents GSH and GSSH successfully produced a soluble scFv protein. The resultant refolded scFv protein showed association and dissociation values of 9.32 × 10−4 M−1·s−1 and 6.29 × 10−3 s−1, respectively, with an affinity value exceeding 107 M−1 (kon/koff), maintaining the original rapid reaction kinetics of the premature antibody. The refolded scFv could provide a platform for protein engineering for the clinical application for diagnosis of heart disease and the development of a continuous biosensor. PMID:25530617

  15. Rapid and Simple Kinetics Screening Assay for Electrophilic Dermal Sensitizers using Nitrobenzenethiol

    PubMed Central

    Chipinda, Itai; Ajibola, Risikat O.; Morakinyo, Moshood K.; Ruwona, Tinashe B.; Simoyi, Reuben H.; Siegel, Paul D.

    2010-01-01

    The need for alternatives to animal based skin sensitization testing has spurred research on the use of in-vitro, in silico and in chemico methods. Glutathione and other select peptides have been used to determine the reactivity of electrophilic allergens to nucleophiles, but these methods are inadequate to accurately measure rapid kinetics observed with many chemical sensitizers. A kinetic spectrophotometric assay involving the reactivity of electrophilic sensitizers to nitrobenzenethiol was evaluated. Stopped flow techniques and conventional UV spectrophotometric measurements enabled determination of reaction rates with half-lives ranging from 0.4 ms (benzoquinone) to 46.2 s (ethyl acrylate). Rate constants were measured for 7 extreme, 5 strong, 7 moderate and 4 weak/non-sensitizers. 17 out of the 23 tested chemicals were pseudo-first order and 3 were second order. In 3 out of the 23 chemicals, deviations from first and second order were apparent where the chemicals exhibited complex kinetics whose rates are mixed order. The reaction rates of the electrophiles correlated positively with their EC3 values within the same mechanistic domain. Nonsensitizers such as benzaldehyde, sodium lauryl sulfate and benzocaine did not react with nitrobenzenethiol. Cyclic anhydrides, diones and aromatic aldehydes proved to be false negatives in this assay. The findings from this simple and rapid absorbance model show that for the same mechanistic domain, skin sensitization is driven mainly by electrophilic reactivity. This simple, rapid and inexpensive absorbance based method has great potential for use as a preliminary screening tool for skin allergens. PMID:20402462

  16. Kinetic investigation of human 5-lipoxygenase with arachidonic acid.

    PubMed

    Mittal, Monica; Kumar, Ramakrishnan B; Balagunaseelan, Navisraj; Hamberg, Mats; Jegerschöld, Caroline; Rådmark, Olof; Haeggström, Jesper Z; Rinaldo-Matthis, Agnes

    2016-08-01

    Human 5-lipoxygenase (5-LOX) is responsible for the formation of leukotriene (LT)A4, a pivotal intermediate in the biosynthesis of the leukotrienes, a family of proinflammatory lipid mediators. 5-LOX has thus gained attention as a potential drug target. However, details of the kinetic mechanism of 5-LOX are still obscure. In this Letter, we investigated the kinetic isotope effect (KIE) of 5-LOX with its physiological substrate, arachidonic acid (AA). The observed KIE is 20±4 on kcat and 17±2 on kcat/KM at 25°C indicating a non-classical reaction mechanism. The observed rates show slight temperature dependence at ambient temperatures ranging from 4 to 35°C. Also, we observed low Arrhenius prefactor ratio (AH/AD=0.21) and a small change in activation energy (Ea(D)-Ea(H)=3.6J/mol) which suggests that 5-LOX catalysis involves tunneling as a mechanism of H-transfer. The measured KIE for 5-LOX involves a change in regioselectivity in response to deuteration at position C7, resulting in H-abstraction form C10 and formation of 8-HETE. The viscosity experiments influence the (H)kcat, but not (D)kcat. However the overall kcat/KM is not affected for labeled or unlabeled AA, suggesting that either the product release or conformational rearrangement might be involved in dictating kinetics of 5-LOX at saturating conditions. Investigation of available crystal structures suggests the role of active site residues (F421, Q363 and L368) in regulating the donor-acceptor distances, thus affecting H-transfer as well as regiospecificity. In summary, our study shows that that the H-abstraction is the rate limiting step for 5-LOX and that the observed KIE of 5-LOX is masked by a change in regioselectivity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Arsenate adsorption on ruthenium oxides: A spectroscopic and kinetic investigation

    SciTech Connect

    Luxton, Todd P.; Eick, Matthew J.; Scheckel, Kirk G.

    2008-12-08

    Arsenate adsorption on amorphous (RuO{sub 2} {center_dot} 1.1H{sub 2}O) and crystalline (RuO{sub 2}) ruthenium oxides was evaluated using spectroscopic and kinetic methods to elucidate the adsorption mechanism. Extended X-ray absorption fine structure spectroscopy (EXAFS) was used to determine the local coordination environment of adsorbed arsenate. Additionally, pressure-jump (p-jump) relaxation spectroscopy was used to investigate the kinetics of arsenate adsorption/desorption on ruthenium oxides. Chemical relaxations resulting from the induced pressure change were monitored via electrical conductivity detection. EXAFS data were collected for two initial arsenate solution concentrations, 3 and 33 mM at pH 5. The collected spectra indicated a similar coordination environment for arsenate adsorbed to RuO{sub 2} {center_dot} 1.1H{sub 2}O for both arsenate concentrations. In contrast the EXAFS spectra of RuO{sub 2} indicated differences in the local coordination environments for the crystalline material with increasing arsenate concentration. Data analysis indicated that both mono- and bidentate surfaces complexes were present on both RuO{sub 2} {center_dot} 1.1H{sub 2}O and RuO{sub 2}. Relaxation spectra from the pressure-jump experiments of both ruthenium oxides resulted in a double relaxation event. Based on the relaxation spectra, a two step reaction mechanism for arsenate adsorption is proposed resulting in the formation of a bidentate surface complex. Analysis of the kinetic and spectroscopic data suggested that while there were two relaxation events, arsenate adsorbed to ruthenium oxide surfaces through both mono- and bidentate surface complexes.

  18. Acetylcholine receptor: channel-opening kinetics evaluated by rapid chemical kinetic and single-channel current measurements.

    PubMed Central

    Udgaonkar, J. B.; Hess, G. P.

    1987-01-01

    A combination of rapid chemical kinetic (quench-flow) and single-channel current measurements was used to evaluate kinetic parameters governing the opening of acetylcholine-receptor channels in the electric organ (electroplax) of Electrophorus electricus. Chemical kinetic measurements made on membrane vesicles, prepared from the E. electricus electroplax, using carbamoylcholine (200 microM-20 mM) at 12 degrees C, pH 7.0, and in the absence of a transmembrane voltage, yielded values for K1 (dissociation constant for receptor activation), phi (channel closing equilibrium constant), J (specific reaction rate for ion flux), and alpha max (maximum inactivation rate constant) of 1 mM, 3.4, 4 x 10(7) M-1 s-1, and 12 s-1, respectively. The single-channel current recordings were made with cells also from the E. electricus electroplax, at the same temperature and pH as the chemical kinetic measurements, using carbamoylcholine (50 microM-2 mM), acetylcholine (500 nM), or suberyldicholine (20 nM). Single-channel current measurements indicated the presence of a single, unique open-channel state of the E. electricus receptor, in concurrence with previous, less extensive measurements. The rate constant for channel closing (kc) obtained from the mean open time of the receptor channel is 1,100 s-1 for carbamoylcholine, 1,200 s-1 for acetylcholine, and 360 s-1 for suberyldicholine at zero membrane potential; and it decreases e-fold for an 80 mV decrease in transmembrane voltage in each case. The decrease in mean open times of the receptor channel that is associated with increasing the carbamoylcholine concentration is interpreted to be due to carbamoylcholine binding to the regulatory (inhibitory) site on the receptor. An analysis of data obtained with carbamoylcholine showed that the closed times within a burst of channel activity fit a two-exponential distribution, with a concentration-independent time constant considered to be the time constant for carbamoylcholine to dissociate

  19. Experimental investigation of kinetics and rheology during diagenesis

    SciTech Connect

    Liou, J.G.; Hacker, B.R.

    1998-09-01

    Two processes of enormous economic consequence occur within the upper to middle crust: the formation, migration, entrapment, and degradation of hydrocarbons, and hazardous seismicity. Substantial scientific evidence suggests that both these processes are influenced by devolatilization reactions during diagenesis. However, surprisingly few laboratory studies have been conducted on materials actively undergoing low-grade metamorphism or diagenesis. Because of this, there exists no suitable basis for understanding the rates at which devolatilization occurs, and what effects this process has on deformation at shallow to moderate depths in the crust. The authors are conducting a coordinated deformation and kinetic study of an important devolatilization reaction: the breakdown of laumontite. Laumontite is a common zeolite whose equilibrium phase relations and room-temperature frictional behavior are well understood. Besides serving as a model system for more complicated rocks, laumontite is an important mineral in its own right, particularly for hydrocarbon fields in sandstones and for fault zones in the crust. Hydrostatic experiments are being conducted to investigate the kinetics and mechanism of laumontite dehydration, and triaxial deformation experiments will enable characterization of the effect of differential stress on the reaction and the effect of synkinematic dehydration on the mechanical behavior of rock. The authors anticipate results of significant import for hydrocarbon exploration and recovery and for understanding the strength and seismic potential of crustal fault zones.

  20. Experimental investigation on oxidation kinetics of germanium by ozone

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolei; Zhao, Zhiqian; Xiang, Jinjuan; Wang, Wenwu; Zhang, Jing; Zhao, Chao; Ye, Tianchun

    2016-12-01

    Oxidation kinetics of germanium surface by ozone at low temperature (≤400 °C) is experimentally investigated. The growth process contains two regions: initial linear growth region and following parabolic growth region. The GeOx thickness vs. oxidation time plot obeys the well-known Deal-Grove or linear parabolic model. The linear growth region contains reaction of oxygen atoms with surface bond and back bonds of outmost Ge layer. And the activation energy is experimentally estimated to be 0.06 eV. Such small activation energy indicates that the linear growth region is nearly barrier-less. The parabolic growth region starts when the oxygen atoms diffuse into back bonds of second outmost Ge layers. And the activation energy for this process is found to be 0.54 eV. Furthermore, in the ozone oxidation it is not O3 molecules but O radicals that go through the GeOx film.

  1. Investigation of kinetic friction using an iPhone

    NASA Astrophysics Data System (ADS)

    Baldock, Clive; Johnson, Roger

    2016-11-01

    The iPhone is particularly suitable for mechanics experiments using the in-built acceleration sensor or accelerometer in-conjunction with the on-board data collection facility and a downloadable so-called ‘app’. In this work the iPhone has been used to investigate the acceleration due to gravity and determine the coefficient of kinetic friction, μ k of the iPhone as an object sliding down an inclined plane. This method is more accurate than that usually employed in the laboratory where the ‘fits and starts’ of the block sliding down the inclined plane potentially invalidate the required assumption that the velocity is constant. In its simplest form the measurement of acceleration is required to be undertaken for only 2 angles.

  2. Investigation kinetics mechanisms of adsorption malachite green onto activated carbon.

    PubMed

    Onal, Y; Akmil-Başar, C; Sarici-Ozdemir, C

    2007-07-19

    Lignite was used to prepare activated carbon (T3K618) by chemical activation with KOH. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N2 adsorption isotherm. BET surface area of activated carbon is determined as 1000 m2/g. Adsorption capacity of malachite green (MG) onto T3K618 activated carbon was investigated in a batch system by considering the effects of various parameters like initial concentration (100, 150 and 200 mg/L) and temperature (25, 40 and 50 degrees C). The adsorption process was relatively fast and equilibrium was reached after about 20 min for 100, 150 mg/L at all adsorption temperature. Equilibrium time for 200 mg/L was determined as 20 min and 40 min at 298, 313 and 323 K, respectively. Simple mass and kinetic models were applied to the experimental data to examine the mechanisms of adsorption and potential rate controlling steps such as external mass transfer, intraparticle diffusion. Pseudo second-order model was found to explain the kinetics of MG adsorption most effectively. It was found that both mass transfer and pore diffusion are important in determining the adsorption rates. The intraparticle diffusion rate constant, external mass transfer coefficient, film and pore diffusion coefficient at various temperatures were evaluated. The activation energy (Ea) was determined as 48.56, 63.16, 67.93 kJ/mol for 100, 150, 200 mg/L, respectively. The Langmiur and Freundlich isotherm were used to describe the adsorption equilibrium studies at different temperatures. Langmiur isotherm shows better fit than Freundlich isotherm in the temperature range studied. The thermodynamic parameters, such as DeltaG degrees, DeltaS and DeltaH degrees were calculated. The thermodynamics of dyes-T3K618 system indicates endothermic process.

  3. Kinetic study of rapid transfer of tetraethylammonium at the 1,2-dichloroethane/water interface by nanopipet voltammetry of common ions.

    PubMed

    Wang, Yixian; Velmurugan, Jeyavel; Mirkin, Michael V; Rodgers, Patrick J; Kim, Jiyeon; Amemiya, Shigeru

    2010-01-01

    Steady-state voltammetry at the pipet-supported liquid/liquid interface has previously been used to measure kinetics of simple and facilitated ion transfer (IT) processes. Recently, we showed that the conventional experimental protocol and data analysis produce large uncertainties in kinetic parameters of rapid IT processes extracted from pipet voltammograms. Here, we used a new mode of nanopipet voltammetry, in which a transferable ion is initially present as a common ion in both liquid phases, and improved methodology for silanization of the outer pipet wall to investigate the kinetics of the rapid transfer of tetraethylammonium (TEA(+)) at the 1,2-dichloroethane/water interface. This reaction was often employed as a model system to check the IT theory. The determined standard rate constant and transfer coefficient of the TEA(+) transfer are compared with previously reported values to demonstrate limitations of conventional nanopipet voltammetry with a transferrable ion present only in one liquid phase.

  4. Hydrothermal Oxidation of Fecal Sludge: Experimental Investigations and Kinetic Modeling

    PubMed Central

    2016-01-01

    Hydrothermal oxidation (HTO) provides an efficient technique to completely destroy wet organic wastes. In this study, HTO was applied to treat fecal sludge at well-defined experimental conditions. Four different kinetic models were adjusted to the obtained data. Among others, a distributed activation energy model (DAEM) was applied. A total of 33 experiments were carried out in an unstirred batch reactor with pressurized air as the oxidant at temperatures of <470 °C, oxygen-to-fuel equivalence ratios between 0 and 1.9, feed concentrations between 3.9 and 9.8 molTOC L–1 (TOC = total organic carbon), and reaction times between 86 and 1572 s. Decomposition of the fecal sludge was monitored by means of the conversion of TOC to CO2 and CO. In the presence of oxygen, ignition of the reaction was observed around 300 °C, followed by further rapid decomposition of the organic material. The TOC was completely decomposed to CO2 within 25 min at 470 °C and an oxygen-to-fuel equivalence ratio of 1.2. CO was formed as an intermediate product, and no other combustible products were found in the gas. At certain reaction conditions, the formation of unwanted coke and tarlike products occurred. The reaction temperature and oxygen-to-fuel equivalence ratio showed a significant influence on TOC conversion, while the initial TOC concentration did not. Conversion of TOC to CO2 could be well described with a first-order rate law and an activation energy of 39 kJ mol–1. PMID:28539700

  5. Automated rapid particle investigation using scanning electron microscopy

    NASA Astrophysics Data System (ADS)

    Wilkins, Jerod Laurence

    The chemical composition of fly ash particles has been known to vary significantly depending on a number of factors. Current bulk methods of investigation including X-Ray Fluorescence and X-Ray Diffraction are thought to be inadequate in determining the performance of fly ash in concrete. It is the goal of this research to develop a method of Automated Rapid Particle Investigation that will not look at fly ash as a bulk material but as individual particles. By examining each particle individually scientists and engineers will have the ability to study the variation in chemical composition by comparing the chemistry present in each particle. The method of investigation developed by this research provides a practical technique that will allow the automated chemical analysis of hundreds, or even thousands, of fly ash particles in a matter of minutes upon completion of sample preparation and automated scanning electron microscope (ASEM) scanning. This research does not examine the significance of the chemical compounds discovered; rather, only the investigation methodology is discussed. Further research will be done to examine the importance of the chemistry discovered with this automated rapid particle investigation technique.

  6. In vivo kinetics and nonradioactive imaging of rapidly proliferating cells in graft-versus-host disease.

    PubMed

    Buxbaum, Nataliya P; Farthing, Donald E; Maglakelidze, Natella; Lizak, Martin; Merkle, Hellmut; Carpenter, Andrea C; Oliver, Brittany U; Kapoor, Veena; Castro, Ehydel; Swan, Gregory A; Dos Santos, Liliane M; Bouladoux, Nicolas J; Bare, Catherine V; Flomerfelt, Francis A; Eckhaus, Michael A; Telford, William G; Belkaid, Yasmine; Bosselut, Remy J; Gress, Ronald E

    2017-06-15

    Hematopoietic stem cell transplantation (HSCT) offers a cure for cancers that are refractory to chemotherapy and radiation. Most HSCT recipients develop chronic graft-versus-host disease (cGVHD), a systemic alloimmune attack on host organs. Diagnosis is based on clinical signs and symptoms, as biopsies are risky. T cells are central to the biology of cGVHD. We found that a low Treg/CD4+ T effector memory (Tem) ratio in circulation, lymphoid, and target organs identified early and established mouse cGVHD. Using deuterated water labeling to measure multicompartment in vivo kinetics of these subsets, we show robust Tem and Treg proliferation in lymphoid and target organs, while Tregs undergo apoptosis in target organs. Since deuterium enrichment into DNA serves as a proxy for cell proliferation, we developed a whole-body clinically relevant deuterium MRI approach to nonradioactively detect cGVHD and potentially allow imaging of other diseases characterized by rapidly proliferating cells.

  7. In vivo kinetics and nonradioactive imaging of rapidly proliferating cells in graft-versus-host disease

    PubMed Central

    Buxbaum, Nataliya P.; Farthing, Donald E.; Maglakelidze, Natella; Lizak, Martin; Merkle, Hellmut; Carpenter, Andrea C.; Oliver, Brittany U.; Kapoor, Veena; Castro, Ehydel; Swan, Gregory A.; dos Santos, Liliane M.; Bouladoux, Nicolas J.; Bare, Catherine V.; Flomerfelt, Francis A.; Eckhaus, Michael A.; Telford, William G.; Belkaid, Yasmine; Bosselut, Remy J.; Gress, Ronald E.

    2017-01-01

    Hematopoietic stem cell transplantation (HSCT) offers a cure for cancers that are refractory to chemotherapy and radiation. Most HSCT recipients develop chronic graft-versus-host disease (cGVHD), a systemic alloimmune attack on host organs. Diagnosis is based on clinical signs and symptoms, as biopsies are risky. T cells are central to the biology of cGVHD. We found that a low Treg/CD4+ T effector memory (Tem) ratio in circulation, lymphoid, and target organs identified early and established mouse cGVHD. Using deuterated water labeling to measure multicompartment in vivo kinetics of these subsets, we show robust Tem and Treg proliferation in lymphoid and target organs, while Tregs undergo apoptosis in target organs. Since deuterium enrichment into DNA serves as a proxy for cell proliferation, we developed a whole-body clinically relevant deuterium MRI approach to nonradioactively detect cGVHD and potentially allow imaging of other diseases characterized by rapidly proliferating cells. PMID:28614804

  8. Sensitive and rapid laser diagnostic for shock tube kinetics studies using cavity-enhanced absorption spectroscopy.

    PubMed

    Sun, Kai; Wang, Shengkai; Sur, Ritobrata; Chao, Xing; Jeffries, Jay B; Hanson, Ronald K

    2014-04-21

    We report the first application of cavity-enhanced absorption spectroscopy (CEAS) using a coherent light source for sensitive and rapid gaseous species time-history measurements in a shock tube. Off-axis alignment and fast scanning of the laser wavelength were used to minimize coupling noise in a low-finesse cavity. An absorption gain factor of 83 with a measurement time resolution of 20 µs was demonstrated for C2H2 detection using a near-infrared transition near 1537 nm, corresponding to a noise-equivalent detection limit of 20 ppm at 296 K and 76 ppm at 906 K at 50 kHz. This substantial gain in signal, relative to conventional single-pass absorption, will enable ultra-sensitive species detection in shock tube kinetics studies, particularly useful for measurements of minor species and for studies of dilute reactive systems.

  9. A Tracer Bolus Method for Investigating Glutamine Kinetics in Humans

    PubMed Central

    Mori, Maiko; Smedberg, Marie; Klaude, Maria; Tjäder, Inga; Norberg, Åke; Rooyackers, Olav; Wernerman, Jan

    2014-01-01

    Glutamine transport between tissues is important for the outcome of critically ill patients. Investigation of glutamine kinetics is, therefore, necessary to understand glutamine metabolism in these patients in order to improve future intervention studies. Endogenous glutamine production can be measured by continuous infusion of a glutamine tracer, which necessitates a minimum measurement time period. In order to reduce this problem, we used and validated a tracer bolus injection method. Furthermore, this method was used to measure the glutamine production in healthy volunteers in the post-absorptive state, with extra alanine and with glutamine supplementation and parenteral nutrition. Healthy volunteers received a bolus injection of [1-13C] glutamine, and blood was collected from the radial artery to measure tracer enrichment over 90 minutes. Endogenous rate of appearance (endoRa) of glutamine was calculated from the enrichment decay curve and corrected for the extra glutamine supplementation. The glutamine endoRa of healthy volunteers was 6.1±0.9 µmol/kg/min in the post-absorptive state, 6.9±1.0 µmol/kg/min with extra alanyl-glutamine (p = 0.29 versus control), 6.1±0.4 µmol/kg/min with extra alanine only (p = 0.32 versus control), and 7.5±0.9 µmol/kg/min with extra alanyl-glutamine and parenteral nutrition (p = 0.049 versus control). In conclusion, a tracer bolus injection method to measure glutamine endoRa showed good reproducibility and small variation at baseline as well as during parenteral nutrition. Additionally, we showed that parenteral nutrition including alanyl-glutamine increased glutamine endoRa in healthy volunteers, which was not attributable to the alanine part of the dipeptide. PMID:24810895

  10. Rapid monocyte kinetics in acute myocardial infarction are sustained by extramedullary monocytopoiesis

    PubMed Central

    Leuschner, Florian; Rauch, Philipp J.; Ueno, Takuya; Gorbatov, Rostic; Marinelli, Brett; Lee, Won Woo; Dutta, Partha; Wei, Ying; Robbins, Clinton; Iwamoto, Yoshiko; Sena, Brena; Chudnovskiy, Aleksey; Panizzi, Peter; Keliher, Edmund; Higgins, John M.; Libby, Peter; Moskowitz, Michael A.; Pittet, Mikael J.; Swirski, Filip K.

    2012-01-01

    Monocytes (Mo) and macrophages (MΦ) are emerging therapeutic targets in malignant, cardiovascular, and autoimmune disorders. Targeting of Mo/MΦ and their effector functions without compromising innate immunity’s critical defense mechanisms first requires addressing gaps in knowledge about the life cycle of these cells. Here we studied the source, tissue kinetics, and clearance of Mo/MΦ in murine myocardial infarction, a model of acute inflammation after ischemic injury. We found that a) Mo tissue residence time was surprisingly short (20 h); b) Mo recruitment rates were consistently high even days after initiation of inflammation; c) the sustained need of newly made Mo was fostered by extramedullary monocytopoiesis in the spleen; d) splenic monocytopoiesis was regulated by IL-1β; and e) the balance of cell recruitment and local death shifted during resolution of inflammation. Depending on the experimental approach, we measured a 24 h Mo/MΦ exit rate from infarct tissue between 5 and 13% of the tissue cell population. Exited cells were most numerous in the blood, liver, and spleen. Abrogation of extramedullary monocytopoiesis proved deleterious for infarct healing and accelerated the evolution of heart failure. We also detected rapid Mo kinetics in mice with stroke. These findings expand our knowledge of Mo/MΦ flux in acute inflammation and provide the groundwork for novel anti-inflammatory strategies for treating heart failure. PMID:22213805

  11. Rapid kinetics of 2-adrenergic agonist binding and inhibition of adenylate cyclase

    SciTech Connect

    Thomsen, W.; Neubig, R.R.

    1987-05-01

    Activation of 2-adrenergic receptors in human platelets results in inhibition of adenylate cyclase (AC). To elucidate the relation between agonist binding and response, the authors have used a novel rapid-mix quench method to compare the kinetics of binding and response. At functionally effective concentrations, the time course of binding of the full 2-agonist, (TH)UK14,304 (UK), to purified platelet membranes was faster than could be measured manually. Using the rapid-mix quench method, agonist binding was quantitated for times for 0.3 to 60 seconds. UK binding exhibited biexponential kinetics. The rate constant of the fast binding component increases linearly with agonist concentration from 1 to 100 nM with a second order rate constant and 7 x 10WM s (at 25C). The slow rate constant was nearly independent of agonist concentration. The half times of the fast and slow components of binding for 100 nM UK are 1.5 seconds and approximately 2 minutes respectively. The rate and magnitude of the fast binding was unaffected by 10 M GTP whereas the magnitude of the slow phase was markedly reduced. Inhibition of forskolin stimulated AC by 100 M epinephrine occurs with a lag of 5-10 seconds in the presence of 10 M GTP. At lower GTP concentrations, this lag is prolonged. The observation that the fast component of agonist binding precedes inhibition even at agonist concentrations 20-fold lower than the EC40 for responses indicates that the rate limiting step in inhibition of AC is distal to the binding of agonist.

  12. [New relations for steady-state enzyme kinetics and their application to rapid equilibrium assumption].

    PubMed

    Vrzheshch, P V

    2013-01-01

    With the use of a graph theory new relations for steady-state enzyme kinetics are derived and strictly proved for the arbitrary mechanism of an enzyme-catalysed reaction containing a reversible segment. Using these relations, a general principle for rapid equilibrium assumption is formulated and proved: the reversible bound segment can be considered as an equilibrium segment only when the values of the base trees that are not proper to this segment can be neglected (within a prescribed accuracy) in relation to the values of the base trees that belong to this segment. In contrast with the foreign base trees the base trees that are proper to the segment have the following properties: the tree that is directed to the base within this segment does not contain the edges leaving this segment; and the tree that is directed to the base outside the segment contains only one edge leaving this segment. Equilibrium variations are assessed for steady-state intermediates concentrations of the equilibrium segment, numerical expressions are obtained for the accuracy of determination of the intermediates concentrations as well as for the accuracy of determination of the rate of enzyme-catalysed reaction in case of using rapid equilibrium assumption.

  13. Arsenate Adsorption On Ruthenium Oxides: A Spectroscopic And Kinetic Investigation

    EPA Science Inventory

    Arsenate adsorption on amorphous (RuO2•1.1H2O) and crystalline (RuO2) ruthenium oxides was evaluated using spectroscopic and kinetic methods to elucidate the adsorption mechanism. Extended X-ray absorption fine structure spectroscopy (EXAFS) was ...

  14. Arsenate Adsorption On Ruthenium Oxides: A Spectroscopic And Kinetic Investigation

    EPA Science Inventory

    Arsenate adsorption on amorphous (RuO2•1.1H2O) and crystalline (RuO2) ruthenium oxides was evaluated using spectroscopic and kinetic methods to elucidate the adsorption mechanism. Extended X-ray absorption fine structure spectroscopy (EXAFS) was ...

  15. Rapid quantification and analysis of kinetic • OH radical footprinting data using SAFA

    PubMed Central

    Simmons, Katrina; Martin, Joshua S.; Shcherbakova, Inna; Laederach, Alain

    2010-01-01

    The use of highly reactive chemical species to probe the structure and dynamics of nucleic acids is greatly simplified by software that enables rapid quantification of the gel images that result from these experiments. SAFA (Semi-Automated Footprinting Analysis) allows a user to quickly and reproducibly quantify a chemical footprinting gel image through a series of steps that rectify, assign, and integrate the relative band intensities. The output of this procedure is raw band intensities that report on the relative reactivity of each nucleotide with the chemical probe. We describe here how to obtain these raw band intensities using SAFA and the subsequent normalization and analysis procedures required to process this data. In particular, we focus on analyzing time-resolved hydroxyl radical (•OH) data, which we use to monitor the kinetics of folding of a large RNA (the L-21 T. thermophila group I intron). Exposing the RNA to bursts of •OH radicals at specific time-points during the folding process monitors the time-progress of the reaction. Specifically, we identify protected (nucleotides that become inaccessible to the •OH radical probe when folded) and invariant (nucleotides with constant accessibility to the •OH probe) residues that we use for monitoring and normalization of the data. With this analysis, we obtain time-progress curves from which we determine kinetic rates of folding. We also report on a data visualization tool implemented in SAFA that allows users to map data onto a secondary structure diagram. PMID:20946764

  16. Unusual Kinetic and Structural Properties Control Rapid Assembly and Turnover of Actin in the Parasite Toxoplasma gondiiD⃞

    PubMed Central

    Sahoo, Nivedita; Beatty, Wandy; Heuser, John; Sept, David; Sibley, L. David

    2006-01-01

    Toxoplasma is a protozoan parasite in the phylum Apicomplexa, which contains a number of medically important parasites that rely on a highly unusual form of motility termed gliding to actively penetrate their host cells. Parasite actin filaments regulate gliding motility, yet paradoxically filamentous actin is rarely detected in these parasites. To investigate the kinetics of this unusual parasite actin, we expressed TgACT1 in baculovirus and purified it to homogeneity. Biochemical analysis showed that Toxoplasma actin (TgACT1) rapidly polymerized into filaments at a critical concentration that was 3-4-fold lower than conventional actins, yet it failed to copolymerize with mammalian actin. Electron microscopic analysis revealed that TgACT1 filaments were 10 times shorter and less stable than rabbit actin. Phylogenetic comparison of actins revealed a limited number of apicomplexan-specific residues that likely govern the unusual behavior of parasite actin. Molecular modeling identified several key alterations that affect interactions between monomers and that are predicted to destabilize filaments. Our findings suggest that conserved molecular differences in parasite actin favor rapid cycles of assembly and disassembly that govern the unusual form of gliding motility utilized by apicomplexans. PMID:16319175

  17. Rapid kinetics of serum IgA after vaccination with Prevnar(®)13 followed by Pneumovax(®)23.

    PubMed

    Crowther, Rebecca R; Collins, Christine M; Conley, Cheryl; Lopez, Osvaldo J

    2017-02-01

    Streptococcus pneumoniae is a causative agent of community-acquired pneumonias. The recommendations of the 2012 Advisory Committee on Immunization Practices include vaccination with Prevnar(®)13 (protein-polysaccharide conjugate vaccine; PCV), followed by Pneumovax(®)23 (polysaccharide-based vaccine; PSV) in adults 65+ or the immunocompromised. In this experiment, a group of 4 healthy volunteers were vaccinated with PCV followed by PSV 60 days later. ELISAs were optimized to study kinetics of IgA, IgM, total IgG and its four subclasses against 14 polysaccharides of the pneumococcal capsule. Although this is a small sample, results from volunteers consistently showed that rapid induction of monomeric IgA followed by rapid decline is typical for both vaccines. IgA was not detected after PSV vaccination in those serotypes present in PCV, suggesting the population of B cells secreting IgA is not renewed within 60 days of activation by PCV. In contrast to mice, human neutrophils expressed a functional receptor for the constant region of monomeric IgA. Thus, the role of IgA early in the human immune response should be further investigated.

  18. Investigations of vibrational kinetics relaxation within air shock wave plasma

    NASA Astrophysics Data System (ADS)

    Su, W.; Bruno, D.; Babou, Y.

    2017-02-01

    A vibrationally detailed kinetic model is used to study the relaxation behind shock waves in air. The role of recently published data for the rate coefficients of the Zeldovich reactions of NO formation is studied in detail. Results allow to study the radiation emitted from the shock-heated gas. Comparison with some emission spectroscopy study performed in a shock tube facility shows only qualitative agreement with the model predictions but it allows to identify directions for model improvement.

  19. Streamlined purification of fluorescently labeled Escherichia coli phosphate-binding protein (PhoS) suitable for rapid-kinetics applications.

    PubMed

    Smith, Dustin D; Girodat, Dylan; Wieden, Hans-Joachim; Selinger, L Brent

    2017-09-20

    Fluorescently labeled phosphate-binding proteins can be used as biomolecular tools to measure the release of inorganic phosphate (Pi) from enzymes in real time, enabling the detailed kinetic analysis of dephosphorylating enzymes using rapid-kinetics approaches. Previously reported methods to purify fluorescently labeled phosphate-binding proteins (PhoS) from Escherichia coli are laborious, and a simplified approach is needed. Here, we report the characterization of a cytosol-localized variant (A197C) of PhoS that allows a streamlined purification for subsequent covalent conjugation with a fluorescent dye. We demonstrate that export of PhoS into the periplasmic space is not required for the fluorescence-based detection of Pi binding. Furthermore, we report the addition of a C-terminal His-tag, simplifying the purification of PhoS from the cytosol via Ni(2+)-affinity chromatography, yielding a fully functional fusion protein (HC PhoS A197C). We demonstrate the utility of fluorescently labeled HC PhoS A197C for rapid-kinetics applications by measuring, using stopped-flow, the Pi release kinetics from LepA/EF4 following 70S ribosome-stimulated GTP hydrolysis. Altogether, the approach developed here allows for the high-yield and simplified in-house production of a Pi detection system suitable for rapid-kinetics approaches with comparable sensitivity to the commercially available Phosphate Sensor. Copyright © 2017. Published by Elsevier Inc.

  20. A New Strategy to Rapidly Evaluate Kinetics of Glucuronide Efflux by Breast Cancer Resistance Protein (BCRP/ABCG2)

    PubMed Central

    Wu, Baojian; Jiang, Wen; Yin, Taijun; Gao, Song

    2013-01-01

    Purpose The efflux transporter breast cancer resistance protein (BCRP/ABCG2) plays an important role in excretion of anionic drugs and metabolites including glucuronides in humans. Methods In this article, our recently published cell model (i.e., HeLa cells over-expressing UGT1A9 (HeLa1A9)) is used to determine the kinetic parameters of BCRP-mediated transport of glucuronides. Results After incubation of the aglycone with the cells, a steady-state (i.e., zero-order or near zero-order) excretion of its glucuronide is rapidly achieved and then maintained. Kinetic profiling with different (intracellular) glucuronide concentrations and their corresponding excretion rates is enabled by varying the concentration of the aglycone, which allows for the determination of kinetic parameters responsible for BCRP-mediated efflux of glucuronides. This approach was validated theoretically using a cellular pharmacokinetic model incorporating various enzymatic and transporter-mediated kinetic processes. It was also validated experimentally in that kinetic parameters of efflux of glucuronides of 6-hydroxyflavone and 4-methylumberiferone in the HeLa1A9 cell model were shown to be consistent with those derived with BCRP-overexpressing membrane vesicles. Conclusion This study provides a new strategy for rapidly evaluating the kinetics of glucuronide efflux by BCRP. PMID:22752253

  1. Detailed Chemical Kinetic Reaction Mechanisms for Autoignition of Isomers of Heptane Under Rapid Compression

    SciTech Connect

    Westbrook, C K; Pitz, W J; Boercker, J E; Curran, H J; Griffiths, J F; Mohamed, C; Ribaucour, M

    2001-12-17

    Detailed chemical kinetic reaction mechanisms are developed for combustion of all nine isomers of heptane (C{sub 7}H{sub 16}), and these mechanisms are tested by simulating autoignition of each isomer under rapid compression machine conditions. The reaction mechanisms focus on the manner in which the molecular structure of each isomer determines the rates and product distributions of possible classes of reactions. The reaction pathways emphasize the importance of alkylperoxy radical isomerizations and addition reactions of molecular oxygen to alkyl and hydroperoxyalkyl radicals. A new reaction group has been added to past models, in which hydroperoxyalkyl radicals that originated with abstraction of an H atom from a tertiary site in the parent heptane molecule are assigned new reaction sequences involving additional internal H atom abstractions not previously allowed. This process accelerates autoignition in fuels with tertiary C-H bonds in the parent fuel. In addition, the rates of hydroperoxyalkylperoxy radical isomerization reactions have all been reduced so that they are now equal to rates of analogous alkylperoxy radical isomerizations, significantly improving agreement between computed and experimental ignition delay times in the rapid compression machine. Computed ignition delay times agree well with experimental results in the few cases where experiments have been carried out for specific heptane isomers, and predictive model calculations are reported for the remaining isomers. The computed results fall into three general groups; the first consists of the most reactive isomers, including n-heptane, 2-methyl hexane and 3-methyl hexane. The second group consists of the least reactive isomers, including 2,2-dimethyl pentane, 3,3-dimethyl pentane, 2,3-dimethyl pentane, 2,4-dimethyl pentane and 2,2,3-trimethyl butane. The remaining isomer, 3-ethyl pentane, was observed computationally to have an intermediate level of reactivity. These observations are generally

  2. Microsecond Microfluidic Mixing for Investigation of Protein Folding Kinetics

    SciTech Connect

    Hertzog, D E; Santiago, J G; Bakajin, O

    2005-02-10

    We have developed and characterized a mixer to study the reaction kinetics of protein folding on a microsecond timescale. The mixer uses hydrodynamic focusing of pressure-driven flow in a microfluidic channel to reduce diffusion times as first demonstrated by Knight et al.[1]. Features of the mixer include 1 {micro}s mixing times, sample consumptions of order 1 nl/s, loading sample volumes on the order of microliters, and the ability to manufacture in fused silica for compatibility with most spectroscopic methods.

  3. Microsecond Microfluidic Mixing for Investigation of Protein Folding Kinetics

    SciTech Connect

    Hertzog, D E; Santiago, J G; Bakajin, O

    2003-06-25

    We have developed and characterized a mixer to study the reaction kinetics of protein folding on a microsecond timescale. The mixer uses hydrodynamic focusing of pressure-driven flow in a microfluidic channel to reduce diffusion times as first demonstrated by Knight et al.[1]. Features of the mixer include 1 {micro}s mixing times, sample consumptions of order 1 nl/s, loading sample volumes on the order of microliters, and the ability to manufacture in fused silica for compatibility with most spectroscopic methods.

  4. Pulsed ion beam investigation of the kinetics of surface reactions

    NASA Technical Reports Server (NTRS)

    Horton, C. C.; Eck, T. G.; Hoffman, R. W.

    1989-01-01

    Pulsed ion beam measurements of the kinetics of surface reactions are discussed for the case where the width of the ion pulse is comparable to the measured reaction time, but short compared to the time between successive pulses. Theoretical expressions are derived for the time dependence of the ion-induced signals for linear surface reactions. Results are presented for CO emission from surface carbon and CF emission from Teflon induced by oxygen ion bombardment. The strengths and limitations of this technique are described.

  5. Rapid Cl⁻/HCO⁻₃exchange kinetics of AE1 in HEK293 cells and hereditary stomatocytosis red blood cells.

    PubMed

    Frumence, Etienne; Genetet, Sandrine; Ripoche, Pierre; Iolascon, Achille; Andolfo, Immacolata; Le Van Kim, Caroline; Colin, Yves; Mouro-Chanteloup, Isabelle; Lopez, Claude

    2013-09-15

    Anion exchanger 1 (AE1) or band 3 is a membrane protein responsible for the rapid exchange of chloride for bicarbonate across the red blood cell membrane. Nine mutations leading to single amino-acid substitutions in the transmembrane domain of AE1 are associated with dominant hereditary stomatocytosis, monovalent cation leaks, and reduced anion exchange activity. We set up a stopped-flow spectrofluorometry assay coupled with flow cytometry to investigate the anion transport and membrane expression characteristics of wild-type recombinant AE1 in HEK293 cells, using an inducible expression system. Likewise, study of three stomatocytosis-associated mutations (R730C, E758K, and G796R), allowed the validation of our method. Measurement of the rapid and specific chloride/bicarbonate exchange by surface expressed AE1 showed that E758K mutant was fully active compared with wild-type (WT) AE1, whereas R730C and G796R mutants were inactive, reinforcing previously reported data on other experimental models. Stopped-flow analysis of AE1 transport activity in red blood cell ghost preparations revealed a 50% reduction of G796R compared with WT AE1 corresponding to a loss of function of the G796R mutated protein, in accordance with the heterozygous status of the AE1 variant patients. In conclusion, stopped-flow led to measurement of rapid transport kinetics using the natural substrate for AE1 and, conjugated with flow cytometry, allowed a reliable correlation of chloride/bicarbonate exchange to surface expression of AE1, both in recombinant cells and ghosts and therefore a fine comparison of function between different stomatocytosis samples. This technical approach thus provides significant improvements in anion exchange analysis in red blood cells.

  6. Analyzing complicated protein folding kinetics rapidly by analytical Laplace inversion using a Tikhonov regularization variant.

    PubMed

    Mulligan, Vikram Khipple; Hadley, Kevin Charles; Chakrabartty, Avijit

    2012-02-01

    Kinetic experiments provide much information about protein folding mechanisms. Time-resolved signals are often best described by expressions with many exponential terms, but this hinders the extraction of rate constants by nonlinear least squares (NLS) fitting. Numerical inverse Laplace transformation, which converts a time-resolved dataset into a spectrum of amplitudes as a function of rate constant, allows easy estimation of the rate constants, amplitudes, and number of processes underlying the data. Here, we present a Tikhonov regularization-based method that converts a dataset into a rate spectrum, subject to regularization constraints, without requiring an iterative search of parameter space. This allows more rapid generation of rate spectra as well as analysis of datasets too noisy to process by existing iterative search algorithms. This method's simplicity also permits highly objective, largely automatic analysis with minimal human guidance. We show that this regularization method reproduces results previously obtained by NLS fitting and that it is effective for analyzing datasets too complex for traditional fitting methods. This method's reliability and speed, as well as its potential for objective, model-free analysis, make it extremely useful as a first step in analysis of complicated noisy datasets and an excellent guide for subsequent NLS analysis. Copyright © 2011 Elsevier Inc. All rights reserved.

  7. Transient drug supersaturation kinetics of beclomethasone dipropionate in rapidly drying films.

    PubMed

    Reid, Monica L; Jones, Stuart A; Brown, Marc B

    2009-04-17

    Supersaturation is an effective method to enhance the delivery of active compounds into the skin, however the long-term instability of the drug in these formulations that exceed thermodynamic unity prevents clinical use. The creation of supersaturation in situ by volatile solvent evaporation after application may overcome this. The aim of this study was to determine how altering the kinetics of transient supersaturation and recrystallisation would effect the rate of beclomethasone dipropionate (BDP) release from metered dose aerosols (MDA) that also consisted of hydrofluoroalkane 134a, ethanol (EtOH), and poly(vinyl pyrrolidone) (PVP) K90. An MDA containing 10% EtOH generated a sub-saturated concentration of BDP immediately after dose actuation and did not become supersaturated until 30 min post-actuation. Increasing the EtOH to 20% (w/w) and thus the BDP to 1.76% created supersaturation upon dose actuation but the drug recyrstallised within minutes of application. It was shown that the formulations with higher DS had accelerated rates of release despite rapid recrystallisation (444.9+/-79.3 microg/(cm2 h) for the fastest compared to 206.5+/-23.0 microg/(cm2 h) for the slowest). In highly volatile sprays maintaining BDP supersaturation for extended periods of time was less important than generating instantaneous, high levels of supersaturation to enhance drug release.

  8. Rapid Kinetics of Dehalogenation Promoted by Iodotyrosine Deiodinase from Human Thyroid

    PubMed Central

    2015-01-01

    Reductive dehalogenation such as that catalyzed by iodotyrosine deiodinase (IYD) is highly unusual in aerobic organisms but necessary for iodide salvage from iodotyrosine generated during thyroxine biosynthesis. Equally unusual is the dependence of this process on flavin. Rapid kinetics have now been used to define the basic processes involved in IYD catalysis. Time-dependent quenching of flavin fluorescence was used to monitor halotyrosine association to IYD. The substrates chloro-, bromo-, and iodotyrosine bound with similar rate constants (kon) ranging from 1.3 × 106 to 1.9 × 106 M–1 s–1. Only the inert substrate analogue fluorotyrosine exhibited a significantly (5-fold) slower kon (0.3 × 106 M–1 s–1). All data fit a standard two-state model and indicated that no intermediate complex accumulated during closure of the active site lid induced by substrate. Subsequent halide elimination does not appear to limit reactions of bromo- and iodotyrosine since both fully oxidized the reduced enzyme with nearly equivalent second-order rate constants (7.3 × 103 and 8.6 × 103 M–1 s–1, respectively) despite the differing strength of their carbon–halogen bonds. In contrast to these substrates, chlorotyrosine reacted with the reduced enzyme approximately 20-fold more slowly and revealed a spectral intermediate that formed at approximately the same rate as the bromo- and iodotyrosine reactions. PMID:26151430

  9. Very rapid phosphorylation kinetics suggest a unique role for Lhcb2 during state transitions in Arabidopsis

    PubMed Central

    Leoni, Claudia; Pietrzykowska, Malgorzata; Kiss, Anett Z; Suorsa, Marjaana; Ceci, Luigi R; Aro, Eva-Mari; Jansson, Stefan

    2013-01-01

    Light-harvesting complex II (LHCII) contains three highly homologous chlorophyll-a/b-binding proteins (Lhcb1, Lhcb2 and Lhcb3), which can be assembled into both homo- and heterotrimers. Lhcb1 and Lhcb2 are reversibly phosphorylated by the action of STN7 kinase and PPH1/TAP38 phosphatase in the so-called state-transition process. We have developed antibodies that are specific for the phosphorylated forms of Lhcb1 and Lhcb2. We found that Lhcb2 is more rapidly phosphorylated than Lhcb1: 10 sec of ‘state 2 light’ results in Lhcb2 phosphorylation to 30% of the maximum level. Phosphorylated and non-phosphorylated forms of the proteins showed no difference in electrophoretic mobility and dephosphorylation kinetics did not differ between the two proteins. In state 2, most of the phosphorylated forms of Lhcb1 and Lhcb2 were present in super- and mega-complexes that comprised both photosystem (PS)I and PSII, and the state 2-specific PSI–LHCII complex was highly enriched in the phosphorylated forms of Lhcb2. Our results imply distinct and specific roles for Lhcb1 and Lhcb2 in the regulation of photosynthetic light harvesting. PMID:23888908

  10. Evolutionary optimization of peptide substrates for proteases that exhibit rapid hydrolysis kinetics.

    PubMed

    Boulware, Kevin T; Jabaiah, Abeer; Daugherty, Patrick S

    2010-06-15

    Protease cleavage site recognition motifs can be identified using protease substrate discovery methodologies, but typically exhibit non-optimal specificity and activity. To enable evolutionary optimization of substrate cleavage kinetics, a two-color cellular library of peptide substrates (CLiPS) methodology was developed. Two-color CLiPS was applied to identify peptide substrates for the tobacco etch virus (TEV) protease from a random pentapeptide library, which were then optimized by screening of a focused, extended substrate library. Quantitative library screening yielded seven amino acid substrates exhibiting rapid hydrolysis by TEV protease and high sequence similarity to the native seven-amino-acid substrate, with a strong consensus of EXLYPhiQG. Comparison of hydrolysis rates for a family of closely related substrates indicates that the native seven-residue TEV substrate co-evolved with TEV protease to facilitate highly efficient hydrolysis. Consensus motifs revealed by screening enabled database identification of a family of related, putative viral protease substrates. More generally, our results suggest that substrate evolution using CLiPS may be useful for optimizing substrate selectivity and activity to enable the design of more effective protease activity probes, molecular imaging agents, and prodrugs.

  11. A kinetics investigation of several reactions involving chlorine containing compounds

    NASA Technical Reports Server (NTRS)

    Davis, D. D.

    1978-01-01

    The technique of flash photolysis-resonance fluorescence was utilized to study nine reactions of stratospheric importance. The tropospheric degradation reactions of seven halogenated hydrocarbons were studied to assess their possible influx into the stratosphere. There are reactions of either Cl, OH, or O(3P) species with hydrogenated species, O3 or chlorinated compounds. Apart from the kinetic measurements, the quantum yield for the production of O(1D) from O3 in the crucial wavelength region of 293 to 316.5 nm was studied by utilizing a narrow wavelength laser as the photolysis source. The product formation was monitored by measuring the fluorescence of NO2 formed through O(1D) reaction with N2O followed by NO reaction with O3 to give NO2.

  12. Folding Kinetics of Staphylococcal Nuclease Studied by Tryptophan Engineering and Rapid Mixing Methods

    PubMed Central

    Maki, Kosuke; Cheng, Hong; Dolgikh, Dimitry A.; Roder, Heinrich

    2007-01-01

    To monitor the development of tertiary structural contacts during folding, a unique tryptophan residue was introduced at seven partially buried locations (residues 15, 27, 61, 76, 91, 102 and 121) of a tryptophan-free variant of staphylococcal nuclease (P47G/P117G/H124L/W140H). Thermal unfolding measurements by circular dichroism indicate that the variants are destabilized, but maintain the ability to fold into a native-like structure. For the variants with Trp at positions 15, 27 and 61, the intrinsic fluorescence is significantly quenched in the native state due to close contact with polar side chains that act as intramolecular quenchers. All other variants exhibit enhanced fluorescence under native conditions consistent with burial of the tryptophans in an apolar environment. The kinetics of folding was observed by continuous- and stopped-flow fluorescence measurements over refolding times ranging from 100 μs to 10 s. The folding kinetics of all variants is quantitatively described by a mechanism involving a major pathway with a series of intermediate states and a minor parallel channel. The engineered tryptophans in the β-barrel and the N-terminal part of the α-helical domain become partially shielded from the solvent at an early stage (< 1 ms), indicating that this region of the protein undergoes a rapid specific collapse and remains uncoupled from the rest of the α-helical domain until the late stages of folding. For several variants, a major increase in fluorescence coincides with the rate-limiting step of folding on the 100 ms time scale, indicating that these tryptophans reach their buried native environment only during the late stages of folding. Other variants show more complex behavior with a transient increase in fluorescence during the 10 ms phase followed by a decrease during the rate-limiting phase. These observations are consistent with burial of these probes in a collapsed, but loosely packed intermediate, followed by the rate

  13. Investigation of ozonation kinetics and transformation products of sucralose.

    PubMed

    Hu, Ruikang; Zhang, Lifeng; Hu, Jiangyong

    2017-12-15

    Sucralose is one of widely used artificial sweeteners, which has been ubiquitously detected in various water sources, such as wastewater and randomly in reservoir water. It is also reported to be persistent to various water treatment techniques. Although there are some studies on removal of sucralose by advanced oxidation process, limited information, in terms of reaction kinetics, transformation products and degradation pathway etc., was reported in its ozonation process. In this study, the reaction kinetics, removal efficiency, influence of pH, humic acid and carbonate on sucralose degradation by ozone, have been studied systematically. The results demonstrated that ozonation of sucralose was initiated by the formation of OH radical. Sucralose could be completely removed with excess O3 at neutral and basic conditions in ultrapure water. The rate of degradation decreased significantly in acidic condition and in the presence of carbonate and OH radical scavenger (e.g. tert-butanol). The acidity was the key factor affecting the degradation of sucralose. The rate constant was about 500 times higher at pH7 than that at pH4. Transformation products study indicated that the ozonation of sucralose were more complex than that in photolysis reaction. Although ozonation of sucralose was initiated by OH radical, both OH radical and O3 might be involved in the formation of transformation products and total organic carbon (TOC) removal. Various transformation products, such as aldehydes, carboxylic acids and probable chloride containing products, were identified and characterized in details. An ozonation degradation pathway of sucralose was proposed as well. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Antimicrobial Protegrin-1 Forms Amyloid-Like Fibrils with Rapid Kinetics Suggesting a Functional Link

    PubMed Central

    Jang, Hyunbum; Arce, Fernando Teran; Mustata, Mirela; Ramachandran, Srinivasan; Capone, Ricardo; Nussinov, Ruth; Lal, Ratnesh

    2011-01-01

    Protegrin-1 (PG-1) is an 18 residues long, cysteine-rich β-sheet antimicrobial peptide (AMP). PG-1 induces strong cytotoxic activities on cell membrane and acts as a potent antibiotic agent. Earlier we reported that its cytotoxicity is mediated by its channel-forming ability. In this study, we have examined the amyloidogenic fibril formation properties of PG-1 in comparison with a well-defined amyloid, the amyloid-β (Aβ1–42) peptide. We have used atomic force microscopy (AFM) and thioflavin-T staining to investigate the kinetics of PG-1 fibrils growth and molecular dynamics simulations to elucidate the underlying mechanism. AFM images of PG-1 on a highly hydrophilic surface (mica) show fibrils with morphological similarities to Aβ1–42 fibrils. Real-time AFM imaging of fibril growth suggests that PG-1 fibril growth follows a relatively fast kinetics compared to the Aβ1–42 fibrils. The AFM results are in close agreement with results from thioflavin-T staining data. Furthermore, the results indicate that PG-1 forms fibrils in solution. Significantly, in contrast, we do not detect fibrillar structures of PG-1 on an anionic lipid bilayer 2-dioleoyl-sn-glycero-3-phospho-L-serine/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine; only small PG-1 oligomers can be observed. Molecular dynamics simulations are able to identify the presence of these small oligomers on the membrane bilayer. Thus, our current results show that cytotoxic AMP PG-1 is amyloidogenic and capable of forming fibrils. Overall, comparing β-rich AMPs and amyloids such as Aβ, in addition to cytotoxicity and amyloidogenicity, they share a common structural motif, and are channel forming. These combined properties support a functional relationship between amyloidogenic peptides and β-sheet-rich cytolytic AMPs, suggesting that amyloids channels may have an antimicrobial function. PMID:21463591

  15. Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification

    SciTech Connect

    Choi, Jeong

    2011-01-01

    The research program reported here is focused on critical issues that represent conspicuous gaps in current understanding of rapid solidification, limiting our ability to predict and control microstructural evolution (i.e. morphological dynamics and microsegregation) at high undercooling, where conditions depart significantly from local equilibrium. More specifically, through careful application of phase-field modeling, using appropriate thin-interface and anti-trapping corrections and addressing important details such as transient effects and a velocity-dependent (i.e. adaptive) numerics, the current analysis provides a reasonable simulation-based picture of non-equilibrium solute partitioning and the corresponding oscillatory dynamics associated with single-phase rapid solidification and show that this method is a suitable means for a self-consistent simulation of transient behavior and operating point selection under rapid growth conditions. Moving beyond the limitations of conventional theoretical/analytical treatments of non-equilibrium solute partitioning, these results serve to substantiate recent experimental findings and analytical treatments for single-phase rapid solidification. The departure from the equilibrium solid concentration at the solid-liquid interface was often observed during rapid solidification, and the energetic associated non-equilibrium solute partitioning has been treated in detail, providing possible ranges of interface concentrations for a given growth condition. Use of these treatments for analytical description of specific single-phase dendritic and cellular operating point selection, however, requires a model for solute partitioning under a given set of growth conditions. Therefore, analytical solute trapping models which describe the chemical partitioning as a function of steady state interface velocities have been developed and widely utilized in most of the theoretical investigations of rapid solidification. However, these

  16. Thermal Decomposition of 3-Bromopropene. A Theoretical Kinetic Investigation.

    PubMed

    Tucceri, María E; Badenes, María P; Bracco, Larisa L B; Cobos, Carlos J

    2016-04-21

    A detailed kinetic study of the gas-phase thermal decomposition of 3-bromopropene over wide temperature and pressure ranges was performed. Quantum chemical calculations employing the density functional theory methods B3LYP, BMK, and M06-2X and the CBS-QB3 and G4 ab initio composite models provide the relevant part of the potential energy surfaces and the molecular properties of the species involved in the CH2═CH-CH2Br → CH2═C═CH2 + HBr (1) and CH2═CH-CH2Br → CH2═CH-CH2 + Br (2) reaction channels. Transition-state theory and unimolecular reaction rate theory calculations show that the simple bond fission reaction ( 2 ) is the predominant decomposition channel and that all reported experimental studies are very close to the high-pressure limit of this process. Over the 500-1400 K range a rate constant for the primary dissociation of k2,∞ = 4.8 × 10(14) exp(-55.0 kcal mol(-1)/RT) s(-1) is predicted at the G4 level. The calculated k1,∞ values lie between 50 to 260 times smaller. A value of 10.6 ± 1.5 kcal mol(-1) for the standard enthalpy of formation of 3-bromopropene at 298 K was estimated from G4 thermochemical calculations.

  17. Investigation of blistering kinetics in hydrogen implanted aluminium nitride

    NASA Astrophysics Data System (ADS)

    Singh, R.; Scholz, R.; Christiansen, S. H.; Gösele, U.

    2008-04-01

    Epitaxial layers of aluminium nitride (AlN) grown on sapphire by hydride vapour phase epitaxy (HVPE) were implanted with 100 keV hydrogen, H+2, ions with doses in the range of 5 × 1016-2.5 × 1017 cm-2 and subsequently annealed in ambient air at temperatures between 450 and 750 °C in order to determine the kinetics of surface blister formation in AlN. The Arrhenius plot of the blistering time versus temperature shows two different activation energies for the formation of surface blisters: 0.44 eV in the higher temperature regime of 550-750 °C and 1.16 eV in the lower temperature regime of 450-550 °C. The implantation-induced damage was analyzed by cross-sectional transmission electron microscopy, which revealed a band of defects extending from 330 to 550 nm from the surface of AlN. The XTEM image of the implanted and annealed AlN displayed clearly the formation of microcracks that ultimately lead to the formation of surface blisters.

  18. Exact and user-friendly kinetic analysis of the two-step rapid equilibrium Michaelis-Menten mechanism.

    PubMed

    Garneau-Tsodikova, Sylvie; Shkel, Irina A; Tsodikov, Oleg V

    2009-04-15

    Most enzyme kinetic experiments are carried out under pseudo-first-order conditions, that is, when one of the reactant species (the enzyme or the substrate) is in a large excess of the other species. More accurate kinetic information about the system can be gained without the restrictions of the pseudo-first-order conditions. We present a practical and general method of analysis of the common two-step rapid equilibrium Michaelis-Menten mechanism. The formalism is exact in that it does not involve any other approximations such as the steady-state, limitations on the reactant concentrations or on reaction times. We apply this method to the global analysis of kinetic progress curves for bovine alkaline phosphatase assays carried out under both pseudo-first-order and pseudo-second-order conditions.

  19. Investigating Molecular Kinetics by Variationally Optimized Diffusion Maps.

    PubMed

    Boninsegna, Lorenzo; Gobbo, Gianpaolo; Noé, Frank; Clementi, Cecilia

    2015-12-08

    Identification of the collective coordinates that describe rare events in complex molecular transitions such as protein folding has been a key challenge in the theoretical molecular sciences. In the Diffusion Map approach, one assumes that the molecular configurations sampled have been generated by a diffusion process, and one uses the eigenfunctions of the corresponding diffusion operator as reaction coordinates. While diffusion coordinates (DCs) appear to provide a good approximation to the true dynamical reaction coordinates, they are not parametrized using dynamical information. Thus, their approximation quality could not, as yet, be validated, nor could the diffusion map eigenvalues be used to compute relaxation rate constants of the system. Here we combine the Diffusion Map approach with the recently proposed Variational Approach for Conformation Dynamics (VAC). Diffusion Map coordinates are used as a basis set, and their optimal linear combination is sought using the VAC, which employs time-correlation information on the molecular dynamics (MD) trajectories. We have applied this approach to ultra-long MD simulations of the Fip35 WW domain and found that the first DCs are indeed a good approximation to the true reaction coordinates of the system, but they could be further improved using the VAC. Using the Diffusion Map basis, excellent approximations to the relaxation rates of the system are obtained. Finally, we evaluate the quality of different metric spaces and find that pairwise minimal root-mean-square deviation performs poorly, while operating in the recently introduced kinetic maps based on the time-lagged independent component analysis gives the best performance.

  20. Kinetic and Mechanistic Investigations of Atom Abstraction Reactions

    NASA Astrophysics Data System (ADS)

    Stevens, Philip Stanford

    1990-01-01

    A discharge-flow system at 1-4 torr total pressure, employing resonance fluorescence detection of Br, Cl, O, H, N, and D, and laser magnetic resonance detection of OH and ClO, was used to measure the rate constants for a number of hydrogen and non-hydrogen atom abstraction reactions. The rate constants are examined within established reactivity trends in order to reveal the dominant forces governing the potential-energy surfaces. The activation energies for the F + rm H_2O/D_2O reactions are found to be smaller than that defined by the Evans-Polyani relationship between activation energy and exothermicity. The low activation energy and enhanced kinetic isotope effect for these reactions suggests that this deviation may be the result of quantum -mechanical tunneling. The rate constants for these and other heavy-light-heavy reactions are interpreted using transition-state theory and a one-dimensional tunneling model, in conjunction with ab initio calculations, to gain insight into the mechanism of these reactions. For the reactions of X + ClOCl to Products (X = Br, Cl, F, N), the rate constants correlate with the electron affinity of the radical, indicating that these mechanisms are dominated by electron transfer from ClOCl to X, similar to the reactivity of other non -hydrogen abstractions. The reactions of O and OH with ClOCl do not follow this trend, suggesting that electron transfer is not the only driving force in these reactions. These deviations are interpreted in terms of long-range attractive forces forming stable intermediates. The ClO + O_3 to ClOO + O_2 reaction has been proposed as an additional mechanism for ozone destruction within the antarctic vortex. Upper limits for the bimolecular rate constant for the ClO + O _3 reaction were measured directly between 233 and 413 K at 1-2 torr. The rate constants are several orders-of-magnitude smaller than estimated from the trend for non-hydrogen abstractions. From these results, it is concluded that this

  1. A U-shaped bioartificial pancreas with rapid glucose-insulin kinetics. In vitro evaluation and kinetic modelling.

    PubMed

    Reach, G; Jaffrin, M Y; Desjeux, J F

    1984-08-01

    The lag in insulin release in response to glucose is an obstacle to the development of hybrid pancreatic devices, in which an artificial membrane protects transplanted islets against immune rejection. We designed a U-shaped bioartificial pancreas, in which the blood channel surrounds the islet chamber consisting of two flat membranes; blood circulates successively above the first membrane and then in the reverse direction, below the second membrane. Isolated rat islets were introduced into the chamber, which was perfused with Krebs buffer, and the kinetics of insulin release in response to glucose was determined. During a 20-min, 2.8-20-mM, square-wave glucose stimulation, insulin release in the effluent of the device rose from 0.7 +/- 0.2 to 3.2 +/- 1.0 ng/100 islets/min (P less than 0.05) within 3 min, and reached a maximal level of 12.8 +/- 3.3 ng/100 islets/min at 10 min; 5 min after the return of the glucose concentration to substimulatory level, insulin release dropped from 11.3 +/- 1.5 to 8.0 +/- 1.7 ng/100 islets/min (P less than 0.05), and reached basal value (1.0 +/- 0.2 ng/100 islets/min) 40 min after the end of the stimulation. A 0.1-mM/L/min ramp increase in glucose concentration triggered a significant rise in insulin release (P less than 0.02) when the glucose concentration reached 5.3 +/- 0.2 mM; islets concomitantly perifused within a chamber set up without membrane responded to the same glucose stimulation 5 min earlier. For up to 1000 islets, insulin release in response to glucose was linearly correlated to the number of islets (N = 12, P less than 0.01), indicating that insulin did not significantly inhibit its own secretion in this system. Finally, during glucose stimulation, the insulin concentration in the effluent from the chamber was found to be four times the concentration present at the turning point of the blood channel, suggesting that insulin was transferred into the perfusing medium in part by a countercurrent flux of ultrafiltrate

  2. Mechanistic investigation leads to a synthetic improvement in the hydrolytic kinetic resolution of terminal epoxides.

    PubMed

    Nielsen, Lars P C; Stevenson, Christian P; Blackmond, Donna G; Jacobsen, Eric N

    2004-02-11

    The mechanism of the hydrolytic kinetic resolution (HKR) of terminal epoxides was investigated by kinetic analysis using reaction calorimetry. The chiral (salen)Co-X complex (X = OAc, OTs, Cl) undergoes irreversible conversion to (salen)Co-OH during the course of the HKR and thus serves as both precatalyst and cocatalyst in a cooperative bimetallic catalytic mechanism. This insight led to the identification of more active catalysts for the HKR of synthetically useful terminal epoxides.

  3. Oxidation kinetics of Si and SiGe by dry rapid thermal oxidation, in-situ steam generation oxidation and dry furnace oxidation

    NASA Astrophysics Data System (ADS)

    Rozé, Fabien; Gourhant, Olivier; Blanquet, Elisabeth; Bertin, François; Juhel, Marc; Abbate, Francesco; Pribat, Clément; Duru, Romain

    2017-06-01

    The fabrication of ultrathin compressively strained SiGe-On-Insulator layers by the condensation technique is likely a key milestone towards low-power and high performances FD-SOI logic devices. However, the SiGe condensation technique still requires challenges to be solved for an optimized use in an industrial environment. SiGe oxidation kinetics, upon which the condensation technique is founded, has still not reached a consensus in spite of various studies which gave insights into the matter. This paper aims to bridge the gaps between these studies by covering various oxidation processes relevant to today's technological needs with a new and quantitative analysis methodology. We thus address oxidation kinetics of SiGe with three Ge concentrations (0%, 10%, and 30%) by means of dry rapid thermal oxidation, in-situ steam generation oxidation, and dry furnace oxidation. Oxide thicknesses in the 50 Å to 150 Å range grown with oxidation temperatures between 850 and 1100 °C were targeted. The present work shows first that for all investigated processes, oxidation follows a parabolic regime even for thin oxides, which indicates a diffusion-limited oxidation regime. We also observe that, for all investigated processes, the SiGe oxidation rate is systematically higher than that of Si. The amplitude of the variation of oxidation kinetics of SiGe with respect to Si is found to be strongly dependent on the process type. Second, a new quantitative analysis methodology of oxidation kinetics is introduced. This methodology allows us to highlight the dependence of oxidation kinetics on the Ge concentration at the oxidation interface, which is modulated by the pile-up mechanism. Our results show that the oxidation rate increases with the Ge concentration at the oxidation interface.

  4. Platelet adhesion to collagen type I, collagen type IV, von Willebrand factor, fibronectin, laminin and fibrinogen: rapid kinetics under shear.

    PubMed

    Polanowska-Grabowska, R; Simon, C G; Gear, A R

    1999-01-01

    Extracellular matrix proteins in the blood vessel wall fulfill an essential role in haemostasis by promoting platelet adhesion at the site of vessel injury. We have combined a continuous-flow system with affinity chromatography to study platelet adhesion under conditions mimicking arterial flow and have examined the adhesion kinetics of unstimulated platelets to collagens type I and IV, von Willebrand factor (vWf), fibronectin, laminin and to fibrinogen. In the absence of red cells, in ACD-prepared plasma adhesion to collagens type I and IV or vWf was rapid, efficient (>50% in <1 s ) and independent of shear rates from 650 to 3400 s(-1) with kinetics following an inverse exponential decay curve. We introduced a simple mathematical model in which this type of kinetics arises, and which may be more generally applicable to various adhesion processes under flow conditions. The model is characterized by the rate of platelet deposition on the adhesive surface being proportional to the number of platelets in the flow. Adhesion to fibronectin was independent of shear rate, but revealed a lag phase of approximately 1.5 s before significant adhesion began. Laminin and fibrinogen supported efficient adhesion at low shear rates (650-1000 s(-1)), but a lag phase of approximately 1.5 s was seen at high shear rates (1700-3400 s(-1)). Control proteins (albumin and gelatin) supported minimal adhesion. Nonspecific adhesion to poly-L-lysine differed from that to other substrate proteins in that the kinetics were linear. In conclusion, human platelets adhered specifically, rapidly (within seconds) and efficiently to several proteins under flow conditions and the kinetics of adhesion depended on the protein serving as substrate as well as on shear rate.

  5. Investigations of non-hydrostatic, stably stratified and rapidly rotating flows

    NASA Astrophysics Data System (ADS)

    Julien, K. A.; Nieves, D.; Grooms, I.; Weiss, J.

    2016-12-01

    We present an investigation of rapidly rotating (small Rossby number Ro << 1) stratified turbulence where the stratification strength is varied from weak (large Froude number Fr >> 1) to strong (Fr << 1). The investigation is set in the context of a reduced model derived from the Boussinesq equations that retains anisotropic inertia-gravity waves with order-one frequencies and highlights a regime of wave-eddy interactions. Numerical simulations of the reduced model are performed where energy is injected by a stochastic forcing of vertical velocity, which forces wave modes only. The simulations reveal two regimes characterized by the presence of well-formed, persistent and thin turbulent layers of locally-weakened stratification at small Froude numbers, and by the absence of layers at large Froude numbers. Both regimes are characterized by a large- scale barotropic dipole enclosed by small-scale turbulence. When the Reynolds number is not too large a direct cascade of barotropic kinetic energy is observed, leading to total energy equilibration. We examine net energy exchanges that occur through vortex stretching and vertical buoyancy flux and diagnose the horizontal scales active in these exchanges. We find that the baroclinic motions inject energy directly to the largest scales of the barotropic mode, implying that the large-scale barotropic dipole is not the end result of an inverse cascade within the barotropic mode.

  6. Quasigeostrophic investigations of non-hydrostatic, stably- stratified and rapidly rotating flows

    NASA Astrophysics Data System (ADS)

    Julien, Keith; Nieves, David; Grooms, Ian; Weiss, Jeffrey

    2016-11-01

    We present an investigation of rapidly rotating stratified turbulence where the stratification strength is varied from weak to strong. The investigation is set in the context of a reduced model derived from the Boussinesq equations that retains anisotropic inertia-gravity waves with order-one frequencies and highlights a regime of wave-eddy interactions. Numerical simulations are performed where energy is injected by a stochastic forcing of vertical velocity, which forces wave modes only. The simulations reveal two regimes characterized by the presence of well-formed, persistent and thin turbulent layers of locally weakened stratification at small Froude numbers, and by the absence of layers at large Froude numbers. Both regimes are characterized by a large-scale barotropic dipole enclosed by small-scale turbulence. When the Reynolds number is not too large, a direct cascade of barotropic kinetic energy is observed, leading to total energy equilibration. We examine net energy exchanges that occur through vortex stretching and vertical buoyancy flux. We find that the baroclinic motions inject energy directly to the largest scales of the barotropic mode, implying that the large-scale barotropic dipole is not the end result of an inverse cascade within the barotropic mode. NSF DMS 1317666, 1444503; NSF EAR 1067944, NSF OCE 1245944.

  7. First-Principles Investigation of Li Intercalation Kinetics in Phospho-Olivines

    NASA Astrophysics Data System (ADS)

    Malik, Rahul

    agreement with experiments on large LiFePO4 single crystals. Third, we investigate why LiFePO4 can be charged and discharged rapidly despite having to undergo a first-order phase transition. Conventional wisdom dictates that a system with strong equilibrium Li segregation behavior requires both nucleation and growth in the charge and discharge process, which should impede the overall kinetics. Rather, through first-principles calculations, we determine the minimal energy required to access a non-equilibrium transformation path entirely through the solid solution. Not only does this transformation mechanism require little driving force, but it also rationalizes how a kinetically favorable but nonequilibrium path is responsible for the extremely high rate performance associated with this material. The consequences of a rapid non-equilibrium single-particle transformation mechanism on (dis)charging a multi-particle assembly, as is the case in porous electrodes, are discussed and compared to experimental observations. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

  8. Phenomenological Investigation of Rapid Projectile Penetration in Granular Media

    NASA Astrophysics Data System (ADS)

    Omidvar, Mehdi

    There has been a recent flurry of research in rapid penetration into granular media, motivated by military and civilian applications including underground target penetration, design of fortifications, drilling for resource extraction, offshore foundations and anchors, probing of in situ mechanical properties, and study of high strain rate response of granular media, among others. The present study contributes to the state of the art in rapid penetration into granular media, by producing data at the macro and meso scales. In-house projectile accelerators are used to launch projectiles into laboratory scale physical models. The experimental program is divided into two sections. In the first section, penetration tests are performed at impact velocities in the range of 60-300 m/s. High-speed imaging and photonic Doppler velocimetry are used to record time history of penetration. In the second section, low velocity penetration tests are performed in refractive index matched transparent soils. Images are acquired form a mid plane within the sample. Digital image correlation is employed to describe granular kinematics. Macro scale test results point to the existence of at least two transition regimes in penetration resistance. The first, occurring at penetration velocities of approximately 60- 80 m/s, may be due the role of particle crushing, while the second is linked to frictional resistance dominating over inertial resistance at penetration velocities below approximately 15 m/s. It is also found that the role of nose shape is related to particle crushing. An attached false cone forms ahead of the projectile due to significant particle crushing, rendering nose shape effects less significant. Packing density and saturation are also found to affect penetration characteristics. Penetration tests in transparent soils reveal significant differences between quasi-static and dynamic penetration. Greater vertical displacements occur ahead of the projectile in dynamic

  9. The Rapid Acquisition Imaging Spectrograph Experiment (RAISE) Sounding Rocket Investigation

    NASA Astrophysics Data System (ADS)

    Laurent, Glenn T.; Hassler, Donald M.; Deforest, Craig; Slater, David D.; Thomas, Roger J.; Ayres, Thomas; Davis, Michael; de Pontieu, Bart; Diller, Jed; Graham, Roy; Michaelis, Harald; Schuele, Udo; Warren, Harry

    2016-03-01

    We present a summary of the solar observing Rapid Acquisition Imaging Spectrograph Experiment (RAISE) sounding rocket program including an overview of the design and calibration of the instrument, flight performance, and preliminary chromospheric results from the successful November 2014 launch of the RAISE instrument. The RAISE sounding rocket payload is the fastest scanning-slit solar ultraviolet imaging spectrograph flown to date. RAISE is designed to observe the dynamics and heating of the solar chromosphere and corona on time scales as short as 100-200ms, with arcsecond spatial resolution and a velocity sensitivity of 1-2km/s. Two full spectral passbands over the same one-dimensional spatial field are recorded simultaneously with no scanning of the detectors or grating. The two different spectral bands (first-order 1205-1251Å and 1524-1569Å) are imaged onto two intensified Active Pixel Sensor (APS) detectors whose focal planes are individually adjusted for optimized performance. RAISE reads out the full field of both detectors at 5-10Hz, recording up to 1800 complete spectra (per detector) in a single 6-min rocket flight. This opens up a new domain of high time resolution spectral imaging and spectroscopy. RAISE is designed to observe small-scale multithermal dynamics in Active Region (AR) and quiet Sun loops, identify the strength, spectrum and location of high frequency waves in the solar atmosphere, and determine the nature of energy release in the chromospheric network.

  10. Kinetic investigation of recombinant human hyaluronidase PH20 on hyaluronic acid.

    PubMed

    Fang, Shiping; Hays Putnam, Anna-Maria A; LaBarre, Michael J

    2015-07-01

    The kinetic investigation of hyaluronidases using physiologically relevant hyaluronic acid (HA or hyaluronan) substrate will provide useful and important clues to their catalytic behavior and function in vivo. We present here a simple and sensitive method for kinetic measurement of recombinant human hyaluronidase PH20 (rHuPH20) on HA substrates with sizes ranging from 90 to 752 kDa. The method is based on 2-aminobenzamide labeling of hydrolyzed HA products combined with separation by size exclusion-ultra performance liquid chromatography coupled with fluorescence detection. rHuPH20 was found to follow Michaelis-Menten kinetics during the initial reaction time. Optimal reaction rates were observed in the pH range of 4.5-5.5. The HA substrate size did not have significant effects on the initial rate of the reaction. By studying HA substrates of 215, 357, and 752 kDa, the kinetic parameters Km, Vmax, and kcat were determined to be 0.87-0.91 mg/ml, 1.66-1.74 NM s(-1), and 40.5-42.4 s(-1), respectively. This method allows for direct measurement of kinetics using physiologically relevant HA substrates and can be applied to other hyaluronidase kinetic measurements.

  11. A hybrid computer program for rapidly solving flowing or static chemical kinetic problems involving many chemical species

    NASA Technical Reports Server (NTRS)

    Mclain, A. G.; Rao, C. S. R.

    1976-01-01

    A hybrid chemical kinetic computer program was assembled which provides a rapid solution to problems involving flowing or static, chemically reacting, gas mixtures. The computer program uses existing subroutines for problem setup, initialization, and preliminary calculations and incorporates a stiff ordinary differential equation solution technique. A number of check cases were recomputed with the hybrid program and the results were almost identical to those previously obtained. The computational time saving was demonstrated with a propane-oxygen-argon shock tube combustion problem involving 31 chemical species and 64 reactions. Information is presented to enable potential users to prepare an input data deck for the calculation of a problem.

  12. Investigating High-School Chemical Kinetics: The Greek Chemistry Textbook and Students' Difficulties

    ERIC Educational Resources Information Center

    Gegios, Theodoros; Salta, Katerina; Koinis, Spyros

    2017-01-01

    In this study we present an analysis of how the structure and content of the Greek school textbook approaches the concepts of chemical kinetics, and an investigation of the difficulties that 11th grade Greek students face regarding these concepts. Based on the structure and content of the Greek textbook, a tool was developed and applied to…

  13. An investigation of the structure and function of antistaphylococcal endolysins using kinetic methods

    USDA-ARS?s Scientific Manuscript database

    Peculiarities of the structures and functions of phage phi11 and phi80a antistaphylococcal endolysins were investigated by kinetic measurements. In spite of the high level of homology in their primary structures, both enzymes possess some differences in their optimal conditions for functioning. As...

  14. Investigating High-School Chemical Kinetics: The Greek Chemistry Textbook and Students' Difficulties

    ERIC Educational Resources Information Center

    Gegios, Theodoros; Salta, Katerina; Koinis, Spyros

    2017-01-01

    In this study we present an analysis of how the structure and content of the Greek school textbook approaches the concepts of chemical kinetics, and an investigation of the difficulties that 11th grade Greek students face regarding these concepts. Based on the structure and content of the Greek textbook, a tool was developed and applied to…

  15. FmRα analysis: Rapid and direct estimation of relaxation and kinetic parameters from dynamic nuclear polarization time courses.

    PubMed

    Pagès, Guilhem; Kuchel, Philip W

    2015-06-01

    To introduce a direct method for estimating relaxation and kinetic parameter values from rapid dissolution dynamic nuclear polarization (RD-DNP) NMR time courses. The analysis relied on a kinetic model that is often used to analyze data in these studies-a unidirectional (bio)chemical reaction with rate constant k1 , coupled to longitudinal relaxation of the magnetization of substrate and product that is characterized by the time constant T1 . The latter value was estimated from the width of the product curve (peak) at the height α relative to the maximum height. We showed α ∼ 0.8 under most conditions, so we measured the interval between the falling and rising parts of the curve at the relative height 0.8. We called this the "fall-minus-rise time at height α," or FmRα , and found that FmR0.8 ∼ T1 . The ratio β = (product signal/substrate signal) when the product is maximal was shown to be equal to k1 T1 . Therefore, k1 = β/FmR0.8 . FmRα analysis was demonstrated with (13) C NMR RD-DNP data recorded from hemolysates and from previously published data. FmRα analysis enables immediate estimates of kinetic and relaxation parameters from (13) C NMR RD-DNP data. The values can be used as initial estimates in more extensive computer-based data-regression analysis. © 2014 Wiley Periodicals, Inc.

  16. Thermodynamic and kinetic investigation on the crucial factors affecting adefovir dipivoxil-saccharin cocrystallization.

    PubMed

    Ma, Kun; Zhang, Ying; Kan, Hongliang; Cheng, Linfeng; Luo, Ling; Su, Qing; Gao, Jing; Gao, Yuan; Zhang, Jianjun

    2014-07-01

    The aim of this study was to perform a thermodynamic and kinetic investigation on the crucial factors affecting the cocrystallization between adefovir dipivoxil (AD) and saccharin (SAC). Phase solubility diagrams and ternary phase diagrams were constructed based on the solubility data of AD, SAC and their cocrystals in ethanol, isopropanol and ethyl acetate at different temperatures. The conductimetric method was used to determine the induction time. A quantitative and intuitive technique modified from dissolution testing was employed to investigate the cocrystallization kinetics. AD-SAC cocrystals exhibited different crystal habits but only one cocrystal polymorph was confirmed. The effects of several crucial factors, including the input amounts of two components, AD/SAC ratio, solvent and temperature, on the crystallization of single-component alone, cocrystal formation, cocrystal stability, supersaturation, nucleation, crystal growth and cocrystal yield were determined. Thermodynamic and kinetic parameters provided the rationale for this spontaneous cocrystallization system without the need of solvent evaporation and temperature change. This systemic investigation enriched the present understanding of thermodynamics and kinetics of cocrystals and built the groundwork for AD-SAC cocrystal scale-up.

  17. Rapid kinetics of endocytosis at rod photoreceptor synapses depends upon endocytic load and calcium.

    PubMed

    Cork, Karlene M; Thoreson, Wallace B

    2014-05-01

    Release from rods is triggered by the opening of L-type Ca2+ channels that lie beneath synaptic ribbons. After exocytosis, vesicles are retrieved by compensatory endocytosis. Previous work showed that endocytosis is dynamin-dependent in rods but dynamin-independent in cones. We hypothesized that fast endocytosis in rods may also differ from cones in its dependence upon the amount of Ca2+ influx and/or endocytic load. We measured exocytosis and endocytosis from membrane capacitance (C m) changes evoked by depolarizing steps in voltage clamped rods from tiger salamander retinal slices. Similar to cones, the time constant for endocytosis in rods was quite fast, averaging <200 ms. We manipulated Ca2+ influx and the amount of vesicle release by altering the duration and voltage of depolarizing steps. Unlike cones, endocytosis kinetics in rods slowed after increasing Ca2+ channel activation with longer step durations or more strongly depolarized voltage steps. Endocytosis kinetics also slowed as Ca2+ buffering was decreased by replacing BAPTA (10 or 1 mM) with the slower Ca2+ buffer EGTA (5 or 0.5 mM) in the pipette solution. These data provide further evidence that endocytosis mechanisms differ in rods and cones and suggest that endocytosis in rods is regulated by both endocytic load and local Ca2+ levels.

  18. Rapid kinetics of endocytosis at rod photoreceptor synapses depends upon endocytic load and calcium

    PubMed Central

    CORK, KARLENE M.; THORESON, WALLACE B.

    2015-01-01

    Release from rods is triggered by the opening of L-type Ca2+ channels that lie beneath synaptic ribbons. After exocytosis, vesicles are retrieved by compensatory endocytosis. Previous work showed that endocytosis is dynamin-dependent in rods but dynamin-independent in cones. We hypothesized that fast endocytosis in rods may also differ from cones in its dependence upon the amount of Ca2+ influx and/or endocytic load. We measured exocytosis and endocytosis from membrane capacitance (Cm) changes evoked by depolarizing steps in voltage clamped rods from tiger salamander retinal slices. Similar to cones, the time constant for endocytosis in rods was quite fast, averaging <200 ms. We manipulated Ca2+ influx and the amount of vesicle release by altering the duration and voltage of depolarizing steps. Unlike cones, endocytosis kinetics in rods slowed after increasing Ca2+ channel activation with longer step durations or more strongly depolarized voltage steps. Endocytosis kinetics also slowed as Ca2+ buffering was decreased by replacing BAPTA (10 or 1 mM) with the slower Ca2+ buffer EGTA (5 or 0.5 mM) in the pipette solution. These data provide further evidence that endocytosis mechanisms differ in rods and cones and suggest that endocytosis in rods is regulated by both endocytic load and local Ca2+ levels. PMID:24735554

  19. On the thermodynamic and kinetic investigations of a [c2]daisy chain polymer

    SciTech Connect

    Hmadeh, Mohamad; Fang, Lei; Trabolsi, Ali; Elhabiri, Mourad; Albrecht-Gary, Anne-Marie; Stoddart, J. Fraser

    2010-01-01

    We report a variety of [c2]daisy chain molecules which undergo quantitative, efficient, and fully reversible molecular movements upon the addition of base/acid in organic solvents. Such externally triggered molecular movements can induce the contraction and extension of the [c2]daisy chain molecule as a whole. A linear polymer of such a bistable [c2]daisy chain exerts similar types of movements and can be looked upon as a candidate for the development of artificial muscles. The spectrophotometric investigations of both the monomeric and polymeric bistable [c2]daisy chains, as well as the corresponding model compounds, were performed in MeCN at room temperature, in order to obtain the thermodynamic parameters for these mechanically interlocked molecules. Based on their spectrophotometric and thermodynamic characteristics, kinetic analysis of the acid/base-induced contraction and extension of the [c2]daisy chain monomer and polymer were conducted by employing a stopped-flow technique. These kinetic data suggest that the rates of contraction and extension for these [c2]daisy chain molecules are determined by the thermodynamic stabilities of the corresponding kinetic intermediates. Faster switching rates for both the contraction and extension processes of the polymeric [c2]daisy chain were observed when compared to those of its monomeric counterpart. These kinetic and thermodynamic investigations on [c2]daisy chain-based muscle-like compounds provide important information for those seeking an understanding of the mechanisms of actuation in mechanically interlocked macromolecules.

  20. Selectin-like kinetics and biomechanics promote rapid platelet adhesion in flow: the GPIb(alpha)-vWF tether bond.

    PubMed Central

    Doggett, Teresa A; Girdhar, Gaurav; Lawshé, Avril; Schmidtke, David W; Laurenzi, Ian J; Diamond, Scott L; Diacovo, Thomas G

    2002-01-01

    The ability of platelets to tether to and translocate on injured vascular endothelium relies on the interaction between the platelet glycoprotein receptor Ib alpha (GPIb(alpha)) and the A1 domain of von Willebrand factor (vWF-A1). To date, limited information exists on the kinetics that govern platelet interactions with vWF in hemodynamic flow. We now report that the GPIb(alpha)-vWF-A1 tether bond displays similar kinetic attributes as the selectins including: 1) the requirement for a critical level of hydrodynamic flow to initiate adhesion, 2) short-lived tethering events at sites of vascular injury in vivo, and 3) a fast intrinsic dissociation rate constant, k(0)(off) (3.45 +/- 0.37 s(-1)). Values for k(off), as determined by pause time analysis of transient capture/release events, were also found to vary exponentially (4.2 +/- 0.8 s(-1) to 7.3 +/- 0.4 s(-1)) as a function of the force applied to the bond (from 36 to 217 pN). The biological importance of rapid bond dissociation in platelet adhesion is demonstrated by kinetic characterization of the A1 domain mutation, I546V that is associated with type 2B von Willebrand disease (vWD), a bleeding disorder that is due to the spontaneous binding of plasma vWF to circulating platelets. This mutation resulted in a loss of the shear threshold phenomenon, a approximately sixfold reduction in k(off), but no significant alteration in the ability of the tether bond to resist shear-induced forces. Thus, flow dependent adhesion and rapid and force-dependent kinetic properties are the predominant features of the GPIb(alpha)-vWF-A1 tether bond that in part may explain the preferential binding of platelets to vWF at sites of vascular injury, the lack of spontaneous platelet aggregation in circulating blood, and a mechanism to limit thrombus formation. PMID:12080112

  1. Microwave gallium-68 radiochemistry for kinetically stable bis(thiosemicarbazone) complexes: structural investigations and cellular uptake under hypoxia.

    PubMed

    Alam, Israt S; Arrowsmith, Rory L; Cortezon-Tamarit, Fernando; Twyman, Frazer; Kociok-Köhn, Gabriele; Botchway, Stanley W; Dilworth, Jonathan R; Carroll, Laurence; Aboagye, Eric O; Pascu, Sofia I

    2016-01-07

    We report the microwave synthesis of several bis(thiosemicarbazones) and the rapid gallium-68 incorporation to give the corresponding metal complexes. These proved kinetically stable under 'cold' and 'hot' biological assays and were investigated using laser scanning confocal microscopy, flow cytometry and radioactive cell retention studies under normoxia and hypoxia. (68)Ga complex retention was found to be 34% higher in hypoxic cells than in normoxic cells over 30 min, further increasing to 53% at 120 min. Our data suggests that this class of gallium complexes show hypoxia selectivity suitable for imaging in living cells and in vivo tests by microPET in nude athymic mice showed that they are excreted within 1 h of their administration.

  2. Ultrasound-assisted rapid extraction and kinetic modelling of influential factors: Extraction of camptothecin from Nothapodytes nimmoniana plant.

    PubMed

    Patil, Dhiraj M; Akamanchi, Krishnacharya G

    2017-07-01

    Ultrasound-assisted extraction (UAE) of commercially important natural product camptothecin (CPT) from Nothapodytes nimmoniana plant has been investigated. The influences of process factors such as electric acoustic intensity, solid to liquid ratio, duty cycle, temperature and particle size on the maximum extraction yield and kinetic mechanisms of the entire extraction process have been investigated. The kinetics results showed that increasing the intensity, duty cycle, solid to liquid ratio and decreasing the particle size lead to substantial increase in extraction yields compared to classical stirring extraction. Different kinetic models were applied to fit the experimental data. The second order rate model appears to be the best. The extraction rate constant, initial extraction rate and the equilibrium concentration for all experimental conditions have been calculated. SEM analysis of spent plant material clearly showed hollow openings on cell structure, which could be directly correlated to explosive disruption by the action of ultrasound waves. Overall 1.7-fold increase in extraction yields of CPT (0.32% w/w) and decrease in time from 6h to 18min was observed over the stirring method. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. An investigation on the catalytic capacity of dolomite in transesterification and the calculation of kinetic parameters.

    PubMed

    Niu, Sheng-Li; Huo, Meng-Jia; Lu, Chun-Mei; Liu, Meng-Qi; Li, Hui

    2014-04-01

    The catalytic capacity of dolomite in transesterification was investigated and the kinetic parameters were calculated. The activated dolomites as transesterification catalyst were characterized by X-ray diffraction, nitrogen adsorption and desorption and Hammett indicator method, where the original dolomite was analyzed by thermogravimetric and X-ray fluorescence in advance. Its potential catalytic capacity was validated from aspects of the activated temperature and the reused property, where the reliability of the experimental system was also examined. Then, influences of the catalyst added amount, the mole ratio of methanol to oil, the transesterification temperature and the transesterification time on the catalytic capacity were investigated. Finally, kinetic parameters of the transesterification catalyzed by the activated dolomite were calculated.

  4. Investigation of detailed kinetic scheme performance on modelling of turbulent non-premixed sooting flames

    NASA Astrophysics Data System (ADS)

    Yunardi, Y.; Darmadi, D.; Hisbullah, H.; Fairweather, M.

    2011-12-01

    This paper presents the results of an application of a first-order conditional moment closure (CMC) approach coupled with a semi-empirical soot model to investigate the effect of various detailed combustion chemistry schemes on soot formation and destruction in turbulent non-premixed flames. A two-equation soot model representing soot particle nucleation, growth, coagulation and oxidation, was incorporated into the CMC model. The turbulent flow-field of both flames is described using the Favre-averaged fluid-flow equations, applying a standard k-ɛ turbulence model. A number of five reaction kinetic mechanisms having 50-100 species and 200-1000 elementary reactions called ABF, Miller-Bowman, GRI-Mech3.0, Warnatz, and Qin were employed to study the effect of combustion chemistry schemes on soot predictions. The results showed that of various kinetic schemes being studied, each yields similar accuracy in temperature prediction when compared with experimental data. With respect to soot prediction, the kinetic scheme containing benzene elementary reactions tends to result in a better prediction on soot concentrations in comparison to those contain no benzene elementary reactions. Among five kinetic mechanisms being studied, the Qin combustion scheme mechanism turned to yield the best prediction on both flame temperature and soot levels.

  5. Kinetic modeling of rapid enzymatic hydrolysis of crystalline cellulose after pretreatment by NMMO.

    PubMed

    Khodaverdi, Mahdi; Jeihanipour, Azam; Karimi, Keikhosro; Taherzadeh, Mohammad J

    2012-03-01

    Pretreatment of cellulose with an industrial cellulosic solvent, N-methylmorpholine-N-oxide, showed promising results in increasing the rate of subsequent enzymatic hydrolysis. Cotton linter was used as high crystalline cellulose. After the pretreatment, the cellulose was almost completely hydrolyzed in less than 12 h, using low enzyme loading (15 FPU/g cellulose). The pretreatment significantly decreased the total crystallinity of cellulose from 7.1 to 3.3, and drastically increased the enzyme adsorption capacity of cellulose by approximately 42 times. A semi-mechanistic model was used to describe the relationship between the cellulose concentration and the enzyme loading. In this model, two reactions for heterogeneous reaction of cellulose to glucose and cellobiose, and a homogenous reaction for cellobiose conversion to glucose was incorporated. The Langmuir model was applied to model the adsorption of cellulase onto the treated cellulose. The competitive inhibition was also considered for the effects of sugar inhibition on the rate of enzymatic hydrolysis. The kinetic parameters of the model were estimated by experimental results and evaluated.

  6. Kinetics of killing Listeria monocytogenes by macrophages: rapid killing accompanying phagocytosis

    SciTech Connect

    Davies, W.A.

    1983-08-01

    The kinetics of bactericidal activity of activated macrophages can be precisely described by a mathematical model in which phagocytosis, killing, digestion, and release of degraded bacterial material are considered to occur continuously. To gain a better understanding of these events, I have determined the period of time between first contact of bacteria with macrophages and the onset of killing. Activated rat peritoneal macrophages were incubated for various times up to 15 min with Listeria monocytogenes previously labeled with /sup 3/H-thymidine and the unassociated bacteria removed by two centrifugations through a density interface. Both cell-associated radioactivity and cell-associated viable bacteria, determined as colony forming units after sonication of the cell pellet, increased with time of incubation. However, the specific viability of these bacteria, expressed as the ratio of number of viable bacteria per unit radioactivity declined with time, as an approximate inverse exponential, after a lag period of 2.9 +/- 0.8 min. Evidence is given that other possible causes for this decline in specific viability, other than death of the bacteria, such as preferential ingestion of dead Listeria, clumping of bacteria, variations in autolytic activity, or release of Listericidins are unlikely. I conclude therefore that activated macrophages kill Listeria approximately 3 min after the cell and the bacterium first make contact.

  7. FLYCHK: generalized population kinetics and spectral model for rapid spectroscopic analysis for all elements

    SciTech Connect

    Chung, H; Chen, M; Morgan, W L; Ralchenko, Y; Lee, R W

    2005-06-17

    FLYCHK is a straightforward, rapid tool to provide ionization and population distributions of plasmas in zero dimension with accuracy sufficient for most initial estimates and in many cases applicable for more sophisticated analysis. FLYCHK solves rate equations for level population distributions by considering collisional and radiative atomic processes. The code is designed to be straightforward to use and yet is general enough to apply for most laboratory plasmas. Further, it can be applied for low-to-high Z ions and in either steady-state or time-dependent situations. Plasmas with arbitrary electron energy distributions, single or multiple electron temperatures can be studied as well as radiation-driven plasmas. To achieve this versatility and accuracy in a code that provides rapid response we employ schematic atomic structures, scaled hydrogenic cross-sections and read-in tables. It also employs the jj configuration averaged atomic states and oscillator strengths calculated using the Dirac-Hartree-Slater model for spectrum synthesis. Numerous experimental and calculational comparisons performed in recent years show that FLYCHK provides meaningful estimates of ionization distributions, well within a charge state for most laboratory applications.

  8. RAPID ARSENITE OXIDATION BY THERMUS AQUATICUS AND THERMUS THERMOPHILUS: FIELD AND LABORATORY INVESTIGATIONS. (R826189)

    EPA Science Inventory

    Thermus aquaticus and Thermus thermophilus, common inhabitants of terrestrial hot springs and thermally polluted domestic and industrial waters, have been found to rapidly oxidize arsenite to arsenate. Field investigations at a hot spring in Yellowstone National Park revealed ...

  9. RAPID ARSENITE OXIDATION BY THERMUS AQUATICUS AND THERMUS THERMOPHILUS: FIELD AND LABORATORY INVESTIGATIONS. (R826189)

    EPA Science Inventory

    Thermus aquaticus and Thermus thermophilus, common inhabitants of terrestrial hot springs and thermally polluted domestic and industrial waters, have been found to rapidly oxidize arsenite to arsenate. Field investigations at a hot spring in Yellowstone National Park revealed ...

  10. Tocopheramines and tocotrienamines as antioxidants: ESR spectroscopy, rapid kinetics and DFT calculations.

    PubMed

    Bamonti, Luca; Hosoya, Takashi; Pirker, Katharina F; Böhmdorfer, Stefan; Mazzini, Francesco; Galli, Francesco; Netscher, Thomas; Rosenau, Thomas; Gille, Lars

    2013-09-01

    Tocopheramines (TNH2) and tocotrienamines (T3NH2) are analogues of tocopherols (TOH) and tocotrienols in which phenolic OH is replaced by NH2. It was shown in previous studies that TNH2 and T3NH2 act as potent antioxidants. In this study we compared the one-electron oxidation of TNH2/T3NH2 by diphenyl picryl hydrazyl (DPPH) and galvinoxyl (GOX) radicals with the one of α-TOH as a reference compound using ESR spectroscopy, stopped flow spectrophotometry and density functional theory (DFT) calculations. ESR spectroscopy revealed the presence of tocopheramine radicals during electrochemical oxidation of α-TNH2. Kinetic measurements demonstrated that in apolar n-hexane TNH2/T3NH2 derivatives reacted two to three orders of magnitude slower than α-TOH with the model radicals. DFT calculations indicated that this correlates well with the higher bond dissociation energy (BDE) for N-H in TNH2 than for O-H in α-TOH in pure H-atom transfer (HAT). In the more polar medium ethanol TNH2/T3NH2 derivatives partially reacted faster than α-TOH depending on the reaction partner. DFT calculations suggest that this is due to reaction mechanisms alternative to HAT. According to thermochemistry data sequential proton loss and electron transfer (SPLET) is more favored for α-TOH in ethanol than for TNH2. Therefore, for TNH2 a contribution of the alternative mechanism of sequential electron transfer-proton transfer (SET-PT) could be a possible explanation. These data show that the antioxidant reactivity strongly depends on the structure, reaction partners and environment. According to these findings TNH2/T3NH2 should be superior as antioxidants over α-TOH in polar head group regions of membranes but not in the apolar core of lipid bilayers. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Crystallization kinetics in Si-1 at%Sn during rapid solidification in undercooled melt

    NASA Astrophysics Data System (ADS)

    Kuribayashi, K.; Ozawa, S.; Nagayama, K.; Inatomi, Y.

    2017-06-01

    In order to elucidate the cause of the morphological transition of crystals growing in an undercooled melt of semiconducting materials, we carried out the containerless solidification of undoped Si and Si-1 at%Sn using a CO2 laser-equipped electromagnetic levitator (EML). The crystallization of these materials was successfully achieved under controlled undercooling. The relation between the shape of growing crystals and the degree of undercooling in Si-1 at%Sn was similar to that in undoped Si; that is, plate-like needle crystals were observed at low undercooling, whereas at medium and high undercooling the shape of growing crystals changed to massive dendrites. The grain-size of as-solidified samples of Si-1 at%Sn was remarkably small compared with that of undoped Si. The surface morphologies of samples solidified by dropping the melt onto a chill plate of mirror-polished silicon consisted of typical twin-related <110> dendrites. On the other hand, samples that were dropped from the undercooled state consisted of twin-free <100> dendrites. The nucleation rate of two-dimensional nuclei calculated on the basis of two mechanisms, which are the twin-plane re-entrant edge mechanism and the twin-free mechanism, suggested that the morphological transition to twin-free <100> dendrites from twin-related <110> dendrites occurs when the degree of undercooling becomes larger than the critical value. These results indicate that the cause of the morphological transition of Si growing in the undercooled melt is not the roughening transition of the crystal-melt interface but the transition of the nucleation kinetics to the twin-free mechanism from the twin-related mechanism.

  12. New Channelrhodopsin with a Red-Shifted Spectrum and Rapid Kinetics from Mesostigma viride

    PubMed Central

    Govorunova, Elena G.; Spudich, Elena N.; Lane, C. Elizabeth; Sineshchekov, Oleg A.; Spudich, John L.

    2011-01-01

    ABSTRACT Light control of motility behavior (phototaxis and photophobic responses) in green flagellate algae is mediated by sensory rhodopsins homologous to phototaxis receptors and light-driven ion transporters in prokaryotic organisms. In the phototaxis process, excitation of the algal sensory rhodopsins leads to generation of transmembrane photoreceptor currents. When expressed in animal cells, the algal phototaxis receptors function as light-gated cation channels, which has earned them the name “channelrhodopsins.” Channelrhodopsins have become useful molecular tools for light control of cellular activity. Only four channelrhodopsins, identified in Chlamydomonas reinhardtii and Volvox carteri, have been reported so far. By screening light-induced currents among algal species, we identified that the phylogenetically distant flagellate Mesostigma viride showed photoelectrical responses in vivo with properties suggesting a channelrhodopsin especially promising for optogenetic use. We cloned an M. viride channelrhodopsin, MChR1, and studied its channel activity upon heterologous expression. Action spectra in HEK293 cells match those of the photocurrents observed in M. viride cells. Comparison of the more divergent MChR1 sequence to the previously studied phylogenetically clustered homologs and study of several MChR1 mutants refine our understanding of the sequence determinants of channelrhodopsin function. We found that MChR1 has the most red-shifted and pH-independent spectral sensitivity so far reported, matches or surpasses known channelrhodopsins’ channel kinetics features, and undergoes minimal inactivation upon sustained illumination. This combination of properties makes MChR1 a promising candidate for optogenetic applications. PMID:21693637

  13. Rapid-reaction kinetic characterization of the pathway of streptokinase-plasmin catalytic complex formation.

    PubMed

    Verhamme, Ingrid M; Bock, Paul E

    2008-09-19

    Binding of the fibrinolytic proteinase plasmin (Pm) to streptokinase (SK) in a tight stoichiometric complex transforms Pm into a potent proteolytic activator of plasminogen. SK binding to the catalytic domain of Pm, with a dissociation constant of 12 pm, is assisted by SK Lys(414) binding to a Pm kringle, which accounts for a 11-20-fold affinity decrease when Pm lysine binding sites are blocked by 6-aminohexanoic acid (6-AHA) or benzamidine. The pathway of SK.Pm catalytic complex formation was characterized by stopped-flow kinetics of SK and the Lys(414) deletion mutant (SKDeltaK414) binding to Pm labeled at the active site with 5-fluorescein ([5F]FFR-Pm) and the reverse reactions by competitive displacement of [5F]FFR-Pm with active site-blocked Pm. The rate constants for the biexponential fluorescence quenching caused by SK and SKDeltaK414 binding to [5F]FFR-Pm were saturable as a function of SK concentration, reporting encounter complex affinities of 62-110 nm in the absence of lysine analogs and 4900-6500 and 1430-2200 nm in the presence of 6-AHA and benzamidine, respectively. The encounter complex with SKDeltaK414 was approximately 10-fold weaker in the absence of lysine analogs but indistinguishable from that of native SK in the presence of 6-AHA and benzamidine. The studies delineate for the first time the sequence of molecular events in the formation of the SK.Pm catalytic complex and its regulation by kringle ligands. Analysis of the forward and reverse reactions supports a binding mechanism in which SK Lys(414) binding to a Pm kringle accompanies near-diffusion-limited encounter complex formation followed by two slower, tightening conformational changes.

  14. Measurements of crystal growth kinetics at extreme deviations from equilibrium. [Rapid solidification processing

    SciTech Connect

    Aziz, M.J.

    1993-05-07

    We have measured solute trapping of Sn in Al over a wide enough range of velocities to make a quantitative test of theory. The Continuous Growth Model of Aziz is the only one-parameter model that fits the data. We have also measured the diffusive speed - the growth rate at which interfacial partitioning is in mid-transition between equilibrium partitioning and complete solute trapping - for several solutes in A1. We have found an inverse correlation between the equilibrium partition coefficient and the diffusive speed. Taken together, these results give us heretofore unprecedented predictive capability in modeling rapid solidification processing. We have also examined theoretically short-range diffusion-limited growth, characteristic of incomplete solute trapping, and interface-limited growth, characteristic of complete solute trapping, in alloy solidification and have shown that the two regimes fall naturally out of a single unified theory of solidification.

  15. RAPID BIOCATALYTIC POLYTRANSESTERIFICATION: REACTION KINETICS IN AN EXOTHERMIC REACTION. (R825338)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  16. RAPID BIOCATALYTIC POLYTRANSESTERIFICATION: REACTION KINETICS IN AN EXOTHERMIC REACTION. (R825338)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  17. [The accuracy of rapid equilibrium assumption in steady-state enzyme kinetics is the function of equilibrium segment structure and properties].

    PubMed

    Vrzheshch, P V

    2015-01-01

    Quantitative evaluation of the accuracy of the rapid equilibrium assumption in the steady-state enzyme kinetics was obtained for an arbitrary mechanism of an enzyme-catalyzed reaction. This evaluation depends only on the structure and properties of the equilibrium segment, but doesn't depend on the structure and properties of the rest (stationary part) of the kinetic scheme. The smaller the values of the edges leaving equilibrium segment in relation to values of the edges within the equilibrium segment, the higher the accuracy of determination of intermediate concentrations and reaction velocity in a case of the rapid equilibrium assumption.

  18. Experimental Investigation and Modeling of Kinetic Processes in a KrF Laser

    NASA Astrophysics Data System (ADS)

    Bychkov, Yu. I.; Yastremskii, A. G.; Yampolskaya, S. A.; Losev, V. F.; Dudarev, V. V.; Panchenko, Yu. N.; Puchikin, A. V.

    2014-11-01

    The KrF laser with radiation pulse duration at half maximum of 20 ns is experimentally investigated. A self-consistent model is developed considering the electric circuit, the kinetic processes in the active medium, and the formation of laser radiation in a resonator. Time dependences of the discharge current and voltage on the capacitor and discharge electrodes, plasma particle concentration, and rate constants of the processes determining the characteristics of the discharge and laser radiation are presented. Processes are revealed that determines the characteristics of the space charge and laser radiation. The kinetics of the processes of production and annihilation of KrF excimer molecules is studied in detail. It is demonstrated that high rates of destruction of excimer molecules increases the time of delay of generation thereby decreasing the efficiency of laser generation and limiting the possibility of decreasing laser radiation pulse duration.

  19. Investigation of molecule-adsorption kinetics by a pulsed laser desorption technique

    NASA Astrophysics Data System (ADS)

    Varakin, V. N.; Lozovskii, A. D.; Panesh, A. M.; Simonov, A. P.

    1987-02-01

    The laser thermal desorption technique is used to measure the adsorption kinetics of SO2 and CO molecules on stainless steel with the aim of investigating the initial stage of oxidation of the steel by adsorbed CO molecules. Attention is given to the dependence of the rate of establishment of the equilibrium concentration of adsorbed molecules on SO2-gas pressure; CO adsorption kinetics on stainless steel at a gas pressure of 9 x 10 to the -8th torr; and the dependence of the concentration of adsorbed CO molecules on exposure in the gas at a pressure of 9 x 10 to the -8th torr under irradiation by laser pulses with repetition periods of 1-2, 2-4, 3-6, and 4-8 min.

  20. Investigation of the alpha(1)-glycine receptor channel-opening kinetics in the submillisecond time domain.

    PubMed Central

    Grewer, C

    1999-01-01

    The activation and desensitization kinetics of the human alpha(1)-homooligomeric glycine receptor, which was transiently expressed in HEK 293 cells, were studied with a 100-microseconds time resolution to determine the rate and equilibrium constants of individual receptor reaction steps. Concentration jumps of the activating ligands glycine and beta-alanine were initiated by photolysis of caged, inactive precursors and were followed by neurotransmitter binding, receptor-channel opening, and receptor desensitization steps that were separated along the time axis. Analysis of the ligand concentration-dependence of these processes allows the determination of 1) the rate constants of glycine binding, k(+1) approximately 10(7) M(-1) s(-1), and dissociation, k(-1) = 1900 s(-1); 2) the rates of receptor-channel opening, k(op) = 2200 s(-1), and closing, k(cl) = 38 s(-1); 3) the receptor desensitization rate, alpha = 0.45 s(-1); 4) the number of occupied ligand binding sites necessary for receptor-channel activation and desensitization, n >/= 3; and 5) the maximum receptor-channel open probability, p(0) > 0.95. The kinetics of receptor-channel activation are insensitive to the transmembrane potential. A general model for glycine receptor activation explaining the experimental data consists of a sequential mechanism based on rapid ligand-binding steps preceding a rate-limiting receptor-channel opening reaction and slow receptor desensitization. PMID:10423421

  1. Investigating the kinetic stability and transformation of vapor-deposited glasses with AC nanocalorimetry experiments

    NASA Astrophysics Data System (ADS)

    Tylinski, Michael Tod

    This thesis presents experiments and discussion that advance the understanding of vapor-deposited glasses. When vapor-deposited glasses exhibit high kinetic stability, they're known as stable glasses. Stable glasses are known to transform into the liquid state via a front mechanism. My first project introduced a quantitative evaluation of the uniformity of these fronts over time and space. I found that the front velocity varies by less than 4% over the duration of the transformation. For films 280 nm thick, the transformation rates at different spatial positions in the film differ by about 25%; this quantity may be related to spatially heterogeneous dynamics in the stable glass. In my second project, I established that vapor deposition could be used to prepare stable glasses of an alcohol molecule. It was previously unknown if this was possible. I also found that while at least one alcohol molecule can be used to prepare a stable glass, several other alcohol molecules formed glasses with minimal kinetic stability when using standard deposition conditions. The wide range of kinetic stabilities is useful for investigating the factors that control stable glass formation. I compared the kinetic stability of vapor deposited glasses prepared from 14 molecules and found a correlation with the value of taualpha at 1.25 Tg. In my final research project, I performed experiments that tested various hypotheses for why 2-ethyl-1-hexanol forms vapor-deposited glasses with limited kinetic stability when using standard preparation conditions. The experiments supported the hypothesis that the surface mobility is less than for other molecules that are used to prepare stable glasses. My analysis of the data led to the estimation that at the substrate temperature commonly used to deposit stable glasses, 2-ethyl-1-hexanol molecules at the surface move more than 104 times slower compared to molecules that do form highly stable glasses using typical preparation conditions. The thesis

  2. Curing kinetics of visible light curing dental resin composites investigated by dielectric analysis (DEA).

    PubMed

    Steinhaus, Johannes; Hausnerova, Berenika; Haenel, Thomas; Großgarten, Mandy; Möginger, Bernhard

    2014-03-01

    During the curing process of light curing dental composites the mobility of molecules and molecule segments is reduced leading to a significant increase of the viscosity as well as the ion viscosity. Thus, the kinetics of the curing behavior of 6 different composites was derived from dielectric analysis (DEA) using especially redesigned flat sensors with interdigit comb electrodes allowing for irradiation at the top side and measuring the ion viscosity at the bottom side. As the ion viscosities of dental composites change 1-3 orders of magnitude during the curing process, DEA provides a sensitive approach to evaluate their curing behavior, especially in the phase of undisturbed chain growth. In order to determine quantitative kinetic parameters a kinetic model is presented and examined for the evaluation of the ion viscosity curves. From the obtained results it is seen that DEA might be employed in the investigation of the primary curing process, the quality assurance of ingredients as well as the control of processing stability of the light curing dental composites.

  3. Molecular-Level Investigations of Nucleation Mechanisms and Kinetics of Formation of Environmental Nanoparticles

    SciTech Connect

    Young-Shin Jun; Glenn A. Waychunas

    2007-04-19

    Environmental nanoparticles are often poorly-crystalline or metastable structures, whose kinetics of formation and growth are poorly understood. Further, the sorption or growth of nanoparticles on mineral surfaces may control the mineral surface's reactivity and modify its ability to influence contaminant transport. Due to the characteristic length scale, a holistic understanding of the nucleation mechanisms and kinetics of nanoparticle formation on mineral surfaces is difficult to achieve with traditional methodology. In this work, our intent is to determine the molecular nature of nucleation on surfaces, the kinetics of surface nucleation and growth, and the effect of crystal surface topology using new synchrotron-based techniques. We have approached these objectives by: (1) combining state-of-the-art crystal-truncation rod diffraction (CTR) and grazing incidence x-ray absorption fine structure spectroscopy (GIXAS) techniques to investigate the three-dimensional molecular-scale geometry of silicate monomer sorption on the r-plane of hematite; and (2) developing a new grazing-incidence small angle x-ray scattering (GISAXS) setup at SSRL (0.08 nm{sup -1} < q < 8 nm{sup -1}) to explore the initial development of environmental nanoparticles on various mineral surfaces. This study also includes complementary techniques such as atomic force microscopy (AFM), bulk SAXS, dynamic light scattering (DLS), XRD, and TEM.

  4. Kinetics and Microstructural Investigation of High-Temperature Oxidation of IN-738LC Super Alloy

    NASA Astrophysics Data System (ADS)

    Hamidi, S.; Rahimipour, M. R.; Eshraghi, M. J.; Hadavi, S. M. M.; Esfahani, H.

    2017-02-01

    The present study was carried out to investigate the kinetics and the surface chemistry of the oxide layers formed on the IN-738LC super alloy during high-temperature oxidation at 950 °C in air from 1 to 260 h. Oxidation kinetics were studied by mass gain measurement. The oxide layers were characterized by field emission scanning electron microscope, elemental distribution map, energy-dispersive spectroscopy as well as x-ray diffractometry (XRD). The oxidation kinetics followed the parabolic law. The XRD analysis revealed that the oxide scale contained mainly NiO, Ni (Cr, Al)2O4, Al2O3, TiO2 and Cr2O3. The oxide structure, from the top surface down to the substrate, was clarified by elemental map distribution studies as Ni-Ti oxides, Cr-Ti oxides, Cr2O3 oxide band, Ni-Co-Cr-W oxide and finally a blocky Al2O3 region. The oxidation scales were composed of three distinct layers of the outer and mid layers enriched by TiO2 and Cr2O3, NiCr2O4 oxide, respectively, and the innermost layer was composed of Al2O3 and matrix alloy. The depleted gamma prime layer was formed under the oxidation scales due to the impoverishment of Al and Ti which were induced by the formation of Al2O3 and TiO2.

  5. Hardening kinetics investigation of alkali-activated binder by small amplitude oscillatory rheometry

    NASA Astrophysics Data System (ADS)

    Rieger, D.; Kullová, L.; Čekalová, M.; Kovářík, T.

    2017-01-01

    In this study, the rheological behavior of geopolymeric inorganic binder was determined. This binder was synthesized by alkaline activation of mixture, comprising calcined claystone powder and milled blast furnace slag. As an alkaline activator of hardening process, the potassium silicate solution was used. For the investigation of hardening kinetics, the strain controlled small amplitude oscillatory rheometry was used with strain of 0.01%. The reproducibility and versatility of this method is demonstrated for determination of hardening process evolution. The changes of loss tangent shape were studied in this experiment and applied for determination of gelation time. All experiments were conducted at isothermal conditions in temperature range 27-70°C and parallel plate geometry. The results indicate that reaction kinetics is directly depending on temperature. The hardening kinetics was mathematically described and these calculations were compared with self-contained experiment conducted at 2°C. This experiment is described in details and the results of gelation time measurements confirmed calculated data.

  6. Kinetics and Microstructural Investigation of High-Temperature Oxidation of IN-738LC Super Alloy

    NASA Astrophysics Data System (ADS)

    Hamidi, S.; Rahimipour, M. R.; Eshraghi, M. J.; Hadavi, S. M. M.; Esfahani, H.

    2016-12-01

    The present study was carried out to investigate the kinetics and the surface chemistry of the oxide layers formed on the IN-738LC super alloy during high-temperature oxidation at 950 °C in air from 1 to 260 h. Oxidation kinetics were studied by mass gain measurement. The oxide layers were characterized by field emission scanning electron microscope, elemental distribution map, energy-dispersive spectroscopy as well as x-ray diffractometry (XRD). The oxidation kinetics followed the parabolic law. The XRD analysis revealed that the oxide scale contained mainly NiO, Ni (Cr, Al)2O4, Al2O3, TiO2 and Cr2O3. The oxide structure, from the top surface down to the substrate, was clarified by elemental map distribution studies as Ni-Ti oxides, Cr-Ti oxides, Cr2O3 oxide band, Ni-Co-Cr-W oxide and finally a blocky Al2O3 region. The oxidation scales were composed of three distinct layers of the outer and mid layers enriched by TiO2 and Cr2O3, NiCr2O4 oxide, respectively, and the innermost layer was composed of Al2O3 and matrix alloy. The depleted gamma prime layer was formed under the oxidation scales due to the impoverishment of Al and Ti which were induced by the formation of Al2O3 and TiO2.

  7. A model stomach system to investigate disintegration kinetics of solid foods during gastric digestion.

    PubMed

    Kong, F; Singh, R P

    2008-06-01

    Knowledge of the disintegration kinetics of food particulates in the human stomach is essential for assessing the bioaccessibility of nutrients in solid foods and understanding stomach emptying. The objective of this study was to develop a model stomach system and to investigate the kinetics of food disintegration. Our system consisted mainly of a turntable and a jacketed glass chamber containing simulated gastric juice in which plastic beads were added to simulate food particulates as well as provide a suitable mechanical destructive force on food samples. The mechanical force on the samples was simultaneously measured using the load cell of a TA-XT2 texture analyzer. Cylindrical carrots and ham samples were used as representative foods. The system is capable of simulating the in vivo stomach in terms of providing a wide range of continuous and periodic forces comparable to those measured in vivo. The modified power exponential function of the form y(t)= 1 - (1 -e(-kt))(beta), where y(t) is the mass retention ratio at time t, provided a reasonable description for the disintegration performance of tested foods. The mass retention curve can be either a sigmoidal decay with an initial delay or an exponential decay, which are decided largely by the hardness of the foods during digestion and the extent of physical force acting on the foods. A good match was observed between the kinetics of food disintegration and in vivo stomach emptying.

  8. Continuous production of biodiesel under supercritical methyl acetate conditions: Experimental investigation and kinetic model.

    PubMed

    Farobie, Obie; Matsumura, Yukihiko

    2017-10-01

    In this study, biodiesel production by using supercritical methyl acetate in a continuous flow reactor was investigated for the first time. The aim of this study was to elucidate the reaction kinetics of biodiesel production by using supercritical methyl. Experiments were conducted at various reaction temperatures (300-400°C), residence times (5-30min), oil-to-methyl acetate molar ratio of 1:40, and a fixed pressure of 20MPa. Reaction kinetics of biodiesel production with supercritical methyl acetate was determined. Finally, biodiesel yield obtained from this method was compared to that obtained with supercritical methanol, ethanol, and MTBE (methyl tertiary-butyl ether). The results showed that biodiesel yield with supercritical methyl acetate increased with temperature and time. The developed kinetic model was found to fit the experimental data well. The reactivity of supercritical methyl acetate was the lowest, followed by that of supercritical MTBE, ethanol, and methanol, under the same conditions. Copyright © 2017. Published by Elsevier Ltd.

  9. Investigation of DNA Damage Dose-Response Kinetics after Ionizing Radiation Schemes Similar to CT Protocols.

    PubMed

    Elgart, S Robin; Bostani, Maryam; Mok, Karen C; Adibi, Ali; Ruehm, Stefan; Enzmann, Dieter; McNitt-Gray, Michael; Iwamoto, Keisuke S

    2015-06-01

    Although there has been extensive research done on the biological response to doses of ionizing radiation relevant to radiodiagnostic procedures, very few studies have examined radiation schemes similar to those frequently utilized in CT exams. Instead of a single exposure, CT exams are often made up of a series of scans separated on the order of minutes. DNA damage dose-response kinetics after radiation doses and schemes similar to CT protocols were established in both cultured (ESW-WT3) and whole blood lymphocytes and compared to higher dose exposures. Both the kinetics and extent of H2AX phosphorylation were found to be dose dependent. Damage induction and detection showed a clear dose response, albeit different, at all time points and differences in the DNA repair kinetics of ESW-WT3 and whole blood lymphocytes were characterized. Moreover, using a modified split-dose in vitro experiment, we show that phosphorylation of H2AX is significantly reduced after exposure to CT doses fractionated over a few minutes compared to the same total dose delivered as a single exposure. Because the split-dose exposures investigated here are more similar to those experienced during a CT examination, it is essential to understand why and how these differences occur. This work provides compelling evidence supporting differential biological responses not only between high and low doses, but also between single and multiple exposures to low doses of ionizing radiation.

  10. Investigation of equilibration and growth of stepped surfaces by Kinetic Monte Carlo in one dimension

    NASA Astrophysics Data System (ADS)

    Türkan, A.; Esen, M.; Tüzemen, A. Türker; Özdemir, M.

    2017-02-01

    In this study, the equilibration and in the case of a particle flux to the surface, the growth of a one dimensional semi-conductor surface of "V" initial shape is investigated by kinetic Monte Carlo method. The initial surface is assumed to consist of atomic height steps separated by terraces. In Monte Carlo simulations, the following processes are considered: the diffusion of free particles on the surface, the attachment/detachment of particles to/from step edges from/to a terrace in front of a step or to a terrace above the step. In the simulations the Ehrlich-Schwoebel barrier is also taken into account. The equilibration of "V" initial shape at various temperatures is investigated. Moreover, the effect of particle bonding energy on the surface profile and on the evolution of the surface is also investigated. In the case of a particle flux to the surface, the surface profile and its growth kinetics are investigated at various temperatures and flux values.

  11. An investigation of the dosimetric and kinetic properties of sand using ESR and TL techniques.

    PubMed

    Aydaş, Canan; Aydın, Talat

    2015-07-01

    In this research, the general dosimetric and kinetic properties of sand from a beach in southern Turkey were investigated using electron spin resonance (ESR) and thermoluminescence (TL) techniques. The ESR dose response curve presents linear behaviour in the dose range of 250-1000 Gy followed by sublinear behaviour in the dose range of 2-8 kGy. Kinetic behaviors and activation energy of the free radical were also calculated using the data obtained from annealing studies performed at four different temperatures (220, 240, 260 and 280°C). The activation energy value was calculated as 1.47 eV. The long-term fading of the ESR signal at room temperature turned out to be best described by a second-order kinetic decay function. The presence of measurable ESR signal intensity even after a storage period of 90 days was considered as providing an opportunity in the dose estimation of irradiated sand sample. Although the TL glow curve of the natural (unirradiated) sand sample only has a single broad peak at 317°C, the glow curve of the irradiated sample has four glow peaks located at ~115°C, ~156°C, ~231°C and ~308°C and their intensity tends to be increased with absorbed dose.Tmax-Tstop and glow curve fitting results showed that presence of at least five peaks located at ∼116°C, 149°C, 228°C, 306°C and 360°C. This result suggests that the apparently single glow peak D may consist of two or more overlapping glow peaks. According to the thermal fading of the sand sample at room temperature, the TL signal intensities (23°C and 308°C) were found to be quite large after 30 days of storage this allows a more accurate measurement of the glow peak intensity. The additive dose method, variable heating rate method (VHRM), Tmax-Tstop and glow curve fitting method were used to number of peaks, dosimetric properties and kinetic parameters. This study shows that ESR and TL techniques could be successfully used to investigate the kinetics and dosimetric properties of sand

  12. Investigation of reaction kinetics and interfacial phase formation in Ti3Al + Nb composites

    NASA Technical Reports Server (NTRS)

    Wawner, F. E.; Gundel, D. B.

    1992-01-01

    Titanium aluminide metal matrix composites are prominent materials systems being considered for high temperature aerospace applications. One of the major problems with this material is the reactivity between existing reinforcements and the matrix after prolonged thermal exposure. This paper presents results from an investigation of reaction kinetics between Ti-14Al-21Nb (wt pct) and SCS-6 fibers and SiC fibers with surface coatings of TiB2, TiC, TiN, W, and Si. Microstructural evaluation of the reaction layers as well as matrix regions around the fibers is presented.

  13. Investigation of reaction kinetics and interfacial phase formation in Ti3Al + Nb composites

    NASA Technical Reports Server (NTRS)

    Wawner, F. E.; Gundel, D. B.

    1992-01-01

    Titanium aluminide metal matrix composites are prominent materials systems being considered for high temperature aerospace applications. One of the major problems with this material is the reactivity between existing reinforcements and the matrix after prolonged thermal exposure. This paper presents results from an investigation of reaction kinetics between Ti-14Al-21Nb (wt pct) and SCS-6 fibers and SiC fibers with surface coatings of TiB2, TiC, TiN, W, and Si. Microstructural evaluation of the reaction layers as well as matrix regions around the fibers is presented.

  14. Single-Site Palladium(II) Catalyst for Oxidative Heck Reaction: Catalytic Performance and Kinetic Investigations

    SciTech Connect

    Duan, Hui; Li, Mengyang; Zhang, Guanghui; Gallagher, James R.; Huang, Zhiliang; Sun, Yu; Luo, Zhong; Chen, Hongzhong; Miller, Jeffrey T.; Zou, Ruqiang; Lei, Aiwen; Zhao, Yanli

    2015-01-01

    ABSTRACT: The development of organometallic single-site catalysts (SSCs) has inspired the designs of new heterogeneous catalysts with high efficiency. Nevertheless, the application of SSCs in certain modern organic reactions, such as C-C bond formation reactions, has still been less investigated. In this study, a single-site Pd(II) catalyst was developed, where 2,2'-bipyridine-grafted periodic mesoporous organosilica (PMO) was employed as the support of a Pd(II) complex. The overall performance of the single-site Pd(II) catalyst in the oxidative Heck reaction was then investigated. The investigation results show that the catalyst displays over 99% selectivity for the product formation with high reaction yield. Kinetic profiles further confirm its high catalytic efficiency, showing that the rate constant is nearly 40 times higher than that for the free Pd(II) salt. X-ray absorption spectroscopy reveals that the catalyst has remarkable lifetime and recyclability.

  15. The investigation of kinetic and isotherm of fluoride adsorption onto functionalize pumice stone.

    PubMed

    Asgari, Ghorban; Roshani, Babak; Ghanizadeh, Ghader

    2012-05-30

    In this research work, pumice that is functionalized by the cationic surfactant, hexadecyltrimethyl ammonium (HDTMA), is used as an adsorbent for the removal of fluoride from drinking water. This work was carried out in two parts. The effects of HDTMA loading, pH (3-10), reaction time (5-60 min) and the adsorbent dosage (0.15-2.5 g L(-1)) were investigated on the removal of fluoride as a target contaminate from water through the design of different experimental sets in the first part. The results from this first part revealed that surfactant-modified pumice (SMP) exhibited the best performance at dose 0.5 g L(-1), pH 6, and it adsorbs over 96% of fluoride from a solution containing 10 mg L(-1) fluoride after 30 min of mixing time. The four linear forms of the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms model were applied to determine the best fit of equilibrium expressions. Apart from the regression coefficient (R(2)), four error functions were used to validate the isotherm and kinetics data. The experimental adsorption isotherm complies with Langmuir equation model type 1. The maximum amount of adsorption (Q(max)) was 41 mg g(-1). The kinetic studies indicated that the adsorption of fluoride best fitted with the pseudo-second-order kinetic type 1. Thermodynamic parameters evaluation of fluoride adsorption on SMP showed that the adsorption process under the selected conditions was spontaneous and endothermic. The suitability of SMP in defluoridation at field condition was investigated with natural groundwater samples collected from a nearby fluoride endemic area in the second part of this study. Based on this study's results, SMP was shown to be an affordable and a promising option for the removal of fluoride in drinking water. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Numerical simulation on the opto-electro-kinetic patterning for rapid concentration of particles in a microchannel

    PubMed Central

    Kim, Dong; Shim, Jaesool; Chuang, Han-Sheng; Kim, Kyung Chun

    2015-01-01

    This paper presents a mathematical model for laser-induced rapid electro-kinetic patterning (REP) to elucidate the mechanism for concentrating particles in a microchannel non-destructively and non-invasively. COMSOL®(v4.2a) multiphysics software was used to examine the effect of a variety of parameters on the focusing performance of the REP. A mathematical model of the REP was developed based on the AC electrothermal flow (ACET) equations, the dielectrophoresis (DEP) equation, the energy balance equation, the Navier-Stokes equation, and the concentration-distribution equation. The medium was assumed to be a diluted solute, and different electric potentials and laser illumination were applied to the desired place. Gold (Au) electrodes were used at the top and bottom of a microchannel. For model validation, the simulation results were compared with the experimental data. The results revealed the formation of a toroidal microvortex via the ACET effect, which was generated due to laser illumination and joule-heating in the area of interest. In addition, under some conditions, such as the frequency of AC, the DEP velocity, and the particle size, the ACET force enhances and compresses resulting in the concentration of particles. The conditions of the DEP velocity and the ACET velocity are presented in detail with a comparison of the experimental results. PMID:26015839

  17. Numerical simulation on the opto-electro-kinetic patterning for rapid concentration of particles in a microchannel.

    PubMed

    Kim, Dong; Shim, Jaesool; Chuang, Han-Sheng; Kim, Kyung Chun

    2015-05-01

    This paper presents a mathematical model for laser-induced rapid electro-kinetic patterning (REP) to elucidate the mechanism for concentrating particles in a microchannel non-destructively and non-invasively. COMSOL(®)(v4.2a) multiphysics software was used to examine the effect of a variety of parameters on the focusing performance of the REP. A mathematical model of the REP was developed based on the AC electrothermal flow (ACET) equations, the dielectrophoresis (DEP) equation, the energy balance equation, the Navier-Stokes equation, and the concentration-distribution equation. The medium was assumed to be a diluted solute, and different electric potentials and laser illumination were applied to the desired place. Gold (Au) electrodes were used at the top and bottom of a microchannel. For model validation, the simulation results were compared with the experimental data. The results revealed the formation of a toroidal microvortex via the ACET effect, which was generated due to laser illumination and joule-heating in the area of interest. In addition, under some conditions, such as the frequency of AC, the DEP velocity, and the particle size, the ACET force enhances and compresses resulting in the concentration of particles. The conditions of the DEP velocity and the ACET velocity are presented in detail with a comparison of the experimental results.

  18. Investigation of the kinetics of water uptake into partially saturated shales

    NASA Astrophysics Data System (ADS)

    Roshan, H.; Andersen, M. S.; Rutlidge, H.; Marjo, C. E.; Acworth, R. I.

    2016-04-01

    Several processes have been proposed to describe the low recovery of hydraulic fracturing fluid in unconventional shale reservoirs which has caused both technical and environmental concerns. This study describes novel hydraulic experiments to quantitatively investigate the kinetics of water uptake into partially saturated shale through investigating the pressure response of injecting fluids (NaCl, KCl, MgCl2, and CaCl2 with different ionic concentrations) into crushed and sieved shale fragments. The results of the study indicate that the cumulative water uptake under pressure is likely to be controlled by three processes: surface hydration, capillary hydration including advective flow, and osmotic hydration. Each of these processes is a function of the differences between the in situ pore fluid and the injection fluid (solution chemistry and concentration) and the shale physicochemical properties, in particular the contact surface area, pore diameter, and the Cation Exchange Capacity (CEC). The uptake is not instantaneous, but is diffusion limited, with the rate governed by a number of kinetic processes. Uptake proceeds in three stages, each associated with a different process: (1) predominantly surface hydration, (2) predominantly capillary hydration and finally, (3) predominantly osmotic hydration. It was also shown that shale can take up a significant amount of water compared to its available solid volume. However, contrary to the conventional understanding, the increase in salinity of the injection fluid does not necessarily lead to reduced water uptake into shales, but is dependent on the type and concentration of cations within the shale and injecting fluid.

  19. Investigation of Horseradish Peroxidase Kinetics in an "Organelle-Like" Environment.

    PubMed

    Baumann, Patric; Spulber, Mariana; Fischer, Ozana; Car, Anja; Meier, Wolfgang

    2017-05-01

    In order to mimic cell organelles, artificial nanoreactors have been investigated based on polymeric vesicles with reconstituted channel proteins (outer membrane protein F) and coencapsulated enzymes horseradish peroxidase (HRP) along with a crowding agent (Ficoll or polyethylene glycol) inside the cavity. Importantly, the presence of macromolecules has a strong impact on the enzyme kinetics, but no influence on the integrity of vesicles up to certain concentrations. This particular design allows for the first time the determination of HRP kinetics inside nanoreactors with crowded milieu. The values of the Michaelis-Menten constant (K m ) measured for HRP in a confined space (encapsulated in nanoreactors) in the absence of macromolecules are ≈50% lower than in free conditions, and the presence of a crowding agent results in a further pronounced decrease. These results clearly suggest that activities of enzymes in confined spaces can be tuned by varying the concentrations of crowding compounds. The present investigation represents an advance in nanoreactor design by considering the influence of environmental factors on enzymatic performance, and it demonstrates that both encapsulation and the presence of a crowding environment increase the enzyme-substrate affinity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Experimental Investigation of the Kinetics of a Ruthenium-Catalyzed Deconstruction of Lignin Model Compounds

    SciTech Connect

    Bu, L.; Nimlos, M. R.; Shirts, M. R.; Himmel, M. E.; Crowley, M. F.; Beckham, G. T.

    2012-01-01

    Lignin is a major component of plant cell walls that is typically underutilized in selective conversion strategies for renewable fuels and chemicals. The mechanisms by which thermal and catalytic treatments deconstruct lignin remain elusive. In this work, we have investigated the kinetics of the catalytic deconstruction of lignin model compounds using a ruthenium catalyst reported by Bergman et al. in 2010. A series of investigations using NMR spectroscopy and GC/MS will be presented. In addition, we propose detailed mechanisms for lignin depolymerization with ruthenium catalysts. We have also used DFT to compute transition state geometries of catalytic cycle intermediates and compare the values determined computationally with those observed experimentally. Ultimately, our objective is to apply our methods to the design of new homogeneous and heterogeneous catalysts for the effective deconstruction and valorization of lignin.

  1. Equilibrium, thermodynamic and kinetic investigations for biosorption of uranium with green algae (Cladophora hutchinsiae).

    PubMed

    Bağda, Esra; Tuzen, Mustafa; Sarı, Ahmet

    2017-09-01

    Removal of toxic chemicals from environmental samples with low-cost methods and materials are very useful approach for especially large-scale applications. Green algae are highly abundant biomaterials which are employed as useful biosorbents in many studies. In the present study, an interesting type of green algae, Cladophora hutchinsiae (C. hutchinsiae) was used for removal of highly toxic chemical such as uranium. The pH, biosorbent concentration, contact time and temperature were optimized as 5.0, 12 g/L, 60 min and 20 °C, respectively. For the equilibrium calculations, three well known isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich) were employed. The maximum biosorption capacity of the biosorbent was calculated as about 152 mg/g under the optimum batch conditions. The mean energy of biosorption was calculated as 8.39 kJ/mol from the D-R biosorption isotherm. The thermodynamic and kinetic characteristics of biosorption were also investigated to explain the nature of the process. The kinetic data best fits the pseudo-second-order kinetic model with a regression coefficient of >0.99 for all studied temperatures. The calculated ΔH° and ΔG° values showed that the biosorption process is exothermic and spontaneous for temperatures between 293 and 333 K. Furthermore, after seven cycling process, the sorption and desorption efficiencies of the biosorbent were found to be 70, and 58%, respectively meaning that the biosorbent had sufficiently high reusability performance as a clean-up tool. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. A suggested schedule for the rapid investigation of acute haemostatic failure

    PubMed Central

    Ingram, G. I. C.

    1961-01-01

    A small group of tests is proposed for the rapid investigation of acute bleeding states. These techniques are within the compass of many clinical laboratories, and the whole scheme may be run through in one to one-and-a-half hours. PMID:13717713

  3. Micromodel investigation of transport effect on the kinetics of reductive dissolution of hematite.

    PubMed

    Zhang, Changyong; Liu, Chongxuan; Shi, Zhi

    2013-05-07

    Reductive dissolution of hematite in porous media was investigated using a micromodel (8.1 × 4.5 × 0.028 mm) with realistic pore network structures that include distinctive advection domain, macropores and micropores created in silicon substrate. The micromodel pore surface was sputter deposited with a thin layer (230 nm) of hematite. The hematite in the micromodel was reduced by injecting pH-varying solutions (pH 5.0, 6.0, 7.0) containing a reduced form of flavin mononucleotide (FMNH2, 100 μM), a biogenic soluble electron transfer mediator produced by Shewanella species. The reduction kinetics was determined by measuring effluent Fe(II) (aq) concentration and by spectroscopically monitoring the hematite dissolution front in the micromodel. Batch experiment was also performed to estimate the hematite reduction rate under the well-mixed condition. Results showed significant spatial variation in local redox reaction rate that was controlled by the coupled transport and reaction. The overall rate of the redox reaction in the micromodel required a three-domain numerical model to effectively describe reaction kinetics either with distinctive apparent rate parameters or mass transfer coefficients in different pore domains. Results from this study demonstrated the feasibility of a domain-based modeling approach for scaling reaction rates from batch to porous media systems where reactions may be significantly limited by transport.

  4. A detailed investigation on electro-Fenton treatment of propachlor: Mineralization kinetic and degradation intermediates.

    PubMed

    Gençten, Metin; Özcan, Ali

    2015-10-01

    In this study, electrochemical removal of propachlor from water has been investigated by electro-Fenton process which provides continuous electrochemical production of hydroxyl radical which is a highly oxidizing agent. This radical can react with propachlor unselectively and can oxidize it into carbon dioxide and water. Effects of applied current, catalyst (Fe2(SO4)3) and supporting electrolyte (Na2SO4) concentrations on the degradation rate of propachlor have been examined and determined as 200 mA, 0.20 mM and 25 mM, respectively. The oxidation reaction showed a second-order reaction kinetic with an absolute rate constant value of (3.6±0.2)×10(9) M(-1) s(-1) which was determined by competition kinetic experiments. Total organic carbon analysis was employed to follow the mineralization of propachlor. The total mineralization was completed in a seven-hour electrolysis at 300 mA indicating that the electro-Fenton process is very effective in the mineralization of propachlor in water. Oxidation of propachlor with hydroxyl radical led to the formation of intermediate species. Some of these species were detected and quantified by chromatographic and spectroscopic methods such as HPLC, GC-MS and IC. A plausible mineralization pathway for the electrochemical removal of propachlor was proposed based on the identified by-products. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Investigation of kinetic interactions between approved oximes and human acetylcholinesterase inhibited by pesticide carbamates.

    PubMed

    Wille, Timo; Kaltenbach, Lisa; Thiermann, Horst; Worek, Franz

    2013-12-05

    Carbamates are widely used for pest control and act primarily by inhibition of insect and mammalian acetylcholinesterase (AChE). Accidental or intentional uptake of carbamates may result in typical signs and symptoms of cholinergic overstimulation which cannot be discriminated from those of organophosphorus pesticide poisoning. There is an ongoing debate whether standard treatment with atropine and oximes should be recommended for human carbamate poisoning as well, since in vitro and in vivo animal data indicate a deleterious effect of oximes when used in combination with the N-methyl carbamate carbaryl. Therefore, we performed an in vitro kinetic study to investigate the effect of clinically used oximes on carbamoylation and decarbamoylation of human AChE. It became evident that pralidoxime and obidoxime in therapeutic concentrations aggravate the inhibition of AChE by carbaryl and propoxur, with obidoxime being substantially more potent compared to 2-PAM. However, obidoxime had no impact on the decarbamoylation kinetics. Hence, the administration of 2-PAM and especially of obidoxime to severely propoxur and carbaryl poisoned humans cannot be recommended. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  6. Numerical investigation of kinetic energy dynamics during autoignition of n-heptane/air mixture

    NASA Astrophysics Data System (ADS)

    Lucena Kreppel Paes, Paulo; Brasseur, James; Xuan, Yuan

    2015-11-01

    Many engineering applications involve complex turbulent reacting flows, where nonlinear, multi-scale turbulence-combustion couplings are important. Direct representation of turbulent reacting flow dynamics is associated with prohibitive computational costs, which makes it necessary to employ turbulent combustion models to account for the effects of unresolved scales on resolved scales. Classical turbulence models are extensively employed in reacting flow simulations. However, they rely on assumptions about the energy cascade, which are valid for incompressible, isothermal homogeneous isotropic turbulence. A better understanding of the turbulence-combustion interactions is required for the development of more accurate, physics-based sub-grid-scale models for turbulent reacting flows. In order to investigate the effects of reaction-induced density, viscosity, and pressure variations on the turbulent kinetic energy, Direct Numerical Simulation (DNS) of autoignition of partially-premixed, lean n-heptane/air mixture in three-dimensional homogeneous isotropic turbulence has been performed. This configuration represents standard operating conditions of Homogeneous-Charge Compression-Ignition (HCCI) engines. The differences in the turbulent kinetic energy balance between the present turbulent reacting flow and incompressible, isothermal homogeneous isotropic turbulence are highlighted at different stages during the autoignition process.

  7. Use of surface plasmon resonance to investigate lateral wall deposition kinetics and properties of polydopamine films.

    PubMed

    Li, Hui; Cui, Dafu; Cai, Haoyuan; Zhang, Lulu; Chen, Xing; Sun, Jianhai; Chao, Yapeng

    2013-03-15

    Dopamine (DA) is a particularly important neurotransmitter. Polydopamine (pDA) films have been demonstrated to be important materials for the immobilization of biomolecules onto almost any type of solid substrate. In this study, a surface plasmon resonance (SPR)-based sensor system with the sensor chip surface parallel to the direction of gravity was used to investigate the lateral wall deposition kinetics and properties of pDA films. The deposition kinetics of pDA Films are limited by the oxidation process. The pDA film could not be removed from the sensor chip completely by a strongly alkaline solution, indicating that the pDA film was heterogeneous in the direction of deposition. The pDA film formed near the interior of the solution was less stable than the film formed near the gold-solution interface. Adsorption of proteins on pDA film was studied compared with that on bare gold and dextran sensor chip. The reduction of Au(111) cations by the pDA film, forming a layer of gold particles, was monitored using SPR.

  8. Investigation of rehydration kinetics of open-sun dried okra samples

    NASA Astrophysics Data System (ADS)

    Gökçe Kocabay, Özlem; İsmail, Osman

    2017-01-01

    In this study rehydration kinetics of open-sun dried okra, which dried naturally and two pre-treatment, was investigated at 25 and 50 °C. By the obtained data, parameters with respect to rehydration kinetics and diffusion mechanism were calculated. In dehydration experiments, it was determined that blanching pre-treatment has influence on the drying time and okra samples were dried at 18 h. On the contrary in rehydration experiments maximum equilibrium rehydration values were achieved with the okras dried naturally. Experimental equilibrium rehydration (R eq ), theoretical equilibrium rehydration (R max ) and diffusion coefficient (D) of okra dried naturally at 50 °C were calculated as 5.57 (g water/g dry matter), 5.96 (g water/g dry matter) and 2.17 × 10-10 (m2/s), respectively. Rehydration exponent (n) value, which is also important to identify the diffusion type of dried okra, was determined as between 0.332 and 0.383. Because of the exponent value n < 0.50, diffusion was defined as natural Fick type.

  9. Investigation on silicon alloying kinetics during lithiation by galvanostatic impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Ko, Younghoon; Hwang, Chihyun; Song, Hyun-Kon

    2016-05-01

    The parameters characterizing lithiation processes in silicon anodes of lithium ion batteries (LIBs) are compared between μm- and nm-sized silicon particles. Galvanostatic electrochemical impedance spectroscopy (GS-EIS) is used to investigate the silicon-lithium alloying reaction in a practical charging operation (galvanostatic lithiation). Effective kinetic parameters depending on lithiation C-rates are obtained along lithiation progress from a large body of impedance data. Nanosizing benefits of nanoparticles over micro-particles are confirmed such as lower polarization resistance (Rp) and thinner solid-electrolyte interphase layer (SEI layer) over the whole lithiation range. Based on the kinetic information obtained from the non-stationary conditions, a lithiation strategy consisting of multiple galvanostatic steps is designed to lithiate silicon anodes in a faster way. 75% of full capacity is lithiated by a galvanostatic sequence of 4C-2C-1C-0.5C within 20 min. However, only 43% and 21% are achieved by a single-rate galvanostatic lithiation at 1 C and 0.5 C, respectively.

  10. Thermoactivated persulfate oxidation of pesticide chlorpyrifos in aquatic system: kinetic and mechanistic investigations.

    PubMed

    Zhou, Lei; Zhang, Ya; Ying, Rongrong; Wang, Guoqing; Long, Tao; Li, Jianhua; Lin, Yusuo

    2017-03-20

    The widespread occurrence of organophosphorus pesticides (OPPs) in the environment poses risks to both ecologic system as well as human health. This study investigated the oxidation kinetics of chlorpyrifos (CP), one of the typical OPPs, by thermoactivated persulfate (PS) oxidation process, and evaluated the influence of key kinetic factors, such as PS concentrations, pH, temperature, bicarbonate, and chloride ions. The reaction pathways and mechanisms were also proposed based on products identification by LC-MS techniques. Our results revealed that increasing initial PS concentration and temperature favored the decomposition of CP, whereas the oxidation efficiency was not affected by pH change ranging from 3 to 11. Bicarbonate was found to play a detrimental role on CP removal rates, while chloride showed no effect. The oxidation pathways including initial oxidation of P=S bond to P=O, dechlorination, dealkylation, and the dechlorination-hydroxylation were proposed, and the detailed underlying mechanisms were also discussed. Molecular orbital (MO) calculations indicated that P=S bond was the most favored oxidation site of the molecule. The toxicity of reaction solution was believed to increase due to the formation of products with P=O structures. This work demonstrates that OPPs can readily react with SO4(·-) and provides important information for further research on the oxidation of these contaminants.

  11. Investigation of rehydration kinetics of open-sun dried okra samples

    NASA Astrophysics Data System (ADS)

    Gökçe Kocabay, Özlem; İsmail, Osman

    2017-06-01

    In this study rehydration kinetics of open-sun dried okra, which dried naturally and two pre-treatment, was investigated at 25 and 50 °C. By the obtained data, parameters with respect to rehydration kinetics and diffusion mechanism were calculated. In dehydration experiments, it was determined that blanching pre-treatment has influence on the drying time and okra samples were dried at 18 h. On the contrary in rehydration experiments maximum equilibrium rehydration values were achieved with the okras dried naturally. Experimental equilibrium rehydration ( R eq ), theoretical equilibrium rehydration ( R max ) and diffusion coefficient ( D) of okra dried naturally at 50 °C were calculated as 5.57 (g water/g dry matter), 5.96 (g water/g dry matter) and 2.17 × 10-10 (m2/s), respectively. Rehydration exponent (n) value, which is also important to identify the diffusion type of dried okra, was determined as between 0.332 and 0.383. Because of the exponent value n < 0.50, diffusion was defined as natural Fick type.

  12. Electrochemical oxidation of an azo dye in aqueous media investigation of operational parameters and kinetics.

    PubMed

    Parsa, J Basiri; Rezaei, M; Soleymani, A R

    2009-09-15

    In this research two types of electrochemical reactors for the treatment of simulated wastewaters containing Direct blue 71 azo dye (DB71) were used: (1) Laboratory scale undivided electrolysis cell system (450 mL volume) with one 2 cm x 2 cm platinum plate as the anode placed in the middle of the cell and two 2 cm x 8 cm steel plates (SS-304) as cathodes placed in the sides of the cell 2 cm from the central anode. (2) Pilot scale reactor (9L volume), equipped with two 3 cm x 23 cm stainless steel plates as anode and cathode, with distance of 3 cm apart. The influence of supporting electrolyte, applied voltage and pH were studied. The UV-vis spectra of samples during the electrochemical oxidation showed the rapid decolorization of the dye solution. During the process, the COD and current were measured in order to evaluate the degree of mineralization, energy consumption, current and anode efficiencies. The optimum supporting electrolyte and applied voltage were NaCl (5 g L(-1)) and 15 V. Using the lab scale reactor resulted in complete decolorization and mineralization of the dye solutions after ca. 90 and 120 min, respectively. Similar results were obtained using the pilot plant reactor under the same conditions. The good fit of the data to pseudo-first-order kinetics for COD removal at all applied voltages (except 20 V) was taken as proof of the involvement of indirect oxidation pathways in the process.

  13. A kinetic investigation of high-temperature mercury oxidation by chlorine.

    PubMed

    Wilcox, Jennifer

    2009-06-18

    First-stage mercury oxidation reactions typical of coal combustion flue gases were investigated. The present study is a determination of the kinetic and thermodynamic parameters of the bimolecular reactions, Hg + Cl(2) <--> HgCl + Cl, Hg + HCl <--> HgCl + H, and Hg + HOCl <--> HgCl + OH, at the B3LYP/RCEP60 VDZ level of theory over a temperature range of 298.15 to 2000 K at atmospheric pressure. Conventional transition state theory was used to predict the forward and reverse rate constants for each reaction and ab initio based equilibrium constant expressions were calculated as a function of temperature. Reasonable agreement was achieved between the calculated equilibrium constants and the available experimental values.

  14. A study to investigate phase transitions and nucleation kinetics of nickel and copper

    NASA Astrophysics Data System (ADS)

    Celik, F. A.; Yildiz, A. K.

    2016-04-01

    In this study, we investigate the homogeneous nucleation kinetics of copper and nickel system during cooling process using molecular dynamics simulation (MDS). The calculation is carried out for a different number of atoms consisting of 500, 2048, 8788 and 13,500 based on embedded atom method (EAM). It is observed that the melting points for the both model increases with increasing the size of systems (i.e. the number of atoms) as expected from Parrinello and Rahman MD method. The interfacial free energies and critical nucleus radius of nickel and copper are also determined by molecular dynamics, and the results are consistent with the classical nucleation theory. The structural development and phase transformation are also determined from the radial distribution function (RDF) and local bond orientational order parameters (LBOO).

  15. Investigation of electroreduction kinetics on modified p-InP in alkaline electrolyte

    SciTech Connect

    Cook, R.L.; Dempsey, P.P.; Sammells, A.F.

    1985-06-01

    The electroreduction kinetics of surface modified p-InP were investigated. The surface was modifie by electrodeposition of Co, Ru, Rh, Pt, Co/Pt, Ru/Pt, and Rh/Pt. Exchange current densities (i/sub 0/) for hydrogen evolution were obtained both in the dark and under 100 mW/cm/sub 2/ illumination. For sequentially deposited metals i/sub 0/ values are lower compared to individually deposited metals during hydrogen evolution. Cathodic currents observed positive of the hydrogen-evolution region can be explained by electron-transfer processes involving p-InP surface states. In this latter potential region, i/sub 0/ values are higher for the sequentially deposited metals.

  16. Kinetic investigation of microbial souring in porous media using microbial consortia from oil reservoirs.

    PubMed

    Chen, C I; Reinsel, M A; Mueller, R F

    1994-07-01

    Microbial souring (H2S production) in porous media was investigated in an anaerobic upflow porous media reactor at 60 degrees C using microbial consortia obtained from oil reservoirs. Multiple carbon sources (formate, acetate, propionate, iso- and n-butyrates) found in reservoir waters as well as sulfate as the electron acceptor was used. Kinetics and rates of souring in the reactor system were analyzed. Higher volumetric substrate consumption rates (organic acids and sulfate) and a higher volumetric H(2)S production rate were found at the from part of the reactor column after H(2)S production had stabilized. Concentration gradients for the substrates (organic acids and sulfate) and H(2)S were generated along the column. Biomass accumulation throughout the entire column was observed. The average specific sulfate reduction rate (H(2)S production rate) in the present reactor after H(2)S production had stabilized was calculated to be 11062 +/-2.22 mg sulfate-S/day g biomass.

  17. Kinetics of the E46Q mutant of photoactive yellow protein investigated by transient grating spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Cheolhee; Kim, Tae Wu; Kim, Youngmin; Choi, Jungkweon; Lee, Sang Jin; Ihee, Hyotcherl

    2017-09-01

    To elucidate the role of internal proton transfer in the photodynamics of photoactive yellow protein (PYP), the photocycle of the Glu46Gln mutant of PYP (E46Q-PYP) is investigated by transient grating (TG) spectroscopy. Compared with wild-type PYP (wt-PYP), the first spectrally blue-shifted intermediate of E46Q-PYP is formed more slowly, which is consistent with the absence of direct protonation from Glu46 residue, if the parallel kinetic model for wt-PYP is invoked. The smaller conformational change in E46Q-PYP, as manifested by the smaller change in the diffusion coefficient, mainly arises from the relatively larger volume of the ground state E46Q-PYP than wt-PYP rather than from the smaller volume of the pB state.

  18. Laboratory investigation of the role of desorption kinetics on americium transport associated with bentonite colloids.

    PubMed

    Dittrich, Timothy Mark; Boukhalfa, Hakim; Ware, Stuart Douglas; Reimus, Paul William

    2015-10-01

    Understanding the parameters that control colloid-mediated transport of radionuclides is important for the safe disposal of used nuclear fuel. We report an experimental and reactive transport modeling examination of americium transport in a groundwater-bentonite-fracture fill material system. A series of batch sorption and column transport experiments were conducted to determine the role of desorption kinetics from bentonite colloids in the transport of americium through fracture materials. We used fracture fill material from a shear zone in altered granodiorite collected from the Grimsel Test Site (GTS) in Switzerland and colloidal suspensions generated from FEBEX bentonite, a potential repository backfill material. The colloidal suspension (100 mg L(-1)) was prepared in synthetic groundwater that matched the natural water chemistry at GTS and was spiked with 5.5 × 10(-10) M (241)Am. Batch characterizations indicated that 97% of the americium in the stock suspension was adsorbed to the colloids. Breakthrough experiments conducted by injecting the americium colloidal suspension through three identical columns in series, each with mean residence times of 6 h, show that more than 95% of the bentonite colloids were transported through each of the columns, with modeled colloid filtration rates (k(f)) of 0.01-0.02 h(-1). Am recoveries in each column were 55-60%, and Am desorption rate constants from the colloids, determined from 1-D transport modeling, were 0.96, 0.98, and 0.91 h(-1) in the three columns, respectively. The consistency in Am recoveries and desorption rate constants in each column indicates that the Am was not associated with binding sites of widely-varying strengths on the colloids, as one binding site with fast kinetics represented the system accurately for all three sequential columns. Our data suggest that colloid-mediated transport of Am in a bentonite-fracture fill material system is unlikely to result in transport over long distance scales because

  19. Laboratory investigation of the role of desorption kinetics on americium transport associated with bentonite colloids

    SciTech Connect

    Dittrich, Timothy Mark; Boukhalfa, Hakim; Ware, Stuart Douglas; Reimus, Paul William

    2015-07-13

    Understanding the parameters that control colloid-mediated transport of radionuclides is important for the safe disposal of used nuclear fuel. We report an experimental and reactive transport modeling examination of americium transport in a groundwater–bentonite–fracture fill material system. A series of batch sorption and column transport experiments were conducted to determine the role of desorption kinetics from bentonite colloids in the transport of americium through fracture materials. We used fracture fill material from a shear zone in altered granodiorite collected from the Grimsel Test Site (GTS) in Switzerland and colloidal suspensions generated from FEBEX bentonite, a potential repository backfill material. The colloidal suspension (100 mg L–1) was prepared in synthetic groundwater that matched the natural water chemistry at GTS and was spiked with 5.5 × 10–10 M241Am. Batch characterizations indicated that 97% of the americium in the stock suspension was adsorbed to the colloids. Breakthrough experiments conducted by injecting the americium colloidal suspension through three identical columns in series, each with mean residence times of 6 h, show that more than 95% of the bentonite colloids were transported through each of the columns, with modeled colloid filtration rates (kf) of 0.01–0.02 h–1. Am recoveries in each column were 55–60%, and Am desorption rate constants from the colloids, determined from 1-D transport modeling, were 0.96, 0.98, and 0.91 h–1 in the three columns, respectively. The consistency in Am recoveries and desorption rate constants in each column indicates that the Am was not associated with binding sites of widely-varying strengths on the colloids, as one binding site with fast kinetics represented the system accurately for all three sequential columns. As a result, our data suggest that colloid-mediated transport of Am in a bentonite-fracture fill

  20. Laboratory investigation of the role of desorption kinetics on americium transport associated with bentonite colloids

    DOE PAGES

    Dittrich, Timothy Mark; Boukhalfa, Hakim; Ware, Stuart Douglas; ...

    2015-07-13

    Understanding the parameters that control colloid-mediated transport of radionuclides is important for the safe disposal of used nuclear fuel. We report an experimental and reactive transport modeling examination of americium transport in a groundwater–bentonite–fracture fill material system. A series of batch sorption and column transport experiments were conducted to determine the role of desorption kinetics from bentonite colloids in the transport of americium through fracture materials. We used fracture fill material from a shear zone in altered granodiorite collected from the Grimsel Test Site (GTS) in Switzerland and colloidal suspensions generated from FEBEX bentonite, a potential repository backfill material. Themore » colloidal suspension (100 mg L–1) was prepared in synthetic groundwater that matched the natural water chemistry at GTS and was spiked with 5.5 × 10–10 M241Am. Batch characterizations indicated that 97% of the americium in the stock suspension was adsorbed to the colloids. Breakthrough experiments conducted by injecting the americium colloidal suspension through three identical columns in series, each with mean residence times of 6 h, show that more than 95% of the bentonite colloids were transported through each of the columns, with modeled colloid filtration rates (kf) of 0.01–0.02 h–1. Am recoveries in each column were 55–60%, and Am desorption rate constants from the colloids, determined from 1-D transport modeling, were 0.96, 0.98, and 0.91 h–1 in the three columns, respectively. The consistency in Am recoveries and desorption rate constants in each column indicates that the Am was not associated with binding sites of widely-varying strengths on the colloids, as one binding site with fast kinetics represented the system accurately for all three sequential columns. As a result, our data suggest that colloid-mediated transport of Am in a bentonite-fracture fill material system is unlikely to result in transport over long

  1. Incubation behavior of silicon nanowire growth investigated by laser-assisted rapid heating

    SciTech Connect

    Ryu, Sang-gil; Kim, Eunpa; Grigoropoulos, Costas P.; Allen, Frances I.; Minor, Andrew M.; Hwang, David J.

    2016-08-15

    We investigate the early stage of silicon nanowire growth by the vapor-liquid-solid mechanism using laser-localized heating combined with ex-situ chemical mapping analysis by energy-filtered transmission electron microscopy. By achieving fast heating and cooling times, we can precisely determine the nucleation times for nanowire growth. We find that the silicon nanowire nucleation process occurs on a time scale of ∼10 ms, i.e., orders of magnitude faster than the times reported in investigations using furnace processes. The rate-limiting step for silicon nanowire growth at temperatures in the vicinity of the eutectic temperature is found to be the gas reaction and/or the silicon crystal growth process, whereas at higher temperatures it is the rate of silicon diffusion through the molten catalyst that dictates the nucleation kinetics.

  2. Incubation behavior of silicon nanowire growth investigated by laser-assisted rapid heating

    NASA Astrophysics Data System (ADS)

    Ryu, Sang-gil; Kim, Eunpa; Allen, Frances I.; Hwang, David J.; Minor, Andrew M.; Grigoropoulos, Costas P.

    2016-08-01

    We investigate the early stage of silicon nanowire growth by the vapor-liquid-solid mechanism using laser-localized heating combined with ex-situ chemical mapping analysis by energy-filtered transmission electron microscopy. By achieving fast heating and cooling times, we can precisely determine the nucleation times for nanowire growth. We find that the silicon nanowire nucleation process occurs on a time scale of ˜10 ms, i.e., orders of magnitude faster than the times reported in investigations using furnace processes. The rate-limiting step for silicon nanowire growth at temperatures in the vicinity of the eutectic temperature is found to be the gas reaction and/or the silicon crystal growth process, whereas at higher temperatures it is the rate of silicon diffusion through the molten catalyst that dictates the nucleation kinetics.

  3. Enantioselective Supramolecular Carriers for Nucleoside Drugs. A Thermodynamic and Kinetic Gas Phase Investigation

    NASA Astrophysics Data System (ADS)

    Fraschetti, Caterina; Filippi, Antonello; Crestoni, Maria Elisa; Villani, Claudio; Roselli, Graziella; Mortera, Stefano Levi; Speranza, Maurizio

    2012-10-01

    The enantioselective interactions between chiral tetra-amidic receptors and nucleosides have been investigated by the ESI-IT-MS and ESI-FT-ICR-MS methodologies. Configurational effects on the CID fragmentation of diastereomeric [ M H 2 •H•A] + aggregates (A = 2'-deoxycytidine dC, citarabine ( ara-C) were found to be mostly offset by isotope effect in [ S X 2 •H•A] + (X = H, D) differently from the results obtained on the analogues (A = cytidine C and gemcitabine G). This result points the involvement of two different nucleoside/tetraamide isoforms. The structural differences of the [ M H 2 •H•A] + (A = C and G) complexes vs. the [ M H 2 •H•A] + ( dC and ara-C) ones is fully confirmed by the kinetics of their uptake of the 2-aminobutane enantiomers, measured by FT-ICR mass spectrometry. Indeed, uptake of the 2-aminobutane enantiomers by [ M H n •H•A] + (n = 1,2; A = dC and ara-C) complexes is reversible, while that by [ M H n •H•A] + (n = 1,2; A = C and G) is not. The most encouraging result concerning the measured fragmentation and kinetic differences between C and ara-C, that are just epimers, indicates the possibility to subtly modulate the non-covalent drug/receptor interactions, through the electronic properties of the 2'-substituent on the nucleoside furanose ring, and furthermore on its three-dimensional position.

  4. The BioFilm Ring Test: a Rapid Method for Routine Analysis of Pseudomonas aeruginosa Biofilm Formation Kinetics

    PubMed Central

    Olivares, Elodie; Badel-Berchoux, Stéphanie; Provot, Christian; Jaulhac, Benoît; Prévost, Gilles; Bernardi, Thierry

    2015-01-01

    Currently, few techniques are available for the evaluation of bacterial biofilm adhesion. These detection tools generally require time for culture and/or arduous handling steps. In this work, the BioFilm Ring Test (BRT), a new technology, was used to estimate the biofilm formation kinetics of 25 strains of Pseudomonas aeruginosa, isolated from the sputum of cystic fibrosis (CF) patients. The principle of the new assay is based on the mobility measurement of magnetic microbeads mixed with a bacterial suspension in a polystyrene microplate. If free to move under the magnetic action, particles gather to a visible central spot in the well bottom. Therefore, the absence of spot formation in the plate reflects the bead immobilization by a biofilm in formation. The BRT device allowed us to classify the bacterial strains into three general adhesion profiles. Group 1 consists of bacteria, which are able to form a solid biofilm in <2 h. Group 2 comprises the strains that progressively set up a biofilm during 24 h. Lastly, group 3 includes the strains that stay in a planktonic form. The grouping of our strains did not differ according to culture conditions, i.e., the use of different sets of beads or culture media. The BRT is shown to be an informative tool for the characterization of biofilm-forming bacteria. Various application perspectives may be investigated for this device, such as the addition of antibiotics to the bacterial suspension to select which would have the ability to inhibit the biofilm formation. PMID:26719437

  5. CO{sub 2} adsorption: Experimental investigation with kinetics verification and CFD reactor model validation

    SciTech Connect

    Breault, Ronald W,; Huckaby, Ernest D.; Shadle, Lawrence J; Spenik, James L.

    2013-01-01

    The National Energy Technology Laboratory is investigating a new process for CO{sub 2} capture from large sources such as utility power generation facilities as an alternative to liquid amine based absorption processes. Many, but not all of these advanced dry processes are based upon sorbents composed of supported polyamines. In this analysis, experiments have been conducted in a small facility at different temperatures and compared to CFD reactor predictions using kinetics obtained from TGA tests. This particular investigation compares the predicted performance and the experimental performance of one of these new class of sorbents in a fluidized bed reactor. In the experiment, the sorbent absorbs CO{sub 2} from simulated flue gas in a riser reactor, separates the carbonated particles from the de-carbonated flue gas in a cyclone and then regenerates the sorbent, creating a concentrated stream of pure CO{sub 2} for sequestration. In this work, experimental measurements of adsorption are compared to predictions from a 3-dimensional non-isothermal reacting multiphase flow model. The effects of the gas flow rate and reactor temperature are explored. It is shown that the time duration for CO{sub 2} adsorption decreased for an increase in the gas flow. The details of the experimental facility and the model as well as the comparative analysis between the data and the simulation results are discussed.

  6. A kinetic investigation on the gas-phase reaction of ozone with four sesquiterpenes

    NASA Astrophysics Data System (ADS)

    Richters, Stefanie; Herrmann, Hartmut; Berndt, Torsten

    2014-05-01

    Sesquiterpenes (C15H24, SQT) are emitted by plants with a global emission rate of about 15 Tg per year (Seinfeld and Pankow, 2003). They are possibly an important source of secondary organic aerosol (SOA) but their oxidation processes are scarcely examined. This study focusses on the kinetics of the reaction of ozone with four atmospherically relevant SQT: β-caryophyllene, α-humulene, α-cedrene and isolongifolene. Up to now there are only two studies available in the literature describing kinetic measurements of the ozonolysis of a series of SQT, (Shu and Atkinson, 1994; Ghalaieny et al., 2012). As a result of these studies the rate coefficients of the ozone reaction with β-caryophyllene and α-humulene differ by three orders of magnitude making a reinvestigation necessary. Both literature studies were carried out in a reaction chamber with long reaction times. Shu and Atkinson (1994) used high concentrations of [SQT] = 2.4 • 1013 molecules cm-3 and [O3] = 2.5 • 1012 molecules cm-3 making particle formation and consecutive reactions relevant. The latter study of Ghalaieny et al. (2012) investigated the reaction at even higher concentrations ([SQT] = (2.1 - 3.5) • 1014 molecules cm-3, [O3] > 2.1 • 1015 molecules cm-3) at elevated temperatures (366 K) to avoid particle formation. Our study was carried out with very low SQT concentrations ((1 - 2) • 1010 molecules cm-3), [O3] = (1 - 15) • 1011 molecules cm-3, in a flow tube at atmospheric pressure and room temperature. The relative rate coefficients were investigated by means of an online GC-MS technique allowing measuring SQT concentrations down to 109 molecules cm-3. Particle formation was detected using an ultrafine condensed particle counter (TSI-3025 with a 50% cut-off size of 2.5 - 3 nm) and was found to be negligible under the chosen reaction conditions. Our study supports the rate coefficients as given by Shu and Atkinson (1994). References: J. H. Seinfeld and J. F. Pankow, Annu. Rev. Phys

  7. Rapid arsenite oxidation by Thermus aquaticus and Thermus thermophilus: Field and laboratory investigations

    USGS Publications Warehouse

    Gihring, T.M.; Druschel, G.K.; McCleskey, R.B.; Hamers, R.J.; Banfield, J.F.

    2001-01-01

    Thermus aquaticus and Thermus thermophilus, common inhabitants of terrestrial hot springs and thermally polluted domestic and industrial waters, have been found to rapidly oxidize arsenite to arsenate. Field investigations at a hot spring in Yellowstone National Park revealed conserved total arsenic transport and rapid arsenite oxidation occurring within the drainage channel. This environment was heavily colonized by Thermus aquaticus. In laboratory experiments, arsenite oxidation by cultures of Thermus aquaticus YT1 (previously isolated from Yellowstone National Park) and Thermus thermophilus HB8 was accelerated by a factor of over 100 relative to abiotic controls. Thermus aquaticus and Thermus thermophilus may therefore play a large and previously unrecognized role in determining arsenic speciation and bioavailability in thermal environments.

  8. The BioFilm Ring Test: a Rapid Method for Routine Analysis of Pseudomonas aeruginosa Biofilm Formation Kinetics.

    PubMed

    Olivares, Elodie; Badel-Berchoux, Stéphanie; Provot, Christian; Jaulhac, Benoît; Prévost, Gilles; Bernardi, Thierry; Jehl, François

    2016-03-01

    Currently, few techniques are available for the evaluation of bacterial biofilm adhesion. These detection tools generally require time for culture and/or arduous handling steps. In this work, the BioFilm Ring Test (BRT), a new technology, was used to estimate the biofilm formation kinetics of 25 strains of Pseudomonas aeruginosa, isolated from the sputum of cystic fibrosis (CF) patients. The principle of the new assay is based on the mobility measurement of magnetic microbeads mixed with a bacterial suspension in a polystyrene microplate. If free to move under the magnetic action, particles gather to a visible central spot in the well bottom. Therefore, the absence of spot formation in the plate reflects the bead immobilization by a biofilm in formation. The BRT device allowed us to classify the bacterial strains into three general adhesion profiles. Group 1 consists of bacteria, which are able to form a solid biofilm in <2 h. Group 2 comprises the strains that progressively set up a biofilm during 24 h. Lastly, group 3 includes the strains that stay in a planktonic form. The grouping of our strains did not differ according to culture conditions, i.e., the use of different sets of beads or culture media. The BRT is shown to be an informative tool for the characterization of biofilm-forming bacteria. Various application perspectives may be investigated for this device, such as the addition of antibiotics to the bacterial suspension to select which would have the ability to inhibit the biofilm formation. Copyright © 2016 Olivares et al.

  9. Investigation of intra-esophageal air kinetics and esophageal sphincters in patients with total laryngectomy during esophageal speech.

    PubMed

    Bozan, Aykut; Vardar, Rukiye; Akyildiz, Serdar; Kirazli, Tayfun; Ogut, Fatih; Yildirim, Esra; Bor, Serhat

    2015-08-01

    The purpose of this study was to evaluate the air kinetics of well- and poor-speaking patients and their upper (UES) and lower (LES) esophageal sphincter pressures . The esophageal speech capability of 23 total laryngectomy patients was assessed with the Wepman scale. LES and UES points and pressures were measured, and air kinetics were compared. All patients were male, with an average age of 58 years. Both the LES and UES pressures were not statistically different between good-speaking and poor-speaking patients (p > 0.05). The ability to speak was estimated only by looking at tracings. Good speakers are able to retain air successfully and on a long-term basis between the upper and lower esophageal sphincters. During short and/or rapid speech, these patients are able to rapidly suck and then expel the air from their upper esophagus. During long speeches, after sucking the air into their distal esophagus, they used the air in the upper part of the esophagus during the speech, only later seeming to fill the lower esophagus with the air as a possible reserve in the stomach. It has been shown that the basic requirement for speaking is the capacity to suck and store the air within the esophagus. For successful speech, the air should be stored inside the esophagus. MII technology contributes to our understanding of speech kinetics and occupies an important place in patient training as a biofeedback technique.

  10. In-depth investigation on the pyrolysis kinetics of raw biomass. Part I: kinetic analysis for the drying and devolatilization stages.

    PubMed

    Chen, Dengyu; Zheng, Yan; Zhu, Xifeng

    2013-03-01

    An in-depth investigation was conducted on the kinetic analysis of raw biomass using thermogravimetric analysis (TGA), from which the activation energy distribution of the whole pyrolysis process was obtained. Two different stages, namely, drying stage (Stage I) and devolatilization stage (Stage II), were shown in the pyrolysis process in which the activation energy values changed with conversion. The activation energy at low conversions (below 0.15) in the drying stage ranged from 10 to 30 kJ/mol. Such energy was calculated using the nonisothermal Page model, known as the best model to describe the drying kinetics. Kinetic analysis was performed using the distributed activation energy model in a wide range of conversions (0.15-0.95) in the devolatilization stage. The activation energy first ranged from 178.23 to 245.58 kJ/mol and from 159.66 to 210.76 kJ/mol for corn straw and wheat straw, respectively, then increasing remarkably with an irregular trend. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Micromodel Investigation of Transport Effect on the Kinetics of Reductive Dissolution of Hematite

    SciTech Connect

    Zhang, Changyong; Liu, Chongxuan; Shi, Zhi

    2013-03-13

    Reductive dissolution of hematite in porous media was investigated using a micromodel with realistic pore network structures that include distinctive advection domain, macro-pores and micro-pores created in silicon substrate. The micromodel pore surface was sputter deposited with a thin layer (230 nm) of hematite. The hematite in the micromodel was reduced by injecting pH-varying solutions containing a reduced form of flavin mononucleotide (FMNH2), a biogenic soluble electron transfer mediator produced by Shewanella species. The reduction kinetics was determined by measuring effluent Fe(II) concentration and by spectroscopically monitoring the hematite dissolution front in the micromodel. Batch experiment was also performed to estimate the hematite reduction rate under the well-mixed condition. The results showed a significant spatial variation in local redox reaction rate that was controlled by the coupled diffusion and reaction. The overall rate of the redox reaction in the micromodel required a three-domain numerical model to effectively describe with distinctive rate parameters in different pore domains. Results from this study demonstrated the important scaling effect when extrapolating geochemical or biogeochemical reaction rate from batch reactor to porous media and indicated a significant control of physical transport mechanisms on the reaction rate scaling.

  12. Investigation of the kinetics of reduction of nickel tungstate by hydrogen

    SciTech Connect

    Sridhar, S. . Dept. of Materials Science and Engineering); Du Sichen; Seetharaman, S. . Dept. of Metallurgy)

    1994-06-01

    In the present work, the kinetics of reduction of nickel tungstate, NiWO[sub 4], by hydrogen was investigated by a thermogravimetric method in the temperature range 891 to 1,141 K. The experiments were conducted under both isothermal and nonisothermal conditions. The products were examined by X-ray diffraction analysis. The results indicate that the reduction reaction proceeds in two steps; first, reduction of NiWO[sub 4] to nickel as well as WO[sub 2] and then WO[sub 2] to tungsten. From the isothermal experiments, the activation energies of the two reaction steps were calculated to be 95.3 [+-] 4.9 and 80.8 [+-] 6.4 kJ [center dot] mol[sup [minus]1], respectively. The activation energy value obtained from nonisothermal experiments for the first step is in agreement with the isothermal experiments. The values are compared with the activation energies reported in other literature for the individual oxides.

  13. Purification of lactoperoxidase from bovine whey and investigation of kinetic parameters

    PubMed Central

    Borzouee, Fatemeh; Mofid, Mohammad Reza; Varshosaz, Jaleh; Samsam Shariat, Seyed Ziyae Aldin

    2016-01-01

    Background: Lactoperoxidase (LPO) is related to mammalian peroxidase family which contains a wide spectrum of biological activities. Despite the wide studies on the LPO, there is little study has been performed to simplify and shorten the procedure of enzyme purification. The aim of this project was to purify the enzyme through a simple method, and investigating enzyme kinetic parameters. Materials and Methods: LPO was purified from bovine whey through modified method of Yoshida (1990) using two steps of ammonium sulfate precipitation and ion-exchange chromatography. The purity of isolated enzyme was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Results: The enzyme was purified 59.13-fold with a recovery of 10.26 having a specific activity of 5.78 U/mg protein and an Rz value of 0.8. The enzyme activity was measured using guaiacol as a chromogenic substrate in phosphate buffer pH 6. SDS-PAGE showed a single bond with molecular weight of 78 kDa. The purified enzyme displayed optimum activity at pH 6 in 30 mM phosphate buffer and at a temperature of 50°C, with a Km value of 178 mM and Vmax 0.63 U/ml.min for guaiacol. Conclusion: Using only one step ion-exchange chromatography, LPO was isolated from bovine whey in high purity. PMID:28028529

  14. Kinetic and spectral investigation of allosteric interaction of coenzymes with 2-oxo acid dehydrogenase complexes

    NASA Astrophysics Data System (ADS)

    Strumiło, S.; Czygier, M.; Kondracikowska, J.; Dobrzyń, P.; Czerniecki, J.

    2002-09-01

    The possible role of thiamine pyrophosphate (TPP) in the regulation of both multienzyme pyruvate dehydrogenase complex (PDC) and 2-oxoglutarate dehydrogenase complex (OGDC) has been investigated by kinetic and spectral methods. The purified PDC and OGDC from animal heart muscle were near saturated with endogenous TPP. The PDC containing the bound coenzyme showed hysteretic behaviour manifested in a lag phase of the catalysed reaction after the contact of PDC with substrates. Exogenous TPP added to the full reaction medium led to a disappearance of the lag phase and to strong reduction of the Michaelis constant ( Km) value for pyruvate, and more moderate decrease of Km for both coenzyme A and NAD. In the case of OGDC exogenous TPP also decreased S 0.5 ( Km) for substrate 2-oxoglutarate. In addition, exogenous TPP changed both the UV and circular dichroism spectra of PDC and last one of OGDC, and lowered the fluorescence emission of the multienzyme complexes containing bound molecules of endogenous coenzyme in their active sites. Thiamine pyrophosphate seems to play, besides its coenzyme function, the role of positive allosteric effector which causes conformational changes of the multienzyme complexes and increases their affinity to substrates.

  15. Survey of high-enthalpy shock facilities in the perspective of radiation and chemical kinetics investigations

    NASA Astrophysics Data System (ADS)

    Reynier, Philippe

    2016-08-01

    This contribution is a survey of the capabilities of the main facilities, shock-tubes, shock-tunnels, expansion tubes and hot-shots that allow the experimental investigation of chemical kinetics and radiation of hypersonic flows encountered during atmospheric entry. At first, the capabilities of the main facilities available in Australia, Asia, Europe, and United States, have been surveyed using the available literature, and the specific use of each facility identified. The second step of the study consists in an analysis of each type of shock facility to identify their advantages and drawbacks. The main objective of this analysis is to support a trade-off for the selection of the type of facility to be developed in order to give Europe a ground test with the capabilities to support future exploration and sample return missions. The last point of the study has been to identify the experimental datasets related to the targeted application, and to select the most attractive for the validation of the future facility.

  16. Kinetic investigation and lifetime prediction of Cs-NIPAM-MBA-based thermo-responsive hydrogels.

    PubMed

    Othman, Muhammad Bisyrul Hafi; Khan, Abbas; Ahmad, Zulkifli; Zakaria, Muhammad Razlan; Ullah, Faheem; Akil, Hazizan Md

    2016-01-20

    This study attempted to clarify the influence of a cross-linker, N,N-methylenebisacrylamide (MBA), and N-isopropylacrylamide (NIPAM) on the non-isothermal kinetic degradation, solid state and lifetime of hydrogels using the Flynn-Wall-Ozawa (F-W-O), Kissinger, and Coats-Redfern (C-Red) methods. The series of dual-responsive Cs-PNIPAM-MBA microgels were synthesized by soapless-emulsion free radical copolymerization in an aqueous medium at 70 °C. The thermal properties were investigated using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) under nitrogen atmosphere. The apparent activation energy using the chosen Flynn-Wall-Ozawa and Kissinger methods showed that they fitted each other. Meanwhile, the type of solid state mechanism was determined using the Coats-Redfern method proposed for F1 (pure Cs) and F2 (Cs-PNIPAM-MBA hydrogel series) types, which comprise random nucleation with one nucleus reacting on individual particles, and random nucleation with two nuclei reacting on individual particles, respectively. On average, a higher Ea was attributed to the greater cross-linking density of the Cs hydrogel. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Kinetic investigation of microbial souring in porous media using microbial consortia from oil reservoirs

    SciTech Connect

    Chen, C.I.; Reinsel, M.A.; Mueller, R.F. . National Science Foundation Engineering Research Center for Biofilm Engineering)

    1994-07-01

    Microbial souring (H[sub 2]S production) in porous media was investigated in an anaerobic upflow porous media reactor at 60 C using microbial consortia obtained from oil reservoirs. Multiple carbon sources (formate, acetate, propionate, iso and n-butyrates) found in reservoir waters as well as sulfate as the electron acceptor were used. Kinetics and rates of souring in the reactor system were analyzed. Higher volumetric substrate consumption rates (organic acids and sulfate) and a higher volumetric H[sub 2]S production rate were found at the front part of the reactor column after H[sub 2]S production had stabilized. Concentration gradients for the substrates (organic acids and sulfate) and H[sub 2]S were generated along the column. Biomass accumulation throughout the entire column was observed. The average specific sulfate reduction rate (H[sub 2]S production rate) in the present reactor after H[sub 2]S production had stabilized was calculated to be 11.62 [+-] 2.22 mg sulfate-S/day g biomass.

  18. Investigation of the combustion kinetics and polycyclic aromatic hydrocarbon emissions from polycaprolactone combustion.

    PubMed

    Chien, Y C; Yang, S H

    2013-01-01

    Polycaprolactone (PCL) is one of the most attractive biodegradable plastics that has been widely used in medicine and agriculture fields. Because of the large increase in biodegradable plastics usage, the production of waste biodegradable plastics will be increasing dramatically, producing a growing environmental problem. Generally, waste PCL is collected along with municipal solid wastes and then incinerated. This study investigates the combustion kinetics and emission factors of 16 US Environmental Protection Agency (EPA) priority polycyclic aromatic hydrocarbons (PAHs) in the PCL combustion. Experimentally, two reactions are involved in the PCL combustion process, possibly resulting in the emission of carbon dioxide, propanal, protonated caprolactone and very small amounts of PAH produced by incomplete combustion. The intermediate products may continuously be oxidized to form CO2. The emission factors for 16 US EPA priority PAHs are n.d. -2.95 microg/g, which are much lower than those of poly lactic acid and other plastics combustion. The conversion of PCL is 100%. Results from this work suggest that combustion is a good choice for the waste PCL disposal.

  19. Experimental investigation of magnetic-field-induced aggregation kinetics in nonaqueous ferrofluids.

    PubMed

    Laskar, Junaid M; Philip, John; Raj, Baldev

    2010-08-01

    We investigate the influence of field ramp rate on the kinetics of magnetic dipole-dipole induced chainlike structure formation in a nonaqueous nanoparticle dispersion using light scattering studies. With increase in magnetic field, at a constant ramp rate, the transmitted light intensity diminishes and the transmitted light spot is transformed to a diffused ring due to scattering from the self-assembled linear aggregates. The decay rate of transmitted intensity increases up to an optimum ramp rate, above which the trend becomes reverse. At an optimum ramp rate, the minimum time for initial aggregation coincides with the exposure time where the intensity decay is fastest. The variation of transmitted intensity at different ramp rate is explained on the basis of initial aggregation time that depends on Brownian motion, dipolar magnetic attraction and multibody hydrodynamic interactions. The slope of the transmitted light intensity after the removal of magnetic field depends on the time required for dissociation of ordered linear structures. Disappearance of the ring pattern and the reappearance of original light spot, upon removal of the magnetic field, confirm the perfect reversibility of the linear aggregates. The observed concentration dependant decay rates are in good agreement with aggregation theory.

  20. A kinetic Monte Carlo approach to investigate antibiotic translocation through bacterial porins

    NASA Astrophysics Data System (ADS)

    Ceccarelli, Matteo; Vargiu, Attilio V.; Ruggerone, Paolo

    2012-03-01

    Many relevant biological processes take place on time scales not reachable by standard all-atom computer simulations. The translocation of antibiotics through non-specific bacterial porins is an example. Microscopic effects compete to determine penetration routes and, consequently, free energy barriers to be overcome. Since bacteria can develop resistance to treatment also by reducing their antibiotic permeability, to understand the microscopic aspects of antibiotic translocation is an important step to rationalize drug design. Here, to investigate the translocation we propose a complete numerical model that combines the diffusion-controlled rate theory and a kinetic Monte Carlo scheme based on both experimental data and microscopically well-founded all-atom simulations. Within our model, an antibiotic translocating through an hour-glass-shaped channel can be described as a molecule moving on a potential of mean force featuring several affinity sites and a high central barrier. The implications of our results for the characterization of antibiotic translocation at in vivo concentrations are discussed. The presence of an affinity site close to the mouth of the channel seems to favor the translocation of antibiotics, the affinity site acting as a particle reservoir. Possible connections between results and the appearance of mutations in clinical strains are also outlined.

  1. Kinetic and thermodynamic investigation on ascorbate oxidase activity and stability of a Cucurbita maxima extract.

    PubMed

    Porto, Tatiana S; Porto, Camila S; Cavalcanti, Maria T H; Filho, José L Lima; Perego, Patrizia; Porto, Ana L F; Converti, Attilio; Pessoa, Adalberto

    2006-01-01

    The kinetic and thermodynamic properties of ascorbate oxidase (AO) activity and stability of a Cucurbita maxima extract were investigated. Activity tests performed at 25 degrees C using initial ascorbic acid concentration in the range 50-750 M allowed estimating the Michaelis constant for this substrate (Km = 126 microM) and the maximum initial rate of ascorbic acid oxidation (A0,max = 1.57 mM min-1). The main thermodynamic parameters of the enzyme reaction (DeltaH* = 10.3 kJ mol-1; DeltaG* = 87.2 kJ mol-1; DeltaS* = -258 J mol-1 K-1) were estimated through activity tests performed at 25-48 C. Within such a temperature range, no decrease in the initial reaction rate was detected. The long-term thermostability of the raw extract was then investigated by means of residual activity tests carried out at 10-70 degrees C, which allowed estimating the thermodynamic parameters of the irreversible enzyme inactivation as well (DeltaH*D = 51.7 kJ mol-1; DeltaG*D = 103 kJ mol-1; S*D = -160 J mol-1 K-1). Taking into account the specific rate of AO inactivation determined at different temperatures, we also estimated the enzyme half-life (1047 min at 10 degrees C and 21.2 min at 70 degrees C) and predicted the integral activity of a continuous system using this enzyme preparation. This work should be considered as a preliminary attempt to characterize the AO activity of a C. maxima extract before its concentration by liquid-liquid extraction techniques.

  2. In Situ Biospectroscopic Investigation of Rapid Ischemic and Postmortem Induced Biochemical Alterations in the Rat Brain

    PubMed Central

    2015-01-01

    Rapid advances in imaging technologies have pushed novel spectroscopic modalities such as Fourier transform infrared spectroscopy (FTIR) and X-ray absorption spectroscopy (XAS) at the sulfur K-edge to the forefront of direct in situ investigation of brain biochemistry. However, few studies have examined the extent to which sample preparation artifacts confound results. Previous investigations using traditional analyses, such as tissue dissection, homogenization, and biochemical assay, conducted extensive research to identify biochemical alterations that occur ex vivo during sample preparation. In particular, altered metabolism and oxidative stress may be caused by animal death. These processes were a concern for studies using biochemical assays, and protocols were developed to minimize their occurrence. In this investigation, a similar approach was taken to identify the biochemical alterations that are detectable by two in situ spectroscopic methods (FTIR, XAS) that occur as a consequence of ischemic conditions created during humane animal killing. FTIR and XAS are well suited to study markers of altered metabolism such as lactate and creatine (FTIR) and markers of oxidative stress such as aggregated proteins (FTIR) and altered thiol redox (XAS). The results are in accordance with previous investigations using biochemical assays and demonstrate that the time between animal death and tissue dissection results in ischemic conditions that alter brain metabolism and initiate oxidative stress. Therefore, future in situ biospectroscopic investigations utilizing FTIR and XAS must take into consideration that brain tissue dissected from a healthy animal does not truly reflect the in vivo condition, but rather reflects a state of mild ischemia. If studies require the levels of metabolites (lactate, creatine) and markers of oxidative stress (thiol redox) to be preserved as close as possible to the in vivo condition, then rapid freezing of brain tissue via decapitation into

  3. Rapid kinetics of iron responsive element (IRE) RNA/iron regulatory protein 1 and IRE-RNA/eIF4F complexes respond differently to metal ions

    PubMed Central

    Khan, Mateen A.; Ma, Jia; Walden, William E.; Merrick, William C.; Theil, Elizabeth C.; Goss, Dixie J.

    2014-01-01

    Metal ion binding was previously shown to destabilize IRE-RNA/IRP1 equilibria and enhanced IRE-RNA/eIF4F equilibria. In order to understand the relative importance of kinetics and stability, we now report rapid rates of protein/RNA complex assembly and dissociation for two IRE-RNAs with IRP1, and quantitatively different metal ion response kinetics that coincide with the different iron responses in vivo. kon, for FRT IRE-RNA binding to IRP1 was eight times faster than ACO2 IRE-RNA. Mn2+ decreased kon and increased koff for IRP1 binding to both FRT and ACO2 IRE-RNA, with a larger effect for FRT IRE-RNA. In order to further understand IRE-mRNA regulation in terms of kinetics and stability, eIF4F kinetics with FRT IRE-RNA were determined. kon for eIF4F binding to FRT IRE-RNA in the absence of metal ions was 5-times slower than the IRP1 binding to FRT IRE-RNA. Mn2+ increased the association rate for eIF4F binding to FRT IRE-RNA, so that at 50 µM Mn2+ eIF4F bound more than 3-times faster than IRP1. IRP1/IRE-RNA complex has a much shorter life-time than the eIF4F/IRE-RNA complex, which suggests that both rate of assembly and stability of the complexes are important, and that allows this regulatory system to respond rapidly to change in cellular iron. PMID:24728987

  4. Investigation of thermoluminescence and kinetic parameters of CaMgB2O5: Dy3+ nanophosphor

    NASA Astrophysics Data System (ADS)

    Manhas, M.; Kumar, Vinay; Ntwaeaborwa, O. M.; Swart, H. C.

    2016-05-01

    In this paper, thermoluminescence (TL) properties of Dy3+ (1.5 mol %) doped CaMgB2O5 nanophosphor after being exposed to ultraviolet (UV) radiations (λ=254nm) were investigated. In UV exposed samples, the thermoluminescence glow curve consists of a broad glow peak located at 380 K with a small shoulder at 507 K. A shift in glow peak temperature from 367 K to 380 K after the UV exposure for 80 min was observed, which clearly shows that glow peaks follow the second order kinetics. The TL intensity of the peaks increases with an increase in the exposure time of UV rays (10-180 min). The TL Anal program was used to analyze the glow curve. The kinetic parameters such as activation energy (E), the frequency factor (s) and the order of kinetics (b) were calculated for CaMgB2O5: Dy3+ nanophosphors.

  5. Investigation of the transition between hydrodynamic and kinetic regimes for DT exploding pushers at OMEGA and the NIF

    NASA Astrophysics Data System (ADS)

    Simpson, R.; Kabadi, N.; Frenje, J. A.; Gatu Johnson, M.; Li, C. K.; Seguin, F. H.; Sio, H.; Petrasso, R. D.; Rosenberg, M.; Betti, R.; Rinderknecht, H.; Nikroo, A.; Casey, D. T.; Kwan, T.; Simakov, A.; Atzeni, S.; Bellei, C.

    2016-10-01

    Previous experiments were conducted to study the transition from hydrodynamic-like to ion kinetic regimes for D3He exploding pushers, demonstrating the importance of an ion kinetic approach for formulating more robust predictions of implosion characteristics. This presentation details a series of planned experiments at the OMEGA Facility and the NIF using thin-glass exploding pushers with DT fuel. D and T ions have the same charge, unlike D and 3He, yet their masses are unaltered from the D and 3He case. This allows for the investigation of whether ion-thermal decoupling and species separation are largely a result of charge or mass. The initial gas fill pressure will be varied in order to scan the transition from strongly hydrodynamic to strongly kinetic implosions, while leveraging the expansive diagnostic suite developed at NIF and OMEGA. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

  6. Use of Digital Pens for Rapid Epidemiologic Data Collection During a Foodborne Outbreak Investigation.

    PubMed

    Mathewson, Abigail A; Daly, Elizabeth R; Cavallo, Steffany J; Alic, Adnela

    2015-08-01

    Public health investigations require rapid assessment, response, and initiation of control measures. In 2012, the New Hampshire Department of Health and Human Services used digital pens to rapidly acquire epidemiologic data during a gastrointestinal illness outbreak. Menus were obtained and a standard questionnaire was administered to exposed persons using digital pens. Questionnaire data were downloaded into an electronic file for analysis. Sixty-nine (74%) of 93 exposed persons completed a questionnaire. Of 6389 data entries made on digital paper, 218 (3%) required correction; of these, 201 (92%) involved a free-form variable and 17 (8%) involved a check-box variable. Digital pens saved an estimated 5 to 6 hours of data-entry time. This outbreak provided an opportunity to assess the value of digital pens for decreasing data-entry burden and allowing more timely data analysis in an emergent setting. Depending on the size of the outbreak and complexity of the survey, there is likely a threshold when use of digital pens would provide a clear benefit to outbreak response. As new technology becomes available for use in emergency preparedness settings, public health agencies must continuously review and update response plans and evaluate investigation tools to ensure timely disease control and response activities.

  7. A Preliminary Investigation of Rapid Depressurization Phenomena Following a Sudden DLOFC in a VHTR

    SciTech Connect

    Richard C. Martineau; Ray A. Berry; Dana A. Knoll

    2009-03-01

    Air ingress has been identified as a potential threat for Very High Temperature gas-cooled Reactors (VHTR). Reactor components constructed of graphite will, at high temperatures, produce exothermic reactions in the presence of oxygen. The danger lies in the possibility of fuel element damage and core structural failure. Previous investigations of air ingress mechanisms have focused on thermal and molecular diffusion, density-driven stratified flow, and natural convection. Here, we investigate the possibility of a rapid ingress of air due to a Taylor wave expansion after a hypothetical sudden loss of coolant accident (LOCA) scenario in a VHTR. Our analysis starts with a one-dimensional shock tube simulation to simply illustrate the development of a Taylor wave with resulting reentrant flow. Then, a simulation is performed of an idealized two-dimensional axisymmetric representation of the lower plenum of General Atomics GT-MHR subjected to a hypothetical catastrophic break of the hot duct. Analysis shows the potential for significant and rapid air ingress into the reactor vessel in the case of a large break in the cooling system.

  8. A Preliminary Investigation of Rapid Depressurization Phenomena Following a Sudden DLOFC in a VHTR

    SciTech Connect

    Richard C. Martineau; Ray A. Berry

    2010-05-01

    Air ingress has been identified as a potential threat for Very High Temperature gas-cooled Reactors (VHTR). Reactor components constructed of graphite will, at high temperatures, produce exothermic reactions in the presence of oxygen. The danger lies in the possibility of fuel element damage and core structural failure. Previous investigations of air ingress mechanisms have focused on thermal and molecular diffusion, density-driven stratified flow due to hydrodynamic instability, and natural convection. Here, we investigate the possibility of a rapid flow reversal of helium coolant due to a Taylor (rarefaction) wave expansion after a hypothetical sudden Depressurized Loss of Forced Cooling (DLOFC) scenario in a VHTR. Conceivably, flow reversal of the helium coolant could entrain significant quantities of air into the reactor vessel. Our analysis starts with a one-dimensional shock tube simulation to simply illustrate the development of a Taylor wave with resulting reentrant flow. Then, a simulation is performed of an idealized two-dimensional axisymmetric representation of the lower plenum of General Atomics GT-MHR subjected to a hypothetical catastrophic break of the hot duct. Analysis shows the potential for significant and rapid air ingress into the reactor vessel in the case of a large break in the cooling system.

  9. Very rapid virologic response and early HCV response kinetics, as quick measures to compare efficacy and guide a personalized response-guided therapy

    PubMed Central

    Yakoot, Mostafa; Abdo, Alaa M; Yousry, Ahmed; Helmy, Sherine

    2016-01-01

    Background This is the second and final report for our study designed to compare two generic sofosbuvir products for the degree and speed of virologic response to a dual anti-hepatitis C virus (HCV) treatment protocol. We aimed to test the applicability of the early virus response kinetics and the very rapid virologic response (vRVR) rate as quick outcome measures for accelerated comparative efficacy studies and as a foundation for a personalized response-guided therapy. Methods Fifty eligible chronic HCV patients were randomized to either one of two generic sofosbuvir products (Gratisovir or Grateziano) at a daily dose of one 400 mg tablet plus a weight-based ribavirin dose. Data were compared between the groups for early virus response kinetics and vRVR rates in relation to the rates of final sustained virologic response at week 12 posttreatment (SVR12). Results The Log10 transformed virus load (Log polymerase chain reaction) curves showed fairly similar rapid decline during the first 2 weeks, with no significant difference between the groups at four analysis points throughout the study by repeated-measures factorial analysis of variance test (P=0.48). The SVR12 rates were 96% (95% confidence interval, 79.6%–99.9%) in Gratisovir group (24/25) and 95.7% (95% confidence interval, 78%–99.9%) in Grateziano group (22/23). There was no statistically significant difference found by exact test (P>0.999). There was a significant association between the vRVR and the SVR12, with 100% positive predictive value (38/38 of those who had vRVR, achieved a final SVR12) and 82.6% sensitivity (among the total 46 with SVR12, 38 were having vRVR). Conclusion We can conclude from our study that the early HCV response kinetics and the vRVR rates could be used as sensitive quick markers for efficacy (with a very high positive predictive value for SVR12), based on our accelerated comparative efficacy research model. This might open the way for new models of accelerated equivalence

  10. Very rapid virologic response and early HCV response kinetics, as quick measures to compare efficacy and guide a personalized response-guided therapy.

    PubMed

    Yakoot, Mostafa; Abdo, Alaa M; Yousry, Ahmed; Helmy, Sherine

    2016-01-01

    This is the second and final report for our study designed to compare two generic sofosbuvir products for the degree and speed of virologic response to a dual anti-hepatitis C virus (HCV) treatment protocol. We aimed to test the applicability of the early virus response kinetics and the very rapid virologic response (vRVR) rate as quick outcome measures for accelerated comparative efficacy studies and as a foundation for a personalized response-guided therapy. Fifty eligible chronic HCV patients were randomized to either one of two generic sofosbuvir products (Gratisovir or Grateziano) at a daily dose of one 400 mg tablet plus a weight-based ribavirin dose. Data were compared between the groups for early virus response kinetics and vRVR rates in relation to the rates of final sustained virologic response at week 12 posttreatment (SVR12). The Log10 transformed virus load (Log polymerase chain reaction) curves showed fairly similar rapid decline during the first 2 weeks, with no significant difference between the groups at four analysis points throughout the study by repeated-measures factorial analysis of variance test (P=0.48). The SVR12 rates were 96% (95% confidence interval, 79.6%-99.9%) in Gratisovir group (24/25) and 95.7% (95% confidence interval, 78%-99.9%) in Grateziano group (22/23). There was no statistically significant difference found by exact test (P>0.999). There was a significant association between the vRVR and the SVR12, with 100% positive predictive value (38/38 of those who had vRVR, achieved a final SVR12) and 82.6% sensitivity (among the total 46 with SVR12, 38 were having vRVR). We can conclude from our study that the early HCV response kinetics and the vRVR rates could be used as sensitive quick markers for efficacy (with a very high positive predictive value for SVR12), based on our accelerated comparative efficacy research model. This might open the way for new models of accelerated equivalence efficacy studies along with the

  11. Investigation of the electrode kinetics in a solid oxide fuel cell and an oxygen sensor

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, Rajesh

    This dissertation investigates the electrode kinetics in a solid oxide fuel cell and an oxygen sensor. The first chapter describes the basics of fuel cell and motivation behind the studies. The second chapter investigates the dependence of cathodic charge transfer reaction resistance (Rct), on three-phase boundary length (lTPB) at various temperatures and oxygen partial pressures ( pO2 ). Impedance spectra were obtained using three-electrode configuration on discs having cathodes with definite lTPB to investigate the La0.8Sr0.2MnO3 (LSM)-Y 0.16Zr0.84O2 (YSZ), platinum (Pt)-YSZ and La 0.8Sr0.2CoO3 (LSC)-Ce0.8Sm0.2 O2 (SDC) half cell reactions at temperatures between 650--800°C and pO2 between 10-3 to 1 atm. For LSM-YSZ and Pt-YSZ, 1/Rct varies linearly with lTPB. LSC-SDC system did not show any specific dependence between R ct and lTPB. The third chapter examines the use of an electrolyte supported cell with externally applied voltage to determine the single electrode overpotential and extending the parameters derived to that of an anode supported fuel cell having thin film electrolyte operating under a chemical potential gradient. Spatial distributions of the electrochemical potential of electrons (ϕ) and oxygen ions ( m˜O-2 ), and chemical potential of oxygen ( mO2 ) for these two cases were obtained. Under fuel cell operating conditions, ϕ, m˜O-2 and mO2 , decreases monotonically from higher value to lower value. For electrolyte supported cell under externally applied voltage mO2 does not vary monotonically; it reaches values above or below that of the boundary values, leading to development of internal electromotive forces (EMFs), which can in turn affect the activity of the interface. The fourth chapter describes design microfabrication and characterization of a series connected potentiometric oxygen sensor. A drawback of potentiometric sensors in general is that the output signal is low when the ratio of the partial pressures at the two electrodes is low

  12. Investigation of Copper Ammonia Leaching from Smelter Slags: Characterization, Leaching and Kinetics

    NASA Astrophysics Data System (ADS)

    Bidari, Ehsan; Aghazadeh, Valeh

    2015-10-01

    Although ammonia leaching of copper from slags has been reported generally as a part of copper slag utilization methods, but no detailed studies have been reported in the literature. In this research, we tried to investigate the effect of different parameters on ammonia leaching of copper from copper smelting slag by identifying different copper-bearing phases and following them during leaching time. Mineralogical characterization of the smelting slag (1.7 pct Cu) was done using X-ray fluorescence, X-ray diffraction, optical microscopy, diagnostic leaching tests, and scanning electron microscopy. The characterization studies indicated that main copper-bearing species are soluble copper oxides and chalcocite along with minor amount of covellite, bornite, blister copper particles, and chalcopyrite. It was also found that only approximately 0.2 pct Cu was present in the insoluble bulk silicate phases. These results suggest that approximately 88 pct of the total copper of slag could be extracted by ammonia sulfide leaching. Leaching tests were carried out and the effects of various parameters, namely pH, ammonia concentration, temperature, presence of oxygen, stirring speed, and pulp density were examined on copper leaching. The temperature and stirring speed had the most pronounced effect on the copper leaching, whereas ammonia affected the leaching yield at low concentrations of ammonia. It was found that 78 pct of Cu could be extracted within 4 hours and under optimum conditions: T = 343 K (70 °C), 2M ammonia, pH 10.5, stirring speed = 900 rpm, pulp density = 10 pct ( w s/ v). The kinetic data were analyzed with the shrinking core models, and it was found that the leaching process is controlled by both the interfacial transfer and diffusion across the product layer and the activation energy is calculated to be 49.4 kJ mol-1.

  13. Ex-Situ Kinetic Investigations of the Formation of the Poly-Oxo Cluster U38.

    PubMed

    Falaise, Clément; Volkringer, Christophe; Hennig, Christoph; Loiseau, Thierry

    2015-11-09

    The ex-situ qualitative study of the kinetic formation of the poly-oxo cluster U38 , has been investigated after the solvothermal reaction. The resulting products have been characterized by means of powder XRD and scanning electron microscopy (SEM) for the solid phase and UV/Vis, X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and NMR spectroscopies for the supernatant liquid phase. The analysis of the different synthesis batches, stopped at different reaction times, revealed the formation of spherical crystallites of UO2 from t=3 h, after the formation of unknown solid phases at an early stage. The crystallization of U38 occurred from t=4 h at the expense of UO2 , and is completed after t=8 h. Starting from pure uranium(IV) species in solution (t=0-1 h), oxidation reactions are observed with a U(IV) /U(VI) ratio of 70:30 for t=1-3 h. Then, the ratio is inversed with a U(IV) /U(VI) ratio of 25/75, when the precipitation of UO2 occurs. Thorough SEM observations of the U38 crystallites showed that the UO2 aggregates are embedded within. This may indicate that UO2 acts as reservoir of uranium(IV), for the formation of U38 , stabilized by benzoate and THF ligands. During the early stages of the U38 crystallization, a transient crystallized phase appeared at t=4 h. Its crystal structure revealed a new dodecanuclear moiety (U12 ), based on the inner hexanuclear core of {U6 O8 } type, decorated by three additional pairs of dinuclear U2 units. The U12 motif is stabilized by benzoate, oxalates, and glycolate ligands.

  14. Purification of 6-phosphogluconate dehydrogenase from parsley (Petroselinum hortense) leaves and investigation of some kinetic properties.

    PubMed

    Demir, Hülya; Ciftçi, Mehmet; Küfrevioğlu, O Irfan

    2003-02-01

    In this study, 6-phosphogluconate dehydrogenase (E.C.1.1.44; 6PGD) was purified from parsley (Petroselinum hortense) leaves, and analysis of the kinetic behavior and some properties of the enzyme were investigated. The purification consisted of three steps that are preparation of homogenate ammonium sulfate fractionation and on DEAE-Sephadex A50 ion exchange. The enzyme was obtained with a yield of 49% and had a specific activity of 18.3 U (mg proteins)(-1) (Lehninger, A.L.; Nelson, D.L.; Cox, M.M. Principles of Biochemistry, 2nd Ed.; Worth Publishers Inc.: N.Y., 2000, 558-560). The overall purification was about 339-fold. A temperature of +4 degrees C was maintained during the purification process. Enzyme activity was spectrophotometrically measured according to the Beutler method at 340 mn. In order to control the purification of the enzyme, SDS-polyacrylamide gel electrophoresis was carried out in 4% and 10% acrylamide for stacking and running gel, respectively. SDS-polyacrylamide gel electrophoresis showed a single band for enzyme. The molecular weight was found to be 97.5 kDa by Sephadex G-150 gel filtration chromatography. A protein band corresponding to a subunit molecular weight of 24.1 kDa was obtained on SDS-polyacrylamide gel electrophoresis. For the enzymes, the stable pH, optimum pH, and optimum temperature were found as 8.0, 8.0, and 50 degrees C, respectively. In addition, KM and Vmax values for NADP+ and G6-P at optimum pH and 25 degrees C were determined by means of Lineweaver-Burk plots.

  15. The nature of the intermediates in the reactions of Fe(III)- and Mn(III)-microperoxidase-8 with H(2)O(2): a rapid kinetics study.

    PubMed

    Primus, Jean-Louis; Grunenwald, Sylvie; Hagedoorn, Peter-Leon; Albrecht-Gary, Anne-Marie; Mandon, Dominique; Veeger, Cees

    2002-02-20

    Kinetic studies were performed with microperoxidase-8 (Fe(III)MP-8), the proteolytic breakdown product of horse heart cytochrome c containing an octapeptide linked to an iron protoporphyrin IX. Mn(III) was substituted for Fe(III) in Mn(III)MP-8. The mechanism of formation of the reactive metal-oxo and metal-hydroperoxo intermediates of M(III)MP-8 upon reaction of H(2)O(2) with Fe(III)MP-8 and Mn(III)MP-8 was investigated by rapid-scan stopped-flow spectroscopy and transient EPR. Two steps (k(obs1) and k(obs2)) were observed and analyzed for the reaction of hydrogen peroxide with both catalysts. The plots of k(obs1) as function of [H(2)O(2)] at pH 8.0 and pH 9.1 for Fe(III)MP-8, and at pH 10.2 and pH 10.9 for Mn(III)MP-8, exhibit saturation kinetics, which reveal the accumulation of an intermediate. Double reciprocal plots of 1/k(obs1) as function of 1/[H(2)O(2)] at different pH values reveal a competitive effect of protons in the oxidation of M(III)MP-8. This effect of protons is confirmed by the linear dependence of 1/k(obs1) on [H(+)] showing that k(obs1) increases with the pH. The UV-visible spectra of the intermediates formed at the end of the first step (k(obs1)) exhibit a spectrum characteristic of a high-valent metal-oxo intermediate for both catalysts. Transient EPR of Mn(III)MP-8 incubated with an excess of H(2)O(2), at pH 11.5, shows the detection of a free radical signal at g approximately equal to 2 and of a resonance at g approximately equal to 4 characteristic of a Mn(IV) (S = 3/2) species. On the basis of these results, the following mechanism is proposed: (i) M(III)MP-8-OH(2) is deprotonated to M(III)MP-8-OH in a rapid preequilibrium step, with a pK(a) = 9.2 +/- 0.9 for Fe(III)MP-8 and a pK(a) = 11.2 +/- 0.3 for Mn(III)MP-8; (ii) M(III)MP-8-OH reacts with H(2)O(2) to form Compound 0, M(III)MP8-OOH, with a second-order rate constant k(1) = (1.3 +/- 0.6) x 10(6) M(-1) x s(-1) for Fe(III)MP-8 and k(1) = (1.6 +/- 0.9) x 10(5) M(-1) x s(-1) for Mn

  16. An investigation of the kinetics for hydrogen chemisorption on iron metal surfaces

    NASA Technical Reports Server (NTRS)

    Shanabarger, M. R.

    1980-01-01

    A quasi-isothermal approach was used to study the kinetics of hydrogen and hydrogen sulfide chemisorption onto iron film in an effort to understand the environmental degradation of steels. The coverage of chemisorbed hydrogen or chemisorbed sulfur was observed as a function of time for fixed conditions of substrate temperature. Auger electron spectroscopy was used to observe the sulfur and chemisorption-induced resistance change was employed to monitor hydrogen coverage. To compare the results obtained from studying the kinetics by two different techniques, the kinetics of oxygen chemisorption onto iron films was also studied. A reaction model utilized to interpret the H2/Fe2 chemisorption kinetics was applied to data from an earlier study on the desorption kinetics for H2 chemisorbed onto nicket films in the vicinity of the Curie temperature of the film. This analysis permitted a separation of the gross desorption process into individual components so that the influence of the magnetic phase transition on the rate constants could be determined.

  17. An investigation on the modelling of kinetics of thermal decomposition of hazardous mercury wastes.

    PubMed

    Busto, Yailen; M G Tack, Filip; Peralta, Luis M; Cabrera, Xiomara; Arteaga-Pérez, Luis E

    2013-09-15

    The kinetics of mercury removal from solid wastes generated by chlor-alkali plants were studied. The reaction order and model-free method with an isoconversional approach were used to estimate the kinetic parameters and reaction mechanism that apply to the thermal decomposition of hazardous mercury wastes. As a first approach to the understanding of thermal decomposition for this type of systems (poly-disperse and multi-component), a novel scheme of six reactions was proposed to represent the behaviour of mercury compounds in the solid matrix during the treatment. An integration-optimization algorithm was used in the screening of nine mechanistic models to develop kinetic expressions that best describe the process. The kinetic parameters were calculated by fitting each of these models to the experimental data. It was demonstrated that the D₁-diffusion mechanism appeared to govern the process at 250°C and high residence times, whereas at 450°C a combination of the diffusion mechanism (D₁) and the third order reaction mechanism (F3) fitted the kinetics of the conversions. The developed models can be applied in engineering calculations to dimension the installations and determine the optimal conditions to treat a mercury containing sludge.

  18. Experimental investigation of ≈130 keV kinetic energy antiprotons annihilation on nuclei

    NASA Astrophysics Data System (ADS)

    Aghai-Khozani, H.; Barna, D.; Corradini, M.; Hayano, R.; Hori, M.; Kobayashi, T.; Leali, M.; Lodi-Rizzini, E.; Mascagna, V.; Prest, M.; Soter, A.; Todoroki, K.; Vallazza, E.; Venturelli, L.; Zurlo, N.

    2014-04-01

    The study of the antiproton ( bar {p}) annihilation cross section on nuclei at low energies (eV-MeV region) has implications for fundamental cosmology as well as for nuclear physics. Concerning the former, different models try to explain the matter/antimatter asymmetry in the universe assuming the existence of the so-called "islands" where antinucleon-nucleon annihilations occur in the border region (Cohen et al. Astrophys. J. 495, 539-549, 1998), while, from the nuclear physics point of view, the annihilation process is a valuable tool to evaluate the neutron/proton ratio in order to probe the external region of the nucleus (Gupta et al. Nucl. Phys. B 70(3), 414-424, 1974). The existing data of antinucleon-nucleon (or -nucleus) annihilation cross-sections are mainly confined to energies above ≈1 MeV, while the cross section measured at LEAR in the 80's-90's (mostly with light targets Agnello et al. Phys. Lett. B 256, 349-353, 1991; Bertin et al. Phys. Lett. B 369, 77-85, 1996; Bertin et al. Phys. Lett. B 414, 220-228, 1997; Zenoni et al. Phys. Lett. B 461, 405-412, 1999; Bianconi et al. Phys. Lett. B 481, 194-198, 2000; Bianconi et al. Phys. Lett. B 492, 254-258, 2000) showed an unexpected behaviour for energies below 1 MeV (Bianconi et al. Phys. Lett. B 483, 353-359, 2000; Bianconi et al. Phys. Rev. C 62, 014611-7, 2000; Batty et al. Nucl. Phys. A 689, 721-740, 2001). The results showed a saturation with the atomic mass number against the A 2/3 trend which is observed for higher energies (being A the target mass number). The ASACUSA collaboration at CERN recently measured antiproton annihilation cross section on different kinds of nuclei with a bar {p} kinetic energy of 5.3 MeV (Bianconi et al. Phys. Lett. B 704, 461-466, 2011; Corradini et al. Nucl. Instr. Methods A 711, 12-20, 2013). Such results proved compatibility with the black-disk model with the Coulomb correction. But till now experimental difficulties prevented the investigation at energies below ≈1

  19. Kinetic study for phenol degradation by ZVI-assisted Fenton reaction and related iron corrosion investigated by X-ray absorption spectroscopy.

    PubMed

    Yoon, In-Ho; Yoo, Gursong; Hong, Hye-Jin; Kim, Jungmin; Kim, Min Gyu; Choi, Wang-Kyu; Yang, Ji-Won

    2016-02-01

    In this study, we investigated phenol degradation via zero-valent iron (ZVI)-assisted Fenton reaction through kinetic and spectroscopic analysis. In batch experiments, 100 mg/L of phenol was completely degraded, and 75% of TOC was removed within 3 min under an optimal hydrogen peroxide (H2O2) concentration (50 mM) via the Fenton reaction. In the absence of H2O2, oxygen (O2) was dissolved into the solution and produced H2O2, which resulted in phenol degradation. However, phenol removal efficiency was not very high compared to external H2O2 input. The Fenton reaction rapidly occurred at the surface of ZVI, and then phenol mobility from the solution to the ZVI surface was the rate determining step of the whole reaction. The pseudo-second order adsorption kinetic model well describes phenol removal, and its rate increased according to the H2O2 concentration. X-ray absorption spectroscopic analysis revealed that iron oxide (Fe-O bonding) was formed on ZVI with [H2O2] > 50 mM. A high concentration of H2O2 led to rapid degradation of phenol and caused corrosion on the ZVI surface, indicating that Fe(2+) ions were rapidly oxidized to Fe(3+) ions due to the Fenton reaction and that Fe(3+) was precipitated as iron oxide on the ZVI surface. However, ZVI did not show corroded characteristics in the absence of H2O2 due to the insufficient ZVI-assisted Fenton reaction and oxidation of Fe(2+) to Fe(3+).

  20. CP: AN INVESTIGATION OF COEFFICIENT OF THERMAL EXPANSION, DECOMPOSITION KINETICS, AND REACTION TO VARIOUS STIMULI

    SciTech Connect

    Weese, R K; Burnham, A K; Fontes, A T

    2005-03-23

    The properties of pentaamine (5-cyano-2H-tetrazolato-N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook-off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear heating rates, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 10,000 psi and analyzed over a dynamic temperature range of -20 C to 70 C. Using differential scanning calorimetry, DSC, CP was decomposed at linear heating rates of 1, 3, and 7 C/min and the kinetic triplet calculated using the LLNL code Kinetics05. Values are also reported for spark, friction, and impact sensitivity.

  1. Molecular mechanism of promoter selection in gene transcription. I. Development of a rapid mixing-photocrosslinking technique to study the kinetics of Escherichia coli RNA polymerase binding to T7 DNA.

    PubMed

    Park, C S; Hillel, Z; Wu, C W

    1982-06-25

    A combined rapid mixing-photocrosslinking technique has been developed to investigate the kinetics of the interaction between Escherichia coli RNA polymerase and T7 DNA. The reactants were rapidly mixed in a modified Durrum stopped-flow apparatus, and the intermediates formed at different stages of the binding process were "frozen" by photocrosslinking with a UV light pulse of 10-mus duration at various times after mixing. The results indicate that the initial binding between RNA polymerase and T7 DNA is a diffusion-controlled reaction. Furthermore, the extents of initial contracts with DNA made with the beta, beta', and sigma subunits of RNA polymerase are roughly proportional to the sizes of these subunits, suggesting that complex formation occurs through random collision between the two reactants. After the initial complex formation, the rate of transfer of polymerase between individual DNA molecules is slow, implying that the polymerase molecules are undergoing predominantly intramolecular transfer during the promoter search. From the kinetic studies of subunit-DNA contacts during RNA polymerase binding to T7 DNA, it can be inferred that the beta, beta', and sigma subunits are directly participating in the promoter search process.

  2. The development of an experimental facility and investigation of rapidly maneuvering Micro-Air-Vehicle wings

    NASA Astrophysics Data System (ADS)

    Wilson, Lee Alexander

    Vertical Takeoff-and-Landing (VTOL) Micro Air Vehicles (MAVs) provide a versatile operational platform which combines the capabilities of fixed wing and rotary wing MAVs. In order to improve performance of these vehicles, a better understanding of the rapid transition between horizontal and vertical flight is required. This study examines the flow structures around the Mini-Vertigo VTOL MAV using flow visualization techniques. This will gives an understanding of the flow structures which dominate the flight dynamics of rapid pitching maneuvers. This study consists of three objectives: develop an experimental facility, use flow visualization to investigate the flow around the experimental subject during pitching, and analyze the results. The flow around the Mini-Vertigo VTOL MAV is dominated by the slipstream from its propellers. The slipstream delays LE separation and causes drastic deflection in the flow. While the frequency of the vortices shed from the LE and TE varies with flow speed, the non-dimensional frequency does not. It does, however, vary slightly with the pitching rate. These results are applicable across a wide range of flight conditions. The results correlate to previous research done to examine the aerodynamic forces on the MAV.

  3. Investigation of rapidly solidified aluminum by using diamond turning and a magnetorheological finishing process

    NASA Astrophysics Data System (ADS)

    Cheng, Yuan-Chieh; Hsu, Wei-Yao; Kuo, Ching-Hsiang; Abou-El-Hossein, Khaled; Otieno, Timothy

    2015-08-01

    The metal mirror has been widely used in optical application for a longtime. Especially the aluminum 6061 is often considered the preferred material for manufacturing optical components for ground-based astronomical applications. One reason for using this material is its high specific stiffness and excellent thermal properties. However, a large amount of data exists for this material and commercially available aluminum 6061 using single point diamond turning (SPDT) and polishing process can achieve surface roughness values of approximately 2 to 4 nm, which is adequate for applications that involve the infrared spectral range, but not for the shorter spectral range. A novel aluminum material, fabricated using a rapid solidification process that is equivalent to the conventional aluminum 6061 alloy grade has been used in optical applications in recent years because of its smaller grain size. In this study, the surface quality of the rapid solidification aluminum after single point diamond turning and followed by magnetorheological finish (MRF) process is investigated and compared with conventional aluminum 6061. Both the surface roughness Ra was evaluated using white light interferometers. Finally, indicators such as optimal fabrication parameter combination and optical performance are discussed.

  4. Investigating the feasibility of rapid MRI for image-guided motion management in lung cancer radiotherapy.

    PubMed

    Sawant, Amit; Keall, Paul; Pauly, Kim Butts; Alley, Marcus; Vasanawala, Shreyas; Loo, Billy W; Hinkle, Jacob; Joshi, Sarang

    2014-01-01

    Cycle-to-cycle variations in respiratory motion can cause significant geometric and dosimetric errors in the administration of lung cancer radiation therapy. A common limitation of the current strategies for motion management is that they assume a constant, reproducible respiratory cycle. In this work, we investigate the feasibility of using rapid MRI for providing long-term imaging of the thorax in order to better capture cycle-to-cycle variations. Two nonsmall-cell lung cancer patients were imaged (free-breathing, no extrinsic contrast, and 1.5 T scanner). A balanced steady-state-free-precession (b-SSFP) sequence was used to acquire cine-2D and cine-3D (4D) images. In the case of Patient 1 (right midlobe lesion, ~40 mm diameter), tumor motion was well correlated with diaphragmatic motion. In the case of Patient 2, (left upper-lobe lesion, ~60 mm diameter), tumor motion was poorly correlated with diaphragmatic motion. Furthermore, the motion of the tumor centroid was poorly correlated with the motion of individual points on the tumor boundary, indicating significant rotation and/or deformation. These studies indicate that image quality and acquisition speed of cine-2D MRI were adequate for motion monitoring. However, significant improvements are required to achieve comparable speeds for truly 4D MRI. Despite several challenges, rapid MRI offers a feasible and attractive tool for noninvasive, long-term motion monitoring.

  5. Using the Deepwater Horizon Disaster to Investigate Natural Biogeochemical Cycling Associated with Rapid Methane Emissions (Invited)

    NASA Astrophysics Data System (ADS)

    Kessler, J. D.; Valentine, D. L.; Yvon-Lewis, S. A.; Heintz, M. B.; Hu, L.; Garcia Tigreros, F.; Du, M.; Chan, E. W.

    2010-12-01

    On April 20, a violent methane discharge severed the Deepwater Horizon rig from its well and oil and gas began spilling into the deep Gulf of Mexico at depths of ca. 1.5 km simulating a natural, rapid, and short-term methane release in deepwater. Given the estimated rates of emission of total material as well as the fraction methane by weight, one can estimate that a total of 0.1 to 0.3 Tg (10^12 g) of methane were emitted from a localized area in only 83 days. Measurements of methane oxidation and sea-air methane flux were measured in June indicating that at that time, oxidation rates were slow and sea-air fluxes were relatively insignificant. A deepwater methane plume was identified and in June 2010, the depth of the methane plume was on average from 950 - 1150 m with the maximum methane concentration measured being 183 μM. Analyses of diffusion, advective mixing, and methane oxidation were used to estimate that this plume has a lifetime of years to decades with the main controlling factor being the rate of methane oxidation. The persistent nature of this deepwater methane plume allows it to be used as a natural laboratory to investigate key hypotheses concerning the biogeochemical cycling of methane and oxygen associated with rapid, short-term methane discharges.

  6. Investigating rapid eye movement sleep without atonia in Parkinson's disease using the rapid eye movement sleep behavior disorder screening questionnaire.

    PubMed

    Bolitho, Samuel J; Naismith, Sharon L; Terpening, Zoe; Grunstein, Ron R; Melehan, Kerri; Yee, Brendon J; Coeytaux, Alessandra; Gilat, Moran; Lewis, Simon J G

    2014-05-01

    Rapid eye movement (REM) sleep behavior disorder (RBD) is frequently observed in patients with Parkinson's disease (PD). Accurate diagnosis is essential for managing this condition. Furthermore, the emergence of idiopathic RBD in later life can represent a premotor feature, heralding the development of PD. Reliable, accurate methods for identifying RBD may offer a window for early intervention. This study sought to identify whether the RBD screening questionnaire (RBDSQ) and three questionnaires focused on dream enactment were able to correctly identify patients with REM without atonia (RWA), the neurophysiological hallmark of RBD. Forty-six patients with PD underwent neurological and sleep assessment in addition to completing the RBDSQ, the RBD single question (RBD1Q), and the Mayo Sleep Questionnaire (MSQ). The REM atonia index was derived for all participants as an objective measure of RWA. Patients identified to be RBD positive on the RBDSQ did not show increased RWA on polysomnography (80% sensitivity and 55% specificity). However, patients positive for RBD on questionnaires specific to dream enactment correctly identified higher degrees of RWA and improved the diagnostic accuracy of these questionnaires. This study suggests that the RBDSQ does not accurately identify RWA, essential for diagnosing RBD in PD. Furthermore, the results suggest that self-report measures of RBD need to focus questions on dream enactment behavior to better identify RWA and RBD. Further studies are needed to develop accurate determination and quantification of RWA in RBD to improve management of patients with PD in the future.

  7. Rapid three-dimensional microfluidic mixer for high viscosity solutions to unravel earlier folding kinetics of G-quadruplex under molecular crowding conditions.

    PubMed

    Liu, Chao; Li, Ying; Li, Yiwei; Chen, Peng; Feng, Xiaojun; Du, Wei; Liu, Bi-Feng

    2016-01-01

    Rapid mixing of highly viscous solutions is a great challenge, which helps to analyze the reaction kinetics in viscous liquid phase, particularly to discover the folding kinetics of macromolecules under molecular crowding conditions mimicking the conditions inside cells. Here, we demonstrated a novel microfluidic mixer based on Dean flows with three-dimensional (3D) microchannel configuration for fast mixing of high-viscosity fluids. The main structure contained three consecutive subunits, each consisting of a "U"-type channel followed by a chamber with different width and height. Thus, the two solutions injected from the two inlets would undergo a mixing in the first "U"-type channel due to the Dean flow effect, and simultaneous vortices expansions in both horizontal and vertical directions in the following chamber. Numerical simulations and experimental characterizations confirmed that the micromixer could achieve a mixing time of 122.4μs for solutions with viscosities about 33.6 times that of pure water. It was the fastest micromixer for high viscosity solutions compared with previous reports. With this highly efficient 3D microfluidic mixer, we further characterized the early folding kinetics of human telomere G-quadruplex under molecular crowding conditions, and unravelled a new folding process within 550μs.

  8. Investigation of ion kinetic effects in direct-drive exploding-pusher implosions at the NIF

    SciTech Connect

    Rosenberg, M. J. Zylstra, A. B.; Séguin, F. H.; Rinderknecht, H. G.; Frenje, J. A.; Gatu Johnson, M.; Sio, H.; Waugh, C. J.; Sinenian, N.; Li, C. K.; Petrasso, R. D.; McKenty, P. W.; Hohenberger, M.; Radha, P. B.; Delettrez, J. A.; Glebov, V. Yu.; Betti, R.; Goncharov, V. N.; Knauer, J. P.; Sangster, T. C.; and others

    2014-12-15

    Measurements of yield, ion temperature, areal density (ρR), shell convergence, and bang time have been obtained in shock-driven, D{sub 2} and D{sup 3}He gas-filled “exploding-pusher” inertial confinement fusion (ICF) implosions at the National Ignition Facility to assess the impact of ion kinetic effects. These measurements probed the shock convergence phase of ICF implosions, a critical stage in hot-spot ignition experiments. The data complement previous studies of kinetic effects in shock-driven implosions. Ion temperature and fuel ρR inferred from fusion-product spectroscopy are used to estimate the ion-ion mean free path in the gas. A trend of decreasing yields relative to the predictions of 2D DRACO hydrodynamics simulations with increasing Knudsen number (the ratio of ion-ion mean free path to minimum shell radius) suggests that ion kinetic effects are increasingly impacting the hot fuel region, in general agreement with previous results. The long mean free path conditions giving rise to ion kinetic effects in the gas are often prevalent during the shock phase of both exploding pushers and ablatively driven implosions, including ignition-relevant implosions.

  9. Investigation of Coal-biomass Catalytic Gasification using Experiments, Reaction Kinetics and Computational Fluid Dynamics

    SciTech Connect

    Battaglia, Francine; Agblevor, Foster; Klein, Michael; Sheikhi, Reza

    2015-12-31

    A collaborative effort involving experiments, kinetic modeling, and computational fluid dynamics (CFD) was used to understand co-gasification of coal-biomass mixtures. The overall goal of the work was to determine the key reactive properties for coal-biomass mixed fuels. Sub-bituminous coal was mixed with biomass feedstocks to determine the fluidization and gasification characteristics of hybrid poplar wood, switchgrass and corn stover. It was found that corn stover and poplar wood were the best feedstocks to use with coal. The novel approach of this project was the use of a red mud catalyst to improve gasification and lower gasification temperatures. An important results was the reduction of agglomeration of the biomass using the catalyst. An outcome of this work was the characterization of the chemical kinetics and reaction mechanisms of the co-gasification fuels, and the development of a set of models that can be integrated into other modeling environments. The multiphase flow code, MFIX, was used to simulate and predict the hydrodynamics and co-gasification, and results were validated with the experiments. The reaction kinetics modeling was used to develop a smaller set of reactions for tractable CFD calculations that represented the experiments. Finally, an efficient tool was developed, MCHARS, and coupled with MFIX to efficiently simulate the complex reaction kinetics.

  10. An investigation of the kinetics of hydrogen chemisorption on iron metal surfaces

    NASA Technical Reports Server (NTRS)

    Shanabarger, M. R.

    1982-01-01

    The isothermal kinetics of H2, H2S, and O2 chemisorption onto epitaxially grown (III) oriented Fe films were studied. The measurements were made using the techniques of chemisorption induced resistance change and Auger electron spectroscopy (for adsorbed sulfur and oxygen). Also the origin of the chemisorption induced resistance change for these systems and its applicability to kinetic measurements were established. The chemisorption kinetics were interpreted as dissociative chemisorption via an adsorbed molecular species. The applicable rate constants were established. In none of the studies were the rate constants observed to be coverage dependent. By comparing the temperature dependence of the rate constants with absolute rate theory, the binding energies and activation energies of all the kinetic processes were obtained for the H2/Fe system. The initial sticking coefficient was pressure dependent for both the H2/Fe and H2S/Fe systems. This results from the step between the adsorbed molecular state and the dissociated chemisorbed state being the rate limiting step for absorption at certain pressures and temperatures. Estimates were obtained for the temperature dependence of the rate constants for the O2/Fe system.

  11. Investigation of ion kinetic effects in direct-drive exploding-pusher implosions at the NIF

    NASA Astrophysics Data System (ADS)

    Rosenberg, M. J.; Zylstra, A. B.; Séguin, F. H.; Rinderknecht, H. G.; Frenje, J. A.; Gatu Johnson, M.; Sio, H.; Waugh, C. J.; Sinenian, N.; Li, C. K.; Petrasso, R. D.; McKenty, P. W.; Hohenberger, M.; Radha, P. B.; Delettrez, J. A.; Glebov, V. Yu.; Betti, R.; Goncharov, V. N.; Knauer, J. P.; Sangster, T. C.; LePape, S.; Mackinnon, A. J.; Pino, J.; McNaney, J. M.; Rygg, J. R.; Amendt, P. A.; Bellei, C.; Benedetti, L. R.; Berzak Hopkins, L.; Bionta, R. M.; Casey, D. T.; Divol, L.; Edwards, M. J.; Glenn, S.; Glenzer, S. H.; Hicks, D. G.; Kimbrough, J. R.; Landen, O. L.; Lindl, J. D.; Ma, T.; MacPhee, A.; Meezan, N. B.; Moody, J. D.; Moran, M. J.; Park, H.-S.; Remington, B. A.; Robey, H.; Rosen, M. D.; Wilks, S. C.; Zacharias, R. A.; Herrmann, H. W.; Hoffman, N. M.; Kyrala, G. A.; Leeper, R. J.; Olson, R. E.; Kilkenny, J. D.; Nikroo, A.

    2014-12-01

    Measurements of yield, ion temperature, areal density (ρR), shell convergence, and bang time have been obtained in shock-driven, D2 and D3He gas-filled "exploding-pusher" inertial confinement fusion (ICF) implosions at the National Ignition Facility to assess the impact of ion kinetic effects. These measurements probed the shock convergence phase of ICF implosions, a critical stage in hot-spot ignition experiments. The data complement previous studies of kinetic effects in shock-driven implosions. Ion temperature and fuel ρR inferred from fusion-product spectroscopy are used to estimate the ion-ion mean free path in the gas. A trend of decreasing yields relative to the predictions of 2D draco hydrodynamics simulations with increasing Knudsen number (the ratio of ion-ion mean free path to minimum shell radius) suggests that ion kinetic effects are increasingly impacting the hot fuel region, in general agreement with previous results. The long mean free path conditions giving rise to ion kinetic effects in the gas are often prevalent during the shock phase of both exploding pushers and ablatively driven implosions, including ignition-relevant implosions.

  12. A theoretical investigation of DNA dynamics and desolvation kinetics for zinc finger proteinZif268

    PubMed Central

    2015-01-01

    Background Transcription factors, regulating the expression inventory of a cell, interact with its respective DNA subjugated by a specific recognition pattern, which if well exploited may ensure targeted genome engineering. The mostly widely studied transcription factors are zinc finger proteins that bind to its target DNA via direct and indirect recognition levels at the interaction interface. Exploiting the binding specificity and affinity of the interaction between the zinc fingers and the respective DNA can help in generating engineered zinc fingers for therapeutic applications. Experimental evidences lucidly substantiate the effect of indirect interaction like DNA deformation and desolvation kinetics, in empowering ZFPs to accomplish partial sequence specificity functioning around structural properties of DNA. Exploring the structure-function relationships of the existing zinc finger-DNA complexes at the indirect recognition level can aid in predicting the probable zinc fingers that could bind to any target DNA. Deformation energy, which defines the energy required to bend DNA from its native shape to its shape when bound to the ZFP, is an effect of indirect recognition mechanism. Water is treated as a co-reactant for unfurling the affinity studies in ZFP-DNA binding equilibria that takes into account the unavoidable change in hydration that occurs when these two solvated surfaces come into contact. Results Aspects like desolvation and DNA deformation have been theoretically investigated based on simulations and free energy perturbation data revealing a consensus in correlating affinity and specificity as well as stability for ZFP-DNA interactions. Greater loss of water at the interaction interface of the DNA calls for binding with higher affinity, eventually distorting the DNA to a greater extent accounted by the change in major groove width and DNA tilt, stretch and rise. Conclusion Most prediction algorithms for ZFPs do not account for water loss at the

  13. Effects of dopamine replacement therapy on lower extremity kinetics and kinematics during a rapid force production task in persons with Parkinson disease.

    PubMed

    Foreman, K Bo; Singer, Madeline L; Addison, Odessa; Marcus, Robin L; LaStayo, Paul C; Dibble, Leland E

    2014-01-01

    Postural instability appears to be a dopamine resistance motor deficit in persons with Parkinson disease (PD); however, little is known about the effects of dopamine replacement on the relative biomechanical contributions of individual lower extremity joints during postural control tasks. To gain insight, we examined persons with PD using both clinical and laboratory measures. For a clinical measure of motor severity we utilized the Unified Parkinson Disease Rating Scale motor subsection during both OFF and ON medication conditions. For the laboratory measure we utilized data gathered during a rapid lower extremity force production task. Kinematic and kinetic variables at the hip, knee, and ankle were gathered during a counter movement jump during both OFF and ON medication conditions. Sixteen persons with PD with a median Hoehn and Yahr severity of 2.5 completed the study. Medication resulted in significant improvements of angular displacement for the hip, knee, and ankle. Furthermore, significant improvements were revealed only at the hip for peak net moments and average angular velocity compared to the OFF medication condition. These results suggest that dopamine replacement medication result in decreased clinical motor disease severity and have a greater influence on kinetics and kinematics proximally. This proximally focused improvement may be due to active recruitment of muscle force and reductions in passive restraint during lower extremity rapid force production.

  14. Dielectric approach to investigation of erythrocyte aggregation. II. Kinetics of erythrocyte aggregation-disaggregation in quiescent and flowing blood.

    PubMed

    Pribush, A; Meiselman, H J; Meyerstein, D; Meyerstein, N

    2000-01-01

    A method based on dielectric properties of dispersed systems was applied to investigate the kinetics of RBC aggregation and the break-up of the aggregates. Experimentally, this method consists of measuring the capacitance at a frequency in the beginning of the beta-dispersion. Two experimental protocols were used to investigate the aggregation process. In the first case, blood samples were fully dispersed and then the flow was decreased or stopped to promote RBC aggregation. It was found that the initial phases of RBC aggregation are not affected by the shear rate. This finding indicates that RBC aggregation is a slow coagulation process. In the second case, RBCs aggregated under flow conditions at different shear rates and after the capacitance reached plateau levels, the flow was ceased. The steady-state capacitance of the quiescent blood and the kinetics of RBC aggregation after stoppage of shearing depend on the prior shear rate. To clarify the reasons for this effect, the kinetics of the disaggregation process was studied. In these experiments, time courses of the capacitance were recorded under different flow conditions and then a higher shear stress was applied to break up RBC aggregates. It was found that the kinetics of the disaggregation process depend on both the prior and current shear stresses. Results obtained in this study and their analysis show that the kinetics of RBC aggregation in stasis consists of two consecutive phases: At the onset, red blood cells interact face-to-face to form linear aggregates and then, after an accumulation of an appropriate concentration of these aggregates, branched rouleaux are formed via reactions of ends of the linear rouleaux with sides of other rouleaux (face-to-side interactions). Branching points are broken by low shear stresses whereas dispersion of the linear rouleaux requires significantly higher energy.

  15. 75 FR 11938 - Meridian Automotive Systems, Grand Rapids, MI; Notice of Termination of Investigation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-12

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR Employment and Training Administration Meridian Automotive Systems, Grand Rapids, MI; Notice of Termination... Meridian Automotive Systems, Grand Rapids, Michigan (Meridian Automotive). The petitioning group of workers...

  16. Identification of a novel laser dye substrate of mammalian cytochromes P450: application in rapid kinetic analysis, inhibitor screening, and directed evolution.

    PubMed

    Kumar, Santosh

    2007-08-01

    The author sought to develop a high-throughput activity screening assay to carry out rapid kinetic analysis, inhibitor screening, and directed evolution of cytochrome P450 2C enzymes. Initially, of the 9 fluorescent substrates and 10 P450 2C enzymes tested, several P450 2C enzymes showed > 1 nmol/min/nmol P450 activity in cumene hydroperoxide (CuOOH)-supported reaction with a laser dye, 7-dimethylamino-4-trifluoromethylcoumarin (C152). A high-throughput steady-state kinetic analysis of the human P450 2C8, 2C9, and 2C19 showed 1) k(cat) = 3 to 6 min(-1), 2) K(m, CuOOH) = 100 to 200 microM, and 3) S(50, C152) = 10 to 20 microM in the CuOOH system. In addition, P450 2C9 and 2C19 showed a very high k(ca)t (27 and 38 min(-1), respectively) in the nicotinamide adenine dinucleotide phosphate (NADPH)-supported reaction. Subsequently, when mammalian P450s from the other subfamilies were tested, P450 2B1dH, 2B4dH, 2B5dH, 3A4, and 3A5 exhibited a significant activity in both CuOOH and NADPH systems. Furthermore, a high-throughput activity screening assay using whole-cell suspensions of the human P450 2C8, 2C9, and 2C19 was optimized. Overall, the data suggested that C152 can be used as a model substrate for mammalian P450s in CuOOH-supported reaction to perform rapid kinetic analysis, inhibitor screening, and directed evolution.

  17. Three-stage autoignition of gasoline in an HCCI engine: An experimental and chemical kinetic modeling investigation

    SciTech Connect

    Machrafi, Hatim; Cavadias, Simeon

    2008-12-15

    The alternative HCCI combustion mode presents a possible means for decreasing the pollution with respect to conventional gasoline or diesel engines, while maintaining the efficiency of a diesel engine or even increasing it. This paper investigates the possibility of using gasoline in an HCCI engine and analyzes the autoignition of gasoline in such an engine. The compression ratio that has been used is 13.5, keeping the inlet temperature at 70 C, varying the equivalence ratio from 0.3 to 0.54, and the EGR (represented by N{sub 2}) ratio from 0 to 37 vol%. For comparison, a PRF95 and a surrogate containing 11 vol% n-heptane, 59 vol% iso-octane, and 30 vol% toluene are used. A previously validated kinetic surrogate mechanism is used to analyze the experiments and to yield possible explanations to kinetic phenomena. From this work, it seems quite possible to use the high octane-rated gasoline for autoignition purposes, even under lean inlet conditions. Furthermore, it appeared that gasoline and its surrogate, unlike PRF95, show a three-stage autoignition. Since the PRF95 does not contain toluene, it is suggested by the kinetic mechanism that the benzyl radical, issued from toluene, causes this so-defined ''obstructed preignition'' and delaying thereby the final ignition for gasoline and its surrogate. The results of the kinetic mechanism supporting this explanation are shown in this paper. (author)

  18. Study on biodegradation of Mazut by newly isolated strain Enterobacter cloacae BBRC10061: improving and kinetic investigation

    PubMed Central

    2013-01-01

    Mazut as a source content of various hydrocarbons is hard to be degraded and its cracking could turn mazut into useful materials. Nevertheless degradation of mazut by routine methods is too expensive but application of indigenous microorganisms as biocatalysts could be effective and important to lower the costs and expand its consumption. Mazut biodegradation can be improved using various strategies; Therefore in this study newly isolated strain Enterobacter cloacae BBRC 10061 was used in a method of gradual addition of mazut into medium and its results were compared with simple addition method. To investigate degradation of mazut by BBRC 10061, influence of increase of mazut concentration was assayed based on gradual addition method. Also different kinetic models were used to evaluate kinetics of the process. Results showed that gradual addition method has been a beneficial technique for improvement of mazut degradation because bacterial induction to produce biosurfactant and essential enzymes for cracking mazut was higher during process. Although addition of more mazut increased the rate of biodegradation but percentage of degradation decreased. pH of medium decreased during biodegradation period while electric potential increased. Also the biodegradation kinetics was not fitted with the biokinetic models; therefore kinetics of biodegradation of mazut has to be studied by new models. PMID:23369455

  19. Crystallization kinetics of rapidly quenched Cu50Zr50 and Cu46Zr46Al8 glass-forming alloys

    NASA Astrophysics Data System (ADS)

    Kulikova, T. V.; Ryltseva, A. A.; Bykov, V. A.; Estemirova, S. Kh; Shuhyaev, K. Yu

    2017-01-01

    We studied the crystallization processes, the structure and thermal properties of amorphous alloys Cu50Zr50 and Cu46Zr46Al8 in a wide temperature range. Comparative study of the crystallization kinetics of these amorphous alloys was carried out for the first time using multivariate non-linear regression. It was found that mechanisms of the crystallization of studied metallic glasses are substantially different. The binary alloy is crystallized by branched reaction complex in four steps. For the ternary system was proposed two-step kinetic model of the crystallization process with consecutive reactions. The values of the total energy of activation for each crystallization stage reach to Cu50Zr50: E1 (345.2 kJ/mol); E2 (307.9 kJ/mol), E3 (281.1 kJ/mol), E4 (259.51 kJ/mol) and Cu46Zr46Al8: E1 (350.7 kJ/mol); E2 (150.4 kJ/mol).

  20. Geometrical investigation of the kinetic evolution of the magnetic field in a periodic flux rope

    SciTech Connect

    Restante, A. L.; Lapenta, G.; Markidis, S.; Intrator, T.

    2013-08-15

    Flux ropes are bundles of magnetic field wrapped around an axis. Many laboratory, space, and astrophysics processes can be represented using this idealized concept. Here, a massively parallel 3D kinetic simulation of a periodic flux rope undergoing the kink instability is studied. The focus is on the topology of the magnetic field and its geometric structures. The analysis considers various techniques such as Poincaré maps and the quasi-separatrix layer (QSL). These are used to highlight regions with expansion or compression and changes in the connectivity of magnetic field lines and consequently to outline regions where heating and current may be generated due to magnetic reconnection. The present study is, to our knowledge, the first QSL analysis of a fully kinetic 3D particle in cell simulation and focuses the existing QSL method of analysis to periodic systems.

  1. Magnetic reconnection in multispecies plasmas investigated by a kinetic fluid code

    NASA Astrophysics Data System (ADS)

    Dong, Chuanfei; Wang, Liang; Bhattacharjee, Amitava; Hakim, Ammar; Huang, Yi-Min; Germaschewski, Kai

    2016-10-01

    We first study the reconnection process in multispecies plasmas by using Gkeyll, which is a kinetic fluid code solving the continuity, momentum and energy equations of each species, and the full Maxwell equations. Thus, there is no assumption by solving the generalized ohm's law in Gkeyll. We studied the reconnection processes in the plasma consisting of electrons, protons and oxygen ions. If time allows, we also plan to show some preliminary results of magnetic reconnection in dusty plasmas with negatively charged dust.

  2. Wide-dynamic-range kinetic investigations of deep proton tunnelling in proteins

    NASA Astrophysics Data System (ADS)

    Salna, Bridget; Benabbas, Abdelkrim; Sage, J. Timothy; van Thor, Jasper; Champion, Paul M.

    2016-09-01

    Directional proton transport along ‘wires’ that feed biochemical reactions in proteins is poorly understood. Amino-acid residues with high pKa are seldom considered as active transport elements in such wires because of their large classical barrier for proton dissociation. Here, we use the light-triggered proton wire of the green fluorescent protein to study its ground-electronic-state proton-transport kinetics, revealing a large temperature-dependent kinetic isotope effect. We show that ‘deep’ proton tunnelling between hydrogen-bonded oxygen atoms with a typical donor-acceptor distance of 2.7-2.8 Å fully accounts for the rates at all temperatures, including the unexpectedly large value (2.5 × 109 s-1) found at room temperature. The rate-limiting step in green fluorescent protein is assigned to tunnelling of the ionization-resistant serine hydroxyl proton. This suggests how high-pKa residues within a proton wire can act as a ‘tunnel diode’ to kinetically trap protons and control the direction of proton flow.

  3. Quantum chemistry investigation of secondary reaction kinetics in acrylate-based copolymers.

    PubMed

    Cuccato, Danilo; Mavroudakis, Evangelos; Moscatelli, Davide

    2013-05-30

    Recently, a growing amount of attention has been focused on the influence of secondary reactions on the free radical polymerization features and the properties and microstructure of the final polymer, particularly in the context of acrylate copolymers. One of the most challenging aspects of this research is the accurate determination of the corresponding reaction kinetics. In this paper, this problem is addressed using quantum chemistry. The reaction rate coefficients of various backbiting, propagation, and β-scission steps are estimated considering different chain configurations of a terpolymer system composed of methyl acrylate, styrene, and methyl methacrylate. The replacement of methyl acrylate radical units with styrene and methyl methacrylate globally decreases the backbiting probability and shifts the equilibrium toward the reactants, while the effect of replacing adjacent units is weaker and more dependent upon the specific substituting monomer. Propagation kinetics is affected primarily by the replacement of the radical units, while this effect appears to be particularly effective on midchain radical reactivity. The overall results clarify the different physicochemical behavior of chain-end, midchain, and short-branch radicals as a function of copolymer composition, providing new insights into free radical polymerization kinetics.

  4. Investigating the robustness of the classical enzyme kinetic equations in small intracellular compartments

    PubMed Central

    2009-01-01

    Background Classical descriptions of enzyme kinetics ignore the physical nature of the intracellular environment. Main implicit assumptions behind such approaches are that reactions occur in compartment volumes which are large enough so that molecular discreteness can be ignored and that molecular transport occurs via diffusion. Though these conditions are frequently met in laboratory conditions, they are not characteristic of the intracellular environment, which is compartmentalized at the micron and submicron scales and in which active means of transport play a significant role. Results Starting from a master equation description of enzyme reaction kinetics and assuming metabolic steady-state conditions, we derive novel mesoscopic rate equations which take into account (i) the intrinsic molecular noise due to the low copy number of molecules in intracellular compartments (ii) the physical nature of the substrate transport process, i.e. diffusion or vesicle-mediated transport. These equations replace the conventional macroscopic and deterministic equations in the context of intracellular kinetics. The latter are recovered in the limit of infinite compartment volumes. We find that deviations from the predictions of classical kinetics are pronounced (hundreds of percent in the estimate for the reaction velocity) for enzyme reactions occurring in compartments which are smaller than approximately 200 nm, for the case of substrate transport to the compartment being mediated principally by vesicle or granule transport and in the presence of competitive enzyme inhibitors. Conclusion The derived mesoscopic rate equations describe subcellular enzyme reaction kinetics, taking into account, for the first time, the simultaneous influence of both intrinsic noise and the mode of transport. They clearly show the range of applicability of the conventional deterministic equation models, namely intracellular conditions compatible with diffusive transport and simple enzyme

  5. Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality

    SciTech Connect

    Morrison, Glenn Charles

    1999-12-01

    In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, and separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10

  6. Rapid renaturation of complementary DNA strands mediated by cationic detergents: a role for high-probability binding domains in enhancing the kinetics of molecular assembly processes.

    PubMed Central

    Pontius, B W; Berg, P

    1991-01-01

    The rate of renaturation for complementary DNA strands can be enhanced greater than 10(4)-fold by the addition of simple cationic detergents, and the reaction is qualitatively and quantitatively very similar to that found with purified heterogeneous nuclear ribonucleoprotein A1 protein. Under optimal conditions, renaturation rates are greater than 2000-fold faster than reactions run in 1 M NaCl at 68 degrees C. The reaction is second-order with respect to DNA concentration, and reaction rates approach or equal the rate with which complementary strands are expected to encounter each other in solution. Renaturation can even be observed well above the expected melting temperature of the duplex DNA, demonstrating that some cationic detergents have DNA double-helix-stabilizing properties. The reaction is also extremely rapid in the presence of up to a 10(6)-fold excess of noncomplementary sequences, establishing that renaturation is specific and relatively independent of heterologous DNA. This finding also implies that up to several thousand potential target sequences can be sampled per strand per second. Such reagents may be useful for procedures that require rapid nucleic acid renaturation, and these results suggest ways to identify and design other compounds that increase the kinetics of association reactions. Moreover, this work provides further support for a model relating the existence of flexible, weakly interacting, repeating domains to their function in rapid molecular assembly processes in vitro and in vivo. PMID:1896475

  7. Investigation of the effect of rapidly solidified braze ribbons on the microstructure of brazed joints

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Wiesner, S.; Rochala, P.; Mayer, J.; Aretz, A.; Iskandar, R.; Schwedt, A.

    2017-03-01

    Shrinkage and warpage due to melting and solidification are crucial for the geometric precision of related components. In order to assure a high geometric precision, the formation of the microstructure in the joint during brazing must be taken into consideration. An extensive interaction can occur between liquid melt and base material, resulting in the formation of distinctive phases. This interaction depends on the parameters of the brazing process. However, the consequences of the interaction between phase formation and process parameters in terms of geometric precision cannot be estimated yet. Insufficient quality of the joint can be a result. In this study, investigations focus on the process of solidification in terms of time dependent diffusion behavior of elements. Therefore, microcrystalline and amorphous braze ribbons based on Ti are produced by rapid solidification and are used for joining. The microstructure of the braze ribbons as well as the melting behavior and phase formation during brazing are considered to be of particular importance for the mechanical properties of the brazed components.

  8. A Pilot Study Investigating the Potential of High-Intensity Focused Ultrasound to Treat Tumours Rapidly

    NASA Astrophysics Data System (ADS)

    Cranston, Jonathan M.; Rivens, Ian; ter Haar, Gail; Kennedy, James

    2007-05-01

    The aim of this project was to investigate the possibility of rapid tumour destruction by a novel method of treating the periphery of a tumour and inducing ischemia by impeding the blood supply. Ex vivo experiments were initially carried out in bovine liver to determine the optimum conditions for focal depth, gantry transducer speed circle diameter and intensity of the ultrasound beam. In vivo experiments were then performed in PGV rat livers implanted with a HSN fibrosarcoma cell line. The tumours were treated by novel technique of creating an annular lesion around the perimeter of the tumour. Macroscopic and microscopic examination of the lesion at post mortem was performed. In addition histological examination of the untreated tumour which was within the annular circle of treatment was examined. This showed evidence of karyolytic nuclei a week after treatment suggesting death by infarction within this area. There was also some evidence of endothelial damage in the blood vessels with fragmented nuclei visible in the lumen. The work presented here adds to our understanding of how high intensity focused ultrasound may be used to treat tumours in as faster and more efficient way. Further work in this area will facilitate the design of future therapeutic interventions in the medical and veterinary world.

  9. PFD: a database for the investigation of protein folding kinetics and stability.

    PubMed

    Fulton, Kate F; Devlin, Glyn L; Jodun, Rachel A; Silvestri, Linda; Bottomley, Stephen P; Fersht, Alan R; Buckle, Ashley M

    2005-01-01

    We have developed a new database that collects all protein folding data into a single, easily accessible public resource. The Protein Folding Database (PFD) contains annotated structural, methodological, kinetic and thermodynamic data for more than 50 proteins, from 39 families. A user-friendly web interface has been developed that allows powerful searching, browsing and information retrieval, whilst providing links to other protein databases. The database structure allows visualization of folding data in a useful and novel way, with a long-term aim of facilitating data mining and bioinformatics approaches. PFD can be accessed freely at http://pfd.med.monash.edu.au.

  10. An investigation of the kinetics of the mesophase transformations in petroleum pitch by the ESR method

    SciTech Connect

    Samoilov, V.M.; Frolov, V.I.; Kotosonov, A.S.; Ostronov, B.G.; Rumyantsev, S.M.

    1983-01-01

    The amount of ..cap alpha../sub 1/ fraction, the concentration of paramagnetic centers, and the width of the line of the ESR signal have been determined for samples of mesophase pitches obtained by treating an initial petroleum pitch at 400-440/sup 0/C. The applicability of the ESR method for studying the kinetics and mechanism of the process of mesophase transformations has been shown. From the change in the parameters studied the rate constants and activation energies of the processes of the formation and growth of the aromatic regions of polyconjugation and of the accumulation of mesophase have been calculated.

  11. Dosimetric and kinetic investigations of γ-irradiated sodium tartrate dihydrate.

    PubMed

    Tuner, H; Kayikçi, M A

    2012-03-01

    Effects of gamma radiation on solid sodium tartrate dihydrate (NaTA) were studied using electron spin resonance (ESR) spectroscopy. One main singlet located at g = 2.0034 and many weak lines located at low and high magnetic field sides were found in the irradiated samples. Dosimetric and kinetic features of the radical species responsible for the experimental ESR spectra were explored through the variations in the signal intensities with respect to applied microwave power, temperature and storage time. Activation energies of the involved radical species were also determined using data derived from annealing studies.

  12. Kinetic investigation of catalytic disproportionation of superoxide ions in the non-aqueous electrolyte used in Li–air batteries

    DOE PAGES

    Wang, Qiang; Zheng, Dong; McKinnon, Meaghan E.; ...

    2014-10-28

    Superoxide reacts with carbonate solvents in Li–air batteries. Tris(pentafluorophenyl)borane is found to catalyze a more rapid superoxide (O2-) disproportionation reaction than the reaction between superoxide and propylene carbonate (PC). With this catalysis, the negative impact of the reaction between the electrolyte and O2-produced by the O2 reduction can be minimized. A simple kinetic study using ESR spectroscopy was reported to determine reaction orders and rate constants for the reaction between PC and superoxide, and the disproportionation of superoxide catalyzed by Tris(pentafluorophenyl)borane and Li ions. As a result, the reactions are found to be first order and the rate constants aremore » 0.033 s-1 M-1, 0.020 s-1 M-1and 0.67 s-1M-1 for reactions with PC, Li ion and Tris(pentafluorophenyl)borane, respectively.« less

  13. Kinetic and Thermodynamic Investigation of Hydrogen Release from Ethane 1,2-di-amineborane

    SciTech Connect

    Neiner, Doinita; Karkamkar, Abhijeet J.; Bowden, Mark; Choi, Young Joon; Luedtke, Avery T.; Holladay, Jamelyn D.; Fisher, Allison M.; Szymczak, Nathaniel; Autrey, Thomas

    2011-07-18

    The thermodynamics and kinetics of hydrogen (H2) release from ethane 1,2-di-amineborane (EDAB, BH3NH2CH2CH2NH2BH3) were measured using Calvet and differential scanning calorimetry (DSC), pressure-composition isotherms, and volumetric gas-burette experiments. The results presented here indicate that EDAB releases ~ 9 wt.% H2 at temperatures ranging from 100 °C to 200 °C in two moderately exothermic steps, approximately -10±1 kJ/mol H2 and -3.8±1 kJ/mol H2. Isothermal kinetic analysis shows that EDAB is more stable than ammonia borane (AB) at temperatures lower than 100°C; however, the rates of hydrogen release are faster for EDAB than for AB at temperatures higher than 120°C. In addition, no volatile impurities in the H2 released by EDAB were detected by mass spectrometry upon heating with 1°C/min to 200°C in a calorimeter.

  14. Advanced kinetic plasma model implementation for new large-scale investigations

    NASA Astrophysics Data System (ADS)

    Reddell, Noah; Shumlak, Uri

    2013-10-01

    A kinetic plasma model for of one or more particle species described by the Vlasov equation and coupled to fully dynamic electromagnetic forces is presented. The model is implemented as evolving continuous PDF (probability density function) in particle phase space (position-velocity) as opposed to particle-in-cell (PIC) methods which discretely sample the PDF. A new boundary condition for the truncated velocity-space edge, motivated by physical properties of the PDF tail, is introduced. The hyperbolic model is evolved using the discontinuous Galerkin numerical method, conserving system mass, momentum, and energy - an advantage compared to PIC. Simulations of two- to six-dimensional phase space are computationally expensive. To maximize performance and scaling to large simulations, a new framework, WARPM, has been developed for many-core (e.g. GPU) computing architectures. WARPM supports both multi-fluid and continuum kinetic plasma models as coupled hyperbolic systems with nearest neighbor predictable communication. Exemplary physics results and computational performance are presented.

  15. Kinetic Roughening and Energetics of Tetragonal Lysozyme Crystal Growth: A Preliminary Atomic Force Microscopy Investigation

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2004-01-01

    We examined particulars of crystal growth from measurements obtained at both microscopic and molecular levels. The crystal growth measurements performed at the microscopic level are well characterized by a model that balances the flux of macromolecules towards the crystal surface with the flux of the crystal surface. Numerical evaluation of model with measurements of crystal growth, in time, provided accurate estimates for the average growth velocities. Growth velocities thus obtained were also interpreted using well-established phenomenological theories. Moreover, we find that microscopic measurements of growth velocity measurements obtained as a function of temperature best characterizes changes in crystal growth modes, when present. We also examined the possibility of detecting a change in crystal growth modes at the molecular level using atomic force microscopy, AFM. From preliminary AFM measurements performed at various supersaturations, we find that magnitude of surface height fluctuations, h(x), increases with supersaturation. Further examination of surface height fluctuations using methods established for fluctuation spectroscopy also enabled the discovery of the existence of a characteristic length, c, which may possibly determine the mode of crystal growth. Although the results are preliminary, we establish the non- critical divergence of 5 and the root-mean-square (rms) magnitude of height-height fluctuations as the kinetic roughening transition temperatures are approached. Moreover, we also examine approximate models for interpreting the non-critical behavior of both 6 and rms magnitude of height-height fluctuations, as the solution supersaturation is increased towards the kinetic roughening supersaturation.

  16. Kinetic Roughening and Energetics of Tetragonal Lysozyme Crystal Growth: A Preliminary Atomic Force Microscopy Investigation

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2004-01-01

    We examined particulars of crystal growth from measurements obtained at both microscopic and molecular levels. The crystal growth measurements performed at the microscopic level are well characterized by a model that balances the flux of macromolecules towards the crystal surface with the flux of the crystal surface. Numerical evaluation of model with measurements of crystal growth, in time, provided accurate estimates for the average growth velocities. Growth velocities thus obtained were also interpreted using well-established phenomenological theories. Moreover, we find that microscopic measurements of growth velocity measurements obtained as a function of temperature best characterizes changes in crystal growth modes, when present. We also examined the possibility of detecting a change in crystal growth modes at the molecular level using atomic force microscopy, AFM. From preliminary AFM measurements performed at various supersaturations, we find that magnitude of surface height fluctuations, h(x), increases with supersaturation. Further examination of surface height fluctuations using methods established for fluctuation spectroscopy also enabled the discovery of the existence of a characteristic length, c, which may possibly determine the mode of crystal growth. Although the results are preliminary, we establish the non- critical divergence of 5 and the root-mean-square (rms) magnitude of height-height fluctuations as the kinetic roughening transition temperatures are approached. Moreover, we also examine approximate models for interpreting the non-critical behavior of both 6 and rms magnitude of height-height fluctuations, as the solution supersaturation is increased towards the kinetic roughening supersaturation.

  17. Rapid hydrolysis of model phosphate diesters by alkaline-earth cations in aqueous DMSO: speciation and kinetics.

    PubMed

    Taran, Olga; Medrano, Felipe; Yatsimirsky, Anatoly K

    2008-12-14

    Kinetics of the cleavage of two phosphate diesters, bis(4-nitrophenyl) phosphate and 2-hydroxypropyl 4-nitrophenyl phosphate and a triester, 4-nitrophenyl diphenyl phosphate, in the presence of Mg(II), Ca(II) and Sr(II) were studied in 90% vol. DMSO at 37 degrees C. The alkaline hydrolysis of the triester was inhibited by all cations, but with both phosphodiesters strong catalytic effects were observed. Potentiometric titrations of metal perchlorates by Bu4N(OH) revealed formation of M2(OH)3+, M(OH)+, M(OH)2 and M2(OH)5- species. Rate constants for phosphodiester cleavage by individual species were obtained from analysis of rate-concentration profiles. Observed first-order rate constants in the presence of 1-2 mM Mg(II) or Ca(II) in neutral and weakly basic solutions were 10(8)-10(11) times higher than those for background hydrolysis at the same pH while in water additions of up to 50 mM metal produced <100-fold accelerations. Possible structures of DMSO solvated catalyst-substrate complexes were modeled by DFT calculations with Mg(II). The increased catalytic activity in 90% DMSO is attributed to stronger association of hydroxide ions and anionic phosphodiesters with metal ions and to preferable solvation of cations by DMSO, which creates favorable for reaction anhydrous microenvironment in the coordination sphere of the catalyst.

  18. Rapid and direct spectrophotometric method for kinetics studies and routine assay of peroxidase based on aniline diazo substrates.

    PubMed

    Mirazizi, Fatemeh; Bahrami, Azita; Haghbeen, Kamahldin; Shahbani Zahiri, Hossein; Bakavoli, Mehdi; Legge, Raymond L

    2016-12-01

    Peroxidases are ubiquitous enzymes that play an important role in living organisms. Current spectrophotometrically based peroxidase assay methods are based on the production of chromophoric substances at the end of the enzymatic reaction. The ambiguity regarding the formation and identity of the final chromophoric product and its possible reactions with other molecules have raised concerns about the accuracy of these methods. This can be of serious concern in inhibition studies. A novel spectrophotometric assay for peroxidase, based on direct measurement of a soluble aniline diazo substrate, is introduced. In addition to the routine assays, this method can be used in comprehensive kinetics studies. 4-[(4-Sulfophenyl)azo]aniline (λmax = 390 nm, ɛ = 32 880 M(-1) cm(-1) at pH 4.5 to 9) was introduced for routine assay of peroxidase. This compound is commercially available and is indexed as a food dye. Using this method, a detection limit of 0.05 nmol mL(-1) was achieved for peroxidase.

  19. Kinetic anharmonic coupling in the trihalomethanes: A mechanism for rapid intramolecular redistribution of CH stretch vibrational energy

    SciTech Connect

    Green, W.H. Jr.; Lawrance, W.D.; Moore, C.B.

    1987-06-01

    The coupling of CH stretching and CH bending vibrations in trisubstituted methanes is analyzed. Improved spectroscopic constants, especially the cubic anharmonic stretch--bend coupling constants, are extracted from Fermi resonances in the overtone spectra of HCF/sub 3/ and HCCl/sub 3/. Both harmonic oscillator and Morse oscillator basis functions are used in the analysis and the results compared. That part of the coupling which arises from the kinetic energy as expressed in curvilinear coordinates is calculated and compared to the coupling calculated using the more conventional rectilinear treatment. Use of curvilinear coordinates is found to provide significant advantages. The formalism for curvilinear normal coordinates is clarified and generalized. From these calculations and the spectral analysis, one of the cubic anharmonic constants of the potential energy surface is extracted for comparison with ab initio calculations. The curvilinear model of the CH stretch--bend interaction tested for these isolated CH chromophores is expected to be useful in understanding CH bonds and vibrational energy flow in larger hydrocarbons.

  20. Rapid Whole-Genome Sequencing for Investigation of a Neonatal MRSA Outbreak

    PubMed Central

    Köser, Claudio U.; Holden, Matthew T.G.; Ellington, Matthew J.; Cartwright, Edward J.P.; Brown, Nicholas M.; Ogilvy-Stuart, Amanda L.; Hsu, Li Yang; Chewapreecha, Claire; Croucher, Nicholas J.; Harris, Simon R.; Sanders, Mandy; Enright, Mark C.; Dougan, Gordon; Bentley, Stephen D.; Parkhill, Julian; Fraser, Louise J.; Betley, Jason R.; Schulz-Trieglaff, Ole B.; Smith, Geoffrey P.; Peacock, Sharon J.

    2013-01-01

    Background Isolates of methicillin-resistant Staphylococcus aureus (MRSA) belonging to a single lineage are often indistinguishable by means of current typing techniques. Whole-genome sequencing may provide improved resolution to define transmission pathways and characterize outbreaks. Methods We investigated a putative MRSA outbreak in a neonatal intensive care unit. By using rapid high-throughput sequencing technology with a clinically relevant turnaround time, we retrospectively sequenced the DNA from seven isolates associated with the outbreak and another seven MRSA isolates associated with carriage of MRSA or bacteremia in the same hospital. Results We constructed a phylogenetic tree by comparing single-nucleotide polymorphisms (SNPs) in the core genome to a reference genome (an epidemic MRSA clone, EMRSA-15 [sequence type 22]). This revealed a distinct cluster of outbreak isolates and clear separation between these and the nonoutbreak isolates. A previously missed transmission event was detected between two patients with bacteremia who were not part of the outbreak. We created an artificial “resistome” of antibiotic-resistance genes and demonstrated concordance between it and the results of phenotypic susceptibility testing; we also created a “toxome” consisting of toxin genes. One outbreak isolate had a hypermutator phenotype with a higher number of SNPs than the other outbreak isolates, highlighting the difficulty of imposing a simple threshold for the number of SNPs between isolates to decide whether they are part of a recent transmission chain. Conclusions Whole-genome sequencing can provide clinically relevant data within a time frame that can influence patient care. The need for automated data interpretation and the provision of clinically meaningful reports represent hurdles to clinical implementation. (Funded by the U.K. Clinical Research Collaboration Translational Infection Research Initiative and others.) PMID:22693998

  1. The degradation products of aniline in the solutions with ozone and kinetic investigations.

    PubMed

    Turhan, Kadir; Uzman, Suheyla

    2007-10-01

    Aromatic compounds are extensively used in several industries and can cause pollution in water sources. This work aims at examining the degradability of aniline in aqueous solutions by ozone-induced cleavage, and at determining the kinetics of the cited cleavage reactions. Aniline was prepared in four different concentrations and the flow rate of ozone supplied to each solution was selected. Aniline solutions were ozonated at low and high pH, so as to compare both molecular and hydroxyl free radical mechanisms, respectively. The main identified aromatic by-products were nitrobenzene and azobenzene when the experiment was carried out at acidic pH. Formation of nitrobenzene, azobenzene, azoxybenzene and 2-pyridine carboxylic acid (picolinic acid) was observed when the ozonization was carried out at basic pH. All the aromatic by-products found were less toxic than the raw materials. The pseudo-first-order constants in aniline concentrations were calculated.

  2. Experimental Investigation on Reduction Kinetics of Stainless Steel-Making Slag in Iron Bath Smelting Reduction

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Liu, Jienan; Yang, Yanfeng; Liu, Luming; Liu, Jiechao; Luo, Lijian; Ma, Yubao; Hong, Xin

    Reduction kinetics of stainless steel slag in iron bath smelting reduction was studied at the temperature of 1500°C ˜ 1650°C. It was concluded that the reduction process consisted of two parts. That is to say smelting reduction was controlled by stainless steel slag melting initially and by interface reaction later. In order to increase smelting reaction rate, the melting point of slag should be decreased at the first stage and adjust the liquidity of slag at later stage. Smelting reaction rate will be accelerated by means of optimize the slag content. The optimal reduction result that all most all of the chromium in slag been recovered was obtained in temperature was 1500°C, basicity of slag was 1.0˜1.2, the value of Al2O3+MgO was 25%.

  3. NO binding kinetics in myoglobin investigated by picosecond Fe K-edge absorption spectroscopy

    PubMed Central

    Silatani, Mahsa; Lima, Frederico A.; Penfold, Thomas J.; Rittmann, Jochen; Reinhard, Marco E.; Rittmann-Frank, Hannelore M.; Borca, Camelia; Grolimund, Daniel; Milne, Christopher J.; Chergui, Majed

    2015-01-01

    Diatomic ligands in hemoproteins and the way they bind to the active center are central to the protein’s function. Using picosecond Fe K-edge X-ray absorption spectroscopy, we probe the NO-heme recombination kinetics with direct sensitivity to the Fe-NO binding after 532-nm photoexcitation of nitrosylmyoglobin (MbNO) in physiological solutions. The transients at 70 and 300 ps are identical, but they deviate from the difference between the static spectra of deoxymyoglobin and MbNO, showing the formation of an intermediate species. We propose the latter to be a six-coordinated domed species that is populated on a timescale of ∼200 ps by recombination with NO ligands. This work shows the feasibility of ultrafast pump–probe X-ray spectroscopic studies of proteins in physiological media, delivering insight into the electronic and geometric structure of the active center. PMID:26438842

  4. Investigation on nucleation kinetics, growth and characterization of urea oxalic acid-ferroelectric single crystal

    NASA Astrophysics Data System (ADS)

    Dhivya, R.; Ezhil Vizhi, R.; Rajan Babu, D.

    2017-06-01

    Nucleation and growth kinetics renders the information about the crystal growth process, which can be adopted to grow large size crystals. Urea oxalic acid was synthesized by slow evaporation method. Solubility was analyzed gravimetrically and it was observed that it exhibits positive temperature coefficient of solubility which is suitable for bulk growth. Metastable zonewidth was observed by adopting polythermal method. Induction period was measured by isothermal method for the saturation temperature by varying the degrees of supersaturation. Based on the classical theory of nucleation, the other nucleation parameters such as interfacial energy, Gibbs critical free energy and radius of critical nuclei were calculated. Urea oxalic acid (UOA) was synthesized and subsequently grown by a slow cooling technique. Single crystal X-ray diffraction study confirms that the crystal belongs to a monoclinic system. Dielectric analysis affirms the ferroelectric property of the material and the results were further discussed in detail.

  5. Nantenine as an acetylcholinesterase inhibitor: SAR, enzyme kinetics and molecular modeling investigations

    PubMed Central

    Pecic, Stevan; McAnuff, Marie A.; Harding, Wayne W.

    2015-01-01

    Nantenine, as well as a number of flexible analogs, were evaluated for acetylcholinesterase (AChE) inhibitory activity in microplate spectrophotometric assays based on Ellman’s method. It was found that the rigid aporphine core of nantenine is an important structural requirement for its anticholinesterase activity. Nantenine showed mixed inhibition kinetics in enzyme assays. Molecular docking experiments suggest that nantenine binds preferentially to the catalytic site of AChE but is also capable of interacting with the peripheral anionic site (PAS) of the enzyme, thus accounting for its mixed inhibition profile. The aporphine core of nantenine may thus be a useful template for the design of novel PAS or dual-site AChE inhibitors. Inhibiting the PAS is desirable for prevention of aggregation of the amyloid peptide Aβ, a major causative factor in the progression of Alzheimer’s disease (AD). PMID:20583856

  6. Theoretical investigation of the mechanism and kinetics for HCO + HCN ⇄ HCHO + CN

    NASA Astrophysics Data System (ADS)

    Wen, Lin Feng; Yan, Wang; Shao, Wen Zhang; Xian, Yong Pang

    1997-02-01

    The mechanism and kinetics for HCO + HCN ⇄ HCNO + CN have been studied theoretically. The potential energy profile along the intrinsic reaction coordinate (IRC) has been obtained at ab initio QCISD/6-31G ∗∗//UHF/6-31G ∗∗ and CCSD/6-31G ∗∗//UHF/6-31G ∗∗ levels. The forward activation barriers are about 136.45 adn 140.94 kJ mol -1 at these levels, respectively, and the reverse barriers are 2.71 and 1.26 kJ mol -1, respectively. The canonical rate constants for the forward and reverse reactions have been calculated by using statistical theory.

  7. Kinetic investigation of sulfidizing annealing of scorodite in processing of refractory oxidized gold-containing ores

    NASA Astrophysics Data System (ADS)

    Boboev, I. R.; Strizhko, L. S.; Bobozoda, Sh.; Gorbunov, E. P.

    2016-03-01

    The results of kinetic studies on the removal of arsenic from scorodite using sulfidizing annealing are presented. The reaction order with respect to the reactant and the activation energy are established from the experimental data. The rate-determining step of the sulfidizing annealing process is determined. The main reactions that occur during the sulfidizing of arsenic in scorodite are proposed on the basis of the obtained results and confirmed by thermodynamic calculations and chemical analyses. The major results of testing this technology, as applied to the refractory oxidized ores in which arsenic is mainly concentrated in scorodite, are presented. Arsenic removal from this ore is confirmed by chemical and quantitative X-ray diffraction analyses and by qualitative phase analysis. Industrial use of this technology provides safe and efficient processing of refractory gold-containing ores, where arsenic is mainly concentrated in scorodite.

  8. Wetting of biopolymer coatings: contact angle kinetics and image analysis investigation.

    PubMed

    Farris, Stefano; Introzzi, Laura; Biagioni, Paolo; Holz, Torsten; Schiraldi, Alberto; Piergiovanni, Luciano

    2011-06-21

    The surface wetting of five biopolymers, used as coating materials for a plastic film, was monitored over a span of 8 min by means of the optical contact angle technique. Because most of the total variation was observed to occur during the first 60 s, we decided to focus on this curtailed temporal window. Initial contact angle values (θ(0)) ranged from ∼91° for chitosan to ∼30° for pullulan. However, the water drop profile began to change immediately following drop deposition for all biocoatings, confirming that the concept of water contact angle equilibrium is not applicable to most biopolymers. First, a three-parameter decay equation [θ(t) = θ(0) exp(kt(n))] was fit to the experimental contact angle data to describe the kinetics of the contact angle change for each biocoating. Interestingly, the k constant correlated well with the contact angle evolution rate and the n exponent seemed to be somehow linked to the physicochemical phenomena underlying the overall kinetics process. Second, to achieve a reliable description of droplet evolution, the contact angle (CA) analysis was coupled with image analysis (IA) through a combined geometric/trigonometric approach. Absorption and spreading were the key factors governing the overall mechanism of surface wetting during the 60 s analysis, although the individual quantification of both phenomena demonstrated that spreading provided the largest contribution for all biopolymers, with the only exception of gelatin, which showed two quasi-equivalent and counterbalancing effects. The possible correlation between these two phenomena and the topography of the biopolymer surfaces are then discussed on the basis of atomic force microscopy analyses.

  9. Kinetic investigations of the rate-limiting step in human 12- and 15-lipoxygenase.

    PubMed

    Segraves, Erika N; Holman, Theodore R

    2003-05-13

    Mammalian lipoxygenases have been implicated in several inflammatory disorders; however, the details of the kinetic mechanism are still not well understood. In this paper, human platelet 12-lipoxygenase (12-hLO) and human reticulocyte 15-lipoxygenase-1 (15-hLO) were tested with arachidonic acid (AA) and linoleic acid (LA), respectively, under a variety of changing experimental conditions, such as temperature, dissolved oxygen concentration, and viscosity. The data that are presented show that 12-hLO and 15-hLO have slower rates of product release (k(cat)) than soybean lipoxygenase-1 (sLO-1), but similar or better rates of substrate capture for the fatty acid (k(cat)/K(M)) or molecular oxygen [k(cat)/K(M(O)2)]. The primary, kinetic isotope effect (KIE) for 15-hLO with LA was determined to be temperature-independent and large ((D)k(cat) = 40 +/- 8), over the range of 10-35 degrees C, indicating that C-H bond cleavage is the sole rate-limiting step and proceeds through a tunneling mechanism. The (D)k(cat)/K(M) for 15-hLO, however, was temperature-dependent, consistent with our previous results [Lewis, E. R., Johansen, E., and Holman, T. R. (1999) J. Am. Chem. Soc. 121, 1395-1396], indicating multiple rate-limiting steps. This was confirmed by a temperature-dependent, k(cat)/K(M) solvent isotope effect (SIE), which indicated a hydrogen bond rearrangement step at low temperatures, similar to that of sLO-1 [Glickman, M. H., and Klinman, J. P. (1995) Biochemistry 34, 14077-14092]. The KIE could not be determined for 12-hLO due to its inability to efficiently catalyze LA, but the k(cat)/K(M) SIE was temperature-independent, indicating distinct rate-limiting steps from both 15-hLO and sLO-1.

  10. A novel bench-scale column assay to investigate site-specific nitrification biokinetics in biological rapid sand filters.

    PubMed

    Tatari, K; Smets, B F; Albrechtsen, H-J

    2013-10-15

    A bench-scale assay was developed to obtain site-specific nitrification biokinetic information from biological rapid sand filters employed in groundwater treatment. The experimental set-up uses granular material subsampled from a full-scale filter, packed in a column, and operated with controlled and continuous hydraulic and ammonium loading. Flowrates and flow recirculation around the column are chosen to mimic full-scale hydrodynamic conditions, and minimize axial gradients. A reference ammonium loading rate is calculated based on the average loading experienced in the active zone of the full-scale filter. Effluent concentrations of ammonium are analyzed when the bench-scale column is subject to reference loading, from which removal rates are calculated. Subsequently, removal rates above the reference loading are measured by imposing short-term loading variations. A critical loading rate corresponding to the maximum removal rate can be inferred. The assay was successfully applied to characterize biokinetic behavior from a test rapid sand filter; removal rates at reference loading matched those observed from full-scale observations, while a maximum removal capacity of 6.9 g NH4(+)-N/m(3) packed sand/h could easily be determined at 7.5 g NH4(+)-N/m(3) packed sand/h. This assay, with conditions reflecting full-scale observations, and where the biological activity is subject to minimal physical disturbance, provides a simple and fast, yet powerful tool to gain insight in nitrification kinetics in rapid sand filters.

  11. Confocal-based method for quantification of diffusion kinetics in microwell plates and its application for identifying a rapid mixing method for high-content/throughput screening.

    PubMed

    Song, Ok Ryul; Kim, Tae-Hee; Perrodon, Xavier; Lee, Changbok; Jeon, Hee Kyoung; Seghiri, Zahir; Kwon, Ho Jeong; Cechetto, Jonathan; Christophe, Thierry

    2010-02-01

    Rapid mixing in microplates is still an underappreciated challenge in screening assay development, particularly with the use of noncontact nanoliter liquid handlers. In high-content/throughput screening (HC/TS), fast and efficient mixing between compounds and cell culture medium is even more critical as biological kinetics dictates speed of mixing, usually within a few minutes. Moreover, mixing in HC/TS should be gentle enough to avoid any negative disruption in cell layer. Here the authors introduce a method to accurately quantify drop diffusion into a microplate well, independently of buffer, liquid handler, or dispensing protocol. This method was used to determine the effect of various mixing methods on the diffusion of a nanoliter drop of pure DMSO in aqueous buffer in 384-well plates. Rapid plate shaking and additional buffer addition were shown to be the most efficient and effective mixing methods for HC/TS. However, efficient mixing by plate shaking is limited by assay volume. Bulk addition shows fast and efficient mixing, without negative effects on cells. Moreover, this simple, fast, and inexpensive method can be easily adapted on any platform.

  12. Insights into the mechanism of Pseudomonas dacunhae aspartate beta-decarboxylase from rapid-scanning stopped-flow kinetics.

    PubMed

    Phillips, Robert S; Lima, Santiago; Khristoforov, Roman; Sudararaju, Bakthavatsalam

    2010-06-22

    The mechanism of wild-type and R37A mutant Pseudomonas dacunhae aspartate beta-decarboxylase (ABDC) was studied by rapid-scanning stopped-flow spectrophotometry. Mixing wild-type ABDC with 50 mM disodium l-Asp resulted in the formation of a 325 nm absorption peak within the dead time of the stopped-flow instrument, likely the ketimine of pyridoxamine 5'-phosphate and oxaloacetate or pyruvate. After consumption of the l-Asp, the 360 nm feature of the resting enzyme was restored. Thus, the 325 nm species is a catalytically competent intermediate. In contrast, mixing wild-type ABDC with the disodium salt of either threo- or erythro-beta-hydroxy-dl-Asp at 50 mM resulted in a much slower formation of the 325 nm complex, with an apparent rate constant of approximately 1 or 0.006 s(-1), respectively. When wild-type ABDC is mixed with disodium succinate, a nonreactive analogue of l-Asp, formation of a new peak at 425 nm is observed. The apparent rate constant for formation of the 425 nm band exhibits a hyperbolic dependence on succinate concentration, showing that there is a rapid binding equilibrium, followed by a slower reaction in which the internal aldimine is protonated on the Schiff base N. Hydrostatic pressure shifts the spectrum from the 425 nm form to the 360 nm form, consistent with a conformational change. It is likely that the binding of substrate or analogues induces a conformational change that releases strain in the Lys pyridoxal 5'-phosphate Schiff base and increases the pK(a), resulting in protonation of the Schiff base to initiate transaldimination. Mixing of R37A mutant ABDC with 50 mM l-Asp also results in the formation of the 325 nm complex, but with an apparent rate constant of 0.2 s(-1), at least 5000-fold slower than the rate of wild-type ABDC. In contrast to wild-type ABDC, R37A ABDC shows no change in the cofactor spectrum when mixed with disodium succinate. These results suggest that Arg-37, a conserved active site residue in ABDC, plays a role

  13. Kinetics of rapid Ca2+ release by sarcoplasmic reticulum. Effects of Ca2+, Mg2+, and adenine nucleotides

    SciTech Connect

    Meissner, G.; Darling, E.; Eveleth, J.

    1986-01-14

    A radioisotope flux-rapid-quench-Millipore filtration method is described for determining the effects of Ca2+, adenine nucleotides, and Mg2+ on the Ca2+ release behaviour of heavy sarcoplasmic reticulum (SR) vesicles. Rapid 45Ca2+ efflux from passively loaded vesicles was blocked by the addition of Mg2+ and ruthenium red. At pH 7 and 10(-9) M Ca2+, vesicles released 45Ca2+ with a low rate (k = 0.1 s-1). An increase in external Ca2+ concentration to 4 microM or the addition of 5 mM ATP or the ATP analogue adenosine 5'-(beta,gamma-methylenetriphosphate) (AMP-PCP) resulted in intermediate 45Ca2+ release rates. The maximal release rate was observed in media containing 4 microM Ca2+ and 5 mM AMP-PCP and had a first-order rate constant of 30-100 s-1. Mg2+ partially inhibited Ca2+- and nucleotide-induced 45Ca2+ efflux. In the absence of AMP-PCP, 45Ca2+ release was fully inhibited at 5 mM Mg2+ or 5 mM Ca2+. The composition of the release media was systematically varied, and the flux data were expressed in the form of Hill equations. The apparent n values of activation of Ca2+ release by ATP and AMP-PCP were 1.6-1.9. The Hill coefficient of Ca2+ activation (n = 0.8-2.1) was dependent on nucleotide and Mg2+ concentrations, whereas the one of Mg2+ inhibition (n = 1.1-1.6) varied with external Ca2+ concentration. These results suggest that heavy SR vesicles contain a Ca2+ release channel which is capable of conducting Ca2+ at rates comparable with those found in intact muscle. Ca2+, AMP-PCP (ATP), and Mg2+ appear to act at noninteracting or interacting sites of the channel.

  14. Structural investigation of oxovanadium(IV) Schiff base complexes: X-ray crystallography, electrochemistry and kinetic of thermal decomposition.

    PubMed

    Asadi, Mozaffar; Asadi, Zahra; Savaripoor, Nooshin; Dusek, Michal; Eigner, Vaclav; Shorkaei, Mohammad Ranjkesh; Sedaghat, Moslem

    2015-02-05

    A series of new VO(IV) complexes of tetradentate N2O2 Schiff base ligands (L(1)-L(4)), were synthesized and characterized by FT-IR, UV-vis and elemental analysis. The structure of the complex VOL(1)⋅DMF was also investigated by X-ray crystallography which revealed a vanadyl center with distorted octahedral coordination where the 2-aza and 2-oxo coordinating sites of the ligand were perpendicular to the "-yl" oxygen. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeOkinetic aspects of their thermal decomposition. The formation constants with various substituents on the aldehyde ring follow the trend 5-OMe>5-H>5-Br>5-Cl. Furthermore, the kinetic parameters of thermal decomposition were calculated by using the Coats-Redfern equation. According to the Coats-Redfern plots the kinetics of thermal decomposition of studied complexes is of the first-order in all stages, the free energy of activation for each following stage is larger than the previous one and the complexes have good thermal stability. The preparation of VOL(1)⋅DMF yielded also another compound, one kind of vanadium oxide [VO]X, with different habitus of crystals, (platelet instead of prisma) and without L(1) ligand, consisting of a V10O28 cage, diaminium moiety and dimethylamonium as a counter ions. Because its crystal structure was also new, we reported it along with the targeted complex. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Structural investigation of oxovanadium(IV) Schiff base complexes: X-ray crystallography, electrochemistry and kinetic of thermal decomposition

    NASA Astrophysics Data System (ADS)

    Asadi, Mozaffar; Asadi, Zahra; Savaripoor, Nooshin; Dusek, Michal; Eigner, Vaclav; Shorkaei, Mohammad Ranjkesh; Sedaghat, Moslem

    2015-02-01

    A series of new VO(IV) complexes of tetradentate N2O2 Schiff base ligands (L1-L4), were synthesized and characterized by FT-IR, UV-vis and elemental analysis. The structure of the complex VOL1ṡDMF was also investigated by X-ray crystallography which revealed a vanadyl center with distorted octahedral coordination where the 2-aza and 2-oxo coordinating sites of the ligand were perpendicular to the "-yl" oxygen. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO < H < Br < Cl. We also studied the thermodynamics of formation of the complexes and kinetic aspects of their thermal decomposition. The formation constants with various substituents on the aldehyde ring follow the trend 5-OMe > 5-H > 5-Br > 5-Cl. Furthermore, the kinetic parameters of thermal decomposition were calculated by using the Coats-Redfern equation. According to the Coats-Redfern plots the kinetics of thermal decomposition of studied complexes is of the first-order in all stages, the free energy of activation for each following stage is larger than the previous one and the complexes have good thermal stability. The preparation of VOL1ṡDMF yielded also another compound, one kind of vanadium oxide [VO]X, with different habitus of crystals, (platelet instead of prisma) and without L1 ligand, consisting of a V10O28 cage, diaminium moiety and dimethylamonium as a counter ions. Because its crystal structure was also new, we reported it along with the targeted complex.

  16. Time resolved spectroscopic investigation of SiD2 + D2: kinetic study

    NASA Astrophysics Data System (ADS)

    Al-Rubaiey, Najem A.; Walsh, Robin

    2017-03-01

    Silylenes (silanediyls) have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD) of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2) are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas) at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using Lindemann

  17. An Initial Ultraviolet Investigation of Rapidly Evolving Short Period Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Shaw, J. Scott

    A new class of short period, strongly interacting eclipsing binary systems undergoing rapid mass exchange and/or mass loss has been recently identified by one of us (JSS). This group of close binary systems is akin to W UMa-type systems but has somewhat longer orbital periods and components of very dissimilar temperatures. The systems SW Lyn, V1010 Oph, and RT Scl are the best known members of this class of binaries. These Systems appear to be in an early stage of case A binary evolution prior to becoming contact systems in which the more massive hotter (A to F) component is close to or at its Roche limiting surface. Analyses of their asymmetric light curves and period changes indicate substantial mass exchange and/or mass loss. Present groundbased spectra show variable asymmetric line profiles. The photometric studies indicate that the observed asymmetries in the light curves can be explained by the presence of a bright shock region ("hot spot") produced on the receding hemisphere of the cooler component, by the impact of a gas stream from the more massive component. In this initial UV study we propose to observe a small, but representative sample of these stars with the IUE satellite in the wavelength region 1175-3200 using the SWP and LWR cameras. Low dispersion SWP and LWR spectra will be taken during eclipses and at elongations to allow us to identify and map out gas flows and the interacting plasmas using resonance lines of Fe II and Mg II h and k in the near UV and lines such as CIII, CIV, NIV, NV, and SiIII and SiIV in the far UV. High dispersion UV spectra of the brightest member of the class, V1010 Oph, will be obtained for a detailed investigation of the velocities of the expected gas streaming as well as the thermal and mass flow properties of the interacting plasmas. We plan to obtain ground-based spectroscopic and photometric observations of V1010 Oph at or near the time the UV observations are made.

  18. Investigation on microstructure characterization and property of rapidly solidified Mg-Zn-Ca-Ce-La alloys

    SciTech Connect

    Zhou Tao; Chen Zhenhua; Yang Mingbo; Hu Jianjun; Xia Hua

    2012-01-15

    Rapidly solidified (RS) Mg-Zn-Ca-Ce-La (wt.%) alloys have been produced via atomizing the alloy melt and subsequent splat-quenching on the water-cooled copper twin-rollers in the form of flakes. Microstructure characterization, phase compositions and thermal stability of the alloys have been systematically investigated. The results showed that with addition of RE (Ce and La) to the Mg-6Zn-5Ca alloy, the stable intermetallic compounds i.e. the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (about 3 at.%), shortened as the T Prime phase, were formed at the expense of the binary Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases, which was possibly beneficial to the enhanced thermal stability of the alloy. In the Mg-6Zn-5Ca-3Ce-0.5La alloy, the composition of the T Prime phase in the grain interior was different from that at the grain boundaries, in which the segregation of the La elements was found, and the atomic percentage ratio of Zn to Ce in the T Prime phase within the grains was close to 2. Moreover, the stable Mg{sub 2}Ca phases were detected around the T Prime phases at the grain boundaries in the alloy. - Research Highlights: Black-Right-Pointing-Pointer The phase constitution of RS Mg-6Zn-5Ca alloy can be improved by RE additions. Black-Right-Pointing-Pointer In the Mg-Zn-Ca-Ce-La alloys, the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (T Prime phase) is formed. Black-Right-Pointing-Pointer The formation of the T Prime phase leads to the loss of the Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases. Black-Right-Pointing-Pointer The composition of the T Prime phase differs from the grain interior to the grain boundary.

  19. Mechanisms and Kinetics of Amyloid Aggregation Investigated by a Phenomenological Coarse-Grained Model

    NASA Astrophysics Data System (ADS)

    Magno, Andrea; Pellarin, Riccardo; Caflisch, Amedeo

    Amyloid fibrils are ordered polypeptide aggregates that have been implicated in several neurodegenerative pathologies, such as Alzheimer's, Parkinson's, Huntington's, and prion diseases, [1, 2] and, more recently, also in biological functionalities. [3, 4, 5] These findings have paved the way for a wide range of experimental and computational studies aimed at understanding the details of the fibril-formation mechanism. Computer simulations using low-resolution models, which employ a simplified representation of protein geometry and energetics, have provided insights into the basic physical principles underlying protein aggregation in general [6, 7, 8] and ordered amyloid aggregation. [9, 10, 11, 12, 13, 14, 15] For example, Dokholyan and coworkers have used the Discrete Molecular Dynamics method [16, 17] to shed light on the mechanisms of protein oligomerization [18] and the conformational changes that take place in proteins before the aggregation onset. [19, 20] One challenging observation, which is difficult to observe by computer simulations, is the wide range of aggregation scenarios emerging from a variety of biophysical measurements. [21, 22] Atomistic models have been employed to study the conformational space of amyloidogenic polypeptides in the monomeric state, [23, 24, 25] the very initial steps of amyloid formation, [26, 27, 28, 29, 30, 31, 32] and the structural stability of fibril models. [33, 34, 35) However, all-atom simulations of the kinetics of fibril formation are beyond what can be done with modern computers.

  20. A methyl methacrylate-HEMA-CL(n) copolymerization investigation: from kinetics to bioapplications.

    PubMed

    Ferrari, Raffaele; Rooney, Thomas R; Lupi, Monica; Ubezio, Paolo; Hutchinson, Robin A; Moscatelli, Davide

    2013-10-01

    The radical copolymerization kinetics of methyl methacrylate (MMA) and poly-ϵ-caprolactone macromonomer functionalized with a vinyl end group (HEMA-CL(n)) is studied using a pulsed-laser technique. The reactivity ratios for this system are near unity, while a linear relationship between k(p,cop), the copolymer-averaged propagation rate coefficient, and the composition of macromonomer in the feed (0-80 wt% range) is determined. At 50 wt% macromonomer in the feed, a 1.67 ± 0.02 and 1.64 ± 0.06 increase in k(p,cop)/k(p,MMA) is determined for HEMA-CL3 and HEMA-CL2, respectively. These macromonomers are adopted to synthesize nanoparticles (NPs) in the range of 100-150 nm through batch emulsion free radical polymerization (BEP) to produce partially degradable drug delivery carriers. The produced NPs are tested in 4T1 cell line and show excellent characteristics as carriers: they do not affect cell proliferation, and a relevant number of NPs, thousands per cell, are internalized.

  1. Nitrite dismutase reaction mechanism: kinetic and spectroscopic investigation of the interaction between nitrophorin and nitrite.

    PubMed

    He, Chunmao; Howes, Barry D; Smulevich, Giulietta; Rumpel, Sigrun; Reijerse, Edward J; Lubitz, Wolfgang; Cox, Nicholas; Knipp, Markus

    2015-04-01

    Nitrite is an important metabolite in the physiological pathways of NO and other nitrogen oxides in both enzymatic and nonenzymatic reactions. The ferric heme b protein nitrophorin 4 (NP4) is capable of catalyzing nitrite disproportionation at neutral pH, producing NO. Here we attempt to resolve its disproportionation mechanism. Isothermal titration calorimetry of a gallium(III) derivative of NP4 demonstrates that the heme iron coordinates the first substrate nitrite. Contrary to previous low-temperature EPR measurements, which assigned the NP4-nitrite complex electronic configuration solely to a low-spin (S = 1/2) species, electronic absorption and resonance Raman spectroscopy presented here demonstrate that the NP4-NO2(-) cofactor exists in a high-spin/low-spin equilibrium of 7:3 which is in fast exchange in solution. Spin-state interchange is taken as evidence for dynamic NO2(-) coordination, with the high-spin configuration (S = 5/2) representing the reactive species. Subsequent kinetic measurements reveal that the dismutation reaction proceeds in two discrete steps and identify an {FeNO}(7) intermediate species. The first reaction step, generating the {FeNO}(7) intermediate, represents an oxygen atom transfer from the iron bound nitrite to a second nitrite molecule in the protein pocket. In the second step this intermediate reduces a third nitrite substrate yielding two NO molecules. A nearby aspartic acid residue side-chain transiently stores protons required for the reaction, which is crucial for NPs' function as nitrite dismutase.

  2. Investigation of contact-induced charging kinetics on variably modified glass surfaces

    NASA Astrophysics Data System (ADS)

    Agnello, G.; Hamilton, J.; Manley, R.; Streltsova, E.; LaCourse, W.; Cormack, A.

    2015-11-01

    The accumulation and dissipation of electrical charge on glass surfaces is of considerable academic and industrial interest. The purpose of the present article, is to report on the differences in charging kinetics of several flat alumina-borosilicate (low alkali content) glass surfaces via a rolling sphere test (RST) [1] that have been physically and/or chemically modified by different approaches and exposed to variable environmental conditions (i.e. relative humidity). Methods used for surface modification include chemical etching (HF based chemistries of variable molarity) and plasma processing/thin film deposition (CH4 via Reactive Ion Etch (RIE) and/or Atmospheric Pressure Plasma Chemical Vapor Deposition (APPCVD)). Trends in glass surface charge rates, along with corresponding surface resistivity, energy and zeta potential measurements indicate that glass surface, and perhaps bulk, chemistry (specifically a surface' reactivity/affinity with/to water) play critical roles in charge dynamics. Based on the results, we propose an ion-based transfer model facilitated by surface-water molecular interactions as the primary mechanism responsible for contact electrification in glass-metal contact systems.

  3. Thermodynamic and kinetic investigations of PO3-4 adsorption on blast furnace slag.

    PubMed

    Oguz, Ensar

    2005-01-01

    The kinetics of adsorption of PO(3-)(4) by blast furnace slag were found to be fast, reaching equilibrium in 20 min and following a pseudo-second-order rate equation. The adsorption behavior of PO(3-)(4) on blast furnace slag has been studied as a function of the solution agitation speed, pH, and temperature. Results have been analyzed by Freundlich, Langmuir, BET, and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption, 10.31 kJ mol(-1), was calculated from the D-R adsorption isotherm. The rate constants were calculated for 293, 298, 303, and 308 K using a pseudo-second-order rate equation and the activation energy (E(a)) was derived using the Arrhenius equation. Thermodynamic parameters such as DeltaH(0), DeltaS(0), and DeltaG(0) were calculated from the slope and intercept of linear plot of lnK(D) against 1/T. The DeltaH(0) and DeltaG(0) values of PO(3-)(4) adsorption on the blast furnace slag show endothermic heat of adsorption. But there is a negative free energy value, indicating that the process of PO(3-)(4) adsorption is favored at high temperatures.

  4. Investigating the nitrification and denitrification kinetics under aerobic and anaerobic conditions by Paracoccus denitrificans ISTOD1.

    PubMed

    Medhi, Kristina; Singhal, Anjali; Chauhan, D K; Thakur, Indu Shekhar

    2017-03-16

    Municipal wastewater contains multiple nitrogen contaminants such as ammonia, nitrate and nitrite. Two heterotrophic nitrifier and aerobic denitrifiers, bacterial isolates ISTOD1 and ISTVD1 were isolated from domestic wastewater. On the basis of removal efficiency of ammonia, nitrate and nitrite under both aerobic and anaerobic conditions, ISTOD1 was selected and identified as Paracoccus denitrificans. Aerobically, NH4(+)-N had maximum specific nitrogen removal rate (Rxi) of 7.6g/gDCW/h and anaerobically, NO3(-)N showed Rxi of 2.5*10(-1)g/g DCW/h. Monod equation described the bioprocess kinetic coefficients, µmax and Ks, obtained by regression. Error functions were calculated to validate the Monod equation experimental data. Aerobic NO3(-)N showed the highest YW of 0.372mg DCW/mg NO3(-)N among the five conditions. ISTOD1 serves as a potential candidate for treating nitrogen rich wastewater using simultaneous nitrification and aerobic denitrification. It can be used in bioaugmentation studies under varied condition.

  5. Towards in situ fluorescence spectroscopy and microscopy investigations of asphaltene precipitation kinetics.

    PubMed

    Franco, Juliana C; Gonçalves, Grasiele; Souza, Monique S; Rosa, Samantha B C; Thiegue, Larissa M; Atvars, Teresa D Z; Rosa, Paulo T V; Nome, René A

    2013-12-16

    We perform a spectroscopic analysis of asphaltene in solution and in crude oil with the goal of designing an optical probe of asphaltene precipitation inside high-pressure cells. Quantitative analysis of steady-state spectroscopic data is employed to identify fluorescence and Raman contributions to the observed signals. Time-resolved fluorescence spectroscopy indicates that fluorescence lifetime can be used as a spectroscopic probe of asphaltene in crude oil. Quantitative confocal laser-scanning microscopy studies of asphaltene in n-heptane are used to calculate particle-size distributions as a function of time, both at the sample surface and asphaltene interior. The resulting precipitation kinetics is well described by stochastic numerical simulations of diffusion-limited aggregation. Based on these results, we present the design and construction of an apparatus to optically probe the in situ precipitation of asphaltene suitable for studies inside high pressure cells. Design considerations include the use of a spatial light modulator for aberration correction in microscopy measurements, together with the design of epi-fluorescence spectrometer, both fiber-based and for remote sensing fluorescence spectroscopy.

  6. Multivalent interaction of cyclodextrin vesicles, carbohydrate guests, and lectins: a kinetic investigation.

    PubMed

    Vico, Raquel V; Voskuhl, Jens; Ravoo, Bart Jan

    2011-02-15

    An artificial glycocalix self-assembles when unilamellar bilayer vesicles of amphiphilic β-cyclodextrins are decorated with maltose- and lactose-adamantane conjugates by host-guest interactions. The maltose-decorated vesicles aggregate in the presence of lectin concanavalin A whereas the lactose-decorated vesicles aggregate in the presence of lectin peanut agglutinin. The kinetics of the orthogonal multivalent interfacial interactions present in this ternary system of vesicles, carbohydrates, and lectins were studied by time-dependent measurements of the optical density at 400 nm. The average vesicle and vesicle aggregate sizes were monitored by dynamic light scattering. The aggregation process was evaluated as a function of lectin concentration, vesicle concentration, and surface coverage of the vesicles by the carbohydrate-adamantane conjugates. The initial rate of vesicle aggregation scales linearly with the lectin as well as the cyclodextrin vesicle concentration. Furthermore, each lectin requires a characteristic critical density of carbohydrates at the vesicle surface. These observations allow a prediction of the response of the ternary supramolecular system at different concentrations of its components. Also, the effective binding site separation in a multivalent receptor such as a multiple binding site protein can be accurately determined. This methodology can be extended to multivalent noncovalent interactions in other ligand-receptor systems at interfaces.

  7. Human enteropeptidase light chain: bioengineering of recombinants and kinetic investigations of structure and function.

    PubMed

    Smith, Eliot T; Johnson, David A

    2013-05-01

    The serine protease enteropeptidase exhibits a high level of substrate specificity for the cleavage sequence DDDDK∼ X, making this enzyme a useful tool for the separation of recombinant protein fusion domains. In an effort to improve the utility of enteropeptidase for processing fusion proteins and to better understand its structure and function, two substitution variants of human enteropeptidase, designated R96Q and Y174R, were created and produced as active (>92%) enzymes secreted by Pichia pastoris with yields in excess of 1.7 mg/Liter. The Y174R variant showed improved specificities for substrates containing the sequences DDDDK (kcat /KM = 6.83 × 10⁶ M⁻¹ sec⁻¹) and DDDDR (kcat /KM = 1.89 × 10⁷ M⁻¹ sec⁻¹) relative to all other enteropeptidase variants reported to date. BPTI inhibition of Y174R was significantly decreased. Kinetic data demonstrate the important contribution of the positively charged residue 96 to extended substrate specificity in human enteropeptidase. Modeling shows the importance of the charge-charge interactions in the extended substrate binding pocket.

  8. Curing behavior and reaction kinetics of binder resins for 3D-printing investigated by dielectric analysis (DEA)

    NASA Astrophysics Data System (ADS)

    Möginger, B.; Kehret, L.; Hausnerova, B.; Steinhaus, J.

    2016-05-01

    3D-Printing is an efficient method in the field of additive manufacturing. In order to optimize the properties of manufactured parts it is essential to adapt the curing behavior of the resin systems with respect to the requirements. Thus, effects of resin composition, e.g. due to different additives such as thickener and curing agents, on the curing behavior have to be known. As the resin transfers from a liquid to a solid glass the time dependent ion viscosity was measured using DEA with flat IDEX sensors. This allows for a sensitive measurement of resin changes as the ion viscosity changes two to four decades. The investigated resin systems are based on the monomers styrene and HEMA. To account for the effects of copolymerization in the calculation of the reaction kinetics it was assumed that the reaction can be considered as a homo-polymerization having a reaction order n≠1. Then the measured ion viscosity curves are fitted with the solution of the reactions kinetics - the time dependent degree of conversion (DC-function) - for times exceeding the initiation phase representing the primary curing. The measured ion viscosity curves can nicely be fitted with the DC-function and the determined fit parameters distinguish distinctly between the investigated resin compositions.

  9. Long-Term Follow-up Investigation of Isolated Rapid Eye Movement Sleep Without Atonia Without Rapid Eye Movement Sleep Behavior Disorder: A Pilot Study

    PubMed Central

    Stefani, Ambra; Gabelia, David; Högl, Birgit; Mitterling, Thomas; Mahlknecht, Philipp; Stockner, Heike; Poewe, Werner; Frauscher, Birgit

    2015-01-01

    Study Objectives: Idiopathic rapid eye movement (REM) sleep behavior disorder (RBD) is a harbinger of synuclein-mediated neurodegenerative diseases. It is unknown if this also applies to isolated REM sleep without atonia (RWA). We performed a long-term follow-up investigation of subjects with isolated RWA. Methods: Participants were recruited from 50 subjects with isolated RWA who were identified at the sleep laboratory of the Department of Neurology at the Medical University of Innsbruck between 2003 and 2005. Eligible subjects underwent follow-up clinical examination, polysomnography, and assessment of neurodegenerative biomarkers (cognitive impairment, finger speed deficit, impaired color vision, olfactory dysfunction, orthostatic hypotension, and substantia nigra hyperechogenicity). Results: After a mean of 8.6 ± 0.9 y, 1 of 14 participating subjects (7.3%) progressed to RBD. Ten of 14 RWA subjects (71.4%) were positive for at least one neurodegenerative biomarker. Substantia nigra hyperechogenicity and presence of mild cognitive impairment were both present in 4 of 14 subjects with isolated RWA. Electromyographic activity measures increased significantly from baseline to follow-up polysomnography (“any” mentalis and both anterior tibialis muscles: 32.5 ± 9.4 versus 52.2 ± 16.6%; p = 0.004). Conclusion: This study provides first evidence that isolated RWA is an early biomarker of synuclein-mediated neurodegeneration. These results will have to be replicated in larger studies with longer observational periods. If confirmed, these disease findings have implications for defining at-risk cohorts for Parkinson disease. Citation: Stefani A, Gabelia D, Högl B, Mitterling T, Mahlknecht P, Stockner H, Poewe W, Frauscher B. Long-term follow-up investigation of isolated rapid eye movement sleep without atonia without rapid eye movement sleep behavior disorder: a pilot study. J Clin Sleep Med 2015;11(11):1273–1279. PMID:26156949

  10. Rapid kinetics of insertion and accessibility of spin-labeled phospholipid analogs in lipid membranes: a stopped-flow electron paramagnetic resonance approach.

    PubMed Central

    Marx, U; Lassmann, G; Wimalasena, K; Müller, P; Herrmann, A

    1997-01-01

    Spin-labeled phospholipid analogs have been employed to probe the transbilayer distribution of endogenous phospholipids in various membrane systems. To determine the transmembrane distribution of the spin-labeled analogs, the analogs are usually inserted into the membrane of interest and subsequently the amount of analog in the outer membrane leaflet is determined either by chemical reduction with ascorbate or by back-exchange to bovine serum albumin (BSA). For accurate determination of the transbilayer distribution of analogs, both the kinetics of incorporation and those of accessibility of analogs to ascorbate or BSA have to be fast in comparison to their transbilayer movement. By means of stopped-flow electron paramagnetic resonance (EPR) spectroscopy, we have studied the kinetics of incorporation of the spin-labeled phosphatidylcholine (PC) analog 1-palmitoyl-2-(4-doxylpentanoyl)-sn-glycero-3-phosphocholine (SL-PC) and of its accessibility to chemical reduction and to back-exchange at room temperature. Incorporation of SL-PC into the outer leaflet of egg phosphatidylcholine (EPC) and red cell ghost membranes was essentially completed within 5 s. Ninety percent of the SL-PC molecules located in the outer membrane leaflet of those membranes were extracted by BSA within 15 s. All exterior-facing SL-PC molecules were reduced by ascorbate in a pseudo-first-order reaction within 60 s in EPC membranes and within 90 s in red cell ghost membranes. The rate of the reduction process could be enhanced by approximately 30-fold when 6-O-phenyl-ascorbic acid was used instead of ascorbate as the reducing agent. The results are discussed in light of assaying rapid transbilayer movement of spin-labeled analogs in biological membranes. PMID:9284331

  11. Colloidal nanoparticle size control: experimental and kinetic modeling investigation of the ligand-metal binding role in controlling the nucleation and growth kinetics.

    PubMed

    Mozaffari, Saeed; Li, Wenhui; Thompson, Coogan; Ivanov, Sergei; Seifert, Soenke; Lee, Byeongdu; Kovarik, Libor; Karim, Ayman M

    2017-09-21

    Despite the major advancements in colloidal metal nanoparticles synthesis, a quantitative mechanistic treatment of the ligand's role in controlling their size remains elusive. We report a methodology that combines in situ small angle X-ray scattering (SAXS) and kinetic modeling to quantitatively capture the role of ligand-metal binding (with the metal precursor and the nanoparticle surface) in controlling the synthesis kinetics. We demonstrate that accurate extraction of the kinetic rate constants requires using both, the size and number of particles obtained from in situ SAXS to decouple the contributions of particle nucleation and growth to the total metal reduction. Using Pd acetate and trioctylphosphine in different solvents, our results reveal that the binding of ligands with both the metal precursor and nanoparticle surface play a key role in controlling the rates of nucleation and growth and consequently the final size. We show that the solvent can affect the metal-ligand binding and consequently ligand coverage on the nanoparticles surface which has a strong effect on the growth rate and final size (1.4 nm in toluene and 4.3 nm in pyridine). The proposed kinetic model quantitatively predicts the effects of varying the metal concentration and ligand/metal ratio on nanoparticle size for our work and literature reports. More importantly, we demonstrate that the final size is exclusively determined by the nucleation and growth kinetics at early times and not how they change with time. Specifically, the nanoparticle size in this work and many literature reports can be predicted using a single, model independent kinetic descriptor, (growth-to-nucleation rate ratio)(1/3), despite the different metals and synthetic conditions. The proposed model and kinetic descriptor could serve as powerful tools for the design of colloidal nanoparticles with specific sizes.

  12. Colloidal nanoparticle size control: Experimental and kinetic modeling investigation of the ligand-metal binding role in controlling the nucleation and growth kinetics

    DOE PAGES

    Mozaffari, Saeed; Li, Wenhui; Thompson, Coogan; ...

    2017-09-01

    Despite the major advancements in colloidal metal nanoparticles synthesis, a quantitative mechanistic treatment of the ligand’s role in controlling their size remains elusive. We report a methodology that combines in-situ small angle x-ray scattering (SAXS) and kinetic modeling to quantitatively capture the role of ligand-metal binding (with the metal precursor and the nanoparticle surface) in controlling the synthesis kinetics. We demonstrate that accurate extraction of the kinetic rate constants requires using both, the size and number of particles obtained from in-situ SAXS to decouple the contributions of particle nucleation and growth to the total metal reduction. Using Pd acetate andmore » trioctylphosphine in different solvents, our results reveal that the binding of ligands with both the metal precursor and nanoparticle surface play a key role in controlling the rates of nucleation and growth and consequently the final size. We show that the solvent can affect the metal-ligand binding and consequently ligand coverage on the nanoparticles surface which has a strong effect on the growth rate and final size (1.4 nm in toluene and 4.3 nm in pyridine). The proposed kinetic model quantitatively predicts the effects of varying the metal concentration and ligand/metal ratio on nanoparticle size for our work and literature reports. More importantly, we demonstrate that the final size is exclusively determined by the nucleation and growth kinetics at early times and not how they change with time. Specifically, the nanoparticle size in this work and many literature reports can be predicted using a single, model independent kinetic descriptor, (Growth-to-Nucleation rate ratio)1/3, despite the different metals and synthetic conditions. The proposed model and kinetic descriptor could serve as powerful tools for the design of colloidal nanoparticles with specific sizes.« less

  13. Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

    NASA Astrophysics Data System (ADS)

    Pankin, A. Y.; Rafiq, T.; Kritz, A. H.; Park, G. Y.; Snyder, P. B.; Chang, C. S.

    2017-06-01

    The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. The neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] is used in carrying out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. Simulations with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. However, the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new

  14. The Investigation of Demand for a Rapid Document Delivery Service for the University of Pittsburgh Library System. Final Report.

    ERIC Educational Resources Information Center

    Montgomery, K. Leon; And Others

    A joint project of the University of Pittsburgh Library System and the School of Library and Information Science investigated the need for a rapid document delivery service within the University Library System (ULS). Two instruments were designed to answer questions about library patrons' uses of bibliographic citations retrieved in online…

  15. Kinetic Investigations of the Role of Factor Inhibiting Hypoxia-inducible Factor (FIH) as an Oxygen Sensor*

    PubMed Central

    Tarhonskaya, Hanna; Hardy, Adam P.; Howe, Emily A.; Loik, Nikita D.; Kramer, Holger B.; McCullagh, James S. O.; Schofield, Christopher J.; Flashman, Emily

    2015-01-01

    The hypoxia-inducible factor (HIF) hydroxylases regulate hypoxia sensing in animals. In humans, they comprise three prolyl hydroxylases (PHD1–3 or EGLN1–3) and factor inhibiting HIF (FIH). FIH is an asparaginyl hydroxylase catalyzing post-translational modification of HIF-α, resulting in reduction of HIF-mediated transcription. Like the PHDs, FIH is proposed to have a hypoxia-sensing role in cells, enabling responses to changes in cellular O2 availability. PHD2, the most important human PHD isoform, is proposed to be biochemically/kinetically suited as a hypoxia sensor due to its relatively high sensitivity to changes in O2 concentration and slow reaction with O2. To ascertain whether these parameters are conserved among the HIF hydroxylases, we compared the reactions of FIH and PHD2 with O2. Consistent with previous reports, we found lower Kmapp(O2) values for FIH than for PHD2 with all HIF-derived substrates. Under pre-steady-state conditions, the O2-initiated FIH reaction is significantly faster than that of PHD2. We then investigated the kinetics with respect to O2 of the FIH reaction with ankyrin repeat domain (ARD) substrates. FIH has lower Kmapp(O2) values for the tested ARDs than HIF-α substrates, and pre-steady-state O2-initiated reactions were faster with ARDs than with HIF-α substrates. The results correlate with cellular studies showing that FIH is active at lower O2 concentrations than the PHDs and suggest that competition between HIF-α and ARDs for FIH is likely to be biologically relevant, particularly in hypoxic conditions. The overall results are consistent with the proposal that the kinetic properties of individual oxygenases reflect their biological capacity to act as hypoxia sensors. PMID:26112411

  16. Freeze concentration effects on ice (photo) chemical kinetics investigated by UV-Vis spectroscopy

    NASA Astrophysics Data System (ADS)

    Newberg, J. T.; Arble, C.; Zhang, J.

    2013-12-01

    We will describe the setup of a fiber coupled UV-Vis spectrometer to investigate the chemistry and photochemistry of aqueous solutions before and after freezing. The photochemical degradation of pyranine at the isosbestic point was investigated. Direct photochemical degradation was minor compared to indirect degradation through hydroxyl radical (OH) attack at room temperature. At -10 C indirect OH degradation was increased relative to room temperature studies, and has been attributed to the freeze concentration effect. The reaction of bromate with bromide in the presence of acid to form molecular bromine was investigated. Upon freezing the formation rate of bromine significantly increases, which we attribute to the freeze concentration effect.

  17. Investigating Rapid Uplift and Subsidence Near Norris, Yellowstone, During 2013-2014

    NASA Astrophysics Data System (ADS)

    Stovall, W. K.; Cervelli, P. F.; Shelly, D. R.

    2014-12-01

    Although Yellowstone's last magmatic eruption occurred about 70,000 years ago, hydrothermal explosions, earthquakes, and ground deformation still occur as testament to ongoing volcanic and tectonic processes. Since the late 1990s, a network of continuously recording Global Positioning System (GPS) receivers has recorded uplift and subsidence of the caldera and northwest caldera margin near Norris Geyser Basin. Previous deformation episodes have shown opposing vertical motion at the two sites, which has been attributed to temporal variations in magmatic fluid flux from the caldera laterally through the Norris-Mammoth fault corridor that intersects the caldera's northwest margin (Dzurisin et al., 2012; Wicks et al., 2006). These episodes have exhibited gradual changes, transitioning from uplift to subsidence (and vice versa) over weeks to months. Large earthquake swarms accompanied transitions from caldera uplift to subsidence in 1985 and 2010. Recent deformation in Yellowstone differs from previously observed episodes. In the latter half of 2013, uplift began around Norris, and by January of 2014 it reached rates of over 15 cm/yr. Also at the start of 2014, caldera deformation shifted from approximately 4 years of slow subsidence to slow uplift. On March 30, 2014, a M4.8 earthquake, the largest in Yellowstone since 1980, occurred northwest of Norris Geyser Basin near the center of uplift. Shortly after the event, deformation near Norris abruptly reversed to rapid subsidence (over 20 cm/yr). Caldera uplift began to accelerate around the same time. Thus, uplift can occur simultaneously in both the caldera and the Norris area, and dramatic reversals from rapid uplift to rapid subsidence can occur within a matter of days. While the complexity of the deformation defies a simple explanation, we hypothesize that the rapid transition from uplift to subsidence at Norris may indicate that the M4.8 earthquake opened a pathway for fluid migration away from Norris and allowed an

  18. Kinetics and mechanism of the degradation of methyl parathion in aqueous hydrogen sulfide solution: investigation of natural organic matter effects.

    PubMed

    Guo, Xiaofen; Jans, Urs

    2006-02-01

    The kinetics of the transformation of methyl parathion have been investigated in aqueous solution containing reduced sulfur species and small concentrations of natural organic matter (NOM) from different sources such as soil, river, and peat. It was shown that NOM mediates the degradation of methyl parathion in aqueous solutions containing hydrogen sulfide. After evaluating and quantifying the effect of the NOM concentration on the degradation kinetics of methyl parathion in the presence of hydrogen sulfide, it was found that the observed pseudo-first-order reaction rate constants (k(obs)) were proportional to NOM concentrations. The influence of pH on the degradation of methyl parathion in the aqueous solutions containing hydrogen sulfide and NOM has been studied. The rate of degradation of methyl parathion was strongly pH dependent. The results indicate k(obs) with a commercially available humic acid has a maximum value at approximately pH 8.3. Two main reaction mechanisms are identified to dominate the degradation of methyl parathion in aqueous solution containing hydrogen sulfide and NOM based on the products aminomethyl parathion and desmethyl methyl parathion. The two mechanisms are nitro-group reduction and nucleophilic attack at the methoxy-carbon. The reduction of the nitro-group is only observed in the presence of NOM. The results of this study form an important base for the evaluation and interpretation of transformation processes of methyl parathion in the environment.

  19. Irradiation deformation near different atomic grain boundaries in α-Zr: An investigation of thermodynamics and kinetics of point defects

    PubMed Central

    Arjhangmehr, A.; Feghhi, S. A. H.

    2016-01-01

    Understanding radiation performance of nanocrystalline Zr-based alloys is essential to develop internal components and external cladding materials with self-healing capabilities for longer and safer life cycles in harsh reactor environments. However, the precise role of interfaces in modifying defect production and evolution in α-Zr is not yet determined. Using atomistic simulation methods, we investigate the influence of different atomic grain boundaries (GBs) in thermodynamic and kinetic properties of defects on short timescales. We observe that the sink efficiency and sink strength of interfaces vary significantly with the boundary structures, with a preference to absorb interstitials (vacancies) when the GBs are semi-parallel (semi-perpendicular) relative to the basal planes. Further, we identify three distinct primary cascade geometries, and find that the residual defect clustering in grain interiors depends on how the atomic GBs modify the spatial distribution of defects within the crystal structure. Finally, we explain and discuss the dynamic results in terms of energetic and kinetic behaviors of defects near the pristine and damaged boundaries. Eventually, these will provide a microscopic reference for further improving the radiation response of Zr by using fine grains or by introducing a high density of dispersoids in material metallurgy. PMID:27004606

  20. A numerical investigation of the scale-up effects on flow, heat transfer, and kinetics processes of FCC units.

    SciTech Connect

    Chang, S. L.

    1998-08-25

    Fluid Catalytic Cracking (FCC) technology is the most important process used by the refinery industry to convert crude oil to valuable lighter products such as gasoline. Process development is generally very time consuming especially when a small pilot unit is being scaled-up to a large commercial unit because of the lack of information to aide in the design of scaled-up units. Such information can now be obtained by analysis based on the pilot scale measurements and computer simulation that includes controlling physics of the FCC system. A Computational fluid dynamic (CFD) code, ICRKFLO, has been developed at Argonne National Laboratory (ANL) and has been successfully applied to the simulation of catalytic petroleum cracking risers. It employs hybrid hydrodynamic-chemical kinetic coupling techniques, enabling the analysis of an FCC unit with complex chemical reaction sets containing tens or hundreds of subspecies. The code has been continuously validated based on pilot-scale experimental data. It is now being used to investigate the effects of scaled-up FCC units. Among FCC operating conditions, the feed injection conditions are found to have a strong impact on the product yields of scaled-up FCC units. The feed injection conditions appear to affect flow and heat transfer patterns and the interaction of hydrodynamics and cracking kinetics causes the product yields to change accordingly.

  1. Investigation of the first-order phase transition kinetics using the method of pulsed photothermal surface deformation: radial measurements

    NASA Astrophysics Data System (ADS)

    Vintzentz, S. V.; Sandomirsky, V. B.

    1992-09-01

    An extension of the photothermal surface deformation (PTSD) method to study the macroscopic kinetics of the first-order phase transition (PTr) is given. The movement of the phase interface (PI) over a surface with a PTr locally induced in the subsurface volume by a focused laser pulse is investigated for the first time using radial measurements of the PTSD kinetics. For the known metal-to-semiconductor PTr in VO 2 (a good model system) a procedure is suggested for measuring the maximum size rsm of the "hot" (metal) phase on the surface (a parameter most difficult to determine) as well as for estimating the velocity of the PI movement over the surface, vs, and in the bulk, vb. Besides, it is shown that the PTSD method may be used to determine the "local" threshold energy E0 needed for the laser-induced PTr and the "local" latent heat L of the PTr. This demonstrates the feasibility of scanning surface E0- and L-microscopy.

  2. Irradiation deformation near different atomic grain boundaries in α-Zr: An investigation of thermodynamics and kinetics of point defects.

    PubMed

    Arjhangmehr, A; Feghhi, S A H

    2016-03-23

    Understanding radiation performance of nanocrystalline Zr-based alloys is essential to develop internal components and external cladding materials with self-healing capabilities for longer and safer life cycles in harsh reactor environments. However, the precise role of interfaces in modifying defect production and evolution in α-Zr is not yet determined. Using atomistic simulation methods, we investigate the influence of different atomic grain boundaries (GBs) in thermodynamic and kinetic properties of defects on short timescales. We observe that the sink efficiency and sink strength of interfaces vary significantly with the boundary structures, with a preference to absorb interstitials (vacancies) when the GBs are semi-parallel (semi-perpendicular) relative to the basal planes. Further, we identify three distinct primary cascade geometries, and find that the residual defect clustering in grain interiors depends on how the atomic GBs modify the spatial distribution of defects within the crystal structure. Finally, we explain and discuss the dynamic results in terms of energetic and kinetic behaviors of defects near the pristine and damaged boundaries. Eventually, these will provide a microscopic reference for further improving the radiation response of Zr by using fine grains or by introducing a high density of dispersoids in material metallurgy.

  3. Microstructural investigation to the controlled release kinetics of monolith osmotic pump tablets via synchrotron radiation X-ray microtomography.

    PubMed

    Li, Haiyan; Yin, Xianzhen; Ji, Junqiu; Sun, Lixin; Shao, Qun; York, Peter; Xiao, Tiqiao; He, You; Zhang, Jiwen

    2012-05-10

    Tomographic imaging techniques are attractive tools for the visualization of the internal structural characteristics of pharmaceutical solid dosage forms. In this paper, the internal structure of the tablet core for a monolith osmotic drug delivery system, felodipine sustained-release tablet, was visualized via synchrotron radiation X-ray computed microtomography during the drug release process. The surface areas and three dimensional parameters of the tablet core were calculated based on the three dimensional reconstruction of the images. At different stages of the drug release process, the surface morphology, the hydration, the swelling, and the structure changing of the tablet, were visualized from the two dimensional monochrome X-ray images. The three dimensional volumes of the remaining tablet core correlated well with the percentages of felodipine (R=0.9988). Also, the three dimensional surface area almost unchanged during the drug release process, which clearly demonstrated the intrinsic drug release mechanism of the osmotic drug delivery system. In conclusion, the synchrotron radiation X-ray computed microtomography, with rapid acquisition, high intensity and micro-scale spatial resolution, was found to be a useful tool for the quantitative elucidation of the intrinsic drug release kinetics and the three dimensional parameters such as surface areas of the remained core obtained by the synchrotron radiation. Thus, X-ray computed microtomography can be considered as a new and complimentary analytical tool to standard compendial pharmaceutical tests for quality control of osmotic drug delivery systems.

  4. Kinetic investigation of catalytic disproportionation of superoxide ions in the non-aqueous electrolyte used in Li–air batteries

    SciTech Connect

    Wang, Qiang; Zheng, Dong; McKinnon, Meaghan E.; Yang, Xiao -Qing; Qu, Deyang

    2014-10-28

    Superoxide reacts with carbonate solvents in Li–air batteries. Tris(pentafluorophenyl)borane is found to catalyze a more rapid superoxide (O2-) disproportionation reaction than the reaction between superoxide and propylene carbonate (PC). With this catalysis, the negative impact of the reaction between the electrolyte and O2-produced by the O2 reduction can be minimized. A simple kinetic study using ESR spectroscopy was reported to determine reaction orders and rate constants for the reaction between PC and superoxide, and the disproportionation of superoxide catalyzed by Tris(pentafluorophenyl)borane and Li ions. As a result, the reactions are found to be first order and the rate constants are 0.033 s-1 M-1, 0.020 s-1 M-1and 0.67 s-1M-1 for reactions with PC, Li ion and Tris(pentafluorophenyl)borane, respectively.

  5. Investigation of the aluminum phthalocyanine nanoparticles colloidal solutions pH-dependent photoluminescence kinetics in pico- and nanosecond time range

    NASA Astrophysics Data System (ADS)

    Bystrov, F. G.; Makarov, V. I.; Loschenov, V. B.

    2016-08-01

    In this study, the fluorescence intensity decay of aluminum phthalocyanine nanoparticles colloidal solutions at different pH was investigated. Hamamatsu Streak-Camera (C10627 - 13 Hamamatsu Photonics) with picosecond temporal resolution (15 ps) was used to carry out the measurements. For excitation we used Hamamatsu Picosecond Light Pulser PLP - 10 with 637 nm wavelength and 65 ps pulse duration. The changes in fluorescence decay kinetics were found during the experiment. The number of fluorescence lifetime components and duration of lifetimes depends on pH. At pH 2 the presence of two fluorescence lifetimes was recorded: the first one was 5 ns, which corresponded to the molecular form in solution, and 1.5 ns, which corresponded to bound state of phthalocyanine molecules. This work is a preparatory step towards a model which describes the interaction of aluminum phthalocyanine nanoparticles with environment in biological tissue.

  6. An Investigation of the Effect of Surface Impurities on the Adsorption Kinetics of Hydrogen Chemisorbed onto Iron

    NASA Technical Reports Server (NTRS)

    Shanabarger, M. R.

    1997-01-01

    The original goal of this program was to investigate the effect surface impurities have on the heterogeneous kinetic processes of those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. However, shortly after the initiation of the original program, the program's NASA Technical Monitor, Dr. Howard Nelson, requested that the effort supported by this Co-operative Agreement be redirected to study more pressing materials issues associated to the development of the National Aero-Space Plane (NASP). The results of these efforts are outlined in this report. Detailed discussions of specific work, including experimental techniques and procedures, will be found in the publications listed with the subsection discussing that specific work as well and in Section 5. No inventions were generated or disclosed within this Agreement.

  7. Kinetic modeling of the polymer-derived ceramics route: investigation of the thermal decomposition kinetics of poly[B-(methylamino)borazine] precursors into boron nitride.

    PubMed

    Bernard, Samuel; Fiaty, Koffi; Cornu, David; Miele, Philippe; Laurent, Pierre

    2006-05-11

    A complete kinetic modeling of the polymer-derived ceramics (PDCs) route is achieved for the first time through the investigation of the solid-state decomposition of a typical melt-spinnable poly[B-(methylamino)borazine] into boron nitride fibers at various heating rates. Through the use of the Lorentz fitting approach, it is shown that the two-step weight loss associated with the polymer-to-ceramic conversion is governed by a complex interplay of five diffusion-type transport mechanisms that are independent of the applied heating schedule. The application of the Friedman method to dynamic thermogravimetry data yields Ea and ln A values that are seen to increase with the extent of the ceramic conversion from region one (Ea = 38.73 kJ mol(-1)) to region five (Ea = 146.64 kJ mol(-1)). This fact indicates that both the mechanisms within those regions are parallel routes to the formation of the final solid-state material and their complexity increases with the conversion progress. The cross-linking process (first weight loss) of the polymer is governed by three dependent poorly energetic mechanisms. The first weight loss is activated by ammonolysis reactions that provide a modified polymer capable of undergoing condensation reactions in regions two and three to yield a highly cross-linked polymer. A large evolution of methylamine is identified during this process. Mineralization (region four) and ceramization (region five) steps are represented by two highly energetic multistep mechanisms. The mineralization step is associated with a large evolution of methylamine and occurs during the transition between the cross-linking and ceramization processes through the cleavage of the inter-ring B-N bonds. Ceramization represents the end of the polymer-to-ceramic conversion in which the planar consolidation of BN hexagons occurs through complex structural rearrangements of the borazine units (cleavage of the intraring B-N bonds) accompanied with an ammonia evolution. Finally

  8. Frijolito Watershed: Integrated investigations of a rapidly eroding pinyon-juniper hillslope

    SciTech Connect

    Wilcox, B.P.; Pitlick, J.; Allen, C.D.

    1995-12-31

    The dramatic acceleration of erosion associated with the expansion of pinyon-juniper woodlands over the past 100 years has been widely recognized, but few process-based studies of this phenomenon have been undertaken. In an attempt to identify the underlying causes, and the factors that affect erosion processes, we have initiated an interdisciplinary study of a rapidly eroding pinyon-juniper woodland in northern New Mexico. Since July 1993, we have collected data on runoff, erosion, and weather conditions from a 1-ha catchment study area and have conducted surveys of topography, soils, and vegetation. Our preliminary results indicate that although runoff makes up less than 10% of the annual water budget, runoff events - which are frequent in the summer - are capable of moving large amounts of sediment. We estimate that between July 1993 and October 1994, between 25,000 and 50,000 kg of sediment has eroded and been transported from the catchment. The information gained from such studies is essential to our ability to formulate effective strategies for managing these rapidly eroding woodlands.

  9. Experimental investigation of convective drying kinetics of kiwi under different conditions

    NASA Astrophysics Data System (ADS)

    Darıcı, Selçuk; Şen, Soner

    2015-08-01

    The effects of air temperature, velocity and humidity on drying characteristics of kiwi are experimentally investigated for the temperatures in the range of 50-80 °C, of the velocities 0.5-2.0 m/s, of the relative humidity values of 5-20 % and for two slice thicknesses. It is observed that there is a very close agreement between the model of Midilli et al. (Dry Technol 20:1503-1513, 2002) and the present study with coefficients of correlation R2 of 0.9949-0.9996.

  10. An experimental and kinetic investigation of premixed furan/oxygen/argon flames

    PubMed Central

    Tian, Zhenyu; Yuan, Tao; Fournet, Rene; Glaude, Pierre-Alexandre; Sirjean, Baptiste; Battin-Leclerc, Frédérique; Zhang, Kuiwen; Qi, Fei

    2013-01-01

    The detailed chemical structures of three low-pressure (35 Torr) premixed laminar furan/oxygen/argon flames with equivalence ratios of 1.4, 1.8 and 2.2 have been investigated by using tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. About 40 combustion species including hydrocarbons and oxygenated intermediates have been identified by measurements of photoionization efficiency spectra. Mole fraction profiles of the flame species including reactants, intermediates and products have been determined by scanning burner position with some selected photon energies near ionization thresholds. Flame temperatures have been measured by a Pt-6%Rh/Pt-30%Rh thermocouple. A new mechanism involving 206 species and 1368 reactions has been proposed whose predictions are in reasonable agreement with measured species profiles for the three investigated flames. Rate-of-production and sensitivity analyses have been performed to track the key reaction paths governing furan consumption for different equivalence ratios. Both experimental and modeling results indicate that few aromatics could be formed in these flames. Furthermore, the current model has been validated against previous pyrolysis results of the literature obtained behind shock waves and the agreement is reasonable as well. PMID:23814311

  11. Experimental and Theoretical Investigations on the Nanoscale Kinetic Friction in Ambient Environmental Conditions.

    PubMed

    Gueye, Birahima; Zhang, Yan; Wang, Yujuan; Chen, Yunfei

    2015-07-08

    The liquid lubrication, thermolubricity and dynamic lubricity due to mechanical oscillations are investigated with an atomic force microscope in ambient environmental conditions with different relative humidity (RH) levels. Experimental results demonstrate that high humidity at low-temperature regime enhances the liquid lubricity while at high-temperature regime it hinders the effect of the thermolubricity due to the formation of liquid bridges. Friction response to the dynamic lubricity in both high- and low-temperature regimes keeps the same trends, namely the friction force decreases with increasing the amplitude of the applied vibration on the tip regardless of the RH levels. An interesting finding is that for the dynamic lubricity at high temperature, high-humidity condition leads to the friction forces higher than that at low-humidity condition while at low temperature the opposite trend is observed. An extended two-dimensional dynamic model accounting for the RH is proposed to interpret the frictional mechanism in ambient conditions.

  12. Investigation of pyrolysis kinetics of humic acids from low rank Anatolian coal by thermal analysis

    SciTech Connect

    Tonbul, Y.; Erdogan, S.

    2007-07-01

    Thermogravimetric analysis (TGA) of humic acid samples from low rank Anatolian (east of Turkey, Bingol) coal were investigated under atmospheric pressure. The samples were subjected for the decomposition of organic matter ambient to 800{sup o} C at four different heating rates (5, 10, 15, and 20 degrees C min{sup -1}). The humic acid samples were started at decomposition between 170 - 206{sup o}C and amount of residues varied 55-60% according to heating rate. Each of samples showed a single step mass loss. TG/DTG data of samples were analyzed to determine activation energy values by Coats and Redfern method and Arrhenius method. Activation energy values are similar obtained from Coats and Redfern method and Arrhenius method and varied from 25 to 29 kJ mol{sup -1}.

  13. Cyanide inhibition of cytochrome c oxidase. A rapid-freeze e.p.r. investigation.

    PubMed Central

    Jensen, P; Wilson, M T; Aasa, R; Malmström, B G

    1984-01-01

    The inhibition of cytochrome c oxidase by cyanide, starting either with the resting or the pulsed enzyme, was studied by rapid-freeze quenching followed by quantitative e.p.r. It is found that a partial reduction of cytochrome oxidase by transfer of 2 electron equivalents from ferrocytochrome c to cytochrome a and CuA will induce a transition from a closed to an open enzyme conformation, rendering the cytochrome a3-CuB site accessible for cyanide binding, possibly as a bridging ligand. A heterogeneity in the enzyme is observed in that an e.p.r. signal from the cytochrome a3 3+-HCN complex is only found in 20% of the molecules, whereas the remaining cyanide-bound a3-CuB sites are e.p.r.-silent. PMID:6098268

  14. UDP-Glucuronosyltransferase (UGT) 1A9-Overexpressing HeLa Cells Is an Appropriate Tool to Delineate the Kinetic Interplay between Breast Cancer Resistance Protein (BRCP) and UGT and to Rapidly Identify the Glucuronide Substrates of BCRP

    PubMed Central

    Jiang, Wen; Xu, Beibei; Wu, Baojian; Yu, Rong

    2012-01-01

    The interplay between phase II enzymes and efflux transporters leads to extensive metabolism and low bioavailability for flavonoids. To investigate the simplest interplay between one UDP-glucuronosyltransferase isoform and one efflux transporter in flavonoid disposition, engineered HeLa cells stably overexpressing UGT1A9 were developed, characterized, and further applied to investigate the metabolism of two model flavonoids (genistein and apigenin) and excretion of their glucuronides. The results indicated that the engineered HeLa cells overexpressing UGT1A9 rapidly excreted the glucuronides of genistein and apigenin. The kinetic characteristics of genistein or apigenin glucuronidation were similar with the use of UGT1A9 overexpressed in HeLa cells or the commercially available UGT1A9. Small interfering (siRNA)-mediated UGT1A9 silencing resulted in a substantial decrease in glucuronide excretion (>75%, p < 0.01). Furthermore, a potent inhibitor of breast cancer resistance protein (BCRP), 3-(6-isobutyl-9-methoxy-1,4-dioxo-1,2,3,4,6,7,12,12a-octahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indol-3-yl)-propionic acid tert-butyl ester (Ko143), caused, in a dose-dependent manner, a substantial and marked reduction of the clearance (74–94%, p < 0.01), and a substantial increase in the intracellular glucuronide levels (4–8-fold, p < 0.01), resulting in a moderate decrease in glucuronide excretion (19–59%, p < 0.01). In addition, a significant, albeit moderate, reduction in the fraction of genistein metabolized (fmet) in the presence of Ko143 was observed. In contrast, leukotriene C4 and siRNA against multidrug resistance protein (MRP) 2 and MRP3 did not affect excretion of flavonoid glucuronides. In conclusion, the engineered HeLa cells overexpressing UGT1A9 is an appropriate model to study the kinetic interplay between UGT1A9 and BCRP in the phase II disposition of flavonoids. This simple cell model should also be very useful to rapidly identify whether a phase II

  15. An experimental and theoretical investigation of the rapid consolidation of continuously reinforced, metal-matrix composites

    SciTech Connect

    Nicolaou, P.D.; Semiatin, S.L.; Goetz, R.L.

    1996-06-01

    The feasibility of the rapid consolidation of Ti-14Al-21Nb/SCS-6 foil/fiber/foil composites using a forging approach was established as an alternative to slower and more expensive processes such as those based on hot isostatic pressing (HIP) or vacuum hot pressing (VHP). A firm basis for the technique was developed through theoretical analyses of temperature transients, forging pressures, and fiber fracture. These analyses demonstrated that there exists an optimal forging speed at which the consolidation stresses are a minimum. It was also shown that the flow stress of the encapsulation material relative to that of the densifying layup is an important consideration in achieving full consolidation during forging. Specifically, the difference in flow stress between the two materials influences the magnitude and sign of the in-plane (secondary) stresses that are developed during forging and therefore the rate of pore closure during the latter stages of the process. With regard to fiber fracture, analyses were performed to estimate the axial and tangential stresses during rapid consolidation. The theoretical work was validated by experimental trials using the Ti-14Al-21Nb matrix/silicon carbide fiber system. Measured forging pressures were in good agreement wit h predictions. Fiber fracture observations indicated that tangential tensile stresses developed in the fiber control failure; a forging window to avoid such failures was thus developed. Finally, it was demonstrated that matrix microstructures and mechanical properties similar to those of conventionally consolidated Ti-14Al-21Nb/silicon carbide composites can be achieved by the forge-consolidation technique.

  16. An experimental and theoretical investigation of the rapid consolidation of continuously reinforced, metal-matrix Composites

    NASA Astrophysics Data System (ADS)

    Nicolaou, P. D.; Semiatin, S. L.; Goetz, R. L.

    1996-06-01

    The feasibility of the rapid consolidation of T-14Al-21Nb/SCS-6 foil/fiber/foil composites using a forging approach was established as an alternative to slower and more expensive processes such as those based on hot isostatic pressing (HIP) or vacuum hot pressing (VHP). A firm basis for the technique was developed through theoretical analyses of temperature transients, forging pressures, and fiber fracture. These analyses demonstrated that there exists an optimal forging speed at which the consolidation stresses are a minimum. It was also shown that the flow stress of the encapsulation material relative to that of the densifying layup is an important consideration in achieving full consolidation during forging. Specifically, the difference in flow stress between the two materials influences the magnitude and sign of the in-plane (secondary) stresses that are developed during forging and therefore the rate of pore closure during the latter stages of the process. With regard to fiber fracture, analyses were performed to estimate the axial and tangential stresses during rapid consolidation. The theoretical work was validated by experimental trials using the Ti-14Al-21Nb matrix/silicon carbide fiber system. Measured forging pressures were in good agreement with predictions. Fiber fracture observations indicated that tangential tensile stresses developed in the fiber control failure; a forging window to avoid such failures was thus developed. Finally, it was demonstrated that matrix microstructures and mechanical properties similar to those of conventionally consolidated Ti-14Al-21Nb/silicon carbide composites can be achieved by the forge-consolidation technique.

  17. What is the true enzyme kinetics in the biological system? An investigation of macromolecular crowding effect upon enzyme kinetics of glucose-6-phosphate dehydrogenase.

    PubMed

    Norris, Matthew G S; Malys, Naglis

    2011-02-18

    Enzyme kinetic parameters for rate equations are vital in metabolic network simulation, a major part of systems biology research efforts. Measurements of Michaelis-Menten kinetic parameters Km and Kcat have been performed for enzymes glucose-6-phosphate dehydrogenase (G6P DH) under crowded conditions using molecular crowding agents bovine serum albumin (BSA) and polyethylene glycol (PEG) of 8000 Da molecular weight. An increase in Kcat was observed at very low concentrations of crowding agent, and also at high crowder concentrations when the experiment was performed at 45 °C with PEG. The observed pattern in Kcat for G6P DH at high crowder concentrations has been explained via modelling using excluded volume theory. An increase in rate was observed at 45 °C for G6P DH versus 30 °C; this has been modelled via the Arrhenius equation.

  18. Investigation of rapid degradation in GaN-based blue laser diodes

    NASA Astrophysics Data System (ADS)

    Wen, Pengyan; Zhang, Shuming; Li, Deyao; Liu, Jianping; Zhang, Liqun; Shi, Dong; Zhou, Kun; Tian, Aiqin; Feng, Shiwei; Yang, Hui

    2016-11-01

    Investigation of the degradation modes in GaN-based blue laser diodes grown by metal organic chemical vapor deposition (MOCVD) is carried out. Early failure of the LDs happened at the initial stage of the aging. After analysis of the electrical and thermal characteristics, local degradation of the active region is observed. Further investigation on the microstructures of the local regions shows that the early failure of the LDs is due to the local structure damage with the formation of gallium metal.

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

    SciTech Connect

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

    2015-02-05

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

  20. Investigation of H2 Concentration and Combustion Instability Effects on the Kinetics of Strained Syngas Flames

    SciTech Connect

    Ahsan R. Choudhuri

    2006-08-07

    The flame extinction limits of syngas (H{sub 2}-CO) flames were measured using a twin-flame-counter-flow burner. Plots of Extinction limits vs. global stretch rates were generated at different mixture compositions and an extrapolation method was used to calculate the flame extinction limit corresponding to an experimentally unattainable zero-stretch condition. The zero-stretch extinction limit of H{sub 2}-CO mixtures decreases (from rich to lean) with the increase in H{sub 2} concentration in the mixture. The average difference between the measured flame extinction limit and the Le Chatelier's calculation is around {approx} 7%. The measured OH{sup -} chemiluminescent data indicates that regardless of mixture compositions the OH radical concentration reduces (within the experimental uncertainties) to an extinction value prior to the flame extinction. Flame extinction limits of H{sub 2}-CO mixtures measured in a flat-flame burner configuration also show a similar relation. Additionally, the measured laminar flame velocity close to the extinction indicates that regardless of fuel composition the premixed flame of hydrogen fuel blends extinguishes when the mixture laminar flame velocity falls below a critical value. The critical laminar flame velocity at extinction for H{sub 2}-CO premixed flames (measured in the flat flame burner configuration) is found to be 3.77({+-}0.38) cm/s. An externally perturbed H{sub 2}-CO twin flame was not experimentally achievable for the mixture conditions used in the present investigation. A slightest perturbation in the flow-field distorts the H{sub 2}-CO twin-flame. The flame becomes highly unstable with the introduction of an externally excited flow oscillation.

  1. Investigating synergies of data fusion and image segmentation in earth observation based rapid mapping workflows

    NASA Astrophysics Data System (ADS)

    Witharana, C.

    2013-12-01

    In humanitarian emergencies, the timeliness of data provision and the short time-window available for dispatching value-added information pose major challenges to the mapping community. We have been engaged with a continuous research effort to explore novel ways to catalyze the EO-based humanitarian crisis information retrieval chain. This paper is an exploratory study, which aimed to discover the synergies of data fusion and image segmentation in the context of EO-based rapid mapping workflows. Our approach pillared on the geographic object-based image analysis (GEOBIA) focusing on multiscale, internally-displaced persons' (IDP) camp information extraction from very high spatial resolution (VHSR) images. We applied twelve pansharpening algorithms to two subsets of a GeoEye-1 image scene that was taken over a former war-induced ephemeral settlement in Sri Lanka. A multidimensional assessment was employed to benchmark pansharpening algorithms with respect to their spectral and spatial fidelity. The multiresolution segmentation (MRS) algorithm of the eCognition Developer software served as the key algorithm in the segmentation process. The first study site was used for comparing segmentation results produced from the twelve fused products at a series of scale, shape, and compactness settings of the MRS algorithm. The segmentation quality and optimum parameter settings of the MRS algorithm were estimated by using empirical discrepancy measures. Non-parametric statistical tests were used to compare the quality of image object candidates, which were derived from the twelve pansharpened products. A wall-to-wall classification was performed based on a support vector machine (SVM) classifier to classify image objects candidates of the fused images. The second site simulated a more realistic crisis information extraction scenario where the domain expertise is crucial in segmentation and classification. We compared segmentation and classification results of the original

  2. Application of SPECT/CT imaging system and radiochemical analysis for investigation of blood kinetics and tissue distribution of radiolabeled plumbagin in healthy and Plasmodium berghei-infected mice.

    PubMed

    Sumsakul, W; Karbwang, J; Na-Bangchang, K

    2016-02-01

    Plumbagin is a derivative of napthoquinone which is isolated from the roots of plants in several families. These compound exhibits a wide range of biological and pharmacological activities including antimalarial, antibacterial, antifungal, and anticancer activities. The aim of the study was to investigate blood kinetics and tissue distribution of plumbagin in healthy and Plasmodium berghei-infected mice using Single-Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) and radiochemical analysis by gamma counter. Plumbagin was labeled with (99m)technetium and the reducing agent stannous chloride dihydrate (50 μg/ml) at pH 6.5. Blood kinetics and tissue distribution of the radiolabeled plumbagin were investigated in healthy and P. berghei-infected mice (2 males and 2 females for each experimental group). In vitro and in vivo stability of plumbagin complex suggested satisfactory stability profiles of (99m)Tc-plumbagin complex in plasma and normal saline (92.21-95.47%) within 24 h. Significant difference in blood kinetics parameters (Cmax, AUC, t1/2, MRT, Vd, and CL) were observed between P. berghei-infected and healthy mice. The labeled complex distributed to all organs of both healthy and infected mice but with high intensity in liver, followed by lung, stomach, large intestine and kidney. Accumulation in spleen was markedly noticeable in the infected mice. Plumbagin-labeled complex was rapidly cleared from blood and major routes of excretion were hepatobiliary and pulmonary routes. In P. berghei-infected mice, t1/2 was significantly decreased, while Vd and CL were increased compared with healthy mice. Result suggests that malaria disease state influenced the pharmacokinetics and disposition of plumbagin. SPECT/CT imaging with radiolabeled (99m)Tc is a viable non-invasive technique that can be applied for investigation of kinetics and biodistribution of plumbagin in animal models.

  3. Effect of morin on pharmacokinetics of piracetam in rats, in vitro enzyme kinetics and metabolic stability assay using rapid UPLC method.

    PubMed

    Sahu, Kapendra; Shaharyar, Mohammad; Siddiqui, Anees A

    2013-07-01

    The aim of this study was to investigate the effect of Morin on the pharmacokinetics of Piracetam in rats, in vitro enzyme kinetics and metabolic stability (high throughput) studies using human liver microsomes in UPLC. For pharmacokinetics studies, male Wistar rats were pretreated with Morin (10 mg/kg) for one week and on the last day, a single dose of Piracetam (50 mg/kg) was given orally. In another group, both Morin and Piracetam were co-administered to evaluate the acute effect of Morin on Piracetam. The control group received oral distilled water for one week and administered with Piracetam on the last day. As Morin is an inhibitor of P- Glycoprotein (P-gp) and CYP 3A, it was anticipated to improve the bioavailability of Piracetam. Amazingly, relative to control, the areas under the concentration time curve and peak plasma concentration of Piracetam were 1.50- and 1.45-fold, respectively, greater in the Morin-pretreated group. However, co-administration of Morin had no significant effect on these parameters. Apart from the aforementioned merits, the results of this study are further confirmed by clinical trials; Piracetam dosages should be adjusted to avoid potential drug interaction when Piracetam is used clinically in combination with Morin and Morin-containing dietary supplements. The in vitro enzyme kinetics were performed to determined km, Vmax & CLins . The in vitro metabolic stability executed for the estimation of metabolic rate constant and half-life of Piracetam. These studies also extrapolate to in vivo intrinsic hepatic clearance (Clint, in vivo ) from in vitro intrinsic hepatic clearance (CLint, in vitro ). Copyright © 2012 John Wiley & Sons, Ltd.

  4. Is rapid growth in Internet usage environmentally sustainable for Australia? An empirical investigation.

    PubMed

    Salahuddin, Mohammad; Alam, Khorshed; Ozturk, Ilhan

    2016-03-01

    This study estimates the short- and long-run effects of Internet usage and economic growth on carbon dioxide (CO2) emissions using annual time series macro data for Australia for the period 1985-2012. Autoregressive distributive lag (ARDL) bounds and Gregory-Hansen structural break cointegration tests are applied. ARDL estimates indicate no significant long-run relationship between Internet usage and CO2 emissions, which implies that the rapid growth in Internet usage is still not an environmental threat for Australia. The study further indicates that higher level of economic growth is associated with lower level of CO2 emissions; however, Internet usage and economic growth have no significant short-run relationship with CO2 emissions. Financial development has both short-run and long-run significant positive association with CO2 emissions. The findings offer support in favor of energy efficiency gains and a reduction in energy intensity in Australia. However, impulse response and variance decomposition analysis suggest that Internet usage, economic growth and financial development will continue to impact CO2 emissions in the future, and as such, this study recommends that in addition to the existing measures to combat CO2 emissions, Australia needs to exploit the potential of the Internet not only to reduce its own carbon footprint but also to utilize information and communication technology (ICT)-enabled emissions abatement potential to reduce emissions in various other sectors across the economy, such as, power, renewable energy especially in solar and wind energy, agriculture, transport and service.

  5. Investigating the fluid dynamics of rapid processes within microfluidic devices using bright-field microscopy.

    PubMed

    Pirbodaghi, Tohid; Vigolo, Daniele; Akbari, Samin; deMello, Andrew

    2015-05-07

    The widespread application of microfluidic devices in the biological and chemical sciences requires the implementation of complex designs and geometries, which in turn leads to atypical fluid dynamic phenomena. Accordingly, a complete understanding of fluid dynamics in such systems is key in the facile engineering of novel and efficient analytical tools. Herein, we present an accurate approach for studying the fluid dynamics of rapid processes within microfluidic devices using bright-field microscopy with white light illumination and a standard high-speed camera. Specifically, we combine Ghost Particle Velocimetry and the detection of moving objects in automated video surveillance to track submicron size tracing particles via cross correlation between the speckle patterns of successive images. The efficacy of the presented technique is demonstrated by measuring the flow field over a square pillar (80 μm × 80 μm) in a 200 μm wide microchannel at high volumetric flow rates. Experimental results are in excellent agreement with those obtained via computational fluid dynamics simulations. The method is subsequently used to study the dynamics of droplet generation at a flow focusing microfluidic geometry. A unique feature of the presented technique is the ability to perform velocimetry analysis of high-speed phenomena, which is not possible using micron-resolution particle image velocimetry (μPIV) approaches based on confocal or fluorescence microscopy.

  6. Investigation on the rapid degradation of congo red catalyzed by activated carbon powder under microwave irradiation.

    PubMed

    Zhang, Zhaohong; Shan, Yabo; Wang, Jun; Ling, Hongjie; Zang, Shuliang; Gao, Wei; Zhao, Zhe; Zhang, Huachun

    2007-08-17

    Azo dyestuff-congo red in aqueous solution can be degraded rapidly under microwave irradiation in the presence of activated carbon powder. The results showed that the degradation ratio could reach 87.79% for 25 mL total volume with 50mg/L congo red and 2.0 g/L activated carbon powder under 1.5 min microwave irradiation. Furthermore, within the same irradiation time, congo red could be degraded fully by increasing addition amount (e.g. 3.6g/L) of activated carbon powder and the degradation ratio was up to 96.49%. Otherwise, with the same addition amount, congo red also could be degraded completely by prolonging irradiation time (e.g. 2.5 min) and the degradation ratio was up to 97.88%. In addition, the influences of microwave irradiation time, initial concentration of congo red, addition amount and used times of activated carbon powder as well as solution acidity on the degradation were discussed in details adopting UV-vis spectra, FT-IR spectra, ion chromatography, high phase liquid chromatography (HPLC) and TOC analysis technologies. Here, the method using activated carbon powder as catalyst under microwave irradiation shows many advantages including high degradation ratios, short reaction time, low costs, no intermediates and no secondary pollution. Therefore, it may be fit for dealing with various azo dyestuff wastewaters on a large scale.

  7. Experimental and Theoretical Investigation on Rapid Evaporation of Ethanol Droplets and Kerosene Droplets During Depressurization

    NASA Astrophysics Data System (ADS)

    Liu, Lu; Bi, Qin-cheng; Liu, Wei-min; Qi, Fang-cheng; Bi, Xin-gang

    2011-01-01

    This paper reports an experimental and theoretical study of rapid evaporation of ethanol droplets and kerosene droplets during depressurization. For experimental method, an ethanol droplet or a kerosene droplet was suspended on a thermocouple, which was also used to measure the droplet center temperature transition. And the droplet shape variation was recorded by a high speed camera. A theoretical analysis was developed based on the heat balance to estimate the droplet center temperature transition, and the evaporation model proposed by Abramzon and Sirignano was used to describe the droplet vaporization. According to the experimental data and theoretical analysis, both of the environmental pressure and the initial droplet diameter have a prominent influence on the droplet temperature transition. Comparing the evaporation processes of ethanol droplets and kerosene droplets with water droplets, the ethanol droplets have the fastest evaporation rate, followed by water, and the evaporation rates of kerosene droplets are the slowest. Also it was found that a bubble can easily emerge within kerosene droplet, and its lifetime is more than 1 s.

  8. Rapid equilibrium kinetic analysis of arsenite methylation catalyzed by recombinant human arsenic (+3 oxidation state) methyltransferase (hAS3MT).

    PubMed

    Wang, Shuping; Li, Xiangli; Song, Xiaoli; Geng, Zhirong; Hu, Xin; Wang, Zhilin

    2012-11-09

    In the human body, arsenic is metabolized by methylation. Understanding this process is important and provides insight into the relationship between arsenic and its related diseases. We used the rapid equilibrium kinetic model to study the reaction sequence of arsenite methylation. The results suggest that the mechanism for arsenite methylation is a completely ordered mechanism that is also of general interest in reaction systems with different reductants, such as tris(2-carboxyethyl)phosphine, cysteine, and glutathione. In the reaction, cysteine residues of recombinant human arsenic (+3 oxidation state) methyltransferase (hAS3MT) coordinate with arsenicals and involve the methyl transfer step. S-Adenosyl-l-methionine (AdoMet) is the first-order reactant, which modulates the conformation of hAS3MT to a best matched state by hydrophobic interaction. As the second-order reactant, reductant reduces the disulfide bond, most likely between Cys-250 and another cysteine residue of hAS3MT, and exposes the active site cysteine residues for binding trivalent inorganic arsenic (iAs(3+)) to give monomethylarsonic dicysteine (MADC(3+)). In addition, the reaction can be extended to further methylate MADC(3+) to dimethylarsinic cysteine (DAMC(3+)). In the methylation reaction, the β-pleated sheet content of hAS3MT is increased, and the hydrophobicity of the microenvironment around the active sites is decreased. Similarly, we confirm that both the high β-pleated sheet content of hAS3MT and the high dissociation ability of the enzyme-AdoMet-reductant improve the yield of dimethylated arsenicals.

  9. An investigation of the effect of rapid slurry chilling on blown pack spoilage of vacuum-packaged beef primals.

    PubMed

    Reid, R; Fanning, S; Whyte, P; Kerry, J; Bolton, D

    2017-02-01

    The aim of this study was to investigate if rapid slurry chilling would retard or prevent blown pack spoilage (BPS) of vacuum-packaged beef primals. Beef primals were inoculated with Clostridium estertheticum subspp. estertheticum (DSMZ 8809), C. estertheticum subspp. laramenise (DSMZ 14864) and C. gasigenes (DSMZ 12272), and vacuum-packaged with and without heat shrinkage (90°C for 3 s). These packs were then subjected to immediate chilling in an ice slurry or using conventional blast chilling systems and stored at 2°C for up to 100 days. The onset and progress of BPS was monitored using the following scale; 0-no gas bubbles in drip; 1-gas bubbles in drip; 2-loss of vacuum; 3-'blown'; 4-presence of sufficient gas inside the packs to produce pack distension and 5-tightly stretched, 'overblown' packs/packs leaking. Rapid slurry chilling (as compared to conventional chilling) did not significantly affect (P > 0.05) the time to the onset or progress of BPS. It was therefore concluded that rapid chilling of vacuum-packaged beef primals, using an ice slurry system, may not be used as a control intervention to prevent or retard blown pack spoilage. This study adds to our growing understanding of blown pack spoilage of vacuum-packaged beef primals and suggests that rapid chilling of vacuum-packaged beef primals is not a control option for the beef industry. The results suggest that neither eliminating the heat shrinkage step nor rapid chilling of vacuum-packaged beef retard the time to blown pack spoilage. © 2016 The Society for Applied Microbiology.

  10. [Investigation of Helicobacter pylori colonization in pharyngeal and palatine tonsils with rapid urease test and immunohistochemical analysis].

    PubMed

    Dağtekin-Ergür, Emine Nur; Eren, Funda; Ustün, Mustafa Burak; Eren, Yusuf; Taş, Ebru; Gürsel, Ali Okan

    2008-01-01

    We investigated the presence and frequency of Helicobacter pylori in palatine and pharyngeal tonsil tissues of children. The study included 20 patients (15 males, 5 females; mean age 8.2 years; range 5 to 13 years) with chronic or recurrent tonsillitis and/or snoring. Of these, 17 patients underwent adenoidectomy and tonsillectomy, two patients underwent adenoidectomy and tonsillectomy with bilateral ventilation tube insertion, and one patient underwent adenoidectomy with bilateral ventilation tube insertion. H. pylori colonization was sought in all tonsillar specimens by rapid urease test and immunohistochemical analysis. Rapid urease test showed H. pylori colonization in the palatine and pharyngeal tonsil specimens of one patient (5%), whereas immunohistochemical analysis showed four H. pylori-positive patients (20%), whose pharyngeal tonsil (n=2) or palatine tonsil (n=2) specimens were individually affected. The presence of H. pylori in both palatine and pharyngeal tonsil tissues of children suggests that these tissues can be a reservoir for H. pylori.

  11. Pharmaceutical solid-state kinetic stability investigation by using moisture-modified Arrhenius equation and JMP statistical software.

    PubMed

    Fu, Mingkun; Perlman, Michael; Lu, Qing; Varga, Csanad

    2015-03-25

    An accelerated stress approach utilizing the moisture-modified Arrhenius equation and JMP statistical software was utilized to quantitatively assess the solid state stability of an investigational oncology drug MLNA under the influence of temperature (1/T) and humidity (%RH). Physical stability of MLNA under stress conditions was evaluated by using XRPD, DSC, TGA, and DVS, while chemical stability was evaluated by using HPLC. The major chemical degradation product was identified as a hydrolysis product of MLNA drug substance, and was subsequently subjected to an investigation of kinetics based on the isoconversion concept. A mathematical model (ln k=-11,991×(1/T)+0.0298×(%RH)+29.8823) based on the initial linear kinetics observed for the formation of this degradant at all seven stress conditions was built by using the moisture-modified Arrhenius equation and JMP statistical software. Comparison of the predicted versus experimental lnk values gave a mean deviation value of 5.8%, an R(2) value of 0.94, a p-value of 0.0038, and a coefficient of variation of the root mean square error CV(RMSE) of 7.9%. These statistics all indicated a good fit to the model for the stress data of MLNA. Both temperature and humidity were shown to have a statistically significant impact on stability by using effect leverage plots (p-value<0.05 for both 1/T and %RH). Inclusion of a term representing the interaction of relative humidity and temperature (%RH×1/T) was shown not to be justified by using Analysis of Covariance (ANCOVA), which supported the use of the moisture-corrected Arrhenius equation modeling theory. The model was found to be of value to aid setting of specifications and retest period, and storage condition selection. A model was also generated using only four conditions, as an example from a resource saving perspective, which was found to provide a good fit to the entire set of data. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Results of paleoflood investigations for Spring, Rapid, Boxedler, and Elk Creeks, Black Hills, western South Dakota

    USGS Publications Warehouse

    Driscoll, Daniel G.; O'Connor, James E.; Harden, Tessa M.

    2012-01-01

    Flood-frequency analyses for the Black Hills area are especially important because of severe flooding of June 9–10, 1972, that was caused by a large mesoscale convective system and resulted in at least 238 deaths. This paper summarizes results of paleoflood investigations for six study reaches in the central Black Hills. Stratigraphic records and resulting long-term flood chronologies, locally extending more than 2,000 years, were combined with observed and historical flood information to derive flood-frequency estimates. Results indicate that floods as large as and even substantially larger than 1972 have affected most of the study reaches. Results of the paleoflood investigations provide better physically based information on low-probability floods than has been previously available, substantially improving estimates of the magnitude and frequency of large floods in the central Black Hills and reducing associated uncertainties. Collectively, the results provide insights regarding regional flood-generation processes and their spatial controls, enable approaches for extrapolation of results for hazard assessment beyond specific study reaches, and provide a millennial-scale perspective on the 1972 flooding.

  13. Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

    DOE PAGES

    Pankin, A. Y.; Rafiq, T.; Kritz, A. H.; ...

    2017-06-08

    The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. We use the neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] to carry out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. In simulationsmore » with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. But the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new

  14. Adsorption of di-l-alanine on Cu(110) investigated with scanning tunneling microscopy [rapid communication

    NASA Astrophysics Data System (ADS)

    Stensgaard, I.

    2003-11-01

    Sub-monolayer growth of a small chiral peptide, di- L-alanine, on Cu(1 1 0) was investigated by variable temperature scanning tunneling microscopy (STM). At low coverage and for temperatures above ≈-220 K the molecules nucleate along the [ 3¯ 3 2] direction to form short, mainly one-dimensional islands. An increase in coverage leads to the formation of [ 3¯ 3 2]-directed, elongated islands. Images with sub-molecular resolution reveal that the orientation of the molecules within one particular island depends on the deposition temperature. At higher coverage, up to one monolayer, the islands coalesce, giving rise to phase boundaries between domains of opposite orientation. An atomic-scale model for di- L-alanine on Cu(1 1 0) is presented.

  15. Mechanistic investigations of the hydrolysis of amides, oxoesters and thioesters via kinetic isotope effects and positional isotope exchange.

    PubMed

    Robins, Lori I; Fogle, Emily J; Marlier, John F

    2015-11-01

    The hydrolysis of amides, oxoesters and thioesters is an important reaction in both organic chemistry and biochemistry. Kinetic isotope effects (KIEs) are one of the most important physical organic methods for determining the most likely transition state structure and rate-determining step of these reaction mechanisms. This method induces a very small change in reaction rates, which, in turn, results in a minimum disturbance of the natural mechanism. KIE studies were carried out on both the non-enzymatic and the enzyme-catalyzed reactions in an effort to compare both types of mechanisms. In these studies the amides and esters of formic acid were chosen because this molecular structure allowed development of methodology to determine heavy-atom solvent (nucleophile) KIEs. This type of isotope effect is difficult to measure, but is rich in mechanistic information. Results of these investigations point to transition states with varying degrees of tetrahedral character that fit a classical stepwise mechanism. This article is part of a special issue entitled: Enzyme Transition States from Theory and Experiment.

  16. Analytical chemical kinetic investigation of the effects of oxygen, hydrogen, and hydroxyl radicals on hydrogen-air combustion

    NASA Technical Reports Server (NTRS)

    Carson, G. T., Jr.

    1974-01-01

    Quantitative values were computed which show the effects of the presence of small amounts of oxygen, hydrogen, and hydroxyl radicals on the finite-rate chemical kinetics of premixed hydrogen-air mixtures undergoing isobaric autoignition and combustion. The free radicals were considered to be initially present in hydrogen-air mixtures at equivalence ratios of 0.2, 0.6, 1.0, and 1.2. Initial mixture temperatures were 1100 K, 1200 K, and 1500 K, and pressures were 0.5, 1.0, 2.0, and 4.0 atm. Of the radicals investigated, atomic oxygen was found to be the most effective for reducing induction time, defined as the time to 5 percent of the total combustion temperature rise. The reaction time, the time between 5 percent and 95 percent of the temperature rise, is not decreased by the presence of free radicals in the initial hydrogen-air mixture. Fuel additives which yield free radicals might be used to effect a compact supersonic combustor design for efficient operation in an otherwise reaction-limited combustion regime.

  17. A new real-time method for investigation of affinity properties and binding kinetics of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Orlov, Alexey V.; Nikitin, Maxim P.; Bragina, Vera A.; Znoyko, Sergey L.; Zaikina, Marina N.; Ksenevich, Tatiana I.; Gorshkov, Boris G.; Nikitin, Petr I.

    2015-04-01

    A method for quantitative investigation of affinity constants of receptors immobilized on magnetic nanoparticles (MP) is developed based on spectral correlation interferometry (SCI). The SCI records with a picometer resolution the thickness changes of a layer of molecules or nanoparticles due to a biochemical reaction on a cover slip, averaged over the sensing area. The method is compatible with other types of sensing surfaces employed in biosensing. The measured values of kinetic association constants of magnetic nanoparticles are 4 orders of magnitude higher than those of molecular antibody association with antigen. The developed method also suggests highly sensitive detection of antigens in a wide dynamic range. The limit of detection of 92 pg/ml has been demonstrated for prostate-specific antigen (PSA) with 50-nm MP employed as labels, which produce 3-order amplification of the SCI signals. The calibration curve features high sensitivity (slope) of 3-fold signal raise per 10-fold increase of PSA concentration within 4-order dynamic range, which is an attractive compromise for precise quantitative and highly sensitive immunoassay. The proposed biosensing technique offers inexpensive disposable sensor chips of cover slips and represents an economically sound alternative to traditional immunoassays for disease diagnostics, detection of pathogens in food and environmental monitoring.

  18. Photodegradation of the azole fungicide fluconazole in aqueous solution under UV-254: kinetics, mechanistic investigations and toxicity evaluation.

    PubMed

    Chen, Zhi-Feng; Ying, Guang-Guo; Jiang, Yu-Xia; Yang, Bin; Lai, Hua-Jie; Liu, You-Sheng; Pan, Chang-Gui; Peng, Fu-Qiang

    2014-04-01

    The azole fungicide fluconazole has been reported to be persistent in conventional wastewater treatment plants. This study investigated the photodegradation of fluconazole under UV-254 in aqueous solutions. The results revealed that the photodegradation of fluconazole was pH-dependent (2.0-12.0) following the pseudo-first-order kinetics with quantum yield values ranging from 0.023 to 0.090 mol einstein(-1), and it underwent a direct and self-sensitized mechanism involving (1)O2. The main photodegradation by-products were identified and semi-quantitated. The proposed photodegradation pathway included hydroxylative defluorination reaction. The 72 h-NOEC and 72 h-LOEC values for fluconazole using a freshwater unicellular green alga Pseudokirchneriella subcapitata were 10 μM and 15 μM. Overall, the photodegradation of fluconazole produced a significant decrease in algal toxicity. It also proved that the photodegradation by-products will not present extra toxicity to this alga than fluconazole itself.

  19. The effect of pressure on the kinetics of γ-anhydrite crystallization investigated by diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Liu, Chuanjiang; Zheng, Haifei; Du, Jianguo; Wang, Duojun

    2015-01-01

    The crystallization kinetics of γ-anhydrite was investigated in the temperature and pressure ranges of 373-473 K and 1094-1903 MPa using a hydrothermal diamond anvil cell (HDAC) and Raman spectroscopy. A calcium sulfate solution was formed by dissolving gypsum in water at high pressure, and γ-anhydrite crystallized due to the increasing temperature. The relationship among the reaction rate, k, the temperature, T, and the pressure, P was established as k=-1.75×10-3+1.83×10-6P+3.57×10-7T, with an R2 value of 0.943, of which the applicable range is 373 K≤T≤473 K and 1196 MPa≤P≤1903 MPa. An elevation of T or P will accelerate the crystallization rate of γ-anhydrite. The time exponent n obtained between 0.96 and 1.29 indicates that the process of crystallization should be controlled by instant nucleation on the grain boundary and diffusion controlled growth. In the process of crystallization, the volume is reduced because of the decrease of pressure, and the volume change ΔV is equal to -6.05×10-6 m3/mol. The calculated activation energy Ea is 10.7 kJ/mol, and the pre-exponential factor A is 2.27×10-2 s-1.

  20. The solution, solid state stability and kinetic investigation in degradation studies of lercanidipine: study of excipients compatibility of lercanidipine.

    PubMed

    Parmar, Nitin; Amin, Saima; Singla, Neelam; Kohli, Kanchan

    2012-01-01

    The objectives of this research were to evaluate the stability of lercanidipine in solution state and solid state and explore the compatibility of drug with oils, surfactants and cosurfactants as excipients. The effect of pH on the degradation in solution state was studied through pH-rate profile of lercanidipine in constant ionic strength buffer solutions in pH range 1-8 which gives the pH of maximum stability. Powdered lercanidipine was stored under 40°C/0%~75% relative humidities (RH) or 0% RH/5~50°C to study the influence of RH and temperature on the stability of lercanidipine in solid state. Binary mixtures of lercanidipine and different excipients were stored at 40°C/75% RH, 40°C and at room temperature for excipient compatibility evaluation. The degradation of lercanidipine at different pH appears to fit a typical first-order reaction, but in solid state, it does not fit any obvious reaction model. Moisture content and temperature both play important roles affecting the degradation rate. Lercanidipine exhibits good compatibility with surfactants, cosurfactants and oils as excipients under stressed conditions of different storage temperature in a 3-week screening study. Moreover, the proposed high-performance liquid chromatography method was utilized to investigate the kinetics of the acidic and alkaline degradation processes of lercanidipine at different temperatures.

  1. Carbonic Anhydrase Activators. Part 191 Spectroscopic and Kinetic Investigations for the Interaction of Isozymes I and II With Primary Amines

    PubMed Central

    Briganti, Fabrizio; Scozzafava, Andrea

    1997-01-01

    The interactions of Zn(II)- and Co(II)-substituted carbonic anhydrase (CA) isozymes I and II with amine type activators such as histamine, serotonin, phenetylamine dopamine and benzylhydrazine have been investigated kinetically, and spectroscopically. All of such activators are of the non-competitive type towards CO2 hydration and 4-nitrophenylacetate hydrolysis for both human isozymes (HCA I and HCA II). The electronic spectra of the adducts of Co(II)CA with amine activators are similar to the spectrum of the previously reported Co(II)CAII-phenol adduct, the only known competitive inhibitor towards CO2 hydration, where the phenol molecule binds into the hydrophobic pocket of the active site. This is a direct spectroscopic evidence that the activator molecules bind within the active site, but not directly to the metal ion. Recent X-ray crystallographic data for the adduct of HCA II with histamine show that the activator molecule is bound at the entrance of the active site cavity, near to residues His 64, Asn 62 and Gln 92, where actively aids in shuttling protons between the active site and the environment. Similar arrangements probably occur for the other activators reported in the present paper. PMID:18475791

  2. Investigating the state of physiologically based kinetic modelling practices and challenges associated with gaining regulatory acceptance of model applications.

    PubMed

    Paini, Alicia; Leonard, Jeremy A; Kliment, Tomas; Tan, Yu-Mei; Worth, Andrew

    2017-09-01

    Physiologically based kinetic (PBK) models are used widely throughout a number of working sectors, including academia and industry, to provide insight into the dosimetry related to observed adverse health effects in humans and other species. Use of these models has increased over the last several decades, especially in conjunction with emerging alternative methods to animal testing, such as in vitro studies and data-driven in silico quantitative-structure-activity-relationship (QSAR) predictions. Experimental information derived from these new approach methods can be used as input for model parameters and allows for increased confidence in models for chemicals that did not have in vivo data for model calibration. Despite significant advancements in good modelling practice (GMP) for model development and evaluation, there remains some reluctance among regulatory agencies to use such models during the risk assessment process. Here, the results of a survey disseminated to the modelling community are presented in order to inform the frequency of use and applications of PBK models in science and regulatory submission. Additionally, the survey was designed to identify a network of investigators involved in PBK modelling and knowledgeable of GMP so that they might be contacted in the future for peer review of PBK models, especially in regards to vetting the models to such a degree as to gain a greater acceptance for regulatory purposes. Copyright © 2017. Published by Elsevier Inc.

  3. Investigation into solar drying of potato: effect of sample geometry on drying kinetics and CO2 emissions mitigation.

    PubMed

    Tripathy, P P

    2015-03-01

    Drying experiments have been performed with potato cylinders and slices using a laboratory scale designed natural convection mixed-mode solar dryer. The drying data were fitted to eight different mathematical models to predict the drying kinetics, and the validity of these models were evaluated statistically through coefficient of determination (R(2)), root mean square error (RMSE) and reduced chi-square (χ (2)). The present investigation showed that amongst all the mathematical models studied, the Modified Page model was in good agreement with the experimental drying data for both potato cylinders and slices. A mathematical framework has been proposed to estimate the performance of the food dryer in terms of net CO2 emissions mitigation potential along with unit cost of CO2 mitigation arising because of replacement of different fossil fuels by renewable solar energy. For each fossil fuel replaced, the gross annual amount of CO2 as well as net amount of annual CO2 emissions mitigation potential considering CO2 emissions embodied in the manufacture of mixed-mode solar dryer has been estimated. The CO2 mitigation potential and amount of fossil fuels saved while drying potato samples were found to be the maximum for coal followed by light diesel oil and natural gas. It was inferred from the present study that by the year 2020, 23 % of CO2 emissions can be mitigated by the use of mixed-mode solar dryer for drying of agricultural products.

  4. Kinetics and Mechanistic Investigations of Atmospheric Oxidation of HFO-1345fz by OH Radical: Insights from Theory.

    PubMed

    Rao, Pradeep Kumar; Gejji, Shridhar P

    2017-01-26

    HFO-1345fz (CF3CF2CH═CH2 or 3,3,4,4,4-pentafluoro-1-butene) belongs to a class of hydrofluoro-olefins and represents a new generation of potential foam expansion agents. Its atmospheric impact and environmental acceptability can be estimated from the studies of kinetics and mechanism of its oxidative degradation. The molecular insights accompanying the reaction pathways in terms of the characterization of intermediates or products and radiative properties should prove useful for large-scale industrial applications. Systematic mechanistic gas-phase kinetics investigations on the reactivity of HFO-1345fz with the (•)OH facilitating a variety of degradation routes have been carried out employing the M06-2x-based density functional theory. Structure and energetics of different reaction pathways such as hydrogen abstraction, (•)OH addition, isomerization-dissociation, or interaction with atmospheric O2 have been analyzed. The formation of gaseous products from the interaction of HFO-1345fz with (•)OH in the absence and presence of NOx atmospheric conditions has been reported. Calculated branching ratios have shown that the addition channel dominates such oxidative degradation, whereas the abstraction channel contributes negligibly to the global rate constant and addition of (•)OH to the terminal carbon is favored over the nonterminal one. The rate constants for all reaction channels were computed by conventional transition state theory (TST) and canonical variation transition state theory (CVT) including small curvature tunneling (SCT) over the temperature range of 200-1000 K at atmospheric pressure. The CVT calculated rate constant for the reaction at 298 K was shown to be 1.17 × 10(-12) cm(3) molecule(-1) s(-1), which compares well with the 1.24 × 10(-12) cm(3) molecule(-1) s(-1) as obtained from TST and is in excellent agreement with the experiments reported earlier. The atmospheric lifetime, radiative efficiency, and global warming potential (GWP) have

  5. Investigation of fluorescence methods for rapid detection of municipal wastewater impact on drinking water sources

    NASA Astrophysics Data System (ADS)

    Peleato, Nicolas M.; Legge, Raymond L.; Andrews, Robert C.

    2017-01-01

    Fluorescence spectroscopy as a means to detect low levels of treated wastewater impact on two source waters was investigated using effluents from five wastewater facilities. To identify how best to interpret the fluorescence excitation-emission matrices (EEMs) for detecting the presence of wastewater, several feature selection and classification methods were compared. An expert supervised regional integration approach was used based on previously identified features which distinguish biologically processed organic matter including protein-like fluorescence and the ratio of protein to humic-like fluorescence. Use of nicotinamide adenine dinucleotide-like (NADH) fluorescence was found to result in higher linear correlations for low levels of wastewater presence. Parallel factors analysis (PARAFAC) was also applied to contrast an unsupervised multiway approach to identify underlying fluorescing components. A humic-like component attributed to reduced semiquinone-like structures was found to best correlate with wastewater presence. These fluorescent features were used to classify, by volume, low (0.1-0.5%), medium (1-2%), and high (5-15%) levels by applying support vector machines (SVMs) and logistic regression. The ability of SVMs to utilize high-dimensional input data without prior feature selection was demonstrated through their performance when considering full unprocessed EEMs (66.7% accuracy). The observed high classification accuracies are encouraging when considering implementation of fluorescence spectroscopy as a water quality monitoring tool. Furthermore, the use of SVMs for classification of fluorescence data presents itself as a promising novel approach by directly utilizing the high-dimensional EEMs.

  6. Rapid adsorption of copper(II) and lead(II) by rice straw/Fe₃O₄ nanocomposite: optimization, equilibrium isotherms, and adsorption kinetics study.

    PubMed

    Khandanlou, Roshanak; Ahmad, Mansor B; Fard Masoumi, Hamid Reza; Shameli, Kamyar; Basri, Mahiran; Kalantari, Katayoon

    2015-01-01

    Rice straw/magnetic nanocomposites (RS/Fe3O4-NCs) were prepared via co-precipitation method for removal of Pb(II) and Cu(II) from aqueous solutions. Response surface methodology (RSM) was utilized to find the optimum conditions for removal of ions. The effects of three independent variables including initial ion concentration, removal time, and adsorbent dosage were investigated on the maximum adsorption of Pb (II) and Cu (II). The optimum conditions for the adsorption of Pb(II) and Cu(II) were obtained (100 and 60 mg/L) of initial ion concentration, (41.96 and 59.35 s) of removal time and 0.13 g of adsorbent for both ions, respectively. The maximum removal efficiencies of Pb(II) and Cu(II) were obtained 96.25% and 75.54%, respectively. In the equilibrium isotherm study, the adsorption data fitted well with the Langmuir isotherm model. The adsorption kinetics was best depicted by the pseudo-second order model. Desorption experiments showed adsorbent can be reused successfully for three adsorption-desorption cycles.

  7. Rapid Adsorption of Copper(II) and Lead(II) by Rice Straw/Fe3O4 Nanocomposite: Optimization, Equilibrium Isotherms, and Adsorption Kinetics Study

    PubMed Central

    Khandanlou, Roshanak; Ahmad, Mansor B.; Fard Masoumi, Hamid Reza; Shameli, Kamyar; Basri, Mahiran; Kalantari, Katayoon

    2015-01-01

    Rice straw/magnetic nanocomposites (RS/Fe3O4-NCs) were prepared via co-precipitation method for removal of Pb(II) and Cu(II) from aqueous solutions. Response surface methodology (RSM) was utilized to find the optimum conditions for removal of ions. The effects of three independent variables including initial ion concentration, removal time, and adsorbent dosage were investigated on the maximum adsorption of Pb (II) and Cu (II). The optimum conditions for the adsorption of Pb(II) and Cu(II) were obtained (100 and 60 mg/L) of initial ion concentration, (41.96 and 59.35 s) of removal time and 0.13 g of adsorbent for both ions, respectively. The maximum removal efficiencies of Pb(II) and Cu(II) were obtained 96.25% and 75.54%, respectively. In the equilibrium isotherm study, the adsorption data fitted well with the Langmuir isotherm model. The adsorption kinetics was best depicted by the pseudo-second order model. Desorption experiments showed adsorbent can be reused successfully for three adsorption-desorption cycles. PMID:25815470

  8. LiDAR data and SAR imagery acquired by an unmanned helicopter for rapid landslide investigation

    NASA Astrophysics Data System (ADS)

    Kasai, M.; Tanaka, Y.; Yamazaki, T.

    2012-12-01

    When earthquakes or heavy rainfall hits a landslide prone area, initial actions require estimation of the size of damage to people and infrastructure. This includes identifying the number and size of newly collapsed or expanded landslides, and appraising subsequent risks from remobilization of landslides and debris materials. In inapproachable areas, the UAV (Unmanned Aerial Vehicles) is likely to be of greatest use. In addition, repeat monitoring of sites after the event is a way of utilizing UAVs, particularly in terms of cost and convenience. In this study, LiDAR (SkEyesBox MP-1) data and SAR (Nano SAR) imagery, acquired over 0.5 km2 landslide prone area, are presented to assess the practicability of using unmanned helicopters (in this case a 10 year old YAMAHA RMAX G1) in these situations. LiDAR data was taken in July 2012, when tree foliage covered the ground surface. However, imagery was of sufficient quality to identify and measure landslide features. Nevertheless, LiDAR data obtained by a manned helicopter in the same area in August 2008 was more detailed, reflecting the function of the LiDAR scanner. On the other hand, 2 m resolution Nano SAR imagery produced reasonable results to elucidate hillslope condition. A quick method for data processing without loss of image quality was also investigated. In conclusion, the LiDAR scanner and UAV employed here could be used to plan immediate remedial activity of the area, before LiDAR measurement with a manned helicopter can be organized. SAR imagery from UAV is also available for this initial activity, and can be further applied to long term monitoring.

  9. Spectroscopic, Structural, and Kinetic Investigation of the Ultrafast Spin Crossover in an Unusual Cobalt(II) Semiquinonate Radical Complex.

    PubMed

    Rupp, Fabian; Chevalier, Katharina; Graf, Michèle; Schmitz, Markus; Kelm, Harald; Grün, Anneken; Zimmer, Manuel; Gerhards, Markus; van Wüllen, Christoph; Krüger, Hans-Jörg; Diller, Rolf

    2017-02-10

    A comprehensive spectroscopic and structural investigation of [Co(II) (l-N4  tBu2 )(dbsq)][B(p-C6 H4 Cl)4 ] (1, l-N4  tBu2 =N,N'-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane, dbsq(1-) =3,5-di-tert-butylsemiquinonate), the first known octahedral complex with a low-spin (ls) Co(II) semiquinonate ground state, is reported. Above 200 K, solids as well as solutions of 1 exhibit thermally induced spin-crossover (SCO) from the ls to the high-spin (hs) Co(II) semiquinonate state instead of the frequently observed valence tautomerism from ls Co(III) catecholate to hs Co(II) semiquinonate. DFT calculations demonstrate that the (closed shell) Co(III) catecholate suffers from a triplet instability leading to the ls Co(II) semiquinonate ground state. The thorough temperature-dependent spectroscopic study of the SCO enables a photophysical investigation. Thus, by selective photoexcitation of the ls fraction of 1 in solution at room temperature, ultrafast conversion to the hs state is observed using femtosecond electronic and IR-vibrational (infrared) transient absorption spectroscopy. The kinetics of the photocycle is described by a stretched exponential with τ=3.3-3.6 ps and β=0.52-0.54, representing an upper limit for the hs-ls relaxation time. This is, to our knowledge, the fastest interconversion ever determined for a SCO complex, and is attributed to the special situation that in 1 a Co(II) complex is coordinated to a π-radical ligand allowing very efficient coupling between the ls and hs spin states. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Purification and investigation of some kinetic properties of glucose-6-phosphate dehydrogenase from parsley (Petroselinum hortense) leaves.

    PubMed

    Coban, T Abdül Kadir; Ciftçi, Mehmet; Küfrevioğlu, O Irfan

    2002-05-01

    In this study, glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ oxidoreductase, EC 1.1.1.49; G6PD) was purified from parsley (Petroselinum hortense) leaves, and analysis of the kinetic behavior and some properties of the enzyme were investigated. The purification consisted of three steps: preparation of homogenate, ammonium sulfate fractionation, and DEAE-Sephadex A50 ion exchange chromatography. The enzyme was obtained with a yield of 8.79% and had a specific activity of 2.146 U (mg protein)(-1). The overall purification was about 58-fold. Temperature of +4 degrees C was maintained during the purification process. Enzyme activity was spectrophotometrically measured according to the Beutler method, at 340 nm. In order to control the purification of enzyme, SDS-polyacrylamide gel electrophoresis was carried out in 4% and 10% acrylamide for stacking and running gel, respectively. SDS-polyacrylamide gel electrophoresis showed a single band for enzyme. The molecular weight was found to be 77.6 kDa by Sephadex G-150 gel filtration chromatography. A protein band corresponding to a molecular weight of 79.3 kDa was obtained on SDS-polyacrylamide gel electrophoresis. For the enzymes, the stable pH, optimum pH, and optimum temperature were found to be 6.0, 8.0, and 60 degrees C, respectively. Moreover, KM and Vmax values for NADP+ and G6-P at optimum pH and 25 degrees C were determined by means of Lineweaver-Burk graphs. Additionally, effects of streptomycin sulfate and tetracycline antibiotics were investigated for the enzyme activity of glucose-6-phosphate dehydrogenase in vitro.

  11. A mechanistic investigation of the kinetic resolution of secondary aromatic alcohols using a ferrocene-based planar chiral 4-(dimethylamino)pyridine catalyst.

    PubMed

    Mesas-Sánchez, Laura; Dinér, Peter

    2015-03-27

    A detailed computational and kinetic analysis of the acetylation of 1-phenylethanol with acetic anhydride catalyzed by planar chiral 4-(dimethylamino)pyridine (DMAP) catalyst (-)-1 is presented. The study includes a computational investigation of the potential-energy surface including the acylation and stereoselective transition states at the DFT level of theory. Experimentally, the kinetic study shows that the reaction proceeds in a first-order manner in catalyst, whereas both substrates, acetic anhydride and 1-phenylethanol, show fractional order, which is in accordance with steady-state conditions. The fractional order depends on an equilibrium between the free catalyst and the acetylated catalyst.

  12. Investigating chemical changes during shelf-life of thermal and high-pressure high-temperature sterilised carrot purees: A 'fingerprinting kinetics' approach.

    PubMed

    Kebede, Biniam T; Grauwet, Tara; Palmers, Stijn; Michiels, Chris; Hendrickx, Marc; Van Loey, Ann

    2015-10-15

    This work investigates chemical changes during shelf-life of thermally and high pressure high temperature (HPHT) sterilised carrot purees using a 'fingerprinting kinetics' approach. Fingerprinting enabled selection of Strecker aldehydes, terpenes, phenylpropanoids, fatty acid derivatives and carotenoid degradation products as volatiles clearly changing during shelf-life. Next, kinetic modelling of these volatiles was performed to compare their reaction kinetics during storage in differently sterilised samples. Immediately after processing, the Strecker aldehydes were detected at higher levels in thermally sterilised samples. During storage, the compounds increased at a comparable rate in thermally and HPHT processed samples. In contrast, immediately after processing, most of the naturally occurring terpenes and phenylpropanoids were better preserved in HPHT treated samples. Nevertheless, by the end of storage, the concentration of these compounds decreased to almost the same level in both thermal and HPHT samples (with a higher degradation rate in HPHT samples).

  13. An investigation into the crystallization tendency/kinetics of amorphous active pharmaceutical ingredients: A case study with dipyridamole and cinnarizine.

    PubMed

    Baghel, Shrawan; Cathcart, Helen; Redington, Wynette; O'Reilly, Niall J

    2016-07-01

    Amorphous drug formulations have great potential to enhance solubility and thus bioavailability of BCS class II drugs. However, the higher free energy and molecular mobility of the amorphous form drive them towards the crystalline state which makes them unstable. Accurate determination of the crystallization tendency/kinetics is the key to the successful design and development of such systems. In this study, dipyridamole (DPM) and cinnarizine (CNZ) have been selected as model compounds. Thermodynamic fragility (mT) was measured from the heat capacity change at the glass transition temperature (Tg) whereas dynamic fragility (mD) was evaluated using methods based on extrapolation of configurational entropy to zero [Formula: see text] , and heating rate dependence of Tg [Formula: see text] . The mean relaxation time of amorphous drugs was calculated from the Vogel-Tammann-Fulcher (VTF) equation. Furthermore, the correlation between fragility and glass forming ability (GFA) of the model drugs has been established and the relevance of these parameters to crystallization of amorphous drugs is also assessed. Moreover, the crystallization kinetics of model drugs under isothermal conditions has been studied using Johnson-Mehl-Avrami (JMA) approach to determine the Avrami constant 'n' which provides an insight into the mechanism of crystallization. To further probe into the crystallization mechanism, the non-isothermal crystallization kinetics of model systems were also analysed by statistically fitting the crystallization data to 15 different kinetic models and the relevance of model-free kinetic approach has been established. The crystallization mechanism for DPM and CNZ at each extent of transformation has been predicted. The calculated fragility, glass forming ability (GFA) and crystallization kinetics are found to be in good correlation with the stability prediction of amorphous solid dispersions. Thus, this research work involves a multidisciplinary approach to

  14. Role of protons in the pump cycle of KdpFABC investigated by time-resolved kinetic experiments.

    PubMed

    Damnjanovic, Bojana; Apell, Hans-Jürgen

    2014-05-20

    The time-resolved kinetics of the KdpFABC complex solubilized in Aminoxide WS-35 was investigated by ATP concentration jump experiments. ATP was photoreleased from its inactive precursor, caged ATP, and charge movements in the membrane domain of the KdpFABC were detected by the electrochromic dye RH421. At low ATP concentrations, the ATP binding step became rate-limiting with an apparent, pH-independent ATP binding affinity of ~70 μM. At saturating ATP concentrations, the rate-limiting step is the conformational transition (E1-P → P-E2) with a rate constant of ~1.7 s(-1) at 20 °C that was independent of K(+) concentration. This observation together with the detected fluorescence decrease indicates that K(+) (or another positive ion) is bound in the membrane domain after enzyme phosphorylation and the conformational transition to the P-E2 state. pH dependence experiments revealed different roles of H(+) in the transport mechanism. Two different functions of protons for the ion pump must be distinguished. On one hand, there are electrogenically bound "functional" protons, which are not transported but prerequisite for the performance of the ATP-driven half-cycle. On the other hand, protons bind to the transport sites, acting as weak congeners of K(+). There possibly are noncompetitively bound protons, affecting the enzyme activity and/or coupling between KdpA and KdpB subunits. Finally, the recently proposed Post-Albers model for the KdpFABC complex was supplemented with stoichiometry factors of 2 for K(+) and 3 for H(+), and additional inhibitory side reactions controlled by H(+) were introduced, which are relevant at pH <6.5 and/or in the absence of K(+).

  15. Stabilities of neutral and basic esters of bendamustine in plasma compared to the parent compound: kinetic investigations by HPLC.

    PubMed

    Huber, S; Antoni, F; Schickaneder, C; Schickaneder, H; Bernhardt, G; Buschauer, A

    2015-02-01

    Esters of the cytostatic bendamustine (1), previously demonstrated to be much more potent than the parent compound as antiproliferative agents in vitro, were investigated for stability in buffer and plasma, as well as against porcine liver esterase in the presence of different amounts of albumin using a validated RP-HPLC method with fluorescence detection. The hydrolysis of the nitrogen mustard moiety was retarded (for 1: approximately 130 vs. 11 min) in the presence of plasma proteins. For the derivatives, both cleavage of ester and nitrogen mustard moieties were analyzed. Enzymatic hydrolysis was very fast in the case of 2-pyrrolidino-, 2-piperidino- and 2-(4-methylpiperazino)-ethyl esters, whereas methyl, ethyl, morpholinoethyl and branched 2-pyrrolidinoethyl esters were considerably more stable (half-lives between 41 and 116 min, compared to <5 min). Inhibition by physostigmine indicated unspecific cholinesterases to be involved in the rapid ester cleavage. Due to lower protein content and higher enzymatic activity in murine compared to human plasma, reduced stability of all investigated esters in mouse plasma (t½<2 min) has to be taken into account with respect to the design of animal studies.

  16. Glutathione reductase: Comparison of steady-state and rapid reaction primary kinetic isotope effects exhibited by the yeast, spinach, and Escherichia coli enzymes

    SciTech Connect

    Vanoni, M.A.; Wong, K.K.; Ballou, D.P.; Blanchard, J.S. )

    1990-06-19

    Kinetic parameters for NADPH and NADH have been determined at pH 8.1 for spinach, yeast, and E. coli glutathione reductases. NADPH exhibited low Km values for all enzymes (3-6 microM), while the Km values for NADH were 100 times higher (approximately 400 microM). Under our experimental conditions, the percentage of maximal velocities with NADH versus those measured with NADPH were 18.4, 3.7, and 0.13% for the spinach, yeast, and E. coli enzymes, respectively. Primary deuterium kinetic isotope effects were independent of GSSG concentration between Km and 15Km levels, supporting a ping-pong kinetic mechanism. For each of the three enzymes, NADPH yielded primary deuterium kinetic isotope effects on Vmax only, while NADH exhibited primary deuterium kinetic isotope effects on both V and V/K. The magnitude of DV/KNADH at pH 8.1 is 4.3 for the spinach enzyme, 2.7 for the yeast enzyme, and 1.6 for the E. coli glutathione reductase. The experimentally determined values of TV/KNADH of 7.4, 4.2, and 2.2 for the spinach, yeast, and E. coli glutathione reductases agree well with those calculated from the corresponding DV/KNADH using the Swain-Schaad expression. This suggests that the intrinsic primary kinetic isotope effect on NADH oxidation is fully expressed. In order to confirm this conclusion, single-turnover experiments have been performed. The measured primary deuterium kinetic isotope effects on the enzyme reduction half-reaction using NADH match those measured in the steady state for each of the three glutathione reductases.

  17. Rapid Prototyping for In Vitro Knee Rig Investigations of Prosthetized Knee Biomechanics: Comparison with Cobalt-Chromium Alloy Implant Material

    PubMed Central

    Schröder, Christian; Steinbrück, Arnd; Müller, Tatjana; Woiczinski, Matthias; Chevalier, Yan; Müller, Peter E.; Jansson, Volkmar

    2015-01-01

    Retropatellar complications after total knee arthroplasty (TKA) such as anterior knee pain and subluxations might be related to altered patellofemoral biomechanics, in particular to trochlear design and femorotibial joint positioning. A method was developed to test femorotibial and patellofemoral joint modifications separately with 3D-rapid prototyped components for in vitro tests, but material differences may further influence results. This pilot study aims at validating the use of prostheses made of photopolymerized rapid prototype material (RPM) by measuring the sliding friction with a ring-on-disc setup as well as knee kinematics and retropatellar pressure on a knee rig. Cobalt-chromium alloy (standard prosthesis material, SPM) prostheses served as validation standard. Friction coefficients between these materials and polytetrafluoroethylene (PTFE) were additionally tested as this latter material is commonly used to protect pressure sensors in experiments. No statistical differences were found between friction coefficients of both materials to PTFE. UHMWPE shows higher friction coefficient at low axial loads for RPM, a difference that disappears at higher load. No measurable statistical differences were found in knee kinematics and retropatellar pressure distribution. This suggests that using polymer prototypes may be a valid alternative to original components for in vitro TKA studies and future investigations on knee biomechanics. PMID:25879019

  18. Decoding the Formation of New Semantics: MVPA Investigation of Rapid Neocortical Plasticity during Associative Encoding through Fast Mapping

    PubMed Central

    Atir-Sharon, Tali; Gilboa, Asaf; Hazan, Hananel; Koilis, Ester; Manevitz, Larry M.

    2015-01-01

    Neocortical structures typically only support slow acquisition of declarative memory; however, learning through fast mapping may facilitate rapid learning-induced cortical plasticity and hippocampal-independent integration of novel associations into existing semantic networks. During fast mapping the meaning of new words and concepts is inferred, and durable novel associations are incidentally formed, a process thought to support early childhood's exuberant learning. The anterior temporal lobe, a cortical semantic memory hub, may critically support such learning. We investigated encoding of semantic associations through fast mapping using fMRI and multivoxel pattern analysis. Subsequent memory performance following fast mapping was more efficiently predicted using anterior temporal lobe than hippocampal voxels, while standard explicit encoding was best predicted by hippocampal activity. Searchlight algorithms revealed additional activity patterns that predicted successful fast mapping semantic learning located in lateral occipitotemporal and parietotemporal neocortex and ventrolateral prefrontal cortex. By contrast, successful explicit encoding could be classified by activity in medial and dorsolateral prefrontal and parahippocampal cortices. We propose that fast mapping promotes incidental rapid integration of new associations into existing neocortical semantic networks by activating related, nonoverlapping conceptual knowledge. In healthy adults, this is better captured by unique anterior and lateral temporal lobe activity patterns, while hippocampal involvement is less predictive of this kind of learning. PMID:26257961

  19. Decoding the Formation of New Semantics: MVPA Investigation of Rapid Neocortical Plasticity during Associative Encoding through Fast Mapping.

    PubMed

    Atir-Sharon, Tali; Gilboa, Asaf; Hazan, Hananel; Koilis, Ester; Manevitz, Larry M

    2015-01-01

    Neocortical structures typically only support slow acquisition of declarative memory; however, learning through fast mapping may facilitate rapid learning-induced cortical plasticity and hippocampal-independent integration of novel associations into existing semantic networks. During fast mapping the meaning of new words and concepts is inferred, and durable novel associations are incidentally formed, a process thought to support early childhood's exuberant learning. The anterior temporal lobe, a cortical semantic memory hub, may critically support such learning. We investigated encoding of semantic associations through fast mapping using fMRI and multivoxel pattern analysis. Subsequent memory performance following fast mapping was more efficiently predicted using anterior temporal lobe than hippocampal voxels, while standard explicit encoding was best predicted by hippocampal activity. Searchlight algorithms revealed additional activity patterns that predicted successful fast mapping semantic learning located in lateral occipitotemporal and parietotemporal neocortex and ventrolateral prefrontal cortex. By contrast, successful explicit encoding could be classified by activity in medial and dorsolateral prefrontal and parahippocampal cortices. We propose that fast mapping promotes incidental rapid integration of new associations into existing neocortical semantic networks by activating related, nonoverlapping conceptual knowledge. In healthy adults, this is better captured by unique anterior and lateral temporal lobe activity patterns, while hippocampal involvement is less predictive of this kind of learning.

  20. Rapid prototyping for in vitro knee rig investigations of prosthetized knee biomechanics: comparison with cobalt-chromium alloy implant material.

    PubMed

    Schröder, Christian; Steinbrück, Arnd; Müller, Tatjana; Woiczinski, Matthias; Chevalier, Yan; Weber, Patrick; Müller, Peter E; Jansson, Volkmar

    2015-01-01

    Retropatellar complications after total knee arthroplasty (TKA) such as anterior knee pain and subluxations might be related to altered patellofemoral biomechanics, in particular to trochlear design and femorotibial joint positioning. A method was developed to test femorotibial and patellofemoral joint modifications separately with 3D-rapid prototyped components for in vitro tests, but material differences may further influence results. This pilot study aims at validating the use of prostheses made of photopolymerized rapid prototype material (RPM) by measuring the sliding friction with a ring-on-disc setup as well as knee kinematics and retropatellar pressure on a knee rig. Cobalt-chromium alloy (standard prosthesis material, SPM) prostheses served as validation standard. Friction coefficients between these materials and polytetrafluoroethylene (PTFE) were additionally tested as this latter material is commonly used to protect pressure sensors in experiments. No statistical differences were found between friction coefficients of both materials to PTFE. UHMWPE shows higher friction coefficient at low axial loads for RPM, a difference that disappears at higher load. No measurable statistical differences were found in knee kinematics and retropatellar pressure distribution. This suggests that using polymer prototypes may be a valid alternative to original components for in vitro TKA studies and future investigations on knee biomechanics.

  1. Comparative meta-analysis and experimental kinetic investigation of column and batch bottle microcosm treatability studies informing in situ groundwater remedial design.

    PubMed

    Driver, Erin M; Roberts, Jeff; Dollar, Peter; Charles, Maurissa; Hurst, Paul; Halden, Rolf U

    2017-02-05

    A systematic comparison was performed between batch bottle and continuous-flow column microcosms (BMs and CMs, respectively) commonly used for in situ groundwater remedial design. Review of recent literature (2000-2014) showed a preference for reporting batch kinetics, even when corresponding column data were available. Additionally, CMs produced higher observed rate constants, exceeding those of BMs by a factor of 6.1±1.1 standard error. In a subsequent laboratory investigation, 12 equivalent microcosm pairs were constructed from fractured bedrock and perchloroethylene (PCE) impacted groundwater. First-order PCE transformation kinetics of CMs were 8.0±4.8 times faster than BMs (rates: 1.23±0.87 vs. 0.16±0.05d(-1), respectively). Additionally, CMs transformed 16.1±8.0-times more mass than BMs owing to continuous-feed operation. CMs are concluded to yield more reliable kinetic estimates because of much higher data density stemming from long-term, steady-state conditions. Since information from BMs and CMs is valuable and complementary, treatability studies should report kinetic data from both when available. This first systematic investigation of BMs and CMs highlights the need for a more unified framework for data use and reporting in treatability studies informing decision-making for field-scale groundwater remediation. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Strain induced directional coarsening in nickel based superalloys: Investigation on kinetics using the small angle neutron scattering (SANS) technique

    SciTech Connect

    Veron, M.; Bastie, P.

    1997-08-01

    Using the small angle neutron scattering technique, the authors have observed rafting in nickel based single crystal superalloys. Kinetics of morphological evolution of the precipitates have been studied in situ. Therefore the authors used a special furnace designed for the ageing of prestrained specimens under a neutron beam. The evolution of both the precipitate aspect ratio and the distance between precipitates confirms the importance of strain in the directional coarsening process. Results are presented and discussed regarding kinetics and microstructural aspects. In such conditions, rafts seem to be different from those obtained after a creep test.

  3. An investigation of the effect of surface impurities on the adsorption kinetics of hydrogen chemisorbed onto iron

    NASA Technical Reports Server (NTRS)

    Shanabarger, Mickey R.

    1993-01-01

    The goal of this program was to develop an understanding of heterogeneous kinetic processes for those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. Although hydrogen degradation of metallic materials is believed to result from dissolved protonic hydrogen, the heterogeneous hydrogen interface transport processes often dominate the kinetics of degradation. The initial step in the interface transport process is the dissociative chemisorption of the molecular species at the metal surface followed by hydrogen absorption into and transport through the bulk. The interaction of hydrogen with the surfaces of alpha-2(Ti3Al) titanium aluminide, gamma(TiAl) titanium aluminide, and beryllium were studied.

  4. Investigation of Near-Surface Defects Induced by Spike Rapid Thermal Annealing in c-SILICON Solar Cells

    NASA Astrophysics Data System (ADS)

    Liu, Guodong; Ren, Pan; Zhang, Dayong; Wang, Weiping; Li, Jianfeng

    2016-01-01

    The defects induced by a spike rapid thermal annealing (RTA) process in crystalline silicon (c-Si) solar cells were investigated by the photoluminescence (PL) technique and the transmission electron microscopy (TEM), respectively. Dislocation defects were found to form in the near-surface junction region of the monocrystalline Si solar cell after a spike RTA process was performed at 1100∘C. Photo J-V characteristics were measured on the Si solar cell before and after the spike RTA treatments to reveal the effects of defects on the Si cell performances. In addition, the Silvaco device simulation program was used to study the effects of defects density on the cell performances by fitting the experimental data of RTA-treated cells. The results demonstrate that there was an obvious degradation in the Si solar cell performances when the defect density after the spike RTA treatment was above 1×1013cm-3.

  5. Theoretical investigation of fission fragment kinetic energy distributions in the symmetric mass region for 233U(nth,f)

    NASA Astrophysics Data System (ADS)

    Chebboubi, Abdelaziz; Serot, Olivier; Kessedjian, Grégoire; Litaize, Olivier; Blanc, Aurelien; Bernard, David; Faust, Herbert; Julien-Laferrière, Sylvain; Köster, Ulli; Letourneau, Alain; Materna, Thomas; Méplan, Olivier; Mutti, Paolo; Rapala, Michal; Sage, Christophe

    2017-09-01

    Fission yields are essential for nuclear reactor studies (decay heat, fuel inventory…) and constitute also one of the main observables needed to improve our understanding of the fission process. The symmetric mass region is of particular interest due to various intriguing properties of the fission fragments already reported in the literature : inversion of the nuclear charge polarization, large width of the fission fragment kinetic energy distribution, strong change of the prompt neutron multiplicity, etc. Recently, measurements of fission yields and kinetic energy distributions in the symmetric mass region were achieved at the LOHENGRIN mass spectrometer of the Institut Laue-Langevin (ILL). This experimental work is challenging due to the low counting rate and the appearance of contaminant masses, leading to pronounced components in the fission fragment kinetic energy distribution. Despite removing the undesirable contributions, the fission fragment kinetic energy distributions still show two components, indicating that the fission process could be modal. To go further and better characterize these components a comparison between our experimental data and Monte Carlo calculations (FIFRELIN code) simulating the de-excitation of the fission fragments for different fission channels will be presented and discussed.

  6. Investigating the state of physiologically based kinetic modelling practices and challenges associated with gaining regulatory acceptance of model applications

    EPA Science Inventory

    Physiologically based kinetic (PBK) models are used widely throughout a number of working sectors, including academia and industry, to provide insight into the dosimetry related to observed adverse health effects in humans and other species. Use of these models has increased over...

  7. Investigating the Mechanism of Heteroaromatic Decarboxylation Using Solvent Kinetic Isotope Effects and Eyring Transition-State Theory

    ERIC Educational Resources Information Center

    Mundle, Scott O. C.; Opinska, Liliana Guevara; Kluger, Ronald; Dicks, Andrew P.

    2011-01-01

    An upper-level mechanistic organic experiment is outlined where undergraduates measure kinetic rate constants for decarboxylation of pyrrole-2-carboxylic acid by the initial-rates method. UV spectroscopy is used to monitor reactant disappearance in both hydrochloric acid and deuterium chloride at different temperatures. Individual data are pooled…

  8. Investigating the Mechanism of Heteroaromatic Decarboxylation Using Solvent Kinetic Isotope Effects and Eyring Transition-State Theory

    ERIC Educational Resources Information Center

    Mundle, Scott O. C.; Opinska, Liliana Guevara; Kluger, Ronald; Dicks, Andrew P.

    2011-01-01

    An upper-level mechanistic organic experiment is outlined where undergraduates measure kinetic rate constants for decarboxylation of pyrrole-2-carboxylic acid by the initial-rates method. UV spectroscopy is used to monitor reactant disappearance in both hydrochloric acid and deuterium chloride at different temperatures. Individual data are pooled…

  9. Investigations on the pharmacokinetics of trofosfamide and its metabolites-first report of 4-hydroxy-trofosfamide kinetics in humans.

    PubMed

    Preiss, Rainer; Baumann, Frank; Stefanovic, Dragan; Niemeyer, Ulf; Pönisch, Wolfgang; Niederwieser, Dietger

    2004-06-01

    Trofosfamide (TRO), like cyclophosphamide (CYCLO) and ifosfamide (IFO), is a prodrug oxazaphosphorine derivative that requires hepatic biotransformation to form the cytotoxically active 4-hydroxy derivative (4-hydroxy-TRO). Individual 4-hydroxyoxazaphosphorines and 4-hydroxy-TRO itself have not been demonstrated in humans up to now. For investigation of the principal pharmacokinetics of TRO and its metabolites, six tumour patients (49-65 years of age, Karnofsky index >70%) with normal liver and renal function were given a single oral dose of 600 mg/m(2) TRO. Plasma was sampled using a bedside technique. Individual 4-hydroxyoxazaphosphorines and TRO together with further metabolites were determined by a specially developed HPLC-UV method and a HPLC-MS method, respectively. With a short apparent half-life (1.2 h) and high apparent clearance (Cl/F 4.0 l/min), TRO was very quickly eliminated from plasma and highly converted to its metabolites, mainly 4-hydroxy-TRO and IFO. In relation to the AUC values of TRO (1.0) the following molar quotients were calculated: 1.59 (4-hydroxy-TRO), 0.40 (4-hydroxy-IFO), 6.90 (IFO) and 0.74 (CYCLO). C(max) values were in the range 10-13 micromol/l for TRO, 4-hydroxy-TRO and IFO and in the range 1.5-4.0 micromol/l for CYCLO, 2- and 3-dechloroethyl-IFO and 4-hydroxy-IFO. Kinetic data indicate that 4-hydroxy-IFO is formed by both hydroxylation of TRO and exocyclic N-dechloroethylation of 4-hydroxy-TRO. 4-hydroxy-CYCLO was not detected above the quantification limit of the method. Only mild haemodepressive side effects were observed after oral administration of 600 mg/m(2) TRO. In relation to known data for IFO, TRO is much more 4-hydroxylated than IFO. The high 4-hydroxy-TRO/TRO ratio found suggests that TRO is a promising tumourstatic agent.

  10. Demonstration of Ion Kinetic Effects in Inertial Confinement Fusion Implosions and Investigation of Magnetic Reconnection Using Laser-Produced Plasmas

    NASA Astrophysics Data System (ADS)

    Rosenberg, M. J.

    2016-10-01

    Shock-driven laser inertial confinement fusion (ICF) implosions have demonstrated the presence of ion kinetic effects in ICF implosions and also have been used as a proton source to probe the strongly driven reconnection of MG magnetic fields in laser-generated plasmas. Ion kinetic effects arise during the shock-convergence phase of ICF implosions when the mean free path for ion-ion collisions (λii) approaches the size of the hot-fuel region (Rfuel) and may impact hot-spot formation and the possibility of ignition. To isolate and study ion kinetic effects, the ratio of N - K =λii /Rfuel was varied in D3He-filled, shock-driven implosions at the Omega Laser Facility and the National Ignition Facility, from hydrodynamic-like conditions (NK 0.01) to strongly kinetic conditions (NK 10). A strong trend of decreasing fusion yields relative to the predictions of hydrodynamic models is observed as NK increases from 0.1 to 10. Hydrodynamics simulations that include basic models of the kinetic effects that are likely to be present in these experiments-namely, ion diffusion and Knudsen-layer reduction of the fusion reactivity-are better able to capture the experimental results. This type of implosion has also been used as a source of monoenergetic 15-MeV protons to image magnetic fields driven to reconnect in laser-produced plasmas at conditions similar to those encountered at the Earth's magnetopause. These experiments demonstrate that for both symmetric and asymmetric magnetic-reconnection configurations, when plasma flows are much stronger than the nominal Alfvén speed, the rate of magnetic-flux annihilation is determined by the flow velocity and is largely insensitive to initial plasma conditions. This work was supported by the Department of Energy Grant Number DENA0001857.

  11. Charge translocation by the Na+/K+-ATPase investigated on solid supported membranes: rapid solution exchange with a new technique.

    PubMed Central

    Pintschovius, J; Fendler, K

    1999-01-01

    Adsorption of Na+/K+-ATPase containing membrane fragments from pig kidney to lipid membranes allows the detection of electrogenic events during the Na+/K+-ATPase reaction cycle with high sensitivity and time resolution. High stability preparations can be obtained using solid supported membranes (SSM) as carrier electrodes for the membrane fragments. The SSMs are prepared using an alkanethiol monolayer covalently linked to a gold surface on a glass substrate. The hydrophobic surface is covered with a lipid monolayer (SAM, self-assembled monolayer) to obtain a double layer system having electrical properties similar to those of unsupported bilayer membranes (BLM). As we have previously shown (, Biophys. J. 64:384-391), the Na+/K+-ATPase on a SSM can be activated by photolytic release of ATP from caged ATP. In this publication we show the first results of a new technique which allows rapid solution exchange at the membrane surface making use of the high mechanical stability of SSM preparations. Especially for substrates, which are not available as a caged substance-such as Na+ and K+-this technique is shown to be capable of yielding new results. The Na+/K+-ATPase was activated by rapid concentration jumps of ATP and Na+ (in the presence of ATP). A time resolution of up to 10 ms was obtained in these experiments. The aim of this paper is to present the new technique together with the first results obtained from the investigation of the Na+/K+-ATPase. A comparison with data taken from the literature shows considerable agreement with our experiments. PMID:9929483

  12. Modeling Investigation of Rapid Formation of a Severe Winter Haze Episode in the Beijing-Tianjin-Hebei Region

    NASA Astrophysics Data System (ADS)

    Du, H.; Li, J.

    2016-12-01

    The Nested Air Quality Prediction Model System (NAQPMS) with an on-line tracer-tagged module was used to investigate the rapid formation and sources of an extremely severe haze episode over a mega-city cluster in North China Plain during 26 November-1 December 2015, when regional daily mean PM2.5 exceeded 500μg/m-3. We found that local contribution dominated in the slow increasing stage (26-29 November). While the accumulation of regional transport at the foot of mountain accounted for the rapid increasing and sustaining stage of highest surface PM2.5 on 30 November-1 December in Beijing, although concentrations of PM2.5 in source regions were lower. In vertical, large differences on region sources appeared on different layers below 1km above ground level in Beijing, even in the stable conditions. Contributions from local emissions and its neighboring regions decreased sharply with height from the ground to 1 km. For regional transport, as the distance from source regions to Beijing became farther, the altitude of main transport body increased slowly. The PM2.5 transported from southern Hebei and Henan province centered around 200-400m and 300-700m, respectively, with a maximum of 100-120μg/m-3. These results suggested that more attention should be paid on point sources at 200-500m in BTH (Beijing-Tianjin-Hebei) and its surrounding provinces because they were located in the effective transport height. Differently from Beijing, Tianjin was controlled by the regional transport, while cities in Hebei provinces mostly resulted from local emissions in this episode. The tagging on time in haze periods showed that PM2.5 on hazy days had been aged because PM2.5 formed one or two days before was about twice of that formed "current day", which suggested that control-measures should be taken two days prior to haze episode.

  13. Tolrestat kinetics

    SciTech Connect

    Hicks, D.R.; Kraml, M.; Cayen, M.N.; Dubuc, J.; Ryder, S.; Dvornik, D.

    1984-10-01

    The kinetics of tolrestat, a potent inhibitor of aldose reductase, were examined. Serum concentrations of tolrestat and of total /sup 14/C were measured after dosing normal subjects and subjects with diabetes with /sup 14/C-labeled tolrestat. In normal subjects, tolrestat was rapidly absorbed and disappearance from serum was biphasic. Distribution and elimination t 1/2s were approximately 2 and 10 to 12 hr, respectively, after single and multiple doses. Unchanged tolrestat accounted for the major portion of /sup 14/C in serum. Radioactivity was rapidly and completely excreted in urine and feces in an approximate ratio of 2:1. Findings were much the same in subjects with diabetes. In normal subjects, the kinetics of oral tolrestat were independent of dose in the 10 to 800 mg range. Repetitive dosing did not result in unexpected cumulation. Tolrestat was more than 99% bound to serum protein; it did not compete with warfarin for binding sites but was displaced to some extent by high concentrations of tolbutamide or salicylate.

  14. Investigation of the electron kinetics in O2 capacitively coupled plasma with the use of a Langmuir probe

    NASA Astrophysics Data System (ADS)

    Kechkar, S.; Swift, P.; Kelly, S.; Kumar, S.; Daniels, S.; Turner, M.

    2017-06-01

    A Langmuir probe was used to measure various electron plasma parameters in O2 capacitively coupled plasma. It was shown that the variation in these plasma parameters was due to changes in the electron heating mechanisms as the discharge conditions varied. The so called ‘α-γ’ mode transition in O2 plasma (100 mTorr) was identified from the power evolution (30-600 W) of the electron energy probability function (EEPF), electron density (n e) and effective electron temperature (T eff). The EEPF evolved from Druyvesteyn to bi-Maxwellian with increasing applied power which resulted in a rapid decrease and an abrupt increase in T eff and n e respectively. Comparisons were made to the same mode transition for similar conditions in Ar plasma. The EEPFs were Druyvesteyn in the α mode and evolved into a Maxwellian like EEPF in the γ mode of an Ar plasma. Two distinct trends of n e versus power was observed, it was shown that the measured rf current and rf voltage had a similar behavior. The pressure evolution of the EEPF, n e, and T eff was also investigated in O2 plasma operated at both 30 and 200 W. At 30 W the number of high energy electrons decreased and flattening of the low energy portion of the EEPF occurred with increasing gas pressure (10-100 mTorr) which indicates a collisionless to collisional heating transition. However, at 200 W the right combination of rf voltage and pressure was met for the discharge to evolve into the γ mode as the pressure increased. This was evident from significant narrowing of the EEPF as the pressure increased.

  15. A novel photochemical system of ferrous sulfite complex: kinetics and mechanisms of rapid decolorization of Acid Orange 7 in aqueous solutions.

    PubMed

    Zhou, Danna; Chen, Long; Zhang, Changbo; Yu, Yingtan; Zhang, Li; Wu, Feng

    2014-06-15

    We previously reported the decolorization of the azo dye Acid Orange 7 (AO7) by sulfate radical (SO4(-)) in the presence of iron(II) sulfite complex and oxygen under UV-vis irradiation (photo-iron(II) sulfite system). This system, however, achieves very limited mineralization of AO7 (in terms of total organic carbon (TOC) removal), which is not in accordance with literature reports on the oxidation of organic contaminants by SO4(-). In the present work, kinetics and products under irradiation of xenon lamp (350 W) were analyzed to reveal the reaction pathway of decolorization of AO7. Steady-state approximation (SSA) of SO4(-) radicals and apparent kinetics of AO7 were examined. The reaction between AO7 and SO4(-) was found to proceed in two steps, namely, electron transfer and SO4(-) addition. The second-order rate constant for the reaction between AO7 and SO4(-) was found to be 8.07 ± 1.07 × 10(9) M(-1) s(-1) by SSA and 6.80 ± 0.68 × 10(9) M(-1) s(-1) by competition kinetics method. The apparent kinetics of the decolorization of AO7 under irradiation closely fits the mechanism of radical chain reactions of various reactive sulfur species. By liquid chromatography coupled with mass spectrometry, we identified the sulfate adduct AO7-SO4 and confirmed the two-step reaction between AO7 and SO4(-). This stable sulfate adduct provides a good explanation of the poor TOC removal during decolorization of AO7 by the photo-iron(II) sulfite system.

  16. Sorption potential of rice husk for the removal of 2,4-dichlorophenol from aqueous solutions: kinetic and thermodynamic investigations.

    PubMed

    Akhtar, Mubeena; Bhanger, M I; Iqbal, Shahid; Hasany, S Moosa

    2006-01-16

    The sorption potential of chemically and thermally treated rice husk (RHT) for the removal of 2,4-dichlorophenol (DCP) from aqueous solutions has been investigated. Sorption of DCP by rice husk was observed over a wide pH range of 1-10. The effect of contact time between liquid and solid phases, sorbent dose, pH, concentration of sorbate and temperature on the sorption of DCP onto rice husk has been studied. The pore area and average pore diameter of RHT by BET method are calculated to be 17+/-0.6 m2g-1 and 51.3+/-1.5 nm, respectively. Maximum sorption (98+/-1.2%) was achieved for RHT from 6.1x10(-5) moldm(-3) of sorbate solution using 0.1g of rice husk for 10 min agitation time at pH 6 and 303K, which is comparable to activated carbon commercial (ACC) 96.6+/-1.2%, but significantly higher than chemically treated rice husk (RHCT) 65+/-1.6% and rice husk untreated (RHUT) 41+/-2.3%. The sorption data obtained at optimized conditions was subjected to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Sorption intensity 1/n (0.31+/-0.01) and sorption capacity multilayer C(m) (12.0+/-1.6 mmolg(-1)) have been evaluated using Freundlich sorption isotherm, whereas the values of sorption capacity monolayer Q (0.96+/-0.03 mmolg(-1)) and binding energy, b, (4.5+/-1.0)x10(4)dm(3)mol(-1) have been estimated by Langmuir isotherm. The Langmuir constant, b, was also used to calculate the dimensionless factor, R(L), in the concentration range (0.6-6.1)x10(-4) moldm(-3), suggesting greater sorption at low concentration. D-R sorption isotherm was employed to calculate sorption capacity X(m) (2.5+/-0.07 mmolg(-1)) and sorption energy E (14.7+/-0.13 kJmol(-1)). Lagergren and Morris-Weber equations were employed to study kinetics of sorption process using 0.2g of RHT, 25 cm(3) of 0.61x10(-4)moldm(-3) sorbate concentration at pH 6, giving values of first-order rate constant, k, and rate constant of intraparticle transport, R(id), (0.48+/-0.04 min(-1) and 6.8+/-0.8 nmolg(-1

  17. Global investigation of potential energy surfaces for the pyrolysis of C(1)-C(3) hydrocarbons: toward the development of detailed kinetic models from first principles.

    PubMed

    Ryazantsev, Mikhail N; Jamal, Adeel; Maeda, Satoshi; Morokuma, Keiji

    2015-11-07

    Detailed kinetic models (DKMs) are the most fundamental "bottom-up" approaches to computational investigation of the pyrolysis and oxidation of fuels. The weakest points of existing DKMs are incomplete information about the reaction types that can be involved in the potential energy surfaces (PESs) in pyrolysis and oxidation processes. Also, the computational thermodynamic parameters available in the literature vary widely with the level of theory employed. More sophisticated models require improvement both in our knowledge of the type of the reactions involved and the consistency of thermodynamic and kinetic parameters. In this paper, we aim to address these issues by developing ab initio models that can be used to describe early stages of pyrolysis of C1-C3 hydrocarbons. We applied a recently developed global reaction route mapping (GRRM) strategy to systematically investigate the PES of the pyrolysis of C1-C3 hydrocarbons at a consistent level of theory. The reactions are classified into 14 reaction types. The critical points on the PES for all reactions in the network are calculated at the highly accurate UCCSD(T)-F12b/cc-pVTZ//UM06-2X/cc-pVTZ level of theory. The data reported in this paper can be used for first principle calculations of kinetic constants and for a subsequent study on modeling the evolution of the species from the reaction network of the pyrolysis and oxidation of C1-C3 hydrocarbons.

  18. Effects of partial sleep deprivation on slow waves during non-rapid eye movement sleep: a high density EEG investigation

    PubMed Central

    Plante, David T.; Goldstein, Michael R.; Cook, Jesse D.; Smith, Richard; Riedner, Brady A.; Rumble, Meredith E.; Jelenchick, Lauren; Roth, Andrea; Tononi, Giulio; Benca, Ruth M.; Peterson, Michael J.

    2015-01-01

    Objective Changes in slow waves during non-rapid eye movement (NREM) sleep in response to acute total sleep deprivation are well-established measures of sleep homeostasis. This investigation utilized high-density electroencephalography (hdEEG) to examine topographic changes in slow waves during repeated partial sleep deprivation. Methods Twenty-four participants underwent a 6-day sleep restriction protocol. Spectral and period-amplitude analyses of sleep hdEEG data were used to examine changes in slow wave energy, count, amplitude, and slope relative to baseline. Results Changes in slow wave energy were dependent on the quantity of NREM sleep utilized for analysis, with widespread increases during sleep restriction and recovery when comparing data from the first portion of the sleep period, but restricted to recovery sleep if the entire sleep episode was considered. Period-amplitude analysis was less dependent on the quantity of NREM sleep utilized, and demonstrated topographic changes in the count, amplitude, and distribution of slow waves, with frontal increases in slow wave amplitude, numbers of high-amplitude waves, and amplitude/slopes of low amplitude waves resulting from partial sleep deprivation. Conclusions Topographic changes in slow waves occur across the course of partial sleep restriction and recovery. Significance These results demonstrate a homeostatic response to partial sleep loss in humans. PMID:26596212

  19. Depth investigation of rapid sand filters for drinking water production reveals strong stratification in nitrification biokinetic behavior.

    PubMed

    Tatari, K; Smets, B F; Albrechtsen, H-J

    2016-09-15

    The biokinetic behavior of NH4(+) removal was investigated at different depths of a rapid sand filter treating groundwater for drinking water preparation. Filter materials from the top, middle and bottom layers of a full-scale filter were exposed to various controlled NH4(+) loadings in a continuous-flow lab-scale assay. NH4(+) removal capacity, estimated from short term loading up-shifts, was at least 10 times higher in the top than in the middle and bottom filter layers, consistent with the stratification of Ammonium Oxidizing Bacteria (AOB). AOB density increased consistently with the NH4(+) removal rate, indicating their primarily role in nitrification under the imposed experimental conditions. The maximum AOB cell specific NH4(+) removal rate observed at the bottom was at least 3 times lower compared to the top and middle layers. Additionally, a significant up-shift capacity (4.6 and 3.5 times) was displayed from the top and middle layers, but not from the bottom layer at increased loading conditions. Hence, AOB with different physiological responses were active at the different depths. The biokinetic analysis predicted that despite the low NH4(+) removal capacity at the bottom layer, the entire filter is able to cope with a 4-fold instantaneous loading increase without compromising the effluent NH4(+). Ultimately, this filter up-shift capacity was limited by the density of AOB and their biokinetic behavior, both of which were strongly stratified. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Effects of partial sleep deprivation on slow waves during non-rapid eye movement sleep: A high density EEG investigation.

    PubMed

    Plante, David T; Goldstein, Michael R; Cook, Jesse D; Smith, Richard; Riedner, Brady A; Rumble, Meredith E; Jelenchick, Lauren; Roth, Andrea; Tononi, Giulio; Benca, Ruth M; Peterson, Michael J

    2016-02-01

    Changes in slow waves during non-rapid eye movement (NREM) sleep in response to acute total sleep deprivation are well-established measures of sleep homeostasis. This investigation utilized high-density electroencephalography (hdEEG) to examine topographic changes in slow waves during repeated partial sleep deprivation. Twenty-four participants underwent a 6-day sleep restriction protocol. Spectral and period-amplitude analyses of sleep hdEEG data were used to examine changes in slow wave energy, count, amplitude, and slope relative to baseline. Changes in slow wave energy were dependent on the quantity of NREM sleep utilized for analysis, with widespread increases during sleep restriction and recovery when comparing data from the first portion of the sleep period, but restricted to recovery sleep if the entire sleep episode was considered. Period-amplitude analysis was less dependent on the quantity of NREM sleep utilized, and demonstrated topographic changes in the count, amplitude, and distribution of slow waves, with frontal increases in slow wave amplitude, numbers of high-amplitude waves, and amplitude/slopes of low amplitude waves resulting from partial sleep deprivation. Topographic changes in slow waves occur across the course of partial sleep restriction and recovery. These results demonstrate a homeostatic response to partial sleep loss in humans. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  1. Investigations of rapid thermal annealing induced structural evolution of ZnO: Ge nanocomposite thin films via GISAXS

    NASA Astrophysics Data System (ADS)

    Ceylan, Abdullah; Ozcan, Yusuf; Orujalipoor, Ilghar; Huang, Yen-Chih; Jeng, U.-Ser; Ide, Semra

    2016-06-01

    In this work, we present in depth structural investigations of nanocomposite ZnO: Ge thin films by utilizing a state of the art grazing incidence small angle x-ray spectroscopy (GISAXS) technique. The samples have been deposited by sequential r.f. and d.c. sputtering of ZnO and Ge thin film layers, respectively, on single crystal Si(100) substrates. Transformation of Ge layers into Ge nanoparticles (Ge-np) has been initiated by ex-situ rapid thermal annealing of asprepared thin film samples at 600 °C for 30, 60, and 90 s under forming gas atmosphere. A special attention has been paid on the effects of reactive and nonreactive growth of ZnO layers on the structural evolution of Ge-np. GISAXS analyses have been performed via cylindrical and spherical form factor calculations for different nanostructure types. Variations of the size, shape, and distributions of both ZnO and Ge nanostructures have been determined. It has been realized that GISAXS results are not only remarkably consistent with the electron microscopy observations but also provide additional information on the large scale size and shape distribution of the nanostructured components.

  2. Effects of rapid grounding line retreat investigated with three-dimensional ice sheet-ice shelf models

    NASA Astrophysics Data System (ADS)

    Pattyn, F.; Docquier, D.; Durand, G.; Favier, L.; Gagliardini, O.; Hindmarsh, R. C.; Zwinger, T.

    2011-12-01

    Understanding and attributing future sea-level changes demands serious efforts on the development of efficient ice sheet - ice shelf models that capture the essential physics and mechanics of grounding line behavior. While semi-analytical solutions for grounding line behavior are available for the flowline case, such solution fails to exist for more complex three-dimensional geometries. A way of evaluating the quality of ice sheet models is to verify them against more complex model solutions under controlled conditions. Given the computational demands of such models, it is extremely attractive from a computational point of view to use flux/thickness parameterizations in 3d models. Here we investigated the transition between ice sheet and ice shelf with series of different numerical models, ranging from full Stokes (Elmer/Ice) models, pseudo-spectral methods to a 2d vertically integrated finite-difference 'shelfy-stream' model, taking into account grounding line dynamics, and using parameterizations by Schoof (2007) and Pollard and DeConto (2009). Rapid grounding line migration was provoked by changing sliding at the grounding line, resulting in curved grounding lines influenced by lateral effects. We tested whether flux parameterizations are still valid under such conditions, especially when buttressing effects are taken into account.

  3. Effect of rapid grounding line migration investigated with 3D ice sheet-ice shelf models (MISMIP3d)

    NASA Astrophysics Data System (ADS)

    Pattyn, F.; Docquier, D.; Durand, G.; Favier, L.; Gagliardini, O.; Hindmarsh, R.; Zwinger, T.; Mismip3d Participants

    2012-04-01

    Understanding and attributing future sea-level changes demands serious efforts on the development of efficient ice sheet-ice shelf models that capture the essential physics and mechanics of grounding line behavior. While semi-analytical solutions for grounding line behavior are available for the flowline case, such solution fails to exist for more complex three-dimensional geometries. A way of evaluating the quality of ice sheet models is to verify them against more complex model solutions under controlled conditions (Marine Ice Sheet Model Intercomparison - MISMIP). Given the computational demands of such models, it is extremely attractive from a computational point of view to use flux/thickness parameterizations in 3d models. Here we investigated the transition between ice sheet and ice shelf with series of different numerical models, ranging from full Stokes (Elmer/Ice) models, pseudo-spectral methods to a 2d vertically integrated finite-difference 'shelfy-stream' model, taking into account grounding line dynamics, and using parameterizations by Schoof (2007) and Pollard and DeConto (2009). Rapid grounding line migration was provoked by changing sliding at the grounding line, resulting in curved grounding lines influenced by lateral effects. We tested whether flux parameterizations are still valid under such conditions, especially when buttressing effects are taken into account. Results of other participants in the intercomparison exercise are presented alongside the initial benchmark results.

  4. Investigations of rapid thermal annealing induced structural evolution of ZnO: Ge nanocomposite thin films via GISAXS

    SciTech Connect

    Ceylan, Abdullah; Ozcan, Yusuf; Orujalipoor, Ilghar; Huang, Yen-Chih; Jeng, U-Ser; Ide, Semra

    2016-06-07

    In this work, we present in depth structural investigations of nanocomposite ZnO: Ge thin films by utilizing a state of the art grazing incidence small angle x-ray spectroscopy (GISAXS) technique. The samples have been deposited by sequential r.f. and d.c. sputtering of ZnO and Ge thin film layers, respectively, on single crystal Si(100) substrates. Transformation of Ge layers into Ge nanoparticles (Ge-np) has been initiated by ex-situ rapid thermal annealing of asprepared thin film samples at 600 °C for 30, 60, and 90 s under forming gas atmosphere. A special attention has been paid on the effects of reactive and nonreactive growth of ZnO layers on the structural evolution of Ge-np. GISAXS analyses have been performed via cylindrical and spherical form factor calculations for different nanostructure types. Variations of the size, shape, and distributions of both ZnO and Ge nanostructures have been determined. It has been realized that GISAXS results are not only remarkably consistent with the electron microscopy observations but also provide additional information on the large scale size and shape distribution of the nanostructured components.

  5. An investigation of the reliability of Rapid Upper Limb Assessment (RULA) as a method of assessment of children's computing posture.

    PubMed

    Dockrell, Sara; O'Grady, Eleanor; Bennett, Kathleen; Mullarkey, Clare; Mc Connell, Rachel; Ruddy, Rachel; Twomey, Seamus; Flannery, Colleen

    2012-05-01

    Rapid Upper Limb Assessment (RULA) is a quick observation method of posture analysis. RULA has been used to assess children's computer-related posture, but the reliability of RULA on a paediatric population has not been established. The purpose of this study was to investigate the inter-rater and intra-rater reliability of the use of RULA with children. Video recordings of 24 school children were independently viewed by six trained raters who assessed their postures using RULA, on two separate occasions. RULA demonstrated higher intra-rater reliability than inter-rater reliability although both were moderate to good. RULA was more reliable when used for assessing the older children (8-12 years) than with the younger children (4-7 years). RULA may prove useful as part of an ergonomic assessment, but its level of reliability warrants caution for its sole use when assessing children, and in particular, younger children. Copyright © 2011 Elsevier Ltd and The Ergonomics Society. All rights reserved.

  6. Parametric Investigation of the Isothermal Kinetics of Growth of Graphene on a Nickel Catalyst in the Process of Chemical Vapor Deposition of Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Futko, S. I.; Shulitskii, B. G.; Labunov, V. A.; Ermolaeva, E. M.

    2016-11-01

    A kinetic model of isothermal synthesis of multilayer graphene on the surface of a nickel foil in the process of chemical vapor deposition, on it, of hydrocarbons supplied in the pulsed regime is considered. The dependences of the number of graphene layers formed and the time of their growth on the temperature of the process, the concentration of acetylene, and the thickness of the nickel foil were calculated. The regime parameters of the process of chemical vapor deposition, at which single-layer graphene and bi-layer graphene are formed, were determined. The dynamics of growth of graphene domains at chemical-vapor-deposition parameters changing in wide ranges was investigated. It is shown that the time dependences of the rates of growth of single-layer graphene and bi-layer graphene are nonlinear in character and that they are determined by the kinetics of nucleation and growth of graphene and the diffusion flow of carbon atoms in the nickel foil.

  7. Flood-frequency analyses from paleoflood investigations for Spring, Rapid, Boxelder, and Elk Creeks, Black Hills, western South Dakota

    USGS Publications Warehouse

    Harden, Tessa M.; O'Connor, Jim E.; Driscoll, Daniel G.; Stamm, John F.

    2011-01-01

    Flood-frequency analyses for the Black Hills area are important because of severe flooding of June 9-10, 1972, that was caused by a large mesoscale convective system and caused at least 238 deaths. Many 1972 peak flows are high outliers (by factors of 10 or more) in observed records that date to the early 1900s. An efficient means of reducing uncertainties for flood recurrence is to augment gaged records by using paleohydrologic techniques to determine ages and magnitudes of prior large floods (paleofloods). This report summarizes results of paleoflood investigations for Spring Creek, Rapid Creek (two reaches), Boxelder Creek (two subreaches), and Elk Creek. Stratigraphic records and resulting long-term flood chronologies, locally extending more than 2,000 years, were combined with observed and adjusted peak-flow values (gaged records) and historical flood information to derive flood-frequency estimates for the six study reaches. Results indicate that (1) floods as large as and even substantially larger than 1972 have affected most of the study reaches, and (2) incorporation of the paleohydrologic information substantially reduced uncertainties in estimating flood recurrence. Canyons within outcrops of Paleozoic rocks along the eastern flanks of the Black Hills provided excellent environments for (1) deposition and preservation of stratigraphic sequences of late-Holocene flood deposits, primarily in protected slack-water settings flanking the streams; and (2) hydraulic analyses for determination of associated flow magnitudes. The bedrock canyons ensure long-term stability of channel and valley geometry, thereby increasing confidence in hydraulic computations of ancient floods from modern channel geometry. Stratigraphic records of flood sequences, in combination with deposit dating by radiocarbon, optically stimulated luminescence, and cesium-137, provided paleoflood chronologies for 29 individual study sites. Flow magnitudes were estimated from elevations of flood

  8. Cesium removal and kinetics equilibrium: Precipitation kinetics

    SciTech Connect

    Barnes, M.J.

    1999-12-17

    This task consisted of both non-radioactive and radioactive (tracer) tests examining the influence of potentially significant variables on cesium tetraphenylborate precipitation kinetics. The work investigated the time required to reach cesium decontamination and the conditions that affect the cesium precipitation kinetics.

  9. An automated image-based method of 3D subject-specific body segment parameter estimation for kinetic analyses of rapid movements.

    PubMed

    Sheets, Alison L; Corazza, Stefano; Andriacchi, Thomas P

    2010-01-01

    Accurate subject-specific body segment parameters (BSPs) are necessary to perform kinetic analyses of human movements with large accelerations, or no external contact forces or moments. A new automated topographical image-based method of estimating segment mass, center of mass (CM) position, and moments of inertia is presented. Body geometry and volume were measured using a laser scanner, then an automated pose and shape registration algorithm segmented the scanned body surface, and identified joint center (JC) positions. Assuming the constant segment densities of Dempster, thigh and shank masses, CM locations, and moments of inertia were estimated for four male subjects with body mass indexes (BMIs) of 19.7-38.2. The subject-specific BSP were compared with those determined using Dempster and Clauser regression equations. The influence of BSP and BMI differences on knee and hip net forces and moments during a running swing phase were quantified for the subjects with the smallest and largest BMIs. Subject-specific BSP for 15 body segments were quickly calculated using the image-based method, and total subject masses were overestimated by 1.7-2.9%.When compared with the Dempster and Clauser methods, image-based and regression estimated thigh BSP varied more than the shank parameters. Thigh masses and hip JC to thigh CM distances were consistently larger, and each transverse moment of inertia was smaller using the image-based method. Because the shank had larger linear and angular accelerations than the thigh during the running swing phase, shank BSP differences had a larger effect on calculated intersegmental forces and moments at the knee joint than thigh BSP differences did at the hip. It was the net knee kinetic differences caused by the shank BSP differences that were the largest contributors to the hip variations. Finally, BSP differences produced larger kinetic differences for the subject with larger segment masses, suggesting that parameter accuracy is more

  10. Kinetic characteristics of debris flows as exemplified by field investigations and discrete element simulation of the catastrophic Jiweishan rockslide, China

    NASA Astrophysics Data System (ADS)

    Zou, Zongxing; Tang, Huiming; Xiong, Chengren; Su, Aijun; Criss, Robert E.

    2017-10-01

    The Jiweishan rockslide of June 5, 2009 in China provides an important opportunity to elucidate the kinetic characteristics of high-speed, long-runout debris flows. A 2D discrete element model whose mechanical parameters were calibrated using basic field data was used to simulate the kinetic behavior of this catastrophic landslide. The model output shows that the Jiweishan debris flow lasted about 3 min, released a gravitational potential energy of about 6 × 10^13 J with collisions and friction dissipating approximately equal amounts of energy, and had a maximum fragment velocity of 60-70 m/s, almost twice the highest velocity of the overall slide mass (35 m/s). Notable simulated characteristics include the high velocity and energy of the slide material, the preservation of the original positional order of the slide blocks, the inverse vertical grading of blocks, and the downslope sorting of the slide deposits. Field observations that verify these features include uprooted trees in the frontal collision area of the air-blast wave, downslope reduction of average clast size, and undamaged plants atop huge blocks that prove their lack of downslope tumbling. The secondary acceleration effect and force chains derived from the numerical model help explain these deposit features and the long-distance transport. Our back-analyzed frictions of the motion path in the PFC model provide a reference for analyzing and predicting the motion of similar geological hazards.

  11. Reaction condition optimization and kinetic investigation of roasting zinc oxide ore using (NH4)2SO4

    NASA Astrophysics Data System (ADS)

    Shao, Hong-mei; Shen, Xiao-yi; Sun, Yi; Liu, Yan; Zhai, Yu-chun

    2016-10-01

    An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using (NH4)2SO4. The optimized reaction conditions are defined as an (NH4)2SO4/zinc molar ratio of 1.4:1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of (NH4)2SO4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric-differential thermal analysis was used for (NH4)2SO4 and zinc mixed in a molar ratio of 1.4:1 at the heating rates of 5, 10, 15, and 20 K·min-1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle-Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.

  12. Low density lipoprotein detection based on antibody immobilized self-assembled monolayer: investigations of kinetic and thermodynamic properties.

    PubMed

    Matharu, Zimple; Bandodkar, Amay Jairaj; Sumana, G; Solanki, Pratima R; Ekanayake, E M I Mala; Kaneto, Keiichi; Gupta, Vinay; Malhotra, B D

    2009-10-29

    Human plasma low density lipoprotein (LDL) immunosensor based on surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) was fabricated by immobilizing antiapolipoprotein B (AAB) onto self-assembled monolayer (SAM) of 4-aminothiophenol (ATP). The AAB/ATP/Au immunosensor can detect LDL up to 0.252 microM (84 mg/dL) and 0.360 microM (120 mg/dL) with QCM and SPR, respectively. The SPR and QCM measurements were further utilized to study the reaction kinetics of the AAB-LDL interaction. The adsorption process involved was explored using Langmuir adsorption isotherm and Freundlich adsorption models. The thermodynamic parameters such as change in Gibb's free energy (DeltaG(ads)), change in enthalpy (DeltaH(ads)), and change in entropy (DeltaS(ads)) determined at 283, 298, and 308 K revealed that the AAB-LDL interaction is endothermic in nature and is governed by entropy. Kinetic, thermodynamic, and sticking probability studies disclosed that desorption of the water molecules from the active sites of AAB and LDL plays a key role in the interaction process and increase in temperature favors binding of LDL with the AAB/ATP/Au immunosensor. Thus, the studies were utilized to unravel the most important subprocess involved in the adsorption of LDL onto AAB-modified ATP/Au surface that may help in the fabrication of LDL immunosensors with better efficiency.

  13. Characterization and scanning electron microscopic investigation of crosslinked freeze dried gelatin matrices for study of drug diffusivity and release kinetics.

    PubMed

    Thakur, Goutam; Mitra, Analava; Basak, Amit; Sheet, Debdoot

    2012-02-01

    Drug delivery is a promising technique to enhance the therapeutic efficacy of the drug. However, properties of carrier materials require intense improvement for effective transport of drug molecules. In the current study, attempts have been made to develop freeze dried gelatin matrices cross linked with genipin at various temperatures (5°C, 15°C and 25°C) prior to freeze-drying (-80°C). The freeze dried matrices thus obtained at the said temperatures are characterized for crosslinking density, compression strength, swelling behaviors. The matrix crosslinked at 25°C showed highest Flory-Rehner crosslinking density (467 ± 46) (p<0.05), highest compressive strength (12.36 ± 0.12) (p<0.05) and lowest equilibrium water content. In this context, scanning electron microscopy (SEM) was performed to study the surface morphology (size and shape of pores) of the crosslinked matrices. These images were further processed for quantitative analysis of morphological features, viz., areas, radius, ferret diameter, length of major and minor axis and eccentricity using MATLAB toolboxes. These quantitative analyses correlate transport and the release kinetics of model anti-inflammatory drug (indomethacin) from crosslinked matrices in vitro to tune as a controllable delivery system. The diffusional exponent (n) for all constructs ranging from 0.61 to 0.69 (p<0.05) (0.45kinetics.

  14. Origins of sequence selectivity in homologous genetic recombination: insights from rapid kinetic probing of RecA-mediated DNA strand exchange.

    PubMed

    Lee, Andrew M; Xiao, Jie; Singleton, Scott F

    2006-07-07

    Despite intense effort over the past 30 years, the molecular determinants of sequence selectivity in RecA-mediated homologous recombination have remained elusive. Here, we describe when and how sequence homology is recognized between DNA strands during recombination in the context of a kinetic model for RecA-mediated DNA strand exchange. We characterized the transient intermediates of the reaction using pre-steady-state kinetic analysis of strand exchange using oligonucleotide substrates containing a single fluorescent G analog. We observed that the reaction system was sensitive to heterology between the DNA substrates; however, such a "heterology effect" was not manifest when functional groups were added to or removed from the edges of the base-pairs facing the minor groove of the substrate duplex. Hence, RecA-mediated recombination must occur without the involvement of a triple helix, even as a transient intermediate in the process. The fastest detectable reaction phase was accelerated when the structure or stability of the substrate duplex was perturbed by internal mismatches or the replacement of G.C by I.C base-pairs. These findings indicate that the sequence specificity in recombination is achieved by Watson-Crick pairing in the context of base-pair dynamics inherent to the extended DNA structure bound by RecA during strand exchange.

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

    PubMed

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

    2012-12-01

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

  16. Electron microscopic investigation of the kinetics of the layer and island crystallization of amorphous V2O3 films deposited by pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Bagmut, A. G.

    2017-06-01

    An electron microscopic investigation was performed on the kinetics of the layer and island crystallization of amorphous V2O3 films deposited by pulsed laser evaporation of vanadium in an oxygen atmosphere. The crystallization was initiated by the action of an electron beam on an amorphous film in the column of a transmission electron microscope. The kinetic curves were plotted on the basis of a frame-by-frame analysis of the video recorded during the crystallization of the film. It was found that the layer crystallization of amorphous films is characterized by a quadratic dependence of the fraction of the crystalline phase x on the time t, whereas the island crystallization is described by an exponential dependence of x on t. The kinetic curves of island crystallization of amorphous films were analyzed on the basis of the α-version of the Kolmogorov model. For each type of crystallization, there are specific values of the dimensionless relative length unit δ0, which is equal to the ratio of the characteristic length unit to the parameter characterizing the unit cell of the crystal. It was established that, for the layer crystallization, the relative length unit lies in the range δ0 4300-4700, whereas for the fine-grained island crystallization, it amounts to δ0 110.

  17. Investigation of thermoluminescence and kinetic parameters of CaMgB{sub 2}O{sub 5}: Dy{sup 3+} nanophosphor

    SciTech Connect

    Manhas, M.; Kumar, Vinay; Ntwaeaborwa, O. M.; Swart, H. C.

    2016-05-06

    In this paper, thermoluminescence (TL) properties of Dy{sup 3+} (1.5 mol %) doped CaMgB{sub 2}O{sub 5} nanophosphor after being exposed to ultraviolet (UV) radiations (λ=254nm) were investigated. In UV exposed samples, the thermoluminescence glow curve consists of a broad glow peak located at 380 K with a small shoulder at 507 K. A shift in glow peak temperature from 367 K to 380 K after the UV exposure for 80 min was observed, which clearly shows that glow peaks follow the second order kinetics. The TL intensity of the peaks increases with an increase in the exposure time of UV rays (10-180 min). The TL Anal program was used to analyze the glow curve. The kinetic parameters such as activation energy (E), the frequency factor (s) and the order of kinetics (b) were calculated for CaMgB{sub 2}O{sub 5}: Dy{sup 3+} nanophosphors.

  18. Investigation of the mechanical interaction of the trabecular core with an external shell using rapid prototype and finite element models.

    PubMed

    Mc Donnell, P; Harrison, N; Lohfeld, S; Kennedy, O; Zhang, Y; Mc Hugh, P E

    2010-01-01

    The mechanical properties of vertebral bone have been widely studied with the ultimate goal of improving fracture risk prediction. However, the mechanical interaction between the cortical shell and the trabecular core is not well understood. The objective of this study was to investigate this interaction and to determine what effect it has on the ultimate strength of the whole bone. This objective was achieved by compression testing rapid prototype (RP) models of cylindrical trabecular bone cores, with and without an integral surrounding shell and incorporating increasing levels of artificially induced bone loss. Corresponding finite element (FE) models were generated and the load sharing of the shell and trabecular core was analysed under linear elastic loading conditions. The results of the physical RP model tests and corresponding FE analyses indicated that there was a reinforcing effect between the cortical shell and the trabecular core for all models tested and that the reinforcing effect became relatively more important to the ultimate strength of the whole bone as the bone volume fraction of the trabecular core decreased. It was found that two mechanisms contributed to the reinforcing effect: (i) load transfer from the highly stressed shell into the connecting outer trabeculae of the core for the shelled model. This did not occur for the un-shelled model where the load dropped off at the outer unsupported trabeculae; (ii) the stiffening effect on the shell due to the support provided by the connecting struts of the trabecular core, which serves to inhibit bending and buckling behaviour in the shell under compression loading. It was found that the stiffening on the shell was the more dominant contributor to the overall reinforcing effect between the shell and the trabecular core.

  19. Effects of oral temazepam on sleep spindles during non-rapid eye movement sleep: a high-density EEG investigation

    PubMed Central

    Plante, DT; Goldstein, MR; Cook, JD; Smith, R; Riedner, BA; Rumble, ME; Jelenchick, L; Roth, A; Tononi, G; Benca, RM; Peterson, MJ

    2015-01-01

    Benzodiazepines are commonly used medications that alter sleep spindles during non-rapid eye movement (NREM) sleep, however the topographic changes to these functionally significant waveforms have yet to be fully elucidated. This study utilized high-density electroencephalography (hdEEG) to investigate topographic changes in sleep spindles and spindle-range activity caused by temazepam during NREM sleep in 18 healthy adults. After an accommodation night, sleep for all participants was recorded on two separate nights after taking either placebo or oral temazepam 15mg. Sleep was monitored using 256-channel hdEEG. Spectral analysis and spindle waveform detection of sleep EEG data were performed for each participant night. Global and topographic data were subsequently compared between temazepam and placebo conditions. Temazepam was associated with significant increases in spectral power from 10.33–13.83Hz. Within this frequency band, temazepam broadly increased sleep spindle duration, and topographically increased spindle amplitude and density in frontal and central-posterior regions, respectively. Higher frequency sleep spindles demonstrated increased spindle amplitude and a paradoxical decrease in spindle density in frontal and centroparietal regions. Further analysis demonstrated temazepam both slowed the average frequency of spindle waveforms and increased the relative proportion of spindles at peak frequencies in frontal and centroparietal regions. These findings suggest that benzodiazepines have diverse effects on sleep spindles that vary by frequency and cortical topography. Further research that explores the relationships between topographic and frequency-dependent changes in pharmacologically-induced sleep spindles and the functional effects of these waveforms is indicated. PMID:26195197

  20. Numerical investigation of non-perturbative kinetic effects of energetic particles on toroidicity-induced Alfvén eigenmodes in tokamaks and stellarators

    SciTech Connect

    Slaby, Christoph; Könies, Axel; Kleiber, Ralf

    2016-09-15

    The resonant interaction of shear Alfvén waves with energetic particles is investigated numerically in tokamak and stellarator geometry using a non-perturbative MHD-kinetic hybrid approach. The focus lies on toroidicity-induced Alfvén eigenmodes (TAEs), which are most easily destabilized by a fast-particle population in fusion plasmas. While the background plasma is treated within the framework of an ideal-MHD theory, the drive of the fast particles, as well as Landau damping of the background plasma, is modelled using the drift-kinetic Vlasov equation without collisions. Building on analytical theory, a fast numerical tool, STAE-K, has been developed to solve the resulting eigenvalue problem using a Riccati shooting method. The code, which can be used for parameter scans, is applied to tokamaks and the stellarator Wendelstein 7-X. High energetic-ion pressure leads to large growth rates of the TAEs and to their conversion into kinetically modified TAEs and kinetic Alfvén waves via continuum interaction. To better understand the physics of this conversion mechanism, the connections between TAEs and the shear Alfvén wave continuum are examined. It is shown that, when energetic particles are present, the continuum deforms substantially and the TAE frequency can leave the continuum gap. The interaction of the TAE with the continuum leads to singularities in the eigenfunctions. To further advance the physical model and also to eliminate the MHD continuum together with the singularities in the eigenfunctions, a fourth-order term connected to radiative damping has been included. The radiative damping term is connected to non-ideal effects of the bulk plasma and introduces higher-order derivatives to the model. Thus, it has the potential to substantially change the nature of the solution. For the first time, the fast-particle drive, Landau damping, continuum damping, and radiative damping have been modelled together in tokamak- as well as in stellarator geometry.

  1. Pre-steady-state kinetic investigation of bypass of a bulky guanine lesion by human Y-family DNA polymerases.

    PubMed

    Tokarsky, E John; Gadkari, Varun V; Zahurancik, Walter J; Malik, Chanchal K; Basu, Ashis K; Suo, Zucai

    2016-10-01

    3-Nitrobenzanthrone (3-NBA), a byproduct of diesel exhaust, is highly present in the environment and poses a significant health risk. Exposure to 3-NBA results in formation of N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone (dG(C8-)(N)(-ABA)), a bulky DNA lesion that is of particular importance due to its mutagenic and carcinogenic potential. If not repaired or bypassed during genomic replication, dG(C8-)(N)(-ABA) can stall replication forks, leading to senescence and cell death. Here we used pre-steady-state kinetic methods to determine which of the four human Y-family DNA polymerases (hPolη, hPolκ, hPolι, or hRev1) are able to catalyze translesion synthesis of dG(C8-)(N)(-ABA)in vitro. Our studies demonstrated that hPolη and hPolκ most efficiently bypassed a site-specifically placed dG(C8-)(N-)(ABA) lesion, making them good candidates for catalyzing translesion synthesis (TLS) of this bulky lesion in vivo. Consistently, our publication (Biochemistry 53, 5323-31) in 2014 has shown that small interfering RNA-mediated knockdown of hPolη and hPolκ in HEK293T cells significantly reduces the efficiency of TLS of dG(C8-)(N)(-ABA). In contrast, hPolι and hRev1 were severely stalled by dG(C8-)(N)(-ABA) and their potential role in vivo was discussed. Subsequently, we determined the kinetic parameters for correct and incorrect nucleotide incorporation catalyzed by hPolη at various positions upstream, opposite, and downstream from dG(C8-)(N-)(ABA). Notably, nucleotide incorporation efficiency and fidelity both decreased significantly during dG(C8-)(N)(-ABA) bypass and the subsequent extension step, leading to polymerase pausing and error-prone DNA synthesis by hPolη. Furthermore, hPolη displayed nucleotide concentration-dependent biphasic kinetics at the two polymerase pause sites, suggesting that multiple enzyme•DNA complexes likely exist during nucleotide incorporation. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Investigating Uranium Concentrations in Groundwaters in the State of Idaho Using Kinetic Phosphorescence Analysis and Inductively Coupled Plasma Mass Spectrometry.

    PubMed

    Tkavadze, Levan; Dunker, Roy E; Brey, Richard R; Dudgeon, John

    2016-11-01

    The determination of uranium concentrations in natural water samples is of great interest due to the environmental consequences of this radionuclide. In this study, 380 groundwater samples from various locations within the state of Idaho were analyzed using two different techniques. The first method was Kinetic Phosphorescence Analysis (KPA), which gives the total uranium concentrations in water samples. The second analysis method was inductively coupled plasma mass spectrometry (ICP- MS). This method determines the total uranium concentration as well as the separate isotope concentrations of uranium. The U/U isotopic ratio was also measured for each sample to confirm that there was no depleted or enriched uranium present. The results were compared and mapped separately from each other. The study also found that in some areas of the state, natural uranium concentrations are relatively high.

  3. Temperature dependence of the electrode kinetics of oxygen reduction at the platinum/Nafion interface - A microelectrode investigation

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Arvind; Srinivasan, Supramanian; Appleby, A. J.; Martin, Charles R.

    1992-01-01

    Results of a study of the temperature dependence of the oxygen reduction kinetics at the Pt/Nafion interface are presented. This study was carried out in the temperature range of 30-80 C and at 5 atm of oxygen pressure. The results showed a linear increase of the Tafel slope with temperature in the low current density region, but the Tafel slope was found to be independent of temperature in the high current density region. The values of the activation energy for oxygen reduction at the platinum/Nafion interface are nearly the same as those obtained at the platinum/trifluoromethane sulfonic acid interface but less than values obtained at the Pt/H3PO4 and Pt/HClO4 interfaces. The diffusion coefficient of oxygen in Nafion increases with temperature while its solubility decreases with temperature. These temperatures also depend on the water content of the membrane.

  4. Numerical investigation of the recrystallization kinetics by means of the KWC phase-field model with special order parameters

    NASA Astrophysics Data System (ADS)

    Kundin, Julia

    2017-06-01

    The present paper proposes an extension to the phase-field model of Kobayashi, Warren and Carter (KWC) as described in (Warren et al 2002 Acta Mater.) to incorporate the recrystallization process which occurs during heat treatments of alloy systems with predeformed defect structure. The standard KWC model is extended by an additional order parameter for recrystallized grains and describes the general results for the steady-state moving boundary. The simulation results of the initial grain growth and recrystallization process in various systems show that the extended phase-field model is able to describe the influence of the initial grain boundaries on the recrystallization kinetics and to incorporate the misorientation dependency of the low angle grain boundary mobility which strongly influences the orientation distribution in the resulting microstructure.

  5. Investigating the kinetics of paramagnetic-beads linked alkaline phosphatase enzyme through microchannel resistance measurement in dielectric microchip.

    PubMed

    Faure, Mathilde; Sotta, Bruno; Gamby, Jean

    2014-08-15

    Real time monitoring of electrolyte resistance changes during hydrolysis of 4-nitrophenylphosphate (pNPP) by alkaline phosphatase (ALP) bound on paramagnetic-beads was performed into a small dielectric channel. The reaction kinetic fit with a non-competitive substrate-inhibition equation. Michaelis-Menten apparent constant, KM(app), was determined as 0.33±0.06mM and the maximum apparent rate, Vmax(app) as 98±5pMs(-1). The detection limits were 15fM for ALP and 0.75mM for pNPP. This miniaturized device constitutes a powerful tool for analysis of interaction between ligands. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Experimental and Numerical Investigation of Guest Molecule Exchange Kinetics based on the 2012 Ignik Sikumi Gas Hydrate Field Trial

    NASA Astrophysics Data System (ADS)

    Ruprecht Yonkofski, C. M.; Horner, J.; White, M. D.

    2015-12-01

    In 2012 the U.S. DOE/NETL, ConocoPhillips Company, and Japan Oil, Gas and Metals National Corporation jointly sponsored the first field trial of injecting a mixture of N2-CO2 into a CH4-hydrate bearing formation beneath the permafrost on the Alaska North Slope. Known as the Ignik Sikumi #1 Gas Hydrate Field Trial, this experiment involved three stages: 1) the injection of a N2-CO2 mixture into a targeted hydrate-bearing layer, 2) a 4-day pressurized soaking period, and 3) a sustained depressurization and fluid production period. Data collected during the three stages of the field trial were made available after a thorough quality check. The Ignik Sikumi #1 data set is extensive, but contains no direct evidence of the guest-molecule exchange process. This study uses numerical simulation to provide an interpretation of the CH4/CO2/N2 guest molecule exchange process that occurred at Ignik Sikumi #1. Simulations were further informed by experimental observations. The goal of the scoping experiments was to understand kinetic exchange rates and develop parameters for use in Iġnik Sikumi history match simulations. The experimental procedure involves two main stages: 1) the formation of CH4 hydrate in a consolidated sand column at 750 psi and 2°C and 2) flow-through of a 77.5/22.5 N2/CO2 molar ratio gas mixture across the column. Experiments were run both above and below the hydrate stability zone in order to observe exchange behavior across varying conditions. The numerical simulator, STOMP-HYDT-KE, was then used to match experimental results, specifically fitting kinetic behavior. Once this behavior is understood, it can be applied to field scale models based on Ignik Sikumi #1.

  7. In situ electrochemical investigations of the kinetic and thermodynamic properties of nickel-metal hydride traction batteries

    NASA Astrophysics Data System (ADS)

    Yang, Xiao Guang; Liaw, Bor Yann

    Although large ampere hour nickel-metal hydride (Ni-MH) traction batteries are in the stage of being commercialized for electric and hybrid vehicle applications, little is known about their performance characteristics. By using a standard Hg/HgO reference electrode in a commercial Ni-MH battery, we were able to conduct in situ measurements to determine both kinetic and thermodynamic properties of the system, including the characteristics of individual electrodes. Using the galvanostatic intermittent titration technique (GITT), we simultaneously and effectively determined the open-circuit voltage of the battery, the equilibrium electrode potentials, and the diffusion coefficient of proton and hydrogen in the nickel and metal hydride electrode, respectively, as a function of the states of charge (SOC). Using the current-step excitation technique, we found that the internal resistance of the battery primarily comes from the metal hydride electrode, which is greater by one order of magnitude than that of the Ni electrode. The cyclic linear micro-polarization experiments, on the other hand, showed that the charge-transfer resistance of the electrochemical reaction at the metal hydride electrode is about twice larger than that of the Ni counterpart above 20% SOC. In comparison, the internal resistance is an order of magnitude smaller than those of the electrochemical charge-transfer reactions. The micro-polarization technique also allowed us to calculate the exchange current densities of the respective electrode electrochemical reactions and the associated specific exchange current densities. These in situ, simple but detailed, characterizations of the thermodynamic and kinetic properties of the Ni-MH system provided valuable information for better understanding of the battery performance.

  8. An investigation of the effect of surface impurities on the adsorption kinetics of hydrogen chemisorbed onto iron

    NASA Technical Reports Server (NTRS)

    Shanabarger, Mickey R.

    1991-01-01

    The goal was to develop an understanding of heterogeneous kinetic processes for those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. Although hydrogen degradation of metallic materials is believed to result from dissolved protonic hydrogen, the heterogeneous hydrogen interface transport processes often dominate the kinetics of the degradation process. The initial step in the interface transport process is the dissociative chemisorption of the molecular species at the metal surface followed by hydrogen absorption into and transport through the bulk. Modern advanced aerospace applications often require the use of structural materials in high pressure hydrogen environments at temperatures which range from low cryogenic temperatures to very high temperatures (1300 K and greater). Materials proposed for these applications, such as the titanium aluminides, beta-titanium alloys, nickel- and cobalt-based superalloys, molybdenum-rhenium alloys, beryllium, and various beryllides, need to possess a high degree of immunity from hydrogen induced degradation of mechanical properties. In the present program, the interaction of hydrogen with the surfaces of alpha-2 (Ti3Al) titanium aluminide, gamma (TiAl) titanium aluminide, and beryllium were studied. The interaction of low pressure hydrogen with gamma titanium aluminide and beryllium was found to be relatively weak, in the sense that adsorption leads to a low surface concentration of dissociated hydrogen, i.e., the chemisorption process is reversible at room temperature (300 K) for gamma titanium aluminide and the sticking coefficient for chemisorption is extremely small for beryllium. Hydrogen was found to interact readily with alpha-2 titanium aluminide to form a stable surface hydride at 300 K. These results correlate well with other recent studies which show that the mechanical properties for alpha-2 titanium aluminide are readily degraded in

  9. Kinetics of α-(2,6-Dimethylphenl)vinyllithium: How To Control Errors Caused by Inefficient Mixing with Pairs of Rapidly Competing Ketones.

    PubMed

    Knorr, Rudolf; Knittl, Monika; Behringer, Claudia; Ruhdorfer, Jakob; Böhrer, Petra

    2017-03-17

    Kinetic studies are a suitable tool to disclose the role of tiny reagent fractions. The title compound 2 reacted in a kinetic reaction order of 0.5 (square root of its concentration) with an excess of the electrophiles ClSiMe3, 1-bromobutane (n-BuBr), or 1-iodobutane (n-BuI) at 32 °C in Et2O or in hydrocarbon solvents. This revealed that the tiny (NMR-invisible) amount of a deaggregated equilibrium component (presumably monomeric 2) was the reactive species, whereas the disolvated dimer 2 was only indirectly involved as a supply depot. Selectivity data (relative rate constants κobs) were collected from competition experiments with the faster reactions of 2 in THF and the addition reactions of 2 to carbonyl compounds. This provided the rate sequences of Et2C═O > dicyclopropyl ketone > t-Bu-C(═O)-Ph > diisopropyl ketone ≫ t-Bu2C═O > ClSiMe3 > n-BuI > n-BuBr ≈ (bromomethyl)cyclopropane (but t-Bu2C═O < ClSiMe3 in THF only) and also of cyclopropanecarbaldehyde > acetone ≥ t-Bu-CH═O. It is suggested that a deceivingly depressed selectivity (1 < κobs < kA/kB), caused by inefficient microscopic mixing of a reagent X with two competing substrates A and B, may become evident toward zero deviation from the correlation line of the usual inverse (1/T) linear temperature dependence of ln κobs.

  10. A Microstructural and Kinetic Investigation of the KCl-Induced Corrosion of an FeCrAl Alloy at 600 °C

    SciTech Connect

    Israelsson, Niklas; Unocic, Kinga A.; Hellström, K.; Jonsson, T.; Norell, M.; Svensson, J. -E.; Johansson, L. -G.

    2015-03-18

    In this paper, the corrosion behaviour of a FeCrAl alloy was investigated at 600 °C in O2 + H2O with solid KCl applied. A kinetics and microstructural investigation showed that KCl accelerates corrosion and that potassium chromate formation depletes the protective scale in Cr, thus triggering the formation of a fast-growing iron-rich scale. Iron oxide was found to grow both inward and outward, on either side of the initial oxide. A chromia layer is formed with time underneath the iron oxide. Finally, it was found that although the alloy does not form a continuous pure alumina scale at the investigated temperature, aluminium is, however, always enriched at the oxide/alloy interface.

  11. Kinetic Monte Carlo Investigation of the Effects of Vacancy Pairing on Oxygen Diffusivity in Yttria-Stabilized Zirconia

    NASA Technical Reports Server (NTRS)

    Good, Brian S.

    2011-01-01

    Yttria-stabilized zirconia s high oxygen diffusivity and corresponding high ionic conductivity, and its structural stability over a broad range of temperatures, have made the material of interest for use in a number of applications, for example, as solid electrolytes in fuel cells. At low concentrations, the stabilizing yttria also serves to increase the oxygen diffusivity through the presence of corresponding oxygen vacancies, needed to maintain charge neutrality. At higher yttria concentration, however, diffusivity is impeded by the larger number of relatively high energy migration barriers associated with yttrium cations. In addition, there is evidence that oxygen vacancies preferentially occupy nearest-neighbor sites around either dopant or Zr cations, further affecting vacancy diffusion. We present the results of ab initio calculations that indicate that it is energetically favorable for oxygen vacancies to occupy nearest-neighbor sites adjacent to Y ions, and that the presence of vacancies near either species of cation lowers the migration barriers. Kinetic Monte Carlo results from simulations incorporating this effect are presented and compared with results from simulations in which the effect is not present.

  12. Investigating the chemical and isotopic kinetics of aerobic methane oxidation in the Northern US Atlantic Margin, Hudson Canyon

    NASA Astrophysics Data System (ADS)

    Chan, E. W.; Kessler, J. D.; Shiller, A. M.; Redmond, M. C.; Arrington, E. C.; Valentine, D. L.

    2015-12-01

    Recent discoveries of methane seepage along the US Atlantic margin have led to speculation on the fate of the released methane. Here we examine the kinetics of aerobic methane oxidation to gain a fundamental understanding of this methane sink. In order to look at this process in its entirety, a unique mesocosm incubation system was developed with a Dissolved Gas Analyzer System (DGAS) to monitor in real time the chemical and isotopic changes involved with aerobic methane oxidation. This system measures changes in methane, carbon dioxide, and oxygen concentrations as well as the stable carbon isotopes of methane and carbon dioxide with time. In addition samples are strategically removed to characterize trace metals, nutrients, cell counts, and microbial community genetics. This presentation will detail the results obtained from samples collected inside the Hudson Canyon at the edge of the methane clathrate stability zone and outside the Hudson Canyon, not influenced by the methane seepage. These results show that in both environments along the Atlantic margin, methane was consumed aggressively but the timing of consumption varied based on location. In addition, these results are leading to insights into the chemical requirements needed for aerobic methane oxidation and the resulting isotopic fractionation.

  13. KINETIC AND STRUCTURAL INVESTIGATIONS INTO THE ALLOSTERIC AND PH EFFECT ON SUBSTRATE SPECIFICITY OF HUMAN EPITHELIAL 15-LIPOXYGENASE-2

    PubMed Central

    Joshi, Netra; Hoobler, Eric K.; Perry, Steven; Diaz, Giovanni; Fox, Brian; Holman, Theodore R.

    2013-01-01

    Lipoxygenases, important enzymes in inflammation, can regulate their substrate specificity by allosteric interactions with its own hydroperoxide products. In the current work, addition of both 13-(S) hydroxy-9Z,11E-octadecadienoic acid (13-(S)-HODE) and 13-(S)-hydroperoxy-6Z,9Z,11E-octadecatrienoic acid (13-(S)-HOTrE) to human epithelial 15-lipoxygenase-2 (15-LOX-2) increases the kcat/KM substrate specificity ratio of arachidonic acid (AA) and (γ)-linolenic acid (GLA) by 4-fold. 13-(S)-HODE achieves this change by activating kcat/KM AA but inhibiting kcat/KM GLA, which indicates that the allosteric structural changes at the active site discriminates between the length and unsaturation differences of AA and GLA to achieve opposite kinetics effects. The substrate specificity ratio is further increased, 11-fold total, by increasing pH, suggesting mechanistic differences between the pH and allosteric effects. Interestingly, the loss of the PLAT domain affects substrate specificity, but does not eliminate the allosteric properties of 15-LOX-2, indicating that the allosteric site is located in the catalytic domain. However, the removal of the PLAT domain does change the magnitude of the allosteric effect. These data suggest that the PLAT domain moderates the communication pathway between the allosteric and catalytic sites, thus affecting substrate specificity. These results are discussed in the context of protein dimerization and other structural changes. PMID:24171444

  14. Thermal stability and crystallization kinetics of Cu-Zr-Al-Ag BMGs investigated with isothermal electrical resistance measurement

    NASA Astrophysics Data System (ADS)

    Wang, Li-Fang; Cui, Xiao; Zhang, Qi-Dong; Zu, Fang-Qiu

    2014-07-01

    The thermal stability and crystallization kinetics of the Cu x Zr84- x Al8Ag8 ( x = 42, 40, 38, and 36) bulk metallic glasses (BMGs) were studied by measurement of isothermal electrical-resistance. As the composition becomes richer in Zr, the longer incubation time at the same relative annealing temperature, and the larger local activation energy needed to achieve the same crystallized volume-fraction, indicate improved thermal stability, which resists crystallization. The improved thermal stability is attributed to a denser atomic random-stacking structure and larger negative heat-of-mixing. During isothermal annealing processes, the four BMGs exhibited the same nucleation mechanism, which is a decreasing rate of nucleation over time. However, the crystal growth mechanisms of the four BMGs are different. The crystallization of the Cu36Zr48Al8Ag8 and Cu38Zr46Al8Ag8 BMGs is interface-controlled growth, contrasting with diffusion-controlled growth for the Cu40Zr44Al8Ag8 and Cu42Zr42Al8Ag8 alloys. The different growth modes may be caused by fluctuations in composition due to changes in the quantity and distribution of Cu-rich and Ag-rich regions.

  15. Hydration kinetics of CA{sub 2} and CA-Investigations performed on a synthetic calcium aluminate cement

    SciTech Connect

    Klaus, S.R. Neubauer, J. Goetz-Neunhoeffer, F.

    2013-01-15

    Much is already known about the hydration of monocalcium aluminate (CA) in calcium aluminate cements (CACs). CA{sub 2} is known to be weakly hydraulic. Therefore, the hydration kinetics of CA{sub 2} were not of as great interest as those of the hydration of CAC. We were able to show that the hydration of CA{sub 2} begins as soon as the hydration rate of CA has reached its maximum and the first precipitation of C{sub 2}AH{sub 8} has started. The hydration of different CA/CA{sub 2} ratios was analyzed by the G-factor quantification. The individual contributions of the phases CA and CA{sub 2} to the heat flow were calculated based on the amounts dissolved by applying thermodynamic data. The heat flow as calculated from XRD data was then compared with the measured heat flow. It obtained a good consistency between the two. The very pronounced influence of CA{sub 2} during hydration of CAC can be clearly demonstrated.

  16. An Investigation Of Photodynamic Therapy In The Treatment Of Pancreatic Carcinoma: Dihematoporphyrin Ether Uptake And Photobleaching Kinetics

    NASA Astrophysics Data System (ADS)

    Mang, Thomas S.; Wieman, Thomas J.

    1988-02-01

    Results of dihematoporphyrin ether (DHE) uptake and fluorescence kinetics show that the concentration in the pancreas is on the order of 40-60 μg DHE/g of tissue at an injected dose of 40 mg/kg. Previously concentrations on this order have only been found in organs of the reticuloendothelial system. Two intrapancreatic carcinoma models, one of acinar origin (rat) and one of ductal orgin (hamster), were studied. Both showed equal or higher concentrations of DHE as compared to normal pancreas when fluorescence measurements and chemical extraction procedures were performed. Photodynamic therapy (PDT) treatment of the normal pancreas and pancreatic tumors yielded atypical results. When the normal pancreas with DHE present is exposed to 630 nm light from a dye laser (75 mW/cm2, 30 min), the normal photobleaching measurable by fluorescence decay does not occur. Yet, the pancreatic tumor responds with a relatively normal fluorescence decay pattern, with hemorrhaging and a resultant loss of measurable DHE concentration. These results represent the emergence of an entirely new modality, with substantial potential for the treatment of cancer of the pancreas.

  17. An Investigation into the Kinetics and Mechanism of the Removal of Cyanobacteria by Extract of Ephedra equisetina Root

    PubMed Central

    Yan, Rong; Ji, Hongli; Wu, Yonghong; Kerr, Philip G.; Fang, Yanming; Yang, Linzhang

    2012-01-01

    An aqueous extract of Ephedra equisetina root was found to induce cyanobacterial cell death. The extract displayed no negative effects on the fish populations but instead, improved the habitat conditions for the growth of macrophytes, zooplankton and bacteria because the inhibiting effects of the extracts on cyanobacteria helped clear up the water column. The removal kinetics of cyanobacteria by E. equisetina extract appears to be a first order process with the rate constant being extract-dose-dependent. Compounds including the flavonoids found in E. equisetina root kill the cyanobacteria in vitro at a dose of 5.0 µg extract per 100 mL water or above. The extract constituents act to disrupt the thylakoid membrane, interrupt the electronic transport, decrease the effective quantum yield, and eventually lead to the failure of photosynthesis in Microcystis aeruginosa. This study presents an easily-deployed, natural and promising approach for controlling cyanobacterial blooms as an emergency measure, and also provides insight into the dynamics and mechanism of the extract consisting of multiple compounds synergistically removing algae. PMID:22870313

  18. An investigation of the effect of surface impurities on the adsorption kinetics of hydrogen chemisorbed onto iron

    NASA Technical Reports Server (NTRS)

    Shanabarger, Mickey R.

    1994-01-01

    The goal of this program has been to develop an understanding of heterogeneous kinetic processes for those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. During the present program, the interaction of hydrogen with the surfaces of alpha-2 (Ti3Al) titanium aluminide, gamma (TiAl) titanium aluminide, and beryllium were studied. The interaction of low pressure hydrogen with gamma titanium aluminide and beryllium was found to be relatively weak. Weak in the sense that adsorption leads to a low surface concentration of dissociated hydrogen, i.e., the chemisorption process is reversible at room temperature (300 K) for gamma titanium aluminide and the sticking coefficient for chemisorption is extremely small for beryllium. Hydrogen was found to interact readily with alpha-2 titanium aluminide to form a stable surface hydride at 300 K. These results correlate well with other recent studies which show that the mechanical properties for alpha-2 titanium aluminide are readily degraded in hydrogen while gamma titanium aluminide exhibits less degradation and beryllium essentially no degradation. The interaction of oxygen with the surface of several of these materials was studied. More recently, preliminary hydrogen permeation studies were completed for three high temperature alloys, Incoloy 909, Mo-47.5Re (wt. %), and this past year, Haynes 188.

  19. Investigation of Kinetics of crystallization Processes of S15-Se85, S15-Se81-Cu4 Chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Samudrala, Kavitha; Babu Devarasetty, Suresh

    2016-09-01

    In the present work, S15-Se85, S15-Se81-Cu4 chalcogenide glasses are prepared by using conventional melt quenching technique. The as-prepared samples are studied by experimental techniques like X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC). XRD studies have confirmed that the as-prepared samples are amorphous in nature. It is clear from DSC studies that the as-prepared samples are glassy in nature. Kinetic analysis of the crystallization process of as-prepared glasses is carried using DSC curves. Activation energy for glass transition and Activation energy for crystallization are determined using Kissinger method. Activation energy for glass transition of S15-Se85 and S15-Se81-Cu4 glasses is found to be 84.5076 and 275.801 KJ/Mole respectively. Activation energy for crystallization of S15-Se85 glass is found to be 106.2622 KJ/Mole for 1st peak while Activation energy for crystallization of S15-Se81-Cu4 glasses is found to be 97.93 KJ/Mole for 1st peak and 84.20 KJ/Mole for 2nd peak. Kauzmann temperature (Tk) is determined from the heating rate dependent glass transition and crystallization temperatures. Tk value for S15-Se85 glass sample is 236.680K (1st peak) and for S15-Se81-Cu4 is 283.530K (1st peak) and 286.330K (2n peak). Avrami Index (n) is also determined for as-prepared glasses. Avrami Index (n) value for S15-Se85 glass sample is 1.8 (1st peak) and for S15-Se81-Cu4 is 2.9 (1st peak) and 1.4 (2nd peak). The crystalline phases by thermal treatment of as-prepared glasses are identified using XRD patterns.

  20. Reaction kinetics of acetone peroxide formation and structure investigations using Raman spectroscopy and X-ray diffraction.

    PubMed

    Jensen, L; Mortensen, P M; Trane, R; Harris, P; Berg, R W

    2009-01-01

    Triacetone triperoxide (TATP) has been prepared in order to study the effect of pH and temperature on the reaction kinetics. Raman spectra of liquid mixtures of acetone and hydrogen peroxide were recorded versus time throughout the experiments. The spectral data of the liquid phases indicate that at 25 degrees C the reaction between acetone and hydrogen peroxide proceeds to form intermediates within one day. Based on the assumption that a likely reaction path involves a sequence of reaction steps between acetone and hydrogen peroxide, calculations of Raman spectra were performed using a density functional theory (DFT)/Hartree-Fock approach. It was not possible from this to assess with certainty which intermediate products formed most extensively in an acetone/hydrogen peroxide mixture. However, it was concluded that the most likely reaction mixture is a mixture of the different intermediate products and that the rate determining step is the ring closure. The reaction rate of TATP formation was found to increase with temperature and with sulfuric acid additions to the acetone/hydrogen peroxide mixture. By correlation of the induction time of TATP crystallization against pH it was shown that the reaction rate is first order with respect to the H+ concentration. Raman spectra of the precipitates from mixtures were in agreement with previous studies done for TATP, except in one case in which a crystal crystallized at 343 K had a distinctly different Raman spectrum. Comparison with calculated spectra revealed that the crystal produced could be diacetone diperoxide (DADP) or tetraacetone tetraperoxide (TrATrP). Single crystal X-ray diffraction analyses revealed that the crystal crystallized at 343 K was DADP.

  1. Experimental and theoretical investigations of the kinetics and mechanism of the Cl + 4-hydroxy-4-methyl-2-pentanone reaction

    NASA Astrophysics Data System (ADS)

    Aslan, L.; Priya, A. Mano; Sleiman, C.; Zeineddine, M. N.; Coddeville, P.; Fittschen, C.; Ballesteros, B.; Canosa, A.; Senthilkumar, L.; El Dib, G.; Tomas, A.

    2017-10-01

    The reaction of 4-hydroxy-4-methyl-2-pentanone (4H4M2P) with Cl atoms was studied for the first time experimentally and theoretically. Relative kinetic measurements were carried out at room temperature and 1 bar of synthetic air/N2 in two different environmental chambers: a 300 L Teflon bag and a 16 L borosilicate glass cell. Reactants, reference compounds and products were monitored either by IR absorption or by GC-FID. Theoretical calculations were performed using the density functional theory method at BH&HLYP level of theory for twelve hydrogen abstraction pathways. The individual rate coefficients for the most favorable H-abstraction pathways were calculated by canonical variational theory using small curvature tunneling method at 298 K. An average experimental rate coefficient of (7.4 ± 0.6) × 10-11 cm3 molecule-1 s-1 was obtained at 298 K, in good agreement with the theoretical rate coefficient. The branching ratios for each reaction channel were evaluated theoretically from the individual rate coefficients of the identified channels. The H-atom abstracted on the -CH2 group appeared to be the dominant channel with a small barrier height. Formaldehyde, acetic acid, HCl, CO2 and CO were identified by IR as the major primary products. The obtained results are presented and discussed in terms of structure-reactivity relationships. A mechanism is suggested for the formation of the observed products. The atmospheric implications of the studied reaction are presented and more particularly, the lifetime of 4H4M2P towards Cl atoms is evaluated to be about 3 days.

  2. Laboratory and numerical investigations of kinetic interface sensitive tracers transport for immiscible two-phase flow porous media systems

    NASA Astrophysics Data System (ADS)

    Tatomir, Alexandru Bogdan A. C.; Sauter, Martin

    2017-04-01

    A number of theoretical approaches estimating the interfacial area between two fluid phases are available (Schaffer et al.,2013). Kinetic interface sensitive (KIS) tracers are used to describe the evolution of fluid-fluid interfaces advancing in two phase porous media systems (Tatomir et al., 2015). Initially developed to offer answers about the supercritical (sc)CO2 plume movement and the efficiency of trapping in geological carbon storage reservoirs, KIS tracers are tested in dynamic controlled laboratory conditions. N-octane and water, analogue to a scCO2 - brine system, are used. The KIS tracer is dissolved in n-octane, which is injected as the non-wetting phase in a fully water saturated porous media column. The porous system is made up of spherical glass beads with sizes of 100-250 μm. Subsequently, the KIS tracer follows a hydrolysis reaction over the n-octane - water interface resulting in an acid and phenol which are both water soluble. The fluid-fluid interfacial area is described numerically with the help of constitutive-relationships derived from the Brooks-Corey model. The specific interfacial area is determined numerically from pore scale calculations, or from different literature sources making use of pore network model calculations (Joekar-Niasar et al., 2008). This research describes the design of the laboratory setup and compares the break-through curves obtained with the forward model and in the laboratory experiment. Furthermore, first results are shown in the attempt to validate the immiscible two phase flow reactive transport numerical model with dynamic laboratory column experiments. Keywords: Fluid-fluid interfacial area, KIS tracers, model validation, CCS, geological storage of CO2

  3. A Microstructural and Kinetic Investigation of the KCl-Induced Corrosion of an FeCrAl Alloy at 600 °C

    DOE PAGES

    Israelsson, Niklas; Unocic, Kinga A.; Hellström, K.; ...

    2015-03-18

    In this paper, the corrosion behaviour of a FeCrAl alloy was investigated at 600 °C in O2 + H2O with solid KCl applied. A kinetics and microstructural investigation showed that KCl accelerates corrosion and that potassium chromate formation depletes the protective scale in Cr, thus triggering the formation of a fast-growing iron-rich scale. Iron oxide was found to grow both inward and outward, on either side of the initial oxide. A chromia layer is formed with time underneath the iron oxide. Finally, it was found that although the alloy does not form a continuous pure alumina scale at the investigatedmore » temperature, aluminium is, however, always enriched at the oxide/alloy interface.« less

  4. Investigation of the Icosahedral Z-Phase in Aluminium Transition Metal Alloys and Rapidly Solidified Al-Alloys

    DTIC Science & Technology

    1986-09-01

    Rev. Lett., 53, 1951 (1984). - A Script& NETALLURGICA Vol. 20, pp. 745-750, 1986 Pergamon Press Ltd. Printed in the U.S.A. All rights reserved...single- and two-sided jet polishing were utilized. In addition, some of the flakes were argon-ion . - - thinned using standard procedures. Subsequently...Reeied 26 Fabruay 198, accepted 14 April 1986) Electrohydrodynamic (EHD) atomization has boen used to rapidly solidify micron and submicron size

  5. Synthesis of ultrathin poly(methyl methacrylate) model coatings bound via organosilanes to zinc and investigation of their delamination kinetics.

    PubMed

    Iqbal, Danish; Rechmann, Julian; Sarfraz, Adnan; Altin, Abdulrahman; Genchev, Georgi; Erbe, Andreas

    2014-10-22

    Polymer coatings are widely used to protect metals from corrosion. Coating adhesion to the base material is critical for good protection, but coatings may fail because of cathodic delamination. Most of the experimental studies on cathodic delamination use polymers to study the corrosion behavior under conditions where the interfacial chemistry at the metal(oxide)/polymer interface is not well-defined. Here, ultrathin linear and cross-linked poly(methyl methacrylate) [PMMA] coatings that are covalently bound to oxide-covered zinc via a silane linker have been prepared. For preparation, zinc was functionalized with vinyltrimethoxysilane (VTS), yielding a vinyl monomer-covered surface. These samples were subjected to thermally initiated free radical polymerization in the presence of methyl methacrylate (MMA) to yield surface-bound ultrathin PMMA films of 10-20 nm thickness, bound to the surface via Zn-O-Si bonds. A similar preparation was also carried out in the presence of different amounts of the cross-linkers ethylene glycol diacrylate and hexanediol diacrylate. Functionalized and polymer-coated zinc samples were characterized by infrared (IR) spectroscopy, secondary ion mass spectrometry (SIMS), ellipsometry, and X-ray photoelectron spectroscopy (XPS). Coating stability toward cathodic delamination has been evaluated by scanning Kelvin probe (SKP) experiments. In all cases, the covalently linked coatings show lower delamination rates of 0.02-0.2 mm h(-1) than coatings attached to the surface without covalent bonds (rates ∼10 mm h(-1)). Samples with a higher fraction of cross-linker delaminate slower, with rates down to 0.03-0.04 mm h(-1), compared to ∼0.3 mm h(-1) without cross-linker. Samples with longer hydrophobic alkyl chains also delaminate slower, with the lowest observed delamination rate of 0.028 mm h(-1) using hexanediol diacrylate. For the coatings studied here, delamination kinetics is not diffusion limited, but the rate is controlled by a chemical

  6. In silico kinetics of alkaline hydrolysis of 1,3,5-trinitro-1,3,5-triazinane (RDX): M06-2X investigation.

    PubMed

    Sviatenko, L K; Gorb, L; Leszczynska, D; Okovytyy, S I; Shukla, M K; Leszczynski, J

    2017-03-22

    Alkaline hydrolysis of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), as one of the most promising methods for nitrocompound remediation, was investigated computationally at the PCM(Pauling)/M06-2X/6-311++G(d,p) level of theory. Computational simulation shows that RDX hydrolysis is a highly exothermic multistep process involving initial deprotonation and nitrite elimination, cycle cleavage, further transformation of cycle-opened intermediates to end products caused by a series of C-N bond ruptures, hydroxide attachments, and proton transfers. Computationally predicted products of RDX hydrolysis such as nitrite, nitrous oxide, formaldehyde, formate, and ammonia correspond to experimentally observed ones. Accounting of specific hydration of hydroxide is critical to create an accurate kinetic model for alkaline hydrolysis. Simulated kinetics of the hydrolysis are in good agreement with available experimental data. A period of one month is necessary for 99% RDX decomposition at pH 10. Computations predict significant increases of the reaction rate of hydrolysis at pH 11, pH 12, and pH 13.

  7. Probing the function of Asp128 in the lower molecular weight protein-tyrosine phosphatase-catalyzed reaction. A pre-steady-state and steady-state kinetic investigation.

    PubMed

    Wu, L; Zhang, Z Y

    1996-04-30

    The role of Asp128 in the catalytic mechanism of the low Mr protein-tyrosine phosphatase (PTPase) from the fission yeast Schizosaccharomyces pombe has been investigated by a combination of site-directed mutagenesis and pre-steady-state and steady-state kinetic analysis. The corresponding aspartic acid in the bovine enzyme is located on a loop adjacent to the phosphate-binding loop and forms a hydrogen bond with the oxygen atom of the bound sulfate or phosphate that is structurally homologous to the ester oxygen in substrates [Su et al. (1994) Nature 370, 575-578; Zhang, M., et al. (1994) Biochemistry 33, 11097-11105]. Asp128 has been replaced by a Glu, an Asn, and an Ala. The kcat for the hydrolysis of p-nitrophenyl phosphate (pNPP) decreases by factors of 6.7, 400, and 650 for the mutants D128E, D128N, and D128A, respectively. Compared to the wild type, the binding affinity for phosphate is decreased 2 and 4.3-fold, respectively, for the D128A and D128N mutants, whereas no change in affinity is observed for the D128E mutant. An evaluation of the burst kinetics demonstrates that Asp128 plays a role in both the phosphoenzyme intermediate formation (k2) and breakdown (k3). Thus, substitution at Asp128 by a Glu, an Asn, or an Ala reduces k2 by 17, 7480, and 11900 and reduces k3 by 6.2, 380, and 40. The greater effect on k2 and k3 is consistent with a dissociative transition-state for the low M(r)PTPase-catalyzed reaction. Results from the rapid kinetics, partition experiments, and leaving group dependence experiments suggest that for the wild type and D128E mutant, the rate-limiting step is k3, whereas k2 has become rate-limiting for the D128N mutant. With the exception of pNPP, k2 may also be rate-limiting for D128A. Taken together, these results are consistent with Asp128 or Glu128 acting as a general acid to donate a proton to the phenolate leaving group in the phosphorylation step, and the carboxylate side chain plays a role as a general base to activate a

  8. In Situ Localized Surface Plasmon Resonance (LSPR) Spectroscopy to Investigate Kinetics of Chemical Bath Deposition of CdS Thin Films

    SciTech Connect

    Kalyanaraman, Ramki; Taz, Humaira; Ruther, Rose E.; Nanda, Jagjit

    2015-02-11

    Techniques that can characterize the early stages of thin film deposition from liquid phase processes can aid greatly in our understanding of mechanistic aspects of chemical bath deposition (CBD). Here we have used localized surface plasmon resonance (LSPR) spectroscopy to monitor in-situ the kinetics of early-stage growth of cadmium sulfide (CdS) thin films on Ag nanoparticle on quartz substrates. Real-time shift during CdS deposition showed that the LSPR wavelength red shifted rapidly due to random deposition of CdS on the substrate, but saturated at longer times. LSPR modeling showed that these features could be interpreted as an initial deposition of CdS islands followed by preferential deposition onto itself. The CdS also showed significantly enhanced Raman signals up to 170 times due to surface enhanced raman scattering (SERS) from the CdS/Ag NP regions. The ex-situ SERS effect supported the LSPR shift suggesting that these techniques could be used to understand nucleation and growth phenomena from the liquid phase.

  9. In Situ Localized Surface Plasmon Resonance (LSPR) Spectroscopy to Investigate Kinetics of Chemical Bath Deposition of CdS Thin Films

    DOE PAGES

    Kalyanaraman, Ramki; Taz, Humaira; Ruther, Rose E.; ...

    2015-02-11

    Techniques that can characterize the early stages of thin film deposition from liquid phase processes can aid greatly in our understanding of mechanistic aspects of chemical bath deposition (CBD). Here we have used localized surface plasmon resonance (LSPR) spectroscopy to monitor in-situ the kinetics of early-stage growth of cadmium sulfide (CdS) thin films on Ag nanoparticle on quartz substrates. Real-time shift during CdS deposition showed that the LSPR wavelength red shifted rapidly due to random deposition of CdS on the substrate, but saturated at longer times. LSPR modeling showed that these features could be interpreted as an initial deposition ofmore » CdS islands followed by preferential deposition onto itself. The CdS also showed significantly enhanced Raman signals up to 170 times due to surface enhanced raman scattering (SERS) from the CdS/Ag NP regions. The ex-situ SERS effect supported the LSPR shift suggesting that these techniques could be used to understand nucleation and growth phenomena from the liquid phase.« less

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

    SciTech Connect

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

    2014-11-01

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

  11. Kinetic Atom.

    ERIC Educational Resources Information Center

    Wilson, David B.

    1981-01-01

    Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)

  12. Kinetic Atom.

    ERIC Educational Resources Information Center

    Wilson, David B.

    1981-01-01

    Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)

  13. Investigation of analytical performance for rapidly synergistic cloud point extraction of trace amounts of copper combined with spectrophotometric determination.

    PubMed

    Wen, Xiaodong; Ye, Liqing; Deng, Qingwen; Peng, Li

    2011-12-01

    In this work, an improved preconcentration method named as rapidly synergistic cloud point extraction (RS-CPE) was established for copper preconcentration and determination. Non-ionic surfactant Triton X-100 (TX-100) was used as extractant. Octanol worked as cloud point revulsant and synergic reagent, which successfully decreased the cloud point temperature (CPT) of TX-100 to realize the room temperature (about 20°C) CPE without heating. The established RS-CPE pretreatment was simple, rapid and effective. Compared with traditional CPE (about 40 min for heating, incubation and cooling), the extraction time of the proposed method was very short (1 min). The improved extraction technique RS-CPE was combined with traditional spectrophotometer to improve the analytical performance and expand the application of spectrophotometric determination. The influence factors relevant to RS-CPE, such as concentrations of TX-100 and octanol, concentration of chelating agent, pH, conditions of phase separation, salt effect, environmental temperature and instrumental conditions, were studied in detail. Under the optimal conditions, the limit of detection (LOD) for copper was 0.4 μg L(-1), with sensitivity enhancement factor (EF) of 18. The proposed method was applied to the determination of trace copper in real samples and certified samples with satisfactory analytical results. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Rapid Ti(III) reduction of perchlorate in the presence of beta-alanine: kinetics, pH effect, complex formation, and beta-alanine effect.

    PubMed

    Wang, Chao; Huang, Zhengdao; Lippincott, Lee; Meng, Xiaoguang

    2010-03-15

    Ti(III) reduction of perchlorate might be a useful method for the treatment of highly perchlorate-contaminated water. Though the reaction rate was usually low, we observed that beta-alanine (HOOCCH(2)CH(2)NH(2)) could significantly promote the reaction. A complete (>99.9%) perchlorate removal was obtained in a solution containing [ClO(4)(-)]=1.0mM, [Ti(III)]=40 mM, and [beta-alanine]=120 mM after 2.5h of reaction under 50 degrees C. The effects of both pH and complex formation on the reaction were then studied. The results showed that without beta-alanine the optimal pH was 2.3. When pH increased from 1.6 to 2.3, the reduction rate increased remarkably. In the pH range >2.3, however, the reduction was significantly inhibited, attributed to the formation of Ti(III) precipitate. The presence of beta-alanine at a molar ratio of [beta-alanine]:[Ti(III)]=3:1 significantly increased the reduction rate of perchlorate even at near neutral pH. This is because beta-alanine formed complexes with Ti(III), which greatly improved the total soluble [Ti(III)] in the pH range between 3.5 and 6. The findings may lead to the development of rapid treatment methods for intermittent and small stream of highly perchlorate-contaminated water, which are resulted from the manufacturing, storage, handling, use and/or disposal of large quantities of perchlorate salts.

  15. Toward mechanistic understanding of nuclear reprocessing chemistries by quantifying lanthanide solvent extraction kinetics via microfluidics with constant interfacial area and rapid mixing.

    PubMed

    Nichols, Kevin P; Pompano, Rebecca R; Li, Liang; Gelis, Artem V; Ismagilov, Rustem F

    2011-10-05

    The closing of the nuclear fuel cycle is an unsolved problem of great importance. Separating radionuclides produced in a nuclear reactor is useful both for the storage of nuclear waste and for recycling of nuclear fuel. These separations can be performed by designing appropriate chelation chemistries and liquid-liquid extraction schemes, such as in the TALSPEAK process (Trivalent Actinide-Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexes). However, there are no approved methods for the industrial scale reprocessing of civilian nuclear fuel in the United States. One bottleneck in the design of next-generation solvent extraction-based nuclear fuel reprocessing schemes is a lack of interfacial mass transfer rate constants obtained under well-controlled conditions for lanthanide and actinide ligand complexes; such rate constants are a prerequisite for mechanistic understanding of the extraction chemistries involved and are of great assistance in the design of new chemistries. In addition, rate constants obtained under conditions of known interfacial area have immediate, practical utility in models required for the scaling-up of laboratory-scale demonstrations to industrial-scale solutions. Existing experimental techniques for determining these rate constants suffer from two key drawbacks: either slow mixing or unknown interfacial area. The volume of waste produced by traditional methods is an additional, practical concern in experiments involving radioactive elements, both from disposal cost and experimenter safety standpoints. In this paper, we test a plug-based microfluidic system that uses flowing plugs (droplets) in microfluidic channels to determine absolute interfacial mass transfer rate constants under conditions of both rapid mixing and controlled interfacial area. We utilize this system to determine, for the first time, the rate constants for interfacial transfer of all lanthanides, minus promethium, plus yttrium, under TALSPEAK

  16. A novel fast and flexible technique of radical kinetic behaviour investigation based on pallet for plasma evaluation structure and numerical analysis

    NASA Astrophysics Data System (ADS)

    Malinowski, Arkadiusz; Takeuchi, Takuya; Chen, Shang; Suzuki, Toshiya; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru; Lukasiak, Lidia; Jakubowski, Andrzej

    2013-07-01

    This paper describes a new, fast, and case-independent technique for sticking coefficient (SC) estimation based on pallet for plasma evaluation (PAPE) structure and numerical analysis. Our approach does not require complicated structure, apparatus, or time-consuming measurements but offers high reliability of data and high flexibility. Thermal analysis is also possible. This technique has been successfully applied to estimation of very low value of SC of hydrogen radicals on chemically amplified ArF 193 nm photoresist (the main goal of this study). Upper bound of our technique has been determined by investigation of SC of fluorine radical on polysilicon (in elevated temperature). Sources of estimation error and ways of its reduction have been also discussed. Results of this study give an insight into the process kinetics, and not only they are helpful in better process understanding but additionally they may serve as parameters in a phenomenological model development for predictive modelling of etching for ultimate CMOS topography simulation.

  17. Spectroscopic investigation on kinetics, thermodynamics and mechanism for electron transfer reaction of iron(III) complex with sulphur centered radical in stimulated biological system.

    PubMed

    Deepalakshmi, S; Sivalingam, A; Kannadasan, T; Subramaniam, P; Sivakumar, P; Brahadeesh, S T

    2014-04-24

    Electron transfer reactions of biological organic sulphides with several metal ions to generate sulphide radical cations are a great concern in biochemical process. To understand the mechanism, a stimulated biological system having model compounds, iron(III)-bipyridyl complex with thio-diglycolic acid (TDGA) was investigated. Spectroscopic study reveals the kinetics and thermodynamics of the reaction in aqueous perchloric acid medium. The reaction follows first and fractional order of 0.412 with respect to [Fe(bpy)3](3+) and TDGA, respectively. The oxidation is insensitive to variation in [H(+)] but slightly decreases with increase in ionic strength ([I]). Addition of acrylamide, a radical scavenger has no effect on the rate of the reaction. The high negative value of ΔS(#) (-74.3±1.09 J K(-1) mol(-1)) indicates the complex formed has a definite orientation higher than the reactants. Based on the above results, a suitable reaction mechanism for this reaction is proposed.

  18. Kinetics of toluene sorption and desorption in Ca- and Cu-montmorillonites investigated with Fourier transform infrared spectroscopy under two different levels of humidity.

    PubMed

    Shih, Yang-Hsin; Wu, Shian-Chee

    2004-09-01

    Clays in soils or groundwater aquifer materials play roles in the sorption of organic pollutants. The intrinsic sorption kinetics of toluene in dry and humid clay films was investigated by tracking the change of infrared absorbance. Under the humid condition, similar toluene-sorbed intensities were found in Ca- and Cu-montmorillonites. However, a higher intensity of sorbed toluene was found in the Cu-form than in the Ca-form under the dry condition, which indicates a stronger interaction occurring in dry Cu-montmorillonite. The general time scale of sorption of toluene on clays is around 100 s. In both forms of montmorillonite, some portion of toluene was desorbed at an extremely slow rate under the dry condition. Some newly identified peaks were persistent against desorption from montmorillonites, suggesting the existence of irreversibly sorbed species and the possibility of toluene transformation occurring in clay systems.

  19. Steam explosion pretreatment of wheat straw to improve methane yields: investigation of the degradation kinetics of structural compounds during anaerobic digestion.

    PubMed

    Theuretzbacher, Franz; Lizasoain, Javier; Lefever, Christopher; Saylor, Molly K; Enguidanos, Ramon; Weran, Nikolaus; Gronauer, Andreas; Bauer, Alexander

    2015-03-01

    Wheat straw can serve as a low-cost substrate for energy production without competing with food or feed production. This study investigated the effect of steam explosion pretreatment on the biological methane potential and the degradation kinetics of wheat straw during anaerobic digestion. It was observed that the biological methane potential of the non steam exploded, ground wheat straw (276 l(N) kg VS(-1)) did not significantly differ from the best steam explosion treated sample (286 l(N) kg VS(-1)) which was achieved at a pretreatment temperature of 140°C and a retention time of 60 min. Nevertheless degradation speed was improved by the pretreatment. Furthermore it was observed that compounds resulting from chemical reactions during the pretreatment and classified as pseudo-lignin were also degraded during the anaerobic batch experiments. Based on the rumen simulation technique, a model was developed to characterise the degradation process. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Spectroscopic and kinetic investigation of the reactions of peroxyacetic acid with Burkholderia pseudomallei catalase-peroxidase, KatG.

    PubMed

    Ivancich, Anabella; Donald, Lynda J; Villanueva, Jacylyn; Wiseman, Ben; Fita, Ignacio; Loewen, Peter C

    2013-10-15

    Catalase-peroxidases or KatGs can utilize organic peroxyacids and peroxides instead of hydrogen peroxide to generate the high-valent ferryl-oxo intermediates involved in the catalase and peroxidase reactions. In the absence of peroxidatic one-electron donors, the ferryl intermediates generated with a low excess (10-fold) of peroxyacetic acid (PAA) slowly decay to the ferric resting state after several minutes, a reaction that is demonstrated in this work by both stopped-flow UV-vis absorption measurements and EPR spectroscopic characterization of Burkholderia pseudomallei KatG (BpKatG). EPR spectroscopy showed that the [Fe(IV)═O Trp330(•+)], [Fe(IV)═O Trp139(•)], and [Fe(IV)═O Trp153(•)] intermediates of the peroxidase-like cycle of BpKatG ( Colin, J. Wiseman, B. Switala, J. Loewen, P. C. Ivancich, A. ( 2009 ) J. Am. Chem. Soc. 131 , 8557 - 8563 ), formed with a low excess of PAA at low temperature, are also generated with a high excess (1000-fold) of PAA at room temperature. However, under high excess conditions, there is a rapid conversion to a persistent [Fe(IV)═O] intermediate. Analysis of tryptic peptides of BpKatG by mass spectrometry before and after treatment with PAA showed that specific tryptophan (including W330, W139, and W153), methionine (including Met264 of the M-Y-W adduct), and cysteine residues are either modified with one, two, or three oxygen atoms or could not be identified in the spectrum because of other undetermined modifications. It was concluded that these oxidized residues were the source of electrons used to reduce the excess of PAA to acetic acid and return the enzyme to the ferric state. Treatment of BpKatG with PAA also caused a loss of catalase activity towards certain substrates, consistent with oxidative disruption of the M-Y-W adduct, and a loss of peroxidase activity, consistent with accumulation of the [Fe(IV)═O] intermediate and the oxidative modification of the W330, W139, and W153. PAA, but not H2O2 or tert

  1. Kinetic and mechanistic investigation of the sequential hydrogenation of phenylacetylene catalyzed by OsHCl(CO)(PR sub 3 ) sub 2 (PR sub 3 = PMe-t-Bu sub 2 and P-i-Pr sub 3 )

    SciTech Connect

    Esteruelas, M.A.; Oro, L.A.; Sola, E.; Valero, C. ); Meyer, U.; Werner, H. ); Andriollo, A.; Sanchez-Delgado, R.A.

    1989-09-13

    The reactivities of the hydrido carbonyl complexes OsHCl(CO)(PR{sub 3}){sub 2} (PR{sub 3} = PMe-t-Bu{sub 2} (1), P-i-Pr{sub 3} (2)) toward hydrogen, alkynes, and oxygen have been studied. The solutions of 1 and 2 are rapidly decolorized upon contact with H{sub 2} under ambient conditions; the decolorized solution of 2 shows in benzene-d{sub 6} a {sup 1}H NMR spectrum that is consistent with the formation of the dihydrogen compound OsHCl({eta}{sup 2}-H{sub 2})(CO)(P-i-Pr{sub 3}){sub 2} (3). The reactivity of 1 and 2 toward alkynes depends on the type of alkyne used. The title complexes react with acetylene, propyne, and phenylacetylene by insertion to give the five-coordinate vinylosmium compounds Os(CH=CHR)Cl(CO)(Pr{sub 3}){sub 2} (7 and 8); the same starting materials in the presence of t-BuC{triple bond}CH and PhC{triple bond}CPh are completely inert. The kinetic investigation of this reaction provides evidence that indicates that the formation of styryl derivatives is the step that determines the selectivity for the hydrogenation to the alkene.

  2. Enzyme Kinetics.

    ERIC Educational Resources Information Center

    Moe, Owen; Cornelius, Richard

    1988-01-01

    Conveys an appreciation of enzyme kinetic analysis by using a practical and intuitive approach. Discusses enzyme assays, kinetic models and rate laws, the kinetic constants (V, velocity, and Km, Michaels constant), evaluation of V and Km from experimental data, and enzyme inhibition. (CW)

  3. Enzyme Kinetics.

    ERIC Educational Resources Information Center

    Moe, Owen; Cornelius, Richard

    1988-01-01

    Conveys an appreciation of enzyme kinetic analysis by using a practical and intuitive approach. Discusses enzyme assays, kinetic models and rate laws, the kinetic constants (V, velocity, and Km, Michaels constant), evaluation of V and Km from experimental data, and enzyme inhibition. (CW)

  4. Macro-kinetic investigation on phenol uptake from air by biofiltration: Influence of superficial gas flow rate and inlet pollutant concentration

    SciTech Connect

    Zilli, M.; Fabiano, B.; Ferraiolo, A.; Converti, A.

    1996-02-20

    The macro-kinetic behavior of phenol removal from a synthetic exhaust gas was investigated theoretically as well as experimentally by means of two identical continuously operating laboratory-scale biological filter bed columns. A mixture of peat and glass beads was used as filter material. After sterilization it was inoculated with a pure strain of Pseudomonas putida, as employed in previous experimental studies. To determine the influence of the superficial gas flow rate on biofilter performance and to evaluate the phenol concentration profiles along the column, two series of continuous tests were carried out varying either the inlet phenol concentration, up to 1,650 mg {center_dot} m{sup {minus}3}, or the superficial gas flow rate, from 30 to 460 m{sup 3} {center_dot} m{sup {minus}2} {center_dot} h{sup {minus}1}. The elimination capacity of the biofilter is proved by a maximum volumetric phenol removal rate of 0.73 kg {center_dot} m{sup {minus}3} {center_dot} h{sup {minus}1}. The experimental results are consistent with a biofilm model incorporating first-order substrate elimination kinetics. The model may be considered a useful tool in scaling-up a biofiltration system. Furthermore, the deodorization capacity of the biofilter was investigated, at inlet phenol concentrations up to 280 mg {center_dot} m{sup {minus}3} and superficial gas flow rates ranging from 30 to 92 m{sup 3} {center_dot} m{sup {minus}2} {center_dot} h{sup {minus}1}. The deodorization of the gas was achieved at a maximum inlet phenol concentration of about 255 mg {center_dot} m{sup {minus}3}, operating at a superficial gas flow rate of 30 m{sup 3} {center_dot} m{sup {minus}2} {center_dot} h{sup {minus}1}.

  5. In-situ investigation of grain boundary and triple junction kinetics in aluminium-10 p.p.m. magnesium.

    PubMed

    Mattissen, D; Waerø, A; Molodov, D A; Shvindlerman, L S; Gottstein, G

    2004-03-01

    A special technique for in-situ observation and recording of triple junction motion is introduced. The described method makes it possible to study the motion of connected grain boundaries, i.e. triple junctions and their geometry. The results of an investigation of the steady-state motion of grain boundary systems with triple junctions in aluminium-magnesium are presented. The analysed triple junctions show a distinctive deviation of contact angle from the equilibrium value 120 degrees as assumed for the deviation of the Von Neumann-Mullins relation. The type of triple junction can have an essential influence on grain boundary motion and thus on grain growth.

  6. Quantitative kinetic investigation of triazole-gold(I) complex catalyzed [3,3]-rearrangement of propargyl ester.

    PubMed

    Xi, Yumeng; Wang, Qiaoyi; Su, Yijin; Li, Minyong; Shi, Xiaodong

    2014-02-28

    The triazole-gold(I) complex catalyzed [3,3]-rearrangement of propargyl ester has been quantitatively investigated through in situ IR. First order dependence of the initial rates on [Au] and [propargyl ester] suggested that the turnover-limiting step is the associative ligand substitution. The activation enthalpy was also determined to be 7.8 kcal mol(-1). TA-Au catalysts with different triazole derivatives were also tested, giving a linear free energy relationship with a ρ value of 0.74.

  7. Kinetics and Thermodynamics of the Reaction between the (•)OH Radical and Adenine: A Theoretical Investigation.

    PubMed

    Milhøj, Birgitte O; Sauer, Stephan P A

    2015-06-18

    The accessibility of all possible reaction paths for the reaction between the nucleobase adenine and the (•)OH radical is investigated through quantum chemical calculations of barrier heights and rate constants at the ωB97X-D/6-311++G(2df,2pd) level with Eckart tunneling corrections. First the computational method is validated by considering the hydrogen abstraction from the heterocyclic N9 nitrogen in adenine as a test system. Geometries for all molecules in the reaction are optimized with four different DFT exchange-correlation functionals (B3LYP, BHandHLYP, M06-2X, and ωB97X-D), in combination with Pople and Dunning basis sets, all of which have been employed in similar investigations in the literature. Improved energies are obtained through single point calculations with CCSD(T) and the same basis sets, and reaction rate constants are calculated for all methods both without tunneling corrections and with the Wigner, Bell, and Eckart corrections. In comparison to CCSD(T)//BHandHLYP/aug-cc-pVTZ reference results, the ωB97X-D/6-311++G(2df,2pd) method combined with Eckart tunneling corrections provides a sensible compromise between accuracy and time. Using this method, all subreactions of the reaction between adenine and the (•)OH radical are investigated. The total rate constants for hydrogen abstraction and addition for adenine are predicted with this method to be 1.06 × 10(-12) and 1.10 × 10(-12) cm(3) molecules(-1) s(-1), respectively. Abstractions of H61 and H62 contribute the most, while only addition to the C8 carbon is found to be of any significance, in contrast to previous claims that addition is the dominant reaction pathway. The overall rate constant for the complete reaction is found to be 2.17 × 10(-12) cm(3) molecules(-1) s(-1), which agrees exceptionally well with experimental results.

  8. X-ray crystallographic and kinetic investigations of 6-sulfamoyl-saccharin as a carbonic anhydrase inhibitor.

    PubMed

    Alterio, V; Tanc, M; Ivanova, J; Zalubovskis, R; Vozny, I; Monti, S M; Di Fiore, A; De Simone, G; Supuran, C T

    2015-04-07

    6-Sulfamoyl-saccharin was investigated as an inhibitor of 11 α-carbonic anhydrase (CA, EC 4.2.1.1) isoforms of human (h) origin, hCA I-XIV, and X-ray crystallographic data were obtained for its adduct with hCA II, the physiologically dominant isoform. This compound possesses two potential zinc-binding groups, the primary sulfamoyl one and the secondary, acylatedsulfonamide. Saccharin itself binds to the Zn(II) ion from the CA active site coordinating with this last group, in deprotonated (SO2N(-)CO) form. Here we explain why 6-sulfamoyl-saccharin, unlike saccharin, binds to the metal ion from the hCA II active site by its primary sulfonamide moiety and not the secondary one as saccharin itself. Our study is useful for shedding new light to the structure-based drug design of isoform-selective CA inhibitors of the sulfonamide type.

  9. COMBINED THEORETICAL AND EXPERIMENTAL INVESTIGATION OF MECHANISMS AND KINETICS OF VAPOR-PHASE MERCURY UPTAKE BY CARBONACOUES SURFACES

    SciTech Connect

    Radisav D. Vidic

    2002-05-01

    The first part of this study evaluated the application of a versatile optical technique to study the adsorption and desorption of model adsorbates representative of volatile polar (acetone) and non-polar (propane) organic compounds on a model carbonaceous surface under ultra high vacuum (UHV) conditions. The results showed the strong correlation between optical differential reflectance (ODR) and adsorbate coverage determined by temperature programmed desorption (TPD). ODR technique was proved to be a powerful tool to investigate surface adsorption and desorption from UHV to high pressure conditions. The effects of chemical functionality and surface morphology on the adsorption/desorption behavior of acetone, propane and mercury were investigated for two model carbonaceous surfaces, namely air-cleaved highly oriented pyrolytic graphite (HOPG) and plasma-oxidized HOPG. They can be removed by thermal treatment (> 500 K). The presence of these groups almost completely suppresses propane adsorption at 90K and removal of these groups leads to dramatic increase in adsorption capacity. The amount of acetone adsorbed is independent of surface heat treatment and depends only on total exposure. The effects of morphological heterogeneity is evident for plasma-oxidized HOPG as this substrate provides greater surface area, as well as higher energy binding sites. Mercury adsorption at 100 K on HOPG surfaces with and without chemical functionalities and topological heterogeneity created by plasma oxidation occurs through physisorption. The removal of chemical functionalities from HOPG surface enhances mercury physisorption. Plasma oxidation of HOPG provides additional surface area for mercury adsorption. Mercury adsorption by activated carbon at atmospheric pressure occurs through two distinct mechanisms, physisorption below 348 K and chemisorption above 348 K. No significant impact of oxygen functionalities was observed in the chemisorption region. The key findings of this study

  10. Influence of C60 co-deposition on the growth kinetics of diindenoperylene-From rapid roughening to layer-by-layer growth in blended organic films

    NASA Astrophysics Data System (ADS)

    Lorch, C.; Novák, J.; Banerjee, R.; Weimer, S.; Dieterle, J.; Frank, C.; Hinderhofer, A.; Gerlach, A.; Carla, F.; Schreiber, F.

    2017-02-01

    We investigated the growth of the two phase-separating materials diindenoperylene (DIP) and buckminsterfullerene C60 with different mixing ratio in real-time and in situ by X-ray scattering experiments. We found that at room temperature, mixtures with an excess of DIP show a growth mode which is very close to the perfect layer-by-layer limit with DIP crystallites forming over the entire film thickness. An unexpected increase in the island size is observed for these mixtures as a function of film thickness. On the other hand, equimolar and C60 dominated mixtures grow with poor crystallinity but form very smooth films. Additionally, it is observed that higher substrate temperatures lead to an increase in the length scale of phase separation with film thickness.

  11. Investigation of the Gas-Phase Photolysis and Temperature-Dependent OH Reaction Kinetics of 4-Hydroxy-2-butanone.

    PubMed

    Bouzidi, Hichem; Aslan, Lina; El Dib, Gisèle; Coddeville, Patrice; Fittschen, Christa; Tomas, Alexandre

    2015-10-20

    Hydroxyketones are key secondary reaction products in the atmospheric oxidation of volatile organic compounds (VOCs). The fate of these oxygenated VOCs is however poorly understood and scarcely taken into account in atmospheric chemistry modeling. In this work, a combined investigation of the photolysis and temperature-dependent OH radical reaction of 4-hydroxy-2-butanone (4H2B) is presented. The objective was to evaluate the importance of the photolysis process relative to OH oxidation in the atmospheric degradation of 4H2B. A photolysis lifetime of about 26 days was estimated with an effective quantum yield of 0.08. For the first time, the occurrence of a Norrish II mechanism was hypothesized following the observation of acetone among photolysis products. The OH reaction rate coefficient follows the Arrhenius trend (280-358 K) and could be modeled through the following expression: k4H2B(T) = (1.26 ± 0.40) × 10(-12) × exp((398 ± 87)/T) in cm(3) molecule(-1) s(-1). An atmospheric lifetime of 2.4 days regarding the OH + 4H2B reaction was evaluated, indicating that OH oxidation is by far the major degradation channel. The present work underlines the need for further studies on the atmospheric fate of oxygenated VOCs.

  12. Investigation of Electro-Kinetic Behavior of Cysteine on Electrodeposition of Ni Through the AC and DC Techniques

    NASA Astrophysics Data System (ADS)

    Ebadi, Mehdi; Basirun, Wan J.; Sim, Yoke-L.; Mahmoudian, Mohammad R.

    2013-11-01

    Electrodeposition of nickel was studied by the AC (as a novel technique) and DC techniques in nickel chloride aqueous solutions, mixed with various amounts of cysteine (0 to 6 mM). Cyclic voltammetry and chronoamperometry data have shown that the electrodeposition of Ni in the presence of cysteine is not diffusion controlled, but is closer to instantaneous nucleation. However, the current distribution decreased with the addition of further cysteine. The nucleation sites were decreased from 1.72 × 106 to 0.190 × 106 (cm-2) when the concentration of cysteine was increased from 0 to 4 mM. AC impedance during electrodeposition shows that the charge transfer resistance is increased from 0.645 to 5.26 Ω cm2 when the concentration of cysteine is increased from 0.5 to 4 mM. The electro-corrosion tests were done to investigate the corrosion behavior of the electrodeposited layers. X-ray diffraction and scanning electron microscopy containing Energy dispersive X-ray were used to estimate the grain size of the electrodeposited layers and capture the micrograph images and roughness of the Ni-electrodeposited surface.

  13. Quantum chemical investigation on the mechanism and kinetics of OH radical-initiated atmospheric oxidation of PCB-47.

    PubMed

    Sun, Yanhui; Zhang, Qingzhu; Wang, Hui; Wang, Wenxing

    2015-08-01

    The OH radical-initiated atmospheric oxidation degradation of 2,2',4,4'-tetrachlorobiphenyl (PCB-47) was investigated by using quantum chemical calculations. All possible pathways involved in the oxidation process were discussed. Potential barriers and reaction heats have been obtained to assess the energetically favorable reaction pathways and the relatively stable products. The study shows that the OH radicals are more likely to attack the C3 and C5 atom of the aromatic ring in the PCB-47 molecule to form PCB-OH adducts. Subsequent reactions are the addition of O2 or NO2 molecule to the PCB-OH adducts at the ortho position of the OH group. Water molecule plays an important role during the whole degradation process. The individual and overall rate constants were calculated by using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory over the temperature range of 180-370K. At 298K, the atmospheric lifetime of PCB-47 determined by OH radicals is about 9.1d. The computational results are crucial to risk assessment and pollution prevention of PCBs.

  14. Experimental model for the investigation of kinetic and/or dynamic interactions between drugs and ethanol in humans.

    PubMed

    Hartmann, D; Flückiger, A; Ziegler, W H; Timm, U; Zell, M

    1988-04-01

    This study was performed to establish an experimental method for the investigation of interactions between ethanol and drugs under predictable and controlled conditions. The model was tested with flumazenil (Ro 15-1788), a short-acting benzodiazepine antagonist with an elimination half-life of 1 h. Six healthy volunteers (5 males, 1 female) were administered ethanol by intravenous infusion with stepwise changing rates. The infusion rates were adapted to each subject on the basis of individual disposition parameters of ethanol, which were derived from preceding short-term infusions of 120 min duration (1.0 mg/kg in males, 0.8 mg/kg in the female). This two-step procedure led to individual ethanol plasma levels between 1.47 +/- 0.04 and 1.71 +/- 0.03 g/L, which were reached after 2.5 h and thereafter maintained over another 6 h. Within the period of constant ethanol levels, single doses of flumazenil and placebo, respectively, were injected intravenously as a bolus (2 min) in a double-blind fashion according to a randomized two-way crossover design. Three subjects received a dose of 0.10 mg/kg of flumazenil, and the remaining three subjects received a dose of 0.20 mg/kg. Evaluation of the plasma concentration time curves of flumazenil did not reveal evidence of an effect of ethanol on the pharmacokinetics of this drug.

  15. [Investigation of the recombination kinetic of photodissoziated myoglobin-CO at low temperatures by Mössbauer spectroscopy (author's transl)].

    PubMed

    Marcolin, H E; Reschke, R; Trautwein, A

    1977-01-01

    Myoglobin-CO (MbCO) has been photodissoziated with white and monochromatic light at low temperatures (5--40 degrees K). The photoproduct Mb* was identified with Mössbauer spectroscopy as ferrous high-spin complex, with isomer shift and quadrupole splitting, which are similar to the corresponding parameters of deoxymyoglobin. From the time-dependent change of the linewidth of the Mb*-Mössbauer-spectrum at 5 degrees K over a time-intervall of 7 hours we conclude, that there exist several slightly different Mb*-conformations with different recombination characteristics. In order to obtain a convenient time resolution of the recombination behavior, we investigate the time-dependence of one of the Mb*-absorptionlines with a Mössbauer drive of constant velocity. The resulting recombination data then are analyzed in various steps of approximation. It is shown that at least two independent exponentials are necessary for the interpretation of experimental data. The attempt to interprete the experimental data on the basis of distribution of energies is in qualitative agreement with corresponding results, which are derived from optical recombination data by Austin et al. Typical activation energies for the recombination process CO leads to Mb* are 2 kcal/mol. At low temperature (T less than 46 degrees K) the recombination behavior is explained by quantum-mechanical tunneling.

  16. Using 13C-labeled benzene and Raman gas spectroscopy to investigate respiration and biodegradation kinetics following soil contamination

    NASA Astrophysics Data System (ADS)

    Jochum, Tobias; Popp, Juergen; Frosch, Torsten

    2016-04-01

    Soil and groundwater contamination with benzene can cause serious environmental damages. However, many soil microorganisms are capable to adapt and known to strongly control the fate of organic contamination. Cavity enhanced Raman gas spectroscopy (CERS) was applied to investigate the short-term response of indigenous soil bacteria to a sudden surface contamination with benzene regarding the temporal variations of gas products and their exchange rates with the adjacent atmosphere. 13C-labeled benzene was spiked on a silty-loamy soil column (sampled from Hainich National Park, Germany) in order to track and separate the changes in heterotrophic soil respiration - involving 12CO2 and O2 - from the microbial process of benzene degradation, which ultimately forms 13CO2.1 The respiratory quotient (RQ) of 0.98 decreased significantly after the spiking and increased again within 33 hours to a value of 0.72. This coincided with maximum 13CO2 concentration rates (0.63 μ mol m-2 s-1), indicating highest benzene degradation at 33 hours after the spiking event. The diffusion of benzene in the headspace and the biodegradation into 13CO2 were simultaneously monitored and 12 days after the benzene spiking no measurable degradation was detected anymore.1 The RQ finally returned to a value of 0.96 demonstrating the reestablished aerobic respiration. In summary, this study shows the potential of combining Raman gas spectroscopy and stable isotopes to follow soil microbial biodegradation dynamics while simultaneously monitoring the underlying respiration behavior. Support by the Collaborative Research Center 1076 Aqua Diva is kindly acknowledged. We thank Beate Michalzik for soil analysis and discussion. 1. T. Jochum, B. Michalzik, A. Bachmann, J. Popp and T. Frosch, Analyst, 2015, 140, 3143-3149.

  17. Experimental investigations and phase-field simulations of triple-phase-separation kinetics within liquid ternary Co-Cu-Pb immiscible alloys

    NASA Astrophysics Data System (ADS)

    Wu, Y. H.; Wang, W. L.; Yan, N.; Wei, B.

    2017-05-01

    The phase-separation kinetics and microstructure evolution mechanisms of liquid ternary C o43C u40P b17 immiscible alloys are investigated by both the drop tube technique and phase-field method. Two successive phase separations take place during droplet falling and lead to the formation of a three-phase three-layer core-shell structure composed of a Co-rich core, a Cu-rich middle layer, and a Pb-rich shell. The Pb-rich shell becomes more and more conspicuous as droplet diameter decreases. Meanwhile, the Co-rich core center gradually moves away from the core-shell center. Theoretical analyses show that a larger temperature gradient inside a smaller alloy droplet induces the accelerated growth of the surface segregation shell during triple-phase separation. The residual Stokes motion and the asymmetric Marangoni convection result in the appearance of an eccentric Co-rich core and the core deviation degree is closely related to the droplet size and initial velocity. A three-dimensional phase-field model of ternary immiscible alloys, which considers the successive phase separations under the combined effects of Marangoni convection and surface segregation, is proposed to explore the formation mechanisms of three-phase core-shell structures. The simulated core-shell morphologies are consistent with the experimental observations, which verifies the model's validity in reproducing the core-shell dynamic evolution. Numerical results reveal that the development of three-phase three-layer core-shell structures can be attributed to the primary and then secondary phase separations dominated simultaneously by Marangoni convection and surface segregation. Furthermore, the effects of droplet temperature gradient on the growth kinetics of the surface segregation shell are analyzed in the light of phase-field theory.

  18. Kinetics of actinide complexation reactions

    SciTech Connect

    Nash, K.L.; Sullivan, J.C.

    1997-09-01

    Though the literature records extensive compilations of the thermodynamics of actinide complexation reactions, the kinetics of complex formation and dissociation reactions of actinide ions in aqueous solutions have not been extensively investigated. In light of the central role played by such reactions in actinide process and environmental chemistry, this situation is somewhat surprising. The authors report herein a summary of what is known about actinide complexation kinetics. The systems include actinide ions in the four principal oxidation states (III, IV, V, and VI) and complex formation and dissociation rates with both simple and complex ligands. Most of the work reported was conducted in acidic media, but a few address reactions in neutral and alkaline solutions. Complex formation reactions tend in general to be rapid, accessible only to rapid-scan and equilibrium perturbation techniques. Complex dissociation reactions exhibit a wider range of rates and are generally more accessible using standard analytical methods. Literature results are described and correlated with the known properties of the individual ions.

  19. Pictures of a thousand words: Investigating the neural mechanisms of reading with extremely rapid event-related fMRI

    PubMed Central

    Yarkoni, Tal; Speer, Nicole K.; Balota, David A.; McAvoy, Mark P.; Zacks, Jeffrey M.

    2008-01-01

    Reading is one of the most important skills human beings can acquire, but has proven difficult to study naturalistically using functional magnetic resonance imaging (fMRI). We introduce a novel Event-Related Reading (ERR) fMRI approach that enables reliable estimation of the neural correlates of single-word processing during reading of rapidly presented narrative text (200–300 ms / word). Application to an fMRI experiment in which subjects read coherent narratives and made no overt responses revealed widespread effects of orthographic, phonological, contextual, and semantic variables on brain activation. Word-level variables predicted activity in classical language areas as well as the inferotemporal visual word form area, specifically supporting a role for the latter in mapping visual forms onto articulatory or acoustic representations. Additional analyses demonstrated that ERR results replicate across experiments and predict reading comprehension. The ERR approach represents a powerful and extremely flexible new approach for studying reading and language behavior with fMRI. PMID:18554928

  20. Investigation of the photochemical reactivity of soot particles derived from biofuels toward NO2. A kinetic and product study.

    PubMed

    Romanías, Manolis N; Dagaut, Philippe; Bedjanian, Yuri; Andrade-Eiroa, Auréa; Shahla, Roya; Emmanouil, Karafas S; Papadimitriou, Vassileios C; Spyros, Apostolos

    2015-03-12

    In the current study, the heterogeneous reaction of NO2 with soot and biosoot surfaces was investigated in the dark and under illumination relevant to atmospheric conditions (J(NO2) = 0.012 s(-1)). A flat-flame burner was used for preparation and collection of soot samples from premixed flames of liquid fuels. The biofuels were prepared by mixing 20% v/v of (i) 1-butanol (CH3(CH2)3OH), (ii) methyl octanoate (CH3(CH2)6COOCH3), (iii) anhydrous diethyl carbonate (C2H5O)2CO and (iv) 2,5 dimethyl furan (CH3)2C4H2O additive compounds in conventional kerosene fuel (JetA-1). Experiments were performed at 293 K using a low-pressure flow tube reactor (P = 9 Torr) coupled to a quadrupole mass spectrometer. The initial and steady-state uptake coefficients, γ0 and γ(ss), respectively, as well as the surface coverage, N(s), were measured under dry and humid conditions. Furthermore, the branching ratios of the gas-phase products NO (∼80-100%) and HONO (<20%) were determined. Soot from JetA-1/2,5-dimethyl furan was the most reactive [γ0 = (29.1 ± 5.8) × 10(-6), γ(ss)(dry) = (9.09 ± 1.82) × 10(-7) and γ(ss)(5.5%RH) = (14.0 ± 2.8)(-7)] while soot from JetA-1/1-butanol [γ0 = (2.72 ± 0.544) × 10(-6), γ(ss)(dry) = (4.57 ± 0.914) × 10(-7), and γ(ss)(5.5%RH) = (3.64 ± 0.728) × 10(-7)] and JetA-1/diethyl carbonate [γ0 = (2.99 ± 0.598) × 10(-6), γ(ss)(dry) = (3.99 ± 0.798) × 10(-7), and γ(ss)(5.5%RH) = (4.80 ± 0.960) × 10(-7)] were less reactive. To correlate the chemical reactivity with the physicochemical properties of the soot samples, their chemical composition was analyzed employing Raman spectroscopy, NMR, and high-performance liquid chromatography. In addition, the Brunauer-Emmett-Teller adsorption isotherms and the particle size distributions were determined employing a Quantachrome Nova 2200e gas sorption analyzer. The analysis of the results showed that factors such as (i) soot mass collection rate, (ii) porosity of the particles formed, (iii

  1. Rapid Metagenomic Next-Generation Sequencing during an Investigation of Hospital-Acquired Human Parainfluenza Virus 3 Infections

    PubMed Central

    Zerr, Danielle M.; Qin, Xuan; Adler, Amanda L.; Sampoleo, Reigran; Kuypers, Jane M.; Englund, Janet A.; Jerome, Keith R.

    2016-01-01

    ABSTRACT Metagenomic next-generation sequencing (mNGS) is increasingly used for the unbiased detection of viruses, bacteria, fungi, and eukaryotic parasites in clinical samples. Whole-genome sequencing (WGS) of clinical bacterial isolates has been shown to inform hospital infection prevention practices, but this technology has not been utilized during potential respiratory virus outbreaks. Here, we report on the use of mNGS to inform the real-time infection prevention response to a cluster of hospital-acquired human parainfluenza 3 virus (HPIV3) infections at a children's hospital. Samples from 3 patients with hospital-acquired HPIV3 identified over a 12-day period on a general medical unit and 10 temporally associated samples from patients with community-acquired HPIV3 were analyzed. Our sample-to-sequencer time was <24 h, while our sample-to-answer turnaround time was <60 h with a hands-on time of approximately 6 h. Eight (2 cases and 6 controls) of 13 samples had sufficient sequencing coverage to yield the whole genome for HPIV3, while 10 (2 cases and 8 controls) of 13 samples gave partial genomes and all 13 samples had >1 read for HPIV3. Phylogenetic clustering revealed the presence of identical HPIV3 genomic sequence in the two of the cases with hospital-acquired infection, consistent with the concern for recent transmission within the medical unit. Adequate sequence coverage was not recovered for the third case. This work demonstrates the promise of mNGS for providing rapid information for infection prevention in addition to microbial detection. PMID:27795347

  2. A rapid dissolution procedure to aid initial nuclear forensics investigations of chemically refractory compounds and particles prior to gamma spectrometry.

    PubMed

    Reading, David G; Croudace, Ian W; Warwick, Phillip E; Britton, Richard

    2015-11-05

    A rapid and effective preparative procedure has been evaluated for the accurate determination of low-energy (40-200 keV) gamma-emitting radionuclides ((210)Pb, (234)Th, (226)Ra, (235)U) in uranium ores and uranium ore concentrates (UOCs) using high-resolution gamma ray spectrometry. The measurement of low-energy gamma photons is complicated in heterogeneous samples containing high-density mineral phases and in such situations activity concentrations will be underestimated. This is because attenuation corrections, calculated based on sample mean density, do not properly correct where dense grains are dispersed within a less dense matrix (analogous to a nugget effect). The current method overcomes these problems using a lithium tetraborate fusion that readily dissolves all components including high-density, self-attenuating minerals/compounds. This is the ideal method for dissolving complex, non-volatile components in soils, rocks, mineral concentrates, and other materials where density reduction is required. Lithium borate fusion avoids the need for theoretical efficiency corrections or measurement of matrix matched calibration standards. The resulting homogeneous quenched glass produced can be quickly dissolved in nitric acid producing low-density solutions that can be counted by gamma spectrometry. The effectiveness of the technique is demonstrated using uranium-bearing Certified Reference Materials and provides accurate activity concentration determinations compared to the underestimated activity concentrations derived from direct measurements of a bulk sample. The procedure offers an effective solution for initial nuclear forensic studies where complex refractory minerals or matrices exist. It is also significantly faster, safer and simpler than alternative approaches. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Investigation of kinetics and thermodynamics of DNA hybridization by means of 2-D fluorescence spectroscopy and soft/hard modeling techniques.

    PubMed

    Ebrahimi, Sara; Kompany-Zareh, Mohsen

    2016-02-04

    Reversible hybridization reaction plays a key role in fundamental biological processes, in many laboratory techniques, and also in DNA based sensing devices. Comprehensive investigation of this process is, therefore, essential for the development of more sophisticated applications. Kinetics and thermodynamics of the hybridization reaction, as a second order process, are systematically investigated with the aid of the soft and hard chemometric methods. Labeling two complementary 21 mer DNA single strands with FAM and Texas red fluorophores, enabled recording of the florescence excitation-emission matrices during the experiments which led to three-way data sets. The presence of fluorescence resonance energy transfer in excitation and emission modes and the closure in concentration mode, made the three-way data arrays rank deficient. To acquire primary chemical information, restricted Tucker3 as a soft method was employed. Herein a model-based method, hard restricted trilinear decomposition, is introduced for in depth analysis of rank deficient three-way data sets. By employing proposed hard method, the nonlinear model parameters as well as the correct profiles could be estimated. In addition, a simple constraint is presented to extract chemically reasonable output profiles regarding the core elements of restricted Tucker3 model.

  4. [Investigations on the physiology of the glands of carnivorous plants : IV. The kinetics of chloride secretion by the gland tissue of Nepenthes].

    PubMed

    Lüttge, U

    1966-03-01

    The transport of chloride in isolated tissue from Nepenthes pitchers was investigated using (36)Cl(-), an Aminco-Cotlove chloride-titrator for the determinations of Cl(-) concentrations, and KCN and AsO 4 (-) -as metabolic inhibitors.The tissue was brought in contact with different experimental solutions (=medium). The surface corresponding to the outside of the pitchers was cut with a razor blade to remove the cutinized epidermal layer. At this surface the Cl(-) uptake from the medium is a metabolic process which depends on the Cl(-)-concentration of the medium in a manner that corresponds to the MICHAELIS-MENTEN kinetics. The Michaelis-constant of this transport step was 3×10(-2)M. The Cl(-)-efflux into the medium, however, is a passive process.The opposite surface of the tissue slices (corresponding to the inside of the pitchers) carries the glands. The chloride secretion taking place here is also dependent on metabolism. In vitro it occurs even when a high gradient of chloride concentration has been set up between the medium and the solution which is in contact with the glands. In vivo the Cl(-)-concentration of the pitcher fluid and the amount of Cl(-) per gram of tissue water are almost equal.The rôle of chloride in the physiology of Nepenthes is still under investigation, A correlation between the chloride content of the pitcher fluid and its enzymatic activity (Casein-test), however, could already be demonstrated.

  5. Crystallization kinetics and spectroscopic investigations on Tb{sup 3+} and Yb{sup 3+} codoped glass ceramics containing CaF{sub 2} nanocrystals

    SciTech Connect

    Huang Lihui; Qin Guanshi; Arai, Yusuke; Jose, Rajan; Suzuki, Takenobu; Ohishi, Yasutake; Yamashita, Tatsuya; Akimoto, Yusuke

    2007-11-01

    Transparent Tb{sup 3+} and Yb{sup 3+} codoped oxyfluoride glass ceramics containing CaF{sub 2} nanocrystals were prepared by melt quenching and subsequent heat treatment. Crystallization kinetics of CaF{sub 2} nanocrystals was investigated by differential scanning calorimetric method. The average apparent activation energy E{sub a} of the crystallization was {approx}498 kJ/mol. Moreover, the value of the Avrami exponent n was 1.01. These results suggest that the crystallization mechanism of CaF{sub 2} is a diffusion controlled growth process of needles and plates of finite long dimensions. X-ray diffraction patterns and transmission electron microscopy image confirmed the CaF{sub 2} nanocrystals in the glass ceramic. Ultraviolet (UV) and visible emission spectra of the as-made glass and the glass ceramic with an excitation of a 974 nm laser diode were recorded at room temperature. An intense UV emission at 381 nm was observed in the glass ceramic. The origin of the enhancement of the emission at 381 nm was investigated using spectroscopic technique and Judd-Ofelt analysis. The enhancement of the emission at 381 nm could be attributed to the change of the ligand field of Tb{sup 3+} ions due to the incorporation of some Tb{sup 3+} and Yb{sup 3+} ions into CaF{sub 2} nanocrystals in the glass ceramic.

  6. Room temperature DNA preservation of soft tissue for rapid DNA extraction: an addition to the disaster victim identification investigators toolkit?

    PubMed

    Graham, E A M; Turk, E E; Rutty, G N

    2008-01-01

    In mass fatality incidents, for example following a vehicle accident or terrorist event, severe fragmentation of bodies may occur, making identification by the use of traditional techniques such as fingerprinting or odontology difficult. In such situations DNA profiling can be employed for individualization and re-association of fragmented remains. As at times disrupted soft tissue may be the predominate tissue type requiring identification and re-association. We have investigated the use of two buffer solutions for preservation of soft tissue samples that may be collected during such investigations, when buccal cells, blood samples or teeth or bone may not be available. Both buffer solutions have shown sufficient DNA preservation over a 12-month period of storage at room temperature to allow for DNA profiling to be successfully performed when 5-1000 mg muscle tissue was stored in each solution.

  7. Basic Research Investigations into Multimode Laser and EM Launchers for Affordable Rapid Access to Space (Volumes 1 and 2)

    DTIC Science & Technology

    2010-08-31

    research effort on pulsed airbreathing/rocket laser propulsion, investigates the physics of laser energy deposit ion into stationary and hypersonic ...campaigns centered on both static and hypersonic experiments with representative 20 and 30 laser-thruster geometries, using the Lumonics TEA-622 (-200J, -1...Aerothermo- dynamics and Hypersonics (HTNLAH). Time-dependent surtace pressure distributions were measured over thrust-generating surtaces following

  8. A novel P700 redox kinetics probe for rapid, non-intrusive and whole-tissue determination of photosystem II functionality, and the stoichiometry of the two photosystems in vivo.

    PubMed

    Jia, Husen; Dwyer, Simon A; Fan, Da-Yong; Han, Yaqin; Badger, Murray R; von Caemmerer, Susanne; Chow, Wah Soon

    2014-11-01

    We sought a rapid, non-intrusive, whole-tissue measure of the functional photosystem II (PS II) content in leaves. Summation of electrons, delivered by a single-turnover flash to P700(+) (oxidized PS I primary donor) in continuous background far-red light, gave a parameter S in absorbance units after taking into account an experimentally determined basal electron flux that affects P700 redox kinetics. S was linearly correlated with the functional PS II content measured by the O(2) yield per single-turnover repetitive flash in Arabidopsis thaliana expressing an antisense construct to the PsbO (manganese-stabilizing protein in PS II) proteins of PS II (PsbO mutants). The ratio of S to z(max) (total PS I content in absorbance units) was comparable to the PS II/PS I reaction-center ratio in wild-type A. thaliana and in control Spinacea oleracea. Both S and S/z(max) decreased in photoinhibited spinach leaf discs. The whole-tissue functional PS II content and the PS II/photosystem I (PS I) ratio can be non-intrusively monitored by S and S/z(max), respectively, using a quick P700 absorbance protocol compatible with modern P700 instruments.

  9. Kinetic investigation of the oxidation of naval excess hazardous materials in supercritical water for the design of a transpiration-wall reactor

    SciTech Connect

    Rice, S.F.; Hanush, R.G.; Hunter, T.B.

    1997-01-01

    Experiments were conducted in Sandia`s supercritical fluids reactor (SFR) to generate data for the design of a transpiration-wall supercritical water oxidation (SCWO) reactor. The reactor is intended for the disposal of hazardous material generated on naval vessels. The design parameters for the system require an accurate knowledge of destruction efficiency vs. time and temperature. Three candidate materials were selected for testing. The experiments consisted of oxidizing these materials in the SFR at isothermal conditions over the temperature range of 400-550C at 24.1 MPa. A small extrapolation of the results shows that these materials can be adequately destroyed (to 99.9% destruction removal efficiency, DRE, based on total organic carbon (TOC) in the effluent) in approximately 5 seconds at 600C. The results vary smoothly and predictably with temperature such that extrapolation to higher temperatures beyond the experimental capabilities of the SFR can be made with reasonable confidence. The preliminary design of the transpiration-wall reactor has a rapid heat-up section within the reactor vessel that requires the addition of a fuel capable of quickly reacting with oxygen at temperatures below 500C. Candidate alcohols and JP-5 jet fuel were evaluated in this context. Oxidation rates for the alcohols were examined using in situ Raman spectroscopy. In addition, the potential utility of supplying the oxidizer line with hydrogen peroxide as an additive to enhance rapid initiation of the feed at unusually low temperatures was investigated. Experiments were conducted in the Supercritical Constant Volume Reactor (SCVR) using hydrogen peroxide as the initial oxidizing species. The results show that this concept as a method of enhancing low temperature reactivity appears to fail because thermal decomposition of the hydrogen peroxide is more rapid than the fuel oxidation rate at low temperatures. 8 refs., 16 figs., 5 tabs.

  10. Investigating and managing the rapid emergence of white-nose syndrome, a novel, fatal, infectious disease of hibernating bats.

    PubMed

    Foley, Janet; Clifford, Deana; Castle, Kevin; Cryan, Paul; Ostfeld, Richard S

    2011-04-01

    White-nose syndrome (WNS) is a fatal disease of bats that hibernate. The etiologic agent of WNS is the fungus Geomyces destructans, which infects the skin and wing membranes. Over 1 million bats in six species in eastern North America have died from WNS since 2006, and as a result several species of bats may become endangered or extinct. Information is lacking on the pathogenesis of G. destructans and WNS, WNS transmission and maintenance, individual and site factors that contribute to the probability of an outbreak of WNS, and spatial dynamics of WNS spread in North America. We considered how descriptive and analytical epidemiology could be used to fill these information gaps, including a four-step (modified) outbreak investigation, application of a set of criteria (Hill's) for assessing causation, compartment models of disease dynamics, and spatial modeling. We cataloged and critiqued adaptive-management options that have been either previously proposed for WNS or were helpful in addressing other emerging diseases of wild animals. These include an ongoing program of prospective surveillance of bats and hibernacula for WNS, treatment of individual bats, increasing population resistance to WNS (through vaccines, immunomodulators, or other methods), improving probability of survival from starvation and dehydration associated with WNS, modifying hibernacula environments to eliminate G. destructans, culling individuals or populations, controlling anthropogenic spread of WNS, conserving genetic diversity of bats, and educating the public about bats and bat conservation issues associated with WNS. Conservation Biology ©2011 Society for Conservation Biology. No claim to original US government works.

  11. Rapid Radiations and the Race to Redundancy: An Investigation of the Evolution of Australian Elapid Snake Venoms.

    PubMed

    Jackson, Timothy N W; Koludarov, Ivan; Ali, Syed A; Dobson, James; Zdenek, Christina N; Dashevsky, Daniel; Op den Brouw, Bianca; Masci, Paul P; Nouwens, Amanda; Josh, Peter; Goldenberg, Jonathan; Cipriani, Vittoria; Hay, Chris; Hendrikx, Iwan; Dunstan, Nathan; Allen, Luke; Fry, Bryan G

    2016-10-26

    Australia is the stronghold of the front-fanged venomous snake family Elapidae. The Australasian elapid snake radiation, which includes approximately 100 terrestrial species in Australia, as well as Melanesian species and all the world's sea snakes, is less than 12 million years old. The incredible phenotypic and ecological diversity of the clade is matched by considerable diversity in venom composition. The clade's evolutionary youth and dynamic evolution should make it of particular interest to toxinologists, however, the majority of species, which are small, typically inoffensive, and seldom encountered by non-herpetologists, have been almost completely neglected by researchers. The present study investigates the venom composition of 28 species proteomically, revealing several interesting trends in venom composition, and reports, for the first time in elapid snakes, the existence of an ontogenetic shift in the venom composition and activity of brown snakes (Pseudonaja sp.). Trends in venom composition are compared to the snakes' feeding ecology and the paper concludes with an extended discussion of the selection pressures shaping the evolution of snake venom.

  12. Rapid Radiations and the Race to Redundancy: An Investigation of the Evolution of Australian Elapid Snake Venoms

    PubMed Central

    Jackson, Timothy N. W.; Koludarov, Ivan; Ali, Syed A.; Dobson, James; Zdenek, Christina N.; Dashevsky, Daniel; op den Brouw, Bianca; Masci, Paul P.; Nouwens, Amanda; Josh, Peter; Goldenberg, Jonathan; Cipriani, Vittoria; Hay, Chris; Hendrikx, Iwan; Dunstan, Nathan; Allen, Luke; Fry, Bryan G.

    2016-01-01

    Australia is the stronghold of the front-fanged venomous snake family Elapidae. The Australasian elapid snake radiation, which includes approximately 100 terrestrial species in Australia, as well as Melanesian species and all the world’s true sea snakes, may be less than 12 million years old. The incredible phenotypic and ecological diversity of the clade is matched by considerable diversity in venom composition. The clade’s evolutionary youth and dynamic evolution should make it of particular interest to toxinologists, however, the majority of species, which are small, typically inoffensive, and seldom encountered by non-herpetologists, have been almost completely neglected by researchers. The present study investigates the venom composition of 28 species proteomically, revealing several interesting trends in venom composition, and reports, for the first time in elapid snakes, the existence of an ontogenetic shift in the venom composition and activity of brown snakes (Pseudonaja sp.). Trends in venom composition are compared to the snakes’ feeding ecology and the paper concludes with an extended discussion of the selection pressures shaping the evolution of snake venom. PMID:27792190

  13. Investigating and managing the rapid emergence of white-nose syndrome, a novel, fatal, infectious disease of hibernating bats

    USGS Publications Warehouse

    Foley, Janet; Clifford, Deana; Castle, Kevin; Cryan, Paul M.; Ostfeld, Richard S.

    2011-01-01

    White-nose syndrome (WNS) is a fatal disease of bats that hibernate. The etiologic agent of WNS is the fungus Geomyces destructans, which infects the skin and wing membranes. Over 1 million bats in six species in eastern North America have died from WNS since 2006, and as a result several species of bats may become endangered or extinct. Information is lacking on the pathogenesis of G. destructans and WNS, WNS transmission and maintenance, individual and site factors that contribute to the probability of an outbreak of WNS, and spatial dynamics of WNS spread in North America. We considered how descriptive and analytical epidemiology could be used to fill these information gaps, including a four-step (modified) outbreak investigation, application of a set of criteria (Hill's) for assessing causation, compartment models of disease dynamics, and spatial modeling. We cataloged and critiqued adaptive-management options that have been either previously proposed for WNS or were helpful in addressing other emerging diseases of wild animals. These include an ongoing program of prospective surveillance of bats and hibernacula for WNS, treatment of individual bats, increasing population resistance to WNS (through vaccines, immunomodulators, or other methods), improving probability of survival from starvation and dehydration associated with WNS, modifying hibernacula environments to eliminate G. destructans, culling individuals or populations, controlling anthropogenic spread of WNS, conserving genetic diversity of bats, and educating the public about bats and bat conservation issues associated with WNS.

  14. Density functional theory investigation of competitive free-radical processes during the thermal cracking of methylated polyaromatics: estimation of kinetic parameters.

    PubMed

    Leininger, J-Philippe; Minot, Christian; Lorant, François; Behar, Françoise

    2007-04-26

    Density functional B3LYP and BH&HLYP calculations with the 6-31G** basis set have been performed to investigate elementary reactions playing an important role in the pyrolysis of 1-methylnaphthalene. The pathways describing the destiny of the main radicals, H, methyl, hydromethylnaphthyl and methylnaphthyl, have been studied. At low temperature, addition of H atoms on the aromatic ring is favored over hydrogen abstraction. Except at low temperature (below 400 K), the hydromethylnaphthyl radical undergoes preferentially a loss of hydrogen rather than a bimolecular hydrogen transfer with methylnaphthalene or addition reaction on methylnaphthalene forming a hydrogenated dimer. In the range 400-750 K, the formation of methane by hydrogen abstraction of methyl radical on methylnaphthalene is predominant compared to the formation of hydrodimethylnaphthalenes by addition reaction. Rate constants of reactions describing the formation of heavy products like methyldinaphthylmethanes or dimethylbinaphthalenes have been calculated and discussed. They are also compared to recombination reactions from the literature. Rate constants of these reactions have been computed using transition state theory and can be integrated in kinetic radical schemes of methylated polyaromatic compounds pyrolysis from geological to laboratory conditions.

  15. Parametric Investigation of the Kinetics of Growth of Carbon-Nanotube Arrays on Iron Nanoparticles in the Process of Chemical Vapor Deposition of Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Futko, S. I.; Shulitski, B. G.; Labunov, V. A.; Ermolaevaa, E. M.

    2015-03-01

    On the basis of the kinetic model of synthesis of carbon nanotubes on iron nanoparticles in the process of chemical vapor deposition of hydrocarbons, the parametric dependences of characteristics of arrays of vertically oriented nanotubes on the temperature of their synthesis, the concentration of acetylene in a reactor, and the diameter of the catalyst nanoparticles were investigated. It is shown that the maximum on the temperature dependence of the rate of growth of carbon nanotubes, detected in experiments at a temperature of ~700oC is due to the competing processes of increasing the catalytic activity of iron nanoparticles and decreasing the acetylene concentration because of the signifi cant gas-phase decomposition of acetylene in the reactor before it enters the substrate with the catalyst. Our calculations have shown that the indicated maximum arises near the transition point separating the low-temperature region where multiwall nanotubes are predominantly synthesized from the higher-temperature region of generation of single-wall nanotubes in the process of chemical vapor deposition of hydrocarbons.

  16. Non-isothermal crystallization kinetics and glass-forming ability of Ti41Zr25Be28Fe6 bulk metallic glass investigated by differential scanning calorimetry

    NASA Astrophysics Data System (ADS)

    Gong, Pan; Zhao, Shaofan; Wang, Xin; Yao, Kefu

    2015-07-01

    The non-isothermal crystallization kinetics and glass-forming ability of Ti41Zr25Be28Fe6 glassy alloy were investigated by differential scanning calorimetry. The activation energies corresponding to the characteristic temperatures have been calculated by Kissinger and Ozawa equations. Based on Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall models, it has been found that the local activation energy is higher at the beginning of the crystallization process for the first exothermic peak. The local Avrami exponent indicates that the first-step crystallization is mainly a high-dimensional nucleation and growth with an increasing nucleation rate. According to the calculated fragility index, Ti41Zr25Be28Fe6 alloy can be classified as "strong glass former." The studied alloy also possesses a critical size up to centimeter order, and the high glass-forming ability is probably related to the relatively low Gibbs energy difference between the liquid and crystalline states. The critical cooling rate of Ti41Zr25Be28Fe6 glassy alloy has also been determined using Barandiaran-Colmenero's method.

  17. A Heavy-Atom Isotope Effect and Kinetic Investigation of the Hydrolysis of Semicarbazide by Urease from Jack Bean (Canavalia ensiformis) †

    PubMed Central

    Marlier, John F.; Fogle, Emily J.; Cleland, W.W.

    2009-01-01

    A kinetic investigation of the hydrolysis of semicarbazide by urease gives a relatively flat log V/K vs. pH plot between pH 5 and 8. A log Vm vs. pH plot shows a shift of the optimum Vm toward lower pH when compared to urea. These results are explained in terms of the binding of the outer-N of the –NHNH2 group in semicarbazide to an active site residue with a relatively low pKa (∼6). Heavy-atom isotope effects for both leaving groups have been determined. For the –NHNH2 side 15kobs = 1.0045, whereas for the –NH2 side 15kobs = 1.0009. This is evidence that –NHNH2 leaves prior to –NH2. Using previous data from the urease-catalyzed hydrolysis of formamide, the commitment factors for semicarbazide and urea hydrolysis are estimated as 2.7 and 1.2, respectively. The carbonyl-C isotope effect is 13kobs = 1.0357 which is consistent with the transition state occurring either during formation or breakdown of the tetrahedral intermediate. PMID:18817416

  18. Experimental and numerical investigations of heat transport and crystallization kinetics in laser-induced modification of barium strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Baldus, O.; Waser, R.

    2005-04-01

    Barium strontium titanate (BST) has a large application potential in microelectronics due to its implementation as a high-permittivity dielectric in thin-film capacitors. Technologies are therefore being investigated for the deposition of the ceramics as thin films onto semiconductor components. A two-step process will be presented in this paper: first, the deposition of an amorphous ceramic thin film on a platinum-coated silicon wafer and, secondly, the laser sintering of this film. A laser process with pulsed UV light of 248-nm and 193-nm wavelength and approximately 20-ns pulse length allows us to reduce the thermal load on the substrate during the sintering process by minimizing the interaction time between the heating source and the ceramic layer. The goal of this work is to investigate fundamental aspects of the solid-state physics and process technology during the laser sintering of amorphous, electroceramic thin films. Adjusting the film thicknesses prevents damage to the ceramic thin films by the laser treatment. Planar test structures are manufactured and characterized structurally and electrically. Characterization of the BST films reveals clearly improved dielectric properties in comparison to the amorphous films. The real part of the dielectric constant can be raised three- to fivefold at 10 kHz, while the imaginary part decreases by nearly an order of magnitude. Chemical analysis does not indicate any significant changes in the stoichiometry of the thin films due to the laser process. The laser-induced changes proceed similarly to the crystallization of the amorphous films in the furnace. Parallel to the experimental work, a numerical simulation model is developed, which, on the basis of thermal conduction, the Johnson-Mehl-Avrami crystallization kinetics, and thermoelasticity, models the temperature, crystallization, and mechanical load of the thin films. The simulation calculations are correlated with the results of the analysis of the laser

  19. Myocardial thallium-201 kinetics and regional flow alterations with 3 hours of coronary occlusion and either rapid reperfusion through a totally patent vessel or slow reperfusion through a critical stenosis

    SciTech Connect

    Granato, J.E.; Watson, D.D.; Flanagan, T.L.; Beller, G.A.

    1987-01-01

    Myocardial thallium-201 kinetics and regional blood flow alterations were examined in a canine model using 3 hours of coronary occlusion and different methods of reperfusion. Group I comprised 10 dogs undergoing a 3 hour left anterior descending artery occlusion and no reperfusion. Group II comprised seven dogs undergoing 3 hours of left anterior descending artery occlusion and rapid reperfusion through a totally patent vessel. Group III comprised 10 dogs undergoing 3 hours of left anterior descending artery occlusion and slow reperfusion through a residual stenosis. All dogs received 1.5 mCi of thallium-201 after 40 minutes of coronary occlusion. During occlusion and 2 hours of reperfusion, serial hemodynamic, blood flow and myocardial thallium-201 activity measurements were made. The relative thallium-201 gradient (normal zone minus ischemic zone activity when initial normal activity is expressed as 100%) during left anterior descending coronary occlusion was similar in all groups. Group I, 87 +/- 3%; Group II, 78 +/- 6%; Group III, 83 +/- 6% (p = NS). After 2 hours of either method of reperfusion, the final relative gradient had decreased to a similar level (Group II, 51 +/- 9%; Group III, 42 +/- 6%). These values were not significantly different from the final relative thallium-201 gradient seen in dogs undergoing a sustained 3 hour occlusion (Group I, 55 +/- 5%). After 2 hours of reperfusion, both methods of reflow were associated with similar degrees of ''no reflow.'' Transmural flows in the central ischemic zone were 89 +/- 10% of normal in Group II and 71 +/- 6% of normal in Group III after reperfusion, with both flows substantially higher than the relative thallium-201 activities in these dogs.

  20. Unanimous Model for Describing the Fast Bioluminescence Kinetics of Ca(2+) -regulated Photoproteins of Different Organisms.

    PubMed

    Eremeeva, Elena V; Bartsev, Sergey I; van Berkel, Willem J H; Vysotski, Eugene S

    2017-03-01

    Upon binding their metal ion cofactors, Ca(2+) -regulated photoproteins display a rapid increase of light signal, which reaches its peak within milliseconds. In the present study, we investigate bioluminescence kinetics of the entire photoprotein family. All five recombinant hydromedusan Ca(2+) -regulated photoproteins-aequorin from Aequorea victoria, clytin from Clytia gregaria, mitrocomin from Mitrocoma cellularia and obelins from Obelia longissima and Obelia geniculata-demonstrate the same bioluminescent kinetics pattern. Based on these findings, for the first time we propose a unanimous kinetic model describing the bioluminescence mechanism of Ca(2+) -regulated photoproteins.

  1. Thermoluminescence and P700 redox kinetics as complementary tools to investigate the cyclic/chlororespiratory electron pathways in stress conditions in barley leaves.

    PubMed

    Peeva, Violeta N; Tóth, Szilvia Z; Cornic, Gabriel; Ducruet, Jean-Marc

    2012-01-01

    Cyclic electron flow around photosystem I drives additional proton pumping into the thylakoid lumen, which enhances the protective non-photochemical quenching and increases ATP synthesis. It involves several pathways activated independently. In whole barley leaves, P700 oxidation under far-red illumination and subsequent P700(+) dark reduction kinetics provide a major probe of the activation of cyclic pathways. Two 'intermediate' and 'slow' exponential reduction phases are always observed and they become faster after high light illumination, but dark inactivation of the Benson-Calvin cycle causes the emergence of both a transient in the P700 oxidation and a 'fast' phase in the P700(+) reduction. We investigate here the afterglow (AG) thermoluminescence emission as another tool to detect the activation of cyclic electron pathways from stroma reductants to the acceptor side of photosystem II. This transfer is activated by warming, yielding an AG band at about 45°C. However, treatments that accelerate the 'intermediate' and 'slow' P700(+) reduction phases (brief anoxia, hexose infiltration, fast dehydration of excised leaves) also produced a downshift of this AG band. This pathway ascribable to NADPH dehydrogenase (NDH) would be triggered by a deficit in ATP, while the 'fast' reduction phase corresponding to the ferredoxin plastoquinone reductase pathway is triggered by an overreduction of the photosystem I acceptor pool and is undetected in thermoluminescence. Contrastingly, slow dehydration of unwatered plants did not cause faster reduction of P700(+) nor temperature downshift of the AG band, that is no induction of the NDH pathway, whereas an increased intensity of the AG band indicated a strong NADPH + ATP assimilatory potential.

  2. A theoretical investigation on kinetics, mechanism, and thermochemistry of the gas-phase reactions of methyl fluoroacetate with OH radicals and fate of alkoxy radical.

    PubMed

    Mishra, Bhupesh Kumar; Deka, Ramesh Chandra

    2014-09-25

    We theoretically investigated OH-initiated hydrogen abstraction reactions of methyl fluoroacetate (MFA) CH2FC(O)OCH3 at the MPWB1K level of theory in conjunction with the 6-31+G(d,p) basis set. Thermodynamic and kinetic data are computed using the comparatively accurate G2(MP2) method. Two most stable conformers of MFA are identified, and the energy difference between them is found to be only 0.32 kcal mol(-1). Both of them are considered for rate coefficient calculations, and the contribution from each of the conformers is found to be quite significant. We propose an indirect mechanism due to validation of pre- and post-reactive complexes. The rate parameters are determined using canonical transition state theory and energetics at the G2(MP2) level. The temperature dependence of the rate constant can be described by the Arrhenius expressions: k = 8.79 × 10(-13) exp[(-377.27 ± 64)/T] cm(3) molecule(-1) s(-1) over a temperature range of 250-450 K. The ΔfH°298 for CH2FC(O)OCH3, CH2FC(O)OC(•)H2, and C(•)HFC(O)OCH3 are also computed using an isodesmic procedure. The OH-driven atmospheric lifetime of MFA was estimated to be 24 days. A mechanistic study to shed light on the atmospheric degradation and the sole fate for the consumption of CH2FC(O)OCH2O(•) radical has also been reported.

  3. Theoretical investigation on the kinetics and mechanisms of hydroxyl radical-induced transformation of parabens and its consequences for toxicity: Influence of alkyl-chain length.

    PubMed

    Gao, Yanpeng; Ji, Yuemeng; Li, Guiying; An, Taicheng

    2016-03-15

    As emerging organic contaminants (EOCs), the ubiquitous presence of preservative parabens in water causes a serious environmental concern. Hydroxyl radical ((•)OH) is a strong oxidant that can degrade EOCs through photochemistry in surface water environments as well as in advanced oxidation processes (AOPs). To better understand the degradation mechanisms, kinetics, and products toxicity of the preservative parabens in aquatic environments and AOPs, the (•)OH-initiated degradation reactions of the four parabens were investigated systematically using a computational approach. The four studied parabens with increase of alkyl-chain length were methylparaben (MPB), ethylparaben (EPB), propylparaben (PPB), and dibutylparaben (BPB). Results showed that the four parabens can be initially attacked by (•)OH through (•)OH-addition and H-abstraction routes. The (•)OH-addition route was more important for the degradation of shorter alkyl-chain parabens like MPB and EPB, while the H-abstraction route was predominant for the degradation of parabens with longer alkyl-chain for example PPB and BPB. In assessing the aquatic toxicity of parabens and their degradation products using the model calculations, the products of the (•)OH-addition route were found to be more toxic to green algae than original parabens. Although all degradation products were less toxic to daphnia and fish than corresponding parental parabens, they could be still harmful to these aquatic organisms. Furthermore, as alkyl-chain length increased, the ecotoxicity of parabens and their degradation products was found to be also increased. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Synthesis, crystal and molecular-electronic structure, and kinetic investigation of two new sterically hindered isomeric forms of the dimethyl[methyl(phenylsulfonyl)amino]benzenesulfonyl chloride

    NASA Astrophysics Data System (ADS)

    Rublova, L.; Zarychta, B.; Olijnyk, V.; Mykhalichko, B.

    2017-06-01

    Two new structural isomers - 2,4-dimethyl-5-[methyl(phenylsulfonyl)amino]benzenesulfonyl chloride (1) and 2,4-dimethyl-3-[methyl(phenylsulfonyl)amino]benzenesulfonyl chloride (2) were synthesized by interaction of N-(2,4-dimethylphenyl)-N-methyl-benzenesulfonamide or N-(2,6-dimethylphenyl)-N-methylbenzenesulfonamide with chlorosulfonic acid. Both compounds have been structurally characterized by X-ray single crystal diffraction at 100 K. The crystals of 1 are triclinic: space group P 1 bar , a = 8.1542(2), b = 11.0728(3), c = 11.2680(3) Å, α = 116.557(3), β = 95.155(2), γ = 108.258(2)°, V = 831.97(4) Å3, Z = 2, R = 0.0251 for 2429 reflections; the crystals of 2 are monoclinic: space group P21/c, a = 11.7428(2), b = 11.3518(2), c = 12.5886(2) Å, β = 93.659(2)°, V = 1674.66(5) Å3, Z = 4, R = 0.0269 for 2622 reflections. The structure of both isomers is organized as molecular crystals. These sterically hindered organic molecules are cross-linked into framework by means of hydrogen bonds of Csbnd H⋯O type (H⋯O distances are in range 2.27(2)-2.76(2) Å). The ab initio quantum-chemical calculations of an electronic structure of the isomeric molecules of 1 and 2 have been performed using the restricted Hartree-Fock method with a 6-31G* basis set. The calculated values of charge density concentrated on the electronegative atoms of the sterically hindered molecules are in good agreement with parameters of the intramolecular hydrogen bonds. The obtained data of the kinetic investigations of the substitution reactions in aqueous solution well correlate with stereo-chemical characteristics of the both molecules of the dimethyl[methyl(phenylsulfonyl)amino]-benzenesulfonyl chloride.

  5. Investigating the chemical mechanisms of the functionalization and fragmentation of hydrocarbons in the heterogeneous oxidation by OH using a stochastic kinetics model

    NASA Astrophysics Data System (ADS)

    Wiegel, A. A.; Wilson, K. R.; Hinsberg, B.; Houle, F. A.

    2014-12-01

    While the heterogeneous oxidation of atmospheric organic aerosols influences their effects on climate, air quality, and visibility, a more detailed understanding of the chemical mechanisms in heterogeneous oxidation is crucial for improving models of their chemical evolution in the atmosphere. Previous experimental work in our lab has shown two general reaction pathways for organic aerosol upon oxidation: functionalization, which adds additional oxygen functional groups to the carbon skeleton, and fragmentation, which leads to C-C bond scission and lower molecular weight oxidized products. Furthermore, these pathways were also found to be dependent on molecular structure, with more branched or oxidized hydrocarbons undergoing more fragmentation than less branched or oxidized hydrocarbons. However, while the mechanisms of hydrocarbon oxidation have been studied extensively in the gas phase, to what extent the gas phase mechanisms of hydrocarbon oxidation can be reliably applied to heterogeneous or bulk oxidation in aerosol remains unclear. To investigate the role of the condensed phase and molecular structure in the mechanism of heterogeneous organic aerosol oxidation, stochastic kinetics models are developed and compared to measurements of the products in the oxidation of hydrocarbons. Within the aerosol bulk, condensed phase rate coefficients and product branching ratios for peroxy reactions lead to different product distributions than those expected from gas phase peroxy reactions due to the presence of the liquid radical cage at the reaction site. As a result, tertiary alcohols and ketones were found to be the predominate products in the oxidation of squalane as observed in experiments. As the aerosol becomes further oxidized, β-scission of alkoxy radicals with neighboring functional groups is the primary fragmentation pathway leading to lower volatility products. In conjunction with this fragmentation mechanism, elimination of CO2 from acyloxy radicals was

  6. Kinetic and Modeling Investigation to Provide Design Guidelines for the NREL Dilute-Acid Process Aimed at Total Hydrolysis/Fractionation of Lignocellulosic Biomass: July 1998

    SciTech Connect

    Lee, Y. Y.; Iyer, P.; Xiang, Q.; Hayes, J.

    2004-08-01

    Following up on previous work, subcontractor investigated three aspects of using NREL ''pretreatment'' technology for total hydrolysis (cellulose as well as hemicellulose) of biomass. Whereas historic hydrolysis of biomass used either dilute acid or concentrated acid technology for hydrolysis of both hemicellulose and cellulose, NREL has been pursuing very dilute acid hydrolysis of hemicellulose followed by enzymatic hydrolysis of cellulose. NREL's countercurrent shrinking-bed reactor design for hemicellulose hydrolysis (pretreatment) has, however, shown promise for total hydrolysis. For the first task, subcontractor developed a mathematical model of the countercurrent shrinking bed reactor operation and, using yellow poplar sawdust as a feedstock, analyzed the effect of: initial solid feeding rate, temperature, acid concentration, acid flow rate, Peclet number (a measure of backmixing in liquid flow), and bed shrinking. For the second task, subcontractor used laboratory trials, with yellow poplar sawdust and 0.07 wt% sulfuric acid at various temperatures, to verify the hydrolysis of cellulose to glucose (desired) and decomposition of glucose (undesired) and determine appropriate parameters for use in kinetic models. Unlike cellulose and hemicellulose, lignins, the third major component of biomass, are not carbohydrates that can be broken down into component sugars. They are, however, aromatic complex amorphous phenolic polymers that can likely be converted into low-molecular weight compounds suitable for production of fuels and chemicals. Oxidative degradation is one pathway for such conversion and hydrogen peroxide would be an attractive reagent for this, as it would leave no residuals. For the third task, subcontractor reacted lignin with hydrogen peroxide under various conditions and analyzed the resulting product mix.

  7. Removal of organic matter from surface water during coagulation with sludge flotation and rapid filtration - a full-scale technological investigation.

    PubMed

    Pruss, Alina

    2015-01-01

    Coagulation with sludge flotation and rapid filtration was selected as a surface water treatment technology to be optimised with a full-scale investigation, which was carried out in Poland between August and October 2013. The river water treated was characterized by low alkalinity, high-temperature variability and a high organic matter content. In the course of technological studies, the processes of coagulation with sludge flotation and rapid filtration were analysed. The studies were performed in the most adverse conditions for the applied technology i.e. during the period of algal bloom and subsequent decomposition of dead plankton. Throughout the study, the river water contained mainly dissolved organic matter, with occasional increases in the concentration of the undissolved fraction during algal bloom. The undissolved total organic carbon (TOC) fraction was effectively removed through coagulation while small doses of ClO₂added prior to coagulation enhanced the process. The process of coagulation using high-coagulant doses at pH = 6.5 did not provide a reduction in the TOC value below the level of 4 mg C/L required for treated water. The effect was achieved by adding powdered activated carbon (PAC) before the filters. The coagulation products were characterised by low-hydraulic resistance which should be taken into account at the stage of water delivery to the filters, after flotation.

  8. A Rapid Evaluation of Activity in Lupus (LFA-REAL(™) ) Correlates with More Complex Disease Activity Instruments Whether Evaluated by Clinical Investigators or Real-World Clinicians.

    PubMed

    Askanase, Anca D; Nguyen, Samantha C; Costenbader, Karen; Lim, S Sam; Kamen, Diane; Aranow, Cynthia; Grossman, Jennifer; Kapoor, Teja M; Baker-Frost, DeAnna; Aberle, Teresa; Thanou-Stavraki, Aikaterini; Hanrahan, Leslie M; Kim, Mimi; Merrill, Joan T

    2017-10-09

    Lupus disease measures such as the SLE Disease Activity Index (SLEDAI) and the British Isles Lupus Assessment Group (BILAG) Index are challenging to interpret. The Lupus Foundation of America-Rapid Evaluation of Activity in Lupus (LFA-REAL) is intended to provide an efficient application of anchored visual analogue scores, each representing the individual severity of active symptoms, with the sum of individual scores deriving an overall disease activity assessment. To compare the performance of LFA-REAL to SLE disease activity assessments and compare scores between trained lupus clinical investigators and clinicians. Investigators scored the SLEDAI, BILAG, PGA, and LFA-REAL, while the clinicians scored the LFA-REAL. The level of agreement between physicians and instruments was determined. The study included 99 patients, 93% women, 31% Caucasian, 43.4 (±13.2) years old. At the first visit, the SLEDAI was 5.5 (±4.5), BILAG 6.7 (±7.8), and PGA 33.6 (±24.5). The investigator REAL was 46.2 (±42.9), and clinician REAL 56.1 (±53.6). At the second visit, the investigator REAL was 41.3 (±36.7), and clinician REAL 48.3 (±42.6). Total REAL scores correlated positively with PGA, SLEDAI, and BILAG (ρ 0.58-0.88, p <0.001). REAL scores produced correlation coefficients ρ > 0.7 for musculoskeletal, mucocutaneous, and renal BILAG domains. The intra-class correlation coefficient between the REAL scores of investigators and clinicians was 0.79 for Visit1 (p < 0.001) and 0.86 for Visit2 (p < 0.001). The LFA-REAL provides a reliable surrogate for more complicated disease activity measures when used by lupus clinical investigators or clinicians. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  9. An investigation of the effect of surface impurities on the adsorption kinetics of hydrogen chemisorbed onto iron. Annual status report, 1 January-31 December 1993

    SciTech Connect

    Shanabarger, M.R.

    1993-01-01

    The goal of this program was to develop an understanding of heterogeneous kinetic processes for those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. Although hydrogen degradation of metallic materials is believed to result from dissolved protonic hydrogen, the heterogeneous hydrogen interface transport processes often dominate the kinetics of degradation. The initial step in the interface transport process is the dissociative chemisorption of the molecular species at the metal surface followed by hydrogen absorption into and transport through the bulk. The interaction of hydrogen with the surfaces of alpha-2(Ti3Al) titanium aluminide, gamma(TiAl) titanium aluminide, and beryllium were studied.

  10. Rapid Evaporation of microbubbles

    NASA Astrophysics Data System (ADS)

    Gautam, Jitendra; Esmaeeli, Asghar

    2008-11-01

    When a liquid is heated to a temperature far above its boiling point, it evaporates abruptly. Boiling of liquid at high temperatures can be explosive and destructive, and poses a potential hazard for a host of industrial processes. Explosive boiling may occur if a cold and volatile liquid is brought into contact with a hot and non-volatile liquid, or if a liquid is superheated or depressurized rapidly. Such possibilities are realized, for example, in the depressurization of low boiling point liquefied natural gas (LNG) in the pipelines or storage tanks as a result of a leak. While boiling of highly heated liquids can be destructive at macroscale, the (nearly) instantaneous pace of the process and the release of large amount of kinetic energy make the phenomena extremely attractive at microscale where it is possible to utilize the released energy to derive micromechanical systems. For instance, there is currently a growing interest in micro-explosion of liquid for generation of micro bubbles for actuation purposes. The aim of the current study is to gain a fundamental understanding of the subject using direct numerical simulations. In particular, we seek to investigate the boundary between stable and unstable nucleus growth in terms of the degree of liquid superheat and to compare the dynamics of unstable and stable growth.

  11. Determination of enzyme mechanisms by radiationless energy transfer kinetics.

    PubMed

    Lobb, R R; Auld, D S

    1979-06-01

    Rigorous definition of the elementary steps of an enzymatic reaction requires visualization of transient enzyme-substrate (ES) complexes. Measurement of radiationless energy transfer (RET) between enzyme tryptophan residues and a fluorescent dansyl (5-dimethylaminonaphthalene-1-sulfonyl) substrate provides a sensitive means to observe ES complexes directly. Analysis of the rate of formation and breakdown of ES complexes by RET can serve as the basis of a rapid kinetic approach to enzyme mechanisms. Both pre-steady-state and steady-state kinetics can be performed in the same RET experiment. Analysis at steady state precisely determines k(cat) and K(m) values by multiple means. Analysis at pre-steady state determines the number of intermediates, the type of reaction mechanism, and all the individual binding and rate constants. Chymotrypsin was chosen as a standard of reference for RET kinetics because extensive investigations have established both the existence of transient intermediates in the course of its catalytic process and the range of values to be expected for pertinent kinetic constants. As predicted, RET kinetics readily detects the two known intermediates in the alpha-chymotrypsincatalyzed hydrolysis of specific ester substrates. The results are both qualitatively and quantitatively in accord with data derived for this enzyme from classical kinetics. Hence, this experimental study both validates and demonstrates the theoretical advantages and potential of RET kinetics. The generality of the approach has been investigated by synthesizing a family of dansyl-labeled substrates designed to meet the specificity requirements of a number of metallo- and nonmetallo- exo- and endopeptidases. In all cases, the ES complex is observed readily at micromolar or lower concentrations of enzyme under stopped-flow conditions. The success of the RET kinetic approach on proteolytic enzymes shows its broad utility.

  12. Microwave gallium-68 radiochemistry for kinetically stable bis(thiosemicarbazone) complexes: structural investigations and cellular uptake under hypoxia† †Electronic supplementary information (ESI) available. CCDC 1001632–1001634. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5dt02537k Click here for additional data file. Click here for additional data file.

    PubMed Central

    Alam, Israt S.; Arrowsmith, Rory L.; Cortezon-Tamarit, Fernando; Twyman, Frazer; Kociok-Köhn, Gabriele; Botchway, Stanley W.; Dilworth, Jonathan R.

    2016-01-01

    We report the microwave synthesis of several bis(thiosemicarbazones) and the rapid gallium-68 incorporation to give the corresponding metal complexes. These proved kinetically stable under ‘cold’ and ‘hot’ biological assays and were investigated using laser scanning confocal microscopy, flow cytometry and radioactive cell retention studies under normoxia and hypoxia. 68Ga complex retention was found to be 34% higher in hypoxic cells than in normoxic cells over 30 min, further increasing to 53% at 120 min. Our data suggests that this class of gallium complexes show hypoxia selectivity suitable for imaging in living cells and in vivo tests by microPET in nude athymic mice showed that they are excreted within 1 h of their administration. PMID:26583314

  13. Comprehensive investigations of kinetics of alkaline hydrolysis of TNT (2,4,6-trinitrotoluene), DNT (2,4-dinitrotoluene), and DNAN (2,4-dinitroanisole).

    PubMed

    Sviatenko, Liudmyla; Kinney, Chad; Gorb, Leonid; Hill, Frances C; Bednar, Anthony J; Okovytyy, Sergiy; Leszczynski, Jerzy

    2014-09-02

    Combined experimental and computational techniques were used to analyze multistep chemical reactions in the alkaline hydrolysis of three nitroaromatic compounds: 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and 2,4-dinitroanisole (DNAN). The study reveals common features and differences in the kinetic behavior of these compounds. The analysis of the predicted pathways includes modeling of the reactions, along with simulation of UV-vis spectra, experimental monitoring of reactions using LC/MS techniques, development of the kinetic model by designing and solving the system of differential equations, and obtaining computationally predicted kinetics for decay and accumulation of reactants and products. Obtained results suggest that DNT and DNAN are more resistant to alkaline hydrolysis than TNT. The direct substitution of a nitro group by a hydroxide represents the most favorable pathway for all considered compounds. The formation of Meisenheimer complexes leads to the kinetic first-step intermediates in the hydrolysis of TNT. Janovsky complexes can also be formed during hydrolysis of TNT and DNT but in small quantities. Methyl group abstraction is one of the suggested pathways of DNAN transformation during alkaline hydrolysis.

  14. Ziegler-Natta and metallocene-catalyzed isotactic polypropylene: A comprehensive investigation and comparison using crystallization kinetics, fiber spinning and thermal spunbonding

    NASA Astrophysics Data System (ADS)

    Bond, Eric Bryan

    Isotactic polypropylene (iPP) can be synthesized using conventional heterogeneous Ziegler-Natta (zniPP) and homogenous metallocene catalysts (miPP). The purpose of this work was to investigate and compare and contrast miPP resins to zniPP resins. The resins in this study were thoroughly characterized by cNMR and solution fractionation to determine the number, type and distribution of defects. The resins were then studied under isothermal and nonisothermal quiescent crystallization conditions to determine the bulk and crystal growth kinetics, crystal structure, crystallinity and thermal properties. The cNMR and xylene fractionation studies indicated the miPP resins had substantially more total defects in the crystallizable material than either of the zniPP resins in this study. Combined results from DSC, SAXS and WAXD indicated the miPP and zniPP resins have similar alpha-monoclinic equilibrium melting temperatures (T m0), despite the differences in defect content, type and distribution. The presence of atactic material was found to lower the observed equilibrium melting temperature of a particular resin, whether miPP or zniPP. The isothermal crystallization studies showed the miPP resins readily produce the gamma-crystal structure. The zniPP resins also produced small amounts of the gamma-structure, at high crystallization temperatures. Defects were found to be excluded from the crystal under isothermal crystallization conditions. For crystallization under isothermal crystallization conditions, the observed linear growth rates were found to be dependent upon defect content. Under nonisothermal conditions, the growth rate was found to depend mostly on the molecular weight. Fiber spinning studies showed that the molecular weight and molecular weight distribution of an iPP resin is largely determined by the point of crystallization in the spinline, the crystallization temperature and as-spun filament properties. Increasing the molecular weight (also increasing the

  15. Investigating the photocatalytic degradation property of Pt, Pd and Ni nanoparticles-loaded TiO2 nanotubes powder prepared via rapid breakdown anodization.

    PubMed

    Manovah David, T; Wilson, P; Mahesh, R; Dhanavel, S; Hussain, Shamima; Jacob Melvin Boby, S; Stephen, A; Ramesh, C; Sagayaraj, P

    2017-09-07

    The present study was performed to investigate the photocatalytic efficiency of the titania (TiO2) nanotubes (NTs) powder prepared via rapid breakdown anodization sensitized individually with Ni, Pd and Pt metal nanoparticles (NPs). The TiO2 NTs powder had the length of 5-6 μm, with the outer diameter between 20 and 25 nm and the wall thickness of 3-4 nm as observed in the scanning and transmission electron microscopes. The crystal structure analysis employing X-ray diffraction indicated the presence of Pt, Pd and Ni NPs in face-centered cubic phase over the anatase TiO2 NTs powder. The photocatalytic degradation of methylene blue (MB) was carried out with these photocatalysts. As a result, the performance of the 2 at.% Pt-loaded Pt-TiO2 NTs nanocomposite was determined to be superior on comparison to other photocatalysts under the current investigation. Fourier-transform infrared spectra confirmed the absence of any adsorption of MB or degraded products onto the surface of all the photocatalysts. The electron paramagnetic resonance analysis substantiated the e(-) transfer interaction from the conduction band of TiO2 NTs to Fermi level of Pt NPs has resulted in the better photodegradation process. The possible degradation mechanism using Pt-TiO2 NTs nanocomposites is discussed.

  16. The Heliopause Electrostatic Rapid Transit System (HERTS) - Design, Trades, and Analyses Performed in a Two Year NASA Investigation of Electric Sail Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Wiegmann, Bruce M.; Scheider, Todd; Heaton, Andrew; Vaughn, Jason; Stone, Nobie; Wright, Ken

    2017-01-01

    Personnel from NASA's MSFC have been investigating the feasibility of an advanced propulsion system known as the Electric Sail (E-Sail) for future scientific exploration missions. This tea