Science.gov

Sample records for rapid kinetic investigation

  1. Experimental investigation and kinetic-theory-based model of a rapid granular shear flow

    NASA Astrophysics Data System (ADS)

    Wildman, R. D.; Martin, T. W.; Huntley, J. M.; Jenkins, J. T.; Viswanathan, H.; Fen, X.; Parker, D. J.

    An experimental investigation of an idealized rapidly sheared granular flow was performed to test the predictions of a model based on the kinetic theory of dry granular media. Glass ballotini beads were placed in an annular shear cell and the lower boundary rotated to induce a shearing motion in the bed. A single particle was tracked using the positron emission particle tracking (PEPT) technique, a method that determines the location of a particle through the triangulation of gamma photons emitted by a radioactive tracer particle. The packing fraction and velocity fields within the three-dimensional flow were measured and compared to the predictions of a model developed using the conservation and balance equations applicable to dissipative systems, and solved incorporating constitutive relations derived from kinetic theory. The comparison showed that kinetic theory is able to capture the general features of a rapid shear flow reasonably well over a wide range of shear rates and confining pressures.

  2. Rapid mixing kinetic techniques.

    PubMed

    Martin, Stephen R; Schilstra, Maria J

    2013-01-01

    Almost all of the elementary steps in a biochemical reaction scheme are either unimolecular or bimolecular processes that frequently occur on sub-second, often sub-millisecond, time scales. The traditional approach in kinetic studies is to mix two or more reagents and monitor the changes in concentrations with time. Conventional spectrophotometers cannot generally be used to study reactions that are complete within less than about 20 s, as it takes that amount of time to manually mix the reagents and activate the instrument. Rapid mixing techniques, which generally achieve mixing in less than 2 ms, overcome this limitation. This chapter is concerned with the use of these techniques in the study of reactions which reach equilibrium; the application of these methods to the study of enzyme kinetics is described in several excellent texts (Cornish-Bowden, Fundamentals of enzyme kinetics. Portland Press, 1995; Gutfreund, Kinetics for the life sciences. Receptors, transmitters and catalysis. Cambridge University Press, 1995).There are various ways to monitor changes in concentration of reactants, intermediates and products after mixing, but the most common way is to use changes in optical signals (absorbance or fluorescence) which often accompany reactions. Although absorbance can sometimes be used, fluorescence is often preferred because of its greater sensitivity, particularly in monitoring conformational changes. Such methods are continuous with good time resolution but they seldom permit the direct determination of the concentrations of individual species. Alternatively, samples may be taken from the reaction volume, mixed with a chemical quenching agent to stop the reaction, and their contents assessed by techniques such as HPLC. These methods can directly determine the concentrations of different species, but are discontinuous and have a limited time resolution. PMID:23729251

  3. 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.

  4. Rapid kinetics investigations of peracid oxidation of ferric cytochrome P450cam: nature and possible function of compound ES.

    PubMed

    Spolitak, Tatyana; Dawson, John H; Ballou, David P

    2006-12-01

    Previously, we reported spectroscopic properties of cytochrome P450cam compound I, (ferryl iron plus a porphyrin pi-cation radical (Fe(IV)=O/Por(+))), as well as compound ES (Fe(IV)=O/Tyr()) in reactions of substrate-free ferric enzyme with m-chloroperbenzoic acid [T. Spolitak, J.H. Dawson, D.P. Ballou, J. Biol. Chem. 280 (2005) 20300-9]. Compound ES arises by intramolecular electron transfer from nearby tyrosines to the porphyrin pi-cation radical of Compound I, and has been characterized by rapid-freeze-quench-Mössbauer/EPR spectroscopy; the tyrosyl radical was assigned to Tyr96 for wild type or to Tyr75 for the Tyr96Phe variant [V. Schünemann, F. Lendzian, C. Jung, J. Contzen, A.L. Barra, S.G. Sligar, A.X. Trautwein, J. Biol. Chem. 279 (2004) 10919-10930]. Here we report rapid-scanning stopped-flow studies of the reactions of peracids with substrate-free ferric Y75F, Y96F, and Y96F/Y75F P450cam variants, showing how these active site changes influence electron transfer from nearby tyrosines and affect formation of intermediates. Curiously, rates of generation of Compounds I and ES for both single mutants were not very different from wild type. Contrasting with the earlier EPR results, the Y96F/Y75F variant was also shown to form an ES-like species, but more slowly. When substrate is not present, or is improperly bound, compound I rapidly converts to compound ES, which can be reduced to form H(2)O and ferric P450, thus avoiding the modification of nearby protein groups or release of reactive oxygen species. PMID:17095096

  5. 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…

  6. DATA ACQUISITION SYSTEM FOR RAPID KINETIC EXPERIMENTS

    EPA Science Inventory

    A data acquisition system has been developed to collect, analyze and store large volumes of rapid kinetic data measured from a stopped-flow spectrophotometer. A digital minicomputer, with an A/D converter, tape drive unit and formatter, analog recorder, oscilloscope, and input/ou...

  7. Rapid lithography: Photopolymerization characterizations and initiation kinetics

    NASA Astrophysics Data System (ADS)

    Stocker, Michael Paul

    In order to improve upon the resolution of photolithography, a technique that is used to produce features for today's micro and nanodevices, techniques must move beyond e-beam and deep-UV sources. Multiphoton absorption polymerization (MAP) uses near-infrared light for the creation of complex, three-dimensional features on the sub-100 nm scale. The resolution of MAP can be enhanced further using a two-beam technique called resolution augmentation through photo-induced deactivation (RAPID) to the reach feature sizes as small as 40 nm. The mechanism and kinetics of photo-induced deactivation are not well understood. To better understand these processes, studies of different photoinitiators have been performed. We find that some photoinitiators are so efficient at deactivation that they are capable of undergoing self-deactivation by addition of another photon from the excitation source. This phenomenon is manifested in a polymerization trend in which feature size has a proportional velocity (PROVE) dependence, the opposite of the conventional velocity dependence. We also demonstrate that the velocity dependence can also be tuned between PROVE and conventional dependences. Kinetic models have been formulated to account for the observed deactivation. By reconciling experimental data for some sample photoinitiators with the kinetic model through the use of simulations, kinetic rate constants are determined. The self-deactivation efficiency of each photoinitiator was determined. The lifetimes of intermediates in the radical photopolymerization process were also determined. The kinetic rate constants associated with photoinitiators should allow for the customization of photoinitiators for specific applications and make RAPID a more efficient process capable of reaching resolution on the level of 30 nm and below.

  8. 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)

  9. 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. PMID:24602867

  10. A kinetic model of rapidly reversible nonphotochemical quenching

    PubMed Central

    Zaks, Julia; Amarnath, Kapil; Kramer, David M.; Niyogi, Krishna K.; Fleming, Graham R.

    2012-01-01

    Oxygen-evolving photosynthetic organisms possess nonphotochemical quenching (NPQ) pathways that protect against photo-induced damage. The majority of NPQ in plants is regulated on a rapid timescale by changes in the pH of the thylakoid lumen. In order to quantify the rapidly reversible component of NPQ, called qE, we developed a mathematical model of pH-dependent quenching of chlorophyll excitations in Photosystem II. Our expression for qE depends on the protonation of PsbS and the deepoxidation of violaxanthin by violaxanthin deepoxidase. The model is able to simulate the kinetics of qE at low and high light intensities. The simulations suggest that the pH of the lumen, which activates qE, is not itself affected by qE. Our model provides a framework for testing hypothesized qE mechanisms and for assessing the role of qE in improving plant fitness in variable light intensity. PMID:22891305

  11. Kinetics investigations of atmospheric chemical reactions

    SciTech Connect

    Hills, A.J.

    1987-01-01

    Two separate gas-phase kinetics investigations were performed using a low-pressure fast-flow system with mass spectrometer detection. The first part of this research was a study of the atmospheric reactivity of diatomic sulfur, S/sub 2/. Rates of the reactions of sulfur with O, O/sub 2/, O/sub 3/, N/sub 2/O, NO, and NO/sub 2/ were investigated at 409 K and low pressure (0.89-3.0 Torr) in a discharge-flow system with mass spectrometric detection. The second investigation involves a study of the synergistic coupling of atmospheric bromine and chlorine chemistry. Recent measurements of ozone in the stratosphere over Antarctica have shown that the springtime ozone column decreased by 40% from 1960 to 1985. Both dynamical and chemical theories have been advanced to explain the formation of the Antarctic ozone hole. Prominent among these theories is that a synergistic interaction between gas-phase BrO and ClO radicals may be responsible for springtime ozone loss. The overall rate constant for the reaction, BrO + ClO ..-->.. Br + OClO ..-->.. Br + Cl + O/sub 2/ ..-->.. BrCl + O/sub 2/, has been measured over the temperature range 241-408 K. The rate constant for the overall reaction equals (8.2 +/- 1.0) 10/sup -12/ cm/sup 3//molecule s, independent of temperature.

  12. Thermodynamic and kinetic investigation of agomelatine polymorph transformation.

    PubMed

    Zhang, Qi; Jiang, Linglei; Mei, Xuefeng

    2016-03-01

    Thermodynamic properties of polymorphic forms I and II of Agomelatine were investigated and the bimorphism was determined to be monotropically related. The phase transition kinetics from metastable form I to thermodynamically stable form II was studied and a quantification method was developed based on X-ray powder diffraction technique. Various solid-state kinetic models were examined and the results were fit to the experimental data. The nucleation kinetic models were found to be the best fit to describe the experimental data across the temperature range. The activation energy of the form transformation was calculated in the range of 116-122 kJ mol(-1), irrespective of which kinetic model selected. PMID:25414117

  13. 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.

  14. 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

  15. Kinetic investigation of the solvation of lithium salts in siloxanes.

    SciTech Connect

    Chen, Z.; Wang, H. H.; Vissers, D. R.; Zhang, L.; West, R.; Lyons, L. J.; Amine, K.; Chemical Sciences and Engineering Division; Univ. of Wisconsin; Grinnell Coll.

    2008-02-14

    The solvation of lithium salts in siloxanes was investigated with the aim to understand the key barriers that limit the ionic conductivity of siloxane-based electrolytes. The conductivity and kinetic data were measured for electrolytes with different salts, different salt concentrations, and solvents. The results show that both the conductivity and the kinetics of ionic transportation were greatly impacted by the specific interactions between ions and the solvent molecules. The high content of ion pairs in the electrolytes can be one of the main reasons for the low ionic conductivity observed in the siloxane-based electrolytes.

  16. Flow-Based Systems for Rapid and High-Precision Enzyme Kinetics Studies

    PubMed Central

    Hartwell, Supaporn Kradtap; Grudpan, Kate

    2012-01-01

    Enzyme kinetics studies normally focus on the initial rate of enzymatic reaction. However, the manual operation of steps of the conventional enzyme kinetics method has some drawbacks. Errors can result from the imprecise time control and time necessary for manual changing the reaction cuvettes into and out of the detector. By using the automatic flow-based analytical systems, enzyme kinetics studies can be carried out at real-time initial rate avoiding the potential errors inherent in manual operation. Flow-based systems have been developed to provide rapid, low-volume, and high-precision analyses that effectively replace the many tedious and high volume requirements of conventional wet chemistry analyses. This article presents various arrangements of flow-based techniques and their potential use in future enzyme kinetics applications. PMID:22577614

  17. 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. PMID:25561012

  18. 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.

  19. Theoretical investigation of germane and germylene decomposition kinetics.

    PubMed

    Polino, Daniela; Barbato, Alessandro; Cavallotti, Carlo

    2010-09-21

    The dissociation kinetics of germane and its decomposition products were studied determining microcanonical kinetic constants with RRKM theory and integrating the master equation using a stochastic approach. Relevant reaction parameters were calculated through first principles calculations. Structures of reactants and transition states were determined at the B3LYP/aug-cc-pvtz level while energies were computed at the CCSD(T) level and extended to the complete basis set limit. Though similar for many aspects to the kinetics of decomposition of SiH(4), GeH(4) has some peculiar features that indicate a different chemical reactivity. It was found that the main decomposition channel leads to the formation of germylene, GeH(2), which rapidly decomposes to atomic Ge and H(2). The dissociation of GeH(2) to Ge and H(2) is a formally spin forbidden reaction characterized by an activation energy of 160.3 kJ mol(-1) calculated at the minimum energy crossing point between the singlet and triplet states. The intersystem crossing probability was explicitly included in the microcanonical simulations through Landau-Zener theory. It was found that its effect on the reaction rate is almost negligible, both because of the large spin-orbit coupling between the singlet and triplet states and for the fall off conditions prevailing in the examined pressure and temperature ranges. Kinetic constants of the main decomposition channels were determined as a function of pressure and temperature between 0.0013 and 10 bar and 1100 and 1700 K. The high and low pressure kinetic constants for GeH(4) decomposition are 6.4 x 10(13) (T/K)(0.272) exp(-26 700 K/T) and 2.7 x 10(48) (T/K)(-9.05) exp(-31 600 K/T), while those for GeH(2) are 6.02 x 10(12) (T/K)(0.203) exp(-19 660 K/T) and 1.6 x 10(26) (T/K)(-3.06) exp(-21 121 K/T), respectively. A quantitative agreement with experimental data for GeH(4) decomposition could be obtained adopting a downward energy transfer parameter of 340 x (T/298 K)(0.85) cm

  20. Kinetic and mechanistic investigations of progesterone reaction with ozone.

    PubMed

    Barron, Emmanuelle; Deborde, Marie; Rabouan, Sylvie; Mazellier, Patrick; Legube, Bernard

    2006-06-01

    The removal of progesterone by ozone in aqueous solution was studied in this work. The absolute rate constant was evaluated and first by-products were identified. The reaction was studied in the 2.0-8.0 pH range and was found to be a second-order reaction, first-order relative to each compound concentration. The rate constant, determined by kinetic experiments in presence of an OH radical scavenger (tert-butanol), was independent of pH. The value was evaluated to be equal to 480+/-30 M(-1)s(-1) by two kinetic methods. Mass spectrometry analyses were performed to investigate primary degradation products generated by the reaction of ozone with progesterone. Two by-products were evidenced. According to these results, a degradation pathway of progesterone reacting with ozone was proposed. PMID:16725173

  1. Kinetics of nucleotide transport in rat heart mitochondria studied by a rapid filtration technique

    SciTech Connect

    Brandolin, G.; Marty, I.; Vignais, P.V. )

    1990-10-01

    A rapid filtration technique has been used to measure at room temperature the kinetics of ADP and ATP transport in rat heart mitochondria in the millisecond time range. Transport was stopped by cessation of the nucleotide supply, without the use of a transport inhibitor, thus avoiding any quenching delay. The kinetics of ({sup 14}C)ADP transport in energized mitochondria were apparently monophasic. The rate of transport of ({sup 14}C)ATP in energized mitochondria was 5-10 times lower than that of ({sup 14}C)ADP. Upon uncoupling, the rate of ({sup 14}C)ATP uptake was enhanced, and that of ({sup 14}C)ADP uptake was decreased. However, the two rates did not equalize, indicating that transport was not exclusively electrogenic. Transport of ({sup 14}C)ADP and ({sup 14}C)ATP by resting mitochondria followed biphasic kinetics. Depletion of nucleotides in resting mitochondria resulted in a greater decrease in the extent of the slow phase than of the rapid one. In addition, about half of the nucleotides taken up at the end of the rapid phase were not discharged into the medium upon addition of carboxyatractyloside. This suggested that matricial nucleotides are compartmentalized in two pools which are exchangeable at different rates with external nucleotides.

  2. 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

  3. Refolded scFv antibody fragment against myoglobin shows rapid reaction kinetics.

    PubMed

    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 V(H)-V(L) 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 (k(on)/k(off)), 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

  4. Force kinetics and individual sarcomere dynamics in cardiac myofibrils after rapid ca(2+) changes.

    PubMed Central

    Stehle, R; Krüger, M; Pfitzer, G

    2002-01-01

    Kinetics of force development and relaxation after rapid application and removal of Ca(2+) were measured by atomic force cantilevers on subcellular bundles of myofibrils prepared from guinea pig left ventricles. Changes in the structure of individual sarcomeres were simultaneously recorded by video microscopy. Upon Ca(2+) application, force developed with an exponential rate constant k(ACT) almost identical to k(TR), the rate constant of force redevelopment measured during steady-state Ca(2+) activation; this indicates that k(ACT) reflects isometric cross-bridge turnover kinetics. The kinetics of force relaxation after sudden Ca(2+) removal were markedly biphasic. An initial slow linear decline (rate constant k(LIN)) lasting for a time t(LIN) was abruptly followed by an ~20 times faster exponential decay (rate constant k(REL)). k(LIN) is similar to k(TR) measured at low activating [Ca(2+)], indicating that k(LIN) reflects isometric cross-bridge turnover kinetics under relaxed-like conditions (see also. Biophys. J. 83:2142-2151). Video microscopy revealed the following: invariably at t(LIN) a single sarcomere suddenly lengthened and returned to a relaxed-type structure. Originating from this sarcomere, structural relaxation propagated from one sarcomere to the next. Propagated sarcomeric relaxation, along with effects of stretch and P(i) on relaxation kinetics, supports an intersarcomeric chemomechanical coupling mechanism for rapid striated muscle relaxation in which cross-bridges conserve chemical energy by strain-induced rebinding of P(i). PMID:12324432

  5. Kinetic Monte Carlo investigation of tetragonal strain on Onsager matrices

    NASA Astrophysics Data System (ADS)

    Li, Zebo; Trinkle, Dallas R.

    2016-05-01

    We use three different methods to compute the derivatives of Onsager matrices with respect to strain for vacancy-mediated multicomponent diffusion from kinetic Monte Carlo simulations. We consider a finite difference method, a correlated finite difference method to reduce the relative statistical errors, and a perturbation theory approach to compute the derivatives. We investigate the statistical error behavior of the three methods for uncorrelated single vacancy diffusion in fcc Ni and for correlated vacancy-mediated diffusion of Si in Ni. While perturbation theory performs best for uncorrelated systems, the correlated finite difference method performs best for the vacancy-mediated Si diffusion in Ni, where longer trajectories are required.

  6. 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. PMID:27363940

  7. Investigation of the diffusion kinetics of borided stainless steels

    NASA Astrophysics Data System (ADS)

    Kayali, Yusuf

    2013-12-01

    In this study, the kinetics of borides formed on AISI 420, AISI 304 and AISI 304L stainless steels was investigated. Boronizing treatment was carried out using Ekabor-II powders at the processing temperatures of 1123, 1173 and 1223 K for 2, 4 and 6 h. The phases of the boride layers of borided AISI 420, AISI 304 and AISI 304L stainless steels were FeB, Fe2B, CrB and NiB, respectively. The thickness of the boride layer formed on the borided steels ranged from 4.6 to 64 μm depending on the boriding temperature, boriding time and alloying elements of the stainless steels. Depending on the chemical composition, temperature and layer thickness, the activation energies of boron in AISI 420, AISI 304 and AISI 304L stainless steels were found to be 206.161, 234.641 and 222.818 kJ/mol, respectively. The kinetics of growth of the boride layers formed on the AISI 420, AISI 304 and AISI 304L stainless steels and the thickness of the boride layers were investigated.

  8. Open channel noise. VI. Analysis of amplitude histograms to determine rapid kinetic parameters.

    PubMed Central

    Heinemann, S H; Sigworth, F J

    1991-01-01

    Recently we reported that rapid fluctuations of ion currents flowing through open gramicidin A channels exceed the expected level of pure transport noise at low ion concentrations (Heinemann, S. H. and F. J. Sigworth. 1990. Biophys. J. 57:499-514). Based on comparisons with kinetic ion transport models we concluded that this excess noise is likely caused by current interruptions lasting approximately 1 microsecond. Here we introduce a method using the higher-order cumulants of the amplitude distribution to estimate the kinetics of channel closing events far below the actual time resolution of the recording system. Using this method on data recorded with 10 kHz bandwidth, estimates for gap time constants on the order of 1 microsecond were obtained, similar to the earlier predictions. PMID:1718467

  9. Fluid/Kinetic: Investigations of the Dynamic Solar Wind

    NASA Astrophysics Data System (ADS)

    Kasper, Justin C.

    2010-05-01

    The supersonic solar wind originates in the hot solar corona and expands through interplanetary space, interacting with planets and carving the heliospheric bubble out of the interstellar medium. We can use direct exploration of the solar wind with instrumented spacecraft to understand the solar wind and as a laboratory for investigating the physics of magnetized astrophysical plasmas. Many of our open questions about fundamental physical processes such as heating, particle acceleration, angular momentum transport, and the production of magnetic fields require an understanding of the kinetic physics of non-Maxwellian plasmas in regimes where fluid physics breaks down. This talk will review current research at this fluid/kinetic interface, including joint measurements of particles and electromagnetic waves in the solar wind and what we have learned about heating, instabilities, and energy flow. Examples of the application of these results to more distant objects such as jets, accretion disks, and galactic dynamos will be presented. Some potential future work will be discussed, including understanding energy flow between ions and electrons and the exciting potential for direct measurements of the solar corona with the proposed NASA Solar Probe Plus mission.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Choi, Jeong Yun

    The departure from the equilibrium solid concentration at the solid-liquid interface was often observed during rapid solidification. The energetic associated non-equilibrium solute partitioning has been treated in detail, providing possible ranges of interface concentrations for a given growth condition. For analytical description of specific single-phase dendritic and cellular operating point selection, analytical models for solute partitioning under a given set of growth conditions have been developed and widely utilized in most of the theoretical investigations of rapid solidification. However, these solute trapping models are not rigorously verified due to the difficulty in experimentally measuring under rapid growth conditions. Moreover, since these solute trapping models include kinetic parameters which are difficult to directly measure from experiments, application of the solute trapping models or the associated analytic rapid solidification model is limited. These theoretical models for steady state rapid solidification which incorporate the solute trapping models do not describe the interdependency of solute diffusion, interface kinetics, and alloy thermodynamics. This research program is focused on critical issues that represent conspicuous gaps in current understanding of rapid solidification, limiting our ability to predict and control microstructural evolution at high undercooling, where conditions depart significantly from local equilibrium. 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 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

  12. Growth of Ni2Si by rapid thermal annealing: Kinetics and moving species

    NASA Astrophysics Data System (ADS)

    Ma, E.; Lim, B. S.; Nicolet, M.-A.; Natan, M.

    1987-10-01

    The growth kinetics is characterized and the moving species is identified for the formation of Ni2Si by Rapid Thermal Annealing (RTA) of sequentially deposited Si and Ni films on a <100> Si substrate. The interfacial Ni2Si layer grows as the square root of time, indicating that the suicide growth process is diffusion-limited. The activation energy is 1.25±0.2 eV in the RTA temperature range of 350 450° C. The results extend those of conventional steady-state furnace annealing quite fittingly, and a common activation energy of 1.3±0.2 eV is deduced from 225° to 450° C. The marker experiment shows that Ni is the dominant moving species during Ni2Si formation by RTA, as is the case for furnace annealing. It is concluded that the two annealing techniques induce the same growth mechanisms in Ni2Si formation.

  13. An optogenetic gene expression system with rapid activation and deactivation kinetics

    PubMed Central

    Motta-Mena, Laura B.; Reade, Anna; Mallory, Michael J.; Glantz, Spencer; Weiner, Orion D.; Lynch, Kristen W.; Gardner, Kevin H.

    2013-01-01

    Optogenetic gene expression systems can control transcription with spatial and temporal detail unequaled with traditional inducible promoter systems. However, current eukaryotic light-gated transcription systems are limited by toxicity, dynamic range, or slow activation/deactivation. Here we present an optogenetic gene expression system that addresses these shortcomings and demonstrate its broad utility. Our approach utilizes an engineered version of EL222, a bacterial Light-Oxygen-Voltage (LOV) protein that binds DNA when illuminated with blue light. The system has a large (>100-fold) dynamic range of protein expression, rapid activation (< 10 s) and deactivation kinetics (< 50 s), and a highly linear response to light. With this system, we achieve light-gated transcription in several mammalian cell lines and intact zebrafish embryos with minimal basal gene activation and toxicity. Our approach provides a powerful new tool for optogenetic control of gene expression in space and time. PMID:24413462

  14. A rapid assay for affinity and kinetics of molecular interactions with nucleic acids.

    PubMed

    Donaldson, Gregory P; Roelofs, Kevin G; Luo, Yiling; Sintim, Herman O; Lee, Vincent T

    2012-04-01

    The Differential Radial Capillary Action of Ligand Assay (DRaCALA) allows detection of protein interactions with low-molecular weight ligands based on separation of the protein-ligand complex by differential capillary action. Here, we present an application of DRaCALA to the study of nucleic acid-protein interactions using the Escherichia coli cyclic AMP receptor protein (CRP). CRP bound in DRaCALA specifically to (32)P-labeled oligonucleotides containing the consensus CRP binding site, but not to oligonucleotides with point mutations known to abrogate binding. Affinity and kinetic studies using DRaCALA yielded a dissociation constant and dissociation rate similar to previously reported values. Because DRaCALA is not subject to ligand size restrictions, whole plasmids with a single CRP-binding site were used as probes, yielding similar results. DNA can also function as an easily labeled carrier molecule for a conjugated ligand. Sequestration of biotinylated nucleic acids by streptavidin allowed nucleic acids to take the place of the protein as the immobile binding partner. Therefore, any molecular interactions involving nucleic acids can be tested. We demonstrate this principle utilizing a bacterial riboswitch that binds cyclic-di-guanosine monophosphate. DRaCALA is a flexible and complementary approach to other biochemical methods for rapid and accurate measurements of affinity and kinetics at near-equilibrium conditions. PMID:22210888

  15. Investigating laser rapid manufacturing for Inconel-625 components

    NASA Astrophysics Data System (ADS)

    Paul, C. P.; Ganesh, P.; Mishra, S. K.; Bhargava, P.; Negi, J.; Nath, A. K.

    2007-06-01

    This paper presents an investigation of laser rapid manufacturing (LRM) for Inconel-625 components. LRM is an upcoming rapid manufacturing technology, it is similar to laser cladding at process level with different end applications. In general, laser-cladding technique is used to deposit materials on the substrate either to improve the surface properties or to refurbish the worn out parts, while LRM is capable of near-net shaping the components by layer-by-layer deposition of the material directly from CAD model. In the present study, a high-power continuous wave (CW) CO 2 laser system, integrated with a co-axial powder-feeding system and a three-axis workstation were used. The effect of processing parameters during LRM of Inconel-625 was studied and the optimum set of parameters for the maximum deposition rate was established employing Orthogonal L9 array of Taguchi technique. Results indicated that the powder feed rate and the scan speed contributed about 56% and 26%, respectively to the deposition rate, while the influence of laser power was limited to 10% only. Fabricated components were subjected to non-destructive testing (like—ultrasonic testing, dye-penetrant testing), tensile testing, impact testing, metallographic examinations and micro-hardness measurement. The test results revealed defect-free material deposition with improved mechanical strength without sacrificing the ductility.

  16. Fundamental electrode kinetics

    NASA Technical Reports Server (NTRS)

    Elder, J. P.

    1968-01-01

    Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics.

  17. 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 ...

  18. 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

  19. Rapid kinetics of liver microsomal glucose-6-phosphatase. Evidence for tight-coupling between glucose-6-phosphate transport and phosphohydrolase activity

    SciTech Connect

    Berteloot, A.; Vidal, H.; van de Werve, G. )

    1991-03-25

    Rapid kinetics of both glucose-6-P uptake and hydrolysis in fasted rat liver microsomes were investigated with a recently developed fast-sampling, rapid-filtration apparatus. Experiments were confronted with both the substrate transport and conformational models currently proposed for the glucose-6-phosphatase system. Accumulation in microsomes of 14C products from (U-14C)glucose-6-P followed biexponential kinetics. From the inside to outside product concentrations, it could be inferred that mostly glucose should accumulate inside the vesicles. While biexponential kinetics are compatible with the mathematical predictions of a simplified substrate transport model, the latter fails in explaining the burst in total glucose production over a similar time scale to that used for the uptake measurements. Since the initial rate of the burst phase in untreated microsomes exactly matched the steady-state rate of glucose production in detergent-treated vesicles, it can be definitely concluded that the substrate transport model does not describe adequately our results. While the conformational model accounts for both the burst of glucose production and the kinetics of glucose accumulation into the vesicles, it cannot explain the burst in 32Pi production from (32P)glucose-6-P measured under the same conditions. Since the amplitude of the observed bursts is not compatible with a presteady state in enzyme activity, we propose that a hysteretic transition best explains our results in both untreated and permeabilized microsomes, thus providing a new rationale to understand the molecular mechanism of the glucose-6-phosphatase system.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. Pauli equation for semiconductor quantum dot photoluminescence kinetics investigation

    NASA Astrophysics Data System (ADS)

    Turkov, Vadim K.; Leonov, Mikhail Y.; Rukhlenko, Ivan D.; Fedorov, Anatoly V.

    2012-11-01

    We develop a theory of secondary emission from a single quantum dot, when the lowest-energy states of its electron-hole pairs are involved in the photoluminescence process. For the sake of definiteness, our model allows for two states contributing to the luminescence. We analyze the dependency of secondary emission intensity on the energy gap between the states, while considering that the gap is determined by the quantum dot's size. An analytical expression for the time-dependent signal of thermalized luminescence is obtained using an analytical solution to the kinetic Pauli equation. This expression yields the signal of stationary luminescence as the spectral width of the excitation pulse tends to zero.

  7. Ion Density Fluctuations at the Kinetic Scale: Experimental Investigations

    NASA Astrophysics Data System (ADS)

    Nemecek, Z.; Safrankova, J.; Nemec, F.; Chen, C. H. K.

    2014-12-01

    It is well established that the solar wind undergoes a heating along its path through the solar system but the sources of this heating are still under debate. Among them, a gradual dissipation of large scale discontinuities toward smaller scales and, eventually, to the heat via turbulent cascades is frequently discussed.The contribution presents the analysis of ion density variations that are measured onboard the Spektr R spacecraft with a unique time resolution of 32 ms. The analysis reveals that (1) the mean frequency spectrum of density variations in the MHD range (up to about 0.05 Hz) is steeper than usually discussed -5/3, and (2) this part is followed by a plateau that is terminated near proton kinetic scales. We study the dependence of the slopes of different parts of the frequency spectra on background plasma parameters and discuss the results in view of present theories of Alfvenic turbulence in the solar wind.

  8. 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.

  9. Rapid enzyme kinetic assays of individual Drosophila and comparisons of field-caught D. melanogaster and D. simulans.

    PubMed

    Clark, A G; Keith, L E

    1989-06-01

    Techniques for performing numerous enzyme kinetic assays with minimum time and effort would be valuable to studies of the evolutionary genetics of metabolic control and the quantitative genetics of determinants of kinetic parameters. Microtiter plate readers have been used for a variety of repetitious analytical techniques, and instruments are available that can take repetitive readings with sufficient speed to perform kinetic assays. The ability of these instruments to assay rapidly the kinetic properties of small samples makes them potentially useful for a number of problems in population genetics. While the ability to handle large numbers of samples is very attractive, the small sample volumes and optical imprecision of microtiter plates result in some sacrifice in accuracy. This paper presents methods for performing kinetic assays on individual field-caught Drosophila, quantifies the precision of these methods, and characterizes differences among Drosophila melanogaster and D. simulans from samples caught in California and Pennsylvania. Comparisons between field-caught and laboratory reared D. melanogaster show that most of the characters are very similar, with the exception of alpha GPDH, which has a threefold higher mean activity among field-caught flies. The phenotypic correlations are presented with a brief discussion of their relevance to assessing the evolution of metabolic control of these enzymes. PMID:2508620

  10. 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. PMID:27023718

  11. Investigation of diamond turning: of rapidly solidified aluminum alloys

    NASA Astrophysics Data System (ADS)

    Cheng, Yuan-Chieh; Hsu, Wei-Yao; Abou-El-Hossein, Khaled; Olufayo, Oluwole; Otieno, Timothy

    2014-09-01

    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. Moreover, a large amount of data exists for this material and commercially available aluminum 6061 can be diamond turned to achieve surface roughness values of approximately 4 to 8 nm, which is adequate for applications that involve the infrared spectral range, but not for the near-ultraviolet wavelength (NUV) spectral range. In this study, we used a novel aluminum material, fabricated using a rapid solidification process that is equivalent to the conventional aluminum 6061 alloy grade. Using rapidly solidified aluminum (RSA) can achieve improved surface finish and enhanced optical performance. The rapid solidification process was realized using a melt spinning operation, which achieves a high cooling rate to yield a fine microstructure. The properties of RSA 6061 are similar to those of conventional aluminum 6061, but its grain size is extremely small. In this paper, the background of RSA is introduced, and the diamond turnability characteristics and coating processes for both traditional aluminum 6061 and RSA are discussed. The surface roughness and grain structure of RSA were evaluated using white light interferometers and the surface roughness during coating of the reflectance multilayers of samples were analyzed using near-ultraviolet wavelengths. Finally, indicators such as optimal cutting parameters and optical performance are discussed.

  12. Dielectric Resonator-Based Flow and Stopped-Flow EPR with Rapid Field Scanning: A Methodology for Increasing Kinetic Information

    NASA Astrophysics Data System (ADS)

    Sienkiewicz, Andrzej; Ferreira, Ana Maria da Costa; Danner, Birgit; Scholes, Charles P.

    1999-02-01

    We report methodology which combines recently developed dielectric resonator-based, rapid-mix, stopped-flow EPR (appropriate for small, aqueous, lossy samples) with rapid scanning of the external (Zeeman) magnetic field where the scanning is preprogrammed to occur at selected times after the start of flow. This methodology gave spectroscopic information complementary to that obtained by stopped-flow EPR at single fields, and with low reactant usage, it yielded more graphic insight into the time evolution of radical and spin-labeled species. We first used the ascorbyl radical as a test system where rapid scans triggered after flow was stopped provided "snapshots" of simultaneously evolving and interacting radical species. We monitored ascorbyl radical populations either as brought on by biologically damaging peroxynitrite oxidant or as chemically and kinetically interacting with a spectroscopically overlapping nitroxide radical. In a different biophysical application, where a spin-label lineshape reflected rapidly changing molecular dynamics of folding spin-labeled protein, rapid scan spectra were taken during flow with different flow rates and correspondingly different times after the mixing-induced inception of protein folding. This flow/rapid scan method is a means for monitoring early immobilization of the spin probe in the course of the folding process.

  13. Single-point kinetic energy density functionals: A pointwise kinetic energy density analysis and numerical convergence investigation

    NASA Astrophysics Data System (ADS)

    Xia, Junchao; Carter, Emily A.

    2015-01-01

    We present a comprehensive study of single-point kinetic energy density functionals (KEDFs) to be used in orbital-free density functional theory (DFT) calculations. We first propose a form of KEDFs based on a pointwise Kohn-Sham (KS) kinetic energy density (KED) and electron localization function (ELF) analysis. We find that the ELF and modified enhancement factor have a very strong and transferable correlation with the reduced density in various bulk metals. The non-self-consistent kinetic energy errors predicted by our KEDF models are decreased greatly compared to previously reported generalized gradient approximation (GGA) KEDFs. Second, we perform self-consistent calculations with various single-point KEDFs and investigate their numerical convergence behavior. We find striking numerical instabilities for previous GGA KEDFs; most of the GGA KEDFs fail to converge and show unphysical densities during the optimization. In contrast, our KEDFs demonstrate stable convergence, and their self-consistent results of various bulk properties agree reasonably well with KSDFT. A further detailed KED analysis reveals an interesting bifurcation phenomenon in defective metals and alloys, which may shed light on directions for future KEDF development.

  14. 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.

  15. 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)

  16. Kinetic and thermodynamic investigation of enzymatic L-ascorbyl acetate synthesis.

    PubMed

    Zhang, Dong-Hao; Li, Chao; Zhi, Gao-Ying

    2013-12-01

    Kinetics and thermodynamics of lipase-catalyzed esterification of l-ascorbic acid in acetone were investigated by using vinyl acetate as acyl donor. The results showed that l-ascorbic acid could generate inhibition effect on lipase activity. A suitable model, Ping-Pong Bi-Bi mechanism having substrate inhibition, was thus introduced to describe the enzymatic kinetics. Furthermore, the kinetic and thermodynamic parameters were calculated from a series of experimental data according to the kinetic model. The inhibition constant of L-ascorbic acid was also obtained, which seemed to imply that enhancing reaction temperature could depress the substrate inhibition. Besides, the activation energy values of the first-step and the second-step reaction were estimated to be 37.31 and 4.94 kJ/mol, respectively, demonstrating that the first-step reaction was the rate-limiting reaction and could be easily improved by enhancing temperature. PMID:24211407

  17. 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.

  18. Optimization of a direct spectrophotometric method to investigate the kinetics and inhibition of sialidases

    PubMed Central

    2012-01-01

    Backgrounds Streptococcus pneumoniae expresses three distinct sialidases, NanA, NanB, and NanC, that are believed to be key virulence factors and thus, potential important drug targets. We previously reported that the three enzymes release different products from sialosides, but could share a common catalytic mechanism before the final step of product formation. However, the kinetic investigations of the three sialidases have not been systematically done thus far, due to the lack of an easy and steady measurement of sialidase reaction rate. Results In this work, we present further kinetic characterization of pneumococcal sialidases by using a direct spectrophotometric method with the chromogenic substrate p-nitrophenyl-N-acetylneuraminic acid (p-NP-Neu5Ac). Using our assay, the measured kinetic parameters of the three purified pneumococcal sialidase, NanA, NanB and NanC, were obtained and were in perfect agreement with the previously published data. The major advantage of this alternative method resides in the direct measurement of the released product, allowing to readily determine of initial reaction rates and record complete hydrolysis time courses. Conclusion We developed an accurate, fast and sensitive spectrophotometric method to investigate the kinetics of sialidase-catalyzed reactions. This fast, sensitive, inexpensive and accurate method could benefit the study of the kinetics and inhibition of sialidases in general. PMID:23031230

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  20. Kinetic modeling of hydrocarbon autoignition at low and intermediate temperatures in a rapid compression machine

    SciTech Connect

    Curran, H J; Pitz, W J; Westbrook, C K; Griffiths, J F; Mohamed, C

    2000-11-01

    A computer model is used to examine oxidation of hydrocarbon fuels in a rapid compression machine. For one of the fuels studied, n-heptane, significant fuel consumption is computed to take place during the compression stroke under some operating conditions, while for the less reactive n-pentane, no appreciable fuel consumption occurs until after the end of compression. The third fuel studied, a 60 PRF mixture of iso-octane and n-heptane, exhibits behavior that is intermediate between that of n-heptane and n-pentane. The model results indicate that computational studies of rapid compression machine ignition must consider fuel reaction during compression in order to achieve satisfactory agreement between computed and experimental results.

  1. A Quantitative Investigation of Cementite Dissolution Kinetics for Continuous Heating of Hypereutectoid Steel

    NASA Astrophysics Data System (ADS)

    Lee, Seok-Jae; Clarke, Kester D.

    2015-09-01

    Cementite dissolution kinetics in austenite was investigated in a hypereutectoid steel alloy during continuous heating. The quantitative change in cementite volume fraction as a function of thermal history was determined from dilation curves by using the martensite start temperature to calculate prior austenite carbon content. Two characteristics of the cementite dissolution kinetics were found: (1) the cementite dissolution rate increased with time regardless of heating rate due to the increased surface area of cementite particles, and (2) the rate of cementite dissolution was strongly affected by heating rate. An empirical equation combining the effects of cementite volume change and heating rate is proposed to describe cementite dissolution kinetics. A continuous heating transformation diagram for hypereutectoid steels was obtained and compared with the DICTRA simulations and metallographic analyses.

  2. 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 ...

  3. 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.

  4. 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.

  5. New channelrhodopsin with a red-shifted spectrum and rapid kinetics from Mesostigma viride.

    PubMed

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

    2011-01-01

    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

  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. Rapid kinetic methods to dissect steroidogenic cytochrome P450 reaction mechanisms.

    PubMed

    Yoshimoto, Francis K; Auchus, Richard J

    2016-07-01

    All cytochrome P450 enzyme reactions involve a catalytic cycle with several discreet physical or chemical steps. This cycle ends with the formation of the reactive heme iron-oxygen complex, which oxygenates substrate. While the steps might be very similar for each P450 enzyme, the rates of each step varies tremendously for each enzyme and sometimes even for different reactions catalyzed by the same enzyme. For example, the rate-limiting step for most bacterial P450 enzymes, with turnover numbers over 1000s(-1), is the second electron transfer. In contrast, steroidogenic P450s from eukaryotes catalyze much slower reactions, with turnover numbers of ∼5-250min(-1); therefore, assumptions about kinetic properties for the mammalian P450 enzymes based on the bacterial enzymes are tenuous. In order to dissect the rates for individual steps, special techniques that isolate individual steps and/or single turnovers are required. This article will review the theoretical principles and practical considerations for several of these techniques, with illustrative published examples. The reader should gain an appreciation for the appropriate methods used to interrogate particular steps in the P450 reaction cycle. PMID:26472553

  8. 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

    2016-01-01

    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. (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. PMID:26583314

  9. Heat acclimation memory: do the kinetics of the deacclimated transcriptome predispose to rapid reacclimation and cytoprotection?

    PubMed

    Tetievsky, Anna; Assayag, Miri; Ben-Hamo, Rotem; Efroni, Sol; Cohen, Gal; Abbas, Atallah; Horowitz, Michal

    2014-12-01

    Faster reinduction of heat acclimation (AC) after its decline indicates "AC memory." Our previous results revealed involvement of epigenetic mechanisms of transcriptional regulation. We hypothesized that the decline of AC (DeAC) is a period of "dormant memory" during which many processes are alerted to enable rapid reacclimation (ReAC). Using a genomewide approach we studied the AC, DeAC, and ReAC transcriptomes, to uncover hallmark pathways linked to "molecular memory" in the cardioacclimatome. Fifty rats subjected to heat acclimation [34°C for 2d (AC2d) or 30d (AC30)], DeAC (24°C, 30 days), ReAC (34°C, 2 days), and untreated controls were used. The GeneChip Rat Gene 1.0 ST Array was employed for left ventricular (cardiac) mRNA hybridization. Three independent bioinformatic analyses showed that 1) during AC2d enrichment of DNA impair/repair-linked genes is seen, and this is the molecular on-switch of acclimation; 2) genes activated in AC30 underlie the qualitative physiological adaptations of cardiac performance; 3) particular molecular programs encompassing constitutive upregulation of p38 MAPK, Jak/Stat, and Akt pathways and targets are specifically activated during DeAC and ReAC; and 4) epigenetic markers such as linker histones (histones H1 cluster), associated with nucleosome spacing, transcriptional chromatin modifiers, poly-(ADP-ribose) polymerase-1 (PARP1) linked to chromatin compaction, and microRNAs are only altered during DeAC/ReAC. The latter are newcomers to the AC/DeAC puzzle. We suggest that these transcriptional responses maintain euchromatin and proteostasis and enable faster physiological recovery upon ReAC by rapidly reestablishing the protected acclimated cardiophenotype. We propose that the cardiac AC model can be applied to acclimation processes in general. PMID:25237184

  10. Two-photon fluorescence coincidence analysis: rapid measurements of enzyme kinetics.

    PubMed Central

    Heinze, Katrin G; Rarbach, Markus; Jahnz, Michael; Schwille, Petra

    2002-01-01

    Dual-color fluorescence cross-correlation analysis is a powerful tool for probing interactions of different fluorescently labeled molecules in aqueous solution. The concept is the selective observation of coordinated spontaneous fluctuations in two separate detection channels that unambiguously reflect the existence of physical or chemical linkages among the different fluorescent species. It has previously been shown that the evaluation of cross-correlation amplitudes, i.e., coincidence factors, is sufficient to extract essential information about the kinetics of formation or cleavage of chemical or physical bonds. Confocal fluorescence coincidence analysis (CFCA) (Winkler et al., Proc. Natl. Acad. Sci. U.S.A. 96:1375-1378, 1999) emphasizes short analysis times and simplified data evaluation and is thus particularly useful for screening applications or measurements on live cells where small illumination doses need to be applied. The recent use of two-photon fluorescence excitation has simplified dual- or multicolor measurements by enabling the simultaneous excitation of largely different dye molecules by a single infra-red laser line (Heinze et al., Proc. Natl. Acad. Sci. U.S.A. 97:10377-10382, 2000). It is demonstrated here that a combination of CFCA with two-photon excitation allows for minimization of analysis times for multicomponent systems down to some hundreds of milliseconds, while preserving all known advantages of two-photon excitation. By introducing crucial measurement parameters, experimental limits for the reduction of sampling times are discussed for the special case of distinguishing positive from negative samples in an endonucleolytic cleavage assay. PMID:12202390

  11. 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. PMID:24583217

  12. Toxicant Induced Changes on Delayed Fluorescence Decay Kinetics of Cyanobacteria and Green Algae: A Rapid and Sensitive Biotest

    PubMed Central

    Leunert, Franziska; Grossart, Hans-Peter; Gerhardt, Volkmar; Eckert, Werner

    2013-01-01

    Algal tests have developed into routine tools for testing toxicity of pollutants in aquatic environments. Meanwhile, in addition to algal growth rates, an increasing number of fluorescence based methods are used for rapid and sensitive toxicity measures. The present study stresses the suitability of delayed fluorescence (DF) as a promising parameter for biotests. DF is based on the recombination fluorescence at the reaction centre of photosystem II, which is emitted only by photosynthetically active cells. We analyzed the effects of three chemicals (3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 3,5 Dichlorophenol (3,5 DCP) and copper) on the shape of the DF decay kinetics for potential use in phytoplankton toxicity tests. The short incubation tests were done with four phytoplankton species, with special emphasis on the cyanobacterium Microcystis aeruginosa. All species exhibited a high sensitivity to DCMU, but cyanobacteria were more affected by copper and less by 3,5 DCP than the tested green algae. Analyses of changes in the DF decay curve in response to the added chemicals indicated the feasibility of the DF decay approach as a rapid and sensitive testing tool. PMID:23646185

  13. Quantitative (1)H NMR method for hydrolytic kinetic investigation of salvianolic acid B.

    PubMed

    Pan, Jianyang; Gong, Xingchu; Qu, Haibin

    2013-11-01

    This work presents an exploratory study for monitoring the hydrolytic process of salvianolic acid B (Sal B) in low oxygen condition using a simple quantitative (1)H NMR (Q-NMR) method. The quantity of the compounds was calculated by the relative ratio of the integral values of the target peak for each compound to the known amount of the internal standard trimethylsilyl propionic acid (TSP). Kinetic runs have been carried out on different initial concentrations of Sal B (5.00, 10.0, 20.0mg/mL) and temperatures of 70, 80, 90°C. The effect of these two factors during the transformation process of Sal B was investigated. The hydrolysis followed pseudo-first-order kinetics and the apparent degradation kinetic constant at 80°C decreased when concentration of Sal B increased. Under the given conditions, the rate constant of overall hydrolysis as a function of temperature obeyed the Arrhenius equation. Six degradation products were identified by NMR and mass spectrometric analysis. Four of these degradation products, i.e. danshensu (DSS), protocatechuic aldehyde (PRO), salvianolic acid D (Sal D) and lithospermic acid (LA) were further identified by comparing the retention times with standard compounds. The advantage of this Q-NMR method was that no reference compounds were required for calibration curves, the quantification could be directly realized on hydrolyzed samples. It was proved to be simple, convenient and accurate for hydrolytic kinetic study of Sal B. PMID:23867115

  14. 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.

  15. 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.

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

    PubMed

    Grewer, C

    1999-08-01

    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

  17. Investigation of the kinetics of surface-limited thin film growth of SiGe alloys

    SciTech Connect

    Sharp, J.W. . Dept. of Physics and Astronomy); Eres, G. )

    1992-11-01

    The kinetics of surface-limited thin film growth of SiGe alloys was investigated by time-resolved surface differential reflectometry. The source gas, mixtures of disilane and digermane in ratios from 1:1 to 6:1 in helium carrier gas, was delivered to a heated substrate by a fast-acting pulsed molecular jet valve. The adsorption and desorption kinetics were determined from the surface differential reflectance signal obtained using a polarized, high-stability HeNe probe laser. Thin film growth was studied in the temperature range of 400--600[degrees]C on Si(001) substrates. Preferential incorporation of digermane into the film produces an alloy composition that depends upon but does not mirror the gas composition. For all gas mixtures, there is a strong temperature dependence of the rate at which the adsorption layer decomposes into film plus by-product. The kinetic data and the alloy compositions provide a basis for deducing some of the characteristics of the reaction sequence that leads to SiGe alloy thin film growth.

  18. Investigation of the kinetics of surface-limited thin film growth of SiGe alloys

    SciTech Connect

    Sharp, J.W.; Eres, G.

    1992-11-01

    The kinetics of surface-limited thin film growth of SiGe alloys was investigated by time-resolved surface differential reflectometry. The source gas, mixtures of disilane and digermane in ratios from 1:1 to 6:1 in helium carrier gas, was delivered to a heated substrate by a fast-acting pulsed molecular jet valve. The adsorption and desorption kinetics were determined from the surface differential reflectance signal obtained using a polarized, high-stability HeNe probe laser. Thin film growth was studied in the temperature range of 400--600{degrees}C on Si(001) substrates. Preferential incorporation of digermane into the film produces an alloy composition that depends upon but does not mirror the gas composition. For all gas mixtures, there is a strong temperature dependence of the rate at which the adsorption layer decomposes into film plus by-product. The kinetic data and the alloy compositions provide a basis for deducing some of the characteristics of the reaction sequence that leads to SiGe alloy thin film growth.

  19. 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.

  20. Investigation of the kinetic process of solid phase microextraction in complex sample.

    PubMed

    Jiang, Ruifen; Xu, Jianqiao; Lin, Wei; Wen, Sijia; Zhu, Fang; Luan, Tiangang; Ouyang, Gangfeng

    2015-11-01

    The presence of complex matrix in the aquatic system affects the environmental behavior of hydrophobic organic compounds (HOCs). In the current study, an automated solid-phase microextraction (SPME) desorption method was employed to study the effect of 2-hydroxypropyl-β-cyclodextrin (β-HPCD) on the kinetic process of 5 selected polyaromatic hydrocarbons (PAHs) desorbing from the fiber in aqueous sample. The results showed that the added β-HPCD facilitated the desorption rates of PAHs from SPME fiber coating, and the enhancement effect can be predicted by a proposed theoretical model. Based on this model, the kinetic parameters of organic compounds desorbing from the SPME fiber can be determined, and the calculated results showed good agreement with the experimental data. In addition, the effect of temperature on the desorption kinetic was investigated. The results found that the SPME desorption time constant increased as the sampling temperature elevated, and followed the Arrhenius equation. Also, the temperature facilitated the desorption of HOCs from the bound matrix so that increased the lability degrees of the bound compounds. Finally, a calibration method based on the proposed theoretical model was developed and applied for the analysis of unknown sample. PMID:26572846

  1. 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. PMID:26015839

  2. 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

  3. Rapid in vivo measurement of β-amyloid reveals biphasic clearance kinetics in an Alzheimer's mouse model.

    PubMed

    Yuede, Carla M; Lee, Hyo; Restivo, Jessica L; Davis, Todd A; Hettinger, Jane C; Wallace, Clare E; Young, Katherine L; Hayne, Margaret R; Bu, Guojun; Li, Chen-Zhong; Cirrito, John R

    2016-05-01

    Findings from genetic, animal model, and human studies support the observation that accumulation of the β-amyloid (Aβ) peptide in the brain plays a central role in the pathogenic cascade of Alzheimer's disease (AD). Human studies suggest that one key factor leading to accumulation is a defect in brain Aβ clearance. We have developed a novel microimmunoelectrode (MIE) to study the kinetics of Aβ clearance using an electrochemical approach. This is the first study using MIEs in vivo to measure rapid changes in Aβ levels in the brains of living mice. Extracellular, interstitial fluid (ISF) Aβ levels were measured in the hippocampus of APP/PS1 mice. Baseline levels of Aβ40 in the ISF are relatively stable and begin to decline within minutes of blocking Aβ production with a γ-secretase inhibitor. Pretreatment with a P-glycoprotein inhibitor, which blocks blood-brain barrier transport of Aβ, resulted in significant prolongation of Aβ40 half-life, but only in the latter phase of Aβ clearance from the ISF. PMID:27069115

  4. 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.

  5. Kinetics of P/sub i/-P/sub i/ exchange in rat liver mitochondria. Rapid filtration experiments in the millisecond time range

    SciTech Connect

    Ligeti, E.; Brandolin, G.; Dupont, Y.; Vignais, P.V.

    1985-07-30

    Phosphate-phosphate exchange through the inorganic phosphate (P/sub i/) carrier of rat liver mitochondria was investigated by a new rapid filtration technique, which does not require the use of transport inhibitors to stop the reaction and offers high time resolution (starting from 10 ms), thus allowing kinetic measurements on a fine time scale even at room temperature. At approximately 22 degrees C, isotopic equilibrium of (TSP)P/sub i/ is achieved within 0.8-2.5 s--depending on the P/sub i/ concentration--and an initial linear phase, lasting for 400-500 ms, is observed. Complete inhibition of P/sub i/ exchange by an excess of mersalyl, a well-known organomercurial inhibitor, required 200 ms, pointing to the insufficiency of this reagent for effective inhibitor stop. On the other hand, investigation of the effect of mersalyl on the initial rate of P/sub i/ exchange supports earlier observations on the protective effect of this inhibitor. In nonrespiring mitochondria, at pH 7.3, P/sub i/ exchange exhibited a K/sub m/ of 1.6 mM and a V/sub max/ of 3.0 mumol min-1 (mg of mitochondrial protein)-1. The maximal velocity of P/sub i/ transport is significantly higher than the maximal velocity of all the other components of oxidative phosphorylation at comparable temperatures. The possible physiological significance of this excess capacity is discussed.

  6. 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. PMID:22476092

  7. 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.

  8. Numerical and experimental investigation of molten metal droplet deposition applied to rapid prototyping

    NASA Astrophysics Data System (ADS)

    Li, SuLi; Wei, ZhengYing; Du, Jun; Zhao, Guangxi; Wang, Xin; Lu, BingHeng

    2016-08-01

    Rapid prototyping based on molten metal droplets deposition is an additive process in which parts are produced from molten materials in a single operation without the use of any mold or other tooling. Near-net shaped parts are fabricated by sequentially depositing molten droplets layer by layer. This paper presents a systematic numerical and experimental investigation of the transient transport phenomenon during the droplets impinging onto a substrate surface. The 3D models based on a volume of fluid (VOF) method were developed to investigate the deposition of molten metal droplets on a horizontally aluminum substrate surface. Based on the above research, a semiquantitative relationship between external morphology and internal microstructure was proposed, which was further certified by investigating the piled vertical columns and the three-dimensional parts. The works should be helpful for the process optimization and non-destructive detection of drop-based rapid prototyping techniques.

  9. 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.

  10. An investigation of the crystallization kinetics of zeotype SAPO-34 crystals synthesized by hydrothermal and sonochemical methods.

    PubMed

    Marzpour Shalmani, Fariba; Halladj, Rouein; Askari, Sima

    2016-03-01

    The kinetics study of SAPO-34 crystallization from a gel containing morpholine as a structure directing agent (SDA) was investigated by means of X-ray diffraction (XRD) patterns in order to determine the kinetics parameters, i.e. induction times, rate constants, frequency factors, and activation energies for the induction and growth stages. The kinetics data of growth period were determined by using the Avrami-Erofeev nucleation growth model. SAPO-34 molecular sieves were synthesized by using both sonochemical-assisted hydrothermal and conventional hydrothermal heating at temperatures of 180, 200, and 220 °C to elucidate the influence of crystallization method on the crystallization kinetics of SAPO-34. The activation energy values indicated that the crystal growth mechanism was enhanced for samples synthesized sonochemically, whereas the induction energy was not greatly affected by using sonication process. Also, the kinetic compensation effect (KCE) was considered in order to obtain the isokinetic temperature. PMID:26585015

  11. Kinetic and mechanistic investigations of mesotrione degradation in aqueous medium by Fenton process.

    PubMed

    Bensalah, Nasr; Khodary, Ahmed; Abdel-Wahab, Ahmed

    2011-05-15

    In this work, chemical oxidation of mesotrione herbicide by Fenton process in acidic medium (pH 3.5) was investigated. Total disappearance of mesotrione and up to 95% removal of total organic carbon (TOC) were achieved by Fenton's reagent under optimized initial concentrations of hydrogen peroxide (H(2)O(2)) and ferrous iron (Fe(2+)) at pH 3.5. The time-dependent degradation profiles of mesotrione were satisfactorily fitted by first-order kinetics. Competition kinetic model was used to evaluate a rate constant of 8.8(± 0.2) × 10(9)M(-1) s(-1) for the reaction of mesotrione with hydroxyl radicals. Aromatic and aliphatic intermediates of mesotrione oxidation were identified and quantified by high performance liquid chromatography (HPLC). It seems that the degradation of mesotrione by Fenton process begins with the rupture of mesotrione molecule into two moieties: cyclohexane-1,3-dione derivative and 2-nitro-4-methylsulfonylbenzoic acid. Hydroxylation and release of sulfonyl and/or nitro groups from 2-nitro-4-methylsulfonylbenzoic acid lead to the formation of polyhydroxylated benzoic acid derivatives which undergo an oxidative opening of benzene ring into carboxylic acids that end to be transformed into carbon dioxide. PMID:21397397

  12. 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. PMID:25989604

  13. 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.

  14. 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.

  15. Investigating the Conformational Stability of Prion Strains through a Kinetic Replication Model

    PubMed Central

    Zampieri, Mattia; Legname, Giuseppe; Altafini, Claudio

    2009-01-01

    Prion proteins are known to misfold into a range of different aggregated forms, showing different phenotypic and pathological states. Understanding strain specificities is an important problem in the field of prion disease. Little is known about which PrPSc structural properties and molecular mechanisms determine prion replication, disease progression and strain phenotype. The aim of this work is to investigate, through a mathematical model, how the structural stability of different aggregated forms can influence the kinetics of prion replication. The model-based results suggest that prion strains with different conformational stability undergoing in vivo replication are characterizable in primis by means of different rates of breakage. A further role seems to be played by the aggregation rate (i.e. the rate at which a prion fibril grows). The kinetic variability introduced in the model by these two parameters allows us to reproduce the different characteristic features of the various strains (e.g., fibrils' mean length) and is coherent with all experimental observations concerning strain-specific behavior. PMID:19578427

  16. 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. PMID:23140668

  17. 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. PMID:26719437

  18. 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

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

    SciTech Connect

    Wilcox, J.

    2009-06-15

    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{sub 2}{leftrightarrow} HgCl + Cl, Hg + HCl {leftrightarrow} HgCl + H, and Hg + HOCl {leftrightarrow} 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.

  20. 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).

  1. Comment on "Single-point kinetic energy density functionals: A pointwise kinetic energy density analysis and numerical convergence investigation"

    NASA Astrophysics Data System (ADS)

    Trickey, S. B.; Karasiev, Valentin V.; Chakraborty, Debajit

    2015-09-01

    We suggest a more nuanced view of the merit and utility of generalized gradient approximations (GGAs) for the noninteracting kinetic energy (KE) than the critique of Xia and Carter (XC) [Phys. Rev. B 91, 045124 (2015), 10.1103/PhysRevB.91.045124]. Specifically, the multiple valuedness of the Pauli term enhancement factor (denoted G [n ] by XC) with respect to the inhomogeneity variable s can be excluded by enforcement of a bound on the Kohn-Sham KE to achieve universality of the functional along with enforcement of proper large-s behavior. This is physically sensible in that the excluded G values occur for s values that correspond to low densities. The behavior is exacerbated by peculiarities of pseudodensities. The VT84F KE GGA, constructed with these constraints, does not have the numerical instability in our older PBE2 functional analyzed by XC.

  2. 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

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

    DOE PAGESBeta

    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. 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

  4. 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

  5. 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.

  6. 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.

  7. Enantioselective supramolecular carriers for nucleoside drugs. A thermodynamic and kinetic gas phase investigation.

    PubMed

    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. PMID:22864826

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. Analytical investigations on the effects of substrate kinetics on macromolecular transport and hybridization through microfluidic channels.

    PubMed

    Das, Siddhartha; Subramanian, Kapil; Chakraborty, Suman

    2007-08-01

    In this paper, a generalized surface-kinetics based model is developed to analytically investigate the influences of the substrate types and the buffer compositions on the macromolecular transport and hybridization in microfluidic channels, under electrokinetic influences. For specific illustration, three typical microchannel substrates, namely silanized glass, polycarbonate and PDMS, are considered, in order to obtain analytical expressions for their zeta potentials as a function of the buffer pH and the substrate compositions. The expressions for the zeta potential are subsequently employed to derive the respective velocity distributions, under the application of electric fields of identical strengths in all cases. It is also taken into consideration that the charged macromolecules introduced into these channels are subjected to electrophoretic influences on account of the applied electric fields. Closed form expressions are derived to predict the transport behaviour of the macromolecules and their subsequent hybridization characteristics. From the analysis presented, it is shown that the modification of the channel surface with silane-treatment becomes useful for enhancing the macromolecular transport and surface hybridization, only if the buffer pH permits a large surface charge density. The analytical solutions are also compared with full-scale numerical solutions of the coupled problem of fluid dynamic and macromolecular transport in presence of the pertinent surface reactions, in order to justify the effectiveness of closed-form expressions derived in this study. PMID:17481862

  14. 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.

  15. Gaucher disease: Physical, kinetic and immunologic investigations of human and canine acid. beta. -glucosidase

    SciTech Connect

    Fabbro, D.E.

    1988-01-01

    Kinetic and immunologic techniques were developed to investigate the nature of the acid {beta}-glucosidase ({beta}-Glc) defects which results in human and canine Gaucher disease (GD). Two new affinity columns, using the potent inhibitors of {beta}-Glc (N-alkyl-deoxynojirimycins) as affinity ligands, were synthesized and methods were developed to obtain homogeneous {beta}-Glc from normal human placenta. Polyclonal and monoclonal (representing 14 different epitopes from 18 clones) antibodies were produced to the pure normal {beta}-Glc. Monospecific polyclonal IgG and tritiated-bromo-conduritol B epoxide (({sup 3}H)Br-CBE), a specific covalent active site directed inhibitor of {beta}-Glc, were used to quantitate the functional catalytic sites in normal and Type 1 Ashkenazi Jewish GD (AJGD) enzyme preparations: The k{sub cat} values for several new substrates with the mutant enzymes from spleen were about 1.5-fold less than the respective normal enzyme, indicating a nearly normal catalytic capacity of the mutant enzymes. Immunoblotting studies with polyclonal or several monoclonal antibodies indicated three molecular forms of {beta}-Glc (M{sub r} = 67,000, 62,000 to 65,000 and 58,000) in fibroblast extracts from normals and Type 1 AJGD patients. In comparison, only one form of cross-reacting immunologic material (CRIM) was detected in fibroblast extracts from Types 2 and 3 or several non-Jewish Type 1 GD patients.

  16. Kinetic and mechanistic investigations of the degradation of sulfamethazine in heat-activated persulfate oxidation process.

    PubMed

    Fan, Yan; Ji, Yuefei; Kong, Deyang; Lu, Junhe; Zhou, Quansuo

    2015-12-30

    Sulfamethazine (SMZ) is widely used in livestock feeding and aquaculture as an antibiotic agent and growth promoter. Widespread occurrence of SMZ in surface water, groundwater, soil and sediment has been reported. In this study, degradation of SMZ by heat-activated persulfate (PS) oxidation was investigated in aqueous solution. Experimental results demonstrated that SMZ degradation followed pseudo-first-order reaction kinetics. The pseudo-first-order rate constant (kobs) was increased markedly with increasing concentration of PS and temperature. Radical scavenging tests revealed that the predominant oxidizing species was SO4·(-) with HO playing a less important role. Aniline moiety in SMZ molecule was confirmed to be the reactive site for SO4·(-) attack by comparison with substructural analogs. Nontarget natural water constituents affected SMZ removal significantly, e.g., Cl(-) and HCO3(-) improved the degradation while fulvic acid reduced it. Reaction products were enriched by solid phase extraction (SPE) and analyzed by liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MS/MS). 6 products derived from sulfonamide S--N bond cleavage, aniline moiety oxidation and Smiles-type rearrangement were identified, and transformation pathways of SMZ oxidation were proposed. Results reveal that heat-activated PS oxidation could be an efficient approach for remediation of water contaminated by SMZ and related sulfonamides. PMID:26151383

  17. Synchrotron-Based Experimental Investigations and Numerical Modeling of the Kinetics of Phase Transformations in the Heat Affected Zone of Welds

    SciTech Connect

    2000-05-04

    Spatially Resolved X-Ray Diffraction (SRXRD) and Time Resolved X-Ray Diffraction (TRXRD) methods are being developed at LLNL for in-situ investigations of phase transformations in the heat-affected zone (HAZ) of welds. In this region of the weld, severe temperature gradients, high peak temperatures and rapid thermal fluctuations occur as the heat source passes through the material. These non-isothermal temperature fluctuations produce HAZ microstructures that cannot be predicted by conventional methods. The unique synchrotron-based experiments being developed here will enable the determination of phase transformation kinetics under true non-isothermal welding conditions, and can be used to aid in the development of models to predict HAZ microstructural evolution under a wide range of welding conditions. Commercially pure titanium, stainless steel alloys and plain carbon steels are currently under investigation.

  18. 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

  19. 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.

  20. 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.

  1. 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. PMID:24619826

  2. Rapid kinetic characterization of hammerhead ribozymes by real-time monitoring of fluorescence resonance energy transfer (FRET).

    PubMed Central

    Singh, K K; Parwaresch, R; Krupp, G

    1999-01-01

    In established methods for analyzing ribozyme kinetics, radiolabeled RNA substrates are primarily used. Each data point requires the cumbersome sampling, gel electrophoretic separation, and quantitation of reaction products, apart from the continuous loss of substrate by radioactive decay. We have used stable, double fluorescent end-labeled RNA substrates. Fluorescence of one fluorophore is quenched by intramolecular energy transfer (FRET). Upon substrate cleavage, both dyes become separated in two RNA products and fluorescence is restored. This can be followed in real time and ribozyme reactions can be analyzed under multiple (substrate excess) and under single (ribozyme excess) turnover conditions. A detailed comparison of unlabeled, single, and double fluorescent-labeled RNAs revealed moderate kinetic differences. Results with two systems, hammerhead ribozymes in I/II (small ribozyme, large substrate) and in I/III format (large ribozyme, small substrate), are reported. PMID:10573125

  3. Luminescence investigation of photosensitizer distribution in skin: correlation of singlet oxygen kinetics with the microarchitecture of the epidermis.

    PubMed

    Schlothauer, Jan C; Falckenhayn, Julian; Perna, Tobias; Hackbarth, Steffen; Röder, Beate

    2013-11-01

    This is the first study showing that singlet oxygen kinetics of topically applied photosensitizers coincides with the microarchitecture of skin, e.g., fissures and hair follicles. The kinetics indicate a chemical interaction of singlet oxygen with the skin, which allows differentiating between residual crème, e.g., in the follicular orifice, and photosensitizer penetrated into the skin. We show the feasibility of an easy-to-use fiber optic application providing the opportunity for in situ investigation, as well as a setup with focused optics for high-resolution two-dimensional scanning of singlet oxygen luminescence kinetics in skin samples. The results show that time-resolved singlet oxygen luminescence detection in tissue is a desirable tool for medical therapy, diagnostics, and evaluation of singlet oxygen interaction with biological environments. PMID:24194061

  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 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

  6. 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. PMID:12693814

  7. 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.

  8. 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...

  9. 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

    2016-03-01

    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. PMID:26717836

  10. 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+). PMID:26692518

  11. A rapid kinetic dye test to predict the adsorption of 2-methylisoborneol onto granular activated carbons and to identify the influence of pore volume distributions.

    PubMed

    Greenwald, Michael J; Redding, Adam M; Cannon, Fred S

    2015-01-01

    The authors have developed a kinetic dye test protocol that aims to predict the competitive adsorption of 2-methylisoborneol (MIB) to granular activated carbons (GACs). The kinetic dye test takes about two hours to perform, and produces a quantitative result, fitted to a model to yield an Intraparticle Diffusion Constant (IDC) during the earlier times of dye sorption. The dye xylenol orange was probed into six coconut-based GACs and five bituminous-based GACs that hosted varied pore distributions. Correlations between xylenol orange IDCs and breakthrough of MIB at 4 ppt in rapid small-scale column tests (RSSCTs) were found with R²s of 0.85 and 0.95 for coconut carbons that processed waters with total organic carbon (TOCs) of 1.9 and 2.2 ppm, respectively, and with an R² of 0.94 for bituminous carbons that processed waters with a TOC of 2.5 ppm. The author sought to study the influence of the pore sizes, which provide the adsorption sites and the diffusion conduits that are necessary for the removal of those compounds. For coconut carbons, a linear correlation was established between the xylenol orange IDCs and the volume of pores in the range of 23.4-31.8 Å widths (R² = 0.98). For bituminous carbons, best correlation was to pores ranging from 74 to 93 Å widths (R² = 0.94). The differences in adsorption between coconut carbons and bituminous carbons have been attributed to the inherently dissimilar graphene layering resulting from the parent materials and the activation processes. When fluorescein dye was employed in the kinetic dye tests, the correlations to RSSCT-MIB performance were not as high as when xylenol orange was used. Intriguingly, it was the same pore size ranges that exhibited the strongest correlation for MIB RSSCT's, xylenol orange kinetics, and fluoroscein kinetics. When methylene blue dye was used, sorption occurred so rapidly as to be out of the scope of the IDC model. PMID:25462782

  12. 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.

  13. An Experimental Approach Using Vesicle Size Distribution (VSD) to Investigate the Kinetics of Vesiculation

    NASA Astrophysics Data System (ADS)

    Nicholis, M. G.; Kilinc, A. I.

    2001-05-01

    The exsolution of volatiles in magma initiates the formation of gas bubbles as a result of the development of a state of supersaturation from either magma ascending in the conduit, decrease in temperature, or the crystallization of anhydrous solid phases. In this analysis bubble-free rhyolitic glasses were isothermally decompressed in a series of controlled nucleation experiments to investigate the kinetics of bubble nucleation and growth. A two-fold approach was used to synthetically saturate the high silica melt. The first method is based on using blocks of solid obsidian placed in gold capsules with > 10 wt.% H2O and saturated for 72 hours. The second technique uses powdered obsidian that was saturated with H2O at a given pressure and temperature for 48 hours, quenched, reground, and then repeated one more time. The use of powdered obsidian in the second method evenly saturates the melt by minimizing the volume to surface area ratio, hence the diffusion distance. In all experiments glass charges were saturated with H2O at 100 MPa and 850\\deg C, and than isothermally decompressed at a rate of approximately 0.26 MPa/sec to a final confining pressure of 30, 50, and 70 MPa. Samples were held at the final pressure for a period ranging from 5 to 300 seconds (residence time) to allow for nucleation to take place. Bubble-bearing glass charges were cut, polished, imaged under SEM and Nikon petrographic microscopes, and digitally analyzed with "Scion Image". All glass charges produced by the block method contained either no bubbles or only a few bubbles. The only indication of bubble nucleation was limited in a zone on the outer periphery of the glass charges. This leads us to believe that in the block method the time given for hydration was insufficient for homogeneous saturation of the melt. We directed our attention to the bubble-bearing glasses generated by the powder experiments. Vesicle Size Distribution (VSD) was used to determine the kinetic behavior of bubbles

  14. 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.

  15. Enzyme Kinetics of the Mitochondrial Deoxyribonucleoside Salvage Pathway Are Not Sufficient to Support Rapid mtDNA Replication

    PubMed Central

    Gandhi, Vishal V.; Samuels, David C.

    2011-01-01

    Using a computational model, we simulated mitochondrial deoxynucleotide metabolism and mitochondrial DNA replication. Our results indicate that the output from the mitochondrial salvage enzymes alone is inadequate to support a mitochondrial DNA replication duration of as long as 10 hours. We find that an external source of deoxyribonucleoside diphosphates or triphosphates (dNTPs), in addition to those supplied by mitochondrial salvage, is essential for the replication of mitochondrial DNA to complete in the experimentally observed duration of approximately 1 to 2 hours. For meeting a relatively fast replication target of 2 hours, almost two-thirds of the dNTP requirements had to be externally supplied as either deoxyribonucleoside di- or triphosphates, at about equal rates for all four dNTPs. Added monophosphates did not suffice. However, for a replication target of 10 hours, mitochondrial salvage was able to provide for most, but not all, of the total substrate requirements. Still, additional dGTPs and dATPs had to be supplied. Our analysis of the enzyme kinetics also revealed that the majority of enzymes of this pathway prefer substrates that are not precursors (canonical deoxyribonucleosides and deoxyribonucleotides) for mitochondrial DNA replication, such as phosphorylated ribonucleotides, instead of the corresponding deoxyribonucleotides. The kinetic constants for reactions between mitochondrial salvage enzymes and deoxyribonucleotide substrates are physiologically unreasonable for achieving efficient catalysis with the expected in situ concentrations of deoxyribonucleotides. PMID:21829339

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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. PMID:11204548

  1. Kinetics and activation energy of recrystallization of intracellular ice in mouse oocytes subjected to interrupted rapid cooling✧

    PubMed Central

    Seki, Shinsuke; Mazur, Peter

    2009-01-01

    Intracellular ice formation (IIF) is almost invariably lethal. In most cases, it results from the too rapid cooling of cells to below −40°C, but in some cases it is manifested, not during cooling, but during warming when cell water that vitrified during cooling first devitrifies and then recrystallizes during warming. Recently, Mazur et al. [Cryobiol. 55 (2007) 158] dealt with one such case in mouse oocytes. It involved rapidly cooling the oocytes to −25°C, holding them 10 min, rapidly cooling them to −70°C, and warming them slowly until thawed. No IIF occurred during cooling but intracellular freezing, as evidenced by blackening of the cells, became detectable at −56°C during warming and was complete by −46°C. The present study differs in that the oocytes were warmed rapidly from −70°C to temperatures between −65°C and −50°C and held for 3 to 60 min. This permitted us to determine the rate of blackening as function of temperature. That in turn allowed us to calculate the activation energy (Ea) for the blackening process; namely, 27.5 kcal/mole. This translates to about a quadrupling of the blackening rate for every 5° rise in temperature. These data then allowed us to compute the degree of blackening as a function of temperature for oocytes warmed at rates ranging from 10 to 10,000°C/min. A 10-fold increase in warming rate increased the temperature at which a given degree of blackening occurred by 8°C. These findings have significant implications both for cryobiology and cryo-electron microscopy. PMID:18359013

  2. 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)

  3. 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

  4. Physiologically based pharmacokinetic modeling to investigate regional brain distribution kinetics in rats.

    PubMed

    Westerhout, Joost; Ploeger, Bart; Smeets, Jean; Danhof, Meindert; de Lange, Elizabeth C M

    2012-09-01

    One of the major challenges in the development of central nervous system (CNS)-targeted drugs is predicting CNS exposure in human from preclinical data. In this study, we present a methodology to investigate brain disposition in rats using a physiologically based modeling approach aiming at improving the prediction of human brain exposure. We specifically focused on quantifying regional diffusion and fluid flow processes within the brain. Acetaminophen was used as a test compound as it is not subjected to active transport processes. Microdialysis probes were implanted in striatum, for sampling brain extracellular fluid (ECF) concentrations, and in lateral ventricle (LV) and cisterna magna (CM), for sampling cerebrospinal fluid (CSF) concentrations. Serial blood samples were taken in parallel. These data, in addition to physiological parameters from literature, were used to develop a physiologically based model to describe the regional brain pharmacokinetics of acetaminophen. The concentration-time profiles of brain ECF, CSF(LV), and CSF(CM) indicate a rapid equilibrium with plasma. However, brain ECF concentrations are on average fourfold higher than CSF concentrations, with average brain-to-plasma AUC(0-240) ratios of 121%, 28%, and 35% for brain ECF, CSF(LV), and CSF(CM), respectively. It is concluded that for acetaminophen, a model compound for passive transport into, within, and out of the brain, differences exist between the brain ECF and the CSF pharmacokinetics. The physiologically based pharmacokinetic modeling approach is important, as it allowed the prediction of human brain ECF exposure on the basis of human CSF concentrations. PMID:22588644

  5. Interaction of circadian rhythm and opiate-induced thermic and kinetic responses: a biotelemetric investigation.

    PubMed

    Dafters, R I; Taggart, P

    1990-01-01

    The thermic and kinetic effects of a low dose of morphine sulphate (5mg/kg) were monitored using a remote biotelemetric procedure. Drug and control (saline) injections were administered at two times of day, during the high and low phases of the circadian temperature/activity cycle respectively. Standard measures of the responses revealed that the effect of a dose of morphine differs significantly according to the phase of the circadian rhythm in which it is administered. In contrast to previous studies employing standard stress-inducing rectal probing techniques of temperature measurement, the direction and time-course of thermic and kinetic responses were uncorrelated. The implications for research on physiological and behavioral drug effects and for theories of drug tolerance/dependence are considered. PMID:2266784

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

    PubMed

    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 × 10(9) 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. PMID:27554414

  7. In situ investigation of mesoporous silicon oxidation kinetics using infrared emittance spectroscopy.

    PubMed

    Bardet, Benjamin; De Sousa Meneses, Domingos; Defforge, Thomas; Billoué, Jérôme; Gautier, Gaël

    2016-07-21

    In this paper, we study the thermal oxidation kinetics of mesoporous silicon layers, synthesized by electrochemical anodization, from 260 °C up to 1100 °C. A specific apparatus is employed to heat the mesoporous samples in air and to record at the same time their infrared emittance. Based on Bruggeman effective medium approximation, an optical model is set up to realistically approximate the dielectric function of the porous material with an emphasis on the surface chemistry and oxide content. A transition temperature of 600 °C is evidenced from data processing which gives evidence of two oxidation mechanisms with distinct kinetics. Between 260-600 °C, the oxidation is surface-limited with kinetics dependent on the hydrogen desorption rate. However, above 600 °C, the oxide growth is limited by oxygen diffusion through the existing oxide layer. A parabolic law is employed to fit the oxidation rate and to extract the high-temperature activation energy (EA = 1.5 eV). A precise control of the oxide growth can thus be achieved. PMID:27333267

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

    SciTech Connect

    Morrison, Glenn C.

    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

  9. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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. The reactions are found to be first order and the rate constants are 0.033 s-1 M-1, 0.020 s-1 M-1 and 0.67 s-1 M-1 for reactions with PC, Li ion and Tris(pentafluorophenyl)borane, respectively.

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

    DOE PAGESBeta

    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 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

  12. 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.

  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. 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.

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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. PMID:21619017

  20. Non-LTE Kinetics Modeling and Experimental Investigation of VUV Emission from Low Temperature Nobel Gas Plasmas

    NASA Astrophysics Data System (ADS)

    Szilagyi, John; Parchamy, Homaira; Masnavi, Majid; Richardson, Martin; One Team

    2013-10-01

    The VUV light sources have applications in various scientific and engineering fields, such as semiconductor industry, nanometer processing, and photochemistry. A detailed multilevel non-LTE atomic model is developed to investigate emissivity and absorption properties of low temperature Nobel gas plasmas around 80 nm based on the Yb/Al multilayer mirrors. We will present the optimum regions for conversion efficiency of Nobel gas targets against target density and laser parameters by means of 1D hydrodynamic coupled to a developed population kinetics codes. We discuss in detailed predictions by comparing calculations to our experimental results.

  1. 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.

  2. 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

  3. Investigation of multiple roots of the resistive wall mode dispersion relation, including kinetic effects

    SciTech Connect

    Berkery, J. W.; Sabbagh, S. A.; Betti, R.

    2011-07-15

    The resistive wall mode instability in tokamak plasmas has a complex frequency which can be determined by a dispersion relation that is cubic, in general, leading to three distinct roots. A simplified model of the dispersion relation, including kinetic effects, is presented and used to explore the behavior of these roots. By changing the plasma rotation frequency, it is shown that one root has a slow mode rotation frequency (less than the inverse wall time) while the other two rotate more quickly, one leading and one lagging the plasma rotation frequency. When realistic experimental parameters from the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)] are used, however, only one slow rotating, near-marginal stability root is found, consistent with present experiments and more detailed calculations with the MISK code [B. Hu et al., Phys. Plasmas 12, 057301 (2005)]. Electron collisionality acts to stabilize one of the rotating roots, while ion collisionality can stabilize the other. In devices with low rotation and low collisionality, these two rotating roots may manifest themselves, but they are likely to remain stable.

  4. Human enteropeptidase light chain: Bioengineering of recombinants and kinetic investigations of structure and function

    PubMed Central

    Smith, Eliot T; Johnson, David A

    2013-01-01

    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 × 106M−1sec−1) and DDDDR (kcat/KM = 1.89 × 107M−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. PMID:23436726

  5. A high throughput method to investigate oligodeoxyribonucleotide hybridization kinetics and thermodynamics.

    PubMed Central

    Mazumder, A; Majlessi, M; Becker, M M

    1998-01-01

    We describe a high throughput microtiter-based assay to measure binding of oligodeoxyribonucleotides to nucleic acid targets. The assay utilizes oligodeoxyribonucleotide probes labeled with a highly chemiluminescent acridinium ester (AE). Reaction of AE with sodium sulfite renders it non-chemiluminescent. When an AE-labeled probe hybridizes to a target nucleic acid AE is protected from reaction with sodium sulfite and thus remains chemiluminescent. In contrast, unhybridized probe readily reacts with sodium sulfite and is rendered non-chemiluminescent. Hybridization of an AE-labeled probe to a target nucleic acid can therefore be detected without physical separation of unhybridized probe by treatment of the hybridization reaction with sodium sulfite and measurement of the remaining chemiluminescence. Using this method we measured hybridization rate constants and thermodynamic affinities of oligodeoxyribonucleotide probes binding to simple synthetic targets as well as large complex biological targets. The kinetic and thermodynamic parameters were measured with a high degree of accuracy and were in excellent agreement with values measured by other established techniques. PMID:9518495

  6. 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.

  7. 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. PMID:24514660

  8. Investigation of metal binding and activation of Escherichia coli glyoxalase I: kinetic, thermodynamic and mutagenesis studies.

    PubMed Central

    Clugston, Susan L; Yajima, Rieko; Honek, John F

    2004-01-01

    GlxI (glyoxalase I) isomerizes the hemithioacetal formed between glutathione and methylglyoxal. Unlike other GlxI enzymes, Escherichia coli GlxI exhibits no activity with Zn(2+) but maximal activation with Ni(2+). To elucidate further the metal site in E. coli GlxI, several approaches were undertaken. Kinetic studies indicate that the catalytic metal ion affects the k (cat) without significantly affecting the K (m) for the substrate. Inductively coupled plasma analysis and isothermal titration calorimetry confirmed one metal ion bound to the enzyme, including Zn(2+), which produces an inactive enzyme. Isothermal titration calorimetry was utilized to determine the relative binding affinity of GlxI for various bivalent metals. Each metal ion examined bound very tightly to GlxI with an association constant ( K (a))>10(7) M(-1), with the exception of Mn(2+) ( K (a) of the order of 10(6) M(-1)). One of the ligands to the catalytic metal, His(5), was altered to glutamine, a side chain found in the Zn(2+)-active Homo sapiens GlxI. The affinity of the mutant protein for all bivalent metals was drastically decreased. However, low levels of activity were now observed for Zn(2+)-bound GlxI. Although this residue has a marked effect on metal binding and activation, it is not the sole factor determining the differential metal activation between the human and E. coli GlxI enzymes. PMID:14556652

  9. Removal of Anionic Dyes from Water by Potash Alum Doped Polyaniline: Investigation of Kinetics and Thermodynamic Parameters of Adsorption.

    PubMed

    Patra, Braja N; Majhi, Deola

    2015-06-25

    Polyaniline was synthesized by the oxidative polymerization method by using ammonium persulfate as an oxidant. The positive charge in the backbone of the polymer was generated by using Potash alum as a dopant. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray fluorescence (XRF), and X-ray diffraction (XRD) techniques were used for characterization of doped polyaniline. The doped polyaniline can be used for selective adsorption of various dyes (selectively sulfonated dyes) from aqueous solution. Adsorption studies regarding the effect of contact time, initial dye concentration, pH, doses of adsorbent, and temperature on adsorption kinetics were investigated. The influence of other anions like Cl(-), NO3(-), and SO4(2-) on the adsorption density of dyes onto doped polyaniline was also explored. Langmuir isotherm and pseudo-second-order kinetics were found to be the most appropriate models to describe the removal of anionic dyes from water through adsorption. Thermodynamic parameters such as free energy (ΔG(0)), enthalpy (ΔH(0)), and entropy (ΔS(0)) changes were also evaluated. The interaction of dyes with doped polyaniline was also investigated by FTIR and UV spectroscopy. PMID:26079693

  10. 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.

  11. Inactivation of yeast hexokinase by Cibacron Blue 3G-A: spectral, kinetic and structural investigations.

    PubMed Central

    Puri, R N; Roskoski, R

    1994-01-01

    Yeast hexokinase, a homodimer (100 kDa), is an important enzyme in the glycolytic pathway. Although Cibacron Blue 3G-A (Reactive Blue 2) has been previously shown to inactivate yeast hexokinase, no comprehensive study exists concerning the nature of interaction(s) between hexokinase and the blue dye. A comparison of the computer-generated three-dimensional (3D) representations showed considerable overlap of the purine ring of ATP, a nucleotide substrate of hexokinase, with the hydrophobic anthraquinone moiety of the blue dye. The visible spectrum of the blue dye showed a characteristic absorption band centred at 628 nm. The visible difference spectrum of increasing concentration of the dye and the same concentrations of the dye plus a fixed concentration of hexokinase exhibited a maximum, a minimum and an isobestic point at 683, 585, and 655 nm respectively. The visible difference spectrum of the blue dye and the dye in 50% ethylene glycol showed a maximum and a minimum at 660 and 570 nm respectively. The visible difference spectrum of the blue dye in the presence of the dye and hexokinase modified at the active site by pyridoxal phosphate, iodoacetamide and o-phthalaldehyde was devoid of bands characteristic of the hexokinase-blue dye complex. Size-exclusion-chromatographic studies in the absence or presence of guanidinium chloride showed that the enzyme inactivated by the blue dye was co-eluted with the unmodified enzyme. The dialysis residue obtained after extensive dialysis of the gel-filtered complex, against a buffer of high ionic strength, showed an absorption maximum at 655 nm characteristic of the dye-enzyme complex. Inactivation data when analysed by 'Kitz-Wilson'-type kinetics for an irreversible inhibitor, yielded values of 0.05 min-1 and 92 microM for maximum rate of inactivation (k3) and dissociation constant (Kd) for the enzyme-dye complex respectively. Sugar and nucleotide substrates protected hexokinase against inactivation by the blue dye. About 2

  12. 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

  13. Spin-label oximetry: kinetic study of cell respiration using a rapid-passage T1-sensitive electron spin resonance display.

    PubMed Central

    Froncisz, W; Lai, C S; Hyde, J S

    1985-01-01

    An unusual ESR display has been developed that exhibits sensitivity to bimolecular collisions of dissolved oxygen in water with nitroxide radical spin probes at oxygen concentrations as low as 0.1 microM, requiring only 1 microliter of sample. The method involves observation of the ESR rapid-passage signal when tuned to the dispersion using a loop-gap resonator. The bimolecular collision rate determines the phase of the signal. The method has been used in a closed-chamber geometry to study respiration of asynchronous populations of Chinese hamster ovary (CHO) cells. An integral of the Michaelis-Menten equation permits direct comparison with experiment and is shown to be incompatible with the data. The theory of diffusion limitation also is developed and shown to be inconsistent with experiment. The average oxygen concentration is found to decrease as Vmaxt, where t is the time after sealing the chamber, to a critical oxygen concentration of 5.2 microM. Below 5.2 microM, the concentration can be fitted to an exponential form, exp(-t/tau), where tau = 15 sec for 4000 cells per microliter. It is believed that this experimental behavior is determined by complex enzyme kinetics. PMID:2982155

  14. Kinetics of Antiviral Activity by Human Immunodeficiency Virus Type 1-Specific Cytotoxic T Lymphocytes (CTL) and Rapid Selection of CTL Escape Virus In Vitro

    PubMed Central

    Van Baalen, C. A.; Schutten, M.; Huisman, R. C.; Boers, P. H. M.; Gruters, R. A.; Osterhaus, A. D. M. E.

    1998-01-01

    The antiviral activity of a CD8+ cytotoxic T-lymphocyte (CTL) clone (TCC108) directed against a newly identified HLA-B14-restricted epitope, human immunodeficiency virus type 1 (HIV-1) Rev(67-75) SAEPVPLQL, was analyzed with respect to its kinetics of target cell lysis and inhibition of HIV-1 production. Addition of TCC108 cells or CD8+ reverse transcriptase-specific CTLs to HLA-matched CD4+ T cells at different times after infection with HIV-1 IIIB showed that infected cells became susceptible to CTL-mediated lysis before peak virus production but after the onset of progeny virus release. When either of these CTLs were added to part of the infected cells immediately after infection, p55 expression and virus production were significantly suppressed. These data support a model in which CTLs, apart from exerting cytolytic activity which may prevent continued virus release, can interfere with viral protein expression during the eclipse phase via noncytolytic mechanisms. TCC108-mediated inhibition of virus replication in peripheral blood mononuclear cells caused rapid selection of a virus with a mutation (69E→K) in the Rev(67-75) CTL epitope which abolished recognition by TCC108 cells. Taken together, these data suggest that both cytolytic and noncytolytic antiviral mechanisms of CTLs can be specifically targeted to HIV-1-infected cells. PMID:9658134

  15. 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.

  16. Kinetic investigation of the relationship between the efficiency of columns and their diameter.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2011-03-25

    Many brands of packing materials made of fine particles are now available in both conventional (4.6 mm i.d.) and narrow-bore (2.1 mm i.d.) columns. It is a general observation that the efficiency of the former tends to be markedly higher than that of the latter. This report provides a detailed illustration of the characteristics of this enigma. The corrected reduced plate heights of three brands of columns packed with shell particles in 4.6 and 2.1 mm I.D. columns were measured. The brands were the 1.7 and 2.6 μm Kinetex-C(18) (Phenomenex, Torrance, CA, USA), the 2.7 μm Poroshell120-C(18) (Agilent Technologies, New Castle, DE, USA), and the 2.7 μm Halo-C(18) (Advanced Material Technologies, Wilmington, DE, USA). The extra-column contributions were minimized by optimizing the configuration of the instrument (injection volume <1.0 μL, 115 μm needle seat capillary, 80 μm connecting tubes, no heat exchanger, 0.8 μL detection cell). The correct peak variances were derived from the numerical integration of the first and second order moments of the experimental band profiles. These experimental results confirm that the kinetic performance of narrow-bore columns is inferior to that of conventional columns for all three brands of shell particles. We demonstrate that this difference is accounted for by a contribution to the column HETP of the long-range eddy diffusion term that is larger in the 2.1 than in the 4.6 mm I.D. columns. While the associated relative velocity biases are of comparable magnitude in both types of columns, the characteristic radial diffusion lengths are of the order of 100 and 40 μm in the wall regions of narrow-bore and conventional columns, respectively. PMID:21333293

  17. 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. PMID:16509335

  18. 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

  19. 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

    2016-01-01

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  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. 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.

  3. 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.

  4. Rapid investigation of cases and clusters of Legionnaires' disease in England and Wales using direct molecular typing.

    PubMed

    Mentasti, Massimo; Afshar, Baharak; Collins, Samuel; Walker, Jimmy; Harrison, Timothy G; Chalker, Vicki

    2016-06-01

    Legionella pneumophila is the leading cause of Legionnaires' disease, a severe pneumonia that can occur as sporadic cases or point-source outbreaks affecting multiple patients. The infection is acquired by inhalation of aerosols from contaminated water systems. In order to identify the probable source and prevent further cases, clinical and environmental isolates are compared using phenotypic and genotypic methods. Typically up to 10 days are required to isolate L. pneumophila prior to the application of standard typing protocols. A rapid protocol using a real-time PCR specific for L. pneumophila and serogroup 1, combined with nested direct molecular typing, was adopted by Public Health England in 2012 to reduce reporting time for preliminary typing results. This rapid protocol was first used to investigate an outbreak that occurred in July/August 2012 and due to the positive feedback from that investigation, it was subsequently applied to other incidents in England and Wales where faster typing results would have aided incident investigation. We present here results from seven incidents that occurred between July 2012 and June 2015 where the use of this rapid approach provided preliminary characterization of the infecting strain in an average 1.58 days (SD 1.01) after sample receipt in contrast to 9.53 days (SD 3.73) when standard protocols were applied. PMID:27046155

  5. 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.

  6. 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

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

    2012-02-01

    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 (f(met)) 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 metabolite

  7. 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

  8. 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

  9. 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.

  10. Investigation of a passenger car's dynamic response due to a flywheel-based kinetic energy recovery system

    NASA Astrophysics Data System (ADS)

    Bischof, Günter; Reisinger, Karl; Singraber, Thomas; Summer, Andreas

    2014-02-01

    With the advent of flywheel-based kinetic energy recovery systems in automotive applications new safety issues arise as a consequence of the flywheel's high rotational speed. While the special structural safety requirements of the components are well discussed in the literature, there is still little research on the influence of gyroscopic effects on vehicle dynamics. The aim of this paper is to investigate the influence of a typical high-speed flywheel on the driving dynamics of an average passenger car. To this end the equations of motion of a gyroscope are derived, which relate the vehicle's roll, pitch and yaw rate with the transverse torque acting on the flywheel. These equations are implemented in a commercial vehicle dynamics simulation program in order to determine the reaction torques acting on the vehicle within a representative range of driving situations. Numerical simulations indicate that the gyroscopic effect can be considered insignificant in standard driving situations.

  11. First-principles-based investigation of kinetic mechanism of SiC(0001) dry oxidation including defect generation and passivation

    NASA Astrophysics Data System (ADS)

    Gavrikov, Alexey; Knizhnik, Andrey; Safonov, Andrey; Scherbinin, Andrey; Bagatur'yants, Alexander; Potapkin, Boris; Chatterjee, Aveek; Matocha, Kevin

    2008-11-01

    The key stages of the dry oxidation of the SiC(0001) surface are analyzed based on first-principles calculations. It is found that an abrupt SiC/SiO2 interface model results in a large activation barrier of oxygen penetration to the silicon carbide, and thus the penetration is probably the rate-limiting step for the entire dry-oxidation process. The subsequent reactions of SiC oxidation after oxygen penetration are investigated, and it is found that CO release is competing with carbon dimer formation. These dimers probably are responsible for near-interface traps in the silica layer generated during SiC oxidation. The possible passivation reactions of a carbon dimer defect by active species, such as O2, NO, and H2 are investigated. It is found that an oxygen molecule can break a Si-C bond via dissociation in the triplet state and finally can produce two CO molecules from the carbon dimer defect. The NO molecule can easily break a Si-C bond of a carbon dimer defect and form cyano groups -CN, which can finally recombine to form a C2N2 molecule. This molecule can hardly diffuse in silica matrix, and it is suggested that it is further oxidized by an NO molecule to CO and N2 molecules. It is suggested that the process of passivation by O2 and NO molecules is restricted by the incorporation of these molecules in small voids near the carbon defect. Based on the calculated results, a simple kinetic mechanism of dry SiC oxidation is proposed and kinetic modeling of the oxidation process is performed. It is found that in the framework of this mechanism, the carbon defect density should weakly depend on temperature.

  12. Effect of low-level laser therapy after rapid maxillary expansion: a clinical investigation.

    PubMed

    Garcia, Valentin Javier; Arnabat, J; Comesaña, Rafael; Kasem, Khaled; Ustrell, Josep Maria; Pasetto, Stefano; Segura, Oscar Pozuelo; ManzanaresCéspedes, Maria Cristina; Carvalho-Lobato, Patricia

    2016-08-01

    To evaluate the effectiveness low-level laser therapy (LLLT) on the repair of the mid palatal suture, after rapid maxillary expansion (RME). A single-operator, randomized single-blind placebo-controlled study was performed at the Orthodontic Department at the Dental Hospital of Bellvitge. Barcelona University, Hospitalet de Llobregat, Spain. Thirty-nine children (range 6-12 years old), completed RME and were randomized to receive active LLLT (n = 20) or placebo (n = 19). The laser parameters and dose were 660 nm, 100 mW, CW, InGaAlP laser, illuminated area 0.26 cm(2), 332 mW/cm(2), 60 s to four points along midpalatal suture, and 30 s to a point each side of the suture. A total of seven applications were made on days 1, 7, 14, 28, 42, 56, and 70 of the retention phase RME. A cone beam computed tomography (CBCT) scan was carried out on the day of the first laser treatment, and at day 75, a second CBCT scan was performed. Two radiologists synchronized the slices of two scans to be assessed. P = 0.05 was considered to be statistically significant. At day 75 of the suture, the irradiated patients presented a greater percentage of approximate zones in the anterior (p = 0.008) and posterior (p = 0.001) superior suture-and less approximation in the posterior superior suture (p = 0.040)-than the placebo group. LLLT appears to stimulate the repair process during retention phase after RME. PMID:27236292

  13. 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. PMID:26527347

  14. 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}.

  15. Mechanistic and kinetic investigation on OH-initiated oxidation of tetrabromobisphenol A.

    PubMed

    He, Maoxia; Li, Xin; Zhang, Shiqing; Sun, Jianfei; Cao, Haijie; Wang, Wenxing

    2016-06-01

    Detailed mechanism of the OH-initiated transformation of tetrabromobisphenol A (TBBPA) has been investigated by quantum chemical methods in this paper. Abstraction reactions of hydrogen atoms from the OH groups and CH3 groups of TBBPA are the dominant pathways of the initial reactions. The produced phenolic-type radical and alkyl-type radical may transfer to 4,4'-(ethene-1,1-diyl)bis(2,6-dibromophenol), 4-acetyl-2,6-dibromophenol and 2,6-dibromobenzoquinone at high temperature. In water, major products are 2,6-dibromo-p-hydroquinone, 4-isopropylene-2,6-dibromophenol and 4-(2-hydroxyisopropyl)-2,6-dibromophenol resulting from the addition reactions. Total rate constants of the initial reaction are 1.02 × 10(-12) cm(3) molecule(-1) s(-1) in gas phase and 1.93 × 10(-12) cm(3) molecule(-1) s(-1) in water at 298 K. PMID:27018518

  16. 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. PMID:26713669

  17. A Microfluidic Device for the Investigation of Rapid Gold Nanoparticle Formation in Continuous Turbulent Flow

    NASA Astrophysics Data System (ADS)

    Hofmann, G.; Tofighi, G.; Rinke, G.; Baier, S.; Ewinger, A.; Urban, A.; Wenka, A.; Heideker, S.; Jahn, A.; Dittmeyer, R.; Grunwaldt, J.-D.

    2016-05-01

    A new setup with an integrated microfluidic chip with small dead time, high time resolution and compatibility with in situ X-ray absorption (XAS) measurements is presented. It can also be combined with a free liquid jet. By using the microfluidic chip the short reaction times from 2 to 20 milliseconds can be observed, beyond that an external cyclone mixer for extended observation times was applied. The reduction of gold ions with tetrakis(hydroxy-methyl)phosphonium (THPC) has been investigated in the microfluidic setup to monitor this reaction yielding small gold nanoparticles, requiring preferentially a free liquid jet.

  18. Kinetics investigation of the hydrogen abstraction reaction between CH3SS and CN radicals.

    PubMed

    Yan, Liu; Wenliang, Wang; Zhongwen, Liu; Hongjiang, Ren

    2016-01-01

    The reaction mechanisms and rates for the H abstraction reactions between CH3SS and CN radicals in the gas phase were investigated with density functional theory (DFT) methods. The geometries, harmonic vibrational frequencies, and energies of all stationary points were obtained at B3PW91/6-311G(d,p) level of theory. Relationships between the reactants, intermediates, transition states and products were confirmed, with the frequency and the intrinsic reaction coordinate (IRC) analysis at the same theoretical level. High accurate energy information was provided by the G3(MP2) method combined with the standard statistical thermodynamics. Gibbs free energies at 298.15 K for all of the reaction steps were reported, and were used to describe the profile diagrams of the potential energy surface. The rate constants were evaluated with both the classical transition state theory and the canonical variational transition state theory, in which the small-curvature tunneling correction was included. A total number of 9 intermediates (IMs) and 17 transition states (TSs) were obtained. It is shown that IM1 is the most stable intermediate by the largest energy release, and the channel of CH3SS + CN → IM3 → TS10  → P1(CH2SS + HCN) is the dominant reaction with the lowest energy barrier of 144.7 kJ mol(-1). The fitted Arrhenius expressions of the calculated CVT/SCT rate constants for the rate-determining step of the favorable channel is k =7.73 × 10(6)  T (1.40)exp(-14,423.8/T) s(-1) in the temperature range of 200-2000 K. The apparent activation energy E a(app.) for the main channel is -102.5 kJ mol(-1), which is comparable with the G3(MP2) energy barrier of -91.8 kJ mol(-1) of TS10 (relative to the reactants). PMID:26781664

  19. Kinetic and mechanism investigation on the gamma irradiation induced degradation of endosulfan sulfate.

    PubMed

    Shah, Noor S; Khan, Javed Ali; Nawaz, Shah; Ismail, M; Khan, Kifayatullah; Khan, Hasan M

    2015-02-01

    The gamma irradiation was investigated for potential removal of endosulfan sulfate, an emerging water pollutant and central nervous system disruptor. A removal efficiency of 99.5% of initially 1.30 μM endosulfan sulfate was observed at an absorbed dose of 1020 Gy. Aqueous electron (eaq(-)) was found to play primary role in the removal of endosulfan sulfate which was possibly due to greater reactivity of eaq(-) with endosulfan sulfate, considering the second-order rate constant of 8.1×10(9) and 3.4×10(10) M(-1) s(-1) for hydroxyl radical (·OH) and eaq(-), respectively, with endosulfan sulfate. The removal efficiency of endosulfan sulfate was affected by the pH of aqueous solution, with observed removal efficiency of 99.5%, 98.3% and 31.3% at pH 6.2, pH 10.0, and pH 2.6, respectively. The efficiency was also influenced by inorganic anions and humic acid in the order of nitrate>nitrite>bicarbonate>carbonate ≃ humic acid. The initial degradation rate increased while degradation constant decreased with increasing initial concentrations of endosulfan sulfate. The degradation pathways showed that oxidative pathway was initiated at the SO2 bond while reductive pathways at the chlorine attached to the ring of endosulfan sulfate. The mass balance showed removal of 98% chloride and 72% sulfate ions from endosulfan sulfate at an absorbed dose of 1020 Gy. The removal of endosulfan sulfate followed by subsequent loss of by-products under extended treatment showed that gamma irradiation is potential technique for the remediation of organic pollutants from a water environment. PMID:25466821

  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. 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.

  2. Optical and analytical investigations on dengue virus rapid diagnostic test for IgM antibody detection.

    PubMed

    Jahanshahi, Peyman; Sekaran, Shamala Devi; Adikan, Faisal Rafiq Mahamd

    2015-08-01

    Evaluation of binding between analytes and its relevant ligands on surface plasmon resonance (SPR) biosensor is of considerable importance for accurate determination and screening of an interference in immunosensors. Dengue virus serotype 2 was used as a case study in this investigation. This research work compares and interprets the results obtained from analytical analysis with the experimental ones. Both the theoretical calculations and experimental results are verified with one sample from each category of dengue serotypes 2 (low, mid, and high positive), which have been examined in the database of established laboratorial diagnosis. In order to perform this investigation, the SPR angle variations are calculated, analyzed, and then validated via experimental SPR angle variations. Accordingly, the error ratios of 5.35, 6.54, and 3.72% were obtained for the low-, mid-, and high-positive-specific immune globulins of patient serums, respectively. In addition, the magnetic fields of the biosensor are numerically simulated to show the effect of different binding mediums. PMID:25791696

  3. Investigating Satellite Formation Around the Rapidly Rotating, Oblong Asteroid 216 Kleopatra

    NASA Astrophysics Data System (ADS)

    Laipert, Frank; Minton, D. A.

    2013-05-01

    Abstract (2,250 Maximum Characters): Located in the asteroid belt, Kleopatra is an approximately 200 km long object shaped much like a dog bone. Recent observations have determined that two moons are in orbit about Kleopatra. Currently, it is not known how these moons, designated S/2008 ((216)) 1 and S/2008 ((216)) 2, came to orbit the asteroid, or how long these satellites have existed. Owing to the gravitational dynamics that result from Kleopatra's unusual shape and high spin rate, several equilibrium points exist near the asteroid, similar to the Lagrange points that result from the three-body dynamics in the Earth-Moon system. Using an ellipsoidal approximation for Kleopatra's gravity field, we show that a special class of trajectories pass through these equilibrium points and result in orbits very similar to the observed satellites. We use the unusual gravitational environment around Kleopatra to investigate a novel satellite formation mechanism. We combine simulations of particles moving in Kleopatra's gravity field with models of the collisional history of Kleopatra in the main belt to determine whether it is feasible for a satellite to form out of the material ejected from collisions over the lifetime of Kleopatra.

  4. 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.

  5. 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

  6. 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. PMID:25656488

  7. Reply to "Comment on `Single-point kinetic energy density functionals: A pointwise kinetic energy density analysis and numerical convergence investigation' "

    NASA Astrophysics Data System (ADS)

    Xia, Junchao; Carter, Emily A.

    2015-09-01

    We find that the multivalued character of the G factor as a function of the reduced gradient (s ) still exists after accounting for pseudopotential artifacts and the kinetic energy global upper bound. We also find that the VT84F functional indeed exhibits stable convergence and more reasonable results for self-consistent bulk properties compared to other generalized gradient approximation (GGA) kinetic energy density functionals (KEDFs) that we tested earlier. However, VT84F generally yields overestimated equilibrium volumes, which may result from its inability (as with all GGAs) to reproduce the G -s multivalued character. The analogous failure to predict the multivalued character of G as a function of the reduced density (d ) is also likely to be responsible for the inaccuracy of our vWGTF functionals reported earlier. Our multivaluedness analysis therefore does not impugn any particular GGA KEDF. Instead, it merely confirms the importance of pointwise analysis for improving KEDFs by emphasizing the need to resolve the multivaluedness of G with respect to various density variables.

  8. Steady-state kinetic investigation of cytochrome P450cam: interaction with redox partners and reaction with molecular oxygen.

    PubMed

    Purdy, Matthew M; Koo, Laura S; Ortiz de Montellano, Paul R; Klinman, Judith P

    2004-01-13

    Cytochrome P450cam (CYP101) is a prokaryotic monooxygenase that requires two proteins, putidaredoxin reductase (PdR) and putidaredoxin (Pdx), to supply electrons from NADH. This study addresses the mechanism by which electrons are transported from PdR to P450cam through Pdx and used to activate O(2) at the heme of P450cam. It is shown that k(cat)/Km(O2) is independent of the PdR concentration and hyperbolically dependent on Pdx. The phenomenon of saturation of reaction rates with either P450cam or PdR at high ratios of one enzyme to the other is investigated and shown to be consistent with a change in the rate limiting step. Either the reduction of Pdx by PdR (high P450) or the reduction of P450 by Pdx (high PdR) determines the rate. These data support a mechanism where Pdx acts as a shuttle for transport of electrons from PdR to P450cam, effectively ruling out the formation of a kinetically significant PdR/Pdx/P450cam complex. PMID:14705955

  9. 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.

  10. 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.

  11. Kinetics, equilibrium, and thermodynamics investigation on the adsorption of lead(II) by coal-based activated carbon.

    PubMed

    Yi, Zhengji; Yao, Jun; Zhu, Mijia; Chen, Huilun; Wang, Fei; Liu, Xing

    2016-01-01

    The goal of this research is to investigate the feasibility of using activated coal-based activated carbon (CBAC) to adsorb Pb(II) from aqueous solutions through batch tests. Effects of contact time, pH, temperature and initial Pb(II) concentration on the Pb(II) adsorption were examined. The Pb(II) adsorption is strongly dependent on pH, but insensitive to temperature. The best pH for Pb(II) removal is in the range of 5.0-5.5 with more than 90 % of Pb(II) removed. The equilibrium time was found to be 60 min and the adsorption data followed the pseudo-second-order kinetics. Isotherm data followed Langmuir isotherm model with a maximum adsorption capacity of 162.33 mg/g. The adsorption was exothermic and spontaneous in nature. The Fourier transform infrared spectroscopy and scanning electron microscopy analysis suggested that CBAC possessed a porous structure and was rich in carboxyl and hydroxyl groups on its surface, which might play a major role in Pb(II) adsorption. These findings indicated that CBAC has great potential as an alternative adsorbent for Pb(II) removal. PMID:27504258

  12. 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.

  13. 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

  14. 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. PMID:25879019

  15. 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

  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. In situ real-time investigation of kinetics of nucleation and growth of sol-gel-derived functional oxide thin films

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Hu, Hao; Pan, Zixiao; Li, Xuefa; Wang, Jin; Dravid, Vinayak P.

    2008-05-01

    Early-stage nucleation and growth kinetics of sol-gel-derived multiferroic BiFeO3 thin films were investigated in situ and in real time by combining transmission electron microscopy and grazing-incidence small-angle x-ray scattering (GISAXS). While the initial phase of the nuclei was identified to be Bi2O2CO3 , the quantitative GISAXS analysis unambiguously revealed that the early-stage kinetic nucleation growth in the thin films was dominated by an oriented-attachment mechanism as opposed to the conventional Ostwald ripening in metallic and ceramic systems.

  18. 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). PMID:25952849

  19. 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

  20. Rapid kinetic studies and structural determination of a cysteine proteinase mutant imply that residue 158 in caricain has a major effect upon the ability of the active site histidine to protonate a dipyridyl probe.

    PubMed

    Katerelos, N A; Goodenough, P W

    1996-11-26

    Cysteine proteinases are endopeptidases whose catalytic activity depends upon the nucleophilicity of the active site cysteine thiol group. An ion pair forms with an active site histidine. The presence in some cysteine proteinases of an aspartic acid close to the ion pair has been used as evidence of a "catalytic triad" as found in the serine proteinases. In these enzymes, the correct alignment of serine, histidine, and aspartate residues controls catalysis. However, the absence of the homologous aspartate residue in the mammalian cysteine proteinases cathepsins B and H argues against this pivotal role for aspartic acid. Instead, an Asn, physically close to the histidine in cysteine proteinases, has been proposed as a member of the catalytic triad. Protein engineering is being used to investigate these questions. In this study, the Asp158Glu mutant of the plant cysteine proteinase caricain was analyzed by stopped-flow rapid kinetics. The probe that was used was 2,2'-dipyridyl disulfide (2 PDS), and the profile of k versus pH gave results more closely allied to a small molecule active site model than the normal profile with cysteine proteinases. Multiple pKa's identified in the profile are as follows: pK1 = 3.4 (Cys 25), pK2 = 3.6, pK3 = 7.0, and pK4 = 8.6 (His 158). The structure of the enzyme with the bound inhibitor E64 was solved (R factor of 19.3%). Although the distance between the imadazolium and the surrounding charged amino acids is only slightly changed in the mutant, the reduced steady state activity and narrower pH range can be related to changes in the hydrogen-bonding capacity of the imadazolium. PMID:8942638

  1. 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.

  2. 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…

  3. 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. PMID:24704906

  4. 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. PMID:27295615

  5. 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.

  6. An in situ XAS investigation of the kinetics of the ammonolysis of Ga(2)O(3) and the oxidation of GaN.

    PubMed

    Brendt, J; Samuelis, D; Weirich, T E; Martin, M

    2009-05-01

    The ammonolysis of beta-Ga(2)O(3) to alpha-GaN and the oxidation of alpha-GaN to beta-Ga(2)O(3) have been studied by means of in situ X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). In situ X-ray absorption measurements on polycrystalline powder particles on the gallium K-edge during both reactions give detailed information about the reaction kinetics. We were able to extract this kinetics by fitting linear combinations of beta-Ga(2)O(3) and alpha-GaN spectra only. The kinetics of the ammonolysis can be described well by an extended Johnson-Mehl-Avrami-Kolmogorow model, while the oxidation kinetics can be modelled by a shrinking core model. Investigations by means of TEM and SEM support the assumptions in both models. Our experimental results and the models are discussed in terms of the reaction energetics and the reaction mechanisms. PMID:19370207

  7. 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.

  8. Physiological Role of Kv1.3 Channel in T Lymphocyte Cell Investigated Quantitatively by Kinetic Modeling

    PubMed Central

    Feng, Jing; Wang, Wei; Wu, Yingliang; Ding, Jiuping

    2014-01-01

    Kv1.3 channel is a delayed rectifier channel abundant in human T lymphocytes. Chronic inflammatory and autoimmune disorders lead to the over-expression of Kv1.3 in T cells. To quantitatively study the regulatory mechanism and physiological function of Kv1.3 in T cells, it is necessary to have a precise kinetic model of Kv1.3. In this study, we firstly established a kinetic model capable to precisely replicate all the kinetic features for Kv1.3 channels, and then constructed a T-cell model composed of ion channels including Ca2+-release activated calcium (CRAC) channel, intermediate K+ (IK) channel, TASK channel and Kv1.3 channel for quantitatively simulating the changes in membrane potentials and local Ca2+ signaling messengers during activation of T cells. Based on the experimental data from current-clamp recordings, we successfully demonstrated that Kv1.3 dominated the membrane potential of T cells to manipulate the Ca2+ influx via CRAC channel. Our results revealed that the deficient expression of Kv1.3 channel would cause the less Ca2+ signal, leading to the less efficiency in secretion. This was the first successful attempt to simulate membrane potential in non-excitable cells, which laid a solid basis for quantitatively studying the regulatory mechanism and physiological role of channels in non-excitable cells. PMID:24594979

  9. Investigation of the enzymatic mechanism of yeast orotidine-5'-monophosphate decarboxylase using sup 13 C kinetic isotope effects

    SciTech Connect

    Smiley, J.A.; Bell, J.B.; Jones, M.E. ); Paneth, P.; O'Leary, M.H. )

    1991-06-25

    Orotidine-5'-monophosphate decarboxylase (ODCase) from Saccharomyces cerevisiae displays an observed {sup 13}C kinetic isotope effect of 1.0247 {plus minus} 0.0008 at 25 C, pH 6.8. The observed isotope effect is sensitive to changes in the reaction medium, such as pH, temperature, or glycerol content. The value of 1.0494 {plus minus} 0.0006 measured at pH 4.0, 25 C, is not altered significantly by temperature or glycerol, and thus the intrinsic isotope effect for the reaction is apparently being observed under these conditions and decarboxylation is almost entirely rate-determining. These data require a catalytic mechanism with freely reversible binding and one in which a very limited contribution to the overall rate is made by chemical steps preceding decarboxylation; the zwitterion mechanism of Beak and Siegel, which involves only protonation of the pyrimidine ring, is such a mechanism. With use of an intrinsic isotope effect of 1.05, a partitioning factor of less than unity is calculated for ODCase at pH 6.0, 25 C. A quantitative kinetic analysis using this result excludes the possibility of an enzymatic mechanism involving covalent attachment of an enzyme nucleophile to C-5 of the pyrimidine ring. These data fit a kinetic model in which an enzyme proton necessary for catalysis is titrated at high pH, thus providing evidence for the catalytic mechanism of Beak and Siegal.

  10. 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

  11. Palladium-Catalyzed Dynamic Kinetic Asymmetric Transformations of Vinyl Aziridines with Nitrogen Heterocycles: Rapid Access to Biologically Active Pyrroles and Indoles

    PubMed Central

    Trost, Barry M.; Osipov, Maksim; Dong, Guangbin

    2010-01-01

    We report that nitrogen heterocycles can serve as competent nucleophiles in the palladium-catalyzed dynamic kinetic asymmetric alkylation of vinyl aziridines. The resulting alkylated products were obtained with high regio-, chemo-, and enantioselectivity. Both substituted 1H-pyrroles and 1H-indoles were successfully employed to give exclusively the branched N-alkylated products. The synthetic utility of this process was demonstrated by applying this method to the preparation of several medicinal chemistry lead compounds and bromopyrrole alkaloids including longamide B, longamide B methyl ester, hanishin, agesamides A and B, and cyclooroidin. PMID:20949972

  12. μ-Rainbow: CdSe Nanocrystal Photoluminescence Gradients via Laser Spike Annealing for Kinetic Investigations and Tunable Device Design.

    PubMed

    Treml, Benjamin E; Jacobs, Alan G; Bell, Robert T; Thompson, Michael O; Hanrath, Tobias

    2016-02-10

    Much of the promise of nanomaterials derives from their size-dependent, and hence tunable, properties. Impressive advances have been made in the synthesis of nanoscale building blocks with precisely tailored size, shape and composition. Significant attention is now turning toward creating thin film structures in which size-dependent properties can be spatially programmed with high fidelity. Nonequilibrium processing techniques present exciting opportunities to create nanostructured thin films with unprecedented spatial control over their optical and electronic properties. Here, we demonstrate single scan laser spike annealing (ssLSA) on CdSe nanocrystal (NC) thin films as an experimental test bed to illustrate how the size-dependent photoluminescence (PL) emission can be tuned throughout the visible range and in spatially defined profiles during a single annealing step. Through control of the annealing temperature and time, we discovered that NC fusion is a kinetically limited process with a constant activation energy in over 2 orders of magnitude of NC growth rate. To underscore the broader technological implications of this work, we demonstrate the scalability of LSA to process large area NC films with periodically modulated PL emission, resulting in tunable emission properties of a large area film. New insights into the processing-structure-property relationships presented here offer significant advances in our fundamental understanding of kinetics of nanomaterials as well as technological implications for the production of nanomaterial films. PMID:26536402

  13. 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. PMID:19810739

  14. 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. PMID:22752542

  15. 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.

  16. 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. PMID:24613971

  17. Investigation of the kinetics of the isothermal peritectoid formation of Zr 3Al and U 3Si

    NASA Astrophysics Data System (ADS)

    Chang-Kyu, Rhee; Su-Il, Pyun

    1991-12-01

    In the present work the kinetics of the isothermal peritectoid transformation have been critically evaluated in the zirconium/Zr 2Al partial system reported previously. In addition, the isothermal peritectoid reaction has been experimentally studied as a function of time from the coarsened U 3Si 2 precipitate/uranium matrix system using optical microscopy. The plots of the Austin-Rickett equation indicated that the time exponents are 2.5 and 1.5 in the early and in the later stage of the isothermal peritectoid reaction, respectively. Also, the impingement exponent was found to be 2. The experimental results indicated that the peritectoid transformation proceeds by nucleation and diffusion-controlled growth in the early stage and by diffusion-controlled growth without nucleation in the later stage, from which formulae describing the isothermal peritectoid transformation are derived.

  18. Investigation of the maximum accessible kinetic energy of fragments in the neutron-induced fission of {sup 238}U nuclei

    SciTech Connect

    Khryachkov, V. A. Bondarenko, I. P.; Ivanova, T. A.; Kuzminov, B. D.; Semenova, N. N.; Sergachev, A. I.

    2013-03-15

    The masses, total kinetic energies (TKE), and emission angles of fragments originating from the fission of {sup 238}U nuclei that was induced by 5- and 6.5-MeV neutrons were measured by using digital methods for processing signals. A detailed analysis of the shape of digital signals made it possible to reduce substantially the contribution of fragments whose TKE values were distorted because of a superimposition of signals from recoil protons and from alpha particles produced in the spontaneous decay of uranium. The total statistics exceeded two million events for either neutron energy, and this permitted performing a detailed analysis of fission-fragment yields in the region of the highest attainable TKE values. An analysis of fragment yields made it possible to draw specific conclusions on the structure of the potential surface of fissile nuclei.

  19. 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

  20. 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.

  1. In-situ neutron investigation of hydrogen absorption kinetics in La(FexSi1-x)13 magnetocaloric alloys for room-temperature refrigeration application

    NASA Astrophysics Data System (ADS)

    Hai, Xueying; Mayer, Charlotte; Colin, Claire V.; Miraglia, Salvatore

    2016-02-01

    Promising magnetocaloric material La(Fe,Si)13 with a first-order magnetic transition has been widely investigated. The observed instability of hydrogen in the material is detrimental for its industrial upscale and a better control of the hydrogen absorption/desorption is necessary to optimize its application potential. In this article, the hydrogen absorption kinetics is studied through an in-situ neutron diffraction experiment. The results allow us to have an inside look at the structure "breathing" to accommodate the interstitial atoms and compare the effect of hydrides with carbohydrides.

  2. Kinetic distinction between cytochromes a and a3 in cytochrome c oxidase. Rapid scanning stopped flow study of anaerobic reduction by a neutral and a negatively charged donor.

    PubMed

    Halaka, F G; Babcock, G T; Dye, J L

    1981-02-10

    Anaerobic reduction of cytochrome c oxidase by 5,10-dihydro-5-methylphenazine (reduced PMS) and by sodium dithionite were studied by rapid scanning stopped flow spectrophotometry. In both cases the decay of the Soret band of the oxidized oxidase is not uniform. With reduced PMS, the reduction involves two molecules of reductant (4 electrons)/oxidase molecule. The first stage of the reduction exhibits an isosbestic point in the Soret region at 437 nm. This shifts to 428 nm in later stages of the reaction. The reduction of the oxidase by sodium dithionite is also complete and apparently involves SO2 radical. In this case the spectra show an isosbestic point at approximately 420 nm which shifts to 432 nm as the reaction proceeds. For each of the reductants the reaction is best described by three phases: the first is a second order reaction between the oxidase and the reductant, followed by two first order processes which appear to describe the intramolecular electron redistribution within the oxidase molecule. The results agree with the assignment of the Soret band of the oxidase molecule to cytochrome a3 with an absorption maximum near 410 nm and to cytochrome a which has its maximum absorption hear 430 nm. If these assignments are correct, the present data show that reduced PMS, an uncharged molecule, reacts more rapidly with cytochrome a than it does with cytochrome a3, while the negatively charged radical anion, SO2, appears to have more direct access to cytochrome a3. PMID:6256379

  3. 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.

  4. A rapid, whole-tissue determination of the functional fraction of PSII after photoinhibition of leaves based on flash-induced P700 redox kinetics.

    PubMed

    Losciale, Pasquale; Oguchi, Riichi; Hendrickson, Luke; Hope, Alexander B; Corelli-Grappadelli, Luca; Chow, Wah Soon

    2008-01-01

    Assaying the number of functional PSII complexes by the oxygen yield from leaf tissue per saturating, single-turnover flash, assuming that each functional PSII evolves one oxygen molecule after four flashes, is one of the most direct methods but time-consuming. The ratio of variable to maximum Chl fluorescence yield (F(v)/F(m)) in leaves can be correlated with the oxygen yield per flash during a progressive loss of PSII activity associated with high-light stress and is rapid and non-intrusive, but suffers from being representative of chloroplasts near the measured leaf surface; consequently, the exact correlation depends on the internal leaf structure and on which leaf surface is being measured. Our results show that the average F(v)/F(m) of the adaxial and abaxial surfaces has a reasonable linear correlation with the oxygen yield per flash after varied extents of photoinactivation of PSII. However, we obtained an even better linear correlation between (1) the integrated, transient electron flow (Sigma) to P700+, the dimeric Chl cation in PSI, after superimposing a single-turnover flash on steady background far-red light and (2) the relative oxygen yield per flash. Leaves of C3 and C4 plants, woody and herbaceous species, wild-type and a Chl-b-less mutant, and monocot and dicot plants gave a single straight line, which seems to be a universal relation for predicting the relative oxygen yield per flash from Sigma. Measurement of Sigma is non-intrusive, representative of the whole leaf tissue, rapid and applicable to attached leaves; it may even be applicable in the field. PMID:18251867

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Rapid purification and reconstitution of a plant vacuolar ATPase using Triton X-114 fractionation: subunit composition and substrate kinetics of the H(+)-ATPase from the tonoplast of Kalanchoë daigremontiana.

    PubMed

    Warren, M; Smith, J A; Apps, D K

    1992-04-29

    A rapid procedure for the purification and reconstitution into proteoliposomes of the H(+)-translocating ATPase of plant vacuolar membranes is reported. It involves fractionation of the tonoplast with Triton X-114, resolubilization of the ATPase with octyl glucoside in the presence of a mixture of phosphatidylcholine, phosphatidylserine and cholesterol (27:53:20, by weight), and removal of the detergent by gel-filtration. Starting with partially purified vacuolar membranes, the procedure can be accomplished in about 2 hours. It has been applied to the H(+)-ATPase from the crassulacean plant Kalanchoë daigremontiana, from which it yields vesicles with a specific ATPase activity of about 3 mumol/min per mg protein. The purified enzyme contains polypeptides of apparent molecular mass 72, 57, 48, 42, 39, 33 and 16 kDa; these polypeptides also co-sediment on centrifugation of the solubilized ATPase through glycerol gradients. The 16-kDa subunit is labelled with [14C]dicyclohexylcarbodiimide. There is no evidence for a larger ATPase subunit in this preparation. The reconstituted ATPase proteoliposomes undergo ATP-dependent acidification, which can be measured by quenching of the fluorescence of 9-aminoacridine. The initial rate of fluorescence quenching is a measure of the rate of H+ translocation, and is directly proportional to the vesicle protein concentration, so the preparation is suitable for studying the kinetics of the tonoplast H(+)-ATPase. The dependence of the rate of fluorescence quenching on the concentration of MgATP is well fitted by the Michaelis equation, with a Km value about 30 microM. ATP can be replaced by dATP, ITP, GTP, UTP or CTP, and Mg2+ by Mn2+ or Ca2+; kinetic parameters for these substrates are reported. In contrast, hydrolysis of MgATP shows complex kinetics, suggestive either of negative cooperativity between nucleotide-binding sites, or of two non-interacting catalytic sites. Both the hydrolytic and the H(+)-translocating activities of

  10. Kinetic, isotherm and thermodynamic investigations of phosphate adsorption onto core-shell Fe₃O₄@LDHs composites with easy magnetic separation assistance.

    PubMed

    Yan, Liang-guo; Yang, Kun; Shan, Ran-ran; Yan, Tao; Wei, Jing; Yu, Shu-jun; Yu, Hai-qin; Du, Bin

    2015-06-15

    In this study, three different magnetic core-shell Fe3O4@LDHs composites, Fe3O4@Zn-Al-, Fe3O4@Mg-Al-, and Fe3O4@Ni-Al-LDH were prepared via a rapid coprecipitation method for phosphate adsorptive removal. The composites were characterized by XRD, FTIR, TEM, VSM and BET analyses. Characterization results proved the successful synthesis of core-shell Fe3O4@LDHs composites with good superparamagnetisms. Batch experiments were conducted to study the adsorption efficiency of phosphate. Optimal conditions for the phosphate adsorption were obtained: 0.05 g of adsorbent, solution pH of 3, and contact time of 60 min. Proposed mechanisms for the removal of phosphate species onto Fe3O4@LDHs composites at different initial solution pH were showed. The kinetic data were described better by the pseudo-second-order kinetic equation and KASRA model. The adsorption isotherm curves showed a three-region behavior in the ARIAN model. It had a good fit with Langmuir model and the maximum adsorption capacity followed the order of Fe3O4@Zn-Al-LDH>Fe3O4@Mg-Al-LDH>Fe3O4@Ni-Al-LDH. Thermodynamic analyses indicated that the phosphate adsorption process was endothermic and spontaneous in nature. The three Fe3O4@LDHs composites could be easily separated from aqueous solution by the external magnetic field in 10s. These novel magnetic core-shell Fe3O4@LDHs adsorbents may offer a simple single step adsorption treatment option to remove phosphate from water without the requirement of pre-/post-treatment for current industrial practice. PMID:25778739