Science.gov

Sample records for kinetic studies progress

  1. Kinetic study on biomass gasification

    SciTech Connect

    Bingyan, X.; Chuangzhi, W.; Zhengfen, L.; Guang, Z.X. )

    1992-09-01

    An experimental apparatus, with the features of fast heating rate and continuous record of reaction parameters, was developed to study kinetics of fast pyrolysis. The temperature effects, at a range of 400 C to 900 C, on pyrolysis rate, products profile, gas quality and quantity, and so on, were studied and the results are listed and analyzed. The effect of secondary reaction of gas phase at 700 C was tested and the regression result is expressed in an experimental formula. Based on the experimental results, the three-stage-reaction mechanism module is suggested. The kinetic expression to calculate gas formation rate is concluded as: d{alpha}/dt = A exp({minus}E/RT)(1 {minus} {alpha}){sup n}. The kinetic parameters of A, E, and n at different temperatures are given in the paper.

  2. An explicit expression for determining cometabolism kinetics using progress curve analysis.

    PubMed

    Goudar, Chetan T

    2012-05-31

    We present an explicit expression for describing the kinetics of cometabolic biotransformation of environmental pollutants. This expression is based on the Lambert W function and explicitly relates the substrate concentration, S, to time, t, the two experimentally measured variables. This explicit relationship simplifies kinetic parameter estimation as differential equation solution and iterative estimation of the substrate concentration are eliminated. The applicability of this new expression for nonlinear kinetic parameter estimation was first demonstrated using noise containing synthetic data where final estimates of the kinetic parameters were very close to their actual values. Subsequently 1.1.1-trichloroethane degradation data at initial concentrations of 750 and 375 μM were described using the explicit expression resulting in r and K(s) estimates of 0.26 μM/mg d and 28.08 μM and 0.30 μM/mg d and 28.70 μM, respectively, very similar to 0.276 μM/mg d and 31.2 μM, respectively, that were reported in the original study. The new explicit expression presented in this study simplifies estimation of cometabolic kinetic parameters and can be easily used across all computational platforms thereby providing an attractive alternative for progress curve analysis.

  3. Thermodynamic and kinetic aspects of surface acidity. Progress report

    SciTech Connect

    Dumesic, J.A.

    1992-04-01

    Our research in the general area of acid catalysis involves the characterization of solid acidity and the corresponding assessment of catalytic performance of acidic materials. Acid characterization studies are required to provide essential information about the type of acid site (i.e., Lewis versus Bronsted), the strength of the sites, and the mobility of molecules adsorbed on the acid sites. An accurate measure of acid strength is given by the heat of adsorption of a basic probe molecule on the acid site. A thermodynamic representation of the mobility of adsorbed species on these sites is given by the entropy of adsorption. Important techniques used in these acid site characterization studies include microcalorimetry, thermogravimetric measurements, temperature programmed desorption, infrared spectroscopy and solid state nuclear magnetic resonance. The combination of these acid site characterization studies with reaction kinetics measurements of selected catalytic processes allows the elucidation of possible relationships between surface thermodynamic and kinetic properties of acidic sites. Such relationships are important milestones in formulating effective strategies for the effective utilization of solid acid catalysts. Current work in this direction involves methylamine syntheses over various zeolites, and the basic probe molecules employed include ammonia, methanol, water and mono-, di- and tri-methylamines. 31 refs., 18 figs., 1 tab.

  4. Kinetics of enzyme action on surface-attached substrates: a practical guide to progress curve analysis in any kinetic situation.

    PubMed

    Anne, Agnès; Demaille, Christophe

    2012-10-16

    In the present work, exact kinetic equations describing the action of an enzyme in solution on a substrate attached to a surface have been derived in the framework of the Michaelis-Menten mechanism but without resorting to the often-used steady-state approximation. The here-derived kinetic equations are cast in a workable format, allowing us to introduce a simple and universal procedure for the quantitative analysis of enzyme surface kinetics that is valid for any kinetic situation. The results presented here should allow experimentalists studying the kinetics of enzyme action on immobilized substrates to analyze their data in a perfectly rigorous way.

  5. Kinetic studies of ICF implosions

    DOE PAGES

    Kagan, Grigory; Herrmann, H. W.; Kim, Y. -H.; ...

    2016-05-26

    Here, kinetic effects on inertial confinement fusion have been investigated. In particular, inter-ion-species diffusion and suprathermal ion distribution have been analyzed. The former drives separation of the fuel constituents in the hot reacting core and governs mix at the shell/fuel interface. The latter underlie measurements obtained with nuclear diagnostics, including the fusion yield and inferred ion burn temperatures. Basic mechanisms behind and practical consequences from these effects are discussed.

  6. Liquefaction chemistry and kinetics: Hydrogen utilization studies

    SciTech Connect

    Rothenberger, K.S.; Warzinski, R.P.; Cugini, A.V.

    1995-12-31

    The objectives of this project are to investigate the chemistry and kinetics that occur in the initial stages of coal liquefaction and to determine the effects of hydrogen pressure, catalyst activity, and solvent type on the quantity and quality of the products produced. The project comprises three tasks: (1) preconversion chemistry and kinetics, (2) hydrogen utilization studies, and (3) assessment of kinetic models for liquefaction. The hydrogen utilization studies work will be the main topic of this report. However, the other tasks are briefly described.

  7. Progress in Chemical Kinetic Modeling for Surrogate Fuels

    SciTech Connect

    Pitz, W J; Westbrook, C K; Herbinet, O; Silke, E J

    2008-06-06

    Gasoline, diesel, and other alternative transportation fuels contain hundreds to thousands of compounds. It is currently not possible to represent all these compounds in detailed chemical kinetic models. Instead, these fuels are represented by surrogate fuel models which contain a limited number of representative compounds. We have been extending the list of compounds for detailed chemical models that are available for use in fuel surrogate models. Detailed models for components with larger and more complicated fuel molecular structures are now available. These advancements are allowing a more accurate representation of practical and alternative fuels. We have developed detailed chemical kinetic models for fuels with higher molecular weight fuel molecules such as n-hexadecane (C16). Also, we can consider more complicated fuel molecular structures like cyclic alkanes and aromatics that are found in practical fuels. For alternative fuels, the capability to model large biodiesel fuels that have ester structures is becoming available. These newly addressed cyclic and ester structures in fuels profoundly affect the reaction rate of the fuel predicted by the model. Finally, these surrogate fuel models contain large numbers of species and reactions and must be reduced for use in multi-dimensional models for spark-ignition, HCCI and diesel engines.

  8. Progress in kinetic inductance thermometers for X-ray calorimeters

    NASA Technical Reports Server (NTRS)

    Rawley, G. L.; Kelley, R. L.; Moseley, S. H.; Szymkowiak, A. E.

    1989-01-01

    Conventional X-ray microcalorimeters have so far used ionimplanted resistors for thermometers. Recently, however, several new methods for sensing small temperature changes have been suggested that are nondissipative. Such devices may have intrinsically better energy resolution by eliminating the Johnson noise present in resistive devices. The use of kinetic inductance thermometers for X-ray microcalorimeters is being investigated. This technique exploits the strong temperature dependence of magnetic penetration depth of thin superconducting films. The prototype system, designed for operation at 1.5 K, uses films of aluminum and tin. Once the expected temperature sensitivity and alpha particle detection have been demonstrated, aluminum will be replaced with titanium or another material with a suitable critical temperature and the device will be operated at 0.3 K. At this temperature, the energy resolution from thermal noise should be sufficiently good to allow X-ray detection.

  9. Heterogeneous kinetics of coal gasification. Quarterly technical progress report, 1 April 1983-30 June 1983

    SciTech Connect

    Calo, J.M.; Ganapathi, R.

    1983-01-01

    In the current quarterly technical progress report we present data and results on transient kinetic studies of the steam-char reaction system for activated coconut and lignite chars. These experiments were conducted in a fashion similar to the previous char-CO/sub 2/ studies, under approximately the same experimental conditions. The two principal product species, H/sub 2/ and CO, were monitored using the automatic mass programming system developed especially for this project. In order to perform the steam-char experiments, the original apparatus was modified by the addition of a steam generation/condensate removal system. The steam-char reaction system, being somewhat more complex than the CO/sub 2/-char reaction system, was modeled with a six-parameter, elementary kinetic scheme. The ''effective'' active site concentrations determined from the steam gasification data were of the same order of magnitude, and behaved in a similar fashion, to those obtained for the CO/sub 2/ gasification studies. The implications of this result are briefly discussed. 21 refs., 23 figs., 2 tabs.

  10. Kinetic studies of elementary chemical reactions

    SciTech Connect

    Durant, J.L. Jr.

    1993-12-01

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

  11. Kinetics, prognostic and predictive values of ESR1 circulating mutations in metastatic breast cancer patients progressing on aromatase inhibitor

    PubMed Central

    Clatot, Florian; Perdrix, Anne; Augusto, Laetitia; Beaussire, Ludivine; Delacour, Julien; Calbrix, Céline; Sefrioui, David; Viailly, Pierre-Julien; Bubenheim, Michael; Moldovan, Cristian; Alexandru, Cristina; Tennevet, Isabelle; Rigal, Olivier; Guillemet, Cécile; Leheurteur, Marianne; Gouérant, Sophie; Petrau, Camille; Théry, Jean-Christophe; Picquenot, Jean-Michel; Veyret, Corinne; Frébourg, Thierry; Jardin, Fabrice

    2016-01-01

    Purpose To assess the prognostic and predictive value of circulating ESR1 mutation and its kinetics before and after progression on aromatase inhibitor (AI) treatment. Patients and methods ESR1 circulating D538G and Y537S/N/C mutations were retrospectively analyzed by digital droplet PCR after first-line AI failure in patients treated consecutively from 2010 to 2012 for hormone receptor-positive metastatic breast cancer. Progression-free survival (PFS) and overall survival (OS) were analyzed according to circulating mutational status and subsequent lines of treatment. The kinetics of ESR1 mutation before (3 and 6 months) and after (3 months) AI progression were determined in the available archive plasmas. Results Circulating ESR1 mutations were found at AI progression in 44/144 patients included (30.6%). Median follow-up from AI initiation was 40 months (range 4-94). The median OS was decreased in patients with circulating ESR1 mutation than in patients without mutation (15.5 versus 23.8 months, P=0.0006). The median PFS was also significantly decreased in patients with ESR1 mutation than in patients without mutation (5.9 vs 7 months, P=0.002). After AI failure, there was no difference in outcome for patients receiving chemotherapy (n = 58) versus non-AI endocrine therapy (n=51) in patients with and without ESR1 mutation. ESR1 circulating mutations were detectable in 75% of all cases before AI progression, whereas the kinetics 3 months after progression did not correlate with outcome. Conclusion ESR1 circulating mutations are independent risk factors for poor outcome after AI failure, and are frequently detectable before clinical progression. Interventional studies based on ESR1 circulating status are warranted. PMID:27801670

  12. Kinetic models for space plasmas: Recent progress for the solar wind and the Earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Pierrard, V.; Moschou, S. P.; Lazar, M.; Borremans, K.; Rosson, G. Lopez

    2016-11-01

    Recent models for the solar wind and the inner magnetosphere have been developed using the kinetic approach. The solution of the evolution equation is used to determine the velocity distribution function of the particles and their moments. The solutions depend on the approximations and assumptions made in the development of the models. Effects of suprathermal particles often observed in space plasmas are taken into account to show their influence on the characteristics of the plasma, with specific applications for coronal heating and solar wind acceleration. We describe in particular the results obtained with the collisionless exospheric approximation based on the Lorentzian velocity distribution function for the electrons and its recent progress in three dimensions. The effects of Coulomb collisions obtained by using a Fokker-Planck term in the evolution equation were also investigated, as well as effects of the whistler wave turbulence at electron scale and the kinetic Alfven waves at the proton scale. For solar wind especially, modelling efforts with both magnetohydrodynamic and kinetic treatments have been compared and combined in order to improve the predictions in the vicinity of the Earth. Photospheric magnetograms serve as observational input in semi-empirical coronal models used for estimating the plasma characteristics up to coronal heliocentric distances taken as boundary conditions in solar wind models. The solar wind fluctuations may influence the dynamics of the space environment of the Earth and generate geomagnetic storms. In the magnetosphere of the Earth, the trajectories of the particles are simulated to study the plasmasphere, the extension of the ionosphere along closed magnetic field lines and to better understand the physical mechanisms involved in the radiation belts dynamics.

  13. Plyometric Long Jump Training With Progressive Loading Improves Kinetic and Kinematic Swimming Start Parameters.

    PubMed

    Rebutini, Vanessa Z; Pereira, Gleber; Bohrer, Roberta C D; Ugrinowitsch, Carlos; Rodacki, André L F

    2016-09-01

    Rebutini, VZ, Pereira, G, Bohrer, RCD, Ugrinowitsch, C, and Rodacki, ALF. Plyometric long jump training with progressive loading improves kinetic and kinematic swimming start parameters. J Strength Cond Res 30(9): 2392-2398, 2016-This study was aimed to determine the effects of a plyometric long jump training program on torque around the lower limb joints and kinetic and kinematics parameters during the swimming jump start. Ten swimmers performed 3 identical assessment sessions, measuring hip and knee muscle extensors during maximal voluntary isometric contraction and kinetic and kinematics parameters during the swimming jump start, at 3 instants: INI (2 weeks before the training program, control period), PRE (2 weeks after INI measurements), and POST (24-48 hours after 9 weeks of training). There were no significant changes from INI to PRE measurements. However, the peak torque and rate of torque development increased significantly from PRE to POST measurements for both hip (47 and 108%) and knee (24 and 41%) joints. There were significant improvements to the horizontal force (7%), impulse (9%), and angle of resultant force (19%). In addition, there were significant improvements to the center of mass displacement (5%), horizontal takeoff velocity (16%), horizontal velocity at water entrance (22%), and peak angle velocity for the knee (15%) and hip joints (16%). Therefore, the plyometric long jump training protocol was effective to enhance torque around the lower limb joints and to control the resultant vector direction, to increase the swimming jump start performance. These findings suggest that coaches should use long jump training instead of vertical jump training to improve swimming start performance.

  14. Measuring cell cycle progression kinetics with metabolic labeling and flow cytometry.

    PubMed

    Fleisig, Helen; Wong, Judy

    2012-05-22

    Precise control of the initiation and subsequent progression through the various phases of the cell cycle are of paramount importance in proliferating cells. Cell cycle division is an integral part of growth and reproduction and deregulation of key cell cycle components have been implicated in the precipitating events of carcinogenesis. Molecular agents in anti-cancer therapies frequently target biological pathways responsible for the regulation and coordination of cell cycle division. Although cell cycle kinetics tend to vary according to cell type, the distribution of cells amongst the four stages of the cell cycle is rather consistent within a particular cell line due to the consistent pattern of mitogen and growth factor expression. Genotoxic events and other cellular stressors can result in a temporary block of cell cycle progression, resulting in arrest or a temporary pause in a particular cell cycle phase to allow for instigation of the appropriate response mechanism. The ability to experimentally observe the behavior of a cell population with reference to their cell cycle progression stage is an important advance in cell biology. Common procedures such as mitotic shake off, differential centrifugation or flow cytometry-based sorting are used to isolate cells at specific stages of the cell cycle. These fractionated, cell cycle phase-enriched populations are then subjected to experimental treatments. Yield, purity and viability of the separated fractions can often be compromised using these physical separation methods. As well, the time lapse between separation of the cell populations and the start of experimental treatment, whereby the fractionated cells can progress from the selected cell cycle stage, can pose significant challenges in the successful implementation and interpretation of these experiments. Other approaches to study cell cycle stages include the use of chemicals to synchronize cells. Treatment of cells with chemical inhibitors of key

  15. Kinetic studies on the pyrolysis of pinewood.

    PubMed

    Mishra, Garima; Kumar, Jitendra; Bhaskar, Thallada

    2015-04-01

    The kinetic study for pyrolysis of pine wood has been studied by a thermogravimetric analyzer in an inert atmosphere. Non isothermal model free kinetic methods were used to evaluate kinetics at six different heating rates of 5-40°C/min. Three zones can be detected from the iso-conversional plot of pine with average activation energy values of 134.32 kJ/mol, 146.89 kJ/mol and 155.76 kJ/mol in the conversion range of 1-22%, 24-84% and 85-90%, respectively. The activation energy values were used to determine the reaction mechanism using master plots and compensation parameters. The results show that the pyrolysis process of pine wood can be described by two dimensional diffusion reaction mechanism in a wide range of conversion up to 0.7, followed by close to one and half order reaction mechanism. The kinetic results were validated by making isothermal predictions from non-isothermal data.

  16. Circadian Kinetics of Cell Cycle Progression in Adult Neurogenic Niches of a Diurnal Vertebrate.

    PubMed

    Akle, Veronica; Stankiewicz, Alexander J; Kharchenko, Vasili; Yu, Lili; Kharchenko, Peter V; Zhdanova, Irina V

    2017-02-15

    The circadian system may regulate adult neurogenesis via intracellular molecular clock mechanisms or by modifying the environment of neurogenic niches, with daily variation in growth factors or nutrients depending on the animal's diurnal or nocturnal lifestyle. In a diurnal vertebrate, zebrafish, we studied circadian distribution of immunohistochemical markers of the cell division cycle (CDC) in 5 of the 16 neurogenic niches of adult brain, the dorsal telencephalon, habenula, preoptic area, hypothalamus, and cerebellum. We find that common to all niches is the morning initiation of G1/S transition and daytime S-phase progression, overnight increase in G2/M, and cycle completion by late night. This is supported by the timing of gene expression for critical cell cycle regulators cyclins D, A2, and B2 and cyclin-dependent kinase inhibitor p20 in brain tissue. The early-night peak in p20, limiting G1/S transition, and its phase angle with the expression of core clock genes, Clock1 and Per1, are preserved in constant darkness, suggesting intrinsic circadian patterns of cell cycle progression. The statistical modeling of CDC kinetics reveals the significant circadian variation in cell proliferation rates across all of the examined niches, but interniche differences in the magnitude of circadian variation in CDC, S-phase length, phase angle of entrainment to light or clock, and its dispersion. We conclude that, in neurogenic niches of an adult diurnal vertebrate, the circadian modulation of cell cycle progression involves both systemic and niche-specific factors.SIGNIFICANCE STATEMENT This study establishes that in neurogenic niches of an adult diurnal vertebrate, the cell cycle progression displays a robust circadian pattern. Common to neurogenic niches located in diverse brain regions is daytime progression of DNA replication and nighttime mitosis, suggesting systemic regulation. Differences between neurogenic niches in the phase and degree of S-phase entrainment to the

  17. Circadian Kinetics of Cell Cycle Progression in Adult Neurogenic Niches of a Diurnal Vertebrate

    PubMed Central

    Stankiewicz, Alexander J.; Kharchenko, Vasili; Yu, Lili; Kharchenko, Peter V.

    2017-01-01

    The circadian system may regulate adult neurogenesis via intracellular molecular clock mechanisms or by modifying the environment of neurogenic niches, with daily variation in growth factors or nutrients depending on the animal's diurnal or nocturnal lifestyle. In a diurnal vertebrate, zebrafish, we studied circadian distribution of immunohistochemical markers of the cell division cycle (CDC) in 5 of the 16 neurogenic niches of adult brain, the dorsal telencephalon, habenula, preoptic area, hypothalamus, and cerebellum. We find that common to all niches is the morning initiation of G1/S transition and daytime S-phase progression, overnight increase in G2/M, and cycle completion by late night. This is supported by the timing of gene expression for critical cell cycle regulators cyclins D, A2, and B2 and cyclin-dependent kinase inhibitor p20 in brain tissue. The early-night peak in p20, limiting G1/S transition, and its phase angle with the expression of core clock genes, Clock1 and Per1, are preserved in constant darkness, suggesting intrinsic circadian patterns of cell cycle progression. The statistical modeling of CDC kinetics reveals the significant circadian variation in cell proliferation rates across all of the examined niches, but interniche differences in the magnitude of circadian variation in CDC, S-phase length, phase angle of entrainment to light or clock, and its dispersion. We conclude that, in neurogenic niches of an adult diurnal vertebrate, the circadian modulation of cell cycle progression involves both systemic and niche-specific factors. SIGNIFICANCE STATEMENT This study establishes that in neurogenic niches of an adult diurnal vertebrate, the cell cycle progression displays a robust circadian pattern. Common to neurogenic niches located in diverse brain regions is daytime progression of DNA replication and nighttime mitosis, suggesting systemic regulation. Differences between neurogenic niches in the phase and degree of S-phase entrainment to

  18. Progress with the COGENT Edge Kinetic Code: Collision operator options

    DOE PAGES

    Dorf, M. A.; Cohen, R. H.; Compton, J. C.; ...

    2012-06-27

    In this study, COGENT is a continuum gyrokinetic code for edge plasmas being developed by the Edge Simulation Laboratory collaboration. The code is distinguished by application of the fourth order conservative discretization, and mapped multiblock grid technology to handle the geometric complexity of the tokamak edge. It is written in v∥-μ (parallel velocity – magnetic moment) velocity coordinates, and making use of the gyrokinetic Poisson equation for the calculation of a self-consistent electric potential. In the present manuscript we report on the implementation and initial testing of a succession of increasingly detailed collision operator options, including a simple drag-diffusion operatormore » in the parallel velocity space, Lorentz collisions, and a linearized model Fokker-Planck collision operator conserving momentum and energy (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)« less

  19. Progress with the COGENT Edge Kinetic Code: Collision operator options

    SciTech Connect

    Dorf, M. A.; Cohen, R. H.; Compton, J. C.; Dorr, M.; Rognlien, T. D.; Angus, J.; Krasheninnikov, S.; Colella, P.; Martin, D.; McCorquodale, P.

    2012-06-27

    In this study, COGENT is a continuum gyrokinetic code for edge plasmas being developed by the Edge Simulation Laboratory collaboration. The code is distinguished by application of the fourth order conservative discretization, and mapped multiblock grid technology to handle the geometric complexity of the tokamak edge. It is written in v∥-μ (parallel velocity – magnetic moment) velocity coordinates, and making use of the gyrokinetic Poisson equation for the calculation of a self-consistent electric potential. In the present manuscript we report on the implementation and initial testing of a succession of increasingly detailed collision operator options, including a simple drag-diffusion operator in the parallel velocity space, Lorentz collisions, and a linearized model Fokker-Planck collision operator conserving momentum and energy (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

  20. Direct determination of enzyme kinetic parameters from single reactions using a new progress curve analysis tool.

    PubMed

    Bäuerle, Felix; Zotter, Agnes; Schreiber, Gideon

    2016-10-15

    With computer-based data-fitting methods becoming a standard tool in biochemistry, progress curve analysis of enzyme kinetics is a feasible, yet seldom used tool. Here we present a versatile Matlab-based tool (PCAT) to analyze catalysis progress curves with three complementary model approaches. The first two models are based on the known closed-form solution for this problem: the first describes the required Lambert W function with an analytical approximation and the second provides a numerical solution of the Lambert W function. The third model is a direct simulation of the enzyme kinetics. Depending on the chosen model, the tools excel in speed, accuracy or initial value requirements. Using simulated and experimental data, we show the strengths and pitfalls of the different fitting models. Direct simulation proves to have the highest level of accuracy, but it also requires reasonable initial values to converge. Finally, we propose a standard procedure to obtain optimized enzyme kinetic parameters from single progress curves.

  1. Kinetic study and mechanism of Niclosamide degradation

    NASA Astrophysics Data System (ADS)

    Zaazaa, Hala E.; Abdelrahman, Maha M.; Ali, Nouruddin W.; Magdy, Maimana A.; Abdelkawy, M.

    2014-11-01

    A spectrophotometric kinetic study of Niclosamide alkaline degradation as a function of drug concentration, alkaline concentration and temperature has been established utilizing double divisor-ratio spectra spectrophotometric method. The developed method allowed determination of Niclosamide in presence of its alkaline degradation products; namely; 2-chloro-4-nitro aniline (DEG I) and 5-chloro salicylic acid (DEG II) with characterization of its degradation mechanism. It was found that degradation kinetic of Niclosamide followed pseudo-first order under the established experimental conditions with a degradation rate constant (k) of 0.0829 mol/h and half life (t1/2) of 8.35 h. The overall degradation rate constant as a function of the temperature under the given conditions obeyed Arrhenius equation where the activation energy was calculated to be 3.41 kcal/mol.

  2. Kinetic study and mechanism of Niclosamide degradation.

    PubMed

    Zaazaa, Hala E; Abdelrahman, Maha M; Ali, Nouruddin W; Magdy, Maimana A; Abdelkawy, M

    2014-11-11

    A spectrophotometric kinetic study of Niclosamide alkaline degradation as a function of drug concentration, alkaline concentration and temperature has been established utilizing double divisor-ratio spectra spectrophotometric method. The developed method allowed determination of Niclosamide in presence of its alkaline degradation products; namely; 2-chloro-4-nitro aniline (DEG I) and 5-chloro salicylic acid (DEG II) with characterization of its degradation mechanism. It was found that degradation kinetic of Niclosamide followed pseudo-first order under the established experimental conditions with a degradation rate constant (k) of 0.0829 mol/h and half life (t1/2) of 8.35 h. The overall degradation rate constant as a function of the temperature under the given conditions obeyed Arrhenius equation where the activation energy was calculated to be 3.41 kcal/mol.

  3. Progressive attenuation of the longitudinal kinetics in the common carotid artery: preliminary in vivo assessment.

    PubMed

    Zahnd, Guillaume; Balocco, Simone; Sérusclat, André; Moulin, Philippe; Orkisz, Maciej; Vray, Didier

    2015-01-01

    Longitudinal kinetics (LOKI) of the arterial wall consists of the shearing motion of the intima-media complex over the adventitia layer in the direction parallel to the blood flow during the cardiac cycle. The aim of this study was to investigate the local variability of LOKI amplitude along the length of the vessel. By use of a previously validated motion-estimation framework, 35 in vivo longitudinal B-mode ultrasound cine loops of healthy common carotid arteries were analyzed. Results indicated that LOKI amplitude is progressively attenuated along the length of the artery, as it is larger in regions located on the proximal side of the image (i.e., toward the heart) and smaller in regions located on the distal side of the image (i.e., toward the head), with an average attenuation coefficient of -2.5 ± 2.0%/mm. Reported for the first time in this study, this phenomenon is likely to be of great importance in improving understanding of atherosclerosis mechanisms, and has the potential to be a novel index of arterial stiffness.

  4. Studies of combustion kinetics and mechanisms

    SciTech Connect

    Gutman, D.

    1993-12-01

    The objective of the current research is to gain new quantitative knowledge of the kinetics and mechanisms of polyatomic free radicals which are important in hydrocarbon combustion processes. The special facility designed and built for these (which includes a heatable tubular reactor coupled to a photoionization mass spectrometer) is continually being improved. Where possible, these experimental studies are coupled with theoretical ones, sometimes conducted in collaboration with others, to obtain an improved understanding of the factors determining reactivity. The decomposition of acetyl radicals, isopropyl radicals, and n-propyl radicals have been studied as well as the oxidation of methylpropargyl radicals.

  5. [Kinetic study on pyrolysis of psoralen].

    PubMed

    Fan, Haiyan; Liao, Kun; Hu, Wei; Su, Jiakun; Tian, Yaowei; Qi, Fei; Cai, Jibao

    2012-01-01

    In this study, products of psoralen pyrolysis were detected using a solid pyrolysis apparatus and synchrotron radiation vacuum ultraviolet photoionization mass spectrum (SVUV-PIMS). The pyrolytic kinetics of psoralen was also studied by calculating its initial pyrolytic route in quantum chemistry. According to the findings with SVUV-PIMS, three pyrolytic products were observed, CO, C9H6O and C10H6O2. Theoretically, three fragment pathways were calculated for psoralen, in which the major primary decomposition route was de-CO, and the major secondary decomposition reaction was de-CO reaction of de-CO products.

  6. Kinetics of Mn-based sorbents for hot coal gas desulfurization: Quarterly progress report, December 15, 1994--March 15, 1995. Task 2 -- Exploratory experimental studies: Single pellet tests; Rate mechanism analysis

    SciTech Connect

    Hepworth, M.T.

    1995-03-15

    In earlier studies, zinc ferrite and zinc titanate were developed as regenerable sorbents capable of removing hydrogen sulfide from hot fuel gases originating from coal gasification. Manganese ore as well as manganese carbonate, precipitated from aqueous solutions, combined with alumina to form indurated pellets hold promise of being a highly-effective, inexpensive, regenerable sorbent for hot fuel gases. Although the thermodynamics for sulfur removal by manganese predicts somewhat higher hydrogen sulfide over-pressures (i.e. poorer degree of desulfurization) than can be accomplished with zinc-based sorbents, zinc tends to be reduced to the metallic state under coal gasification conditions resulting in loss of capacity and reactivity by volatilization of reactive surfaces. This volatilization phenomenon limits the temperatures for which desulfurization can be effectively accomplished to less than 500 C for zinc ferrite and 700 C for zinc titanate; whereas, manganese-based sorbents can be utilized at temperatures well in temperatures exceeding 700 C. Also the regeneration of manganese-based pellets under oxidizing conditions may be superior to that of zinc titanate since they can be loaded from a simulated reducing coal-derived gas and then be regenerated at higher temperatures (up to 1,300 C). The topics that will be addressed by this study include: preparation of an effective manganese-based sorbent, thermodynamics and kinetics of sulfur removal from hot fuel gases by this sorbent, analysis of kinetics and mechanisms by which sulfur is absorbed by the sorbent (i.e., whether by gaseous diffusion, surface-controlled reaction, ore pore diffusion), and cyclic sulfidation and regeneration of the sorbent and recovery of the sulfur.

  7. Adsorption studies of molasse's wastewaters on activated carbon: modelling with a new fractal kinetic equation and evaluation of kinetic models.

    PubMed

    Figaro, S; Avril, J P; Brouers, F; Ouensanga, A; Gaspard, S

    2009-01-30

    Adsorption kinetic of molasses wastewaters after anaerobic digestion (MSWD) and melanoidin respectively on activated carbon was studied at different pH. The kinetic parameters could be determined using classical kinetic equations and a recently published fractal kinetic equation. A linear form of this equation can also be used to fit adsorption data. Even with lower correlation coefficients the fractal kinetic equation gives lower normalized standard deviation values than the pseudo-second order model generally used to fit adsorption kinetic data, indicating that the fractal kinetic model is much more accurate for describing the kinetic adsorption data than the pseudo-second order kinetic model.

  8. Kinetics Studies in a Washing Bottle

    NASA Astrophysics Data System (ADS)

    Teggins, John; Mahaffy, Chris

    1997-05-01

    The kinetics of the decomposition of hydrogen peroxide using iodide ion in aqueous solution is studied in sealed completely-filled washing bottles. Oxygen gas produced by the decomposition of the hydrogen peroxide forces liquid out of a bottom feeding washing bottle. After an initiation period of a few minutes at room temperature, the rate at which the liquid is expelled from the spout of the of the washing bottle stabilizes. A comparison of the rates for different reaction concentrations results in a rate law that is approximately first-order with respect to both hydrogen peroxide and iodide concentrations. Because the need for a gas buret to measure oxygen volumes is not necessary, the experiment can be conveniently performed by a student seated in a wheelchair.

  9. Early axonal damage and progressive myelin pathology define the kinetics of CNS histopathology in a mouse model of multiple sclerosis.

    PubMed

    Recks, Mascha S; Stormanns, Eva R; Bader, Jonas; Arnhold, Stefan; Addicks, Klaus; Kuerten, Stefanie

    2013-10-01

    Studies of MS histopathology are largely dependent on suitable animal models. While light microscopic analysis gives an overview of tissue pathology, it falls short in evaluating detailed changes in nerve fiber morphology. The ultrastructural data presented here and obtained from studies of myelin oligodendrocyte glycoprotein (MOG):35-55-induced experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice delineate that axonal damage and myelin pathology follow different kinetics in the disease course. While myelin pathology accumulated with disease progression, axonal damage coincided with the initial clinical disease symptoms and remained stable over time. This pattern applied both to irreversible axolysis and early axonal pathology. Notably, these histopathological patterns were reflected by the normal-appearing white matter (NAWM), suggesting that the NAWM is also in an active neurodegenerative state. The data underline the need for neuroprotection in MS and suggest the MOG model as a highly valuable tool for the assessment of different therapeutic strategies.

  10. Accurate kinetic parameter estimation during progress curve analysis of systems with endogenous substrate production.

    PubMed

    Goudar, Chetan T

    2011-10-01

    We have identified an error in the published integral form of the modified Michaelis-Menten equation that accounts for endogenous substrate production. The correct solution is presented and the error in both the substrate concentration, S, and the kinetic parameters Vm , Km , and R resulting from the incorrect solution was characterized. The incorrect integral form resulted in substrate concentration errors as high as 50% resulting in 7-50% error in kinetic parameter estimates. To better reflect experimental scenarios, noise containing substrate depletion data were analyzed by both the incorrect and correct integral equations. While both equations resulted in identical fits to substrate depletion data, the final estimates of Vm , Km , and R were different and Km and R estimates from the incorrect integral equation deviated substantially from the actual values. Another observation was that at R = 0, the incorrect integral equation reduced to the correct form of the Michaelis-Menten equation. We believe this combination of excellent fits to experimental data, albeit with incorrect kinetic parameter estimates, and the reduction to the Michaelis-Menten equation at R = 0 is primarily responsible for the incorrectness to go unnoticed. However, the resulting error in kinetic parameter estimates will lead to incorrect biological interpretation and we urge the use of the correct integral form presented in this study.

  11. Thermodynamic and kinetic aspects of surface acidity. Progress report, July 1, 1994--June 30, 1995

    SciTech Connect

    Dumesic, J.A.

    1995-06-01

    Catalytic cracking of isobutane and 2-methyl-hexane over various USY-zeolite catalysts was studied. A kinetic model was developed for isobutane cracking over calcined and steamed Y-zeolite catalysts. Catalyst steaming leads to decreased Bronsted acidity. The studies of catalyst acid and basic properties were broadened to include alumina-supported metal oxides and a sulfated zirconia catalyst (isomerization of normal butane).

  12. Spectroscopy and kinetics of combustion gases at high temperatures. Annual progress report 1991

    SciTech Connect

    Hanson, R.K.; Bowman, C.T.

    1991-12-01

    This program involves two complementary activities: (1) development and application of cw ring dye laser absorption methods for sensitive detection of radical species and measurement of fundamental spectroscopic parameters at high temperatures; and (2) shock tube studies of radical-molecule and radical-radical reactions relevant to combustion. Species currently under investigation in the spectroscopic portion of the research include NO and CH{sub 3}; this has necessitated the development of a unique intracavity frequency-doubling system for our cw laser which operates at wavelengths in the range 210--230 nm. Shock tube studies of reaction kinetics currently are focused on reactions of CH{sub 3} radicals. Work during the current reporting period has been focused on the following activities: High resolution spectroscopy, and methyl diagnostics and kinetics.

  13. Kinetic studies of stress-corrosion cracking

    NASA Technical Reports Server (NTRS)

    Noronha, P. J.

    1977-01-01

    Use of time-to-failure curves for stress-corrosion cracking processes may lead to incorrect estimates of structural life, if material is strongly dependent upon prestress levels. Technique characterizes kinetics of crackgrowth rates and intermediate arrest times by load-level changes.

  14. Kinetic analysis of enzyme systems with suicide substrate in the presence of a reversible competitive inhibitor, tested by simulated progress curves.

    PubMed

    Moruno-Dávila, M A; Garrido-del Solo, C; García-Moreno, M; Havsteen, B H; Garcia-Sevilla, F; Garcia-Cánovas, F; Varón, R

    2001-02-01

    The use of suicide substrates remains a very important and useful method in enzymology for studying enzyme mechanisms and designing potential drugs. Suicide substrates act as modified substrates for the target enzymes and bind to the active site. Therefore the presence of a competitive reversible inhibitor decreases the rate of substrate-induced inactivation and protects the enzyme from this inactivation. This lowering on the inactivation rate has evident physiological advantages, since it allows the easy acquisition of experimental data and facilitates kinetic data analysis by providing another variable (inhibitor concentration). However despite the importance of the simultaneous action of a suicide substrate and a competitive reversible inhibition, to date no corresponding kinetic analysis has been carried out. Therefore we present a general kinetic analysis of a Michaelis-Menten reaction mechanism with double inhibition caused by both, a suicide substrate and a competitive reversible inhibitor. We assume rapid equilibrium of the reversible reaction steps involved, while the time course equations for the reaction product have been derived with the assumption of a limiting enzyme. The goodness of the analytical solutions has been tested by comparison with the simulated curves obtained by numerical integration. A kinetic data analysis to determine the corresponding kinetic parameters from the time progress curve of the product is suggested. In conclusion, we present a complete kinetic analysis of an enzyme reaction mechanism as described above in an attempt to fill a gap in the theoretical treatment of this type of system.

  15. First principle kinetic studies of zeolite-catalyzed methylation reactions.

    PubMed

    Van Speybroeck, Veronique; Van der Mynsbrugge, Jeroen; Vandichel, Matthias; Hemelsoet, Karen; Lesthaeghe, David; Ghysels, An; Marin, Guy B; Waroquier, Michel

    2011-02-02

    Methylations of ethene, propene, and butene by methanol over the acidic microporous H-ZSM-5 catalyst are studied by means of state of the art computational techniques, to derive Arrhenius plots and rate constants from first principles that can directly be compared with the experimental data. For these key elementary reactions in the methanol to hydrocarbons (MTH) process, direct kinetic data became available only recently [J. Catal.2005, 224, 115-123; J. Catal.2005, 234, 385-400]. At 350 °C, apparent activation energies of 103, 69, and 45 kJ/mol and rate constants of 2.6 × 10(-4), 4.5 × 10(-3), and 1.3 × 10(-2) mol/(g h mbar) for ethene, propene, and butene were derived, giving following relative ratios for methylation k(ethene)/k(propene)/k(butene) = 1:17:50. In this work, rate constants including pre-exponential factors are calculated which give very good agreement with the experimental data: apparent activation energies of 94, 62, and 37 kJ/mol for ethene, propene, and butene are found, and relative ratios of methylation k(ethene)/k(propene)/k(butene) = 1:23:763. The entropies of gas phase alkenes are underestimated in the harmonic oscillator approximation due to the occurrence of internal rotations. These low vibrational modes were substituted by manually constructed partition functions. Overall, the absolute reaction rates can be calculated with near chemical accuracy, and qualitative trends are very well reproduced. In addition, the proposed scheme is computationally very efficient and constitutes significant progress in kinetic modeling of reactions in heterogeneous catalysis.

  16. Insights into Coupled Folding and Binding Mechanisms from Kinetic Studies*

    PubMed Central

    Crabtree, Michael D.; Dahal, Liza; Wicky, Basile I. M.; Clarke, Jane

    2016-01-01

    Intrinsically disordered proteins (IDPs) are characterized by a lack of persistent structure. Since their identification more than a decade ago, many questions regarding their functional relevance and interaction mechanisms remain unanswered. Although most experiments have taken equilibrium and structural perspectives, fewer studies have investigated the kinetics of their interactions. Here we review and highlight the type of information that can be gained from kinetic studies. In particular, we show how kinetic studies of coupled folding and binding reactions, an important class of signaling event, are needed to determine mechanisms. PMID:26851275

  17. A kinetic study of lipase-catalyzed reversible kinetic resolution involving verification at miniplant-scale.

    PubMed

    Berendsen, W R; Gendrot, G; Freund, A; Reuss, M

    2006-12-05

    Lipase-catalyzed kinetic resolution of racemates is a popular method for synthesis of chiral synthons. Most of these resolutions are reversible equilibrium limited reactions. For the first time, an extensive kinetic model is proposed for kinetic resolution reactions, which takes into account the full reversibility of the reaction, substrate inhibition by an acyl donor and an acyl acceptor as well as alternative substrate inhibition by each enantiomer. For this purpose, the reversible enantioselective transesterification of (R/S)-1-methoxy-2-propanol with ethyl acetate catalyzed by Candida antarctica lipase B (CAL-B) is investigated. The detailed model presented here is valid for a wide range of substrate and product concentrations. Following model discrimination and the application of Haldane equations to reduce the degree of freedom in parameter estimation, the 11 free parameters are successfully identified. All parameters are fitted to the complete data set simultaneously. Six types of independent initial rate studies provide a solid data basis for the model. The effect of changes in substrate and product concentration on reaction kinetics is discussed. The developed model is used for simulations to study the behavior of reaction kinetics in a fixed bed reactor. The typical plot of enantiomeric excess versus conversion of substrate and product is evaluated at various initial substrate mixtures. The model is validated by comparison with experimental results obtained with a fixed bed reactor, which is part of a fully automated state-of-the-art miniplant.

  18. Progress curve analysis for enzyme and microbial kinetic reactions using explicit solutions based on the Lambert W function.

    PubMed

    Goudar, Chetan T; Harris, Steve K; McInerney, Michael J; Suflita, Joseph M

    2004-12-01

    We present a simple method for estimating kinetic parameters from progress curve analysis of biologically catalyzed reactions that reduce to forms analogous to the Michaelis-Menten equation. Specifically, the Lambert W function is used to obtain explicit, closed-form solutions to differential rate expressions that describe the dynamics of substrate depletion. The explicit nature of the new solutions greatly simplifies nonlinear estimation of the kinetic parameters since numerical techniques such as the Runge-Kutta and Newton-Raphson methods used to solve the differential and integral forms of the kinetic equations, respectively, are replaced with a simple algebraic expression. The applicability of this approach for estimating Vmax and Km in the Michaelis-Menten equation was verified using a combination of simulated and experimental progress curve data. For simulated data, final estimates of Vmax and Km were close to the actual values of 1 microM/h and 1 microM, respectively, while the standard errors for these parameter estimates were proportional to the error level in the simulated data sets. The method was also applied to hydrogen depletion experiments by mixed cultures of bacteria in activated sludge resulting in Vmax and Km estimates of 6.531 microM/h and 2.136 microM, respectively. The algebraic nature of this solution, coupled with its relatively high accuracy, makes it an attractive candidate for kinetic parameter estimation from progress curve data.

  19. Model-based analysis of coupled equilibrium-kinetic processes: indirect kinetic studies of thermodynamic parameters using the dynamic data.

    PubMed

    Emami, Fereshteh; Maeder, Marcel; Abdollahi, Hamid

    2015-05-07

    Thermodynamic studies of equilibrium chemical reactions linked with kinetic procedures are mostly impossible by traditional approaches. In this work, the new concept of generalized kinetic study of thermodynamic parameters is introduced for dynamic data. The examples of equilibria intertwined with kinetic chemical mechanisms include molecular charge transfer complex formation reactions, pH-dependent degradation of chemical compounds and tautomerization kinetics in micellar solutions. Model-based global analysis with the possibility of calculating and embedding the equilibrium and kinetic parameters into the fitting algorithm has allowed the complete analysis of the complex reaction mechanisms. After the fitting process, the optimal equilibrium and kinetic parameters together with an estimate of their standard deviations have been obtained. This work opens up a promising new avenue for obtaining equilibrium constants through the kinetic data analysis for the kinetic reactions that involve equilibrium processes.

  20. Planning a Kinetic and Mechanistic Study with Cerium (IV)

    ERIC Educational Resources Information Center

    Hanna, Samir B.; And Others

    1976-01-01

    Presents a kinetic study that utilizes a method for varying the concentrations of the possible Ce(IV) species and computing the concentration distribution of the sulfato and hydroxo species of Ce(IV). (MLH)

  1. Nuclear Reprogramming: Kinetics of Cell Cycle and Metabolic Progression as Determinants of Success

    PubMed Central

    Balbach, Sebastian Thomas; Esteves, Telma Cristina; Houghton, Franchesca Dawn; Siatkowski, Marcin; Pfeiffer, Martin Johannes; Tsurumi, Chizuko; Kanzler, Benoit; Fuellen, Georg; Boiani, Michele

    2012-01-01

    Establishment of totipotency after somatic cell nuclear transfer (NT) requires not only reprogramming of gene expression, but also conversion of the cell cycle from quiescence to the precisely timed sequence of embryonic cleavage. Inadequate adaptation of the somatic nucleus to the embryonic cell cycle regime may lay the foundation for NT embryo failure and their reported lower cell counts. We combined bright field and fluorescence imaging of histone H2b-GFP expressing mouse embryos, to record cell divisions up to the blastocyst stage. This allowed us to quantitatively analyze cleavage kinetics of cloned embryos and revealed an extended and inconstant duration of the second and third cell cycles compared to fertilized controls generated by intracytoplasmic sperm injection (ICSI). Compared to fertilized embryos, slow and fast cleaving NT embryos presented similar rates of errors in M phase, but were considerably less tolerant to mitotic errors and underwent cleavage arrest. Although NT embryos vary substantially in their speed of cell cycle progression, transcriptome analysis did not detect systematic differences between fast and slow NT embryos. Profiling of amino acid turnover during pre-implantation development revealed that NT embryos consume lower amounts of amino acids, in particular arginine, than fertilized embryos until morula stage. An increased arginine supplementation enhanced development to blastocyst and increased embryo cell numbers. We conclude that a cell cycle delay, which is independent of pluripotency marker reactivation, and metabolic restraints reduce cell counts of NT embryos and impede their development. PMID:22530006

  2. Update on Progress of Space Station Integrated Kinetic Launcher for Orbital Payload Systems (SSIKLOPS) - Cyclops

    NASA Technical Reports Server (NTRS)

    Newswander, Daniel; Smith, James P.; Lamb, Craig R.; Ballard, Perry G.

    2014-01-01

    The Space Station Integrated Kinetic Launcher for Orbital Payload Systems (SSIKLOPS), known as "Cyclops" to the International Space Station (ISS) community, was introduced last August (2013) during Technical Session V: From Earth to Orbit of the 27th Annual AIAA/USU Conference on Small Satellites. Cyclops is a collaboration between the NASA ISS Program, NASA Johnson Space Center Engineering, and Department of Defense (DoD) Space Test Program (STP) communities to develop a dedicated 50-100 kg class ISS small satellite deployment system. This paper will address the progress of Cyclops through its fabrication, assembly, flight certification, and on-orbit demonstration phases. It will also go into more detail regarding its anatomy, its satellite deployment concept of operations, and its satellite interfaces and requirements. Cyclops is manifested to fly on Space-X 4 which is currently scheduled in July 2014 with its initial satellite deployment demonstration of DoD STP's SpinSat and UT/TAMU's Lonestar satellites being late summer or fall of 2014.

  3. Kinetic and thermodynamic studies of sulforaphane adsorption on macroporous resin.

    PubMed

    Yuanfeng, Wu; Lei, Zhang; Jianwei, Mao; Shiwang, Liu; Jun, Huang; Yuru, You; Lehe, Mei

    2016-08-15

    The adsorption equilibrium, kinetic and thermodynamic of sulforaphane (SF) adsorption onto macroporous resin in aqueous phase were studied. The SP850 resin was screened as the appropriate resin for SF purification. From the equilibrium studies, the Redlich-Peterson model was found to be the best for description of the adsorption behavior of SF onto SP850 resin, followed by the Freundlich model and the Langmuir model. Batch equilibrium experiments demonstrated that, in the examined temperature range, the equilibrium adsorption capacity of SP850 resin decreased with increasing adsorption temperature. Thermodynamics studies indicated that the adsorption of SF was a physical, exothermic, and spontaneous process. The adsorption kinetics revealed that the pseudo-second-order kinetic model was suitable to characterize the kinetics of adsorption of SF onto SP850. Finally, the intra-particle diffusion model demonstrated that SF diffused quickly into macropores, and that diffusion slowed down in the meso- and micropores.

  4. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Progress report, June 1991--November 1992

    SciTech Connect

    McInerney, M.J.

    1992-11-16

    The kinetics of benzoate degradation by the anaerobic syntrophic bacterium, Syntrophus buswellii, was studied in coculture with Desulfovibrio strain G11. The threshold value for benzoate degradation was dependent on the acetate concentration with benzoate threshold values ranging from 2.4 {mu}M at 20 mM acetate to 30.0 {mu}M at 65 mM acetate. Increasing acetate concentrations also inhibited the rate of benzoate degradation with a apparent K{sub i} for acetate inhibition of 7.0 mM. Lower threshold values were obtained when nitrate rather than sulfate was the terminal electron acceptor. These data are consistent with a thermodynamic explanation for the threshold, and suggest that there is a minimum Gibbs free energy value required for the degradation of benzoate. An acetoacetyl-CoA thiolase has been isolated from Syntrophomonas wolfei; it is apparently a key enzyme controlling the synthesis of poly-B-hydroxyalkanoate from acetyl-CoA in this organism. Kinetic characterization of the acetoacetyl-CoA thiolase from S. wolfei showed that it is similar in its structural, kinetic, and apparent regulatory properties to other biosynthetic acetoacetyl-CoA thiolases from phylogenetically distinct bacteria that synthesize PHA. Intracellular concentrations of CoA and acetyl-CoA are believed to be critical factors regulating the activity of the acetoacetyl-CoA thiolase in S. wolfei. We have also isolated and characterized several new halophilic anaerobic fermentative anaerobes. Phylogenetic analysis indicates that one of these bacteria is a new species in the genus, Haloanaerobium. Two other species appear to be members of the genus, Halobacteroides. Several halophilic acetoclastic methanogenic bacteria have also been isolated and their physiological properties are currently under investigation. We have also isolated an acetate-using dissimilatory iron-reducing bacterium.

  5. Progressive hemifacial atrophy. A natural history study.

    PubMed Central

    Miller, M T; Spencer, M A

    1995-01-01

    PURPOSE: To describe two very different natural history courses in 2 patients with hemifacial atrophy. Progressive hemifacial atrophy (Parry-Romberg syndrome, Romberg syndrome, PHA) is characterized by slowly progressive atrophy, frequently involving only one side of the face, primarily affecting the subcutaneous tissue and fat. The onset usually occurs during the first 2 decades of life. The cause and pathophysiology are unknown. Ophthalmic involvement is common, with progressive enophthalmos a frequent finding. Pupillary disturbances, heterochromia, uveitis, pigmentary disturbances of the ocular fundus, and restrictive strabismus have also been reported. Neurologic findings may be present, but the natural history and progression of ocular findings are often not described in the literature. METHODS: We studied the records and present findings of 2 patients with progressive hemifacial atrophy who were observed in our institution over a 10-year period. RESULTS: Both patients showed progression of ophthalmic findings, primarily on the affected side. One patient has had chronic uveitis with secondary cataract and glaucoma, in addition to retinal pigmentary changes. She also had a third-nerve paresis of the contralateral eye and mild seizure activity. The other patient had mild uveitis, some progression of unilateral retinal pigmentary changes, and a significant increase in hyperopia in the affected eye, in addition to hypotony at age 19 without a clear cause, but with secondary retinal and refractive changes. CONCLUSION: Ocular manifestations of progressive hemifacial atrophy are varied, but can progress from mild visual impairment to blindness. Images FIGURE 1 FIGURE 2 FIGURE 3A FIGURE 3B FIGURE 4 FIGURE 5 FIGURE 6 PMID:8719679

  6. Nuclear spectroscopic studies. Progress report

    SciTech Connect

    Bingham, C.R.; Guidry, M.W.; Riedinger, L.L.; Sorensen, S.P.

    1994-02-18

    The Nuclear Physics group at UTK is involved in heavy-ion physics including both nuclear structure and reaction mechanisms. During the last year experimental work has been in 3 broad areas: structure of nuclei at high angular momentum, structure of nuclei far from stability, and ultra-relativistic heavy-ion physics. Results in these areas are described in this document under: properties of high-spin states, study of low-energy levels of nuclei far from stability, and high-energy heavy-ion physics (PHENIX, etc.). Another important component of the work is theoretical interpretation of experimental results (Joint Institute for Heavy Ion Research).

  7. Nuclear spectroscopic studies. Progress report

    SciTech Connect

    Bingham, C.R.; Guidry, M.W.; Riedinger, L.L.; Sorensen, S.P.

    1993-02-08

    The Nuclear Physics group at the University of Tennessee, Knoxville is involved in several aspects of heavy-ion physics including both nuclear structure and reaction mechanisms. While our main emphasis is on experimental problems involving heavy-ion accelerators, we have maintained a strong collaboration with several theorists in order to best pursue the physics of our measurements. During the last year we have led several experiments at the Holifield Heavy Ion Research Facility and participated in others at Argonne National Laboratory. Also, we continue to be very active in the collaboration to study ultra-relativistic heavy ion physics utilizing the SPS accelerator at CERN in Geneva, Switzerland and in a RHIC detector R&D project. Our experimental work is in four broad areas: (1) the structure of nuclei at high angular momentum, (2) heavy-ion induced transfer reactions, (3) the structure of nuclei far from stability, and (4) ultra-relativistic heavy-ion physics. The results of studies in these particular areas will be described in this document in sections IIA, IIB, IIC, and IID, respectively. Areas (1), (3), and (4) concentrate on the structure of nuclear matter in extreme conditions of rotational motion, imbalance of neutrons and protons, or very high temperature and density. Area (2) pursues the transfer of nucleons to states with high angular momentum, both to learn about their structure and to understand the transfer of particles, energy, and angular momentum in collisions between heavy ions. An important component of our program is the strong emphasis on the theoretical aspects of nuclear structure and reactions.

  8. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Progress report, November 1993--November 1994

    SciTech Connect

    McInerney, M.J.

    1994-12-06

    Factors influencing the rate and extent of benzoate degradation by the anaerobic syntrophic consortia were studied. Nonlinear regression analysis showed that the cause of the benzoate threshold was not a diminished benzoate degradation capacity. Analysis of cocultures with hydrogen users that differed in their hydrogen utilization capacities showed that the threshold did not depend on the kinetic properties of the syntrophic partner. These data support a thermodynamic explanation for the threshold, and exclude the possibility that a change in the affinity of the enzyme system due to acetate inhibition caused the threshold. Modeling studies showed that the threshold value could be predicted from the concentrations of the end products, assuming a critical Gibb`s free energy value. This work shows that interspecies acetate transfer is important in controlling the extent of metabolism by syntrophic organisms.

  9. Kinetic Uptake Studies of Powdered Materials in Solution

    PubMed Central

    Mohamed, Mohamed H.; Wilson, Lee D.

    2015-01-01

    Challenges exist for the study of time dependent sorption processes for heterogeneous systems, especially in the case of dispersed nanomaterials in solvents or solutions because they are not well suited to conventional batch kinetic experiments. In this study, a comparison of batch versus a one-pot setup in two variable configurations was evaluated for the study of uptake kinetics in heterogeneous (solid/solution) systems: (i) conventional batch method; (ii) one-pot system with dispersed adsorbent in solution with a semi-permeable barrier (filter paper or dialysis tubing) for in situ sampling; and (iii) one-pot system with an adsorbent confined in a semi-permeable barrier (dialysis tubing or filter paper barrier) with ex situ sampling. The sorbent systems evaluated herein include several cyclodextrin-based polyurethane materials with two types of phenolic dyes: p-nitrophenol and phenolphthalein. The one-pot kinetics method with in situ (Method ii) or ex situ (Method iii) sampling described herein offers significant advantages for the study of heterogeneous sorption kinetics of highly dispersed sorbent materials with particles sizes across a range of dimensions from the micron to nanometer scale. The method described herein will contribute positively to the development of advanced studies for heterogeneous sorption processes where an assessment of the relative uptake properties is required at different experimental conditions. The results of this study will be advantageous for the study of nanomaterials with significant benefits over batch kinetic studies for a wide range of heterogeneous sorption processes.

  10. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Progress report, November 1992--November 1993

    SciTech Connect

    McInerney, M.J.

    1993-11-12

    The kinetics of benzoate degradation by the anaerobic syntrophic bacterium, Syntrophus buswellii, in coculture with different sulfate reducers was studied with sulfate or nitrate as the electron acceptor. A threshold value for benzoate degradation dependent on the acetate concentration was observed with sulfate, but not nitrate, as the electron acceptor. No threshold was observed in tricultures containing an acetate-using sulfate reducer. The addition of the acetate-using sulfate reducer to cocultures that had degraded benzoate to its threshold value resulted in further degradation of benzoate to levels below the analytical detection limit (ca. 200 nM). These data are consistent with a thermodynamic explanation for the threshold, and exclude the possibility that the threshold was the result of the inhibitory action of the undissociated form of acetate.

  11. Research in chemical kinetics. Progress report, July 20, 1988--August 30, 1989

    SciTech Connect

    Rowland, F.S.

    1996-09-01

    A major aspect of our research over the past decade under this contract has been the application of radioisotopes generated by nuclear reactions for the study of various kinetic mechanisms. Two general theoretical concepts have been explored in detail by this technique: (a) The addition of halogen atoms to olefins, which have been described for fifty years by the phrase {open_quotes}anti-Markownikoff{close_quotes} to indicate that the preference for one or the other end of an unsymmetric olefin is opposite to that ({open_quotes}Markownikoff addition{close_quotes}) for hydrogen halide addition. (b) The redistribution of internal energy within a molecule after an energetic addition reaction, for which the usual assumption is rapid equilibration into all available degrees of freedom, as calculated by the Rice-Rarnsperger-Kassel-Marcus (RRKM) model. In both instances, significant results have been obtained which expand the overall view of each of these two concepts.

  12. Progress with the COGENT Edge Kinetic Code: Implementing the Fokker-Plank Collision Operator

    SciTech Connect

    Dorf, M. A.; Cohen, R. H.; Dorr, M.; Hittinger, J.; Rognlien, T. D.

    2014-06-20

    Here, COGENT is a continuum gyrokinetic code for edge plasma simulations being developed by the Edge Simulation Laboratory collaboration. The code is distinguished by application of a fourth-order finite-volume (conservative) discretization, and mapped multiblock grid technology to handle the geometric complexity of the tokamak edge. The distribution function F is discretized in v∥ – μ (parallel velocity – magnetic moment) velocity coordinates, and the code presently solves an axisymmetric full-f gyro-kinetic equation coupled to the long-wavelength limit of the gyro-Poisson equation. COGENT capabilities are extended by implementing the fully nonlinear Fokker-Plank operator to model Coulomb collisions in magnetized edge plasmas. The corresponding Rosenbluth potentials are computed by making use of a finite-difference scheme and multipole-expansion boundary conditions. Details of the numerical algorithms and results of the initial verification studies are discussed. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

  13. Kinetic Study on Pyrolysis of Oil Palm Frond

    NASA Astrophysics Data System (ADS)

    Soon, V. S. Y.; Chin, B. L. F.; Lim, A. C. R.

    2016-03-01

    The pyrolysis of oil palm frond is studied using thermogravimetric analysis (TGA) equipment. The present study investigates the thermal degradation behaviour and determination of the kinetic parameters such as the activation energy (EA ) and pre-exponential factor (A) values of oil palm frond under pyrolysis condition. The kinetic data is produced based on first order rate of reaction. In this study, the experiments are conducted at different heating rates of 10, 20, 30, 40 and 50 K/min in the temperature range of 323-1173 K under non-isothermal condition. Argon gas is used as an inert gas to remove any entrapment of gases in the TGA equipment.

  14. A Novel Approach to Experimental Studies of Mineral Dissolution Kinetics

    SciTech Connect

    Chen Zhu; William E. Seyfried

    2005-01-01

    Currently, DOE is conducting pilot CO{sub 2} injection tests to evaluate the concept of geological sequestration. One strategy that potentially enhances CO{sub 2} solubility and reduces the risk of CO{sub 2} leak back to the surface is dissolution of indigenous minerals in the geological formation and precipitation of secondary carbonate phases, which increases the brine pH and immobilizes CO{sub 2}. Clearly, the rates at which these dissolution and precipitation reactions occur directly determine the efficiency of this strategy. However, one of the fundamental problems in modern geochemistry is the persistent two to five orders of magnitude discrepancy between laboratory-measured and field derived feldspar dissolution rates. To date, there is no real guidance as to how to predict silicate reaction rates for use in quantitative models. Current models for assessment of geological carbon sequestration have generally opted to use laboratory rates, in spite of the dearth of such data for compositionally complex systems, and the persistent disconnect between lab and field applications. Therefore, a firm scientific basis for predicting silicate reaction kinetics in CO{sub 2} injected geological formations is urgently needed to assure the reliability of the geochemical models used for the assessments of carbon sequestration strategies. The funded experimental and theoretical study attempts to resolve this outstanding scientific issue by novel experimental design and theoretical interpretation to measure silicate dissolution rates and iron carbonate precipitation rates at conditions pertinent to geological carbon sequestration. In the first year of the project, we have successfully developed a sample preparation method and completed three batch feldspar dissolution experiments at 200 C and 300 bars. The changes of solution chemistry as dissolution experiments progressed were monitored with on-line sampling of the aqueous phase at the constant temperature and pressure

  15. Label-free solution-based kinetic study of aptamer-small molecule interactions by kinetic capillary electrophoresis with UV detection revealing how kinetics control equilibrium.

    PubMed

    Bao, Jiayin; Krylova, Svetlana M; Reinstein, Oren; Johnson, Philip E; Krylov, Sergey N

    2011-11-15

    Here we demonstrate a label-free solution-based approach for studying the kinetics of biopolymer-small molecule interactions. The approach utilizes kinetic capillary electrophoresis (KCE) separation and UV light absorption detection of the unlabeled small molecule. In this proof-of-concept work, we applied KCE-UV to study kinetics of interaction between a small molecule and a DNA aptamer. From the kinetic analysis of a series of aptamers, we found that dissociation rather than binding controls the stability of the complex. Because of its label-free features and generic nature, KCE-UV promises to become a practical tool for challenging kinetic studies of biopolymer-small molecule interactions.

  16. ANALYTICAL METHODS FOR KINETIC STUDIES OF BIOLOGICAL INTERACTIONS: A REVIEW

    PubMed Central

    Zheng, Xiwei; Bi, Cong; Li, Zhao; Podariu, Maria; Hage, David S.

    2015-01-01

    The rates at which biological interactions occur can provide important information concerning the mechanism and behavior of these processes in living systems. This review discusses several analytical methods that can be used to examine the kinetics of biological interactions. These techniques include common or traditional methods such as stopped-flow analysis and surface plasmon resonance spectroscopy, as well as alternative methods based on affinity chromatography and capillary electrophoresis. The general principles and theory behind these approaches are examined, and it is shown how each technique can be utilized to provide information on the kinetics of biological interactions. Examples of applications are also given for each method. In addition, a discussion is provided on the relative advantages or potential limitations of each technique regarding its use in kinetic studies. PMID:25700721

  17. Electrogravimetric real-time and in situ michaelis-menten enzymatic kinetics: progress curve of acetylcholinesterase hydrolysis.

    PubMed

    Bueno, Paulo R; Watanabe, Ailton M; Faria, Ronaldo C; Santos, Márcio L; Riccardi, Carla S

    2010-12-16

    A piezoelectric detection of enzyme-modified surface was performed under Michaelis-Menten presumptions of steady-state condition. The approach herein presented showed promise in the study of enzymatic kinetics by measuring the frequency changes associated with mass changes at the piezoelectric crystal surface. Likewise, real-time frequency shifts, that is, dΔf/dt, indicated the rate of products formation from enzymatic reaction. In this paper, acetylcholinesterase was used as the enzymatic model and acetylcholine as substrate. The enzymatic rate has its maximum value for a short time during the kinetic reaction, for instance, during the first ten minutes of the reaction time scale. The values found for the kinetic constant rate and Michaelis-Menten constant were (1.4 ± 0.8) 10(5) s(-1) and (5.2 ± 3) 10(-4) M, respectively, in agreement with the values found in classical Michaelis-Menten kinetic experiments.

  18. Progress with the COGENT Edge Kinetic Code: Implementing the Fokker-Plank Collision Operator

    DOE PAGES

    Dorf, M. A.; Cohen, R. H.; Dorr, M.; ...

    2014-06-20

    Here, COGENT is a continuum gyrokinetic code for edge plasma simulations being developed by the Edge Simulation Laboratory collaboration. The code is distinguished by application of a fourth-order finite-volume (conservative) discretization, and mapped multiblock grid technology to handle the geometric complexity of the tokamak edge. The distribution function F is discretized in v∥ – μ (parallel velocity – magnetic moment) velocity coordinates, and the code presently solves an axisymmetric full-f gyro-kinetic equation coupled to the long-wavelength limit of the gyro-Poisson equation. COGENT capabilities are extended by implementing the fully nonlinear Fokker-Plank operator to model Coulomb collisions in magnetized edge plasmas.more » The corresponding Rosenbluth potentials are computed by making use of a finite-difference scheme and multipole-expansion boundary conditions. Details of the numerical algorithms and results of the initial verification studies are discussed. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)« less

  19. Raman scattering study of glass crystallization kinetics

    NASA Astrophysics Data System (ADS)

    Balkanski, M.; Haro, E.; Espinosa, G. P.; Phillips, J. C.

    1984-08-01

    Laser induced glass-crystalline transition is studied by light scattering. Three significant effects are observed depending on the incident laser energy density: (i) Spectral band narrowing indicating cluster enlargement constitutes a precursor effect, (ii) an intensity increase effect indicates a rapid rise of the density of clusters attaining microcrystalline size and (iii) a dynamical reversal effect indicative of glass-crystalline instability. Cluster volume and crystallization appear as separate but related threshold phenomena.

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

    ERIC Educational Resources Information Center

    Gozzi, Christel; Bouzidi, Naoual

    2008-01-01

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

  1. Impact of anomalous transport kinetics on the progress of wound healing.

    PubMed

    Javierre, E

    2016-09-01

    This work focuses on the transport kinetics of chemical and cellular species during wound healing. Anomalous transport kinetics, coupling sub- and superdiffusion with chemotaxis, and fractional viscoelasticity of soft tissues are analyzed from a modeling point of view. The paper presents a generalization of well stablished mechano-chemical models of wound contraction (Murphy et al., 2012; Valero et al., 2014) to include the previously mentioned anomalous effects by means of partial differential equations of fractional order. Results show the effect that anomalous dynamics have on the contraction rate and extension and on the distribution of biological species, and indicators of fibroproliferative disorders are identified.

  2. Progress in improving thermodynamics and kinetics of new hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Song, Li-fang; Jiang, Chun-hong; Liu, Shu-sheng; Jiao, Cheng-li; Si, Xiao-liang; Wang, Shuang; Li, Fen; Zhang, Jian; Sun, Li-xian; Xu, Fen; Huang, Feng-lei

    2011-06-01

    Hydrogen storage material has been much developed recently because of its potential for proton exchange membrane (PEM) fuel cell applications. A successful solid-state reversible storage material should meet the requirements of high storage capacity, suitable thermodynamic properties, and fast adsorption and desorption kinetics. Complex hydrides, including boron hydride and alanate, ammonia borane, metal organic frameworks (MOFs), covalent organic frameworks (COFs) and zeolitic imidazolate frameworks (ZIFs), are remarkable hydrogen storage materials because of their advantages of high energy density and safety. This feature article focuses mainly on the thermodynamics and kinetics of these hydrogen storage materials in the past few years.

  3. Effect of sorption on flocculation kinetics: Experimental studies

    SciTech Connect

    Subramaniam, K.; Yiacoumi, S.; Tsouris, C.

    1997-11-01

    Sorption of copper and cadmium ions from aqueous solutions by ferric oxide particles was studied using batch equilibrium and kinetic experiments. The sorption process was found to be pH dependent, with the uptake increasing at high pH values. An increase in equilibrium pH was observed when the initial pH was in the acidic range and a decrease from initial values was observed in the basic range, in the case of both copper and cadmium sorption. The former phenomenon is due to competition between metal and proton binding and the latter is due to precipitation mechanisms at high initial pH values. A large increase in the zeta potential of the particles from baseline values was observed during equilibrium sorption. This increase occurs as a result of surface charge neutralization due to metal ion uptake. Particle destabilization appears to occur as a result of metal ion sorption. Kinetic experiments indicate that the uptake of copper by ferric oxide particles is a slow process. pH histories were similar to those obtained in the sorption equilibrium experiments. Changes in the size distribution of the ferric oxide particles due to aggregate formation during uptake of ions is observed in the kinetic studies. These findings indicate a potential role of metal ion uptake in particle flocculation kinetics through alteration of the surface electrostatic potential.

  4. Kinetic studies of microfabricated biosensors using local adsorption strategy.

    PubMed

    Zhang, Menglun; Huang, Jingze; Cui, Weiwei; Pang, Wei; Zhang, Hao; Zhang, Daihua; Duan, Xuexin

    2015-12-15

    Micro/nano scale biosensors integrated with the local adsorption mask have been demonstrated to have a better limit of detection (LOD) and less sample consumptions. However, the molecular diffusions and binding kinetics in such confined droplet have been less studied which limited further development and application of the local adsorption method and imposed restrictions on discovery of new signal amplification strategies. In this work, we studied the kinetic issues via experimental investigations and theoretical analysis on microfabricated biosensors. Mass sensitive film bulk acoustic resonator (FBAR) sensors with hydrophobic Teflon film covering the non-sensing area as the mask were introduced. The fabricated masking sensors were characterized with physical adsorption of bovine serum albumin (BSA) and specific binding of antibody and antigen. Over an order of magnitude improvement on LOD was experimentally monitored. An analytical model was introduced to discuss the target molecule diffusion and binding kinetics in droplet environment, especially the crucial effects of incubation time, which has been less covered in previous local adsorption related literatures. An incubation time accumulated signal amplification effect was theoretically predicted, experimentally monitored and carefully explained. In addition, device optimization was explored based on the analytical model to fully utilize the merits of local adsorption. The discussions on the kinetic issues are believed to have wide implications for other types of micro/nano fabricated biosensors with potentially improved LOD.

  5. Can We Confidently Study VO2 Kinetics in Young People?

    PubMed Central

    Fawkner, Samantha G.; Armstrong, Neil

    2007-01-01

    The study of VO2 kinetics offers the potential to non-invasively examine the cardiorespiratory and metabolic response to dynamic exercise and limitations to every day physical activity. Its non-invasive nature makes it hugely attractive for use with young people, both healthy and those with disease, and yet the literature, whilst growing with respect to adults, remains confined to a cluster of studies with these special populations. It is most likely that this is partly due to the methodological difficulties involved in studying VO2 kinetics in young people which are not present, or present to a lesser degree, with adults. This article reviews these methodological issues, and explains the main procedures that might be used to overcome them. Key pointsThe VO2 kinetic response to exercise represents the combined efficiency of the cardiovascular, pulmonary and metabolic systems, and an accurate assessment of the response potentially provides a great deal of useful information via non-invasive methodology.An accurate assessment of the VO2 kinetic response is however inherently difficult with children and especially those with reduced exercise tolerance, due primarily to the apparent breath-by-breath noise which masks the true underlying physiological response, and the small amplitudes of the response signal.Despite this, it is possible to assess and quantify the VO2 kinetic response with children if appropriate steps are taken to apply carefully selected methodologies and report response variables with confidence intervals. In this way, both the researcher and the reader can be confident that the data reported is meaningful. PMID:24149413

  6. COMSOL-based Nuclear Reactor Kinetics Studies at the HFIR

    SciTech Connect

    Chandler, David; Freels, James D; Maldonado, G Ivan; Primm, Trent

    2011-01-01

    The computational ability to accurately predict the dynamic behavior of a nuclear reactor core in response to reactivity-induced perturbations is an important subject in reactor physics. Space-time and point kinetics methodologies were developed for the purpose of studying the transient-induced behavior of the High Flux Isotope Reactor s (HFIR) compact core. The space-time simulations employed the three-energy-group neutron diffusion equations, and transients initiated by control cylinder and hydraulic tube rabbit ejections were studied. The work presented here is the first step towards creating a comprehensive multiphysics methodology for studying the dynamic behavior of the HFIR core during reactivity perturbations. The results of these studies show that point kinetics is adequate for small perturbations in which the power distribution is assumed to be time-independent, but space-time methods must be utilized to determine localized effects.

  7. Applications of kinetic theory. Predictive models of circulating fluidized bed combustors: Tenth technical progress report

    SciTech Connect

    Gidaspow, D.

    1992-01-01

    The overall objective of this investigation is to develop experimentally verified models for circulating fluidized bed (CFB) combustors. This report presents the author`s derivation of analytical solutions useful in understanding the operation of a CFB. The report is in a form of a chapter that reviews the kinetic theory applications.

  8. Rupture kinetics of liquid bridges during a pulling process: a kinetic density functional theory study.

    PubMed

    Men, Yumei; Zhang, Xianren; Wang, Wenchuan

    2011-03-28

    Capillary bridge is a common phenomenon in nature and can significantly contribute to the adhesion of biological and artificial micro- and nanoscale objects. Especially, it plays a crucial role in the operation of atomic force microscopy (AFM) and influences in the measured force. In the present work, we study the rupture kinetics and transition pathways of liquid bridges connecting an AFM tip and a flat substrate during a process of pulling the tip off. Depending on thermodynamic conditions and the tip velocity, two regimes corresponding to different transition pathways are identified. In the single-bridge regime, the initial equilibrium bridge persists as a single one during the pulling process until the liquid bridge breaks. While, in the multibridge regime the stretched liquid bridge transforms into an intermediate state with a collection of slender liquid bridges, which then break gradually during the pulling process. Moreover, the critical rupture distance at which the bridges break changes with the tip velocity and thermodynamic conditions, and its maximum value occurs near the boundary between the single-bridge regime and the multibridge regime, where the longest range capillary force is produced. In this work, the effects of tip velocity, tip size, tip-fluid interaction, and humidity on rupture kinetics and transition pathways are also systematically studied.

  9. Covalent binding of aniline to humic substances. 1. Kinetic studies

    USGS Publications Warehouse

    Weber, E.J.; Spidle, D.L.; Thorn, K.A.

    1996-01-01

    The reaction kinetics for the covalent binding of aniline with reconstituted IHSS humic and fulvic acids, unfractionated DOM isolated from Suwannee River water, and whole samples of Suwannee River water have been investigated. The reaction kinetics in each of these systems can be adequately described by a simple second-order rate expression. The effect of varying the initial concentration of aniline on reaction kinetics suggested that approximately 10% of the covalent binding sites associated with Suwannee River fulvic acid are highly reactive sites that are quickly saturated. Based on the kinetic parameters determined for the binding of aniline with the Suwannee River fulvic and humic acid isolates, it was estimated that 50% of the aniline concentration decrease in a Suwannee River water sample could be attributed to reaction with the fulvic and humic acid components of the whole water sample. Studies with Suwannee River fulvic acid demonstrated that the rate of binding decreased with decreasing pH, which parallels the decrease in the effective concentration of the neutral form, or reactive nucleophilic species of aniline. The covalent binding of aniline with Suwannee River fulvic acid was inhibited by prior treatment of the fulvic acid with hydrogen sulfide, sodium borohydride, or hydroxylamine. These observations are consistent with a reaction pathway involving nucleophilic addition of aniline to carbonyl moieties present in the fulvic acid.

  10. Computational Kinetic Study for the Unimolecular Decomposition Pathways of Cyclohexanone.

    PubMed

    Zaras, Aristotelis M; Dagaut, Philippe; Serinyel, Zeynep

    2015-07-16

    There has been evidence lately that several endophytic fungi can convert lignocellulosic biomass into ketones among other oxygenated compounds. Such compounds could prove useful as biofuels for internal combustion engines. Therefore, their combustion properties are of high interest. Cyclohexanone was identified as an interesting second-generation biofuel ( Boot , M. ; et al. Cyclic Oxygenates: A New Class of Second-Generation Biofuels for Diesel Engines? Energy Fuels 2009 , 23 , 1808 - 1817 ; Klein-Douwel , R. J. H. ; et al. Soot and Chemiluminescence in Diesel Combustion of Bio-Derived, Oxygenated and Reference Fuels . Proc. Combust. Inst. 2009 , 32 , 2817 - 2825 ). However, until recently ( Serinyel , Z. ; et al. Kinetics of Oxidation of Cyclohexanone in a Jet- Stirred Reactor: Experimental and Modeling . Proc. Combust. Inst. 2014 ; DOI: 10.1016/j.proci.2014.06.150 ), no previous studies on the kinetics of oxidation of that fuel could be found in the literature. In this work, we present the first theoretical kinetic study of the unimolecular decomposition pathways of cyclohexanone, a cyclic ketone that could demonstrate important fuel potential. Using the quantum composite G3B3 method, we identified six different decomposition pathways for cyclohexanone and computed the corresponding rate constants. The rate constants were calculated using the G3B3 method coupled with Rice-Ramsperger-Kassel-Marcus theory in the temperature range of 800-2000 K. Our calculations show that the kinetically more favorable channel for thermal decomposition is pathway 2 that produces 1,3-butadien-2-ol, which in turn can isomerize easily to methyl vinyl ketone through a small barrier. The results presented here can be used in a future kinetic combustion mechanism.

  11. Quantitative studies in radiopharmaceutical science. Progress report, April 1-August 31, 1986

    SciTech Connect

    Cooper, M.

    1986-09-01

    This report covers progress made during the first reporting period since the redirection of the project. In radiochemistry, achievements in fluorine-18 tracer studies including purification and reaction kinetics of 2-fluorodeoxyglucose and production of 6-fluoroDOPA. Radiopharmaceuticals have been prepared and tested for studies on CNS dopaminergic systems. By use of dynamic positron emission tomography the cerebral transport and metabolism of glucose continues to be studied. 6 figs.

  12. Paradoxical dependencies of tumor dormancy and progression on basic cell kinetics.

    PubMed

    Enderling, Heiko; Anderson, Alexander R A; Chaplain, Mark A J; Beheshti, Afshin; Hlatky, Lynn; Hahnfeldt, Philip

    2009-11-15

    Even after a tumor is established, it can early on enter a state of dormancy marked by balanced cell proliferation and cell death. Disturbances to this equilibrium may affect cancer risk, as they may cause the eventual lifetime clinical presentation of a tumor that might otherwise have remained asymptomatic. Previously, we showed that cell death, proliferation, and migration can play a role in shifting this dynamic, making the understanding of their combined influence on tumor development essential. We developed an individual cell-based computer model of the interaction of cancer stem cells and their nonstem progeny to study early tumor dynamics. Simulations of tumor growth show that three basic components of tumor growth--cell proliferation, migration, and death--combine in unexpected ways to control tumor progression and, thus, clinical cancer risk. We show that increased proliferation capacity in nonstem tumor cells and limited cell migration overall lead to space constraints that inhibit proliferation and tumor growth. By contrast, increasing the rate of cell death produces the expected tumor size reduction in the short term, but results ultimately in paradoxical accelerated long-term growth owing to the liberation of cancer stem cells and formation of self-metastases.

  13. Coordination: southeast continental shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1980-03-01

    The GABEX I experiment is designed to provide synoptic coverage of a series of Gulf Stream wave-like disturbances, the effect of these on the circulation of the entire shelf, and on biological and chemical processes. This study was initiated in February 1980 when current meter arrays were deployed. These meters will be removed in July 1980. In April three ships will simultaneously study the effects of Gulf Stream disturbances on the hydrography, chemistry, and biology of the shelf. One vessel will track a specific wave-like disturbance and provide synoptic coverage of the shelf area. The second vessel will determine the effect of shelf break processes on adjacent shelf water; and the third will study trace metal distributions in and outside of disturbances. Research progress is reported in continental shelf studies, nearshore and estuarine studies (diffusion of freshwater out of nearshore zone), tidal currents and material transport, and mixing of inlet plumes.

  14. A Novel Approach to Experimental Studies of Mineral Dissolution Kinetics

    SciTech Connect

    Chen Zhu

    2006-08-31

    Currently, DOE is conducting pilot CO{sub 2} injection tests to evaluate the concept of geological sequestration. One strategy that potentially enhances CO{sub 2} solubility and reduces the risk of CO{sub 2} leak back to the surface is dissolution of indigenous minerals in the geological formation and precipitation of secondary carbonate phases, which increases the brine pH and immobilizes CO{sub 2}. Clearly, the rates at which these dissolution and precipitation reactions occur directly determine the efficiency of this strategy. However, one of the fundamental problems in modern geochemistry is the persistent two to five orders of magnitude discrepancy between laboratory measured and field derived feldspar dissolution rates. To date, there is no real guidance as to how to predict silicate reaction rates for use in quantitative models. Current models for assessment of geological carbon sequestration have generally opted to use laboratory rates, in spite of the dearth of such data for compositionally complex systems, and the persistent disconnect between laboratory and field applications. Therefore, a firm scientific basis for predicting silicate reaction kinetics in CO2 injected geological formations is urgently needed to assure the reliability of the geochemical models used for the assessments of carbon sequestration strategies. The funded experimental and theoretical study attempts to resolve this outstanding scientific issue by novel experimental design and theoretical interpretation to measure silicate dissolution rates and iron carbonate precipitation rates at conditions pertinent to geological carbon sequestration. In the second year of the project, we completed CO{sub 2}-Navajo sandstone interaction batch and flow-through experiments and a Navajo sandstone dissolution experiment without the presence of CO{sub 2} at 200 C and 250-300 bars, and initiated dawsonite dissolution and solubility experiments. We also performed additional 5-day experiments at the

  15. Kinetic studies of corn stover saccharification using sulphuric acid

    SciTech Connect

    Bhandari, N.; Macdonald, D.G.; Bakhshi, N.N.

    1984-01-01

    The kinetics of crystalline cellulose and hemicellulose hydrolysis in corn stover were studied with a nonisothermal technique. Reactions were arrested at temperatures between 160 and 240/sup 0/C and product sugars were analyzed using a Bio-Rad HPX-85 liquid chromatographic column. A simple first-order series reaction model was used for both cellulose and hemicellulose hydrolysis rections. Kinetic parameters were obtained for three different sulphuric acid concentrations (0.49, 0.92, and 1.47 wt %). Activation energies remained constant over this acid concentration range but the preexponential factors showed an increase with acid concentration. Relationships were obtained between the preexponential factors and acid concentrations. Cellulose hydrolysis and glucose degradation reactions were observed to be of higher order with respect to acid concentration in comparison with the previous studies with other raw materials.

  16. Kinetic studies of corn stover saccharification using sulphuric acid

    SciTech Connect

    Bhandari, N.; Macdonald, D.G.; Bakhshi, N.N.

    1984-04-01

    The kinetics of crystalline cellulose and hemicellulose hydrolysis in corn stover were studied with a nonisothermal technique. Reactions were arrested at temperatures between 160 and 240 degrees C and product sugars were analyzed using a Bio-Rad HPX-85 liquid chromatographic column. A simple first-order series reaction model was used for both cellulose and hemicellulose hydrolysis reactions. Kinetic parameters were obtained for three different sulphuric acid concentrations (0.49, 0.92, and 1.47 weight %). Activation energies remained constant over this acid concentration range but the preexponential factors showed an increase with acid concentration. Relationships were obtained between the preexponential factors and acid concentrations. Cellulose hydrolysis and glucose degradation reactions were observed to be of higher order with respect to acid concentration in comparison with the previous studies with other raw materials. (Refs. 22).

  17. PROGRESS IN DETAILED KINETIC MODELING OF THE COMBUSTION OF OXYGENATED COMPONENTS OF BIOFUELS

    PubMed Central

    Sy Tran, Luc; Sirjean, Baptiste; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique

    2013-01-01

    Due to growing environmental concerns and diminishing petroleum reserves, a wide range of oxygenated species has been proposed as possible substitutes to fossil fuels: alcohols, methyl esters, acyclic and cyclic ethers. After a short review the major detailed kinetic models already proposed in the literature for the combustion of these molecules, the specific classes of reactions considered for modeling the oxidation of acyclic and cyclic oxygenated molecules respectively, are detailed. PMID:23700355

  18. A kinetic study of struvite precipitation recycling technology with NaOH/Mg(OH)2 addition.

    PubMed

    Yu, Rongtai; Ren, Hongqiang; Wang, Yanru; Ding, Lili; Geng, Jingji; Xu, Ke; Zhang, Yan

    2013-09-01

    Struvite precipitation recycling technology is received wide attention in removal ammonium and phosphate out of wastewater. While past study focused on process efficiency, and less on kinetics. The kinetic study is essential for the design and optimization in the application of struvite precipitation recycling technology. The kinetics of struvite with NaOH/Mg(OH)2 addition were studied by thermogravimetry analysis with three rates (5, 10, 20 °C/min), using Friedman method and Ozawa-Flynn-Wall method, respectively. Degradation process of struvite with NaOH/Mg(OH)2 addition was three steps. The stripping of ammonia from struvite was mainly occurred at the first step. In the first step, the activation energy was about 70 kJ/mol, which has gradually declined as the reaction progress. By model fitting studies, the proper mechanism function for struvite decomposition process with NaOH/Mg(OH)2 addition was revealed. The mechanism function was f(α)=α(α)-(1-α)(n), a Prout-Tompkins nth order (Bna) model.

  19. Kinetics study on conventional and microwave pyrolysis of moso bamboo.

    PubMed

    Dong, Qing; Xiong, Yuanquan

    2014-11-01

    A comparative study on the pyrolysis kinetics of moso bamboo has been conducted in a conventional thermogravimetric analyzer and a microwave thermogravimetric analyzer respectively. The effect of heating rate on the pyrolysis process was also discussed. The results showed that both the maximum and average reaction rates increased with the heating rate increasing. The values of activation energy increased from 58.30 to 84.22 kJ/mol with the heating rate decreasing from 135 to 60 °C/min during conventional pyrolysis. The value of activation energy was 24.5 kJ/mol for microwave pyrolysis, much lower than that for conventional pyrolysis at a similar heating rate of 160 °C/min. The pyrolysis of moso bamboo exhibited a kinetic compensation effect. The low activation energy obtained under microwave irradiation suggests that microwaves heating would be a promising method for biomass pyrolysis.

  20. Adsorption of chromium onto activated alumina: kinetics and thermodynamics studies.

    PubMed

    Marzouk, Ikhlass; Dammak, Lassaad; Hamrouni, Béchir

    2013-02-01

    In this study, the removal of chromium (VI) by adsorption on activated alumina was investigated and the results were fitted to Langmuir, Freundlich, Dubinin-Redushkevich, and Temkin adsorption models at various temperatures. The constants of each model were evaluated depending on temperature. Thermodynamic parameters for the adsorption system were determined at 10, 25 and 40 degrees C. (deltaH degrees = -21.18 kJ x mol(-1); deltaG degrees = -8.75 to -7.43 kJ x mol(-1) and deltaS degrees = -0.043 kJ x K(-1) x mol(-1)). The obtained values showed that chromium (VI) adsorption is a spontaneous and exothermic process. The kinetic process was evaluated by first-order, second-order and Elovich kinetic models.

  1. Kinetic Studies of Biological Interactions By Affinity Chromatography

    PubMed Central

    Schiel, John E.; Hage, David S.

    2009-01-01

    The rates at which biological interactions occur can provide important information on the mechanism and behavior of such processes in living systems. This review will discuss how affinity chromatography can be used as a tool to examine the kinetics of biological interactions. This approach, referred to here as biointeraction chromatography, uses a column with an immobilized binding agent to examine the association or dissociation of this agent with other compounds. The use of HPLC-based affinity columns in kinetic studies has received particular attention in recent years. Advantages of using HPLC with affinity chromatography for this purpose include the ability to reuse the same ligand within a column for a large number of experiments, and the good precision and accuracy of this approach. A number of techniques are available for kinetic studies through the use of affinity columns and biointeraction chromatography. These approaches include plate height measurements, peak profiling, peak fitting, split-peak measurements, and peak decay analysis. The general principles for each of these methods are discussed in this review and some recent applications of these techniques are presented. The advantages and potential limitations of each approach are also considered. PMID:19391173

  2. Antioxidant activity and kinetics studies of eugenol and 6-bromoeugenol.

    PubMed

    Mahboub, Radia; Memmou, Faiza

    2015-01-01

    In this work, we report the antioxidant and free radical scavenging activity of 6-bromoeugenol and eugenol. EC50, the concentration providing 50% inhibition, is calculated and the antioxidant activity index (AAI) is evaluated. The antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging method. EC50 values of 6-bromoeugenol, ascorbic acid and eugenol were 34.270 μg/mL, 54.888 μg/mL and 130.485 μg/mL, respectively. 6-Bromoeugenol showed higher AAI value (1.122) followed by ascorbic acid (0.700), then by eugenol (0.295). We also investigate the kinetics of DPPH radical scavenging activity of our products to determine the useful parameter TEC50 to evaluate their antiradical efficiency (ARE). Our results have shown high ARE. This study has provided the following ARE ( × 10(-3)) order for the tested antioxidants: ascorbic acid (70.119)>6-bromoeugenol (34.842) > eugenol (21.313). Finally, we classify ascorbic acid and eugenol as fast kinetics reaction (TEC50 8.82 and 11.38 min, respectively) and 6-bromoeugenol as medium kinetics reaction (TEC50 39.24 min).

  3. Kinetic study of the cetyltrimethylammonium/DNA interaction.

    PubMed

    Grueso, E; Roldan, E; Sanchez, F

    2009-06-18

    A kinetic study of the interaction of the surfactant cetyltrimethylammonium (CTA(+)) with DNA was carried out in water and in salt (NaCl) solutions. The results can be explained in terms of a reaction mechanism involving two consecutive reversible steps. The first step corresponds to the union/separation of the surfactant with/from the DNA. The second step corresponds to a conformational change of the surfactant/DNA complex. The equilibrium constant, calculated from the forward and reverse rate constants of these steps, agrees with the results of a previous thermodynamic study.

  4. Kinetics of enzymatic high-solid hydrolysis of lignocellulosic biomass studied by calorimetry.

    PubMed

    Olsen, Søren N; Lumby, Erik; McFarland, Kc; Borch, Kim; Westh, Peter

    2011-03-01

    Enzymatic hydrolysis of high-solid biomass (>10% w/w dry mass) has become increasingly important as a key step in the production of second-generation bioethanol. To this end, development of quantitative real-time assays is desirable both for empirical optimization and for detailed kinetic analysis. In the current work, we have investigated the application of isothermal calorimetry to study the kinetics of enzymatic hydrolysis of two substrates (pretreated corn stover and Avicel) at high-solid contents (up to 29% w/w). It was found that the calorimetric heat flow provided a true measure of the hydrolysis rate with a detection limit of about 500 pmol glucose s(-1). Hence, calorimetry is shown to be a highly sensitive real-time method, applicable for high solids, and independent on the complexity of the substrate. Dose-response experiments with a typical cellulase cocktail enabled a multidimensional analysis of the interrelationships of enzyme load and the rate, time, and extent of the reaction. The results suggest that the hydrolysis rate of pretreated corn stover is limited initially by available attack points on the substrate surface (<10% conversion) but becomes proportional to enzyme dosage (excess of attack points) at later stages (>10% conversion). This kinetic profile is interpreted as an increase in polymer end concentration (substrate for CBH) as the hydrolysis progresses, probably due to EG activity in the enzyme cocktail. Finally, irreversible enzyme inactivation did not appear to be the source of reduced hydrolysis rate over time.

  5. A kinetic study of rabbit muscle pyruvate kinase

    PubMed Central

    Ainsworth, Stanley; Macfarlane, Neil

    1973-01-01

    The paper reports a study of the kinetics of the reaction between phosphoenolpyruvate, ADP and Mg2+ catalysed by rabbit muscle pyruvate kinase. The experimental results indicate that the reaction mechanism is equilibrium random-order in type, that the substrates and products are phosphoenolpyruvate, ADP, Mg2+, pyruvate and MgATP, and that dead-end complexes, between pyruvate, ADP and Mg2+, form randomly and exist in equilibrium with themselves and other substrate complexes. Values were determined for the Michaelis, dissociation and inhibition constants of the reaction and are compared with values ascertained by previous workers. PMID:4737316

  6. Coke forming reaction kinetic study on petroleum based feeds

    SciTech Connect

    Shigley, J.K.; Fu, Ta-Wei

    1988-08-01

    The carbonization of hydrocarbons is a very complex process. The pyrolysis reactions are predominantly free radical in nature and can be summarized as a polymerization process. The phase transitions from a 199% isotropic phase to an anisotropic mesophase during the carbonization of many feeds is an important and much studied phenomena. This phenomena is capitalized on in industry to produce needle or graphite coke. The kinetics of pitch polymerization and coke formation have historically been studied by measuring the solubility of the heat treated material in various solvents. The concentration of free radicals in the carbonized samples have also been used to investigate the mechanistic and kinetic aspects of the process. A very extensive study was conducted by Greinke using GPC techniques to measure the changes in narrow molecular weight ranges and the overall molecular weight distribution of a pitch during carbonization. This study focuses on the use of product volatile matter as the measure of extent of carbonization of two different feedstocks. It is ideally suited for use in commercial coking operations as a control or quality parameter of green coke.

  7. Reactivity of organic micropollutants with ozone: A kinetic study

    SciTech Connect

    Brambilla, A.; Bolzacchini, E.; Meinardi, S.

    1995-12-01

    Studies about the chemical reactivity of compounds widely used in the environment are needed. The chemical reactivity of triazines (simazine, atrazine, terbutylazine) and phenylureas (linuron and diuron) was studied. The kinetics of the oxidation of the triazines and phenylureas with ozone at pH 3 and the kinetics of the saturation of the solution with ozone were evaluated. These data may be useful for the prediction of the persistency of these compuonds in the environment and for the treatment of wastewaters contaminated with these compounds. The solution was presaturated with ozone before the addition of the substrate, and the reaction constants for the pseudo first order kinetics -d[substrate]/dt = k{sub app} [substrate] at 298{degree}K were obtained, assuming a steady state concentration of ozone of 1.91 10{sup -4} mol L{sup -1} for the phenylureas and of 3.03 10{sup -4} and L{sup -1} for the triazines. The data obtained were: atrazine k = 6.86 (L mol{sup -1}s{sup -1}); simazine: 9.26; t-butylazine 7.26; linuron 11.00; diuron 43.90. The activation parameters for the reaction of simazine were {Delta}H{sup =} = 9.35 kcal mol{sup -1} and {Delta}S{sup =} = -22.3 cal mol{sup -1} {degree}K{sup -1} and for the reaction of diuron were {Delta}H{sup =} = 16.83 Kcal mol{sup -1}, {Delta}S{sup =} = 5.696 cal mol{sup -1} {degree}K{sup -1}.

  8. Adsorption of dyes using peat: equilibrium and kinetic studies.

    PubMed

    Sepúlveda, L; Fernández, K; Contreras, E; Palma, C

    2004-09-01

    In recent years, adsorption has been accepted as one of the most appropriate processes for decolorization of wastewaters. This paper presents experimental results on application of peat for removal of structurally diverse dyes (azo, oxazine, triphenylmethane, thiazine and others) with emphasis on relevant factors such as the adsorbate-adsorbent chemical properties and chemical interaction as well as adsorption conditions. The equilibrium experimental results were fitted to Langmuir and Freundlich isotherms to obtain the characteristic parameters of each model. According to the evaluation using the Langmuir equation, the maximum sorption capacity of basic dyes at 22 degrees C was 667 (mg g(-1)) for Basic Blue 24, 526 (mg g(-1)) for Basic Green 4 and 714 (mg g(-1)) for Basic Violet 4. On the other hand for Acid Black 1 it was only 25 (mg g(-1)). Batch kinetics studies were undertaken and the data evaluated in compliance with chemical sorption mechanisms. For all of the systems studied the pseudo-second order model provided the best correlation of the kinetic experimental data. A film-pore double resistance diffusion model for mass transfer has also been used in this study to determine the effective diffusivity, Deff, for the adsorption of basic dyes in to peat.

  9. Kinetics study on biomass pyrolysis for fuel gas production.

    PubMed

    Chen, Guan-Yi; Fang, Meng-Xiang; Andries, J; Luo, Zhong-Yang; Spliethoff, H; Cen, Ke-Fa

    2003-01-01

    Kinetic knowledge is of great importance in achieving good control of the pyrolysis and gasification process and optimising system design. An overall kinetic pyrolysis scheme is therefore addressed here. The kinetic modelling incorporates the following basic steps: the degradation of the virgin biomass materials into primary products (tar, gas and semi-char), the decomposition of primary tar into secondary products and the continuous interaction between primary gas and char. The last step is disregarded completely by models in the literature. Analysis and comparison of predicted results from different kinetic schemes and experimental data on our fixed bed pyrolyser yielded very positive evidence to support our kinetic scheme.

  10. A progress report on seismic model studies

    USGS Publications Warehouse

    Healy, J.H.; Mangan, G.B.

    1963-01-01

    The value of seismic-model studies as an aid to understanding wave propagation in the Earth's crust was recognized by early investigators (Tatel and Tuve, 1955). Preliminary model results were very promising, but progress in model seismology has been restricted by two problems: (1) difficulties in the development of models with continuously variable velocity-depth functions, and (2) difficulties in the construction of models of adequate size to provide a meaningful wave-length to layer-thickness ratio. The problem of a continuously variable velocity-depth function has been partly solved by a technique using two-dimensional plate models constructed by laminating plastic to aluminum, so that the ratio of plastic to aluminum controls the velocity-depth function (Healy and Press, 1960). These techniques provide a continuously variable velocity-depth function, but it is not possible to construct such models large enough to study short-period wave propagation in the crust. This report describes improvements in our ability to machine large models. Two types of models are being used: one is a cylindrical aluminum tube machined on a lathe, and the other is a large plate machined on a precision planer. Both of these modeling techniques give promising results and are a significant improvement over earlier efforts.

  11. FY-1979 progress report. Hydrotransport plugging study.

    SciTech Connect

    Eyler, L.L.; Lombardo, N.J.

    1980-01-01

    The objective of the Hydrotransport Plugging Study is to investigate phenomena associated with predicting the onset and occurrence of plugging in pipeline transport of coal. This study addresses large particle transport plugging phenomena that may be encountered in run-of-mine operations. The project is being conducted in four tasks: review and analysis of current capabilities and available data, analytical modeling, experimental investigations, and unplugging and static start-up. This report documents work completed in FY-1979 as well as work currently in progress. A review of currently available prediction methods was completed. Applicability of the methods to large particle hydrotransport and the prediction of plugging was evaluated. It was determined that available models were inadequate, either because they are empirical and tuned to a given solid or because they are simplified analytical models incapable of accounting for a wide range of parameters. Complicated regression curve fit models lacking a physical basis cannot be extrapolated with confidence. Several specific conclusions were reached: Recent developments in mechanistic modeling, describing flow conditions at the limit of stationary deposition, provide the best basis for prediction and extrapolation of large particle flow. Certain modeled phenomena require further analytical and experimental investigation to improve confidence levels. Experimental work needs to be performed to support modeling and to provide an adequate data base for comparison purposes. No available model permits treatment of solids mixtures such as coal and rock.

  12. Kinetic and spectrophotometric studies on the renaturation of deoxyribonucleic acid.

    PubMed

    Thrower, K J; Peacocke, A R

    1968-10-01

    The kinetics of the renaturation of Escherichia coli DNA in 0.4-1.0m-sodium chloride at temperatures from 60 degrees to 90 degrees have been studied. The extent of renaturation was a maximum at 65 degrees to 75 degrees and increased with ionic strength, and the rate constant increased with both ionic strength and temperature. The energy and entropy of activation of renaturation were calculated to be 6-7kcal.mole(-1) and -40cal.deg.(-1)mole(-1) respectively. It has been shown that renaturation is a second-order process for 5hr. under most conditions. The results are consistent with a reaction in which the rate-controlling step is the diffusion together of two separated complementary DNA strands and the formation of a nucleus of base pairs between them. The kinetics of the renaturation of T7-phage DNA and Bordetella pertussis DNA have also been studied, and their rates of renaturation related quantitatively to the relative heterogeneity of the DNA samples. By analysis of the spectra of DNA at different stages during renaturation it was shown that initially the renatured DNA was rich in guanine-cytosine base pairs and non-random in base sequence, but that, as equilibrium was approached, the renatured DNA gradually resembled native DNA more closely. The rate constant for the renaturation of guanine-cytosine base pairs was slightly higher than for adenine-thymine base pairs.

  13. Kinetic study on urea uptake with chitosan based sorbent materials.

    PubMed

    Xue, Chen; Wilson, Lee D

    2016-01-01

    A one-pot kinetic uptake study of urea in aqueous solution with various chitosan sorbent materials such as pristine chitosan, cross-linked chitosan with glutaraldehyde from low (C-1) to higher (C-2) glutaraldehyde content, and a Cu(II) complex of a glutaraldehyde cross-linked chitosan material (C-3) is reported herein. The kinetic uptake profiles were analyzed by the pseudo-first order (PFO) and pseudo-second-order (PSO) models, respectively. The uptake rate constant of urea and the sorption capacity (qe) of high molecular weight (HMW) chitosan, C-1, C-2, and C-3 were best described by the PFO model. The uptake rate constant of urea with the various sorbents is listed in ascending order: HMW chitosanstudies. These results further illustrate the rational design of chitosan-based materials for the controlled uptake of urea in aquatic environments.

  14. Reduction of Carbon Dioxide by a Molybdenum-Containing Formate Dehydrogenase: A Kinetic and Mechanistic Study.

    PubMed

    Maia, Luisa B; Fonseca, Luis; Moura, Isabel; Moura, José J G

    2016-07-20

    Carbon dioxide accumulation is a major concern for the ecosystems, but its abundance and low cost make it an interesting source for the production of chemical feedstocks and fuels. However, the thermodynamic and kinetic stability of the carbon dioxide molecule makes its activation a challenging task. Studying the chemistry used by nature to functionalize carbon dioxide should be helpful for the development of new efficient (bio)catalysts for atmospheric carbon dioxide utilization. In this work, the ability of Desulfovibrio desulfuricans formate dehydrogenase (Dd FDH) to reduce carbon dioxide was kinetically and mechanistically characterized. The Dd FDH is suggested to be purified in an inactive form that has to be activated through a reduction-dependent mechanism. A kinetic model of a hysteretic enzyme is proposed to interpret and predict the progress curves of the Dd FDH-catalyzed reactions (initial lag phase and subsequent faster phase). Once activated, Dd FDH is able to efficiently catalyze, not only the formate oxidation (kcat of 543 s(-1), Km of 57.1 μM), but also the carbon dioxide reduction (kcat of 46.6 s(-1), Km of 15.7 μM), in an overall reaction that is thermodynamically and kinetically reversible. Noteworthy, both Dd FDH-catalyzed formate oxidation and carbon dioxide reduction are completely inactivated by cyanide. Current FDH reaction mechanistic proposals are discussed and a different mechanism is here suggested: formate oxidation and carbon dioxide reduction are proposed to proceed through hydride transfer and the sulfo group of the oxidized and reduced molybdenum center, Mo(6+)═S and Mo(4+)-SH, are suggested to be the direct hydride acceptor and donor, respectively.

  15. Study of heavy flavored particles. Progress report

    SciTech Connect

    Not Available

    1991-12-31

    This report discusses progress on the following topics: time-of- flight system; charmed baryon production and decays; D decays to baryons; measurement of sigma plus particles magnetic moments; and strong interaction coupling. (LSP)

  16. Large-scale epitaxial growth kinetics of graphene: A kinetic Monte Carlo study

    SciTech Connect

    Jiang, Huijun; Hou, Zhonghuai

    2015-08-28

    Epitaxial growth via chemical vapor deposition is considered to be the most promising way towards synthesizing large area graphene with high quality. However, it remains a big theoretical challenge to reveal growth kinetics with atomically energetic and large-scale spatial information included. Here, we propose a minimal kinetic Monte Carlo model to address such an issue on an active catalyst surface with graphene/substrate lattice mismatch, which facilitates us to perform large scale simulations of the growth kinetics over two dimensional surface with growth fronts of complex shapes. A geometry-determined large-scale growth mechanism is revealed, where the rate-dominating event is found to be C{sub 1}-attachment for concave growth-front segments and C{sub 5}-attachment for others. This growth mechanism leads to an interesting time-resolved growth behavior which is well consistent with that observed in a recent scanning tunneling microscopy experiment.

  17. Studying dissolution with a model integrating solid-liquid interface kinetics and diffusion kinetics.

    PubMed

    Gao, Jeff Y

    2012-12-18

    A dissolution model that integrates the solid-liquid interface kinetics and the mass transport kinetics is introduced. Such a model reduces to the Noyes-Whitney equation under special conditions, but offers expanded range of applicability and flexibility fitting dissolution profiles when interfacial kinetics and interfacial concentration deviate from the assumptions implied in the Noyes-Whitney equation. General solutions to the integrated dissolution model derived for noninteractive solutes as well as for solutes participating in ionization equilibrium are discussed. Parameters defining the integrated dissolution model are explained conceptually along with practical ways for their determinations. Conditions under which the model exhibits supersaturation features are elaborated. Simulated dissolution profiles using the integrated dissolution model for published experimental data exhibiting supersaturation features are illustrated.

  18. Utilization of kinetic isotope effects for the concentration of tritium. 1998 annual progress report

    SciTech Connect

    Brown, G.M.; Meyer, T.J.

    1998-06-01

    'The objective of this research program is to develop methods for concentrating tritium in water based on large primary isotope effects in catalytic redox processes. Basic research is being conducted to develop the chemistry of a complete cyclic process. Because tritium (generally present as HTO) is in a rapidly established equilibrium with protio-water, it moves with groundwater and separation from water cannot be achieved by the usual pump-and-treat methods using sorbants. The general methodology developed in this work will be applicable to a number of DOE waste streams, and as a consequence of the process tritium will be incorporated into an organic compound that will not readily exchange the tritium with groundwater. The authors intend to develop a process to remove tritium from H{sub 2}O by concentrating it with respect to protio-water. This research involves developing chemical cycles that produce high concentration factors for HTO and T{sub 2}O based on the discrimination of C-H and C-T bonds in oxidation reactions. Several steps are required in a cyclic process for the concentration of tritium in water. In the first step the tritium is incorporated in an organic compound. H-T discrimination occurs as the tritium containing compound is oxidized in a step involving a Ru(IV) oxo complex. Strong primary kinetic isotope effects lead to the oxidation of C-H bonds in preference to C-T bonds, and this reaction leads to concentration of tritium in the organic compound. The reduced form of the ruthenium compound can be reoxidized so that the oxidation step can be made catalytic.'

  19. Lipase-catalyzed ethanolysis of borage oil: a kinetic study.

    PubMed

    Torres, Carlos F; Hill, Charles G; Otero, Cristina

    2004-01-01

    Ethanolysis of borage oil catalyzed by two commercial lipases (from Pseudomonas cepacia and Candida antarctica) was studied using two different methodologies. Multiresponse models derived from a generalized Michaelis-Menten mechanism were utilized to describe the rates of formation of ethyl esters of the primary fatty acids present in the precursor oil. The relative rate constants determined for each of the fatty acid residues indicated that both lipases discriminate against release of gamma-linolenic acid residues under the reaction conditions studied. However, both lipases also released some of the residues located at the sn-2 position, indicating that for the experimental conditions studied, both lipases are nonspecific. Moreover, inactivation of Novozym 435 was rapid. Because the half-life of this enzyme (ca. 2.2 h) is comparable to the half-life of the reaction, the intrinsic reaction rate and enzyme deactivation must both be considered in modeling the kinetics.

  20. Orszag Tang vortex - Kinetic study of a turbulent plasma

    SciTech Connect

    Parashar, T. N.; Servidio, S.; Shay, M. A.; Matthaeus, W. H.; Cassak, P. A.

    2010-03-25

    Kinetic evolution of the Orszag-Tang vortex is studied using collisionless hybrid simulations based on particle in cell ions and fluid electrons. In magnetohydrodynamics (MHD) this configuration leads rapidly to broadband turbulence. An earlier study estimated the dissipation in the system. A comparison of MHD and hybrid simulations showed similar behavior at large scales but substantial differences at small scales. The hybrid magnetic energy spectrum shows a break at the scale where Hall term in the Ohm's law becomes important. The protons heat perpendicularly and most of the energy is dissipated through magnetic interactions. Here, the space time structure of the system is studied using frequency-wavenumber (k-omega) decomposition. No clear resonances appear, ruling out the cyclotron resonances as a likely candidate for the perpendicular heating. The only distinguishable wave modes present, which constitute a small percentage of total energy, are magnetosonic modes.

  1. Kinetic studies of ICF target dynamics with ePLAS

    NASA Astrophysics Data System (ADS)

    Mason, R. J.

    2016-10-01

    The ePLAS code was recently used1 to show that a modeling change from artificial to real viscosity can result in a decrease of the predicted performance of ICF targets. This code typically follows either fluid or PIC electrons with fluid ions in self-consistent E - and B - fields computed by the Implicit Moment Method2. For the present study the ions have instead been run as PIC particles undergoing Krook-like self-collisions. The ePLAS collision model continually redistributes the ion particle properties toward a local Maxwellian, while conserving the mean density, momentum and energy. Whereas the use of real viscosity captures large Knudsen Number effects as the active target dimensions shrink below the ion mean-free-path, the new kinetic modeling can manifest additional effects such as collisional shock precursors3 from the escape and streaming of the fastest particle ions. In 2D cylindrical geometry we will explore how such kinetic shock extensions might affect shell and core compression dynamics in ICF target implosions.

  2. Kinetic Batch Soil Adsorption Studies of 2, 4-dinitroanisole (DNAN)

    NASA Astrophysics Data System (ADS)

    Arthur, J.; Mark, N. W.; Taylor, S.; Brusseau, M. L.; Dontsova, K.

    2014-12-01

    Currently the explosive 2, 4, 6- trinitrotoluene (TNT) is used as a main ingredient in munitions; however the compound has failed to meet sensitivity requirements. The replacement compound being tested is 2, 4-dinitroanisole (DNAN). DNAN is less sensitive to shock, high temperatures, and has good detonation characteristics. However, DNAN is more soluble than TNT, which can influence transport and fate behavior and thus bioavailability and exposure potential. DNAN has been shown to have some human and environmental toxicity. The objective of this study was to investigate the environmental fate of DNAN in soil, with a specific focus on sorption processes. Batch experiments were conducted using 11 soils collected from military installations located across the United States. The soils were characterized for pH, specific surface area, electrical conductivity, cation exchange capacity, and organic carbon content. Adsorption kinetic data determined at room temperature were fitted using the first order kinetic equation. Adsorption isotherms were fitted with linear and Freundlich isotherm equations. The magnitudes of the linear adsorption coefficients ranged from 0.6 to 6 cm3/g. Results indicated that the adsorption of DNAN is strongly dependent on the amount of organic carbon present in the soil.

  3. Sintering kinetic studies in nonstoichiometric strontium titanate ceramics

    SciTech Connect

    Amaral, Luis; Senos, Ana M.R. Vilarinho, Paula M.

    2009-02-04

    The effect of nonstoichiometry on the densification of SrTiO{sub 3} ceramics with Sr/Ti ratios from 0.997 to 1.02 was systematically addressed. The kinetics of densification was studied by dilatometric analysis. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for crystallographic and microstructure characterization. Ti excess enhanced matter transport during sintering whereas Sr excess decreased it. The shrinkage rate and average grain size increased with the decrease of Sr/Ti ratio. Close values of the activation energy for the initial densification and the near constant onset temperature for densification suggest that identical transport mechanisms control the densification of all the compositions. Small excesses of TiO{sub 2} and SrO were mostly incorporated into the perovskite lattice inducing alterations in the defect chemistry of the material and the mass transport during sintering is controlled by Sr vacancies. Very small stoichiometric variations have a strong influence on the sintering kinetics and resulting microstructure of ST ceramics.

  4. Kinetic study of sulphuric acid hydrolysis of protein feathers.

    PubMed

    Ben Hamad Bouhamed, Sana; Kechaou, Nabil

    2017-02-28

    Poultry feather keratin is the most important by-product from the poultry industry due to its abundance. Different methods have been still applied to process this by-product such as enzymatic hydrolysis which is expensive and inapplicable at the industrial level. This paper presents a study of acid hydrolysis of poultry feathers using different types of acids, sulphuric acid concentration, different temperatures and solid to liquid ratio to obtain a liquid product rich in peptides. The feathers analysis revealed a crude protein content of 88.83%. A maximum peptides production of 676 mg/g was reached using sulphuric acid, 1 molar acid concentration and 50 g/l solid to liquid ratio at a temperature of 90 °C after 300 min. A reaction scheme for protein aggregation and decomposition to polypeptides and amino acids was proposed and a kinetic model for peptides production was developed. The proposed kinetic model proved to be well adapted to the experimental data with R (2) = 0.99.

  5. Kinetic and mechanistic studies of methylated liver alcohol dehydrogenase.

    PubMed Central

    Tsai, C S

    1978-01-01

    Reductive methylation of lysine residues activates liver alcohol dehydrogenase in the oxidation of primary alcohols, but decreases the activity of the enzyme towards secondary alcohols. The modification also desensitizes the dehydrogenase to substrate inhibition at high alcohol concentrations. Steady-state kinetic studies of methylated liver alcohol dehydrogenase over a wide range of alcohol concentrations suggest that alcohol oxidation proceeds via a random addition of coenzyme and substrate with a pathway for the formation of the productive enzyme-NADH-alcohol complex. To facilitate the analyses of the effects of methylation on liver alcohol dehydrogenase and factors affecting them, new operational kinetic parameters to describe the results at high substrate concentration were introduced. The changes in the dehydrogenase activity on alkylation were found to be associated with changes in the maximum velocities that are affected by the hydrophobicity of alkyl groups introduced at lysine residues. The desensitization of alkylated liver alcohol dehydrogenase to substrate inhibition is identified with a decrease in inhibitory Michaelis constants for alcohols and this is favoured by the steric effects of substituents at the lysine residues. PMID:697732

  6. New techniques for positron emission tomography in the study of human neurological disorders. Progress report, June 1990--June 1993

    SciTech Connect

    Kuhl, D.E.

    1993-06-01

    This progress report describes accomplishments of four programs. The four programs are entitled (1) Faster,simpler processing of positron-computing precursors: New physicochemical approaches, (2) Novel solid phase reagents and methods to improve radiosynthesis and isotope production, (3) Quantitative evaluation of the extraction of information from PET images, and (4) Optimization of tracer kinetic methods for radioligand studies in PET.

  7. A multicontinuum progressive damage model for composite materials motivated by the kinetic theory of fracture

    NASA Astrophysics Data System (ADS)

    Schumacher, Shane Christian

    2002-01-01

    A conventional composite material for structural applications is composed of stiff reinforcing fibers embedded in a relatively soft polymer matrix, e.g. glass fibers in an epoxy matrix. Although composites have numerous advantages over traditional materials, the presence of two vastly different constituent materials has confounded analysts trying to predict failure. The inability to accurately predict the inelastic response of polymer based composites along with their ultimate failure is a significant barrier to their introduction to new applications. Polymer based composite materials also tend to exhibit rate and time dependent failure characteristics. Lack of knowledge about the rate dependent response and progressive failure of composite structures has led to the current practice of designing these structures with static properties. However, high strain rate mechanical properties can vary greatly from the static properties. The objective of this research is to develop a finite element based failure analysis tool for composite materials that incorporates strain rate hardening effects in the material failure model. The analysis method, referred to as multicontinuum theory (MCT) retains the identity of individual constituents by treating them as separate but linked continua. Retaining the constituent identities allows one to extract continuum phase averaged stress/strain fields for the constituents in a routine structural analysis. Time dependent failure is incorporated in MCT by introducing a continuum damage model into MCT. In addition to modeling time and rate dependent failure, the damage model is capable of capturing the nonlinear stress-strain response observed in composite materials.

  8. Kinetic Study of the Combustion of Phosphorus Containing Species

    SciTech Connect

    Glaude, P.A.; Curran, H.J.; Pitz, W.J.; Westbrook, C.K.

    1999-10-22

    The combustion of organophosphorus compounds is of great interest for the incineration of chemical warfare agent and their use in flame inhibition as halon replacement. The thermochemical data of these species and the reactions involved at high temperature are not well known, despite some recent experimental studies. With BAC-MP4 ab initio estimations as a basis and semi-empirical estimations for many new compounds, the thermochemistry of organophosphorus compounds is studied. New group additivity values are proposed for enthalpies of formation at 298K, entropies and heat capacities of species involving pentavalent phosphorus bonded to carbon, hydrogen, oxygen, fluorine, nitrogen and sulfur atoms. The kinetic of unimolecular elimination is investigated by modeling pyrolysis experiments of DEMP, TEP and DIMP. A new combustion mechanism is described and applied to the modeling of DMMP reaction in a H{sub 2}/O{sub 2} flame.

  9. Kinetic study of hydrolysis of coconut fiber into glucose

    NASA Astrophysics Data System (ADS)

    Muhaimin, Sudiono, Sri

    2017-03-01

    Kinetic study of hydrolysis of coconut fiber into glucose has been done. The aim of this research was to study of the effect of time and temperature to the glucose as the result of the conversion of coconut fiber. The various temperature of the hydrolysis process were 30 °C, 48 °C, 72 °C and 95 °C and the various time of the hydrolysis process were 0, 15, 30, 60, 120, 180, 240, 300 minutes. A quantitative analysis was done by measured the concentration of the glucose as the result of the conversion of coconut fiber. The result showed that the rate constant from the various temperature were 3.10-4 minute-1; 8.10-4 minutees-1; 84.10-4 minute-1, and 205.10-4 minute-1, and the energy activation was 7,69. 103 kJ/mol.

  10. Thermogravimetric kinetic study of agricultural residue biomass pyrolysis based on combined kinetics.

    PubMed

    Wang, Xun; Hu, Mian; Hu, Wanyong; Chen, Zhihua; Liu, Shiming; Hu, Zhiquan; Xiao, Bo

    2016-11-01

    Pyrolytic kinetic of an agricultural residue (AR) feedstock, a mixture of plants (cotton, wheat, rich, corn) stems, was investigated based on combined kinetics. The most suitable mechanism for AR one-step pyrolysis was f(α)=(1-α)(1.1816)α(-1.8428) with kinetic parameters of: apparent activation energy 221.7kJ/mol, pre-exponential factor 4.17E16s(-1). Pyrolysis of AR feedstock could not be described by one-step reaction attributes to heterogeneous features of pyrolysis processes. Combined kinetics three-parallel-reaction (CK-TPR) model fitted the pyrolysis experimental data very well. Reaction mechanisms for pseudo hemicelluloses, cellulose, lignin in CK-TPR model was f(α)=(1-α)(1.6244)α(-0.3371)[-ln(1-α)](-0.0515), f(α)=(1-α)(1.0597)α(-0.6909)[-ln(1-α)](0.9026) and f(α)=(1-α)(2.9577)α(-4.7719), respectively. Apparent activation energy of three pseudo components followed the order of Elignin(197.3kJ/mol)>Ecellulose(176.3kJ/mol)>Ehemicelluloses (151.1kJ/mol). Mechanism of hemicelluloses pyrolysis could be further expressed as f(α)=(1-α)(1.4). The pyrolytic mechanism of cellulose met the Nucleation well. However, mechanism of lignin pyrolysis was complex, which possibly was the combined effects of Nucleation, Diffusion, Geometrical contraction, and Power law.

  11. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts]. Technical progress report

    SciTech Connect

    Not Available

    1993-07-01

    The research has involved the characterization of catalyst acidity, {sup 2}D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  12. Spectroscopy and kinetics of combustion gases at high temperatures. Technical progress report, March 1, 1991--October 31, 1992

    SciTech Connect

    Hanson, R.K.; Bowman, C.T.

    1992-11-01

    This program involves two complementary activities: (1) development and application of cw ring dye laser absorption. methods for sensitive detection of radical species and measurement of fundamental spectroscopic parameters at high temperatures; and (2) shock tube studies of radical-molecule and radical-radical reactions relevant to combustion. Species currently under investigation in the spectroscopic portion of the research include NO and CH{sub 3}; this has necessitated the development of a unique intracavity frequency-doubling system for our cw laser which operates at wavelengths in the range 210--230 nm. Shock tube studies of reaction kinetics currently are focussed on reactions of CH{sub 3} radicals.

  13. Kinetic Study of Denatonium Sorption to Smectite Clay Minerals

    PubMed Central

    Crosson, Garry S.; Sandmann, Emily

    2013-01-01

    Abstract The denatonium cation, as a benzoate salt, is the most bitter cation known to modern society and is frequently added to consumer products to reduce accidental and intentional consumption by humans and animals. Denatonium can enter the environment by accidental discharges, potentially rendering water supplies undrinkable. Interactions of denatonium with soil components (i.e., smectite minerals) ultimately control the environmental fate of denatonium, but the current literature is devoid of studies that evaluate denatonium sorption to smectite minerals. This study investigated the mechanism and kinetics of denatonium sorption to smectite clay minerals as a function of smectite type, temperature, pH and ionic strength. Uptake by synthetic mica montmorillonite (Syn-1), Wyoming montmorillonite (SWy-2), and Texas montmorillonite (STx-1b) at 305K was rapid, with equilibrium being reached within 2 min for all clays. Complete removal of denatonium was observed for STx-1b at pH 6.9, while partial removal was observed for Syn-1 and SWy-2. Kinetic behavior of SWy-2 and Syn-1 is consistent with a pseudo–second-order model at 305K. An activation energy of +25.9 kJ/mol was obtained for sorption to Syn-1 and was independent of temperature between 286K and 338K. Activation-free energy (ΔG*), activation enthalpy (ΔH*), and activation entropy (ΔS*) for Syn-1 were found to be +62.91 kJ/mol, +23.36 kJ/mol, and −0.130 kJ/(K·mol), respectively. Sorption capacities at pH 3.6, 6.9, and 8.2 were constant at 1.3×10−2 g denatonium/g clay; however, the kinetic rate constant increased by 56%, going from acidic to basic solution conditions. Distribution coefficients were negatively correlated with ionic strength, suggesting cation exchange. Collectively, results suggested that smectite minerals can serve as efficient sinks for denatonium cations. This is much-needed information for agencies developing regulations regarding denatonium usage and for water treatment

  14. Kinetic Study of Denatonium Sorption to Smectite Clay Minerals.

    PubMed

    Crosson, Garry S; Sandmann, Emily

    2013-06-01

    The denatonium cation, as a benzoate salt, is the most bitter cation known to modern society and is frequently added to consumer products to reduce accidental and intentional consumption by humans and animals. Denatonium can enter the environment by accidental discharges, potentially rendering water supplies undrinkable. Interactions of denatonium with soil components (i.e., smectite minerals) ultimately control the environmental fate of denatonium, but the current literature is devoid of studies that evaluate denatonium sorption to smectite minerals. This study investigated the mechanism and kinetics of denatonium sorption to smectite clay minerals as a function of smectite type, temperature, pH and ionic strength. Uptake by synthetic mica montmorillonite (Syn-1), Wyoming montmorillonite (SWy-2), and Texas montmorillonite (STx-1b) at 305K was rapid, with equilibrium being reached within 2 min for all clays. Complete removal of denatonium was observed for STx-1b at pH 6.9, while partial removal was observed for Syn-1 and SWy-2. Kinetic behavior of SWy-2 and Syn-1 is consistent with a pseudo-second-order model at 305K. An activation energy of +25.9 kJ/mol was obtained for sorption to Syn-1 and was independent of temperature between 286K and 338K. Activation-free energy (ΔG*), activation enthalpy (ΔH*), and activation entropy (ΔS*) for Syn-1 were found to be +62.91 kJ/mol, +23.36 kJ/mol, and -0.130 kJ/(K·mol), respectively. Sorption capacities at pH 3.6, 6.9, and 8.2 were constant at 1.3×10(-2) g denatonium/g clay; however, the kinetic rate constant increased by 56%, going from acidic to basic solution conditions. Distribution coefficients were negatively correlated with ionic strength, suggesting cation exchange. Collectively, results suggested that smectite minerals can serve as efficient sinks for denatonium cations. This is much-needed information for agencies developing regulations regarding denatonium usage and for water treatment professionals who may

  15. Kinetic studies on the aggregation of Aspergillus niger conidia.

    PubMed

    Grimm, L H; Kelly, S; Hengstler, J; Göbel, A; Krull, R; Hempel, D C

    2004-07-20

    Morphology has a crucial effect on productivity and the supply of substrate for cultures of filamentous fungi. However, cultivation parameters leading to the desired morphology are often chosen empirically as the mechanisms governing the processes involved are usually unknown. For coagulating microorganisms like Aspergillus niger the morphological development is considered to start with the aggregation of conidia right after inoculation. To elucidate the mechanism of this process, kinetic studies were carried out using an in-line particle size analyzer. Based on the data obtained from these experiments a model for conidial aggregation is proposed in this article. It consists of two separate aggregation steps. The first one takes place immediately after inoculation, but only leads to a small decrease of total particle concentration. Most suspended conidia aggregate after a second aggregation step triggered by germination and hyphal growth. Aggregation velocity of this second phase is linearly dependent on the particle growth rate.

  16. Theoretical studies on kinetics of singlet oxygen in nonthermal plasma

    NASA Astrophysics Data System (ADS)

    Frolov, Mikhail P.; Ionin, Andrei A.; Kotkov, Andrei A.; Kochetov, Igor V.; Napartovich, Anatolii P.; Podmarkov, Yurii P.; Seleznev, Leonid V.; Sinitsyn, Dmitrii V.; Vagin, Nikolai P.; Yuryshev, Nikolay N.

    2004-09-01

    An idea to replace singlet delta oxygen (SDO) generator working with wet chemistry by electric discharge generator has got much attention last years. Different kinds of discharge were examined for this purpose, but without a great success. The existing theoretical models are not validated by well-characterized experimental data. To describe complicated kinetics in gas discharge with oxygen one needs to know in detail processes involving numerous electronic excited oxygen molecules and atoms. To gain new knowledge about these processes experimental studies were made on electric discharge properties in gas mixture flow with independent control of inlet SDO concentration. The theoretical model extended to include minor additives like oxygen atoms, water molecules, ozone was developed. Comparison with careful experimental measurements of electric characteristics along with gas composition allows us to verify the model and make theoretical predictions more reliable. Results of numerical simulations using this model for an electron-beam sustained discharge are reported and compared with the experimental data.

  17. Kinetic study on CO2 photoreduction by Re complexes

    NASA Astrophysics Data System (ADS)

    Ono, Y.; Tsuda, M.; Maruo, Y. Y.; Nakamura, J.

    2012-08-01

    The photoreduction of CO2 using Re(btp)(CO)3Cl (btp: bathophenanthroline) was investigated in a CO2-saturated DMF-triethanolamine solution. CO formation was observed during irradiation with 365-nm light. Meanwhile, UV-vis spectral changes suggested that Re(btp)(CO)3Cl was degraded and its amount decreased during irradiation. The degradation of Re(btp)(CO)3Cl could cause CO formation, and the observed CO amount was the sum of CO produced by CO2 reduction and Re(btp)(CO)3Cl degradation. Thus, in the present paper, we discuss how the net amount of CO produced by CO2 reduction could be determined via a kinetic study during UV irradiation which considers the CO production originating from the Re(btp)(CO)3Cl degradation process.

  18. An Experimental and Kinetic Modeling Study of Methyl Decanoate Combustion

    SciTech Connect

    Sarathy, S M; Thomson, M J; Pitz, W J; Lu, T

    2010-02-19

    Biodiesel is typically a mixture of long chain fatty acid methyl esters for use in compression ignition engines. Improving biofuel engine performance requires understanding its fundamental combustion properties and the pathways of combustion. This research study presents new combustion data for methyl decanoate in an opposed-flow diffusion flame. An improved detailed chemical kinetic model for methyl decanoate combustion is developed, which serves as the basis for deriving a skeletal mechanism via the direct relation graph method. The novel skeletal mechanism consists of 648 species and 2998 reactions. This mechanism well predicts the methyl decanoate opposed-flow diffusion flame data. The results from the flame simulations indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene.

  19. Adiabatic molecular-dynamics-simulation-method studies of kinetic friction

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Sokoloff, J. B.

    2005-06-01

    An adiabatic molecular-dynamics method is developed and used to study the Muser-Robbins model for dry friction (i.e., nonzero kinetic friction in the slow sliding speed limit). In this model, dry friction between two crystalline surfaces rotated with respect to each other is due to mobile molecules (i.e., dirt particles) adsorbed at the interface. Our adiabatic method allows us to quickly locate interface potential-well minima, which become unstable during sliding of the surfaces. Since dissipation due to friction in the slow sliding speed limit results from mobile molecules dropping out of such unstable wells, our method provides a way to calculate dry friction, which agrees extremely well with results found by conventional molecular dynamics for the same system, but our method is more than a factor of 10 faster.

  20. Femtomole Mixer for Microsecond Kinetic Studies of Protein Folding

    PubMed Central

    Hertzog, David E.; Michalet, Xavier; Jäger, Marcus; Kong, Xiangxu; Santiago, Juan G.; Weiss, Shimon; Bakajin, Olgica

    2005-01-01

    We have developed a microfluidic mixer for studying protein folding and other reactions with a mixing time of 8 μs and sample consumption of femtomoles. This device enables us to access conformational changes under conditions far from equilibrium and at previously inaccessible time scales. In this paper, we discuss the design and optimization of the mixer using modeling of convective diffusion phenomena and a characterization of the mixer performance using microparticle image velocimetry, dye quenching, and Förster resonance energy-transfer (FRET) measurements of single-stranded DNA. We also demonstrate the feasibility of measuring fast protein folding kinetics using FRET with acyl-CoA binding protein. PMID:15595857

  1. Kinetic studies of cellulose enzymatic hydrolysis from pretreated corn cob

    NASA Astrophysics Data System (ADS)

    Stevanie, Jeannie; Kartawiria, Irvan; Abimanyu, Haznan

    2017-01-01

    Successful utilization of corn cob biomass as raw material in bioethanol production is depending on the hydrolysis process where high level of β-cellulose is converted into glucose. Enzymatic hydrolysis is the common process for this purpose. This study is focusing on the evaluation of hydrolysis of pre-treated corn cob using Novozymes Cellic ® C-Tec2 and H-Tec2 enzymes to obtain the optimum reaction condition and its general reaction kinetics. The corn cob used was pretreated using 10% of NaOH solution. Hydrolysis reactions were conducted in 250 ml Erlenmeyer flask for 72 hour using mixture of C-Tec2 and H-Tec2 enzymes at the fixed ratio of 5:1 and glucose concentration were measured using HPLC. Reaction temperature of 40°C and quantity of 0.5 ml enzyme solution per gram substrate gives the highest reaction rate (0.0123 gram of glucose/gram sample.h) with the glucose yield being 0.089 g glucose/ g substrate. Total conversion of cellulose observed was 11.91 %. Corn cob hydrolysis using C-Tec2 and H-Tec2 enzymes also result in xylose (0.0202 g/g substrate), which can also contribute to bioethanol productivity in further fermentation process. The reaction is following zero order kinetics for the first 8 hours and reaches maximum yield within 10 hours; significantly shorter compared to previous studies of cellulosic material hydrolysis that may take up to 72 hour to complete. Prolonging the hydrolysis of pre-treated corn cob more than 24 hour gives no significant increase in glucose conversion and yield. Hydrolysis temperature range of 40°C to 60°C is in accordance with the manufacturer recommendation for the purpose; however the decrease of reaction rate is observable at temperature 50°C or higher.

  2. Kinetic studies on the tensile state of water in trees.

    PubMed

    Tributsch, Helmut; Cermak, Jan; Nadezhdina, Nadezhda

    2005-09-22

    The solar-powered generation and turnover of tensile, cohesive water in trees is described as a kinetic phenomenon of irreversible thermodynamics. A molecular kinetic model for tensile water formation and turnover is presented, which is found to be mathematically equivalent with an autocatalytic reaction (Brusselator). It is also shown to be consistent with the van der Waals equation for real liquid-gas systems, which empirically considers intermolecular forces. It can therefore be used to explain both the irreversible thermodynamics and the kinetics of the tensile liquid state of water. A nonlinear bistable evaporation behavior of tensile water is predicted, which has not yet been experimentally characterized in trees. Conventional sap flow techniques in combination with infrared imaging of heat flow around a local heat source were used to study the dynamics and energetics of water transport of trees during the eclipse of August 11, 1999. The evaporative "pulling force" in a tree was demonstrated with infrared techniques and shown to respond within seconds. While the ambient temperature during the eclipse did not drop by more than 2 degrees C, evaporative water transport was reduced by a factor of up to 2-3. The expected hysteresis (with an up to 50% decrease in energy-conversion-related entropy production) was measured, reflecting a bistable mode of conversion of solar energy into tensile water flow. This nonlinear (autocatalytic) phenomenon, together with tensile molecular order, damped the oscillating behavior of xylem tensile water, and its occasional all-or-none rupture (cavitation) can thus be explained by the nonlinear nature of intermolecular forces active in the water conduit/parenchyma environment. This characterizes the physical chemistry and energetics of tensile water in trees as an active-solar-energy-driven self-organizing process. Water is handled in the form of microcanonical ensembles and transformed into a stretched, metastable icelike state

  3. Progress in studying scintillator proportionality: Phenomenological model

    SciTech Connect

    Bizarri, Gregory; Cherepy, Nerine; Choong, Woon-Seng; Hull, Giulia; Moses, William; Payne, Sephen; Singh, Jai; Valentine, John; Vasilev, Andrey; Williams, Richard

    2009-04-30

    We present a model to describe the origin of non-proportional dependence of scintillator light yield on the energy of an ionizing particle. The non-proportionality is discussed in terms of energy relaxation channels and their linear and non-linear dependences on the deposited energy. In this approach, the scintillation response is described as a function of the deposited energy deposition and the kinetic rates of each relaxation channel. This mathematical framework allows both a qualitative interpretation and a quantitative fitting representation of scintillation non-proportionality response as function of kinetic rates. This method was successfully applied to thallium doped sodium iodide measured with SLYNCI, a new facility using the Compton coincidence technique. Finally, attention is given to the physical meaning of the dominant relaxation channels, and to the potential causes responsible for the scintillation non-proportionality. We find that thallium doped sodium iodide behaves as if non-proportionality is due to competition between radiative recombinations and non-radiative Auger processes.

  4. Ab initio quantum chemical and kinetic modeling study of the pyrolysis kinetics of pyrrole

    SciTech Connect

    Martoprawiro, M.; Bacskay, G.B.; Mackie, J.C.

    1999-05-20

    The five-membered heterocyclic pyrrole moiety is an important structure in coals and derived tars, and the thermal decomposition reactions of pyrrole are important for production of precursors of the oxides of nitrogen, NO{sub x}, in the combustion of coals. The kinetics of pyrolysis of pyrrole have been investigated theoretically by ab initio quantum chemical techniques and by detailed chemical kinetic modeling of previously reported experimental results. The overall kinetics can be successfully modeled by a 117 step kinetic model that gives good agreement with temperature profiles of major products and also provides an acceptable fit for minor products. The thermochemistry and rate parameters of a number of key reactions have been obtained by ab initio calculations carried out at CASSCF, CASPT2, and G2(MP2) levels of theory. Several reaction pathways were investigated. The major product, HCN, arises principally from a hydrogen migration in pyrrole to form a cyclic carbene with the NH bond intact. Ring scission of this carbene leads to an allenic imine precursor of HCN and propyne. This is the decomposition pathway of lowest energy. Pyrolysis is preceded by the facile tautomerization of pyrrole to 2H-pyrrolenine. The latter can undergo CN fission to form an open chain biradical species, which is the precursor of the butenenitrile isomeric products, cis- and trans-crotononitrile and allyl cyanide. The biradical can also undergo facile H-fission to form cyanoallyl radical, which is an important precursor of acetylene, acetonitrile, and acrylonitrile, H{sub 2} also arises principally from H-fission of the biradical.

  5. Personal Commitment, Support and Progress in Doctoral Studies

    ERIC Educational Resources Information Center

    Martinsuo, Miia; Turkulainen, Virpi

    2011-01-01

    Earlier research on doctoral education has associated study progress with the student's own capabilities and faculty support. The purpose of this study is to investigate how students' personal commitment and various forms of support, as well as their complementary effects, explain progress in doctoral studies. Data were collected by a…

  6. Carbon Dioxide Hydrogenation into Higher Hydrocarbons and Oxygenates: Thermodynamic and Kinetic Bounds and Progress with Heterogeneous and Homogeneous Catalysis.

    PubMed

    Prieto, Gonzalo

    2017-03-22

    Under specific scenarios, the catalytic hydrogenation of CO2 with renewable hydrogen is considered a suitable route for the chemical recycling of this environmentally harmful and chemically refractory molecule into added-value energy carriers and chemicals. The hydrogenation of CO2 into C1 products, such as methane and methanol, can be achieved with high selectivities towards the corresponding hydrogenation product. More challenging, however, is the selective production of high (C2+ ) hydrocarbons and oxygenates. These products are desired as energy vectors, owing to their higher volumetric energy density and compatibility with the current fuel infrastructure than C1 compounds, and as entry platform chemicals for existing value chains. The major challenge is the optimal integration of catalytic functionalities for both reductive and chain-growth steps. This Minireview summarizes the progress achieved towards the hydrogenation of CO2 to C2+ hydrocarbons and oxygenates, covering both solid and molecular catalysts and processes in the gas and liquid phases. Mechanistic aspects are discussed with emphasis on intrinsic kinetic limitations, in some cases inevitably linked to thermodynamic bounds through the concomitant reverse water-gas-shift reaction, which should be considered in the development of advanced catalysts and processes.

  7. Coordination: southeast continental shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1981-02-01

    The objectives are to identify important physical, chemical and biological processes which affect the transfer of materials on the southeast continental shelf, determine important parameters which govern observed temporal and spatial varibility on the continental shelf, determine the extent and modes of coupling between events at the shelf break and nearshore, and determine physical, chemical and biological exchange rates on the inner shelf. Progress in meeting these research objectives is presented. (ACR)

  8. Kinetic studies on the cupric ion oxidation of sheep hemoglobin.

    PubMed

    Brittain, T; Ivanetich, K M

    1980-11-01

    The oxidation of sheep hemoglobin, in both the oxygenated and deoxygenated forms, by cuprous ions have been studied by spectrophotometric and stopped-flow techniques. Mixing of both the oxy and deoxy forms with excess Cu2+ leads to the rapid oxidation of the iron atoms of all four of the hem groups of the tetrameric protein, followed by the slow formation of hemichromes (low spin FeIII forms of hemoglobin). Stopped-flow studies show that the oxidations follow simple monophasic kinetics with second-order rate constants of 65 and 310 M-1 sec-1 for the oxy and deoxy forms, respectively. Variable temperature studies yield Arrhenius activation energies of 43 for the oxy form and 113 kJ mole-1 for the deoxy form. For each form of the protein the activation energy is very similar to the activation enthalpy. While the deoxy form is characterized by an activation energy and enthalpy that is more than twice the corresponding value in the oxy form. The activation entropies show highly significant differences being -128 e.u. and 136 e.u. at 25 degrees C for the oxy and deoxy forms, respectively.

  9. Mechanisms and kinetics of coal hydrogenation. Progress report, January-June 1980

    SciTech Connect

    Gary, J H; Baldwin, R M; Bain, R L

    1980-07-01

    The objective of this task is to utilize the continuous-flow bench-scale coal liquefaction reactor system at CSM to investigate the rate of reaction of different coals at different processing conditions. Particularly, reaction rates at short residence times are to be measured in a Continuous Flow Stirred Tank Reactor (CSTR), and this information used to model reactions in the Plug Flow Reactor (PFR) section of the unit. Work during the past 6 months has focused on completing modifications to the unit itself, as the bench-scale system was originally designed to be operated at residence times just under 30 minutes. The new residence times are to be, at the least, just less than 6 minutes. The experimental portion will be a comparative study of the effect of different processing conditions on the rate of coal liquefaction. During the past six months, work on the continuous unit has been confined to modifications and system tune-up.

  10. An improved pyrite pretreatment protocol for kinetic and isotopic studies

    NASA Astrophysics Data System (ADS)

    Mirzoyan, Natella; Kamyshny, Alexey; Halevy, Itay

    2014-05-01

    An improved pyrite pretreatment protocol for kinetic and isotopic studies Natella Mirzoyan1, Alexey Kamyshny Jr.2, Itay Halevy1 1Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel 2Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel Pyrite is one of the most abundant and widespread of the sulfide minerals with a central role in biogeochemical cycles of iron and sulfur. Due to its diverse roles in the natural and anthropogenic sulfur cycle, pyrite has been extensively studied in various experimental investigations of the kinetics of its dissolution and oxidation, the isotopic fractionations associated with these reactions, and the microbiological processes involved. Pretreatment of pyrite for removal of oxidation impurities to prevent experimental artifacts and inaccuracies is often practiced. While numerous pyrite-cleaning methods have been used in experiments, a common pyrite pretreatment method, often used to investigate pyrite chemistry by the isotopic fractionations associated with it, includes several rinses by HCl, acetone and deionized water. Elemental sulfur (S0) is a common product of incomplete pyrite oxidation. Removal of S0 is desirable to avoid experimental biases associated with its participation in pyrite transformations, but is more complicated than the removal of sulfate. Although rinsing with an organic solvent is in part aimed at removing S0, to the best of our knowledge, the extraction efficiency of S0 in existing protocols has not been assessed. We have developed and tested a new protocol for elemental sulfur removal from the surface of pyrite by ultrasonication with warm acetone. Our data demonstrate the presence of large fractions of S0 on untreated pyrite particle surfaces, of which only approximately 60% was removed by the commonly used pretreatment method. The new protocol described here was found to be more efficient at S0 removal than the commonly used method

  11. Energetics and kinetics of anaerobic aromatic and fatty acid degradation. Progress report, March 1992--June 1995

    SciTech Connect

    McInerney M.J.

    1995-06-23

    Factors affecting the rate and extent of benzoate degradation by anaerobic syntrophic consortia were studied. Cocultures of a syntrophic benzoate degrader, strain SB, with a hydrogen/formate-using sulfate reducer degraded benzoate to a threshold that depended on the amount of substrate and acetate present. The benzoate threshold was not a function of the inhibition of benzoate degradation capacity by acetate or the toxicity of the undissociated form of acetate. Rather, a critical or minimal Gibb`s free energy value may exist where thermodynamic constraints preclude further benzoate degradation. A sensitive assay to detect low formate concentrations was developed to measure the formate levels when the benzoate threshold was reached. We showed that increased acetate concentrations, even when hydrogen and formate levels are low, affects the extent of benzoate degradation, implicating the importance of interspecies acetate transfer. In addition to benzoate, various saturated and unsaturated fatty acids, 2-methylbutyrate, and methyl esters of fatty acids supported growth in coculture with a hydrogen-using partner. SB is the only syntrophic bacterium known to use both benzoate and fatty acids. Phylogenetic analysis showed that SB clustered with sulfate reducers in the delta subclass of the Proteobacteria. SB grew well in coculture with Desulfoarculus baarsii, a sulfate reducer that uses formate but not hydrogen. This unequivocally shows that SB can grow by interspecies formate transfer.

  12. A Validity Study of the Kinetic School Drawing Technique.

    ERIC Educational Resources Information Center

    Prout, H. Thompson; Celmer, David S.

    1984-01-01

    Examined the relationship between Kinetic School Drawing responses and academic achievement in 100 normal fifth-grade students. Significant correlations were found for a number of measures, generally supporting the validity of the technique. (JAC)

  13. Laboratory Kinetic Studies of OH and CO2 Relevant to Upper Atmospheric Radiation Balance

    NASA Technical Reports Server (NTRS)

    Nelson, David D.; Villalta, Peter; Zahniser, Mark S.; Kolb, Charles E.

    1997-01-01

    The purpose of this project was to quantify the rates of two processes which are crucial to our understanding of radiative energy balance in the upper atmosphere. The first process is radiative emission from vibrationally hot OH radicals following the H + O3 reaction in the upper mesosphere. The importance of this process depends strongly on the OH radiative emission coefficients. Our goal was to measure the OH permanent dipole moment in excited vibrational states and to use these measurements to construct an improved OH dipole moment function and improved radiative emission coefficients. Significant progress was made on these experiments including the construction of a supersonic jet source for vibrationally excited OH radicals. Unfortunately, our efforts to transport the OH radicals into a second lower pressure vacuum chamber were not successful, and we were unable to make improved dipole moment measurements for OH. The second key kinetic process which we attempted to quantify during this project is the rate of relaxation of bend-excited CO2 by oxygen atoms. Since excitation of the bending vibrational mode of CO2 is the major cooling mechanism in the upper mesosphere/lower thermosphere, the cooling rate of this region depends crucially on the rate of energy transfer out of this state. It is believed that the most efficient transfer mechanism is via atomic oxygen but the rate for this process has not been directly measured in the laboratory at appropriate temperatures and even the room temperature rate remains controversial. We attempted to directly measure the relaxation rate Of CO2 (010) by oxygen atoms using the discharge flow technique. This experiment was set up at Aerodyne Research. Again, significant progress was achieved in this experiment. A hot CO2 source was set up, bend excited CO2 was detected and the rate of relaxation of bend excited CO2 by He atoms was measured. Unfortunately, the project ran out of time before the oxygen atom kinetic studies could

  14. Plasma Assisted Combustion: Flame Regimes and Kinetic Studies

    DTIC Science & Technology

    2015-01-05

    effect dominant Kinetic effect 1. Plasma Activated Low Temperature Combustion and cool flames for liquid hydrocarbon fuels >1100 K High temperature...better understood) 800-1100 K Intermediate 500-800 K Low Plasma has more kinetic enhancement effect in lower temperature combustion However...species Absorption Dispersion ν ν HO2 energy levels Zeeman splitting New diagnostics: HO2/OH using mid-IR Faraday Rotational Spectroscopy

  15. Thermal degradation studies and kinetic modeling of cardoon (Cynara cardunculus) pyrolysis using thermogravimetric analysis (TGA).

    PubMed

    Damartzis, Th; Vamvuka, D; Sfakiotakis, S; Zabaniotou, A

    2011-05-01

    A key element in the design of sustainable pyrolysis processes is the thermal degradation kinetics of biomass. In this work, pyrolysis tests for cardoon (Cynara carduculus) stems and leaves were performed in a non-isothermal thermogravimetric analyzer (TGA) in order to determine the thermal degradation behavior of both stems and leaves. The kinetic parameters of the process were evaluated using three different kinetic models, the independent parallel reaction model, KAS and OFW iso-conversional model. Good agreement with the experimental TGA data was observed for all models, the best being with the independent parallel reaction model. A variance in the activation energy with conversion was observed when the KAS and OFW models were employed, which reveals that the pyrolysis of cardoon progresses through more complex and multi-step kinetics.

  16. Benchmark Study of Density Cumulant Functional Theory: Thermochemistry and Kinetics.

    PubMed

    Copan, Andreas V; Sokolov, Alexander Yu; Schaefer, Henry F

    2014-06-10

    We present an extensive benchmark study of density cumulant functional theory (DCFT) for thermochemistry and kinetics of closed- and open-shell molecules. The performance of DCFT methods (DC-06, DC-12, ODC-06, and ODC-12) is compared to that of coupled-electron pair methods (CEPA0 and OCEPA0) and coupled-cluster theory (CCSD and CCSD(T)) for the description of noncovalent interactions (A24 database), barrier heights of hydrogen-transfer reactions (HTBH38), radical stabilization energies (RSE30), adiabatic ionization energies (AIE), and covalent bond stretching in diatomic molecules. Our results indicate that out of four DCFT methods the ODC-12 method is the most reliable and accurate DCFT formulation to date. Compared to CCSD, ODC-12 shows superior results for all benchmark tests employed in our study. With respect to coupled-pair theories, ODC-12 outperforms CEPA0 and shows similar accuracy to the orbital-optimized CEPA0 variant (OCEPA0) for systems at equilibrium geometries. For covalent bond stretching, ODC-12 is found to be more reliable than OCEPA0. For the RSE30 and AIE data sets, ODC-12 shows competitive performance with CCSD(T). In addition to benchmark results, we report new reference values for the RSE30 data set computed using coupled cluster theory with up to perturbative quadruple excitations.

  17. Constant composition kinetics study of carbonated apatite dissolution

    NASA Astrophysics Data System (ADS)

    Tang, Ruikang; Henneman, Zachary J.; Nancollas, George H.

    2003-03-01

    The carbonated apatites (CAP) may be more suitable models for biominerals such as bone and dental hard tissues than is pure hydroxyapatite (HAP) since they have similar chemical compositions. Although they contain only a relatively small amount of carbonate, the solubility and dissolution properties are different. The solubility product of the CAP particles used in this dissolution study, 2.88×10 -112 mol 18 l -18, was significantly greater than that of HAP, 5.52×10 -118 mol 18 l -18. The kinetics of dissolution of CAP has been studied using the constant composition (CC) method. At low undersaturations, the dissolution reaction appeared to be controlled mainly by surface diffusion with an effective reaction order of 1.9±0.1 with respect to the relative undersaturation. These results together with those obtained by scanning electron microscopy (SEM) suggest a dissolution model. Based on the surface diffusion theory of Burton, Cabrera and Frank (BCF). The interfacial tension between CAP and the aqueous phase calculated from this dissolution model, 9.0 m J m -2, was consistent with its relatively low solubility. An abnormal but interesting dissolution behavior is that the CAP dissolution rate was relatively insensitive to changes in calcium and phosphate concentrations at higher undersaturations, suggesting the importance of the carbonate component under these conditions.

  18. Ripening kinetics of bubbles: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Watanabe, Hiroshi; Inaoka, Hajime; Ito, Nobuyasu

    2016-09-01

    The ripening kinetics of bubbles is studied by performing molecular dynamics simulations. From the time evolution of a system, the growth rates of individual bubbles are determined. At low temperatures, the system exhibits a t1/2 law and the growth rate is well described by classical Lifshitz-Slyozov-Wagner (LSW) theory for the reaction-limited case. This is direct evidence that the bubble coarsening at low temperatures is reaction-limited. At high temperatures, although the system exhibits a t1/3 law, which suggests that it is diffusion-limited, the accuracy of the growth rate is insufficient to determine whether the form is consistent with the prediction of LSW theory for the diffusion-limited case. The gas volume fraction dependence of the coarsening behavior is also studied. Although the behavior of the system at low temperatures has little sensitivity to the gas volume fraction up to 10%, at high temperatures it deviates from the prediction of LSW theory for the diffusion-limited case as the gas volume fraction increases. These results show that the mean-field-like treatment is valid for a reaction-limited system even with a finite volume fraction, while it becomes inappropriate for a diffusion-limited system since classical LSW theory for the diffusion-limited case is valid at the dilute limit.

  19. Structural and Kinetic Studies of Formate Dehydrogenase from Candida boidinii.

    PubMed

    Guo, Qi; Gakhar, Lokesh; Wickersham, Kyle; Francis, Kevin; Vardi-Kilshtain, Alexandra; Major, Dan T; Cheatum, Christopher M; Kohen, Amnon

    2016-05-17

    The structure of formate dehydrogenase from Candida boidinii (CbFDH) is of both academic and practical interests. First, this enzyme represents a unique model system for studies on the role of protein dynamics in catalysis, but so far these studies have been limited by the availability of structural information. Second, CbFDH and its mutants can be used in various industrial applications (e.g., CO2 fixation or nicotinamide recycling systems), and the lack of structural information has been a limiting factor in commercial development. Here, we report the crystallization and structural determination of both holo- and apo-CbFDH. The free-energy barrier for the catalyzed reaction was computed and indicates that this structure indeed represents a catalytically competent form of the enzyme. Complementing kinetic examinations demonstrate that the recombinant CbFDH has a well-organized reactive state. Finally, a fortuitous observation has been made: the apoenzyme crystal was obtained under cocrystallization conditions with a saturating concentration of both the cofactor (NAD(+)) and inhibitor (azide), which has a nanomolar dissociation constant. It was found that the fraction of the apoenzyme present in the solution is less than 1.7 × 10(-7) (i.e., the solution is 99.9999% holoenzyme). This is an extreme case where the crystal structure represents an insignificant fraction of the enzyme in solution, and a mechanism rationalizing this phenomenon is presented.

  20. Detailed kinetic modeling study of n-pentanol oxidation

    DOE PAGES

    Heufer, K. Alexander; Sarathy, S. Mani; Curran, Henry J.; ...

    2012-09-28

    To help overcome the world’s dependence upon fossil fuels, suitable biofuels are promising alternatives that can be used in the transportation sector. Recent research on internal combustion engines shows that short alcoholic fuels (e.g., ethanol or n-butanol) have reduced pollutant emissions and increased knock resistance compared to fossil fuels. Although higher molecular weight alcohols (e.g., n-pentanol and n-hexanol) exhibit higher reactivity that lowers their knock resistance, they are suitable for diesel engines or advanced engine concepts, such as homogeneous charge compression ignition (HCCI), where higher reactivity at lower temperatures is necessary for engine operation. The present study presents a detailedmore » kinetic model for n-pentanol based on modeling rules previously presented for n-butanol. This approach was initially validated using quantum chemistry calculations to verify the most stable n-pentanol conformation and to obtain C–H and C–C bond dissociation energies. In addition, the proposed model has been validated against ignition delay time data, speciation data from a jet-stirred reactor, and laminar flame velocity measurements. Overall, the model shows good agreement with the experiments and permits a detailed discussion of the differences between alcohols and alkanes.« less

  1. Laminar-flow fluid mixer for fast fluorescence kinetics studies.

    PubMed Central

    Pabit, Suzette A; Hagen, Stephen J

    2002-01-01

    The ability to mix aqueous liquids on microsecond time scales, while consuming minimal amounts of sample and maintaining UV-visible optical access to the mixing region, is highly desirable for a range of biophysical studies of fast protein and nucleic acid interactions and folding. We have constructed a laminar coaxial jet mixer that allows the measurement of UV-excited fluorescence from nanoliter and microliter quantities of material, mixed at microsecond rates. The mixer injects a narrow cylindrical stream (radius a < 1 microm) of fluorescent sample into a larger flow of diluting buffer that moves through a capillary (100 microm i.d.) at a speed approximately 20 cm/s, under laminar flow conditions (Re approximately equal to 14). Construction from a fused silica capillary allows the laser excitation (at 266 nm) and detection (at 350 nm) of tryptophan fluorescence at reasonably low working concentrations, without interference from background fluorescence. Using this mixer we have measured sub-millisecond fluorescence quenching kinetics while consuming fluorescent sample at rates no greater than 6 nl/s. Consumption of the diluting buffer is also very modest (approximately 1-3 microl/s) in comparison with other rapid mixer designs. PMID:12414719

  2. A diaphragmless shock tube for high temperature kinetic studies

    SciTech Connect

    Tranter, Robert S.; Giri, Binod R.

    2008-09-15

    A novel, diaphragmless shock tube (DFST) has been developed for use in high temperature chemical kinetic studies. The design of the apparatus is presented along with performance data that demonstrate the range and reproducibility of reaction conditions that can be generated. The ability to obtain data in the fall off region, confined to much narrower pressure ranges than can be obtained with a conventional shock tube is shown, and results from laser schlieren densitometry experiments on the unimolecular dissociation of phenyl iodide (P{sub 2}=57{+-}9 and 122{+-}7 torr, T{sub 2}=1250-1804 K) are presented. These are compared with results similar to those that would be obtained from a classical shock tube and the implications for extrapolation by theoretical methods are discussed. Finally, the use of the DFST with an online mass spectrometer to create reproducible experiments that can be signal averaged to improve signal/noise and the quality of mass peaks is demonstrated; something that is not possible with a conventional shock tube where each experiment has to be considered unique.

  3. Photodegradation of the acaricide abamectin: a kinetic study.

    PubMed

    Escalada, Juan Pablo; Gianotti, José; Pajares, Adriana; Massad, Walter A; Amat-Guerri, Francisco; García, Norman A

    2008-08-27

    The acaricide abamectin is a mixture of two colorless homologues in a molar ratio of at least 4:1 with the same structure of macrocyclic lactone. The kinetics of its degradation under direct (254 nm) and dye-sensitized (>400 nm) photoirradiation in methanol solution has been studied by UV-vis spectrophotometry, potentiometric detection of dissolved oxygen, stationary fluorescence, laser flash photolysis, and time-resolved detection of singlet molecular oxygen (O2((1)Delta(g))) phosphorescence. The results indicate that the degradation is very efficient under direct irradiation with UV light (254 nm), with a quantum yield of 0.23. On the contrary, under visible-light irradiation, using the natural pigment riboflavin or the synthetic dye rose bengal as sensitizers, the degradation is very inefficient and proceeds through a O2((1)Delta(g))-mediated mechanism, with a bimolecular rate constant for the overall O2((1)Delta(g)) quenching (the sum of physical and chemical quenching) of 5.5 x 10(5) M(-1) s(-1). This value is similar to those reported for the rate constants of the reactions of O2((1)Delta(g)) with isolated double bonds or conjugated dienes and points to similar processes in the case of abamectin.

  4. Kinetic studies on enzymatic acetylation of chloramphenicol in Streptococcus faecalis.

    PubMed Central

    Nakagawa, Y; Nitahara, Y; Miyamura, S

    1979-01-01

    The kinetics of chloramphenicol (CP) acetylation by CP acetyltransferase from Streptococcus faecalis was studied. CP was shown to be acetylated enzymatically to its 3-O-acetyl derivative (3-AcCP) in the presence of acetyl coenzyme A, after which 3-AcCP was converted nonenzymatically to its 1-O-acetyl isomer, 1-O-acetyl CP (1-AcCP). At equilibrium, the 1-AcCP and 3-AcCP were present in a 1:4 ratio. Subsequently the diacetylated product, 1,3-O-O-diacetyl CP [1,3-(Ac)2CP], was enzymatically produced from 1-AcCP by the same enzyme. Theoretical calculation of rate constants (k1, k2, k3) for each successive reaction is as follows: (Formula: see text). This calculation gave k1 = 0.4 min-1, k2 = 0.002 min-1, and k3 = 0.016 min-1. Experimental results agreed closely with these calculated values. Images PMID:119483

  5. Biological conversion of synthesis gas. Mass transfer/kinetic studies

    SciTech Connect

    Klasson, K.T.; Basu, R.; Johnson, E.R.; Clausen, E.C.; Gaddy, J.L.

    1992-03-01

    Mass transfer and kinetic studies were carried out for the Rhodospirillum rubrum and Chlorobium thiosulfatophilum bacterial systems. R. rubrum is a photosynthetic anaerobic bacterium which catalyzes the biological water gas shift reaction: CO + H{sub 2}0 {yields} CO{sub 2} + H{sub 2}. C. thiosulfatophilum is also a H{sub 2}S and COS to elemental sulfur. The growth of R. rubrum may be satisfactorily carried out at 25{degree} and 30{degree}C, while CO uptake and thus the conversion of CO best occurs at temperatures of either 30{degree}, 32{degree} or 34{degree}C. The rate of conversion of COs and H{sub 2}O to CO{sub 2} and H{sub 2}S may be modeled by a first order rate expression. The rate constant at 30{degree}C was found to be 0.243 h{sup {minus}1}. The growth of C. thiosulfatophilum may be modeled in terms of incoming light intensity using a Monod equation: {mu} = {sub 351} + I{sub o}/{sup 0.152}I{sub o}. Comparisons of the growth of R. rubrum and C. thiosulfatophilum shows that the specific growth rate of C. thiosulfatophilum is much higher at a given light intensity.

  6. Kinetic studies of chemical shrinkage and residual stress formation in thermoset epoxy adhesives under confined curing conditions

    NASA Astrophysics Data System (ADS)

    Schumann, M.; Geiß, P. L.

    2015-05-01

    Faultless processing of thermoset polymers in demanding applications requires a profound mastering of the curing kinetics considering both the physico-chemical changes in the transition from the liquid to the solid state and the consolidation of the polymers network in the diffusion controlled curing regime past the gel point. Especially in adhesive joints shrinkage stress occurring at an early state of the curing process under confined conditions is likely to cause defects due to local debonding and thus reduce their strength and durability1. Rheometry is considered the method of choice to investigate the change of elastic and viscous properties in the progress of curing. Drawbacks however relate to experimental challenges in accessing the full range of kinetic parameters of thermoset resins with low initial viscosity from the very beginning of the curing reaction to the post-cure consolidation of the polymer due to the formation of secondary chemical bonds. Therefore the scope of this study was to interrelate rheological data with results from in-situ measurements of the shrinkage stress formation in adhesive joints and with the change of refractive index in the progress of curing. This combination of different methods has shown to be valuable in gaining advanced insight into the kinetics of the curing reaction. The experimental results are based on a multi component thermoset epoxy-amine adhesive.

  7. Multiphase Processing of Isoprene Oxidation Products - Kinetic and Product Studies

    NASA Astrophysics Data System (ADS)

    Hoffmann, D.; Schoene, L.; Schindelka, J.; Herrmann, H.

    2010-12-01

    Isoprene represents a significant fraction of NMHC in the troposphere with recently estimated emission rates of 500-750 TgC yr-1 (1). Due to its enormous source strength, the fate of isoprene and its degradation products is important in atmospheric processes. Possible ascendancies of such oxidation processes are the regional ozone and secondary organic aerosol (SOA) formation. Some aspects of SOA formation from isoprene and its degradation products have already been studied by chamber studies (2,3). Aqueous phase oxidation processes which may occur after phase transfer of ‘early’ oxidation products are often neglected. But these processes provide a potentially important source for organic particle mass constituents such as carboxylic acids. The majority of existing aqueous phase modelling studies focus only on ‘later’ products such as methylglyoxal and oxalic acid. Yet, a recent field study reports much higher aqueous phase concentrations of some ‘earlier’ isoprene oxidation products including methacrolein (MACR) and methyl vinyl ketone (MVK) than expected (4). This indicates a possibly underestimated importance of multiphase chemical processes in the course of the isoprene oxidation as a source for the production of organic particle mass together with known ‘heterogeneous processes’ such as the direct condensation of low-volatility products from gas phase processes onto existing particle surfaces. In order to implement the isoprene multiphase chemistry in atmospheric models detailed kinetic and mechanistic studies are needed. Hence, the temperature dependence of MACR, MVK, methacrylic acid and acrylic acid exposed to NO3, SO4- and OH radicals in the aqueous phase was investigated. The measurements were performed using a laser-photolysis laser long path absorption technique. The analysis confirmed in all cases the much higher reactivity of the OH radical in comparison to SO4- and NO3 radicals. The temperature dependence is most distinct for NO3

  8. The Study of a Simple Redox Reaction as an Experimental Approach to Chemical Kinetics.

    ERIC Educational Resources Information Center

    Elias, Horst; Zipp, Arden P.

    1988-01-01

    Recommends using iodide ions and peroxodisulfate ions for studying rate laws instead of the standard iodine clock for kinetic study. Presents the methodology and a discussion of the kinetics involved for a laboratory experiment for a high school or introductory college course. (ML)

  9. Case study 3. Application of basic enzyme kinetics to metabolism studies: real-life examples.

    PubMed

    Li, Yongmei; McCabe, Michelle; Podila, Lalitha; Tracy, Timothy S; Tweedie, Donald J

    2014-01-01

    An appreciation of the principles of enzyme kinetics can be applied in a number of drug metabolism applications. The concept for this chapter arose from a simple discussion on selecting appropriate time points to most efficiently assess metabolite profiles in a human Phase 1a clinical study (Subheading 4). By considering enzyme kinetics, a logical approach to the issue was derived. The dialog was an important learning opportunity for the participants in the discussion, and we have endeavored to capture this experience with other questions related to determination of K m and V max parameters, a consideration of the value of hepatocytes versus liver microsomes and enzyme inhibition parameters.

  10. Chemical kinetic studies on dry sorbents. Final report. [Sodium bicarbonate

    SciTech Connect

    Davis, W.T.; Keener, T.C.

    1982-02-15

    The scope of this research investigation has included a review of potential additives suitable for dry flue-gas desulfurization (FGD) and a bench scale laboratory study to determine the chemical kinetics for the reaction of five different sorbents with sulfur dioxide. The sorbents chosen included sodium bicarbonate (NaHCO/sub 3/), soda ash (Na/sub 2/CO/sub 3/), trona, lime (CaO) and hydrated lime (Ca(OH)/sub 2/). This study has shown that: (1) The reaction rate increases with temperature for soda ash and calcium oxide. The reaction temperature has an inverse effect on sodium bicarbonate and trona due, primarily, to the simultaneous thermal activation reaction. The calcium hydroxide-SO/sub 2/ reaction increased up to 550/sup 0/F, and then decreased, due to uneven gas flow distribution. (2) The reaction rates for soda ash, calcium oxide and calcium hydroxide were increased by decreasing their particle size. This effect was not confirmed for sodium bicarbonate and trona where reaction temperature was the most important reaction parameter. (3) Reaction with soda ash was found to be limited by the presence of an impervious ash layer which prevented interparticle gaseous diffusion. Calcium oxide and calcium hydroxide were found to be limited by a slow chemical reaction rate. Results on the rate-limiting steps for sodium bicarbonate and trona were inconclusive because of the simultaneous thermal activation reaction. (4) The effect of thermal activation was to increase the reaction rate for sodium bicarbonate and trona at lower temperatures. This effect was less pronounced at higher temperatures. (5) Results obtained for nitric oxide show limited adsorption for the five sorbents tested as compared to the finding for sulfur dioxide.

  11. Kinetic and mechanistic studies of allicin as an antioxidant.

    PubMed

    Okada, Youji; Tanaka, Kaoru; Sato, Eisuke; Okajima, Haruo

    2006-11-21

    We have undertaken a detailed study of the antioxidant activity of allicin, one of the main thiosulfinates in garlic, in order to obtain quantitative information on it as a chain-breaking antioxidant. The antioxidant actions of allicin against the oxidation of cumene and methyl linoleate (ML) in chlorobenzene were studied in detail using HPLC. The hydroperoxides formed during the course of the inhibited oxidation of ML were analyzed as their corresponding alcohols by HPLC, and it is apparent that an allylic hydrogen atom of the allicin is responsible for the antioxidant activity. Furthermore, it is clear that the radical-scavenging reactions of allicin proceed via a one-step hydrogen atom transfer based on the results of the reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH) in the presence of Mg2+ and calculation of the ionization potential value. In addition, we determined the stoichiometric factor (n), the number of peroxyl radicals trapped by one antioxidant molecule, of allicin by measuring the reactivity toward DPPH in chlorobenzene, and the value of n for allicin was about 1.0. Therefore, we measured the rate constants, k(inh), for the reaction of allicin with peroxyl radicals during the induction period of the cumene and the ML oxidation. As a result, we found that allicin reacts with peroxyl radicals derived from cumene and ML with the rate constants k(inh) = 2.6 x 10(3) M(-1)s(-1) and 1.6 x 10(5) M(-1)s(-1) in chlorobenzene, respectively. Our results demonstrate for the first time reliable quantitative kinetic data and the antioxidative mechanism of allicin as an antioxidant.

  12. A kinetic study of methanol oxidation in supercritical water

    SciTech Connect

    Anitescu, G.; Zhang, Z.; Tavlarides, L.L.

    1999-06-01

    The oxidation rate of methanol in supercritical water at 253 bar and temperatures between 673 and 773 K is investigated using an isothermal, isobaric plug-flow tubular reactor and GC/FID and GC/TCD chromatographic methods. Experiments are conducted at a nominal methanol feed concentration of 0.88 mol % (1.53 wt %) using H{sub 2}O{sub 2} as an initial oxidant. In some experiments, the O{sub 2}/MeOH molar ratios are varied from 1.5 to 3.0 and show that the rate of methanol oxidation is independent of the oxygen initial feed concentration. Overall first-order rate constants calculated from the data lead to Arrhenius parameters of A = 10{sup 11.8} s{sup {minus}1} and E{sub a} = 178 kJ/mol (42.5 kcal/mol). The identified reaction products are mainly CO and CO{sub 2}. The temporal variation of the CO yield exhibits a maximum at temperatures of 723 and 748 K, whereas the CO{sub 2} yield increases monotonically over the experimental range of residence time (3--50 s). The experimental data are consistent with a set of consecutive first-order reactions CH{sub 3}OH {yields} CO {yields} CO{sub 2}. The global rate-controlling step in the complete oxidation of methanol is the conversion of CO to CO{sub 2}. The first-order rate constants calculated for CO oxidation to CO{sub 2} lead to A = 10{sup 10.8} s{sup {minus}1} and E{sub a} = 172 kJ/mol (41.0 kcal/mol). Kinetics of this system may be useful to study supercritical water oxidation (SCWO) of polychlorinated biphenyls (PCBs) dissolved in methanol.

  13. Aqueous chlorination of carbamazepine: kinetic study and transformation product identification.

    PubMed

    Soufan, M; Deborde, M; Delmont, A; Legube, B

    2013-09-15

    Carbamazepine reactivity and fate during chlorination was investigated in this study. From a kinetic standpoint, a third-order reaction (first-order relative to the CBZ concentration and second-order relative to the free chlorine concentration) was observed at neutral and slightly acidic pH, whereas a second-order reaction (first order relative to the CBZ concentration and first order relative to the free chlorine concentration) was noted under alkaline conditions. In order to gain insight into the observed pH-dependence of the reaction order, elementary reactions (i.e. reactions of Cl2, Cl2O, HOCl with CBZ and of ClO(-) with CBZ or of HOCl with the ionized form of CBZ) were highlighted and second order rate constants of each of them were calculated. Close correlations between the experimental and modeled values were obtained under these conditions. Cl2 and Cl2O were the main chlorination agents at neutral and acidic pH. These results indicate that, for a 1 mg/L free chlorine concentration and 1-10 mg/L chloride concentration at pH 7, halflives about 52-69 days can be expected. A low reactivity of chlorine with CBZ could thus occur under the chlorination steps used during water treatment. From a mechanistic viewpoint, several transformation products were observed during carbamazepine chlorination. As previously described for the chlorination of polynuclear aromatic or unsaturated compounds, we proposed monohydroxylated, epoxide, diols or chlorinated alcohol derivatives of CBZ for the chemical structures of these degradation products. Most of these compounds seem to accumulate in solution in the presence of excess chlorine.

  14. Kinetics and conformational stability studies of recombinant leucine aminopeptidase.

    PubMed

    Hernández-Moreno, Ana V; Villaseñor, Francisco; Medina-Rivero, Emilio; Pérez, Néstor O; Flores-Ortiz, Luis F; Saab-Rincón, Gloria; Luna-Bárcenas, Gabriel

    2014-03-01

    Leucine aminopeptidase from Vibrio proteolyticus is a broad specificity N-terminal aminopeptidase that is widely used in pharmaceutical processes where the removal of N-terminal residues in recombinant proteins is required. We previously reported the expression of a heterologous construction of the mature protein fused to a 6-histidine tag that presents a reasonable refolding rate for its use at industrial level. Here, we investigate this recombinant leucine aminopeptidase (rLAP) to explain the gain of activity observed when incubated at 37 °C after its production. Unfolding transitions of rLAP as a function of urea concentration were monitored by circular dichroism (CD) and fluorescence (FL) spectroscopy exhibiting single transitions by both techniques. Free energy change for unfolding measured by CD and FL spectroscopy are 2.8 ± 0.4 and 3.7 ± 0.4 kcal mol(-1), respectively. Thermal stability conformation of rLAP is 2.6 ± 0.1 and 6.1 kcal mol(-1) for CD and Nano-Differential Scanning Calorimetry (Nano-DSC), respectively. Enzyme activity was assessed with L-leucine-p-nitroanilide (L-pNA) as substrate. The catalytic efficiency was 3.87 ± 0.10 min(-1) μM(-1) at 37 °C and pH 8.0. Kinetic and conformation studies show differences between the enzyme native and rLAP; however rLAP is selective and specific to remove N-terminal groups from amino acids.

  15. Kinetic study of aluminum adsorption by aluminosilicate clay minerals

    SciTech Connect

    Walker, W.J.; Cronan, C.S.; Patterson, H.H.

    1988-01-01

    The adsorption kinetics of Al/sup 3 +/ by montmorillonite, kaolinite, and vermiculite were investigated as a function of the initial Al concentration, the surface area of the clay, and H/sup +/ concentration, at 25/sup 0/, 18/sup 0/, and 10/sup 0/C. In order to minimize complicated side reactions the pH range was kept between 3.0 and 4.1. Results showed that the adsorption rate was first order with respect to both the initial Al concentration and the clay surface area. Changes in pH within this narrow range had virtually no effect on adsorption rate. This zero order reaction dependence suggested that the H/sup +/, compared to Al, has a weak affinity for the surface. The rates of adsorption decreased in the order of montmorillonite > kaolinite > vermiculite when compared on the basis of equal surface areas, but changed to kaolinite > montmorillonite > vermiculite when the clays were compared on an equal exchange capacity basis. The calculated apparent activation energies were < 32 kJ mol/sup -1/, indicating that over the temperature range of the study the adsorption process is only marginally temperature sensitive. The mechanism is governed by a simple electrostatic cation exchange involving outer sphere complexes between adsorbed Al and the clay surface. Vermiculite, may have a second reaction step governed by both electrostatic attraction and internal ion diffusion. Equilibrium constants for the formation of an adsorbed Al clay complex were also estimated and are 10/sup 5.34/, 10/sup 5.18/, and 10/sup 4.94/ for kaolinite, montmorillonite, and vermiculite, respectively, suggesting that these clays could play a significant role in controlling soil solutions Al concentrations.

  16. Penicillin Hydrolysis: A Kinetic Study of a Multistep, Multiproduct Reaction.

    ERIC Educational Resources Information Center

    McCarrick, Thomas A.; McLafferty, Fred W.

    1984-01-01

    Background, procedures used, and typical results are provided for an experiment in which students carry out the necessary measurements on the acid-catalysis of penicillin in two hours. By applying kinetic theory to the data obtained, the reaction pathways for the hydrolysis of potassium benzyl penicillin are elucidated. (JN)

  17. A Case Study in Chemical Kinetics: The OH + CO Reaction.

    ERIC Educational Resources Information Center

    Weston, Ralph E., Jr.

    1988-01-01

    Reviews some important properties of the bimolecular reaction between the hydroxyl radical and carbon monoxide. Investigates the kinetics of the reaction, the temperature and pressure dependence of the rate constant, the state-to-state dynamics of the reaction, and the reverse reaction. (MVL)

  18. An Undergraduate Laboratory Exercise for Studying Kinetics of Batch Crystallization

    ERIC Educational Resources Information Center

    Louhi­-Kultanen, Marjatta; Han, Bing; Nurkka, Annikka; Hatakka, Henry

    2015-01-01

    The present work describes an undergraduate laboratory exercise for improving understanding of fundamental phenomena in cooling crystallization. The exercise of nucleation and crystal growth kinetics supports learning of theories and models presented in lectures and calculation exercises. The teaching methodology incorporates precepts the…

  19. Kinetic Studies of the Solvolysis of Two Organic Halides

    ERIC Educational Resources Information Center

    Duncan, J. A.; Pasto, D. J.

    1975-01-01

    Describes an undergraduate organic chemistry laboratory experiment which utilizes the solvolysis of organic halides to demonstrate first and second order reaction kinetics. The experiment also investigates the effect of a change of solvent polarity on reaction rate, common-ion and noncommon-ion salt effects, and the activation parameters of a…

  20. [Study progress in Sinomenium acutum (Thunb.) Rehd. et Wils].

    PubMed

    Wang, Yan; Zhou, Liling; Li, Rui

    2002-03-01

    This article reviewed the progress in the study of the pharmacognosy, chemical compositions, pharmacological actions and clinical practices of Sinomenium acutum (Thunb.) Rehd. et Wils. An expectation for the further development and utilization of this plant was put forward.

  1. EPA releases progress report on hydraulic fracturing study

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2013-01-01

    The U.S. Environmental Protection Agency (EPA) provided a 21 December progress report on its ongoing national study about the potential impacts of hydraulic fracturing on drinking water resources. The agency said that a draft of the congressionally requested study will be released in 2014 for public and peer review and that its progress report does not draw conclusions about the potential impacts of hydraulic fracturing, often referred to as fracking.

  2. Case Study Evaluations: A Decade of Progress?

    ERIC Educational Resources Information Center

    Yin, Robert K.

    1997-01-01

    In the last 10 years, there has been increased use of case study methodology, with accompanying refinement and improvement of the methods. Case studies have become legitimate research methods in evaluation, but it is too soon to say whether improvements in methodology are really resulting in improvements in the case studies conducted. (SLD)

  3. Studies in genetic discrimination. Final progress report

    SciTech Connect

    Not Available

    1994-06-01

    We have screened 1006 respondents in a study of genetic discrimination. Analysis of these responses has produced evidence of the range of institutions engaged in genetic discrimination and demonstrates the impact of this discrimination on the respondents to the study. We have found that both ignorance and policy underlie genetic discrimination and that anti-discrimination laws are being violated.

  4. A study of the Sabatier-methanation reaction kinetics

    NASA Technical Reports Server (NTRS)

    Verostko, C. E.; Forsythe, R. K.

    1974-01-01

    The kinetics of the Sabatier methanation reaction, the reduction of carbon dioxide with hydrogen to methane and water, was investigated for 58 percent nickel on kieselguhr catalyst and 20 percent ruthenium on alumina catalyst. Differential rate data from an experimental program were correlated with a power function rate equation both for forward and reverse reactions. The kinetic parameters of activation energy, frequency rate constant and reaction order were determined for the rate equation. The values of these parameters were obtained from an Arrhenius plot of the experimental differential rate data. Also the carbon monoxide side reaction effect was measured and included in the correlation of parameters. The reaction was found to fit the rate equation experimentally within the temperature range 421 K, where the reaction effectively begins, the 800 K where the reaction rate drops and departs from the rate equation form.

  5. Recent Progress in Presolar Grain Studies.

    PubMed

    Amari, Sachiko

    2014-01-01

    Presolar grains are stardust that condensed in stellar outflows or stellar ejecta, and was incorporated in meteorites. They remain mostly intact throughout the journey from stars to the earth, keeping information of their birthplaces. Studies of presolar grains, which started in 1987, have produced a wealth of information about nucleosynthesis in stars, mixing in stellar ejecta, and temporal variations of isotopic and elemental abundances in the Galaxy. Recent instrumental advancements in secondary ion mass spectrometry (SIMS) brought about the identification of presolar silicate grains. Isotopic and mineralogical investigations of sub-μm grains have been performed using a combination of SIMS, transmission electron microscopy (TEM) and focused ion beam (FIB) techniques. Two instruments have been developed to study even smaller grains (∼50 nm) and measure isotopes and elements of lower abundances than those in previous studies.

  6. Recent Progress in Presolar Grain Studies

    PubMed Central

    Amari, Sachiko

    2014-01-01

    Presolar grains are stardust that condensed in stellar outflows or stellar ejecta, and was incorporated in meteorites. They remain mostly intact throughout the journey from stars to the earth, keeping information of their birthplaces. Studies of presolar grains, which started in 1987, have produced a wealth of information about nucleosynthesis in stars, mixing in stellar ejecta, and temporal variations of isotopic and elemental abundances in the Galaxy. Recent instrumental advancements in secondary ion mass spectrometry (SIMS) brought about the identification of presolar silicate grains. Isotopic and mineralogical investigations of sub-μm grains have been performed using a combination of SIMS, transmission electron microscopy (TEM) and focused ion beam (FIB) techniques. Two instruments have been developed to study even smaller grains (∼50 nm) and measure isotopes and elements of lower abundances than those in previous studies. PMID:26819886

  7. Kinetic study of asphaltene dissolution in amphiphile/alkane solutions

    SciTech Connect

    Permsukarome, P.; Chang, C.; Fogler, H.S.

    1997-09-01

    The kinetics of dissolution of pentane-insoluble solid asphaltene precipitates by amphiphile/alkane solutions were investigated using a differential reactor flow system. Two amphiphiles, dodecylbenzenesulfonic acid and nonylphenol, and five alkane solvents, ranging from hexane to hexadecane, were used. Results showed that the rate of asphaltene dissolution in amphiphile/alkane fluids could be approximated with a first-order kinetics with respect to the undissolved asphaltene mass in solution. The specific dissolution rate constant, k, varied with the concentration of amphiphiles, the type of alkane solvents, the temperature, and the fluid flow rate. The rate of asphaltene dissolution displayed a Langmuir-Hinshelwood kinetics with respect to the concentration of amphiphiles. Increasing the temperature of amphiphile/alkane fluids also enhanced the rate of asphaltene dissolution. The apparent activation energy for asphaltene dissolution was approximated to be 4--7 kcal/mol. The rate of asphaltene dissolution was also greater in amphiphile solutions containing lighter alkanes, such as hexane, with lower viscosities. These trends suggest that both surface reaction and mass transfer processes are important to the rate of asphaltene dissolution in amphiphile/alkane fluids.

  8. Enzymatic Synthesis of Furfuryl Alcohol Ester with Oleic Acid by Candida antarctica Lipase B and Its Kinetic Study

    NASA Astrophysics Data System (ADS)

    Sengupta, Avery; Dey, Tanmoy; Ghosh, Mahua; Ghosh, Jaydip; Ghosh, Santinath

    2012-08-01

    This study investigated the successful enzymatic production of furfuryl oleate and its detailed kinetic study by Michaelis-Menten model. Esterification of oleic acid and furfuryl alcohol by Candida antarctica lipase B (Novozym 435 preparation) in a solvent free system was studied in the present work at 1:1 molar ratio of furfuryl alcohol and oleic acid. About 99 % conversion (on the basis of oleic acid) has been achieved within 6 h at 5 % enzyme concentration. Ping-pong bi-bi mechanism (inhibition phenomenon taken into account) was applied to describe the ratios as a complex kinetic model. The kinetic parameters were determined using MATLAB language programme. The two initial rate constants KA and KB respectively were found out by different progress curves plotted with the help of MATLAB language programme. It was concluded from the results that furfuryl alcohol considerably inhibited the enzymatic reaction while oleic acid had negligible inhibitory effect. It was clearly seen that the initial rate was increased with the increase in the furfuryl alcohol concentration until 2 M/L after which there was a drop in the initial rate depicting the inhibitory effect of furfuryl alcohol. Surprisingly, it has been observed that addition of 0.1 mol of product activated the esterification reaction. Finally, the model was found to be statistically fitting well with the experimental data.

  9. ICPP water inventory study progress report

    SciTech Connect

    Richards, B.T.

    1993-05-01

    Recent data from the Idaho Chemical Processing Plant (ICPP) indicate that water is entering the sumps located in the bottom of Tank Firm Vaults in quantities that exceed expected levels. In addition, perched water body(s) exist beneath the northern portion of the ICPP. Questions have been raised concerning the origin of water entering the Tank Farm sumps and the recharge sources for the perched water bodies. Therefore, in an effort to determine the source of water, a project has been initiated to identify the source of water for Tank Farm sumps and the perched water bodies. In addition, an accurate water balance for the ICPP will be developed. The purpose of this report is to present the specific results and conclusions for the ICPP water balance portion of the study. In addition, the status of the other activities being conducted as part of study, along with the associated action plans, is provided.

  10. Progress Report: Pressure Vessel Burst Test Study

    DTIC Science & Technology

    1994-08-01

    report is provided on a program developed to study through test and analysis, the characteristics of blast waves and fragmentation generated by ruptured ...vessels were composite overwrapped pressure vessels ( COPV ) and were cut with a shaped charge (no groove) around its center. The burst location on the...and the shaped charge cut area (shown with dotted lines). BURST INITIATION Longitudinal stress in the circumferential grooves (for developing axial

  11. Progress report on nuclear spectroscopic studies

    SciTech Connect

    Bingham, C.R.; Guidry, M.W.; Riedinger, L.L.; Sorensen, S.P.

    1994-02-18

    The Nuclear Physics group at the University of Tennessee, Knoxville (UTK) is involved in several aspects of heavy-ion physics including both nuclear structure and reaction mechanisms. While the main emphasis is on experimental problems, the authors have maintained a strong collaboration with several theorists in order to best pursue the physics of their measurements. During the last year they have had several experiments at the ATLAS at Argonne National Laboratory, the GAMMASPHERE at the LBL 88 Cyclotron, and with the NORDBALL at the Niels Bohr Institute Tandem. Also, they continue to be very active in the WA93/98 collaboration studying ultra-relativistic heavy ion physics utilizing the SPS accelerator at CERN in Geneva, Switzerland and in the PHENIX Collaboration at the RHIC accelerator under construction at Brookhaven National Laboratory. During the last year their experimental work has been in three broad areas: (1) the structure of nuclei at high angular momentum, (2) the structure of nuclei far from stability, and (3) ultra-relativistic heavy-ion physics. The results of studies in these particular areas are described in this document. These studies concentrate on the structure of nuclear matter in extreme conditions of rotational motion, imbalance of neutrons and protons, or very high temperature and density. Another area of research is heavy-ion-induced transfer reactions, which utilize the transfer of nucleons to states with high angular momentum to learn about their structure and to understand the transfer of particles, energy, and angular momentum in collisions between heavy ions.

  12. Effect of community structure on the kinetics of anaerobic degradation of aromatic compounds. Progress report, March 1989--June 1991

    SciTech Connect

    McInerney, M.J.

    1991-06-01

    The physiology of fatty acid metabolism and the kinetics of benzoate degradation by anaerobic syntrophic bacteria were studied. We have shown that: a threshold for benzoate degradation by a syntrophic coculture of Syntrophus buswellii and Desulfovibrio strain G11 exists and the value of the threshold depends on the amount of benzoate and acetate suggesting a thermodynamic limitation. Syntrophomonas wolfei has the enzymatic ability to produce formate and that low levels of formate are made during growth in pure culture with crotonate or in coculture with butyrate. However, the high specific activities of hydrogenase compared to formate dehydrogenase indicate that hydrogen rather than formate is the intermediate involved in the interspecies transfer of reducing equivalents. We have isolated Syntrophus buswellii and a novel anaerobic bacteria that catalyzes an aryl-ether cleavage reaction using crotonate as the energy source. Several novel obligately halophilic anaerobes from hypersaline oil reservoir brines were isolated and characterized. Two of these degraded pyrogallate with the production of acetate. We have shown that S. wolfei synthesizes poly-{beta}hydroxyalkanoate (PHA) by two routes, directly from a {beta}-oxidation intermediate without cleaving a C-C bond and by the condensation of two acetyl-CoA molecules. The formation of D-3-hydroxyacyl-CoA needed for PHA synthesis occurs by the activity of a acetoacetyl-CoA reductase rather than a enoyl-CoA hydratase. The genes for PHA synthesis in S. wolfei have been cloned into Escherichia coli.

  13. Kinetics and mechanisms of metal retention/release in geochemical processes in soil. 1998 annual progress report

    SciTech Connect

    Taylor, R.W.

    1998-06-01

    'The long-term fate of toxic metals in soils cannot be precisely predicted, and often remediation recommendations and techniques may be ineffective or unnecessary. This work will generate basic knowledge on the kinetics and mechanism(s) of heavy metal retention/release by soil mineral colloids. The information should assist in improving remediation strategies for toxic heavy metal contaminated soils. The objectives are: (1) To determine the effects of residence time on the mechanisms of Cr(VI), Cu(II), Co(II), Cd(II), Pb(II), and Ni(II) sorption/release on Fe and Al oxide and clay mineral surfaces using kinetic studies coupled to extended x-ray absorption fine structure (EXAFS) spectroscopy and fourier transform infrared (FTIR) spectroscopy. (2) To study the effect of temperature, pH, and phosphate on metal sorption by oxides, and derive thermodynamic parameters to describe the sorption process. As of June, 16, 1997 several clay minerals were tested for their efficiency of removing Cr from aqueous systems. The materials tested--smectite, vermiculites, illites, and kaolinite--represent the natural clay minerals that are abundant in soils and sediments. The clays were used in either their original or reduced (reduced with sodium dithionite) forms. The experimental result indicate that the reduced clays acted as an efficient remover of Cr(VI) from an aqueous system. The XANES spectra of Cr-treated clays provided evidence that the clays reduced Cr(VI) to Cr(III) and immobilized Cr in the clays at the same time. Sodium dithionite applied directly into aqueous systems reduced Cr(VI) to Cr(III), but could not immobilize Cr even in the presence of the clays. The Cr(VI) removal capacity varied with the clay mineral type and the structural Fe content. For the clays used in this study, the removal capacity follows the orders of smectites > vermiculites and illites > kaolinite. Within the same type of clay minerals, reduction of Cr(VI) is highly related to the ferrous iron

  14. Progress report on nuclear spectroscopic studies

    SciTech Connect

    Bingham, C.R.; Riedinger, L.L.; Sorensen, S.P.

    1996-01-16

    The experimental program in nuclear physics at the University of Tennessee, Knoxville, is led by Professors Carrol Bingham, Lee Riedinger, and Soren Sorenseni who respectively lead the studies of the exotic decay modes of nuclei far from stability, the program of high-spin research, and our effort in relativistic heavy-ion physics. Over the years, this broad program of research has been successful partially because of the shared University resources applied to this group effort. The proximity of the Oak Ridge National Laboratory has allowed us to build extremely strong programs of joint research, and in addition to play an important leadership role in the Joint Institute for Heavy Ion Research (JIHIR). Our experimental program is also very closely linked with those at other national laboratories: Argonne (collaborations involving the Fragment Mass Analyzer (FMA) and {gamma}-ray arrays), Brookhaven (the RHIC and Phenix projects), and Berkeley (GAMMASPHERE). We have worked closely with a variety of university groups in the last three years, especially those in the UNISOR and now UNIRIB collaborations. And, in all aspects of our program, we have maintained close collaborations with theorists, both to inspire the most exciting experiments to perform and to extract the pertinent physics from the results. The specific areas discussed in this report are: properties of high-spin states; study of low-energy levels of nuclei far from stability; and high energy heavy-ion physics.

  15. Kinetic studies of nitrate removal from aqueous solution using granular chitosan-Fe(III) complex.

    PubMed

    Hu, Qili; Chen, Nan; Feng, Chuanping; Zhang, Jing; Hu, Weiwu; Lv, Long

    2016-01-01

    In the present study, a granular chitosan-Fe(III) complex was prepared as a feasible adsorbent for the removal of nitrate from an aqueous solution. There was no significant change in terms of nitrate removal efficiency over a wide pH range of 3-11. Nitrate adsorption on the chitosan-Fe(III) complex followed the Langmuir-Freundlich isotherm model. In order to more accurately reflect adsorption and desorption behaviors at the solid/solution interface, kinetic model I and kinetic model II were proposed to simulate the interfacial process in a batch system. Nitrate adsorption on the chitosan-Fe(III) complex followed the pseudo-first-order kinetic model and kinetic model I. The proposed half-time could provide useful information for optimizing process design. Adsorption and desorption rate constants obtained from kinetic model I and kinetic model II were beneficial to understanding the interfacial process and the extent of adsorption reaction. Kinetic model I and kinetic model II implied that nitrate uptake exponentially approaches a limiting value.

  16. Electrochemical degradation, kinetics & performance studies of solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Das, Debanjan

    Linear and Non-linear electrochemical characterization techniques and equivalent circuit modelling were carried out on miniature and sub-commercial Solid Oxide Fuel Cell (SOFC) stacks as an in-situ diagnostic approach to evaluate and analyze their performance under the presence of simulated alternative fuel conditions. The main focus of the study was to track the change in cell behavior and response live, as the cell was generating power. Electrochemical Impedance Spectroscopy (EIS) was the most important linear AC technique used for the study. The distinct effects of inorganic components usually present in hydrocarbon fuel reformates on SOFC behavior have been determined, allowing identification of possible "fingerprint" impedance behavior corresponding to specific fuel conditions and reaction mechanisms. Critical electrochemical processes and degradation mechanisms which might affect cell performance were identified and quantified. Sulfur and siloxane cause the most prominent degradation and the associated electrochemical cell parameters such as Gerisher and Warburg elements are applied respectively for better understanding of the degradation processes. Electrochemical Frequency Modulation (EFM) was applied for kinetic studies in SOFCs for the very first time for estimating the exchange current density and transfer coefficients. EFM is a non-linear in-situ electrochemical technique conceptually different from EIS and is used extensively in corrosion work, but rarely used on fuel cells till now. EFM is based on exploring information obtained from non-linear higher harmonic contributions from potential perturbations of electrochemical systems, otherwise not obtained by EIS. The baseline fuel used was 3 % humidified hydrogen with a 5-cell SOFC sub-commercial planar stack to perform the analysis. Traditional methods such as EIS and Tafel analysis were carried out at similar operating conditions to verify and correlate with the EFM data and ensure the validity of the

  17. Evaluation of the National Assessment of Educational Progress. Study Reports

    ERIC Educational Resources Information Center

    Buckendahl, Chad W.; Davis, Susan L.; Plake, Barbara S.; Sireci, Stephen G.; Hambleton, Ronald K.; Zenisky, April L.; Wells, Craig S.

    2009-01-01

    The "Evaluation of the National Assessment of Educational Progress: Study Reports" describes the special studies that comprised the design of the evaluation. In the Final Report, the authors presented a practical discussion of the evaluation studies to its primary, intended audience, namely policymakers. On this accompanying CD, readers…

  18. STUDIES IN LANGUAGE AND LANGUAGE BEHAVIOR. PROGRESS REPORT NO. 3.

    ERIC Educational Resources Information Center

    LANE, HARLAN L.

    THE FOUR STUDIES INCORPORATED IN THIS PROGRESS REPORT ATTEMPTED TO ANALYZE STABILIZED LANGUAGE PROCESSES AND TO EXAMINE THE COMPONENTS OF LANGUAGE PERFORMANCE, RANGING FROM SYSTEMATIC PHONETICS TO LOGICAL DISCOURSE. THE FIRST STUDY REPORTED WORK ON HUMAN AUDITORY SENSITIVITY AS A FUNCTION OF FREQUENCY AND INTENSITY. THE NEXT TWO STUDIES WERE…

  19. Modeling Grade Progression In An Active Surveillance Study

    PubMed Central

    Inoue, Lurdes Y.T.; Trock, Bruce J.; Partin, Alan W.; Carter, H. Ballentine; Etzioni, Ruth

    2013-01-01

    Prostate cancer grade, assessed with the Gleason score, describes how abnormal the tumor tissue and cells appear and it is an important prognostic indicator of disease progression. Whether prostate tumors change grade is a question that has implications for screening and treatment. Empirical data on tumor grade over time have become available from men biopsied regularly as part of active surveillance (AS). However, biopsy grade is subject to misclassification. In this article we develop a model that allows for estimation of the time of grade change while accounting for the misclassification error from biopsy grade. We use misclassification rates from studies of prostate cancer biopsies followed by radical prostatectomy. Estimation of the transition times from true low-grade to high-grade disease is conducted within a Bayesian framework. We apply our model to serial observations on biopsy grade among 627 cases enrolled in a cohort of AS patients at Johns Hopkins University who were biopsied annually and referred to treatment if there was any evidence of disease progression on biopsy. We consider different prior distributions for the time to true grade progression. The estimated likelihood of grade progression within 10 years of study entry ranges from 12% to 24% depending on the prior. We conclude that knowledge of rates of grade misclassification allows for determination of true grade progression rates among men with serial biopsies on AS. While our results are sensitive to prior specifications they indicate that in a non-trivial fraction of the patient population, tumor grade can progress. PMID:24123208

  20. Modeling grade progression in an active surveillance study.

    PubMed

    Inoue, Lurdes Y T; Trock, Bruce J; Partin, Alan W; Carter, Herbert B; Etzioni, Ruth

    2014-03-15

    Prostate cancer grade, assessed with the Gleason score, describes how abnormal the tumor tissue and cells appear, and it is an important prognostic indicator of disease progression. Whether prostate tumors change grade is a question that has implications for screening and treatment. Empirical data on tumor grade over time have become available from men biopsied regularly as part of active surveillance (AS). However, biopsy (BX) grade is subject to misclassification. In this article, we develop a model that allows for estimation of the time of grade change while accounting for the misclassification error from BX grade. We use misclassification rates from studies of prostate cancer BXs followed by radical prostatectomy. Estimation of the transition times from true low-grade to high-grade disease is conducted within a Bayesian framework. We apply our model to serial observations on BX grade among 627 cases enrolled in a cohort of AS patients at Johns Hopkins University who were biopsied annually and referred to treatment if there was any evidence of disease progression on BX. We consider different prior distributions for the time to true grade progression. The estimated likelihood of grade progression within 10 years of study entry ranges from 12% to 24% depending on the prior. We conclude that knowledge of rates of grade misclassification allows for determination of true grade progression rates among men with serial BXs on AS. Although our results are sensitive to prior specifications, they indicate that in a nontrivial fraction of the patient population, tumor grade can progress.

  1. Ion kinetics and thermochemistry pertinent to mass spectrometric organic speciation. Progress report, November 15, 1992--14 November 1995

    SciTech Connect

    Sieck, L.W.

    1998-05-01

    Essentially all of the completed/in progress studies during the last contract period have involved the NIST HPMS unit. Three distinct areas of in-house research are recognizable: (i) determinations of binding energies and entropies for association and cluster ions, which is accomplished by measuring the temperature dependence of the appropriate equilibrium, (ii) measurement of the temperature dependence unimolecular and bimolecular rate constants, and (iii) evaluation of PA`s, HA`s, and IP`s via measurement of variable-temperature equilibria of the type AH{sup +} + B {leftrightarrow} BH{sup +} + A, A{sup -} + BH {leftrightarrow} AH + B{sup -}, and A{sup +} + B {leftrightarrow} B+ + A. Key results from some representative projects are summarized below.

  2. Patella malalignment, pain and patellofemoral progression: The Health ABC Study

    PubMed Central

    Hunter, DJ; Zhang, YQ; Niu, JB; Felson, DT; Kwoh, K; Newman, A; Kritchevsky, S; Harris, T; Carbone, L; Nevitt, M

    2007-01-01

    Objective Patellofemoral (PF) joint OA is strongly correlated with lower extremity disability and knee pain. Risk factors for pain and structural progression in patellofemoral OA are poorly understood. Our objective was to determine the association between patella malalignment and its relation to pain severity, and PF OA disease progression. Methods We conducted an analysis of data from the Health ABC knee OA study. Health ABC is a community based, multi-center cohort study of 3,075 Caucasian and Black men and women aged 70–79 at enrollment. Weight bearing skyline knee x-rays were obtained in a subset (595) of subjects, with and without knee pain, at year 2 and year 5 (mean follow-up 36 months). Films were read paired, and patellofemoral osteophytes (OST) and narrowing (JSN) were scored on a 0–3 scale using the OARSI atlas. We defined progression of PF OA as any increase in JSN score. 3 measures of patella malalignment were made: sulcus angle; patella tilt angle; and patella subluxation medially or laterally (bisect offset). Knee symptoms were assessed using a knee specific WOMAC knee pain subscale. We assessed the relationship between baseline patella malalignment and pain severity (linear regression for WOMAC) and compartment specific PF OA progression (logistic regression for dichotomous outcomes). We classified continuous measures of patella alignment into quartile groups. We performed multivariable adjusted logistic regression models, including age, gender and BMI to assess the relation of baseline patella alignment to the occurrence of PF JSN progression using generalized estimating equations. Results The subjects had a mean age 73.6 (SD 2.9), BMI 28.8 (SD 4.9), 40.3% male, and 46% were Black. Medial displacement of the patella predisposed to medial JSN progression; odds for each quartile 1, 1.2, 1.2, 2.2 (p for trend=0.03), whilst protecting from lateral JSN progression; odds for each quartile 1, 0.7, 0.6, 0.4 (p for trend=0.0004). Increasing patella

  3. Study of the kinetics of catalytic decomposition of hydrazine vapors on palladium

    NASA Technical Reports Server (NTRS)

    Khomenko, A. A.; Apelbaum, L. O.

    1987-01-01

    The decomposition rates of N2H4 on a palladium surface are studied. Experiments were conducted in a circulating unit at atmosphere pressure. The experimental method is described. The laws found for the reaction kinetics are explained by equations.

  4. A kinetic study of hydrolysis of polyester elastomer in magnetic tape

    NASA Technical Reports Server (NTRS)

    Yamamoto, K.; Watanabe, H.

    1994-01-01

    A useful method for kinetic study of the hydrolysis of polyester elastomer is established which uses the number-average molecular weight. The reasonableness of this method is confirmed and the effect of magnetic particles on hydrolysis is considered.

  5. A Study in Enzyme Kinetics Using an Ion-Specific Electrode.

    ERIC Educational Resources Information Center

    Turchi, Sandra; And Others

    1989-01-01

    Describes an undergraduate biochemistry laboratory experiment on enzyme kinetics using the D-amino acid oxidase system and an ammonia electrode. Preparation of an ammonia standard curve, a sample preparation, and inhibition studies are discussed. (YP)

  6. A study of switchgrass pyrolysis: Product variability and reaction kinetics

    NASA Astrophysics Data System (ADS)

    Bovee, Jonathan Matthew

    Samples of the same cultivar of cave-in-rock switchgrass were harvested from plots in Frankenmuth, Roger City, Cass County, and Grand Valley, Michigan. It was determined that variation exists, between locations, among the pyrolytic compounds which can lead to variability in bio-oil and increased processing costs at bio-refineries to make hydrocarbon fuels. Washed and extractives-free switchgrass samples, which contain a lower alkali and alkaline earth metals content than untreated samples, were shown to produce lower amounts of acids, esters, furans, ketones, phenolics, and saccharides and also larger amounts of aldehydes upon pyrolysis. Although the minerals catalyzed pyrolytic reactions, there was no evidence indicating their effect on reducing the production of anhydrosugars, specifically levoglucosan. To further link minerals present in the biomass to a catalytic pathway, mathematic models were employed to determine the kinetic parameters of the switchgrass. While the calculated activation energies of switchgrass, using the FWO and KAS methods, were 227.7 and 217.8 kJ/mol, correspondingly, it was concluded that the activation energies for the switchgrass hemicellulose and cellulose peaks were 115.5 and 158.2 kJ/mol, respectively, using a modified model-fitting method. The minerals that effect the production of small molecules and levoglucosan also have an observable catalytic effect on switchgrass reaction rate, which may be quantifiable through the use of reaction kinetics so as to determine activation energy.

  7. Stable isotope studies of nicotine kinetics and bioavailability

    SciTech Connect

    Benowitz, N.L.; Jacob, P. 3d.; Denaro, C.; Jenkins, R. )

    1991-03-01

    The stable isotope-labeled compound 3',3'-dideuteronicotine was used to investigate the disposition kinetics of nicotine in smokers, the systemic absorption of nicotine from cigarette smoke, and the bioavailability of nicotine ingested as oral capsules. Blood levels of labeled nicotine could be measured for 9 hours after a 30-minute intravenous infusion. Analysis of disposition kinetics in 10 healthy men revealed a multiexponential decline after the end of an infusion, with an elimination half-life averaging 203 minutes. This half-life was longer than that previously reported, indicating the presence of a shallow elimination phase. Plasma clearance averaged 14.6 ml/min/kg. The average intake of nicotine per cigarette was 2.29 mg. A cigarette smoke-monitoring system that directly measured particulate matter in smoke was evaluated in these subjects. Total particulate matter, number of puffs on the cigarette, total puff volume, and time of puffing correlated with the intake of nicotine from smoking. The oral bioavailability of nicotine averaged 44%. This bioavailability is higher than expected based on the systemic clearance of nicotine and suggests that there may be significant extrahepatic metabolism of nicotine.

  8. Social Studies Progress Monitoring and Intervention for Middle School Students

    ERIC Educational Resources Information Center

    Beyers, Sarah J.; Lembke, Erica S.; Curs, Bradley

    2013-01-01

    This study examined the technical adequacy of vocabulary-matching curriculum-based measurement (CBM) to identify and monitor the progress of 148 middle school students in social studies. In addition, the effectiveness of a reading comprehension intervention, Collaborative Strategic Reading (Klingner, Vaughn, Dimino, Schumm, & Bryant, 2001),…

  9. Effects of penconazole on two yeast strains: growth kinetics and molecular studies.

    PubMed

    Jawich, Dalal; Lteif, Roger; Pfohl-Leszkowicz, Annie; Strehaiano, Pierre

    2006-05-01

    The aim of this study consisted to evaluate the impact of a pesticide (penconazole) on the growth kinetics and genotoxicity on two yeast strains (Saccharomyces cerevisiae and Metschnikowia pulcherrima). When the penconazole was added at different phases of the growth of M. pulcherrima, no effect was noticed on the kinetics of yeast growth but DNA adducts were observed when penconazole was added in the exponential phase. Increasing doses (1-15 maximum residue limit) of the pesticide added at the beginning of the fermentation did not induce DNA adducts while kinetics were affected.

  10. Study of Aspect Ratio Effects on Kinetic MHD Instabilities in NSTX and DIII-D

    SciTech Connect

    E.D. Fredrickson; W.W. Heidbrink; C.Z. Cheng; N.N. Gorelenkov; E. Belova; A.W. Hyatt; G.J. Kramer; J. Manickam; J. Menard; R. Nazikian; T.L. Rhodes; E. Ruskov

    2004-10-21

    We report general observations of kinetic instabilities on the low aspect-ratio National Spherical Torus Experiment (NSTX) and describe explicit aspect ratio scaling studies of kinetic instabilities using both the NSTX and the DIII-D tokamak. The NSTX and the DIII-D tokamak are nearly ideal for such experiments, having a factor of two difference in major radius but otherwise similar parameters. We also introduce new theoretical work on the physics of kinetic ballooning modes (KBM), toroidal Alfven eigenmodes (TAE), and compressional Alfven eigenmodes (CAE) with applications to NSTX.

  11. Autoignition chemistry of the hexane isomers: An experimental and kinetic modeling study

    SciTech Connect

    Curran, H.J.; Gaffuri, P.; Pitz, W.J.; Westbrook, C.K.; Leppard, W.R.

    1995-06-01

    Autoignition of the five distinct isomers of hexane is studied experimentally under motored engine conditions and computationally using a detailed chemical kinetic reaction mechanism. Computed and experimental results are compared and used to help understand the chemical factors leading to engine knock in spark-ignited engines and the molecular structure factors contributing to octane rating for hydrocarbon fuels. The kinetic model reproduces observed variations in critical compression ratio with fuel structure, and it also provides intermediate and final product species concentrations in very dose agreement with observed results. In addition, the computed results provide insights into the kinetic origins of fuel octane sensitive.

  12. Characterization study of the sporulation kinetics of Bacillus thuringiensis.

    PubMed

    Liu, B L; Tzeng, Y M

    2000-04-05

    A wild-type and an rDNA strain of Bacillus thuringiensis were cultured in a net-draft-tube modified 20-L airlift bioreactor. A comparison of the sporulation patterns suggests that the early sporulation strain has a lower final spore count. Results from off-gas analysis suggests that the CO(2) profile could be an alternative indication to spore counts for the examination of fermentation performance or even the mortality in bioassay of the cultivation product. The difference in mortality tests exhibited by the microorganism was attributed to different patterns of sporulation as well as different levels of gene control inside the cell itself. The sporulation kinetics of B. thuringiensis was simulated by a simple modified Hill equation, where the initial glucose concentration could affect the timing of the onset of sporulation. The equation matches well with the experimental sporulation data for B. thuringiensis in both wild-type and rDNA strains.

  13. A kinetic study of hypoxanthine oxidation by milk xanthine oxidase.

    PubMed Central

    Escribano, J; Garcia-Canovas, F; Garcia-Carmona, F

    1988-01-01

    The course of the reaction sequence hypoxanthine----xanthine----uric acid catalysed by xanthine:oxygen oxidoreductase from milk was investigated on the basis of u.v. spectra taken during the course of hypoxanthine and xanthine oxidations. It was found that xanthine accumulated in the reaction mixture when hypoxanthine was used as a substrate. The time course of the concentrations of hypoxanthine, xanthine intermediate and uric acid product was simulated numerically. The mathematical model takes into account the competition of substrate, intermediate and product and the accumulation of the intermediate at the enzyme. This type of analysis permits the kinetic parameters of the enzyme for hypoxanthine and xanthine to be obtained. PMID:3196295

  14. Alkaline assisted thermal oil recovery: Kinetic and displacement studies

    SciTech Connect

    Saneie, S.; Yortsos, Y.C.

    1993-06-01

    This report deals with two major issues of chemical assisted flooding - the interaction of caustic, one of the proposed additives to steam flood, with the reservoir rock, and the displacement of oil by a chemical flood at elevated temperatures. A mathematical model simulating the kinetics of silica dissolution and hydroxyl ion consumption in a typical alkaline flooding environment is first developed. The model is based on the premise that dissolution occurs via hydrolysis of active sites through the formation of an intermediate complex, which is in equilibrium with the silicic acid in solution. Both static (batch) and dynamic (core flood) processes are simulated to examine the sensitivity of caustic consumption and silica dissolution to process parameters, and to determine rates of propagation of pH values. The model presented provides a quantitative description of the quartz-alkali interaction in terms of pH, salinity, ion exchange properties, temperature and contact time, which are of significant importance in the design of soluble silicate flooding processes. The modeling of an adiabatic hot waterflood assisted by the simultaneous injection of a chemical additive is next presented. The model is also applicable to the hot alkaline flooding under conditions of negligible adsorption of the generated anionic surfactant and of hydroxide adsorption being Langmuirian. The theory of generalized simple waves (coherence ) is used to develop solutions for the temperature, concentration, and oil saturation profiles, as well as the oil recovery curves. It is shown that, for Langmuir adsorption kinetics, the chemical resides in the heated region of the reservoir if its injection concentration is below a critical value, and in the unheated region if its concentration exceeds this critical value. Results for a chemical slug injection in a tertiary recovery process indicate recovery performance is maximized when chemical resides in the heated region of the reservior.

  15. Kinetic study of antibiotic ciprofloxacin ozonation by MWCNT/MnO2 using Monte Carlo simulation.

    PubMed

    Jalali, Hamed Moradmand

    2016-02-01

    Kinetic Monte Carlo simulation was used to investigate kinetics of antibiotic ciprofloxacin degradation by direct and heterogeneous catalytic (MnO2 and carbon nano-tube loaded with MnO2) ozonation. The reaction kinetic mechanisms of each system have been obtained. The rate constant values for the each step of the reaction mechanisms were attained as adjustable parameters by kinetic Monte Carlo simulation. The carbon nano-tube loaded with MnO2 plays important role as catalyst in the ciprofloxacin ozonation by increasing reactivity of ozone and ciprofloxacin drug on the surface of carbon nano-tube. Optimized amount of ozone and catalysts were obtained via studying the effect of inlet ozone concentration and initial amount of catalyst on the rate of ciprofloxacin degradation using Monte Carlo simulation. The simulation results of this study have reasonably agreement with the present experimental data for the ozonation of ciprofloxacin drug.

  16. New techniques for positron emission tomography in the study of human neurological disorders: Progress report, December 15, 1987-June 14, 1988

    SciTech Connect

    Kuhl, D.E.

    1988-02-01

    A brief progress report is presented describing the preparation and animal testing of /sup 11/C scopolamine and /sup 18/F fluoride. Additional studies entitled ''Automated Arterial Blood Sampling System for PET,'' Rapid Data Analysis Schemes for Functional Imaging in PET,'' and ''Tracer Kinetic Modeling in PET Measures of Cholinergic Receptors'' are described

  17. Kinetics Studies of Radical-Radical Reactions: The NO2 + N2H3 System

    DTIC Science & Technology

    2013-10-01

    investigating the kinetics of this elementary reaction . 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES...Viewgraph 3. DATES COVERED (From - To) September 2013- October 2013 4. TITLE AND SUBTITLE Kinetics Studies of Radical-Radical Reactions (I): The NO2...characteristics in relevant operating environments. Here we report theoretical results obtained on the prototypical radical- radical reaction : NO2 + N2H3

  18. Biological Sciences Curriculum Study Newsletter Number 56, Progress Report.

    ERIC Educational Resources Information Center

    Clark, George M., Ed.

    This newsletter presents a progress report for the 1973-74 year for the Biological Sciences Curriculum Study (BSCS). The program for the Educable Mentally Handicapped is reviewed and a new series of Animal Behavior films is described. Other articles in the newsletter include information on the Human Sciences Program with emphasis on the…

  19. On Studies of Moral Socialization of Students: Progress and Perplexities

    ERIC Educational Resources Information Center

    Zhang, Renjie

    2008-01-01

    Moral socialization of students consists of five elements: process, subject, agent, content and pattern. This paper discusses the studies of the former three: their progress and perplexities, covering the following puzzles: "Why does the youth socialization take longer time?" "Are there any critical periods in student…

  20. Kinetic study of brilliant green adsorption from aqueous solution onto white rice husk ash.

    PubMed

    Tavlieva, Mariana P; Genieva, Svetlana D; Georgieva, Velyana G; Vlaev, Lyubomir T

    2013-11-01

    The present research was focused on the study of adsorption kinetics of brilliant green (BG) onto white rice husk ash from aqueous solutions. The research was performed in the temperature interval 290-320 K in 10° steps and in the concentration range of 3-100 mg L(-1). Batch studies were conducted in order to determine the optimal adsorbent dose, and the time required to reach the adsorption equilibrium at each temperature. The effect of the initial concentration of brilliant green was studied (pH not adjusted), as well as the effect of temperature. The maximum adsorption capacity of the WRHA for BG at 320 K was determined to be 85.56 mg g(-1). The adsorption kinetic data were analyzed employing several kinetic models: pseudo-first-order equation, pseudo-second-order equation, Elovichequation, Banghman's equation, Diffusion-chemisorption model, and Boyd kinetic expression. It was established that the adsorption process obeyed the pseudo-second-order kinetic model. Based on the rate constants obtained by this kinetic model using Arrhenius and Eyring equations, the activation parameters were determined, namely the activation energy (50.04 kJ mol(-1)), the change of entropy (-318.31 J mol(-1) K(-1)), enthalpy (-47.50 kJ mol(-1)), and Gibbs free energy (range 44.81-54.36 kJ mol(-1)) for the formation of activated complex from the reagents.

  1. The kinetics of the oxidation of pyrite by ferric ions and dissolved oxygen: An electrochemical study

    SciTech Connect

    Holmes, P.R.; Crundwell, F.K.

    2000-01-01

    The dissolution of pyrite is important in the geochemical cycling of iron and sulphur, in the formation of acid mine drainage, and in the extraction of metals by bacterial leaching. Many researchers have studied the kinetics of dissolution, and the rate of dissolution has often been found to be half-order in ferric ions or oxygen. Previous work has not adequately explained the kinetics of dissolution of pyrite. The dissolution of pyrite is an oxidation-reduction reaction. The kinetics of the oxidation and reduction half-reactions was studied independently using electrochemical techniques of voltammetry. The kinetics of the overall reaction was studied by the electrochemical technique of potentiometry, which consisted of measuring the mixed potential of a sample of corroding pyrite in solutions of different compositions. The kinetics of the half reactions are related to the kinetics of the overall dissolution reaction by the condition that there is no accumulation of charge. This principle is used to derive expressions for the mixed potential and the rate of dissolution, which successfully describe the mixed potential measurements and the kinetics of dissolution reported in the literature. It is shown that the observations of half-order kinetics and that the oxygen in the sulphate product arises from water are both a direct consequence of the electrochemical mechanism. Thus it is concluded that the electrochemical reaction steps occurring at the mineral-solution interface control the rate of dissolution. Raman spectroscopy was used to analyze reaction products formed on the pyrite surface. The results indicated that small amounts of polysulphides form on the surface of the pyrite. However, it was also found that the mixed (corrosion) potential does not change over a 14-day leaching period. This indicates that even though polysulphide material is present on the surface, it does not influence the rate of the reactions occurring at the surface. Measurement of the

  2. Preface: Recent progress from networked studies based around MST radar

    NASA Astrophysics Data System (ADS)

    Hocking, Wayne K.; Lehmann, Volker; Singer, Werner; Yamamoto, Masayuki

    2014-10-01

    Studies of the mesosphere, stratosphere, and troposphere by radar, application of networks, and multi-instrument studies have grown significantly in recent years, and have covered a wide range of areas in technology, fundamental research, and application. This special issue of the Journal of Atmospheric and Solar-Terrestrial Physics on "Recent progress from networked studies based around MST radar" focuses primarily on selected papers presented at the 13th International Workshops on Scientific and Technical Aspects of MST Radar (MST13).

  3. [Study on Chemical Kinetic Effect of Dielectric Barrier Discharge Plasma].

    PubMed

    Zrang, Peng; Hong, Yan-ji; Shen, Shuang-yan; Ding, Xiao-yu; Ma, Di

    2015-03-01

    To reveal the mechanism of plasma (assisted the ignition process of methane/air further, schematic of dielectric barrier discharge plasma system with atmospheric air was designed and set up, the emission spectrum of dielectric barrier discharge plasma with atmospheric air was measured, and the active particles produced by the interaction of dielectric barrier discharge plasma with atmospheric air were analyzed with the spectrum technology, the ignition model and calculation methods of sensitivity analysis and reaction path analysis were given, effects of NO and O3 on the ignition delay time were simulated, and the chemical kinetics mechanism of NO and O3 assisted ignition was revealed via sensitivity analysis and reaction path analysis. The results show that main excited particles of N2 and O3 are generated via effect of plasma on the atmospheric air, which are converted into active particles of NO(ξ) and O3 in the end, the life of which are longer than any other active particles, effects of plasma on the ignition is simplified as effects of NO(ξ) and O3 on the ignition; NO and O3 could reduce the ignition delay time significantly, but the amplitude decrease with increase of the initial temperature, this is because the rate of ignition is decided by the oxidation rate of CH3, the oxidized pathway of CH3 is R155 and R156 for auto-ignition and their rates are slower when temperature is low, so the ignition delay time of methane/air is longer; NO could reduce the ignition delay time significantly because of the oxidized pathway of CH3 is changed to R327 CH3O2 + NO = CH3O + NO2, R328 CH3 + NO2 = CH3O + NO for NO(ξ) (assisted ignition process from R155 and R156 for auto-ignition; and the chemical kinetic effect is the dominating factor of O3 on the ignition and which change the reaction path.

  4. Thermogravimetric analysis and kinetic study of formation of lithium titanate by solid state route

    NASA Astrophysics Data System (ADS)

    Sonak, Sagar; Jain, Uttam; Sahu, Ashok Kumar; Kumar, Sanjay; Krishnamurthy, Nagaiyar

    2015-02-01

    The kinetics of formation of lithium titanate from the solid state reaction of lithium carbonate and titanium oxide was studied using non-isothermal thermogravimetric technique. Thermogravimetric data for the reaction of lithium carbonate and titanium oxide was obtained at various heating rates. The methods such as Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose were used to estimate the kinetic parameters from the obtained thermogravimetric data. The average activation energy for the formation of lithium titanate by solid state route was found to be 243 kJ/mol K. The reaction mechanism was determined by the method given by Malek. It was found that the three dimensional diffusion model best describes the reaction kinetics. A kinetic equation describing the reaction is proposed and reaction mechanism is discussed.

  5. Study on kinetic model of microwave thermocatalytic treatment of biomass tar model compound.

    PubMed

    Anis, Samsudin; Zainal, Z A

    2014-01-01

    Kinetic model parameters for toluene conversion under microwave thermocatalytic treatment were evaluated. The kinetic rate constants were determined using integral method based on experimental data and coupled with Arrhenius equation for obtaining the activation energies and pre-exponential factors. The model provides a good agreement with the experimental data. The kinetic model was also validated with standard error of 3% on average. The extrapolation of the model showed a reasonable trend to predict toluene conversion and product yield both in thermal and catalytic treatments. Under microwave irradiation, activation energy of toluene conversion was lower in the range of 3-27 kJ mol(-1) compared to those of conventional heating reported in the literatures. The overall reaction rate was six times higher compared to conventional heating. As a whole, the kinetic model works better for tar model removal in the absence of gas reforming within a level of reliability demonstrated in this study.

  6. Kinetic Studies with Ion Selective Electrodes: Determination of Creatinine in Urine with a Picrate Ion Selective Electrode: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Diamandis, E. P.; And Others

    1983-01-01

    The kinetic of the Jaffe reaction with picrate ion selective electrode (ISE) and a kinetic method for determining creatinine in urine is presented. The experiment could be used to familarize students with the application of ISE in kinetic studies and chemical analysis. (Author/JN)

  7. Kinetic studies of clavulanic acid recovery by ion exchange chromatography.

    PubMed

    Barboza, M; Almeida, R M; Hokka, C O

    2001-01-01

    Clavulanic acid (CA) is a beta-lactamase inhibitor produced by strains of Streptomyces clavuligerus. Nowadays, the combination of CA with amoxycillin is the most successful example of the use of a beta-lactam antibiotic sensitive to beta-lactamases together with an inhibitor of these enzymes. Clavulanic acid is purified from fermentation broth by a series of steps consisting mainly of two-phase separation processes such as liquid-liquid extraction, adsorption or ion-exchange chromatography, among others. Amberlite IRA 400, a strong anion-exchange resin, has a very high adsorption capacity for CA (Mayer et al. 1997). This resin can be pre-treated with NaCl (chloride cycle), to remove selectively only those anions, which are able to displace chloride from the resin or with NaOH (hydroxyl cycle), to remove all species of anions. In order to decide the best operating conditions for CA recovery by ion-exchange resins and then to construct a model of this separation process, batch experiments were conducted using Amberlite IRA 400 in the chloride cycle. These runs were carried out in a 200 ml stirred tank, at two different initial solution pH, 6.2 and 4.0; the temperature was maintained at 10 degrees C and 20 degrees C during adsorption and 30 degrees C during the desorption step. It was possible, on the basis of these batch results, to model the separation process, including the adsorption kinetics, equilibrium data and mass transfer limitations.

  8. Kinetic modeling study of toluene pyrolysis at low pressure

    SciTech Connect

    Zhang, Lidong; Cai, Jianghuai; Zhang, Taichang; Qi, Fei

    2010-09-15

    A detailed kinetic model, consisting of 137 species and 530 reactions, was developed to simulate toluene pyrolysis at low pressure within the temperature range from 1270 to 1870 K. The mole fraction profiles predicted for pyrolysis species up to phenanthrene were in good agreement with the experiment. The decomposition pathways of toluene and the growth pathways to polycyclic aromatic hydrocarbons (PAHs) were discussed from reaction flux analysis. Toluene decomposes through the reaction sequence C{sub 6}H{sub 5}CH{sub 3}{yields} C{sub 6}H{sub 5}CH{sub 2}{yields}C{sub 7}H{sub 6}{yields}c-C{sub 5}H{sub 5}{yields}C{sub 3}H{sub 3}, which also has a predominant contribution to the production of acetylene. Furthermore, sensitivity analysis showed that the primary decomposition reactions of toluene, C{sub 6}H{sub 5}CH{sub 3}=C{sub 6}H{sub 5}CH{sub 2}+H and C{sub 6}H{sub 5}CH{sub 3}=C{sub 6}H{sub 5}+CH{sub 3}, have great influences on the formation of small molecules, such as phenyl radical, benzyl radical, C2- and C3-species, which are critical to the formation of PAHs in the pyrolysis of toluene. (author)

  9. Kinetic studies of amylase and biomass production by Calvatia gigantea

    SciTech Connect

    Kekos, D.; Macris, B.J.

    1987-01-01

    Production of alpha-amylase (alpha-4, glucan 4-glucanohydrolase, EC 3.2.1.1) by microorganisms has been practiced for many years in small and large scale operations and the literature on this enzyme is voluminous. Aspergillus niger and Aspergillus oryzae have been reported as the main fungal species used for commercial production of the enzyme. On the other hand, large volumes of low-cost agricultural products such as acorn (the perisperm-free dry seed contains approximately 60% starch) are wasted in many countries and provide a challenge to biotechnology to efficiently utilize these rich sources of starch for the production of high added value products like enzymes. C. gigantea is an edible puffball excreting high levels of alpha-amylase when cultivated on different sources of starch containing elevated quantities of toxic tannic compounds. This fungus has been employed for the production of microbial protein from wastes and acorns containing high levels of toxic tannic compounds. The same fungus was also reported to grow on both hydrolyzable and condensed tannins as sole carbon sources. The present work was undertaken to investigate certain kinetic characteristics of alpha-amylase and biomass production by C. gigantea grown on soluble and acorn starch in a lab fermenter. (Refs. 18).

  10. Fluorescence methods to study DNA translocation and unwinding kinetics by nucleic acid motors.

    PubMed

    Fischer, Christopher J; Tomko, Eric J; Wu, Colin G; Lohman, Timothy M

    2012-01-01

    Translocation of nucleic acid motor proteins (translocases) along linear nucleic acids can be studied by monitoring either the time course of the arrival of the motor protein at one end of the nucleic acid or the kinetics of ATP hydrolysis by the motor protein during translocation using pre-steady state ensemble kinetic methods in a stopped-flow instrument. Similarly, the unwinding of double-stranded DNA or RNA by helicases can be studied in ensemble experiments by monitoring either the kinetics of the conversion of the double-stranded nucleic acid into its complementary single strands by the helicase or the kinetics of ATP hydrolysis by the helicase during unwinding. Such experiments monitor translocation of the enzyme along or unwinding of a series of nucleic acids labeled at one position (usually the end) with a fluorophore or a pair of fluorophores that undergo changes in fluorescence intensity or efficiency of fluorescence resonance energy transfer (FRET). We discuss how the pre-steady state kinetic data collected in these ensemble experiments can be analyzed by simultaneous global nonlinear least squares (NLLS) analysis using simple sequential "n-step" mechanisms to obtain estimates of the macroscopic rates and processivities of translocation and/or unwinding, the rate-limiting step(s) in these mechanisms, the average "kinetic step-size," and the stoichiometry of coupling ATP binding and hydrolysis to movement along the nucleic acid.

  11. Simulation study of overtaking of ion-acoustic solitons in the fully kinetic regime

    NASA Astrophysics Data System (ADS)

    Hosseini Jenab, S. M.; Spanier, F.

    2017-03-01

    The overtaking collisions of ion-acoustic solitons in the presence of trapping effects of electrons are studied based on a fully kinetic simulation approach. The method is able to provide all the kinetic details of the process alongside the fluid-level quantities self consistently. Solitons are produced naturally by utilizing the chain formation phenomenon, and then are arranged in a new simulation box to test the different scenarios of overtaking collisions. Three achievements are reported here. First, simulations prove the long-time life span of the ion-acoustic solitons in the presence of trapping effect of electrons (kinetic effects), which serves as the benchmark of the simulation code. Second, their stability against overtaking mutual collisions is established by creating collisions between solitons with different number and shapes of trapped electrons, i.e., different trapping parameter. Finally, details of solitons during collisions for both ions and electrons are provided on both fluid and kinetic levels. These results show that on the kinetic level, trapped electron population accompanying each of the solitons are exchanged between the solitons during the collision. Furthermore, the behavior of electron holes accompanying solitons contradicts the theory about the electron holes interaction developed based on kinetic theory. They also show behaviors much different from other electron holes witnessed in processes such as nonlinear Landau damping (Bernstein-Greene-Kruskal -BGK- modes) or beam-plasma interaction (like two-beam instability).

  12. Hydride Transfer in DHFR by Transition Path Sampling, Kinetic Isotope Effects, and Heavy Enzyme Studies

    PubMed Central

    Wang, Zhen; Antoniou, Dimitri; Schwartz, Steven D.; Schramm, Vern L.

    2016-01-01

    Escherichia coli dihydrofolate reductase (ecDHFR) is used to study fundamental principles of enzyme catalysis. It remains controversial whether fast protein motions are coupled to the hydride transfer catalyzed by ecDHFR. Previous studies with heavy ecDHFR proteins labeled with 13C, 15N, and nonexchangeable 2H reported enzyme mass-dependent hydride transfer kinetics for ecDHFR. Here, we report refined experimental and computational studies to establish that hydride transfer is independent of protein mass. Instead, we found the rate constant for substrate dissociation to be faster for heavy DHFR. Previously reported kinetic differences between light and heavy DHFRs likely arise from kinetic steps other than the chemical step. This study confirms that fast (femtosecond to picosecond) protein motions in ecDHFR are not coupled to hydride transfer and provides an integrative computational and experimental approach to resolve fast dynamics coupled to chemical steps in enzyme catalysis. PMID:26652185

  13. Noninvasive spatially resolved kinetic study of hydrolyzable camptothecin antitumor drugs in vitro and in vivo by confocal scanning microspectrofluorometry

    NASA Astrophysics Data System (ADS)

    Chourpa, Igor; Charonov, Serguei; Kokota, Alexandre; Riou, Jean-Francois; Manfait, Michel

    1998-04-01

    Hydrolysis of the lactone ring of camptothecins (CPTs) leads to a loss of their antitumor activity. The non-hydrolyzable derivatives are also inactive. Thus, the state of the lactone ring during the drug interaction with biological partners is of a great interest. High performance liquid chromatography currently employed to study the lactone hydrolysis in free CPTs can not be applied to the drug- target complexes and in vivo measurements. We followed kinetics of the lactone hydrolysis in CPTs using hydrolysis- induced time-dependent evolution of their fluorescence spectra. Spectra were obtained from micro-volumes of the samples under the microscope of a computer-controlled confocal microspectrofluorometer (M51, DILOR, France). Spectral recording and treatment (filtering, decomposition into model spectra of the intact and hydrolyzed forms, etc.) were performed using a software package developed in our laboratory. Data obtained for a series of CPTs at very low concentrations, ca. 10-7 M, demonstrated a good reproducibility, even at basic pH, where the hydrolysis is fast. Then the kinetics studies were extended to CPTs in complexes with their potential biological targets, DNA and topoisomerase I, in vitro. The in vivo studies of the lactone status at the level of single living cancer cells treated with CPTs are actually in progress.

  14. A comprehensive kinetics study of coconut shell waste pyrolysis.

    PubMed

    Ali, Imtiaz; Bahaitham, Haitham; Naebulharam, Raed

    2017-03-18

    Model-free and model-fitting methods were compared for pyrolytic conversion of the coconut shell waste. The apparent activation energy, estimated from differential and integral iso-conversional methods, increased with the progression of pyrolytic conversion. The reaction model, f(α)=(1-α)(4)·[-ln(1-α)](0.53), indicate that order-based nucleation and growth mechanisms control the solid-state pyrolysis of the coconut shell waste. The active pyrolysis zone was consisted of overlapping multi-component degradation peaks. Average activation energy of the pseudo-components estimated from the Kissinger's method were 21.9kJ.mol(-1), 106.4kJ.mol(-1) and 108.6kJ.mol(-1) for the dehydration, the degradation of pseudo-cellulose and pseudo-hemicellulose, respectively. Pseudo-lignin decomposed over a wide range of temperature with a slower conversion rate as compared to pseudo-hemicellulose and pseudo-cellulose. Average activation energy range of pseudo-lignin was estimated from the combination of model-free and model-fitting methods as 79.1-226.5kJ.mol(-1).

  15. A Review on Progress in QSPR Studies for Surfactants

    PubMed Central

    Hu, Jiwei; Zhang, Xiaoyi; Wang, Zhengwu

    2010-01-01

    This paper presents a review on recent progress in quantitative structure-property relationship (QSPR) studies of surfactants and applications of various molecular descriptors. QSPR studies on critical micelle concentration (cmc) and surface tension (γ) of surfactants are introduced. Studies on charge distribution in ionic surfactants by quantum chemical calculations and its effects on the structures and properties of the colloids of surfactants are also reviewed. The trends of QSPR studies on cloud point (for nonionic surfactants), biodegradation potential and some other properties of surfactants are evaluated. PMID:20479997

  16. Copper and cobalt complexes of octadentate azamacrocycles: spectrophotometric titration, stopped-flow kinetics and crystallographic study.

    PubMed

    Ozay, Hava; Baran, Yakup; Ishii, Youichi

    2011-12-01

    Details of complex formation kinetics are reported for tetrakis(2-hydroxyethyl) substituted cyclen (L(1)) and cyclam (L(2)) with Cu(II) and Co(II). Stopped-flow kinetics and spectroscopic titration methods were employed for the activation parameters and stability constants, respectively. X-ray studies revealed that the pendant 2-hydroxyethyl groups are not equivalent: two are folded over the macrocycle and maintained by intramolecular hydrogen bonds while the others are extended and pointed away from the macrocyclic cavity. Complex formation kinetics and spectroscopic titration were performed in aqueous acidic buffer solutions. Thermodynamic and kinetic parameters revealed that the ring size of the macrocycles plays an extremely important role for each metal ion studied. Stopped-flow kinetic measurements explained the mechanism of the complex formation process of both Cu(II) and Co(II) which proceed in outer-sphere interactions with ligands. There are two steps in the complex formation of the system studied. The initial step is a second order reaction between the metal ion and macrocycle with a second order rate constant.

  17. Kinetic study of alkaline protease 894 for the hydrolysis of the pearl oyster Pinctada martensii

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Chen, Hua; Cai, Bingna; Liu, Qingqin; Sun, Huili

    2013-05-01

    A new enzyme (alkaline protease 894) obtained from the marine extremophile Flavobacterium yellowsea (YS-80-122) has exhibited strong substrate-binding and catalytic activity, even at low temperature, but the characteristics of the hydrolysis with this enzyme are still unclear. The pearl oyster Pinctada martensii was used in this study as the raw material to illustrate the kinetic properties of protease 894. After investigating the intrinsic relationship between the degree of hydrolysis and several factors, including initial reaction pH, temperature, substrate concentration, enzyme concentration, and hydrolysis time, the kinetics model was established. This study showed that the optimal conditions for the enzymatic hydrolysis were an initial reaction pH of 5.0, temperature of 30°C, substrate concentration of 10% (w/v), enzyme concentration of 2 500 U/g, and hydrolysis time of 160 min. The kinetic characteristics of the protease for the hydrolysis of P. martensii were obtained. The inactivation constant was found to be 15.16/min, and the average relative error between the derived kinetics model and the actual measurement was only 3.04%, which indicated a high degree of fitness. Therefore, this study provides a basis for the investigation of the concrete kinetic characteristics of the new protease, which has potential applications in the food industry.

  18. Kinetics adsorption study of the ethidium bromide by graphene oxide as adsorbent from aqueous matrices

    NASA Astrophysics Data System (ADS)

    Rajabi, M.; Moradi, O.; Zare, K.

    2017-01-01

    In this study of ethidium bromide, adsorption from aqueous matrices by graphene oxide as adsorbent was investigated. Influencing parameters in the adsorption study included contact time, temperature, and pH. The optimum time was selected 17 min, and the best value of pH was determined at 8. All adsorption experiments were performed at 298 K temperature. The maximum wavelength of ethidium bromide was 475 nm. The Elovich, four types of the pseudo-second-order, the pseudo-first-order, and intra-particle diffusion kinetic adsorption models were used for kinetic study, and the results show that adsorption of ethidium bromide on graphene oxide surface best complied with type (I) of the pseudo-second-order kinetic model.

  19. Shock wave, fluid instability and implosion studies with a kinetic particle approach

    NASA Astrophysics Data System (ADS)

    Sagert, Irina; Even, Wesley P.; Strother, Terrance T.

    2016-10-01

    Many problems in laboratory plasma physics are subject to flows that move between the continuum and the kinetic regime. The correct description of these flows is crucial in order to capture their impact on the system's dynamical evolution. Examples are capsule implosions in inertial confinement fusion (ICF). Although their dynamics is predominantly shaped by shock waves and fluid instabilities, non-equilibrium flows in form of deuterium/tritium ions have been shown to play a significant role. We present recent studies with our Monte Carlo kinetic particle code that is designed to capture continuum and kinetic flows in large physical systems with possible applications in ICF studies. Discussed results will include standard shock wave and fluid instability tests and simulations that are adapted towards future ICF studies with comparisons to hydrodynamic simulations. This work used the Wolf TriLAB Capacity Cluster at LANL. I.S. acknowledges support through a Director's fellowship (20150741PRD3) from Los Alamos National Laboratory.

  20. Study Progress on Tissue Culture of Maize Mature Embryo

    NASA Astrophysics Data System (ADS)

    Wang, Hongzhen; Cheng, Jun; Cheng, Yanping; Zhou, Xioafu

    It has been paid more and more attention on maize tissue culture as it is a basic work in maize genetic transformation, especially huge breakthrough has been made in maize tissue culture utilizing mature embryos as explants in the recent years. This paper reviewed the study progress on maize tissue culture and plant regeneration utilizing mature embryos as explants from callus induction, subculture, plant regeneration and browning reduction and so on.

  1. A bioenergetics-kinetics coupled modeling study on subsurface microbial metabolism in a field biostimulation experiment

    NASA Astrophysics Data System (ADS)

    Jin, Q.; Zheng, Z.; Zhu, C.

    2006-12-01

    Microorganisms in nature conserve energy by catalyzing various geochemical reactions. To build a quantitative relationship between geochemical conditions and metabolic rates, we propose a bioenergetics-kinetics coupled modeling approach. This approach describes microbial community as a metabolic network, i.e., fermenting microbes degrade organic substrates while aerobic respirer, nitrate reducer, metal reducer, sulfate reducer, and methanogen consume the fermentation products. It quantifies the control of substrate availability and biological energy conservation on the metabolic rates using thermodynamically consistent rate laws. We applied this simulation approach to study the progress of microbial metabolism during a field biostimulation experiment conducted in Oak Ridge, Tennessee. In the experiment, ethanol was injected into a monitoring well and groundwater was sampled to monitor changes in the chemistry. With time, concentrations of ethanol and SO42- decreased while those of NH4+, Fe2+, and Mn2+ increased. The simulation results fitted well to the observation, indicating simultaneous ethanol degradation and terminal electron accepting processes. The rates of aerobic respiration and denitrification were mainly controlled by substrate concentrations while those of ethanol degradation, sulfate reduction, and methanogenesis were controlled dominantly by the energy availability. The simulation results suggested two different microbial growth statuses in the subsurface. For the functional groups with significant growth, variations with time in substrate concentrations demonstrated a typical S curve. For the groups without significant growth, initial decreases in substrate concentrations were linear with time. Injecting substrates followed by monitoring environmental chemistry therefore provides a convenient approach to characterize microbial growth in the subsurface where methods for direct observation are currently unavailable. This research was funded by the

  2. A kinetic study of lipase-catalyzed alcoholysis of palm kernel oil.

    PubMed

    de Oliveira, D; Alves, T L

    2000-01-01

    The use of lipases as biocatalysts in interesterification reactions has been the object of growing interest, owing to the importance of esters as emulsifiers, intermediates to produce oleochemicals, and fuel alternatives. We consider in this article a kinetic study of lipase-catalyzed alcoholysis of palm kernel oil, using n-hexane as the solvent. In a first step the ester production was maximized by using a Taguchi design, and then an empirical model was built to determine the influence of the process variables. Taking into account the results obtained in the first step, we performed a kinetic study and developed a simple model for this system.

  3. Single-molecule enzymology of steroid transforming enzymes: Transient kinetic studies and what they tell us.

    PubMed

    Penning, Trevor M

    2016-07-01

    Structure-function studies on steroid transforming enzymes often use site-directed mutagenesis to inform mechanisms of catalysis and effects on steroid binding, and data are reported in terms of changes in steady state kinetic parameters kcat, Km and kcat/Km. However, this dissection of function is limited since kcat is governed by the rate-determining step and Km is a complex macroscopic kinetic constant. Often site-directed mutagenesis can lead to a change in the rate-determining step which cannot be revealed by just reporting a decrease in kcat alone. These issues are made more complex when it is considered that many steroid transforming enzymes have more than one substrate and product. We present the case for using transient-kinetics performed with stopped-flow spectrometry to assign rate constants to discrete steps in these multi-substrate reactions and their use to interpret enzyme mechanism and the effects of disease and engineered mutations. We demonstrate that fluorescence kinetic transients can be used to measure ligand binding that may be accompanied by isomerization steps, revealing the existence of new enzyme intermediates. We also demonstrate that single-turnover reactions can provide a klim for the chemical step and Ks for steroid-substrate binding and that when coupled with kinetic isotope effect measurements can provide information on transition state intermediates. We also demonstrate how multiple turnover experiments can provide evidence for either "burst-phase" kinetics, which can reveal a slow product release step, or linear-phase kinetics, in which the chemical step can be rate-determining. With these assignments it becomes more straightforward to analyze the effects of mutations. We use examples from the hydroxysteroid dehydrogenases (AKR1Cs) and human steroid 5β-reductase (AKR1D1) to illustrate the utility of the approach, which are members of the aldo-keto reductase (AKR) superfamily.

  4. Kinetic studies of the yeast His-Asp phosphorelay signaling pathway

    PubMed Central

    Kaserer, Alla O.; Andi, Babak; Cook, Paul F.; West, Ann H.

    2010-01-01

    For both prokaryotic and eukaryotic His-Asp phosphorelay signaling pathways, the rates of protein phosphorylation and dephosphorylation determine the stimulus-to-response time frame. Thus, kinetic studies of phosphoryl group transfer between signaling partners are important for gaining a full understanding of how the system is regulated. In many cases, the phosphotransfer reactions are too fast for rates to be determined by manual experimentation. Rapid quench flow techniques thus provide a powerful method for studying rapid reactions that occur in the millisecond time frame. In this chapter, we describe experimental design and procedures for kinetic characterization of the yeast SLN1-YPD1-SSK1 osmoregulatory phosphorelay system using a rapid quench flow kinetic instrument. PMID:20946842

  5. Local heating of human skin by millimeter waves: a kinetics study.

    PubMed

    Alekseev, S I; Ziskin, M C

    2003-12-01

    Heating rates of human skin exposed locally to 42.25 GHz mm waves, coming from a waveguide (WG) opening or a YAV device designed for therapeutic application, were studied in vivo using infrared (IR) thermography. For both radiators, the power density distribution was described by a circularly symmetrical Gaussian type function on the exposed skin surface. Insertion of a small thermocouple (d = 0.1 mm) in the exposed area did not produce any significant artifact, either in the power density distribution or kinetics measurement, providing it was perpendicular to the E vector. The heating kinetics in the skin exposed with either the WG opening or the YAV device were well fitted to solutions of the 2-D bio-heat transfer equation for homogeneous tissue. Changes in irradiating beam size (1-8 mm) had no detectable effect on the initial (0.3-3.0 s) phase of the heating kinetics. However, the amplitude of the kinetics decreased substantially with decreasing the beam size. As the temperature rise in the time interval necessary for reliable measurement of the initial temperature rise rate was very small, an accurate experimental determination of specific absorption rate (SAR) becomes practically impossible at the low intensities normally used in our experiments. The correct SAR values may be found from fitting of the model to the heating kinetics. Bioelectromagnetics 24:571-581, 2003.

  6. Nanofluidic Fluorescence Microscopy (NFM) for real-time monitoring of protein binding kinetics and affinity studies.

    PubMed

    Teerapanich, Pattamon; Pugnière, Martine; Henriquet, Corinne; Lin, Yii-Lih; Chou, Chia-Fu; Leïchlé, Thierry

    2017-02-15

    Kinetic monitoring of protein interactions offers insights to their corresponding functions in cellular processes. Surface plasmon resonance (SPR) is the current standard tool used for label-free kinetic assays; however, costly and sophisticated setups are required, decreasing its accessibility to research laboratories. We present a cost-effective nanofluidic-based immunosensor for low-noise real-time kinetic measurement of fluorescent-labeled protein binding. With the combination of fluorescence microscopy and reversed buffer flow operation, association and dissociation kinetics can be accessed in one single experiment without extra buffer loading step, which results in a simplified operation and reduced time of analysis compared to typical microfluidic immunoassays. Kinetic constants of two representative protein-ligand binding pairs (streptavidin/biotin; IgG/anti-IgG) were quantified. The good agreement of extracted rate constants with literature values and analogous SPR measurements indicates that this approach is applicable to study protein interactions of medium- and high-affinities with a limit of detection down to 1 pM, regardless of the analyte size.

  7. Study of kinetics of degradation of cyclohexane carboxylic acid by acclimated activated sludge.

    PubMed

    Wang, Chunhua; Shi, Shuian; Chen, Hongyan

    2016-01-01

    Activated sludge contains complex microorganisms, which are highly effective biodegrading agents. In this study, the kinetics of biodegradation of cyclohexane carboxylic acid (CHCA) by an acclimated aerobic activated sludge were investigated. The results showed that after 180 days of acclimation, the activated sludge could steadily degrade >90% of the CHCA in 120 h. The degradation of CHCA by the acclimated activated sludge could be modeled using a first-order kinetics equation. The equations for the degradation kinetics for different initial CHCA concentrations were also obtained. The kinetics constant, kd, decreased with an increase in the CHCA concentration, indicating that, at high concentrations, CHCA had an inhibiting effect on the microorganisms in the activated sludge. The effects of pH on the degradation kinetics of CHCA were also investigated. The results showed that a pH of 10 afforded the highest degradation rate, indicating that basic conditions significantly promoted the degradation of CHCA. Moreover, it was found that the degradation efficiency for CHCA increased with an increase in temperature and concentration of dissolved oxygen under the experimental conditions.

  8. [Progress in molecular biology study of DNA computer].

    PubMed

    Zhang, Zhi-Zhou; Zhao, Jian; He, Lin

    2003-09-01

    DNA (deoxyribonucleotide acids) computer is an emerging new study area that basically combines molecular biology study of DNA molecules and computational study on how to employ these specific molecules to calculate. In 1994 Adleman described his pioneering research on DNA computing in Science. This is the first experimental report on DNA computer study. In 2001 Benenson et al published a paper in Nature regarding a programmable and autonomous DNA computing device. Because of its Turing-like functions, the device is regarded as another milestone progress for DNA computer study. The main features of DNA computer are massively parallel computing ability and potential enormous data storage capacity. Comparing with conventional electronic computers, DNA molecules provide conceptually a revolution in computing, and more and more implications have been found in various disciplines. DNA computer studies have brought great progress not only in its own computing mechanisms, but also in DNA manipulation technologies especially nano-technology. This article presents the basic principles of DNA computer, its applications, its important relationship with genomic research and our comments on all above issues.

  9. Study of atmospheric pollution scavenging. Twenty-fourth progress report

    SciTech Connect

    Williams, A.L.

    1990-08-01

    Atmospheric scavenging research conducted by the Illinois State Water Survey under contract with the Department of Energy has been a significant factor in the historical development of the field of precipitation scavenging. Emphasis of the work during the 1980`s became focused on the problem of acid rain problem with the Survey being chosen as the Central Analytical Laboratory for sample analysis of the National Atmospheric Deposition Program National Trends Network (NADP/NTN). The DOE research was responsible for laying the groundwork from the standpoint of sampling and chemical analysis that has now become routine features of NADP/NTN. A significant aspect of the research has been the participation by the Water Survey in the MAP3S precipitation sampling network which is totally supported by DOE, is the longest continuous precipitation sampling network in existence, and maintains an event sampling protocol. The following review consists of a short description of each of the papers appearing in the Study of Atmospheric Scavenging progress reports starting with the Eighteenth Progress Report in 1980 to the Twenty- Third Progress Report in 1989. In addition a listing of the significant publications and interviews associated with the program are given in the bibliography.

  10. Single-filament kinetic studies provide novel insights into regulation of actin-based motility

    PubMed Central

    Shekhar, Shashank; Carlier, Marie-France

    2016-01-01

    Polarized assembly of actin filaments forms the basis of actin-based motility and is regulated both spatially and temporally. Cells use a variety of mechanisms by which intrinsically slower processes are accelerated, and faster ones decelerated, to match rates observed in vivo. Here we discuss how kinetic studies of individual reactions and cycles that drive actin remodeling have provided a mechanistic and quantitative understanding of such processes. We specifically consider key barbed-end regulators such as capping protein and formins as illustrative examples. We compare and contrast different kinetic approaches, such as the traditional pyrene-polymerization bulk assays, as well as more recently developed single-filament and single-molecule imaging approaches. Recent development of novel biophysical methods for sensing and applying forces will in future allow us to address the very important relationship between mechanical stimulus and kinetics of actin-based motility. PMID:26715420

  11. A kinetic study on the isomerization of hop alpha-acids.

    PubMed

    Jaskula, Barbara; Kafarski, Pawel; Aerts, Guido; De Cooman, Luc

    2008-08-13

    In this article, a detailed study on hop alpha-acid isomerization kinetics is presented. Because of the complex wort matrix and interfering interactions occurring during real wort boiling (i.e., trub formation and alpha-acids/iso-alpha-acids complexation), this investigation on alpha-acid isomerization kinetics was performed in aqueous buffer solution as a function of time (0-90 min) and heating temperature (80-100 degrees C). Rate constants and activation energies for the formation of individual iso-alpha-acids were determined. It was found that iso-alpha-acid formation follows first-order kinetics and Arrhenius behavior. Differences in activation energies for the formation of trans- and cis-isomers were noticed, the activation energy for the formation of trans-iso-alpha-acids being approximately 9 kJmol (-1) lower.

  12. Kinetic study of non-isothermal decomposition of a composite diasporic-boehmitic bauxite

    NASA Astrophysics Data System (ADS)

    Samouhos, M.; Angelopoulos, P.; Pilatos, G.; Taxiarchou, M.; Papageorgiou, S.

    2016-04-01

    In the current study, the kinetic of the thermal decomposition of a composite diasporic-boehmitic bauxite is investigated under non-isothermal heating conditions by means of thermogravimetric analysis. The calculation of activation energy (Ea) has been performed by various methods and the attained values range from 185000 to 190000 J.mol-1 for conversion rate of 0.5. The first-order kinetic model can adequately be used to describe thermal decomposition of bauxite composite, while the pre-exponential factor value was found to be 2.088*1011 min-1. The calculated activation energy value together with pre-exponential factor and the solid state kinetic model factors enable the simulation of the thermal decomposition under various heating conditions by the implementation of an ordinary differential equation. The calculated values are in satisfactory agreement with the experimental ones.

  13. A kinetic study of textile dyeing wastewater degradation by Penicillium chrysogenum.

    PubMed

    Durruty, Ignacio; Fasce, Diana; González, Jorge Froilán; Wolski, Erika Alejandra

    2015-06-01

    The potential of Penicillium chrysogenum to decolorize azo dyes and a real industrial textile wastewater was studied. P. chrysogenum was able to decolorize and degrade three azo dyes (200 mg L(-1)), either independently or in a mixture of them, using glucose as a carbon source. A kinetic model for degradation was developed and it allowed predicting the degradation kinetics of the mixture of the three azo dyes. In addition, P. chrysogenum was able to decolorize real industrial wastewater. The kinetic model proposed was also able to predict the decolorization of the real wastewater. The calibration of the proposed model makes it a useful tool for future wastewater facilities' design and for practical applications.

  14. Kinetic and thermodynamic study of the liquid-phase etherification of isoamylenes with methanol

    SciTech Connect

    Piccoli, R.L. ); Lovisi, H.R. )

    1995-02-01

    The kinetics and thermodynamics of liquid-phase etherification of isoamylenes with methanol on ion exchange catalyst (Amberlyst 15) were studied. Thermodynamic properties and rate data were obtained in a batch reactor operating under 1,013 kPa and 323--353 K. The kinetic equation was modeled following the Langmuir-Hinshelwood-Hougen-Watson formalism according to a proposed surface mechanism where the rate-controlling step is the surface reaction. According to the experimental results, methanol adsorbs very strongly on the active sites, covering them completely, and thus the reaction follows an apparent first-order behavior. The isoamylenes, according to the proposed mechanism, adsorb simultaneously on the same single active center already occupied by methanol, migrating through the liquid layer formed by the alcohol around the catalyst to react in the acidic site. From the proposed mechanism a model was suggested and the kinetic and thermodynamic parameters were obtained using nonlinear estimation methods.

  15. Kinetic and product composition study on the cellulose liquefaction in polyhydric alcohols.

    PubMed

    Shi, Yan; Li, Jingdan; Wang, Jing; Zhao, Tiantian; Yang, Hongmin; Jiang, Jianchun; Jiang, Xiaoxiang

    2016-08-01

    The liquefaction process of cellulose in polyhydric alcohols (PEG 400 and glycerol) was studied by TG-FTIR. Three stages were observed during the solvolysis process and the main liquefaction stage could be further divided into two zones. The differences of liquefaction behavior of cellulose in the two solvents were compared, and the functional groups of volatiles produced by solvolysis were also evaluated. A step-wise procedure based on iso-conversional and Master-plots methods was used for the kinetic and mechanism analysis of the main liquefaction stage. The calculation results based on the kinetic model were in agreement with the experimental data of the conversion rate. The kinetic parameters and mechanism functions between cellulose liquefaction in PEG400 and in glycerol were quite different, which verified that solvolysis behavior and reaction process were seriously influenced by solvent species. Finally, the detailed types of volatiles and product distribution were measured by Py-GC-MS.

  16. A kinetics modeling study on the inhibition of glucose on cellulosome of Clostridium thermocellum.

    PubMed

    Zhang, Pengcheng; Wang, Buyun; Xiao, Qunfang; Wu, Shan

    2015-08-01

    A simplified kinetics model was built to study the inhibition of glucose on cellulosome of Clostridium thermocellum. Suitable reaction conditions were adopted to evaluate the model. The model was evaluated at different temperatures and further with various activated carbon additions as adsorbent for glucose. Investigation results revealed that the model could describe the hydrolysis kinetics of cellulose by cellulosome quite well. Glucose was found to be an inhibitor for cellulosome based on the kinetics analysis. Inhibition increased with the increase in temperature. Activated carbon as adsorbent could lower the inhibition. Parameters in the model were further discussed based on the experiment. The model might also be used to describe the strong inhibition of cellobiose on cellulosome. Saccharification of cellulose by both cellulosome and C. thermocellum could be enhanced efficiently by activated carbon addition.

  17. Kinetic Study of Acetone-Butanol-Ethanol Fermentation in Continuous Culture

    PubMed Central

    Buehler, Edward A.; Mesbah, Ali

    2016-01-01

    Acetone-butanol-ethanol (ABE) fermentation by clostridia has shown promise for industrial-scale production of biobutanol. However, the continuous ABE fermentation suffers from low product yield, titer, and productivity. Systems analysis of the continuous ABE fermentation will offer insights into its metabolic pathway as well as into optimal fermentation design and operation. For the ABE fermentation in continuous Clostridium acetobutylicum culture, this paper presents a kinetic model that includes the effects of key metabolic intermediates and enzymes as well as culture pH, product inhibition, and glucose inhibition. The kinetic model is used for elucidating the behavior of the ABE fermentation under the conditions that are most relevant to continuous cultures. To this end, dynamic sensitivity analysis is performed to systematically investigate the effects of culture conditions, reaction kinetics, and enzymes on the dynamics of the ABE production pathway. The analysis provides guidance for future metabolic engineering and fermentation optimization studies. PMID:27486663

  18. Kinetic study of the complexation of gallic acid with Fe(II)

    NASA Astrophysics Data System (ADS)

    Lu, Li-li; Li, Ying-hua; Lu, Xiu-yang

    2009-10-01

    Kinetic study on the complexation of gallic acid with ferrous sulfate was performed using UV-Vis absorption spectroscopy. Under the experimental conditions, the stoichiometric composition of the formed complex is 1:1. The complexation reaction was found to be a second-order one. The influences of temperature, ionic strength and solvents on the complexation reaction were investigated. According to the Arrhenius equation, the apparent activation energy of the complexation reaction was evaluated to be 71.64 kJ × mol -1. A three-step reaction mechanism was proposed, which can well explain the kinetic results obtained.

  19. Kinetics of Oxygen Reduction in Aprotic Li-O2 Cells: A Model-Based Study.

    PubMed

    Safari, M; Adams, B D; Nazar, L F

    2014-10-16

    A comprehensive and general kinetic model is developed for the oxygen reduction reaction in aprotic Li-O2 cells. The model is based on the competitive uptake of lithium superoxide by the surface and solution. A demonstrative kinetic study is provided to demystify the origin of curvature in Tafel plots as well as the current dependency and aberrant diversity of the nature and morphology of discharge products in these systems. Our results are general and extend to any system where solubilization of superoxide is favored, such as where phase-transfer catalysts play an important role.

  20. Kinetic and thermodynamic study of the behaviour of diphenylcarbazide in aqueous solution with pH.

    PubMed

    Salinas-Hernández, P; Rojas-Hernández, A; Ramírez-Silva, M T

    2003-09-01

    In order to find out about the chemical behaviour of the diphenylcarbazide (DPCI) in water, kinetic and thermodynamic studies were carried out using UV-Vis spectrophotometry within the 0-12 pH range. The kinetic parameters and acidity constant were then determined, and the results show that a pseudo first order reaction rate was observed during hydroxilation, while the reaction rate was also observed to increase with the pH. The acidity constant obtained with the aid of SQUAD was pK(a)=10.718+/-0.027.

  1. Thermodynamics and kinetics of carbon deposits on cobalt: a combined density functional theory and kinetic Monte Carlo study.

    PubMed

    Jansen, Antonius P J; Agrawal, Ravi; Spanu, Leonardo

    2016-10-19

    We have built a lattice gas model for cobalt-carbon interaction to investigate the thermodynamics and kinetics of carbon deposition on Co(0001) surfaces. The formation of carbon structures on cobalt is considered to be one of the causes of deactivation of a cobalt Fischer-Tropsch (FT) catalyst. The formation of graphene - the most thermodynamically stable phase under FT conditions - is kinetically inhibited during the first 30 hours of exposure of the surface to carbon, while the build-up of surface carbide is the fastest reaction. Our simulations clearly show that the kinetics of carbon deposition is the result of two competing effects: a fast subsurface diffusion and a slower surface diffusion to form a carbon-carbon bond.

  2. Kinetic Monte Carlo Studies of the Reaction Kinetics of Crystal Defects that Diffuse One-dimensionally with Occasional Transverse Migration

    SciTech Connect

    Heinisch, Howard L.; Trinkaus, Helmut; Singh, Bachu N.

    2007-08-01

    The reaction kinetics of the various species of mobile defects in irradiated materials are crucially dependent on the dimensionality of their migration. Sink strengths for one-dimensionally (1D) gliding interstitial loops undergoing occasional direction changes have been described analytically and confirmed by kinetic Monte Carlo (KMC) simulations. Here we report on KMC simulations investigating a different transition from 1D to 3D diffusion of 1D gliding loops for which their 1D migration is interrupted by occasional 2D migration due to conservative climb by dislocation core diffusion within a plane transverse to their 1D glide direction. Their transition from 1D to 3D kinetics is significantly different from that due to direction changes. The KMC results are compared to an analytical description of this diffusion mode in the form of a master curve relating the 1D normalized sink strength to the frequency of disturbance of 1D migration.

  3. Kinetic Monte Carlo Studies of The Reaction Kinetics of Crystal Defects That Diffuse One-Dimensionally With Occasional Transverse Migration

    SciTech Connect

    Heinisch, Howard L.; Trinkaus, Helmut; Singh, Bachu N.

    2007-03-19

    The reaction kinetics of the various species of mobile defects in irradiated materials are crucially dependent on the dimensionality of their diffusion processes. Sink strengths for one-dimensionally (1D) gliding interstitial loops undergoing occasional direction changes have been described analytically and confirmed by kinetic Monte Carlo (KMC) simulations. Here we report on KMC simulations investigating the transition from 1D to 3D diffusion for 1D gliding loops whose 1D migration is interrupted by occasional 2D migration due to conservative climb by dislocation core diffusion within a plane transverse to their 1D glide direction. Their transition from 1D to 3D kinetics is significantly different from that due to direction changes. The KMC results are compared to an analytical description of this diffusion mode in the form of a master curve relating the 1D normalized sink strength to the frequency of disturbance of 1D migration.

  4. Kinetic Studies of Nonequilibrium Plasma-Assisted Combustion

    DTIC Science & Technology

    2010-02-25

    Relative atomic oxygen concentration data is put on an absolute scale using the xenon-based optical calibration scheme of Niemi, et al [1,2...and O + O3 —> 20T . In air, the relatively low rate of recombination results in a considerable build-up of O atoms, to mole fractions of up to -1...studies by Bromley, et al .,[3], that trace (a few ppm) quantities of NO accelerate low tcmperature(~650-700 K) oxidation of butane. To study the

  5. Theoretical Studies in Chemical Kinetics - Annual Report, 1970.

    DOE R&D Accomplishments Database

    Karplus, Martin

    1970-10-01

    The research performed includes (a) Alkali-Halide, Alkali-Halide (MX, M’X’) Exchange Reactions; (b) Inversion Problem; (c) Quantum Mechanics of Scattering Processes, (d) Transition State Analysis of Classical Trajectories, (e) Differential Cross Sections from Classical Trajectories; and (f) Other Studies.

  6. Progress report on DOE research project [Thermodynamic and kinetic behavior of systems with intermetallic and intermediate phases

    SciTech Connect

    Tsakalakos, T.; Semenovskaya-Khachaturyan, S.; Khachaturyan, A.G.

    2000-12-13

    A theoretical investigation was made of the coherent displacive phase transformation between two equilibrium single-phase states producing several orientation variants of the product phase. The research was focused on a behavior of coherent systems (martensitic systems, metal and ceramic, and ferroelectric systems) with defects. The computer simulation demonstrated that randomly distributed static defects may drastically affect the thermodynamics, kinetics, and morphology of the transformation. In particular, the interaction of the transformation mode with the defects may be responsible for appearance of two new fields in the phase diagram: (i) the two-phase field describing the tweed microstructure, which consists of the retain parent phase and the variants of the product phase and (ii) the single-phase field describing the tweed microstructure, which consists of the variants of the product phase. These new fields can be attributed to the pre-transitional states observed in some of th e displacive transformations. The microstructure evolution resulting in formation of the thermoelastic equilibrium is path dependent. This unusual behavior is expected in systems with a sharp dependence of the transition temperature on the defect concentration.

  7. Comparative study of thermal inactivation kinetics of Salmonella spp. in peanut butter and peanut butter spread

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Peanut butter has been implicated in multi-state outbreaks of salmonellosis in recent years. Studies have shown that Salmonella exhibited increased thermal resistance in peanut butter. However, little is known about the effect of product formulation on the kinetics of survival of Salmonella during...

  8. Study of kinetics of crystallization of Ge7Se75Sb18 chalcogenide glass

    NASA Astrophysics Data System (ADS)

    Tanwar, Naveen; Saraswat, Vibhav K.

    2014-04-01

    Present paper is an attempt to study kinetics of crystallization of Ge7Se75Sb18 chalcogenide glass by Differential Scanning Calorimetery (DSC) under non-isothermal condition. The sample was prepared by melt quenched technique and amorphous nature has been confirmed by XRD. Activation energy of crystallization has been evaluated using Kissinger, Augis-Bennett and Ozawa models.

  9. Kinetic Monte Carlo models for the study of chemical reactions in the Earth's upper atmosphere

    NASA Astrophysics Data System (ADS)

    Turchak, L. I.; Shematovich, V. I.

    2016-06-01

    A stochastic approach to study the non-equilibrium chemistry in the Earth's upper atmosphere is presented, which has been developed over a number of years. Kinetic Monte Carlo models based on this approach are an effective tool for investigating the role of suprathermal particles both in local variations of the atmospheric chemical composition and in the formation of the hot planetary corona.

  10. Study of kinetic effects arising in simulations of Farley-Buneman instability

    SciTech Connect

    Kovalev, D. V.; Smirnov, A. P.; Dimant, Ya. S.

    2009-05-15

    The Farley-Buneman instability, which has been observed in the E region of the Earth's ionosphere, is studied using fluid equations for electrons, a four-dimensional (in coordinate-velocity space) kinetic equation for ions, and Poisson's equation. Numerical simulations with allowance for Landau damping show that the Farley-Buneman instability results in anisotropy of the ion velocity distribution function.

  11. An Experimental and Kinetic Modeling Study of Methyl Decanoate Combustion

    SciTech Connect

    Sarathy, S M; Thomson, M J; Pitz, W J; Lu, T

    2009-12-04

    Biodiesel is a mixture of long chain fatty acid methyl esters derived from fats and oils. This research study presents opposed-flow diffusion flame data for one large fatty acid methyl ester, methyl decanoate, and uses the experiments to validate an improved skeletal mechanism consisting of 648 species and 2998 reactions. The results indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene.

  12. Kinetics of combustion-related processes at high temperatures. Progress report, June 1, 1991--May 31, 1992

    SciTech Connect

    Kiefer, J.H.

    1992-02-01

    Again this year, progress is mainly reflected in publications. The following lists titles published, in press, or submitted during late 1990--91. Tunable Laser Flash Absorption, High Temperature Pyrolyses of Acetylene and Diacetylene Behind Reflected Shock Waves, Rate of the Retro-Diels-Alder Dissociation of 1,2,3,6-Tetrahydropyridine Over a Wide Temperature Range, The Reaction of C{sub 4}H{sub 2} and H{sub 2} Behind Reflected Shock Waves, Thermal Isomerization of Cyclopropanecarbonitrile, The Homogeneous Pyrolysis of Acetylene II, The Importance Of Hindered Rotations and Other Anharmonic Effects in the Thermal Dissociation of Small Unsaturated Molecules, Dissociation Rates of Propyne and Allene at High Temperatures and the Subsequent Formation of Benzene, and The Formaldehyde Decomposition Chain Mechanism. This report consists of the abstracts, titles, and authors for each of these publications.

  13. Escherichia coli alkaline phosphatase. Kinetic studies with the tetrameric enzyme.

    PubMed

    Halford, S E; Schlesinger, M J; Gutfreund, H

    1972-03-01

    1. The stability of the tetrameric form of Escherichia coli alkaline phosphatase was examined by analytical ultracentrifugation. 2. The stopped-flow technique was used to study the hydrolysis of nitrophenyl phosphates by the alkaline phosphatase tetramer at pH7.5 and 8.3. In both cases transient product formation was observed before the steady state was attained. Both transients consisted of the liberation of 1mol of nitrophenol/2mol of enzyme subunits within the dead-time of the apparatus. The steady-state rates were identical with those observed with the dimer under the same conditions. 3. The binding of 2-hydroxy-5-nitrobenzyl phosphonate to the alkaline phosphatase tetramer was studied by the temperature-jump technique. The self-association of two dimers to form the tetramer is linked to a conformation change within the dimer. This accounts for the differences between the transient phases in the reactions of the dimer and the tetramer with substrate. 4. Addition of P(i) to the alkaline phosphatase tetramer caused it to dissociate into dimers. The tetramer is unable to bind this ligand. It is suggested that the tetramer undergoes a compulsory dissociation before the completion of its first turnover with substrate. 5. On the basis of these findings a mechanism is proposed for the involvement of the alkaline phosphatase tetramer in the physiology of E. coli.

  14. Kinetic studies on sorption of basic dye using Eichhornia crassipes.

    PubMed

    Renganathan, S; Venkatakrishnan, R; Venkataramana, S; Kumar, M Dharmendira; Deepak, S; Miranda, Lima Rose; Velan, M

    2008-10-01

    Sorption capacity of different parts of Eichhornia crassipes, such as rhizome, root, lamina and petiole on basic aurophine-o was studied in a batch system. The equilibrium uptake capacity was observed as 13.65 mg/g (using root), 13.5 mg/g (using lamina), 12.9 mg/g (using rhizome) and 12.75 mg/g (using petiole). It was observed that the equilibrium dye uptake capacity using root was found to be more when compared to all other E. crassipes parts used in the present investigation. The shortcut equations developed are accurate and can be used in the place of experimental data. The shortcut equations form the basis for further research. The intra particle diffusion coefficient (K(i)) and effective diffusion coefficient (D(i)) were evaluated for the removal of dye using root, which were found to be more when compared to all other parts of E. crassipes studied such as, lamina, rhizome and petiole.

  15. Kinetic and Spectroscopic Studies of Heterogeneous Catalytic Reactions

    NASA Astrophysics Data System (ADS)

    Wilke, Todd E.

    1990-01-01

    The selective oxidation of ethylene was studied on a high surface area colloidal silver catalyst. In 0.1 to 1 torr of 20% ethylene in oxygen, the catalyst produced ethylene oxide with a selectivity of 20 to 30% at temperatures between 473 and 573 K. Surface-enhanced Raman (SER) spectra exhibited a distinct feature at 995 cm^ {-1}. This band was also observed for catalysts exposed to just oxygen, and it shifted to 980 cm^{-1} after heating the catalyst to 873 K in ^{18} O_2. No isotopic shift was observed with ^{18}O _2 at temperatures below 573 K. Similar spectral results were obtained at atmospheric pressure. For silver catalysts that contain adsorbed chlorine, SER bands were observed at 240, 1015, and 1045 cm^ {-1} in oxygen-containing atmospheres; the 995 cm^{-1} band was not evident. The extension of SERS to other metals that do not exhibit the surface-enhanced effect was examined by electrodepositing thin layers (2 to 3 monolayers) of platinum, rhodium, and ruthenium on a roughened gold substrate. At atmospheric pressure and temperatures between 298 and 473 K, metal-oxygen features were observed at 500 cm ^{-1}, and 490 and 600 cm ^{-1} in SER spectra of rhodium and ruthenium surfaces exposed to oxygen, respectively. Bands attributed to adsorbed carbon monoxide were observed in SER spectra of platinum (470, 2060, 390, and 1890 cm ^{-1}) and rhodium (465 and 2040 cm^{-1}) surfaces exposed to carbon monoxide and oxygen mixtures. The temporal replacement of adsorbed carbon monoxide by nitric oxide as well as temperature-induced changes in the surface composition were studied on a seconds timescale with a spectrograph -charge coupled device detector arrangement. The adsorption and oxidation of sulfur dioxide was also studied. A band assigned to the S-O stretch of molecularly adsorbed sulfur dioxide was observed at 1130 cm^{-1} on unmodified gold and platinum-coated gold surfaces exposed to sulfur dioxide at 298 K. Dissociative chemisorption of sulfur dioxide on

  16. Bench-scale Kinetics Study of Mercury Reactions in FGD Liquors

    SciTech Connect

    Gary Blythe; John Currie; David DeBerry

    2008-03-31

    This document is the final report for Cooperative Agreement DE-FC26-04NT42314, 'Kinetics Study of Mercury Reactions in FGD Liquors'. The project was co-funded by the U.S. DOE National Energy Technology Laboratory and EPRI. The objective of the project has been to determine the mechanisms and kinetics of the aqueous reactions of mercury absorbed by wet flue gas desulfurization (FGD) systems, and develop a kinetics model to predict mercury reactions in wet FGD systems. The model may be used to determine optimum wet FGD design and operating conditions to maximize mercury capture in wet FGD systems. Initially, a series of bench-top, liquid-phase reactor tests were conducted and mercury species concentrations were measured by UV/visible light spectroscopy to determine reactant and byproduct concentrations over time. Other measurement methods, such as atomic absorption, were used to measure concentrations of vapor-phase elemental mercury, that cannot be measured by UV/visible light spectroscopy. Next, a series of bench-scale wet FGD simulation tests were conducted. Because of the significant effects of sulfite concentration on mercury re-emission rates, new methods were developed for operating and controlling the bench-scale FGD experiments. Approximately 140 bench-scale wet FGD tests were conducted and several unusual and pertinent effects of process chemistry on mercury re-emissions were identified and characterized. These data have been used to develop an empirically adjusted, theoretically based kinetics model to predict mercury species reactions in wet FGD systems. The model has been verified in tests conducted with the bench-scale wet FGD system, where both gas-phase and liquid-phase mercury concentrations were measured to determine if the model accurately predicts the tendency for mercury re-emissions. This report presents and discusses results from the initial laboratory kinetics measurements, the bench-scale wet FGD tests, and the kinetics modeling efforts.

  17. Distributed databases for materials study of thermo-kinetic properties

    NASA Astrophysics Data System (ADS)

    Toher, Cormac

    2015-03-01

    High-throughput computational materials science provides researchers with the opportunity to rapidly generate large databases of materials properties. To rapidly add thermal properties to the AFLOWLIB consortium and Materials Project repositories, we have implemented an automated quasi-harmonic Debye model, the Automatic GIBBS Library (AGL). This enables us to screen thousands of materials for thermal conductivity, bulk modulus, thermal expansion and related properties. The search and sort functions of the online database can then be used to identify suitable materials for more in-depth study using more precise computational or experimental techniques. AFLOW-AGL source code is public domain and will soon be released within the GNU-GPL license.

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

    NASA Astrophysics Data System (ADS)

    Smith, S. J.

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

  19. Kinetic study of wall collisions in a coaxial Hall discharge.

    PubMed

    Meezan, Nathan B; Cappelli, Mark A

    2002-09-01

    Coaxial Hall discharges (also known as Hall thrusters, stationary plasma thrusters, and closed-drift accelerators) are cross-field plasma sources under development for space propulsion applications. The importance of the electron-wall interaction to the Hall discharge operation is studied the through analysis of experimental data and simulation of the electron energy distribution function (EEDF) inside the discharge channel. Experimental time-average plasma property data from a laboratory Hall discharge are used to calculate the electron conductivity and to estimate the rate of wall-loss collisions. The electron Boltzmann equation is then solved in the local field limit, using the experimental results as inputs. The equation takes into account ionization and wall collisions, including secondary electrons produced at the wall. Local electron balances are used to calculate the sheath potential at the insulator walls. Results show an EEDF depleted at high energy due to electron loss to the walls. The calculated EEDFs agree well with experimental electron temperature data when the experimentally determined effective collision frequency is used for electron momentum transport. The electron wall-loss and wall-return frequencies are extremely low compared to those predicted by a Maxwellian of equal average energy. The very low frequency of wall collisions suggests that secondary electrons do not contribute to cross-field transport. This conclusion holds despite significant experimental uncertainty.

  20. Effects of General Medical Health on Alzheimer Progression: the Cache County Dementia Progression Study

    PubMed Central

    Leoutsakos, Jeannie-Marie S.; Han, Dingfen; Mielke, Michelle M.; Forrester, Sarah N.; Tschanz, JoAnn T.; Corcoran, Chris D.; Green, Robert C.; Norton, Maria C.; Welsh-Bohmer, Kathleen A.; Lyketsos, Constantine G.

    2012-01-01

    Background Several observational studies suggested a link between health status and rate of decline among individuals with Alzheimer’s disease (AD). We sought to quantify the relationship in a population-based study of incident AD, and to compare global comorbidity ratings to counts of comorbid conditions and medications as predictors of AD progression. Methods Design Case-only cohort study arising from population-based longitudinal study of memory and aging. Setting Cache County, Utah Participants 335 individuals with incident AD followed for up to 11 years. Measurements Patient descriptors included sex, age, education, dementia duration at baseline, and APOE genotype. Measures of health status made at each visit included the GMHR (General Medical Health Rating), number of comorbid medical conditions, and number of non-psychiatric medications. Dementia outcomes included the Mini-Mental State Exam (MMSE), Clinical Dementia Rating – sum of boxes (CDR-sb), and the Neuropsychiatric Inventory (NPI). Results Health Status tended to fluctuate over time within individuals. None of the baseline medical variables (GMHR, comorbidities, non-psychiatric medications) were associated with differences in rates of decline in longitudinal linear mixed effects models. Over time, low GMHR ratings, but not comorbidities or medications, were associated with poorer outcomes (MMSE: β=−1.07 p=0.01; CDR-sb: β=1.79 p<0.001; NPI: β=4.57 p=0.01) Conclusions Given that time-varying GMHR, but not baseline GMHR, was associated with the outcomes, there is likely a dynamic relationship between medical and cognitive health. GMHR is a more sensitive measure of health than simple counts of comorbidities or medications. Since health status is a potentially modifiable risk factor, further study is warranted. PMID:22687143

  1. Atmospheric Chemistry: Laboratory Studies of Kinetics of Important Reactions.

    NASA Astrophysics Data System (ADS)

    Smith, S. J.

    Available from UMI in association with The British Library. Requires signed TDF. This thesis describes the experiments to measure the rate constants for some reactions of the atmospherically important nitrate radical (NO_3) using the discharge-flow technique. The nitrate radical was monitored by optical absorption at lambda = 662 nm. The reactions of NO_3 with some stable organic and inorganic substrates are reported. The temperature dependences of some of the rate constants have also been determined (298 < T < 523 K). In most cases, computer simulation was used to extract the rate constant for the primary process because the time-dependent behaviour of (NO_3) was affected by secondary reactions of NO_3 with products of the primary interaction. The Arrhenius parameter in parentheses (E _{rm a}/kJ mol^ {-1}, A/cm^3 molecule ^{-1}s^ {-1} respectively) for the following reactions have been determined: ethane (37, 6.7 times 10^{-12}), ethylene (25.8, 6.3 times 10^ {-12}), CH_3OH (21.3, 1.2 times 10^ {-12}), CHCiota_3 (23.4, 8.6 times 10 ^{-13}) and HCl (27.7, 4 times 10^{-12}). The activation energies for the reactions studied between NO_3 and some alkynes are represented well by the value 25 +/- 3 kJ mol^{-1} and the corresponding pre-exponential factors (expressed as ln(10 ^{13}A/cm^3 molecule^{-1}s ^{-1}) are as follows: C_2H_2 (1.6 +/- 1.4), C_3H _4 (5.0 +/- 1.4), 1-C_4H_6 (5.8 +/- 1.0), 1-C_5 H_8 (5.7 +/- 0.6) and 1-C_6H _{10} (4.5 +/- 0.4). Some reactions were studied at room temperature _3(298 +/- 2 K) only and the rate constants found (in units of cm ^3 molecule^{ -1}s^{-1}) are: buta-1,3-diene (1.8 times 10 ^{-13}), isobutene (2.8 times 10^{-13 }), HBr (1.3 times 10 ^{-15}) and hex-2-yne (3.0 times 10^{-14 }). Non-Arrhenius behaviour was found in the reactions of NO_3 with n-butane, isobutane and propene. The empirical variation of these rate constants with temperature is well represented by the three parameter expressions:. k(T) = 1.2 times 10 ^{-46}T^{11

  2. Study of cell kinetics within evolving secondary Haversian systems.

    PubMed Central

    Jaworski, Z F; Hooper, C

    1980-01-01

    A study of the origin, proliferation rate and migration of cells within the secondary evolving Haversian systems was undertaken in young adult Beagle dogs. Autoradiographs of serial longitudinal sections prepared from rib biopsies taken from one hour to eleven days after the injection of tritiated thymidine were subjected to semiquantitative analysis as to the time of appearance, number, location and transformation of various labelled cells. Numerous labelled osteoblasts appeared early (at 14-24 hours) in the most proximal closing cone. With time, this zone was seen to have been left behind the advancing cutting cone and the successive generations of osteoblasts. The first labelled osteocytes were seen at nine days after injection, in the distal closing cone. Labelled nuclei within the osteoclasts were few and appeared late (none before 24 hours). It is apparent that each self renewing cell population within these systems (i.e. osteoclasts, osteoblasts and endothelial cells) derives from its own immediate precursor and evolves at its own speed. The mononuclear osteoclasts' precursors divide locally and infrequently and the turnover of osteoclastic nuclei appears to be slow; consequently their life span and that of the osteoclasts appears to be longer than the time of the observation, i.e. 11 days. The proliferation of osteoblasts' precursors and osteoblasts recruitment is rapid. The life span of osteoblasts was found to be indeterminate; some osteoblasts may become osteocytes within a few days while others may continue to deposit bone for several weeks. Since the recruitment of osteoclastic nuclei is slow while that of the osteoblasts is fast, it is unlikely that the osteoclasts in the sites of lamellar bone remodelling modulate into osteoblasts. Images Fig. 2(cont.) Fig. 2 Fig. 3(cont.) Fig. 3 Fig. 4 Fig. 5 PMID:7440406

  3. Retinopathy and Progression of CKD: The CRIC Study

    PubMed Central

    Pistilli, Maxwell; Ying, Gui-Shuang; Daniel, Ebenezer; Maguire, Maureen G.; Xie, Dawei; Whittock-Martin, Revell; Parker Ostroff, Candace; Lo, Joan C.; Townsend, Raymond R.; Gadegbeku, Crystal A.; Lash, James P.; Fink, Jeffrey C.; Rahman, Mahboob; Feldman, Harold I.; Kusek, John W.

    2014-01-01

    Background and objectives Retinal abnormalities may be associated with changes in the renal vasculature. This study assessed the association between retinopathy and progression of kidney disease in participants of the Chronic Renal Insufficiency Cohort (CRIC) study. Design, setting, participants, & measurements This was a prospective study in which patients with CKD enrolled in CRIC had nonmydriatic fundus photographs of both eyes. All CRIC participants in six clinical sites in which fundus cameras were deployed were offered participation. Photographs were reviewed at a reading center. The presence and severity of retinopathy and vessel calibers were assessed using standard protocols by graders masked to clinical information. The associations of retinal features with changes in eGFR and the need for RRT (ESRD) were assessed. Results Retinal images and renal progression outcomes were obtained from 1852 of the 2605 participants (71.1%) approached. During follow-up (median 2.3 years), 152 participants (8.2%) developed ESRD. Presence and severity of retinopathy at baseline were strongly associated with the risk of subsequent progression to ESRD and reductions in eGFR in unadjusted analyses. For example, participants with retinopathy were 4.4 times (95% confidence interval [95% CI], 3.12 to 6.31) more likely to develop ESRD than those without retinopathy (P<0.001). However, this association was not statistically significant after adjustment for initial eGFR and 24-hour proteinuria. Venular and arteriolar diameter calibers were not associated with ESRD or eGFR decline. The results showed a nonlinear relationship between mean ratio of arteriole/vein calibers and the risk of progression to ESRD; participants within the fourth arteriole/vein ratio quartile were 3.11 times (95% CI, 1.51 to 6.40) more likely to develop ESRD than those in the first quartile (P<0.001). Conclusions The presence and severity of retinopathy were not associated with ESRD and decline in eGFR after

  4. An experimental and kinetic modeling study of combustion of isomers of butanol

    SciTech Connect

    Grana, Roberto; Frassoldati, Alessio; Faravelli, Tiziano; Ranzi, Eliseo; Niemann, Ulrich; Seiser, Reinhard; Cattolica, Robert; Seshadri, Kalyanasundaram

    2010-11-15

    A kinetic model is developed to describe combustion of isomers of butanol - n-butanol (n-C{sub 4}H{sub 9}OH), sec-butanol (sec-C{sub 4}H{sub 9}OH), iso-butanol (iso-C{sub 4}H{sub 9}OH), and tert-butanol (tert-C{sub 4}H{sub 9}OH). A hierarchical approach is employed here. This approach was previously found to be useful for developing detailed and semi-detailed mechanism of oxidation of various hydrocarbon fuels. This method starts from lower molecular weight compounds of a family of species and proceeds to higher molecular weight compounds. The pyrolysis and oxidation mechanisms of butanol isomers are similar to those for hydrocarbon fuels. Here, the development of the complete set of the primary propagation reactions for butanol isomers proceeds from the extension of the kinetic parameters for similar reactions already studied and recently revised for ethanol, n-propanol and iso-propanol. A detailed description leading to evaluation of rate constants for initiation reactions, metathesis reactions, decomposition reactions of alkoxy radicals, isomerization reactions, and four-center molecular dehydration reactions are given. Decomposition and oxidation of primary intermediate products are described using a previously developed semi-detailed kinetic model for hydrocarbon fuels. The kinetic mechanism is made up of more than 7000 reactions among 300 species. The model is validated by comparing predictions made using this kinetic model with previous and new experimental data on counterflow non-premixed flames of n-butanol and iso-butanol. The structures of these flames were measured by removing gas samples from the flame and analyzing them using a gas chromatograph. Temperature profiles were measured using coated thermocouples. The flame structures were measured under similar conditions for both fuels to elucidate the similarities and differences in combustion characteristics of the two isomers. The profiles measured include those of butanol, oxygen, carbon dioxide

  5. Equilibrium, kinetic and thermodynamic studies of uranium biosorption by calcium alginate beads.

    PubMed

    Bai, Jing; Fan, Fangli; Wu, Xiaolei; Tian, Wei; Zhao, Liang; Yin, Xiaojie; Fan, Fuyou; Li, Zhan; Tian, Longlong; Wang, Yang; Qin, Zhi; Guo, Junsheng

    2013-12-01

    Calcium alginate beads are potential biosorbent for radionuclides removal as they contain carboxyl groups. However, until now limited information is available concerning the uptake behavior of uranium by this polymer gel, especially when sorption equilibrium, kinetics and thermodynamics are concerned. In present work, batch experiments were carried out to study the equilibrium, kinetics and thermodynamics of uranium sorption by calcium alginate beads. The effects of initial solution pH, sorbent amount, initial uranium concentration and temperature on uranium sorption were also investigated. The determined optimal conditions were: initial solution pH of 3.0, added sorbent amount of 40 mg, and uranium sorption capacity increased with increasing initial uranium concentration and temperature. Equilibrium data obtained under different temperatures were fitted better with Langmuir model than Freundlich model, uranium sorption was dominated by a monolayer way. The kinetic data can be well depicted by the pseudo-second-order kinetic model. The activation energy derived from Arrhenius equation was 30.0 kJ/mol and the sorption process had a chemical nature. Thermodynamic constants such as ΔH(0), ΔS(0) and ΔG(0) were also evaluated, results of thermodynamic study showed that the sorption process was endothermic and spontaneous.

  6. Equilibrium and kinetic adsorption study of a cationic dye by a natural adsorbent--silkworm pupa.

    PubMed

    Noroozi, B; Sorial, G A; Bahrami, H; Arami, M

    2007-01-02

    In this work the use of silkworm pupa, which is the waste of silk spinning industries has been investigated as an adsorbent for the removal of C.I. Basic Blue 41. The amino acid nature of the pupa provided a reasonable capability for dye removal. Equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of the dye could be described reasonably well by either Langmuir or Freundlich models. The characteristic parameters for each isotherm have been determined. The monolayer adsorption capacity was determined to be 555 mg/g. Kinetic studies indicated that the adsorption follows pseudo-second-order kinetics with a rate constant of 0.0434 and 0.0572 g/min mg for initial dye concentration of 200 mg/l at 20 and 40 degrees C, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process. The rate constant for intra-particle diffusion was estimated to be 1.985 mg/g min(0.5).

  7. The Siblings With Ischemic Stroke Study (SWISS): A Progress Report

    PubMed Central

    Meschia, James F.; Kissela, Brett M.; Brott, Thomas G.; Brown, Robert D.; Worrall, Bradford B.; Beck, Jeanne; Skarp, Alexa N.

    2006-01-01

    There is increasing evidence that genetic factors are associated with ischemic stroke, including multiple recent reports of association with the gene PDE4D, encoding phosphodiesterase 4D, on chromosome 5q12. Genetic studies of stroke are important but can be logistically difficult to perform. This article reviews the design of the Siblings With Ischemic Stroke Study (SWISS) and discusses problems in performing a sibling-based pedigree study where proband-initiated consent is used to enroll pedigree members. Proband-initiated enrollment optimizes privacy protections for family members, but it is associated with a substantial pedigree non-completion rate such that 3 to 4 probands must be identified to obtain one completed sibling pedigree. This report updates the progress of enrollment in the SWISS protocol, discusses barriers to pedigree completion and describes innovative approaches used by the SWISS investigators to enhance enrollment. PMID:16595789

  8. Kinetic studies of elemental mercury adsorption in activated carbon fixed bed reactor.

    PubMed

    Skodras, G; Diamantopoulou, Ir; Pantoleontos, G; Sakellaropoulos, G P

    2008-10-01

    Activated carbons are suitable materials for Hg(0) adsorption in fixed bed operation or in injection process. The fixed bed tests provide good indication of activated carbons effectiveness and service lives, which depend on the rates of Hg(0) adsorption. In order to correlate fixed bed properties and operation conditions, with their adsorptive capacity and saturation time, Hg(0) adsorption tests were realized in a bench-scale unit, consisted of F400 activated carbon fixed bed reactor. Hg(0) adsorption tests were conducted at 50 degrees C, under 0.1 and 0.35 ng/cm(3) Hg(0) initial concentrations and with carbon particle sizes ranging between 75-106 and 150-250 microm. Based on the experimental breakthrough data, kinetic studies were performed to investigate the mechanism of adsorption and the rate controlling steps. Kinetic models evaluated include the Fick's intraparticle diffusion equation, the pseudo-first order model, the pseudo-second order model and Elovich kinetic equation. The obtained experimental results revealed that the increase in particle size resulted in significant decrease of breakthrough time and mercury adsorptive capacity, due to the enhanced internal diffusion limitations and smaller external mass transfer coefficients. Additionally, higher initial mercury concentrations resulted in increased breakthrough time and mercury uptake. From the kinetic studies results it was observed that all the examined models describes efficiently Hg(0) breakthrough curves, from breakpoint up to equilibrium time. The most accurate prediction of the experimental data was achieved by second order model, indicating that the chemisorption rate seems to be the controlling step in the procedure. However, the successful attempt to describe mercury uptake with Fick's diffusion model and the first order kinetic model, reveals that the adsorption mechanism studied was complex and followed both surface adsorption and particle diffusion.

  9. The dissociation kinetics of NO on Rh(111) as studied by temperature programmed static secondary ion mass spectrometry and desorption

    NASA Astrophysics Data System (ADS)

    Borg, H. J.; Reijerse, J. F. C.-J. M.; van Santen, R. A.; Niemantsverdriet, J. W.

    1994-12-01

    Temperature programmed static secondary ion mass spectrometry (TPSSIMS) and temperature programmed desorption (TPD) have been used to study the kinetics of adsorption, dissociation, and desorption of NO on Rh(111). At 100 K, NO adsorption is molecular and proceeds via mobile precursor state kinetics with a high initial sticking probability. SSIMS indicates the presence of two distinct NO adsorption states, indicative of threefold adsorption at low coverage, and occupation of bridge sites at higher coverages. Three characteristic coverage regimes appear with respect to NO dissociation. At low coverages θNO<0.25 ML, NO dissociates completely at temperatures between 275 and 340 K. If we neglect lateral interactions and assume pure first order dissociation kinetics, we find effective values for the activation barrier and preexponential factor of 40±6 kJ/mol and 106±1 s-1 for the dissociation of 0.15-0.20 ML NO. However, if we assume that a NO molecule needs an ensemble of three to four vacant sites in order to dissociate, the preexponential factor and activation energy are ˜1011 s-1 and 65 kJ/mol, in better agreement with transition state theory expectations. The Nads and Oads dissociation products desorb as N2 and O2, respectively, with desorption parameters Edes=118±10 kJ/mol and νdes=1010.1±1.0 s-1 for N2 in the zero coverage limit. At higher coverages, the desorption kinetics of N2 is strongly influenced by the presence of coadsorbed oxygen. In the medium coverage range 0.25<θNO<0.50 ML, part of the NO desorbs molecularly, with an estimated desorption barrier of 113±10 kJ/mol and a preexponential of 1013.5±1.0 s-1. Dissociation of NO becomes progressively inhibited due to site blocking, the onset shifting from 275 K at 0.25 ML to 400 K, coinciding with the NO desorption temperature, at a coverage of 0.50 ML. The accumulation of nitrogen and oxygen atoms on the highly covered surface causes a destabilization of the nitrogen atoms, which results in an

  10. Removal of methylparaben from synthetic aqueous solutions using polyacrylonitrile beads: kinetic and equilibrium studies.

    PubMed

    Forte, Maurizio; Mita, Luigi; Perrone, Rosa; Rossi, Sergio; Argirò, Mario; Mita, Damiano Gustavo; Guida, Marco; Portaccio, Marianna; Godievargova, Tzonka; Ivanov, Yavour; Tamer, Mahmoud T; Omer, Ahmed M; Mohy Eldin, Mohamed S

    2017-01-01

    The removal of methylparaben (MP), a well-known endocrine disruptor, from aqueous solutions using polyacrylonitrile (PAN) beads has been studied under batch conditions, at room temperature and at different initial MP concentrations. The kinetic and equilibrium results have been analyzed. Kinetic modeling analysis has been carried out with three different types of adsorption models: pseudo-first-order, pseudo-second-order, and Elovich model. Kinetic data analysis indicated that the adsorption was a second-order process. The MP adsorption by PAN was also quantitatively evaluated by using the equilibrium adsorption isotherm models of Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin and the applicability of the respective isotherm equations has been compared through the correlation coefficients. Adsorption data resulted well fitted by the Freundlich isotherm model. Data of MP adsorption have also been used to test different adsorption diffusion models. The diffusion rate equations inside particulate of Dumwald-Wagner and the intraparticle diffusion model have been used to calculate the diffusion rate. The actual rate-controlling step involved in the MB adsorption process was determined. The kinetic expression by Boyd gave the right indications. All together, our results indicate that PAN beads are a useful tool to remediate water bodies polluted by endocrine disruptors.

  11. Electrochemical oxidation of COD from real textile wastewaters: Kinetic study and energy consumption.

    PubMed

    Zou, Jiaxiu; Peng, Xiaolan; Li, Miao; Xiong, Ying; Wang, Bing; Dong, Faqin; Wang, Bin

    2017-03-01

    In the present study, the electrochemical oxidation of real wastewaters discharged by textile industry was carried out using a boron-doped diamond (BDD) anode. The effect of operational variables, such as applied current density (20-100 mA·cm(-2)), NaCl concentration added to the real wastewaters (0-3 g·L(-1)), and pH value (2.0-10.0), on the kinetics of COD oxidation and on the energy consumption was carefully investigated. The obtained experimental results could be well matched with a proposed kinetic model, in which the indirect oxidation mediated by electrogenerated strong oxidants would be described through a pseudo-first-order kinetic constant k. Values of k exhibited a linear increase with increasing applied current density and decreasing pH value, and an exponential increase with NaCl concentration. Furthermore, high oxidation kinetics resulted in low specific energy consumption, but this conclusion was not suitable to the results obtained under different applied current density. Under the optimum operational conditions, it only took 3 h to complete remove the COD in the real textile wastewaters and the specific energy consumption could be as low as 11.12 kWh·kg(-1) COD. The obtained results, low energy consumption and short electrolysis time, allowed to conclude that the electrochemical oxidation based on BDD anodes would have practical industrial application for the treatment of real textile wastewater.

  12. Molecular basis of HHQ biosynthesis: molecular dynamics simulations, enzyme kinetic and surface plasmon resonance studies

    PubMed Central

    2013-01-01

    Background PQS (PseudomonasQuinolone Signal) and its precursor HHQ are signal molecules of the P. aeruginosa quorum sensing system. They explicate their role in mammalian pathogenicity by binding to the receptor PqsR that induces virulence factor production and biofilm formation. The enzyme PqsD catalyses the biosynthesis of HHQ. Results Enzyme kinetic analysis and surface plasmon resonance (SPR) biosensor experiments were used to determine mechanism and substrate order of the biosynthesis. Comparative analysis led to the identification of domains involved in functionality of PqsD. A kinetic cycle was set up and molecular dynamics (MD) simulations were used to study the molecular bases of the kinetics of PqsD. Trajectory analysis, pocket volume measurements, binding energy estimations and decompositions ensured insights into the binding mode of the substrates anthraniloyl-CoA and β-ketodecanoic acid. Conclusions Enzyme kinetics and SPR experiments hint at a ping-pong mechanism for PqsD with ACoA as first substrate. Trajectory analysis of different PqsD complexes evidenced ligand-dependent induced-fit motions affecting the modified ACoA funnel access to the exposure of a secondary channel. A tunnel-network is formed in which Ser317 plays an important role by binding to both substrates. Mutagenesis experiments resulting in the inactive S317F mutant confirmed the importance of this residue. Two binding modes for β-ketodecanoic acid were identified with distinct catalytic mechanism preferences. PMID:23916145

  13. Studies of Alfv'enic instabilities by a kinetic-fluid model

    NASA Astrophysics Data System (ADS)

    Nishimura, Y.; Cheng, C. Z.

    2009-11-01

    Employing a kinetic-fluid simulation modelfootnotetextC.Z.Cheng and J.R.Johnson, J. Geophys. Res. 104, 413 (1999)., Alfv'enic instabilities driven by energetic particles are studied in tokamak plasmas. The kinetic-fluid model incorporates all the particle dynamics through the pressure tensor by taking the second order moment of the particle simulation while the electromagnetic field quantities are evolved in the fluid equations. The kinetic-fluid model retains the ion and electron wave-particle interaction for both the bulk and the energetic plarticle components. Global Alfven oscillation, continuum damping, and the generation of the TAE gapfootnotetextC.Z.Cheng and M.S.Chance, Phys. Fluids 29, 3695 (1986). in the toroidal geometry are demonstrated in the MHD limit.footnotetextY.Nishimura, J.D.Callen, C.C.Hegna, Phys. Plasmas 6, 4685 (1999). Kinetic particlesfootnotetextY.Nishimura and M.Azumi, Phys. Plasmas 4, 2365 (1997). footnotetextY.Nishimura, Contrib. Plasma Phys. 48, 224 (2008). are then incorporated into the fluid set of equations to excite the instabilities (bulk ions/electrons replace the pressure evolution equation). This work is supported by National Cheng Kung University Top University Project.

  14. Fluctuating bottleneck model studies on kinetics of DNA escape from α-hemolysin nanopores.

    PubMed

    Bian, Yukun; Wang, Zilin; Chen, Anpu; Zhao, Nanrong

    2015-11-14

    We have proposed a fluctuation bottleneck (FB) model to investigate the non-exponential kinetics of DNA escape from nanometer-scale pores. The basic idea is that the escape rate is proportional to the fluctuating cross-sectional area of DNA escape channel, the radius r of which undergoes a subdiffusion dynamics subjected to fractional Gaussian noise with power-law memory kernel. Such a FB model facilitates us to obtain the analytical result of the averaged survival probability as a function of time, which can be directly compared to experimental results. Particularly, we have applied our theory to address the escape kinetics of DNA through α-hemolysin nanopores. We find that our theoretical framework can reproduce the experimental results very well in the whole time range with quite reasonable estimation for the intrinsic parameters of the kinetics processes. We believe that FB model has caught some key features regarding the long time kinetics of DNA escape through a nanopore and it might provide a sound starting point to study much wider problems involving anomalous dynamics in confined fluctuating channels.

  15. Kinetic Study of Hydroxyl and Sulfate Radical-Mediated Oxidation of Pharmaceuticals in Wastewater Effluents.

    PubMed

    Lian, Lushi; Yao, Bo; Hou, Shaodong; Fang, Jingyun; Yan, Shuwen; Song, Weihua

    2017-02-13

    Advanced oxidation processes (AOPs), such as hydroxyl radical (HO(•))- and sulfate radical (SO4(•-))-mediated oxidation, are alternatives for the attenuation of pharmaceuticals and personal care products (PPCPs) in wastewater effluents. However, the kinetics of these reactions needs to be investigated. In this study, kinetic models for 15 PPCPs were built to predict the degradation of PPCPs in both HO(•)- and SO4(•-)-mediated oxidation. In the UV/H2O2 process, a simplified kinetic model involving only steady state concentrations of HO(•) and its biomolecular reaction rate constants is suitable for predicting the removal of PPCPs, indicating the dominant role of HO(•) in the removal of PPCPs. In the UV/K2S2O8 process, the calculated steady state concentrations of CO3(•-) and bromine radicals (Br(•), Br2(•-) and BrCl(•-)) were 600-fold and 1-2 orders of magnitude higher than the concentrations of SO4(•-), respectively. The kinetic model, involving both SO4(•-) and CO3(•-) as reactive species, was more accurate for predicting the removal of the 9 PPCPs, except for salbutamol and nitroimidazoles. The steric and ionic effects of organic matter toward SO4(•-) could lead to overestimations of the removal efficiencies of the SO4(•-)-mediated oxidation of nitroimidazoles in wastewater effluents.

  16. Kinematic and kinetic interactions during normal and ACL-deficient gait: a longitudinal in vivo study.

    PubMed

    Atarod, Mohammad; Frank, Cyril B; Shrive, Nigel G

    2014-03-01

    The interactions between different tissues within the knee joint and between different kinematic DOF and joint flexion during normal gait were investigated. These interactions change following ACL transection, in both short (4 weeks) and long (20 weeks) term. Ten skeletally mature sheep were used in control (N = 5) and experimental (N = 5) groups. The 6-DOF stifle joint motion was first measured during normal gait. The control group were then euthanized and mounted on a unique robotic testing platform for kinetic measurements. The experimental group underwent ACL transection surgery, and kinematics measurements were repeated 4 and 20 weeks post-operatively. The experimental group were then euthanized and underwent kinetic assessment using the robotic system. Results indicated significant couplings between joint flexion vs. abduction and internal tibial rotation, as well as medial, anterior, and superior tibial translations during both normal and ACL-deficient gait. Distinct kinetic interactions were also observed between different tissues within the knee joint. Direct relationships were found between ACL vs. LM/MM, and PCL vs. MCL loads during normal gait; inverse relationships were detected between ACL vs. PCL and PCL vs. LM/MM loads. These kinetic interaction patterns were considerably altered by ACL injury. Significant inter-subject variability in joint kinematics and tissue loading patterns during gait was also observed. This study provides further understanding of the in vivo function of different tissues within the knee joint and their couplings with joint kinematics during normal gait and over time following ACL transection.

  17. A study on degradation kinetics of ascorbic acid in amla (Phyllanthus emblica L.) during cooking.

    PubMed

    Nisha, P; Singhal, Rekha S; Pandit, Aniruddha B

    2004-08-01

    The kinetics of ascorbic acid degradation in amla (Phyllanthus emblica L.) as well as in pure ascorbic acid solutions at initial concentrations present in amla over a temperature range of 50-120 degrees C (steady-state temperature) has been studied. The ascorbic acid degradation followed first-order reaction kinetics where the rate constant increased with an increase in temperature. The temperature dependence of degradation was adequately modeled by the Arrhenius equation. The activation energies were found to be 4.09 kcal/mole for amla and 4.49 kcal/mole for pure vitamin solution. The degradation kinetics of ascorbic acid was also evaluated in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient EcoCooker (unsteady state heating process). A mathematical model was developed using the steady-state kinetic parameters obtained to predict the losses of ascorbic acid from the time-temperature data of the unsteady state heating processing method. The results obtained indicate the ascorbic acid degradation is of a similar order of magnitude in all the methods of cooking.

  18. Temperature dependence of protein solubility-determination, application to crystallization, and growth kinetics studies

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1993-01-01

    A scintillation method was developed for determinations of the temperature dependence of the solubility, and of nucleation induction times of proteins, in 50-100 mu(l) volumes of solution. Solubility data for lysozyme and horse serum albumin were obtained for various combinations of pH and precipitant concentrations. These data and the nucleation induction information were used for dynamic crystallization control, that is, for the controlled separation of nucleation and growth stages. Individual lysozyme and horse serum albumin crystals were grown in 15-20 mu(l) solution volumes contained in x-ray capillaries. The morphology and kinetics of the growth and dissolution of lysozyme in aqueous solutions with 2.5 percent NaCl and at pH = 4.5 was studied in situ with a depth resolution of 300 A (4 unit cells) by high resolution optical microscopy and digital image processing. The bulk super- or under saturation, sigma, of the solution inside a closed growth cell was controlled by temperature. The growth habit was bound by (110) and (101) faces that grew through layer spreading, although with different growth rate dependencies on supersaturation/temperature. At sigma less than 10 (obtained at higher temperatures) growth was purely kinetic ally controlled, with impurity effects (macrostep formation and kinetic hindrance) becoming significant for sigma less than 2. At sigma greater than 10 (lower temperatures), anisotropies in the interfacial kinetics were more pronounced, with interfacial kinetics and bulk transport becoming equally important to the growth morphology. Growth rates were growth history dependent. The formation of striations (layers of irregularly incorporated solution) was unambiguously correlated with growth temperature variations. Etching exposed dislocations and various high-index faces whose growth morphologies were studied during return to the steady state growth form. Growth steps were observed to originate from two-dimensional nuclei or from outcrops

  19. Kinetic Defects Induced by Melittin in Model Lipid Membranes: A Solution Atomic Force Microscopy Study.

    PubMed

    Pan, Jianjun; Khadka, Nawal K

    2016-05-26

    Quantitative characterization of membrane defects (pores) is important for elucidating the molecular basis of many membrane-active peptides. We study kinetic defects induced by melittin in vesicular and planar lipid bilayers. Fluorescence spectroscopy measurements indicate that melittin induces time-dependent calcein leakage. Solution atomic force microscopy (AFM) is used to visualize melittin-induced membrane defects. After initial equilibration, the most probable defect radius is ∼3.8 nm in 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) bilayers. Unexpectedly, defects become larger with longer incubation, accompanied by substantial shape transformation. The initial defect radius is ∼4.7 nm in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers. Addition of 30 mol % cholesterol to DOPC bilayers suppresses defect kinetics, although the inhibitory impact is negated by longer incubation. Overall, the kinetic rate of defect development follows DLPC > DOPC > DOPC/cholesterol. Kinetic defects are also observed when anionic lipids are present. Based on the observation that defects can occupy as large as 40% of the bilayer surface, we propose a kinetic defect growth model. We also study the effect of melittin on the phase behavior of DOPC/egg-sphingomyelin/cholesterol bilayers. We find that melittin initially suppresses or eliminates liquid-ordered (Lo) domains; Lo domains gradually emerge and become the dominant species with longer incubation; and defects in phase-coexisting bilayers have a most probable radius of ∼5 nm and are exclusively localized in the liquid-disordered (Ld) phase. Our experimental data highlight that melittin-induced membrane defects are not static; conversely, spontaneous defect growth is intrinsically associated with membrane permeabilization exerted by melittin.

  20. Benchmark Studies of the Gyro-Landau-Fluid code and Gyro-kinetic Codes on Kinetic Ballooning Modes

    NASA Astrophysics Data System (ADS)

    Tang, Tengfei; Xu, Xueqiao; Ma, Chenhao; Holland, Chris; Candy, Jeff

    2015-11-01

    A Gyro-Landau-Fluid (GLF) 3 +1 model has been implemented in BOUT + + framework recently, which contains full Finite-Larmor-Radius (FLR) effects, Landau damping and toroidal resonance. A linear global beta scan has been done using the cbm18 series equilibriums, showing that the unstable modes are kinetic ballooning modes (KBMs). In this work, we use the GYRO code, which is a gyrokinetic continuum code widely used for simulation of the plasma microturbulence, to benchmark with GLF 3 +1 code on KBMs. As the modes locate in peak pressure gradient region, a linear local beta scan using the same set of equilibriums has been done at this position for comparison. With the drift kinetic electron module in the GYRO code by including small electron-ion collision to damp electron modes, GYRO generated mode structures and parity suggest that they are kinetic ballooning modes, and the growth rate is comparable to the GLF results. However, a radial scan of the pedestal for a particular cbm18 equilibrium shows that the growth rate of the most unstable mode shifts outward to the bottom of pedestal and the real frequency of what was originally the KBMs steadily approaches and crosses over to the electron diamagnetic drift direction. Prepared by LLNL under Contract DE-AC52-07NA27344.

  1. The Gaseous Explosive Reaction : A Study of the Kinetics of Composite Fuels

    NASA Technical Reports Server (NTRS)

    Stevens, F W

    1929-01-01

    This report deals with the results of a series of studies of the kinetics of gaseous explosive reactions where the fuel under observation, instead of being a simple gas, is a known mixture of simple gases. In the practical application of the gaseous explosive reaction as a source of power in the gas engine, the fuels employed are composite, with characteristics that are apt to be due to the characteristics of their components and hence may be somewhat complex. The simplest problem that could be proposed in an investigation either of the thermodynamics or kinetics of the gaseous explosive reaction of a composite fuel would seem to be a separate study of the reaction characteristics of each component of the fuel and then a study of the reaction characteristics of the various known mixtures of those components forming composite fuels more and more complex. (author)

  2. Ochratoxin A kinetics: a review of analytical methods and studies in rat model.

    PubMed

    Vettorazzi, A; González-Peñas, E; de Cerain, A López

    2014-10-01

    Ochratoxin A (OTA) is a thermostable mycotoxin that contaminates a great variety of foodstuffs. It is nephrotoxic in all of the mammalian species tested, the pig being the most sensitive one; among rodents, rats are the most susceptible to OTA carcinogenicity. Kinetics, by studying the absorption, distribution, metabolism and excretion of xenobiotics, is an important tool in the extrapolation of animal toxicity data for human risk assessment. The most important kinetic studies performed with OTA in rats are reviewed, together with the different methods used for OTA quantification in biological matrices. Twelve studies in Wistar, Sprague-Dawley or F344 rats, using radiolabeled OTA or TLC, HPLC-FLD or LC/MS have been summarized. Very often methods validated for food have been directly applied to tissues. Strain, sex and age differences have been detected but the interpretation is difficult due to the different experimental conditions, and the connection of the several factors that may account for these differences.

  3. Laser microbeam - kinetic studies combined with molecule - structures reveal mechanisms of DNA repair

    NASA Astrophysics Data System (ADS)

    Altenberg, B.; Greulich, K. O.

    2011-10-01

    Kinetic studies on double strand DNA damages induced by a laser microbeam have allowed a precise definition of the temporal order of recruitment of repair molecules. The order is KU70 / KU80 - XRCC4 --NBS1 -- RAD51. These kinetic studies are now complemented by studies on molecular structures of the repair proteins, using the program YASARA which does not only give molecular structures but also physicochemical details on forces involved in binding processes. It turns out that the earliest of these repair proteins, the KU70 / KU80 heterodimer, has a hole with high DNA affinity. The next molecule, XRCC4, has a body with two arms, the latter with extremely high DNA affinity at their ends and a binding site for Ligase 4. Together with the laser microbeam results this provides a detailed view on the early steps of DNA double strand break repair. The sequence of DNA repair events is presented as a movie.

  4. Kinetic, isotherm and thermodynamic studies of amaranth dye biosorption from aqueous solution onto water hyacinth leaves.

    PubMed

    Guerrero-Coronilla, Imelda; Morales-Barrera, Liliana; Cristiani-Urbina, Eliseo

    2015-04-01

    The present study explored the kinetics, equilibrium and thermodynamics of amaranth (acid red 27) anionic dye (AD) biosorption to water hyacinth leaves (LEC). The effect of LEC particle size, contact time, solution pH, initial AD concentration and temperature on AD biosorption was studied in batch experiments. AD biosorption increased with rising contact time and initial AD concentration, and with decreasing LEC particle size and solution pH. Pseudo-second-order chemical reaction kinetics provided the best correlation for the experimental data. Isotherm studies showed that the biosorption of AD onto LEC closely follows the Langmuir isotherm, with a maximum biosorption capacity of about 70 mg g(-1). The thermodynamic parameters confirm that AD biosorption by LEC is non-spontaneous and endothermic in nature. Results indicate that LEC is a strong biosorbent capable of effective detoxification of AD-laden wastewaters.

  5. Studying the unfolding kinetics of proteins under pressure using long molecular dynamic simulation runs.

    PubMed

    Chara, Osvaldo; Grigera, José Raúl; McCarthy, Andrés N

    2007-12-01

    The usefulness of computational methods such as molecular dynamics simulation has been extensively established for studying systems in equilibrium. Nevertheless, its application to complex non-equilibrium biological processes such as protein unfolding has been generally regarded as producing results which cannot be interpreted straightforwardly. In the present study, we present results for the kinetics of unfolding of apomyoglobin, based on the analysis of long simulation runs of this protein in solution at 3 kbar (1 atm = 1.01325, bar = 101,325 Pa). We hereby demonstrate that the analysis of the data collected within a simulated time span of 0.18 mus suffices for producing results, which coincide remarkably with the available unfolding kinetics experimental data. This not only validates molecular dynamics simulation as a valuable alternative for studying non-equilibrium processes, but also enables a detailed analysis of the actual structural mechanism which underlies the unfolding process of proteins under elusive denaturing conditions such as high pressure.

  6. Thermodynamic and kinetic study of phenol degradation by a non-catalytic wet air oxidation process.

    PubMed

    Lefèvre, Sébastien; Boutin, Olivier; Ferrasse, Jean-Henry; Malleret, Laure; Faucherand, Rémy; Viand, Alain

    2011-08-01

    This work is dedicated to an accurate evaluation of thermodynamic and kinetics aspects of phenol degradation using wet air oxidation process. Phenol is a well known polluting molecule and therefore it is important having data of its behaviour during this process. A view cell is used for the experimental study, with an internal volume of 150 mL, able to reach pressures up to 30 MPa and temperatures up to 350°C. Concerning the thermodynamic phase equilibria, experimental and modelling results are obtained for different binary systems (water/nitrogen, water/air) and ternary system (water/nitrogen/phenol). The best model is the Predictive Soave Redlich Kwong one. This information is necessary to predict the composition of the gas phase during the process. It is also important for an implementation in a process simulation. The second part is dedicated to kinetics evaluation of the degradation of phenol. Different compounds have been detected using GC coupled with a MS. A kinetic scheme is deduced, taking into account the evolution of phenol, hydroquinones, catechol, resorcinol and acetic acid. The kinetic parameters are calculated for this scheme. These data are important to evaluate the evolution of the concentration of the different polluting molecules during the process. A simplified kinetic scheme, which can be easily implemented in a process simulation, is also determined for the direct degradation of phenol into H(2)O and CO(2). The Arrhenius law data obtained for the phenol disappearance are the following: k=1.8×10(6)±3.9×10(5)M(-1)s(-1) (pre-exponential factor) and E(a)=77±8 kJ mol(-1) (activation energy).

  7. Waste lubricating oil removal in a batch reactor by mixed bacterial consortium: a kinetic study.

    PubMed

    Bhattacharya, Munna; Guchhait, Sugata; Biswas, Dipa; Datta, Sriparna

    2015-11-01

    The growth kinetics and biodegradation of two waste lubricating oil samples including waste engine oil (WEO) and waste transformer oil (WTO) were studied using pure isolates and mixed culture of Ochrobactrum sp. C1 and Bacillus sp. K1. The mixed culture significantly influenced degradation efficiency of the pure isolates through bioaugmentation process. In particular, the mixed culture was capable of growing on various n-alkanes and polycyclic aromatic hydrocarbons and was able to tolerate unusually high concentrations of waste lubricants (WEO-86.0 g/L and WTO-81.5 g/L). The initial concentration of waste lubricating oils has been varied in the range of 1-10 % (v/v). Under this experimental range, the bacterial growth has been observed to follow Haldane-type kinetics characterizing the presence of substrate inhibition. Haldane model was used to fit the exponential growth data and the following kinetic parameters were obtained: μ max = 0.078 h(-1), K S = 23.101 g/L, K i = 43.844 g/L for WEO; and μ max = 0.044 h(-1), K S = 10.662 g/L, K i = 58.310 g/L for WTO. The values of intrinsic kinetic parameters, like specific growth rate μ max, half saturation constant, K S, inhibition constant, K i and the maximum substrate concentration, S max and growth yield coefficient Y x/s , have been determined using each model hydrocarbon and their mixture as limiting substrate. Relative changes in the values of the kinetic parameters have been correlated to the number of carbon atoms present in n-alkanes. The metabolites from degradation of model hydrocarbon compounds have been identified by GC-MS to elucidate the possible pathway of waste lubricating oil degradation process.

  8. Succinate Overproduction: A Case Study of Computational Strain Design Using a Comprehensive Escherichia coli Kinetic Model.

    PubMed

    Khodayari, Ali; Chowdhury, Anupam; Maranas, Costas D

    2014-01-01

    Computational strain-design prediction accuracy has been the focus for many recent efforts through the selective integration of kinetic information into metabolic models. In general, kinetic model prediction quality is determined by the range and scope of genetic and/or environmental perturbations used during parameterization. In this effort, we apply the k-OptForce procedure on a kinetic model of E. coli core metabolism constructed using the Ensemble Modeling (EM) method and parameterized using multiple mutant strains data under aerobic respiration with glucose as the carbon source. Minimal interventions are identified that improve succinate yield under both aerobic and anaerobic conditions to test the fidelity of model predictions under both genetic and environmental perturbations. Under aerobic condition, k-OptForce identifies interventions that match existing experimental strategies while pointing at a number of unexplored flux re-directions such as routing glyoxylate flux through the glycerate metabolism to improve succinate yield. Many of the identified interventions rely on the kinetic descriptions that would not be discoverable by a purely stoichiometric description. In contrast, under fermentative (anaerobic) condition, k-OptForce fails to identify key interventions including up-regulation of anaplerotic reactions and elimination of competitive fermentative products. This is due to the fact that the pathways activated under anaerobic condition were not properly parameterized as only aerobic flux data were used in the model construction. This study shed light on the importance of condition-specific model parameterization and provides insight on how to augment kinetic models so as to correctly respond to multiple environmental perturbations.

  9. Determining degradation and synthesis rates of arabidopsis proteins using the kinetics of progressive 15N labeling of two-dimensional gel-separated protein spots.

    PubMed

    Li, Lei; Nelson, Clark J; Solheim, Cory; Whelan, James; Millar, A Harvey

    2012-06-01

    The growth and development of plant tissues is associated with an ordered succession of cellular processes that are reflected in the appearance and disappearance of proteins. The control of the kinetics of protein turnover is central to how plants can rapidly and specifically alter protein abundance and thus molecular function in response to environmental or developmental cues. However, the processes of turnover are largely hidden during periods of apparent steady-state protein abundance, and even when proteins accumulate it is unclear whether enhanced synthesis or decreased degradation is responsible. We have used a (15)N labeling strategy with inorganic nitrogen sources coupled to a two-dimensional fluorescence difference gel electrophoresis and mass spectrometry analysis of two-dimensional IEF/SDS-PAGE gel spots to define the rate of protein synthesis (K(S)) and degradation (K(D)) of Arabidopsis cell culture proteins. Through analysis of MALDI-TOF/TOF mass spectra from 120 protein spots, we were able to quantify K(S) and K(D) for 84 proteins across six functional groups and observe over 65-fold variation in protein degradation rates. K(S) and K(D) correlate with functional roles of the proteins in the cell and the time in the cell culture cycle. This approach is based on progressive (15)N labeling that is innocuous for the plant cells and, because it can be used to target analysis of proteins through the use of specific gel spots, it has broad applicability.

  10. Determining Degradation and Synthesis Rates of Arabidopsis Proteins Using the Kinetics of Progressive 15N Labeling of Two-dimensional Gel-separated Protein Spots*

    PubMed Central

    Li, Lei; Nelson, Clark J.; Solheim, Cory; Whelan, James; Millar, A. Harvey

    2012-01-01

    The growth and development of plant tissues is associated with an ordered succession of cellular processes that are reflected in the appearance and disappearance of proteins. The control of the kinetics of protein turnover is central to how plants can rapidly and specifically alter protein abundance and thus molecular function in response to environmental or developmental cues. However, the processes of turnover are largely hidden during periods of apparent steady-state protein abundance, and even when proteins accumulate it is unclear whether enhanced synthesis or decreased degradation is responsible. We have used a 15N labeling strategy with inorganic nitrogen sources coupled to a two-dimensional fluorescence difference gel electrophoresis and mass spectrometry analysis of two-dimensional IEF/SDS-PAGE gel spots to define the rate of protein synthesis (KS) and degradation (KD) of Arabidopsis cell culture proteins. Through analysis of MALDI-TOF/TOF mass spectra from 120 protein spots, we were able to quantify KS and KD for 84 proteins across six functional groups and observe over 65-fold variation in protein degradation rates. KS and KD correlate with functional roles of the proteins in the cell and the time in the cell culture cycle. This approach is based on progressive 15N labeling that is innocuous for the plant cells and, because it can be used to target analysis of proteins through the use of specific gel spots, it has broad applicability. PMID:22215636

  11. Kinetic study on the effect of temperature on biogas production using a lab scale batch reactor.

    PubMed

    Deepanraj, B; Sivasubramanian, V; Jayaraj, S

    2015-11-01

    In the present study, biogas production from food waste through anaerobic digestion was carried out in a 2l laboratory-scale batch reactor operating at different temperatures with a hydraulic retention time of 30 days. The reactors were operated with a solid concentration of 7.5% of total solids and pH 7. The food wastes used in this experiment were subjected to characterization studies before and after digestion. Modified Gompertz model and Logistic model were used for kinetic study of biogas production. The kinetic parameters, biogas yield potential of the substrate (B), the maximum biogas production rate (Rb) and the duration of lag phase (λ), coefficient of determination (R(2)) and root mean square error (RMSE) were estimated in each case. The effect of temperature on biogas production was evaluated experimentally and compared with the results of kinetic study. The results demonstrated that the reactor with operating temperature of 50°C achieved maximum cumulative biogas production of 7556ml with better biodegradation efficiency.

  12. Kinetics studies of d-glucose hydrogenation over activated charcoal supported platinum catalyst

    NASA Astrophysics Data System (ADS)

    Ahmed, Muthanna J.

    2012-02-01

    The kinetics of the catalytic hydrogenation of d-glucose to produce d-sorbitol was studied in a three-phase laboratory scale reactor. The hydrogenation reactions were performed on activated charcoal supported platinum catalyst in the temperature range 25-65°C and in a constant pressure of 1 atm. The kinetic data were modeled by zero, first and second-order reaction equations. In the operating regimes studied, the results show that the hydrogenation reaction was of a first order with respect to d-glucose concentration. Also the activation energy of the reaction was determined, and found to be 12.33 kJ mole-1. A set of experiment was carried out to test the deactivation of the catalyst, and the results show that the deactivation is slow with the ability of using the catalyst for several times with a small decrease in product yield.

  13. Kinetic and equilibrium studies on biosorption of basic blue dye by green macro algae Caulerpa scalpelliformis.

    PubMed

    Aravindhan, Rathinam; Rao, Jonnalagadda Raghava; Nair, Balachandran Unni

    2007-04-01

    Dynamic batch experiments were carried out for the biosorption of basic blue dye on to the green macro algae Caulerpa scalpelliformis. The factors affecting the sorption process such as the initial concentration of the dye, pH of the solution, the adsorbent dosage and the time of contact were studied. It has been observed that the sorption process was significantly affected by the pH of the initial dye solution. The sorption kinetics was found to follow the second-order kinetic model. The Boyd's plot confirmed the external mass transfer as the rate-limiting step. The average effective diffusion coefficient was found to be 1.652 x 10(- 5) cm(2)/s. Sorption equilibrium studies demonstrated that the biosorption followed Freundlich isotherm model, which implies a heterogeneous sorption phenomenon. Optimized parameters were used to treat the commercial effluent containing the dye. Complete color removal was observed in two stages of treatment with the seaweed.

  14. DSC and curing kinetics study of epoxy grouting diluted with furfural -acetone slurry

    NASA Astrophysics Data System (ADS)

    Yin, H.; Sun, D. W.; Li, B.; Liu, Y. T.; Ran, Q. P.; Liu, J. P.

    2016-07-01

    The use of furfural-acetone slurry as active diluents of Bisphenol-A epoxy resin (DGEBA) groutings has been studied by dynamic and non-isothermal DSC for the first time. Curing kinetics study was investigated by non-isothermal differential scanning calorimetries at different heating rates. Activation enery (Ea) was calculated based on Kissinger and Ozawa Methods, and the results showed that Ea increased from 58.87 to 71.13KJ/mol after the diluents were added. The furfural-acetone epoxy matrix could cure completely at the theoretical curing temperature of 365.8K and the curing time of 139mins, which were determined by the kinetic model parameters.

  15. TL kinetics study of LiF nanophosphors for high exposures of gamma-rays

    SciTech Connect

    Sharma, A. K.; Vij, Ankush; Kumar, Ravi; Kumar, Satinder; Lochab, S. P.

    2013-02-05

    We report the thermoluminescence (TL) kinetics study of LiF nanophosphors synthesized by chemical co-precipitation at 8.00 pH and exposed to high gamma dose. XRD and TEM studies confirm the formation of single phase LiF nanophosphors. TL properties of LiF phosphors irradiated with gamma rays at different doses of 100 Gy - 70 KGy shows a major peak around 395 K in addition to other low intensity peaks. The major peak in the TL glow curve is almost resolved from other peaks, which has been analyzed using Chen's peak shape method to determine the TL kinetic parameters. TL intensity almost increases linearly with gamma dose, however TL glow curve shift slightly to lower temperature values as a function of gamma exposure.

  16. XRD study of the kinetics of β ↔ α transformations in tin

    NASA Astrophysics Data System (ADS)

    Nogita, K.; Gourlay, C. M.; McDonald, S. D.; Suenaga, S.; Read, J.; Zeng, G.; Gu, Q. F.

    2013-09-01

    The transformation kinetics of βSn (white tin) to and from αSn (grey tin) are studied by synchrotron X-ray diffraction of seeded powder samples of 99.99% Sn. An analysis of thermal expansion behaviour revealed that the volume change of transformation increases as the temperature decreases. The βSn → αSn transformation was well described by Johnson-Mehl-Avrami kinetics with an Avrami exponent of 3, which was confirmed to be due to three-dimesional growth from pre-existing nuclei by a microstructural study. The αSn → βSn transformation exhibited a decreasing Avrami exponent from ∼4 to ∼1 during the transformation. Time-Temperature-Transformation curves are plotted from the isothermal transformation data and are compared with past work.

  17. Kinetic study of the reaction of chlorine atoms with hydroxyacetone in gas-phase

    NASA Astrophysics Data System (ADS)

    Stoeffler, Clara; Joly, Lilian; Durry, Georges; Cousin, Julien; Dumelié, Nicolas; Bruyant, Aurélien; Roth, Estelle; Chakir, Abdelkhaleq

    2013-12-01

    In this letter the kinetics of the reaction of hydroxyacetone CH3C(O)CH2OH with Cl atoms is investigated using the relative rate technique. Experiments are carried out in a 65 L multipass photoreactor in the temperature range of 281-350 K. A mid-infrared spectrometer based on a quantum cascade laser in external cavity emitting at 9.5 μm is used to analyze the reactants. The determined rate coefficient for the investigated reaction is (1.7 ± 0.3) × 10-11exp(381.5 ± 57.3/T). The results are presented and discussed in terms of precision and compared with those obtained previously. The impact of Cl atoms on the atmospheric life time of hydroxyacetone is also discussed. Developing analytical techniques to quantify this compound in the atmosphere. Several methods of measurement have been used including the technique of proton transfer mass spectrometry (PTR-MS) [2] and derivatization with a chemical agent such as dinitrophenylhydrazine (DNPH) [3,4] followed by GC/MS or HPLC analyses. The HA amount in the troposphere was found to be in the order of a few hundred parts per trillion by volume [4], Performing laboratory experiments in order to study the HA reactivity with atmospheric oxidants. The first study on the kinetic of the reaction between OH radicals and HA was made by Dagault et al. [5] whose work was performed at room temperature by flash photolysis-resonance fluorescence. The determined rate constant implies a lifetime of a few days for HA relative to oxidation by OH radicals. Orlando et al. performed mechanistic and kinetics studies of the reaction of HA with OH radicals and Cl atoms at room temperature using a relative method [6]. Products detection was performed using FTIR spectroscopy. Moreover, these authors studied the photolysis of HA to determine its quantum yield and UV absorption spectrum. These studies showed that HA is principally removed from the atmosphere by reaction with OH radicals. Kinetic studies of the reaction of OH radicals with HA as a

  18. DNA methylation in schizophrenia: progress and challenges of epigenetic studies

    PubMed Central

    2012-01-01

    Schizophrenia is a severe psychiatric disease affecting about 1% of the world's population, with significant effects on patients and society. Genetic studies have identified several candidate risk genes or genomic regions for schizophrenia, and epidemiological studies have revealed several environmental risk factors. However, the etiology of schizophrenia still remains largely unknown. Epigenetic mechanisms such as DNA methylation and histone modifications can explain the interaction between genetic and environmental factors at the molecular level, and accumulating evidence suggests that such epigenetic alterations are involved in the pathophysiology of schizophrenia. However, replication studies to validate previous findings and investigations of the causality of epigenetic alterations in schizophrenia are needed. Here, we review epigenetic studies of schizophrenia patients using postmortem brains or peripheral tissues, focusing mainly on DNA methylation. We also highlight the recent progress and challenges in characterizing the potentially complex and dynamic patterns of epigenomic variations. Such studies are expected to contribute to our understanding of schizophrenia etiology and should provide novel opportunities for the development of therapeutic drugs. PMID:23234572

  19. Benchmark studies of the gyro-Landau-fluid code and gyro-kinetic codes on kinetic ballooning modes

    NASA Astrophysics Data System (ADS)

    Tang, T. F.; Xu, X. Q.; Ma, C. H.; Bass, E. M.; Holland, C.; Candy, J.

    2016-03-01

    A Gyro-Landau-Fluid (GLF) 3 + 1 model has been recently implemented in BOUT++ framework, which contains full Finite-Larmor-Radius effects, Landau damping, and toroidal resonance [Ma et al., Phys. Plasmas 22, 055903 (2015)]. A linear global beta scan has been conducted using the JET-like circular equilibria (cbm18 series), showing that the unstable modes are kinetic ballooning modes (KBMs). In this work, we use the GYRO code, which is a gyrokinetic continuum code widely used for simulation of the plasma microturbulence, to benchmark with GLF 3 + 1 code on KBMs. To verify our code on the KBM case, we first perform the beta scan based on "Cyclone base case parameter set." We find that the growth rate is almost the same for two codes, and the KBM mode is further destabilized as beta increases. For JET-like global circular equilibria, as the modes localize in peak pressure gradient region, a linear local beta scan using the same set of equilibria has been performed at this position for comparison. With the drift kinetic electron module in the GYRO code by including small electron-electron collision to damp electron modes, GYRO generated mode structures and parity suggest that they are kinetic ballooning modes, and the growth rate is comparable to the GLF results. However, a radial scan of the pedestal for a particular set of cbm18 equilibria, using GYRO code, shows different trends for the low-n and high-n modes. The low-n modes show that the linear growth rate peaks at peak pressure gradient position as GLF results. However, for high-n modes, the growth rate of the most unstable mode shifts outward to the bottom of pedestal and the real frequency of what was originally the KBMs in ion diamagnetic drift direction steadily approaches and crosses over to the electron diamagnetic drift direction.

  20. Kinetic Studies on Photodeposition of Polydiacetylene Thin Film from Solution: Preliminary Determination of the Rate Law

    NASA Technical Reports Server (NTRS)

    Paley, M. S.; Armstrong, S.; Witherow, W. K.; Frazier, D. O.

    1996-01-01

    Preliminary kinetic studies were undertaken on the photodeposition of thin films of a polydiacetylene derivative of 2-methyl-4-nitroaniline from monomer solutions onto quartz substrates. Solutions of the monomer, DAMNA, in 1,2-dichloroethane at various concentrations were irradiated at 364 nm using an argon-ion laser at several intensities. It was found that the rate of polydiacetylene (PDAMNA) film photodeposition varies linearly with UV light intensity and as the square root of monomer concentration.

  1. Kinetics study of carbon raiser on the reduction of nickel laterite from Pomalaa, Southeast Sulawesi

    NASA Astrophysics Data System (ADS)

    Petrus, H. T. B. M.; Rhamdani, A. R.; Putera, A. D. P.; Warmada, I. W.; Yuliansyad, A. T.; Perdana, I.

    2016-11-01

    As one of the top ten on nickel laterite ore resources in the world, Indonesia must have been initiating the nickel processing in total amount of about 1.5 million tonnes. In regard to the low nickel laterite processing, one of the possible product is nickel pig iron (NPI) needed for the stainless steel industries. In this study carbon raiser that is waste from oil industries was used to replace metalurgical coke. The kinetic of nickel laterite reduction using carbon raiser was studied and compared with anthrasite coal. In this work, the author conducted the reduction of nickel laterite ores by both carbon raiser and anthrasite coal as reductant, in air and CO2 atmosphere, within the temperature ranged from 800°C and 1000°C. Two models were applied, sphere particle geometry model and Ginstling-Brounhstein diffusion model, to study the kinetic parameters. The results indicated that type of reductants and reduction atmosphere greatly influence the kinetic parameters. The obtained values of activation energy were varied between 17.44-18.12 kcal/mol.

  2. Equilibrium, kinetic and thermodynamic study of the biosorption of uranium onto Cystoseria indica algae.

    PubMed

    Khani, M H; Keshtkar, A R; Ghannadi, M; Pahlavanzadeh, H

    2008-02-11

    Biosorption equilibrium, kinetics and thermodynamics of binding of uranium ions to Cystoseria indica were studied in a batch system with respect to temperature and initial metal ion concentration. Algae biomass exhibited the highest uranium uptake capacity at 15 degrees C at an initial uranium ion concentration of 500 mg l(-1) and an initial pH of 4. Biosorption capacity increased from 198 to 233 mg g(-1) with an decrease in temperature from 45 to 15 degrees C at this initial uranium concentration. The Langmuir isotherm model were applied to experimental equilibrium data of uranium biosorption depending on temperature. Equilibrium data fitted very well to the Langmuir model C. indica algae in the studied concentration range of Uranium ions at all the temperatures studied. The saturation type kinetic model was applied to experimental data at different temperatures changing from 15 to 45 degrees C to describe the batch biosorption kinetics assuming that the external mass transfer limitations in the system can be neglected and biosorption is chemical sorption controlled. The activation energy of biosorption (E(A)) was determined as -6.15 using the Arrhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the thermodynamic constants of biosorption (DeltaG degrees , DeltaH degrees and DeltaS degrees ) were also evaluated.

  3. New approaches to the kinetic study of alcoholic fermentation by chromatographic techniques.

    PubMed

    Lainioti, Georgia Ch; Karaiskakis, George

    2013-09-01

    The kinetics of the fermentation process has gained increasing interest, not only in the scientific community, but in the industrial world as well. Information concerning the improvement of batch fermentation performance may potentially be valuable for the designing of scale-up processes. Intensive studies have been conducted with the use of various chromatographic techniques, such as conventional gas chromatography, reversed-flow gas chromatography (RFGC), high-performance liquid chromatography, field-flow fractionation and others. In the present study, specific focus is placed on the employment of RFGC, a method that can successfully be applied for the determination of physicochemical quantities, such as reaction rate constants and activation energies, at each phase of the alcoholic fermentation. In contrast to conventional chromatographic techniques, RFGC can lead to substantial information referring to the evaluation of fermentation kinetics at any time of the process. Moreover, gravitational field-flow fractionation, a sub-technique of field-flow fractionation, presents the ability to monitor the proliferation of Saccharomyces cerevisiae cells through their elution profiles that can be related to the different cell growth stages. The combination of the two techniques can provide important information for kinetic study and the distinction of the growth phases of yeast cell proliferation during alcoholic fermentations conducted under different environmental conditions.

  4. Studying the Kinetics of n-Butyl-Cyanoacrylate Tissue Adhesive and Its Oily Mixtures

    NASA Astrophysics Data System (ADS)

    Nedvedova, Marie; Kresalek, Vojtech; Vaskova, Hana; Provaznik, Ivo

    2016-10-01

    This study deals with the measurement of the kinetics of tissue adhesives used for supporting the hemostasis and wound closure during surgical intervention. There are available several types of adhesives of different composition which is closely related with their application. When selecting an appropriate adhesive, the time of curing could play an important role because some applications may require very fast polymerization for prompt vessel or wound closure; conversely, some situations need slower solidification because of longer manipulation with the glue during surgery. The terahertz time-domain spectroscopy is used for studying the kinetics of the n-butyl-cyanoacrylate glue in this study. An oily substance is added to the glue samples to slow the reaction rate. The technique of attenuated total reflection is used in this application; the defined amount of glue sample or its mixture is applied on the silicon crystal and the terahertz response is measured in time. This time dependences are analyzed to find time constants for mathematical description of the glue kinetics. Further, the investigated samples were analyzed using light microscopy and Raman spectroscopy for description of the structures and compositions.

  5. Characterization and kinetics study of off-gas emissions from stored wood pellets.

    PubMed

    Kuang, Xingya; Shankar, Tumuluru Jaya; Bi, Xiaotao T; Sokhansanj, Shahab; Lim, C Jim; Melin, Staffan

    2008-11-01

    The full potential health impact from the emissions of biomass fuels, including wood pellets, during storage and transportation has not been documented in the open literature. The purpose of this study is to provide data on the concentration of CO(2), CO and CH(4) from wood pellets stored in sealed vessels and to develop a kinetic model for predicting the transient emission rate factors at different storage temperatures. Five 45-l metal containers (305 mm diameter by 610 mm long) equipped with heating and temperature control devices were used to study the temperature effect on the off-gas emissions from wood pellets. Concurrently, ten 2-l aluminum canisters (100 mm diameter by 250 mm long) were used to study the off-gas emissions from different types of biomass materials. Concentrations of CO(2), CO and CH(4) were measured by a gas chromatograph as a function of storage time and storage temperature. The results showed that the concentrations of CO, CO(2) and CH(4) in the sealed space of the reactor increased over time, fast at the beginning but leveling off after a few days. A first-order reaction kinetics fitted the data well. The maximum concentration and the time it takes for the buildup of gas concentrations can be predicted using kinetic equations.

  6. Electron scattering as a tool to study zero-point kinetic energies of atoms in molecules

    NASA Astrophysics Data System (ADS)

    Moreh, R.; Finkelstein, Y.; Vos, M.

    2015-07-01

    High resolution electron compton scattering (ECS) is being used to study the atomic momentum distributions and hence the zero-point kinetic energies (ZPKE) of the scattering atoms. Such studies have shown that the scattering is from a single atom of the scattering sample. For an electron beam with a well defined incident energy, the scattered electron energy at any angle from each atomic species is Doppler broadened. The broadening reflects the atomic momentum distribution contributed by both the internal and external motions of the molecular system. By measuring the Doppler broadening of the scattered electron lines it was possible to determine the kinetic energy of the scattering atom including that of its zero-point motion. Thus, the atomic kinetic energies in gases such as H2, D2, HD, CH4 and in H2O, D2O and NH3 were measured and compared with those calculated semi-empirically using the measured optical infra red (IR) and Raman frequencies of the internal vibrations of the molecules. In general, good agreement between the measured and calculated values was found. Electron scattering was also used to study the ratio of e-scattering intensities from the H- and O-atoms in water (H2O), where some anomalies were reported to exist.

  7. [Recent progress of neuroimaging studies on sleeping brain].

    PubMed

    Sasaki, Yuka

    2012-06-01

    Although sleep is a familiar phenomenon, its functions are yet to be elucidated. Understanding these functions of sleep is an important focus area in neuroscience. Electroencephalography (EEG) has been the predominantly used method in human sleep research but does not provide detailed spatial information about brain activation during sleep. To supplement the spatial information provided by this method, researchers have started using a combination of EEG and various advanced neuroimaging techniques that have been recently developed, including positron emission tomography (PET) and magnetic resonance imaging (MRI). In this paper, we will review the recent progress in sleep studies, especially studies that have used such advanced neuroimaging techniques. First, we will briefly introduce several neuroimaging techniques available for use in sleep studies. Next, we will review the spatiotemporal brain activation patterns during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, the dynamics of functional connectivity during sleep, and the consolidation of learning and memory during sleep; studies on the neural correlates of dreams, which have not yet been identified, will also be discussed. Lastly, possible directions for future research in this area will be discussed.

  8. Theoretical studies in nuclear reactions and nuclear structure. Progress report

    SciTech Connect

    Not Available

    1992-05-01

    Research in the Maryland Nuclear Theory Group focusses on problems in four basic areas of current relevance. Hadrons in nuclear matter; the structure of hadrons; relativistic nuclear physics and heavy ion dynamics and related processes. The section on hadrons in nuclear matter groups together research items which are aimed at exploring ways in which the properties of nucleons and the mesons which play a role in the nuclear force are modified in the nuclear medium. A very interesting result has been the finding that QCD sum rules supply a new insight into the decrease of the nucleon`s mass in the nuclear medium. The quark condensate, which characterizes spontaneous chiral symmetry breaking of the late QCD vacuum, decreases in nuclear matter and this is responsible for the decrease of the nucleon`s mass. The section on the structure of hadrons contains progress reports on our research aimed at understanding the structure of the nucleon. Widely different approaches are being studied, e.g., lattice gauge calculations, QCD sum rules, quark-meson models with confinement and other hedgehog models. A major goal of this type of research is to develop appropriate links between nuclear physics and QCD. The section on relativistic nuclear physics represents our continuing interest in developing an appropriate relativistic framework for nuclear dynamics. A Lorentz-invariant description of the nuclear force suggests a similar decrease of the nucleon`s mass in the nuclear medium as has been found from QCD sum rules. Work in progress extends previous successes in elastic scattering to inelastic scattering of protons by nuclei. The section on heavy ion dynamics and related processes reports on research into the e{sup +}e{sup {minus}} problem and heavy ion dynamics.

  9. Kinetics of Methane Hydrate Decomposition Studied via in Situ Low Temperature X-ray Powder Diffraction

    SciTech Connect

    Everett, Susan M; Rawn, Claudia J; Keffer, David J.; Mull, Derek L; Payzant, E Andrew; Phelps, Tommy Joe

    2013-01-01

    Gas hydrates are known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice termed self-preservation or anomalous preservation. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Two regions of slowed decomposition for methane hydrate, 180 200 K and 230 260 K, were observed, and the kinetics were studied by in situ low temperature x-ray powder diffraction. The kinetic constants for ice formation from methane hydrate were determined by the Avrami model within each region and activation energies, Ea, were determined by the Arrhenius plot. Ea determined from the data for 180 200 K was 42 kJ/mol and for 230 260 K was 22 kJ/mol. The higher Ea in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.

  10. Synchrotron Study on Crystallization Kinetics of Milk Fat under Shear Flow

    SciTech Connect

    Mazzanti, G.; Marangoni, A; Idziak, S

    2009-01-01

    A detailed synchrotron X-ray diffraction study on the kinetics of crystallization of anhydrous milk fat (AMF) and milk fat triacylglycerols (MFT) was done in a Couette cell at 17 C, 17.5 C and 20 C under shear rates between 0 and 2880 s-1. We observed shear-induced acceleration of the transition from phase ? to ?? and the presence of crystalline orientation, but no effect of shear on the onset time of phase ? was observed. A two stage regime was observed for the growth of phase ??. The first stage follows a series-parallel system of differential equations describing the conversion between liquid and crystalline phases. The second stage follows a diffusion-controlled regime. These mechanisms are consistent with the crystalline orientation, the growth of the crystalline domains and the observed displacement of the diffraction peak positions. The absence of the polar lipids explains the faster kinetics of MFT.

  11. Oxidation of psychotropic drugs by Chloramine-T in acid medium: a kinetic study using spectrophotometry

    NASA Astrophysics Data System (ADS)

    Saldanha, R. J. D.; Ananda, S.; Venkatesha, B. M.; Made Gowda, N. M.

    2002-03-01

    The kinetics of oxidation of psychotropic drugs, chlorpromazine hydrochloride (CPH) and fluphenazine dihydrochloride (FPH), by Chloramine-T (CAT) in pH 1.6 buffer medium has been studied spectrophotometrically at λmax=570 and 530 nm, respectively, at 30°C. The reaction rate shows a fractional-order dependence on [CAT] and first-order dependence on each [substrate]. The reaction rate also shows an inverse fractional-order in [H +]. Additions of halide ions and the reduction product of CAT, p-toluenesulfonamide, and variation of ionic strength and dielectric constant of the medium do not have any significant effect on the reaction rate. The activation parameters for the reaction were evaluated. The proposed general mechanism and the derived rate law are consistent with the observed kinetics.

  12. Kinetic study of free fatty acid esterification reaction catalyzed by recoverable and reusable hydrochloric acid.

    PubMed

    Su, Chia-Hung

    2013-02-01

    The catalytic performance and recoverability of several homogeneous acid catalysts (hydrochloric, sulfuric, and nitric acids) for the esterification of enzyme-hydrolyzed free fatty acid (FFA) and methanol were studied. Although all tested catalysts drove the reaction to a high yield, hydrochloric acid was the only catalyst that could be considerably recovered and reused. The kinetics of the esterification reaction catalyzed by hydrochloric acid was investigated under varying catalyst loading (0.1-1M), reaction temperature (303-343K), and methanol/FFA molar ratio (1:1-20:1). In addition, a pseudo-homogeneous kinetic model incorporating the above factors was developed. A good agreement (r(2)=0.98) between the experimental and calculated data was obtained, thus proving the reliability of the model. Furthermore, the reusability of hydrochloric acid in FFA esterification can be predicted by the developed model. The recoverable hydrochloric acid achieved high yields of FFA esterification within five times of reuse.

  13. New method for spectrophotometric determination of quinones and barbituric acid through their reaction. A kinetic study

    NASA Astrophysics Data System (ADS)

    Medien, H. A. A.

    1996-11-01

    A new and sensitive spectrophotometric method is described for the determination of p-benzoquinone, p-chloranil and 1.4-naphthoquinone. The method is based on the reaction between quinones and barbituric acid, by which a color is developed with maximum absorption between 485 and 555 nm in 50% methyl alcohol-water mixture. The absorption of the product obeys Beer's law within the concentration range 0.025-05 mM of orginal quinone. The kinetics of the reaction between p-benzoquinone and barbituric acid was studied in a range of methyl alcohol-water mixtures. The reaction follows overall second order kinetics, first order in each of the reactants. The rate increases with increasing dielectric constant. The method was applied for determination of barbituric acid with p-benzoquinone in the concentration range of 0.025-0.345 mM. Other barbiturates do not interfere.

  14. Accelerated hydrolysis of substituted cellulose for potential biofuel production: kinetic study and modeling.

    PubMed

    Mu, Bingnan; Xu, Helan; Yang, Yiqi

    2015-11-01

    In this work, kinetics of substitution accelerated cellulose hydrolysis with multiple reaction stages was investigated to lay foundation for mechanism study and molecular design of substituting compounds. High-efficiency hydrolysis of cellulose is critical for cellulose-based bioethanol production. It is known that, substitution could substantially decrease activation energy and increase reaction rate of acidic hydrolysis of glycosidic bonds in cellulose. However, reaction kinetics and mechanism of the accelerated hydrolysis were not fully revealed. In this research, it was proved that substitution therefore accelerated hydrolysis only occurred in amorphous regions of cellulose fibers, and was a process with multiple reaction stages. With molar ratio of substitution less than 1%, the overall hydrolysis rate could be increased for around 10 times. We also quantified the relationship between the hydrolysis rate of individual reaction stage and its major influences, including molar ratio of substitution, activation energy of acidic hydrolysis, pH and temperature.

  15. Adsorption of methylene blue onto jute fiber carbon: kinetics and equilibrium studies.

    PubMed

    Senthilkumaar, S; Varadarajan, P R; Porkodi, K; Subbhuraam, C V

    2005-04-01

    Jute fiber obtained from the stem of a plant was used to prepare activated carbon using phosphoric acid. Feasibility of employing this jute fiber activated carbon (JFC) for the removal of Methylene blue (MB) from aqueous solution was investigated. The adsorption of MB on JFC has found to dependent on contact time, MB concentration and pH. Experimental result follows Langmuir isotherm model and the capacity was found to be 225.64 mg/g. The optimum pH for the MB removal was found to be 5-10. The kinetic data obtained at different concentrations have been analyzed using a pseudo-first-order, pseudo-second-order equation, intraparticle diffusion and Elovich equation. Among the kinetic models studied, the intraparticle diffusion was the best applicable model to describe the adsorption of MB onto JFC.

  16. Thermodynamics and kinetics of graphene chemistry: a graphene hydrogenation prototype study.

    PubMed

    Pham, Buu Q; Gordon, Mark S

    2016-12-07

    The thermodynamic and kinetic controls of graphene chemistry are studied computationally using a graphene hydrogenation reaction and polyaromatic hydrocarbons to represent the graphene surface. Hydrogen atoms are concertedly chemisorped onto the surface of graphene models of different shapes (i.e., all-zigzag, all-armchair, zigzag-armchair mixed edges) and sizes (i.e., from 16-42 carbon atoms). The second-order Z-averaged perturbation theory (ZAPT2) method combined with Pople double and triple zeta basis sets are used for all calculations. It is found that both the net enthalpy change and the barrier height of graphene hydrogenation at graphene edges are lower than at their interior surfaces. While the thermodynamic product distribution is mainly determined by the remaining π-islands of functionalized graphenes (Phys. Chem. Chem. Phys., 2013, 15, 3725-3735), the kinetics of the reaction is primarily correlated with the localization of the electrostatic potential of the graphene surface.

  17. Removal of lead from aqueous solution using Syzygium cumini L.: equilibrium and kinetic studies.

    PubMed

    King, P; Rakesh, N; Beenalahari, S; Prasanna Kumar, Y; Prasad, V S R K

    2007-04-02

    The biosorption of lead ions from aqueous solution by Syzygium cumini L. was studied in a batch adsorption system as a function of pH, contact time, lead ion concentration, adsorbent concentration and adsorbent size. The biosorption capacities and rates of lead ions onto S. cumini L. were evaluated. The Langmuir, Freundlich, Redlich-Peterson and Temkin adsorption models were applied to describe the isotherms and isotherm constants. Biosorption isothermal data could be well interpreted by the Langmuir model followed by Temkin model with maximum adsorption capacity of 32.47 mg/g of lead ion on S. cumini L. leaves biomass. The kinetic experimental data were properly correlated with the second-order kinetic model.

  18. Study of the kinetics and mechanism of the thermal nitridation of SiO2

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Madhukar, A.; Grunthaner, F. J.; Naiman, M. L.

    1985-01-01

    X-ray photoelectron spectroscopy (XPS) has been used to study the nitridation time and temperature dependence of the nitrogen distribution in thermally nitrided SiO2 films. The XPS data show that the maximum nitrogen concentration near the (SiO(x)N(y)/Si interface is initially at the interface, but moves 20-25 A away from the interface with increasing nitridation time. Computer modeling of the kinetic processes involved is carried out and reveals a mechanism in which diffusing species, initially consisting primarily of nitrogen, react with the substrate, followed by formation of the oxygen-rich oxynitride due to reaction of the diffusing oxygen displaced by the slower nitridation of the SiO2. The data are consistent with this mechanism provided the influence of the interfacial strain on the nitridation and oxidation kinetics is explicitly accounted for.

  19. Kinetics and thermodynamics studies of silver ions adsorption onto coconut shell activated carbon.

    PubMed

    Silva-Medeiros, Flávia V; Consolin-Filho, Nelson; Xavier de Lima, Mateus; Bazzo, Fernando Previato; Barros, Maria Angélica S D; Bergamasco, Rosângela; Tavares, Célia R G

    2016-12-01

    The presence of silver in the natural water environment has been of great concern because of its toxicity, especially when it is in the free ion form (Ag(+)). This paper aims to study the adsorption kinetics of silver ions from an aqueous solution onto coconut shell activated carbon using batch methods. Batch kinetic data were fitted to the first-order model and the pseudo-second-order model, and this last equation fits correctly the experimental data. Equilibrium experiments were carried out at 30°C, 40°C, and 50°C. The adsorption isotherms were reasonably fit using Langmuir model, and the adsorption process was slightly influenced by changes in temperature. Thermodynamic parameters (ΔH°, ΔG°, and ΔS°) were determined. The adsorption process seems to be non-favorable, exothermic, and have an increase in the orderness.

  20. [Photosynthetic Parameters Inversion Algorithm Study Based on Chlorophyll Fluorescence Induction Kinetics Curve].

    PubMed

    Qiu, Xiao-han; Zhang, Yu-jun; Yin, Gao-fang; Shi, Chao-yi; Yu, Xiao-ya; Zhao, Nan-jing; Liu, Wen-qing

    2015-08-01

    The fast chlorophyll fluorescence induction curve contains rich information of photosynthesis. It can reflect various information of vegetation, such as, the survival status, the pathological condition and the physiology trends under the stress state. Through the acquisition of algae fluorescence and induced optical signal, the fast phase of chlorophyll fluorescence kinetics curve was fitted. Based on least square fitting method, we introduced adaptive minimum error approaching method for fast multivariate nonlinear regression fitting toward chlorophyll fluorescence kinetics curve. We realized Fo (fixedfluorescent), Fm (maximum fluorescence yield), σPSII (PSII functional absorption cross section) details parameters inversion and the photosynthetic parameters inversion of Chlorella pyrenoidosa. And we also studied physiological variation of Chlorella pyrenoidosa under the stress of Cu(2+).

  1. Degradation of colour in beetroot (Beta vulgaris L.): a kinetics study.

    PubMed

    Chandran, Janu; Nisha, P; Singhal, Rekha S; Pandit, Anirudha B

    2014-10-01

    The kinetics of colour (measured as Hunter 'a/b' value) degradation in beetroot puree (Beta vulgaris L.) was studied over a temperature range of 50-120 °C (isothermal process), and also during normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient 'EcoCooker' (non-isothermal heating process). The degradation of visual colour as measured as Hunter 'a/b' value was found to follow a first order kinetics, where the rate constant increased with an increase in the temperature. The temperature dependence of degradation was adequately modeled by Arrhenius equation. A mathematical model has been developed using the kinetic parameters obtained from the isothermal experiments to predict the losses of color in the non-isothermal heating/processing method based on the time-temperature data for each of the methods. The results obtained indicate a colour degradation of similar magnitude in all the three modes of cooking used in the study.

  2. Kinetic and mechanistic studies of free-radical reactions in combustion

    SciTech Connect

    Tully, F.P.

    1993-12-01

    Combustion is driven by energy-releasing chemical reactions. Free radicals that participate in chain reactions carry the combustion process from reactants to products. Research in chemical kinetics enables us to understand the microscopic mechanisms involved in individual chemical reactions as well as to determine the rates at which they proceed. Both types of information are required for an understanding of how flames burn, why engines knock, how to minimize the production of pollutants, and many other important questions in combustion. In this program the authors emphasize accurate measurements over wide temperature ranges of the rates at which ubiquitous free radicals react with stable molecules. The authors investigate a variety of OH, CN, and CH + stable molecule reactions important to fuel conversion, emphasizing application of the extraordinarily precise technique of laser photolysis/continuous-wave laser-induced fluorescence (LP/cwLIF). This precision enables kinetic measurements to serve as mechanistic probes. Since considerable effort is required to study each individual reaction, prudent selection is critical. Two factors encourage selection of a specific reaction: (1) the rates and mechanisms of the subject reaction are required input to a combustion model; and (2) the reaction is a chemical prototype which, upon characterization, will provide fundamental insight into chemical reactivity, facilitate estimation of kinetic parameters for similar reactions, and constrain and test the computational limits of reaction-rate theory. Most studies performed in this project satisfy both conditions.

  3. Kinetic Study to Predict Sigma Phase Formation in Duplex Stainless Steels

    NASA Astrophysics Data System (ADS)

    dos Santos, Daniella Caluscio; Magnabosco, Rodrigo

    2016-04-01

    This work presents an improved kinetic study of sigma phase formation during isothermal aging between 973 K and 1223 K (700 °C and 950 °C), based on Kolmogorov-Johnson-Mehl-Avrami (K-J-M-A) model, established from volume fraction of sigma phase determined in backscattered electron images over polished surfaces of aged samples. The kinetic study shows a change in the main mechanism of sigma formation between 973 K and 1173 K (700 °C and 900 °C), from a nucleation-governed stage to a diffusion-controlled growth-coarsening stage, confirmed by a double inclination in K-J-M-A plots and microstructural observations. A single inclination in K-J-M-A plots was observed for the 1223 K (950 °C) aging temperature, showing that kinetic behavior in this temperature is only related to diffusion-controlled growth of sigma phase. The estimated activation energies for the nucleation of sigma phase are close to the molybdenum diffusion in ferrite, probably the controlling mechanism of sigma phase nucleation. The proposed time-temperature-transformation (TTT) diagram shows a "double c curve" configuration, probably associated to the presence of chi-phase formed between 973 K and 1073 K (700 °C and 800 °C), which acts as heterogeneous nuclei for sigma phase formation in low aging temperatures.

  4. Study of the diffusion of points defects in crystalline silicon using the kinetic ART method

    NASA Astrophysics Data System (ADS)

    Trochet, Mickael; Brommer, Peter; Beland, Laurent-Karim; Joly, Jean-Francois; Mousseau, Normand

    2013-03-01

    Because of the long-time scale involved, the activated diffusion of point defects is often studied in standard molecular dynamics at high temperatures only, making it more difficult to characterize complex diffusion mechanisms. Here, we turn to the study of point defect diffusion in crystalline silicon using kinetic ART (kART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building based on the activation-relaxation technique (ART nouveau). By generating catalogs of diffusion mechanisms and fully incorporating elastic and off-lattice effects, kART is a unique tool for characterizing this problem. More precisely, using kART with the standard Stillinger-Weber potential we consider the evolution of crystalline cells with 1 to 4 vacancies and 1 to 4 interstitials at various temperatures and to provide a detailed picture of both the atomistic diffusion mechanisms and overall kinetics in addition to identifying special configurations such as a 2-interstitial super-diffuser.

  5. Understanding long-time vacancy aggregation in iron: A kinetic activation-relaxation technique study

    NASA Astrophysics Data System (ADS)

    Brommer, Peter; Béland, Laurent Karim; Joly, Jean-François; Mousseau, Normand

    2014-10-01

    Vacancy diffusion and clustering processes in body-centered-cubic (bcc) Fe are studied using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities. For monovacancies and divacancies, k-ART recovers previously published results while clustering in a 50-vacancy simulation box agrees with experimental estimates. Applying k-ART to the study of clustering pathways for systems containing from one to six vacancies, we find a rich set of diffusion mechanisms. In particular, we show that the path followed to reach a hexavacancy cluster influences greatly the associated mean-square displacement. Aggregation in a 50-vacancy box also shows a notable dispersion in relaxation time associated with effective barriers varying from 0.84 to 1.1 eV depending on the exact pathway selected. We isolate the effects of long-range elastic interactions between defects by comparing to simulations where those effects are deliberately suppressed. This allows us to demonstrate that in bcc Fe, suppressing long-range interactions mainly influences kinetics in the first 0.3 ms, slowing down quick energy release cascades seen more frequently in full simulations, whereas long-term behavior and final state are not significantly affected.

  6. Thermal behavior and kinetic study for catalytic co-pyrolysis of biomass with plastics.

    PubMed

    Zhang, Xuesong; Lei, Hanwu; Zhu, Lei; Zhu, Xiaolu; Qian, Moriko; Yadavalli, Gayatri; Wu, Joan; Chen, Shulin

    2016-11-01

    The present study aims to investigate the thermal decomposition behaviors and kinetics of biomass (cellulose/Douglas fir sawdust) and plastics (LDPE) in a non-catalytic and catalytic co-pyrolysis over ZSM-5 catalyst by using a thermogravimetric analyzer (TGA). It was found that there was a positive synergistic interaction between biomass and plastics according to the difference of weight loss (ΔW), which could decrease the formation of solid residue at the end of the experiment. The first order reaction model well fitted for both non-catalytic and catalytic co-pyrolysis of biomass with plastics. The activation energy (E) of Cellulose-LDPE-Catalyst and DF-LDPE-Catalyst are only 89.51 and 54.51kJ/mol, respectively. The kinetics analysis showed that adding catalyst doesn't change the decomposition mechanism. As a result, the kinetic study on catalytic co-pyrolysis of biomass with plastics was suggested that the catalytic co-pyrolysis is a promising technique that can significantly reduce the energy input.

  7. Chemical kinetic study of the oxidation of toluene and related cyclic compounds

    SciTech Connect

    Mehl, M; Frassoldati, A; Fietzek, R; Faravelli, T; Pitz, W; Ranzi, E

    2009-10-01

    Chemical kinetic models of hydrocarbons found in transportation fuels are needed to simulate combustion in engines and to improve engine performance. The study of the combustion of practical fuels, however, has to deal with their complex compositions, which generally involve hundreds of compounds. To provide a simplified approach for practical fuels, surrogate fuels including few relevant components are used instead of including all components. Among those components, toluene, the simplest of the alkyl benzenes, is one of the most prevalent aromatic compounds in gasoline in the U.S. (up to 30%) and is a promising candidate for formulating gasoline surrogates. Unfortunately, even though the combustion of aromatics been studied for a long time, the oxidation processes relevant to this class of compounds are still matter of discussion. In this work, the combustion of toluene is systematically approached through the analysis of the kinetics of some important intermediates contained in its kinetic submechanism. After discussing the combustion chemistry of cyclopentadiene, benzene, phenol and, finally, of toluene, the model is validated against literature experimental data over a wide range of operating conditions.

  8. Equilibrium, kinetic and thermodynamic study of cesium adsorption onto nanocrystalline mordenite from high-salt solution.

    PubMed

    Lee, Keun-Young; Park, Minsung; Kim, Jimin; Oh, Maengkyo; Lee, Eil-Hee; Kim, Kwang-Wook; Chung, Dong-Yong; Moon, Jei-Kwon

    2016-05-01

    In this study, the equilibrium, kinetics and thermodynamics of cesium adsorption by nanocrystalline mordenite were investigated under cesium contamination with high-salt solution, simulating the case of an operation and decommissioning of nuclear facilities or an accident during the processes. The adsorption rate constants were determined using a pseudo second-order kinetic model. The kinetic results strongly demonstrated that the cesium adsorption rate of nano mordenite is extremely fast, even in a high-salt solution, and much faster than that of micro mordenite. In the equilibrium study, the Langmuir isotherm model fit the cesium adsorption data of nano mordenite better than the Freundlich model, which suggests that cesium adsorption onto nano mordenite is a monolayer homogeneous adsorption process. The obtained thermodynamic parameters indicated that the adsorption involved a very stable chemical reaction. In particular, the combination of rapid particle dispersion and rapid cesium adsorption of the nano mordenite in the solution resulted in a rapid and effective process for cesium removal without stirring, which may offer great advantages for low energy consumption and simple operation.

  9. Current progress of DNA vaccine studies in humans.

    PubMed

    Lu, Shan; Wang, Shixia; Grimes-Serrano, Jill M

    2008-03-01

    Despite remarkable progress in the field of DNA vaccine research since its discovery in the early 1990 s, the formal acceptance of this novel technology as a new modality of human vaccines depends on the successful demonstration of its safety and efficacy in advanced clinical trials. Although clinical trials conducted so far have provided overwhelming evidence that DNA vaccines are well tolerated and have an excellent safety profile, the early designs of DNA vaccines failed to demonstrate sufficient immunogenicity in humans. However, studies conducted over the last few years have led to promising results, particularly when DNA vaccines were used in combination with other forms of vaccines. Here, we provide a review of the data from reported DNA vaccine clinical studies with an emphasis on the ability of DNA vaccines to elicit antigen-specific, cell-mediated and antibody responses in humans. The majority of these trials are designed to test candidate vaccines against several major human pathogens and the remaining studies tested the immunogenicity of therapeutic vaccines against cancer.

  10. Kafirin adsorption on ion-exchange resins: isotherm and kinetic studies.

    PubMed

    Kumar, Prashant; Lau, Pei Wen; Kale, Sandeep; Johnson, Stuart; Pareek, Vishnu; Utikar, Ranjeet; Lali, Arvind

    2014-08-22

    Kafirin is a natural, hydrophobic and celiac safe prolamin protein obtained from sorghum seeds. Today kafirin is found to be useful in designing delayed delivery systems and coatings of pharmaceuticals and nutraceuticals where its purity is important and this can be obtained by adsorptive chromatography. This study is the first scientific insight into the isotherm and kinetic studies of kafirin adsorption on anion- and cation-exchange resins for practical applications in preparative scale chromatography. Adsorption isotherms of kafirin were determined for five anion- and two cation-exchange resins in batch systems. Isotherm parameters such as maximum binding capacity and dissociation constant were determined from Langmuir isotherm, and adsorptive capacity and affinity constant from Freundlich isotherm. Langmuir isotherm was found to fit the adsorption equilibrium data well. Batch uptake kinetics for kafirin adsorption on these resins was also carried out and critical parameters including the diffusion coefficient, film mass transfer coefficient, and Biot number for film-pore diffusion model were calculated. Both the isotherm and the kinetic parameters were considered for selection of appropriate resin for kafirin purification. UNOsphere Q (78.26 mg/ml) and Toyopearl SP-650M (57.4 mg/ml) were found to offer better kafirin binding capacities and interaction strength with excellent uptake kinetics under moderate operating conditions. With these adsorbents, film diffusion resistance was found to be major governing factor for adsorption (Bi<10 and δ<1). Based on designer objective function, UNOsphere Q was found be best adsorbent for binding of kafirin. The data presented is valuable for designing large scale preparative adsorptive chromatographic kafirin purification systems.

  11. Kinetics and mechanisms of NO{sub x} - char reduction. Quarterly technical progress report, May 1, 1995--July 31, 1995

    SciTech Connect

    Suuberg, E.M.

    1995-12-01

    The emission of nitrogen oxides from combustion of coal remains a problem of considerable interest, whether the concern is with acid rain, stratospheric ozone chemistry, or {open_quotes}greenhouse{close_quotes} gases. Whereas earlier the concern was focused mainly on NO (as a primary combustion product) and to a lesser extent NO{sub 2} (since it is mainly a secondary product of combustion), in recent years the emissions of N{sub 2}O have also captured considerable attention, particularly in the context of fluidized bed combustion, in which the problem appears to be most acute. The research community has only recently begun to take solid hold on the N{sub 2}O problem. This is in part because earlier estimates of the importance of N{sub 2}O in combustion processes were clouded by artifacts in sampling which have now been resolved. This project is concerned with the mechanism of reduction of both NO and N{sub 2}O by carbons. It was recognized some years ago that NO formed during fluidized bed coal combustion can be heterogeneously reduced in-situ by the carbonaceous solid intermediates of combustion. This has been recently supplemented by the knowledge that heterogeneous reaction with carbon can also play an important role in reducing emissions of N{sub 2}O, but that the NO-carbon reactions might also contribute to formation of N{sub 2}O. The precise role of carbon in N{sub 2}O reduction and formation has yet to be established, since in one case the authors of a recent study were compelled to comment that {open_quotes}the basic knowledge of N{sub 2}O formation and reduction still has to be improved{close_quotes}. The same can be said of the NO-carbon system. In this program, carbons studied include graphite, resin char, coconut char, and a Wyodak coal char.

  12. Biosorption Behavior of Ciprofloxacin onto Enteromorpha prolifera: Isotherm and Kinetic Studies.

    PubMed

    Wu, Shaoling; Li, Yanhui; Zhao, Xindong; Du, Qiuju; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

    2015-01-01

    The studies aimed at the feasibility of using Enteromorpha prolifera for the removal of ciprofloxacin from aqueous solutions. Batch experiments were carried out for the biosorption of ciprofloxacin onto Enteromorpha prolifera. The factors affecting the biosorption process such as the initial concentration, dosage, pH and the contact time were studied. Enteromorpha prolifera exhibited a maximum biosorption capacity of 21.7 mg/g. The pseudo-second-order kinetic model described the ciprofloxacin biosorption process with a good fitting. The optimum pH of ciprofloxacin adsorbed by Enteromorpha prolifera was 10. Biosorption equilibrium studies demonstrated that the biosorption followed Freundlich isotherm model, which implied a heterogeneous biosorption phenomenon.

  13. Kinetics and mechanisms of NOx - char reduction. Quarterly technical progress report, August 1, 1995--October 31, 1995

    SciTech Connect

    Suuberg, E.M.; Lilly, W.D.; Aarna, I.

    1996-05-01

    The emission of nitrogen oxides from combustion of coal remains a problem of considerable interest, whether the concern is with acid rain, stratospheric ozone chemistry, or {open_quotes}greenhouse{close_quotes} gases. Whereas earlier the concern was focused mainly on NO (as a primary combustion product) and to a lesser extent NO{sub 2} (since it is mainly a secondary product of combustion), in recent years the emissions of N{sub 2}O have also captured considerable attention, particularly in the context of fluidized bed combustion, in which the problem appears to be most acute. The research community has only recently begun to take solid hold on the N{sub 2}O problem. This is in part because earlier estimates of the importance of N{sub 2}O in combustion processes were clouded by artifacts in sampling which have now been resolved. This project is concerned with the mechanism of reduction of both NO and N{sub 2}O by carbons. It was recognized some years ago that NO formed during fluidized bed coal combustion can be heterogeneously reduced in-situ by the carbonaceous solid intermediates of combustions. This has been recently supplemented by the knowledge that heterogeneous reaction with carbon can also play an important role in reducing emissions of N{sub 2}O, but that the NO-carbon reactions might also contribute to formation of N{sub 2}O. The precise role of carbon in N{sub 2}O reduction and formation has yet to be established, since in one case the authors of a recent study were compelled to comment that the basic knowledge of N{sub 2}O formation and reduction still has to be improved. The same can be said of the NO-carbon system.

  14. Kinetics of Mn-based sorbents for hot coal gas desulfurization. Quarterly progress report, July 15, 1995--September 15, 1995

    SciTech Connect

    Hepworth, M.T.

    1995-09-15

    The Morgantown Energy Technology Center (METC) of the U.S. Department of Energy (DOE) is actively pursuing the development of reliable and cost-effective processes to clean coal gasifier gases for application to integrated gasification combined cycle (IGCC) and molten carbonate fuel cell (MCFC) power plants. A large portion of gas cleanup research has been directed towards hot gas desulfurization using Zn-based sorbents. However, zinc titinate sorbents undergo reduction to the metal at temperatures approaching 700{degrees}C. In addition, sulfate formation during regeneration leads to spalling of reactive 293 surfaces. Due to zinc-based sorbent performance, METC has shown interest in formulating and testing manganese-based sorbents. Westmoreland and Harrison evaluated numerous candidate sulfur sorbents and identified Mn as a good candidate. Later, Turkdogan and Olsson tested manganese-based sorbents which demonstrated superior desulfurization capacity under high temperatures, and reducing conditions. Recently, Ben-Slimane and Hepworth conducted several studies on formulating Mn-sorbents and desulfurizing a simulated fuel gas. Although thermodynamics predicts higher over-pressures with Mn verses Zn, under certain operating conditions Mn-based sorbents may obtain < 20 ppmv. In addition, the manganese-sulfur-oxygen (Mn-S-O) system does not reduce to the metal under even highly reducing gases at high temperatures (550-900{degrees}C). Currently, many proposed IGCC processes include a water quench prior to desulfurization. This is for two reasons; limitations in the process hardware (1000{degrees}C), and excessive Zn-based sorbent loss (about 700{degrees}C). With manganese the water quench is obviated due to sorbent loss, as Mn-based sorbents have been shown to retain reactivity under cycling testing at 900{degrees}C. This reduces system hardware, and increases thermal efficiency while decreasing the equilibrium H{sub 2}S over-pressure obtainable with a manganese sorbent.

  15. The Progress of Metabolomics Study in Traditional Chinese Medicine Research.

    PubMed

    Wang, Pengcheng; Wang, Qiuhong; Yang, Bingyou; Zhao, Shan; Kuang, Haixue

    2015-01-01

    Traditional Chinese medicine (TCM) has played important roles in health protection and disease treatment for thousands of years in China and has gained the gradual acceptance of the international community. However, many intricate issues, which cannot be explained by traditional methods, still remain, thus, new ideas and technologies are needed. As an emerging system biology technology, the holistic view adopted by metabolomics is similar to that of TCM, which allows us to investigate TCM with complicated conditions and multiple factors in depth. In this paper, we tried to give a timely and comprehensive update about the methodology progression of metabolomics, as well as its applications, in different fields of TCM studies including quality control, processing, safety and efficacy evaluation. The herbs investigated by metabolomics were selected for detailed examination, including Anemarrhena asphodeloides Bunge, Atractylodes macrocephala Kidd, Pinellia ternate, etc.; furthermore, some valuable results have been obtained and summarized. In conclusion, although the study of metabolomics is at the early phase and requires further scrutiny and validation, it still provides bright prospects to dissect the synergistic action of multiple components from TCM. Overall, with the further development of analytical techniques, especially multi-analysis techniques, we expect that metabolomics will greatly promote TCM research and the establishment of international standards, which is beneficial to TCM modernization.

  16. Infrared absorption spectroscopy and chemical kinetics of free radicals. Progress report, February 1, 1991--March 1, 1994

    SciTech Connect

    Curl, R.F.; Glass, G.P.

    1994-08-01

    Rate of reaction of ketenyl radical with O{sub 2} at room temperature was determined as 6.5(6) {times} 10-{sup {minus}13} CM{sup 3} molecules{sup {minus}1} s{sup {minus}1} and an upper bound of 1 {times} 10{sup {minus}13} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} was estimated for the reaction rate of acetylene with ketenyl. The high resolution spectrum of the {nu}1 acetylenic CH stretch of propargy1 radical (HCCCH{sub 2}) near 3322 cm{sup {minus}1} has obtained and analyzed. Nuclear spin weights demonstrate that the CH{sub 2} hydrogen atoms are in the carbon atom plane. We have attempted to measure the propargy1 recombination rate constant at 296 K; however, the observed rate constant of (1.2{times}0.2) x 10{sup {minus}10} cc-molecule{sup {minus}1}-s{sup {minus}1} may be affected by other reactions. The CH stretch fundamental, {nu}1, of HCCN has been observed, assigned, and analyzed. Analysis of the hot bands associated with bending shows that HCCN is a quasilinear molecule with a very floppy potential function for the HCC bending angle. The barrier to linearity is estimated to be about 100 cm{sup {minus}1}. Rate of the reaction between C{sub 2}H and H{sub 2} has been measured at 295--855 K. The rate constant exhibited a non-Arrhenius form well represented by k = (9.44{plus_minus}0.50) {times} 10{sup {minus}14}T{sup 0.9}exp(-1003{plus_minus}40/T)cm{sup 3}molecule{sup {minus}1}s{sup {minus}1}. The reaction between atomic oxygen and the amidogen radical, NH{sub 2} has been studied at 295 K; the room temperature rate constant was measured as (6.5 {plus_minus} 1.3) {times} 10{sup {minus}1} s{sup {minus}1}. The minor channel leading to NH + OH was observed but accounted for at most about 8% of the NH{sub 2} reacting. The rate constant for the reaction NH+O was determined from fitting the NH time profile to be 6.6{plus_minus}10{sub {minus}11} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}.

  17. Use of a Reliable Homemade Dilatometer To Study the Kinetics of the Radical Chain Polymerization of PMMA: An Undergraduate Polymer Chemistry Laboratory Kinetics Experiment

    NASA Astrophysics Data System (ADS)

    Mendicuti, Francisco; Martín, Olga; Tarazona, Maria Pilar

    1998-11-01

    In this laboratory experiment, a simple, reliable homemade dilatometer was used to study the kinetics of the radical chain polymerization of PMMA. The reaction was carried out in toluene with benzoyl peroxide as the initiator at a temperature of 80 °C. Each student studied the kinetics at a different initiator concentration constant. Pseudo-first-order plots permit students to obtain kapp and to demonstrate order 1 with respect to the monomer concentration. Finally, a log-log plot of kapp versus the initiator concentration from the data collected by each student demonstrates order 0.5 with respect to the initiator concentration. Results also agree with the rate constants of the process implicated in this type of polymerization.

  18. Progressive statistics for studies in sports medicine and exercise science.

    PubMed

    Hopkins, William G; Marshall, Stephen W; Batterham, Alan M; Hanin, Juri

    2009-01-01

    Statistical guidelines and expert statements are now available to assist in the analysis and reporting of studies in some biomedical disciplines. We present here a more progressive resource for sample-based studies, meta-analyses, and case studies in sports medicine and exercise science. We offer forthright advice on the following controversial or novel issues: using precision of estimation for inferences about population effects in preference to null-hypothesis testing, which is inadequate for assessing clinical or practical importance; justifying sample size via acceptable precision or confidence for clinical decisions rather than via adequate power for statistical significance; showing SD rather than SEM, to better communicate the magnitude of differences in means and nonuniformity of error; avoiding purely nonparametric analyses, which cannot provide inferences about magnitude and are unnecessary; using regression statistics in validity studies, in preference to the impractical and biased limits of agreement; making greater use of qualitative methods to enrich sample-based quantitative projects; and seeking ethics approval for public access to the depersonalized raw data of a study, to address the need for more scrutiny of research and better meta-analyses. Advice on less contentious issues includes the following: using covariates in linear models to adjust for confounders, to account for individual differences, and to identify potential mechanisms of an effect; using log transformation to deal with nonuniformity of effects and error; identifying and deleting outliers; presenting descriptive, effect, and inferential statistics in appropriate formats; and contending with bias arising from problems with sampling, assignment, blinding, measurement error, and researchers' prejudices. This article should advance the field by stimulating debate, promoting innovative approaches, and serving as a useful checklist for authors, reviewers, and editors.

  19. Kinetics and thermodynamic studies for removal of acid blue 129 from aqueous solution by almond shell

    PubMed Central

    2014-01-01

    Efficiency and performance of Almond shell (AS) adsorbent for the removal and recovery of Acid Blue 129 (AB129) from wastewater is presented in this report. The influence of variables including pH, initial dye concentration, adsorbent dosage, particle size, contact time and temperature on the dye removal have been investigated in batch method by one at a time optimization method. The experimental equilibrium data were tested by four widely used isotherm models namely, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich (D–R). It was found that adsorption of AB129 on AS well with the Langmuir isotherm model, implying monolayer coverage of dye molecules onto the surface of the adsorbent. More than 98% removal efficiency was obtained within 14 min at adsorbent dose of 0.4 g for initial dye concentration of 40 mg/L at pH 2. Kinetics of the adsorption process was tested by pseudo-first-order and pseudo-second-order kinetics, and intraparticle diffusion mechanism. Pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order model. Calculation of various thermodynamic parameters such as, Gibb’s free energy, entropy and enthalpy of the on-going adsorption process indicate feasibility and endothermic nature of AB129 adsorption on all adsorbents. This work can be used in design of adsorption columns for dyes removal. PMID:24620822

  20. Kinetics, thermodynamics and mechanistic studies of carbofuran removal using biochars from tea waste and rice husks.

    PubMed

    Vithanage, Meththika; Mayakaduwa, S S; Herath, Indika; Ok, Yong Sik; Mohan, Dinesh

    2016-05-01

    This study reports the thermodynamic application and non-linear kinetic models in order to postulate the mechanisms and compare the carbofuran adsorption behavior onto rice husk and tea waste derived biochars. Locally available rice husk and infused tea waste biochars were produced at 700 °C. Biochars were characterized by using proximate, ultimate and surface characterization methods. Batch experiments were conducted at 25, 35, and 45 °C for a series of carbofuran solutions ranging from 5 to 100 mg L(-1) with a biochar dose of 1 g L(-1) at pH 5.0 with acetate buffer. Molar O/C ratios indicated that rice husk biochar (RHBC700) is more hydrophilic than tea waste biochar (TWBC700). Negative ΔG (Gibbs free energy change) values indicated the feasibility of carbofuran adsorption on biochar. Increasing ΔG values with the rise in temperature indicated high favorability at higher temperatures for both RHBC and TWBC. Enthalpy values suggested the involvement of physisorption type interactions. Kinetic data modeling exhibited contribution of both physisorption, via pore diffusion, π*-π electron donor-acceptor interaction, H-bonding, and van der Waals dispersion forces and chemisorption via chemical bonding with phenolic, and amine groups. Equilibrium adsorption capacities of RHBC and TWBC determined by pseudo second order kinetic model were 25.2 and 10.2 mg g(-1), respectively.

  1. Equilibrium and kinetics study on hexavalent chromium adsorption onto diethylene triamine grafted glycidyl methacrylate based copolymers.

    PubMed

    Maksin, Danijela D; Nastasović, Aleksandra B; Milutinović-Nikolić, Aleksandra D; Suručić, Ljiljana T; Sandić, Zvjezdana P; Hercigonja, Radmila V; Onjia, Antonije E

    2012-03-30

    Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25-70°C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q(max), at pH 1.8 and 25°C was 143 mg g(-1) for PGME2-deta (sample with the highest amino group concentration) while at 70°C Q(max) reached the high value of 198 mg g(-1). Thermodynamic parameters revealed spontaneous and endothermic nature of Cr(VI) adsorption onto PGME-deta.

  2. Binding kinetics of triclosan (Irgasan) to alloplastic vascular grafts: an in vitro study.

    PubMed

    Hernández-Richter, T; Schardey, H M; Löhlein, F; Fleischer, C T; Walli, A K; Boos, K S; Schildberg, F W

    2000-07-01

    The aim of this study was to investigate the binding kinetics of triclosan (Irgasan) to alloplastic vascular grafts and to examine its antimicrobial activity against various microbial pathogens in vitro. Vascular grafts made by Intergard (Intervascular), Fluoropassiv (Vascutek), and Gore-tex (Gore) were examined. Grafts were incubated in 10 g/L triclosan (Irgasan), dried, sterilized, and incubated in RPMI medium. One-centimeter segments of the grafts were resected under sterile conditions at intervals of minutes, then hours, followed by days and up to 4 weeks. Samples were stored frozen at -20 degrees C for the measurement of triclosan bound to the vascular graft by high-performance liquid chromatography (HPLC). The binding kinetics under perfusion conditions were determined for Intergard grafts, which were perfused with 50 mL of nutrient medium for 24 hr. Samples were taken at various time intervals for the measurement of triclosan. The antimicrobial activity of triclosan against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans as well as Enterococcus faecium was determined. Triclosan effectively binds to vascular graft without the use of intermediate binding substances. It stayed on the graft for the duration of 4 weeks. Under both static and perfusion conditions, the binding kinetics are similar. Triclosan binds most effectively to Intergard grafts, less so to Fluoropassiv grafts, and not at all to Gore-tex material. Antimicrobial activity of triclosan is very effective against S. aureus and E. faecium but not against P. aeruginosa.

  3. Comparative Studies of the Pyrolytic and Kinetic Characteristics of Maize Straw and the Seaweed Ulva pertusa

    PubMed Central

    Ye, Naihao; Li, Demao; Chen, Limei; Zhang, Xiaowen; Xu, Dong

    2010-01-01

    Seaweed has attracted considerable attention as a potential biofuel feedstock. The pyrolytic and kinetic characteristics of maize straw and the seaweed Ulva pertusa were studied and compared using heating rates of 10, 30 and 50°C min−1 under an inert atmosphere. The activation energy, and pre-exponential factors were calculated by the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Popescu methods. The kinetic mechanism was deduced by the Popescu method. The results indicate that there are three stages to the pyrolysis; dehydration, primary devolatilization and residual decomposition. There were significant differences in average activation energy, thermal stability, final residuals and reaction rates between the two materials. The primary devolatilization stage of U. pertusa can be described by the Avramic-Erofeev equation (n = 3), whereas that of maize straw can be described by the Mampel Power Law (n = 2). The average activation energy of maize straw and U. pertusa were 153.0 and 148.7 KJ mol−1, respectively. The pyrolysis process of U.pertusa would be easier than maize straw. And co-firing of the two biomass may be require less external heat input and improve process stability. There were minor kinetic compensation effects between the pre-exponential factors and the activation energy. PMID:20844751

  4. Kinetic study on the isothermal and nonisothermal crystallization of monoglyceride organogels.

    PubMed

    Meng, Zong; Yang, Lijun; Geng, Wenxin; Yao, Yubo; Wang, Xingguo; Liu, Yuanfa

    2014-01-01

    The isothermal and nonisothermal crystallization kinetics of monoglyceride (MAG) organogels were studied by pulsed nuclear magnetic resonance (pNMR) and differential scanning calorimetry (DSC), respectively. The Avrami equation was used to describe the isothermal crystallization kinetics and experimental data fitted the equation fairly well. Results showed that the crystal growth of MAG organogels was a rod-like growth of instantaneous nuclei at higher degrees of supercooling and a plate-like form with high nucleation rate at lower degrees of supercooling. The exothermic peak in nonisothermal DSC curves for the MAG organogels became wider and shifted to lower temperature when the cooling rate increased, and nonisothermal crystallization was analyzed by Mo equation. Results indicated that at the same crystallization time, to get a higher degree of relative crystallinity, a higher cooling rate was necessary. The activation energy of nonisothermal crystallization was calculated as 739.59 kJ/mol according to the Kissinger method. Therefore, as the results of the isothermal and nonisothermal crystallization kinetics for the MAG organogels obtained, the crystallization rate, crystal nucleation, and growth during the crystallization process could be preliminarily monitored through temperature and cooling rate regulation, which laid the foundation for the real industrial manufacture and application of the MAG organogels.

  5. Kinetic study of the mass transfer of bovine serum albumin in anion-exchange chromatography.

    PubMed

    Miyabe, K; Guiochon, G

    2000-01-14

    A kinetic study was made on the mass transfer phenomena of bovine serum albumin (BSA) in two different anion-exchange columns (Resource-Q and TSK-GEL-DEAE-5PW). The analysis of the concentration dependence of the lumped mass transfer rate coefficient (km,L) provided the information about the kinetics of the several mass transfer processes in the columns and the anion exchangers, i.e., the axial dispersion, the fluid-to-particle mass transfer, the intraparticle diffusion, and the adsorption/desorption. In the Resource-Q column, the intraparticle diffusion had a dominant contribution to the band broadening compared with those of the other processes. The surface diffusion coefficient (Ds) of BSA showed a positive concentration dependence, by which the linear dependence of km,L on the BSA concentration seemed to be interpreted. On the other hand, in the TSK-GEL-DEAE-5PW column, the contribution of the adsorption/desorption was also important and almost same as that due to the intraparticle diffusion. There are some differences between the intrinsic properties of the mass transfer kinetics inside the two anion exchangers. It was likely that the positive concentration dependence of Ds was explained by the heterogeneous surface model.

  6. Study the oxidation kinetics of uranium using XRD and Rietveld method

    NASA Astrophysics Data System (ADS)

    Zhang, Yanzhi; Guan, Weijun; Wang, Qinguo; Wang, Xiaolin; Lai, Xinchun; Shuai, Maobing

    2010-03-01

    The surface oxidation of uranium metal has been studied by X-ray diffraction (XRD) and Rietveld method in the range of 50~300°C in air. The oxidation processes are analyzed by XRD to determine the extent of surface oxidation and the oxide structure. The dynamics expression for the formation of UO2 was derived. At the beginning, the dynamic expression was nonlinear, but switched to linear subsequently for uranium in air and humid oxygen. That is, the growth kinetics of UO2 can be divided into two stages: nonlinear portion and linear portion. Using the kinetic data of linear portion, the activation energy of reaction between uranium and air was calculated about 46.0 kJ/mol. However the content of oxide as a function of time was linear in humid helium ambience. Contrast the dynamics results, it prove that the absence of oxygen would accelerate the corrosion rate of uranium in the humid gas. We can find that the XRD and Rietveld method are a useful convenient method to estimate the kinetics and thermodynamics of solid-gas reaction.

  7. Kinetic study for copper adsorption onto soil minerals in the absence and presence of humic acid.

    PubMed

    Komy, Zanaty R; Shaker, Ali M; Heggy, Said E M; El-Sayed, Mohamed E A

    2014-03-01

    Equilibrium and kinetics of Cu(2+) adsorption onto soil minerals (kaolinite and hematite) in the absence and presence of humic acid have been investigated under various conditions. The influences of ionic strength, pH and solution cations on the rate of the adsorption have been studied. The rate and the amount of adsorbed Cu(2+) onto soil minerals in the absence or the presence of humic acid increased with decreasing ionic strength, increasing pH and in the presence of the background electrolyte K(+) rather than Ca(2+). Humic acid enhanced the rate and the amount of adsorbed Cu(2+) onto soil minerals. The adsorption equilibrium data showed that adsorption behavior of Cu(2+) could be described more reasonably by Langmiur adsorption isotherm than Freundlich isotherm in the absence or presence of humic acid. Pseudo first and pseudo second order models were used to evaluate the kinetic data and the rate constants. The results indicated that the adsorption of Cu(2+) onto hematite and kaolinite in the absence and presence of humic acid is more conforming to pseudo second order kinetics.

  8. Multinuclear magnetic resonance and kinetic studies of single amino acid replacements in staphylococcal nuclease

    SciTech Connect

    Grissom, C.B.; Alexandrescu, A.T.; Ulrich, E.L.; Mills, D.A.; Markley, J.L.

    1986-05-01

    Staphylococcal nuclease hydrolyzes the 5'-phosphate bond of deoxythymidine 5'-p-nitrophenylphosphate to yield p-nitrophenyl phosphate (PNPP) and deoxythymidine in the presence of Ca/sup 2 +/. The PNPP produced can be hydrolyzed to p-nitrophenol and inorganic phosphate by alkaline phosphatase in a coupled assay to provide a chromophore suitable for kinetic studies. By using this assay, the following single amino acid replacements have been characterized at 20 mM Ca/sup 2 +/ and pH 9.25 with the following results (kinetic parameters are expressed relative to those for SNase). SNase, Km = 2.5 mM, V = 1, V/K = 1; substitution of Tyr for Phe at position 85 (Y85F), Km = 61 mM, V/K = 1; H124R, Km = 3.8 mM, V = 3, V/K = 6; H46Y, Km = 2.5 mM, V = 0.78, V/K = 0.66; F76V, Km = 2.4 mM, V = 2.1, and V/K = 2. Only a small perturbation in the kinetic constants is seen for H124R, H46Y, and F76V. Removal of the hydroxyl from tyrosine 85 diminishes the affinity for substrate. Interactions of the wild-type and variant nucleases with metal ions and inhibitors are being investigated by /sup 1/H, /sup 13/C, and /sup 113/Cd NMR.

  9. Kinetic evaluation study on the bioactivity of silver doped hydroxyapatite-polyvinyl alcohol nanocomposites.

    PubMed

    Mostafa, Amany A; Oudadesse, Hassane; El Sayed, Mayyada M H; Kamal, Gehan; Kamel, Mohamed; Foad, Enas

    2014-12-01

    This work investigates the effect of adding silver nanoparticles (NPs) in ppm on the bioactivity of hydroxyapatite/polyvinyl alcohol nanocomposites (HAV). HAV prepared by an in situ biomimetic approach was doped with different concentrations of silver NPs (HAV-Ag), and the formed powder samples were characterized by different techniques such as Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-EOS), X-ray diffraction, transmission electron microscope, and Fourier Transform Infrared Spectroscopy. Bioactivity was evaluated in simulated body fluid through studying the kinetics of Ca and P uptake onto the different HAV-Ag nanocomposites. Uptake profiles of Ca and P were well described by a pseudo-second order kinetic model, and the obtained kinetic parameters confirmed that the highest uptake capacities were achieved by adding less than 0.001 ppm of silver NPs which is an amount not detectable by ICP. Furthermore, HAV-Ag nanocomposites were shown to be non-toxic as well as have a strong antibacterial effect. Silver NPs significantly enhanced the bioactivity of HAV nanocomposites and thus the developed nanocomposites promise to be excellent biomaterials for bone and reconstructive surgery applications.

  10. Study on the thermal decomposition kinetics of nano-sized calcium carbonate.

    PubMed

    Li, Dai-Xi; Shi, Hong-Yun; Jie, Deng; Xu, Yuan-Zhi

    2003-01-01

    This study of the thermal decomposition kinetics of various average diameter nano-particles of calcium carbonate by means of TG-DTA ( thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters; their pseudo-active energy (a); and that the top-temperature of decomposition T(p) decreases gently in the scope of micron-sized diameter, but decreases sharply when the average diameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reactions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both E(a) and T(p) to decline sharply with the decrease of the average diameter of nano-particles.

  11. Evidence for Alkene cis-Aminocupration, an Aminooxygenation Case Study: Kinetics, EPR Spectroscopy, and DFT Calculations

    PubMed Central

    Paderes, Monissa C.; Belding, Lee; Fanovic, Branden; Dudding, Travis; Keister, Jerome B.

    2012-01-01

    Alkene difunctionalization reactions are important in organic synthesis. We have recently shown that copper(II) complexes can promote and catalyze intramolecular alkene aminooxygenation, carboamination, and diamination reactions. In this contribution, we report a combined experimental and theoretical examination of the mechanism of the copper(II)-promoted olefin aminooxygenation reaction. Kinetics experiments revealed a mechanistic pathway involving an equilibrium reaction between a copper(II) carboxylate complex and the γ-alkenyl sulfonamide substrate and a rate-limiting intramolecular cis-addition of N–Cu across the olefin. Kinetic isotope effect studies support that the cis-aminocupration is the rate-determining step. UV/Vis spectra support a role for the base in the break-up of copper(II) carboxylate dimer to monomeric species. Electron paramagnetic resonance (EPR) spectra provide evidence for a kinetically competent N–Cu intermediate with a CuII oxidation state. Due to the highly similar stereochemical and reactivity trends among the CuII-promoted and catalyzed alkene difunctionalization reactions we have developed, the cis-aminocupration mechanism can reasonably be generalized across the reaction class. The methods and findings disclosed in this report should also prove valuable to the mechanism analysis and optimization of other copper(-II) carboxylate promoted reactions, especially those that take place in aprotic organic solvents. PMID:22237868

  12. Pulsed IR heating studies of single-molecule DNA duplex dissociation kinetics and thermodynamics.

    PubMed

    Holmstrom, Erik D; Dupuis, Nicholas F; Nesbitt, David J

    2014-01-07

    Single-molecule fluorescence spectroscopy is a powerful technique that makes it possible to observe the conformational dynamics associated with biomolecular processes. The addition of precise temperature control to these experiments can yield valuable thermodynamic information about equilibrium and kinetic rate constants. To accomplish this, we have developed a microscopy technique based on infrared laser overtone/combination band absorption to heat small (≈10(-11) liter) volumes of water. Detailed experimental characterization of this technique reveals three major advantages over conventional stage heating methods: 1), a larger range of steady-state temperatures (20-100°C); 2), substantially superior spatial (≤20 μm) control; and 3), substantially superior temporal (≈1 ms) control. The flexibility and breadth of this spatial and temporally resolved laser-heating approach is demonstrated in single-molecule fluorescence assays designed to probe the dissociation of a 21 bp DNA duplex. These studies are used to support a kinetic model based on nucleic acid end fraying that describes dissociation for both short (<10 bp) and long (>10 bp) DNA duplexes. These measurements have been extended to explore temperature-dependent kinetics for the 21 bp construct, which permit determination of single-molecule activation enthalpies and entropies for DNA duplex dissociation.

  13. Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

    NASA Astrophysics Data System (ADS)

    Ni, Yunyan; Ma, Qisheng; Ellis, Geoffrey S.; Dai, Jinxing; Katz, Barry; Zhang, Shuichang; Tang, Yongchun

    2011-05-01

    Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2 cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using δD values in ethane from several basins in the world are in close agreement with similar predictions based on the δ 13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that δD values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that δD values in ethane might be more suitable for modeling than comparable values in methane and propane.

  14. Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

    USGS Publications Warehouse

    Ni, Y.; Ma, Q.; Ellis, G.S.; Dai, J.; Katz, B.; Zhang, S.; Tang, Y.

    2011-01-01

    Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using ??D values in ethane from several basins in the world are in close agreement with similar predictions based on the ??13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that ??D values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that ??D values in ethane might be more suitable for modeling than comparable values in methane and propane. ?? 2011 Elsevier Ltd.

  15. A Three-Dimensional Kinematic and Kinetic Study of the College-Level Female Softball Swing

    PubMed Central

    Milanovich, Monica; Nesbit, Steven M.

    2014-01-01

    This paper quantifies and discusses the three-dimensional kinematic and kinetic characteristics of the female softball swing as performed by fourteen female collegiate amateur subjects. The analyses were performed using a three-dimensional computer model. The model was driven kinematically from subject swings data that were recorded with a multi-camera motion analysis system. Each subject used two distinct bats with significantly different inertial properties. Model output included bat trajectories, subject/bat interaction forces and torques, work, and power. These data formed the basis for a detailed analysis and description of fundamental swing kinematic and kinetic quantities. The analyses revealed that the softball swing is a highly coordinated and individual three-dimensional motion and subject-to-subject variations were significant in all kinematic and kinetic quantities. In addition, the potential effects of bat properties on swing mechanics are discussed. The paths of the hands and the centre-of-curvature of the bat relative to the horizontal plane appear to be important trajectory characteristics of the swing. Descriptions of the swing mechanics and practical implications are offered based upon these findings. Key Points The female softball swing is a highly coordinated and individual three-dimensional motion and subject-to-subject variations were significant in all kinematic and kinetic quantities. The paths of the grip point, bat centre-of-curvature, CG, and COP are complex yet reveal consistent patterns among subjects indicating that these patterns are fundamental components of the swing. The most important mechanical quantity relative to generating bat speed is the total work applied to the bat from the batter. Computer modeling of the softball swing is a viable means for study of the fundamental mechanics of the swing motion, the interactions between the batter and the bat, and the energy transfers between the two. PMID:24570623

  16. Progress of pharmacological studies on alkaloids from Apocynaceae.

    PubMed

    Liu, Lu; Cao, Jian-Xin; Yao, Yuan-Cheng; Xu, Sheng-Ping

    2013-01-01

    Alkaloid was a kind of biological active ingredient. There were various types of alkaloids in Apocynaceae. This paper reviewed the progress on alkaloids from Apocynaceae, which contained origin, structure, and pharmacological activity.

  17. Stabilization and transformation of amorphous calcium carbonate: structural and kinetic studies

    NASA Astrophysics Data System (ADS)

    Schmidt, Millicent Promise

    Amorphous calcium carbonate (ACC) is a common transient precursor in the formation of more stable crystalline calcium carbonate minerals, most notably calcite, vaterite, and aragonite. Formation of ACC from calcium carbonate rich aqueous solution rather than direct crystallization of crystalline polymorphs by organisms provides several advantages: control of morphology, grain size, orientation, hardness, and other bulk properties as well as reduction of energy costs during growth cycles. Despite decades of study, stabilization and transformation mechanisms of synthetic and biogenic ACC remain unclear. In particular, the roles of H2O and inorganic phosphate in ACC structure and transformation, and the variables affecting transformation kinetics and polymorph selection are understudied. In this research, we addressed structure and kinetic behavior of ACC through four complementary investigations: two studies focus on synthetic ACC stabilization and two focus on synthetic and biogenic ACC transformation behavior in solution at ambient temperatures. We explored ACC stabilization via compositional and thermal analyses, X-ray scattering, X-ray absorption spectroscopy, and nuclear magnetic resonance spectroscopy. Transformation experiments used a novel method of in situ structural analysis that provided quantitative kinetic and structural data and allowed us to visualize the ACC transformation pathway. Results revealed the complexity of H2O structure in ACC samples synthesized from three methods, indicating that the distinct hydrous populations produced define ACC behavior. Transformation kinetics and polymorph selection were strongly affected by the hydration state and type of synthetic ACC reacted. In situ transformation experiments also showed differences in kinetic behavior due to reaction medium. The structural role of hydrous components was again evident in in situ transformation experiments for ACC from a biogenic lobster gastrolith (LG) reacted with water. LG

  18. Theoretical and experimental study of kinetics of photoexcited carriers in wide band gap semiconductors

    NASA Astrophysics Data System (ADS)

    Shishehchi, Sara; Rudin, Sergey; Garrett, Gregory; Wraback, Michael; Bellotti, Enrico

    2013-03-01

    We present a theoretical and experimental study of the subpicosecond kinetics of photo-excited carriers in the wide band gap semiconductors GaN and ZnO. In the theoretical model, interaction with a photo-excitation laser pulse is treated coherently and a generalized Monte Carlo simulation is used to account for scattering and dephasing. The scattering mechanisms included are carrier interactions with polar optical phonons and acoustic phonons, and carrier-carrier Coulomb interactions. For comparison, experimental time-resolved photoluminescence studies on GaN and ZnO samples are performed over a range of temperatures and excitation powers.

  19. Progress on upwelling studies in the China seas

    NASA Astrophysics Data System (ADS)

    Hu, Jianyu; Wang, Xiao Hua

    2016-09-01

    East Asian marginal seas surrounding China exhibit rich ocean upwelling, mostly in response to the southwesterly summer monsoon. Upwelling in the China seas, namely, the South China Sea, the Taiwan Strait, the East China Sea, the Yellow Sea, and the Bohai Sea, has become increasingly important because the potential changes in the upwelling may have dramatic ecosystem, socioeconomic, and climate impacts. This paper reviews the progress of upwelling studies in the China seas since the year 2000, by presenting the principal characteristics and new understanding of 12 major upwelling regions in the China seas. Upwelling exhibits long-term variability at intraseasonal to multidecadal scales as well as short-term variability frequently caused by tropical cyclones. It is also associated with the El Niño-Southern Oscillation, local environmental variation, and biogeochemical factors. The coastal upwelling around Hainan Island and the upwelling or cold dome northeast of Taiwan Island are specifically highlighted because they have attracted great interest for decades. This paper summarizes upwelling mechanisms in terms of wind, topography, tide, stratification, and background flow, with applications mostly to the China seas. Finally, we propose some topics for future upwelling research, i.e., potential intensification of coastal upwelling under global climate change, downwelling, intrusion of upwelling into coastal embayments, and the influence of upwelling on fishery and biogeochemical processes.

  20. Kinetic study on removal of heavy metal ions from aqueous solution by using soil.

    PubMed

    Lim, Soh-Fong; Lee, Agnes Yung Weng

    2015-07-01

    In the present study, the feasibility of soil used as a low-cost adsorbent for the removal of Cu(2+), Zn(2+), and Pb(2+) ions from aqueous solution was investigated. The kinetics for adsorption of the heavy metal ions from aqueous solution by soil was examined under batch mode. The influence of the contact time and initial concentration for the adsorption process at pH of 4.5, under a constant room temperature of 25 ± 1 °C were studied. The adsorption capacity of the three heavy metal ions from aqueous solution was decreased in order of Pb(2+) > Cu(2+) > Zn(2+). The soil was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopic-energy dispersive X-ray (SEM-EDX), and Brunauer, Emmett, and Teller (BET) surface area analyzer. From the FTIR analysis, the experimental data was corresponded to the peak changes of the spectra obtained before and after adsorption process. Studies on SEM-EDX showed distinct adsorption of the heavy metal ions and the mineral composition in the study areas were determined to be silica (SiO2), alumina (Al2O3), and iron(III) oxide (FeO3). A distinct decrease of the specific surface area and total pore volumes of the soil after adsorption was found from the BET analysis. The experimental results obtained were analyzed using four adsorption kinetic models, namely pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion. Evaluating the linear correlation coefficients, the kinetic studies showed that pseudo-second-order equation described the data appropriable than others. It was concluded that soil can be used as an effective adsorbent for removing Cu(2+), Zn(2+), and Pb(2+) ions from aqueous solution.

  1. Progressive macular hypomelanosis among Egyptian patients: a clinicopathological study

    PubMed Central

    Selim, Mohamed Khaled; Ahmed, El-Shahat Farag; Abdelgawad, Mamdouh Morsy; El-Kamel, Mohammed Fawzy

    2011-01-01

    Background: Progressive macular hypomelanosis (PMH) is a disease of unclear etiology. Propionbacterium acnes (P. acnes) was claimed to be an etiological factor. Objectives: The purpose of this study was to document the clinicopathological features of PMH in Egyptian patients and to evaluate the therapeutic outcome. Methods: Patients with clinical features of PMH were recruited. Wood’s lamp examination, skin scrapings for fungi, and skin biopsy specimens were obtained. Biopsies were stained with hematoxylin and eosin, PAS, Fontana-Masson, and S100 protein. Patients received either narrow-band UVB (nbUVB) or nbUVB plus daily topical clindamycin 1% and benzoyl peroxide gel 5% (bcUVB). The period of active treatment was 14 weeks followed by a follow-up period of 24 weeks. Results: Twenty-nine patients were included. Microscopic evaluation of skin biopsy specimens showed no significant differences between lesional and normal skin. Fontana-Masson stained sections showed overall reduction of melanin granules in the basal layer of lesional skin only and S100 staining did not detect significant differences in the number of melanocytes in lesional and normal skin. Nearly complete repigmentation was reported in 10 patients treated with bcUVB compared to 9 patients treated with nbUVb with no significant differences between both groups after 14 weeks. Only 2 patients in each group retained the pigmentation and the remaining patients returned to the baseline color before treatment. Conclusions: This study documented the clinicopathological features of PMH among Egyptians. No permanently effective treatment is available. Further studies are needed to prove or disprove the pathogenic role of P. acnes in PMH. PMID:24396712

  2. Progress in preliminary studies at Ottana Solar Facility

    NASA Astrophysics Data System (ADS)

    Demontis, V.; Camerada, M.; Cau, G.; Cocco, D.; Damiano, A.; Melis, T.; Musio, M.

    2016-05-01

    The fast increasing share of distributed generation from non-programmable renewable energy sources, such as the strong penetration of photovoltaic technology in the distribution networks, has generated several problems for the management and security of the whole power grid. In order to meet the challenge of a significant share of solar energy in the electricity mix, several actions aimed at increasing the grid flexibility and its hosting capacity, as well as at improving the generation programmability, need to be investigated. This paper focuses on the ongoing preliminary studies at the Ottana Solar Facility, a new experimental power plant located in Sardinia (Italy) currently under construction, which will offer the possibility to progress in the study of solar plants integration in the power grid. The facility integrates a concentrating solar power (CSP) plant, including a thermal energy storage system and an organic Rankine cycle (ORC) unit, with a concentrating photovoltaic (CPV) plant and an electrical energy storage system. The facility has the main goal to assess in real operating conditions the small scale concentrating solar power technology and to study the integration of the two technologies and the storage systems to produce programmable and controllable power profiles. A model for the CSP plant yield was developed to assess different operational strategies that significantly influence the plant yearly yield and its global economic effectiveness. In particular, precise assumptions for the ORC module start-up operation behavior, based on discussions with the manufacturers and technical datasheets, will be described. Finally, the results of the analysis of the: "solar driven", "weather forecasts" and "combined storage state of charge (SOC)/ weather forecasts" operational strategies will be presented.

  3. A KINETIC STUDY OF THE METHANOLYSIS OF THE SULFONYLUREAS BENSULFURON METHYL AND SULFOMETURON METHYL USING CAPILLARY ELECTROPHORESIS

    EPA Science Inventory

    The instability of sulfonylureas in solution in methanol has led us to a kinetic study of methanolysis of two sulfonylureas using capillary electrophoresis. In a preliminary experiment solutions of the seven compounds, bensulfuron methyl, sulfometuron methyl, nicosulfuron, chlori...

  4. LLNL Chemical Kinetics Modeling Group

    SciTech Connect

    Pitz, W J; Westbrook, C K; Mehl, M; Herbinet, O; Curran, H J; Silke, E J

    2008-09-24

    The LLNL chemical kinetics modeling group has been responsible for much progress in the development of chemical kinetic models for practical fuels. The group began its work in the early 1970s, developing chemical kinetic models for methane, ethane, ethanol and halogenated inhibitors. Most recently, it has been developing chemical kinetic models for large n-alkanes, cycloalkanes, hexenes, and large methyl esters. These component models are needed to represent gasoline, diesel, jet, and oil-sand-derived fuels.

  5. A study of the kinetic energy generation with general circulation models

    NASA Technical Reports Server (NTRS)

    Chen, T.-C.; Lee, Y.-H.

    1983-01-01

    The history data of winter simulation by the GLAS climate model and the NCAR community climate model are used to examine the generation of atmospheric kinetic energy. The contrast between the geographic distributions of the generation of kinetic energy and divergence of kinetic energy flux shows that kinetic energy is generated in the upstream side of jets, transported to the downstream side and destroyed there. The contributions from the time-mean and transient modes to the counterbalance between generation of kinetic energy and divergence of kinetic energy flux are also investigated. It is observed that the kinetic energy generated by the time-mean mode is essentially redistributed by the time-mean flow, while that generated by the transient flow is mainly responsible for the maintenance of the kinetic energy of the entire atmospheric flow.

  6. Gold cementation on copper in thiosulfate solution: Kinetic, electrochemical, and morphological studies

    NASA Astrophysics Data System (ADS)

    Lee, Jaeheon

    2003-08-01

    Cyanidation has been used for more than a century for precious metal recovery and it is still in use today. Cyanide is a very toxic chemical and if not used appropriately will cause environmental problems. There is considerable attention devoted to the development of non-cyanide lixiviants for the process of gold and silver ores. Thiosulfate solution is one of the proposed alternatives to cyanide and gold cementation by copper has been suggested as a promising method for gold recovery from leaching solution. Copper powder and rotating disc electrode were used for the kinetic study. The rate of gold cementation on copper disc is proportional to the initial gold concentration and disc rotating speed. The cementation reaction exhibited two distinct kinetic regions, an initial slow rate followed by an enhanced rate. The activation energy of the reaction was 5.9 kJ/mol at low copper concentration and the reaction is mass transport controlled. With 30 ppm initial copper concentration, there was noticeable decrease in the reaction rate in high temperature range. EDS, XRD, and XPS analysis revealed that the deposits are a Au-Cu alloy instead of pure gold. The alloy composition ranged from Au 3Cu to AuCu3 depending on the initial Cu/Au mole ratio in solution and applied potential. Electrochemical studies were performed using rotating disc electrode and electrochemical quartz crystal nanobalance. Evans' diagrams were constructed under various experimental conditions. Corrosion current increased with increasing gold concentration, disc rotating speed, as well as thiosulfate concentration. These results confirmed those obtained in the kinetic study. Corrosion potential measurements indicated that passivation onset time was changed by gold concentration, copper concentration and disc rotating speed. Gold(I)-thiosulfate reduction was found to occur at approximately -250 mV vs. SHE using EQCN. Copper adions on the gold surface contributed to the underpotential deposition of

  7. Small-angle neutron scattering study of structure and kinetics of temperature-induced protein gelation.

    PubMed

    Chodankar, S; Aswal, V K; Kohlbrecher, J; Vavrin, R; Wagh, A G

    2009-02-01

    The phase diagram, structural evolution, and kinetics of temperature-induced protein gelation of protein Bovine Serum Albumin (BSA) have been studied as a function of solution pH and protein concentration. The protein gelation temperature represents the onset of turbidity in the protein solution, which increases significantly with increasing pH beyond the isoelectric pH of the protein molecule. On the other hand, the gelation temperature decreases with an increase in protein concentration only in the low-protein-concentration regime and shows a small increasing trend at higher protein concentrations. The structural evolution and kinetics of protein gelation have been studied using small-angle neutron scattering. The structure of the protein molecule remains stable up to temperatures very close to the gelation temperature. On increasing the temperature above the gelation temperature, the protein solution exhibits a fractal structure, an indication of gel formation due to aggregation. The fractal dimension of the gel increases with increasing temperature, suggesting an increase in branching between the aggregates, which leads to stronger gels. The increase in both solution pH and protein concentration is found to delay the growth in the fractal structure and its saturation. The kinetics of gelation has been studied using the temperature-jump process of heating. It is found that the structure of the protein gels remains invariant after the heating time ( approximately 1 min), indicating a rapid formation of gel structure within this time. The protein gels prepared through gradual and temperature-jump heating routes do not always show the same structure. In particular, at higher temperatures (e.g., 85 degrees C ), while gradual heating shows a fractal structure, there is collapse of such fractal structure during temperature-jump heating.

  8. Kinetic study of carbon dioxide absorption into glycine promoted diethanolamine (DEA)

    NASA Astrophysics Data System (ADS)

    Pudjiastuti, Lily; Susianto, Altway, Ali; IC, Maria Hestia; Arsi, Kartika

    2015-12-01

    In industry, especially petrochemical, oil and natural gas industry, required separation process of CO2 gas which is a corrosive gas (acid gas). This characteristic can damage the plant utility and piping systems as well as reducing the caloric value of natural gas. Corrosive characteristic of CO2 will appear in areas where there is a decrease in temperature and pressure, such as at the elbow pipe, tubing, cooler and injector turbine. From disadvantages as described above, then it is important to do separation process in the CO2 gas stream, one of the method for remove CO2 from the gas stream is reactive absorption using alkanolamine based solution with promotor. Therefore, this study is done to determine the kinetics constant of CO2 absorption in diethanolamine (DEA) solution using a glycine promoter. Glycine is chosen as a promoter because glycine is a primary amine compound which is reactive, moreover, glycine has resistance to high temperatures so it will not easy to degradable and suitable for application in industry. The method used in this study is absorption using laboratory scale wetted wall column equipment at atmospheric of pressure. This study will to provide the reaction kinetics data information in order to optimize the separation process of CO2 in the industrialized world. The experimental results show that rising temperatures from 303,15 - 328,15 K and the increase of concentration of glycine from 1% - 3% weight will increase the absorption rate of carbon dioxide in DEA promoted with glycine by 24,2% and 59,764% respectively, also the reaction kinetic constant is 1.419 × 1012 exp (-3634/T) (m3/kmol.s). This result show that the addition of glycine as a promoter can increase absorption rate of carbon dioxide in diethanolamine solution and cover the weaknesses of diethanolamine solution.

  9. A Kinetic Degradation Study of Curcumin in Its Free Form and Loaded in Polymeric Micelles.

    PubMed

    Naksuriya, Ornchuma; van Steenbergen, Mies J; Torano, Javier S; Okonogi, Siriporn; Hennink, Wim E

    2016-05-01

    Curcumin, a phenolic compound, possesses many pharmacological activities and is under clinical evaluation to treat different diseases. However, conflicting data about its stability have been reported. In this study, the kinetic degradation of curcumin from a natural curcuminoid mixture under various conditions (pH, temperature, and dielectric constant of the medium) was investigated. Moreover, the degradation of pure curcumin at some selected conditions was also determined. To fully solubilize curcumin and to prevent precipitation of curcumin that occurs when low concentrations of co-solvent are present, a 50:50 (v/v) aqueous buffer/methanol mixture was used as standard medium to study its degradation kinetics. The results showed that degradation of curcumin both as pure compound and present in the curcuminoid mixture followed first order kinetic reaction. It was further shown that an increasing pH, temperature, and dielectric constant of the medium resulted in an increase in the degradation rate. Curcumin showed rapid degradation due to autoxidation in aqueous buffer pH = 8.0 with a rate constant of 280 × 10(-3) h(-1), corresponding with a half-life (t1/2) of 2.5 h. Dioxygenated bicyclopentadione was identified as the final degradation product. Importantly, curcumin loaded as curcuminoid mixture in ω-methoxy poly (ethylene glycol)-b-(N-(2-benzoyloxypropyl) methacrylamide) (mPEG-HPMA-Bz) polymeric micelles and in Triton X-100 micelles was about 300-500 times more stable than in aqueous buffer. Therefore, loading of curcumin into polymeric micelles is a promising approach to stabilize this compound and develop formulations suitable for further pharmaceutical and clinical studies.

  10. Modelling and kinetics studies of a corn-rape blend combustion in an oxy-fuel atmosphere.

    PubMed

    López, R; Fernández, C; Martínez, O; Sánchez, M E

    2015-05-01

    A kinetic oxy-combustion study of a previously optimized lignocellulose blend is proposed. Kinetic and diffusion control mechanism are considered. The proposed correlations fit properly with the experimental results and diffusion effects are identified as be important enough to be taken into account. Afterwards, with the results obtained in the kinetic study, a detailed consecutive and parallel kinetic scheme is proposed for modelling the oxy-combustion of the blend. A discussion of the temperature and concentration profiles are included. Variation of products final distribution is considered. Smaller particles than 0.001 m are proposed for reducing temperature and concentration profiles and obtaining a good final product distribution. CO2-char reaction is identified as one of the most important step to be optimized for obtaining the lowest final residue. In this study, char is mainly oxidised at 950 K and this situation is attributed to an optimized blending of the bioresidues.

  11. Removal of ibuprofen, naproxen and carbamazepine in aqueous solution onto natural clay: equilibrium, kinetics, and thermodynamic study

    NASA Astrophysics Data System (ADS)

    Khazri, Hassen; Ghorbel-Abid, Ibtissem; Kalfat, Rafik; Trabelsi-Ayadi, Malika

    2016-04-01

    This study aimed to describe the adsorption of three pharmaceuticals compounds (ibuprofen, naproxen and carbamazepine) onto natural clay on the basis of equilibrium parameters such as a function of time, effect of pH, varying of the concentration and the temperature. Adsorption kinetic data were modeled using the Lagergren's first-order and the pseudo-second-order kinetic equations. The kinetic results of adsorption are described better using the pseudo-second order model. The isotherm results were tested in the Langmuir, Freundlich and Dubinin-Radushkevich models. The thermodynamic parameters obtained indicate that the adsorption of pharmaceuticals on the clay is a spontaneous and endothermic process.

  12. Simulation of atomic diffusion in the Fcc NiAl system: A kinetic Monte Carlo study

    SciTech Connect

    Alfonso, Dominic R.; Tafen, De Nyago

    2015-04-28

    The atomic diffusion in fcc NiAl binary alloys was studied by kinetic Monte Carlo simulation. The environment dependent hopping barriers were computed using a pair interaction model whose parameters were fitted to relevant data derived from electronic structure calculations. Long time diffusivities were calculated and the effect of composition change on the tracer diffusion coefficients was analyzed. These results indicate that this variation has noticeable impact on the atomic diffusivities. A reduction in the mobility of both Ni and Al is demonstrated with increasing Al content. As a result, examination of the pair interaction between atoms was carried out for the purpose of understanding the predicted trends.

  13. Synthesis and kinetic studies of a low-molecular weight organocatalyst for phosphate hydrolysis in water.

    PubMed

    Merschky, Michael; Schmuck, Carsten

    2009-12-07

    Kinetic studies of a low-molecular weight organocatalyst 1 are presented. Compound 1 contains two histidines and one cationic side chain attached to a central aromatic core. In aqueous solution 1 accelerates the hydrolysis of a prototypal phosphodiester with rate enhancements of up to two orders of magnitude. A detailed HPLC analysis of hydrolysis experiments in Bis-Tris-buffer showed that the buffer itself can act as a nucleophile at least with the cyclic phosphate 16. Compound 1 is also an efficient host for the binding of bis-(para-nitrophenyl)-phosphate 14 with extraordinary high affinity of K(ass) = 24,400 M(-1) in buffered water.

  14. Flow-through immobilized enzyme reactors based on monoliths: II. Kinetics study and application.

    PubMed

    Vlakh, Evgenia G; Tennikova, Tatiana B

    2013-03-01

    In the last decade, the application of monolithic materials has rapidly expanded to the realization of flow-through bioconversion processes. Up to these days, different classes of enzymes such as hydrolases, lyases, and oxidoreductases have been immobilized on organic, inorganic, or hybrid monolithic materials to prepare the effective flow-through enzymes reactors for application in proteomics, biotechnology, pharmaceutics, organic synthesis, and biosensoring. Current review describes the results of kinetic study and specialties of flow-through immobilized enzyme reactors based on the existing monolithic materials.

  15. High temperature chemical kinetic study of the H2-CO-CO2-NO reaction system

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.

    1975-01-01

    An experimental study of the kinetics of the H2-CO-CO2-NO reaction system was made behind incident shock waves at temperatures of 2460 and 2950 K. The overall rate of the reaction was measured by monitoring radiation from the CO + O yields CO2 + h upoilon reaction. Correlation of these data with a detailed reaction mechanism showed that the high-temperature rate of the reaction N + OH yields NO + H can be described by the low-temperature (320 K) rate coefficient. Catalytic dissociation of molecular hydrogen was an important reaction under the tests conditions.

  16. Defluoridation using biomimetically synthesized nano zirconium chitosan composite: kinetic and equilibrium studies.

    PubMed

    Prasad, Kumar Suranjit; Amin, Yesha; Selvaraj, Kaliaperumal

    2014-07-15

    The present study reports a novel approach for synthesis of Zr nanoparticles using aqueous extract of Aloe vera. Resulting nanoparticles were embedded into chitosan biopolymer and termed as CNZr composite. The composite was subjected to detailed adsorption studies for removal of fluoride from aqueous solution. The synthesized Zr nanoparticles showed UV-vis absorption peak at 420nm. TEM result showed the formation of polydispersed, nanoparticles ranging from 18nm to 42nm. SAED and XRD analysis suggested an fcc (face centered cubic) Zr crystallites. EDAX analysis suggested that Zr was an integral component of synthesized nanoparticles. FT-IR study indicated that functional group like NH, CO, CN and CC were involved in particle formation. The adsorption of fluoride on to CNZr composite worked well at pH 7.0, where ∼99% of fluoride was found to be adsorbed on adsorbent. Langmuir isotherm model best fitted the equilibrium data since it presented higher R(2) value than Freundlich model. In comparison to pseudo-first order kinetic model, the pseudo-second order model could explain adsorption kinetic behavior of F(-) onto CNZr composite satisfactorily with a good correlation coefficient. The present study revealed that CNZr composite may work as an effective tool for removal of fluoride from contaminated water.

  17. Kinetic modeling and docking study of immobilized lipase catalyzed synthesis of furfuryl acetate.

    PubMed

    Mathpati, Ashwini C; Badgujar, Kirtikumar C; Bhanage, Bhalchandra M

    2016-03-01

    The present work deals with the kinetic modeling and docking study for the furfuryl acetate synthesis using immobilized Burkholderia cepacia (BCL) lipase. Initially various lipases were immobilized on hydroxypropyl methyl cellulose (HPMC) and poly vinyl alcohol (PVA) base hybrid polymer matrix. After screening of various immobilized biocatalysts, HPMC:PVA:BCL was found to be a robust biocatalyst. Various reaction conditions were optimized using response surface methodology (RSM) based on a four-factor-three-level Box-Behnken design. The optimal conditions were obtained at molar ratio of 1:2 of furfuryl alcohol to acyl donor, temperature 50°C with catalyst loading of 30mg in 3mL of non-aqueous media toluene. Under these conditions 99.98% yield was obtained in 3h. The Arrhenius plot showed that the activation energy for furfuryl acetate synthesis was 10.68kcal/mol. The kinetics of reaction was studied close to optimized conditions which obey order bi-bi model. Molecular docking study was carried out to understand the active site of BCL which is responsible for the reaction. It was observed that the reaction proceeds via acylation of the active serine of BCL and demonstrating strong hydrogen bond between the substrate and histidine site. The catalyst recyclability study was carried up to five cycles.

  18. Study on carvacrol and cinnamaldehyde polymeric films: mechanical properties, release kinetics and antibacterial and antibiofilm activities.

    PubMed

    Nostro, A; Scaffaro, R; D'Arrigo, M; Botta, L; Filocamo, A; Marino, A; Bisignano, G

    2012-11-01

    Polyethylene-co-vinylacetate (EVA) films with different concentrations (3.5 wt% and 7 wt%) of essential oil constituents, carvacrol or cinnamaldehyde, were prepared and characterized by mechanical, antibacterial and antibiofilm properties. The incorporation of the compounds into copolymer films affected their elastic modulus, tensile stress and elongation at break. Carvacrol and cinnamaldehyde act as plasticizers which reduce the intermolecular forces of polymer chains, thus improving the flexibility and extensibility of the film. The analysis of the surface characteristics demonstrated that essential oil constituents lowered the contact angle values without causing any remarkable variation of the surface roughness. The films allowed progressive diffusion of the bioactive molecules and the kinetic of release was correlated with the damaging effect on bacterial growth. The kill curves proved that the film with essential oil constituents (7 wt%) had a significant bactericidal effect (reduction of 4 and 2 log CFU) against Staphylococcus aureus and Escherichia coli and a bacteriostatic effect against Staphylococcus epidermidis and Listeria monocytogenes (reduction of about 1 log CFU). With regard to biofilm formation the biomass formed on polymeric films surface was significantly reduced if compared with the pure copolymer control. The results were confirmed by fluorescence microscopy images by Live/dead staining. The reduction in the surface tension coupled to an inherent bactericidal property of carvacrol and cinnamaldehyde could in turn affect the initial attachment phase of bacteria and compromise the normal biofilm development.

  19. Effect of intracellular P content on phosphate removal in Scenedesmus sp. Experimental study and kinetic expression.

    PubMed

    Ruiz-Martínez, A; Serralta, J; Romero, I; Seco, A; Ferrer, J

    2015-01-01

    The present work determines the effect of phosphorus content on phosphate uptake rate in a mixed culture of Chlorophyceae in which the genus Scenedesmus dominates. Phosphate uptake rate was determined in eighteen laboratory batch experiments, with samples taken from a progressively more P-starved culture in which a minimum P content of 0.11% (w/w) was achieved. The results obtained showed that the higher the internal biomass P content, the lower the phosphate removal rate. The highest specific phosphate removal rate was 6.5mgPO4-PgTSS(-1)h(-1). Microalgae with a P content around 1% (w/w) attained 10% of this highest removal rate, whereas those with a P content of 0.6% (w/w) presented 50% of the maximum removal rate. Different kinetic expressions were used to reproduce the experimental data. Best simulation results for the phosphate uptake process were obtained combining Steele equation and Hill function to represent the effect of light and intracellular phosphorus content, respectively.

  20. [Electromagnetic studies of nuclear structure and reactions]. Progress summary

    SciTech Connect

    Not Available

    1992-12-31

    The experimental goals are focused on developing an understanding of strong interactions and the structure of hadronic systems by determination of the electromagnetic response; these goals will be accomplished through coincidence detection of final states. Nuclear modeling objectives are to organize and interpret the data through a consistent description of a broad spectrum of reaction observables; calculations are performed in a nonrelativistic diagrammatic framework as well as a relativistic QHD approach. Work is described according to the following arrangement: direct knockout reactions (completion of {sup 16}O(e,e{prime}p), {sup 12}C(e,e{prime}pp) progress, large acceptance detector physics simulations), giant resonance studies (intermediate-energy experiments with solid-state detectors, the third response function in {sup 12}C(e,e{prime}p{sub 0}) and {sup 16}O(e,e{prime}p{sub 0}), comparison of the {sup 12}C(e, e{prime}p{sub 0}) and {sup 16}O(e,e{prime}p{sub 3}) reactions, quadrupole strength in the {sup 16}O(e,e{prime}{alpha}{sub 0}) reaction, quadrupole strength in the {sup 12}C(e,e{prime}{alpha}) reaction, analysis of the {sup 12}C(e,e{prime}p{sub 1}) and {sup 16}O(e,e{prime}p{sub 3}) angular distributions, analysis of the {sup 40}Ca(e,e{prime}x) reaction at low q, analysis of the higher-q {sup 12}C(e,e{prime}x) data from Bates), models of nuclear structure (experimental work, Hartree-Fock calculations, phonon excitations in spherical nuclei, shell model calculations, variational methods for relativistic fields), and instrumentation development efforts (developments at CEBAF, CLAS contracts, BLAST developments).

  1. Chemical and Biological Kinetics

    NASA Astrophysics Data System (ADS)

    Emanuel', N. M.

    1981-10-01

    Examples of the application of the methods and ideas of chemical kinetics in various branches of chemistry and biology are considered and the results of studies on the kinetics and mechanisms of autoxidation and inhibited and catalysed oxidation of organic substances in the liquid phase are surveyed. Problems of the kinetics of the ageing of polymers and the principles of their stabilisation are discussed and certain trends in biological kinetics (kinetics of tumour growth, kinetic criteria of the effectiveness of chemotherapy, problems of gerontology, etc.) are considered. The bibliography includes 281 references.

  2. Adsorption kinetic and equilibrium study for removal of mercuric chloride by CuCl2-impregnated activated carbon sorbent.

    PubMed

    Li, Xin; Liu, Zhouyang; Lee, Joo-Youp

    2013-05-15

    The intrinsic adsorption kinetics of mercuric chloride (HgCl2) was studied for raw, 4% and 10% CuCl2-impregnated activated carbon (CuCl2-AC) sorbents in a fixed-bed system. An HgCl2 adsorption kinetic model was developed for the AC sorbents by taking into account the adsorption kinetics, equilibrium, and internal and external mass transfer. The adsorption kinetic constants determined from the comparisons between the simulation and experimental results were 0.2, 0.3, and 0.5m(3)/(gs) for DARCO-HG, 4%(wt), and 10%(wt) CuCl2-AC sorbents, respectively, at 140 °C. CuCl2 loading was found to slightly increase the adsorption kinetic constant or at least not to decrease it. The HgCl2 equilibrium adsorption data based on the Langmuir isotherm show that high CuCl2 loading can result in high binding energy of the HgCl2 adsorption onto the carbon surface. The adsorption equilibrium constant was found to increase by ~10 times when CuCl2 loading varied from 0 to 10%(wt), which led to a decrease in the desorption kinetic constant (k2) by ~10 times and subsequently the desorption rate by ~50 times. Intraparticle pore diffusion considered in the model showed good accuracy, allowing for the determination of intrinsic HgCl2 adsorption kinetics.

  3. Decay kinetics of benzophenone triplets and corresponding free radicals in soft and rigid polymers studied by laser flash photolysis.

    PubMed

    Levin, Peter P; Efremkin, Alexei F; Sultimova, Natalie B; Kasparov, Valery V; Khudyakov, Igor V

    2014-01-01

    The kinetics of transients formed under photoexcitation of benzophenone (B) dissolved in three different polymers was studied by ns laser flash photolysis. These polymers were the soft rubbers poly (ethylene-co-butylene) (EB), polystyrene block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) and hard polystyrene (PS). We monitored the decay kinetics of triplet state (3)B(*) and of ketyl radicals BH(●). We observed exponential decay of (3)B(*) and two-stage decay kinetics of BH(●) in EB. The first stage is a fast cage recombination of a radical pair (BH(●), radical of polymer R(●)). The second slow stage of BH(●) decay follows the second-order law with a relatively high rate constant, which corresponds to recombination of BH(●) in a homogeneous liquid with a viscosity of only ~0.1 P (about five times of 2-propanol viscosity). Application of a magnetic field (MF) of 0.2 T leads to deceleration of both stages of BH(●) decay in EB by approximately 20%. Decay kinetics of both transients were observed in SEBS. There was no MF effect on BH(●) decay in SEBS. We only observed (3)B(*) in PS. Decay kinetics of (3)B(*) in this case were described as polychromatic dispersive first-order kinetics. We discuss the effects of polymer structure on transient kinetics and the MF effect.

  4. Kinetic and isotherm studies of adsorption and biosorption processes in the removal of phenolic compounds from aqueous solutions: comparative study

    PubMed Central

    2013-01-01

    The phenolic compounds are known by their carcinogenicity and high toxicity as well as creating unpleasant taste and odor in water resources. The present study develops a cost-effective technology for the treatment of water contaminated with phenolic compounds, including Phenol (Ph), 2-chlorophenol (2-CP), and 4-chlorophenol (4-CP). So, two sorbents, rice bran ash (RBA) and biomass of brown algae, Cystoseiraindica, were used and results were compared with the commercially granular activated carbon (GAC). The phenolic compounds were determined using a high performance liquid chromatography (HPLC) under batch equilibrium conditions. The effects of contact time, pH, initial adsorbate concentration, and adsorbent dosages on the removal efficiency were studied. The adsorption data were simulated by isotherm and kinetic models. Results indicated that RBA and GAC had the lowest efficiency for the removal of 2-CP, while the order of removal efficiency for C. indica biomass was as follows: 2-CP > 4-CP > phenol. The efficiency of GAC was higher than those of other adsorbents for all of the phenolic compounds. Furthermore, the adsorption capacity of RBA was found to be higher than that of C. indica biomass. The optimal initial pH for the removal of phenol, 2-CP and 4-CP was determined to be 5, 7, and 7 for RBA, GAC, and algal biomass, respectively. Kinetic studies suggested that the pseudo-second order best fitted the kinetic data. PMID:24355013

  5. Amino Acid Specific Effects on RNA Tertiary Interactions: Single-Molecule Kinetic and Thermodynamic Studies.

    PubMed

    Sengupta, Abhigyan; Sung, Hsuan-Lei; Nesbitt, David J

    2016-10-10

    In light of the current models for an early RNA-based universe, the potential influence of simple amino acids on tertiary folding of ribozymal RNA into biochemically competent structures is speculated to be of significant evolutionary importance. In the present work, the folding-unfolding kinetics of a ubiquitous tertiary interaction motif, the GAAA tetraloop-tetraloop receptor (TL-TLR), is investigated by single-molecule fluorescence resonance energy transfer spectroscopy in the presence of natural amino acids both with (e.g., lysine, arginine) and without (e.g., glycine) protonated side chain residues. By way of control, we also investigate the effects of a special amino acid (e.g., proline) and amino acid mimetic (e.g., betaine) that contain secondary or quaternary amine groups rather than a primary amine group. This combination permits systematic study of amino acid induced (or amino acid like) RNA folding dynamics as a function of side chain complexity, pKa, charge state, and amine group content. Most importantly, each of the naturally occurring amino acids is found to destabilize the TL-TLR tertiary folding equilibrium, the kinetic origin of which is dominated by a decrease in the folding rate constant (kdock), also affected by a strongly amino acid selective increase in the unfolding rate constant (kundock). To further elucidate the underlying thermodynamics, single-molecule equilibrium constants (Keq) for TL-TLR folding have been probed as a function of temperature, which reveal an amino acid dependent decrease in both overall exothermicity (ΔΔH° > 0) and entropic cost (-TΔΔS° < 0) for the overall folding process. Temperature-dependent studies on the folding/unfolding kinetic rate constants reveal analogous amino acid specific changes in both enthalpy (ΔΔH(⧧)) and entropy (ΔΔS(⧧)) for accessing the transition state barrier. The maximum destabilization of the TL-TLR tertiary interaction is observed for arginine, which is consistent with early

  6. Atmospheric reactions of gaseous mercury with ozone and hydroxyl radical: Kinetics and product studies

    NASA Astrophysics Data System (ADS)

    Biswajit, P.; Parisa, A. A.

    2003-05-01

    The dominant form of mercury in the atmosphere is Hg^0. The oxidation processes are of great importance since oxidized mercury undergoes deposition and can become subject to bioaccumulation. Experimental data on the gaseous reactions of elemental mercury are very limited with compare to the reactions of Hg^0 in solutions. We herein carried out kinetic and product studies on the reactions of gaseous Hg^0 with O3 and hydroxyl radical (HO) under near atmospheric pressure (750 ± 1 Torr) and room temperature (298 ± 1 K) in air and N2. O3 was produced in a silent discharge generator (OL 100/SB). Hydroxyl radicals were produced from the photolysis of isopropyl nitrite in the presence of NO. Kinetics of the reactions with O3/HO was studied using absolute and relative techniques by gas chromatography with mass spectroscopic detection (GCMS). The gas phase reaction between elemental Hg^0 with O3 has been studied in different surface-to-volume (s/v) ratios, and evidence for heterogeneous reactions was observed. Existence of mercuric oxide, Hg^0 by the reaction of atomic Hg^0 with O3 has been determined in the gas phase from the suspended aerosols using high temperature mass spectrometry.

  7. Synthesis, kinetic mechanism and docking studies of vanillin derivatives as inhibitors of mushroom tyrosinase.

    PubMed

    Ashraf, Zaman; Rafiq, Muhammad; Seo, Sung-Yum; Babar, Mustafeez Mujtaba; Zaidi, Najam-us-Sahar Sadaf

    2015-09-01

    The purpose of the present study was to discover the extent of contribution to antityrosinase activity by adding hydroxy substituted benzoic acid, cinnamic acid and piperazine residues to vanillin. The study showed the transformation of vanillin into esters as shown in (4a-4d), (6a-6b), and (8a-8b). In addition, the relationship between structures of these esters and their mushroom tyrosinase inhibitory activity was explored. The kinetics of inhibition on mushroom tyrosinase by these esters was also investigated. It was found that hydroxyl substituted benzoic acid derivatives were weak inhibitors; however hydroxy or chloro substituted cinnamic acid and piperazine substituted derivatives were able to induce significant tyrosinase inhibition. The mushroom tyrosinase (PDBID 2ZWE) was docked with synthesized vanillin derivatives and their calculated binding energies were compared with experimental IC50 values which provided positive correlation. The most potent derivative 2-(4-formyl-2-methoxyphenoxy)-2-oxoethyl (2E)-3-(4-hydroxyphenyl)prop-2-enoate (6a) possesses hydroxy substituted cinnamic acid scaffold having IC50 value 16.13 μM with binding energy of -7.2 kcal/mol. The tyrosinase inhibitory activity of (6a) is comparable with standard kojic acid. Kinetic analysis indicated that compound 6a was mixed-type tyrosinase inhibitor with inhibition constant values Ki (13 μM) and Ki' (53 μM) and formed reversible enzyme inhibitor complex. The active vanillin analog (6a) was devoid of toxic effects as shown in cytotoxic studies.

  8. Kinetic and Product Studies of the Reaction Between Oxidized Mercury Species and Selected Thiols

    NASA Astrophysics Data System (ADS)

    Si, L.; Ariya, P.

    2008-12-01

    Mercury is a global pollutant with severe potential toxicity. The reduction of oxidized mercury species (Hg(II)) to elemental mercury (Hg(0)) affects the global distribution of mercury and competes for methylation processes of mercury in aquatic environment. This study focused on the reduction of Hg(II) by several selected thiols using a suite of complementary mass spectrometry and cold vapor fluorescence spectroscopy (CVAFS). Previous studies showed that irradiation of benzene solution of six mercury dimercaptides (benzyl, n-propyl, isopropyl, cyclopentyl, t-butyl and phenyl sulfide) at part-per-million level by a mercury arc lamp under a nitrogen atmosphere caused the formation of Hg(0) to occur. The reaction kinetics was studied using CVAFS, and the products of the reaction were analyzed using Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass spectrometry (MALDI-TOF-MS) and Gas Chromatography-Mass spectrometry (GC-MS). The kinetic data were obtained for 1-butanethiol, and 1-pentanethiol, 1-hexanethiol at environmental relevant conditions. The effects of light, pH, dissolved oxygen and chloride ion on reaction rates were also investigated. We will present our results and discuss their potential environmental implications on mercury cycling.

  9. A detailed kinetic study of Mox-1, a plasmid-encoded class C beta-lactamase.

    PubMed

    Alba, Jimena; Bauvois, Cedric; Ishii, Yoshikazu; Galleni, Moreno; Masuda, Katsuyoshi; Ishiguro, Masaji; Ito, Masahiko; Frere, Jean-Marie; Yamaguchi, Keizo

    2003-08-29

    Surveys of beta-lactamases in different parts of the world show an important increase in class C beta-lactamases, thus the study of these enzymes is becoming an important issue. We created an overproduction system for Mox-1, a plasmid class C beta-lactamase, by cloning the gene encoding this enzyme, and placing it under the control of a T7 promoter, using vector pET 28a. The enzyme, purified by ion exchange chromatography, was used to obtain the molecular mass (38246), the N-terminal sequence (GEASPVDPLRPVV), and pI (8.9), and to perform a detailed kinetic study. Cephalotin was used as reporter substrate in the case of poor substrates. The kinetic study showed that benzylpenicillin, cephalotin, cefcapene and moxalactam were good substrates for Mox-1 (k(cat)/K(m) values >2.5 x 10(6) M(-1) s(-1)). On the other hand, ceftazidime and cefepime were poor substrates for this enzyme (K(m) values >200 microM). Clavulanic acid had no inhibitory effect on Mox-1 (K(m)=30.2 mM), however aztreonam behaved as an inhibitor of Mox-1 (K(i)=2.85 microM).

  10. Studying the Unfolding Kinetics of Proteins under Pressure Using Long Molecular Dynamic Simulation Runs

    PubMed Central

    Chara, Osvaldo; Grigera, José Raúl

    2008-01-01

    The usefulness of computational methods such as molecular dynamics simulation has been extensively established for studying systems in equilibrium. Nevertheless, its application to complex non-equilibrium biological processes such as protein unfolding has been generally regarded as producing results which cannot be interpreted straightforwardly. In the present study, we present results for the kinetics of unfolding of apomyoglobin, based on the analysis of long simulation runs of this protein in solution at 3 kbar (1 atm = 1.01325, bar = 101 325 Pa). We hereby demonstrate that the analysis of the data collected within a simulated time span of 0.18 μs suffices for producing results, which coincide remarkably with the available unfolding kinetics experimental data. This not only validates molecular dynamics simulation as a valuable alternative for studying non-equilibrium processes, but also enables a detailed analysis of the actual structural mechanism which underlies the unfolding process of proteins under elusive denaturing conditions such as high pressure. PMID:19669536

  11. Progress in pathogenesis studies of spinocerebellar ataxia type 1.

    PubMed

    Cummings, C J; Orr, H T; Zoghbi, H Y

    1999-06-29

    Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited disorder characterized by progressive loss of coordination, motor impairment and the degeneration of cerebellar Purkinje cells, spinocerebellar tracts and brainstem nuclei. Many dominantly inherited neurodegenerative diseases share the mutational basis of SCA1: the expansion of a translated CAG repeat coding for glutamine. Mice lacking ataxin-1 display learning deficits and altered hippocampal synaptic plasticity but none of the abnormalities seen in human SCA1; mice expressing ataxin-1 with an expanded CAG tract (82 glutamine residues), however, develop Purkinje cell pathology and ataxia. These results suggest that mutant ataxin-1 gains a novel function that leads to neuronal degeneration. This novel function might involve aberrant interaction(s) with cell-specific protein(s), which in turn might explain the selective neuronal pathology. Mutant ataxin-1 interacts preferentially with a leucine-rich acidic nuclear protein that is abundantly expressed in cerebellar Purkinje cells and other brain regions affected in SCA1. Immunolocalization studies in affected neurons of patients and SCA1 transgenic mice showed that mutant ataxin-1 localizes to a single, ubiquitin-positive nuclear inclusion (NI) that alters the distribution of the proteasome and certain chaperones. Further analysis of NIs in transfected HeLa cells established that the proteasome and chaperone proteins co-localize with ataxin-1 aggregates. Moreover, overexpression of the chaperone HDJ-2/HSDJ in HeLa cells decreased ataxin-1 aggregation, suggesting that protein misfolding might underlie NI formation. To assess the importance of the nuclear localization of ataxin-1 and its role in SCA1 pathogenesis, two lines of transgenic mice were generated. In the first line, the nuclear localization signal was mutated so that full-length mutant ataxin-1 would remain in the cytoplasm; mice from this line did not develop any ataxia or pathology. This

  12. Minimizing adsorption of histidine-tagged proteins for the study of protein-deoxyribonucleic acid interactions by kinetic capillary electrophoresis.

    PubMed

    Liyanage, Ruchi; Krylova, Svetlana M; Krylov, Sergey N

    2013-12-27

    Affinity interactions between DNA and proteins play a crucial role in many cellular processes. Kinetic Capillary Electrophoresis is a highly efficient tool for kinetic and equilibrium studies of protein-DNA interactions. Recombinant proteins, which are typically used for in vitro studies of protein-DNA interactions, are often expressed with a His tag to aid in their purification. In this work, we study how His tags affect Kinetic Capillary Electrophoresis analysis of protein-DNA interactions. We found that the addition of a His tag can increase or decrease protein adsorption to a bare-silica capillary wall, dependent on the protein. For Kinetic Capillary Electrophoresis measurements, it is essential to have as little protein adsorption as possible. We screened a number of capillary coatings to reduce adsorption of the His-tagged DNA mismatch repair protein MutS to the capillary wall and found that UltraTrol LN was the most effective coating. The effectiveness of the coating was confirmed with the prevention of adsorption of His-tagged fat mass and obesity-associated protein. Under typical conditions, the coating reduced protein adsorption to a level at which accurate Kinetic Capillary Electrophoresis analysis of protein-DNA interactions was possible. We further used Kinetic Capillary Electrophoresis to study how the His tag affected Kd of protein-DNA interactions for the MutS protein. Using UltraTrol LN, we found that the effect of the His tag was insignificant.

  13. Pewaukee School District, Wisconsin. Case Study: Measures of Academic Progress

    ERIC Educational Resources Information Center

    Northwest Evaluation Association, 2015

    2015-01-01

    For more than a decade, Pewaukee School District Superintendent JoAnn Sternke has watched her district get better and better at its mission: opening the door to each student's future. The Wisconsin district began using Measures of Academic Progress® (MAP®) computer adaptive interim assessments from Northwest Evaluation Association™ (NWEA™) in 2004…

  14. Studies in iodine metabolism. Progress report, 1982-1983

    SciTech Connect

    Van Middlesworth, L.

    1983-01-01

    Research progress is reported for the period 1982 to 1983 in the following areas: (1) monitoring of animal thyroids for /sup 129/I, /sup 125/I, /sup 131/I, /sup 226/Ra, and /sup 228/Ra; and (2) neonatal hypo-l thyroidism in laboratory rats. (ACR)

  15. Adsorption of crystal violet onto functionalised multi-walled carbon nanotubes: Equilibrium and kinetic studies.

    PubMed

    Sabna, V; Thampi, Santosh G; Chandrakaran, S

    2016-12-01

    Synthetic dyes present in effluent from textile, paper and paint industries contain crystal violet (CV), a known carcinogenic agent. This study investigates the modification of multiwalled carbon nanotubes by acid reflux method and equilibrium and kinetic behaviour of adsorption of CV onto functionalized multi-walled carbon nanotubes (fMWNTs) in batch system. High stability of the fMWNTs suspension in water indicates the hydrophilicity of fMWNTs induced due to the formation of functional groups that make hydrogen bonds with water molecules. fMWNTs were characterized by Fourier Transform Infra Red (FTIR) spectroscopy and the functional groups present on the fMWNTs were confirmed. Characteristic variation was observed in the FTIR spectra of fMWNTs after adsorption of crystal violet onto it. Adsorption characteristics were evaluated as a function of system variables such as contact time, dosage of fMWNTs and initial concentration and pH of the crystal violet solution. Adsorption capacity of fMWNTs and percentage removal of the dye increased with increase in contact time, adsorbent dosage and pH but declined with increase in initial concentration of the dye. fMWNTs showed higher adsorption capacity compared to that of pristine MWNTs. Data showed good fit with the Langmuir and Freundlich isotherm models and the pseudo-second order kinetic model; the maximum adsorption capacity was 90.52mg/g. Kinetic parameters such as rate constants, equilibrium adsorption capacities and regression coefficients were estimated. Results indicate that fMWNTs are an effective adsorbent for the removal of crystal violet from aqueous solution.

  16. Model-based analysis for kinetic complexation study of Pizda and Cu(II)

    NASA Astrophysics Data System (ADS)

    Vosough, M.; Maeder, M.; Jalali-Heravi, M.; Norman, S. E.

    2008-08-01

    In the present work, the multivariate kinetic complexation of a new synthesized ligand, 1-(2″-hydroxyl cyclohexyl)-3'-[aminopropyl]-4-[3'-aminopropyl]piperazine (Pizda) and Cu 2+ in 50% ethanol-water solution is investigated using the UV-vis stopped-flow technique and state-of-the-art multi-wavelength numerical analysis. Model-based least squares fitting analysis or hard modeling is a specific part of chemometrics which is based on mathematical relationships for describing the measurements. Some recent developments include the incorporation of the effects of non-ideal experimental conditions into the fitting algorithm so it can substantially simplify experimental procedures. In this study no buffers are required because pH changes are taken into computations. Some 21 multi-wavelength kinetic measurements, taken at various initial concentrations of [H +] were analyzed globally, i.e. simultaneously applying an all inclusive reaction mechanism and a common set of species spectra. Using numerical analysis, the pH of the experimental solutions was allowed to vary as a consequence of the proceeding reactions. This enabled the complete kinetic analysis of the formation and dissociation of Cu(Pizda) n+ . Here protonation equilibria have been directly incorporated into the rate law, so thus variable pH values have been allowed during each measurement. Using the independently estimated stability constants (from spectrophotometric and potentiometric measurements) for the Cu(Pizda) n+ complexes, a total of six rate constants and one protonation constant could be elucidated. The results of the analysis include the concentration distribution and spectra of all chemical species involved in the reaction. A low standard deviation and residual profiles obtained validate the results.

  17. The Study of Kinetics of Diffusion and Phase Formation in the Layered Iron-Beryllium System

    NASA Astrophysics Data System (ADS)

    Kuterbekov, K. A.; Nurkenov, S. A.; Kislitsin, S. B.; Kuketayev, T. A.; Nurakhmetov, T. N.

    2017-02-01

    The methods of Mössbauer spectroscopy with X-ray phase analysis and Rutherford backscattering of protons were used to study the kinetics of diffusion and phase transformations in the layered iron-beryllium system. For the first time, the authors suggested and implemented a method for retardation of diffusion and phase formation processes in the layered iron-beryllium system using the barrier layer. It was established that the barrier layer limits the zone of beryllium dissolution in the area of implanted layer. The impact of the barrier layer on kinetics of thermally induced processes of diffusion and phase transformations in the layered Fe-Be system was determined using the example of Fe (10 μm): O+ - Be (0.7 μm) - 57Fe (0.1 μm). The authors suggested and implemented a method for recovery of the distribution function of the admixture atom concentration in the solid matrix-admixture solution on the basis of the X-ray diffraction data. The kinetics of mutual diffusion was determined for Fe and Be atoms in the α-Fe(Be) solution for both sides of the layered systems with a barrier layer and without it using the suggested method for recovery of the distribution function of the Be atom concentration. It was established that for the system without a barrier layer, the share of iron atoms ends at tann 5 h on the coating side and at tann 7.5 h on the iron side, while for the barrier layer case - at tann 20 h on the coating side and at tann 40 h on the iron side.

  18. [Study on apparent kinetics of photocatalytic oxidation degradation Rhodamine B by photo-Fenton reaction].

    PubMed

    Li, Hong; Zheng, Huai-Li; Li, Xiao-Hong; Xie, Li-Guo; Tang, Xue

    2008-11-01

    The Fenton process, mixed by hydrogen peroxide and iron salts with highly oxidative effect, is recognized as one of powerful advanced oxidation technologies available and can be used to destroy a variety of persistent organic pollutants. The oxidation power of Fenton reagent is due to the generation of hydroxyl radical (* OH) during the iron catalysed decomposition of hydrogen peroxide in acid medium. The hydroxyl radical with a high oxidation potential (2.8 eV) attacks and completely destroys the pollutants in Fenton process. The degradation of pollutants can be considerably improved by using sunlight radiation, which is due to the generation of additional hydroxyl radicals. This photo-Fenton process had been effectively used to degrade the pollutants. In this paper, the definite quantity of Fenton reagent was added in the definite concentration of Rhodamine B solution. The degradation reaction was carried out at pH 3.5 under natural sunlight. The factors influencing on photocatalytic oxidation degradation rate of Rhodamine B were studied following: the initial concentration of Rhodamine B, initial concentrateions of Fe2+ and H2O2. The orders of degradation reaction were obtained by solving exponential kinetics equations of curve fitting, thereby gaining the kinetic parameters and reaction dynamics equation of the reaction system. The research contents included mainly: the UV-Vis spectra of Rhodamine B solution, the concentration-absorbency work curve of Rhodamine B solution, the analysis of the reaction system at various initial Rhodamine B concentrations, the analysis of the reaction system at various initial Fe2+ concentrateions, the analysis of the reaction system at various initial H2O2 concentrations, and the calculation of the apparent kinetics parameters in reaction dynamics equation. The reaction dynamics equation from experiments was constructed: V = 5 x 10(-9) P1.28 F0.366 E0.920, and overall reaction order was 2.57.

  19. Crystallization kinetics of orthorhombic paracetamol from supercooled melts studied by non-isothermal DSC.

    PubMed

    Nikolakakis, Ioannis; Kachrimanis, Kyriakos

    2017-02-01

    A simple and highly reproducible procedure was established for the study of orthorhombic paracetamol crystallization kinetics, comprising melting, quench-cooling of the melt and scanning the formed glass by DSC at different heating rates. Results were analyzed on the basis of the mean as well as local values of the Avrami exponent, n, the energy of activation, as well as the Šesták-Berggren two-parameter autocatalytic kinetic model. The mean value of the Avrami kinetic exponent, n, ranged between 3 and 5, indicating deviation from the nucleation and growth mechanism underlying the Johnson-Mehl, Avrami-Kolmogorov (JMAK) model. To verify the extent of the deviation, local values of the Avrami exponent as a function of the volume fraction transformed were calculated. Inspection of the local exponent values indicates that the crystallization mechanism changes over time, possibly reflecting the uncertainty of crystallization onset, instability of nucleation due to an autocatalytic effect of the crystalline phase, and growth anisotropy due to impingement of spherulites in the last stages of crystallization. The apparent energy of activation, Ea, has a rather low mean value, close to 81 kJ/mol, which is in agreement with the observed instability of glassy-state paracetamol. Isoconversional methods revealed that Ea tends to decrease with the volume fraction transformed, possibly because of the different energy demands of nucleation and growth. The exponents of the Šesták-Berggren two-parameter model showed that the crystallized fraction influences the process, confirming the complexity of the crystallization mechanism.

  20. Model-based analysis for kinetic complexation study of Pizda and Cu(II).

    PubMed

    Vosough, M; Maeder, M; Jalali-Heravi, M; Norman, S E

    2008-08-01

    In the present work, the multivariate kinetic complexation of a new synthesized ligand, 1-(2''-hydroxyl cyclohexyl)-3'-[aminopropyl]-4-[3'-aminopropyl]piperazine (Pizda) and Cu(2+) in 50% ethanol-water solution is investigated using the UV-vis stopped-flow technique and state-of-the-art multi-wavelength numerical analysis. Model-based least squares fitting analysis or hard modeling is a specific part of chemometrics which is based on mathematical relationships for describing the measurements. Some recent developments include the incorporation of the effects of non-ideal experimental conditions into the fitting algorithm so it can substantially simplify experimental procedures. In this study no buffers are required because pH changes are taken into computations. Some 21 multi-wavelength kinetic measurements, taken at various initial concentrations of [H(+)] were analyzed globally, i.e. simultaneously applying an all inclusive reaction mechanism and a common set of species spectra. Using numerical analysis, the pH of the experimental solutions was allowed to vary as a consequence of the proceeding reactions. This enabled the complete kinetic analysis of the formation and dissociation of Cu(Pizda)(n+). Here protonation equilibria have been directly incorporated into the rate law, so thus variable pH values have been allowed during each measurement. Using the independently estimated stability constants (from spectrophotometric and potentiometric measurements) for the Cu(Pizda)(n+) complexes, a total of six rate constants and one protonation constant could be elucidated. The results of the analysis include the concentration distribution and spectra of all chemical species involved in the reaction. A low standard deviation and residual profiles obtained validate the results.

  1. Advances in Studies of Electrode Kinetics and Mass Transport in AMTEC Cells (abstract)

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; Kisor, A.; O'Connor, D.; Kikkert, S.

    1993-01-01

    Previous work reported from JPL has included characterization of electrode kinetics and alkali atom transport from electrodes including Mo, W, WRh(sub x), WPt(sub x)(Mn), in sodium AMTEC cells and vapor exposure cells, and Mo in potassium vapor exposure cells. These studies were generally performed in cells with small area electrodes (about 1 to 5 cm(sup 2)), and device geometry had little effect on transport. Alkali diffusion coefficients through these electrodes have been characterized, and approximate surface diffusion coefficients derived in cases of activated transport. A basic model of electrode kinetic at the alkali metal vapor/porous metal electrode/alkali beta'-alumina solid electrolyte three phase boundary has been proposed which accounts for electrochemical reaction rates with a collision frequency near the three phase boundary and tunneling from the porous electrode partially covered with adsorbed alkali metal atoms. The small electrode effect in AMTEC cells has been discussed in several papers, but quantitative investigations have described only the overall effect and the important contribution of electrolyte resistance. The quantitative characterization of transport losses in cells with large area electrodes has been limited to simulations of large area electrode effects, or characterization of transport losses from large area electrodes with significant longitudinal temperature gradients. This paper describes new investigations of electrochemical kinetics and transport, particularily with WPt(sub 3.5) electrodes, including the influence of electrode size on the mass transport loss in the AMTEC cell. These electrodes possess excellent sodium transport properties making verification of device limitations on transport much more readily attained.

  2. Levofloxacin oxidation by ozone and hydroxyl radicals: kinetic study, transformation products and toxicity.

    PubMed

    Hamdi El Najjar, Nasma; Touffet, Arnaud; Deborde, Marie; Journel, Romain; Leitner, Nathalie Karpel Vel

    2013-10-01

    This work was carried out to investigate the fate of the antibiotic levofloxacin upon oxidation with ozone and hydroxyl radicals. A kinetic study was conducted at 20 °C for each oxidant. Ozonation experiments were performed using a competitive kinetic method with carbamazepin as competitor. Significant levofloxacin removal was observed during ozonation and a rate constant value of 6.0×10(4) M(-1) s(-1) was obtained at pH 7.2. An H2O2/UV system was used for the formation of hydroxyl radicals HO. The rate constant of HO was determined in the presence of a high H2O2 concentration. The kinetic expressions yielded a [Formula: see text] value of 4.5×10(9) M(-1) s(-1) at pH 6.0 and 5.2×10(9) M(-1) s(-1) at pH 7.2. These results were used to develop a model to predict the efficacy of the ozonation process and pharmaceutical removal was estimated under different ozonation conditions (i.e. oxidant concentrations and contact times). The results showed that levofloxacin was completely degraded by molecular ozone during ozonation of water and that hydroxyl radicals had no effect in real waters conditions. Moreover, LC/MS/MS and toxicity assays using Lumistox test were performed to identify ozonation transformation products. Under these conditions, four transformation products were observed and their chemical structures were proposed. The results showed an increase in toxicity during ozonation, even after degradation of all of the observed transformation products. The formation of other transformation products not identified under our experimental conditions could be responsible for the observed toxicity. These products might be ozone-resistant and more toxic to Vibrio fisheri than levofloxacin.

  3. Kinetic and Thermochemical Studies of Weakly-Bound HO2 Complexes with Carboxylic acids

    NASA Astrophysics Data System (ADS)

    Zhao, Z.; Nicovich, J. M.; McKee, M. L.; Wine, P. H.

    2008-12-01

    Numerous theoretical and experimental studies have suggested that HO2 radicals are able to form strong hydrogen bonds with some closed-shell species, which can potentially influence our understanding of HO2 chemistry in the upper troposphere and lower stratosphere. In this study, a laser flash photolysis-tunable diode laser absorption spectroscopy technique has been employed to study the formation of HO2 complexes with formic and acetic acids. At low temperatures, equilibration kinetics have been observed, allowing adduct formation and dissociation rate coefficients to be obtained and adduct binding enthalpies to be determined. This is the first experimental study of the HO2-carboxylic acid complexes and the binding energies are in good agreement with the most recent theoretical estimates. The potential role of HO2-RC(O)OH adducts in atmospheric chemistry will be discussed.

  4. Adsorption kinetics and equilibrium study of nitrogen species onto radiata pine (Pinus radiata) sawdust.

    PubMed

    Harmayani, Kadek D; Faisal Anwar, A H M

    Nitrogen species (NH3-N, NO3-N, and NO2-N) are found as one of the major dissolved constituents in wastewater or stormwater runoff. In this research, laboratory experiments were conducted to remove these pollutants from the water environment using radiata pine (Pinus radiata) sawdust. A series of batch tests was conducted by varying initial concentration, dosage, particle size, pH, and contact time to check the removal performance. Test results confirmed the effectiveness of radiata pine sawdust for removing these contaminants from the aqueous phase (100% removal of NO3-N, and NO2-N; 55% removal of NH3-N). The adsorbent dosage and initial concentration showed a significantly greater effect on the removal process over pH or particle sizes. The optimum dosage for contaminant removal on a laboratory scale was found to be 12 g. Next, the adsorption kinetics were studied using intraparticle diffusion, liquid-film diffusion, and a pseudo-first order and pseudo-second order model. The adsorption of all species followed a pseudo-second order model but NO2-N adsorption followed both models. In addition, the kinetics of NO2-N adsorption showed two-step adsorption following intraparticle diffusion and liquid-film diffusion. The isotherm study showed that NO3-N and NO2-N adsorption fitted slightly better with the Freundlich model but that NH3-N adsorption followed both Freundlich and Langmuir models.

  5. Mass transfer, kinetics and equilibrium studies for the biosorption of methylene blue using Paspalum notatum.

    PubMed

    Kumar, K Vasanth; Porkodi, K

    2007-07-19

    Batch experiments were carried out for the sorption of methylene blue onto Paspalum notatum. The operating variables studied were initial dye concentration, initial solution pH, adsorbent dosage and contact time. Experimental equilibrium data were fitted to Freundlich, Langmuir and Redlich-Peterson isotherms by non-linear regression method. Six error functions was used to determine the optimum isotherm by non-linear regression method. The present study shows r2 as the best error function to determine the parameters involved in both two- and three-parameter isotherms. Langmuir isotherm was found to be the optimum isotherm for methylene blue onto P. notatum. The monolayer methylene blue sorption capacity of P. notatum was found to be 31 mg/g. The kinetics of methylene blue onto P. notatum was found to follow a pseudo second order kinetics. A Boyd plot confirms the external mass transfer as the rate-limiting step in the dye sorption process. The influence of initial dye concentration on the dye sorption process was represented in the form of dimensionless mass transfer numbers (Sh/Sc0.33) and was found to vary as C(0)-5x10(-6).

  6. Kinetic studies of lycopene isomerization in a tributyrin model system at gastric pH.

    PubMed

    Moraru, Catalin; Lee, Tung-Ching

    2005-11-16

    A semi-preparative HPLC method was developed in order to isolate and purify the 13-cis-lycopene isomer in tomato-based materials. The result was compared with the naturally predominant all-trans-lycopene isomer, in terms of stability to gastric pH at physiological temperature in a tributyrin model system. Kinetic experiments confirmed that lycopene isomerization is a reversible reaction, and under these conditions the all-trans isomer is more stable than the 13-cis isomer. In addition, it was found that at gastric pH 13-cis-lycopene would predominantly isomerize to the all-trans form rather than undergo oxidation/breakdown. A simulation based on the rate constants calculated in the kinetic study indicated that at gastric pH the lycopene isomeric distribution aimed toward an equilibrium characterized by approx 16% 13-cis-, 16% 9-cis-, and 68% all-trans-lycopene. This study suggests that pH-driven isomerization in the stomach is at least partially responsible for the relatively high cis-lycopene proportion found in vivo.

  7. Isotherm and kinetics study for acrylic acid removal using powdered activated carbon.

    PubMed

    Kumar, Arvind; Prasad, B; Mishra, I M

    2010-04-15

    The potential of powdered activated carbon (PAC) for the adsorption of acrylic acid (AA) from aqueous solution was studied at the initial concentration (C(0)) in the range of 50-500 mg/l over the temperature range of 303-348 K. The equilibrium adsorption studies were carried out to evaluate the effect of adsorbent dosage and contact time, change in pH by adding adsorbents and the initial concentration. Langmuir, Freundlich and Redlich-Peterson (R-P) equilibrium isotherm models were tested to represent the data. Error functions were used to test their validity to fit of the adsorption data with the isotherm and kinetic models. The Freundlich isotherm equation is found to best represent the equilibrium separation data in the temperature range of 303-348 K. The maximum adsorption capacity of AA onto PAC was obtained as q(m)=36.23 mg/g with an optimum PAC dosage w=20 g/l at 303 K for C(0)=100 mg/l. The pseudo-second-order kinetics is found to represent the experimental AA-PAC data. The negative value of DeltaG(ad)(o) (-16.60 to -18.18 kJ/mol K) indicate the feasibility and spontaneity of the adsorption process.

  8. Optimization and Kinetic Studies on Biodiesel Production from Kusum (Schleichera triguga) Oil Using Response Surface Methodology.

    PubMed

    Sarve, Antaram; Varma, Mahesh N; Sonawane, Shriram S

    2015-01-01

    In the present study, the low-cost non-edible kusum (Schleichera triguga) oil with a substantial amount of free fatty acid (FFA) was utilized for biodiesel synthesis. In pretreatment step, FFA was reduced by the acid catalyzed esterification method. Then, response surface method (RSM) in conjunction with centre composite design (CCD) containing 30 experimental runs were statistically employed for process optimization and kinetic study for the base catalyzed transesterification process. A statistical model predicted highest fatty acid methyl ester (FAME) yield of 97.37% at the optimal values of process parameters as follows: sodium methoxide concentration 0.9 wt% of oil, Methanol to oil molar ratio 9:1, temperature 58.9 ℃ and reaction time 58.5 min. Using these optimal parameters under experimental conditions in three independent replicates an actual FAME content of 98.14% was obtained which was in reasonable agreement with predicted one. The developed kinetic model suggested a 1.8(th) order reaction with activation energy of 31.42 kcal mol(-1) and frequency factor of 5.53×10(19) L mol(-1)min(-1). Furthermore, Important fuel properties of kusum oil biodiesel (KOB) was compared with ASTM 6751 and DIN EN 14214. The viscosity was found to be 5.34 Cst at 40 °C and the flash point was 152°C.

  9. A quantitative multiplexed mass spectrometry assay for studying the kinetic of residue-specific histone acetylation.

    PubMed

    Kuo, Yin-Ming; Henry, Ryan A; Andrews, Andrew J

    2014-12-01

    Histone acetylation is involved in gene regulation and, most importantly, aberrant regulation of histone acetylation is correlated with major human diseases. Although many lysine acetyltransferases (KATs) have been characterized as being capable of acetylating multiple lysine residues on histones, how different factors such as enzyme complexes or external stimuli (e.g. KAT activators or inhibitors) alter KAT specificity remains elusive. In order to comprehensively understand how the homeostasis of histone acetylation is maintained, a method that can quantitate acetylation levels of individual lysines on histones is needed. Here we demonstrate that our mass spectrometry (MS)-based method accomplishes this goal. In addition, the high throughput, high sensitivity, and high dynamic range of this method allows for effectively and accurately studying steady-state kinetics. Based on the kinetic parameters from in vitro enzymatic assays, we can determine the specificity and selectivity of a KAT and use this information to understand what factors influence histone acetylation. These approaches can be used to study the enzymatic mechanisms of histone acetylation as well as be adapted to other histone modifications. Understanding the post-translational modification of individual residues within the histones will provide a better picture of chromatin regulation in the cell.

  10. On the applicability of the standard kinetic theory to the study of nanoplasmas

    SciTech Connect

    D'Angola, A.; Boella, E.

    2014-08-15

    Kinetic theory applies to systems with a large number of particles, while nanoplasma generated by the interaction of ultra–short laser pulses with atomic clusters are systems composed by a relatively small number (10{sup 2} ÷ 10{sup 4}) of electrons and ions. In the paper, the applicability of the kinetic theory for studying nanoplasmas is discussed. In particular, two typical phenomena are investigated: the collisionless expansion of electrons in a spherical nanoplasma with immobile ions and the formation of shock shells during Coulomb explosions. The analysis, which is carried out comparing ensemble averages obtained by solving the exact equations of motion with reference solutions of the Vlasov-Poisson model, shows that for the dynamics of the electrons the error of the usually employed models is of the order of few percents (but the standard deviation in a single experiment can be of the order of 10%). Instead, special care must be taken in the study of shock formation, as the discrete structure of the electric charge can destroy or strongly modify the phenomenon.

  11. Hydrolysis of Sulfur Dioxide in Small Clusters of Sulfuric Acid: Mechanistic and Kinetic Study.

    PubMed

    Liu, Jingjing; Fang, Sheng; Wang, Zhixiu; Yi, Wencai; Tao, Fu-Ming; Liu, Jing-Yao

    2015-11-17

    The deposition and hydrolysis reaction of SO2 + H2O in small clusters of sulfuric acid and water are studied by theoretical calculations of the molecular clusters SO2-(H2SO4)n-(H2O)m (m = 1,2; n = 1,2). Sulfuric acid exhibits a dramatic catalytic effect on the hydrolysis reaction of SO2 as it lowers the energy barrier by over 20 kcal/mol. The reaction with monohydrated sulfuric acid (SO2 + H2O + H2SO4 - H2O) has the lowest energy barrier of 3.83 kcal/mol, in which the cluster H2SO4-(H2O)2 forms initially at the entrance channel. The energy barriers for the three hydrolysis reactions are in the order SO2 + (H2SO4)-H2O > SO2 + (H2SO4)2-H2O > SO2 + H2SO4-H2O. Furthermore, sulfurous acid is more strongly bonded to the hydrated sulfuric acid (or dimer) clusters than the corresponding reactant (monohydrated SO2). Consequently, sulfuric acid promotes the hydrolysis of SO2 both kinetically and thermodynamically. Kinetics simulations have been performed to study the importance of these reactions in the reduction of atmospheric SO2. The results will give a new insight on how the pre-existing aerosols catalyze the hydrolysis of SO2, leading to the formation and growth of new particles.

  12. Chemical kinetic studies of atmospheric reactions using tunable diode laser spectroscopy

    NASA Technical Reports Server (NTRS)

    Worsnop, Douglas R.; Nelson, David D.; Zahniser, Mark S.

    1993-01-01

    IR absorption using tunable diode laser spectroscopy provides a sensitive and quantitative detection method for laboratory kinetic studies of atmospheric trace gases. Improvements in multipass cell design, real time signal processing, and computer controlled data acquisition and analysis have extended the applicability of the technique. We have developed several optical systems using off-axis resonator mirror designs which maximize path length while minimizing both the sample volume and the interference fringes inherent in conventional 'White' cells. Computerized signal processing using rapid scan (300 kHz), sweep integration with 100 percent duty cycle allows substantial noise reduction while retaining the advantages of using direct absorption for absolute absorbance measurements and simultaneous detection of multiple species. Peak heights and areas are determined by curve fitting using nonlinear least square methods. We have applied these techniques to measurements of: (1) heterogeneous uptake chemistry of atmospheric trace gases (HCl, H2O2, and N2O5) on aqueous and sulfuric acid droplets; (2) vapor pressure measurements of nitric acid and water over prototypical stratospheric aerosol (nitric acid trihydrate) surfaces; and (3) discharge flow tube kinetic studies of the HO2 radical using isotopic labeling for product channel and mechanistic analysis. Results from each of these areas demonstrate the versatility of TDL absorption spectroscopy for atmospheric chemistry applications.

  13. Fundamental study of the mechanism and kinetics of cellulose hydrolysis by acids and enzymes

    NASA Astrophysics Data System (ADS)

    Gong, C. S.; Chang, M.

    1981-02-01

    There are three basic enzymes e.g., endoglucanase (C/sub x/), exoglucanase (C1) and cellobiase comprising the majority of extracellular cellulase enzymes produced by the cellulolytic mycelial fungi, Trichoderma reesei, and other cellulolytic microorganisms. The kinetics of cellobiase were developed on the basis of applying the pseudo-steady state assumption to hydrolyze cellobiose to glucose. The results indicated that cellobiase was bjected to end-product inhibition by glucose. The kinetic modeling of exoglucanase (C1) with respect to cellodextrins was studied. Both glucose and cellobiose were found to be inhibitors of this enzyme with cellobiose being a stronger inhibitor than glucose. Similarly, endoglucanase (C/sub x) is subject to end-product inhibition by glucose. Crystallinity of the cellulose affects the rate of hydrolysis by cellulases. Hence, the changes in crystallinity of cellulose in relation to chemical pretreatment and enzyme hydrolysis was compared. The study of cellulase biosynthesis resulted in the conclusion that exo-and endo-glucanases are coinduced while cellobiase is synthesized independent of the other two enzymes.

  14. Relaxation Kinetic Study of Eudragit® NM30D Film Based on Complex Modulus Formalism.

    PubMed

    Penumetcha, Sai Sumana; Byrn, Stephen R; Morris, Kenneth R

    2015-10-01

    This study is aimed at resolving and characterizing the primary (α) and secondary relaxations (β) in Eudragit® NM30D film based on apparent activation energies derived from complex modulus formalism using dielectric analysis (DEA). The glass transition (T g) of the film was determined using differential scanning calorimetry (DSC). The α relaxation corresponding to T g and the β relaxations occurring below T g were probed using DEA. The occurrence of α and β relaxations in Eudragit® NM30D film was elucidated using the complex modulus of the dielectric response employing loss modulus and permittivity data. Activation energies of these relaxations and the fundamental frequency so determined support the assignment of the relaxation pattern in the Eudragit® NM30D film. DEA methodology of the complex modulus formalism is a useful tool for differentiating the α and β relaxation kinetics in Eudragits® not easily studied using traditional thermal methods such as DSC. The kinetics associated with α and β relaxations so determined will provide formulation design support for solid orals that incorporate Eudragit® polymers. As mobility changes can affect stability and diffusion, the dipolar α and β relaxations revealed through DEA analysis may enable a better correlation to functionality of Eudragit® based pharmaceutical dosage forms.

  15. Equilibrium and kinetic studies of methyl violet sorption by agricultural waste.

    PubMed

    Hameed, B H

    2008-06-15

    In this work, sunflower (Helianthus annuus L.) seed hull (SSH), an agricultural waste, was evaluated for its ability to remove methyl violet (MV) from aqueous solutions. Sorption isotherm of MV onto the SSH was determined at 30 degrees C with the initial concentrations of MV in the range of 25-300 mg/L. The equilibrium data were analyzed using the Langmuir, Freundlich and Temkin isotherm models. The equilibrium process was described well by the Freundlich isotherm model. The maximum SSH sorption capacity was found to be 92.59 mg/L at 30 degrees C. The kinetic data were studied in terms of the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The pseudo-second-order model best described the sorption process. A single-stage batch-adsorber design of the adsorption of MV onto SSH was studied based on the Freundlich isotherm equation. The results indicated that sunflower seed hull was an attractive candidate for removing methyl violet from aqueous solution.

  16. Kinetic study of phase transformation of n-octane using hydrothermal diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Liu, Chuanjiang; Zheng, Haifei; Wang, Duojun

    2016-02-01

    A kinetic study of phase transformation of n-octane has been performed using a hydrothermal diamond anvil cell. The results show that pressure has a negative effect on the solid-liquid reaction rate. The increase of pressure can accelerate the liquid-solid transformation rate. Upon the liquid-solid transformation, the light transmittance showed a decreased trend with time in the early stage, which was caused by the formation of a large quantity of crystal nuclei. In the later stage, the light transmittance almost remained the same, thus indicating a growth stage of crystal nuclei. The activation volume yields a value of 2.16×10-5 and -1.35×10-5 m3/mol for the solid-liquid and liquid-solid transformations. Based on the obtained activation energy, the solid-liquid transformation is dominated by the interfacial reaction and diffusion, and the liquid-solid transformation is controlled by diffusion. This technique is an effective and powerful tool for the transformation kinetics study of n-octane.

  17. Applications of SXPS for studying surface structure, reaction mechanisms and kinetics

    SciTech Connect

    Mullins, D.R.; Huntley, D.R.; Overbury, S.H.

    1994-12-31

    Soft x-ray photoelectron spectroscopy (SXPS) from the S 2p core level has been used to study adsorbate induced reconstruction, identify reaction intermediates and study reaction kinetics on the Ni(111) surface. The S 2p binding energy is affected by the nature of the surface adsorption site. It has been determined from the number of S 2p states and their relative binding energies that adsorbed S induces a reconstruction of the Ni(111) surface and that the S adsorbs in fourfold sites on terraces and in troughs. S 2p SXPS has also been used to identify adsorbed species during the thermal decomposition of methanethiol on Ni(111). CH{sub 3}SH adsorbs as CH{sub 3}S{minus} at low temperatures. Above 200 K, the CH{sub 3}S{minus} changes adsorption site and the C-S bond begins to cleave. The relative concentrations of CH{sub 3}S{minus} in the two different sites and of atomic S have been monitored as a function of temperature and initial coverage. As a result of the sensitivity and resolution available in SXPS, reaction rates and kinetic parameters have been obtained for the decomposition of benzenethiol on Ni(111) by monitoring the changes in the surface composition continuously as a function of temperature and time.

  18. Preliminary study: kinetics of oil extraction from sandalwood by microwave-assisted hydrodistillation

    NASA Astrophysics Data System (ADS)

    Kusuma, H. S.; Mahfud, M.

    2016-04-01

    Sandalwood and its oil, is one of the oldest known perfume materials and has a long history (more than 4000 years) of use as mentioned in Sanskrit manuscripts. Sandalwood oil plays an important role as an export commodity in many countries and its widely used in the food, perfumery and pharmaceuticals industries. The aim of this study is to know and verify the kinetics and mechanism of microwave-assisted hydrodistillation of sandalwood based on a second-order model. In this study, microwave-assisted hydrodistillation is used to extract essential oils from sandalwood. The extraction was carried out in ten extraction cycles of 15 min to 2.5 hours. The initial extraction rate, the extraction capacity and the second-order extraction rate constant were calculated using the model. Kinetics of oil extraction from sandalwood by microwave-assisted hydrodistillation proved that the extraction process was based on the second-order extraction model as the experimentally done in three different steps. The initial extraction rate, h, was 0.0232 g L-1 min-1, the extraction capacity, C S, was 0.6015 g L-1, the second-order extraction rate constant, k, was 0.0642 L g-1 min-1 and coefficient of determination, R 2, was 0.9597.

  19. Utility of ten-second uptake periods for kinetic studies of serotonin uptake by intact platelets

    SciTech Connect

    Costa, J.L.; Kirk, K.L.; Stark, H.

    1981-09-01

    When washed human platelets accumulate serotonin (5HT), it is possible with the use of formaldehyde fixative to measure uptake over periods as short as 10 seconds. To evaluate the utility of these short times for kinetic studies of 5HT uptake, we have examined the accuracy with which the 10 second uptake rate reflects changes in the extracellular 5HT concentration. The amount of 5HT taken up over a 10 second period appears to be determined by the concentration of 5HT present in the extracellular medium during that time period, and the uptake rate can change rapidly following sudden changes in the extracellular 5HT concentration. However, the extent of inhibition of 5HT uptake in the presence of imipramine of extracellular 5HT concentrations greater than 10-5M is somewhat different depending on whether the 5HT is allowed to accumulate for a 10-second or a 5- or 10-minute uptake period. A 10-second uptake period thus appears to be useful for kinetic studies of initial 5HT uptake velocities under normal conditions, but under inhibitory conditions may give results differing from those obtained with minute-long periods.

  20. Kinetics studies with fruit bromelain (Ananas comosus) in the presence of cysteine and divalent ions.

    PubMed

    Kaur, Tajwinder; Kaur, Amandeep; Grewal, Ravneet K

    2015-09-01

    The kinetics of cysteine and divalent ion modulation viz. Ca(2+), Cu(2+), Hg(2+) of fruit bromelain (EC 3.4.22.33) have been investigated in the present study. Kinetic studies revealed that at pH 4.5, cysteine induced V-type activation of bromelain catalyzed gelatin hydrolysis. At pH 3.5, Ca(2+) inhibited the enzyme noncompetitively, whereas, both K-and V-type activations of bromelain were observed in the presence of 0.5 mM Ca(2+) at pH 4.5 and 7.5. Bromelain was inhibited competitively at 0.6 mM Cu(2+) ions at pH 3.5, which changed to an uncompetitive inhibition at pH 4.5 and 7.5. An un-competitive inhibition of bromelain catalyzed gelatin hydrolysis was observed in the presence of 0.6 mM Hg(2+) at pH 3.5 and 4.5. These findings suggest that divalent ions modulation of fruit bromelain is pH dependent.

  1. Lipase-catalysed hydrolysis of short-chain substrates in solution and in emulsion: a kinetic study.

    PubMed

    Nini, L; Sarda, L; Comeau, L C; Boitard, E; Dubès, J P; Chahinian, H

    2001-11-30

    We have studied the enzymatic hydrolysis of solutions and emulsions of vinyl propionate, vinyl butyrate and tripropionin by lipases of various origin and specificity. Kinetic studies of the hydrolysis of short-chain substrates by microbial triacylglycerol lipases from Rhizopus oryzae, Mucor miehei, Candida rugosa, Candida antarctica A and by (phospho)lipase from guinea-pig pancreas show that these lipolytic enzymes follow the Michaelis-Menten model. Surprisingly, the activity against solutions of tripropionin and vinyl esters ranges from 70% to 90% of that determined against emulsions. In contrast, a non-hyperbolic (sigmoidal) dependence of enzyme activity on ester concentration is found with human pancreatic lipase, triacylglycerol lipase from Humicola lanuginosa (Thermomyces lanuginosa) and partial acylglycerol lipase from Penicillium camembertii and the same substrates. In all cases, no abrupt jump in activity (interfacial activation) is observed at substrate concentration corresponding to the solubility limit of the esters. Maximal lipolytic activity is always obtained in the presence of emulsified ester. Despite progress in the understanding of structure-function of lipases, interpretation of the mode of action of lipases active against solutions of short-chain substrates remains difficult. Actually, it is not known whether these enzymes, which possess a lid structure, are in open or/and closed conformation in the bulk phase and whether the opening of the lid that gives access to the catalytic triad is triggered by interaction of the enzyme molecule with monomeric substrates or/and multimolecular aggregates (micelles) both present in the bulk phase. From the comparison of the behaviour of lipases used in this study which, in some cases, follow the Michaelis-Menten model and, in others, deviate from classical kinetics, it appears that the activity of classical lipases against soluble short-chain vinyl esters and tripropionin depends not only on specific

  2. Combustion synthesis of advanced materials: Studies of the influence of gravity and reaction kinetics

    NASA Astrophysics Data System (ADS)

    Pelekh, Aleksey Yevgeuyevich

    Combustion synthesis is an attractive technique to synthesize a wide variety of advanced materials that include powders and near-net shape products of ceramics, intermetallics, composites and functionally gradient materials. It is also considered to be a valuable method for space applications, because of low energy requirements and simple equipment. However, it is necessary to understand how microgravity influences the combustion mechanism and properties of the synthesized materials. In this work, combustion synthesis experiments were conducted both in normal and in low-gravity conditions, using a unique setup designed and developed for this purpose. Microgravity experiments were done in NASA Lewis Research Center using Drop Tower which provided 2.2 s of 10-5 g level, as well as on-board DC-9 aircraft (20 s of 10-2 g). It was clearly demonstrated that gravity plays an important role during combustion synthesis. It significantly influences both the combustion and structure formation processes. It was also shown that microgravity conditions allow the synthesis of materials with improved micro- and macrostructures. The study of chemical reaction kinetics in combustion synthesis systems is of critical importance. The measurement of kinetic parameters (especially activation energy) and a comparison with known elementary processes provides an insight into the controlling step of the mechanism. In this work, a computer-assisted electrothermography method was developed to determine the intrinsic kinetics of reactions under conditions similar to those realized during combustion synthesis of materials. This technique was applied to investigate the kinetics and other features associated with the reaction of titanium with nitrogen at 1 atm pressure. It was shown that at temperatures below the melting point of titanium, the reaction follows parabolic rate law. The obtained activation energy value is in good agreement with literature data. At higher temperatures, however, the

  3. The pyrolysis of 2-methylfuran: a quantum chemical, statistical rate theory and kinetic modelling study.

    PubMed

    Somers, Kieran P; Simmie, John M; Metcalfe, Wayne K; Curran, Henry J

    2014-03-21

    Due to the rapidly growing interest in the use of biomass derived furanic compounds as potential platform chemicals and fossil fuel replacements, there is a simultaneous need to understand the pyrolysis and combustion properties of such molecules. To this end, the potential energy surfaces for the pyrolysis relevant reactions of the biofuel candidate 2-methylfuran have been characterized using quantum chemical methods (CBS-QB3, CBS-APNO and G3). Canonical transition state theory is employed to determine the high-pressure limiting kinetics, k(T), of elementary reactions. Rice-Ramsperger-Kassel-Marcus theory with an energy grained master equation is used to compute pressure-dependent rate constants, k(T,p), and product branching fractions for the multiple-well, multiple-channel reaction pathways which typify the pyrolysis reactions of the title species. The unimolecular decomposition of 2-methylfuran is shown to proceed via hydrogen atom transfer reactions through singlet carbene intermediates which readily undergo ring opening to form collisionally stabilised acyclic C5H6O isomers before further decomposition to C1-C4 species. Rate constants for abstraction by the hydrogen atom and methyl radical are reported, with abstraction from the alkyl side chain calculated to dominate. The fate of the primary abstraction product, 2-furanylmethyl radical, is shown to be thermal decomposition to the n-butadienyl radical and carbon monoxide through a series of ring opening and hydrogen atom transfer reactions. The dominant bimolecular products of hydrogen atom addition reactions are found to be furan and methyl radical, 1-butene-1-yl radical and carbon monoxide and vinyl ketene and methyl radical. A kinetic mechanism is assembled with computer simulations in good agreement with shock tube speciation profiles taken from the literature. The kinetic mechanism developed herein can be used in future chemical kinetic modelling studies on the pyrolysis and oxidation of 2-methylfuran

  4. Experimental Studies of the Growth Kinetics of Methane Clathrate Hydrates & Superfluid Hydrodynamics on the Nanoscale

    NASA Astrophysics Data System (ADS)

    Botimer, Jeffrey David

    This thesis details the experimental findings of three distinct research projects. The first studies the growth kinetics of methane clathrate hydrates grown under the influence of multiple factors including surfactants, porous media, substrate wetting properties, and salt content. The second investigates the flow behaviors of superfluid helium through single, high aspect ratio nanopipes. The third models the frequency response of a quartz tuning fork in high pressure normal and superfluid helium and demonstrates how quartz tuning forks can be used as cheap, small, in situ, cryogenic pressure gauges. The first project reports studies of the kinetics of growth of methane hydrates from liquid water containing small amounts of surfactant (<500 ppm of sodium dodecyl sulfate, SDS). The kinetics are monitored using simultaneous measurements of the uptake of methane detected by a pressure drop in the gas phase, and either visual observations of the amount of liquid water and solid phase in the reaction vessel, or in situ micro-Raman measurements or in situ NMR measurements. These diagnostics show that the uptake of methane and the conversion of liquid water to a solid phase do not occur simultaneously; the uptake of gas always lags the visual and spectroscopic signatures of the disappearance of liquid water and the formation of solid. The evidence suggests that the SDS causes water to form an intermediate immobile solid-like state before combining with the methane to form hydrate. The growth mechanism is related to the surfactant and disappears for low SDS concentrations (<25 ppm). Also reported are studies of the growth rates of methane hydrates as a function of substrate wetting properties, driving force, and growth media. The second project studies pressure driven flow of superfluid helium through single high aspect ratio glass nanopipes into a vacuum has been studied for a wide range of pressure drop (0--30 atm), reservoir temperature (0.8--2.5K), pipe lengths (1-30mm

  5. Study of ethane hydrate formation kinetics using the chemical affinity model with and without presence of surfactants

    NASA Astrophysics Data System (ADS)

    Karimi, Reza; Varaminian, Farshad; Izadpanah, Amir A.

    2014-12-01

    In this article, we examine ethane hydrate formation kinetics with and without the presence of various surfactants. Firstly, the influences of stirring rate and initial pressure without the presence of surfactants are studied. The effects of four surfactants containing Sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), Polyoxyethylene (20) sorbitanmonopalmitate (Tween® 40), and TritonX-100 (TX-100) on ethane hydrate formation kinetics were experimentally investigated. Then the chemical affinity model is applied to model the ethane hydrate formation kinetics with and without surfactants. The kinetic parameters of the chemical affinity model were computed for the ethane hydrate formation with and without surfactants. We will see that the results of the modeling are in good agreement with the experimental data.

  6. Single-biomolecule kinetics: the art of studying a single enzyme.

    PubMed

    Claessen, Victor I; Engelkamp, Hans; Christianen, Peter C M; Maan, Jan C; Nolte, Roeland J M; Blank, Kerstin; Rowan, Alan E

    2010-01-01

    The potential of single-enzyme studies to unravel the complex energy landscape of these polymeric catalysts is the next critical step in enzymology. From its inception in Rotman's emulsion experiments in the 1960s, the field of single-molecule enzymology has now advanced into the time-resolved age. Technological advances have enabled individual enzymatic turnover reactions to be observed with a millisecond time resolution. A number of initial studies have revealed the underlying static and dynamic disorder in the catalytic rates originating from conformational fluctuations. Although these experiments are still in their infancy, they may be able to relate the topography of the energy landscape to the biological function and regulation of enzymes. This review summarizes some of the experimental techniques and data-analysis methods that have been used to study individual enzyme molecules in search of a deeper understanding of their kinetics.

  7. Filtration method for studies of the kinetics of hypo-osmotic pore closure in erythrocyte.

    PubMed

    Shurkhina, E S; Nesterenko, V M; Tsvetaeva, N V; Kolodey, S V; Nikulina, O F

    2010-11-01

    Filterability of erythrocytes through small (3 μ) pores decreases with decreasing osmolarity of suspension medium because of hypo-osmotic swelling of cells. After appearance of lytic pores, erythrocyte filterability increases for some time, while after recovery of membrane integrity it decreases again. We suggest filtration method for studies of the kinetics of hypo-osmotic lytic pores closure. The dynamics of changes in erythrocyte filterability was studied in 2 patients with paroxysmal nocturnal hemoglobinuria and 6 donors (Ht 0.01%, Na phosphate buffer 5 mM, pH 7.4, 35 mOsm, 24°C). The method can be used for studies of erythrocyte membrane characteristics in various diseases and for evaluation of the membranotropic effects of drugs, infusion media, hemolysins, ethanol, etc.

  8. [Progress on study of achromatopsia and targeted gene therapy].

    PubMed

    Dai, Xu-feng; Pang, Ji-jing

    2012-08-01

    Achromatopsia is an early onset retinal dystrophy that causes severe visual impairment. To date, four genes have been found to be implicated in achromatopsia-associated mutations: guanine nucleotide-binding protein (GNAT2), cyclic nucleotide-gated channel alpha-3 (CNGA3), cyclic nucleotide-gated channel beta-3 (CNGB3) and phosphodiesterase 6C (PDE6C). Even with early onset, the slow progress and the good responses to gene therapy in animal models render achromatopsia a very attractive candidate for human gene therapy after the successful of the Phase I clinical trials of Leber's congenital amaurosis. With the development of molecular genetics and the therapeutic gene replacement technology, the adeno-associated viral (AAV) vector-mediated gene therapy for achromatopsia in the preclinical animal experiments achieved encouraging progress in the past years. This article briefly reviews the recent research achievements of achromatopsia with gene therapy.

  9. Progressive Failure Studies of Composite Panels with and without Cutouts

    NASA Technical Reports Server (NTRS)

    Jaunky, Navin; Ambur, Damodar R.; Davila, Carlos G.; Hilburger, Mark; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    Progressive failure analyses results are presented for composite panels with and without a cutout and subjected to in-plane shear loading and compression loading well into their postbuckling regime. Ply damage modes such as matrix cracking, fiber-matrix shear, and fiber failure are modeled by degrading the material properties. Results from finite element analyses are compared with experimental data. Good agreement between experimental data and numerical results are observed for most structural configurations when initial geometric imperfections are appropriately modeled.

  10. [Study on simplification of extraction kinetics model and adaptability of total flavonoids model of Scutellariae radix].

    PubMed

    Chen, Yang; Zhang, Jin; Ni, Jian; Dong, Xiao-Xu; Xu, Meng-Jie; Dou, Hao-Ran; Shen, Ming-Rui; Yang, Bo-Di; Fu, Jing

    2014-01-01

    Because of irregular shapes of Chinese herbal pieces, we simplified the previously deduced general extraction kinetic model for TCMs, and integrated particle diameters of Chinese herbs that had been hard to be determined in the final parameter "a". The reduction of the direct determination of particle diameters of Chinese herbs was conducive to increase the accuracy of the model, expand the application scope of the model, and get closer to the actual production conditions. Finally, a simplified model was established, with its corresponding experimental methods and data processing methods determined. With total flavonoids in Scutellariae Radix as the determination index, we conducted a study on the adaptability of total flavonoids extracted from Scutellariae Radix with the water decoction method in the model. The results showed a good linear correlation among the natural logarithm value of the mass concentration of total flavonoids in Scutellariae Radix, the time and the changes in the natural logarithm of solvent multiple. Through calculating and fitting, efforts were made to establish the kinetic model of extracting total flavonoids from Scutellariae Radix with the water decoction method, and verify the model, with a good degree of fitting and deviation within the range of the industrial production requirements. This indicated that the model established by the method has a good adaptability.

  11. Isotherm, thermodynamic, kinetics and adsorption mechanism studies of methyl orange by surfactant modified silkworm exuviae.

    PubMed

    Chen, Hao; Zhao, Jie; Wu, Junyong; Dai, Guoliang

    2011-08-15

    This paper reports on the development of organo-modified silkworm exuviae (MSE) adsorbent prepared by using hexadecyltrimethylammonium bromide (HDTMAB) for removing methyl orange (MO), a model anionic dye, from aqueous solution. The natural and modified samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FT-IR). Batch adsorption experiments were carried out to remove MO from its aqueous solutions using SE and MSE. It was observed that the adsorption capacity of MSE is 5-6 times of SE. The different parameters effecting on the adsorption capacity such as pH of the solution, initial dye concentration, temperature and contact time have been investigated. Analysis of adsorption results obtained at different temperatures showed that the adsorption pattern on the MSE can be described perfectly with Langmuir isotherm model compared with Freundlich and Dubinin-Radushkevich (D-R) isotherm models, and the characteristic parameters for each adsorption isotherm were also determined. The adsorption process has been found exothermic in nature and thermodynamic parameters have been calculated. The adsorption kinetic followed the pseudo-second order kinetic model. The results of FT-IR, EDS and desorption studies all suggest that methyl orange adsorption onto the MSE should be mainly controlled by the hydrophobic interaction mechanism, along with a considerable contribution of the anionic exchange mechanism. The results indicate that HDTMAB-modified silkworm exuviae could be employed as low-cost material for the removal of methyl orange anionic dye from wastewater.

  12. Kinetic study of solid waste pyrolysis using distributed activation energy model.

    PubMed

    Bhavanam, Anjireddy; Sastry, R C

    2015-02-01

    The pyrolysis characteristics of municipal solid waste, agricultural residues such as ground nut shell, cotton husk and their blends are investigated using non-isothermal thermogravimetric analysis (TGA) with in a temperature range of 30-900 °C at different heating rates of 10 °C, 30 °C and 50 °C/min in inert atmosphere. From the thermograms obtained from TGA, it is observed that the maximum rate of degradation occurred in the second stage of the pyrolysis process for all the solid wastes. The distributed activation energy model (DAEM) is used to study the pyrolysis kinetics of the solid wastes. The kinetic parameters E (activation energy), k0 (frequency factor) are calculated from this model. It is found that the range of activation energies for agricultural residues are lower than the municipal solid waste. The activation energies for the municipal solid waste pyrolysis process drastically decreased with addition of agricultural residues. The proposed DAEM is successfully validated with TGA experimental data.

  13. A dehydroxylation kinetics study of brucite Mg(OH)2 at elevated pressure and temperature

    NASA Astrophysics Data System (ADS)

    Liu, Chuanjiang; Wang, Duojun; Zheng, Haifei; Liu, Tao

    2016-11-01

    We performed an in situ dehydroxylation kinetics study of brucite under water-saturated conditions in the pressure and temperature ranges of 593-633 K and 668-1655 MPa using a hydrothermal diamond anvil cell. The kinetic analysis of the isothermal-isobaric data using an Avrami-type model involving nucleation and growth processes yields values for the dehydroxylation rate and reaction order compatible with a reaction mechanism limited by the monodimensional diffusion of water molecules from structural OH groups. Our results show a negative pressure dependence on the reaction rate k and a positive temperature dependence on the k. The dehydroxylation of brucite yields an activation volume ∆V value of 5.03 cm3/mol. Following the Arrhenius relationship, the apparent activation energy E a of the process is calculated to be 146 kJ/mol within the experimental P-T ranges. It is determined that the fluid production rates varying from 4.4 × 10-7 to 10.7 × 10-7 {m}_{fluid}3 {m}_{rock}^{ - 3} {s}^{ - 1} are a few orders of magnitude greater than the strain rate of the mantle serpentinites, which may be fast enough to result in the brittle fracture of rocks. Moreover, the rate of fluid production will be enhanced when brucite occurs in the non-/low H2O environments of the subduction zone.

  14. A kinetic study of pyrolysis and combustion of microalgae Chlorella vulgaris using thermo-gravimetric analysis.

    PubMed

    Agrawal, Ankit; Chakraborty, Saikat

    2013-01-01

    This work uses thermo-gravimetric, differential thermo-gravimetric and differential thermal analyses to evaluate the kinetics of pyrolysis (in inert/N(2) atmosphere) and (oxidative) combustion of microalgae Chlorella vulgaris by heating from 50 to 800 °C at heating rates of 5-40 °C/min. This study shows that combustion produces higher biomass conversion than pyrolysis, and that three stages of decomposition occur in both cases, of which, the second one--consisting of two temperature zones--is the main stage of devolatization. Proteins and carbohydrates are decomposed in the first of the two zones at activation energies of 51 and 45 kJ/mol for pyrolysis and combustion, respectively, while lipids are decomposed in its second zone at higher activation energies of 64 and 63 kJ/mol, respectively. The kinetic expressions of the reaction rates in the two zones for pyrolysis and combustion have been obtained and it has been shown that increased heating rates result in faster and higher conversion.

  15. Kinetic studies on the inhibition of GABA-T by gamma-vinyl GABA and taurine.

    PubMed

    Sulaiman, Saba A J; Suliman, Fakhr Eldin O; Barghouthi, Samira

    2003-08-01

    Gamma-aminobutyric acid transaminase (GABA-T, EC 2.6.1.19) is a pyridoxal phosphate (PLP) dependent enzyme that catalyzes the degradation of gamma-aminobutyric acid. The kinetics of this reaction are studied in vitro, both in the absence, and in the presence of two inhibitors: gamma-vinyl GABA (4-aminohex-5-enoic acid), and a natural product, taurine (ethylamine-2-sulfonic acid). A kinetic model that describes the transamination process is proposed. GABA-T from Pseudomonas fluorescens is inhibited by gamma-vinyl GABA and taurine at concentrations of 51.0 and 78.5 mM. Both inhibitors show competitive inhibition behavior when GABA is the substrate and the inhibition constant (Ki) values for gamma-vinyl GABA and taurine were found to be 26 +/- 3 mM and 68 +/- 7 mM respectively. The transamination process of alpha-ketoglutarate was not affected by the presence of gamma-vinyl GABA, whereas, taurine was a noncompetitive inhibitor of GABA-T when alpha-ketoglutarate was the substrate. The inhibition dissociation constant (Kii) for this system was found to be 96 +/- 10 mM. The Michaelis-Menten constant (Km) in the absence of inhibition, was found to be 0.79 +/- 0.11 mM, and 0.47 +/- 0.10 mM for GABA and alpha-ketoglutarate respectively.

  16. Kinetic and theoretical study of the reaction of Cl atoms with a series of linear thiols

    SciTech Connect

    Garzon, Andres; Albaladejo, Jose

    2008-11-21

    The reactions of Cl with a series of linear thiols: 1-propanethiol (k{sub 1}), 1-butanethiol (k{sub 2}), and 1-pentanethiol (k{sub 3}) were investigated as a function of temperature (in the range of 268-379 K) and pressure (in the range of 50-200 Torr) by laser photolysis-resonance fluorescence. Only 1-propanethiol has previously been studied, but at 1 Torr of total pressure. The derived Arrhenius expressions obtained using our kinetic data were as follows: k{sub 1}=(3.97{+-}0.44)x10{sup -11} exp[(410{+-}36)/T], k{sub 2}=(1.01{+-}0.16)x10{sup -10} exp[(146{+-}23)/T], and k{sub 3}=(1.28{+-}0.10)x10{sup -10} exp[(129{+-}25)/T] (in units of cm{sup 3} molecule{sup -1} s{sup -1}). Moreover, a theoretical insight into mechanisms of these reactions has also been pursued through ab initio Moeller-Plesset second-order perturbation treatment calculations with 6-311G** basis set. Optimized geometries have been obtained for transition states and molecular complexes appearing along the different reaction pathways. Furthermore, molecular energies have been calculated at QCISD(T) level in order to get an estimation of the activation energies. Finally, the nature of the molecular complexes and transitions states is analyzed by using kinetic-potential and natural bond orbital total energy decomposition schemes.

  17. Kinetics and thermodynamic study of aniline adsorption by multi-walled carbon nanotubes from aqueous solution.

    PubMed

    Al-Johani, Hind; Abdel Salam, Mohamed

    2011-08-15

    Multi-walled carbon nanotubes (MWCNTs) were used in the adsorptive removal of aniline, an organic pollutant, from an aqueous solution. It was found that carbon nanotubes with a higher specific surface area adsorbed and removed more aniline from an aqueous solution. The adsorption was dependent on factors, such as MWCNTs dosage, contact time, aniline concentration, solution pH and temperature. The adsorption study was analyzed kinetically, and the results revealed that the adsorption followed pseudo-second order kinetics with good correlation coefficients. In addition, it was found that the adsorption of aniline occurred in two consecutive steps, including the slow intra-particle diffusion of aniline molecules through the nanotubes. Various thermodynamic parameters, including the Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°), were calculated. The results indicated that the spontaneity of the adsorption, exothermic nature of the adsorption and the decrease in the randomness reported as ΔG°, ΔH° and ΔS°, respectively, were all negative.

  18. Impacts of heterogeneous organic matter on phenanthrene sorption--Equilibrium and kinetic studies with aquifer material

    USGS Publications Warehouse

    Karapanagioti, Hrissi K.; Kleineidam, Sybille; Sabatini, David A.; Grathwohl, Peter; Ligouis, Bertrand

    2000-01-01

    Sediment organic matter heterogeneity in sediments is shown to impact the sorption behavior of contaminants. We investigated the sorptive properties as well as the composition of organic matter in different subsamples (mainly grain size fractions) of the Canadian River Alluvium (CRA). Organic petrography was used as a new tool to describe and characterize the organic matter in the subsamples. The samples studied contained many different types of organic matter including bituminous coal particles. Differences in sorption behavior were explained based on these various types of organic matter. Subsamples containing predominately coaly, particulate organic matter showed the highest Koc, the highest nonlinearity of sorption isotherms and the slowest sorption kinetics. Soil subsamples with organic matter present as organic coatings around the quartz grains evidenced the lowest Koc, the most linear sorption isotherms and the fastest sorption kinetics, which was not limited by slow intraparticle diffusion. Due to the high sorption capacity of the coaly particles even when it is present as only a small fraction of the composite organic content (<3%) causes Koc values which are much higher than expected for soil organic matter (e.g. Koc − Kow relationships). The results show that the identification and quantification of the coaly particles within a sediment or soil sample is a prerequisite in order to understand or predict sorption behavior of organic pollutants.

  19. Efficient removal of cadmium using magnetic multiwalled carbon nanotube nanoadsorbents: equilibrium, kinetic, and thermodynamic study

    NASA Astrophysics Data System (ADS)

    Pashai Gatabi, Maliheh; Milani Moghaddam, Hossain; Ghorbani, Mohsen

    2016-07-01

    Adsorptive potential of maghemite decorated multiwalled carbon nanotubes (MWCNTs) for the removal of cadmium ions from aqueous solution was investigated. The magnetic nanoadsorbent was synthesized using a versatile and cost effective chemical route. Structural, magnetic and surface charge properties of the adsorbent were characterized using FTIR, XRD, TEM, VSM analysis and pHPZC determination. Batch adsorption experiments were performed under varied system parameters such as pH, contact time, initial cadmium concentration and temperature. Highest cadmium adsorption was obtained at pH 8.0 and contact time of 30 min. Adsorption behavior was kinetically studied using pseudo first-order, pseudo second-order, and Weber-Morris intra particle diffusion models among which data were mostly correlated to pseudo second-order model. Adsorbate-adsorbent interactions as a function of temperature was assessed by Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models from which Freundlich model had the highest consistency with the data. The adsorption capacity increased with increasing temperature and maximum Langmuir's adsorption capacity was found to be 78.81 mg g-1 at 298 K. Thermodynamic parameters and activation energy value suggest that the process of cadmium removal was spontaneous and physical in nature, which lead to fast kinetics and high regeneration capability of the nanoadsorbent. Results of this work are of great significance for environmental applications of magnetic MWCNTs as promising adsorbent for heavy metals removal from aqueous solutions.

  20. Kinetic, structural and molecular docking studies on the inhibition of tyrosinase induced by arabinose.

    PubMed

    Hu, Wei-Jiang; Yan, Li; Park, Daeui; Jeong, Hyoung Oh; Chung, Hae Young; Yang, Jun-Mo; Ye, Zhuo Ming; Qian, Guo-Ying

    2012-04-01

    Tyrosinase plays a central role in biological pigment formation, and hence knowledge of tyrosinase catalytic mechanisms and regulation may have medical, cosmetic, and agricultural applications. We found in this study that arabinose significantly inhibited tyrosinase, and this was accompanied by conformational changes in enzyme structure. Kinetic analysis showed that arabinose-mediated inactivation followed first-order kinetics, and single and multiple classes of rate constants were measured. Arabinose displayed a mixed-type inhibitory mechanism with K(i)=0.22±0.07 mM. Measurements of intrinsic and ANS-binding fluorescence showed that arabinose induced tyrosinase to unfold and expose inner hydrophobic regions. We simulated the docking between tyrosinase and arabinose (binding energies were -26.28 kcal/mol for Dock6.3 and -2.02 kcal/mol for AutoDock4.2) and results suggested that arabinose interacts mostly with His61, Asn260, and Met280. The present strategy of predicting tyrosinase inhibition by simulation of docking by hydroxyl groups may prove useful in screening for potential tyrosinase inhibitors, as shown here for arabinose.

  1. Steady state kinetic studies of purified yeast plasma membrane proton-translocating ATPase.

    PubMed

    Koland, J G; Hammes, G G

    1986-05-05

    The plasma membrane H+-ATPase from bakers' yeast was purified and reconstituted with phosphatidylserine. The steady state kinetics of ATP hydrolysis catalyzed by the H+-ATPase were studied over a wide range of Mg2+ and ATP concentrations. Whereas MgATP was the substrate hydrolyzed, excess concentrations of either Mg2+ or ATP were inhibitory. The dependence of the steady state initial velocity of ATP hydrolysis on the concentration of MgATP at a fixed concentration of Mg2+ was sigmoidal rather than hyperbolic. This precluded mechanisms involving only activation and inhibition by Mg2+ and competitive inhibition by ATP. Two alternative interpretations of these results are: 1) the enzyme possesses multiple catalytic sites which interact cooperatively; or 2) the enzyme can exist in multiple conformational states which catalyze MgATP hydrolysis by parallel pathways. The rate laws for both mechanisms are identical so that the two mechanisms cannot be distinguished on the basis of the kinetic data. The data are well fit by the rate law for these mechanisms with the inclusion of competitive inhibition by Mg2+ and ATP and an independent inhibition site for Mg2+.

  2. Dye adsorption of cotton fabric grafted with PPI dendrimers: Isotherm and kinetic studies.

    PubMed

    Salimpour Abkenar, Samera; Malek, Reza Mohammad Ali; Mazaheri, Firouzmehr

    2015-11-01

    In this research, the cotton fabrics grafted with two generations of the poly(propylene imine) dendrimers were applied to adsorb textile dyes from aqueous solutions. Direct Red 80 (anionic dye), Disperse Yellow 42 (nonionic dye) and Basic Blue 9 (cationic dye) were selected as model dyes. The effect of various experimental parameters such as initial concentration of dyes, charge of dyes molecule, salt and pH was investigated on the adsorption process. Furthermore, kinetics and equilibrium of the adsorption process on the grafted samples were studied. It was found that maximum adsorption of anionic and disperse dyes took place at around pH 3, while cationic dye could be adsorbed at around pH 11. The Langmuir equation was able to describe the mechanism of dyes adsorption. In addition, the second-order equation was found to be fit with the kinetics data. Interestingly, it seems that the dye adsorption of the grafted fabrics is strongly pH dependent.

  3. Kinetic Reaction Mechanism of Sinapic Acid Scavenging NO2 and OH Radicals: A Theoretical Study

    PubMed Central

    Lu, Yang; Wang, AiHua; Shi, Peng; Zhang, Hui; Li, ZeSheng

    2016-01-01

    The mechanism and kinetics underlying reactions between the naturally-occurring antioxidant sinapic acid (SA) and the very damaging ·NO2 and ·OH were investigated through the density functional theory (DFT). Two most possible reaction mechanisms were studied: hydrogen atom transfer (HAT) and radical adduct formation (RAF). Different reaction channels of neutral and anionic sinapic acid (SA-) scavenging radicals in both atmosphere and water medium were traced independently, and the thermodynamic and kinetic parameters were calculated. We find the most active site of SA/SA- scavenging ·NO2 and ·OH is the –OH group in benzene ring by HAT mechanism, while the RAF mechanism for SA/SA- scavenging ·NO2 seems thermodynamically unfavorable. In water phase, at 298 K, the total rate constants of SA eliminating ·NO2 and ·OH are 1.30×108 and 9.20×109 M-1 S-1 respectively, indicating that sinapic acid is an efficient scavenger for both ·NO2 and ·OH. PMID:27622460

  4. Kinetic studies of the strengthening effect on liquid hot water pretreatments by organic acids.

    PubMed

    Lyu, Huisheng; Lv, Chunliu; Zhang, Minhua; Liu, Jiatao; Meng, Fanmei; Geng, Zhong Feng

    2017-03-22

    The liquid hot water (LHW) pretreatments would be accelerated by the organic acids produced from the process. In the study, the organic acids included not only acetic acid but also lactic acid during LHW hydrolysis of reeds, at 180-220°C and for 15-135min. The lactic acid was presumably produced from xylose degradation in the pretreatment process. The different organic acids, such as acetic acid, lactic acid and acetic-lactic acids, were used to strengthen the LHW pretreatments for increasing xylose production. Moreover, the work presented kinetic models of xylose and hemicellulose at different conditions, considering the generation of lactic acid. The experimental and kinetic results both indicated that acetic-lactic acids had synergistic catalytic effect on the reaction, which could not only inhibit the degradation of xylose, but also promote the hydrolysis of hemicellulose. Besides, the highest concentration of xylose of 7.323g/L was obtained at 200°C, for 45min and with 1wt% acetic-lactic acids.

  5. Eriobotrya japonica seed biocomposite efficiency for copper adsorption: Isotherms, kinetics, thermodynamic and desorption studies.

    PubMed

    Mushtaq, Mehwish; Bhatti, Haq Nawaz; Iqbal, Munawar; Noreen, Saima

    2016-07-01

    Adsorption techniques are widely used to remove pollutants from wastewater; however, composites are gaining more importance due to their excellent adsorption properties. Bentonite composite with Eriobotrya japonica seed was prepared and used for the adsorption of copper (Cu) metal from aqueous media. The process variables such as pH, Cu(II) ions initial concentration, adsorbent dose, contact time and temperature were optimized for maximum Cu(II) adsorption. At pH 5, adsorbent dose 0.1 g, contact time 45 min, Cu(II) ions initial concentration 75 mg/L and temperature 45 °C, maximum Cu(II) adsorption was achieved. Desorption studies revealed that biocomposite is recyclable. Langmuir, Freundlich and Harkins-Jura isotherms as well as pseudo-first and pseudo-second-order kinetics models were applied to understand the adsorption mechanism. Thermodynamic parameters (ΔG(0), ΔH(0) and ΔS(0)) suggest that the adsorption process was spontaneous and endothermic in nature. The pseudo-second-order kinetic model and Langmuir isotherm fitted well to the adsorption data. Results showed that biocomposite was more efficient for Cu(II) adsorption in comparison to individuals native Eriobotrya japonica seed biomass and Na-bentonite.

  6. Thermochemical conversion pathways of Kappaphycus alvarezii granules through study of kinetic models.

    PubMed

    Das, Prasanta; Mondal, Dibyendu; Maiti, Subarna

    2017-03-10

    Kappaphycus alvarezii seaweed belongs to the class of red alga (Rhodophyta). The granules obtained after recovery of "sap" (liquid plant stimulant) from freshly harvested alga is a promising biomass feedstock for energy application. Herein we report the kinetic behaviour of the granules using thermogravimetric analysis (TGA) at different heating rates in N2 atmosphere and thermogravimetric-mass spectrometry (TG-MS) analysis. Sawdust as lignocellulosic biomass is considered for comparative study. Four different kinetic models (i) multilinear regression technique, (ii) Friedman method, (iii) Flynn-Wall-Ozawa (FWO) method and (iv) Kissinger-Akahira-Sunose (KAS) method are used to evaluate the apparent activation energy (Ea), the pre-exponential factor (Aα) and the overall reaction order (n). Maximum SO2 peak at 300°C and 950°C (from TG-MS), indicates that slow pyrolysis at 500°C, with a packed bed lime scrubber at the outlet during temperature rise, is the best suited thermochemical pathway for energy harnessing.

  7. Microwave assisted synthesis and optimization of Aegle marmelos-g-poly(acrylamide): release kinetics studies.

    PubMed

    Setia, A; Kumar, R

    2014-04-01

    Microwave assisted grafting of poly(acrylamide) on to Aegle marmelos gum was carried out employing 3-factor 3-level full factorial design. Microwave power, microwave exposure time and concentration of gum were selected as independent variable and grafting efficiency was taken as dependent variable. A. marmelos-g-poly(acrylamide) was characterized by FTIR, DSC, X-ray diffraction and scanning electron microscopy. Microwave power, microwave exposure time had synergistic effect on grafting efficiency where as concentration of the gum did not contributed much to grafting efficiency. Batch having microwave power - 80%, microwave exposure time -120 s and concentration of A. marmelos gum - 2% was selected as the optimized formulation. Comparative release behaviour of diclofenac sodium from the matrix tablets of A. marmelos gum and A. marmelos-g-polyacrylamide was evaluated. The results of kinetic studies revealed that the graft copolymer matrix, marketed tablets and polymer matrix tablets of A. marmelos gum released the drug by zero order kinetics and with n value greater than 1, indicating that the mechanism for release as super case II transport i.e. dominated by the erosion and swelling of the polymer.

  8. Thermoluminescence of kunzite: A study of kinetic processes and dosimetry characteristics

    NASA Astrophysics Data System (ADS)

    Ogundare, F. O.; Alatishe, M. A.; Chithambo, M. L.; Costin, G.

    2016-04-01

    Since the use of natural minerals for dating and dose reconstruction using luminescence techniques is well-established and always of interest, we present thermoluminescence characteristics of kunzite, a gem variety of spodumene. The chemical composition of the sample was determined using an Electron Probe MicroAnalyzer to be (Li0.996Na0.009Mn0.006)∑ = 1.016(Al0.981Cr0.003Fe2+0.001)∑ = 0.995[(Si1.993Al0.008)∑ = 2.000O6]. Thermoluminescence glow curves measured at 0.5 K/s after laboratory irradiation consist of three prominent peaks at 338 K (labelled as peak I), 454 K (peak II) and 681 K (peak III). The dose response of these three peaks is linear in the range 20-308 Gy studied. The position of each of the peaks is independent of dose, an archetypical feature of first order behaviour. However, detailed kinetic analyses showed that in fact, the peaks are not subject to first order kinetics. Each of the three peaks is affected by thermal quenching with an associated activation energy of thermal quenching estimated to be 0.70, 1.35 and 0.54 eV for peaks I, II and III respectively. In terms of dosimetry use, only peak III was found to be reliable for possible use in luminescence dating and dose reconstruction.

  9. Isotherm and kinetic studies of Burazol Blue ED dye biosorption by dried anaerobic sludge.

    PubMed

    Caner, Necmettin; Kiran, Ismail; Ilhan, Semra; Iscen, Cansu Filik

    2009-06-15

    Biosorption potential of dried anaerobic sludge (DAS) for Burazol Blue ED (BB) was studied with respect to pH, equilibrium time, initial dye concentrations and temperature to determine equilibrium and kinetic models. The most suitable pH, equilibrium time and initial dye concentration were determined as 0.5+/-0.03, 75 min and 150 mg/L, respectively, at a biomass dosage of 0.4 g/L and 25 degrees C+/-1.0. The equilibrium data was best described by the Langmuir isotherm model. Maximum uptake capacity (q(m)) of DAS for the dyestuff (BB) were 118.3, 125.8 and 127.5mg/g biomass at temperatures of 25, 40 and 50 degrees C, respectively, indicating that the biosorption process is spontaneous and favored at higher temperatures. The overall biosorption process was best described by pseudo-second-order kinetic model. Gibbs free energy changes were calculated as -356.8, -519.7 and -520.6J/mol at 25, 40 and 50 degrees C, respectively.

  10. Riboflavin-sensitized photooxidation of Ceftriaxone and Cefotaxime. Kinetic study and effect on Staphylococcus aureus.

    PubMed

    Reynoso, Eugenia; Spesia, Mariana B; García, Norman A; Biasutti, María A; Criado, Susana

    2015-01-01

    Trace amounts of the widely used β-lactam antibiotics (Atbs) in waste water may cause adverse effects on the ecosystems and contribute to the proliferation of antibiotic-resistant bacteria. On these grounds, kinetic and mechanistic aspects of photosensitized degradation of Ceftriaxone (Cft) and Cefotaxime (Ctx), have been studied in pure water by stationary and time-resolved techniques. Additionally, possible implications of these photoprocesses on the antimicrobial activity of the Atbs have also been investigated. Photoirradiation of aqueous solutions of Cft and Ctx produces the degradation of both Atbs in the presence of Riboflavin (vitamin B2), a well known pigment dissolved in natural aquatic systems. The process occurs through Type I and Type II mechanisms, with effective prevalence of the former. The participation of O2(-), OH and O2((1)Δg) is supported by experiments of oxygen consumption carried out in the presence of specific scavengers for such reactive oxygen species. Microbiological assays exhibit a parallelism between the rate of Cft and Ctx photodegradation and the loss of their bactericidal capacity on Staphylococcus aureus strains. Results contribute to both understanding kinetic and mechanism aspects of the degradation and predicting on natural decay of Atbs waste water-contaminants.

  11. Clinical study of quantitative diagnosis of early cervical cancer based on the classification of acetowhitening kinetics

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Cheung, Tak-Hong; Yim, So-Fan; Qu, Jianan Y.

    2010-03-01

    A quantitative colposcopic imaging system for the diagnosis of early cervical cancer is evaluated in a clinical study. This imaging technology based on 3-D active stereo vision and motion tracking extracts diagnostic information from the kinetics of acetowhitening process measured from the cervix of human subjects in vivo. Acetowhitening kinetics measured from 137 cervical sites of 57 subjects are analyzed and classified using multivariate statistical algorithms. Cross-validation methods are used to evaluate the performance of the diagnostic algorithms. The results show that an algorithm for screening precancer produced 95% sensitivity (SE) and 96% specificity (SP) for discriminating normal and human papillomavirus (HPV)-infected tissues from cervical intraepithelial neoplasia (CIN) lesions. For a diagnostic algorithm, 91% SE and 90% SP are achieved for discriminating normal tissue, HPV infected tissue, and low-grade CIN lesions from high-grade CIN lesions. The results demonstrate that the quantitative colposcopic imaging system could provide objective screening and diagnostic information for early detection of cervical cancer.

  12. Extracellular mercury sequestration by exopolymeric substances produced by Yarrowia spp.: Thermodynamics, equilibria, and kinetics studies.

    PubMed

    Oyetibo, Ganiyu Oladunjoye; Miyauchi, Keisuke; Suzuki, Hitoshi; Ishikawa, Satoru; Endo, Ginro

    2016-12-01

    Exopolymeric substances (EPS) produced by highly mercury-resistant strains of the yeast Yarrowia spp. (Idd1 and Idd2) were isolated and studied for their mercury binding potential. Excellent yield (approximately 0.3 g EPS per gram biomass) of soluble EPS in medium with 3% glucose was observed in the Yarrowia cultures 7 day post-inoculation. A gram dry weight of the EPS consists mainly of carbohydrates (0.4 g), protein (0.3-0.4 g), uronic acid (0.02 g), and nucleic acids (0.002 g). Mercury interactions with the biopolymer were measured as uptake kinetics from a simulated aquatic system and modelled with thermodynamics and calculated mass action equilibria. The EPS forms a complex with Hg(2+) in water with small activation energy (≤2 kJ mol(-1)), achieving about 30 mg Hg(2+) adsorption per gram dry weight of EPS. The adsorption models confirmed complexation of Hg(2+) by the EPS via heterogeneous multilayer adsorption that obey second-order kinetics at constant rate of 4.0 and 8.1 mg g(-1) min(-1). The EPS used chemisorption as rate-limiting step that controls the uptake of Hg(2+) from aquatic systems during micro-precipitation as bio-removal strategy. The EPS are promising biotechnological tools to design bioreactors for treatment of mercury-rich industrial wastewater.

  13. Experimental and kinetic studies for phycoremediation and dye removal by Chlorella pyrenoidosa from textile wastewater.

    PubMed

    Pathak, Vinayak V; Kothari, Richa; Chopra, A K; Singh, D P

    2015-11-01

    Potential of Chlorella pyrenoidosa was experimentally investigated for phycoremediation and dye removal from textile wastewater (TWW) in batch cultures. Growth of alga was observed at various concentration of textile wastewater (25%, 50%, 75% and 100%) and was found in a range of 8.1-14 μg ml(-1) day(-1). Growth study revealed that alga potentially grows up to 75% concentrated textile wastewater and reduces phosphate, nitrate and BOD by 87%, 82% and 63% respectively. Methylene blue dye (MB) removal was also observed by using dry and wet algal biomass harvested after phycoremediation. Adsorption isotherms (Langmuir and Freundlich) and kinetic models (pseudo first and second order) were applied on adsorption process. Dry algal biomass (DAB) was found more efficient biosorbent with large surface area and showed high binding affinity for MB dye in compare to wet algal biomass (WAB). The RL value for both biosorbent showed feasible adsorption process as the obtained value was between 0 and 1. Pseudo second order kinetic model with high degree of correlation coefficient and low sum of error squares (SSE %) value was found more suitable for representation of adsorption process in case of both biosorbents, however pseudo first order also showed high degree of correlation for both biosorbents.

  14. A kinetic study of the interaction between atomic oxygen and aerosols

    NASA Technical Reports Server (NTRS)

    Akers, F. I.; Wightman, J. P.

    1976-01-01

    This study was concerned with the effects of NH4Cl and (NH4)2SO4 aerosols on the kinetics of disappearance of atomic oxygen. Atomic oxygen was generated by a 2.45-GHz microwave discharge and the kinetics of disappearance measured in a fast flow system using NO2 titration. Values of the recombination coefficient for heterogeneous wall recombination were determined for clean, H2SO4-coated, and (NH4)2SO4-coated Pyrex to be 0.000050, 0.000020, and 0.000019, respectively. A rapid exothermic chemical reaction was found to occur between atomic oxygen and an NH4Cl wall coating; the products were NH3, NO, H2O, and HCl. The NH4Cl aerosol was generated by gas phase reaction of NH3 with HCl. The aerosol particles were approximately spherical and nearly monodisperse with a mean diameter of 1.6 plus or minus 0.2 micron. The rate constant for the disappearance of atomic oxygen in the presence of NH4Cl aerosol was measured. No significant decrease was observed in the rate of disappearance of atomic oxygen in the presence of an (NH4)2SO4 aerosol at a concentration of 285 mg per cu m.

  15. Ambient reaction kinetics of atmospheric oxygenated organics with the OH radical: a computational methodology study.

    PubMed

    Elm, Jonas; Jørgensen, Solvejg; Bilde, Merete; Mikkelsen, Kurt V

    2013-06-28

    The gas phase hydrogen abstraction reaction kinetics of short chained oxygenated hydrocarbons of atmospheric relevance has been studied using density functional theory, basis set extrapolation procedures, Møller-Plesset second order perturbation theory and Coupled-Cluster Singles Doubles. The rate constants for the reaction of the OH radical with nine different oxygenated compounds: CH3OH, CH3CH2OH, H2CO, CH3CHO, CH3COCH3, CH3OCH3, HCOOH, CH3COOH, HCOOCH3 with a total of 18 individual hydrogen abstraction reactions have been computationally determined and compared to experimental data. The performance of DFT in predicting the imaginary vibrational frequency of the nuclear motion at the transition state has been evaluated to assess tunnelling effects using Wigner, Bell and Eckart tunnelling corrections. Several different hybrid methodologies utilizing DFT/MP2 structures, vibrational frequencies and explicitly correlated Coupled Cluster single point energy corrections have been investigated to identify an approach for obtaining reliable reaction kinetics. Our investigation shows that CCSD(T)-F12a/VTZ-F12//BH&HLYP/aug-cc-pVTZ using a Bell or Eckart tunnelling correction yields rate constants within a factor of ~3 of experimental data and branching ratios within experimental uncertainty for the test set of short chained oxygenated compounds of atmospheric relevance.

  16. Photodegradation of levofloxacin in aqueous and organic solvents: a kinetic study.

    PubMed

    Ahmad, Iqbal; Bano, Raheela; Sheraz, Muhammad Ali; Ahmed, Sofia; Mirza, Tania; Ansari, Shakeel Ahmad

    2013-06-01

    The kinetics of photodegradation of levofloxacin in solution on UV irradiation in the pH range 2.0-12.0 has been studied using a HPLC method. Levofloxacin undergoes first-order kinetics in the initial stages of the reaction and the apparent first-order rate constants are of the order of 0.167 to 1.807×10-3 min-1. The rate-pH profile is represented by a curve indicating the presence of cationic, dipolar and anionic species during the reaction. The singly ionized form of the molecule is non-fluorescent and is less susceptible to photodegradation. The increase in the degradation rate in the pH range 5.0-9.0 may be due to greater reactivity of the ionized species existing in that range. The rate appears to vary with a change in the degree of ionization of the species present in a particular pH range and their susceptibility to photodegradation. Above pH 9, the decrease in the rate of photodegradation may be a result of deprotonation of the piperazinyl group. The levofloxacin molecule is more stable in the pH range around 7, which is then suitable for formulation purposes. The photodegradation of levofloxacin was found to be affected by the dielectric constant and viscosity of the medium.

  17. [Study on Kinetic of Hg2+ from Wastewater Absorbed by Lemon Residues].

    PubMed

    Shen, Wang-qing; Wang, Miao; Yang, Ting

    2016-03-01

    With low price and its superior adsorption performance after modification, currently agricultural waste is used as adsorbent of heavy metals in wastewater, which has become a hot research topic. To study on Hg2+ from wastewater absorbed by lemon residues that has been modified by 15% concentration of sulphuric acid. The pore volume, pore size and other properties of the adsorbent were test. The samples were characterized by differential thermal analysis, IR, electron microscopy and spectroscopy. The result showed that the adsorption rate was controlled by membrane diffusion kinetics that was viewed as the first order kinetics equation of the Lagergren, which was physically absorbed. The adsorption properties of modified lemon residues were improved greatly, and the pore size distribution mainly was medium. There were three losses-weight process. There was a endothermic peak around 66 degrees C and two exotherm near 316 degrees C and 494 degrees C. Basic framework of Lemon residues was not changed and structure of Lemon residues was amorphous; the surface of modified lemon residues loosen and many pores formed, and Hg2+ have been adsorbed effectively.

  18. Experimental and numerical studies of burning velocities and kinetic modeling for practical and surrogate fuels

    NASA Astrophysics Data System (ADS)

    Zhao, Zhenwei

    To help understand the fuel oxidation process in practical combustion environments, laminar flame speeds and high temperature chemical kinetic models were studied for several practical fuels and "surrogate" fuels, such as propane, dimethyl ether (DME), and primary reference fuel (PRF) mixtures, gasoline and n-decane. The PIV system developed for the present work is described. The general principles for PIV measurements are outlined and the specific considerations are also reported. Laminar flame speeds were determined for propane/air over a range of equivalence ratios at initial temperature of 298 K, 500 K and 650 K and atmospheric pressure. Several data sets for propane/air laminar flame speeds with N 2 dilution are also reported. These results are compared to the literature data collected at the same conditions. The propane flame speed is also numerically calculated with a detailed kinetic model and multi component diffusion, including Soret effects. This thesis also presents experimentally determined laminar flame speeds for primary reference fuel (PRF) mixtures of n-heptane/iso-octane and real gasoline fuel at different initial temperature and at atmospheric pressure. Nitrogen dilution effects on the laminar flame speed are also studied for selected equivalence ratios at the same conditions. A minimization of detailed kinetic model for PRF mixtures on laminar flame speed conditions was performed and the measured flame speeds were compared with numerical predictions using this model. The measured laminar flame speeds of n-decane/air mixtures at 500 K and at atmospheric pressure with and without dilution were determined. The measured flame speeds are significantly different that those predicted using existing published kinetic models, including a model validated previously against high temperature data from flow reactor, jet-stirred reactor, shock tube ignition delay, and burner stabilized flame experiments. A significant update of this model is described which

  19. Kinetics of Cytotoxic Lymphocytes Reconstitution after Induction Chemotherapy in Elderly AML Patients Reveals Progressive Recovery of Normal Phenotypic and Functional Features in NK Cells.

    PubMed

    Rey, Jérôme; Fauriat, Cyril; Kochbati, Eloïse; Orlanducci, Florence; Charbonnier, Aude; D'Incan, Evelyne; Andre, Pascale; Romagne, François; Barbarat, Bernadette; Vey, Norbert; Olive, Daniel

    2017-01-01

    NK cells are defective in acute myeloid leukemia (AML) at diagnosis. Here, we studied the kinetic of expression of the major activating and inhibitory receptors of NK, CD8 T, and γδ T cells in patients undergoing chemotherapy (CT) for the treatment of AML (n = 29). We showed that NK cells are the main affected population at diagnosis and that expression of activating receptors is partially restored within a few weeks after CT. CD8 T cells and γδ T cells are only weakly affected at diagnosis. Killer cell immunoglobulin-like receptor expression by NK cells, but not NKG2A and CD85j, was downregulated. Interestingly, the development of NK cells appeared altered as the most immature CD56(bright) NK cells were seriously underrepresented. Finally, we showed that NK cell functions were only partially restored 6 weeks after CT as degranulation capabilities of NK cells recovered, whereas cytokine production remained low. Our data point out NK cells as antitumor effectors peculiarly hampered by leukemic cells. This study may indicate a timeline when NK-mediated therapies or other immunotherapies could be performed, particularly for patients excluded of hematopoietic stem cell transplantation.

  20. Kinetics of Cytotoxic Lymphocytes Reconstitution after Induction Chemotherapy in Elderly AML Patients Reveals Progressive Recovery of Normal Phenotypic and Functional Features in NK Cells

    PubMed Central

    Rey, Jérôme; Fauriat, Cyril; Kochbati, Eloïse; Orlanducci, Florence; Charbonnier, Aude; D’Incan, Evelyne; Andre, Pascale; Romagne, François; Barbarat, Bernadette; Vey, Norbert; Olive, Daniel

    2017-01-01

    NK cells are defective in acute myeloid leukemia (AML) at diagnosis. Here, we studied the kinetic of expression of the major activating and inhibitory receptors of NK, CD8 T, and γδ T cells in patients undergoing chemotherapy (CT) for the treatment of AML (n = 29). We showed that NK cells are the main affected population at diagnosis and that expression of activating receptors is partially restored within a few weeks after CT. CD8 T cells and γδ T cells are only weakly affected at diagnosis. Killer cell immunoglobulin-like receptor expression by NK cells, but not NKG2A and CD85j, was downregulated. Interestingly, the development of NK cells appeared altered as the most immature CD56bright NK cells were seriously underrepresented. Finally, we showed that NK cell functions were only partially restored 6 weeks after CT as degranulation capabilities of NK cells recovered, whereas cytokine production remained low. Our data point out NK cells as antitumor effectors peculiarly hampered by leukemic cells. This study may indicate a timeline when NK-mediated therapies or other immunotherapies could be performed, particularly for patients excluded of hematopoietic stem cell transplantation. PMID:28210257

  1. Fouling of an anion exchange chromatography operation in a monoclonal antibody process: Visualization and kinetic studies

    PubMed Central

    Close, Edward J; Salm, Jeffrey R; Iskra, Timothy; Sørensen, Eva; Bracewell, Daniel G

    2013-01-01

    Fouling of chromatographic resins over their operational lifetimes can be a significant problem for commercial bioseparations. In this article, scanning electron microscopy (SEM), batch uptake experiments, confocal laser scanning microscopy (CLSM) and small-scale column studies were applied to characterize a case study where fouling had been observed during process development. The fouling was found to occur on an anion exchange (AEX) polishing step following a protein A affinity capture step in a process for the purification of a monoclonal antibody. Fouled resin samples analyzed by SEM and batch uptake experiments indicated that after successive batch cycles, significant blockage of the pores at the resin surface occurred, thereby decreasing the protein uptake rate. Further studies were performed using CLSM to allow temporal and spatial measurements of protein adsorption within the resin, for clean, partially fouled and extensively fouled resin samples. These samples were packed within a miniaturized flowcell and challenged with fluorescently labeled albumin that enabled in situ measurements. The results indicated that the foulant has a significant impact on the kinetics of adsorption, severely decreasing the protein uptake rate, but only results in a minimal decrease in saturation capacity. The impact of the foulant on the kinetics of adsorption was further investigated by loading BSA onto fouled resin over an extended range of flow rates. By decreasing the flow rate during BSA loading, the capacity of the resin was recovered. These data support the hypothesis that the foulant is located on the particle surface, only penetrating the particle to a limited degree. The increased understanding into the nature of the fouling can help in the continued process development of this industrial example. Scanning electron microscopy (SEM), batch uptake experiments, confocal laser scanning microscopy (CLSM) and small-scale column experiments were applied to characterize a

  2. 21 CFR 601.70 - Annual progress reports of postmarketing studies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... received or otherwise obtained during the annual reporting interval which ends on the U.S. anniversary date... 21 Food and Drugs 7 2010-04-01 2010-04-01 false Annual progress reports of postmarketing studies... SERVICES (CONTINUED) BIOLOGICS LICENSING Postmarketing Studies § 601.70 Annual progress reports...

  3. Kinetic study of microwave-assisted alkaline hydrolysis of Jatropha curcas oil

    NASA Astrophysics Data System (ADS)

    Yusuf, Nur'aini Raman; Kamil, Ruzaimah Nik Mohamad; Yusup, Suzana

    2016-11-01

    The kinetics of hydrolysis of Jatropha curcas oil under microwave irradation in the presence of alkaline solution was studied. The temperature of 50°C, 65°C and 80°C were studied in the range of optimum condition of 1.75 M catalyst, solvent/oil ratio of (1: 68) and 15 minutes reaction time. The rate constants of oil hydrolysis are corresponding to triglyceride disappearance concentration. The rates of reaction for fatty acids production was determined by pseudo first order. The activation energy (Ea) achieved at 30.61 kJ/mol is lower using conventional method. This conclude that the rate of reaction via microwave heating is less temperature sensitive therefore reaction can be obtained at lower temperature.

  4. Kinetic study of mannitol production using cashew apple juice as substrate.

    PubMed

    Fontes, Cláudia P M L; Honorato, Talita L; Rabelo, Maria Cristiane; Rodrigues, Sueli

    2009-06-01

    The use of agriculture excess as substrate in industrial fermentations became an interesting alternative to reduce production costs and to reduce negative environmental impact caused by the disposal of these products. In this work, a kinetic study of mannitol production using cashew apple juice as substrate was studied. The carbohydrates of cashew apple juice are glucose and fructose. Sucrose addition favored the yield of mannitol (85%) at the expense of lower productivity. The best results were obtained applying only cashew apple juice as substrate, containing 50 g L(-1) of total reducing sugar (28 g L(-1) of fructose), yielding 18 g L(-1) of mannitol with 67% of fructose conversion into mannitol and productivity of 1.8 g L(-1) h(-1).

  5. In situ X-ray diffraction study on the growth kinetics of NiO nanoparticles.

    PubMed

    Meneses, C T; Almeida, J M A; Sasaki, J M

    2010-05-01

    The growth kinetics of NiO nanoparticles have been studied by in situ X-ray diffraction using two detection systems (conventional and imaging plate). NiO nanoparticles were formed by thermal decomposition after heating of an amorphous compound formed by the coprecipitation method. It was found that the detection method using an imaging plate is more efficient than the conventional detection mode for observing changes in the crystallite growth of nanocrystalline materials. Studies have been carried out to investigate the effects of the heating rates on the particles growth. The results suggest that the growth process of the particles is accelerated when the samples are treated at low heating rates. The evolution of particles size and the diffusion coefficient obtained from X-ray powder diffraction patterns are discussed in terms of the thermal conditions for the two types of detection.

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

    PubMed

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

    2014-04-21

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

  7. Study on the Kinetics of Aluminum Removal from Liquid Silicon to Slag with Mechanical Stirring

    NASA Astrophysics Data System (ADS)

    Lee, Jaewoo; White, Jesse F.; Hildal, Kjetil; Sichen, Du

    2016-12-01

    The kinetics of aluminum removal from silicon melt to CaO-SiO2-Al2O3 slag was studied. A recently designed experimental setup using mechanical stirring was employed to focus the study on the chemical reaction. The slag and metal were found to reach chemical equilibrium in 300 seconds. A simple model could reproduce the experimental data satisfactorily. Both the experimental results and the model prediction further confirmed that the process was controlled by the chemical reaction, since the reaction rate constant was found to be independent of the amount of slag and the initial slag composition. The experimental data at equilibrium were compared with the model calculations. The discrepancy between the model calculations and the experimental data strongly suggests the need for careful thermodynamic measurements.

  8. Lymphoid cell kinetics under continuous low dose-rate gamma irradiation: A comparison study

    NASA Technical Reports Server (NTRS)

    Foster, B. R.

    1975-01-01

    A comparison study was conducted of the effects of continuous low dose-rate gamma irradiation on cell population kinetics of lymphoid tissue (white pulp) of the mouse spleen with findings as they relate to the mouse thymus. Experimental techniques employed included autoradiography and specific labeling with tritiated thymidine (TdR-(h-3)). The problem studied involved the mechanism of cell proliferation of lymphoid tissue of the mouse spleen and thymus under the stress of continuous irradiation at a dose rate of 10 roentgens (R) per day for 105 days (15 weeks). The aim was to determine whether or not a steady state or near-steady state of cell population could be established for this period of time, and what compensatory mechanisms of cell population were involved.

  9. A laboratory study of the nucleation kinetics of nitric acid hydrates under stratospheric conditions

    NASA Astrophysics Data System (ADS)

    James, Alexander D.; Murray, Benjamin J.; Plane, John M. C.

    2016-04-01

    Measurements of the kinetics of crystallisation of ternary H2O-H2SO4-HNO3 mixtures to produce nitric acid hydrate phases, as occurs in the lower stratosphere, have been a long-standing challenge for investigators in the laboratory. Understanding polar stratospheric chlorine chemistry and thereby ozone depletion is increasingly limited by descriptions of nucleation processes. Meteoric smoke particles have been considered in the past as heterogeneous nuclei, however recent studies suggest that these particles will largely dissolve, leaving mainly silica and alumina as solid inclusions. In this study the nucleation kinetics of nitric acid hydrate phases have been measured in microliter droplets at polar stratospheric cloud (PSC) temperatures, using a droplet freezing assay. A clear heterogeneous effect was observed when silica particles were added. A parameterisation based on the number of droplets activated per nuclei surface area (ns) has been developed and compared to global model data. Nucleation experiments on identical droplets have been performed in an X-Ray Diffractometer (XRD) to determine the nature of the phase which formed. β-Nitric Acid Trihydrate (NAT) was observed alongside a mixture of Nitric Acid Dihydrate (NAD) phases. It is not possible to determine whether NAT nucleates directly or is formed by a phase transition from NAD (likely requiring the presence of a mediating liquid phase). Regardless, these results demonstrate the possibility of forming NAT on laboratory timescales. In the polar stratosphere, sulfuric acid (present at several weight percent of the liquid under equilibrium conditions) could provide such a liquid phase. This study therefor provides insight into previous discrepancies between phases formed in the laboratory and those observed in the atmosphere. It also provides a basis for future studies into atmospheric nucleation of solid PSCs.

  10. Nonlinear absorption kinetics of self-emulsifying drug delivery systems (SEDDS) containing tocotrienols as lipophilic molecules: in vivo and in vitro studies.

    PubMed

    Alqahtani, Saeed; Alayoubi, Alaadin; Nazzal, Sami; Sylvester, Paul W; Kaddoumi, Amal

    2013-07-01

    Self-emulsifying drug delivery systems (SEDDS) have been broadly used to promote the oral absorption of poorly water-soluble drugs. The purpose of the current study was to evaluate the in vivo oral bioavailability of vitamin E isoforms, δ-tocotrienol (δ-T3) and γ-tocotrienol (γ-T3) administered as SEDDS, as compared to commercially available UNIQUE E® Tocotrienols capsules. Results from studies in rats showed that low dose treatment with δ-T3 (90%) and γ-T3 (10%) formulated SEDDS showed bioavailability of 31.5% and 332%, respectively. However, bioavailability showed a progressive decrease with increased treatment dose that displayed nonlinear absorption kinetics. Additional in vitro studies examining cellular uptake studies in Caco 2 cells revealed that the SEDDS formulation increased passive permeability of δ-T3 and γ-T3 by threefold as compared to the commercial capsule formulation. These studies also showed that free surfactants decreased δ-T3 and γ-T3 absorption. Specifically, combined treatment cremophor EL or labrasol with tocotrienols caused a 60-85% reduction in the cellular uptake of δ-T3 and γ-T3 and these effects appear to result from surfactant-induced inhibition of the δ-T3 and γ-T3 transport protein Niemann-Pick C1-like 1 (NPC1L1). In summary, results showed that SEDDS formulation significantly increases the absorption and bioavailability δ-T3 and γ-T3. However, this effect is self-limiting because treatment with increasing doses of SEDDS appears to be associated with a corresponding increase in free surfactants levels that directly and negatively impact tocotrienol transport protein function and results in nonlinear absorption kinetics and a progressive decrease in δ-T3 and γ-T3 absorption and bioavailability.

  11. The recent progress in astroseismology study in Yunnan

    NASA Astrophysics Data System (ADS)

    Luo, Bao-Rong

    The recent progress in astroseismology study in Yunnan after 1996 is summarized in this paper. The breakthrough in some scientific fields is specially discussed. The main contents are as follows: 1. The triggering effect of the tidal force on the seismic event (1) The seismic events responding to the different triggering effects have different distribution in location. The seismic events are often triggered in a relatively concentrated period. (2) The seismic center with the largest tidal force is not the sub-stellar point of the Sun and the Moon. The Sun and the Moon are even not in the elevated region of 54.7° where is the zenith distance of the seismic event center, but are about 90°. In other words, the Sun, the Moon, the Earth center and the seismic center are not in one straight line. Judging from this, the main factor of triggering the seismic event is the horizontal component of the tidal force. (3) It is demonstrated that the triggering effect of the tidal force on the seismic event is, in substance, the effect of the advance slide on the seismic fault. 2. The relation between other special positions of the heave solar system objects and the seismic event. Some special points are called as astronomical strange points. The points include that at which certain planets are in opposition or conjunction to the Moon, and the points at which some of the heave solar system objects are in the elevated region of 54.7° where is the zenith distance of the seismic event center. And some special positions of the lunar longitude ascending node, as well as some special phases of the obliquity of the lunar path and equator are all belong to this category. It is shown that the astronomical strange points and eruptions of the seismic event are closely related. 3. The relation among the Earth rotation, the time-latitude residual and the eruption of the seismic event. It is found that the increase of the Earth rotation speed can cause large seismic event. The unusual time

  12. AN EQUIVALENT ELECTRIC CIRCUIT APPROACH TO THE STUDY OF HYDROCARBON OXIDATION KINETICS.

    DTIC Science & Technology

    HYDROCARBONS, *OXIDATION), (*PROPANE, OXIDATION), (*FUEL CELLS, ELECTROCHEMISTRY), ELECTRIC DOUBLE LAYER, PLATINUM, ELECTRODES, REACTION KINETICS, ACETIC ACID , ELECTROLYTES, HALOGENATED HYDROCARBONS, FLUORINE COMPOUNDS

  13. Progressive Failure Studies of Composite Panels With and Without Cutouts

    NASA Technical Reports Server (NTRS)

    Ambur, Damodar R.; Jaunky, Navin; Davila, Carlos G.; Hilburger, Mark

    2001-01-01

    Progressive failure analyses results are presented for composite panels with and without a cutout and are subjected to in-plane shear loading and compression loading well into their post-buckling regime. Ply damage modes such as matrix cracking, fiber-matrix shear, and fiber failure are modeled by degrading the material properties. Results from finite element analyses are compared with experimental data. Good agreement between experimental data and numerical results are observed for most structural configurations when initial geometric imperfections are appropriately modeled.

  14. A Kinetic Study of Furan Formation in Wheat Flour-Based Model Systems during Frying.

    PubMed

    Mariotti-Celis, María S; Zúñiga, Rommy N; Cortés, Pablo; Pedreschi, Franco

    2017-01-01

    Furan is a possible human carcinogen, which is formed in worldwide highly consumed fried starchy foods. In order to elucidate the mechanisms responsible for its occurrence in this food category and propose techniques for its mitigation, the kinetics of furan formation, oil absorption, lipid oxidation, and color change were studied in wheat flour-based model systems during frying at 160, 170, 180, and 190 °C up to 13 min and data were fitted to mathematical models. Additionally, an Arrhenius-type dependency with temperature was evaluated for all studied responses. More drastic frying conditions increased significantly (P ≤ 0.05) the furan content of fried samples. Furan formation followed a sigmoid trend with frying time only for frying temperature of 190 °C (RMS190°C : 7.6%). At lower temperatures, furan generation did not reach the asymptotic concentration level. Color change, lipid oxidation, and oil absorption increased with frying temperature and followed asymptotic relationships with frying time. For all evaluated temperatures, color change (RMS: 4.4% to 12.5%) and polar compound generation (RMS: 2.6% to 7.4%) presented good fit to a first-order kinetic model. Oil absorption was successfully fit to a mass balance-based model (RMS: 10.0% to 19.8%). Under the experimental conditions studied, only color change (EA : 15.47 kJ/mol), lipid oxidation (EA : 6.67 kJ/mol), and oil absorption (EA : 76.98 kJ/mol) presented good fit (RMS: 0.7% to 6.3%) to an Arrhenius-type equation. Based on our results, the keeping of frying temperature below 180 °C and the reduction of the frying time would contribute to reduce not only the final furan occurrence in fried foods but also their oil content.

  15. Multiple dose bioequivalence study with josamycin propionate, a drug with highly variable kinetics, in healthy volunteers.

    PubMed

    Van Hoogdalem, E J; Terpstra, I J; Krauwinkel, W J; Volkers-Kamermans, N J; Baven, A L; Verschoor, J S

    1996-05-01

    Josamycin is a macrolide antibiotic with considerable intra- and interindividual variability in kinetics. In the present study bioequivalence of an intact and dispersed josamycin Solutab tablet, containing 1,000 mg of josamycin in the form of josamycin propionate ester, was tested versus a Josacine 1,000 mg reference sachet. The design of this bioequivalence study was adapted to the drug's pharmacokinetic variability, comprising testing in steady-state, testing the reference in replicate, and maintaining a widened bioequivalence margin. The study was performed in a group of 24 male and 12 female healthy subjects, according to a 3-treatment 4-period crossover design. Blood sampling for establishing josamycin propionate and josamycin base serum level profiles were collected during the 12 h dosing interval on day 4. Steady-state serum levels were reached on day 4. With the reference sachet mean peak levels of 1.02 micrograms/ml and 0.36 microgram/ml were observed for parent drug and metabolite, respectively, reached at peak times of 1.5 h and 1.8 h. Comparable profiles were observed with the intact and dispersed Solutab tablets, both tending towards higher serum levels than the sachet. In terms of josamycin propionate levels as well as josamycin base levels, the intact and dispersed Solutab tablet was bioequivalent with the referent sachet within the preset 0.70-1.43 margins. Variability in josamycin kinetics proved to be substantial, maximum differences in peak levels and AUC values being about 10-fold between individuals, and 3-fold within individuals. Retrospectively, the multiple dosing regimen appeared not to result in a clear reduction of intrasubject variability.

  16. A study of hydriding kinetics of metal hydrides using a physically based model

    NASA Astrophysics Data System (ADS)

    Voskuilen, Tyler G.

    The reaction of hydrogen with metals to form metal hydrides has numerous potential energy storage and management applications. The metal hydrogen system has a high volumetric energy density and is often reversible with a high cycle life. The stored hydrogen can be used to produce energy through combustion, reaction in a fuel cell, or electrochemically in metal hydride batteries. The high enthalpy of the metal-hydrogen reaction can also be used for rapid heat removal or delivery. However, improving the often poor gravimetric performance of such systems through the use of lightweight metals usually comes at the cost of reduced reaction rates or the requirement of pressure and temperature conditions far from the desired operating conditions. In this work, a 700 bar Sievert system was developed at the Purdue Hydrogen Systems Laboratory to study the kinetic and thermodynamic behavior of high pressure hydrogen absorption under near-ambient temperatures. This system was used to determine the kinetic and thermodynamic properties of TiCrMn, an intermetallic metal hydride of interest due to its ambient temperature performance for vehicular applications. A commonly studied intermetallic hydride, LaNi5, was also characterized as a base case for the phase field model. The analysis of the data obtained from such a system necessitate the use of specialized techniques to decouple the measured reaction rates from experimental conditions. These techniques were also developed as a part of this work. Finally, a phase field model of metal hydride formation in mass-transport limited interstitial solute reactions based on the regular solution model was developed and compared with measured kinetics of LaNi5 and TiCrMn. This model aided in the identification of key reaction features and was used to verify the proposed technique for the analysis of gas-solid reaction rates determined volumetrically. Additionally, the phase field model provided detailed quantitative predictions of the

  17. Equilibrium and kinetic studies on complex formation and decomposition and the movement of Cu(2+)metal ions within polytopic receptors.

    PubMed

    Castillo, Carmen Ester; González-García, Jorge; Llinares, José M; Máñez, M Angeles; Jimenez, Hermas R; García-España, Enrique; Basallote, Manuel G

    2013-05-07

    Potentiometric studies carried out on the interaction of two tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties are linked with 2,9-dimethylphenanthroline (L1) and 2,6-dimethylpyridine (L2) establish the formation of mono-, bi- and trinuclear Cu(2+) complexes. The values of the stability constants and paramagnetic (1)H NMR studies permit one to infer the most likely coordination modes of the various complexes formed. Kinetic studies on complex formation and decomposition have also been carried out. Complex formation occurs with polyphasic kinetics for both receptors, although a significant difference is found between both ligands with respect to the relative values of the rate constants for the metal coordination steps and the structural reorganizations following them. Complex decomposition occurs with two separate kinetic steps, the first one being so fast that it occurs within the stopped-flow mixing time, whereas the second one is slow enough to allow kinetic studies using a conventional spectrophotometer. As a whole, the kinetic experiments also provide information about the movement of the metal ion within the receptors. The differences observed between the different receptors can be interpreted in terms of changes in the network of hydrogen bonds formed in the different species.

  18. Kinetic and spectroscopic study of catalysts for water-gas shift and nitrogen oxide removal

    NASA Astrophysics Data System (ADS)

    Kispersky, Vincent Frederick

    adsorbed CO2 proved less competitive for NOx sorption sites, explaining the weak reduction of NSC by CO2 on low Ba loadings. Contrary to CO2, H2O exhibited both beneficial and inhibitory effects on the NSC. Over long periods of time, and at high Ba loadings, the addition of H2O in the feed increased the NSC, attributed to enhanced O2 spillover on the hydroxylated Ba surface allowing greater access to available NOx storage sites. When the Ba loading was reduced, the interaction sphere of Pt particles with the Ba storage component required for O2 to spillover to assist in NOx storage was reduced. Thus, despite the enhanced spillover capacity of oxygen on the hydroxylated storage component other NSC decreasing effects of H2O addition, such as Ba agglomeration, became more dominant and reduced the NSC. Recent developments in selective catalytic reduction have shown Cu and Fe/chabazite (CHA) based zeolites to be particularly well suited to sustaining high catalytic rates without degradation in the harsh environment of diesel engine exhaust. Little has been published about these catalysts as the academic community has just recently learned about the materials and their commercial implementation. Using operando X-ray absorption spectroscopy, combined with first-principles thermodynamics simulations and kinetic analysis, we have studied the nature of the Cu active site on Cu/SSZ-13, Cu/SAPO-34 and Cu/ZSM-5. Examining the catalysts under operando standard SCR conditions (300 ppm NO, 300 ppm NH3, 5% O2, 5% H2O and 5% CO2) showed the catalyst to be in a mixed Cu(I)-Cu(II) oxidation state. Neither the amount of Cu(I) nor Cu(II) individually correlated with the different rates measured on the various zeolite catalysts, and so we proposed that the SCR reaction progresses via a redox mechanism requiring both Cu(I) and Cu(II). First principles thermodynamic calculations found that the redox couple of Cu(I)H2O and Cu(II)(OH)2 were the most thermodynamically stable species of any of the Ox

  19. Effects of kinetics on the crystallization of quartz normative basalt 15597 - An experimental study

    NASA Technical Reports Server (NTRS)

    Grove, T. L.; Raudsepp, M.

    1978-01-01

    Equilibrium experiments on a residual liquid composition from the dynamic crystallization study on quartz normative basalt (QNB) 15597 are used to evaluate the effects of kinetics on the crystallization of pyroxene-porphyritic basalts. The results indicate that the liquids coexisting with pyroxene phenocryst rims before the precipitation of groundmass plagioclase + pyroxene have left the equilibrium liquid line of descent and metastably penetrated the plagioclase primary phase volume. The precipitation of groundmass plagioclase + pyroxene brings the basalt system closer to equilibrium with respect to the residual liquid and crystals. At rapid cooling rates pyroxene phenocryst growth produces substantial compositional gradients in the residual silicate liquid at the pyroxene/liquid interface. The compositional gradients enhance the nucleation and growth of groundmass phases at the phenocryst interface, because effects related to constitutional supercooling for these phases (e.g., plagioclase, pyroxene, etc.) favor nucleation at the interface.

  20. Semi-aerobic stabilized landfill leachate treatment by ion exchange resin: isotherm and kinetic study

    NASA Astrophysics Data System (ADS)

    Zamri, Mohd Faiz Muaz Ahmad; Kamaruddin, Mohamad Anuar; Yusoff, Mohd Suffian; Aziz, Hamidi Abdul; Foo, Keng Yuen

    2015-03-01

    This study was carried out to investigate the treatability of ion exchange resin (Indion MB 6 SR) for the removal of chromium (VI), aluminium (III), zinc (II), copper (II), iron (II), and phosphate (PO4)3-, chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and colour from semi-aerobic stabilized leachate by batch test. A range of ion exchange resin dosage was tested towards the removal efficiency of leachate parameters. It was observed that equilibrium data were best represented by the Langmuir model for metal ions and Freundlich was ideally fit for COD, NH3-N and colour. Intra particle diffusion model, pseudo first-order and pseudo second-order isotherm models were found ideally fit with correlation of the experimental data. The findings revealed that the models could describe the ion exchange kinetic behaviour efficiently, which further suggests comprehensive outlook for the future research in this field.

  1. Beam tracking strategies for studies of kinetic scales in the solar wind with THOR-CSW

    NASA Astrophysics Data System (ADS)

    De Keyser, Johan; Lavraud, Benoit; Neefs, Eddy; Berkenbosch, Sophie; Anciaux, Michel; Maggiolo, Romain

    2016-04-01

    Modern plasma spectrometers for monitoring the solar wind attempt to intelligently track the energy and direction of the solar wind beam in order to obtain solar wind velocity distributions more efficiently. Such beam tracking strategies offer some benefits, but also have their limitations and drawbacks. Benefits include an improved resolution and/or a faster velocity distribution function acquisition time. Limitations are due to instrument characteristics that tend to be optimized for a particular range of particle energies and arrival directions. A drawback is the risk to miss an important part of the velocity distribution or to lose track of the beam altogether. A comparison is presented of different beam tracking strategies under consideration for the THOR-CSW instrument in order to highlight a number of design decisions and their impact on the acquired velocity distributions. The gain offered by beam tracking in terms of increased time resolution turns out to be essential for studies of solar wind physics at kinetic scales.

  2. Adsorption thermodynamic and kinetic studies of trihalomethanes on multiwalled carbon nanotubes.

    PubMed

    Lu, Chungsying; Chung, Yao-Lei; Chang, Kuan-Foo

    2006-11-16

    Multiwalled carbon nanotubes (MWCNTs) were purified by mixed HNO3/H2SO4 solution and were employed as adsorbents to study adsorption kinetics and thermodynamics of trihalomethanes (THMs) from chlorinated drinking water. The amount of THMs adsorbed onto CNTs decreased with a rise in temperature and high adsorption capacities were found at 5 and 15 degrees C. Under the same conditions, the purified CNTs possess two to three times more adsorption capacities of CHCl3, which accounts for a major portion of THMs in the chlorinated drinking water, than the commercially available PAC suggesting that CNTs are efficient adsorbents. The thermodynamic analysis revealed that the adsorption of THMs onto CNTs is exothermic and spontaneous.

  3. Pseudohomogeneous kinetic study on a two-liquid-phase fermentation process.

    PubMed

    Li, Y; Cao, Z; Yuan, N

    1994-01-01

    The fermentation process for producing undecane dicarboxylic acid from tridecane, which includes gas-oil-water-cell four phases (two-liquid-phase), was studied. The metabolic characters of the cell growth phase and the production phase of the process were analyzed. It was proposed that cell growth can be identified by the carbon dioxide production rate (CPR) before the production phase. The kinetic models of both the cell growth phase and the production phase were established, respectively. The parameters of the models have been estimated by regression. The calculated curves fit the experimental data very well. The average deviation between those over the cell growth phase and the production phase are 2.4% and 3.6%, respectively.

  4. A detailed kinetic modeling study of aromatics formation in laminar premixed acetylene and ethylene flames

    SciTech Connect

    Wang, H.; Frenklach, M.

    1997-07-01

    A computational study was performed for the formation and growth of polycyclic aromatic hydrocarbons (PAHs) in laminar premixed acetylene and ethylene flames. A new detailed reaction mechanism describing fuel pyrolysis and oxidation, benzene formation, and PAH mass growth and oxidation is presented and critically tested. It is shown that the reaction model predicts reasonably well the concentration profiles of major and intermediate species and aromatic molecules in a number of acetylene and ethylene flames reported in the literature. It is demonstrated that reactions of n-C{sub 4}H{sub x} + C{sub 2}H{sub 2} leading to the formation of one-ring aromatics are as important as the propargyl recombination, and hence must be included in kinetic modeling of PAH formation in hydrocarbon flames. It is further demonstrated that the mass growth of PAHs can be accounted for by the previously proposed H-abstraction-C{sub 2}H{sub 2}-addiction mechanism.

  5. Simulation of atomic diffusion in the Fcc NiAl system: A kinetic Monte Carlo study

    DOE PAGES

    Alfonso, Dominic R.; Tafen, De Nyago

    2015-04-28

    The atomic diffusion in fcc NiAl binary alloys was studied by kinetic Monte Carlo simulation. The environment dependent hopping barriers were computed using a pair interaction model whose parameters were fitted to relevant data derived from electronic structure calculations. Long time diffusivities were calculated and the effect of composition change on the tracer diffusion coefficients was analyzed. These results indicate that this variation has noticeable impact on the atomic diffusivities. A reduction in the mobility of both Ni and Al is demonstrated with increasing Al content. As a result, examination of the pair interaction between atoms was carried out formore » the purpose of understanding the predicted trends.« less

  6. Kinetic Studies on the Interaction of Bacteriophage Type 71 Staphylococcal Bacteriocin with Susceptible Bacteria

    PubMed Central

    Dajani, Adnan S.; Wannamaker, Lewis W.

    1973-01-01

    Kinetic studies on the interaction of the bacteriocin produced by phage type 71 Staphylococcus aureus with susceptible bacterial cells were undertaken. Survivors among susceptible bacteria to which the bacteriocin has been added can be rescued after trypsin treatment. The bacteriocin adsorbs very rapidly to susceptible streptococcal cells at a time when killing of the cells is only minimal. Heat-killed or mechanically disrupted cells are also effective in adsorbing the bacteriocin. Adsorption is comparable at 37 C and 25 C, but is less pronounced at 4 C. Elution of adsorbed bacteriocin could not be achieved by heating, by varying pH, or by using different concentrations of sodium chloride solutions. Surface M protein of streptococcal cells plays no role in the adsorptive process. Adsorption is specific in that only susceptible bacteria, but not resistant ones, are capable of adsorbing the bacteriocin. PMID:4267533

  7. Oxidative folding of peptides with cystine-knot architectures: kinetic studies and optimization of folding conditions.

    PubMed

    Reinwarth, Michael; Glotzbach, Bernhard; Tomaszowski, Michael; Fabritz, Sebastian; Avrutina, Olga; Kolmar, Harald

    2013-01-02

    Bioactive peptides often contain several disulfide bonds that provide the main contribution to conformational rigidity and structural, thermal, or biological stability. Among them, cystine-knot peptides-commonly named "knottins"-make up a subclass with several thousand natural members. Hence, they are considered promising frameworks for peptide-based pharmaceuticals. Although cystine-knot peptides are available through chemical and recombinant synthetic routes, oxidative folding to afford the bioactive isomers still remains a crucial step. We therefore investigated the oxidative folding of ten protease-inhibiting peptides from two knottin families, as well as that of an HIV entry inhibitor and of aprotinin, under two conventional sets of folding conditions and by a newly developed procedure. Kinetic studies identified folding conditions that resulted in correctly folded miniproteins with high rates of conversion even for highly hydrophobic and aggregation-prone peptides in concentrated solutions.

  8. Kinetic study of model reactions in the gas phase at the early stage of coke formation

    SciTech Connect

    Nohara, D.; Sakai, T. )

    1992-01-01

    This paper reports that the most probable gas-phase reactions at the early stage of coke formation were elucidated by kinetic study on the model reactions adopted for formation of cyclic compounds and growth of ring. It was revealed that the formation and growth of ring proceeded mainly through cycloaddition of butadiene or allyl radicals to unsaturated hydrocarbons at relatively low temperatures ({approximately}600{degrees}C), i.e., through a Diels-Alder type reaction. On the other hand, such growth of ring as formation of biphenyl accompanying dehydrogenation from benzene can proceed only at the higher temperatures. It was also revealed that in the growth of the ring, cycloaddition of butadiene favors a cyclic olefin molecule that possesses a nonconjugated double bond and a nearly planar structure.

  9. Functionalized graphene sheets as immobilization matrix for Fenugreek β-amylase: enzyme kinetics and stability studies.

    PubMed

    Srivastava, Garima; Singh, Kritika; Talat, Mahe; Srivastava, Onkar Nath; Kayastha, Arvind M

    2014-01-01

    β-Amylase finds application in food and pharmaceutical industries. Functionalized graphene sheets were customised as a matrix for covalent immobilization of Fenugreek β-amylase using glutaraldehyde as a cross-linker. The factors affecting the process were optimized using Response Surface Methodology based Box-Behnken design of experiment which resulted in 84% immobilization efficiency. Scanning and Transmission Electron Microscopy (SEM, TEM) and Fourier Tansform Infrared (FTIR) spectroscopy were employed for the purpose of characterization of attachment of enzyme on the graphene. The enzyme kinetic studies were carried out for obtaining best catalytic performance and enhanced reusability. Optimum temperature remained unchanged, whereas optimum pH showed shift towards acidic range for immobilized enzyme. Increase in thermal stability of immobilized enzyme and non-toxic nature of functionalized graphene can be exploited for production of maltose in food and pharmaceutical industries.

  10. Surface kinetic roughening caused by dental erosion: An atomic force microscopy study

    NASA Astrophysics Data System (ADS)

    Quartarone, Eliana; Mustarelli, Piercarlo; Poggio, Claudio; Lombardini, Marco

    2008-05-01

    Surface kinetic roughening takes place both in case of growth and erosion processes. Teeth surfaces are eroded by contact with acid drinks, such as those used to supplement mineral salts during sporting activities. Calcium-phosphate based (CPP-ACP) pastes are known to reduce the erosion process, and to favour the enamel remineralization. In this study we used atomic force microscopy (AFM) to investigate the surface roughening during dental erosion, and the mechanisms at the basis of the protection role exerted by a commercial CPP-ACP paste. We found a statistically significant difference (p<0.01) in the roughness of surfaces exposed and not exposed to the acid solutions. The treatment with the CPP-ACP paste determined a statistically significant reduction of the roughness values. By interpreting the AFM results in terms of fractal scaling concepts and continuum stochastic equations, we showed that the protection mechanism of the paste depends on the chemical properties of the acid solution.

  11. Thermodynamics and kinetics of ion speciation in supercritical aqueous solutions: A molecular based study

    SciTech Connect

    Chialvo, A.A.; Cummings, P.T. |; Simonson, J.M.; Mesmer, R.E.

    1997-05-01

    Molecular simulation of infinitely dilute NaCl aqueous solutions are performed to study the Na{sup +}/Cl{sup -} ion pairing in a polarizable and a nonpolarizable solvent at supercritical conditions. The Simple Point Charge, Pettitt-Rossky, and Fumi-Tosi models for the water-water, ion-water, and ion-ion interactions are used in determining the degree of dissociation, its temperature and density dependence, and the kinetics of the interconversion between ion-pair configurations in a nonpolarizable medium. To assess the effect of the solvent polarizability on the stability of the ion-pair configurations, we replace the Simple Point Charge by the Polarizable Point Charge water model and determine the anion-cation potential of mean force at T{sub r}=1.20 and {rho}{sub r}=1.5.

  12. Improvements in Mixing Time and Mixing Uniformity in Devices Designed for Studies of Protein Folding Kinetics

    SciTech Connect

    Yao, Shuhuai; Bakajin, Olgica

    2007-08-01

    Using a microfluidic laminar flow mixer designed for studies of protein folding kinetics, we demonstrate a mixing time of 1 +/- 1 micros with sample consumption on the order of femtomoles. We recognize two limitations of previously proposed designs: (1) size and shape of the mixing region, which limits mixing uniformity and (2) the formation of Dean vortices at high flow rates, which limits the mixing time. We address these limitations by using a narrow shape-optimized nozzle and by reducing the bend of the side channel streamlines. The final design, which combines both of these features, achieves the best performance. We quantified the mixing performance of the different designs by numerical simulation of coupled Navier-Stokes and convection-diffusion equations and experiments using fluorescence resonance energy-transfer (FRET)-labeled DNA.

  13. Thermal oxidation of single-crystal silicon carbide - Kinetic, electrical, and chemical studies

    NASA Technical Reports Server (NTRS)

    Petit, J. B.; Neudeck, P. G.; Matus, L. G.; Powell, J. A.

    1992-01-01

    This paper presents kinetic data from oxidation studies of the polar faces for 3C and 6H SiC in wet and dry oxidizing ambients. Values for the linear and parabolic rate constants were obtained, as well as preliminary results for the activation energies of the rate constants. Examples are presented describing how thermal oxidation can be used to map polytypes and characterize defects in epitaxial layers grown on low tilt angle 6H SiC substrates. Interface widths were measured using Auger electron spectroscopy (AES) with Ar ion beam depth profiling and variable angle spectroscopic ellipsometry (VASE) with effective medium approximation (EMA) models. Preliminary electrical measurements of MOS capacitors are also presented.

  14. [Studying kinetics of oxime-induced reactivation of malathion-inhibited cholinesterase].

    PubMed

    Iudin, M A; Lantukhov, D V; Vengerovich, N G

    2013-01-01

    The kinetics of oxime-induced reactivation of malathion-inhibited cholinesterase has been experimentally studied in vitro. It is shown that oximes do not restore the activity of inhibited butyrylcholinesterase. Acetylcholinesterase reactivation peak (5-mins long) was found to take place upon introduction of dipyroxime (32.5%), pralidoxime (18%), carboxyme (16%) at a concentration of 2.5 x 10(-4) mol/l or toxogonine (26%) at a concentration of 5 x 10(-4) mol/l. Toxogonine demonstrated the maximum affinity to phosphorylated enzyme, while dipyroxime is characterized by a high reactivity with respect to oxime. Significant reactivating ability of these preparations (kR -2300 mol(-1) min(-1) makes them promising solution for the treatment of malathion intoxication.

  15. Kinetics study of crystallization with the disorder-bcc-fcc phase transition of charged colloidal dispersions.

    PubMed

    Zhou, Hongwei; Xu, Shenghua; Sun, Zhiwei; Du, Xuan; Liu, Lixia

    2011-06-21

    Structure transformation (disorder-bcc-fcc) in charged colloidal dispersions, as a manifestation of the Ostwald's step rule, was confirmed by means of reflection spectrum (RS) measurements in our previous study. By taking advantage of a reflection spectrum containing plenty of information about the crystallization behaviors, time-dependent changes of parameters associated with the crystal structure and composition during the disorder-bcc-fcc transition are reported by treating the data from RS in this article. In addition, Avrami's model is adopted to analyze the transition process and investigate the transition rate. On the basis of the above investigations, associated kinetic features of crystallization with the disorder-bcc-fcc transition are described.

  16. 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).

  17. Mechanistic and kinetic studies of the thermal decomposition of TNAZ and NDNAZ

    SciTech Connect

    Anderson, K.; Homsy, J.; Behrens, R.; Bulusu, S.

    1998-12-31

    The authors have studied the mechanism and detailed reaction kinetics of the thermal decomposition of 1,3,3-trinitroazetidine (TNAZ), and separately, its key decomposition intermediate, 1-nitroso-3,3-dinitroacetidine (NDNAZ), using a simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS). These decompositions were conducted in a sealed alumina cell with a 2.5 {micro}m orifice, at varying temperatures and at a range of isothermal temperatures (at 10 C intervals from 120--160 C for NDNAZ and 160--210 C for TNAZ). The gaseous products have been identified and their rates of formation have been measured as a function of time, temperature, and pressure. This system is complex, with TNAZ decomposing by four separate routes, one of which leads to NDNAZ, which itself decomposes by at least two distinct routes.

  18. Kinetic studies of simulated polluted atmospheres. Final report January 1976-April 1979

    SciTech Connect

    Calvert, J.G.

    1980-01-01

    The kinetics and reaction mechanisms of several important atmospheric contaminants - SO2, formaldehyde, nitrous acid, and the nitrosamines - were assessed to help quantify some key aspects of the chemistry of polluted atmospheres. The reactions and lifetimes of excited sulfur dioxide with various atmospheric components including hydroxyl, hydroperoxy, and methylperoxy radicals were studied. These data and other published rate data were reviewed and evaluated. The photolysis of formaldehyde was investigated as a major source of hydroperoxyl radicals, and a quantitative evaluation made of its apparent first order rate constants at various solar zenith angles. The absolute extinction coefficients for nitrous acid were determined, and estimates made of the rates of hydroxyl radical generation in the troposphere by photolysis of nitrous acid. Long path Fourier transform infrared spectroscopy was used to help evaluate the potential for nitrosamine formation in the polluted atmosphere.

  19. Phenol oxidation by mushroom waste extracts: a kinetic and thermodynamic study.

    PubMed

    Pigatto, Gisele; Lodi, Alessandra; Aliakbarian, Bahar; Converti, Attilio; da Silva, Regildo Marcio Gonçalves; Palma, Mauri Sérgio Alves

    2013-09-01

    Tyrosinase activity of mushroom extracts was checked for their ability to degrade phenol. Phenol oxidation kinetics was investigated varying temperature from 10 to 60 °C and the initial values of pH, enzyme activity and phenol concentration in the ranges 4.5-8.5, 1.43-9.54 U/mL and 50-600 mg/L, respectively. Thermodynamic parameters of phenol oxidation and tyrosinase reversible inactivation were estimated. Tyrosinase thermostability was also investigated through residual activity tests after extracts exposition at 20-50 °C, whose results allowed exploring the thermodynamics of enzyme irreversible thermoinactivation. This study is the first attempt to separate the effects of reversible unfolding and irreversible denaturation of tyrosinase on its activity. Extracts were finally tested on a real oil mill wastewater.

  20. Theoretical study on the mechanism and kinetics of acetaldehyde and hydroperoxyl radical: An important atmospheric reaction

    NASA Astrophysics Data System (ADS)

    Farnia, Solaleh; Vahedpour, Morteza; Abedi, Mostafa; Farrokhpour, Hossein

    2013-09-01

    A systematic theoretical study was performed on the mechanism and kinetics of the atmospheric reaction of acetaldehyde (CH3CHO) and hydroperoxyl radical (HO2) in the gas phase. The DFT-B3LYP/6-311++G(3df,3pd) and CCSD(T)/6-311++G(d,p) methods were employed for calculations. Based on the calculations, this reaction leads to four different products through radical addition and hydrogen abstraction mechanisms which are very important in atmospheric and combustion chemistry. The favorable reaction paths begin with α-hydroxyethylperoxy radical, CH3CH(OO)OH, in a exothermic process and finally leads to the product P1 (CH3COOH + OH). The overall rate constants for favorite reaction paths have been calculated at different temperatures (200-2500 K).