Note: This page contains sample records for the topic yield kinetic parameters from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Estimation of yield, maintenance, and product formation kinetic parameters in anaerobic fermentations  

SciTech Connect

In many anaerobic processes, high energy bonds in adenosine triphosphate (ATP) are produced when available electrons are converted from organic substrate into extracellular organic products such as ethanol. The true growth yield and maintenance parameters are directly related to the product formation kinetic parameters for these anaerobic processes. Methods are presented which allow all of the experimental measurements to be used simultaneously to estimate these parameters. Results are presented for several different anaerobic fermentations. 36 references.

Oner, M.D.; Erickson, L.E.; Yang, S.S.

1984-12-01

2

Inhomogeneous electrochemiluminescence. I: Integral encounter theory of kinetics and yield  

NASA Astrophysics Data System (ADS)

The generation of excited triplet luminophor by recombination of electrochemically injected ions is calculated. The reversibility of triplet production is shown to affect insignificantly the triplet accumulation and their quantum yield. The free energy dependence of the latter is specified and fitted to the available experimental data. The maximal quantum yield of triplet luminescence found experimentally is sometimes less than 1, even when the excitation is the sole result of charge recombination. This phenomenon may be a result of the biexcitonic annihilation of triplets produced in a narrow strip at the border between the space separated anions and cations. The kinetics of this process is calculated and the maximal yield of fluorescence is shown to decrease with excitation life time and increase with triplet diffusion out of the strip. Alternatively, the maximal quantum yield may be reduced due to the trivial triplet quenching by neutral precursors of ions.

Gladkikh, V.; Burshtein, A. I.

2005-10-01

3

?-Amylase kinetic parameters modulation by lecithin vesicles: binding versus entrapment  

Microsoft Academic Search

The effect of ?-amylase–lipid interaction and entrapment inside lipidic soybean lecithin (PC) vesicles on the kinetic parameters of the enzyme was investigated. Human saliva was used as enzyme source and starch as substrate. Reaction kinetics were followed by measuring the consumption of starch as revealed by the decrease in the absorbance at 600 nm of the I2–starch complex. The presence

Julieta M Sanchez; Maria A Perillo

2000-01-01

4

Kinetic parameter reconstruction for motion compensation in transmission tomography  

NASA Astrophysics Data System (ADS)

Model based iterative reconstruction (MBIR) algorithms have recently been applied to computed tomography and demonstrated superior image quality. This algorithmic framework also provides us the flexibility to incorporate more sophisticated models of the data acquisition process. In this paper, we present the kinetic parameter iterative reconstruction (KPIR) algorithm which estimates voxel values as a function of time in the MBIR framework. We introduce a parametric kinetic model for each voxel, and estimate the kinetic parameters directly from the data. Results on phantom study and clinical data show that the proposed method can significantly reduce motion artifacts in the reconstruction.

Yu, Zhou; Thibault, Jean-Baptiste; Wang, Jiao; Bouman, Charles A.; Sauer, Ken D.

2011-02-01

5

Parameter estimation for models of ligninolytic and cellulolytic enzyme kinetics  

Microsoft Academic Search

While soil enzymes have been explicitly included in the soil organic carbon (SOC) decomposition models, there is a serious lack of suitable data for model parameterization. This study provides well-documented enzymatic parameters for application in enzyme-driven SOC decomposition models from a compilation and analysis of published measurements. In particular, we developed appropriate kinetic parameters for five typical ligninolytic and cellulolytic

Gangsheng Wang; Wilfred M Post; Melanie Mayes; Joshua T Frerichs; Sindhu Jagadamma

2012-01-01

6

Kinetic parameter estimation from attenuated SPECT projection measurements  

SciTech Connect

Conventional analysis of dynamically acquired nuclear medicine data involves fitting kinetic models to time-activity curves generated from regions of interest defined on a temporal sequence of reconstructed images. However, images reconstructed from the inconsistent projections of a time-varying distribution of radiopharmaceutical acquired by a rotating SPECT system can contain artifacts that lead to biases in the estimated kinetic parameters. To overcome this problem the authors investigated the estimation of kinetic parameters directly from projection data by modeling the data acquisition process. To accomplish this it was necessary to parametrize the spatial and temporal distribution of the radiopharmaceutical within the SPECT field of view. In a simulated transverse slice, kinetic parameters were estimated for simple one compartment models for three myocardial regions of interest, as well as for the liver. Myocardial uptake and washout parameters estimated by conventional analysis of noiseless simulated data had biases ranging between 1--63%. Parameters estimated directly from the noiseless projection data were unbiased as expected, since the model used for fitting was faithful to the simulation. Predicted uncertainties (standard deviations) of the parameters obtained for 500,000 detected events ranged between 2--31% for the myocardial uptake parameters and 2--23% for the myocardial washout parameters.

Reutter, B.W. [Lawrence Berkeley National Lab., CA (United States). Center for Functional Imaging; Gullberg, G.T. [Univ. of Utah, Salt Lake City, UT (United States). Dept. of Radiology

1998-12-01

7

Parameter identification of in vivo kinetic models: limitations and challenges.  

PubMed

Systems metabolic engineering of metabolic networks by genetic techniques requires kinetic equations for each enzyme present. In vitro studies of singular enzymes have limitations for predicting in vivo behavior, and in vivo experiments are constrained to retain viable cells. The estimation of kinetic parameters in vivo is a challenge due to the complexity of the internal cell environment. This concise review analyzes the limitations of in vitro and in vivo approaches, and shows that not all parameters can be determined and that multicollinearity exists. On the other hand, this review also shows that cell metabolism is adequately described with a smaller number of parameters and with approximative or reduced models. A major hurdle is the identification and quantification of allosteric effectors. Despite limitations, in vivo kinetic experiments are adequate in providing a quantitative description of the cell as a system. PMID:23813763

Heijnen, Joseph J; Verheijen, Peter J T

2013-07-01

8

Measurement of kinetic parameters in the fast subcritical core MASURCA  

Microsoft Academic Search

In the MUSE shared cost action of the European Fifth Framework Program measurements have been performed to investigate the neutronic behavior of the fast subcritical core MASURCA coupled with the GENEPI accelerator. The aim is to examine the applicability of different measurement techniques for the determination of the main kinetic parameters. The measurement of Rossi-alpha distributions, recorded with the accelerator

Peter Baeten

2004-01-01

9

Determining crystal growth kinetic parameters using optical fibre sensors  

NASA Astrophysics Data System (ADS)

The capability of an ‘intrinsic exposed core optical fibre sensor’ (IECOFS) as a monitoring device of scale formation has been evaluated. The IECOFS has been used to measure kinetics parameters of calcium carbonate heterogeneous crystal growth such as the activation energy, the crystal growth rate and the induction time. The IECOFS was able to evaluate crystal growth inhibition through the use of chemical inhibitors.

Boerkamp, M.; Lamb, D. W.; Lye, P. G.

2012-12-01

10

Kinetic limit of the ethane and ethylene yield in the gas phase condensation of methane  

SciTech Connect

A kinetic simulation of the initiated oxidative condensation of methane in the gas phase showed that the additional generation of methyl radicals via the reaction CH{sub 4} + O{sub 2} {yields} CH{sub 3} + HO{sub 2} causes a nearly tenfold increase in the C{sub 2} hydrocarbon yield. However, a kinetic limit of the yield exists that is close to that determined in experiments on the catalytic oxidative condensation of methane.

Vedeneev, V.I.; Arutyunov, V.S.; Basevich, V.Ya. [N.N. Semenov Institute of Chemical Physics, Moscow (Russian Federation)

1995-08-01

11

Parameter sensitivity analysis for designing experiments in kinetics.  

PubMed

For the Michaelis-Menten binding kinetics and for a two- and a three-compartmental model a parameter sensitivity analysis is performed to design experiments. According to the mathematical results in the case of the binding kinetics the substrate concentrations s approximately Km are optimal in view to the variance of the Michaelis constant Km. In the case of the two-compartment model the results of the calculations are tested by the use of computer-simulated data. The correspondence between the sensitivity and simulation results is satisfactory. PMID:754446

Kanyár, B

1978-01-01

12

LDEF's map experiment foil perforations yield hypervelocity impact penetration parameters  

NASA Astrophysics Data System (ADS)

The space exposure of LDEF for 5.75 years, forming a host target in low earth orbit (LEO) orbit to a wide distribution of hypervelocity particulates of varying dimensions and different impact velocities, has yielded a multiplicity of impact features. Although the projectile parameters are generally unknown and, in fact not identical for any two impacts on a target, the great number of impacts provides statistically meaningful basis for the valid comparison of the response of different targets. Given sufficient impacts for example, a comparison of impact features (even without knowledge of the project parameters) is possible between: (1) differing material types (for the same incident projectile distribution); (2) differing target configurations (e.g., thick and thin targets for the same material projectiles; and (3) different velocities (using LDEF's different faces). A comparison between different materials is presented for infinite targets of aluminum, Teflon, and brass in the same pointing direction; the maximum finite-target penetration (ballistic limit) is also compared to that of the penetration of similar materials comprising of a semi-infinite target. For comparison of impacts on similar materials at different velocities, use is made of the pointing direction relative to LDEF's orbital motion. First, however, care must be exercised to separate the effect of spatial flux anisotropies from those resulting from the spacecraft velocity through a geocentrically referenced dust distribution. Data comprising thick and thin target impacts, impacts on different materials, and in different pointing directions is presented; hypervelocity impact parameters are derived. Results are also shown for flux modeling codes developed to decode the relative fluxes of Earth orbital and unbound interplanetary components intercepting LDEF. Modeling shows the west and space pointing faces are dominated by interplanetary particles and yields a mean velocity of 23.5 km/s at LDEF, corresponding to a V(infinity) Earth approach velocity = 20.9 km/s. Normally resolved average impact velocities on LDEF's cardinal point faces are shown. As 'excess' flux on the east, north, and south faces is observed, compatible with an Earth orbital component below some 5 microns in particle diameter.

McDonnell, J. A. M.

1992-06-01

13

Stimulus Parameters for Goldmann Kinetic Perimetry in Nonorganic Visual Loss  

Microsoft Academic Search

Objective: To investigate the influence of the stimulus parameters on perimetry at various distances and draw conclusions for the clinical exploration of nonorganic visual loss. Methods: Visual field testing using Goldmann kinetic perimetry was performed on 15 healthy volunteers. The I\\/1e isopter at 33 cm was compared to the I\\/1e, II\\/1e and I\\/2e isopters at 66 cm. The 0\\/1e isopter

Andreas Ebneter; Niccolo Pellanda; Andrea Kunz; Stefania Mojon; Daniel S. Mojon

2010-01-01

14

Incremental parameter estimation of kinetic metabolic network models  

PubMed Central

Background An efficient and reliable parameter estimation method is essential for the creation of biological models using ordinary differential equation (ODE). Most of the existing estimation methods involve finding the global minimum of data fitting residuals over the entire parameter space simultaneously. Unfortunately, the associated computational requirement often becomes prohibitively high due to the large number of parameters and the lack of complete parameter identifiability (i.e. not all parameters can be uniquely identified). Results In this work, an incremental approach was applied to the parameter estimation of ODE models from concentration time profiles. Particularly, the method was developed to address a commonly encountered circumstance in the modeling of metabolic networks, where the number of metabolic fluxes (reaction rates) exceeds that of metabolites (chemical species). Here, the minimization of model residuals was performed over a subset of the parameter space that is associated with the degrees of freedom in the dynamic flux estimation from the concentration time-slopes. The efficacy of this method was demonstrated using two generalized mass action (GMA) models, where the method significantly outperformed single-step estimations. In addition, an extension of the estimation method to handle missing data is also presented. Conclusions The proposed incremental estimation method is able to tackle the issue on the lack of complete parameter identifiability and to significantly reduce the computational efforts in estimating model parameters, which will facilitate kinetic modeling of genome-scale cellular metabolism in the future.

2012-01-01

15

Mathematical modeling to investigate temperature effect on kinetic parameters of ethanol fermentation  

Microsoft Academic Search

A mathematical model was developed to describe the effects of temperature on the kinetic parameters of ethanol fermentation by the flocculating yeast, Saccharomyces cerevisiae M30, using cane molasses as the substrate. Three state variables, biomass, ethanol and the substrate and 12 kinetics parameters were used to describe the phenomenon. The kinetic parameters of the model were determined by using the

Muenduen Phisalaphong; Nuttapan Srirattana; Wiwut Tanthapanichakoon

2006-01-01

16

Effect of extraction parameters on curcumin yield from turmeric.  

PubMed

Effect of 4 independent variables - temperature (50-90°C), particle size (0.42-0.85 mm), mixing time (10-50 min) and solvent (ethanol) to meal ratio (10-50) on curcumin yield from turmeric (Curcuma longa L) was studied using central composite rotatable design. The experimental value of curcumin yield ranged between 4.49 and 12.89%. The second order model obtained for curcumin yield revealed a coefficient of determination (R(2)) of 0.78 and standard error of 0.72. The linear, square and interaction terms were significant at p <0.05 while lack of fit was non-significant at p >0.05. Surface graphs were plotted to optimize the curcumin extraction. The maximum curcumin yield was obtained when temperature, particle size, mixing time and solvent to meal ratio were 60°C, 0.42 mm, 30 min and 50, respectively. PMID:23572641

Sogi, D S; Sharma, S; Oberoi, D P S; Wani, I A

2010-07-29

17

Albite [yields] jadeite + quartz transformation in rock: Mechanism and kinetics  

SciTech Connect

Recent work on the calcite [yields] aragonite transformation using fully dense marble revealed significant differences from earlier experiments on powders and single-crystals. The reaction rate is retarded by a factor of > 1,000 and reaction mechanisms and resultant textures are considerably more complex. Stimulated by this, the authors conducted a study of the albite [yields] jadeite + quartz/coesite transformation in a fully dense albitite. Again the results are in marked contrast with previous powder-based studies of this archetypal metamorphic reaction. Solid cores of albitite were held at temperatures of 500-1,200 C and at pressure oversteps of 500 MPa into the jadeite + quartz stability field for 1--8 days in piston-cylinder apparatus. Samples that were dried in vacuum transformed appreciably only at temperatures in excess of 1,000 C. At all grain boundaries there is subequal transformation to micron-scale intergrowths of jadeite + quartz. Samples that were vacuum-impregnated with 1 wt% water contain jadeite + quartz to temperatures as low as 600 C. In contrast to the dried samples, transformation is much less homogeneous. The jadeite + quartz intergrowths do not form rows of subparallel crystals on grain boundaries, but rather are flower-shaped clusters that radiate outward from single nucleation sites at 3-grain edges and 4-grain corners. Compared to powders, pressure oversteps a factor of 10 greater are necessary to induce equivalent reaction in albitite. The sluggishness of this reaction has important implications for the evolution of the lower continental crust and subducting oceanic crust in terms of their (1) seismic velocity profiles, (2) petrological evolution, and (3) buoyancy forces, stresses and vertical crustal movements connected with densification and dilatational reactions.

Bohlen, S.R.; Kirby, S.H. (Geological Survey, Menlo Park, CA (United States)); Hacker, B.R.

1992-01-01

18

Measurement of the slope parameter for the {eta}{yields}3{pi}{sup 0} decay in the pp{yields}pp{eta} reaction  

SciTech Connect

The CELSIUS-WASA setup is used to measure the 3{pi}{sup 0} decay of {eta} mesons produced in pp interactions with beam kinetic energies of 1.36 and 1.45 GeV. The efficiency-corrected Dalitz plot and density distributions for this decay are shown, together with a fit of the quadratic slope parameter {alpha} yielding {alpha}=-0.026{+-}0.010(stat){+-}0.010(syst). This value is compared to recent experimental results and theoretical predictions.

Bashkanov, M.; Clement, H.; Meier, R.; Skorodko, T.; Wagner, G. J. [Physikalisches Institut der Universitaet Tuebingen, Tuebingen (Germany); Bogoslawsky, D.; Ivanov, G.; Jiganov, E.; Kuznetsov, A.; Morosov, B.; Petukhov, Y.; Povtorejko, A.; Tikhomirov, V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Calen, H.; Ekstroem, C.; Fransson, K.; Kupsc, A.; Marciniewski, P.; Ruber, R. J. M. Y. [The Svedberg Laboratory, Uppsala (Sweden); Capellaro, F. [Institutionen foer Kaern-och Partikelfysik, Uppsala University, Uppsala (Sweden)] (and others)

2007-10-15

19

APPLICATION OF MODIS DERIVED PARAMETERS FOR REGIONAL YIELD ASSESSMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Integration of operational satellites data with crop growth models allows assessing crop condition and yield at regional scale. Monitoring regional agricultural crop condition has traditionally been accomplished using NOAA AVHRR 1 km spatial resolution data. Daily coverage of MODIS imagery at 250 m....

20

Unscented Kalman filter with parameter identifiability analysis for the estimation of multiple parameters in kinetic models  

PubMed Central

In systems biology, experimentally measured parameters are not always available, necessitating the use of computationally based parameter estimation. In order to rely on estimated parameters, it is critical to first determine which parameters can be estimated for a given model and measurement set. This is done with parameter identifiability analysis. A kinetic model of the sucrose accumulation in the sugar cane culm tissue developed by Rohwer et al. was taken as a test case model. What differentiates this approach is the integration of an orthogonal-based local identifiability method into the unscented Kalman filter (UKF), rather than using the more common observability-based method which has inherent limitations. It also introduces a variable step size based on the system uncertainty of the UKF during the sensitivity calculation. This method identified 10 out of 12 parameters as identifiable. These ten parameters were estimated using the UKF, which was run 97 times. Throughout the repetitions the UKF proved to be more consistent than the estimation algorithms used for comparison.

2011-01-01

21

Influence of sucrose solution concentration on kinetics and yield during osmotic dehydration of mango  

Microsoft Academic Search

The effect of the sucrose solution concentration on the process kinetics and yield during osmotic dehydration of mango (Kent var.) cylinders has been studied. Processes were carried out at 30 °C, using 35, 45, 55 and 65 °Brix sucrose, at atmospheric pressure (osmotic dehydration) and by applying a vacuum pulse (50 mbar for 10 min) at the beginning of the

G. Giraldo; P. Talens; P. Fito; A. Chiralt

2003-01-01

22

Impact of sustaining a controlled residual growth on polyhydroxybutyrate yield and production kinetics in Cupriavidus necator.  

PubMed

In this study a complementary modeling and experimental approach was used to explore how growth controls the NADPH generation and availability, and the resulting impact on PHB (polyhydroxybutyrate) yields and kinetics. The results show that the anabolic demand allowed the NADPH production through the Entner-Doudoroff (ED) pathway, leading to a high maximal theoretical PHB production yield of 0.89CmoleCmole(-1); whereas without biomass production, NADPH regeneration is only possible via the isocitrate dehydrogenase leading to a theoretical yield of 0.67CmoleCmole(-1). Furthermore, the maximum specific rate of NADPH produced at maximal growth rate (to fulfil biomass requirement) was found to be the maximum set in every conditions, which by consequence determines the maximal PHB production rate. These results imply that sustaining a controlled residual growth improves the PHB specific production rate without altering production yield. PMID:24035890

Grousseau, Estelle; Blanchet, Elise; Déléris, Stéphane; Albuquerque, Maria G E; Paul, Etienne; Uribelarrea, Jean-Louis

2013-08-26

23

Morpholinecarbonyl-Rhodamine 110 based substrates for the determination of protease activity with accurate kinetic parameters.  

PubMed

Commonly used fluorogenic substrate analogues for the detection of protease activity contain two enzyme-cleavable bonds conjugated to the fluorophore. Enzymatic cleavage follows a two-step reaction with a monoamide intermediate. This intermediate shows fluorescence at the same wavelength as the final product complicating the kinetic analysis of fluorescence-based assays. Fluorogenic substrate analogues for ?-chymotrypsin with one cleavable peptide bond have been prepared from morpholinecarbonyl-Rhodamine 110 (MC-Rh110). A comparison of their kinetic properties with the corresponding (peptide)(2)-Rh110 derivatives revealed that these frequently used double-substituted substrate analogues yield only apparent K(m) and k(cat) values that are quite different from the kinetic parameters obtained from the monosubstituted MC-Rh110 based substrate analogues. Although both the monoamide intermediate and MC-Rh110 are monosubstituted Rhodamine 110 derivatives, they show different spectroscopic properties. The data from the spectroscopic analysis clearly show that these properties are directly related to the electron structure of the fluorophore and not to the previously proposed equilibrium between the lactone form and the open ionic form of the fluorophore. This knowledge about the determinants of the spectroscopic properties of monosubstituted Rhodamine 110 introduces a way for a more systematic development of new fluorogenic protease substrate analogues. PMID:21905728

Terentyeva, Tatyana G; Van Rossom, Wim; Van der Auweraer, Mark; Blank, Kerstin; Hofkens, Johan

2011-09-23

24

A Novel Method for Determining Kinetic Parameters of Dissociating Enzyme Systems  

Microsoft Academic Search

The theoretical analysis has been presented for the kinetics of dissociating–associating enzyme-catalyzed reactions. On the basis of the kinetic equation of substrate reaction, a general procedure is developed for determining the kinetic constants of dissociating–associating enzyme reactions. By analyzing the experimental data of initial velocity and steady-state velocity as functions of enzyme and substrate concentration, all unknown kinetic parameters can

Zhi-Xin Wang

1998-01-01

25

Growth parameter and yield component response of field corn to simulated acid rain  

SciTech Connect

Acid rain occurs in the midwest. Studies to date have suggested minimal yield response of field corn to acid rain. However, small but significant reductions in yield have been shown for some cultivars under extreme conditions. To define further these yield changes the study examined the effect of simulated acid rain on parameters associated with corn yield. Cultivars B73 x Mo17 and Pioneer 3377 were shielded from ambient rain by two movable rain exclusion shelters. Six simulated rain treatments were applied biweekly within these shelters through the use of a nozzle distribution system. For the most part, growth and yield parameters were unaffected by simulated rain treatment. While the only significant yield reduction was a contrast of pH 3.0 and the average of all other treatments for B73 x Mo17, the reduction appears to be the result both of slightly fewer ears and slightly less successful ear fill.

Banwart, W.L.; Porter, P.M.; Ziegler, E.L.; Hassett, J.J.

1988-01-01

26

USE OF ORAL CONTRACEPTIVES ALTERS ZINC KINETIC PARAMETERS IN WOMEN  

Technology Transfer Automated Retrieval System (TEKTRAN)

Oral contraceptives (OCs) were known to affect metabolism of minerals including zinc (Prasad, Am J Clin Nutr 28:377, 1975; Vijayalakshmi, Indian J Nutr Diet 21:225, 1984). To define effects of OCs on Zn metabolism, Zn kinetics was measured in 15 OC users and 35 nonusers of similar socioeconomic stat...

27

Identification of the catalytic mechanism and estimation of kinetic parameters for fumarase.  

PubMed

The enzyme fumarase catalyzes the reversible hydration of fumarate to malate. The reaction catalyzed by fumarase is critical for cellular energetics as a part of the tricarboxylic acid cycle, which produces reducing equivalents to drive oxidative ATP synthesis. A catalytic mechanism for the fumarase reaction that can account for the kinetic behavior of the enzyme observed in both isotope exchange studies and initial velocity studies has not yet been identified. In the present study, we develop an 11-state kinetic model of the enzyme based on the current consensus on its catalytic mechanism and design a series of experiments to estimate the model parameters and identify the major flux routes through the mechanism. The 11-state mechanism accounts for competitive binding of inhibitors and activation by different anions, including phosphate and fumarate. The model is identified from experimental time courses of the hydration of fumarate to malate obtained over a wide range of buffer and substrate concentrations. Further, the 11-state model is found to effectively reduce to a five-state model by lumping certain successive steps together to yield a mathematically less complex representation that is able to match the data. Analysis suggests the primary reaction route of the catalytic mechanism, with fumarate binding to the free unprotonated enzyme and a proton addition prior to malate release in the fumarate hydration reaction. In the reverse direction (malate dehydration), malate binds the protonated form of the enzyme, and a proton is generated before fumarate is released from the active site. PMID:21498518

Mescam, Muriel; Vinnakota, Kalyan C; Beard, Daniel A

2011-04-15

28

Chemical-kinetic prediction of critical parameters in gaseous detonations  

SciTech Connect

A theoretical model including a detailed chemical kinetic reaction mechanism for hydrogen and hydrocarbon oxidation is used to examine the effects of variations in initial pressure and temperature on the detonation properties of gaseous fuel-oxidizer mixtures. Fuels considered include hydrogen, methane, ethane, ethylene, and acetylene. Induction lengths are computed for initial pressures between 0.1 and 10.0 atmospheres and initial temperatures between 200K and 500K. These induction lengths are then compared with available experimental data for critical energy and critical tube diameter for initiation of spherical detonation, as well as detonation limits in linear tubes. Combined with earlier studies concerning variations in fuel-oxidizer equivalence ratio and degree of dilution with N/sub 2/, the model provides a unified treatment of fuel oxidation kinetics in detonations. 4 figures, 1 table.

Westbrook, C.K.; Urtiew, P.A.

1982-01-12

29

Crop yield prediction using piecewise linear regression with a break point and weather and agricultural parameters  

US Patent & Trademark Office Database

Crop yield may be assessed and predicted using a piecewise linear regression method with break point and various weather and agricultural parameters, such as NDVI, surface parameters (soil moisture and surface temperature) and rainfall data. These parameters may help aid in estimating and predicting crop conditions. The overall crop production environment can include inherent sources of heterogeneity and their nonlinear behavior. A non-linear multivariate optimization method may be used to derive an empirical crop yield prediction equation. Quasi-Newton method may be used in optimization for minimizing inconsistencies and errors in yield prediction. Minimization of least square loss function through iterative convergence of pre-defined empirical equation can be based on piecewise linear regression method with break point. This non-linear method can achieve acceptable lower residual values with predicted values very close to the observed values. The present invention can be modified and tailored for different crops worldwide.

2010-04-20

30

Kinetic parameters of electroextraction of cobalt from aqueous solutions of cobalt and manganese sulfates  

Microsoft Academic Search

The effect exerted by cobalt(II) concentration in the initial solution and temperature on the kinetics of cobalt(II) electroextraction\\u000a from cobalt(II) and manganese(II) sulfate solutions was studied. The kinetic parameters of the process were determined.

L. A. Voropanova; L. P. Khomenko

2007-01-01

31

[Analysis of hydrodynamics parameters of runoff erosion and sediment-yielding on unpaved road].  

PubMed

By the method of field runoff washout experiment, a simulation study was conducted on the relationships between the soil detachment rate and the hydrodynamic parameters on unpaved road, and the related quantitative formulas were established. Under the conditions of different flow discharges and road gradients, the averaged soil detachment rate increased with increasing flow discharge and road gradient, and the relationships between them could be described by a power function. As compared with road gradient, flow discharge had greater effects on the soil detachment rate. The soil detachment rate had a power relation with water flow velocity and runoff kinetic energy, and the runoff kinetic energy was of importance to the soil detachment rate. The soil detachment rate was linearly correlated with the unit runoff kinetic energy. The averaged soil erodibility was 0.120 g m-1.J-F-1, and the averaged critical unit runoff kinetic energy was 2.875 g.m-1.J-1. Flow discharge, road gradient, and unit runoff kinetic energy could be used to accurately describe the soil erosion process and calculate the soil erosion rate on unpaved road. PMID:23705397

Huang, Peng-Fei; Wang, Wen-Long; Luo, Ting; Wang, Zhen; Wang, Zheng-Li; Li, Ren

2013-02-01

32

Methods for Calibration of Prout-Tompkins Kinetics Parameters Using EZM Iteration and GLO.  

National Technical Information Service (NTIS)

This document contains information regarding the standard procedures used to calibrate chemical kinetics parameters for the extended Prout-Tompkins model to match experimental data. Two methods for calibration are mentioned: EZM calibration and GLO calibr...

A. K. Burnham A. P. Wemhoff

2006-01-01

33

Parameter Estimates in Differential Equation Models for Chemical Kinetics  

ERIC Educational Resources Information Center

|We discuss the need for devoting time in differential equations courses to modelling and the completion of the modelling process with efforts to estimate the parameters in the models using data. We estimate the parameters present in several differential equation models of chemical reactions of order n, where n = 0, 1, 2, and apply more general…

Winkel, Brian

2011-01-01

34

Predicting peak kinematic and kinetic parameters from gait speed  

Microsoft Academic Search

Objective: The aim of this study is to assess the predictability of the relationships between gait speed and common peak sagittal plane parameters in order to provide a set of reference parameter values. Design: Lower extremity biomechanical data were collected in 64 healthy adults while walking barefoot at his\\/her comfortable walking speed, then at self-selected fast, slow and very slow

Jennifer L Lelas; Gregory J Merriman; Patrick O Riley; D. Casey Kerrigan

2003-01-01

35

Propagation of Blood Function Errors to the Estimates of Kinetic Parameters with Dynamic PET  

PubMed Central

Dynamic PET, in contrast to static PET, can identify temporal variations in the radiotracer concentration. Mathematical modeling of the tissue of interest in dynamic PET can be simplified using compartment models as a linear system where the time activity curve of a specific tissue is the convolution of the tracer concentration in the plasma and the impulse response of the tissue containing kinetic parameters. Since the arterial sampling of blood to acquire the value of tracer concentration is invasive, blind methods to estimate both blood input function and kinetic parameters have recently drawn attention. Several methods have been developed, but the effect of accuracy of the estimated blood function on the estimation of the kinetic parameters is not studied. In this paper, we present a method to compute the error in the kinetic parameter estimates caused by the error in the blood input function. Computer simulations show that analytical expressions we derive are sufficiently close to results obtained from numerical methods. Our findings are important to observe the effect of the blood function on kinetic parameter estimation, but also useful to evaluate various blind methods and observe the dependence of kinetic parameter estimates to certain parts of the blood function.

Cheng, Yafang; Yetik, Imam Samil

2011-01-01

36

Small-signal RF yield analysis of MMIC circuits based on physical device parameters  

Microsoft Academic Search

A technique is presented for computing the small-signal RF yield of monolithic microwave integrated circuits (MMICs) based on the sensitivity of electrical model parameters to physical device parameters. Because GaAs MMICs are increasingly being used in large-scale production programs, the producibility of a given design must be considered at the beginning of the design process. The technique considered uses commonly

D. L. Allen; J. Beall; M. King

1992-01-01

37

Rapid estimation of kinetic parameters for thermal decomposition of penicillins by modulated thermogravimetric analysis.  

PubMed

Modulated thermogravimetic analysis (MTGA) is evaluated for the rapid estimation of thermal stability using several penicillin antibiotics as model compounds. The MTGA technique utilizes an oscillatory temperature program to obtain Arrhenius kinetic parameters through a mass loss during thermal degradation. To evaluate the reliability of this technique, activation energies (E(a)), log pre-exponential factor (logZ), and log first order rate constants (logk) obtained by MTGA for the thermal decomposition of ampicillin anhydrous, ampicillin trihydrate, ampicillin sodium salt, and penicillin G potassium salt are compared to existing literature values. The logk values estimated by MTGA agreed well with literature values when the weight loss observed by MTGA was shown to be due to the first decomposition step of the compound. The E(a) and logZ values determined by MTGA did not consistently agree with literature values as these parameters increased with decreasing heating rate (beta). The increase in E(a) and logZ values with decreasing beta seemed to offset each other to some extent to yield a relatively consistent logk estimate regardless of beta. PMID:15030881

Miller, Jonathan M; Kale, Uma J; Lau, Siu-Man Kelvin; Greene, Landon; Wang, Henry Y

2004-04-01

38

Radiative Corrections to Asymmetry Parameter in the {Omega}{sup -{yields}{Lambda}}+K{sup -} Decay  

SciTech Connect

We compute the radiative corrections, to first order in the fine structure constant {alpha}, to the asymmetry parameter {alpha}{sub {Omega}}of the {Omega}{sup -{yields}{Lambda}}+K{sup -} decay. We use previous results where Sirlin's procedure is used to separate the radiative corrections into two parts, one independent model contribution and a model dependent one.

Queijeiro, A. [Departamento de Fisica, Esc. Sup. de Fisica y Matematicas Instituto Politecnico Nacional, U.P. Adolfo Lopez Mateos, Mexico D.F. 07738 (Mexico)

2010-07-29

39

RESPONSE AND CORRELATED RESPONSE OF YIELD PARAMETERS TO SELECTION FOR SALT TOLERANCE IN RICE  

Technology Transfer Automated Retrieval System (TEKTRAN)

One of the major reasons for the limited success in salt tolerance breeding is the lack of reliable selection criteria in the screening for salt tolerance. This study was designed to determine the responses of yield parameters in rice plants to the selection for salt tolerance. F2 populations were...

40

Determining the Kinetic Parameters Characteristic of Microalgal Growth.  

ERIC Educational Resources Information Center

|An activity in which students obtain a growth curve for algae, identify the exponential and linear growth phases, and calculate the parameters which characterize both phases is described. The procedure, a list of required materials, experimental conditions, analytical technique, and a discussion of the interpretations of individual results are…

Martinez Sancho, Maria Eugenie; And Others

1991-01-01

41

Nanosecond flash studies of reduction of benzophenone by aliphatic amines. Quantum yields and kinetic isotope effects  

SciTech Connect

Nanosecond flash photolysis, steady irradiation, and deuterium substitution studies have been carried out on solutions of benzophenone with added reductants. Quantum yields (phi/sub ketyl/) for reduction in benzene of benzophenone triplet to ketyl radical, based on phi = 2 for benzhydrol (I), were approx. 1 for cyclohexane (II), tert-butylamine (III), 2-aminobutane (IV), cyclohexylamine (V), di-n-propylamine (VI), and triethylamine (VII), approx. 0.7 for 1,4-diazabicyclo(2.2.2)octane (VIII), and approx. 0 for tert-butyl alcohol (IX). Thus, quenching, without radical formation by H abstraction from N and/or ..cap alpha..-C, does not occur with common aliphatic amines but does with Dabco (VIII). The latter quenching is markedly increased by small additions of acetonitrile; the flash spectrum from this compound indicates formation of a triplet amine CT complex or radical ion pair. Triplet-reductant interaction rate constants, k/sur ir/, are high for the amines (approx. 10/sup 8/-10/sup 9/ M/sup -1/ s/sup -1/) but also show significant deuterium kinetic isotope effects: 1.9 with III-N-d/sub 2/; 1.4 with IV-N-d/sub 2/; 1.2-1.3 with IV-..cap alpha..-C-d. It is proposed that k/sub ir/ measures H atom abstraction, favored in the transition state by an initial charge-transfer interaction. Overall steady irradiation quantum yields of reduction by amines, phi/sub Red/, are much lower than phi/sub ketyl/. This is attributed to disproportionationreactions of ketyl and alkylaminyl radicals for primary and secondary amines, and, possibly, aminoalkyl radicals for tertiary amines. In the case of tert-butylamine, the rate constant for disproportionation is obtained from the decay kinetics of ketyl radical and leads to phi/sub Red/ in agreement with that directly measured.

Inbar, S.; Linschitz, H.; Cohen, S.G.

1981-03-11

42

Estimating Kinetic and Thermodynamic Parameters from Single Molecule Enzyme-Inhibitor Interactions  

PubMed Central

We report the application of recently developed microscopic models to estimate the apparent kinetic and thermodynamic parameters in a single molecule force spectroscopy study of the carbonic anhydrase enzyme and a complementary sulfonamide inhibitor. The most probable rupture force for the enzyme-inhibitor interaction shows a non-linear dependency on the log-loading rate. Estimates for the kinetic and thermodynamic parameters were obtained by fitting the non-linear dependency to linear cubic potential and cusp potential models and compared to the standard Bell-Evans model. The reliability of the estimated parameters was verified by modeling the experimental rupture force distributions by the theoretically predicted distributions at rupture. We also report that linkers that are attached to the enzyme and inhibitor show appreciable effects on the apparent kinetic and thermodynamic parameters.

Porter-Peden, Laura; Kamper, Sarah G.; Wal, Mark Vander; Blankespoor, Ronald; Sinniah', Kumar

2008-01-01

43

Relaxation Kinetics by Fluorescence Correlation Spectroscopy: Determination of Kinetic Parameters in the Presence of Fluorescent Impurities  

PubMed Central

The use of Fluorescence Correlation Spectroscopy (FCS) in combination with Förster Resonance Energy Transfer (FRET) is gaining popularity as a tool to investigate kinetics in equilibrium conditions. The technique is based on the study of fluorescence fluctuations in small numbers of molecules, and is particularly well-suited to investigate conformational dynamics in biopolymers. In practice, its applicability is often hindered by the presence of certain impurities such as partially labeled biomolecules, excess of free fluorophore, or partially dissociated multi-subunit complexes. Here, we show that the simultaneous measurement of the fluctuations in the donor and acceptor intensities allows the determination of the kinetic relaxation time of the reaction in the presence of donor-only particles when cross-talk is negligible, or in cases where all species have the same diffusion coefficient. Theoretical predictions are supported with the results of Monte Carlo simulations, and demonstrate that the applicability of the technique is more general than previously thought.

Levitus, Marcia

2010-01-01

44

Estimation of flotation kinetic parameters by considering interactions of the operating variables  

Microsoft Academic Search

In this study, the classical first-order kinetic model was combined with a properly built statistical model based on a factorial experimental design, in order to accurately predict the rougher flotation efficiency for various flotation conditions. A three-level, three-factor experimental design was used to develop a statistical model to predict each of the kinetic model parameters as a function of the

E. C. Çilek

2004-01-01

45

An Artificial Neural Network Model for Crop Yield Responding to Soil Parameters  

Microsoft Academic Search

\\u000a This paper presents an artificial neural network model for crop yield responding to soil parameters. The experimental data\\u000a had been obtained via a precision agriculture experiment, which is carried out by PAC in a demo farm locating in Shunyi district,\\u000a Beijing in 2000. The model has been established by training a back propagation neural network with 58 samples and tested

Gang Liu; Xuehong Yang; Minzan Li

2005-01-01

46

Complete Michel parameter analysis of the inclusive semileptonic b{yields}c transition  

SciTech Connect

We perform a complete 'Michel parameter' analysis of all possible helicity structures which can appear in the process B{yields}X{sub c}l{nu}{sub l}. We take into account the full set of operators parametrizing the effective Hamiltonian and include the complete one-loop QCD corrections as well as the nonperturbative contributions. The moments of the leptonic energy as well as the combined moments of the hadronic energy and hadronic invariant mass are calculated including the nonstandard contributions.

Dassinger, Benjamin; Feger, Robert; Mannel, Thomas [Fachbereich Physik, Universitaet Siegen, D-57068 Siegen (Germany)

2009-04-01

47

Impact of industrial air pollutants on some biochemical parameters and yield in wheat and mustard plants  

Microsoft Academic Search

The present study was carried out to determine the impacts of SO2, NO\\u000a x\\u000a , SPM and RSPM, the most common air pollutants, generated mainly due to industries and vehicles, on some biochemical parameters\\u000a and yield in wheat and mustard plants during 2006. The concentration of SO2, NO\\u000a x\\u000a , SPM and RSPM was determined at the polluted sites across

Namita Joshi; Avnish Chauhan; P. C. Joshi

2009-01-01

48

Effects of Supercritical Fluid Extraction Parameters on Unsaturated Fatty Acid Yields of Pistacia terebinthus Berries  

Microsoft Academic Search

Utilization of renewable resources and development of new processes aimed at converting these materials into value added bio-products\\u000a are gaining more emphasis. The scope of this study was to optimize supercritical CO2 extraction (SFE) parameters such as pressure, temperature and flow rate for the yields of unsaturated fatty acids from Pistacia terebinthus berries by a Box-Behnken statistical design. All samples

Deniz Senyay-Oncel; Hasan Ertas; Ozlem Yesil-Celiktas

2011-01-01

49

Solid State Kinetic Parameters and Chemical Mechanism of the Dehydration of CoCl2.6H2O.  

ERIC Educational Resources Information Center

|Presents an experimental example illustrating the most common methods for the determination of kinetic parameters. Discusses the different theories and equations to be applied and the mechanism derived from the kinetic results. (CW)|

Ribas, Joan; And Others

1988-01-01

50

A comparative study of seed yield parameters in Arabidopsis thaliana mutants and transgenics.  

PubMed

Because seed yield is the major factor determining the commercial success of grain crop cultivars, there is a large interest to obtain more understanding of the genetic factors underlying this trait. Despite many studies, mainly in the model plant Arabidopsis thaliana, have reported transgenes and mutants with effects on seed number and/or seed size, knowledge about seed yield parameters remains fragmented. This study investigated the effect of 46 genes, either in gain- and/or loss-of-function situations, with a total of 64 Arabidopsis lines being examined for seed phenotypes such as seed size, seed number per silique, number of inflorescences, number of branches on the main inflorescence and number of siliques. Sixteen of the 46 genes, examined in 14 Arabidopsis lines, were reported earlier to directly affect in seed size and/or seed number or to indirectly affect seed yield by their involvement in biomass production. Other genes involved in vegetative growth, flower or inflorescence development or cell division were hypothesized to potentially affect the final seed size and seed number. Analysis of this comprehensive data set shows that of the 14 lines previously described to be affected in seed size or seed number, only nine showed a comparable effect. Overall, this study provides the community with a useful resource for identifying genes with effects on seed yield and candidate genes underlying seed QTL. In addition, this study highlights the need for more thorough analysis of genes affecting seed yield. PMID:22332878

Van Daele, Inge; Gonzalez, Nathalie; Vercauteren, Ilse; de Smet, Lien; Inzé, Dirk; Roldán-Ruiz, Isabel; Vuylsteke, Marnik

2012-02-15

51

Novel photocatalytic reactor for the destruction of airborne pollutants reaction kinetics and quantum yields  

SciTech Connect

Photocatalytic conversion of a model pollutant (toluene) is studied in a newly designed batch photoreactor, called Photo-CREC-Air. In this unit TiO{sub 2} is supported on a filter mesh with good contact with near UV light, TiO{sub 2}, and air. Photo-CREC-Air is designed with special features including a Venturi section and a heated perforated plate. The heated perforated plate minimizes water adsorption on the mesh and consequently water effects on the reaction rate. The system performance is examined for different toluene concentrations and two humidity levels. After assessing the insignificant toluene adsorption observed under the selected operating conditions, a pseudohomogeneous model is postulated for kinetics modeling. Initial photodegradation rates of toluene at 100 C in Photo-CREC-Air, in the range of model pollutant concentrations and humidity level studied, were 0.005--0.05 {mu}mol/(gcat s). Apparent quantum yields were estimated to be in many cases greater than 100% and as high as 450%.

Ibrahim, H.; Lasa, H. de [Science Univ. of Western Ontario, London (Canada). Chemical Reactor Engineering Center

1999-09-01

52

A Comparison of Isoconversional and Model-Fitting Approaches to Kinetic Parameter Estimation and Application Predictions  

SciTech Connect

Chemical kinetic modeling has been used for many years in process optimization, estimating real-time material performance, and lifetime prediction. Chemists have tended towards developing detailed mechanistic models, while engineers have tended towards global or lumped models. Many, if not most, applications use global models by necessity, since it is impractical or impossible to develop a rigorous mechanistic model. Model fitting acquired a bad name in the thermal analysis community after that community realized a decade after other disciplines that deriving kinetic parameters for an assumed model from a single heating rate produced unreliable and sometimes nonsensical results. In its place, advanced isoconversional methods (1), which have their roots in the Friedman (2) and Ozawa-Flynn-Wall (3) methods of the 1960s, have become increasingly popular. In fact, as pointed out by the ICTAC kinetics project in 2000 (4), valid kinetic parameters can be derived by both isoconversional and model fitting methods as long as a diverse set of thermal histories are used to derive the kinetic parameters. The current paper extends the understanding from that project to give a better appreciation of the strengths and weaknesses of isoconversional and model-fitting approaches. Examples are given from a variety of sources, including the former and current ICTAC round-robin exercises, data sets for materials of interest, and simulated data sets.

Burnham, A K

2006-05-17

53

Thermodynamic characterization of five key kinetic parameters that define neuronal nitric oxide synthase catalysis.  

PubMed

NO synthase (NOS) enzymes convert l-arginine to NO in two sequential reactions whose rates (kcat1 and kcat2 ) are both limited by the rate of ferric heme reduction (kr ). An enzyme ferric heme-NO complex forms as an immediate product complex and then undergoes either dissociation (at a rate that we denote as kd ) to release NO in a productive manner, or reduction (kr ) to form a ferrous heme-NO complex that must react with O2 (at a rate that we denote as kox ) in a NO dioxygenase reaction that regenerates the ferric enzyme. The interplay of these five kinetic parameters (kcat1 , kcat2 , kr , kd and kox ) determines NOS specific activity, O2 concentration response, and pulsatile versus steady-state NO generation. In the present study, we utilized stopped-flow spectroscopy and single catalytic turnover methods to characterize the individual temperature dependencies of the five kinetic parameters of rat neuronal NOS. We then incorporated the measured kinetic values into computer simulations of the neuronal NOS reaction using a global kinetic model to comprehensively model its temperature-dependent catalytic behaviours. The results obtained provide new mechanistic insights and also reveal that the different temperature dependencies of the five kinetic parameters significantly alter neuronal NOS catalytic behaviours and NO release efficiency as a function of temperature. PMID:23789902

Haque, Mohammad Mahfuzul; Tejero, Jesús; Bayachou, Mekki; Wang, Zhi-Qiang; Fadlalla, Mohammed; Stuehr, Dennis J

2013-07-15

54

Genetic parameters for the weights and yields of carcass cuts in Chianina cattle.  

PubMed

Chianina is the tallest and heaviest beef cattle breed in the world and 1 of the most appreciated breeds on the Italian meat market. A selection program focused on improving Chianina carcass quality could provide a further economic advantage to Chianina breeders. However, the current European carcass scoring system [i.e., the SEUROP (S=superior, E=excellent, U= very good, R=good, O=fair, and P=poor) grid] is not suitable for use in selective breeding programs; methods based on carcass cuts would be much more efficient. Here, the genetic parameters of weights and yields (percentage of carcass weight) of the main commercial cuts were estimated on 842 Chianina carcasses (heifers and bullocks) using a mixed model that takes into account the fixed effects of herd, year of slaughter, and sex and the random additive effect of the animal; the carcass weight was also considered in cuts yield. The average carcass weights were 492.6 ± 86.52 kg (males) and 312.1 ± 68.74 kg (females), and the largest cut was the round, with a weight of 58.6 ± 19.35 kg and yield of 24.4 ± 1.28% in males and 40.2 ± 17.59 kg and 25.3 ± 1.41% in females. The variability in cut weight was greater than that in yield percentage. The cut weight heritabilities ranged from 0.74 (chuck) to 0.21 (short plate) whereas the yield heritabilities ranged from 0.88 (loin) to 0.40 (brisket). The genetic correlations were generally high and positive between weights; correlation values with yields were lower and could be positive or negative. These findings suggest that a selection program to improve the carcass quality of Chianina beef using cuts data could potentially achieve good results. PMID:23881686

Sarti, F M; Pieramati, C; Lubricchio, E; Giontella, A; Lasagna, E; Panella, F

2013-07-23

55

On-line estimation of kinetic parameters in anaerobic digestion using observer-based estimators and multiwavelength fluorometry.  

PubMed

Observer-based estimators (OBE) were used for estimation of state variables and kinetic parameters in an anaerobic digestion (AD) process. A simplified first-order model with time-varying kinetic parameters was used to design an OBE for kinetic parameter estimation. This approach was validated on a laboratory-scale anaerobic reactor equipped with a multiwavelength fluorometer for on-line measurements of COD and VFA concentrations in the reactor effluent. The proposed estimators provide continuous adjustment of kinetic parameters and can be used for predictions of state variables between samples acquisition and during sensor failure. PMID:16722057

Morel, E; Tartakovsky, B; Guiot, S R; Perrier, M

2006-01-01

56

An EXCEL template for calculation of enzyme kinetic parameters by non-linear regression.  

PubMed

MOTIVATION: An EXCEL template has been developed for the calculation of enzyme kinetic parameters by non-linear regression techniques. The tool is accurate, inexpensive, as well as easy to use and modify. AVAILABILITY: The program is available from http://www.ebi.ac.uk/biocat/biocat.html CONTACT: agustin. hernandez@bio.kuleuven.ac.be PMID:9545460

Hernández, A; Ruiz, M T

1998-01-01

57

Kinetic Parameters for the Noncatalyzed and Enzyme-Catalyzed Mutarotation of Glucose Using a Blood Glucometer  

ERIC Educational Resources Information Center

|The kinetic parameters for the conversion of alpha-D-glucose to beta-D-glucose were measured using a blood glucometer. The reaction order, rate constant, and Arrhenius activation energy are reported for the noncatalyzed reaction and turnover number and Michaelis constant are reported for the reaction catalyzed by porcine kidney mutarotase. The…

Hardee, John R.; Delgado, Bryan; Jones, Wray

2011-01-01

58

Study of the kinetic parameters for synthesis and hydrolysis of pharmacologically active salicin isomer catalyzed by baker's yeast maltase  

NASA Astrophysics Data System (ADS)

One of the key elements for understanding enzyme reactions is determination of its kinetic parameters. Since transglucosylation is kinetically controlled reaction, besides the reaction of synthesis, very important is the reaction of enzymatic hydrolysis of created product. Therefore, in this study, kinetic parameters for synthesis and secondary hydrolysis of pharmacologically active ? isosalicin by baker's yeast maltase were calculated, and it was shown that specifity of maltase for hydrolysis is approximately 150 times higher then for synthesis.

Veli?kovi?, D. V.; Dimitrijevi?, A. S.; Bihelovi?, F. J.; Jankov, R. M.; Milosavi?, N.

2011-12-01

59

The effects of different experimental designs on parameter es- timation in the kinetics of a reversible chemical reaction  

Microsoft Academic Search

Using the e xperimental design methods, instead o f deterministic ones commonly used by chemists, to estimate the kinetic constants is a very important subject in chemical re- searches, since such-obtained kinetic parameters have much better statistical properties. D-optimum design is a popular statistical technique, which emphasizes to obtain the es- timated parameters with the smallest content of the confidence

Qing-Song Xu; Yi-Zeng Liang; Kai-Tai Fang

2000-01-01

60

Characterisation of sugar cane straw waste as pozzolanic material for construction: Calcining temperature and kinetic parameters  

SciTech Connect

This paper reports on the influence of calcining temperature (800 and 1000 deg. C) on the pozzolanic activation of sugar cane straw (SCS). The reaction kinetics of SCS ash-lime mixtures were inferred from physicochemical characteristics (X-ray diffraction patterns and thermogravimetry analysis. The fitting of a kinetic-diffusive model to the experimental data (fixed lime versus time) allowed the computing of the kinetic parameters (reaction rate constant) of the pozzolanic reaction. Results obtained confirm that the sugar cane straw ash (SCSA) calcined at 800 and 1000 deg. C have properties indicative of very high pozzolanic activity. No influence of calcining temperature on the pozzolanic activity was observed. Also, no crystalline compounds during the pozzolanic reaction were identified up to 90 days of reaction. Environmental durability and strength of the consequential mortars remain to be assessed.

Frias, Moises [Eduardo Torroja Institute (CSIC), c/ Serrano Galvache 4, 28033 Madrid (Spain)], E-mail: mfrias@ietcc.csic.es; Villar-Cocina, E.; Valencia-Morales, E. [Department of Physics, Central University of Las Villas, Santa Clara 54830 (Cuba)

2007-07-01

61

Thermoluminescence kinetic parameters of microwave chemically vapour-deposited diamond films at different gamma dose rates  

NASA Astrophysics Data System (ADS)

Microwave chemically vapour-deposited (MWCVD) diamond films have been successfully used in dosimetric applications including radiotherapy and industrial dose assessments. The thermoluminescence (TL) properties and dose response, in a suitable MWCVD diamond film thermoluminescent dosimeter, should be independent of the irradiation dose rate used. Dose rate effects have been reported to exist, affecting the TL performance of polycrystalline CVD diamond. In the present work, dose rate effects on the TL kinetic parameters of two MWCVD diamond films of 6 and 12 ?m thickness, exposed to 60Co gamma dose rates of 2.4, 5.94 and 13.1 Gy/min, were investigated using a computerised glow curve deconvolution method. The TL glow curves featured a single TL peak at different dose rates, which were best fitted with a first-order kinetic curve having 2-3% figure of merit. No significant dose rate effects on the TL kinetic properties of the studied samples were observed.

Cruz-Zaragoza, E.; Favalli, A.; Gastélum, S.; Furetta, C.; Meléndrez, R.; Barboza-Flores, M.

62

Thermoluminescence systems with two or more glow peaks described by anomalous kinetic parameters  

SciTech Connect

The usual first and second order TL kinetic expressions are based on a number of assumptions, including the usually unstated assumption that charges released from one type of trap, giving rise to one glow peak, are not retrapped on other types of traps, associated with other glow peaks. Equations have been developed describing TL systems in which charges released from one type of trap may be retrapped in other types of traps. Called interactive kinetic equations, they are quite simple but have been studied by numerical methods. In particular, glow curves computed from the interactive kinetic equations have been regarded as data and analyzed by fitting them to the usual first and second order kinetic expressions. All of the anomalous features described above are reproduced. For example, usually the computed glow peaks are well fitted by the first and second order expressions over their upper 60 to 80% but not in the wings. This explains why the usual analysis methods, especially those utilizing peak temperature, full width, etc. appear to describe such peaks. Often unrealistic kinetic parameters are often obtained. Furthermore, the computed glow curves often reproduce the observed dependence on dose.

Levy, P.W.

1983-01-01

63

A methodology for modeling photocatalytic reactors for indoor pollution control using previously estimated kinetic parameters.  

PubMed

A methodology for modeling photocatalytic reactors for their application in indoor air pollution control is carried out. The methodology implies, firstly, the determination of intrinsic reaction kinetics for the removal of formaldehyde. This is achieved by means of a simple geometry, continuous reactor operating under kinetic control regime and steady state. The kinetic parameters were estimated from experimental data by means of a nonlinear optimization algorithm. The second step was the application of the obtained kinetic parameters to a very different photoreactor configuration. In this case, the reactor is a corrugated wall type using nanosize TiO(2) as catalyst irradiated by UV lamps that provided a spatially uniform radiation field. The radiative transfer within the reactor was modeled through a superficial emission model for the lamps, the ray tracing method and the computation of view factors. The velocity and concentration fields were evaluated by means of a commercial CFD tool (Fluent 12) where the radiation model was introduced externally. The results of the model were compared experimentally in a corrugated wall, bench scale reactor constructed in the laboratory. The overall pollutant conversion showed good agreement between model predictions and experiments, with a root mean square error less than 4%. PMID:22030272

Passalía, Claudio; Alfano, Orlando M; Brandi, Rodolfo J

2011-10-06

64

Effects of sonication on the kinetics of orange juice quality parameters.  

PubMed

The effects of sonication on pH, degrees Brix, titratable acidity (TA), cloud, browning index, and color parameters ( L*, a*, and b*) of freshly squeezed orange juice samples were studied. Ultrasonic intensity (UI) levels of 8.61, 9.24, 10.16, 17.17, and 22.79 W/cm2 and treatment times of 0 (control), 2, 4, 6, 8, and 10 min were investigated. No significant changes in pH, degrees Brix, and TA ( p < 0.05) were found. Cloud value, browning index, and color parameters were significantly affected by ultrasonic intensity and treatment time. Changes in cloud value followed first-order kinetics, whereas browning index, L*, a*, and b* values followed zero-order kinetics. Reaction rate constants were linearly correlated ( R2 > 0.90) to ultrasonic intensity. PMID:18321054

Tiwari, B K; Muthukumarappan, K; O'Donnell, C P; Cullen, P J

2008-03-06

65

Kinetic Parameter Estimation Using a Closed-Form Expression via Integration-by-Parts  

PubMed Central

Dynamic emission computed tomographic imaging with compartment modeling can quantify in vivo physiologic processes, eliciting more information regarding underlying molecular disease processes than is obtained from static imaging. However, estimation of kinetic rate parameters for multi-compartment models can be computationally demanding and problematic due to local minima. A number of techniques for kinetic parameter estimation have been studied and are in use today, generally offering a tradeoff between computation time, robustness of fit, and flexibility with differing sets of assumptions. This paper presents a means to eliminate all differential operations by using the integration-by-parts method to provide closed-form formulas, so that the mathematical model is less sensitive to data sampling and noise. A family of closed-form formulas can be obtained. Computer simulations show that the proposed method is robust without having to specify the initial condition.

Zeng, Gengsheng L.; Hernandez, Andrew; Kadrmas, Dan J.; Gullberg, Grant T.

2012-01-01

66

Determination of kinetic parameters, Km and kcat, with a single experiment on a chip.  

PubMed

We have demonstrated a multistep enzyme reaction on a chip to determine the key kinetic parameters of enzyme reaction. We designed and fabricated a fully integrated microfluidic chip to have sample metering, mixing, and incubation functionalities. The chip generates a gradient of reagent concentrations in 11 parallel processors. We used beta-galactosidase and its substrate, resorufin-beta-D-galactopyranoside, as the model system of the enzyme reaction. With a single experiment on the chip, we determined the key parameters for the enzyme kinetics, K(m) and k(cat), and evaluated the effect of inhibitor concentrations on the reaction rates. This study provides a new tool for evaluating various effectors, such as inhibitors and cofactors, on the initial rate of an enzyme reaction, and it could be applied to a comprehensive bio/chemical reaction study. PMID:19338287

Jambovane, Sachin; Duin, Evert C; Kim, Se-Kwon; Hong, Jong Wook

2009-05-01

67

Kinetic parameters for reversal of the multidrug pump as measured for drug accumulation and cell killing  

Microsoft Academic Search

We determined the kinetic parameters that describe the effect of 20 different modulators of the multidrug resistance pump\\u000a on the reversal of cytotoxin accumulation in a resistant strain of P388 leukemia cells (P388\\/ADR), and on the reversal of\\u000a cell killing for these cells. When measured by a direct comparison of the amplitude of the pertinent protocol (accumulation\\u000a or cell killing),

Lu-Bin Lan; Suhail Ayesh; Elena Lyubimov; Irina Pashinsky; Wilfred D. Stein

1996-01-01

68

A longitudinal, five year survey of urea kinetic parameters in CAPD patients  

Microsoft Academic Search

A longitudinal, five year survey of urea kinetic parameters in CAPD patients. This study reports on the five years' evolution of the KT\\/V urea index and protein catabolic rate (PCR) in 16 CAPD patients who were treated with a constant daily dialysis dose. Total KT\\/V urea index decreased with time from a value of 0.96 ± 0.06 at the start

Norbert H Lameire; Raymond Vanholder; Denise Veyt; Marie-Christine Lambert; Severin Ringoir

1992-01-01

69

Determination of mechanical parameters related to the kinetics of swelling in an electrically activated contractile gel  

Microsoft Academic Search

We report on an analytical model and related experiments to determine the mechanical parameters governing the kinetics of\\u000a mechanical readjustment of a thermally crosslinked polyacrylic acid (20% by weight) and polyvinylalcohol (80% by weight) (PAA-PVA)\\u000a gel.\\u000a \\u000a Either thin films on spherical samples have been used in the experiments. The characteristic time of swelling in the case\\u000a of a thin film

P. Chiarelli; D. De Rossi

70

The determination of kinetic parameters from DTG curves — fact or fiction?  

Microsoft Academic Search

One way to determine the kinetic parameters of a reaction with an associated loss in mass is by the production of a log plot viz. ln[(d?\\/dt)\\/(fn(?))]=lnA?E\\/(RT). The situation that arises when two or more reactions are occurring simultaneously is discussed. It is shown that the log plot can often help to elucidate that a complex reaction is proceeding, even when

F. W. Wilburn

1999-01-01

71

The kinetic parameters and energy cost of the Hsp70 chaperone as a polypeptide unfoldase  

Microsoft Academic Search

Hsp70-Hsp40-NEF and possibly Hsp100 are the only known molecular chaperones that can use the energy of ATP to convert stably pre-aggregated polypeptides into natively refolded proteins. However, the kinetic parameters and ATP costs have remained elusive because refolding reactions have only been successful with a molar excess of chaperones over their polypeptide substrates. Here we describe a stable, misfolded luciferase

Sandeep K Sharma; Paolo De Los Rios; Philipp Christen; Ariel Lustig; Pierre Goloubinoff

2010-01-01

72

A Comparison Between Shaker and Bioreactor Performance Based on the Kinetic Parameters of Xanthan Gum Production  

Microsoft Academic Search

Xanthan gum production was studied using sugarcane broth as the raw material and batch fermentation by Xanthomonas campestris pv. campestris NRRL B-1459. The purpose of this study was to optimize the variables of sucrose, yeast extract, and ammonium nitrate concentrations\\u000a and to determine the kinetic parameters of this bioreaction under optimized conditions. The effects of yeast extract and ammonium\\u000a nitrate

S. Faria; P. A. Vieira; M. M. Resende; F. P. França; V. L. Cardoso

2009-01-01

73

The relationship between muscle kinetic parameters and kinematic variables in a complex movement  

Microsoft Academic Search

Summary  Kinematic variables of the vertical jump (jumping height, jump phase durations and joint angles) were measured on 39 male\\u000a physical education students. In addition, kinetic parameters of the hip and knee extensors, and of the plantar flexors (maxima\\u000a voluntary force and its rate of development) were recorded on the same subjects, in isometric conditions. The results demonstrated\\u000a significant positive correlations

Slobodan Jari?; Dušan Ristanovi?; Daniel M. Corcos

1989-01-01

74

The dynamics of local kinetic parameters of glutamate dehydrogenase in rat liver  

Microsoft Academic Search

Kinetic parameters of glutamate dehydrogenase (GDH, EC 1.4.1.2) for glutamate were determined in periportal and pericentral\\u000a zones of adult male and female rat liver lobules under normal fed conditions and after starvation for 24 h. GDH activity was\\u000a measured as formazan production over time against a range of glutamate concentrations in serial cryostat sections using image\\u000a analysis. Captured gray value

Ard Jonker; Willie J. C. Geerts; Rob Charles; Wouter H. Lamers; Cornelis J. F. Van Noorden

1996-01-01

75

Genetic and phenotypic parameters for conformation and yield traits in three Swiss dairy cattle breeds.  

PubMed

This study presents genetic parameters for conformation traits and their genetic and phenotypic correlations with milk production traits and somatic cell score (SCS) in three Swiss dairy cattle breeds. Data on first lactations from Holstein (67,839), Brown Swiss (173,372) and Red & White breeds (53,784) were available. Analysed conformation traits were stature and heart girth (both in cm), and linear scores of body depth, rump width, dairy character or muscularity, and body condition score (only in Holstein). A sire model, with relationships among sires, was used for all breeds and traits and variance components were estimated using AS-REML. Heritabilities for stature were high (0.6-0.8), and for the linear type traits ranged from 0.3 to 0.5, for all breeds. Genetic correlations with production traits (milk, fat and protein yield) and SCS differed between the dairy breeds. Most markedly, stronger correlations were found between SCS and some conformation traits in Brown Swiss and Red & White, indicating that a focus on a larger and more 'dairy' type in these breeds would lead to increased SCS. Another marked difference was that rump width correlated positively with milk yield traits in Holstein and Red & White, but negative in Brown Swiss. Results indicate that conformation traits generally can be used as predictors for various purposes in dairy cattle breeding, but may require specific adaptation for each breed. PMID:17302955

de Haas, Y; Janss, L L G; Kadarmideen, H N

2007-02-01

76

Reliability of spatiotemporal and kinetic gait parameters determined by a new instrumented treadmill system  

PubMed Central

Background Despite the emerging use of treadmills integrated with pressure platforms as outcome tools in both clinical and research settings, published evidence regarding the measurement properties of these new systems is limited. This study evaluated the within– and between–day repeatability of spatial, temporal and vertical ground reaction force parameters measured by a treadmill system instrumented with a capacitance–based pressure platform. Methods Thirty three healthy adults (mean age, 21.5?±?2.8 years; height, 168.4?±?9.9 cm; and mass, 67.8?±?18.6 kg), walked barefoot on a treadmill system (FDM–THM–S, Zebris Medical GmbH) on three separate occasions. For each testing session, participants set their preferred pace but were blinded to treadmill speed. Spatial (foot rotation, step width, stride and step length), temporal (stride and step times, duration of stance, swing and single and double support) and peak vertical ground reaction force variables were collected over a 30–second capture period, equating to an average of 52?±?5 steps of steady–state walking. Testing was repeated one week following the initial trial and again, for a third time, 20 minutes later. Repeated measures ANOVAs within a generalized linear modelling framework were used to assess between–session differences in gait parameters. Agreement between gait parameters measured within the same day (session 2 and 3) and between days (session 1 and 2; 1 and 3) were evaluated using the 95% repeatability coefficient. Results There were statistically significant differences in the majority (14/16) of temporal, spatial and kinetic gait parameters over the three test sessions (P?parameters, 14% and 33% for spatial parameters, and 4% and 20% for kinetic parameters between days. Within–day repeatability was similar to that observed between days. Temporal and kinetic gait parameters were typically more consistent than spatial parameters. The 95% repeatability coefficient for vertical force peaks ranged between?±?53 and?±?63 N. Conclusions The limits of agreement in spatial parameters and ground reaction forces for the treadmill system encompass previously reported changes with neuromuscular pathology and footwear interventions. These findings provide clinicians and researchers with an indication of the repeatability and sensitivity of the Zebris treadmill system to detect changes in common spatiotemporal gait parameters and vertical ground reaction forces.

2013-01-01

77

Application of lab derived kinetic biodegradation parameters at the field scale  

NASA Astrophysics Data System (ADS)

Estimating the intrinsic remediation potential of an aquifer typically requires the accurate assessment of the biodegradation kinetics, the level of available electron acceptors and the flow field. Zero- and first-order degradation rates derived at the laboratory scale generally overpredict the rate of biodegradation when applied to the field scale, because limited electron acceptor availability and microbial growth are typically not considered. On the other hand, field estimated zero- and first-order rates are often not suitable to forecast plume development because they may be an oversimplification of the processes at the field scale and ignore several key processes, phenomena and characteristics of the aquifer. This study uses the numerical model BIO3D to link the laboratory and field scale by applying laboratory derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at Canadian Forces Base (CFB) Borden. All additional input parameters were derived from laboratory and field measurements or taken from the literature. The simulated results match the experimental results reasonably well without having to calibrate the model. An extensive sensitivity analysis was performed to estimate the influence of the most uncertain input parameters and to define the key controlling factors at the field scale. It is shown that the most uncertain input parameters have only a minor influence on the simulation results. Furthermore it is shown that the flow field, the amount of electron acceptor (oxygen) available and the Monod kinetic parameters have a significant influence on the simulated results. Under the field conditions modelled and the assumptions made for the simulations, it can be concluded that laboratory derived Monod kinetic parameters can adequately describe field scale degradation processes, if all controlling factors are incorporated in the field scale modelling that are not necessarily observed at the lab scale. In this way, there are no scale relationships to be found that link the laboratory and the field scale, accurately incorporating the additional processes, phenomena and characteristics, such as a) advective and dispersive transport of one or more contaminants, b) advective and dispersive transport and availability of electron acceptors, c) mass transfer limitations and d) spatial heterogeneities, at the larger scale and applying well defined lab scale parameters should accurately describe field scale processes.

Schirmer, M.; Barker, J. F.; Butler, B. J.; Frind, E. O.

2003-04-01

78

Removal kinetics of organic compounds and sum parameters under field conditions for managed aquifer recharge.  

PubMed

Managed aquifer recharge (MAR) provides efficient removal for many organic compounds and sum parameters. However, observed in situ removal efficiencies tend to scatter and cannot be predicted easily. In this paper, a method is introduced which allows to identify and eliminate biased samples and to quantify simultaneously the impact of (i) redox conditions (ii) kinetics (iii) residual threshold values below which no removal occurs and (iv) field site specifics. It enables to rule out spurious correlations between these factors and therefore improves the predictive power. The method is applied to an extensive database from three MAR field sites which was compiled in the NASRI project (2002-2005, Berlin, Germany). Removal characteristics for 38 organic parameters are obtained, of which 9 are analysed independently in 2 different laboratories. Out of these parameters, mainly pharmaceutically active compounds (PhAC) but also sum parameters and industrial chemicals, four compounds are shown to be readily removable whereas six are persistent. All partly removable compounds show a redox dependency and most of them reveal either kinetic dependencies or residual threshold values, which are determined. Differing removal efficiencies at different field sites can usually be explained by characteristics (i) to (iii). PMID:21835424

Wiese, Bernd; Massmann, Gudrun; Jekel, Martin; Heberer, Thomas; Dünnbier, Uwe; Orlikowski, Dagmar; Grützmacher, Gesche

2011-07-22

79

[Kinetic parameters of calcium binding to tissue structures in human acute hypercalcaemia].  

PubMed

Calcium binding kinetic by tissue structures was analysed in 19 health volunteers (13 men and 6 women) of the age group of 33 +/- 6.5 under conditions of acute hypercalcaemia followed by a drip i.v. infusion of calcium gluconate over 2.5 hours. At the end of each 30-minute period the calcium amount retained by tissue structures was recorded and the kinetic parameters of calcium binding were determined according to Langmuir and Scatchard. In all volunteers there was a segment of binding isotherm with positive cooperativity (direct regression in Scatchard) with analogous buffer capacity (beta) for calcium in Langmuir (0.58 +/- 0.24 L kg). One half of volunteers demonstrated cooperativity at [Ca++] 1.3-1.5, while another--at [Ca++] 1.0-1.3 mmol/L which corresponded to the differences in the association constant (Ka) and the number of interactive sites (n) with [Ca++] 1 mmol/L. Additionally, two segments of binding isotherm were detected with the successive binding of calcium to one set of noninteractive sites with similar kinetic parameters of calcium binding (beta, K(a), n). Four different curves of calcium binding in healthy volunteers were established. This study may serve as the basis for a functional diagnostic test of disorders of the tissue calcium-binding properties in different pathological conditions. PMID:23789388

Ermakova, I P; Potanina, T V; Buzulina, V P; Pronchenko, I A; Larina, I M; Shmerko, N P; Sevast'ianov, V I

80

Kinetics of Bacterial Phospholipase C Activity at Micellar Interfaces: Effect of Substrate Aggregate Microstructure and a Model for the Kinetic Parameters  

PubMed Central

Activity at micellar interfaces of bacterial phospholipase C from Bacillus cereus on phospholipids solubilized in micelles was investigated with the goal of elucidating the role of the interface microstructure and developing further an existing kinetic model. Enzyme kinetics and physicochemical characterization of model substrate aggregates were combined; thus enabling the interpretation of kinetics in the context of the interface. Substrates were diacylphosphatidylcholine of different acyl chain lengths in the form of mixed micelles with dodecyldimethylammoniopropanesulfonate. An early kinetic model, reformulated to reflect the interfacial nature of the kinetics, was applied to the kinetic data. A better method of data treatment is proposed, use of which makes the presence of microstructure effects quite transparent. Models for enzyme-micelle binding and enzyme-lipid binding are developed and expressions incorporating the microstructural properties are derived for the enzyme-micelle dissociation constant KS and the interface Michaelis-Menten constant, KM. Use of these expressions in the interface kinetic model brings excellent agreement between the kinetic data and the model. Numerical values for the thermodynamic and kinetic parameters are determined. Enzyme-lipid binding is found to be an activated process with an acyl chain length dependent free energy of activation that decreases with micelle lipid molar fraction with a coefficient of about ?15 RT and correlates with the tightness of molecular packing in the substrate aggregate. Thus the physical insight obtained includes a model for the kinetic parameters that shows that these parameters depend on the substrate concentration and acyl chain length of the lipid. Enzyme-micelle binding is indicated to be hydrophobic and solvent mediated with a dissociation constant of 1.2 mM.

Singh, Jasmeet; Ranganathan, Radha; Hajdu, Joseph

2009-01-01

81

Kinetic rate laws derived from order parameter theory IV: Kinetics of Al,Si disordering in Na-feldspars  

NASA Astrophysics Data System (ADS)

The kinetic rate laws of Al-Si disordering under dry conditions ( T = 1353K, 1253 K, 1223 K, 1183 K) and in the presence of water (p = 1 kbar, T = 1023 K, 1073 K, 1103 K) were studied both experimentally and theoretically. A gradual change of the degree of order was found under dry conditions. For intermediate degrees of order broad distributions of the order parameter Q od occur. The variations of Q od are correlated with structural modulations as observed in the transmission electron microscope. The time evolution of the mean value of Q od can be well described by the rate law: 269_2004_Article_BF00202240_TeX2GIFE1.gif {dQ_{od} }/{dt} = - ? /{RT}exp sumlimits_{i = 1}^n {X_i^2 } left[ {{ - (G_a^0 + \\varepsilon (? Q_{od} )^2 )}/{RT}} right]{dG}/{dQ_{od }} with the excess Gibbs energy G and G {a/0}= 433.8 kJ/mol, ?= -27.4 kJ/mol, ? = 1.687 · 1014 h -1. Under wet conditions, two processes were found which occur simultaneously. Firstly, some material renucleated with the equilibrium degree of order. Secondly, the bulk of the material transformed following the same rate law as under dry conditions but with the reduced activation energy G {a/0}= 332.0 kJ/mol and ? = -43.0 kJ/ mol, ? = 1.047 · 1013 h-1. The applicability of the kinetic theory is discussed and some ideas for the analysis of geological observations are evolved.

Wruck, Bernd; Salje, Ekhard K. H.; Graeme-Barber, Ann

1991-05-01

82

Study of kinetic parameters in a mechanistic model for enzymatic hydrolysis of sugarcane bagasse subjected to different pretreatments.  

PubMed

The goal of this work is to evaluate the influence of different pretreatments in the kinetics of enzymatic hydrolysis of sugarcane bagasse and to propose a reliable methodology to easily perform sensitivity analysis and updating kinetic parameters whenever necessary. A kinetic model was modified to represent the experimental data of the batch enzymatic hydrolysis of sugarcane bagasse pretreated with alkaline hydrogen peroxide. The simultaneous estimation of kinetic parameters of the mathematical model was performed using the Pikaia genetic algorithm using batch hydrolysis experimental data obtained with different enzymatic loads. Subsequently, Plackett-Burman designs were used to identify the kinetic parameters with the higher influence on the dynamic behavior of the process variables, which were re-estimated to describe experimental data of the hydrolysis of bagasse pretreated with phosphoric acid + sodium hydroxide. The methodology was accurate and straightforward and can be used whenever there are changes in pretreatment conditions and/or fluctuations in biomass composition in different harvests. PMID:23474967

Neto, João Moreira; Dos Reis Garcia, Daniella; Rueda, Sandra Marcela Gómez; da Costa, Aline Carvalho

2013-03-09

83

Joint estimation of subject motion and tracer kinetic parameters of dynamic PET data in an EM framework  

NASA Astrophysics Data System (ADS)

Dynamic Positron Emission Tomography is a powerful tool for quantitative imaging of in vivo biological processes. The long scan durations necessitate motion correction, to maintain the validity of the dynamic measurements, which can be particularly challenging due to the low signal-to-noise ratio (SNR) and spatial resolution, as well as the complex tracer behaviour in the dynamic PET data. In this paper we develop a novel automated expectation-maximisation image registration framework that incorporates temporal tracer kinetic information to correct for inter-frame subject motion during dynamic PET scans. We employ the Zubal human brain phantom to simulate dynamic PET data using SORTEO (a Monte Carlo-based simulator), in order to validate the proposed method for its ability to recover imposed rigid motion. We have conducted a range of simulations using different noise levels, and corrupted the data with a range of rigid motion artefacts. The performance of our motion correction method is compared with pairwise registration using normalised mutual information as a voxel similarity measure (an approach conventionally used to correct for dynamic PET inter-frame motion based solely on intensity information). To quantify registration accuracy, we calculate the target registration error across the images. The results show that our new dynamic image registration method based on tracer kinetics yields better realignment of the simulated datasets, halving the target registration error when compared to the conventional method at small motion levels, as well as yielding smaller residuals in translation and rotation parameters. We also show that our new method is less affected by the low signal in the first few frames, which the conventional method based on normalised mutual information fails to realign.

Jiao, Jieqing; Salinas, Cristian A.; Searle, Graham E.; Gunn, Roger N.; Schnabel, Julia A.

2012-02-01

84

Identification of the crystallization kinetic parameters of a semi-crystalline polymer by using PVT? measurement  

NASA Astrophysics Data System (ADS)

Injection molding is the most widely used process in the plastic industry. In the case of semi-crystalline polymer, crystallization kinetics impacts directly the quality of the piece, both on dimensional and mechanical aspects. The characterization of these kinetics is therefore of primary importance to model the process, in particular during the cooling phase. To be representative, this characterization must be carried out under conditions as close as possible to those encountered in the process: high pressure, high cooling rate, shearing, and potential presence of fibers. However, conventional apparatus such as the differential scanning calorimeter do not allow to reach these conditions. A PVT? apparatus, initially developed in the laboratory for the characterization of thermoset composites, was adapted to identify the crystallization kinetics. The aim of the presented study is to demonstrate the feasibility of the identification. This device allows the molding of a circular sample of 40 mm diameter and 6 mm thick by controlling the applied pressure on the sample and the temperature field on its surfaces. This mold is designed such as heat transfer is 1D within the thickness of the sample. It is equipped with two heat flux sensors to determine the average crystallization rate through the thickness and a displacement sensor for the determination of the volume change. The heat transfer problem between the polymer and the molding cavity is modeled by using a 1D conduction problem with a moving boundary, in which the control volume is a uniform temperature disk with a variable volume, and coupled to a crystallization kinetic model. An inverse method is used to identify the parameters of the crystallization kinetic model by minimizing an objective function based on the difference between the evolutions of the experimental and computed volume of the sample. The first validation of this methodology was to compare the kinetic parameters identified with this apparatus with those obtained from DSC experiments, i.e. without additional pressure and at low cooling rates. A good agreement was obtained between both methods. A second validation was to compare experimental and computed temperatures at the center of the plastic part. In this case also, a very good agreement was found. The feasibility of the methodology is now demonstrated. The device is being adapted to increase the level of applied pressure as well as the cooling rate to achieve injection conditions.

Tardif, X.; Sobotka, V.; Boyard, N.; Delaunay, D.

2011-05-01

85

Supercritical fluid extraction from rosemary ( Rosmarinus officinalis): Kinetic data, extract's global yield, composition, and antioxidant activity  

Microsoft Academic Search

In the present work the global yields isotherms and the overall extraction curves for the system rosemary (Rosmarinus officinalis)+CO2, the chemical composition and antioxidant activity of the extracts were determined. The experiments were performed in two supercritical extraction units. The following bed height to bed diameter ratios were used: 0.67, 1.34, 2.8, 5.6, and 8.4. The global yields were determined

Raul N. Carvalho; Lucinewton S. Moura; Paulo T. V. Rosa; M. Angela A. Meireles

2005-01-01

86

The effects of different experimental designs on parameter estimation in the kinetics of a reversible chemical reaction  

Microsoft Academic Search

The common methods used by chemists to obtain the estimates of the kinetic rate constants are deterministic ones. The statistical methods, such as D-optimum design (DOD), can offer a better way to deal with this problem. But the kinetic model of a reversible reaction is nonlinear, the DOD is locally optimal at the value of the initial chosen parameters. The

Qing-Song Xu; Yi-Zeng Liang; Kai-Tai Fang

2000-01-01

87

Effect of neutron field parameters on the yield of ²⁵²Cf  

Microsoft Academic Search

This paper attempts to determine the basic behavior of the Cf-252 yield indexes in the most general case, when the thermal and epithermal neutron flux density are varied together with the irradiation time. The parent material used is a mixture of heavy isotopes of curium, and the optimization criterion is the Cf-252 yield. The Cf-252 yield is plotted against the

A. V. Klinov; A. V. Mamelin; Y. G. Toporov

1985-01-01

88

Kinetic Parameter Extraction of Square Wave Voltammograms from DNA-Modified Gold Electrodes  

NASA Astrophysics Data System (ADS)

The field of surface bound electrochemistry is important in a variety of applications specifically sensing. A fundamental understanding of the processes involved could help to improve detection limits, optimize rates of detection and direct changes in device design. Accurate extraction of electrochemical kinetic parameters such as the rate constant k and charge transfer coefficient ? from cyclic voltammograms can be challenging when confronted with large background currents and relatively weak signals. The commonly used technique of Laviron analysis is both time consuming and somewhat subjective. Square wave voltammetry (SWV) is therefore an ideal alternative method given that it maximizes signal while minimizing capacitive effects. In this experiment kinetic parameters of DNA-modified gold electrodes are obtained from SWV curves through background subtraction followed by nonlinear least squares fitting using a first order quasi-reversible surface process model. The fitting is accomplished using the Nelder-Mead simplex algorithm with standard parameters and a convergence condition of less than 0.0001%. General agreement with experimental data is shown with varying levels of confidence. Difficulties specific to this experiment are discussed as well as the possible benefits of utilizing the Bayesian statistical approach of nested sampling when confronted with multiple peaks of interest and the background source is well defined.

McWilliams, Marc; Wohlgamuth, Chris; Slinker, Jason

2012-10-01

89

Calculating kinetics parameters and reactivity changes with continuous-energy Monte Carlo  

SciTech Connect

The iterated fission probability interpretation of the adjoint flux forms the basis for a method to perform adjoint weighting of tally scores in continuous-energy Monte Carlo k-eigenvalue calculations. Applying this approach, adjoint-weighted tallies are developed for two applications: calculating point reactor kinetics parameters and estimating changes in reactivity from perturbations. Calculations are performed in the widely-used production code, MCNP, and the results of both applications are compared with discrete ordinates calculations, experimental measurements, and other Monte Carlo calculations.

Kiedrowski, Brian C [Los Alamos National Laboratory; Brown, Forrest B [Los Alamos National Laboratory; Wilson, Paul [UNIV. WISCONSIN

2009-01-01

90

Influence of predeformation and agEing of an Al–Zn–Mg alloy—II. Modeling of precipitation kinetics and yield stress  

Microsoft Academic Search

We present a model for precipitation kinetics integrating nucleation growth and coarsening. This model allows the description of competitive kinetics of heterogenous and homogeneous precipitation. The precipitation model is coupled to a model for structural hardening predicting the yield stress. This structural hardening model includes the possibility of taking into account the distribution of precipitate size and strength. The model

A. Deschamps; Y. Brechet

1998-01-01

91

Thermodynamic and kinetic parameters of ofloxacin adsorption from aqueous solution onto modified coal fly ash  

NASA Astrophysics Data System (ADS)

Batch adsorption experiments were carried out for the removal of ofloxacin from aqueous solution using modified coal fly ash as adsorbent. The effects of various parameters such as contact time, initial solution concentration and temperature on the adsorption system were investigated. The optimum contact time was found to be 150 min. The adsorption isotherm data fit well with the Langmuir model, and the kinetic data fit well with the pseudo-second order and the intra-particle diffusion model. Intra-particle diffusion analysis demonstrates that ofloxacin diffuses quickly among the particles at the beginning of the adsorption process, and then the diffusion slows down and stabilizes. Thermodynamic parameters such as ? G, ? H, and ? S were also calculated. The negative Gibbs free energy change and the positive enthalpy change indicated the spontaneous and endothermic nature of the adsorption, and the positive entropy change indicated that the adsorption process was aided by increased randomness.

Zhang, C.-L.; Zhao, F.; Wang, Y.

2012-04-01

92

Prediction of biogas yield and its kinetics in reed canary grass using near infrared reflectance spectroscopy and chemometrics.  

PubMed

A rapid method is needed to assess biogas and methane yield potential of various kinds of substrate prior to anaerobic digestion. This study reports near infrared reflectance spectroscopy (NIRS) as a rapid alternative method to the conventional batch methods for prediction of specific biogas yield (SBY), specific methane yield (SMY) and kinetics of biogas yield (k-SBY) of reed canary grass (RCG) biomass. Dried and powdered RCG biomass with different level of maturity was used for biochemical composition analysis, batch assays and NIRS analysis. Calibration models were developed using partial least square (PLS) regression from NIRS spectra. The calibration models for SBY (R(2)=0.68, RPD=1.83) and k-SBY (R(2)=0.71, RPD=1.75) were better than the model for SMY (R(2)=0.53, RPD=1.49). Although the PLS model for SMY was less successful, the model performance was better compared to the models based on chemical composition. PMID:23941712

Kandel, Tanka P; Gislum, René; Jørgensen, Uffe; Lærke, Poul E

2013-07-26

93

Nutrient Uptake by Microorganisms according to Kinetic Parameters from Theory as Related to Cytoarchitecture  

PubMed Central

The abilities of organisms to sequester substrate are described by the two kinetic constants specific affinity, a°, and maximal velocity Vmax. Specific affinity is derived from the frequency of substrate-molecule collisions with permease sites on the cell surface at subsaturating concentrations of substrates. Vmax is derived from the number of permeases and the effective residence time, ?, of the transported molecule on the permease. The results may be analyzed with affinity plots (v/S versus v, where v is the rate of substrate uptake), which extrapolate to the specific affinity and are usually concave up. A third derived parameter, the affinity constant KA, is similar to KM but is compared to the specific affinity rather than Vmax? and is defined as the concentration of substrate necessary to reduce the specific affinity by half. It can be determined in the absence of a maximal velocity measurement and is equal to the Michaelis constant for a system with hyperbolic kinetics. Both are taken as a measure of ?, with departure of KM from KA being affected by permease/enzyme ratios. Compilation of kinetic data indicates a 108-fold range in specific affinities and a smaller (103-fold) range in Vmax values. Data suggest that both specific affinities and maximal velocities can be underestimated by protocols which interrupt nutrient flow prior to kinetic analysis. A previously reported inverse relationship between specific affinity and saturation constants was confirmed. Comparisons of affinities with ambient concentrations of substrates indicated that only the largest a°S values are compatible with growth in natural systems.

Button, D. K.

1998-01-01

94

Kinetic Parameters of the Conversion of Methane Precursors to Methane in a Hypereutrophic Lake Sediment †  

PubMed Central

The kinetic parameters Km, Vmax, Tt (turnover time), and v (natural velocity) were determined for H2 and acetate conversion to methane by Wintergreen Lake sediment, using short-term (a few hours) methods and incubation temperatures of 10 to 14°C. Estimates of the Michaelis-Menten constant, Km, for both the consumption of hydrogen and the conversion of hydrogen to methane by sediment microflora averaged about 0.024 ?mol g?1 of dry sediment. The maximal velocity, Vmax, averaged 4.8 ?mol of H2 g?1 h?1 for hydrogen consumption and 0.64 ?mol of CH4 g?1 h?1 for the conversion of hydrogen to methane during the winter. Estimated natural rates of hydrogen consumption and hydrogen conversion to methane could be calculated from the Michaelis-Menten equation and estimates of Km, Vmax, and the in situ dissolved-hydrogen concentration. These results indicate that methane may not be the only fate of hydrogen in the sediment. Among several potential hydrogen donors tested, only formate stimulated the rate of sediment methanogenesis. Formate conversion to methane was so rapid that an accurate estimate of kinetic parameters was not possible. Kinetic experiments using [2-14C]acetate and sediments collected in the summer indicated that acetate was being converted to methane at or near the maximal rate. A minimum natural rate of acetate conversion to methane was estimated to be about 110 nmol of CH4 g?1 h?1, which was 66% of the Vmax (163 nmol of CH4 g?1 h?1). A 15-min preincubation of sediment with 5.0 × 10?3 atm of hydrogen had a pronounced effect on the kinetic parameters for the conversion of acetate to methane. The acetate pool size, expressed as the term Km + Sn (Sn is in situ substrate concentration), decreased by 37% and Tt decreased by 43%. The Vmax remained relatively constant. A preincubation with hydrogen also caused a 37% decrease in the amount of labeled carbon dioxide produced from the metabolism of [U-14C]valine by sediment heterotrophs. Images

Strayer, Richard F.; Tiedje, James M.

1978-01-01

95

Retrievals of chlorine chemistry kinetic parameters from Antarctic ClO microwave radiometer measurements  

NASA Astrophysics Data System (ADS)

Key kinetic parameters governing the partitioning of chlorine species in the Antarctic polar stratosphere were retrieved from 28 days of chlorine monoxide (ClO) microwave radiometer measurements made during the late winter/early spring of 2005 at Scott Base (77.85° S, 166.75° E). During day-time the loss of the ClO dimer chlorine peroxide (ClOOCl) occurs mainly by photolysis. Some time after sunrise, a photochemical equilibrium is established and the ClO/ClOOCl partitioning is determined by the ratio of the photolysis frequency, J, and the dimer formation rate, kf. The values of J and kf from laboratory studies remain uncertain to a considerable extent, and as a complement to these ongoing studies, the goal of this work is to provide a constraint on that uncertainty based on observations of ClO profiles in the Antarctic. First an optimal estimation technique was used to derive J/kf ratios for a range of Keq values. The optimal estimation forward model was a photochemical box model that takes J, kf, and Keq as inputs, together with a priori profiles of activated chlorine (ClOx = ClO+2×ClOOCl), profiles of ozone, temperature, and pressure. JPL06 kinetics are used as a priori in the optimal estimation and for all other chemistry in the forward model. Using the more recent JPL09 kinetics results in insignificant differences in the retrieved value of J/kf. A complementary approach was used to derive the optimal kinetic parameters; the full parameter space of J, kf, Keq and ClOx was sampled to find the minimum in differences between measured and modelled ClO profiles. Furthermore, values of Keq up to 2.0 times larger than recommended by JPL06 were explored to test the sensitivity of the J/kf ratio to changes in Keq. The results show that the retrieved J/kf ratios bracket the range of 1.23 to 1.97 times the J/kf value recommended by JPL06 over the range of Keq values considered. The retrieved J/kf ratios lie in the lower half of the large uncertainty range of J/kf recommended by JPL06 and towards the upper portion of the smaller uncertainty range recommended by JPL09.

Kremser, S.; Schofield, R.; Bodeker, G. E.; Connor, B. J.; Rex, M.; Barret, J.; Mooney, T.; Salawitch, R. J.; Canty, T.; Frieler, K.; Chipperfield, M. P.; Langematz, U.; Feng, W.

2011-06-01

96

Retrievals of chlorine chemistry kinetic parameters from Antarctic ClO microwave radiometer measurements  

NASA Astrophysics Data System (ADS)

Key kinetics parameters governing the partitioning of chlorine species in the Antarctic polar stratosphere were retrieved from 28 days of chlorine monoxide (ClO) microwave radiometer measurements made during the late-winter/early spring of 2005 at Scott Base (77.85° S, 166.75° E). During day-time the ratio of the photolysis rate, J, and the dimer formation rate, kf, determines the partitioning of ClO and its dimer, chlorine peroxide (ClOOCl). This ratio J/kf remains uncertain and, as a complement to ongoing laboratory studies, the goal of this work is to provide a constraint on that uncertainty based on observations of ClO profiles in the Antarctic. First an optimal estimation technique was used to derive J/kf ratios for a range of Keq values. The optimal estimation forward model was a photochemical box model that takes J, kf, and Keq as inputs, together with a priori of activated chlorine (ClOx=ClO+2×ClOOCl), ozone, temperature and pressure profiles. JPL06 kinetics are used as a priori in the optimal estimation and for all other chemistry in the forward model. Using the more recent JPL09 kinetics results in insignificant differences in the retrieved value of J/kf. A complementary approach was used to derive the optimal kinetic parameters; the full parameter space of J, kf, Keq and ClOx was sampled to find the minimum in differences between measured and modelled ClO profiles. Furthermore, values of Keq up to 2.0 times larger than recommended by JPL06 were explored to test the sensitivity of the J/kf ratio to changes in Keq. The results show that the retrieved J/kf ratios bracket the range of 1.97 to 1.23×(J/kf)JPL06 over the range of Keq values considered. The retrieved J/kf ratios lie in the lower half of the large uncertainty range of J/kf recommended by JPL06 and towards the upper portion of the smaller uncertainty range recommended by JPL09.

Kremser, S.; Schofield, R.; Bodeker, G. E.; Connor, B. J.; Rex, M.; Barret, J.; Mooney, T.; Salawitch, R. J.; Canty, T.; Frieler, K.; Chipperfield, M. P.; Langematz, U.; Feng, W.

2010-11-01

97

Maximum likelihood estimation of protein kinetic parameters under weak assumptions from unfolding force spectroscopy experiments  

NASA Astrophysics Data System (ADS)

Single molecule force spectroscopy (SMFS) is extensively used to characterize the mechanical unfolding behavior of individual protein domains under applied force by pulling chimeric polyproteins consisting of identical tandem repeats. Constant velocity unfolding SMFS data can be employed to reconstruct the protein unfolding energy landscape and kinetics. The methods applied so far require the specification of a single stretching force increase function, either theoretically derived or experimentally inferred, which must then be assumed to accurately describe the entirety of the experimental data. The very existence of a suitable optimal force model, even in the context of a single experimental data set, is still questioned. Herein, we propose a maximum likelihood (ML) framework for the estimation of protein kinetic parameters which can accommodate all the established theoretical force increase models. Our framework does not presuppose the existence of a single force characteristic function. Rather, it can be used with a heterogeneous set of functions, each describing the protein behavior in the stretching time range leading to one rupture event. We propose a simple way of constructing such a set of functions via piecewise linear approximation of the SMFS force vs time data and we prove the suitability of the approach both with synthetic data and experimentally. Additionally, when the spontaneous unfolding rate is the only unknown parameter, we find a correction factor that eliminates the bias of the ML estimator while also reducing its variance. Finally, we investigate which of several time-constrained experiment designs leads to better estimators.

Aioanei, Daniel; Samorì, Bruno; Brucale, Marco

2009-12-01

98

Measurement of Kinetic Parameters in Skeletal Muscle by Magnetic Resonance Imaging With an Intravascular Agent  

PubMed Central

The purpose of this work was to investigate the use of an intravascular contrast agent to determine perfusion kinetics in skeletal muscle. A two-compartment kinetic model was used to represent the flux of contrast agent between the intravascular space and extravascular extracellular space (EES). The relationship between the image signal-to-noise ratio (SNR) and errors in estimating permeability surface area product (Ktrans), interstitial volume (ve), and plasma volume (vp) for linear and nonlinear curve-fitting methods was estimated from Monte Carlo simulations. Similar results were obtained for both methods. For an image SNR of 60, the estimated errors in these parameters were 10%, 22%, and 17%, respectively. In vivo experiments were conducted in rabbits to examine physiological differences between these parameters in the soleus (SOL) and tibialis anterior (TA) muscles in the hind limb. Values for Ktrans were significantly higher in the SOL (3.2 ± 0.9 vs. 2.0 ± 0.5 × 10?3 min?1), as were values for vp (3.4 ± 0.8 vs. 2.1 ± 0.7%). Differences in ve for the two muscles (8.7 ± 2.2 vs. 8.5 ± 1.6%) were not found to be significant. These results demonstrate that relevant physiological metrics can be calculated in skeletal muscle using MRI with an intravascular contrast agent.

Faranesh, Anthony Z.; Kraitchman, Dara L.; McVeigh, Elliot R.

2007-01-01

99

Growth Parameter and Yield Component Response of Field Corn to Simulated Acid Rain.  

National Technical Information Service (NTIS)

Acid rain occurs in the midwest. Studies to date have suggested minimal yield response of field corn to acid rain. However, small but significant reductions in yield have been shown for some cultivars under extreme conditions. To define further these yiel...

W. L. Banwart P. M. Porter E. L. Ziegler J. J. Hassett

1988-01-01

100

Use of vegetation index and meteorological parameters for the prediction of crop yield in India  

Microsoft Academic Search

Monsoon rainfall distribution over the Indian sub?continent is inconsistent every year. Due to uncertainty and dependence on the monsoon onset and weather conditions, estimation of crop yield in India is difficult. In this paper, analyses of the crop yield, normalized difference vegetation index, soil moisture, surface temperature and rainfall data for 16 years (from 1984 to 1999) have been carried

A. K. Prasad; R. P. Singh; V. Tare; M. Kafatos

2007-01-01

101

Supercritical fluid extraction from rosemary ( Rosmarinus officinalis): Kinetic data, extract's global yield, composition, and antioxidant activity  

Microsoft Academic Search

In the present work the global yields isotherms and the overall extraction curves for the system rosemary ( Rosmarinus officinalis )+C O 2, the chemical composition and antioxidant activity of the extracts were determined. The experiments were performed in two supercritical extraction units. The following bed height to bed diameter ratios were used: 0.67, 1.34, 2.8, 5.6, and 8.4. The

Raul N. Carvalho Jr; Lucinewton S. Moura; Paulo T. V. Rosa; M. Angela; A. Meireles

2005-01-01

102

Role of carrier diffusion and picosecond exciton kinetics in nonproportionality of scintillator light yield  

NASA Astrophysics Data System (ADS)

The effect of high excitation density in promoting nonlinear quenching that is 2nd or 3rd order in electron-hole density is generally understood to be a root cause of nonproportionality in scintillators. We report and discuss quantitative data on just how fast these nonlinear channels are in specific cases. Kinetic rate constants for the creation of excitons from electrons and holes and for their quenching by dipole-dipole transfer have been measured in CsI and NaI. We show in addition that the strong radial concentration gradient in an electron track gives rise to fast (~ picoseconds) diffusion phenomena that act both as a competitor in reducing excitation density during the relevant time of nonlinear quenching, and as a determiner of branching between independent carriers and pairs (excitons), where the branching ratio changes along the primary electron track. We use the experimentally measured nonlinear quenching rate constants and values of electron and hole carrier mobilities to carry out quantitative modeling of diffusion, drift, and nonlinear quenching evaluated spatially and temporally within an electron track which is assumed cylindrical in this version of the model. Magnitude and inequality of electron and hole mobilities has consequences for quenching and kinetic order that vary with dE/dx along the path of an electron and therefore affect nonproportionality. It will be demonstrated that in a material with high mobilities like high-purity germanium, Auger recombination is effectively turned off by diffusive carrier dilution within < 1 fs in all parts of the track. In alkali halide scintillators like CsI and CsI:Tl, electron confinement and high-order quenching are accentuated toward the end of a particle track because of hole self-trapping, while separation of geminate carriers is accentuated toward the beginning of the track, leading to 2nd order radiative recombination and opening additional opportunities for linear trapping.

Williams, R. T.; Li, Q.; Grim, Joel Q.; Ucer, K. B.; Bizarri, G. A.; Moses, W. W.

2010-08-01

103

{sup 82}Rb kinetic parameter variability due to depth of anesthesia in the anesthetized canine  

SciTech Connect

The effect of {open_quotes}depth of anesthesia{close_quotes} on {sup 82}Rb kinetic parameter estimates in the myocardium was tested in a series of replicated studies on six dogs using the Donner 600-Crystal Positron Tomograph. A single lateral slice through the myocardium was imaged following each of four successive injections of {sup 82}Rb. For three of the injections the animals were lightly anesthetized (mean blood pressure about 90 mmHg). For the second injection, the amount of anesthetic was increased until blood pressure dipped to about 70 mHg. The fourth injection was preceded by an infusion of dipyridamole to induce a stress-state. The entire sequence was repeated at least twice with each of the six animals. A two compartment model with parameters k{sub 1} (uptake rate), k{sub 2} (wash-out rate), and f{sub v} (vascular fraction) was fit to the data. There was a consistent finding of a 20% to 30% decrease in k{sub 1} during the deeply anesthetized state compared with the two lightly anesthetized rest states. Analysis of variance showed that the difference observed is significant, though small in comparison with the difference between the rest and stress states (60% to 160% increase). The difference between the two lightly anesthetized states was not significant. Kinetic PET studies using dogs are routinely carried out with the animal anesthetized. Depth of anesthesia has been suspected as as source of variability in parameter estimates, but this conjecture has not previously been systematically investigated. These studies at extremes in the depth of anesthesia show a small but predictable effect on the uptake k{sub 1} of {sup 82}Rb.

Coxson, P.G.; Brennan, K.M.; Yang, L. [Lawrence Berkeley Laboratory, CA (United States)] [and others

1995-05-01

104

AgNOR clusters as a parameter of cell kinetics in chronic lymphocytic leukaemia  

PubMed Central

Aims—To study correlations between the pattern of silver stained nucleolar organiser regions (AgNORs) in chronic lymphocytic leukaemia (CLL) and parameters of tumour kinetics. To investigate whether quantitation of the AgNOR pattern can be used to discriminate between patients with stable and progressive disease. Methods—Peripheral blood smears from 48 patients with CLL, classified as having either stable or progressive disease (Rai stage III or IV; bulky lymph nodes or massive splenomegaly; or peripheral lymphocytes >100 × 109/1), were studied. For each patient, total tumour mass (TTM) and for patients undergoing a period of observation without treatment, the TTM duplication time (DT) and the lymphocyte doubling time (LDT) were calculated. Results—Four cell types could be distinguished according to their AgNOR pattern: (1) cells with a single cluster; (2) cells with a single compact nucleolus; (3) cells with two compact nucleoli; and (4) cells with several scattered dots. The percentage of cells with clusters was the AgNOR parameter which correlated best with TTM and LDT. Correlations were also seen between the proportion of cells with clusters and age and haemoglobin concentration. A significant correlation with DT could be detected only when age was kept constant. Linear discriminant analysis revealed that the percentage of cells with clusters was the most important prognostic factor. This alone classified 94% of the patients correctly (jackknive procedure) as either stable or progressive CLL. Conclusions—The percentage of circulating lymphocytes with clusters of AgNORs can be used as a parameter of tumour kinetics in CLL and helps to discriminate between patients with stable and progressive disease. For practical purposes, a value of more than 13% of cells with clusters is suggestive of progressive disease. Images

Lorand-Metze, Irene; Metze, Konradin

1996-01-01

105

The role of test parameters on the kinetics and thermodynamics of glass leaching. [None  

SciTech Connect

The relative durabilities of nuclear waste, natural, and ancient glasses have been assessed by standard laboratory leach tests. Different test conditions result in different glass surface areas (SA), leachant volumes (V), and test durations (t). Leachate concentrations are known to be a parabolic function of the kinetic test parameter SAV/center dot/t. Based on durability experiments of glass monoliths at low (SAV)/center dot/ glass durability has been shown to be a logarithmic function of the thermodynamic hydration free energy, ..delta..G/sub hyd/. The thermodynamic hydration free energy, ..delta..G/sub hyd/, can be calculated from glass composition and solution pH. In the repository environment high effective glass surface areas to solution volume ratios may occur as a result of slow groundwater flow rates. The application of hydration thermodynamics to crushed glass, high (SAV)/center dot/t, durability tests has been demonstrated. The relative contributions of the kinetic test parameters, (SAV)/center dot/t, and the thermodynamic parameter, ..delta..G/sub hyd/, have been shown to define a plane in ..delta..G/sub hyd/-concentration-(SAV)/center dot/t space. At constant test conditions, e.g. constant (SAV/center dot/t, the intersection with this surface indicates that all /delta G//sub hyd/-concentration plots should have similar slopes and predict the same relative durabilities for various glasses as a function of glass composition. Using this approach, the durability of nuclear waste glasses has been interpolated to be -- 10/sup 6/ years and no less than 10/sup 3/ years. 28 refs., 24 figs.

Jantzen, C M

1988-01-01

106

COMPARISON OF YIELD PARAMETERS AND DISEASE INCIDENCE OF TRADITIONAL SEEDCANE SOURCES AND KLEENTEK, A COMMERCIAL TISSUE-CULTURE BASED SEEDCANE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Yield parameters and incidence of Leifsonia xyli subsp. Xyli (Lxx), the causal agent of ratoon stunt and Sugarcane yellow leaf virus (SCYLV), causal agent of yellow leaf were compared in tradition seedcane and Kleentek®, a commercial tissue-culture based seedcane. Two adjacent field sections locate...

107

The effects of process parameters on yield and properties of iron nanoparticles from ferrocene in a low-pressure plasma  

Microsoft Academic Search

The effects of process parameters on iron nanoparticle formation and properties while using ferrocene as a precursor in a low-pressure capacitively coupled plasma are investigated. The L18 array of the Taguchi method, followed by the L4 array, is used with the notional objective of increasing the yield of nanoparticles. A study of the size, shape and composition of the particles

V. Panchal; G. Lahoti; U. Bhandarkar; M. Neergat

2011-01-01

108

Importance of soil moisture measurements for inferring parameters in hydrologic models of low-yielding ephemeral catchments  

Microsoft Academic Search

Low-yielding catchments with ephemeral streams provide a stern test of the capability of conceptual catchment models for predicting the hydrologic response of the natural landscape. Sustained periods of little or no flow mean that the information content of the streamflow time-series for parameter estimation is limited. During periods with no streamflow, such ephemeral catchments also offer no information on a

S. A. Wooldridge; J. D. Kalma; J. P. Walker

2003-01-01

109

Effect of drip irrigation and mulches on physiological parameters, soil temperature, picking patterns and yield in capsicum (Capsicum annuum L.)  

Microsoft Academic Search

Water and temperature are critical for producing vegetable crops, especially during winter, when the availability of water is meager and temperature falls. Studies of drip irrigation and mulch were undertaken to find the effect on different growth and yield parameters in pepper (Capsicum annuum L.). The experiment was laid out in a split-plot design with four main and four subplots.

V. K. Choudhary; M. C. Bhambri; N. Pandey; H. G. Sharma

2011-01-01

110

Effect of drip irrigation and mulches on physiological parameters, soil temperature, picking patterns and yield in capsicum (Capsicum annuum L.)  

Microsoft Academic Search

Water and temperature are critical for producing vegetable crops, especially during winter, when the availability of water is meager and temperature falls. Studies of drip irrigation and mulch were undertaken to find the effect on different growth and yield parameters in pepper (Capsicum annuum L.). The experiment was laid out in a split-plot design with four main and four subplots.

V. K. Choudhary; M. C. Bhambri; N. Pandey; H. G. Sharma

2012-01-01

111

Effect of combined nitrogen and sulphur fertilization on yield and qualitative parameters of Camelina sativa [L.] Crtz. (false flax)  

Microsoft Academic Search

Camelina (Camelina sativa (L.) Crtz., false flax) is described as a species requiring fewer inputs than other oilseed crops thus making it an interesting alternative in sustainable cropping systems. As information on the combined effects of nitrogen and sulphur on camelina yield and quality parameters is meagre, a pot fertilization experiment was carried out with nitrogen applied as NH4NO3 at

Tomas Lošák; Jaroslav Hlusek; Jiri Martinec; Johann Vollmann; Jiri Peterka; Radek Filipcik; Ladislav Varga; Ladislav Ducsay; Anna Martensson

2011-01-01

112

Influence of Various Irrigation Methods on Tree Growth and Fruit Yield Parameters in Apple under the Conditions of Southern Romania  

Microsoft Academic Search

Condensed abstract: The paper shows the effects of various irrigation methods on some fruit tree yield and growth parameters of the Golden Delicious apple cultivar grafted on MM 106 rootstock under the specific condi- tions of the hilly regions of the southern part of Romania. In this experiment 7 years old more irrigation methods were used: sprinkler irrigation (SI), micro-sprinkler

N. Tanasescu

113

Relation of smoking parameters to the yield, colour and sensory quality of smoked Atlantic salmon ( Salmo salar)  

Microsoft Academic Search

The relations between smoking parameters and the characteristics of salmon raw material were investigated with respect to yield, colour, flesh content of phenol and salt, and sensory properties. The fish studied were ocean ranched salmon harvested in Iceland in July 1998 and farmed salmon from Norway slaughtered in October 1998 and April 1999. Seven treatments were applied on fresh or

Mireille Cardinal; Camille Knockaert; Ole Torrissen; Sjofn Sigurgisladottir; Turid Mørkøre; Magny Thomassen; Jean Luc Vallet

2001-01-01

114

Dependence of tar, nicotine and carbon monoxide yields on physical parameters: implications for exposure, emissions control and monitoring  

PubMed Central

Objective To estimate the extent to which tar, nicotine and carbon monoxide (TNCO) yields are dependent on cigarette design features such as burn rate, filter ventilation and paper porosity, and to consider the implications for human exposure and the regulation of TNCO emissions. A related aim is to determine whether accurate prediction of TNCO yields is possible using only simple physical parameters. Design and methods Datasets that include quantitative design parameters as well as measurements of TNCO yields collected under standard conditions with vents unblocked (International Organization for Standardization) and under intense conditions with vents fully blocked (Health Canada) were compiled from the literature (primarily US and UK brands). Forward stepwise multiple regression analysis is used to assess the relative importance of each design feature in explaining variability in the observed emissions. Using randomly split data subsets, multiple linear regression is used to model the dependence of TNCO yields on design features in the training subset and validated against the test subset. Tar and carbon monoxide correlate with many of the particulate? and volatile?phase toxins in smoke, and brand values normalised to nicotine yield are used as surrogate measures of exposure within the bounds defined by non?intense and intense smoking protocols. Results and conclusions Filter ventilation is the dominant control on measured TNCO emissions, but other factors including burn rate, amount of tobacco and paper porosity also contribute. Yields are predictable with reasonable accuracy and precision using only measured physical parameters. Surrogate exposure indicators suggest that filter ventilation does not lead to any reduction in exposure and that highly ventilated (low?yield) brands may actually increase exposure to the more volatile toxins.

Stephens, W E

2007-01-01

115

Characterization of nicotinamidases: steady state kinetic parameters, classwide inhibition by nicotinaldehydes, and catalytic mechanism.  

PubMed

Nicotinamidases are metabolic enzymes that hydrolyze nicotinamide to nicotinic acid. These enzymes are widely distributed across biology, with examples found encoded in the genomes of Mycobacteria, Archaea, Eubacteria, Protozoa, yeast, and invertebrates, but there are none found in mammals. Although recent structural work has improved our understanding of these enzymes, their catalytic mechanism is still not well understood. Recent data show that nicotinamidases are required for the growth and virulence of several pathogenic microbes. The enzymes of Saccharomyces cerevisiae, Drosophila melanogaster, and Caenorhabditis elegans regulate life span in their respective organisms, consistent with proposed roles in the regulation of NAD(+) metabolism and organismal aging. In this work, the steady state kinetic parameters of nicotinamidase enzymes from C. elegans, Sa. cerevisiae, Streptococcus pneumoniae (a pathogen responsible for human pneumonia), Borrelia burgdorferi (the pathogen that causes Lyme disease), and Plasmodium falciparum (responsible for most human malaria) are reported. Nicotinamidases are generally efficient catalysts with steady state k(cat) values typically exceeding 1 s(-1). The K(m) values for nicotinamide are low and in the range of 2 -110 ?M. Nicotinaldehyde was determined to be a potent competitive inhibitor of these enzymes, binding in the low micromolar to low nanomolar range for all nicotinamidases tested. A variety of nicotinaldehyde derivatives were synthesized and evaluated as inhibitors in kinetic assays. Inhibitions are consistent with reaction of the universally conserved catalytic Cys on each enzyme with the aldehyde carbonyl carbon to form a thiohemiacetal complex that is stabilized by a conserved oxyanion hole. The S. pneumoniae nicotinamidase can catalyze exchange of (18)O into the carboxy oxygens of nicotinic acid with H(2)(18)O. The collected data, along with kinetic analysis of several mutants, allowed us to propose a catalytic mechanism that explains nicotinamidase and nicotinic acid (18)O exchange chemistry for the S. pneumoniae enzyme involving key catalytic residues, a catalytic transition metal ion, and the intermediacy of a thioester intermediate. PMID:20979384

French, Jarrod B; Cen, Yana; Vrablik, Tracy L; Xu, Ping; Allen, Eleanor; Hanna-Rose, Wendy; Sauve, Anthony A

2010-11-15

116

Kinetic paths of B2 and DO sub 3 order parameters: Theory  

SciTech Connect

It is shown that a binary alloy with an AB{sub 3} stoichiometry on a bcc lattice may develop various combinations of B2 and DO{sub 3} order along its kinetic path toward equilibrium. The temporal evolution of these two order parameters is analyzed with an activated-state rate theory. Individual vacancy jumps are treated in a master equation formalism that involves first-nearest-neighbor (1nn) and second-nearest-neighbor (2nn) interactions. In our formulation, a set of coupled differential equations is obtained describing the time-dependence of six order parameters. These equations were integrated numerically for a variety of interatomic interactions and initial conditions. It was found that the {ital relative} rates of B2 and DO{sub 3} ordering, and hence the path of the alloy through the space spanned by the B2 and DO{sub 3} order parameters, depend on the relative strengths of the interatomic interaction potentials and on the temperature. For very strong 2nn interactions, a transient B32 structure was observed to develop at early times, although this phase disappeared as equilibrium was approached.

Anthony, L.; Fultz, B. (Department of Materials Science 138-78, California Institute of Technology, Pasadena, California 91125 (US))

1989-09-01

117

The effect of process parameters on kinetics and mechanisms of Co2+ removal by bone char.  

PubMed

Bone char powder, composed mainly of poorly crystalline hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2)), carbon and CaCO(3), has potential applicability in the removal of Co(2+) ions from contaminated effluents. In the present study, the influence of process parameters: particle size, agitation speed, initial pH and initial sorbate concentration, onto kinetics and mechanism of Co(2+)sorption was studied and discussed. In order to describe and compare time evolution of the process under different conditions, the experimental data were analyzed using pseudo-first, pseudo-second and Vermeulen's kinetic models. Generally, experimental results were best fitted with the pseudo-second-order model, which accurately predicted the equilibrium sorbed amounts. The pseudo-second-order rate constant was the most influenced by variations in initial metal concentration and pH, in the investigated ranges. The conclusions about sorption mechanism were derived based on Co(2+) amounts sorbed during time, as well as considering solution pH changes, changes of Ca(2+) amounts released into liquid phase and Ca(2+)/Co(2+) molar ratios. It was concluded that rapid sorption stage was governed by surface complexation reactions, whereas the contribution of the ion-exchange mechanism increased with time and became more significant in the second, slower phase. Experimentally determined maximum sorption capacity towards Co(2+), under optimal conditions, was found to be 0.38 mmol/g. The results show that bone char represents cost-effective alternative to synthetic hydroxyapatite sorbent. PMID:22029698

Dimovi?, Slavko D; Smi?iklas, Ivana D; Sljivi?-Ivanovi?, Marija Z; Ple?aš, Ilija B; Slavkovi?-Beškoski, Latinka

2011-01-01

118

Kinetic parameters for thermal decomposition of supramolecular polymers derived from diclofenac-meglumine supramolecular adducts.  

PubMed

Meglumine is an aminocarbohydrate able to form supramolecular adducts with organic acids. The recognition is based on hydrogen bonds and the structures resulting from the complexation have high solubility in water. This property has been exploited by the pharmaceutical industry in the improvement of existing drugs, and the successful example of this approach involves the poorly soluble non-steroidal anti-inflammatory drugs (NSAIDs). Investigation of the thermal behavior of adduct obtained from meglumine and the NSAID diclofenac revealed that a polymer-like material is formed from the self-assembly of diclofenac-meglumine adducts in the melt. This polymer showed a high molecular weight around 2.0×10(5)kDa. The kinetic parameters for the thermal decomposition step of the polymer were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and heating rates of 5, 10, 15 and 20°Cmin(-1), the E(?) and B(?) terms could be determined, and consequently the pre-exponential factor, A(?), as well as the kinetic model, g(?). PMID:22561058

Cassimiro, Douglas L; Ferreira, Leonardo M B; Capela, Jorge M V; Crespi, Marisa S; Ribeiro, Clóvis A

2012-04-24

119

Sensitivity of natural gas HCCI combustion to fuel and operating parameters using detailed kinetic modeling  

SciTech Connect

This paper uses the HCT (Hydrodynamics, Chemistry and Transport) chemical kinetics code to analyze natural gas HCCI combustion in an engine. The HCT code has been modified to better represent the conditions existing inside an engine, including a wall heat transfer correlation. Combustion control and low power output per displacement remain as two of the biggest challenges to obtaining satisfactory performance out of an HCCI engine, and these are addressed in this paper. The paper considers the effect of natural gas composition on HCCI combustion, and then explores three control strategies for HCCI engines: DME (dimethyl ether) addition, intake heating and hot EGR addition. The results show that HCCI combustion is sensitive to natural gas composition, and an active control may be required to compensate for possible changes in composition. The three control strategies being considered have a significant effect in changing the combustion parameters for the engine, and should be able to control HCCI combustion.

Aceves, S; Dibble, R; Flowers, D; Smith, J R; Westbrook, C K

1999-07-19

120

Parameter identification and on-line estimation for reduced kinetic model  

SciTech Connect

The base hydrolysis process for the destruction of energetic or explosive materials results is a high pH hydrolysate solution with reaction products that include a series of carboxylic acid salts, glycolates, amines, and nitrates. The hydrolysate solutions obtained from this process contain from two to ten wt% of organic carbon and nitrogen compounds that must be further treated before disposal. Hydrothermal oxidation at elevated temperatures (450 C) and pressure (14,000 psi) was selected as the treatment process for the hydrolysate solutions obtained from hydrolysis of the high explosive PBX 9404 at the Department of Energy Pantex facility in Amarillo, Texas. In this work, the authors describe the use of receding horizon identification and estimation techniques to determine the model parameters for a reduced kinetic model describing the oxidation-reduction reactions in a hydrothermal oxidation reactor. This model is used in a model predictive controller that minimizes the total aqueous nitrogen in the hydrothermal oxidation reactor effluent.

Littel, J.D.; Muske, K.R. [Villanova Univ., PA (United States). Dept. of Chemical Engineering; Del`Orco, P.C.; Le, L.A.; Flesner, R.L. [Los Alamos National Lab., NM (United States). High Explosives Science and Technology Group

1998-08-07

121

Kinetics and Product Yields in the Heterogeneous Reactions of HOBr with Reactive Halide Surfaces  

NASA Astrophysics Data System (ADS)

Routine episodes of ozone destruction in the springtime Arctic boundary layer have been well documented in recent years. After polar sunrise, field researchers working in Alaska and northern Canada report the almost complete loss of ozone from stable air masses in coastal regions. Ozone destruction is very fast, developing on a time scale from hours to days. Low ozone levels are correlated with elevated filterable bromine concentrations, suggesting that high levels of active bromine compounds are present in the atmosphere during ozone loss events. Based on these and other observations, a number of heterogeneous mechanisms involving bromine radicals have been proposed to explain the ozone-depleting chemistry. The central reactions in many of these theories are the interactions of gaseous HOBr with sea salt components in marine aerosols, snow crystals, or sea ice. Recent modeling studies suggest that tropospheric ozone destruction can not be simulated in agreement with field observations unless heterogeneous reactions with HOBr are included. The interactions of HOBr with sea salt halides also drive a proposed autocatalytic mechanism that explains many aspects of the rapid and nearly wholesale loss of ozone in the Arctic troposphere. Motivated by the central role of HOBr in these modeling studies, we have investigated its heterogeneous reactions with reactive halide-ice surfaces using a coated wall, low-pressure flow tube coupled to a quadrupole mass spectrometer. Gas-surface reaction probabilities and product yields are presented for two different temperatures and a range of halide and hydrogen ion concentrations in ice. Compared to results for similar experiments with HOCl that have been conducted previously, HOBr reaction probability values are smaller than expected, but still significant. The relative yields of gas-phase products Br2 and BrCl depend on the temperature, composition, and acidity of the reactive halide-ice surfaces. Overall, our data suggest that the heterogeneous reactions of HOBr on sea ice and snow crystals may be a significant source of active bromine in the Arctic boundary layer.

Huff, A. K.; Huff, A. K.; Abbatt, J. P.

2001-12-01

122

Kinetic and temporospatial parameters in male and female cats walking over a pressure sensing walkway  

PubMed Central

Background Several factors may influence kinetic data measurements, including body conformation and body mass. In addition, gender differences in gait pattern have been observed in healthy humans. Therefore, the aim of this study was to compare the kinetic and temporospatial parameters in clinically healthy male and female cats using a pressure-sensitive walkway. Eighteen crossbreed adult cats were divided into two groups: G1 had ten male cats (nine neutered) aged from 1 to 4 years and body mass 3.1-6.8 kg; G2 had eight spayed female cats, aged from 1 to 6 years and body mass 3.3-4.75 kg. The data from the first five valid trials were collected for each cat. A trial was considered valid if the cat maintained a velocity between 0.54-0.74 m/s and acceleration from -0.20 to 0.20 m/s2. The peak vertical force (PVF), vertical impulse (VI), gait cycle time, stance time, swing time, stride length, and percentage body weight distribution among the four limbs were determined. In addition, the lengths of each forelimb and each hind limb were measured using a tape with the animal standing. Results No significant differences were observed in each group in either the forelimbs or the hind limbs or between the left and right sides for any of the variables. For both groups, the PVF (%BW), the VI, and the percentage body weight distribution were higher at the forelimbs than the hind limbs. The stride length was larger for males; however, the other kinetic and temporospatial variables did not show any statistically significant differences between the groups. The lengths of the forelimbs and hind limbs were larger in the male cats. There was a significant moderate positive correlation between the stride length and the length of the limbs. Conclusions In conclusion, the only difference observed between male and female cats was the stride length, and this was due to the greater body size of male cats. This difference did not affect other temporospatial or kinetics variables.

2013-01-01

123

Parameters influencing the yield and composition of the essential oil from Cretan Vitex agnus-castus fruits.  

PubMed

Mature and immature fruits of a Cretan Vitex agnus-castus L. population were chosen to investigate different parameters such as comminution, maturity, distillation period and extraction method influencing the essential oil yield and composition. The effect of the comminution and the maturity of the plant material showed highly significant differences in yield and composition of the essential oils obtained, as well as the distillation duration from one to five hours and the method applied (hydrodistillation and simultaneous distillation extraction). The variation of 36 essential oil components due to the parameters applied was studied. The results showed that many different essential oil qualities can be obtained from the same plant material according to the parameters employed in its extraction. Entire fruits hydrodistilled for one hour yielded an oil much richer in monoterpene hydrocarbons and oxygenated compounds whereas the best combination to obtain an oil rich in less volatile compounds is by SDE of comminuted fruits for five hours. For mature fruits the main components varied as follows due to the parameters studied: sabinene 16.4-44.1%, 1,8-cineole 8.4-15.2%, beta-caryophyllene 2.1-5.0%, and trans-beta-farnesene 5.0-11.7%. PMID:10821051

Sørensen, J M; Katsiotis, S T

2000-04-01

124

Study of kinetic parameters in a mechanistic model for bioethanol production through a screening technique and optimization.  

PubMed

The accurate description of the kinetics and robust modeling of biotechnological processes can only be achieved by incorporating reliable methodologies to easily update the model when there are changes in operational conditions. The purpose of this work is to provide a systematic approach with which to perform model parameters screening and updating in biotechnological processes. Batch experiments are performed to develop a mechanistic model, considering the effect of temperature on the kinetics, and further experiments (batch fermentations using sugar cane molasses from a different harvest) are used to validate the effectiveness of screening before parameters updating. The reduction in the number of kinetic parameters to be re-estimated enabled by the screening procedure reduces significantly the complexity of the optimization, which makes the updating procedure to be significantly quicker, while resulting in accurate performance of the updated model. PMID:19125302

de Andrade, Rafael Ramos; Rivera, Elmer Ccopa; Atala, Daniel I P; Filho, Rubens Maciel; Filho, Francisco Maugeri; Costa, Aline C

2009-01-06

125

Bayesian inference of biochemical kinetic parameters using the linear noise approximation  

PubMed Central

Background Fluorescent and luminescent gene reporters allow us to dynamically quantify changes in molecular species concentration over time on the single cell level. The mathematical modeling of their interaction through multivariate dynamical models requires the deveopment of effective statistical methods to calibrate such models against available data. Given the prevalence of stochasticity and noise in biochemical systems inference for stochastic models is of special interest. In this paper we present a simple and computationally efficient algorithm for the estimation of biochemical kinetic parameters from gene reporter data. Results We use the linear noise approximation to model biochemical reactions through a stochastic dynamic model which essentially approximates a diffusion model by an ordinary differential equation model with an appropriately defined noise process. An explicit formula for the likelihood function can be derived allowing for computationally efficient parameter estimation. The proposed algorithm is embedded in a Bayesian framework and inference is performed using Markov chain Monte Carlo. Conclusion The major advantage of the method is that in contrast to the more established diffusion approximation based methods the computationally costly methods of data augmentation are not necessary. Our approach also allows for unobserved variables and measurement error. The application of the method to both simulated and experimental data shows that the proposed methodology provides a useful alternative to diffusion approximation based methods.

Komorowski, Michal; Finkenstadt, Barbel; Harper, Claire V; Rand, David A

2009-01-01

126

Insights into T cell recognition of antigen: significance of two-dimensional kinetic parameters.  

PubMed

The T cell receptor (TCR) interacts with peptide-major histocompatibility complex (pMHC) to enable T cell development and trigger adaptive immune responses. For this reason, TCR:pMHC interactions have been intensely studied for over two decades. However, the details of how various binding parameters impact T cell activation remain elusive. Most measurements were made using recombinant proteins by surface plasmon resonance, a three-dimensional (3D) technique in which fluid-phase receptors and ligands are removed from their cellular environment. This approach found TCR:pMHC interactions with relatively low affinities and slow off-rates for agonist peptides. Newer generation techniques have analyzed TCR:pMHC interactions in two dimensions (2D), with both proteins anchored in apposing plasma membranes. These approaches reveal in situ TCR:pMHC interaction kinetics that are of high affinity and exhibit rapid on- and off-rates upon interaction with agonist ligands. Importantly, 2D binding parameters correlate better with T cell functional responses to a spectrum of ligands than 3D measures. PMID:22566966

Edwards, Lindsay J; Zarnitsyna, Veronika I; Hood, Jennifer D; Evavold, Brian D; Zhu, Cheng

2012-04-20

127

Insights into T Cell Recognition of Antigen: Significance of Two-Dimensional Kinetic Parameters  

PubMed Central

The T cell receptor (TCR) interacts with peptide-major histocompatibility complex (pMHC) to enable T cell development and trigger adaptive immune responses. For this reason, TCR:pMHC interactions have been intensely studied for over two decades. However, the details of how various binding parameters impact T cell activation remain elusive. Most measurements were made using recombinant proteins by surface plasmon resonance, a three-dimensional (3D) technique in which fluid-phase receptors and ligands are removed from their cellular environment. This approach found TCR:pMHC interactions with relatively low affinities and slow off-rates for agonist peptides. Newer generation techniques have analyzed TCR:pMHC interactions in two dimensions (2D), with both proteins anchored in apposing plasma membranes. These approaches reveal in situ TCR:pMHC interaction kinetics that are of high affinity and exhibit rapid on- and off-rates upon interaction with agonist ligands. Importantly, 2D binding parameters correlate better with T cell functional responses to a spectrum of ligands than 3D measures.

Edwards, Lindsay J.; Zarnitsyna, Veronika I.; Hood, Jennifer D.; Evavold, Brian D.; Zhu, Cheng

2012-01-01

128

Estimation of genetic parameters for yield traits in globe artichoke (Cynara scolymus L.)  

Microsoft Academic Search

Ten yield and phenological traits were evaluated in a population of 23 globe artichoke (Cynara scolymus L.) clones in order\\u000a to estimate broad sense heritability, genetic coefficient of variation, expected selection gain and genetic correlations.\\u000a The variation among clones was highly significant (p < 0.01) for all the characters, while the clone x year interaction was\\u000a highly significant (p <

Fernando S. López Anido; Inés T. Firpo; Stella M. García; Enrique L. Cointry

1998-01-01

129

Measurement of the {alpha} asymmetry parameter for the {omega}{sup -}{yields}{lambda}K{sup -} Decay  

SciTech Connect

We have measured the {alpha} parameter of the {omega}{sup -}{yields}{lambda}K{sup -} decay using data collected with the HyperCP spectrometer during the 1997 fixed-target run at Fermilab. Analyzing a sample of 0.96x10{sup 6} {omega}{sup -}{yields}{lambda}K{sup -}, {lambda}{yields}p{pi}{sup -} decays, we obtain {alpha}{sub {omega}}{alpha}{sub {lambda}}=[1.33{+-}0.33(stat){+-}0.52(syst)]x10{sup -2}. With the accepted value of {alpha}{sub {lambda}}, {alpha}{sub {omega}} is found to be [2.07{+-}0.51(stat){+-}0.81(syst)]x10{sup -2}.

Chen, Y.C.; Chan, A.; Ho, C.; Teng, P.K. [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Burnstein, R.A.; Chakravorty, A.; Kaplan, D.M.; Lederman, L.M.; Luebke, W.; Rajaram, D.; Rubin, H.A.; White, C.G.; White, S.L. [Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Choong, W.S.; Luk, K.B. [University of California, Berkeley, California 94720 (United States); Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Clark, K.; Jenkins, C.M. [University of South Alabama, Mobile, Alabama 36688 (United States); Dukes, E.C.; Durandet, C.; Holmstrom, T. [University of Virginia, Charlottesville, Virginia 22904 (United States)] [and others

2005-03-01

130

Adsorption of methylene blue onto hazelnut shell: Kinetics, mechanism and activation parameters  

Microsoft Academic Search

The adsorption kinetics of methylene blue (MB) on the hazelnut shell with respect to the initial dye concentration, pH, ionic strength, particle size and temperature were investigated. The rate and the transport\\/kinetic processes of MB adsorption were described by applying the first-order Lagergren, the pseudo-second-order, mass transfer coefficient and the intraparticle diffusion models. Kinetic studies showed that the kinetic data

Mehmet Do?an; Harun Abak; Mahir Alkan

2009-01-01

131

Studies on the effect of caffeine on growth and yield parameters in Helianthus annuus L. variety Modern  

Microsoft Academic Search

In present investigation, the seeds of Helianthus annuus L. variety Modern were treated with nine different concentrations (0.05%, 0.25%, 0.50%, 0.75%, 1.00%, 1.25%, 1.50%, 1.75% and 2.00%) of caffeine to raise the M1 generation and the effect of caffeine on seedling height on 30 th day of sowing, mature plant height, days to maturity and yield parameters was observed. Generally,

T Khursheed; MYK Ansari; D Shahab

132

POTENTIAL USE OF NITROGEN REFLECTANCE INDEX TO ESTIMATE PLANT PARAMETERS AND YIELD OF MAIZE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Estimating the spatial variability of various plant parameters during the growing season can assist in timely correction of stress conditions within a field. This research illustrates that the nitrogen reflectance index (NRI) developed to estimate plant nitrogen status can be used to estimate plant...

133

Kinetic-energy dependence of the secondary-electron yield for low-energy O(5S) metastables on a Cu-Be-O surface  

Microsoft Academic Search

The secondary-electron yield gammam for O(5S) metastables on a Cu-Be-O multiplier surface was measured as a function of metastable kinetic energy from near thermal to several eV. This measurement, which seems to be the first of its kind, was made possible by the simultaneous detection of the metastables by secondary-electron emission from surfaces and in-flight radiative decay. Unlike the yield

W. L. Borst; G. Nowak; J. Fricke

1978-01-01

134

Re-examination of safety parameters using kinetic theory of nano-granular flows  

NASA Astrophysics Data System (ADS)

The origin of the kinetic theory of granular flow was originally credited to Bagnold [1]. By using a very primitive expression of the particle collision frequency, he derived an expression for the repulsive pressure of the particles in uniform shear flows. His repulsive pressure was proportional to the square of the velocity gradient and the particle diameter and directly proportional to the particle density. This theory was later extended by Savage [2] and Gidaspow [3]. Such theories provide insight on the dependence of the viscosity, and various moduli (elastic, non elastic, viscous...) in terms of the granular temperature and the associated shear-rates. Until recently, such parameters were difficult to measure because of the lack of specifically designed equipment. This challenge was successfully taken up and resolved by P. Marchal of ENSIC who designed a new rheometer for powders (figure 1). This equipment can put in evidence the importance of the granular temperature on the elastic and viscous behaviors of the granular flows. Such rheological behavior is important in risk analysis for nanopowders, because as the nanopowder may be subjected to process shear rates and stresses, its structural and topological changes, in terms of the transformation of agglomerates into primary nanoparticles, have strong impacts on emission factors of nanosized particles that can be released in the environment or into a workplace from such dense-phase nanopowder processes. Such transformation can be analyzed by studying the nano-granular rheological signature of the system. Such risk assessment approach using these new fundamental rheological safety parameters is described in this paper.

Bouillard, Jacques Xavier; Marchal, Philippe; Henry, François; Vignes, Alexis; Dufaud, Olivier; Perrin, Laurent; Plasari, Edouard

2011-07-01

135

Influence of erythropoietin treatment on urea kinetic parameters in hemodialysis patients.  

PubMed

Urea kinetic parameters were studied by means of dialysate collection in 8 stable hemodialysis patients before and after treatment with recombinant human erythropoietin (r-HuEPO), in order to investigate the impact of a rising hematocrit (Ht) on dialyzer performance and nutritional status. After 6 months, the average in vivo dialyzer urea clearance had fallen from 152 to 132 ml/min and consequently Kt/V values had become undesirably low in most of the patients in whom the relatively short dialysis regimens had been kept unchanged. There was also a significant decrease of protein intake. As a result of both changes there was only a moderate increase of predialysis mean blood urea concentration. These findings indicate that after correction of anemia by r-HuEPO dialyzer performance decreased. The concomitant decrease of protein intake seems to contrast to the improved general physical condition and appetite as indicated in the questionnaires. Although body weight remained the same, there might have been a tendency to avoid protein consumption with maintained total calory intake as a result of slight underdialysis. Therefore, in individual cases dialysis prescriptions may need reconsideration when Ht levels rise after r-HuEPO administration, especially in short dialysis regimens. PMID:1855319

van Geelen, J A; Nubé, M J; Zuurbier, P A

1991-04-01

136

Quantification of kinetic parameters for heterotrophic bacteria via respirometry in a hybrid reactor.  

PubMed

Over the last decade new technologies are emerging even more for wastewater treatment. Among the new technologies, a recent possible solution regards Moving Bed Biofilm Reactors (MBBRs) that represent an effective alternative to conventional processes. More specifically such systems consist in the introduction of plastic elements inside the aerobic reactor as carrier material for the growth of attached biomass. Recently, one of the mostly used alternatives is to couple the Moving Bed Biofilm Reactor (MBBR) process with the conventional activated sludge process, and the resulting process is usually called HMBBR (Hybrid MBBR). In the MBBR process the biofilm grows attached on small plastic elements that are kept in constant motion throughout the entire volume of the reactor. Indeed, in such a system, a competition between the two biomasses, suspended and attached, can arise for the availability of the substrates, leading, as a consequence, to a modification in the biokinetic parameters of the two biomasses, compared to that of a pure suspended or attached biomass process. This paper presents the first results of a study aimed at estimating the kinetic heterotrophic constants in a HMBBR pilot plant using respirometric techniques. The pilot plant was built at the Acqua dei Corsari (Palermo) wastewater treatment plant and consisted of two parallel lines realized in a pre-anoxic scheme, in one of which the carrier material was added to the aerobic reactor with a filling ratio of 30%. PMID:20371934

Trapani, Daniele Di; Mannina, Giorgio; Torregrossa, Michele; Viviani, Gaspare

2010-01-01

137

Determination of the kinetic parameters of the CALIBAN metallic core reactor from stochastic neutron measurements  

SciTech Connect

Several experimental devices are operated by the Criticality and Neutron Science Research Dept. of the CEA Valduc Laboratory. One of these is the Caliban metallic core reactor. The purpose of this study is to develop and perform experiments allowing to determinate some of fundamental kinetic parameters of the reactor. The prompt neutron decay constant and particularly its value at criticality can be measured with reactor noise techniques such as Rossi-{alpha} and Feynman variance-to-mean methods. Subcritical, critical, and even supercritical experiments were performed. Fission chambers detectors were put nearby the core and measurements were analyzed with the Rossi-{alpha} technique. A new value of the prompt neutron decay constant at criticality was determined, which allows, using the Nelson number method, new evaluations of the effective delayed neutron fraction and the in core neutron lifetime. As an introduction of this paper, some motivations of this work are given in part 1. In part 2, principles of the noise measurements experiments performed at the CEA Valduc Laboratory are reminded. The Caliban reactor is described in part 3. Stochastic neutron measurements analysis techniques used in this study are then presented in part 4. Results of fission chamber experiments are summarized in part 5. Part 6 is devoted to the current work, improvement of the experimental device using He 3 neutron detectors and first results obtained with it. Finally, conclusions and perspectives are given in part 7. (authors)

Casoli, P.; Authier, N.; Chapelle, A. [Commissariat a l'Energie Atomique et Aux Energies Alternatives, CEA, DAM, F-21120 Is sur Tille (France)

2012-07-01

138

[Comparison of kinematic and kinetic parameters between the locomotion patterns in nordic walking, walking and running].  

PubMed

Based on a higher cardio-pulmonary and cardio-vascular benefit and a promised reduction of mechanical load of the musculoskeletal system Nordic Walking (NW) shows an increased market potential. The present study should investigate whether there are biomechanical differences between the locomotion patterns NW, walking and running. Moreover possible resultant load differences should be determined. Eleven subjects, who were already experienced with the NW-technique, participated in this experiment. The kinematic data were collected using two high-speed camera systems from posterior and from lateral at the same time. Simultaneously the ground reaction forces were recorded. The kinematic and the kinetic data reveal differences between the three analyzed locomotion patterns. For NW as well as walking the mechanical load of the lower extremity is lower compared to running. None of the kinematic parameters suggest a "physiological benefit" of NW compared to walking. Moreover NW shows higher vertical and horizontal forces during landing. Exclusively the lower vertical force peak during push off indicates a lower mechanical load for NW in comparison to walking. Consequently it is questionable is NW -- based on its promised "biomechanical benefits" compared to walking -- should be still recommended for overweight people and for people with existing musculoskeletal problems of the lower limb. PMID:16544213

Kleindienst, F I; Michel, K J; Schwarz, J; Krabbe, B

2006-03-01

139

The interrelationship of biological marker maturity parameters and molecular yields during contact metamorphism  

SciTech Connect

Jurassic siltstone samples were collected, on a centimeter scale, as a function of increasing distance from a dolerite dyke (Isle of Skye, northwest Scotland). The constant origin and type of the organic matter in this single lithological horizon is indicated by organic petrological observations as well as organic geochemical analyses. Therefore, changes in biological marker distributions, with distance from the dyke contact, can be unequivocally correlated with the thermal influence of the intrusion. The vitrinite reflectance (R[sub 0] Average) values of these samples increase gradually from 0.35% to 3.60% as the dyke contact is approached. Four classical biological marker maturity parameters (20S/(20S + 20R), TA/(TA + MA), C[sub 20]/(C[sub 20] + C[sub 28]), and 22S/(22S + 22R)), have been measured from GCMS analyses of the sample extracts. Changes in these molecular parameters were compared with changes in the concentrations of the individual biological marker compounds, expressed relative to mass of rock extracted. This comparison revealed that these molecular parameters are not governed by the conventional product-reactant relationships (chiral isomerization, aromatization or side-chain cracking reactions) operating solely in the free saturated or aromatic hydrocarbon structures. Release/formation from macromolecular and/or functionalized moieties (hydrocarbon or non-hydrocarbon) followed by compound loss provide an alternative paradigm in all four cases in this particularly thermal regime. Direct chiral isomerization in the free sterane or homohopane cannot, however, be completely ruled out as a contributor to an admixture of processes. Similarly, aromatization in the free hydrocarbon fraction may account for a proportion of the triaromatic steroids. 31 refs., 7 figs.

Bishop, A.N.; Abbott, G.D. (The University, Newcastle upon Tyne (United Kingdom))

1993-08-01

140

Effects of plasma kinetic parameters on turbulent layer formation by the Kelvin-Helmholtz instability  

NASA Astrophysics Data System (ADS)

We have recently shown by 2D MHD simulations of the Kelvin-Helmholtz instability (KHI) in a highly asymmetric density layer in a large simulation domain that rapid formation of a broad plasma turbulent layer can be achieved by forward and inverse energy cascades of the KHI [Matsumoto and Seki, JGR, in press.]. The forward cascade is triggered by the growth of the secondary Rayleigh-Taylor instability (RTI) excited during the nonlinear evolution. The inverse cascade is accomplished by a nonlinear coupling of the fastest growing mode of the KHI with other unstable modes. We suggested that the proposed mechanism well explained the observational requirements of the LLBL formation, although some issues are remained to be understood. One major issue, which is not treated accurately in the MHD simulation, is the mixing process itself; the mixing of plasmas is due to the numerical dissipation implicitly or explicitly added in the simulation. To understand all the mechanisms ranging from the dissipating scale to the scale of the largest vortex in a self-consistent manner, we have carried out 2D fully kinetic particle-in-cell (PIC) simulations of the KHI in a large simulation domain which allows growth of multiple KH unstable modes. As a result, we found the inverse energy cascade among the KH unstable modes as have been shown by the 2D MHD simulation. It is also found that the direct energy cascade results in plasma mixing by exciting strong electric fields embedded in electron inertial scales with amplitudes larger than the initial convective electric field. The locally excited electric field is the key agent for the mixing. We have also found two-component distribution functions in the mixed region for the ion and the electron which have been reported by in-situ observations. In this presentation, we show that both direct and inverse energy cascades of the KHI contribute to formation of a large scale plasma mixing layer in a time scale much faster than we expect from the linear theory of the KHI. Also, dependence of the mixing efficiency on the mass ratio (M/m) and the ratio of plasma to gyro frequencies (?pe/?ge) are discussed by results from simulation runs with various kinetic parameters.

Matsumoto, Y.; Seki, K.

2010-12-01

141

Fuzzy c-mean clustering on kinetic parameter estimation with generalized linear least square algorithm in SPECT  

NASA Astrophysics Data System (ADS)

Dynamic Single Photon Emission Computed Tomography (SPECT) has the potential to quantitatively estimate physiological parameters by fitting compartment models to the tracer kinetics. The generalized linear least square method (GLLS) is an efficient method to estimate unbiased kinetic parameters and parametric images. However, due to the low sensitivity of SPECT, noisy data can cause voxel-wise parameter estimation by GLLS to fail. Fuzzy C-Mean (FCM) clustering and modified FCM, which also utilizes information from the immediate neighboring voxels, are proposed to improve the voxel-wise parameter estimation of GLLS. Monte Carlo simulations were performed to generate dynamic SPECT data with different noise levels and processed by general and modified FCM clustering. Parametric images were estimated by Logan and Yokoi graphical analysis and GLLS. The influx rate (K1), volume of distribution (Vd) were estimated for the cerebellum, thalamus and frontal cortex. Our results show that (1) FCM reduces the bias and improves the reliability of parameter estimates for noisy data, (2) GLLS provides estimates of micro parameters (K1-k4) as well as macro parameters, such as volume of distribution (Vd) and binding potential (BP1 & BP2) and (3) FCM clustering incorporating neighboring voxel information does not improve the parameter estimates, but improves noise in the parametric images. These findings indicated that it is desirable for pre-segmentation with traditional FCM clustering to generate voxel-wise parametric images with GLLS from dynamic SPECT data.

Choi, Hon-Chit; Wen, Lingfeng; Eberl, Stefan; Feng, Dagan

2006-03-01

142

Evaluation of kinetic parameters for enzymatic interesterification synthesis of L-ascorbyl lactate by response surface methodology.  

PubMed

The kinetics of lipase-catalyzed interesterification synthesis of L-ascorbyl lactate was studied. To determine the enzyme kinetic constants of the interesterification, a three-factor and five-level central composite design was used. The factors studied were ethyl lactate concentration, reaction temperature (T), and water content (w). Moreover, a statistical approach called the response surface method (RSM) was used to predict the kinetic constants. Finally, the relationships between the kinetic constants (Vm and Km) and the reaction parameters (T and w) were obtained. To assess the accuracy of the RSM approach for determining Vm and Km, detailed validation experiments were carried out by the conventional approach at four different reaction parameters(35 degrees C, 10 microL; 45 degrees C, 20 microL; 55 degrees C, 15 microL; 65 degrees C, 18 microL). The results indicated that the RSM approach gave reasonable results for the determination of Vm and Km in the range of tested parameters. PMID:17496337

Gao, Jing; Jiang, Yanjun; Huang, Zhihong; Zhou, Liya

2007-02-01

143

Two-parameter kinetic model based on a time-dependent activity coefficient accurately describes enzymatic cellulose digestion.  

PubMed

Lignocellulosic biomass is a potential source of renewable, low-carbon-footprint liquid fuels. Biomass recalcitrance and enzyme cost are key challenges associated with the large-scale production of cellulosic fuel. Kinetic modeling of enzymatic cellulose digestion has been complicated by the heterogeneous nature of the substrate and by the fact that a true steady state cannot be attained. We present a two-parameter kinetic model based on the Michaelis-Menten scheme ( Michaelis, L., and Menten, M. L. ( 1913 ) Biochem. Z. , 49 , 333 - 369 ) with a time-dependent activity coefficient analogous to fractal-like kinetics formulated by Kopelman ( Kopelman, R. ( 1988 ) Science 241 , 1620 - 1626 ). We provide a mathematical derivation and experimental support to show that one of the parameters is a total activity coefficient and the other is an intrinsic constant that reflects the ability of the cellulases to overcome substrate recalcitrance. The model is applicable to individual cellulases and their mixtures at low-to-medium enzyme loads. Using biomass degrading enzymes from cellulolytic bacterium Thermobifida fusca , we show that the model can be used for mechanistic studies of enzymatic cellulose digestion. We also demonstrate that it applies to the crude supernatant of the widely studied cellulolytic fungus Trichoderma reesei ; thus it can be used to compare cellulases from different organisms. The two parameters may serve a similar role to Vmax, KM, and kcat in classical kinetics. A similar approach may be applicable to other enzymes with heterogeneous substrates and where a steady state is not achievable. PMID:23837567

Kostylev, Maxim; Wilson, David

2013-07-24

144

Interaction between chitosan and uranyl ions. Role of physical and physicochemical parameters on the kinetics of sorption  

SciTech Connect

This work corresponds to the first part of our studies on the interactions between chitosan particles dispersed in water and uranyl ions. The measurements were obtained by ICP, and we considered the role of various physical and physicochemical parameters related to chitosan. We showed that the crystallinity, the particle dimensions, and the swelling in water of chitosan are parameters which are connected together and govern the kinetic laws of metal diffusion and sorption. The molecular mobility of the polymer chains is then essential parameter. 31 refs., 5 figs., 3 tabs.

Piron, E. [Universite Claude Bernard, Villeurbanne (France)]|[COGEMA, Velizy-Villacoublay (France); Accominotti, M. [Hopital Edouard Heriot, Lyon (France); Domard, A. [Universite Claude Bernard, Villeurbanne (France)

1997-03-19

145

Comparative Analysis of Linear and Nonlinear Methods of Estimating the Pseudo-Second-Order Kinetic Parameters for Sorption of Malachite Green onto Pretreated Rice Husk  

Microsoft Academic Search

Batch sorption experiments were carried out for removal of malachite green from aqueous solution using pretreated rice husk. The equilibrium kinetic data were analyzed using pseudo-second-order kinetic model. A comparison between linear and nonlinear methods of estimating the kinetic parameters was carried out. Four pseudo-second-order kinetic linear equations were discussed. The coefficient of determination (r ) and chi-square (?) test

Shamik Chowdhury; Papita Das Saha

2011-01-01

146

Kinetics  

NSDL National Science Digital Library

Conceptual questions about kinetics. For example, "[w]hat are the reaction velocity, the rates of formation of N2 and H2, and the rate of decomposition of ammonia for the decomposition of ammonia on a tungsten surface under the conditions reflected in the figure."

Nurrenbern, Susan C.; Robinson, William R.

2008-02-27

147

A Gurson-type criterion for porous ductile solids containing arbitrary ellipsoidal voids—II: Determination of yield criterion parameters  

NASA Astrophysics Data System (ADS)

The aim of this paper is to fully determine the parameters of the approximate homogenized yield criterion for porous ductile solids containing arbitrary ellipsoidal cavities proposed in Part I. This is done through improvements of the limit-analysis of some representative hollow cell presented there. The improvements are of two kinds. For hydrostatic loadings, the limit-analysis is refined by performing micromechanical finite element computations in a number of significant cases, so as to replace Leblond and Gologanu (2008)'s trial velocity field representing the expansion of the void by the exact, numerically determined one. For deviatoric loadings, limit-analysis is dropped and direct use is made of some general rigorous results for nonlinear composites derived by Ponte-Castaneda (1991), Willis (1991) and Michel and Suquet (1992) using the earlier work of Willis (1977) and the concept of “linear comparison material”. This hybrid approach is thought to lead to the best possible expressions of the yield criterion parameters. The criterion proposed reduces to (variants of) classical approximate criteria proposed by Gurson (1977) and Gologanu et al. (1993, 1994, 1997) in the specific cases of spherical or spheroidal, prolate or oblate cavities. An overview of the validation of this criterion through micromechanical finite element computations is finally presented.

Madou, Komlanvi; Leblond, Jean-Baptiste

2012-05-01

148

Comparison of Isoconversional and Model Fitting Approaches to Kinetic Parameter Estimation and Application Predictions.  

National Technical Information Service (NTIS)

Chemical kinetic modeling has been used for many years in process optimization, estimating real-time material performance, and lifetime prediction. Chemists have tended towards developing detailed mechanistic models, while engineers have tended towards gl...

A. K. Burnham

2006-01-01

149

Kinetics and activation parameter analysis for the prebiotic oligocytidylate formation on Na(+)-montmorillonite at 0-100 degrees C.  

PubMed

The kinetic analysis of the temperature dependence of the formation of oligocytidylate (oligo(C)) from the 5'-monophosphorimidazolide moiety of cytidine (ImpC) in the presence of Na (+)-montmorillonite (Na (+)-Mont) catalyst has been carried out at 0-100 degrees C. The rate constants for the formation of oligo(C), hydrolysis of ImpC with and without Na (+)-Mont and degradation of oligo(C) were determined. The apparent activation parameters were 30.8 +/- 3.9 kJ mol (-1) ( Ea), 28.3 +/- 4.0 kJ mol (-1) (Delta H++), and -231 +/- 13 J mol (-1) K (-1) (Delta S++) for the formation of the 2-mer; 45.6 +/- 2.9 kJ mol (-1) ( Ea), 43.0 +/- 3.0 kJ mol (-1) (Delta H++), -164 +/- 10 J mol (-1) K (-1) (Delta S++) for the 3-mer; and 45.2 +/- 0.6 kJ mol (-1) ( Ea), 42.7 +/- 0.7 kJ mol (-1) (Delta H++), -159 +/- 2 J mol (-1) K (-1) (Delta S++) for the 4-mer in the presence of Na (+)-Mont. An increasing trend for the rate constants for the formation of oligo(C) in the order 2-mer < 3-mer <4-mer was observed at high temperatures, which is consistent with that observed at low temperatures. These analyses implied for the first time that the associate formation between an activated nucleotide monomer and an elongating oligonucleotide prior to the phosphodiester bond formation during the elongation of an oligonucleotide on a clay surface would be based on the interaction between the two reactants at the phosphoester and/or ribose moieties rather than at the nucleotide bases. The hydrolysis rate of ImpC at 25-100 degrees C was 5.3-10.6 times greater in the presence of Na (+)-Mont than in its absence. Although the degradation of oligo(C) in the presence of Na (+)-Mont was slower than the formation of the 3-mer and longer oligo(C) on Na (+)-Mont, its yield decreased with temperature. This is mainly because the ratios of the rate constant of the 2-mer formation to those of ImpC hydrolysis and the 3-mer and 4-mer formation decrease with an increase in temperature, which is attributed to the enthalpy and entropy changes for the formation of the 2-mer. This trend resembles the case of the template-directed formation of oligo(G) on a poly(C) template but is different from the Pb (2+)-ion-catalyzed oligo(C) formation. According to the kinetics and activation parameter analyses regarding the clay reaction and other prebiotic polymerase models, the possible pathways for the oligonucleotide formation are discussed and compared. PMID:18693705

Kawamura, Kunio; Maeda, Jun

2008-08-12

150

Kinetic parameters of dehydrogenase in the assessment of the response of soil to vermicompost and inorganic fertilisers  

Microsoft Academic Search

Kinetic parameters (V\\u000a max and K\\u000a m) of dehydrogenase activity were determined in order to assess the metabolic response of a soil about 1?year after organic\\u000a and mineral treatments. The soil was planted with maize (Zea mays) and treated with the following fertilisers: organic (vermicompost; VC), mineral (ammonium phosphate and urea), and an organo-mineral\\u000a mixture. V\\u000a max, which represents a

G. Masciandaro; B. Ceccanti; V. Ronchi; C. Bauer

2000-01-01

151

The role of the kinetic parameter in the stability of two-relaxation-time advection–diffusion lattice Boltzmann schemes  

Microsoft Academic Search

In general, explicit numerical schemes are only conditionally stable. A particularity of lattice Boltzmann multiple-relaxation-time (MRT) schemes is the presence of free (“kinetic”) relaxation parameters. They do not appear in the transport coefficients of the modelled second-order (macroscopic) equations but they have an impact on the effective accuracy and stability of the algorithm. The simplest uniform choice (the well known

A. Kuzmin; I. Ginzburg; A. A. Mohamad

2011-01-01

152

Using the DTG curve fitting method to determine the apparent kinetic parameters of thermal decomposition of polymers  

Microsoft Academic Search

A new method, called the DTG curve fitting method, has been used to determine the kinetic parameters of six major plastic materials found among urban refuse: high-density polyethylene, low-density polyethylene, polystyrene, polypropylene, poly(vinyl chloride), and poly(ethylene terephthalate). This method involves first measuring the weight loss behaviour by using thermogravimetry (TG) and then using the Arrhenius equation to fit the DTG

J. Yang; R. Miranda; C. Roy

2001-01-01

153

Fourier domain closed-form formulas for estimation of kinetic parameters in reversible multi-compartment models  

PubMed Central

Background Compared with static imaging, dynamic emission computed tomographic imaging with compartment modeling can quantify in vivo physiologic processes, providing useful information about molecular disease processes. Dynamic imaging involves estimation of kinetic rate parameters. For multi-compartment models, kinetic parameter estimation can be computationally demanding and problematic with local minima. Methods This paper offers a new perspective to the compartment model fitting problem where Fourier linear system theory is applied to derive closed-form formulas for estimating kinetic parameters for the two-compartment model. The proposed Fourier domain estimation method provides a unique solution, and offers very different noise response as compared to traditional non-linear chi-squared minimization techniques. Results The unique feature of the proposed Fourier domain method is that only low frequency components are used for kinetic parameter estimation, where the DC (i.e., the zero frequency) component in the data is treated as the most important information, and high frequency components that tend to be corrupted by statistical noise are discarded. Computer simulations show that the proposed method is robust without having to specify the initial condition. The resultant solution can be fine tuned using the traditional iterative method. Conclusions The proposed Fourier-domain estimation method has closed-form formulas. The proposed Fourier-domain curve-fitting method does not require an initial condition, it minimizes a quadratic objective function and a closed-form solution can be obtained. The noise is easier to control, simply by discarding the high frequency components, and emphasizing the DC component.

2012-01-01

154

Environmental and Kinetic Parameters for Cr(VI) Bioreduction by a Bacterial Monoculture Purified from Cr(VI)Resistant Consortium  

Microsoft Academic Search

Hexavalent chromium, Cr(VI), is toxic to living systems. Widespread contamination of water and soil by Cr(VI) present a serious\\u000a public health problem. Chromium-resistant bacteria can reduce and detoxify Cr(VI). Twelve bacteria resistant to high concentrations\\u000a of Cr(VI) were isolated from soil enrichment cultures. Environmental parameters and kinetic parameters of Cr(VI) bioreduction\\u000a by one monoculture isolate, identified by 16S rRNA gene

Benedict C. Okeke; Jeffery Laymon; Shakena Crenshaw; Charles Oji

2008-01-01

155

Antioxidative effects of melatonin on kinetics, microscopic and oxidative parameters of cryopreserved bull spermatozoa.  

PubMed

Reactive oxygen species generated during the freeze-thawing process may reduce sperm quality. This study evaluates the effects of melatonin supplementation as an antioxidant in the semen extender on post-thaw parameters of bull spermatozoa. Melatonin was added to the citrate-egg yolk extender to yield six different final concentrations: 0, 0.1, 1, 2, 3 and 4mM. Ejaculates were collected from six proven Holstein bulls. Semen was diluted in the extender packaged in straws, which was frozen with liquid nitrogen. The semen extender supplemented with various doses of melatonin increased (p<0.05) total motility, progressive motility, linearity, sperm track straightness, lateral head displacement, viability, integrity of the sperm membrane and total normal morphology of sperm after the freeze-thawing process. The most effective concentration of melatonin in microscopic evaluations of the bull sperm freezing extender was 2mM. The highest (p<0.05) value of total antioxidant capacity (48.9±2.7) and the lowest value of lipid peroxidation (2.7±0.8) were achieved by inclusion of 3mM concentration of melatonin in the semen extender and the highest activity of catalase (0.7±0.1) was obtained by 2mM melatonin. Four millimolar concentration of melatonin were reduced (p<0.05) the progressive motility and straight linear velocity. In conclusion, supplementation of 2 or 3mM concentration of melatonin in the semen extender improved the quality of post-thawed semen, which may associate with a reduction in lipid peroxidation as well as an increase in the total antioxidant capacity and antioxidant enzyme activity. PMID:23664651

Ashrafi, Iraj; Kohram, Hamid; Ardabili, Farhad Farrokhi

2013-04-13

156

Kinetic-energy-driven enhancement of secondary-electron yields of highly charged ions impinging on thin films of C60 on Au  

NASA Astrophysics Data System (ADS)

The secondary electron yields as a result of slow highly charged ions (Ar4+,Ar13+) impinging on clean Au(111), highly oriented pyrolitic graphite, and thin films of C60 on Au are presented. In order to investigate the dynamics of the neutralization of the highly charged ions in front of the surface, angular scans have been performed. The results give a clear indication that the observed increase in electron yield seen on C60 compared to Au stems from kinetic-energy-driven processes and not from processes driven by the potential energy carried by the highly charged ion.

Bodewits, E.; Hoekstra, R.; Dobes, K.; Aumayr, F.

2012-12-01

157

Hydrothermal pyrolysis of swine manure to bio-oil: Effects of operating parameters on products yield and characterization of bio-oil  

Microsoft Academic Search

Advanced hydrothermal pyrolysis technology was used to process swine manure for waste reduction and energy production. The effect of operating parameters on products yield was investigated to determine the optimal condition for the process. Operating temperature, retention time, and the initial pressure of process gas were all found to affect oil yield. Increasing the temperature from 260°C to 340°C was

Shuangning Xiu; Abolghasem Shahbazi; Vestel Shirley; Dan Cheng

2010-01-01

158

A novel yield optimization technique for digital CMOS circuits design by means of process parameters run-time estimation and body bias active control  

Microsoft Academic Search

This work presents a novel approach to optimize digital integrated circuits yield referring to speed, dynamic power and leakage power constraints. The method is based on process parameter estimation circuits and active control of body bias performed by an on-chip digital controller. The associated design flow allows us to quantitatively predict the impact of the method on the expected yield

Mauro Olivieri; Giuseppe Scotti; Alessandro Trifiletti

2005-01-01

159

Time of erythema onset after application of methyl nicotinate ointments as response parameter: influence of penetration kinetics and enhancing agents.  

PubMed

The time of erythema onset may be used as a response parameter for quantification of the cutaneous erythema response induced by methyl nicotinate. The vehicles light mineral oil (LMO; test) and medium chain triglycerides (MCT; standard) were compared with regard to the pharmacodynamic response. Moreover, the influence of penetration enhancers on the time of erythema onset was investigated under zero order penetration kinetics. The enhancers dimethyl sulfoxide, diethylene glycol monoethyl ether and three different glycerides in different concentrations were added to MCT as a standard vehicle. All preparations were applied to the forearms of volunteers under infinite dose conditions at different thermodynamic drug activity levels (0.2-3.2% of the saturation level) and different drug concentrations (0.051-0.816%), respectively. Different penetration kinetics do not influence data of erythema onset, as these data are comparable to those obtained under finite dose conditions (first order penetration kinetics). With regard to the penetration enhancers, a significantly enhanced penetration of methyl nicotinate could be observed only for diethylene glycol monoethyl ether and dimethyl sulfoxide. However, no significant difference between light mineral oil and MCT could be found with regard to penetration enhancement. The time of erythema onset is an easy and efficient parameter for quantification of the pharmacodynamic response caused by nicotinates. PMID:16931897

Remane, Y; Leopold, C S

2006-08-23

160

Dry mechanochemical synthesis of hydroxyapatites from DCPD and CaO: influence of instrumental parameters on the reaction kinetics.  

PubMed

Mechanochemistry is a possible route to synthesize calcium deficient hydroxyapatite (CDHA) with an expected molar calcium-to-phosphate (Ca/P) ratio +/-0.01. To optimize the experimental conditions of CDHA preparation from dicalcium phosphate dihydrate (DCPD) and calcium oxide by dry mechanosynthesis reaction, we performed the kinetic study varying some experimental parameters. This kinetic study was carried out with two different planetary ball mills (Retsch or Fritsch Instuments). Results obtained with the two mills led to the same conclusions although the values of the rate constants of DCPD disappearance and times for complete reaction were very different. Certainly, the origin of these differences was from the mills used, thus we investigated the influence of instrumental parameters such as the mass and the surface area of the balls or the rotation velocity on the mechanochemical reaction kinetics of DCPD with CaO. Results show that the DCPD reaction rate constant and the inverse of the time for complete disappearance of CaO both vary linearly with (i) the square of the rotation velocity, (ii) the square of eccentricity of the vial on the rotating disc and (iii) the product of the mass by the surface area of the balls. These observations comply with theoretical models developed for mechanical alloying. The consideration of these four parameters allows the transposition of experimental conditions from one mill to another or the comparison between results obtained with different planetary ball mills. These instrumental parameters have to be well described in papers concerning mechanochemistry or when grinding is an important stage in a process. PMID:14643588

Mochales, Carolina; El Briak-BenAbdeslam, Hassane; Ginebra, Maria Pau; Terol, Alain; Planell, Josep A; Boudeville, Philippe

161

Kinetic parameters for plasma. beta. -endorphin in lean and obese Zucker rats  

SciTech Connect

To determine plasma clearance kinetics for {beta}-endorphin (BE) by empirical compartmental analysis, a bolus of radioactive labeled 125I-BE was rapidly injected into a carotid artery catheter of unanesthetized lean (L) and obese (O) Zucker rats. The plasma disappearance of 125I was followed over a 3-h period. A 3-component exponential equation provided the best fit for plasma data. Plasma transit times were very short (10 s); however, plasma fractional catabolic rate was much slower. Plasma mean residence time was similar for both groups (50 min) as was recycle time (1.3 min). These data suggest that BE plasma disappearance kinetics are similar in L and O rats.

Rodd, D.; Farrell, P.A.; Caston, A.L.; Green, M.H. (Department of Exercise and Sport Science, Pennsylvania State University, University Park (USA))

1991-03-01

162

Kinetic parameters of the University of Maryland reactor by the interval distribution method  

Microsoft Academic Search

The Rossi alpha of the University of Maryland Reactor was measured at criticality and at shutdown by the Babala interval-distribution method. At criticality, ..cap alpha..\\/sub c\\/ = 145.8 +- 2.9 s⁻¹. At shutdown, ..cap alpha..\\/sub s\\/ = 1025.8 +- 4.1 s⁻¹. The shutdown reactivity was found to be rho\\/sub s\\/..beta.. = -6.04 +- 0.14 dollars. An inverse kinetics analysis of

J. A. Rawlins; S. C. Simonson

1978-01-01

163

Assessment of kinetic parameters for the mesophilic anaerobic biodegradation of two-phase olive pomace  

Microsoft Academic Search

A kinetic study of the anaerobic biodegradation of two-phase olive pomace (TPOP) was carried out using a laboratory-scale stirred tank reactor. The reactor was operated at 35°C. The influent contained between 20% and 100% TPOP, representing in terms of total chemical oxygen demand (TCOD) 34.5–187.9gTCODl?1. The hydraulic retention times (HRTs) were set between 40.0 and 8.3d. It was found that

R. Borja; B. Rincón; F. Raposo; E. Sánchez; A. Mart??n

2004-01-01

164

Determination of Kinetic Parameters in Laminar Flow Reactors. II. Experimental Aspects  

Microsoft Academic Search

In the present contribution laser spectroscopic studies are described in which the chemical kinetics of benchmark elementary\\u000a reaction steps in different laminar flow reactors were experimentally investigated along with detailed numerical modeling\\u000a calculations (see the article Carraro\\/Heuveline\\/Rannacher [5] in this vol-ume). Coherent anti-Stokes Raman spectroscopy (CARS) was utilized to study the collisional relaxation and vibrational\\u000a energy transfer of vibrationally excited

A. Hanf; H.-R. Volpp; J. Wolfrum

165

Kinetics of hydrolysis of dansyl peptide substrates by thermolysin: analysis of fluorescence changes and determination of steady-state kinetic parameters.  

PubMed

The stopped-flow fluorescence technique has been used to study the hydrolysis of 10 dansyl peptides by thermolysin. The origin of the fluorescence changes observed during the reactions has been investigated in detail. Depending on the substrate and the excitation wavelength, the dansyl fluorescence changes observed arise either from energy transfer (maximal at lambda ex = 230 and 280 nm) between Trp residues of thermolysin and the dansyl group of the substrate in enzyme-substrate (ES) complexes or from both sources. These excitation (maximal at lambda ex = 245 and 340 nm) of the free substrate and product, or from both sources. These two types of fluorescence signals reflect the concentrations of ESi and free substrate, respectively. Both types of fluorescence changes have been used to monitor the reaction progress, and different mathematical formalisms have been used to determine the kinetic parameters for the reactions with results that are in good agreement. The efficiency of Trp quenching by a series of five dansyl tripeptides is shown to be related to the fractional saturation of enzyme and follows the KM-1 values for the substrates. The quenching efficiency for a dansyl tetrapeptide is weaker due to the greater distance between the dansyl group and the Trp-115 donor in thermolysin. On the basis of these studies, substrates capable of supporting more detailed kinetic studies of thermolysin have been identified. PMID:8204585

Yang, J J; Van Wart, H E

1994-05-31

166

Kinetics of carbon dioxide absorption and desorption in aqueous alkanolamine solutions using a novel hemispherical contactor—II: Experimental results and parameter estimation  

Microsoft Academic Search

In Part 1 of this paper, detailed design of the hemispherical apparatus and a rigorous mathematical model applied to CO2 absorption and desorption in and from aqueous alkanolamine solutions was presented with some preliminary results. This part of the paper provides detailed results on CO2–amine kinetics under absorption and desorption conditions and present new estimates of the kinetic parameter for

Aqil Jamal; Axel Meisen; C. Jim Lim

2006-01-01

167

Relevance of thermodynamic and kinetic parameters of chemical vapor deposition precursors.  

PubMed

We have studied various metallorganic and organometallic compounds by simultaneous nonisothermal thermogravimetric and differential thermogravimetric analyses to confirm their volatility and thermal stability. The equilibrium vapor pressures of the metallorganic and organometallic compounds were determined by horizontal dual arm single furnace thermoanalyzer as transpiration apparatus. Antoine coefficients were calculated from the temperature dependence equilibrium vapor pressure data. The model-fitting solid-state kinetic analyses of Al(acac)3, (acac = acetylacetonato), Cr(CO)6, Fe(Cp)2, (Cp-cyclopentadienyl), Ga(acac)3, Mn(tmhd)3, and Y(tmhd)3 (tmhd = 2,2,6,6,-tetramethyl-3,5-heptanedionato) revealed that the processes follow diffusion controlled, contracting area and zero order model sublimation or evaporation kinetics. The activation energy for the sublimation/evaporation processes were calculated by model-free kinetic methods. Thin films of nickel and lanthanum-strontium-manganite (LSM) are grown on silicon substrate at 573 K using selected metallorganic complexes of Ni[(acac)2en], La(tmhd)3, Sr(tmhd)2 and Mn(tmhd)3 as precursors by plasma assisted liquid injection chemical vapor deposition (PA-LICVD). The deposited films were characterized by scanning electron microscopy and energy dispersive X-ray analysis for their composition and morphology. PMID:22097553

Selvakumar, J; Nagaraja, K S; Sathiyamoorthy, D

2011-09-01

168

Uncertainties in Kinetic and Photochemical Parameters of Ozone Depleting Substances and the Impact on Atmospheric Lifetime Calculations  

NASA Astrophysics Data System (ADS)

The SPARC (Stratospheric Processes And their Role in Climate) initiative "Reevaluation of the Lifetimes of Dominant Stratospheric Ozone-Depleting Substances (ODSs)" is aimed toward providing a critical evaluation of atmospheric lifetimes for a number of key compounds. The atmospheric lifetimes of ODSs and greenhouse gases play a key role in the evaluation of ozone loss/recovery and climate change. Therefore, it is critically important to have accurate estimates of lifetimes as well as their uncertainty. The initiative has identified 26 key compounds to be included in this study. The compounds were chosen primarily due to their contribution to ozone depletion, their use as ODS replacements, and their contribution as climate forcing agents. Model calculated atmospheric lifetimes rely on kinetic and photochemical input parameters that are obtained from laboratory studies. Important gas-phase loss processes include reaction with OH, O(1D), and Cl atoms as well as EUV (Lyman-?) and UV photolysis where the relative importance of these processes depends on the properties of the individual compound. As part of the initiative, an evaluation of the model kinetic input parameters and their uncertainties was performed. Here, an assessment of the atmospheric loss processes and associated uncertainties for the target compounds will be presented. Two-dimensional (2D) atmospheric model calculations are used to characterize the globally/annually averaged vertical profiles of the target compounds, loss processes and uncertainties, and their atmospheric lifetimes. The 2D model results are used to highlight the limitations of atmospheric lifetime calculations due to uncertainties in the kinetic and photochemical input parameters, which in some cases are substantial. This component of the initiative also identifies areas where more accurate laboratory studies are needed in order to reduce uncertainties in calculated atmospheric lifetimes for these key species.

Burkholder, J. B.; Kurylo, M. J.; Wallington, T.; Fleming, E. L.; Jackman, C. H.

2011-12-01

169

Fast pyrolysis of palm kernel shells: influence of operation parameters on the bio-oil yield and the yield of phenol and phenolic compounds.  

PubMed

Palm kernel shells were pyrolyzed in a pyrolysis plant equipped with a fluidized-bed reactor and a char-separation system. The influence of reaction temperature, feed size and feed rate on the product spectrum was also investigated. In addition, the effect of reaction temperature on the yields of phenol and phenolic compounds in the bio-oil was examined. The maximum bio-oil yield was 48.7 wt.% of the product at 490 degrees C. The maximum yield of phenol plus phenolic compounds amounted to about 70 area percentage at 475 degrees C. The yield of pyrolytic lignin after its isolation from the bio-oil was approximately 46 wt.% based on the water and ash free oil. The pyrolytic lignin was mainly composed of phenol, phenolic compounds and oligomers of coniferyl, sinapyl and p-coumaryl alcohols. From the result of a GPC analysis, the number average molecular weight and the weight average molecular weight were 325 and 463 g/mol, respectively. PMID:20667720

Kim, Seon-Jin; Jung, Su-Hwa; Kim, Joo-Sik

2010-07-27

170

Non-isothermal kinetic parameters and models of crystallization for amorphous Fe-Co-Nb-Cu-B alloys  

NASA Astrophysics Data System (ADS)

The non-isothermal differential scanning calorimetry (DSC) measurements are often used to study kinetics of amorphous alloys. However non-isothermal kinetic parameters and models of amorphous alloy crystallization process were unclear. In our research, amorphous (FexCo1-x)NbCuB (x=0.33, 0.5 and 0.75) alloys were produced in the form of ribbon by a single roller melt-spinning method. DSC curves at heating rate 5, 10, 15, 20 and 25 K/min were obtained. Kissinger, Ozawa and model-free methods obtain identical activation energies at each exothermic peak of all compositions. We conclude that first exothermic reaction is determined by the migration activation energy of Fe or Co atom; second reaction determined by the energy between parent and product boride phases; and the third reaction determined by the energy between parent ?-FeCo phase and product bcc-Fe/fcc-Co phases. We hypothesized a non-isothermal kinetic modelf(?)=?(1, which fit our experiment results well. In this model, m depends on nucleus shape and growth dimension, and n are determined by lattice positions participated in new phase formation.

Wang, Xin; Deng, Longjiang; Xie, Jianliang; Liang, Difei

2013-02-01

171

Multi-parameter single-cell kinetic analysis reveals multiple modes of cell death in primary pancreatic ?-cells.  

PubMed

Programmed ?-cell death plays an important role in both type 1 and type 2 diabetes. Most of what is known about the mechanisms of ?-cell death comes from single time-point, single parameter measurements of bulk populations of mixed cells. Such approaches are inadequate for determining the true extent of the heterogeneity in death mechanisms. Here, we characterized the timing and order of molecular events associated with cell death in single ?-cells under multiple diabetic stress conditions, including hyperglycemia, cytokine exposure, nutrient deprivation and endoplasmic reticulum (ER) stress. We simultaneously measured the kinetics of six distinct cell death mechanisms by using a caspase-3 sensor and three vital dyes, together with brightfield imaging. We identified several cell death modes where the order of events that usually define apoptosis were not observed. This we termed 'partial apoptosis'. Remarkably, complete classical apoptosis, defined as cells with plasma membrane blebbing, caspase-3 activity, nuclear condensation and membrane annexin V labeling prior to loss of plasma membrane integrity, was found in only half of the cytokine-treated primary ?-cells and never in cells stressed by serum removal. By contrast, in the MIN6 cell line, death occurred almost exclusively through complete classical apoptosis. Ambient glucose modulated the cell death mode and kinetics in primary ?-cells. Taken together, our data define the kinetic progression of ?-cell death mechanisms under different conditions and illustrate the heterogeneity and plasticity of cell death modes in ?-cells. We conclude that apoptosis is not the primary mode of adult primary ?-cell death. PMID:23843629

Yang, Yu Hsuan Carol; Johnson, James D

2013-07-10

172

Kinetic and thermodynamic parameters of alkaline phosphatase and ?—glutamyl transferase inactivation in bovine milk  

Microsoft Academic Search

Kinetic and thermodynamic studies were carried out at different time–temperature combinations in order to evaluate the suitability\\u000a of alkaline phosphatase (ALP) and ?-glutamyl transferase (GGT) as markers for the heat treatment of milk. The average activities\\u000a of the enzymes in bovine milk were 0.46?±?0.02 U.mL?1 for ALP and 4.05?±?0.26 and 4.55?±?0.24 U.mL?1 for GGT in milk with different fat levels. A detailed

Nicoleta St?nciuc; Alina Ardelean; Veronica Diaconu; Gabriela Râpeanu; Silvius Stanciu; Anca Nicolau

173

Genetic and phenotypic parameters of milk yield, milk composition and age at first kidding in Saanen goats from Mexico  

Microsoft Academic Search

A total of 4007 lactation records from 1520 Saanen goats kidding from 1999 to 2006 and obtained from 10 herds in Guanajuato, Mexico, were analyzed to estimate the heritabilities, repeatabilities, as well as genetic, environmental and phenotypic correlations for milk yield (MILK), fat yield (FAT), protein yield (PROT), fat content (%FAT), protein content (%PROT) and age at fist kidding (AFK).

J. A. Torres-Vázquez; M. Valencia-Posadas; H. Castillo-Juárez; H. H. Montaldo

2009-01-01

174

Calculating glass-forming ability in absence of key kinetic and thermodynamic parameters  

NASA Astrophysics Data System (ADS)

Glass-forming ability (GFA) as defined by a critical cooling rate Rc to vitrify a liquid upon solidification is a complex function of many parameters. Some of the parameters, such as liquid-crystal interfacial energy, temperature-dependent liquid viscosity, and influence of heterogeneities, are crucial but their accurate experimental determination is challenging. Here, instead of relying on the experimental data, we draw random values for the difficult parameters and use the classical theory to examine probabilistic distributions of Rc for two well-known metallic glasses. Direct random parameterization produces extremely broad distributions spanning tens of orders of magnitude. Dramatically sharpened distributions are obtained around experimental Rc upon guiding the random parameterization with limited calorimetric data. The results suggest that it is plausible to determine GFA even in absence of data for crucial parameters.

Xu, Donghua; Wirth, Brian D.; Schroers, Jan; Johnson, William L.

2010-07-01

175

A Soybean Proteinase Inhibitor. Thermodynamic and Kinetic Parameters of Association with Enzymes.  

National Technical Information Service (NTIS)

Examination of the thermodynamic parameters and activation energies for the association of the Bowman-Birk soybean proteinase inhibitor with trypsin and with chymotrypsin suggests that conformational changes may occur upon association. The data suggest th...

J. B. Harry R. F. Steiner

1970-01-01

176

Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile/buffer mobile phases  

SciTech Connect

The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at 25 {+-} 2 C. The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this distribution, the adsorption data were modeled using a tri-Langmuir isotherm equation and the best estimates of the isotherm parameters were determined. The intraparticle mass transfer parameters were derived by comparing the profiles of experimental overloaded bands and the profiles calculated using the isotherm model and the lumped pore diffusion (POR) model of chromatography. These results showed that different adsorption and mass transfer mechanisms exist in mobile phases made of acetonitrile/aqueous buffer and of acetonitrile/acetic acid solutions.

Kim, Hyunjung [University of Tennessee, Knoxville (UTK); Kaczmarski, Krzysztof [University of Tennessee and Rzeszow University of Technology, Poland; Guiochon, Georges A [ORNL

2006-03-01

177

First-order kinetic gas generation model parameters for wet landfills  

Microsoft Academic Search

Landfill gas collection data from wet landfill cells were analyzed and first-order gas generation model parameters were estimated for the US EPA landfill gas emissions model (LandGEM). Parameters were determined through statistical comparison of predicted and actual gas collection. The US EPA LandGEM model appeared to fit the data well, provided it is preceded by a lag phase, which on

Ayman A. Faour; Debra R. Reinhart; Huaxin You

2007-01-01

178

Crystallization kinetics of lithium niobate glass: determination of the Johnson-Mehl-Avrami-Kolmogorov parameters.  

PubMed

The formation of crystalline LiNbO3 (LN) from LN glass has been studied by means of differential scanning calorimetry and in situ synchrotron X-ray diffraction. The LN glass with no glass former was prepared by the polymerized complex method. The isothermal kinetics of the crystallization process is described using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation and the Avrami exponent n is found to be ~2.0, indicating that the crystallization mechanism is diffusion-controlled growth with a decreasing nucleation rate. The effective activation energy of crystallization calculated from isothermal measurements is 6.51 eV. It is found that the LN glass directly transforms into a rhombohedral LN crystal without any intermediate crystalline phase and most crystal grains are confined within the size of ~40 nm irrespective of different isothermal temperatures. Application of JMAK theory to the non-isothermal thermoanalytical study of crystallization of LN glass is discussed. PMID:23677338

Choi, H W; Kim, Y H; Rim, Y H; Yang, Y S

2013-05-15

179

Data analysis of the inactivation of foodborne microorganisms under high hydrostatic pressure to establish global kinetic parameters and influencing factors.  

PubMed

The inactivation rate of foodborne microorganisms under high hydrostatic pressure (HHP) is influenced by factors such as substrate, species, strain, temperature, pH, and stage of growth of the cell. In this study, 445 D(P)-values from previously published data were analyzed, including those from bacterial spores, vegetative cells, and yeasts. Three secondary linear inactivation models with pressure and/or temperature as process parameters were tested to estimate global log D(P)-, z(P)-, and z(T)-values, and the influence of these parameters and additional factors was assessed. The results show that significant differences in microbial resistance are mainly the result of temperature, highlighting the need for its inclusion as a process parameter. Perhaps due to the large number of data and very distinct factors, the remaining factors showed no significant differences in microbial resistance, except in the case of Clostridium spp. in soy milk, which showed decreased resistance in this substrate compared with its behavior in other products. These results serve to establish priorities among factors influencing HHP inactivation and to estimate global kinetic parameters as a basis for setting target levels of inactivation. Moreover, they can be used as a benchmark for comparison of microbial HHP inactivation data gathered in future studies. PMID:22186050

Santillana Farakos, Sofía M; Zwietering, Marcel H

2011-12-01

180

Sensitivity analysis of large system of chemical kinetic parameters for engine combustion simulation  

SciTech Connect

In this study, the authors applied the state-of-the art sensitivity methods to downselect system parameters from 4000+ to 8, (23000+ -> 4000+ -> 84 -> 8). This analysis procedure paves the way for future works: (1) calibrate the system response using existed experimental observations, and (2) predict future experiment results, using the calibrated system.

Hsieh, H; Sanz-Argent, J; Petitpas, G; Havstad, M; Flowers, D

2012-04-19

181

Kinetic parameters for the oxidation of pulverised coal as measured from drop tube tests  

Microsoft Academic Search

The methodology for measuring the oxidation parameters for pulverised coal combustion from drop-tube tests is reviewed, and some modifications to the traditional procedure (based on Arrhenius plots) are proposed. The work includes the experimental characterisation of an anthracite's combustion in a drop-tube furnace, which will be used as the reference data. One of the main points in the discussion is

Javier Ballester; Santiago Jiménez

2005-01-01

182

Kinetic Modeling and Parameter Estimation in a Tower Bioreactor for Bioethanol Production  

NASA Astrophysics Data System (ADS)

In this work, a systematic method to support the building of bioprocess models through the use of different optimization techniques is presented. The method was applied to a tower bioreactor for bioethanol production with immobilized cells of Saccharomyces cerevisiae. Specifically, a step-by-step procedure to the estimation problem is proposed. As the first step, the potential of global searching of real-coded genetic algorithm (RGA) was applied for simultaneous estimation of the parameters. Subsequently, the most significant parameters were identified using the Placket-Burman (PB) design. Finally, the quasi-Newton algorithm (QN) was used for optimization of the most significant parameters, near the global optimum region, as the initial values were already determined by the RGA global-searching algorithm. The results have shown that the performance of the estimation procedure applied in a deterministic detailed model to describe the experimental data is improved using the proposed method (RGA-PB-QN) in comparison with a model whose parameters were only optimized by RGA.

Rivera, Elmer Ccopa; da Costa, Aline Carvalho; Lunelli, Betânia Hoss; Maciel, Maria Regina Wolf; Filho, Rubens Maciel

183

Kinetics Parameters of VVER-1000 Core with 3 MOX Lead Test Assemblies To Be Used for Accident Analysis Codes  

SciTech Connect

The present work is a part of Joint U.S./Russian Project with Weapons-Grade Plutonium Disposition in VVER Reactor and presents the neutronics calculations of kinetics parameters of VVER-1000 core with 3 introduced MOX LTAs. MOX LTA design has been studied in [1] for two options of MOX LTA: 100% plutonium and of ''island'' type. As a result, zoning i.e. fissile plutonium enrichments in different plutonium zones, has been defined. VVER-1000 core with 3 introduced MOX LTAs of chosen design has been calculated in [2]. In present work, the neutronics data for transient analysis codes (RELAP [3]) has been obtained using the codes chain of RRC ''Kurchatov Institute'' [5] that is to be used for exploitation neutronics calculations of VVER. Nowadays the 3D assembly-by-assembly code BIPR-7A and 2D pin-by-pin code PERMAK-A, both with the neutronics constants prepared by the cell code TVS-M, are the base elements of this chain. It should be reminded that in [6] TVS-M was used only for the constants calculations of MOX FAs. In current calculations the code TVS-M has been used both for UOX and MOX fuel constants. Besides, the volume of presented information has been increased and additional explications have been included. The results for the reference uranium core [4] are presented in Chapter 2. The results for the core with 3 MOX LTAs are presented in Chapter 3. The conservatism that is connected with neutronics parameters and that must be taken into account during transient analysis calculations, is discussed in Chapter 4. The conservative parameters values are considered to be used in 1-point core kinetics models of accident analysis codes.

Pavlovitchev, A.M.

2000-03-08

184

Batch Tests To Determine Activity Distribution and Kinetic Parameters for Acetate Utilization in Expanded-Bed Anaerobic Reactors  

PubMed Central

Batch tests to measure maximum acetate utilization rates were used to determine the distribution of acetate utilizers in expanded-bed sand and expanded-bed granular activated carbon (GAC) reactors. The reactors were fed a mixture of acetate and 3-ethylphenol, and they contained the same predominant aceticlastic methanogen, Methanothrix sp. Batch tests were performed both on the entire reactor contents and with media removed from the reactors. Results indicated that activity was evenly distributed within the GAC reactors, whereas in the sand reactor a sludge blanket on top of the sand bed contained approximately 50% of the activity. The Monod half-velocity constant (Ks) for the acetate-utilizing methanogens in two expanded-bed GAC reactors was searched for by combining steady-state results with batch test data. All parameters necessary to develop a model with Monod kinetics were experimentally determined except for Ks. However, Ks was a function of the effluent 3-ethylphenol concentration, and batch test results demonstrated that maximum acetate utilization rates were not a function of the effluent 3-ethylphenol concentration. Addition of a competitive inhibition term into the Monod expression predicted the dependence of Ks on the effluent 3-ethylphenol concentration. A two-parameter search determined a Ks of 8.99 mg of acetate per liter and a Ki of 2.41 mg of 3-ethylphenol per liter. Model predictions were in agreement with experimental observations for all effluent 3-ethylphenol concentrations. Batch tests measured the activity for a specific substrate and determined the distribution of activity in the reactor. The use of steady-state data in conjunction with batch test results reduced the number of unknown kinetic parameters and thereby reduced the uncertainty in the results and the assumptions made.

Fox, Peter; Suidan, Makram T.

1990-01-01

185

Yields of clustered DNA damage induced by charged-particle radiations of similar kinetic energy per nucleon: LET dependence in different DNA microenvironments  

SciTech Connect

To determine the linear energy transfer (LET) dependence of the biological effects of densely ionizing radiation in relation to changes in the ionization density along the track, we measured the yields and spectrum of clustered DNA damages induced by charged particles of different atomic number but similar kinetic energy per nucleon in different DNA microenvironments. Yeast DNA embedded in agarose in solutions of different free radical scavenging capacity was irradiated with 1 GeV protons, 1 GeV/nucleon oxygen ions, 980 MeV/nucleon titanium ions or 968 MeV/nucleon iron ions. The frequencies of double-strand breaks (DSBs), abasic sites and oxypurine clusters were quantified. The total DNA damage yields per absorbed dose induced in non-radioquenching solution decreased with LET, with minor variations in radioquenching conditions being detected. However, the total damage yields per particle fluence increased with LET in both conditions, indicating a higher efficiency per particle to induce clustered DNA damages. The yields of DSBs and non-DSB clusters as well as the damage spectra varied with LET and DNA milieu, suggesting the involvement of more than one mechanism in the formation of the different types of clustered damages.

Keszenman, D.J.; Sutherland, B. M.

2010-08-01

186

Substrate specificity and kinetic parameters of GLUT3 in rat cerebellar granule neurons.  

PubMed Central

This study examines the apparent affinity, catalytic-centre activity ("turnover number') and stereospecificity of the neuronal glucose transporter GLUT3 in primary cultured cerebellar granule neurons. Using a novel variation of the 3-O-[14C]methylglucose transport assay, by measuring zero-trans kinetics at 25 degrees C, GLUT3 was determined to be a high-apparent-affinity, high-activity, glucose transporter with a K(m) of 2.87 +/- 0.23 mM (mean +/- S.E.M.) for 3-O-methylglucose, a Vmax of 18.7 +/- 0.48 nmol/min per 10(6) cells, and cells, and a corresponding catalytic-centre activity of 853 s-1. Transport of 3-O-methylglucose was competed by glucose, mannose, 2-deoxyglucose and galactose, but not by fructose. This methodology is compared with the more common 2-[3H]deoxyglucose methodology and the [U-14C]-glucose transport method. The high affinity and transport activity of the neuronal glucose transporter GLUT3 appears to be an appropriate adaptation to meet the demands of neuronal metabolism at prevailing interstitial brain glucose concentrations (1-2 mM).

Maher, F; Davies-Hill, T M; Simpson, I A

1996-01-01

187

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

PubMed

In this research two types of electrochemical reactors for the treatment of simulated wastewaters containing Direct blue 71 azo dye (DB71) were used: (1) Laboratory scale undivided electrolysis cell system (450 mL volume) with one 2 cm x 2 cm platinum plate as the anode placed in the middle of the cell and two 2 cm x 8 cm steel plates (SS-304) as cathodes placed in the sides of the cell 2 cm from the central anode. (2) Pilot scale reactor (9L volume), equipped with two 3 cm x 23 cm stainless steel plates as anode and cathode, with distance of 3 cm apart. The influence of supporting electrolyte, applied voltage and pH were studied. The UV-vis spectra of samples during the electrochemical oxidation showed the rapid decolorization of the dye solution. During the process, the COD and current were measured in order to evaluate the degree of mineralization, energy consumption, current and anode efficiencies. The optimum supporting electrolyte and applied voltage were NaCl (5 g L(-1)) and 15 V. Using the lab scale reactor resulted in complete decolorization and mineralization of the dye solutions after ca. 90 and 120 min, respectively. Similar results were obtained using the pilot plant reactor under the same conditions. The good fit of the data to pseudo-first-order kinetics for COD removal at all applied voltages (except 20 V) was taken as proof of the involvement of indirect oxidation pathways in the process. PMID:19345003

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

2009-03-09

188

Kinetic parameters for high density lipoprotein apoprotein AI and cholesteryl ester transport in the hamster.  

PubMed Central

These studies were undertaken to determine the kinetic characteristics of high density lipoprotein (HDL) apo AI and cholesteryl ester transport in the hamster in vivo. Saturable HDL apo AI transport was demonstrated in the kidneys, adrenal glands, and liver. Saturable HDL cholesteryl ester transport was highest in the adrenal glands and liver. In the liver and adrenal glands, maximal transport rates (J(m)) for receptor dependent uptake were similar for the protein and cholesteryl ester moieties; however, the concentration of HDL necessary to achieve half-maximal transport (K(m)) was 20- to 30-fold higher for apo AI. Consequently, at normal plasma HDL concentrations, the clearance of HDL cholesteryl ester exceeded that of HDL apo AI by approximately 10-fold in the adrenal glands and by approximately fivefold in the liver. At normal HDL concentrations, the majority of HDL cholesteryl ester (76%) was cleared by the liver whereas the majority of HDL apo AI (77%) was cleared by extrahepatic tissues. The rate of HDL cholesteryl ester uptake by the liver equaled the rate of cholesterol acquisition by all extrahepatic tissues suggesting that HDL cholesteryl ester uptake by the liver accurately reflects the rate of "reverse cholesterol transport." Receptor dependent HDL cholesteryl ester uptake by the liver was maximal (saturated) at normal plasma HDL concentrations. Consequently, changes in plasma HDL concentrations are not accompanied by parallel changes in the delivery of HDL cholesteryl ester to the liver unless the number or affinity of transporters is also regulated.

Woollett, L A; Spady, D K

1997-01-01

189

Quantifiable patterns of limb loading and unloading during hemiparetic gait: Relation to kinetic and kinematic parameters.  

PubMed

Persons with poststroke hemiparesis are characterized by asymmetry in limb loading (LL) and limb unloading (LU), which has been reported in static and quasi-static tasks but has not been quantified during walking. The purpose of this study was to determine the asymmetry in magnitude and duration of LL and LU in individuals with hemiparesis and its relationship with functional walking status and specific kinematic and kinetic variables during walking. Forty-four participants with chronic hemiparesis walked at their self-selected speeds and eighteen nondisabled control subjects of similar ages walked at predetermined matched speeds while three-dimensional ground reaction forces and body-segment kinematics were recorded. Magnitude of paretic LL was reduced, while duration was increased compared with the nonparetic leg and nondisabled controls walking at matched speeds. The paretic LL and LU was significantly correlated with average leg angle, while the nonparetic leg significantly correlated with average knee angle. Three different patterns of LL and LU were identified (concave, convex, and linear). Individuals with hemiparesis make several biomechanical adjustments that minimize LL of the paretic leg. LL deviations were more pronounced with increased lateral placement of the paretic foot and with decreased functional gait speed. Characterization of these deviations may inspire new strategies for rehabilitation. PMID:23408212

Raja, Bhavana; Neptune, Richard R; Kautz, Steven A

2012-12-01

190

Model-based blind estimation of kinetic parameters in dynamic contrast enhanced (DCE)-MRI.  

PubMed

A method to simultaneously estimate the arterial input function (AIF) and pharmacokinetic model parameters from dynamic contrast-enhanced (DCE)-MRI data was developed. This algorithm uses a parameterized functional form to model the AIF and k-means clustering to classify tissue time-concentration measurements into a set of characteristic curves. An iterative blind estimation algorithm alternately estimated parameters for the input function and the pharmacokinetic model. Computer simulations were used to investigate the algorithm's sensitivity to noise and initial estimates. In 12 patients with sarcomas, pharmacokinetic parameter estimates were compared with "truth" obtained from model regression using a measured AIF. When arterial voxels were included in the blind estimation algorithm, the resulting AIF was similar to the measured input function. The "true" K(trans) values in tumor regions were not significantly different than the estimated values, 0.99 +/- 0.41 and 0.86 +/- 0.40 min(-1), respectively, P = 0.27. "True" k(ep) values also matched closely, 0.70 +/- 0.24 and 0.65 +/- 0.25 min(-1), P = 0.08. When only tissue curves free of significant vascular contribution are used (v(p) < 0.05), the resulting AIF showed substantial delay and dispersion consistent with a more local AIF such as has been observed in dynamic susceptibility contrast imaging in the brain. PMID:19859949

Fluckiger, Jacob U; Schabel, Matthias C; Dibella, Edward V R

2009-12-01

191

3 Tesla Dynamic Contrast Enhanced Magnetic Resonance Imaging of the Breast: Pharmacokinetic Parameters versus Conventional Kinetic Curve Analysis  

PubMed Central

Purpose To evaluate the incremental value of pharmacokinetic analysis of dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI) compared to conventional breast MRI (morphology plus kinetic curve type analysis) in characterizing breast lesions as malignant or benign. Patients and Methods The study was approved by our institutional review board. Patients underwent 3D high resolution T1 (3DT1) contrast enhanced MRI and dynamic contrast enhancement (DCE) MRI at 3T, and had pathology proven diagnosis (95%) or more than 2 years follow up confirming lesion stability (5%). Lesions were identified using the high-spatial resolution post-contrast MRI. Morphologic features (margin, enhancement pattern) and conventional DCE-MRI results (kinetic curve types I, II or III) or pharmacokinetic parameters (wash-in rate Ktrans, washout rate Kep, and leakage space volume Ve), were included in multivariate models for prediction of benign versus malignant diagnosis. Results 95 patients with 101 lesions were included: 52% of patients were pre-menopausal and 48% post-menopausal. Sixty eight lesions (67.3%) were malignant and 33 (32.7%) were benign. There was a significant association between Ktrans and Kep and the diagnosis of benign versus malignant (p<0.001). The AUC for morphologic features (lesion margin and enhancement pattern) was 0.85, while inclusion of Ktrans or Kep in the model showed similar modest improvement in performance (AUC, 0.88–0.89). Conclusion The use of kinetic curve type assessment or pharmacokinetic modeling in conjunction with high resolution 3D breast MRI appears to offer similar improvement in diagnostic performance..

El Khouli, Riham H.; Macura, Katarzyna J.; Kamel, Ihab R.; Jacobs, Michael A.; Bluemke, David A.

2012-01-01

192

Effects of pH on kinetic parameters of the Na-HCO3 cotransporter in renal proximal tubule.  

PubMed Central

The effects of pH on cotransporter kinetics were studied in renal proximal tubule cells. Cells were grown to confluence on permeable support, mounted in an Ussing-type chamber, and permeabilized apically to small monovalent ions with amphotericin B. The steady-state, dinitrostilbene-disulfonate-sensitive current (DeltaI) was Na+ and HCO3- dependent and therefore was taken as flux through the cotransporter. When the pH of the perfusing solution was changed between 6.0 and 8.0, the conductance attributable to the cotransporter showed a maximum between pH 7.25 and pH 7.50. A similar profile was observed in the presence of a pH gradient when the pH of the apical solutions was varied between 7.0 and 8.0 (basal pH lower by 1), but not when the pH of the basal solution was varied between 7.0 and 8.0 (apical pH lower by 1 unit). To delineate the kinetic basis for these observations, DeltaI-voltage curves were obtained as a function of Na+ and HCO3- concentrations and analyzed on the basis of a kinetic cotransporter model. Increases in pH from 7.0 to 8.0 decreased the binding constants for the intracellular and extracellular substrates by a factor of 2. Furthermore, the electrical parameters that describe the interaction strength between the electric field and substrate binding or charge on the unloaded transporter increased by four- to fivefold. These data can be explained by a channel-like structure of the cotransporter, whose configuration is modified by intracellular pH such that, with increasing pH, binding of substrate to the carrier is sterically hindered but electrically facilitated.

Gross, E; Hopfer, U

1999-01-01

193

Morphological Manipulation of Solvothermal Prepared CdSe Nanostructures by Controlling the Growth Rate of Nanocrystals as a Kinetic Parameter  

NASA Astrophysics Data System (ADS)

The morphological manipulation, structural characterization, and optical properties of different cadmium selenide (CdSe) nanostructures are reported. Two different CdSe nanostructures, i.e., nanorods and nanoparticles, were grown by controlling the concentration of precursors (i.e., cadmium nitrate and selenium dioxide) in ethanolamine solvent. By manipulating the kinetic parameter of the process (i.e., growth rate) under constant growth driving force (i.e., degree of supersaturation), the morphology of CdSe nanostructures can be tailored from nanorods to nanoparticles. The optical properties of CdSe nanostructures were investigated using ultraviolet-visible (UV-vis) spectroscopy. The absorption edge of the samples showed a blue-shift. CdSe nanostructures prepared under optimized conditions showed good microstructural and optical properties for solar cell applications.

Zarghami, V.; Mohammadi, M. R.; Fray, D. J.

2012-11-01

194

Influence of the silica module of pentasils on diffusion and kinetics parameters in the reaction of xylene isomerization  

SciTech Connect

The influence of the acidity of pentasils on the values of both kinetic and diffusion parameters of xylene isomerization is studied. True rate constants and activation energies for xylene isomerization, adsorption coefficients and heats of adsorption of active sites, diffusivities and activation energies for diffusion of o- and p-xylenes are measured for pentasils with the silica module (SiO{sub 2}/Al{sub 2}O{sub 3}) values ranging from 37 to 111. The rise in the module value leads to a decrease of catalytic activity. A noticeable fall in both activation energies and adsorption heats is observed only upon the module rise from 55 to 111. Diffusivities of xylenes decrease upon increasing of the module, but the change in diffusion activation energies is insignificant.

Yushchenko, V.V.; Romanovskii, B.V. [Moscow State Univ. (Russian Federation)

1994-09-01

195

Simultaneous versus sequential optimal experiment design for the identification of multi-parameter microbial growth kinetics as a function of temperature.  

PubMed

Optimal experiment design for parameter estimation (OED/PE) has become a popular tool for efficient and accurate estimation of kinetic model parameters. When the kinetic model under study encloses multiple parameters, different optimization strategies can be constructed. The most straightforward approach is to estimate all parameters simultaneously from one optimal experiment (single OED/PE strategy). However, due to the complexity of the optimization problem or the stringent limitations on the system's dynamics, the experimental information can be limited and parameter estimation convergence problems can arise. As an alternative, we propose to reduce the optimization problem to a series of two-parameter estimation problems, i.e., an optimal experiment is designed for a combination of two parameters while presuming the other parameters known. Two different approaches can be followed: (i) all two-parameter optimal experiments are designed based on identical initial parameter estimates and parameters are estimated simultaneously from all resulting experimental data (global OED/PE strategy), and (ii) optimal experiments are calculated and implemented sequentially whereby the parameter values are updated intermediately (sequential OED/PE strategy). This work exploits OED/PE for the identification of the Cardinal Temperature Model with Inflection (CTMI) (Rosso et al., 1993). This kinetic model describes the effect of temperature on the microbial growth rate and encloses four parameters. The three OED/PE strategies are considered and the impact of the OED/PE design strategy on the accuracy of the CTMI parameter estimation is evaluated. Based on a simulation study, it is observed that the parameter values derived from the sequential approach deviate more from the true parameters than the single and global strategy estimates. The single and global OED/PE strategies are further compared based on experimental data obtained from design implementation in a bioreactor. Comparable estimates are obtained, but global OED/PE estimates are, in general, more accurate and reliable. PMID:20064532

Van Derlinden, E; Bernaerts, K; Van Impe, J F

2010-01-11

196

Estimation of transport and degradation parameters for naphthalene and anthracene: influence of mass transfer on kinetics.  

PubMed

The method of temporal moment solutions (MOM) for one-dimensional convective-dispersive solute transport involving linear equilibrium sorption and first-order degradation for time pulse sources has been applied to analyze experimental data from a soil microcosm reactor. Estimation of the pore water velocity V for a nonreactive solute was aided by the use of only the first normalized moment while the dispersion coefficient D, first-order degradation rate constant lambda, and the retardation factor R were estimated using both first and second normalized moments. These transport and degradation parameters were compared to those obtained by a transport model using a nonlinear least square curve-fitting program CXTFIT (version 2.0). Results obtained showed that the MOM fits the breakthrough curve with tailing better than the CXTFIT. The initial estimates of these parameters aided the reduction of the dimensionality of the search process of the non- steady-state model. A residual concentration of 1.12E-5 and 1.48 mg/l for naphthalene and 7.67E-4 and 1.61 mg/l for anthracene, in the axial and radial directions, respectively, suggests the preference of naphthalene during the biodegradation process. The surface concentration as depicted using three-dimensional plots showed that there is occlusion of the aromatics (naphthalene and anthracene) within the soil micropores, thereby limiting their bioavailability and in the long run increasing their toxicity. PMID:19911293

Owabor, Chiedu N; Ogbeide, Samuel E; Susu, Alfred A

2009-11-13

197

Mild hydrocracking of bitumen-derived coker and hydrocracker heavy gas oils; Kinetics, product yields, and product properties  

SciTech Connect

The authors describe bitumen-derived coker and hydrocracker heavy gas oils hydrotreated at 350-400{sup 0}C, 7-11 MPa, 0.7-1.5h/sup -1/ LHSV, and 600 S m/sup 3/ of H/sub 2//m/sup 3/ of feed in a pilot-scale trickle-bed reactor, over presulfided commercial NiMo/Al/sub 2/O/sub 3/ catalysts. The conversion of HGO materials (343+ {sup 0}C) in feed to naphtha (195- {sup 0}C) and LGO (195/343 {sup 0}C) was determined by gas chromatographic simulated distillation. The degree of conversion was analyzed with modified first-order kinetics, which incorporate power terms for LHSV and hydrogen partial pressure. The equations were based on three cracking schemes; parallel, consecutive, and combined parallel-consecutive conversion.

Yui, S.M.; Sanford, E.C. (Research Dept., Syncrude Canada Ltd., PO Box 5790, Edmonton, Alberta (CA))

1989-09-01

198

The Effects of Different Primary Colored Polyethylene (PE) Covers on Yield and Quality Parameters of Tomato (Lycopersicon esculentum L.) Grown in Low Tunnels  

Microsoft Academic Search

This study was conducted in the Research and Practice Farm of Suleyman Demirel University Faculty of Agriculture in order to determine the effects of different primary colored polyethylene (PE) covers on yield and quality parameters in tomato. Violet, blue, green, yellow, orange and red PE with transparent covers and open field conditions were compared using Bahgera F1 tomato cultivar. The

Hüsnü ÜNLÜ; Halime ÖZDAMAR ÜNLÜ; Hüseyin PADEM

199

The Effects of Dietary Yucca Schidigera on Egg Yield Parameters and Egg Shell Quality of Laying Japanese Quails (Coturnix coturnix japonica)  

Microsoft Academic Search

The present study was carried out to determine whether dietary Yucca schidigera powder would affect egg yield parameters and egg shell quality of laying Japanese quail (Coturnix coturnix Japonica). In this study, 30 female Japanese quails were used. The experimental quails were divided into two dietary treatment groups of similar mean weight comprising 30 birds each, which was divided into

2005-01-01

200

Impact of Organic Matter and Method of Addition on Selected Soil Parameters, Growth and Yields of Mungbean Grown an a Minor Season in the Humid Tropics  

Microsoft Academic Search

A field experiment was conducted over a minor (dry) season to ascertain the impact of two organic materials (Gliricidia leaves and rice straw) applied as a surface mulch or incorporated into the root zone, on selected soil parameters, growth, nodulation and yields of mung bean (Vigna radiata L. R. Wilcz). The beneficial effects were compared to soils and the growth

U. R. Sangakkara; G Pietsch; M. Gollner; B. Freyer

201

EFFECTS OF SILICON ON YIELD CONTRIBUTING PARAMETERS AND ITS ACCUMULATION IN ABAXIAL EPIDERMIS OF SUGARCANE LEAF BLADES USING ENERGY DISPERSIVE X-RAY ANALYSIS  

Microsoft Academic Search

Effects of silicon (Si), supplied as calcium silicate (Ca-silicate) fertilizer on yield contributing parameters in sugarcane like chlorophyll content, gas exchange characteristics, leaf nutrient concentrations and its effects on soil fertility were evaluated. Seven rates of Ca-silicate (0, 20, 40, 60, 80, 120 and 150 g pot) were applied with traditional fertilizers and plants were grown in a greenhouse. The

S. M. Bokhtiar; Hai-Rong Huang; Yang-Rui Li; V. A. Dalvi

2012-01-01

202

Ethylene metabolism in Pisum sativum L.: Kinetic parameters, the effects of propylene, silver and carbon dioxide and comparison with other systems  

Microsoft Academic Search

The kinetic parameters of in vivo ethylene metabolism by seedlings of Pisum sativum L. cv. Alaska have been determined. The oxidation of ethylene to CO2, (Ox) and the incorporation of ethylene into the tissue (TI) were both shown to display Michaelis-Menten kinetics (Km Ox = 0.9 × 10-6 M liquid phase, Vmax Ox = 2.4 × 10-10 moles g- dry

D. E. Evans; A. R. Smith; J. E. Taylor; M. A. Halo

1984-01-01

203

Decay kinetics and quantum yields of fluorescence in photosystem I from Synechococcus elongatus with P700 in the reduced and oxidized state: are the kinetics of excited state decay trap-limited or transfer-limited?  

PubMed Central

Transfer and trapping of excitation energy in photosystem I (PS I) trimers isolated from Synechococcus elongatus have been studied by an approach combining fluorescence induction experiments with picosecond time-resolved fluorescence measurements, both at room temperature (RT) and at low temperature (5 K). Special attention was paid to the influence of the oxidation state of the primary electron donor P700. A fluorescence induction effect has been observed, showing a approximately 12% increase in fluorescence quantum yield upon P700 oxidation at RT, whereas at temperatures below 160 K oxidation of P700 leads to a decrease in fluorescence quantum yield ( approximately 50% at 5 K). The fluorescence quantum yield for open PS I (with P700 reduced) at 5 K is increased by approximately 20-fold and that for closed PS I (with P700 oxidized) is increased by approximately 10-fold, as compared to RT. Picosecond fluorescence decay kinetics at RT reveal a difference in lifetime of the main decay component: 34 +/- 1 ps for open PS I and 37 +/- 1 ps for closed PS I. At 5 K the fluorescence yield is mainly associated with long-lived components (lifetimes of 401 ps and 1.5 ns in closed PS I and of 377 ps, 1.3 ns, and 4.1 ns in samples containing approximately 50% open and 50% closed PS I). The spectra associated with energy transfer and the steady-state emission spectra suggest that the excitation energy is not completely thermally equilibrated over the core-antenna-RC complex before being trapped. Structure-based modeling indicates that the so-called red antenna pigments (A708 and A720, i.e., those with absorption maxima at 708 nm and 720 nm, respectively) play a decisive role in the observed fluorescence kinetics. The A720 are preferentially located at the periphery of the PS I core-antenna-RC complex; the A708 must essentially connect the A720 to the reaction center. The excited-state decay kinetics turn out to be neither purely trap limited nor purely transfer (to the trap) limited, but seem to be rather balanced.

Byrdin, M; Rimke, I; Schlodder, E; Stehlik, D; Roelofs, T A

2000-01-01

204

Measurements of fluorescence yield of electrons in air under atmospheric conditions: A key parameter for energy of cosmic rays  

NASA Astrophysics Data System (ADS)

The measurement of the fluorescence yield and its dependence on atmospheric properties such as pressure, temperature or pollutants, are essential to obtain a reliable measurement of the primary energy of cosmic rays. A new type of absolute measurement of the nitrogen fluorescence yield in the air will be performed at LAL using 3 items which will yield an unprecedented precision in all conditions of pressure, temperature, and pollutants. A 5 MeV electron beam will be provided by the new electron accelerator PHIL at LAL(Laboratoire de l'Accélérateur Linéaire, Univ Paris-Sud, CNRS/IN2P3, Orsay). This source will induce florescence yield inside an integrating sphere. The sphere will be surrounded by a spherical envelope to create a temperature controlled chamber (a Dewar). With this setup it will be possible to vary the temperature from -60 C to +40 C and the pressure from 1 to 0.01 atm. An output device on this sphere will be equipped with a set of optical fibers driving the fluorescence light to a Jobin-Yvon spectrometer equipped with an LN_{2} cooled CCD. The fluorescence spectrum in the 300-430 nm range will be accurately measured in steps of 0.1 nm resolution. A PMT equipped with a BG3 filter (the same as on JEM-EUSO) will be set on the sphere to measure the integrated yield. The expected precision of the yield should be better than 5%.

Monnier Ragaigne, D.; Gorodetzky, P.; Blacksley, C.; Wicek, F.; Monard, H.; Dagoret-Campagne, S.

2012-12-01

205

Effects of sulfate reduction on the bacterial community and kinetic parameters of a dechlorinating culture under chemostat growth conditions.  

PubMed

Results are presented from a chemostat study where the reductive dehalogenation of PCE was evaluated in the absence and presence of sulfate. Two chemostats inoculated with the Point Mugu culture, which contains strains of Dehalococcoides mccartyi, were operated at a 50 day HRT and fed PCE (1.12 mM) and lactate (4.3 mM). The control chemostat (PM-5L, no sulfate), achieved pseudo-steady-state transformation of PCE to ethene (98%) and VC (2%) at 2.4 nM of H(2). Batch kinetic tests with chemostat harvested cells showed the maximum rate (k(max)X) value for each dehalogenation step remained fairly constant, while hupL clone library analyses showed maintenance of a diverse D. mccartyi community. Sulfate (1 mM) was introduced to the second chemostat, PM-2L. Effective sulfate reduction was achieved 110 days later, resulting in 600 ?M of total sulfide. PCE dechlorination efficiency decreased following complete sulfate reduction, yielding ethene (25%), VC (67%), and cis-DCE (8%). VC dechlorination was most affected, with k(max)X values decreasing by a factor of 50. The decrease was associated with the enrichment of the Cornell group of D. mccartyi and decline of the Pinellas group. Long-term exposure to sulfides and/or competition for H(2) may have been responsible for the community shift. PMID:23316874

Berggren, Dusty R V; Marshall, Ian P G; Azizian, Mohammad F; Spormann, Alfred M; Semprini, Lewis

2013-01-28

206

HIV-1 polymerase inhibition by nucleoside analogs: cellular- and kinetic parameters of efficacy, susceptibility and resistance selection.  

PubMed

Nucleoside analogs (NAs) are used to treat numerous viral infections and cancer. They compete with endogenous nucleotides (dNTP/NTP) for incorporation into nascent DNA/RNA and inhibit replication by preventing subsequent primer extension. To date, an integrated mathematical model that could allow the analysis of their mechanism of action, of the various resistance mechanisms, and their effect on viral fitness is still lacking. We present the first mechanistic mathematical model of polymerase inhibition by NAs that takes into account the reversibility of polymerase inhibition. Analytical solutions for the model point out the cellular- and kinetic aspects of inhibition. Our model correctly predicts for HIV-1 that resistance against nucleoside analog reverse transcriptase inhibitors (NRTIs) can be conferred by decreasing their incorporation rate, increasing their excision rate, or decreasing their affinity for the polymerase enzyme. For all analyzed NRTIs and their combinations, model-predicted macroscopic parameters (efficacy, fitness and toxicity) were consistent with observations. NRTI efficacy was found to greatly vary between distinct target cells. Surprisingly, target cells with low dNTP/NTP levels may not confer hyper-susceptibility to inhibition, whereas cells with high dNTP/NTP contents are likely to confer natural resistance. Our model also allows quantification of the selective advantage of mutations by integrating their effects on viral fitness and drug susceptibility. For zidovudine triphosphate (AZT-TP), we predict that this selective advantage, as well as the minimal concentration required to select thymidine-associated mutations (TAMs) are highly cell-dependent. The developed model allows studying various resistance mechanisms, inherent fitness effects, selection forces and epistasis based on microscopic kinetic data. It can readily be embedded in extended models of the complete HIV-1 reverse transcription process, or analogous processes in other viruses and help to guide drug development and improve our understanding of the mechanisms of resistance development during treatment. PMID:22275860

von Kleist, Max; Metzner, Philipp; Marquet, Roland; Schütte, Christof

2012-01-19

207

Use of extant kinetic parameters to predict effluent concentrations of specific organic compounds at full-scale facilities.  

PubMed

To use the results of kinetic tests to predict effluent concentrations of specific contaminants in activated sludge systems, the fraction of the biomass that has an ability to degrade the test compound (i.e., competent biomass) must be estimated. A calibration procedure was developed to assess the competent biomass concentration because the chemical oxygen demand (COD) fraction tended to underestimate the degrading fraction for three of the four test compounds. Acetone, for instance, had a measured influent COD fraction of 0.08%, and the actual competent fraction was estimated to be 2.3%, based on the model calibration. Once the competent biomass fraction in the mixed liquor was determined, the extant kinetic parameters were subsequently used to predict activated sludge system performance. Predicted effluent concentrations were within 2, 5, and 16% of the average measured concentrations for acetone, linear alkylbenzene sulfonate, and furfural, respectively. Day-to-day predictions for these compounds were less accurate, possibly because of the non-steady-state nature of the activated sludge systems studied. The difference between the fraction of the influent COD contributed by the target compounds and the competent biomass fraction in the mixed liquor was found to be more significant when the target compound contributed less than 1% of the influent organic matter. The chemical structure of the target compound and chemical composition of the influent likely had an effect on the resulting competent biomass concentration. The total maximum growth rate, microX, was observed to be independent of the influent concentration of acetone and furfural, thus suggesting that the competent biomass concentration for these compounds was not affected by the changes in their influent concentrations. Consequently, a majority of competent biomass growth resulted from the degradation of other substrates, resulting in a competent biomass concentration significantly higher than predicted based on the influent COD fraction contributed by the test compound. PMID:15523790

Ellis, Timothy G; Eliosov, Boris

208

Determination of creatine kinase kinetic parameters in rat brain by NMR magnetization transfer. Correlation with brain function.  

PubMed

The pseudo first-order rate constant kf of the creatine kinase (CK) forward reaction as well as the CK forward flux FCK,f have been shown to correlate better with cardiac performance than the steady-state levels of ATP and PCr (Bittl, J. A., and Ingwall, J. S. (1985) J. Biol. Chem. 260, 3512-3517). In order to elucidate the relationship between the CK kinetic parameters and brain activity, we have determined, using the non-invasive NMR technique of magnetization transfer, kf and FCK,f in rats, in which brain activity was experimentally varied by administration of either thiopental sodium or bicuculline to decrease or increase electro-encephalogram (EEG) intensity, respectively. The steady-state levels of ATP and PCr, as well as the accumulation of deoxyglucose 6-phosphate (DG-6P) in brain following intraperitoneal administration of deoxyglucose, were determined simultaneously by the NMR technique, whereas the cortical EEG was recorded in a separate experiment. The EEG intensity (range, 1-20 Hz), taken as a measure for brain performance, as well as the amount of DG-6P formed in brain, reflecting the synthesis rate of high energy phosphates (ATP and PCr), linearly correlated with kf. Despite large changes in both EEG intensity (50-250%) and kf (0.12-0.69 s-1) between thiopental sodium- and bicuculline-treated rats, the ATP levels remained constant, whereas the PCr levels decreased with high EEG activity. In contrast to the expectation based on model calculations of CK kinetics, the PCr levels did not increase above control values at reduced EEG intensity (50% of controls). At EEG intensities exceeding control values (bicuculline-treated rats) FCK,f increased as predicted by CK equilibrium. In conclusion, we have shown that in the rat brain, like in the heart, the CK forward rate constant kf, in contrast to ATP and PCr levels, is a sensitive reliable indicator of both increased and reduced function. PMID:8514755

Sauter, A; Rudin, M

1993-06-25

209

The effect of two different loading schemes and recovery types on kinematic and kinetic parameters in squat exercise  

Microsoft Academic Search

Understanding the kinematic and kinetic determinants associated with resistanceloading schemes is crucial to maximise neuromuscular adaptations especially musclehypertrophy to resistance training. The main purposes of this research was to determinewhether loading the muscle with lighter load-higher velocity movements would providesimilar or superior kinematics and kinetics to more traditional loading, heavy load-slowvelocity. In addition to understanding the kinematics and kinetics associated

Nur I. Mohamad

2010-01-01

210

Estimates of Genetic Parameters for a Test Day Model with Random Regressions for Yield Traits of First Lactation Holsteins  

Microsoft Academic Search

A model that contains both fixed and random linear regressions is described for analyzing test day records of dairy cows. Estimation of the variances and covariances for this model was achieved by Bayesian methods utilizing the Gibbs sampler to generate sam- ples from the marginal posterior distributions. A single-trait model was applied to yields of milk, fat, and protein of

J. Jamrozik; L. R. Schaeffer

1997-01-01

211

Estimation of genetic parameters for daily milk yield of primiparous Ayrshire cows by random regression test-day models  

Microsoft Academic Search

Test-day data comprising of 63,331 test-day milk records of 6310 primiparous Finnish Ayrshire cows were used to estimate genetic parameters for daily milk production. Two alternative random regression (RR) sub-models were used to describe breeding values for the shape of lactation curves of individual cows: a five parameter logarithmic polynomial (ASM) or a normalised third order orthogonal polynomial. Permanent environment

Anne Kettunen; Esa A. Mäntysaari; Jukka Pösö

2000-01-01

212

Infrared warming reduced winter wheat yields and some physiological parameters, which were mitigated by irrigation and worsened by delayed sowing.  

PubMed

Winter wheat has a central role in ensuring the food security and welfare of 1.3 billion people in China. Extensive previous studies have concluded that winter wheat yields would decrease with higher temperatures, owing to warming-induced soil drying or shortening of phenophase. Temperature in China is predicted to increase by 1-5°C by 2100, which may greatly impact plant production and cause other negative effects. We performed a manipulative field experiment, creating diverse growth regimes for wheat by infrared radiation (IR) warming day and night, including IR warming only (DW), IR warming + delayed sowing dates (DS), IR warming + increased irrigation (IW), and a control (CK). The results show that IR warming increased daily average wheat canopy and soil temperatures by 2.0°C and 2.3°C, respectively. DW was associated with an advanced maturity of 10 days and yield reduction of 8.2%. IR-warming effects on the photosynthetic apparatus of wheat varied with season as well as significant differences were found in the booting stage. DS represented a worsened situation, lowering yield per plant by 16.4%, with a significant decline in aboveground biomass and functional leaf area. Wheat under DS showed double-peak patterns of diurnal gas exchange during booting stages and, consequently, lower photosynthetic capacity with high transpiration for cooling. Significantly lower actual water use efficiency and intrinsic water use efficiency from jointing to anthesis stages were also found under DS. However, IW had no significant difference from CK, irrespective of yield and photosynthesis. Therefore, we concluded that delayed sowing date may not be a good choice for winter wheat, whereas a thoroughly-watered wheat agroecosystem should be promoted in the context of global warming. PMID:23874424

Fang, Shibo; Su, Hua; Liu, Wei; Tan, Kaiyan; Ren, Sanxue

2013-07-09

213

Carbon reaction and diffusion on Ni(111), Ni(100), and Fe(110): Kinetic parameters from x-ray photoelectron spectroscopy and density functional theory analysis  

SciTech Connect

This paper investigates the reactivity of elemental carbon films deposited from the vapor phase with Fe and Ni substrates at room temperature. X-ray photoelectron spectroscopy (XPS) measurements are presented as a method for evaluating kinetic reaction data. Carbon films are deposited on different surface orientations representing geometries from a dense atom packing as in fcc (111) to an open surface structure as in fcc (100). During annealing experiments several reactions are observed (carbon subsurface diffusion, carbide formation, carbide decomposition, and graphite ordering). These reactions and the respective kinetic parameters are analyzed and quantified by XPS measurements performed while annealing at elevated temperatures (620-820 K). The resulting activation barriers for carbon subsurface diffusion are compared with calculated values using the density functional theory. The determined kinetic parameters are used to reproduce the thermal behavior of carbon films on nickel surfaces.

Wiltner, A.; Linsmeier, Ch. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching b. Muenchen (Germany); Jacob, T. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

2008-08-28

214

Scale-up effects on kinetic parameters and on predictions of a yeast recycle continuous ethanol fermentation model incorporating loss of cell viability  

Microsoft Academic Search

The scale-up effects on kinetic parameters and on predictions of a yeast recycle continuous ethanol fermentation model incorporating loss of cell viability were evaluated. The average level of cell viability estimated for large scale was similar to that estimated for small scale, although with a major standard deviation. The values of specific rate of cell viability loss were equal for

S. C. Oliveira; H. F. De Castro; A. E. S. Visconti; R. Giudici

2000-01-01

215

Using peak properties of a DTG curve to estimate the kinetic parameters of the pyrolysis reaction: application to high density polyethylene  

Microsoft Academic Search

This paper introduces the peak property method (PPM) which can concurrently estimate the three kinetic parameters (reaction order, activation energy, and pre-exponential factor) of a pyrolysis reaction from a single derivative thermogravimetry (DTG) curve. A key assumption of the PPM is that a specific combination of three peak properties (peak temperature, peak height, and conversion at peak temperature) of a

Seungdo Kim; Eun-Suk Jang; Dae-Hyun Shin; Kyong-Hwan Lee

2004-01-01

216

Effect of Simultaneous Inoculation with Yeast and Bacteria on Fermentation Kinetics and Key Wine Parameters of Cool-Climate Chardonnay  

PubMed Central

Inoculating grape musts with wine yeast and lactic acid bacteria (LAB) concurrently in order to induce simultaneous alcoholic fermentation (AF) and malolactic fermentation (MLF) can be an efficient alternative to overcome potential inhibition of LAB in wines because of high ethanol concentrations and reduced nutrient content. In this study, the simultaneous inoculation of yeast and LAB into must was compared with a traditional vinification protocol, where MLF was induced after completion of AF. For this, two suitable commercial yeast-bacterium combinations were tested in cool-climate Chardonnay must. The time courses of glucose and fructose, acetaldehyde, several organic acids, and nitrogenous compounds were measured along with the final values of other key wine parameters. Sensory evaluation was done after 12 months of storage. The current study could not confirm a negative impact of simultaneous AF/MLF on fermentation success and kinetics or on final wine parameters. While acetic acid concentrations were slightly increased in wines after simultaneous AF/MLF, the differences were of neither practical nor legal significance. No statistically significant differences were found with regard to the final values of pH or total acidity and the concentrations of ethanol, acetaldehyde, glycerol, citric and lactic acids, and the nitrogen compounds arginine, ammonia, urea, citrulline, and ornithine. Sensory evaluation by a semiexpert panel confirmed the similarity of the wines. However, simultaneous inoculation led to considerable reductions in overall fermentation durations. Furthermore, differences of physiological and microbiological relevance were found. Specifically, we report the vinification of “super-dry” wines devoid of glucose and fructose after simultaneous inoculation of yeast and bacteria.

Jussier, Delphine; Dube Morneau, Amelie; Mira de Orduna, Ramon

2006-01-01

217

Photooxidation of benzene-structured compounds: influence of substituent type on degradation kinetic and sum water parameters.  

PubMed

The combined influence of substituent type and UV/H(2)O(2) process parameters on the degradation of four aromatic water pollutants was investigated using modified 3(3) full factorial design and response surface methodology. Degradation kinetics was described by the quadratic polynomial model. According to the applied ANOVA, besides pH and [H(2)O(2)], model terms related with the pollutant structure are found to be significant. Different optimal operating conditions and values of observed degradation rate constants were determined for each of the pollutants indicating that the type of substituent influences the overall process effectiveness over structurally defined degradation pathway. Biodegradability (BOD(5)/COD) and toxicity (TU) were evaluated prior to the treatment and at the reference time intervals t(1/2)(P), t(3/4)(P), t(1/4)(OC) and t(1/2)(OC) corresponding to the real time required to reduce the concentration of parent pollutant and organic content for 1/2, 3/4, 1/4 and 1/2 of initial amount. The observed differences are correlated to the structural differences of studied aromatics. PMID:22463859

Juretic, Daria; Kusic, Hrvoje; Koprivanac, Natalija; Loncaric Bozic, Ana

2012-03-15

218

Comparison of dual-echo DSC-MRI- and DCE-MRI-derived contrast agent kinetic parameters  

PubMed Central

The application of dynamic susceptibility contrast (DSC) MRI methods to assess brain tumors is often confounded by the extravasation of contrast agent (CA). Disruption of the blood–brain barrier allows CA to leak out of the vasculature leading to additional T1, T2 and T2? relaxation effects in the extravascular space, thereby affecting the signal intensity time course in a complex manner. The goal of this study is to validate a dual-echo DSC-MRI approach that separates and quantifies the T1 and T2? contributions to the acquired signal and enables the estimation of the volume transfer constant, Ktrans, and the volume fraction of the extravascular extracellular space, ?e. To test the validity of this approach, DSC-MRI- and dynamic contrast enhanced (DCE) MRI-derived Ktrans and ?e estimates were spatially compared in both 9L and C6 rat brain tumor models. A high degree of correlation (concordance correlation coefficients >0.83, Pearson's r>0.84) and agreement was found between the DSC-MRI- and DCE-MRI-derived measurements. These results indicate that dual-echo DSC-MRI can be used to simultaneously extract reliable DCE-MRI kinetic parameters in brain tumors in addition to conventional blood volume and blood flow metrics.

Quarles, C. Chad; Gore, John C.; Xu, Lei; Yankeelov, Thomas E.

2012-01-01

219

NIRS-aided monitoring and prediction of biogas yields from maize silage at a full-scale biogas plant applying lumped kinetics.  

PubMed

The aim of this study was to apply near-infrared spectroscopy (NIRS), available biogas plant data and lumped degradation kinetics to predict biogas production (BPr) of maize silage. A full-scale agricultural biogas plant was equipped with NIRS-metrology at the feeding station. Continuously NIR-spectra were collected for 520 d. Substrate samples were analyzed by means of feedstuff analysis. Biogas potential of the samples was calculated from the laboratory analysis results and for a sample-subset practically assessed by "Hohenheim biogas tests". NIRS-regression-models for all mentioned parameters were calibrated. Continuously gathered spectra, NIRS-models, actual plant-feeding data and degradation kinetics were used to calculate time-series of theoretically expectable BPr. Results were validated against measured gas quantity. Determination coefficients between calculated and measured BPr were up to 58.2%. This outcome was mainly due to the positive correlation between BPr and input amount since the substrate was very homogeneous. The use of NIRS seems more promising for plants with stronger substrate heterogeneity. PMID:22055101

Jacobi, H Fabian; Ohl, Susanne; Thiessen, Eiko; Hartung, Eberhard

2011-10-12

220

Influence of process parameters on yield and composition of gluten fractions obtained in a laboratory scale dough batter procedure  

Microsoft Academic Search

The influence of process parameters during the dough formation step on wheat flour gluten agglomeration and composition in a laboratory scale gluten–starch separation process was studied. In the process, in which a dough was transformed into a batter then poured over a set of vibrating sieves (400, 250 and 125 ?m), increasing water contents, mixing times and speeds during dough

S. A Frederix; C. M Courtin; J. A Delcour

2004-01-01

221

Effects of ambient and elevated level of ozone on Brassica campestris L. with special reference to yield and oil quality parameters.  

PubMed

Tropospheric ozone (O(3)) has become a serious threat to growth and yield of important agricultural crops over Asian regions including India. Effect of elevated O(3) (ambient+10ppb) was studied on Brassica campestris L. (cv. Sanjukta and Vardan) in open top chambers under natural field conditions. Eight hourly mean ambient O(3) concentration varied from 26.3ppb to 69.5ppb during the growth period. Plants under O(3) exposure showed reductions in photosynthetic rate, reproductive parameters, yield as well as seed and oil quality. Cultivar Sanjukta showed more reduction in photosynthetic characteristics, reproductive structures and seed and oil quality. However, total yield was more affected in Vardan. Exposure of O(3) increased the degree of unsaturation and level of PUFA, ?-6fatty acid, linolenic acid and erucic acid in oil indicating the deterioration of its quality. The study further confirmed that there is a correspondence between O(3) induced change in photosynthetic processes, reproductive development and yield and did not find any compensatory response in the final yield. PMID:22986091

Tripathi, Ruchika; Agrawal, S B

2012-09-15

222

n-alkanes on Pt(111) and on C(0001)/Pt(111): Chain Length Dependence of Kinetic Desorption Parameters  

SciTech Connect

We have measured the desorption of seven small n-alkanes (CNH2N+2, N = 1-4, 6, 8, 10) from the Pt(111) and C(0001) surfaces by temperature programmed desorption. We compare these results to our recent study of the desorption kinetics of these molecules on MgO(100) [J. Chem. Phys. 122, 164708 (2005)]. There we showed an increase in the desorption pre-exponential factor by several orders of magnitude with increasing n-alkane chain length and a linear desorption energy scaling with a small y-intercept value. We suggest that the significant increase in desorption prefactor with chain length is not particular to the MgO(100) surface, but is a general effect for desorption of the small n-alkanes. This argument is supported by statistical mechanical arguments for the increase in the entropy gain of the molecules upon desorption. In this work, we demonstrate that this hypothesis holds true on both a metal surface and a graphite surface. We observe an increase in prefactor by five orders of magnitude over the range of n-alkane chain lengths studied here. On each surface, the desorption energies of the n-alkanes are found to increase linearly with the molecule chain length and have a small y-intercept value. Prior results of other groups have yielded a linear desorption energy scaling with chain length that has unphysically large y-intercept values. We demonstrate that by allowing the prefactor to increase according to our model, a reanalysis of their data resolves this y-intercept problem to some degree.

Tait, Steven L.; Dohnalek, Zdenek; Campbell, Charles T.; Kay, Bruce D.

2006-12-21

223

A film repassivation kinetic model for potential-controlled slower electrode straining  

Microsoft Academic Search

Potential-controlled slower electrode straining method was used to study film rupture and repassivation (FRR) kinetics. A model was developed to extract the kinetic parameters by correlating the anodic current transients measured vs. test time. Through comparison against experimental data, the model yields film repassivation kinetic values in reasonable agreement with the experimentally generated data and with those reported in the

F. M. Song; K. S. Raja; D. A. Jones

2006-01-01

224

Measurement of CP violation observables and parameters for the decays B{sup {+-}}{yields}DK*{sup {+-}}  

SciTech Connect

We study the decay B{sup -}{yields}DK*{sup -} using a sample of 379x10{sup 6} {upsilon}(4S){yields}BB events collected with the BABAR detector at the PEP-II B factory. We perform a Gronau-London-Wyler analysis where the D meson decays into either a CP-even (CP+) eigenstate (K{sup +}K{sup -}, {pi}{sup +}{pi}{sup -}), CP-odd (CP-) eigenstate (K{sub S}{sup 0}{pi}{sup 0}, K{sub S}{sup 0}{phi}, K{sub S}{sup 0}{omega}) or a non-CP state (K{sup -}{pi}{sup +}). We also analyze D meson decays into K{sup +}{pi}{sup -} from a Cabibbo-favored D{sup 0} decay or doubly suppressed D{sup 0} decay [Atwood-Dunietz-Soni (ADS) analysis]. We measure observables that are sensitive to the Cabibbo-Kobayashi-Maskawa angle {gamma}: the partial-rate charge asymmetries A{sub CP{+-}}, the ratios R{sub CP{+-}} of the B-decay branching fractions in CP{+-} and non-CP decay, the ratio R{sub ADS} of the charge-averaged branching fractions, and the charge asymmetry A{sub ADS} of the ADS decays: A{sub CP+}=0.09{+-}0.13{+-}0.06, A{sub CP-}=-0.23{+-}0.21{+-}0.07, R{sub CP+}=2.17{+-}0.35{+-}0.09, R{sub CP-}=1.03{+-}0.27{+-}0.13, R{sub ADS}=0.066{+-}0.031{+-}0.010, and A{sub ADS}=-0.34{+-}0.43{+-}0.16, where the first uncertainty is statistical and the second is systematic. Combining all the measurements and using a frequentist approach yields the magnitude of the ratio between the Cabibbo-suppressed and favored amplitudes, r{sub B}=0.31 with a one (two) sigma confidence level interval of [0.24, 0.38] ([0.17, 0.43]). The value r{sub B}=0 is excluded at the 3.3 sigma level. A similar analysis excludes values of {gamma} in the intervals [0, 7] deg., [55, 111] deg., and [175, 180] deg. ([85, 99] deg.) at the one (two) sigma confidence level.

Aubert, B.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V. [Laboratoire d'Annecy-le-Vieux de Physique des Particules (LAPP), Universite de Savoie, CNRS/IN2P3, F-74941 Annecy-Le-Vieux (France); Garra Tico, J.; Grauges, E. [Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona (Spain); Martinelli, M.; Palano, A.; Pappagallo, M. [INFN Sezione di Bari, I-70126 Bari (Italy); Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); Eigen, G.; Stugu, B.; Sun, L. [University of Bergen, Institute of Physics, N-5007 Bergen (Norway); Battaglia, M.; Brown, D. N.; Kerth, L. T.; Kolomensky, Yu. G.; Lynch, G. [Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720 (United States)] (and others)

2009-11-01

225

Photoactive yellow protein from the purple phototrophic bacterium, Ectothiorhodospira halophila. Quantum yield of photobleaching and effects of temperature, alcohols, glycerol, and sucrose on kinetics of photobleaching and recovery.  

PubMed

A water-soluble yellow protein from E. halophila was previously shown to be photoactive (Meyer, T. E., E. Yakali, M. A. Cusanovich, and G. Tollin. 1987. Biochemistry. 26:418-423). Pulsed laser excitation in the protein visible absorption band (maximum at 445 nm) causes a rapid bleach of color (k = 7.5 x 10(3) s-1) followed by a slower dark recovery (k = 2.6 s-1). This is analogous to the photocycle of sensory rhodopsin II from Halobacterium (which also has k = 2.6 s-1 for recovery). We have now determined the quantum yield of the photobleaching process to be 0.64, which is comparable with that of bacteriorhodopsin (0.25), and is thus large enough to be biologically significant. Although the photoreactions of yellow protein were previously shown to be relatively insensitive to pH, ionic strength and the osmoregulator betaine, the present experiments demonstrate that temperature, glycerol, sucrose, and various alcohol-water mixtures strongly influence the kinetics of photobleaching and recovery. The effect of temperature follows normal Arrhenius behavior for the bleach reaction (Ea = 15.5 kcal/mol). The rate constant for the recovery reaction increases with temperature between 5 degrees C and 35 degrees C, but decreases above 35 degrees C indicating alternate conformations with differing kinetics. There is an order of magnitude decrease in the rate constant for photobleaching in both glycerol and sucrose solutions that can be correlated with the changes in viscosity. We conclude from this that the protein undergoes a conformational change as a consequence of the photoinduced bleach. Recovery kinetics are affected by glycerol and sucrose to a much smaller extent and in a more complicated manner. Aliphatic, monofunctional alcohol-water solutions increase the rate constant for the bleach reaction and decrease the rate constant for the recovery reaction, each by an order of magnitude. These effects do not correlate with dielectric constant, indicating that the photocycle probably does not involve separation or recombination of charge accessible to the protein surface. However, the effects on both bleaching and recovery correlate well with the relative hydrophobicity(as measured by partition coefficients in detergent/water mixtures), in the order of increasing effectiveness:methanol < ethanol < iso-propanol

Meyer, T E; Tollin, G; Hazzard, J H; Cusanovich, M A

1989-09-01

226

Model of curing shrinkage and kinetic parameters of an acrylate-based ultraviolet-embossing resist based on free volume theory  

NASA Astrophysics Data System (ADS)

Free volume theory and a model of polymerization kinetics are introduced to predict and analyze the curing shrinkage and kinetic parameters of an acrylate-based ultraviolet-embossing resist. Curing shrinkage tests have been designed and performed to verify the accuracy of the model. The experimental results are in good agreement with the simulated results of the conversion behavior. The reaction coefficients of polymerization predicted by this model are essentially correct when compared to the classical experimental values. Moreover, the dynamic shrinkage during polymerization determined experimentally matches the simulated result predicted by our model.

Liu, Nan; Liu, Jingbei; Lin, Jie; Davies, Graham; Jin, Peng; Zhang, Dou

2013-04-01

227

Determination of the equilibrium, kinetic and thermodynamic parameters of the batch biosorption of nickel(II) ions onto Chlorella vulgaris  

Microsoft Academic Search

Although the search for new and innovative treatment technologies has focused attention on the metal binding capacities of various microorganisms, the kinetics of the metal uptake process and the description of the thermal properties of biosorption remain essentially unknown. Biosorption equilibrium, kinetics and thermodynamics of nickel(II) ions to Chlorella vulgaris were studied in a batch system with respect to temperature

Z. Aksu

2002-01-01

228

Estimation of insulin secretion rates from C-peptide levels. Comparison of individual and standard kinetic parameters for C-peptide clearance.  

PubMed

Insulin secretion rates can be accurately estimated from plasma C-peptide levels with a two-compartment model for C-peptide distribution and degradation. In previous studies, the kinetic parameters of C-peptide clearance were derived in each subject from the decay curve observed after bolus intravenous injection of biosynthetic human C-peptide. To determine whether standard parameters for C-peptide clearance could be defined and used to calculate insulin secretion without obtaining a decay curve in each subject, we analyzed 200 decay curves of biosynthetic human C-peptide obtained in normal, obese, and non-insulin-dependent diabetes mellitus subjects studied in our laboratory. This analysis showed that the volume of distribution and kinetic parameters of C-peptide distribution and metabolism vary by less than 30% in a population highly heterogeneous in terms of age, sex, degree of obesity, and degree of glucose tolerance. The volume of distribution correlated with the degree of obesity as quantified by body surface area (BSA). This dependence of C-peptide distribution volume on BSA was more marked in men than in women. The long half-life was slightly longer in elderly subjects than in younger adults. When effects of BSA, sex, and age were taken into account, the parameters of C-peptide kinetics were very similar in normal, obese, and diabetic subjects. Based on these findings, a simple procedure to derive standard parameters for C-peptide clearance taking into account degree of obesity, sex, and age was defined. These standard parameters resulted in estimations of mean insulin secretion rates, which differed in each subject by only 10-12% from those obtained with individual parameters. The approach of using standard rather than individual parameters did not systematically underestimate or overestimate insulin secretion so that group values for the fasting secretion rate, the mean 24-h secretion rate, and the number and the amplitude of secretory pulses obtained with standard parameters differed by only 1-2% from the values obtained with individual parameters. Furthermore, the accuracy of measurements based on standard parameters was not different from that associated with replicate determinations of the parameters of C-peptide clearance in the same subject. We conclude that it is possible to estimate insulin secretion rates from plasma C-peptide levels with standard parameters for C-peptide clearance rather than individually derived parameters without significant loss of accuracy. PMID:1551497

Van Cauter, E; Mestrez, F; Sturis, J; Polonsky, K S

1992-03-01

229

Effect of farming systems on the yield, quality parameters and sensory properties of conventionally and organically grown potato (Solanum tuberosum L.) tubers.  

PubMed

The objectives of this two-year research were to study the impact of two different farming types, conventional and organic, on the yield and sensory properties of five Lithuanian varieties of potato tuber. The parameters and properties examined were: phenolic acids; dry matter and starch content; and the spread and intensity of Phytophthora infestans growth. It was determined that potato yield fluctuates with the variety, but for conventional farming it is significantly (p<0.05) higher than that obtained by organic farming. The farming type has no significant effect (p>0.05) on the content of phenolic acids. No significant effect (p>0.05) of farming type on dry matter and starch content, or sensory properties was found. No significant relation (p>0.05) was found between the content of phenolic acids and P. infestans spread. The spread of P. infestans was faster and infection was heavier in organically grown potatoes. PMID:24128562

Brazinskiene, V; Asakaviciute, R; Miezeliene, A; Alencikiene, G; Ivanauskas, L; Jakstas, V; Viskelis, P; Razukas, A

2013-09-11

230

VERY LONG BASELINE NEUTRINO OSCILLATION EXPERIMENTS FOR PRECISE MEASURMENTS OF OSCILLATION PARAMETERS AND SEARCH FOR N MU YIELDS N EPSILON.  

SciTech Connect

Brookhaven National Laboratory and collaborators started a neutrino working group to identify new opportunities in the field of neutrino oscillations and explore how our laboratory facilities can be used to explore this field of research. The memo to the working group and the charge are included in Appendix I. This report is the result of the deliberations of the working group. Previously, we wrote a letter of intent to build a new high intensity neutrino beam at BNL. A new intense proton beam will be used to produce a conventional horn focused neutrino beam directed at a detector located in either the Homestake mine in Lead, South Dakota at 2540 km or the Waste Isolation Pilot Plant (WIPP) in Carlsbad, NM at 2880 km. As a continuation of the study that produced the letter of intent, this report examines several items in more detail. We mainly concentrate on the use of water Cherenltov detectors because of their size, resolution, and background rejection capability, and cost. We examine the prospects of building such a detector in the Homestake mine. The accelerator upgrade will be carried out in phases. We expect the first phase to yield a 0.4 MW proton beam and the second phase to result in a 1.0 MW beam. The details of this upgrade will be reported in a companion report. In this report we assume accelerator intensity of 1 MW for calculating event rates and spectra. We also assume a total experimental duration of 5 years with running time of 10{sup 7} seconds per year. We examine the target station and the horn produced neutrino beam with focus on two topics: target and horn design for a 1 MW beam and the broad band spectrum of neutrinos from a 28 GeV proton beam.

DIWAN,M.; MARCIANO,W.; WENG,W.; BEAVIS,D.; BRENNAN,M.; CHEN,M.C.; FERNOW,R.; ET AL

2002-10-18

231

Erbium hydride decomposition kinetics.  

SciTech Connect

Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.

Ferrizz, Robert Matthew

2006-11-01

232

Measurement of kinetic rate law parameters on a Na?Ca?Al borosilicate glass for low-activity waste  

Microsoft Academic Search

The dissolution kinetics of a Na?Ca?Al borosilicate glass, being studied for immobilization of low-activity waste, were measured between 20 and 90°C and solution pH between 6 and 12 using the single-pass flow-through method. Dissolution kinetics measurements are needed to parameterize a mechanistic model that is being used to compute the corrosion rate of the glass waste form as a function

B. P. McGrail; W. L. Ebert; A. J. Bakel; D. K. Peeler

1997-01-01

233

Oxygenase Domain of Drosophila melanogaster Nitric Oxide Synthase:  Unique Kinetic Parameters Enable a More Efficient NO Release †  

Microsoft Academic Search

Although nitric oxide (NO) is important for cell signaling and nonspecific immunity in the fruit fly Drosophila melanogaster, little is known about its single NO synthase (dNOS). We expressed the oxygenase domain of dNOS (dNOSoxy), characterized its spectroscopic, kinetic, and catalytic properties, and interpreted them in light of a global kinetic model for NO synthesis. Single turnover reactions with ferrous

Sougata Sinha Ray; Jesús Tejero; Zhi-Qiang Wang; Tanmay Dutta; Arindam Bhattacharjee; Michael Regulski; Tim Tully; Sanjay Ghosh; Dennis J. Stuehr

2007-01-01

234

Extracting kinetic parameters for homogeneous [Os(bpy)2ClPyCOOH]+ mediated enzyme reactions from cyclic voltammetry and simulations  

PubMed Central

The homogeneous reaction between glucose oxidase and osmium bipyridine–pyridine carboxylic acid in the presence of glucose has been studied in detail by cyclic voltammetry and digital simulation. Combination of the analytical equations that describe the dependence of the amperometric response on enzyme, substrate and co-substrate concentrations for the limiting cases with digital simulation of the coupled enzyme reaction diffusion problem allows us to extract kinetic parameters for the substrate–enzyme reaction: KMS = 10.8 mM, kcat = 254 s? 1 and for the redox mediator–enzyme reaction, k = 2.2 × 105 M? 1 s? 1. The accurate determination of the kinetic parameters at low substrate concentrations (< 7 mM) is limited by depletion of the substrate close to the electrode surface. At high substrate concentrations (> 20 mM) inactivation of the reduced form of glucose oxidase in the bulk solution must be taken into account in the analysis of the results.

Flexer, V.; Ielmini, M.V.; Calvo, E.J.; Bartlett, P.N.

2008-01-01

235

Effect of Tannin-Binding Agents (Polyethylene Glycol and Polyvinylpyrrolidone) Supplementation on In Vitro Gas Production Kinetics of Some Grape Yield Byproducts  

PubMed Central

The effects of polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) on in vitro gas production characteristics, organic matter digestibility (OMD), and metabolizable energy (ME) contents of some grape yield byproducts were investigated. The gas production was recorded after 2, 4, 6, 8, 12, 16, 24, 36, and 48?h of incubation. The gas production profiles in triplicate fitted with equation Y = A (1 – e?ct). The data was analyzed using completely randomized design. Total phenol (TP) and total tannin (TT) contents were highest for raisin waste (RW). The TP content (g/kg DM) ranged from 30.1 in grape pomace (GP) to 96.3 in RW, which also had the higher TT (72.1?g/kg DM). The potential gas production (a + b) of DGB, GP, and RW were 239.43, 263.49, and 208.22?mL/g DM, respectively. In the absence of PEG and PVP, rate constant of gas production (c) for GP was highest among the feedstuffs (0.1073?mL/h), but in presence of PEG or PVP, RW had highest fraction (c) among the feedstuffs. Addition of PEG and PVP inactivated effects of tannins and increased gas production, ME, NE1, OMD, and VFA in grape yield byproducts. Addition of PEG and PVP could overcome adverse effects of tannins on nutrient availability as indicated by gas production parameters.

Besharati, Maghsoud; Taghizadeh, Akbar

2011-01-01

236

First phase viral kinetic parameters and prediction of response to interferon alpha-2b\\/ribavirin combination therapy in patients with chronic hepatitis C  

Microsoft Academic Search

The aim of the present study was to assess parameters in early phase HCV dynamics for predicting the outcome of interferon (IFN)\\/ribavirin combination therapy in patients with chronic hepatitis C (CH-C). Sixty-five CH-C patients who received IFN alpha-2b\\/ribavirin combination therapy were enrolled. The serum levels of HCV RNA 0h and 3 months after commencing therapy were serially quantified. HCV kinetic

Akiko Makiyama; Yoshito Itoh; Kohichiroh Yasui; Kohjiroh Mori; Mika Okita; Mika Nakayama; Junko Yamaoka; Masahito Minami; Tomoki Nakajima; Takeshi Okanoue

2006-01-01

237

Determination of the Kinetic Parameters for Phospholipase C ( Bacillus cereus) on Different Phospholipid Substrates Using a Chromogenic Assay Based on the Quantitation of Inorganic Phosphate  

Microsoft Academic Search

The kinetic parameters of the phosphatidylcholine-preferring phospholipase C fromBacillus cereus(PLCBc) have been evaluated for phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine substrates with a new assay based on the quantitation of inorganic phosphate (Pi). Treatment of the phosphomonoester product of the PLCBc-catalyzed hydrolysis of these phospholipids with alkaline phosphatase releases Pi. This Pi forms a complex with ammonium molybdate that is then reduced

Paul J. Hergenrother; Stephen F. Martin

1997-01-01

238

Measurement of minimum substrate concentration (Smin) in a recycling fermentor and its prediction from the kinetic parameters of Pseudomonas strain B13 from batch and chemostat cultures.  

PubMed

The minimum substrate concentration required for growth, Smin, was measured for Pseudomonas sp. strain B13 with 3-chlorobenzoate (3CB) and acetate in a recycling fermentor. The substrates were provided alone or in a mixture. Smin values predicted with kinetic parameters from resting-cell batches and chemostat cultures differed clearly from the values measured in the recycling fermentor. When 3CB and acetate were fed as single substrates, the measured Smin values were higher than the individual Smin values in the mixture. The Smin in the mixture reflected the relative energy contributions of the two substrates in the fermentor feed. The energy-based maintenance coefficients during zero growth in the recycling fermentor were comparable for all influent compositions (mean +/- standard deviation, 0.34 +/- 0.07 J mg [dry weight]-1 h-1). Maintenance coefficient values for acetate were significantly higher in chemostat experiments than in recycling-fermentor experiments. 3CB maintenance coefficients were comparable in both experimental systems. The parameters for 3CB consumption kinetics varied remarkably with the experimental growth conditions in batch, chemostat, and recycling-fermentor environments. The results demonstrate that the determination of kinetic parameters in the laboratory for prediction of microbial activity in complex natural systems should be done under conditions which best mimic the system under consideration. PMID:8967775

Tros, M E; Bosma, T N; Schraa, G; Zehnder, A J

1996-10-01

239

Measurement of minimum substrate concentration (Smin) in a recycling fermentor and its prediction from the kinetic parameters of Pseudomonas strain B13 from batch and chemostat cultures.  

PubMed Central

The minimum substrate concentration required for growth, Smin, was measured for Pseudomonas sp. strain B13 with 3-chlorobenzoate (3CB) and acetate in a recycling fermentor. The substrates were provided alone or in a mixture. Smin values predicted with kinetic parameters from resting-cell batches and chemostat cultures differed clearly from the values measured in the recycling fermentor. When 3CB and acetate were fed as single substrates, the measured Smin values were higher than the individual Smin values in the mixture. The Smin in the mixture reflected the relative energy contributions of the two substrates in the fermentor feed. The energy-based maintenance coefficients during zero growth in the recycling fermentor were comparable for all influent compositions (mean +/- standard deviation, 0.34 +/- 0.07 J mg [dry weight]-1 h-1). Maintenance coefficient values for acetate were significantly higher in chemostat experiments than in recycling-fermentor experiments. 3CB maintenance coefficients were comparable in both experimental systems. The parameters for 3CB consumption kinetics varied remarkably with the experimental growth conditions in batch, chemostat, and recycling-fermentor environments. The results demonstrate that the determination of kinetic parameters in the laboratory for prediction of microbial activity in complex natural systems should be done under conditions which best mimic the system under consideration.

Tros, M E; Bosma, T N; Schraa, G; Zehnder, A J

1996-01-01

240

Systematics of Fission-Product Yields  

SciTech Connect

Empirical equations representing systematics of fission-product yields have been derived from experimental data. The systematics give some insight into nuclear-structure effects on yields, and the equations allow estimation of yields from fission of any nuclide with atomic number Z{sub F} = 90 thru 98, mass number A{sub F} = 230 thru 252, and precursor excitation energy (projectile kinetic plus binding energies) PE = 0 thru {approx}200 MeV--the ranges of these quantities for the fissioning nuclei investigated. Calculations can be made with the computer program CYFP. Estimates of uncertainties in the yield estimates are given by equations, also in CYFP, and range from {approx} 15% for the highest yield values to several orders of magnitude for very small yield values. A summation method is used to calculate weighted average parameter values for fast-neutron ({approx} fission spectrum) induced fission reactions.

A.C. Wahl

2002-05-01

241

Ranking the Potential Yield of Salinity and Selenium from Subbasins in the Lower Gunnison River Basin Using Seasonal, Multi-parameter Regression Models  

NASA Astrophysics Data System (ADS)

Elevated levels of salinity and dissolved selenium can detrimentally effect the quality of water where anthropogenic and natural uses are concerned. In areas, such as the lower Gunnison Basin of western Colorado, salinity and selenium are such a concern that control projects are implemented to limit their mobilization. To prioritize the locations in which control projects are implemented, multi-parameter regression models were developed to identify subbasins in the lower Gunnison River Basin that were most likely to have elevated salinity and dissolved selenium levels. The drainage area is about 5,900 mi2 and is underlain by Cretaceous marine shale, which is the most common source of salinity and dissolved selenium. To characterize the complex hydrologic and chemical processes governing constituent mobilization, geospatial variables representing 70 different environmental characteristics were correlated to mean seasonal (irrigation and nonirrigation seasons) salinity and selenium yields estimated at 154 sampling sites. The variables generally represented characteristics of the physical basin, precipitation, soil, geology, land use, and irrigation water delivery systems. Irrigation and nonirrigation seasons were selected due to documented effects of irrigation on constituent mobilization. Following a stepwise approach, combinations of the geospatial variables were used to develop four multi-parameter regression models. These models predicted salinity and selenium yield, within a 95 percent confidence range, at individual points in the Lower Gunnison Basin for irrigation and non-irrigation seasons. The corresponding subbasins were ranked according to their potential to yield salinity and selenium and rankings were used to prioritize areas that would most benefit from control projects.

Linard, J.; Leib, K.; Colorado Water Science Center

2010-12-01

242

Sensitivity analysis of the kinetic behaviour of a Gas Cooled Fast Reactor to variations of the delayed neutron parameters  

Microsoft Academic Search

In advanced Generation IV (fast) reactors an integral fuel cycle is envisaged, where all Heavy Metal is recycled in the reactor. This leads to a nuclear fuel with a considerable content of Minor Actinides. For many of these isotopes the nuclear data is not very well known. In this paper the sensitivity of the kinetic behaviour of the reactor to

W. F. G. van Rooijen; D. Lathouwers

243

Comparison of Chemometric and Chromatographic Methods to Obtain Kinetic Parameters for Textile Dyes during a Biodegradation Process  

Microsoft Academic Search

The concentrations of three industrial-grade textile dyes were determined in a mixture after degradation by the fungus Ganoderma sp, by using the methods of UV-Vis spectrophotometry associated with Partial Least Squares regression and HPLC and comparing the results obtained from both methods. Using the concentrations calculated from the two methods, a kinetic study of the biodegradation mediated by the fungus

Wagner José Barreto; Nathalia DElboux Bernardino; Suely Mayumi Obara Doi; Renata Afonso

2012-01-01

244

Sodium--potassium adenosine triphosphatase activity of human lymphocyte membrane vesicles: kinetic parameters, substrate specificity, and effects of phytohemagglutinin  

Microsoft Academic Search

We have prepared human blood lymphocyte membrane vesicles of high purity in sufficient quantity for detailed enzyme analysis. This was made possible by the use of plateletpheresis residues, which contain human lymphocytes in amounts equivalent to thousands of milliliters of blood. The substrate specificity and the kinetics of the cofactor and substrate requirements of the human lymphocyte membrane Na\\/sup +\\/,

George B. Segel; George Kovach; Marshall A. Lichtman

1979-01-01

245

A review on zinc and nickel adsorption on natural and modified zeolite, bentonite and vermiculite: examination of process parameters, kinetics and isotherms.  

PubMed

Adsorption and ion exchange can be effectively employed for the treatment of metal-contaminated wastewater streams. The use of low-cost materials as sorbents increases the competitive advantage of the process. Natural and modified minerals have been extensively employed for the removal of nickel and zinc from water and wastewater. This work critically reviews existing knowledge and research on the uptake of nickel and zinc by natural and modified zeolite, bentonite and vermiculite. It focuses on the examination of different parameters affecting the process, system kinetics and equilibrium conditions. The process parameters under investigation are the initial metal concentration, ionic strength, solution pH, adsorbent type, grain size and concentration, temperature, agitation speed, presence of competing ions in the solution and type of adsorbate. The system's performance is evaluated with respect to the overall metal removal and the adsorption capacity. Furthermore, research works comparing the process kinetics with existing reaction kinetic and diffusion models are reviewed as well as works examining the performance of isotherm models against the experimental equilibrium data. PMID:23644019

Malamis, S; Katsou, E

2013-03-18

246

Assessment of metabolic properties and kinetic parameters of methanogenic sludge by on-line methane production rate measurements.  

PubMed

This report presents a new approach to studying the metabolic and kinetic properties of anaerobic sludge from single batch experiments. The two main features of the method are that the methane production is measured on-line with a relatively cheap system, and that the methane production data can be plotted as rate vs time curves. The case studies of specific methanogenic activity, biodegradability and toxicity tests here presented show that very accurate kinetic data can be obtained. The method is specifically useful in experiments in which strong changes in methane production occur, and it is proposed as a powerful tool to study methanogenic systems. Furthermore, the method is simple and could be implemented by industry in the routine analysis of sludge. PMID:11876419

Gonzalez-Gil, G; Kleerebezem, R; Lettinga, G

2002-02-01

247

In vitro characterization of rosiglitazone metabolites and determination of the kinetic parameters employing rat liver microsomal fraction  

Microsoft Academic Search

Rosiglitazone (RSG), a thiazolidinedione antidiabetic drug, is metabolized by CYP450 enzymes into two main metabolites: N-desmethyl rosiglitazone (N-Dm-R) and ?-hydroxy rosiglitazone (?-OH-R). In humans, CYP2C8 appears to have a major role in RSG metabolism. On the other\\u000a hand, the in vitro metabolism of RSG in animals has not been described in literature yet. Based on these concerns, the kinetic\\u000a metabolism

Leandro Augusto Calixto; Anderson Rodrigo Moraes de Oliveira; Valquíria Aparecida Polisel Jabor; Pierina Sueli Bonato

248

The moments of the breakthrough curves of instantaneously and kinetically sorbing solutes in heterogeneous geologic media: Prediction and parameter inference from field measurements  

NASA Astrophysics Data System (ADS)

This paper presents a concise methodology for estimating the moments of the breakthrough curves for tracers and reactive solutes in heterogeneous aquifers. Under some conditions these are also the temporal or travel time moments between a source and a given destination downstream. The temporal moments of tracers as well as instantaneously or kinetically sorbing solutes, characterized by linear isotherms, are expressed in terms of a few parameters which characterize the chemical reactions and the spatial distribution and correlation structure of the hydraulic conductivity. The chemical reaction parameters are assumed to be homogeneous. The estimated moments can also be made conditional to field measurements. Applications for the case of uniform mean flow are presented, but the general approach can be applied for other flow regimes such as injection-pumping well doublets. Physical and chemical nonequilibrium processes are represented by mobile-immobile domains and two-site models, respectively. The estimated temporal moments can be used for both predictive purposes as well as for interpretation of field experiments. These two objectives are pursued in this paper. A significant advantage of the solution is that it does not require the assumptions of Gaussianity or log Gaussianity of the travel times. Throughout the discussion the combined and relative effects of the mass transfer and kinetic parameters and the spatial variability of the conductivity on the travel time moments are evaluated.

Rubin, Yoram; Cushey, Mark A.; Wilson, Amy

1997-11-01

249

Effects of conjugated linoleic acids and dietary concentrate proportion on performance, milk composition, milk yield and metabolic parameters of periparturient dairy cows.  

PubMed

The study aimed to examine effects of supplemented conjugated linoleic acids (CLA) to periparturient cows receiving different concentrate proportions ante partum (a.p.) to investigate CLA effects on lipid mobilisation and metabolism. Compared to adapted feeding, a high-concentrate diet a.p. should induce a ketogenic metabolic situation post partum (p.p.) to better understand how CLA works. Sixty-four pregnant German Holstein cows had ad libitum access to partial mixed rations 3 weeks prior to calving until day 60 p.p. Ante partum, cows received control fat (CON) or a CLA supplement at 100 g/d, either in a low-concentrate (CON-20, CLA-20) or high-concentrate diet (CON-60, CLA-60). Post partum, concentrate proportion was adjusted, while fat supplementation continued. After day 32 p.p., half of the animals of CLA-groups changed to CON supplementation (CLA-20-CON, CLA-60-CON). A ketogenic metabolic situation p.p. was not achieved and therefore impacts of CLA could not be examined. Live weight, milk yield and composition, blood parameters remained unaffected by the treatments. Only a slightly reduced milk fat yield (not significant) was recorded for Group CLA-20. The proportion of trans-10,cis-12 (t10,c12) CLA in milk fat was significantly increased in CLA-groups compared to CON-groups. With the exception of a reversible CLA effect on milk fat in Group CLA-20, no post-treatment effects occurred. Dry matter intake (DMI) of Group CLA-60 was highest before calving, resulting in a significantly improved estimated energy balance after calving. Ante partum, net energy intakes were significantly increased in high-concentrate groups. Overall, supplemented CLA preparation did not relieve metabolism and lipid mobilisation of early lactating cows. But feeding CLA in a high-concentrate diet a.p. seems to increase DMI and thereby improve the energy balance of cows immediately after calving. PMID:23678986

Petzold, Maria; Meyer, Ulrich; Kersten, Susanne; Spilke, Joachim; Kramer, Ronny; Jahreis, Gerhard; Dänicke, Sven

2013-05-16

250

The effect of waste paper on the kinetics of biogas yield from the co-digestion of cow dung and water hyacinth  

Microsoft Academic Search

The effect of waste paper on biogas yield produced by co-digesting fixed amount of cow dung and water hyacinth in five digesters A–E was studied at room temperature. Waste paper was observed to improve biogas yield in digesters B–E with digester A acting as the control. However, as the amount of waste paper increased the biogas yield was observed to

Momoh O. L. Yusuf; Nwaogazie L. Ify

2011-01-01

251

Extracting kinetic parameters for homogeneous [Os(bpy)2ClPyCOOH]+ mediated enzyme reactions from cyclic voltammetry and simulations.  

PubMed

The homogeneous reaction between glucose oxidase and osmium bipyridine-pyridine carboxylic acid in the presence of glucose has been studied in detail by cyclic voltammetry and digital simulation. Combination of the analytical equations that describe the dependence of the amperometric response on enzyme, substrate and co-substrate concentrations for the limiting cases with digital simulation of the coupled enzyme reaction diffusion problem allows us to extract kinetic parameters for the substrate-enzyme reaction: K(MS)=10.8 mM, k(cat)=254 s(-1) and for the redox mediator-enzyme reaction, k=2.2x10(5) M(-1) s(-1). The accurate determination of the kinetic parameters at low substrate concentrations (<7 mM) is limited by depletion of the substrate close to the electrode surface. At high substrate concentrations (>20 mM) inactivation of the reduced form of glucose oxidase in the bulk solution must be taken into account in the analysis of the results. PMID:18824418

Flexer, V; Ielmini, M V; Calvo, E J; Bartlett, P N

2008-08-12

252

Determination of kinetic parameters in the biosorption of copper(II) on Cladophora sp., in a packed bed column reactor  

Microsoft Academic Search

In this study, the biosorption of copper(II) ions to the green alga Cladophora sp. was investigated in a packed bed column reactor as a function of flow rate and inlet copper(II) concentration. These two parameters affected the external mass transfer and adsorption rates directly. Mass transfer coefficients were determined from the Wakao Equation evaluating the breakthrough curves obtained at different

Z. Aksu; T. Kutsal

1998-01-01

253

Performance evaluation of the non-linear and linear estimation methods for determining kinetic parameters in dynamic FDG-PET study  

NASA Astrophysics Data System (ADS)

Dynamic positron emission tomography (PET) is a promising diagnostic tool to quantitatively predict biological and physiological changes in vivo through estimation of kinetic parameters. In this work, several popular linear and non-linear estimation methods for determining kinetic parameters using PET imaging with Fluorine-18 fluorodeoxyglucose ([18F]FDG) are compared and evaluated. The simulation studies are presented. The linear estimation methods include linear least squares (LLS), generalized linear least squares (GLLS) and total least squares (TLS), while the non-linear estimation methods include non-linear least squares (NLS), weighted nonlinear least squares using noisy tissue time activity data (WNLS-N), weighted non-linear least squares using noise-free tissue time activity data (WNLS-NF) and iteratively re-weighted non-linear least squares (IRWNLS). There are several findings: 1. Compared with non-linear estimation methods, GLLS performs well when noise level is low, but worse especially in determining k3 and k4 when noise level is high. What's more, GLLS does not show obvious advantage in running time. 2. The choice of weights plays an important role in nonlinear estimation methods. Weighting using noisy data should be avoided. WNLS-NF and IRWNLS perform best. Since the noise-free data can not be obtained in clinical and IRWNLS is time-consuming, NLS is most recommended. 3. Non-linear estimation methods are prone to produce lower-biased, higher-precision parameter estimates, however, also more easily affected by noise. Linear estimation methods are prone to be more biased, however, much more computational efficient and noise robust.

Dai, Xiaoqian; Tian, Jie; Chen, Zhe

2010-03-01

254

Structure-Kinetic Relationships-An Overlooked Parameter in Hit-to-Lead Optimization: A Case of Cyclopentylamines as Chemokine Receptor 2 Antagonists.  

PubMed

Preclinical models of inflammatory diseases (e.g., neuropathic pain, rheumatoid arthritis, and multiple sclerosis) have pointed to a critical role of the chemokine receptor 2 (CCR2) and chemokine ligand 2 (CCL2). However, one of the biggest problems of high-affinity inhibitors of CCR2 is their lack of efficacy in clinical trials. We report a new approach for the design of high-affinity and long-residence-time CCR2 antagonists. We developed a new competition association assay for CCR2, which allows us to investigate the relation of the structure of the ligand and its receptor residence time [i.e., structure-kinetic relationship (SKR)] next to a traditional structure-affinity relationship (SAR). By applying combined knowledge of SAR and SKR, we were able to re-evaluate the hit-to-lead process of cyclopentylamines as CCR2 antagonists. Affinity-based optimization yielded compound 1 with good binding (Ki = 6.8 nM) but very short residence time (2.4 min). However, when the optimization was also based on residence time, the hit-to-lead process yielded compound 22a, a new high-affinity CCR2 antagonist (3.6 nM), with a residence time of 135 min. PMID:24028535

Vilums, Maris; Zweemer, Annelien J M; Yu, Zhiyi; de Vries, Henk; Hillger, Julia M; Wapenaar, Hannah; Bollen, Ilse A E; Barmare, Farhana; Gross, Raymond; Clemens, Jeremy; Krenitsky, Paul; Brussee, Johannes; Stamos, Dean; Saunders, John; Heitman, Laura H; Ijzerman, Adriaan P

2013-09-27

255

Calculation of reactivities using ionization chamber currents with different sets of kinetic parameters for reduced scram system efficiency in the VVER-1000 of the third unit of the Kalinin nuclear power plant at the stage of physical start-up  

SciTech Connect

The effectiveness of the VVER-1000 reactor scram system is analyzed using ionization chamber currents with different sets of kinetic parameters with allowance for the isotopic composition in the calculation of these parameters. The most 'correct, aesthetically acceptable' results are obtained using the eight-group constants of the ROSFOND (BNAB-RF) library. The difference between the maximum and minimum values of the scram system effectiveness calculated with different sets of kinetic parameters slightly exceeds 2{beta}. The problems of introducing corrections due to spatial effects are not considered in this study.

Zizin, M. N., E-mail: zizin@adis.vver.kiae.ru [Russian Research Centre Kurchatov Institute (Russian Federation); Zizina, S. N.; Kryakvin, L. V.; Pitilimov, V. A.; Tereshonok, V. A. [JSC VNIIAES (Russian Federation)

2011-12-15

256

Kinetic Parameters of Secondary Carbide Precipitation in High-Cr White Iron Alloyed by Mn-Ni-Mo-V Complex  

NASA Astrophysics Data System (ADS)

This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white cast iron during the destabilization heat treatment. The as-cast iron was heat treated at temperatures in the range of 800-1100 °C with soaking up to 6 h. Investigation was carried out by optical and electron microscopy, dilatometric analysis, Ms temperature measurement, and bulk hardness evaluation. TTT-curve of precipitation process of secondary carbides (M7C3, M23C6, M3C2) has been constructed in this study. It was determined that the precipitation occurs at the maximum rate at 950 °C where the process is started after 10 s and completed within 160 min further. The precipitation leads to significant increase of Ms temperature and bulk hardness; large soaking times at destabilization temperatures cause coarsening of secondary carbides and decrease in particles number, followed by decrease in hardness. The results obtained are discussed in terms of solubility of carbon in the austenite and diffusion activation of Cr atoms. The precipitation was found to consist of two stages with activation energies of 196.5 kJ/g-mole at the first stage and 47.1 kJ/g-mole at the second stage.

Efremenko, V. G.; Chabak, Yu. G.; Brykov, M. N.

2013-05-01

257

Rationalization and prediction of in vivo metabolite exposures: The role of metabolite kinetics, clearance predictions and in vitro parameters  

PubMed Central

Importance of the field Due to growing concerns over toxic or active metabolites, significant efforts have been focused on qualitative identification of potential in vivo metabolites from in vitro data. However, limited tools are available to quantitatively predict their human exposures. Areas covered in this review Theory of clearance predictions and metabolite kinetics is reviewed together with supporting experimental data. In vitro and in vivo data of known circulating metabolites and their parent drugs was collected and the predictions of in vivo exposures of the metabolites were evaluated. What the reader will gain The theory and data reviewed will be useful in early identification of human metabolites that will circulate at significant levels in vivo and help in designing in vivo studies that focus on characterization of metabolites. It will also assist in rationalization of metabolite-to-parent ratios used as markers of specific enzyme activity. Take home message The relative importance of a metabolite in comparison to the parent compound as well as other metabolites in vivo can only be predicted using the metabolites in vitro formation and elimination clearances, and the in vivo disposition of a metabolite can only be rationalized when the elimination pathways of that metabolite are known.

Lutz, Justin D.; Fujioka, Yasushi; Isoherranen, Nina

2010-01-01

258

In vitro characterization of rosiglitazone metabolites and determination of the kinetic parameters employing rat liver microsomal fraction.  

PubMed

Rosiglitazone (RSG), a thiazolidinedione antidiabetic drug, is metabolized by CYP450 enzymes into two main metabolites: N-desmethyl rosiglitazone (N-Dm-R) and ?-hydroxy rosiglitazone (?-OH-R). In humans, CYP2C8 appears to have a major role in RSG metabolism. On the other hand, the in vitro metabolism of RSG in animals has not been described in literature yet. Based on these concerns, the kinetic metabolism study of RSG using rat liver microsomal fraction is described for the first time. Maximum velocity (V (max)) values of 87.29 and 51.09 nmol/min/mg protein were observed for N-Dm-R and ?-OH-R, respectively. Michaelis-Menten constant (K(m)) values were of 58.12 and 78.52 ?M for N-Dm-R and ?-OH-R, respectively. Therefore, these results demonstrated that this in vitro metabolism model presents the capacity of forming higher levels of N-Dm-R than of ?-OH-R, which also happens in humans. Three other metabolites were identified employing mass spectrometry detection under positive electrospray ionization: ortho-hydroxy-rosiglitazone (?-OH-R) and two isomers of N-desmethyl hydroxy-rosiglitazone. These metabolites have also been observed in humans. The results observed in this study indicate that rats could be a satisfactory model for RSG metabolism. PMID:21499911

Calixto, Leandro Augusto; de Oliveira, Anderson Rodrigo Moraes; Jabor, Valquíria Aparecida Polisel; Bonato, Pierina Sueli

2011-04-17

259

A protocol for the measurement of all the parameters of the mass transfer kinetics in columns used in liquid chromatography  

SciTech Connect

Band broadening in chromatography results from the combination of the dispersive effects that are associated with the different steps involved in the migration of compound bands along the column. These steps include longitudinal diffusion, trans-particle mass transfer, external film mass transfer, overall eddy diffusion, including trans-column, short-range inter-channel, trans-channel eddy diffusion, and the possible, additional mass transfer contributions arising from heat friction and the thermal heterogeneity of the column. We describe a series of experiments that provide the data needed to determine the coefficients of the contributions to band broadening of each one of these individual mass transfer steps. This specifically designed protocol can provide key information regarding the kinetic performance of columns used in liquid chromatography and explain why different columns behave so differently. The limitations, accuracy and precision of these methods are discussed. Further avenues of research that could improve the characterization of the mass transfer mechanisms in chromatographic columns, possibly contributing to the development of better columns, are suggested.

Gritti, Fabrice [University of Tennessee, Knoxville (UTK); Guiochon, Georges A [ORNL

2010-01-01

260

Biodegradation Kinetics and Effects of Operating Parameters on the Performance of a Methyl TertButyl Ether Degrading Biofilter  

Microsoft Academic Search

The goals of the study were to determine the effectiveness of a laboratory-scale biofilter on the removal of methyl tert-butyl ether (MTBE) and investigate the operating parameter effects on biofilter performance. The experimental results show that average MTBE removals of 53.6–93.2% were observed at loads of 2.5–20.1 gm?3 h?1 and an empty-bed residence time of three minutes, after continuous operation

Yi-Cheng Chiu; Chi-Wen Lin; Tsang-Chih Kao; Xiao-Yan Tang

2006-01-01

261

Influence of operational parameters and kinetics analysis on the photocatalytic reduction of Cr(VI) by immobilized ZnO  

Microsoft Academic Search

In the present work the performance of immobilized ZnO on a glass plate with the heat attachment method has been described for photoreduction of Cr(VI) to the less harmful Cr(III) at different operational parameters. The photoreduction of Cr(VI) on the surface of the immobilized ZnO catalyst was studied as a function of the pH of solution, initial Cr(VI) concentration and

Mohammad A. Behnajady; Nafiseh Mansoriieh; Nasser Modirshahla; Mohammad Shokri

2011-01-01

262

Influence of operational parameters and kinetics analysis on the photocatalytic reduction of Cr(VI) by immobilized ZnO  

Microsoft Academic Search

In the present work the performance of immobilized ZnO on a glass plate with the heat attachment method has been described for photoreduction of Cr(VI) to the less harmful Cr(III) at different operational parameters. The photoreduction of Cr(VI) on the surface of the immobilized ZnO catalyst was studied as a function of the pH of solution, initial Cr(VI) concentration and

Mohammad A. Behnajady; Nafiseh Mansoriieh; Nasser Modirshahla; Mohammad Shokri

2012-01-01

263

Photooxidative degradation of Malachite Green (MG) by UV\\/H 2O 2: Influence of operational parameters and kinetic modeling  

Microsoft Academic Search

The decolorization of Malachite Oxalate Green (MG), a dye containing three groups of aryls was investigated using UV radiation in the presence of H2O2 in a batch photoreactor at different light intensities. H2O2 and UV-light showed negligible effect when they were used independently. Removal efficiency of MG was sensitive to the operational parameters such as initial concentrations of H2O2, MG

N. Modirshahla; M. A. Behnajady

2006-01-01

264

Determination of the equilibrium, kinetic and thermodynamic parameters of adsorption of copper(II) ions onto seeds of Capsicum annuum  

Microsoft Academic Search

Adsorption of copper ions onto Capsicum annuum (red pepper) seeds was investigated with the variation in the parameters of pH, contact time, adsorbent and copper(II) concentrations and temperature. The nature of the possible adsorbent and metal ion interactions was examined by the FTIR technique. The copper(II) adsorption equilibrium was attained within 60min. Adsorption of copper(II) ions onto C. annuum seeds

Adnan Özcan; A. Safa Özcan; Sibel Tunali; Tamer Akar; Ismail Kiran

2005-01-01

265

TEACHERS TOPICS The Relationship Among Pharmacokinetic Parameters: Effects of Altered Kinetics on the Drug Plasma Concentration-Time Profiles  

Microsoft Academic Search

The learning tools used by this instructor in a pharmacokinetics course offered to entry level PharmD students are presented for the topic of relationship among pharmacokinetic parameters. These tools consist of specific outcomes\\/objectives, a reading handout, a practice problem as a focus of in-class dis- cussion, several online web-based computer simulation modules, a take-home online assignment sim- ilar to the

Reza Mehvar

2004-01-01

266

The RNA-N-glycosidase activity of Shiga-like toxin I: kinetic parameters of the native and activated toxin.  

PubMed

Shiga toxin and Shiga-like toxins are ribosome-inactivating proteins with RNA-N-glycosidase activity which remove a specific adenine from 28S RNA. The toxins are composed of an A subunit non-covalently associated to a multimer of receptor-binding B subunits. Near the COOH-terminus of the A subunit, a disulfide-bonded loop contains two trypsin-sensitive arginine residues. Proteolytic nicking at these sites, followed by reduction, removes from the A subunit the C-terminal end together with the associated B subunits. The requirement of such cleavage for biological activity of Shiga toxin and Shiga-like toxins has been recently questioned. The present paper reports the kinetic constants of the adenine release from highly purified Artemia salina ribosomes catalysed by Shiga-like toxin I and by its A subunit before and after treatment with trypsin, urea and dithiothreitol or urea and dithiothreitol alone. All reactions had approximately the same Km (1 microM). The Kcat was 0.6 min-1 for the untreated holotoxin and 6 min-1 for the isolated A subunit, respectively. The trypsin treatment increased 1000-fold the Kcat of the holotoxin (770 min-1) and 100-fold the Kcat of the A subunit (640 min-1). The same Kcat (693 min -1) was also observed when the A subunit was treated only with urea and dithiothreitol. Thus the full activity of Shiga-like toxin I required not only removal of the B subunits but also activation of the A subunit itself. Such activation could be largely induced in vitro by drastic loosening of the molecule induced by urea and dithiothreitol, but in vivo would probably require a proteolytic cleavage of the toxin. Inactivation of ribosomes by Shiga-like toxin I did not require sensitization of ribosomes by ATP and macromolecular cofactors present in postribosomal supernatants. PMID:9403966

Brigotti, M; Carnicelli, D; Alvergna, P; Mazzaracchio, R; Sperti, S; Montanaro, L

1997-09-01

267

Dependence of the kinetic and thermodynamic parameters on hydrophilic-lipophilic character of alprazolam, clonazepam, diazepam, doxepin and haloperidol in alkaline environment.  

PubMed

Examination of the stability of clonazepam, diazepam, alprazolam, haloperidol, and doxepin in basic solutions was performed, together with an assessment of the kinetic (k, t0.1i t0.5) and thermodynamic (Ea, ?H(++)i ?S(++)) stability-indicating parameters, which were compared with the lipophilicity (logP) of the studied drugs. It was observed that the calculated values of Ea, ?H(++) and ?S(++) for the studied drugs increased from 41.04kJ/mol to 125.50kJ/mol, from 37.82kJ/mol to 122.24kJ/mol and from -167.09J/Kmol to 53.02J/Kmol, respectively, along with an increase of lipophilicity (logP) from 2.12 to 4.30 for the most hydrophilic alprazolam to the most lipophilic haloperidol. The degradation products were identified using UPLC/MS/MS method. PMID:23916826

Ma?lanka, Anna; Krzek, Jan; Szlósarczyk, Marek; Zmudzki, Pawe?; Wach, Katarzyna

2013-07-31

268

Implications of the thermal properties and kinetic parameters of dehydroxylation of mica minerals for fault weakening, frictional heating, and earthquake energetics  

NASA Astrophysics Data System (ADS)

Transient frictional heating during earthquake slip induces dehydroxylation of phyllosilicate minerals. As this reaction is endothermic and releases H 2O, it affects dynamic fault weakening and the energetics of earthquakes. To quantitatively evaluate this effect, accurate determination of both the kinetic parameters of the reaction and the thermal properties of the minerals is needed. We chose an illite-muscovite sample as representative of the phyllosilicates found in active crustal faults. For this sample, we measured the specific heat capacity and thermal diffusivity, investigated their temperature dependencies, and determined the weight loss and enthalpy of the dehydroxylation reaction to be 5.22 wt.% and 0.2895 kJ g - 1 , respectively. We applied Friedman analysis to the weight loss data from heating experiments and found that the dehydroxylation reactions were well fitted by two-step reactions of an n-dimensional nucleation mechanism according to the Avrami-Erofeev equation with n = 0.5 (first step) and two-dimensional diffusion (second step). On the basis of these experimental results, we performed numerical analyses of dynamic fault weakening, which demonstrated that the fluids released by dehydroxylation contribute to pressurization of pore fluids inducing a decrease in effective normal stress on faults, and that the dehydroxylation reaction absorbs heat from the energy released. We also performed a sensitivity analysis on the kinetic function and parameters and the thermal properties, which showed that the contribution of these to fault weakening is considerably smaller than those of frictional coefficient and slip-zone thickness.

Hirono, Tetsuro; Tanikawa, Wataru

2011-07-01

269

Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions: Part 1 - general equations, parameters, and terminology  

NASA Astrophysics Data System (ADS)

Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It allows to describe mass transport and chemical reactions at the gas-particle interface and to link aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion correction, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependencies; flexible inclusion/omission of chemical species and physicochemical processes; flexible convolution/deconvolution of species and processes; and full compatibility with traditional resistor model formulations. Exemplary practical applications and model calculations illustrating the relevance of the above aspects will be presented in a companion paper (Ammann and Pöschl, 2005). We expect that the presented model framework will serve as a useful tool and basis for experimental and theoretical studies investigating and describing atmospheric aerosol and cloud surface chemistry and gas-particle interactions. In particular, it is meant to support the planning and design of laboratory experiments for the elucidation and determination of kinetic parameters; the establishment, evaluation, and quality assurance of comprehensive and self-consistent collections of rate parameters; and the development of detailed master mechanisms for process models and the derivation of simplified but yet realistic parameterizations for atmospheric and climate models.

Pöschl, U.; Rudich, Y.; Ammann, M.

2005-04-01

270

Determination of mechanism functions and kinetic parameters of thermodecomposition of complexes with the Schiff base derived from 3-methoxysalicylaldehyde and diamine with non-isothermal TG and DTG curves  

Microsoft Academic Search

The paper studies non-isothermal kinetics of monoaqua 3-methoxysalicylaldehyde-o-phenyldiamine copper(II) (cp1), 3-methoxysalicylaldehyde-o-phenyldiamine nickel(II) monohydrate (cp2), monoaqua 3-methoxysalicylaldehyde-ethyldiamine copper(II) (cp3) and 3-methoxysalicylaldehyde-ethyldiamine nickel(II) monohydrate (cp4) by use of non-isothermal TG and DTG curves. The kinetic parameters were analyzed by means of integral and differential methods, and mechanism functions of thermodecomposition reactions in their second steps were proposed. Thermodecomposition kinetic equations of the

Shu-Lan Li; De-Xin Liu; Sheng-Qiang Zhang; Hong Wang; Zhao-He Yang

1996-01-01

271

A Kinetics Study on Hydrothermal Liquefaction of High-diversity Grassland Perennials  

Microsoft Academic Search

Modeling of the liquefaction reaction kinetics for the low-input high-diversity mixtures of native grassland perennials was studied. The highest liquid yield of 82% was achieved within a short residence time of 1 minute at 374°C and 22.1 MPa. Seven possible reaction schemes and kinetic models were developed and compared. The unknown kinetic parameters of each model were estimated by nonlinear

B. Zhang; H.-J. Huang; S. Ramaswamy

2012-01-01

272

Assessment of the aerobic preparation and bottom ash addition as pretreatment steps before landfilling: impact on methanogenesis kinetics and leachate parameters.  

PubMed

This work focuses on assessing the impact of two types of waste pretreatment: addition of bottom ashes and aerobic pretreatment on both the onset and kinetics of methanogenesis and the evolution of different parameters in the leachate. It also studies the correlation between methane production and the different parameters measured in the leachate produced. A total of six 68-L pilots were thus used with fresh municipal solid waste (MSW) shredded to a 40-mm size. After 14 months of landfilling, the control has produced less than 10 NLkg(-1)DM, which corresponds to around 7% of its biochemical methane potential (BMP). Nevertheless, on one hand for aerobically pretreated waste, the lag phase before the onset of methanogenesis is significantly reduced to 0.9 month compared to more than 1 year for the control. In addition to that, on average 110 NLkg(-1)DM (90% of the BMP) is produced within around 6.5 months. On the other hand, the waste with added bottom ash shows a slight improvement of the lag phase over the control for one of the duplicate: 6.1 months of lag phase. At this stage, on average of 26 NLkg(-1)DM waste are detected (22% of the BMP) no final conclusion concerning the impact of bottom ashes could be made. The data obtained for the leachate parameters agrees with the observations on methane production. Statistical correlation study shows that the two components of the corrected PCA interpret 76% of the variability of the data: SUVA (specific UV absorbance at 254 nm) and HPI(*) (% of hydrophilic compounds) are identified as interesting parameters for following up the biodegradation in landfill conditions. PMID:22640801

Mansour, Alicia A; Motte, Antoine; Pallier, Virginie; Feuillade-Cathalifaud, Geneviève; Ponthieux, Arnaud

2012-05-27

273

Analysis of kinetic and operational parameters in a structured model for acrylic acid production through experimental design.  

PubMed

In biotechnological processes, a great number of factors can influence the income productivity and conversion. Normally, it is not evident which of these factors are the most important and how they interact. In this work, multivariate analysis techniques are used as experimental design coupled to a detailed deterministic model to identify the parameters with the most significant impact on the model to represent well the acrylic acid production process. It is proposed as an alternative process, having sugarcane as feedstock, to the petrochemical-based ones that have significant environmental impacts for their production. To increase the competitiveness of renewable acrylic-acid-based process, it is necessary to find out working conditions near the optimal region, which is not an easy task, as the process is multivariable and non-linear. The mapping of the dynamics of the developed process is made using techniques of factorial design together with the methodology of Plackett-Burman. It is shown that it is possible to increase the process performance by choosing optimized conditions for the reactor operation. PMID:18418750

Lunelli, B H; Rivera, E C; Vasco de Toledo, E C; Wolf Maciel, M R; Maciel Filho, R

2007-10-24

274

Toward full-chip prediction of yield-limiting contact patterning failure: correlation of simulated image parameters to advanced contact metrology metrics  

NASA Astrophysics Data System (ADS)

Electrical failure due to incomplete contacts or vias has arisen as one of the primary modes of yield loss for 130 nm and below designs in manufacturing. Such failures are generally understood to arise from both random and systematic sources. The addition of redundant vias, where possible, has long been an accepted DFM practice for mitigating the impact of random defects. Incomplete vias are often characterized by having a diameter near the target dimension but a depth of less than 100% of target. As such, it is a difficult problem to diagnose and debug in-line, since bright and dark field optical inspection systems cannot typically distinguish between a closed, partially open and fully open contact. Advanced metrology systems have emerged in recent years to meet this challenge, but no perfect manufacturing solution has yet been identified for full field verification of all contacts. Voltage Contrast (VC) SEM metrology biases the wafer to directly measure electrical conductivity after fill / polish, and can therefore easily discern a lack of electrical connection to the underlying conductor caused by incomplete photo, etch, or fill processing. While an entire wafer can in principal be VC scanned, throughput limitations dictate very sparse sampling in manufacturing. SEM profile grading (PG) leverages the rich content of the secondary electron waveform to decipher information about the bottom of the contact. Several authors have demonstrated an excellent response of the Profile Grade to intentional defocus vectors. However, the SEM can only target discreet or single digit groupings of contacts, and therefore requires intelligent guidance to identify those contacts which are most prone to failure, enabling protection of the fab WIP. An a-priori knowledge of which specific contacts in a layout are most likely to fail would prove very useful for proactive inspection in manufacturing. Model based pre-manufacturing verification allows for such knowledge to be communicated to manufacturing. This paper will focus on 130 nm node contact patterning, and will correlate SEM Profile Grade output to the extensive suite of model-based image tags from the CalibreTM opc-verification engine. With an understanding of which image parameters are most highly correlated to the occurrence of incomplete contact formation for a given process, the process model can be used to automatically direct inspection metrology to those layout instances that pose the highest risk of patterning failure through the lithographic process window. Such an approach maximizes the value content of in-line metrology.

Sturtevant, John L.; Chou, Dyiann

2006-04-01

275

Modeling intrinsic kinetics of enzymatic cellulose hydrolysis.  

PubMed

A multistep approach was taken to investigate the intrinsic kinetics of the cellulase enzyme complex as observed with hydrolysis of noncrystalline cellulose (NCC). In the first stage, published initial rate mechanistic models were built and critically evaluated for their performance in predicting time-course kinetics, using the data obtained from enzymatic hydrolysis experiments performed on two substrates: NCC and alpha-cellulose. In the second stage, assessment of the effect of reaction intermediates and products on intrinsic kinetics of enzymatic hydrolysis was performed using NCC hydrolysis experiments, isolating external factors such as mass transfer effects, physical properties of substrate, etc. In the final stage, a comprehensive intrinsic kinetics mechanism was proposed. From batch experiments using NCC, the time-course data on cellulose, cello-oligosaccharides (COS), cellobiose, and glucose were taken and used to estimate the parameters in the kinetic model. The model predictions of NCC, COS, cellobiose, and glucose profiles show a good agreement with experimental data generated from hydrolysis of different initial compositions of substrate (NCC supplemented with COS, cellobiose, and glucose). Finally, sensitivity analysis was performed on each model parameter; this analysis provides some insights into the yield of glucose in the enzymatic hydrolysis. The proposed intrinsic kinetic model parametrized for dilute cellulose systems forms a basis for modeling the complex enzymatic kinetics of cellulose hydrolysis in the presence of limiting factors offered by substrate and enzyme characteristics. PMID:17465526

Peri, Suma; Karra, Srinivas; Lee, Y Y; Karim, M Nazmul

2007-04-28

276

Highly luminescent and quantum-yielding CdSe/ZnS core/shell quantum dots synthesized by a kinetically controlled succession route in 18DMA.  

PubMed

Highly luminescent and quantum-yielding (QY) CdSe/ZnS core/shell quantum dots (CS QDs) were synthesised via a new succession route in a non-toxic solvent, N,N-Dimethyl-octadecyl-tertiary-amine(18DMA) at a mild temperature. The CS QDs were also proven to be as efficient in reaching high quantum yields (up to 74%) as their reported high-temperature synthesis with organic phosphine ligands. It was demonstrated that the synthesis temperatures directly determine the size by controlling the rate of the monomer diffusion and adsorption. It was also found that the amount of surfactant oleic acid determined the QY of the QDs, whereas it had little influence on the crystallisation. PMID:22755054

Duan, Hongyan; Liu, Xinmei; Liu, Chao; Han, Tingting; Lan, Xinzheng; Jiang, Yang

2012-03-01

277

EFFECTS OF SINGLE, DUAL AND TRIPLE INOCULATIONS WITH BACILLUS SUBTILIS, BACILLUS MEGATERIUM AND RHIZOBIUM LEGUMINOSARUM BV. PHASEOLI ON NODULATION, NUTRIENT UPTAKE, YIELD AND YIELD PARAMETERS OF COMMON BEAN (PHASEOLUS VULGARIS L. CV. ‘ELKOCA-05’)  

Microsoft Academic Search

This study was conducted in order to investigate the effects of single, dual, and triple inoculations with Rhizobium, N2-fixing Bacillus subtilis (OSU-142), and P-solubilizing Bacillus megaterium (M-3) on nodulation, plant growth, nutrient uptake and seed yield of common bean (Phaseolus vulgaris L. cv. ‘Elkoca-05’) in comparison to control and mineral fertilizer application under field conditions in 2006 and 2007 in

Erdal Elkoca; Metin Turan; M. Figen Donmez

2010-01-01

278

Direct kinetic study of radical transformation reaction Me sub 2 COH + Ph sub 2 CO yields Me sub 2 CO + Ph sub 2 COH  

SciTech Connect

Reaction Me{sub 2}COH + Ph{sub 2}CO {yields} Me{sub 2}CO + Ph{sub 2}COH (5) was studied by laser flash photolysis under such experimental conditions where the changes in the concentrations of ketyl radicals with reaction time were controlled by this radical transformation process. Diphenylketyl radical concentration profiles were obtained by monitoring transient absorption at 540 nm and the rate coefficient k{sub 5} was extracted from that part of the concentration trajectory which was determined solely by reaction 5. Thus, k{sub 5} = (3.6 {plus minus} 0.6) {times} 10{sup 5} dm{sup 3} mol{sup {minus}1} s{sup {minus}1} was determined at 298 K in acetonitrile, which is higher than the two recently reported values derived from quantum yields measured under steady-state conditions. A reaction mechanism for the radical transformation process (5) is proposed in which hydrogen-bonded species formed from ketyl radical and benzophenone participate.

Demeter, A.; Berces, T. (Central Research Inst. for Chemistry, Budapest (Hungary))

1991-02-07

279

Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions - Part 1: General equations, parameters, and terminology  

NASA Astrophysics Data System (ADS)

Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It enables a detailed description of mass transport and chemical reactions at the gas-particle interface, and it allows linking aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined and consistent rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependences (transient and steady-state conditions); flexible addition of unlimited numbers of chemical species and physicochemical processes; optional aggregation or resolution of intermediate species, sequential processes, and surface layers; and full compatibility with traditional resistor model formulations. The outlined double-layer surface concept and formalisms represent a minimum of model complexity required for a consistent description of the non-linear concentration and time dependences observed in experimental studies of atmospheric multiphase processes (competitive co-adsorption and surface saturation effects, etc.). Exemplary practical applications and model calculations illustrating the relevance of the above aspects are presented in a companion paper (Ammann and Pöschl, 2007). We expect that the presented model framework will serve as a useful tool and basis for experimental and theoretical studies investigating and describing atmospheric aerosol and cloud surface chemistry and gas-particle interactions. It shall help to end the "Babylonian confusion" that seems to inhibit scientific progress in the understanding of heterogeneous chemical reactions and other multiphase processes in aerosols and clouds. In particular, it shall support the planning and design of laboratory experiments for the elucidation and determination of fundamental kinetic parameters; the establishment, evaluation, and quality assurance of comprehensive and self-consistent collections of rate parameters; and the development of detailed master mechanisms for process models and derivation of simplified but yet realistic parameterizations for atmospheric and climate models.

Pöschl, U.; Rudich, Y.; Ammann, M.

2007-12-01

280

Excitation functions of spin correlation parameters A{sub NN},A{sub SS}, and A{sub SL} in elastic ({yields}/p)({yields}/p) scattering between 0.45 and 2.5 GeV  

SciTech Connect

Excitation functions of the spin correlation coefficients A{sub NN}(p{sub lab},{theta}{sub c.m.}),A{sub SS}(p{sub lab},{theta}{sub c.m.}), and A{sub SL}(p{sub lab},{theta}{sub c.m.}) have been measured with the polarized proton beam of the Cooler Synchrotron and an internal polarized atomic beam target. Data were taken continuously during the acceleration for proton momenta p{sub lab} ranging from 1000 to 3300 MeV/c (kinetic energies T{sub lab} 450-2500 MeV) as well as for discrete momenta of 1430 MeV/c and above 1950 MeV/c covering angles {theta}{sub c.m.} between 30 deg. and 90 deg. The data are of high internal consistency. Whereas A{sub SL}(p{sub lab,}{theta}{sub c.m.}) is small and without structures in the whole range, A{sub NN} and, even more, A{sub SS} show a pronounced energy dependence. The angular distributions for A{sub SS} are at variance with predictions of existing phase-shift analyses at energies beyond 800 MeV. The impact of our results on phase-shift solutions is discussed. The direct reconstruction of the scattering amplitudes from all available pp elastic scattering data considerably reduces the ambiguities of solutions.

Bauer, F.; Buesser, K.; Colberg, T.; Demiroers, L.; Eyser, K.O.; Greiff, J.; Jonas, E.; Krause, H.; Lehmann, C.; Lindlein, J.; Pauly, C.; Schirm, N.; Scobel, W.; Wolf, T. [Institut fuer Experimentalphysik, Universitaet Hamburg, D-22761 Hamburg (Germany); Bisplinghoff, J.; Busch, M.; Dahl, C.; Eversheim, P.D.; Hinterberger, F.; Meinerzhagen, A. [Helmholtz-Institut fuer Strahlen- und Kernphysik, Universitaet Bonn, D-53115 Bonn (Germany)] [and others

2005-05-01

281

Total Fluorescence Quantum Yield and Red Shift of Total Fluorescence Maximum as Parameters to Investigate Polycyclic Aromatic Compounds Present in Diesel Fuel  

Microsoft Academic Search

A method has been developed to find out total fluorescence quantum yield (?F ) of petroleum products like diesel, which provides the overall fluorescence quantum efficiency of a fluorophore at various possible excitation wavelengths. This simple method is suitable for characterization of petroleum products like diesel. The concentration dependent quantitative investigation of PACs present in diesel with respect to variation

Digambara Patra; A. K. Mishra

2002-01-01

282

Studies on the efficacy of sulphate of potash (SOP) on the physiological, yield and quality parameters of banana cv. Robusta (Cavendish AAA)  

Microsoft Academic Search

The investigation was carried out to assess the comparative efficacy of sulphate of potash (SOP) and muriate of motash (MOP) to improve the growth, yield and quality of the Robusta banana through enhanced physiological processes. The chlorophyll content, relative water content, NRase activity, soluble protein, photosynthetic efficacy and gas exchange characters were found to be higher with 150 per cent

Alagarsamy Ramesh Kumar; Neelakandan Kumar

283

Subcritical hydrothermal liquefaction of cattle manure to bio-oil: Effects of conversion parameters on bio-oil yield and characterization of bio-oil  

Microsoft Academic Search

In this study, cattle manure was converted to bio-oil by subcritical hydrothermal liquefaction in the presence of NaOH. The effects of conversion temperature, process gas, initial conversion pressure, residence time and mass ratio of cattle manure to water on the bio-oil yield were studied. The bio-oil was characterized in terms of elemental composition, higher heating value, ultraviolet–visible (UV\\/Vis) spectroscopy, Fourier

Sudong Yin; Ryan Dolan; Matt Harris; Zhongchao Tan

2010-01-01

284

Yield-SAFE: A parameter-sparse, process-based dynamic model for predicting resource capture, growth, and production in agroforestry systems  

Microsoft Academic Search

1.Silvoarable agroforestry (SAF) is the cultivation of trees and arable crops on the same parcel of land. SAF may contribute to modern diversified land use objectives in Europe, such as enhanced biodiversity and productivity, reduced leaching of nitrogen, protection against flooding and erosion, and attractiveness of the landscape. Long-term yield predictions are needed to assess long-term economic profitability of SAF.2.A

Wopke van der Werf; Karel Keesman; Paul Burgess; Anil Graves; David Pilbeam; L. D. Incoll; Klaas Metselaar; Martina Mayus; Roel Stappers; Herman van Keulen; João Palma; Christian Dupraz

2007-01-01

285

Subcritical hydrothermal liquefaction of cattle manure to bio-oil: Effects of conversion parameters on bio-oil yield and characterization of bio-oil.  

PubMed

In this study, cattle manure was converted to bio-oil by subcritical hydrothermal liquefaction in the presence of NaOH. The effects of conversion temperature, process gas, initial conversion pressure, residence time and mass ratio of cattle manure to water on the bio-oil yield were studied. The bio-oil was characterized in terms of elemental composition, higher heating value, ultraviolet-visible (UV/Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Results showed that the bio-oil yield depended on the conversion temperature and the process gas. Higher initial conversion pressure, longer residence time and larger mass ratio of cattle manure to water, however, had negative impacts on the bio-oil yield. The higher heating value of bio-oil was 35.53MJ/kg on average. The major non-polar components of bio-oil were toluene, ethyl benzene and xylene, which are components of crude oil, gasoline and diesel. PMID:20083403

Yin, Sudong; Dolan, Ryan; Harris, Matt; Tan, Zhongchao

2010-01-18

286

Multisubstrate biodegradation kinetics of naphthalene, phenanthrene, and pyrene mixtures  

SciTech Connect

Biodegradation kinetics of naphthalene, phenanthrene and pyrene were studied in sole-substrate systems, and in binary and ternary mixtures to examine substrate interactions. The experiments were conducted in aerobic batch aqueous systems inoculated with a mixed culture that had been isolated from soils contaminated with polycyclic aromatic hydrocarbons (PAHs). Monod kinetic parameters and yield coefficients for the individual parameters and yield coefficients for the individual compounds were estimated from substrate depletion and CO{sub 2} evolution rate data in sole-substrate experiments. In all three binary mixture experiments, biodegradation kinetics were comparable to the sole-substrate kinetics. In the ternary mixture, biodegradation of naphthalene was inhibited and the biodegradation rates of phenanthrene and pyrene were enhanced. A multisubstrate form of the Monod kinetic model was found to adequately predict substrate interactions in the binary and ternary mixtures using only the parameters derived from sole-substrate experiments. Numerical simulations of biomass growth kinetics explain the observed range of behaviors in PAH mixtures. In general, the biodegradation rates of the more degradable and abundant compounds are reduced due to competitive inhibition, but enhanced biodegradation of the more recalcitrant PAHs occurs due to simultaneous biomass growth on multiple substrates. In PAH-contaminated environments, substrate interactions may be very large due to additive effects from the large number of compounds present.

Guha, S.; Peters, C.A.; Jaffe, P.R.

1999-12-05

287

The influence of thiourea on kinetic parameters on the cathodic and anodic reaction at different metals in H 2SO 4 solution  

Microsoft Academic Search

The effect of addition of thiourea on the kinetics of anodic dissolution and cathodic reaction on copper and iron in acidic sulfate solutions has been studied using potentiodynamic polarization measurements. The results obtained in the presence of thiourea indicate that it has a very strong influence on the kinetics of discharge processes at different metals. The presence of this organic

Z. D. Stankovi?; M. Vukovi?

1996-01-01

288

Sediment Loads and Yield, and Selected Water-Quality Parameters in Clear Creek, Carson City and Douglas County, Nevada, Water Years 2004-07  

USGS Publications Warehouse

Some reaches of Clear Creek above U.S. Highway 395 have experienced severe erosion as a result of fires, extreme precipitation events, and past and current human activities in the basin. Previous evaluations of erosion in the basin have concluded that most of the sediment produced and transported in the basin was associated with U.S. Highway 50, a four-lane highway that roughly parallels Clear Creek through much of the basin. During this study (water years 2004-07), construction of roads and a large residential area and golf course in the area began and are likely to affect water quality and sediment transport in the basin. Sediment data were collected between October 2003 and September 2007 (water years 2004-07) from three sites along Clear Creek. Annual suspended-sediment load was estimated to range from 1,456 tons in water year 2006 to only 100 tons in water year 2004, which corresponds to suspended-sediment yields of 93.9 tons per square mile per year in 2006 to 6.4 tons per square mile per year in 2004. In water year 2006, the suspended-sediment load on December 31, 2005, alone exceeded the combined annual load for water years 2004, 2005, and 2007. Bedload sediment was estimated to comprise 73 percent of total sediment load in the creek. Mean annual suspended-sediment yield in Clear Creek basin was much greater than yields in the Logan House, Edgewood, and Glenbrook Creek basins in the adjacent Lake Tahoe basin. Comparison of data collected during this study with data collected by university researchers in the 1970s is inconclusive as to whether fundamental changes in basin sediment characteristics have occurred during the 30-year period because different methods and sampling locations were used in the earlier studies.

Seiler, Ralph L.; Wood, James L.

2009-01-01

289

Grease Yields.  

National Technical Information Service (NTIS)

The invention is directed to lubricating grease compositions, more particularly to the use of certain agents to improve the yield of calcium base greases. The yields of grease compositions are increased by incorporating therein an oil-soluble polyglycol p...

D. W. Criddle

1965-01-01

290

Biohydrogen production based on the evaluation of kinetic parameters of a mixed microbial culture using glucose and fruit-vegetable waste as feedstocks.  

PubMed

Hydrogen (H2) production from the organic fraction of solid waste such as fruit and vegetable waste (FVW) is a novel and feasible energy technology. Continuous application of this process would allow for the simultaneous treatment of organic residues and energy production. In this study, batch experiments were conducted using glucose as substrate, and data of H2 production obtained were successfully adjusted by a logistic model. The kinetic parameters (? max?=?0.101 h(-1), K s?=?2.56 g/L) of an H2-producing microbial culture determined by the Monod and Haldane-Andrews growth models were used to establish the continuous culture conditions. This strategy led to a productive steady state in continuous culture. Once the steady state was reached in the continuous reactor, a maximum H2 production of 700 mL was attained. The feasibility of producing H2 from the FVW obtained from a local market in Mexico City was also evaluated using batch conditions. The effect of the initial FVW concentration on the H2 production and waste organic material degradation was determined. The highest H2 production rate (1.7 mmol/day), the highest cumulative H2 volume (310 mL), and 25 % chemical oxygen demand (COD) removal were obtained with an initial substrate (FVW) concentration of 37 g COD/L. The lowest H2 production rates were obtained with relatively low initial substrate concentrations of 5 and 11 g COD/L. The H2 production rates with FVW were also characterized by the logistic model. Similar cumulative H2 production was obtained when glucose and FVW were used as substrates. PMID:23832860

Garcia-Peña, E I; Canul-Chan, M; Chairez, I; Salgado-Manjarez, E; Aranda-Barradas, J

2013-07-06

291

Studies on the adaptation of intact leaves to changing light intensities by a kinetic analysis of chlorophyll fluorescence and oxygen evolution as measured by the photoacoustic signal  

Microsoft Academic Search

A detailed quantitative study of the kinetics of photochemical and non-photochemical quenching was achieved by a linear analysis of the yields of chlorophyll fluorescence and of oxygen evolution (as measured by the photoacoustic effect) by their responses to sinusoidal changes of actinic light. The results of this analysis were given in terms of the parameters of the kinetic phases obtained

Holger Dau; Ulf-Peter Hansen

1989-01-01

292

Lineshape of {psi}(3770) and low-lying vector charmonium resonance parameters in e{sup +}e{sup -{yields}}DD  

SciTech Connect

We investigate the DD production in e{sup +}e{sup -} annihilations near threshold in an effective Lagrangian approach. This shows that the lineshape of the cross section near threshold is sensitive to the contributions from {psi}{sup '}, though it is below the DD threshold. The recent experimental data from the BES and Belle collaborations allow us to determine the {psi}{sup '}DD coupling constant, which appears to be consistent with other theoretical studies. As a consequence, the {psi}{sup '}-{psi}(3770) mixing parameter can be extracted around the {psi}(3770) mass region. Resonance parameters for {psi}(3770), X(3900), {psi}(4040), and {psi}(4160) are also investigated. The X(3900) appears as an enhancement at around 3.9 GeV in the Belle data. In addition to treating it as a resonance, we also study the mechanism through which the enhancement is produced by the DD*+c.c. open channel effects. Our result shows that such a possibility cannot be eliminated.

Zhang Yuanjiang [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhao Qiang [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Theoretical Physics Center for Science Facilities, CAS, Beijing 100049 (China)

2010-02-01

293

Experimental validation of a kinetic multi-component mechanism in a wide HCCI engine operating range for mixtures of n-heptane, iso-octane and toluene: Influence of EGR parameters  

Microsoft Academic Search

The parameters that are present in exhaust gas recirculation (EGR) are believed to provide an important contribution to control the auto-ignition process of the homogeneous charge compression ignition (HCCI) in an engine. For the investigation of the behaviour of the auto-ignition process, a kinetic multi-component mechanism has been developed in former work, containing 62 reactions and 49 species for mixtures

Hatim Machrafi

2008-01-01

294

Kinetics of ethanol production from sugarcane bagasse enzymatic hydrolysate concentrated with molasses under cell recycle.  

PubMed

In this work, a kinetic model for ethanol fermentation from sugarcane bagasse enzymatic hydrolysate concentrated with molasses was developed. A model previously developed for fermentation of pure molasses was modified by the inclusion of a new term for acetic acid inhibition on microorganism growth rate and the kinetic parameters were estimated as functions of temperature. The influence of the hydrolysate on the kinetic parameters is analyzed by comparing with the parameters from fermentation of pure molasses. The impact of cells recycling in the kinetic parameters is also evaluated, as well as on the ethanol yield and productivity. The model developed described accurately most of the fermentations performed in several successive batches for temperatures from 30 to 38°C. PMID:23313680

de Andrade, Rafael Ramos; Maugeri Filho, Francisco; Maciel Filho, Rubens; da Costa, Aline Carvalho

2012-12-20

295

New kinetic parameters for rat liver arginase measured at near-physiological steady-state concentrations of arginine and Mn2+.  

PubMed Central

A cytosolic cell-free system from rat liver containing the last three enzymes of the urea cycle, a number of cofactors and the substrates aspartate and citrulline was shown to synthesize urea at near-physiological rates ranging between 0.40 and 1.25 mumol/min per g of liver. This system was used to determine the kinetic parameters for arginase. With saturating amounts of Mn2+ (30 microM), arginine remained at a steady-state concentration of 5-35 microM depending on the aspartate and citrulline supply. Vmax. at micromolar arginine concentrations was between 1.10 and 1.25 mumol/min per g of liver, the K0.5 (arginine) between 6.0 and 6.5 microM and positive co-operativity was observed (Hill coefficient 2). Omission of Mn2+ caused a significant accumulation of arginine during the incubation, suggesting a regulatory effect of arginase. Under these conditions, Vmax. was 1.10-1.65 mumol/min per g of liver and the Km (arginine) increased up to 14.4-21.1 microM. The apparent Ka for Mn2+ in the presence of physiological concentrations of ATP, Mg2+ and arginine was calculated to be maximally 8 microM. Initial-velocity experiments with millimolar arginine concentrations as the direct substrate gave the following results, which are in good agreement with literature data. In the absence of Mn2+, Vmax. was 71.3 mumol/min per g of liver and the Km (arginine) 1.58 mM. With 30 microM-Mn2+, Vmax. was 69.4 mumol/min per g of liver and the Km (arginine) decreased to 0.94 mM. On the basis of our results, we propose the presence of high-affinity and low-affinity sites for arginine on rat liver arginase and postulate that alterations in arginase activity arising from changes in the concentration of arginine and of the cofactor Mn2+ may contribute to the regulation of ureagenesis in vivo.

Maggini, S; Stoecklin-Tschan, F B; Morikofer-Zwez, S; Walter, P

1992-01-01

296

Molar growth yields and bioenergetic parameters of extremely alkaliphilic Bacillus species in batch cultures, and growth in a chemostat at pH 10.5.  

PubMed

Alkaliphilic Bacillus species that grow at pH 10.5 must cope with a low protonmotive force (-50 mV) due to a reversed transmembrane pH gradient at least 2 pH units more acid inside. Here we demonstrate that strictly alkaliphilic B. firmus RAB and two strains of B. alcalophilus (ATCC 27467 and DSM 485) grow exponentially in batch cultures with a doubling time of less than 1 h in 100 mM buffered medium, while the actual medium pH remains above 10.2. The ATCC strain continued to grow rapidly for at least 7 h, but the growth rate of the DSM strain declined dramatically after 3 h. However, both the B. alcalophilus strains, B. firmus RAB and facultatively alkaliphilic B. firmus OF4 were readily maintained for at least 24 h between pH 10.4 and 10.6 in a chemostat where nutrients were constantly replenished. A critical nutrient may be limiting in batch cultures of the DSM strain of B. alcalophilus. The facultative alkaliphile grew equally well in batch cultures at an initial pH of 7.5 or 10.5. Its molar growth yield (23 mg dry wt mmol-1) on malate (Ymal) was the same at the two pH values and was comparable to Ymal for B. subtilis grown at neutral pH. B. firmus RAB and B. alcalophilus ATCC 27467 grown at pH 10.5 also showed Ymal values at least as high as the neutralphile, indicating efficient use of the energy source even at low protonmotive force. Moreover, the phosphorylation potential of B. firmus OF4 grown at pH 7.5 (45.2 kJ mol-1) or pH 10.5 (46 kJ mol-1) was in a conventional range for bacteria. PMID:1770352

Guffanti, A A; Hicks, D B

1991-10-01

297

Measurement of D{sup 0}-D{sup 0} Mixing Parameters Using D{sup 0}{yields}K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and D{sup 0}{yields}K{sub S}{sup 0}K{sup +}K{sup -} Decays  

SciTech Connect

We report a direct measurement of D{sup 0}-D{sup 0} mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D{sup 0}{yields}K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and, for the first time, D{sup 0}{yields}K{sub S}{sup 0}K{sup +}K{sup -} decays. The low-momentum pion {pi}{sub s}{sup +} in the decay D{sup *+{yields}}D{sup 0{pi}}{sub s}{sup +} identifies the flavor of the neutral D meson at its production. Using 468.5 fb{sup -1} of e{sup +}e{sup -} colliding-beam data recorded near {radical}(s)=10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x=[1.6{+-}2.3(stat){+-}1.2(syst){+-}0.8(model)]x10{sup -3}, and y=[5.7{+-}2.0(stat){+-}1.3(syst){+-}0.7(model)]x10{sup -3}. These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing.

Amo Sanchez, P. del; Lees, J. P.; Poireau, V.; Prencipe, E.; Tisserand, V. [Laboratoire d'Annecy-le-Vieux de Physique des Particules (LAPP), Universite de Savoie, CNRS/IN2P3, F-74941 Annecy-Le-Vieux (France); Garra Tico, J.; Grauges, E. [Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona (Spain); Martinelli, M.; Palano, A.; Pappagallo, M. [INFN Sezione di Bari, I-70126 Bari (Italy); Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); Eigen, G.; Stugu, B.; Sun, L. [University of Bergen, Institute of Physics, N-5007 Bergen (Norway); Battaglia, M.; Brown, D. N.; Hooberman, B.; Kerth, L. T.; Kolomensky, Yu. G.; Lynch, G.; Osipenkov, I. L. [Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720 (United States)

2010-08-20

298

On the kinetics of the ?–? phase transformation in an Al-doped Fe–Cr alloy  

Microsoft Academic Search

The influence of aluminium on the kinetics of the ?-phase formation in a quasi-equiatomic Fe–Cr alloy with fine- and coarse-grained structure was studied using 57Fe Mössbauer Spectroscopy. The amount of the ?-phase precipitated could be well described by use of the Johnson–Avrami–Mehl equation which yielded the kinetics parameters k and n. Assuming the k-values follow the Arrhenius law, the effective

A Blachowski; S. M Dubiel; J Zukrowski; J Cie?lak; B Sepiol

2000-01-01

299

Growth kinetics of thermophilic Methanosarcina spp. isolated from full-scale biogas plants treating animal manures  

Microsoft Academic Search

This study determines the growth kinetics of thermophilic strains of Methanosarcina spp. from full-scale thermophilic biogas plants. The complete set of kinetic parameters, including maximum specific growth rate ?max, half saturation constant KS, acetate threshold concentration and cell growth yield YX\\/S, were determined for six Methanosarcina strains newly isolated from full-scale reactors and the type strain Methanosarcina thermophila TM-1T. The

Zuzana Mladenovska; Birgitte Kiær Ahring

2000-01-01

300

Determination of the partition coefficients and absorption kinetic parameters of chemicals in a lipophilic membrane\\/water system by using a membrane-coated fiber technique  

Microsoft Academic Search

The absorption kinetics of chemicals in a lipophilic membrane\\/water system was studied with a membrane-coated fiber (MCF) technique, in which the partition coefficient, membrane diffusivity and boundary layer adjacent to the membrane were taken into account. The cumulative amount permeated into the membrane was expressed as a function of absorption time in an exponential equation. Two constants were introduced into

Xin-Rui Xia; Ronald E. Baynes; Nancy A. Monteiro-Riviere; Jim E. Riviere

2005-01-01

301

Parsimonious Modeling of Yield Curves  

Microsoft Academic Search

This paper introduces a parametrically parsimonious model for yield curves that has the ability to represent the shapes generally associated with yield curves: monotonic, humped, and S-shaped. The authors find that the model explains 96 percent of the variation in bill yields across maturities during the period 1981-83. The movement of the parameters through time reflects and confirms a change

Charles R. Nelson; Andrew F. Siegel

1987-01-01

302

Evaluation of mixed-salt effects on thermodynamic and kinetic parameters of RNA polymerase-promoter DNA complexes in terms of equivalent salt concentrations. General applicability to DNA complexes.  

PubMed

Facile evaluation of mixed-salt effect on the strongly salt-dependent thermodynamic and kinetic parameters of protein-DNA complexes is of importance for relevant biochemical and biophysical studies. In pursuit of this aim, binding isotherms for open transcription complex (RPo) of Escherichia coli RNA polymerase (R) at lambdaP(R) promoter DNA (P) were determined as a function of salt concentration in pure NaCl and Tris/HCl solutions, and as a function of [NaCl] in the presence of fixed concentrations of MgCl(2) and Tris/HCl. A concept of equivalent salt concentrations, i.e. concentrations at which the binding equilibrium constant is the same, was introduced and applied for prediction of binding isotherms in mixed salt solutions. Full coincidence between the experimental and predicted isotherms indicated that individual contributions of salts to the global salt-effect are additive in a broad range of salt concentrations. A generalized formula for calculation of salt equivalents characteristic for any of the thermodynamic or kinetic parameters of a complex (e.g., free energy, binding equilibrium and association/dissociation kinetic rate constants) is presented and its applicability to a number of protein-DNA complexes and dsDNA melting demonstrated using authors' own and literature data. PMID:19898692

?ozi?ski, Tomasz; Wierzchowski, Kazimierz L

2009-11-05

303

Erbium hydride thermal desorption : controlling kinetics.  

SciTech Connect

Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report show that hydride film processing parameters directly impact thermal stability. Issues to be addressed include desorption kinetics for dihydrides and trihydrides, and the effect of film growth parameters, loading parameters, and substrate selection on desorption kinetics.

Ferrizz, Robert Matthew

2007-08-01

304

Pyromat II micropyrolysis of source rocks and oil shales: Effects of native content and sample size on T sub max values and kinetic parameters  

SciTech Connect

The Pyromat 2 micropyrolyzer can routinely measure kinetics on standard shales and source rocks. However, when examining samples which have high native bitumen contents, samples with high TOC and native bitumen contents, asphaltenes, tar sands, and other non-kerogen type materials, the pyrolysis profiles sometimes deviate from normal expected behavior. Some of the deviant features are: (1) evolution before the maximum assigned to kerogen breakdown, (2) broadening of the maximum assigned to kerogen breakdown and shifting in T{sub max} with increasing sample size, and (3) artifacts in activation energy distributions derived in kinetic analyses. This report examines these features in more detail and offers potential experimental solutions to circumvent problems created by these features. 9 refs., 9 figs., 5 tabs.

Reynolds, J.G.; Murray, A.

1991-01-01

305

An alternative analysis of enzyme systems based on the whole reaction time: evaluation of the kinetic parameters and initial enzyme concentration  

Microsoft Academic Search

This work presents an alternative analysis of the integrated rate equations corresponding to the simple Michaelis-Menten mechanism\\u000a without product inhibition. The suggested new results are reached under a minimal set of assumptions and include, as a particular\\u000a case, the classical integrated Michaelis–Menten equation. Experimental designs and a kinetic data analysis are suggested to\\u000a the estimation of the maximum steady-state rate,

R. Varón; M. Garcia-Moreno; J. Masiá-Pérez; F. García-Molina; F. García-Cánovas; E. Arias; E. Arribas; F. García-Sevilla

2007-01-01

306

Growth kinetics and stoichiometry of Mentha citrata shooty teratomas transformed by Agrobacterium tumefaciens  

Microsoft Academic Search

Culture characteristics of genetically transformed Mentha citrata shooty teratomas were studied in liquid Murashige and Skoog and Gamborg's B5 media. Based on calculated kinetic and yield parameters, a stoichiometric equation was developed to describe growth in media containing both nitrate and ammonia. Measurements of oxygen uptake rate showed that delivery of adequate oxygen to completely submerged shoots depends on the

M. Ahkam Subroto; John D. Hamill; Pauline M. Doran

1995-01-01

307

Multifactorial analysis of acetaldehyde kinetics during alcoholic fermentation by Saccharomyces cerevisiae  

Microsoft Academic Search

Acetaldehyde is the terminal electron acceptor in the alcoholic fermentation by Saccharomyces cerevisiae. Quantitatively the most important carbonyl by-product, it has relevance for ethanol production yields as well as product stabilization and toxicology. The aim of this study was to investigate the effect of various enological parameters on acetaldehyde kinetics during alcoholic fermentations. Two commercial yeast strains were tested in

J. N. Jackowetz; S. Dierschke; R. Mira de Orduña

2011-01-01

308

EVALUATION OF CHEMICAL REACTION MECHANISMS FOR PHOTOCHEMICAL SMOG. PART 3. SENSITIVITY OF EKMA (EMPIRICAL KINETIC MODELING APPROACH) TO CHEMICAL MECHANISM AND INPUT PARAMETERS  

EPA Science Inventory

Six chemical reaction mechanisms for photochemical smog were used to study the effect of input parameters on volatile organic compound (VOC) control requirements needed to reduce ozone. The parameters studied were initial VOC composition, dilution rate, post 8-A.M. emissions, bas...

309

Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants  

PubMed Central

Apart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fully-expanded leaf, half-way along the stem, in the transition zone between the autotrophic and heterotrophic part of the stem, and in the root axis. A top-to-bottom membrane potential gradient of sieve elements was observed along the stem (?130 mV to ?110 mV), while the membrane potential of the phloem parenchyma cells was stable (approx. ?100 mV). In roots, the membrane potential of sieve elements dropped abruptly to ?55 mV. Bathing solutions having various sucrose concentrations were administered and sucrose/H+-induced depolarizations were recorded. Data analysis by non-linear least-square data fittings as well as by linear Eadie–Hofstee (EH) -transformations pointed at biphasic Michaelis–Menten kinetics (2 MM, EH: Km1 1.2–1.8 mM, Km2 6.6–9.0 mM) of sucrose uptake by sieve elements. However, Akaike's Information Criterion (AIC) favored single MM kinetics. Using single MM as the best-fitting model, Km values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher Km values (EH: Km1 10 mM, Km2 70 mM) as compared to sieve elements were found. In preliminary patch-clamp experiments with sieve-element protoplasts, small sucrose-coupled proton currents (?0.1 to ?0.3 pA/pF) were detected in the whole-cell mode. In conclusion (a) Km values for sucrose uptake measured by electrophysiology are similar to those obtained with heterologous systems, (b) electrophysiology provides a useful tool for in situ determination of Km values, (c) As yet, it remains unclear if one or two uptake systems are involved in sucrose uptake by sieve elements, (d) Affinity for sucrose uptake by sieve elements exceeds by far that by phloem parenchyma cells, (e) Patch-clamp studies provide a feasible basis for quantification of sucrose uptake by single cells. The consequences of the findings for whole-plant carbohydrate partitioning are discussed.

Hafke, Jens B.; Holl, Sabina-Roxana; Kuhn, Christina; van Bel, Aart J. E.

2013-01-01

310

Kinetic Rate Law Parameter Measurements on a Borosilicate Waste Glass: Effect of Temperature, pH, and Solution Composition on Alkali Ion Exchange  

SciTech Connect

The reaction kinetics of glass is controlled by matrix dissolution and ion exchange (IEX). Dissolution of an alkali-rich simulated borosilicate waste glass was investigated using single-pass flow-through (SPFT) experiments. Experiments were conducted as a function of temperature, pH, and solution composition by varying the SiO2 (aq) activity in the influent solution. Results showed that under dilute conditions matrix dissolution increased with increasing pH and temperature, and decreased with increasing SiO2 (aq) activity. IEX rates decreased with increasing pH and temperature, and increased with increasing SiO2 (aq) activity. Over the solution composition range interrogated in this study the dominant dissolution mechanism changed from matrix dissolution to IEX. These results suggest that “secondary” reactions may become dominant under certain environmental conditions and emphasize the need to incorporate these reactions into dissolution rate models.

Pierce, Eric M.; McGrail, B. Peter; Icenhower, Jonathan P.; Cordova, Elsa A.; Steele, Jackie L.; Baum, Steven R.

2004-08-01

311

Combustion Kinetics of Tetrafluoroethylene.  

National Technical Information Service (NTIS)

The thermal dissociation of carbonyl fluoride (CF2O) in excess argon, CF20 yields CFO +F, was studied behind both incident and reflected shock waves. Preliminary kinetic data have been obtained in the temperature and total pressure ranges 2500-3100K and 0...

R. A. Matula

1970-01-01

312

Kinetic and Chemical Mechanism of Malate Synthase from Mycobacterium tuberculosis  

PubMed Central

Malate synthase catalyzes the Claisen-like condensation of acetyl-coenzyme A and glyoxylate in the glyoxylate shunt of the citric acid cycle. The Mycobacterium tuberculosis malate synthase G gene, glcB, was cloned, and the N-terminal His6 tagged 80 kDa protein was expressed in soluble form and purified by metal affinity chromatography. A chromogenic 4,4?-dithiodipyridine assay did not yield linear kinetics, but the generation of an active site directed mutant, C619S, gave an active enzyme and linear kinetics. The resulting mutant exhibited comparable kinetics to wild type and was used for the full kinetic analysis. Initial velocity studies were intersecting suggesting a sequential mechanism, which was confirmed by product and dead-end inhibition. The inhibition studies delineated the ordered binding of glyoxylate followed by AcCoA and the ordered release of CoA followed by malate. The pH dependence of kcat and kcat/Kgly are both bell-shaped and catalysis depends on a general base (pK 5.3) and a general acid (pK 9.2). Primary kinetic isotope effects determined using [C2H3-methyl] acetyl-CoA suggested that proton removal and carbon-carbon bond formation were partially rate-limiting. Solvent kinetic isotope effects on kcat suggested the hydrolysis of the malyl-CoA intermediate was also partially rate-limiting. Multiple kinetic isotope effects, utilizing D2O and [C2H3-methyl] acetyl-CoA, confirmed a stepwise mechanism in which the step exhibiting primary kinetic isotope effects precedes the step exhibiting the solvent isotope effects. The kinetic data and the pH dependence of the kinetic parameters were combined with existing structural and mutagenesis data to propose a chemical mechanism for malate synthase from Mycobacterium tuberculosis.

Quartararo, Christine E.; Blanchard, John S.

2011-01-01

313

Good relationship between saliva cotinine kinetics and plasma cotinine kinetics after smoking one cigarette.  

PubMed

This study investigated the relationship between plasma and saliva cotinine kinetics after smoking one cigarette and the relationship between cotinine kinetics and estimated nicotine intake, which was calculated as mouth level exposure (MLE) of nicotine, from smoking two test cigarettes with different nicotine yields. This study was conducted in 16 healthy adult Japanese smokers, who did not have null nor reduced-activity alleles of CYP2A6, with a quasi-randomized crossover design of smoking a low-tar cigarette or a high-tar cigarette. Saliva cotinine showed similar concentration profiles to plasma cotinine, and all of the calculated pharmacokinetic parameters of cotinine showed the same values in plasma and saliva. The Cmax and AUC of cotinine showed almost the same dose-responsiveness to the estimated MLE of nicotine between plasma and saliva, but the tmax and t1/2 of cotinine were not affected by the estimated MLE of nicotine in either plasma or saliva. The results show that saliva cotinine kinetics reflects plasma cotinine kinetics, and measurement of saliva cotinine concentration gives the same information as plasma cotinine on the nicotine intake. Thus, saliva cotinine would be a good and less-invasive exposure marker of cigarette smoke, reflecting the plasma cotinine concentration and kinetics. PMID:23933006

Yuki, Dai; Kikuchi, Akira; Miura, Naoki; Kakehi, Aoi; Onozawa, Masahiro

2013-08-08

314

Glucose metabolic rate kinetic model parameter determination in humans: the lumped constants and rate constants for (/sup 18/F)fluorodeoxyglucose and (/sup 11/C)deoxyglucose  

SciTech Connect

The rate constants and lumped constants (LCs) for (/sup 18/F)fluorodeoxyglucose ((/sup 18/F)FDG) and (/sup 11/C)deoxyglucose ((/sup 11/C)DG) were determined in humans for the glucose metabolic rate kinetic model used to measure local cerebral glucose consumption. The mean values of the LCs for (/sup 18/F)FDG and (/sup 11/C)DG are 0.52 and 0.56, respectively. The mean values of the rate constants k*1, k*2, k*3, and k*4 for (/sup 18/F)FDG for gray matter are 0.095, 0.125, 0.069, and 0.0055, respectively. The corresponding values for white matter are 0.065, 0.126, 0.066, and 0.0054, respectively. Using these values and previously published values for the rate constants for (/sup 11/C)DG, the average whole-brain metabolic rates for glucose in normal subjects measured with (/sup 18/F)FDG and (/sup 11/C)DG are 5.66 and 4.99 mg/100 g/min, respectively. These values are not significantly different and agree well with reported values in the literature determined by means of the Kety-Schmidt technique.

Reivich, M.; Alavi, A.; Wolf, A.; Fowler, J.; Russell, J.; Arnett, C.; MacGregor, R.R.; Shiue, C.Y.; Atkins, H.; Anand, A.

1985-06-01

315

Characterization of the atrazine sorption process on Andisol and Ultisol volcanic ash-derived soils: kinetic parameters and the contribution of humic fractions.  

PubMed

Atrazine sorption was studied in six Andisol and Ultisol soils. Humic and fulvic acids and humin contributions were established. Sorption on soils was well described by the Freundlich model. Kf values ranged from 2.2-15.6 ?g(1-1/n)mL(1/n)g(-1). The relevance of humic acid and humin was deduced from isotherm and kinetics experiments. KOC values varied between 221 and 679 mLg(-1) for these fractions. Fulvic acid presented low binding capacity. Sorption was controlled by instantaneous equilibrium followed by a time-dependent phase. The Elovich equation, intraparticle diffusion model, and a two-site nonequilibrium model allowed us to conclude that (i) there are two rate-limited phases in Andisols related to intrasorbent diffusion in organic matter and retarded intraparticle diffusion in the organo-mineral complex and that (ii) there is one rate-limited phase in Ultisols attributed to the mineral composition. The lower organic matter content of Ultisols and the slower sorption rate and mechanisms involved must be considered to assess the leaching behavior of atrazine. PMID:23711282

Báez, María E; Fuentes, Edwar; Espinoza, Jeannette

2013-06-19

316

Density functional theory investigation of competitive free-radical processes during the thermal cracking of methylated polyaromatics: estimation of kinetic parameters.  

PubMed

Density functional B3LYP and BH&HLYP calculations with the 6-31G** basis set have been performed to investigate elementary reactions playing an important role in the pyrolysis of 1-methylnaphthalene. The pathways describing the destiny of the main radicals, H, methyl, hydromethylnaphthyl and methylnaphthyl, have been studied. At low temperature, addition of H atoms on the aromatic ring is favored over hydrogen abstraction. Except at low temperature (below 400 K), the hydromethylnaphthyl radical undergoes preferentially a loss of hydrogen rather than a bimolecular hydrogen transfer with methylnaphthalene or addition reaction on methylnaphthalene forming a hydrogenated dimer. In the range 400-750 K, the formation of methane by hydrogen abstraction of methyl radical on methylnaphthalene is predominant compared to the formation of hydrodimethylnaphthalenes by addition reaction. Rate constants of reactions describing the formation of heavy products like methyldinaphthylmethanes or dimethylbinaphthalenes have been calculated and discussed. They are also compared to recombination reactions from the literature. Rate constants of these reactions have been computed using transition state theory and can be integrated in kinetic radical schemes of methylated polyaromatic compounds pyrolysis from geological to laboratory conditions. PMID:17394290

Leininger, J-Philippe; Minot, Christian; Lorant, François; Behar, Françoise

2007-03-30

317

The effect of ultrasonic frequency and intensity upon electrode kinetic parameters for the Ag(S2O3)23?\\/Ag redox couple  

Microsoft Academic Search

This paper describes the effect of ultrasound on electrochemical parameters important in the removal of silver from photographic processing solutions. Decomposition voltages (obtained galvanostatically) and discharge potentials (obtained potentiostatically) for the reduction of the silver complex, Ag(S2O3)23- was studied in dilute aqueous Na2S2O3\\/NaHSO3 solution on stainless steel and carbon disc electrodes in both the absence and presence of ultrasound. Under

B. Pollet; J. P. Lorimer; S. S. Phull; T. J. Mason; D. J. Walton; J. Y. Hihn; V. Ligier; M. Wéry

1999-01-01

318

Decolorization of an azo dye Orange G in aqueous solution by Fenton oxidation process: Effect of system parameters and kinetic study  

Microsoft Academic Search

To establish cost-efficient operating conditions for potential application of Fenton oxidation process to treat wastewater containing an azo dye Orange G (OG), some important operating parameters such as pH value of solutions, dosages of H2O2 and Fe2+, temperature, presence\\/absence of chloride ion and concentration of the dye, which effect on the decolorization of OG in aqueous solution by Fenton oxidation

Sheng-Peng Sun; Cheng-Jie Li; Jian-Hui Sun; Shao-Hui Shi; Mao-Hong Fan; Qi Zhou

2009-01-01

319

Study of kinetic parameters related to the decolourization and mineralization of reactive dyes from textile dyeing using Fenton and photo-Fenton processes  

Microsoft Academic Search

The decolourization and mineralization of two reactive azo dyes, Procion Red H-E7B (CI Reactive Red 141) and Cibacron Red FN-R (CI Reactive Red 238), under Fenton's and photo-Fenton's conditions have been investigated. Some parameters, like temperature, initial concentrations of Fe(II) and H2O2 and the use of natural or artificial light were evaluated aiming to find the optimal conditions to promote

Lluís Núñez; José Antonio García-Hortal; Francesc Torrades

2007-01-01

320

SABIO Reaction Kinetics Database (Homepage)  

NSDL National Science Digital Library

The SABIO-RK (System for the Analysis of Biochemical Pathways - Reaction Kinetics) is a web-based application based on the SABIO relational database that contains information about biochemical reactions, their kinetic equations with their parameters, and the experimental conditions under which these parameters were measured. It aims to support modellers in the setting-up of models of biochemical networks, but it is also useful for experimentalists or researchers with interest in biochemical reactions and their kinetics. Information about reactions and their kinetics can be exported in SBML (Systems Biology Mark-Up Language) format.

Scientific Databases And Visualization Group At The Eml Research In Heidelberg, Germany

321

Characterization of the binding of drugs to human intestinal fatty acid binding protein (IFABP): potential role of IFABP as an alternative to albumin for in vitro-in vivo extrapolation of drug kinetic parameters.  

PubMed

This work characterized for the first time the binding of acidic, neutral, and basic drugs to human intestinal fatty acid binding protein (IFABP) and, for comparison, to bovine serum albumin (BSA). In addition, the study investigated whether IFABP can substitute for BSA as a constituent in incubations of human liver microsomes (HLMs) in in vitro-in vivo extrapolation (IV-IVE) studies. Each molecule of purified IFABP bound a single molecule of the fluorescent probe 1-anilino-8-naphthalene sulfonate or arachidonic acid with K(d) values similar to those reported for rat IFABP. Basic drugs bound negligibly to IFABP. Based on fraction unbound (f(u)) at a protein concentration of 0.5% (w/v), binding of acidic and neutral drugs ranged from minor (f(u) > 0.8) to moderate (f(u) 0.5-0.8). Of the compounds screened, highest binding to IFABP was observed for sulfinpyrazone (an acid) and beta-estradiol (a neutral compound). However, binding to IFABP was lower than to BSA for all the drugs investigated. To determine the potential suitability of IFABP as an alternative to BSA for enhancing the prediction accuracy of IV-IVE based on human liver microsomal kinetic data, the kinetics of zidovudine (AZT) glucuronidation by HLM were characterized in the absence and presence of BSA and IFABP (0.5-2.5%, w/v). Each protein reduced the K(m) for AZT glucuronidation in a concentration-dependent manner, although a higher content of IFABP in incubations (2.5 versus 1-1.5% for BSA) was necessary for a 10-fold reduction in this parameter. The results indicate that IFABP is likely to have advantages over BSA in microsomal kinetic studies with drugs that bind extensively to albumin. PMID:19398502

Rowland, Andrew; Knights, Kathleen M; Mackenzie, Peter I; Miners, John O

2009-04-27

322

Nonphotochemical hole burning and dispersive kinetics in amorphous solids  

SciTech Connect

Results covering burn intensities in the nW to {mu}W/cm{sup 2} range, of dispersive hole growth kinetics are reported for Oxazine 720 in glycerol glasses and polyvinyl alcohol polymer films and their deuterated analogues. A theoretical model which employs a distribution function for the hole burning rate constant based upon a Gaussian distribution for the tunnel parameter is shown to accurately describe the kinetic data. This model incorporates the linear electron-phonon coupling. A method for calculating the nonphotochemical quantum yield is presented which utilizes the Gaussian distribution of tunnel parameters. The quantum yield calculation can be extended to determine a quantum yield as a function of hole depth. The effect of spontaneous hole filling is shown to be insignificant over the burn intensity range studied. Average relaxation rates for hole burning are {approximately}8 orders of magnitude greater than for hole filling. The dispersive kinetics of hole burning are observed to be independent over the temperature range of these experiments, 1.6 to 7.0 K. 6 refs., 20 figs., 1 tab.

Kenney, M.J.

1990-09-21

323

Kinetics of activation and inactivation of swelling-stimulated K+/Cl- transport. The volume-sensitive parameter is the rate constant for inactivation  

PubMed Central

Red blood cells of several species are known to exhibit a ouabain- insensitive, anion-dependent K+ (Rb+) flux that is stimulated by cell swelling. We have used rabbit red cells to study the kinetics of activation and inactivation of the flux upon step changes in tonicity. Sudden hypotonic swelling (210 mosmol) activates the flux after a lag period of 10 min at 37 degrees C and 30-50 min at 25 degrees C. In cells that were preswollen to activate the transporter, sudden shrinkage (by addition of hypertonic NaCl) causes a rapid inactivation of the flux; the time lag for inactivation is less than 2 min at 37 degrees C. A minimal model of the volume-sensitive KCl transport system requires two states of the transporter. The activated (A) state catalyzes transport at some finite rate (turnover number unknown because the number of transporters is unknown). The resting (R) state has a much lower or possibly zero transport rate. The interconversion between the states is characterized by unimolecular rate constants R k12 in equilibrium with k21 A. The rate of relaxation to any new steady state is equal to the sum of the rate constants k12 + k21. Because the rate of transport activation in a hypotonic medium is lower than the rate of inactivation in an isotonic medium, we conclude that the volume- sensitive rate process is inactivation (the A to R transition); that is, cell swelling activates transport by lowering k21. Three phosphatase inhibitors (fluoride, orthovanadate, and inorganic phosphate) all inhibit the swelling-activated flux and also slow down the rate of approach to the swollen steady state. This finding suggests that a net dephosphorylation is necessary for activation of the flux and that the net dephosphorylation takes place as a result of swelling- induced inhibition of a kinase rather than stimulation of a phosphatase.

1990-01-01

324

Cytochrome b2, an electron carrier between flavocytochrome b2 and cytochrome c. Rapid kinetic characterization of the electron-transfer parameters with ionic-strength-dependence.  

PubMed Central

The oxidation-reduction properties of free cytochrome b2 isolated by controlled proteolysis from flavocytochrome b2, i.e. the flavodehydrogenase-bound cytochrome b2, were investigated by using stopped-flow spectrophotometry. The rapid kinetics of the reduction of cytochrome b2 by flavocytochrome b2 in the presence of L-lactate are reported. The self-exchange rate constant between reduced cytochrome b2 bound to the flavodehydrogenase and free cytochrome b2 was determined to be 10(5) M-1 X S-1 at 5 degrees C, I 0.2 and pH 7.0. The specific electron-transfer reaction between reduced cytochrome b2 and cytochrome c was also studied, giving an apparent second-order rate constant of 10(7) M-1 X S-1 at 5 degrees C, I 0.2 and pH 7.0. This electron-exchange rate is slightly modulated by ionic strength, following the Debye-Hückel relationship with a charge factor Z1Z2 = -1.9. Comparison of these data with those for the reduction of cytochrome c by flavodehydrogenase-bound cytochrome b2 [Capeillère-Blandin (1982) Eur. J. Biochem. 128, 533-542] leads to the conclusion that the intramolecular electron exchange between haem b2 and haem c within the reaction complex occurs at a rate very similar to that determined experimentally in presence of the flavodehydrogenase domain. The low reaction rate observed with free cytochrome b2 is ascribed to the low stability of the reaction complex formed between free cytochrome b2 and cytochrome c.

Capeillere-Blandin, C; Albani, J

1987-01-01

325

A calculator program for least-squares parameter estimation according to the one-compartment kinetic model with zero-order input.  

PubMed

A calculator program that performs a nonlinear least-squares fit to data conforming to the one-compartment model with zero-order input is described. The program, which is designed for the Hewlett-Packard HP-41 CV calculator, is based on the Gauss-Newton iterative algorithm as modified by Hartley. A subroutine for calculation of initial parameter estimates is incorporated into the program. Plasma concentration data relative to a single oral dose of a sustained-release theophylline formulation are used to demonstrate the practical application of the program. PMID:6547651

Messori, A; Donati-Cori, G; Tendi, E

326

Enzyme Kinetics.  

ERIC Educational Resources Information Center

|Conveys an appreciation of enzyme kinetic analysis by using a practical and intuitive approach. Discusses enzyme assays, kinetic models and rate laws, the kinetic constants (V, velocity, and Km, Michaels constant), evaluation of V and Km from experimental data, and enzyme inhibition. (CW)|

Moe, Owen; Cornelius, Richard

1988-01-01

327

Fluorescent intercalator displacement replacement (FIDR) assay: determination of relative thermodynamic and kinetic parameters in triplex formation--a case study using triplex-forming LNAs  

PubMed Central

Triplex forming oligonucleotides (TFOs) are the most commonly used approach for site-specific targeting of double stranded DNA (dsDNA). Important parameters describing triplex formation include equilibrium binding constants (Keq) and association/dissociation rate constants (kon and koff). The ‘fluorescent intercalator displacement replacement’ (FIDR) assay is introduced herein as an operationally simple approach toward determination of these parameters for triplexes involving TC-motif TFOs. Briefly described, relative rate constants are determined from fluorescence intensity changes upon: (i) TFO-mediated displacement of pre-intercalated and fluorescent ethidium from dsDNA targets (triplex association) and (ii) Watson–Crick complement-mediated displacement of the TFO and replacement with ethidium (triplex dissociation). The assay is used to characterize triplexes between purine-rich dsDNA targets and TC-motif TFOs modified with six different locked nucleic acid (LNA) monomers, i.e. conventional and C5-alkynyl-functionalized LNA and ?-L-LNA pyrimidine monomers. All of the studied monomers increase triplex stability by decreasing the triplex dissociation rate. LNA-modified TFOs form more stable triplexes than ?-L-LNA-modified counterparts owing to slower triplex dissociation. Triplexes modified with C5-(3-aminopropyn-1-yl)-LNA-U monomer Z are particularly stable. The study demonstrates that three affinity-enhancing features can be combined into one high-affinity TFO monomer: conformational restriction of the sugar ring, expansion of the pyrimidine ?-stacking surface and introduction of an exocyclic amine.

Sau, Sujay P.; Kumar, Pawan; Sharma, Pawan K.; Hrdlicka, Patrick J.

2012-01-01

328

Determination of kinetic parameters in the biosorption of Cr (VI) on immobilized Bacillus cereus M(1)(16) in a continuous packed bed column reactor.  

PubMed

Due to technological advancement, environment suffers from untreated toxic heavy metal bearing effluent coming from different industries. Chromium (VI) is one of those heavy metals having adverse impact on ecological balance, human, and plant health because of its carcinogenic properties. Biosorption is presented as an alternative to traditional technologies which are costly and inefficient for treatment of industrial wastes containing low amount of heavy metals. In this study, bioremediation of Cr (VI) ions by immobilized Bacillus cereus M(1) (16) was investigated in a laboratory scale packed bed up-flow column reactor. The effect of important parameters, such as the inlet flow rate, influent concentration, and effective bed height, has been studied. External mass transfer, surface adsorption, and intrabead mass transfer were also studied to conclude the rate limiting step for removal of Cr (VI) and to determine the process parameters which are important for biosorption optimization. The external mass transfer coefficient was calculated at different flow rates (6.51 x 10(-2) to 7.58 x 10(-2) cm/min). Using the model, the surface adsorption rate constant (k(ad)) and the intrabead mass transfer coefficient (k (i)) were predicted as 0.0267 x 10(-3) and 0.7465 x 10(-3) l/g/min, respectively. Both are much lower than the external mass transfer coefficient (k(e)). The surface adsorption phenomenon is acting as the rate-limiting step due to its high resistance for removal of Cr (VI). PMID:19333567

Maiti, Soumen K; Bera, Debabrata; Chattopadhyay, Parimal; Ray, Lalitagauri

2009-03-31

329

General solutions for the oxidation kinetics of polymers  

SciTech Connect

The simplest general kinetic schemes applicable to the oxidation of polymers are presented, discussed and analyzed in terms of the underlying kinetic assumptions. For the classic basic autoxidation scheme (BAS), which involves three bimolecular termination steps and is applicable mainly to unstabilized polymers, typical assumptions used singly or in groups include (1) long kinetic chain length, (2) a specific ratio of the termination rate constants and (3) insensitivity to the oxygen concentration (e.g., domination by a single termination step). Steady-state solutions for the rate of oxidation are given in terms of one, two, three, or four parameters, corresponding respectively to three, two, one, or zero kinetic assumptions. The recently derived four-parameter solution predicts conditions yielding unusual dependencies of the oxidation rate on oxygen concentration and on initiation rate, as well as conditions leading to some unusual diffusion-limited oxidation profile shapes. For stabilized polymers, unimolecular termination schemes are typically more appropriate than bimolecular. Kinetics incorporating unimolecular termination reactions are shown to result in very simple oxidation expressions which have been experimentally verified for both radiation-initiated oxidation of an EPDM and thermoxidative degradation of nitrile and chloroprene elastomers.

Gillen, K.T.; Clough, R.L.; Wise, J.

1996-08-01

330

Processing parameters and kinetics of bromination and chlorination in the YBa sub 2 Cu sub 3 O sub 6+x system  

SciTech Connect

This paper reports on the introduction of halogens such as Cl{sub 2}Br{sub 2} that restore 90 K superconductivity to oxygen deficient YBa{sub 2}Cu{sub 3}O{sub 6 + x}. This is potentially important for applications to thin film devices due to the low processing temperatures required relative to reprocessing with oxygen. Low temperature 260{degrees}C and short time ({gt}5 minute) bromination has been shown to convert initially insulating YBa{sub 2}Cu{sub 3}O{sub 6.2} powder to a high temperature superconductor with properties similar to the standard O{sub 7} material. This process has now been extended to single crystals as well, but with somewhat different processing parameters. Thermal gravimetric analysis (TGA) coupled with mass spectrometry indicates that the Br becomes strongly bonded, with no release of Br observed in taking powder samples to 1000{degrees}C in flowing forming gas (2% H{sub 2}/98% N{sub 2}).

Radousky, H.B.; Glass, R.S.; Back, D.; Chin, A.H.; Fluss, M.J. (Lawrence Livermore National Lab., CA (United States)); Liu, L.Z.; Mosly, W.D.; Klavins, P.; Shelton, R.N. (California Univ., Davis, CA (United States). Dept. of Physics)

1991-03-01

331

Processing parameters and kinetics of bromination and chlorination in the YBa sub 2 Cu sub 3 O sub 6+x system  

SciTech Connect

The introduction of halogens such as Cl{sub 2}, Br{sub 2} can restore 90 K superconductivity to oxygen deficient YBa{sub 2}Cu{sub 3}O{sub 6+x}. This is potentially important for applications to thin film devices due to the low processing temperatures required relative to reprocessing with oxygen. Low temperature 260{degrees}C and short time (>5 minute) bromination has been shown to convert initially insulting YBa{sub 2}Cu{sub 3}O{sub 6.2} powder to a high temperature superconductor with properties similar to the standard O{sub 7} material. This process has now been extended to single crystals as well, but with somewhat different processing parameters. Thermal gravimetric analysis (TGA) coupled with mass spectrometry indicates that the Br becomes strongly bonded, with no release of Br observed in taking powder samples to 1000{degree}C in flowing forming gas (2%H{sub 2}/98%N{sub 2}). The reaction has also been found to be highly exothermic for both Br and Cl treatments, which is consistent with the strong bonding of the bromine discussed above.

Radousky, H.B.; Glass, R.S.; Back, D.; Chin, A.H.; Fluss, M.J. (Lawrence Livermore National Lab., CA (USA)); Liu, J.Z.; Mosly, W.D.; Klavins, P.; Shelton, R.N. (California Univ., Davis, CA (USA). Dept. of Physics)

1990-09-01

332

Kinetics and mechanism of X + ClNO yields XCl + NO (X = Cl, F, Br, OH, O, N) from 220 to 450 K. Correlation of reactivity and activation energy with electron affinity of X  

SciTech Connect

The rate constants for a series of radical reactions with ClNO, X + ClNO {yields} products where X = Cl, F, Br, OH, O, N, have been measured as a function of temperature in discharge flow systems at pressures between 1 and 2 Torr of helium buffer gas. Radicals were detected by resonance fluorescence (X = Cl, Br, OH, O), laser magnetic resonance (X = OH), and chemical conversion/resonance fluorescence (X = F, N). The rate constants, with units of cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} and to 95% confidence level, are for Cl + ClNO {yields} Cl{sub 2} + NO, ((6.6 {plus minus} 1.2) {times} 10{sup {minus}11}) e{sup (128{plus minus}46)/T}; for F + ClNO {yields} FCl + NO, ((1.4 {plus minus} 0.4) {times} 10{sup {minus}10}) e{sup ({minus}28{plus minus}84)/T}; for Br + ClNO {yields} BrCl + NO, ((1.5 {plus minus} 0.2) {times} 10{sup {minus}11}) e{sup ({minus}52{plus minus}43)/T}; for OH + ClNO {yields} ClOH + NO, ((9.0 {plus minus} 4.5) {times} 10{sup {minus}12}) e{sup ({minus}1130{plus minus}170)/T}; for OH + ClNO {yields} HONO + Cl, ((9.2 {plus minus} 6.5) {times} 10{sup {minus}14}) e{sup (240{plus minus}130)/T}; for O + ClNO {yields} ClO + NO, ((8.3 {plus minus} 0.9) {times} 10{sup {minus}12}) e{sup ({minus}1520{plus minus}35)/T}; and for N + ClNO {yields} NCl + NO, ((9.2 {plus minus} 2.2) {times} 10{sup {minus}12}) e{sup ({minus}2250{plus minus}90)/T}. Both the reaction activation energies and the logarithms of the room temperature rate constants are found to correlate strongly with the electron affinity of the radical in such a way that high electron affinity leads to enhanced reactivity. The reactivity trend is rationalized by a frontier orbital interaction dominated by the ease with which electron transfer from the ClNO molecule to the X radical can occur to stabilize a polar transition state, a mechanism shown to be widely prevalent in radical-molecule systems.

Abbatt, J.P.D.; Toohey, D.W.; Fenter, F.F.; Stevens, P.S.; Brune, W.H.; Anderson, J.G. (Harvard Univ., Cambridge, MA (USA))

1989-02-09

333

Mesophilic digestion kinetics of manure slurry.  

PubMed

Anaerobic digestion kinetics study of cow manure was performed at 35 degrees C in bench-scale gas-lift digesters (3.78 l working volume) at eight different volatile solids (VS) loading rates in the range of 1.11-5.87 g l-1 day-1. The digesters produced methane at the rates of 0.44-1.18 l l-1 day-1, and the methane content of the biogas was found to increase with longer hydraulic retention time (HRT). Based on the experimental observations, the ultimate methane yield and the specific methane productivity were estimated to be 0.42 l CH4 (g VS loaded)-1 and 0.45 l CH4 (g VS consumed)-1, respectively. Total and dissolved chemical oxygen demand (COD) consumptions were calculated to be 59-17% and 78-43% at 24.4-4.6 days HRTs, respectively. Maximum concentration of volatile fatty acids in the effluent was observed as 0.7 g l-1 at 4.6 days HRT, while it was below detection limit at HRTs longer than 11 days. The observed methane production rate did not compare well with the predictions of Chen and Hashimoto's [1] and Hill's [2] models using their recommended kinetic parameters. However, under the studied experimental conditions, the predictions of Chen and Hashimoto's [1] model compared better to the observed data than that of Hill's [2] model. The nonlinear regression analysis of the experimental data was performed using a derived methane production rate model, for a completely mixed anaerobic digester, involving Contois kinetics [3] with endogenous decay. The best fit values for the maximum specific growth rate (micro m) and dimensionless kinetic parameter (K) were estimated as 0.43 day-1 and 0.89, respectively. The experimental data were found to be within 95% confidence interval of the prediction of the derived methane production rate model with the sum of residual squared error as 0.02. PMID:18025584

Karim, Khursheed; Klasson, K Thomas; Drescher, Sadie R; Ridenour, Whitney; Borole, Abhijeet P; Al-Dahhan, Muthanna H

2007-09-01

334

Influence of the errors made in the measurement of the extra-column volume on the accuracies of estimates of the column efficiency and the mass transfer kinetics parameters.  

PubMed

The influences of the errors made in the measurement of the extra-column volume of an instrument on the accuracies of the estimates made of the column efficiency and of the parameters of the mass transfer kinetics were investigated from an experimental point of view. A standard HP1090 apparatus (extra-column volume, approximately 50 micro L) was used to measure the efficiency of a Sunfire-C(18) RPLC column (column hold-up volume, approximately 1.50 mL). The first and second moments of the peaks of phenol (a retained compound) and of thiourea (a practically non-retained compound) were measured at six different temperatures between 22 and 78 degrees C, for flow rates between 0.10 and 4.70 mL/min (i.e., for linear velocities between 0.025 and 1.179 cm/s). Each series of measurements was successively made with the instrument being fitted with and without the column. The experimental HETP data must be corrected for the solute dispersion in the connected tubes in order properly to assess the true column efficiency. Even with a modern, high performance instrument, the dispersion of a non-retained compound is essentially due to the band broadening phenomena that take place in the extra-column volumes, the sum of all these extra-column band broadening contributions accounting for more than 80% of the total band broadening measured. The contribution of the sampling device is particularly deleterious since, for a 2 mu L injection, the maximum solute concentration in the peak that enters into the column is nearly ten-fold lower than that of the sample. Nevertheless, the impact of the extra-column volumes on the estimates of the kinetic parameters (e.g., molecular diffusion coefficient D(m) and effective particle diffusivity D(e)) remains negligible. Obviously, the relative error made on the column efficiency of a retained compound depends much on its retention factor. It decreases from 8 to 1% when the retention factor increases from 5 to 17. PMID:17046003

Gritti, Fabrice; Felinger, Attila; Guiochon, Georges

2006-10-13

335

Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State  

PubMed Central

Several kinetic models for the macrocyclization of a C2 pseudopeptide with a dihalide through a SN2 reaction have been developed. These models not only focus on the kinetic analysis of the main macrocyclization reaction, but also consider the competitive oligomerization/polymerization processes yielding undesired oligomeric/polymeric byproducts. The effect of anions has also been included in the kinetic models, as they can act as catalytic templates in the transition state reducing and stabilizing the transition state. The corresponding differential equation systems for each kinetic model can be solved numerically. Through a comprehensive analysis of these results, it is possible to obtain a better understanding of the different parameters that are involved in the macrocyclization reaction mechanism and to develop strategies for the optimization of the desired processes.

Marti-Centelles, Vicente; Burguete, M. Isabel; Luis, Santiago V.

2012-01-01

336

A new method to study biodegradation kinetics of organic trace pollutants by activated sludge.  

PubMed

A reliable prediction of the behaviour of organic trace compounds in activated sludge plants requires an accurate input of the biodegradation kinetics. Often these kinetics are extrapolated from the results of standardised biodegradation tests. However, these tests generally are not designed to yield kinetic information and do not reflect the conditions in activated sludge plants. To overcome these problems a new test method was developed which is referred to as a 'by-pass' test. The test methodology is explained and examples are given for three compounds: the C(12)-homologue of linear alkylbenzene sulfonate, nitrilotriacetic acid and toluene. More experience with the test is required, particularly with respect to selection of the proper test settings, which are compound related. The test is a suitable tool in a research environment, for example to investigate the effect of plant operational parameters on the biodegradation kinetics. PMID:12729705

Temmink, Hardy; Klapwijk, Bram

2003-07-01

337

Reaction kinetics, geospeedometry, and relaxation theory  

Microsoft Academic Search

This paper explores the application of homogeneous reaction kinetics to geospeedometry and to structural relaxation theory. Numerical simulations of reaction kinetics during cooling for some first- and second-order elementary reactions have been carried out to systematically examine the effects of kinetic parameters and cooling histories on the final speciation. An analytical solution for a special case of first-order reaction A

Youxue Zhang

1994-01-01

338

Multiple heating rate kinetic parameters, thermal, X-ray diffraction studies of newly synthesized octahedral copper complexes based on bromo-coumarins along with their antioxidant, anti-tubercular and antimicrobial activity evaluation.  

PubMed

Series of new Cu(II) complexes were synthesized by classical thermal technique. The biologically potent ligands (L) were prepared by refluxing 6-brom 3-acetyl coumarin with aldehydes in the presence of piperidine in ethanol. The Cu(II) complexes have been synthesized by mixing an aqueous solution of Cu(NO(3))(2) in 1:1 molar ratios with ethanolic bidentate ligands and Clioquinol. The structures of the ligands and their copper complexes were investigated and confirmed by the elemental analysis, FT-IR, (1)H NMR, (13)C NMR, mass spectral and powder X-ray diffraction studies respectively. Thermal behaviour of newly synthesized mixed ligand Cu(II) complexes were investigated by means of thermogravimetry, differential thermogravimetry, differential scanning calorimetry, electronic spectra and magnetic measurements. Dynamic scan of DSC experiments for Cu(II) complexes were taken at different heating rates (2.5-20 °C min(-1)). Kinetic parameters for second step degradation of all complexes obtained by Kissinger's and Ozawa's methods were in good agreement. On the basis of these studies it is clear that ligands coordinated to metal atom in a monobasic bidentate mode, by OO and ON donor system. Thus, suitable octahedral geometry for hexa-coordinated state has been suggested for the metal complexes. Both the ligands as well as its complexes have been screened for their in vitro antioxidant, anti-tubercular and antimicrobial activities. All were found to be significant potent compared to parent ligands employed for complexation. PMID:22728283

Patel, Ketan S; Patel, Jiten C; Dholariya, Hitesh R; Patel, Kanuprasad D

2012-06-04

339

Calculation of Kinetics Parameters for the NBSR  

SciTech Connect

The delayed neutron fraction and prompt neutron lifetime have been calculated at different times in the fuel cycle for the NBSR when fueled with both high-enriched uranium (HEU) and low-enriched uranium (LEU) fuel. The best-estimate values for both the delayed neutron fraction and the prompt neutron lifetime are the result of calculations using MCNP5-1.60 with the most recent ENDFB-VII evaluations. The best-estimate values for the total delayed neutron fraction from fission products are 0.00665 and 0.00661 for the HEU fueled core at startup and end-of-cycle, respectively. For the LEU fuel the best estimate values are 0.00650 and 0.00648 at startup and end-of-cycle, respectively. The present recommendations for the delayed neutron fractions from fission products are smaller than the value reported previously of 0.00726 for the HEU fuel. The best-estimate values for the contribution from photoneutrons will remain as 0.000316, independent of the fuel or time in the cycle.The values of the prompt neutron lifetime as calculated with MCNP5-1.60 are compared to values calculated with two other independent methods and the results are in reasonable agreement with each other. The recommended, conservative values of the neutron lifetime for the HEU fuel are 650 {micro}s and 750 {micro}s for the startup and end-of-cycle conditions, respectively. For LEU fuel the recommended, conservative values are 600 {micro}s and 700 {micro}s for the startup and end-of-cycle conditions, respectively. In all three calculations, the prompt neutron lifetime was determined to be longer for the end-of-cycle equilibrium condition when compared to the startup condition. The results of the three analyses were in agreement that the LEU fuel will exhibit a shorter prompt neutron lifetime when compared to the HEU fuel.

Hanson A. L.; Diamond D.

2012-03-06

340

Purification and kinetic characterization of the liverwort Pallavicinia lyelli (Hook.) S. Gray. cytosolic ascorbate peroxidase  

Microsoft Academic Search

Ascorbate peroxidase (APX) of the liverwort Pallavicinia lyelli was extracted and purified through ammonium sulfate precipitation, Butyl-Toyopearl, DEAE-Cellulofine and Sephadex G-75 chromatography. The purification factor for APX was 285 with 7.9% yield. The enzyme was characterized for thermal stability, pH and kinetic parameters. The molecular mass of APX was approximately 28 kDa estimated by SDS-PAGE. The purity was checked by native

S. Sajitha Rajan; K. Murugan

2010-01-01

341

Precipitation kinetics, mechanical strength and electrical conductivity of AlZnMgCu alloys  

Microsoft Academic Search

The aging of AlZnMgCu alloys in a temperature range where the metastable phase ?? precipitates homogeneously, is examined with a three-fold point of view using the microstructural parameters measured previously by in situ small angle X-ray scattering experiments. The precipitation kinetics is first analysed and the late LSW coarsening stage is unambiguously characterized. The yield stress is then quantified in

P. Guyot; L. Cottignies

1996-01-01

342

Kinetic Study on Ethanol Fermentation of Grape Waste using Saccharomyces cerevisiae Yeast Isolated from Toddy  

Microsoft Academic Search

° . At sugar concentration of 150 g\\/l, the maximum ethanol concentration and ethanol productivity of 73.7 g\\/l and 0.84 g\\/ l-h are obtained with 0.5g\\/g ethanol yield and 95% of sugar utilization. The kinetic parameters are calculated in the exponential growth phase. Both yeast growth and ethanol inhibition are obtained at higher sugar concentration of 200 g\\/l. The yeast

K Pramanik

2005-01-01

343

Heparin Kinetics.  

National Technical Information Service (NTIS)

The author has studied the kinetics of heparin and heparin fractions after intravenous administration in humans and in this thesis the results of this study are reported. Basic knowledge about the physico-chemical properties of heparin and its interaction...

C. A. M. Swart

1983-01-01

344

Enzyme Kinetics  

NSDL National Science Digital Library

This resrouce provides detailed protocols for performing a laboratory exercise in enzyme kinetics. The activity of enzymes are characterized both by reaction rates and the effect of different concentrations of substrates.

Carl Stiefbold (University of Oregon;); Karen Sprague (University of Oregon;); Will Goodwin (University of Oregon;); Sam Donovan (University of Oregon;); Vicki Chandler (University of Oregon;)

1998-01-01

345

Adsorption kinetics of methyl violet onto perlite  

Microsoft Academic Search

This study examines adsorption kinetics and activation parameters of methyl violet on perlite. The effect of process parameters like contact time, concentration of dye, temperature and pH on the extent of methyl violet adsorption from solution has been investigated. Results of the kinetic studies show that the adsorption reaction is first order with respect to dye solution concentration with activation

Mehmet Do?an; Mahir Alkan

2003-01-01

346

Systematics of fission fragment total kinetic energy release  

Microsoft Academic Search

Recent data for the most probable total kinetic energy release in fission have been combined with earlier results in order to reevaluate the systematic dependence of these values on the Coulomb parameter Z2\\/A1\\/3. A least-squares analysis of the current data base yields =0.1189Z2\\/A1\\/3+7. 3 MeV, where Z2\\/A1\\/3 refers to the fissioning nucleus. This expression exhibits a somewhat steeper slope

V. E. Viola; K. Kwiatkowski; M. Walker

1985-01-01

347

Yield, evapotranspiration and water productivity of rice ( Oryza sativa L.)–wheat ( Triticum aestivum L.) system in Punjab (India) as influenced by transplanting date of rice and weather parameters  

Microsoft Academic Search

Rice–wheat cropping system being highly productive and profitable, dominates the irrigated alluvial tract of Indo-Gangetic Plain of South Asia. In this region, the transplanting is staggered over a longer period (starting from early May to end of June) due to scarcity of migratory labour and power supply. Yield response of rice to different transplanting dates gets varied with weather conditions

G. B. S. Chahal; Anil Sood; S. K. Jalota; B. U. Choudhury; P. K. Sharma

2007-01-01

348

Parameters of bacterial killing and regrowth kinetics and antimicrobial effect examined in terms of area under the concentration-time curve relationships: action of ciprofloxacin against Escherichia coli in an in vitro dynamic model.  

PubMed Central

Although many parameters have been described to quantitate the killing and regrowth of bacteria, substantial shortcomings are inherent in most of them, such as low sensitivity to pharmacokinetic determinants of the antimicrobial effect, an inability to predict a total effect, insufficient robustness, and uncertain interrelations between the parameters that prevent an ultimate determination of the effect. To examine different parameters, the kinetics of killing and regrowth of Escherichia coli (MIC, 0.013 microg/ml) were studied in vitro by simulating a series of ciprofloxacin monoexponential pharmacokinetic profiles. Initial ciprofloxacin concentrations varied from 0.02 to 19.2 microg/ml, whereas the half-life of 4 h was the same in all experiments. The following parameters were calculated and estimated: the time to reduce the initial inoculum (N0) 10-, 100-, and 1,000-fold (T90%, T99%, and T99.9%, respectively), the rate constant of bacterial elimination (k(elb)), the nadir level (Nmin) in the viable count (N)-versus-time (t) curve, the time to reach Nmin (t(min)), the numbers of bacteria that survived (Ntau) by the end of the observation period (tau), the area under the bacterial killing and regrowth curve (log N(A)-t curve) from the zero point (time zero) to tau (AUBC), the area above this curve (AAC), the area between the control growth curve (log N(C)-t curve) and the bacterial killing and regrowth curve (log N(A)-t curve) from the zero point to tau (ABBC) or to the time point when log N(A) reaches the maximal values observed in the log N(C)-t curve (I(E); intensity of the effect), and the time shift between the control growth and regrowth curves (T(E); duration of the effect). Being highly sensitive to the AUC, I(E), and T(E) showed the most regular AUC relationships: the effect expressed by I(E) or T(E) increased systematically when the AUC or initial concentration of ciprofloxacin rose. Other parameters, especially T90%, T99%, T99.9%, t(min), and log N0 - log Nmin = delta log Nmin, related to the AUC less regularly and were poorly sensitive to the AUC. T(E) proved to be the best predictor and t(min) proved to be the worst predictor of the total antimicrobial effect reflected by I(E). Distinct feedback relationships between the effect determination and the experimental design were demonstrated. It was shown that unjustified shortening of the observation period, i.e., cutting off the log N(A)-t curves, may lead to the degeneration of the AUC-response relationships, as expressed by log N0 - log Ntau = delta log Ntau, AUBC, AAC, or ABBC, to a point where it gives rise to the false idea of an AUC- or concentration-independent effect. Thus, use of I(E) and T(E) provides the most unbiased, robust, and comprehensive means of determining the antimicrobial effect.

Firsov, A A; Vostrov, S N; Shevchenko, A A; Cornaglia, G

1997-01-01

349

Kinetic modeling of hydrocracking of heavy oil fractions: A review  

Microsoft Academic Search

An exhaustive review of the scientific literature on kinetic modeling of heavy petroleum fraction hydrocracking is reported in this paper. Kinetic models for hydrocracking of model compounds were not analyzed. The review includes models based on the lumping technique, continuous mixtures, structure oriented lumping, and single event models. Experimental data, reaction networks, main characteristics of kinetic approaches, and kinetic parameter

Jorge Ancheyta; Sergio Sánchez; Miguel A. Rodríguez

2005-01-01

350

Vacuum pyrolysis of PVC I. Kinetic study  

Microsoft Academic Search

Vacuum pyrolysis of PVC has been studied emphasizing two aspects: the kinetics of PVC pyrolysis reactions and the yields of pyrolysis products. The purpose of the kinetic study is to identify each apparent reaction involved in PVC pyrolysis. Three stages of weight loss have been evidenced by TG analysis during PVC decomposition both under vacuum and in nitrogen atmosphere, while

Rosa Miranda; Jin Yang; Christian Roy; Cornelia Vasile

1999-01-01

351

Kinetics of Nylon and Phenolic Pyrolysis.  

National Technical Information Service (NTIS)

The report describes the pyrolysis kinetics of nylon 6-6 and phenolic CTL 91-LD, as derived from thermogravimetric analysis data (TGA). Individual rate equations and kinetic coefficients for the two polymers are presented and combined to yield a multi-ste...

H. E. Goldstein

1965-01-01

352

Representation of the Kinetics of Leaching of Galena by Ferric Chloride in Concentrated Sodium Chloride Solutions by a Modified Mixed Kinetics Model  

NASA Astrophysics Data System (ADS)

Galena (PbS) is leached by a solution concentrated in NaCl and containing ferrous and ferric chloride. The ferric ion concentration is kept constant by adding KMnO4 or the potential is kept constant by adding a concentrated ferric chloride solution. The ferrous concentration of the solution has no effect upon the kinetics, the temperature and the chloride concentration have only a weak effect, whereas the radius of solid particles and the concentration of the ferric ion have the major influences. The kinetics are represented by a shrinking core model for up to 99 pet of ore dissolved. Both the aqueous diffusion of ferric ion in the pores of the sulfur layer and the chemical reaction at the surface are involved in the kinetic model. Taking into account the self blockage improves the representation of the end of reaction and yields a more consistent set of parameters.

Morin, D.; Gaunand, A.; Renon, H.

1985-12-01

353

Kinetics of biomass catalytic pyrolysis  

Microsoft Academic Search

The Coats–Redfern method was used to analyze the kinetic characteristics of biomass catalytic pyrolysis, indicating that it can be described by multi-step reactions, rather than as a simple first-order reaction. Friedman model-free calculations were used to describe the starting reaction types and the corresponding initial kinetic parameters. Finally, nonlinear regression of biomass catalytic pyrolysis showed that the reaction mechanism of

Changbo Lu; Wenli Song; Weigang Lin

2009-01-01

354

Measuring Surface Binding Thermodynamics and Kinetics by using Total Internal Reflection with Fluorescence Correlation Spectroscopy: Practical Considerations  

PubMed Central

The combination of total internal reflection illumination and fluorescence correlation spectroscopy (TIR-FCS) is an emerging method useful for, among a number of things, measuring the thermodynamic and kinetic parameters describing the reversible association of fluorescently labeled ligands in solution with immobilized, nonfluorescent surface binding sites. However, there are many parameters (both instrumental and intrinsic to the interaction of interest) that determine the nature of the acquired fluorescence fluctuation autocorrelation functions. In this work, we define criteria necessary for successful measurements, and then systematically explore the parameter space to define conditions that meet the criteria. The work is intended to serve as a guide for experimental design; in other words, to provide a methodology to identify experimental conditions that will yield reliable values of the thermodynamic and kinetic parameters for a given interaction.

Thompson, Nancy L.; Navaratnarajah, Punya; Wang, Xiang

2011-01-01

355

Kinetic Energy  

NSDL National Science Digital Library

Part of a comprehensive physics tutorial for high school students, this page describes kinetic energy conceptually and mathematically, provides examples enhanced by illustrations, and problems for practice with drop down boxes for your answers and feedback. In the left navigation bar, click on Potential Energy to get parallel information on potential energy.

2010-01-01

356

Development of a kinetic model for alcohol synthesis over a cesium-promoted Cu/ZnO catalyst  

SciTech Connect

This paper reports on a kinetic reaction network developed for the synthesis of oxygenates from synthesis gave over Cs-promoted Cu/ZnO catalysts in a differential reaction regime. The most important carbon- carbon bond forming reactions of the model are linear growth by addition of an oxygenated C{sub 1} intermediate to an alcohol chain that yields linear alcohols and a {beta}-addition aldol condensation type mechanism between an oxygenated C{sub 1} intermediate and an aldehydic C{sub n} intermediate that yields 2-methyl-branched primary alcohols. The most important carbon-oxygen bond forming reaction is a methoxide addition, {eta}{sub 0}, that yields methyl esters. Estimates of the kinetic parameters show that the {beta} addition is faster than linear growth, which results in high selectivities to branched alcohols, i.e., 2-methyl-1- propanol.

Herman, R.G.; Klier, K. (Zettlemoyer Center for Surface Studies, Dept. of Chemistry, Lehigh Univ., Bethlehem, PA (US)); Smith, K.J. (Alberta Research Council, Coal and Hydrocarbon Processing Div., Devon, Alberta T0C 1E0 (CA)); Young, C.W. (China Steel Corp., New Material R and D Dept. T6, Hsiao Kang, Kaohsiung 81233 (TW))

1991-01-01

357

YIELD STRESS DETERMINATION OF ASPHALT EMULSIONS  

Microsoft Academic Search

The yield stress of asphalt emulsions was investigated as a potential quality control parameter. Viscometric data were determined using concentric cylinder, parallel plate, and cone and plate geometries. The use of a novel slotted-plate technique was investigated to determine the yield stress of asphalt emulsions in a direct way, that is to say, without extrapolation. The Saybolt viscosity was determined

Max Hetzer; Kyle Frederic; Daniel De Kee; Christopher D. Abadie

2007-01-01

358

Chemical Kinetics  

Microsoft Academic Search

\\u000a While thermodynamics provides steady-state information of the combustion process, chemical kinetics describes the transient\\u000a states of the system during the combustion process. Particularly important is information related to the rate at which species\\u000a are consumed and produced, and the rate at which the heat is released. Combustion chemistry has two important characteristics\\u000a not commonly observed in other chemical systems. First,

Sara McAllister; Jyh-Yuan Chen; A. Carlos Fernandez-Pello

359

Kinetic Sculpture  

NSDL National Science Digital Library

In this design challenge activity, learners build a tower thatâs at least 12 inches high with two or more parts that move (spin, sway, or flap) in the wind. This art meets construction activity allows learners to think about design challenges while creating a kinetic sculpture (a sculpture that moves). This is an excellent follow-up activity to "High Rise" from the same source.

Wgbh

2010-01-01

360

Models for mineralization kinetics with the variables of substrate concentration and population density.  

PubMed Central

The rates of mineralization of [14C]benzoate by an induced population of Pseudomonas sp. were measured at initial substrate concentrations ranging from 10 ng/ml to 100 micrograms/ml. Plots of the radioactivity remaining in the culture were fit by nonlinear regression to six kinetic models derived from the Monod equation. These models incorporate only the variables of substrate concentration and cell density. Plots of the mineralization kinetics in cultures containing low, intermediate, and high initial substrate concentrations were well fit by first-order, integrated Monod, and logarithmic kinetics, respectively. Parameters such as maximum specific growth rate, half-saturation constant, and initial population density divided by yield agreed between cultures to within a factor of 3.4. Benzoate mineralization by microorganisms in acclimated sewage was shown to fit logistic (sigmoidal), Monod, and logarithmic kinetics when the compound was added at initial concentrations of 0.1, 1.0, and 10 micrograms/ml, respectively. The mineralization of 10 micrograms of benzoate per ml in sewage also followed logarithmic kinetics in the absence of protozoa. It is concluded that much of the diversity in shapes of mineralization curves is a result of the interactions of substrate concentration and population density. Nonlinear regression with models incorporating these variables is a valuable means for analysis of microbial mineralization kinetics.

Simkins, S; Alexander, M

1984-01-01

361

Measurement of B{sub s}{sup 0} Mixing Parameters from the Flavor-Tagged Decay B{sub s}{sup 0}{yields}J/{psi}{phi}  

SciTech Connect

From an analysis of the flavor-tagged decay B{sub s}{sup 0}{yields}J/{psi}{phi} we obtain the width difference between the B{sub s}{sup 0} light and heavy mass eigenstates, {delta}{gamma}{sub s}=0.19{+-}0.07(stat){sub -0.01}{sup +0.02}(syst) ps{sup -1}, and the CP-violating phase, {phi}{sub s}=-0.57{sub -0.30}{sup +0.24}(stat){sub -0.02}{sup +0.08}(syst). The allowed 90% CL intervals of {delta}{gamma}{sub s} and {phi}{sub s} are 0.06<{delta}{gamma}{sub s}<0.30 ps{sup -1} and -1.20<{phi}{sub s}<0.06, respectively. The data sample corresponds to an integrated luminosity of 2.8 fb{sup -1} accumulated with the D0 detector at the Fermilab Tevatron collider.

Abazov, V. M.; Alexeev, G. D.; Kalinin, A. M.; Kharzheev, Y. M.; Malyshev, V. L.; Tokmenin, V. V.; Vertogradov, L. S.; Yatsunenko, Y. A. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Abbott, B.; Gutierrez, P.; Hossain, S.; Jain, S.; Rominsky, M.; Severini, H.; Skubic, P.; Strauss, M. [University of Oklahoma, Norman, Oklahoma 73019 (United States); Abolins, M.; Benitez, J. A.; Brock, R.; Dyer, J. [Michigan State University, East Lansing, Michigan 48824 (United States)] (and others)

2008-12-12

362

Composing Motion Grammar of Kinetic Typography  

Microsoft Academic Search

The research presented proposes a method for controlling dynamic motions of kinetic typography for expressing Kansei information. We researched Kansei words about Japanese onomatopoeia, and disclosed factors for control of dynamic motions, and we constructed a script model for generating dynamic motion with parameters which were obtained from research. The script model can make some dynamic motions of kinetic typography

Yasufumi Uekita; Junji Sakamoto; Masahiko Furukata

2000-01-01

363

Kinetic Modeling of Hydrodenitrogenation of Pyridine  

Microsoft Academic Search

This study is aimed at developing a kinetic model for the hydrodenitrogenation (HDN) of pyridine. The developed model deals with the selectivity of piperidine, one of the products obtained from the HDN of pyridine and with the conversion of pyridine to piperidine. Kinetic parameters were estimated from the results of the experimental data obtained from literature sources where the reactions

L. O. Oyekunle; O. A. Edafe

2009-01-01

364

A Comprehensive Enzyme Kinetic Exercise for Biochemistry  

ERIC Educational Resources Information Center

|This article describes a comprehensive treatment of experimental enzyme kinetics strongly coupled to electronic data acquisition and use of spreadsheets to organize data and perform linear and nonlinear least-squares analyses, all in a manner that promotes development of important reasoning skills. Kinetic parameters are obtained for the stable…

Barton, Janice S.

2011-01-01

365

Nucleation kinetics of vapor bubbles in a liquid with arbitrary viscosity  

NASA Astrophysics Data System (ADS)

The multivariable theory of nucleation in Langevin's approach [N.V. Alekseechkin, J. Chem. Phys. 124, 124512 (2006); N.V. Alekseechkin, J. Chem. Phys. 129, 024512 (2008)] is applied to the problem of vapor bubbles formation in a liquid with arbitrary viscosity. The obtained expression for the nucleation rate of bubbles is valid for arbitrary relations between the kinetic parameters controlling the nucleation process: viscosity, inertia of a liquid, the rate of evaporation into a bubble and the rate of heat exchange between the bubble and ambient liquid. So, the presented theory yields a complete description of the vapor-bubbles nucleation kinetics in single-component liquids. Limiting cases with respect to the mentioned parameters are considered, in particular, the low-viscosity limit. It is shown that the low- and high-viscosity nucleation rates differ from each other qualitatively and quantitatively. The possibility of application of the theory to cavitation in superfluid helium-4 is discussed.

Alekseechkin, Nikolay V.

2013-09-01

366

Probabilistic multicompartmental model for interpreting DGT kinetics in sediments.  

PubMed

Extensive research has been performed on the use of the DIFS (DGT-Induced Fluxes in Soils and Sediments) model to interpret diffusive gradients in thin-film, or DGT, measurements in soils and sediments. The current report identifies some areas where the DIFS model has been shown to yield poor results and proposes a model to address weaknesses. In particular, two major flaws in the current approaches are considered: (i) many studies of accumulation kinetics in DGT exhibit multiple kinetic stages and (ii) several combinations of the two fitted DIFS parameters can yield identical results, leaving the question of how to select the 'best' combination. Previously, problem (i) has been addressed by separating the experimental data sets into distinct time segments. To overcome these problems, a model considering two types of particulate binding sites is proposed, instead of the DIFS model which assumed one single particulate pool. A probabilistic approach is proposed to fit experimental data and to determine the range of possible physical parameters using Probability Distribution Functions (PDFs), as opposed to single values without any indication of their uncertainty. The new probabilistic model, called DGT-PROFS, was tested on three different formulated sediments which mainly differ in the presence or absence of iron oxides. It was shown that a good fit can be obtained for the complete set of data (instead of DIFS-2D) and that a range of uncertainty values for each modeling parameter can be obtained. The interpretation of parameter PDFs allows one to distinguish between a variety of geochemical behaviors, providing useful information on metal dynamics in sediments. PMID:21707053

Ciffroy, P; Nia, Y; Garnier, J M

2011-10-26

367

Kinetics of coal pyrolysis and devolatilization  

SciTech Connect

Research continued on coal pyrolysis and devolatilization. The effects of reaction process on the transient temperature history of a particle have been examined. The reaction process is found to significantly reduce the temperature gradient across a burning particle relative to a nonreactive particle. The pyrolysis process, on the other hand, does not severely affect the temperature history of a heating particle for the kinetic parameters employed. Devolatilization experiments have been performed on various size cuts on an HVA Bituminous coal in entrained flow and heated grid reactors. Weight loss measurements were made in the entrained flow reactor (EFR) and tar yields and molecular weight distributions were measured for the heated grid reactor (HGR) experiments. The results imply the initial phase of the devolatilization of the HVA Bituminous coal is heat transfer controlled because the rate of tar information and evolution is heat transfer controlled. The invariance in EFR ultimate weight loss and low pressure tar yields and characteristics with change in particle size can be explained by morphological considerations of the parent coal particles. The non-symmetric, irregular shapes of the coal particles result in an intraparticle mass distribution much nearer an interphase surface area than that of an equivalent sphere or cube. 5 refs., 37 figs., 9 tabs.

Seery, D.J.; Freihaut, J.D.; Proscia, W.M.

1991-01-01

368

Tolrestat kinetics  

SciTech Connect

The kinetics of tolrestat, a potent inhibitor of aldose reductase, were examined. Serum concentrations of tolrestat and of total /sup 14/C were measured after dosing normal subjects and subjects with diabetes with /sup 14/C-labeled tolrestat. In normal subjects, tolrestat was rapidly absorbed and disappearance from serum was biphasic. Distribution and elimination t 1/2s were approximately 2 and 10 to 12 hr, respectively, after single and multiple doses. Unchanged tolrestat accounted for the major portion of /sup 14/C in serum. Radioactivity was rapidly and completely excreted in urine and feces in an approximate ratio of 2:1. Findings were much the same in subjects with diabetes. In normal subjects, the kinetics of oral tolrestat were independent of dose in the 10 to 800 mg range. Repetitive dosing did not result in unexpected cumulation. Tolrestat was more than 99% bound to serum protein; it did not compete with warfarin for binding sites but was displaced to some extent by high concentrations of tolbutamide or salicylate.

Hicks, D.R.; Kraml, M.; Cayen, M.N.; Dubuc, J.; Ryder, S.; Dvornik, D.

1984-10-01

369

Yield Improvement in Steel Casting (Yield II)  

SciTech Connect

This report presents work conducted on the following main projects tasks undertaken in the Yield Improvement in Steel Casting research program: Improvement of Conventional Feeding and Risering Methods, Use of Unconventional Yield Improvement Techniques, and Case Studies in Yield Improvement. Casting trials were conducted and then simulated using the precise casting conditions as recorded by the participating SFSA foundries. These results present a statistically meaningful set of experimental data on soundness versus feeding length. Comparisons between these casting trials and casting trials performed more than forty years ago by Pellini and the SFSA are quite good and appear reasonable. Comparisons between the current SFSA feeding rules and feeding rules based on the minimum Niyama criterion reveal that the Niyama-based rules are generally less conservative. The niyama-based rules also agree better with both the trials presented here, and the casting trails performed by Pellini an d the SFSA years ago. Furthermore, the use of the Niyama criterion to predict centerline shrinkage for horizontally fed plate sections has a theoretical basis according to the casting literature reviewed here. These results strongly support the use of improved feeding rules for horizontal plate sections based on the Niyama criterion, which can be tailored to the casting conditions for a given alloy and to a desired level of soundness. The reliability and repeatability of ASTM shrinkage x-ray ratings was investigated in a statistical study performed on 128 x-rays, each of which were rated seven different times. A manual ''Feeding and Risering Guidelines for Steel Castings' is given in this final report. Results of casting trials performed to test unconventional techniques for improving casting yield are presented. These use a stacked arrangement of castings and riser pressurization to increase the casting yield. Riser pressurization was demonstrated to feed a casting up to four time s the distance of a non-pressurized riser, and can increase casting yield by decreasing the required number of risers. All case studies for this projects were completed and compiled into an SFSA Technical Report that is submitted part of this Final Report

Richard A. Hardin; Christoph Beckermann; Tim Hays

2002-02-18

370

Crystallization kinetics of palm oil  

Microsoft Academic Search

The quality and yield of oils obtained by fractionation processes depend mainly on the separation efficiency of fat crystals\\u000a from the mother liquor; this process is, to a large extent, determined by crystal-size distributions. The size of the crystals\\u000a is influenced by the crystallization conditions applied, and the quantitative data on crystallization kinetics are a useful\\u000a tool to optimize and

K. P. A. M. van Putte; B. H. Bakker

1987-01-01

371

Reconstructing kinetic pathways from single-molecule FRET experiments using Bayesian inference  

NASA Astrophysics Data System (ADS)

Single-molecule FRET studies have enabled observation of conformational transitions in individual molecules, allowing targeted investigations into the mechanistic function of molecular machines. Like in many single-molecule platforms, sm-FRET studies yield observations of hundreds of noisy time series, which report on the same underlying conformational steps, but exhibit significant variations in photophysical properties and kinetic rates. Reconstruction of a consensus kinetic pathway from such noisy measurements is statistically challenging. Hidden Markov Models are widely used to identify states and estimate the associated kinetic rates. Existing techniques perform inference on one time series at a time, yielding variable parameter estimates that must now be `averaged' using ad-hoc experiment specific post-processing steps. Here, we propose a technique known as Empirical Bayes estimation, which performs simultaneous analysis on a collection of trajectories in an experiment. This results in a single estimate for a consensus kinetic model, as well as a significantly reduced estimation error. By comparing models with different constraints, we show how these methods may be used to test detailed mechanistic hypotheses in a statistically principled, adaptable manner.

van de Meent, Jan-Willem; Gonzalez, Ruben L., Jr.; Wiggins, Chris H.

2013-03-01

372

Analysis of thermoluminescence kinetics of CaF2(Tm) peaks with glow curve deconvolution  

Microsoft Academic Search

The purpose of this study is to achieve detailed information on kinetic parameters of the peaks of a dosimetric material. First and general order kinetic formulas are applied with a computerized deconvolution technique to CaF2(Tm) thermoluminescence glow curves. A comparison is presented between deconvolution kinetic parameters and parameters obtained applying Chen's method.

C. Bacci; P. Bernardini; A. di Domenico; C. Furetta; B. Rispoli

1990-01-01

373

Kinetic energy of rain and its functional relationship with intensity  

Microsoft Academic Search

The rain kinetic energy (KE) is a widely used indicator of the potential ability of rain to detach soil. However, rain kinetic energy is not a commonly measured meteorological parameter. Therefore, empirical laws linking the rain kinetic energy to the more easily available rain intensity (I) have been proposed based on drop-size and drop-velocity measurements. The various mathematical expressions used

Christian Salles; Jean Poesen; Daniel Sempere-Torres

2002-01-01

374

Reed canarygrass yield improvement  

Technology Transfer Automated Retrieval System (TEKTRAN)

Reed canarygrass is well adapted to the northern USA. Eight cultivars and 72 accessions collected in rural landscapes from Iowa to New Hampshire were evaluated for yield. Accessions produced on average 7% higher biomass yield compared to existing cultivars. Naturalized populations of reed canarygras...

375

Reaction kinetics of the hydrothermal treatment of lignin.  

PubMed

Lignins derived from abundant and renewable resources are nontoxic and extremely versatile in performance, qualities that have made them increasingly important in many industrial applications. We have shown recently that liquefaction of lignin extracted from aspen wood resulted in a 90% yield of liquid. In this paper, the hydrothermal treatment of five types of lignin and biomass residues was studied: Kraft pine lignin provided by MeadWestvaco, Kraft pine lignin from Sigma-Aldrich, organosolv lignin extracted from oat hull, the residues of mixed southern hardwoods, and switchgrass after hydrolysis. The yields were found dependent on the composition or structure of the raw materials, which may result from different pretreatment processes. We propose a kinetic model to describe the hydrothermal treatment of Kraft pine lignin and compare it with another model from the literature. The kinetic parameters of the presented model were estimated, including the reaction constants, the pre-exponential factor, and the activation energy of the Arrhenius equations. Results show that the presented model is well in agreement with the experiments. PMID:18401758

Zhang, Bo; Huang, Hua-Jiang; Ramaswamy, Shri

2007-10-23

376

Molecular dynamics and kinetic study of carbon coagulation in the release wave of detonation products  

NASA Astrophysics Data System (ADS)

We present a combined molecular dynamics and kinetic study of a carbon cluster aggregation process in thermodynamic conditions relevant for the detonation products of oxygen deficient explosives. Molecular dynamics simulations with the LCBOPII potential under gigapascal pressure and high temperatures indicate that (i) the cluster motion in the detonation gas is compatible with Brownian diffusion and (ii) the coalescence probability is 100% for two clusters entering the interaction cutoff distance. We used these results for a subsequent kinetic study with the Smoluchowski model, with realistic models applied for the physical parameters such as viscosity and cluster size. We found that purely aggregational kinetics yield too fast clustering, with moderate influence of the model parameters. In agreement with previous studies, the introduction of surface reactivity through a simple kinetic model is necessary to approach the clustering time scales suggested by experiments (1000 atoms after 100 ns, 10 000 atoms after 1 ?s). However, these models fail to reach all experimental criteria simultaneously and more complex modelling of the surface process seems desirable to go beyond these current limitations.

Chevrot, Guillaume; Sollier, Arnaud; Pineau, Nicolas

2012-02-01

377

Dose dependent oxidation kinetics of lipids in fish during irradiation processing  

NASA Astrophysics Data System (ADS)

Kinetic aspects of the development of lipid oxidation in complex foods as fish in the course of irradiation were analyzed with respect to the associated formation of malonaldehyde (MA) through the reactions modified so as to be consistent with those in complex foods as fish. Air-packed anchovy (Engraulis encrasicholus) samples in polyethylene pouches were irradiated at the doses of 1, 2, 5, 10, 15, 20 and 25 kGy at 20°C in a Cs-137 gamma irradiator of 1.806 kGy/h dose rate. Immediately after each irradiation, MA contents of irradiated and unirradiated samples were determined by thiobarbituric acid test. Based on the MA formation, a kinetic model to simulate the apparent oxidation of lipid in fish as a function of irradiation dose was derived from the rate equations consistent with modified reactions. Kinetic parameters and simulation were related to conditions of lipid oxidation, and associated rancidity state of fish with respect to the doses applied in different irradiation-preservation processes. Numerical values of kinetic parameters based on the MA formation were found as a threshold dose of 0.375 kGy, an apparent yield of 1.871 ?mol/kg kGy, and a maximum attainable concentration of 15.853 ?mol/kg which may be used for process control and dosimetry.

Tükenmez, ?brahi?m.; Ersen, M. Sitki; Bak.¨o?lu, A. Tayfur; Bi?çer, Ahmet; Pamuk, Veci?h.?

1997-10-01

378

Antigen kinetics determines immune reactivity  

PubMed Central

A current paradigm in immunology is that the strength of T cell responses is governed by antigen dose, localization, and costimulatory signals. This study investigates the influence of antigen kinetics on CD8 T cell responses in mice. A fixed cumulative antigen dose was administered by different schedules to produce distinct dose-kinetics. Antigenic stimulation increasing exponentially over days was a stronger stimulus for CD8 T cells and antiviral immunity than a single dose or multiple dosing with daily equal doses. The same was observed for dendritic cell vaccination, with regard to T cell and anti-tumor responses, and for T cells stimulated in vitro. In conclusion, stimulation kinetics per se was shown to be a separate parameter of immunogenicity. These findings warrant a revision of current immunization models and have implications for vaccine development and immunotherapy.

Johansen, Pal; Storni, Tazio; Rettig, Lorna; Qiu, Zhiyong; Der-Sarkissian, Ani; Smith, Kent A.; Manolova, Vania; Lang, Karl S.; Senti, Gabriela; Mullhaupt, Beat; Gerlach, Tilman; Speck, Roberto F.; Bot, Adrian; Kundig, Thomas M.

2008-01-01

379

Evaluation of chemical reaction mechanisms for photochemical smog. Part 3. Sensitivity of EKMA (Empirical Kinetic Modeling Approach) to chemical mechanism and input parameters. Final report, March 1984-Feburary 1985  

Microsoft Academic Search

Six chemical reaction mechanisms for photochemical smog were used to study the effect of input parameters on volatile organic compound (VOC) control requirements needed to reduce ozone. The parameters studied were initial VOC composition, dilution rate, post 8-A.M. emissions, base case (present day) Oâ levels, entrainment from aloft of VOC and ozone, initial HONO and initial VOC\\/NOx ratio. The Empirical

T. B. Shafer; J. H. Seinfeld

1985-01-01

380

Prediction of Submerged Arc Welding Yield Parameters through Graphical Technique  

Microsoft Academic Search

In submerged arc welding (SAW), selecting appropriate values for process variables is essential in order to control bead size and quality. Also, condition must be selected that will ensure a predictable weld bead, which is critical for obtaining high quality. In this investigation, mathematical models (based on multi-regression method) have been developed and side by side prediction through artificial neural

Aniruddha Ghosh; Somnath Chattopadhyaya; R. K. Das; P. K. sarkar

2011-01-01

381

Substituent effect on the photoreduction kinetics of benzophenone.  

PubMed

The kinetics of the photoreduction of four benzophenone derivatives by isopropyl alcohol was examined in acetonitrile, namely, tetra-meta-trifluoromethyl-, di-para-trifluoromethyl-, di-para-methoxy benzophenone, and, for comparison, the unsubstituted molecule itself. The basic spectroscopic (absorption and phosphorescence spectra) and photophysical (quantum yields and excited state energies) properties were established, and the key kinetic parameters were determined by the laser flash photolysis transient absorption technique. The rate coefficients of both the primary and secondary photoreduction reaction show remarkable dependence on ring substitution. This substantial effect is caused by the considerable change in the activation energy of the corresponding process. The experimental results as well as DFT quantum chemical calculations clearly indicate that these benzophenone derivatives all react as n-?* excited ketones, and the rate as well as the activation energy of the reduction steps change parallel with the reaction enthalpies, the determining factor being the stability of the forming aromatic ketyl radicals. The secondary photoreduction of benzophenones by the aliphatic ketyl radical formed in the primary step occurs via a hydrogen bonded complex. The binding energy of the hydrogen bonded complex between the aliphatic ketyl radical reactant and a solvent molecule is a critical parameter influencing the observable rate of the secondary photoreduction. PMID:23980872

Demeter, Attila; Horváth, Klaudia; Bö?r, Katalin; Molnár, Laura; Soós, Tibor; Lendvay, György

2013-09-17

382

TNT Prout-Tompkins Kinetics Calibration with PSUADE.  

National Technical Information Service (NTIS)

We used the code PSUADE to calibrate Prout-Tompkins kinetic parameters for pure recrystallized TNT. The calibration was based on ALE3D simulations of a series of One Dimensional Time to Explosion (ODTX) experiments. The resultant kinetic parameters differ...

A. P. Wemhoff H. Hsieh

2007-01-01

383

Plasma Kinetics  

NASA Astrophysics Data System (ADS)

In Chapter 7 of ISSI SR-001, Schwartz et al. [1998] explain the basic ideas of analysis by means of plasma kinetics: Liouville mapping and finite gyroradius effects. Liouville mapping can be used to relate features of distribution functions such as heating, anisotropies or beams, to the field variations. It is based on the conservation of phase space density along particle trajectories in collisionless plasmas, and therefore requires that particle trajectories (or at least their initial and final states) can be accurately approximated. This requirement generally relies on invariants of the particle motion such as the energy and adiabatic invariants and some knowledge of the electromagnetic fields along the trajectories. The large gyroradius of energetic ions has the consequence that ions detected at different directions are actually probing conditions at considerable distances around the space- craft. Density gradients then appear as gyrophase anisotropies in the angular distributions. This effect was first employed by Kaufmann and Konradi [1973] to probe the magnetopause. Section 7.5 of Schwartz et al. [1998] explain how it can be used to remotely sense sharp boundaries in ion densities. In particular, see Figures 7.4 and 7.6 in that chapter for a graphical demonstration. For a historical perspective on these topics, see also the classic paper by Northrop and Teller [1960] on the motion of charged particles in the Earth's magnetic field. In addition, Whipple et al. [1998] present an alternative framework that builds on the underlying concepts, while Whipple et al. [1986] describe extensions to the classic adiabatic theory that apply even in regions of strong gradients.

Daly, Patrick W.; Schwartz, Steven J.; Lefebvre, Betrand

384

Modelling the effects of sprinkler irrigation uniformity on crop yield  

Microsoft Academic Search

This study reports the development and testing of a model which relates yield to irrigation amount and uniformity. Required input data are the Christiansen uniformity coefficient (CUC) and a parameter describing the sensitivity of crop yield to water deficits obtained from empirical relationships between evapotranspiration and crop yield.The model was used to determine optimum irrigation amounts for corn at Cordoba

E. C. Mantovani; F. J. Villalobos; F. Organ; E. Fereres

1995-01-01

385

Oxidation of hydrochlorothiazide by UV radiation, hydroxyl radicals and ozone: Kinetics and elimination from water systems  

Microsoft Academic Search

Hydrochlorothiazide (6-chloro-1,1-dioxo-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide), a thiazidic diuretic very frequently used in the treatment of hypertension, has been oxidized by means of UV radiation, Fenton's reagent and ozone. The influence of some operating variables was established, and the main kinetic parameters were determined. Specifically, for the photodegradation process, quantum yields ranging between 0.028 and 0.048molEins?1 were obtained depending on the temperature and pH.

Francisco J. Real; Juan L. Acero; F. Javier Benitez; Gloria Roldán; Luz C. Fernández

2010-01-01

386

Herschel-Bulkley rheology from lattice kinetic theory of soft glassy materials  

NASA Astrophysics Data System (ADS)

We provide clear evidence that a two-species mesoscopic Lattice Boltzmann (LB) model with competing, short-range attractive and mid-range repulsive, interactions supports emergent Herschel-Bulkley (HB) rheology, i.e. a power-law dependence of the shear stress as a function of the strain rate, beyond a given yield stress threshold. This kinetic formulation supports a seamless transition from flowing to non-flowing behaviour, through a smooth tuning of the parameters governing the mesoscopic interactions between the two species. The present model may become a valuable computational tool for the investigation of the rheology of soft glassy materials on scales of experimental interest.

Benzi, R.; Bernaschi, M.; Sbragaglia, M.; Succi, S.

2010-07-01

387

Kinetics of stress fibers  

NASA Astrophysics Data System (ADS)

Stress fibers are contractile cytoskeletal structures, tensile actomyosin bundles which allow sensing and production of force, provide cells with adjustable rigidity and participate in various processes such as wound healing. The stress fiber is possibly the best characterized and most accessible multiprotein cellular contractile machine. Here we develop a quantitative model of the structure and relaxation kinetics of stress fibers. The principal experimentally known features are incorporated. The fiber has a periodic sarcomeric structure similar to muscle fibers with myosin motor proteins exerting contractile force by pulling on actin filaments. In addition the fiber contains the giant spring-like protein titin. Actin is continuously renewed by exchange with the cytosol leading to a turnover time of several minutes. In order that steady state be possible, turnover must be regulated. Our model invokes simple turnover and regulation mechanisms: actin association and dissociation occur at filament ends, while actin filament overlap above a certain threshold in the myosin-containing regions augments depolymerization rates. We use the model to study stress fiber relaxation kinetics after stimulation, as observed in a recent experimental study where some fiber regions were contractile and others expansive. We find that two distinct episodes ensue after stimulation: the turnover overlap system relaxes rapidly in seconds, followed by the slow relaxation of sarcomere lengths in minutes. For parameter values as they have been characterized experimentally, we find the long time relaxation of sarcomere length is set by the rate at which actin filaments can grow or shrink in response to the forces exerted by the elastic and contractile elements. Consequently, the stress fiber relaxation time scales inversely with both titin spring constant and the intrinsic actin turnover rate. The model's predicted sarcomere velocities and contraction expansion kinetics are in good quantitative agreement with experiment.

Stachowiak, Matthew R.; O'Shaughnessy, Ben

2008-02-01

388

Glutathione synthesis and turnover in the human erythrocyte: alignment of a model based on detailed enzyme kinetics with experimental data.  

PubMed

The erythrocyte is exposed to reactive oxygen species in the circulation and also to those produced by autoxidation of hemoglobin. Consequently, erythrocytes depend on protection by the antioxidant glutathione. Mathematical models based on realistic kinetic data have provided valuable insights into the regulation of biochemical pathways within the erythrocyte but none have satisfactorily accounted for glutathione metabolism. In the current model, rate equations were derived for the enzyme-catalyzed reactions, and for each equation the nonlinear algebraic relationship between the steady-state kinetic parameters and the unitary rate constants was derived. The model also includes the transport processes that supply the amino acid constituents of glutathione and the export of oxidized glutathione. Values of the kinetic parameters for the individual reactions were measured predominately using isolated enzymes under conditions that differed from the intracellular environment. By comparing the experimental and simulated results, the values of the enzyme-kinetic parameters of the model were refined to yield conformity between model simulations and experimental data. Model output accurately represented the steady-state concentrations of metabolites in erythrocytes suspended in plasma and the changing glutathione concentrations in whole and hemolyzed erythrocytes under specific experimental conditions. Analysis indicated that feedback inhibition of gamma-glutamate-cysteine ligase by glutathione had a limited effect on steady-state glutathione concentrations and was not sufficiently potent to return glutathione concentrations to normal levels in erythrocytes exposed to sustained increases in oxidative load. PMID:20498365

Raftos, Julia E; Whillier, Stephney; Kuchel, Philip W

2010-05-24

389

Testing biochemistry revisited: how in vivo metabolism can be understood from in vitro enzyme kinetics.  

PubMed

A decade ago, a team of biochemists including two of us, modeled yeast glycolysis and showed that one of the most studied biochemical pathways could not be quite understood in terms of the kinetic properties of the constituent enzymes as measured in cell extract. Moreover, when the same model was later applied to different experimental steady-state conditions, it often exhibited unrestrained metabolite accumulation.Here we resolve this issue by showing that the results of such ab initio modeling are improved substantially by (i) including appropriate allosteric regulation and (ii) measuring the enzyme kinetic parameters under conditions that resemble the intracellular environment. The following modifications proved crucial: (i) implementation of allosteric regulation of hexokinase and pyruvate kinase, (ii) implementation of V(max) values measured under conditions that resembled the yeast cytosol, and (iii) redetermination of the kinetic parameters of glyceraldehyde-3-phosphate dehydrogenase under physiological conditions.Model predictions and experiments were compared under five different conditions of yeast growth and starvation. When either the original model was used (which lacked important allosteric regulation), or the enzyme parameters were measured under conditions that were, as usual, optimal for high enzyme activity, fructose 1,6-bisphosphate and some other glycolytic intermediates tended to accumulate to unrealistically high concentrations. Combining all adjustments yielded an accurate correspondence between model and experiments for all five steady-state and dynamic conditions. This enhances our understanding of in vivo metabolism in terms of in vitro biochemistry. PMID:22570597

van Eunen, Karen; Kiewiet, José A L; Westerhoff, Hans V; Bakker, Barbara M

2012-04-26

390

Automatic kinetic typography composer  

Microsoft Academic Search

Animated text, commonly called kinetic typography, is any attractive visual expression used in films, TV programs, video games, etc. Previous studies have developed tools that support the authoring and rendering of kinetic typography. However, authoring kinetic typography is not easy because its methodology is still at an early stage. Hence, we systematize expression elements in kinetic typography and propose an

Mitsuru Minakuchi; Katsumi Tanaka

2005-01-01

391

Di- and triorganotin(IV) derivatives of 5-amino-3H-1,3,4-thiadiazole-2-thione as precursors for SnS/SnO{sub 2}: Thermal studies and related kinetic parameters  

SciTech Connect

Thermogravimetric analysis (TGA) with simultaneous differential thermal analysis (DTA) of R{sub 2}SnL{sub 2} (R = methyl (1), n-butyl (2), n-octyl (3) and phenyl (4)) and R{sub 3}SnL (R = methyl (5), n-propyl (6), n-butyl (7) and phenyl (8); L = anion of 5-amino-3H-1,3,4-thiadiazole-2-thione) show that in air and nitrogen, diorganotin(IV) thiadiazolates decompose in a different manner, whereas triorganotin(IV) thiadiazolates decompose in a similar way. The decomposition of di- and triorganotin(IV) thiadiazolates occur in two or three steps. The first step of decomposition corresponds to the loss of a ligand/a part of ligand moiety, which is followed by the loss of remaining ligand moiety (in case of diorganotin(IV) thiadiazolates) and the organic groups attached to tin. In case of compounds (3) and (5), tin is partially lost to the gas phase due to sublimation. The residues obtained by thermal decomposition of these compounds are SnS and/or Sn in nitrogen and SnO{sub 2} in air, which are characterized by infrared (IR), far-infrared (far-IR), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Mathematical analysis of thermogravimetric analysis data shows that the first step of decomposition in compounds (4) (6) and (8) in both air and nitrogen follows first order kinetics. Kinetic and thermodynamic data, such as energy of activation (E*), pre-exponential factor (A), entropy of activation (S*), free energy of activation (G*) and enthalpy of activation (H*) of the first step of decomposition have also been calculated.

Nath, M. [Department of Chemistry, Indian Institute of Technology, Roorkee, 247667 Uttaranchal (India)]. E-mail: malanfcy@iitr.ernet.in; Sulaxna [Department of Chemistry, Indian Institute of Technology, Roorkee, 247667 Uttaranchal (India)

2006-01-05

392

Kinetic theory of rf current drive and helicity injection.  

National Technical Information Service (NTIS)

Current drive and helicity injection by plasma waves are examined with the use of kinetic theory. The Vlasov equation yields a general current drive formula which contains resonant and nonresonant contributions. Standard quasilinear current drive is descr...

R. R. Mett

1991-01-01

393

Effects of Experimental Conditions on Extraction Yield of Extracellular Polymeric Substances by Cation Exchange Resin  

PubMed Central

Effects of experimental conditions on the yield of extracellular polymeric substances (EPSs) extraction by cation exchange resin (CER) were investigated using activated sludge flocs. The experimental variables included resin dose, extraction time, sample dilution, and storage time. An empirical model was proposed to describe the kinetics of extraction process. The extraction yield increases with the extraction time and CER dose until it reached the maximum amount of EPS extraction. The maximum yield of EPS was affected as well by the sample dilution, exhibiting a decreasing trend with increasing dilution factor. It was also found that the amount of EPS extracted from a raw sample depends on the storage time. Once EPS was extracted from the sample, however, the EPS keeps its original quantity under storage at 4°C. Based on the model, the maximum amount of EPS extraction and yield rate could be estimated for different conditions. Comparing the model parameters allows one to quantitatively compare the extraction efficiencies under various extracting conditions. Based on the results, we recommend the original sample should be diluted with the volume ratio of above 1?:?2 and a raw sample should be treated quickly to prevent the reduction of sample homogeneity and original integrity.

Cho, Jinwoo; Hermanowicz, Slawomir W.; Hur, Jin

2012-01-01

394

Reaction kinetics of cellulose hydrolysis in subcritical and supercritical water  

NASA Astrophysics Data System (ADS)

The uncertainties in the continuous supply of fossil fuels from the crisis-ridden oil-rich region of the world is fast shifting focus on the need to utilize cellulosic biomass and develop more efficient technologies for its conversion to fuels and chemicals. One such technology is the rapid degradation of cellulose in supercritical water without the need for an enzyme or inorganic catalyst such as acid. This project focused on the study of reaction kinetics of cellulose hydrolysis in subcritical and supercritical water. Cellulose reactions at hydrothermal conditions can proceed via the homogeneous route involving dissolution and hydrolysis or the heterogeneous path of surface hydrolysis. The work is divided into three main parts. First, the detailed kinetic analysis of cellulose reactions in micro- and tubular reactors was conducted. Reaction kinetics models were applied, and kinetics parameters at both subcritical and supercritical conditions were evaluated. The second major task was the evaluation of yields of water soluble hydrolysates obtained from the hydrolysis of cellulose and starch in hydrothermal reactors. Lastly, changes in molecular weight distribution due to hydrothermolytic degradation of cellulose were investigated. These changes were also simulated based on different modes of scission, and the pattern generated from simulation was compared with the distribution pattern from experiments. For a better understanding of the reaction kinetics of cellulose in subcritical and supercritical water, a series of reactions was conducted in the microreactor. Hydrolysis of cellulose was performed at subcritical temperatures ranging from 270 to 340 °C (tau = 0.40--0.88 s). For the dissolution of cellulose, the reaction was conducted at supercritical temperatures ranging from 375 to 395 °C (tau = 0.27--0.44 s). The operating pressure for the reactions at both subcritical and supercritical conditions was 5000 psig. The results show that the rate-limiting step in converting cellulose to fermentable sugars in subcritical and supercritical water differs because of the difference in their activation energies. Cellulose and starch were both hydrolyzed in micro- and tubular reactors and at subcritical and supercritical conditions. Due to the difficulty involved in generating an aqueous based dissolved cellulose and having it reacted in subcritical water, dissolved starch was used instead. Better yield of water soluble hydrolysates, especially fermentable sugars, were observed from the hydrolysis of cellulose and dissolved starch in subcritical water than at supercritical conditions. The concluding phase of this project focuses on establishing the mode of scission of cellulose chains in the hydrothermal reactor. This was achieved by using the simulated degradation pattern generated based on different scission modes to fingerprint the degradation pattern obtained from experiment.

Olanrewaju, Kazeem Bode

395

Kinetics of phosphorothioate oligonucleotide metabolism in biological fluids.  

PubMed Central

The in vitro stability and metabolism of GEM[91, a 25mer phosphorothioate antisense oligonucleotide complementary to the gag mRNA region of HIV-1, was investigated using capillary electrophoresis (CE). The in vitro degradation of the parent compound at 37 degrees C was followed over the course of 120 h in human plasma. A CE method using laser-induced fluorescence detection was able to detect 5'-end intact metabolites including the parent compound extracted from biological fluids. Because the primary metabolic pathway is believed to be via 3'-exonuclease activity, the results of this study were compared with the stability of the compound in a solution containing 3'-exonuclease. The numerical solution of sequential first-order reactions was used to obtain kinetic parameters. Exonuclease digestion of the parent compound, as measured using an automated CE-UV instrument, yielded striking similarities between the two in vitro systems as well as between in vitro and in vivo systems.

Gilar, M; Belenky, A; Smisek, D L; Bourque, A; Cohen, A S

1997-01-01

396

Oxidation kinetics of tricresyl phosphate (TCP) using differential scanning calorimetry (DSC)  

Microsoft Academic Search

Oxidation kinetics of tricresyl phosphate (TCP) have been studied using differential scanning calorimetry (DSC). A kinetic model for the oxidation process was evaluated and several kinetic parameters were determined. The oxidation process in TCP appeared to be pseudo first order. Non-isothermal kinetic data was used to estimate isothermal oxidation behavior of TCP. Validity of the predicted isothermal behavior was checked

S. Shankwalkar; D. Placek

1994-01-01

397

Simple kinetic models of petroleum formation. Part I: oil and gas generation from kerogen  

Microsoft Academic Search

Modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks. The global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age; this is useful in areas of low geochemical knowledge, including exploration frontiers. Five kerogen kinetic organofacies, each characterized by a specific organic matter input and early

Andrew S. Pepper; Peter J. Corvi

1995-01-01

398

On a Kinetic Model for a Simple Market Economy  

Microsoft Academic Search

In this paper, we consider a simple kinetic model of economy involving both exchanges between agents and speculative trading. We show that the kinetic model admits non trivial quasi-stationary states with power law tails of Pareto type. In order to do this we consider a suitable asymptotic limit of the model yielding a Fokker–Planck equation for the distribution of wealth

Stephane Cordier; Lorenzo Pareschi; Giuseppe Toscani

2005-01-01

399

Determining kinetic and nonequilibrium sorption behavior for chlopyrifos using a hybrid batch/column experiment.  

PubMed

Pesticide mobility in soil is strongly coupled to the chemical's sorption characteristics. A modified soil column batch experiment was conducted to measure the transient nature of chlorpyrifos sorption and desorption from Cecil soil. This experimental system minimizes many shortcomings associated with obtaining sorption parameters by fitting soil column data to an advective-dispersive transport equation. Several chlorpyrifos formulations were investigated to determine how formulations affect soil sorption, and if this effect is adequately described using transient sorption/desorption algorithms. Both a second-order sorption with first-order desorption kinetic model and the two-site kinetic/equilibrium model were found to yield reasonable comparisons to experimental observations. In general, the formulation temporarily decreases the sorptivity of chlorpyrifos and alters the time for equilibrium to be achieved. Care must be exercised when extrapolating sorption data for a pure molecule in a laboratory setting to formulated materials used in field applications when environmental fate predictions are sought. PMID:15884846

Cryer, Steven A

2005-05-18

400

Investigation of kinetic and thermodynamic characteristics of removal of tetracycline with sponge like, tannin based cryogels.  

PubMed

The removal of tetracycline (TC) from aqueous environment by new type of sorbents, tannin based cryogels (TAB CRGs) and control cryogels (CRGs) was studied in a batch system. The experimental parameters that affect the sorption of TC were optimized to achieve maximum removal yield. Prepared cryogels were characterized by SEM imaging, IR spectroscopy (ATR). Produced TAB cryogels have thin polymeric walls and interconnected large pores. The TAB cryogels are elastic and sponge like; its water content can easily be removed by only compressed with hand. The TAB cryogels restore their original shape and size within seconds after soaked in water. On the other, elasticity of blank CRG is lower. The Freundlich and Langmuir adsorption isotherms were conducted to deduce the mechanism of the process. The kinetics of TC adsorption was moderately fast and almost reached equilibrium in 150 min and the results followed pseudo-second-order kinetic model. PMID:23298591

Er?an, Mehtap; Ba?da, Esra; Ba?da, Efkan

2012-12-07

401

Biodynamic Preparations Cause Opposite Yield Effects Depending Upon Yield Levels  

Microsoft Academic Search

Crop yields of cereals, carrots, beetroots and potatoes from 28 different field plot and pot experiments (on a site near Marburg\\/Germany) were compared to determine the influence of the biodynamic preparations 500 and 501 on yields. Under generally low yields the preparations tended to increase the yields. When the yields reach a medium level this positive effect was smaller. At

Joachim Raupp; Uli Johannes König

1996-01-01

402

Kinetics of continuous cultivation of the oleaginous yeast Rhodosporidium toruloides.  

PubMed

Microbial lipids are potential alternative feedstock for biofuel and oleochemical industries. The oleaginous yeast Rhodosporidium toruloides AS 2.1389 is an excellent lipid producer. To attain parameters for the understanding of the lipid production process, we performed continuous cultivation experiments under either carbon or nitrogen limitation. The maintenance coefficient and maximum cell mass yield for this yeast were determined as 5.7mg glucose/g cell/h and 0.42g cell/g glucose, respectively, under carbon limitation. Under nitrogen limitation, the highest lipid yield of 0.19g/g was observed at the dilution rate of 0.02h(-1) while the highest specific lipid formation rate of 0.058g/g cell/h at the dilution rate of 0.08h(-1). A kinetic model of lipid formation under steady state conditions was developed, parameters estimated, and optimal continuous cultivation conditions forecasted. These data should be very helpful to develop and design more efficient bioprocesses for microbial lipid production. PMID:23965273

Shen, Hongwei; Gong, Zhiwei; Yang, Xiaobing; Jin, Guojie; Bai, Fengwu; Zhao, Zongbao K

2013-08-18

403

Physisorption kinetics  

NASA Astrophysics Data System (ADS)

A quantum statistical theory of phonon-mediated physisorption has been developed by setting up the initial value problem within nonequilibrium statistical mechanics and calculating the desorption times appropriate for the various experimental procedures, i.e. virgin adsorption, isothermal desorption and flash desorption. We calculate desorption times for various gas-solid systems like helium-constantan, He-LiF, He—graphite, He-Ar, Xe-W, etc. which compare favorably with experiments. We are able to delimit the temperature range over which the Arrhenius-Frenkel parameterization of the desorption time td = t0dexp(Q/kBT) is acceptable. We can correlate isothermal and flash desorption times and suggest the temperature range where differences in these times can be detected. A complete fourth-order calculation enables us to delineate the range of validity of the one-phonon (second-order) theory and of the relaxation time approach to desorption. Desorption via phonon cascades is calculated. Our theory, which is essentially parameter-free, produces prefactors t0d in the whole experimental range of physisorption from 10-7 s to 10-14 s.

Kreuzer, H. J.

1981-03-01

404

Kinetics of Quality Changes During Food Frying  

Microsoft Academic Search

This paper deals with kinetics of quality changes during food frying. The quality parameters of interests include color, texture, viscoelastic properties, volume\\/density, and nutraceuticals (Omega 3 fatty acids). The kinetic theory and determination methodology under isothermal\\/non-isothermal conditions are also reviewed. This paper presents the reported reaction rate constant, order of reaction, and activation energy for specific quality changes including phenomenological

Fransiskus Hindra; Oon-Doo Baik

2006-01-01

405

Step-Flow Kinetics in Nanowire Growth  

NASA Astrophysics Data System (ADS)

Nanowire growth occurs by step flow at the wire-catalyst interface, with strikingly different step-flow kinetics for solid versus liquid catalysts. Here we report quantitative in situ measurements of step flow together with a kinetic model that reproduces the behavior. This allows us to identify the key parameters controlling step-flow growth, evaluate changes in the catalyst composition during growth, and identify the most favorable conditions for growing abrupt heterojunctions in nanowires.

Wen, C.-Y.; Tersoff, J.; Reuter, M. C.; Stach, E. A.; Ross, F. M.

2010-11-01

406

Generalized yield stress equation for electrorheological fluids.  

PubMed

A new generalized yield stress scaling equation for electrorheological (ER) fluids was developed by introducing the critical electric field (Ec) and material parameter. This equation can be used to describe the dependency of the yield stress on an electric field not only for conventional ER suspensions with a change in slope from 2.0 to 1.5, but also for giant ER fluids with a change in slope from 2.0 to 1.0. The yield stress data obtained from different ER fluid systems with different material parameters was collapsed onto a single curve for the entire range of electric field strengths using the proper scaling method proposed in this study. PMID:23993784

Zhang, Ke; Liu, Ying Dan; Jhon, Myung S; Choi, Hyoung Jin

2013-08-11

407

Biotechnology of Forest Yield  

Microsoft Academic Search

Silvicultural and genetic manipulation of Douglas fir and loblolly pine plantations have increased their productivity 70 and 300 percent, respectively, over natural forests on the same sites. Yet these intensively managed plantations are achieving less than 50 percent of their potential productivity. Future increases in yield will result from optimization of nutritional treatments, control of noncrop vegetation, and advances in

Peter Farnum; Roger Timmis; J. Laurence Kulp

1983-01-01

408

Determining enzyme kinetics via isothermal titration calorimetry.  

PubMed

Isothermal titration calorimetry (ITC) has emerged as a powerful tool for determining the thermodynamic properties of chemical or physical equilibria such as protein-protein, ligand-receptor, and protein-DNA binding interactions. The utility of ITC for determining kinetic information, however, has not been fully recognized. Methods for collecting and analyzing data on enzyme kinetics are discussed here. The step-by-step process of converting the raw heat output rate into the kinetic parameters of the Michaelis-Menten equation is explicitly stated. The hydrolysis of sucrose by invertase is used to demonstrate the capability of the instrument and method. PMID:23423886

Demarse, Neil A; Killian, Marie C; Hansen, Lee D; Quinn, Colette F

2013-01-01

409

A liquefaction kinetic research needs assessment  

SciTech Connect

In February 1989, the Department of Energy released its assessment of the research needs for coal liquefaction. Under direct liquefaction, 4 of the 12 recommendations focused on developing models and determining kinetics. Reasons accompanying these recommendations stressed the need to understand the retrograde reactions, the reactions taking place as the coal is heated to the reaction temperature, and the effects Of coal types and solvent on liquefaction reactions. By understanding the liquefaction process better, suggestions for improving the process may be made. A good kinetic model would provide a basis for testing suggestions which would attempt to control reactions or effects in the development of improved liquefaction technologies. Brandes et al. suggests that a kinetic model could also possibly have a large impact on the economics of coal liquefaction! Cost factors which could be studied using a kinetic model include: coal preparations, reactor throughput, hydrogen usage, catalyst usage, yields and selectivity, and process control.

Ferrance, J.; Warzinski, R.P. [Pittsburgh Energy Technology Center, PA (United States)

1996-12-31

410

Chemical and Biological Kinetics  

NASA Astrophysics Data System (ADS)

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.

Emanuel', N. M.

1981-10-01

411

Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid  

SciTech Connect

The reaction kinetics of the esterification of ethylene glycol with acetic acid in the presence of cation exchange resin has been studied and kinetic models based on empirical and Langmuir approach has been developed. The Langmuir based model involving eight kinetic parameters fits experimental data much better compared to empirical model involving four kinetic parameters. The effect of temperature and catalyst loading on the reaction system has been analyzed. Further, the activation energy and frequency factor of the rate constants for Langmuir based model has been estimated.

Yadav, Vishnu P.; Maity, Sunil K. [Department of Chemical Engineering, Indian Institute of Technology, Hyderabad, Ordnance Factory Estate, Yeddumailiram-502205, Andhra Pradesh (India); Mukherjee, Rudra Palash [Department of Chemical Engineering, National Institute of Technology, Durgapur, Mahatma Gandhi Avenue, Durgapur-713209, West Bengal (India); Bantraj, Kandi [Department of Chemical Engineering, National Institute of Technology, Rourkela-769008, Orissa (India)

2010-10-26

412

Structural, spectroscopic, and kinetic investigation of the molybdenum dialkylhydrazido complexes [MoBr(NNC5H10)(dppe)2]Br and [Mo(NNC5H10)(dppe)2]: activation parameters and revised mechanism for N-N cleavage.  

PubMed

The reaction of [Mo(NNC(5)H(10))(dppe)(2)] (B(Mo)) with an excess of acid, HNEt(3)BPh(4), is investigated applying temperature-dependent stopped-flow measurements. The kinetic data indicate a biphasic process with rate constants k(obs(1)) and k(obs(2)) which are both slower than the single rate constant reported by Henderson et al. (Henderson, R. A.; Leigh, G. J.; Pickett, C. J., J. Chem. Soc., Dalton Trans. 1989, 425-430). Moreover, both rate constants exhibit a linear dependence on the acid concentration with a large intercept which is attributed to acid-dependent and acid-independent components of each reaction phase, respectively. All four reaction channels exhibit temperature-dependent reaction rates. Furthermore, B(Mo) and its Mo(IV) analogue [MoBr(NNC(5)H(10))(dppe)(2)]Br (A(Mo)) are characterized structurally and spectroscopically. Density-functional theory calculations are performed to locate possible barriers in the overall reaction scheme and determine their energies, providing additional information for the formulation of a mechanism. The temperature-dependent rate of N-N cleavage is explained by a revised mechanism which involves an alpha-protonated intermediate that is inert with respect to N-N cleavage and is generated from its beta-protonated counterpart by a rapid 1,2-proton shift. The implications of these results with respect to N(2) reduction in the Chatt cycle and the enzyme nitrogenase are discussed. PMID:19235969

Dreher, Ameli; Mersmann, Klaus; Näther, Christian; Ivanovic-Burmazovic, Ivana; van Eldik, Rudi; Tuczek, Felix

2009-03-01

413

Regression Models For Saffron Yields in Iran  

NASA Astrophysics Data System (ADS)

Saffron is an important crop in social and economical aspects in Khorassan Province (Northeast of Iran). In this research wetried to evaluate trends of saffron yield in recent years and to study the relationship between saffron yield and the climate change. A regression analysis was used to predict saffron yield based on 20 years of yield data in Birjand, Ghaen and Ferdows cities.Climatologically data for the same periods was provided by database of Khorassan Climatology Center. Climatologically data includedtemperature, rainfall, relative humidity and sunshine hours for ModelI, and temperature and rainfall for Model II. The results showed the coefficients of determination for Birjand, Ferdows and Ghaen for Model I were 0.69, 0.50 and 0.81 respectively. Also coefficients of determination for the same cities for model II were 0.53, 0.50 and 0.72 respectively. Multiple regression analysisindicated that among weather variables, temperature was the key parameter for variation ofsaffron yield. It was concluded that increasing temperature at spring was the main cause of declined saffron yield during recent years across the province. Finally, yield trend was predicted for the last 5 years using time series analysis.

S. H, Sanaeinejad; S. N, Hosseini

414

Fission Yield Predictions with TALYS  

SciTech Connect

The nuclear model code TALYS has been extended to enable the prediction of fission yields. The mass yield curves are extracted from temperature-dependent multi-modal random-neck rupture calculations. Charge yields of the fission fragment are determined using the scission-point model and subsequently folded with the mass yields. We present a comparison of several fission-fragment mass yields and isotopic yields with experimental data.

Duijvestijn, M.C.; Koning, A.J. [Nuclear Research and Consultancy Group NRG, P.O. Box 25, NL-1755 ZG Petten (Netherlands)

2005-05-24

415

SYSTEMS BIOLOGY FROM MICROORGANISMS TO HUMAN METABOLIC DISEASES - THE ROLE OF DETAILED KINETIC MODELS  

PubMed Central

Human metabolic diseases are typically network diseases. This holds not only for multifactorial diseases, such as metabolic syndrome or type II diabetes: even when a single gene defect is the primary cause, the adaptive response of the entire network determines the severity of disease. The latter may differ between individuals carrying the same mutation. Understanding the adaptive responses of human metabolism naturally requires a systems biology approach. Modelling of metabolic pathways in micro-organisms and some mammalian tissues has yielded many insights - qualitative as well as quantitative - into their control and regulation. Yet, even for a well-known pathway like glycolysis precise predictions of metabolite dynamics from experimentally determined enzyme-kinetics have been only moderately successful. Here, we compare kinetic models of glycolysis in three cell types (African trypanosomes, yeast and skeletal muscle), evaluate their predictive power and identify limitations in our understanding. While each of these models has its own merits and shortcomings, they also share common features. For example, in each case independently measured enzyme kinetic parameters were used as input. Based on these ‘lessons from glycolysis’, we will discuss how to make best use of kinetic computer models to advance our understanding of human metabolic diseases.

van Eunen, Karen; Jeneson, Jeroen A.L.; van Riel, Natal A.W.; Bruggeman, Frank J.; Teusink, Bas

2012-01-01

416

Button/Plate Yielding  

SciTech Connect

An aluminum button and plate were yielded to compare the experimental and calculated button to plate stress ratios. Using the fact that compressive stress is directly proportional to area and load, the calculated button to plate stress ratio is equal to the plate to button area ratio for a constant load. The loads that caused the button and plate to yield were estimated from a load test cell graph obtained from the materials testing facility. The button was simply compressed, but the plate was compressed with a steel cylinder of the same diameter as the aluminum button. The experimental and calculated stress ratios for the button and plate are the same within experimental error. The equation for the plate bearing area is therefore correct.

Wintercorn, S.; /Fermilab

1987-06-17

417

Modeling bromide effects on yields and speciation of dihaloacetonitriles formed in chlorinated drinking water.  

PubMed

This study examined effects of bromide on yields and speciation of dihaloacetonitrile (DHAN) species that included dichloro-, bromochloro- and dibromoacetonitriles generated in chlorinated water. Experimental data obtained using two water sources, varying concentrations and characters of Natural Organic Matter (NOM), bromide concentrations, reaction times, chlorine doses, temperatures and pHs were interpreted using a semi-phenomenological model that assumed the presence of three kinetically distinct sites in NOM (denoted as sites S1, S2 and S3) and the occurrence of sequential incorporation of bromine and chlorine into them. One site was found to react very fast with the chlorine and bromine but its contribution in the DHAN generation was very low. The site with the highest contribution to the yield of DHAN (>70%) has the lowest reaction rates. The model introduced dimensionless coefficients (denoted as ?1(DHAN), ?2(DHAN) and ?3(DHAN)) applicable to the initial DHAN generation sites and their monochlorinated and monobrominated products, respectively. These parameters were used to quantify the kinetic preference to bromine incorporation over that of chlorine. Values of these coefficients optimized for DHAN formation were indicative of the strongly preferential incorporation of bromine into the engaged NOM sites. The same set of ?i(DHAN) coefficients could be used to model the speciation of DHAN released from their kinetically different precursors. The dimensionless speciation coefficients ?i(DHAN) were determined to be site specific and dependent on the NOM content and character as well as pH. The presented model of DHAN formation and speciation can help quantify in more detail the generation of DHAN and provide more insight necessary for further assessment of their potential health effects. PMID:24035655

Roccaro, Paolo; Chang, Hyun-Shik; Vagliasindi, Federico G A; Korshin, Gregory V

2013-07-31

418

Biotechnology of forest yield  

SciTech Connect

Silvicultural and genetic manipulation of Douglas fir and loblolly pine plantations have increased their productivity 70 and 300 percent, respectively, over natural forests on the same sites. Yet these intensively managed plantations are achieving less than 50 percent of their potential productivity. Future increases in yield will result from optimization of nutritional treatments, control of noncrop vegetation, and advances in tree breeding and tissue culture techniques. (Refs. 90).

Farnum, P.; Timmis, R.; Kulp, J.L.

1983-02-11

419

Statistical and kinetic studies of the changes in soybean quality during storage as related to soymilk and tofu making.  

PubMed

The objective of this study was to develop statistical equations and kinetic models to describe the changes of soybean quality during storage. Significant correlations (P < 0.0001) were found among most of quality attributes including color param