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1

A robust method for the joint estimation of yield coefficients and kinetic parameters in bioprocess models.  

PubMed

Bioprocess model structures that require nonlinear parameter estimation, thus initialization values, are often subject to poor identification performances because of the uncertainty on those initialization values. Under some conditions on the model structure, it is possible to partially circumvent this problem by an appropriate decoupling of the linear part of the model from the nonlinear part of it. This article provides a procedure to be followed when these structural conditions are not satisfied. An original method for decoupling two sets of parameters, namely, kinetic parameters from maximum growth, production, decay rates, and yield coefficients, is presented. It exhibits the advantage of requiring only initialization of the first subset of parameters. In comparison with a classical nonlinear estimation procedure, in which all the parameters are freed, results show enhanced robustness of model identification with regard to parameter initialization errors. This is illustrated by means of three simulation case studies: a fed-batch Human Embryo Kidney cell cultivation process using a macroscopic reaction scheme description, a process of cyclodextrin-glucanotransferase production by Bacillus circulans, and a process of simultaneous starch saccharification and glucose fermentation to lactic acid by Lactobacillus delbrückii, both based on a Luedeking-Piret model structure. Additionally, perspectives of the presented procedure in the context of systematic bioprocess modeling are promising. PMID:19455623

Vastemans, V; Rooman, M; Bogaerts, Ph

2009-01-01

2

Identification of Kinetic Parameters  

Microsoft Academic Search

\\u000a This chapter provides a general introduction to the identification of mathematical models and to the methods for estimating\\u000a the relevant adjustable parameters. First, the Bayesian approach is briefly discussed as compared to Popper’s falsificationism.\\u000a Then, the maximum likelihood and weighted least squares criteria are derived from the concept of conditioned probability.\\u000a The different optimization techniques for parameter estimation are reviewed,

Fabrizio Caccavale; Mario Iamarino; Francesco Pierri; Vincenzo Tufano

3

Kinetic parameters from thermogravimetric analysis  

NASA Technical Reports Server (NTRS)

High performance polymeric materials are finding increased use in aerospace applications. Proposed high speed aircraft will require materials to withstand high temperatures in an oxidative atmosphere for long periods of time. It is essential that accurate estimates be made of the performance of these materials at the given conditions of temperature and time. Temperatures of 350 F (177 C) and times of 60,000 to 100,000 hours are anticipated. In order to survey a large number of high performance polymeric materials on a reasonable time scale, some form of accelerated testing must be performed. A knowledge of the rate of a process can be used to predict the lifetime of that process. Thermogravimetric analysis (TGA) has frequently been used to determine kinetic information for degradation reactions in polymeric materials. Flynn and Wall studied a number of methods for using TGA experiments to determine kinetic information in polymer reactions. Kinetic parameters, such as the apparent activation energy and the frequency factor, can be determined in such experiments. Recently, researchers at the McDonnell Douglas Research Laboratory suggested that a graph of the logarithm of the frequency factor against the apparent activation energy can be used to predict long-term thermo-oxidative stability for polymeric materials. Such a graph has been called a kinetic map. In this study, thermogravimetric analyses were performed in air to study the thermo-oxidative degradation of several high performance polymers and to plot their kinetic parameters on a kinetic map.

Kiefer, Richard L.

1993-01-01

4

Obtaining and Estimating Kinetic Parameters from the Literature  

NSDL National Science Digital Library

This Teaching Resource provides lecture notes, slides, and a student assignment for a lecture on strategies for the development of mathematical models. Many biological processes can be represented mathematically as systems of ordinary differential equations (ODEs). Simulations with these mathematical models can provide mechanistic insight into the underlying biology of the system. A prerequisite for running simulations, however, is the identification of kinetic parameters that correspond closely with the biological reality. This lecture presents an overview of the steps required for the development of kinetic ODE models and describes experimental methods that can yield kinetic parameters and concentrations of reactants, which are essential for the development of kinetic models. Strategies are provided to extract necessary parameters from published data. The homework assignment requires students to find parameters appropriate for a well-studied biological regulatory system, convert these parameters into appropriate units, and interpret how different values of these parameters may lead to different biological behaviors.

Susana R. Neves (New York;Mount Sinai School of Medicine REV)

2011-09-20

5

Compositional kinetic parameters on selected type II kerogens  

SciTech Connect

Three Type II kerogens were evaluated to measure the composition of products generated, total yields, and rates of generation (kinetic parameters). The three samples evaluated in this study are a Monterey shale, Kimmeridge shale, and Woodford shale. These sample were selected on the basis of differences in their measured bulk kinetic parameters for hydrocarbon generation. The samples are similar to the Type IIA (Type IIS), IIB, and IID of Hunt et al (1993) who reported kinetic analysis based on hydrous pyrolysis experiments. Each sample was analyzed by multiple cold trap pyrolysis gas chromatography with flame ionization and mass spectrometer detectors. Isothermal and nonisothermal constant heating rate experiments were used to determine the kinetic parameters. Four compositional ranges (C1, C2-C4, C5-C15, and C15+) as well as selected specific compounds were measured and compared. In addition the samples were artificially matured in a closed system (microscale sealed vessel) and the products formed analyzed by gas chromatography. Residues from these experiments were analyzed by both bulk pyrolysis and pyrolysis/gas chromatography to evaluate the remaining kerogen generation potential. The remaining potential was used to calculate the reaction kinetics based on measured change from the initial starting material.

Jarvie, D.M.; Lundell, L.L. [Humble Geochemical Services, Humble, TX (United States)

1995-12-01

6

Kinetic parameters and thermodynamic values of ?-xylosidase production by Kluyveromyces marxianus  

Microsoft Academic Search

Kinetic parameters for production of ?-xylosidase by Kluyveromyces marxianus were determined in growth media containing glucose, xylose, cellobiose, sucrose and lactose as carbon sources. K. marxianus achieved maximum ?-xylosidase specific product yield (YP\\/X) when grown on xylose. Basal level of activity was achieved in cultures grown on glucose. Kinetic parameters of enzyme production and cell mass formation were correlated. Enzyme

M. I. Rajoka

2007-01-01

7

Yield parameters in young jojoba plants and their relation to actual yield in later years  

Microsoft Academic Search

A total of 30 jojoba clones, among them six already commercial clones and 24 newly selected ones were characterized in terms of yield parameters, chilling requirements and morphological traits. The aim was to supply farmers (from Israel and abroad) better yielding clones. Considerable variability was found among the clones in all the parameters. Some clones exhibited excellent vegetative traits related

Aliza Benzioni; E Shiloh; M Ventura

1999-01-01

8

Effect of microwave processing on water soluble vitamins: Kinetic parameters  

Microsoft Academic Search

The effects of microwave processing on water soluble vitamins (ascorbic acid, niacin, thiamin, and riboflavin) were determined. The kinetic parameters of vitamin degradation reactions for microwave heating were determined for model vitamin systems. The degradation reactions were found to be first?order reactions. The kinetic parameters at different temperatures were also determined.

Zinet Aytanga Okmen; A. Levent Bayindirli

1999-01-01

9

Robust estimation of kinetic parameters in dynamic PET imaging.  

PubMed

Dynamic PET imaging provides important information for biological research, clinical diagnosis and pharmacokinetic analysis through kinetic modeling and data-driven parameter estimation. Kinetic parameters quantitatively describe dynamic material exchange and metabolism of radiotracers in plasma and tissues. While many efforts have been devoted to estimate kinetic parameters from dynamic PET, the poor statistical properties of the measurement data in low count dynamic acquisition and the uncertainties in estimating the arterial input function have limited the accuracy and reliability of the kinetic parameter estimation. Additionally, the quantitative analysis of individual kinetic parameters is not yet implemented. In this paper, we present a robust kinetic parameter estimation framework which is robust to both the poor statistical properties of measurement data in dynamic PET and the uncertainties in estimated arterial input function, and is able to analyze every single kinetic parameter quantitatively. The strategy is optimized with robust H infinity estimation under minimax criterion. Experiments are conducted on Monte Carlo simulated data set for quantitative analysis and validation, and on real patient scans for assessment of clinical potential. PMID:22003654

Gao, Fei; Liu, Huafeng; Shi, Pengcheng

2011-01-01

10

Aerosol Formation by Oligomerization: Kinetics and Aerosol Yields  

NASA Astrophysics Data System (ADS)

Methylglyoxal, along with glyoxal, is a common constituent of cloudwater. We explore the ability of both compounds to oligomerize via self-reaction during the evaporation of simulated cloud droplets. We also explore oligomerization reactions between these compounds and other nucleophiles present in clouds, such as amino acids, methylamine, and polyols. NMR kinetics data for several of these reactions, along with quantitative measurements of residual particle size, are used to determine which reactions are most likely to significantly affect aerosol formation rates during cloud processing in the atmosphere.

de Haan, D. O.; Wood, S. E.; Turley, J. J.

2009-12-01

11

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

NASA Technical Reports Server (NTRS)

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.

1992-01-01

12

Role of thermodynamic and kinetic parameters in gadolinium chelate stability.  

PubMed

In recent years there has been a renewed interest in the physicochemical properties of gadolinium chelates (GC). The aim of this review is to discuss the physicochemical properties of marketed GC with regard to possible biological consequences. GC can be classified according to three key molecular features: 1) the nature of the chelating moiety: either macrocyclic molecules in which Gd(3+) is caged in the preorganized cavity of the ligand, or linear, open-chain molecules; 2) ionicity: the ionicity of the molecule varies from neutral to tri-anionic agents; and 3) the presence or absence of an aromatic lipophilic moiety, which has a profound impact on the biodistribution of the GC. These parameters can also explain why GC differ considerably with regard to their thermodynamic stability constants and kinetic stability, as demonstrated by numerous studies. The concept of thermodynamic and kinetic stability is critically discussed, as it remains somewhat controversial, especially in predicting the amount of free gadolinium that may result from decomplexation of chelates in physiologic or pathologic situations. This review examines the possibility that the high kinetic stability provided by the macrocyclic structure combined with a high thermodynamic stability (reinforced by ionicity for macrocyclic chelates) can minimize the amount of free Gd(3+) released in the body. J. Magn. Reson. Imaging 2009;30:1249-1258. (c) 2009 Wiley-Liss, Inc. PMID:19938037

Idée, Jean-Marc; Port, Marc; Robic, Caroline; Medina, Christelle; Sabatou, Monique; Corot, Claire

2009-12-01

13

Parameter estimation for models of ligninolytic and cellulolytic enzyme kinetics  

SciTech Connect

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 enzymes ( -glucosidase, cellobiohydrolase, endo-glucanase, peroxidase, and phenol oxidase). The kinetic parameters included the maximum specific enzyme activity (Vmax) and half-saturation constant (Km) in the Michaelis-Menten equation. The activation energy (Ea) and the pH optimum and sensitivity (pHopt and pHsen) were also analyzed. pHsen was estimated by fitting an exponential-quadratic function. The Vmax values, often presented in different units under various measurement conditions, were converted into the same units at a reference temperature (20 C) and pHopt. Major conclusions are: (i) Both Vmax and Km were log-normal distributed, with no significant difference in Vmax exhibited between enzymes originating from bacteria or fungi. (ii) No significant difference in Vmax was found between cellulases and ligninases; however, there was significant difference in Km between them. (iii) Ligninases had higher Ea values and lower pHopt than cellulases; average ratio of pHsen to pHopt ranged 0.3 0.4 for the five enzymes, which means that an increase or decrease of 1.1 1.7 pH units from pHopt would reduce Vmax by 50%. (iv) Our analysis indicated that the Vmax values from lab measurements with purified enzymes were 1 2 orders of magnitude higher than those for use in SOC decomposition models under field conditions.

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

2012-01-01

14

Differential Evolution Approach for Obtaining Kinetic Parameters in Nonisothermal Pyrolysis of Biomass  

Microsoft Academic Search

Pyrolysis, a first step in the biomass gasification, is the thermal decomposition of organic matter under inert atmospheric conditions, leading to the release of volatiles and formation of char. As pyrolysis is a kinetically controlled reaction, kinetic parameter estimation is very important in the design of pyrolysis reactors. In the proposed kinetic model of this study, the kinetic scheme of

Pratik N. Sheth; B. V. Babu

2008-01-01

15

Effect of flow parameters of rumen digesta on effective degradability and microbial yield in sheep.  

PubMed

The aim of this experiment was to examine the effect of rumen digesta flow parameters on effective degradability (EDG) and microbial nitrogen (MBN) yield in sheep fed diets of identical provision of both metabolizable energy and rumen degradable nitrogen (RDN). Ruminal degradation parameters of early-harvested perennial ryegrass hay (EH), late-harvested perennial ryegrasses hay (LH) and winter sown barley straw (BS) were determined by a nylon bag technique. Subsequently, three experimental diets (EHD, LHD and BSD) were formulated using the tested forages, sucrose and urea as supplements. An in vivo feeding study was conducted using four rumen cannulated sheep in a partial Latin square design. Digestibility, rate constants of rumen particle breakdown and passage, ruminal fermentation parameters and MBN supply to the small intestine were determined. Animals thoroughly consumed the forages fed at a restricted level. Digestion coefficients were greater for EHD than for LHD and were lowest for BSD (P < 0.05). The rate constant of large particle breakdown was 4.3, 5.9 and 6.7 %/h, respectively, and small particle passage was 5.3, 4.7 and 6.3 %/h for EHD, LHD and BSD, respectively. The estimates differed (P < 0.05) between the diets. The overall passage rate constant of total rumen particles was estimated to be higher for BSD than that for EHD or LHD (P < 0.05). Ruminal fermentation parameters were unaffected by dietary treatments (P > 0.05). Intake levels of rumen degradable organic matter (RDOM) and RDN were estimated to be greater for LHD than that for EHD or BSD (P < 0.05). Although dietary arrangements were made to give identical microbial efficiency, the estimated value was higher for EHD than that for LHD or BSD (P < 0.05); and the MBN yield for BSD was estimated to be lower than that for EHD or LHD (P < 0.05). Rumen kinetic parameters of degradation and particle flow of forage affected EDG values and MBN yield from forage-related RDN intake, although those had little effect on the efficiency of MBN yield from forage-related RDOM intake. PMID:20163598

Ichinohe, Toshiyoshi; Fujihara, Tsutomu

2009-08-01

16

Spectral and kinetic parameters of phosphorescence of triplet chlorophyll a in the photosynthetic apparatus of plants.  

PubMed

Spectral and kinetic parameters and quantum yield of IR phosphorescence accompanying radiative deactivation of the chlorophyll a (Chl a) triplet state were compared in pigment solutions, greening and mature plant leaves, isolated chloroplasts, and thalluses of macrophytic marine algae. On the early stages of greening just after the Shibata shift, phosphorescence is determined by the bulk Chl a molecules. According to phosphorescence measurement, the quantum yield of triplet state formation is not less than 25%. Further greening leads to a strong decrease in the phosphorescence yield. In mature leaves developing under normal irradiation conditions, the phosphorescence yield declined 1000-fold. This parameter is stable in leaves of different plant species. Three spectral forms of phosphorescence-emitting chlorophyll were revealed in the mature photosynthetic apparatus with the main emission maxima at 955, 975, and 995 nm and lifetimes ~1.9, ~1.5, and 1.1-1.3 ms. In the excitation spectra of chlorophyll phosphorescence measured in thalluses of macrophytic green and red algae, the absorption bands of Chl a and accessory pigments - carotenoids, Chl b, and phycobilins - were observed. These data suggest that phosphorescence is emitted by triplet chlorophyll molecules that are not quenched by carotenoids and correspond to short wavelength forms of Chl a coupled to the normal light harvesting pigment complex. The concentration of the phosphorescence-emitting chlorophyll molecules in chloroplasts and the contribution of these molecules to chlorophyll fluorescence were estimated. Spectral and kinetic parameters of the phosphorescence corresponding to the long wavelength fluorescence band at 737 nm were evaluated. The data indicate that phosphorescence provides unique information on the photophysics of pigment molecules, molecular organization of the photosynthetic apparatus, and mechanisms and efficiency of photodynamic stress in plants. PMID:24910208

Krasnovsky, A A; Kovalev, Yu V

2014-04-01

17

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

Microsoft Academic Search

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

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

1988-01-01

18

Fluidized-bed pyrolysis of oil shale: Oil yield, composition, and kinetics  

NASA Astrophysics Data System (ADS)

A quartz isothermal fluidized bed reactor was used to measure kinetics and oil properties relevant to surface processing of oil shale. The rate of oil formation was described with two sequential first order rate equations characterized by two rate constants. These rate constants together with an expression for the appropriate weighting coefficients describe approximately 97% of the total oil produced. The results of different attempts to mathematically describe the data in a manner suitable for modeling applications are related. Preliminary results for species selective kinetics of methane, ethene, ethane and hydrogen, where the latter is clearly distinguished as the product of a distinct intermediate are also presented. Oil yields from Western oil shale are approximately 100% Fischer assay. Oil composition is based on previous work and the higher heating rates inherent in fluidized pyrolysis. Neither the oil yield, composition nor the kinetics varied with particle size between 0.2 and 2.0 mm within experimental error. The qualitatively expected change in oil composition due to cracking was observed over the temperature range studied. Eastern shale exhibited significantly faster kinetics and higher oil yields than did Western shale.

Richardson, J. H.; Huss, E. B.; Ott, L. L.; Clarkson, J. E.; Bishop, M. O.; Taylor, J. R.; Gregory, L. J.; Morris, C. J.

1982-09-01

19

Kinetic parameters of uracil dosimeter in simulated extraterrestrial UV radiation  

NASA Astrophysics Data System (ADS)

Studies of the solar UV environment on Earth 2.0 Gyr to 3.8 Gyr ago suggest that the terrestrial atmosphere was essentially anoxic, resulting in an ozone column abundance insufficient for protecting the planetary surface in the UV-B (280 nm - 315 nm) and the UV-C (200 nm - 280 nm) ranges. Since, short wavelength solar UV radiation in the UV-B and UV-C range penetrated through the atmosphere to the unprotected early Earth's surface, associated biological consequences may be expected. We discuss experimental data obtained as follows: Radiation sources applied were solar simulator and high power deuterium lamp, the wavelength were adjusted by interference filters (210, 230, 250 nm) and the irradiances were measured by OL754 spectroradiometer. The photo-reverse effect depends highly on the wavelength of the exposed radiation. Shorter wavelength UV radiation of about 200 nm is strongly effective in monomerization, while the longer wavelengths prefer the production of dimerization. In case of polychromatic light, like in space or on a planetary surface which is unprotected by an ozone layer the two processes run parallel. We could demonstrate experimentally, for the case of a uracil thin-layer that the photo-reaction process of the nucleotides can be both dimerization and the reverse process: monomerization. These results are important for the study of solar UV effects on organisms in the early terrestrial environment as well as for the search for life on Mars since we can show that biological harmful effects can also be reduced by shorter wavelength UV radiation, which is of importance in reducing DNA damages provoked by wavelengths longer than about 240 nm. Our earlier results showed that dimerization of the pyrimidin base uracil can be described by a first order kinetics, and this reaction gives the possibility to determine the dose of the UV source applied. This work is a theoretical and experimental approach to the relevant parameters of the first order kinetics.

Kovács, G.; Gróf, P.; Bérces, A.; Patel, M. R.; Lammer, H.; Rontó, Gy.

20

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 0.89 C mole C mole(-1); whereas without biomass production, NADPH regeneration is only possible via the isocitrate dehydrogenase leading to a theoretical yield of 0.67 C mole C mole(-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

2013-11-01

21

Optimum Designs for the Equality of Parameters in Enzyme Inhibition Kinetic  

E-print Network

Optimum Designs for the Equality of Parameters in Enzyme Inhibition Kinetic Models Anthony C Abstract A general model for enzyme kinetics with inhibition, the "mixed" inhibi- tion model, simplifies Establishing the equality of parameters is important in the building of the non- linear models used for enzyme

22

Determination of reaction kinetic parameters from variable temperature DSC or DTA  

Microsoft Academic Search

An equation is derived for evaluating the kinetic parameters of a transformation from variable temperature DSC or DTA, taking account of the variation in the reaction rate constant with time and temperature. Kinetic parameters for the crystallization of a ZrF4-BaF2-LaF3 glass are calculated using this equation.

N. P. Bansal; R. H. Doremus

1984-01-01

23

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

24

Changes in chemical and physical quality parameters of maize grain during three decades of yield improvement  

Microsoft Academic Search

Concern exists that the grain quality of maize (Zea mays L.) may decline due to breeding for increased yield. This study quantified chemical- and physical-quality parameters of maize grain for hybrids representing three decades of grain yield improvement in Ontario, Canada. Six hybrids that were commercially important in Ontario from 1959 to 1988 were grown at two locations in southern

T. J Vyn; M Tollenaar

1998-01-01

25

Understanding the regulation of aspartate metabolism using a model based on measured kinetic parameters  

E-print Network

fluxes in competing pathways. In addition, the model shows that enzyme isoforms are not functionally, very few pub- lished models have been based on kinetic measurements on enzymes in conditions relevant four systems that have been modeled kinetically with realistic measured parameters: glycolysis

26

Kinetic Parameters for the Thermal Inactivation of Quality-Related Enzymes in Carrots and Potatoes  

Microsoft Academic Search

Kinetic parameters for the thermal inactivation of several enzymes in carrot and potato homogenates have been determined. In carrots the most heat-resistant activity was polygalacturonase, followed by peroxidase and pectinmethylesterase. In potatoes peroxidase was the most resistant, followed by pectin methylesterase, polyphenol oxidase, and lipoxygenase. There were several notable similarities between the inactivation kinetics in the two vegetables. In both

Gordon E. Anthon; Diane M. Barrett

2002-01-01

27

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

28

Determination of the Kinetic Parameters of Atom Transfer Radical Polymerizations  

E-print Network

and the local minima trapping. By applying second minimization algorithm, the parameter estimation algorithm that using literature values. This is because the current method uses fewer assumptions than other literature

29

Parameter Optimization for Enhancement of Ethanol Yield by Atmospheric Pressure DBD-Treated Saccharomyces cerevisiae  

NASA Astrophysics Data System (ADS)

In this study, Saccharomyces cerevisiae (S. cerevisiae) was exposed to dielectric barrier discharge plasma (DBD) to improve its ethanol production capacity during fermentation. Response surface methodology (RSM) was used to optimize the discharge-associated parameters of DBD for the purpose of maximizing the ethanol yield achieved by DBD-treated S. cerevisiae. According to single factor experiments, a mathematical model was established using Box-Behnken central composite experiment design, with plasma exposure time, power supply voltage, and exposed-sample volume as impact factors and ethanol yield as the response. This was followed by response surface analysis. Optimal experimental parameters for plasma discharge-induced enhancement in ethanol yield were plasma exposure time of 1 min, power voltage of 26 V, and an exposed sample volume of 9 mL. Under these conditions, the resulting yield of ethanol was 0.48 g/g, representing an increase of 33% over control.

Dong, Xiaoyu; Yuan, Yulian; Tang, Qian; Dou, Shaohua; Di, Lanbo; Zhang, Xiuling

2014-01-01

30

Estimation of kinetic parameters related to biochemical interactions between hydrogen peroxide and signal transduction proteins  

PubMed Central

The lack of kinetic data concerning the biological effects of reactive oxygen species is slowing down the development of the field of redox signaling. Herein, we deduced and applied equations to estimate kinetic parameters from typical redox signaling experiments. H2O2-sensing mediated by the oxidation of a protein target and the switch-off of this sensor, by being converted back to its reduced form, are the two processes for which kinetic parameters are determined. The experimental data required to apply the equations deduced is the fraction of the H2O2 sensor protein in the reduced or in the oxidized state measured in intact cells or living tissues after exposure to either endogenous or added H2O2. Either non-linear fittings that do not need transformation of the experimental data or linearized plots in which deviations from the equations are easily observed can be used. The equations were shown to be valid by fitting to them virtual time courses simulated with a kinetic model. The good agreement between the kinetic parameters estimated in these fittings and those used to simulate the virtual time courses supported the accuracy of the kinetic equations deduced. Finally, equations were successfully tested with real data taken from published experiments that describe redox signaling mediated by the oxidation of two protein tyrosine phosphatases, PTP1B and SHP-2, which are two of the few H2O2-sensing proteins with known kinetic parameters. Whereas for PTP1B estimated kinetic parameters fitted in general the present knowledge, for SHP-2 results obtained suggest that reactivity toward H2O2 as well as the rate of SHP-2 regeneration back to its reduced form are higher than previously thought. In conclusion, valuable quantitative kinetic data can be estimated from typical redox signaling experiments, thus improving our understanding about the complex processes that underlie the interplay between oxidative stress and redox signaling responses.

Brito, Paula M.; Antunes, Fernando

2014-01-01

31

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

32

Discharge pumped iodine monofluoride laser: operating parameters and collisional kinetics  

SciTech Connect

Lasing has been observed at five different wavelengths ranging from 472 to 497 nm from discharge pumped iodine monofluoride (IF). At the optimum output coupling 4 mJ was measured in a 30 ns FWHM pulse with a peak power of 140 kW. The merits and deficiencies of both HI and CF/sub 3/I as iodine donors are discussed. Measurements show the small signal gain to be greater than or equal to 1% cm/sup -1/ from approx. 478 to 497 nm, while much of the absorption is due to excited state of He. Limited line tunability is also demonstrated by using an internally mounted Littrow prism. Quenching measurements of the upper and lower laser level show the lower level to be removed more rapidly, thereby avoiding bottlenecking. In addition, the upper level spontaneous emission lifetime is measured to be 17.2 +- 4.0 ns. Finally studies of the formation kinetics of the upper laser level of IF have shown I*(/sup 4/P) atoms to be an immediate precursor, while the F*(/sup 4/P) atoms are unimportant.

Dlabal, M.L.

1981-01-01

33

Microstructure, optical and kinetics parameters of oxysulfide tellurite glass  

NASA Astrophysics Data System (ADS)

A glasses with the compositions 75TeO2·10Nb2O5·10Bi2O3·5ZnO and 75TeO2·10Nb2O5·10Bi2O3·5ZnS in mol% were prepared by a melting technique. A systematic characterization of thermal, optical properties and structure of the prepared glass was carried out. The optical absorption was measured in the wavelength range from 300 to 2.500 nm). From the absorption edge studies, the value of optical band gap has been evaluated. The glass transition temperature, activation energy of relaxation structure and activation energy of crystallization were determined by non-isothermal differential scanning calorimetry (DSC). The crystal structure of the glass was investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results and SEM micrograph reveal the presence of two crystalline phase: ?-TeO2 and Bi2Te4O11 phases during the crystallization process of the prepared glass. The Avrami kinetic exponent for the crystallization process was calculated.

Yousef, El Sayed; Hegazy, H. H.; Almojadah, Samar

2013-09-01

34

Effects of physical and chemical parameters on the tar yield during rapid pyrolysis of wood  

SciTech Connect

Effects of temperature (200-1000{degrees}C), solid residence time (0-30 sec), heating rate (100 to 10,000{degrees}C/s), particle size (50 to 500 {mu}m), and mineral matters on the yield and formation rate of tar from rapid pyrolysis of beech-wood under 1 atm helium pressure were studied. Wood particles were pyrolyzed for known and independently selectable temperature, time, nominal heating rates in an electrical screen beater reactor; and the tar yield was measured as a function of temperature for every parameter tested. The tar yield from pyrolysis of beech-wood was accounted for up to 70% of the original wood above 400{degrees}C. Due to the post-pyrolysis reactions of tar, its yield exhibits a maximum with pyrolysis temperature for almost all the physical parameters tested in this study. Among the physical parameters particle size and among the chemical parameters Na{sup +} cation are more effective in reducing the tar yield than others. The maximum tar yield drops to 37% with larger particle size, and to 32% with particles enriched with Na{sup +} cation. Tar was also analyzed with GPC for the effects of above parameters on the tar molecular weight. The tar molecular weight remains relatively constant (M{sub w} = 300 amu, Mn = 155 amu, and Mz = 483 amu) over the pyrolysis temperature; it increases with heating rate (M{sub w} = 375 amu, Mn = 210 amu, and Mz = 700 amu), but decreases with increasing particle size (M{sub w} = 210 amu, Mn = 110 amu, and Mz = 320 amu) or use of active cations such as K{sup +} and Na{sup +} (M{sub w} = 190 amu, Mn = 100 amu, and Mz = 350 amu).

Nik-Azar, M.; Hajaligol, M.R.; Sohrabi, M. [Amir-Kabir Univ. of Technology, Teheran (Iran, Islamic Republic of)

1995-12-01

35

Nonlinear regression technique to estimate kinetic parameters and confidence intervals in unsteady-state conduction-heated foods  

E-print Network

­E and the D­z model were used. Three case studies were used. Kinetic parameters for microbial death (Cases 1 kinetic parameters in high-moisture foods include heating liquid samples in cap- illary tubes, and heating temperature. The kinetics could apply to nutrient destruction or microbial death, for example. These meth- ods

36

Elimination of 4-chlorophenol by soybean peroxidase and hydrogen peroxide: Kinetic model and intrinsic parameters  

Microsoft Academic Search

A kinetic model for the initial rate reaction, based on the Ping-Pong Bi-Bi mechanism, has been assumed for the removal of 4-chlorophenol with soybean peroxidase and hydrogen peroxide. Several sets of experimental data, obtained in a batch reactor at different concentrations of hydrogen peroxide and 4-chorophenol, were used to estimate the kinetic parameters. A new method for determining the intrinsic

Antonio Bódalo; José L. Gómez; Elisa Gómez; Asunción M. Hidalgo; María Gómez; Ana M. Yelo

2007-01-01

37

Derivation of hydrous pyrolysis kinetic parameters from open-system pyrolysis  

Microsoft Academic Search

Kinetic information is essential to predict the temperature, timing or depth of hydrocarbon generation within a hydrocarbon system. The most common experiments for deriving kinetic parameters are mainly by open-system pyrolysis. However, it has been shown that the conditions of open-system pyrolysis are deviant from nature by its low near-ambient pressure and high temperatures. Also, the extrapolation of heating rates

Yu-Hsin Tseng; Wuu-Liang Huang

2010-01-01

38

Effects of heating rate on slow pyrolysis behavior, kinetic parameters and products properties of moso bamboo.  

PubMed

Effects of heating rate on slow pyrolysis behaviors, kinetic parameters, and products properties of moso bamboo were investigated in this study. Pyrolysis experiments were performed up to 700°C at heating rates of 5, 10, 20, and 30°C/min using thermogravimetric analysis (TGA) and a lab-scale fixed bed pyrolysis reactor. The results show that the onset and offset temperatures of the main devolatilization stage of thermogravimetry/derivative thermogravimetry (TG/DTG) curves obviously shift toward the high-temperature range, and the activation energy values increase with increasing heating rate. The heating rate has different effects on the pyrolysis products properties, including biochar (element content, proximate analysis, specific surface area, heating value), bio-oil (water content, chemical composition), and non-condensable gas. The solid yields from the fixed bed pyrolysis reactor are noticeably different from those of TGA mainly because the thermal hysteresis of the sample in the fixed bed pyrolysis reactor is more thorough. PMID:25063973

Chen, Dengyu; Zhou, Jianbin; Zhang, Qisheng

2014-10-01

39

A robust methodology for kinetic model parameter estimation for biocatalytic reactions.  

PubMed

Effective estimation of parameters in biocatalytic reaction kinetic expressions are very important when building process models to enable evaluation of process technology options and alternative biocatalysts. The kinetic models used to describe enzyme-catalyzed reactions generally include several parameters, which are strongly correlated with each other. State-of-the-art methodologies such as nonlinear regression (using progress curves) or graphical analysis (using initial rate data, for example, the Lineweaver-Burke plot, Hanes plot or Dixon plot) often incorporate errors in the estimates and rarely lead to globally optimized parameter values. In this article, a robust methodology to estimate parameters for biocatalytic reaction kinetic expressions is proposed. The methodology determines the parameters in a systematic manner by exploiting the best features of several of the current approaches. The parameter estimation problem is decomposed into five hierarchical steps, where the solution of each of the steps becomes the input for the subsequent step to achieve the final model with the corresponding regressed parameters. The model is further used for validating its performance and determining the correlation of the parameters. The final model with the fitted parameters is able to describe both initial rate and dynamic experiments. Application of the methodology is illustrated with a case study using the ?-transaminase catalyzed synthesis of 1-phenylethylamine from acetophenone and 2-propylamine. PMID:22736412

Al-Haque, Naweed; Santacoloma, Paloma A; Neto, Watson; Tufvesson, Pär; Gani, Rafiqul; Woodley, John M

2012-01-01

40

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

41

Sputtering Yields for C60 and Au3 Bombardment of Water Ice as a Function of Incident Kinetic Energy  

PubMed Central

The total sputtering yields for water ice due to kiloelectronvolt cluster bombardment have been measured and compared to the predictions made by the mesoscale energy deposition footprint (MEDF) model. For C60 bombardment the experimental yield varies almost linearly from 820 water molecule equivalents at an incident kinetic energy of 10 keV to 10100 water molecule equivalents at a kinetic energy of 120 keV. For Au3 bombardment the experimental yield varies almost linearly from 630 water molecule equivalents at an incident energy of 10 keV and rises to 1200 water molecule equivalents at 25 keV. The MEDF model is used to calculate relative yield trends with respect to incident energy using short time molecular dynamics simulations. The results of these calculations indicate that the model can effectively predict the yield trends observed for these two clusters in experiments, although there is a consistent overestimate of the predicted induced C60 yield. It is hypothesized that this overestimate can be explained by the absence of reactions and ionization processes in the current simulations. Despite this omission experimental yield trends can be accurately predicted using relatively small amounts of computer time. The success of the model in predicting the yield of water from ice films using a variety of energies and projectiles suggests this approach may greatly aid in the optimization of experimental configurations. PMID:17503768

Russo, Michael F.; Szakal, Christopher; Kozole, Joseph; Winograd, Nicholas; Garrison, Barbara J.

2008-01-01

42

Effect of experimental and sample factors on dehydration kinetics of mildronate dihydrate: mechanism of dehydration and determination of kinetic parameters.  

PubMed

The dehydration kinetics of mildronate dihydrate [3-(1,1,1-trimethylhydrazin-1-ium-2-yl)propionate dihydrate] was analyzed in isothermal and nonisothermal modes. The particle size, sample preparation and storage, sample weight, nitrogen flow rate, relative humidity, and sample history were varied in order to evaluate the effect of these factors and to more accurately interpret the data obtained from such analysis. It was determined that comparable kinetic parameters can be obtained in both isothermal and nonisothermal mode. However, dehydration activation energy values obtained in nonisothermal mode showed variation with conversion degree because of different rate-limiting step energy at higher temperature. Moreover, carrying out experiments in this mode required consideration of additional experimental complications. Our study of the different sample and experimental factor effect revealed information about changes of the dehydration rate-limiting step energy, variable contribution from different rate limiting steps, as well as clarified the dehydration mechanism. Procedures for convenient and fast determination of dehydration kinetic parameters were offered. PMID:24729295

B?rzi?š, Agris; Acti?š, Andris

2014-06-01

43

Evaluation of Anaerobic Biofilm Reactor Kinetic Parameters Using Ant Colony Optimization  

PubMed Central

Abstract Fixed bed reactors with naturally attached biofilms are increasingly used for anaerobic treatment of industry wastewaters due their effective treatment performance. The complex nature of biological reactions in biofilm processes often poses difficulty in analyzing them experimentally, and mathematical models could be very useful for their design and analysis. However, effective application of biofilm reactor models to practical problems suffers due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, an inverse modeling approach based on ant colony optimization is proposed and applied to estimate the kinetic and film thickness model parameters of wastewater treatment process in an anaerobic fixed bed biofilm reactor. Experimental data of pharmaceutical industry wastewater treatment process are used to determine the model parameters as a consequence of the solution of the rigorous mathematical models of the process. Results were evaluated for different modeling configurations derived from the combination of mathematical models, kinetic expressions, and optimization algorithms. Analysis of results showed that the two-dimensional mathematical model with Haldane kinetics better represents the pharmaceutical wastewater treatment in the biofilm reactor. The mathematical and kinetic modeling of this work forms a useful basis for the design and optimization of industry wastewater treating biofilm reactors. PMID:24065871

Satya, Eswari Jujjavarapu; Venkateswarlu, Chimmiri

2013-01-01

44

Thermodynamic Characterization of Five Key Kinetic Parameters that Define Neuronal Nitric Oxide Synthase Catalysis  

PubMed Central

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 (FeIINO) 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) determine NOS specific activity, O2 concentration response, and pulsatile versus steady-state NO generation. Here 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 (nNOS). We then incorporated the measured kinetic values into computer simulations of the nNOS reaction using a global kinetic model to comprehensively model its temperature-dependent catalytic behaviors. Our results provide new mechanistic insights and also reveal that the different temperature dependencies of the five kinetic parameters significantly alter nNOS catalytic behaviors 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.

2013-01-01

45

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

46

Multi-Parameter Yield Zone Model for Predicting Spectrum Crack Growth  

NASA Technical Reports Server (NTRS)

A systematic technique is presented for modeling crack growth load interaction effects due to spectrum loading. The Multi-Parameter Yield Zone (MPYZ) model accounts for crack growth retardation, acceleration, and underload effects. The load interactions are attributed to the residual stress intensity due to the plastic deformation at the crack tip. Fatigue crack growth was predicted and compared with test data for a variety of spectrum loadings.

Johnson, W. S.

1980-01-01

47

Innovative methods for the measurement of I* quantum yields and kinetics by diode laser gain-versus-absorption  

NASA Technical Reports Server (NTRS)

The quantum yields of a variety of candidate molecules for solar lasant materials to produce I* were tested. The absorption spectrum was measured for each compound and the I* yield determined by the diode laser or by infrared emission, using C3F7I as a standard. The results of these measurements are summarized. A GaAsInP diode laser system was developed to probe I and I* atoms to obtain yields and kinetics. A technique of gain-versus-absorption spectroscopy was investigated to measure quantum yields with high accuracy. The errors in the yield data were reduced to +/- 2% or less. In addition, experiments were set up to measure the rates of F-sublevel changing collisions in both the I ground state and the I* excited state. Finally, experiments and modelling were carried out to explore the possibility of measuring the recombination rates of I* with C3F7 radicals.

Leone, Stephen R.

1987-01-01

48

Solid–liquid extraction of protopine from Fumaria officinalis L.—Kinetic modelling of influential parameters  

Microsoft Academic Search

The influences of such parameters as percentage of ethanol in solvent, solid–liquid weight ratio and pH of medium on the protopine extraction from Fumaria officinalis particles with mean radius of 0.4–0.5mm was studied. A mathematical model, describing the importance of each parameter on the extraction of protopine with pseudo-second-order kinetics was proposed and the results were discussed. A numerical solution

L. Rakotondramasy-Rabesiaka; J.-L. Havet; C. Porte; H. Fauduet

2009-01-01

49

Calculation, measurement and sensitivity analysis of kinetic parameters of Tehran Research Reactor  

Microsoft Academic Search

Effective delayed neutron fraction ?eff and neutron generation time ? are important factors in reactor physics calculation and transient analysis. In the first stage of this research, these kinetic parameters have been calculated for two states of Tehran Research Reactor (TRR), i.e. cold (fuel, clad and coolant temperatures equal to 20°C) and hot (fuel, clad and coolant temperatures of 65,

S. A. Hosseini; N. Vosoughi; M. B. Ghofrani; M. Gharib

2010-01-01

50

Compost mixture influence of interactive physical parameters on microbial kinetics and substrate fractionation  

E-print Network

Compost mixture influence of interactive physical parameters on microbial kinetics and substrate 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 Composting is a feasible by selecting an initial compost recipe with physical properties that enhance microbial activity. The present

Paris-Sud XI, Université de

51

Z .Biophysical Chemistry 77 1999 139 152 Quantifying the kinetic parameters of prion replication  

E-print Network

Z .Biophysical Chemistry 77 1999 139 152 Quantifying the kinetic parameters of prion replication in revised form 4 February 1999; accepted 4 February 1999 Abstract The mechanism of protein-only prion replication is controversial. A detailed mathematical model of prion replication by nucleated polymerisation

Nowak, Martin A.

52

IEEE TRANSACTIONS ON MEDICAL IMAGING 1 Estimating Kinetic Parameter Maps from Dynamic  

E-print Network

estimates can be reduced thus leading to smaller root mean square error (RMSE). Since the numberIEEE TRANSACTIONS ON MEDICAL IMAGING 1 Estimating Kinetic Parameter Maps from Dynamic Contrast DCE-MR images show a clear reduction of RMSE and variance as well as, in some cases, reduced

Hamprecht, Fred A.

53

Comparison of gasification kinetics parameters of different types of nuclear graphite  

SciTech Connect

A chemical-reaction kinetics model of nuclear graphite gasification has recently been developed and successfully validated with gasification rate measurements for nuclear graphite grades of IG-110, IG-430, NBG-18 and NBG-25. The model employs 4 elementary chemical reactions with applicable parameters, including the values and Gaussian-like distributions of the specific activation energies, the pre-exponential coefficients for adsorption of oxygen and desorption of CO and CO{sub 2} gases, and the surface area of free active sites. These parameters are determined from the reported measurements of the total gasification and transient weight loss using a multi-parameter optimization algorithm. The determined chemical kinetics parameters for IG-100 and NB-25 are nearly the same, but slightly different from those for NBG-18 and IG-430. The initial specific area of free active sites is inversely proportional to the square root of the mass or volume of the graphite specimens used in experiments. The recommended chemical kinetics parameters in this paper for these grades of nuclear graphite should be applicable to future safety analysis of high-temperature gas cooled reactors in the unlikely event of a massive air ingress accident. (authors)

El-Genk, M. S. [Inst. for Space and Nuclear Power Studies, Univ. of New Mexico, Albuquerque, NM (United States); Chemical and Nuclear Engineering Dept., Univ. of New Mexico, Albuquerque, NM (United States); Mechanical Engineering Dept., Univ. of New Mexico, Albuquerque, NM (United States); Tournier, J. M. P. [Inst. for Space and Nuclear Power Studies, Univ. of New Mexico, Albuquerque, NM (United States); Chemical and Nuclear Engineering Dept., Univ. of New Mexico, Albuquerque, NM (United States)

2012-07-01

54

Parameters-related uncertainty in modeling sugar cane yield with an agro-Land Surface Model  

NASA Astrophysics Data System (ADS)

Agro-Land Surface Models (agro-LSM) have been developed from the coupling of specific crop models and large-scale generic vegetation models. They aim at accounting for the spatial distribution and variability of energy, water and carbon fluxes within soil-vegetation-atmosphere continuum with a particular emphasis on how crop phenology and agricultural management practice influence the turbulent fluxes exchanged with the atmosphere, and the underlying water and carbon pools. A part of the uncertainty in these models is related to the many parameters included in the models' equations. In this study, we quantify the parameter-based uncertainty in the simulation of sugar cane biomass production with the agro-LSM ORCHIDEE-STICS on a multi-regional approach with data from sites in Australia, La Reunion and Brazil. First, the main source of uncertainty for the output variables NPP, GPP, and sensible heat flux (SH) is determined through a screening of the main parameters of the model on a multi-site basis leading to the selection of a subset of most sensitive parameters causing most of the uncertainty. In a second step, a sensitivity analysis is carried out on the parameters selected from the screening analysis at a regional scale. For this, a Monte-Carlo sampling method associated with the calculation of Partial Ranked Correlation Coefficients is used. First, we quantify the sensitivity of the output variables to individual input parameters on a regional scale for two regions of intensive sugar cane cultivation in Australia and Brazil. Then, we quantify the overall uncertainty in the simulation's outputs propagated from the uncertainty in the input parameters. Seven parameters are identified by the screening procedure as driving most of the uncertainty in the agro-LSM ORCHIDEE-STICS model output at all sites. These parameters control photosynthesis (optimal temperature of photosynthesis, optimal carboxylation rate), radiation interception (extinction coefficient), root uptake of water (root profile), and transpiration and respiration (stomatal conductance, growth and maintenance respiration coefficients). We find that the optimal carboxylation rate and optimal photosynthesis temperature parameters contribute most to the uncertainty in NPP and GPP simulations whereas stomatal conductance is the most sensitive parameter controlling SH, followed by optimal photosynthesis temperature and optimal carboxylation rate. The spatial variation of the ranked correlation between input parameters and output variables is well explained by rain and temperature drivers, suggesting that climate mediated regionally different sensitivities of modeled sugarcane yield to the model parameters, for Australia and Brazil.

Valade, A.; Ciais, P.; Vuichard, N.; Viovy, N.; Ruget, F.; Gabrielle, B.

2012-12-01

55

Combining ability analyses of stability parameters and forage yield in smooth bromegrass.  

PubMed

Twenty-one progenies of smooth bromegrass (Bromus inermis Leyss.) from a 7 X 7 half diallel cross, with their parents, were evaluated for three years at four locations in Alberta for the genetic variation of stability in expression of their annual yield. The linear response and deviation from linear response for each genotype were the two stability parameters considered, together with mean performance in the evaluation of each genotype. Four high yielding genotypes, namely 12, 13, 16, and 26, had general adaptability, while genotype 23 was especially suited to a poor environment. Combining ability analysis showed that general combining ability (GCA) and specific combining ability (SCA) were both important in the expression of yield. Inheritance of linear regression was controlled predominantly by GCA whereas both GCA and SCA were equally important in the expression of deviation. The presence of a substantial proportion of variability due to the additive genetic component in the linear response suggests that it should be possible to exploit this fraction of variability in developing high yielding stable cultivars. PMID:24301013

Tan, W K; Tan, G Y

1980-07-01

56

Estimating maize grain yield from crop biophysical parameters using remote sensing  

NASA Astrophysics Data System (ADS)

The overall objective of this investigation was to develop a robust technique to predict maize (Zea mays L.) grain yield that could be applied at a regional level using remote sensing with or without a simple crop growth simulation model. This study evaluated capabilities and limitations of the Moderate Resolution Imaging Spectroradiometer (MODIS) Vegetation Index 250-m and MODIS surface reflectance 500-m products to track and retrieve information over maize fields. Results demonstrated the feasibility of using MODIS data to estimate maize green leaf area index (LAIg). Estimates of maize LAIg obtained from Wide Dynamic Range Vegetation Index using data retrieved from MODIS 250-m products (e.g. MOD13Q1) can be incorporated in crop simulation models to improve LAIg simulations by the Muchow-Sinclair-Bennet (MSB) model reducing the RMSE of LAIg simulations for all years of study under irrigation. However, more accurate estimates of LAIg did not necessarily imply better final yield (FY) predictions in the MSB maize model. The approach of incorporating better LAIg estimates into crop simulation models may not offer a panacea for problem solving; this approach is limited in its ability to simulate other factors influencing crop yields. On the other hand, the approach of relating key crop biophysical parameters at the optimum stage with maize grain final yields is a robust technique to early FY estimation over large areas. Results suggest that estimates of LAI g obtained during the mid-grain filling period can used to detect variability of maize grain yield and this technique offers a rapid and accurate (RMSE < 900 kg ha-1) method to detect FY at county level using MODIS 250-m products.

Guindin-Garcia, Noemi

57

Genetic parameters for test day milk yields of first lactation Holstein cows by random regression models.  

PubMed

Covariance components for test day milk yield using 263 390 first lactation records of 32 448 Holstein cows were estimated using random regression animal models by restricted maximum likelihood. Three functions were used to adjust the lactation curve: the five-parameter logarithmic Ali and Schaeffer function (AS), the three-parameter exponential Wilmink function in its standard form (W) and in a modified form (W*), by reducing the range of covariate, and the combination of Legendre polynomial and W (LEG+W). Heterogeneous residual variance (RV) for different classes (4 and 29) of days in milk was considered in adjusting the functions. Estimates of RV were quite similar, rating from 4.15 to 5.29 kg2. Heritability estimates for AS (0.29 to 0.42), LEG+W (0.28 to 0.42) and W* (0.33 to 0.40) were similar, but heritability estimates used W (0.25 to 0.65) were highest than those estimated by the other functions, particularly at the end of lactation. Genetic correlations between milk yield on consecutive test days were close to unity, but decreased as the interval between test days increased. The AS function with homogeneous RV model had the best fit among those evaluated. PMID:22444330

de Melo, C M R; Packer, I U; Costa, C N; Machado, P F

2007-03-01

58

Separation of L-Phenylalanine by Nondispersive Extraction and Backextraction. Equilibrium and Kinetic Parameters  

Microsoft Academic Search

The objective of this work is the evaluation of the separation\\/concentration of L-phenylalanine by means of nondispersive extraction and backextraction in hollow fiber modules and the determination of the equilibrium and kinetic parameters, which will allow the description of the separation process. An organic solution based on Aliquat 336, 30% (v\\/v); isodecanol, 30% (v\\/v); and kerosene is used as a

Humberto Escalante; Ana I. Alonso; Inmaculada Ortiz; Angel Irabien

1998-01-01

59

Determination of apparent kinetic parameters for competitive product inhibition in packed-bed immobilized enzyme reactors  

Microsoft Academic Search

In this study, a simple and effective technique for characterizing Michaelis–Menten type kinetics with competitive product inhibition in packed-bed re-circulated immobilized enzyme reactors is presented, where the use of nonlinear regression techniques for multi-parameter estimation are not required. In order to demonstrate the new technique introduced in this work, enzymatic conversion of lactose in a recycling packed-bed reactor is envisaged

Ahmet R. Özdural; Deniz Tanyolaç; ?smail H. Boyac?; Mehmet Mutlu; Colin Webb

2003-01-01

60

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

61

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. PMID:23964707

2013-01-01

62

Effects of parameters affecting biomass yield and thermal behaviour of Chlorella vulgaris.  

PubMed

Conventional fossil fuels are facing a global challenge which lead scientists to explore alternative fuel production from biological sources. The algae-based fuels are gaining rapid attention as it has potential to replace petroleum-based fuels. An indigenous high lipid producing microalgae was isolated from a freshwater pond in the KwaZulu-Natal province of South Africa. The isolate was later identified as Chlorella vulgaris, based on partial 28S large subunit ribosomal RNA gene sequence. The growth kinetics, pyrolytic characteristics and photosynthetic efficiency of Chlorella was evaluated in vitro. The optimized conditions for higher biomass yield of the selected strain were at 4% CO(2), 0.5 g l(-1) NO(3) and 0.04 g l(-1) PO(4), respectively. The pulse amplitude modulation results indicated that C. vulgaris could withstand a light intensity ranging from 150 to 350 ?mol photons m(-2)s(-1). Further increase in light intensity resulted in a decline of the electron transport rate. Carbon fixation rate, lipid content and calorific value of C. vulgaris was 6.17 mg l(-1)h(-1), 21% and 17.44 kJ g(-1), respectively. The pyrolitic studies under inert atmosphere at different heating rates of 15, 30, 40 and 50°C min(-1) from ambient temperature to 800°C showed that the overall final weight loss recorded for the four different heating rates was in the range of 78.9-81%. These studies could be useful to appraise the biofuel potential of the isolated C. vulgaris strain, which can later be taken for pilot scale production. PMID:21185776

Bhola, Virthie; Desikan, Ramesh; Santosh, Sheena Kumari; Subburamu, Karthikeyan; Sanniyasi, Elumalai; Bux, Faizal

2011-03-01

63

Tailoring wet explosion process parameters for the pretreatment of cocksfoot grass for high sugar yields.  

PubMed

The pretreatment of lignocellulosic biomass is crucial for efficient subsequent enzymatic hydrolysis and ethanol fermentation. In this study, wet explosion (WEx) pretreatment was applied to cocksfoot grass and pretreatment conditions were tailored for maximizing the sugar yields using response surface methodology. The WEx process parameters studied were temperature (160-210 °C), retention time (5-20 min), and dilute sulfuric acid concentration (0.2-0.5 %). The pretreatment parameter set E, applying 210 °C for 5 min and 0.5 % dilute sulfuric acid, was found most suitable for achieving a high glucose release with low formation of by-products. Under these conditions, the cellulose and hemicellulose sugar recovery was 94 % and 70 %, respectively. The efficiency of the enzymatic hydrolysis of cellulose under these conditions was 91 %. On the other hand, the release of pentose sugars was higher when applying less severe pretreatment conditions C (160 °C, 5 min, 0.2 % dilute sulfuric acid). Therefore, the choice of the most suitable pretreatment conditions is depending on the main target product, i.e., hexose or pentose sugars. PMID:23709291

Njoku, S I; Ahring, B K; Uellendahl, H

2013-08-01

64

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

65

A BAYESIAN METHOD OF ESTIMATING KINETIC PARAMETERS FOR THE INACTIVATION OF CRYPTOSPORIDIUM PARVUM OOCYSTS WITH CHLORINE DIOXIDE AND OZONE  

EPA Science Inventory

The main objective of this paper is to use Bayesian methods to estimate the kinetic parameters for the inactivation kinetics of Cryptosporidium parvum oocysts with chlorine dioxide or ozone which are characterized by the delayed Chick-Watson model, i.e., a lag phase or shoulder f...

66

Measurement of Kinetic Energy Distributions, Mass and Isotopic Yields in the Heavy Fission Products Region at Lohengrin  

NASA Astrophysics Data System (ADS)

Mass yields and kinetic energy distribution functions for heavy mass fission products from thermal neutron induced fission of 235U and 239Pu have been measured at the spectrometer Lohengrin at the high flux reactor of the Institut Laue-Langevin in Grenoble. In addition to these measurements where an ionization chamber was used for the mass identification, we also performed gamma spectrometry to quantify the isotopic and isomeric yields. This setup using Ge-detectors has been commissioned with the system 241Pu(nth,f). In order to extend the data to less abundant fission products, a proportional counter for beta detection has been constructed, allowing to reduce the background by beta-gamma coincidences.

Bail, A.; Serot, O.; Litaize, O.; Faust, H. R.; Köster, U.; Materna, T.; Letourneau, A.; Dupont, E.

2008-04-01

67

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

68

Quantitative genetic parameters for yield, plant growth and cone chemical traits in hop (Humulus lupulus L.)  

PubMed Central

Background Most traits targeted in the genetic improvement of hop are quantitative in nature. Improvement based on selection of these traits requires a comprehensive understanding of their inheritance. This study estimated quantitative genetic parameters for 20 traits related to three key objectives for the genetic improvement of hop: cone chemistry, cone yield and agronomic characteristics. Results Significant heritable genetic variation was identified for ?-acid and ?-acid, as well as their components and relative proportions. Estimates of narrow-sense heritability for these traits (h 2 ?=?0.15 to 0.29) were lower than those reported in previous hop studies, but were based on a broader suite of families (108 from European, North American and hybrid origins). Narrow-sense heritabilities are reported for hop growth traits for the first time (h 2 ?=?0.04 to 0.20), relating to important agronomic characteristics such as emergence, height and lateral morphology. Cone chemistry and growth traits were significantly genetically correlated, such that families with more vigorous vegetative growth were associated with lower ?-acid and ?-acid levels. This trend may reflect the underlying population structure of founder genotypes (European and North American origins) as well as past selection in the Australian environment. Although male and female hop plants are thought to be indistinguishable until flowering, sex was found to influence variation in many growth traits, with male and female plants displaying differences in vegetative morphology from emergence to cone maturity. Conclusions This study reveals important insights into the genetic control of quantitative hop traits. The information gained will provide hop breeders with a greater understanding of the additive genetic factors which affect selection of cone chemistry, yield and agronomic characteristics in hop, aiding in the future development of improved cultivars. PMID:24524684

2014-01-01

69

Determination of immobilized enzyme apparent kinetic parameters in packed-bed reactors: Presentation of a new methodology  

Microsoft Academic Search

A new explicit equation is proposed for the determination of immobilized enzyme apparent Michaelis–Menten kinetic parameters in packed-bed reactors. The mathematical analysis is based on recycling systems. The present methodology is easily applicable for a wide range of operating conditions. It is free from the probable limitations of the single-pass apparent immobilized enzyme kinetic parameter estimation technique that requires simultaneous

A. R. Özdural; A. Alkan-Sungur; I. H. Boyaci; C. Webb

2008-01-01

70

Behaviors of biomass and kinetic parameter for nitrifying species in a(2)o process at different sludge retention time.  

PubMed

The effect of sludge retention time (SRT) on biomass, kinetic parameters, and stoichiometric parameters of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in anaerobic/anoxic/oxic (A(2)O) process were explored in this study. The results showed that the growth rate constants were 1.52, 1.22, and 0.85 day(-1), respectively, for AOB, those were 1.59, 1.19, and 0.87 day(-1), respectively, for NOB when SRT was 20, 10, and 5 days. The lysis rate constants of AOB and NOB were 0.14 and 0.09 day(-1), respectively. The yield coefficients were 0.23 and 0.22, respectively, for AOB and NOB. They did not change with SRT obviously. The biomass of AOB was 50.94, 26.35, and 14.68 mg L(-1), respectively, and the biomass of NOB was 116.77, 60.00, and 44.25 mg L(-1), respectively, at SRT of 20, 10, and 5 days. When SRT diminished from 20 to 5 days, the biomass of AOB and NOB diminished by 36.26 and 75.52 mg L(-1), respectively. The removal efficiency of NH4 (+)-N diminished by 68.9 %. The removal efficiency of total nitrogen diminished by 42.9 %. PMID:25234396

Pai, Tzu-Yi; Lo, Huang-Mu; Wan, Terng-Jou; Wang, Shun-Cheng; Yang, Pei-Yu; Huang, Yu-Ting

2014-12-01

71

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. PMID:9729603

Button, D. K.

1998-01-01

72

Associations of fiber quality parameters and lint yield components in six diverse cotton genotypes  

E-print Network

High yielding cotton, Gossypium hirsutum L., cultivars with improved fiber bundle strength are needed for today's spinning technology. This study was initiated to determine the effects of selection for improved fiber quality on within-boll yield...

Golladay, Gwendolyn Kay

2012-06-07

73

Fiber quality parameters and within-boll yield components of Gossypium arboreum L. putative mutant lines  

E-print Network

mean fiber length (UBM), fiber bundle strength, micronaire, and uniformity index. Lint yield components, using the ontogenetic yield model proposed by Worley et al. included: lint percentage (LP), seeds per boll (S/BOLL), seed cotton per seed (SC...

Naivar, Kevin Scott

2012-06-07

74

Parameters and kinetics of olive mill wastewater dephenolization by immobilized Rhodotorula glutinis cells.  

PubMed

Olive mill wastewater (OMW) with total phenol (TP) concentration range of 300-1200 mg/L was treated with alginate-immobilized Rhodotorula glutinis cells in batch system. The effects of pellet properties (diameter, alginate concentration and cell loading (CL)) and operational parameters (initial TP concentration, agitation rate and reusability of pellets) on dephenolization of OMW were studied. Up to 87% dephenolization was obtained after 120 h biodegradations. The utilization number of pellets increased with the addition of calcium ions into the biodegradation medium. The overall effectiveness factors calculated for different conditions showed that diffusional limitations arising from pellet size and pellet composition could be neglected. Mass transfer limitations appeared to be more effective at high substrate concentrations and low agitation rates. The parameters of logistic model for growth kinetics of R. glutinis in OMW were estimated at different initial phenol concentrations of OMW by curve-fitting of experimental data with the model. PMID:25244135

Bozkoyunlu, Gaye; Takaç, Serpil

2014-12-01

75

Sensitivity of benzene natural attenuation to variations in kinetic and transport parameters in Liwa Aquifer, UAE.  

PubMed

Dissolved benzene was detected in the shallow unconfined Liwa aquifer (UAE). This aquifer represents the main freshwater source for a nearby residence camp area. A finite element model is used to simulate the fate, transport, and attenuation of the dissolved benzene plume to help decision makers assess natural attenuation as a viable remediation option. Sensitivity of benzene attenuation to uncertainties in the estimation of some of the kinetic and transport parameters is studied. It was found that natural attenuation is more sensitive to microbial growth rate and half saturation coefficients of both benzene and oxygen than initial biomass concentration and dispersivity coefficients. Increasing microbial growth rate by fourfold increased natural attenuation effectiveness after 40 years by 10%; while decreasing it by fourfold decreased natural attenuation effectiveness by 77%. On the other hand, increasing half saturation coefficient by fourfold decreased natural attenuation effectiveness by 46% in 40 years. Decreasing the same parameter fourfold caused natural attenuation effectiveness to increase by 9%. PMID:20237911

Mohamed, Mohamed M; Saleh, Nawal E; Sherif, Mohsen M

2010-04-01

76

Radiographic Parameters of Segmental Instability in Lumbar Spine Using Kinetic MRI  

PubMed Central

Objective To investigate the effectiveness of radiographic parameters on segmental instability in the lumbar spine using Kinetic magnetic resonance imaging (MRI). Methods Segmental motion, defined as excessive (more than 3 mm) translational motion from flexion to extension, was investigated in 309 subjects (927 segments) using Kinetic MRI. Radiographic parameters which can help indicate segmental instability include disc degeneration (DD), facet joint osteoarthritis (FJO), and ligament flavum hypertrophy (LFH). These three radiographic parameters were simultaneously evaluated, and the combinations corresponding to significant segmental instability at each level were determined. Results The overall incidence of segmental instability was 10.5% at L3-L4, 16.5% at L4-L5, and 7.3% at L5-S1. DD and LFH at L3-L4 and FJO and LFH at L4-L5 were individually associated with segmental instability (p<0.05). At L4-L5, the following combinations had a higher incidence of segmental instability (p<0.05) when compared to other segments : (1) Grade IV DD with grade 3 FJO, (2) Grade 2 or 3 FJO with the presence of LFH, and (3) Grade IV DD with the presence of LFH. At L5-S1, the group with Grade III disc and Grade 3 FJO had a higher incidence of segmental instability than the group with Grade I or II DD and Grade 1 FJO. Conclusion This study showed that the presences of either Grade IV DD or grade 3 FJO with LFH at L4-L5 were good indicators for segmental instability. Therefore, using these parameters simultaneously in patients with segmental instability would be useful for determining candidacy for surgical treatment. PMID:19242567

Jang, Se Youn; Hymanson, Henry J.; Jin, Tae Kyung; Song, Kwan Young; Wang, Jeffrey C.

2009-01-01

77

Pion Yield Studies for Proton Driver Beams of 2-8 GeV Kinetic Energy for Stopped Muon and Low-Energy Muon Decay Experiments  

NASA Astrophysics Data System (ADS)

Energy dependence of slow pion yield in proton-nucleus interactions is analyzed. Experimental data of the HARP collaboration is fitted using two-fireball model with ?2/nd ~ 1 from 3 to 8 GeV/c. It is shown that low momentum negative pion yield rises almost linearly with proton kinetic energy. Normalized low momentum positive pion yield is larger at lower proton energy.

Striganov, S. I.

2010-06-01

78

Chemical kinetics parameters and model validation for the gasification of PCEA nuclear graphite  

NASA Astrophysics Data System (ADS)

A series of gasification experiments, using two right cylinder specimens (?12.7 × 25.4 mm and 25.4 × 25.4 mm) of PCEA nuclear graphite in ambient airflow, measured the total gasification flux at weight losses up to 41.5% and temperatures (893-1015 K) characteristics of those for in-pores gasification Mode (a) and in-pores diffusion-limited Mode (b). The chemical kinetics parameters for the gasification of PCEA graphite are determined using a multi-parameters optimization algorithm from the measurements of the total gasification rate and transient weight loss in experiments. These parameters are: (i) the pre-exponential rate coefficients and the Gaussian distributions and values of specific activation energies for adsorption of oxygen and desorption of CO gas; (ii) the specific activation energy and pre-exponential rate coefficient for the breakup of stable un-dissociated C(O2) oxygen radicals to form stable (CO) complexes; (iii) the specific activation energy and pre-exponential coefficient for desorption of CO2 gas and; (iv) the initial surface area of reactive free sites per unit mass. This area is consistently 13.5% higher than that for nuclear graphite grades of NBG-25 and IG-110 and decreases inversely proportional with the square root of the initial mass of the graphite specimens in the experiments. Experimental measurements successfully validate the chemical-reactions kinetics model that calculates continuous Arrhenius curves of the total gasification flux and the production rates of CO and CO2 gases. The model results at different total weight losses agree well with measurements and expand beyond the temperatures in the experiments to the diffusion-limited mode of gasification. Also calculated are the production rates of CO and CO2 gases and their relative contributions to the total gasification rate in the experiments as functions of temperature, for total weight losses of 5% and 10%.

El-Genk, Mohamed S.; Tournier, Jean-Michel P.; Contescu, Cristian I.

2014-01-01

79

Decay kinetics of the excited S{sub 1} state of the cyanine dye Cy{sup +}I{sup -} (thiacarbocyanine iodide): The computation of quantum yields for different pathways  

SciTech Connect

This work explains the unordinary solvent effect which was observed in the photochemical decay kinetics for the cyanine dye thiacarbocyanine iodide (Cy{sup +}I{sup -}) in binary solvent mixtures toluene/dimethylsulfoxide. The interpretation is formulated in terms of the probability density F(R) describing the distribution of interionic distances R in the ion pair Cy{sup +}I{sup -} and depending on the solvent composition. The proper normalization of this distribution is expressed via the degree of association {alpha} for the ion pair in a given solvent mixture. The {alpha} values are, in turn, extracted by means of the mass action law from the ionic association constants computed in a separate publication. The detailed kinetic scheme includes the empirical parametrization of the R-dependent kinetic constants for different decay channels. The multiparameter fitting procedure represents, with the reasonable parameter values, the dependence of the observed quantum yields on the solvent composition.

Odinokov, A. V.; Basilevsky, M. V.; Petrov, N. Kh. [Photochemistry Center RAS, Novatorov Str. 7a, 119421 Moscow (Russian Federation)

2011-10-14

80

Estimation of kinetic parameters by progress curve analysis for the synthesis of (R)-mandelonitrile by Prunus amygdalus hydroxynitrile lyase.  

PubMed

Consistent sets of kinetic parameters were estimated for the synthesis of (R)-mandelonitrile, catalyzed by Prunus amygdalus hydroxynitrile lyase, at 5 and 25 degrees C and pH 5.5 by progress curve analysis. The rate constants and equilibrium constants of the nonenzymatic reaction were determined separately to reduce the number of parameters to be estimated simultaneously. At a lower temperature the equilibrium is much more favorable and the formation of rac-mandelonitrile by the nonenzymatic reaction is suppressed. The estimated kinetic parameters were used to identify that the rate determining step in the catalytic cycle is the release of (R)-mandelonitrile from the ternary complex. PMID:10938422

Willeman; Hanefeld; Straathof; Heijnen

2000-09-01

81

Seasonal Variation of the Canopy Structure Parameters and Its Correlation with Yield-Related Traits in Sugarcane  

PubMed Central

Population structure determines sugarcane yield, of which canopy structure is a key component. To fully understand the relations between sugarcane yield and parameters of the canopy structure, 17 sugarcane varieties were investigated at five growth stages. The results indicated that there were significant differences between characterized parameters among sugarcane populations at different growth stages. During sugarcane growth after planting, leaf area index (LAI) and leaf distribution (LD) increased, while transmission coefficient for diffuse radiation (TD), mean foliage inclination angle (MFIA), transmission coefficient for solar beam radiation penetration (TR), and extinction coefficient (K) decreased. Significant negative correlations were found between sugarcane yield and MFIA, TD, TR, and K at the early elongation stage, while a significant positive correlation between sugarcane yield and LD was found at the same stage. A regression for sugarcane yield, with relative error of yield fitting less than 10%, was successfully established: sugarcane yield = 2380.12 + 46.25 × LD ? 491.82 × LAI + 1.36 × MFIA + 614.91 × TD ? 1908.05 × TR ? 182.53 ×??K + 1281.75 × LD ? 1.35 × MFIA + 831.2 × TR ? 407.8 ×??K + 8.21 × MFIA ? 834.50 × TD ? 1695.49 ×??K??(R2 = 0.94**). PMID:24453909

Luo, Jun; Que, Youxiong; Zhang, Hua; Xu, Liping

2013-01-01

82

Kinetics and activation parameters of the reaction of organoarsenic(V) compounds with glutathione.  

PubMed

In this work the kinetics of the reaction of glutathione (GSH) with the organoarsenic(V) compounds phenylarsonic acid (PAA), 4-hydroxy-3-nitrophenylarsonic acid (HNPAA), p-aminophenylarsonic acid (p-APAA) and o-aminophenylarsonic acid (o-APAA) as well as monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) is investigated. The reaction progress is monitored in real time by (1)H NMR, allowing the determination of rate coefficients and half-lives as well as activation parameters. The reaction consists of two steps: redox reaction and conjugation. In all investigated systems the conjugation is fast compared to the redox reaction and, therefore, rate determining. All investigated phenylarsonic acids follow the same rate law, showing overall reaction orders of 3 and half-lives between 47.7±0.2 and 71.0±3.6min. The methylated compounds react slower, showing half-lives of 76.6±0.4 and 444±10min for DMAA and MMAA, respectively. Enthalpies of activation range from 20 to 36 (±2)kJmol(-1) and the entropies of activation are within -154 and -97(±7)Jmol(-1)K(-1). The results reveal a correlation of the toxicity of the arsenic compound and the reaction rate with GSH. This may pave the way for the estimation of the toxicity of such compounds by simple kinetic studies. PMID:25238190

Kretzschmar, Jerome; Brendler, Erica; Wagler, Jörg; Schmidt, Anne-Christine

2014-09-15

83

Measurement of the depolarization parameter and the spin transfer parameter in the charge-exchange reaction [bar p]p[yields][bar n]n at LEAR  

SciTech Connect

Experiment PS199 at LEAR studied the charge-exchange [bar p]p[yields][bar n]n reaction and, in particular, its spin structure. Data for the measurement of the depolarization parameter for a polarized target (D[sub 0n0n]) and the polarization-transfer parameter from the target to the scattered particle (K[sub 0n0n]) have been collected during 1990. The determination of these parameters requires n and [bar n] polarimetry. Polarimeters are described, and their performances are given. 10 refs., 7 figs.

Birsa, R.; Bradamante, F.; Dalla Torre-Colautti, S.; Giorgi, M.; Lamanna, M.; Martin, A.; Penzo, A.; Schiavon, P.; Tessarotto, F. (INFN Trieste and Univ. of Trieste, Trieste (Italy)); Macciotta, M.P. (and others)

1992-05-01

84

Breath-by-breath pulmonary O2 uptake kinetics: effect of data processing on confidence in estimating model parameters.  

PubMed

To improve the signal-to-noise ratio of breath-by-breath pulmonary O2 uptake (V?O2p) data, it is common practice to perform multiple step transitions, which are subsequently processed to yield an ensemble-averaged profile. The effect of different data-processing techniques on phase II V?O2p kinetic parameter estimates (V?O2p amplitude, time delay and phase II time constant (?V?O2p)] and model confidence [95% confidence interval (CI95)] was examined. Young (n = 9) and older men (n = 9) performed four step transitions from a 20 W baseline to a work rate corresponding to 90% of their estimated lactate threshold on a cycle ergometer. Breath-by-breath V?O2p was measured using mass spectrometry and volume turbine. Mono-exponential kinetic modelling of phase II V?O2p data was performed on data processed using the following techniques: (A) raw data (trials time aligned, breaths of all trials combined and sorted in time); (B) raw data plus interpolation (trials time aligned, combined, sorted and linearly interpolated to second by second); (C) raw data plus interpolation plus 5 s bin averaged; (D) individual trial interpolation plus ensemble averaged [trials time aligned, linearly interpolated to second by second (technique 1; points joined by straight-line segments), ensemble averaged]; (E) 'D' plus 5 s bin averaged; (F) individual trial interpolation plus ensemble averaged [trials time aligned, linearly interpolated to second by second (technique 2; points copied until subsequent point appears), ensemble averaged]; and (G) 'F' plus 5 s bin averaged. All of the model parameters were unaffected by data-processing technique; however, the CI95 for ?V?O2p in condition 'D' (4 s) was lower (P < 0.05) than the CI95 reported for all other conditions (5-10 s). Data-processing technique had no effect on parameter estimates of the phase II V?O2p response. However, the narrowest interval for CI95 occurred when individual trials were linearly interpolated and ensemble averaged. PMID:25063837

Keir, Daniel A; Murias, Juan M; Paterson, Donald H; Kowalchuk, John M

2014-11-01

85

Calculation of Reactor Kinetics Parameters ?eff and ? with Monte Carlo Differential Operator Sampling  

NASA Astrophysics Data System (ADS)

The methods to calculate the kinetics parameters of ?eff and ? with the differential operator sampling have been reviewed. The comparison of the results obtained with the differential operator sampling and iterated fission probability approaches has been performed. It is shown that the differential operator sampling approach gives the same results as the iterated fission probability approach within the statistical uncertainty. In addition, the prediction accuracy of the evaluated nuclear data library JENDL-4.0 for the measured ?eff/? and ?eff values is also examined. It is shown that JENDL-4.0 gives a good prediction except for the uranium-233 systems. The present results imply the need for revisiting the uranium-233 nuclear data evaluation and performing the detailed sensitivity analysis.

Nagaya, Yasunobu

2014-06-01

86

Growth kinetics and yield study on Chlorella pyrenoidosa in chemically defined media  

SciTech Connect

A Chlorella culture free from heterotrophic bacteria was obtained by eliminating the bacteria with successive use of antibiotics and agar plants. The purified Chlorella was cultured in chemically defined media. Under a photon flux (16.7 mw/cmS) similar to insolation, both heterotrophic and mixotrophic cultures were luxurious but the growth rates of autotrophic cultures were reduced substantially. The Chlorella culture grew most rapidly at 30 C in the absence of heterotrophic bacteria, and the highest specific growth rates were 1.43 x 10 h and 0.46 x 10 h for mixotrophic and autotrophic cultures, respectively. The highest photosynthetic efficiency over its growth period was 2.9% for autotrophic cultures. Elimination of heterotrophic bacteria from Chlorella cultures improved the algal growth rate as well as biomass yield significantly. A parasite of 0.1- m size was identified. The motile microorganism played an important role in the growth of the Chlorella and appeared to be common to green algae. 16 references, 2 tables.

Joung, J.J.; Akin, C.

1983-01-01

87

Ammonium Removal from Aqueous Solutions by Clinoptilolite: Determination of Isotherm and Thermodynamic Parameters and Comparison of Kinetics by the Double Exponential Model and Conventional Kinetic Models  

PubMed Central

The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R2) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (?G°), enthalpy (?H°) and entropy (?S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients. PMID:22690177

Tosun, ?smail

2012-01-01

88

Determination of kinetics parameters of glass transition in glassy Se and glassy Se98M2 alloys using DSC technique  

NASA Astrophysics Data System (ADS)

Glassy Se and Se98M2 (M = Ag, Cd, Zn) alloys are obtained by the melt quenching technique. Differential Scanning Calorimetry (DSC) technique (under non-isothermal conditions) has been applied to see the effects of Ag, Cd, and Zn additives on the glass transition kinetics of Se-rich glassy alloys at different heating rates. The variation of glass transition temperature, T g with the heating rate, ? has been used to investigate the glass transition kinetics. The values of various kinetic parameters such as glass transition temperature, activation energy of glass transition, overall mean bond energy < E>, heat of atomization H S , bond strength (Se-M) have also been calculated.

Dohare, C.; Mehta, N.

2014-02-01

89

Steady-state and transient Zener parameters in viscoplasticity: Drag strength versus yield strength  

NASA Technical Reports Server (NTRS)

A hypothesis is put forth which enables the viscoplastician to formulate a theory of viscoplasticity that reduces, in closed form, to the classical theory of creep. This hypothesis is applied to a variety of drag and yield strength models. Because of two theoretical restrictions that are a consequence of this hypothesis, three different yield strength models and one drag strength model are shown to be theoretically admissible. One of these yield strength models is selected as being the most appropriate representation for isotropic hardening.

Freed, A. D.; Walker, K. P.

1990-01-01

90

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

91

Aqueous oxidation of green leaf volatiles by hydroxyl radical as a source of SOA: Kinetics and SOA yields  

NASA Astrophysics Data System (ADS)

Green leaf volatiles (GLVs) are a class of oxygenated hydrocarbons released from vegetation, especially during mechanical stress or damage. The potential for GLVs to form secondary organic aerosol (SOA) via aqueous-phase reactions is not known. Fog events over vegetation will lead to the uptake of GLVs into water droplets, followed by aqueous-phase reactions with photooxidants such as the hydroxyl radical (OH). In order to determine if the aqueous oxidation of GLVs by OH can be a significant source of secondary organic aerosol, we studied the partitioning and reaction of five GLVs: cis-3-hexen-1-ol, cis-3-hexenyl acetate, methyl salicylate, methyl jasmonate, and 2-methyl-3-butene-2-ol. For each GLV we measured the kinetics of aqueous oxidation by OH, and the corresponding SOA mass yield. The second-order rate constants for GLVs with OH were all near diffusion controlled, (5.4-8.6) × 109 M-1 s-1 at 298 K, and showed a small temperature dependence, with an average activation energy of 9.3 kJ mol-1 Aqueous-phase SOA mass yields ranged from 10 to 88%, although some of the smaller values were not statistically different from zero. Methyl jasmonate was the most effective aqueous-phase SOA precursor due to its larger Henry's law constant and high SOA mass yield (68 ± 8%). While we calculate that the aqueous-phase SOA formation from the five GLVs is a minor source of aqueous-phase SOA, the availability of other GLVs, other oxidants, and interfacial reactions suggest that GLVs overall might be a significant source of SOA via aqueous reactions.

Richards-Henderson, Nicole K.; Hansel, Amie K.; Valsaraj, Kalliat T.; Anastasio, Cort

2014-10-01

92

Interactions of viruses in Cowpea: effects on growth and yield parameters.  

PubMed

The study was carried out to investigate the effects of inoculating three cowpea cultivars: "OLO II", "OLOYIN" and IT86D-719 with three unrelated viruses: Cowpea aphid-borne mosaic virus (CABMV), genus Potyvirus, Cowpea mottle virus (CMeV), genus Carmovirus and Southern bean mosaic virus (SBMV), genus Sobemovirus singly and in mixture on growth and yield of cultivars at 10 and 30 days after planting (DAP). Generally, the growth and yield of the buffer inoculated control plants were significantly higher than those of the virus inoculated plants. Inoculation of plants at an early age of 10 DAP resulted in more severe effect than inoculations at a later stage of 30 DAP. The average values of plant height and number of leaves produced by plants inoculated 30 DAP were higher than those produced by plants inoculated 10 DAP. Most of the plants inoculated 10 DAP died and did not produce seeds. However, " OLOYIN" cultivar was most tolerant and produced reasonable yields when infected 30 DAP. The effect of single viruses on growth and yield of cultivars showed that CABMV caused more severe effects in IT86D-719, SBMV had the greatest effect on "OLO II" while CMeV induced the greatest effect on "OLOYIN". Yield was greatly reduced in double infections involving CABMV in combination with either CMeV or SBMV in "OLOYIN" and "OLO II", however, there was complete loss in yield of IT86D-719. Triple infection led to complete yield loss in all the three cultivars. PMID:17286870

Kareem, K T; Taiwo, M A

2007-01-01

93

Kinetic parameters, bleaching and radiation response of thermoluminescence glow peaks separated by deconvolution on Korean calcite  

NASA Astrophysics Data System (ADS)

Calcite has been of particular interest in studies of thermoluminescence (TL) because of its geological and archeological importance. Although extensive research on the TL glow curves of calcite has been conducted, most previous works have been based on the TL intensity integrated over a particular temperature range on the glow curve, without any separation of peaks. In this paper, the physical characteristics of the overlapping peaks in the TL glow curves of a calcite sample are investigated. These properties can provide useful information for determining the radiation dose absorbed to the sample in radiation dosimetry and luminescence dating research. The Tm-Tstop method is employed to identify the number of hidden glow peaks, and the kinetic parameters of each separated glow peak, including the thermal activation energy, kinetic order, and frequency factor, are evaluated using a computerized glow curve deconvolution (CGCD) method. The Tm-Tstop method indicates that the glow curve of calcite is the superposition of at least four components (P1 - P4) in the temperature range between room temperature and 450 °C. A bleaching experiment for two separated glow peaks (P3 and P4) using a solar simulator revealed that the bleaching rates of peak P3 show two exponential decays, and after bleaching, the TL intensity of peak P3 is reduced to approximately 4% of the initial value. In contrast, peak P4 is bleached exponentially to approximately 30% of the initial TL intensity and thereafter shows no detectable change in intensity. In addition, in a study of the radiation dose response of the two peaks, both peaks have a similar pattern, exhibiting a linear increment up to the maximum dose investigated, 520 Gy.

Kim, Ki-Bum; Hong, Duk-Geun

2014-10-01

94

Effect of climatic, design and operational parameters on the yield of a simple solar still  

Microsoft Academic Search

This paper reports the use of a mathematical model to predict the productivity of a simple solar still under different climatic, design and operational parameters in Oman. The shallow water basin, 23° cover tilt angle, 0.1 m insulation thickness and asphalt coating of the solar still were found to be the optimum design parameters that produced an average annual solar

H. Al-Hinai; M. S. Al-Nassri; B. A. Jubran

2002-01-01

95

Genetic parameters of milk yield and composition and their relationships with alternative breeding goals  

Microsoft Academic Search

Milk records on 32,077 Holstein cows in first lactation from 1116 herds on the Quebec Dairy Herd Analysis Service between 1973 and 1983 were used to estimate heritabilities of and genetic correlations between milk, fat, protein, and carrier (water, lactose, ash) yields; fat, protein, and carrier percentages; and ratios of protein to fat and protein plus fat to carrier. The

D. de Jager; B. W. Kennedy

1987-01-01

96

Thermodynamic, Kinetic, and Equilibrium Parameters for the Removal of Lead and Cadmium from Aqueous Solutions with Calcium Alginate Beads  

PubMed Central

The sorption of cadmium (Cd) and lead (Pb) by calcium alginate beads (CAB) from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4?mg/g and 150.4?mg/g for lead, at 25°C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7. PMID:24587740

Alfaro-Cuevas-Villanueva, Ruth; Hidalgo-Vazquez, Aura Roxana; Cortes Penagos, Consuelo de Jesus; Cortes-Martinez, Raul

2014-01-01

97

The influence of Aphanomyces cochlioides on selected physiological processes in sugar beet leaves and yield parameters  

Microsoft Academic Search

Alterations in some physiological processes in source leaves of sugar beet—such as chlorophyll and carbohydrate concentrations,\\u000a stomatal conductance, rate of net photosynthesis and transpiration, and activity of the photosynthetic apparatus during root\\u000a interaction with Aphanomyces cochlioides, were investigated. The influence of time of infection on plant health, yield quality and quantity was also examined. Plants\\u000a were infected at different times

Danuta Cho?uj; Ewa B. Moliszewska

98

Modelling Escherichia coli concentration in a wastewater reservoir using an operational parameter MRT%FE and first order kinetics  

Microsoft Academic Search

The operational parameter MRT%FE, representing the mean residence time of different ages fractions of effluent within a completely mixed reactor, was evaluated and integrated with first order kinetics. The parameter was used to model Escherichia coli concentrations in a municipal wastewater reservoir managed under different operating conditions (continuous and discontinuous).The study was conducted during 2004–2005 in a reservoir receiving effluents

Giuseppe Luigi Cirelli; Simona Consoli; Marcelo Juanicó

2009-01-01

99

Estimation of kinetic parameters by progress curve analysis for the synthesis of ( R)-mandelonitrile by Prunus amygdalus hydroxynitrile lyase  

Microsoft Academic Search

Consistent sets of kinetic parameters were estimated for the synthesis of (R)-mandelonitrile, catalyzed by Prunus amygdalus hydroxynitrile lyase, at 5 and 25°C and pH 5.5 by progress curve analysis. The rate constants and equilibrium constants of the nonenzymatic reaction were determined separately to reduce the number of parameters to be estimated simultaneously. At a lower temperature the equilibrium is much

W. F Willeman; U Hanefeld; A. J. J Straathof; J. J Heijnen

2000-01-01

100

Non-Isothermic Chemical Kinetics in the Undergraduate Laboratory: Arrhenius Parameters from Experiments with Hyperbolic Temperature Variation.  

ERIC Educational Resources Information Center

Describes a method which adapts itself to the characteristics of the kinetics of a chemical reaction in solution, enabling students to determine the Arrhenius parameters with satisfactory accuracy by means of a single non-isothermic experiment. Both activation energy and the preexponential factor values can be obtained by the method. (JN)

Salvador, F.; And Others

1984-01-01

101

Covariance of Kinetic Parameter Estimators Based on Time Activity Curve Reconstructions: Preliminary Study on 1D Dynamic Imaging  

Microsoft Academic Search

We provide approximate expressions for the covariance ma- trix of kinetic parameter estimators based on time activity curve (TAC) reconstructions when TACs are modeled as a linear combination of temporal basis functions such as B- splines. The approximations are useful tools for assessing and optimizing the basis functions for TACs and the tempo- ral bins for data in terms of

Sangtae Ahn; Jeffrey A. Fessler; Thomas E. Nichols; Robert A. Koeppe

2004-01-01

102

Kinetic parameters of interstellar neutral helium: updated results from the ULYSSES/GAS-instrument  

NASA Astrophysics Data System (ADS)

The GAS-instrument onboard the space probe ULYSSES (ULS) is designed to measure the local angular distribution of the flow of interstellar neutral He-atoms within ?3 AU distance from the sun; it allows to infer the kinetic parameters (velocity vector, temperature and density) of these particles outside the heliosphere ("at infinity"). Around the second fast latitude scan of ULYSSES, from 9/2000 to 9/2002 more than 200 new observations were obtained. The average values derived from these observations together with the results of all previous observations, which were recalculated with a refined pointing calibration, are velocity ( v?=26.3±0.4 km/s), flow direction (ecliptic longitude l?=74.7°±0.5°, ecliptic latitude b?=-5.2°±0.2°) and temperature ( T?=6300±340 K). From 1990 to 2002, covering a complete solar cycle, no significant temporal variations of these parameters were observed nor variations with solar latitude. In contrast to that, variations in the density n? values derived from the local observations were obvious and are interpreted to be due to variations in the loss processes, predominantly photo ionization, the particles experience on their way to the observer. While the temporal variations of the ionization rate can be taken into account from instantaneous values of solar EUV-irradiances, which became available from the CELIAS/SEM instrument on SOHO, the residual variations can be explained by latitudinal variations of the solar irradiance. As a result of a simple model a density n? in the range (1.2-1.6 × 10 -2 cm -3) is deduced.

Witte, M.; Banaszkiewicz, M.; Rosenbauer, H.; McMullin, D.

2004-01-01

103

A study of line widths and kinetic parameters of ions in the solar corona  

NASA Astrophysics Data System (ADS)

Solar extreme-ultraviolet (EUV) lines emitted by highly charged ions have been extensively studied to discuss the issue of coronal heating and solar wind acceleration. Based on observations of the polar corona by the SUMER/SOHO spectrometer, this paper investigates the relation between the line widths and kinetic parameters of ions. It is shown that there exists a strongly linear correlation between two variables ( ?/ ?)2 and M -1, where ?, ? and M are the half-width of the observed line profile at , the wavelength and the ion mass, respectively. The Pearson product-moment correlation coefficients exceed 0.9. This finding tends to suggest that the ions from a given height of polar corona have a common temperature and a common non-thermal velocity in terms of existing equation. The temperature and non-thermal velocity are obtained by linear least-square fit. The temperature is around 2.8 MK at heights of 57? and 102?. The non-thermal velocity is typical 21.6 km s-1 at height of 57? and 25.2 km s-1 at height of 102?.

Zhao, G. Q.; Wu, D. J.; Wang, C. B.

2014-10-01

104

A study of line widths and kinetic parameters of ions in the solar corona  

E-print Network

Solar extreme-ultraviolet (EUV) lines emitted by highly charged ions have been extensively studied to discuss the issue of coronal heating and solar wind acceleration. Based on observations of the polar corona by the SUMER/SOHO spectrometer, this paper investigates the relation between the line widths and kinetic parameters of ions. It is shown that there exists a strongly linear correlation between two variables $(\\sigma/\\lambda)^2$ and $M^{-1}$, where $\\sigma$, $\\lambda$ and $M$ are the half-width of the observed line profile at $1/\\sqrt{e}$, the wavelength and the ion mass, respectively. The Pearson product-moment correlation coefficients exceed 0.9. This finding tends to suggest that the ions from a given height of polar corona have a common temperature and a common non-thermal velocity in terms of existing equation. The temperature and non-thermal velocity are obtained by linear least-square fit. The temperature is around $2.8$ MK at heights of 57$''$ and 102$''$. The non-thermal velocity is typical 21.6...

Zhao, G Q; Wang, C B

2014-01-01

105

Properties of inelastic yielding zones generated by in-plane dynamic ruptures—II. Detailed parameter-space study  

NASA Astrophysics Data System (ADS)

We perform a detailed parameter-space study on properties of yielding zones generated by 2-D in-plane dynamic ruptures on a planar fault with different friction laws and parameters, different initial stress conditions, different rock cohesion values, and different contrasts of elasticity and mass density across the fault. The focus is on cases corresponding to large strike-slip faults having high angle (?) to the maximum compressive background stress. The simulations and analytical scaling results show that for crack-like ruptures (1) the maximum yielding zone thickness Tmax linearly increases with rupture distance L and the ratio Tmax/L is inversely proportional to (1 +S)2 with S being the relative strength parameter; (2) the potency density ? decays logarithmically with fault normal distance at a rate depending on the stress state and S; (3) increasing rock cohesion reduces Tmax/L, resulting in faster rupture speed and higher inclination angle ? of expected microfractures on the extensional side of the fault. For slip pulses in quasi-steady state, T is approximately constant along strike with local values correlating with the maximum slip velocity (or final slip) at a location. For a bimaterial interface with ?, the energy dissipation to yielding contributes to developing macroscopically asymmetric rupture (at the scale of rupture length) with the same preferred propagation direction predicted for purely elastic cases with Coulomb friction. When ?, representative for thrust faulting, the energy dissipation to yielding leads to opposite preferred rupture propagation. In all cases, ? is higher on average on the compliant side. For both crack and pulse ruptures with ?, T decreases and ? increases for conditions representing greater depth. Significant damage asymmetry of the type observed across several large strike-slip faults likely implies persistent macroscopic rupture asymmetry (unilateral cracks, unilateral pulses or asymmetric bilateral pulses). The results on various features of yielding zones expected from this and other studies are summarized in a table along with observations from the field and laboratory experiments.

Xu, Shiqing; Ben-Zion, Yehuda; Ampuero, Jean-Paul

2012-12-01

106

Determination of design and operation parameters for upper atmospheric research instrumentation to yield optimum resolution with deconvolution  

NASA Technical Reports Server (NTRS)

The final report for work on the determination of design and operation parameters for upper atmospheric research instrumentation to yield optimum resolution with deconvolution is presented. Papers and theses prepared during the research report period are included. Among all the research results reported, note should be made of the specific investigation of the determination of design and operation parameters for upper atmospheric research instrumentation to yield optimum resolution with deconvolution. A methodology was developed to determine design and operation parameters for error minimization when deconvolution is included in data analysis. An error surface is plotted versus the signal-to-noise ratio (SNR) and all parameters of interest. Instrumental characteristics will determine a curve in this space. The SNR and parameter values which give the projection from the curve to the surface, corresponding to the smallest value for the error, are the optimum values. These values are constrained by the curve and so will not necessarily correspond to an absolute minimum in the error surface.

Ioup, George E.; Ioup, Juliette W.

1991-01-01

107

Modeling the sorption kinetic of metsulfuron-methyl on Andisols and Ultisols volcanic ash-derived soils: kinetics parameters and solute transport mechanisms.  

PubMed

Metsulfuron-methyl sorption kinetic was studied in Andisol and Ultisol soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Different kinetic models were applied to the experimental results. The pseudo-second-order model fitted sorption kinetics data better than the pseudo-first-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the different behavior of metsulfuron-methyl in both kinds of soils, both parameters being the highest for Andisol. The application of Elovich equation, intraparticle diffusion model and a two-site nonequilibrium model (TSNE) allowed to conclude that: (i) the high organic matter content is the governing factor for Andisols where mass transfer across the boundary layer, and in a lesser degree, intraparticle diffusion were the two processes controlling sorption kinetic and (ii) the mineral composition was more relevant in Ultisols where rate was controlled almost exclusively by intraparticle diffusion into macropores and micropores. The slower sorption rate on Ultisols, the mechanism involved and the lower sorption capacity of this kind of soils must be taken into account to assess leaching behavior of this herbicide. PMID:20399011

Cáceres, Lizethly; Escudey, Mauricio; Fuentes, Edwar; Báez, María E

2010-07-15

108

Respirometric kinetic parameter calculations of a batch jet loop bioreactor treating leachate and oxygen uptake rate estimation by DTM.  

PubMed

A novel circulating jet loop bioreactor adapted for organic matter oxidation has been designed and constructed. In this study, the input was leachate samples collected from Kemerburgaz Odayeri waste landfill site located on the European side of Istanbul. Controlling the jet loop bioreactor to realize high rates of purification depends on maintaining the appropriate loadings and operating conditions. This requires collecting various system data to estimate the dynamics of the system satisfactorily with the aim of keeping certain parameters within the specified range. The differential transform method (DTM) based solution of the state equations reveals the current state of the process so that any deviation in the system parameters can be immediately detected and regulated accordingly. The respirometric method for kinetic parameter calculations for biodegradation has been used for some time. In many studies, the respirometer was designed separately, usually in bench-scale. However, when a separate respirometer is used, the scale effect and parameters that affect the hydrodynamic structure of the system should be taken into consideration. In this study, therefore, the jet loop reactor itself was used as a respirometer. Thus, the kinetic parameters found reflecting the characteristics of microorganisms used for biodegradation would be more realistic. If the main reactor, here the jet loop reactor, would be used as the respirometer, the kinetic parameter changes can easily be monitored in the long run. Using the bioreactor as a respirometer, the most important kinetic parameters, Ks, kd and micromax were found to be 11,000 mg L(-1), 0.019 day(-1), and 0.21 day(-1), respectively. The stoichiometric coefficient, Y, was found to be 0.28 gr gr(-1) for the present system. PMID:17997217

Ince, M; Yildiz, F; Engin, G Onkal; Engin, S N; Keskinler, B

2008-05-30

109

Silica coating and photocatalytic activities of ZnO nanoparticles: Effect of operational parameters and kinetic study  

NASA Astrophysics Data System (ADS)

Silica-coating ZnO nanoparticles were prepared using the hydrothermal method. The prepared nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray Spectroscopy (EDX). It was found that ultrafine core/shell structured silica-coating ZnO nanoparticles were successfully obtained. TEM analysis revealed a continuous and uniform silica coating layer of about 8 nm in thickness on the surface of ZnO nanoparticles. The photocatalytic performance of silica-coating ZnO core/shell nanoparticles in methylene blue aqueous solution was investigated. The effects of some operational parameters such as pH value, nanocatalyst loading and initial MB concentration on the degradation efficiency were discussed. Kinetic parameters were experimentally determined and a pseudo-first-order kinetic was observed. Thus, the main advantage of the coating is the stability of the photocatalysts and the better performance in acidic or alkaline solutions. Compared to ZnO the maximum apparent rate constant is obtained at pH 8.5 (pH 11.5 in case of bare ZnO). Moreover, the Langmuir adsorption model was applied to describe the equilibrium isotherm at different MB concentration. The applicability of the Langmuir isotherm suggests monolayer coverage of the MB onto surface of silica-coating ZnO nanoparticles. The kinetics of the adsorption with respect to the initial dye concentration, were also investigated. The pseudo-first-order and second-order kinetic models were used and the rate constants were evaluated. The kinetic studies revealed that the pseudo-second-order kinetic model better represented the adsorption kinetics, suggesting that the adsorption process may be chemisorption.

Ismail, L. F. M.; Emara, M. M.; El-Moselhy, M. M.; Maziad, N. A.; Hussein, O. K.

2014-10-01

110

Cerium Oxide Nanoparticles Impact Yield and Modify Nutritional Parameters in Wheat (Triticum aestivum L.).  

PubMed

The implications of engineered nanomaterials on crop productivity and food quality are not yet well understood. The impact of cerium oxide nanoparticles (nCeO2) on growth and yield attributes and nutritional composition in wheat (Triticum aestivum L.) was examined. Wheat was cultivated to grain production in soil amended with 0, 125, 250, and 500 mg of nCeO2/kg (control, nCeO2-L, nCeO2-M, and nCeO2-H, respectively). At harvest, grains and tissues were analyzed for mineral, fatty acid, and amino acid content. Results showed that, relative to the control, nCeO2-H improved plant growth, shoot biomass, and grain yield by 9.0%, 12.7%, and 36.6%, respectively. Ce accumulation in roots increased at increased nCeO2 concentration but did not change across treatments in leaves, hull, and grains, indicating a lack of Ce transport to the above-ground tissues. nCeO2 modified S and Mn storage in grains. nCeO2-L modified the amino acid composition and increased linolenic acid by up to 6.17% but decreased linoleic acid by up to 1.63%, compared to the other treatments. The findings suggest the potential of nanoceria to modify crop physiology and food quality with unknown consequences for living organisms. PMID:25220448

Rico, Cyren M; Lee, Sang Chul; Rubenecia, Rosnah; Mukherjee, Arnab; Hong, Jie; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

2014-10-01

111

Sorption of selenate on soils and pure phases: kinetic parameters and stabilisation.  

PubMed

This study was conducted to identify the principle selenate carrier phases for two selected soils, by comparing their reactivity with selenate to that of pure phases of the solids. Silica, calcium carbonate, aluminium hydroxide, goethite, bentonite and humic acid were selected as the main soil carrier phases. Comparisons were made first on the parameter values obtained with the best fit of a kinetic sorption model which can discriminate instantaneous sorption from kinetically limited sorption. Then comparisons were made of the ability for each solid to stabilise selenate by measuring the ratio of the partition coefficient for sorption (Kd(sorption)) over that of the desorption (Kd(desorption)). Kinetics and stabilisation were used to help elucidate the nature of interactions with the test solid phases for a large range of selenate concentrations. The experiments were conducted over 165 h in batch reactors, the solid being isolated from the solution by dialysis tubing, at two pH (5.4 and 8) and three selenate concentrations (1 × 10(-3), 1 × 10(-6) and 1 × 10(-8) mol L(-1)). The results obtained showed that only aluminium hydroxide can sorb selenate throughout the studied pH range (pH 5.4 to 8.0). The sorption capacity on this mineral was high (Kd(sorption) > 100 to 1 × 10(4) L kg(-1)) and the selenate was mainly stabilized by the formation of inner sphere complexes. The sorption on goethite occurred at pH 5.4 (Kd(sorption) 52 L kg(-1)), mainly as outer sphere complexes, and was null at pH 8. On silica, a weak sorption was observed only at pH 5.4 and at 165 h (Kd(sorption) 4 L kg(-1)). On bentonite, calcium carbonate and humic acid no significant sorption was observed. Concerning the two soils studied, different behaviours were observed for selenate. For soil Ro (pH 5.4), Kd(sorption) was low (8 L kg(-1)) compared to soil Bu (pH 8) (70 L kg(-1)). The sorption behaviour of selenate on soil Ro was mainly due to outer sphere complexes, as for goethite, whereas for soil Bu the sorption was mainly attributed to inner sphere complexes followed by reduction mechanisms, probably initiated by microorganisms, in which no steady state was reached at the end of the 165 h experiments. The sorption of selenate decreased when concentrations reached 1 × 10(-3) mol L(-1), due to solid saturation, except for aluminium hydroxide. Reduction of selenate seemed also to occur on goethite and soil Ro, for the same concentration, but without preventing a decrease in sorption. Thus, this work shows that the comparison of selenate behaviour between soil and pure phases helps to elucidate the main carrier phases and sorption mechanisms in soil. PMID:21683486

Loffredo, N; Mounier, S; Thiry, Y; Coppin, F

2011-09-01

112

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 (K I), volume of distribution (V d) 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 (K I-k 4) as well as macro parameters, such as volume of distribution (Vd) and binding potential (BP I & BP II) 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

113

Kinetic parameters for nutrient enhanced crude oil biodegradation in intertidal marine sediments  

PubMed Central

Availability of inorganic nutrients, particularly nitrogen and phosphorous, is often a primary control on crude oil hydrocarbon degradation in marine systems. Many studies have empirically determined optimum levels of inorganic N and P for stimulation of hydrocarbon degradation. Nevertheless, there is a paucity of information on fundamental kinetic parameters for nutrient enhanced crude oil biodegradation that can be used to model the fate of crude oil in bioremediation programmes that use inorganic nutrient addition to stimulate oil biodegradation. Here we report fundamental kinetic parameters (Ks and qmax) for nitrate- and phosphate-stimulated crude oil biodegradation under nutrient limited conditions and with respect to crude oil, under conditions where N and P are not limiting. In the marine sediments studied, crude oil degradation was limited by both N and P availability. In sediments treated with 12.5 mg/g of oil but with no addition of N and P, hydrocarbon degradation rates, assessed on the basis of CO2 production, were 1.10 ± 0.03 ?mol CO2/g wet sediment/day which were comparable to rates of CO2 production in sediments to which no oil was added (1.05 ± 0.27 ?mol CO2/g wet sediment/day). When inorganic nitrogen was added alone maximum rates of CO2 production measured were 4.25 ± 0.91 ?mol CO2/g wet sediment/day. However, when the same levels of inorganic nitrogen were added in the presence of 0.5% P w/w of oil (1.6 ?mol P/g wet sediment) maximum rates of measured CO2 production increased more than four-fold to 18.40 ± 1.04 ?mol CO2/g wet sediment/day. Ks and qmax estimates for inorganic N (in the form of sodium nitrate) when P was not limiting were 1.99 ± 0.86 ?mol/g wet sediment and 16.16 ± 1.28 ?mol CO2/g wet sediment/day respectively. The corresponding values for P were 63 ± 95 nmol/g wet sediment and 12.05 ± 1.31 ?mol CO2/g wet sediment/day. The qmax values with respect to N and P were not significantly different (P < 0.05). When N and P were not limiting Ks and qmax for crude oil were 4.52 ± 1.51 mg oil/g wet sediment and 16.89 ± 1.25 ?mol CO2/g wet sediment/day. At concentrations of inorganic N above 45 ?mol/g wet sediment inhibition of CO2 production from hydrocarbon degradation was evident. Analysis of bacterial 16S rRNA genes indicated that Alcanivorax spp. were selected in these marine sediments with increasing inorganic nutrient concentration, whereas Cycloclasticus spp. were more prevalent at lower inorganic nutrient concentrations. These data suggest that simple empirical estimates of the proportion of nutrients added relative to crude oil concentrations may not be sufficient to guarantee successful crude oil bioremediation in oxic beach sediments. The data we present also help define the maximum rates and hence timescales required for bioremediation of beach sediments. PMID:24782848

Singh, Arvind K.; Sherry, Angela; Gray, Neil D.; Jones, D. Martin; Bowler, Bernard F. J.; Head, Ian M.

2014-01-01

114

Determination of char combustion kinetics parameters: Comparison of point detector and imaging-based particle-sizing pyrometry  

NASA Astrophysics Data System (ADS)

In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption kinetics. The performance of the specialized systems is compared for two different combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles' burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%-30% are recommended for kinetic rate measurements on 100 ?m particles.

Schiemann, Martin; Geier, Manfred; Shaddix, Christopher R.; Vorobiev, Nikita; Scherer, Viktor

2014-07-01

115

Determination of char combustion kinetics parameters: comparison of point detector and imaging-based particle-sizing pyrometry.  

PubMed

In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption kinetics. The performance of the specialized systems is compared for two different combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles' burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%-30% are recommended for kinetic rate measurements on 100 ?m particles. PMID:25085180

Schiemann, Martin; Geier, Manfred; Shaddix, Christopher R; Vorobiev, Nikita; Scherer, Viktor

2014-07-01

116

ITC recommendations for transporter kinetic parameter estimation and translational modeling of transport-mediated PK and DDIs in humans.  

PubMed

This white paper provides a critical analysis of methods for estimating transporter kinetics and recommendations on proper parameter calculation in various experimental systems. Rational interpretation of transporter-knockout animal findings and application of static and dynamic physiologically based modeling approaches for prediction of human transporter-mediated pharmacokinetics and drug-drug interactions (DDIs) are presented. The objective is to provide appropriate guidance for the use of in vitro, in vivo, and modeling tools in translational transporter science. PMID:23588311

Zamek-Gliszczynski, M J; Lee, C A; Poirier, A; Bentz, J; Chu, X; Ellens, H; Ishikawa, T; Jamei, M; Kalvass, J C; Nagar, S; Pang, K S; Korzekwa, K; Swaan, P W; Taub, M E; Zhao, P; Galetin, A

2013-07-01

117

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

118

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

119

Determination of kinetic parameters of 1,3-propanediol fermentation by Clostridium diolis using statistically optimized medium.  

PubMed

1,3-propanediol (1,3-PD) is a chemical compound of immense importance primarily used as a raw material for fiber and textile industry. It can be produced by the fermentation of glycerol available abundantly as a by-product from the biodiesel plant. The present study was aimed at determination of key kinetic parameters of 1,3-PD fermentation by Clostridium diolis. Initial experiments on microbial growth inhibition were followed by optimization of nutrient medium recipe by statistical means. Batch kinetic data from studies in bioreactor using optimum concentration of variables obtained from statistical medium design was used for estimation of kinetic parameters of 1,3-PD production. Direct use of raw glycerol from biodiesel plant without any pre-treatment for 1,3-PD production using this strain investigated for the first time in this work gave results comparable to commercial glycerol. The parameter values obtained in this study would be used to develop a mathematical model for 1,3-PD to be used as a guide for designing various reactor operating strategies for further improving 1,3-PD production. An outline of protocol for model development has been discussed in the present work. PMID:22331102

Kaur, Guneet; Srivastava, Ashok K; Chand, Subhash

2012-09-01

120

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

121

How is the Monoclonal Antibodies Kinetic Affected by Changes of Their Physical Parameters?  

E-print Network

The study of monoclonal antibodies (MAb) is a field of great interest to science medicine, for example, anti-TNF agents (infliximab and adalimumab) represent an important tool for the management of autoimmune and inflammatory disorders. In this work we focus on the physical description of the transport kinetics of MAb in a fluid with laminar flow and parabolic profile. To simulate the kinetics of the MAb, standard equations were solved numerically (using The Verlet algorithm) to calculate the motion of a particle with a spherically symmetric inside of parabolic laminar flow, in order to find the time evolution of the antibody velocity in blood plasma in function of the increase of the radius, mass and density of the MAb, and the fluid pressure in blood vessels. In the case of we fixed the value of the antibody density, their kinetics increased when the pressure in the vessels increased. When we fixed the pressure in the vessels we found: if we reduce the antibody radius their kinetics increased, and when we i...

Delgado-Correal, Camilo; Lizarazo-Pérez, Heidy Alexandra

2010-01-01

122

N,S-Dimethyldithiocarbamyl oxalates as precursors for determining kinetic parameters for oxyacyl radicals.  

PubMed

N,S-Dimethyldithiocarbamyl oxalates (e.g., ) are novel, readily prepared precursors to alkyloxyacyl radicals that are more suitable for kinetic studies than existing precursors; has allowed the determination of accurate rate data for the cyclization of the butenyloxyacyl radical 5 (kc = 1.2 × 10(7) s(-1) at 21 °C). PMID:25171586

Kyne, Sara H; Schiesser, Carl H

2014-09-16

123

Application of lab derived kinetic biodegradation parameters at the field scale  

Microsoft Academic Search

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

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

2003-01-01

124

Remote plasma-enhanced CVD of silicon: Reaction kinetics as a function of growth parameters  

Microsoft Academic Search

The reaction kinetics in Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD) have been studied for a chamber pressure\\u000a of 200 mTorr, rf powers between 4 and 8 W, diluted silane flow rates between 5 and 40 sccm, and temperatures between 190 and\\u000a 480 C. The observed temperature dependence of growth rate reveals a change in activation energy at 300–325 C, suggesting

B. Anthony; T. Hsu; L. Breaux; R. Qian; S. Banerjee; A. Tasch

1990-01-01

125

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

126

The association of fiber quality parameters and lint yield components of the F3 derived F4 progeny of two upland cotton populations  

E-print Network

parameters, determined by high volume instrument, were: micronaire, upper half mean fiber length (UHM), unifon-nity index (UI), fiber strength, and elongation. Within-boll yield components, determined by direct measurements or through calculations included...

Basal, Huseyin

2012-06-07

127

Model of 2,3-bisphosphoglycerate metabolism in the human erythrocyte based on detailed enzyme kinetic equations: equations and parameter refinement.  

PubMed Central

Over the last 25 years, several mathematical models of erythrocyte metabolism have been developed. Although these models have identified the key features in the regulation and control of erythrocyte metabolism, many important aspects remain unexplained. In particular, none of these models have satisfactorily accounted for 2,3-bisphosphoglycerate (2,3-BPG) metabolism. 2,3-BPG is an important modulator of haemoglobin oxygen affinity, and hence an understanding of the regulation of 2,3-BPG concentration is important for understanding blood oxygen transport. A detailed, comprehensive, and hence realistic mathematical model of erythrocyte metabolism is presented that can explain the regulation and control of 2,3-BPG concentration and turnover. The model is restricted to the core metabolic pathways, namely glycolysis, the 2,3-BPG shunt and the pentose phosphate pathway (PPP), and includes membrane transport of metabolites, the binding of metabolites to haemoglobin and Mg(2+), as well as pH effects on key enzymic reactions and binding processes. The model is necessarily complex, since it is intended to describe the regulation and control of 2,3-BPG metabolism under a wide variety of physiological and experimental conditions. In addition, since H(+) and blood oxygen tension are important external effectors of 2,3-BPG concentration, it was important that the model take into account the large array of kinetic and binding phenomena that result from changes in these effectors. Through an iterative loop of experimental and simulation analysis many values of enzyme-kinetic parameters of the model were refined to yield close conformity between model simulations and 'real' experimental data. This iterative process enabled a single set of parameters to be found which described well the metabolic behaviour of the erythrocyte under a wide variety of conditions. PMID:10477269

Mulquiney, P J; Kuchel, P W

1999-01-01

128

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

129

Kinetic parameters obtained from area integration of single peak thermal desorption spectra  

Microsoft Academic Search

This paper presents a method to analyze thermal desorption spectra based on area integration of the desorption peaks. An expression is derived for the rate of desorption in a thermal-activated process which permits evaluation of the rate from the intensity and area values for each point of the curve. Arrhenius plots of the rate data yield the activation energy and

A. L. Cabrera

1990-01-01

130

Kinetics of the reaction OH (v equals 0) plus O3 yields HO2 plus O2  

NASA Technical Reports Server (NTRS)

The rate constant (kl) of the reaction OH(v=o) + O3 yields HO2 + O2 measured over the temperature range 220 to 450 K at total pressures between 2 and 5 torr using ultraviolet fluorescent scattering for the detection of OH radicals. An Arrhenius expression was obtained, and the rate constant for the reaction HO2 + O3 yields OH + 2O2 was inferred to be less than 0.1 kl over the entire temperature interval.

Anderson, J. G.; Kaufman, F.

1973-01-01

131

Pion yield studies for proton drive beams of 2-8 GeV kinetic energy for stopped  

E-print Network

spectrometer data vs MARS models. Pion kinetic energy of 40 MeV corresponds to momentum of 113 MeV/c #12;HARP #12;MARS - dash-dotted lines #12;#12;#12;HARP collaboration conclusion #12;#12;HARP vs HARP-CDP #12- dependence of each fireball) #12;Two-fireball model vs HARP data Large angles only - 2/ndf =0.94 All angles

McDonald, Kirk

132

Kinetics and yields of OH radical from the CH 3OCH 2 + O 2 reaction using a new photolytic source  

Microsoft Academic Search

The methoxymethyl radical, CH3OCH2, formed from the photodissociation of CH3OCH2Br at 248nm, was observed to form OH on reaction with O2. The kinetics of OH formation were measured as a function of pressure at 295K using this new photolytic methoxymethyl radical precursor, detecting OH by LIF, giving rate coefficients in good agreement with the literature values for CH3OCH2+O2 (R2). This

A. J. Eskola; S. A. Carr; M. A. Blitz; M. J. Pilling; P. W. Seakins

2010-01-01

133

Enzymatic esterification in organic media: role of water and organic solvent in kinetics and yield of butyl butyrate synthesis  

Microsoft Academic Search

The respective roles of organic solvent and of water in butyl butyrate synthesis from n-butanol and n-butyric acid in n-hexane by Mucor miehei lipase have been investigated by analysis of the kinetics and the reaction balances. Esterificaton was found to take place in both low water systems containing solid enzyme in hexane and in biphasic aqueous enzyme solution\\/hexane systems. In

Frédéric Monot; Frédérique Borzeix; Marc Bardin; Jean-Paul Vandecasteele

1991-01-01

134

A compilation of kinetic parameters for the thermal degradation of n-alkane molecules  

Microsoft Academic Search

A list of several hundred free-radical reactions which occur during the low temperature (700–850 K) pyrolysis of small n-alkane molecules has been assembled and a set of reliable, self-consistent Arrhenius rate parameters has been assigned on the basis of experiment, theory, thermochemical estimates and structural analogy. Rate parameters have been recommended for the following types of reactions, with the number

D. L. Allara; Robert Shaw

1980-01-01

135

A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O  

NASA Technical Reports Server (NTRS)

Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

Wine, P. H.; Semmes, D. H.; Ravishankara, A. R.

1981-01-01

136

Yield and kinetic constants estimation in the production of hydroxy fatty acids from oleic acid in a bioreactor by Pseudomonas aeruginosa 42A2.  

PubMed

We modelled the production of hydroxy fatty acids from oleic acid by Pseudomonas aeruginosa 42A2 in a bioreactor with a non-dispersive aeration system. First, we designed an adapted wetted-wall gas-absorption column, offering a k La value of 39.9 h(-1), to enhance oxygen absorption in the culture media and prevent foam formation. Then, we analysed different kinetic models to simulate the yield coefficients and the kinetic constants in this bacterial transformation. Monod model fitting (? max1?=?0.51 h(-1), K S1?=?1.60 C-mol l(-1), ? max2?=?0.12 h(-1), K S2?=?0.035 C-mol l(-1), and k 2?=?0.033 h(-1)) showed a good accuracy with the experimental data sets and was chosen for its simplicity. Lastly, mass balances were carried out to establish the stoichiometry of this biotransformation with the following yield coefficients, ? X/OA, ? X/(10S)-HPOME and ? (10S)-HPOME/(7S10S)-HPOME of 0.172, 0.347 and 2.388 C-mol C-mol(-1), respectively. PMID:25193418

Martin-Arjol, Ignacio; Llacuna, Joan Llorens; Manresa, Angeles

2014-12-01

137

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

138

Compilation of Kinetic Parameters for the Thermal Degradation of n-Alkane Molecules.  

National Technical Information Service (NTIS)

A list of several hundred free-radical reactions which occur during the low temperature (700-850 K) pyrolysis of small n-alkane molecules has been assembled and a set of reliable, self-consistent Arrhenius rate parameters has been assigned on the basis of...

D. L. Allara, R. Shaw

1980-01-01

139

Characteristic parameter method for studying kinetics of opposing reactions in calorimeter  

Microsoft Academic Search

According to the theoretical basis of thermokinetics, the integral and differential thermokinetic equations of opposing reactions have been derived, and a novel thermokinetic research method, the characteristic parameter method for opposing reactions which taking place in a batch conduction calorimeter under isothermal condition, has been proposed in this paper. Only needing the characteristic thermoanalytical data corresponding to tm and 2tm

Y. Chen; H. Yan; B. Zhang; X. C. Zeng

2002-01-01

140

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

141

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. PMID:16348175

Fox, Peter; Suidan, Makram T.

1990-01-01

142

Treatment of biodiesel wastewater by adsorption with commercial chitosan flakes: parameter optimization and process kinetics.  

PubMed

The possibility of using commercial chitosan flakes as an adsorbent for the removal of pollutants from biodiesel wastewater was evaluated. The effect of varying the adsorption time (0.5-5 h), initial wastewater pH (2-8), adsorbent dose (0.5-5.5 g/L) and mixing rate (120-350 rpm) on the efficiency of pollutant removal was explored by univariate analysis. Under the derived optimal conditions, greater than 59.3%, 87.9% and 66.2% of the biological oxygen demand (BOD), chemical oxygen demand (COD) and oil & grease, respectively, was removed by a single adsorption. Nevertheless, the remaining BOD, COD and oil & grease were still higher than the acceptable Thai government limits for discharge into the environment. When the treatment was repeated, a greater than 93.6%, 97.6% and 95.8% removal of the BOD, COD and oil & grease, respectively, was obtained. The reusability of commercial chitosan following NaOH washing (0.05-0.2 M) was not suitable, with less than 40% efficiency after just one recycling and declining rapidly thereafter. The adsorption kinetics of all pollutant types by the commercial chitosan flakes was controlled by a mixed process of diffusion and adsorption of the pollutants during the early treatment period (0-1.5 h) and then solely controlled by adsorption after 2 h. PMID:24412591

Pitakpoolsil, Wipawan; Hunsom, Mali

2014-01-15

143

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. PMID:10920029

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

2000-01-01

144

Photooxidative degradation of Acid Red 27 (AR27): modeling of reaction kinetic and influence of operational parameters.  

PubMed

The decolorization and mineralization of Acid Red 27 (AR27), an anionic monoazo dye of acid class, were studied by UV/H202 process in laboratory and real samples. Effects of different process parameters such as initial H2O2 and AR27 concentrations, pH and EtOH as an electron scavenger have been studied. H2O2 and UV light have a negligible effect when they were used on their own. The decolorization rate follows pseudo-first order kinetic with respect to the dye concentration. The rate constant of the attack of *OH radicals to the AR27 has been estimated through the adoption of a simplified kinetic model (1.03 x 10(8)M(-1)s(-1)). This model allows predicting the pseudo-first order rate constant and concentration of AR27 in different illumination times for different initial concentrations of H2O2. Mineralization studies showed, the formation of sulfate ions, the decrease of pH and 85% of COD reduction occur in less than 60 min. In the real wastewater color removal could be achieved after only 75 min, whereas 45% of COD reduction occurs after 105 min of illumination. PMID:15478925

Daneshvar, Nezameddin; Rabbani, Mohammad; Modirshahla, Nasser; Behnajady, Mohammad-Ali

2004-01-01

145

Modeling and estimation of kinetic parameters and replicative fitness of HIV-1 from flow-cytometry-based growth competition experiments.  

PubMed

Growth competition assays have been developed to quantify the relative fitness of HIV-1 mutants. In this article, we develop mathematical models to describe viral/cellular dynamic interactions in the assay system from which the competitive fitness indices or parameters are defined. In our previous HIV-viral fitness experiments, the concentration of uninfected target cells was assumed to be constant (Wu et al. 2006). But this may not be true in some experiments. In addition, dual infection may frequently occur in viral fitness experiments and may not be ignorable. Here, we relax these two assumptions and extend our earlier viral fitness model (Wu et al. 2006). The resulting models then become nonlinear ODE systems for which closed-form solutions are not achievable. In the new model, the viral relative fitness is a function of time since it depends on the target cell concentration. First, we studied the structure identifiability of the nonlinear ODE models. The identifiability analysis showed that all parameters in the proposed models are identifiable from the flow-cytometry-based experimental data that we collected. We then employed a global optimization approach (the differential evolution algorithm) to directly estimate the kinetic parameters as well as the relative fitness index in the nonlinear ODE models using nonlinear least square regression based on the experimental data. Practical identifiability was investigated via Monte Carlo simulations. PMID:18648886

Miao, Hongyu; Dykes, Carrie; Demeter, Lisa M; Cavenaugh, James; Park, Sung Yong; Perelson, Alan S; Wu, Hulin

2008-08-01

146

Determination of kinetic parameters of crystal growth rate of borax in aqueous solution by using the rotating disc technique  

NASA Astrophysics Data System (ADS)

Growth rate of polycrystalline disc of borax compressed at different pressure and rotated at various speed has been measured in a rotating disc crystallizer under well-defined conditions of supersaturation. It was found that the mass transfer coefficient, K, increased while overall growth rate constant, Kg, and surface reaction constant, kr, decreased with increasing smoothness of the disc. It was also determined that kinetic parameters (kr,r,K,g) of crystal growth rate of borax decreased with increasing rotating speed of the polycrystalline disc. The effectiveness factor was calculated from the growth rate data to evaluate the relative magnitude of the steps in series bulk diffusion through the mass transfer boundary layer and the surface integration. At low rotating speed of disc, the crystal growth rate of borax is mainly controlled by integration. However, both diffusion and integration steps affect the growth rate of borax at higher rotating speed of polycrystalline disc.

Sahin, Omer; Aslan, Fevzi; Ozdemir, Mustafa; Durgun, Mustafa

2004-10-01

147

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

148

Differences between elite, junior and non-rowers in kinematic and kinetic parameters during ergometer rowing.  

PubMed

This paper presents an analysis of the rowing parameters of differently skilled rowers. The study focuses on technique dependency on stroke rate. Five elite, five junior and five non-rowers participated, and the biomechanics of rowing on an ergometer was analyzed at stroke rates of 20, 26 and 34 str/min. The results show that elite rowers use a similar, consistent rowing technique at all stroke rates, the technique of junior rowers follows similar principles, while the technique of non-rowers varies. Elite rowers' stroke length, handle motion and body posture do not change with stroke rate while the ratio of stroke phases, maximum forces, stroke work and joint loadings are constant at the same stroke rate but dependent on stroke rate. Junior rowers with stroke rate change also the stroke length. In non-rowers the differences can be observed in the handle motion and body posture during the stroke, their stroke length changes with stroke rate while the ratio of stroke phases stays constant. Although different movement execution is evident and variable with stroke rate, non-rowers demonstrate a consistent pattern at the same stroke rate. On the basis of the results, the crucial parameters that differentiate elite, junior, and non-rowers are identified. PMID:23756001

Cerne, Tomaž; Kamnik, Roman; Vesnicer, Boštjan; Zganec Gros, Jerneja; Munih, Marko

2013-08-01

149

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

2010-10-01

150

Micropollutant biotransformation kinetics associate with WWTP process parameters and microbial community characteristics.  

PubMed

The objective of this work was to identify relevant wastewater treatment plant (WWTP) parameters and underlying microbial processes that influence the biotransformation of a diverse set of micropollutants. To do this, we determined biotransformation rate constants for ten organic micropollutants in batch reactors seeded with activated sludge from ten diverse WWTPs. The estimated biotransformation rate constants for each compound ranged between one and four orders of magnitude among the ten WWTPs. The biotransformation rate constants were tested for statistical associations with various WWTP process parameters, amoA transcript abundance, and acetylene-inhibited monooxygenase activity. We determined that (i) ammonia removal associates with oxidative micropollutant biotransformation reaction rates; (ii) archaeal but not bacterial amoA transcripts associate with both ammonia removal and oxidative micropollutant biotransformation reaction rates; and (iii) the activity of acetylene-inhibited monooxygenases (including ammonia monooxygenase) associates with ammonia removal and the biotransformation rate of isoproturon, but does not associate with all oxidative micropollutant biotransformations. In combination, these results lead to the conclusion that ammonia removal and amoA transcript abundance can potentially be predictors of oxidative micropollutant biotransformation reactions, but that the biochemical mechanism is not necessarily linked to ammonia monooxygenase activity. PMID:22938719

Helbling, Damian E; Johnson, David R; Honti, Mark; Fenner, Kathrin

2012-10-01

151

Pharmacokinetic and Pharmacodynamic Parameters for Antimicrobial Effects of Cefotaxime and Amoxicillin in an In Vitro Kinetic Model  

PubMed Central

An in vitro kinetic model was used to study the relation between pharmacokinetic and pharmacodynamic (PK-PD) parameters for antimicrobial effect, e.g., the time above MIC (T>MIC), maximum concentration in serum (Cmax), and area under the concentration-time curve (AUC). Streptococcus pyogenes and Escherichia coli were exposed to cefotaxime, and the activity of amoxicillin against four strains of Streptococcus pneumoniae with different susceptibilities to penicillin was studied. The drug elimination rate varied so that the T>MIC ranged from 20 to 100% during 24 h, while the AUC and/or the initial concentration (Cmax) were kept constant. For S. pyogenes and E. coli, the maximal antimicrobial effect (Emax) at 24 h occurred when the antimicrobial concentration exceeded the MIC for 50 and 80% of the strains tested, respectively. The penicillin-susceptible pneumococci (MIC, 0.03 mg/liter) and the penicillin-intermediate strain (MIC, 0.25 mg/liter) showed maximal killing by amoxicillin at a T>MIC of 50%. For a strain for which the MIC was 2 mg/liter, Cmax needed to be increased to achieve the Emax. Under the condition that Cmax was 10 times the MIC, Emax was obtained at a T>MIC of 60%, indicating that Cmax, in addition to T>MIC, may be an important parameter for antimicrobial effect on moderately penicillin-resistant pneumococci. For the strain for which the MIC was 4 mg/liter, the reduction of bacteria varied from ?0.4 to ?3.6 log10 CFU/ml at a T>MIC of 100%, despite an initial antimicrobial concentration of 10 times the MIC. Our studies have shown that the in vitro kinetic model is a useful complement to animal models for studying the PK-PD relationship for antimicrobial effect of antibiotics. PMID:11502511

Gustafsson, I.; Lowdin, E.; Odenholt, I.; Cars, O.

2001-01-01

152

Picosecond decay kinetics and quantum yield of fluorescence of the photoactive yellow protein from the halophilic purple phototrophic bacterium, Ectothiorhodospira halophila.  

PubMed

The photoactive yellow protein (PYP) has been previously shown to be partially bleached and red shifted (in less than 10 ns) by a pulse of laser excitation at the wavelength maximum (445 nm), to further bleach (k = 7.5 x 10(3) s(-1)), and then to slowly recover in the dark (k = 2.6 s(-1)) (Meyer, T. E., G. Tollin, J. H. Hazzard, and M. A. Cusanovich. 1989. Biophys. J. 56:559-564). The quantum yield for the formation of the fully bleached form was found to be 0.64. We have now shown that the yellow protein is weakly fluorescent with an emission maximum at 495 nm (which mirrors excitation at 445 nm) and a fluorescence quantum yield of 1.4 x 10(-3). Measurement of the picosecond kinetics of the fluorescence decay shows that approximately 90% of the emission occurs with a lifetime of 12 ps. This is in good agreement with the quantum yield determination, which suggests that a single quenching process (presumably the photochemical event) is primarily responsible for the excited state decay. The lifetime of the excited state of PYP is remarkably similar to that for the rise of the first photochemical intermediate of bacteriorhodopsin, and underscores the fundamental similarity in their photocycles despite a lack of structural relationship. PMID:19431791

Meyer, T E; Tollin, G; Causgrove, T P; Cheng, P; Blankenship, R E

1991-05-01

153

The effect of sustained static kneeling on kinetic and kinematic knee joint gait parameters.  

PubMed

Despite epidemiological evidence for kneeling as an occupational risk factor for knee osteoarthritis, biomechanical evidence is lacking. Gait knee joint mechanics, a common measure used to study knee osteoarthritis initiation, were used in the present study to investigate the effect of sustained static kneeling on the knee. Ten healthy male subjects (24.1 years ± 3.5) performed ten baseline walking trials, followed by a 30-min kneeling protocol and a second set of walking trials. Knee joint moments and angles were calculated during the stance phase. Within-subject root mean squared differences were compared within and between the pre- and post-kneeling gait trials. Differences were observed between the pre-kneeling and post-kneeling walking trails for flexion and adduction knee moments (0.12 Nm/kg ± 0.03, 0.07 Nm/kg ± 0.02) and angles (3.18° ± 1.22 and 1.64° ± 1.15), indicating that sustained static deep-knee flexion kneeling does acutely alter knee joint gait parameters. PMID:25172306

Kajaks, Tara; Costigan, Patrick

2015-01-01

154

Interactive Effects of Elevated CO2 Concentration and Irrigation on Photosynthetic Parameters and Yield of Maize in Northeast China  

PubMed Central

Maize is one of the major cultivated crops of China, having a central role in ensuring the food security of the country. There has been a significant increase in studies of maize under interactive effects of elevated CO2 concentration ([CO2]) and other factors, yet the interactive effects of elevated [CO2] and increasing precipitation on maize has remained unclear. In this study, a manipulative experiment in Jinzhou, Liaoning province, Northeast China was performed so as to obtain reliable results concerning the later effects. The Open Top Chambers (OTCs) experiment was designed to control contrasting [CO2] i.e., 390, 450 and 550 µmol·mol?1, and the experiment with 15% increasing precipitation levels was also set based on the average monthly precipitation of 5–9 month from 1981 to 2010 and controlled by irrigation. Thus, six treatments, i.e. C550W+15%, C550W0, C450W+15%, C450W0, C390W+15% and C390W0 were included in this study. The results showed that the irrigation under elevated [CO2] levels increased the leaf net photosynthetic rate (Pn) and intercellular CO2 concentration (Ci) of maize. Similarly, the stomatal conductance (Gs) and transpiration rate (Tr) decreased with elevated [CO2], but irrigation have a positive effect on increased of them at each [CO2] level, resulting in the water use efficiency (WUE) higher in natural precipitation treatment than irrigation treatment at elevated [CO2] levels. Irradiance-response parameters, e.g., maximum net photosynthetic rate (Pnmax) and light saturation points (LSP) were increased under elevated [CO2] and irrigation, and dark respiration (Rd) was increased as well. The growth characteristics, e.g., plant height, leaf area and aboveground biomass were enhanced, resulting in an improved of yield and ear characteristics except axle diameter. The study concluded by reporting that, future elevated [CO2] may favor to maize when coupled with increasing amount of precipitation in Northeast China. PMID:24848097

Meng, Fanchao; Zhang, Jiahua; Yao, Fengmei; Hao, Cui

2014-01-01

155

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

156

Measurement of spin transfer parameters in the p-bar p yields n-bar n charge-exchange reaction at LEAR.  

National Technical Information Service (NTIS)

The experiment PS199 at LEAR investigates the spin structure of the charge-exchange reaction p-bar p yields n-bar n. Data for the measurement of the spin transfer parameters for both neutron and antineutron were collected during 1990 and preliminary resul...

J. Arvieux, M. Agnello, A. Ahmidouch, M. Lamanna

1991-01-01

157

Determination of bacterial and viral transport parameters in a gravel aquifer assuming linear kinetic sorption and desorption  

NASA Astrophysics Data System (ADS)

The bacteria Escherichia coli and Pseudomonas putida, and the bacteriophage virus H40/1 are examined both for their transport behaviour relative to inert solute tracers and for their modelability under natural flow conditions in a gravel aquifer. The microbes are attenuated in the following sequence: H40/1? P. putida? E. coli. The latter is desorbed almost completely within a few days. Breakthrough and recovery curves of the simultaneously injected non-reactive tracers are simulated with the 2D and 1D dispersion equation, in order to ascertain longitudinal dispersivity ( ?L) and mean flow time ( T0). Mathematical modelling is difficult due to the aquifer heterogeneity, which results in preferential flow paths between injection and observation wells. Therefore, any attempt of fitting the dispersion model (DM) to the entire inert-tracer breakthrough curve (BTC) fails. Adequate fitting of the model to measured data only succeeds using a DM consisting of a superposition of several BTCs, each representing another set of flow paths. This gives rise to a multimodal, rather than a Gaussian groundwater velocity distribution. Only hydraulic parameters derived from the fastest partial curve, which is fitted to the rising part of the Uranine BTC, are suitable to model microbial breakthroughs. The hydraulic parameters found using 2D and 1D models were nearly identical. Their values were put into an analytical solution of 1D advective-dispersive transport combined with two-site reaction model introduced by Cameron and Klute [Cameron, D.R., Klute, A., 1977. Convective-dispersive solute transport with a combined equilibrium and kinetic adsorption model. Water Resour. Res. 13, 183-189], in order to identify reactive transport parameters (sorption/desorption) and attenuation mechanisms for the microbes migration. This shows that the microbes are almost entirely transported through preferential flow paths, which are represented by the first partial curve. Inert tracers, however, also spread along less permeable pathways.

Mallén, G.; Maloszewski, P.; Flynn, R.; Rossi, P.; Engel, M.; Seiler, K.-P.

2005-05-01

158

Kinetics and product yields of the acetyl peroxy + HO2 radical reaction studied by photoionization mass spectrometry  

NASA Astrophysics Data System (ADS)

The acetyl peroxy radical (CH3C(O)O2) is a key intermediate in the oxidation of carbonyl-containing hydrocarbons in the troposphere. Reaction of acetyl peroxy radicals with HO2 has been suggested as a source of OH radicals in low-NOx environments. Previous work on this reaction observed only two product channels forming (1) peracetic acid and (2) acetic acid. Recent experiments have shown that there is a third channel that generates the radicals OH and acetoxy: CH3C(O)O2 + HO2 ? (1) CH3C(O)OOH + O2 (2) CH3C(O)OH + O3 (3) CH3C(O)O + O2 + OH This last pathway to OH formation would then contribute to the apparent isoprene OH recycling suggested by discrepancies between atmospheric models and field observations of OH. There have, however, been significant disagreements among experiments on the yield of OH from reaction of acetyl peroxy radicals with HO2. We report our preliminary studies of acetyl peroxy self-reaction and its reaction with HO2 at 298 K and 8 Torr. Experiments were conducted at the Advanced Light Source synchrotron at the Lawerence Berkeley National Laboratory using tunable VUV ionizing radiation coupled to the Sandia National Laboratory pulsed-laser-photolysis multiplexed photoionization mass spectrometer to detect the time- and isomer-resolved formation of radical intermediates and products. From these results, we report new branching fractions of the three product channels in the acetyl peroxy + HO2 radical reaction.

Dodson, L. G.; Shen, L.; Savee, J. D.; Eddingsaas, N. C.; Welz, O.; Taatjes, C. A.; Osborn, D. L.; Sander, S. P.; Okumura, M.

2013-12-01

159

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

2012-01-01

160

Parameter-induced uncertainty quantification of crop yields, soil N2O and CO2 emission for 8 arable sites across Europe using the LandscapeDNDC model  

NASA Astrophysics Data System (ADS)

When using biogeochemical models to estimate greenhouse gas emissions at site to regional/national levels, the assessment and quantification of the uncertainties of simulation results are of significant importance. The uncertainties in simulation results of process-based ecosystem models may result from uncertainties of the process parameters that describe the processes of the model, model structure inadequacy as well as uncertainties in the observations. Data for development and testing of uncertainty analisys were corp yield observations, measurements of soil fluxes of nitrous oxide (N2O) and carbon dioxide (CO2) from 8 arable sites across Europe. Using the process-based biogeochemical model LandscapeDNDC for simulating crop yields, N2O and CO2 emissions, our aim is to assess the simulation uncertainty by setting up a Bayesian framework based on Metropolis-Hastings algorithm. Using Gelman statistics convergence criteria and parallel computing techniques, enable multi Markov Chains to run independently in parallel and create a random walk to estimate the joint model parameter distribution. Through means distribution we limit the parameter space, get probabilities of parameter values and find the complex dependencies among them. With this parameter distribution that determines soil-atmosphere C and N exchange, we are able to obtain the parameter-induced uncertainty of simulation results and compare them with the measurements data.

Santabarbara, Ignacio; Haas, Edwin; Kraus, David; Herrera, Saul; Klatt, Steffen; Kiese, Ralf

2014-05-01

161

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

162

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

2013-01-01

163

Observations on the effect of process parameters on dioxin\\/furan yield in municipal waste and coal systems  

Microsoft Academic Search

Effects of fly ash loading; ash-borne, extractable organics; sulfur dioxide (SO2) and hydrogen chloride (HCl) concentration; and combustion quality on the formation of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD\\/F) were evaluated in pilot scale tests simulating municipal waste combustion and coal\\/waste co-combustion testing. Similar PCDD\\/F yields from reinjection of as-received and extracted fly ash injection along with testing under “poor

Brian K. Gullett; K. Raghunathan

1997-01-01

164

Genetic parameters for body weight, carcass chemical composition and yield in a broiler-layer cross developed for QTL mapping.  

PubMed

The objective of this study was to estimate genetic and phenotypic correlations of body weight at 6 weeks of age (BW6), as well as final carcass yield, and moisture, protein, fat and ash contents, using data from 3,422 F2 chickens originated from reciprocal cross between a broiler and a layer line. Variance components were estimated by the REML method, using animal models for evaluating random additive genetic and fixed contemporary group (sex, hatch and genetic group) effects. The heritability estimates (h(2)) for BW6, carcass yield and percentage of carcass moisture were 0.31 ± 0.07, 0.20 ± 0.05 and 0.33 ± 0.07, respectively. The h(2) for the percentages of protein, fat and ash on a dry matter basis were 0.48 ± 0.09, 0.55 ± 0.10 and 0.36 ± 0.08, respectively. BW6 had a positive genetic correlation with fat percentage in the carcass, but a negative one with protein and ash contents. Carcass yield, thus, appears to have only low genetic association with carcass composition traits. The genetic correlations observed between traits, measured on a dry matter basis, indicated that selection for carcass protein content may favor higher ash content and a lower percentage of carcass fat. PMID:21931515

Nunes, Beatriz do Nascimento; Ramos, Salvador Boccaletti; Savegnago, Rodrigo Pelicioni; Ledur, Mônica Corrêa; Nones, Kátia; Klein, Claudete Hara; Munari, Danísio Prado

2011-07-01

165

Olive oil pilot-production assisted by pulsed electric field: Impact on extraction yield, chemical parameters and sensory properties.  

PubMed

The impact of the use of pulsed electric field (PEF) technology on Arroniz olive oil production in terms of extraction yield and chemical and sensory quality has been studied at pilot scale in an industrial oil mill. The application of a PEF treatment (2kV/cm; 11.25kJ/kg) to the olive paste significantly increased the extraction yield by 13.3%, with respect to a control. Furthermore, olive oil obtained by PEF showed total phenolic content, total phytosterols and total tocopherols significantly higher than control (11.5%, 9.9% and 15.0%, respectively). The use of PEF had no negative effects on general chemical and sensory characteristics of the olive oil, maintaining the highest quality according to EU legal standards (EVOO; extra virgin olive oil). Therefore, PEF could be an appropriate technology to improve olive oil yield and produce EVOO enriched in human-health-related compounds, such as polyphenols, phytosterols and tocopherols. PMID:25149017

Puértolas, Eduardo; Martínez de Marañón, Iñigo

2015-01-15

166

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

167

A laser flash photolysis-resonance fluorescence kinetics study of the reaction Cl/2P/ + CH4 yields CH3 + HCl  

NASA Technical Reports Server (NTRS)

The technique of laser flash photolysis-resonance fluorescence is employed to study the kinetics of the reaction Cl(2P) + CH4 yields CH3 + HCl over the temperature range 221-375 K. At temperatures less than or equal to 241 K the apparent bimolecular rate constant is found to be dependent upon the identity of the chemically inert gases in the reaction mixture. For Cl2/CH4/He reaction mixtures (total pressure = 50 torr) different bimolecular rate constants are measured at low and high methane concentrations. For Cl2/CH4/CCl/He and Cl2/CH4/Ar reaction mixtures, the bimolecular rate constant is independent of methane concentration, being approximately equal to the rate constant measured at low methane concentrations for Cl2/CH4/He mixtures. These rate constants are in good agreement with previous results obtained using the discharge flow-resonance fluorescence and competitive chlorination techniques. At 298 K the measured bimolecular rate constant is independent of the identity of the chemically inert gases in the reaction mixture and in good agreement with all previous investigations. The low-temperature results obtained in this investigation and all previous investigations can be rationalized in terms of a model which assumes that the Cl(2P 1/2) state reacts with CH4 much faster than the Cl(2P 3/2) state. Extrapolation of this model to higher temperatures, however, is not straightforward.

Ravishankara, A. R.; Wine, P. H.

1980-01-01

168

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

169

Kinetic parameters of interstellar neutral helium. Review of results obtained during one solar cycle with the Ulysses/GAS-instrument  

NASA Astrophysics Data System (ADS)

The GAS-instrument onboard the space probe Ulysses is designed to measure the local angular distribution of the flow of interstellar neutral He-atoms within ?3 AU distance from the sun. It allows to infer the kinetic parameters (velocity vector, temperature and density) of these particles outside the heliosphere (``at infinity''). During three observational periods, 1990/1991, shortly after launch and during the two fast latitude scans of Ulysses, from 9/1994 to 8/1996 and from 9/2000 to 8/2002, more than 300 measurements of the distributions were obtained and analyzed in detail. Known issues that relate to the pointing accuracy of the detector and to the efficiency calibration along with their impact on the results are addressed in this paper. The average values, derived from these observations and their refined analysis, are the bulk speed (vHe?= 26.3 ± 0.4 km s-1), the flow direction (ecliptic longitude ?? = 74.7° ± 0.5°, ecliptic latitude ?? = -5.2° ± 0.2°) and temperature (THe? = 6300 K ± 340 K). From 1990 to 2002, covering a complete solar cycle, no significant temporal variations of these parameters were observed, nor variations with solar latitude. In contrast, in the density nHe?, derived from the series of local observations along the Ulysses-orbit, substantial apparent variations were seen. After a first attempt to explain these by an inadequate energy calibration of the efficiency they are now interpreted as variations in the loss processes (predominantly photo-ionization), which the neutral gas experiences along its trajectory to the observer. While the temporal variations of the ionization rate were taken into account using the measured solar EUV irradiance (from CELIAS/SEM on SOHO), the residual latitudinal variation has been attributed to a dependence of the solar irradiance on latitude, which thus far has not been accessible to direct observations. As a result of a simple model that includes these effects a density nHe?= 0.015 ± 0.003 cm-3 has been deduced, which is in good agreement with an independent result from pickup ion observations.

Witte, M.

2004-11-01

170

Voxel-based estimation of kinetic model parameters of the L-[1-11C]leucine PET method for determination of regional rates of cerebral protein synthesis: Validation and comparison with region-of-interest based methods  

PubMed Central

We adapted and validated a basis function method (BFM) to estimate at the voxel level parameters of the kinetic model of the L-[1-11C]leucine PET method and regional rates of cerebral protein synthesis (rCPS). In simulation at noise levels typical of voxel data, BFM yielded low bias estimates of rCPS; in measured data, BFM and nonlinear least squares parameter estimates were in good agreement. We also examined whether there are advantages to using voxel-level estimates averaged over regions of interest (ROI) in place of estimates obtained by directly fitting ROI time-activity curves (TACs). In both simulated and measured data, fits of ROI TACs were poor, likely due to tissue heterogeneity not taken into account in the kinetic model. In simulation, rCPS determined from fitting ROI TACs was substantially overestimated and BFM-estimated rCPS averaged over all voxels in a ROI was slightly underestimated. In measured data, rCPS determined by regional averaging of voxel estimates was lower than rCPS determined from ROI TACs, consistent with simulation. In both simulated and measured data, intersubject variability of BFM-estimated rCPS averaged over all voxels in a ROI was low. We conclude that voxelwise estimation is preferable to fitting ROI TACs with a homogeneous tissue model. PMID:19436319

Tomasi, Giampaolo; Bertoldo, Alessandra; Bishu, Shrinivas; Unterman, Aaron; Smith, Carolyn Beebe; Schmidt, Kathleen C

2009-01-01

171

Using Kaon Regeneration to Probe the Quark Mixing Parameter cos2{beta} in B {yields}{psi}K Decays  

SciTech Connect

We suggest a novel method to determine the sign of cos2{beta} in the decays B{yields}{psi}K , by creating interference between K{sub L} and K{sub S} final states via ''regeneration,'' that is propagation through a matter target region to convert some K{sub L} to K{sub S} . The determination of this quantity resolves an ambiguity between {beta} and 90{sup o}-{beta} that remains after the standard measurements of sin2{beta} and may turn out to be important in resolving whether the result is in agreement with standard model predictions or indicates the presence of new physics. We find the measurement is feasible at a B factory, but requires several years of high-luminosity running with a regeneration target affecting a significant fraction of the detector.

Quinn, Helen R.; Schietinger, Thomas; Silva, Joao P.; Snyder, Arthur E.

2000-12-18

172

A Procedure for the Joint Evaluation of Substrate Partitioning and Kinetic Parameters for Reactions Catalyzed by Enzymes in Reverse Micellar Solutions  

Microsoft Academic Search

A simple method useful for the joint evaluation of substrate partitioning and kinetic parameters for reactions catalyzed by enzymes entrapped in reverse micelles is proposed. The method is applied to the hydrolysis of 2-naphthyl acetate (2-NA) catalyzed by lipase in sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT)\\/buffer\\/heptane reverse micellar solutions. In the presence of micelles, the relationship between the initial reaction rate and

Luis Felipe Aguilar; Elsa Abuin; Eduardo Lissi

2001-01-01

173

Are the parameters of V O 2 , heart rate and muscle deoxygenation kinetics affected by serial moderate-intensity exercise transitions in a single day?  

Microsoft Academic Search

This study compared the parameter estimates of pulmonary oxygen uptake (VO2p), heart rate (HR) and muscle deoxygenation (?[HHb]) kinetics when several moderate-intensity exercise transitions (MODs)\\u000a were performed during a single visit versus several MODs performed during separate visits. Nine subjects (24 ± 5 years, mean ± SD)\\u000a each completed two successive cycling MODs on six occasions (1-6A and 1-6B) from 20 W to a work rate

Matthew D. Spencer; Juan M. Murias; Heather P. Lamb; John M. Kowalchuk; Donald H. Paterson

2011-01-01

174

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

2014-02-15

175

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

176

Alcoholysis catalyzed by Candida antarctica lipase B in a gas/solid system : effects of water on kinetic parameters  

E-print Network

1 Alcoholysis catalyzed by Candida antarctica lipase B in a gas/solid system : effects of water from Candida antarctica ­ kinetics ­ transesterification ­ water ­ solid/gas biocatalysis - hydration propionate and n-propanol catalyzed by immobilized lipase B from Candida antarctica was studied

Paris-Sud XI, Université de

177

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

2013-05-15

178

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

179

Multisubstrate Biodegradation Kinetics of Naphthalene, Phenanthrene, and  

E-print Network

the observed range of behaviors in PAH mixtures. In general, the biodegrada- tion rates of the more degradable of PAHs and degradation pathways (Evans et al., 1965; Gibson and Subramanium, 1984; Bossert and Bartha aromatic hydrocarbons (PAHs). Monod kinetic parameters and yield coefficients for the indi- vidual

Peters, Catherine A.

180

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Kinetics and quantum yield of photoluminescence of EuFOD3 doped into a nanoporous glass with the help of supercritical CO2  

NASA Astrophysics Data System (ADS)

The kinetics of photoluminescence of a EuFOD3 metalloorganic compound doped into a nanoporous Vycor glass by the method of supercritical fluid impregnation is studied. The lifetime of luminescence of EuFOD3 molecules in pores excited by an excimer XeCl laser was 40 ?s, which is considerably smaller than this lifetime (150—890 ?s) in solutions. The quantum yield of luminescence of EuFOD3 was estimate as ?4×10-4.

Bagratashvili, V. N.; Gerasimova, V. I.; Gordienko, V. M.; Tsypina, S. I.; Chutko, E. A.

2008-08-01

181

Convergence of spectroscopic and kinetic electron transfer parameters for mixed-valence binuclear dipyridylamide ruthenium ammine complexes  

Microsoft Academic Search

A series of binuclear ruthenium(II,III) pentaammine complexes bridged by 4-pyridyl isonicotinamide (iso-apy) and methyl,4-pyridyl isonicotinamide (iso-mapy), and their mononuclear congeners, were studied by spectroscopic and kinetic techniques. The amide functionality provides asymmetry between the electronic environments of the metal ions bound to the aminopyridine (apy) and pyridine carbonyl (iso) ends. The resulting difference is observed in the charge transfer spectra

Alison J. Distefano; James F. Wishart; Stephan S. Isied

2005-01-01

182

Capacity of activated carbon in the removal of acid brilliant blue: Determination of equilibrium and kinetic model parameters  

Microsoft Academic Search

The adsorption of acid brilliant blue onto thermally activated coir pith carbon in aqueous solution was studied in a batch system with respect to contact time, pH, and temperature. Acidic pH was favorable for the adsorption of this dye. The surface characterization of thermally activated coir pith carbon was performed using the FT-IR technique. Kinetic studies showed that the adsorption

D. Kavitha; C. Namasivayam

2008-01-01

183

The determination of kinetics parameters of the hydrogen evolution on Ti?Ni alloys by ac impedance  

Microsoft Academic Search

The kinetics and mechanism of hydrogen evolution at Ti?Ni alloys electrode has been studied by means of steady-state potentiostatic polarization and ac impedance spectrum measurements. Complex-plane spectrum plots are derived for the h.e.r. at one of the most inactive, typical hydridic, Ti?Ni, and one of the most active, typical electrocatalytic, Ti?Ni3, intermetallic alloy compounds at various potentials. The rate constants

N. V. Krstaji?; B. N. Grgur; N. S. Mladenovi?; M. V. Vojnovi?

1997-01-01

184

Modeling sugarcane yield with a process-based model from site to continental scale: uncertainties arising from model structure and parameter values  

NASA Astrophysics Data System (ADS)

Agro-land surface models (agro-LSM) have been developed from the integration of specific crop processes into large-scale generic land surface models that allow calculating the spatial distribution and variability of energy, water and carbon fluxes within the soil-vegetation-atmosphere continuum. When developing agro-LSM models, particular attention must be given to the effects of crop phenology and management on the turbulent fluxes exchanged with the atmosphere, and the underlying water and carbon pools. A part of the uncertainty of agro-LSM models is related to their usually large number of parameters. In this study, we quantify the parameter-values uncertainty in the simulation of sugarcane biomass production with the agro-LSM ORCHIDEE-STICS, using a multi-regional approach with data from sites in Australia, La Réunion and Brazil. In ORCHIDEE-STICS, two models are chained: STICS, an agronomy model that calculates phenology and management, and ORCHIDEE, a land surface model that calculates biomass and other ecosystem variables forced by STICS phenology. First, the parameters that dominate the uncertainty of simulated biomass at harvest date are determined through a screening of 67 different parameters of both STICS and ORCHIDEE on a multi-site basis. Secondly, the uncertainty of harvested biomass attributable to those most sensitive parameters is quantified and specifically attributed to either STICS (phenology, management) or to ORCHIDEE (other ecosystem variables including biomass) through distinct Monte Carlo runs. The uncertainty on parameter values is constrained using observations by calibrating the model independently at seven sites. In a third step, a sensitivity analysis is carried out by varying the most sensitive parameters to investigate their effects at continental scale. A Monte Carlo sampling method associated with the calculation of partial ranked correlation coefficients is used to quantify the sensitivity of harvested biomass to input parameters on a continental scale across the large regions of intensive sugarcane cultivation in Australia and Brazil. The ten parameters driving most of the uncertainty in the ORCHIDEE-STICS modeled biomass at the 7 sites are identified by the screening procedure. We found that the 10 most sensitive parameters control phenology (maximum rate of increase of LAI) and root uptake of water and nitrogen (root profile and root growth rate, nitrogen stress threshold) in STICS, and photosynthesis (optimal temperature of photosynthesis, optimal carboxylation rate), radiation interception (extinction coefficient), and transpiration and respiration (stomatal conductance, growth and maintenance respiration coefficients) in ORCHIDEE. We find that the optimal carboxylation rate and photosynthesis temperature parameters contribute most to the uncertainty in harvested biomass simulations at site scale. The spatial variation of the ranked correlation between input parameters and modeled biomass at harvest is well explained by rain and temperature drivers, suggesting different climate-mediated sensitivities of modeled sugarcane yield to the model parameters, for Australia and Brazil. This study reveals the spatial and temporal patterns of uncertainty variability for a highly parameterized agro-LSM and calls for more systematic uncertainty analyses of such models.

Valade, A.; Ciais, P.; Vuichard, N.; Viovy, N.; Caubel, A.; Huth, N.; Marin, F.; Martiné, J.-F.

2014-06-01

185

Modeling sugar cane yield with a process-based model from site to continental scale: uncertainties arising from model structure and parameter values  

NASA Astrophysics Data System (ADS)

Agro-Land Surface Models (agro-LSM) have been developed from the integration of specific crop processes into large-scale generic land surface models that allow calculating the spatial distribution and variability of energy, water and carbon fluxes within the soil-vegetation-atmosphere continuum. When developing agro-LSM models, a particular attention must be given to the effects of crop phenology and management on the turbulent fluxes exchanged with the atmosphere, and the underlying water and carbon pools. A part of the uncertainty of Agro-LSM models is related to their usually large number of parameters. In this study, we quantify the parameter-values uncertainty in the simulation of sugar cane biomass production with the agro-LSM ORCHIDEE-STICS, using a multi-regional approach with data from sites in Australia, La Réunion and Brazil. In ORCHIDEE-STICS, two models are chained: STICS, an agronomy model that calculates phenology and management, and ORCHIDEE, a land surface model that calculates biomass and other ecosystem variables forced by STICS' phenology. First, the parameters that dominate the uncertainty of simulated biomass at harvest date are determined through a screening of 67 different parameters of both STICS and ORCHIDEE on a multi-site basis. Secondly, the uncertainty of harvested biomass attributable to those most sensitive parameters is quantified and specifically attributed to either STICS (phenology, management) or to ORCHIDEE (other ecosystem variables including biomass) through distinct Monte-Carlo runs. The uncertainty on parameter values is constrained using observations by calibrating the model independently at seven sites. In a third step, a sensitivity analysis is carried out by varying the most sensitive parameters to investigate their effects at continental scale. A Monte-Carlo sampling method associated with the calculation of Partial Ranked Correlation Coefficients is used to quantify the sensitivity of harvested biomass to input parameters on a continental scale across the large regions of intensive sugar cane cultivation in Australia and Brazil. Ten parameters driving most of the uncertainty in the ORCHIDEE-STICS modeled biomass at the 7 sites are identified by the screening procedure. We found that the 10 most sensitive parameters control phenology (maximum rate of increase of LAI) and root uptake of water and nitrogen (root profile and root growth rate, nitrogen stress threshold) in STICS, and photosynthesis (optimal temperature of photosynthesis, optimal carboxylation rate), radiation interception (extinction coefficient), and transpiration and respiration (stomatal conductance, growth and maintenance respiration coefficients) in ORCHIDEE. We find that the optimal carboxylation rate and photosynthesis temperature parameters contribute most to the uncertainty in harvested biomass simulations at site scale. The spatial variation of the ranked correlation between input parameters and modeled biomass at harvest is well explained by rain and temperature drivers, suggesting climate-mediated different sensitivities of modeled sugar cane yield to the model parameters, for Australia and Brazil. This study reveals the spatial and temporal patterns of uncertainty variability for a highly parameterized agro-LSM and calls for more systematic uncertainty analyses of such models.

Valade, A.; Ciais, P.; Vuichard, N.; Viovy, N.; Huth, N.; Marin, F.; Martiné, J.-F.

2014-01-01

186

Effects of structural and kinetic parameters on the performance of chromatographic columns packed with perfusive and purely diffusive adsorbent particles  

Microsoft Academic Search

A mathematical model describing dynamic adsorption in columns with spherical bidisperse perfusive or spherical bidisperse purely diffusive absorbent particles is used to study the effects of the structural parameters of the adsorbent particles and of the parameters of the adsorption mechanism on the performance of chromatographic systems involving the adsorption of bovine serum albumin onto anion-exchange porous adsorbent particles. Four

G. A. Heeter; A. I. Liapis

1996-01-01

187

Quantitative Genetics and Functional-Structural Plant Growth Models: Simulation of Quantitative Trait Loci Detection for Model Parameters and Application to Potential Yield Optimization  

E-print Network

Background and Aims: Prediction of phenotypic traits from new genotypes under untested environmental conditions is crucial to build simulations of breeding strategies to improve target traits. Although the plant response to environmental stresses is characterized by both architectural and functional plasticity, recent attempts to integrate biological knowledge into genetics models have mainly concerned specific physiological processes or crop models without architecture, and thus may prove limited when studying genotype x environment interactions. Consequently, this paper presents a simulation study introducing genetics into a functional-structural growth model, which gives access to more fundamental traits for quantitative trait loci (QTL) detection and thus to promising tools for yield optimization. Methods: The GreenLab model was selected as a reasonable choice to link growth model parameters to QTL. Virtual genes and virtual chromosomes were defined to build a simple genetic model that drove the settings ...

Letort, Veronique; Cournède, Paul-Henry; De Reffye, Philippe; Courtois, Brigitte; 10.1093/aob/mcm197

2010-01-01

188

Sorption of SO(2) and NO from simulated flue gas over rice husk ash (RHA)/CaO/CeO(2) sorbent: evaluation of deactivation kinetic parameters.  

PubMed

In this study, the kinetic parameters of rice husk ash (RHA)/CaO/CeO(2) sorbent for SO(2) and NO sorptions were investigated in a laboratory-scale stainless steel fixed-bed reactor. Data experiments were obtained from our previous results and additional independent experiments were carried out at different conditions. The initial sorption rate constant (k(0)) and deactivation rate constant (k(d)) for SO(2)/NO sorptions were obtained from the nonlinear regression analysis of the experimental breakthrough data using deactivation kinetic model. Both the initial sorption rate constants and deactivation rate constants increased with increasing temperature, except at operating temperature of 170 °C. The activation energy and frequency factor for the SO(2) sorption were found to be 18.0 kJ/mol and 7.37 × 10(5)cm(3)/(g min), respectively. Whereas the activation energy and frequency factor for the NO sorption, were estimated to be 5.64 kJ/mol and 2.19 × 10(4)cm(3)/(g min), respectively. The deactivation kinetic model was found to give a very good agreement with the experimental data of the SO(2)/NO sorptions. PMID:21071143

Dahlan, Irvan; Lee, Keat Teong; Kamaruddin, Azlina Harun; Mohamed, Abdul Rahman

2011-01-30

189

Exact relativistic kinetic theory of an electron beam-plasma system: hierarchy of the competing modes in the system parameter space  

E-print Network

Besides being one of the most fundamental basic issues of plasma physics, the stability analysis of an electron beam-plasma system is of critical relevance in many areas of physics. Surprisingly, decades of extensive investigation had not yet resulted in a realistic unified picture of the multidimensional unstable spectrum within a fully relativistic and kinetic framework. All attempts made so far in this direction were indeed restricted to simplistic distribution functions and/or did not aim at a complete mapping of the beam-plasma parameter space. The present paper comprehensively tackles this problem by implementing an exact linear model. We show that three kinds of modes compete in the linear phase, which can be classified according to the direction of their wavenumber with respect to the beam. We then determine their respective domain of preponderance in a three-dimensional parameter space. All these results are supported by multidimensional particle-in-cell simulations.

A. Bret; L. Gremillet; D. Benisti; E. Lefebvre

2008-05-07

190

Network topology and parameter estimation: from experimental design methods to gene regulatory network kinetics using a community based approach  

PubMed Central

Background Accurate estimation of parameters of biochemical models is required to characterize the dynamics of molecular processes. This problem is intimately linked to identifying the most informative experiments for accomplishing such tasks. While significant progress has been made, effective experimental strategies for parameter identification and for distinguishing among alternative network topologies remain unclear. We approached these questions in an unbiased manner using a unique community-based approach in the context of the DREAM initiative (Dialogue for Reverse Engineering Assessment of Methods). We created an in silico test framework under which participants could probe a network with hidden parameters by requesting a range of experimental assays; results of these experiments were simulated according to a model of network dynamics only partially revealed to participants. Results We proposed two challenges; in the first, participants were given the topology and underlying biochemical structure of a 9-gene regulatory network and were asked to determine its parameter values. In the second challenge, participants were given an incomplete topology with 11 genes and asked to find three missing links in the model. In both challenges, a budget was provided to buy experimental data generated in silico with the model and mimicking the features of different common experimental techniques, such as microarrays and fluorescence microscopy. Data could be bought at any stage, allowing participants to implement an iterative loop of experiments and computation. Conclusions A total of 19 teams participated in this competition. The results suggest that the combination of state-of-the-art parameter estimation and a varied set of experimental methods using a few datasets, mostly fluorescence imaging data, can accurately determine parameters of biochemical models of gene regulation. However, the task is considerably more difficult if the gene network topology is not completely defined, as in challenge 2. Importantly, we found that aggregating independent parameter predictions and network topology across submissions creates a solution that can be better than the one from the best-performing submission. PMID:24507381

2014-01-01

191

Exact quantum mechanical study of kinetic isotope effects in the collinear reaction Cl + Hâ $Yields$ HCl + H. The Hâ\\/Dâ and the Hâ\\/Tâ isotope effects  

Microsoft Academic Search

Exact quantum mechanical probabilities for the collinear reaction of ; chlorine atoms with Hâ, Dâ, and Tâ, in their ground and fi rst ; vibrational excited states, were calculated for a semiempirical LEPS potential ; energy surface. These probabilites were used to calculate the kinetic isotope ; effects k\\/sub Cl + Hâ\\/K\\/sub Cl + Dâ\\/ and K\\/sub Cl + Tâ

A. Persky; M. Baer

1974-01-01

192

Influence of rete testis fluid deprivation on the kinetic parameters of goat epididymal 5 alpha-reductase.  

PubMed

A surgical technique to cannulate the rete testis of the goat was utilized to examine the effects of rete testis fluid (RTF) deprivation on the enzymatic activity of epididymal 5 alpha-reductase. Kinetic techniques were used to determine whether the regional enzymatic effect of RTF deprivation is to decrease the apparent number of 5 alpha-reductase active sites or the catalytic activity of each active site within the epididymal epithelium. Paired comparisons of (Vmax)app and (Km)app values between control and RTF-deprived epididymides indicated that RTF deprivation affected the value of (Vmax)app with no apparent change in the values of (Km)app in caput, corpus, and cauda epididymal regions. We conclude that RTF deprivation in the goat epididymis for 7 days results in a decreased number of apparent 5 alpha-reductase active sites within the epididymal epithelium. PMID:2309255

Kelce, W R; Lubis, A M; Braun, W F; Youngquist, R S; Ganjam, V K

1990-01-01

193

Heat transfer and kinetics in the pyrolysis of shrinking biomass particle  

Microsoft Academic Search

The impact of shrinkage on pyrolysis of biomass particles is studied employing a kinetic model coupled with heat transfer model using a practically significant kinetic scheme consisting of physically measurable parameters. The numerical model is used to examine the impact of shrinkage on particle size, pyrolysis time, product yields, specific heat capacity and Biot number considering cylindrical geometry. Finite difference

B. V. Babu; A. S. Chaurasia

2004-01-01

194

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

195

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

196

Self-emulsifying pellets: relations between kinetic parameters of drug release and emulsion reconstitution-influence of formulation variables.  

PubMed

The effects of surfactant type and content on the kinetics of emulsion reconstitution and release of drugs differing in lipophilicity from self-emulsifying microcrystalline cellulose pellets were studied. Furosemide and propranolol were the drugs, medium-chain triglyceride was the oil, and Cremophors ELP, RH40, and RH60 were the surfactants. Pellets were prepared by extrusion/spheronization with emulsions (75% water and 25%, w/w, oil/surfactant/drug). Stability of the emulsions was evaluated from changes in the back-scattered light, and re-emulsification and drug release from light transmittance and UV spectroscopy, respectively. Emulsion stability increased because of the incorporation of the drugs. Re-emulsification depended only on the surfactant content and was expressed by a simple power equation (Ra2 > 0.945, Q(2) > 0.752). Drug release was expressed by two biexponential equations (Ra2 > 0.989, Q(2) > 0.699 and Ra2 > 0.947, Q(2) > 0.693) implying initial burst and terminal slow release phase and by the linear form (Lineweaver-Burke) of Michaelis-Menten equation (Ra2 > 0.726, Q(2) > 0.397). Relationships exist between the rate constants of the equations describing emulsion reconstitution and drug release, for propranolol compositions (R(2) = 0.915), and for compositions of both drugs with less hydrophilic ELP and RH40 (R(2) = 0.511), and also, among dissolution efficiency, drug solubility in oil/surfactant, and emulsion reconstitution ability, indicating the importance of drug solubilization in oil/surfactant and re-emulsification ability on drug release. PMID:24596121

Nikolakakis, Ioannis; Malamataris, Stavros

2014-05-01

197

Prediction and evaluation of fetal toxicity induced by NSAIDs using transplacental kinetic parameters obtained from human placental perfusion studies  

PubMed Central

AIM The use of nonsteroidal anti-inflammatory drugs (NSAIDs) in full-term pregnant women leads to fetal or neonatal toxicity, such as constriction of the ductus arteriosus (DA) and persistent pulmonary hypertension in the newborn. The aim of this study was to predict quantitatively the fetal toxicity of three NSAIDs (antipyrine, salicylic acid and diclofenac) using the transplacental pharmacokinetic parameters obtained from our previous placental perfusion studies. METHODS Human fetal plasma concentration profile after oral administration of each NSAID to the mother was estimated using the transplacental pharmacokinetic parameters and pharmacokinetic parameters in adult women. The fetal plasma concentration–response relationship for the three NSAIDs was estimated by pharmacokinetic/pharmacodynamic analysis of the results of previous studies investigating the effects of NSAIDs on the ratio of inner diameter of the DA to that of the pulmonary artery (DA/PA) in rats and the plasma concentration profiles of NSAIDs in pregnant rats. RESULTS The risk of constriction of the DA was well predicted by the model. Mean DA/PA ratio after oral administration of diclofenac to the mother was estimated to be 39.0%, whereas both of the corresponding values after oral administration of antipyrine and salicylic acid were estimated to be 5.9%. These results suggest that the fetal risk of diclofenac is higher than those of salicylic acid and antipyrine. CONCLUSIONS This study presents a novel approach to predict quantitatively the fetal risk of NSAIDs administered to the mother. Human placental perfusion study and pharmacokinetic/pharmacodynamic analysis may provide basic data for predicting human fetal toxicity of drugs. PMID:21261677

Shintaku, Kyohei; Hori, Satoko; Satoh, Hiroki; Tsukimori, Kiyomi; Nakano, Hitoo; Fujii, Tomoyuki; Taketani, Yuji; Ohtani, Hisakazu; Sawada, Yasufumi

2012-01-01

198

REPLY: Reply to Comments on 'Effect of heating rate on kinetic parameters of ?-irradiated Li2B4O7:Cu,Ag,P in TSL measurements'  

NASA Astrophysics Data System (ADS)

We appreciate the opportunity to respond to comments regarding the paper published by Ege et al (2007 Effect of heating rate on kinetic parameters of ?-irradiated Li2B4O7:Cu,Ag,P in TSL measurements Meas. Sci. Technol. 18 889). We would like to thank the authors for taking the time to tell us about their opinion, but unfortunately we do not agree with them completely. In the article presented by Kumar and Chourasiya some comment is advanced to the analysis of the glow curves measured with different heating rates, presented in our recent study. According to our study, the area under the glow curve decreases with increasing heating rate in TL-temperature plots due to the quenching effects. Contrary to this, Kumar and Chourasiya suggest that this decrease is due to the normalization process. Here we hope to clarify any confusion regarding our published study.

Ege, A. Turkler; Tekin, E. Ekdal; Karali, T.; Can, N.; Proki?, M.

2009-05-01

199

Rates of reactions catalysed by a dimeric enzyme. Effects of the reaction scheme and the kinetic parameters on co-operativity.  

PubMed Central

For the reaction S in equilibrium P catalysed by a dimeric enzyme, the reaction schemes are considered on the basis of the KNF model. For each of the ten possible schemes, the rate equation is derived on the basis of the combined steady-state and rapid-equilibrium assumptions. The curves of the plots of initial velocity v versus the substrate concentration [S] and the Hill coefficients h calculated from the rate equations depend strongly on the reaction scheme and the parameter X1. This parameter is defined by log (KS2/KS1) and is a measure of the relative affinities of the first and second protomers for the substrate. When X1 less than 0, v-[S] curves for some schemes exhibit negative co-operativity (h less than 1.0) and v-[S] curves for other schemes are similar to that of the Michaelis-Menten scheme, indicating that, even if there is interaction between the distinct protomers, sigmoidal rate behaviour is not necessarily observed. When X1 greater than 0, all the reaction schemes except one, which shows substrate-inhibition kinetic behaviour, exhibit sigmoidal kinetic behaviour (h greater than 1.0), and at the limit of X1 much greater than 0 the Hill coefficients attain the maximum possible value of 2.0. Furthermore, we have found that, even if X1 = 0, the v-[S] curve for almost all the schemes considered in the present work does not necessarily agree with that for the Michaelis-Menten scheme. This means that the deviation of the v-[S] curve from a hyperbola can be observed even if there is no interaction between the distinct protomers. PMID:1741741

Ishikawa, H; Ogino, H; Oshida, H

1991-01-01

200

Calibration-free estimates of batch process yields and detection of process upsets using in situ spectroscopic measurements and nonisothermal kinetic models: 4-(dimethylamino)pyridine- catalyzed esterification of butanol.  

PubMed

In this paper, we report the use of an NIR fiber-optic spectrometer with a high-speed diode array for calibration-free monitoring and modeling of the reaction of acetic anhydride with butanol using the catalyst 4-(dimethylamino)pyridine in a microscale batch reactor. Acquisition of spectra at 5 ms/scan gave information relevant for modeling these fast batch processes with a single multibatch kinetic model. Nonlinear fitting of a first-principles model directly to the reaction spectra gave calibration-free estimates of time-dependent concentration profiles and pure component spectra. The amount of catalyst was varied between different batches to permit accurate estimation of its effect in the multiway model. A wide range of different models with increasing complexity could be fit to each batch individually with low residuals and apparent low lack of fit. However, only one model properly estimated the concentration profiles when all five batches were fitted simultaneously in a multiway kinetic model. Inclusion of on-line temperature measurements and use of an Arrhenius model for the estimated rate constant gave significantly improved model fits compared to an isothermal kinetic model. Augmentation of prerun batches with data from an additional batch permitted model-based forecasts of reaction trajectories, reaction yield, reaction end points, and process upsets. One batch with added water to simulate a process upset was easily detected by the calibration free process model. PMID:15117200

Gemperline, Paul; Puxty, Graeme; Maeder, Marcel; Walker, Dwight; Tarczynski, Frank; Bosserman, Mary

2004-05-01

201

Photolysis of 2,3-pentanedione and 2,3-hexanedione: Kinetics, quantum yields, and product study in a simulation chamber  

NASA Astrophysics Data System (ADS)

The gas phase photolysis of two ?-diketones, 2,3-pentanedione (PTD) and 2,3-hexanedione (HEX), has been studied in a Teflon simulation chamber using UV lamps in the 330-480 nm wavelength range. Photolysis rates have been determined at room temperature and atmospheric pressure. Using NO2 actinometry allows estimating the lifetime of PTD and HEX in the atmosphere to be about 2.5 h, assessing the dominance of the photolysis loss process over the OH reaction for such ?-dicarbonyl compounds. Effective quantum yields for PTD and HEX have also been calculated over the whole wavelength range: ?PTD = 0.20 ± 0.02 and ?HEx = 0.18 ± 0.03, consistent with literature values on ?-dicarbonyls. Various end-products from the photolysis of PTD and HEX have been identified and quantified. For PTD, CH2O and CH3CHO have been detected with molar yields of (48 ± 0.5)% and (41 ± 0.7)%, respectively. For HEX, CH2O and C2H5CHO have been detected with molar yields of (45 ± 1.1)% and (37 ± 0.8)%, respectively. Small amounts of CO have also been observed, with yields of about 2%, as well as organic acids. Experiments performed in the absence of OH-radical scavengers showed significantly faster photolysis rates and higher CO yields (?7%), indicating clear formation of OH radicals in the chemical systems. A reaction mechanism was developed for PTD and HEX photolysis based on the product observations, which allowed simulating the reactant and product time profiles with very good agreement. The present work represents the first study of 2,3-pentanedione and 2,3-hexanedione photolysis, to our knowledge, and may contribute to a better understanding of the photolysis of the ?-diketones in the troposphere.

Bouzidi, H.; Fittschen, C.; Coddeville, P.; Tomas, A.

2014-01-01

202

Insights into organogelation and its kinetics from Hansen solubility parameters. Toward a priori predictions of molecular gelation.  

PubMed

Many small molecules can self-assemble by non-covalent interactions into fibrous networks and thereby induce gelation of organic liquids. However, no capability currently exists to predict whether a molecule in a given solvent will form a gel, a low-viscosity solution (sol), or an insoluble precipitate. Gelation has been recognized as a phenomenon that reflects a balance between solubility and insolubility; however, the distinction between these regimes has not been quantified in a systematic fashion. In this work, we focus on a well-known gelator, 1,3:2,4-dibenzylidene sorbitol (DBS), and study its self-assembly in various solvents. From these data, we build a framework for DBS gelation based on Hansen solubility parameters (HSPs). While the HSPs for DBS are not known a priori, the HSPs are available for each solvent and they quantify the solvent's ability to interact via dispersion, dipole-dipole, and hydrogen bonding interactions. Using the three HSPs, we construct three-dimensional plots showing regions of solubility (S), slow gelation (SG), instant gelation (IG), and insolubility (I) for DBS in the different solvents at a given temperature and concentration. Our principal finding is that the above regions radiate out as concentric shells: i.e., a central solubility (S) sphere, followed in order by spheres corresponding to SG, IG, and I regions. The distance (R0) from the origin of the central sphere quantifies the incompatibility between DBS and a solvent-the larger this distance, the more incompatible the pair. The elastic modulus of the final gel increases with R0, while the time required for a super-saturated sol to form a gel decreases with R0. Importantly, if R0 is too small, the gels are weak, but if R0 is too large, insolubility occurs-thus, strong gels fall within an optimal window of incompatibility between the gelator and the solvent. Our approach can be used to design organogels of desired strength and gelation time by judicious choice of a particular solvent or a blend of solvents. The above framework can be readily extended to many other gelators, including those with molecular structures very different from that of DBS. We have developed a MATLAB program that will be freely available (upon request) to the scientific community to replicate and extend this approach to other gelators of interest. PMID:24647411

Diehn, Kevin K; Oh, Hyuntaek; Hashemipour, Reza; Weiss, Richard G; Raghavan, Srinivasa R

2014-04-21

203

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

204

Pressure and temperature dependence kinetics study of the NO + BrO yielding NO2 + Br reaction - Implications for stratospheric bromine photochemistry  

NASA Technical Reports Server (NTRS)

The reactivity of NO with BrO radicals over a wide range of pressure (100-700 torr) and temperature (224-398 K) is investigated using the flash photolysis-ultraviolet absorption technique. The flash photolysis system consists of a high-pressure xenon arc light source, a reaction cell/gas filter/flash lamp combination, and a 216.5 half-meter monochromator/polychromator/spectrography for wavelength selectivity. The details of the reaction and its corresponding Arrhenius expression are identified. The results are compared with previous measurements, and atmospheric implications of the reaction are discussed. The NO + BrO yielding NO2 + Br reaction is shown to be important in controlling the concentration ratios of BrO/Br and BrO/HBr in the stratosphere, but this reaction does not affect the catalytic efficiency of BrOx in ozone destruction.

Watson, R. T.; Sander, S. P.; Yung, Y. L.

1979-01-01

205

Kinetics of O(1D) + H2O and O(1D) + H2: absolute rate coefficients and O(3P) yields between 227 and 453 K.  

PubMed

The rate coefficients for the crucial atmospheric reactions of O((1)D) with H(2)O and H(2), k(1) and k(2), were measured over a wide temperature range using O((1)D) detection based on the chemiluminescence reaction of O((1)D) with C(2)H. Analyzing the decays of the chemiluminescence intensities yielded a value for k(1)(T) of (1.70 x 10(-10)exp[36 K/T]) cm(3) s(-1). Multiplying or dividing k(1)(T) by a factor f(T) = 1.04 exp(5.59(|1 K/T- 1/287|)), gives the 95% confidence limits; our new determination, in good agreement with previous studies, further reduces the uncertainty in k(1). An extended study of k(2) yielded a temperature independent rate constant of (1.35 +/- 0.05) x 10(-10) cm(3) s(-1). This precise value, based on an extended set of determinations with very low scatter, is significantly larger than the current recommendations, as were two other recent k(2) determinations. Secondly, the fractions of O((1)D) quenched to O((3)P) by H(2)O and H(2), k(1b)/k(1) and k(2b)/k(2), were precisely determined from fits to chemiluminescence decays. A temperature-independent value for k(1b)/k(1) of 0.010 +/- 0.003 was found. For the quenching fraction k(2b)/k(2) a value of 0.007 +/- 0.007 was obtained at room temperature. Both determinations are significantly smaller than values and upper limits from previous studies. PMID:20577663

Vranckx, Stijn; Peeters, Jozef; Carl, Shaun

2010-08-28

206

Assessment of total- and partial-body irradiation in a baboon model: preliminary results of a kinetic study including clinical, physical, and biological parameters.  

PubMed

This biodosimetry study used irradiated baboons to investigate the efficacy of a kinetic multiparameter (clinical, physical, and biological) approach for discriminating partial-body irradiation (PBI) and total-body irradiation (TBI). Animals were unilaterally (front) exposed to 60Co gamma rays (8 to 32 cGy min) using either TBI or vertical left hemi-body irradiation (HBI), as follows: 2.5 Gy TBI (n = 2), 5 Gy TBI (n = 2), 5 Gy HBI (n = 2), and 10 Gy HBI (n = 2). Midline tissue doses were measured at the anterior iliac crest level with an ionization chamber, and body dosimetry was performed using thermoluminescent dosimeters. Blood samples were collected before exposure and from 1 h until 200 d after irradiation. Clinical status, complete blood cell count, biochemical parameters, and cytogenetic analysis were evaluated. The partial least square discriminant analysis chosen for statistical analysis showed that the four groups of irradiated baboons were clearly separated. However, the dicentric chromosome assay may not distinguish HBI from TBI in confounding situations where equivalent whole-body doses are similar and the time of exposure is sufficient for peripheral blood lymphocyte homogenization. Interestingly, as bone marrow shielding in HBI animals prevented aplasia from happening, hematologic parameters such as the platelet count and Flt-3 ligand level helped to distinguish HBI and TBI. Moreover, the ratio of neutrophil to lymphocyte counts, creatine kinase, and citrulline levels may be discriminating biomarkers of dose or injury. Both early and delayed clinical signs and bioindicators appear to be useful for assessment of heterogeneous irradiation. PMID:22951472

Hérodin, Francis; Richard, Sandrine; Grenier, Nancy; Arvers, Philippe; Gérome, Patrick; Baugé, Stéphane; Denis, Josiane; Chaussard, Hervé; Gouard, Stéphane; Mayol, Jean-François; Agay, Diane; Drouet, Michel

2012-08-01

207

Propham mineralization in aqueous medium by anodic oxidation using boron-doped diamond anode: influence of experimental parameters on degradation kinetics and mineralization efficiency.  

PubMed

This study aims the removal of a carbamate herbicide, propham, from aqueous solution by direct electrochemical advanced oxidation process using a boron-doped diamond (BDD) anode. This electrode produces large quantities of hydroxyl radicals from oxidation of water, which leads to the oxidative degradation of propham up to its total mineralization. Effect of operational parameters such as current, temperature, pH and supporting electrolyte on the degradation and mineralization rate was studied. The applied current and temperature exert a prominent effect on the total organic carbon (TOC) removal rate of the solutions. The mineralization of propham can be performed at any pH value between 3 and 11 without any loss in oxidation efficiency. The propham decay and its overall mineralization reaction follows a pseudo-first-order kinetics. The apparent rate constant value of propham oxidation was determined as 4.8 x 10(-4)s(-1) at 100 mA and 35 degrees C in the presence of 50mM Na(2)SO(4) in acidic media (pH: 3). A general mineralization sequence was proposed considering the identified oxidation intermediates. PMID:18377944

Ozcan, Ali; Sahin, Yücel; Koparal, A Sava?; Oturan, Mehmet A

2008-06-01

208

Dynamic determination of kinetic parameters for the interaction between polypeptide hormones and cell-surface receptors in the perfused rat liver by the multiple-indicator dilution method  

SciTech Connect

Hepatic elimination of epidermal growth factor (EGF) via receptor-mediated endocytosis was studied by a multiple-indicator dilution method in the isolated perfused rat liver, in which cell polarity and spatial organization are maintained. In this method EGF was given with inulin, an extracellular reference, as a bolus into the portal vein, and dilution curves of both compounds in the hepatic vein effluent were analyzed. Analysis of the dilution curve for EGF, compared with that for somatostatin, which showed no specific binding to isolated liver plasma membranes, resulted as follows: (i) both extraction ratio and distribution volume of {sup 125}I-labeled EGF decreased as the injected amount of unlabeled EGF increased; (ii) the ratio plot of the dilution curve for EGF exhibited an upward straight line initially for a short period of time, whereas the ratio plot of somatostatin gradually decreased. The multiple-indicator dilution method was used for other peptides also. Insulin and glucagon, known to have hepatocyte receptors, behaved similarly to EGF in shape of their ratio plots. The kinetic parameters calculated by this analysis were comparable with reported values obtained by in vitro direct binding measurements at equilibrium using liver homogenates. They conclude that the multiple-indicator dilution method is a good tool for analyzing the dynamics of peptide hormones-cell-surface receptor interaction under a condition in which spatial architecture of the liver is maintained.

Sato, H.; Sugiyama, Y.; Sawada, Y.; Iga, T.; Sakamoto, S.; Fuwa, T.; Hanano, M. (Univ. of Tokyo (Japan))

1988-11-01

209

Glucuronidation of paracetamol by human liver microsomes in vitro / enzyme kinetic parameters and interactions with short-chain aliphatic alcohols and opiates.  

PubMed

In this study, glucuronidation of paracetamol (CAS 103-90-2) by human liver microsomes and the effects of aliphatic alcohols and opiates were investigated. Paracetamol glucuronidation was optimised for various incubation conditions. Ten different aliphatic alcohols and the opiates morphine, codeine and dihydrocodeine were analysed as inhibitors of paracetamol glucuronidation. Furthermore, the effects of paracetamol on morphine-3 and codeine glucuronidation were investigated. Enzyme kinetic analysis was carried out via determination of the parameters Km, Vmax, Ki and the type of inhibition. Except for methanol and ethanol, all Investigated alcohols inhibited glucuronidation of paracetamol. Ki values ranged between 4.59 mmol/l (n-pentanol) and 340.54 mmol/l (2-propanol). Extent of inhibition strongly depended on the structure and clearly increased with the length of the alkyl chain. All tested opiates inhibited paracetamol glucuronidation with Ki values between 4.02 mmol/l (dihydrocodeine) and 11.44 mmol/l (morphine). Paracetamol itself turned out to be an inhibitor of opiate glucuronidation. The apparent Ki values were 4.62 mmol/l (inhibition of morphine-3 glucuronidation) and 9.44 mmol/l (inhibition of codeine glucuronidation). A mixed inhibition type was determined for all substances. The in vitro studies show a great inhibition potential for the analysed substances. Transferring the results to the in vivo situation, a higher liver toxicity of paracetamol can be assumed, if concomitantly a lot of alcoholic beverages with congener alcohols--e.g. fruit schnapps or whisky--are drunk or if opiates--as analgesics or narcotics--are taken in higher doses. PMID:18380412

Boldt, Petra; Rothschild, Markus A; Kaeferstein, Herbert

2007-01-01

210

A coupled transport and solid mechanics formulation with improved reaction kinetics parameters for modeling oxidation and decomposition in a uranium hydride bed.  

SciTech Connect

Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. An advanced type of storage bed has been proposed that utilizes oxidation of uranium hydride to heat and decompose the hydride, releasing the hydrogen. To reduce the cost and time required to develop these systems experimentally, a valid computational model is required that simulates the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. This SAND report discusses the advancements made in FY12 (since our last SAND report SAND2011-6939) to the model developed as a part of an ASC-P&EM project to address the shortcomings of the previous model. The model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion are accounted for. These expansions result in mechanical stresses that lead to bed deformation. To describe this, a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation is developed. By using this solid mechanics model, the agreement between our reacting bed model and the experimental data is improved. Additionally, more accurate uranium hydride oxidation kinetics parameters are obtained by fitting the experimental results from a pure uranium hydride oxidation measurement to the ones obtained from the coupled transport-solid mechanics model. Finally, the coupled transport-solid mechanics model governing equations and boundary conditions are summarized and recommendations are made for further development of ARIA and other Sandia codes in order for them to sufficiently implement the model.

Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.

2013-03-01

211

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

212

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

2010-05-01

213

Conceptualizing yield  

Microsoft Academic Search

This paper develops a framework for employing the concept of tourism yield in a multidimensional manner, in particular applied to various quality of life aspects promoted by sustainable development. Most analysts employ a narrow economic definition of yield while paying some attention to the triple bottom line. Here, a framework is proposed that not only seeks to conceptualize tourism yield

Jeremy Northcote; Jim Macbeth

2006-01-01

214

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

2013-02-01

215

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

216

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

217

Neutron monitors and muon detectors for solar modulation studies: Interstellar flux, yield function, and assessment of critical parameters in count rate calculations  

E-print Network

Particles count rates at given Earth location and altitude result from the convolution of (i) the interstellar (IS) cosmic-ray fluxes outside the solar cavity, (ii) the time-dependent modulation of IS into Top-of-Atmosphere (TOA) fluxes, (iii) the rigidity cut-off (or geomagnetic transmission function) and grammage at the counter location, (iv) the atmosphere response to incoming TOA cosmic rays (shower development), and (v) the counter response to the various particles/energies in the shower. Count rates from neutron monitors or muon counters are therefore a proxy to solar activity. In this paper, we review all ingredients, discuss how their uncertainties impact count rate calculations, and how they translate into variation/uncertainties on the level of solar modulation $\\varphi$ (in the simple Force-Field approximation). The main uncertainty for neutron monitors is related to the yield function. However, many other effects have a significant impact, at the 5-10\\% level on $\\varphi$ values. We find no clear ranking of the dominant effects, as some depend on the station position and/or the weather and/or the season. An abacus to translate any variation of count rates (for neutron and $\\mu$ detectors) to a variation of the solar modulation $\\varphi$ is provided.

D. Maurin; A. Cheminet; L. Derome; A. Ghelfi; G Hubert

2014-03-06

218

Neutron Monitors and muon detectors for solar modulation studies: Interstellar flux, yield function, and assessment of critical parameters in count rate calculations  

E-print Network

Particles count rates at given Earth location and altitude result from the convolution of (i) the interstellar (IS) cosmic-ray fluxes outside the solar cavity, (ii) the time-dependent modulation of IS into Top-of-Atmosphere (TOA) fluxes, (iii) the rigidity cut-off (or geomagnetic transmission function) and grammage at the counter location, (iv) the atmosphere response to incoming TOA cosmic rays (shower development), and (v) the counter response to the various particles/energies in the shower. Count rates from neutron monitors or muon counters are therefore a proxy to solar activity. In this paper, we review all ingredients, discuss how their uncertainties impact count rate calculations, and how they translate into variation/uncertainties on the level of solar modulation $\\phi$ (in the simple Force-Field approximation). The main uncertainty for neutron monitors is related to the yield function. However, many other effects have a significant impact, at the 5-10% level on $\\phi$ values. We find no clear ranking...

Maurin, D; Derome, L; Ghelfi, A; Hubert, G

2014-01-01

219

Diffusional and electrostatic effects on apparent kinetic parameters of reactions catalyzed by enzyme immobilized on the external surface of a support  

Microsoft Academic Search

Diffusional and electrostatic effects on the apparent maximum reaction rate Vmapp and the apparent Michaelis constant Kmapp were investigated theoretically for a system in which an enzyme immobilized on the external surface of a solid support catalyzes a reaction according to Michaelis-Menten kinetics. In such a system, the dependence of Vmapp and Kmapp on the substrate concentration can be expressed

Fumihide Shiraishi

1995-01-01

220

HCl yield and chemical kinetics study of the reaction of Cl atoms with CH3I at the 298 K temperature using the infra-red tunable diode laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Pulsed ArF excimer laser (193 nm) - CW infrared(IR) tunable diode laser Herriott type absorption spectroscopic technique has been made for the detection of product hydrochloric acid HCl. Absorption spectroscopic technique is used in the reaction chlorine atoms with methyl iodide (Cl + CH3I) to the study of kinetics on reaction Cl + CH3I and the yield of (HCl). The reaction of Cl + CH3I has been studied with the support of the reaction Cl + C4H10 (100% HCl) at temperature 298 K. In the reaction Cl + CH3I, the total pressure of He between 20 and 125 Torr at the constant concentration of [CH3I] 7.0 × 1014 molecule cm-3. In the present work, we estimated adduct formation is very important in the reaction Cl + CH3I and reversible processes as well and CH3I molecule photo-dissociated in the methyl [CH3] radical. The secondary chemistry has been studied as CH3 + CH3ICl = product, and CH3I + CH3ICl = product2. The system has been modeled theoretically for secondary chemistry in the present work. The calculated and experimentally HCl yield nearly 65% at the concentration 1.00 × 1014 molecule cm-3 of [CH3I] and 24% at the concentration 4.0 × 1015 molecule cm-3 of [CH3I], at constant concentration 4.85 × 1012 molecule cm-3 of [CH3], and at 7.3 × 1012 molecule cm-3 of [Cl]. The pressure dependent also studied product of HCl at the constant [CH3], [Cl] and [CH3I]. The experimental results are also very good matching with the modelling work at the reaction CH3 + CH3ICl = product (k = (2.75 ± 0.35) × 10-10 s-1) and CH3I + CH3ICl = product2 (k = 1.90 ± 0.15) × 10-12 s-1. The rate coefficients of the reaction CH3 + CH3ICl and CH3I + CH3ICl has been made in the present work. The experimental results has been studied by two method (1) phase locked and (2) burst mode.

Sharma, R. C.; Blitz, M.; Wada, R.; Seakins, P. W.

2014-07-01

221

Kinetic analyses of energy storage in a chemically pumped iodine laser  

Microsoft Academic Search

A set of 16 kinetic rate equations is numerically integrated to yield energy storage lifetimes in a chemically pumped iodine laser (CPIL) for various experimental parameters. Storage times greater than 3 ms are possible at room temperature, making the CPIL an interesting candidate for a high efficiency pulsed fusion laser. At low temperatures, storage times may even exceed 1 s.

G. E. Busch

1981-01-01

222

Effects of Operation Conditions on Removal Rate Constant and Quantum Yield of Gaseous Chlorobenzene Degradation in a Photochemical Reactor  

Microsoft Academic Search

A photochemical reactor with a low-pressure mercury ultraviolet (UV) lamp was established to treat waste gas containing chlorobenzene. Operation conditions such as light intensity, gas humidity, and inlet chlorobenzene concentration were varied. Two significant parameters, the removal rate constant and the quantum yield (relating to removal kinetic and light energy utilization), were investigated under each set of conditions. The experimental

Can Wang; Jin-Ying Xi; Hong-Ying Hu; Mohammad Arhami; Andrea Polidori; Ralph Delfino; Thomas Tjoa; Constantinos Sioutas; Adriano Pacheco; Maria Freitas; Gregory Pratt; Mary Dymond; Judi Krzyzanowski; Huan-Lin Luo; Wei-Che Chang; Deng-Fong Lin; Kelly Pennell; Ozgur Bozkurt; Eric Suuberg; Vlad Isakov; Jawad Touma; Janet Burke; Danelle Lobdell; Ted Palma; Arlene Rosenbaum; Frederick Lipfert; Ronald Wyzga; Jack Baty; J. Miller; Richard Mohan; Giovanni Leonardi; Alan Robins; Stephan Jefferis; Joanne Coy; Jeremy Wight; Virginia Murray

2009-01-01

223

Temperature-Dependent Kinetics Studies of the Reactions Br((sup 2)P3/2) + H2S yields SH + HBr and Br((sup 2)P3/2) + CH3SH yields CH3S + HBr. Heats of Formation of SH and CH3S Radicals  

NASA Technical Reports Server (NTRS)

Time resolved resonance fluorescence detection of Br(sup 2)P3/2) atom disappearance or appearance following 266-nm laser flash photolysis of CF2Br2/H2S/H2/N2, CF2Br2/CH3SH/H2/N2, Cl2CO/H2S/HBr/N2, and CH3SSCH3/HBr/H2/N2 mixtures has been employed to study the kinetics of the reactions Br((sup 2)P3/2) + H2S = SH + HBr (1,-1) and Br((sup2)P3/2) + CH3SH = CH3S + HBr (2, -2) as a function of temperature over the range 273-431K. Arrhenius expressions in units of 10(exp -12) cu cm/molecule/s which describe the results are k1 = (14.2 +/- 3.4) exp[(-2752 +/- 90)/T],(k-1) = (4.40 +/- 0.92) exp[(-971 +/- 73)/T],k(2) = (9.24 +/- 1.15) exp[(-386 +/- 41)/T], and k(-2) = (1.46 +/-0.21) exp[(-399 +/-41)/T; errors are 2 sigma and represent precision only. By examining Br((sup 2)P3/2) equilibrium kinetics following 355nm laser flash photolysis of Br2/CH3SH/H2/N2 mixtures, a 298 K rate coefficient of (1.7 +/- 0.5) x 10(exp -10) cu cm/molecule/s has been obtained for the reaction CH3S + Br2 yields CH3SBr + Br. To our knowledge, these are the first kinetic data reported for each of the reactions studied. Measured rate coefficients, along with known rate coefficients for similar radical + H2S, CH3SH, HBr,Br2 reactions are considered in terms of possible correlations of reactivity with reaction thermochemistry and with IP - EA, the difference between the ionization potential of the electron donor and the electron affinity of the electron acceptor. Both thermochemical and charge-transfer effects appear to be important in controlling observed reactivities. Second and third law analyses of the equilibrium data for reactions 1 and 2 have been employed to obtain the following enthalpies of reaction in units of kcal/mol: for reaction 1, Delta-H(298) = 3.64 +/- 0.43 and Delta-H(0) = 3.26 +/-0.45; for reaction 2, Delta-H(298) = -0.14 +/- 0.28 and Delta-H(0) = -0.65 +/- 0.36. Combining the above enthalpies of reaction with the well-known heats of formation of Br, HBr, H2S, and CH3SH gives the following heats of formation for the RS radicals in units of kcal/mol: Delta-H(sub f)(sub 0)(SH) = 34.07 +/- 0.72, Delta-H(sub f)(sub 298)(SH) = 34.18 +/- 0.68, Delta-H(sub f)(sub 0)(CH3S) = 31.44 +/- 0.54, Delta-H(sub f)(sub 298)(CH3S) = 29.78 +/- 0.44; errors are 2 sigma and represent estimates of absolute accuracy. The SH heat of formation determined from our data agrees well with literature values but has reduced error limits compared to other available values. The CH3S heat of formation determined from our date is near the low end of the range of previous estimates and is 3-4 kcal/mol lower than values derived from recent molecular beam photofragmentation studies.

Nicovich, J. M.; Kreutter, K. D.; vanDijk, C. A.; Wine, P. H.

1997-01-01

224

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...

225

Estimation of kinetic parameters in an S-system equation model for a metabolic reaction system using the Newton-Raphson method.  

PubMed

Metabolic reaction systems can be modeled easily in terms of S-system type equations if their metabolic maps are available. This study therefore proposes a method for estimating parameters in decoupled S-system equations on the basis of the Newton-Raphson method and elucidates the performance of this estimation method. Parameter estimation from the time-course data of metabolite concentrations reveals that the parameters estimated are highly accurate, indicating that the estimation algorithm has been constructed correctly. The number of iterations is small and the calculation converges in a very short time (usually less than 1s). The method is also applied to time course data with noise and found to estimate parameters efficiently. Results indicate that the present method has the potential to be extended to a method for estimating parameters in large-scale metabolic reaction systems. PMID:24291302

Iwata, Michio; Sriyudthsak, Kansuporn; Hirai, Masami Yokota; Shiraishi, Fumihide

2014-02-01

226

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. PMID:23914194

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

2013-01-01

227

Kinetic Atom.  

ERIC Educational Resources Information Center

Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)

Wilson, David B.

1981-01-01

228

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

229

Comparison between genetic parameters of cheese yield and nutrient recovery or whey loss traits measured from individual model cheese-making methods or predicted from unprocessed bovine milk samples using Fourier-transform infrared spectroscopy.  

PubMed

Cheese yield is an important technological trait in the dairy industry. The aim of this study was to infer the genetic parameters of some cheese yield-related traits predicted using Fourier-transform infrared (FTIR) spectral analysis and compare the results with those obtained using an individual model cheese-producing procedure. A total of 1,264 model cheeses were produced using 1,500-mL milk samples collected from individual Brown Swiss cows, and individual measurements were taken for 10 traits: 3 cheese yield traits (fresh curd, curd total solids, and curd water as a percent of the weight of the processed milk), 4 milk nutrient recovery traits (fat, protein, total solids, and energy of the curd as a percent of the same nutrient in the processed milk), and 3 daily cheese production traits per cow (fresh curd, total solids, and water weight of the curd). Each unprocessed milk sample was analyzed using a MilkoScan FT6000 (Foss, Hillerød, Denmark) over the spectral range, from 5,000 to 900 wavenumber×cm(-1). The FTIR spectrum-based prediction models for the previously mentioned traits were developed using modified partial least-square regression. Cross-validation of the whole data set yielded coefficients of determination between the predicted and measured values in cross-validation of 0.65 to 0.95 for all traits, except for the recovery of fat (0.41). A 3-fold external validation was also used, in which the available data were partitioned into 2 subsets: a training set (one-third of the herds) and a testing set (two-thirds). The training set was used to develop calibration equations, whereas the testing subsets were used for external validation of the calibration equations and to estimate the heritabilities and genetic correlations of the measured and FTIR-predicted phenotypes. The coefficients of determination between the predicted and measured values in cross-validation results obtained from the training sets were very similar to those obtained from the whole data set, but the coefficient of determination of validation values for the external validation sets were much lower for all traits (0.30 to 0.73), and particularly for fat recovery (0.05 to 0.18), for the training sets compared with the full data set. For each testing subset, the (co)variance components for the measured and FTIR-predicted phenotypes were estimated using bivariate Bayesian analyses and linear models. The intraherd heritabilities for the predicted traits obtained from our internal cross-validation using the whole data set ranged from 0.085 for daily yield of curd solids to 0.576 for protein recovery, and were similar to those obtained from the measured traits (0.079 to 0.586, respectively). The heritabilities estimated from the testing data set used for external validation were more variable but similar (on average) to the corresponding values obtained from the whole data set. Moreover, the genetic correlations between the predicted and measured traits were high in general (0.791 to 0.996), and they were always higher than the corresponding phenotypic correlations (0.383 to 0.995), especially for the external validation subset. In conclusion, we herein report that application of the cross-validation technique to the whole data set tended to overestimate the predictive ability of FTIR spectra, give more precise phenotypic predictions than the calibrations obtained using smaller data sets, and yield genetic correlations similar to those obtained from the measured traits. Collectively, our findings indicate that FTIR predictions have the potential to be used as indicator traits for the rapid and inexpensive selection of dairy populations for improvement of cheese yield, milk nutrient recovery in curd, and daily cheese production per cow. PMID:25108864

Bittante, G; Ferragina, A; Cipolat-Gotet, C; Cecchinato, A

2014-10-01

230

Dual-point competition association assay: a fast and high-throughput kinetic screening method for assessing ligand-receptor binding kinetics.  

PubMed

The concept of ligand-receptor binding kinetics is emerging as an important parameter in the early phase of drug discovery. Since the currently used kinetic assays are laborious and low throughput, we developed a method that enables fast and large format screening. It is a so-called dual-point competition association assay, which measures radioligand binding at two different time points in the absence or presence of unlabeled competitors. Specifically, this assay yields the kinetic rate index (KRI), which is a measure for the binding kinetics of the unlabeled ligands screened. As a prototypical drug target, the adenosine A(1) receptor (A(1)R) was chosen for assay validation and optimization. A screen with 35 high-affinity A(1)R antagonists yielded seven compounds with a KRI value above 1.0, which indicated a relatively slow dissociation from the target. All other compounds had a KRI value below or equal to 1.0, predicting a relatively fast dissociation rate. Several compounds were selected for follow-up kinetic quantifications in classical kinetic assays and were shown to have kinetic rates that corresponded to their KRI values. The dual-point assay and KRI value may have general applicability at other G-protein-coupled receptors, as well as at drug targets from other protein families. PMID:23093571

Guo, Dong; van Dorp, Erika J H; Mulder-Krieger, Thea; van Veldhoven, Jacobus P D; Brussee, Johannes; Ijzerman, Adriaan P; Heitman, Laura H

2013-03-01

231

Ibuprofen release kinetics from controlled-release tablets granulated with aqueous polymeric dispersion of ethylcellulose II: Influence of several parameters and coexcipients  

Microsoft Academic Search

The objective of this study was to investigate the mechanism of ibuprofen (IBF) release from tablets prepared by wet granulation method, using Surelease as a granulating agent. The influence of certain parameters such as the levels of Surelease solids content (SSC), pH of dissolution media, selected dissolution method, and agitation speed on the release profiles of IBF was investigated. The

Gul Majid Khan; Jia Bi Zhu

1998-01-01

232

Fluorescence kinetic parameters and cyclic electron transport in guard cell chloroplasts of chlorophyll-deficient leaf tissues from variegated weeping fig (Ficus benjamina L.).  

PubMed

Residual chlorophyll in chlorophyll-deficient (albino) areas of variegated leaves of Ficus benjamina originates from guard cell chloroplasts. Photosynthetic features of green and albino sectors of F. benjamina were studied by imaging the distribution of the fluorescence decrease ratio Rfd within a leaf calculated from maximum (Fm) and steady-state leaf chlorophyll fluorescence (Fs) at 690 and 740 nm. Local areas of albino sectors demonstrated an abnormally high Rfd(740)/Rfd(690) ratio. Fluorescence transients excited in albino sectors at red (640 and 690 nm) wavelengths showed an abrupt decrease of the Rfd values (0.4 and 0.1, correspondingly) as compared with those excited at blue wavelengths (1.7-2.4). This "Red Drop" was not observed for green sectors. Normal and chlorophyll-deficient leaf sectors of F. benjamina were also tested for linear and cyclic electron transport in thylakoids. The tests have been performed studying fluorescence at a steady-state phase with CO(2)-excess impulse feeding, photoacoustic signal generated by pulse light source at wavelengths selectively exciting PSI, fluorescence kinetics under anaerobiosis and fluorescence changes observed by dual-wavelength excitation method. The data obtained for albino sectors strongly suggest the possibility of a cyclic electron transport simultaneously occurring in guard cell thylakoids around photosystems I and II under blue light, whereas linear electron transport is absent or insufficient. PMID:22134781

Lysenko, Vladimir

2012-05-01

233

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

234

Causal network inference using biochemical kinetics  

PubMed Central

Motivation: Networks are widely used as structural summaries of biochemical systems. Statistical estimation of networks is usually based on linear or discrete models. However, the dynamics of biochemical systems are generally non-linear, suggesting that suitable non-linear formulations may offer gains with respect to causal network inference and aid in associated prediction problems. Results: We present a general framework for network inference and dynamical prediction using time course data that is rooted in non-linear biochemical kinetics. This is achieved by considering a dynamical system based on a chemical reaction graph with associated kinetic parameters. Both the graph and kinetic parameters are treated as unknown; inference is carried out within a Bayesian framework. This allows prediction of dynamical behavior even when the underlying reaction graph itself is unknown or uncertain. Results, based on (i) data simulated from a mechanistic model of mitogen-activated protein kinase signaling and (ii) phosphoproteomic data from cancer cell lines, demonstrate that non-linear formulations can yield gains in causal network inference and permit dynamical prediction and uncertainty quantification in the challenging setting where the reaction graph is unknown. Availability and implementation: MATLAB R2014a software is available to download from warwick.ac.uk/chrisoates. Contact: c.oates@warwick.ac.uk or sach@mrc-bsu.cam.ac.uk Supplementary information: Supplementary data are available at Bioinformatics online. PMID:25161235

Oates, Chris J.; Dondelinger, Frank; Bayani, Nora; Korkola, James; Gray, Joe W.; Mukherjee, Sach

2014-01-01

235

Quantitative surface analysis by total electron yield.  

PubMed

When the surface of a solid sample is irradiated under vacuum by x-rays an electron emission, owing to photoabsorption, can be measured. As the electrons are detected under neglection of their kinetic energies the total electron yield (TEY) is determined. With a tuneable x-ray monochromator the TEY is measured below and above of one of the absorption edges of a given element. A jumplike increase of the TEY signal, due to the additional photoabsorptions in the corresponding atomic level, can be observed - qualitative analysis. The height of this jump can be correlateted to the concentration - quantitative analysis. It can be shown by a fundamental parameter approach for primary and secondary excitations how to use TEY for a quantitative analysis. The information depth lambda of this new method is approximately 2-400 nm depending on the chemical elements and on the original kinetic energies of Auger and photoelectrons. Thus, TEY is located between photoelectron spectrometry and x-ray fluorescence analysis. PMID:15048496

Ebel, H; Zagler, N; Svagera, R; Ebel, M; Kaitna, R

1995-10-01

236

Kinetic modeling of ethanol production by Scheffersomyces stipitis from xylose.  

PubMed

This work focuses on the kinetics of ethanol production by Scheffersomyces stipitis on xylose with the development of a mathematical model considering the effect of substrate and product concentrations on growth rate. Experiments were carried out in batch and continuous modes, with substrate concentration varying from 7.2 to 145 g L(-1). Inhibitory effects on cell growth, substrate uptake, and ethanol production rates were found to be considerable. Kinetic parameters were obtained through linear and non-linear regression methods. Experiments in continuous mode were performed at different dilution rates to evaluate the inhibitory effect of ethanol. A mixed mathematical model which combined Andrews and Levenspiel's models, combining substrate and product inhibition, was used. A quasi-Newton routine was applied to obtain a more accurate fitting of kinetic parameters. The parameters such as cell to product factor (YP/X) and limiting cell yield (YX) were shown to be dependent on substrate concentration. The kinetic model fitted satisfactorily the experimental data. PMID:24078256

Farias, Daniele; R de Andrade, Rafael; Maugeri-Filho, Francisco

2014-01-01

237

Effect of interband scattering on kinetic coefficients and estimates of the parameters of the band spectrum of Sb2Te3  

NASA Astrophysics Data System (ADS)

It has been shown that uncertainties in the interpretation of experimental data on transport phenomena in Sb2Te3 are resolved in the two-band model with the consistent inclusion of the interband hole scattering. The performed calculation is in quantitative agreement with the experimental data in the temperature range from 77 to 400 K for the following parameters of the band spectrum: the effective mass of the density of states of light holes m d1 ? 0.6 m 0 (where m 0 is the free electron mass), the effective mass of the density of states of heavy holes m d2 ? 1.8 m 0, and the energy gap between nonequivalent extrema of the valence band ? E v( T) ? 0.15-2.5 × 10-4 T eV.

Nemov, S. A.; Blagikh, N. M.; Ivanova, L. D.

2014-09-01

238

Transdermal iontophoresis of dexamethasone sodium phosphate in vitro and in vivo: effect of experimental parameters and skin type on drug stability and transport kinetics.  

PubMed

The aim of this study was to investigate the cathodal iontophoresis of dexamethasone sodium phosphate (DEX-P) in vitro and in vivo and to determine the feasibility of delivering therapeutic amounts of the drug for the treatment of chemotherapy-induced emesis. Stability studies, performed to investigate the susceptibility of the phosphate ester linkage to hydrolysis, confirmed that conversion of DEX-P to dexamethasone (DEX) upon exposure to samples of human, porcine and rat dermis for 7 h was limited (82.2+/-0.4%, 72.5+/-4.8% and 78.6+/-6.0% remained intact) and did not point to any major inter-species differences. Iontophoretic transport of DEX-P across dermatomed porcine skin (0.75 mm thickness) was studied in vitro as a function of concentration (10, 20, 40 mM) and current density (0.1, 0.3, 0.5 mA cm(-2)) using flow-through diffusion cells. Increasing concentration of DEX-P from 10 to 40 mM resulted in a approximately 4-fold increase in cumulative permeation (35.65+/-23.20 and 137.90+/-53.90 microg cm(-2), respectively). Good linearity was also observed between DEX-P flux and the applied current density (i(d); 0.1, 0.3, 0.5 mA cm(-2); J(DEX) (microg cm(2) h(-1))=237.98 i(d)-21.32, r(2)=0.96). Moreover, separation of the DEX-P formulation from the cathode compartment by means of a salt bridge - hence removing competition from Cl(-) ions generated at the cathode - produced a 2-fold increase in steady-state iontophoretic flux (40 mM, 0.3 mA cm(-2); 20.98+/-7.96 and 41.82+/-11.98 microg cm(-2) h(-1), respectively). Pharmacokinetic parameters were determined in Wistar rats (40 mM DEX-P; 0.5 mA cm(-2) for 5h with Ag/AgCl electrodes and salt bridges). Results showed that DEX-P was almost completely converted to DEX in the bloodstream, and significant DEX levels were achieved rapidly. The flux across rat skin in vivo (1.66+/-0.20 microg cm(-2) min(-1)), calculated from the input rate, was not statistically different from the flux obtained in vitro across dermatomed porcine skin (1.79+/-0.49 microg cm(-2) min(-1)). The results suggest that DEX-P delivery rates would be sufficient for the management of chemotherapy-induced emesis. PMID:20332024

Cázares-Delgadillo, J; Balaguer-Fernández, C; Calatayud-Pascual, A; Ganem-Rondero, A; Quintanar-Guerrero, D; López-Castellano, A C; Merino, V; Kalia, Y N

2010-06-01

239

Kinetic models of opinion formation  

E-print Network

We introduce and discuss certain kinetic models of (continuous) opinion formation involving both exchange of opinion between individual agents and diffusion of information. We show conditions which ensure that the kinetic model reaches non trivial stationary states in case of lack of diffusion in correspondence of some opinion point. Analytical results are then obtained by considering a suitable asymptotic limit of the model yielding a Fokker-Planck equation for the distribution of opinion among individuals.

G. Toscani

2006-05-17

240

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

241

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

2012-10-01

242

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  

NASA Astrophysics Data System (ADS)

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(NO3)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, 1H NMR, 13C 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 Osbnd O and Osbnd N 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.

Patel, Ketan S.; Patel, Jiten C.; Dholariya, Hitesh R.; Patel, Kanuprasad D.

2012-10-01

243

Fokker-Planck equation for physisorption kinetics: General formulation for isothermal desorption  

Microsoft Academic Search

Isothermal desorption is studied with use of the Fokker-Planck equation previously derived from the phonon-cascade-model master equation for physisorption kinetics. First, correct initial and boundary conditions appropriate to isothermal desorption are derived, within van Kampen's large-parameter scheme, for the Fokker-Planck equation. Then, the latter is solved with the use of a small-eigenvalue expansion method. This yields both integral and approximate

D. B. Jack; Z. W. Gortel; H. J. Kreuzer

1987-01-01

244

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

245

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

246

Chemical Oscillations in Enzyme Kinetics  

Microsoft Academic Search

The Higgins model is a two variable model in enzyme kinetics. In contrast with other popular simple dynamical models like the Lotka-Volterra model, the Higgins model shows steady states, damped oscillations and stable limit cycles. For these three dynamical behaviors, stability analysis yields expressions of the eigenvalues, which are easy to obtain either analytically or with the use of Mathematica.

Katherine L. Queeney; Ethan P. Marin; Cory M. Campbell; Enrique Peacock-Lopez

1996-01-01

247

Comparison of egg and high yielding MDCK cell-derived live attenuated influenza virus for commercial production of trivalent influenza vaccine: in vitro cell susceptibility and influenza virus replication kinetics in permissive and semi-permissive cells.  

PubMed

Currently MedImmune manufactures cold-adapted (ca) live, attenuated influenza vaccine (LAIV) from specific-pathogen free (SPF) chicken eggs. Difficulties in production scale-up and potential exposure of chicken flocks to avian influenza viruses especially in the event of a pandemic influenza outbreak have prompted evaluation and development of alternative non-egg based influenza vaccine manufacturing technologies. As part of MedImmune's effort to develop the live attenuated influenza vaccine (LAIV) using cell culture production technologies we have investigated the use of high yielding, cloned MDCK cells as a substrate for vaccine production by assessing host range and virus replication of influenza virus produced from both SPF egg and MDCK cell production technologies. In addition to cloned MDCK cells the indicator cell lines used to evaluate the impact of producing LAIV in cells on host range and replication included two human cell lines: human lung carcinoma (A549) cells and human muco-epidermoid bronchiolar carcinoma (NCI H292) cells. The influenza viruses used to infect the indicators cell lines represented both the egg and cell culture manufacturing processes and included virus strains that composed the 2006-2007 influenza seasonal trivalent vaccine (A/New Caledonia/20/99 (H1N1), A/Wisconsin/67/05 (H3N2) and B/Malaysia/2506/04). Results from this study demonstrate remarkable similarity between influenza viruses representing the current commercial egg produced and developmental MDCK cell produced vaccine production platforms. MedImmune's high yielding cloned MDCK cells used for the cell culture based vaccine production were highly permissive to both egg and cell produced ca attenuated influenza viruses. Both the A549 and NCI H292 cells regardless of production system were less permissive to influenza A and B viruses than the MDCK cells. Irrespective of the indicator cell line used the replication properties were similar between egg and the cell produced influenza viruses. Based on these study results we conclude that the MDCK cell produced and egg produced vaccine strains are highly comparable. PMID:20307595

Hussain, Althaf I; Cordeiro, Melissa; Sevilla, Elizabeth; Liu, Jonathan

2010-05-14

248

Der Einfluss unterschiedlicher Anbaukonzentrationen und Anbaupausen auf Bodeneigenschaften und Erträge im Zuckerrübenfruchtfolgeversuch Etzdorf Effect of various rotations and fallow periods on soil quality parameters and yield in the sugar beet rotation experiment Etzdorf  

Microsoft Academic Search

The effect of various rotations and fallow periods on development of sugar beet, product quality and nematode infestation as well as soil physical parameters have been studied in the sugar beet rotation experiment Etzdorf, which had been started in 1970 on a Haplic Chernozem in the state Saxony-Anhalt, Germany. In 2006, for the first time various soil physical parameters have

Peter Deumelandt; B. Hofmann; Olaf Christen

2010-01-01

249

Simple model relating recombination rates and non-proportional light yield in scintillators  

SciTech Connect

We present a phenomenological approach to derive an approximate expression for the local light yield along a track as a function of the rate constants of different kinetic orders of radiative and quenching processes for excitons and electron-hole pairs excited by an incident {gamma}-ray in a scintillating crystal. For excitons, the radiative and quenching processes considered are linear and binary, and for electron-hole pairs a ternary (Auger type) quenching process is also taken into account. The local light yield (Y{sub L}) in photons per MeV is plotted as a function of the deposited energy, -dE/dx (keV/cm) at any point x along the track length. This model formulation achieves a certain simplicity by using two coupled rate equations. We discuss the approximations that are involved. There are a sufficient number of parameters in this model to fit local light yield profiles needed for qualitative comparison with experiment.

Moses, William W.; Bizarri, Gregory; Singh, Jai; Vasil'ev, Andrey N.; Williams, Richard T.

2008-09-24

250

Compartmental analysis of (11C)flumazenil kinetics for the estimation of ligand transport rate and receptor distribution using positron emission tomography  

SciTech Connect

The in vivo kinetic behavior of (11C)flumazenil ((11C)FMZ), a non-subtype-specific central benzodiazepine antagonist, is characterized using compartmental analysis with the aim of producing an optimized data acquisition protocol and tracer kinetic model configuration for the assessment of (11C)FMZ binding to benzodiazepine receptors (BZRs) in human brain. The approach presented is simple, requiring only a single radioligand injection. Dynamic positron emission tomography data were acquired on 18 normal volunteers using a 60- to 90-min sequence of scans and were analyzed with model configurations that included a three-compartment, four-parameter model, a three-compartment, three-parameter model, with a fixed value for free plus nonspecific binding; and a two-compartment, two-parameter model. Statistical analysis indicated that a four-parameter model did not yield significantly better fits than a three-parameter model. Goodness of fit was improved for three- versus two-parameter configurations in regions with low receptor density, but not in regions with moderate to high receptor density. Thus, a two-compartment, two-parameter configuration was found to adequately describe the kinetic behavior of (11C)FMZ in human brain, with stable estimates of the model parameters obtainable from as little as 20-30 min of data. Pixel-by-pixel analysis yields functional images of transport rate (K1) and ligand distribution volume (DV), and thus provides independent estimates of ligand delivery and BZR binding.

Koeppe, R.A.; Holthoff, V.A.; Frey, K.A.; Kilbourn, M.R.; Kuhl, D.E. (University of Michigan, Ann Arbor (USA))

1991-09-01

251

Deuterium kinetic isotope effect and stopped-flow kinetic studies of the quinoprotein methylamine dehydrogenase  

Microsoft Academic Search

Stopped-flow kinetic studies of the reductive half-reaction of methylamine dehydrogenase from Paracoccus denitrificans yielded kinetic constants for the reversible formation of the imine intermediate formed between the substrate and the tryptophan tryptophylquinone (TTQ) prosthetic group and for the hydrogen abstraction step which occurs concomitantly with TTQ reduction. When CD3NH2 was used as a substrate, deuterium kinetic isotope effects of 4.2

Harold B. Brooks; Limei Hsu Jones; Victor L. Davidson

1993-01-01

252

Baryon resonance yields after QGP hadronization  

NASA Astrophysics Data System (ADS)

We study the yields of ?(1232), ?(1385) and ?(1520) baryon resonances in the framework of a kinetic master equations for the case of entropy rich QGP fast hadronization leading to initial above chemical equilibrium yields of hadrons. In this case the resonance yield in a rapidly expanding system does not follow the chemical equilibrium yield as function of time. We find that a significant additional yields of ?(1232), ?(1385) can be produced by the back-reaction of the over- abundance of the decay products of resonances. A more complex situation arises for a relatively narrow resonance such as ?(1520), which can be in part seen as a stable state, which is depopulated to increase the heavier resonance yield. We find that a suppression of yield of such resonances, as compared to statistical hadronization model, is possible. The pattern of deviation of hadron resonance yields from expectations based on statistical hadronization model are another characteristic signature for a fast hadronization of entropy rich QGP. The total yields of the ground state baryons used in analysis of data (such as N, ?) are not affected. The results are in agreement with yields of these resonances reported by RHIC experiments.

Kuznetsova, Inga; Rafelski, Johann

2009-05-01

253

Kinetic Theory  

NSDL National Science Digital Library

This page contains two Physlets that are able to share data using their common superclass, SApplet. The Molecular Physlet is able to tag a particle as a data source. In particular, any tagged particle can deliver x, y, vx, and vy values to a data listener. This script tags two particles and assigns these data sources to two different series in the DataGraph Physlet. The connection can show any analytic function of the position and velocity components including the particle speed or kinetic energy.

Christian, Wolfgang; Belloni, Mario

2008-02-09

254

Chemical kinetics modeling  

SciTech Connect

This project emphasizes numerical modeling of chemical kinetics of combustion, including applications in both practical combustion systems and in controlled laboratory experiments. Elementary reaction rate parameters are combined into mechanisms which then describe the overall reaction of the fuels being studied. Detailed sensitivity analyses are used to identify those reaction rates and product species distributions to which the results are most sensitive and therefore warrant the greatest attention from other experimental and theoretical research programs. Experimental data from a variety of environments are combined together to validate the reaction mechanisms, including results from laminar flames, shock tubes, flow systems, detonations, and even internal combustion engines.

Westbrook, C.K.; Pitz, W.J. [Lawrence Livermore National Laboratory, CA (United States)

1993-12-01

255

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

256

Determining enzyme kinetics for systems biology with nuclear magnetic resonance spectroscopy.  

PubMed

Enzyme kinetics for systems biology should ideally yield information about the enzyme's activity under in vivo conditions, including such reaction features as substrate cooperativity, reversibility and allostery, and be applicable to enzymatic reactions with multiple substrates. A large body of enzyme-kinetic data in the literature is based on the uni-substrate Michaelis-Menten equation, which makes unnatural assumptions about enzymatic reactions (e.g., irreversibility), and its application in systems biology models is therefore limited. To overcome this limitation, we have utilised NMR time-course data in a combined theoretical and experimental approach to parameterize the generic reversible Hill equation, which is capable of describing enzymatic reactions in terms of all the properties mentioned above and has fewer parameters than detailed mechanistic kinetic equations; these parameters are moreover defined operationally. Traditionally, enzyme kinetic data have been obtained from initial-rate studies, often using assays coupled to NAD(P)H-producing or NAD(P)H-consuming reactions. However, these assays are very labour-intensive, especially for detailed characterisation of multi-substrate reactions. We here present a cost-effective and relatively rapid method for obtaining enzyme-kinetic parameters from metabolite time-course data generated using NMR spectroscopy. The method requires fewer runs than traditional initial-rate studies and yields more information per experiment, as whole time-courses are analyzed and used for parameter fitting. Additionally, this approach allows real-time simultaneous quantification of all metabolites present in the assay system (including products and allosteric modifiers), which demonstrates the superiority of NMR over traditional spectrophotometric coupled enzyme assays. The methodology presented is applied to the elucidation of kinetic parameters for two coupled glycolytic enzymes from Escherichia coli (phosphoglucose isomerase and phosphofructokinase). 31P-NMR time-course data were collected by incubating cell extracts with substrates, products and modifiers at different initial concentrations. NMR kinetic data were subsequently processed using a custom software module written in the Python programming language, and globally fitted to appropriately modified Hill equations. PMID:24957764

Eicher, Johann J; Snoep, Jacky L; Rohwer, Johann M

2012-01-01

257

Kinetics of coal pyrolysis and devolatilization  

SciTech Connect

Research continued on coal devolatilization. Results are presented for rapid devolatilization experiments performed with the 20 -- 30 micron size cut of the reference coal - PSOC 1451D - a high volatile bituminous, Appalachian Province coal. In agreement with behavior observed in rapid, radiant transient heating experiments -flash lamp - and moderate heating rate - heated grid - experiments for the same coal, the devolatilization process is observed to occur in four distinct phases: intraparticle heavy hydrocarbon detachment and transport; heavy hydrocarbon desorption; low temperature reformation reactions producing light gases; high temperature secondary reactions of tars and char degassing. Mass fraction yields light fast yields and tar and char characteristics are presented for a range of reactor temperatures which support the phenomenological picture. A phenomenological model is presented which indicates the distinct phases of devolatilization and the importance of heat transfer conditions on both the overall rate of particle mass loss and the observable volatiles product distribution. The approach taken to model heat transfer conditions in each of the devolatilization reactors employed in the overall investigation is outlined. Predicted weight loss results are shown for three different sets of overall devolatilization kinetic parameters given heat transfer conditions in the UTRC Hot Wall - Hot Gas reactor. 47 figs., 1 tab.

Not Available

1986-01-01

258

Large-scale reactive molecular dynamics simulation and kinetic modeling of high-temperature pyrolysis of the Gloeocapsomorphaprisca microfossils.  

PubMed

The ability to predict accurately the thermal conversion of complex carbonaceous materials is of value in both petroleum exploration and refining operations. Modeling the thermal cracking of kerogen under basinal heating conditions improves the predrill prediction of oil and gas yields and quality, thereby ultimately lowering the exploration risk. Modeling the chemical structure and reactivity of asphaltene from petroleum vacuum residues enables prediction of coke formation and properties in refinery processes, thereby lowering operating cost. The chemical structure-chemical yield modeling (CS-CYM) developed by Freund et al. is more rigorous, time-consuming, and requires a great deal of chemical insight into reaction network and reaction kinetics. The present work explores the applicability of a more fundamental atomistic simulation using the quantum mechanically based reactive force field to predict the product yield and overall kinetics of decomposition of two biopolymers, namely, the Kukersite and Gutternberg. Reactive molecular dynamics (RMD) simulations were performed on systems consisting of 10(4) to 10(5) atoms at different densities and temperatures to derive the overall kinetic parameters and a lumped kinetic model for pyrolysis. The kinetic parameters derived from the simulated pyrolysis of an individual component and the mixture of all four components in Guttenberg reveal the role of cross-talk between the fragments and enhanced reactivity of component A by radicals from other components. The Arrhenius extrapolation of the model yields reasonable prediction for the overall barrier for cracking. Because simulations were run at very high temperature (T > 1500 K) to study cracking within the simulation time of up to 1 ns, it, however, led to the entropically favored ethylene formation as a dominant decomposition route. Future work will focus on evaluating the applicability of accelerated reactive MD approaches to study cracking. PMID:24821589

Zou, Chenyu; Raman, Sumathy; van Duin, Adri C T

2014-06-12

259

Asphalt Oxidation Kinetics and Pavement Oxidation Modeling  

E-print Network

simplified model. And the experimental effort and time to obtain these kinetics parameters were significantly reduced. Furthermore, to investigate the mechanism of asphalt oxidation, two antioxidants were studied on their effectiveness. Asphalt oxidation...

Jin, Xin

2012-07-16

260

Nucleation kinetics of emulsified triglyceride mixtures  

Microsoft Academic Search

The purpose of this study is to determine character istic nucleation parameters such as the surface free energy for nucleus\\u000a formation in mixtures of fully hydrogenated palm oil (HP) in sunflower oil (SF). These parameters will be used to model the\\u000a bulk crystallization kinetics of the same mixtures. This was achieved by determining the crystallization kinetics in emulsified\\u000a triglyceride mixtures

William Kloek; Pieter Walstra; Ton van Vliet

2000-01-01

261

The yield stress myth?  

Microsoft Academic Search

New experimental data obtained from constant stress rheometers are used to show that the yield stress concept is an idealization, and that, given accurate measurements, no yield stress exists. The simple Cross model is shown to be a useful empiricism for many non-Newtonian fluids, including those which have hitherto been thought to possess a yield stress.

H. A. Barnes; K. Walters

1985-01-01

262

Reaction Kinetics of the Hydrothermal Treatment of Lignin  

NASA Astrophysics Data System (ADS)

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.

Zhang, Bo; Huang, Hua-Jiang; Ramaswamy, Shri

263

Calculation of the total electron excitation cross section in the Born approximation using Slater wave functions for the Li (2s yields 2p), Li (2s yields 3p), Na (3s yields 4p), Mg (3p yields 4s), Ca (4s yields 4p) and K (4s yields 4p) excitations. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Excitation of neutral atoms by inelastic scattering of incident electrons in gaseous nebulae were investigated using Slater Wave functions to describe the initial and final states of the atom. Total cross sections using the Born Approximation are calculated for: Li(2s yields 2p), Na(3s yields 4p), k(4s yields 4p). The intensity of emitted radiation from gaseous nebulae is also calculated, and Maxwell distribution is employed to average the kinetic energy of electrons.

Simsic, P. L.

1974-01-01

264

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

265

Yield of green peas  

Microsoft Academic Search

Green peas (cv.‘Victory Freezer’) were grown at five plant densities (52, 90, 105, 182, 358 plants\\/m) and three soil moisture treatments: natural rainfall, irrigation at flowering and pod swelling, and water stress at these periods. Both total green yield and green pea yield increased with increasing density, although green pea yield dropped slightly below 182 plants\\/m. No significant differences occurred

J. A. D. Anderson; J. G. H. White

1974-01-01

266

Evaporation of an emulsion trapped in a yield stress fluid  

NASA Astrophysics Data System (ADS)

The present work deals with emulsions of volatile alkanes in an aqueous clay suspension, Laponite, which forms a yield stress fluid. For a large enough yield stress (i.e. Laponite concentration), the oil droplets are prevented from creaming and the emulsions are thus mechanically stabilized. We have studied the evaporation kinetics of the oil phase of those emulsions in contact with the atmosphere. We show that the evaporation process is characterized by the formation of a sharp front separating the emulsion from a droplet-free Laponite phase, and that the displacement of the front vs. time follows a diffusion law. Experimental data are confronted to a diffusion-controlled model, in the case where the limiting step is the diffusion of the dissolved oil through the aqueous phase. The nature of the alkane, as well as its volume fraction in the emulsion, has been varied. Quantitative agreement with the model is achieved without any adjustable parameter and we describe the mechanism leading to the formation of a front.

Guéna, G.; Corde, J.; Fouilloux, S.; D'Espinose, J.-B.; Lequeux, F.; Talini, L.

2009-04-01

267

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

2013-10-10

268

Kinetics of acid hydrolysis of hardwood in a continuous plug flow reactor  

SciTech Connect

This thesis was undertaken to investigate the kinetics of dilute acid catalyzed hydrolysis of hardwood in an isothermally operated continuous plug flow reactor at steady state. Sulphuric acid catalyst concentration ranged from 0.05 to 2.5 wt% and the reaction temperatures were between 160/sup 0/C and 265/sup 0/C. The residence time was limited to between 0.1 and 0.5 minutes while the wood slurry concentration varied from 5 wt% to 10 wt%. Kinetic models, as functions of the reaction conditions, were obtained for the hemicelluloses (xylan) to xylose, xylose to furfural, fufural decomposition, and cellulose (glucan) to glucose reactions. Numerical solutions (Runge-Kutta Methods) to a system of first order differential equations which provided a composite description of the kinetic model for furfural production from xylan were also presented. Furfural yields of up to 87% were verified. Xylose appearance from hardwood xylan could be modelled by a sequence of two irreversible consecutive first-order reactions. The proposed model, however, underestimated xylose yields at the conditions of quantitative yields (1 wt% 2 wt%, 0.25 minutes and 190/sup 0/C to 210/sup 0/C). For the cellulose to glucose reaction, a similar model with different parameters produced yields of up to 56% at 240/sup 0/C to 260/sup 0/C. Two approaches for the carbohydrate recovery and utilization in acid hydrolysis were proposed as follows. 1) Two-stage hydrolysis: in this mode, the first stage is at the conditions for maximum xylose recovery. This is then followed by a second-stage hydrolysis at higher temperatures for glucose recovery. 2) Single-stage hydrolysis: since the conditions for high furfural yields coincide with those for glucose, a single stage hydrolysis for their simultaneous recovery can also be achieved.

Kwarteng, I.K.

1983-01-01

269

Testing Biochemistry Revisited: How In Vivo Metabolism Can Be Understood from In Vitro Enzyme Kinetics  

PubMed Central

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 Vmax 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.

2012-01-01

270

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

271

Cyanide uptake from wastewater by modified natrolite zeolite-iron oxyhydroxide system: application of isotherm and kinetic models.  

PubMed

A method for the removal of cyanides from wastewater is described. The method involves the adsorption of cyanides by a modified natural zeolite (natrolite) using batch technique. A new iron oxyhydroxide-natrolite system was used in this study. A combination of XRD, XRF and FTIR spectroscopies, as well as TG/DSC thermal analyses was used for characterization of zeolitic materials. Effects of parameters such as pH, amount of adsorbent and contact time on the cyanide removing yield are studied. It was observed that the yield increases by increasing dosage of adsorbent and contact time at a fixed pH 7.5. A yield of 82% was achieved at optimum conditions for removing cyanide from industrial wastewaters. The experimental data obtained for optimum conditions were selected for modeling the adsorption behavior of the materials using six isotherm equations (Freundlich, Langmuir, Langmuir-Freundlich, Dubinin-Radushkevich, Redlich-Peterson and Toth). The obtained modeling results indicated that, although the three-parameter models, taking into account the surface heterogeneity, provided the closest approach to the measurement data, the parameters estimates could be highly biased. The kinetic studies proved that the second-order kinetic was the applicable model. PMID:19144469

Noroozifar, Meissam; Khorasani-Motlagh, Mozhgan; Fard, Parisa Ahmadzadeh

2009-07-30

272

Ozone mass transfer and kinetics experiments  

SciTech Connect

Experiments were conducted at the Hanford Site to determine the most efficient pH and temperature levels for the destruction of complexants in Hanford high-level defense waste. These complexants enhance migration of radionuclides in the soil and inhibit the growth of crystals in the evaporator-crystallizer. Ozone mass transfer and kinetics tests have been outlined for the determination of critical mass transfer and kinetics parameters of the ozone-complexant reaction.

Bollyky, L.J.; Beary, M.M.

1981-12-01

273

Automatic alignment of renal DCE-MRI image series for improvement of quantitative tracer kinetic studies  

Microsoft Academic Search

Tracer kinetic modeling with dynamic contrast enhanced MRI (DCE-MRI) and the quantification of the kinetic parameters are active fields of research which have the potential to improve the measurement of renal function. However, the strong coronal motion of the kidney in the time series inhibits an accurate assessment of the kinetic parameters. Automatic motion correction is challenging due to the

Darko Zikic; Steven Sourbron; Xinxing Feng; Henrik J. Michaely; Ali Khamene; Nassir Navab

2008-01-01

274

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. PMID:22919352

Cho, Jinwoo; Hermanowicz, Slawomir W.; Hur, Jin

2012-01-01

275

Reaction {pi}N {yields} {pi}{pi}N near threshold  

SciTech Connect

The LAMPF E1179 experiment used the {pi}{sup 0} spectrometer and an array of charged particle range counters to detect and record {pi}{sup +}{pi}{sup 0}, {pi}{sup 0}p, and {pi}{sup +}{pi}{sup 0}p coincidences following the reaction {pi}{sup +}p {yields} {pi}{sup 0}{pi}{sup +}p near threshold. The total cross sections for single pion production were measured at the incident pion kinetic energies 190, 200, 220, 240, and 260 MeV. Absolute normalizations were fixed by measuring {pi}{sup +}p elastic scattering at 260 MeV. A detailed analysis of the {pi}{sup 0} detection efficiency was performed using cosmic ray calibrations and pion single charge exchange measurements with a 30 MeV {pi}{sup {minus}} beam. All published data on {pi}N {yields} {pi}{pi}N, including our results, are simultaneously fitted to yield a common chiral symmetry breaking parameter {xi} ={minus}0.25{plus_minus}0.10. The threshold matrix element {vert_bar}{alpha}{sub 0}({pi}{sup 0}{pi}{sup +}p){vert_bar} determined by linear extrapolation yields the value of the s-wave isospin-2 {pi}{pi} scattering length {alpha}{sub 0}{sup 2}({pi}{pi}) = {minus}0.041{plus_minus}0.003 m{sub {pi}}{sup {minus}1}, within the framework of soft-pion theory.

Frlez, E.

1993-11-01

276

Biohydrogen production and kinetic modeling using sediment microorganisms of Pichavaram mangroves, India.  

PubMed

Mangrove sediments host rich assemblages of microorganisms, predominantly mixed bacterial cultures, which can be efficiently used for biohydrogen production through anaerobic dark fermentation. The influence of process parameters such as effect of initial glucose concentration, initial medium pH, and trace metal (Fe(2+)) concentration was investigated in this study. A maximum hydrogen yield of 2.34, 2.3, and 2.6 mol H2 mol(-1) glucose, respectively, was obtained under the following set of optimal conditions: initial substrate concentration-10,000 mg L(-1), initial pH-6.0, and ferrous sulphate concentration-100 mg L(-1), respectively. The addition of trace metal to the medium (100 mg L(-1) FeSO4 ·7H2O) enhanced the biohydrogen yield from 2.3 mol H2 mol(-1) glucose to 2.6 mol H2 mol(-1) glucose. Furthermore, the experimental data was subjected to kinetic analysis and the kinetic constants were estimated with the help of well-known kinetic models available in the literature, namely, Monod model, logistic model and Luedeking-Piret model. The model fitting was found to be in good agreement with the experimental observations, for all the models, with regression coefficient values >0.92. PMID:24319679

Mullai, P; Rene, Eldon R; Sridevi, K

2013-01-01

277

Biohydrogen Production and Kinetic Modeling Using Sediment Microorganisms of Pichavaram Mangroves, India  

PubMed Central

Mangrove sediments host rich assemblages of microorganisms, predominantly mixed bacterial cultures, which can be efficiently used for biohydrogen production through anaerobic dark fermentation. The influence of process parameters such as effect of initial glucose concentration, initial medium pH, and trace metal (Fe2+) concentration was investigated in this study. A maximum hydrogen yield of 2.34, 2.3, and 2.6?mol H2 mol?1 glucose, respectively, was obtained under the following set of optimal conditions: initial substrate concentration—10,000?mg?L?1, initial pH—6.0, and ferrous sulphate concentration—100?mg?L?1, respectively. The addition of trace metal to the medium (100?mg?L?1 FeSO4·7H2O) enhanced the biohydrogen yield from 2.3?mol H2?mol?1 glucose to 2.6?mol H2 mol?1 glucose. Furthermore, the experimental data was subjected to kinetic analysis and the kinetic constants were estimated with the help of well-known kinetic models available in the literature, namely, Monod model, logistic model and Luedeking-Piret model. The model fitting was found to be in good agreement with the experimental observations, for all the models, with regression coefficient values >0.92. PMID:24319679

Mullai, P.; Sridevi, K.

2013-01-01

278

Potential and kinetic energy  

NSDL National Science Digital Library

What is the difference between potential and kinetic energy? This informational piece, part of a series about the future of energy, introduces students to kinetic and potential energy. The law of conservation of energy is explained, using the example of turning natural gas into electricity. Definitions and examples of potential energy and kinetic energy are provided. Copyright 2005 Eisenhower National Clearinghouse

Project, Iowa P.

2004-01-01

279

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

280

[Physico-chemical mechanisms of organic acid transport in the apical membrane cells of the proximal kidney tubules in rats. I. Kinetic transport parameters and effect of the lipid phasic state on transport].  

PubMed

The kinetics of the transport of 3H-para-aminohippuric acid (PAH) and the influence of the temperature on the initial rate of transport were studied on the vesicles of a purified fraction of the apical membrane isolated from cells of kidney proximal tubules. The PAH transport is accomplished owing to the facilitate diffusion mechanism. The apparent Michaelis constant at 36 degrees C was equal to 7.0 + 1.0 mM, the maximum rate was 15 nmol/min on 1 mg of protein, the inhibition constant for the PAH transport by probenecid being 0.5 mM. At 22 degrees C the apparent Michaelis constant was drastically increased. When the temperature dependence of the initial rate of PAH transport into vesicles was replotted in the form of the Arrhenius plot, there was a turning-point of the line at 28-30 degrees C. The same turning-point is shown on the Arrhenius plot for temperature dependence of alkaline phosphatase activity (a marker enzyme for the apical membrane). The electron paramagnetic resonance spectra analysis of 5-doxylstearate-labeled apical membrane preparation reveals a thermotropic transition near 21-29 degrees C. It is concluded that the function of the carrier and the activity of alkaline phosphatase depend on the phasic state of membrane lipids; the normal function of membrane proteins is possible under the liquid-crystalline state of the lipid bilayer. PMID:2829399

Bresler, V M; Val'ter, S N; Isaev-Ivanov, V V; Kazbekov, E N; Kle?ner, A P

1987-10-01

281

Ecosystem Viable Yields  

E-print Network

The World Summit on Sustainable Development (Johannesburg, 2002) encouraged the application of the ecosystem approach by 2010. However, at the same Summit, the signatory States undertook to restore and exploit their stocks at maximum sustainable yield (MSY), a concept and practice without ecosystemic dimension, since MSY is computed species by species, on the basis of a monospecific model. Acknowledging this gap, we propose a definition of "ecosystem viable yields" (EVY) as yields compatible i) with biological viability levels for all time and ii) with an ecosystem dynamics. To the difference of MSY, this notion is not based on equilibrium, but on viability theory, which offers advantages for robustness. For a generic class of multispecies models with harvesting, we provide explicit expressions for the EVY. We apply our approach to the anchovy--hake couple in the Peruvian upwelling ecosystem between the years 1971 and 1981.

De Lara, Michel; Oliveros-Ramos, Ricardo; Tam, Jorge

2011-01-01

282

Estimating Corn Grain Yields  

E-print Network

to potential crop insurance claims, ? A corn crop for harvest as silage during the milk stage (R3), and ? Grain yields of corn at the dent (R5) or physiological maturity (R6) stage of development when planning harvest and post-harvest grain storage needs... to potential crop insurance claims, ? A corn crop for harvest as silage during the milk stage (R3), and ? Grain yields of corn at the dent (R5) or physiological maturity (R6) stage of development when planning harvest and post-harvest grain storage needs...

Blumenthal, Jurg M.; Thompson, Wayne

2009-06-12

283

Metaanalysis of Input\\/Output Kinetics in Lactating Dairy Cows  

Microsoft Academic Search

The kinetics of dry matter intake, raw milk yield, milk fat yield, and body weight of 140 treatment groups of cows reported in 37 articles published between 1959 and 1999 were collected in a database. The majority of these experiments were performed with Holstein- Friesian cows (primiparous: n = 51, multiparous: n = 89). Animals were fed with forages and

O. Martin; D. Sauvant

2002-01-01

284

Combustion kinetics and reaction pathways  

SciTech Connect

This project is focused on the fundamental chemistry of combustion. The overall objectives are to determine rate constants for elementary reactions and to elucidate the pathways of multichannel reactions. A multitechnique approach that features three independent experiments provides unique capabilities in performing reliable kinetic measurements over an exceptionally wide range in temperature, 300 to 2500 K. Recent kinetic work has focused on experimental studies and theoretical calculations of the methane dissociation system (CH{sub 4} + Ar {yields} CH{sub 3} + H + Ar and H + CH{sub 4} {yields} CH{sub 3} + H{sub 2}). Additionally, a discharge flow-photoionization mass spectrometer (DF-PIMS) experiment is used to determine branching fractions for multichannel reactions and to measure ionization thresholds of free radicals. Thus, these photoionization experiments generate data that are relevant to both reaction pathways studies (reaction dynamics) and fundamental thermochemical research. Two distinct advantages of performing PIMS with high intensity, tunable vacuum ultraviolet light at the National Synchrotron Light Source are high detection sensitivity and exceptional selectivity in monitoring radical species.

Klemm, R.B.; Sutherland, J.W. [Brookhaven National Laboratory, Upton, NY (United States)

1993-12-01

285

Parameter estimation for 2-parameter generalized pareto distribution by POME  

NASA Astrophysics Data System (ADS)

The principle of maximum entropy (POME) was employed to derive a new method of parameter estimation for the 2-parameter generalized Pareto (GP2) distribution. Monte Carlo simulated data were used to evaluate this method and compare it with the methods of moments (MOM), probability weighted moments (PWM), and maximum likelihood estimation (MLE). The parameter estimates yielded by POME were comparable or better within certain ranges of sample size and coefficient of variation.

Singh, V. P.; Guo, H.

1997-06-01

286

A kinetic-based approach to understanding heterologous mevalonate pathway function in E. coli.  

PubMed

To aid in debugging efforts to increase yield, titer, and productivity of engineered metabolic pathways, computational models are increasingly needed to predict how changes in experimentally manipulable variables such as enzyme expression map to changes in pathway flux. Here, an ordinary differential equation model is developed for a heterologous mevalonate pathway in E. coli using kinetic parameters culled from literature and enzyme concentrations derived from Selective Reaction Monitoring Mass Spectrometry (SRM-MS). To identify parameters most important to further experimental investigation, a global sensitivity analysis was performed, which pointed to amorphadiene synthase activity as the main limiting factor for amorphadiene production. Furthermore, the model predicted that in this local enzyme expression regime, the overall pathway flux is insensitive to farnesyl pyrophosphate (FPP)-mediated inhibition of mevalonate kinase, not supporting a hypothesis that had previously been posited to be limiting amorphadiene production. To test these predictions experimentally, two strains were constructed: (1) a strain containing a homologous mevalonate kinase with weaker feedback inhibition, and (2) a strain with greater amorphadiene synthase expression. The experimental results validate the qualitative model hypotheses and accurately match the predicted productivities for the two strains, particularly when an in vivo-derived kcat for amorphadiene synthase was substituted for the literature value. These results demonstrate the utility of using kinetic representations of engineered metabolic pathways parameterized with experimentally derived protein concentrations and enzyme kinetic constants to predict productivities and test hypotheses about engineering strategies. Biotechnol. Bioeng. 2015;112: 111-119. © 2014 Wiley Periodicals, Inc. PMID:24981116

Weaver, Lane J; Sousa, Mirta M L; Wang, George; Baidoo, Edward; Petzold, Christopher J; Keasling, Jay D

2015-01-01

287

Transient kinetics of the acetylcholinesterase catalyzed hydrolysis of N-methylindoxyl acetate.  

PubMed

An experimental study has been made of the kinetics of the hydrolysis of N-methylindoxyl acetate catalyzed by electric-eel acetylcholinesterase, both in the steady state and the pre-steady statemstopped-flow and temperature-jump experiments revealed a fast transient and a slow one. The fast transient is correlated with the conventional mechanism E+A in equilibrium EA yields X-yieldsEA' YIELDS E+Y. The slow transient is attributed to conformational changes involving E or EA. Analysis of it revealed two exponential terms of the form e- minus lambda t, and the two lambda values were obtained over the temperature range 5Yand 25Ydegrees C. The results are interpreted in terms of two alternative mechanisms; in one, the enzyme undergoes a conformational change before it adds on the substrate molecule; in the other, the conformational change occurs after the substrate addition. Both mechanisms may be involved, but the results exclude a concerted mechanism in whivh the conformational change occurs concurrently with the addition of substrate. Kinetic parameters (delta S not equal to and E) are obtained for this conformational change and for the conversion of EA into EA'+X. PMID:1125821

Sadar, M H; Laidler, K J

1975-03-01

288

Retorting of oil shale followed by solvent extraction of spent shale: Experiment and kinetic analysis  

SciTech Connect

Samples of El-Lajjun oil shale were thermally decomposed in a laboratory retort system under a slow heating rate (0.07 K/s) up to a maximum temperature of 698--773 K. After decomposition, 0.02 kg of spent shale was extracted by chloroform in a Soxhlet extraction unit for 2 h to investigate the ultimate amount of shale oil that could be produced. The retorting results indicate an increase in the oil yields from 3.24% to 9.77% of oil shale feed with retorting temperature, while the extraction results show a decrease in oil yields from 8.10% to 3.32% of spent shale. The analysis of the data according to the global first-order model for isothermal and nonisothermal conditions shows kinetic parameters close to those reported in literature.

Khraisha, Y.H.

2000-05-01

289

Resolution, Line-Edge Roughness, Sensitivity Tradeoff, and Quantum Yield of High Photo Acid Generator Resists for Extreme Ultraviolet Lithography  

NASA Astrophysics Data System (ADS)

Ultrahigh loadings of photoacid generators (PAGs) in phenolic extreme ultraviolet (EUV) resists have generated the highest known film quantum yields (FQYs). We evaluate the performance of these resists in terms of resolution, line-edge roughness (LER), and sensitivity and collectively evaluate these three parameters (known as RLS) in terms of KLUP and Z-Parameter figures of merit. An analytical model describing the kinetics of photodecomposition was developed to explain the relationship between film quantum yield and PAG concentration. Resists were prepared using a broad range of concentrations of iodonium (DTBPI-PFBS), sulfonium (TPS-PFBS), and non-ionic (NDI-PFBS) PAGs. The model fits the experimental data (correlation coefficient R2 = 0.998, 0.994, and 0.995) and compares the rate at which electrons react with PAGs or recombine with holes. Resists prepared with 15-20 wt % of iodonium nonaflate PAG exhibit both high quantum yields and the best RLS performance as determined using both KLUP and Z-Parameter methodologies. The improvement in RLS performance correlates with the increase in FQY at higher PAG concentrations.

Higgins, Craig D.; Szmanda, Charles R.; Antohe, Alin; Denbeaux, Greg; Georger, Jacque; Brainard, Robert L.

2011-03-01

290

Isothermal reduction kinetics of nickel oxide using hydrogen: Conventional and Weibull kinetic analysis  

NASA Astrophysics Data System (ADS)

The powder sample of nickel oxide was synthesized by sol gel procedure. The isothermal reduction of nickel oxide using hydrogen was investigated by thermogravimetric analysis at five operating temperatures: 245, 255, 265, 275 and 300 °C. The kinetic triplet (Ea, A and f(?)) was determined using conventional and Weibull kinetic analysis. Both the kinetically procedures show that the reduction process considered can be explained with a two-step kinetic model. It is established that at lower temperatures (245 °C?T?255 °C), the reduction process considered is governed by two-parameter Šesták-Berggren autocatalytic model (first step) and at higher temperatures (T?265 °C), the reduction process is governed by Fn reaction model with different values of parameter n (second step). In this paper, the complex manner of dependence of the Weibull shape parameter (?) on temperature is established. With alterations of Weibull shape parameter from lower temperatures (?>1) to higher temperatures (?<1), it was concluded that isothermal reduction process of NiO using hydrogen can be described by a multistep reaction mechanism. These results are confirmed by the evaluated density distribution functions (ddf) of apparent activation energies (Ea), which show variations in basic characteristics at lower and higher operating temperature regions. Also, in this paper, it was shown that the shape parameter (?) of Weibull distribution function can represent the behaviour index, which indicates the kinetic pattern of the mechanism controlling the process studied.

Jankovi?, B.

2007-12-01

291

Kinetics and mechanism of oxidation of (aqua-2-aminomethyl-pyridine) chromium(III) by N -bromosuccinimide  

Microsoft Academic Search

Summary  The kinetics of oxidation of (aqua-2-aminomethyl-pyridine) CrIII by N-bromosuccinimide (NBS) in aqueous solution to yield chromium(VI) has been studied spectrophotometrically over the 25–40 C\\u000a range. The reaction rate is first order with respect to both [NBS] and [CrIII], and increases with increasing pH between 7.6 and 8.6. The thermodynamic activation parameters were calculated. The experimental\\u000a rate law is consistent with

Ayed S. M. Al-Shihri; Alaa El-Din M. Abdel-Hady

1996-01-01

292

Comparative pyrolysis and combustion kinetics of oil shales  

Microsoft Academic Search

In this research, thermal characteristics and kinetic parameters of eight Turkish oil shale samples were determined by thermogravimetry (TG\\/DTG) at non-isothermal heating conditions both for pyrolysis and combustion processes. A general computer program was developed and the methods are compared with regard to their accuracy and the ease of interpretation of the kinetics of thermal decomposition. Activation energies of the

Mustafa Versan Kök; M. Reha Pamir

2000-01-01

293

Original article Compared kinetics of plasma creatine kinase activity  

E-print Network

Original article Compared kinetics of plasma creatine kinase activity in rabbits after intravenous 1993) Summary ― The purpose of this study was to compare the disposition parameters of creatine muscle damage. creatine kinase / kinetics / muscle damage / rabbit Résumé ― Cinétiques comparées

Boyer, Edmond

294

Modulation of calcium oxalate monohydrate crystallization kinetics in vitro  

Microsoft Academic Search

Modulation of calcium oxalate monohydrate crystallization kinetics in vitro. The effects of several low and high molecular weight (mol wt) compounds on the kinetics of calcium oxalate crystallization were examined using a seeded crystal growth method in which the solubility, the growth and the agglomeration of calcium oxalate crystals were measured as three separate and system-independent parameters. Git-rate, magnesium, phosphate,

Dik J Kok; Socrates E Papafoulos; Leo J M J Blomen; Olav L M Bijvoet; S E Papapoulos

1988-01-01

295

UNCONVENTIONAL METHODS FOR YIELD IMPROVEMENT  

E-print Network

/average casting weight (yield decreases with its increase). VARIABLES IMPACTING YIELD IN STEEL CASTING of Iowa researchers are conducting a casting yield survey to deter- mine the average metal yield in steel techniques for decreasing the size and number of risers re- quired to produce quality castings

Beckermann, Christoph

296

Solar corona heating by kinetic Alfven waves  

Microsoft Academic Search

The nonlinear mechanism of the kinetic Alfven waves (KAW) generation in the solar corona with small plasma parameter beta <<1 is investigated. The parametric instability, where the magnetosound wave (MSW) is the pump wave, is considered as the generation mechanism,. Using a two-fluid magnetohydrodynamics and Maxwell's equation, we derive a nonlinear dispersion relation governing this three-wave interaction process and the

A. D. Voitsekhovskaia; V. N. Fedun; A. K. Yukhimuk

2004-01-01

297

Single-event kinetics of catalytic cracking  

Microsoft Academic Search

A fundamental kinetic model of catalytic cracking on zeolite catalysts has been developed. The complete network of elementary steps of the carbenium ion reaction intermediates is generated by means of an algorithm based on Boolean relation matrices. Elementary steps on Lewis and Broensted sites are taken into consideration. Single-event rate parameters are estimated for the cracking of paraffins, accounting for

Wu Feng; Erik Vynckier; Gilbert F. Froment

1993-01-01

298

Nucleation and growth transformation kinetics  

NASA Astrophysics Data System (ADS)

As a result of the reassessment of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory for the kinetics of nucleation and growth transformations, an integral-equation formulation has been developed instead of the well-known and widely used Avrami equation. The presented formulation considers interfacial and diffusional growths, in one, two, and three dimensions, with both time-dependent and time-invariant nucleation and growth rates. The integral-equation model corrects reported inadequacies of the KJMA theory when applied in numerous experiments and various solid-state transformations. It is shown that in the example cases examined in this paper, crystallization from the amorphous state in melt-spun ribbons, isothermal aging of CuAlZn, pearlitic transition in an eutectoid steel, and crystallization in a PEKK polymer, the thermodynamic and kinetic interpretation and parameters extracted from best fits of the Avrami equations to the experimental data are erroneous. The KJMA formulation is a simplification of the real physical conditions. The main limitation of the new model is that almost all the integral equations representing the kinetics of solid-state transformations have no analytical solutions.

Erukhimovitch, V.; Baram, J.

1995-03-01

299

Extraction of astaxanthin from giant tiger ( Panaeus monodon) shrimp waste using palm oil: Studies of extraction kinetics and thermodynamic  

Microsoft Academic Search

Study of extraction of astaxanthin from giant tiger (Panaeus monodon) shrimp waste using palm oil was conducted to determine the extraction kinetics and thermodynamic parameters. Two extraction models were proposed: mass transfer kinetic model and reaction kinetic model. It was found that both of mass transfer and reaction kinetic control the extraction of astaxanthin from shrimp waste using palm oil.

Akdes Dewi Handayani; Sutrisno; Nani Indraswati; Suryadi Ismadji

2008-01-01

300

Comparison of petroleum generation kinetics by isothermal hydrous and nonisothermal open-system pyrolysis  

Microsoft Academic Search

This study compares kinetic parameters determined by open-system pyrolysis and hydrous pyrolysis using aliquots of source rocks containing different kerogen types. Kinetic parameters derived from these two pyrolysis methods not only differ in the conditions employed and products generated, but also in the derivation of the kinetic parameters (i.e., isothermal linear regression and non-isothermal nonlinear regression). Results of this comparative

M. D. Lewan; T. E. Ruble

2002-01-01

301

Shale Oil Cracking Kinetics and Diagnostics  

Microsoft Academic Search

Kinetic equations and diagnostic expressions are given for cracking of shale oil. Shale oil was produced in a fluidized bed at 450°C and then passed through a packed-bed cracker in which the residence time and temperature could be varied. The maximum yield obtained was approximately 110% of Fischer assay for 0.3 s at 450° in the cracking reactor. The lowest

Eugene R. Bissell; R. L. Braun; A. K. Burnham

1985-01-01

302

Transesterification kinetics of soybean oil 1  

Microsoft Academic Search

Transesterification of soybean oil (SBO) and other triglycerides with alcohols, in the presence of a catalyst, yields fatty\\u000a esters and glycerol. Di- and monoglycerides are intermediates. Reactions are consecutive and reversible. Rate constants have\\u000a been determined for each reaction with a computerized kinetic program. The effects of the type of alcohol, 1-butanol or methanol\\u000a (MeOH); molar ratio of alcohol to

Bernard Freedman; Royden O. Butterfield; Everett H. Pryde

1986-01-01

303

Oxidation kinetics of aluminum diboride  

SciTech Connect

The oxidation characteristics of aluminum diboride (AlB{sub 2}) and a physical mixture of its constituent elements (Al+2B) were studied in dry air and pure oxygen using thermal gravimetric analysis to obtain non-mechanistic kinetic parameters. Heating in air at a constant linear heating rate of 10 °C/min showed a marked difference between Al+2B and AlB{sub 2} in the onset of oxidation and final conversion fraction, with AlB{sub 2} beginning to oxidize at higher temperatures but reaching nearly complete conversion by 1500 °C. Kinetic parameters were obtained in both air and oxygen using a model-free isothermal method at temperatures between 500 and 1000 °C. Activation energies were found to decrease, in general, with increasing conversion for AlB{sub 2} and Al+2B in both air and oxygen. AlB{sub 2} exhibited O{sub 2}-pressure-independent oxidation behavior at low conversions, while the activation energies of Al+2B were higher in O{sub 2} than in air. Differences in the composition and morphology between oxidized Al+2B and AlB{sub 2} suggested that Al{sub 2}O{sub 3}–B{sub 2}O{sub 3} interactions slowed Al+2B oxidation by converting Al{sub 2}O{sub 3} on aluminum particles into a Al{sub 4}B{sub 2}O{sub 9} shell, while the same Al{sub 4}B{sub 2}O{sub 9} developed a needle-like morphology in AlB{sub 2} that reduced oxygen diffusion distances and increased conversion. The model-free kinetic analysis was critical for interpreting the complex, multistep oxidation behavior for which a single mechanism could not be assigned. At low temperatures, moisture increased the oxidation rate of Al+2B and AlB{sub 2}, but both appear to be resistant to oxidation in cool, dry environments. - Graphical abstract: Isothermal kinetic data for AlB{sub 2} in air, showing a constantly decreasing activation energy with increasing conversion. Model-free analysis allowed for the calculation of global kinetic parameters despite many simultaneous mechanisms occurring concurrently. (a) Time–temperature plots, (b) conversion as a function of time, (c) Arrhenius plots used to calculate activation energies, and (d) activation energy as a function of conversion. Display Omitted - Highlights: • First reported kinetic parameters for AlB{sub 2} and Al+2B oxidation in air and O{sub 2}. • Possible mechanism of enhanced boron combustion presented. • Moisture sensitivity shown to be problematic for AlB{sub 2}, less for Al+2B.

Whittaker, Michael L., E-mail: michaelwhittaker2016@u.northwestern.edu [Department of Materials Science and Engineering, University of Utah, 122S. Central Campus Drive, Salt Lake City, UT 84112 (United States); Sohn, H.Y. [Department of Metallurgical Engineering, University of Utah, 135S 1460 E, Rm 00412, Salt Lake City, UT 84112 (United States); Cutler, Raymond A. [Ceramatec, Inc., 2425S. 900W., Salt Lake City, UT 84119 (United States)

2013-11-15

304

Part I. Evaluation of thermodynamic and kinetic parameters for electron transfer and following chemical reaction from a global analysis of current-potential-time data. Part II. Electro-catalytic detection in high-performance liquid chromatography of vitamin B[sub 12] and other molecules of biological and environmental interest  

SciTech Connect

Simultaneous evaluation of electron transfer rate constant, k[sup 0], following chemical reaction rate constant, k[sub f], electron transfer coefficient, [alpha] and standard potential, E[sup 0][prime] for an electrochemical reaction following the EC mechanism is described. A mathematical model for the current response to a potential step is developed, starting with the Butler-Volmer equation for electrode kinetics and concentration expressions for the redox couple. The resulting integral equations are solved numerically via the Step Function method. Current-potential and current-time curves are simulated and tested under limiting conditions. The four parameters of the system are evaluated by fitting simulated current-voltage-time (i-E-t) surface to the theoretical equation. The method is applied to study an important biological molecule, viz., methyl cobalamin, in DMSO. Included in the discussion part is the use of kinetic zone diagrams to depict chronoamperometric current response as a function of dimensionless rate constants for the EC reaction scheme. This compact display of the influence of the two rate constants on current in all time windows can be used to select the best data for analysis. Theoretical limits of measurable rate constants can be estimated from the zone diagram. The development of a dropping mercury electrode detector for High Performance Liquid Chromatography (HPLC) and its application to analysis of B[sub 12] and other vitamins is described. This EC detector is able to achieve high levels of sensitivity by exploiting the catalytic hydrogen evolution undergone by many nitrogenous organic molecules. Vitamin B[sub 12], thiamine, riboflavin and niacinamide were analyzed individually and in mixtures on reverse phase C18 column. Preliminary results from the analysis of commercial multivitamin preparations are also discussed.

Kumar, V.T.

1992-01-01

305

Oxidation kinetics of aluminum diboride  

NASA Astrophysics Data System (ADS)

The oxidation characteristics of aluminum diboride (AlB2) and a physical mixture of its constituent elements (Al+2B) were studied in dry air and pure oxygen using thermal gravimetric analysis to obtain non-mechanistic kinetic parameters. Heating in air at a constant linear heating rate of 10 °C/min showed a marked difference between Al+2B and AlB2 in the onset of oxidation and final conversion fraction, with AlB2 beginning to oxidize at higher temperatures but reaching nearly complete conversion by 1500 °C. Kinetic parameters were obtained in both air and oxygen using a model-free isothermal method at temperatures between 500 and 1000 °C. Activation energies were found to decrease, in general, with increasing conversion for AlB2 and Al+2B in both air and oxygen. AlB2 exhibited O2-pressure-independent oxidation behavior at low conversions, while the activation energies of Al+2B were higher in O2 than in air. Differences in the composition and morphology between oxidized Al+2B and AlB2 suggested that Al2O3-B2O3 interactions slowed Al+2B oxidation by converting Al2O3 on aluminum particles into a Al4B2O9 shell, while the same Al4B2O9 developed a needle-like morphology in AlB2 that reduced oxygen diffusion distances and increased conversion. The model-free kinetic analysis was critical for interpreting the complex, multistep oxidation behavior for which a single mechanism could not be assigned. At low temperatures, moisture increased the oxidation rate of Al+2B and AlB2, but both appear to be resistant to oxidation in cool, dry environments.

Whittaker, Michael L.; Sohn, H. Y.; Cutler, Raymond A.

2013-11-01

306

Cotranslational Folding Increases GFP Folding Yield  

PubMed Central

Protein sequences evolved to fold in cells, including cotranslational folding of nascent polypeptide chains during their synthesis by the ribosome. The vectorial (N- to C-terminal) nature of cotranslational folding constrains the conformations of the nascent polypeptide chain in a manner not experienced by full-length chains diluted out of denaturant. We are still discovering to what extent these constraints affect later, posttranslational folding events. Here we directly address whether conformational constraints imposed by cotranslational folding affect the partitioning between productive folding to the native structure versus aggregation. We isolated polyribosomes from Escherichia coli cells expressing GFP, analyzed the nascent chain length distribution to determine the number of nascent chains that were long enough to fold to the native fluorescent structure, and calculated the folding yield for these nascent chains upon ribosome release versus the folding yield of an equivalent concentration of full-length, chemically denatured GFP polypeptide chains. We find that the yield of native fluorescent GFP is dramatically higher upon ribosome release of nascent chains versus dilution of full-length chains from denaturant. For kinetically trapped native structures such as GFP, folding correctly the first time, immediately after release from the ribosome, can lead to lifelong population of the native structure, as opposed to aggregation. PMID:20371331

Ugrinov, Krastyu G.; Clark, Patricia L.

2010-01-01

307

5Lump kinetic model for gas oil catalytic cracking  

Microsoft Academic Search

A new 5-lump kinetic model is proposed to describe the gas oil catalytic cracking (FCC) process. The model contains eight kinetic constants, including one for catalyst deactivation, taking into account LPG (combined C3–C4), dry gas (C2 and lighter) and coke yields separately from other lumps (unconverted gas oil and gasoline). Apparent activation energies were determined from experiments obtained in a

Jorge Ancheyta-Juárez; Felipe López-Isunza; Enrique Aguilar-Rodr??guez

1999-01-01

308

Reactivity parameters for safety analysis  

SciTech Connect

The reactor core model in the most commonly used computer programs for safety analysis is a point kinetics model. The core average fission rate is calculated knowing the reactivity, neutron generation time and delayed-neutron parameters. The reactivity is a time dependent function taking account of the effect of changes in water density and temperature, fuel temperature, control rod position and soluble boron concentration. In this presentation some of the alternative ways of representing this reactivity function are reviewed.

Diamond, D.J.

1985-01-01

309

Accurate argon cluster-ion sputter yields: Measured yields and effect of the sputter threshold in practical depth-profiling by x-ray photoelectron spectroscopy and secondary ion mass spectrometry  

SciTech Connect

Argon Gas Cluster-Ion Beam sources are likely to become widely used on x-ray photoelectron spectroscopy and secondary ion mass spectrometry instruments in the next few years. At typical energies used for sputter depth profiling the average argon atom in the cluster has a kinetic energy comparable with the sputter threshold, meaning that for the first time in practical surface analysis a quantitative model of sputter yields near threshold is needed. We develop a simple equation based on a very simple model. Though greatly simplified it is likely to have realistic limiting behaviour and can be made useful for estimating sputter yields by fitting its three parameters to experimental data. We measure argon cluster-ion sputter yield using a quartz crystal microbalance close to the sputter threshold, for silicon dioxide, poly(methyl methacrylate), and polystyrene and (along with data for gold from the existing literature) perform least-squares fits of our new sputter yield equation to this data. The equation performs well, with smaller residuals than for earlier empirical models, but more importantly it is very easy to use in the design and quantification of sputter depth-profiling experiments.

Cumpson, Peter J.; Portoles, Jose F.; Barlow, Anders J.; Sano, Naoko [National EPSRC XPS User's Service (NEXUS), School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom)] [National EPSRC XPS User's Service (NEXUS), School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom)

2013-09-28

310

Yield strength predictions from the plastic zone around nanocontacts  

Microsoft Academic Search

Using a simplified version of Johnson’s core model analysis of the plastic zone, one may determine the plastic zone size around a contact or, alternatively, determine the yield strength by measuring the plastic zone. The theoretical model contains three parameters: indentation load, yield strength and zone size so that knowing any two gives the third. This is experimentally demonstrated for

D. Kramer; H. Huang; M. Kriese; J. Robach; J. Nelson; A. Wright; D. Bahr; W. W. Gerberich

1998-01-01

311

RESEARCH ARTICLE Climate change model predicts 33 % rice yield decrease  

E-print Network

RESEARCH ARTICLE Climate change model predicts 33 % rice yield decrease in 2100 in Bangladesh online: 12 June 2012 # INRA and Springer-Verlag, France 2012 Abstract In Bangladesh, projected climate parameters on rice. The effects of climate change on yield of a popular winter rice cultivar in Bangladesh

Boyer, Edmond

312

Dimension scaling effects on the yield sensitivity of HEMT digital circuits  

NASA Technical Reports Server (NTRS)

In our previous works, using a graphical tool, yield factor histograms, we studied the yield sensitivity of High Electron Mobility Transistors (HEMT) and HEMT circuit performance with the variation of process parameters. This work studies the scaling effects of process parameters on yield sensitivity of HEMT digital circuits. The results from two HEMT circuits are presented.

Sarker, Jogendra C.; Purviance, John E.

1992-01-01

313

Timescales in creep and yielding of attractive gels.  

PubMed

The stress-induced yielding scenario of colloidal gels is investigated under rough boundary conditions by means of rheometry coupled with local velocity measurements. Under an applied shear stress ?, the fluidization of gels made of attractive carbon black particles dispersed in a mineral oil is shown to involve a previously unreported shear rate response ? dot above(t) characterized by two well-defined and separated timescales ?c and ?f. First ? dot above decreases as a weak power law strongly reminiscent of the primary creep observed in numerous crystalline and amorphous solids, coined the "Andrade creep". We show that the bulk deformation remains homogeneous at the micron scale, which demonstrates that whether plastic events take place or whether any shear transformation zone exists, such phenomena occur at a smaller scale. As a key result of this paper, the duration ?c of this creep regime decreases as a power law of the viscous stress, defined as the difference between the applied stress and the yield stress ?c, i.e. ?c ? (? - ?c)(-?), with ? = 2-3 depending on the gel concentration. The end of this first regime is marked by a jump of the shear rate by several orders of magnitude, while the gel slowly slides as a solid block experiencing strong wall slip at both walls, despite rough boundary conditions. Finally, a second sudden increase of the shear rate is concomitant with the full fluidization of the material which ends up being homogeneously sheared. The corresponding fluidization time ?f robustly follows an exponential decay with the applied shear stress, i.e. ?f = ?0?exp(-?/?0), as already reported for smooth boundary conditions. Varying the gel concentration C in a systematic fashion shows that the parameter ?0 and the yield stress ?c exhibit similar power-law dependences with C. Finally, we highlight a few features that are common to attractive colloidal gels and to solid materials by discussing our results in the framework of theoretical approaches of solid rupture (kinetic, fiber bundle, and transient network models). PMID:24651869

Grenard, Vincent; Divoux, Thibaut; Taberlet, Nicolas; Manneville, Sébastien

2014-03-14

314

Investigation of intrinsic hydrodesulphurization kinetics of a VGO in a trickle bed reactor with backmixing effects  

Microsoft Academic Search

Intrinsic hydrodesulphurization kinetics of a VGO has been investigated in a bench scale trickle bed reactor using three different catalysts. Kinetic equations have been determined by using the plug-flow model for the liquid phase as well as by using the axial dispersion model. The differences observed in the kinetic parameters and the reaction rates are discussed. Discrepancies in predicted reactor

D. Tsamatsoulis; N. Papayannakos

1998-01-01

315

Fully kinetic simulations of megajoule-scale dense plasma focus  

NASA Astrophysics Data System (ADS)

Dense plasma focus (DPF) Z-pinch devices are sources of copious high energy electrons and ions, x-rays, and neutrons. Megajoule-scale DPFs can generate 1012 neutrons per pulse in deuterium gas through a combination of thermonuclear and beam-target fusion. However, the details of the neutron production are not fully understood and past optimization efforts of these devices have been largely empirical. Previously, we reported on the first fully kinetic simulations of a kilojoule-scale DPF and demonstrated that both kinetic ions and kinetic electrons are needed to reproduce experimentally observed features, such as charged-particle beam formation and anomalous resistivity. Here, we present the first fully kinetic simulation of a MegaJoule DPF, with predicted ion and neutron spectra, neutron anisotropy, neutron spot size, and time history of neutron production. The total yield predicted by the simulation is in agreement with measured values, validating the kinetic model in a second energy regime.

Schmidt, A.; Link, A.; Welch, D.; Meehan, B. T.; Tang, V.; Halvorson, C.; May, M.; Hagen, E. C.

2014-10-01

316

Yield enhancement with DFM  

NASA Astrophysics Data System (ADS)

A set of design for manufacturing (DFM) techniques have been developed and applied to 45nm, 32nm and 28nm logic process technologies. A noble technology combined a number of potential confliction of DFM techniques into a comprehensive solution. These techniques work in three phases for design optimization and one phase for silicon diagnostics. In the DFM prevention phase, foundation IP such as standard cells, IO, and memory and P&R tech file are optimized. In the DFM solution phase, which happens during ECO step, auto fixing of process weak patterns and advanced RC extraction are performed. In the DFM polishing phase, post-layout tuning is done to improve manufacturability. DFM analysis enables prioritization of random and systematic failures. The DFM technique presented in this paper has been silicon-proven with three successful tape-outs in Samsung 32nm processes; about 5% improvement in yield was achieved without any notable side effects. Visual inspection of silicon also confirmed the positive effect of the DFM techniques.

Paek, Seung Weon; Kang, Jae Hyun; Ha, Naya; Kim, Byung-Moo; Jang, Dae-Hyun; Jeon, Junsu; Kim, DaeWook; Chung, Kun Young; Yu, Sung-eun; Park, Joo Hyun; Bae, SangMin; Song, DongSup; Noh, WooYoung; Kim, YoungDuck; Song, HyunSeok; Choi, HungBok; Kim, Kee Sup; Choi, Kyu-Myung; Choi, Woonhyuk; Jeon, JoongWon; Lee, JinWoo; Kim, Ki-Su; Park, SeongHo; Chung, No-Young; Lee, KangDuck; Hong, YoungKi; Kim, BongSeok

2012-03-01

317

Non-enzymatic dynamic kinetic resolution of secondary aryl alcohols: planar chiral ferrocene and ruthenium catalysts in cooperation.  

PubMed

"Ruth" helps iron! A novel method for the non-enzymatic dynamic kinetic resolution (DKR) of secondary aryl alcohols by the use of the planar chiral ferrocene derivative (+)-1 in combination with the ruthenium racemization catalyst 2 yields acetylated alcohols in high enantioselectivity and yield. This development opens opportunities for new developments in the field of non-enzymatic dynamic kinetic resolution. PMID:23225694

Díaz-Álvarez, Alba E; Mesas-Sánchez, Laura; Dinér, Peter

2013-01-01

318

Kinetics and advanced digester design for anaerobic digestion of water hyacinth and primary sludge  

SciTech Connect

A research program centered around a facility located at Walt Disney World (WDW) is in progress to evaluate the use of water hyacinth (WH) for secondary and tertiary wastewater treatment, to optimize growth of WH under these conditions, and to convert the resultant primary sludge (PS) and WH to methane via anaerobic digestion. This article describes the status of the biogasification component of this program, which includes baseline and advanced digestion experiments with individual feeds and blends and the design of an experimental test unit (ETU) to be installed at WDW. Experiments with several blends demonstrated that methane yields can be predicted from the fractional content and methane yield of each component. The process was found to adhere to the Monod kinetic model for microbial growth, and associated kinetic parameters were developed for various feed combinations. A novel upflow digester is achieving significantly higher conversion than a stirred-tank digester. Of several pretreatment techniques used, only alkaline treatment resulted in increased biodegradability. A larger scale (4.5 m/sup 3/) experimental test unit is being designed for installation at WDW in 1982. 13 figures, 4 tables.

Chynoweth, D.P.; Dolenc, D.A.; Ghosh, S.; Henry, M.P.; Jerger, D.E.; Srivastava, V.J.

1982-01-01

319

Kinetic analysis of nitroxide radical formation under oxygenated photolysis: toward quantitative singlet oxygen topology.  

PubMed

Reaction kinetics for two sterically hindered secondary amines with singlet oxygen have been studied in detail. A water soluble porphyrin sensitizer, 5,10,15,20-tetrakis-(4-sulfunatophenyl)-21,23H-porphyrin (TPPS), was irradiated in oxygenated aqueous solutions containing either 2,2,6,6-tetramethylpiperidin-4-one (TMPD) or 4-[N,N,N-trimethyl-ammonium]-2,2,6,6-tetramethylpiperidinyl chloride (N-TMPCl). The resulting sensitization reaction produced singlet oxygen in high yield, ultimately leading to the formation of the corresponding nitroxide free radicals (R2NO) which were detected using steady-state electron paramagnetic resonance (EPR) spectroscopy. Careful actinometry and EPR calibration curves, coupled with a detailed kinetic analysis, led to a simple and compact expression relating the nitroxide quantum yield ?R2NO (from the doubly-integrated EPR signal intensity) to the initial amine concentration [R2NH]i. With all other parameters held constant, a plot of ?R2NOvs. [R2NH]i gave a straight line with a slope proportional to the rate constant for nitroxide formation, kR2NO. This establishment of a rigorous quantitative relationship between the EPR signal and the rate constant provides a mechanism for quantifying singlet oxygen production as a function of its topology in heterogeneous media. Implications for in vivo assessment of singlet oxygen topology are briefly discussed. PMID:25369860

Zigler, David F; Ding, Eva Chuheng; Jarocha, Lauren E; Khatmullin, Renat R; DiPasquale, Vanessa M; Sykes, R Brendan; Tarasov, Valery F; Forbes, Malcolm D E

2014-12-12

320

Absolute quantum yield measurement of powder samples.  

PubMed

Measurement of fluorescence quantum yield has become an important tool in the search for new solutions in the development, evaluation, quality control and research of illumination, AV equipment, organic EL material, films, filters and fluorescent probes for bio-industry. Quantum yield is calculated as the ratio of the number of photons absorbed, to the number of photons emitted by a material. The higher the quantum yield, the better the efficiency of the fluorescent material. For the measurements featured in this video, we will use the Hitachi F-7000 fluorescence spectrophotometer equipped with the Quantum Yield measuring accessory and Report Generator program. All the information provided applies to this system. Measurement of quantum yield in powder samples is performed following these steps: 1. Generation of instrument correction factors for the excitation and emission monochromators. This is an important requirement for the correct measurement of quantum yield. It has been performed in advance for the full measurement range of the instrument and will not be shown in this video due to time limitations. 2. Measurement of integrating sphere correction factors. The purpose of this step is to take into consideration reflectivity characteristics of the integrating sphere used for the measurements. 3. Reference and Sample measurement using direct excitation and indirect excitation. 4. Quantum Yield calculation using Direct and Indirect excitation. Direct excitation is when the sample is facing directly the excitation beam, which would be the normal measurement setup. However, because we use an integrating sphere, a portion of the emitted photons resulting from the sample fluorescence are reflected by the integrating sphere and will re-excite the sample, so we need to take into consideration indirect excitation. This is accomplished by measuring the sample placed in the port facing the emission monochromator, calculating indirect quantum yield and correcting the direct quantum yield calculation. 5. Corrected quantum yield calculation. 6. Chromaticity coordinates calculation using Report Generator program. The Hitachi F-7000 Quantum Yield Measurement System offer advantages for this application, as follows: High sensitivity (S/N ratio 800 or better RMS). Signal is the Raman band of water measured under the following conditions: Ex wavelength 350 nm, band pass Ex and Em 5 nm, response 2 sec), noise is measured at the maximum of the Raman peak. High sensitivity allows measurement of samples even with low quantum yield. Using this system we have measured quantum yields as low as 0.1 for a sample of salicylic acid and as high as 0.8 for a sample of magnesium tungstate. Highly accurate measurement with a dynamic range of 6 orders of magnitude allows for measurements of both sharp scattering peaks with high intensity, as well as broad fluorescence peaks of low intensity under the same conditions. High measuring throughput and reduced light exposure to the sample, due to a high scanning speed of up to 60,000 nm/minute and automatic shutter function. Measurement of quantum yield over a wide wavelength range from 240 to 800 nm. Accurate quantum yield measurements are the result of collecting instrument spectral response and integrating sphere correction factors before measuring the sample. Large selection of calculated parameters provided by dedicated and easy to use software. During this video we will measure sodium salicylate in powder form which is known to have a quantum yield value of 0.4 to 0.5. PMID:22617474

Moreno, Luis A

2012-01-01

321

Cobalt Ferrite in YSZ for Use as Reactive Material in Solar Thermochemical Water and Carbon Dioxide Splitting, Part II: Kinetic Modeling  

NASA Astrophysics Data System (ADS)

The kinetics of 10 wt.% cobalt ferrite (CoFe2O4) in 8 mol.% yttria-stabilized zirconia, synthesized via the co-precipitation method and formed into a porous structure, are investigated in support of simulating the performance of a solar thermochemical reactor. Kinetic parameters for the thermal reduction (T-R) of CoFe2O4 at temperatures of 1325-1500°C were investigated by thermogravimetry. A nonlinear best fit of a uniform conversion model was used to determine kinetic parameters from experimental data. In the temperature range of 1375-1450°C, the activation energy and preexponential term were found to be 386 ± 13 kJ mol-1 and 8.8 × 109 ± 2.0 × 108 min-1, respectively, while increasing at higher temperatures. Simultaneous thermogravimetric analysis and differential scanning calorimetry studies showed an increase in the reaction rate of T-R upon the onset of melting (1440°C). Oxidation studies of the material using CO2 yield an activation energy and preexponential term of 52.1 ± 6.8 kJ mol-1 and 2.86 ± 0.2 min-1, respectively, which is in good agreement with past work. The reaction order for CO2 was determined to be 0.750 ± 0.08. The reaction kinetics for oxidation using CO2 were best described by a 3-D diffusion Jander model.

Allen, Kyle M.; Auyeung, Nick; Rahmatian, Nima; Klausner, James F.; Coker, Eric N.

2013-12-01

322

Discharge pumped iodine monofluoride laser: Operating parameters and collisional kinetics  

Microsoft Academic Search

Lasing was observed at five different wavelengths ranging from 472 to 497 nm from discharge pumped iodine monofluoride (IF). At the optimum output coupling 4 mJ was measured in a 30 ns FWHM pulse with a peak power of 140 kW. The merits and deficiencies of both HI and CF3I as iodine donors are discussed. Measurements show the small signal

M. L. Dlabal

1981-01-01

323

Kinetic parameter estimation using nonisothermal trickle-bed reactor data  

E-print Network

as shown in Eqns. 21 through 23. 13 (&f/nT) &j(ujnj) cm (m (21) ( out)m = (koETpb )*Z, (W , exp(E/RT (1 ? T /T, m )) / (noLRZ((wte/0(m)) (22) T 2 m Hom + HlmZ + . . . + 8k Ek (23) Eq. 22 provides the means for estimating ko and E through... as shown in Eqns. 21 through 23. 13 (&f/nT) &j(ujnj) cm (m (21) ( out)m = (koETpb )*Z, (W , exp(E/RT (1 ? T /T, m )) / (noLRZ((wte/0(m)) (22) T 2 m Hom + HlmZ + . . . + 8k Ek (23) Eq. 22 provides the means for estimating ko and E through...

Mensik, Michael Allen

2012-06-07

324

FIRST ORDER KINETIC GAS GENERATION MODEL PARAMETERS FOR WET LANDFILLS  

EPA Science Inventory

Landfill gas is produced as a result of a sequence of physical, chemical, and biological processes occurring within an anaerobic landfill. Landfill operators, energy recovery project owners, regulators, and energy users need to be able to project the volume of gas produced and re...

325

Estimation of kinetic model parameters in fluorescence optical diffusion tomography  

E-print Network

et al.13 mea- sured the dynamics of two light-absorbing dyes, ICG and methylene blue to its small molecular weight of 373.9 Da, the methylene blue temporal dynamics were dominated by blood flow effects. From the methylene blue measurements, the authors observed variations in perfu- sion

326

Parameter estimation in stochastic kinetic models James B. Rawlings  

E-print Network

Virus Virus Cell Simple Viral Infection Model cccDNA k3 k4 k5 k2 rcDNA 0 5 10 15 20 25 30 35 0 50 100 150 200 cccDNA Time (sec) Deterministic Stoch 1 Stoch 2 0 5 10 15 20 0 50 100 150 200 cccDNA Time (sec

Liblit, Ben

327

Effects of process parameters on hydrothermal carbonization  

NASA Astrophysics Data System (ADS)

In recent years there has been increased research activity in renewable energy, especially upgrading widely available lignicellulosic biomass, in a bid to counter the increasing environmental concerns related with the use of fossil fuels. Hydrothermal carbonization (HTC), also known as wet torrefaction or hot water pretreatment, is a process for pretreatment of diverse lignocellulosic biomass feedstocks, where biomass is treated under subcritical water conditions in short contact time to produce high-value products. The products of this process are: a solid mass characterized as biochar/biocoal/biocarbon, which is homogeneous, energy dense, and hydrophobic; a liquid stream composed of five and six carbon sugars, various organic acids, and 5-HMF; and a gaseous stream, mainly CO2. A number of process parameters are considered important for the extensive application of the HTC process. Primarily, reaction temperature determines the characteristics of the products. In the solid product, the oxygen carbon ratio decreases with increasing reaction temperature and as a result, HTC biochar has the similar characteristics to low rank coal. However, liquid and gaseous stream compositions are largely correlated with the residence time. Biomass particle size can also limit the reaction kinetics due to the mass transfer effect. Recycling of process water can help to minimize the utility consumption and reduce the waste treatment cost as a result of less environmental impact. Loblolly pine was treated in hot compressed water at 200 °C, 230 °C, and 260 °C with 5:1 water:biomass mass ratio to investigate the effects of process parameters on HTC. The solid product were characterized by their mass yields, higher heating values (HHV), and equilibrium moisture content (EMC), while the liquid were characterized by their total organic carbon content and pH value.

Uddin, Md. Helal

328

(S)-selective kinetic resolution and chemoenzymatic dynamic kinetic resolution of secondary alcohols.  

PubMed

(S)-Selective kinetic resolution was achieved through the use of a commercially available protease, which was activated with a combination of two different surfactants. The kinetic resolution (KR) process was optimized with respect to activation of the protease and to the acyl donor. The KR proved to be compatible with a range of functionalized sec-alcohols, giving good to high enantiomeric ratio values (up to >200). The enzymatic resolution was combined with a ruthenium-catalyzed racemization to give an (S)-selective dynamic kinetic resolution (DKR) of sec-alcohols. The DKR process works under very mild reaction conditions to give the corresponding esters in high yields and with excellent enantioselectivities. PMID:16267860

Borén, Linnéa; Martín-Matute, Belén; Xu, Yongmei; Córdova, Armando; Bäckvall, Jan-E

2005-12-16

329

Kinetic modelling of plant metabolic pathways.  

PubMed

This paper provides a review of kinetic modelling of plant metabolic pathways as a tool for analysing their control and regulation. An overview of different modelling strategies is presented, starting with those approaches that only require a knowledge of the network stoichiometry; these are referred to as structural. Flux-balance analysis, metabolic flux analysis using isotope labelling, and elementary mode analysis are briefly mentioned as three representative examples. The main focus of this paper, however, is a discussion of kinetic modelling, which requires, in addition to the stoichiometry, a knowledge of the kinetic properties of the constituent pathway enzymes. The different types of kinetic modelling analysis, namely time-course simulation, steady-state analysis, and metabolic control analysis, are explained in some detail. An overview is presented of strategies for obtaining model parameters, as well as software tools available for simulation of such models. The kinetic modelling approach is exemplified with discussion of three models from the general plant physiology literature. With the aid of kinetic modelling it is possible to perform a control analysis of a plant metabolic system, to identify potential targets for biotechnological manipulation, as well as to ascertain the regulatory importance of different enzymes (including isoforms of the same enzyme) in a pathway. Finally, a framework is presented for extending metabolic models to the whole-plant scale by linking biochemical reactions with diffusion and advective flow through the phloem. Future challenges include explicit modelling of subcellular compartments, as well as the integration of kinetic models on the different levels of the cellular and organizational hierarchy. PMID:22419742

Rohwer, Johann M

2012-03-01

330

The effect of cell line, phylogenetics and medium on baculovirus budded virus yield and quality.  

PubMed

The performance of bioprocesses involving baculoviruses largely depends on an efficient infection of cells by concentrated budded virus (BV) inoculums. Baculovirus expression vector systems have been established using Autographa californica nucleopolyhedrovirus (AcMNPV), a group I NPV that displays rapid virus kinetics, whereas bioprocesses using group II baculovirus-based biopesticides such as Helicoverpa armigera nucleopolyhedrovirus (HearNPV) have the limitation of low levels of BV, as these viruses often display poor BV production kinetics. In this study, the effect of key parameters involved in the quality of progeny virions, including cell line, virus phylogenetics and medium, on viral DNA replication, virus trafficking to the extracellular environment, and the yield of recombinant protein or polyhedra were investigated in synchronous infections of HearNPV and AcMNPV. HearNPV showed higher vDNA replication in its optimum medium, SF900III, when compared to AcMNPV, but both viruses had similar specific extracellular virion content. However, the ratio of AcMNPV extracellular virions to the total number of progeny virions produced was higher, and their quality was tenfold higher than that of HearNPV extracellular virions. The results of infection of two different cell lines, High Five and Sf9, with AcMNPV, along with HearNPV infection of HzAM1 cells in three different media, suggest that the host cells and the nutritional state of the medium as well as the phylogenetics of the virus affect the BV yields produced by different baculovirus/cell line/medium combinations. PMID:23884632

Matindoost, Leila; Hu, Hao; Chan, Leslie C L; Nielsen, Lars K; Reid, Steven

2014-01-01

331

Generalised yield criteria of porous sintered powder metallurgy metals  

Microsoft Academic Search

A new form of yield criterion considering an anisotropic parameter for porous sintered powder metallurgy metals has been proposed in this technical paper. In addition to the above, the flow rule with anisotropic parameter for porous metal is introduced. The mathematical expression for the calculation of flow stress in the case of simple compression or tension test is deduced from

R. Narayanasamy; R. Ponalagusamy; K. R. Subramanian

2001-01-01

332

NADH peroxidase: kinetic mechanism and nucleotide specificity  

SciTech Connect

NADH peroxidase is a flavoprotein reductase isolated from Streptococcus faecalis which catalyzes the pyridine nucleotide dependent reduction of hydrogen peroxide to water. Initial velocity, product and dead-end inhibition studies have been performed and all support a ping-pong kinetic mechanism. Further support for the ping-pong nature of the kinetic mechanism are the hydrogen peroxide independent transhydrogenase activity of the enzyme, measured either with thio-NAD or with radiolabeled NAD (isotope exchange studies). Kinetic parameters will be presented for a number of reduced pyridine nucleotide analogs. Analogs which have been modified in the adenine ring exhibit much higher K/sub m/'s relative to their adenine analogs. NADH peroxidase catalyzes the stereo-specific removal of the 4S hydrogen of NADH and primary deuterium kinetic isotope effects have been determined for a number of these substrates with 4S-deuterated molecules. There is a strong correlation between their steady-state K/sub m/ and /sup D/V/K. Small values for /sup D/V are interpreted as supporting rate-limitation in the oxidative half-reaction. These data will be discussed in terms of a kinetic and chemical mechanism proposed for NADH peroxidase.

Stoll, V.S.; Blanchard, J.S.

1987-05-01

333

Kinetics of Materials  

NASA Astrophysics Data System (ADS)

A classroom-tested textbook providing a fundamental understanding of basic kinetic processes in materials This textbook, reflecting the hands-on teaching experience of its three authors, evolved from Massachusetts Institute of Technology's first-year graduate curriculum in the Department of Materials Science and Engineering. It discusses key topics collectively representing the basic kinetic processes that cause changes in the size, shape, composition, and atomistic structure of materials. Readers gain a deeper understanding of these kinetic processes and of the properties and applications of materials. Topics are introduced in a logical order, enabling students to develop a solid foundation before advancing to more sophisticated topics. Kinetics of Materials begins with diffusion, offering a description of the elementary manner in which atoms and molecules move around in solids and liquids. Next, the more complex motion of dislocations and interfaces is addressed. Finally, still more complex kinetic phenomena, such as morphological evolution and phase transformations, are treated. Throughout the textbook, readers are instilled with an appreciation of the subject's analytic foundations and, in many cases, the approximations commonly used in the field. The authors offer many extensive derivations of important results to help illuminate their origins. While the principal focus is on kinetic phenomena in crystalline materials, select phenomena in noncrystalline materials are also discussed. In many cases, the principles involved apply to all materials. Exercises with accompanying solutions are provided throughout Kinetics of Materials, enabling readers to put their newfound knowledge into practice. In addition, bibliographies are offered with each chapter, helping readers to investigate specialized topics in greater detail. Several appendices presenting important background material are also included. With its unique range of topics, progressive structure, and extensive exercises, this classroom-tested textbook provides an enriching learning experience for first-year graduate students.

Balluffi, Robert W.; Allen, Samuel M.; Carter, W. Craig

2005-09-01

334

Kinetic modeling of petroleum formation in the Maracaibo Basin: Final report, Annex 12  

SciTech Connect

The purpose of this project is to develop and test improved kinetic models of petroleum generation and cracking, pore pressure buildup, and fluid expulsion. The work was performed jointly between Lawrence Livermore National Laboratory and Research Organization of the Venezuelan National Petroleum Company under Annex 12 of an agreement between DOE and the Venezuelan Ministry of Energy and Mines. Laboratory experiments were conducted at both LLNL and INTEVEP to obtain the reaction rate and product composition information needed to develop chemical kinetic models. Experiments at INTEVEP included hydrous pyrolysis and characterization of oils by gas and liquid chromatography. Experiments at LLNL included programmed pyrolysis in open and self-purging reactors, sometimes including on-line gas analysis by tandem mass spectrometry, and characterization of oils by gas chromatography and nuclear magnetic resonance. The PMOD code was used to develop a detailed pyrolysis mechanism from the extensive laboratory data. This mechanism is able to predict yield of bitumen, oil, and gas as a function of time and temperature for such diverse laboratory conditions as hydrous pyrolysis and rapid, programmed, open pyrolysis. PMOD calculations were compared to geologic observations for 22 wells in the Maracaibo basin. When permeability parameters are chosen to match calculated pore pressures with measured present day values, the PMOD calculations indicate that organic maturation reactions contribute a significant fraction of the overpressure during oil generation and early oil cracking. Calculations agreed with observed geochemical maturity parameters of the source rock. 37 refs., 64 figs., 20 tabs.

Burnham, A.K.; Braun, R.L.; Sweeney, J.J.; Reynolds, J.G. [Lawrence Livermore National Lab., CA (United States); Vallejos, C.; Talukdar, S. [INTEVEP, Filial de Petroleos de Venezuela, SA, Caracas (Venezuela)

1992-07-01

335

Dissolution Kinetics of Zirconia Calcine  

SciTech Connect

Liquid radioactive raffinates from nuclear fuel reprocessing at the Idaho National Engineering and Environmental Laboratory were solidified, or calcines, in a fluidized bed reactor at approximately 500 C to form a dry granular material. This calcine has been provisionally stored near-surface in concrete-encased stainless steel bins at the Idaho Nuclear Technology Engineering Center. Research addressing the permanent immobilization of radioactive waste has been ongoing. One option is to separate the radioactive constituents from the calcine, thereby reducing the radioactive waste volume to be ultimately stored at a national nuclear waste repository. Nitric acid dissolution of the calcine is a key front-end unit operation in the separations option. In order to design calcine dissolution equipment, quantification of dissolution reaction rate parameters is required. A pilot-plant-produced, non-radioactive calcine was utilized to study the dissolution kinetics of a zirconia-type calcine. A heterogeneous overall calcine dissolution rate expression has been developed from the dissolution kinetics experimental data. This modeling work indicates that internal diffusion is the predominate controlling mechanism during dissolution of zirconia-type calcine. A shrinking core model with an exponentially decreasing internal diffusion as dissolution progresses fits that data best. However, this simple heterogeneous reaction model is not adequate to completely describe calcine dissolution.

T. A. Batcheller

1999-06-01

336

Kinetics of infective juvenile production of the entomopathogenic nematode Steinernema carpocapsae in submerged monoxenic culture  

Microsoft Academic Search

The effects of culture medium formulations on the kinetics of infective juvenile (IJ) production of the entomopathogenic nematode\\u000a Steinernema carpocapsae in submerged monoxenic culture, were studied at the cylindrical-bottle scale using six culture media containing agave juice\\u000a from Agave spp. among other ingredients. The IJ production kinetics was well modelled through a re-parameterised 3-parameter Gompertz\\u000a model with kinetic parameters: IJ-lag

Norberto Chavarría-Hernández; Marco-Antonio Islas-López; Gabriela Maciel-Vergara; Martha Gayosso-Canales; Adriana-Inés Rodríguez-Hernández

2008-01-01

337

Glucagon kinetics in growing rats fed different levels of protein and/or energy  

E-print Network

Glucagon kinetics in growing rats fed different levels of protein and/or energy Michèle BALAGE, J parameters of glucagon in growing rats divided into three groups : T, H and E. Group T (Control group %). In all cases, the animals were fed a meal every 4 hours. The kinetic parameters of glucagon metabolism

Paris-Sud XI, Université de

338

Modeling Taylor dispersion injections: determination of kinetic/affinity interaction constants and diffusion coefficients in label-free biosensing.  

PubMed

A new method based on Taylor dispersion has been developed that enables an analyte gradient to be titrated over a ligand-coated surface for kinetic/affinity analysis of interactions from a minimal number of injections. Taylor dispersion injections generate concentration ranges in excess of four orders of magnitude and enable the analyte diffusion coefficient to be reliably estimated as a fitted parameter when fitting binding interaction models. A numerical model based on finite element analysis, Monte Carlo simulations, and statistical profiling were used to compare the Taylor dispersion method with standard fixed concentration injections in terms of parameter correlation, linearity of parameter error space, and global versus local model fitting. A dramatic decrease in parameter correlations was observed for TDi curves relative to curves from standard fixed concentration injections when surface saturation was achieved. In FCI the binding progress is recorded with respect to injection time, whereas in TDi the second time dependency encoded in the analyte gradient increases resolving power. This greatly lowers the dependence of all parameters on each other and on experimental interferences. When model parameters were fitted locally, the performance of TDis remained comparable to global model fitting, whereas fixed concentration binding response curves yielded unreliable parameter estimates. PMID:22197421

Quinn, John G

2012-02-15

339

Lepton flavor violating decays {tau}{yields}lll and {mu}{yields}e{gamma} in the Higgs triplet model  

SciTech Connect

Singly and doubly charged Higgs bosons in the Higgs triplet model mediate the lepton flavor violating (LFV) decays {tau}{yields}lll and {mu}{yields}e{gamma}. The lepton flavor violating decay rates are proportional to products of two triplet Yukawa couplings (h{sub ij}) which can be expressed in terms of the parameters of the neutrino mass matrix and an unknown triplet vacuum expectation value. We determine the parameter space of the neutrino mass matrix in which a signal for {tau}{yields}lll and/or {mu}{yields}e{gamma} is possible at ongoing and planned experiments. The conditions for respecting the stringent upper limit for {mu}{yields}eee are studied in detail, with emphasis given to the possibility of |h{sub ee}|{approx_equal}0, which can only be realized if Majorana phases are present.

Akeroyd, A. G. [Department of Physics, National Central University, Jhongli 320, Taiwan (China); Aoki, Mayumi [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Sugiyama, Hiroaki [SISSA, via Beirut 2-4, I-34014 Trieste (Italy); Department of Physics, Ritsumeikan University, Kusatsu, Shiga 525-8577 (Japan)

2009-06-01

340

Validating continuous kraft digester kinetic models with online NIR measurements  

Microsoft Academic Search

Representative families of models for the chemical kinetics of kraft pulping taken from the literature spanning the last three decades are compared using data obtained from a series of autoclave cooks and an instrumented laboratory circulation digester. The differences within families is slight, and they reasonably explain the data with fitted parameters, and more crucially, even when using original parameters.

Niclas Andersson; David I. Wilson; U. Germgard

2002-01-01

341

Study of the growth and switching kinetics on ferroelectric nanocrystals of copolymer vinylidene fluoride and trifluoroethylene on an atomic force microscope  

SciTech Connect

The growth of nanocrystals obtained from Langmuir-Blodgett films of ferroelectric copolymer consisting of 70% vinylidene fluoride and 30% trifluoroethylene has been investigated by atomic force microscopy (AFM). The radius and concentration of nanocrystals are found to depend on the annealing time of the film. A model for nanocrystal growth is proposed which yields adequate time dependences for nanocrystal size parameters. The switching kinetics of individual ferroelectric nanocrystals with an average diameter of 100-200 nm and a height of 15-20 nm has been investigated in the piezoelectric response mode. It is shown that the switching of nanocrystals has an activation character.

Gaynutdinov, R. V., E-mail: lolga1@rambler.ru; Lysova, O. A.; Tolstikhina, A. L.; Fridkin, V. M.; Yudin, S. G. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)] [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Ducharme, S. [University of Nebraska, Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience (United States)] [University of Nebraska, Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience (United States)

2013-03-15

342

Erosion of a yield-stress fluid  

NASA Astrophysics Data System (ADS)

Bed erosion induced by rapid gravity flows of complex fluids, such as mudflows or avalanches, remains still poorly understood. A specificity of these natural flows is that, mostly, the material forming the static bed has mechanical properties similar to those of the flowing material (mud/mud, snow/snow). In this experimental study, yield-stress fluids are implemented to model both the eroding flow and the eroded bed with an original approach that captures the process of erosion in terms of solid-fluid transition. The hydrodynamics of erosion is studied in an inclined channel configuration, where a yield-stress fluid flows on a thick layer of the same fluid having an equal or a greater yield stress. In this work, we chose to use a micro-gel polymer (Carbopol) because of its elasto-viscoplastic rheology and its transparency, which is exploited for internal visualization techniques such as Particle Image Velocimetry (PIV). Our approach aims to investigate the dominant physical mechanisms of erosion by combining an accurate rheological characterization of the yield-stress fluid using a rheometer (Hershel-Bulkley law), with the observation of the morphological evolution of the system substratum / flow and the local measurement of related hydrodynamic parameters. The main goal is to relate the erosion law at the substrate/flow interface with the constitutive law of the complex fluid involved, in order to refine this latter in the vicinity of the transition between the quasi-static and the liquid regimes.

Luu, Li-Hua; Philippe, Pierre; Chambon, Guillaume

2013-04-01

343

Kinetics of thermochemical pretreatment of lignocellulosic materials  

Microsoft Academic Search

The results of an experimental study of the acid hydrolysis of hardwood are presented in the form of values for the three\\u000a parameters, activation energy, power on the acid concentration, and pre-exponen-tial factor, of the first order kinetic constants\\u000a for each of the following reaction participants: xylan remaining, glucan remaining, xylose formed, and xylose decomposed.\\u000a These are used as a

A. O. Converse; I. K. Kwarteng; H. E. Grethlein; H. Ooshima

1989-01-01

344

Fractal reaction kinetics.  

PubMed

Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal "memories." The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of "fractal-like kinetics" are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds. PMID:17820893

Kopelman, R

1988-09-23

345

Modeling of hydrogen production methods: Single particle model and kinetics assessment  

SciTech Connect

The investigation carried out by the Jet Propulsion Laboratory (JPL) is devoted to the modeling of biomass pyrolysis reactors producing an oil vapor (tar) which is a precursor to hydrogen. This is an informal collaboration with NREL whereby JPL uses the experimentally-generated NREL data both as initial and boundary conditions for the calculations, and as a benchmark for model validation. The goal of this investigation is to find drivers of biomass fast-pyrolysis in the low temperature regime. The rationale is that experimental observations produce sparse discrete conditions for model validation, and that numerical simulations produced with a validated model are an economic way to find control parameters and an optimal operation regime, thereby circumventing costly changes in hardware and tests. During this first year of the investigation, a detailed mathematical model has been formulated for the temporal and spatial accurate modeling of solid-fluid reactions in biomass particles. These are porous particles for which volumetric reaction rate data is known a priori and both the porosity and the permeability of the particle are large enough to allow for continuous gas phase flow. The methodology has been applied to the pyrolysis of spherically symmetric biomass particles by considering previously published kinetics schemes for both cellulose and wood. The results show that models which neglect the thermal and species boundary layers exterior to the particle will generally over predict both the pyrolysis rates and experimentally obtainable tar yields. An evaluation of the simulation results through comparisons with experimental data indicates that while the cellulose kinetics is reasonably accurate, the wood pyrolysis kinetics is not accurate; particularly at high reactor temperatures. Current effort in collaboration with NREL is aimed at finding accurate wood kinetics.

Miller, R.S.; Bellan, J. [California Institute of Technology, Pasadena, CA (United States)

1996-10-01

346

Roll-your-own smoke yields: theoretical and practical aspects  

PubMed Central

OBJECTIVE—To identify the key parameters that influence smoke yields from roll-your-own (RYO) cigarettes and to compare smoke yields of cigarettes made under laboratory conditions with those made by habitual RYO consumers.?DESIGN AND SETTING—One-way parametric variations in the laboratory-based production of RYO cigarettes complemented by a consumer survey conducted in a busy street at Romford, Essex, United Kingdom.?SUBJECTS—26 habitual RYO consumers.?MAIN OUTCOME MEASURES—Cigarette weights, puff numbers, and yields (carbon monoxide, nicotine, and tar).?RESULTS—Smoke yields vary for specimen changes in weight of tobacco used, paper porosity, and the incorporation of a filter in the cigarette. Yields of cigarettes produced by 26 RYO smokers ranged from 9.9 to 21.0 mg tar per cigarette and from 0.9 to 1.8 mg nicotine per cigarette, and were generally lower than yields of laboratory-produced RYO cigarettes.?CONCLUSIONS—Laboratory studies can provide useful information concerning the parameters that affect smoke yields of RYO cigarettes such as the incorporation of a filter to reduce yields. However, such studies must be complemented by surveys of cigarettes made by actual current RYO smokers. In one such investigation, it was found that the mean tar yields from cigarettes produced by 57% of the smokers were above the current maximum of 15 mg per cigarette for manufactured cigarettes. Currently 8% of manufactured cigarettes in the UK have a declared nicotine yield of greater than 1.1 mg per cigarette whereas 77% of RYO smokers produced cigarettes with a nicotine yield greater than this value.???Keywords: roll-your-own cigarettes; smoke yield; carbon monoxide; tar; nicotine PMID:9789936

Darrall, K.; Figgins, J.

1998-01-01

347

Kinetic theory viscosity  

E-print Network

We show how the viscous evolution of Keplerian accretion discs can be understood in terms of simple kinetic theory. Although standard physics texts give a simple derivation of momentum transfer in a linear shear flow using kinetic theory, many authors, as detailed by Hayashi & Matsuda 2001, have had difficulties applying the same considerations to a circular shear flow. We show here how this may be done, and note that the essential ingredients are to take proper account of, first, isotropy locally in the frame of the fluid and, second, the geometry of the mean flow.

C. J. Clarke; J. E. Pringle

2004-03-17

348

Kinetics of uncatalyzed thermochemical sulfate reduction by sulfur-free paraffin  

USGS Publications Warehouse

To determine kinetic parameters of sulfate reduction by hydrocarbons (HC) without the initial presence of low valence sulfur, we carried out a series of isothermal gold-tube hydrous-pyrolysis experiments at 320, 340, and 360 °C under a constant confined pressure of 24.1 MPa. The reactants used consisted of saturated HC (sulfur-free) and CaSO4 in an aqueous solution buffered to three different pH conditions without the addition of elemental sulfur (S8) or H2S as initiators. H2S produced in the course of reaction was proportional to the extent of the reduction of CaSO4 that was initially the only sulfur-containing reactant. Our results show that the in situ pH of the aqueous solution (herein, in situ pH refers to the calculated pH value of the aqueous solution at certain experimental conditions) can significantly affect the rate of the thermochemical sulfate reduction (TSR) reaction. A substantial increase in the TSR reaction rate was observed with a decrease in the in situ pH. Our experimental results show that uncatalyzed TSR is a first-order reaction. The temperature dependence of experimentally measured H2S yields from sulfate reduction was fit with the Arrhenius equation. The determined activation energy for HC (sulfur-free) reacting with View the MathML sourceHSO4? in our experiments is 246.6 kJ/mol at pH values ranging from 3.0 to 3.5, which is slightly higher than the theoretical value of 227.0 kJ/mol using ab initio quantum chemical calculations on a similar reaction. Although the availability of reactive sulfate significantly affects the rate of reaction, a consistent rate constant was determined by accounting for the HSO4? ion concentration. Our experimental and theoretical approach to the determination of the kinetics of TSR is further validated by a reevaluation of several published experimental TSR datasets without the initial presence of native sulfur or H2S. When the effect of reactive sulfate concentration is appropriately accounted for, the published experimental TSR data yield kinetic parameters that are consistent with our values. Assuming MgSO4 contact-ion-pair ([MgSO4]CIP) as the reactive form of sulfate in petroleum reservoir formation waters, a simple extrapolation of our experimentally derived HSO4? reduction kinetics as a proxy for [MgSO4]CIP to geologically reasonable conditions predicts onset temperatures (130–140 °C) that are comparable to those observed in nature.

Zhang, Tongwei; Ellis, Geoffrey S.; Ma, Qisheng; Amrani, Alon; Tang, Yongchun

2012-01-01

349

Evaluation of reaction kinetics for gas-powder systems  

Microsoft Academic Search

Kinetic models for the reaction between a gas and powder are presented and discussed. Rates from the progressive conversion model are dependent on the amount of material present. This model is described by an equation that yields both the rate constant and the reaction order. The phase boundary model produces rates for topochemical reactions which are dependent on the powder

J. L. Stakebake; G. E. Bixby

1979-01-01

350

KINETIC MODEL OF FLUORIDE METABOLISM IN THE RABBIT  

EPA Science Inventory

Sodium fluoride, in small doses, was given to rabbits intravenously or by stomach tube, and the appearance of fluoride in the blood and urine was then monitored frequently over the next 10 hours. Compartmental analysis of the data yielded a kinetic model of fluoride metabolism co...

351

Kinetic energy budgets in areas of intense convection  

NASA Technical Reports Server (NTRS)

A kinetic energy budget analysis of the AVE-SESAME 1 period which coincided with the deadly Red River Valley tornado outbreak is presented. Horizontal flux convergence was found to be the major kinetic energy source to the region, while cross contour destruction was the major sink. Kinetic energy transformations were dominated by processes related to strong jet intrusion into the severe storm area. A kinetic energy budget of the AVE 6 period also is presented. The effects of inherent rawinsonde data errors on widely used basic kinematic parameters, including velocity divergence, vorticity advection, and kinematic vertical motion are described. In addition, an error analysis was performed in terms of the kinetic energy budget equation. Results obtained from downward integration of the continuity equation to obtain kinematic values of vertical motion are described. This alternate procedure shows promising results in severe storm situations.

Fuelberg, H. E.; Berecek, E. M.; Ebel, D. M.; Jedlovec, G. J.

1980-01-01

352

A periodic charge-dipole electrostatic model. II. A kinetic-exchange-correlation correction  

NASA Astrophysics Data System (ADS)

We extend the periodic charge-dipole electrostatic model, see I. V. Bodrenko, M. Sierka, E. Fabiano, and F. Della Sala, J. Chem. Phys. 137, 134702 (2012), to include a kinetic-exchange-correlation (KXC) correction. The KXC correction is approximated by means of an extended-Hückel-type formula, it is exact in the infinite jellium model and it is also computationally efficient as it requires only the computation of overlap integrals. Tests on the linear response of silver slabs to an external electrostatic perturbation show that the KXC correction yields a very accurate description of induced dipole and of the whole induced charge density profile. We also show that the KXC parameters are quite transferable and related to the atomic polarizability.

Bodrenko, I. V.; Della Sala, F.

2013-10-01

353

A periodic charge-dipole electrostatic model. II. A kinetic-exchange-correlation correction.  

PubMed

We extend the periodic charge-dipole electrostatic model, see I. V. Bodrenko, M. Sierka, E. Fabiano, and F. Della Sala, J. Chem. Phys. 137, 134702 (2012), to include a kinetic-exchange-correlation (KXC) correction. The KXC correction is approximated by means of an extended-Hu?ckel-type formula, it is exact in the infinite jellium model and it is also computationally efficient as it requires only the computation of overlap integrals. Tests on the linear response of silver slabs to an external electrostatic perturbation show that the KXC correction yields a very accurate description of induced dipole and of the whole induced charge density profile. We also show that the KXC parameters are quite transferable and related to the atomic polarizability. PMID:24116605

Bodrenko, I V; Della Sala, F

2013-10-14

354

Development of dynamic kinetic resolution on large scale for (?)-1-phenylethylamine  

PubMed Central

Summary Candida antarctica lipase B (CALB) and racemization catalyst 4 were combined in the dynamic kinetic resolution (DKR) of (±)-1-phenylethylamine (1). Several reaction parameters have been investigated to modify the method for application on multigram scale. A comparison of isopropyl acetate and alkyl methoxyacetates as acyl donors was carried out. It was found that lower catalyst loadings could be used to obtain (R)-2-methoxy-N-(1-phenylethyl)acetamide (3) in good yield and high ee when alkyl methoxyacetates were used as acyl donors compared to when isopropyl acetate was used as the acyl donor. The catalyst loading could be decreased to 1.25 mol % Ru-catalyst 4 and 10 mg CALB per mmol 1 when alkyl methoxyacetates were used as the acyl donor. PMID:20978623

Thalen, Lisa K

2010-01-01

355

Comparison of petroleum generation kinetics by isothermal hydrous and nonisothermal open-system pyrolysis  

USGS Publications Warehouse

This study compares kinetic parameters determined by open-system pyrolysis and hydrous pyrolysis using aliquots of source rocks containing different kerogen types. Kinetic parameters derived from these two pyrolysis methods not only differ in the conditions employed and products generated, but also in the derivation of the kinetic parameters (i.e., isothermal linear regression and non-isothermal nonlinear regression). Results of this comparative study show that there is no correlation between kinetic parameters derived from hydrous pyrolysis and open-system pyrolysis. Hydrous-pyrolysis kinetic parameters determine narrow oil windows that occur over a wide range of temperatures and depths depending in part on the organic-sulfur content of the original kerogen. Conversely, open-system kinetic parameters determine broad oil windows that show no significant differences with kerogen types or their organic-sulfur contents. Comparisons of the kinetic parameters in a hypothetical thermal-burial history (2.5 ??C/my) show open-system kinetic parameters significantly underestimate the extent and timing of oil generation for Type-US kerogen and significantly overestimate the extent and timing of petroleum formation for Type-I kerogen compared to hydrous pyrolysis kinetic parameters. These hypothetical differences determined by the kinetic parameters are supported by natural thermal-burial histories for the Naokelekan source rock (Type-IIS kerogen) in the Zagros basin of Iraq and for the Green River Formation (Type-I kerogen) in the Uinta basin of Utah. Differences in extent and timing of oil generation determined by open-system pyrolysis and hydrous pyrolysis can be attributed to the former not adequately simulating natural oil generation conditions, products, and mechanisms.

Lewan, M. D.; Ruble, T. E.

2002-01-01

356

Rx for low cash yields.  

PubMed

Certain strategies can offer not-for-profit hospitals potentially greater investment yields while maintaining stability and principal safety. Treasury inflation-indexed securities can offer good returns, low volatility, and inflation protection. "Enhanced cash" strategies offer liquidity and help to preserve capital. Stable value "wrappers" allow hospitals to pursue higher-yielding fixed-income securities without an increase in volatility. PMID:14560584

Tobe, Chris

2003-10-01

357

Parameterization of annealing kinetics in pharmaceutical glasses.  

PubMed

Numerical simulations indicate that neglecting the canonical nonlinearity of glassy-state annealing kinetics in pharmaceutical (and other) glasses leads to good KWW fits to the dependence of enthalpy on annealing time, but with spurious KWW parameters that are affected by nonlinearity. A simplified treatment of nonlinearity that uses the Struik shift factor is found to be a useful approximation for these analyses, and can account for previously reported differences between linear and nonlinear KWW parameters (Kawakami K, Pikal MJ. 2005. J Pharm Sci 94:948-965). PMID:23661359

Hodge, Ian M

2013-07-01

358

Estimation of Rainfall Kinetic Energy by Rain Intensity and/or Radar Reflectivity Factor  

NASA Astrophysics Data System (ADS)

This study presents an approach to estimate the rainfall kinetic energy (KE) by rain intensity (R) and radar reflectivity factor (Z) separately, or jointly, on the basis of a one- or two-moment scaled formulation. This formulation considers the raindrop size distribution (DSD) as a combination of bulk rainfall variable(s) (R or/and Z) and an intrinsic distribution g(x), which is in function of the scaled raindrop diameter x. Results from previous studies showed that g(x) remains more or less constant, hence the variability of DSD is mainly explained by the bulk rainfall variable(s). In this study, the Gamma probability density function (pdf) with two parameters is used to model the g(x). Considered the self-consistent relationships between parameters, a robust method is proposed to estimate three climatological g(x), in R-, Z- and RZ-scaled formulation respectively, with a 28-month DSD dataset collected in the Cevennes-Vivarais region, France. Three relationships (KE-R, KE-Z and KE-(R,Z)), which link the observations (R and/or Z) to rainfall kinetic energy (KE), are established based on three climatological g(x). As expected, the combination of R and Z yields a significant improvement of the estimation of KE compared to the single-moment formulations. And Z yields a better performance in KE estimating compared to the KE-R relationship. In terms of the application of these relationships based on real radar reflectivity factors and/or rain gauge measurements, the combination of R and Z yields also the best performance in estimation of KE among the three relationships. Different from the application of the disdrometer data, the performance of the real KE-Z relationship degrades compared to the real KE-R relationship, which is probably due to the sampling error of radar. However, KE estimated by radar possess the advantages in spatialization of kinetic energy over that based on rain gauge stations. This study was supported financially by the HYDRATE project of the European Community (GOCE 037024). The first author would also like to thank the SOERE RBV project which provides the travel grants for participation in AGU meeting.

Yu, N.; Delrieu, G.; Boudevillain, B.; Hazenberg, P.; Uijlenhoet, R.

2011-12-01

359

Parameter estimation for 3-parameter generalized pareto distribution by the principle of maximum entropy (POME)  

Microsoft Academic Search

The principle of maximum entropy (POME) is employed to derive a new method of parameter estimation for the 3-parameter generalized Pareto (GP) distribution. Monte Carlo simulated data are used to evaluate this method and compare it with the methods of moments (MOM), probability weighted moments (PWM), and maximum likelihood estimation (MLE). The parameter estimates yielded by the POME are either

V. P. SINGH; H. GUO

1995-01-01

360

Sampled-current voltammetry at microdisk electrodes: kinetic information from pseudo steady state voltammograms.  

PubMed

In sampled-current voltammetry (SCV), current transients acquired after stepping the potential along the redox wave of interest are sampled at a fixed time to produce a sigmoidal current-potential curve akin to a pseudo steady state voltammogram. Repeating the sampling for different times yields a family of sampled-current voltammograms, one for each time scale. The concept has been used to describe the current-time-potential relationship at planar electrodes but rarely employed as an electroanalytical method except in normal pulse voltammetry where the chronoamperograms are sampled once to produce a single voltammogram. Here we combine the unique properties of microdisk electrodes with SCV and report a simple protocol to analyze and compare the microdisk sampled-current voltammograms irrespective of sampling time. This is particularly useful for microelectrodes where cyclic voltammograms change shape as the mass transport regime evolves from planar diffusion at short times to hemispherical diffusion at long times. We also combine microdisk sampled-current voltammetry (MSCV) with a conditioning waveform to produce voltammograms where each data point is recorded with the same electrode history and demonstrate that the waveform is crucial to obtaining reliable sampled-current voltammograms below 100 ms. To facilitate qualitative analysis of the voltammograms, we convert the current-potential data recorded at different time scales into a unique sigmoidal curve, which clearly highlights kinetic complications. To quantitatively model the MSCVs, we derive an analytical expression which accounts for the diffusion regime and kinetic parameters. The procedure is validated with the reduction of Ru(NH3)6(3+), a model one electron outer sphere process, and applied to the derivation of the kinetic parameters for the reduction of Fe(3+) on Pt microdisks. The methodology reported here is easily implemented on computer controlled electrochemical workstations as a new electroanalytical method to exploit the unique properties of microelectrodes, in particular at short times. PMID:25178385

Perry, Samuel C; Al Shandoudi, Laila M; Denuault, Guy

2014-10-01

361

H theorem and kinetic equations for a reacting gas  

NASA Technical Reports Server (NTRS)

A previously developed set of kinetic model equations for a chemically-reacting gas is modified. By examining closely the H theorem, a new set of constraints is obtained. These conditions are then used to determine the inelastic collision parameters proposed in the model. The kinetic equations so obtained are able to produce exactly the same rate equations as prescribed by the actual chemical reactions.

Fang, T.-M.

1973-01-01

362

Rhealogical studies of tautomerization kinetics in supercooled glibenclamide drug  

SciTech Connect

Rheological measurements have been applied to study the tautomerization of the pharmaceutically active compound glibenclamide. The rate constant and activation energy of the imidic-acid-amide transformation have been successfully determined by monitoring the evolution of shear viscosity. The kinetic parameters from rheological measurements agree reasonably well with the data previously obtained from dielectric spectroscopy. The present Brief Report demonstrates that rheology can provide a fast and precise way to characterize the reaction kinetics of tautomerization.

Wojnarowska, S [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland; Wang, Yangyang [ORNL; Sokolov, Alexei P [ORNL; Paluch, Marian W [ORNL

2012-01-01

363

Kinetic studies of corn stover saccharification using sulphuric acid  

Microsoft Academic Search

The kinetics of crystalline cellulose and hemicellulose hydrolysis in corn stover were studied with a nonisothermal technique. Reactions were arrested at temperatures between 160 and 240°C and product sugars were analyzed using a Bio-Rad HPX-85 liquid chromatographic column. A simple first-order series reaction model was used for both cellulose and hemicellulose hydrolysis rections. Kinetic parameters were obtained for three different

Nandan Bhandari; Douglas G. Macdonald; Narendra N. Bakhshi

1984-01-01

364

Improved Electron Yield and Spin-Polarizaton from III-V Photocathodes Via Bias Enhanced Carrier Drift  

SciTech Connect

Spin-polarized electrons are commonly used in high energy physics. Future work will benefit from greater polarization. Polarizations approaching 90% have been achieved at the expense of yield. The primary paths to higher polarization are material design and electron transport. Our work addresses the latter. Photoexcited electrons may be preferentially emitted or suppressed by an electric field applied across the active region. We are tuning this forward bias for maximum polarization and yield, together with other parameters, e.g., doping profile. Preliminary measurements have been carried out on bulk and thin film GaAs. As expected, the yield change far from the bandgap is quite large for bulk material. The bias is applied to the bottom (non-activated) side of the cathode so that the accelerating potential as measured with respect to the ground potential chamber walls is unchanged for different front-to-back cathode bias values. The size of the bias to cause an appreciable effect is rather small reflecting the low drift kinetic energy in the zero bias case.

Mulhollan, Gregory A.; Bierman, John; /Saxet Surface Sci.; Brachmann, Axel; Clendenin, James E.; Garwin, Edward; Kirby, Robert; Luh, Dah-An; Maruyama, Takashi; /SLAC; Prepost, Richard; /Wisconsin U., Madison

2005-09-14

365

Kinetic tetrazolium microtiter assay  

NASA Technical Reports Server (NTRS)

A method for conducting an in vitro cell assay using a tetrazolium indicator is disclosed. The indicator includes a nonionic detergent which solubilizes a tetrazolium reduction product in vitro and has low toxicity for the cells. The incubation of test cells in the presence of zolium bromide and octoxynol (TRITON X-100) permits kinetics of the cell metabolism to be determined.

Pierson, Duane L. (inventor); Stowe, Raymond P. (inventor); Koeing, David W. (inventor)

1992-01-01

366

Kinetics and Catalysis Demonstrations.  

ERIC Educational Resources Information Center

Eleven videotaped kinetics and catalysis demonstrations are described. Demonstrations include the clock reaction, oscillating reaction, hydrogen oxidation in air, hydrogen-oxygen explosion, acid-base properties of solids, high- and low-temperature zeolite reactivity, copper catalysis of ammonia oxidation and sodium peroxide decomposition, ammonia…

Falconer, John L.; Britten, Jerald A.

1984-01-01

367

Kinetic Theory I  

NSDL National Science Digital Library

This Java applet simulates a 2 dimensional gas of hard spheres. It illustrates several important concepts in statistical mechanics/kinetic theory, such as: mean free path and average time between collisions, the approach to thermal equilibrium and the Maxwell-Boltzmann speed distribution, and the question of macroscopic irreversibility vs. microscopic reversibility.

Gea-Banacloche, Julio

368

Chemoenzymatic dynamic kinetic resolution.  

PubMed

During the past decade a new concept has appeared in asymmetric catalysis involving the combination of a biocatalyst and a chemocatalyst in one 'pot' leading to efficient deracemization via dynamic kinetic resolution (DKR). Here, we outline the different strategies that have been developed for efficient chemoenzymatic DKR, in particular the powerful combination of an enzyme and a metal catalyst. PMID:15036863

Pàmies, Oscar; Bäckvall, Jan-E

2004-03-01

369

Chemical Kinetics: Isolation Method  

NSDL National Science Digital Library

This site offers an interactive tutorial that guides the student through the Method of Isolation used for the determination of chemical reaction rate laws and rate constants. This tutorial is coupled to others to further guide the student to a better understanding of chemical kinetics.

Blauch, David N.

370

Parameter estimation in cardiac ionic models  

Microsoft Academic Search

We examine the problem of parameter estimation in mathematical models of excitable cell cardiac electrical activity using the well-known Beeler–Reuter (1977) ionic equations for the ventricular action potential. The estimation problem can be regarded as equivalent to the accurate reconstruction of ionic current kinetics and amplitudes in an excitable cell model, given only action potential experimental data. We show that

Socrates Dokos; Nigel H. Lovell

2004-01-01

371

Kinetics of nanobubble generation around overheated nanoparticles.  

PubMed

We report on the formation and growth of nanobubbles around laser-heated gold nanoparticles in water. Using a hydrodynamic free-energy model, we show that the temporal evolution of the nanobubble radius is asymmetrical: the expansion is found to be adiabatic, while the collapse is best described by an isothermal evolution. We unveil the critical role of the thermal boundary resistance in the kinetics of formation of the nanobubbles: close to the vapor production threshold, nanobubble generation is very long, yielding optimal conditions for laser-energy conversion. Furthermore, the long appearance times allow nanoparticle melting before the onset of vaporization. PMID:24679307

Lombard, Julien; Biben, Thierry; Merabia, Samy

2014-03-14

372

Kinetics of Nanobubble Generation Around Overheated Nanoparticles  

NASA Astrophysics Data System (ADS)

We report on the formation and growth of nanobubbles around laser-heated gold nanoparticles in water. Using a hydrodynamic free-energy model, we show that the temporal evolution of the nanobubble radius is asymmetrical: the expansion is found to be adiabatic, while the collapse is best described by an isothermal evolution. We unveil the critical role of the thermal boundary resistance in the kinetics of formation of the nanobubbles: close to the vapor production threshold, nanobubble generation is very long, yielding optimal conditions for laser-energy conversion. Furthermore, the long appearance times allow nanoparticle melting before the onset of vaporization.

Lombard, Julien; Biben, Thierry; Merabia, Samy

2014-03-01

373

Cellulose thermal decomposition kinetics: Global mass loss kinetics  

Microsoft Academic Search

The kinetics of cellulose pyrolysis have received considerable attention during the past few decades. Despite intensive study, there remains controversy in the literature even on a topic as basic as the global kinetics of pyrolysis. The reported kinetics have been reconsidered in light of new experimental results that suggest a simple resolution to that part of the controversy concerning the

Ivan Milosavljevic; Eric M. Suuberg

1995-01-01

374

Maximizing the ExoEarth Candidate Yield from a Future Direct Imaging Mission  

NASA Astrophysics Data System (ADS)

ExoEarth yield is a critical science metric for future exoplanet imaging missions. Here we estimate exoEarth candidate yield using single visit completeness for a variety of mission design and astrophysical parameters. We review the methods used in previous yield calculations and show that the method choice can significantly impact yield estimates as well as how the yield responds to mission parameters. We introduce a method, called Altruistic Yield Optimization, that optimizes the target list and exposure times to maximize mission yield, adapts maximally to changes in mission parameters, and increases exoEarth candidate yield by up to 100% compared to previous methods. We use Altruistic Yield Optimization to estimate exoEarth candidate yield for a large suite of mission and astrophysical parameters using single visit completeness. We find that exoEarth candidate yield is most sensitive to telescope diameter, followed by coronagraph inner working angle, followed by coronagraph contrast, and finally coronagraph contrast noise floor. We find a surprisingly weak dependence of exoEarth candidate yield on exozodi level. Additionally, we provide a quantitative approach to defining a yield goal for future exoEarth-imaging missions.

Stark, Christopher C.; Roberge, Aki; Mandell, Avi; Robinson, Tyler D.

2014-11-01

375

Yield and yield components of saffron under different cropping systems  

Microsoft Academic Search

This study was conducted to evaluate yield and yield components of saffron (Crocus sativus L.) in response to (i) production system (PS) (irrigated vs. non-irrigated); (ii) corm size (CS) (medium ?2.25 to 3cm diameter vs. small corms <2.25cm diameter); (iii) planting depth (PD) (10cm vs. 20cm); and iv) planting density (PDEN) (51cormsm?2 vs. 69cormsm?2).This fully replicated multifactorial design was started

José Arturo de Juan; Horacio López Córcoles

2009-01-01

376

A data-oriented semi-process model for evaluating the yields of major crops at global scale (PRYSBI-2)  

NASA Astrophysics Data System (ADS)

Demand for major cereal crops will double by 2050 compared to the amount in 2005 due to the population growth, dietary change, and increase in biofuel use. This requires substantial efforts to increase crop yields under changing climate, water resources, and land use. In order to explore possible paths to meet the supply target, global crop modeling is a useful approach. To that end, we developed a process-based large-area crop model (called PRYSBIE-2) for major crops, including soybean. This model consisted of the enzyme kinetics model for photosynthetic carbon assimilation and soil water balance model from SWAT. The parameter values on water stress, nitrogen stress were calibrated over global croplands from one grid cell to another (1.125° in latitude and longitude) using Markov Chain Monte Carlo (MCMC) methods. The historical yield data collected from major crop-producing countries on a state, county, or prefecture scale were used as the calibration data. Then we obtained the model parameter sets that can give high correlation coefficients between the historical and estimated yield time series for the period 1980-2006. We analyzed the impacts on soybean yields in the three top soybean-producing countries (the USA, China, and Brazil) associated with the changes in climate and CO2 during the period 1980-2006, using the model. We found that, given the simulated yields and reported harvested areas, the estimated average net benefit from the CO2 fertilization effect (with one standard deviation) in the USA, Brazil, and China in the years was 42.70×32.52 Mt, 35.30×28.55 Mt, and 12.52×15.11 Mt, respectively. Results suggest that the CO2-induced increases in soybean yields in the USA and China likely offset a part of the negative impacts on yields due to the historical temperature rise. In contrast, the net effect of the past change in climate and CO2 in Brazil appeared to be positive. This study demonstrates a quantitative estimation of the impacts of the changes in climate and CO2 during the past few decades using a new global crop model.

Sakurai, G.; Iizumi, T.; Yokozawa, M.

2013-12-01

377

Grapevine canopy reflectance and yield  

NASA Technical Reports Server (NTRS)

Field spectroradiometric and airborne multispectral scanner data were applied in a study of Concord grapevines. Spectroradiometric measurements of 18 experimental vines were collected on three dates during one growing season. Spectral reflectance, determined at 30 intervals from 0.4 to 1.1 microns, was correlated with vine yield, pruning weight, clusters/vine, and nitrogen input. One date of airborne multispectral scanner data (11 channels) was collected over commercial vineyards, and the average radiance values for eight vineyard sections were correlated with the corresponding average yields. Although some correlations were significant, they were inadequate for developing a reliable yield prediction model.

Minden, K. A.; Philipson, W. R.

1982-01-01

378

Steady-state and stopped-flow kinetic measurements of the primary deuterium isotope effect in the reaction catalyzed by p-cresol methylhydroxylase  

SciTech Connect

Steady-state kinetic studies for the reaction of the flavocytochrome p-cresol methylhydroxylase with the reducing substrates (S) p-cresol, 4-ethylphenol, and their corresponding ..cap alpha..-deuterated analogues are presented. The results from these experiments and those from studies involving various reoxidizing substrates support the proposed apparent ping-pong mechanism. With phenazine methosulfate (PMS) as the reoxidant for studies at pH 7.6 and 6 or 25 /sup 0/C, the isotope effects on k/sub cat/ are lower than the intrinsic isotope effect. The values for /sup D/(k/sub cat//K/sub S/) are equal to the intrinsic effect for p-cresol at 25 /sup 0/C and for 4-ethylphenol at both 6 and 25 /sup 0/C. However, the value for this steady-state parameter at 6 /sup 0/C for p-cresol is lower than the intrinsic effect. The values for /sup D/(k/sub cat//K/sub PMS/) are nearly equal to 1.0 under all conditions. In contrast, the steady-state kinetic analysis for the isolated flavoprotein subunit of p-cresol methylhydroxylase involving p-cresol and PMS as substrates indicates that a random-binding mechanism is operating. Additionally, several of the steady-state parameters yield values for the apparent intrinsic isotope effect for the flavoprotein. The results of stopped-flow kinetic studies are also reported. At pH 7.6 the intrinsic isotope effect (/sup D/k/sub 2/) for the reduction of the enzyme by 4-ethylphenol is 4.8-5.0 at 25 /sup 0/C and 4.0 at 6 /sup 0/C. This technique yields a value for /sup D/k/sub 2/ of 7.05 at 6 /sup 0/C and pH 7.6 for p-cresol. The combined results from the stopped-flow and steady-state kinetic experiments at pH 7.6 and 6 /sup 0/C for p-cresol also allow the calculation of several important kinetic parameters for this enzyme. These calculations are viewed with caution, since some discrepancies develop when a comparison of the data from the two kinetic methods is made for both p-cresol and 4-ethylphenol.

McIntire, W.S.; Hopper, D.J.; Singer, T.P.

1987-06-30

379

[Kinetic model of enhanced biological phosphorus removal with mixed acetic and propionic acids as carbon sources. (II): Process simulation].  

PubMed

Two groups of sequencing batch reactors were used to study the metabolism substrate transformation of phosphorus-accumulating organisms (PAO) and glycogen-accumulating organisms (GAO) fed with mixed acetic and propionic acids. Seven stoichiometry parameters and 24 kinetic parameters were contained in the PAO and GAO kinetic model, and stoichiometry parameters were deduced from the stoichiometry models, while kinetic parameters were determined by experimental results. The kinetic model parameters of stoichiometry and kinetics were determined according the experiments and the literature. Subsequently, the substrate transformations of PAO and GAO were calculated by the Matlab software. The model curves matched the SBR experimental data well, indicating that the kinetic model based on SCFAs metabolism could be used to simulate PAO and GAO in anaerobic-aerobic conditions. PMID:23745407

Zhang, Chao; Chen, Yin-Guang

2013-03-01

380

LLNL Chemical Kinetics Modeling Group  

SciTech Connect

The LLNL chemical kinetics modeling group has been responsible for much progress in the development of chemical kinetic models for practical fuels. The group began its work in the early 1970s, developing chemical kinetic models for methane, ethane, ethanol and halogenated inhibitors. Most recently, it has been developing chemical kinetic models for large n-alkanes, cycloalkanes, hexenes, and large methyl esters. These component models are needed to represent gasoline, diesel, jet, and oil-sand-derived fuels.

Pitz, W J; Westbrook, C K; Mehl, M; Herbinet, O; Curran, H J; Silke, E J

2008-09-24

381

Kinetics of cross-slope running.  

PubMed

The purpose of the present study was to identify kinetic responses to running on mediolaterally elevated (cross-sloped) running surfaces. Ground reaction forces (GRFs), GRF lever arms and joint moment characteristics of 19 male runners were analyzed when running at 3.5m/s on a custom-made, tiltable runway. Tilt angles of 3° and 6° for medial and lateral elevation were analyzed using a 10 camera Vicon Nexus system and a force platform. The point of force application of the GRF showed a systematic shift in the order of 1-1.5cm to either the lateral or medial aspect of the foot for lateral or medial inclinations, respectively. Consequently, the strongest significant effects of tilt orientation and level on joint kinetics and ground reaction force lever arms were identified at the ankle, knee and hip joint in the frontal plane of movement. External eversion moments at the ankle were significantly increased by 35% for 6° of lateral elevation and decreased by 16% for 6° of medial elevation. Altering the cross-slope of the running surface changed the pattern of ankle joint moments in the transversal plane. Effect sizes were on average larger for laterally elevated conditions, indicating a higher sensitivity of kinetic parameters to this kind of surface tilt. These alterations in joint kinetics should be considered in the choice of the running environment, especially for specific risk groups, like runners in rehabilitation processes. PMID:24074942

Willwacher, Steffen; Fischer, Katina Mira; Benker, Rita; Dill, Stephan; Brüggemann, Gert-Peter

2013-11-15

382

Kinetic equilibrium and relativistic thermodynamics  

E-print Network

Relativistic thermodynamics is treated from the point of view of kinetic theory. It is shown that the generalized J\\"uttner distribution suggested in [1] is compatible with kinetic equilibrium. The requirement of compatibility of kinetic and thermodynamic equilibrium reveals several generalizations of the Gibbs relation where the velocity field is an independent thermodynamic variable.

P. Ván

2011-02-01

383

Kinetics of O{sub 2}({sup 1{Sigma}}) formation in the reaction O{sub 2}({sup 1{Delta}}) + O{sub 2}({sup 1{Delta}}) {yields} O{sub 2}({sup 1{Sigma}}) + O{sub 2}({sup 3{Sigma}})  

SciTech Connect

The dependence of the ratio of specific powers of dimole radiation of singlet oxygen in the 634 nm band and in the b - X band of the O{sub 2}({sup 1{Sigma}}) molecule in the O{sub 2}(X) - O{sub 2}({sup 1{Delta}}) - O{sub 2}({sup 1{Sigma}}) - H{sub 2}O - CO{sub 2} mixture on the CO{sub 2} concentration is measured. As a result, the rate constant of the reaction O{sub 2}({sup 1{Delta}}) + O{sub 2}({sup 1{Delta}}) {yields} O{sub 2}({sup 1{Sigma}}) + O{sub 2}({sup 3{Sigma}}) at the temperature {approx}330 K is found to equal (4.5 {+-} 1.1) 10{sup -17} cm{sup 3} s{sup -1}. (active media)

Zagidullin, M V; Khvatov, N A; Nyagashkin, A Yu [Samara Branch of the P.N. Lebedev Physical Institute, Russian Academy of Sciences, Samara (Russian Federation)

2011-02-28

384

Can yeast glycolysis be understood in terms of in vitro kinetics of the constituent enzymes? Testing biochemistry  

Microsoft Academic Search

This paper examines whether the in vivo behavior of yeast glycolysis can be understood in terms of the in vitro kinetic properties of the constituent enzymes. In nongrowing, anaerobic, compressed Saccharomyces cerevisiae the values of the kinetic parameters of most glycolytic enzymes were determined. For the other enzymes appropriate literature values were collected. By inserting these values into a kinetic

Bas Teusink; Jutta Passarge; Corinne A. Reijenga; Eugenia Esgalhado; Coen C. van der Weijden; Mike Schepper; Michael C. Walsh; Barbara M. Bakker; Karel van Dam; Hans V. Westerhoff; Jacky L. Snoep

2000-01-01

385

Experimental studies and kinetics of single drop drying and their relevance in drying of sugar?rich foods: A review  

Microsoft Academic Search

Levitation and free?flight techniques applied to investigate the drying kinetics and morphology of single drops containing dissolved solids and suspensions are reviewed. A review of works related to receding interface model proposed to quantify the drying kinetics of single drops along with techniques to measure the kinetic parameters such as moisture diffusivity, thermal conductivity and specific heat capacity is presented.

B. Adhikari; T. Howes; B. R. Bhandari; V. Truong

2000-01-01

386

Maximum Sustainable Yield Lives On  

Microsoft Academic Search

I examined 142 papers published from 1977 through 1985 that used the concept of maximum sustainable yield (MSY). I classified them as to how MSY was used, year of publication, subject, and publication forum. The primary uses of MSY were in estimating long-term yield (28.9%), evaluating stock condition (28.2%), and analyzing policy (21.8%). The number of such publications declined significantly

Willard E. Barber

1988-01-01

387

Multistep Kinetic Behavior in the Thermal Degradation of Poly(l-Lactic Acid): A Physico-Geometrical Kinetic Interpretation.  

PubMed

A physico-geometrical kinetic interpretation of the thermal degradation of poly(l-lactic acid) (PLLA) is described based on the results of a kinetic study using thermogravimetry (TG) and the microscopic observation of the reaction process. From the physico-geometrical viewpoint, the reaction process is separated into two different stages characterized by a surface reaction of the molten PLLA in the initial reaction stage followed by continuous bubble formation and disappearance in the established reaction stage. The generally reported trend of variation in the apparent activation energy as the reaction advances is explained by the partial overlapping of these two reaction stages. The kinetic rate data obtained using TG were kinetically separated into those for the respective reaction stages by optimizing the kinetic parameters. The significance of the kinetic results is discussed in terms of the physico-geometrical characteristics of the reaction. Such systematic kinetic analyses demonstrate the importance of considering the physico-geometrical perspective when interpreting the kinetic results for the thermal degradation of polymers. PMID:25184744

Yoshikawa, Masahiro; Goshi, Yuri; Yamada, Shuto; Koga, Nobuyoshi

2014-09-25

388

Ternary particle yields in 249Cf(nth,f)  

NASA Astrophysics Data System (ADS)

An experiment measuring ternary particle yields in 249Cf(nth,f) was carried out at the high flux reactor of the Institut Laue-Langevin using the Lohengrin recoil mass separator. Parameters of energy distributions were determined for 27 ternary particles up to 30Mg and their yields were calculated. The yields of 17 further ternary particles were estimated on the basis of the systematics developed. The heaviest particles observed in the experiment are 37Si and 37S; their possible origin is discussed.

Tsekhanovich, I.; Büyükmumcu, Z.; Davi, M.; Denschlag, H. O.; Gönnenwein, F.; Boulyga, S. F.

2003-03-01

389

Kinetic Inductance Magnetometer  

E-print Network

Ultrasensitive magnetic field detection is utilized in the fields of science, medicine and industry. We report on a novel magnetometer relying on the kinetic inductance of superconducting material. The kinetic inductance exhibits a non-linear response with respect to DC current, a fact that is exploited by applying magnetic flux through a superconducting loop to generate a shielding current and a change in the inductance of the loop. The magnetometer is arranged into a resonator, allowing readout through a transmission measurement that makes the device compatible with radio frequency multiplexing techniques. The device is fabricated using a single thin-film layer of NbN, simplifying the fabrication process compared to existing magnetometer technologies considerably. Our experimental data, supported by theory, demonstrates a magnetometer having potential to replace established technology in applications requiring ultra-high sensitivity.

Luomahaara, Juho; Grönberg, Leif; Hassel, Juha

2014-01-01

390

Yield functions that account for the effects of initial and subsequent plastic anisotropy  

Microsoft Academic Search

Summary A descriptive initial yield function is presented from an examination of experimentally determined yield loci, component plastic strain paths and Lode's parameters that indicate either a severe textural anisotropy in a material or a slight departure from the von Mises condition. The transition from the initial function to one that describes a subsequent yield surface which translates with the

D. W. A. Rees

1982-01-01

391

Kinetics of illite formation  

Microsoft Academic Search

An activation energy of 19.6 +- 3.5 kcal\\/mole was found for conversion of synthetic beidellite with the composition AlâSiâ.ââAlâ.ââOââ(OH)âKâ.ââ to mixed-layer illite\\/smectite. The size of this activation energy and the rate constants suggest that (1) the alteration of smectite to illite during diagenesis involves the breaking of chemical bonds in the 2:1 layers; (2) either an equilibrium or a kinetic

DENNIS EBERL; JOHN HOWER

1976-01-01

392

Effect of heating rate and kinetic model selection on activation energy of nonisothermal crystallization of amorphous felodipine.  

PubMed

The nonisothermal crystallization kinetics of amorphous materials is routinely analyzed by statistically fitting the crystallization data to kinetic models. In this work, we systematically evaluate how the model-dependent crystallization kinetics is impacted by variations in the heating rate and the selection of the kinetic model, two key factors that can lead to significant differences in the crystallization activation energy (Ea ) of an amorphous material. Using amorphous felodipine, we show that the Ea decreases with increase in the heating rate, irrespective of the kinetic model evaluated in this work. The model that best describes the crystallization phenomenon cannot be identified readily through the statistical fitting approach because several kinetic models yield comparable R(2) . Here, we propose an alternate paired model-fitting model-free (PMFMF) approach for identifying the most suitable kinetic model, where Ea obtained from model-dependent kinetics is compared with those obtained from model-free kinetics. The most suitable kinetic model is identified as the one that yields Ea values comparable with the model-free kinetics. Through this PMFMF approach, nucleation and growth is identified as the main mechanism that controls the crystallization kinetics of felodipine. Using this PMFMF approach, we further demonstrate that crystallization mechanism from amorphous phase varies with heating rate. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3950-3957, 2014. PMID:25351553

Chattoraj, Sayantan; Bhugra, Chandan; Li, Zheng Jane; Sun, Changquan Calvin

2014-12-01

393

Homogeneous nucleation kinetics  

NASA Technical Reports Server (NTRS)

Homogeneous nucleation kinetics are rederived in a manner fundamentally similar to the approach of classical nucleation theory with the following modifications and improvements. First, the cluster is a parent phase cluster and does not require energization to the parent state. Second, the thermodynamic potential used to describe phase stability is a continuous function along the pathway of phase decomposition. Third, the kinetics of clustering corresponds directly to the diffusional flux of monomers through the cluster distribution and are formally similar to classical theory with the resulting kinetic equation modified by two terms in the preexponential factor. These terms correct for the influence of a supersaturation dependent clustering within the parent phase and for the influence of an asymmetrical cluster concentration as a function of cluster size at the critical cluster size. Fourth, the supersaturation dependence of the nucleation rate is of the same form as that given by classical nucleation theory. This supersaturation dependence must however be interpreted in terms of a size dependent surface tension. Finally, there are two scaling laws which describe supersaturation to either constant nucleation rate or to the thermodynamically determined physical spinodal.

Rasmussen, D. H.; Appleby, M. R.; Leedom, G. L.; Babu, S. V.; Naumann, R. J.

1983-01-01

394

Homogeneous nucleation kinetics  

NASA Astrophysics Data System (ADS)

Homogeneous nucleation kinetics are rederived in a manner fundamentally similar to the approach of classical nucleation theory with the following modifications and improvements. First, the cluster is a parent phase cluster and does not require energization to the parent state. Second, the thermodynamic potential used to describe phase stability is a continuous function along the pathway of phase decomposition. Third, the kinetics of clustering corresponds directly to the diffusional flux of monomers through the cluster distribution and are formally similar to classical theory with the resulting kinetic equation modified by two terms in the preexponential factor. These terms correct for the influence of a supersaturation dependent clustering within the parent phase and for the influence of an asymmetrical cluster concentration as a function of cluster size at the critical cluster size. Fourth, the supersaturation dependence of the nucleation rate is of the same form as that given by classical nucleation theory. This supersaturation dependence must however be interpreted in terms of a size dependent surface tension. Finally, there are two scaling laws which describe supersaturation to either constant nucleation rate or to the thermodynamically determined physical spinodal.

Rasmussen, D. H.; Appleby, M. R.; Leedom, G. L.; Babu, S. V.; Naumann, R. J.

1983-11-01

395

DEVELOPMENT OF A KINETIC MODEL OF BOEHMITE DISSOLUTION IN CAUSTIC SOLUTIONS APPLIED TO OPTIMIZE HANFORD WASTE PROCESSING  

SciTech Connect

Boehmite (e.g., aluminum oxyhydroxide) is a major non-radioactive component in Hanford and Savannah River nuclear tank waste sludge. Boehmite dissolution from sludge using caustic at elevated temperatures is being planned at Hanford to minimize the mass of material disposed of as high-level waste (HLW) during operation of the Waste Treatment Plant (WTP). To more thoroughly understand the chemistry of this dissolution process, we have developed an empirical kinetic model for aluminate production due to boehmite dissolution. Application of this model to Hanford tank wastes would allow predictability and optimization of the caustic leaching of aluminum solids, potentially yielding significant improvements to overall processing time, disposal cost, and schedule. This report presents an empirical kinetic model that can be used to estimate the aluminate production from the leaching of boehmite in Hanford waste as a function of the following parameters: (1) hydroxide concentration; (2) temperature; (3) specific surface area of boehmite; (4) initial soluble aluminate plus gibbsite present in waste; (5) concentration of boehmite in the waste; and (6) (pre-fit) Arrhenius kinetic parameters. The model was fit to laboratory, non-radioactive (e.g. 'simulant boehmite') leaching results, providing best-fit values of the Arrhenius A-factor, A, and apparent activation energy, E{sub A}, of A = 5.0 x 10{sup 12} hour{sup -1} and E{sub A} = 90 kJ/mole. These parameters were then used to predict boehmite leaching behavior observed in previously reported actual waste leaching studies. Acceptable aluminate versus leaching time profiles were predicted for waste leaching data from both Hanford and Savannah River site studies.

DISSELKAMP RS

2011-01-06

396

Force fluctuations impact kinetics of biomolecular systems.  

PubMed

A wide array of biological processes occur at rates that vary significantly with force. Instantaneous molecular forces fluctuate due to thermal noise and active processes, leading to concomitant fluctuations in biomolecular rate constants. We demonstrate that such fluctuations have a dramatic effect on the transition kinetics of force-dependent processes. As an illustrative, biologically relevant example, we model the pausing of eukaryotic RNA polymerase as it transcribes nucleosomal DNA. Incorporating force fluctuations in the model yields qualitatively different predictions for the pausing time scales when compared to behavior under the average force alone. We use our model to illustrate the broad range of behaviors that can arise in biomolecular processes that are susceptible to force fluctuations. The fluctuation time scale, which varies significantly for in vivo biomolecular processes, yields very different results for overall rates and dramatically alters the force regime of relevance to the transition. Our results emphasize the importance of transient high-force behavior for determining kinetics in the fluctuating environment of a living cell. PMID:23005451

Koslover, Elena F; Spakowitz, Andrew J

2012-07-01

397

Kinetic modeling in PET imaging of hypoxia  

PubMed Central

Tumor hypoxia is associated with increased therapeutic resistance leading to poor treatment outcome. Therefore the ability to detect and quantify intratumoral oxygenation could play an important role in future individual personalized treatment strategies. Positron Emission Tomography (PET) can be used for non-invasive mapping of tissue oxygenation in vivo and several hypoxia specific PET tracers have been developed. Evaluation of PET data in the clinic is commonly based on visual assessment together with semiquantitative measurements e.g. standard uptake value (SUV). However, dynamic PET contains additional valuable information on the temporal changes in tracer distribution. Kinetic modeling can be used to extract relevant pharmacokinetic parameters of tracer behavior in vivo that reflects relevant physiological processes. In this paper, we review the potential contribution of kinetic analysis for PET imaging of hypoxia.

Li, Fan; Joergensen, Jesper T; Hansen, Anders E; Kjaer, Andreas

2014-01-01

398

Pseudo-Second-Order Kinetic Model for Biosorption of Methylene Blue onto Tamarind Fruit Shell: Comparison of Linear and Nonlinear Methods  

Microsoft Academic Search

In this study, the sorption of methylene blue, a basic dye, onto tamarind fruit shell was studied by performing batch kinetic sorption experiments. The equilibrium kinetic data were analyzed using the pseudo-second-order kinetic model. A comparison between linear least squares method and nonlinear regression method of estimating the kinetic parameters was examined. Four pseudo-second-order kinetic linear equations were discussed. The

Shamik Chowdhury; Papita Saha

2010-01-01

399

Thermal behaviour and kinetics of alga Polysiphonia elongata biomass during pyrolysis.  

PubMed

The pyrolysis characteristics and kinetics of Polysiphonia elongata were investigated using a thermogravimetric analyzer. The main decomposition of samples occurred between 225°C and 485°C at heating rates of 5-40°C/min; owing to release of 78-82% of total volatiles. The heating rate effected pyrolysis characteristics such as maximum devolatilization rate and decomposition temperature. However, total volatile matter yield was not significantly affected by heating rate. The activation energy of pyrolysis reaction was calculated by model free Friedman and Kissenger-Akahira-Sunose methods and mean values were 116.23kJ/mol and 126.48kJ/mol, respectively. A variance in the activation energy with the proceeding conversions was observed for the models applied, which shows that the pyrolysis process was composed of multi-step kinetics. The Coats-Redfern method was used to determine pre-exponential factor and reaction order. The obtained parameters were used in simulation of pyrolysis process and results were in a good agreement with experimental data. PMID:25194914

Ceylan, Selim; Topcu, Y?ld?ray; Ceylan, Zeynep

2014-11-01

400

Arsenic uptake and depuration kinetics in Microcystis aeruginosa under different phosphate regimes.  

PubMed

Strategies used by Microcystis aeruginosa, bloom-forming cyanobacteria, for potential inorganic arsenic (arsenate and arsenite) uptake, and depuration kinetics under phosphate-enriched (+P) and depleted (-P) treatments were examined via short- and long-term experiments. Phosphate depletion improved arsenate or arsenite uptake rate constants. M. aeruginosa arsenite influx occurred considerably faster than arsenate influx under +P or -P treatments. Different phosphate regimes yielded significant impacts on long-term but not on short-term arsenic (As) uptake. In addition, considerable differences were observed in short-term As efflux between live and dead cells after arsenate or arsenite pre-exposure. Arsenic depuration rates in live M. aeruginosa cells were affected not only by accumulation rates of different As inorganic species but also by phosphate concentrations in tested media, which was inferred from estimated kinetic parameters. Specifically, +P was clearly found to inhibit As efflux after live M. aeruginosa cells were pre-exposed to As(V). Efflux was higher for dead cells no matter the inorganic As species involved. Owing to higher As uptake and depuration rates under -P treatments, P deficiency will considerably accelerate As uptake and efflux processes in aquatic environments. PMID:24922097

Wang, Zhenhong; Luo, Zhuanxi; Yan, Changzhou; Che, Feifei; Yan, Yameng

2014-07-15

401

Hydrogen Donor-Acceptor Fluctuations from Kinetic Isotope Effects: A Phenomenological Model  

PubMed Central

Kinetic isotope effects (KIEs) and their temperature dependence can probe the structural and dynamic nature of enzyme-catalyzed proton or hydride transfers. The molecular interpretation of their temperature dependence requires expensive and specialized QM/MM calculations to provide a quantitative molecular understanding. Currently available phenomenological models use a non-adiabatic assumption that is not appropriate for most hydride and proton-transfer reactions, while others require more parameters than the experimental data justify. Here we propose a phenomenological interpretation of KIEs based on a simple method to quantitatively link the size and temperature dependence of KIEs to a conformational distribution of the catalyzed reaction. The present model assumes adiabatic hydrogen tunneling, and by fitting experimental KIE data, the model yields a population distribution for fluctuations of the distance between donor and acceptor atoms. Fits to data from a variety of proton and hydride transfers catalyzed by enzymes and their mutants, as well as non-enzymatic reactions, reveal that steeply temperature-dependent KIEs indicate the presence of at least two distinct conformational populations, each with different kinetic behaviors. We present the results of these calculations for several published cases and discuss how the predictions of the calculations might be experimentally tested. The current analysis does not replace molecular quantum mechanics/molecular mechanics (QM/MM) investigations, but it provides a fast and accessible way to quantitatively interpret KIEs in the context of a Marcus-like model. PMID:22857146

Roston, Daniel; Cheatum, Christopher M.; Kohen, Amnon

2012-01-01

402

Definition of Architectural Ideotypes for Good Yield Capacity in Coffea canephora  

PubMed Central

• Background Yield capacity is a target trait for selection of agronomically desirable lines; it is preferred to simple yields recorded over different harvests. Yield capacity is derived using certain architectural parameters used to measure the components of yield capacity. • Methods Observation protocols for describing architecture and yield capacity were applied to six clones of coffee trees (Coffea canephora) in a comparative trial. The observations were used to establish architectural databases, which were explored using AMAPmod, a software dedicated to the analyses of plant architecture data. The traits extracted from the database were used to identify architectural parameters for predicting the yield of the plant material studied. • Conclusions Architectural traits are highly heritable and some display strong genetic correlations with cumulated yield. In particular, the proportion of fruiting nodes at plagiotropic level 15 counting from the top of the tree proved to be a good predictor of yield over two fruiting cycles. PMID:16394023

CILAS, CHRISTIAN; BAR-HEN, AVNER; MONTAGNON, CHRISTOPHE; GODIN, CHRISTOPHE

2006-01-01

403

Defining and managing sustainable yield.  

PubMed

Ground water resource management programs are paying increasing attention to the integration of ground water and surface water in the planning process. Many plans, however, show a sophistication in approach and presentation that masks a fundamental weakness in the overall analysis. The plans usually discuss issues of demand and yield, yet never directly address a fundamental issue behind the plan--how to define sustainable yield of an aquifer system. This paper points out a number of considerations that must be addressed in defining sustainable yield in order to make the definition more useful in practical water resource planning studies. These include consideration for the spatial and temporal aspects of the problem, the development of a conceptual water balance, the influence of boundaries and changes in technology on the definition, the need to examine water demand as well as available supply, the need for stakeholder involvement, and the issue of uncertainty in our understanding of the components of the hydrologic system. PMID:15584295

Maimone, Mark

2004-01-01

404

Sensitivity of Yield Optimized Superoscillations  

E-print Network

Super oscillating signals are band limited signals that oscillate in some region faster than their largest Fourier component. Such signals have many obvious scientific and technological applications, yet their practical use is strongly limited by the fact that an overwhelming proportion of the energy goes into that part of the signal, which is not superoscillating. In a recent article the problem of optimization of such signals has been studied. In that article the concept of superoscillation yield is defined as the ratio of the energy in the super oscillations to the total energy of the signal, given the range in time and frequency of the superoscillations, which is imposed by forcing the signal to interpolate among a set of predetermined points. The optimization of the superoscillation yield consists of obtaining the Fourier coefficients of the low frequency components of which the signal consists, that maximize the yield under the interpolation constraint. Since in practical applications it is impossible t...

Schwartz, Moshe

2014-01-01

405

Yield Strength of bcc Tantalum  

NASA Astrophysics Data System (ADS)

We have determined the quasi-static yield strength of bcc tantalum at room temperature and pressures up to 60 GPa, using two independent methods with the diamond-anvil cell. In the first method, synchrotron x-ray diffraction patterns of samples having varying degrees of hydrostaticity yield results that are consistent with theoretically predicted values. Radial pressure gradients, determined from ruby flourescence in the second method, compare well with the diffraction results. In addition, the equation of state of tantalum obtained in the present study can be compared to previously published static - as well as shock-compression results in order to distinguish pressure from strain-rate and temperature effects.

Nguyen, Jeffrey H.; Kruger, Michael B.; Caldwell, Wendell A.; Benedetti, Laura Robin; Chen, Bin; Jeanloz, Raymond; Holmes, Neil C.

1998-03-01

406

An evolutionary yield function based on Barlat 2000 yield function for the superconducting niobium sheet  

NASA Astrophysics Data System (ADS)

Superconducting radio frequency (SRF) niobium cavities are widely used in high-energy physics to accelerate particle beams in particle accelerators. The performance of SRF cavities is affected by the microstructure and purity of the niobium sheet, surface quality, geometry, etc. Following optimum strain paths in the forming of these cavities can significantly control these parameters. To select these strain paths, however, information about the mechanical behavior, microstructure, and formability of the niobium sheet is required. In this study the Barlat 2000 yield function has been used as a yield function for high purity niobium. Results from this study showed that, due to intrinsic behavior, it is necessary to evolve the anisotropic coefficients of Barlat's yield function in order to properly model the plastic behavior of the niobium sheet. The accuracy of the newly developed evolutionary yield function was verified by applying it to the modeling of the hydrostatic bulging of the niobium sheet. Also, in a separate attempt crystal plasticity finite element method was use to model the behavior of the polycrystalline niobium sheet with a particular initial texture.

Darbandi, Payam; Pourboghrat, Farhang

2011-08-01

407

An evolutionary yield function based on Barlat 2000 yield function for the superconducting niobium sheet  

SciTech Connect

Superconducting radio frequency (SRF) niobium cavities are widely used in high-energy physics to accelerate particle beams in particle accelerators. The performance of SRF cavities is affected by the microstructure and purity of the niobium sheet, surface quality, geometry, etc. Following optimum strain paths in the forming of these cavities can significantly control these parameters. To select these strain paths, however, information about the mechanical behavior, microstructure, and formability of the niobium sheet is required. In this study the Barlat 2000 yield function has been used as a yield function for high purity niobium. Results from this study showed that, due to intrinsic behavior, it is necessary to evolve the anisotropic coefficients of Barlat's yield function in order to properly model the plastic behavior of the niobium sheet. The accuracy of the newly developed evolutionary yield function was verified by applying it to the modeling of the hydrostatic bulging of the niobium sheet. Also, in a separate attempt crystal plasticity finite element method was use to model the behavior of the polycrystalline niobium sheet with a particular initial texture.

Darbandi, Payam; Pourboghrat, Farhang [Mechanical Engineering Department, Michigan State University, East Lansing, MI 48824 (United States)

2011-08-22

408

Large Area Crop Inventory Experiment (LACIE). Feasibility of assessing crop condition and yield from LANDSAT data  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Yield modelling for crop production estimation derived a means of predicting the within-a-year yield and the year-to-year variability of yield over some fixed or randomly located unit of area. Preliminary studies indicated that the requirements for interpreting LANDSAT data for yield may be sufficiently similar to those of signature extension that it is feasible to investigate the automated estimation of production. The concept of an advanced yield model consisting of both spectral and meteorological components was endorsed. Rationale for using meteorological parameters originated from known between season and near harvest dynamics in crop environmental-condition-yield relationships.

1978-01-01

409

Purification and kinetic studies of recombinant gibberellin dioxygenases  

PubMed Central

Background The 2-oxoglutarate-dependent dioxygenases (2ODDs) of gibberellin (GA) biosynthesis have a key role in the metabolism of a major plant hormone. The activity of recombinant GA 2ODDs from many species has been characterised in detail, however little information relates to enzyme purification. Native GA 2ODDs displayed lability during purification. Results Two GA 2ODDs were expressed in Escherichia coli and purified to homogeneity. The GA 2-oxidase from Pisum sativum L., PsGA2OX1, was expressed as a glutathione s-transferase (GST) fusion. It was purified in the three steps of affinity chromatography, GST removal and gel filtration. Highly pure PsGA2OX1 was obtained at a yield of 0.3 mg/g of cells. It displayed a Km of 0.024 ?M and a Vmax of 4.4 pkat/mg toward [1?,2?,3?-3H3]GA20. The GA 3-oxidase from Arabidopsis thaliana, AtGA3OX4, was expressed as a poly(His)-tagged thioredoxin fusion. It was purified by Immobilised Metal Affinity Chromatography followed by gel filtration. Cleavage of the fusion took place between the two purification steps. Highly pure AtGA3OX4 was obtained at a yield of 0.01 mg/g of cells. It displayed a Km of 0.82 ?M and Vmax of 52,500 pkat/mg toward [1?,2?,3?-3H3]GA20. Conclusion Fusion tags were required to stabilise and solubilise PsGA2OX1 and AtGA3OX4 during E. coli expression. The successful purification of milligram quantities of PsGA2OX1 enables mechanistic and structural studies not previously possible on GA 2ODDs. A moderate yield of pure AtGA3OX4 requires the further optimisation of the latter stages of the enzyme purification schedule. PsGA2OX1's action in planta as deduced from the effect of the null mutation sln on GA levels in seeds is in agreement with the kinetic parameters of the recombinant enzyme. PMID:16181493

Lester, Diane R; Phillips, Andy; Hedden, Peter; Andersson, Inger

2005-01-01

410

Curing kinetics of lignin-novolac phenolic resins using non-isothermal methods  

Microsoft Academic Search

The curing kinetics of lignin-novolac and methylolated lignin-novolac resins were studied using non-isothermal methods employing\\u000a differential scanning calorimetry (DSC) at different heating rates. The Belichmeier, Ozawa and Kissinger methods were applied,\\u000a which give the kinetic parameters of the curing process studied. In addition, the model-fitting Coats-Redfern method was used\\u000a to analyze the experimental data. The kinetic study evaluated the effect

J. M. Pérez; F. Rodríguez; M. V. Alonso; M. Oliet; J. C. Domínguez

2009-01-01

411

Nonisothermal determination of the intrinsic kinetics of oil generation from oil shale  

Microsoft Academic Search

A nonisothermal technique using various heating rates has been applied to the determination of the intrinsic kinetics of oil generation from oil shale. From an engineering standpoint the rate of oil generation can adequately be described by overall first-order kinetics with a constant activation energy of 199 kJ\\/mol. Various methods are applied to the determination of the kinetics parameters. The

S.-M. Shih; H. Y. Sohn

1980-01-01

412

Kinetics of serum prostate-specific antigen after external beam radiation for clinically localized prostate cancer  

Microsoft Academic Search

Background and purpose: To determine the kinetics of serum prostate-specific antigen (PSA) after radiation therapy of localized prostate cancer and to evaluate whether such kinetics provide prognostic information.Materials and methods: Eight hundred forty-one men with serial PSA determinations who underwent external beam radiation without androgen ablation were analyzed to determine postradiation PSA kinetic parameters (half-life and doubling time) and to

Gunar K. Zagars; Alan Pollack

1997-01-01

413

Evaluation of Kinetic Data for Crystallization of Tio2 Prepared by Hydrolysis Method  

Microsoft Academic Search

The formation of TiO2 prepared by hydrolysis method was presented. Thermodynamics and kinetics of anatase crystallization reaction were investigated.\\u000a Differential method of kinetic data evaluation in non-isothermal conditions according toKissinger, Ozawa and Kazeev-Yerofeev\\u000a was applied. Starting, crystallized and thermally treated powders were determined using X-ray powder diffraction analysis.\\u000a The characteristic parameters (the activation energy, constant rate and formal kinetic order

B. D. Stojanovi?; Z. V. Marinkovi?; G. O. Brankovi?; E. Fidan?evska

2000-01-01

414

Kinetic model of the evaporation process of benzylbutyl phthalate from plasticized poly(vinyl chloride)  

Microsoft Academic Search

The kinetic model of the physical process of evaporation of plasticizer from plasticized PVC foils was developed from the results of isothermal thermogravimetric investigation of evaporation of benzyl-butyl phthalate in the temperature range 120–150°C under nitrogen flow. The kinetic parameters were estimated by integral method of analysis. Mathematical modeling of the kinetic of plasticizers evaporation was performed on the basis

Željko Mrkli?; Davor Ruši?; Tonka Kova?i?

2004-01-01

415

Kinetics of ultrafiltration hemodialysis  

Microsoft Academic Search

The expressions of Wolfet al. (1951) and Renkin (1956) for the kinetics of artificial kidneys are generalized to include the effects of filtration. IfB is the bath volume,b the relevant volume of distribution,f the filtration rate,t the time, andA\\u000a 0,B\\u000a 0,b\\u000a 0 representA, B, andb at timet=0, then the plasma concentrationA is given by\\u000a \\u000a \\u000a \\u000a \\u000a $$\\\\frac{A}{{A_0 }} = \\\\frac{{B_0 }}{{B_0 +

Robert I. Macey; A. V. Wolf

1960-01-01

416

Fragg Virus - Kinetic City  

NSDL National Science Digital Library

The Fragg Virus is a learning module centered learning the importance of systems; it is a part of the Kinetic City-Mission to Vearth site. In general this module is concerned with how different parts work within a system. The Fragg Virus module is equipped with a computer simulation mind game, creative writing exercises for independent study, and art-centered exercises, as well as lesson plans for hands on games and activities designed for a group. The focus of the activities is evolution and the features of an animal that helps the animal survive in its environment. Certain features explored are the giraffes neck, polar bears fir, and a birds beak.

American Association for the Advancement of Science (;)

2008-04-17

417

Kinetics of growth and enhanced sophorolipids production by Candida bombicola using a low-cost fermentative medium.  

PubMed

In this study, effect of various parameters on sophorolipid (SL) production by the yeast Candida bombicola was investigated fo