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1

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

2

Obtaining and estimating kinetic parameters from the literature.  

PubMed

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. PMID:21934111

Neves, Susana R

2011-09-20

3

Sensitivity of cloud condensation nuclei activation processes to kinetic parameters  

E-print Network

Sensitivity of cloud condensation nuclei activation processes to kinetic parameters P. Y. Chuang1 circumstances. Here the sensitivity of particle activation to parameters that are related to kinetic processes adiabatic parcel models. We conclude that activation is not very sensitive to the thermal accommodation

Chuang, Patrick Y.

4

Kinetic parameters in thermophilic methane fermentation of swine manure  

SciTech Connect

A laboratory study was conducted to investigate the kinetic parameters important in the design and operation of thermophilic digestion of unmedicated swine manure. The experimental design was set up to test the effects of temperature, retention time, and feed concentration on these parameters using the modified Contois model. Feed concentrations of 3%, 4% and 6% VS in influent were tried at 5-, 8- and 13-days RT at 50 C to determine a non-inhibitory concentration. Based on the evidence collected, 3% VS was then chosen for the temperature treatments at 45, 50, 55 and 60 C at RTs of 4, 5, 8, 10 and 13 days. The manure was from 3 to 7 days old, and had an average TS content of about 10%, of which 85% were VS. The ultimate methane yield of the manure (0.508 L CH/sub 4//g VS fed) was determined by extrapolation using steady-state data. Inhibition played a significant role in the determination of the ultimate methane yield. A hypothesis was set forth to describe the effects of three types of inhibition on this value. Regression analysis of the calculated and the measured methane production rates gave a coefficient of determination of 0.93. At 45 and 50 C, the gas production rates were similar. Gas production rates at 55 C were generally not as high. Digestion at 60 C was unstable as indicated by the low gas production rates and the high volatile acids concentrations. The average methane percentages ranged from about 45 to 65% of the biogas. It was demonstrated that loading rates of up to 6 g VS/L/day (at 3% VS) at temperatures of 45 and 50 C provided from 58% to 80% of the ultimate methane yield at retention times of from 5 to 13 days.

Chen, T.H.

1983-01-01

5

A model of crosslink kinetics in the expanding plant cell wall: yield stress and enzyme action.  

PubMed

The plant primary cell wall is a composite material containing stiff cellulose microfibrils that are embedded within a pectin matrix and crosslinked through a network of hemicellulose polymers. This microstructure endows the wall with nonlinear anisotropic mechanical properties and allows enzymatic regulation of expansive cell growth. We present a mathematical model of hemicellulose crosslink dynamics in an expanding cell wall incorporating strain-enhanced breakage and enzyme-mediated crosslink kinetics. The model predicts the characteristic yielding behaviour in the relationship between stress and strain-rate seen experimentally, and suggests how the effective yield and extensibility of the wall depend on microstructural parameters and on the action of enzymes of the XTH and expansin families. The model suggests that the yielding behaviour encapsulated in the classical Lockhart equation can be explained by the strongly nonlinear dependence of crosslink breakage rate on crosslink elongation. The model also demonstrates how enzymes that target crosslink binding can be effective in softening the wall in its pre-yield state, whereas its post-yield extensibility is determined primarily by the pectin matrix. PMID:22584249

Dyson, R J; Band, L R; Jensen, O E

2012-08-21

6

A model of crosslink kinetics in the expanding plant cell wall: yield stress and enzyme action  

PubMed Central

The plant primary cell wall is a composite material containing stiff cellulose microfibrils that are embedded within a pectin matrix and crosslinked through a network of hemicellulose polymers. This microstructure endows the wall with nonlinear anisotropic mechanical properties and allows enzymatic regulation of expansive cell growth. We present a mathematical model of hemicellulose crosslink dynamics in an expanding cell wall incorporating strain-enhanced breakage and enzyme-mediated crosslink kinetics. The model predicts the characteristic yielding behaviour in the relationship between stress and strain-rate seen experimentally, and suggests how the effective yield and extensibility of the wall depend on microstructural parameters and on the action of enzymes of the XTH and expansin families. The model suggests that the yielding behaviour encapsulated in the classical Lockhart equation can be explained by the strongly nonlinear dependence of crosslink breakage rate on crosslink elongation. The model also demonstrates how enzymes that target crosslink binding can be effective in softening the wall in its pre-yield state, whereas its post-yield extensibility is determined primarily by the pectin matrix. PMID:22584249

Dyson, R.J.; Band, L.R.; Jensen, O.E.

2012-01-01

7

Breakdown parameter for kinetic modeling of multiscale gas flows  

NASA Astrophysics Data System (ADS)

Multiscale methods built purely on the kinetic theory of gases provide information about the molecular velocity distribution function. It is therefore both important and feasible to establish new breakdown parameters for assessing the appropriateness of a fluid description at the continuum level by utilizing kinetic information rather than macroscopic flow quantities alone. We propose a new kinetic criterion to indirectly assess the errors introduced by a continuum-level description of the gas flow. The analysis, which includes numerical demonstrations, focuses on the validity of the Navier-Stokes-Fourier equations and corresponding kinetic models and reveals that the new criterion can consistently indicate the validity of continuum-level modeling in both low-speed and high-speed flows at different Knudsen numbers.

Meng, Jianping; Dongari, Nishanth; Reese, Jason M.; Zhang, Yonghao

2014-06-01

8

Theoretical study of the kinetics of the reactions Se + O{sub 2} {yields} Se + O and As + HCl {yields} AsCl + H  

SciTech Connect

Selenium and arsenic reactions believed to take place in the flue gases of coal combustion facilities were investigated. Prior theoretical work involving various As and Se species was completed using DFT and a broad range of ab initio methods. Building upon that work, the present study is a determination of the kinetic and thermodynamic parameters of the reactions, Se + O{sub 2} {yields} SeO + O and As + HCl {yields} AsCl + H at the CCSD/RCEP28VDZ and QCISD(T)/6-311++G(3df, 3pd) levels of theory, respectively. Transition state theory was used in determining the kinetic rate constants along with collision theory as a means of comparison. The calculated K{sub eq} values are compared to experimental data, where available.

Urban, D.R.; Wilcox, J. [Worcester Polytechnic Institute, Worcester, MA (United States). Dept. of Chemical Engineering

2006-07-20

9

Nitric oxide ferrohemes: kinetics of formation and photodissociation quantum yields  

Microsoft Academic Search

The quantum yield for NO photodissociation from iron protoporphyrin 1-methylimidazole nitrosyl, FePP(1-MeIm)(NO), in the presence of excess 1-MeIm is wavelength independent, phi⁠= 0.08-0.1, and the NO binding rate to the five coordinate heme, Fe(PP)(1-MeIm), is Kâ\\/sup NO\\/ = 1.7 +\\/- 0.7 x 10⁸ M⁻¹ s⁻¹; for Fe(PP)(NO), phi⁠= 0.05-0.08. This quantum yield is much higher than believed earlier

Emily J. Rose; Brian M. Hoffman

1983-01-01

10

Kinetics and Yields of Pesticide Biodegradation at Low Substrate Concentrations and under Conditions Restricting Assimilable Organic Carbon  

PubMed Central

The fundamentals of growth-linked biodegradation occurring at low substrate concentrations are poorly understood. Substrate utilization kinetics and microbial growth yields are two critically important process parameters that can be influenced by low substrate concentrations. Standard biodegradation tests aimed at measuring these parameters generally ignore the ubiquitous occurrence of assimilable organic carbon (AOC) in experimental systems which can be present at concentrations exceeding the concentration of the target substrate. The occurrence of AOC effectively makes biodegradation assays conducted at low substrate concentrations mixed-substrate assays, which can have profound effects on observed substrate utilization kinetics and microbial growth yields. In this work, we introduce a novel methodology for investigating biodegradation at low concentrations by restricting AOC in our experiments. We modified an existing method designed to measure trace concentrations of AOC in water samples and applied it to systems in which pure bacterial strains were growing on pesticide substrates between 0.01 and 50 mg liter?1. We simultaneously measured substrate concentrations by means of high-performance liquid chromatography with UV detection (HPLC-UV) or mass spectrometry (MS) and cell densities by means of flow cytometry. Our data demonstrate that substrate utilization kinetic parameters estimated from high-concentration experiments can be used to predict substrate utilization at low concentrations under AOC-restricted conditions. Further, restricting AOC in our experiments enabled accurate and direct measurement of microbial growth yields at environmentally relevant concentrations for the first time. These are critical measurements for evaluating the degradation potential of natural or engineered remediation systems. Our work provides novel insights into the kinetics of biodegradation processes and growth yields at low substrate concentrations. PMID:24317077

Hammes, Frederik; Egli, Thomas; Kohler, Hans-Peter E.

2014-01-01

11

Kinetic parameter estimation using nonisothermal trickle-bed reactor data  

E-print Network

(Member) J. C. Holste (Member) M. T, L gneckez (Member) D. Holland (Head of Department) May 1985 ABSTRACT Kinetic Parameter Estimation Using Nonisothermal Trickle-Bed Reactor Data (May 1985) Michael Allen Mensik, B. S, , University of Houston... Multiple Reaction Case Component Selection Data Error and Sample Size Effects Initial Guesses 35 35 41 44 47 50 CONCLUSIONS AND RECOMMENDATIONS 57 NOTATION 60 LITERATURE CITED 63 Table of Contents (Continued) Page SINGLE REACTION INPUT DATA...

Mensik, Michael Allen

2012-06-07

12

Kinetic parameters for the thermal inactivation of quality-related enzymes in carrots and potatoes.  

PubMed

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 cases peroxidase activity gave simple first-order inactivation kinetics but yielded a curved Arrhenius plot for the temperature dependence. Pectin methylesterase in both commodities consisted of a labile and a resistant form. The relative amounts of the two forms and the temperature dependences for their inactivation were also similar. PMID:12083894

Anthon, Gordon E; Barrett, Diane M

2002-07-01

13

Kinetic parameters of thermophilic digestion of swine manure  

SciTech Connect

A laboratory study was conducted to investigate the kinetic parameters important in the design and operation of thermophilic digestion of swine manure. The experimental design was set up to test the effects of temperature, retention time (RT) and feed concentration (So) on these parameters as presented in Chen-Hashimoto model. Feed concentrations of 3%, 4%, 5% and 6% VS were tried at 5-, 8-, and 13-day RT at 50 degrees C to determine a non-inhibitory concentration. Based on the results from the above experiments, 3% VS was chosen for temperature treatments of 45, 50, 55 and 60 degrees C at RTs of 4, 5, 8, 10 and 13 days. Inhibition played a significant role in thermophilic digestion of swine manure. Possible mechanisms involved were discussed. 28 references.

Chen, T.L.; Day, D.L.; Pfeffer, J.T.; Bryant, M.D.; Vanderholm, D.H.

1984-09-01

14

membrane fusion Ensemble molecular dynamics yields submillisecond kinetics and intermediates of  

E-print Network

to detect rare transitions, a systematic process for analyzing reaction pathways, and the ability to develop/32/11916 etc., can be found at: High-resolution figures, a citation map, links to PubMed and Google Scholar.pnas.org/misc/reprints.shtml To order reprints, see: Notes: #12;Ensemble molecular dynamics yields submillisecond kinetics

Hinrichs, Nina Singhal

15

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

16

Pyrolysis of Sawdust, Rice Husk and Sugarcane Bagasse: Kinetic Modeling and Estimation of Kinetic Parameters using Different Optimization Tools  

NASA Astrophysics Data System (ADS)

The present study provides the kinetic model to describe the pyrolysis of sawdust, rice-husk and sugarcane bagasse as biomass. The kinetic scheme used for modelling of primary pyrolysis consisting of the two parallel reactions giving gaseous volatiles and solid char. Estimation of kinetic parameters for pyrolysis process has been carried out for temperature range of 773-1,173 K. As there are serious issues regarding non-convergence of some of the methods or solutions converging to local-optima, the proposed kinetic model is optimized to predict the best values of kinetic parameters for the system using three approaches—Two-dimensional surface fitting non-linear regression technique, MS-Excel Solver Tool and COMSOL software. The model predictions are in agreement with experimental data over a wide range of pyrolysis conditions. The estimated value of kinetic parameters are compared with earlier researchers and found to be matching well.

Khonde, Ruta Dhanram; Chaurasia, Ashish Subhash

2015-01-01

17

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

18

Electrochemical evaluation of glutathione S-transferase kinetic parameters.  

PubMed

Glutathione S-transferases (GSTs), are a family of enzymes belonging to the phase II metabolism that catalyse the formation of thioether conjugates between the endogenous tripeptide glutathione and xenobiotic compounds. The voltammetric behaviour of glutathione (GSH), 1-chloro-2,4-dinitrobenzene (CDNB) and glutathione S-transferase (GST), as well as the catalytic conjugation reaction of GSH to CDNB by GST was investigated at room temperature, T=298.15K (25°C), at pH6.5, for low concentration of substrates and enzyme, using differential pulse (DP) voltammetry at a glassy carbon electrode. Only GSH can be oxidized; a sensitivity of 0.14nA/?M and a LOD of 6.4?M were obtained. The GST kinetic parameter electrochemical evaluation, in relation to its substrates, GSH and CDNB, using reciprocal Michaelis-Menten and Lineweaver-Burk double reciprocal plots, was determined. A value of KM~100?M was obtained for either GSH or CDNB, and Vmax varied between 40 and 60?mol/min per mg of GST. PMID:25086278

Enache, Teodor Adrian; Oliveira-Brett, Ana Maria

2015-02-01

19

Evaluation of different phenol hydroxylase-possessing phenol-degrading pseudomonads by kinetic parameters.  

PubMed

Phenol-degrading pseudomonads possessing different phenol hydroxylases (PH) were evaluated by the values of apparent half-saturation constant for phenol-oxygenating activity (K ( S )), maximum specific growth rate (mu (max)), lag-time length (lambda), inhibition constant (K ( I )) and growth yield factor (Y ( X/S )). Strains of the same PH type showed similar kinetic parameters: single-component PH (sPH) harbouring strains had higher values of K ( S ) and lower values of mu (max) than the strains having multicomponent PH (mPH). However, the values of K ( I ) and the dependencies of the lag-time length on initial phenol concentration were strain-specific. The elevated ratio between specific activities of catechol 1,2-dioxygenase (C12O) and muconate cycloisomerase in sPH-strains caused irreversible accumulation of a high amount of exogenous cis,cis-muconate (CCM) which resulted in decreased Y ( X/S ) values. Co-presence of sPH and mPH genes did not give the strains PC16 and P69 any extra advantage and according to determined kinetic parameters only one PH was active during phenol degradation. At the same time simultaneous functioning of catechol ortho and meta cleavage pathways (strain PC20) resulted in higher mu (max) and Y ( X/S ) values. Evaluation of strains showed that the type of PH determined the efficiency of phenol degradation, whereas the tolerance to elevated phenol concentrations was strain-specific. PMID:18283541

Viggor, Signe; Heinaru, Eeva; Künnapas, Allan; Heinaru, Ain

2008-09-01

20

The behavior of kinetic parameters in production of pectinase and xylanase by solid-state fermentation.  

PubMed

Solid-state fermentation (SSF) is defined as the growth of microbes without a free-flowing aqueous phase. The feasibility of using a citrus peel for producing pectinase and xylanase via the SSF process by Aspergillus niger F3 was evaluated in a 2 kg bioreactor. Different aeration conditions were tested to optimize the pectinase and xylanase production. The best air flow intensity was 1 V kg M (volumetric air flow per kilogram of medium), which allowed a sufficient amount of O2 for the microorganism growth producing 265 U/g and 65 U/g pectinases and xylanases, respectively. A mathematical model was applied to determine the different kinetic parameters related to SSF. The specific growth rate and biomass oxygen yield decreased during fermentation, whereas an increase in the maintenance coefficient for the different employed carbon sources was concurrently observed. PMID:21945204

Rodríguez-Fernández, D E; Rodríguez-León, J A; de Carvalho, J C; Sturm, W; Soccol, C R

2011-11-01

21

Relationship between latex yield of Hevea brasiliensis and antecedent environmental parameters  

NASA Astrophysics Data System (ADS)

A study on the relationship between latex yield and antecedent environmental data was undertaken for five clones (RRII203, RRII118, RRIM600, RRII105 and GT1) of Hevea brasiliensis (rubber) in Agartala, northeast India, a region in which rubber is not traditionally cultivated. The explained variance for the regression equations based on parameters determined on the day of tapping and up to 3 days prior to it, varied from 72% to 37% during the NWT period and 94 83% during the WT period. Soil moisture storage, 1 and 3 days prior to tapping, was found to be the primary parameter affecting yield for the NWT and WT periods, respectively. It was observed that the clone RRII105, with a comparatively lower yield to that of RRIM600, was more susceptible to daily WD conditions during the non-winter season. RRIM600 and RRII105 being high-yielding clones were also found to be fairly dependent on the AT of the day prior to tapping. The mean lag period correlation of this parameter with yield was also found to be higher during the WT period than during the NWT period. As a whole, the mean lag period based on prior measurements of environmental variables showed optimum correlation with yield at 15 20 days prior to the day of tapping. The study also confirms that varied responses of yield with environmental factors in this non-traditional region of rubber cultivation depend on clonal character.

Raj, Shammi; Das, Gitali; Pothen, Jacob; Dey, Sushil Kumar

2005-01-01

22

Equilibrium determination of H20 desorption kinetic parameters of H20/K/Ni(lll)  

E-print Network

layer of adsorbed water is similar for potassium precoverages lower than 0.15 ML. INTRODUCTION reliable and coverage dependent kinetic data are recently available. This fact may be due present equilibrium measurements of the kinetic parameters of water desorption from pure and potassium

Kuch, Wolfgang

23

PARAMETER ESTIMATION OF MONOD KINETICS WITHOUT BIOMASS DATA AND INITIAL SUBSTRATE CONCENTRATION  

Microsoft Academic Search

The uniqueness of the parameters in a Monod kinetics model estimated from substrate depletion and product growth data were analyzed using nonlinear regression. The initial substrate and biomass concentrations were considered as unknown (unmeasured) parameters. Simulated data containing known measurement errors were generated first using specified parameters and then these data were used for the analysis. Sensitivity coefficients were determined

PADMANABAN KESAVAN; VICTOR J. LAW

1998-01-01

24

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

SciTech Connect

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

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

1981-03-11

25

Parameter Estimates in Differential Equation Models for Chemical Kinetics  

ERIC Educational Resources Information Center

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

Winkel, Brian

2011-01-01

26

Simulating large-scale crop yield by using perturbed-parameter ensemble method  

NASA Astrophysics Data System (ADS)

Toshichika Iizumi, Masayuki Yokozawa, Gen Sakurai, Motoki Nishimori Agro-Meteorology Division, National Institute for Agro-Environmental Sciences, Japan Abstract One of concerning issues of food security under changing climate is to predict the inter-annual variation of crop production induced by climate extremes and modulated climate. To secure food supply for growing world population, methodology that can accurately predict crop yield on a large scale is needed. However, for developing a process-based large-scale crop model with a scale of general circulation models (GCMs), 100 km in latitude and longitude, researchers encounter the difficulties in spatial heterogeneity of available information on crop production such as cultivated cultivars and management. This study proposed an ensemble-based simulation method that uses a process-based crop model and systematic parameter perturbation procedure, taking maize in U.S., China, and Brazil as examples. The crop model was developed modifying the fundamental structure of the Soil and Water Assessment Tool (SWAT) to incorporate the effect of heat stress on yield. We called the new model PRYSBI: the Process-based Regional-scale Yield Simulator with Bayesian Inference. The posterior probability density function (PDF) of 17 parameters, which represents the crop- and grid-specific features of the crop and its uncertainty under given data, was estimated by the Bayesian inversion analysis. We then take 1500 ensemble members of simulated yield values based on the parameter sets sampled from the posterior PDF to describe yearly changes of the yield, i.e. perturbed-parameter ensemble method. The ensemble median for 27 years (1980-2006) was compared with the data aggregated from the county yield. On a country scale, the ensemble median of the simulated yield showed a good correspondence with the reported yield: the Pearson’s correlation coefficient is over 0.6 for all countries. In contrast, on a grid scale, the correspondence is still high in most grids regardless of the countries. However, the model showed comparatively low reproducibility in the slope areas, such as around the Rocky Mountains in South Dakota, around the Great Xing'anling Mountains in Heilongjiang, and around the Brazilian Plateau. As there is a wide-ranging local climate conditions in the complex terrain, such as the slope of mountain, the GCM grid-scale weather inputs is likely one of major sources of error. The results of this study highlight the benefits of the perturbed-parameter ensemble method in simulating crop yield on a GCM grid scale: (1) the posterior PDF of parameter could quantify the uncertainty of parameter value of the crop model associated with the local crop production aspects; (2) the method can explicitly account for the uncertainty of parameter value in the crop model simulations; (3) the method achieve a Monte Carlo approximation of probability of sub-grid scale yield, accounting for the nonlinear response of crop yield to weather and management; (4) the method is therefore appropriate to aggregate the simulated sub-grid scale yields to a grid-scale yield and it may be a reason for high performance of the model in capturing inter-annual variation of yield.

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

2010-12-01

27

Kinetics and Lumped Parameter Model of Tardive Excess Thermal Power  

NASA Astrophysics Data System (ADS)

The time-integral of tardive excess thermal power (TETP) was previously misnamed "heat after death"ootnotetextPons, S., Fleischman, M., Trans Fusion Tech, 26, 4T, Part 2, p. 87 (1994).. We have examined the kinetics of tardive excess thermal power (TETP) which occurs after driving, fully loaded, activated, spiral wound cold fusion Phusor cathodes (Pd/D2O/Pt;ootnotetextSwartz. M., G. Verner, Proc. ICCF-10 (2004).^,ootnotetextSwartz. M., Proc.ICCF-10 (2003).) at their optimal operating pointootnotetextSwartz, M., Fusion Technology, 31, 63-74 (1997).. TETP, after input electrical power produced an excess power (compared to an ohmic joule control) of 165+/-15 percent [excess power 1.3 Watts], had kinetics suggestive of two distinct sources or physical active regions within the latticeootnotetextSwartz. M., G. Verner, ICCF-11 (2004).. An electrical engineering TETP model had good correlation. The active palladium lattice has a deuteron-loading capacitance of 64 micromoles per volt*. The lattice admittance for the TETP reactions ( 7 picomoles/[sec-volt*]) is dwarfed by the admittance for outgassing deuteron loss ( 15 nanomoles/[sec-volt*]).

Swartz, Mitchell

2005-03-01

28

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. PMID:25325054

Brito, Paula M.; Antunes, Fernando

2014-01-01

29

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

30

Determination of the kinetic parameters for the electrothermal atomization of gold with and without chemical modifiers  

Microsoft Academic Search

The effect of various experimental parameters and the presence of chemical modifiers on the atomization kinetics of gold have been investigated. The dissipation process of the atomic vapour is also studied and the diffusion parameters calculated in the absence and in the presence of chemical modifiers. The chemical modifiers studied are ascorbic acid, rhenium, palladium and rhodium. In the absence

Nikolaos S. Thomaidis; Efrosini A. Piperaki

1999-01-01

31

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

PubMed Central

We report the application of recently developed microscopic models to estimate the apparent kinetic and thermodynamic parameters in a single molecule force spectroscopy study of the carbonic anhydrase enzyme and a complementary sulfonamide inhibitor. The most probable rupture force for the enzyme-inhibitor interaction shows a non-linear dependency on the log-loading rate. Estimates for the kinetic and thermodynamic parameters were obtained by fitting the non-linear dependency to linear cubic potential and cusp potential models and compared to the standard Bell-Evans model. The reliability of the estimated parameters was verified by modeling the experimental rupture force distributions by the theoretically predicted distributions at rupture. We also report that linkers that are attached to the enzyme and inhibitor show appreciable effects on the apparent kinetic and thermodynamic parameters. PMID:18808161

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

2008-01-01

32

Validity of repeated initial rise thermoluminescence kinetic parameter determinations  

SciTech Connect

The validity of thermoluminescence (TL) analysis by repeated initial rise measurements has been studied by computer simulation. Thermoluminescence described by 1st Order, 2nd Order, General One Trap and Interactive TL Kinetics was investigated. In the simulation each of the repeated temperature increase and decrease cycles contains a linear temperature increase followed by a decrease appropriate for radiative cooling, i.e. the latter is approximated by a decreasing exponential. The activation energies computed from the simulated emission are readily compared with those used to compute the TL emission. In all cases studied, the repeated initial rise technique provides reliable results only for single peak glow curves or for glow curves containing peaks that do not overlap and, if sufficiently separated, the lowest temperature peak in multipeak curves. Also the temperatures, or temperature cycles corresponding to correct activation energies occur on the low temperature side of the normal glow curve, often well below the peak temperature. A variety of misleading and/or incorrect results an be obtained when the repeated initial rise technique is applied to TL systems that produce overlapping peaks in the usual glow curve. 6 refs., 10 figs.

Kierstead, J.A.; Levy, P.W.

1990-01-01

33

Sputtering yields for C60 and Au3 bombardment of water ice as a function of incident kinetic energy.  

PubMed

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 10 100 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

2007-06-15

34

The determination of pulsed reactor kinetic behavior based upon prepulse parameter measurements  

NASA Astrophysics Data System (ADS)

This dissertation develops a method to allow the determination of the SPR III fast burst reactor's kinetic behavior based on pre-pulse measurements. The purpose is to reduce the vulnerability of pulse operations to human errors, and to improve understanding of the reactor's interactions with experiments. First, the operational history of SPR III over a wide range of experimental conditions was evaluated, looking for relationships among measured parameters. Second, the physical bases for the observed relationships were determined. Finally, the theoretical models were modified to account for the observed relationships. Computer simulations were utilized to validate the resulting models. Fast Burst Reactors (FBR) are a unique class of research reactors that generate high yield, self-terminated, short duration power pulses. Electromechanical shutdown mechanisms cannot respond quickly enough to truncate a pulse once it has been initiated, but can only mitigate post-pulse heat generation. These reactors are designed to accommodate a wide range of experimental conditions. Therefore, potential exists for an unintentional over-insertion of reactivity during a pulse operation, producing a yield capable of damaging the reactor. The safe operation of an FBR depends directly upon the knowledge, experience, skill, and judgment of the operating staff to compensate for the limitations of safety systems. This dissertation enhances the safety of these operations by identifying the mechanisms by which experiments influence the reactor's behavior, and improving the operating staff's ability to determine the impact of those influences on the reactor. Using pre-pulse reactivity measurements, this dissertation allows the operating staff to predict the change in the reactivity worth of the pulse element caused by the experiment before actually measuring it. It is also demonstrated that experiments neutronically behave as loosely-coupled reflectors, and the kinetic behavior of the reflected reactor during a pulse can be adequately modeled by treating the reflected neutrons in a manner analogous to additional delayed neutron groups. Observed changes in the reactor's negative temperature feedback coefficient due to experiments are also evaluated and explained.

Minnema, Douglas Martin

35

Effects of secondary yield parameter variation on predicted equilibrium potential of an object in a charging environment. [using computerized simulation  

NASA Technical Reports Server (NTRS)

The sensitivity of predicted equilibrium potential to changes in secondary electron yield parameters was investigated using MATCHG, a simple charging code which incorporates the NASCAP material property formulations. The equilibrium potential was found to be a sensitive function of one of the two parameters specifying secondary electron yield due to proton impact and of essentially all the parameters specifying yield due to electron impact. The information on the electron generated secondary yield parameters was discovered to be obtainable from monoenergetic beam charging data if charging rates as well as equilibrium potentials are accurately recorded.

Purvis, C. K.

1979-01-01

36

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

37

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

PubMed

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

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

2013-09-01

38

Catalytic Hydrodeoxygenation of Methyl-Substituted Phenols: Correlations of Kinetic Parameters with Molecular Properties  

E-print Network

Catalytic Hydrodeoxygenation of Methyl-Substituted Phenols: Correlations of Kinetic Parameters was carried out in a flow microreactor at 300 °C and 2.85 MPa hydrogen pressure over a sulfided CoMo/Al2O3 to be the same for both reactions, suggesting that a single catalytic site center is operative in both reactions

Simons, Jack

39

Molecular-level Thermodynamic and Kinetic Parameters for the Self-assembly of Apoferritin  

E-print Network

Molecular-level Thermodynamic and Kinetic Parameters for the Self-assembly of Apoferritin Molecules Association, Marshal Space Flight Center, Huntsville AL 35875, USA The self-assembly of apoferritin molecules biological and biomedical phenomena, as well as for pro- tein and virus self-assembly. We use the atomic

Vekilov, Peter

40

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

41

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

ERIC Educational Resources Information Center

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

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

2011-01-01

42

Curcumin and kaempferol prevent lysozyme fibril formation by modulating aggregation kinetic parameters.  

PubMed

Interaction of small molecule inhibitors with protein aggregates has been studied extensively, but how these inhibitors modulate aggregation kinetic parameters is little understood. In this work, we investigated the ability of two potential aggregation inhibiting drugs, curcumin and kaempferol, to control the kinetic parameters of aggregation reaction. Using thioflavin T fluorescence and static light scattering, the kinetic parameters such as amplitude, elongation rate constant and lag time of guanidine hydrochloride-induced aggregation reactions of hen egg white lysozyme were studied. We observed a contrasting effect of inhibitors on the kinetic parameters when aggregation reactions were measured by these two probes. The interactions of these inhibitors with hen egg white lysozyme were investigated using fluorescence quench titration method and molecular dynamics simulations coupled with binding free energy calculations. We conclude that both the inhibitors prolong nucleation of amyloid aggregation through binding to region of the protein which is known to form the core of the protein fibril, but once the nucleus is formed the rate of elongation is not affected by the inhibitors. This work would provide insight into the mechanism of aggregation inhibition by these potential drug molecules. PMID:24468532

Borana, Mohanish S; Mishra, Pushpa; Pissurlenkar, Raghuvir R S; Hosur, Ramakrishna V; Ahmad, Basir

2014-03-01

43

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

44

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.

45

Evaluation of kinetic parameters for water soluble crystals by thermo gravimetric analysis  

NASA Astrophysics Data System (ADS)

This work elevates the relevance of kinetic parameters of nucleation and thermal decomposition for water soluble crystals. The positive soluble Potassium Dihydrogen Phosphate (KDP) and negative soluble Lithium Sulfate Monohydrate (LSMH) materials were chosen for the kinetic evaluation. The results obtained from the classical nucleation theory are verified with the kinetic parameters which are evaluated from thermo gravimetric analysis. Nucleation parameters of a crystallization process such as interfacial energy (?), volume free energy (?Gv), critical energy barrier for nucleation (?G*), radius of the critical nucleus (r*) and nucleation rate (J) of the positive (KDP) and negative solubility (LSMH) crystals are determined from the classical nucleation theory of solubility-enthalpy relation. The kinetic parameters viz. the order of reaction, enthalpy, Gibbs free energy of activation, frequency factor, and entropy of activation are obtained from the TG based models viz. Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova. The effect of varying temperature with relative variation on Gibbs free energy for both positive and negative solubility crystals is also discussed. The developed model holds good for both positive and negative solubility crystals.

Rama, S.; Surendra Dilip, C.; Perumal, Rajesh Narayana

2015-01-01

46

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

47

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

48

A new method for determination of apparent kinetics parameters in recirculating packed-bed immobilized enzyme reactors  

Microsoft Academic Search

In this study, a simple and effective technique for characterizing Michaelis–Menten apparent kinetic parameters in packed-bed immobilized enzyme reactors is presented. The apparent kinetic parameters of immobilized glucose oxidase on weak base ion exchanger resin (Duolite A 568) were determined for different substrate flow rates in a recirculation system and compared with those for soluble glucose oxidase. It was observed

Ahmet R. Özdural; Deniz Tanyolaç; Zafer Demircan; ?smail H. Boyaci; Mehmet Mutlu; Colin Webb

2001-01-01

49

Nonlinear estimation of Monod growth kinetic parameters from a single substrate depletion curve.  

PubMed Central

Monod growth kinetic parameters were estimated by fitting sigmoidal substrate depletion data to the integrated Monod equation, using nonlinear least-squares analysis. When the initial substrate concentration was in the mixed-order region, nonlinear estimation of simulated data sets containing known measurement errors provided accurate estimates of the mu max, Ks, and Y values used to create these data. Nonlinear regression analysis of sigmoidal substrate depletion data was also evaluated for H2-limited batch growth of Desulfovibrio sp. strain G11. The integrated Monod equation can be more convenient for the estimation of growth kinetic parameters, particularly for gaseous substrates, but it must be recognized that the estimates of mu max, Ks, and Y obtained may be influenced by the growth rate history of the inoculum. PMID:6870238

Robinson, J A; Tiedje, J M

1983-01-01

50

Kinetic parameters of hepatic oxidation of cyclic fatty acid monomers formed from linoleic and linolenic acids  

Microsoft Academic Search

Cyclic fatty acid monomers (CFAM) occur from linoleic (CFAM-18:2) or linolenic (CFAM-18:3) acids present in some edible oils as a result of domestic frying or industrial refining. They present adverse effects in pups and weaning rats. In the present work, we studied the importance of hepatic oxidation in the metabolism of CFAM. For this purpose, kinetic parameters of Carnitine Palmitoyl

Florent Joffre; Jean-Charles Martin; Martine Genty; Luc Demaison; Olivier Loreau; Jean-Pierre Noël; Jean-Louis Sébédio

2001-01-01

51

Effects of J couplings and unobservable minor states on kinetics parameters extracted from CEST data  

NASA Astrophysics Data System (ADS)

Chemical exchange saturation transfer (CEST) experiments have emerged as a powerful tool for characterizing dynamics and sparse populated conformers of protein in slow exchanging systems. We show that J couplings and 'invisible' minor states can cause systematic errors in kinetics parameters and chemical shifts extracted from CEST data. For weakly coupled spin systems, the J coupling effect can be removed using an approximation method. This method is warranted through detailed theoretical derivation, supported by results from simulations and experiments on an acyl carrier protein domain. Simulations demonstrate that the effect of 'invisible' minor states on the extracted kinetics parameters depends on the chemical shifts, populations, exchange rates of the 'invisible' states to the observed major or minor state and exchange models. Moreover, the extracted chemical shifts of the observed minor state can also be influenced by the 'invisible' minor states. The presence of an off-pathway folding intermediate in the acyl carrier protein domain explains why the exchange rates obtained with a two-state model from individual residues that displayed only two obvious CEST dips varied significantly and the extracted exchange rates for 15N and 13CO spins located in the same peptide bond could be very different. The approximation method described here simplifies CEST data analysis in many situations where the coupling effect cannot be ignored and decoupling techniques are not desirable. In addition, this study also raises alerts for 'invisible' minor states which can cause errors in not only kinetics parameters but also chemical shifts of the observed minor state.

Zhou, Yang; Yang, Daiwen

2014-12-01

52

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

53

A novel mechanism and kinetic model to explain enhanced xylose yields from dilute sulfuric acid compared to hydrothermal pretreatment of corn stover  

E-print Network

A novel mechanism and kinetic model to explain enhanced xylose yields from dilute sulfuric acid stover Dilute sulfuric acid Hydrothermal pretreatment Kinetic model Xylose a b s t r a c t Pretreatment of corn stover in 0.5% sulfuric acid at 160 °C for 40 min realized a maximum monomeric plus oligomeric

California at Riverside, University of

54

The effect of photoirradiation on high-yield pulps: spectroscopy and kinetics  

Microsoft Academic Search

Fluorescence, UV-visible reflectance and diffuse reflectance IR Fourier transform spectroscopy were used to study the changes caused by photoirradiation of unbleached, peroxide-bleached and ozone-bleached mechanical and chemimechanical pulps. Irradiations were performed selectively at 350 nm and emission spectra were obtained using the same excitation wavelength. Kinetic curves were obtained by plotting the integrated emission intensity against the irradiation time. Different

Henrik Tylli; Ingegerd Forsskåhl; Carola Olkkonen

1995-01-01

55

Optimization of kinetic parameters for the degradation of plasmid DNA in rat plasma  

NASA Astrophysics Data System (ADS)

Biotechnology is a rapidly growing area of research work in the field of pharmaceutical sciences. The study of pharmacokinetics of plasmid DNA (pDNA) is an important area of research work. It has been observed that the process of gene delivery faces many troubles on the transport of pDNA towards their target sites. The topoforms of pDNA has been termed as super coiled (S-C), open circular (O-C) and linear (L), the kinetic model of which will be presented in this paper. The kinetic model gives rise to system of ordinary differential equations (ODEs), the exact solution of which has been found. The kinetic parameters, which are responsible for the degradation of super coiled, and the formation of open circular and linear topoforms have a great significance not only in vitro but for modeling of further processes as well, therefore need to be addressed in great detail. For this purpose, global optimization techniques have been adopted, thus finding the optimal results for the said model. The results of the model, while using the optimal parameters, were compared against the measured data, which gives a nice agreement.

Chaudhry, Q. A.

2014-12-01

56

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

57

Different singularities in the functions of extended kinetic theory at the origin of the yield stress in granular flows  

NASA Astrophysics Data System (ADS)

We use previous results from discrete element simulations of simple shear flows of rigid, identical spheres in the collisional regime to show that the volume fraction-dependence of the stresses is singular at the shear rigidity. Here, we identify the shear rigidity, which is a decreasing function of the interparticle friction, as the maximum volume fraction beyond which a random collisional assembly of grains cannot be sheared without developing force chains that span the entire domain. In the framework of extended kinetic theory, i.e., kinetic theory that accounts for the decreasing in the collisional dissipation due to the breaking of molecular chaos at volume fractions larger than 0.49, we also show that the volume fraction-dependence of the correlation length (measure of the velocity correlation) is singular at random close packing, independent of the interparticle friction. The difference in the singularities ensures that the ratio of the shear stress to the pressure at shear rigidity is different from zero even in the case of frictionless spheres: we identify that with the yield stress ratio of granular materials, and we show that the theoretical predictions, once the different singularities are inserted into the functions of extended kinetic theory, are in excellent agreement with the results of numerical simulations.

Berzi, Diego; Vescovi, Dalila

2015-01-01

58

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...

59

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

60

Closed-Form Kinetic Parameter Estimation Solution to the Truncated Data Problem  

PubMed Central

In a dedicated cardiac single photon emission computed tomography (SPECT) system, the detectors are focused on the heart and the background is truncated in the projections. Reconstruction using truncated data results in biased images, leading to inaccurate kinetic parameter estimates. This paper has developed a closed-form kinetic parameter estimation solution to the dynamic emission imaging problem. This solution is insensitive to the bias in the reconstructed images that is caused by the projection data truncation. This paper introduces two new ideas: (1) it includes background bias as an additional parameter to estimate, and (2) it presents a closed-form solution for compartment models. The method is based on the following two assumptions: (i) the amount of the bias is directly proportional to the truncated activities in the projection data, and (ii) the background concentration is directly proportional to the concentration in the myocardium. In other words, the method assumes that the image slice contains only the heart and the background, without other organs; that the heart is not truncated; and that the background radioactivity is directly proportional to the radioactivity in the blood pool. As long as the background activity can be modeled, the proposed method is applicable regardless of the number of compartments in the model. For simplicity, the proposed method is presented and verified using a single compartment model with computer simulations using both noise-less and noisy projections. PMID:21098917

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

2011-01-01

61

Formation of gas-phase peptide ions and their dissociation in MALDI: Insights from kinetic and ion yield studies.  

PubMed

Insights on mechanisms for the generation of gas-phase peptide ions and their dissociation in matrix-assisted laser desorption ionization (MALDI) gained from the kinetic and ion yield studies are presented. Even though the time-resolved photodissociation technique was initially used to determine the dissociation kinetics of peptide ions and their effective temperature, it was replaced by a simpler method utilizing dissociation yields from in-source decay (ISD) and post-source decay (PSD). The ion yields for a matrix and a peptide were measured by repeatedly irradiating a region on a sample and collecting ion signals until the sample in the region was completely depleted. Matrix- and peptide-derived gas-phase cations were found to be generated by pre-formed ion emission or by ion-pair emission followed by anion loss, but not by laser-induced ionization. The total number of ions, that is, matrix plus peptide, was found to be equal to the number of ions emitted from a pure matrix. A matrix plume was found to cool as it expanded, from around 800-1,000?K to 400-500?K. Dissociation of peptide ions along b/y channels was found to occur statistically, that is, following RRKM behavior. Small critical energy (E0 ?=?0.6-0.7?eV) and highly negative critical entropy (?S(‡) ?=?-30 to -25?eu) suggested that the transition structure was stabilized by multiple intramolecular interactions. © 2014 Wiley Periodicals, Inc. Mass Spec Rev 34: 94-115, 2015. PMID:24863621

Moon, Jeong Hee; Yoon, Sohee; Bae, Yong Jin; Kim, Myung Soo

2015-04-01

62

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

63

Measuring the kinetic parameters of saltating sand grains using a high-speed digital camera  

NASA Astrophysics Data System (ADS)

A high-speed digital camera is used to record the saltation of three sand samples (diameter range: 300-500, 200-300 and 100-125 ?m). This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains. The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport. Moreover, the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory, and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air.

Zhang, Yang; Wang, Yuan; Jia, Pan

2014-06-01

64

Measuring the kinetic parameters of saltating sand grains using a high-speed digital camera  

NASA Astrophysics Data System (ADS)

A high-speed digital camera is used to record the saltation of three sand samples (diameter range: 300-500, 200-300 and 100-125 ?m). This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains. The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport. Moreover, the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory, and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air.

Zhang, Yang; Wang, Yuan; Jia, Pan

2014-04-01

65

Tyrosinase subcellular distribution and kinetic parameters in wild type and C-locus mutant C57BL/6J mice.  

PubMed

The distribution and kinetic parameters of tyrosinase (EC 1.14.-18.1) from anagen hair follicles of the C57BL/6J mouse and several c-locus mutants were investigated. The results showed that c-locus mutations not only influenced the total tyrosinase activity, but the subcellular distribution as well. The kinetic parameters of tyrosinase were not influenced by the pigment mutations, suggesting that the mutations were not influencing the structure of the enzyme. PMID:6793688

Townsend, D; Witkop, C J; Mattson, J

1981-04-01

66

Classical nucleation theory of homogeneous freezing of water: thermodynamic and kinetic parameters.  

PubMed

The probability of homogeneous ice nucleation under a set of ambient conditions can be described by nucleation rates using the theoretical framework of Classical Nucleation Theory (CNT). This framework consists of kinetic and thermodynamic parameters, of which three are not well-defined (namely the interfacial tension between ice and water, the activation energy and the prefactor), so that any CNT-based parameterization of homogeneous ice formation is less well-constrained than desired for modeling applications. Different approaches to estimate the thermodynamic and kinetic parameters of CNT are reviewed in this paper and the sensitivity of the calculated nucleation rate to the choice of parameters is investigated. We show that nucleation rates are very sensitive to this choice. The sensitivity is governed by one parameter - the interfacial tension between ice and water, which determines the energetic barrier of the nucleation process. The calculated nucleation rate can differ by more than 25 orders of magnitude depending on the choice of parameterization for this parameter. The second most important parameter is the activation energy of the nucleation process. It can lead to a variation of 16 orders of magnitude. By estimating the nucleation rate from a collection of droplet freezing experiments from the literature, the dependence of these two parameters on temperature is narrowed down. It can be seen that the temperature behavior of these two parameters assumed in the literature does not match with the predicted nucleation rates from the fit in most cases. Moreover a comparison of all possible combinations of theoretical parameterizations of the dominant two free parameters shows that one combination fits the fitted nucleation rates best, which is a description of the interfacial tension coming from a molecular model [Reinhardt and Doye, J. Chem. Phys., 2013, 139, 096102] in combination with the activation energy derived from self-diffusion measurements [Zobrist et al., J. Phys. Chem. C, 2007, 111, 2149]. However, some fundamental understanding of the processes is still missing. Further research in future might help to tackle this problem. The most important questions, which need to be answered to constrain CNT, are raised in this study. PMID:25627933

Ickes, Luisa; Welti, André; Hoose, Corinna; Lohmann, Ulrike

2015-02-10

67

Parameter Identification and On-line Estimation of a Reduced Kinetic Model  

SciTech Connect

In this work, we present the estimation techniques used to update the model parameters in a reduced kinetic model describing the oxidation-reduction re- actions in a hydrothermal oxidation reactor. The model is used in a nonlinear model-based controller that minimizes the total aqueous nitrogen in the reac- tor effluent. Model reduction is accomplished by com- bining similar reacting compounds into one of four component groups and considering the global reac- tion pathways for each of these groups. The reduced kinetic model developed for thk reaction system pro- vides a means to characterize the complex chemical reaction system without considering each chemicaJ species present and the reaction kinetics of every pos- sible reaction pathway. For the reaction system under study, model reduction is essential in order to reduce the computational requirement so that on-line imple- mentation of the nonlinear model-based controller is possible and also to reduce the amount of a priori information required for the model.

Dellorco, P.C.; Flesner, R.L.; Le, L.A.; Littell, J.D.; Muske, K.R.

1999-02-01

68

On the estimation of kinetic parameters of organic matters using linearization methods  

NASA Astrophysics Data System (ADS)

Kinetic parameters obtained by various thermal analysis methods are widely used in petroleum and other industries. These methods are restricted to relatively simple models that consist of a single equation and have usually uneven sensitivity on the uncertainty of the experimental data due to logarithmic conversions. An important consideration affecting the success of the linearization methods is that the proper selection of the beginning and the end of the linear section. A new method was implemented in advanced, portable and user-friendly thermal analysis software that does not suffer the typical shortcomings of the linearization processes. The developed software can accurately identify different reaction regions by means of a numerical technique. The uses and the advantages of the developed software and the methodology were evaluated by analyzing reaction kinetics of an asphaltite and a coal sample with single and multiple reaction regions. Using a least-squares minimization technique the software can be used to match experimental data with three different kinetic models (Arrhenius, Coats and Redfern, and Ingraham and Marrier) for determining the activation energies of samples. It was observed that there is a good relation between the correlation coefficient and the success of the estimation.

Uraz, Irtek; Akin, Serhat; Versan Kok, Mustafa

2004-08-01

69

Nonlinear estimation of kinetic parameters for solid-state hydrolysis of water-soluble drugs.  

PubMed

Nonlinear-regression analysis was applied to estimate the kinetic parameters for the solid-state hydrolysis of meclofenoxate hydrochloride [2-(dimethylamino)ethyl (4-chlorophenoxy)acetate hydrochloride; 1] and propantheline bromide [(2-hydroxyethyl)diisopropylmethylammonium bromide xanthene-9-carboxylate; 2]. The percent decomposed (x) at the initial stage of decomposition was found to conform to the empirical equation x = ktn, where n and k are constants. The goodness of fit of the data was better than with the Prout-Tompkins equation. The parameters indicating the dependence of the rate on temperature (T) and water vapor pressure (P) were estimated by nonlinear-regression analysis based on the equation: x = x0 exp[(Ea/R)(1/298-1/T)] (P/18.167)s(t/50)n, where xo is the percent decomposed at t = 50 d, T = 298 K and P = 18.167 mmHg, and Ea (activation energy), s, and n are constants. For the hydrolysis at a relative humidity (RH) above the critical relative humidity (CRH), nonlinear parameter estimation provided statistically meaningful estimates of Ea, s, x0, and n, and it was suggested that these parameters could be regarded as constants in the experimental range. For the hydrolysis at RH below the CRH, however, the parameters could not be converged by nonlinear-regression analysis, and Ea and/or s were assumed not to be constant in this RH range. PMID:3090232

Yoshioka, S; Uchiyama, M

1986-05-01

70

Sparsity Constrained Mixture Modeling for the Estimation of Kinetic Parameters in Dynamic PET.  

PubMed

The estimation and analysis of kinetic parameters in dynamic PET is frequently confounded by tissue heterogeneity and partial volume effects. We propose a new constrained model of dynamic PET to address these limitations. The proposed formulation incorporates an explicit mixture model in which each image voxel is represented as a mixture of different pure tissue types with distinct temporal dynamics.We use Cram´er-Rao lower bounds to demonstrate that the use of prior information is important to stabilize parameter estimation with this model. As a result, we propose a constrained formulation of the estimation problem that we solve using a two-stage algorithm. In the first stage, a sparse signal processing method is applied to estimate the rate parameters for the different tissue compartments from the noisy PET time series. In the second stage, tissue fractions and the linear parameters of different time activity curves are estimated using a combination of spatial-regularity and fractional mixture constraints. A block coordinate descent algorithm is combined with a manifold search to robustly estimate these parameters. The method is evaluated with both simulated and experimental dynamic PET data. PMID:24216681

Lin, Yanguang; Haldar, Justin; Li, Quanzeng; Conti, Peter; Leahy, Richard

2013-11-01

71

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

72

Hydrolysis of a Lipid Membrane by Single Enzyme Molecules: Accurate Determination of Kinetic Parameters.  

PubMed

The accurate determination of the maximum turnover number and Michaelis constant for membrane enzymes remains challenging. Here, this problem has been solved by observing in parallel the hydrolysis of thousands of individual fluorescently labeled immobilized liposomes each processed by a single phospholipase A2 molecule. The release of the reaction product was tracked using total internal reflection fluorescence microscopy. A statistical analysis of the hydrolysis kinetics was shown to provide the Michaelis-Menten parameters with an accuracy better than 20?% without variation of the initial substrate concentration. The combined single-liposome and single-enzyme mode of operation made it also possible to unravel a significant nanoscale dependence of these parameters on membrane curvature. PMID:25429738

Rabe, Michael; Tabaei, Seyed R; Zetterberg, Henrik; Zhdanov, Vladimir P; Höök, Fredrik

2014-11-27

73

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

74

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

75

Nonlinear estimation of the parameters of Monod kinetics that best describe mineralization of several substrate concentrations by dissimilar bacterial densities.  

PubMed Central

The kinetics of mineralization of a wide range of concentrations of benzoate, glucose, and benzylamine by Pseudomonas sp., Salmonella typhimurium, and microorganisms in acclimated sewage was studied. The treatment of initial substrate concentration and population density as independent variables in nonlinear regression analysis permitted the estimation of a single value for each of the parameters of Monod kinetics that best described the mineralization of substrate at each concentration by the pure cultures and the sewage microflora. One value for each of the parameters of Monod kinetics was used for each of the three compounds to produce theoretical curves which lay close to the observed data on mineralization. Statistically significant differences existed in the values of the parameters of Monod kinetics that best described mineralization in cultures differing only in initial substrate concentration and cell density. However, for the compounds tested, the variance left by analyses using one value for each parameter of Monod kinetics was less than double the unexplained variance left by individual analyses of the data from each treatment. Although significant, this increase is small compared with the amount of variance that could be explained using only one value for each parameter of Monod kinetics. PMID:3909965

Simkins, S; Alexander, M

1985-01-01

76

Kinetics of the reaction HO2 + NO2 + M yields HO2NO2 + M  

NASA Technical Reports Server (NTRS)

The flash photolysis/ultraviolet absorption technique was used to measure the rate constants for the reaction HO2 + NO2 + M yields HO2NO2 + M over the pressure range 50-700 torr and temperature range 229-362 K using He, O2, and N2 as diluent gases. The data were fit to the expression derived by Troe (1979) and co-workers for describing the pressure and temperature dependence of reactions in the falloff region. By combining these data with recent measurements of the rate constant for HO2NO2 thermal decomposition values of 73.8 + or - 2 eu for the standard entropy and -12.6 + or - kcal/mol for the standard enthalpy of formation of HO2NO2 were obtained. A significant enhancement in the rate constant was observed when water vapor was added to the system.

Sander, S. P.; Peterson, M. E.

1984-01-01

77

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

SciTech Connect

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

Jantzen, C M

1988-01-01

78

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

SciTech Connect

A series of gasification experiments, using two right cylinder specimens (~ 12.7 x 25.4 mm and 25.4 x 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 [University of New Mexico, Albuquerque] [University of New Mexico, Albuquerque; Tournier, Jean-Michel [University of New Mexico, Albuquerque] [University of New Mexico, Albuquerque; Contescu, Cristian I [ORNL] [ORNL

2014-01-01

79

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

SciTech Connect

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

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

1995-05-01

80

KiPar, a tool for systematic information retrieval regarding parameters for kinetic modelling of yeast metabolic pathways  

Microsoft Academic Search

Motivation: Most experimental evidence on kinetic parameters is buried in the literature, whose manual searching is complex, time consuming and partial. These shortcomings become particularly acute in systems biology, where these parameters need to be integrated into detailed, genome-scale, metabolic models. These problems are addressed by KiPar, a dedicated information retrieval system designed to facilitate access to the literature relevant

Irena Spasic; Evangelos Simeonidis; Hanan L. Messiha; Norman W. Paton; Douglas B. Kell

2009-01-01

81

Spatial variability of switchgrass ( Panicum virgatum L.) yield as related to soil parameters in a small field  

Microsoft Academic Search

The harvested biomass of switchgrass (Panicum virgatum L.) is generally much lower than its potential; this may be due to several factors including not recovering all the biomass at harvest, weed competition, pests, disease and spatial variation of soil features. The objective of this research was to quantify the yield spatial variation of switchgrass and relate it to soil parameters,

Nicola Di Virgilio; Andrea Monti; Gianpietro Venturi

2007-01-01

82

Modeling and estimation of failure probability due to parameter variations in nano-scale SRAMs for yield enhancement  

Microsoft Academic Search

In this paper we have analyzed and modeled the failure probabilities (access time failure, read\\/write stability failure, and hold stability failure in the stand-by mode) of SRAM cells due to process parameter variations. A method to predict the yield of a memory chip designed with a cell is proposed based on the cell failure probability. The developed method can be

Saibal Mukhopadhyay; Hamid Mahmoodi-Meimand; Kaushik Roy

2004-01-01

83

ESTIMATES OF GENETIC PARAMETERS FOR FIRST LACTATION TEST-DAY YIELDS OF HOLSTEIN COWS WITH A CUBIC SPLINE MODEL  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective was to estimate genetic parameters for individual test-day milk, fat, and protein yields with a cubic spline model. A total of 196,687 test-day records in the first 305-d of 38,172 first lactation Holstein cows that calved between 1994 and early 1999 were obtained from Dairy Records Ma...

84

Estimates of genetic parameters for Holstein cows for test-day yield traits with a random regression cubic spline model  

Technology Transfer Automated Retrieval System (TEKTRAN)

Genetic parameters were estimated with REML for individual test-day milk, fat, and protein yields and SCS with a random regression cubic spline model. Test-day records of Holstein cows that calved from 1994 through early 1999 were obtained from Dairy Records Management Systems in Raleigh, North Car...

85

Fixed-bed pyrolysis of safflower seed: influence of pyrolysis parameters on product yields and compositions  

Microsoft Academic Search

Fixed-bed slow pyrolysis experiments have been conducted on a sample of safflower seed to determine particularly the effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rate on the pyrolysis product yields and their chemical compositions. The maximum oil yield of 44% was obtained at the final pyrolysis temperature of 500°C, particle size range of +0.425–1.25 mm,

S. H. Beis; Ö. Onay; Ö. M. Koçkar

2002-01-01

86

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

87

Kinetic Parameters and Cytotoxic Activity of Recombinant Methionine ?-Lyase from Clostridium tetani, Clostridium sporogenes, Porphyromonas gingivalis and Citrobacter freundii  

PubMed Central

The steady-state kinetic parameters of pyridoxal 5’-phosphate-dependent recombinant methionine ? -lyase from three pathogenic bacteria, Clostridium tetani, Clostridium sporogenes, and Porphyromonas gingivalis, were determined in ?- and ?-elimination reactions. The enzyme from C. sporogenes is characterized by the highest catalytic efficiency in the ?-elimination reaction of L-methionine. It was demonstrated that the enzyme from these three sources exists as a tetramer. The N-terminal poly-histidine fragment of three recombinant enzymes influences their catalytic activity and facilitates the aggregation of monomers to yield dimeric forms under denaturing conditions. The cytotoxicity of methionine ?-lyase from C. sporogenes and C. tetani in comparison with Citrobacter freundii was evaluated using K562, PC-3, LnCap, MCF7, SKOV-3, and L5178y tumor cell lines. K562 (IC50=0.4–1.3 U/ml), PC-3 (IC50=0.1–0.4 U/ml), and MCF7 (IC50=0.04–3.2 U/ml) turned out to be the most sensitive cell lines. PMID:24303205

Morozova, E. A.; Kulikova, V. V.; Yashin, D. V.; Anufrieva, N. V.; Anisimova, N. Y.; Revtovich, S. V.; Kotlov, M. I.; Belyi, Y. F.; Pokrovsky, V. S.; Demidkina, T. V.

2013-01-01

88

Parameter identification and on-line estimation for reduced kinetic model  

SciTech Connect

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

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

1998-08-07

89

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

90

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

91

Genetic Parameters And Selection Response For Yield Traits In Bread Wheat Under Irrigated And Rainfed Environments  

NASA Astrophysics Data System (ADS)

A set of 22 F5:7 experimental wheat lines along with four check cultivars (Dera-98, Fakhr-e-Sarhad, Ghaznavi-98 and Tatara) were evaluated as independent experiments under irrigated and rainfed environments using a randomized complete block design at NWFP Agricultural University, Peshawar during 2004-05. The two environments were statistically different for days to heading and spike length only. Highly significant genetic variability existed among the wheat lines (P<0.01) in the combined analysis across environments for all traits. Genotype×environment interactions were non-significant for all traits except 1000-grain weight indicating consistent performance of wheat genotypes across the two environments. Wheat lines and check cultivars were 2 to 5 days early in heading under rainfed environment compared to the irrigated. Plant height, spike length, 1000-grain weight, biological and grain yields were generally reduced under rainfed environment. Genetic variances were of greater magnitude than environmental variances for most of the traits in both environments. The heritability estimates were of higher magnitude (0.74 to 0.96) for days to heading, plant height, spike length, biological and grain yield, while medium (0.31 to 0.51) for 1000-grain weight. Selection differentials were negative for heading (-7.3 days in irrigated vs -9.4 days in rainfed) and plant height (-9.0 cm in irrigated vs -8.7 cm in rainfed) indicating possibility of selecting wheat genotypes with early heading and short plant stature. Positive selection differentials of 1.3 vs 1.6 cm for spike length, 3.8 vs 3.4 g for 1000-grain weight, 2488.2 vs 3139.7 kg ha-1 for biological yield and 691.6 vs 565.4 kg ha-1 for grain yield at 20% selection intensity were observed under irrigated and rainfed environments, respectively. Expected selection responses were 7.98 vs 8.91 days for heading, 8.20 vs 9.52 cm for plant height, 1.01 vs 1.61 cm for spike length, 2.12 vs 1.15 g for 1000-grain weight, 1655.8 vs 2317.2 kg ha-1 for biological yield and 691.6 vs 565.4 kg ha-1 for grain yield under the two test environments, respectively. The differential heritability and selection responses for yield and related traits suggest the simultaneous evaluation and selection of wheat lines under the two environments.

Khalil, Iftikhar Hussain; at-ur-Rahman, Hiday; Khan, Imran

2008-01-01

92

Kinetic parameters of the oxidation of zirconium alloys in simulated WWER water Effect of KOH content  

NASA Astrophysics Data System (ADS)

The pre-transition oxides formed on two different types of zirconium alloys (Zircaloy 4 and E110) have been characterised in situ using electrochemical impedance spectroscopy (EIS) in high-temperature electrolyte simulating WWER conditions at 310 °C. To obtain a correlation between the oxide film thickness, the oxide growth rate and the impedance parameters, the EIS data have been fitted to a transfer function derived from the mixed-conduction model for oxide films, allowing for the contribution of both an inner, barrier type of oxide and a more defective outer layer. The values of the total oxide film thickness based on the model calculations have proved to be in a good agreement with the values measured from the cross-section micrographs of the specimens using scanning electron microscopy. The main kinetic and transport parameters characterising the oxidation process have been estimated and discussed with regard to the effect of KOH content and alloy type on the mechanism of conduction through the formed oxide.

Bojinov, Martin; Cai, Wei; Kinnunen, Petri; Saario, Timo

2008-08-01

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

Genetic parameters for lactation traits of milking ewes: protein content and composition, fat, somatic cells and individual laboratory cheese yield  

PubMed Central

The effects of some environmental variation factors and the genetic parameters for total milk traits (fat content, protein content, casein content, serum protein content, lactation mean of individual laboratory cheese yield (LILCY), lactation mean of somatic cell count (LSCC), and milk yield) were estimated from the records of 1 111 Churra ewes. Genetic parameters were estimated by multivariate REML. Heritability for fat content was low (0.10) as is usually found in the Churra breed. Heritabilities for protein content, casein content, serum protein content, LILCY, milk yield and somatic cell count were 0.31, 0.30, 0.22, 0.09, 0.26 and 0.11, respectively. The highest heritability estimates were for protein and casein contents. Casein content is not advisable as an alternative to protein content as a selection criterion for cheese yield improvement; it does not have any compelling advantages and its measurement is costly. Our results for LSCC indicated that efforts should focus on improving the level of management rather than selecting for somatic cells, in the actual conditions of the Churra breed. PMID:12427387

Othmane, Med Houcine; Carriedo, Juan Antonio; San Primitivo, Fermin; De la Fuente, Luis Fernando

2002-01-01

95

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

Microsoft Academic Search

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

T Khursheed; MYK Ansari; D Shahab

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-Vázquez, Aura Roxana; Cortés Penagos, Consuelo de Jesús; Cortés-Martínez, Raúl

2014-01-01

97

Dynamic yield, compressional, and elastic parameters for several lightweight intermetallic compounds  

Microsoft Academic Search

Dynamic yield strengths, compression data under uniaxial shock-wave loading, and sonic velocities at 1 bar are reported for polycrystalline TiB2, SiC, Be4B, Be4B+8 wt% BeO, Be2B, AlB12, TiBe12, and ZrBe13. Hugoniot elastic limits were measured as 86, 80, 74, 77, 65, 87, 53, and 71 kbar, respectively. Evidence of phase transitions was seen for the Be4B materials at 500 kbar

W. H. Gust; A. C. Holt; E. B. Royce

1973-01-01

98

Kinetics  

NSDL National Science Digital Library

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

Nurrenbern, Susan C.; Robinson, William R.

2008-02-27

99

Predicting heavy metals' adsorption edges and adsorption isotherms on MnO2 with the parameters determined from Langmuir kinetics.  

PubMed

Although surface complexation models have been widely used to describe the adsorption of heavy metals, few studies have verified the feasibility of modeling the adsorption kinetics, edge, and isotherm data with one pH-independent parameter. A close inspection of the derivation process of Langmuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model, KS-kinetic, is theoretically equivalent to the adsorption constant in Langmuir isotherm, KS-Langmuir. The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed. The MLK model was employed to simulate the adsorption kinetics of Cu(II), Co(II), Cd(II), Zn(II) and Ni(II) on MnO2 at pH3.2 or 3.3 to get the values of KS-kinetic. The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model), and the values of KS-Langmuir were obtained. The values of KS-kinetic and KS-Langmuir are very close to each other, validating that the constants obtained by these two methods are basically the same. The MMP model with KS-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations. Moreover, the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the KS-kinetic constants. PMID:25597679

Hu, Qinghai; Xiao, Zhongjin; Xiong, Xinmei; Zhou, Gongming; Guan, Xiaohong

2015-01-01

100

Determination of major kinetic parameters of the Syrian MNSR for different fuel loading using Monte Carlo technique  

Microsoft Academic Search

A comprehensive 3-D model of the Syrian MNSR reactor has been developed using the MCNP-4C code aiming at accurate predicting of key core physics parameters. For the currently utilized HEU fuel (89.87% UAl4-Al) and two possible alternative LEU fuels (UO2 12%, and UO2 20%) the main core kinetics parameters like prompt neutron generation time, effective delayed neutron fraction, clean cold

A. Hainoun; H. Haj Hassan; N. Ghazi

2009-01-01

101

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

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

Study of kinetic parameters for the production of recombinant rabies virus glycoprotein.  

PubMed

Gene expression in insect cells is an advantageous system for recombinant protein production, mainly because of its capacity to produce complex proteins with correct post-translational modifications. Recently, we identified and purified a protein from Lonomia obliqua hemolymph able to increase the production of rabies virus glycoprotein, expressed in Drosophila melanogaster cells, by about 60%. In this work, the kinetic parameters for cell growth and recombinant rabies virus glycoprotein production were determined in cultures of transfected Drosophila melanogaster Schneider 2 (S2) cells expressing recombinant rabies virus glycoprotein (rRVGP), enriched and non-enriched with the hemolymph of Lonomia obliqua (Hb). The highest concentration of rRVGP was achieved at the beginning of the culture enriched with Hb, indicating that the cells produce greater amounts of rRVGP per cell (specific rRVGP concentration) at the early exponential growth phase. After day 8, a decrease in the concentration of rRVGP (ng/mL) was observed, probably due to protein decomposition. The average specific rRVGP production rate (mu(rRVGP)) was 30 ng rRVGP/10(7)cell.day, higher than that observed in the non-enriched culture. PMID:19842054

Mendonça, Ronaldo Z; Greco, Katia N; Moraes, Roberto H P; Astray, Renato M; Barral, M

2009-07-01

105

Rate Equations and Kinetic Parameters of the Reactions Involved in Pyrite Oxidation by Thiobacillus ferrooxidans  

PubMed Central

Rate equations and kinetic parameters were obtained for various reactions involved in the bacterial oxidation of pyrite. The rate constants were 3.5 ?M Fe2+ per min per FeS2 percent pulp density for the spontaneous pyrite dissolution, 10 ?M Fe2+ per min per mM Fe3+ for the indirect leaching with Fe3+, 90 ?M O2 per min per mg of wet cells per ml for the Thiobacillus ferrooxidans oxidation of washed pyrite, and 250 ?M O2 per min per mg of wet cells per ml for the T. ferrooxidans oxidation of unwashed pyrite. The Km values for pyrite concentration were similar and were 1.9, 2.5, and 2.75% pulp density for indirect leaching, washed pyrite oxidation by T. ferrooxidans, and unwashed pyrite oxidation by T. ferrooxidans, respectively. The last reaction was competitively inhibited by increasing concentrations of cells, with a Ki value of 0.13 mg of wet cells per ml. T. ferrooxidans cells also increased the rate of Fe2+ production from Fe3+ plus pyrite. PMID:16348054

Lizama, Hector M.; Suzuki, Isamu

1989-01-01

106

2-Naphthol aliphatic amine exciplex systems: a method for approximate estimation of kinetic parameters  

NASA Astrophysics Data System (ADS)

The fluorescence quenching behavior of 2-naphthol was studied with aliphatic and alcohol amines (diethylamine, triethylamine, n-propylamine, n-butylamine, ethanolamine, diethanolamine, triethanolamine) as quenchers in solvents of varying polarity (cyclohexane, acetonitrile and methanol). The quenching proceeded via the formation of an emissive exciplex. The equilibrium constant for the formation of the exciplex ( KE) in the first excited state was calculated from the fluorescence intensities of the monomer and exciplex intensities. All the rate constants appearing in the kinetic scheme ( k1 to k6) for the two state system were then estimated with this equilibrium constant ( KE) by using an approximate but essentially steady-state method based on the Ware's mechanism. Variable temperature experiments were carried out to obtain certain thermodynamic parameters like the entropy (? SE0), enthalpy (? HE0), free energy of formation (? GE0) and the formation constant ( KE) for the exciplex. The equilibrium constant ( KE) calculated from both the methods agreed very well. AM1 calculations were also done to obtain information about the ground and excited geometry of the naphthol-amine complex.

Hariharan, Chithra; Rath, M. C.; Mukherjee, T.; Mishra, A. K.

1999-09-01

107

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

108

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

SciTech Connect

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

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

1997-03-19

109

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

110

A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modeling  

USGS Publications Warehouse

Geochemical reaction path modeling is useful for rapidly assessing the extent of water-aqueous-gas interactions both in natural systems and in industrial processes. Modeling of some systems, such as those at low temperature with relatively high hydrologic flow rates, or those perturbed by the subsurface injection of industrial waste such as CO2 or H2S, must account for the relatively slow kinetics of mineral-gas-water interactions. We have therefore compiled parameters conforming to a general Arrhenius-type rate equation, for over 70 minerals, including phases from all the major classes of silicates, most carbonates, and many other non-silicates. The compiled dissolution rate constants range from -0.21 log moles m-2 s-1 for halite, to -17.44 log moles m-2 s-1 for kyanite, for conditions far from equilibrium, at 25 ?C, and pH near neutral. These data have been added to a computer code that simulates an infinitely well-stirred batch reactor, allowing computation of mass transfer as a function of time. Actual equilibration rates are expected to be much slower than those predicted by the selected computer code, primarily because actual geochemical processes commonly involve flow through porous or fractured media, wherein the development of concentration gradients in the aqueous phase near mineral surfaces, which results in decreased absolute chemical affinity and slower reaction rates. Further differences between observed and computed reaction rates may occur because of variables beyond the scope of most geochemical simulators, such as variation in grain size, aquifer heterogeneity, preferred fluid flow paths, primary and secondary mineral coatings, and secondary minerals that may lead to decreased porosity and clogged pore throats.

Palandri, James L.; Kharaka, Yousif K.

2004-01-01

111

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

PubMed

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

Kawamura, Kunio; Maeda, Jun

2008-09-01

112

ITC Recommendations for Transporter Kinetic Parameter Estimation and Translational Modeling of Transport-Mediated PK and DDIs in Humans  

PubMed Central

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, MJ; Lee, CA; Poirier, A; Bentz, J; Chu, X; Ellens, H; Ishikawa, T; Jamei, M; Kalvass, JC; Nagar, S; Pang, KS; Korzekwa, K; Swaan, PW; Taub, ME; Zhao, P; Galetin, A

2013-01-01

113

Monoculture parameters successfully predict coculture growth kinetics of Bacteroides thetaiotaomicron and two Bifidobacterium strains.  

PubMed

Microorganisms rarely live in isolation but are most often found in a consortium. This provides the potential for cross-feeding and nutrient competition among the microbial species, which make it challenging to predict the growth kinetics in coculture. In this paper we developed a mathematical model to describe substrate consumption and subsequent microbial growth and metabolite production for bacteria grown in monoculture. The model characterized substrate utilization kinetics of 18 Bifidobacterium strains. Some bifidobacterial strains demonstrated preferential degradation of oligofructose in that sugars with low degree of polymerization (DP) (DP?3 or 4) were metabolized before sugars of higher DP, or vice versa. Thus, we expanded the model to describe the preferential degradation of oligofructose. In addition, we adapted the model to describe the competition between human colonic bacteria Bacteroides thetaiotaomicron LMG 11262 and Bifidobacterium longum LMG 11047 or Bifidobacterium breve Yakult for inulin as well as cross-feeding of breakdown products from the extracellular hydrolysis of inulin by B. thetaiotaomicron LMG 11262. We found that the coculture growth kinetics could be predicted based on the respective monoculture growth kinetics. Using growth kinetics from monoculture experiments to predict coculture dynamics will reduce the number of in vitro experiments required to parameterize multi-culture models. PMID:25282609

Van Wey, A S; Cookson, A L; Roy, N C; McNabb, W C; Soboleva, T K; Shorten, P R

2014-11-17

114

A new graphical method for determining parameters in Michaelis-Menten-type kinetics for enzymatic lactose hydrolysis.  

PubMed

A new graphical method was developed to determine the kinetic parameters in the Michaelis-Menten-type equation. This method was then applied to studying the kinetics of lactose hydrolysis by Aspergillus niger beta-galactosidase. In this study, the reaction temperature ranged between 8 and 60 degrees C, and the initial lactose concentration ranged between 2.5 and 20%. A kinetic model similar to the conventional Michaelis-Menten equation with competitive product inhibition by galactose was tested using this graphical method as well as a nonlinear computer regression method. The experimental data and the model fit together fairly well at 50 degrees C. However, a relative large disparity was found for reactions at 30 degrees C. A three-parameter integrated model derived from the reversible reaction mechanism simulates the experimental data very well at all temperatures studied. However, this reversible reaction model does not follow the Arrhenius temperature dependence. Nevertheless, reaction rate constants for the proposed model involving the enzyme-galactose complex (in addition to the Michaelis complex) as an intermediate in lactose hydrolysis follow the Arrhenius temperature dependence fairly well, suggesting that this model can be best used for describing the enzymatic lactose hydrolysis. The lack of fit between the model predictions and data may be largely attributed to the effects of galactose mutarotation and oligosaccharide formation during lactose hydrolysis. PMID:18588163

Yang, S T; Okos, M R

1989-09-01

115

Estimation of kinetic parameters of the passive state of carbon steel in mildly alkaline solutions from electrochemical impedance spectroscopic and X-ray photoelectron spectroscopic data  

Microsoft Academic Search

The unambiguous interpretation of electrochemical impedance spectra of complex systems such as passive metals and alloys in terms of an unique kinetic model is often hampered by the large number of adjustable modeling parameters. In this paper, a combination of in situ electrochemical data and ex situ surface analytical information is employed to validate the estimates of kinetic and transport

X. Zhang; J. C. Wren; I. Betova; M. Bojinov

2011-01-01

116

Estimation of kinetic parameters in the inactivation of an enzyme by a suicide substrate.  

PubMed

A method was developed to estimate the extended Michaelis constant and maximum velocity of a suicide substrate from the time-course of remaining enzyme activity with the use of simulation data calculated from the representative kinetic model for a suicide substrate proposed by Walsh et al. (Walsh, C., Cromartie, T., Marcotte, P. and Spencer, R. (1978) Methods Enzymol. 53, 437-448). For this purpose an analytical equation for the time-course of remaining enzyme activity, based on the suicide kinetic model, was derived by the steady-state method reported by Tatsunami et al. (Tatsunami, S., Yago, N. and Hosoe, M. (1981) Biochim. Biophys. Acta 662, 226-235). The accuracy of this analytical solution was proved by comparing the result with the exact solution obtained by numerical computation. A method was also developed to estimate the most important factor for a suicide substrate, the partition ratio, from the time-course of remaining enzyme activity. PMID:2049382

Funaki, T; Takanohashi, Y; Fukazawa, H; Kuruma, I

1991-05-30

117

Global Chapman-Ferraro problem in large scale kinetics: 3d magnetotail/solar coronal streamer with new kinetic plasma scales and dimensionless parameters  

NASA Astrophysics Data System (ADS)

In terms of the Vlasov-Maxwell kinetic approach we consider analytically the global Chapman- Ferraro problem (CFP) of inductive generation by the solar wind plasma flow of 3D magnetotail/solar streamer (M/S) structures in the process of electromagnetic (e.m.) interaction of the flow with the magnetized region. The input undisturbed flow is a hot collisionless plasma with an isotropic velocity distribution function (VDF) of any form, characterized by the introduced dimensionless kinetic parameter G. The 3D analytical stationary solution and set of new CFP parameters are a result of the classical simplification method based on separation of plasma particles in the velocity phase space into "trapped" and "flyby" groups that interact electromagnetically. The "flyby" particles form the "flowing media" with large scale kinetic inductive e.m. plasma eigenmodes disturbing the plasma VDF. The trapped particles in the magnetic dipole field form the prescribed "magnetic quasiparticle". The quasiparticle is described as stationary 3D spatial magnetization formed by the superposition of dipole like magnetization with N and S poles and toroidal circular magnetization without the poles. The spatial scale of the "quasiparticle", the ratio of the integral currents in the dipole and the toroidal components, and angle of mutual orientation of the components are the "quasiparticle" parameters. The "quasiparticle" models magnetic loop, sigma and helmet magnetoactive structures for the Sun and models circular and partial ring currents in the internal magnetosphere. The "quasiparticle" induces downflow the elongated quasicylindrical "dipole"-like and "toroidal"-like 3D M/S structures with fine multyrope and multicurrent sheets forming magnetic reconnection topology inside described by the package of inductive modes. Currents in the structures have resistive and diamagnetic components, which are related with "thin" structures inside "thick" current systems, respectively. Current scales are related with two different e.m. plasma kinetic spatial dispersion scales induced by the flow. They are defined by two dimensionless parameters of the plasma flow anisotropy. The anomalous skin scale defined via the "flow pulse" anisotropy stipulated by "resonant" particles which, in turn, provide resistivity in the flow. The magnetic Debye skin scale defined via the "flow energy" anisotropy formed by "nonresonant" particles which provide the diamagnetizm. We obtain these effects only in the subthermal (with respect to electrons) regime of the flow velocity. Squared ratio of two scales defines "quality" G equal to cotangent of the "losses angle" which measures the flow reactivity also and G can be a new characteristic for space weather. The value of G depends only on the form factor of the VDF and determines topology of the M/S states. We obtain the asymmetric "the resistive elongated state" for M/S when G is small with possibility of adiabatic transition to symmetric "the diamagnetic dipolized state" when G is large. Nonadiabatic transitions can be considered as substorm/CME relaxation substructure in the M/S structures.

Gubchenko, Vladimir

118

Enzymatic kinetic parameters for polyfluorinated alkyl phosphate hydrolysis by alkaline phosphatase.  

PubMed

The hydrolysis kinetics of three polyfluorinated alkyl phosphate monoesters (monoPAPs), differing in fluorinated chain length, were measured using bovine intestinal alkaline phosphatase to catalyze the reaction. Kinetic values were also measured for analogous hydrogenated phosphate monoesters to elucidate the effects of the fluorinated chain on the rate of enzymatic hydrolysis. Michaelis constants (K(m)) were obtained by a competition kinetics technique in the presence of p-nitrophenyl phosphate (PNPP) using UV-vis spectroscopy. Compared with K(m) (PNPP), Michaelis constants for monoPAPs ranged from 0.9 to 2.1 compared with hydrogenated phosphates, which ranged from 4.0 to 13.0. Apparent bimolecular rate constants (k(cat)/K(m)) were determined by monitoring rates of product alcohol formation at low substrate concentrations using gas chromatography-mass spectrometry. The experimental values for k(cat)/K(m) averaged as 1.1 × 10(7) M(-1) s(-1) for monoPAPs compared with 3.8 × 10(5) M(-1) s(-1) for hexyl phosphate. This suggests that the electron-withdrawing nature of the fluorinated chain enhanced the alcohol leaving group ability. The results were used in a simple model to suggest that monoPAPs in a typical mammalian digestive tract would hydrolyze in approximately 100 s, supporting a previous study that showed its absence after a dosing study in rats. PMID:22714665

Jackson, Derek A; Mabury, Scott A

2012-09-01

119

A comparison of region-based and pixel-based CEUS kinetics parameters in the assessment of arthritis  

NASA Astrophysics Data System (ADS)

Inflammatory rheumatic diseases are leading causes of disability and constitute a frequent medical disorder, leading to inability to work, high comorbidity and increased mortality. The gold-standard for diagnosing and differentiating arthritis is based on patient conditions and radiographic findings, as joint erosions or decalcification. However, early signs of arthritis are joint effusion, hypervascularization and synovial hypertrophy. In particular, vascularization has been shown to correlate with arthritis' destructive behavior, more than clinical assessment. Contrast Enhanced Ultrasound (CEUS) examination of the small joints is emerging as a sensitive tool for assessing vascularization and disease activity. The evaluation of perfusion pattern rely on subjective semi-quantitative scales, that are able to capture the macroscopic degree of vascularization, but are unable to detect the subtler differences in kinetics perfusion parameters that might lead to a deeper understanding of disease progression and a better management of patients. Quantitative assessment is mostly performed by means of the Qontrast software package, that requires the user to define a region of interest, whose mean intensity curve is fitted with an exponential function. We show that using a more physiologically motivated perfusion curve, and by estimating the kinetics parameters separately pixel per pixel, the quantitative information gathered is able to differentiate more effectively different perfusion patterns. In particular, we will show that a pixel-based analysis is able to provide significant markers differentiating rheumatoid arthritis from simil-rheumatoid psoriatic arthritis, that have non-significant differences in clinical evaluation (DAS28), serological markers, or region-based parameters.

Grisan, E.; Raffeiner, B.; Coran, A.; Rizzo, G.; Ciprian, L.; Stramare, R.

2014-03-01

120

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

121

Studies on the constancy of the blue and green fluorescence yield during the chlorophyll fluorescence induction kinetics (Kautsky effect).  

PubMed

Blue (F450) and green (F530) leaf fluorescence were studied together with the red chlorophyll fluorescence (emission maxima F690 and F735) during light-induced chlorophyll fluorescence induction kinetics (Kautsky effect) in predarkened leaves of wheat (Triticum aestivum L.) and soybean (Glycine max L.). The intensity of the red chlorophyll fluorescence decreased from maximum fluorescence Fm to steady-state fluorescence Fs, and the fluorescence ratio F690/F735 decreased by about 10% from Fm to Fs. However, blue and green fluorescence intensities remained constant throughout the measuring time. Consequently, the ratio of blue to red fluorescence (F450/F690) increased during chlorophyll fluorescence induction kinetics, whereas the ratio of blue to green fluorescence (F450/F530) remained unchanged within the same period. The knowledge of these ratios will be a prerequisite for the interpretation of remote sensing data from terrestrial vegetation. PMID:8310130

Stober, F; Lichtenthaler, H K

1993-01-01

122

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

123

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

Microsoft Academic Search

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

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

124

Evaluation of kinetic parameters of natural phytoalexin in resveratrol orally administered in wine to rats.  

PubMed

In view of the increasing interest in the biological activity of resveratrol, one of the components of red wine which is considered to be one of the main ingredients responsible for the beneficial effect of wine on human health, we have studied plasma kinetics and tissue bioavailability of this compound after red wine oral administration in rats. Plasma pharmacokinetics after oral administration of resveratrol could be described by an open one- or two-compartment model. Tissue concentrations show a significant cardiac bioavailability, and a strong affinity for the liver and kidneys. PMID:9604148

Bertelli, A A; Giovannini, L; Stradi, R; Urien, S; Tillement, J P; Bertelli, A

1998-01-01

125

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

PubMed

To determine the linear energy transfer (LET) dependence of the biological effects of densely ionizing radiation in relation to changes in the ionization density along the track, we measured the yields and spectrum of clustered DNA damages induced by charged particles of different atomic number but similar kinetic energy per nucleon in different DNA microenvironments. Yeast DNA embedded in agarose in solutions of different free radical scavenging capacity was irradiated with 1 GeV protons, 1 GeV/nucleon oxygen ions, 980 MeV/nucleon titanium ions or 968 MeV/nucleon iron ions. The frequencies of double-strand breaks (DSBs), abasic sites and oxypurine clusters were quantified. The total DNA damage yields per absorbed dose induced in non-radioquenching solution decreased with LET, with minor variations in radioquenching conditions being detected. However, the total damage yields per particle fluence increased with LET in both conditions, indicating a higher efficiency per particle to induce clustered DNA damages. The yields of DSBs and non-DSB clusters as well as the damage spectra varied with LET and DNA milieu, suggesting the involvement of more than one mechanism in the formation of the different types of clustered damages. PMID:20681790

Keszenman, Deborah J; Sutherland, Betsy M

2010-08-01

126

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

127

Deduction of kinetics parameters in composition: Tellurite-phosphate-sodium oxide  

NASA Astrophysics Data System (ADS)

Three samples from tellurophosphate glasses with the compositions (85 - x) TeO2·15P2O5·xNa2O with x = 15, 20 and 25 mol% were prepared by a melting technique. The crystallization behavior and the kinetics of the glasses were investigated using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The mean value of the activation energy () for structural relaxation decreases from 352 to 317 ± 5 kJ mol-1. Otherwise the activation energy for crystallization () was calculated to increase from 164, 195 and 201 ± 5 kJ mol-1 with increasing Na2O concentration. The values of the Avrami exponents for the exothermic peaks are closed to 1.0 and 2.0. The crystalline phase Te2P2O9 was detected and it grow as sheets disperse in the matrix.

Yousef, El Sayed

2013-05-01

128

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

NASA Astrophysics Data System (ADS)

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

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

129

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

130

Characterization of Kinetic and Thermodynamic Parameters of Cyanidin-3-glucoside Methyl and Glucuronyl Metabolite Conjugates.  

PubMed

The determination of rate and equilibrium constants of anthocyanin metabolites with in vivo occurrence, cyanidin-4'-O-methyl-3-glucoside (Cy4'Me3glc) and cyanidin-7-O-glucuronyl-3-glucoside (Cy7Gluc3glc), was carried out for the first time by means of direct and reverse pH jumps. The thermodynamics and kinetics of these compounds are similar to the anthocyanin monoglucosides in particular for the analogous cyanidin-3-glucoside (Cy3glc) and peonidin-3-glucoside (Peo3glc). The rate and equilibrium constants of metabolites were also compared with malvin (malvidin 3,5-diglucoside) and with a bioinspired compound 3',4'-dihydroxy-7-O-glucopyranosyloxyflavylium (DGF). In Cy4'Me3glc and Cy7Gluc3glc the rate of hydration for a fixed pH value is slower than in DGF and the dominant species at moderately acidic solutions is the hemiketal. Oppositely, in DGF trans-chalcone is the dominant species at moderately acidic solutions. PMID:25622073

Cruz, Luís; Basílio, Nuno; Mateus, Nuno; Pina, Fernando; de Freitas, Victor

2015-02-01

131

Visualization and Curve-Parameter Estimation Strategies for Efficient Exploration of Phenotype Microarray Kinetics  

PubMed Central

Background The Phenotype MicroArray (OmniLog® PM) system is able to simultaneously capture a large number of phenotypes by recording an organism's respiration over time on distinct substrates. This technique targets the object of natural selection itself, the phenotype, whereas previously addressed ‘-omics’ techniques merely study components that finally contribute to it. The recording of respiration over time, however, adds a longitudinal dimension to the data. To optimally exploit this information, it must be extracted from the shapes of the recorded curves and displayed in analogy to conventional growth curves. Methodology The free software environment R was explored for both visualizing and fitting of PM respiration curves. Approaches using either a model fit (and commonly applied growth models) or a smoothing spline were evaluated. Their reliability in inferring curve parameters and confidence intervals was compared to the native OmniLog® PM analysis software. We consider the post-processing of the estimated parameters, the optimal classification of curve shapes and the detection of significant differences between them, as well as practically relevant questions such as detecting the impact of cultivation times and the minimum required number of experimental repeats. Conclusions We provide a comprehensive framework for data visualization and parameter estimation according to user choices. A flexible graphical representation strategy for displaying the results is proposed, including 95% confidence intervals for the estimated parameters. The spline approach is less prone to irregular curve shapes than fitting any of the considered models or using the native PM software for calculating both point estimates and confidence intervals. These can serve as a starting point for the automated post-processing of PM data, providing much more information than the strict dichotomization into positive and negative reactions. Our results form the basis for a freely available R package for the analysis of PM data. PMID:22536335

Vaas, Lea A. I.; Sikorski, Johannes; Michael, Victoria; Göker, Markus; Klenk, Hans-Peter

2012-01-01

132

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

133

Thermoluminescence dosimetry properties and kinetic parameters of lithium potassium borate glass co-doped with titanium and magnesium oxides.  

PubMed

Lithium potassium borate (LKB) glasses co-doped with TiO2 and MgO were prepared using the melt quenching technique. The glasses were cut into transparent chips and exposed to gamma rays of (60)Co to study their thermoluminescence (TL) properties. The TL glow curve of the Ti-doped material featured a single prominent peak at 230 °C. Additional incorporation of MgO as a co-activator enhanced the TL intensity threefold. LKB:Ti,Mg is a low-Z material (Z(eff)=8.89) with slow signal fading. Its radiation sensitivity is 12 times lower that the sensitivity of TLD-100. The dose response is linear at doses up to 10(3) Gy. The trap parameters, such as the kinetics order, activation energy, and frequency factor, which are related to the glow peak, were determined using TolAnal software. PMID:24929526

Hashim, S; Alajerami, Y S M; Ramli, A T; Ghoshal, S K; Saleh, M A; Abdul Kadir, A B; Saripan, M I; Alzimami, K; Bradley, D A; Mhareb, M H A

2014-09-01

134

Kinetic electron emission yield induced by H + and He 2+ ions versus stopping power for Al, Cu, Ag and Au  

NASA Astrophysics Data System (ADS)

For H + and He 2+ ions impinging on Al, Cu, Ag and Au targets we measured simultaneously the yield, ?, of emitted electrons and the electronic energy loss, Se, in the energy range 0.5 to 4.8 MeV. The targets were prepared under high-vacuum conditions before they were transferred to an ultra-high-vacuum chamber without breaking the vacuum. The targets were sputter cleaned and their composition was examined by Auger electron spectrometry. The values of ? were obtained by current integration and Se was determined from the energy width of Rutherford backscattering spectra. For H + ions impinging on Cu, Ag or Au and He 2+ on Al and Cu, the expected proportionality between ? and Se was found within the experimental errors of 2%. For H + ions on Al and He 2+ ions on Ag and Au targets, significant deviations were observed.

Benka, O.; Steinbauer, E.; Bauer, P.

1994-05-01

135

Determination of kinetic and thermodynamic parameters that describe isothermal seed germination: A student research project  

NASA Astrophysics Data System (ADS)

Students under the supervision of a faculty member can collect data and fit the data to the theoretical mathematical model that describes the rate of isothermal seed germination. The best-fit parameters are interpreted as an initial substrate concentration, product concentration, and the autocatalytic reaction rate. The thermodynamic model enables one to calculate the activation energy for the substrate and product, the activation energy for the autocatalytic reaction, and changes in enthalpy, entropy, and the Gibb's free energy. Turnip, lettuce, soybean, and radish seeds have been investigated. All data fit the proposed model.

Hageseth, Gaylord T.

1982-02-01

136

Dynamic determination of kinetic parameters, computer simulation, and probabilistic analysis of growth of Clostridium perfringens in cooked beef during cooling.  

PubMed

The objective of this research was to develop a new one-step methodology that uses a dynamic approach to directly construct a tertiary model for prediction of the growth of Clostridium perfringens in cooked beef. This methodology was based on simultaneous numerical analysis and optimization of both primary and secondary models using multiple dynamic growth curves obtained under different conditions. Once the models were constructed, the bootstrap method was used to calculate the 95% confidence intervals of kinetic parameters, and a Monte Carlo simulation method was developed to validate the models using the growth curves not previously used in model development. The results showed that the kinetic parameters obtained from this study accurately matched the common characteristics of C. perfringens, with the optimum temperature being 45.3°C. The results also showed that the predicted growth curves matched accurately with experimental observations used in validation. The mean of residuals of the predictions is -0.02logCFU/g, with a standard deviation of only 0.23logCFU/g. For relative growths <1logCFU/g, the residuals of predictions are <0.4logCFU/g. Overall, 74% of the residuals of predictions are <0.2logCFU/g, 7.7% are >0.4logCFU/g, while only 1.5% are >0.8logCFU/g. In addition, the dynamic model also accurately predicted four isothermal growth curves arbitrarily chosen from the literature. Finally, the Monte Carlo simulation was used to provide the probability of >1 and 2logCFU/g relative growths at the end of cooling. The results of this study will provide a new and accurate tool to the food industry and regulatory agencies to assess the safety of cooked beef in the event of cooling deviation. PMID:25500276

Huang, Lihan

2015-02-16

137

Interactive effects of elevated CO2 concentration and irrigation on photosynthetic parameters and yield of maize in Northeast China.  

PubMed

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

138

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

139

Estimation of Genetic and Phenotypic Parameters for Clinical Mastitis, Somatic Cell Production Deviance, and Protein Yield in Dairy Cattle Using Gibbs Sampling  

Microsoft Academic Search

When including clinical mastitis in the breeding goal, it is useful to know what measure of the trait is most appropriate and its relationship to the primary production traits and indicator traits in the relevant population. In this paper, genetic and phenotypic parameters for clinical mastitis, somatic cell produc- tion deviance, and protein yield were estimated for the dairy breed

M. S. Lund; J. Jensen; P. H. Petersen

1999-01-01

140

Radiographic trabecular 2D and 3D parameters of proximal femoral bone cores correlate with each other and with yield stress  

Microsoft Academic Search

Summary  Radiographic images of bone cores taken from cadaver proximal femora provided two-dimensional parameters of projected trabecular\\u000a patterns that correlated highly with conceptually equivalent three-dimensional parameters in the same cores. Measurements\\u000a also highly correlated with yield stress, suggesting that both parameters have similar biomechanical qualities.\\u000a \\u000a \\u000a \\u000a Introduction  We compared morphometric measurements of trabecular patterns in two-dimensional (2D) projection radiographic images of cores\\u000a from

D. Steines; S.-W. Liew; C. Arnaud; R. Vargas-Voracek; A. Nazarian; R. Müller; B. Snyder; P. Hess; P. Lang

2009-01-01

141

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

PubMed

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

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

2013-02-19

142

HIV-1 Polymerase Inhibition by Nucleoside Analogs: Cellular- and Kinetic Parameters of Efficacy, Susceptibility and Resistance Selection  

PubMed Central

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

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

2012-01-01

143

Monitoring yield and fruit quality parameters in open-canopy tree crops under water stress. Implications for ASTER  

Microsoft Academic Search

Work on water stress detection at tree and orchard levels using a high-spatial airborne thermal sensor is presented, showing its connection with yield and some fruit quality indicators in olive and peach commercial orchards under different irrigation regimes. Two airborne campaigns were conducted with the Airborne Hyperspectral Scanner (AHS) over olive and peach orchards located in Córdoba, southern Spain. The

G. Sepulcre-Cantó; P. J. Zarco-Tejada; J. C. Jiménez-Muñoz; J. A. Sobrino; M. A. Soriano; E. Fereres; V. Vegad; M. Pastor

2007-01-01

144

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

145

Infrared Warming Reduced Winter Wheat Yields and Some Physiological Parameters, Which Were Mitigated by Irrigation and Worsened by Delayed Sowing  

PubMed Central

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

146

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

PubMed Central

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 (h2) 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 h2 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

2011-01-01

147

The merits of cell kinetic parameters for the assessment of intrinsic cellular radiosensitivity to photon and high linear energy transfer neutron irradiation  

Microsoft Academic Search

Purpose: Differences in tumor response and intrinsic cellular radiosensitivity make the selection of patients for specific radiation modalities very difficult. The reasons for these differences are still unclear, but are though to be due to genomic and cellular characteristics. Because radiosensitivities vary between cell cycle stages and because S phase cells are very radioresistant, cell cycle kinetic parameters could be

Therina Theron; Jacobus Slabbert; Antonio Serafin; Lothar Böhm

1997-01-01

148

The effect of temperature on oil quality and yield parameters of high- and low-erucic acid Cruciferae seeds (rape and mustard)  

Microsoft Academic Search

The oil content, seed yield parameters and fatty acid composition of high- and low-erucic acid Brassica (napus and hirta) seed oils were studied under three different controlled-temperature regimes: low, 12\\/17 °C; medium, 17\\/22 °C; and high, 22\\/27 °C. No fruit set was obtained beyond 27 °C.Under low temperatures, seeds of high-erucic acid Brassica napus var. Norin and Brassica hirta (Sinapis

Zohara Yaniv; D. Schafferman; M. Zur

1995-01-01

149

Characterization of cold-adapted Atlantic cod (Gadus morhua) trypsin I--kinetic parameters, autolysis and thermal stability.  

PubMed

Atlantic cod trypsin I is a highly active cold-adapted protease. This study aimed at further characterization of this enzyme with respect to kinetic parameters, sites of autolysis and stability. For that purpose, trypsin I was purified by anion exchange chromatography. Its purity and identity was verified by SDS-PAGE analysis and mass spectrometry. Concomitantly, another cod trypsin isozyme, trypsin X, previously only described from its cDNA sequence was detected in a separate peak from the ion exchange chromatogram. There was a stepwise increase in the catalytic efficiency (k(cat)/K(m)) of cod trypsin I obtained with substrates containing one to three amino acid residues. As expected, the activity of trypsin I was maintained for longer periods of time at 15 degrees C than at higher temperatures. The residues of the trypsin I molecule most sensitive to autolysis were identified using Edman degradation. Eleven autolytic cleavage sites were detected within the trypsin I molecule. Unfolding experiments demonstrated that autolysis is a contributing factor in the stability of trypsin I. In addition, the data shows that cod trypsin I is less stable towards thermal unfolding than its mesophilic bovine analogue. PMID:19913635

Stefansson, Bjarki; Helgadóttir, Linda; Olafsdottir, Sigridur; Gudmundsdottir, Agústa; Bjarnason, Jón B

2010-02-01

150

Optimization of laccase fermentation and evaluation of kinetic and thermodynamic parameters of a partially purified laccase produced by Daedalea flavida.  

PubMed

Studies on laccase production by Daedalea flavida were carried out in static and low-speed shake cultures. The enzyme production was reduced drastically at a high speed of shaking. Optimal production conditions are necessary to assess the quality of laccase suitable for a specific application. Thus, the production of laccase was optimized by the application of response surface methodology. Laccase production was 8-fold and 7.5-fold more in static and low-speed shake conditions, respectively, in an optimal medium composition than in an unoptimized medium. Laccase obtained using the optimal culture medium of D. flavida was tested for its stability at different temperatures and pH conditions. The partially purified enzyme was most stable at 30°C and pH 5. The half-life of laccase is 87 min at 60°C and at pH 6. The kinetic and thermodynamic parameters were evaluated for the inactivation of the partially purified laccase. The entropy change of inactivation of the enzyme is least at pH 4. PMID:24547974

Singha, Siddhartha; Panda, Tapobrata

2015-01-01

151

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

152

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

PubMed

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

Tripathi, Ruchika; Agrawal, S B

2012-11-01

153

Effect of parity on milk yield, composition, somatic cell count, renneting parameters and bacteria counts of Comisana ewes.  

PubMed

Twenty-four Comisana ewes, with no history of mastitis, were included in this study, with eight ewes each in parities 1, 2 and 3. Groups were separately penned on straw litter and ewes were individually checked for yield, composition, renneting properties and bacteriological characteristics of milk from January, when separated from their lambs (50+/-3 days after lambing), to May. Samples with more than 3.5x10(5) somatic cells/ml were cultured for mastitis related pathogens. Milk yield was not significantly affected by parity. The P3 ewes had significantly higher milk protein, casein and fat contents compared to the P1 and P2 ewes. The P3 ewes also had improved renneting ability of milk as compared to the P1 ewes. Quality of milk decreased with lower lactations. The milk of P1 ewes had significantly greater amounts of mesophilic bacteria than the P2 and P3 ewes, as well as higher concentrations of psychrotrophs and total coliforms in their milk with respect to the P3 ewes. Somatic cell counts in milk and the prevalence of subclinical mastitis were not changed by parity, although mastitis infection set in progressively earlier as the number of lactations decreased. These results suggest that ewes in first or second lactation have a less favourable milk secretion status in relation to mastitis than ewes with a higher number of lactations. Milk yield and quality of younger ewes may be improved by offering feed rations that take into account this reduced capacity to mobilise body reserves. Also, most scrupulous control of sanitation of housing, equipment and personnel is necessary. PMID:10818309

Sevi; Taibi; Albenzio; Muscio; Annicchiarico

2000-07-01

154

Variations in the digestible lysine requirement of broiler chickens due to sex, performance parameters, rearing environment, and processing yield characteristics.  

PubMed

Four experiments were conducted to evaluate variations in the digestible lysine (DLYS) requirement estimates of broilers due to rearing environment, sex, or growth performance during the starter period (7 to 21 d) and due to sex, growth, and carcass yield characteristics during the grower period (21 to 38 d). In the first 3 experiments, chicks were allocated to either battery or floor pens. The fourth experiment was conducted during the grower period with birds reared in floor pens only. All the studies used a lysine-deficient corn-soybean meal-corn gluten meal basal diet formulated to be isonitrogenous and isocaloric. Treatments consisted of 5 graded levels of DLYS varying from 0.70 to 1.21% in the first 3 experiments and from 0.73 to 1.13% in the fourth experiment. The DLYS requirement was estimated by broken-line methodology based on body weight gain (BWG) and gain:feed ratio (G:F) for the starter period, and the same variables plus breast meat yield for the grower period. During the starter period, the average DLYS requirement of males based on BWG was slightly higher than that of females reared in battery (0.96 vs. 0.94%) or floor pens (0.98 vs. 0.93%). However, based on G:F, the average DLYS requirement of females was slightly higher than that of males reared in both battery (0.99 vs. 0.96%) and floor pens (1.01 vs. 0.99). The DLYS requirement based on G:F was higher than that based on BWG only for females in both rearing environments. Rearing environment did not affect the DLYS requirement of broilers during the starter period. In the grower period, the DLYS requirement of males was higher than that of females based on BWG (0.97 vs. 0.93%), but for G:F it was similar for both sexes (0.96%). The DLYS requirement for females based on G:F was higher than that based on BWG. The DLYS requirement for maximum breast meat yield of males (0.98%) or females (0.90%) was similar to the estimate for maximal growth performance. PMID:16553282

Garcia, A R; Batal, A B; Baker, D H

2006-03-01

155

Effects of supercritical carbon dioxide extraction parameters on virgin coconut oil yield and medium-chain triglyceride content  

Microsoft Academic Search

The extraction of coconut oil has been performed using supercritical carbon dioxide (SC-CO2). The extractions were performed at pressure and temperature ranges of 20.7–34.5MPa and 40–80°C, respectively. It was observed that almost all (more than 99%) of the total oil could be extracted. Response surface methodology (RSM) was applied to evaluate the effects of the parameters (pressure, temperature and CO2

N. A. Nik Norulaini; W. B. Setianto; I. S. M. Zaidul; A. H. Nawi; C. Y. M. Azizi; A. K. Mohd Omar

2009-01-01

156

Global Chapman-Ferraro problem in large scale kinetics: 3d magnetotail\\/solar coronal streamer with new kinetic plasma scales and dimensionless parameters  

Microsoft Academic Search

In terms of the Vlasov-Maxwell kinetic approach we consider analytically the global Chapman- Ferraro problem (CFP) of inductive generation by the solar wind plasma flow of 3D magnetotail\\/solar streamer (M\\/S) structures in the process of electromagnetic (e.m.) interaction of the flow with the magnetized region. The input undisturbed flow is a hot collisionless plasma with an isotropic velocity distribution function

Vladimir Gubchenko

2008-01-01

157

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

158

Suicide inactivation of peroxidase by H2O2: kinetic equations for peroxidatic oxidation reaction of guaiacol and determination of the kinetic parameters.  

PubMed

The kinetics of horseradish peroxidase (HRP) in oxidation reaction of guaiacol (AH) by hydrogen peroxide was studied, taking into account the inactivation of enzyme during reaction by its suicide substrate, H2O2. Those ranges of concentrations were selected in which: 1) the reaction was first-order in relation to [AH] and 2) [H2O2] > [AH]. By combination of rate equations of the two concurrent reactions, consumption of AH and suicide inactivation of HRP, the overall kinetic equations were obtained which define the progress curve of reactions. The compatibility between equations and kinetic behaviour of reaction were evaluated in different ways. A close match was found between equations and experimental data. These equations can be used for determining 1) intact value of enzyme activity at start time of reaction and 2) apparent rate constant of suicide inactivation (ki') in a given concentration of H2O2, by processing of the data of the progress curve. The ki' value was found to be 0.178 +/- 0.003 min.-1 at 10 mM of H2O2 and 0.04 +/- 0.002 at 3 mM H2O2, at 27 degrees C and sodium phosphate buffer, pH = 7.0. PMID:10354950

Moosavi Movahedi, A A; Nazari, K; Ghadermarzi, M

1999-03-01

159

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

160

Kinetics of excited states of pigment clusters in solubilized light-harvesting complex II: photon density-dependent fluorescence yield and transmittance.  

PubMed Central

Relative fluorescence yield, phi F, and transmittance, T, were measured in solubilized light-harvesting complex II (LHCII) as a function of photon density, Ip, of monochromatic 645-nm laser pulses (duration: approximately 2.5 ns). Special efforts were made in constructing an optical set-up that allows the accurate determination of the fluorescence from an area of constant Ip, phi F(Ip) starts to decline at approximately 10(14) and drops to values below 0.01% at maximum Ip (approximately 10(19) photons cm-2 pulse-1). T(Ip) decreases only slightly at photon densities of approximately 10(15) but increases steeply at values of > 10(17) photons cm-2 pulse-1. The interpretation of the phi F(Ip) data using the saturation limit of Mauzerall's multiple hit model leads to a unit size of about 10-15 chlorophyll molecules. One interpretation is to attribute this result to a very fast exciton-exciton annihilation of multiple excited states generated within this small domain. Alternatively, based on the assumption that delocalized cluster states within the monomeric/trimeric subunit of LHCII exist, the results can be consistently described by a kinetic model comprising ground, monoexcitonic, and biexcitonic states of clusters and a triplet state that is quenched by carotenoids in LHCII. Within the framework of this model the annihilation of multiple excitations is explained as ultrafast radiationless relaxation of higher excited cluster states. Comparative measurements in diluted acetonic Chl a solution are consistently described by the depletion of the ground state, taking the absorption cross section at the used wavelength. Images FIGURE 1 PMID:8968606

Schödel, R; Hillmann, F; Schrötter, T; Voigt, J; Irrgang, K D; Renger, G

1996-01-01

161

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

162

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

163

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

164

Impact of process parameters on the breakage kinetics of poorly water-soluble drugs during wet stirred media milling: a microhydrodynamic view.  

PubMed

Wet stirred media milling has proven to be a robust process for producing nanoparticle suspensions of poorly water-soluble drugs. As the process is expensive and energy-intensive, it is important to study the breakage kinetics, which determines the cycle time and production rate for a desired fineness. Although the impact of process parameters on the properties of final product suspensions has been investigated, scant information is available regarding their impact on the breakage kinetics. Here, we elucidate the impact of stirrer speed, bead concentration, and drug loading on the breakage kinetics via a microhydrodynamic model for the bead-bead collisions. Suspensions of griseofulvin, a model poorly water-soluble drug, were prepared in the presence of two stabilizers: hydroxypropyl cellulose and sodium dodecyl sulfate. Laser diffraction, scanning electron microscopy, and rheometry were used to characterize them. Various microhydrodynamic parameters including a newly defined milling intensity factor was calculated. An increase in either the stirrer speed or the bead concentration led to an increase in the specific energy and the milling intensity factor, consequently faster breakage. On the other hand, an increase in the drug loading led to a decrease in these parameters and consequently slower breakage. While all microhydrodynamic parameters provided significant physical insight, only the milling intensity factor was capable of explaining the influence of all parameters directly through its strong correlation with the process time constant. Besides guiding process optimization, the analysis rationalizes the preparation of a single high drug-loaded batch (20% or higher) instead of multiple dilute batches. PMID:24036164

Afolabi, Afolawemi; Akinlabi, Olakemi; Bilgili, Ecevit

2014-01-23

165

Genetic parameters of coagulation properties, milk yield, quality, and acidity estimated using coagulating and noncoagulating milk information in Brown Swiss and Holstein-Friesian cows.  

PubMed

The aim of this study was to estimate heritabilities of rennet coagulation time (RCT) and curd firmness (a(30)) and their genetic correlations with test-day milk yield, composition (fat, protein, and casein content), somatic cell score, and acidity (pH and titratable acidity) using coagulating and noncoagulating (NC) milk information. Data were from 1,025 Holstein-Friesian (HF) and 1,234 Brown Swiss (BS) cows, which were progeny of 54 HF and 58 BS artificial insemination sires, respectively. Milk coagulation properties (MCP) of each cow were measured once using a computerized renneting meter and samples not exhibiting coagulation within 31 min after rennet addition were classified as NC milk. For NC samples, RCT was unobserved. Multivariate analyses, using Bayesian methodology, were performed to estimate the genetic relationships of RCT or a(30) with the other traits and statistical inference was based on the marginal posterior distributions of parameters of concern. For analyses involving RCT, a right-censored Gaussian linear model was used and records of NC milk samples, being censored records, were included as unknown parameters in the model implementing a data augmentation procedure. Rennet coagulation time was more heritable [heritability (h(2))=0.240 and h(2)=0.210 for HF and BS, respectively] than a(30) (h(2)=0.148 and h(2)=0.168 for HF and BS, respectively). Milk coagulation properties were more heritable than a single test-day milk yield (h(2)=0.103 and h(2)=0.097 for HF and BS, respectively) and less heritable than milk composition traits whose heritability ranged from 0.275 to 0.275, with the only exception of fat content of BS milk (h(2)=0.108). A negative genetic correlation, lower than -0.85, was estimated between RCT and a(30) for both breeds. Genetic relationships of MCP with yield and composition were low or moderate and favorable. The genetic correlation of somatic cell score with RCT in BS cows was large and positive and even more positive were those of RCT with pH and titratable acidity in both breeds, ranging from 0.80 to 0.94. Including NC milk information in the data affected the estimated correlations and decreased the uncertainty associated with the estimation process. On the basis of the estimated heritabilities and genetic correlations, enhancement of MCP through selective breeding with no detrimental effects on yield and composition seems feasible in both breeds. Milk acidity may play a role as an indicator trait for indirect enhancement of MCP. PMID:21787956

Cecchinato, A; Penasa, M; De Marchi, M; Gallo, L; Bittante, G; Carnier, P

2011-08-01

166

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

167

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

168

Kinetics and Activation Parameters for Oxidations of Styrene by Compounds I from Cytochrome P450BM-3 (CYP102A1) Heme Domain and from CYP119†  

PubMed Central

Cytochrome P450 (CYP or P450) enzymes are ubiquitous in nature where they catalyze a vast array of oxidation reactions. The active oxidants in P450s have long been assumed to be iron(IV)-oxo porphyrin radical cations termed Compounds I, but P450 Compounds I have proven difficult to prepare. The recent development of an entry to these transients by photo-oxidation of the corresponding iron(IV)-oxo neutral porphyrin species (Compounds II) permits spectroscopic and kinetic studies. We report here application of the photo-oxidation method for production of Compound I from the heme domain of CYP102A1 (cytochrome P450BM-3), and product and kinetic studies of reactions of styrene with this Compound I transient and also Compound I from CYP119. The studies were performed at low temperatures in 1:1 (v:v) mixtures of glycerol--phosphate buffer. Single turnover reactions at 0 °C gave styrene oxide in good yields. In kinetic studies conducted between ?10 and ?50 °C, both Compounds I displayed saturation kinetics permitting determinations of binding constants and first-order oxidation rate constants. Temperature-dependent functions for the binding constants and rate constants were determined for both Compounds I. In the temperature range studied, the Compound I transient from CYP102A1 heme domain bound styrene more strongly than Compound I from CYP119, but the rate constants for oxidations of styrene by the latter were somewhat larger than those for the former. The temperature dependent functions for the first-order oxidation reactions are log k = 13.2 – 15.2/2.303RT and log k = 13.3 – 14.6/2.303RT (kcal/mol) for Compounds I from CYP102A1 heme domain and CYP119, respectively. PMID:19708688

Yuan, Xinting; Wang, Qin; Horner, John H.; Sheng, Xin; Newcomb, Martin

2009-01-01

169

Parameter identifiability and Extended Multiple Studies Analysis of a compartmental model for human vitamin A kinetics: fixing fractional transfer coefficients for the initial steps in the absorptive process.  

PubMed

In the existing compartmental models of human vitamin A metabolism, parameters related to the absorption of the isotopic oral dose have not been well identified. We hypothesised that fixing some poorly identified parameters related to vitamin A absorption would improve parameter identifiability and add statistical certainty to such models. In the present study, data for serum vitamin A kinetics in nine subjects given [2H8]retinyl acetate orally and a model with absorption fixed at 75 % were used to test this hypothesis. In addition to absorption efficiency, we fixed two other fractional transfer coefficients: one representing the initial processing of the ingested dose and the other representing the direct secretion of retinol bound to retinol-binding protein (RBP) from enterocytes into the plasma. The Windows version of Simulation, Analysis and Modeling software (WinSAAM) was used to fit serum tracer data v. time for each subject. Then, a population model was generated by WinSAAM's Extended Multiple Studies Analysis. All the parameters had fractional standard deviations < 0·5, and none of the pairs of parameters had a correlation coefficient >0·8 (accepted criteria for well-identified parameters). Similar to the values predicted by the original model, total traced mass for retinol was 1160 (sd 468) ?mol, and the time for retinol to appear in the plasma bound to RBP was 31·3 (sd 4·4) h. In conclusion, we suggest that this approach holds promise for advancing compartmental modelling of vitamin A kinetics in humans when the dose must be administered orally. PMID:24229649

Park, Hyunjin; Green, Michael H

2014-03-28

170

Chemical modification and pH dependence of kinetic parameters to identify functional groups in a glucosyltransferase from Strep. Mutans  

Microsoft Academic Search

A glucosyltransferase, forming a predominantly al-6 linked glucan, was partially purified from the culture filtrate of S. mutans GS-5. The kinetic properties of the enzyme, assessed using the transfer of ¹⁴C glucose from sucrose into total glucan, were studied at pH values from pH 3.5 to 6.5. From the dependence of km on pH, a group with pKa = 5.5

J. E. Bell; A. Leone; E. T. Bell

1986-01-01

171

Productive and unproductive lysozyme-chitosaccharide complexes. Kinetic investigations.  

PubMed

Flow and relaxation methods were used to study the kinetics of oligosaccharides binding to lysozyme and the pre-steady-state kinetics of the lysozyme-catalyzed, hydrolysis of chitohexose. The minimal mechanism demonstrated, and the kinetics parameters pertaining to the elementary steps, allow interpretations of previous equilibrium and steady-state kinetic measurements which had yielded only complex constants, reflecting both productive and unproductive lysozyme-substrate complexes. In contrast to previous assumptions, the data presented in this paper provide evidence for "stable" productive lysozyme-substrate complexes. Our proposed mechanism utilizes structural information and accounts for the difference in efficiency of lysozyme-catalyzed hydrolysis of chitopentose and chitohexose. PMID:1138867

Holler, E; Rupley, J A; Hess, G P

1975-06-01

172

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

173

Evaluation of steady-state kinetic parameters for enzymes solubilized in water-in-oil microemulsion systems.  

PubMed Central

1. Equations are derived for the steady-state kinetics of substrate conversion by enzymes confined within the water-droplets of water-in-oil microemulsion systems. 2. Water-soluble substrates initially confined within droplets that do not contain enzyme are assumed to be converted into product only after they enter enzyme-containing droplets via the inter-droplet exchange process. 3. Hyperbolic (Michaelis-Menten) kinetics are predicted when the substrate concentration is varied in microemulsions of fixed composition. Both kcat. and Km are predicted to be dependent on the size and concentration of the water-droplets in the microemulsion. 4. The predicted behaviour is shown to be supported by published experimental data. A physical interpretation of the form of the rate equation is presented. 5. The rate equation for an oil-soluble substrate was derived assuming a pseudo-two-phase (oil & water) model for the microemulsion. Both kcat. and Km are shown to be independent of phi aq. Km is larger than the aqueous solution value by a factor approximately equal to the oil/water partition coefficient of the substrate. The validity of the rate equation is confirmed by published data. PMID:2264819

Oldfield, C

1990-01-01

174

Errors in Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) Kinetic Temperature Caused by Non-Local Thermodynamic Equilibrium Model Parameters  

NASA Technical Reports Server (NTRS)

The vast set of near global and continuous atmospheric measurements made by the SABER instrument since 2002, including daytime and nighttime kinetic temperature (T(sub k)) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 micron CO2 limb emission. This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO2 vibrational state non-LTE populations in the retrieval algorithm above 70 km. Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known. We consider current uncertainties in the rates of quenching of CO2 (v2 ) by N2 , O2 and O, and the CO2 (v2 ) vibrational-vibrational exchange to estimate their impact on SABER T(sub k) for different atmospheric conditions. The T(sub k) is more sensitive to the uncertainty in the latter two and their effects depend on altitude. The T(sub k) combined systematic error due to non-LTE kinetic parameters does not exceed +/- 1.5 K below 95 km and +/- 4-5 K at 100 km for most latitudes and seasons (except for polar summer) if the Tk profile does not have pronounced vertical structure. The error is +/- 3 K at 80 km, +/- 6 K at 84 km and +/- 18 K at 100 km under the less favourable polar summer conditions. For strong temperature inversion layers, the errors reach +/- 3 K at 82 km and +/- 8 K at 90 km. This particularly affects tide amplitude estimates, with errors of up to +/- 3 K.

Garcia-Comas, Maya; Lopez-Puertas, M.; Funke, B.; Bermejo-Pantaleon, D.; Marshall, Benjamin T.; Mertens, Christopher J.; Remsberg, Ellis E.; Mlynczak, Martin G.; Gordley, L. L.; Russell, James M.

2008-01-01

175

Kinetics of the reactions of HBr with O3 and HO2: The yield of HBr from HO2 + BrO  

NASA Technical Reports Server (NTRS)

An upper limit on the yield of HBr from reaction (R1) (HO2 + BrO yields products) has been determined by measuring an upper limit for the rate coefficient of the reverse reaction (R1') (HBr + O3 yields HO2 + BrO). The limits measured at 300 and 441 K were extrapolated to low temperatures to determine that the yield of HBr from reaction (R1) is negligible throughout the stratosphere (less than 0.01% of k(sub 1)). An upper limit for the rate coefficient of the reaction of HO2 with HBr was also determined to be very low less than or equal to 3 x 10(exp -17) cu cm/molecule/sec at 300 K and less than or equal to 3 x 10(exp -16) cu cm/molecule/sec at 400 K. The implications of these results to stratospheric chemistry are discussed.

Mellouki, Abdelwahid; Talukdar, Ranajit K.; Howard, Carleton J.

1994-01-01

176

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

177

Surface density of cellobiohydrolase on crystalline celluloses. A critical parameter to evaluate enzymatic kinetics at a solid-liquid interface.  

PubMed

The enzymatic kinetics of glycoside hydrolase family 7 cellobiohydrolase (Cel7A) towards highly crystalline celluloses at the solid-liquid interface was evaluated by applying the novel concept of surface density (rho) of the enzyme, which is defined as the amount of adsorbed enzyme divided by the maximum amount of adsorbed enzyme. When the adsorption levels of Trichoderma viride Cel7A on cellulose I(alpha) from Cladophora and cellulose I(beta) from Halocynthia were compared, the maximum adsorption of the enzyme on cellulose I(beta) was approximately 1.5 times higher than that on cellulose I(alpha), although the rate of cellobiose production from cellulose I(beta) was lower than that from cellulose I(alpha). This indicates that the specific activity (k) of Cel7A adsorbed on cellulose I(alpha) is higher than that of Cel7A adsorbed on cellulose I(beta). When k was plotted versus rho, a dramatic decrease of the specific activity was observed with the increase of surface density (rho-value), suggesting that overcrowding of enzyme molecules on a cellulose surface lowers their activity. An apparent difference of the specific activity was observed between crystalline polymorphs, i.e. the specific activity for cellulose I(alpha) was almost twice that for cellulose I(beta). When cellulose I(alpha) was converted to cellulose I(beta) by hydrothermal treatment, the specific activity of Cel7A decreased and became similar to that of native cellulose I(beta) at the same rho-value. These results indicate that the hydrolytic activity (rate) of bound Cel7A depends on the nature of the crystalline cellulose polymorph, and an analysis that takes surface density into account is an effective means to evaluate cellulase kinetics at a solid-liquid interface. PMID:16759230

Igarashi, Kiyohiko; Wada, Masahisa; Hori, Ritsuko; Samejima, Masahiro

2006-07-01

178

The Formulae for Parameters of the Secondary Electron Yield of Insulators from 10 keV to 30 keV  

NASA Astrophysics Data System (ADS)

Based on the formula for the average energy required to produce an internal secondary electron (?) in emitter, the energy band of insulator and the assumption that the maximum exit energy of secondary electron in insulator is reverse to the width of forbidden band, the formula for ? in insulator is deduced. On the basis of the formula for the number of internal secondary electrons produced in the direction of the velocity of primary electrons per unit path length, the energy band of insulator and the characteristic of secondary electron emission, the formula for the probability of secondary electrons passing over the surface barrier of insulator into the vacuum (B) is also deduced. According to some relationship between the parameters of secondary electron yield from insulator, the formula for the mean escape depth (1/?) is successfully deduced. The formulae for ? and 1/? are experimentally proven, respectively, and thereafter the formula for B is indirectly proven to be true by the experimental results. It is concluded that the formulae for ?, B and 1/? are universal to estimate ?, B and 1/? under the condition that primary electrons from 10 keV to 30 keV hit on an insulator, respectively.

Xie, Ai-Gen; Li, Qing-Fang; Chen, Yun-Yun; Wu, Hong-Yan

2013-12-01

179

Influence of Laser Processing Parameters on Microstructure and Corrosion Kinetics of Laser-Treated ZE41 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

In the present study, surface melting of a magnesium alloy, ZE41, was performed with an Nd:YAG laser using different laser parameters. The microstructure of the laser-treated and untreated specimens was analyzed by optical and scanning electron microscopy and X-ray diffraction. Corrosion resistance of the different laser-treated specimens along with the untreated alloy was characterized using electrochemical impedance spectroscopy and weight loss measurements in 0.001 M sodium chloride solution. Although the laser processing parameters influenced the microstructure and the melt depth of the laser-treated zone, these had little effect on the corrosion resistance of the alloy.

Chakraborty Banerjee, P.; Singh Raman, R. K.; Durandet, Y.; McAdam, G.

2013-05-01

180

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

NASA Astrophysics Data System (ADS)

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

Dai, Xiaoqian; Tian, Jie; Chen, Zhe

2010-03-01

181

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

Microsoft Academic Search

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

Z. Aksu; T. Kutsal

1998-01-01

182

Kinetic parameters and inhibition response of ammonia- and nitrite-oxidizing bacteria in membrane bioreactors and conventional activated sludge processes.  

PubMed

Ammonium and nitrite oxidizing biomasses (AOB and NOB) were investigated in parallel pilot plants: a membrane bioreactor (MBR) and a conventional activated sludge process (CASP) fed with domestic wastewater. The kinetics of AOB and NOB were monitored through titrimetric tests. The maximum specific growth rate of the AOB (micro(max,AOB)) was affected by the solids' retention time (SRT) maintained during the start up: by varying the start up SRT from 20 d to 8 d, micro(max,AOB) in the CASP varied from 0.45 d(-1) +/- 0.04 to 0.72 d(-1) +/- 0.2 respectively; the mean value of micro(max,AOB) in the MBR samples (always maintained at SRT = 20 d) was in the range 0.45-0.49 d(-1). The endogenous decay coefficients of the NOB and AOB and the maximum specific growth rates of the NOB were similar in both MBR and CASP. Inhibition tests with different concentrations of allylthiourea (ATU) were carried out on samples from both activated sludge systems: the MBR sludge exhibited higher sensitivity to a low ATU concentration; however, the maximum nitrification activity recovered more rapidly than the CASP sludge. PMID:21275252

Munz, G; Mori, G; Vannini, C; Lubello, C

2010-12-14

183

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

184

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

185

Influence of instrumental parameters on the kinetic energy of ions and plasma temperature for a hexapole collision/reaction-cell-based inductively coupled plasma quadrupole mass spectrometer.  

PubMed

Inductively coupled plasma mass spectrometry (ICP-MS) is widely used in inorganic analytical chemistry for element and/or isotope ratio measurements. The presence of interferences, which is one of the main limitations of this method, has been addressed in recent years with the introduction of collision/reaction cell devices on ICP-MS apparatus. The study of ion-molecule reactions in the gas phase then became of great importance for the development of new analytical strategies. Knowing the kinetic energy and the electronic states of the ions prior to their entrance into the cell, i.e., just before they react, thereby constitutes crucial information for the interpretation of the observed reactivities. Such studies on an ICP-MS commonly used for routine analyses require the determination of the influence of different instrumental parameters on the energy of the ions and on the plasma temperature from where ions are sampled. The kinetic energy of ions prior to their entrance into the cell has been connected to the voltage applied to the hexapole according to a linear relationship determined from measurements of ion energy losses due to collisions with neutral gas molecules. The effects of the plasma forward power, sampling depth, and the addition of a torch shield to the ICP source were then examined. A decrease of the plasma potential due to the torch shielding, already mentioned in the literature, has been quantified in this study at about 3 V. PMID:19215651

Favre, Georges; Brennetot, René; Chartier, Frédéric; Tortajada, Jeanine

2009-02-01

186

Comparison of kinematic and kinetic parameters calculated using a cluster-based model and Vicon's plug-in gait.  

PubMed

Gait analysis is an important clinical tool. A variety of models are used for gait analysis, each yielding different results. Errors in model outputs can occur due to inaccurate marker placement and skin motion artefacts, which may be reduced using a cluster-based model. We aimed to compare a custom-made cluster model (ClusBB) with Vicon's plug-in gait. A total of 21 healthy subjects wore marker sets for the ClusBB and plug-in gait models simultaneously while walking on a 6-m walkway. Marker and force plate data were captured synchronously and joint angles/moments were calculated using both models. There was good correlation between the models (coefficient of multiple correlations > 0.65) and good intra-session correlation for both models (coefficient of multiple correlations > 0.80). Inter-subject variability was high, ranging from 15° to 40° in the sagittal plane and 11° to 52° in the coronal and transverse planes. Intra-subject variability was small for both ClusBB and plug-in gait models. Inter-subject variance tended to be high in both models for knee abduction/adduction, but particularly so for plug-in gait, suggesting that a cluster-based model may reduce the variability. The inter-subject variance in out-of-sagittal plane data is of particular importance clinically, given the reliance on these datasets in clinical decision-making. PMID:24449800

Duffell, Lynsey D; Hope, Natalie; McGregor, Alison H

2014-02-01

187

Steam explosion pretreatment of wheat straw to improve methane yields: Investigation of the degradation kinetics of structural compounds during anaerobic digestion.  

PubMed

Wheat straw can serve as a low-cost substrate for energy production without competing with food or feed production. This study investigated the effect of steam explosion pretreatment on the biological methane potential and the degradation kinetics of wheat straw during anaerobic digestion. It was observed that the biological methane potential of the non steam exploded, ground wheat straw (276lNkgVS(-1)) did not significantly differ from the best steam explosion treated sample (286lNkgVS(-1)) which was achieved at a pretreatment temperature of 140°C and a retention time of 60min. Nevertheless degradation speed was improved by the pretreatment. Furthermore it was observed that compounds resulting from chemical reactions during the pretreatment and classified as pseudo-lignin were also degraded during the anaerobic batch experiments. Based on the rumen simulation technique, a model was developed to characterise the degradation process. PMID:25549903

Theuretzbacher, Franz; Lizasoain, Javier; Lefever, Christopher; Saylor, Molly K; Enguidanos, Ramon; Weran, Nikolaus; Gronauer, Andreas; Bauer, Alexander

2015-03-01

188

Kinetics of microbial growth on pentachlorophenol.  

PubMed

Batch and fed-batch experiments were conducted to examine the kinetics of pentachlorophenol utilization by an enrichment culture of pentachlorophenol-degrading bacteria. The Haldane modification of the Monod equation was found to describe the relationship between the specific growth rate and substrate concentration. Analysis of the kinetic parameters indicated that the maximum specific growth rate and yield coefficients are low, with values of 0.074 h-1 and 0.136 g/g, respectively. The Monod constant (Ks) was estimated to be 60 micrograms/liter, indicating a high affinity of the microorganisms for the substrate. However, high concentrations (KI = 1,375 micrograms/liter) were shown to be inhibitory for metabolism and growth. These kinetic parameters can be used to define the optimal conditions for the removal of pentachlorophenol in biological treatment systems. PMID:3977315

Klecka, G M; Maier, W J

1985-01-01

189

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

Microsoft Academic Search

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

Erdal Elkoca; Metin Turan; M. Figen Donmez

2010-01-01

190

Isotopic discrimination and kinetic parameters of RubisCO from the marine bloom-forming diatom, Skeletonema costatum.  

PubMed

The cosmopolitan, bloom-forming diatom, Skeletonema costatum, is a prominent primary producer in coastal oceans, fixing CO2 with ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) that is phylogenetically distinct from terrestrial plant RubisCO. RubisCOs are subdivided into groups based on sequence similarity of their large subunits (IA-ID, II, and III). ID is present in several major oceanic primary producers, including diatoms such as S. costatum, coccolithophores, and some dinoflagellates, and differs substantially in amino acid sequence from the well-studied IB enzymes present in most cyanobacteria and in green algae and plants. Despite this sequence divergence, and differences in isotopic discrimination apparent in other RubisCO enzymes, stable carbon isotope compositions of diatoms and other marine phytoplankton are generally interpreted assuming enzymatic isotopic discrimination similar to spinach RubisCO (IB). To interpret phytoplankton ?(13) C values, S. costatum RubisCO was characterized via sequence analysis, and measurement of its KCO2 and Vmax , and degree of isotopic discrimination. The sequence of this enzyme placed it among other diatom ID RubisCOs. Michaelis-Menten parameters were similar to other ID enzymes (KCO2  = 48.9 ± 2.8 ?m; Vmax  = 165.1 ± 6.3 nmol min(-1 ) mg(-1) ). However, isotopic discrimination (? = [(12) k/(13) k - 1] × 1000) was low (18.5‰; 17.0-19.9, 95% CI) when compared to IA and IB RubisCOs (22-29‰), though not as low as ID from coccolithophore, Emiliania huxleyi (11.1‰). Variability in ?-values among RubisCOs from primary producers is likely reflected in ?(13) C values of oceanic biomass. Currently, ?(13) C variability is ascribed to physical or chemical factors (e.g. illumination, nutrient availability) and physiological responses to these factors (e.g. carbon-concentrating mechanisms). Estimating the importance of these factors from ?(13) C measurements requires an accurate ?-value, and a mass-balance model using the ?-value for S. costatum RubisCO is presented. Clearly, appropriate ?-values must be included in interpreting ?(13) C values of environmental samples. PMID:25302659

Boller, A J; Thomas, P J; Cavanaugh, C M; Scott, K M

2015-01-01

191

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

192

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

SciTech Connect

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

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

2005-05-01

193

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

194

Magnetic hyperthermia properties of nanoparticles inside lysosomes using kinetic Monte Carlo simulations: Influence of key parameters and dipolar interactions, and evidence for strong spatial variation of heating power  

NASA Astrophysics Data System (ADS)

Understanding the influence of dipolar interactions in magnetic hyperthermia experiments is of crucial importance for fine optimization of nanoparticle (NP) heating power. In this study we use a kinetic Monte Carlo algorithm to calculate hysteresis loops that correctly account for both time and temperature. This algorithm is shown to correctly reproduce the high-frequency hysteresis loop of both superparamagnetic and ferromagnetic NPs without any ad hoc or artificial parameters. The algorithm is easily parallelizable with a good speed-up behavior, which considerably decreases the calculation time on several processors and enables the study of assemblies of several thousands of NPs. The specific absorption rate (SAR) of magnetic NPs dispersed inside spherical lysosomes is studied as a function of several key parameters: volume concentration, applied magnetic field, lysosome size, NP diameter, and anisotropy. The influence of these parameters is illustrated and comprehensively explained. In summary, magnetic interactions increase the coercive field, saturation field, and hysteresis area of major loops. However, for small amplitude magnetic fields such as those used in magnetic hyperthermia, the heating power as a function of concentration can increase, decrease, or display a bell shape, depending on the relationship between the applied magnetic field and the coercive/saturation fields of the NPs. The hysteresis area is found to be well correlated with the parallel or antiparallel nature of the dipolar field acting on each particle. The heating power of a given NP is strongly influenced by a local concentration involving approximately 20 neighbors. Because this local concentration strongly decreases upon approaching the surface, the heating power increases or decreases in the vicinity of the lysosome membrane. The amplitude of variation reaches more than one order of magnitude in certain conditions. This transition occurs on a thickness corresponding to approximately 1.3 times the mean distance between two neighbors. The amplitude and sign of this variation is explained. Finally, implications of these various findings are discussed in the framework of magnetic hyperthermia optimization. It is concluded that feedback on two specific points from biology experiments is required for further advancement of the optimization of magnetic NPs for magnetic hyperthermia. The present simulations will be an advantageous tool to optimize magnetic NPs heating power and interpret experimental results.

Tan, R. P.; Carrey, J.; Respaud, M.

2014-12-01

195

Interference effect in the dipole and nondipole anisotropy parameters of the Kr 4p photoelectrons in the vicinity of the Kr (3d){sup -1{yields}}np resonant excitations  

SciTech Connect

The angular distribution of the Kr 4p photoelectrons was investigated in the photon energy range of the (3d){sup -1{yields}}np resonant excitations. The experimental dipole ({beta}) and nondipole ({gamma} and {delta}) anisotropy parameters were determined for the spin-orbit components of the Kr 4p shell. A simple theoretical model was developed for the description of the photoionization and excitation processes. An interference effect was observed between the direct photoionization and the resonant excitation participator Auger decay processes in the photon energy dependence of the experimental anisotropy parameters.

Ricz, S.; Ricsoka, T. [Institute of Nuclear Research of Hungarian Academy of Sciences, Debrecen, P.O. Box 51, H-4001 (Hungary); Institute for Atomic and Molecular Physics, Justus-Liebig University Giessen, D-35392 Giessen (Germany); Holste, K.; Borovik, A. Jr.; Bernhardt, D.; Schippers, S.; Mueller, A. [Institute for Atomic and Molecular Physics, Justus-Liebig University Giessen, D-35392 Giessen (Germany); Koever, A.; Varga, D. [Institute of Nuclear Research of Hungarian Academy of Sciences, Debrecen, P.O. Box 51, H-4001 (Hungary)

2010-04-15

196

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

197

Kinetic parameters of human and rabbit liver D-fructose 1,6-diphosphate 1-phosphohydrolase determined at 25 and 37 degrees C.  

PubMed

1. Kinetic parameters of human and rabbit liver D-fructose 1,6-diphosphate 1-phosphohydrolase (EC 3.1.3.11) (FDP-ase) at 25 and 37 degrees C have been determined. 2. Km determined at 25 degrees C were 1.4 microM for human and 1.6 microM for rabbit enzyme; at 37 degrees C, corresponding values were 1.7 and 1.8 microM. 3. Both enzymes are allosterically inhibited by AMP. Respective values of I0.5 were 7.2 microM for human and 13.2 microM for rabbit at 25 degrees C, and 16.6 microM for human and 27.3 microM for rabbit at 37 degrees C. 4. Fructose 2,6-diphosphate, a potent regulator of gluconeogenesis, is more effective at 25 than at 37 degrees C. Ki determined at 25 degrees C was 0.07 microM for human and 0.035 microM for rabbit in comparison with 0.17 microM for human and 0.09 microM for rabbit at 37 degrees C. 5. Affinity of FDP-ase for magnesium is also dependent on temperature. For the human enzyme, Km at 25 degrees C was 226 microM and at 37 degrees C, 176 microM. For the rabbit enzyme, corresponding values were 256 and 240 microM. 6. Both enzymes are activated by KCl. Determined values of A0.5 were 91 mM for human, and 50 mM for rabbit enzyme at 25 degrees C, and 129 mM for human and 100 mM for rabbit enzyme at 37 degrees C. PMID:8395376

Dziewulska-Szwajkowska, D; Ska?ecki, K; Dzugaj, A

1993-06-01

198

Bayesian inference of genetic parameters for test-day milk yield, milk quality traits, and somatic cell score in Burlina cows.  

PubMed

The aim of the study was to infer (co)variance components for daily milk yield, fat and protein contents, and somatic cell score (SCS) in Burlina cattle (a local breed in northeast Italy). Data consisted of 13,576 monthly test-day records of 666 cows (parities 1 to 8) collected in 10 herds between 1999 and 2009. Repeatability animal models were implemented using Bayesian methods. Flat priors were assumed for systematic effects of herd test date, days in milk, and parity, as well as for permanent environmental, genetic, and residual effects. On average, Burlina cows produced 17.0 kg of milk per day, with 3.66 and 3.33 percent of fat and protein, respectively, and 358,000 cells per mL of milk. Marginal posterior medians (highest posterior density of 95%) of heritability were 0.18 (0.09-0.28), 0.28 (0.21-0.36), 0.35 (0.25-0.49), and 0.05 (0.01-0.11) for milk yield, fat content, protein content, and SCS, respectively. Marginal posterior medians of genetic correlations between the traits were low and a 95 percent Bayesian confidence region included zero, with the exception of the genetic correlation between fat and protein contents. Despite the low number of animals in the population, results suggest that genetic variance for production and quality traits exists in Burlina cattle. PMID:21063066

Penasa, M; Cecchinato, A; Battagin, M; De Marchi, M; Pretto, D; Cassandro, M

2010-01-01

199

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

200

Increasing Yield  

Technology Transfer Automated Retrieval System (TEKTRAN)

Maize yield improvement in the 20th century represents one of the great success stories of plant breeding and agronomy. Maize grain yield in the United States has increased on average by 0.122 metric tons per hectare per year since 1945 (Figure 1). This is in sharp contrast to essentially zero gain ...

201

The study of lithium ion de-insertion\\/insertion in LiMn 2O 4 and determination of kinetic parameters in aqueous Li 2SO 4 solution using electrochemical impedance spectroscopy  

Microsoft Academic Search

In this work, we report a basic study on the mechanism of lithium ion de-insertion\\/insertion process from\\/into LiMn2O4 cathode material in aqueous Li2SO4 solution using electrochemical impedance spectroscopy (EIS). An equivalent circuit distinguishing the kinetic parameters of lithium ion de-insertion\\/insertion is used to simulate the experimental impedance data. The fitting results are in good agreement with the experimental results and

H. Manjunatha; K. C. Mahesh; G. S. Suresh; T. V. Venkatesha

2011-01-01

202

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

NASA Astrophysics Data System (ADS)

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 ? (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 ? 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 ? detectors) to a variation of the solar modulation ? is provided.

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

2015-01-01

203

DIRECT COMPARISON OF KINETIC AND LOCAL EQUILIBRIUM FORMULATIONS FOR SOLUTE TRANSPORT AFFECTED BY SURFACE REACTIONS.  

USGS Publications Warehouse

Modeling transport of reacting solutes in porous media often requires a choice between models based on the local equilibrium assumption (LEA) and models involving reaction kinetics. Direct comparison of the mathematical formulations for these two types of transport models can aid in this choice. For cases of transport affected by surface reaction, such a comparison is made possible by a new derivation procedure. This procedure yields a kinetics-based formulation that is the sum of the LEA formulation and one or more kinetically influenced terms. The dimensionless form of the new kinetics-based formulation facilitates identification of critical parameter groupings which control the approach to transport behavior consistent with LEA model predictions. Results of numerical experiments demonstrate that criteria for LEA applicability can be expressed conveniently in terms of these parameter groupings. The derivation procedure is demonstrated for examples of surface reactions including first-order reversible sorption, Langmuir-type kinetics and binary, homovalent ion exchange.

Bahr, Jean M.; Rubin, Jacob

1987-01-01

204

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

PubMed

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] 7.0×10(14) 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 1.00×10(14) molecule cm(-3) of [CH3I] and 24% at the concentration 4.0×10(15) molecule cm(-3) of [CH3I], at constant concentration 4.85×10(12) molecule cm(-3) of [CH3], and at 7.3×10(12) 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. PMID:24667422

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

2014-07-15

205

Erbium hydride thermal desorption : controlling kinetics.  

SciTech Connect

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

Ferrizz, Robert Matthew

2007-08-01

206

An analytical model of nonproportional scintillator light yield in terms of recombination rates  

SciTech Connect

Analytical expressions for the local light yield as a function of the local deposited energy (-dE/dx) and total scintillation yield integrated over the track of an electron of initial energy E are derived from radiative and/or nonradiative rates of first through third order in density of electronic excitations. The model is formulated in terms of rate constants, some of which can be determined independently from time-resolved spectroscopy and others estimated from measured light yield efficiency as a constraint assumed to apply in each kinetic order. The rates and parameters are used in the theory to calculate scintillation yield versus primary electron energy for comparison to published experimental results on four scintillators. Influence of the track radius on the yield is also discussed. Results are found to be qualitatively consistent with the observed scintillation light yield. The theory can be applied to any scintillator if the rates of the radiative and nonradiative processes are known.

Bizarri, G.; Moses, W. W. [Lawrence Berkeley Laboratory, Berkeley, California 94720-8119 (United States); Singh, J. [School of Engineering and IT, Charles Darwin University, Darwin NT 0909 (Australia); Vasil'ev, A. N. [Institute of Nuclear Physics, Moscow State University, Moscow 119991 (Russian Federation); Williams, R. T. [Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109 (United States)

2009-02-15

207

Errors in Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) kinetic temperature caused by non-local-thermodynamic-equilibrium model parameters  

Microsoft Academic Search

The vast set of near-global and continuous atmospheric measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument since 2002, including daytime and nighttime kinetic temperature (Tk) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 ?m CO2 limb emission. This emission separates

M. García-Comas; M. López-Puertas; B. T. Marshall; P. P. Wintersteiner; B. Funke; D. Bermejo-Pantaleón; C. J. Mertens; E. E. Remsberg; L. L. Gordley; M. G. Mlynczak; J. M. Russell

2008-01-01

208

Parallel versus off-pathway Michaelis-Menten mechanism for single-enzyme kinetics of a fluctuating enzyme  

E-print Network

Recent fluorescence spectroscopy measurements of the turnover time distribution of single-enzyme turnover kinetics of $\\beta$-galactosidase provide evidence of Michaelis-Menten kinetics at low substrate concentration. However, at high substrate concentrations, the dimensionless variance of the turnover time distribution shows systematic deviations from the Michaelis-Menten prediction. This difference is attributed to conformational fluctuations in both the enzyme and the enzyme-substrate complex and to the possibility of both parallel and off-pathway kinetics. Here, we use the chemical master equation to model the kinetics of a single fluctuating enzyme that can yield a product through either parallel or off-pathway mechanisms. An exact expression is obtained for the turnover time distribution from which the mean turnover time and randomness parameters are calculated. The parallel and off-pathway mechanisms yield strikingly different dependences of the mean turnover time and the randomness parameter on the su...

Kumar, Ashutosh; Dua, Arti

2015-01-01

209

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

SciTech Connect

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

Reynolds, J.G.; Murray, A.

1991-01-01

210

Determination of Equilibrium and Kinetic Parameters of the Adsorption of Cr(III) and Cr(VI) from Aqueous Solutions to Agave Lechuguilla Biomass  

PubMed Central

This investigation reveals the capability of Agave lechuguilla for trivalent and hexavalent chromium removal from aqueous solutions. Experimentation included pH profile, time dependence, adsorption capacity (KF and QL), adsorption intensity (n and RL) and saturation capacity (q s) studies. Batch experiments were conducted at 22?C to characterize and model the adsorption equilibrium as well as biomass adsorption rates. pH 4 was the optimum for Cr(III) binding, while Cr(VI) optimum binding was at pH 2. Time profile experiments indicated that the adsorption of Cr(VI) by lechuguilla biomass was time-dependent and that of Cr(III) was not. Kinetic models demonstrated that a pseudo-second order reaction model best described the kinetic data for Cr(VI). The adsorption isotherms showed that the binding pattern for Cr(VI) followed the Freundlich isotherm model, while that for Cr(III) followed the Langmuir isotherm. PMID:18365089

Romero-González, Jaime; Peralta-Videa, José R.; Rodríguez, Elena

2005-01-01

211

A comparative study on determination of the equilibrium, kinetic and thermodynamic parameters of biosorption of copper(II) and lead(II) ions onto pretreated Aspergillus niger  

Microsoft Academic Search

The kinetics and thermodynamics of copper(II) and lead(II) biosorption onto Aspergillus niger pretreated with NaOH were studied with respect to pH, temperature and initial metal ion concentration. The optimum pH values were determined as 5.0 and 4.0 for copper(II) and lead(II) at 25°C, respectively. Biosorption capacity values of the biomass increased with increasing initial metal ion concentration and temperature. The

Arzu Y. Dursun

2006-01-01

212

Measurement of D{sup 0}-D{sup 0} Mixing Parameters in D{sup 0}{yields}K{sub s}{pi}{sup +}{pi}{sup -} Decays  

SciTech Connect

We report a measurement of D{sup 0}-D{sup 0} mixing parameters in D{sup 0}{yields}K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} decays using a time-dependent Dalitz-plot analysis. We first assume CP conservation and subsequently allow for CP violation. The results are based on 540 fb{sup -1} of data accumulated with the Belle detector at the KEKB e{sup +}e{sup -} collider. Assuming negligible CP violation, we measure the mixing parameters x=(0.80{+-}0.29{sub -0.07-0.14}{sup +0.09+0.10})% and y=(0.33{+-}0.24{sub -0.12-0.08}{sup +0.08+0.06})%, where the errors are statistical, experimental systematic, and systematic due to the Dalitz decay model, respectively. Allowing for CP violation, we obtain the CP-violating parameters |q/p|=0.86{sub -0.29-0.03}{sup +0.30+0.06}{+-}0.08 and arg(q/p)=(-14{sub -18-3-4}{sup +16+5+2}) deg.

Zhang, L. M.; Zhang, Z. P. [University of Science and Technology of China, Hefei (China); Adachi, I.; Brodzicka, J.; Haba, J.; Hazumi, M.; Itoh, R.; Iwasaki, Y.; Kichimi, H.; Krokovny, P.; Nakamura, I.; Nakao, M.; Nishida, S.; Ozaki, H.; Sakai, Y.; Schuemann, J.; Sumisawa, K.; Tajima, O.; Takasaki, F.; Tamai, K. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (and others)

2007-09-28

213

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...

214

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

215

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

216

Kinetics of changes in shelf life parameters during storage of pearl millet based kheer mix and development of a shelf life prediction model.  

PubMed

Pearl millet, dairy whitener and sugar powder were blended for preparing pearl millet kheer mix. Pearl millet based kheer mix samples were stored at 8, 25, 37 and 45 °C under nitrogen flushing environment. Changes in HMF and TBA formation in the dry mix and sensory changes in reconstituted kheer were studied upto 180 days. In fresh dry mix, the average value of HMF recorded was 4.87 ?mol/g which increased to 11.23, 13.67, 18.13, and 21.43 ?mol/g at 8, 25, 37 and 45 °C, respectively after 180 days of storage. From an initial value of 0.067, the TBA value increased to 0.219, 0.311, 0.432 and 0.613 at 532 nm at 8, 25, 37 and 45 °C, respectively after 180 days of storage. Data generated from the chemical kinetics of HMF and TBA development that progressed during storage of pearl millet kheer mix were modeled using Arrhenius equations to predict the shelf life of the product. Changes in HMF and TBA followed first order reaction kinetics. It was found that the potential shelf life of the pearl millet based kheer mix was 396 days at 8 and 288 days at 25 °C, respectively. PMID:25477640

Bunkar, Durga Shankar; Jha, Alok; Mahajan, Ankur; Unnikrishnan, V S

2014-12-01

217

Estimation of the effective parameter of spinorbital interaction of electrons in intermetallic Er-In system compounds from the kinetic and magnetic properties  

NASA Astrophysics Data System (ADS)

Normal, R 0 and anomalous, R S components of the Hall coefficient are determined from the results of experimental investigations of temperature dependences of the Hall coefficient, magnetic susceptibility, and specific electrical resistance for intermetallic Er2In, ErIn, and Er3In5 compounds. Effective parameters of spinorbital interaction ?SO of intermetallic compounds are calculated from anomalous components RS of the Hall coefficient and specific electrical resistance. The results calculated for the band parameters and effective parameters of spin-orbital interaction ?SO for Er-In system intermetallides coincide by orders of magnitude with the results obtained in [4,7,8] from the optical spectra of pure rare-earth metals.

Kuvandikov, O. K.; Hamraev, N. S.; Razhabov, R. M.; Éshkulov, A. A.

2012-05-01

218

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

219

Dynamic crystallization kinetics and nucleation parameters of a new generation of nanocomposites based on isotactic polypropylene and MoS2 inorganic nanotubes.  

PubMed

Differential scanning calorimetry (DSC) and time-resolved synchrotron X-ray diffraction have been used to investigate the dynamic crystallization behavior and crystalline structure of novel nanocomposites based on isotactic polypropylene (iPP) and molybdenum disulfide inorganic nanotubes (INT-MoS(2)). The influence of the INT-MoS(2) content and different cooling rates on the crystallization behavior has been studied. The crystallization exothermic peak shifted to higher temperature, and the overall crystallization time was reduced by increasing the INT-MoS(2). The dynamic crystallization kinetics was analyzed using the Ozawa-Avrami method, which was successful in describing the dynamic crystallization behavior of these new nanocomposites. On the other hand, study of the nucleation activity using the Dobreva method revealed that the INT-MoS(2) had an efficient nucleation effect on the monoclinic crystal form of iPP. Moreover, this effect was corroborated by the results of the crystallization activation energy, calculated using Kissinger and Takhor methods, which also confirmed the fact that the addition of INT-MoS(2) made the molecular chains easier to crystallize and increased the crystallization rate of iPP. PMID:21388105

Naffakh, Mohammed; Remskar, Maja; Marco, Carlos; Gómez-Fatou, Marián A

2011-03-31

220

Dynamic contrast-enhanced CT of head and neck tumors: perfusion measurements using a distributed-parameter tracer kinetic model. Initial results and comparison with deconvolution-based analysis.  

PubMed

The objective of this work was to evaluate the feasibility of a two-compartment distributed-parameter (DP) tracer kinetic model to generate functional images of several physiologic parameters from dynamic contrast-enhanced CT data obtained of patients with extracranial head and neck tumors and to compare the DP functional images to those obtained by deconvolution-based DCE-CT data analysis. We performed post-processing of DCE-CT studies, obtained from 15 patients with benign and malignant head and neck cancer. We introduced a DP model of the impulse residue function for a capillary-tissue exchange unit, which accounts for the processes of convective transport and capillary-tissue exchange. The calculated parametric maps represented blood flow (F), intravascular blood volume (v(1)), extravascular extracellular blood volume (v(2)), vascular transit time (t(1)), permeability-surface area product (PS), transfer ratios k(12) and k(21), and the fraction of extracted tracer (E). Based on the same regions of interest (ROI) analysis, we calculated the tumor blood flow (BF), blood volume (BV) and mean transit time (MTT) by using a modified deconvolution-based analysis taking into account the extravasation of the contrast agent for PS imaging. We compared the corresponding values by using Bland-Altman plot analysis. We outlined 73 ROIs including tumor sites, lymph nodes and normal tissue. The Bland-Altman plot analysis revealed that the two methods showed an accepted degree of agreement for blood flow, and, thus, can be used interchangeably for measuring this parameter. Slightly worse agreement was observed between v(1) in the DP model and BV but even here the two tracer kinetic analyses can be used interchangeably. Under consideration of whether both techniques may be used interchangeably was the case of t(1) and MTT, as well as for measurements of the PS values. The application of the proposed DP model is feasible in the clinical routine and it can be used interchangeably for measuring blood flow and vascular volume with the commercially available reference standard of the deconvolution-based approach. The lack of substantial agreement between the measurements of vascular transit time and permeability-surface area product may be attributed to the different tracer kinetic principles employed by both models and the detailed capillary tissue exchange physiological modeling of the DP technique. PMID:17921579

Bisdas, Sotirios; Konstantinou, George N; Lee, Puor Sherng; Thng, Choon Hua; Wagenblast, Jens; Baghi, Mehran; Koh, Tong San

2007-10-21

221

Dynamic contrast-enhanced CT of head and neck tumors: perfusion measurements using a distributed-parameter tracer kinetic model. Initial results and comparison with deconvolution-based analysis  

NASA Astrophysics Data System (ADS)

The objective of this work was to evaluate the feasibility of a two-compartment distributed-parameter (DP) tracer kinetic model to generate functional images of several physiologic parameters from dynamic contrast-enhanced CT data obtained of patients with extracranial head and neck tumors and to compare the DP functional images to those obtained by deconvolution-based DCE-CT data analysis. We performed post-processing of DCE-CT studies, obtained from 15 patients with benign and malignant head and neck cancer. We introduced a DP model of the impulse residue function for a capillary-tissue exchange unit, which accounts for the processes of convective transport and capillary-tissue exchange. The calculated parametric maps represented blood flow (F), intravascular blood volume (v1), extravascular extracellular blood volume (v2), vascular transit time (t1), permeability-surface area product (PS), transfer ratios k12 and k21, and the fraction of extracted tracer (E). Based on the same regions of interest (ROI) analysis, we calculated the tumor blood flow (BF), blood volume (BV) and mean transit time (MTT) by using a modified deconvolution-based analysis taking into account the extravasation of the contrast agent for PS imaging. We compared the corresponding values by using Bland-Altman plot analysis. We outlined 73 ROIs including tumor sites, lymph nodes and normal tissue. The Bland-Altman plot analysis revealed that the two methods showed an accepted degree of agreement for blood flow, and, thus, can be used interchangeably for measuring this parameter. Slightly worse agreement was observed between v1 in the DP model and BV but even here the two tracer kinetic analyses can be used interchangeably. Under consideration of whether both techniques may be used interchangeably was the case of t1 and MTT, as well as for measurements of the PS values. The application of the proposed DP model is feasible in the clinical routine and it can be used interchangeably for measuring blood flow and vascular volume with the commercially available reference standard of the deconvolution-based approach. The lack of substantial agreement between the measurements of vascular transit time and permeability-surface area product may be attributed to the different tracer kinetic principles employed by both models and the detailed capillary tissue exchange physiological modeling of the DP technique.

Bisdas, Sotirios; Konstantinou, George N.; Sherng Lee, Puor; Thng, Choon Hua; Wagenblast, Jens; Baghi, Mehran; San Koh, Tong

2007-10-01

222

Measurement of blood protease kinetic parameters with self-assembled monolayer ligand binding assays and label-free MALDI-TOF MS.  

PubMed

We report novel ligand binding assay (LBA) surface modalities that permit plasma protease catalytic efficiency (kcat/km) determination by MALDI-TOF MS without the use of liquid chromatography or internal standards such as chemical or metalized labels. Two model LBAs were constructed on planar self-assembled monolayers (SAMs) and used to evaluate the clinically relevant metalloprotease ADAMTS-13 kinetics in plasma. The SAM chemistries were designed to improve biosampling efficiency by minimization of nonspecific adsorption of abundant proteins present at ~100,000× the concentration of the endogenous enzyme. In the first protocol, in-solution digestion of the ADAMTS-13 substrate (vWFh) was performed with immunoaffinity enrichment of the reaction substrate and product to SAM arrays. The second configuration examined protease kcat/km via a surface digestion modality where different substrates were covalently immobilized to the SAM at controlled surface density for optimized protease screens. The results show the MALDI-TOF MS LBA platforms provide limits of quantitation to ~1% protease activity (~60 pM enzyme concentration) in <1 h analysis time, a ~16× improvement over other MS-based LBA formats. Implementation of a vacuum-sublimed MALDI matrix provided good MALDI-TOF MS intra- and interday repeatability, ~1.2 and ~6.6% RSD, respectively. Platform reliability permitted kcat/km determination without internal standards with observed values ~10× improved versus conventional fluorophoric assays. Application of the assays to 12 clinical plasma samples demonstrated proof-of-concept for clinical applications. Overall, this work demonstrates that rationally designed surface chemistries for MALDI-TOF MS may serve as an alternative, label-free methodology with potential for a wide range of biotechnology applications related to targeted enzyme molecular diagnostics. PMID:24107006

Patrie, Steven M; Roth, Michael J; Plymire, Daniel A; Maresh, Erica; Zhang, Junmei

2013-11-01

223

Comparative kinetic analysis of raw and cleaned coals  

Microsoft Academic Search

In this research, thermogravimetry (TG\\/DTG) was used to determine the kinetic analysis of different coals and effect of cleaning process on kinetic parameters of raw and cleaned coal samples from Soma, Tuncbilek and Afsin Elbistan regions. Kinetic parameters of the samples were determined using Arrhenius and Coats and Redfern kinetic models and the results are discussed.

K. E. Ozbas; M. V. Kök; C. Hicyilmaz

2002-01-01

224

Kinetic Turbulence  

NASA Astrophysics Data System (ADS)

The weak collisionality typical of turbulence in many diffuse astrophysical plasmas invalidates an MHD description of the turbulent dynamics, motivating the development of a more comprehensive theory of kinetic turbulence. In particular, a kinetic approach is essential for the investigation of the physical mechanisms responsible for the dissipation of astrophysical turbulence and the resulting heating of the plasma. This chapter reviews the limitations of MHD turbulence theory and explains how kinetic considerations may be incorporated to obtain a kinetic theory for astrophysical plasma turbulence. Key questions about the nature of kinetic turbulence that drive current research efforts are identified. A comprehensive model of the kinetic turbulent cascade is presented, with a detailed discussion of each component of the model and a review of supporting and conflicting theoretical, numerical, and observational evidence.

Howes, Gregory G.

225

Fluorescent intercalator displacement replacement (FIDR) assay: determination of relative thermodynamic and kinetic parameters in triplex formation—a case study using triplex-forming LNAs  

PubMed Central

Triplex forming oligonucleotides (TFOs) are the most commonly used approach for site-specific targeting of double stranded DNA (dsDNA). Important parameters describing triplex formation include equilibrium binding constants (Keq) and association/dissociation rate constants (kon and koff). The ‘fluorescent intercalator displacement replacement’ (FIDR) assay is introduced herein as an operationally simple approach toward determination of these parameters for triplexes involving TC-motif TFOs. Briefly described, relative rate constants are determined from fluorescence intensity changes upon: (i) TFO-mediated displacement of pre-intercalated and fluorescent ethidium from dsDNA targets (triplex association) and (ii) Watson–Crick complement-mediated displacement of the TFO and replacement with ethidium (triplex dissociation). The assay is used to characterize triplexes between purine-rich dsDNA targets and TC-motif TFOs modified with six different locked nucleic acid (LNA) monomers, i.e. conventional and C5-alkynyl-functionalized LNA and ?-L-LNA pyrimidine monomers. All of the studied monomers increase triplex stability by decreasing the triplex dissociation rate. LNA-modified TFOs form more stable triplexes than ?-L-LNA-modified counterparts owing to slower triplex dissociation. Triplexes modified with C5-(3-aminopropyn-1-yl)-LNA-U monomer Z are particularly stable. The study demonstrates that three affinity-enhancing features can be combined into one high-affinity TFO monomer: conformational restriction of the sugar ring, expansion of the pyrimidine ?-stacking surface and introduction of an exocyclic amine. PMID:22855561

Sau, Sujay P.; Kumar, Pawan; Sharma, Pawan K.; Hrdlicka, Patrick J.

2012-01-01

226

Effect of driver impedance on dense plasma focus Z-pinch neutron yield  

NASA Astrophysics Data System (ADS)

The Z-pinch phase of a dense plasma focus (DPF) heats the plasma by rapid compression and accelerates ions across its intense electric fields, producing neutrons through both thermonuclear and beam-target fusion. Driver characteristics have empirically been shown to affect performance, as measured by neutron yield per unit of stored energy. We are exploring the effect of driver characteristics on DPF performance using particle-in-cell (PIC) simulations of a kJ scale DPF. In this work, our PIC simulations are fluid for the run-down phase and transition to fully kinetic for the pinch phase, capturing kinetic instabilities, anomalous resistivity, and beam formation during the pinch. The anode-cathode boundary is driven by a circuit model of the capacitive driver, including system inductance, the load of the railgap switches, the guard resistors, and the coaxial transmission line parameters. It is known that the driver impedance plays an important role in the neutron yield: first, it sets the peak current achieved at pinch time; and second, it affects how much current continues to flow through the pinch when the pinch inductance and resistance suddenly increase. Here we show from fully kinetic simulations how total neutron yield depends on the impedance of the driver and the distributed parameters of the transmission circuit. Direct comparisons between the experiment and simulations enhance our understanding of these plasmas and provide predictive design capability for neutron source applications.

Sears, Jason; Link, Anthony; Schmidt, Andrea; Welch, Dale

2014-12-01

227

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

228

Fluorescent intercalator displacement replacement (FIDR) assay: determination of relative thermodynamic and kinetic parameters in triplex formation--a case study using triplex-forming LNAs.  

PubMed

Triplex forming oligonucleotides (TFOs) are the most commonly used approach for site-specific targeting of double stranded DNA (dsDNA). Important parameters describing triplex formation include equilibrium binding constants (K(eq)) and association/dissociation rate constants (k(on) and k(off)). The 'fluorescent intercalator displacement replacement' (FIDR) assay is introduced herein as an operationally simple approach toward determination of these parameters for triplexes involving TC-motif TFOs. Briefly described, relative rate constants are determined from fluorescence intensity changes upon: (i) TFO-mediated displacement of pre-intercalated and fluorescent ethidium from dsDNA targets (triplex association) and (ii) Watson-Crick complement-mediated displacement of the TFO and replacement with ethidium (triplex dissociation). The assay is used to characterize triplexes between purine-rich dsDNA targets and TC-motif TFOs modified with six different locked nucleic acid (LNA) monomers, i.e. conventional and C5-alkynyl-functionalized LNA and ?-L-LNA pyrimidine monomers. All of the studied monomers increase triplex stability by decreasing the triplex dissociation rate. LNA-modified TFOs form more stable triplexes than ?-L-LNA-modified counterparts owing to slower triplex dissociation. Triplexes modified with C5-(3-aminopropyn-1-yl)-LNA-U monomer Z are particularly stable. The study demonstrates that three affinity-enhancing features can be combined into one high-affinity TFO monomer: conformational restriction of the sugar ring, expansion of the pyrimidine ?-stacking surface and introduction of an exocyclic amine. PMID:22855561

Sau, Sujay P; Kumar, Pawan; Sharma, Pawan K; Hrdlicka, Patrick J

2012-11-01

229

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

PubMed

Kinetic model parameters for toluene conversion under microwave thermocatalytic treatment were evaluated. The kinetic rate constants were determined using integral method based on experimental data and coupled with Arrhenius equation for obtaining the activation energies and pre-exponential factors. The model provides a good agreement with the experimental data. The kinetic model was also validated with standard error of 3% on average. The extrapolation of the model showed a reasonable trend to predict toluene conversion and product yield both in thermal and catalytic treatments. Under microwave irradiation, activation energy of toluene conversion was lower in the range of 3-27 kJ mol(-1) compared to those of conventional heating reported in the literatures. The overall reaction rate was six times higher compared to conventional heating. As a whole, the kinetic model works better for tar model removal in the absence of gas reforming within a level of reliability demonstrated in this study. PMID:24231266

Anis, Samsudin; Zainal, Z A

2014-01-01

230

Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State  

PubMed Central

Several kinetic models for the macrocyclization of a C2 pseudopeptide with a dihalide through a SN2 reaction have been developed. These models not only focus on the kinetic analysis of the main macrocyclization reaction, but also consider the competitive oligomerization/polymerization processes yielding undesired oligomeric/polymeric byproducts. The effect of anions has also been included in the kinetic models, as they can act as catalytic templates in the transition state reducing and stabilizing the transition state. The corresponding differential equation systems for each kinetic model can be solved numerically. Through a comprehensive analysis of these results, it is possible to obtain a better understanding of the different parameters that are involved in the macrocyclization reaction mechanism and to develop strategies for the optimization of the desired processes. PMID:22666148

Martí-Centelles, Vicente; Burguete, M. Isabel; Luis, Santiago V.

2012-01-01

231

Assessment of bioethanol yield by S. cerevisiae grown on oil palm residues: Monte Carlo simulation and sensitivity analysis.  

PubMed

Oil palm trunk (OPT) sap was utilized for growth and bioethanol production by Saccharomycescerevisiae with addition of palm oil mill effluent (POME) as nutrients supplier. Maximum yield (YP/S) was attained at 0.464g bioethanol/g glucose presence in the OPT sap-POME-based media. However, OPT sap and POME are heterogeneous in properties and fermentation performance might change if it is repeated. Contribution of parametric uncertainty analysis on bioethanol fermentation performance was then assessed using Monte Carlo simulation (stochastic variable) to determine probability distributions due to fluctuation and variation of kinetic model parameters. Results showed that based on 100,000 samples tested, the yield (YP/S) ranged 0.423-0.501g/g. Sensitivity analysis was also done to evaluate the impact of each kinetic parameter on the fermentation performance. It is found that bioethanol fermentation highly depend on growth of the tested yeast. PMID:25459850

Samsudin, Mohd Dinie Muhaimin; Mat Don, Mashitah

2014-10-30

232

Processing parameters and kinetics of bromination and chlorination in the YBa sub 2 Cu sub 3 O sub 6+x system  

SciTech Connect

The introduction of halogens such as Cl{sub 2}, Br{sub 2} can restore 90 K superconductivity to oxygen deficient YBa{sub 2}Cu{sub 3}O{sub 6+x}. This is potentially important for applications to thin film devices due to the low processing temperatures required relative to reprocessing with oxygen. Low temperature 260{degrees}C and short time (>5 minute) bromination has been shown to convert initially insulting YBa{sub 2}Cu{sub 3}O{sub 6.2} powder to a high temperature superconductor with properties similar to the standard O{sub 7} material. This process has now been extended to single crystals as well, but with somewhat different processing parameters. Thermal gravimetric analysis (TGA) coupled with mass spectrometry indicates that the Br becomes strongly bonded, with no release of Br observed in taking powder samples to 1000{degree}C in flowing forming gas (2%H{sub 2}/98%N{sub 2}). The reaction has also been found to be highly exothermic for both Br and Cl treatments, which is consistent with the strong bonding of the bromine discussed above.

Radousky, H.B.; Glass, R.S.; Back, D.; Chin, A.H.; Fluss, M.J. (Lawrence Livermore National Lab., CA (USA)); Liu, J.Z.; Mosly, W.D.; Klavins, P.; Shelton, R.N. (California Univ., Davis, CA (USA). Dept. of Physics)

1990-09-01

233

Development of a chemical kinetic model for a biosolids fluidized-bed gasifier and the effects of operating parameters on syngas quality.  

PubMed

In an effort to decrease the land disposal of sewage sludge biosolids and to recover energy, gasification has become a viable option for the treatment of waste biosolids. The process of gasification involves the drying and devolatilization and partial oxidation of biosolids, followed closely by the reduction of the organic gases and char in a single vessel. The products of gasification include a gaseous fuel composed largely of N2, H2O, CO2, CO, H2, CH4, and tars, as well as ash and unburned solid carbon. A mathematical model was developed using published devolatilization, oxidation, and reduction reactions, and calibrated using data from three different experimental studies of laboratory-scale fluidized-bed sewage sludge gasifiers reported in the literature. The model predicts syngas production rate, composition, and temperature as functions of the biosolids composition and feed rate, the air input rate, and gasifier bottom temperature. Several data sets from the three independent literature sources were reserved for model validation, with a focus placed on five species of interest (CO, CO2, H2, CH4, and C6H6). The syngas composition predictions from the model compared well with experimental results from the literature. A sensitivity analysis on the most important operating parameters of a gasifier (bed temperature and equivalence ratio) was performed as well, with the results of the analysis offering insight into the operations of a biosolids gasifier. PMID:24654385

Champion, Wyatt M; Cooper, C David; Mackie, Kevin R; Cairney, Paul

2014-02-01

234

[Weibull equation and dissolution kinetics].  

PubMed

On modelling the kinetics of dissolution, two variants of Weibull equation in a two-parameter or tree-parameter form are used, the estimations of their parameters not being quite comparable. The introductory part of the paper sums up four variants of the equation and chracterized their relationship to granulometric Rosin-Rammler-Sperling equation. The kinetics of liberation of pilocarpinium chloride from lyophilized lamellae with graded amounts of hydroxypropylmethylcellulose is expressed by the above-mentioned equations and their parameters are compared. The conclusions generally discusses the usability of equations and their correct interperetation in modelling dissolution of active ingrediens from dosage forms. PMID:15631003

Zatloukal, Z

2004-11-01

235

Purification and kinetic characterization of polyphenol oxidase from Barbados cherry ( Malpighia glabra L.)  

Microsoft Academic Search

Polyphenol oxidase (PPO) of Barbados cherry was extracted and purified through ammonium sulfate precipitation, gel filtration, and affinity chromatography. The purification factor for PPO was 60% with 8.3% yield. The enzyme was characterized for thermal stability, pH and kinetic parameters. The molecular mass of PPO was approximately the sum of 52 and 38kDa estimated by SDS–PAGE. The purity was checked

V. B. Anil Kumar; T. C. Kishor Mohan; K. Murugan

2008-01-01

236

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

237

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

238

Igneous microstructures from kinetic models of crystallization  

Microsoft Academic Search

During crystallization, a variety of competing kinetic processes determine the evolution of the igneous microstructure, yet, the relative contribution of each process remains elusive. To this end, a stochastic algorithm is developed to yield a detailed spatial representation of the igneous microstructure during progressive crystallization. This algorithm is used to test a variety of kinetic models for nucleation and crystal

Taber G. Hersum; Bruce D. Marsh

2006-01-01

239

Investigation of the efficiency of a tubular continuous-flow photoreactor with supported titanium dioxide nanoparticles in the removal of 4-nitrophenol: operational parameters, kinetics analysis and mineralization studies.  

PubMed

In this study, to investigate the application of heterogeneous photocatalysis in the removal of organic contaminants from aqueous media a novel tubular continuous-flow photoreactor with supported TiO2-P25 on glass plates was designed and constructed. The photoreactor comprises six quartz tubes and a UV lamp which was placed in the center of the quartz tubes. 4-nitrophenol (4-NP) as a most refractory pollutant was chosen as a probe pollutant to examine the photoreactor efficiency for environmental cleaning applications. Results of experiments show that the removal efficiency of 4-NP in this photoreactor is a function of photoreactor length, gas and liquid flow rates and 4-NP initial concentration. Kinetics analysis indicates that degradation of 4-NP in continuous-mode can be modeled with the Langmuir-Hinshelwood (L-H) model (k(L-H) = 1.5 mg L(-1) min(-1), K(ads) = 0.11 mg(-1) L). A design equation was obtained with a combination of L-H modified equation and tubular reactor design equation. This equation can be used for estimation of 4-NP concentration in different photoreactor lengths under various operational parameters. Mineralization study was followed through total organic carbon (TOC) analysis and measurement of nitrite and nitrate as final degradation products. PMID:22053458

Behnajady, Mohammad A; Amirmohammadi-Sorkhabi, Sadegh; Modirshahla, Nasser; Shokri, Mohammad

2011-01-01

240

Ratings of kinetic depth in multidot displays.  

PubMed

Subjects saw kinetic depth displays whose shape (sphere or cylinder) was defined by luminous dots distributed randomly on the surface or in the volume of the object. Subjects rated perceived 3-D depth, rigidity, and coherence. Despite individual differences, all 3 ratings increased with the number of dots. Dots in the volume yielded ratings equal to or greater than surface dots. Each rating varied with 3 of 4 factors (shape, distribution, numerosity, and perspective), but the ratings either between trials or between conditions were often uncorrelated. Object shape affected rigidity but not depth ratings. Veridically perceived polar displays had slightly lower rigidity but higher depth ratings than parallel projection displays. (Reversed polar displays were always grossly nonrigid.) The interaction of ratings and stimulus parameters requires theories and experiments in which different KDE ratings are not treated interchangeably. PMID:2531213

Dosher, B A; Landy, M S; Sperling, G

1989-11-01

241

Coal tar phototoxicity: kinetics and exposure parameters  

SciTech Connect

Two manifestations of coal tar phototoxicity were examined: delayed erythema and skin pain (tar smarts) by quantifying the amount (dose) of UVA and exposure conditions required to induce these phenomena in normal human skin. The minimal UVA dose required to induce delayed erythema (minimal phototoxic dose or MPD) and the minimal UVA dose required to induce an immediate smarting reaction (minimal smarting dose or MSD) were recorded in 32 subjects in a variety of settings. A log-log dose-response model described the relation between the interval of time tar was left on the skin and lowering of MPD. We examined 4 different methods of tar removal and showed that several methods using more than water alone were equally effective--judging by resultant phototoxicity. The time between tar removal and UVA irradiation is important. Even 30 min was sufficient for the MPD to increase from 3.77 +/- 1.55 to 6.1 +/- 4.0 J/cm2. The smarting reaction shows a similar dependence on the time interval between tar removal and exposure. The mean MSD was less than the mean MPD at all times tested. Both manifestations of coal tar phototoxicity, reduced delayed erythema threshold and susceptibility to the smarting reaction, persisted at least 30 h after tar removal.

Diette, K.M.; Gange, R.W.; Stern, R.S.; Arndt, K.A.; Parrish, J.A.

1983-10-01

242

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

243

Recovery Kinetics of Cold-Deformed Cr-Mo Steels  

NASA Astrophysics Data System (ADS)

The recovery kinetics of cold deformed (2.6 and 7 pct) Cr-Mo steel during isothermally and continuous annealing was studied in the 450 °C to 680 °C temperature range. The recovery evolution was monitored by measuring the annealed material yield stress at room temperature, and the microstructure was characterized by the Williamson Hall X-ray diffraction (XRD) technique. Different responses of the material were observed after long annealing times depending on the amount of prestrain. For low prestrains (2.6 pct), complete recovery was found. For high prestrains (7 pct), partial recovery was observed after long annealing times, with asymptotic yield stress values that depend on the annealing temperature. From XRD measurements, this was ascribed to the formation during annealing of stable structures characterized by low annihilation kinetics with no formation of cells within the grains. This was confirmed by transmission electron observations. To describe the recovery kinetics, a model based on the solution of the differential equation of the dislocation density was used; the process was assumed to be thermally activated, with an activation energy that depends on the dislocation density. The model parameters were fitted with the isothermal annealing results, and an excellent agreement was found when compared to the continuous annealing results.

Vicente Alvarez, M. A.; Marchena, M.; Perez, T.

2008-12-01

244

Iso-conversional analysis of glass transition and crystallization in as-synthesis high yield of glassy Se98Cd2 nanorods  

NASA Astrophysics Data System (ADS)

In the present work, we have prepared high yield of glassy Se98Cd2 nanorods using melt-quench technique. The morphology and micro-structural analysis of as-prepared nanorods are characterized by SEM, XRD and EDX techniques. The glass transition and crystallization kinetics of glassy Se98Cd2 nanorods are studied at different heating rates (5, 10, 15, 20 K/min) using differential scanning calorimetric (DSC) technique. Four iso-conversional methods [Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), Tang and Straink] were used to determine the various kinetic parameters (crystallization temperature T ?c, transition temperature T ?g, activation energy of crystallization E ?c, activation energy of glass transition E ?g, order parameter n) of glass transition and crystallization process in non-isothermal mode. The monotonous decrease in activation energy E ? with the crystallization fraction ? confirm the complex kinetic mechanism of the glassy Se98Cd2 nanorods.

Dohare, C.; Mehta, N.

2013-08-01

245

Measuring surface binding thermodynamics and kinetics by using total internal reflection with fluorescence correlation spectroscopy: practical considerations.  

PubMed

The combination of total internal reflection illumination and fluorescence correlation spectroscopy (TIR-FCS) is an emerging method useful for, among a number of things, measuring the thermodynamic and kinetic parameters describing the reversible association of fluorescently labeled ligands in solution with immobilized, nonfluorescent surface binding sites. However, there are many parameters (both instrumental and intrinsic to the interaction of interest) that determine the nature of the acquired fluorescence fluctuation autocorrelation functions. In this work, we define criteria necessary for successful measurements and then systematically explore the parameter space to define conditions that meet the criteria. The work is intended to serve as a guide for experimental design, in other words, to provide a methodology to identify experimental conditions that will yield reliable values of the thermodynamic and kinetic parameters for a given interaction. PMID:21166379

Thompson, Nancy L; Navaratnarajah, Punya; Wang, Xiang

2011-01-13

246

Kinetic Sculpture  

NSDL National Science Digital Library

In this design challenge activity, learners build a tower thatâs at least 12 inches high with two or more parts that move (spin, sway, or flap) in the wind. This art meets construction activity allows learners to think about design challenges while creating a kinetic sculpture (a sculpture that moves). This is an excellent follow-up activity to "High Rise" from the same source.

Wgbh

2010-01-01

247

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

248

Arbitrary amplitude kinetic Alfven solitary waves and double layers in a non-Maxwellian plasma  

SciTech Connect

To investigate the existence of kinetic Alfven wave solitons, warm adiabatic ions and kappa distributed electrons are considered in a magnetized plasma. The kappa distribution (having the spectral index {kappa}) is a velocity distribution that has a high energy tail but approaches the Maxwellian when {kappa}{yields}{infinity}. In this work, by using the Sagdeev pseudopotential method, an exact analytical expression for arbitrary amplitude solitary kinetic Alfven wave is derived. For different sets of plasma parameter values, the Sagdeev potential {Psi} ({phi}) has been calculated numerically. It is found that the spectral index {kappa} plays a significant role in determining the shape and size of the solitary waves and double layers. Also, it is observed that both compressive solitary waves and double layers exist depending on the values of different plasma parameters.

Gogoi, Runmoni; Khan, Manoranjan [Department of Instrumentation Science and Centre for Plasma Studies, Jadavpur University, Jadavpur, Kolkata 700032 (India)

2010-11-15

249

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

250

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

251

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

252

Kinetics of tetrataenite disordering  

NASA Astrophysics Data System (ADS)

Tetrataenite is a chemically ordered L10-type Fe50Ni50 alloy detected for the first time in 1977 by 57Fe Mössbauer spectroscopy studies in iron meteorites. The thermal history of meteorites, in particular short thermal events like those associated to hypervelocity impacts, can be constrained by tracing the presence of tetrataenite or its disordering into taenite. The knowledge of the disordering kinetics of tetrataenite, that is associated with changes in its magnetic properties, is still very fragmentary so that the time-temperature history of these meteorites cannot be constrained in details. Furthermore, knowledge of disordering kinetics is important due to potential technological application of tetrataenite as a rare-earth free strong magnet. Thus, this work provides the first time-temperature data for disordering reaction of tetrataenite. We have shown that disordering is not an instantaneous process but is a kinetic limited reaction. It was shown that disordering may take place at any temperature above the order-disorder transition for L10 superstructure phase (~320 °C) when the appropriate time-scale is considered. This result means that the apparent Curie point for tetrataenite is not an absolute property in the sense that any estimate of this parameter should be referred to a given time-scale.

Dos Santos, E.; Gattacceca, J.; Rochette, P.; Fillion, G.; Scorzelli, R. B.

2015-02-01

253

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

254

Kinetic buffers.  

PubMed

This paper proposes a new type of molecular device that is able to act as an inverse proton sponge to slowly decrease the pH inside a reaction vessel. This makes the automatic monitoring of the concentration of pH-sensitive systems possible. The device is a composite formed of an alkyl chloride, which kinetically produces acidity, and a buffer that thermodynamically modulates the variation in pH value. Profiles of pH versus time (pH-t plots) have been generated under various experimental conditions by computer simulation, and the device has been tested by carrying out automatic spectrophotometric titrations, without using an autoburette. To underline the wide variety of possible applications, this new system has been used to realize and monitor HCl uptake by a di-copper(II) bistren complex in a single run, in a completely automatic experiment. PMID:25387452

Alibrandi, Giuseppe; Fabbrizzi, Luigi; Licchelli, Maurizio; Puglisi, Antonio

2015-01-12

255

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

256

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

257

The platinum microelectrode/Nafion interface - An electrochemical impedance spectroscopic analysis of oxygen reduction kinetics and Nafion characteristics  

NASA Technical Reports Server (NTRS)

The objectives of this study were to use electrochemical impedance spectroscopy (EIS) to study the oxygen-reduction reaction under lower humidification conditions than previously studied. The EIS technique permits the discrimination of electrode kinetics of oxygen reduction, mass transport of O2 in the membrane, and the electrical characteristics of the membrane. Electrode-kinetic parameters for the oxygen-reduction reaction, corrosion current densities for Pt, and double-layer capacitances were calculated. The production of water due to electrochemical reduction of oxygen greatly influenced the EIS response and the electrode kinetics at the Pt/Nafion interface. From the finite-length Warburg behavior, a measure of the diffusion coefficient of oxygen in Nafion and diffusion-layer thickness was obtained. An analysis of the EIS data in the high-frequency domain yielded membrane and interfacial characteristics such as ionic conductivity of the membrane, membrane grain-boundary capacitance and resistance, and uncompensated resistance.

Parthasarathy, Arvind; Dave, Bhasker; Srinivasan, Supramaniam; Appleby, John A.; Martin, Charles R.

1992-01-01

258

Molecular dynamics and kinetic study of carbon coagulation in the release wave of detonation products.  

PubMed

We present a combined molecular dynamics and kinetic study of a carbon cluster aggregation process in thermodynamic conditions relevant for the detonation products of oxygen deficient explosives. Molecular dynamics simulations with the LCBOPII potential under gigapascal pressure and high temperatures indicate that (i) the cluster motion in the detonation gas is compatible with Brownian diffusion and (ii) the coalescence probability is 100% for two clusters entering the interaction cutoff distance. We used these results for a subsequent kinetic study with the Smoluchowski model, with realistic models applied for the physical parameters such as viscosity and cluster size. We found that purely aggregational kinetics yield too fast clustering, with moderate influence of the model parameters. In agreement with previous studies, the introduction of surface reactivity through a simple kinetic model is necessary to approach the clustering time scales suggested by experiments (1000 atoms after 100 ns, 10 000 atoms after 1 ?s). However, these models fail to reach all experimental criteria simultaneously and more complex modelling of the surface process seems desirable to go beyond these current limitations. PMID:22380052

Chevrot, Guillaume; Sollier, Arnaud; Pineau, Nicolas

2012-02-28

259

Molecular dynamics and kinetic study of carbon coagulation in the release wave of detonation products  

NASA Astrophysics Data System (ADS)

We present a combined molecular dynamics and kinetic study of a carbon cluster aggregation process in thermodynamic conditions relevant for the detonation products of oxygen deficient explosives. Molecular dynamics simulations with the LCBOPII potential under gigapascal pressure and high temperatures indicate that (i) the cluster motion in the detonation gas is compatible with Brownian diffusion and (ii) the coalescence probability is 100% for two clusters entering the interaction cutoff distance. We used these results for a subsequent kinetic study with the Smoluchowski model, with realistic models applied for the physical parameters such as viscosity and cluster size. We found that purely aggregational kinetics yield too fast clustering, with moderate influence of the model parameters. In agreement with previous studies, the introduction of surface reactivity through a simple kinetic model is necessary to approach the clustering time scales suggested by experiments (1000 atoms after 100 ns, 10 000 atoms after 1 ?s). However, these models fail to reach all experimental criteria simultaneously and more complex modelling of the surface process seems desirable to go beyond these current limitations.

Chevrot, Guillaume; Sollier, Arnaud; Pineau, Nicolas

2012-02-01

260

Statistical circuit design for yield improvement in CMOS circuits  

NASA Technical Reports Server (NTRS)

This paper addresses the statistical design of CMOS integrated circuits for improved parametric yield. The work uses the Monte Carlo technique of circuit simulation to obtain an unbiased estimation of the yield. A simple graphical analysis tool, the yield factor histogram, is presented. The yield factor histograms are generated by a new computer program called SPICENTER. Using the yield factor histograms, the most sensitive circuit parameters are noted, and their nominal values are changed to improve the yield. Two basic CMOS example circuits, one analog and one digital, are chosen and their designs are 'centered' to illustrate the use of the yield factor histograms for statistical circuit design.

Kamath, H. J.; Purviance, J. E.; Whitaker, S. R.

1990-01-01

261

Antigen kinetics determines immune reactivity  

PubMed Central

A current paradigm in immunology is that the strength of T cell responses is governed by antigen dose, localization, and costimulatory signals. This study investigates the influence of antigen kinetics on CD8 T cell responses in mice. A fixed cumulative antigen dose was administered by different schedules to produce distinct dose-kinetics. Antigenic stimulation increasing exponentially over days was a stronger stimulus for CD8 T cells and antiviral immunity than a single dose or multiple dosing with daily equal doses. The same was observed for dendritic cell vaccination, with regard to T cell and anti-tumor responses, and for T cells stimulated in vitro. In conclusion, stimulation kinetics per se was shown to be a separate parameter of immunogenicity. These findings warrant a revision of current immunization models and have implications for vaccine development and immunotherapy. PMID:18362362

Johansen, Pål; Storni, Tazio; Rettig, Lorna; Qiu, Zhiyong; Der-Sarkissian, Ani; Smith, Kent A.; Manolova, Vania; Lang, Karl S.; Senti, Gabriela; Müllhaupt, Beat; Gerlach, Tilman; Speck, Roberto F.; Bot, Adrian; Kündig, Thomas M.

2008-01-01

262

Argentina corn yield model  

NASA Technical Reports Server (NTRS)

A model based on multiple regression was developed to estimate corn yields for the country of Argentina. A meteorological data set was obtained for the country by averaging data for stations within the corn-growing area. Predictor variables for the model were derived from monthly total precipitation, average monthly mean temperature, and average monthly maximum temperature. A trend variable was included for the years 1965 to 1980 since an increasing trend in yields due to technology was observed between these years.

Callis, S. L.; Sakamoto, C.

1984-01-01

263

Investigations on a particular yield mapping system for combine harvesters  

Microsoft Academic Search

Spatially variable field operations depend on various parameters such as in-field variations of soil and crop yield. A yield map can provide local information on nutrient absorption, variability of soil and effects of special treatment strategies. In order to monitor the spatial variations of yield the combine harvester has to be equipped at least with data acquisition for locating and

P. Reitz; H. D. Kutzbach

1996-01-01

264

Yielding of binary colloidal glasses  

E-print Network

The rheological response, in particular the non-linear response, to oscillatory shear is experimentally investigated in colloidal glasses. The glasses are highly concentrated binary hard-sphere mixtures with relatively large size disparities. For a size ratio of 0.2, a strong reduction of the normalized elastic moduli, the yield strain and stress and, for some samples, even melting of the glass to a fluid is observed upon addition of the second species. This is attributed to the more efficient packing, as indicated by the shift of random close packing to larger total volume fractions. This leads to an increase in free volume which favours cage deformations and hence a loosening of the cage. Cage deformations are also favoured by the structural heterogeneity introduced by the second species. For a limited parameter range, we furthermore found indications of two-step yielding, as has been reported previously for attractive glasses. In samples containing spheres with more comparable sizes, namely a size ratio of 0.38, the cage seems less distorted and structural heterogeneities on larger length scales seem to become important. The limited structural changes are reflected in only a small reduction of the moduli, yield strain and stress.

T. Sentjabrskaja; E. Babaliari; J. Hendricks; M. Laurati; G. Petekidis; S. U. Egelhaaf

2013-01-31

265

Rate theory of yield in boron nitride nanotubes Traian Dumitric* and Boris I. Yakobson  

E-print Network

Rate theory of yield in boron nitride nanotubes Traian Dumitric* and Boris I. Yakobson Department with a probabilistic rate approach, we investigate the bond-rotation mode of plastic yield in boron nitride nanotubes to predict the kinetic and thermodynamic strength. Relative to carbon nanotubes, the boron nitride yield

Dumitrica,Traian

266

Kinetic and thermodynamic characterization of lysine production process in Brevibacterium lactofermentum.  

PubMed

Detailed kinetic and thermodynamic parameters for lysine production from Brevibacterium lactofermentum are investigated for the first time in this study. Production of the essential amino acid, L-lysine, by B. lactofermentum was assessed in a flask and a continuously stirred tank fermentor (22 L). Maximum lysine production was achieved after 40 h of growth and at 35 °C. The effect of different nitrogen sources such as NH(4)NO(3), (NH(4))(2)SO(4), (NH(4))(2)HPO(4), corn steep liquor, NaNO(3), and urea showed that corn steep liquor gave a better lysine yield. Lysine production was increased when dissolved oxygen was maintained at 50 % saturation. The use of dissolved oxygen was critical for high productivity. This indicates that dissolved oxygen greatly affects L-lysine productivity. Kinetic and thermodynamic parameters during lysine production from molasses and glucose mixture showed that B. lactofermentum efficiently converted the substrate mixture into cell mass and lysine. Kinetic and thermodynamic parameters were significantly higher compared with other microorganisms which may be due to the high metabolic activity of B. lactofermentum. This study will have a significant impact on future strategies for lysine production at industrial scale. PMID:23475286

Ahmed, Sibtain; Afzal, Munazza; Rajoka, Muhammad Ibrahim

2013-05-01

267

Kinetic modeling of rhamnolipid production by Pseudomonas aeruginosa PAO1 including cell density-dependent regulation.  

PubMed

The production of rhamnolipid biosurfactants by Pseudomonas aeruginosa is under complex control of a quorum sensing-dependent regulatory network. Due to a lack of understanding of the kinetics applicable to the process and relevant interrelations of variables, current processes for rhamnolipid production are based on heuristic approaches. To systematically establish a knowledge-based process for rhamnolipid production, a deeper understanding of the time-course and coupling of process variables is required. By combining reaction kinetics, stoichiometry, and experimental data, a process model for rhamnolipid production with P. aeruginosa PAO1 on sunflower oil was developed as a system of coupled ordinary differential equations (ODEs). In addition, cell density-based quorum sensing dynamics were included in the model. The model comprises a total of 36 parameters, 14 of which are yield coefficients and 7 of which are substrate affinity and inhibition constants. Of all 36 parameters, 30 were derived from dedicated experimental results, literature, and databases and 6 of them were used as fitting parameters. The model is able to describe data on biomass growth, substrates, and products obtained from a reference batch process and other validation scenarios. The model presented describes the time-course and interrelation of biomass, relevant substrates, and products on a process level while including a kinetic representation of cell density-dependent regulatory mechanisms. PMID:24770383

Henkel, Marius; Schmidberger, Anke; Vogelbacher, Markus; Kühnert, Christian; Beuker, Janina; Bernard, Thomas; Schwartz, Thomas; Syldatk, Christoph; Hausmann, Rudolf

2014-08-01

268

Real-time monitoring and kinetic parameter estimation of the affinity interaction of jArtinM and rArtinM with peroxidase glycoprotein by the electrogravimetric technique.  

PubMed

ArtinM is a D-mannose binding lectin that has been arousing increasing interest because of its biomedical properties, especially those involving the stimulation of Th1 immune response, which confers protection against intracellular pathogens. The potential pharmaceutical applications of ArtinM have motivated the production of its recombinant form (rArtinM) so that it is important to compare the sugar-binding properties of jArtinM and rArtinM in order to take better advantage of the potential applications of the recombinant lectin. In this work, a biosensor framework based on a Quartz Crystal Microbalance was established with the purpose of making a comparative study of the activity of native and recombinant ArtinM protein. The QCM transducer was strategically functionalized to use a simple model of protein binding kinetics. This approach allowed for the determination of the binding/dissociation kinetics rate and affinity equilibrium constant of both forms of ArtinM with horseradish peroxidase glycoprotein (HRP), a N-glycosylated protein that contains the trimannoside Man?1-3[Man?1-6]Man, which is a known ligand for jArtinM (Jeyaprakash et al., 2004). Monitoring of the real-time binding of rArtinM shows that it was able to bind HRP, leading to an analytical curve similar to that of jArtinM, with statistically equivalent kinetic rates and affinity equilibrium constants for both forms of ArtinM. The lower reactivity of rArtinM with HRP than jArtinM was considered to be due to a difference in the number of Carbohydrate Recognition Domains (CRDs) per molecule of each lectin form rather than to a difference in the energy of binding per CRD of each lectin form. PMID:20605432

Pesquero, N C; Pedroso, M M; Watanabe, A M; Goldman, M H S; Faria, R C; Roque-Barreira, M C; Bueno, P R

2010-09-15

269

Nutrient-limited microbial growth kinetics: overview and recent advances  

Microsoft Academic Search

Traditional concepts of nutrient uptake and growth kinetics as linked by cell yield are presented. Phenomena affecting the kinetics are examined along with a discussion of those which lead to ambiguity. Concepts of flux control are presented to help understand the distribution of material along metabolic pathways. Specific affinity is described to relate nutrient accumulation rates to transporter density. It

D. K. Button

1993-01-01

270

DRYING KINETICS OF ONION AND GREEN PEPPER  

Microsoft Academic Search

Drying kinetics were examined by introducing one-parameter empirical mass aansfer model, where the characteristic parameter (drying constant), is a function of process variables. The model was tested with data produced in an experimental through dryer, using direct regression analysis. Investigation involved two vegetables (namely, green pepper and onion) and a wide range of characteristic dimensions of samples and air conditions

C. T. Kiranoudis; Z. B. Maroulis; D. Marinos-Kouris

1992-01-01

271

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

272

Kinetics of Bose-Einstein condensation in a dimple potential  

NASA Astrophysics Data System (ADS)

We model the dynamics of condensation in a bimodal trap, consisting of a large reservoir region, and a tight "dimple" whose depth can be controlled. Experimental investigations have found that such dimple traps provide an efficient means of achieving condensation. In our kinetic equations, we include two- and three-body processes. The two-body processes populate the dimple, and lead to loss when one of the colliding atoms is ejected from the trap. The three-body processes produce heating and loss. We explain the principal trends, give a detailed description of the dynamics, and provide quantitative predictions for time scales and condensate yields. From these simulations, we extract optimal parameters for future experiments.

Dutta, Shovan; Mueller, Erich J.

2015-01-01

273

Ratings of kinetic depth in multidot displays  

Microsoft Academic Search

Subjects saw kinetic depth displays whose shape (sphere or cylinder) was defined by luminous dots distributed randomly on the surface or in the volume of the object. Subjects rated perceived 3-D depth, rigidity, and coherence. Despite individual differences, all 3 ratings increased with the number of dots. Dots in the volume yielded ratings equal to or greater than surface dots.

Barbara A. Dosher; Michael S. Landy; George Sperling

1989-01-01

274

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

275

Kinetic model for supercritical water gasification of algae.  

PubMed

The article reports the first quantitative kinetics model for supercritical water gasification (SCWG) of real biomass (algae) that describes the formation of the individual gaseous products. The phenomenological model is based on a set of reaction pathways that includes two types of compounds being intermediate between the algal biomass and the final gaseous products. To best correlate the experimental gas yields obtained at 450, 500 and 550 °C, the model allowed one type of intermediate to react to gases more quickly than the other type of intermediate. The model parameters indicate that gas yields increase with temperature because higher temperatures favor production of the more easily gasified intermediate and the production of gas at the expense of char. The model can accurately predict the qualitative influence of the biomass loading and water density on the gas yields. Sensitivity analysis and reaction rate analysis indicate that steam reforming of intermediates is an important source of H(2), whereas direct decomposition of the intermediate species is the main source of CO, CO(2) and CH(4). PMID:22286322

Guan, Qingqing; Wei, Chaohai; Savage, Phillip E

2012-03-01

276

Mass yields in 229 Th(n,f)  

Microsoft Academic Search

Cumulative yields of 27 fission products have been determined in 229Th(n,f) by recoil catcher technique followed by gamma-ray spectrometry. Absolute fission yields were arrived at from the fission\\u000a rate measured by track etch counting method. Mass yields were obtained from the cumulative yields using the charge distribution\\u000a parameters reported in the literature. The values agree well with the reported values

C. Agarwal; A. Goswami; P. C. Kalsi; S. Singh; A. Mhatre; A. Ramaswami

2008-01-01

277

Improved Experimental and Computational Methodology for Determining the Kinetic Equation and the Extant Kinetic Constants of Fe(II) Oxidation by Acidithiobacillus ferrooxidans?  

PubMed Central

The variety of kinetics expressions encountered in the literature and the unreasonably broad range of values reported for the kinetics constants of Acidithiobacillus ferrooxidans underscore the need for a unifying experimental procedure and for the development of a reliable kinetics equation. Following an extensive and critical review of reported experimental techniques, a method based on batch pH-controlled kinetics experiments lasting less than one doubling time was developed for the determination of extant kinetics constants. The Fe(II) concentration in the experiments was measured by a method insensitive to Fe(III) interference. Kinetics parameters were determined by nonlinear fitting of the integrated form of the Monod equation to yield a KS of 31 ± 4 mg Fe2+ liter?1 (mean ± standard deviation), a KP of 139 ± 20 mg Fe3+ liter?1, and a ?max of 0.082 ± 0.002 h?1. The corresponding kinetics equation was as follows: \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}\\frac{dS}{dt}= \\left \\left(-\\frac{0.082}{2.3{\\cdot}10^{7}}\\right) \\right \\frac{S{\\cdot}X}{31(1+\\displaystyle\\frac{P_{0}+S_{0}-S}{139})+S}\\end{equation*}\\end{document} where S represents the Fe(II) concentration in mg liter?1, P0 represents the initial Fe(III) concentration in mg liter?1, X represents the suspended bacterial cell concentration in cells ml?1, and t represents time in hours. The measured data fit this equation exceptionally well, with an R2 of >0.99. Fe(III) inhibition was found to be of a competitive nature. Contrary to previous reports, the results show that the concentration of Acidithiobacillus ferrooxidans cells has no affect on the kinetics constants. The kinetics equation can be considered applicable only to A. ferrooxidans cells grown under environmental conditions similar to those of the inoculum tested in the study. In contrast, the experimental and computational procedure is completely general and can be applied to A. ferrooxidans irrespective of the culture history. PMID:17261516

Molchanov, Sharon; Gendel, Yuri; Ioslvich, Ilya; Lahav, Ori

2007-01-01

278

Kinetics of Quality Changes During Food Frying  

Microsoft Academic Search

This paper deals with kinetics of quality changes during food frying. The quality parameters of interests include color, texture, viscoelastic properties, volume\\/density, and nutraceuticals (Omega 3 fatty acids). The kinetic theory and determination methodology under isothermal\\/non-isothermal conditions are also reviewed. This paper presents the reported reaction rate constant, order of reaction, and activation energy for specific quality changes including phenomenological

Fransiskus Hindra; Oon-Doo Baik

2006-01-01

279

Effect of annealing on the kinetic properties and band parameters of Hg{sub 1?x?y}Cd{sub x}Eu{sub y}Se semiconductor crystals  

SciTech Connect

The results of studies of the kinetic properties of Hg{sub 1?x?y}Cd{sub x}Eu{sub y}Se semiconductor crystals in the ranges of temperatures T = 77–300 K and magnetic fields H = 0.5–5 kOe before and after heat treatment of the samples in Se vapors are reported. It is established that annealing of the samples in Se vapors induces a decrease in the electron concentration. From the concentration dependence of the electron effective mass at the Fermi level, the band gap, the matrix element of interband interaction, and the electron effective mass at the bottom of the conduction band are determined.

Kovalyuk, T. T., E-mail: tarik-1006@mail.ru; Maistruk, E. V.; Maryanchuk, P. D. [Chernivtsy National University (Ukraine)

2014-12-15

280

Biotechnology of Forest Yield  

Microsoft Academic Search

Silvicultural and genetic manipulation of Douglas fir and loblolly pine plantations have increased their productivity 70 and 300 percent, respectively, over natural forests on the same sites. Yet these intensively managed plantations are achieving less than 50 percent of their potential productivity. Future increases in yield will result from optimization of nutritional treatments, control of noncrop vegetation, and advances in

Peter Farnum; Roger Timmis; J. Laurence Kulp

1983-01-01

281

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

282

Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid  

NASA Astrophysics Data System (ADS)

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.; Mukherjee, Rudra Palash; Bantraj, Kandi; Maity, Sunil K.

2010-10-01

283

Binary fission-fragment yields from the reaction 251Cf(nth, f)  

Microsoft Academic Search

The recoil mass spectrometer LOHENGRIN of the Laue-Langevin Institute, Grenoble has been used to measure the light fission-fragment mass yield and kinetic energy distributions from neutron-induced 252Cf*, using 251Cf as target material.

E. Birgersson; S. Oberstedt; A. Oberstedt; F.-J. Hambsch; D. Rochman; I. Tsekhanovitsch

2005-01-01

284

Regression Models For Saffron Yields in Iran  

NASA Astrophysics Data System (ADS)

Saffron is an important crop in social and economical aspects in Khorassan Province (Northeast of Iran). In this research wetried to evaluate trends of saffron yield in recent years and to study the relationship between saffron yield and the climate change. A regression analysis was used to predict saffron yield based on 20 years of yield data in Birjand, Ghaen and Ferdows cities.Climatologically data for the same periods was provided by database of Khorassan Climatology Center. Climatologically data includedtemperature, rainfall, relative humidity and sunshine hours for ModelI, and temperature and rainfall for Model II. The results showed the coefficients of determination for Birjand, Ferdows and Ghaen for Model I were 0.69, 0.50 and 0.81 respectively. Also coefficients of determination for the same cities for model II were 0.53, 0.50 and 0.72 respectively. Multiple regression analysisindicated that among weather variables, temperature was the key parameter for variation ofsaffron yield. It was concluded that increasing temperature at spring was the main cause of declined saffron yield during recent years across the province. Finally, yield trend was predicted for the last 5 years using time series analysis.

S. H, Sanaeinejad; S. N, Hosseini

285

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

Iowa Public Television. Explore More Project

2004-01-01

286

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

287

On fast reactor kinetics studies  

SciTech Connect

The results and the program of fast reactor core time and space kinetics experiments performed and planned to be performed at the IPPE critical facility is presented. The TIMER code was taken as computation support of the experimental work, which allows transient equations to be solved in 3-D geometry with multi-group diffusion approximation. The number of delayed neutron groups varies from 6 to 8. The code implements the solution of both transient neutron transfer problems: a direct one, where neutron flux density and its derivatives, such as reactor power, etc, are determined at each time step, and an inverse one for the point kinetics equation form, where such a parameter as reactivity is determined with a well-known reactor power time variation function. (authors)

Seleznev, E. F.; Belov, A. A. [Nuclear Safety Inst. of the Russian Academy of Sciences IBRAE (Russian Federation); Matveenko, I. P.; Zhukov, A. M.; Raskach, K. F. [Inst. for Physics and Power Engineering IPPE (Russian Federation)

2012-07-01

288

The effect of particle inlet conditions on FCC riser hydrodynamics and product yields.  

SciTech Connect

Essential to today's modern refineries and the gasoline production process are fluidized catalytic cracking units. By using a computational fluid dynamics (CFD) code developed at Argonne National Laboratory to simulate the riser, parametric and sensitivity studies were performed to determine the effect of catalyst inlet conditions on the riser hydrodynamics and on the product yields. Simulations were created on the basis of a general riser configuration and operating conditions. The results of this work are indications of riser operating conditions that will maximize specific product yields. The CFD code is a three-dimensional, multiphase, turbulent, reacting flow code with phenomenological models for particle-solid interactions, droplet evaporation, and chemical kinetics. The code has been validated against pressure, particle loading, and product yield measurements. After validation of the code, parametric studies were performed on various parameters such as the injection velocity of the catalyst, the angle of injection, and the particle size distribution. The results indicate that good mixing of the catalyst particles with the oil droplets produces a high degree of cracking in the riser.

Chang, S. L.; Golchert, B.; Lottes, S. A.; Zhou, C. Q.; Huntsinger, A.; Petrick, M.

1999-10-11

289

Kinetic ELISA in Microfluidic Channels  

PubMed Central

In this article, we describe the kinetic ELISA of Blue Tongue and Epizootic Hemorrhagic Disease viral antibodies in microfluidic channels by monitoring the rate of generation of the enzyme reaction product under static conditions. It has been shown that this format of the immunoassay allows very reliable quantitation of the target species using inexpensive glass microchips and a standard epifluorescence microscope system coupled to a CCD camera. For the viral antibodies assayed here, the limit of detection (LOD) for the analyte concentration in our microchips was established to be 3–5 times lower than that obtained on commercial microwell plates using a fiftieth of the sample volume and less than a third of the incubation time. Our analyses further show that when compared to the end-point ELISA format, the kinetic mode of this assay yields an improvement in the LOD by over an order of magnitude in microfluidic devices. This benefit is primarily realized as the observed variation in the background fluorescence (signal at the start of the enzyme reaction period) was significantly larger than that in the rate of signal generation upon repeating these assays in different microchannels/microchips. Because the kinetic ELISA results depend only on the latter quantity, the noise level in them was substantially lower compared to that in its end-point counterpart in which the absolute fluorescence measurements are of greater significance. While a similar benefit was also recorded through implementation of kinetic ELISAs on the microwell platform, the improvement in LOD registered in that system was not as significant as was observed in the case of microfluidic assays.

Yanagisawa, Naoki; Dutta, Debashis

2011-01-01

290

Yields of single-strand breaks in double-stranded calf thymus DNA irradiated in aqueous solution in the presence of oxygen and scavengers  

SciTech Connect

Yields of radiation-induced single-strand breaks in double-stranded calf thymus DNA have been measured as a function of OH scavenger concentration in N{sub 2}O/O{sub 2}-saturated aqueous solution. The experimental data are well represented by a theoretical model based on non-homogeneous reaction kinetics, without the need to adjust any parameter. The good agreement between experimental and theoretical data is taken as evidence that, in the presence of oxygen, the main effect of added scavengers with respect to the formation of single-strand breaks in double-stranded DNA is OH radical scavenging. 30 refs., 3 figs., 1 tab.

Udovicic, Lj.; Mark, F.; Bothe, E. [Max-Planck-Institut fuer Strahlenchemie, Ruhr (Germany)

1994-11-01

291

Reconstructing DNA replication kinetics from small DNA fragments  

NASA Astrophysics Data System (ADS)

In higher organisms, DNA replicates simultaneously from many origins. Recent in vitro experiments have yielded large amounts of data on the state of replication of DNA fragments. From measurements of the time dependence of the average size of replicated and nonreplicated domains, one can estimate the rate of initiation of DNA replication origins, as well as the average rate at which DNA bases are copied. One problem in making such estimates is that, in the experiments, the DNA is broken up into small fragments, whose finite size can bias downward the measured averages. Here, we present a systematic way of accounting for this bias by deriving theoretical relationships between the original domain-length distributions and fragment-domain length distributions. We also derive unbiased average-domain-length estimators that yield accurate results, even in cases where the replicated (or nonreplicated) domains are larger than the average DNA fragment. Then we apply these estimators to previously obtained experimental data to extract improved estimates of replication kinetics parameters.

Zhang, Haiyang; Bechhoefer, John

2006-05-01

292

Kinetic characterization of dopamine as a suicide substrate of tyrosinase.  

PubMed

A kinetic study of the inactivation of frog epidermis tyrosinase by a suicide substrate dopamine hydrochloride is described. The kinetic parameters and constants which characterize this reaction have been determined and the effects of pH and the stoichiometric inhibition by chloride have been considered. PMID:3149665

Tudela, J; Garcia-Canovas, F; Varón, R; Jimenez, M; Garcia-Carmona, F; Lozano, J A

1987-01-01

293

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

294

Influence of coal briquette size on the combustion kinetics  

Microsoft Academic Search

In this study, the effects of one of the most important parameters in coal briquetting process, the briquette size, on the combustion behaviour of coal briquettes were determined from the view of combustion kinetics, i.e. their liability to ignite and combust. Effect of size on the combustion kinetics was treated by two different approaches. The first one consists of combustion

N. Emre Altun; Cahit Hicyilmaz; A. Suat Bagci

2004-01-01

295

Mechanisms and kinetics of nuclear track etching and annealing: Free energy analysis of damage in fission fragment tracks  

NASA Astrophysics Data System (ADS)

Mechanisms and kinetics of etching and annealing of fission fragment tracks in CR-39 have been investigated. Kinetics of bulk etching and that of fission fragment track etching in CR-39 are described in a systematic manner. Activation energies of etching and annealing were determined from the experimental results through Arrhenius type, t=to exp(Ea/kBT), empirical relationships and models. The increase of free energy in fission fragment track formation in CR-39 is also determined from the measurements of track parameters. Activation barriers of bulk etching, track etching and track annealing in CR-39 are compared and discussed. This paper presents an anatomy of fission fragment tracks. Analyses of experimental results and comparison of above mentioned energies have yielded the important physics information usable in nuclear track methodologies, including nuclear geophysics and geochemistry, and radiation damage in solids.

Rana, Mukhtar Ahmed

2012-04-01

296

Apparatus for storing kinetic energy  

NASA Astrophysics Data System (ADS)

A kinetic energy storage system comprising a flywheel mounted on a rotatable shaft, mounted on bearings, is presented. The flywheel is located in a housing constructed to contain the flywheel or fragments thereof in the event of failure. Means for maintaining a reduced pressure within the housing, and to effect cooling, preferably by circulating oil, of the bearings on which the rotatable shaft is mounted are provided. Sensors measure oil temperature, oil pressure, speed of rotation of the flywheel, vibration of the housing, and pressure within the housing. A monitor capable of interpreting signals from the sensors and determining whether the system is operating within predetermined parameters is included.

Duff-Barclay, Ian; Mayer, Rayner Michael

1986-05-01

297

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

298

Crop modelling and remote sensing for yield production  

Microsoft Academic Search

Methods for the application of crop growth models, remote sensing and their integrative use for yield forecasting and prediction are presented. First, the general principles of crop growth models are explained. When crop simulation models are used on regional scales, uncertainty and spatial variation in model parameters can result in broad bands of simulated yield. Remote sensing can be used

B. A. M. Bouman

1995-01-01

299

Original article Influence of increasing breast meat yield  

E-print Network

Original article Influence of increasing breast meat yield on muscle histology and meat quality chickens from two lines (ten birds from each line) diver- gently selected for breast meat yield were compared. Moreover, some quality parameters (ie, drip loss, ultimate pH value and meat colour

Paris-Sud XI, Université de

300

Heterotroph anoxic yield in anoxic aerobic activated sludge systems treating municipal wastewater  

Microsoft Academic Search

As input to the steady state design and kinetic simulation models for the activated sludge system, the correct value for the heterotroph anoxic yield is essential to provide reliable estimates for the system denitrification potential. This paper examines activated sludge anoxic yield values in the literature, and presents experimental data quantifying the value. In the literature, in terms of the

A. Muller; M. C. Wentzel; R. E. Loewenthal; G. A. Ekama

2003-01-01

301

Degradation of contaminated plastics: a kinetic study  

Microsoft Academic Search

The thermal degradation of polypropylene (PP), polyacrylonitrile butadiene styrene (ABS), polyurethane (PU) and polyvinyl chloride (PVC) have been studied in the presence of copper, iron oxide and dirt. The rate constants and kinetic parameters for the degradation processes have been measured using the variable heating rate isoconversion method. The results suggest that the presence of metal contamination in these polymer

M. Day; J. D. Cooney; M. MacKinnon

1995-01-01

302

Multisite Kinetic Modeling of 13C Metabolic MR Using [1-13C]Pyruvate  

PubMed Central

Hyperpolarized 13C imaging allows real-time in vivo measurements of metabolite levels. Quantification of metabolite conversion between [1-13C]pyruvate and downstream metabolites [1-13C]alanine, [1-13C]lactate, and [13C]bicarbonate can be achieved through kinetic modeling. Since pyruvate interacts dynamically and simultaneously with its downstream metabolites, the purpose of this work is the determination of parameter values through a multisite, dynamic model involving possible biochemical pathways present in MR spectroscopy. Kinetic modeling parameters were determined by fitting the multisite model to time-domain dynamic metabolite data. The results for different pyruvate doses were compared with those of different two-site models to evaluate the hypothesis that for identical data the uncertainty of a model and the signal-to-noise ratio determine the sensitivity in detecting small physiological differences in the target metabolism. In comparison to the two-site exchange models, the multisite model yielded metabolic conversion rates with smaller bias and smaller standard deviation, as demonstrated in simulations with different signal-to-noise ratio. Pyruvate dose effects observed previously were confirmed and quantified through metabolic conversion rate values. Parameter interdependency allowed an accurate quantification and can therefore be useful for monitoring metabolic activity in different tissues. PMID:25548671

Gómez Damián, Pedro A.; Sperl, Jonathan I.; Janich, Martin A.; Khegai, Oleksandr; Wiesinger, Florian; Glaser, Steffen J.; Haase, Axel; Schwaiger, Markus; Schulte, Rolf F.; Menzel, Marion I.

2014-01-01

303

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

304

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

305

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

306

Kinetic studies of the hydrolysis of organophosphate insecticides by phosphotriesterase  

E-print Network

.S.A., were measured. The kinetic parameters for these insecticides were determined. Some of these insecticidal substrates such as propetamphos and profenofos are chiral compounds. The PTE specificity toward these chiral substrates has been assessed...

Zaitoun, Basel M.

2002-01-01

307

Simulation of O_2(^1?) yields in mixtures of O2 and inert gases in low pressure plasmas  

NASA Astrophysics Data System (ADS)

Current trends in pumping chemical oxygen-iodine lasers (COIL) involve producing the O_2(^1?) energy donor in electric discharges, thereby circumventing the hazards and complexity of conventional O_2(^1?) production via liquid chemistries. In this work we have investigated the scaling of O_2(^1?) yield with energy deposition in mixtures of O2 with He and Ar in rf discharges at pressures of a few to 10 Torr using a global plasma kinetics model. The global model was modified to address steady-state plug flow with one-dimensional gas hydrodynamics. We found that O_2(^1?) yield increases linearly with energy deposition per molecule of O2 up to a few eV per molecule, with yields peaking around 40 percent near 10 eV. We also found that further increases in energy deposition serve only to increase gas dissociation and heating, thereby reducing the O_2(^1?) yield. We will also discuss secondary effects from other parameters such as gas mixture and pressure, including results from a one-dimensional hydrodynamics model.

Stafford, D. Shane; Kushner, Mark J.

2003-10-01

308

Influence of soil, plant and meteorological factors on water relations and yield in Hevea brasiliensis  

Microsoft Academic Search

Influence of factors governing the soil-plantatmosphere system on components of water relations and yield was studied in two clones of rubber tree,Hevea brasiliensis, viz. RRII 105 and RRII 118. Clonal variations were evident in yield and yield components and associated physiological parameters in response to soil moisture status and meteorological factors. Observations made during different seasons indicatedvariations in yield are

G. Gururaja Rao; P. Sanjeeva Rao; R. Rajagopal; A. S. Devakumar; K. R. Vijayakumar; M. R. Sethuraj

1990-01-01

309

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

310

Starting Block Performance in Sprinters: A Statistical Method for Identifying Discriminative Parameters of the Performance and an Analysis of the Effect of Providing Feedback over a 6-Week Period  

PubMed Central

The purpose of this study was twofold: (a) to examine if kinetic and kinematic parameters of the sprint start could differentiate elite from sub-elite sprinters and, (b) to investigate whether providing feedback (FB) about selected parameters could improve starting block performance of intermediate sprinters over a 6-week training period. Twelve male sprinters, assigned to an elite or a sub-elite group, participated in Experiment 1. Eight intermediate sprinters participated in Experiment 2. All athletes were required to perform three sprint starts at maximum intensity followed by a 10-m run. To detect differences between elite and sub-elite groups, comparisons were made using t-tests for independent samples. Parameters reaching a significant group difference were retained for the linear discriminant analysis (LDA). The LDA yielded four discriminative kinetic parameters. Feedback about these selected parameters was given to sprinters in Experiment 2. For this experiment, data acquisition was divided into three periods. The first six sessions were without specific FB, whereas the following six sessions were enriched by kinetic FB. Finally, athletes underwent a retention session (without FB) 4 weeks after the twelfth session. Even though differences were found in the time to front peak force, the time to rear peak force, and the front peak force in the retention session, the results of the present study showed that providing FB about selected kinetic parameters differentiating elite from sub-elite sprinters did not improve the starting block performance of intermediate sprinters. Key Points The linear discriminative analysis allows the identification of starting block parameters differentiating elite from sub-elite athletes. 6-week of feedback does not alter starting block performance in training context. The present results failed to confirm previous studies since feedback did not improve targeted kinetic parameters of the complex motor task in real-world context. PMID:24431969

Fortier, Sylvie; Basset, Fabien A.; Mbourou, Ginette A.; Favérial, Jérôme; Teasdale, Normand

2005-01-01

311

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

312

Enhancement of Sputtering Yields by Low-Energy Molecular Ions  

NASA Astrophysics Data System (ADS)

Sputtering yields from polycrystalline gold targets bombarded with N_2^+, O_2^+, N^+, and O^+ ions were measured at low kinetic energies, near-threshold. When sputtering yields are normalized to the number of incident atoms, an unexpected and pronounced enhancement is observed for the molecular species relative to the corresponding atomic species. For N_2^+ and N^+ this occurs below kinetic energies of 500 eV per atom. For O_2^+ and O^+ it is only observed below 100 eV per atom. The degree of enhancement increases with decreasing projectile energy. A simple molecular-dynamics model is proposed to explain this effect in terms of the relative values of the vibrational period of the incident molecule and the collision time.

Hargitai, Zsuzsanna; Yao, Y.; Albert, M. M.; Barnes, A. V.; Gilligan, J. M.; Gordon, V. D.; Lüpke, G.; Pratt-Ferguson, B.; Puckett, A.; Tolk, N. H.; Betz, G.; Tully, J.

1997-11-01

313

Exploring Kinetics of Phenol Biodegradation by Cupriavidus taiwanesis 187  

PubMed Central

Phenol biodegradation in batch systems using Cupriavidus taiwanesis 187 has been experimentally studied. To determine the various parameters of a kinetic model, combinations of rearranged equations have been evaluated using inverse polynomial techniques for parameter estimation. The correlations between lag phase and phase concentration suggest that considering phenol inhibition in kinetic analysis is helpful for characterizing phenol degradation. This study proposes a novel method to determine multiplicity of steady states in continuous stirred tank reactors (CSTRs) in order to identify the most appropriate kinetics to characterize the dynamics of phenol biodegradation. PMID:21614192

Wei, Yu-Hong; Chen, Wei-Chuan; Chang, Shan-Ming; Chen, Bor-Yann

2010-01-01

314

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

2014-12-01

315

Fully kinetic simulations of megajoule-scale dense plasma focus  

SciTech Connect

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 10{sup 12} 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.; Tang, V.; Halvorson, C.; May, M. [Lawrence Livermore National Laboratory, Livermore California 94550 (United States); Welch, D. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); Meehan, B. T.; Hagen, E. C. [National Security Technologies, LLC, Las Vegas, Nevada 89030 (United States)

2014-10-15

316

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

317

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

318

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

319

Kinetics of quality changes during food frying.  

PubMed

This paper deals with kinetics of quality changes during food frying. The quality parameters of interests include color, texture, viscoelastic properties, volume/density, and nutraceuticals (Omega 3 fatty acids). The kinetic theory and determination methodology under isothermal/non-isothermal conditions are also reviewed. This paper presents the reported reaction rate constant, order of reaction, and activation energy for specific quality changes including phenomenological observations and important speculations. The changes of color, textural, and viscoelastic properties generally followed a first order reaction. In some studies, activation energy analysis could have been improved by applying corresponding system temperatures for the quality change reactions of interest. The kinetic information on volume/density changes and thermal degradation of nutraceutical is still limited to experimental observations of the changes. PMID:16527755

Hindra, Fransiskus; Baik, Oon-Doo

2006-01-01

320

Chemical Kinetics Database  

National Institute of Standards and Technology Data Gateway

SRD 17 NIST Chemical Kinetics Database (Web, free access)   The NIST Chemical Kinetics Database includes essentially all reported kinetics results for thermal gas-phase chemical reactions. The database is designed to be searched for kinetics data based on the specific reactants involved, for reactions resulting in specified products, for all the reactions of a particular species, or for various combinations of these. In addition, the bibliography can be searched by author name or combination of names. The database contains in excess of 38,000 separate reaction records for over 11,700 distinct reactant pairs. These data have been abstracted from over 12,000 papers with literature coverage through early 2000.

321

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

322

Development of off-gas emission kinetics for stored wood pellets.  

PubMed

A lumped three-reaction kinetic model for off-gas emissions of stored wood pellets in sealed containers has been developed accounting for the formation of CO and CO(2) and the depletion of O(2). Off-gas emission data at different conditions were used to extract kinetic model parameters by numerically fitting the proposed model equations. The fitted kinetic model parameters for different cases showed consistency with one another. With properly estimated model parameters, the current kinetic model can be used to predict off-gas emissions, oxygen depletion, and the buildup of toxic air pollutants in wood pellet storage containers/vessels. PMID:22826538

Fan, Chuigang; Bi, Xiaotao T

2013-01-01

323

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

324

Growth kinetic models for phenol biodegradation in a batch culture of Pseudomonas putida.  

PubMed

Biodegradation of phenol with pure culture of Pseudomonas putida was investigated. P. putida (PTCC 1694) was grown in facultative anaerobic condition at 27 degrees C and media pH value of 7. The effect of initial phenol concentration on the biodegradation rate was studied. The initial concentrations of phenol varied from 300 to 1000 mg/l. Experiments were performed for the duration of seven days while daily samples were withdrawn. The initial rate of biodegradation of phenol increased with initial concentration of 300-500 mg/l. Further increase in phenol concentration resulted in a slight decrease in the rate of biodegradation due to phenol inhibition. It was observed that by increasing the concentration of phenol, the lag phase was prolonged. Phenol is known to be an inhibitory substrate, thus Monod, Haldane and logistic kinetic models were applied to evaluate the growth kinetic parameters. The Monod model was unable to present the growth parameters over the defined concentration range. However, Haldane and logistic models perfectly fitted with the experimental data. The yield coefficients for the growth on phenol at concentrations of 300, 500, 700 and 1000 mg/l were 0.177, 0.062, 0.035 and 0.012 mg/mg, respectively. PMID:22439571

Bakhshi, Zeinab; Najafpour, Ghasem; Kariminezhad, Esmaeel; Pishgar, Roya; Mousavi, Nafise; Taghizade, Tahere

2011-12-01

325

Glutathione reductase: Comparison of steady-state and rapid reaction primary kinetic isotope effects exhibited by the yeast, spinach, and Escherichia coli enzymes  

SciTech Connect

Kinetic parameters for NADPH and NADH have been determined at pH 8.1 for spinach, yeast, and E. coli glutathione reductases. NADPH exhibited low Km values for all enzymes (3-6 microM), while the Km values for NADH were 100 times higher (approximately 400 microM). Under our experimental conditions, the percentage of maximal velocities with NADH versus those measured with NADPH were 18.4, 3.7, and 0.13% for the spinach, yeast, and E. coli enzymes, respectively. Primary deuterium kinetic isotope effects were independent of GSSG concentration between Km and 15Km levels, supporting a ping-pong kinetic mechanism. For each of the three enzymes, NADPH yielded primary deuterium kinetic isotope effects on Vmax only, while NADH exhibited primary deuterium kinetic isotope effects on both V and V/K. The magnitude of DV/KNADH at pH 8.1 is 4.3 for the spinach enzyme, 2.7 for the yeast enzyme, and 1.6 for the E. coli glutathione reductase. The experimentally determined values of TV/KNADH of 7.4, 4.2, and 2.2 for the spinach, yeast, and E. coli glutathione reductases agree well with those calculated from the corresponding DV/KNADH using the Swain-Schaad expression. This suggests that the intrinsic primary kinetic isotope effect on NADH oxidation is fully expressed. In order to confirm this conclusion, single-turnover experiments have been performed. The measured primary deuterium kinetic isotope effects on the enzyme reduction half-reaction using NADH match those measured in the steady state for each of the three glutathione reductases.

Vanoni, M.A.; Wong, K.K.; Ballou, D.P.; Blanchard, J.S. (Albert Einstein College of Medicine, Bronx, NY (USA))

1990-06-19

326

Caged Naloxone Reveals Opioid Signaling Deactivation Kinetics  

PubMed Central

The spatiotemporal dynamics of opioid signaling in the brain remain poorly defined. Photoactivatable opioid ligands provide a means to quantitatively measure these dynamics and their underlying mechanisms in brain tissue. Although activation kinetics can be assessed using caged agonists, deactivation kinetics are obscured by slow clearance of agonist in tissue. To reveal deactivation kinetics of opioid signaling we developed a caged competitive antagonist that can be quickly photoreleased in sufficient concentrations to render agonist dissociation effectively irreversible. Carboxynitroveratryl-naloxone (CNV-NLX), a caged analog of the competitive opioid antagonist NLX, was readily synthesized from commercially available NLX in good yield and found to be devoid of antagonist activity at heterologously expressed opioid receptors. Photolysis in slices of rat locus coeruleus produced a rapid inhibition of the ionic currents evoked by multiple agonists of the ?-opioid receptor (MOR), but not of ?-adrenergic receptors, which activate the same pool of ion channels. Using the high-affinity peptide agonist dermorphin, we established conditions under which light-driven deactivation rates are independent of agonist concentration and thus intrinsic to the agonist-receptor complex. Under these conditions, some MOR agonists yielded deactivation rates that are limited by G protein signaling, whereas others appeared limited by agonist dissociation. Therefore, the choice of agonist determines which feature of receptor signaling is unmasked by CNV-NLX photolysis. PMID:23960100

Banghart, Matthew R.; Shah, Ruchir C.; Lavis, Luke D.

2013-01-01

327

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...

328

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

329

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

330

Kinetics of colour change of kiwifruits during hot air and microwave drying  

Microsoft Academic Search

The kinetics of colour changes of kiwifruits, due to drying by hot air, microwave (MW) and hot air–MW finish drying, were studied. Kinetic parameters for the colour change were determined using Hunter L-, a-, b-values, chroma, Hue, total colour difference and browning index (BI) values. The drying process changed all three colour parameters (L, a, b), causing a colour shift

Medeni Maskan

2001-01-01

331

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

332

Kinetic modeling of individual gaseous component formed from coal in a confined system  

Microsoft Academic Search

Kinetic modeling of individual hydrocarbon formation is important for gas compositional and stable carbon isotopic prediction in a gas field. However, the maximum yields of individual gaseous hydrocarbons vary with heating rates in a confined system. This makes it impossible to kinetically model their formation directly on the basis of first-order reaction models due to the difficulty in assessment of

Yanhua Shuai; Ping’an Peng; Yan-Rong Zou; Shuichang Zhang

2006-01-01

333

Kinetic Profiles in NSTX Plasmas  

SciTech Connect

The National Spherical Torus Experiment (NSTX) is a low aspect ratio (R/a approximately 1.3) device with auxiliary heating from neutral-beam injection (NBI) and high-harmonic fast-wave heating (HHFW). Typical NSTX parameters are R(subscript ''0'') = 85 cm, a = 67 cm, I(subscript ''p'') = 0.7-1.4 MA, B(subscript ''phi'') = 0.25-0.45 T. Three co-directed deuterium neutral-beam sources have injected P(subscript ''NB'') less than or equal to 4.7 MW. HHFW plasmas typically have delivered P(subscript ''RF'') less than or equal to 3 MW. Important to the understanding of NSTX confinement are the new kinetic profile diagnostics: a multi-pulse Thomson scattering system (MPTS) and a charge-exchange recombination spectroscopy (CHERS) system. The MPTS diagnostic currently measures electron density and temperature profiles at 30 Hz at ten spatial locations. The CHERS system has recently become available to measure carbon ion temperature and toroidal flow at 17 radial positions spanning the outer half of the minor radius with 20 msec time resolution during NBI. Experiments conducted during the last year have produced a wide range of kinetic profiles in NSTX. Some interesting examples are presented below.

R.E. Bell; B.P. LeBlanc; C. Bourdelle; D.R. Ernst; E.D. Fredrickson; D.A. Gates; J.C. Hosea; D.W. Johnson; S.M. Kaye; R. Maingi; S. Medley; J.E. Menard; D. Mueller; M. Ono; F. Paoletti; M. Peng; S.A. Sabbagh; D. Stutman; D.W. Swain; E.J. Synakowski; and J.R. Wilson

2001-07-10

334

Kinetic models of immediate exchange  

NASA Astrophysics Data System (ADS)

We propose a novel kinetic exchange model differing from previous ones in two main aspects. First, the basic dynamics is modified in order to represent economies where immediate wealth exchanges are carried out, instead of reshufflings or uni-directional movements of wealth. Such dynamics produces wealth distributions that describe more faithfully real data at small values of wealth. Secondly, a general probabilistic trading criterion is introduced, so that two economic units can decide independently whether to trade or not depending on their profit. It is found that the type of the equilibrium wealth distribution is the same for a large class of trading criteria formulated in a symmetrical way with respect to the two interacting units. This establishes unexpected links between and provides a microscopic foundations of various kinetic exchange models in which the existence of a saving propensity is postulated. We also study the generalized heterogeneous version of the model in which units use different trading criteria and show that suitable sets of diversified parameter values with a moderate level of heterogeneity can reproduce realistic wealth distributions with a Pareto power law.

Heinsalu, Els; Patriarca, Marco

2014-08-01

335

Ginzburg-Landau theory of the bcc-liquid interface kinetic coefficient  

NASA Astrophysics Data System (ADS)

We extend the Ginzburg-Landau (GL) theory of atomically rough bcc-liquid interfaces [Wu et al., Phys. Rev. B 73, 094101 (2006), 10.1103/PhysRevB.73.094101] outside of equilibrium. We use this extension to derive an analytical expression for the kinetic coefficient, which is the proportionality constant ? (n ?) between the interface velocity along a direction n ? normal to the interface and the interface undercooling. The kinetic coefficient is expressed as a spatial integral along the normal direction of a sum of gradient square terms corresponding to different nonlinear density wave profiles. Anisotropy arises naturally from the dependence of those profiles on the angles between the principal reciprocal lattice vectors K?i and n ?. Values of the kinetic coefficient for the (100 ) ,(110 ) , and (111 ) interfaces are compared quantitatively to the prediction of linear Mikheev-Chernov (MC) theory [J. Cryst. Growth 112, 591 (1991), 10.1016/0022-0248(91)90340-B] and previous molecular dynamics (MD) simulation studies of crystallization kinetics for a classical model of Fe. Additional MD simulations are carried out here to compute the relaxation time of density waves in the liquid in order to make this comparison free of fit parameters. The GL theory predicts an expression for ? similar to the MC theory but yields a better agreement with MD simulations for both its magnitude and anisotropy due to a fully nonlinear description of density wave profiles across the solid-liquid interface. In particular, the overall magnitude of ? predicted by GL theory is an order of magnitude larger than predicted by the MC theory. GL theory is also used to derive an inverse relation between ? and the solid-liquid interfacial free energy. The general methodology used here to derive an expression for ? (n ?) also applies to amplitude equations derived from the phase-field-crystal model, which only differ from GL theory by the choice of cubic and higher order nonlinearities in the free-energy density.

Wu, Kuo-An; Wang, Ching-Hao; Hoyt, Jeffrey J.; Karma, Alain

2015-01-01

336

Antibiotic Attack (Kinetic City)  

NSDL National Science Digital Library

This game is a part of the Tau Pack of the Kinetic City site (see description below). In this simulation, the patient's bodies are filled with bacteria. The object is to cure as many patients as possible. Learning concepts enforced here are that antibiotics are specific for the type of bacteria they treat, their strength, and that the bacteria may also become resistant to the bacteria by mutations.KINETIC CITY DESCRIPTION: "Kinetic City" (www.kineticcity.com) is a fun, Web-based after-school science club for kids, ages 8 through 11. It combines exciting online animations and activities with boxes of hands-on science experiments. Children earn "Kinetic City" power points and collect stickers as they complete missions and learn standards-based science content. Here's how it works: The "Kinetic City" super crew (Keisha, Curtis, Megan and Max) needs the help of Earth kids to save their planet Vearth, from the science-distorting computer virus Deep Delete. Each of Deep Delete's 60 hideous strains attacks a different area of science with disastrous consequences. After each attack, teams of Earth kids fight back by viewing a short online animation describing the situation on Vearth; performing a series of activities to re-learn the lost science and going on a mission to Vearth during which they answer science questions and gobble up Deep Delete viruses. Their scores appear on their own Kinetic City Club Web page. "Kinetic City" is produced by the American Association for the Advancement of Science (AAAS), with a grant from the National Science Foundation. AAAS writes the "Project 2061 Benchmarks for Science Literacy," which forms the basis of most state science standards.

American Association for the Advancement of Science (;)

2005-01-01

337

Vanadium (IV) sorption by chitosan: Kinetics and equilibrium  

Microsoft Academic Search

The adsorption of vanadium (IV) by chitosan, a naturally occurring material, is studied according to equilibrium and kinetics. Sorption isotherms are determined and single mechanisms of diffusion are studied. These are regarded as the main limiting steps. The parameters studied are: pH, the initial metal concentration, the particle size of the polymer and the stirring speed. While the fourth parameter

M. Jansson-Charrier; E. Guibal; J. Roussy; B. Delanghe; P. Le Cloirec

1996-01-01

338

Sensitivity, robustness, and identifiability in stochastic chemical kinetics models  

E-print Network

Sensitivity, robustness, and identifiability in stochastic chemical kinetics models Michal' performances is sensitivity analysis (2). Large sensitivity to a parameter suggests that the system's output in an insensitive parameter will have little effect on the behavior. Traditionally, the concept of sensitivity has

Millar, Andrew J.

339

Gas breakdown and secondary electron yields  

NASA Astrophysics Data System (ADS)

In this paper we present a systematic study of the gas breakdown potentials. An analysis of the key elementary processes in low-current low-pressure discharges is given, with an aim to illustrate how such discharges are used to determine swarm parameters and how such data may be applied to modeling discharges. Breakdown data obtained in simple parallel-plate geometry are presented for a number of atomic and molecular gases. Ionization coefficients, secondary electron yields and their influence on breakdown are analyzed, with special attention devoted to non-hydrodynamic conditions near cathode.

Mari?, Dragana; Savi?, Marija; Sivoš, Jelena; Škoro, Nikola; Radmilovi?-Radjenovi?, Marija; Malovi?, Gordana; Petrovi?, Zoran Lj.

2014-06-01

340

Microstructure and Mechanical Properties in Hot-Rolled Extra High-Yield-Strength Steel Plates for Offshore Structure and Shipbuilding  

NASA Astrophysics Data System (ADS)

Key parameters for a thermomechanically controlled processing and accelerated cooling process (TMCP-AcC) were determined for integrated mass production to produce extra high-yield-strength microalloyed low carbon SiMnCrNiCu steel plates for offshore structure and bulk shipbuilding. Confocal scanning microscopy was used to make in-situ observations on the austenite grain growth during reheating. A Gleeble 3800 thermomechanical simulator was employed to investigate the flow stress behavior, static recrystallization (SRX) of austenite, and decomposition behavior of the TMCP conditioned austenite during continuous cooling. The Kocks-Mecking model was employed to describe the constitutive behavior, while the Johnson-Mehl-Avrami-Kolmogorov (JMAK) approach was used to predict the SRX kinetics. The effects of hot rolling schedule and AcC on microstructure and properties were investigated by test-scale rolling trials. The bridging between the laboratory observations and the process parameter determination to optimize the mass production was made by integrated industrial production trials on a set of a 5-m heavy plate mill equipped with an accelerated cooling system. Successful production of 60- and 50-mm-thick plates with yield strength in excess of 460 MPa and excellent toughness at low temperature (213 K (-60 °C)) in the parent metal and the simulated coarse-grained heat affected zone (CGHAZ) provides a useful integrated database for developing advanced high-strength steel plates via TMCP-AcC.

Liu, Dongsheng; Li, Qingliang; Emi, Toshihiko

2011-05-01

341

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

342

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

343

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

344

Dynamic structural effects and ultrafast biomolecular kinetics in photoinduced charge transfer reactions  

SciTech Connect

During the first budget significant progress was made in three areas: (1) assessment of dynamic structural effects accompanying charge transfer, (2) electrochemical assessment of site-to-site electronic coupling in simple inorganic systems, and (3) direct observation of intramolecular electron transfer kinetics in mixed-valence systems. In area 1 the most significant finding was that Franck-Condon parameters for electron transfer (i.e. normal coordinate displacements, vibrational frequencies, and single-mode vibrational reorganizational energy components) could be obtained for weakly interacting (ion-paired) redox systems (J.Phys.Chem., 1991, 95, 10535). Studies in area 3 have yielded results in both the ultrafast (femtosecond/picosecond) time regime (J.Phys.Chem. 1991, 95, 5712) and the intermediate (microsecond/millisecond) time regime (J.Am.Chem. Soc., submitted).

Hupp, J.T.

1992-01-01

345

Kinetic study of biological hydrogen production by anaerobic fermentation  

Microsoft Academic Search

The growth kinetics of hydrogen producing bacteria using three different substrates, namely sucrose, non-fat dry milk (NFDM), and food waste were investigated in dark fermentation through a series of batch experiments. The results showed that hydrogen production potential and hydrogen production rate increased with an increasing substrate concentration. The maximum hydrogen yields from sucrose, NFDM, and food waste were 234,

Wen-Hsing Chen; Shen-Yi Chen; Samir Kumar Khanal; Shihwu Sung

2006-01-01

346

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

347

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

348

Maximum energy yield approach for CPV tracker design  

NASA Astrophysics Data System (ADS)

Foton HC Systems has developed a new CPV tracker model, specially focused on its tracking efficiency and the effect of the tracker control techniques on the final energy yield of the system. This paper presents the theoretical work carried out into determining the energy yield for a CPV system, and illustrates the steps involved in calculating and understanding how energy consumption for tracking is opposed to tracker pointing errors. Additionally, the expressions to compute the optimum parameters are presented and discussed.

Aldaiturriaga, E.; González, O.; Castro, M.

2012-10-01

349

A LQ-based kinetic model formulation for exploring dynamics of treatment response of tumours in patients.  

PubMed

A kinetic bio-mathematical, linear-quadratic (LQ) based model description for clonogenic survival is presented. In contrast to widely used formulations of models, a dynamic approach based on ordinary differential equations for coupling a repair model with a tumour growth model is used to allow analysis of intercellular process dynamics and submodel interference. The purpose of the model formulation is to find a quantitative framework for investigation of tumour response to radiotherapy in vivo. It is not the intention of the proposed model formulation to give a mechanistic explanation for cellular repair processes. This article addresses bio-mathematical aspects of the simplistic kinetic approach used for description of repair. The model formulation includes processes for cellular death, repopulation and cellular repair. The explicit use of the population size in the model facilitates the coupling of the sub-models including aspects of tissue dynamics (competition, oxygenation). The cellular repair is summarized by using a kinetic model for a dose equivalent ? describing production and elimination of sublethal lesions. This dose equivalent replaces the absorbed dose used in the common LQ- model. Therefore, this approach is called the ?- LQ- formulation. A comparison with two kinetic radiobiological models (the LPL model of Curtis and the compartmental model of Carlone) is carried out. The resulting differential equations are solved by numerical integration using a Runge-Kutta algorithm. The comparison reveals a good agreement between the ?- LQ- formulation and the models of Curtis and Carlone under certain, defined conditions: The proposed formulation leads to results which are identical to the model of Carlone over a wide range of investigated biological parameters and different fractionation schemes when using first order repair kinetics. The comparison with experimental data and the LPL- model of Curtis shows a good agreement of the ?- LQ- formulation using second order repair kinetics over a wide range of dose rate. Over a limited range, the use of second order repair in the ?- LQ- formulation approximates the same dose rate dependency of clonogenic survival using only one additional parameter to those of the common LQ model. Within the investigated range of parameters, the presented ?-LQ- formulation may be used to describe the in-vivo tumour response to radiation. The influence of repopulation, oxygenation and other aspects of tissue dynamics may override the differences between the intrinsic radiosensitivity yielded by each of the models. The proposed model formulation can be extended with additional static and dynamic tissue behaviours. This may be useful for the understanding of the reaction of tissues to heat (hyperthermia) or combined anti-cancer treatments (chemo-radiotherapy). PMID:21237624

Scheidegger, Stephan; Lutters, Gerd; Bodis, Stephan

2011-09-01

350

Diode laser welding of high yield steel  

NASA Astrophysics Data System (ADS)

The following article describes results of investigations on influence of laser welding parameters on the weld shape, quality and mechanical properties of 2.5 mm thick butt joints of thermo-mechanically rolled, high yield strength steel for cold forming S420MC (according to EN 10149 - 3 and 060XLK according to ASTM) welded with high power diode laser HPDL ROFIN SINAR DL 020 with rectangular laser beam spot and 2.2 kW output power, and 808 nm wavelength. The investigations at the initial stage were focused on detailed analysis of influence of the basic laser welding parameters such as laser power and welding speed on the shape and quality of single bead produced during bead-on-plate welding. Then the optimal parameters were chosen for laser welding of 2.5 mm thick butt joints of the thermo-mechanically rolled, high yield strength steel sheets for cold forming S420MC. The test joints were prepared as single square groove and one-side laser welded without an additional material, at a flat position. Edges of steel sheets were melted in argon atmosphere by the laser beam focused on the top joint surface. The test welded joints were investigated by visual inspection, metallographic examinations, mechanical tests such as tensile tests and bending tests. It was found that the high power diode laser may be applied successfully for one-side welding of the S420MC steel butt joints. Additionally it was found that in the optimal range of laser welding parameters the high quality joint were produced.

Lisiecki, Aleksander

2013-01-01

351

Application of progress curve analysis to in situ enzyme kinetics using 1H NMR spectroscopy.  

PubMed

The steady-state kinetics of enzymes in tissues, cells, and concentrated lysates can be characterized using high-resolution nuclear magnetic resonance spectroscopy; this is possible because almost invariably there are differences in the spectra of substrates and products of a reaction and these spectra are obtainable even from optically opaque samples. We used 1H spin-echo NMR spectroscopy to study the hydrolysis of alpha-L-glutamyl-L-alanine by cytosolic peptidases of lysed human erythrocytes. Nonlinear regression of the integrated Michaelis-Menten expression onto the progress-curve data yielded, directly, estimates of Vmax and Km for the hydrolase; a procedure for analyzing progress curves in this manner was adapted and compared with a commonly used procedure which employs the Newton-Raphson algorithm. We also performed a sensitivity analysis of the integrated Michaelis-Menten expression; this yielded equations that indicate under what conditions estimates of Km and Vmax are most sensitive to variations in experimental observables. Specifically, we showed that the most accurate estimates of the steady-state parameters from analysis of progress curves are obtained when the initial substrate concentration is much greater than Km. Furthermore, estimates of these parameters obtained by such an analysis are most sensitive to data obtained when the reaction is 60-80% complete, having started with the highest practicable initial substrate concentration. PMID:3013046

Vandenberg, J I; Kuchel, P W; King, G F

1986-05-15

352

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

353

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

354

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

355

Acid soil infertility effects on peanut yields and yield components  

SciTech Connect

The interpretation of soil amelioration experiments with peanuts is made difficult by the unpredictibility of the crop and by the many factors altered when ameliorating acid soils. The present study was conducted to investigate the effects of lime and gypsum applications on peanut kernel yield via the three first order yield components, pods per ha, kernels per pod, and kernel mass. On an acid medium sandy loam soil (typic Plinthustult), liming resulted in a highly significant kernel yield increase of 117% whereas gypsum applications were of no significant benefit. As indicated by path coefficient analysis, an increase in the number of pods per ha was markedly more important in increasing yield than an increase in either the number of kernels per pod or kernel mass. Furthermore, exch. Al was found to be particularly detrimental to pod number. It was postulated that poor peanut yields resulting from acid soil infertility were mainly due to the depressive effect of exch. Al on pod number. Exch. Ca appeared to play a secondary role by ameliorating the adverse effects of exch. Al.

Blamey, F.P.C.

1983-01-01

356

ExoEarth Yield Estimates for a Future Large Aperture Direct Imaging Mission  

NASA Astrophysics Data System (ADS)

ExoEarth yield is a critical science metric that will constrain the required aperture of a future exoplanet-imaging mission. I will present a numerically efficient method for maximizing the yield of exoEarth candidates by simultaneously optimizing the exposure time of every star, number of visits per star, and delay time between visits, while maximally adapting the target list to the mission's capabilities. This method can potentially double the exoEarth candidate yield compared to previous methods. I will show how the yield scales with mission parameters, including aperture size and high level coronagraph parameters, and address the impact of astrophysical uncertainties on exoEarth yield.

Stark, Christopher C.; Roberge, Aki; Mandell, Avi; Domagal-Goldman, Shawn; Stapelfeldt, Karl R.; Robinson, Tyler

2015-01-01

357

Gravitationally Induced Particle Production: Thermodynamics and Kinetic Theory  

E-print Network

A relativistic kinetic description for the irreversible thermodynamic process of gravitationally induced particle production is proposed in the context of an expanding Friedmann-Robertson-Walker (FRW) geometry. We show that the covariant thermodynamic treatment referred to as "adiabatic" particle production provoked by the cosmic time-varying gravitational field has a consistent kinetic counterpart. The variation of the distribution function is associated to a non-collisional kinetic term of quantum-gravitational origin which is proportional to the ratio $\\Gamma/H$, where $\\Gamma$ is the gravitational particle production rate and H is the Hubble parameter. For $\\Gamma reaction effects in the cosmic background.

J. A. S. Lima; I. P. Baranov

2014-11-24

358

A Fluid-kinetic Hybrid Electron Model for Electromagnetic Simulations  

SciTech Connect

A fluid-kinetic hybrid electron model for electromagnetic simulations of finite-beta plasmas is developed based on an expansion of the electron response using the electron-ion mass ratio as a small parameter (Here beta is the ratio of plasma pressure to magnetic pressure.) The model accurately recovers low-frequency plasma dielectric responses and faithfully preserves nonlinear kinetic effects (e.g., phase space trapping). Maximum numerical efficiency is achieved by overcoming the electron Courant condition and suppressing high-frequency modes. This method is most useful for nonlinear kinetic (particle-in-cell or Vlasov) simulations of electromagnetic microturbulence and Alfvenic instabilities in magnetized plasmas.

Zhihong Lin; Liu Chen

2001-01-30

359

End-growth/evaporation living polymerization kinetics revisited  

NASA Astrophysics Data System (ADS)

End-growth/evaporation kinetics in living polymer systems with "association-ready" free unimers (no initiator) is considered theoretically. The study is focused on the systems with long chains (typical aggregation number N ? 1) at long times. A closed system of continuous equations is derived and is applied to study the kinetics of the chain length distribution (CLD) following a jump of a parameter (T-jump) inducing a change of the equilibrium mean chain length from N0 to N. The continuous approach is asymptotically exact for t ? t1, where t1 is the dimer dissociation time. It yields a number of essentially new analytical results concerning the CLD kinetics in some representative regimes. In particular, we obtained the asymptotically exact CLD response (for N ? 1) to a weak T-jump (? = N0/N - 1 ? 1). For arbitrary T-jumps we found that the longest relaxation time tmax = 1/? is always quadratic in N (? is the relaxation rate of the slowest normal mode). More precisely tmax ?4N2 for N0 < 2N and tmax ?NN0/(1 - N/N0) for N0 > 2N. The mean chain length Nn is shown to change significantly during the intermediate slow relaxation stage t1 ? t ? tmax . We predict that N_n(t)-N_n(0)? ?{t} in the intermediate regime for weak (or moderate) T-jumps. For a deep T-quench inducing strong increase of the equilibrium Nn (N ? N0 ? 1), the mean chain length follows a similar law, N_n(t)? ?{t}, while an opposite T-jump (inducing chain shortening, N0 ? N ? 1) leads to a power-law decrease of Nn: Nn(t)?t-1/3. It is also shown that a living polymer system gets strongly polydisperse in the latter regime, the maximum polydispersity index r = Nw/Nn being r* ? 0.77N0/N ? 1. The concentration of free unimers relaxes mainly during the fast process with the characteristic time tf ˜ t1N0/N2. A nonexponential CLD dominated by short chains develops as a result of the fast stage in the case of N0 = 1 and N ? 1. The obtained analytical results are supported, in part, by comparison with numerical results found both previously and in the present paper.

Semenov, A. N.; Nyrkova, I. A.

2011-03-01

360

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

361

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

362

Electrode kinetics: reactions  

Microsoft Academic Search

This is Volume 27 in the Comprehensive Chemical Kinetics series. The contributors are Calvo (Argentina), Hamnett (England), O'Sullivan (United States), and Weaver (United States). The book's chapters cover Redox Reactions at Metal-Solution Interfaces, Semiconductor Electrochemistry, and Reactions at Metal Oxide Electrodes. The references date from the 1960s to the mid-1980s. An index is included.

1987-01-01

363

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.

364

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

365

Kinetics of Emulsion Polymerization  

Microsoft Academic Search

As a basis for understanding emulsion polymerization, the kinetics of free radical reactions in isolated loci is discussed subject to the condition that the free radicals are supplied to the loci from an external source. Three cases of interest are considered: that in which the average number of free radicals per locus is small compared with unity, that in which

Wendell V. Smith; Roswell H. Ewart

1948-01-01

366

THE KINETICS OF OSMOSIS  

PubMed Central

It is shown that by combining the osmotic pressure and rate of diffusion laws an equation can be derived for the kinetics of osmosis. The equation has been found to agree with experiments on the rate of osmosis for egg albumin and gelatin solutions with collodion membranes. PMID:19872368

Northrop, John H.

1927-01-01

367

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

368

Analysis of Enzyme Kinetic Data Analysis of Enzyme Kinetic Data  

E-print Network

Analysis of Enzyme Kinetic Data #12;To Marilú #12;Analysis of Enzyme Kinetic Data ATHEL CORNISH., without restriction. It will be appreciated, however, if any use of it in published work is apopropriately provide a theoretical account of statistical analysis of kinetic data for enzyme-catalysed reactions

369

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

370

Modeling of Fusarium redolens Dzf2 mycelial growth kinetics and optimal fed-batch fermentation for beauvericin production.  

PubMed

Beauvericin (BEA) is a cyclic hexadepsipeptide mycotoxin with notable phytotoxic and insecticidal activities. Fusarium redolens Dzf2 is a highly BEA-producing fungus isolated from a medicinal plant. The aim of the current study was to develop a simple and valid kinetic model for F. redolens Dzf2 mycelial growth and the optimal fed-batch operation for efficient BEA production. A modified Monod model with substrate (glucose) and product (BEA) inhibition was constructed based on the culture characteristics of F. redolens Dzf2 mycelia in a liquid medium. Model parameters were derived by simulation of the experimental data from batch culture. The model fitted closely with the experimental data over 20-50 g l(-1) glucose concentration range in batch fermentation. The kinetic model together with the stoichiometric relationships for biomass, substrate and product was applied to predict the optimal feeding scheme for fed-batch fermentation, leading to 54% higher BEA yield (299 mg l(-1)) than in the batch culture (194 mg l(-1)). The modified Monod model incorporating substrate and product inhibition was proven adequate for describing the growth kinetics of F. redolens Dzf2 mycelial culture at suitable but not excessive initial glucose levels in batch and fed-batch cultures. PMID:21082211

Xu, Li-Jian; Liu, Yuan-Shuai; Zhou, Li-Gang; Wu, Jian-Yong

2011-09-01

371

Relativistic kinetic theory: An introduction  

NASA Astrophysics Data System (ADS)

We present a brief introduction to the relativistic kinetic theory of gases with emphasis on the underlying geometric and Hamiltonian structure of the theory. Our formalism starts with a discussion on the tangent bundle of a Lorentzian manifold of arbitrary dimension. Next, we introduce the Poincaré one-form on this bundle, from which the symplectic form and a volume form are constructed. Then, we define an appropriate Hamiltonian on the bundle which, together with the symplectic form yields the Liouville vector field. Whenever the corresponding flow is restricted to special submanifolds of the tangent bundle, referred to as future mass shells, its projection onto the base manifold describes families of future-directed timelike geodesics. A collisionless simple gas is described by a distribution function on a particular mass shell, satisfying the Liouville equation. Fibre integrals of the distribution function determine the particle current density and the stress-energy tensor. We show that the stress-energy tensor satisfies the familiar energy conditions and that both the current density and stress-energy tensor are divergence-free. Our discussion also includes the generalization to charged gases, a summary of the Einstein-Maxwell-Vlasov system in any dimensions, as well as a brief introduction to the general relativistic Boltzmann equation for a simple gas.

Sarbach, Olivier; Zannias, Thomas

2013-07-01

372

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

373

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

374

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

375

An empirical formula for angular dependence of sputtering yields  

Microsoft Academic Search

An analytic empirical formula for the angular dependence of light-ion sputtering and heavy-ion sputtering has been proposed. The present empirical formula has two adjustable parameters which are determined by the least-squares method. One of the two parameters corresponds to Sigmundf, and the other is the angle of incidence at the maximum yield. The present empirical formula is found to be

Y. Yamamura; Shigeru Shindo

1984-01-01

376

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

377

An Introductory Level Kinetics Investigation.  

ERIC Educational Resources Information Center

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

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

1980-01-01

378

Accuracy Analysis of Anisotropic Yield Functions based on the Root-Mean Square Error  

SciTech Connect

This paper evaluates the accuracy of popular anisotropic yield functions based on the root-mean square error (RMSE) of the yield stresses and the R-values. The yield functions include Hill48, Yld89, Yld91, Yld96, Yld2000-2d, BBC2000 and Yld2000-18p yield criteria. Two kind steels and five kind aluminum alloys are selected for the accuracy evaluation. The anisotropic coefficients in yield functions are computed from the experimental data. The downhill simplex method is utilized for the parameter evaluation for the yield function except Hill48 and Yld89 yield functions after the error functions are constructed. The yield stresses and the R-values at every 15 deg. from the rolling direction (RD) and the yield stress and R-value at equibiaxial tension conditions are predicted from each yield function. The predicted yield stresses and R-values are then compared with the experimental data. The root-mean square errors (RMSE) are computed to quantitatively evaluate the yield function. The RMSEs are calculated for the yield stresses and the R-values separately because the yield stress difference is much smaller that the difference in the R-values. The RMSEs of different yield functions are compared for each material. The Hill48 and Yld89 yield functions are the worst choices for the anisotropic description of the yield stress anisotropy while Yld91 yield function is the last choice for the modeling of the R-value directionality. Yld2000-2d and BBC2000 yield function have the same accuracy on the modeling of both the yield stress anisotropy and the R-value anisotropy. The best choice is Yld2000-18 yield function to accurately describe the yield tress and R-value directionalities of sheet metals.

Huh, Hoon; Lou, Yanshan; Bae, Gihyun; Lee, Changsoo [School of Mechanical, Aerospace, and Systems Engineering, KAIST, 335, Gwahangno, Daedoek Science Town, Daejeon, 305-701 (Korea, Republic of)

2010-06-15

379

Parameter identification of thermophilic anaerobic degradation of valerate.  

PubMed

The considered mathematical model of the decomposition of valerate presents three unknown kinetic parameters, two unknown stoichiometric coefficients, and three unknown initial concentrations for biomass. Applying a structural identifiability study, we concluded that it is necessary to perform simultaneous batch experiments with different initial conditions for estimating these parameters. Four simultaneous batch experiments were conducted at 55 degrees C, characterized by four different initial acetate concentrations. Product inhibition of valerate degradation by acetate was considered. Practical identification was done optimizing the sum of the multiple determination coefficients for all measured state variables and for all experiments simultaneously. The estimated values of kinetic parameters and stoichiometric coefficients were characterized by the parameter correlation matrix, the confidence interval, and the student's t-test at 5% significance level with positive results except for the saturation constant, for which more experiments for improving its identifiability should be conducted. In this article, we discuss kinetic parameter estimation methods. PMID:12794283

Flotats, Xavier; Ahring, Birgitte K; Angelidaki, Irini

2003-01-01

380

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

381

Kinetic modeling of [{sup 99m}Tc]TRODAT-1: A novel compound for imaging the dopamine transporter  

SciTech Connect

The purpose of this study was to characterize the in vivo binding potential and kinetic rate constants in baboons. A series of three SPECT scans were performed in each of two baboons with a mean bolus injection of 717 {+-} 78 Mbq (19.38 {+-} 2.12 mCi). Dynamic images of the brain were acquired over four hours using a triple-headed camera equipped with fan-beam collimators. Arterial and venous blood compartments were frequently sampled using a peristaltic pump throughout the duration of the study. SPECT images were reconstructed and corrected for attenuation. Regions of interest (ROIs) were placed on the corresponding MRI reference scan to which each functional image was coregistered. Arterial and venous blood samples were corrected for metabolism and converted to units of concentration in the reconstruction domain using experimentally measured calibration factors for the camera. Using analytical solutions to the three-compartment model with the Levenberg-Marquardt minimization technique, each study was individually fit to a kinetic parameter vector. Additionally within each subject the three corresponding studies were fit to a single parameter vector by constraining the binding potential, distribution volume, and dissociation rate constant to improve the identifiability of the convergent solutions. A Monte Carlo simulator provided covariance matrix estimates for parameter vectors. The results showed that [{sup 99m}Tc]TRODAT-1 localized in the basal ganglia. SPECT image analysis of the caudate yielded binding potential values of 2.16 and 2.91 in the first baboon and 3.30, 2.70, and 2.89 in the second baboon. The respective binding potential values for these subjects using the simultaneous fitting technique yielded values of 2.30 and 1.95. Similar values were obtained for the putamen.

Kushner, S.A.; McElgin, W.T.; Kung, M.P. [Univ. of Pennsylvania, Philadelphia, PA (United States)] [and others

1997-05-01

382

Kinetic studies for advanced iodine laser concepts  

NASA Astrophysics Data System (ADS)

Recent studies of the iodine dissociation mechanism for COIL systems have prompted new investigations of the energy transfer kinetics of O2(b1?+). Additional motivation for these studies, and for investigation of the quenching of I* by O atoms, is derived from efforts to build non-chemical singlet oxygen generators. Discharge generators produce relatively high concentrations of O2(b) and O atoms. Dissociations of I2 by the reagent streams from these generators will follow different kinetic pathways than those that are most important when the flow from a chemical generator is used. To improve our understanding of conventional COIL systems, and gain insights concerning the dissociation kinetics that will be relevant for discharge driven COIL devices we have examined the quenching of O2(b) and O2(a) by I2, and the deactivation of I* by atomic oxygen. The primary findings are: (1) Quenching of O2(b) by I2 is fast (5.8x10-11 cm3 s-1) with a branching fraction of 0.4 for the channel O2(b)+I2-->O2(a)+I2. (2) The quantum yield for dissociation of I2 by O2(b) is relatively high (>0.5) and (3) The upper bound for the rate constant for quenching of I* by O atoms is k<2x10-12 cm3 s-1.

Han, Jiande; Komissarov, Anatoly V.; Tinney, Scott P.; Heaven, Michael C.; Davis, Steven J.; Lee, Seonkyung

2005-03-01

383

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

384

A mechanistic description of radiation-induced damage to normal tissue and its healing kinetics  

NASA Astrophysics Data System (ADS)

We introduce a novel mechanistic model of the yield of tissue damage at the end of radiation treatment and of the subsequent healing kinetics. We find explicit expressions for the total number of functional proliferating cells as well as doomed (functional but non-proliferating) cells as a function of time post treatment. This leads to the possibility of estimating—for any given cohort of patients undergoing radiation therapy—the probability distribution of those kinetic parameters (e.g. proliferation rates) that determine times to injury onset and ensuing resolution. The model is suitable for tissues with simple duplication organization, meaning that functionally competent cells are also responsible for tissue renewal or regeneration following injury. An extension of the model to arbitrary temporal patterns of dose rate is presented. To illustrate the practical utility of the model, as well as its limitations, we apply it to data on the time course of urethral toxicity following fractionated radiation treatment and brachytherapy for prostate cancer.

Hanin, Leonid; Zaider, Marco

2013-02-01

385

Pentachlorophenol aerobic removal in a sequential reactor: start-up procedure and kinetic study.  

PubMed

This study has demonstrated the applicability of a simple technology such as the sequencing batch reactor (SBR), operated with suspended biomass, to the aerobic biodegradation of a highly toxic compound, the pentachlorophenol (PCP). An enrichment of a microbial consortium, originated from the biomass of an urban wastewater treatment plant, was performed and 70 days were sufficient to achieve removal efficiencies of ?90% with the compound fed as only carbon and energy source Once completed the start-up period, the SBR was operated with the acclimatized biomass for 60 days at a feed concentration of PCP in the range of 10-20?mg?L(-1). Improved performance was observed at increased influent concentration and the reached removal efficiency for the highest concentrations was stable at values ?90%. Kinetic and stoichiometric characterization of the acclimated biomass was performed with biodegradation tests carried out in the bioreactor during the reaction phase. The classical and a modified four-parameter forms of the Haldane equation were applied to model the substrate inhibited kinetics. Both models provided reliable predictions with high correlation coefficients (>0.99). The biomass characterization was completed with the evaluation of the growth yield coefficient, Y (0.075 on chemical oxygen demand base) and endogenous respiration rate, b (0.054?d(-1)). The aerobic SBR, operated in the metabolic mode with a mixed culture, showed superior performance in comparison to continuous systems applied in the same range of PCP influent loads and achieved removal rates are suitable for application. PMID:25514134

Mosca Angelucci, Domenica; Tomei, M Concetta

2015-02-01

386

Dissociation Kinetics of the Streptavidin-Biotin Interaction Measured Using Direct Electrospray Ionization Mass Spectrometry Analysis  

NASA Astrophysics Data System (ADS)

Dissociation rate constants ( k off ) for the model high affinity interaction between biotin (B) and the homotetramer of natural core streptavidin (S4) were measured at pH 7 and temperatures ranging from 15 to 45 °C using electrospray ionization mass spectrometry (ESI-MS). Two different approaches to data analysis were employed, one based on the initial rate of dissociation of the (S4 + 4B) complex, the other involving nonlinear fitting of the time-dependent relative abundances of the (S4 + iB) species. The two methods were found to yield k off values that are in good agreement, within a factor of two. The Arrhenius parameters for the dissociation of the biotin-streptavidin interaction in solution were established from the k off values determined by ESI-MS and compared with values measured using a radiolabeled biotin assay. Importantly, the dissociation activation energies determined by ESI-MS agree, within 1 kcal mol-1, with the reported value. In addition to providing a quantitative measure of k off , the results of the ESI-MS measurements revealed that the apparent cooperative distribution of (S4 + iB) species observed at short reaction times is of kinetic origin and that sequential binding of B to S4 occurs in a noncooperative fashion with the four ligand binding sites being kinetically and thermodynamically equivalent and independent.

Deng, Lu; Kitova, Elena N.; Klassen, John S.

2013-01-01

387

Dispersive kinetics of nonphotochemical hole burning and spontaneous hole filling: Cresyl Violet in polyvinyl films  

SciTech Connect

The dispersive kinetics of nonphotochemical burning and spontaneous filling of the zero-phonon hole of Cresyl Violet in polyvinyl alcohol at 1.6 K are analyzed in terms of the standard external two-level system (TLS{sub {ital ezt}}) model for probe--glass systems and a distribution function for the tunnel frequency derived from a normal distribution function for the tunnel parameter {lambda}. Average values for the relaxation rates for burning and filling are determined. It is shown that the dominant mechanism for filling is not global spectral diffusion but rather antihole reversion. A high degree of positive correlation between the rates of burning and filling associated with the TLS{sub {ital ext}} is found. A new methodology that permits a more physically reasonable interpretation of spontaneous hole-filling kinetics is described. It is based on the hypothesis that only a fraction of burned sites, on reversion to the ground state, yield sites with resonance frequencies that lie within the hole profile.

Shu, L.; Small, G.J. (Department of Chemistry and Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, Iowa 50011 (United States))

1992-05-01

388

hp calculators HP 50g Bond Yield  

E-print Network

rate the bond pays is fixed when the bond is first sold or issued, but changes in the market interesthp calculators HP 50g Bond Yield The FINANCE menu Bond Yield Practice solving for the yield of a bond #12;hp calculators HP 50g Bond Yield hp calculators - 2 - HP 50g Bond Yield The FINANCE menu

Vetter, Frederick J.

389

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

390

Reversible Chemical Kinetics Model  

NSDL National Science Digital Library

The Reversible Chemical Kinetics Model illustrates the time evolution of a reversible chemical reaction, from a given set of initial reactants concentration until chemical equilibrium is reached. The concentrations are plotted against time and the respective numerical values are periodically displayed at the data Table. As chemical equilibrium is attained, the concentrations become constant, the reaction quotient (Q) equalizes the equilibrium constant and Gibbs's energy change (G/RT) approaches zero. The Reversible Chemical Kinetics Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Fernandes, Fernando S.

2012-10-20

391

Kinetic Actviation Relaxation Technique  

E-print Network

We present a detailed description of the kinetic Activation-Relaxation Technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si, self-interstitial diffusion in Fe and structural relaxation in amorphous silicon.

Béland, Laurent Karim; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand

2011-01-01

392

Running kinetic inflation  

SciTech Connect

We study a recently proposed running kinetic inflation model in which the inflaton potential becomes flat due to rapid growth of the kinetic term at large inflaton field values. As concrete examples, we build a variety of chaotic inflation models in supergravity with e.g. quadratic, linear, and fractional-power potentials. The power of the potential generically increases after inflation, and the inflaton is often massless at the potential minimum in the supersymmetric limit, which leads to many interesting phenomena. First, the light inflaton mass greatly relaxes severe thermal and non-thermal gravitino problems. Secondly, the kination epoch is naturally present after inflation, which may enhance the gravity waves. Thirdly, since the inflaton is light, it is likely coupled to the Higgs sector for successful reheating. The inflaton and its superpartner, inflatino, may be produced at the LHC. Interestingly, the inflatino can be dark matter, if it is the lightest supersymmetric particle.

Nakayama, Kazunori [Theory Center, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Takahashi, Fuminobu, E-mail: kazunori@post.kek.jp, E-mail: fuminobu.takahashi@ipmu.jp [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Chiba 277-8583 (Japan)

2010-11-01

393

Kinetic Tetrazolium Microtiter Assay  

NASA Technical Reports Server (NTRS)

Kinetic tetrazolium microtiter assay (KTMA) involves use of tetrazolium salts and Triton X-100 (or equivalent), nontoxic, in vitro color developer solubilizing colored metabolite formazan without injuring or killing metabolizing cells. Provides for continuous measurement of metabolism and makes possible to determine rate of action of antimicrobial agent in real time as well as determines effective inhibitory concentrations. Used to monitor growth after addition of stimulatory compounds. Provides for kinetic determination of efficacy of biocide, greatly increasing reliability and precision of results. Also used to determine relative effectiveness of antimicrobial agent as function of time. Capability of generating results on day of test extremely important in treatment of water and waste, disinfection of hospital rooms, and in pharmaceutical, agricultural, and food-processing industries. Assay also used in many aspects of cell biology.

Pierson, Duane L.; Stowe, Raymond; Koenig, David

1993-01-01

394

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

395

Stochastic Convenience Yield and the Pricing of Oil Contingent Claims  

Microsoft Academic Search

This paper develops and empirically tests a two-factor model for pricing financial and real assets contingent on the price of oil. The factors are the spot price of oil and the instantaneous convenience yield. The parameters of the model are estimated using weekly oil futures contract prices from January 1984 to November 1988, and the model's performance is assessed out

Rajna Gibson; Eduardo S. Schwartz

1990-01-01

396

Kinetic resolution of ?-substituted alkanoic acids promoted by homobenzotetramisole.  

PubMed

A new method for catalytic nonenzymatic kinetic resolution of ?-substituted alkanoic acids has been developed, which relies on their activation with DCC followed by enantioselective alcoholysis of the intermediate symm-anhydrides in the presence of the amidine-based catalyst homobenzotetramisole (HBTM). Moderate to excellent selectivity factors (s=5-96) have been obtained in the case of several classes of substrates, namely, ?-aryl-, ?-aryloxy/alkoxy-, ?-halo-, ?-azido-, and ?-phthalimido-alkanoic acids. Under similar conditions, ?-(arylthio/alkylthio)-alkanoic acids undergo dynamic kinetic resolution providing corresponding esters in up to 92% ee and up to 93% yield. PMID:21922562

Yang, Xing; Birman, Vladimir B

2011-09-26

397

Silicate precursors: chemical kinetics  

SciTech Connect

This study employed high resolution /sup 29/Si NMR spectroscopy to measure the time evolution of the chemical species in the acid catalyzed Si(OCH/sub 3/)/sub 4/:CH/sub 3/OH:H/sub 2/O sol-gel system. Results support a theoretical model in which the reaction kinetics are described by three functional group rate constants and appropriate statistical factors.

Kay, Bruce D.; Assink, R.A.

1987-01-01

398

Nova Dust Nucleation: Kinetics and Photodissociation  

E-print Network

Dust is observed to form in nova ejecta. The grain temperature is determined by the diluted nova radiation field rather than the gas kinetic temperature, making classical nucleation theory inapplicable. We used kinetic equations to calculate the growth of carbon nuclei in these ejecta. For expected values of the parameters too many clusters grew, despite the small sticking probability of atoms to small clusters, and the clusters only reached radii of about 100\\AA\\ when the carbon vapor was depleted. We then included the effects of cluster photodissociation by ultraviolet radiation from the nova. This suppresses nucleation, but too well, and no grains form at all. Finally we suggest that a few growing carbon nuclei may be protected from photodissociation by a sacrificial surface layer of hydrogen.

D. J. Johnson; M. W. Friedlander; J. I. Katz

1992-04-30

399

Nova dust nucleation - Kinetics and photodissociation  

NASA Technical Reports Server (NTRS)

Dust is observed to form in nova ejecta. The grain temperature is determined by the diluted nova radiation field rather than the gas kinetic temperature, making classical nucleation theory inapplicable. We used kinetic equations to calculate the growth of carbon nuclei in these ejecta. For expected values of the parameters too many clusters grew, despite the small sticking probability of atoms to small clusters, and the clusters only reached radii of about 100 A when the carbon vapor was depleted. We then included the effects of cluster photodissociation by ultraviolet radiation from the nova. This suppresses nucleation, but too well, and no grains form at all. Finally we suggest that a few growing carbon nuclei may be protected from photodissociation by a sacrificial surface layer of hydrogen.

Johnson, D. J.; Friedlander, M. W.; Katz, J. I.

1993-01-01

400

Optimal Experimental Design for Parameter Estimation of a Cell Signaling Model  

PubMed Central

Differential equation models that describe the dynamic changes of biochemical signaling states are important tools to understand cellular behavior. An essential task in building such representations is to infer the affinities, rate constants, and other parameters of a model from actual measurement data. However, intuitive measurement protocols often fail to generate data that restrict the range of possible parameter values. Here we utilized a numerical method to iteratively design optimal live-cell fluorescence microscopy experiments in order to reveal pharmacological and kinetic parameters of a phosphatidylinositol 3,4,5-trisphosphate (PIP3) second messenger signaling process that is deregulated in many tumors. The experimental approach included the activation of endogenous phosphoinositide 3-kinase (PI3K) by chemically induced recruitment of a regulatory peptide, reversible inhibition of PI3K using a kinase inhibitor, and monitoring of the PI3K-mediated production of PIP3 lipids using the pleckstrin homology (PH) domain of Akt. We found that an intuitively planned and established experimental protocol did not yield data from which relevant parameters could be inferred. Starting from a set of poorly defined model parameters derived from the intuitively planned experiment, we calculated concentration-time profiles for both the inducing and the inhibitory compound that would minimize the predicted uncertainty of parameter estimates. Two cycles of optimization and experimentation were sufficient to narrowly confine the model parameters, with the mean variance of estimates dropping more than sixty-fold. Thus, optimal experimental design proved to be a powerful strategy to minimize the number of experiments needed to infer biological parameters from a cell signaling assay. PMID:19911077

Bandara, Samuel; Schlöder, Johannes P.; Eils, Roland; Bock, Hans Georg; Meyer, Tobias

2009-01-01

401

Chemical Kinetic Modeling of Hydrogen Combustion Limits  

SciTech Connect

A detailed chemical kinetic model is used to explore the flammability and detonability of hydrogen mixtures. In the case of flammability, a detailed chemical kinetic mechanism for hydrogen is coupled to the CHEMKIN Premix code to compute premixed, laminar flame speeds. The detailed chemical kinetic model reproduces flame speeds in the literature over a range of equivalence ratios, pressures and reactant temperatures. A series of calculation were performed to assess the key parameters determining the flammability of hydrogen mixtures. Increased reactant temperature was found to greatly increase the flame speed and the flammability of the mixture. The effect of added diluents was assessed. Addition of water and carbon dioxide were found to reduce the flame speed and thus the flammability of a hydrogen mixture approximately equally well and much more than the addition of nitrogen. The detailed chemical kinetic model was used to explore the detonability of hydrogen mixtures. A Zeldovich-von Neumann-Doring (ZND) detonation model coupled with detailed chemical kinetics was used to model the detonation. The effectiveness on different diluents was assessed in reducing the detonability of a hydrogen mixture. Carbon dioxide was found to be most effective in reducing the detonability followed by water and nitrogen. The chemical action of chemical inhibitors on reducing the flammability of hydrogen mixtures is discussed. Bromine and organophosphorus inhibitors act through catalytic cycles that recombine H and OH radicals in the flame. The reduction in H and OH radicals reduces chain branching in the flame through the H + O{sub 2} = OH + O chain branching reaction. The reduction in chain branching and radical production reduces the flame speed and thus the flammability of the hydrogen mixture.

Pitz, W J; Westbrook, C K

2008-04-02

402

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 for the enhancing of its production by employing L18 orthogonal array design of experiments. At optimum conditions of sugarcane molasses 50 g l(-1), soybean oil 50 g l(-1), inoculum size 5% (v/v), temperature 30 degrees C, inoculum age 2 days, and agitation 200 rpm, the yeast produced almost equal amounts of the product in batch shake flasks and in a 3-l fermentor without any pH control (45 and 47 g l(-1), respectively). However, the yield increased to 60 g l(-1) in the fermentor under controlled pH environment. Time course of SL production, yeast biomass growth, and utilization of sugarcane molasses and soybean oil at these optimized conditions were fitted to existing kinetic models reported in the literature. Estimated kinetic parameters from these models suggested that conventional medium containing glucose can very well be replaced with the present low-cost fermentative medium. PMID:19834651

Daverey, Achlesh; Pakshirajan, Kannan

2010-04-01

403

Reaction kinetics, geospeedometry, and relaxation theory  

NASA Astrophysics Data System (ADS)

This paper explores the application of homogeneous reaction kinetics to geospeedometry and to structural relaxation theory. Numerical simulations of reaction kinetics during cooling for some first- and second-order elementary reactions have been carried out to systematically examine the effects of kinetic parameters and cooling histories on the final speciation. An analytical solution for a special case of first-order reaction A ? B has also been obtained. On the basis of both the analytical solution and the numerical simulation, the cooling rate ( -dT/dt) at the apparent equilibrium temperature ( T ae, obtained by measuring 'quenched' speciation) and the relaxation time scale ( ? r, the time for the departure from equilibrium to decrease to 1/e of the initial departure) at T ae can be approximately related as follows: (-dT/dt)| T=T ae ? 2RT ae/max( E f, E b) where R is the gas constant, and max( E f, E b) is the greater of E f and E b, which are the activation energies of the forward and backward reactions. This approximation works well when the initial temperature ( T 0) is high such that ? r(T 0) is small compared to the cooling time scale. Using the above relation, the cooling rate at T ae can be estimated easily and the cooling history of a natural assemblage can be inferred if enough homogeneous reactions are characterized. Relaxation of homogeneous reactions during the quench of a silicate melt into a glass can be studied quantitatively using the above method if the kinetic parameters are known. Melt-glass transitions probably involve the quenching of many homogeneous reactions that may have different T ae for a given quench rate, and are thus complicated. Authors have previously discussed relaxation of a reaction during cooling using the idea of a melt-glass transition. Because glass relaxation is complicated and the theory is still in its infancy, whereas reaction kinetics can be understood and quantified, it may be more productive to study the relaxation of homogeneous reactions directly and to study glass relaxation using the concept of reaction kinetics instead.

Zhang, Youxue

1994-04-01

404

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

405

Kinetics of inorganic carbon utilization by microalgal biofilm in a flat plate photoreactor.  

PubMed

A kinetic model was developed to describe inorganic carbon utilization by microalgae biofilm in a flat plate photoreactor. The model incorporates the fundamental mechanisms of diffusive mass transport and biological reaction of inorganic carbon by microalgal biofilm. An advanced numerical technique, the orthogonal collocation method and Gear's method, was employed to solve this kinetic model. The model solutions included the concentration profiles of inorganic carbon in the microalgal biofilm, the growths of suspended microalgae and microalgal biofilm, the effluent concentrations of inorganic carbon, and the flux of inorganic carbon from bulk liquid into biofilm. The batch kinetic test was independently conducted to determine biokinetic parameters used in the microalgal biofilm model simulation while initial thickness of microalgal biofilm were assumed. A laboratory-scale flat plate photoreactor with a high recycle flow rate was setup and conducted to verify the model. The volume of photoreactor is 60 l which yields a hydraulic retention time of 1.67 days. The model-generated inorganic carbon and the suspended microalgae concentration curves agreed well with those obtained in the laboratory-scale test. The fixation efficiencies of HCO(3)(-) and CO(2) are 98.5% and 90% at a steady-state condition, respectively. The concentration of suspended microalgal cell reached up to 12 mg/l at a maximum growth rate while the thickness of microalgal biofilm was estimated to be 104 microm at a steady-state condition. The approaches of experiments and model simulation presented in this study could be employed for the design of a flat plate photoreactor to treat CO(2) by microalgal biofilm in a fossil-fuel power plant. PMID:13129518

Lin, Yen H; Leu, Jyh Y; Lan, Chi R; Lin, P-Hsiu P; Chang, Fuh L

2003-11-01

406

Metastable Solution Thermodynamic Properties and Crystal Growth Kinetics  

NASA Technical Reports Server (NTRS)

The crystal growth rates of NH4H2PO4, KH2PO4, (NH4)2SO4, KAl(SO4)2 central dot 12H2O, NaCl, and glycine and the nucleation rates of KBr, KCl, NaBr central dot 2H2O, (NH4)2Cl, and (NH4)2SO4 were expressed in terms of the fundamental driving force of crystallization calculated from the activity of supersaturated solutions. The kinetic parameters were compared with those from the commonly used kinetic expression based on the concentration difference. From the viewpoint of thermodynamics, rate expressions based on the chemical potential difference provide accurate kinetic representation over a broad range of supersaturation. The rates estimated using the expression based on the concentration difference coincide with the true rates of crystallization only in the concentration range of low supersaturation and deviate from the true kinetics as the supersaturation increases.

Kim, Soojin; Myerson, Allan S.

1996-01-01

407

Hole transfer kinetics of DNA.  

PubMed

Not long after the discovery of the double-helical structure of DNA in 1952, researchers proposed that charge transfer along a one-dimensional ?-array of nucleobases might be possible. At the end of the 1990s researchers discovered that a positive charge (a hole) generated in DNA migrates more than 200 Å along the structure, a discovery that ignited interest in the charge-transfer process in DNA. As a result, DNA became an interesting potential bottom-up material for constructing nanoelectronic sensors and devices because DNA can form various complex two-dimensional and three-dimensional structures, such as smiley faces and cubes. From the fundamental aspects of the hole transfer process, DNA is one of the most well-studied organic molecules with many reports on the synthesis of artificial nucleobase analogues. Thus, DNA offers a unique system to study how factors such as the HOMO energy and molecular flexibility affect hole transfer kinetics. Understanding the hole transfer mechanism requires a discussion of the hole transfer rate constants (kHT). This Account reviews the kHT values determined by our group and by Lewis and Wasielewski's group, obtained by a combination of the synthesis of modified DNA and time-resolved spectroscopy. DNA consists of G/C and A/T base pairs; the HOMO localizes on the purine bases G and A, and G has a lower oxidation potential and a higher energy HOMO. Typically, long-range hole transfer proceeded via sequential hole transfer between G/C's. The kinetics of this process in DNA sequences, including those with mismatches, is reproducible via kinetic modeling using the determined kHT for each hole transfer step between G/C's. We also determined the distance dependence parameter (?), which describes the steepness of the exponential decrease of kHT. Because of this value, >0.6 Å(-1) for hole transfer in DNA, DNA itself does not serve as a molecular wire. Interestingly, hole transfer proceeded exceptionally fast for some sequences in which G/C's are located close to each other, an observation that we cannot explain by a simple sequential hole transfer between G/C's but rather through hole delocalization over the nucleobases. To further investigate and refine the factors that affect kHT, we examined various artificial nucleobases. We clearly demonstrated that kHT depends strongly on the HOMO energy gap between the bases (?HOMO), and that kHT can be increased with decreasing ?HOMO. We reduced ?HOMO between the two type of base pairs by replacing adenines (A's) with deazaadenines ((z)A's) or diaminopurines (D's) and showed that the hole transfer rate through the G/C and A/T mix sequence increased by more than 3 orders of magnitude. We also investigated how DNA flexibility affects kHT. Locked nucleic acid (LNA) modification, which makes DNA more rigid, lowered kHT by more than 2 orders of magnitude. On the other hand, 5-Me-2'-deoxyzebularine (B) modification, which increases DNA flexibility, increased kHT by more than 1 order of magnitude. These new insights in hole transfer kinetics obtained from modified DNAs may aid in the design of new molecular-scale conducting materials. PMID:23805774

Kawai, Kiyohiko; Majima, Tetsuro

2013-11-19

408

Deep subthreshold photofission yields analysis  

Microsoft Academic Search

Photofission yield measurements on ²³²Th and \\/sup 235,236,238\\/U, showing the ''shelf effect,'' have been analyzed in terms of a double-humped fission barrier. From the characteristic of the shelf it was possible to evaluate the excitation energy E\\/sub II\\/ of the shape isomer. In the framework of the double-humped barrier, with the competition between ..gamma.. decay to the shape isomer and

G. Bellia; A. Del Zoppo; E. Migneco; R. C. Barna; D. De Pasquale

1979-01-01

409

Controlled reforestation can raise yield  

SciTech Connect

Reforestation in tropical countries by means of controlled man-made plantations of exotic species could increase the yield of fiber by something in the order of 20 to 30 cubic metres per hectare per annum. With the move away from wood in the solid to reconstituted wood products, this enormous annual increment could have significant effects on supply prospects and reduce the need for tropical forest destruction.

Gammie, J.I.

1981-04-25

410

Identification of slow molecular order parameters for Markov model construction  

E-print Network

Identification of slow molecular order parameters for Markov model construction Guillermo Pérez JOURNAL OF CHEMICAL PHYSICS 139, 015102 (2013) Identification of slow molecular order parameters-equation models, and kinetic network models, start by discretizing the high-dimensional state space

411

EFFECT OF SELECTED PARAMETERS ON PREDICTIONS OF A PHOTOCHEMICAL MODEL  

EPA Science Inventory

A sensitivity study was undertaken to assess the effect of selected parameters on the predictions of a photochemical kinetics model. The model was previously developed for use in designing control requirements for ozone reduction in urban areas. The parameters varied in the prese...

412

Estimates of Sputter Yields of Solar-Wind Heavy Ions of Lunar Regolith Materials  

NASA Technical Reports Server (NTRS)

At energies of approximately 1 keV/amu, solar-wind protons and heavy ions interact with the lunar surface materials via a number of microscopic interactions that include sputtering. Solar-wind induced sputtering is a main mechanism by which the composition of the topmost layers of the lunar surface can change, dynamically and preferentially. This work concentrates on sputtering induced by solar-wind heavy ions. Sputtering associated with slow (speeds the electrons speed in its first Bohr orbit) and highly charged ions are known to include both kinetic and potential sputtering. Potential sputtering enjoys some unique characteristics that makes it of special interest to lunar science and exploration. Unlike the yield from kinetic sputtering where simulation and approximation schemes exist, the yield from potential sputtering is not as easy to estimate. This work will present a preliminary numerical scheme designed to estimate potential sputtering yields from reactions relevant to this aspect of solar-wind lunar-surface coupling.

Barghouty, Abdulmasser F.; Adams, James H., Jr.

2008-01-01

413

Potassium kinetics during hemodialysis.  

PubMed

Hyperkalemia in hemodialysis patients is associated with high mortality, but prescription of low dialysate potassium concentrations to decrease serum potassium levels is associated with a high incidence of sudden cardiac arrest or sudden death. Improved clinical outcomes for these patients may be possible if rapid and substantial intradialysis decreases in serum potassium concentration can be avoided while maintaining adequate potassium removal. Data from kinetic modeling sessions during the HEMO Study of the dependence of serum potassium concentration on time during hemodialysis treatments and 30 minutes postdialysis were evaluated using a pseudo one-compartment model. Kinetic estimates of potassium mobilization clearance (KM ) and predialysis central distribution volume (Vpre ) were determined in 551 hemodialysis patients. The studied patients were 58.8?±?14.4 years of age with predialysis body weight of 72.1?±?15.1?kg; 306 (55.4%) of the patients were female and 337 (61.2%) were black. KM and Vpre for all patients were non-normally distributed with values of 158 (111, 235) (median [interquartile range]) mL/min and 15.6 (11.4, 22.8) L, respectively. KM was independent of dialysate potassium concentration (P?>?0.2), but Vpre was lower at higher dialysate potassium concentration (R?=?-0.188, P?kinetics during hemodialysis can be described using a pseudo one-compartment model. PMID:25091596

Agar, Baris U; Culleton, Bruce F; Fluck, Richard; Leypoldt, John K

2015-01-01

414

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

415

Analysis of Crystallization Kinetics  

NASA Technical Reports Server (NTRS)

A realistic computer model for polymorphic crystallization (i.e., initial and final phases with identical compositions), which includes time-dependent nucleation and cluster-size-dependent growth rates, is developed and tested by fits to experimental data. Model calculations are used to assess the validity of two of the more common approaches for the analysis of crystallization data. The effects of particle size on transformation kinetics, important for the crystallization of many systems of limited dimension including thin films, fine powders, and nanoparticles, are examined.

Kelton, Kenneth F.

1997-01-01

416

Kinetic database for astrochemistry  

NASA Astrophysics Data System (ADS)

KIDA (for KInetic Database for Astrochemistry) is a project initiated by different communities in order to 1) improve the interaction between astrochemists and physico-chemists and 2) simplify the work of modeling the chemistry of astrophysical environments. KIDA was designed to group at the same place and with the same format all gas-phase chemical reactions useful for astrochemical simulations of the interstellar medium and planetary atmospheres. From KIDA, a subset of chemical reactions has been extracted for the cold and dense interstellar medium: kida.uva.2001.

Wakelam, V.; KIDA Team

2012-02-01

417

Global limits on kinetic Alfvenon speed in quasineutral plasmas  

SciTech Connect

Large-amplitude kinetic Alfvenon (exact Alfven soliton) matching condition is investigated in quasineutral electron-ion and electron-positron-ion plasmas immersed in a uniform magnetic field. Using the standard pseudopotential method, the magnetohydrodynamics equations are exactly solved, and a global allowed matching condition for propagation of kinetic solitary waves is derived. It is remarked that, depending on the plasma parameters, the kinetic solitons can be sub-Alfvenic or super-Alfvenic, in general. It is further revealed that, either upper or lower soliton speed-limit is independent of fractional plasma parameters. Furthermore, the soliton propagation angle with respect to that of the uniform magnetic field is found to play a fundamental role in controlling the soliton matching speed-range.

Akbari-Moghanjoughi, M. [Department of Physics, Faculty of Sciences, Azarbaijan University of Tarbiat Moallem, 51745-406 Tabriz (Iran, Islamic Republic of)

2011-04-15

418

Optimal estimation of ion-channel kinetics from macroscopic currents.  

PubMed

Markov modeling provides an effective approach for modeling ion channel kinetics. There are several search algorithms for global fitting of macroscopic or single-channel currents across different experimental conditions. Here we present a particle swarm optimization(PSO)-based approach which, when used in combination with golden section search (GSS), can fit macroscopic voltage responses with a high degree of accuracy (errors within 1%) and reasonable amount of calculation time (less than 10 hours for 20 free parameters) on a desktop computer. We also describe a method for initial value estimation of the model parameters, which appears to favor identification of global optimum and can further reduce the computational cost. The PSO-GSS algorithm is applicable for kinetic models of arbitrary topology and size and compatible with common stimulation protocols, which provides a convenient approach for establishing kinetic models at the macroscopic level. PMID:22536358

Wang, Wei; Xiao, Feng; Zeng, Xuhui; Yao, Jing; Yuchi, Ming; Ding, Jiuping

2012-01-01

419

Monosaccharide production in an acid sulfite process: kinetic modeling.  

PubMed

Spent sulfite liquor is a lignocellulosic waste obtained after the sulfite pulping process. It is mainly formed by sugars and lignosulfonates which are isolated from the pulp during the cooking process. The current work investigates the kinetic modeling of the sulfite process from a biorefinery point of view since monosaccharides present in the spent liquor can be used as a raw material in further biorefinery processes to produce other value-added products. Kinetic parameters of carbohydrate degradation have been determined following sugar and inhibitors from wood to spent liquor, using laboratory scale reactors and different temperatures, 130, 140 and 150 °C. Three types of reaction schemes were developed. Kinetic parameters were obtained for each one using first and n order reactions, using Aspen Custom Modeler. Results show that the best temperature to be used in the process is 130 °C, giving the maximum sugar conversion, 33.91 mol% and obtaining 13.81 mol% of decomposition products. PMID:25458268

Rueda, C; Fernández-Rodríguez, J; Ruiz, G; Llano, T; Coz, A

2015-02-13

420

Optimal Estimation of Ion-Channel Kinetics from Macroscopic Currents  

PubMed Central

Markov modeling provides an effective approach for modeling ion channel kinetics. There are several search algorithms for global fitting of macroscopic or single-channel currents across different experimental conditions. Here we present a particle swarm optimization(PSO)-based approach which, when used in combination with golden section search (GSS), can fit macroscopic voltage responses with a high degree of accuracy (errors within 1%) and reasonable amount of calculation time (less than 10 hours for 20 free parameters) on a desktop computer. We also describe a method for initial value estimation of the model parameters, which appears to favor identification of global optimum and can further reduce the computational cost. The PSO-GSS algorithm is applicable for kinetic models of arbitrary topology and size and compatible with common stimulation protocols, which provides a convenient approach for establishing kinetic models at the macroscopic level. PMID:22536358

Zeng, Xuhui; Yao, Jing; Yuchi, Ming; Ding, Jiuping

2012-01-01

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