Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State

Directory of Open Access Journals (Sweden)

Vicente Martí-Centelles

2012-01-01

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.

Reactor kinetics - pulse and steady state

Energy Technology Data Exchange (ETDEWEB)

Estes, B F; Morris, F M [Sandia Laboratories (United States)

1974-07-01

An analytical model has been developed which couples the nuclear and thermal characteristics of the Annular Core Pulse Reactor (ACPR) into a solution which describes both the neutron kinetics of the reactor and the temperature behavior of a fuel-moderator element. The model describes both pulse and steady state operations. This paper describes the important aspects of the reactor, the fuel- moderator elements, the neutron kinetic equations of the reactor, and the time-temperature behavior of a fuel-moderator element that is being subjected to the maximum power density in the core. The parameters which are utilized in the equations are divided into two classes, those that can be measured directly and those that are assumed to be known (each is described briefly). Some of the solutions which demonstrate the versatility of the analytical model are described. (author)

Variational estimates of point-kinetics parameters

International Nuclear Information System (INIS)

Favorite, J.A.; Stacey, W.M. Jr.

1995-01-01

Variational estimates of the effect of flux shifts on the integral reactivity parameter of the point-kinetics equations and on regional power fractions were calculated for a variety of localized perturbations in two light water reactor (LWR) model problems representing a small, tightly coupled core and a large, loosely coupled core. For the small core, the flux shifts resulting from even relatively large localized reactivity changes (∼600 pcm) were small, and the standard point-kinetics approximation estimates of reactivity were in error by only ∼10% or less, while the variational estimates were accurate to within ∼1%. For the larger core, significant (>50%) flux shifts occurred in response to local perturbations, leading to errors of the same magnitude in the standard point-kinetics approximation of the reactivity worth. For positive reactivity, the error in the variational estimate of reactivity was only a few percent in the larger core, and the resulting transient power prediction was 1 to 2 orders of magnitude more accurate than with the standard point-kinetics approximation. For a large, local negative reactivity insertion resulting in a large flux shift, the accuracy of the variational estimate broke down. The variational estimate of the effect of flux shifts on reactivity in point-kinetics calculations of transients in LWR cores was found to generally result in greatly improved accuracy, relative to the standard point-kinetics approximation, the exception being for large negative reactivity insertions with large flux shifts in large, loosely coupled cores

Kinetic parameter estimation from SPECT cone-beam projection measurements

International Nuclear Information System (INIS)

Huesman, Ronald H.; Reutter, Bryan W.; Zeng, G. Larry; Gullberg, Grant T.

1998-01-01

Kinetic parameters are commonly estimated from dynamically acquired nuclear medicine data by first reconstructing a dynamic sequence of images and subsequently fitting the parameters to time-activity curves generated from regions of interest overlaid upon the image sequence. Biased estimates can result from images reconstructed using inconsistent projections of a time-varying distribution of radiopharmaceutical acquired by a rotating SPECT system. If the SPECT data are acquired using cone-beam collimators wherein the gantry rotates so that the focal point of the collimators always remains in a plane, additional biases can arise from images reconstructed using insufficient, as well as truncated, projection samples. To overcome these problems we have investigated the estimation of kinetic parameters directly from SPECT cone-beam projection data by modelling the data acquisition process. To accomplish this it was necessary to parametrize the spatial and temporal distribution of the radiopharmaceutical within the SPECT field of view. In a simulated chest image volume, kinetic parameters were estimated for simple one-compartment models for four myocardial regions of interest. Myocardial uptake and washout parameters estimated by conventional analysis of noiseless simulated cone-beam data had biases ranging between 3-26% and 0-28%, respectively. Parameters estimated directly from the noiseless projection data were unbiased as expected, since the model used for fitting was faithful to the simulation. Statistical uncertainties of parameter estimates for 10 000 000 events ranged between 0.2-9% for the uptake parameters and between 0.3-6% for the washout parameters. (author)

Practical steady-state enzyme kinetics.

Science.gov (United States)

Lorsch, Jon R

2014-01-01

Enzymes are key components of most biological processes. Characterization of enzymes is therefore frequently required during the study of biological systems. Steady-state kinetics provides a simple and rapid means of assessing the substrate specificity of an enzyme. When combined with site-directed mutagenesis (see Site-Directed Mutagenesis), it can be used to probe the roles of particular amino acids in the enzyme in substrate recognition and catalysis. Effects of interaction partners and posttranslational modifications can also be assessed using steady-state kinetics. This overview explains the general principles of steady-state enzyme kinetics experiments in a practical, rather than theoretical, way. Any biochemistry textbook will have a section on the theory of Michaelis-Menten kinetics, including derivations of the relevant equations. No specific enzymatic assay is described here, although a method for monitoring product formation or substrate consumption over time (an assay) is required to perform the experiments described. © 2014 Elsevier Inc. All rights reserved.

Alternative definitions of kinetic parameters for accelerator driven systems

International Nuclear Information System (INIS)

Talamo, Alberto; Gohar, Yousry; Dulla, Sandra; Ravetto, Piero

2012-01-01

Highlights: ► New definition of kinetic parameters for accelerator driven systems. ► Difference between effective and average delayed neutron fraction. ► Difference between effective and average prompt neutron lifetime. ► Effect of the neutron source (Cf, D–D, D–T) on k src . ► Effect of the (n, xn) reactions and source energy-angle distribution on k src . - Abstract: This study introduces a new formulation of kinetic parameters for accelerator driven systems and it is structured into two parts. The first part is dedicated to the classic definition of the kinetic parameters and compares different calculation methodologies. The second part considers a new definition of the kinetic parameters for subcritical assemblies, with particular emphasis on the delayed neutron fraction and the prompt neutron lifetime. This new definition takes into account neutrons from the external neutron source and (n, xn) reactions, which increase the fraction of prompt neutrons. The developed theoretical framework has been applied by Monte Carlo and deterministic calculations to the YALINA Thermal subcritical assembly located in Belarus. This facility can be driven by californium, deuterium–deuterium (D–D), or deuterium–tritium (D–T) external neutron sources. For the D–T neutron source, (n, xn) reactions must be taken into account in order to produce accurate results because the average energy of D–T source neutrons is 14.1 MeV, a value which is much higher than the threshold energy of the (n, 2n) cross section of uranium isotopes.

Estimation of beech pyrolysis kinetic parameters by Shuffled Complex Evolution.

Science.gov (United States)

Ding, Yanming; Wang, Changjian; Chaos, Marcos; Chen, Ruiyu; Lu, Shouxiang

2016-01-01

The pyrolysis kinetics of a typical biomass energy feedstock, beech, was investigated based on thermogravimetric analysis over a wide heating rate range from 5K/min to 80K/min. A three-component (corresponding to hemicellulose, cellulose and lignin) parallel decomposition reaction scheme was applied to describe the experimental data. The resulting kinetic reaction model was coupled to an evolutionary optimization algorithm (Shuffled Complex Evolution, SCE) to obtain model parameters. To the authors' knowledge, this is the first study in which SCE has been used in the context of thermogravimetry. The kinetic parameters were simultaneously optimized against data for 10, 20 and 60K/min heating rates, providing excellent fits to experimental data. Furthermore, it was shown that the optimized parameters were applicable to heating rates (5 and 80K/min) beyond those used to generate them. Finally, the predicted results based on optimized parameters were contrasted with those based on the literature. Copyright © 2015 Elsevier Ltd. All rights reserved.

Kinetic Parameters of Thermal Degradation of Polymers

Institute of Scientific and Technical Information of China (English)

朱新生; 程嘉祺

2003-01-01

The derivative expressions between activation energy (E) and the temperature at the maximum mass loss rate(Tmax) and between activation energy (E) and exponent (N) were deduced in the light of Arrhenius theory. It was found that the increase of activation energy results in the decrease of exponent and the increase of Tmax. The kinetic parameters were involved in the analysis of the thermal degradation of several polymers. The degradation kinetics of these polymers well complied with the prediction of the derivative expressions for the polymer degradation with single mechanism dominated.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Kinetic parameter estimation model for anaerobic co-digestion of waste activated sludge and microalgae.

Science.gov (United States)

Lee, Eunyoung; Cumberbatch, Jewel; Wang, Meng; Zhang, Qiong

2017-03-01

Anaerobic co-digestion has a potential to improve biogas production, but limited kinetic information is available for co-digestion. This study introduced regression-based models to estimate the kinetic parameters for the co-digestion of microalgae and Waste Activated Sludge (WAS). The models were developed using the ratios of co-substrates and the kinetic parameters for the single substrate as indicators. The models were applied to the modified first-order kinetics and Monod model to determine the rate of hydrolysis and methanogenesis for the co-digestion. The results showed that the model using a hyperbola function was better for the estimation of the first-order kinetic coefficients, while the model using inverse tangent function closely estimated the Monod kinetic parameters. The models can be used for estimating kinetic parameters for not only microalgae-WAS co-digestion but also other substrates' co-digestion such as microalgae-swine manure and WAS-aquatic plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Using linear time-invariant system theory to estimate kinetic parameters directly from projection measurements

International Nuclear Information System (INIS)

Zeng, G.L.; Gullberg, G.T.

1995-01-01

It is common practice to estimate kinetic parameters from dynamically acquired tomographic data by first reconstructing a dynamic sequence of three-dimensional reconstructions and then fitting the parameters to time activity curves generated from the time-varying reconstructed images. However, in SPECT, the pharmaceutical distribution can change during the acquisition of a complete tomographic data set, which can bias the estimated kinetic parameters. It is hypothesized that more accurate estimates of the kinetic parameters can be obtained by fitting to the projection measurements instead of the reconstructed time sequence. Estimation from projections requires the knowledge of their relationship between the tissue regions of interest or voxels with particular kinetic parameters and the project measurements, which results in a complicated nonlinear estimation problem with a series of exponential factors with multiplicative coefficients. A technique is presented in this paper where the exponential decay parameters are estimated separately using linear time-invariant system theory. Once the exponential factors are known, the coefficients of the exponentials can be estimated using linear estimation techniques. Computer simulations demonstrate that estimation of the kinetic parameters directly from the projections is more accurate than the estimation from the reconstructed images

Generation of a library of two-group diffusion and kinetics parameters for DYN3D

International Nuclear Information System (INIS)

Petkov, P.T.; Christoskov, I.D.; Kamenov, K.; Antov, A.

2002-01-01

A library of two-group diffusion and kinetics parameters has been generated for the neutron kinetics code DYN3D for analysis of reactivity initiated accidents for the WWER-440 reactors, based on the MAGRU approximation methodology for the diffusion and kinetics parameters. The accuracy of this methodology has been tested and the conclusion is that it is not adequate. A new approximation methodology, based on interpolation for the most widely varying parameters, i.e. the moderator temperature and density, and on approximation for all other independent parameters, is presented. The methodology of calculation of the kinetics parameters using primary data from ENDF-B/VI is described in detail (Authors)

Determination of Model Kinetics for Forced Unsteady State Operation of Catalytic CH4 Oxidation

Directory of Open Access Journals (Sweden)

Effendy Mohammad

2016-01-01

Full Text Available The catalytic oxidation of methane for abating the emission vented from coal mine or natural gas transportation has been known as most reliable method. A reverse flow reactor operation has been widely used to oxidize this methane emission due to its capability for autothermal operation and heat production. The design of the reverse flow reactor requires a proper kinetic rate expression, which should be developed based on the operating condition. The kinetic rate obtained in the steady state condition cannot be applied for designing the reactor operated under unsteady state condition. Therefore, new approach to develop the dynamic kinetic rate expression becomes indispensable, particularly for periodic operation such as reverse flow reactor. This paper presents a novel method to develop the kinetic rate expression applied for unsteady state operation. The model reaction of the catalytic methane oxidation over Pt/-Al2O3 catalyst was used with kinetic parameter determined from laboratory experiments. The reactor used was a fixed bed, once-through operation, with a composition modulation in the feed gas. The switching time was set at 3 min by varying the feed concentration, feed flow rate, and reaction temperature. The concentrations of methane in the feed and product were measured and analysed using gas chromatography. The steady state condition for obtaining the kinetic rate expression was taken as a base case and as a way to judge its appropriateness to be applied for dynamic system. A Langmuir-Hinshelwood reaction rate model was developed. The time period during one cycle was divided into some segments, depending on the ratio of CH4/O2. The experimental result shows that there were kinetic regimes occur during one cycle: kinetic regime controlled by intrinsic surface reaction and kinetic regime controlled by external diffusion. The kinetic rate obtained in the steady state operation was not appropriate when applied for unsteady state operation

Estimation of apparent kinetic parameters of polymer pyrolysis with complex thermal degradation behavior

International Nuclear Information System (INIS)

Srimachai, Taranee; Anantawaraskul, Siripon

2010-01-01

Full text: Thermal degradation behavior during polymer pyrolysis can typically be described using three apparent kinetic parameters (i.e., pre-exponential factor, activation energy, and reaction order). Several efficient techniques have been developed to estimate these apparent kinetic parameters for simple thermal degradation behavior (i.e., single apparent pyrolysis reaction). Unfortunately, these techniques cannot be directly extended to the case of polymer pyrolysis with complex thermal degradation behavior (i.e., multiple concurrent reactions forming single or multiple DTG peaks). In this work, we proposed a deconvolution method to determine the number of apparent reactions and estimate three apparent kinetic parameters and contribution of each reaction for polymer pyrolysis with complex thermal degradation behavior. The proposed technique was validated with the model and experimental pyrolysis data of several polymer blends with known compositions. The results showed that (1) the number of reaction and (2) three apparent kinetic parameters and contribution of each reaction can be estimated reasonably. The simulated DTG curves with estimated parameters also agree well with experimental DTG curves. (author)

Kinetics parameter measurements on RSG-GAS, a low-enriched fuel reactor

International Nuclear Information System (INIS)

Jujuratisbela, U; Arbie, B; Pinem, S.; Tukiran; Suparlina, L.; Singh, O.P.

1995-01-01

Kinetics parameter measurements, such as reactivity worths of control rods and fuel elements, beam tube void reactivity, power reactivity coefficient and xenon poisoning reactivity have been performed on different cores of Reaktor Serba Guna G.A. Siwabessy (RSG-GAS). In parallel, a programme was also initiated to measure the other kinetics parameters like effective delayed neutron life time, prompt neutron decay constant, validation of period reactivity relationship and zero power frequency response function. The paper provides the results of these measurements. (author)

Estimating kinetic mechanisms with prior knowledge I: Linear parameter constraints.

Science.gov (United States)

Salari, Autoosa; Navarro, Marco A; Milescu, Mirela; Milescu, Lorin S

2018-02-05

To understand how ion channels and other proteins function at the molecular and cellular levels, one must decrypt their kinetic mechanisms. Sophisticated algorithms have been developed that can be used to extract kinetic parameters from a variety of experimental data types. However, formulating models that not only explain new data, but are also consistent with existing knowledge, remains a challenge. Here, we present a two-part study describing a mathematical and computational formalism that can be used to enforce prior knowledge into the model using constraints. In this first part, we focus on constraints that enforce explicit linear relationships involving rate constants or other model parameters. We develop a simple, linear algebra-based transformation that can be applied to enforce many types of model properties and assumptions, such as microscopic reversibility, allosteric gating, and equality and inequality parameter relationships. This transformation converts the set of linearly interdependent model parameters into a reduced set of independent parameters, which can be passed to an automated search engine for model optimization. In the companion article, we introduce a complementary method that can be used to enforce arbitrary parameter relationships and any constraints that quantify the behavior of the model under certain conditions. The procedures described in this study can, in principle, be coupled to any of the existing methods for solving molecular kinetics for ion channels or other proteins. These concepts can be used not only to enforce existing knowledge but also to formulate and test new hypotheses. © 2018 Salari et al.

A method for estimation of elasticities in metabolic networks using steady state and dynamic metabolomics data and linlog kinetics

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van Gulik Walter M

2006-12-01

Full Text Available Abstract Background Dynamic modeling of metabolic reaction networks under in vivo conditions is a crucial step in order to obtain a better understanding of the (disfunctioning of living cells. So far dynamic metabolic models generally have been based on mechanistic rate equations which often contain so many parameters that their identifiability from experimental data forms a serious problem. Recently, approximative rate equations, based on the linear logarithmic (linlog format have been proposed as a suitable alternative with fewer parameters. Results In this paper we present a method for estimation of the kinetic model parameters, which are equal to the elasticities defined in Metabolic Control Analysis, from metabolite data obtained from dynamic as well as steady state perturbations, using the linlog kinetic format. Additionally, we address the question of parameter identifiability from dynamic perturbation data in the presence of noise. The method is illustrated using metabolite data generated with a dynamic model of the glycolytic pathway of Saccharomyces cerevisiae based on mechanistic rate equations. Elasticities are estimated from the generated data, which define the complete linlog kinetic model of the glycolysis. The effect of data noise on the accuracy of the estimated elasticities is presented. Finally, identifiable subset of parameters is determined using information on the standard deviations of the estimated elasticities through Monte Carlo (MC simulations. Conclusion The parameter estimation within the linlog kinetic framework as presented here allows the determination of the elasticities directly from experimental data from typical dynamic and/or steady state experiments. These elasticities allow the reconstruction of the full kinetic model of Saccharomyces cerevisiae, and the determination of the control coefficients. MC simulations revealed that certain elasticities are potentially unidentifiable from dynamic data only

Kinetics parameters of a slurry remediation process in rotating drum bioreactors

International Nuclear Information System (INIS)

Esquivel-Rios, I.; Rodriguez-Meza, M. A.; Barrera-Cortes, J.

2009-01-01

The knowledge of biotransformation pollution dynamics in any systems is important for design and optimization purposes of biochemical processes involved. this is focus to the determination of kinetics parameters such as the maximum specific growth rate (μMAX), saturation constant (Ks), biomass yield (YX/S; X: biomass, S: substrate) and oxygen consumption (YO 2 /S; O 2 : oxygen). Several approximations, based on Monod equation, have been developed for estimating kinetics parameters in terms of concentration and type of substrate, bioprocess type and microflora available. (Author)

On the analysis of glow curves with the general order kinetics: Reliability of the computed trap parameters

Energy Technology Data Exchange (ETDEWEB)

Ortega, F. [Facultad de Ingeniería (UNCPBA) and CIFICEN (UNCPBA – CICPBA – CONICET), Av. del Valle 5737, 7400 Olavarría (Argentina); Santiago, M.; Martinez, N.; Marcazzó, J.; Molina, P.; Caselli, E. [Instituto de Física Arroyo Seco (UNCPBA) and CIFICEN (UNCPBA – CICPBA – CONICET), Pinto 399, 7000 Tandil (Argentina)

2017-04-15

Nowadays the most employed kinetics for analyzing glow curves is the general order kinetics (GO) proposed by C. E. May and J. A. Partridge. As shown in many articles this kinetics might yield wrong parameters characterizing trap and recombination centers. In this article this kinetics is compared with the modified general order kinetics put forward by M. S. Rasheedy by analyzing synthetic glow curves. The results show that the modified kinetics gives parameters, which are more accurate than that yield by the original general order kinetics. A criterion is reported to evaluate the accuracy of the trap parameters found by deconvolving glow curves. This criterion was employed to assess the reliability of the trap parameters of the YVO{sub 4}: Eu{sup 3+} compounds.

The influence of pH adjustment on kinetics parameters in tapioca wastewater treatment using aerobic sequencing batch reactor system

Science.gov (United States)

Mulyani, Happy; Budianto, Gregorius Prima Indra; Margono, Kaavessina, Mujtahid

2018-02-01

The present investigation deals with the aerobic sequencing batch reactor system of tapioca wastewater treatment with varying pH influent conditions. This project was carried out to evaluate the effect of pH on kinetics parameters of system. It was done by operating aerobic sequencing batch reactor system during 8 hours in many tapioca wastewater conditions (pH 4.91, pH 7, pH 8). The Chemical Oxygen Demand (COD) and Mixed Liquor Volatile Suspended Solids (MLVSS) of the aerobic sequencing batch reactor system effluent at steady state condition were determined at interval time of two hours to generate data for substrate inhibition kinetics parameters. Values of the kinetics constants were determined using Monod and Andrews models. There was no inhibition constant (Ki) detected in all process variation of aerobic sequencing batch reactor system for tapioca wastewater treatment in this study. Furthermore, pH 8 was selected as the preferred aerobic sequencing batch reactor system condition in those ranging pH investigated due to its achievement of values of kinetics parameters such µmax = 0.010457/hour and Ks = 255.0664 mg/L COD.

A way for evaluating parameters of electron transport in non-polar molecular liquids derived from analysis of the trapped electron recombination kinetics

International Nuclear Information System (INIS)

Lukin, L.V.

2012-01-01

The geminate recombination kinetics of electron-ion pairs produced by high energy radiation in liquid hydrocarbons is considered in the two state model of electron transport. The purpose of the study is to relate the trapped electron transient optical absorption, observed in the pulse radiolysis experiments, to fundamental parameters of electron transport in liquid. It is shown that measurements of the half-life time and amplitude of the trapped electron decay curve allow one to find the electron life time in a localized state. - Highlights: ► A two state electron model is applied to geminate charge recombination. ► Time dependence of trapped electrons is computed for liquid isooctane and squalane. ► Electron decay kinetics depends on electron life time in a localized state. ► Key parameters of electron transport are found from the pulse radiolysis studies.

Determination of thermoluminescence kinetic parameters of thulium doped lithium calcium borate

International Nuclear Information System (INIS)

Jose, M.T.; Anishia, S.R.; Annalakshmi, O.; Ramasamy, V.

2011-01-01

For the first time kinetic parameters of thulium doped Lithium calcium borate (LCB) Thermoluminescence (TL) material are reported here. Irradiated LCB:Tm 3+ powder has revealed two intense TL glow peaks one at 510 (peak 1) and the other at 660 K (peak 2). Activation energy (E), frequency factor (s) and order of kinetics (b) of these peaks were determined by various heating rate (VHR), initial rise (IR), and peak shape (PS) methods. The trap depth and frequency factor determined for peaks 1 and 2 of LCB:Tm phosphor using VHR and IR methods are in good agreement. The average activation energy of peaks 1 and 2 obtained by these methods is 1.62 and 1.91 eV respectively. The frequency factors of peaks 1 and 2 are in the range of 10 13-16 and 10 12-14 sec -1 respectively. The E and s values estimated using the glow peak shape dependent parameters are relatively less compared to the values obtained from other methods. The large difference in these values is due to the complex nature of the glow curves. The order of the kinetics process for complex glow curve peaks could not be assigned on the basis of shape parameters alone but T m response on absorbed dose is to be considered for final confirmation. Glow peaks 1 and 2 of LCB:Tm 3+ obey first and general order kinetics respectively. - Highlights: → Trap depth and frequency factor are determined for the peaks at 510 and 660 K of LCB:Tm. → Parameters obtained by various heating rate and initial rise methods are in good agreement. → Trap depth of peak 1 and peak 2 is 1.61 eV and 1.91 eV respectively. → T m response to absorbed dose is used to distinguish a first order or non-first order kinetics.

An equation of state for purely kinetic k-essence inspired by cosmic topological defects

Energy Technology Data Exchange (ETDEWEB)

Cordero, Ruben; Gonzalez, Eduardo L.; Queijeiro, Alfonso [Instituto Politecnico Nacional, Departamento de Fisica, Escuela Superior de Fisica y Matematicas, Ciudad de Mexico (Mexico)

2017-06-15

We investigate the physical properties of a purely kinetic k-essence model with an equation of state motivated in superconducting membranes. We compute the equation of state parameter w and discuss its physical evolution via a nonlinear equation of state. Using the adiabatic speed of sound and energy density, we restrict the range of parameters of the model in order to have an acceptable physical behavior. We study the evolution of the scale factor and address the question of the possible existence of finite-time future singularities. Furthermore, we analyze the evolution of the luminosity distance d{sub L} with redshift z by comparing (normalizing) it with the ΛCDM model. Since the equation of state parameter is z-dependent the evolution of the luminosity distance is also analyzed using the Alcock-Paczynski test. (orig.)

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

Energy Technology Data Exchange (ETDEWEB)

Passalia, Claudio; Alfano, Orlando M. [INTEC - Instituto de Desarrollo Tecnologico para la Industria Quimica, CONICET - UNL, Gueemes 3450, 3000 Santa Fe (Argentina); FICH - Departamento de Medio Ambiente, Facultad de Ingenieria y Ciencias Hidricas, Universidad Nacional del Litoral, Ciudad Universitaria, 3000 Santa Fe (Argentina); Brandi, Rodolfo J., E-mail: rbrandi@santafe-conicet.gov.ar [INTEC - Instituto de Desarrollo Tecnologico para la Industria Quimica, CONICET - UNL, Gueemes 3450, 3000 Santa Fe (Argentina); FICH - Departamento de Medio Ambiente, Facultad de Ingenieria y Ciencias Hidricas, Universidad Nacional del Litoral, Ciudad Universitaria, 3000 Santa Fe (Argentina)

2012-04-15

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

Determination of the kinetic parameters of BeO thermoluminescent samples using different methods

Energy Technology Data Exchange (ETDEWEB)

Algarve, Fábio J.; Caldas, Linda V.E., E-mail: fjalgarve@ipen.br, E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

2017-07-01

The objective of this work was to determine the kinetic parameters of BeO thermoluminescent (TL) samples. The knowledge of the kinetic parameters is important for the general description of the physical characteristics of a thermoluminescent material. Using a linear heating rate of 5K/s{sup -1}, the BeO peak temperatures obtained were (474.7 ± 1.2) K and (620.5 ± 1.2) K, respectively, for the first and second TL peaks. The peak shape and the glow curve area measurement methods and the Urbach formula have been used for the trap parameter determination. A kinetic order of about two was determined for the first peak, whereas the second peak followed the first-order kinetics according to the geometrical factor. The energy activation values obtained using different kinds of measurements are in good agreement, including the Kitis method for deconvolution of the glow curve. Furthermore the results agree with those presented by other authors. (author)

Estimation of Adjoint-Weighted Kinetics Parameters in Monte Carlo Wieland Calculations

International Nuclear Information System (INIS)

Choi, Sung Hoon; Shim, Hyung Jin

2013-01-01

The effective delayed neutron fraction, β eff , and the prompt neutron generation time, Λ, in the point kinetics equation are weighted by the adjoint flux to improve the accuracy of the reactivity estimate. Recently the Monte Carlo (MC) kinetics parameter estimation methods by using the self-consistent adjoint flux calculated in the MC forward simulations have been developed and successfully applied for the research reactor analyses. However these adjoint estimation methods based on the cycle-by-cycle genealogical table require a huge memory size to store the pedigree hierarchy. In this paper, we present a new adjoint estimation in which the pedigree of a single history is utilized by applying the MC Wielandt method. The effectiveness of the new method is demonstrated in the kinetics parameter estimations for infinite homogeneous two-group problems and the Godiva critical facility

Kinetics of solid state phase transformations: Measurement and ...

Indian Academy of Sciences (India)

Administrator

heating or cooling rate can also exert a crucial influence on the kinetic outcome is stressed. The kinetic ... A simple and general modelling methodology for understanding the kinetics of ... state is of interest on both basic and applied grounds.

Effect of long-term physical aging on the kinetic parameters in a common pharmaceutical drug: Flutab

International Nuclear Information System (INIS)

Abu-Sehly, A.A.; Elabbar, A.A.

2011-01-01

Differential scanning calorimetry (DSC) measurements were performed to investigate the effects of long-term physical aging on kinetic parameters of the pharmaceutical drug (Flutab). Kinetics parameters such as activation energy (E) and fragility parameter (m) of the glass transition for aged and rejuvenated glasses were determined using different kinetic models. Evidence of variation of E with temperature is presented. It is shown in this work that natural storage of the drug introduced significant physical aging as indicated by changes in the glass transition temperature, activation energy and fragility parameter.

State switching kinetics for quasi-one-dimensional nanosystems: Effects of Finite length and irradiation

Energy Technology Data Exchange (ETDEWEB)

Petukhov, B. V., E-mail: petukhov@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” (Russian Federation)

2017-01-15

The state switching in an extended quasi-one-dimensional material is modeled by the stochastic formation of local new-state nuclei and their subsequent growth along the system axis. An analytical approach is developed to describe the influence of defects, dividing a sample into an ensemble of finite-length segments, on its state switching kinetics. As applied to magnetic systems, the method makes it possible to calculate magnetization curves for different defect concentrations and parameters of material.

Calculation of statistic estimates of kinetic parameters from substrate uncompetitive inhibition equation using the median method

Directory of Open Access Journals (Sweden)

Pedro L. Valencia

2017-04-01

Full Text Available We provide initial rate data from enzymatic reaction experiments and tis processing to estimate the kinetic parameters from the substrate uncompetitive inhibition equation using the median method published by Eisenthal and Cornish-Bowden (Cornish-Bowden and Eisenthal, 1974; Eisenthal and Cornish-Bowden, 1974. The method was denominated the direct linear plot and consists in the calculation of the median from a dataset of kinetic parameters Vmax and Km from the Michaelis–Menten equation. In this opportunity we present the procedure to applicate the direct linear plot to the substrate uncompetitive inhibition equation; a three-parameter equation. The median method is characterized for its robustness and its insensibility to outlier. The calculations are presented in an Excel datasheet and a computational algorithm was developed in the free software Python. The kinetic parameters of the substrate uncompetitive inhibition equation Vmax, Km and Ks were calculated using three experimental points from the dataset formed by 13 experimental points. All the 286 combinations were calculated. The dataset of kinetic parameters resulting from this combinatorial was used to calculate the median which corresponds to the statistic estimator of the real kinetic parameters. A comparative statistical analyses between the median method and the least squares was published in Valencia et al. [3].

Kinetic parameters evaluation of PWRs using static cell and core calculation codes

International Nuclear Information System (INIS)

Jahanbin, Ali; Malmir, Hessam

2012-01-01

Highlights: ► In this study, we have calculated effective delayed neutron fraction and prompt neutron lifetime in PWRs. ► New software has been developed to link the WIMS, BORGES and CITATION codes in Visual C computer programming language. ► This software is used for calculation of the kinetic parameters in a typical VVER-1000 and NOK Beznau reactor. ► The ratios ((β eff ) i )/((β eff ) core ) , which are the important input data for the reactivity accident analysis, are also calculated. - Abstract: In this paper, evaluation of the kinetic parameters (effective delayed neutron fraction and prompt neutron lifetime) in PWRs, using static cell and core calculation codes, is reported. A new software has been developed to link the WIMS, BORGES and CITATION codes in Visual C computer programming language. Using the WIMS cell calculation code, multigroup microscopic cross-sections and number densities of different materials can be generated in a binary file. By the use of BORGES code, these binary-form cross-sections and number densities are converted to a format readable by the CITATION core calculation code, by which the kinetic parameters can be finally obtained. This software is used for calculation of the kinetic parameters in a typical VVER-1000 and NOK Beznau reactor. The ratios ((β eff ) i )/((β eff ) core ) , which are the important input data for the reactivity accident analysis, are also calculated. Benchmarking of the results against the final safety analysis report (FSAR) of the aforementioned reactors shows very good agreements with these published documents.

Reactor thermal behaviors under kinetics parameters variations in fast reactivity insertion

Energy Technology Data Exchange (ETDEWEB)

Abou-El-Maaty, Talal [Reactors Department, Atomic Energy Authority, Cairo 13759 (Egypt)], E-mail: talal22969@yahoo.com; Abdelhady, Amr [Reactors Department, Atomic Energy Authority, Cairo 13759 (Egypt)

2009-03-15

The influences of variations in some of the kinetics parameters affecting the reactivity insertion are considered in this study, it has been accomplished in order to acquire knowledge about the role that kinetic parameters play in prompt critical transients from the safety point of view. The kinetics parameters variations are limited to the effective delayed neutron fraction ({beta}{sub eff}) and the prompt neutron generation time ({lambda}). The reactor thermal behaviors under the variations in effective delayed neutron fraction and prompt neutron generation time included, the reactor power, maximum fuel temperature, maximum clad temperature, maximum coolant temperature and the mass flux variations at the hot channel. The analysis is done for a typical swimming pool, plate type research reactor with low enriched uranium. The scram system is disabled during the accidents simulations. Calculations were done using PARET code. As a result of simulations, it is concluded that, the reactor (ETRR2) thermal behavior is considerably more sensitive to the variation in the effective delayed neutron fraction than to the variation in prompt neutron generation time and the fast reactivity insertion in both cases causes a flow expansion and contraction at the hot channel exit. The amplitude of the oscillated flow is a qualitatively increases with the decrease in both {beta}{sub eff} and {lambda}.

Inverse modeling approach for evaluation of kinetic parameters of a biofilm reactor using tabu search.

Science.gov (United States)

Kumar, B Shiva; Venkateswarlu, Ch

2014-08-01

The complex nature of biological reactions in biofilm reactors often poses difficulties in analyzing such reactors experimentally. Mathematical models could be very useful for their design and analysis. However, application of biofilm reactor models to practical problems proves somewhat ineffective due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, we propose an inverse modeling approach based on tabu search (TS) to estimate the parameters of kinetic and film thickness models. TS is used to estimate these parameters as a consequence of the validation of the mathematical models of the process with the aid of measured data obtained from an experimental fixed-bed anaerobic biofilm reactor involving the treatment of pharmaceutical industry wastewater. The results evaluated for different modeling configurations of varying degrees of complexity illustrate the effectiveness of TS for accurate estimation of kinetic and film thickness model parameters of the biofilm process. The results show that the two-dimensional mathematical model with Edward kinetics (with its optimum parameters as mu(max)rho(s)/Y = 24.57, Ks = 1.352 and Ki = 102.36) and three-parameter film thickness expression (with its estimated parameters as a = 0.289 x 10(-5), b = 1.55 x 10(-4) and c = 15.2 x 10(-6)) better describes the biofilm reactor treating the industry wastewater.

Pyrolysis characteristics and kinetics of microalgae via thermogravimetric analysis (TGA): A state-of-the-art review.

Science.gov (United States)

Bach, Quang-Vu; Chen, Wei-Hsin

2017-12-01

Pyrolysis is a promising route for biofuels production from microalgae at moderate temperatures (400-600°C) in an inert atmosphere. Depending on the operating conditions, pyrolysis can produce biochar and/or bio-oil. In practice, knowledge for thermal decomposition characteristics and kinetics of microalgae during pyrolysis is essential for pyrolyzer design and pyrolysis optimization. Recently, the pyrolysis kinetics of microalgae has become a crucial topic and received increasing interest from researchers. Thermogravimetric analysis (TGA) has been employed as a proven technique for studying microalgae pyrolysis in a kinetic control regime. In addition, a number of kinetic models have been applied to process the TGA data for kinetic evaluation and parameters estimation. This paper aims to provide a state-of-the art review on recent research activities in pyrolysis characteristics and kinetics of various microalgae. Common kinetic models predicting the thermal degradation of microalgae are examined and their pros and cons are illustrated. Copyright © 2017 Elsevier Ltd. All rights reserved.

Determination of Kinetic Parameters for the Thermal Decomposition of Parthenium hysterophorus

Directory of Open Access Journals (Sweden)

Dhaundiyal Alok

2018-02-01

Full Text Available A kinetic study of pyrolysis process of Parthenium hysterophorous is carried out by using thermogravimetric analysis (TGA equipment. The present study investigates the thermal degradation and determination of the kinetic parameters such as activation E and the frequency factor A using model-free methods given by Flynn Wall and Ozawa (FWO, Kissinger-Akahira-Sonuse (KAS and Kissinger, and model-fitting (Coats Redfern. The results derived from thermal decomposition process demarcate decomposition of Parthenium hysterophorous among the three main stages, such as dehydration, active and passive pyrolysis. It is shown through DTG thermograms that the increase in the heating rate caused temperature peaks at maximum weight loss rate to shift towards higher temperature regime. The results are compared with Coats Redfern (Integral method and experimental results have shown that values of kinetic parameters obtained from model-free methods are in good agreement. Whereas the results obtained through Coats Redfern model at different heating rates are not promising, however, the diffusion models provided the good fitting with the experimental data.

3D nozzle flow simulations including state-to-state kinetics calculation

Science.gov (United States)

Cutrone, L.; Tuttafesta, M.; Capitelli, M.; Schettino, A.; Pascazio, G.; Colonna, G.

2014-12-01

In supersonic and hypersonic flows, thermal and chemical non-equilibrium is one of the fundamental aspects that must be taken into account for the accurate characterization of the plasma. In this paper, we present an optimized methodology to approach plasma numerical simulation by state-to-state kinetics calculations in a fully 3D Navier-Stokes CFD solver. Numerical simulations of an expanding flow are presented aimed at comparing the behavior of state-to-state chemical kinetics models with respect to the macroscopic thermochemical non-equilibrium models that are usually used in the numerical computation of high temperature hypersonic flows. The comparison is focused both on the differences in the numerical results and on the computational effort associated with each approach.

Maps of Fe-Al phases formation kinetics parameters during isothermal sintering

Energy Technology Data Exchange (ETDEWEB)

Pochec, Ewelina, E-mail: epochec@wat.edu.pl [Department of Advanced Materials and Technology, Military University of Technology (Poland); Jozwiak, Stanislaw; Karczewski, Krzysztof; Bojar, Zbigniew [Department of Advanced Materials and Technology, Military University of Technology (Poland)

2012-10-10

Highlights: Black-Right-Pointing-Pointer The sintering temperature and compaction pressure have a strong influence on the sinters structure. Black-Right-Pointing-Pointer The measurements confirmed the presence of the high-aluminium phases from Fe-Al equilibrium system in tested sinters. Black-Right-Pointing-Pointer The kinetics of Fe-Al phase formation can be described by Johnson-Mehl-Avrami modelling. - Abstract: The influence of technological parameters (compaction pressure and sintering temperature) on Fe-Al phase formation was investigated. The kinetics of phase transformation preceding and during an SHS reaction was studied in isothermal conditions by DSC using the JMA (Johnson-Mehl-Avrami) model. This model allowed us to determine basic kinetic parameters, including the Avrami exponent, which characterises the rate and manner of particular phase nucleation. The activation energy (E{sub a}) of particular phase formation was determined by the Kissinger method. XRD analysis and SEM observations of sintered material showed that not only Fe{sub 2}Al{sub 5} phase and low-aluminium solid solution in iron but also aluminium-rich FeAl{sub 2} and FeAl{sub 3} phases are formed during the sintering of an FeAl50 elementary powder mixture in isothermal conditions with an SHS reaction. The above conclusions were confirmed by iron-based solid solution lattice parameter studies and microhardness measurements.

Cell kinetic parameters of a solid mammary adenocarcinoma

International Nuclear Information System (INIS)

Porschen, R.; Feinendegen, L.E.

1978-01-01

Several cell kinetic parameters of the mammary adenocarcinoma EO 771 were evaluated by means of tumor volume measurements and of 125 I-UdR. The in-situ measured activity loss rate is disturbed by a slow elimination of labelled necrotic cells and by reutilization of 125 I-UdR. The restrictions of the I-UdR method are mentioned and the measured activity loss rates are compared with calculated volume loss rates. (orig./MG) [de

Comparison Of A Neutron Kinetics Parameter For A Polyethylene Moderated Highly Enriched Uranium System

Energy Technology Data Exchange (ETDEWEB)

McKenzie, IV, George Espy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Goda, Joetta Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Grove, Travis Justin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sanchez, Rene Gerardo [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-04-17

This paper examines the comparison of MCNP® code’s capability to calculate kinetics parameters effectively for a thermal system containing highly enriched uranium (HEU). The Rossi-α parameter was chosen for this examination because it is relatively easy to measure as well as easy to calculate using MCNP®’s kopts card. The Rossi-α also incorporates many other parameters of interest in nuclear kinetics most of which are more difficult to precisely measure. The comparison looks at two different nuclear data libraries for comparison to the experimental data. These libraries are ENDF/BVI (.66c) and ENDF/BVII (.80c).

Determination of kinetic parameters for 123-I thyroid uptake in healthy Japanese

Science.gov (United States)

Kusuhara, Hiroyuki; Maeda, Kazuya

2017-09-01

The purpose of this study was to compare the kinetic parameters for iodide thyroid accumulation in Japanese today with previously reported values. We determined the thyroid uptake of 123-I at 24 hours after the oral administration in healthy male Japanese without any diet restriction. The mean value was 16.1±5.4%, which was similar or rather lower than those previously reported in Japan (1958-1972). Kinetic model analysis was conducted to obtain the clearance for thyroid uptake from the blood circulation. The thyroid uptake clearance of 123-I was 0.540±0.073 ml/min, which was almost similar to those reported previously. There is no obvious difference in the thyroid uptake for 24 hours, and kinetic parameters in healthy Japanese for these 50 years. The fraction of distributed to the thyroid gland is lower than the ICRP reference man, and such difference must be taken into consideration to estimate the radiation exposure upon Fukushima accident in Japan.

Determination of the kinetic parameters of BeO using isothermal decay method

International Nuclear Information System (INIS)

Nieto, Juan Azorin; Vega, Claudia Azorin; Montalvo, Teodoro Rivera; Cabrera, Eugenio Torijano

2016-01-01

Most of the existing methods for obtaining the frequency factors make use of the trap depth (activation energy) making some assumptions about the order of the kinetics. This causes inconsistencies in the reported values of trapping parameters due that the values of the activation energy obtained by different methods differ appreciably among them. Then, it is necessary to use a method independent of the trap depth making use of the isothermal luminescence decay (ILD) method. The trapping parameters associated with the prominent glow peak of BeO (280 °C) are reported using ILD method. As a check, the trap parameters are also calculated by glow curve shape (Chen's) method after isolating the prominent glow peak by thermal cleaning technique. Our results show a very good agreement between the trapping parameters calculated by the two methods. ILD method was used for determining the trapping parameters of BeO. Results obtained applying this method are in good agreement with those obtained using other methods, except in the value of the frequency factor. - Highlights: • Kinetic parameters of BeO were determined. • Isothermal decay method was used. • Frecuency factor not agree with those obtained by other methods.

Effects of reaction-kinetic parameters on modeling reaction pathways in GaN MOVPE growth

Science.gov (United States)

Zhang, Hong; Zuo, Ran; Zhang, Guoyi

2017-11-01

In the modeling of the reaction-transport process in GaN MOVPE growth, the selections of kinetic parameters (activation energy Ea and pre-exponential factor A) for gas reactions are quite uncertain, which cause uncertainties in both gas reaction path and growth rate. In this study, numerical modeling of the reaction-transport process for GaN MOVPE growth in a vertical rotating disk reactor is conducted with varying kinetic parameters for main reaction paths. By comparisons of the molar concentrations of major Ga-containing species and the growth rates, the effects of kinetic parameters on gas reaction paths are determined. The results show that, depending on the values of the kinetic parameters, the gas reaction path may be dominated either by adduct/amide formation path, or by TMG pyrolysis path, or by both. Although the reaction path varies with different kinetic parameters, the predicted growth rates change only slightly because the total transport rate of Ga-containing species to the substrate changes slightly with reaction paths. This explains why previous authors using different chemical models predicted growth rates close to the experiment values. By varying the pre-exponential factor for the amide trimerization, it is found that the more trimers are formed, the lower the growth rates are than the experimental value, which indicates that trimers are poor growth precursors, because of thermal diffusion effect caused by high temperature gradient. The effective order for the contribution of major species to growth rate is found as: pyrolysis species > amides > trimers. The study also shows that radical reactions have little effect on gas reaction path because of the generation and depletion of H radicals in the chain reactions when NH2 is considered as the end species.

On enzyme kinetic parameters modification of gamma irradiation

International Nuclear Information System (INIS)

Ferdes, O.S.; Ferdes, M.; Turcu, G.R.

1993-01-01

To elucidate the molecular mechanisms of gamma-ray action on biomolecules there were investigated the modifications in activity and other kinetic parameters for some enzymes irradiated in pure dry state at relative high doses. There were considered bacterial and fungal α-amylases, glucoamylase and Mucor sp. protease irradiated by a 60 Co gamma-ray source in the dose range 1.0-30.0 kGy, at different dose-rates between 0.5-2.0 kGy/h, at room temperature. Considering the enzyme inactivation in this dose range, the dose-effect relationships have an expected form and depend on the irradiation conditions but not significantly on the dose rate. The catalytic properties of enzymes were modified by irradiation. By usual methods it is evidenced a direct correlation between the enzymatic activities, Michaelis-Menten constant, K m , reaction velocities, v, and the irradiation dose. These experimental findings can support a self-consistent theoretical approach on biophysical radiation action on biological active molecules like enzymes. At the same time, some enzyme behaviour to irradiation could be considered like a good biological indicator of radiation response. (Author) 4 Figs., 19 Refs

New Methods for Processing and Quantifying VO2 Kinetics to Steady State: VO2 Onset Kinetics

Directory of Open Access Journals (Sweden)

Craig R. McNulty

2017-09-01

Full Text Available Current methods of oxygen uptake (VO2 kinetics data handling may be too simplistic for the complex physiology involved in the underlying physiological processes. Therefore, the aim of this study was to quantify the VO2 kinetics to steady state across the full range of sub-ventilatory threshold work rates, with a particular focus on the VO2 onset kinetics. Ten healthy, moderately trained males participated in five bouts of cycling. Each bout involved 10 min at a percentage of the subject's ventilation threshold (30, 45, 60, 75, 90% from unloaded cycling. The VO2 kinetics was quantified using the conventional mono-exponential time constant (tau, τ, as well as the new methods for VO2 onset kinetics. Compared to linear modeling, non-linear modeling caused a deterioration of goodness of fit (main effect, p < 0.001 across all exercise intensities. Remainder kinetics were also improved using a modified application of the mono-exponential model (main effect, p < 0.001. Interestingly, the slope from the linear regression of the onset kinetics data is similar across all subjects and absolute exercise intensities, and thereby independent of subject fitness and τ. This could indicate that there are no functional limitations between subjects during this onset phase, with limitations occurring for the latter transition to steady state. Finally, the continuing use of mono-exponential modeling could mask important underlying physiology of more instantaneous VO2 responses to steady state. Consequently, further research should be conducted on this new approach to VO2 onset kinetics.

Determination of the temperature coefficients and the kinetic parameters for the HTTR safety analysis

International Nuclear Information System (INIS)

Tokuhara, K.; Nakata, T.; Murata, I.; Yamashita, K.; Shindo, R.

1991-01-01

This report describes the calculational methods which were employed to determine the temperature coefficients and the kinetic parameters for the safety analysis in the HTTR (High Temperature Engineering Test Reactor). The temperature coefficients (doppler, moderator temperature) and the kinetic parameters (prompt neutron life time; l, effective delayed neutron fraction; β eff) are important for the point model core dynamic analysis and should be evaluated properly. The temperature coefficients were calculated by the whole core model. Doppler coefficient was evaluated under the conditions of all control rods withdrawn and the uniform change of fuel temperature. The minimum and the maximum value of the evaluated doppler coefficients in a burnup cycle are -4.6x10 -5 and -1.5x10 -5 ΔK/K/deg. C respectively. The moderator temperature coefficient was evaluated under the conditions of all control rods withdrawn and the uniform change of moderator temperature. The minimum and the maximum value of the evaluated moderator temperature coefficients in a burnup cycle are -17.1x10 -5 and 0.99x10 -5 ΔK/K/deg. C respectively. In spite of positive moderator temperature coefficient, the power coefficient is always negative. Therefore the HTTR possesses inherent power-suppressing feed back characteristic in all operating condition. We surveyed the effects of the Xe existence, the control rods existence, the fuel temperature and the region in which the temperature was changed on the moderator temperature coefficients. The kinetic parameters were calculated by the perturbation method with the whole core model. The minimum and the maximum value of the evaluated effective delayed neutron fraction (β eff) are 0.0047 and 0.0065 respectively. These of the evaluated prompt neutron life time (l) are 0.67 and 0.78 ms respectively. We have surveyed the effects of the fuel depletion and the core power level on these parameters, and considered these effects on the kinetic parameters. From

Assessing the impact of azadirachtin application to soil on ureaseactivity and its kinetic parameters

OpenAIRE

KIZILKAYA, RIDVAN; SAMOFALOVA, IRAIDA; MUDRYKH, NATALYA; MİKAİLSOY, FARİZ; AKÇA, İZZET; SUSHKOVA, SVETLANA; MINKINA, TATIANA

2015-01-01

Abstract: The kinetic parameters of soil urease have attracted considerable attention; however, little information is available on its kinetic parameters and behaviors in response to azadirachtin application to the soil. A short (14-day) field experiment was conducted using Albic Luvisol soil (loam texture; pH 6.70; electrical conductivity 0.81 dS m-1; CaCO3 content 0.04%; total organic carbon 0.99%) as the experimental soil in the Perm region of the Russian Federation to investigate the effe...

Activity, stability and kinetic parameters for α-chymotrypsin catalysed ...

Indian Academy of Sciences (India)

Three typical surfactants were selected based on their head group charges: a non-ionic surfactant Triton-X 100 and two zwitterionic sulphobetaine surfactants of the type CH2+1N+Me2 (CH2)3 SO 3 − (n = 10; SB3-10, n = 16; SB3-16). The kinetic parameters (such as cat and M) of the -CT at 27°C were determined ...

Two-detector cross-correlation noise technique and its application in measuring reactor kinetic parameters

International Nuclear Information System (INIS)

Lu Guiping; Peng Feng; Yi Jieyi

1988-01-01

The two-detector cross-correlation noise technique is a new method of measuring reactor kinetic parameters developed in the sixties. It has the advantages of non-perturbation in core, high signal to noise ratio, low space dependent effect, and simple and reliable in measurement. A special set of cross-correlation analyzer has been prepared for measuring kinetic parameters of several reactor assemblies, such as the High Flux Engineering Test Reactor, its zero power mock up facility and a low enriched uranium light water lattice zero power facility

Transition state kinetics of Hg(II) adsorption at gibbsite-water interface

International Nuclear Information System (INIS)

Weerasooriya, Rohan; Tobschall, Heinz J.; Seneviratne, Wasana; Bandara, Atula

2007-01-01

Kinetics of adsorption plays a pivotal factor in determining the bio-availability and mobility of Hg(II) in the environment. The kinetics of Hg(II) adsorption on gibbsite was examined as a function of pH, temperature and electrolyte type. Adsorption of Hg(II) was highly non-linear where the rate of Hg(II) retention was rapid initially and was followed by gradual or somewhat slow retention behavior with increasing contact time. The respective rate constants designated as k 1 (S-1: fast step) and k 2 (S-2: slow step). Always k 1 follows the order: k 1 ClO 4 >=k 1 (NO 3 ) 4 >>k 1 Cl . Such a relationship was not observed for the S-2 route. A two-step reaction model with pseudo-first order kinetics successfully described the adsorption rates of Hg(II) on gibbsite. Arrhenius and Erying models determined the thermodynamic parameters at activation states, which correspond to S-1 and S-2 routes. In a given system, always the activation energies showed a decrease with the pH. Gibbs free energy (ΔG numbersign ), enthalpy (ΔH numbersign ), and entropy (ΔS numbersign ) values of activation states were almost similar both in NaClO 4 and NaNO 3 which signal a similar Hg(II) adsorptive mechanism on gibbsite. The configurations of different Hg(II)-surface complexes were elucidated by transmission vibration spectroscopy

EQUILIBRIUM AND KINETIC PARAMETERS FOR THE SEDIMENTATION OF TARTARIC SALTS IN YOUNG WINES

Directory of Open Access Journals (Sweden)

Ecaterina Covaci

2015-06-01

Full Text Available In young wines potassium hydrogen tartrate is always present in supersaturating concentration and crystallizes spontaneously. The aim of this study is to obtain kinetic parameters, which explain the stability of young wines during the stabilization treatments. The kinetic and equilibrium parameters were evaluated and discussed. The heating factor has a decisive influence on the reaction rate of potassium hydrogen tartrate precipitation in young wines. An increase of temperature leads to a decrease in efficiency of stabilization process and to an enhancement of the activation energy of the system. According to the obtained experimental results, the optimal regime for production and stabilization of young wines has been established.

Thermoluminescence kinetic parameters of different amount La-doped ZnB2O4

International Nuclear Information System (INIS)

Kucuk, Nil; Gozel, Aziz Halit; Yüksel, Mehmet; Dogan, Tamer; Topaksu, Mustafa

2015-01-01

The kinetic parameters of 1%, 2%, 3% and 4% La-doped ZnB 2 O 4 phosphors (i.e. ZnB 2 O 4 :0.01La, ZnB 2 O 4 :0.02La, ZnB 2 O 4 :0.03La and ZnB 2 O 4 :0.04La) synthesized by nitric acid method have been calculated. Thermoluminescence (TL) glow curves of ZnB 2 O 4 :La phosphors after beta-irradiation showed a very well defined main peak having the maximum temperature at around 200 °C and a shoulder peak at around 315 °C with a constant heating rate of 5 °C/s. The kinetic parameters of ZnB 2 O 4 :La phosphors TL glow peaks (i.e. order of kinetics (b), activation energies (E a ) and frequency factors (s)) have been determined and evaluated by Computerized Glow Curve Deconvolution (CGCD), and Peak Shape (PS) methods using the glow curve data. From the results, it can conclude that the values of E a obtained with these methods for ZnB 2 O 4 :La phosphors are consistent with each other, but the s values differ considerably. - Highlights: • Calculation of TL kinetic parameters for La-doped ZnB 2 O 4 . • La-doped ZnB 2 O 4 was synthesized by nitric acid method. • Well defined main peak at about 200 °C

Thermoluminescent kinetic parameters of the perovskite, KMgF3, activated with lanthanum

International Nuclear Information System (INIS)

Sepulveda M, F.; Azorin N, J.; Rivera M, T.; Furetta, C.; Sanipoli, C.

2004-01-01

The thermoluminescent curves induced by the beta radiation in the perovskite KMgF 3 were investigated activated with lanthanum. The classic methods were used to determine the kinetic parameters (the kinetic order b, the activation energy E and the frequency of escape intent s) associated with the peaks of the thermoluminescent curve (Tl) in the KMgF 3 activated with lanthanum after the irradiation with beta rays. The method is based on the position of the thermoluminescent peaks, obtained of the temperature change of the peak in the maximum emission caused by the change in the heating rapidity to which the samples were measured. In this work, the samples in form of pellets were re cooked previously at 400 C during one hour before irradiating them with beta particles. The Tl measures were made with a Tl reader system using three different heating rapidities and storing the glow curves. To calculate the depth of the E traps and the frequency factor s, the parameters of the glow curve were determined experimentally of the shame of the glow curve by means of the mensuration of the shame of the maximum temperature of the peak, T M like a function of the heating rapidity. The results indicate that the values of the kinetic parameters are very near among if when they are obtained indistinctly of anyone of the different methods. (Author)

Parameter and State Estimator for State Space Models

Directory of Open Access Journals (Sweden)

Ruifeng Ding

2014-01-01

Full Text Available This paper proposes a parameter and state estimator for canonical state space systems from measured input-output data. The key is to solve the system state from the state equation and to substitute it into the output equation, eliminating the state variables, and the resulting equation contains only the system inputs and outputs, and to derive a least squares parameter identification algorithm. Furthermore, the system states are computed from the estimated parameters and the input-output data. Convergence analysis using the martingale convergence theorem indicates that the parameter estimates converge to their true values. Finally, an illustrative example is provided to show that the proposed algorithm is effective.

Study of the kinetics parameters for subcritical media driven by source

International Nuclear Information System (INIS)

Lee, S.M.; Maiorino, J.R.

2009-01-01

This paper presents a theoretical study of reactor kinetics focusing on the methodology of calculation and the experimental measurements of the so-called kinetic parameters. A comparison between the methodology based on the Dulla's formalism and the classical method is made. The objective is to exhibit the dependence of the parameters on sub criticality level and perturbation. Two different slab type systems were considered: thermal one and fast one, both with homogeneous media. One group diffusion model was used for the fast reactor, and for the thermal system, two group diffusion model, considering, in both case only one precursor's family. For reason of simplicity, several additional assumptions were made for calculation of two group method: no up-scattering, fission reaction occurring only in thermal group, etc. The solutions for subcritical systems were obtained using the expansion method, and for critical systems, the methods presented in classical textbooks of reactor physics were applied. The numerical results presented their dependence on sub criticality level and perturbation. (author)

A novel optimization approach to estimating kinetic parameters of the enzymatic hydrolysis of corn stover

Directory of Open Access Journals (Sweden)

Fenglei Qi

2016-01-01

Full Text Available Enzymatic hydrolysis is an integral step in the conversion of lignocellulosic biomass to ethanol. The conversion of cellulose to fermentable sugars in the presence of inhibitors is a complex kinetic problem. In this study, we describe a novel approach to estimating the kinetic parameters underlying this process. This study employs experimental data measuring substrate and enzyme loadings, sugar and acid inhibitions for the production of glucose. Multiple objectives to minimize the difference between model predictions and experimental observations are developed and optimized by adopting multi-objective particle swarm optimization method. Model reliability is assessed by exploring likelihood profile in each parameter space. Compared to previous studies, this approach improved the prediction of sugar yields by reducing the mean squared errors by 34% for glucose and 2.7% for cellobiose, suggesting improved agreement between model predictions and the experimental data. Furthermore, kinetic parameters such as K2IG2, K1IG, K2IG, K1IA, and K3IA are identified as contributors to the model non-identifiability and wide parameter confidence intervals. Model reliability analysis indicates possible ways to reduce model non-identifiability and tighten parameter confidence intervals. These results could help improve the design of lignocellulosic biorefineries by providing higher fidelity predictions of fermentable sugars under inhibitory conditions.

TU-C-12A-11: Comparisons Between Cu-ATSM PET and DCE-CT Kinetic Parameters in Canine Sinonasal Tumors

Energy Technology Data Exchange (ETDEWEB)

La Fontaine, M; Bradshaw, T [University of Wisconsin, Madison, Wisconsin (United States); Kubicek, L [University of Florida, Gainesville, Florida (United States); Forrest, L [University of Wisconsin-Madison, Madison, Wisconsin (United States); Jeraj, R [University of Wisconsin, Madison, WI (United States)

2014-06-15

Purpose: Regions of poor perfusion within tumors may be associated with higher hypoxic levels. This study aimed to test this hypothesis by comparing measurements of hypoxia from Cu-ATSM PET to vasculature kinetic parameters from DCE-CT kinetic analysis. Methods: Ten canine patients with sinonasal tumors received one Cu-ATSM PET/CT scan and three DCE-CT scans prior to treatment. Cu-ATSM PET/CT and DCE-CT scans were registered and resampled to matching voxel dimensions. Kinetic analysis was performed on DCE-CT scans and for each patient, the resulting kinetic parameter values from the three DCE-CT scans were averaged together. Cu-ATSM SUVs were spatially correlated (r{sub spatial}) on a voxel-to-voxel basis against the following DCE-CT kinetic parameters: transit time (t{sub 1}), blood flow (F), vasculature fraction (v{sub 1}), and permeability (PS). In addition, whole-tumor comparisons were performed by correlating (r{sub ROI}) the mean Cu-ATSM SUV (SUV{sub mean}) with median kinetic parameter values. Results: The spatial correlations (r{sub spatial}) were poor and ranged from -0.04 to 0.21 for all kinetic parameters. These low spatial correlations may be due to high variability in the DCE-CT kinetic parameter voxel values between scans. In our hypothesis, t{sub 1} was expected to have a positive correlation, while F was expected to have a negative correlation to hypoxia. However, in wholetumor analysis the opposite was found for both t{sub 1} (r{sub ROI} = -0.25) and F (r{sub ROI} = 0.56). PS and v{sub 1} may depict angiogenic responses to hypoxia and found positive correlations to Cu-ATSM SUV for PS (r{sub ROI} = 0.41), and v{sub 1} (r{sub ROI} = 0.57). Conclusion: Low spatial correlations were found between Cu-ATSM uptake and DCE-CT vasculature parameters, implying that poor perfusion is not associated with higher hypoxic regions. Across patients, the most hypoxic tumors tended to have higher blood flow values, which is contrary to our initial hypothesis. Funding

Estimating the kinetic parameters of activated sludge storage using weighted non-linear least-squares and accelerating genetic algorithm.

Science.gov (United States)

Fang, Fang; Ni, Bing-Jie; Yu, Han-Qing

2009-06-01

In this study, weighted non-linear least-squares analysis and accelerating genetic algorithm are integrated to estimate the kinetic parameters of substrate consumption and storage product formation of activated sludge. A storage product formation equation is developed and used to construct the objective function for the determination of its production kinetics. The weighted least-squares analysis is employed to calculate the differences in the storage product concentration between the model predictions and the experimental data as the sum of squared weighted errors. The kinetic parameters for the substrate consumption and the storage product formation are estimated to be the maximum heterotrophic growth rate of 0.121/h, the yield coefficient of 0.44 mg CODX/mg CODS (COD, chemical oxygen demand) and the substrate half saturation constant of 16.9 mg/L, respectively, by minimizing the objective function using a real-coding-based accelerating genetic algorithm. Also, the fraction of substrate electrons diverted to the storage product formation is estimated to be 0.43 mg CODSTO/mg CODS. The validity of our approach is confirmed by the results of independent tests and the kinetic parameter values reported in literature, suggesting that this approach could be useful to evaluate the product formation kinetics of mixed cultures like activated sludge. More importantly, as this integrated approach could estimate the kinetic parameters rapidly and accurately, it could be applied to other biological processes.

A new general method for simultaneous fitting of temperature and concentration dependence of reaction rates yields kinetic and thermodynamic parameters for HIV reverse transcriptase specificity.

Science.gov (United States)

Li, An; Ziehr, Jessica L; Johnson, Kenneth A

2017-04-21

Recent studies have demonstrated the dominant role of induced fit in enzyme specificity of HIV reverse transcriptase and many other enzymes. However, relevant thermodynamic parameters are lacking, and equilibrium thermodynamic methods are of no avail because the key parameters can only be determined by kinetic measurement. By modifying KinTek Explorer software, we present a new general method for globally fitting data collected over a range of substrate concentrations and temperatures and apply it to HIV reverse transcriptase. Fluorescence stopped-flow methods were used to record the kinetics of enzyme conformational changes that monitor nucleotide binding and incorporation. The nucleotide concentration dependence was measured at temperatures ranging from 5 to 37 °C, and the raw data were fit globally to derive a single set of rate constants at 37 °C and a set of activation enthalpy terms to account for the kinetics at all other temperatures. This comprehensive analysis afforded thermodynamic parameters for nucleotide binding ( K d , Δ G , Δ H , and Δ S at 37 °C) and kinetic parameters for enzyme conformational changes and chemistry (rate constants and activation enthalpy). Comparisons between wild-type enzyme and a mutant resistant to nucleoside analogs used to treat HIV infections reveal that the ground state binding is weaker and the activation enthalpy for the conformational change step is significantly larger for the mutant. Further studies to explore the structural underpinnings of the observed thermodynamics and kinetics of the conformational change step may help to design better analogs to treat HIV infections and other diseases. Our new method is generally applicable to enzyme and chemical kinetics. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Mathematical modeling of CA125 kinetics in recurrent ovarian cancer (ROC) patients treated with chemotherapy and predictive value of early modeled kinetic parameters in CALYPSO trial: A GCIG study

DEFF Research Database (Denmark)

You, Benoit; Colomban, Olivier; Heywood, Mark

2011-01-01

Background: Although CA125 kinetic profiles may be related with relapse risk in ovarian cancer patients treated with chemotherapy, no reliable kinetic parameters have been reported. Mathematical modeling may help describe CA125 decline dynamically and determine parameters predictive of relapse....... Methods: Data from CALYPSO phase III trial data comparing 2 carboplatin-based regimens in ROC patients were analyzed. Based on population kinetic approach (Monolix software), a semi-mechanistic model was used to fit serum log (CA125) concentration-time profiles with following parameters: tumor growth rate...... the first 50 treatment days were tested regarding progression free survival (PFS) against other reported prognostic factors using Cox-models: treatment arm; platinum-free interval (PFI), metastatic site number, largest tumor size, elevated WBC and measurable disease. Results: The CA125 kinetics from 898...

Kinetic studies following state-selective laser excitation

International Nuclear Information System (INIS)

Keto, J.W.

1991-01-01

During the past year, we have made measurements of state-to-state energy transfer cross sections and radiative lifetimes for Xe*(6p,6p',7p) and Kr*(5p) states in xenon and krypton buffer gases. These results are relevant to kinetic models of both excimer lasers and the infrared xenon laser; and they are a significant improvement in the precision of the known radiative lifetimes. 3 refs., 2 figs., 2 tabs

Excited state kinetics of anthracene-bridge-aniline intramolecular exciplexes

DEFF Research Database (Denmark)

Thyrhaug, Erling; Hammershøj, Peter; Kjær, Kasper Skov

2014-01-01

excited anthracene state (LE) and an excited state complex (exciplex, EP) in non-polar solvents. The kinetics of the excited state processes were established in decalin from the time-resolved emission, and was shown to be strongly influenced by an electron-transfer state (ET). For quantitative studies...

Understanding system dynamics of an adaptive enzyme network from globally profiled kinetic parameters.

Science.gov (United States)

Chiang, Austin W T; Liu, Wei-Chung; Charusanti, Pep; Hwang, Ming-Jing

2014-01-15

A major challenge in mathematical modeling of biological systems is to determine how model parameters contribute to systems dynamics. As biological processes are often complex in nature, it is desirable to address this issue using a systematic approach. Here, we propose a simple methodology that first performs an enrichment test to find patterns in the values of globally profiled kinetic parameters with which a model can produce the required system dynamics; this is then followed by a statistical test to elucidate the association between individual parameters and different parts of the system's dynamics. We demonstrate our methodology on a prototype biological system of perfect adaptation dynamics, namely the chemotaxis model for Escherichia coli. Our results agreed well with those derived from experimental data and theoretical studies in the literature. Using this model system, we showed that there are motifs in kinetic parameters and that these motifs are governed by constraints of the specified system dynamics. A systematic approach based on enrichment statistical tests has been developed to elucidate the relationships between model parameters and the roles they play in affecting system dynamics of a prototype biological network. The proposed approach is generally applicable and therefore can find wide use in systems biology modeling research.

A critical look at the kinetic models of thermoluminescence-II. Non-first order kinetics

International Nuclear Information System (INIS)

Sunta, C M; Ayta, W E F; Chubaci, J F D; Watanabe, S

2005-01-01

Non-first order (FO) kinetics models are of three types; second order (SO), general order (GO) and mixed order (MO). It is shown that all three of these have constraints in their energy level schemes and their applicable parameter values. In nature such restrictions are not expected to exist. The thermoluminescence (TL) glow peaks produced by these models shift their position and change their shape as the trap occupancies change. Such characteristics are very unlike those found in samples of real materials. In these models, in general, retrapping predominates over recombination. It is shown that the quasi-equilibrium (QE) assumption implied in the derivation of the TL equation of these models is quite valid, thus disproving earlier workers' conclusion that QE cannot be held under retrapping dominant conditions. However notwithstanding their validity, they suffer from the shortcomings as stated above and have certain lacunae. For example, the kinetic order (KO) parameter and the pre-exponential factor which are assumed to be the constant parameters of the GO kinetics expression turn out to be variables when this expression is applied to plausible physical models. Further, in glow peak characterization using the GO expression, the quality of fit is found to deteriorate when the best fitted value of KO parameter is different from 1 and 2. This means that the found value of the basic parameter, namely the activation energy, becomes subject to error. In the MO kinetics model, the value of the KO parameter α would change with dose, and thus in this model also, as in the GO model, no single value of KO can be assigned to a given glow peak. The paper discusses TL of real materials having characteristics typically like those of FO kinetics. Theoretically too, a plausible physical model of TL emission produces glow peaks which have characteristics of FO kinetics under a wide variety of parametric combinations. In the background of the above findings, it is suggested that

Modelling fungal solid-state fermentation: The role of inactivation kinetics

NARCIS (Netherlands)

Smits, J.P.; Sonsbeek, H.M. van; Knol, W.; Tramper, J.; Geelhoed, W.; Peeters, M.; Rinzema, A.

1999-01-01

The theoretical mathematical models described in this paper are used to evaluate the effects of fungal biomass inactivation kinetics on a non- isothermal tray solid-state fermentation (SSF). The inactivation kinetics, derived from previously reported experiments done under isothermal conditions and

A study of calculation methodology and experimental measurements of the kinetic parameters for source driven subcritical systems

International Nuclear Information System (INIS)

Lee, Seung Min

2009-01-01

This work presents a theoretical study of reactor kinetics focusing on the methodology of calculation and the experimental measurements of the so-called kinetic parameters. A comparison between the methodology based on the Dulla's formalism and the classical method is made. The objective is to exhibit the dependence of the parameters on subcriticality level and perturbation. Two different slab type systems were considered: thermal one and fast one, both with homogeneous media. One group diffusion model was used for the fast reactor, and for the thermal system, two groups diffusion model, considering, in both case, only one precursor's family. The solutions were obtained using the expansion method. Also, descriptions of the main experimental methods of measurements of the kinetic parameters are presented in order to put a question about the compatibility of these methods in subcritical region. (author)

Closed-form kinetic parameter estimation solution to the truncated data problem

International Nuclear Information System (INIS)

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

2010-01-01

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 noiseless and noisy projections.

Revealing kinetics and state-dependent binding properties of IKur-targeting drugs that maximize atrial fibrillation selectivity

Science.gov (United States)

Ellinwood, Nicholas; Dobrev, Dobromir; Morotti, Stefano; Grandi, Eleonora

2017-09-01

The KV1.5 potassium channel, which underlies the ultra-rapid delayed-rectifier current (IKur) and is predominantly expressed in atria vs. ventricles, has emerged as a promising target to treat atrial fibrillation (AF). However, while numerous KV1.5-selective compounds have been screened, characterized, and tested in various animal models of AF, evidence of antiarrhythmic efficacy in humans is still lacking. Moreover, current guidelines for pre-clinical assessment of candidate drugs heavily rely on steady-state concentration-response curves or IC50 values, which can overlook adverse cardiotoxic effects. We sought to investigate the effects of kinetics and state-dependent binding of IKur-targeting drugs on atrial electrophysiology in silico and reveal the ideal properties of IKur blockers that maximize anti-AF efficacy and minimize pro-arrhythmic risk. To this aim, we developed a new Markov model of IKur that describes KV1.5 gating based on experimental voltage-clamp data in atrial myocytes from patient right-atrial samples in normal sinus rhythm. We extended the IKur formulation to account for state-specificity and kinetics of KV1.5-drug interactions and incorporated it into our human atrial cell model. We simulated 1- and 3-Hz pacing protocols in drug-free conditions and with a [drug] equal to the IC50 value. The effects of binding and unbinding kinetics were determined by examining permutations of the forward (kon) and reverse (koff) binding rates to the closed, open, and inactivated states of the KV1.5 channel. We identified a subset of ideal drugs exhibiting anti-AF electrophysiological parameter changes at fast pacing rates (effective refractory period prolongation), while having little effect on normal sinus rhythm (limited action potential prolongation). Our results highlight that accurately accounting for channel interactions with drugs, including kinetics and state-dependent binding, is critical for developing safer and more effective pharmacological anti

Evaluation of energy collapsing effect on reactor kinetics parameters by diffusion theory

International Nuclear Information System (INIS)

Unesaki, Hironobu

1989-01-01

Reactor kinetics parameters play an important role as scaling factors between observed and calculated reactivities in the analysis of reactor physics experiments. In this report, energy collapsing errors in two kinetic parameters, the effective delayed neutron fraction and the neutron life time, are investigated by means of the diffusion theory. Coarse group calculations are made for various energy group structures. Cores of various moderator-to-fuel volume ratios are selected to investigate the influence of neutron spectrum changes on the energy collapsing error. The energy collapsing errors in the effective delayed neutron fraction and neutron life time are much larger than those in k eff . This might be because the former two parameters are functions of both the foward and adjoint flux, whereas the latter is a function of the forward flux alone. The use of coarse constants will cause errors in both fluxes, and the resulting errors in the former will be much more emphasized. As the effective delayed neutron fraction is sensitive to the treatment of an energy region in the vicinity of the fission spectrum peak, the coarse group error in it might differ between cores with different enrichment and composition. Inaccurate weighting of group constants leads to neutron spectra which do not conserve the fine group spectra, and those errors will be emphasized in calculated integral parameters. (N.K.)

Determination of kinetic parameters of Fe sup 3+ reduction mediated by a polyaniline film using steady-state and impedance methods

Energy Technology Data Exchange (ETDEWEB)

Deslouis, C. (LP15 du CNRS, Physique des Liquides et Electrochimie, Lab. de l' Univ. Pierre et Marie Curie, 75252 Paris Cedex 05 (FR)); Musiani, M.M.; Pagura, C.; Tribollet, C. (Inst. di Polarografia de Elettrochimica Preparativa del CNR, Corso Stati Uniti, 4, 35020 Camin, Padova (IT))

1991-09-01

This paper discusses the Fe{sup 3+} reduction reaction studied at Pt and polyaniline rotating disk electrodes by steady-state and impedance methods with the aim of testing the possibility of achieving the charge transfer resistance (R{sub ts}) of a redox reaction mediated by a conducting polymer film by ac impedance R{sub ts} was obtained as a function of electrode potential and rotation rate by nonlinear least squares fitting of a previously developed kinetic equation to the experimental data. These R{sub ts} values were combined with steady-state ones to calculate b{sub c} and k{sup 0}.

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.

Science.gov (United States)

Tosun, Ismail

2012-03-01

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 (R(2)) 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.

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

Directory of Open Access Journals (Sweden)

İsmail Tosun

2012-03-01

Full Text Available 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.

Determination of kinetic parameters of heterogeneous isotopic exchange reaction

International Nuclear Information System (INIS)

Huang, Ting-Chia; Tsai, Fuan-Nan

1977-01-01

A mathematical model has been proposed for a heterogeneous isotopic exchange reaction which involves film diffusion, surface chemical reaction and intraparticle diffusion. The exchange equation to predict the exchange fraction as a function of time for the spherical particles immersed in a solution of finite volume has been derived. The relations between the exchange fraction and dimensionless time are plotted with xi(=ak sub(f)/KD sub(e)), xi 1 (=K 1 a 2 /D sub(e)) and final fractional uptake as parameters. From the values of the kinetic parameters xi and xi 1 , the relative importance of each limiting step is discussed. Experimental results of the isotopic exchange reaction of calcium ion in both system CaCO 3 (s)/Ca 2+ (aq) and system calcium type resin Dowex 50W-X8/Ca 2+ (aq) are coincident with the theoretical equation proposed in this study. (auth.)

Malonic acid concentration as a control parameter in the kinetic analysis of the Belousov-Zhabotinsky reaction under batch conditions.

Science.gov (United States)

Blagojević, Slavica M; Anić, Slobodan R; Cupić, Zeljko D; Pejić, Natasa D; Kolar-Anić, Ljiljana Z

2008-11-28

The influence of the initial malonic acid concentration [MA]0 (8.00 x 10(-3) sulfuric acid (1.00 mol dm(-3)) and cerium sulfate (2.50 x 10(-3) mol dm(-3)) on the dynamics and the kinetics of the Belousov-Zhabotinsky (BZ) reactions was examined under batch conditions at 30.0 degrees C. The kinetics of the BZ reaction was analyzed by the earlier proposed method convenient for the examinations of the oscillatory reactions. In the defined region of parameters where oscillograms with only large-amplitude relaxation oscillations appeared, the pseudo-first order of the overall malonic acid decomposition with a corresponding rate constant of 2.14 x 10(-2) min(-1) was established. The numerical results on the dynamics and kinetics of the BZ reaction, carried out by the known skeleton model including the Br2O species, were in good agreement with the experimental ones. The already found saddle node infinite period (SNIPER) bifurcation point in transition from a stable quasi-steady state to periodic orbits and vice versa is confirmed by both experimental and numerical investigations of the system under consideration. Namely, the large-amplitude relaxation oscillations with increasing periods between oscillations in approaching the bifurcation points at the beginning and the end of the oscillatory domain, together with excitability of the stable quasi-steady states in their vicinity are obtained.

Platelet kinetics: the state of the art

International Nuclear Information System (INIS)

Heyns, A. duP

1984-01-01

In this paper an overview of the state of the art of platelet kinetics 1982 is presented. The subjects considered include a discussion of the advantages and disadvantages of some of the many radionuclide platelet labels, viz 51 Cr, 111 In, focussing briefly on models for analysis of platelets survival. (Auth.)

Effects of correlated parameters and uncertainty in electronic-structure-based chemical kinetic modelling

Science.gov (United States)

Sutton, Jonathan E.; Guo, Wei; Katsoulakis, Markos A.; Vlachos, Dionisios G.

2016-04-01

Kinetic models based on first principles are becoming common place in heterogeneous catalysis because of their ability to interpret experimental data, identify the rate-controlling step, guide experiments and predict novel materials. To overcome the tremendous computational cost of estimating parameters of complex networks on metal catalysts, approximate quantum mechanical calculations are employed that render models potentially inaccurate. Here, by introducing correlative global sensitivity analysis and uncertainty quantification, we show that neglecting correlations in the energies of species and reactions can lead to an incorrect identification of influential parameters and key reaction intermediates and reactions. We rationalize why models often underpredict reaction rates and show that, despite the uncertainty being large, the method can, in conjunction with experimental data, identify influential missing reaction pathways and provide insights into the catalyst active site and the kinetic reliability of a model. The method is demonstrated in ethanol steam reforming for hydrogen production for fuel cells.

Verification of kinetic parameters of coupled fast-thermal core HERBE

International Nuclear Information System (INIS)

Pesic, M.; Marinkovic, P.; Milosevic, M.; Nikolic, D.; Zavaljevski, N.; Milovanovic, S.; Ljubenov, V.

1997-03-01

The HERBE system is a new coupled fast-thermal core constructed in 1989 at the RB critical heavy water assembly at the VINCA Institute. It was designed with the aim to improve experimental possibilities in fast neutron fields and for experimental verification of reactor design-oriented methods. This paper overviews experiments for kinetic parameters verification carried out at HERBE system. Their short description and comparison of experimental and calculation results are included. A brief introduction to the computer codes used in the calculations is presented too. (author)

Experimental test of a four-level kinetic model for excited-state intramolecular proton transfer dye lasers

Energy Technology Data Exchange (ETDEWEB)

Costela, A; Munnoz, J M; Douhal, A; Figuera, J M; Acuna, A U [Inst. de Quimica Fisica ' ' Rocasolano' ' , C.S.I.C., Madrid (Spain)

1989-11-01

The nanosecond pulses of a dye laser oscillator based on the excited-state intramolecular proton-transfer reaction (IPT) of salicylamide and 2'-hydroxylphenyl benzimidazole dyes have been studied as a function of several experimental parameters. To explain the operation of this laser a numerical four-level kinetic model was developed until the lasing properties of these dyes, in the presence of a variable oxygen concentration and pumped with a double pulse technique, could be reproduced. This was possible only by assuming that the efficiency of the laser is controlled by the absorption cross-section of a transient state with a lifetime in the nanosecond-picosecond range, which was tentatively identified as a ground state tautomeric species. (orig.).

The measurement and calculation of the kinetic parameter {beta}{sub eff}/{Lambda} of a small high-temperature like, critical system

Energy Technology Data Exchange (ETDEWEB)

Wallerbos, E.J.M.; Hoogenboom, J.E. [Interfaculty Reactor Inst., Delft Univ. of Technology, Delft (Netherlands)

1998-01-01

This paper demonstrates that it is well possible to determine the kinetic parameter {beta}{sub eff}/{Lambda} in a neutronically very slow system by means of noise measurements in the critical state. The advantages of this technique are that it can be conducted in a critical reactor directly, and that no special measurement equipment is needed. The comparison to calculated values for four configurations, which differ in the amount of moderation in the core region, shows a satisfactory agreement. (author)

Two-order parameters theory of the metal-insulator phase transition kinetics in the magnetic field

Science.gov (United States)

Dubovskii, L. B.

2018-05-01

The metal-insulator phase transition is considered within the framework of the Ginzburg-Landau approach for the phase transition described with two coupled order parameters. One of the order parameters is the mass density which variation is responsible for the origin of nonzero overlapping of the two different electron bands and the appearance of free electron carriers. This transition is assumed to be a first-order phase one. The free electron carriers are described with the vector-function representing the second-order parameter responsible for the continuous phase transition. This order parameter determines mostly the physical properties of the metal-insulator transition and leads to a singularity of the surface tension at the metal-insulator interface. The magnetic field is involved into the consideration of the system. The magnetic field leads to new singularities of the surface tension at the metal-insulator interface and results in a drastic variation of the phase transition kinetics. A strong singularity in the surface tension results from the Landau diamagnetism and determines anomalous features of the metal-insulator transition kinetics.

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

Science.gov (United States)

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

2012-09-01

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

Initial state dependence of nonlinear kinetic equations: The classical electron gas

International Nuclear Information System (INIS)

Marchetti, M.C.; Cohen, E.G.D.; Dorfman, J.R.; Kirkpatrick, T.R.

1985-01-01

The method of nonequilibrium cluster expansion is used to study the decay to equilibrium of a weakly coupled inhomogeneous electron gas prepared in a local equilibrium state at the initial time, t=0. A nonlinear kinetic equation describing the long time behavior of the one-particle distribution function is obtained. For consistency, initial correlations have to be taken into account. The resulting kinetic equation-differs from that obtained when the initial state of the system is assumed to be factorized in a product of one-particle functions. The question of to what extent correlations in the initial state play an essential role in determining the form of the kinetic equation at long times is discussed. To that end, the present calculations are compared wih results obtained before for hard sphere gases and in general with strong short-range forces. A partial answer is proposed and some open questions are indicated

Multi-GPU unsteady 2D flow simulation coupled with a state-to-state chemical kinetics

Science.gov (United States)

Tuttafesta, Michele; Pascazio, Giuseppe; Colonna, Gianpiero

2016-10-01

In this work we are presenting a GPU version of a CFD code for high enthalpy reacting flow, using the state-to-state approach. In supersonic and hypersonic flows, thermal and chemical non-equilibrium is one of the fundamental aspects that must be taken into account for the accurate characterization of the plasma and state-to-state kinetics is the most accurate approach used for this kind of problems. This model consists in writing a continuity equation for the population of each vibrational level of the molecules in the mixture, determining at the same time the species densities and the distribution of the population in internal levels. An explicit scheme is employed here to integrate the governing equations, so as to exploit the GPU structure and obtain an efficient algorithm. The best performances are obtained for reacting flows in state-to-state approach, reaching speedups of the order of 100, thanks to the use of an operator splitting scheme for the kinetics equations.

Antioxidant pool in beer and kinetics of EPR spin-trapping.

Science.gov (United States)

Kocherginsky, Nikolai M; Kostetski, Yuri Yu; Smirnov, Alex I

2005-08-24

The kinetics of spin-trap adduct formation in beer oxidation exhibits an induction period if the reaction is carried out at elevated temperatures and in the presence of air. This lag period lasts until the endogenous antioxidants are almost completely depleted, and its duration is used as an indicator of the flavor stability and shelf life of beer. This paper demonstrates that the total kinetics of the process can be characterized by three parameters-the lag period, the rate of spin-trap adduct formation, and, finally, the steady-state spin-adduct concentration. A steady-state chain reaction mechanism is described, and quantitative estimates of the main kinetic parameters such as the initiation rate, antioxidant pool, effective content of organic molecules participating in the chain reactions, and the rate constant of the 1-hydroxyethyl radical EtOH(*) spin-adduct disappearance are given. An additional new dimensionless parameter is suggested to characterize the antioxidant pool-the product of the lag time and the rate of spin-trap radical formation immediately after the lag time, normalized by the steady-state concentration of the adducts. The results of spin-tapping EPR experiments are compared with the nitroxide reduction kinetics measured in the same beer samples. It is shown that although the kinetics of nitroxide reduction in beer can be used to evaluate the reducing power of beer, the latter parameter does not correlate with the antioxidant pool. The relationship of free radical processes, antioxidant pool, reducing power, and beer staling is discussed.

Synergistic improvement of gas sensing performance by micro-gravimetrically extracted kinetic/thermodynamic parameters

International Nuclear Information System (INIS)

Guo, Shuanbao; Xu, Pengcheng; Yu, Haitao; Cheng, Zhenxing; Li, Xinxin

2015-01-01

Highlights: • Sensing material can be comprehensively optimized by using gravimetric cantilever. • Kinetic-thermodynamic model parameters are quantitatively extracted by experiment • Sensing-material performance is synergistically optimized by extracted parameters. - Abstract: A novel method is explored for comprehensive design/optimization of organophosphorus sensing material, which is loaded on mass-type microcantilever sensor. Conventionally, by directly observing the gas sensing response, it is difficult to build quantitative relationship with the intrinsic structure of the material. To break through this difficulty, resonant cantilever is employed as gravimetric tool to implement molecule adsorption experiment. Based on the sensing data, key kinetic/thermodynamic parameters of the material to the molecule, including adsorption heat −ΔH°, adsorption/desorption rate constants K a and K d , active-site number per unit mass N′ and surface coverage θ, can be quantitatively extracted according to physical–chemistry theories. With gaseous DMMP (simulant of organophosphorus agents) as sensing target, the optimization route for three sensing materials is successfully demonstrated. Firstly, a hyper-branched polymer is evaluated. Though suffering low sensitivity due to insufficient N′, the bis(4-hydroxyphenyl)-hexafluoropropane (BHPF) sensing-group exhibits satisfactory reproducibility due to appropriate −ΔH°. To achieve more sensing-sites, KIT-5 mesoporous-silica with higher surface-area is assessed, resulting in good sensitivity but too high −ΔH° that brings poor repeatability. After comprehensive consideration, the confirmed BHPF sensing-group is grafted on the KIT-5 carrier to form an optimized DMMP sensing nanomaterial. Experimental results indicate that, featuring appropriate kinetic/thermodynamic parameters of −ΔH°, K a , K d , N′ and θ, the BHPF-functionalized KIT-5 mesoporous silica exhibits synergistic improvement among

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

Science.gov (United States)

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

2016-09-01

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

Evolution of inhibitor-resistant natural mutant forms of HIV-1 protease probed by pre-steady state kinetic analysis.

Science.gov (United States)

Zakharova, Maria Yu; Kuznetsova, Alexandra A; Kaliberda, Elena N; Dronina, Maria A; Kolesnikov, Alexander V; Kozyr, Arina V; Smirnov, Ivan V; Rumsh, Lev D; Fedorova, Olga S; Knorre, Dmitry G; Gabibov, Alexander G; Kuznetsov, Nikita A

2017-11-01

Pre-steady state kinetic analysis of mechanistic features of substrate binding and processing is crucial for insight into the evolution of inhibitor-resistant forms of HIV-1 protease. These data may provide a correct vector for rational drug design assuming possible intrinsic dynamic effects. These data should also give some clues to the molecular mechanism of protease action and resistance to inhibitors. Here we report pre-steady state kinetics of the interaction of wild type or mutant forms of HIV-1 protease with a FRET-labeled peptide. The three-stage "minimal" kinetic scheme with first and second reversible steps of substrate binding and with following irreversible peptide cleavage step adequately described experimental data. For the first time, a set of "elementary" kinetic parameters of wild type HIV-1 protease and its natural mutant inhibitor-resistant forms MDR-HM, ANAM-11 and prDRV4 were compared. Inhibitors of the first and second generation were used to estimate the inhibitory effects on HIV-1 protease activity. The resulting set of kinetic data supported that the mutant forms are kinetically unaffected by inhibitors of the first generation, proving their functional resistance to these compounds. The second generation inhibitor darunavir inhibited mutant forms MDR-HM and ANAM-11, but was ineffective against prDRV4. Our kinetic data revealed that these inhibitors induced different conformational changes in the enzyme and, thereby they have different mode of binding in the enzyme active site. These data confirmed hypothesis that the driving force of the inhibitor-resistance evolution is disruption of enzyme-inhibitor complex by changing of the contact network in the inhibitor binding site. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Cell kinetics of GM-CFC in the steady state

International Nuclear Information System (INIS)

Hagan, M.P.; MacVittie, T.J.; Dodgen, D.P.

1985-01-01

The kinetics of cell turnover for myeloid/monocyte cells that form colonies in agar (GM-CFC) were measured through the progressive increase in their sensitivity to 313-nm light during a period of cell labeling with BrdCyd. Two components of cell killing with distinctly separate labeling kinetics revealed both the presence of two generations within the GM-CFC compartment and the properties of the kinetics of the precursors of the GM-CFC. These precursors of the GM-CFC were not assayable in a routine GM-CFC assay when pregnant mouse uterus extract and mouse L-cell-conditioned medium were used to stimulate colony formation but were revealed by the labeling kinetics of the assayable GM-CFC. Further, these precursor cells appeared to enter the assayable GM-CFC population from a noncycling state. This was evidenced by the failure of the majority of these cells to incorporate BrdCyd during five days of infusion. The half-time for cell turnover within this precursor compartment was measured to be approximately 5.5 days. Further, these normally noncycling cells proliferated rapidly in response to endotoxin. High-proliferative-potential colony-forming cells (HPP-CFC) were tested as a candidate for this precursor population. The results of the determination of the kinetics for these cells showed that the HPP-CFC exist largely in a Go state, existing at an average rate of once every four days. The slow turnover time for these cells and their response to endotoxin challenge are consistent with a close relationship between the HPP-CFC and the Go pool of cells that is the direct precursor of the GM-CFC

Estimation of fundamental kinetic parameters of polyhydroxybutyrate fermentation process of Azohydromonas australica using statistical approach of media optimization.

Science.gov (United States)

Gahlawat, Geeta; Srivastava, Ashok K

2012-11-01

Polyhydroxybutyrate or PHB is a biodegradable and biocompatible thermoplastic with many interesting applications in medicine, food packaging, and tissue engineering materials. The present study deals with the enhanced production of PHB by Azohydromonas australica using sucrose and the estimation of fundamental kinetic parameters of PHB fermentation process. The preliminary culture growth inhibition studies were followed by statistical optimization of medium recipe using response surface methodology to increase the PHB production. Later on batch cultivation in a 7-L bioreactor was attempted using optimum concentration of medium components (process variables) obtained from statistical design to identify the batch growth and product kinetics parameters of PHB fermentation. A. australica exhibited a maximum biomass and PHB concentration of 8.71 and 6.24 g/L, respectively in bioreactor with an overall PHB production rate of 0.75 g/h. Bioreactor cultivation studies demonstrated that the specific biomass and PHB yield on sucrose was 0.37 and 0.29 g/g, respectively. The kinetic parameters obtained in the present investigation would be used in the development of a batch kinetic mathematical model for PHB production which will serve as launching pad for further process optimization studies, e.g., design of several bioreactor cultivation strategies to further enhance the biopolymer production.

Using the computerized glow curve deconvolution method and the R package tgcd to determination of thermoluminescence kinetic parameters of chilli powder samples by GOK model and OTOR one

Energy Technology Data Exchange (ETDEWEB)

Sang, Nguyen Duy, E-mail: ndsang@ctu.edu.vn [College of Rural Development, Can Tho University, Can Tho 270000 (Viet Nam); Faculty of Physics and Engineering Physics, University of Science, Ho Chi Minh 700000 (Viet Nam); Van Hung, Nguyen [Nuclear Research Institute, VAEI, Dalat 670000 (Viet Nam); Van Hung, Tran; Hien, Nguyen Quoc [Research and Development Center for Radiation Technology, VAEI, Ho Chi Minh 700000 (Viet Nam)

2017-03-01

Highlights: • TL analysis aims to calculate the kinetic parameters of the chilli powder. • There is difference of the kinetic parameters caused by the difference of radiation doses. • There is difference of the kinetic parameters due to applying GOK model or OTOR one. • The software R is apllied for the first time in TL glow curve analysis of the chilli powder. - Abstract: The kinetic parameters of thermoluminescence (TL) glow peaks of chilli powder irradiated by gamma rays with the different doses of 0, 4 and 8 kGy have been calculated and estimate by computerized glow curve deconvolution (CGCD) method and the R package tgcd by using the TL glow curve data. The kinetic parameters of TL glow peaks (i.e. activation energies (E), order of kinetics (b), trapping and recombination probability coefficients (R) and frequency factors (s)) are fitted by modeled general-orders of kinetics (GOK) and one trap-one recombination (OTOR). The kinetic parameters of the chilli powder are different toward the difference of the sample time-storage, radiation doses, GOK model and OTOR one. The samples spending the shorter period of storage time have the smaller the kinetic parameters values than the samples spending the longer period of storage. The results obtained as comparing the kinetic parameters values of the three samples show that the value of non-irradiated samples are lowest whereas the 4 kGy irradiated-samples’ value are greater than the 8 kGy irradiated-samples’ one time.

The basal kinetic parameters of glycogen synthase in human myotube cultures are not affected by chronic high insulin exposure

DEFF Research Database (Denmark)

Gaster, M; Schrøder, H D; Handberg, A

2001-01-01

results show that chronic exposure of human myotubes to high insulin with or without high glucose did not affect the basal kinetic parameters but abolished the reactivity of GS to acute insulin stimulation. We suggest that insulin induced insulin resistance of GS is caused by a failure of acute insulin......There is no consensus regarding the results from in vivo and in vitro studies on the impact of chronic high insulin and/or high glucose exposure on acute insulin stimulation of glycogen synthase (GS) kinetic parameters in human skeletal muscle. The aim of this study was to evaluate the kinetic...... parameters of glycogen synthase activity in human myotube cultures at conditions of chronic high insulin combined or not with high glucose exposure, before and after a subsequent acute insulin stimulation. Acute insulin stimulation significantly increased the fractional activity (FV(0.1)) of GS, increased...

Analysis of Kinetic Parameter Effect on Reactor Operation Stability of the RSG-GAS Reactor

International Nuclear Information System (INIS)

Rokhmadi

2007-01-01

Kinetic parameter has influence to behaviour on RSG-GAS reactor operation. In this paper done is the calculation of reactivity curve, period-reactivity relation and low power transfer function in silicide fuel. This parameters is necessary and useful for reactivity characteristic analysis and reactor stability. To know the reactivity response, it was done reactivity insertion at power 1 watt using POKDYN code because at this level of power no feedback reactivity so important for reactor operation safety. The result of calculation showed that there is no change of significant a period-reactivity relation and transfer function at low power for 2.96 gU/cc, 3.55 gU/cc and 4.8 gU/cc density of silicide fuels. The result of the transfer function at low power showed that the reactor is critical stability with no feedback. The result of calculation also showed that reactivity response no change among three kinds of fuel densities. It can be concluded that from kinetic parameter point of view period-reactivity relation, transfer function at low power, and reactivity response are no change reactor operation from reactivity effect when fuel exchanged. (author)

Ethanol Production from Whey by Kluyveromyces marxianus in Batch Fermentation System: Kinetics Parameters Estimation

Directory of Open Access Journals (Sweden)

Dessy Ariyanti

2013-03-01

Full Text Available Whey is the liquid remaining after milk has been curdled and strained. It is a by-product of the manufacture of cheese or casein and has several commercial uses. In environmental point of view, whey is kind of waste which has high pollution level due to it’s contain high organic compound with BOD and COD value 50 and 80 g/L respectively. On the other side, whey also contain an amount of lactose (4.5%-5%; lactose can be used as carbon source and raw material for producing ethanol via fermentation using yeast strain Kluyveromyces marxianus. The objective of this research is to investigate the ethanol production kinetics from crude whey through fermentation using Kluyveromyces marxianus and to predict the model kinetics parameter. The yeast was able to metabolize most of the lactose within 16 h to give 8.64 g/L ethanol, 4.43 g/L biomass, and remain the 3.122 g/L residual lactose. From the results presented it also can be concluded that common kinetic model for microbial growth, substrate consumption, and product formation is a good alternative to describe an experimental batch fermentation of Kluyveromyces marxianus grown on a medium composed of whey. The model was found to be capable of reflecting all batch culture phases to a certain degree of accuracy, giving the parameter value: μmax, Ks, YX/S, α, β : 0.32, 10.52, 0.095, 1.52, and 0.11 respectively. © 2013 BCREC UNDIP. All rights reserved(Selected Paper from International Conference on Chemical and Material Engineering (ICCME 2012Received: 27th September 2012; Revised: 29th November 2012; Accepted: 7th December 2012[How to Cite: D. Ariyanti, H. Hadiyanto, (2013. Ethanol Production from Whey by Kluyveromyces marxianus in Batch Fermentation System: Kinetics Parameters Estimation. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (3: 179-184. (doi:10.9767/bcrec.7.3.4044.179-184][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.7.3.4044.179-184 ] View in  |

Role of conformational dynamics in kinetics of an enzymatic cycle in a nonequilibrium steady state

Science.gov (United States)

Min, Wei; Xie, X. Sunney; Bagchi, Biman

2009-08-01

Enzyme is a dynamic entity with diverse time scales, ranging from picoseconds to seconds or even longer. Here we develop a rate theory for enzyme catalysis that includes conformational dynamics as cycling on a two-dimensional (2D) reaction free energy surface involving an intrinsic reaction coordinate (X) and an enzyme conformational coordinate (Q). The validity of Michaelis-Menten (MM) equation, i.e., substrate concentration dependence of enzymatic velocity, is examined under a nonequilibrium steady state. Under certain conditions, the classic MM equation holds but with generalized microscopic interpretations of kinetic parameters. However, under other conditions, our rate theory predicts either positive (sigmoidal-like) or negative (biphasic-like) kinetic cooperativity due to the modified effective 2D reaction pathway on X-Q surface, which can explain non-MM dependence previously observed on many monomeric enzymes that involve slow or hysteretic conformational transitions. Furthermore, we find that a slow conformational relaxation during product release could retain the enzyme in a favorable configuration, such that enzymatic turnover is dynamically accelerated at high substrate concentrations. The effect of such conformation retainment in a nonequilibrium steady state is evaluated.

Determination of the kinetic parameters of Be O using isothermal decay method

Energy Technology Data Exchange (ETDEWEB)

Azorin N, J.; Torijano C, E. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Azorin V, C.; Rivera M, T., E-mail: azorin@xanum.uam.mx [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico)

2015-10-15

Full text: Most of the existing methods for obtaining the frequency factors make use of the trap depth (activation energy) making some assumptions about the order of the kinetics. This causes inconsistencies in the reported values of trapping parameters due that the values of the activation energy obtained by different methods differ appreciably among them. Then, it is necessary to use a method independent of the trap depth making use of the isothermal luminescence decay method. The trapping parameters associated with the prominent glow peak of Be O (280 degrees C) are reported using isothermal luminescence decay method. As a check, the trap parameters are also calculated by glow curve shape (Chen s) method after isolating the prominent glow peak by thermal cleaning technique. Our results show a very good agreement between the trapping parameters calculated by the two methods. Isothermal luminescence decay method was used for determining the trapping parameters of Be O. Results obtained applying this method are in good agreement with those obtained using other methods, except in the value of the frequency factor. (Author)

Some parameters of radionuclide kinetics

International Nuclear Information System (INIS)

Prokof'ev, O.N.; Smirnov, V.A.; Belen'kij, E.I.

1978-01-01

Numerical values of the rates of radionuclide absorption into, and elimination from, bovine organs were determined. Kinetic rate constants of radionuclides such as 89 Sr, 99 Mo, 131 I, 132 Tl, and 140 Be were calculated. The calculations were done for muscle, liver, and kidney

Unification of the Two-Parameter Equation of State and the Principle of Corresponding States

DEFF Research Database (Denmark)

Mollerup, Jørgen

1998-01-01

A two-parameter equation of state is a two-parameter corresponding states model. A two-parameter corresponding states model is composed of two scale factor correlations and a reference fluid equation of state. In a two-parameter equation of state the reference equation of state is the two-paramet...

Determination of kinetics parameters using stochastic methods in a 252Cf system

International Nuclear Information System (INIS)

Difilippo, F.C.

1988-01-01

Safety analysis and control system design of nuclear systems require the knowledge of neutron kinetics related parameters like effective delayed neutron fraction, neutron lifetime, time between neutron generations and subcriticality margins. Many methods, deterministic and stochastic, are being used, some since the beginning of nuclear power, to measure these important parameters. The method based on the use of the 252 Cf neutron source has been under intense study at the Oak Ridge National Laboratory, both experimentally and theoretically, during the last years. The increasing demand for this isotope in industrial and medical applications and new designs of advanced high flux reactors to produce it make the isotope available as neutron source (only few micrograms are necessary). A thin layer of 252 Cf is deposited in one of the electrodes of a fission chamber which produces pulses each time the 252 Cf disintegrates via α or spontaneous fission decay; the smaller pulses associated with the α decay can be easily discriminated with the important result that we known the time when v/sub c/ neutrons are injected into the system (number of neutrons per fission of 252 Cf). Thus, a small (few cm 3 ) and nonintrusive device can be used as a random pulsed neutron source with known natural properties that do no depend on biases associated with more complex interrogating devices like accelerators. This paper presents a general formalism that relates the kinetics parameters with stochastic descriptors that naturally appear because of the random nature of the production and transport of neutrons

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

Science.gov (United States)

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

2011-10-15

Managed aquifer recharge (MAR) provides efficient removal for many organic compounds and sum parameters. However, observed in situ removal efficiencies tend to scatter and cannot be predicted easily. In this paper, a method is introduced which allows to identify and eliminate biased samples and to quantify simultaneously the impact of (i) redox conditions (ii) kinetics (iii) residual threshold values below which no removal occurs and (iv) field site specifics. It enables to rule out spurious correlations between these factors and therefore improves the predictive power. The method is applied to an extensive database from three MAR field sites which was compiled in the NASRI project (2002-2005, Berlin, Germany). Removal characteristics for 38 organic parameters are obtained, of which 9 are analysed independently in 2 different laboratories. Out of these parameters, mainly pharmaceutically active compounds (PhAC) but also sum parameters and industrial chemicals, four compounds are shown to be readily removable whereas six are persistent. All partly removable compounds show a redox dependency and most of them reveal either kinetic dependencies or residual threshold values, which are determined. Differing removal efficiencies at different field sites can usually be explained by characteristics (i) to (iii). Copyright © 2011 Elsevier Ltd. All rights reserved.

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

Directory of Open Access Journals (Sweden)

Ruth Alfaro-Cuevas-Villanueva

2014-01-01

Full Text Available 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.

Differential equation methods for simulation of GFP kinetics in non-steady state experiments.

Science.gov (United States)

Phair, Robert D

2018-03-15

Genetically encoded fluorescent proteins, combined with fluorescence microscopy, are widely used in cell biology to collect kinetic data on intracellular trafficking. Methods for extraction of quantitative information from these data are based on the mathematics of diffusion and tracer kinetics. Current methods, although useful and powerful, depend on the assumption that the cellular system being studied is in a steady state, that is, the assumption that all the molecular concentrations and fluxes are constant for the duration of the experiment. Here, we derive new tracer kinetic analytical methods for non-steady state biological systems by constructing mechanistic nonlinear differential equation models of the underlying cell biological processes and linking them to a separate set of differential equations governing the kinetics of the fluorescent tracer. Linking the two sets of equations is based on a new application of the fundamental tracer principle of indistinguishability and, unlike current methods, supports correct dependence of tracer kinetics on cellular dynamics. This approach thus provides a general mathematical framework for applications of GFP fluorescence microscopy (including photobleaching [FRAP, FLIP] and photoactivation to frequently encountered experimental protocols involving physiological or pharmacological perturbations (e.g., growth factors, neurotransmitters, acute knockouts, inhibitors, hormones, cytokines, and metabolites) that initiate mechanistically informative intracellular transients. When a new steady state is achieved, these methods automatically reduce to classical steady state tracer kinetic analysis. © 2018 Phair. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Pre-steady-state kinetics of Escherichia coli aspartate aminotransferase catalyzed reactions and thermodynamic aspects of its substrate specificity

International Nuclear Information System (INIS)

Kuramitsu, Seiki; Hiromi, Keitaro; Hayashi, Hideyuki; Morino, Yoshimasa; Kagamiyama, Hiroyuki

1990-01-01

The four half-transamination reactions [the pyridoxal form of Escherichia coli aspartate aminotransferase (AspAT) with aspartate or glutamate and the pyridoxamine form of the enzyme with oxalacetate or 2-oxoglutarate] were followed in a stopped-flow spectrometer by monitoring the absorbance change at either 333 or 358 nm. The reaction progress curves in all cases gave fits to a monophasic exponential process. Kinetic analyses of these reactions showed that each half-reaction is composed of the following three processes: (1) the rapid binding of an amino acid substrate to the pyridoxal form of the enzyme; (2) the rapid binding of the corresponding keto acid to the pyridoxamine form of the enzyme; (3) the rate-determining interconversion between the two complexes. This mechanism was supported by the findings that the equilibrium constants for half- and overall-transamination reactions and the steady-state kinetic constants agreed well with the predicted values on the basis of the above mechanism using pre-steady-state kinetic parameters. The significant primary kinetic isotope effect observed in the reaction with deuterated amino acid suggests that the withdrawal of the α-proton of the substrates is rate determining. The pyridoxal form of E. coli AspAT reacted with a variety of amino acids as substrates. The substrate specificity of the E. coli enzyme was much broader than that of pig isoenzymes, reflecting some subtle but distinct difference in microenvironment accommodating the side chain of the substrate between e. coli and mammalian AspATs

Steady state likelihood ratio sensitivity analysis for stiff kinetic Monte Carlo simulations.

Science.gov (United States)

Núñez, M; Vlachos, D G

2015-01-28

Kinetic Monte Carlo simulation is an integral tool in the study of complex physical phenomena present in applications ranging from heterogeneous catalysis to biological systems to crystal growth and atmospheric sciences. Sensitivity analysis is useful for identifying important parameters and rate-determining steps, but the finite-difference application of sensitivity analysis is computationally demanding. Techniques based on the likelihood ratio method reduce the computational cost of sensitivity analysis by obtaining all gradient information in a single run. However, we show that disparity in time scales of microscopic events, which is ubiquitous in real systems, introduces drastic statistical noise into derivative estimates for parameters affecting the fast events. In this work, the steady-state likelihood ratio sensitivity analysis is extended to singularly perturbed systems by invoking partial equilibration for fast reactions, that is, by working on the fast and slow manifolds of the chemistry. Derivatives on each time scale are computed independently and combined to the desired sensitivity coefficients to considerably reduce the noise in derivative estimates for stiff systems. The approach is demonstrated in an analytically solvable linear system.

RA reactor kinetic parameters - Progress report; Kineticki parametri reaktora RA - Izvestaj o napredovanju -

Energy Technology Data Exchange (ETDEWEB)

Petrovic, M; Obradovic, D; Jevtovic, V; Velickovic, Lj [Institute of nuclear sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

1965-11-15

The objective of nuclear reactor kinetics study is to analyze the stability of reactor operation in practice. The obtained parameters should define the needed properties of automatic control system relevant for the stability of the designed reactor system. Refining the analytical models is done by using the analysis and interpretation of experimental data. Results of measured the reactor response obtained by using the reactor oscillator ROB-1 are explained by using the space independent model of the zero power reactor, by power reactor model with one feedback circuit, and by a complex model. It was assumed that the perturbations of the system are small and that linearized kinetic equations could be used. Linearized kinetic equation of the reactor system are transformed into the frequency region in order to analyze the measured values directly. The objective of this paper is to measure the RA reactor kinetics parameters, and analyze the stability of reactor operation at power levels high than nominal. Istrazivanja u oblasti kinetike nuklearnih reaktora imaju za cilj da dovedu analizu stabilnosti rada reaktora na nivo 'radne tehnologije'. Dobijeni pararametri treba da specificiraju potrebne karakteristike sistema automatske kontrole za odgovarajucu stabilnost projektovanog reaktorskog sistema. Doterivanjem analitickih modela do takvog nivoa da se zapazeni fenomeni mogu anailitcki predvideti ide preko analize i interpretacije eksperimentalnih podataka. Eksperimentalni rezultati merenja odziva reaktora, izvedeni reaktorskim oscilatorom ROB-1, interpretirani su na osnovu prostorno nezavisnog modela za reaktor nulte snage, modelom reaktora snage sa jednim kolom povratne sprege, kao i kompleksnim modelom. U ovom radu se poslo od toga da su perturbacije parametara sistema male, pa se mogu upotrebiti linearizovane kineticke jednacine. Linearizovane kineticke jednacine reaktorskog sistema transformirane su u frekventno podrucje s ciljem direktne analize mernih rezultata

Steady-state and pre-steady-state kinetic analysis of halopropane conversion by a Rhodococcus haloalkane dehalogenase

NARCIS (Netherlands)

Bosma, T; Pikkemaat, MG; Kingma, Jacob; Dijk, J; Janssen, DB

2003-01-01

Haloalkane dehalogenase from Rhodococcus rhodochrous NCIMB 13064 (DhaA) catalyzes the hydrolysis of carbon-halogen bonds in a wide range of haloalkanes. We examined the steady-state and pre-steady-state kinetics of halopropane conversion by DhaA to illuminate mechanistic details of the

An Evaluation of Kinetic Parameters of Cadmium and Copper Biosorption by Immobilized Cells

Directory of Open Access Journals (Sweden)

Nelly Georgieva

2007-10-01

Full Text Available Bioremediation is the use of living organisms to reduce or eliminate environmental hazards resulting from the accumulation of toxic chemicals and other hazardous wastes. This technology is based on the utilization of microorganisms to transform organic and inorganic compounds. The filamentous yeast Trichosporon cutaneum strain R57, immobilized and free cells was cultivated as batch culture on a liquid medium in the presence of various concentrations of cadmium and copper ions. The simultaneous uptake and accumulation of Cd2+ and Cu2+ ions by Tr. cutaneum cells depending on the initial concentration of Cd2+ and Cu2+ in the medium were studied. The potential use of the free and immobilized cells of Trichosporon cutaneum to remove cadmium and copper ions, from aqueous solutions was evaluated. Two important physicochemical aspects for the evaluation of the sorption process as a unit operation are the equilibrium of sorption and the kinetics. The Cd2+ and Cu2+ ions biosorption capacities of all tested adsorbent were presented as a function of the initial concentration of metal ions within the aqueous biosorption medium. The individual, as well as bicomponent sorption kinetics of copper and cadmium ions by immobilised cells of Trichosporon cutaneum R57 is presented. A second order kinetic model obtains kinetic parameters for the copper and cadmium ions.

Experimental kinetic parameters in the thermo-fluid-dynamic modelling of coal combustion

International Nuclear Information System (INIS)

Migliavacca, G.; Perini, M.; Parodi, E.

2001-01-01

The designing and the optimisation of modern and efficient combustion systems are nowadays frequently based on calculation tools for mathematical modelling, which are able to predict the evolution of the process starting from the first principles of physics. Otherwise, in many cases, specific experimental parameters are needed to describe the specific nature of the materials considered in the calculations. It is especially true in the modelling of coal combustion, which is a complex process strongly dependent on the chemical and physical features of the fuel. This paper describes some experimental techniques used to estimate the fundamental kinetic parameters of coal combustion and shows how this data may be introduced in a model calculation to predict the pollutant emissions from a real scale combustion plant [it

Does Vibration Warm-up Enhance Kinetic and Temporal Sprint Parameters?

Science.gov (United States)

Cochrane, D J; Cronin, M J; Fink, P W

2015-08-01

The aim of this study was to investigate the efficacy of vibration warm-up to enhance sprint performance. 12 males involved in representative team sports performed 4 warm-up conditions in a randomised order performed at least 24 h apart; VbX warm-up (VbX-WU); Neural activation warm-up (Neu-WU); Dynamic warm-up (Dyn-WU) and Control (No VbX). Participants completed 5 m sprint at 30 s, 2:30 min and 5 min post warm-up where sprint time, kinetics, and temporal components were recorded. There was no significant (p>0.05) main effect or interaction effect between the split sprint times of 1 m, 2.5 m, and 5 m. There was a condition effect where vertical mean force was significantly higher (p0.05) main and interaction effects in sprint kinetic and temporal parameters existed. Overall, all 4 warm-up conditions produced comparable results for sprint performance, and there was no detrimental effect on short-duration sprint performance using VbX-WU. Therefore, VbX could be useful for adding variety to the training warm-up or be included into the main warm-up routine as a supplementary modality. © Georg Thieme Verlag KG Stuttgart · New York.

Assessment of input function distortions on kinetic model parameters in simulated dynamic 82Rb PET perfusion studies

International Nuclear Information System (INIS)

Meyer, Carsten; Peligrad, Dragos-Nicolae; Weibrecht, Martin

2007-01-01

Cardiac 82 rubidium dynamic PET studies allow quantifying absolute myocardial perfusion by using tracer kinetic modeling. Here, the accurate measurement of the input function, i.e. the tracer concentration in blood plasma, is a major challenge. This measurement is deteriorated by inappropriate temporal sampling, spillover, etc. Such effects may influence the measured input peak value and the measured blood pool clearance. The aim of our study is to evaluate the effect of input function distortions on the myocardial perfusion as estimated by the model. To this end, we simulate noise-free myocardium time activity curves (TACs) with a two-compartment kinetic model. The input function to the model is a generic analytical function. Distortions of this function have been introduced by varying its parameters. Using the distorted input function, the compartment model has been fitted to the simulated myocardium TAC. This analysis has been performed for various sets of model parameters covering a physiologically relevant range. The evaluation shows that ±10% error in the input peak value can easily lead to ±10-25% error in the model parameter K 1 , which relates to myocardial perfusion. Variations in the input function tail are generally less relevant. We conclude that an accurate estimation especially of the plasma input peak is crucial for a reliable kinetic analysis and blood flow estimation

Combined Yamamoto approach for simultaneous estimation of adsorption isotherm and kinetic parameters in ion-exchange chromatography.

Science.gov (United States)

Rüdt, Matthias; Gillet, Florian; Heege, Stefanie; Hitzler, Julian; Kalbfuss, Bernd; Guélat, Bertrand

2015-09-25

Application of model-based design is appealing to support the development of protein chromatography in the biopharmaceutical industry. However, the required efforts for parameter estimation are frequently perceived as time-consuming and expensive. In order to speed-up this work, a new parameter estimation approach for modelling ion-exchange chromatography in linear conditions was developed. It aims at reducing the time and protein demand for the model calibration. The method combines the estimation of kinetic and thermodynamic parameters based on the simultaneous variation of the gradient slope and the residence time in a set of five linear gradient elutions. The parameters are estimated from a Yamamoto plot and a gradient-adjusted Van Deemter plot. The combined approach increases the information extracted per experiment compared to the individual methods. As a proof of concept, the combined approach was successfully applied for a monoclonal antibody on a cation-exchanger and for a Fc-fusion protein on an anion-exchange resin. The individual parameter estimations for the mAb confirmed that the new approach maintained the accuracy of the usual Yamamoto and Van Deemter plots. In the second case, offline size-exclusion chromatography was performed in order to estimate the thermodynamic parameters of an impurity (high molecular weight species) simultaneously with the main product. Finally, the parameters obtained from the combined approach were used in a lumped kinetic model to simulate the chromatography runs. The simulated chromatograms obtained for a wide range of gradient lengths and residence times showed only small deviations compared to the experimental data. Copyright © 2015 Elsevier B.V. All rights reserved.

The determination of kinetic parameters of LiF : Mg,Ti from thermal decaying curves of optical absorption bands

CERN Document Server

Yazici, A N

2003-01-01

In this paper, the thermal bleaching curves (TBCs) of specific optical absorption bands of LiF : Mg,Ti were measured as a function of temperature. The TBCs obtained were analysed to extract the kinetic parameters (the thermal activation energy (E) and the frequency factor (s)) of some TL glow peaks of LiF : Mg,Ti on the basis of the developed first-order kinetic model over a specified temperature region.

Measures of the zero power nuclear reactor's kinetic parameters with application of noise analysis

International Nuclear Information System (INIS)

Martins, F.R.

1992-01-01

The purpose of this work was to establish an experimental technique based on noise analysis for measuring the ratio of kinetic parameters β/ Λ and the power of the Zero Power Nuclear Reactor IPEN-MB 01. A through study of the microscopic and macroscopic noise analysis techniques has been carried out. The Langevin technique and the point kinetic model were chosen to describe the stochastic phenomena that occur in the zero power reactor. Measurements have been made using two compensated ionization chambers localized in the water reflector at symmetric positions in order to minimize spatial effects on the neutron flux fluctuation. Power calibrations based on the low frequency plateau of the cross-power spectral density has also been carried out. (author)

The importance of variables and parameters in radiolytic chemical kinetics modeling

International Nuclear Information System (INIS)

Piepho, M.G.; Turner, P.J.; Reimus, P.W.

1989-01-01

Many of the pertinent radiochemical reactions are not completely understood, and most of the associated rate constants are poorly characterized. To help identify the important radiochemical reactions, rate constants, species, and environmental conditions, an importance theory code, SWATS (Sensitivitiy With Adjoint Theory-Sparse version)-LOOPCHEM, has been developed for the radiolytic chemical kinetics model in the radiolysis code LOOPCHEM. The LOOPCHEM code calculates the concentrations of various species in a radiolytic field over time. The SWATS-LOOPCHEM code efficiently calculates: the importance (relative to a defined response of interest) of each species concentration over time, the sensitivity of each parameter of interest, and the importance of each equation in the radiolysis model. The calculated results will be used to guide future experimental and modeling work for determining the importance of radiolysis on waste package performance. A demonstration (the importance of selected concentrations and the sensitivities of selected parameters) of the SWATS-LOOPCHEM code is provided for illustrative purposes

Fluorescence lifetime components reveal kinetic intermediate states upon equilibrium denaturation of carbonic anhydrase II.

Science.gov (United States)

Nemtseva, Elena V; Lashchuk, Olesya O; Gerasimova, Marina A; Melnik, Tatiana N; Nagibina, Galina S; Melnik, Bogdan S

2017-12-21

In most cases, intermediate states of multistage folding proteins are not 'visible' under equilibrium conditions but are revealed in kinetic experiments. Time-resolved fluorescence spectroscopy was used in equilibrium denaturation studies. The technique allows for detecting changes in the conformation and environment of tryptophan residues in different structural elements of carbonic anhydrase II which in its turn has made it possible to study the intermediate states of carbonic anhydrase II under equilibrium conditions. The results of equilibrium and kinetic experiments using wild-type bovine carbonic anhydrase II and its mutant form with the substitution of leucine for alanine at position 139 (L139A) were compared. The obtained lifetime components of intrinsic tryptophan fluorescence allowed for revealing that, the same as in kinetic experiments, under equilibrium conditions the unfolding of carbonic anhydrase II ensues through formation of intermediate states.

An Inverse Michaelis–Menten Approach for Interfacial Enzyme Kinetics

DEFF Research Database (Denmark)

Kari, Jeppe; Andersen, Morten; Borch, Kim

2017-01-01

Interfacial enzyme reactions are ubiquitous both in vivo and in technical applications, but analysis of their kinetics remains controversial. In particular, it is unclear whether conventional Michaelis–Menten theory, which requires a large excess of substrate, can be applied. Here, an extensive...... experimental study of the enzymatic hydrolysis of insoluble cellulose indeed showed that the conventional approach had a limited applicability. Instead we argue that, unlike bulk reactions, interfacial enzyme catalysis may reach a steady-state condition in the opposite experimental limit, where...... for kinetic analyses of interfacial enzyme reactions and that its analogy to established theory provides a bridge to the accumulated understanding of steady-state enzyme kinetics. Finally, we show that the ratio of parameters from conventional and inverted Michaelis–Menten analysis reveals the density...

Application of the exact distribution pjk in the determination of kinetic parameters in a reactor

International Nuclear Information System (INIS)

Alcala Ruiz, F.

1982-01-01

In this report one distribution of neutron counts obtained by a detector placed in a reactor is studied in order to be used in the determination of reactor kinetic parameters such as β/Λ and reactivities. The parameters accuracy from this new method is compared with the Feynman and Mogilner method, based too in Reactor Neutron Noise Analysis. These three methods have been applied to JEN-2 reactor and the better accuracy and faster collection of experimental data give some interest to the new method which only requires a good footing code. (Author) 68 refs

A two-phase kinetic model for fungal growth in solid-state cultivation

NARCIS (Netherlands)

Hamidi-Esfahani, Z.; Hejazi, P.; Abbas Shojaosadati, S.; Hoogschagen, M.J.; Vasheghani-Farahani, E.; Rinzema, A.

2007-01-01

A new two-phase kinetic model including exponential and logistic models was applied to simulate the growth rate of fungi at various temperatures. The model parameters, expressed as a function of temperature, were determined from the oxygen consumption rate of Aspergillus niger during cultivation on

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

International Nuclear Information System (INIS)

Frias, Moises; Villar-Cocina, E.; Valencia-Morales, E.

2007-01-01

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

The strong prognostic value of KELIM, a model-based parameter from CA 125 kinetics in ovarian cancer

DEFF Research Database (Denmark)

You, Benoit; Colomban, Olivier; Heywood, Mark

2013-01-01

Unexpected results were recently reported about the poor surrogacy of Gynecologic Cancer Intergroup (GCIG) defined CA-125 response in recurrent ovarian cancer (ROC) patients. Mathematical modeling may help describe CA-125 decline dynamically and discriminate prognostic kinetic parameters....

Solid-state reaction kinetics of neodymium doped magnesium hydrogen phosphate system

Science.gov (United States)

Gupta, Rashmi; Slathia, Goldy; Bamzai, K. K.

2018-05-01

Neodymium doped magnesium hydrogen phosphate (NdMHP) crystals were grown by using gel encapsulation technique. Structural characterization of the grown crystals has been carried out by single crystal X-ray diffraction (XRD) and it revealed that NdMHP crystals crystallize in orthorhombic crystal system with space group Pbca. Kinetics of the decomposition of the grown crystals has been studied by non-isothermal analysis. The estimation of decomposition temperatures and weight loss has been made from the thermogravimetric/differential thermo analytical (TG/DTA) in conjuncture with DSC studies. The various steps involved in the thermal decomposition of the material have been analysed using Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova equations for evaluating various kinetic parameters.

Kinetic studies following state-selective laser excitation

International Nuclear Information System (INIS)

Keto, J.W.

1992-01-01

We have made measurements of state-to-state deactivation cross sections and radiative lifetimes for Xe*(6p,6p',7p) and Kr*(5p) states in xenon and krypton buffer gases. These results are relevant to kinetic models and both excimer lasers and the infrared xenon laser; and they are a significant improvement in the precision of the known radiative lifetimes. This type of experiment can now be compared with recent calculations of state-to-state collisional relaxation in rare-gases by Hickman, Huestis, and Saxon. We have also made significant progress in the study of the electronic spectra of small molecules of the rare gases. Spectra have been obtained for Xe 2 , Xe 3 , Xe 4 , and larger clusters. As guidance for the larger clusters of the rare gases we have obtained the first multiphoton spectra for excitons in condensed xenon. In collaboration with research on the multiphoton spectra of the rare gases, we have continued experiments using synchrotron radiation in collaboration with the University of Hamburg. In experiments there we have observed excitation and fluorescence spectra for single xenon atoms at the surface, within the second layer, and within the bulk of large argon clusters

Neutron kinetics developments of the SIMMER-III safety code for APS application

International Nuclear Information System (INIS)

Rineiski, A.; Kiefhaber, E.; Merk, B.; Maschek, W.

2000-01-01

Recent developments extending the capabilities of the SIMMER-III code for dealing with transients and accidents in an ADS are presented. The impact of weighting functions on the point-kinetics parameters at steady-state is shown. Some preliminary results of using a space-time kinetics model for beam-trip related transients are highlighted. (orig.)

Modelling and determination of the kinetic parameters of the pyrolysis of Dichrostachys cinerea

International Nuclear Information System (INIS)

Abreu Naranjo, Reinier; Romero Romero, Osvaldo

2011-01-01

In the present study were analyzed biomass samples of Dichrostachys cinerea, commonly known in Cuba as marabou, by thermogravimetric method at various heating rates of devolatilization in nitrogen atmosphere at 5, 10 and 20 C min-1. On the kinetic analysis was used a mechanism of three independent reactions of order 1, generally attributed to three chief components of this kind of lignocellulose materials, hemicelluloses, cellulose and lignin. The values of activation energy, pre-exponential factor and contribution factor were similar to those reported in previous research for this type of biomass. The proposed model predicts with acceptable correlation the experimental and calculated curves of the decomposition of D. cinerea, with a deviation factor less than 5% for the temperature range studied. On the other hand, the kinetic parameters of the thermal decomposition coupled at equations of transport phenomena are essential to optimize the design and use of biomass thermochemical conversion processes, hence the importance of the research. (author)

Non-equilibrium plasma kinetics of reacting CO: an improved state to state approach

Science.gov (United States)

Pietanza, L. D.; Colonna, G.; Capitelli, M.

2017-12-01

Non-equilibrium plasma kinetics of reacting CO for conditions typically met in microwave discharges have been developed based on the coupling of excited state kinetics and the Boltzmann equation for the electron energy distribution function (EEDF). Particular attention is given to the insertion in the vibrational kinetics of a complete set of electron molecule resonant processes linking the whole vibrational ladder of the CO molecule, as well as to the role of Boudouard reaction, i.e. the process of forming CO2 by two vibrationally excited CO molecules, in shaping the vibrational distribution of CO and promoting reaction channels assisted by vibrational excitation (pure vibrational mechanisms, PVM). PVM mechanisms can become competitive with electron impact dissociation processes (DEM) in the activation of CO. A case study reproducing the conditions of a microwave discharge has been considered following the coupled kinetics also in the post discharge conditions. Results include the evolution of EEDF in discharge and post discharge conditions highlighting the role of superelastic vibrational and electronic collisions in shaping the EEDF. Moreover, PVM rate coefficients and DEM ones are studied as a function of gas temperature, showing a non-Arrhenius behavior, i.e. the rate coefficients increase with decreasing gas temperature as a result of a vibrational-vibrational (V-V) pumping up mechanism able to form plateaux in the vibrational distribution function. The accuracy of the results is discussed in particular in connection to the present knowledge of the activation energy of the Boudouard process.

Effect of resonance decays on extracted kinetic freeze-out parameters in heavy ion collisions at RHIC

International Nuclear Information System (INIS)

Molnar, Levente; Barannikova, Olga; Wang, Fuqiang

2006-01-01

Statistical model fit to particle ratios in Au+Au collisions at RHIC suggests chemical freeze-out near phase transition boundary. Model interpretations of evolution from chemical to kinetic freeze-out vary. Results of the blast-wave fit to the STAR experimental data, where resonance contributions are not accounted for, suggest significant cooling and expansion between the freezeouts for central Au+Au collisions. Other models including resonances, argue for instant single freezeout with temperature close to the phase transition temperature. By combined thermal and blast-wave model parametrization including resonances, we systematically investigate the effect of resonance decays on the extracted kinetic freeze-out parameters. (authors)

Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism.

Science.gov (United States)

Fleming, R M T; Thiele, I; Provan, G; Nasheuer, H P

2010-06-07

The quantitative analysis of biochemical reactions and metabolites is at frontier of biological sciences. The recent availability of high-throughput technology data sets in biology has paved the way for new modelling approaches at various levels of complexity including the metabolome of a cell or an organism. Understanding the metabolism of a single cell and multi-cell organism will provide the knowledge for the rational design of growth conditions to produce commercially valuable reagents in biotechnology. Here, we demonstrate how equations representing steady state mass conservation, energy conservation, the second law of thermodynamics, and reversible enzyme kinetics can be formulated as a single system of linear equalities and inequalities, in addition to linear equalities on exponential variables. Even though the feasible set is non-convex, the reformulation is exact and amenable to large-scale numerical analysis, a prerequisite for computationally feasible genome scale modelling. Integrating flux, concentration and kinetic variables in a unified constraint-based formulation is aimed at increasing the quantitative predictive capacity of flux balance analysis. Incorporation of experimental and theoretical bounds on thermodynamic and kinetic variables ensures that the predicted steady state fluxes are both thermodynamically and biochemically feasible. The resulting in silico predictions are tested against fluxomic data for central metabolism in Escherichia coli and compare favourably with in silico prediction by flux balance analysis. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Comparison of kinetic and fluid neutral models for attached and detached state

International Nuclear Information System (INIS)

Furubayashi, M.; Hoshino, K.; Toma, M.; Hatayama, A.; Coster, D.; Schneider, R.; Bonnin, X.; Kawashima, H.; Asakura, N.; Suzuki, Y.

2009-01-01

Neutral behavior has an important role in the transport simulations of the edge plasma. Most of the edge plasma transport codes treat neutral particles by a simple fluid model or a kinetic model. The fluid model allows faster calculations. However, the applicability of the fluid model is limited. In this study, simulation results of JT-60U from kinetic neutral model and fluid neutral model are compared under the attached and detached state, using the 2D edge plasma code package, SOLPS5.0. In the SOL region, no significant differences are observed in the upstream plasma profiles between kinetic and fluid neutral models. However, in the divertor region, large differences are observed in plasma and neutral profiles. Therefore, further optimization of the fluid neutral model should be performed. Otherwise kinetic neutral model should be used to analyze the divertor region.

Determination of kinetic parameters in the pyrolysis operation and thermal behavior of Prosopis juliflora using thermogravimetric analysis.

Science.gov (United States)

Chandrasekaran, Arunkumar; Ramachandran, Sethumadhavan; Subbiah, Senthilmurugan

2017-06-01

This paper deals with the pyrolysis of Prosopis juliflora fuelwood using thermogravimetric analysis to determine the kinetic parameters at six different heating rates of 2, 5, 10, 15, 20 and 25°C/min. The activation energy of pyrolysis was calculated using different methods, namely Kissinger, Kissinger-Akahira-Sunose, Ozawa-Flynn-Wall and Friedman model and corresponding calculated activation energy were found to be 164.6, 204, 203.2, and 219.3kJ/mol, respectively for each method. The three-pseudo component model was applied to calculate the following three kinetic parameters: activation energy, pre-exponential factor and order of reaction. The experimental results were validated with model prediction for all the six heating rates. The three-pseudo component model is able to predict experimental results much accurately while considering variable order reaction model (n≠1). Copyright © 2017 Elsevier Ltd. All rights reserved.

Physicochemical analysis and nonisothermal kinetic study of sertraline–lactose binary mixtures

Directory of Open Access Journals (Sweden)

Faranak Ghaderi

2017-07-01

Full Text Available In the present study the physicochemical stability of sertraline with lactose was evaluated in drug-excipient binary mixtures. Different physicochemical methods such as differential scanning calorimetry (DSC, Fourier-transform infrared spectroscopy, and mass spectrometry were applied to confirm the incompatibility. The final aim of this study was to evaluate the kinetic parameters using a fast and sensitive DSC method. Solid-state kinetic parameters were derived from nonisothermally stressed physical mixtures using different thermal models such as Friedman, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose. Overall, the instability of sertraline with lactose was successfully evaluated. Further confirmation was made by tracking the Maillard reaction product of sertraline and lactose by mass spectrometry. DSC scans provided important information about the stability of sertraline in solid-state condition and also revealed the related thermokinetic parameters in order to understand the nature of the chemical instability.

Physicochemical analysis and nonisothermal kinetic study of sertraline-lactose binary mixtures.

Science.gov (United States)

Ghaderi, Faranak; Nemati, Mahboob; Siahi-Shadbad, Mohammad Reza; Valizadeh, Hadi; Monajjemzadeh, Farnaz

2017-07-01

In the present study the physicochemical stability of sertraline with lactose was evaluated in drug-excipient binary mixtures. Different physicochemical methods such as differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy, and mass spectrometry were applied to confirm the incompatibility. The final aim of this study was to evaluate the kinetic parameters using a fast and sensitive DSC method. Solid-state kinetic parameters were derived from nonisothermally stressed physical mixtures using different thermal models such as Friedman, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose. Overall, the instability of sertraline with lactose was successfully evaluated. Further confirmation was made by tracking the Maillard reaction product of sertraline and lactose by mass spectrometry. DSC scans provided important information about the stability of sertraline in solid-state condition and also revealed the related thermokinetic parameters in order to understand the nature of the chemical instability. Copyright © 2016. Published by Elsevier B.V.

Calculation of Kinetic Parameters of TRIGA Reactor

International Nuclear Information System (INIS)

Snoj, Luka; Kavcic, Andrej; Zerovnik, Gasper; Ravnik, Matjaz

2008-01-01

Modern Monte Carlo transport codes in combination of fast computer clusters enable very accurate calculations of the most important reactor kinetic parameters. Such are the effective delayed neutron fraction, β eff , and mean neutron generation time, Λ. We calculated the β eff and Λ for various realistic and hypothetical annular TRIGA Mark II cores with different types and amount of fuel. It can be observed that the effective delayed neutron fraction strongly depends on the number of fuel elements in the core or on the core size. E.g., for 12 wt. % uranium standard fuel with 20 % enrichment, β eff varies from 0.0080 for a small core (43 fuel rods) to 0.0075 for a full core (90 fuel rods). It is interesting to note that calculated value of β eff strongly depends also on the delayed neutron nuclear data set used in calculations. The prompt neutron life-time mainly depends on the amount (due to either content or enrichment) of 235 U in the fuel as it is approximately inversely proportional to the average absorption cross-section of the fuel. E.g., it varies from 28 μs for 30 wt. % uranium content fuelled core to 48 μs for 8.5 wt. % uranium content LEU fuelled core. The results are especially important for pulse mode operation and analysis of the pulses. (authors)

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

International Nuclear Information System (INIS)

Theron, Therina; Slabbert, Jacobus; Serafin, Antonio; Boehm, Lothar

1997-01-01

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 thought 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 a candidate for predicting intrinsic radiosensitivity. Methods and Materials: A panel of 15 tumor cell lines was analyzed for S phase content and potential doubling times (T pot ), and the influence of these parameters on the intrinsic radiosensitivity to 60 Coγ- and p(66)/Be neutron irradiation was assessed. Results: S phase content and T pot show a statistically significant correlation with the mean inactivation dose for photons. The correlation between cell kinetic parameters and the mean inactivation dose for neutrons showed the same trend as photon sensitivity but this was not found to be statistically significant. Conclusions: S phase content and T pot were identified as suitable criteria for predicting photon sensitivity. It is suggested that cell kinetic parameters could play a role in identifying neutron sensitive tumors if both tumor and normal cells are analyzed

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

Science.gov (United States)

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

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.

A benchmark on the calculation of kinetic parameters based on reactivity effect experiments in the CROCUS reactor

International Nuclear Information System (INIS)

Paratte, J.M.; Frueh, R.; Kasemeyer, U.; Kalugin, M.A.; Timm, W.; Chawla, R.

2006-01-01

Measurements in the CROCUS reactor at EPFL, Lausanne, are reported for the critical water level and the inverse reactor period for several different sets of delayed supercritical conditions. The experimental configurations were also calculated by four different calculation methods. For each of the supercritical configurations, the absolute reactivity value has been determined in two different ways, viz.: (i) through direct comparison of the multiplication factor obtained employing a given calculation method with the corresponding value for the critical case (calculated reactivity: ρ calc ); (ii) by application of the inhour equation using the kinetic parameters obtained for the critical configuration and the measured inverse reactor period (measured reactivity: ρ meas ). The calculated multiplication factors for the reference critical configuration, as well as ρ calc for the supercritical cases, are found to be in good agreement. However, the values of ρ meas produced by two of the applied calculation methods differ appreciably from the corresponding ρ calc values, clearly indicating deficiencies in the kinetic parameters obtained from these methods

The combination of kinetic and flow cytometric semen parameters as a tool to predict fertility in cryopreserved bull semen.

Science.gov (United States)

Gliozzi, T M; Turri, F; Manes, S; Cassinelli, C; Pizzi, F

2017-11-01

Within recent years, there has been growing interest in the prediction of bull fertility through in vitro assessment of semen quality. A model for fertility prediction based on early evaluation of semen quality parameters, to exclude sires with potentially low fertility from breeding programs, would therefore be useful. The aim of the present study was to identify the most suitable parameters that would provide reliable prediction of fertility. Frozen semen from 18 Italian Holstein-Friesian proven bulls was analyzed using computer-assisted semen analysis (CASA) (motility and kinetic parameters) and flow cytometry (FCM) (viability, acrosomal integrity, mitochondrial function, lipid peroxidation, plasma membrane stability and DNA integrity). Bulls were divided into two groups (low and high fertility) based on the estimated relative conception rate (ERCR). Significant differences were found between fertility groups for total motility, active cells, straightness, linearity, viability and percentage of DNA fragmented sperm. Correlations were observed between ERCR and some kinetic parameters, and membrane instability and some DNA integrity indicators. In order to define a model with high relation between semen quality parameters and ERCR, backward stepwise multiple regression analysis was applied. Thus, we obtained a prediction model that explained almost half (R 2=0.47, P<0.05) of the variation in the conception rate and included nine variables: five kinetic parameters measured by CASA (total motility, active cells, beat cross frequency, curvilinear velocity and amplitude of lateral head displacement) and four parameters related to DNA integrity evaluated by FCM (degree of chromatin structure abnormality Alpha-T, extent of chromatin structure abnormality (Alpha-T standard deviation), percentage of DNA fragmented sperm and percentage of sperm with high green fluorescence representative of immature cells). A significant relationship (R 2=0.84, P<0.05) was observed between

State and parameter estimation in biotechnical batch reactors

NARCIS (Netherlands)

Keesman, K.J.

2000-01-01

In this paper the problem of state and parameter estimation in biotechnical batch reactors is considered. Models describing the biotechnical process behaviour are usually nonlinear with time-varying parameters. Hence, the resulting large dimensions of the augmented state vector, roughly > 7, in

Drug-Target Kinetics in Drug Discovery.

Science.gov (United States)

Tonge, Peter J

2018-01-17

The development of therapies for the treatment of neurological cancer faces a number of major challenges including the synthesis of small molecule agents that can penetrate the blood-brain barrier (BBB). Given the likelihood that in many cases drug exposure will be lower in the CNS than in systemic circulation, it follows that strategies should be employed that can sustain target engagement at low drug concentration. Time dependent target occupancy is a function of both the drug and target concentration as well as the thermodynamic and kinetic parameters that describe the binding reaction coordinate, and sustained target occupancy can be achieved through structural modifications that increase target (re)binding and/or that decrease the rate of drug dissociation. The discovery and deployment of compounds with optimized kinetic effects requires information on the structure-kinetic relationships that modulate the kinetics of binding, and the molecular factors that control the translation of drug-target kinetics to time-dependent drug activity in the disease state. This Review first introduces the potential benefits of drug-target kinetics, such as the ability to delineate both thermodynamic and kinetic selectivity, and then describes factors, such as target vulnerability, that impact the utility of kinetic selectivity. The Review concludes with a description of a mechanistic PK/PD model that integrates drug-target kinetics into predictions of drug activity.

State Estimation-based Transmission line parameter identification

Directory of Open Access Journals (Sweden)

Fredy Andrés Olarte Dussán

2010-01-01

Full Text Available This article presents two state-estimation-based algorithms for identifying transmission line parameters. The identification technique used simultaneous state-parameter estimation on an artificial power system composed of several copies of the same transmission line, using measurements at different points in time. The first algorithm used active and reactive power measurements at both ends of the line. The second method used synchronised phasor voltage and current measurements at both ends. The algorithms were tested in simulated conditions on the 30-node IEEE test system. All line parameters for this system were estimated with errors below 1%.

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

Directory of Open Access Journals (Sweden)

S. Kremser

2011-06-01

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

Determination of kinetic parameters of Phlomis bovei de Noé using thermogravimetric analysis.

Science.gov (United States)

Yahiaoui, Meriem; Hadoun, Hocine; Toumert, Idir; Hassani, Aicha

2015-11-01

This paper reports the pyrolysis study of Phlomis bovei biomass by thermogravimetric experiments in order to determine the thermal degradation behavior and kinetic parameters. The weight losses were found to occur in three stages. In the DTG thermograms, an increase of the heating rate tended to delay thermal degradation processes towards higher temperatures. The average values of activation energy and pre-exponential factor calculated from Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose and Kissinger methods are 134.83, 134.06, 223.31kJ/mol and 4.1610(13), 1.1810(10), 2.8110(11)/s, respectively. The three-pseudo-component method shows that the activation energy increases with increasing the heating rate for hemicellulose and cellulose while the activation energy of the lignin decreased with an increase of the heating rate. Predicted results and experimental data exhibit similar tendencies and the three pseudo-components model with n different from unity 1 is recommended as the most suitable for prediction of kinetic behavior of Phlomis bovei de Noé. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mechanistic and kinetic aspects of microbial inactivation in food irradiation processes

International Nuclear Information System (INIS)

Tukenmez, I.

2004-01-01

Full text: A proper reaction mechanism was searched by analyzing the inactivation processes of microorganisms during food irradiation by ionizing radiation. By employing transition-state theory, it was assumed that the overall inactivation process involves a reversible sub-lethal stress and repair reactions to form reversibly injured cell or sensitized cell, which then undergoes irreversible injury leading to dead cell. A shoulder in low dose range in survival kinetics was associated with the repair process. Depending on the postulated mechanism, kinetic model equations were derived. The kinetics of cell inactivation by irradiation was expressed as depending on irradiation dose. By using experimental data in the developed model the inactivation parameters including threshold dose, radiation yield, decimal reduction dose and minimum sterilization dose were evaluated and microbial inactivation by irradiation was simulated by using the numerical values of the parameters. Developed model and model parameters may be used for the process control and the assessment of product quality in radiation preservation of food

Thermodynamic-state and kinetic-process dependent dual ferromagnetic states in high-Si content FeMn(PSi) alloys

International Nuclear Information System (INIS)

Li, Guijiang; Eriksson, Olle; Johansson, Börje; Vitos, Levente

2015-01-01

We have found that thermodynamic state and kinetic process co-determine the dual ferromagnetic (FM) orders in high-Si content FeMnP 1−x Si x (0.25 < x < 0.5). Alloys undergoing high temperature annealing and quenching process prefer a high magnetic moment FM state in a chemically partial disordered structure with low c/a ratio. This mechanism is suggested to be responsible for the often discussed virgin effect as well. A chemically ordered structure obtained by a slow cooling process from a relatively low annealing temperature and the increase in Si content stabilize a metastable lattice with high c/a ratio and FM order with low magnetic moment. The non-simultaneity of the magnetic and structural transitions can be responsible for the occurrence of FM state in the high c/a range. Thus, a c/a ratio that changes from high to low is physically plausible to stabilize the metastable FM order at low temperature. Our theoretical observations indicate that suitable thermodynamic state and kinetic diffusion process is crucial for optimizing magnetocaloric properties and exploring feasible magnetocaloric materials

Comparison of safflower oil extraction kinetics under two characteristic moisture conditions: statistical analysis of non-linear model parameters

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E. Baümler

2014-06-01

Full Text Available In this study the kinetics of oil extraction from partially dehulled safflower seeds under two moisture conditions (7 and 9% dry basis was investigated. The extraction assays were performed using a stirred batch system, thermostated at 50 ºC, using n-hexane as solvent. The data obtained were fitted to a modified diffusion model in order to represent the extraction kinetics. The model took into account a washing and a diffusive step. Fitting parameters were compared statistically for both moisture conditions. The oil yield increased with the extraction time in both cases, although the oil was released at different rates. A comparison of the parameters showed that both the portion extracted in the washing phase and the effective diffusion coefficient were moisture-dependent. The effective diffusivities were 2.81 10-12 and 8.06 10-13 m²s-1 for moisture contents of 7% and 9%, respectively.

Substrate inhibition kinetics of phenol degradation by binary mixed ...

African Journals Online (AJOL)

Steady states of a continuous culture with an inhibitory substrate were used to estimate kinetic parameters under substrate limitation (chemo stat operation). Mixed cultures of an indigenous Pseudomonas fluorescence and Pseudomonas aeruginosa were grown in continuous culture on phenol as the sole source of carbon ...

Point kinetics equations for subcritical systems based on the importance function associated to an external neutron source

International Nuclear Information System (INIS)

Carvalho Gonçalves, Wemerson de; Martinez, Aquilino Senra; Carvalho da Silva, Fernando

2015-01-01

Highlights: • We define the new function importance. • We calculate the kinetic parameters Λ, β, Γ and Q to: 0.95, 0.96, 0.97, 0.98 and 0.99. • We compared the results with those obtained by the main important functions. • We found that the calculated kinetic parameters are physically consistent. - Abstract: This paper aims to determine the parameters for a new set of equations of point kinetic subcritical systems, based on the concept of importance of Heuristic Generalized Perturbation Theory (HGPT). The importance function defined here is related to both the subcriticality and the external neutron source worth (which keeps the system at steady state). The kinetic parameters defined in this work are compared with the corresponding parameters when adopting the importance functions proposed by Gandini and Salvatores (2002), Dulla et al. (2006) and Nishihara et al. (2003). Furthermore, the point kinetics equations developed here are solved for two different transients, considering the parameters obtained with different importance functions. The results collected show that there is a similar behavior of the solution of the point kinetics equations, when used with the parameters obtained by the importance functions proposed by Gandini and Salvatores (2002) and Dulla et al. (2006), specially near the criticality. However, this is not verified as the system gets farther from criticality

Kinetic modeling of solid-state partitioning phase transformation with simultaneous misfit accommodation

International Nuclear Information System (INIS)

Song, Shaojie; Liu, Feng

2016-01-01

Considering a spherical misfitting precipitate growing into a finite elastic-perfectly plastic supersaturated matrix, a kinetic modeling for such solid-state partitioning phase transformation is presented, where the interactions of interface migration, solute diffusion and misfit accommodation are analyzed. The linkage between interface migration and solute diffusion proceeds through interfacial composition and interface velocity; their effects on misfit accommodation are mainly manifested in an effective transformation strain, which depends on instantaneous composition field and precipitate size. Taking γ to α transformation of a binary Fe-0.5 at.% C alloy under both isothermal and continuous cooling conditions as examples, the effects of misfit accommodation on the coupling interface migration and solute diffusion are well evaluated and discussed. For the isothermal transformation, a counterbalancing influence between mechanical and chemical driving forces is found so that the mixed-mode transformation kinetics is not sensitive with respect to the elastic–plastic accommodation of the effective misfit strain. Different from the isothermal process, during the continuous cooling condition, the effects of misfit accommodation on the kinetics of solid-state partitioning phase transformation are mainly manifested in the great decrease of the transformation starting temperature and the thermodynamic equilibrium composition. The present kinetic modeling was applied to predict the experimentally measured γ/α transformation of Fe-0.47 at.% C alloy conducted with a cooling rate of 10 K min −1 and a good agreement was achieved.

Calculation of kinetic parameters of Caliban metallic core experimental reactor from stochastic neutron measurements

Energy Technology Data Exchange (ETDEWEB)

Casoli, P.; Authier, N.; Baud, J. [Commissariat a l' energie Atomique, Centre de Valduc, 21120 Is-sur-Tille (France)

2009-07-01

Several experimental devices are operated by the Criticality and Neutron Science Research Department of the CEA Valduc Laboratory. One of these is the metallic core reactor Caliban. The knowledge of the fundamental kinetic parameters of the reactor is very useful, indeed necessary, to the operator. The purpose of this study was to develop and perform experiments allowing to determinate some of these parameters. The prompt neutron decay constant and particularly its value at criticality can be measured with reactor noise techniques such as the interval-distribution, the Feynman variance-to-mean, and the Rossi-{alpha} methods. By introducing the Nelson number, the effective delayed neutron fraction and the average neutron lifetime can also be calculated with the Rossi-{alpha} method. Subcritical, critical, and even supercritical experiments were performed. With the Rossi-{alpha} technique, it was found that the prompt neutron decay constant at criticality was (6.02*10{sup 5} {+-} 9%). Experiments also brought out the limitations of the used experimental parameters. (authors)

Calcite Dissolution Kinetics

Science.gov (United States)

Berelson, W.; Subhas, A.; Dong, S.; Naviaux, J.; Adkins, J. F.

2016-12-01

A geological buffer for high atmospheric CO2 concentrations is neutralization via reaction with CaCO3. We have been studying the dissolution kinetics of carbonate minerals using labeled 13C calcite and Picarro-based measurements of 13C enrichments in solution DIC. This methodology has greatly facilitated our investigation of dissolution kinetics as a function of water carbonate chemistry, temperature and pressure. One can adjust the saturation state Omega by changing the ion activity product (e.g. adjusting carbonate ion concentration), or by changing the solubility product (e.g. adjusting temperature or pressure). The canonical formulation of dissolution rate vs. omega has been refined (Subhas et al. 2015) and shows distinct non-linear behavior near equilibrium and rates in sea water of 1-3 e-6 g/cm2day at omega = 0.8. Carbonic anhydrase (CA), an enzyme that catalyzes the hydration of dissolved CO2 to carbonic acid, was shown (in concentrations 500x. This result points to the importance of carbonic acid in enhancing dissolution at low degrees of undersaturation. CA activity and abundance in nature must be considered regarding the role it plays in catalyzing dissolution. We also have been investigating the role of temperature on dissolution kinetics. An increase of 16C yields an order of magnitude increase in dissolution rate. Temperature (and P) also change Omega critical, the saturation state where dissolution rates change substantially. Increasing pressure (achieved in a pressure reaction chamber we built) also shifts Omega critical closer to equilibrium and small pressure increases have large impact on dissolution kinetics. Dissolution rates are enhanced by an order of magnitude for a change in pressure of 1500 psi relative to the dissolution rate achieved by water chemistry effects alone for an omega of 0.8. We've shown that the thermodynamic determination of saturation state does not adequately describe the kinetics of dissolution. The interplay of mineral

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

Science.gov (United States)

Bozkoyunlu, Gaye; Takaç, Serpil

2014-01-01

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.

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

Science.gov (United States)

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

2015-01-01

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. Copyright © 2014. Published by Elsevier B.V.

Some Considerations on the Fundamentals of Chemical Kinetics: Steady State, Quasi-Equilibrium, and Transition State Theory

Science.gov (United States)

Perez-Benito, Joaquin F.

2017-01-01

The elementary reaction sequence A ? I ? Products is the simplest mechanism for which the steady-state and quasi-equilibrium kinetic approximations can be applied. The exact integrated solutions for this chemical system allow inferring the conditions that must fulfill the rate constants for the different approximations to hold. A graphical…

Kinetics study of hydrochlorothiazide lactose liquid state interaction using conventional isothermal arrhenius method under basic and neutral conditions

Directory of Open Access Journals (Sweden)

Faranak Ghaderi

Full Text Available ABSTRACT The Maillard reaction of hydrochlorothiazide (HCTZ and lactose has been previously demonstrated in pharmaceutical formulations. In this study, the activation energy of - hydrohlorothiazide and lactose interaction in the liquid state was ascertained under basic and neutral conditions. Conventional isothermal High Performance Liquid Chromatography (HPLC technique was employed to ascertain the kinetic parameters using Arrhenius method. Results: The activation energy obtained was 82.43 and 100.28 kJ/mol under basic and neutral conditions, respectively. Consequently, it can be inferred that Maillard reaction is significantly affected by pH, which can be used as a control factor whenever the reaction potentially occurs.

Bringing metabolic networks to life: integration of kinetic, metabolic, and proteomic data

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Klipp Edda

2006-12-01

Full Text Available Abstract Background Translating a known metabolic network into a dynamic model requires reasonable guesses of all enzyme parameters. In Bayesian parameter estimation, model parameters are described by a posterior probability distribution, which scores the potential parameter sets, showing how well each of them agrees with the data and with the prior assumptions made. Results We compute posterior distributions of kinetic parameters within a Bayesian framework, based on integration of kinetic, thermodynamic, metabolic, and proteomic data. The structure of the metabolic system (i.e., stoichiometries and enzyme regulation needs to be known, and the reactions are modelled by convenience kinetics with thermodynamically independent parameters. The parameter posterior is computed in two separate steps: a first posterior summarises the available data on enzyme kinetic parameters; an improved second posterior is obtained by integrating metabolic fluxes, concentrations, and enzyme concentrations for one or more steady states. The data can be heterogenous, incomplete, and uncertain, and the posterior is approximated by a multivariate log-normal distribution. We apply the method to a model of the threonine synthesis pathway: the integration of metabolic data has little effect on the marginal posterior distributions of individual model parameters. Nevertheless, it leads to strong correlations between the parameters in the joint posterior distribution, which greatly improve the model predictions by the following Monte-Carlo simulations. Conclusion We present a standardised method to translate metabolic networks into dynamic models. To determine the model parameters, evidence from various experimental data is combined and weighted using Bayesian parameter estimation. The resulting posterior parameter distribution describes a statistical ensemble of parameter sets; the parameter variances and correlations can account for missing knowledge, measurement

Simulating kinetic parameters in transporter mediated permeability across Caco-2 cells. A case study on estrange-3-sulphate

DEFF Research Database (Denmark)

Rolsted, Kamilla; Rapin, Nicolas; Steffansen, Bente

2011-01-01

Substances that compete for the same saturable intestinal transporters may when dosed together lead to altered permeability and hence influence bioavailability. The aim was to simulate kinetic parameters, i.e. K(m) and J(max), for transporter mediated E(1)S permeability across Caco-2 cells...

Kinetics of disorder-to-fcc phase transition via an intermediate bcc state

International Nuclear Information System (INIS)

Liu Yongsheng; Nie Huifen; Bansil, Rama; Steinhart, Milos; Bang, Joona; Lodge, Timothy P.

2006-01-01

Time-resolved small-angle x-ray scattering measurements reveal that a long-lived intermediate bcc state forms when a poly(styrene-b-isoprene) diblock copolymer solution in an isoprene selective solvent is rapidly cooled from the disordered micellar fluid at high temperature to an equilibrium fcc state. The kinetics of the epitaxial growth of the [111] fcc peak from the [110] bcc peak was obtained by fitting the scattering data to a simple model of the transformation. The growth of the [111] fcc peak agrees with the Avrami model of nucleation and growth kinetics with an exponent n=1.4, as does the initial decay of the [110] bcc peak, with an exponent n=1.3. The data were also found to be in good agreement with the Cahn model of grain boundary nucleation and growth

Interplay of bistable kinetics of gene expression during cellular growth

International Nuclear Information System (INIS)

Zhdanov, Vladimir P

2009-01-01

In cells, the bistable kinetics of gene expression can be observed on the level of (i) one gene with positive feedback between protein and mRNA production, (ii) two genes with negative mutual feedback between protein and mRNA production, or (iii) in more complex cases. We analyse the interplay of two genes of type (ii) governed by a gene of type (i) during cellular growth. In particular, using kinetic Monte Carlo simulations, we show that in the case where gene 1, operating in the bistable regime, regulates mutually inhibiting genes 2 and 3, also operating in the bistable regime, the latter genes may eventually be trapped either to the state with high transcriptional activity of gene 2 and low activity of gene 3 or to the state with high transcriptional activity of gene 3 and low activity of gene 2. The probability to get to one of these states depends on the values of the model parameters. If genes 2 and 3 are kinetically equivalent, the probability is equal to 0.5. Thus, our model illustrates how different intracellular states can be chosen at random with predetermined probabilities. This type of kinetics of gene expression may be behind complex processes occurring in cells, e.g., behind the choice of the fate by stem cells

Effect of lattice-level adjoint-weighting on the kinetics parameters of CANDU reactors

International Nuclear Information System (INIS)

Nichita, Eleodor

2009-01-01

Space-time kinetics calculations for CANDU reactors are routinely performed using the Improved Quasistatic (IQS) method. The IQS method calculates kinetics parameters such as the effective delayed-neutron fraction and generation time using adjoint weighting. In the current implementation of IQS, the direct flux, as well as the adjoint, is calculated using a two-group cell-homogenized reactor model which is inadequate for capturing the effect of the softer energy spectrum of the delayed neutrons. Additionally, there may also be fine spatial effects that are lost because the intra-cell adjoint shape is ignored. The purpose of this work is to compare the kinetics parameters calculated using the two-group cell-homogenized model with those calculated using lattice-level fine-group heterogeneous adjoint weighting and to assess whether the differences are large enough to justify further work on incorporating lattice-level adjoint weighting into the IQS method. A second goal is to evaluate whether the use of a fine-group cell-homogenized lattice-level adjoint, such as is the current practice for Light Water Reactors (LWRs), is sufficient to capture the lattice effects in question. It is found that, for CANDU lattices, the generation time is almost unaffected by the type of adjoint used to calculate it, but that the effective delayed-neutron fraction is affected by the type of adjoint used. The effective delayed-neutron fraction calculated using the two-group cell-homogenized adjoint is 5.2% higher than the 'best' effective delayed-neutron fraction value obtained using the detailed lattice-level fine-group heterogeneous adjoint. The effective delayed-neutron fraction calculated using the fine-group cell-homogenized adjoint is only 1.7% higher than the 'best' effective delayed-neutron fraction value but is still not equal to it. This situation is different from that encountered in LWRs where weighting by a fine-group cell-homogenized adjoint is sufficient to calculate the

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

Science.gov (United States)

Mohajer, Ardavan; Tremier, Anne; Barrington, Suzelle; Teglia, Cecile

2010-01-01

Composting is a feasible biological treatment for the recycling of wastewater sludge as a soil amendment. The process can be optimized by selecting an initial compost recipe with physical properties that enhance microbial activity. The present study measured the microbial O(2) uptake rate (OUR) in 16 sludge and wood residue mixtures to estimate the kinetics parameters of maximum growth rate mu(m) and rate of organic matter hydrolysis K(h), as well as the initial biodegradable organic matter fractions present. The starting mixtures consisted of a wide range of moisture content (MC), waste to bulking agent (BA) ratio (W/BA ratio) and BA particle size, which were placed in a laboratory respirometry apparatus to measure their OUR over 4 weeks. A microbial model based on the activated sludge process was used to calculate the kinetic parameters and was found to adequately reproduced OUR curves over time, except for the lag phase and peak OUR, which was not represented and generally over-estimated, respectively. The maximum growth rate mu(m), was found to have a quadratic relationship with MC and a negative association with BA particle size. As a result, increasing MC up to 50% and using a smaller BA particle size of 8-12 mm was seen to maximize mu(m). The rate of hydrolysis K(h) was found to have a linear association with both MC and BA particle size. The model also estimated the initial readily biodegradable organic matter fraction, MB(0), and the slower biodegradable matter requiring hydrolysis, MH(0). The sum of MB(0) and MH(0) was associated with MC, W/BA ratio and the interaction between these two parameters, suggesting that O(2) availability was a key factor in determining the value of these two fractions. The study reinforced the idea that optimization of the physical characteristics of a compost mixture requires a holistic approach. 2010 Elsevier Ltd. All rights reserved.

Kinetic Parameters during Bis-GMA and TEGDMA Monomer Polymerization by ATR-FTIR: The Influence of Photoinitiator and Light Curing Source

Directory of Open Access Journals (Sweden)

Aline B. Denis

2016-01-01

Full Text Available This study aimed to analyze the kinetic parameters of two monomers using attenuated total reflectance Fourier transform infrared (ATR-FTIR: 2,2-bis-[4-(2-hydroxy-3-methacryloxypropyl-1-oxy-phenyl] propane (Bis-GMA and triethylene glycol dimethacrylate (TEGDMA. The following were calculated to evaluate the kinetic parameters: maximum conversion rate (Rpmax, time at the maximum polymerization rate (tmax, conversion at Rpmax, and total conversion recorded at the maximum conversion point after 300 s. Camphorquinone (CQ and phenyl propanedione (PPD were used in this study as photoinitiators, whereas N,N-dimethyl-p-toluidine (DMPT amine was used as a coinitiator. LED apparatus and halogen lamp were used in turn to evaluate the effect that light source had on the monomer kinetics. The mass concentration ratio for the three resin preparations was 0.7 : 0.3 for Bis-GMA and TEGDMA: R1 (CQ + DMPT, R2 (PPD + DMPT, and R3 (PPD + CQ + DMPT. The PPD association with the CQ photoinitiator altered the polymerization kinetics compared to a resin containing only the CQ photoinitiator. The light sources exhibited no significant differences for tmax of R1 and R3. Resins containing only the PPD initiator exhibited a higher tmax than those containing only CQ. However, the Rpmax decreased for resins containing the PPD photoinitiator.

Comparison of morphological and kinetic parameters in distinction of benign and malignant breast lesions in dynamic contrast enhanced magnetic resonance imaging

Directory of Open Access Journals (Sweden)

Direnç Özlem Aksoy

2013-12-01

Full Text Available Objective: To evaluate the value of qualitative morphologicaland kinetic data and quantitative kinetic data indistinction of malignancy in dynamic contrast enhancedmagnetic resonance imaging (DCE-MRI of the breast.Methods: DCE-MRIs of 49 subjects were evaluated.Morphological and contrast enhancement parameters of95 lesions were recorded in these subjects. Post-contrastkinetic behavior of these lesions were also investigated.Among the quantitative parameters, relative enhancements(E1, E2, Epeak, time-to-peak (Tpeak, slope ofcurve (Slope, signal enhancement ratio (SER, and maximumintensity time ratio (MITR were calculated. Theseresults were compared with the pathological diagnosis.Results: Spiculated contour (100%, rim enhancement(97.87%, irregular shape (95.74%, and irregular margin(91.49% were the most specific morphological featuresof malignancy in mass lesions. In non-mass lesions, focalzone (91.49% was the most specific feature of malignancy.74.5% of the benign lesions showed type 1, 77.1%of the malignant lesions showed type 2 and 3 curves accordingto the kinetic curve evaluation. All quantitativeparameters except Epeak were found to be statisticallysignificant in distinction of malignancy.Conclusion: None of the morphological features of thebenign lesions were found to be significantly specific.More specific features can be described for malignantlesions. Early behavior of the kinetic curve is not usefulfor diagnosis of malignancy but the intermediate and latebehavior gives useful information. Quantitative data involvedin this study might be promising.Key words: Morphological, kinetic, breast lesions, magnetic resonance imaging, dynamic

FY2014 Parameters for Helions and Gold Ions in Booster, AGS, and RHIC

Energy Technology Data Exchange (ETDEWEB)

Gardner, C. J. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.

2014-08-15

The nominal parameters for helions (helion is the bound state of two protons and one neutron, the nucleus of a helium-3 atom) and gold ions in Booster, AGS, and RHIC are given for the FY2014 running period. The parameters are found using various formulas to derive mass, helion anomalous g-factor, kinetic parameters, RF parameters, ring parameters, etc..

Simultaneous determination of thermodynamic and kinetic parameters of aminopolycarbonate complexes of cobalt(II) and nickel(II) based on isothermal titration calorimetry data.

Science.gov (United States)

Tesmar, Aleksandra; Wyrzykowski, Dariusz; Muñoz, Eva; Pilarski, Bogusław; Pranczk, Joanna; Jacewicz, Dagmara; Chmurzyński, Lech

2017-04-01

The influence of the different side chain residues on the thermodynamic and kinetic parameters for complexation reactions of the Co 2 + and Ni 2 + ions has been investigated by using the isothermal titration calorimetry (ITC) technique supported by potentiometric titration data. The study was concerned with the 2 common tripodal aminocarboxylate ligands, namely, nitrilotriacetic acid and N-(2-hydroxyethyl) iminodiacetic acid. Calorimetric measurements (ITC) were run in the 2-(N-morpholino)ethanesulfonic acid hydrate (2-(N-morpholino) ethanesulfonic acid), piperazine-N,N'-bis(2-ethanesulfonic acid), and dimethylarsenic acid buffers (0.1 mol L -1 , pH 6) at 298.15 K. The quantification of the metal-buffer interactions and their incorporation into the ITC data analysis enabled to obtain the pH-independent and buffer-independent thermodynamic parameters (K, ΔG, ΔH, and ΔS) for the reactions under study. Furthermore, the kinITC method was applied to obtain kinetic information on complexation reactions from the ITC data. Correlations, based on kinetic and thermodynamic data, between the kinetics of formation of Co 2 + and Ni 2 + complexes and their thermodynamic stabilities are discussed. Copyright © 2016 John Wiley & Sons, Ltd.

Thermodynamics, kinetics and process control of nitriding

DEFF Research Database (Denmark)

Mittemeijer, Eric J.; Somers, Marcel A. J.

1999-01-01

As a prerequisite for predictability of properties obtained by a nitriding treatment of iron-based workpieces, the relation between the process parameters and the composition and structure of the surface layer produced must be known. At present (even) the description of thermodynamic equilibrium...... of pure iron-nitrogen phases has not been achieved fully. It has been shown that taking into account ordering of nitrogen in the epsilon and gamma' iron-nitride phases, leads to an improved understanding of the Fe-N phase diagram. Although thermodynamics indicate the state the system strives for......, the nitriding result is determined largely by the kinetics of the process. The nitriding kinetics have been shown to be characterised by the occurring local near-equilibria and stationary states at surfaces and interfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data have...

Isotope exchange kinetic of phosphorus in soils from Pernambuco State -Brazil

International Nuclear Information System (INIS)

Figueiredo, F.J.B. de.

1989-12-01

The applicability of isotopic exchange kinetics of 32 p to characterize phosphorus available to plants and to diagnose the reactivity of soil-fertilizer-P in six soils from Pernambuco is described. This methodology was compared with anion exchange resin, isotopic exchange equilibrium methods (E-value and L-value) and P absorption by plants. The first greenhouse experiment had the following treatments: 1) with P and, 2) with addition of 43.7 mg P/Kg of soil, incubated for O, 42 and 84 days before seeding. The kinetic of isotopic exchange (KIE), resin-P and E-value were determined before seeding and after harvesting pearl millet grown for 42 days. Results indicated that the KIE parameters rated the soils more efficiently, in terms of available P and soil-fertilizer-P reactivity, than resin-P, E-value and L-value. (author). 38 refs, 2 figs, 18 tabs

Imperfect dark energy from kinetic gravity braiding

Energy Technology Data Exchange (ETDEWEB)

Deffayet, Cédric [AstroParticule and Cosmologie, UMR7164-CNRS, Université Denis Diderot-Paris 7, CEA, Observatoire de Paris, 10 rue Alice Domon et Léonie Duquet, F-75205 Paris Cedex 13 (France); Pujolàs, Oriol [CERN, Theory Division, CH-1211 Geneva 23 (Switzerland); Sawicki, Ignacy; Vikman, Alexander, E-mail: deffayet@iap.fr, E-mail: oriol.pujolas@cern.ch, E-mail: ignacy.sawicki@nyu.edu, E-mail: alexander.vikman@nyu.edu [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States)

2010-10-01

We introduce a large class of scalar-tensor models with interactions containing the second derivatives of the scalar field but not leading to additional degrees of freedom. These models exhibit peculiar features, such as an essential mixing of scalar and tensor kinetic terms, which we have named kinetic braiding. This braiding causes the scalar stress tensor to deviate from the perfect-fluid form. Cosmology in these models possesses a rich phenomenology, even in the limit where the scalar is an exact Goldstone boson. Generically, there are attractor solutions where the scalar monitors the behaviour of external matter. Because of the kinetic braiding, the position of the attractor depends both on the form of the Lagrangian and on the external energy density. The late-time asymptotic of these cosmologies is a de Sitter state. The scalar can exhibit phantom behaviour and is able to cross the phantom divide with neither ghosts nor gradient instabilities. These features provide a new class of models for Dark Energy. As an example, we study in detail a simple one-parameter model. The possible observational signatures of this model include a sizeable Early Dark Energy and a specific equation of state evolving into the final de-Sitter state from a healthy phantom regime.

Imperfect dark energy from kinetic gravity braiding

International Nuclear Information System (INIS)

Deffayet, Cédric; Pujolàs, Oriol; Sawicki, Ignacy; Vikman, Alexander

2010-01-01

We introduce a large class of scalar-tensor models with interactions containing the second derivatives of the scalar field but not leading to additional degrees of freedom. These models exhibit peculiar features, such as an essential mixing of scalar and tensor kinetic terms, which we have named kinetic braiding. This braiding causes the scalar stress tensor to deviate from the perfect-fluid form. Cosmology in these models possesses a rich phenomenology, even in the limit where the scalar is an exact Goldstone boson. Generically, there are attractor solutions where the scalar monitors the behaviour of external matter. Because of the kinetic braiding, the position of the attractor depends both on the form of the Lagrangian and on the external energy density. The late-time asymptotic of these cosmologies is a de Sitter state. The scalar can exhibit phantom behaviour and is able to cross the phantom divide with neither ghosts nor gradient instabilities. These features provide a new class of models for Dark Energy. As an example, we study in detail a simple one-parameter model. The possible observational signatures of this model include a sizeable Early Dark Energy and a specific equation of state evolving into the final de-Sitter state from a healthy phantom regime

KINETICS OF SLURRY PHASE FISCHER-TROPSCH SYSTHESIS

International Nuclear Information System (INIS)

Dragomir B. Bukur; Gilbert F. Froment; Tomasz Olewski

2005-01-01

This report covers the third year of this research grant under the University Coal Research program. The overall objective of this project is to develop a comprehensive kinetic model for slurry phase Fischer-Tropsch synthesis (FTS) on iron catalysts. This model will be validated with experimental data obtained in a stirred tank slurry reactor (STSR) over a wide range of process conditions. The model will be able to predict molar flow rates and concentrations of all reactants and major product species (H 2 O, CO 2 , linear 1- and 2-olefins, and linear paraffins) as a function of reaction conditions in the STSR. During the reporting period we utilized experimental data from the STSR, that were obtained during the first two years of the project, to perform vapor-liquid equilibrium (VLE) calculations and estimate kinetic parameters. We used a modified Peng-Robinson (PR) equation of state (EOS) with estimated values of binary interaction coefficients for the VLE calculations. Calculated vapor phase compositions were in excellent agreement with experimental values from the STSR under reaction conditions. Occasional discrepancies (for some of the experimental data) between calculated and experimental values of the liquid phase composition were ascribed to experimental errors. The VLE calculations show that the vapor and the liquid are in thermodynamic equilibrium under reaction conditions. Also, we have successfully applied the Levenberg-Marquardt method (Marquardt, 1963) to estimate parameters of a kinetic model proposed earlier by Lox and Froment (1993b) for FTS on an iron catalyst. This kinetic model is well suited for initial studies where the main goal is to learn techniques for parameter estimation and statistical analysis of estimated values of model parameters. It predicts that the chain growth parameter (α) and olefin to paraffin ratio are independent of carbon number, whereas our experimental data show that they vary with the carbon number. Predicted molar flow

Sensitivity analysis in oxidation ditch modelling: the effect of variations in stoichiometric, kinetic and operating parameters on the performance indices

NARCIS (Netherlands)

Abusam, A.A.A.; Keesman, K.J.; Straten, van G.; Spanjers, H.; Meinema, K.

2001-01-01

This paper demonstrates the application of the factorial sensitivity analysis methodology in studying the influence of variations in stoichiometric, kinetic and operating parameters on the performance indices of an oxidation ditch simulation model (benchmark). Factorial sensitivity analysis

A Study on the Pyrolysis of Peanut Shells at Different Isothermal Conditions and Determination of the Kinetic Parameters

Directory of Open Access Journals (Sweden)

Şeyda Taşar

2015-12-01

Full Text Available The pyrolysis process, which is applied for the aim of producing energy and raw materials which are implemented for the chemical industry from biomass sources, is a thermal conversion process. Determination of the pyrolysis kinetic parameters are important In order to suitable equipment and process design. In this target, in the study the pyrolysis of peanut shells was conducted in a muffle furnace at static atmosphere with temperatures ranging from 300-700 °C. The effects of various parameters on the rate of thermal decomposition rate and the solid yield were determined. The parameters of interest were temperature 300-700 °C, particle size 4-50 mesh, pelletizing, and pelletizing pressure 1.103-5.103 kgf/cm2. Regression coefficients for the total decomposition step were obtained using the thermographs were obtained as a result of the pyrolysis of the peanut shells, and 20 different theoretical model equations that represented the degradation by the Coast-Redfern method. According to regression coefficients of the theoretical model equations, we determined the kinetic model that best represented the degradation. Using this model to represent the degradation, the activation energy (Ea and Arhenius frequency factor ln(A for the total reaction were calculated to be 38.245 kJ/mol and 8.124, respectively.

Esterification of fatty acids using nylon-immobilized lipase in n-hexane: kinetic parameters and chain-length effects.

Science.gov (United States)

Zaidi, A; Gainer, J L; Carta, G; Mrani, A; Kadiri, T; Belarbi, Y; Mir, A

2002-02-28

The esterification of long-chain fatty acids in n-hexane catalyzed by nylon-immobilized lipase from Candida rugosa has been investigated. Butyl oleate (22 carbon atoms), oleyl butyrate (22 carbon atoms) and oleyl oleate (36 carbon atoms) were produced at maximum reaction rates of approximately equal to 60 mmol h(-1) g(-1) immobilized enzyme when the substrates were present in equimolar proportions at an initial concentration of 0.6 mol l(-1). The observed kinetic behavior of all the esterification reactions is found to follow a ping-pong bi-bi mechanism with competitive inhibition by both substrates. The effect of the chain-length of the fatty acids and the alcohols could be correlated to some mechanistic models, in accordance with the calculated kinetic parameters.

Computer controlled automated assay for comprehensive studies of enzyme kinetic parameters.

Directory of Open Access Journals (Sweden)

Felix Bonowski

Full Text Available Stability and biological activity of proteins is highly dependent on their physicochemical environment. The development of realistic models of biological systems necessitates quantitative information on the response to changes of external conditions like pH, salinity and concentrations of substrates and allosteric modulators. Changes in just a few variable parameters rapidly lead to large numbers of experimental conditions, which go beyond the experimental capacity of most research groups. We implemented a computer-aided experimenting framework ("robot lab assistant" that allows us to parameterize abstract, human-readable descriptions of micro-plate based experiments with variable parameters and execute them on a conventional 8 channel liquid handling robot fitted with a sensitive plate reader. A set of newly developed R-packages translates the instructions into machine commands, executes them, collects the data and processes it without user-interaction. By combining script-driven experimental planning, execution and data-analysis, our system can react to experimental outcomes autonomously, allowing outcome-based iterative experimental strategies. The framework was applied in a response-surface model based iterative optimization of buffer conditions and investigation of substrate, allosteric effector, pH and salt dependent activity profiles of pyruvate kinase (PYK. A diprotic model of enzyme kinetics was used to model the combined effects of changing pH and substrate concentrations. The 8 parameters of the model could be estimated from a single two-hour experiment using nonlinear least-squares regression. The model with the estimated parameters successfully predicted pH and PEP dependence of initial reaction rates, while the PEP concentration dependent shift of optimal pH could only be reproduced with a set of manually tweaked parameters. Differences between model-predictions and experimental observations at low pH suggest additional protonation

An improved hybrid of particle swarm optimization and the gravitational search algorithm to produce a kinetic parameter estimation of aspartate biochemical pathways.

Science.gov (United States)

Ismail, Ahmad Muhaimin; Mohamad, Mohd Saberi; Abdul Majid, Hairudin; Abas, Khairul Hamimah; Deris, Safaai; Zaki, Nazar; Mohd Hashim, Siti Zaiton; Ibrahim, Zuwairie; Remli, Muhammad Akmal

2017-12-01

Mathematical modelling is fundamental to understand the dynamic behavior and regulation of the biochemical metabolisms and pathways that are found in biological systems. Pathways are used to describe complex processes that involve many parameters. It is important to have an accurate and complete set of parameters that describe the characteristics of a given model. However, measuring these parameters is typically difficult and even impossible in some cases. Furthermore, the experimental data are often incomplete and also suffer from experimental noise. These shortcomings make it challenging to identify the best-fit parameters that can represent the actual biological processes involved in biological systems. Computational approaches are required to estimate these parameters. The estimation is converted into multimodal optimization problems that require a global optimization algorithm that can avoid local solutions. These local solutions can lead to a bad fit when calibrating with a model. Although the model itself can potentially match a set of experimental data, a high-performance estimation algorithm is required to improve the quality of the solutions. This paper describes an improved hybrid of particle swarm optimization and the gravitational search algorithm (IPSOGSA) to improve the efficiency of a global optimum (the best set of kinetic parameter values) search. The findings suggest that the proposed algorithm is capable of narrowing down the search space by exploiting the feasible solution areas. Hence, the proposed algorithm is able to achieve a near-optimal set of parameters at a fast convergence speed. The proposed algorithm was tested and evaluated based on two aspartate pathways that were obtained from the BioModels Database. The results show that the proposed algorithm outperformed other standard optimization algorithms in terms of accuracy and near-optimal kinetic parameter estimation. Nevertheless, the proposed algorithm is only expected to work well in

A stochastic model of enzyme kinetics

Science.gov (United States)

Stefanini, Marianne; Newman, Timothy; McKane, Alan

2003-10-01

Enzyme kinetics is generally modeled by deterministic rate equations, and in the simplest case leads to the well-known Michaelis-Menten equation. It is plausible that stochastic effects will play an important role at low enzyme concentrations. We have addressed this by constructing a simple stochastic model which can be exactly solved in the steady-state. Throughout a wide range of parameter values Michaelis-Menten dynamics is replaced by a new and simple theoretical result.

Adsorption of a cationic dye (Yellow Basic 28 ontothe calcined mussel shells: Kinetics, Isotherm and Thermodynamic Parameters

Directory of Open Access Journals (Sweden)

Imane EL Ouahabi

2015-11-01

Full Text Available The aim of this study is to valorise the mussel shells and evaluate the adsorption capacity of calcined mussel shells for the cationic dyes.  The adsorbent was characterized by DRX, FTIR, BET and SEM, respectively. The adsorption of Yellow Basic28 on calcined mussel shells was investigated using the parameters such as concentrations (10-50mg/L, pH (3-10, ionic strength (0-2 mol / L and temperature (288 - 318 °C.  The adsorption rate data were analysed according to the first and second-order kinetic models.  The adsorption kinetics was found to be best represented by the pseudo-second-order kinetic model.  The experimental isotherm data were analyzed using Langmuir, Freundlich, Temkin, Elovich and Dubinin–Radushkevich isotherm equations on the dye-adsorbent system. The experimental data yielded excellent fits with Freundlich isotherm equation (R² = 0.966. It was indicative of the heterogeneity of the adsorption sites on the CMS particles.  Various thermodynamic parameters such as enthalpy of adsorption ΔH°, free energy change ΔG°and entropy ΔS° were estimated.  The positive value of ΔH°(30.321 kJ/mol and negative values of ΔG° (from -5.392 to -2.873 kJ/mol show the process is endothermic and spontaneous.  The negative value of entropy ΔS° (-87.172 J/mol K suggest the decreased randomness at the solid-liquid interface during the adsorption of dyes onto calcined mussel shells.

Kinetic insights over a PEMFC operating on stationary and oscillatory states.

Science.gov (United States)

Mota, Andressa; Gonzalez, Ernesto R; Eiswirth, Markus

2011-12-01

Kinetic investigations in the oscillatory state have been carried out in order to shed light on the interplay between the complex kinetics exhibited by a proton exchange membrane fuel cell fed with poisoned H(2) (108 ppm of CO) and the other in serie process. The apparent activation energy (E(a)) in the stationary state was investigated in order to clarify the E(a) observed in the oscillatory state. The apparent activation energy in the stationary state, under potentiostatic control, rendered (a) E(a) ≈ 50-60 kJ mol(-1) over 0.8 V < E < 0.6 V and (b) E(a) ≈ 10 kJ mol(-1) at E = 0.3 V. The former is related to the H(2) adsorption in the vacancies of the surface poisoned by CO and the latter is correlated to the process of proton conductivity in the membrane. The dependence of the period-one oscillations on the temperature yielded a genuine Arrhenius dependence with two E(a) values: (a) E(a) around 70 kJ mol(-1), at high temperatures, and (b) E(a) around 10-15 kJ mol(-1), at lower temperatures. The latter E(a) indicates the presence of protonic mass transport coupled to the essential oscillatory mechanism. These insights point in the right direction to predict spatial couplings between anode and cathode as having the highest strength as well as to speculate the most likely candidates to promote spatial inhomogeneities. © 2011 American Chemical Society

A global resource allocation strategy governs growth transition kinetics of Escherichia coli.

Science.gov (United States)

Erickson, David W; Schink, Severin J; Patsalo, Vadim; Williamson, James R; Gerland, Ulrich; Hwa, Terence

2017-11-02

A grand challenge of systems biology is to predict the kinetic responses of living systems to perturbations starting from the underlying molecular interactions. Changes in the nutrient environment have long been used to study regulation and adaptation phenomena in microorganisms and they remain a topic of active investigation. Although much is known about the molecular interactions that govern the regulation of key metabolic processes in response to applied perturbations, they are insufficiently quantified for predictive bottom-up modelling. Here we develop a top-down approach, expanding the recently established coarse-grained proteome allocation models from steady-state growth into the kinetic regime. Using only qualitative knowledge of the underlying regulatory processes and imposing the condition of flux balance, we derive a quantitative model of bacterial growth transitions that is independent of inaccessible kinetic parameters. The resulting flux-controlled regulation model accurately predicts the time course of gene expression and biomass accumulation in response to carbon upshifts and downshifts (for example, diauxic shifts) without adjustable parameters. As predicted by the model and validated by quantitative proteomics, cells exhibit suboptimal recovery kinetics in response to nutrient shifts owing to a rigid strategy of protein synthesis allocation, which is not directed towards alleviating specific metabolic bottlenecks. Our approach does not rely on kinetic parameters, and therefore points to a theoretical framework for describing a broad range of such kinetic processes without detailed knowledge of the underlying biochemical reactions.

Importance of (n,xn) reactions in evaluating kinetic parameters of subcritical assemblies: from classic to modern formalism

Energy Technology Data Exchange (ETDEWEB)

Talamo, Alberto; Gohar, Yousry, E-mail: alby@anl.gov [Argonne National Laboratory, Lemont, IL (United States); Dulla, Sandra; Ravetto, Piero [Politecnico di Torino (Italy)

2011-07-01

The importance of (n,xn) reactions must be taken into consideration while calculating the kinetic parameters of subcritical assemblies driven by an external neutron source. This study is divided into two parts, the first part is dedicated to the classic definition of the neutron source multiplication factor and two alternative calculation methodologies are compared. The second part considers a new definition of the kinetic parameters for subcritical assemblies, with particular emphasis on the delayed neutron fraction and generation time. This new definition has been modified to take into account the external neutron source and (n,xn) reactions, which increase the fraction of prompt neutrons. The developed theoretical framework has been applied by Monte Carlo and deterministic calculations to the YALINA Thermal subcritical assembly in Belarus. This facility can be driven by californium, deuterium-deuterium (D-D), or deuterium-tritium (D-T) external neutron sources. For the D-T neutron source, (n,xn) reactions must be taken into account in order to produce accurate results because the average energy of D-T source neutrons is 14.1 MeV, a value much higher than the threshold energy of the (n,2n) cross section of uranium isotopes. (author)

Importance of (n,xn) reactions in evaluating kinetic parameters of subcritical assemblies: from classic to modern formalism

International Nuclear Information System (INIS)

Talamo, Alberto; Gohar, Yousry; Dulla, Sandra; Ravetto, Piero

2011-01-01

The importance of (n,xn) reactions must be taken into consideration while calculating the kinetic parameters of subcritical assemblies driven by an external neutron source. This study is divided into two parts, the first part is dedicated to the classic definition of the neutron source multiplication factor and two alternative calculation methodologies are compared. The second part considers a new definition of the kinetic parameters for subcritical assemblies, with particular emphasis on the delayed neutron fraction and generation time. This new definition has been modified to take into account the external neutron source and (n,xn) reactions, which increase the fraction of prompt neutrons. The developed theoretical framework has been applied by Monte Carlo and deterministic calculations to the YALINA Thermal subcritical assembly in Belarus. This facility can be driven by californium, deuterium-deuterium (D-D), or deuterium-tritium (D-T) external neutron sources. For the D-T neutron source, (n,xn) reactions must be taken into account in order to produce accurate results because the average energy of D-T source neutrons is 14.1 MeV, a value much higher than the threshold energy of the (n,2n) cross section of uranium isotopes. (author)

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

Science.gov (United States)

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

2014-03-01

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.

A feasible kinetic model for the hydrogen oxidation on ruthenium electrodes

International Nuclear Information System (INIS)

Rau, M.S.; Gennero de Chialvo, M.R.; Chialvo, A.C.

2010-01-01

The hydrogen oxidation reaction (hor) was studied on a polycrystalline ruthenium electrode in H 2 SO 4 solution at different rotation rates (ω). The experimental polarization curves recorded on steady state show the existence of a maximum current with a non-linear dependence of the current density on ω 1/2 . On the basis of the Tafel-Heyrovsky-Volmer kinetic mechanism, coupled with a process of inhibition of active sites by the reversible electroadsorption of hydroxyl species, it was possible to appropriately describe the origin of the maximum current. The corresponding set of kinetic parameters was also calculated from the correlation of the experimental results with the proposed kinetic model.

Anisotropic superconducting state parameters of Tl-2212 superconductors

International Nuclear Information System (INIS)

Khaskalam, Amit K.; Singh, R.K.; Varshney, Dinesh

2001-01-01

We have estimated the superconducting state parameters and their anisotropy in thallium based superconductors (Tl-2212), in the frame work of Fermi liquid approach. Determination of the effective mass of the charge carriers from the Fermi velocity and estimated anisotropic superconducting state parameters, particularly, the magnetic penetration depth along and perpendicular to the conducting plane. The coherence length along and perpendicular to the ab plane is evaluated and appears to be higher. The temperature dependence of penetration depth, their anisotropy and Ginsburg Landau parameter for optimised doped Tl based cuprates shows the power law. The technique permits a consistency with the reported data. (author)

Determination of kinetic parameters during the thermal decomposition of epoxy/carbon fiber composite material

International Nuclear Information System (INIS)

Lee, Jae Hun; Kim, Kwang Seok; Kim, Hyo

2013-01-01

An in-depth study to determine the thermal decomposition kinetics parameters such as the activation energy E_a, the reaction order n, and the pre-exponential factor A of epoxy/carbon fiber composite material has been conducted. We employ not only the modified peak property method that is proposed here, but also the conventional method in analyzing the experimental data, and compare the results to show the performance of the proposed model. The pyrolysis tests for the epoxy/carbon fiber composite materials are conducted by using thermogravimetric analyser at various heating rates. As a result, the best prediction to the experimental data can be obtained by the modified peak property method. Besides, among the methods applied here, the modified peak property method provides most convenient way to recover the parameters: it does not require a curve fitting of the data nor a long iterative computation

Lumping procedure for a kinetic model of catalytic naphtha reforming

Directory of Open Access Journals (Sweden)

H. M. Arani

2009-12-01

Full Text Available A lumping procedure is developed for obtaining kinetic and thermodynamic parameters of catalytic naphtha reforming. All kinetic and deactivation parameters are estimated from industrial data and thermodynamic parameters are calculated from derived mathematical expressions. The proposed model contains 17 lumps that include the C6 to C8+ hydrocarbon range and 15 reaction pathways. Hougen-Watson Langmuir-Hinshelwood type reaction rate expressions are used for kinetic simulation of catalytic reactions. The kinetic parameters are benchmarked with several sets of plant data and estimated by the SQP optimization method. After calculation of deactivation and kinetic parameters, plant data are compared with model predictions and only minor deviations between experimental and calculated data are generally observed.

Experimental estimations of the kinetics parameters of the IBR-2M reactor by stochastic noises

International Nuclear Information System (INIS)

Pepelyshev, Yu.N.; Tajybov, L.A.; Garibov, A.A.; Mekhtieva, R.N.

2012-01-01

Experimental investigations of stochastic fluctuations of pulse energy of the IBR-2M reactor have been carried out which allowed us to obtain some of the parameters of the reactor kinetics. At different levels of average power a sequence of values of pulse energy was recorded with the calculation of the distribution parameters. An ionization chamber with boron installed near the active zone was used as a neutron detector. The research results allowed us to estimate the average lifetime of prompt neutrons τ = (6.53±0.2)·10 -8 s, absolute power of the reactor and intensity of the source of spontaneous neutrons S sp ≤(6.72±0.12)·10 6 s -1 . It was shown that the experimental results are close to the calculated ones

Measurement of kinetic parameters in the fast subcritical core MASURCA

International Nuclear Information System (INIS)

Baeten, Peter; Abderrahim, Hamid Aiet

2004-01-01

In the MUSE shared cost action of the European Fifth Framework Program measurements have been performed to investigate the neutronic behavior of the fast subcritical core MASURCA coupled with the GENEPI accelerator. The aim is to examine the applicability of different measurement techniques for the determination of the main kinetic parameters. The measurement of Rossi-alpha distributions, recorded with the accelerator turned off, showed that the analysis of the obtained distributions is feasible for deep subcritical levels, but with strongly deteriorated statistics. From Rossi-alpha distributions, recorded with the pulsed neutron source in operation, the alpha decay constant was easily derived due to good statistics on the correlated signal resulting from the strong intensity of the neutron pulse. When applying the pulsed neutron source analysis, the reactivity (in dollars) together with the ratio of the mean neutron lifetime l and the effective delayed neutron fraction β eff is immediately derived. Although these first results are very promising, further measurements are needed to qualify the method at larger subcritical levels which are representative for future ADS

An improved state-parameter analysis of ecosystem models using data assimilation

Science.gov (United States)

Chen, M.; Liu, S.; Tieszen, L.L.; Hollinger, D.Y.

2008-01-01

Much of the effort spent in developing data assimilation methods for carbon dynamics analysis has focused on estimating optimal values for either model parameters or state variables. The main weakness of estimating parameter values alone (i.e., without considering state variables) is that all errors from input, output, and model structure are attributed to model parameter uncertainties. On the other hand, the accuracy of estimating state variables may be lowered if the temporal evolution of parameter values is not incorporated. This research develops a smoothed ensemble Kalman filter (SEnKF) by combining ensemble Kalman filter with kernel smoothing technique. SEnKF has following characteristics: (1) to estimate simultaneously the model states and parameters through concatenating unknown parameters and state variables into a joint state vector; (2) to mitigate dramatic, sudden changes of parameter values in parameter sampling and parameter evolution process, and control narrowing of parameter variance which results in filter divergence through adjusting smoothing factor in kernel smoothing algorithm; (3) to assimilate recursively data into the model and thus detect possible time variation of parameters; and (4) to address properly various sources of uncertainties stemming from input, output and parameter uncertainties. The SEnKF is tested by assimilating observed fluxes of carbon dioxide and environmental driving factor data from an AmeriFlux forest station located near Howland, Maine, USA, into a partition eddy flux model. Our analysis demonstrates that model parameters, such as light use efficiency, respiration coefficients, minimum and optimum temperatures for photosynthetic activity, and others, are highly constrained by eddy flux data at daily-to-seasonal time scales. The SEnKF stabilizes parameter values quickly regardless of the initial values of the parameters. Potential ecosystem light use efficiency demonstrates a strong seasonality. Results show that the

Variability and reproducibility of rubidium-82 kinetic parameters in the myocardium of the anesthetized canine

International Nuclear Information System (INIS)

Coxson, P.G.; Brennan, K.M.; Huesman, R.H.

1995-01-01

Kinetic analysis of 82 Rb (I) dynamic PET data produces quantitative measures which could be used to evaluate ischemic heart disease. These measures have the potential to generate objective comparisons of different patients or the same patient at different times. To achieve this potential, it is essential to determine the variability and reproducibility of the kinetic parameters. A total of 48 I dynamic PET datasets were acquired from two pure bred beagles. Each animal underwent eight I PET studies with essentially the same protocol for three successive weeks. Data were acquired with the Donner 600-Crystal Positron Tomograph (PET600). In each week, single-slice dynamic I PET datasets were collected with the animal at rest at three different gantry positions separated by 5 mm. Additional dataset were collected after dipyridamole infusion and after administration of aminophylline to induce a return to rest. A two-compartment kinetic model with correction for myocardial vasculature and spillover from the left ventricular blood pool was used to analyze the dynamic datasets. Model parameters for uptake (k 1 ), washout (k 2 ) and vascular fraction (f v ) were estimated in 11-14 myocardial regions of interest (ROIs) using a weighted least-squares criterion. Statistical fluctuation due to the PET acquisition process was minimized by using a relatively high I dose (about 30 mCi) to take advantage of the high count rate capacity of the PET600. The variation in mean k 1 , where the mean is taken over the myocardial ROIs was 10%-20% (Dog 1) and 15%-50% (Dog 2) among the rest studies conducted on the same data. Similar variation was evident in comparing studies in the same animal for different weeks. Spatial and temporal variation in estimates of the uptake rate (k 1 ) of I in the resting myocardium of the anesthetized canine are small in relation to the functional increase in k 1 , following dipyridamole stress. 17 refs., 14 figs

Chemical mechanism of D-amino acid oxidase from Rhodotorula gracilis: pH dependence of kinetic parameters.

Science.gov (United States)

Ramón, F; Castillón, M; De La Mata, I; Acebal, C

1998-01-01

The variation of kinetic parameters of d-amino acid oxidase from Rhodotorula gracilis with pH was used to gain information about the chemical mechanism of the oxidation of D-amino acids catalysed by this flavoenzyme. d-Alanine was the substrate used. The pH dependence of Vmax and Vmax/Km for alanine as substrate showed that a group with a pK value of 6.26-7.95 (pK1) must be unprotonated and a group with a pK of 10.8-9.90 (pK2) must be protonated for activity. The lower pK value corresponded to a group on the enzyme involved in catalysis and whose protonation state was not important for binding. The higher pK value was assumed to be the amino group of the substrate. Profiles of pKi for D-aspartate as competitive inhibitor showed that binding is prevented when a group on the enzyme with a pK value of 8.4 becomes unprotonated; this basic group was not detected in Vmax/Km profiles suggesting its involvement in binding of the beta-carboxylic group of the inhibitor. PMID:9461524

Presteady-state and steady-state kinetic properties of human cytochrome c oxidase. Identification of rate-limiting steps in mammalian cytochrome c oxidase

NARCIS (Netherlands)

van Kuilenburg, A. B.; Gorren, A. C.; Dekker, H. L.; Nieboer, P.; van Gelder, B. F.; Muijsers, A. O.

1992-01-01

Human cytochrome c oxidase was purified in a fully active form from heart and skeletal muscle. The enzyme was selectively solubilised with octylglucoside and KCl from submitochondrial particles followed by ammonium sulphate fractionation. The presteady-state and steady-state kinetic properties of

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

Science.gov (United States)

Remane, Y; Leopold, C S

2006-01-01

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

State-to-state modeling of non-equilibrium air nozzle flows

Science.gov (United States)

Nagnibeda, E.; Papina, K.; Kunova, O.

2018-05-01

One-dimensional non-equilibrium air flows in nozzles are studied on the basis of the state-to-state description of vibrational-chemical kinetics. Five-component mixture N2/O2/NO/N/O is considered taking into account Zeldovich exchange reactions of NO formation, dissociation, recombination and vibrational energy transitions. The equations for vibrational and chem-ical kinetics in a flow are coupled to the conservation equations of momentum and total energy and solved numerically for different conditions in a nozzle throat. The vibrational distributions of nitrogen and oxygen molecules, number densities of species as well as the gas temperature and flow velocity along a nozzle axis are analysed using the detailed state-to-state flow description and in the frame of the simplified one-temperature thermal equilibrium kinetic model. The comparison of the results showed the influence of non-equilibrium kinetics on macroscopic nozzle flow parameters. In the state-to-state approach, non-Boltzmann vibrational dis-tributions of N2 and O2 molecules with a plateau part at intermediate levels are found. The results are found with the use of the complete and simplified schemes of reactions and the impact of exchange reactions, dissociation and recombination on variation of vibrational level populations, mixture composition, gas velocity and temperature along a nozzle axis is shown.

Intrinsic kinetic parameters of substrate utilization by immobilized anaerobic sludge.

Science.gov (United States)

Zaiat, M; Vieira, L G; Foresti, E

1997-01-20

This article presents a method for evaluating the intrinsic kinetic parameters of the specific substrate utilization rate (r) equation and discusses the results obtained for anaerobic sludge-bed samples taken from a horizontal-flow anaerobic immobilized sludge (HAIS) reactor. This method utilizes a differential reactor filled with polyurethane foam matrices containing immobilized anaerobic sludge which is subjected to a range of feeding substrate flow rates. The range of liquid superficial velocities thus obtained are used for generating data of observed specific substrate utilization rates (r(obs)) under a diversity of external mass transfer resistance conditions. The r(obs) curves are then adjusted to permit their extrapolation for the condition of no external mass transfer resistance, and the values determined are used as a test for the condition of absence of limitation of internal mass transfer. The intrinsic parameters r(max), the maximum specific substrate utilization rate, and K(s), the half-velocity coefficient, are evaluated from the r values under no external mass transfer resistance and no internal mass transfer limitation. The application of such a method for anaerobic sludge immobilized in polyurethane foam particles treating a glucose substrate at 30 degrees C resulted in intrinsic r(max) and K(s), respectively, of 0.330 mg chemical oxygen demand (COD) . mg(-1) volatile suspended solids (VSS) . h(-1) and 72 mg COD . L(-1). In comparison with the values found in the literature, intrinsic r(max) is significantly high and intrinsic K(s) is relatively low. (c) 1997 John Wiley & Sons, Inc.

Nonequilibrium steady state of biochemical cycle kinetics under non-isothermal conditions

Science.gov (United States)

Jin, Xiao; Ge, Hao

2018-04-01

The nonequilibrium steady state of isothermal biochemical cycle kinetics has been extensively studied, but that under non-isothermal conditions has been much less extensively investigated. When the heat exchange between subsystems is slow, the isothermal assumption of the whole system breaks down, as is true for many types of living organisms. Here, starting with a four-state model of molecular transporter across the cell membrane, we generalize the nonequilibrium steady-state theory of isothermal biochemical cycle kinetics to the circumstances with non-uniform temperatures of subsystems in terms of general master equation models. We obtain a new thermodynamic relationship between the chemical reaction rates and thermodynamic potentials in non-isothermal circumstances, based on the overdamped dynamics along the continuous reaction coordinate. We show that the entropy production can vary up to 3% in real cells, even when the temperature difference across the cell membrane is only approximately 1 K. We then decompose the total thermodynamic driving force into its thermal and chemical components and predict that the net flux of molecules transported by the molecular transporter can potentially go against the temperature gradient in the absence of a chemical driving force. Furthermore, we demonstrate that the simple application of the isothermal transition-state rate formula for each chemical reaction in terms of only the reactant’ temperature is not thermodynamically consistent. Therefore, we mathematically derive several revised reaction rate formulas that are not only consistent with the new thermodynamic relationship but also approximate the exact reaction rate better than Kramers’ rate formula under isothermal conditions.

IBIS, FBR 3-D Steady-State and Kinetics with Thermohydraulic Feedback

International Nuclear Information System (INIS)

Konomura, Mamoru; Tada, Nobuo; Oka, Yoshiaki; An, Shigehiro

1987-01-01

1 - Description of program or function: The IBIS code performs steady state and kinetics calculations based on a three-dimensional nuclear diffusion kinetics with thermal hydraulic feedback. It can calculate the following values in hexagonal-Z geometry of a fast breeder reactor core through the progress of transient: (1) Net reactivity; (2) Total and group-wise delayed neutron fraction; (3) Group-wise delayed neutron precursor concentration; (4) Total power and energy; (5) Space dependent neutron flux in each energy group; (6) Space dependent temperature of each material; (7) Maximum temperature of each material and its location. 2 - Method of solution: The quasi-static method is adopted to solve the three-dimensional nuclear diffusion kinetics problem. The method is the same as employed in the code QX1. The shape function equation is solved with the finite difference treatment as used in the codes CITATION and HONEYCOMB. One-dimensional thermo-hydraulics is solved with a model similar to that given in the code SASLA. Sodium boiling can be taken into account. 3 - Restrictions on the complexity of the problem: The number of neutron energy groups is fixed to 3 groups in the present version of the code

Kinetic parameter estimation and fluctuation analysis of CO at SnO 2 single nanowires

KAUST Repository

Tulzer, Gerhard

2013-07-12

In this work, we present calculated numerical values for the kinetic parameters governing adsorption/desorption processes of carbon monoxide at tin dioxide single-nanowire gas sensors. The response of such sensors to pulses of 50 ppm carbon monoxide in nitrogen is investigated at different temperatures to extract the desired information. A rate-equation approach is used to model the reaction kinetics, which results in the problem of determining coefficients in a coupled system of nonlinear ordinary differential equations. The numerical values are computed by inverse-modeling techniques and are then used to simulate the sensor response. With our model, the dynamic response of the sensor due to the gas-surface interaction can be studied in order to find the optimal setup for detection, which is an important step towards selectivity of these devices. We additionally investigate the noise in the current through the nanowire and its changes due to the presence of carbon monoxide in the sensor environment. Here, we propose the use of a wavelet transform to decompose the signal and analyze the noise in the experimental data. This method indicates that some fluctuations are specific for the gas species investigated here. © 2013 IOP Publishing Ltd.

Kinetic parameter estimation and fluctuation analysis of CO at SnO 2 single nanowires

KAUST Repository

Tulzer, Gerhard; Baumgartner, Stefan; Brunet, Elise; Mutinati, Giorgio C; Steinhauer, Stephan; Kö ck, Anton; Barbano, Paolo E; Heitzinger, Clemens

2013-01-01

In this work, we present calculated numerical values for the kinetic parameters governing adsorption/desorption processes of carbon monoxide at tin dioxide single-nanowire gas sensors. The response of such sensors to pulses of 50 ppm carbon monoxide in nitrogen is investigated at different temperatures to extract the desired information. A rate-equation approach is used to model the reaction kinetics, which results in the problem of determining coefficients in a coupled system of nonlinear ordinary differential equations. The numerical values are computed by inverse-modeling techniques and are then used to simulate the sensor response. With our model, the dynamic response of the sensor due to the gas-surface interaction can be studied in order to find the optimal setup for detection, which is an important step towards selectivity of these devices. We additionally investigate the noise in the current through the nanowire and its changes due to the presence of carbon monoxide in the sensor environment. Here, we propose the use of a wavelet transform to decompose the signal and analyze the noise in the experimental data. This method indicates that some fluctuations are specific for the gas species investigated here. © 2013 IOP Publishing Ltd.

A robust state-space kinetics-guided framework for dynamic PET image reconstruction

International Nuclear Information System (INIS)

Tong, S; Alessio, A M; Kinahan, P E; Liu, H; Shi, P

2011-01-01

Dynamic PET image reconstruction is a challenging issue due to the low SNR and the large quantity of spatio-temporal data. We propose a robust state-space image reconstruction (SSIR) framework for activity reconstruction in dynamic PET. Unlike statistically-based frame-by-frame methods, tracer kinetic modeling is incorporated to provide physiological guidance for the reconstruction, harnessing the temporal information of the dynamic data. Dynamic reconstruction is formulated in a state-space representation, where a compartmental model describes the kinetic processes in a continuous-time system equation, and the imaging data are expressed in a discrete measurement equation. Tracer activity concentrations are treated as the state variables, and are estimated from the dynamic data. Sampled-data H ∞ filtering is adopted for robust estimation. H ∞ filtering makes no assumptions on the system and measurement statistics, and guarantees bounded estimation error for finite-energy disturbances, leading to robust performance for dynamic data with low SNR and/or errors. This alternative reconstruction approach could help us to deal with unpredictable situations in imaging (e.g. data corruption from failed detector blocks) or inaccurate noise models. Experiments on synthetic phantom and patient PET data are performed to demonstrate feasibility of the SSIR framework, and to explore its potential advantages over frame-by-frame statistical reconstruction approaches.

The Kinetics of Joined Action of Triplet-Triplet Annihilation and First-Order Decay of Molecules in T1 State in the Case of Nondominant First-Order Process: The Kinetic Model in the Case of Spatially Periodic Excitation

Directory of Open Access Journals (Sweden)

Paweł Borowicz

2013-01-01

Full Text Available In this paper the model developed for estimation of the diffusion coefficient of the molecules in the triplet state is presented. The model is based on the intuitive modification of the Smoluchowski equation for the time-dependent rate parameter. Since the sample is irradiated with the spatially periodic pattern nonexponential effects can be expected in the areas of the constructive interference of the exciting laser beams. This nonexponential effects introduce changes in the observed kinetics of the diffusion-controlled triplet-triplet annihilation. Due to irradiation with so-called long excitation pulse these non-exponential effects are very weak, so they can be described with introducing very simple correction to the kinetic model described in the first paper of this series. The values of diffusion coefficient of anthracene are used to calculate the annihilation radius from the data for spatially homogeneous excitation.

Investigation of thermoluminescence and kinetic parameters of CaMgB{sub 2}O{sub 5}: Dy{sup 3+} nanophosphor

Energy Technology Data Exchange (ETDEWEB)

Manhas, M. [School of Physics, Shri Mata Vaishno Devi University, Katra-182320 J& K (India); Kumar, Vinay, E-mail: vinaykumar@smvdu.ac.in [School of Physics, Shri Mata Vaishno Devi University, Katra-182320 J& K (India); Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300 (South Africa); Ntwaeaborwa, O. M.; Swart, H. C. [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300 (South Africa)

2016-05-06

In this paper, thermoluminescence (TL) properties of Dy{sup 3+} (1.5 mol %) doped CaMgB{sub 2}O{sub 5} nanophosphor after being exposed to ultraviolet (UV) radiations (λ=254nm) were investigated. In UV exposed samples, the thermoluminescence glow curve consists of a broad glow peak located at 380 K with a small shoulder at 507 K. A shift in glow peak temperature from 367 K to 380 K after the UV exposure for 80 min was observed, which clearly shows that glow peaks follow the second order kinetics. The TL intensity of the peaks increases with an increase in the exposure time of UV rays (10-180 min). The TL Anal program was used to analyze the glow curve. The kinetic parameters such as activation energy (E), the frequency factor (s) and the order of kinetics (b) were calculated for CaMgB{sub 2}O{sub 5}: Dy{sup 3+} nanophosphors.

Combination of Markov state models and kinetic networks for the analysis of molecular dynamics simulations of peptide folding.

Science.gov (United States)

Radford, Isolde H; Fersht, Alan R; Settanni, Giovanni

2011-06-09

Atomistic molecular dynamics simulations of the TZ1 beta-hairpin peptide have been carried out using an implicit model for the solvent. The trajectories have been analyzed using a Markov state model defined on the projections along two significant observables and a kinetic network approach. The Markov state model allowed for an unbiased identification of the metastable states of the system, and provided the basis for commitment probability calculations performed on the kinetic network. The kinetic network analysis served to extract the main transition state for folding of the peptide and to validate the results from the Markov state analysis. The combination of the two techniques allowed for a consistent and concise characterization of the dynamics of the peptide. The slowest relaxation process identified is the exchange between variably folded and denatured species, and the second slowest process is the exchange between two different subsets of the denatured state which could not be otherwise identified by simple inspection of the projected trajectory. The third slowest process is the exchange between a fully native and a partially folded intermediate state characterized by a native turn with a proximal backbone H-bond, and frayed side-chain packing and termini. The transition state for the main folding reaction is similar to the intermediate state, although a more native like side-chain packing is observed.

Relativistic nuclear fluid dynamics and VUU kinetic theory

International Nuclear Information System (INIS)

Molitoris, J.J.; Hahn, D.; Alonso, C.; Collazo, I.; D'Alessandris, P.; McAbee, T.; Wilson, J.; Zingman, J.

1987-01-01

Relativistic kinetic theory may be used to understand hot dense hadronic matter. We address the questions of collective flow and pion production in a 3 D relativistic fluid dynamic model and in the VUU microscopic theory. The GSI/LBL collective flow and pion data point to a stiff equation of state. The effect of the nuclear equation of state on the thermodynamic parameters is discussed. The properties of dense hot hadronic matter are studied in Au + Au collisions from 0.1 to 10 GeV/nucleon. 22 refs., 5 figs

Ground-state kinetics of bistable redox-active donor-acceptor mechanically interlocked molecules.

Science.gov (United States)

Fahrenbach, Albert C; Bruns, Carson J; Li, Hao; Trabolsi, Ali; Coskun, Ali; Stoddart, J Fraser

2014-02-18

The ability to design and confer control over the kinetics of theprocesses involved in the mechanisms of artificial molecular machines is at the heart of the challenge to create ones that can carry out useful work on their environment, just as Nature is wont to do. As one of the more promising forerunners of prototypical artificial molecular machines, chemists have developed bistable redox-active donor-acceptor mechanically interlocked molecules (MIMs) over the past couple of decades. These bistable MIMs generally come in the form of [2]rotaxanes, molecular compounds that constitute a ring mechanically interlocked around a dumbbell-shaped component, or [2]catenanes, which are composed of two mechanically interlocked rings. As a result of their interlocked nature, bistable MIMs possess the inherent propensity to express controllable intramolecular, large-amplitude, and reversible motions in response to redox stimuli. In this Account, we rationalize the kinetic behavior in the ground state for a large assortment of these types of bistable MIMs, including both rotaxanes and catenanes. These structures have proven useful in a variety of applications ranging from drug delivery to molecular electronic devices. These bistable donor-acceptor MIMs can switch between two different isomeric states. The favored isomer, known as the ground-state co-conformation (GSCC) is in equilibrium with the less favored metastable state co-conformation (MSCC). The forward (kf) and backward (kb) rate constants associated with this ground-state equilibrium are intimately connected to each other through the ground-state distribution constant, KGS. Knowing the rate constants that govern the kinetics and bring about the equilibration between the MSCC and GSCC, allows researchers to understand the operation of these bistable MIMs in a device setting and apply them toward the construction of artificial molecular machines. The three biggest influences on the ground-state rate constants arise from

Determination of kinetic parameters in Tl dosemeters of LiF: Mg, Cu, P + PTFE developed in the ININ

International Nuclear Information System (INIS)

Basurto G, B.S.

2002-01-01

The objective of this work, is the one of determining the kinetic parameters of the dosemeter of LiF: Mg, Cu, P + Ptfe; starting from the curves Tl obtained at being irradiated with alpha radiation (α), beta (β) and gamma (γ). As like to compare its sensitivity with each radiation type, considering the sensitivity of the TLD-100 as the unit. In the Chapter 1, the fundamental structure of the matter is described, making emphasis in the different radiation types, and their interaction with this. In the Chapter 2, the units are described but used in the dosimetry of the radiation. In the Chapter 3, the basic concepts of the phenomenon of Tl are described and those are explained characteristic of the deconvolution method to determine the kinetics of the one phenomenon. In the Chapter 4, the methodology is detailed that was used in the elaboration of this thesis work, describing the material Tl that were considered like reference, as well as the sources of ionizing radiation, with those that the dosemeters were irradiated and the equipment in the one that the curves Tl was obtained. Reference is made to the software used to carry out the deconvolution of the curves Tl that were obtained in the one experimental development. In the Chapter 5, the obtained results of this study are presented, showing the tables of homogenization of dosemeters and the reading of the same one; they are observed the curves Tl obtained to different radiation doses (alpha, beta and gamma), the intensity Tl in function of the dose. Also they are tabulated, the obtained results in the kinetic parameters of the three different study materials (TLD-100H, USA; TLD-100, USA and LiF: Mg, Cu, P + Ptfe developed in the l.N.l.N). They are analyzed shortly for each material Tl their sensitivity to the ionizing radiation as well as their kinetic parameters. The obtained results showed that the Tl dosemeters of LiF: Mg,Cu,P + Ptfe, they presented a bigger sensitivity that the TLD-100 when being

On-line adaptive battery impedance parameter and state estimation considering physical principles in reduced order equivalent circuit battery models part 2. Parameter and state estimation

Science.gov (United States)

Fleischer, Christian; Waag, Wladislaw; Heyn, Hans-Martin; Sauer, Dirk Uwe

2014-09-01

Lithium-ion battery systems employed in high power demanding systems such as electric vehicles require a sophisticated monitoring system to ensure safe and reliable operation. Three major states of the battery are of special interest and need to be constantly monitored. These include: battery state of charge (SoC), battery state of health (capacity fade determination, SoH), and state of function (power fade determination, SoF). The second paper concludes the series by presenting a multi-stage online parameter identification technique based on a weighted recursive least quadratic squares parameter estimator to determine the parameters of the proposed battery model from the first paper during operation. A novel mutation based algorithm is developed to determine the nonlinear current dependency of the charge-transfer resistance. The influence of diffusion is determined by an on-line identification technique and verified on several batteries at different operation conditions. This method guarantees a short response time and, together with its fully recursive structure, assures a long-term stable monitoring of the battery parameters. The relative dynamic voltage prediction error of the algorithm is reduced to 2%. The changes of parameters are used to determine the states of the battery. The algorithm is real-time capable and can be implemented on embedded systems.

Displacement cascades and defect annealing in tungsten, Part III: The sensitivity of cascade annealing in tungsten to the values of kinetic parameters

Energy Technology Data Exchange (ETDEWEB)

Nandipati, Giridhar, E-mail: giridhar.nandipati@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA (United States); Setyawan, Wahyu; Heinisch, Howard L. [Pacific Northwest National Laboratory, Richland, WA (United States); Roche, Kenneth J. [Pacific Northwest National Laboratory, Richland, WA (United States); Department of Physics, University of Washington, Seattle, WA 98195 (United States); Kurtz, Richard J. [Pacific Northwest National Laboratory, Richland, WA (United States); Wirth, Brian D. [University of Tennessee, Knoxville, TN (United States)

2015-07-15

A study has been performed using object kinetic Monte Carlo (OKMC) simulations to investigate various aspects of cascade aging in bulk tungsten (W) and to determine its sensitivity to the kinetic parameters. The primary focus is on how the kinetic parameters affect the intracascade recombination of defects. Results indicate that, due to the disparate mobilities of SIA and vacancy clusters, annealing is dominated by SIA migration even at 2050 K. It was found that for 100 keV cascades initiated at 300 K, recombination is dominated by the annihilation of large defect clusters, while for all the other primary knock-on atom (PKA) energies and temperatures, recombination is primarily due to the migration and rotation of small SIA clusters, while the large SIA clusters escape the simulation cell. The annealing efficiency exhibits an inverse U-shaped curve behavior with increasing temperature, especially at large PKA energies, caused by the asymmetry in SIA and vacancy clustering assisted by the large differences in their mobilities. This behavior is unaffected by the dimensionality of SIA migration, and it persists over a broad range of relative mobilities of SIAs and vacancies.

Determining "small parameters" for quasi-steady state

Science.gov (United States)

Goeke, Alexandra; Walcher, Sebastian; Zerz, Eva

2015-08-01

For a parameter-dependent system of ordinary differential equations we present a systematic approach to the determination of parameter values near which singular perturbation scenarios (in the sense of Tikhonov and Fenichel) arise. We call these special values Tikhonov-Fenichel parameter values. The principal application we intend is to equations that describe chemical reactions, in the context of quasi-steady state (or partial equilibrium) settings. Such equations have rational (or even polynomial) right-hand side. We determine the structure of the set of Tikhonov-Fenichel parameter values as a semi-algebraic set, and present an algorithmic approach to their explicit determination, using Groebner bases. Examples and applications (which include the irreversible and reversible Michaelis-Menten systems) illustrate that the approach is rather easy to implement.

Displacement cascades and defect annealing in tungsten, Part III: The sensitivity of cascade annealing in tungsten to the values of kinetic parameters

Energy Technology Data Exchange (ETDEWEB)

Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

2015-07-01

Object kinetic Monte Carlo (OKMC) simulations have been performed to investigate various aspects of cascade aging in bulk tungsten and to determine the sensitivity of the results to the kinetic parameters. The primary focus is on how the kinetic parameters affect the initial recombination of defects in the first few ns of a simulation. The simulations were carried out using the object kinetic Monte Carlo (OKMC) code KSOME (kinetic simulations of microstructure evolution), using a database of cascades obtained from results of molecular dynamics (MD) simulations at various primary knock-on atom (PKA) energies and directions at temperatures of 300, 1025 and 2050 K. The OKMC model was parameterized using defect migration barriers and binding energies from ab initio calculations. Results indicate that, due to the disparate mobilities of SIA and vacancy clusters in tungsten, annealing is dominated by SIA migration even at temperatures as high as 2050 K. For 100 keV cascades initiated at 300 K recombination is dominated by annihilation of large defect clusters. But for all other PKA energies and temperatures most of the recombination is due to the migration and rotation of small SIA clusters, while all the large SIA clusters escape the cubic simulation cell. The inverse U-shape behavior exhibited by the annealing efficiency as a function of temperature curve, especially for cascades of large PKA energies, is due to asymmetry in SIA and vacancy clustering assisted by the large difference in mobilities of SIAs and vacancies. This annealing behavior is unaffected by the dimensionality of SIA migration persists over a broad range of relative mobilities of SIAs and vacancies.

The nonextensive gas: a kinetic approach

International Nuclear Information System (INIS)

Lima, J.A.S.; Silva, R.

2005-01-01

We discuss a kinetic nonextensive generalization of the Maxwellian ideal gas. The analysis rests on two basic assumptions: (i) instead of the standard Gaussian form, the q-gas is described by a power-law velocity distribution as suggested in the nonextensive Tsallis' framework (ii) the q-nonextensive generalization of the Boltzmann entropy formula governs the behavior of the q-gas. In this context, we show that the pressure and the internal energy are kinetically modified, but the general equation of state, PV=2U/3, remains valid. The adiabatic index is now a function of the nonextensive parameter, γ=C p /C V =5/3q. However, the standard expression relating the specific heats (at constant pressure and volume) with the coefficient of expansion and the isothermal compressibility, C P -C V =TVα 2 /κ T , is not modified

Crystallization Kinetics within a Generic Modeling Framework

DEFF Research Database (Denmark)

Meisler, Kresten Troelstrup; von Solms, Nicolas; Gernaey, Krist V.

2014-01-01

of employing a well-structured model library for storage, use/reuse, and analysis of the kinetic models are highlighted. Examples illustrating the application of the modeling framework for kinetic model discrimination related to simulation of specific crystallization scenarios and for kinetic model parameter......A new and extended version of a generic modeling framework for analysis and design of crystallization operations is presented. The new features of this framework are described, with focus on development, implementation, identification, and analysis of crystallization kinetic models. Issues related...... to the modeling of various kinetic phenomena like nucleation, growth, agglomeration, and breakage are discussed in terms of model forms, model parameters, their availability and/or estimation, and their selection and application for specific crystallization operational scenarios under study. The advantages...

Determination Of Enzyme Kinetic Parameters on Sago Starch Hydrolysis By Linearized Graphical Methods

International Nuclear Information System (INIS)

Lai, L.W.; Teo, C.L.; Suzana Wahidin; Mohamad Suffian Mohamad Annuar

2014-01-01

Amyloglucosidase (E.C. 3.2.1.3) from Aspergillus niger was used to hydrolyze the sago (Metro xylon sagu) starch into reducing sugars. The experiment was conducted at constant temperature, 55 degree Celsius; pH, 4.5 and enzyme amount, 0.2 U/ ml, respectively. In this investigation, the substrate concentration was varied ranging from 1.0 - 7.0 g/ L. The obtained data were then fixed into linearized plots namely Lineweaver-Burk and Langmuir models to calculate enzyme kinetic parameters, K m and V max . Both of the K m and V max (mM, mol/min) values from each plot were: Lineweaver-Burk (26.53, 3.31) and Langmuir (13.52, 2.35). Among the linearized models, K m and V max values acquired from Langmuir plot was chosen. (author)

A self-organizing state-space-model approach for parameter estimation in hodgkin-huxley-type models of single neurons.

Directory of Open Access Journals (Sweden)

Dimitrios V Vavoulis

Full Text Available Traditional approaches to the problem of parameter estimation in biophysical models of neurons and neural networks usually adopt a global search algorithm (for example, an evolutionary algorithm, often in combination with a local search method (such as gradient descent in order to minimize the value of a cost function, which measures the discrepancy between various features of the available experimental data and model output. In this study, we approach the problem of parameter estimation in conductance-based models of single neurons from a different perspective. By adopting a hidden-dynamical-systems formalism, we expressed parameter estimation as an inference problem in these systems, which can then be tackled using a range of well-established statistical inference methods. The particular method we used was Kitagawa's self-organizing state-space model, which was applied on a number of Hodgkin-Huxley-type models using simulated or actual electrophysiological data. We showed that the algorithm can be used to estimate a large number of parameters, including maximal conductances, reversal potentials, kinetics of ionic currents, measurement and intrinsic noise, based on low-dimensional experimental data and sufficiently informative priors in the form of pre-defined constraints imposed on model parameters. The algorithm remained operational even when very noisy experimental data were used. Importantly, by combining the self-organizing state-space model with an adaptive sampling algorithm akin to the Covariance Matrix Adaptation Evolution Strategy, we achieved a significant reduction in the variance of parameter estimates. The algorithm did not require the explicit formulation of a cost function and it was straightforward to apply on compartmental models and multiple data sets. Overall, the proposed methodology is particularly suitable for resolving high-dimensional inference problems based on noisy electrophysiological data and, therefore, a

Kinetics of phase transformations

International Nuclear Information System (INIS)

Thompson, M.O.; Aziz, M.J.; Stephenson, G.B.

1992-01-01

This volume contains papers presented at the Materials Research Society symposium on Kinetics of Phase Transformations held in Boston, Massachusetts from November 26-29, 1990. The symposium provided a forum for research results in an exceptionally broad and interdisciplinary field. Presentations covered nearly every major class of transformations including solid-solid, liquid-solid, transport phenomena and kinetics modeling. Papers involving amorphous Si, a dominant topic at the symposium, are collected in the first section followed by sections on four major areas of transformation kinetics. The symposium opened with joint sessions on ion and electron beam induced transformations in conjunction with the Surface Chemistry and Beam-Solid Interactions: symposium. Subsequent sessions focused on the areas of ordering and nonlinear diffusion kinetics, solid state reactions and amorphization, kinetics and defects of amorphous silicon, and kinetics of melting and solidification. Seven internationally recognized invited speakers reviewed many of the important problems and recent results in these areas, including defects in amorphous Si, crystal to glass transformations, ordering kinetics, solid-state amorphization, computer modeling, and liquid/solid transformations

"Batch" kinetics in flow: online IR analysis and continuous control.

Science.gov (United States)

Moore, Jason S; Jensen, Klavs F

2014-01-07

Currently, kinetic data is either collected under steady-state conditions in flow or by generating time-series data in batch. Batch experiments are generally considered to be more suitable for the generation of kinetic data because of the ability to collect data from many time points in a single experiment. Now, a method that rapidly generates time-series reaction data from flow reactors by continuously manipulating the flow rate and reaction temperature has been developed. This approach makes use of inline IR analysis and an automated microreactor system, which allowed for rapid and tight control of the operating conditions. The conversion/residence time profiles at several temperatures were used to fit parameters to a kinetic model. This method requires significantly less time and a smaller amount of starting material compared to one-at-a-time flow experiments, and thus allows for the rapid generation of kinetic data. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Probabilistic parameter estimation in a 2-step chemical kinetics model for n-dodecane jet autoignition

Science.gov (United States)

Hakim, Layal; Lacaze, Guilhem; Khalil, Mohammad; Sargsyan, Khachik; Najm, Habib; Oefelein, Joseph

2018-05-01

This paper demonstrates the development of a simple chemical kinetics model designed for autoignition of n-dodecane in air using Bayesian inference with a model-error representation. The model error, i.e. intrinsic discrepancy from a high-fidelity benchmark model, is represented by allowing additional variability in selected parameters. Subsequently, we quantify predictive uncertainties in the results of autoignition simulations of homogeneous reactors at realistic diesel engine conditions. We demonstrate that these predictive error bars capture model error as well. The uncertainty propagation is performed using non-intrusive spectral projection that can also be used in principle with larger scale computations, such as large eddy simulation. While the present calibration is performed to match a skeletal mechanism, it can be done with equal success using experimental data only (e.g. shock-tube measurements). Since our method captures the error associated with structural model simplifications, we believe that the optimised model could then lead to better qualified predictions of autoignition delay time in high-fidelity large eddy simulations than the existing detailed mechanisms. This methodology provides a way to reduce the cost of reaction kinetics in simulations systematically, while quantifying the accuracy of predictions of important target quantities.

Parameter identification technique for uncertain chaotic systems using state feedback and steady-state analysis.

Science.gov (United States)

Zaher, Ashraf A

2008-03-01

A technique is introduced for identifying uncertain and/or unknown parameters of chaotic dynamical systems via using simple state feedback. The proposed technique is based on bringing the system into a stable steady state and then solving for the unknown parameters using a simple algebraic method that requires access to the complete or partial states of the system depending on the dynamical model of the chaotic system. The choice of the state feedback is optimized in terms of practicality and causality via employing a single feedback signal and tuning the feedback gain to ensure both stability and identifiability. The case when only a single scalar time series of one of the states is available is also considered and it is demonstrated that a synchronization-based state observer can be augmented to the state feedback to address this problem. A detailed case study using the Lorenz system is used to exemplify the suggested technique. In addition, both the Rössler and Chua systems are examined as possible candidates for utilizing the proposed methodology when partial identification of the unknown parameters is considered. Finally, the dependence of the proposed technique on the structure of the chaotic dynamical model and the operating conditions is discussed and its advantages and limitations are highlighted via comparing it with other methods reported in the literature.

Influence of oxalic acid on the dissolution kinetics of manganese oxide

Science.gov (United States)

Godunov, E. B.; Artamonova, I. V.; Gorichev, I. G.; Lainer, Yu. A.

2012-11-01

The kinetics and electrochemical processes of the dissolution of manganese oxides with various oxidation states in sulfuric acid solutions containing oxalate ion additives is studied under variable conditions (concentration, pH, temperature). The parameters favoring a higher degree of the dissolution of manganese oxides in acidic media are determined. The optimal conditions are found for the dissolution of manganese oxides in acidic media in the presence of oxalate ions. The mechanism proposed for the dissolution of manganese oxides in sulfuric acid solutions containing oxalic acid is based on the results of kinetic and electrochemical studies. The steps of the dissolution mechanism are discussed.

Kinetic study of the anaerobic biodegradation of alkyl polyglucosides and the influence of their structural parameters.

Science.gov (United States)

Ríos, Francisco; Fernández-Arteaga, Alejandro; Lechuga, Manuela; Jurado, Encarnación; Fernández-Serrano, Mercedes

2016-05-01

This paper reports a study of the anaerobic biodegradation of non-ionic surfactants alkyl polyglucosides applying the method by measurement of the biogas production in digested sludge. Three alkyl polyglucosides with different length alkyl chain and degree of polymerization of the glucose units were tested. The influence of their structural parameters was evaluated, and the characteristics parameters of the anaerobic biodegradation were determined. Results show that alkyl polyglucosides, at the standard initial concentration of 100 mgC L(-1), are not completely biodegradable in anaerobic conditions because they inhibit the biogas production. The alkyl polyglucoside having the shortest alkyl chain showed the fastest biodegradability and reached the higher percentage of final mineralization. The anaerobic process was well adjusted to a pseudo first-order equation using the carbon produced as gas during the test; also, kinetics parameters and a global rate constant for all the involved metabolic process were determined. This modeling is helpful to evaluate the biodegradation or the persistence of alkyl polyglucosides under anaerobic conditions in the environment and in the wastewater treatment.

Monin-Obukhov Similarity Functions of the Structure Parameter of Temperature and Turbulent Kinetic Energy Dissipation Rate in the Stable Boundary Layer

NARCIS (Netherlands)

Hartogensis, O.K.; Debruin, H.A.R.

2005-01-01

The Monin-Obukhov similarity theory (MOST) functions fepsi; and fT, of the dissipation rate of turbulent kinetic energy (TKE), ¿, and the structure parameter of temperature, CT2, were determined for the stable atmospheric surface layer using data gathered in the context of CASES-99. These data cover

Evaluation of kinetic parameters of 1, 1'-dibenzoylferrocene in non aqueous methanol solution by cyclic voltammetry (abstract)

International Nuclear Information System (INIS)

Parveen, R.; Kirmani, M.Z.; Naqvi, I.I.

2011-01-01

The electrochemical Kinetic study of 1, 1/sup '/- Dibenzoylferrocene (DBF) at a platinum working electrode in 0.1 mol dm/sup -3/ NaClO/sub 4/ non aqueous medium has been studied by Cyclic voltammetry. The heterogeneous electron transfer rate constants (ks) and the diffusion coefficients (Do) of DBF were estimated at various temperatures (283 - 323 K) and at different scan rates (0.05 - 0.5 V s/sup -1/). A calibration curve, linear over the range of 1 X 10/sup -3/ - 9 X 10/sup -3/ mol dm/sup -3/ ,was plotted at the scan rate of 0.25 Vs/sup -1/. This plot can be used to analyze an unknown sample of the compound. The kinetic data was also used to evaluate the Activation energy (Ea). The thermodynamic parameters such as enthalpy change of activation (delta H/sup */), Entropy change (delta S/sup */) and Gibbs free energy change (delta GH/sup */) were also investigated during the study. (author)

PADÉ APPROXIMANTS FOR THE EQUATION OF STATE FOR RELATIVISTIC HYDRODYNAMICS BY KINETIC THEORY

Energy Technology Data Exchange (ETDEWEB)

Tsai, Shang-Hsi; Yang, Jaw-Yen, E-mail: shanghsi@gmail.com [Institute of Applied Mechanics, National Taiwan University, Taipei 10764, Taiwan (China)

2015-07-20

A two-point Padé approximant (TPPA) algorithm is developed for the equation of state (EOS) for relativistic hydrodynamic systems, which are described by the classical Maxwell–Boltzmann statistics and the semiclassical Fermi–Dirac statistics with complete degeneracy. The underlying rational function is determined by the ratios of the macroscopic state variables with various orders of accuracy taken at the extreme relativistic limits. The nonunique TPPAs are validated by Taub's inequality for the consistency of the kinetic theory and the special theory of relativity. The proposed TPPA is utilized in deriving the EOS of the dilute gas and in calculating the specific heat capacity, the adiabatic index function, and the isentropic sound speed of the ideal gas. Some general guidelines are provided for the application of an arbitrary accuracy requirement. The superiority of the proposed TPPA is manifested in manipulating the constituent polynomials of the approximants, which avoids the arithmetic complexity of struggling with the modified Bessel functions and the hyperbolic trigonometric functions arising from the relativistic kinetic theory.

Kinetics of Slurry Phase Fischer-Tropsch Synthesis

Energy Technology Data Exchange (ETDEWEB)

Dragomir B. Bukur; Gilbert F. Froment; Tomasz Olewski; Lech Nowicki; Madhav Nayapati

2006-12-31

The overall objective of this project is to develop a comprehensive kinetic model for slurry-phase Fischer-Tropsch synthesis (FTS) employing iron-based catalysts. This model will be validated with experimental data obtained in a stirred-tank slurry reactor (STSR) over a wide range of process conditions. Three STSR tests of the Ruhrchemie LP 33/81 catalyst were conducted to collect data on catalyst activity and selectivity under 25 different sets of process conditions. The observed decrease in 1-olefin content and increase in 2-olefin and n-paraffin contents with the increase in conversion are consistent with a concept that 1-olefins participate in secondary reactions (e.g. 1-olefin hydrogenation, isomerization and readsorption), whereas 2-olefins and n-paraffins are formed in these reactions. Carbon number product distribution showed an increase in chain growth probability with increase in chain length. Vapor-liquid equilibrium calculations were made to check validity of the assumption that the gas and liquid phases are in equilibrium during FTS in the STSR. Calculated vapor phase compositions were in excellent agreement with experimental values from the STSR under reaction conditions. Discrepancies between the calculated and experimental values for the liquid-phase composition (for some of the experimental data) are ascribed to experimental errors in the amount of wax collected from the reactor, and the relative amounts of hydrocarbon wax and Durasyn 164 oil (start-up fluid) in the liquid samples. Kinetic parameters of four kinetic models (Lox and Froment, 1993b; Yang et al., 2003; Van der Laan and Beenackers, 1998, 1999; and an extended kinetic model of Van der Laan and Beenackers) were estimated from experimental data in the STSR tests. Two of these kinetic models (Lox and Froment, 1993b; Yang et al., 2003) can predict a complete product distribution (inorganic species and hydrocarbons), whereas the kinetic model of Van der Laan and Beenackers (1998, 1999) can

Kinetics of Slurry Phase Fischer-Tropsch Synthesis

International Nuclear Information System (INIS)

Dragomir B. Bukur; Gilbert F. Froment; Tomasz Olewski; Lech Nowicki; Madhav Nayapati

2006-01-01

The overall objective of this project is to develop a comprehensive kinetic model for slurry-phase Fischer-Tropsch synthesis (FTS) employing iron-based catalysts. This model will be validated with experimental data obtained in a stirred-tank slurry reactor (STSR) over a wide range of process conditions. Three STSR tests of the Ruhrchemie LP 33/81 catalyst were conducted to collect data on catalyst activity and selectivity under 25 different sets of process conditions. The observed decrease in 1-olefin content and increase in 2-olefin and n-paraffin contents with the increase in conversion are consistent with a concept that 1-olefins participate in secondary reactions (e.g. 1-olefin hydrogenation, isomerization and readsorption), whereas 2-olefins and n-paraffins are formed in these reactions. Carbon number product distribution showed an increase in chain growth probability with increase in chain length. Vapor-liquid equilibrium calculations were made to check validity of the assumption that the gas and liquid phases are in equilibrium during FTS in the STSR. Calculated vapor phase compositions were in excellent agreement with experimental values from the STSR under reaction conditions. Discrepancies between the calculated and experimental values for the liquid-phase composition (for some of the experimental data) are ascribed to experimental errors in the amount of wax collected from the reactor, and the relative amounts of hydrocarbon wax and Durasyn 164 oil (start-up fluid) in the liquid samples. Kinetic parameters of four kinetic models (Lox and Froment, 1993b; Yang et al., 2003; Van der Laan and Beenackers, 1998, 1999; and an extended kinetic model of Van der Laan and Beenackers) were estimated from experimental data in the STSR tests. Two of these kinetic models (Lox and Froment, 1993b; Yang et al., 2003) can predict a complete product distribution (inorganic species and hydrocarbons), whereas the kinetic model of Van der Laan and Beenackers (1998, 1999) can

Solution of non-steady-state substrate concentration in the action of biosensor response at mixed enzyme kinetics

Science.gov (United States)

Senthamarai, R.; Jana Ranjani, R.

2018-04-01

In this paper, a mathematical model of an amperometric biosensor at mixed enzyme kinetics and diffusion limitation in the case of substrate inhibition has been developed. The model is based on time dependent reaction diffusion equation containing a non -linear term related to non -Michaelis - Menten kinetics of the enzymatic reaction. Solution for the concentration of the substrate has been derived for all values of parameters using the homotopy perturbation method. All the approximate analytic expressions of substrate concentration are compared with simulation results using Scilab/Matlab program. Finally, we have given a satisfactory agreement between them.

Solid-state reaction kinetics and optical studies of cadmium doped magnesium hydrogen phosphate crystals

Science.gov (United States)

Verma, Madhu; Gupta, Rashmi; Singh, Harjinder; Bamzai, K. K.

2018-04-01

The growth of cadmium doped magnesium hydrogen phosphate was successfully carried out by using room temperature solution technique i.e., gel encapsulation technique. Grown crystals were confirmed by single crystal X-ray diffraction (XRD). The structure of the grown crystal belongs to orthorhombic crystal system and crystallizes in centrosymmetric space group. Kinetics of the decomposition of the grown crystals were studied by non-isothermal analysis. Thermo gravimetric / differential thermo analytical (TG/DTA) studies revealed that the grown crystal is stable upto 119 °C. The various steps involved in the thermal decomposition of the material have been analysed using Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova equations for evaluating various kinetic parameters. The optical studies shows that the grown crystals possess wide transmittance in the visible region and significant optical band gap of 5.5ev with cut off wavelength of 260 nm.

Numerical simulation of nonequilibrium flows by using the state-to-state approach in commercial software

Science.gov (United States)

Kunova, O. V.; Shoev, G. V.; Kudryavtsev, A. N.

2017-01-01

Nonequilibrium flows of a two-component oxygen mixture O2/O behind a shock wave are studied with due allowance for the state-to-state vibrational and chemical kinetics. The system of gas-dynamic equations is supplemented with kinetic equations including contributions of VT (TV)-exchange and dissociation processes. A method of the numerical solution of this system with the use of the ANSYS Fluent commercial software package is proposed, which is used in a combination with the authors' code that takes into account nonequilibrium kinetics. The computed results are compared with parameters obtained by solving the problem in the shock-fitting formulation. The vibrational temperature is compared with experimental data. The numerical tool proposed in the present paper is applied to study the flow around a cylinder.

[Molecular-kinetic parameters of thiamine enzymes and the mechanism of antivitamin action of hydroxythiamine in animal organisms].

Science.gov (United States)

Ostrovskiĭ KuM; Voskoboev, A I; Gorenshtenĭn, B I; Dosta, G A

1979-09-01

The molecula-kinetic parameters (Km, Ki) of three thiamine enzymes, e. g. thiamine pyrophosphokinase (EC 2.7.6.2), pyruvate dehydrogenase (EC 1.2.4.1) and transketolase (EC 2.2.1.1) with respect to the effects of the thiamine antimetabolite hydroxythiamine in the whole animal organism have been compared. It has been shown that only the first two enzymes, which interact competitively with the vitamin, antivitamin or their pyrophosphate ethers, obey the kinetic parameters obtained for the purified enzymes in vitro. The anticoenzymic effect of hydroxythiamine pyrophosphate with respect to transketolase is not observed in vivo at maximal concentration of the anticoenzyme in tissues due to the absence of competitive interactions with thiamine pyrophosphate. The incorporation of the true and false coenzymes into transketolase occurs only during de novo transketolase synthesis (the apoform is absent in tissues, with the exception of erythrocytes) and proceeds slowly with a half-life time equal to 24--30 hrs. After a single injection of hydroxythiamine at a large dose (70--400 mg/kg) the maximal inhibition of the transketolase activity in tissues (liver, heart, kidney, muscle, spleen, lungs adrenal grands) manifests itself by the 48th--72nd hour, when the concentration of free hydroxythiamine and its pyrophosphate is minimal and the whole anticoenzyme is tightly bound to the protein, forming the false holoenzyme. The use of hydroxythiamine for inhibition of pyruvate dehydrogenase or transketolase in animal organism is discussed.

Modeling the degradation kinetics of ascorbic acid.

Science.gov (United States)

Peleg, Micha; Normand, Mark D; Dixon, William R; Goulette, Timothy R

2018-06-13

Most published reports on ascorbic acid (AA) degradation during food storage and heat preservation suggest that it follows first-order kinetics. Deviations from this pattern include Weibullian decay, and exponential drop approaching finite nonzero retention. Almost invariably, the degradation rate constant's temperature-dependence followed the Arrhenius equation, and hence the simpler exponential model too. A formula and freely downloadable interactive Wolfram Demonstration to convert the Arrhenius model's energy of activation, E a , to the exponential model's c parameter, or vice versa, are provided. The AA's isothermal and non-isothermal degradation can be simulated with freely downloadable interactive Wolfram Demonstrations in which the model's parameters can be entered and modified by moving sliders on the screen. Where the degradation is known a priori to follow first or other fixed order kinetics, one can use the endpoints method, and in principle the successive points method too, to estimate the reaction's kinetic parameters from considerably fewer AA concentration determinations than in the traditional manner. Freeware to do the calculations by either method has been recently made available on the Internet. Once obtained in this way, the kinetic parameters can be used to reconstruct the entire degradation curves and predict those at different temperature profiles, isothermal or dynamic. Comparison of the predicted concentration ratios with experimental ones offers a way to validate or refute the kinetic model and the assumptions on which it is based.

Improving estimation of kinetic parameters in dynamic force spectroscopy using cluster analysis

Science.gov (United States)

Yen, Chi-Fu; Sivasankar, Sanjeevi

2018-03-01

Dynamic Force Spectroscopy (DFS) is a widely used technique to characterize the dissociation kinetics and interaction energy landscape of receptor-ligand complexes with single-molecule resolution. In an Atomic Force Microscope (AFM)-based DFS experiment, receptor-ligand complexes, sandwiched between an AFM tip and substrate, are ruptured at different stress rates by varying the speed at which the AFM-tip and substrate are pulled away from each other. The rupture events are grouped according to their pulling speeds, and the mean force and loading rate of each group are calculated. These data are subsequently fit to established models, and energy landscape parameters such as the intrinsic off-rate (koff) and the width of the potential energy barrier (xβ) are extracted. However, due to large uncertainties in determining mean forces and loading rates of the groups, errors in the estimated koff and xβ can be substantial. Here, we demonstrate that the accuracy of fitted parameters in a DFS experiment can be dramatically improved by sorting rupture events into groups using cluster analysis instead of sorting them according to their pulling speeds. We test different clustering algorithms including Gaussian mixture, logistic regression, and K-means clustering, under conditions that closely mimic DFS experiments. Using Monte Carlo simulations, we benchmark the performance of these clustering algorithms over a wide range of koff and xβ, under different levels of thermal noise, and as a function of both the number of unbinding events and the number of pulling speeds. Our results demonstrate that cluster analysis, particularly K-means clustering, is very effective in improving the accuracy of parameter estimation, particularly when the number of unbinding events are limited and not well separated into distinct groups. Cluster analysis is easy to implement, and our performance benchmarks serve as a guide in choosing an appropriate method for DFS data analysis.

A critical look at the kinetic parameter values used in simulating the thermoluminescence glow-curve

Energy Technology Data Exchange (ETDEWEB)

Sadek, A.M., E-mail: dr_amrsadek@hotmail.com [Ionizing Radiation Metrology Department, National Institute for Standards, El-Haram, Giza (Egypt); Kitis, G. [Nuclear Physics and Elementary Particles Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Makedonia (Greece)

2017-03-15

Objections against utilizing the peak fitting method in computing the kinetics parameters of thermoluminescence (TL) glow-peaks were discussed previously in the literature. These objections came through testing the accuracy of the peak fitting by applying on simulated peaks. The results showed that in some cases the simulated peaks may have unusual geometrical properties and do not reflect the real properties of TL peaks. Thereby, estimating the accuracy of the peak fitting by applying on such peaks would be misleading. Two main reasons may lead to unrealistic simulated peaks; the improper selection of the simulation inputs, and performing the TL simulation process via the heating stage only. It has been proved that considering the irradiation and the relaxation stages in the simulation process is crucial. However, there are other cases in which the analytical methods were not able to reveal the real values of the simulated peaks. These cases were successfully resolved using analytical expressions derived from the one trap-one recombination (OTOR) level model and the non-interactive multiple trap system (NMTS) model. A general conclusion can be drawn that the accuracy of the peak fitting method is critically dependent on the TL analytical expressions utilized in this method. The failure of this method in estimating the TL kinetic parameters should be attributed to the TL model equation utilized in fitting process. - Highlights: • Objections against using the TL peak fitting method are discussed. • Improper selection of simulation inputs may lead to non realistic TL peaks. • Considering the irradiation and the relaxation stages in simulation is crucial. • TL expressions could not describe TL peaks with unrealistic geometrical properties. • The accuracy of the peak fitting method depends on the model used in the fitting.

Inference from some pharmacokinetic and pharmacodynamic parameters of busulfan through the analysis of its induction kinetics of micronuclei polychromated erythrocytes

International Nuclear Information System (INIS)

Lopez I, M.R.; Vallarino K, T.; Morales R, P.

2001-01-01

The induction kinetics of micronuclei polychromated eritrocites (EPC-MN) which is produced by busulfan and compared with that produced by the ionizing radiation, allows to make inferences over the pharmacokinetics and pharmacodynamics of busulfan. Observing two induction mechanisms of MN, this one early at low doses and other later at high doses, this last is presented to a critical dose being very sheer and associated with an increase of the cytotoxicity. The data suggest the transformation or dependence between these two types of leisures, which to determine the narrow therapeutical margin of busulfan. The pharmacokinetic parameters determined in the early mechanisms kinetics indicate a latency period, a time of effective activity and of half life 5.7, 5.2 and 2.6 h respectively. (Author)

Detectable states, cycle fluxes, and motility scaling of molecular motor kinesin: An integrative kinetic graph theory analysis

Science.gov (United States)

Ren, Jie

2017-12-01

The process by which a kinesin motor couples its ATPase activity with concerted mechanical hand-over-hand steps is a foremost topic of molecular motor physics. Two major routes toward elucidating kinesin mechanisms are the motility performance characterization of velocity and run length, and single-molecular state detection experiments. However, these two sets of experimental approaches are largely uncoupled to date. Here, we introduce an integrative motility state analysis based on a theorized kinetic graph theory for kinesin, which, on one hand, is validated by a wealth of accumulated motility data, and, on the other hand, allows for rigorous quantification of state occurrences and chemomechanical cycling probabilities. An interesting linear scaling for kinesin motility performance across species is discussed as well. An integrative kinetic graph theory analysis provides a powerful tool to bridge motility and state characterization experiments, so as to forge a unified effort for the elucidation of the working mechanisms of molecular motors.

Transition-state analysis of a Vmax mutant of AMP nucleosidase by the application of heavy-atom kinetic isotope effects

International Nuclear Information System (INIS)

Parkin, D.W.; Mentch, F.; Banks, G.A.; Horenstein, B.A.; Schramm, V.L.

1991-01-01

The transition state of the V max mutant of AMP nucleosidase from Azotobacter vinelandii has been characterized by heavy-atom kinetic isotope effects in the presence and absence of MgATP, the allosteric activator. The enzyme catalyzes hydrolysis of the N-glycosidic bond of AMP at approximately 2% of the rate of the normal enzyme with only minor changes in the K m for substrate, the activation constant for MgATP, and the K i for formycin 5'-phosphate, a tight-binding competitive inhibitor. Isotope effects were measured as a function of the allosteric activator concentration that increases the turnover number of the enzyme from 0.006 s -1 . The kinetic isotope effects were measured with the substrates [1'- 3 H]AMP, [2'- 2 H]AMP, [9- 15 N]AMP, and [1',9- 14 C, 15 N]AMP. All substrates gave significant kinetic isotope effects in a pattern that establishes that the reaction expresses intrinsic kinetic isotope effects in the presence or absence of MgATP. Transition-state analysis using bond-energy and bond-order vibrational analysis indicated that the transition state for the mutant enzyme has a similar position in the reaction coordinate compared to that for the normal enzyme. The mutant enzyme is less effective in stabilizing the carbocation-like intermediate and in the ability to protonate N7 of adenine to create a better leaving group. This altered transition-state structure was confirmed by an altered substrate specificity for the mutant protein

Effect of ball mill treatment on kinetics of amorphous Ni78Si10B12 alloy crystallization

International Nuclear Information System (INIS)

Tomilin, I.A.; Mochalova, T.Yu.; Kaloshkin, S.D.; Kostyukovich, T.G.; Lopatina, E.A.

1993-01-01

The effect of the parameters of Ni 78 Si 10 B 12 alloy amorphous strip milling in a ball planetary mill on the stability of powder amorphous state, crytallization kinetics and dispersity is studied by the methods of differential scanning microcaloremetry and X-ray diffraction analysis. Energy intensity of milling conditions is assessed. An increase of input energy results in a decrease of activation energy of powder crystallization. Strip milling parameters which enable to avaintain the amorphous state of the material are determined

Kinetic and electron-electron energies for convex sums of ground state densities with degeneracies and fractional electron number

Energy Technology Data Exchange (ETDEWEB)

Levy, Mel, E-mail: ayers@mcmaster.ca, E-mail: mlevy@tulane.edu [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Department of Physics, North Carolina A and T State University, Greensboro, North Carolina 27411 (United States); Department of Chemistry, Tulane University, New Orleans, Louisiana 70118 (United States); Anderson, James S. M.; Zadeh, Farnaz Heidar; Ayers, Paul W., E-mail: ayers@mcmaster.ca, E-mail: mlevy@tulane.edu [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario (Canada)

2014-05-14

Properties of exact density functionals provide useful constraints for the development of new approximate functionals. This paper focuses on convex sums of ground-level densities. It is observed that the electronic kinetic energy of a convex sum of degenerate ground-level densities is equal to the convex sum of the kinetic energies of the individual degenerate densities. (The same type of relationship holds also for the electron-electron repulsion energy.) This extends a known property of the Levy-Valone Ensemble Constrained-Search and the Lieb Legendre-Transform refomulations of the Hohenberg-Kohn functional to the individual components of the functional. Moreover, we observe that the kinetic and electron-repulsion results also apply to densities with fractional electron number (even if there are no degeneracies), and we close with an analogous point-wise property involving the external potential. Examples where different degenerate states have different kinetic energy and electron-nuclear attraction energy are given; consequently, individual components of the ground state electronic energy can change abruptly when the molecular geometry changes. These discontinuities are predicted to be ubiquitous at conical intersections, complicating the development of universally applicable density-functional approximations.

On-rate based optimization of structure-kinetic relationship--surfing the kinetic map.

Science.gov (United States)

Schoop, Andreas; Dey, Fabian

2015-10-01

In the lead discovery process residence time has become an important parameter for the identification and characterization of the most efficacious compounds in vivo. To enable the success of compound optimization by medicinal chemistry toward a desired residence time the understanding of structure-kinetic relationship (SKR) is essential. This article reviews various approaches to monitor SKR and suggests using the on-rate as the key monitoring parameter. The literature is reviewed and examples of compound series with low variability as well as with significant changes in on-rates are highlighted. Furthermore, findings of kinetic on-rate changes are presented and potential underlying rationales are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

A new mathematical model for coal flotation kinetics

OpenAIRE

Guerrero-Pérez, Juan Sebastián; Barraza-Burgos, Juan Manuel

2017-01-01

Abstract This study describes the development and formulation of a novel mathematical model for coal flotation kinetic. The flotation rate was considered as a function of chemical, operating and petrographic parameters for a global flotation order n. The equation for flotation rate was obtained by dimensional analysis using the Rayleigh method. It shows the dependency of flotation kinetic on operating parameters, such as air velocity and particle size; chemical parameters, such as reagents do...

Non-isothermal degradation and evaluation of kinetic parameters of some Schiff base metal complexes

International Nuclear Information System (INIS)

Mishra, A.P.; Soni, Monika

2008-01-01

Thermal decomposition of VO (II)-methyl isobutyl ketone-nicotinamide, VO (II)-2-furfurylidine-3,4-dichloroaniline, Co(II)-4-dimethyl amino benzylidine-3-chloro-4-fluoroaniline, VO(II)-2-pyridine carboxylidine-4-aminobenzoic acid complexes have been carried out by thermogravimetric method. The TG curves of complexes were recorded at a uniform rate of 20 deg C/min in nitrogen. The thermogram of the three VO(II) complexes exhibit single stage decomposition whereas the Co(II) complex shows a double stage decomposition. Various kinetic parameters i. e., energy of activation (E), entropy (AS) and frequency factor (Z) have been evaluated by using Coats-Redfern and Piloyan-Novikova equations and their comparable values are reported. The order of thermal stability of first decomposition stage is as: 4=2>1>3. (author)

Evaluation of the kinetic parameters of CaF2:Tm (TLD-300) thermoluminescence dosemeters

International Nuclear Information System (INIS)

Azorin, Juan; Gutierrez, Alicia; Furetta, Claudio

1989-01-01

The kinetic parameters of the first, third and fifth peaks of CaF 2 :Tm (TLD-300) dosemeters were determined experimentally using methods based on initial rise, peak shape, different heating rates, isothermal decay and numerical fitting method and a comparison was made between the results obtained. The average activation energy values determined by the methods used here were 0.72, 1.16 and 1.77 eV, with mean values for the frequency factor of 2.58 x 10 8 , 2.89 x 10 13 and 6.16 x 10 16 s -1 for the first, third and fifth peaks respectively. The values of activation energy obtained for each peak using the different methods covered a spread of about 4%. However, the spread for each of the frequency factors was very high. (author)

Mechanistic studies with solubilized rat liver steroid 5 alpha-reductase: Elucidation of the kinetic mechanism

International Nuclear Information System (INIS)

Levy, M.A.; Brandt, M.; Greway, A.T.

1990-01-01

A solubilized preparation of steroid 5 alpha-reductase from rat liver has been used in studies focused toward an understanding of the kinetic mechanism associated with enzyme catalysis. From the results of analyses with product and dead-end inhibitors, a preferentially ordered binding of substrates and release of products from the surface of the enzyme is proposed. The observations from these experiments were identical with those using the steroid 5 alpha-reductase activity associated with rat liver microsomes. The primary isotope effects on steady-state kinetic parameters when [4S-2H]NADPH was used also were consistent with an ordered kinetic mechanism. Normal isotope effects were observed for all three kinetic parameters (Vm/Km for both testosterone and NADPH and Vm) at all substrate concentrations used experimentally. Upon extrapolation to infinite concentration of testosterone, the isotope effect on Vm/Km for NADPH approached unity, indicating that the nicotinamide dinucleotide phosphate is the first substrate binding to and the second product released from the enzyme. The isotope effects on Vm/Km for testosterone at infinite concentration of cofactor and on Vm were 3.8 +/- 0.5 and 3.3 +/- 0.4, respectively. Data from the pH profiles of these three steady-state parameters and the inhibition constants (1/Ki) of competitive inhibitors versus both substrates indicate that the binding of nicotinamide dinucleotide phosphate involves coordination of its anionic 2'-phosphate to a protonated enzyme-associated base with an apparent pK near 8.0. From these results, relative limits have been placed on several of the internal rate constants used to describe the ordered mechanism of the rat liver steroid 5 alpha-reductase

Systematic construction of kinetic models from genome-scale metabolic networks.

Directory of Open Access Journals (Sweden)

Natalie J Stanford

Full Text Available The quantitative effects of environmental and genetic perturbations on metabolism can be studied in silico using kinetic models. We present a strategy for large-scale model construction based on a logical layering of data such as reaction fluxes, metabolite concentrations, and kinetic constants. The resulting models contain realistic standard rate laws and plausible parameters, adhere to the laws of thermodynamics, and reproduce a predefined steady state. These features have not been simultaneously achieved by previous workflows. We demonstrate the advantages and limitations of the workflow by translating the yeast consensus metabolic network into a kinetic model. Despite crudely selected data, the model shows realistic control behaviour, a stable dynamic, and realistic response to perturbations in extracellular glucose concentrations. The paper concludes by outlining how new data can continuously be fed into the workflow and how iterative model building can assist in directing experiments.

Systematic Construction of Kinetic Models from Genome-Scale Metabolic Networks

Science.gov (United States)

Smallbone, Kieran; Klipp, Edda; Mendes, Pedro; Liebermeister, Wolfram

2013-01-01

The quantitative effects of environmental and genetic perturbations on metabolism can be studied in silico using kinetic models. We present a strategy for large-scale model construction based on a logical layering of data such as reaction fluxes, metabolite concentrations, and kinetic constants. The resulting models contain realistic standard rate laws and plausible parameters, adhere to the laws of thermodynamics, and reproduce a predefined steady state. These features have not been simultaneously achieved by previous workflows. We demonstrate the advantages and limitations of the workflow by translating the yeast consensus metabolic network into a kinetic model. Despite crudely selected data, the model shows realistic control behaviour, a stable dynamic, and realistic response to perturbations in extracellular glucose concentrations. The paper concludes by outlining how new data can continuously be fed into the workflow and how iterative model building can assist in directing experiments. PMID:24324546

Characterization of excited-state reactions with instant spectra of fluorescence kinetics

International Nuclear Information System (INIS)

Tomin, Vladimir I.; Ushakou, Dzmitryi V.

2015-01-01

Comprehensible knowledge of the excited-state proton transfer processes in organic compounds is overwhelmingly important not only for physics, but also chemistry and Life Sciences, since they play a key role in main processes of photosynthesis and functioning of biological organisms. Moreover compounds with Excited-State Intramolecular Proton Transfer (ESIPT) are in the focus of the interest of scientists throughout the world, because dual fluorescence spectra of such objects corresponding to two forms of molecular structure (normal and photoproduct) are very sensitive to characteristics of molecular microenvironment. This property allows to use such substances as fluorescent probes for diverse applications in chemistry and Life Sciences. But at the same time studying of proton transfer processes is not simple, because this process is characterized by extremely fast times (on picoseconds time scale and less order) and very often contribution of reverse reactions is essentially complicates an interpretation of observed properties of dual fluorescence. Hence, understanding of a role of reversible reactions is crucial for a comprehensive description of all processes accompanying excited state reactions. We discuss new approach for treatment ESIPT reaction on the basis of experimentally measured instant spectra of dual fluorescence and temporal behavior of ratiometric signal of normal to tautomer form intensities. Simple analytical expressions show in transparent way how to distinguish a degree of reverse reaction contribution to ratiometric signal. A validation of the approach under consideration is fulfilled with two different flavonols – 3-hydroxyflavone and 4′-(Dimethylamino)-3-hydroxyflavone – representing two extreme cases in affecting reversible reaction on dual emission. A comparing of new approach and traditional method when we analyze kinetics of separate the N* and T* fluorescence bands decays, has been carried out. - Highlights: • The excited-state

Characterization of excited-state reactions with instant spectra of fluorescence kinetics

Energy Technology Data Exchange (ETDEWEB)

Tomin, Vladimir I., E-mail: tomin@apsl.edu.pl; Ushakou, Dzmitryi V.

2015-10-15

Comprehensible knowledge of the excited-state proton transfer processes in organic compounds is overwhelmingly important not only for physics, but also chemistry and Life Sciences, since they play a key role in main processes of photosynthesis and functioning of biological organisms. Moreover compounds with Excited-State Intramolecular Proton Transfer (ESIPT) are in the focus of the interest of scientists throughout the world, because dual fluorescence spectra of such objects corresponding to two forms of molecular structure (normal and photoproduct) are very sensitive to characteristics of molecular microenvironment. This property allows to use such substances as fluorescent probes for diverse applications in chemistry and Life Sciences. But at the same time studying of proton transfer processes is not simple, because this process is characterized by extremely fast times (on picoseconds time scale and less order) and very often contribution of reverse reactions is essentially complicates an interpretation of observed properties of dual fluorescence. Hence, understanding of a role of reversible reactions is crucial for a comprehensive description of all processes accompanying excited state reactions. We discuss new approach for treatment ESIPT reaction on the basis of experimentally measured instant spectra of dual fluorescence and temporal behavior of ratiometric signal of normal to tautomer form intensities. Simple analytical expressions show in transparent way how to distinguish a degree of reverse reaction contribution to ratiometric signal. A validation of the approach under consideration is fulfilled with two different flavonols – 3-hydroxyflavone and 4′-(Dimethylamino)-3-hydroxyflavone – representing two extreme cases in affecting reversible reaction on dual emission. A comparing of new approach and traditional method when we analyze kinetics of separate the N* and T* fluorescence bands decays, has been carried out. - Highlights: • The excited-state

Dose dependent oxidation kinetics of lipids in fish during irradiation processing

International Nuclear Information System (INIS)

Tukenmez, I.; Ersen, M.S.; Bakioglu, A.T.; Bicer, A.; Pamuk, V.

1997-01-01

Kinetic aspects of the development of lipid oxidation in complex foods as fish in the course of irradiation were analyzed with respect to the associated formation of malonaldehyde (MA) through the reactions modified so as to be consistent with those in complex foods as fish. Air-packed anchovy (Engraulis encrasicholus) samples in polyethylene pouches were irradiated at the doses of 1, 2, 5, 10, 15,20 and 25 kGy at 20 o C in a Cs-137 gamma irradiator of 1.806 kGy/h dose rate. Immediately after each irradiation, MA contents of irradiated and unirradiated samples were determined by thiobarbituric acid test. Based on the MA formation, a kinetic model to simulate the apparent oxidation of lipid in fish as a function of irradiation dose was derived from the rate equations consistent with modified reactions. Kinetic parameters and simulation were related to conditions of lipid oxidation, and associated rancidity state of fish with respect to the doses applied in different irradiation-preservation processes. Numerical values of kinetic parameters based on the MA formation were found as a threshold dose of 0.375 kGy, an apparent yield of 1.871 μmol/kg kGy, and a maximum attainable concentration of 15.853 μmol/kg which may be used for process control and dosimetry. (author)

Sulfide toxicity kinetics of a uasb reactor

Directory of Open Access Journals (Sweden)

D. R. Paula Jr.

2009-12-01

Full Text Available The effect of sulfide toxicity on kinetic parameters of anaerobic organic matter removal in a UASB (up-flow anaerobic sludge blanket reactor is presented. Two lab-scale UASB reactors (10.5 L were operated continuously during 12 months. The reactors were fed with synthetic wastes prepared daily using glucose, ammonium acetate, methanol and nutrient solution. One of the reactors also received increasing concentrations of sodium sulfide. For both reactors, the flow rate of 16 L.d-1 was held constant throughout the experiment, corresponding to a hydraulic retention time of 15.6 hours. The classic model for non-competitive sulfide inhibition was applied to the experimental data for determining the overall kinetic parameter of specific substrate utilization (q and the sulfide inhibition coefficient (Ki. The application of the kinetic parameters determined allows prediction of methanogenesis inhibition and thus the adoption of operating parameters to minimize sulfide toxicity in UASB reactors.

Kinetic modeling and exploratory numerical simulation of chloroplastic starch degradation

Directory of Open Access Journals (Sweden)

Nag Ambarish

2011-06-01

Full Text Available Abstract Background Higher plants and algae are able to fix atmospheric carbon dioxide through photosynthesis and store this fixed carbon in large quantities as starch, which can be hydrolyzed into sugars serving as feedstock for fermentation to biofuels and precursors. Rational engineering of carbon flow in plant cells requires a greater understanding of how starch breakdown fluxes respond to variations in enzyme concentrations, kinetic parameters, and metabolite concentrations. We have therefore developed and simulated a detailed kinetic ordinary differential equation model of the degradation pathways for starch synthesized in plants and green algae, which to our knowledge is the most complete such model reported to date. Results Simulation with 9 internal metabolites and 8 external metabolites, the concentrations of the latter fixed at reasonable biochemical values, leads to a single reference solution showing β-amylase activity to be the rate-limiting step in carbon flow from starch degradation. Additionally, the response coefficients for stromal glucose to the glucose transporter kcat and KM are substantial, whereas those for cytosolic glucose are not, consistent with a kinetic bottleneck due to transport. Response coefficient norms show stromal maltopentaose and cytosolic glucosylated arabinogalactan to be the most and least globally sensitive metabolites, respectively, and β-amylase kcat and KM for starch to be the kinetic parameters with the largest aggregate effect on metabolite concentrations as a whole. The latter kinetic parameters, together with those for glucose transport, have the greatest effect on stromal glucose, which is a precursor for biofuel synthetic pathways. Exploration of the steady-state solution space with respect to concentrations of 6 external metabolites and 8 dynamic metabolite concentrations show that stromal metabolism is strongly coupled to starch levels, and that transport between compartments serves to

Problems of low-parameter equations of state

Science.gov (United States)

Petrik, G. G.

2017-11-01

The paper focuses on the system approach to problems of low-parametric equations of state (EOS). It is a continuation of the investigations in the field of substantiated prognosis of properties on two levels, molecular and thermodynamic. Two sets of low-parameter EOS have been considered based on two very simple molecular-level models. The first one consists of EOS of van der Waals type (a modification of van der Waals EOS proposed for spheres). The main problem of these EOS is a weak connection with the micro-level, which raise many uncertainties. The second group of EOS has been derived by the author independently of the ideas of van der Waals based on the model of interacting point centers (IPC). All the parameters of the EOS have a meaning and are associated with the manifestation of attractive and repulsive forces. The relationship between them is found to be the control parameter of the thermodynamic level. In this case, EOS IPC passes into a one-parameter family. It is shown that many EOS of vdW-type can be included in the framework of the PC model. Simultaneously, all their parameters acquire a physical meaning.

State orthogonality, boson bunching parameter and bosonic enhancement factor

Science.gov (United States)

Marchewka, Avi; Granot, Er'el

2016-04-01

It is emphasized that the bunching parameter β ≡ p B / p D , i.e. the ratio between the probability to measure two bosons and two distinguishable particles at the same state, is a constant of motion and depends only on the overlap between the initial wavefunctions. This ratio is equal to β = 2 / (1 + I 2), where I is the overlap integral between the initial wavefunctions. That is, only when the initial wavefunctions are orthogonal this ratio is equal to 2, however, this bunching ratio can be reduced to 1, when the two wavefunctions are identical. This simple equation explains the experimental evidences of a beam splitter. A straightforward conclusion is that by measuring the local bunching parameter β (at any point in space and time) it is possible to evaluate a global parameter I (the overlap between the initial wavefunctions). The bunching parameter is then generalized to arbitrary number of particles, and in an analogy to the two-particles scenario, the well-known bosonic enhancement appears only when all states are orthogonal.

Kinetics and

Directory of Open Access Journals (Sweden)

Mojtaba Ahmadi

2016-11-01

Full Text Available The aqueous degradation of Reactive Yellow 84 (RY84 by potassium peroxydisulfate (K2S2O8 has been studied in laboratory scale experiments. The effect of the initial concentrations of potassium peroxydisulfate and RY84, pH and temperature on RY84 degradation were also examined. Experimental data were analyzed using first and second-order kinetics. The degradation kinetics of RY84 of the potassium peroxydisulfate process followed the second-order reaction kinetics. These rate constants have an extreme values similar to of 9.493 mM−1min−1 at a peroxydisulfate dose of 4 mmol/L. Thermodynamic parameters such as activation (Ea and Gibbs free energy (ΔG° were also evaluated. The negative value of ΔGo and Ea shows the spontaneous reaction natural conditions and exothermic nature.

Influence of external mass transfer limitation on apparent kinetic parameters of penicillin G acylase immobilized on nonporous ultrafine silica particles.

Science.gov (United States)

Kheirolomoom, Azadeh; Khorasheh, Farhad; Fazelinia, Hossein

2002-01-01

Immobilization of enzymes on nonporous supports provides a suitable model for investigating the effect of external mass transfer limitation on the reaction rate in the absence of internal diffusional resistance. In this study, deacylation of penicillin G was investigated using penicillin acylase immobilized on ultrafine silica particles. Kinetic studies were performed within the low-substrate-concentration region, where the external mass transfer limitation becomes significant. To predict the apparent kinetic parameters and the overall effectiveness factor, knowledge of the external mass transfer coefficient, k(L)a, is necessary. Although various correlations exist for estimation of k(L)a, in this study, an optimization scheme was utilized to obtain this coefficient. Using the optimum values of k(L)a, the initial reaction rates were predicted and found to be in good agreement with the experimental data.

Saffman-Taylor fingers with kinetic undercooling

KAUST Repository

Gardiner, Bennett P. J.

2015-02-23

© 2015 American Physical Society. The mathematical model of a steadily propagating Saffman-Taylor finger in a Hele-Shaw channel has applications to two-dimensional interacting streamer discharges which are aligned in a periodic array. In the streamer context, the relevant regularization on the interface is not provided by surface tension but instead has been postulated to involve a mechanism equivalent to kinetic undercooling, which acts to penalize high velocities and prevent blow-up of the unregularized solution. Previous asymptotic results for the Hele-Shaw finger problem with kinetic undercooling suggest that for a given value of the kinetic undercooling parameter, there is a discrete set of possible finger shapes, each analytic at the nose and occupying a different fraction of the channel width. In the limit in which the kinetic undercooling parameter vanishes, the fraction for each family approaches 1/2, suggesting that this "selection" of 1/2 by kinetic undercooling is qualitatively similar to the well-known analog with surface tension. We treat the numerical problem of computing these Saffman-Taylor fingers with kinetic undercooling, which turns out to be more subtle than the analog with surface tension, since kinetic undercooling permits finger shapes which are corner-free but not analytic. We provide numerical evidence for the selection mechanism by setting up a problem with both kinetic undercooling and surface tension and numerically taking the limit that the surface tension vanishes.

Saffman-Taylor fingers with kinetic undercooling

KAUST Repository

Gardiner, Bennett P. J.; McCue, Scott W.; Dallaston, Michael C.; Moroney, Timothy J.

2015-01-01

© 2015 American Physical Society. The mathematical model of a steadily propagating Saffman-Taylor finger in a Hele-Shaw channel has applications to two-dimensional interacting streamer discharges which are aligned in a periodic array. In the streamer context, the relevant regularization on the interface is not provided by surface tension but instead has been postulated to involve a mechanism equivalent to kinetic undercooling, which acts to penalize high velocities and prevent blow-up of the unregularized solution. Previous asymptotic results for the Hele-Shaw finger problem with kinetic undercooling suggest that for a given value of the kinetic undercooling parameter, there is a discrete set of possible finger shapes, each analytic at the nose and occupying a different fraction of the channel width. In the limit in which the kinetic undercooling parameter vanishes, the fraction for each family approaches 1/2, suggesting that this "selection" of 1/2 by kinetic undercooling is qualitatively similar to the well-known analog with surface tension. We treat the numerical problem of computing these Saffman-Taylor fingers with kinetic undercooling, which turns out to be more subtle than the analog with surface tension, since kinetic undercooling permits finger shapes which are corner-free but not analytic. We provide numerical evidence for the selection mechanism by setting up a problem with both kinetic undercooling and surface tension and numerically taking the limit that the surface tension vanishes.

Conformational kinetics of aliphatic tails

Science.gov (United States)

Ferrarini, Alberta; Moro, Giorgio; Nordio, Pier Luigi

The master equation describing the random walk between sites identified with the stable conformers of a chain molecule, represents the extension to the time domain of the Rotational Isomeric State model. The asymptotic analysis of the multidimensional diffusion equation in the continuous torsional variables subjected to the configurational potential, provides a rigorous justification for the discrete models, and it supplies, without resorting to phenomenological parameters, molecular definitions of the kinetic rates for the conformational transitions occurring at each segment of the chain. The coupling between the torsional variables is fully taken into account, giving rise to cooperative effects. A complete calculation of the specific correlation functions which describe the time evolution of the angular functions probed by N.M.R. and dielectric relaxation measurements, has been performed for alkyl chains attached to a massive core. The resulting behaviour has been compared with the decay of trans and gauche populations of specific bonds, expressed in terms of suitable correlation functions whose time integrals lead quite naturally to the definition of effective kinetic constants for the conformational transitions.

Development of simple kinetic models and parameter estimation for ...

African Journals Online (AJOL)

In order to describe and predict the growth and expression of recombinant proteins by using a genetically modified Pichia pastoris, we developed a number of unstructured models based on growth kinetic equation, fed-batch mass balance and the assumptions of constant cell and protein yields. The growth of P. pastoris on ...

Nodal kinetics model upgrade in the Penn State coupled TRAC/NEM codes

International Nuclear Information System (INIS)

Beam, Tara M.; Ivanov, Kostadin N.; Baratta, Anthony J.; Finnemann, Herbert

1999-01-01

The Pennsylvania State University currently maintains and does development and verification work for its own versions of the coupled three-dimensional kinetics/thermal-hydraulics codes TRAC-PF1/NEM and TRAC-BF1/NEM. The subject of this paper is nodal model enhancements in the above mentioned codes. Because of the numerous validation studies that have been performed on almost every aspect of these codes, this upgrade is done without a major code rewrite. The upgrade consists of four steps. The first two steps are designed to improve the accuracy of the kinetics model, based on the nodal expansion method. The polynomial expansion solution of 1D transverse integrated diffusion equation is replaced with a solution, which uses a semi-analytic expansion. Further the standard parabolic polynomial representation of the transverse leakage in the above 1D equations is replaced with an improved approximation. The last two steps of the upgrade address the code efficiency by improving the solution of the time-dependent NEM equations and implementing a multi-grid solver. These four improvements are implemented into the standalone NEM kinetics code. Verification of this code was accomplished based on the original verification studies. The results show that the new methods improve the accuracy and efficiency of the code. The verification of the upgraded NEM model in the TRAC-PF1/NEM and TRAC-BF1/NEM coupled codes is underway

Pre-steady-state Kinetics for Hydrolysis of Insoluble Cellulose by Cellobiohydrolase Cel7A

DEFF Research Database (Denmark)

Cruys-Bagger, Nicolaj; Olsen, Jens Elmerdahl; Præstgaard, Eigil

2012-01-01

The transient kinetic behavior of enzyme reactions prior to the establishment of steady state is a major source of mechanistic information, yet this approach has not been utilized for cellulases acting on their natural substrate, insoluble cellulose. Here, we elucidate the pre-steady-state regime...... for the exo-acting cellulase Cel7A using amperometric biosensors and an explicit model for processive hydrolysis of cellulose. This analysis allows the identification of a pseudo-steady-state period and quantification of a processivity number as well as rate constants for the formation of a threaded enzyme...... to unveil fundamental reasons for the distinctive variability in hydrolytic activity found in different cellulase-substrate systems....

Evaluation of reaction mechanisms and the kinetic parameters for the transesterification of castor oil by liquid enzymes

DEFF Research Database (Denmark)

Andrade, Thalles Allan; Errico, Massimiliano; Christensen, Knud Villy

2017-01-01

of the transesterification of castor oil with methanol using the enzyme Eversa® Transform as catalyst were investigated. Reactions were carried out for 8 hours at 35 °C with: an alcohol-to-oil molar ratio equal to 6:1, a 5 wt% of liquid enzyme solution and addition of 5 wt% of water by weight of castor oil. From...... methanolysis rates of glycerides obtained, indicated that transesterification dominates over hydrolysis. The mechanism among the four models proposed that gave the best fit could be simplified, eliminating the kinetic parameters with negligible effects on the reaction rates. This model was able to fit...

Principles of chemical kinetics

CERN Document Server

House, James E

2007-01-01

James House's revised Principles of Chemical Kinetics provides a clear and logical description of chemical kinetics in a manner unlike any other book of its kind. Clearly written with detailed derivations, the text allows students to move rapidly from theoretical concepts of rates of reaction to concrete applications. Unlike other texts, House presents a balanced treatment of kinetic reactions in gas, solution, and solid states. The entire text has been revised and includes many new sections and an additional chapter on applications of kinetics. The topics covered include quantitative rela

Kinetics of potassium, rubidium and cesium in rat

International Nuclear Information System (INIS)

Natsuhori, Masahiro; Kosaka, Shigetoshi; Nishikawa, Miki; Okida, Masato; Ito, Nobuhiko

1998-01-01

Apparent incorporation rates of K and Rb into red blood cells were investigated in rats in consideration of passive diffusion to clarify in vivo kinetics of alkali metals. First, the incorporation rates of K and Rb into blood cells were determined by incubating blood samples from SD rat with 42 K and 86 Rb-buffers. And parameters involving in these incorporations such as Vmax (maximum rate of active transport), {S} (substrate concentration), Km (Michaelis constant), n (cooperativity of active transport), etc. were evaluated based on the time-course changes in K and Rb incorporation. Then, K and Rb were given to SD rats and the respective levels in plasma, red blood cells and urine were determined. The parameters were evaluated based on the time course changes in these levels by using compartment model. Similarly, the kinetics of Cs were investigated in rats. The absorption, distribution and disappearance of alkali metals were investigated in vivo to compare in vivo kinetics among the metals. By applying the kinetic parameters analyzed, Cs kinetics, in vivo could be estimated and Cs intake was able to be also estimated by determining the Cs levels of blood cells, urine and plasma. (M.N.)

Critical Analysis of Underground Coal Gasification Models. Part II: Kinetic and Computational Fluid Dynamics Models

Directory of Open Access Journals (Sweden)

Alina Żogała

2014-01-01

Originality/value: This paper presents state of art in the field of coal gasification modeling using kinetic and computational fluid dynamics approach. The paper also presents own comparative analysis (concerned with mathematical formulation, input data and parameters, basic assumptions, obtained results etc. of the most important models of underground coal gasification.

Fundamental aspects of plasma chemical physics kinetics

CERN Document Server

Capitelli, Mario; Colonna, Gianpiero; Esposito, Fabrizio; Gorse, Claudine; Hassouni, Khaled; Laricchiuta, Annarita; Longo, Savino

2016-01-01

Describing non-equilibrium "cold" plasmas through a chemical physics approach, this book uses the state-to-state plasma kinetics, which considers each internal state as a new species with its own cross sections. Extended atomic and molecular master equations are coupled with Boltzmann and Monte Carlo methods to solve the electron energy distribution function. Selected examples in different applied fields, such as microelectronics, fusion, and aerospace, are presented and discussed including the self-consistent kinetics in RF parallel plate reactors, the optimization of negative ion sources and the expansion of high enthalpy flows through nozzles of different geometries. The book will cover the main aspects of the state-to-state kinetic approach for the description of nonequilibrium cold plasmas, illustrating the more recent achievements in the development of kinetic models including the self-consistent coupling of master equations and Boltzmann equation for electron dynamics. To give a complete portrayal, the...

Higher adsorption capacity of Spirulina platensis alga for Cr(VI) ions removal: parameter optimisation, equilibrium, kinetic and thermodynamic predictions.

Science.gov (United States)

Gunasundari, Elumalai; Senthil Kumar, Ponnusamy

2017-04-01

This study discusses about the biosorption of Cr(VI) ion from aqueous solution using ultrasonic assisted Spirulina platensis (UASP). The prepared UASP biosorbent was characterised by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer-Emmet-Teller, scanning electron spectroscopy and energy dispersive X-ray and thermogravimetric analyses. The optimum condition for the maximum removal of Cr(VI) ions for an initial concentration of 50 mg/l by UASP was measured as: adsorbent dose of 1 g/l, pH of 3.0, contact time of 30 min and temperature of 303 K. Adsorption isotherm, kinetics and thermodynamic parameters were calculated. Freundlich model provided the best results for the removal of Cr(VI) ions by UASP. The adsorption kinetics of Cr(VI) ions onto UASP showed that the pseudo-first-order model was well in line with the experimental data. In the thermodynamic study, the parameters like Gibb's free energy, enthalpy and entropy changes were evaluated. This result explains that the adsorption of Cr(VI) ions onto the UASP was exothermic and spontaneous in nature. Desorption of the biosorbent was done using different desorbing agents in which NaOH gave the best result. The prepared material showed higher affinity for the removal of Cr(VI) ions and this may be an alternative material to the existing commercial adsorbents.

Effect of Utilization of Silicide Fuel with the Density 4.8 gU/cc on the Kinetic Parameters of RSG-GAS Reactor

International Nuclear Information System (INIS)

Setiyanto; Sembiring, Tagor M.; Pinem, Surian

2007-01-01

Presently, the RSG-GAS reactor using silicide fuel element of 2.96 gU/cc. For increasing reactor operation time, its planning to change to higher density fuel. The kinetic calculation of silicide core with density 4.8 gU/cc has been carried out, since it has an influence on the reactor operation safety. The calculated kinetic parameters are the effective delayed neutron fraction, the delayed neutron decay constant, prompt neutron lifetime and feedback reactivity coefficient very important for reactor operation safety. the calculation is performed in 2-dimensional neutron diffusion-perturbation method using modified Batan-2DIFF code. The calculation showed that the effective delayed neutron fraction is 7. 03256x10 -03 , total delay neutron time constant is 7.85820x10 -02 s -1 and the prompt neutron lifetime is 55.4900 μs. The result of prompt neutron lifetime smaller 10 % compare with silicide fuel of 4.8 gU/cc. The calculated results showed that all of the feedback reactivity coefficient silicide core 4.8 gU/cc is negative. Totally, the feedback reactivity coefficient of silicide fuel of 4.8 gU/cc is 10% less than that of silicide fuel of 2.96 gU/cc. The results shown that kinetic parameters result decrease compared with the silicide core with density 2.96 gU/cc, but no significant influence in the RSG-GAS reactor operation. (author)

Analytical Expressions for the Mixed-Order Kinetics Parameters of TL Glow Peaks Based on the two Heating Rates Method.

Science.gov (United States)

Maghrabi, Mufeed; Al-Abdullah, Tariq; Khattari, Ziad

2018-03-24

The two heating rates method (originally developed for first-order glow peaks) was used for the first time to evaluate the activation energy (E) from glow peaks obeying mixed-order (MO) kinetics. The derived expression for E has an insignificant additional term (on the scale of a few meV) when compared with the first-order case. Hence, the original expression for E using the two heating rates method can be used with excellent accuracy in the case of MO glow peaks. In addition, we derived a simple analytical expression for the MO parameter. The present procedure has the advantage that the MO parameter can now be evaluated using analytical expression instead of using the graphical representation between the geometrical factor and the MO parameter as given by the existing peak shape methods. The applicability of the derived expressions for real samples was demonstrated for the glow curve of Li 2 B 4 O 7 :Mn single crystal. The obtained parameters compare very well with those obtained by glow curve fitting and with the available published data.

State orthogonality, boson bunching parameter and bosonic enhancement factor

International Nuclear Information System (INIS)

Marchewka, A.; Granot, E.

2016-01-01

Bosons bunching is the tendency of bosons to bunch together with respect to distinguishable particles. It is emphasized that the bunching parameter β = p_B/p_D, i.e. the ratio between the probability to measure 2 bosons and 2 distinguishable particles at the same state, is a constant of motion and depends only on the overlap between the initial wavefunctions. This ratio is equal to β = 2/(1 + l"2), where l is the overlap integral between the initial wavefunctions. That is, only when the initial wavefunctions are orthogonal this ratio is equal to 2, however, this bunching ratio can be reduced to 1, when the two wavefunctions are identical. This simple equation explains the experimental evidences of a beam splitter. A straightforward conclusion is that by measuring the local bunching parameter β (at any point in space and time) it is possible to evaluate a global parameter l (the overlap between the initial wavefunctions). The bunching parameter is then generalized to arbitrary number of particles, and in an analogy to the two-particles scenario, the well-known bosonic enhancement appears only when all states are orthogonal

Relativistic Kinetic Theory

Science.gov (United States)

Vereshchagin, Gregory V.; Aksenov, Alexey G.

2017-02-01

Preface; Acknowledgements; Acronyms and definitions; Introduction; Part I. Theoretical Foundations: 1. Basic concepts; 2. Kinetic equation; 3. Averaging; 4. Conservation laws and equilibrium; 5. Relativistic BBGKY hierarchy; 6. Basic parameters in gases and plasmas; Part II. Numerical Methods: 7. The basics of computational physics; 8. Direct integration of Boltzmann equations; 9. Multidimensional hydrodynamics; Part III. Applications: 10. Wave dispersion in relativistic plasma; 11. Thermalization in relativistic plasma; 12. Kinetics of particles in strong fields; 13. Compton scattering in astrophysics and cosmology; 14. Self-gravitating systems; 15. Neutrinos, gravitational collapse and supernovae; Appendices; Bibliography; Index.

Environment-sensitive quinolone demonstrating long-lived fluorescence and unusually slow excited-state intramolecular proton transfer kinetics

Czech Academy of Sciences Publication Activity Database

Zamotaiev, O. M.; Shvadchak, Volodymyr; Sych, T. P.; Melnychuk, N. A.; Yushchenko, Dmytro A.; Mely, Y.; Pivovarenko, V. G.

2016-01-01

Roč. 4, č. 3 (2016), č. článku 034004. ISSN 2050-6120 Institutional support: RVO:61388963 Keywords : quinolone * fluorescent probes * local polarity * hydration * excited-state intramolecular proton transfer * kinetics Subject RIV: CC - Organic Chemistry Impact factor: 2.656, year: 2016

Thermal oxidative degradation kinetics of agricultural residues using distributed activation energy model and global kinetic model.

Science.gov (United States)

Ren, Xiu'e; Chen, Jianbiao; Li, Gang; Wang, Yanhong; Lang, Xuemei; Fan, Shuanshi

2018-08-01

The study concerned the thermal oxidative degradation kinetics of agricultural residues, peanut shell (PS) and sunflower shell (SS). The thermal behaviors were evaluated via thermogravimetric analysis and the kinetic parameters were determined by using distributed activation energy model (DAEM) and global kinetic model (GKM). Results showed that thermal oxidative decomposition of two samples processed in three zones; the ignition, burnout, and comprehensive combustibility between two agricultural residues were of great difference; and the combustion performance could be improved by boosting heating rate. The activation energy ranges calculated by the DAEM for the thermal oxidative degradation of PS and SS were 88.94-145.30 kJ mol -1 and 94.86-169.18 kJ mol -1 , respectively. The activation energy obtained by the GKM for the oxidative decomposition of hemicellulose and cellulose was obviously lower than that for the lignin oxidation at identical heating rate. To some degree, the determined kinetic parameters could acceptably simulate experimental data. Copyright © 2018 Elsevier Ltd. All rights reserved.

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

Science.gov (United States)

Pöschl, U.; Rudich, Y.; Ammann, M.

2007-12-01

Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It enables a detailed description of mass transport and chemical reactions at the gas-particle interface, and it allows linking aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined and consistent rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependences (transient and steady-state conditions); flexible addition of unlimited numbers of chemical species and physicochemical processes; optional aggregation or resolution

Kinetics of particle deposition at heterogeneous surfaces

Science.gov (United States)

Stojiljković, D. Lj.; Vrhovac, S. B.

2017-12-01

The random sequential adsorption (RSA) approach is used to analyze adsorption of spherical particles of fixed diameter d0 on nonuniform surfaces covered by square cells arranged in a square lattice pattern. To characterize such pattern two dimensionless parameters are used: the cell size α and the cell-cell separation β, measured in terms of the particle diameter d0. Adsorption is assumed to occur if the particle (projected) center lies within a cell area. We focus on the kinetics of deposition process in the case when no more than a single disk can be placed onto any square cell (α deposition process is not consistent with the power law behavior. However, if the geometry of the pattern approaches towards ;noninteracting conditions; (β > 1), when adsorption on each cell can be decoupled, approach of the coverage fraction θ(t) to θJ becomes closer to the exponential law. Consequently, changing the pattern parameters in the present model allows to interpolate the deposition kinetics between the continuum limit and the lattice-like behavior. Structural properties of the jammed-state coverings are studied in terms of the radial distribution function g(r) and spatial distribution of particles inside the cell. Various, non-trivial spatial distributions are observed depending on the geometry of the pattern.

Realization of multi-parameter and multi-state in fault tree computer-aided building software

International Nuclear Information System (INIS)

Guo Xiaoli; Tong Jiejuan; Xue Dazhi

2004-01-01

More than one parameter and more than one failed state of a parameter are often involved in building fault tree, so it is necessary for fault tree computer-aided building software to deal with multi-parameter and multi-state. Fault Tree Expert System (FTES) has the target of aiding the FT-building work of hydraulic systems. This paper expatiates on how to realize multi-parameter and multi-state in FTES with focus on Knowledge Base and Illation Engine. (author)

Kinetics model development of cocoa bean fermentation

Science.gov (United States)

Kresnowati, M. T. A. P.; Gunawan, Agus Yodi; Muliyadini, Winny

2015-12-01

Although Indonesia is one of the biggest cocoa beans producers in the world, Indonesian cocoa beans are oftenly of low quality and thereby frequently priced low in the world market. In order to improve the quality, adequate post-harvest cocoa processing techniques are required. Fermentation is the vital stage in series of cocoa beans post harvest processing which could improve the quality of cocoa beans, in particular taste, aroma, and colours. During the fermentation process, combination of microbes grow producing metabolites that serve as the precursors for cocoa beans flavour. Microbial composition and thereby their activities will affect the fermentation performance and influence the properties of cocoa beans. The correlation could be reviewed using a kinetic model that includes unstructured microbial growth, substrate utilization and metabolic product formation. The developed kinetic model could be further used to design cocoa bean fermentation process to meet the expected quality. Further the development of kinetic model of cocoa bean fermentation also serve as a good case study of mixed culture solid state fermentation, that has rarely been studied. This paper presents the development of a kinetic model for solid-state cocoa beans fermentation using an empirical approach. Series of lab scale cocoa bean fermentations, either natural fermentations without starter addition or fermentations with mixed yeast and lactic acid bacteria starter addition, were used for model parameters estimation. The results showed that cocoa beans fermentation can be modelled mathematically and the best model included substrate utilization, microbial growth, metabolites production and its transport. Although the developed model still can not explain the dynamics in microbial population, this model can sufficiently explained the observed changes in sugar concentration as well as metabolic products in the cocoa bean pulp.

Fisher information, kinetic energy and uncertainty relation inequalities

International Nuclear Information System (INIS)

Luo Shunlong

2002-01-01

By interpolating between Fisher information and mechanical kinetic energy, we introduce a general notion of kinetic energy with respect to a parameter of Schroedinger wavefunctions from a statistical inference perspective. Kinetic energy is the sum of Fisher information and an integral of a parametrized analogue of quantum mechanical current density related to phase. A family of integral inequalities concerning kinetic energy and moments are established, among which the Cramer-Rao inequality and the Weyl-Heisenberg inequality, are special cases. In particular, the integral inequalities involving the negative order moments are relevant to the study of electron systems. Moreover, by specifying the parameter to a scale, we obtain a family of inequalities of uncertainty relation type which incorporate the position and momentum observables symmetrically in a single quantity. (author)

State transitions, hysteresis, and control parameters on DIII-D

International Nuclear Information System (INIS)

Thomas, D.M.; Groebner, R.J.; Carlstrom, T.N.; Osborne, T.H.; Petrie, T.W.

1998-07-01

The theory of turbulence decorrelation by ExB velocity shear is the leading candidate to explain the changes in turbulence and transport that are seen at the plasma edge at the L to H transition. Based on this, a key question is: What are the conditions or control parameters needed to begin the formation of the E r shear layer and thus trigger the L to H transition? On the DIII-D tokamak, the authors are attacking this question both through direct tests of the various theories and by trying to gain insight into the fundamental physics by investigating the control parameters which have a major effect on the power threshold. In this paper the authors describe results of studies on oscillating discharges where the plasma transitions continuously between L and H states. By following the dynamics of the plasma state through the forward and back transitions, they can represent the evolution of various control parameter candidates as a trajectory in various parametric spaces. The shape of these control curves can illustrate the specific nonlinearities governing the L-H transition problem, and under the proper conditions may be interpreted in the context of various phase-transition based models. In particular, the hysteresis exhibited in the various curves may help to clarify causality (what are the critical parameters) and may serve as tests of the models, given sufficient experimental accuracy. At present they are looking at T e , E r and ballooning/diamagnetic parameters as possible control parameter candidates

Adsorption kinetic parameters of Fe3+ and Ni2+ ions by gyrolite

Directory of Open Access Journals (Sweden)

Kestutis Baltakys

2015-03-01

Full Text Available In this work the adsorption kinetic parameters for Fe3+ and Ni2+ ions by gyrolite are presented. Additionally, the adsoption mechanism was described by using pseudo first order and pseudo second order  equations. It was determined that the adsorption capacity of gyrolite and intrusion of heavy metals ions in its structure depends on reaction time and the pH value of adsorptive. It was observed that the incorporation of Fe3+ ions occurs more intensive than Ni2+ ions. It was found that in the acidic solution the intrusion of Fe3+ ions into gyrolite structure proceeds by two types of chemical reaction mechanisms: substitution and addition. Meanwhile, nickel ions were participated only in substitution reaction: gyrolite-Ca0 + Mex+ ↔ gyrolite-Me0 + Ca2+. It was observed that the pseudo second order model fit well for iron and nickel ions adsorption mechanism. It was estimated that the adsorption reactions are not reversible process and the crystal structure of gyrolite is stable. Moreover, synthetic adsorbent and the products of sorption were characterized by XRD, STA and FT-IR methods.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5735

Characterization of electron states in dense plasmas and its use in atomic kinetics modeling

International Nuclear Information System (INIS)

Fisher, D.V.; Maron, Y.

2003-01-01

We describe a self-consistent statistical approach to account for plasma density effects in collisional-radiative kinetics. The approach is based on the characterization of three distinct types of electron states, namely, bound, collectivized, and free, and on the formalism of the effective statistical weights (ESW) of the bound states. The present approach accounts for individual and collective effects of the surrounding electrons and ions on atomic (ionic) electron states. High-accuracy expressions for the ESWs of bound states have been derived. The notions of ionization stage population, free electron density, and rate coefficient are redefined in accordance with the present characterization scheme. The modified expressions for the probabilities of electron-impact induced transitions as well as spontaneous and induced radiative transitions are then obtained. The influence of collectivized states on a dense plasma ionization composition is demonstrated to be strong. Examples of calculated ESWs and populations of ionic quantum states for steady state and transient plasmas are given

Kinetic partitioning mechanism of HDV ribozyme folding

Energy Technology Data Exchange (ETDEWEB)

Chen, Jiawen; Gong, Sha; Wang, Yujie; Zhang, Wenbing, E-mail: wbzhang@whu.edu.cn [Department of Physics, Wuhan University, Wuhan, Hubei 430072 (China)

2014-01-14

RNA folding kinetics is directly tied to RNA biological functions. We introduce here a new approach for predicting the folding kinetics of RNA secondary structure with pseudoknots. This approach is based on our previous established helix-based method for predicting the folding kinetics of RNA secondary structure. In this approach, the transition rates for an elementary step: (1) formation, (2) disruption of a helix stem, and (3) helix formation with concomitant partial melting of an incompatible helix, are calculated with the free energy landscape. The folding kinetics of the Hepatitis delta virus (HDV) ribozyme and the mutated sequences are studied with this method. The folding pathways are identified by recursive searching the states with high net flux-in(out) population starting from the native state. The theory results are in good agreement with that of the experiments. The results indicate that the bi-phasic folding kinetics for the wt HDV sequence is ascribed to the kinetic partitioning mechanism: Part of the population will quickly fold to the native state along the fast pathway, while another part of the population will fold along the slow pathway, in which the population is trapped in a non-native state. Single mutation not only changes the folding rate but also the folding pathway.

Determination of the kinetic parameters of K{sub 2}Y F{sub 5}: Tb; Determinacion de los parametros cineticos de K{sub 2}Y F{sub 5}: Tb

Energy Technology Data Exchange (ETDEWEB)

Gallegos, A.A. [CICATA-IPN, Legaria 694, Col. Irrigacion, 11500 Mexico D.F. (Mexico); Khaidukov, N.M. [Kurnakov Institute of General and Inorganic Chemistry, Moscow (Russian Federation); Azorin, J. [UAM-I, 09340 Mexico D.F. (Mexico)

2005-07-01

In this work the K{sub 2}Y doped materials with percentages of 0.01 and 0.2 of F{sub 5} and, 0.8 and 0.99 of Tb{sup 3+} were studied to determine the kinetic parameters (activation energy and frequency factor) of TL peaks with the purpose of comparing those sensitive qualities of the materials at the doping with TR and their candidacy for tests of TL dosimetry (linearity of the response with the absorbed dose and the reproducibility of the measures of the dose). The samples were irradiated with a beta source of {sup 90} Sr/{sup 90} Y, to ambient temperature, giving its a dose of 236.6 mGy, later the kinetic parameters with different experimental procedures were determined: isothermal decay to ambient temperature and erased of peaks not desired to greater temperature than the ambient. The glow curves (TL curves) were obtained with an TL analyzer Harshaw 4000, with interface to CPU for the handling of the data of the curves, which were treated with the curve form method and the models of: Chen first approach and Chen modified, corrected Lushchik approach and Grossweiner approach, to calculate the kinetic parameters of the sample. (Author)

Kinetic parameters of grinding media in ball mills with various liner design and mill speed based on DEM modeling

Science.gov (United States)

Khakhalev, P. A.; Bogdanov, VS; Kovshechenko, V. M.

2018-03-01

The article presents analysis of the experiments in the ball mill of 0.5x0.3 m with four different liner types based on DEM modeling. The numerical experiment always complements laboratory research and allow obtaining high accuracy output data. An important property of the numerical experiment is the possibility of visualization of the results. The EDEM software allows calculating trajectory of the grinding bodies and kinetic parameters of each ball for the relative mill speed and the different types of mill’s liners.

Validation of Bayesian analysis of compartmental kinetic models in medical imaging.

Science.gov (United States)

Sitek, Arkadiusz; Li, Quanzheng; El Fakhri, Georges; Alpert, Nathaniel M

2016-10-01

Kinetic compartmental analysis is frequently used to compute physiologically relevant quantitative values from time series of images. In this paper, a new approach based on Bayesian analysis to obtain information about these parameters is presented and validated. The closed-form of the posterior distribution of kinetic parameters is derived with a hierarchical prior to model the standard deviation of normally distributed noise. Markov chain Monte Carlo methods are used for numerical estimation of the posterior distribution. Computer simulations of the kinetics of F18-fluorodeoxyglucose (FDG) are used to demonstrate drawing statistical inferences about kinetic parameters and to validate the theory and implementation. Additionally, point estimates of kinetic parameters and covariance of those estimates are determined using the classical non-linear least squares approach. Posteriors obtained using methods proposed in this work are accurate as no significant deviation from the expected shape of the posterior was found (one-sided P>0.08). It is demonstrated that the results obtained by the standard non-linear least-square methods fail to provide accurate estimation of uncertainty for the same data set (P<0.0001). The results of this work validate new methods for a computer simulations of FDG kinetics. Results show that in situations where the classical approach fails in accurate estimation of uncertainty, Bayesian estimation provides an accurate information about the uncertainties in the parameters. Although a particular example of FDG kinetics was used in the paper, the methods can be extended for different pharmaceuticals and imaging modalities. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Kinetic modeling in pre-clinical positron emission tomography

Energy Technology Data Exchange (ETDEWEB)

Kuntner, Claudia [AIT Austrian Institute of Technology GmbH, Seibersdorf (Austria). Biomedical Systems, Health and Environment Dept.

2014-07-01

Pre-clinical positron emission tomography (PET) has evolved in the last few years from pure visualization of radiotracer uptake and distribution towards quantification of the physiological parameters. For reliable and reproducible quantification the kinetic modeling methods used to obtain relevant parameters of radiotracer tissue interaction are important. Here we present different kinetic modeling techniques with a focus on compartmental models including plasma input models and reference tissue input models. The experimental challenges of deriving the plasma input function in rodents and the effect of anesthesia are discussed. Finally, in vivo application of kinetic modeling in various areas of pre-clinical research is presented and compared to human data.

Investigation of transfer parameters from the radiochromium on erythrocyte kinetic

International Nuclear Information System (INIS)

Tavares, J.L.M.

1980-01-01

This study analyzes and interprets results of destruction and survival data from 51 Cr labeled red cells to the more common and realistic situations for diagnostic applications in clinical and nuclear hematology. The destructive process and the deviation of the cell system from the equilibrium state can be conveniently studied in terms of the disappearance rate of labeled red blood cells, using some transfer parameters. The investigation was concentrated on selection and study of a mathematical model to describe significantly the elimination process and to improve and simplify the computational analysis of data in chromium erythrokinetics from patients and normal individuals for control. (author)

Quantum correlations responsible for remote state creation: strong and weak control parameters

Science.gov (United States)

Doronin, S. I.; Zenchuk, A. I.

2017-03-01

We study the quantum correlations between the two remote qubits (sender and receiver) connected by the transmission line (homogeneous spin-1/2 chain) depending on the parameters of the sender's and receiver's initial states (control parameters). We consider two different measures of quantum correlations: the entanglement (a traditional measure) and the informational correlation (based on the parameter exchange between the sender and receiver). We find the domain in the control parameter space yielding (i) zero entanglement between the sender and receiver during the whole evolution period and (ii) non-vanishing informational correlation between the sender and receiver, thus showing that the informational correlation is responsible for the remote state creation. Among the control parameters, there are the strong parameters (which strongly effect the values of studied measures) and the weak ones (whose effect is negligible), therewith the eigenvalues of the initial state are given a privileged role. We also show that the problem of small entanglement (concurrence) in quantum information processing is similar (in certain sense) to the problem of small determinants in linear algebra. A particular model of 40-node spin-1/2 communication line is presented.

Parameter and State Estimation of Large-Scale Complex Systems Using Python Tools

Directory of Open Access Journals (Sweden)

M. Anushka S. Perera

2015-07-01

Full Text Available This paper discusses the topics related to automating parameter, disturbance and state estimation analysis of large-scale complex nonlinear dynamic systems using free programming tools. For large-scale complex systems, before implementing any state estimator, the system should be analyzed for structural observability and the structural observability analysis can be automated using Modelica and Python. As a result of structural observability analysis, the system may be decomposed into subsystems where some of them may be observable --- with respect to parameter, disturbances, and states --- while some may not. The state estimation process is carried out for those observable subsystems and the optimum number of additional measurements are prescribed for unobservable subsystems to make them observable. In this paper, an industrial case study is considered: the copper production process at Glencore Nikkelverk, Kristiansand, Norway. The copper production process is a large-scale complex system. It is shown how to implement various state estimators, in Python, to estimate parameters and disturbances, in addition to states, based on available measurements.

Ensemble Kinetic Modeling of Metabolic Networks from Dynamic Metabolic Profiles

Directory of Open Access Journals (Sweden)

Gengjie Jia

2012-11-01

Full Text Available Kinetic modeling of metabolic pathways has important applications in metabolic engineering, but significant challenges still remain. The difficulties faced vary from finding best-fit parameters in a highly multidimensional search space to incomplete parameter identifiability. To meet some of these challenges, an ensemble modeling method is developed for characterizing a subset of kinetic parameters that give statistically equivalent goodness-of-fit to time series concentration data. The method is based on the incremental identification approach, where the parameter estimation is done in a step-wise manner. Numerical efficacy is achieved by reducing the dimensionality of parameter space and using efficient random parameter exploration algorithms. The shift toward using model ensembles, instead of the traditional “best-fit” models, is necessary to directly account for model uncertainty during the application of such models. The performance of the ensemble modeling approach has been demonstrated in the modeling of a generic branched pathway and the trehalose pathway in Saccharomyces cerevisiae using generalized mass action (GMA kinetics.

Conformational Diffusion and Helix Formation Kinetics

International Nuclear Information System (INIS)

Hummer, Gerhard; Garcia, Angel E.; Garde, Shekhar

2000-01-01

The time, temperature, and sequence dependences of helix formation kinetics of fully atomistic peptide models in explicit solvent are described quantitatively by a diffusive search within the coil state with barrierless transitions into the helical state. Conformational diffusion leads to nonexponential kinetics and jump-width dependences in temperature jump experiments. (c) 2000 The American Physical Society

Conformational Diffusion and Helix Formation Kinetics

Energy Technology Data Exchange (ETDEWEB)

Hummer, Gerhard [Laboratory of Chemical Physics, Building 5, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States); Garcia, Angel E. [Theoretical Biology and Biophysics Group T-10, MS K710, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Garde, Shekhar [Department of Chemical Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States)

2000-09-18

The time, temperature, and sequence dependences of helix formation kinetics of fully atomistic peptide models in explicit solvent are described quantitatively by a diffusive search within the coil state with barrierless transitions into the helical state. Conformational diffusion leads to nonexponential kinetics and jump-width dependences in temperature jump experiments. (c) 2000 The American Physical Society.

Oxidation Kinetics of Ferritic Alloys in High-Temperature Steam Environments

Science.gov (United States)

Parker, Stephen S.; White, Josh; Hosemann, Peter; Nelson, Andrew

2018-02-01

High-temperature isothermal steam oxidation kinetic parameters of several ferritic alloys were determined by thermogravimetric analysis. The oxidation kinetic constant ( k) was measured as a function of temperature from 900°C to 1200°C. The results show a marked increase in oxidation resistance compared to reference Zircaloy-2, with kinetic constants 3-5 orders of magnitude lower across the experimental temperature range. The results of this investigation supplement previous findings on the properties of ferritic alloys for use as candidate cladding materials and extend kinetic parameter measurements to high-temperature steam environments suitable for assessing accident tolerance for light water reactor applications.

Thermoluminescent kinetic parameters of the perovskite, KMgF{sub 3}, activated with lanthanum; Parametros cineticos termoluminiscentes de la perovskita, KMgF{sub 3}, activada con lantano

Energy Technology Data Exchange (ETDEWEB)

Sepulveda M, F. [ESFM-IPN, 07738 Mexico D.F. (Mexico); Azorin N, J.; Rivera M, T. [UAM-I, 09340 Mexico D.F. (Mexico); Furetta, C.; Sanipoli, C. [Physics Department, Universita di Roma ' ' La Sapienza' ' , Piazzale A. Moro 2, 00185 Roma (Italy)

2004-07-01

The thermoluminescent curves induced by the beta radiation in the perovskite KMgF{sub 3} were investigated activated with lanthanum. The classic methods were used to determine the kinetic parameters (the kinetic order b, the activation energy E and the frequency of escape intent s) associated with the peaks of the thermoluminescent curve (Tl) in the KMgF{sub 3} activated with lanthanum after the irradiation with beta rays. The method is based on the position of the thermoluminescent peaks, obtained of the temperature change of the peak in the maximum emission caused by the change in the heating rapidity to which the samples were measured. In this work, the samples in form of pellets were re cooked previously at 400 C during one hour before irradiating them with beta particles. The Tl measures were made with a Tl reader system using three different heating rapidities and storing the glow curves. To calculate the depth of the E traps and the frequency factor s, the parameters of the glow curve were determined experimentally of the shame of the glow curve by means of the mensuration of the shame of the maximum temperature of the peak, T{sub M} like a function of the heating rapidity. The results indicate that the values of the kinetic parameters are very near among if when they are obtained indistinctly of anyone of the different methods. (Author)

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

International Nuclear Information System (INIS)

Pavlovitchev, A.M.

2000-01-01

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

Tantalum high-temperature oxidation kinetics

International Nuclear Information System (INIS)

Grigor'ev, Yu.M.; Sarkisyan, A.A.; Merzhanov, A.G.

1981-01-01

Kinetics of heat release and scale growth during tantalum oxidation within 650-1300 deg C temperature range in oxygen-containing media is investigated. Kinetic equations and temperature and pressure dependences of constants are ound Applicability of the kinetic Lorie mechanism for the description of the tantalum oxidation kinetics applicably to rapid-passing processes is shown. It is stated that the process rate (reaction ability) is determined by adsorption desorption factors on the external surface of the ''protective'' oxide for the ''linear'' oxidation stage [ru

Noise-Induced Modulation of the Relaxation Kinetics around a Non-Equilibrium Steady State of Non-Linear Chemical Reaction Networks

OpenAIRE

Ramaswamy, Rajesh; Sbalzarini, Ivo F; González-Segredo, Nélido

2011-01-01

Stochastic effects from correlated noise non-trivially modulate the kinetics of non-linear chemical reaction networks. This is especially important in systems where reactions are confined to small volumes and reactants are delivered in bursts. We characterise how the two noise sources confinement and burst modulate the relaxation kinetics of a non-linear reaction network around a non-equilibrium steady state. We find that the lifetimes of species change with burst input and confinement. Confi...

Development of Kinetics for Soot Oxidation at High Pressures Under Fuel-Lean Conditions

Energy Technology Data Exchange (ETDEWEB)

Lighty, JoAnn [Univ. of Utah, Salt Lake City, UT (United States); Vander Wal, Randy [Pennsylvania State Univ., University Park, PA (United States)

2014-04-21

The focus of the proposed research was to develop kinetic models for soot oxidation with the hope of developing a validated, predictive, multi-­scale, combustion model to optimize the design and operation of evolving fuels in advanced engines for transportation applications. The work focused on the relatively unstudied area of the fundamental mechanism for soot oxidation. The objectives include understanding of the kinetics of soot oxidation by O2 under high pressure which require: 1) development of intrinsic kinetics for the surface oxidation, which takes into account the dependence of reactivity upon nanostructure and 2) evolution of nanostructure and its impact upon oxidation rate and 3) inclusion of internal surface area development and possible fragmentation resulting from pore development and /or surface oxidation. These objectives were explored for a variety of pure fuel components and surrogate fuels. This project was a joint effort between the University of Utah (UU) and Pennsylvania State University (Penn State). The work at the UU focuses on experimental studies using a two-­stage burner and a high- pressure thermogravimetric analyzer (TGA). Penn State provided HRTEM images and guidance in the fringe analysis algorithms and parameter quantification for the images. This report focuses on completion done under supplemental funding.

A Poisson-like closed-form expression for the steady-state wealth distribution in a kinetic model of gambling

Science.gov (United States)

Garcia, Jane Bernadette Denise M.; Esguerra, Jose Perico H.

2017-08-01

An approximate but closed-form expression for a Poisson-like steady state wealth distribution in a kinetic model of gambling was formulated from a finite number of its moments, which were generated from a βa,b(x) exchange distribution. The obtained steady-state wealth distributions have tails which are qualitatively similar to those observed in actual wealth distributions.

Kinetic parameters of protein metabolism in rats during protein-free feeding

International Nuclear Information System (INIS)

Krawielitzki, K.; Schadereit, R.; Wuensche, J.

1987-01-01

16 male rats of 100 g live weight were given 50 mg of a mixture containing 15 N-labelled amino acids as a single dose within a protein-free feeding period. Following this the 15 N excretion in feces and urine as well as the development of the 15 N excess in different organs and tissues were estimated over 3 days by slaughtering the animals within given 7 time intervals. Using a 3 pool model and the computer program for the interpretation of 15 N tracer experiments by Toewe et al. (1984), kinetic parameters such as the rate of protein synthesis, protein breakdown and the rate of reutilization were calculated. Despite a negative N balance (- 41.8 mg N/d) under protein-free conditions the protein metabolism of the rat shows high dynamics characterized by a high flux rate (225 mg N/d) and a high rate of body protein synthesis (181 mg/d). The reutilization was 85 %. Depending on time the 15 N excess in the tested organs and tissues showed significant differences and seems to demonstrate that under these conditions protein synthesis mainly takes place in the most important organs (e.g. intestinal tract, liver). Under protein-free feeding conditions protein synthesis and protein breakdown of the whole body seems to be slightly increased in comparison to N balanced feeding conditions. (author)

Studies of ruthenium complexes, 8. Kinetic studies of the thermal substitution reaction of hexaammine and cis--dihalogenotetraammineruthenium(III) complexes in the solid state

Energy Technology Data Exchange (ETDEWEB)

Ohyoshi, A; Hiraki, S; Odate, T; Kohata, S; Oda, J [Kumamoto Univ. (Japan). Faculty of Engineering

1975-01-01

The kinetics of the thermal substitution reaction of hexaamineruthenium (III) halides and cis-dihalogenotetraamineruthenium (III) halides have been studied in the solid state. The reaction rates and kinetic parameters were determined for these two reactions; (Ru(NH/sub 3/)/sub 6/)X/sub 3/..-->..(RuX(NH/sub 3/)/sub 5/)X/sub 2/+NH/sub 3/, (X=Br, I) and cis - (RuX/sub 2/(NH/sub 3/)/sub 4/)X..-->..(RuX/sub 3/(NH/sub 3/)/sub 3/)+NH/sub 3/, (X=Cl, Br). The values of the rate constant, the activation energy, and the activation entropy were 2.10x10/sup -5/ s/sup -1/ (at 161/sup 0/C), 23.2 kcal mol/sup -1/, and -29.3 e.u. for the hexaamine bromide, and 2.92x10/sup -5/ s/sup -1/ (at 162/sup 0/C), 31.3 kcal mol/sup -1/, and -10.1 e.u. for the cis-dibromotetraamine bromide. The Ssub(N)2 mechanism is more probable for the former reaction, while the Ssub(N)1 mechanism is more probable for the latter reaction.

Path dependent magnetic states and evidence of kinetically arrested states in Nd doped LaFe{sub 11.5}Al{sub 1.5}

Energy Technology Data Exchange (ETDEWEB)

Bag, Pallab; Nath, R., E-mail: rnath@iisertvm.ac.in

2017-03-15

First order antiferromagnetic to ferromagnetic transition and path dependent magnetic states in La{sub 1−x}Nd{sub x}Fe{sub 11.5}Al{sub 1.5} for x∼0.1 are studied at low temperatures via powder x-ray diffraction, magnetization, and specific heat measurements. X-ray diffraction measurements suggest that around 8% of high temperature antiferromagnetic phase is converted to ferromagnetic phase at low temperatures in zero field cooling. A systematic study of temperature and magnetic field dependent magnetization measurements show a non-monotonic variation of upper critical field and re-entrant antiferromagnetic-ferromagnetic-antiferromagnetic transition while warming at an applied magnetic field under zero-field-cooled condition. This has been interpreted in the framework of kinetic arrest model for first order magnetic transition. It is also found that the antiferromagnetic phase is in the non-equilibrium state and behaves as a glass-like magnetic state at low temperatures. The specific heat in field-temperature space is studied and found to have a lower electronic contribution for the non-equilibrium antiferromagnetic state, compared to the equilibrium ferromagnetic state in this compound. - Highlights: • Structural and magnetic properties of La{sub 0.9}Nd{sub 0.1}Fe{sub 11.5}Al{sub 1.5} are investigated. • It shows coexistence and path dependent AFM and FM phases at low temperatures. • The AFM and FM phase fractions were estimated from the x-ray diffraction pattern. • Re-entrant transition and a non-monotonic variation of upper critical field. • The glass like AFM state is explained by the kinetic arrest model.

Parameter Estimation

DEFF Research Database (Denmark)

Sales-Cruz, Mauricio; Heitzig, Martina; Cameron, Ian

2011-01-01

of optimisation techniques coupled with dynamic solution of the underlying model. Linear and nonlinear approaches to parameter estimation are investigated. There is also the application of maximum likelihood principles in the estimation of parameters, as well as the use of orthogonal collocation to generate a set......In this chapter the importance of parameter estimation in model development is illustrated through various applications related to reaction systems. In particular, rate constants in a reaction system are obtained through parameter estimation methods. These approaches often require the application...... of algebraic equations as the basis for parameter estimation.These approaches are illustrated using estimations of kinetic constants from reaction system models....

A Comprehensive Enzyme Kinetic Exercise for Biochemistry

Science.gov (United States)

Barton, Janice S.

2011-01-01

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…

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-04-19

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.

Effect of Temperature and pH on Formulating the Kinetic Growth Parameters and Lactic Acid Production of Lactobacillus bulgaricus

Directory of Open Access Journals (Sweden)

Marzieh Aghababaie

2014-09-01

Results: Second order model for Xmax, μmax, P and K was significant but product formation parameters were almost constant. The optimum values of temperature and pH for attaining maximum biomass, maximum specific growth rate, and maximum acid production were obtained at 44 °C and 5.7, respectively. Conclusions: The attained empirical mathematical correlations of RSM alongside the kinetic equations could be used to determine growth conditions under predefined temperature and pH in the fermentation process. Keywords: Lactobacillus bulgaricus, Richards model, Response surface methodology, Lactic acid production, Luedeking-Piret model

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

DEFF Research Database (Denmark)

Tofts, P.S.; Brix, G; Buckley, D.L.

1999-01-01

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K......-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer...

Growth kinetic and fuel quality parameters as selective criterion for screening biodiesel producing cyanobacterial strains.

Science.gov (United States)

Gayathri, Manickam; Shunmugam, Sumathy; Mugasundari, Arumugam Vanmathi; Rahman, Pattanathu K S M; Muralitharan, Gangatharan

2018-01-01

The efficiency of cyanobacterial strains as biodiesel feedstock varies with the dwelling habitat. Fourteen indigenous heterocystous cyanobacterial strains from rice field ecosystem were screened based on growth kinetic and fuel parameters. The highest biomass productivity was obtained in Nostoc punctiforme MBDU 621 (19.22mg/L/day) followed by Calothrix sp. MBDU 701 (13.43mg/L/day). While lipid productivity and lipid content was highest in Nostoc spongiaeforme MBDU 704 (4.45mg/L/day and 22.5%dwt) followed by Calothrix sp. MBDU 701 (1.54mg/L/day and 10.75%dwt). Among the tested strains, Nostoc spongiaeforme MBDU 704 and Nostoc punctiforme MBDU 621 were selected as promising strains for good quality biodiesel production by Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE) and Graphical Analysis for Interactive Assistance (GAIA) analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Kinetics of photochromic processes in substituted dihydropyridines in the solid state and in solution

Czech Academy of Sciences Publication Activity Database

Sworakowski, J.; Nešpůrek, Stanislav; Lipinski, J.; Lewanowicz, A.; Sliwinska, E.

2001-01-01

Roč. 356, - (2001), s. 163-173 ISSN 1058-725X. [International Conference on the Chemistry of the Organic Solid State /14./. Cambridge, 25.07.1999-30.07.1999] R&D Projects: GA AV ČR IAA1050901; GA AV ČR KSK4050111 Institutional research plan: CEZ:AV0Z4050913 Keywords : dihydropyridine * photochromism * reaction kinetics Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.457, year: 2001

Size dependence of adsorption kinetics of nano-MgO: a theoretical and experimental study

International Nuclear Information System (INIS)

Wang, Shuting; Wen, Yanzhen; Cui, Zixiang; Xue, Yongqiang

2016-01-01

Nanoparticles present tremendous differences in adsorption kinetics compared with corresponding bulk particles which have great influences on the applications of nanoparticles. A size-dependent adsorption kinetic theory was proposed, the relations between adsorption kinetic parameters, respectively, and particle size of nano-adsorbent were derived theoretically, and the influence mechanism of particle size on the adsorption kinetic parameters was discussed. In experiment, nanoscale magnesium oxide (nano-MgO) with different diameters between 11.5 and 41.4 nm with narrow size distribution and low agglomeration were prepared, and the kinetic parameters of adsorption of benzene on nano-MgO in aqueous solution were obtained. Then the influence regularities of the particle size on the adsorption kinetic parameters were obtained. The experimental results are consistent with the nano-adsorption kinetic theory. With particle size decreasing, the adsorption rate constant increases; the adsorption activation energy and the adsorption pre-exponential factor decrease. Furthermore, the logarithm of adsorption rate constant, the adsorption activation energy, and the logarithm of adsorption pre-exponential factor are linearly related to the reciprocal of particle diameter, respectively. The mechanism of particle size influence on the kinetic parameters is that the activation energy is influenced by the molar surface enthalpy of nano-adsorbent, the pre-exponential factor by the molar surface entropy, and the rate constant by both the molar surface enthalpy and the molar surface entropy

Moisture removal of paddy by agricultural residues: basic physical parameters and drying kinetics modeling

Directory of Open Access Journals (Sweden)

Saniso, E.

2007-05-01

Full Text Available The objectives of this research were to study basic physical parameters of three agricultural residues that could be used for prediction of paddy drying kinetics using desiccants, to investigate a suitable methodfor moisture reduction of fresh paddy using 3 absorbents, and to modify the drying model of Inoue et al. for determining the evolution of moisture transfer during the drying period. Rice husk, sago palm rachis andcoconut husk were used as moisture desiccants in these experiments. From the results, it was concluded that the apparent density of all adsorbents was a linear function of moisture content whilst an equilibriummoisture content equation following Hendersonís model gave the best fit to the experimental results. From studying the relationship between moisture ratio and drying time under the condition of drying temperaturesof 30, 50 and 70oC, air flow rate of 1.6 m/s and initial moisture content of absorbents of 15, 20 and 27% dry-basis, it was shown that the moisture ratio decreased when drying time increased. In addition, thethin-layer desiccant drying equation following of the Page model can appropriately explain the evolution of moisture content of paddy over the drying time. The diffusion coefficient of all absorbents, which was in therange of 1x10-8 to 6x10-8 m2/h, was relatively dependent on drying temperature and inversely related to drying time. The diffusivity of coconut husk had the highest value compared to the other absorbents.The simulating modified mathematical model to determine drying kinetics of paddy using absorption technique and the simulated results had good relation to the experimental results for all adsorbents.

Chemical kinetics and reaction mechanism

International Nuclear Information System (INIS)

Jung, Ou Sik; Park, Youn Yeol

1996-12-01

This book is about chemical kinetics and reaction mechanism. It consists of eleven chapters, which deal with reaction and reaction speed on reaction mechanism, simple reaction by rate expression, reversible reaction and simultaneous reaction, successive reaction, complicated reaction mechanism, assumption for reaction mechanism, transition state theory, successive reaction and oscillating reaction, reaction by solution, research method high except kinetics on reaction mechanism, high reaction of kinetics like pulsed radiolysis.

Inflationary dynamics of kinetically-coupled gauge fields

DEFF Research Database (Denmark)

Ferreira, Ricardo J. Z.; Ganc, Jonathan

2015-01-01

We investigate the inflationary dynamics of two kinetically-coupled massless U(1) gauge fields with time-varying kinetic-term coefficients. Ensuring that the system does not have strongly coupled regimes shrinks the parameter space. Also, we further restrict ourselves to systems that can be quant......We investigate the inflationary dynamics of two kinetically-coupled massless U(1) gauge fields with time-varying kinetic-term coefficients. Ensuring that the system does not have strongly coupled regimes shrinks the parameter space. Also, we further restrict ourselves to systems that can...... be quantized using the standard creation, annihilation operator algebra. This second constraint limits us to scenarios where the system can be diagonalized into the sum of two decoupled, massless, vector fields with a varying kinetic-term coefficient. Such a system might be interesting for magnetogenesis...... because of how the strong coupling problem generalizes. We explore this idea by assuming that one of the gauge fields is the Standard Model U(1) field and that the other dark gauge field has no particles charged under its gauge group. We consider whether it would be possible to transfer a magnetic field...

Microscopic theory of warm ionized gases: equation of state and kinetic Schottky anomaly

International Nuclear Information System (INIS)

Capolupo, A; Giampaolo, S M; Illuminati, F

2013-01-01

Based on accurate Lennard-Jones type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analogue in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed.

Evaluation for Bearing Wear States Based on Online Oil Multi-Parameters Monitoring

Science.gov (United States)

Hu, Hai-Feng

2018-01-01

As bearings are critical components of a mechanical system, it is important to characterize their wear states and evaluate health conditions. In this paper, a novel approach for analyzing the relationship between online oil multi-parameter monitoring samples and bearing wear states has been proposed based on an improved gray k-means clustering model (G-KCM). First, an online monitoring system with multiple sensors for bearings is established, obtaining oil multi-parameter data and vibration signals for bearings through the whole lifetime. Secondly, a gray correlation degree distance matrix is generated using a gray correlation model (GCM) to express the relationship of oil monitoring samples at different times and then a KCM is applied to cluster the matrix. Analysis and experimental results show that there is an obvious correspondence that state changing coincides basically in time between the lubricants’ multi-parameters and the bearings’ wear states. It also has shown that online oil samples with multi-parameters have early wear failure prediction ability for bearings superior to vibration signals. It is expected to realize online oil monitoring and evaluation for bearing health condition and to provide a novel approach for early identification of bearing-related failure modes. PMID:29621175

Maximizing kinetic performance in supercritical fluid chromatography using state-of-the-art instruments.

Science.gov (United States)

Grand-Guillaume Perrenoud, Alexandre; Hamman, Chris; Goel, Meenakshi; Veuthey, Jean-Luc; Guillarme, Davy; Fekete, Szabolcs

2013-11-01

Recently, there has been a renewed interest in supercritical fluid chromatography (SFC), due to the introduction of state-of-the-art instruments and dedicated columns packed with small particles. However, the achievable kinetic performance and practical possibilities of such modern SFC instruments and columns has not been described in details until now. The goal of the present contribution was to provide some information about the optimal column dimensions (i.e. length, diameter and particle size) suitable for such state-of the-art systems, with respect to extra-column band broadening and system upper pressure limit. In addition, the reliability of the kinetic plot methodology, successfully applied in RPLC, was also evaluated under SFC conditions. Taking into account the system variance, measured at ∼85μL(2), on modern SFC instruments, a column of 3mm I.D. was ideally suited for the current technology, as the loss in efficiency remained reasonable (i.e. less than 10% decrease for k>6). Conversely, these systems struggle with 2.1mm I.D. columns (55% loss in N for k=5). Regarding particle size, columns packed with 5μm particles provided unexpectedly high minimum reduced plate height values (hmin=3.0-3.4), while the 3.5 and 1.7μm packing provided lower reduced plate heights hmin=2.2-2.4 and hmin=2.7-3.2, respectively. Considering the system upper pressure limit, it appears that columns packed with 1.7μm particles give the lowest analysis time for efficiencies up to 40,000-60,000 plates, if the mobile phase composition is in the range of 2-19% MeOH. The 3.5μm particles were attractive for higher efficiencies, particularly when the modifier percentage was above 20%, while 5μm was never kinetically relevant with modern SFC instruments, due to an obvious limitation in terms of upper flow rate value. The present work also confirms that the kinetic plot methodology could be successfully applied to SFC, without the need for isopycnic measurements, as the difference

Rescaling of three-parameter equations of state: PC-SAFT and SPHCT

DEFF Research Database (Denmark)

Cismondi, Martin; Brignole, Esteban A.; Mollerup, Jørgen

2005-01-01

Two-parameter equations of state like PR or SRK predict a universal critical compressibility, factor for pure compounds, being intrinsically unable to reasonably describe the PVT properties of different fluids and their asymmetric mixtures, which require at least three component specific paramete...

Erbium hydride decomposition kinetics.

Energy Technology Data Exchange (ETDEWEB)

Ferrizz, Robert Matthew

2006-11-01

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

Uniqueness of thermodynamic projector and kinetic basis of molecular individualism

Science.gov (United States)

Gorban, Alexander N.; Karlin, Iliya V.

2004-05-01

Three results are presented: First, we solve the problem of persistence of dissipation for reduction of kinetic models. Kinetic equations with thermodynamic Lyapunov functions are studied. Uniqueness of the thermodynamic projector is proven: There exists only one projector which transforms any vector field equipped with the given Lyapunov function into a vector field with the same Lyapunov function for a given anzatz manifold which is not tangent to the Lyapunov function levels. Second, we use the thermodynamic projector for developing the short memory approximation and coarse-graining for general nonlinear dynamic systems. We prove that in this approximation the entropy production increases. ( The theorem about entropy overproduction.) In example, we apply the thermodynamic projector to derive the equations of reduced kinetics for the Fokker-Planck equation. A new class of closures is developed, the kinetic multipeak polyhedra. Distributions of this type are expected in kinetic models with multidimensional instability as universally as the Gaussian distribution appears for stable systems. The number of possible relatively stable states of a nonequilibrium system grows as 2 m, and the number of macroscopic parameters is in order mn, where n is the dimension of configuration space, and m is the number of independent unstable directions in this space. The elaborated class of closures and equations pretends to describe the effects of “molecular individualism”. This is the third result.

Biodegradation of phenol with chromium(VI) reduction in an anaerobic fixed-biofilm process-Kinetic model and reactor performance

International Nuclear Information System (INIS)

Lin, Yen-Hui; Wu, Chih-Lung; Hsu, Chih-Hao; Li, Hsin-Lung

2009-01-01

A mathematical model system was derived to describe the simultaneous removal of phenol biodegradation with chromium(VI) reduction in an anaerobic fixed-biofilm reactor. The model system incorporates diffusive mass transport and double Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A laboratory-scale column reactor was employed to validate the kinetic model system. Batch kinetic tests were conducted independently to evaluate the biokinetic parameters used in the model simulation. The removal efficiencies of phenol and chromium(VI) in an anaerobic fixed-biofilm process were approximately 980 mg/g and 910 mg/g, respectively, under a steady-state condition. In the steady state, model-predicted biofilm thickness reached up to 350 μm and suspended cells in the effluent were 85 mg cell/l. The experimental results agree closely with the results of the model simulations.

Study on the agglomeration kinetics of uranium peroxide

International Nuclear Information System (INIS)

Bertrand, M.; Mojica Rodriguez, L.A.; Muhr, H.; Plasari, E.; Auger, F.

2016-01-01

Considering the previous study dealing with thermodynamic and kinetic phenomena (nucleation and crystal growth) during the uranium peroxide precipitation, this work focuses on the agglomeration mechanism. It provides the results obtained from the experiments carried out in a mixed suspension - mixed product removal (MSMPR) mixer operating at steady state. The influence of the operating parameters on the uranium peroxide agglomerates was studied in order to identify the agglomeration kernel. The method is based on the resolution of the population balance equation using the method of moments and the experimental particle size distributions. The results lead to a size-independent kernel directly proportional to the crystal growth rate. Under the stirring conditions studied, the agglomeration appears to be significantly reduced by mixing which results in a kernel inversely proportional to the average shear rate. The agglomeration kinetic law obtained in this study will be used for the process modelling in a further study. (authors)

Study on the agglomeration kinetics of uranium peroxide

Energy Technology Data Exchange (ETDEWEB)

Bertrand, M.; Mojica Rodriguez, L.A. [CEA, Centre de Marcoule, Nuclear Energy Division, RadioChemistry and Process Department, 17171, Bagnols-sur-Ceze 30207 (France); Muhr, H.; Plasari, E. [Reaction and Process Engineering Laboratory, CNRS, University of Lorraine. 1 rue Grandville, BP 20451, Nancy 54001 (France); Auger, F. [Areva Mines/SEPA. 2 route de Lavaugrasse, Bessines-sur-Gartempe 87250 (France)

2016-07-01

Considering the previous study dealing with thermodynamic and kinetic phenomena (nucleation and crystal growth) during the uranium peroxide precipitation, this work focuses on the agglomeration mechanism. It provides the results obtained from the experiments carried out in a mixed suspension - mixed product removal (MSMPR) mixer operating at steady state. The influence of the operating parameters on the uranium peroxide agglomerates was studied in order to identify the agglomeration kernel. The method is based on the resolution of the population balance equation using the method of moments and the experimental particle size distributions. The results lead to a size-independent kernel directly proportional to the crystal growth rate. Under the stirring conditions studied, the agglomeration appears to be significantly reduced by mixing which results in a kernel inversely proportional to the average shear rate. The agglomeration kinetic law obtained in this study will be used for the process modelling in a further study. (authors)

Visual evaluation of kinetic characteristics of PET probe for neuroreceptors using a two-phase graphic plot analysis.

Science.gov (United States)

Ito, Hiroshi; Ikoma, Yoko; Seki, Chie; Kimura, Yasuyuki; Kawaguchi, Hiroshi; Takuwa, Hiroyuki; Ichise, Masanori; Suhara, Tetsuya; Kanno, Iwao

2017-05-01

Objectives In PET studies for neuroreceptors, tracer kinetics are described by the two-tissue compartment model (2-TCM), and binding parameters, including the total distribution volume (V T ), non-displaceable distribution volume (V ND ), and binding potential (BP ND ), can be determined from model parameters estimated by kinetic analysis. The stability of binding parameter estimates depends on the kinetic characteristics of radioligands. To describe these kinetic characteristics, we previously developed a two-phase graphic plot analysis in which V ND and V T can be estimated from the x-intercept of regression lines for early and delayed phases, respectively. In this study, we applied this graphic plot analysis to visual evaluation of the kinetic characteristics of radioligands for neuroreceptors, and investigated a relationship between the shape of these graphic plots and the stability of binding parameters estimated by the kinetic analysis with 2-TCM in simulated brain tissue time-activity curves (TACs) with various binding parameters. Methods 90-min TACs were generated with the arterial input function and assumed kinetic parameters according to 2-TCM. Graphic plot analysis was applied to these simulated TACs, and the curvature of the plot for each TAC was evaluated visually. TACs with several noise levels were also generated with various kinetic parameters, and the bias and variation of binding parameters estimated by kinetic analysis were calculated in each TAC. These bias and variation were compared with the shape of graphic plots. Results The graphic plots showed larger curvature for TACs with higher specific binding and slower dissociation of specific binding. The quartile deviations of V ND and BP ND determined by kinetic analysis were smaller for radioligands with slow dissociation. Conclusions The larger curvature of graphic plots for radioligands with slow dissociation might indicate a stable determination of V ND and BP ND by kinetic analysis. For

Exploiting intrinsic fluctuations to identify model parameters.

Science.gov (United States)

Zimmer, Christoph; Sahle, Sven; Pahle, Jürgen

2015-04-01

Parameterisation of kinetic models plays a central role in computational systems biology. Besides the lack of experimental data of high enough quality, some of the biggest challenges here are identification issues. Model parameters can be structurally non-identifiable because of functional relationships. Noise in measured data is usually considered to be a nuisance for parameter estimation. However, it turns out that intrinsic fluctuations in particle numbers can make parameters identifiable that were previously non-identifiable. The authors present a method to identify model parameters that are structurally non-identifiable in a deterministic framework. The method takes time course recordings of biochemical systems in steady state or transient state as input. Often a functional relationship between parameters presents itself by a one-dimensional manifold in parameter space containing parameter sets of optimal goodness. Although the system's behaviour cannot be distinguished on this manifold in a deterministic framework it might be distinguishable in a stochastic modelling framework. Their method exploits this by using an objective function that includes a measure for fluctuations in particle numbers. They show on three example models, immigration-death, gene expression and Epo-EpoReceptor interaction, that this resolves the non-identifiability even in the case of measurement noise with known amplitude. The method is applied to partially observed recordings of biochemical systems with measurement noise. It is simple to implement and it is usually very fast to compute. This optimisation can be realised in a classical or Bayesian fashion.

Identifyability measures to select the parameters to be estimated in a solid-state fermentation distributed parameter model.

Science.gov (United States)

da Silveira, Christian L; Mazutti, Marcio A; Salau, Nina P G

2016-07-08

Process modeling can lead to of advantages such as helping in process control, reducing process costs and product quality improvement. This work proposes a solid-state fermentation distributed parameter model composed by seven differential equations with seventeen parameters to represent the process. Also, parameters estimation with a parameters identifyability analysis (PIA) is performed to build an accurate model with optimum parameters. Statistical tests were made to verify the model accuracy with the estimated parameters considering different assumptions. The results have shown that the model assuming substrate inhibition better represents the process. It was also shown that eight from the seventeen original model parameters were nonidentifiable and better results were obtained with the removal of these parameters from the estimation procedure. Therefore, PIA can be useful to estimation procedure, since it may reduce the number of parameters that can be evaluated. Further, PIA improved the model results, showing to be an important procedure to be taken. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:905-917, 2016. © 2016 American Institute of Chemical Engineers.

Kinetic equations in dirty superconductors

International Nuclear Information System (INIS)

Kraehenbuehl, Y.

1981-01-01

Kinetic equations for superconductors in the dirty limit are derived using a method developed for superfluid systems, which allows a systematic expansion in small parameters; exact charge conservation is obeyed. (orig.)

Numerical simulations of subcritical reactor kinetics in thermal hydraulic transient phases

Energy Technology Data Exchange (ETDEWEB)

Yoo, J; Park, W S [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1999-12-31

A subcritical reactor driven by a linear proton accelerator has been considered as a nuclear waste incinerator at Korea Atomic Energy Research Institute (KAERI). Since the multiplication factor of a subcritical reactor is less than unity, to compensate exponentially decreasing fission neutrons, external neutrons form spallation reactions are essentially required for operating the reactor in its steady state. Furthermore, the profile of accelerator beam currents is very important in controlling a subcritical reactor, because the reactor power varies in accordance to the profile of external neutrons. We have developed a code system to find numerical solutions of reactor kinetics equations, which are the simplest dynamic model for controlling reactors. In a due course of our previous numerical study of point kinetics equations for critical reactors, however, we learned that the same code system can be used in studying dynamic behavior of the subcritical reactor. Our major motivation of this paper is to investigate responses of subcritical reactors for small changes in thermal hydraulic parameters. Building a thermal hydraulic model for the subcritical reactor dynamics, we performed numerical simulations for dynamic responses of the reactor based on point kinetics equations with a source term. Linearizing a set of coupled differential equations for reactor responses, we focus our research interest on dynamic responses of the reactor to variations of the thermal hydraulic parameters in transient phases. 5 refs., 8 figs. (Author)

Numerical simulations of subcritical reactor kinetics in thermal hydraulic transient phases

Energy Technology Data Exchange (ETDEWEB)

Yoo, J.; Park, W. S. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1998-12-31

A subcritical reactor driven by a linear proton accelerator has been considered as a nuclear waste incinerator at Korea Atomic Energy Research Institute (KAERI). Since the multiplication factor of a subcritical reactor is less than unity, to compensate exponentially decreasing fission neutrons, external neutrons form spallation reactions are essentially required for operating the reactor in its steady state. Furthermore, the profile of accelerator beam currents is very important in controlling a subcritical reactor, because the reactor power varies in accordance to the profile of external neutrons. We have developed a code system to find numerical solutions of reactor kinetics equations, which are the simplest dynamic model for controlling reactors. In a due course of our previous numerical study of point kinetics equations for critical reactors, however, we learned that the same code system can be used in studying dynamic behavior of the subcritical reactor. Our major motivation of this paper is to investigate responses of subcritical reactors for small changes in thermal hydraulic parameters. Building a thermal hydraulic model for the subcritical reactor dynamics, we performed numerical simulations for dynamic responses of the reactor based on point kinetics equations with a source term. Linearizing a set of coupled differential equations for reactor responses, we focus our research interest on dynamic responses of the reactor to variations of the thermal hydraulic parameters in transient phases. 5 refs., 8 figs. (Author)

Hot kinetic model as a guide to improve organic photovoltaic materials.

Science.gov (United States)

Sosorev, Andrey Yu; Godovsky, Dmitry Yu; Paraschuk, Dmitry Yu

2018-01-31

The modeling of organic solar cells (OSCs) can provide a roadmap for their further improvement. Many OSC models have been proposed in recent years; however, the impact of the key intermediates from photons to electricity-hot charge-transfer (CT) states-on the OSC efficiency is highly ambiguous. In this study, we suggest an analytical kinetic model for OSC that considers a two-step charge generation via hot CT states. This hot kinetic model allowed us to evaluate the impact of different material parameters on the OSC performance: the driving force for charge separation, optical bandgap, charge mobility, geminate recombination rate, thermalization rate, average electron-hole separation distance in the CT state, dielectric permittivity, reorganization energy and charge delocalization. In contrast to a widespread trend of lowering the material bandgap, the model predicts that this approach is only efficient along with improvement of the other material properties. The most promising ways to increase the OSC performance are decreasing the reorganization energy, i.e., an energy change accompanying CT from the donor molecule to the acceptor, increasing the dielectric permittivity and charge delocalization. The model suggests that there are no fundamental limitations that can prevent achieving the OSC efficiency above 20%.

Kinetic behaviour of low-Co AB5-type metal hydride electrodes

International Nuclear Information System (INIS)

Tliha, M.; Boussami, S.; Mathlouthi, H.; Lamloumi, J.; Percheron-Guegan, A.

2010-01-01

The kinetic behaviour of the LaNi 3.55 Mn 0.4 Al 0.3 Co 0.4 Fe 0.35 metal hydride, used as a negative electrode in the nickel/metal hydride (Ni/MH) batteries, was investigated using electrochemical impedance spectroscopy (EIS) at different state of charge (SOC). Impedance measurements were performed in the frequency range from 50 kHz to 1 mHz. Electrochemical impedance spectrum of the metal hydride electrode was interpreted by an equivalent circuit including the different electrochemical processes taking place on the interface between the MH electrode and the electrolyte. Electrochemical kinetic parameters such as the charge-transfer resistance R tc , the exchange current density I 0 and the hydrogen diffusion coefficient D H were determined at different state of charge. The results of EIS measurements indicate that the electrochemical reaction activity of the LaNi 3.55 Mn 0.4 Al 0.3 Co 0.4 Fe 0.35 metal hydride electrode was markedly improved with increasing state of charge (SOC). The transformation α-β is probably a limiting step in the mechanisms of hydrogenation of metal hydride electrode.

Release of Virus from Lymphoid Tissue Affects Human Immunodeficiency Virus Type 1 and Hepatitis C Virus Kinetics in the Blood

NARCIS (Netherlands)

Müller, Viktor; Marée, Athanasius F.M.; Boer, R.J. de

2000-01-01

Kinetic parameters of human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) infections have been estimated from plasma virus levels following perturbation of the chronically infected (quasi-) steady state. We extend previous models by also considering the large pool of virus

Parameter and state estimation in nonlinear dynamical systems

Science.gov (United States)

Creveling, Daniel R.

This thesis is concerned with the problem of state and parameter estimation in nonlinear systems. The need to evaluate unknown parameters in models of nonlinear physical, biophysical and engineering systems occurs throughout the development of phenomenological or reduced models of dynamics. When verifying and validating these models, it is important to incorporate information from observations in an efficient manner. Using the idea of synchronization of nonlinear dynamical systems, this thesis develops a framework for presenting data to a candidate model of a physical process in a way that makes efficient use of the measured data while allowing for estimation of the unknown parameters in the model. The approach presented here builds on existing work that uses synchronization as a tool for parameter estimation. Some critical issues of stability in that work are addressed and a practical framework is developed for overcoming these difficulties. The central issue is the choice of coupling strength between the model and data. If the coupling is too strong, the model will reproduce the measured data regardless of the adequacy of the model or correctness of the parameters. If the coupling is too weak, nonlinearities in the dynamics could lead to complex dynamics rendering any cost function comparing the model to the data inadequate for the determination of model parameters. Two methods are introduced which seek to balance the need for coupling with the desire to allow the model to evolve in its natural manner without coupling. One method, 'balanced' synchronization, adds to the synchronization cost function a requirement that the conditional Lyapunov exponents of the model system, conditioned on being driven by the data, remain negative but small in magnitude. Another method allows the coupling between the data and the model to vary in time according to a specific form of differential equation. The coupling dynamics is damped to allow for a tendency toward zero coupling

The dependence of fidelity on the squeezing parameter in teleportation of the squeezed coherent states

Institute of Scientific and Technical Information of China (English)

Zhang Jing-Tao; He Guang-Qiang; Ren Li-Jie; Zeng Gui-Hua

2011-01-01

This paper investigates an analytical expression of teleportation fidelity in the teleportation scheme of a single mode of electromagnetic field. The fidelity between the original squeezed coherent state and the teleported one is expressed in terms of the squeezing parameter r and the quantum channel parameter (two-mode squeezed state) p. The results of analysis show that the fidelity increases with the increase of the quantum channel parameter p, while the fidelity decreases with the increase of the squeezing parameter r of the squeezed state. Thus the coherent state (r = 0)is the best quantum signal for continuous variable quantum teleportation once the quantum channel is built.

Kinetics from Replica Exchange Molecular Dynamics Simulations.

Science.gov (United States)

Stelzl, Lukas S; Hummer, Gerhard

2017-08-08

Transitions between metastable states govern many fundamental processes in physics, chemistry and biology, from nucleation events in phase transitions to the folding of proteins. The free energy surfaces underlying these processes can be obtained from simulations using enhanced sampling methods. However, their altered dynamics makes kinetic and mechanistic information difficult or impossible to extract. Here, we show that, with replica exchange molecular dynamics (REMD), one can not only sample equilibrium properties but also extract kinetic information. For systems that strictly obey first-order kinetics, the procedure to extract rates is rigorous. For actual molecular systems whose long-time dynamics are captured by kinetic rate models, accurate rate coefficients can be determined from the statistics of the transitions between the metastable states at each replica temperature. We demonstrate the practical applicability of the procedure by constructing master equation (Markov state) models of peptide and RNA folding from REMD simulations.

Evaluation for Bearing Wear States Based on Online Oil Multi-Parameters Monitoring

Directory of Open Access Journals (Sweden)

Si-Yuan Wang

2018-04-01

Full Text Available As bearings are critical components of a mechanical system, it is important to characterize their wear states and evaluate health conditions. In this paper, a novel approach for analyzing the relationship between online oil multi-parameter monitoring samples and bearing wear states has been proposed based on an improved gray k-means clustering model (G-KCM. First, an online monitoring system with multiple sensors for bearings is established, obtaining oil multi-parameter data and vibration signals for bearings through the whole lifetime. Secondly, a gray correlation degree distance matrix is generated using a gray correlation model (GCM to express the relationship of oil monitoring samples at different times and then a KCM is applied to cluster the matrix. Analysis and experimental results show that there is an obvious correspondence that state changing coincides basically in time between the lubricants’ multi-parameters and the bearings’ wear states. It also has shown that online oil samples with multi-parameters have early wear failure prediction ability for bearings superior to vibration signals. It is expected to realize online oil monitoring and evaluation for bearing health condition and to provide a novel approach for early identification of bearing-related failure modes.

Efficient Ensemble State-Parameters Estimation Techniques in Ocean Ecosystem Models: Application to the North Atlantic

Science.gov (United States)

El Gharamti, M.; Bethke, I.; Tjiputra, J.; Bertino, L.

2016-02-01

Given the recent strong international focus on developing new data assimilation systems for biological models, we present in this comparative study the application of newly developed state-parameters estimation tools to an ocean ecosystem model. It is quite known that the available physical models are still too simple compared to the complexity of the ocean biology. Furthermore, various biological parameters remain poorly unknown and hence wrong specifications of such parameters can lead to large model errors. Standard joint state-parameters augmentation technique using the ensemble Kalman filter (Stochastic EnKF) has been extensively tested in many geophysical applications. Some of these assimilation studies reported that jointly updating the state and the parameters might introduce significant inconsistency especially for strongly nonlinear models. This is usually the case for ecosystem models particularly during the period of the spring bloom. A better handling of the estimation problem is often carried out by separating the update of the state and the parameters using the so-called Dual EnKF. The dual filter is computationally more expensive than the Joint EnKF but is expected to perform more accurately. Using a similar separation strategy, we propose a new EnKF estimation algorithm in which we apply a one-step-ahead smoothing to the state. The new state-parameters estimation scheme is derived in a consistent Bayesian filtering framework and results in separate update steps for the state and the parameters. Unlike the classical filtering path, the new scheme starts with an update step and later a model propagation step is performed. We test the performance of the new smoothing-based schemes against the standard EnKF in a one-dimensional configuration of the Norwegian Earth System Model (NorESM) in the North Atlantic. We use nutrients profile (up to 2000 m deep) data and surface partial CO2 measurements from Mike weather station (66o N, 2o E) to estimate

Kinetics of the thermal decomposition of pine needles

Directory of Open Access Journals (Sweden)

Dhaundiyal Alok

2015-12-01

Full Text Available A kinetic study of the pyrolysis process of pine needles was examined using a thermogravimetric analyser. The weight loss was measured in nitrogen atmosphere at a purge flow rate of 100 ml/min. The samples were heated over a range of temperature of 19°C–600°C with a heating rate of 10°C/min. The results obtained from the thermal decomposition process indicate that there are three main stages: dehydration, active and passive pyrolysis. The kinetic parameters for the different samples, such as activation energy and pre-exponential factor, are obtained by the shrinking core model (reaction-controlled regime, the model-free, and the first-order model. Experimental results showed that the shrinking model is in good agreement and can be successfully used to understand degradation mechanism of loose biomass. The result obtained from the reaction-controlled regime represented actual values of kinetic parameters which are the same for the whole pyrolysis process; whereas the model-free method presented apparent values of kinetic parameters, as they are dependent on the unknown function ϕ(C, on the sum of the parameters of the physical processes, and on the chemical reactions that happen simultaneously during pyrolysis. Experimental results showed that values of kinetic constant from the first-order model and the SCM are in good agreement and can be successfully used to understand the behaviour of loose biomass (pine needles in the presence of inert atmosphere. Using TGA results, the simulating pyrolysis can be done, with the help of computer software, to achieve a comprehensive detail of the devolatilization process of different types of biomasses.

Chemical kinetic functional sensitivity analysis: Elementary sensitivities

International Nuclear Information System (INIS)

Demiralp, M.; Rabitz, H.

1981-01-01

Sensitivity analysis is considered for kinetics problems defined in the space--time domain. This extends an earlier temporal Green's function method to handle calculations of elementary functional sensitivities deltau/sub i//deltaα/sub j/ where u/sub i/ is the ith species concentration and α/sub j/ is the jth system parameter. The system parameters include rate constants, diffusion coefficients, initial conditions, boundary conditions, or any other well-defined variables in the kinetic equations. These parameters are generally considered to be functions of position and/or time. Derivation of the governing equations for the sensitivities and the Green's funciton are presented. The physical interpretation of the Green's function and sensitivities is given along with a discussion of the relation of this work to earlier research

A Bayesian consistent dual ensemble Kalman filter for state-parameter estimation in subsurface hydrology

KAUST Repository

Ait-El-Fquih, Boujemaa; El Gharamti, Mohamad; Hoteit, Ibrahim

2016-01-01

Ensemble Kalman filtering (EnKF) is an efficient approach to addressing uncertainties in subsurface ground-water models. The EnKF sequentially integrates field data into simulation models to obtain a better characterization of the model's state and parameters. These are generally estimated following joint and dual filtering strategies, in which, at each assimilation cycle, a forecast step by the model is followed by an update step with incoming observations. The joint EnKF directly updates the augmented state-parameter vector, whereas the dual EnKF empirically employs two separate filters, first estimating the parameters and then estimating the state based on the updated parameters. To develop a Bayesian consistent dual approach and improve the state-parameter estimates and their consistency, we propose in this paper a one-step-ahead (OSA) smoothing formulation of the state-parameter Bayesian filtering problem from which we derive a new dual-type EnKF, the dual EnKF(OSA). Compared with the standard dual EnKF, it imposes a new update step to the state, which is shown to enhance the performance of the dual approach with almost no increase in the computational cost. Numerical experiments are conducted with a two-dimensional (2-D) synthetic groundwater aquifer model to investigate the performance and robustness of the proposed dual EnKFOSA, and to evaluate its results against those of the joint and dual EnKFs. The proposed scheme is able to successfully recover both the hydraulic head and the aquifer conductivity, providing further reliable estimates of their uncertainties. Furthermore, it is found to be more robust to different assimilation settings, such as the spatial and temporal distribution of the observations, and the level of noise in the data. Based on our experimental setups, it yields up to 25% more accurate state and parameter estimations than the joint and dual approaches.

A Bayesian consistent dual ensemble Kalman filter for state-parameter estimation in subsurface hydrology

KAUST Repository

Ait-El-Fquih, Boujemaa

2016-08-12

Ensemble Kalman filtering (EnKF) is an efficient approach to addressing uncertainties in subsurface ground-water models. The EnKF sequentially integrates field data into simulation models to obtain a better characterization of the model\\'s state and parameters. These are generally estimated following joint and dual filtering strategies, in which, at each assimilation cycle, a forecast step by the model is followed by an update step with incoming observations. The joint EnKF directly updates the augmented state-parameter vector, whereas the dual EnKF empirically employs two separate filters, first estimating the parameters and then estimating the state based on the updated parameters. To develop a Bayesian consistent dual approach and improve the state-parameter estimates and their consistency, we propose in this paper a one-step-ahead (OSA) smoothing formulation of the state-parameter Bayesian filtering problem from which we derive a new dual-type EnKF, the dual EnKF(OSA). Compared with the standard dual EnKF, it imposes a new update step to the state, which is shown to enhance the performance of the dual approach with almost no increase in the computational cost. Numerical experiments are conducted with a two-dimensional (2-D) synthetic groundwater aquifer model to investigate the performance and robustness of the proposed dual EnKFOSA, and to evaluate its results against those of the joint and dual EnKFs. The proposed scheme is able to successfully recover both the hydraulic head and the aquifer conductivity, providing further reliable estimates of their uncertainties. Furthermore, it is found to be more robust to different assimilation settings, such as the spatial and temporal distribution of the observations, and the level of noise in the data. Based on our experimental setups, it yields up to 25% more accurate state and parameter estimations than the joint and dual approaches.

Photoluminescence and thermoluminescence of K2 Mg(SO4 )2 :Eu and evaluation of its kinetic parameters.

Science.gov (United States)

Deshpande, Archana; Dhoble, N S; Gedam, S C; Dhoble, S J

2017-08-01

The K 2 Mg(SO 4 ) 2 :Eu phosphor, synthesized by a solid-state diffusion method, was studied for its photoluminescence (PL) and thermoluminescence (TL) characteristics. The X-ray diffraction (XRD) pattern of the material was matched with the standard JCPDF No. 36-1499. For PL characteristics, K 2 Mg(SO 4 ) 2 :Eu 2 + showed an emission peak at 474 nm when excited at 340 nm, while it showed Eu 3 + emission at 580 nm, and 594 nm splitting at 613 nm and 618 nm for an excitation of 396 nm wavelength due to radiative transitions from 5 D 0 to 7 F j (j = 0, 1, 2, 3). The Commission International de I' Eclairage (CIE) chromaticity coordinates were also calculated for the K 2 Mg(SO 4 ) 2 :Eu phosphor, and were close to the NTSC standard values. For the TL study, the prepared sample was irradiated using a 60 Co source of γ-irradiation at the dose rate of 0.322 kGy/h for 2 min. The formation of traps in K 2 Mg (SO 4 ) 2 :Eu and the effects of γ-radiation dose on the glow curve are discussed. Well defined broad glow peaks were obtained at 186°C. With increasing γ-ray dose, the sample showed linearity in intensity. The presence of a single glow peak indicated that there was only one set of traps being activated within the particular temperature range. The presented phosphors were also studied for their fading, reusability and trapping parameters. There was just 2% fading during a period of 30 days, indicating no serious fading problem. Kinetic parameters were calculated using the initial rise method and Chen's half-width method. Activation energy and frequency factor were found to be 0.77 eV and 1.41 × 10 6  sec -1 . Copyright © 2016 John Wiley & Sons, Ltd.

Kinetics of phosphorus sorption in soils in the state of Paraíba¹

Directory of Open Access Journals (Sweden)

Hemmannuella Costa Santos

2011-08-01

Full Text Available The soil P sorption capacity has been studied for many years, but little attention has been paid to the rate of this process, which is relevant in the planning of phosphate fertilization. The purpose of this experiment was to assess kinetics of P sorption in 12 representative soil profiles of the State of Paraíba (Brazil, select the best data fitting among four equations and relate these coefficients to the soil properties. Samples of 12 soils with wide diversity of physical, chemical and mineralogical properties were agitated in a horizontal shaker, with 10 mmo L-1 CaCl2 solution containing 6 and 60 mg L-1 P, for periods of 5, 15, 30, 45, 60, 90, 120, 420, 720, 1,020, and 1,440 min. After each shaking period, the P concentration in the equilibrium solution was measured and three equations were fitted based on the Freundlich equation and one based on the Elovich equation, to determine which soil had the highest sorption rate (kinetics and which soil properties correlated to this rate. The kinetics of P sorption in soils with high maximum P adsorption capacity (MPAC was fast for 30 min at the lower initial P concentration (6 mg L-1. No difference was observed between soils at the higher initial P concentration (60 mg L-1. The P adsorption kinetics were positively correlated with clay content, MPAC and the amount of Al extracted with dithionite-citrate-bicarbonate. The data fitted well to Freundlich-based equations equation, whose coefficients can be used to predict P adsorption rates in soils.

Reaction network modelling for kinetic parameters of pyrolytic reactions of CHON extractants in nuclear fuel processing waste management. Contributed Paper IT-07

International Nuclear Information System (INIS)

Gaikar, Vilas G.; Thaore, Vaishali

2014-01-01

The recovery and purification of plutonium (Pu) from uranium (U) and of U from Thorium (Th) in spent nuclear fuel reprocessing is accomplished by processes that employ organophosphorous compounds as extractants.The main objective of the present work was to develop a suitable kinetic model and to determine the kinetic parameters of the set of reactions involved in the pyrolysis of amides by fitting the experimental data in the reaction network model. The experimental data and analysis are expected to be useful in the steam pyrolysis of amide waste in fuel reprocessing in the nuclear industry. The basic approach was to understand the reaction mechanism of the steam pyrolysis of amides and then to estimate the reaction rate constants for the generation and consumption of different species by solving the model equations, allowing for the determination of important species in the reaction network

A kinetic model for chemical neurotransmission

Science.gov (United States)

Ramirez-Santiago, Guillermo; Martinez-Valencia, Alejandro; Fernandez de Miguel, Francisco

Recent experimental observations in presynaptic terminals at the neuromuscular junction indicate that there are stereotyped patterns of cooperativeness in the fusion of adjacent vesicles. That is, a vesicle in hemifusion process appears on the side of a fused vesicle and which is followed by another vesicle in a priming state while the next one is in a docking state. In this talk we present a kinetic model for this morphological pattern in which each vesicle state previous to the exocytosis is represented by a kinetic state. This chain states kinetic model can be analyzed by means of a Master equation whose solution is simulated with the stochastic Gillespie algorithm. With this approach we have reproduced the responses to the basal release in the absence of stimulation evoked by the electrical activity and the phenomena of facilitation and depression of neuromuscular synapses. This model offers new perspectives to understand the underlying phenomena in chemical neurotransmission based on molecular interactions that result in the cooperativity between vesicles during neurotransmitter release. DGAPA Grants IN118410 and IN200914 and Conacyt Grant 130031.

Kinetics of propionate conversion in anaerobic continuously stirred tank reactors

DEFF Research Database (Denmark)

Bangsø Nielsen, Henrik; Mladenovska, Zuzana; Ahring, Birgitte Kiær

2008-01-01

The kinetic parameters of anaerobic propionate degradation by biomass from 7 continuously stirred tank reactors differing in temperature, hydraulic retention time and substrate composition were investigated. In substrate-depletion experiments (batch) the maximum propionate degradation rate, A......-m, was estimated. The results demonstrate that the rate of endogenous substrate (propionate) production should be taken into account when estimating kinetic parameters in biomass from manure-based anaerobic reactors....

Stochastic theory of interfacial enzyme kinetics: A kinetic Monte Carlo study

International Nuclear Information System (INIS)

Das, Biswajit; Gangopadhyay, Gautam

2012-01-01

Graphical abstract: Stochastic theory of interfacial enzyme kinetics is formulated. Numerical results of macroscopic phenomenon of lag-burst kinetics is obtained by using a kinetic Monte Carlo approach to single enzyme activity. Highlights: ► An enzyme is attached with the fluid state phospholipid molecules on the Langmuir monolayer. ► Through the diffusion, the enzyme molecule reaches the gel–fluid interface. ► After hydrolysing a phospholipid molecule it predominantly leaves the surface in the lag phase. ► The enzyme is strictly attached to the surface with scooting mode of motion and the burst phase appears. - Abstract: In the spirit of Gillespie’s stochastic approach we have formulated a theory to explore the advancement of the interfacial enzyme kinetics at the single enzyme level which is ultimately utilized to obtain the ensemble average macroscopic feature, lag-burst kinetics. We have provided a theory of the transition from the lag phase to the burst phase kinetics by considering the gradual development of electrostatic interaction among the positively charged enzyme and negatively charged product molecules deposited on the phospholipid surface. It is shown that the different diffusion time scales of the enzyme over the fluid and product regions are responsible for the memory effect in the correlation of successive turnover events of the hopping mode in the single trajectory analysis which again is reflected on the non-Gaussian distribution of turnover times on the macroscopic kinetics in the lag phase unlike the burst phase kinetics.

A Critical View on In Vitro Analysis of P-glycoprotein (P-gp) Transport Kinetics.

Science.gov (United States)

Saaby, Lasse; Brodin, Birger

2017-09-01

Transport proteins expressed in the different barriers of the human body can have great implications on absorption, distribution, and excretion of drug compounds. Inhibition or saturation of a transporter can potentially alter these absorbtion, distribution, metabolism and elimination properties and thereby also the pharmacokinetic profile and bioavailability of drug compounds. P-glycoprotein (P-gp, ABCB1) is an efflux transporter which is present in most of the barriers of the body, including the small intestine, the blood-brain barrier, the liver, and the kidney. In all these tissues, P-gp may mediate efflux of drug compounds and may also be a potential site for drug-drug interactions. Consequently, there is a need to be able to predict the saturation and inhibition of P-gp and other transporters in vivo. For this purpose, Michaelis-Menten steady-state analysis has been applied to estimate kinetic parameters, such as K m and V max , for carrier-mediated transport, whereas half-maximal inhibitor concentration (IC 50 ) and the disassociation constant for an inhibitor/P-gp complex (K i ) have been determined to estimate P-gp inhibition. This review addresses in vitro methods commonly used to study P-gp transport kinetics and aims at providing a critical evaluation of the application of steady-state Michaelis-Menten analysis of kinetic parameters for substrate/P-gp interactions. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Nonlinear Adaptive Descriptor Observer for the Joint States and Parameters Estimation

KAUST Repository

2016-08-29

In this note, the joint state and parameters estimation problem for nonlinear multi-input multi-output descriptor systems is considered. Asymptotic convergence of the adaptive descriptor observer is established by a sufficient set of linear matrix inequalities for the noise-free systems. The noise corrupted systems are also considered and it is shown that the state and parameters estimation errors are bounded for bounded noises. In addition, if the noises are bounded and have zero mean, then the estimation errors asymptotically converge to zero in the mean. The performance of the proposed adaptive observer is illustrated by a numerical example.

Nonlinear Adaptive Descriptor Observer for the Joint States and Parameters Estimation

KAUST Repository

Unknown author

2016-01-01

In this note, the joint state and parameters estimation problem for nonlinear multi-input multi-output descriptor systems is considered. Asymptotic convergence of the adaptive descriptor observer is established by a sufficient set of linear matrix inequalities for the noise-free systems. The noise corrupted systems are also considered and it is shown that the state and parameters estimation errors are bounded for bounded noises. In addition, if the noises are bounded and have zero mean, then the estimation errors asymptotically converge to zero in the mean. The performance of the proposed adaptive observer is illustrated by a numerical example.

On-line adaptive battery impedance parameter and state estimation considering physical principles in reduced order equivalent circuit battery models. Part 1. Requirements, critical review of methods and modeling

Science.gov (United States)

Fleischer, Christian; Waag, Wladislaw; Heyn, Hans-Martin; Sauer, Dirk Uwe

2014-08-01

Lithium-ion battery systems employed in high power demanding systems such as electric vehicles require a sophisticated monitoring system to ensure safe and reliable operation. Three major states of the battery are of special interest and need to be constantly monitored, these include: battery state of charge (SoC), battery state of health (capcity fade determination, SoH), and state of function (power fade determination, SoF). In a series of two papers, we propose a system of algorithms based on a weighted recursive least quadratic squares parameter estimator, that is able to determine the battery impedance and diffusion parameters for accurate state estimation. The functionality was proven on different battery chemistries with different aging conditions. The first paper investigates the general requirements on BMS for HEV/EV applications. In parallel, the commonly used methods for battery monitoring are reviewed to elaborate their strength and weaknesses in terms of the identified requirements for on-line applications. Special emphasis will be placed on real-time capability and memory optimized code for cost-sensitive industrial or automotive applications in which low-cost microcontrollers must be used. Therefore, a battery model is presented which includes the influence of the Butler-Volmer kinetics on the charge-transfer process. Lastly, the mass transport process inside the battery is modeled in a novel state-space representation.

Ozone mass transfer and kinetics experiments

International Nuclear Information System (INIS)

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

1981-12-01

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

Effects of deuterium on the kinetics of beef heart mitochondrial ATPase

International Nuclear Information System (INIS)

Urbauer, J.L.; Dorgan, L.J.; Schuster, S.M.

1984-01-01

A study was done examining the steady-state kinetics of F1-catalyzed ATP and ITP hydrolyses in the presence or absence of D2O as a function of temperature. The steady-state kinetic parameters kcat and kcat/Km were obtained. For ATP hydrolysis, kcat/Km was independent of temperature in the presence or absence of D2O, while kcat/Km for ITP hydrolysis increased in both cases. The relative magnitudes of change of kcat and kcat/Km in the presence and absence of D2O over the temperature range studied were much different for the cases of ATP and ITP hydrolysis. A normal isotope effect was observed in plots of kcat H2O/kcat D2O versus temperature for ATP hydrolysis, which increased then leveled off as temperature increased. An inverse isotope effect at low temperatures changed to a normal isotope effect and increased dramatically as temperature increased during ITP hydrolysis. The results are discussed in terms of the nature and location of the rate-limiting steps in the reaction mechanisms

Kinetics of the H 2O 2-dependent ligninase-catalyzed oxidation of veratryl alcohol in the presence of cationic surfactant studied by spectrophotometric technique

Science.gov (United States)

Liu, Airong; Huang, Xirong; Song, Shaofang; Wang, Dan; Lu, Xuemei; Qu, Yinbo; Gao, Peiji

2003-09-01

The kinetics of ligninase-catalyzed oxidation of veratryl alcohol (VA) by H 2O 2 in the aqueous medium containing cationic surfactant cetyltrimethylammonium bromide (CTAB) has been investigated using spectrophotometric technique. Steady-state kinetic studies at different concentrations of CTAB indicate that the reaction follows a ping pong mechanism and the mechanism always holds but the kinetic parameters vary with CTAB concentrations. CTAB is a weak inhibitor for ligninase; it lowers the maximum initial velocity. CTAB also causes the Michaelis constant of H 2O 2 to decrease dramatically and that of VA to increase markedly. Based on the changes in kinetic parameters of the enzyme-catalyzed reaction at different CTAB concentrations (lower than, near to and larger than its critical micelle concentration) and the effects of the CTAB monomer and the micelles on the spectra of VA and its corresponding aldehyde, a conclusion could be made that modification of the enzymatic protein by the surfactant monomer should be responsible for the above-mentioned results.

A kinetics database and scripts for PHREEQC

Science.gov (United States)

Hu, B.; Zhang, Y.; Teng, Y.; Zhu, C.

2017-12-01

Kinetics of geochemical reactions has been increasingly used in numerical models to simulate coupled flow, mass transport, and chemical reactions. However, the kinetic data are scattered in the literature. To assemble a kinetic dataset for a modeling project is an intimidating task for most. In order to facilitate the application of kinetics in geochemical modeling, we assembled kinetics parameters into a database for the geochemical simulation program, PHREEQC (version 3.0). Kinetics data were collected from the literature. Our database includes kinetic data for over 70 minerals. The rate equations are also programmed into scripts with the Basic language. Using the new kinetic database, we simulated reaction path during the albite dissolution process using various rate equations in the literature. The simulation results with three different rate equations gave difference reaction paths at different time scale. Another application involves a coupled reactive transport model simulating the advancement of an acid plume in an acid mine drainage site associated with Bear Creek Uranium tailings pond. Geochemical reactions including calcite, gypsum, and illite were simulated with PHREEQC using the new kinetic database. The simulation results successfully demonstrated the utility of new kinetic database.

Kinetics of the generation of the petroleum: Principles and application in the Colombian basins

International Nuclear Information System (INIS)

Goncalves, F T T; Garcia, D F; Penteado, H L B; Giraldo, B N; Bedregal, R P; Gomez

2001-01-01

Most of the mathematical models that describe the conversion of kerogen into petroleum are based on the formulations of first-order kinetics. Although the application of such models requires the knowledge of the kinetic parameters (activation energies and frequency factor) of the kerogen, the usual practice in basin modeling studies is to use kinetic data of standard kerogen types (I, II or III) when measured data are not available. In this study, Rock-Eval pyrolysis under different heating rates and numerical optimization techniques were used to determine the kinetic parameters of cretaceous and tertiary source rocks of the upper Magdalena and llanos basins. The obtained kinetic parameters revealed a significant variability, which appears to be unrelated to the kerogen type classification based on hydrogen and oxygen indices. Modeling exercises under a constant heating rate (1.25 degrades C/M.y., 274.5K/M.y.) using the measured kinetic data indicates that kerogen conversion of organic facies with distinct kinetic parameters may be out of phase by 20-30M.y. therefore, petroleum generation and expulsion history might be longer and more complex than if the kinetic behavior of these rocks was considered homogeneous. These differences are critical in defining the timing between petroleum generations a trap formation/destruction, particularly in the case of the Colombian sedimentary basins, characterized by a highly complex tectonic evolution

Effect of sepsis on VLDL kinetics: responses in basal state and during glucose infusion

International Nuclear Information System (INIS)

Wolfe, R.R.; Shaw, J.H.; Durkot, M.J.

1985-01-01

The effect of gram-negative sepsis on the kinetics and oxidation of very low-density lipoprotein (VLDL) fatty acids was assessed in conscious dogs in the normal state and 24 h after infusion of live Escherichia coli. VLDL, labeled with [2- 3 H]glycerol and [1- 14 C]palmitic acid, was used to trace VLDL kinetics and oxidation, and [1- 13 C]palmitic acid bound to albumin was infused simultaneously to quantify kinetics and oxidation of free fatty acid (FFA) in plasma. Sepsis caused a fivefold increase in the rate of VLDL production (RaVLDL). In the control dogs, the direct oxidation of VLDL-fatty acids was not an important contributor to their overall energy metabolism, but in dogs with sepsis, 17% of the total rate of CO2 production could be accounted for by VLDL-fatty acid oxidation. When glucose was infused into dogs with insulin and glucagon levels clamped at basal levels (by means of infusion of somatostatin and replacement of the hormones), RaVLDL increased significantly in the control dogs, but it did not increase further in dogs with sepsis. The authors conclude that the increase in triglyceride concentration in fasting dogs with gram-negative sepsis is the result of an increase in VLDL production and that the fatty acids in VLDL can serve as an important source of energy in sepsis

Theory of warm ionized gases: equation of state and kinetic Schottky anomaly.

Science.gov (United States)

Capolupo, A; Giampaolo, S M; Illuminati, F

2013-10-01

Based on accurate Lennard-Jones-type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analog in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed. In particular, the predicted plasma electron density in a sonoluminescent bubble turns out to be in good agreement with the value measured in recent experiments.

Nuclear matter equation of state and σ-meson parameters

Indian Academy of Sciences (India)

We try to determine phenomenologically the extent of in-medium modification of -meson parameters so that the saturation observables of the nuclear matter equation of state (EOS) are reproduced. To calculate the EOS we have used Brueckner–Bethe–Goldstone formalism with Bonn potential as two-body interaction.

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

International Nuclear Information System (INIS)

Rodd, D.; Farrell, P.A.; Caston, A.L.; Green, M.H.

1991-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1991-03-01

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

Accuracy and precision of protein–ligand interaction kinetics determined from chemical shift titrations

International Nuclear Information System (INIS)

Markin, Craig J.; Spyracopoulos, Leo

2012-01-01

NMR-monitored chemical shift titrations for the study of weak protein–ligand interactions represent a rich source of information regarding thermodynamic parameters such as dissociation constants (K D ) in the micro- to millimolar range, populations for the free and ligand-bound states, and the kinetics of interconversion between states, which are typically within the fast exchange regime on the NMR timescale. We recently developed two chemical shift titration methods wherein co-variation of the total protein and ligand concentrations gives increased precision for the K D value of a 1:1 protein–ligand interaction (Markin and Spyracopoulos in J Biomol NMR 53: 125–138, 2012). In this study, we demonstrate that classical line shape analysis applied to a single set of 1 H– 15 N 2D HSQC NMR spectra acquired using precise protein–ligand chemical shift titration methods we developed, produces accurate and precise kinetic parameters such as the off-rate (k off ). For experimentally determined kinetics in the fast exchange regime on the NMR timescale, k off ∼ 3,000 s −1 in this work, the accuracy of classical line shape analysis was determined to be better than 5 % by conducting quantum mechanical NMR simulations of the chemical shift titration methods with the magnetic resonance toolkit GAMMA. Using Monte Carlo simulations, the experimental precision for k off from line shape analysis of NMR spectra was determined to be 13 %, in agreement with the theoretical precision of 12 % from line shape analysis of the GAMMA simulations in the presence of noise and protein concentration errors. In addition, GAMMA simulations were employed to demonstrate that line shape analysis has the potential to provide reasonably accurate and precise k off values over a wide range, from 100 to 15,000 s −1 . The validity of line shape analysis for k off values approaching intermediate exchange (∼100 s −1 ), may be facilitated by more accurate K D measurements from NMR

Accuracy and precision of protein-ligand interaction kinetics determined from chemical shift titrations.

Science.gov (United States)

Markin, Craig J; Spyracopoulos, Leo

2012-12-01

NMR-monitored chemical shift titrations for the study of weak protein-ligand interactions represent a rich source of information regarding thermodynamic parameters such as dissociation constants (K ( D )) in the micro- to millimolar range, populations for the free and ligand-bound states, and the kinetics of interconversion between states, which are typically within the fast exchange regime on the NMR timescale. We recently developed two chemical shift titration methods wherein co-variation of the total protein and ligand concentrations gives increased precision for the K ( D ) value of a 1:1 protein-ligand interaction (Markin and Spyracopoulos in J Biomol NMR 53: 125-138, 2012). In this study, we demonstrate that classical line shape analysis applied to a single set of (1)H-(15)N 2D HSQC NMR spectra acquired using precise protein-ligand chemical shift titration methods we developed, produces accurate and precise kinetic parameters such as the off-rate (k ( off )). For experimentally determined kinetics in the fast exchange regime on the NMR timescale, k ( off ) ~ 3,000 s(-1) in this work, the accuracy of classical line shape analysis was determined to be better than 5 % by conducting quantum mechanical NMR simulations of the chemical shift titration methods with the magnetic resonance toolkit GAMMA. Using Monte Carlo simulations, the experimental precision for k ( off ) from line shape analysis of NMR spectra was determined to be 13 %, in agreement with the theoretical precision of 12 % from line shape analysis of the GAMMA simulations in the presence of noise and protein concentration errors. In addition, GAMMA simulations were employed to demonstrate that line shape analysis has the potential to provide reasonably accurate and precise k ( off ) values over a wide range, from 100 to 15,000 s(-1). The validity of line shape analysis for k ( off ) values approaching intermediate exchange (~100 s(-1)), may be facilitated by more accurate K ( D ) measurements

Kinetics of hydrogen peroxide decomposition by catalase: hydroxylic solvent effects.

Science.gov (United States)

Raducan, Adina; Cantemir, Anca Ruxandra; Puiu, Mihaela; Oancea, Dumitru

2012-11-01

The effect of water-alcohol (methanol, ethanol, propan-1-ol, propan-2-ol, ethane-1,2-diol and propane-1,2,3-triol) binary mixtures on the kinetics of hydrogen peroxide decomposition in the presence of bovine liver catalase is investigated. In all solvents, the activity of catalase is smaller than in water. The results are discussed on the basis of a simple kinetic model. The kinetic constants for product formation through enzyme-substrate complex decomposition and for inactivation of catalase are estimated. The organic solvents are characterized by several physical properties: dielectric constant (D), hydrophobicity (log P), concentration of hydroxyl groups ([OH]), polarizability (α), Kamlet-Taft parameter (β) and Kosower parameter (Z). The relationships between the initial rate, kinetic constants and medium properties are analyzed by linear and multiple linear regression.

Smoothing-based compressed state Kalman filter for joint state-parameter estimation: Applications in reservoir characterization and CO2 storage monitoring

Science.gov (United States)

Li, Y. J.; Kokkinaki, Amalia; Darve, Eric F.; Kitanidis, Peter K.

2017-08-01

The operation of most engineered hydrogeological systems relies on simulating physical processes using numerical models with uncertain parameters and initial conditions. Predictions by such uncertain models can be greatly improved by Kalman-filter techniques that sequentially assimilate monitoring data. Each assimilation constitutes a nonlinear optimization, which is solved by linearizing an objective function about the model prediction and applying a linear correction to this prediction. However, if model parameters and initial conditions are uncertain, the optimization problem becomes strongly nonlinear and a linear correction may yield unphysical results. In this paper, we investigate the utility of one-step ahead smoothing, a variant of the traditional filtering process, to eliminate nonphysical results and reduce estimation artifacts caused by nonlinearities. We present the smoothing-based compressed state Kalman filter (sCSKF), an algorithm that combines one step ahead smoothing, in which current observations are used to correct the state and parameters one step back in time, with a nonensemble covariance compression scheme, that reduces the computational cost by efficiently exploring the high-dimensional state and parameter space. Numerical experiments show that when model parameters are uncertain and the states exhibit hyperbolic behavior with sharp fronts, as in CO2 storage applications, one-step ahead smoothing reduces overshooting errors and, by design, gives physically consistent state and parameter estimates. We compared sCSKF with commonly used data assimilation methods and showed that for the same computational cost, combining one step ahead smoothing and nonensemble compression is advantageous for real-time characterization and monitoring of large-scale hydrogeological systems with sharp moving fronts.

Influence of Prolonged Spaceflight on Heart Rate and Oxygen Uptake Kinetics

Science.gov (United States)

Hoffmann, U.; Moore, A.; Drescher, U.

2013-02-01

During prolonged spaceflight, physical training is used to minimize cardiovascular deconditioning. Measurement of the kinetics of cardiorespiratory parameters, in particular the kinetic analysis of heart rate, respiratory and muscular oxygen uptake, provides useful information with regard to the efficiency and regulation of the cardiorespiratory system. Practically, oxygen uptake kinetics can only be measured at the lung site (V’O2 resp). The dynamics of V’O2 resp, however, is not identical with the dynamics at the site of interest: skeletal muscle. Eight Astronauts were tested pre- and post-flight using pseudo random binary workload changes between 30 and 80 W. Their kinetic responses of heart rate, respiratory as well as muscular V’O2 kinetics were estimated by using time-series analysis. Statistical analysis revealed that the kinetic responses of respiratory as well as muscular V’O2 kinetics are slowed post-flight than pre-flight. Heart rate seems not to be influenced following flight. The influence of other factors (e. g. astronauts’ exercise training) may impact these parameters and is an area for future studies.

Evaluation of rate law approximations in bottom-up kinetic models of metabolism

DEFF Research Database (Denmark)

Du, Bin; Zielinski, Daniel C.; Kavvas, Erol S.

2016-01-01

mass action rate law that removes the role of the enzyme from the reaction kinetics. We utilized in vivo data for the human red blood cell to compare the effect of rate law choices against the backdrop of physiological flux and concentration differences. We found that the Michaelis-Menten rate law......Background: The mechanistic description of enzyme kinetics in a dynamic model of metabolism requires specifying the numerical values of a large number of kinetic parameters. The parameterization challenge is often addressed through the use of simplifying approximations to form reaction rate laws....... These approximate rate laws were: 1) a Michaelis-Menten rate law with measured enzyme parameters, 2) a Michaelis-Menten rate law with approximated parameters, using the convenience kinetics convention, 3) a thermodynamic rate law resulting from a metabolite saturation assumption, and 4) a pure chemical reaction...

Tunable submillimeter sources applied to the excited state rotational spectroscopy and kinetics of CH3F

International Nuclear Information System (INIS)

Blumberg, W.A.M.; Fetterman, H.R.; Peck, D.D.; Goldsmith, P.F.

1979-01-01

Tunable submillimeter radiation, generated and detected using optically pumped lasers and Schottky diode mixers, has been used in an infrared-submillimeter double resonance investigation of CH 3 F. This technique permits the direct observation of the molecular rotational spectra and kinetics of excited vibrational states and is particularly important for those molecules which are candidates for optically pumped submillimeter lasers

Space-time reactor kinetics for heterogeneous reactor structure

Energy Technology Data Exchange (ETDEWEB)

Raisic, N [Boris Kidric Institute of nuclear sciences Vinca, Belgrade (Yugoslavia)

1969-11-15

An attempt is made to formulate time dependent diffusion equation based on Feinberg-Galanin theory in the from analogue to the classical reactor kinetic equation. Parameters of these equations could be calculated using the existing codes for static reactor calculation based on the heterogeneous reactor theory. The obtained kinetic equation could be analogues in form to the nodal kinetic equation. Space-time distribution of neutron flux in the reactor can be obtained by solving these equations using standard methods.

Kinetic Model of Growth of Arthropoda Populations

Science.gov (United States)

Ershov, Yu. A.; Kuznetsov, M. A.

2018-05-01

Kinetic equations were derived for calculating the growth of crustacean populations ( Crustacea) based on the biological growth model suggested earlier using shrimp ( Caridea) populations as an example. The development cycle of successive stages for populations can be represented in the form of quasi-chemical equations. The kinetic equations that describe the development cycle of crustaceans allow quantitative prediction of the development of populations depending on conditions. In contrast to extrapolation-simulation models, in the developed kinetic model of biological growth the kinetic parameters are the experimental characteristics of population growth. Verification and parametric identification of the developed model on the basis of the experimental data showed agreement with experiment within the error of the measurement technique.

Radio-Oxidation in Polyolefins: Non-Stationary Kinetic Conditions

International Nuclear Information System (INIS)

Dely, N.

2006-01-01

In the last fifty years, many authors have been interested in the radio-oxidation processes occurring in polymers. The polymer degradation under ionising radiations in presence of dioxygen is well described by a radical chemistry. The radio-oxidation process occurs in three steps: the first one is the production of radicals P degree by interaction between the polymer and the ionising radiations; then radicals P degree react spontaneously with O 2 solved in the polymer giving a peroxy radical POO degree which attacks the polymer forming a hydroperoxide POOH and a new radical P degree (propagation). The third step corresponds to the termination step, that is bimolecular reactions between radicals. It is generally assumed that the stationary state is rapidly reached and consequently that the oxidation induced during the built-up period of the radical concentration can be neglected. However, to our best knowledge, the temporal evolution of radical concentrations before reaching the steady state regime has never been studied in details. We recently performed a complete study of oxygen consumption under electron irradiation for an EPDM elastomer. An analysis, as function of dose rate and oxygen pressure, and assuming steady state conditions, allowed extracting all the kinetic constants. Starting for these experimental data, we calculated the build-up of the radical concentration by solving numerically the differential equations with help of the Minichem code. We conclude that, in fact, the oxidation induced during the built-up period is negligible. In this paper we show that [P degree] could present a quasi-stationary plateau before reaching its stationary level. Consequently, the full radical time evolution is essentially determined by two characteristic times for reaching the quasi and stationary levels and three concentrations: [P degree] and [POO degree] at the stationary level and [P degree] at the quasi-stationary plateau. We show that realistic approximations can

Transformation kinetics for nucleus clusters

International Nuclear Information System (INIS)

Villa, Elena; Rios, Paulo R.

2009-01-01

A rigorous mathematical approach based on stochastic geometry concepts is presented to extend previous Johnson-Mehl, Avrami, Kolmogorov treatment of transformation kinetics to situations in which nuclei are not homogeneously located in space but are located in clusters. An exact analytical solution is presented here for the first time assuming that nucleation sites follow a Matern cluster process. The influence of Matern cluster process parameters on subsequent growth kinetics and the microstructural path are illustrated by means of numerical examples. Moreover, using the superposition principle, exact analytical solutions are also obtained when nucleation takes place by a combination of a Matern cluster process and an inhomogeneous Poisson point process. The new solutions presented here significantly increase the number of exactly solvable cases available to formal kinetics.

Investigation of two and three parameter equations of state for cryogenic fluids

International Nuclear Information System (INIS)

Jenkins, S.L.; Majumdar, A.K.; Hendricks, R.C.

1990-01-01

Two-phase flows are a common occurrence in cryogenic engines and an accurate evaluation of the heat-transfer coefficient in two-phase flow is of significant importance in their analysis and design. The thermodynamic equation of state plays a key role in calculating the heat transfer coefficient which is a function of thermodynamic and thermophysical properties. An investigation has been performed to study the performance of two- and three-parameter equations of state to calculate the compressibility factor of cryogenic fluids along the saturation loci. The two-parameter equations considered here are van der Waals and Redlich-Kwong equations of state. The three-parameter equation represented here is the generalized Benedict-Webb-Rubin (BWR) equation of Lee and Kesler. Results have been compared with the modified BWR equation of Bender and the extended BWR equations of Stewart. Seven cryogenic fluids have been tested; oxygen, hydrogen, helium, nitrogen, argon, neon, and air. The performance of the generalized BWR equation is poor for hydrogen and helium. The van der Waals equation is found to be inaccurate for air near the critical point. For helium, all three equations of state become inaccurate near the critical point. 13 refs

Rate kernel theory for pseudo-first-order kinetics of diffusion-influenced reactions and application to fluorescence quenching kinetics.

Science.gov (United States)

Yang, Mino

2007-06-07

Theoretical foundation of rate kernel equation approaches for diffusion-influenced chemical reactions is presented and applied to explain the kinetics of fluorescence quenching reactions. A many-body master equation is constructed by introducing stochastic terms, which characterize the rates of chemical reactions, into the many-body Smoluchowski equation. A Langevin-type of memory equation for the density fields of reactants evolving under the influence of time-independent perturbation is derived. This equation should be useful in predicting the time evolution of reactant concentrations approaching the steady state attained by the perturbation as well as the steady-state concentrations. The dynamics of fluctuation occurring in equilibrium state can be predicted by the memory equation by turning the perturbation off and consequently may be useful in obtaining the linear response to a time-dependent perturbation. It is found that unimolecular decay processes including the time-independent perturbation can be incorporated into bimolecular reaction kinetics as a Laplace transform variable. As a result, a theory for bimolecular reactions along with the unimolecular process turned off is sufficient to predict overall reaction kinetics including the effects of unimolecular reactions and perturbation. As the present formulation is applied to steady-state kinetics of fluorescence quenching reactions, the exact relation between fluorophore concentrations and the intensity of excitation light is derived.

Kinetics of the biodegradation of green table olive wastewaters by aerobic and anaerobic treatments

International Nuclear Information System (INIS)

Beltran, J.; Gonzalez, T.; Garcia, J.

2008-01-01

The biodegradation of the organic pollutant matter present in green table olive wastewater (GTOW) is studied in batch reactors by an aerobic biodegradation and by an anaerobic digestion. In the aerobic biodegradation, the evolution of the substrate (in terms of chemical and biochemical oxygen demand), biomass, and total polyphenolic compounds present in the wastewater are followed during the process, and a kinetic study is performed using Contois' model, which when applied to the experimental results provides the kinetic parameter of this model, resulting in a modified Contois' equation (q = 3.3S/(0.31S 0 X + X), gCOD/gVSS d -1 ). Other kinetic parameters were determined: the cellular yield coefficient (Y X/S = 5.7 x 10 -2 gVSS/gCOD) and the kinetic constant of cellular death phase (k d = 0.16 d -1 ). Similarly, in the anaerobic digestion, the evolution of the substrate digested and the methane produced are followed, and the kinetic study is conducted using a modified Monod model combined with the Levenspiel model, due to the presence of inhibition effects. This model leads to the determination of the kinetic parameters: kinetic constant when no inhibitory substance is present (k M0 = 8.4 x 10 -2 h -1 ), critical substrate concentration of inhibition (TP* = 0.34 g/L) and inhibitory parameter (n = 2.25)

Hydrogen electrode reaction: A complete kinetic description

International Nuclear Information System (INIS)

Quaino, P.M.; Gennero de Chialvo, M.R.; Chialvo, A.C.

2007-01-01

The kinetic description of the hydrogen electrode reaction (HER) in the whole range of overpotentials (-0.2 < η (V) < 0.40) is presented. The Volmer-Heyrovsky-Tafel mechanism was solved considering simultaneously the following items: (i) the diffusional contribution of the molecular hydrogen from and towards the electrode surface, (ii) the forward and backward reaction rates of each elementary step and (iii) a Frumkin type adsorption for the reaction intermediate. In order to verify the descriptive capability of the kinetic expressions derived, an experimental study of the HER was carried out on a rotating platinum disc electrode in acid solution. From the correlation of these results the elementary kinetic parameters were evaluated and several aspects related to the kinetic mechanism were discussed. Finally, the use of these kinetic expressions to interpret results obtained on microelectrodes is also analysed

Kinetics and mechanical stability of the fibril state control fibril formation time of polypeptide chains: A computational study

Science.gov (United States)

Kouza, Maksim; Co, Nguyen Truong; Li, Mai Suan; Kmiecik, Sebastian; Kolinski, Andrzej; Kloczkowski, Andrzej; Buhimschi, Irina Alexandra

2018-06-01

Fibril formation resulting from protein misfolding and aggregation is a hallmark of several neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Despite much progress in the understanding of the protein aggregation process, the factors governing fibril formation rates and fibril stability have not been fully understood. Using lattice models, we have shown that the fibril formation time is controlled by the kinetic stability of the fibril state but not by its energy. Having performed all-atom explicit solvent molecular dynamics simulations with the GROMOS43a1 force field for full-length amyloid beta peptides Aβ40 and Aβ42 and truncated peptides, we demonstrated that kinetic stability can be accessed via mechanical stability in such a way that the higher the mechanical stability or the kinetic stability, the faster the fibril formation. This result opens up a new way for predicting fibril formation rates based on mechanical stability that may be easily estimated by steered molecular dynamics.

Simulation of styrene polymerization reactors: kinetic and thermodynamic modeling

Directory of Open Access Journals (Sweden)

A. S. Almeida

2008-06-01

Full Text Available A mathematical model for the free radical polymerization of styrene is developed to predict the steady-state and dynamic behavior of a continuous process. Special emphasis is given for the kinetic and thermodynamic models, where the most sensitive parameters were estimated using data from an industrial plant. The thermodynamic model is based on a cubic equation of state and a mixing rule applied to the low-pressure vapor-liquid equilibrium of polymeric solutions, suitable for modeling the auto-refrigerated polymerization reactors, which use the vaporization rate to remove the reaction heat from the exothermic reactions. The simulation results show the high predictive capability of the proposed model when compared with plant data for conversion, average molecular weights, polydispersity, melt flow index, and thermal properties for different polymer grades.

Strain-induced structural changes and chemical reactions. 1: Thermomechanical and kinetic models

International Nuclear Information System (INIS)

Levitas, V.I.; Nesterenko, V.F.; Meyers, M.A.

1998-01-01

Strain-induced chemical reactions were observed recently (Nesterenko et al) in experiments in the shear band in both Ti-Si and Nb-Si mixtures. Reactions can start in the solid state or after melting of at least one component. One of the aims is to find theoretically whether there are possible macroscopic mechanisms of mechanical intensification of the above and other chemical reactions due to plastic shear in the solid state. Continuum thermodynamical theory of structural changes with an athermal kinetics, which includes martensitic phase transformations, plastic strain-induced chemical reactions and polymorphic transformations, is developed at finite strains. The theory includes kinematics, criterion of structural change and extremum principle for determination of all unknown variable parameters for the case with neglected elastic strains. Thermodynamically consistent kinetic theory of thermally activated structural changes is suggested. The concept of the effective temperature is introduced which takes into account that temperature can vary significantly (on 1,000 K) during the chemical reactions under consideration. The theory will be applied in Part 2 of the paper for the description of chemical reactions in the shear band

Computer-Aided Construction of Chemical Kinetic Models

Energy Technology Data Exchange (ETDEWEB)

Green, William H. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

2014-12-31

The combustion chemistry of even simple fuels can be extremely complex, involving hundreds or thousands of kinetically significant species. The most reasonable way to deal with this complexity is to use a computer not only to numerically solve the kinetic model, but also to construct the kinetic model in the first place. Because these large models contain so many numerical parameters (e.g. rate coefficients, thermochemistry) one never has sufficient data to uniquely determine them all experimentally. Instead one must work in “predictive” mode, using theoretical rather than experimental values for many of the numbers in the model, and as appropriate refining the most sensitive numbers through experiments. Predictive chemical kinetics is exactly what is needed for computer-aided design of combustion systems based on proposed alternative fuels, particularly for early assessment of the value and viability of proposed new fuels before those fuels are commercially available. This project was aimed at making accurate predictive chemical kinetics practical; this is a challenging goal which requires a range of science advances. The project spanned a wide range from quantum chemical calculations on individual molecules and elementary-step reactions, through the development of improved rate/thermo calculation procedures, the creation of algorithms and software for constructing and solving kinetic simulations, the invention of methods for model-reduction while maintaining error control, and finally comparisons with experiment. Many of the parameters in the models were derived from quantum chemistry calculations, and the models were compared with experimental data measured in our lab or in collaboration with others.

A century of enzyme kinetic analysis, 1913 to 2013.

Science.gov (United States)

Johnson, Kenneth A

2013-09-02

This review traces the history and logical progression of methods for quantitative analysis of enzyme kinetics from the 1913 Michaelis and Menten paper to the application of modern computational methods today. Following a brief review of methods for fitting steady state kinetic data, modern methods are highlighted for fitting full progress curve kinetics based upon numerical integration of rate equations, including a re-analysis of the original Michaelis-Menten full time course kinetic data. Finally, several illustrations of modern transient state kinetic methods of analysis are shown which enable the elucidation of reactions occurring at the active sites of enzymes in order to relate structure and function. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Topological and kinetic determinants of the modal matrices of dynamic models of metabolism.

Directory of Open Access Journals (Sweden)

Bin Du

Full Text Available Large-scale kinetic models of metabolism are becoming increasingly comprehensive and accurate. A key challenge is to understand the biochemical basis of the dynamic properties of these models. Linear analysis methods are well-established as useful tools for characterizing the dynamic response of metabolic networks. Central to linear analysis methods are two key matrices: the Jacobian matrix (J and the modal matrix (M-1 arising from its eigendecomposition. The modal matrix M-1 contains dynamically independent motions of the kinetic model near a reference state, and it is sparse in practice for metabolic networks. However, connecting the structure of M-1 to the kinetic properties of the underlying reactions is non-trivial. In this study, we analyze the relationship between J, M-1, and the kinetic properties of the underlying network for kinetic models of metabolism. Specifically, we describe the origin of mode sparsity structure based on features of the network stoichiometric matrix S and the reaction kinetic gradient matrix G. First, we show that due to the scaling of kinetic parameters in real networks, diagonal dominance occurs in a substantial fraction of the rows of J, resulting in simple modal structures with clear biological interpretations. Then, we show that more complicated modes originate from topologically-connected reactions that have similar reaction elasticities in G. These elasticities represent dynamic equilibrium balances within reactions and are key determinants of modal structure. The work presented should prove useful towards obtaining an understanding of the dynamics of kinetic models of metabolism, which are rooted in the network structure and the kinetic properties of reactions.

Dual kinetic curves in reversible electrochemical systems.

Directory of Open Access Journals (Sweden)

Michael J Hankins

Full Text Available We introduce dual kinetic chronoamperometry, in which reciprocal relations are established between the kinetic curves of electrochemical reactions that start from symmetrical initial conditions. We have performed numerical and experimental studies in which the kinetic curves of the electron-transfer processes are analyzed for a reversible first order reaction. Experimental tests were done with the ferrocyanide/ferricyanide system in which the concentrations of each component could be measured separately using the platinum disk/gold ring electrode. It is shown that the proper ratio of the transient kinetic curves obtained from cathodic and anodic mass transfer limited regions give thermodynamic time invariances related to the reaction quotient of the bulk concentrations. Therefore, thermodynamic time invariances can be observed at any time using the dual kinetic curves for reversible reactions. The technique provides a unique possibility to extract the non-steady state trajectory starting from one initial condition based only on the equilibrium constant and the trajectory which starts from the symmetrical initial condition. The results could impact battery technology by predicting the concentrations and currents of the underlying non-steady state processes in a wide domain from thermodynamic principles and limited kinetic information.

Maximum likelihood estimation of biophysical parameters of synaptic receptors from macroscopic currents

Directory of Open Access Journals (Sweden)

Andrey eStepanyuk

2014-10-01

Full Text Available Dendritic integration and neuronal firing patterns strongly depend on biophysical properties of synaptic ligand-gated channels. However, precise estimation of biophysical parameters of these channels in their intrinsic environment is complicated and still unresolved problem. Here we describe a novel method based on a maximum likelihood approach that allows to estimate not only the unitary current of synaptic receptor channels but also their multiple conductance levels, kinetic constants, the number of receptors bound with a neurotransmitter and the peak open probability from experimentally feasible number of postsynaptic currents. The new method also improves the accuracy of evaluation of unitary current as compared to the peak-scaled non-stationary fluctuation analysis, leading to a possibility to precisely estimate this important parameter from a few postsynaptic currents recorded in steady-state conditions. Estimation of unitary current with this method is robust even if postsynaptic currents are generated by receptors having different kinetic parameters, the case when peak-scaled non-stationary fluctuation analysis is not applicable. Thus, with the new method, routinely recorded postsynaptic currents could be used to study the properties of synaptic receptors in their native biochemical environment.

Cell proliferation kinetics and radiation response in 9L tumor spheroids

Energy Technology Data Exchange (ETDEWEB)

Sweigert, S.E.

1984-05-01

Cell kinetic parameters, including population doubling-time, cell cycle time, and growth fraction, were measured in 9L gliosarcoma spheroids. These parameters were studied as the spheroids grew from 50 ..mu..m to over 900 ..mu..m in diameter. Experiments relating the cell kinetic parameters to the radiation response of 9L spheroids were also carried out. The major findings were that the average cell cycle time (T/sub c/), is considerably longer in large spheroids than in exponentially-growing monolayers, the radiosensitivity of noncycling (but still viable) cells in spheroids is not significantly different from that of cycling spheroid cells, and the radiation-induced division delay is approximately twice as long in spheroid cells as in monolayer cells given equal radiation doses. The cell loss factor for spheroids of various sizes was calculated, by using the measured kinetic parameters in the basic equations for growth of a cell population. 157 references, 6 figures, 3 tables.

Cell proliferation kinetics and radiation response in 9L tumor spheroids

International Nuclear Information System (INIS)

Sweigert, S.E.

1984-05-01

Cell kinetic parameters, including population doubling-time, cell cycle time, and growth fraction, were measured in 9L gliosarcoma spheroids. These parameters were studied as the spheroids grew from 50 μm to over 900 μm in diameter. Experiments relating the cell kinetic parameters to the radiation response of 9L spheroids were also carried out. The major findings were that the average cell cycle time (T/sub c/), is considerably longer in large spheroids than in exponentially-growing monolayers, the radiosensitivity of noncycling (but still viable) cells in spheroids is not significantly different from that of cycling spheroid cells, and the radiation-induced division delay is approximately twice as long in spheroid cells as in monolayer cells given equal radiation doses. The cell loss factor for spheroids of various sizes was calculated, by using the measured kinetic parameters in the basic equations for growth of a cell population. 157 references, 6 figures, 3 tables

KINETICS OF SLURRY PHASE FISCHER-TROPSCH SYNTHESIS. FOURTH ANNUAL TECHNICAL PROGRESS REPORT

International Nuclear Information System (INIS)

Bukur, Dragomir B.; Froment, Gilbert F.; Olewski, Tomasz

2006-01-01

This report covers the fourth year of a research project conducted under the University Coal Research Program. The overall objective of this project is to develop a comprehensive kinetic model for slurry-phase Fischer-Tropsch synthesis (FTS) employing iron-based catalysts. This model will be validated with experimental data obtained in a stirred-tank slurry reactor (STSR) over a wide range of process conditions. The model will be able to predict molar flow rates and concentrations of all reactants and major product species (water, carbon dioxide, linear 1- and 2-olefins, and linear paraffins) as a function of reaction conditions in the STSR. During the fourth year of the project, an analysis of experimental data collected during the second year of this project was performed. Kinetic parameters were estimated utilizing product distributions from 27 mass balances. During the reporting period two kinetic models were employed: a comprehensive kinetic model of Dr. Li and co-workers (Yang et al., 2003) and a hydrocarbon selectivity model of Van der Laan and Beenackers (1998, 1999) The kinetic model of Yang et al. (2003) has 24 parameters (20 parameters for hydrocarbon formation, and 4 parameters for the water-gas-shift (WGS) reaction). Kinetic parameters for the WGS reaction and FTS synthesis were estimated first separately, and then simultaneously. The estimation of these kinetic parameters employed the Levenberg-Marquardt (LM) method and the trust-region reflective Newton large-scale (LS) method. A genetic algorithm (GA) was incorporated into estimation of parameters for FTS reaction to provide initial estimates of model parameters. All reaction rate constants and activation energies were found to be positive, but at the 95% confidence level the intervals were large. Agreement between predicted and experimental reaction rates has been fair to good. Light hydrocarbons are predicted fairly accurately, whereas the model underpredicts values of higher molecular weight

Co-pyrolysis of biomass and plastic wastes: investigation of apparent kinetic parameters and stability of pyrolysis oils

Science.gov (United States)

Fekhar, B.; Miskolczi, N.; Bhaskar, T.; Kumar, J.; Dhyani, V.

2018-05-01

This work is dedicated to the co-pyrolysis of real waste high density polyethylene (HDPE) and biomass (rice straw) obtained from agriculture. Mixtures of raw materials were pyrolyzed in their 0%/100%, 30%/70%, 50%/50%, 70%/30%, 100%/0% ratios using a thermograph. The atmosphere was nitrogen, and a constant heating rate was used. Based on weight loss and DTG curves, the apparent reaction kinetic parameters (e.g., activation energy) were calculated using first-order kinetic approach and Arrhenius equation. It was found that decomposition of pure plastic has approximately 280 kJ/mol activation energy, while that of was considerably less in case of biomass. Furthermore, HDPE decomposition takes by one stage, while that of biomass was three stages. The larger amount of raw materials (100 g) were also pyrolyzed in the batch rig at 550°C to obtain products for analysis focussing to their long-term application. Pyrolysis oils were investigated by Fourier transformed infrared spectroscopy and standardized methods, such as density, viscosity, boiling range determination. It was concluded, that higher plastic ratio in raw material had the advantageous effect to the pyrolysis oil long-term application. E.g., the concentration of oxygenated compounds, such as aldehydes, ketones, carboxylic acids or even phenol and its derivate could be significantly decreased, which had an advantageous effect to their corrosion property. Lower average molecular weight, viscosity, and density were measured as a function of plastic content.

Kinetics of the cooperative binding of glucose to dimeric yeast hexokinase P-I.

Science.gov (United States)

Hoggett, J G; Kellett, G L

1995-01-15

Kinetic studies of the cooperative binding of glucose to yeast hexokinase P-I at pH 6.5 have been carried out using the fluorescence temperature-jump technique. Three relaxation effects were observed: a fast low-amplitude effect which could only be resolved at low glucose concentrations (tau 1(-1) = 500-800 s-1), an intermediate effect (tau 2) which showed a linear dependence of reciprocal relaxation time on concentration, and a slow effect (tau 3) which showed a curved dependence on glucose concentration, increasing from approximately 28 s-1 at low concentrations to 250 s-1 at high levels. The findings are interpreted in terms of the concerted Monod-Wyman-Changeux mechanism, the two faster relaxations being assigned to binding to the R and T states, and the slow relaxation to isomerization between the states. Quantitative fitting of the kinetic data to the mechanism has been carried out using independent estimates of the equilibrium parameters of the model; these have been derived from equilibrium dialysis data and by determining the enhancement of the intrinsic ATPase activity of the enzyme by the non-phosphorylatable sugar lyxose, which switches the conformation of the enzyme to the active R state.

Kinetics of Pressurized Water Reactors with Hot or Cold Moderators

Energy Technology Data Exchange (ETDEWEB)

Norinder, O

1960-11-15

The set of neutron kinetic equations developed in this report permits the use of long integration steps during stepwise integration. Thermal relations which describe the transfer of heat from fuel to coolant are derived. The influence upon the kinetic behavior of the reactor of a number of parameters is studied. A comparison of the kinetic properties of the hot and cold moderators is given.

The sensitivity of a water distribution system to regional state parameter variations

CSIR Research Space (South Africa)

Page, Philip R

2018-05-01

Full Text Available ]. The following types of parameters fall in each category: Proportional Change Parameters 𝑋𝑖. (i) Pipe lengths 𝐿 (ii) Pipe diameters𝐷 (iii) Pipe roughness coefficients 𝐶 (Hazen-Williams), 𝑁 (Chezy-Manning) or for Darcy-Weisbach (iv) Minor loss coefficients... for the case where there is a single state parameter region. 5. Pipe Parameter Scaling Laws Assume that the major friction loss in a pipe is described by either the Hazen-Williams (H-W) or Chezy-Manning (C-M) formulae (defined in the Appendix), with 𝐶 and𝑁...

The application of polynomial chaos methods to a point kinetics model of MIPR: An Aqueous Homogeneous Reactor

International Nuclear Information System (INIS)

Cooling, C.M.; Williams, M.M.R.; Nygaard, E.T.; Eaton, M.D.

2013-01-01

Highlights: • A point kinetics model for the Medical Isotope Production Reactor is formulated. • Reactivity insertions are simulated using this model. • Polynomial chaos is used to simulate uncertainty in reactor parameters. • The computational efficiency of polynomial chaos is compared to that of Monte Carlo. -- Abstract: This paper models a conceptual Medical Isotope Production Reactor (MIPR) using a point kinetics model which is used to explore power excursions in the event of a reactivity insertion. The effect of uncertainty of key parameters is modelled using intrusive polynomial chaos. It is found that the system is stable against reactivity insertions and power excursions are all bounded and tend towards a new equilibrium state due to the negative feedbacks inherent in Aqueous Homogeneous Reactors (AHRs). The Polynomial Chaos Expansion (PCE) method is found to be much more computationally efficient than that of Monte Carlo simulation in this application

Kinetics of Texture and Colour Changes in Chicken Sausage during Superheated Steam Cooking

Directory of Open Access Journals (Sweden)

Abdulhameed Asmaa A.

2016-07-01

Full Text Available The aim of this study was to develop a kinetic model to describe the texture and colour changes of chicken sausage during superheated steam cooking. Chicken sausages were cooked at temperature ranging from 150-200°C with treatment times ranging from 2-6 mins. The texture profile was evaluated in terms of hardness, cohesiveness, gumminess, and chewiness, while the colour parameters were estimated in terms of lightness (L*, redness (a*, yellowness (b*, and total colour difference (∆E. Experimental data showed a gradual reduction in texture parameters as cooking times and temperatures increased. The L* value of the colour showed a linear reduction with cooking condition, while the a*, b*, and ∆E values showed a contrary effects. The decrease in texture parameters and L*-value of colour parameter followed the first-order kinetic model. While, zero-order kinetic model was adapted to fit the a* and b*. The modified first order kinetic showed a good fit for total ∆E. Significant correlations between colour and texture parameters were observed, which showed that a* alone could be used to predict the texture of chicken sausage.

Properties of Griffin-Hill-Wheeler spaces - 2. one-parameters and two-conjugate parameter families of generator states

International Nuclear Information System (INIS)

Passos, E.J.V. de; Toledo Piza, A.F.R. de.

The properties of the subspaces of the many-body Hilbert space which are associated with the use of the Generator Coordinate Method (GCM) in connection with one parameter, and with two-conjugate parameter families of generator states are examined in detail. It is shown that natural orthonormal base vectors in each case are immediately related to Peierls-Voccoz and Peierls-Thouless projections respectively. Through the formal consideration of a canonical transformation to collective, P and Q, and intrinsic degrees of freedom, the properties of the GCM subspaces with respect to the kinematical separation of these degrees of freedom are discussed in detail. An application is made, using the ideas developed in this paper, a) to translation; b) to illustrate the qualitative understanting of the content of existing GCM calculations of giant ressonances in light nuclei and c) to the definition of appropriate asymptotic states in current GCM descriptions of scattering [pt

Pyrolysis kinetics and thermodynamic parameters of castor (Ricinus communis) residue using thermogravimetric analysis.

Science.gov (United States)

Kaur, Ravneet; Gera, Poonam; Jha, Mithilesh Kumar; Bhaskar, Thallada

2018-02-01

Castor plant is a fast-growing, perennial shrub from Euphorbiaceae family. More than 50% of the residue is generated from its stems and leaves. The main aim of this work is to study the pyrolytic characteristics, kinetics and thermodynamic properties of castor residue. The TGA experiments were carried out from room temperature to 900 °C under an inert atmosphere at different heating rates of 5, 10, 15, 20, 30 and 40 °C/min. The kinetic analysis was carried using different models namely Kissinger, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The average E ɑ calculated by FWO and KAS methods were 167.10 and 165.86 kJ/mole respectively. Gibbs free energy varied from 150.62-154.33 to 150.59-154.65 kJ/mol for FWO and KAS respectively. The HHV of castor residue was 14.43 MJ/kg, considered as potential feedstock for bio-energy production. Kinetic and thermodynamic results will be useful input for the design of pyrolytic process using castor residue as feedstock. Copyright © 2017 Elsevier Ltd. All rights reserved.

Prediction of vapour-liquid equilibria for the kinetic study of processes based on synthesis gas

Energy Technology Data Exchange (ETDEWEB)

Di Serio, M.; Tesser, R.; Cozzolino, M.; Santacesaria, E. [Naples Univ., Napoli (Italy). Dept. of Chemistry

2006-07-01

Syngas is normally used in the production of a broad range of chemicals and fuels. In many of these processes multiphase reactors, gas-liquid or gas-liquid-solid are used. Kinetic studies in multiphase systems are often complicated by the non-ideal behaviour of reagents and/or products that are consistently partitioned between the liquid and the vapour phase. Moreover, as often kinetic data are collected in batch conditions for the liquid phase, activity coefficients of the partitioned components can consistently change during the time as a consequence of changing the composition of the reaction mixture. Therefore, it is necessary, in these cases, to known the vapor-liquid equilibria (VLE) in order to collect and to interpret correctly the kinetic data. The description of phase equilibria, at high pressures, is usually performed by means of an EOS (Equation of State) allowing the calculation of fugacity coefficients, for each component, in both phases and determining the partition coefficients but the EOS approach involves the experimental determination of the interaction parameters for all the possible binary system of the mixture. For multicomponent mixtures a complete experimental determination of vapourliquid equilibria is very hard, also considering the high pressure and temperatures used. Some predictive group contribution methods have been recently developed. In this paper, we will describe in detail the application of these methods to the methanol homologation, as an example, with the scope of determining more reliable kinetic parameters for this reaction. (orig.)

Determination of steady state and nonsteady-state glycerol kinetics in humans using deuterium-labeled tracer

International Nuclear Information System (INIS)

Beylot, M.; Martin, C.; Beaufrere, B.; Riou, J.P.; Mornex, R.

1987-01-01

Using deuterium-labeled glycerol as tracer and gas-liquid chromatography-mass spectrometry techniques for the determination of isotopic enrichment, we have developed a simple and ethically acceptable method of determining glycerol appearance rate in humans under steady-state and nonsteady-state conditions. In normal subjects, the appearance rate of glycerol in the post-absorptive state was 2.22 +/- 0.20 mumol X kg-1 X min-1, a value in agreement with those reported in studies with radioactively labeled tracers. The ratio nonesterified fatty acid (NEFA) appearance rate/glycerol appearance rate ranged from 1.95 to 3.40. In insulin-dependent diabetic patients with a mild degree of metabolic control, the appearance rate of glycerol was 2.48 +/- 0.29 mumol X kg-1 X min-1. The volume of distribution of glycerol, determined by the bolus injection technique, was (mean) 0.306 l X kg-1 in normal subjects and 0.308 l X kg-1 in insulin-independent diabetic patients. To evaluate the usefulness of the method for determination of glycerol kinetics in nonsteady-state conditions, we infused six normal subjects with natural glycerol and calculated the isotopically determined glycerol appearance rate using a single compartment model (volume of distribution 0.31 l X kg-1). During these tests, the expected glycerol appearance rates were successively 5.03 +/- 0.33, 7.48 +/- 0.39, 9.94 +/- 0.34, 7.48 +/- 0.39, and 5.03 +/- 0.33 mumol +/- kg-1 X min-1, whereas the corresponding isotopically determined appearance rates were 4.62 +/- 0.45, 6.95 +/- 0.56, 10.85 +/- 0.51, 7.35 +/- 0.34, and 5.28 +/- 0.12 mumol X kg-1 X min-1

Kinetic modelling of anaerobic hydrolysis of solid wastes, including disintegration processes

Energy Technology Data Exchange (ETDEWEB)

García-Gen, Santiago [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain); Sousbie, Philippe; Rangaraj, Ganesh [INRA, UR50, Laboratoire de Biotechnologie de l’Environnement, Avenue des Etangs, Narbonne F-11100 (France); Lema, Juan M. [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain); Rodríguez, Jorge, E-mail: jrodriguez@masdar.ac.ae [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain); Institute Centre for Water and Environment (iWater), Masdar Institute of Science and Technology, PO Box 54224 Abu Dhabi (United Arab Emirates); Steyer, Jean-Philippe; Torrijos, Michel [INRA, UR50, Laboratoire de Biotechnologie de l’Environnement, Avenue des Etangs, Narbonne F-11100 (France)

2015-01-15

Highlights: • Fractionation of solid wastes into readily and slowly biodegradable fractions. • Kinetic coefficients estimation from mono-digestion batch assays. • Validation of kinetic coefficients with a co-digestion continuous experiment. • Simulation of batch and continuous experiments with an ADM1-based model. - Abstract: A methodology to estimate disintegration and hydrolysis kinetic parameters of solid wastes and validate an ADM1-based anaerobic co-digestion model is presented. Kinetic parameters of the model were calibrated from batch reactor experiments treating individually fruit and vegetable wastes (among other residues) following a new protocol for batch tests. In addition, decoupled disintegration kinetics for readily and slowly biodegradable fractions of solid wastes was considered. Calibrated parameters from batch assays of individual substrates were used to validate the model for a semi-continuous co-digestion operation treating simultaneously 5 fruit and vegetable wastes. The semi-continuous experiment was carried out in a lab-scale CSTR reactor for 15 weeks at organic loading rate ranging between 2.0 and 4.7 g VS/L d. The model (built in Matlab/Simulink) fit to a large extent the experimental results in both batch and semi-continuous mode and served as a powerful tool to simulate the digestion or co-digestion of solid wastes.

Action-reaction based parameters identification and states estimation of flexible systems

OpenAIRE

Khalil, Islam; Kunt, Emrah Deniz; Şabanoviç, Asif; Sabanovic, Asif

2012-01-01

This work attempts to identify and estimate flexible system's parameters and states by a simple utilization of the Action-Reaction law of dynamical systems. Attached actuator to a dynamical system or environmental interaction imposes an action that is instantaneously followed by a dynamical system reaction. The dynamical system's reaction carries full information about the dynamical system including system parameters, dynamics and externally applied forces that arise due to system interaction...

Parameter retrieval of chiral metamaterials based on the state-space approach.

Science.gov (United States)

Zarifi, Davoud; Soleimani, Mohammad; Abdolali, Ali

2013-08-01

This paper deals with the introduction of an approach for the electromagnetic characterization of homogeneous chiral layers. The proposed method is based on the state-space approach and properties of a 4×4 state transition matrix. Based on this, first, the forward problem analysis through the state-space method is reviewed and properties of the state transition matrix of a chiral layer are presented and proved as two theorems. The formulation of a proposed electromagnetic characterization method is then presented. In this method, scattering data for a linearly polarized plane wave incident normally on a homogeneous chiral slab are combined with properties of a state transition matrix and provide a powerful characterization method. The main difference with respect to other well-established retrieval procedures based on the use of the scattering parameters relies on the direct computation of the transfer matrix of the slab as opposed to the conventional calculation of the propagation constant and impedance of the modes supported by the medium. The proposed approach allows avoiding nonlinearity of the problem but requires getting enough equations to fulfill the task which was provided by considering some properties of the state transition matrix. To demonstrate the applicability and validity of the method, the constitutive parameters of two well-known dispersive chiral metamaterial structures at microwave frequencies are retrieved. The results show that the proposed method is robust and reliable.

Comparison of one-dimensional and point kinetics for various light water reactor transients

International Nuclear Information System (INIS)

Naser, J.A.; Lin, C.; Gose, G.C.; McClure, J.A.; Matsui, Y.

1985-01-01

The object of this paper is to compare the results from the three kinetics options: 1) point kinetics; 2) point kinetics by not changing the shape function; and 3) one-dimensional kinetics for various transients on both BWRs and PWRs. A systematic evaluation of the one-dimensional kinetics calculation and its alternatives is performed to determine the status of these models and to identify additional development work. In addition, for PWRs, the NODEP-2 - NODETRAN and SIMULATE - SIMTRAN paths for calculating kinetics parameters are compared. This type of comparison has not been performed before and is needed to properly evaluate the RASP methodology of which these codes are a part. It should be noted that RASP is in its early pre-release stage and this is the first serious attempt to examine the consistency between these two similar but different methods of generating physics parameters for the RETRAN computer code

Mechanistic study of manganese-substituted glycerol dehydrogenase using a kinetic and thermodynamic analysis.

Science.gov (United States)

Fang, Baishan; Niu, Jin; Ren, Hong; Guo, Yingxia; Wang, Shizhen

2014-01-01

Mechanistic insights regarding the activity enhancement of dehydrogenase by metal ion substitution were investigated by a simple method using a kinetic and thermodynamic analysis. By profiling the binding energy of both the substrate and product, the metal ion's role in catalysis enhancement was revealed. Glycerol dehydrogenase (GDH) from Klebsiella pneumoniae sp., which demonstrated an improvement in activity by the substitution of a zinc ion with a manganese ion, was used as a model for the mechanistic study of metal ion substitution. A kinetic model based on an ordered Bi-Bi mechanism was proposed considering the noncompetitive product inhibition of dihydroxyacetone (DHA) and the competitive product inhibition of NADH. By obtaining preliminary kinetic parameters of substrate and product inhibition, the number of estimated parameters was reduced from 10 to 4 for a nonlinear regression-based kinetic parameter estimation. The simulated values of time-concentration curves fit the experimental values well, with an average relative error of 11.5% and 12.7% for Mn-GDH and GDH, respectively. A comparison of the binding energy of enzyme ternary complex for Mn-GDH and GDH derived from kinetic parameters indicated that metal ion substitution accelerated the release of dioxyacetone. The metal ion's role in catalysis enhancement was explicated.

Mechanistic study of manganese-substituted glycerol dehydrogenase using a kinetic and thermodynamic analysis.

Directory of Open Access Journals (Sweden)

Baishan Fang

Full Text Available Mechanistic insights regarding the activity enhancement of dehydrogenase by metal ion substitution were investigated by a simple method using a kinetic and thermodynamic analysis. By profiling the binding energy of both the substrate and product, the metal ion's role in catalysis enhancement was revealed. Glycerol dehydrogenase (GDH from Klebsiella pneumoniae sp., which demonstrated an improvement in activity by the substitution of a zinc ion with a manganese ion, was used as a model for the mechanistic study of metal ion substitution. A kinetic model based on an ordered Bi-Bi mechanism was proposed considering the noncompetitive product inhibition of dihydroxyacetone (DHA and the competitive product inhibition of NADH. By obtaining preliminary kinetic parameters of substrate and product inhibition, the number of estimated parameters was reduced from 10 to 4 for a nonlinear regression-based kinetic parameter estimation. The simulated values of time-concentration curves fit the experimental values well, with an average relative error of 11.5% and 12.7% for Mn-GDH and GDH, respectively. A comparison of the binding energy of enzyme ternary complex for Mn-GDH and GDH derived from kinetic parameters indicated that metal ion substitution accelerated the release of dioxyacetone. The metal ion's role in catalysis enhancement was explicated.

Kinetics of laser irradiated nanoparticles cloud

Science.gov (United States)

Mishra, S. K.; Upadhyay Kahaly, M.; Misra, Shikha

2018-02-01

A comprehensive kinetic model describing the complex kinetics of a laser irradiated nanoparticle ensemble has been developed. The absorbed laser radiation here serves dual purpose, viz., photoenhanced thermionic emission via rise in its temperature and direct photoemission of electrons. On the basis of mean charge theory along with the equations for particle (electron) and energy flux balance over the nanoparticles, the transient processes of charge/temperature evolution over its surface and mass diminution on account of the sublimation (phase change) process have been elucidated. Using this formulation phenomenon of nanoparticle charging, its temperature rise to the sublimation point, mass ablation, and cloud disintegration have been investigated; afterwards, typical timescales of disintegration, sublimation and complete evaporation in reference to a graphite nanoparticle cloud (as an illustrative case) have been parametrically investigated. Based on a numerical analysis, an adequate parameter space describing the nanoparticle operation below the sublimation temperature, in terms of laser intensity, wavelength and nanoparticle material work function, has been identified. The cloud disintegration is found to be sensitive to the nanoparticle charging through photoemission; as a consequence, it illustrates that radiation operating below the photoemission threshold causes disintegration in the phase change state, while above the threshold, it occurs with the onset of surface heating.

Uptake kinetics of arsenic by lettuce cultivars under hydroponics ...

African Journals Online (AJOL)

Arsenic (As) uptake ability based on kinetic parameters by two lettuce cultivars; Sijibaiye (SJBY) and Texuanyanlingsun (TXYLS) was investigated in nutrient solution containing eight levels of arsenic (As). Depletion of As from solution was monitored over a period of 24 h at regular time to estimate As uptake kinetics of the ...

Development and application of a three-parameter RK-PR equation of state

DEFF Research Database (Denmark)

Cismondi, Martin; Mollerup, Jørgen

2005-01-01

In this work, we confirm the somehow previously expressed but not widespread idea that the limitations of cubic equations of state like Soave-Redlich-Kwong equation (SRK) or Peng-Robinson equation (PR) are a consequence of their two-parameter density dependence rather than of their empiric......-PR) equation offers the best performance among cubic three-parameter density functionalities. A simple temperature dependence was developed and a straightforward parameterization procedure established. This simple - and optimized from pure compound data - three-parameter equation of state (3P-EoS) will allow...... in a later stage, by systematic study and comparison to other types of 3P-EoS, to find out what the actual possibilities and limitations of cubic EoS are in the modelling of phase equilibria for asymmetric systems. (c) 2005 Elsevier B.V. All rights reserved....

Response-based estimation of sea state parameters - Influence of filtering

DEFF Research Database (Denmark)

Nielsen, Ulrik Dam

2007-01-01

Reliable estimation of the on-site sea state parameters is essential to decision support systems for safe navigation of ships. The wave spectrum can be estimated from procedures based on measured ship responses. The paper deals with two procedures—Bayesian Modelling and Parametric Modelling...

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

Science.gov (United States)

Chen, Dengyu; Zhou, Jianbin; Zhang, Qisheng

2014-10-01

Effects of heating rate on slow pyrolysis behaviors, kinetic parameters, and products properties of moso bamboo were investigated in this study. Pyrolysis experiments were performed up to 700 °C at heating rates of 5, 10, 20, and 30 °C/min using thermogravimetric analysis (TGA) and a lab-scale fixed bed pyrolysis reactor. The results show that the onset and offset temperatures of the main devolatilization stage of thermogravimetry/derivative thermogravimetry (TG/DTG) curves obviously shift toward the high-temperature range, and the activation energy values increase with increasing heating rate. The heating rate has different effects on the pyrolysis products properties, including biochar (element content, proximate analysis, specific surface area, heating value), bio-oil (water content, chemical composition), and non-condensable gas. The solid yields from the fixed bed pyrolysis reactor are noticeably different from those of TGA mainly because the thermal hysteresis of the sample in the fixed bed pyrolysis reactor is more thorough. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Novel Coupled State/Input/Parameter Identification Method for Linear Structural Systems

Directory of Open Access Journals (Sweden)

Zhimin Wan

2018-01-01

Full Text Available In many engineering applications, unknown states, inputs, and parameters exist in the structures. However, most methods require one or two of these variables to be known in order to identify the other(s. Recently, the authors have proposed a method called EGDF for coupled state/input/parameter identification for nonlinear system in state space. However, the EGDF method based solely on acceleration measurements is found to be unstable, which can cause the drift of the identified inputs and displacements. Although some regularization methods can be adopted for solving the problem, they are not suitable for joint input-state identification in real time. In this paper, a strategy of data fusion of displacement and acceleration measurements is used to avoid the low-frequency drift in the identified inputs and structural displacements for linear structural systems. Two numerical examples about a plane truss and a single-stage isolation system are conducted to verify the effectiveness of the proposed modified EGDF algorithm.

Estimating Arrhenius parameters using temperature programmed molecular dynamics

International Nuclear Information System (INIS)

Imandi, Venkataramana; Chatterjee, Abhijit

2016-01-01

Kinetic rates at different temperatures and the associated Arrhenius parameters, whenever Arrhenius law is obeyed, are efficiently estimated by applying maximum likelihood analysis to waiting times collected using the temperature programmed molecular dynamics method. When transitions involving many activated pathways are available in the dataset, their rates may be calculated using the same collection of waiting times. Arrhenius behaviour is ascertained by comparing rates at the sampled temperatures with ones from the Arrhenius expression. Three prototype systems with corrugated energy landscapes, namely, solvated alanine dipeptide, diffusion at the metal-solvent interphase, and lithium diffusion in silicon, are studied to highlight various aspects of the method. The method becomes particularly appealing when the Arrhenius parameters can be used to find rates at low temperatures where transitions are rare. Systematic coarse-graining of states can further extend the time scales accessible to the method. Good estimates for the rate parameters are obtained with 500-1000 waiting times.

Estimating Arrhenius parameters using temperature programmed molecular dynamics

Energy Technology Data Exchange (ETDEWEB)

Imandi, Venkataramana; Chatterjee, Abhijit, E-mail: abhijit@che.iitb.ac.in [Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India)

2016-07-21

Kinetic rates at different temperatures and the associated Arrhenius parameters, whenever Arrhenius law is obeyed, are efficiently estimated by applying maximum likelihood analysis to waiting times collected using the temperature programmed molecular dynamics method. When transitions involving many activated pathways are available in the dataset, their rates may be calculated using the same collection of waiting times. Arrhenius behaviour is ascertained by comparing rates at the sampled temperatures with ones from the Arrhenius expression. Three prototype systems with corrugated energy landscapes, namely, solvated alanine dipeptide, diffusion at the metal-solvent interphase, and lithium diffusion in silicon, are studied to highlight various aspects of the method. The method becomes particularly appealing when the Arrhenius parameters can be used to find rates at low temperatures where transitions are rare. Systematic coarse-graining of states can further extend the time scales accessible to the method. Good estimates for the rate parameters are obtained with 500-1000 waiting times.

Thermodynamic study of fluid in terms of equation of state containing physical parameters

International Nuclear Information System (INIS)

Khasare, S. B.

2015-01-01

We introduce a simple condition for one mole fluid by considering the thermodynamics of molecules pointing towards the effective potential for the cluster. Efforts are made to estimate new physical parameter f in liquid state using the equation of state containing only two physical parameters such as the hard sphere diameter and binding energy. The temperature dependence of the structural properties and the thermodynamic behavior of the clusters are studied. Computations based on f predict the variation of numbers of particles at the contact point of the molecular cavity (radial distribution function). From the thermodynamic profile of the fluid, the model results are discussed in terms of the cavity due to the closed surface along with suitable energy. The present calculation is based upon the sample thermodynamic data for n-hexanol, such as the ultrasonic wave, density, volume expansion coefficient, and ratio of specific heat in the liquid state, and it is consistent with the thermodynamic relations containing physical parameters such as size and energy. Since the data is restricted to n-hexanol, we avoid giving the physical meaning of f, which is the key parameter studied in the present work. (paper)

Influence of excited molecules on electron swarm transport coefficients and gas discharge kinetics