DEFF Research Database (Denmark)
Chen, B. H.; Micheletti, M.; Baganz, F.;
2009-01-01
design. It incorporates a model driven approach to the experimental design that minimises the number of experiments to be performed, while still generating accurate values of kinetic parameters. The approach has been illustrated with the transketolase mediated asymmetric synthesis of L...... experimental design.]it comparison with conventional methodology, the modelling approach enabled a nearly 4-fold decrease in the number of experiments while the microwell experimentation enabled a 45-fold decrease in material requirements and a significant increase in experimental throughput. The approach......Reliable models of enzyme kinetics are required for the effective design of bioconversion processes. Kinetic expressions of the enzyme-catalysed reaction rate however, are frequently complex and establishing accurate values of kinetic parameters normally requires a large number of experiments...
An empirical model on extractive lactic acid bioconversion.
Srivastava, A; Yunus, R; Roychoudhury, P K
1999-01-01
The commercial production of lactic acid through fermentation process has always been in competition with its chemical synthesis process (Kirk Othmer, 1995). Lactic acid produced through the fermentation process has to cope with the problems of purification to meet the required quality standards. An attempt to improve the fermentative production is possible by proper design of an industrial process involving low capital cost for the plant. Also, the low energy costs both in its fermentation and purification, are required. In the commercial interest, the investment cost should be minimised, which is possible only when the cell density in fermenter is high. It means that the inhibitory effect of the product on process kinetics must be minimised. Based on these requirements, the extractive bioconversion technique is one of the approaches to achieve the commercially viable lactic acid production. Extractive lactic acid bioconversion using ion-exchange resin process has already been described in our earlier publications (Srivastava e al., 1992: Roychoudhury et al., 1995) It is always an advantage to develop a process model, thus opening an area of biotechnological improvements to the process. In the present paper, an empirical mathematical model has been described to explain this extractive bioconversion using ion-exchange resin process. It was based on generalised Monod's growth model and Leudeking and Piret equation. The system was defined with the assumption that the microbial growth can be represented as a single reaction; only a very little part of the substrate is utilised for the maintenance of the cells. The effect of end product inhibition on growth and product formation kinetics has also been considered in this model. A non-linear regression technique was used for evaluation of bioconversion kinetic parameters. The fourth order Runge Kutta method was used for solving the differential equations. The results of this process simulation are also discussed in the
Advanced modelling, monitoring, and process control of bioconversion systems
Schmitt, Elliott C.
Production of fuels and chemicals from lignocellulosic biomass is an increasingly important area of research and industrialization throughout the world. In order to be competitive with fossil-based fuels and chemicals, maintaining cost-effectiveness is critical. Advanced process control (APC) and optimization methods could significantly reduce operating costs in the biorefining industry. Two reasons APC has previously proven challenging to implement for bioprocesses include: lack of suitable online sensor technology of key system components, and strongly nonlinear first principal models required to predict bioconversion behavior. To overcome these challenges batch fermentations with the acetogen Moorella thermoacetica were monitored with Raman spectroscopy for the conversion of real lignocellulosic hydrolysates and a kinetic model for the conversion of synthetic sugars was developed. Raman spectroscopy was shown to be effective in monitoring the fermentation of sugarcane bagasse and sugarcane straw hydrolysate, where univariate models predicted acetate concentrations with a root mean square error of prediction (RMSEP) of 1.9 and 1.0 g L-1 for bagasse and straw, respectively. Multivariate partial least squares (PLS) models were employed to predict acetate, xylose, glucose, and total sugar concentrations for both hydrolysate fermentations. The PLS models were more robust than univariate models, and yielded a percent error of approximately 5% for both sugarcane bagasse and sugarcane straw. In addition, a screening technique was discussed for improving Raman spectra of hydrolysate samples prior to collecting fermentation data. Furthermore, a mechanistic model was developed to predict batch fermentation of synthetic glucose, xylose, and a mixture of the two sugars to acetate. The models accurately described the bioconversion process with an RMSEP of approximately 1 g L-1 for each model and provided insights into how kinetic parameters changed during dual substrate
DEFF Research Database (Denmark)
Fitamo, Temesgen Mathewos; Boldrin, Alessio; Dorini, G.;
2016-01-01
strategies for controlling and optimising the co-digestion process. The model parameters were maintained in the same way as the original dynamic bioconversion model, albeit with minor adjustments, to simulate the co-digestion of food and garden waste with mixed sludge from a wastewater treatment plant......Mathematical anaerobic bioconversion models are often used as a convenient way to simulate the conversion of organic materials to biogas. The aim of the study was to apply a mathematical model for simulating the anaerobic co-digestion of various types of urban organic waste, in order to develop...... in a continuously stirred tank reactor. The model's outputs were validated with experimental results obtained in thermophilic conditions, with mixed sludge as a single substrate and urban organic waste as a co-substrate at hydraulic retention times of 30, 20, 15 and 10 days. The predicted performance parameter...
Hoang, Nguyen Huu; Huong, Nguyen Lan; Kim, Byul; Park, Je Won
2016-12-01
Kinetics of a recombinant uridine diphosphate-glucose: sterol glycosyltransferase from Micromonospora rhodorangea ATCC 27932 (MrSGT) were studied using a number of sterols (including phytosterols) as glycosyl acceptors. The lowest K m value and the highest catalytical efficiency (k cat/K m) were found when β-sitosterol was the glycosyl acceptor in the enzymatic reaction. In contrast to the enzyme's flexibility toward the glycosyl acceptor substrate, this recombinant enzyme was highly specific to uridine diphosphate (UDP)-glucose as the donor substrate. Besides, the UDP-glucose-dependent MrSGT was able to attach one glucose moiety specifically onto the C-3 hydroxyl group of other phytosterols such as fucosterol and gramisterol, yielding stereo-specific fucosterol-3-O-β-D-glucoside and gramisterol-3-O-β-D-glucoside, respectively. Based on kinetic data obtained from the enzyme's reactions using five different sterol substrates, the significance of the alkene (or ethylidene) side chains on the C-24 position in the sterol scaffolds was described and the possible relationship between the substrate structure and enzyme activity was discussed. This is the first report on the enzymatic bioconversion of the above two phytosteryl 3-O-β-glucosides, as well as on the discovery of a stereospecific bacterial SGT which can attach a glucose moiety in β-conformation at the C-3 hydroxyl group of diverse sterols, thus highlighting the catalytic potential of this promiscuous glycosyltransferase to expand the structural diversity of steryl glucosides. PMID:27485517
Bioconversion of lignin model compounds with oleaginous Rhodococci
Energy Technology Data Exchange (ETDEWEB)
Kosa, Matyas; Ragauskas, Arthur J. [Georgia Institute of Technology, Atlanta, GA (United States). Dept. of Chemistry and Biochemistry
2012-01-15
Although economically efficient biomass conversion depends on the utilization of the complete cell wall (biorefinery concept), including polysaccharides and lignin, current biofuels research concentrate mostly on cellulose conversion, while lignin is viewed as a side-product that is used primarily as a thermal resource. Microbiological conversion of lignin is almost exclusive to fungi, usually resulting in increased cell mass and lignolytic enzymes. Some bacteria can also degrade lignin-related compounds using the {beta}-ketoadipate pathway; for example, Rhodococcus opacus DSM 1069 can degrade coniferyl alcohol and grow on it as sole carbon source. Moreover, this strain belongs to the actinomycetes group that is also known for oleaginous species with lipid accumulation over 20%. Present work shows that R. opacus DSM 1069 and PD630 strains under nitrogen limiting conditions can convert lignin model compounds into triacylglycerols, also known as neutral lipids. 4-Hydroxybenzoic and vanillic acid lignin model compounds were used as sole carbon sources, and after brief adaptation periods, the cells not only began growing but accumulated lipids to the level of oleaginicity. These lipids were extracted for transesterification and analysis of fatty acid methyl esters showed good composition for biodiesel applications with no aromatics. Furthermore, the two strains showed distinct substrate metabolism and product profiles. (orig.)
International Nuclear Information System (INIS)
A normalized form of the point kinetics equations, a prompt jump approximation, and the Nordheim-Fuchs model are used to model nuclear systems. Reactivity feedback mechanisms considered include volumetric expansion, thermal neutron temperature effect, Doppler effect and void formation. A sample problem of an excursion occurring in a plutonium solution accidentally formed in a glovebox is presented
Oxidative desulfurization: Kinetic modelling
Energy Technology Data Exchange (ETDEWEB)
Dhir, S.; Uppaluri, R. [Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India); Purkait, M.K. [Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India)], E-mail: mihir@iitg.ernet.in
2009-01-30
Increasing environmental legislations coupled with enhanced production of petroleum products demand, the deployment of novel technologies to remove organic sulfur efficiently. This work represents the kinetic modeling of ODS using H{sub 2}O{sub 2} over tungsten-containing layered double hydroxide (LDH) using the experimental data provided by Hulea et al. [V. Hulea, A.L. Maciuca, F. Fajula, E. Dumitriu, Catalytic oxidation of thiophenes and thioethers with hydrogen peroxide in the presence of W-containing layered double hydroxides, Appl. Catal. A: Gen. 313 (2) (2006) 200-207]. The kinetic modeling approach in this work initially targets the scope of the generation of a superstructure of micro-kinetic reaction schemes and models assuming Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms. Subsequently, the screening and selection of above models is initially based on profile-based elimination of incompetent schemes followed by non-linear regression search performed using the Levenberg-Marquardt algorithm (LMA) for the chosen models. The above analysis inferred that Eley-Rideal mechanism describes the kinetic behavior of ODS process using tungsten-containing LDH, with adsorption of reactant and intermediate product only taking place on the catalyst surface. Finally, an economic index is presented that scopes the economic aspects of the novel catalytic technology with the parameters obtained during regression analysis to conclude that the cost factor for the catalyst is 0.0062-0.04759 US $ per barrel.
Oxidative desulfurization: kinetic modelling.
Dhir, S; Uppaluri, R; Purkait, M K
2009-01-30
Increasing environmental legislations coupled with enhanced production of petroleum products demand, the deployment of novel technologies to remove organic sulfur efficiently. This work represents the kinetic modeling of ODS using H(2)O(2) over tungsten-containing layered double hydroxide (LDH) using the experimental data provided by Hulea et al. [V. Hulea, A.L. Maciuca, F. Fajula, E. Dumitriu, Catalytic oxidation of thiophenes and thioethers with hydrogen peroxide in the presence of W-containing layered double hydroxides, Appl. Catal. A: Gen. 313 (2) (2006) 200-207]. The kinetic modeling approach in this work initially targets the scope of the generation of a superstructure of micro-kinetic reaction schemes and models assuming Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms. Subsequently, the screening and selection of above models is initially based on profile-based elimination of incompetent schemes followed by non-linear regression search performed using the Levenberg-Marquardt algorithm (LMA) for the chosen models. The above analysis inferred that Eley-Rideal mechanism describes the kinetic behavior of ODS process using tungsten-containing LDH, with adsorption of reactant and intermediate product only taking place on the catalyst surface. Finally, an economic index is presented that scopes the economic aspects of the novel catalytic technology with the parameters obtained during regression analysis to conclude that the cost factor for the catalyst is 0.0062-0.04759 US $ per barrel. PMID:18541367
Modeling chemical kinetics graphically
A. Heck
2012-01-01
In literature on chemistry education it has often been suggested that students, at high school level and beyond, can benefit in their studies of chemical kinetics from computer supported activities. Use of system dynamics modeling software is one of the suggested quantitative approaches that could h
Energy Technology Data Exchange (ETDEWEB)
Westbrook, C.K.; Pitz, W.J. [Lawrence Livermore National Laboratory, CA (United States)
1993-12-01
This project emphasizes numerical modeling of chemical kinetics of combustion, including applications in both practical combustion systems and in controlled laboratory experiments. Elementary reaction rate parameters are combined into mechanisms which then describe the overall reaction of the fuels being studied. Detailed sensitivity analyses are used to identify those reaction rates and product species distributions to which the results are most sensitive and therefore warrant the greatest attention from other experimental and theoretical research programs. Experimental data from a variety of environments are combined together to validate the reaction mechanisms, including results from laminar flames, shock tubes, flow systems, detonations, and even internal combustion engines.
Modelling heart rate kinetics.
Directory of Open Access Journals (Sweden)
Maria S Zakynthinaki
Full Text Available The objective of the present study was to formulate a simple and at the same time effective mathematical model of heart rate kinetics in response to movement (exercise. Based on an existing model, a system of two coupled differential equations which give the rate of change of heart rate and the rate of change of exercise intensity is used. The modifications introduced to the existing model are justified and discussed in detail, while models of blood lactate accumulation in respect to time and exercise intensity are also presented. The main modification is that the proposed model has now only one parameter which reflects the overall cardiovascular condition of the individual. The time elapsed after the beginning of the exercise, the intensity of the exercise, as well as blood lactate are also taken into account. Application of the model provides information regarding the individual's cardiovascular condition and is able to detect possible changes in it, across the data recording periods. To demonstrate examples of successful numerical fit of the model, constant intensity experimental heart rate data sets of two individuals have been selected and numerical optimization was implemented. In addition, numerical simulations provided predictions for various exercise intensities and various cardiovascular condition levels. The proposed model can serve as a powerful tool for a complete means of heart rate analysis, not only in exercise physiology (for efficiently designing training sessions for healthy subjects but also in the areas of cardiovascular health and rehabilitation (including application in population groups for which direct heart rate recordings at intense exercises are not possible or not allowed, such as elderly or pregnant women.
International Nuclear Information System (INIS)
Highlights: ► We have studied the coupling among gas, plasma and surface in the divertor region. ► A one-dimensional PIC-DSMC model has been developed. ► Profiles of density and temperature of all the species involved have been provided. ► MAR processes are effective in a region smaller than 1.5 mm from the divertor plate. ► For regions more distant, the ionization of atoms, produced by MAR, starts to occur. - Abstract: The coupled dynamics and kinetics between gas and plasma in the divertor region is studied by means of a one-dimensional Particle in Cell-Direct Simulation Monte Carlo (PIC-DSMC) model. In particular, the collision-induced vibrational excitation/relaxation of H2 molecules and particle–surface interaction (vibrational relaxation and recombinative desorption) have been considered in detail to estimate the importance of plasma volumetric recombination by molecular assisted reaction (MAR). Spatially resolved results show that MAR processes are effective very close to the divertor plate in a region smaller than 1.5 mm from the divertor plate. For regions more distant the ionization of atoms, produced by MAR, starts to make molecular assisted recombination an ineffective reaction.
Crystallization Kinetics within a Generic Modelling Framework
DEFF Research Database (Denmark)
Meisler, Kresten Troelstrup; von Solms, Nicolas; Gernaey, Krist;
2013-01-01
An existing generic modelling framework has been expanded with tools for kinetic model analysis. The analysis of kinetics is carried out within the framework where kinetic constitutive models are collected, analysed and utilized for the simulation of crystallization operations. A modelling...... procedure is proposed to gain the information of crystallization operation kinetic model analysis and utilize this for faster evaluation of crystallization operations....
A comprehensive model of anaerobic bioconversion of complex substrates to biogas
DEFF Research Database (Denmark)
Angelidaki, Irini; Ellegaard, Lars; Ahring, Birgitte Kiær
1999-01-01
.e., carbohydrates, lipids, and proteins, the concentration of intermediates such as volatile fatty acids and long-chain fatty acids, and important inorganic components, i.e., ammonia, phosphate, cations, and anions. This allows dynamic changes of the process during a shift of substrate composition to be simulated......) constitute the primary modulating factors in the model. The model was rested with success in lab-scale reactors codigesting manure with glycerol trioleate or manure with gelatin. Finally, the model was validated using results from a full-scale biogas plant codigesting manure together with a proteinous...
Chemical kinetics and combustion modeling
Energy Technology Data Exchange (ETDEWEB)
Miller, J.A. [Sandia National Laboratories, Livermore, CA (United States)
1993-12-01
The goal of this program is to gain qualitative insight into how pollutants are formed in combustion systems and to develop quantitative mathematical models to predict their formation rates. The approach is an integrated one, combining low-pressure flame experiments, chemical kinetics modeling, theory, and kinetics experiments to gain as clear a picture as possible of the process in question. These efforts are focused on problems involved with the nitrogen chemistry of combustion systems and on the formation of soot and PAH in flames.
Kinetic Modeling of Biological Systems
Energy Technology Data Exchange (ETDEWEB)
Resat, Haluk; Petzold, Linda; Pettigrew, Michel F.
2009-04-21
The dynamics of how its constituent components interact define the spatio-temporal response of a natural system to stimuli. Modeling the kinetics of the processes that represent a biophysical system has long been pursued with the aim of improving our understanding of the studied system. Due to the unique properties of biological systems, in addition to the usual difficulties faced in modeling the dynamics of physical or chemical systems, biological simulations encounter difficulties that result from intrinsic multiscale and stochastic nature of the biological processes. This chapter discusses the implications for simulation of models involving interacting species with very low copy numbers, which often occur in biological systems and give rise to significant relative fluctuations. The conditions necessitating the use of stochastic kinetic simulation methods and the mathematical foundations of the stochastic simulation algorithms are presented. How the well-organized structural hierarchies often seen in biological systems can lead to multiscale problems, and possible ways to address the encountered computational difficulties are discussed. We present the details of the existing kinetic simulation methods, and discuss their strengths and shortcomings. A list of the publicly available kinetic simulation tools and our reflections for future prospects are also provided.
Quantum kinetic Heisenberg models: a unique dynamics
International Nuclear Information System (INIS)
We suggest that the dynamics Glauber embodied in his kinetic Ising model can be introduced similarly and in an apparently unique way, into the quantum statistical mechanics of the quantum-integrable models like the Heisenberg, sine-Gordon and Massive Thirring models. The latter may suggest an extension of the theory to unique kinetic Ising models in two dimensions. The kinetic repulsive bose gas which is studied in detail in the steady state seems to be a solvable kinetic model. (author)
Kinetic models of conjugated metabolic cycles
Ershov, Yu. A.
2016-01-01
A general method is developed for the quantitative kinetic analysis of conjugated metabolic cycles in the human organism. This method is used as a basis for constructing a kinetic graph and model of the conjugated citric acid and ureapoiesis cycles. The results from a kinetic analysis of the model for these cycles are given.
Kinetics model for lutate dosimetry
International Nuclear Information System (INIS)
The use of compartmental analysis to predict the behavior of drugs in the organism is considered the better option among numerous methods employed in pharmacodynamics. A six compartments model was developed to determinate the kinetic constants of 177Lu-DOTATATO biodistribution using data from one published study with 67 patients treated by PRRT (Peptide receptor radionuclide therapy) and followed by CT during 68,25 hours. The compartmental analysis was made using the software AnaComp®. The influence of the time pos-injection over the dose assessment was studied taking into account the renal excretion management by aminoacid coinfusion, whose direct effects persist in the first day. The biodistribution curve was split in five sectors: 0-0.25h; 0-3.25h; 3.25-24.25h; 24.25-68.25h and 3.25-68.25h. After the examination of that influence, the study was concentrated in separate the biodistribution curve in two phases. Phase 1: governed by uptake from the blood, considering the time pos-injection until 3.25h and phase 2: governed by renal excretion, considering the time pos-injection from 3.25h to 68.25h. The model considered the organs and tissues superposition in the CT image acquisition by sampling parameters as the contribution of the the activity concentration in blood and relation between the sizes of the whole body and measured organs. The kinetic constants obtained from each phase (1 and 2) were used in dose assessment to patients in 26 organs and tissues described by MIRD. Dosimetry results were in agreement with the available results from literature, restrict to whole body, kidneys, bone marrow, spleen and liver. The advantage of the proposed model is the compartmental method quickness and power to estimate dose in organs and tissues, including tumor that, in the most part, were not discriminate by voxels of phantoms built using CT images. (author)
Crystallization Kinetics within a Generic Modeling Framework
DEFF Research Database (Denmark)
Meisler, Kresten Troelstrup; von Solms, Nicolas; Gernaey, Krist V.;
2014-01-01
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...... 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...
Chemical Kinetic Modeling of 2-Methylhexane Combustion
Mohamed, Samah Y.
2015-03-30
Accurate chemical kinetic combustion models of lightly branched alkanes (e.g., 2-methylalkanes) are important for investigating the combustion behavior of diesel, gasoline, and aviation fuels. Improving the fidelity of existing kinetic models is a necessity, as new experiments and advanced theories show inaccuracy in certain portions of the models. This study focuses on updating thermodynamic data and kinetic model for a gasoline surrogate fuel, 2-methylhexane, with recently published group values and rate rules. These update provides a better agreement with rapid compression machine measurements of ignition delay time, while also strengthening the fundamental basis of the model.
A mathematical model for iodine kinetics
International Nuclear Information System (INIS)
A mathematical model for the iodine kinetics in thyroid is presented followed by its analytical solution. An eletroanalogical model is also developed for a simplified stage and another is proposed for the main case
Modeling of Reactor Kinetics and Dynamics
Energy Technology Data Exchange (ETDEWEB)
Matthew Johnson; Scott Lucas; Pavel Tsvetkov
2010-09-01
In order to model a full fuel cycle in a nuclear reactor, it is necessary to simulate the short time-scale kinetic behavior of the reactor as well as the long time-scale dynamics that occur with fuel burnup. The former is modeled using the point kinetics equations, while the latter is modeled by coupling fuel burnup equations with the kinetics equations. When the equations are solved simultaneously with a nonlinear equation solver, the end result is a code with the unique capability of modeling transients at any time during a fuel cycle.
Kinetic exchange models for social opinion formation
Lallouache, Mehdi; Chakrabarti, Bikas K
2010-01-01
We propose a minimal model for the collective dynamics of opinion formation in the society, by modifying kinetic exchange dynamics studied in the context of income, money or wealth distributions in a society.
Chemical Kinetic Modeling of Advanced Transportation Fuels
Energy Technology Data Exchange (ETDEWEB)
PItz, W J; Westbrook, C K; Herbinet, O
2009-01-20
Development of detailed chemical kinetic models for advanced petroleum-based and nonpetroleum based fuels is a difficult challenge because of the hundreds to thousands of different components in these fuels and because some of these fuels contain components that have not been considered in the past. It is important to develop detailed chemical kinetic models for these fuels since the models can be put into engine simulation codes used for optimizing engine design for maximum efficiency and minimal pollutant emissions. For example, these chemistry-enabled engine codes can be used to optimize combustion chamber shape and fuel injection timing. They also allow insight into how the composition of advanced petroleum-based and non-petroleum based fuels affect engine performance characteristics. Additionally, chemical kinetic models can be used separately to interpret important in-cylinder experimental data and gain insight into advanced engine combustion processes such as HCCI and lean burn engines. The objectives are: (1) Develop detailed chemical kinetic reaction models for components of advanced petroleum-based and non-petroleum based fuels. These fuels models include components from vegetable-oil-derived biodiesel, oil-sand derived fuel, alcohol fuels and other advanced bio-based and alternative fuels. (2) Develop detailed chemical kinetic reaction models for mixtures of non-petroleum and petroleum-based components to represent real fuels and lead to efficient reduced combustion models needed for engine modeling codes. (3) Characterize the role of fuel composition on efficiency and pollutant emissions from practical automotive engines.
Directory of Open Access Journals (Sweden)
Bonomi A.
1997-01-01
Full Text Available In 1990, the Biotechnology and the Control Systems Groups of IPT started developing a system for the control and automation of fermentation processes, applied to the oxidation of sorbitol to sorbose by the bacteria Gluconobacter oxydans, the microbial step of the vitamin C production process, that was chosen as a case study. Initially, a thirteen-parameter model was fitted to represent the batch operation of the system utilizing a nonlinear regression analysis, the flexible polyhedron method. Based on these results, a model for the continuous process (with the same kinetic equations was constructed and its optimum operating point obtained
Kinetic models for polymers with inertial effects
Degond, Pierre; Liu, Hailiang
2009-01-01
Novel kinetic models for both Dumbbell-like and rigid-rod like polymers are derived, based on the probability distribution function $f(t, x, n, \\dot n)$ for a polymer molecule positioned at $x$ to be oriented along direction $n$ while embedded in a $\\dot n$ environment created by inertial effects. It is shown that the probability distribution function of the extended model, when converging, will lead to well accepted kinetic models when inertial effects are ignored such as the Doi models for ...
Kinetic modeling of Moorella thermoacetica growth on single and dual-substrate systems.
Schmitt, Elliott; Bura, Renata; Gustafson, Rick; Ehsanipour, Mandana
2016-10-01
Acetic acid is an important chemical raw material that can be produced directly from sugars in lignocellulosic biomass. Development of kinetic models that capture the bioconversion dynamics of multiple sugar systems will be critical to optimization and process control in future lignocellulosic biorefinery processes. In this work, a kinetic model was developed for the single- and dual-substrate conversion of xylose and glucose to acetic acid using the acetogen Moorella thermoacetica. Batch fermentations were performed experimentally at 20 g L(-1) total sugar concentration using synthetic glucose, xylose, and a mixture of glucose and xylose at a 1:1 ratio. The product yield, calculated as total product formed divided by total sugars consumed, was 79.2, 69.9, and 69.7 % for conversion of glucose, xylose, and a mixture of glucose and xylose (1:1 ratio), respectively. During dual-substrate fermentation, M. thermoacetica demonstrated diauxic growth where xylose (the preferred substrate) was almost entirely consumed before consumption of glucose began. Kinetic parameters were similar for the single-substrate fermentations, and a strong linear correlation was determined between the maximum specific growth rate μ max and substrate inhibition constant, K s . Parameters estimated for the dual-substrate system demonstrated changes in the specific growth rate of both xylose and glucose consumption. In particular, the maximum growth rate related to glucose tripled compared to the single-substrate system. Kinetic growth is affected when multiple substrates are present in a fermentation system, and models should be developed to reflect these features. PMID:27262717
A kinetic model for predicting biodegradation.
Dimitrov, S; Pavlov, T; Nedelcheva, D; Reuschenbach, P; Silvani, M; Bias, R; Comber, M; Low, L; Lee, C; Parkerton, T; Mekenyan, O
2007-01-01
Biodegradation plays a key role in the environmental risk assessment of organic chemicals. The need to assess biodegradability of a chemical for regulatory purposes supports the development of a model for predicting the extent of biodegradation at different time frames, in particular the extent of ultimate biodegradation within a '10 day window' criterion as well as estimating biodegradation half-lives. Conceptually this implies expressing the rate of catabolic transformations as a function of time. An attempt to correlate the kinetics of biodegradation with molecular structure of chemicals is presented. A simplified biodegradation kinetic model was formulated by combining the probabilistic approach of the original formulation of the CATABOL model with the assumption of first order kinetics of catabolic transformations. Nonlinear regression analysis was used to fit the model parameters to OECD 301F biodegradation kinetic data for a set of 208 chemicals. The new model allows the prediction of biodegradation multi-pathways, primary and ultimate half-lives and simulation of related kinetic biodegradation parameters such as biological oxygen demand (BOD), carbon dioxide production, and the nature and amount of metabolites as a function of time. The model may also be used for evaluating the OECD ready biodegradability potential of a chemical within the '10-day window' criterion.
Kinetic models with randomly perturbed binary collisions
Bassetti, Federico; Toscani, Giuseppe
2010-01-01
We introduce a class of Kac-like kinetic equations on the real line, with general random collisional rules, which include as particular cases models for wealth redistribution in an agent-based market or models for granular gases with a background heat bath. Conditions on these collisional rules which guarantee both the existence and uniqueness of equilibrium profiles and their main properties are found. We show that the characterization of these stationary solutions is of independent interest, since the same profiles are shown to be solutions of different evolution problems, both in the econophysics context and in the kinetic theory of rarefied gases.
Kinetic and hydrodynamic models of chemotactic aggregation
Chavanis, Pierre-Henri
2007-01-01
We derive general kinetic and hydrodynamic models of chemotactic aggregation that describe certain features of the morphogenesis of biological colonies (like bacteria, amoebae, endothelial cells or social insects). Starting from a stochastic model defined in terms of N coupled Langevin equations, we derive a nonlinear mean field Fokker-Planck equation governing the evolution of the distribution function of the system in phase space. By taking the successive moments of this kinetic equation and using a local thermodynamic equilibrium condition, we derive a set of hydrodynamic equations involving a damping term. In the limit of small frictions, we obtain a hyperbolic model describing the formation of network patterns (filaments) and in the limit of strong frictions we obtain a parabolic model which is a generalization of the standard Keller-Segel model describing the formation of clusters (clumps). Our approach connects and generalizes several models introduced in the chemotactic literature. We discuss the anal...
Kinetic modeling of reactions in Foods
Boekel, van M.A.J.S.
2008-01-01
The level of quality that food maintains as it travels down the production-to-consumption path is largely determined by the chemical, biochemical, physical, and microbiological changes that take place during its processing and storage. Kinetic Modeling of Reactions in Foods demonstrates how to effec
Kinetics model development of cocoa bean fermentation
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.
Modeling inhomogeneous DNA replication kinetics.
Directory of Open Access Journals (Sweden)
Michel G Gauthier
Full Text Available In eukaryotic organisms, DNA replication is initiated at a series of chromosomal locations called origins, where replication forks are assembled proceeding bidirectionally to replicate the genome. The distribution and firing rate of these origins, in conjunction with the velocity at which forks progress, dictate the program of the replication process. Previous attempts at modeling DNA replication in eukaryotes have focused on cases where the firing rate and the velocity of replication forks are homogeneous, or uniform, across the genome. However, it is now known that there are large variations in origin activity along the genome and variations in fork velocities can also take place. Here, we generalize previous approaches to modeling replication, to allow for arbitrary spatial variation of initiation rates and fork velocities. We derive rate equations for left- and right-moving forks and for replication probability over time that can be solved numerically to obtain the mean-field replication program. This method accurately reproduces the results of DNA replication simulation. We also successfully adapted our approach to the inverse problem of fitting measurements of DNA replication performed on single DNA molecules. Since such measurements are performed on specified portion of the genome, the examined DNA molecules may be replicated by forks that originate either within the studied molecule or outside of it. This problem was solved by using an effective flux of incoming replication forks at the model boundaries to represent the origin activity outside the studied region. Using this approach, we show that reliable inferences can be made about the replication of specific portions of the genome even if the amount of data that can be obtained from single-molecule experiments is generally limited.
Bioconversion of Cheese Waste (Whey)
International Nuclear Information System (INIS)
The US dairy industry produces 67 billion pounds of cheese whey annually. A waste by-product of cheese production, whey consists of water, milk sugar (lactose), casein (protein), and salts amounting to about 7% total solids. Ultrafiltration is used to concentrate cheese whey into a protein-rich foodstuff; however, it too produces a waste stream, known as ''whey permeate,'' (rejected water, lactose, and salts from the membrane). Whey permeate contains about 4.5% lactose and requires treatment to reduce the high BOD (biological oxygen demand) before disposal. Ab Initio, a small business with strong chemistry and dairy processing background, desired help in developing methods for bioconversion of whey permeate lactose into lactic acid. Lactic acid is an organic acid primarily used as an acidulant in the food industry. More recently it has been used to produce polylactic acid, a biodegradable polymer and as a new method to treat meat carcasses to combat E. coli bacteria. Conversion of whey permeate to lactic acid is environmentally sound because it produces a valued product from an otherwise waste stream. FM and T has expertise in bioconversion processes and analytical techniques necessary to characterize biomass functions. The necessary engineering and analytical services for pilot biomass monitoring, process development, and purification of crude lactic acid were available at this facility
Compartmental modeling and tracer kinetics
Anderson, David H
1983-01-01
This monograph is concerned with mathematical aspects of compartmental an alysis. In particular, linear models are closely analyzed since they are fully justifiable as an investigative tool in tracer experiments. The objective of the monograph is to bring the reader up to date on some of the current mathematical prob lems of interest in compartmental analysis. This is accomplished by reviewing mathematical developments in the literature, especially over the last 10-15 years, and by presenting some new thoughts and directions for future mathematical research. These notes started as a series of lectures that I gave while visiting with the Division of Applied ~1athematics, Brown University, 1979, and have developed in to this collection of articles aimed at the reader with a beginning graduate level background in mathematics. The text can be used as a self-paced reading course. With this in mind, exercises have been appropriately placed throughout the notes. As an aid in reading the material, the e~d of a ...
A kinetic model for chemical neurotransmission
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.
A mathematical model on germinal center kinetics andtermination
DEFF Research Database (Denmark)
Kesmir, Can; De Boer, R.J.
1999-01-01
We devise a mathematical model to study germinal center (GC) kinetics. Earlier models for GC kinetics areextended by explicitly modeling 1) the cell division history of centroblasts, 2) the Ag uptake by centrocytes,and 3) T cell dynamics. Allowing for T cell kinetics and T-B cell interactions, we...
MATHEMATICAL MODELING OF ORANGE SEED DRYING KINETICS
Directory of Open Access Journals (Sweden)
Daniele Penteado Rosa
2015-06-01
Full Text Available Drying of orange seeds representing waste products from juice processing was studied in the temperatures of 40, 50, 60 and 70 °C and drying velocities of 0.6, 1.0 and 1.4 m/s. Experimental drying kinetics of orange seeds were obtained using a convective air forced dryer. Three thin-layer models: Page model, Lewis model, and the Henderson-Pabis model and the diffusive model were used to predict the drying curves. The Henderson-Pabis and the diffusive models show the best fitting performance and statistical evaluations. Moreover, the temperature dependence on the effective diffusivity followed an Arrhenius relationship, and the activation energies ranging from 16.174 to 16.842 kJ/mol
Cluster kinetics model for mixtures of glassformers.
Brenskelle, Lisa A; McCoy, Benjamin J
2007-10-14
For glassformers we propose a binary mixture relation for parameters in a cluster kinetics model previously shown to represent pure compound data for viscosity and dielectric relaxation as functions of either temperature or pressure. The model parameters are based on activation energies and activation volumes for cluster association-dissociation processes. With the mixture parameters, we calculated dielectric relaxation times and compared the results to experimental values for binary mixtures. Mixtures of sorbitol and glycerol (seven compositions), sorbitol and xylitol (three compositions), and polychloroepihydrin and polyvinylmethylether (three compositions) were studied. PMID:17935407
Thermodynamic and kinetic modelling: creep resistant materials
DEFF Research Database (Denmark)
Hald, John; Korcakova, L.; Danielsen, Hilmar Kjartansson;
2008-01-01
The use of thermodynamic and kinetic modelling of microstructure evolution in materials exposed to high temperatures in power plants is demonstrated with two examples. Precipitate stability in martensitic 9–12%Cr steels is modelled including equilibrium phase stability, growth of Laves phase...... particles and coarsening of MX, M23C6 and Laves phase particles. The modelling provided new insight into the long term stability of new steels. Modelling of the detrimental precipitation of Z phase Cr(V,Nb)N is described, which points to new approaches in alloy development for higher temperatures....... Predictions of interdiffusion between a MCrAlY coating and an IN738 bulk alloy by multicomponent diffusion calculations provide a highly versatile tool for life assessment of service exposed gas turbine components as well as for the development of improved coatings....
Thermodynamically consistent model calibration in chemical kinetics
Directory of Open Access Journals (Sweden)
Goutsias John
2011-05-01
Full Text Available Abstract Background The dynamics of biochemical reaction systems are constrained by the fundamental laws of thermodynamics, which impose well-defined relationships among the reaction rate constants characterizing these systems. Constructing biochemical reaction systems from experimental observations often leads to parameter values that do not satisfy the necessary thermodynamic constraints. This can result in models that are not physically realizable and may lead to inaccurate, or even erroneous, descriptions of cellular function. Results We introduce a thermodynamically consistent model calibration (TCMC method that can be effectively used to provide thermodynamically feasible values for the parameters of an open biochemical reaction system. The proposed method formulates the model calibration problem as a constrained optimization problem that takes thermodynamic constraints (and, if desired, additional non-thermodynamic constraints into account. By calculating thermodynamically feasible values for the kinetic parameters of a well-known model of the EGF/ERK signaling cascade, we demonstrate the qualitative and quantitative significance of imposing thermodynamic constraints on these parameters and the effectiveness of our method for accomplishing this important task. MATLAB software, using the Systems Biology Toolbox 2.1, can be accessed from http://www.cis.jhu.edu/~goutsias/CSS lab/software.html. An SBML file containing the thermodynamically feasible EGF/ERK signaling cascade model can be found in the BioModels database. Conclusions TCMC is a simple and flexible method for obtaining physically plausible values for the kinetic parameters of open biochemical reaction systems. It can be effectively used to recalculate a thermodynamically consistent set of parameter values for existing thermodynamically infeasible biochemical reaction models of cellular function as well as to estimate thermodynamically feasible values for the parameters of new
Modeling in applied sciences a kinetic theory approach
Pulvirenti, Mario
2000-01-01
Modeling complex biological, chemical, and physical systems, in the context of spatially heterogeneous mediums, is a challenging task for scientists and engineers using traditional methods of analysis Modeling in Applied Sciences is a comprehensive survey of modeling large systems using kinetic equations, and in particular the Boltzmann equation and its generalizations An interdisciplinary group of leading authorities carefully develop the foundations of kinetic models and discuss the connections and interactions between model theories, qualitative and computational analysis and real-world applications This book provides a thoroughly accessible and lucid overview of the different aspects, models, computations, and methodology for the kinetic-theory modeling process Topics and Features * Integrated modeling perspective utilized in all chapters * Fluid dynamics of reacting gases * Self-contained introduction to kinetic models * Becker–Doring equations * Nonlinear kinetic models with chemical reactions * Kinet...
The kinetic regime of the Vicsek model
Chepizhko, A. A.; Kulinskii, V. L.
2009-12-01
We consider the dynamics of the system of self-propelling particles modeled via the Vicsek algorithm in continuum time limit. It is shown that the alignment process for the velocities can be subdivided into two regimes: "fast" kinetic and "slow" hydrodynamic ones. In fast kinetic regime the alignment of the particle velocity to the local neighborhood takes place with characteristic relaxation time. So, that the bigger regions arise with the velocity alignment. These regions align their velocities thus giving rise to hydrodynamic regime of the dynamics. We propose the mean-field-like approach in which we take into account the correlations between density and velocity. The comparison of the theoretical predictions with the numerical simulations is given. The relation between Vicsek model in the zero velocity limit and the Kuramoto model is stated. The mean-field approach accounting for the dynamic change of the neighborhood is proposed. The nature of the discontinuity of the dependence of the order parameter in case of vectorial noise revealed in Gregorie and Chaite, Phys. Rev. Lett., 92, 025702 (2004) is discussed and the explanation of it is proposed.
Holographic kinetic k-essence model
Energy Technology Data Exchange (ETDEWEB)
Cruz, Norman [Departamento de Fisica, Facultad de Ciencia, Universidad de Santiago de Chile, Casilla 307, Santiago (Chile)], E-mail: ncruz@lauca.usach.cl; Gonzalez-Diaz, Pedro F.; Rozas-Fernandez, Alberto [Colina de los Chopos, Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain)], E-mail: a.rozas@cfmac.csic.es; Sanchez, Guillermo [Departamento de Matematica y Ciencia de la Computacion, Facultad de Ciencia, Universidad de Santiago de Chile, Casilla 307, Santiago (Chile)], E-mail: gsanchez@usach.cl
2009-08-31
We consider a connection between the holographic dark energy density and the kinetic k-essence energy density in a flat FRW universe. With the choice c{>=}1, the holographic dark energy can be described by a kinetic k-essence scalar field in a certain way. In this Letter we show this kinetic k-essential description of the holographic dark energy with c{>=}1 and reconstruct the kinetic k-essence function F(X)
Kinetic model of excess activated sludge thermohydrolysis.
Imbierowicz, Mirosław; Chacuk, Andrzej
2012-11-01
Thermal hydrolysis of excess activated sludge suspensions was carried at temperatures ranging from 423 K to 523 K and under pressure 0.2-4.0 MPa. Changes of total organic carbon (TOC) concentration in a solid and liquid phase were measured during these studies. At the temperature 423 K, after 2 h of the process, TOC concentration in the reaction mixture decreased by 15-18% of the initial value. At 473 K total organic carbon removal from activated sludge suspension increased to 30%. It was also found that the solubilisation of particulate organic matter strongly depended on the process temperature. At 423 K the transfer of TOC from solid particles into liquid phase after 1 h of the process reached 25% of the initial value, however, at the temperature of 523 K the conversion degree of 'solid' TOC attained 50% just after 15 min of the process. In the article a lumped kinetic model of the process of activated sludge thermohydrolysis has been proposed. It was assumed that during heating of the activated sludge suspension to a temperature in the range of 423-523 K two parallel reactions occurred. One, connected with thermal destruction of activated sludge particles, caused solubilisation of organic carbon and an increase of dissolved organic carbon concentration in the liquid phase (hydrolysate). The parallel reaction led to a new kind of unsolvable solid phase, which was further decomposed into gaseous products (CO(2)). The collected experimental data were used to identify unknown parameters of the model, i.e. activation energies and pre-exponential factors of elementary reactions. The mathematical model of activated sludge thermohydrolysis appropriately describes the kinetics of reactions occurring in the studied system. PMID:22951329
Electrothermal Model of Kinetic Inductance Detectors
Thomas, Christopher N; Goldie, David J
2014-01-01
An electrothermal model of Kinetic Inductance Detectors (KIDs) is described. The non-equilibrium state of the resonator's quasiparticle system is characterized by an effective temperature, which because of readout-power heating is higher than that of the bath. By balancing the flow of energy into the quasiparticle system, it is possible to calculate the steady-state large-signal, small-signal and noise behaviour. Resonance-curve distortion and hysteretic switching appear naturally within the framework. It is shown that an electrothermal feedback process exists, which affects all aspects of behaviour. It is also shown that generation-recombination noise can be interpreted in terms of the thermal fluctuation noise in the effective thermal conductance that links the quasiparticle and phonon systems of the resonator. Because the scheme is based on electrothermal considerations, multiple elements can be added to simulate the behaviour of complex devices, such as resonators on membranes, again taking into account r...
Bioconversion of Rebaudioside I from Rebaudioside A
Indra Prakash; Cynthia Bunders; Devkota, Krishna P.; Romila D. Charan; Catherine Ramirez; Snyder, Tara M.; Christopher Priedemann; Avetik Markosyan; Cyrille Jarrin; Robert Ter Halle
2014-01-01
To supply the increasing demand of natural high potency sweeteners to reduce the calories in food and beverages, we have looked to steviol glycosides. In this work we report the bioconversion of rebaudioside A to rebaudioside I using a glucosyltransferase enzyme. This bioconversion reaction adds one sugar unit with a 1→3 linkage. We utilized 1D and 2D NMR spectroscopy (1H, 13C, COSY, HSQC-DEPT, HMBC, 1D TOCSY and NOESY) and mass spectral data to fully characterize rebaudioside I.
Bioconversion of Rebaudioside I from Rebaudioside A
Directory of Open Access Journals (Sweden)
Indra Prakash
2014-10-01
Full Text Available To supply the increasing demand of natural high potency sweeteners to reduce the calories in food and beverages, we have looked to steviol glycosides. In this work we report the bioconversion of rebaudioside A to rebaudioside I using a glucosyltransferase enzyme. This bioconversion reaction adds one sugar unit with a 1→3 linkage. We utilized 1D and 2D NMR spectroscopy (1H, 13C, COSY, HSQC-DEPT, HMBC, 1D TOCSY and NOESY and mass spectral data to fully characterize rebaudioside I.
Aerosol kinetic code "AERFORM": Model, validation and simulation results
Gainullin, K. G.; Golubev, A. I.; Petrov, A. M.; Piskunov, V. N.
2016-06-01
The aerosol kinetic code "AERFORM" is modified to simulate droplet and ice particle formation in mixed clouds. The splitting method is used to calculate condensation and coagulation simultaneously. The method is calibrated with analytic solutions of kinetic equations. Condensation kinetic model is based on cloud particle growth equation, mass and heat balance equations. The coagulation kinetic model includes Brownian, turbulent and precipitation effects. The real values are used for condensation and coagulation growth of water droplets and ice particles. The model and the simulation results for two full-scale cloud experiments are presented. The simulation model and code may be used autonomously or as an element of another code.
Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid
International Nuclear Information System (INIS)
The reaction kinetics of the esterification of ethylene glycol with acetic acid in the presence of cation exchange resin has been studied and kinetic models based on empirical and Langmuir approach has been developed. The Langmuir based model involving eight kinetic parameters fits experimental data much better compared to empirical model involving four kinetic parameters. The effect of temperature and catalyst loading on the reaction system has been analyzed. Further, the activation energy and frequency factor of the rate constants for Langmuir based model has been estimated.
Chemical Kinetic Modeling of Biofuel Combustion
Sarathy, Subram Maniam
Bioalcohols, such as bioethanol and biobutanol, are suitable replacements for gasoline, while biodiesel can replace petroleum diesel. Improving biofuel engine performance requires understanding its fundamental combustion properties and the pathways of combustion. This study's contribution is experimentally validated chemical kinetic combustion mechanisms for biobutanol and biodiesel. Fundamental combustion data and chemical kinetic mechanisms are presented and discussed to improve our understanding of biofuel combustion. The net environmental impact of biobutanol (i.e., n-butanol) has not been studied extensively, so this study first assesses the sustainability of n-butanol derived from corn. The results indicate that technical advances in fuel production are required before commercializing biobutanol. The primary contribution of this research is new experimental data and a novel chemical kinetic mechanism for n-butanol combustion. The results indicate that under the given experimental conditions, n-butanol is consumed primarily via abstraction of hydrogen atoms to produce fuel radical molecules, which subsequently decompose to smaller hydrocarbon and oxygenated species. The hydroxyl moiety in n-butanol results in the direct production of the oxygenated species such as butanal, acetaldehyde, and formaldehyde. The formation of these compounds sequesters carbon from forming soot precursors, but they may introduce other adverse environmental and health effects. Biodiesel is a mixture of long chain fatty acid methyl esters derived from fats and oils. This research study presents high quality experimental data for one large fatty acid methyl ester, methyl decanoate, and models its combustion using an improved skeletal mechanism. The results indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which ultimately lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular
Holographic kinetic k-essence model
Cruz, N.; González Díaz, Pedro F.; Rozas Fernández, Alberto; Sánchez, G.
2008-01-01
We consider a connection between the holographic dark energy density and the kinetic k-essence energy density in a flat FRW universe. With the choice c ≥ 1, the holographic dark energy can be described by a kinetic k-essence scalar field in a certain way. In this Letter we show this kinetic k-essential description of the holographic dark energy with c ≥ 1 and reconstruct the kinetic k-essence function F (X). © 2009 Elsevier B.V. All rights reserved.
Shear-Driven Reconnection in Kinetic Models
Black, C.; Antiochos, S. K.; Germaschewski, K.; Karpen, J. T.; DeVore, C. R.; Bessho, N.
2015-12-01
The explosive energy release in solar eruptive phenomena is believed to be due to magnetic reconnection. In the standard model for coronal mass ejections (CME) and/or solar flares, the free energy for the event resides in the strongly sheared magnetic field of a filament channel. The pre-eruption force balance consists of an upward force due to the magnetic pressure of the sheared field countered by a downward tension due to overlying unsheared field. Magnetic reconnection disrupts this force balance; therefore, it is critical for understanding CME/flare initiation, to model the onset of reconnection driven by the build-up of magnetic shear. In MHD simulations, the application of a magnetic-field shear is a trivial matter. However, kinetic effects are dominant in the diffusion region and thus, it is important to examine this process with PIC simulations as well. The implementation of such a driver in PIC methods is challenging, however, and indicates the necessity of a true multiscale model for such processes in the solar environment. The field must be sheared self-consistently and indirectly to prevent the generation of waves that destroy the desired system. Plasma instabilities can arise nonetheless. In the work presented here, we show that we can control this instability and generate a predicted out-of-plane magnetic flux. This material is based upon work supported by the National Science Foundation under Award No. AGS-1331356.
Kinetic modelling of krypton fluoride laser systems
International Nuclear Information System (INIS)
A kinetic model has been developed for the KrF* rare gas halide laser system, specifically for electron-beam pumped mixtures of krypton, fluorine, and either helium or argon. The excitation produced in the laser gas by the e-beam was calculated numerically using an algorithm checked by comparing the predicted ionization yields in the pure rare gases with their experimental values. The excitation of the laser media by multi-kilovolt x-rays was also modeled and shown to be similar to that produced by high energy electrons. A system of equations describing the transfer of the initial gas excitation into the laser upper level was assembled using reaction rate constants from both experiment and theory. A one-dimensional treatment of the interaction of the laser radiation with the gas was formulated which considered spontaneous and stimulated emission and absorption. The predictions of this model were in good agreement with the fluorescence signals and gain and absorption measured experimentally
Thermoluminescence of zircon: a kinetic model
Turkin, A A; Vainshtein, D I; Hartog, H W D
2003-01-01
The mineral zircon, ZrSiO sub 4 , belongs to a class of promising materials for geochronometry by means of thermoluminescence (TL) dating. The development of a reliable and reproducible method for TL dating with zircon requires detailed knowledge of the processes taking place during exposure to ionizing radiation, long-term storage, annealing at moderate temperatures and heating at a constant rate (TL measurements). To understand these processes one needs a kinetic model of TL. This paper is devoted to the construction of such a model. The goal is to study the qualitative behaviour of the system and to determine the parameters and processes controlling TL phenomena of zircon. The model considers the following processes: (i) Filling of electron and hole traps at the excitation stage as a function of the dose rate and the dose for both (low dose rate) natural and (high dose rate) laboratory irradiation. (ii) Time dependence of TL fading in samples irradiated under laboratory conditions. (iii) Short time anneali...
Kinetic modelling of krypton fluoride laser systems
Energy Technology Data Exchange (ETDEWEB)
Jancaitis, K.S.
1983-11-01
A kinetic model has been developed for the KrF* rare gas halide laser system, specifically for electron-beam pumped mixtures of krypton, fluorine, and either helium or argon. The excitation produced in the laser gas by the e-beam was calculated numerically using an algorithm checked by comparing the predicted ionization yields in the pure rare gases with their experimental values. The excitation of the laser media by multi-kilovolt x-rays was also modeled and shown to be similar to that produced by high energy electrons. A system of equations describing the transfer of the initial gas excitation into the laser upper level was assembled using reaction rate constants from both experiment and theory. A one-dimensional treatment of the interaction of the laser radiation with the gas was formulated which considered spontaneous and stimulated emission and absorption. The predictions of this model were in good agreement with the fluorescence signals and gain and absorption measured experimentally.
Nassereldeen Ahmed Kabbashi; Md. Zahangir Alam; M. Fahrurrazi Tompang
2010-01-01
The bioethanol production was conducted by utilizing agriculture waste, palm oil empty fruit bunches (EFB) with the aid of T. harzianum and yeast, Saccharomyces cerevisiae using solid state bioconversion method. The compatibility of various fungal strains was done as to develop the direct bioconversion process of compatible mixed culture. Analyzes such ethanol estimation, reducing sugar and glucosamine as growth indicator were conducted in order to select the best experimented run for ...
Reflected kinetics model for nuclear space reactor kinetics and control scoping calculations
International Nuclear Information System (INIS)
The objective of this research is to develop a model that offers an alternative to the point kinetics (PK) modelling approach in the analysis of space reactor kinetics and control studies. Modelling effort will focus on the explicit treatment of control drums as reactivity input devices so that the transition to automatic control can be smoothly done. The proposed model is developed for the specific integration of automatic control and the solution of the servo mechanism problem. The integration of the kinetics model with an automatic controller will provide a useful tool for performing space reactor scoping studies for different designs and configurations. Such a tool should prove to be invaluable in the design phase of a space nuclear system from the point of view of kinetics and control limitations
Numerical optimisation for model evaluation in combustion kinetics
Fischer, Marc; Jiang, Xi
2015-01-01
Numerical optimisation related to the estimation of kinetic parameters and model evaluation is playing an increasing role in combustion as well as in other areas of applied energy research. The present work aims at presenting the current probability-based approaches along applications to real problems of combustion chemical kinetics. The main methods related to model and parameter evaluation have been explicated. An in-house program for the systematic adjustment of kinetic parameters to exper...
Kinetic modeling of cell metabolism for microbial production.
Costa, Rafael S; Hartmann, Andras; Vinga, Susana
2016-02-10
Kinetic models of cellular metabolism are important tools for the rational design of metabolic engineering strategies and to explain properties of complex biological systems. The recent developments in high-throughput experimental data are leading to new computational approaches for building kinetic models of metabolism. Herein, we briefly survey the available databases, standards and software tools that can be applied for kinetic models of metabolism. In addition, we give an overview about recently developed ordinary differential equations (ODE)-based kinetic models of metabolism and some of the main applications of such models are illustrated in guiding metabolic engineering design. Finally, we review the kinetic modeling approaches of large-scale networks that are emerging, discussing their main advantages, challenges and limitations. PMID:26724578
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.
Model for crystallization kinetics: Deviations from Kolmogorov-Johnson-Mehl-Avrami kinetics
Castro, Mario; Domínguez-Adame Acosta, Francisco; Sánchez, A; Rodriguez, T.
1999-01-01
We propose a simple and versatile model to understand the deviations from the well-known Kolmogorov-Johnson-Mehl-Avrami kinetics theory found in metal recrystallization and amorphous semiconductor crystallization. We analyze the kinetics of the transformation and the grain-size distribution of the product material, finding a good overall agreement between our model and available experimental data. The information so obtained could help to relate the mentioned experimental deviations due to pr...
A Review of Kinetic Modeling Methodologies for Complex Processes
Directory of Open Access Journals (Sweden)
de Oliveira Luís P.
2016-05-01
Full Text Available In this paper, kinetic modeling techniques for complex chemical processes are reviewed. After a brief historical overview of chemical kinetics, an overview is given of the theoretical background of kinetic modeling of elementary steps and of multistep reactions. Classic lumping techniques are introduced and analyzed. Two examples of lumped kinetic models (atmospheric gasoil hydrotreating and residue hydroprocessing developed at IFP Energies nouvelles (IFPEN are presented. The largest part of this review describes advanced kinetic modeling strategies, in which the molecular detail is retained, i.e. the reactions are represented between molecules or even subdivided into elementary steps. To be able to retain this molecular level throughout the kinetic model and the reactor simulations, several hurdles have to be cleared first: (i the feedstock needs to be described in terms of molecules, (ii large reaction networks need to be automatically generated, and (iii a large number of rate equations with their rate parameters need to be derived. For these three obstacles, molecular reconstruction techniques, deterministic or stochastic network generation programs, and single-event micro-kinetics and/or linear free energy relationships have been applied at IFPEN, as illustrated by several examples of kinetic models for industrial refining processes.
Innovative first order elimination kinetics working model for easy learning
Directory of Open Access Journals (Sweden)
Navin Budania
2016-06-01
Conclusions: First order elimination kinetics is easily understood with the help of above working model. More and more working models could be developed for teaching difficult topics. [Int J Basic Clin Pharmacol 2016; 5(3.000: 862-864
The kinetic modelling from domestic ores using software tools
Krstev, Aleksandar; Krstev, Boris; Gocev, Zivko; Golomeov, Blagoj; Golomeova, Mirjana; Zendelska, Afrodita
2013-01-01
To improve kinetic models, many first - order flotation kinetics models with distributions of flotation rate constants were redefined so that they could all be represented by the same set of three model parameters. As a result, the width of the distribution become independent of its mean, and parameters of the model and the curve fitting errors, became virtually the same, independent of the chosen distribution function. In our case, investigations of the chalcopyrite ores are carried out usin...
Kinetic models in spin chemistry. 1. The hyperfine interaction
DEFF Research Database (Denmark)
Mojaza, M.; Pedersen, J. B.
2012-01-01
Kinetic models for quantum systems are quite popular due to their simplicity, although they are difficult to justify. We show that the transformation from quantum to kinetic description can be done exactly for the hyperfine interaction of one nuclei with arbitrary spin; more spins are described w...... induced enhancement of the reaction yield. (C) 2012 Elsevier B.V. All rights reserved....
KAOS: A Kinetic Theory Tool for Modeling Complex Social Systems
Directory of Open Access Journals (Sweden)
Bruneo Dario
2016-01-01
Full Text Available The kinetic theory approach is successfully used to model complex phenomena related to social systems, allowing to predict the dynamics and emergent behavior of large populations of agents. In particular, kinetic theory for active particles (KTAP models are usually analyzed by numerically solving the underlying Boltzmann-type differential equations through ad-hoc implementations. In this paper, we present KAOS: a kinetic theory of active particles modeling and analysis software tool. To the best of our knowledge, KAOS represents the first attempt to design and implement a comprehensive tool that assists the user in all the steps of the modeling process in the framework of the kinetic theories, from the model definition to the representation of transient solutions. To show the KAOS features, we present a new model capturing the competition/cooperation dynamics of a socio-economic system with welfare dynamics, in different socio-political conditions
Dynamics and kinetics of model biological systems
Mirigian, Stephen
In this work we study three systems of biological interest: the translocation of a heterogeneously charged polymer through an infinitely thin pore, the wrapped of a rigid particle by a soft vesicle and the modification of the dynamical properties of a gel due to the presence of rigid inclusions. We study the kinetics of translocation for a heterogeneously charged polyelectrolyte through an infinitely narrow pore using the Fokker-Planck formalism to compute mean first passage times, the probability of successful translocation, and the mean successful translocation time for a diblock copolymer. We find, in contrast to the homopolymer result, that details of the boundary conditions lead to qualitatively different behavior. Under experimentally relevant conditions for a diblock copolymer we find that there is a threshold length of the charged block, beyond which the probability of successful translocation is independent of charge fraction. Additionally, we find that mean successful translocation time exhibits non-monotonic behavior with increasing length of the charged fraction; there is an optimum length of the charged block where the mean successful translocation time is slowest and there can be a substantial range of charge fraction where it is slower than a minimally charged chain. For a fixed total charge on the chain, we find that finer distributions of the charge along the chain leads to a significant reduction in mean translocation time compared to the diblock distribution. Endocytosis is modeled using a simple geometrical model from the literature. We map the process of wrapping a rigid spherical bead onto a one-dimensional stochastic process described by the Fokker-Planck equation to compute uptake rates as a function of membrane properties and system geometry. We find that simple geometrical considerations pick an optimal particle size for uptake and a corresponding maximal uptake rate, which can be controlled by altering the material properties of the
Fungal bioconversion of lignocellulosic residues; opportunities & perspectives.
Dashtban, Mehdi; Schraft, Heidi; Qin, Wensheng
2009-01-01
The development of alternative energy technology is critically important because of the rising prices of crude oil, security issues regarding the oil supply, and environmental issues such as global warming and air pollution. Bioconversion of biomass has significant advantages over other alternative energy strategies because biomass is the most abundant and also the most renewable biomaterial on our planet. Bioconversion of lignocellulosic residues is initiated primarily by microorganisms such as fungi and bacteria which are capable of degrading lignocellulolytic materials. Fungi such as Trichoderma reesei and Aspergillus niger produce large amounts of extracellular cellulolytic enzymes, whereas bacterial and a few anaerobic fungal strains mostly produce cellulolytic enzymes in a complex called cellulosome, which is associated with the cell wall. In filamentous fungi, cellulolytic enzymes including endoglucanases, cellobiohydrolases (exoglucanases) and beta-glucosidases work efficiently on cellulolytic residues in a synergistic manner. In addition to cellulolytic/hemicellulolytic activities, higher fungi such as basidiomycetes (e.g. Phanerochaete chrysosporium) have unique oxidative systems which together with ligninolytic enzymes are responsible for lignocellulose degradation. This review gives an overview of different fungal lignocellulolytic enzymatic systems including extracellular and cellulosome-associated in aerobic and anaerobic fungi, respectively. In addition, oxidative lignocellulose-degradation mechanisms of higher fungi are discussed. Moreover, this paper reviews the current status of the technology for bioconversion of biomass by fungi, with focus on mutagenesis, co-culturing and heterologous gene expression attempts to improve fungal lignocellulolytic activities to create robust fungal strains. PMID:19774110
Fungal Bioconversion of Lignocellulosic Residues; Opportunities & Perspectives
Directory of Open Access Journals (Sweden)
Mehdi Dashtban, Heidi Schraft, Wensheng Qin
2009-01-01
Full Text Available The development of alternative energy technology is critically important because of the rising prices of crude oil, security issues regarding the oil supply, and environmental issues such as global warming and air pollution. Bioconversion of biomass has significant advantages over other alternative energy strategies because biomass is the most abundant and also the most renewable biomaterial on our planet. Bioconversion of lignocellulosic residues is initiated primarily by microorganisms such as fungi and bacteria which are capable of degrading lignocellulolytic materials. Fungi such as Trichoderma reesei and Aspergillus niger produce large amounts of extracellular cellulolytic enzymes, whereas bacterial and a few anaerobic fungal strains mostly produce cellulolytic enzymes in a complex called cellulosome, which is associated with the cell wall. In filamentous fungi, cellulolytic enzymes including endoglucanases, cellobiohydrolases (exoglucanases and β-glucosidases work efficiently on cellulolytic residues in a synergistic manner. In addition to cellulolytic/hemicellulolytic activities, higher fungi such as basidiomycetes (e.g. Phanerochaete chrysosporium have unique oxidative systems which together with ligninolytic enzymes are responsible for lignocellulose degradation. This review gives an overview of different fungal lignocellulolytic enzymatic systems including extracellular and cellulosome-associated in aerobic and anaerobic fungi, respectively. In addition, oxidative lignocellulose-degradation mechanisms of higher fungi are discussed. Moreover, this paper reviews the current status of the technology for bioconversion of biomass by fungi, with focus on mutagenesis, co-culturing and heterologous gene expression attempts to improve fungal lignocellulolytic activities to create robust fungal strains.
Modeling Biodegradation Kinetics on Benzene and Toluene and Their Mixture
Directory of Open Access Journals (Sweden)
Aparecido N. Módenes
2007-10-01
Full Text Available The objective of this work was to model the biodegradation kinetics of toxic compounds toluene and benzene as pure substrates and in a mixture. As a control, Monod and Andrews models were used. To predict substrates interactions, more sophisticated models of inhibition and competition, and SKIP (sum kinetics interactions parameters model were applied. The models evaluation was performed based on the experimental data from Pseudomonas putida F1 activities published in the literature. In parameter identification procedure, the global method of particle swarm optimization (PSO was applied. The simulation results show that the better description of the biodegradation process of pure toxic substrate can be achieved by Andrews' model. The biodegradation process of a mixture of toxic substrates is modeled the best when modified competitive inhibition and SKIP models are used. The developed software can be used as a toolbox of a kinetics model catalogue of industrial wastewater treatment for process design and optimization.
Biomass torrefaction: modeling of volatile and solid product evolution kinetics.
Bates, Richard B; Ghoniem, Ahmed F
2012-11-01
The aim of this work is the development of a kinetics model for the evolution of the volatile and solid product composition during torrefaction conditions between 200 and 300°C. Coupled to an existing two step solid mass loss kinetics mechanism, this model describes the volatile release kinetics in terms of a set of identifiable chemical components, permitting the solid product composition to be estimated by mass conservation. Results show that most of the volatiles released during the first stage include highly oxygenated species such as water, acetic acid, and carbon dioxide, while volatiles released during the second step are composed primarily of lactic acid, methanol, and acetic acid. This kinetics model will be used in the development of a model to describe reaction energy balance and heat release dynamics.
Mathematical modelling of water radiolysis kinetics under reactor conditions
International Nuclear Information System (INIS)
Experimental data on coolant radiolysis (RBMK-1000 reactor) were used to construct mathematical model of water radiolysis kinetics under reactor conditions. Good agreement of calculation results with the experiment is noted
Kinetic modelling of the Maillard reaction between proteins and sugars
Brands, C.M.J.
2002-01-01
Keywords: Maillard reaction, sugar isomerisation, kinetics, multiresponse modelling, brown colour formation, lysine damage, mutagenicity, casein, monosaccharides, disaccharides, aldoses, ketosesThe aim of this thesis was to determine the kinetics of the Maillard reaction between proteins and sugars, taking into account other simultaneously occurring sugar reactions. Model systems of foods, consisting of the protein casein and various sugars in a buffered solution, were studied. The reaction c...
Existence of weak solutions to kinetic flocking models
Karper, Trygve; Trivisa, Konstantina
2012-01-01
We establish the global existence of weak solutions to a class of kinetic flocking equations. The models under consideration include the kinetic Cucker-Smale equation with possibly non-symmetric flocking potential, the Cucker-Smale equation with additional strong local alignment, and a newly proposed model by Motsch and Tadmor. The main tools employed in the analysis are the velocity averaging lemma and the Schauder fixed point theorem along with various integral bounds.
A Kinetic Model for the Energy Transfer in Phycobilisomes
Suter, Georg W.; Holzwarth, Alfred R.
1987-01-01
A kinetic model for the energy transfer in phycobilisome (PBS) rods of Synechococcus 6301 is presented, based on a set of experimental parameters from picosecond studies. It is shown that the enormous complexity of the kinetic system formed by 400-500 chromophores can be greatly simplified by using symmetry arguments. According to the model the transfer along the phycocyanin rods has to be taken into account in both directions, i.e., back and forth along the rods. The corresponding forward ra...
An integral representation of functions in gas-kinetic models
Perepelitsa, Misha
2016-08-01
Motivated by the theory of kinetic models in gas dynamics, we obtain an integral representation of lower semicontinuous functions on {{{R}}^d,} {d≥1}. We use the representation to study the problem of compactness of a family of the solutions of the discrete time BGK model for the compressible Euler equations. We determine sufficient conditions for strong compactness of moments of kinetic densities, in terms of the measures from their integral representations.
HCCI in a CFR engine: experiments and detailed kinetic modeling
Energy Technology Data Exchange (ETDEWEB)
Flowers, D; Aceves, S; Smith, R; Torres, J; Girard, J; Dibble, R
1999-11-05
Single cylinder engine experiments and chemical kinetic modeling have been performed to study the effect of variations in fuel, equivalence ratio, and intake charge temperature on the start of combustion and the heat release rate. Neat propane and a fuel blend of 15% dimethyl-ether in methane have been studied. The results demonstrate the role of these parameters on the start of combustion, efficiency, imep, and emissions. Single zone kinetic modeling results show the trends consistent with the experimental results.
A kinetic model for the penicillin biosynthetic pathway in
DEFF Research Database (Denmark)
Nielsen, Jens; Jørgensen, Henrik
1996-01-01
A kinetic model for the first two steps in the penicillin biosynthetic pathway, i.e. the ACV synthetase (ACVS) and the isopenicillin N synthetase (IPNS) is proposed. The model is based on Michaelis-Menten type kinetics with non-competitive inhibition of the ACVS by ACV, and competitive inhibition...... that there is a shift in the flux control from the ACVS to the IPNS during the cultivation....
Kinetic Modelling of Pesticidal Degradation and Microbial Growth in Soil
Institute of Scientific and Technical Information of China (English)
LIUDUO－SEN; WANGZONG－SHENG; 等
1994-01-01
This paper discusses such models for the degradation kinetics of pesticides in soil as the model expressing the degradation rate as a function of two varables:the pesticide concentration and the number of pesticide degrading microorganisms,the model expressing the pesticide concentration as explicit or implicit function of time ,and the model exprssing the pesticide loss rate constants as functions of temperature,These models may interpret the degradation curves with an inflection point.A Kinetic model describing the growth processes of microbial populations in a closed system is reported as well.
New mass loss kinetic model for thermal decomposition of biomass
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Based on non-isothermal experimental results for eight Chinese biomass species, a new kinetic model,named as the "pseudo bi-component separate-stage model (PBSM)", is developed in this note to describe the mass loss behavior of biomass thermal decomposition. This model gains an advantage over the commonly used "pseudo single-component overall model (PSOM)" and "pseudo multi-component overall model (PMOM)". By means of integral analysis it is indicated that the new model is suitable to describe the mass loss kinetics of wood and leaf samples under relatively low heating rates (e.g. 10°C/rin, used in this work).``
Discrete Kinetic Models and Conservation Laws
Vinerean, Mirela Cristina
2005-01-01
Classical kinetic theory of gases is based on the Boltzmann equation (BE) which describes the evolution of a system of particles undergoing collisions preserving mass, momentum and energy. Discretization methods have been developed on the idea of replacing the original BE by a finite set of nonlinear hyperbolic PDEs corresponding to the densities linked to a suitable finite set of velocities. One open problem related to the discrete BE is the construction of normal (fulfilling only physical c...
Detailed Chemical Kinetic Modeling of Cyclohexane Oxidation
Energy Technology Data Exchange (ETDEWEB)
Silke, E J; Pitz, W J; Westbrook, C K; Ribaucour, M
2006-11-10
A detailed chemical kinetic mechanism has been developed and used to study the oxidation of cyclohexane at both low and high temperatures. Reaction rate constant rules are developed for the low temperature combustion of cyclohexane. These rules can be used for in chemical kinetic mechanisms for other cycloalkanes. Since cyclohexane produces only one type of cyclohexyl radical, much of the low temperature chemistry of cyclohexane is described in terms of one potential energy diagram showing the reaction of cyclohexyl radical + O{sub 2} through five, six and seven membered ring transition states. The direct elimination of cyclohexene and HO{sub 2} from RO{sub 2} is included in the treatment using a modified rate constant of Cavallotti et al. Published and unpublished data from the Lille rapid compression machine, as well as jet-stirred reactor data are used to validate the mechanism. The effect of heat loss is included in the simulations, an improvement on previous studies on cyclohexane. Calculations indicated that the production of 1,2-epoxycyclohexane observed in the experiments can not be simulated based on the current understanding of low temperature chemistry. Possible 'alternative' H-atom isomerizations leading to different products from the parent O{sub 2}QOOH radical were included in the low temperature chemical kinetic mechanism and were found to play a significant role.
Information cascade, Kirman's ant colony model, and kinetic Ising model
Hisakado, Masato; Mori, Shintaro
2015-01-01
In this paper, we discuss a voting model in which voters can obtain information from a finite number of previous voters. There exist three groups of voters: (i) digital herders and independent voters, (ii) analog herders and independent voters, and (iii) tanh-type herders. In our previous paper Hisakado and Mori (2011), we used the mean field approximation for case (i). In that study, if the reference number r is above three, phase transition occurs and the solution converges to one of the equilibria. However, the conclusion is different from mean field approximation. In this paper, we show that the solution oscillates between the two states. A good (bad) equilibrium is where a majority of r select the correct (wrong) candidate. In this paper, we show that there is no phase transition when r is finite. If the annealing schedule is adequately slow from finite r to infinite r, the voting rate converges only to the good equilibrium. In case (ii), the state of reference votes is equivalent to that of Kirman's ant colony model, and it follows beta binomial distribution. In case (iii), we show that the model is equivalent to the finite-size kinetic Ising model. If the voters are rational, a simple herding experiment of information cascade is conducted. Information cascade results from the quenching of the kinetic Ising model. As case (i) is the limit of case (iii) when tanh function becomes a step function, the phase transition can be observed in infinite size limit. We can confirm that there is no phase transition when the reference number r is finite.
Chemical Kinetic Models for HCCI and Diesel Combustion
Energy Technology Data Exchange (ETDEWEB)
Pitz, W J; Westbrook, C K; Mehl, M; Sarathy, S M
2010-11-15
Predictive engine simulation models are needed to make rapid progress towards DOE's goals of increasing combustion engine efficiency and reducing pollutant emissions. These engine simulation models require chemical kinetic submodels to allow the prediction of the effect of fuel composition on engine performance and emissions. Chemical kinetic models for conventional and next-generation transportation fuels need to be developed so that engine simulation tools can predict fuel effects. The objectives are to: (1) Develop detailed chemical kinetic models for fuel components used in surrogate fuels for diesel and HCCI engines; (2) Develop surrogate fuel models to represent real fuels and model low temperature combustion strategies in HCCI and diesel engines that lead to low emissions and high efficiency; and (3) Characterize the role of fuel composition on low temperature combustion modes of advanced combustion engines.
Energy Technology Data Exchange (ETDEWEB)
Li, Yulan; Hu, Shenyang Y.; Sun, Xin; Khaleel, Mohammad A.
2011-06-15
Microstructure evolution kinetics in irradiated materials has strongly spatial correlation. For example, void and second phases prefer to nucleate and grow at pre-existing defects such as dislocations, grain boundaries, and cracks. Inhomogeneous microstructure evolution results in inhomogeneity of microstructure and thermo-mechanical properties. Therefore, the simulation capability for predicting three dimensional (3-D) microstructure evolution kinetics and its subsequent impact on material properties and performance is crucial for scientific design of advanced nuclear materials and optimal operation conditions in order to reduce uncertainty in operational and safety margins. Very recently the meso-scale phase-field (PF) method has been used to predict gas bubble evolution, void swelling, void lattice formation and void migration in irradiated materials,. Although most results of phase-field simulations are qualitative due to the lake of accurate thermodynamic and kinetic properties of defects, possible missing of important kinetic properties and processes, and the capability of current codes and computers for large time and length scale modeling, the simulations demonstrate that PF method is a promising simulation tool for predicting 3-D heterogeneous microstructure and property evolution, and providing microstructure evolution kinetics for higher scale level simulations of microstructure and property evolution such as mean field methods. This report consists of two parts. In part I, we will present a new phase-field model for predicting interstitial loop growth kinetics in irradiated materials. The effect of defect (vacancy/interstitial) generation, diffusion and recombination, sink strength, long-range elastic interaction, inhomogeneous and anisotropic mobility on microstructure evolution kinetics is taken into account in the model. The model is used to study the effect of elastic interaction on interstitial loop growth kinetics, the interstitial flux, and sink
Kinetic Modelling of Macroscopic Properties Changes during Crosslinked Polybutadiene Oxidation
Audouin, Ludmila; Coquillat, Marie; Colin, Xavier; Verdu, Jacques; Nevière, Robert
2008-08-01
The thermal oxidation of additive free hydroxyl-terminated polybutadiene (HTPB) isocyanate crosslinked rubber bulk samples has been studied at 80, 100 and 120 °C in air. The oxidation kinetics has been monitored by gravimetry and thickness distribution of oxidation products was determined by FTIR mapping. Changes of elastic shear modulus G' during oxidation were followed during oxidation at the same temperatures. The kinetic model established previously for HTPB has been adapted for bulk sample oxidation using previously determined set of kinetic parameters. Oxygen diffusion control of oxidation has been introduced into the model. The mass changes kinetic curves and oxidation products profiles were simulated and adequate fit was obtained. Using the rubber elasticity theory the elastic modulus changes were simulated taking into account the elastically active chains concentration changes due to chain scission and crosslinking reactions. The reasonable fit of G' as a function of oxidation time experimental curves was obtained.
A Kinetic Model of Chromium in a Flame
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Chromium has been identified as a carcinogenic metal.Incineration is the useful method for disposal of toxic chromium hazard waste and a chromium kinetic model in a flame is very important to study chromium oxidation.Chromium chemical kinetics over a range of temperatures of a hydrogen/air flame is proposed.Nine chromium compounds and fifty-eight reversible chemical reactions were considered The forward reaction rates are calculated based on the molecular collision approach for unknown ones and Arrhenius's Law for known ones.The backward reaction rates were calculated according to forward reaction rates, the equilibrium constants and chemical thermodynamics.It is verified by several equilibrium cases and is tested by a hydrogen/air diffusion flame.The results show that the kinetic model could be used in cases in which the chromium kinetics play an important role in a flame
Physiologically based kinetic modeling of the bioactivation of myristicin
Al-Malahmeh, Amer J.; Al-Ajlouni, Abdelmajeed; Wesseling, Sebastiaan; Soffers, Ans E.M.F.; Al-Subeihi, A.; Kiwamoto, Reiko; Vervoort, Jacques; Rietjens, Ivonne M.C.M.
2016-01-01
The present study describes physiologically based kinetic (PBK) models for the alkenylbenzene myristicin that were developed by extension of the PBK models for the structurally related alkenylbenzene safrole in rat and human. The newly developed myristicin models revealed that the formation of th
Kinetic exchange models: From molecular physics to social science
Patriarca, Marco
2013-01-01
We discuss several multi-agent models that have their origin in the kinetic exchange theory of statistical mechanics and have been recently applied to a variety of problems in the social sciences. This class of models can be easily adapted for simulations in areas other than physics, such as the modeling of income and wealth distributions in economics and opinion dynamics in sociology.
Chemical kinetic modeling of H{sub 2} applications
Energy Technology Data Exchange (ETDEWEB)
Marinov, N.M.; Westbrook, C.K.; Cloutman, L.D. [Lawrence Livermore National Lab., CA (United States)] [and others
1995-09-01
Work being carried out at LLNL has concentrated on studies of the role of chemical kinetics in a variety of problems related to hydrogen combustion in practical combustion systems, with an emphasis on vehicle propulsion. Use of hydrogen offers significant advantages over fossil fuels, and computer modeling provides advantages when used in concert with experimental studies. Many numerical {open_quotes}experiments{close_quotes} can be carried out quickly and efficiently, reducing the cost and time of system development, and many new and speculative concepts can be screened to identify those with sufficient promise to pursue experimentally. This project uses chemical kinetic and fluid dynamic computational modeling to examine the combustion characteristics of systems burning hydrogen, either as the only fuel or mixed with natural gas. Oxidation kinetics are combined with pollutant formation kinetics, including formation of oxides of nitrogen but also including air toxics in natural gas combustion. We have refined many of the elementary kinetic reaction steps in the detailed reaction mechanism for hydrogen oxidation. To extend the model to pressures characteristic of internal combustion engines, it was necessary to apply theoretical pressure falloff formalisms for several key steps in the reaction mechanism. We have continued development of simplified reaction mechanisms for hydrogen oxidation, we have implemented those mechanisms into multidimensional computational fluid dynamics models, and we have used models of chemistry and fluid dynamics to address selected application problems. At the present time, we are using computed high pressure flame, and auto-ignition data to further refine the simplified kinetics models that are then to be used in multidimensional fluid mechanics models. Detailed kinetics studies have investigated hydrogen flames and ignition of hydrogen behind shock waves, intended to refine the detailed reactions mechanisms.
The Nonlinear Magnetosphere: Expressions in MHD and in Kinetic Models
Hesse, Michael; Birn, Joachim
2011-01-01
Like most plasma systems, the magnetosphere of the Earth is governed by nonlinear dynamic evolution equations. The impact of nonlinearities ranges from large scales, where overall dynamics features are exhibiting nonlinear behavior, to small scale, kinetic, processes, where nonlinear behavior governs, among others, energy conversion and dissipation. In this talk we present a select set of examples of such behavior, with a specific emphasis on how nonlinear effects manifest themselves in MHD and in kinetic models of magnetospheric plasma dynamics.
Kinetic model for the collisionless sheath of a collisional plasma
Tang, Xian-Zhu; Guo, Zehua
2016-08-01
Collisional plasmas typically have mean-free-path still much greater than the Debye length, so the sheath is mostly collisionless. Once the plasma density, temperature, and flow are specified at the sheath entrance, the profile variation of electron and ion density, temperature, flow speed, and conductive heat fluxes inside the sheath is set by collisionless dynamics, and can be predicted by an analytical kinetic model distribution. These predictions are contrasted here with direct kinetic simulations, showing good agreement.
Unravelling the Maillard reaction network by multiresponse kinetic modelling
Martins, S.I.F.S.
2003-01-01
The Maillard reaction is an important reaction in food industry. It is responsible for the formation of colour and aroma, as well as toxic compounds as the recent discovered acrylamide. The knowledge of kinetic parameters, such as rate constants and activation energy, is necessary to predict its extent and, consequently, to optimise it. Each of the chapters presented in this thesis can be seen as a necessary step to succeed in applying multiresponse kinetic modelling in a complex reaction, su...
A tool model for predicting atmospheric kinetics with sensitivity analysis
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A package( a tool model) for program of predicting atmospheric chemical kinetics with sensitivity analysis is presented. The new direct method of calculating the first order sensitivity coefficients using sparse matrix technology to chemical kinetics is included in the tool model, it is only necessary to triangularize the matrix related to the Jacobian matrix of the model equation. The Gear type procedure is used to integrate amodel equation and its coupled auxiliary sensitivity coefficient equations. The FORTRAN subroutines of the model equation, the sensitivity coefficient equations, and their Jacobian analytical expressions are generated automatically from a chemical mechanism. The kinetic representation for the model equation and its sensitivity coefficient equations, and their Jacobian matrix is presented. Various FORTRAN subroutines in packages, such as SLODE, modified MA28, Gear package, with which the program runs in conjunction are recommended.The photo-oxidation of dimethyl disulfide is used for illustration.
Wang, Zhandong
2015-07-01
Ethylcyclohexane (ECH) is a model compound for cycloalkanes with long alkyl side-chains. A preliminary investigation on ECH (Wang et al., Proc. Combust. Inst., 35, 2015, 367-375) revealed that an accurate ECH kinetic model with detailed fuel consumption mechanism and aromatic growth pathways, as well as additional ECH pyrolysis and oxidation data with detailed species concentration covering a wide pressure and temperature range are required to understand the ECH combustion kinetics. In this work, the flow reactor pyrolysis of ECH at various pressures (30, 150 and 760Torr) was studied using synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS) and gas chromatography (GC). The mole fraction profiles of numerous major and minor species were evaluated, and good agreement was observed between the PIMS and GC data sets. Furthermore, a fuel-rich burner-stabilized laminar premixed ECH/O
Repopulation Kinetics and the Linear-Quadratic Model
O'Rourke, S. F. C.; McAneney, H.; Starrett, C.; O'Sullivan, J. M.
2009-08-01
The standard Linear-Quadratic (LQ) survival model for radiotherapy is used to investigate different schedules of radiation treatment planning for advanced head and neck cancer. We explore how these treament protocols may be affected by different tumour repopulation kinetics between treatments. The laws for tumour cell repopulation include the logistic and Gompertz models and this extends the work of Wheldon et al. [1], which was concerned with the case of exponential repopulation between treatments. Treatment schedules investigated include standarized and accelerated fractionation. Calculations based on the present work show, that even with growth laws scaled to ensure that the repopulation kinetics for advanced head and neck cancer are comparable, considerable variation in the survival fraction to orders of magnitude emerged. Calculations show that application of the Gompertz model results in a significantly poorer prognosis for tumour eradication. Gaps in treatment also highlight the differences in the LQ model with the effect of repopulation kinetics included.
Kinetic modeling of the Townsend breakdown in argon
Macheret, S. O.; Shneider, M. N.
2013-10-01
Kinetic modeling of the Townsend breakdown in argon was performed in the "forward-back" approximation. The kinetic model was found to adequately describe the left branch of the Paschen curve, and the important role of ionization by fast ions and atoms near the cathode, as well as the increase in secondary emission coefficient in strong electric fields described in the literature, was confirmed. The modeling also showed that the electron energy distribution function develops a beam of high-energy electrons and that the runaway effect, i.e., the monotonic increase of the mean electron energy with the distance from the cathode, occurs at the left branch of the Paschen curve.
On a kinetic model for a simple market economy
Cordier, Stéphane; Pareschi, Lorenzo; Toscani, Giuseppe
2004-01-01
In this paper, we consider a simple kinetic model of economy involving both exchanges between agents and speculative trading. We show that the kinetic model admits non trivial quasi-stationary states with power law tails of Pareto type. In order to do this we consider a suitable asymptotic limit of the model yielding a Fokker-Planck equation for the distribution of wealth among individuals. For this equation the stationary state can be easily derived and shows a Pareto power law tail. Numeric...
Information cascade, Kirman's ant colony model, and kinetic Ising model
Hisakado, Masato
2014-01-01
In this paper, we discuss a voting model in which voters can obtain information from a finite number of previous voters. There exist three groups of voters: (i) digital herders and independent voters, (ii) analog herders and independent voters, and (iii) tanh-type herders. In our previous paper, we used the mean field approximation for case (i). In that study, if the reference number r is above three, phase transition occurs and the solution converges to one of the equilibria. In contrast, in the current study, the solution oscillates between the two equilibria, that is, good and bad equilibria. In this paper, we show that there is no phase transition when r is finite. If the annealing schedule is adequately slow from finite r to infinite r, the voting rate converges only to the good equilibrium. In case (ii), the state of reference votes is equivalent to that of Kirman's ant colony model, and it follows beta binomial distribution. In case (iii), we show that the model is equivalent to the finite-size kinetic...
A kinetic model for the burst phase of processive cellulases
DEFF Research Database (Denmark)
Præstgaard, Eigil; Olsen, Jens Elmerdahl; Murphy, Leigh;
2011-01-01
is negligible. Here, we propose an explicit kinetic model for this behavior, which uses classical burst phase theory as the starting point. The model is tested against calorimetric measurements of the activity of the cellobiohydrolase Cel7A from Trichoderma reesei on amorphous cellulose. A simple version...
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.
Kinetic modelling for zinc (II) ions biosorption onto Luffa cylindrica
Oboh, I.; Aluyor, E.; Audu, T.
2015-03-01
The biosorption of Zinc (II) ions onto a biomaterial - Luffa cylindrica has been studied. This biomaterial was characterized by elemental analysis, surface area, pore size distribution, scanning electron microscopy, and the biomaterial before and after sorption, was characterized by Fourier Transform Infra Red (FTIR) spectrometer. The kinetic nonlinear models fitted were Pseudo-first order, Pseudo-second order and Intra-particle diffusion. A comparison of non-linear regression method in selecting the kinetic model was made. Four error functions, namely coefficient of determination (R2), hybrid fractional error function (HYBRID), average relative error (ARE), and sum of the errors squared (ERRSQ), were used to predict the parameters of the kinetic models. The strength of this study is that a biomaterial with wide distribution particularly in the tropical world and which occurs as waste material could be put into effective utilization as a biosorbent to address a crucial environmental problem.
Kinetic modelling for zinc (II) ions biosorption onto Luffa cylindrica
Energy Technology Data Exchange (ETDEWEB)
Oboh, I., E-mail: innocentoboh@uniuyo.edu.ng [Department of Chemical and Petroleum Engineering, University of Uyo, Uyo (Nigeria); Aluyor, E.; Audu, T. [Department of Chemical Engineering, University of Uyo, BeninCity, BeninCity (Nigeria)
2015-03-30
The biosorption of Zinc (II) ions onto a biomaterial - Luffa cylindrica has been studied. This biomaterial was characterized by elemental analysis, surface area, pore size distribution, scanning electron microscopy, and the biomaterial before and after sorption, was characterized by Fourier Transform Infra Red (FTIR) spectrometer. The kinetic nonlinear models fitted were Pseudo-first order, Pseudo-second order and Intra-particle diffusion. A comparison of non-linear regression method in selecting the kinetic model was made. Four error functions, namely coefficient of determination (R{sup 2}), hybrid fractional error function (HYBRID), average relative error (ARE), and sum of the errors squared (ERRSQ), were used to predict the parameters of the kinetic models. The strength of this study is that a biomaterial with wide distribution particularly in the tropical world and which occurs as waste material could be put into effective utilization as a biosorbent to address a crucial environmental problem.
Sum rule limitations of kinetic particle-production models
International Nuclear Information System (INIS)
Photoproduction and absorption sum rules generalized to systems at finite temperature provide a stringent check on the validity of kinetic models for the production of hard photons in intermediate energy nuclear collisions. We inspect such models for the case of nuclear matter at finite temperature employed in a kinetic regime which copes those encountered in energetic nuclear collisions, and find photon production rates which significantly exceed the limits imposed by the sum rule even under favourable concession. This suggests that coherence effects are quite important and the production of photons cannot be considered as an incoherent addition of individual NNγ production processes. The deficiencies of present kinetic models may also apply for the production of probes such as the pion which do not couple perturbatively to the nuclear currents. (orig.)
Kinetic models for irreversible processes on a lattice
Energy Technology Data Exchange (ETDEWEB)
Wolf, N.O.
1979-04-01
The development and application of kinetic lattice models are considered. For the most part, the discussions are restricted to lattices in one-dimension. In Chapter 1, a brief overview of kinetic lattice model formalisms and an extensive literature survey are presented. A review of the kinetic models for non-cooperative lattice events is presented in Chapter 2. The development of cooperative lattice models and solution of the resulting kinetic equations for an infinite and a semi-infinite lattice are thoroughly discussed in Chapters 3 and 4. The cooperative models are then applied to the problem of theoretically dtermining the sticking coefficient for molecular chemisorption in Chapter 5. In Chapter 6, other possible applications of these models and several model generalizations are considered. Finally, in Chapter 7, an experimental study directed toward elucidating the mechanistic factors influencing the chemisorption of methane on single crystal tungsten is reported. In this it differs from the rest of the thesis which deals with the statistical distributions resulting from a given mechanism.
Khonde, Ruta Dhanram; Chaurasia, Ashish Subhash
2015-04-01
The present study provides the kinetic model to describe the pyrolysis of sawdust, rice-husk and sugarcane bagasse as biomass. The kinetic scheme used for modelling of primary pyrolysis consisting of the two parallel reactions giving gaseous volatiles and solid char. Estimation of kinetic parameters for pyrolysis process has been carried out for temperature range of 773-1,173 K. As there are serious issues regarding non-convergence of some of the methods or solutions converging to local-optima, the proposed kinetic model is optimized to predict the best values of kinetic parameters for the system using three approaches—Two-dimensional surface fitting non-linear regression technique, MS-Excel Solver Tool and COMSOL software. The model predictions are in agreement with experimental data over a wide range of pyrolysis conditions. The estimated value of kinetic parameters are compared with earlier researchers and found to be matching well.
Directory of Open Access Journals (Sweden)
Ramez Alhazzaa
Full Text Available This study aimed to establish optimal conditions for a cell culture system that would allow the measurement of 18:3n-3 (ALA bioconversion into n-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA, and to determine the overall pathway kinetics. Using rat hepatocytes (FaO as model cells, it was established that a maximum 20:5n-3 (EPA production from 50 µM ALA initial concentration was achieved after 3 days of incubation. Next, it was established that a gradual increase in the ALA concentration from 0 up to 125 µM lead to a proportional increase in EPA, without concomitant increase in further elongated or desaturated products, such as 22:5n-3 (DPA and 22:6n-3 (DHA in 3 day incubations. Of interest, ALA bioconversion products were observed in the culture medium. Therefore, in vitro experiments disregarding the medium fatty acid content are underestimating the metabolism efficiency. The novel application of the fatty acid mass balance (FAMB method on cell culture system (cells with medium enabled quantifying the apparent enzymatic activities for the biosynthesis of n-3 LC-PUFA. The activity of the key enzymes was estimated and showed that, under these conditions, 50% (Km of the theoretical maximal (V max = 3654 µmol.g(-1 of cell protein.hour(-1 Fads2 activity on ALA can be achieved with 81 µM initial ALA. Interestingly, the apparent activity of Elovl2 (20:5n-3 elongation was the slowest amongst other biosynthesis steps. Therefore, the possible improvement of Elovl2 activity is suggested toward a more efficient DHA production from ALA. The present study proposed and described an ad hoc optimised cell culture conditions and methodology towards achieving a reliable experimental platform, using FAMB, to assist in studying the efficiency of ALA bioconversion into n-3 LC-PUFA in vitro. The FAMB proved to be a powerful and inexpensive method to generate a detailed description of the kinetics of n-3 LC-PUFA biosynthesis enzymes activities in vitro.
Bioconversion of anhydrosugars: Emerging concepts and strategies.
Bacik, John-Paul; Jarboe, Laura R
2016-09-01
As methods for the use of anhydrosugars in chemical and biofuel production continue to develop, our collective knowledge of anhydrosugar processing enzymes continues to improve, including their mechanistic details, structural dynamics and modes of substrate binding. Of particular interest, anhydrosugar kinases, such as levoglucosan kinase (LGK) and 1,6-anhydro-N-acetylmuramic acid kinase (AnmK), utilize an unusual mechanism whereby the sugar substrate is both cleaved and phosphorylated. The phosphorylated sugar can then be routed to other metabolic pathways, thereby allowing its further bioconversion. Advanced engineering efforts to improve the catalytic efficiency and stability of LGK have been steadily progressing. Other enzymes that cleave the glycosidic bond of disaccharide sugars containing an anhydrosugar component are also being identified and characterized. Accordingly, the potential future use of these enzymes in large-scale production strategies is becoming increasingly viable. Here, a mini-review of the observed characteristics of anhydrosugar processing enzymes is presented along with recent developments in the bioconversion of these sugars. © 2016 IUBMB Life 68(9):700-708, 2016. PMID:27416973
Bayesian inference of chemical kinetic models from proposed reactions
Galagali, Nikhil
2015-02-01
© 2014 Elsevier Ltd. Bayesian inference provides a natural framework for combining experimental data with prior knowledge to develop chemical kinetic models and quantify the associated uncertainties, not only in parameter values but also in model structure. Most existing applications of Bayesian model selection methods to chemical kinetics have been limited to comparisons among a small set of models, however. The significant computational cost of evaluating posterior model probabilities renders traditional Bayesian methods infeasible when the model space becomes large. We present a new framework for tractable Bayesian model inference and uncertainty quantification using a large number of systematically generated model hypotheses. The approach involves imposing point-mass mixture priors over rate constants and exploring the resulting posterior distribution using an adaptive Markov chain Monte Carlo method. The posterior samples are used to identify plausible models, to quantify rate constant uncertainties, and to extract key diagnostic information about model structure-such as the reactions and operating pathways most strongly supported by the data. We provide numerical demonstrations of the proposed framework by inferring kinetic models for catalytic steam and dry reforming of methane using available experimental data.
A kinetic model of carbon burnout in pulverized coal combustion
Energy Technology Data Exchange (ETDEWEB)
Hurt, R.; Jian-Kuan Sun; Lunden, M. [Brown University, Providence, RI (United States). Division of Engineering
1998-04-01
The degree of carbon burnout is an important operating characteristic of full-scale suspension-fired coal combustion systems affecting boiler efficiency, electrostatic precipitator operation and the value of fly ash as a saleable product. Prediction of carbon loss requires special char combustion kinetics valid through the very high conversions targeted in industry (typically {gt} 99.5%), and valid for a wide-range of particle temperature histories occurring in full-scale furnaces. The paper presents high-temperature kinetic data for five coal chars in the form of time-resolved burning profiles that include the late stages of combustion. It then describes the development and validation of the Carbon Burnout Kinetic Model (CBK), a coal-general kinetics package that is specifically designed to predict the total extent of carbon burnout and ultimate fly ash carbon content for prescribed temperature/oxygen histories typical of pulverized coal combustion systems. The model combines the single-film treatment of cha oxidation with quantitative descriptions of thermal annealing, statistical kinetics, statistical densities, and ash inhibition in the late stages of combustion. In agreement with experimental observations, the CBK model predicts (1) low reactivities for unburned carbon residues extracted from commercial ash samples, (2) reactivity loss in the late stages of laboratory combustion, (3) the observed sensitivity of char reactivity to high-temperature heat treatment on second and subsecond time scales, and (4) the global reaction inhibition by mineral matter in the late stages of combustion observed in single-particle imaging studies. The model ascribes these various char deactivation phenomena to the combined effects of thermal annealing, ash inhibition, and the preferential consumption of more reactive particles (statistical kinetics), the relative contributions of which vary greatly with combustion conditions. 39 refs., 4 figs., 4 tabs., 1 app.
Kinetic roughening in models of molecular-beam epitaxy growth
International Nuclear Information System (INIS)
A brief survey of recent progress in understanding the kinetic roughening in growth models with surface diffusion, which are relevant for growth by molecular-beam epitaxy, in given. The main emphasis is on results of computer simulations. Properties of several different models are described and compared. In particular, results for two models, the Wolf-Villain model (and its modifications) and the full diffusion model, in 1+1, 2+1 and also in higher dimensions are presented. The asymptotic behaviour of the Wolf-Villain model is of an Edwards-Wilkinson type. Both models show an unusual scaling behaviour of the height-height correlation function
A Discrete Velocity Traffic Kinetic Model Including Desired Speed
Directory of Open Access Journals (Sweden)
Shoufeng Lu
2013-05-01
Full Text Available We introduce the desired speed variable into the table of games and formulate a new table of games and the corresponding discrete traffic kinetic model. We use the hybrid programming technique of VB and MATLAB to develop the program. Lastly, we compared the proposed model result and the detector data. The results show that the proposed model can describe the traffic flow evolution.
Energetic Mapping of Ni Catalysts by Detailed Kinetic Modeling
DEFF Research Database (Denmark)
Bjørgum, Erlend; Chen, De; Bakken, Mari G.;
2005-01-01
precursor seems to result in more steplike sites, kinks, and defects for carbon monoxide dissociation. A detailed kinetic modeling of the TPO results based on elementary reaction steps has been conducted to give an energetic map of supported Ni catalysts. Experimental results from the ideal Ni surface fit...
Estimation of Kinetic Parameters in an Automotive SCR Catalyst Model
DEFF Research Database (Denmark)
Åberg, Andreas; Widd, Anders; Abildskov, Jens;
2016-01-01
A challenge during the development of models for simulation of the automotive Selective Catalytic Reduction catalyst is the parameter estimation of the kinetic parameters, which can be time consuming and problematic. The parameter estimation is often carried out on small-scale reactor tests, or p...
Kinetics and modeling of anaerobic digestion process
DEFF Research Database (Denmark)
Gavala, Hariklia N.; Angelidaki, Irini; Ahring, Birgitte Kiær
2003-01-01
Anaerobic digestion modeling started in the early 1970s when the need for design and efficient operation of anaerobic systems became evident. At that time not only was the knowledge about the complex process of anaerobic digestion inadequate but also there were computational limitations. Thus, th...
Laplace transform in tracer kinetic modeling
Energy Technology Data Exchange (ETDEWEB)
Hauser, Eliete B., E-mail: eliete@pucrs.br [Instituto do Cerebro (InsCer/FAMAT/PUC-RS), Porto Alegre, RS, (Brazil). Faculdade de Matematica
2013-07-01
The main objective this paper is to quantify the pharmacokinetic processes: absorption, distribution and elimination of radiopharmaceutical(tracer), using Laplace transform method. When the drug is administered intravenously absorption is complete and is available in the bloodstream to be distributed throughout the whole body in all tissues and fluids, and to be eliminated. Mathematical modeling seeks to describe the processes of distribution and elimination through compartments, where distinct pools of tracer (spatial location or chemical state) are assigned to different compartments. A compartment model is described by a system of differential equations, where each equation represents the sum of all the transfer rates to and from a specific compartment. In this work a two-tissue irreversible compartment model is used for description of tracer, [{sup 18}F]2-fluor-2deoxy-D-glucose. In order to determine the parameters of the model, it is necessary to have information about the tracer delivery in the form of an input function representing the time-course of tracer concentration in arterial blood or plasma. We estimate the arterial input function in two stages and apply the Levenberg-Marquardt Method to solve nonlinear regressions. The transport of FDG across de arterial blood is very fast in the first ten minutes and then decreases slowly. We use de Heaviside function to represent this situation and this is the main contribution of this study. We apply the Laplace transform and the analytical solution for two-tissue irreversible compartment model is obtained. The only approach is to determinate de arterial input function. (author)
Chemical kinetics and combustion modelling with CFX 4
Energy Technology Data Exchange (ETDEWEB)
Stopford, P. [AEA Technology, Computational Fluid Dynamics Services Harwell, Oxfordshire (United Kingdom)
1997-12-31
The presentation describes some recent developments in combustion and kinetics models used in the CFX software of AEA Technology. Three topics are highlighted: the development of coupled solvers in a traditional `SIMPLE`-based CFD code, the use of detailed chemical kinetics mechanism via `look-up` tables and the application of CFD to large-scale multi-burner combustion plant. The aim is identify those physical approximations and numerical methods that are likely to be most useful in the future and those areas where further developments are required. (author) 6 refs.
Second-order kinetic Kohn-Sham lattice model
Solórzano, S.; Mendoza, M.; Herrmann, H. J.
2016-06-01
In this work, we introduce a semi-implicit second-order correction scheme to the kinetic Kohn-Sham lattice model. This approach is validated by performing realistic exchange-correlation energy calculations of atoms and dimers of the first two rows of the Periodic Table, finding good agreement with the expected values. Additionally, we simulate the ethane molecule, where we recover the bond lengths and compare the results with standard methods. Finally, we discuss the current applicability of pseudopotentials within the lattice kinetic Kohn-Sham approach.
Second order kinetic Kohn-Sham lattice model
Solorzano, Sergio; Herrmann, Hans
2016-01-01
In this work we introduce a new semi-implicit second order correction scheme to the kinetic Kohn-Sham lattice model. The new approach is validated by performing realistic exchange-correlation energy calculations of atoms and dimers of the first two rows of the periodic table finding good agreement with the expected values. Additionally we simulate the ethane molecule where we recover the bond lengths and compare the results with standard methods. Finally, we discuss the current applicability of pseudopotentials within the lattice kinetic Kohn-Sham approach.
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.
Kinetics of Model Reactions for Interfacial Polymerization
Directory of Open Access Journals (Sweden)
Henry Hall
2012-02-01
Full Text Available To model the rates of interfacial polycondensations, the rates of reaction of benzoyl chloride and methyl chloroformate with various aliphatic monoamines in acetonitrile were determined at 25 °C. Buffering with picric acid slowed these extremely fast reactions so the rate constants could be determined from the rate of disappearance of picrate ion. The rates of the amine reactions correlated linearly with their Swain-Scott nucleophilicities.
Kinetics of Model Reactions for Interfacial Polymerization
Henry Hall; Robert Bates; Jeffrey Robertson; Anne Padias; Trevor Centeno-Hall
2012-01-01
To model the rates of interfacial polycondensations, the rates of reaction of benzoyl chloride and methyl chloroformate with various aliphatic monoamines in acetonitrile were determined at 25 °C. Buffering with picric acid slowed these extremely fast reactions so the rate constants could be determined from the rate of disappearance of picrate ion. The rates of the amine reactions correlated linearly with their Swain-Scott nucleophilicities.
Detailed kinetic modeling of the thermal degradation of lignins
International Nuclear Information System (INIS)
The aim of this kinetic work is to provide a better understanding of the pyrolysis of lignin and biomasses not only in terms of devolatilazation rate but also of the volatile species released. The complexity of both lignin structure and its degradation mechanism meant that a lumping approach suitable for handling the huge amount of initial, intermediate and final products had to be used. Despite these simplifications, the proposed semi-detailed kinetic scheme involves about 100 molecular and radical species in 500 elementary and lumped reactions. It has already been proved that this lignin devolatilization model correctly predicts the degradation rates and the detail of the released products. This work constitutes an initial yet significant step towards deriving a complete kinetic scheme of biomass devolatilization.
Intrinsic Kinetic Modeling of Thermal Dimerization of C5 Fraction
Institute of Scientific and Technical Information of China (English)
Guo Liang; Wang Tiefeng; Li Dongfeng; Wang Jinfu
2016-01-01
This work aims to investigate the intrinsic kinetics of thermal dimerization of C5 fraction in the reactive distilla-tion process. Experiments are conducted in an 1000-mL stainless steel autoclave under some selected design conditions. By means of the weighted least squares method, the intrinsic kinetics of thermal dimerization of C5 fraction is established, and the corresponding pre-exponential factor as well as the activation energy are determined. For example, the pre-exponential factor A is equal to 4.39×105 and the activation energy Ea is equal to 6.58×104 J/mol for the cyclopentadiene dimerization re-action. The comparison between the experimental and calculated results shows that the kinetics model derived in this work is accurate and reliable, which can be used in the design of reactive distillation columns.
A spatially resolved surface kinetic model for forsterite dissolution
Maher, Kate; Johnson, Natalie C.; Jackson, Ariel; Lammers, Laura N.; Torchinsky, Abe B.; Weaver, Karrie L.; Bird, Dennis K.; Brown, Gordon E.
2016-02-01
The development of complex alteration layers on silicate mineral surfaces undergoing dissolution is a widely observed phenomenon. Given the complexity of these layers, most kinetic models used to predict rates of mineral-fluid interactions do not explicitly consider their formation. As a result, the relationship between the development of the altered layers and the final dissolution rate is poorly understood. To improve our understanding of the relationship between the alteration layer and the dissolution rate, we developed a spatially resolved surface kinetic model for olivine dissolution and applied it to a series of closed-system experiments consisting of three-phases (water (±NaCl), olivine, and supercritical CO2) at conditions relevant to in situ mineral carbonation (i.e. 60 °C, 100 bar CO2). We also measured the corresponding δ26/24Mg of the dissolved Mg during early stages of dissolution. Analysis of the solid reaction products indicates the formation of Mg-depleted layers on the olivine surface as quickly as 2 days after the experiment was started and before the bulk solution reached saturation with respect to amorphous silica. The δ26/24Mg of the dissolved Mg decreased by approximately 0.4‰ in the first stages of the experiment and then approached the value of the initial olivine (-0.35‰) as the steady-state dissolution rate was approached. We attribute the preferential release of 24Mg to a kinetic effect associated with the formation of a Mg-depleted layer that develops as protons exchange for Mg2+. We used experimental data to calibrate a surface kinetic model for olivine dissolution that includes crystalline olivine, a distinct "active layer" from which Mg can be preferentially removed, and secondary amorphous silica precipitation. By coupling the spatial arrangement of ions with the kinetics, this model is able to reproduce both the early and steady-state long-term dissolution rates, and the kinetic isotope fractionation. In the early stages of
Homogeneous gas phase models of relaxation kinetics in neon afterglow
Directory of Open Access Journals (Sweden)
Marković Vidosav Lj.
2007-01-01
Full Text Available The homogeneous gas phase models of relaxation kinetics (application of the gas phase effective coefficients to represent surface losses are applied for the study of charged and neutral active particles decay in neon afterglow. The experimental data obtained by the breakdown time delay measurements as a function of the relaxation time td (τ (memory curve is modeled in early, as well as in late afterglow. The number density decay of metastable states can explain neither the early, nor the late afterglow kinetics (memory effect, because their effective lifetimes are of the order of milliseconds and are determined by numerous collision quenching processes. The afterglow kinetics up to hundreds of milliseconds is dominated by the decay of molecular neon Ne2 + and nitrogen ions N2 + (present as impurities and the approximate value of N2 + ambipolar diffusion coefficient is determined. After the charged particle decay, the secondary emitted electrons from the surface catalyzed excitation of nitrogen atoms on the cathode determine the breakdown time delay down to the cosmic rays and natural radioactivity level. Due to the neglecting of number density spatial profiles, the homogeneous gas phase models give only the approximate values of the corresponding coefficients, but reproduce correctly other characteristics of afterglow kinetics from simple fits to the experimental data.
Enzymatic hydrolysis of protein:mechanism and kinetic model
Institute of Scientific and Technical Information of China (English)
Qi Wei; He Zhimin
2006-01-01
The bioreaction mechanism and kinetic behavior of protein enzymatic hydrolysis for preparing active peptides were investigated to model and characterize the enzymatic hydrolysis curves.Taking into account single-substrate hydrolysis,enzyme inactivation and substrate or product inhibition,the reaction mechanism could be deduced from a series of experimental results carried out in a stirred tank reactor at different substrate concentrations,enzyme concentrations and temperatures based on M-M equation.An exponential equation dh/dt = aexp(-bh) was also established,where parameters a and b have different expressions according to different reaction mechanisms,and different values for different reaction systems.For BSA-trypsin model system,the regressive results agree with the experimental data,i.e.the average relative error was only 4.73%,and the reaction constants were determined as Km = 0.0748 g/L,Ks = 7.961 g/L,kd = 9.358/min,k2 =38.439/min,Ea= 64.826 kJ/mol,Ed= 80.031 kJ/mol in accordance with the proposed kinetic mode.The whole set of exponential kinetic equations can be used to model the bioreaction process of protein enzymatic hydrolysis,to calculate the thermodynamic and kinetic constants,and to optimize the operating parameters for bioreactor design.
Developments in kinetic modelling of chalcocite particle oxidation
Energy Technology Data Exchange (ETDEWEB)
Jaervi, J.; Ahokainen, T.; Jokilaakso, A. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Materials Processing and Powder Metallurgy
1997-12-31
A mathematical model for simulating chalcocite particle oxidation is presented. Combustion of pure chalcocite with oxygen is coded as a kinetic module which can be connected as a separate part of commercial CFD-package, PHOENICS. Heat transfer, fluid flow and combustion phenomena can be simulated using CFD-calculation together with the kinetic model. Interaction between gas phase and particles are taken into account by source terms. The aim of the kinetic model is to calculate the particle temperature, contents of species inside the particle, oxygen consumption and formation of sulphur dioxide. Four oxidation reactions are considered and the shrinking core model is used to describe the rate of the oxidation reactions. The model is verified by simulating the particle oxidation reactions in a laboratory scale laminar-flow furnace under different conditions and the model predicts the effects of charges correctly. In the future, the model validation will be done after experimental studies in the laminar flow-furnace. (author) 18 refs.
Cleaner combustion developing detailed chemical kinetic models
Battin-Leclerc, Frédérique; Blurock, Edward
2013-01-01
This overview compiles the on-going research in Europe to enlarge and deepen the understanding of the reaction mechanisms and pathways associated with the combustion of an increased range of fuels. Focus is given to the formation of a large number of hazardous minor pollutants and the inability of current combustion models to predict the Â formation of minor products such as alkenes, dienes, aromatics, aldehydes and soot nano-particles which have a deleterious impact on both the environment and on human health. Cleaner Combustion describes, at a fundamental level, the reactive chemistry of min
Vlasiator: Global Kinetic Magnetospheric Modeling Tool
Sandroos, A.; von Alfthan, S.; Hoilijoki, S.; Honkonen, I.; Kempf, Y.; Pokhotelov, D.; Palmroth, M.
2015-10-01
We present Vlasiator, a novel code based on Vlasov's equation, developed for modeling magnetospheric plasma on a global scale. We have parallelized the code to petascale supercomputers with a hybrid OpenMP-MPI approach to answer the high computational cost of propagating ion distribution functions in six dimensions. The accuracy of the numerical method is demonstrated by comparing simulated wave dispersion plots to analytical results. Simulations of Earth's bow shock region were able to reproduce many well-known plasma phenomena, such as compressional magnetosonic waves in the foreshock region, and mirror mode instability in the magnetosheath.
Chemistry Resolved Kinetic Flow Modeling of TATB Based Explosives
Energy Technology Data Exchange (ETDEWEB)
Vitello, P A; Fried, L E; Howard, W M; Levesque, G; Souers, P C
2011-07-21
Detonation waves in insensitive, TATB based explosives are believed to have multi-time scale regimes. The initial burn rate of such explosives has a sub-microsecond time scale. However, significant late-time slow release in energy is believed to occur due to diffusion limited growth of carbon. In the intermediate time scale concentrations of product species likely change from being in equilibrium to being kinetic rate controlled. They use the thermo-chemical code CHEETAH linked to an ALE hydrodynamics code to model detonations. They term their model chemistry resolved kinetic flow as CHEETAH tracks the time dependent concentrations of individual species in the detonation wave and calculates EOS values based on the concentrations. A HE-validation suite of model simulations compared to experiments at ambient, hot, and cold temperatures has been developed. They present here a new rate model and comparison with experimental data.
Modeling Kinetics of Distortion in Porous Bi-layered Structures
DEFF Research Database (Denmark)
Tadesse Molla, Tesfaye; Frandsen, Henrik Lund; Bjørk, Rasmus;
2013-01-01
Shape distortions during constrained sintering experiment of bi-layer porous and dense cerium gadolinium oxide (CGO) structures have been modeled. Technologies like solid oxide fuel cells require co-firing thin layers with different green densities, which often exhibit differential shrinkage...... because of different sintering rates of the materials resulting in undesired distortions of the component. An analytical model based on the continuum theory of sintering has been developed to describe the kinetics of densification and distortion in the sintering processes. A new approach is used...... to extract the material parameters controlling shape distortion through optimizing the model to experimental data of free shrinkage strains. The significant influence of weight of the sample (gravity) on the kinetics of distortion is taken in to consideration. The modeling predictions indicate good agreement...
Encapsulates for Food Bioconversions and Metabolite Production
Breguet, Véronique; Vojinovic, Vojislav; Marison, Ian W.
The control of production costs in the food industry must be very strict as a result of the relatively low added value of food products. Since a wide variety of enzymes and/or cells are employed in the food industry for starch processing, cheese making, food preservation, lipid hydrolysis and other applications, immobilization of the cells and/or enzymes has been recognized as an attractive approach to improving food processes while minimizing costs. This is due to the fact that biocatalyst immobilization allows for easier separation/purification of the product and reutilization of the biocatalyst. The advantages of the use of immobilized systems are many, and they have a special relevance in the area of food technology, especially because industrial processes using immobilized biosystems are usually characterized by lower capital/energy costs and better logistics. The main applications of immobilization, related to the major processes of food bioconversions and metabolite production, will be described and discussed in this chapter.
Agent dynamics in kinetic models of wealth exchange
Chatterjee, Arnab
2010-01-01
We study the dynamics of individual agents in some kinetic models of wealth exchange, particularly, the models with savings. For the model with uniform savings, agents perform simple random walks in the `"wealth space". On the other hand, we observe ballistic diffusion in the model with distributed savings. There is an associated skewness in the gain-loss distribution which explains the steady state behavior in such models. We find that in general an agent gains while interacting with an agent with a larger saving propensity.
Ab initio and kinetic modeling studies of formic acid oxidation
DEFF Research Database (Denmark)
Marshall, Paul; Glarborg, Peter
2015-01-01
A detailed chemical kinetic model for oxidation of formic acid (HOCHO) in flames has been developed, based on theoretical work and data from literature. Ab initio calculations were used to obtain rate coefficients for reactions of HOCHO with H, O, and HO2. Modeling predictions with the mechanism ...... as the fate of HOCO, determines the oxidation rate of formic acid. At lower temperatures HO2, formed from HOCO + O2, is an important chain carrier and modeling predictions become sensitive to the HOCHO + HO2 reaction. © 2014 The Combustion Institute.......A detailed chemical kinetic model for oxidation of formic acid (HOCHO) in flames has been developed, based on theoretical work and data from literature. Ab initio calculations were used to obtain rate coefficients for reactions of HOCHO with H, O, and HO2. Modeling predictions with the mechanism...... on calculations with the kinetic model. Formic acid is consumed mainly by reaction with OH, yielding OCHO, which dissociates rapidly to CO2 + H, and HOCO, which may dissociate to CO + OH or CO2 + H, or react with H, OH, or O2 to form more stable products. The branching fraction of the HOCHO + OH reaction, as well...
Modeling the kinetics of the nitriding and nitrocarburizing of iron
DEFF Research Database (Denmark)
Somers, Marcel A. J.; Mittemeijer, Eric J.
1998-01-01
The growth kinetics of the iron-nitride compound layer during nitriding and nitrocarburizing of pure iron has been investigated for various temperatures and various combinations of imposed nitrogen and carbon activities. The results indicate that no local equilibrium occurs at the gas/solid inter......The growth kinetics of the iron-nitride compound layer during nitriding and nitrocarburizing of pure iron has been investigated for various temperatures and various combinations of imposed nitrogen and carbon activities. The results indicate that no local equilibrium occurs at the gas....../solid interface during nitriding/nitrocarburizing, due to the slow kinetics of ammonia dissociation, the development and subsequent desorption of molecular nitrogen gas at the surface and, for the case of nitrocarburizing, the fast initial carbon uptake. The kinetics of gaseous nitriding of pure iron can...... be adequately described by a model that adopts local equilibrium at the solid/solid interfaces and a composition-weighted intrinsic diffusion coefficient of nitrogen in the Fe-N phases. For nitrocarburizing modeling appears not possible yet, due to compositions at gas/solid and solid/solid interfaces which...
Plasma sheath studies using the kinetic trajectory simulation model
International Nuclear Information System (INIS)
Plasma sheath formed in front of a material wall for different cases have been studied. For given electron and ion distributions at the sheath entrance we use Kinetic Trajectory Simulation (KTS) model to obtain the solution to a non-neutral, time-independent, collisionless plasma sheath. The characteristic feature of the KTS method is that the distribution functions of the particle species involved are calculated directly by solving the related kinetic equations along the respective collisionless particle trajectories. For a given potential distribution, we calculate the exact ion distribution function by integrating Vlasov's equation along its characteristics and taking into account the scraping-off effect at the wall. The electron distribution, on the other hand, is calculated analytically, however taking into account the cut-off introduced by electron absorption at the wall.We also present a scheme for coupling a quasineutral two-fluid (electron-ion) presheath solution to a non-neutral, collisionless kinetic sheath solution for a 1d1v case. It has been observed that the sheath structure is highly influenced by the magnitude of potential applied to the wall. The applied kinetic model is thus expected to give better insight to the sheath phenomena. (author)
Kinetic model of induced codeposition of Ni-Mo alloys
Institute of Scientific and Technical Information of China (English)
ZENG, Yue; MA, Ming; XIAO, Xiao-Ming; LI, Ze-Lin; LIAN, Shi-Xun; ZHOU, Shao-Min
2000-01-01
The kinetic model of induced codeposition of nickel-molybdenum alloys from ammoniun citrate solution was studied on rotating disk electrodes to predict the behavior of the electrodeposition. Ihe molybdate (MoO42-) could be firstly electrochemically reduced to MoO2, and subsequently undergoes a chemical reduction with atomic hydrogen previously adsorbed on the inducing metal nickel to form molybdenum in alloys.The kinetic equations were derived, and the kinetic parameters were obtained from a comparison of experimental results and the kinetic equations. The electrochemical rate constants for discharge of nickel, molybdenum and water could been expressed as k1 ( E ) = 1. 23 × 10-9 CNexp( - 0. 198FE/ RT )mol/(dm2. s), k2 (E) = 3.28 × 10-10 CMoexp ( - 0.208FE/RT) mol/(dm2·s) and k3(E) = 1.27 × 10-6exp( - 0.062FE/RT) mol/(dm2 ·s), where CN and CMo are the concentrations of the nickel ion and molybdate, respectively, and E is the applied potential vs, saturated calornel electrode (SCE).The codeposition process could be well simulated by this model.
Kinetic model of the Buyers’ market
Zhykharsky, Alexander V.
2013-09-01
In this work the following results are received. The closed mathematical apparatus describing the process of interaction of the Buyers’ market with retail Shop is created. The “statistical analogy” between the vacuum electrostatic diode and the Buyers’ market co-operating with retail Shop is considered. On the basis of the spent analysis the closed mathematical apparatus describing process of interaction of the Buyers’ market with retail Shop is created. The analytical expressions connecting a stream of Buyers, come to Shop, and a stream of the gain of Shop, with parameters of the Buyers’ market are received. For check of adequacy of the received model it is solved of some real “market” problems. On the basis of the spent researches principles of construction of Information-analytical Systems of new type which provide direct measurements of parameters of the Buyers’ market are developed. Actually these Systems are devices for measurement of parameters of this market. In this work it is shown that by means of the device developed for measurement of parameters of the Buyers’ market, creation of a new science-“demandodynamics” the Buyers’ market, is possible. Here the term “demandodynamics the Buyers’ market” is accepted by analogy to the term “thermodynamics” in physics. (In this work it is shown that for the Buyers’ market concept “demand” is similar to concept “temperature” in physics.) The construction methodology “demandodynamics” the Buyers’ market is defined and is shown that within the limits of this science working out of a technique of a direct control by a condition of the Buyers’ market is possible.
A kinetic-MHD model for low frequency phenomena
International Nuclear Information System (INIS)
A hybrid kinetic-MHD model for describing low-frequency phenomena in high beta anisotropic plasmas that consist of two components: a low energy core component and an energetic component with low density. The kinetic-MHD model treats the low energy core component by magnetohydrodynamic (MHD) description, the energetic component by kinetic approach such as the gyrokinetic equation, and the coupling between the dynamics of these two components through plasma pressure in the momentum equation. The kinetic-MHD model optimizes both the physics contents and the theoretical efforts in studying low frequency MHD waves and transport phenomena in general magnetic field geometries, and can be easily modified to include the core plasma kinetic effects if necessary. It is applicable to any magnetized collisionless plasma system where the parallel electric field effects are negligibly small. In the linearized limit two coupled eigenmode equations for describing the coupling between the transverse Alfven type and the compressional Alfven type waves are derived. The eigenmode equations are identical to those derived from the full gyrokinetic equation in the low frequency limit and were previously analyzed both analytically nd numerically to obtain the eigenmode structure of the drift mirror instability which explains successfully the multi-satellite observation of antisymmetric field-aligned structure of the compressional magnetic field of Pc 5 waves in the magnetospheric ring current plasma. Finally, a quadratic form is derived to demonstrate the stability of the low-frequency transverse and compressional Alfven type instabilities in terms of the pressure anisotropy parameter τ and the magnetic field curvature-pressure gradient parameter. A procedure for determining the stability of a marginally stable MHD wave due to wave-particle resonances is also presented
A kinetic-MHD model for low frequency phenomena
Energy Technology Data Exchange (ETDEWEB)
Cheng, C.Z.
1991-07-01
A hybrid kinetic-MHD model for describing low-frequency phenomena in high beta anisotropic plasmas that consist of two components: a low energy core component and an energetic component with low density. The kinetic-MHD model treats the low energy core component by magnetohydrodynamic (MHD) description, the energetic component by kinetic approach such as the gyrokinetic equation, and the coupling between the dynamics of these two components through plasma pressure in the momentum equation. The kinetic-MHD model optimizes both the physics contents and the theoretical efforts in studying low frequency MHD waves and transport phenomena in general magnetic field geometries, and can be easily modified to include the core plasma kinetic effects if necessary. It is applicable to any magnetized collisionless plasma system where the parallel electric field effects are negligibly small. In the linearized limit two coupled eigenmode equations for describing the coupling between the transverse Alfven type and the compressional Alfven type waves are derived. The eigenmode equations are identical to those derived from the full gyrokinetic equation in the low frequency limit and were previously analyzed both analytically nd numerically to obtain the eigenmode structure of the drift mirror instability which explains successfully the multi-satellite observation of antisymmetric field-aligned structure of the compressional magnetic field of Pc 5 waves in the magnetospheric ring current plasma. Finally, a quadratic form is derived to demonstrate the stability of the low-frequency transverse and compressional Alfven type instabilities in terms of the pressure anisotropy parameter {tau} and the magnetic field curvature-pressure gradient parameter. A procedure for determining the stability of a marginally stable MHD wave due to wave-particle resonances is also presented.
Kinetic modeling of the Townsend breakdown in argon
Energy Technology Data Exchange (ETDEWEB)
Macheret, S. O.; Shneider, M. N. [Department of Mechanical and Aerospace Engineering, Princeton University, D-414 Engineering Quadrangle, Princeton, New Jersey 08544 (United States)
2013-10-15
Kinetic modeling of the Townsend breakdown in argon was performed in the “forward-back” approximation. The kinetic model was found to adequately describe the left branch of the Paschen curve, and the important role of ionization by fast ions and atoms near the cathode, as well as the increase in secondary emission coefficient in strong electric fields described in the literature, was confirmed. The modeling also showed that the electron energy distribution function develops a beam of high-energy electrons and that the runaway effect, i.e., the monotonic increase of the mean electron energy with the distance from the cathode, occurs at the left branch of the Paschen curve.
Pre-reheating magnetogenesis in the kinetic coupling model
Fujita, Tomohiro; Namba, Ryo
2016-08-01
Recent blazar observations provide growing evidence for the presence of magnetic fields in the extragalactic regions. While natural speculation is to associate the production with inflationary physics, it is known that magnetogenesis solely from inflation is quite challenging. We therefore study a model in which a noninflaton field χ coupled to the electromagnetic field through its kinetic term, -I2(χ )F2/4 , continues to move after inflation until the completion of reheating. This leads to a postinflationary amplification of the electromagnetic field. We compute all the relevant contributions to the curvature perturbation, including gravitational interactions, and impose the constraints from the CMB scalar fluctuations on the strength of magnetic fields. We, for the first time, explicitly verify both the backreaction and CMB constraints in a simple yet successful magnetogenesis scenario without invoking a dedicated low-scale inflationary model in the weak-coupling regime of the kinetic coupling model.
Reproducing Phenomenology of Peroxidation Kinetics via Model Optimization
Ruslanov, Anatole D.; Bashylau, Anton V.
2010-06-01
We studied mathematical modeling of lipid peroxidation using a biochemical model system of iron (II)-ascorbate-dependent lipid peroxidation of rat hepatocyte mitochondrial fractions. We found that antioxidants extracted from plants demonstrate a high intensity of peroxidation inhibition. We simplified the system of differential equations that describes the kinetics of the mathematical model to a first order equation, which can be solved analytically. Moreover, we endeavor to algorithmically and heuristically recreate the processes and construct an environment that closely resembles the corresponding natural system. Our results demonstrate that it is possible to theoretically predict both the kinetics of oxidation and the intensity of inhibition without resorting to analytical and biochemical research, which is important for cost-effective discovery and development of medical agents with antioxidant action from the medicinal plants.
Modelling of an ASR countercurrent pyrolysis reactor with nonlinear kinetics
Energy Technology Data Exchange (ETDEWEB)
Chiarioni, A.; Reverberi, A.P.; Dovi, V.G. [Universita degli Studi di Genova (Italy). Dipartimento di Ingegneria Chimica e di Processo ' G.B. Bonino' ; El-Shaarawi, A.H. [National Water Research Institute, Burlington, Ont. (Canada)
2003-10-01
The main objective of this work is focused on the modelling of a steady-state reactor where an automotive shredder residue (ASR) is subject to pyrolysis. The gas and solid temperature inside the reactor and the relevant density profiles of both phases are simulated for fixed values of the geometry of the apparatus and a lumped kinetic model is adopted to take into account the high heterogeneity of the ASR material. The key elements for the simulation are the inlet solid temperature and the outlet gas temperature. The problem is modelled by a system of first-order boundary-value ordinary differential equations and it is solved by means of a relaxation technique owing to the nonlinearities contained in the chemical kinetic expression. (author)
Kinetic modeling of Nernst effect in magnetized hohlraums
Joglekar, A. S.; Ridgers, C. P.; Kingham, R. J.; Thomas, A. G. R.
2016-04-01
We present nanosecond time-scale Vlasov-Fokker-Planck-Maxwell modeling of magnetized plasma transport and dynamics in a hohlraum with an applied external magnetic field, under conditions similar to recent experiments. Self-consistent modeling of the kinetic electron momentum equation allows for a complete treatment of the heat flow equation and Ohm's law, including Nernst advection of magnetic fields. In addition to showing the prevalence of nonlocal behavior, we demonstrate that effects such as anomalous heat flow are induced by inverse bremsstrahlung heating. We show magnetic field amplification up to a factor of 3 from Nernst compression into the hohlraum wall. The magnetic field is also expelled towards the hohlraum axis due to Nernst advection faster than frozen-in flux would suggest. Nonlocality contributes to the heat flow towards the hohlraum axis and results in an augmented Nernst advection mechanism that is included self-consistently through kinetic modeling.
Schokker, E.P.
1997-01-01
The kinetics of heat inactivation of the extracellular proteinase from Pseudomonas fluorescens 22F was studied. It was established, by making use of kinetic modelling, that heat inactivation in the temperature range 35 - 70 °C was most likely caused by intermolecular autoproteolysis, where unfolded
Stepwise kinetic equilibrium models of quantitative polymerase chain reaction
Directory of Open Access Journals (Sweden)
Cobbs Gary
2012-08-01
Full Text Available Abstract Background Numerous models for use in interpreting quantitative PCR (qPCR data are present in recent literature. The most commonly used models assume the amplification in qPCR is exponential and fit an exponential model with a constant rate of increase to a select part of the curve. Kinetic theory may be used to model the annealing phase and does not assume constant efficiency of amplification. Mechanistic models describing the annealing phase with kinetic theory offer the most potential for accurate interpretation of qPCR data. Even so, they have not been thoroughly investigated and are rarely used for interpretation of qPCR data. New results for kinetic modeling of qPCR are presented. Results Two models are presented in which the efficiency of amplification is based on equilibrium solutions for the annealing phase of the qPCR process. Model 1 assumes annealing of complementary targets strands and annealing of target and primers are both reversible reactions and reach a dynamic equilibrium. Model 2 assumes all annealing reactions are nonreversible and equilibrium is static. Both models include the effect of primer concentration during the annealing phase. Analytic formulae are given for the equilibrium values of all single and double stranded molecules at the end of the annealing step. The equilibrium values are then used in a stepwise method to describe the whole qPCR process. Rate constants of kinetic models are the same for solutions that are identical except for possibly having different initial target concentrations. Analysis of qPCR curves from such solutions are thus analyzed by simultaneous non-linear curve fitting with the same rate constant values applying to all curves and each curve having a unique value for initial target concentration. The models were fit to two data sets for which the true initial target concentrations are known. Both models give better fit to observed qPCR data than other kinetic models present in the
A review of the kinetic statistical strength model
Energy Technology Data Exchange (ETDEWEB)
Attia, A.V.
1996-03-11
This is a review of the Kinetic-Statistical Strength (KSS) model described in the report ``Models of Material Strength, Fracture and Failure`` by V. Kuropatenko and V. Bychenkov. The models for metals subjected to high strain rates (explosions) are focussed on. Model implementation appears possible in a hydrocode. Applying the model to the shock response of metals will require a data source for the Weibull parameter {alpha}{sub u}, short of measuing the strength of specimens of various sizes. Model validation will require more detail on the experiments successfully calculated by SPRUT. Evaluation of the KSS model is needed against other existing rate-dependent models for metals such as the Steinberg-Lund or MTS model on other shock experiments.
Progress in Chemical Kinetic Modeling for Surrogate Fuels
Energy Technology Data Exchange (ETDEWEB)
Pitz, W J; Westbrook, C K; Herbinet, O; Silke, E J
2008-06-06
Gasoline, diesel, and other alternative transportation fuels contain hundreds to thousands of compounds. It is currently not possible to represent all these compounds in detailed chemical kinetic models. Instead, these fuels are represented by surrogate fuel models which contain a limited number of representative compounds. We have been extending the list of compounds for detailed chemical models that are available for use in fuel surrogate models. Detailed models for components with larger and more complicated fuel molecular structures are now available. These advancements are allowing a more accurate representation of practical and alternative fuels. We have developed detailed chemical kinetic models for fuels with higher molecular weight fuel molecules such as n-hexadecane (C16). Also, we can consider more complicated fuel molecular structures like cyclic alkanes and aromatics that are found in practical fuels. For alternative fuels, the capability to model large biodiesel fuels that have ester structures is becoming available. These newly addressed cyclic and ester structures in fuels profoundly affect the reaction rate of the fuel predicted by the model. Finally, these surrogate fuel models contain large numbers of species and reactions and must be reduced for use in multi-dimensional models for spark-ignition, HCCI and diesel engines.
Kinetic models of gene expression including non-coding RNAs
Zhdanov, Vladimir P.
2011-03-01
In cells, genes are transcribed into mRNAs, and the latter are translated into proteins. Due to the feedbacks between these processes, the kinetics of gene expression may be complex even in the simplest genetic networks. The corresponding models have already been reviewed in the literature. A new avenue in this field is related to the recognition that the conventional scenario of gene expression is fully applicable only to prokaryotes whose genomes consist of tightly packed protein-coding sequences. In eukaryotic cells, in contrast, such sequences are relatively rare, and the rest of the genome includes numerous transcript units representing non-coding RNAs (ncRNAs). During the past decade, it has become clear that such RNAs play a crucial role in gene expression and accordingly influence a multitude of cellular processes both in the normal state and during diseases. The numerous biological functions of ncRNAs are based primarily on their abilities to silence genes via pairing with a target mRNA and subsequently preventing its translation or facilitating degradation of the mRNA-ncRNA complex. Many other abilities of ncRNAs have been discovered as well. Our review is focused on the available kinetic models describing the mRNA, ncRNA and protein interplay. In particular, we systematically present the simplest models without kinetic feedbacks, models containing feedbacks and predicting bistability and oscillations in simple genetic networks, and models describing the effect of ncRNAs on complex genetic networks. Mathematically, the presentation is based primarily on temporal mean-field kinetic equations. The stochastic and spatio-temporal effects are also briefly discussed.
Kinetic model of metabolic network for xiamenmycin biosynthetic optimisation.
Xu, Min-juan; Chen, Yong-cong; Xu, Jun; Ao, Ping; Zhu, Xiao-mei
2016-02-01
Xiamenmycins, a series of prenylated benzopyran compounds with anti-fibrotic bioactivities, were isolated from a mangrove-derived Streptomyces xiamenensis. To fulfil the requirements of pharmaceutical investigations, a high production of xiamenmycin is needed. In this study, the authors present a kinetic metabolic model to evaluate fluxes in an engineered Streptomyces lividans with xiamenmycin-oriented genetic modification based on generic enzymatic rate equations and stability constraints. Lyapunov function was used for a viability optimisation. From their kinetic model, the flux distributions for the engineered S. lividans fed on glucose and glycerol as carbon sources were calculated. They found that if the bacterium can utilise glucose simultaneously with glycerol, xiamenmycin production can be enhanced by 40% theoretically, while maintaining the same growth rate. Glycerol may increase the flux for phosphoenolpyruvate synthesis without interfering citric acid cycle. They therefore believe this study demonstrates a possible new direction for bioengineering of S. lividans. PMID:26816395
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
Kinetic model of carbonate dissolution in Martian meteorite ALH84001
Kopp, Robert E.; Humayun, Munir
2003-01-01
The magnetites and sulfides located in the rims of carbonate globules in the Martian meteorite ALH84001 have been claimed as evidence of past life on Mars. Here, we consider the possibility that the rims were formed by dissolution and reprecipitation of the primary carbonate by the action of water. To estimate the rate of these solution-precipitation reactions, a kinetic model of magnesite-siderite carbonate dissolution was applied and used to examine the physicochemical conditions under whic...
A model for recovery kinetics of aluminum after large strain
DEFF Research Database (Denmark)
Yu, Tianbo; Hansen, Niels
2012-01-01
A model is suggested to analyze recovery kinetics of heavily deformed aluminum. The model is based on the hardness of isothermal annealed samples before recrystallization takes place, and it can be extrapolated to longer annealing times to factor out the recrystallization component of the hardness...... for conditions where recovery and recrystallization overlap. The model is applied to the isothermal recovery at temperatures between 140 and 220°C of commercial purity aluminum deformed to true strain 5.5. EBSD measurements have been carried out to detect the onset of discontinuous recrystallization. Furthermore...
Physiologically based kinetic modeling of the bioactivation of myristicin
Al-Malahmeh, Amer J.; Al-Ajlouni, Abdelmajeed; Wesseling, Sebastiaan; Soffers, Ans E. M. F.; Al-Subeihi, A.; Kiwamoto, Reiko; Vervoort, Jacques; Rietjens, Ivonne M.C.M.
2016-01-01
The present study describes physiologically based kinetic (PBK) models for the alkenylbenzene myristicin that were developed by extension of the PBK models for the structurally related alkenylbenzene safrole in rat and human. The newly developed myristicin models revealed that the formation of the proximate carcinogenic metabolite 1′-hydroxymyristicin in liver is at most 1.8 fold higher in rat than in human and limited for the ultimate carcinogenic metabolite 1′-sulfoxymyristicin to (2.8–4.0)...
Simplified kinetic models of methanol oxidation on silver
DEFF Research Database (Denmark)
Andreasen, A.; Lynggaard, H.; Stegelmann, C.;
2005-01-01
Recently the authors developed a microkinetic model of methanol oxidation on silver [A. Andreasen, H. Lynggaard, C. Stegelmann, P. Stoltze, Surf. Sci. 544 (2003) 5-23]. The model successfully explains both surface science experiments and kinetic experiments at industrial conditions applying...... physically realistic parameters. Unfortunately the rate expression based on this microkinetic model is complex and impractical to apply for reactor engineering purposes. In this paper the rate expression is simplified by a number of approximations to make it suitable for practical applications without...
Simplified kinetic models of methanol oxidation on silver
DEFF Research Database (Denmark)
Andreasen, Anders; Lynggaard, Hasse Harloff; Stegelmann, Carsten;
2005-01-01
Recently the authors developed a microkinetic model of methanol oxidation on silver [A. Andreasen, H. Lynggaard, C. Stegelmann, P. Stoltze, Surf. Sci. 544 (2003) 5–23]. The model successfully explains both surface science experiments and kinetic experiments at industrial conditions applying...... physically realistic parameters. Unfortunately the rate expression based on this microkinetic model is complex and impractical to apply for reactor engineering purposes. In this paper the rate expression is simplified by a number of approximations to make it suitable for practical applications without...
Kinetic model on coke oven gas with steam reforming
Institute of Scientific and Technical Information of China (English)
ZHANG Jia-yuan; ZHOU Jie-min; YAN Hong-jie
2008-01-01
The effects of factors such as the molar ratio of H2O to CH4 (n(H2O)/n(CH4)), methane conversion temperature and time on methane conversion rate were investigated to build kinetic model for reforming of coke-oven gas with steam. The results of experiments show that the optimal conditions for methane conversion are that the molar ratio of H2O to CH4 varies from 1.1 to 1.3and the conversion temperature varies from 1 223 to 1 273 K. The methane conversion rate is more than 95% when the molar ratio ofH2O to CH4 is 1.2, the conversion temperature is above 1 223 K and the conversion time is longer than 0.75 s. Kinetic model of methane conversion was proposed. All results demonstrate that the calculated values by the kinetic model accord with the experimental data well, and the error is less than 1.5%.
Kinetic Modeling of Sunflower Grain Filling and Fatty Acid Biosynthesis.
Durruty, Ignacio; Aguirrezábal, Luis A N; Echarte, María M
2016-01-01
Grain growth and oil biosynthesis are complex processes that involve various enzymes placed in different sub-cellular compartments of the grain. In order to understand the mechanisms controlling grain weight and composition, we need mathematical models capable of simulating the dynamic behavior of the main components of the grain during the grain filling stage. In this paper, we present a non-structured mechanistic kinetic model developed for sunflower grains. The model was first calibrated for sunflower hybrid ACA855. The calibrated model was able to predict the theoretical amount of carbohydrate equivalents allocated to the grain, grain growth and the dynamics of the oil and non-oil fraction, while considering maintenance requirements and leaf senescence. Incorporating into the model the serial-parallel nature of fatty acid biosynthesis permitted a good representation of the kinetics of palmitic, stearic, oleic, and linoleic acids production. A sensitivity analysis showed that the relative influence of input parameters changed along grain development. Grain growth was mostly affected by the specific growth parameter (μ') while fatty acid composition strongly depended on their own maximum specific rate parameters. The model was successfully applied to two additional hybrids (MG2 and DK3820). The proposed model can be the first building block toward the development of a more sophisticated model, capable of predicting the effects of environmental conditions on grain weight and composition, in a comprehensive and quantitative way. PMID:27242809
Kinetic Modeling of Sunflower Grain Filling and Fatty Acid Biosynthesis
Durruty, Ignacio; Aguirrezábal, Luis A. N.; Echarte, María M.
2016-01-01
Grain growth and oil biosynthesis are complex processes that involve various enzymes placed in different sub-cellular compartments of the grain. In order to understand the mechanisms controlling grain weight and composition, we need mathematical models capable of simulating the dynamic behavior of the main components of the grain during the grain filling stage. In this paper, we present a non-structured mechanistic kinetic model developed for sunflower grains. The model was first calibrated for sunflower hybrid ACA855. The calibrated model was able to predict the theoretical amount of carbohydrate equivalents allocated to the grain, grain growth and the dynamics of the oil and non-oil fraction, while considering maintenance requirements and leaf senescence. Incorporating into the model the serial-parallel nature of fatty acid biosynthesis permitted a good representation of the kinetics of palmitic, stearic, oleic, and linoleic acids production. A sensitivity analysis showed that the relative influence of input parameters changed along grain development. Grain growth was mostly affected by the specific growth parameter (μ′) while fatty acid composition strongly depended on their own maximum specific rate parameters. The model was successfully applied to two additional hybrids (MG2 and DK3820). The proposed model can be the first building block toward the development of a more sophisticated model, capable of predicting the effects of environmental conditions on grain weight and composition, in a comprehensive and quantitative way. PMID:27242809
Kinetic models for nucleocytoplasmic transport of messenger RNA.
Schröder, H C; Müller, W E; Agutter, P S
1995-05-21
Much is known about the mechanism by which mRNAs cross the nuclear envelope (the translocation stage of nucleocytoplasmic transport), but far less is known about the preceding (intranuclear migration/release) and succeeding (cytoplasmic binding) stages. Therefore, existing information suffices for articulating detailed kinetic models of translocation, but not models for the overall mRNA transport process. In this paper, we show that simple kinetic models of translocation can (i) accommodate data about nucleocytoplasmic distributions of endogenous transcripts; (ii) predict the overall effects on these distributions of effectors such as insulin and epidermal growth factor; (iii) throw some light on the mechanism(s) of action of the HIV-1 protein Rev and produce experimentally testable predictions about this mechanism; and (iv) account for the action of influenza virus NS1 protein. However, the simplest forms of translocation models apparently fail to account for some properties of viral regulators such as HIV Rev and adenovirus E1B-E4 complex. To elucidate these topics, less narrowly focused models of mRNA transport are required, describing intranuclear binding/release as well as translocation. On the basis of our examination of translocation models, we suggest some criteria that the requisite broadly based models must satisfy.
Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism.
Fleming, R M T; Thiele, I; Provan, G; Nasheuer, H P
2010-06-01
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.
Alkaline Hydrolysis Kinetics Modeling of Bagasse Pentosan Dissolution
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Yuxin Liu
2013-11-01
Full Text Available The main pentosan components of sugarcane bagasse, which can be subjected to alkaline hydrolysis, are xylose, arabinose, glucose, and galactose. The pentosan reaction mechanism was considered for alkali-treated bagasse with variation of temperature and time. The kinetics of pentosan degradation were studied concurrently at temperatures of 50 °C, 70 °C, and 90 °C, with a solid-liquid mass ratio of 1:15, a stirring speed of 500 revolutions/min, and different holding times for bagasse alkali pre-extraction. With respect to residual pentosan content and the losses of raw material, the hydrolysis rates of alkali pre-extraction and pentosan degradation reactions of bagasse all followed pseudo-first-order kinetic models. Finally, the main degradation activation energy was determined to be 20.86 KJ/mol, and the residual degradation activation energy was 28.75 KJ/mol according to the Arrhenius equation.
Modeling interface-controlled phase transformation kinetics in thin films
Pang, E. L.; Vo, N. Q.; Philippe, T.; Voorhees, P. W.
2015-05-01
The Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation is widely used to describe phase transformation kinetics. This description, however, is not valid in finite size domains, in particular, thin films. A new computational model incorporating the level-set method is employed to study phase evolution in thin film systems. For both homogeneous (bulk) and heterogeneous (surface) nucleation, nucleation density and film thickness were systematically adjusted to study finite-thickness effects on the Avrami exponent during the transformation process. Only site-saturated nucleation with isotropic interface-kinetics controlled growth is considered in this paper. We show that the observed Avrami exponent is not constant throughout the phase transformation process in thin films with a value that is not consistent with the dimensionality of the transformation. Finite-thickness effects are shown to result in reduced time-dependent Avrami exponents when bulk nucleation is present, but not necessarily when surface nucleation is present.
Kinetic modeling of ethylbenzene dehydrogenation over hydrotalcite catalysts
Atanda, Luqman
2011-07-01
Kinetics of ethylbenzene dehydrogenation to styrene was investigated over a series of quaternary mixed oxides of Mg3Fe0.25Me0.25Al0.5 (Me=Co, Mn and Ni) catalysts prepared by calcination of hydrotalcite-like compounds and compared with commercial catalyst. The study was carried out in the absence of steam using a riser simulator at 400, 450, 500 and 550°C for reaction times of 5, 10, 15 and 20s. Mg3Fe0.25Mn0.25Al0.5 afforded the highest ethylbenzene conversion of 19.7% at 550°C. Kinetic parameters for the dehydrogenation process were determined using the catalyst deactivation function based on reactant conversion model. The apparent activation energies for styrene production were found to decrease as follows: E1-Ni>E1-Co>E1-Mn. © 2011 Elsevier B.V.
Isothermal crystallization kinetic modeling of poly(etherketoneketone) (PEKK)
Choupin, T.; Paris, C.; Cinquin, J.; Fayolle, B.; Régnier, G.
2016-05-01
Isothermal melt and cold crystallization kinetics of poly(etherketoneketone) (PEKK) have been investigated by differential scanning calorimetry. A modified Avrami model has been used to describe the two-stage crystallization of PEKK. The primary crystallization stage is assumed to be a two dimensional nucleation growth with an Avrami exponent of 2 whereas the secondary stage is assumed to be a one dimensional nucleation growth with an Avrami exponent of 1. The evolution of the crystallization constant rates depending on temperature has been modeled with the Hoffman and Lauritzen growth equation. The activation energy of nucleation constants Kg for both crystallizations are presented.
Small velocity and finite temperature variations in kinetic relaxation models
Markowich, Peter
2010-01-01
A small Knuden number analysis of a kinetic equation in the diffusive scaling is performed. The collision kernel is of BGK type with a general local Gibbs state. Assuming that the flow velocity is of the order of the Knudsen number, a Hilbert expansion yields a macroscopic model with finite temperature variations, whose complexity lies in between the hydrodynamic and the energy-transport equations. Its mathematical structure is explored and macroscopic models for specific examples of the global Gibbs state are presented. © American Institute of Mathematical Sciences.
Strain in the mesoscale kinetic Monte Carlo model for sintering
DEFF Research Database (Denmark)
Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.;
2014-01-01
Shrinkage strains measured from microstructural simulations using the mesoscale kinetic Monte Carlo (kMC) model for solid state sintering are discussed. This model represents the microstructure using digitized discrete sites that are either grain or pore sites. The algorithm used to simulate...... anisotropic strains for homogeneous powder compacts with aspect ratios different from unity. It is shown that the line direction biases shrinkage strains in proportion the compact dimension aspect ratios. A new algorithm that corrects this bias in strains is proposed; the direction for collapsing the column...
Kinetic energy for the nuclear Yang-Mills collective model
Rosensteel, George; Sparks, Nick
2015-10-01
The Bohr-Mottelson-Frankfurt model of nuclear rotations and quadrupole vibrations is a foundational model in nuclear structure physics. The model, also called the geometrical collective model or simply GCM, has two hidden mathematical structures, one Lie group theoretic and the other differential geometric. Although the group structure has been understood for some time, the geometric structure is a new unexplored feature that shares the same mathematical origin as Yang-Mills, viz., a vector bundle with a non-abelian structure group and a connection. Using the de Rham Laplacian ▵ = * d * d from differential geometry for the kinetic energy extends significantly the physical scope of the GCM model. This Laplacian contains a ``magnetic'' term due to the coupling between base manifold rotational and fiber vorticity degrees of freedom. When the connection specializes to irrotational flow, the Laplacian reduces to the Bohr-Mottelson kinetic energy operator. More generally, the connection yields a moment of inertia that is intermediate between the extremes of irrotational flow and rigid body motion.
Directory of Open Access Journals (Sweden)
Nassereldeen Ahmed Kabbashi
2010-09-01
Full Text Available The bioethanol production was conducted by utilizing agriculture waste, palm oil empty fruit bunches (EFB with the aid of T. harzianum and yeast, Saccharomyces cerevisiae using solid state bioconversion method. The compatibility of various fungal strains was done as to develop the direct bioconversion process of compatible mixed culture. Analyzes such ethanol estimation, reducing sugar and glucosamine as growth indicator were conducted in order to select the best experimented run for optimization. The optimization of process conditions, by using central composite design (CCD was carried out. Optimization of process condition was done with varied level of moisture content, pH, inoculum size, concentration of co-substrate (wheat flour and mineral solutions. Statistical analysis showed that the optimum process condition for moisture content was 50% (v/w, pH of 4, inoculum size of 10% (v/v, concentration of wheat flour of 1% (v/v and mineral solutions 1%(v/v. In this study, the application levels of the methods of environmental management in regards to the maximum production were determined. The final optimization with the developed process conditions indicated that the maximum production was increased from 14.315 (v/v to 34.785(v/v.
Kinetic model of ductile iron solidification with experimental verification
Directory of Open Access Journals (Sweden)
W. Kapturkiewicz
2009-10-01
Full Text Available A solidification model for ductile iron, including Weibull formula for nodule count has been presented. From this model, the following can be determined: cooling curves, kinetics of austenite and eutectic nucleation, austenite and eutectic growth velocity, volume fraction, distribution of Si and P both in austenite and eutectic grain with distribution in casting section.In the developed model of nodular graphite iron casting solidification, the correctness of the mathematical model has been experimentally verified in the range of the most significant factors, which include temperature field, the value of maximum undercooling, and the graphite nodule count interrelated with the casting cross-section. Literature offers practically no data on so confronted process model and simulation program.
7-lump kinetic model for residual oil catalytic cracking
Institute of Scientific and Technical Information of China (English)
XU Ou-guan; SU Hong-ye; MU Sheng-jing; CHU Jian
2006-01-01
In this paper a novel 7-lump kinetic model is proposed to describe residual oil catalytic cracking, in which coke is lumped separately for accurate prediction. The reactor block is modeled as a combination of an ideal pipe flow reactor (PFR)and a continuously stirred tank reactor (CSTR). Unit factors are designed to correct the deviation between model predictions and practical plant data and tuned by modified Levenberg-Marquardt algorithm. The parameters estimated are reliable and good agreement between the model predictions and plant observations is observed. The model helps us get good insight into the performance of an industrial riser reactor that would be useful for optimization of residual oil catalytic cracking.
Kinetic modeling of virus transport at the field scale.
Schijven, Jack F; Simůnek, Jirí
2002-03-01
Bacteriophage removal by soil passage in two field studies was re-analyzed with the goal to investigate differences between one- and two-dimensional modeling approaches, differences between one- and two-site kinetic sorption models, and the role of heterogeneities in the soil properties. The first study involved removal of bacteriophages MS2 and PRDI by dune recharge, while the second study represented removal of MS2 by deep well injection. In both studies, removal was higher during the first meters of soil passage than thereafter. The software packages HYDRUS-ID and HYDRUS-2D, which simulate water flow and solute transport in one- and two-dimensional variably saturated porous media, respectively, were used. The two codes were modified by incorporating reversible adsorption to two types of kinetic sites. Tracer concentrations were used first to calibrate flow and transport parameters of both models before analyzing transport of bacteriophages. The one-dimensional one-site model did not fully describe the tails of the measured breakthrough curves of MS2 and PRD1 from the dune recharge study. While the one-dimensional one-site model predicted a sudden decrease in virus concentrations immediately after the peaks, measured data displayed much smoother decline and tailing. The one-dimensional two-site model simulated the overall behavior of the breakthrough curves very well. The two-dimensional one-site model predicted a more gradual decrease in virus concentrations after the peaks than the one-dimensional one-site model, but not as good as the one-dimensional two-site model. The dimensionality of the problem hence can partly explain the smooth decrease in concentration after peak breakthrough. The two-dimensional two-site model provided the best results. Values for k(att2) and k(det2) could not be determined at the last two of four monitoring wells, thus suggesting that either a second type of kinetic sites is present in the first few meters of dune passage and not
Kinetic modelling of cadmium and lead removal by aquatic mosses
Directory of Open Access Journals (Sweden)
R. J. E. Martins
2014-03-01
Full Text Available Because biosorption is a low cost and effective method for treating metal-bearing wastewaters, understanding the process kinetics is relevant for design purposes. In the present study, the performance of the aquatic moss Fontinalis antipyretica for removing cadmium and lead from simulated wastewaters has been evaluated. Five kinetic models (first-order, pseudo-first-order, Elovich, modified Ritchie second-order and pseudo-second-order were fitted to the experimental data and compared. Previously, the effect of parameters such as the initial solution pH, contact time, and initial metal ion concentration on biosorption was investigated. The initial pH of the solution was found to have an optimum value in the range of 4.0-6.0. The equilibrium sorption capacity of cadmium and lead by Fontinalis antipyretica increased with the initial metal concentration. For an initial metal concentration of 10 mg L-1, the uptake capacity of the moss, at equilibrium, is the same for both metals (4.8 mg g-1. Nevertheless, when the initial concentration increases up to 100 mg L-1, the uptake of Pb(II was higher than 78%. The pseudo-second order biosorption kinetics provided the better correlation with the experimental data (R² ≥ 0.999.
Microbially Mediated Kinetic Sulfur Isotope Fractionation: Reactive Transport Modeling Benchmark
Wanner, C.; Druhan, J. L.; Cheng, Y.; Amos, R. T.; Steefel, C. I.; Ajo Franklin, J. B.
2014-12-01
Microbially mediated sulfate reduction is a ubiquitous process in many subsurface systems. Isotopic fractionation is characteristic of this anaerobic process, since sulfate reducing bacteria (SRB) favor the reduction of the lighter sulfate isotopologue (S32O42-) over the heavier isotopologue (S34O42-). Detection of isotopic shifts have been utilized as a proxy for the onset of sulfate reduction in subsurface systems such as oil reservoirs and aquifers undergoing uranium bioremediation. Reactive transport modeling (RTM) of kinetic sulfur isotope fractionation has been applied to field and laboratory studies. These RTM approaches employ different mathematical formulations in the representation of kinetic sulfur isotope fractionation. In order to test the various formulations, we propose a benchmark problem set for the simulation of kinetic sulfur isotope fractionation during microbially mediated sulfate reduction. The benchmark problem set is comprised of four problem levels and is based on a recent laboratory column experimental study of sulfur isotope fractionation. Pertinent processes impacting sulfur isotopic composition such as microbial sulfate reduction and dispersion are included in the problem set. To date, participating RTM codes are: CRUNCHTOPE, TOUGHREACT, MIN3P and THE GEOCHEMIST'S WORKBENCH. Preliminary results from various codes show reasonable agreement for the problem levels simulating sulfur isotope fractionation in 1D.
Experimental kinetic study and modeling of calcium oxide carbonation
International Nuclear Information System (INIS)
Anthropogenic carbon dioxide (CO2) emissions, major contributors to the greenhouse effect, are considered as the main cause of global warming. So, decrease of CO2 emitted by large industrial combustion sources or power plants, is an important scientific goal. One of the approaches is based on CO2 separation and capture from flue gas, followed by sequestration in a wide range of geological formations. In this aim, CO2 is captured by sorbents like calcium oxide (CaO) in multi-cycle process of carbonation/de-carbonation. However, it was shown that the most important limitations of such process are related to the reversibility of reaction. CaO rapidly loses activity towards CO2, so the maximum extent of carbonation decreases as long as the number of cycles increases. In order to well understand the processes and parameters influencing the capture capacity of CaO-based sorbents, it appears important to get details on the kinetic law governing the reaction, which have not been really studied up to now. To investigate this reaction, CaO carbonation kinetics was followed by means of thermogravimetric analysis (TGA) on divided materials. Special care was given to the validation of the usual kinetic assumptions such as steady state and rate-determining step assumptions. The aim was to obtain a model describing the reaction in order to explain the influence of intensive variables such as carbonation temperature and CO2 partial pressure. TGA curves obtained under isothermal and isobaric conditions showed an induction period linked to the nucleation process and a strong slowing down of the reaction rate once a given fractional conversion was reached. Both phenomena were observed to depend on carbonation temperature and CO2 partial pressure. To explain these results, the evolution of texture and microstructure of the solid during the reaction was regarded as essential. Reaction at the grain scale induces a volume increase from CaO to CaCO3 which causes a change in the porosity
Kinetic Model for 1D aggregation of yeast ``prions''
Kunes, Kay; Cox, Daniel; Singh, Rajiv
2004-03-01
Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeast have proteins which can undergo similar reconformation and aggregation processes to PrP; yeast forms are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein(1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics(2). The model assumes reconformation only upon aggregation, and includes aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates. We will compare to a more realistic stochastic kinetics model and present prelimary attempts to describe recent experiments on SUP35 strains. *-Supported by U.S. Army Congressionally Mandated Research Fund. 1) P. Chien and J.S. Weissman, Nature 410, 223 (2001); http://online.kitp.ucsb.edu/online/bionet03/collins/. 2) J. Masel, V.A.> Jansen, M.A. Nowak, Biophys. Chem. 77, 139 (1999).
Investigation of kinetics model of dc reactive sputtering
Institute of Scientific and Technical Information of China (English)
朱圣龙; 王福会; 吴维叓
1996-01-01
A novel physical sputtering kinetics model for reactive sputtering is presented.Reactive gas gettering effects and interactions among the characteristic parameters have been taken into account in the model.The data derived from the model accorded fairly well with experimental results.The relationship between the values of initial oxide coverage on the target and the ready states was depicted in the model.This relationship gives reasons for the difference of the threshold of reactive gas fluxes (Q) from the metal sputtering region to the oxide sputtering region and in reverse direction.The discontinuities in oxide coverage on the target surface (θ) versus reactive gas fluxes (Q) are referred to as the effects of reactive gas partial pressure (p) upon the forming rates of oxide on the surfaces of target (V0).The diversity of the oxygen flux threshold results from the variance of the initial values of oxide coverage on target.
Study on Lumped Kinetic Model for FDFCC II. Validation and Prediction of Model
Institute of Scientific and Technical Information of China (English)
Wu Feiyue; Weng Huixin; Luo Shixian
2008-01-01
On the basis of formulating the 9-lump kinetic model for gasoline catalytic upgrading and the 12-lump kinetic model for heavy oil FCC, this paper is aimed at development of a combined kinetic model for a typical FDFCC process after analyzing the coupled relationship and combination of these two models. The model is also verified by using commercial data, the results of which showed that the model can better predict the product yields and their quality, with the relative errors between the main products of the unit and commercial data being less than five percent. Furthermore, the combined model is used to predict and optimize the operating conditions for gasoline riser and heavy oil riser in FDFCC. So this paper can offer some guidance for the processing of FDFCC and is instructive to model research and development of such multi-reactor process and combined process.
Tracer kinetic modelling in MRI: estimating perfusion and capillary permeability
International Nuclear Information System (INIS)
The tracer-kinetic models developed in the early 1990s for dynamic contrast-enhanced MRI (DCE-MRI) have since become a standard in numerous applications. At the same time, the development of MRI hardware has led to increases in image quality and temporal resolution that reveal the limitations of the early models. This in turn has stimulated an interest in the development and application of a second generation of modelling approaches. They are designed to overcome these limitations and produce additional and more accurate information on tissue status. In particular, models of the second generation enable separate estimates of perfusion and capillary permeability rather than a single parameter Ktrans that represents a combination of the two. A variety of such models has been proposed in the literature, and development in the field has been constrained by a lack of transparency regarding terminology, notations and physiological assumptions. In this review, we provide an overview of these models in a manner that is both physically intuitive and mathematically rigourous. All are derived from common first principles, using concepts and notations from general tracer-kinetic theory. Explicit links to their historical origins are included to allow for a transfer of experience obtained in other fields (PET, SPECT, CT). A classification is presented that reveals the links between all models, and with the models of the first generation. Detailed formulae for all solutions are provided to facilitate implementation. Our aim is to encourage the application of these tools to DCE-MRI by offering researchers a clearer understanding of their assumptions and requirements. (topical review)
Tracer kinetic modelling in MRI: estimating perfusion and capillary permeability
Sourbron, S. P.; Buckley, D. L.
2012-01-01
The tracer-kinetic models developed in the early 1990s for dynamic contrast-enhanced MRI (DCE-MRI) have since become a standard in numerous applications. At the same time, the development of MRI hardware has led to increases in image quality and temporal resolution that reveal the limitations of the early models. This in turn has stimulated an interest in the development and application of a second generation of modelling approaches. They are designed to overcome these limitations and produce additional and more accurate information on tissue status. In particular, models of the second generation enable separate estimates of perfusion and capillary permeability rather than a single parameter Ktrans that represents a combination of the two. A variety of such models has been proposed in the literature, and development in the field has been constrained by a lack of transparency regarding terminology, notations and physiological assumptions. In this review, we provide an overview of these models in a manner that is both physically intuitive and mathematically rigourous. All are derived from common first principles, using concepts and notations from general tracer-kinetic theory. Explicit links to their historical origins are included to allow for a transfer of experience obtained in other fields (PET, SPECT, CT). A classification is presented that reveals the links between all models, and with the models of the first generation. Detailed formulae for all solutions are provided to facilitate implementation. Our aim is to encourage the application of these tools to DCE-MRI by offering researchers a clearer understanding of their assumptions and requirements.
Kinetics of solid state phase transformations: Measurement and modelling of some basic issues
Indian Academy of Sciences (India)
S Raju; E Mohandas
2010-01-01
A brief review of the issues involved in modelling of the solid state transformation kinetics is presented. The fact that apart from the standard thermodynamic parameters, certain path variables like heating or cooling rate can also exert a crucial influence on the kinetic outcome is stressed. The kinetic specialties that are intrinsic to phase changes proceeding under varying thermal history are enumerated. A simple and general modelling methodology for understanding the kinetics of non-isothermal transformations is outlined.
Thermal decomposition kinetics of sodium alkoxides - model independent method
International Nuclear Information System (INIS)
Sodium alkoxides namely sodium methoxide and sodium ethoxide were synthesized and characterized by various analytical techniques. Thermal decomposition of these compounds was studied under constant heating rate using thermogravimetric analyzer coupled with mass spectrometer (TGA-MS). On decomposition, these sodium alkoxides form gaseous products of saturated and unsaturated hydrocarbons and leave sodium carbonate, sodium hydroxide and free carbon as residue. Kinetic parameters namely activation energy and pre-exponential factor were deduced from the dynamic TGA data by physical model independent (iso-conversion) method. (author)
Validation of multipoint kinetics model against 3D Trikin Code
International Nuclear Information System (INIS)
Validation of multipoint kinetics formulation for RELAP5 code has been carried out against 3D TRIKIN code. Core behavior of an asymmetric reactivity transient has been simulated through artificial tuning of lattice constants in 3D code. Individual node normalized reactivity has been conserved and power estimates from multipoint model have been compared with 3D simulation. It has been observed that localized peak power estimates from multipoint simulation are on higher side and therefore are conservative in nature. Improvements in multipoint formulation in regards to evolving coupling coefficients and involving more number of nodes can help in improving its accuracy to some extent. (author)
Kinetic mixing effect in the 3 -3 -1 -1 model
Dong, P. V.; Si, D. T.
2016-06-01
We show that the mixing effect of the neutral gauge bosons in the 3 -3 -1 -1 model comes from two sources. The first one is due to the 3 -3 -1 -1 gauge symmetry breaking as usual, whereas the second one results from the kinetic mixing between the gauge bosons of U (1 )X and U (1 )N groups, which are used to determine the electric charge and baryon minus lepton numbers, respectively. Such mixings modify the ρ -parameter and the known couplings of Z with fermions. The constraints that arise from flavor-changing neutral currents due to the gauge boson mixings and nonuniversal fermion generations are also given.
Warped Higgsless Models with IR-Brane Kinetic Terms
Davoudiasl, H; Lillie, Benjamin Huntington; Rizzo, T G
2004-01-01
We examine a warped Higgsless $SU(2)_L\\times SU(2)_R\\times U(1)_{B-L}$ model in 5--$d$ with IR(TeV)--brane kinetic terms. It is shown that adding a brane term for the $U(1)_{B-L}$ gauge field does not affect the scale ($\\sim 2-3$ TeV) where perturbative unitarity in $W_L^+ W_L^- \\to W_L^+ W_L^-$ is violated. This term could, however, enhance the agreement of the model with the precision electroweak data. In contrast, the inclusion of a kinetic term corresponding to the $SU(2)_D$ custodial symmetry of the theory delays the unitarity violation in $W_L^\\pm$ scattering to energy scales of $\\sim 6-7$ TeV for a significant fraction of the parameter space. This is about a factor of 4 improvement compared to the corresponding scale of unitarity violation in the Standard Model without a Higgs. We also show that null searches for extra gauge bosons at the Tevatron and for contact interactions at LEP II place non-trivial bounds on the size of the IR-brane terms.
Kinetic model of DNA replication in eukaryotic organisms
Herrick, J; Bensimon, A; Herrick, John; Bechhoefer, John; Bensimon, Aaron
2001-01-01
We formulate a kinetic model of DNA replication that quantitatively describes recent results on DNA replication in the in vitro system of Xenopus laevis prior to the mid-blastula transition. The model describes well a large amount of different data within a simple theoretical framework. This allows one, for the first time, to determine the parameters governing the DNA replication program in a eukaryote on a genome-wide basis. In particular, we have determined the frequency of origin activation in time and space during the cell cycle. Although we focus on a specific stage of development, this model can easily be adapted to describe replication in many other organisms, including budding yeast.
Kinetic and Stochastic Models of 1D yeast ``prions"
Kunes, Kay
2005-03-01
Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeasts have proteins, which can undergo similar reconformation and aggregation processes to PrP; yeast ``prions" are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein (1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics along with our own stochastic approach (2). Both models assume reconformation only upon aggregation, and include aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates.
The Origin of the RNA World a Kinetic Model
Wattis, J A D; Wattis, Jonathan A. D.; Coveney, Peter V.
1999-01-01
The aims of this paper are to propose, construct and analyse microscopic kinetic models for the emergence of long chains of RNA from monomeric beta-D-ribonucleotide precursors in prebiotic circumstances. Our theory starts out from similar but more general chemical assumptions to those of Eigen, namely that catalytic replication can lead to a large population of long chains. In particular, our models incorporate the possibility of (i) direct chain growth, (ii) template-assisted synthesis and (iii) catalysis by RNA replicase ribozymes, all with varying degrees of efficiency. However, in our models the reaction mechanisms are kept `open'; we do not assume the existence of closed hypercycles which sustain a population of long chains. Rather it is the feasibility of the initial emergence of a self-sustaining set of RNA chains from monomeric nucleotides which is our prime concern. We confront directly the central nonlinear features of the problem, which have often been overlooked in previous studies. Our detailed m...
Hydrodynamic limit of the kinetic Cucker-Smale flocking model
Karper, Trygve; Trivisa, Konstantina
2012-01-01
The hydrodynamic limit of a kinetic Cucker-Smale model is investigated. In addition to the free-transport of individuals and the Cucker-Smale alignment operator, the model under consideration includes a strong local alignment term. This term was recently derived as the singular limit of an alignment operator due to Motsch and Tadmor. The model is enhanced with the addition of noise and a confinement potential. The objective of this work is the rigorous investigation of the singular limit corresponding to strong noise and strong local alignment. The proof relies on the relative entropy method and entropy inequalities which yield the appropriate convergence results. The resulting limiting system is an Euler-type flocking system.
Upper D region chemical kinetic modeling of LORE relaxation times
Gordillo-Vázquez, F. J.; Luque, A.; Haldoupis, C.
2016-04-01
The recovery times of upper D region electron density elevations, caused by lightning-induced electromagnetic pulses (EMP), are modeled. The work was motivated from the need to understand a recently identified narrowband VLF perturbation named LOREs, an acronym for LOng Recovery Early VLF events. LOREs associate with long-living electron density perturbations in the upper D region ionosphere; they are generated by strong EMP radiated from large peak current intensities of ±CG (cloud to ground) lightning discharges, known also to be capable of producing elves. Relaxation model scenarios are considered first for a weak enhancement in electron density and then for a much stronger one caused by an intense lightning EMP acting as an impulsive ionization source. The full nonequilibrium kinetic modeling of the perturbed mesosphere in the 76 to 92 km range during LORE-occurring conditions predicts that the electron density relaxation time is controlled by electron attachment at lower altitudes, whereas above 79 km attachment is balanced totally by associative electron detachment so that electron loss at these higher altitudes is controlled mainly by electron recombination with hydrated positive clusters H+(H2O)n and secondarily by dissociative recombination with NO+ ions, a process which gradually dominates at altitudes >88 km. The calculated recovery times agree fairly well with LORE observations. In addition, a simplified (quasi-analytic) model build for the key charged species and chemical reactions is applied, which arrives at similar results with those of the full kinetic model. Finally, the modeled recovery estimates for lower altitudes, that is <79 km, are in good agreement with the observed short recovery times of typical early VLF events, which are known to be associated with sprites.
Kinetic modeling can describe in vivo glycolysis in Entamoeba histolytica.
Saavedra, Emma; Marín-Hernández, Alvaro; Encalada, Rusely; Olivos, Alfonso; Mendoza-Hernández, Guillermo; Moreno-Sánchez, Rafael
2007-09-01
Glycolysis in the human parasite Entamoeba histolytica is characterized by the absence of cooperative modulation and the prevalence of pyrophosphate-dependent (over ATP-dependent) enzymes. To determine the flux-control distribution of glycolysis and understand its underlying control mechanisms, a kinetic model of the pathway was constructed by using the software gepasi. The model was based on the kinetic parameters determined in the purified recombinant enzymes, and the enzyme activities, and steady-state fluxes and metabolite concentrations determined in amoebal trophozoites. The model predicted, with a high degree of accuracy, the flux and metabolite concentrations found in trophozoites, but only when the pyrophosphate concentration was held constant; at variable pyrophosphate, the model was not able to completely account for the ATP production/consumption balance, indicating the importance of the pyrophosphate homeostasis for amoebal glycolysis. Control analysis by the model revealed that hexokinase exerted the highest flux control (73%), as a result of its low cellular activity and strong AMP inhibition. 3-Phosphoglycerate mutase also exhibited significant flux control (65%) whereas the other pathway enzymes showed little or no control. The control of the ATP concentration was also mainly exerted by ATP consuming processes and 3-phosphoglycerate mutase and hexokinase (in the producing block). The model also indicated that, in order to diminish the amoebal glycolytic flux by 50%, it was required to decrease hexokinase or 3-phosphoglycerate mutase by 24% and 55%, respectively, or by 18% for both enzymes. By contrast, to attain the same reduction in flux by inhibiting the pyrophosphate-dependent enzymes pyrophosphate-phosphofructokinase and pyruvate phosphate dikinase, they should be decreased > 70%. On the basis of metabolic control analysis, steps whose inhibition would have stronger negative effects on the energy metabolism of this parasite were identified
Reduced Models in Chemical Kinetics via Nonlinear Data-Mining
Directory of Open Access Journals (Sweden)
Eliodoro Chiavazzo
2014-01-01
Full Text Available The adoption of detailed mechanisms for chemical kinetics often poses two types of severe challenges: First, the number of degrees of freedom is large; and second, the dynamics is characterized by widely disparate time scales. As a result, reactive flow solvers with detailed chemistry often become intractable even for large clusters of CPUs, especially when dealing with direct numerical simulation (DNS of turbulent combustion problems. This has motivated the development of several techniques for reducing the complexity of such kinetics models, where, eventually, only a few variables are considered in the development of the simplified model. Unfortunately, no generally applicable a priori recipe for selecting suitable parameterizations of the reduced model is available, and the choice of slow variables often relies upon intuition and experience. We present an automated approach to this task, consisting of three main steps. First, the low dimensional manifold of slow motions is (approximately sampled by brief simulations of the detailed model, starting from a rich enough ensemble of admissible initial conditions. Second, a global parametrization of the manifold is obtained through the Diffusion Map (DMAP approach, which has recently emerged as a powerful tool in data analysis/machine learning. Finally, a simplified model is constructed and solved on the fly in terms of the above reduced (slow variables. Clearly, closing this latter model requires nontrivial interpolation calculations, enabling restriction (mapping from the full ambient space to the reduced one and lifting (mapping from the reduced space to the ambient one. This is a key step in our approach, and a variety of interpolation schemes are reported and compared. The scope of the proposed procedure is presented and discussed by means of an illustrative combustion example.
Ultra-local models of modified gravity without kinetic term
Brax, Philippe; Valageas, Patrick
2016-01-01
We present a class of modified-gravity theories which we call ultra-local models. We add a scalar field, with negligible kinetic terms, to the Einstein-Hilbert action. We also introduce a conformal coupling to matter. This gives rise to a new screening mechanism which is not entirely due to the non-linearity of the scalar field potential or the coupling function but to the absence of the kinetic term. As a result this removes any fifth force between isolated objects in vacuum. The predictions of these models only depend on a single free function, as the potential and the coupling function are degenerate, with an amplitude given by a parameter $\\alpha \\lesssim 10^{-6}$, whose magnitude springs from requiring a small modification of Newton's potential astrophysically and cosmologically. This singles out a redshift $z_{\\alpha} \\sim \\alpha^{-1/3} \\gtrsim 100$ where the fifth force is the greatest. The cosmological background follows the $\\Lambda$-CDM history within a $10^{-6}$ accuracy, while cosmological perturb...
Rotational and divergent kinetic energy in the mesoscale model ALADIN
Directory of Open Access Journals (Sweden)
V. Blažica
2013-03-01
Full Text Available Kinetic energy spectra from the mesoscale numerical weather prediction (NWP model ALADIN with horizontal resolution 4.4 km are split into divergent and rotational components which are then compared at horizontal scales below 300 km and various vertical levels. It is shown that about 50% of kinetic energy in the free troposphere in ALADIN is divergent energy. The percentage increases towards 70% near the surface and in the upper troposphere towards 100 hPa. The maximal percentage of divergent energy is found at stratospheric levels around 100 hPa and at scales below 100 km which are not represented by the global models. At all levels, the divergent energy spectra are characterised by shallower slopes than the rotational energy spectra, and the difference increases as horizontal scales become larger. A very similar vertical distribution of divergent energy is obtained by using the standard ALADIN approach for the computation of spectra based on the extension zone and by applying detrending approach commonly used in mesoscale NWP community.
Study on Lumped Kinetic Model for FDFCC I. Establishment of Model
Institute of Scientific and Technical Information of China (English)
Wu Feiyue; Weng Huixin; Luo Shixian
2008-01-01
According to the process features and the reaction mechanism of FDFCC technology, its two reaction subsystems, one for heavy oil riser reactor, the other for gasoline riser reactor, were respectively studied. Correspondingly, a 12-lump kinetic model for heavy oil FCC and a 9-lump kinetic model for gasoline catalytic upgrading were presented. Based on this work, mathematical correlation of the lumps in the feeds and products involved in the reaction subsystems and those of the overall reaction system were analyzed in detail. Then, a combined kinetic model for FDFCC, which was based on the data recovered from a commercial unit, was put forward. The reaction performance embodied by the kinetic constants for the combined model of FDFCC was in accordance with catalytic cracking reaction mechanism. The model-calculated values were close to the data obtained in commercial scale. The model was easy to be applied in practice and could also provide some theoretical groundwork for further research on kinetic model for FDFCC.
RES1/384: Spreading the Use of Kinetic Modeling Techniques by JAVA Analysis Software
Rudnicki, P; Mikolajczyk, K.; Grodzki, M; Burger, C
1999-01-01
Introduction Kinetic modeling is the method of choice for assessing the behaviour of new PET (Positron Emission Tomography) tracers. For suitable tracers, kinetic models allow to derive unique functional information from the acquired PET data, for instance the absolute perfusion or the density of specific receptors in brain tissue. However, the processing steps required are sophisticated. As there has no comprehensive modeling software been available in the past, kinetic models could only be ...
High Temperature Chemical Kinetic Combustion Modeling of Lightly Methylated Alkanes
Energy Technology Data Exchange (ETDEWEB)
Sarathy, S M; Westbrook, C K; Pitz, W J; Mehl, M
2011-03-01
Conventional petroleum jet and diesel fuels, as well as alternative Fischer-Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed high temperature chemical kinetic mechanism for n-octane and three lightly branched isomers octane (i.e., 2-methylheptane, 3-methylheptane, and 2,5-dimethylhexane). The model is validated against experimental data from a variety of fundamental combustion devices. This new model is used to show how the location and number of methyl branches affects fuel reactivity including laminar flame speed and species formation.
Kinetic modelling of runaway electrons in dynamic scenarios
Stahl, A; Papp, G; Landreman, M; Fülöp, T
2016-01-01
Improved understanding of runaway-electron formation and decay processes are of prime interest for the safe operation of large tokamaks, and the dynamics of the runaway electrons during dynamical scenarios such as disruptions are of particular concern. In this paper, we present kinetic modelling of scenarios with time-dependent plasma parameters; in particular, we investigate hot-tail runaway generation during a rapid drop in plasma temperature. With the goal of studying runaway-electron generation with a self-consistent electric-field evolution, we also discuss the implementation of a conservative collision operator and demonstrate its properties. An operator for avalanche runaway-electron generation, which takes the energy dependence of the scattering cross section and the runaway distribution into account, is investigated. We show that the simpler avalanche model of Rosenbluth & Putvinskii [Nucl. Fusion 37, 1355 (1997)] can give very inaccurate results for the avalanche growth rate (either lower or hig...
Kinetic hierarchy and propagation of chaos in biological swarm models
Carlen, Eric; Degond, Pierre; Wennberg, Bernt
2011-01-01
We consider two models of biological swarm behavior. In these models, pairs of particles interact to adjust their velocities one to each other. In the first process, called 'BDG', they join their average velocity up to some noise. In the second process, called 'CL', one of the two particles tries to join the other one's velocity. This paper establishes the master equations and BBGKY hierarchies of these two processes. It investigates the infinite particle limit of the hierarchies at large time-scale. It shows that the resulting kinetic hierarchy for the CL process does not satisfy propagation of chaos. Numerical simulations indicate that the BDG process has similar behavior to the CL process.
Kinetic modeling of oxidative desulfurization and catalyst deactivation
Energy Technology Data Exchange (ETDEWEB)
Tam, P.S.W.
1986-01-01
An oxidative-desulfurization (ODS) process was used to remove sulfur from diesel oils. The oxidants used were nitrogen dioxide and nitric acid. The feedstock under investigation was Atmospheric Gas Oil (AGO). Extraction of the oxidized oil with el-butyrolactone was used to remove additional sulfur from the oil. For a given solvent-to-oil (S/O) ratio, the extraction results from oxidized AGO showed higher sulfur removal than from the unoxidized oil. The ODS reactions are chain, free radical, auto-catalytic polymerization reactions similar to those in the sediment formation in fuel oil upon storage. Removal of sulfur by oxidation is from the deposition of co-product (residue) with high sulfur content. Increasing the oxidant concentration leads to increased residue formation, resulting in greater sulfur removal. A mathematical kinetic model is presented to describe the kinetics of sulfur removal in the oxidation of AGO using a CSTR. This model employs lumping of the sulfur compounds in the oil into three groups, according to their retention times in the gas chromatograph. Sulfur and nitrogen compounds usually poison catalysts in hydrocarbon processing. Models were developed to predict the cracking rate and catalyst activity in the cracking of cumene in the presence of organic nitrogen-containing poisons. A new mathematical definition of catalyst activity was used, including the adsorbed poison on active sites. Experimental data were used to fit the derived models, with excellent results. Finally, the use of exponential integral techniques to solve, analytically, the band-aging catalyst deactivation problem in an adiabatic fixed bed reactor is presented.
Ultralocal models of modified gravity without kinetic term
Brax, Philippe; Rizzo, Luca Alberto; Valageas, Patrick
2016-08-01
We present a class of modified-gravity theories which we call ultralocal models. We add a scalar field, with negligible kinetic terms, to the Einstein-Hilbert action. We also introduce a conformal coupling to matter. This gives rise to a new screening mechanism which is not entirely due to the nonlinearity of the scalar-field potential or the coupling function but to the absence of the kinetic term. As a result this removes any fifth force between isolated objects in vacuum. It turns out that these models are similar to chameleon-type theories with a large mass when considered outside the Compton wavelength but differ on shorter scales. The predictions of these models only depend on a single free function, as the potential and the coupling function are degenerate, with an amplitude given by a parameter α ≲10-6 , whose magnitude springs from requiring a small modification of Newton's potential astrophysically and cosmologically. This singles out a redshift zα˜α-1 /3≳100 where the fifth force is the greatest. The cosmological background follows the Λ cold dark matter (Λ CDM ) history within a 10-6 accuracy, while cosmological perturbations are significantly enhanced (or damped) on small scales, k ≳2 h Mpc-1 at z =0 . The spherical collapse and the halo mass function are modified in the same manner. We find that the modifications of gravity are greater for galactic or subgalactic structures. We also present a thermodynamic analysis of the nonlinear and inhomogeneous fifth-force regime where we find that the Universe is not made more inhomogeneous before zα when the fifth force dominates, and does not lead to the existence of clumped matter on extra small scales inside halos for large masses while this possibility exists for masses M ≲1 011M⊙ where the phenomenology of ultralocal models would be most different from Λ CDM .
Bioconversion potential of plant enzymes for the production of pharmaceuticals
Pras, N; Woerdenbag, HJ; vanUden, W
1995-01-01
Plant enzymes are able to catalyze regio- and stereospecific reactions. Freely suspended and immobilized plant cells as well as enzyme preparations can therefore be applied for the production of pharmaceuticals by bioconversion, as such or in combination with chemical syntheses. This review paper de
Integration Strategies for Efficient Multizone Chemical Kinetics Models
Energy Technology Data Exchange (ETDEWEB)
McNenly, M J; Havstad, M A; Aceves, S M; Pitz, W J
2009-10-15
Three integration strategies are developed and tested for the stiff, ordinary differential equation (ODE) integrators used to solve the fully coupled multizone chemical kinetics model. Two of the strategies tested are found to provide more than an order of magnitude of improvement over the original, basic level of usage for the stiff ODE solver. One of the faster strategies uses a decoupled, or segregated, multizone model to generate an approximate Jacobian. This approach yields a 35-fold reduction in the computational cost for a 20 zone model. Using the same approximate Jacobian as a preconditioner for an iterative Krylov-type linear system solver, the second improved strategy achieves a 75-fold reduction in the computational cost for a 20 zone model. The faster strategies achieve their cost savings with no significant loss of accuracy. The pressure, temperature and major species mass fractions agree with the solution from the original integration approach to within six significant digits; and the radical mass fractions agree with the original solution to within four significant digits. The faster strategies effectively change the cost scaling of the multizone model from cubic to quadratic, with respect to the number of zones. As a consequence of the improved scaling, the 40 zone model offers more than a 250-fold cost savings over the basic calculation.
Pyrolysis Kinetic Modelling of Wheat Straw from the Pannonian Region
Directory of Open Access Journals (Sweden)
Ivan Pešenjanski
2016-01-01
Full Text Available The pyrolysis/devolatilization is a basic step of thermochemical processes and requires fundamental characterization. In this paper, the kinetic model of pyrolysis is specified as a one-step global reaction. This type of reaction is used to describe the thermal degradation of wheat straw samples by measuring rates of mass loss of solid matter at a linear increase in temperature. The mentioned experiments were carried out using a derivatograph in an open-air environment. The influence of different factors was investigated, such as particle size, humidity levels, and the heating rate in the kinetics of devolatilization. As the measured values of mass loss and temperature functions transform in Arrhenius coordinates, the results are shown in the form of saddle curves. Such characteristics cannot be approximated with one equation in the form of Arrhenius law. For use in numerical applications, transformed functions can be approximated by linear regression for three separate intervals. Analysis of measurement resulting in granulation and moisture content variations shows that these factors have no significant influence. Tests of heating rate variations confirm the significance of this impact, especially in warmer regions. The influence of this factor should be more precisely investigated as a general variable, which should be the topic of further experiments.
Directory of Open Access Journals (Sweden)
Budiyono
2014-04-01
Full Text Available Anaerobic treatment using anaerobic digestion can convert organic materials of vinasse into biogas. The purpose of this study was modeling kinetic of biogas production using modified Gompertz model and first order kinetic model at variation of initial pH. Substrates were consisted of two kinds of compositions, which were vinasse+rumen (VR and vinasse+rumen+urea (VRU. Initial pH in each substrate was 6, 7 and 8. Degradation process was done in 30 days using batch anaerobic digesters at room temperature. Both, at VR and VRU, initial pH of 7 generated the more total biogas than the others two (initial pH of 6 and 8. Biogas formed at substrate of VRU was more than that at substrate of VR. The best condition was substrate of VRU and initial pH of 7. At best condition, kinetic constants of biogas production model using modified Gompertz were ym (biogas production potential = 6.49 mL/g VS; U (maximum biogas production rate = 1.24 mL/g VS. day; &lambda (minimum time to produce biogas = 1.79 days. Whereas kinetic constants of biogas production model using first order kinetic were ym (biogas production potential = 6.78 mL/g VS; k (biogas production rate = 0.176 /day. The difference between the predicted and measured biogas yield (fitting error was higher with the first-order kinetic model (1.54-7.50% than with the modified Gompertz model (0.76-3.14%.
Kinetic modeling and sensitivity analysis of plasma-assisted combustion
Togai, Kuninori
Plasma-assisted combustion (PAC) is a promising combustion enhancement technique that shows great potential for applications to a number of different practical combustion systems. In this dissertation, the chemical kinetics associated with PAC are investigated numerically with a newly developed model that describes the chemical processes induced by plasma. To support the model development, experiments were performed using a plasma flow reactor in which the fuel oxidation proceeds with the aid of plasma discharges below and above the self-ignition thermal limit of the reactive mixtures. The mixtures used were heavily diluted with Ar in order to study the reactions with temperature-controlled environments by suppressing the temperature changes due to chemical reactions. The temperature of the reactor was varied from 420 K to 1250 K and the pressure was fixed at 1 atm. Simulations were performed for the conditions corresponding to the experiments and the results are compared against each other. Important reaction paths were identified through path flux and sensitivity analyses. Reaction systems studied in this work are oxidation of hydrogen, ethylene, and methane, as well as the kinetics of NOx in plasma. In the fuel oxidation studies, reaction schemes that control the fuel oxidation are analyzed and discussed. With all the fuels studied, the oxidation reactions were extended to lower temperatures with plasma discharges compared to the cases without plasma. The analyses showed that radicals produced by dissociation of the reactants in plasma plays an important role of initiating the reaction sequence. At low temperatures where the system exhibits a chain-terminating nature, reactions of HO2 were found to play important roles on overall fuel oxidation. The effectiveness of HO2 as a chain terminator was weakened in the ethylene oxidation system, because the reactions of C 2H4 + O that have low activation energies deflects the flux of O atoms away from HO2. For the
Bioconversion of heavy oil : influence on reservoir recovery
Energy Technology Data Exchange (ETDEWEB)
Kotlar, H.K. [Statoil Research Centre, Trondheim (Norway); Markussen, S.; Winnberg, A.A. [SINTEF Materials and Chemistry, Trondheim (Norway). Dept. of Biotechnology
2009-07-01
Most of the world reserves of fossil hydrocarbons lie within heavy to extra heavy oil reservoirs. Enhancing the recovery rate by just a small percentage would provide significant economic incentive to develop these reservoirs. Moreover, if this could be done by a bio-process, it would have significant implications for environmental issues raised against heavy oil extraction. However, one of the major challenges, is the huge mobility ratio between the water phase and the oil phase. Different process technologies are available to extract these oils. These include steam assisted gravity drainage, vapour extraction and cold heavy oil extraction with sand. However, they are all expensive, energy-intensive, and high emission technologies and are also associated with other environmental concerns. This paper focused on the use of extremophile microorganisms as in situ biocatalysts for conversion of heavy oils. The paper outlined the experimental set-ups designed to mimic reservoir conditions, with particular emphasis on the biocatalytic processes involved in reducing the viscosity of the heavy oil components. However, another major challenge is the control and the regulation of these in situ bioprocesses in the oil reservoir. The paper also discussed the design of two different prototype reservoir models, introducing radial flow, including one with a central horizontal production well and one with a central vertical production well. The paper described the collection of enrichment cultures and injection of biocatalysts into the reservoir models. Testing of 5 different types of heavy oil was also described. The study results provide strong evidence of heavy oil bioconversion activities of several microbial consortia/ inoculums. 1 ref., 6 figs.
Formulation and kinetic modeling of curcumin loaded intranasal mucoadhesive microemulsion
Directory of Open Access Journals (Sweden)
B Mikesh Patel
2012-01-01
Full Text Available It is a challenge to develop the optimum dosage form of poorly water-soluble drugs and to target them due to limited bioavailability, intra and inter subject variability. In this investigation, mucoadhesive microemulsion of curcumin was developed by water titration method taking biocompatible components for intranasal delivery and was characterized. Nasal ciliotoxicity studies were carried out using excised sheep nasal mucosa. in vitro release studies of formulations and PDS were performed. Labrafil M 1944 CS based microemulsion was transparent, stable and nasal non-ciliotoxic having particle size 12.32±0.81nm (PdI=0.223 and from kinetic modeling, the release was found to be Fickian diffusion for mucoadhesive microemulsion.
An Experimental and Kinetic Modeling Study of Methyl Decanoate Combustion
Energy Technology Data Exchange (ETDEWEB)
Sarathy, S M; Thomson, M J; Pitz, W J; Lu, T
2010-02-19
Biodiesel is typically a mixture of long chain fatty acid methyl esters for use in compression ignition engines. Improving biofuel engine performance requires understanding its fundamental combustion properties and the pathways of combustion. This research study presents new combustion data for methyl decanoate in an opposed-flow diffusion flame. An improved detailed chemical kinetic model for methyl decanoate combustion is developed, which serves as the basis for deriving a skeletal mechanism via the direct relation graph method. The novel skeletal mechanism consists of 648 species and 2998 reactions. This mechanism well predicts the methyl decanoate opposed-flow diffusion flame data. The results from the flame simulations indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene.
Incorporation of chemical kinetic models into process control
International Nuclear Information System (INIS)
An important consideration in chemical process control is to determine the precise rationing of reactant streams, particularly when a large time delay exists between the mixing of the reactants and the measurement of the product. In this paper, a method is described for incorporating chemical kinetic models into the control strategy in order to achieve optimum operating conditions. The system is first characterized by determining a reaction rate surface as a function of all input reactant concentrations over a feasible range. A nonlinear constrained optimization program is then used to determine the combination of reactants which produces the specified yield at minimum cost. This operating condition is then used to establish the nominal concentrations of the reactants. The actual operation is determined through a feedback control system employing a Smith predictor. The method is demonstrated on a laboratory bench scale enzyme reactor
Phase transition in kinetic exchange opinion models with independence
Crokidakis, Nuno
2014-01-01
In this work we study the critical behavior of a three-state ($+1$, $-1$, $0$) opinion model with independence. Each agent has a probability $q$ to act as independent, i.e., he/she can choose his/her opinion independently of the opinions of the other agents. On the other hand, with the complementary probability $1-q$ the agent interacts with a randomly chosen individual through a kinetic exchange. Our analytical and numerical results show that the independence mechanism acts as a noise that induce an order-disorder transition at critical points $q_{c}$ that depend on the individuals' flexibility. For a special value of this flexibility the system undergoes a transition to an absorbing state with all opinions $0$.
Thermal stability of n-dodecane : experiments and kinetic modelling
Herbinet, Olivier; Battin-Leclerc, Frédérique; Fournet, René
2007-01-01
The thermal decomposition of n-dodecane, a component of some jet fuels, has been studied in a jet-stirred reactor at temperatures from 793 to 1093 K, for residence times between 1 and 5 s and at atmospheric pressure. Thermal decomposition of hydrocarbon fuel prior the entrance in the combustion chamber is an envisaged way to cool the wall of hypersonic vehicles. The products of the reaction are mainly hydrogen, methane, ethane, 1,3-butadiene and 1-alkenes from ethylene to 1-undecene. For higher temperatures and residence times acetylene, allene, propyne, cyclopentene, 1,3-cyclopentadiene and aromatic compounds from benzene to pyrene through naphthalene have also been observed. A previous detailed kinetic model of the thermal decomposition of n-dodecane generated using EXGAS software has been improved and completed by a sub-mechanism explaining the formation and the consumption of aromatic compounds.
Phase transition in kinetic exchange opinion models with independence
International Nuclear Information System (INIS)
In this work we study the critical behavior of a three-state (+1, −1, 0) opinion model with independence. Each agent has a probability q to act as independent, i.e., he/she can choose his/her opinion independently of the opinions of the other agents. On the other hand, with the complementary probability 1−q the agent interacts with a randomly chosen individual through a kinetic exchange. Our analytical and numerical results show that the independence mechanism acts as a noise that induces an order–disorder transition at critical points qc that depend on the individuals' flexibility. For a special value of this flexibility the system undergoes a transition to an absorbing state with all opinions 0.
Kinetic Model for a Spherical Rolling Robot with Soft Shell in a Beeline Motion
Directory of Open Access Journals (Sweden)
Sheng Zhang
2014-02-01
Full Text Available A simplified kinetic model called Spring Pendulum is developed for a spherical rolling robot with soft shell in order to meet the needs of attitude stabilization and controlling for the robot. The elasticity and plasticity of soft shell is represented by some uniform springs connected to the bracket in this model. The expression of the kinetic model is deduced from Newtonian mechanics principles. Testing data of the driving angle acquired from a prototype built by authors indicate that testing data curve accords to the theoretic kinetic characteristic curve, so the kinetic model is validated
Gompertz kinetics model of fast chemical neurotransmission currents.
Easton, Dexter M
2005-10-01
At a chemical synapse, transmitter molecules ejected from presynaptic terminal(s) bind reversibly with postsynaptic receptors and trigger an increase in channel conductance to specific ions. This paper describes a simple but accurate predictive model for the time course of the synaptic conductance transient, based on Gompertz kinetics. In the model, two simple exponential decay terms set the rates of development and decline of transmitter action. The first, r, triggering conductance activation, is surrogate for the decelerated rate of growth of conductance, G. The second, r', responsible for Y, deactivation of the conductance, is surrogate for the decelerated rate of decline of transmitter action. Therefore, the differential equation for the net conductance change, g, triggered by the transmitter is dg/dt=g(r-r'). The solution of that equation yields the product of G(t), representing activation, and Y(t), which defines the proportional decline (deactivation) of the current. The model fits, over their full-time course, published records of macroscopic ionic current associated with fast chemical transmission. The Gompertz model is a convenient and accurate method for routine analysis and comparison of records of synaptic current and putative transmitter time course. A Gompertz fit requiring only three independent rate constants plus initial current appears indistinguishable from a Markov fit using seven rate constants.
Detailed kinetic modeling study of n-pentanol oxidation
Heufer, Karl Alexander
2012-10-18
To help overcome the world\\'s dependence upon fossil fuels, suitable biofuels are promising alternatives that can be used in the transportation sector. Recent research on internal combustion engines shows that short alcoholic fuels (e.g., ethanol or n-butanol) have reduced pollutant emissions and increased knock resistance compared to fossil fuels. Although higher molecular weight alcohols (e.g., n-pentanol and n-hexanol) exhibit higher reactivity that lowers their knock resistance, they are suitable for diesel engines or advanced engine concepts, such as homogeneous charge compression ignition (HCCI), where higher reactivity at lower temperatures is necessary for engine operation. The present study presents a detailed kinetic model for n-pentanol based on modeling rules previously presented for n-butanol. This approach was initially validated using quantum chemistry calculations to verify the most stable n-pentanol conformation and to obtain C-H and C-C bond dissociation energies. The proposed model has been validated against ignition delay time data, speciation data from a jet-stirred reactor, and laminar flame velocity measurements. Overall, the model shows good agreement with the experiments and permits a detailed discussion of the differences between alcohols and alkanes. © 2012 American Chemical Society.
Construction of the simplest model to explain complex receptor activation kinetics
DEFF Research Database (Denmark)
Bywater, RP; Sorensen, A; Røgen, Peter;
2002-01-01
We study the mathematical solutions to the kinetic equations arising from various simple ligand-reactor models. Focusing on the prediction of the various models for the activity vs. concentration curve, we find that solutions to the kinetic equations arising from the so-called dimer model exibit...
Kinetic modelling of runaway electrons in dynamic scenarios
Stahl, A.; Embréus, O.; Papp, G.; Landreman, M.; Fülöp, T.
2016-11-01
Improved understanding of runaway-electron formation and decay processes are of prime interest for the safe operation of large tokamaks, and the dynamics of the runaway electrons during dynamical scenarios such as disruptions are of particular concern. In this paper, we present kinetic modelling of scenarios with time-dependent plasma parameters; in particular, we investigate hot-tail runaway generation during a rapid drop in plasma temperature. With the goal of studying runaway-electron generation with a self-consistent electric-field evolution, we also discuss the implementation of a collision operator that conserves momentum and energy and demonstrate its properties. An operator for avalanche runaway-electron generation, which takes the energy dependence of the scattering cross section and the runaway distribution into account, is investigated. We show that the simplified avalanche model of Rosenbluth and Putvinskii (1997 Nucl. Fusion 37 1355) can give inaccurate results for the avalanche growth rate (either lower or higher) for many parameters, especially when the average runaway energy is modest, such as during the initial phase of the avalanche multiplication. The developments presented pave the way for improved modelling of runaway-electron dynamics during disruptions or other dynamic events.
Kinetic Model of Hypophosphite Oxidation on a Nickel Electrode in D2O Solution
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Kinetic model of hypophosphite oxidation on a nickel electrode was studied in D2Osolution in order to reach a better understanding of the oxidation mechanism. In the model the electrooxidation of hypophosphite undergo a H abstraction of hypophosphite from the P-H bond to form the phosphorus-centered radical PHO2-, which subsequently is electrochemically reacted with water to form the final product, phosphite. The kinetic equations were derived, and the kinetic parameters were obtained from a comparison of experimental results and the kinetic equations. The process of hypophosphite electrooxidation could be well simulated by this model
Applicaiton of a Kinetic Multireaction Model for Studying Metolachlor Adsorption in Soil
Institute of Scientific and Technical Information of China (English)
ZHUHONGXIA; MALIWANG; 等
1997-01-01
Metolachlor retention on a Sharkey clay soil was quantified using a kinetic batch method for different initial solution concentrations.Time-dependent adsorption was carried out by monitoring solution concentration at different reaction times.Adsorption was kinetic multireaction model which includes reverible and irreversible retention processes of the equilibrium and kinetic types,The predictive capability of the model for the dexcription of experimental results for metolachlor retention was examined and proved to be adequate。
Modeling turbulence structure. Chemical kinetics interaction in turbulent reactive flows
Energy Technology Data Exchange (ETDEWEB)
Magnussen, B.F. [The Norwegian Univ. of Science and Technology, Trondheim (Norway)
1997-12-31
The challenge of the mathematical modelling is to transfer basic physical knowledge into a mathematical formulation such that this knowledge can be utilized in computational simulation of practical problems. The combustion phenomena can be subdivided into a large set of interconnected phenomena like flow, turbulence, thermodynamics, chemical kinetics, radiation, extinction, ignition etc. Combustion in one application differs from combustion in another area by the relative importance of the various phenomena. The difference in fuel, geometry and operational conditions often causes the differences. The computer offers the opportunity to treat the individual phenomena and their interactions by models with wide operational domains. The relative magnitude of the various phenomena therefore becomes the consequence of operational conditions and geometry and need not to be specified on the basis of experience for the given problem. In mathematical modelling of turbulent combustion, one of the big challenges is how to treat the interaction between the chemical reactions and the fluid flow i.e. the turbulence. Different scientists adhere to different concepts like the laminar flamelet approach, the pdf approach of the Eddy Dissipation Concept. Each of these approaches offers different opportunities and problems. All these models are based on a sound physical basis, however none of these have general validity in taking into consideration all detail of the physical chemical interaction. The merits of the models can only be judged by their ability to reproduce physical reality and consequences of operational and geometric conditions in a combustion system. The presentation demonstrates and discusses the development of a coherent combustion technology for energy conversion and safety based on the Eddy Dissipation Concept by Magnussen. (author) 30 refs.
Micellization kinetics in block copolymer solutions : Scaling model
Dormidontova, EE
1999-01-01
The kinetics of micelle evolution of diblock copolymers from unimers toward the equilibrium state is studied analytically on the basis of consideration of the kinetic equations. The association/dissociation rate constants for unimer insertion/expulsion and micelle fusion/fission are calculated by ap
Numerical modeling of radiation physics in kinetic plasmas [II
Paraschiv, Ioana; Sentoku, Yasuhiko; Mancini, Roberto
2014-10-01
X-ray radiation is an important feature of ultra-intense laser interactions with high Z materials. In order to take into account the radiation effects in the high energy density plasmas created by such interactions, we have modified the collisional particle-in-cell code PICLS to self-consistently model the x-ray radiation transport (RT). Solving the equation of radiation transport requires the creation of a non-LTE database of emissivities and opacities as functions of photon frequency for given densities, bulk electron temperatures, hot electron temperatures, and hot electron fractions. The database was generated using results computed by a non-equilibrium, collisional-radiative atomic kinetics code. Using the two-dimensional RT-PICLS code we have studied the X-ray transport in an ultrafast heated target and the dependence of the emitted K- α radiation on the fast electron dynamics in the solid target. The details of these results obtained from the implementation of the radiation transport model into the PICLS calculations will be reported in this presentation. Work supported by the DOE Office of Science Grant No. DE-SC0008827 and by the NNSA/DOE Grants No. DE-FC52-06NA27616 and DE-NA0002075.
Kinetic theories for spin models for cooperative relaxation dynamics
Pitts, Steven Jerome
The facilitated kinetic Ising models with asymmetric spin flip constraints introduced by Jackle and co-workers [J. Jackle, S. Eisinger, Z. Phys. B 84, 115 (1991); J. Reiter, F. Mauch, J. Jackle, Physica A 184, 458 (1992)] exhibit complex relaxation behavior in their associated spin density time correlation functions. This includes the growth of relaxation times over many orders of magnitude when the thermodynamic control parameter is varied, and, in some cases, ergodic-nonergodic transitions. Relaxation equations for the time dependence of the spin density autocorrelation function for a set of these models are developed that relate this autocorrelation function to the irreducible memory function of Kawasaki [K. Kawasaki, Physica A 215, 61 (1995)] using a novel diagrammatic series approach. It is shown that the irreducible memory function in a theory of the relaxation of an autocorrelation function in a Markov model with detailed balance plays the same role as the part of the memory function approximated by a polynomial function of the autocorrelation function with positive coefficients in schematic simple mode coupling theories for supercooled liquids [W. Gotze, in Liquids, Freezing and the Glass Transition, D. Levesque, J. P. Hansen, J. Zinn-Justin eds., 287 (North Holland, New York, 1991)]. Sets of diagrams in the series for the irreducible memory function are summed which lead to approximations of this type. The behavior of these approximations is compared with known results from previous analytical calculations and from numerical simulations. For the simplest one dimensional model, relaxation equations that are closely related to schematic extended mode coupling theories [W. Gotze, ibid] are also derived using the diagrammatic series. Comparison of the results of these approximate theories with simulation data shows that these theories improve significantly on the results of the theories of the simple schematic mode coupling theory type. The potential
Pas, N.C.A. van de; Rullmann, J.A.C.; Woutersen, R.A.; Ommen, B. van; Rietjens, I.M.C.M.; Graaf, A.A. de
2014-01-01
We used a previously developed physiologically based kinetic (PBK) model to analyze the effect of individual variations in metabolism and transport of cholesterol on pravastatin response. The PBK model is based on kinetic expressions for 21 reactions that interconnect eight different body cholestero
Disposition of smoked cannabis with high [Delta]9-tetrahydrocannabinol content: A kinetic model.
Hunault, C.C.; van Eijkeren, J.C.; Mensinga, T.T.; de Vries, I.; Leenders, M.E.C.; Meulenbelt, J.
2010-01-01
Introduction No model exists to describe the disposition and kinetics of inhaled cannabis containing a high THC dose. We aimed to develop a kinetic model providing estimates of the THC serum concentrations after smoking cannabis cigarettes containing high THC doses (up to 69 mg THC).Methods Twenty-f
A kinetic model for runaway electrons in the ionosphere
Directory of Open Access Journals (Sweden)
G. Garcia
2006-09-01
Full Text Available Electrodynamic models and measurements with satellites and incoherent scatter radars predict large field aligned current densities on one side of the auroral arcs. Different authors and different kinds of studies (experimental or modeling agree that the current density can reach up to hundreds of µA/m^{2}. This large current density could be the cause of many phenomena such as tall red rays or triggering of unstable ion acoustic waves. In the present paper, we consider the issue of electrons moving through an ionospheric gas of positive ions and neutrals under the influence of a static electric field. We develop a kinetic model of collisions including electrons/electrons, electrons/ions and electrons/neutrals collisions. We use a Fokker-Planck approach to describe binary collisions between charged particles with a long-range interaction. We present the essential elements of this collision operator: the Langevin equation for electrons/ions and electrons/electrons collisions and the Monte-Carlo and null collision methods for electrons/neutrals collisions. A computational example is given illustrating the approach to equilibrium and the impact of the different terms (electrons/electrons and electrons/ions collisions on the one hand and electrons/neutrals collisions on the other hand. Then, a parallel electric field is applied in a new sample run. In this run, the electrons move in the z direction parallel to the electric field. The first results show that all the electron distribution functions are non-Maxwellian. Furthermore, runaway electrons can carry a significant part of the total current density, up to 20% of the total current density.
Dsc cure kinetics of an unsaturated polyester resin using empirical kinetic model
International Nuclear Information System (INIS)
In this paper, the kinetics of curing of unsaturated polyester resin initiated with benzoyl peroxide was studied. In case of unsaturated polyester (UP) resin, isothermal test alone could not predict correctly the curing time of UP resin. Therefore, isothermal kinetic analysis through isoconventional adjustment was used to correctly predict the curing time and temperature of UP resin. Isothermal kinetic analysis through isoconversional adjustment indicated that 97% of UP resin cures in 33 min at 120 degree C. Curing of UP resin through microwaves was also studied and found that 67% of UP resin cures in 1 min at 120 degree C. The crosslinking reaction of UP resin is so fast at 120 degree C that it becomes impossible to predict correctly the curing time of UP resin using isothermal test and the burial of C=C bonds in microgels makes it impossible to be fully cured by microwaves at 120 degree C. The rheological behaviour of unsaturated polyester resin was also studied to observe the change in viscosity with respect to time and temperature. (author)
Oil cracking to gases: Kinetic modeling and geological significance
Institute of Scientific and Technical Information of China (English)
TIAN Hui; WANG Zhaoming; XIAO Zhongyao; LI Xianqing; XIAO Xianming
2006-01-01
ATriassic oil sample from LN14 of Tarim Basin was pyrolyzed using the sealed gold tubes at 200-620℃ under a constant pressure of 50 MPa.The gaseous and residual soluble hydrocarbons were analyzed. The results show that the cracking of oil to gas can be divided into two distinct stages: the primary generation of total C1-5 gases from liquid oil characterized by the dominance of C2-5 hydrocarbons and the secondary or further cracking of C2-5gases to methane and carbon-rich matters leading to the progressive dryness of gases. Based on the experimental data, the kinetic parameters were determined for the primary generation and secondary cracking of oil cracking gases and extrapolated to geological conditions to predict the thermal stability and cracking extent of crude oil. Finally, an evolution model for the thermal destruction of crude oil was proposed and its implications to the migration and accumulation of oil cracking gases were discussed.
KINETIC MODELS STUDY OF HYDRODESULPHURIZATION VACUUM DISTILLATE REACTION
Directory of Open Access Journals (Sweden)
AbdulMunem A. Karim
2013-05-01
Full Text Available This study deals with kinetics of hydrodesulphurization (HDS reaction of vacuum gas oil (611-833 K which was distillated from Kirkuk crude oil and which was obtained by blending the fractions, light vacuum gas oil (611 - 650 K, medium vacuum gas oil (650-690 K, heavy vacuum gas oil (690-727 K and very heavy vacuum gas oil (727-833 K. The vacuum gas oil was hydrotreated on a commercial cobalt-molybdenum alumina catalyst presulfied at specified conditions in a laboratory trickle bed reactor. The reaction temperature range (583-643 K,liquid hourly space velocity range (1.5-3.75 h-1 and hydrogen pressure was kept constant at 3.5 MPa with hydrogen to oil ratio about 250 lt/lt. The conversion results for desulphurization reaction appeared to obey the second order reaction. According to this model, the rate constants for desulphurization reaction were determined. Finally, the apparent activation energy (Ea, enthalpy of activation ( H* and entropy ( S* were calculated based on the values of rate constant (k2 and were equal 80.3792 KJ/mole, 75.2974 KJ/mole and 197.493 J/mole, respectively.
Bacterial biodegradation and bioconversion of industrial lignocellulosic streams.
Mathews, Stephanie L; Pawlak, Joel; Grunden, Amy M
2015-04-01
Lignocellulose is a term for plant materials that are composed of matrices of cellulose, hemicellulose, and lignin. Lignocellulose is a renewable feedstock for many industries. Lignocellulosic materials are used for the production of paper, fuels, and chemicals. Typically, industry focuses on transforming the polysaccharides present in lignocellulose into products resulting in the incomplete use of this resource. The materials that are not completely used make up the underutilized streams of materials that contain cellulose, hemicellulose, and lignin. These underutilized streams have potential for conversion into valuable products. Treatment of these lignocellulosic streams with bacteria, which specifically degrade lignocellulose through the action of enzymes, offers a low-energy and low-cost method for biodegradation and bioconversion. This review describes lignocellulosic streams and summarizes different aspects of biological treatments including the bacteria isolated from lignocellulose-containing environments and enzymes which may be used for bioconversion. The chemicals produced during bioconversion can be used for a variety of products including adhesives, plastics, resins, food additives, and petrochemical replacements.
Modelling of the enzymatic kinetically controlled synthesis of cephalexin
Schroën, C.G.P.H.; Fretz, C.B.; Bruin, de V.H.; Berendsen, W.; Moody, H.M.; Roos, E.C.; Roon, van J.L.; Kroon, P.J.; Strubel, M.; Janssen, A.E.M.; Tramper, J.
2002-01-01
In this study the influence of diffusion limitation on enzymatic kinetically controlled cephalexin synthesis from phenylglycine amide and 7-aminodeacetoxycephalosporinic acid (7-ADCA) was investigated systematically. It was found that if diffusion limitation occurred, both the synthesis/hydrolysis r
Pas, van de N.C.A.; Woutersen, R.A.; Ommen, van B.; Rietjens, I.M.C.M.; Graaf, de A.A.
2012-01-01
Increased plasma cholesterol concentration is associated with increased risk of cardiovascular disease. This study describes the development, validation, and analysis of a physiologically based kinetic (PBK) model for the prediction of plasma cholesterol concentrations in humans. This model was dire
DEFF Research Database (Denmark)
Chambon, Julie Claire Claudia; Bjerg, Poul Løgstrup; Scheutz, Charlotte;
2013-01-01
Reductive dechlorination is a major degradation pathway of chlorinated ethenes in anaerobic subsurface environments, and reactive kinetic models describing the degradation process are needed in fate and transport models of these contaminants. However, reductive dechlorination is a complex biologi...
Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: from fluid to kinetic modeling
Henri, P; Califano, F; Pegoraro, F; Rossi, C; Faganello, M; Šebek, O; Trávníček, P M; Hellinger, P; Frederiksen, J T; Nordlund, Å; Markidis, S; Keppens, R; Lapenta, G
2013-01-01
The nonlinear evolution of collisionless plasmas is typically a multi-scale process where the energy is injected at large, fluid scales and dissipated at small, kinetic scales. Accurately modelling the global evolution requires to take into account the main micro-scale physical processes of interest. This is why comparison of different plasma models is today an imperative task aiming at understanding cross-scale processes in plasmas. We report here the first comparative study of the evolution of a magnetized shear flow, through a variety of different plasma models by using magnetohydrodynamic, Hall-MHD, two-fluid, hybrid kinetic and full kinetic codes. Kinetic relaxation effects are discussed to emphasize the need for kinetic equilibriums to study the dynamics of collisionless plasmas in non trivial configurations. Discrepancies between models are studied both in the linear and in the nonlinear regime of the magnetized Kelvin-Helmholtz instability, to highlight the effects of small scale processes on the nonl...
Analysis of a kinetic multi-segment foot model. Part I: Model repeatability and kinematic validity.
Bruening, Dustin A; Cooney, Kevin M; Buczek, Frank L
2012-04-01
Kinematic multi-segment foot models are still evolving, but have seen increased use in clinical and research settings. The addition of kinetics may increase knowledge of foot and ankle function as well as influence multi-segment foot model evolution; however, previous kinetic models are too complex for clinical use. In this study we present a three-segment kinetic foot model and thorough evaluation of model performance during normal gait. In this first of two companion papers, model reference frames and joint centers are analyzed for repeatability, joint translations are measured, segment rigidity characterized, and sample joint angles presented. Within-tester and between-tester repeatability were first assessed using 10 healthy pediatric participants, while kinematic parameters were subsequently measured on 17 additional healthy pediatric participants. Repeatability errors were generally low for all sagittal plane measures as well as transverse plane Hindfoot and Forefoot segments (mediansegment rigidity analysis suggested rigid body behavior for the Shank and Hindfoot, with the Forefoot violating the rigid body assumptions in terminal stance/pre-swing. Joint excursions were consistent with previously published studies.
A detailed chemical kinetic model for pyrolysis of the lignin model compound chroman
Directory of Open Access Journals (Sweden)
James Bland
2013-12-01
Full Text Available The pyrolysis of woody biomass, including the lignin component, is emerging as a potential technology for the production of renewable fuels and commodity chemicals. Here we describe the construction and implementation of an elementary chemical kinetic model for pyrolysis of the lignin model compound chroman and its reaction intermediate ortho-quinone methide (o-QM. The model is developed using both experimental and theoretical data, and represents a hybrid approach to kinetic modeling that has the potential to provide molecular level insight into reaction pathways and intermediates while accurately describing reaction rates and product formation. The kinetic model developed here can replicate all known aspects of chroman pyrolysis, and provides new information on elementary reaction steps. Chroman pyrolysis is found to proceed via an initial retro-Diels–Alder reaction to form o-QM + ethene (C2H4, followed by dissociation of o-QM to the C6H6 isomers benzene and fulvene (+ CO. At temperatures of around 1000–1200 K and above fulvene rapidly isomerizes to benzene, where an activation energy of around 270 kJ mol-1 is required to reproduce experimental observations. A new G3SX level energy surface for the isomerization of fulvene to benzene supports this result. Our modeling also suggests that thermal decomposition of fulvene may be important at around 950 K and above. This study demonstrates that theoretical protocols can provide a significant contribution to the development of kinetic models for biomass pyrolysis by elucidating reaction mechanisms, intermediates, and products, and also by supplying realistic rate coefficients and thermochemical properties.
Modeling of hydrogen production methods: Single particle model and kinetics assessment
Energy Technology Data Exchange (ETDEWEB)
Miller, R.S.; Bellan, J. [California Institute of Technology, Pasadena, CA (United States)
1996-10-01
The investigation carried out by the Jet Propulsion Laboratory (JPL) is devoted to the modeling of biomass pyrolysis reactors producing an oil vapor (tar) which is a precursor to hydrogen. This is an informal collaboration with NREL whereby JPL uses the experimentally-generated NREL data both as initial and boundary conditions for the calculations, and as a benchmark for model validation. The goal of this investigation is to find drivers of biomass fast-pyrolysis in the low temperature regime. The rationale is that experimental observations produce sparse discrete conditions for model validation, and that numerical simulations produced with a validated model are an economic way to find control parameters and an optimal operation regime, thereby circumventing costly changes in hardware and tests. During this first year of the investigation, a detailed mathematical model has been formulated for the temporal and spatial accurate modeling of solid-fluid reactions in biomass particles. These are porous particles for which volumetric reaction rate data is known a priori and both the porosity and the permeability of the particle are large enough to allow for continuous gas phase flow. The methodology has been applied to the pyrolysis of spherically symmetric biomass particles by considering previously published kinetics schemes for both cellulose and wood. The results show that models which neglect the thermal and species boundary layers exterior to the particle will generally over predict both the pyrolysis rates and experimentally obtainable tar yields. An evaluation of the simulation results through comparisons with experimental data indicates that while the cellulose kinetics is reasonably accurate, the wood pyrolysis kinetics is not accurate; particularly at high reactor temperatures. Current effort in collaboration with NREL is aimed at finding accurate wood kinetics.
Institute of Scientific and Technical Information of China (English)
陈振兴; 李洪桂; 王零森
2004-01-01
The method to calculate internal surface effective factor of cylinder-type vanadium catalyst Ls-9 was given. Based on hypothesis of subjunctive one dimension diffusion and combined shape adjustment factor with threestep catalytic mechanism model, the macroscopic kinetic model equation about SO2 oxidation on Ls-9 was deduced.With fixed-bed integral reactor and under the conditions of temperature 350 - 410 ℃, space velocity 1 800 - 5 000h-1, SO2 inlet content 7 %- 12%, the macroscopic kinetic data were detected. Through model parameter estimation,the macroscopic kinetic model equation was obtained.
Kinetic modelling of RDF pyrolysis: Model-fitting and model-free approaches.
Çepelioğullar, Özge; Haykırı-Açma, Hanzade; Yaman, Serdar
2016-02-01
In this study, refuse derived fuel (RDF) was selected as solid fuel and it was pyrolyzed in a thermal analyzer from room temperature to 900°C at heating rates of 5, 10, 20, and 50°C/min in N2 atmosphere. The obtained thermal data was used to calculate the kinetic parameters using Coats-Redfern, Friedman, Flylnn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. As a result of Coats-Redfern model, decomposition process was assumed to be four independent reactions with different reaction orders. On the other hand, model free methods demonstrated that activation energy trend had similarities for the reaction progresses of 0.1, 0.2-0.7 and 0.8-0.9. The average activation energies were found between 73-161kJ/mol and it is possible to say that FWO and KAS models produced closer results to the average activation energies compared to Friedman model. Experimental studies showed that RDF may be a sustainable and promising feedstock for alternative processes in terms of waste management strategies. PMID:26613830
Kinetic modelling of RDF pyrolysis: Model-fitting and model-free approaches.
Çepelioğullar, Özge; Haykırı-Açma, Hanzade; Yaman, Serdar
2016-02-01
In this study, refuse derived fuel (RDF) was selected as solid fuel and it was pyrolyzed in a thermal analyzer from room temperature to 900°C at heating rates of 5, 10, 20, and 50°C/min in N2 atmosphere. The obtained thermal data was used to calculate the kinetic parameters using Coats-Redfern, Friedman, Flylnn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. As a result of Coats-Redfern model, decomposition process was assumed to be four independent reactions with different reaction orders. On the other hand, model free methods demonstrated that activation energy trend had similarities for the reaction progresses of 0.1, 0.2-0.7 and 0.8-0.9. The average activation energies were found between 73-161kJ/mol and it is possible to say that FWO and KAS models produced closer results to the average activation energies compared to Friedman model. Experimental studies showed that RDF may be a sustainable and promising feedstock for alternative processes in terms of waste management strategies.
Childers, W Lee; Kogler, Géza F
2014-01-01
People with amputation move asymmetrically with regard to kinematics (joint angles) and kinetics (joint forces and moments). Clinicians have traditionally sought to minimize kinematic asymmetries, assuming kinetic asymmetries would also be minimized. A cycling model evaluated locomotor asymmetries. Eight individuals with unilateral transtibial amputation pedaled with 172 mm-length crank arms on both sides (control condition) and with the crank arm length shortened to 162 mm on the amputated side (CRANK condition). Pedaling kinetics and limb kinematics were recorded. Joint kinetics, joint angles (mean and range of motion [ROM]), and pedaling asymmetries were calculated from force pedals and with a motion capture system. A one-way analysis of variance with tukey post hoc compared kinetics and kinematics across limbs. Statistical significance was set to p kinetic asymmetries as clinically assumed. We propose that future research should concentrate on defining acceptable asymmetry.
Indian Academy of Sciences (India)
Jai Prakash
2013-01-01
Ionic thermocurrent (ITC) spectrum is much similar to a thermoluminescence (TL) glow curve involving monomolecular kinetics. It has already been reported that different orders of kinetics are involved in TL processes, which depend specifically on the extent of recombination and simultaneous retrapping. It is found that the involvement of different orders of kinetics in ITC spectrum depends on the experimental conditions of polarization and rate of rapid cooling. Consequently, order of kinetics involved in the ITC spectrum does not represent any specific feature of the system under investigation. An equation is developed which explains the occurrence of ITC spectrum involving any order of kinetics. Dielectric relaxation parameters, order of kinetics and approximate number of dipoles per unit volume are evaluated conveniently and easily following the proposed model.
Kinetic modeling of antimony(III) oxidation and sorption in soils.
Cai, Yongbing; Mi, Yuting; Zhang, Hua
2016-10-01
Kinetic batch and saturated column experiments were performed to study the oxidation, adsorption and transport of Sb(III) in two soils with contrasting properties. Kinetic and column experiment results clearly demonstrated the extensive oxidation of Sb(III) in soils, and this can in return influence the adsorption and transport of Sb. Both sorption capacity and kinetic oxidation rate were much higher in calcareous Huanjiang soil than in acid red Yingtan soil. The results indicate that soil serve as a catalyst in promoting oxidation of Sb(III) even under anaerobic conditions. A PHREEQC model with kinetic formulations was developed to simulate the oxidation, sorption and transport of Sb(III) in soils. The model successfully described Sb(III) oxidation and sorption data in kinetic batch experiment. It was less successful in simulating the reactive transport of Sb(III) in soil columns. Additional processes such as colloid facilitated transport need to be quantified and considered in the model. PMID:27214003
Chen, Xiangjun; Xiao, Namin; Cai, Minghui; Li, Dianzhong; Li, Guangyao; Sun, Guangyong; Rolfe, Bernard F.
2016-06-01
An inverse model is proposed to construct the mathematical relationship between continuous cooling transformation (CCT) kinetics with constant rates and the isothermal one. The kinetic parameters in JMAK equations of isothermal kinetics can be deduced from the experimental CCT kinetics. Furthermore, a generalized model with a new additive rule is developed for predicting the kinetics of nucleation and growth during diffusional phase transformation with arbitrary cooling paths based only on CCT curve. A generalized contribution coefficient is introduced into the new additivity rule to describe the influences of current temperature and cooling rate on the incubation time of nuclei. Finally, then the reliability of the proposed model is validated using dilatometry experiments of a microalloy steel with fully bainitic microstructure based on various cooling routes.
Comparative evaluation of kinetic, equilibrium and semi-equilibrium models for biomass gasification
Energy Technology Data Exchange (ETDEWEB)
Buragohain, Buljit [Center for Energy, Indian Institute of Technology Guwahati, Guwahati – 781 039, Assam (India); Chakma, Sankar; Kumar, Peeush [Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati – 781 039, Assam (India); Mahanta, Pinakeswar [Center for Energy, Indian Institute of Technology Guwahati, Guwahati – 781 039, Assam (India); Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati – 781 039, Assam (India); Moholkar, Vijayanand S. [Center for Energy, Indian Institute of Technology Guwahati, Guwahati – 781 039, Assam (India); Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati – 781 039, Assam (India)
2013-07-01
Modeling of biomass gasification has been an active area of research for past two decades. In the published literature, three approaches have been adopted for the modeling of this process, viz. thermodynamic equilibrium, semi-equilibrium and kinetic. In this paper, we have attempted to present a comparative assessment of these three types of models for predicting outcome of the gasification process in a circulating fluidized bed gasifier. Two model biomass, viz. rice husk and wood particles, have been chosen for analysis, with gasification medium being air. Although the trends in molar composition, net yield and LHV of the producer gas predicted by three models are in concurrence, significant quantitative difference is seen in the results. Due to rather slow kinetics of char gasification and tar oxidation, carbon conversion achieved in single pass of biomass through the gasifier, calculated using kinetic model, is quite low, which adversely affects the yield and LHV of the producer gas. Although equilibrium and semi-equilibrium models reveal relative insensitivity of producer gas characteristics towards temperature, the kinetic model shows significant effect of temperature on LHV of the gas at low air ratios. Kinetic models also reveal volume of the gasifier to be an insignificant parameter, as the net yield and LHV of the gas resulting from 6 m and 10 m riser is same. On a whole, the analysis presented in this paper indicates that thermodynamic models are useful tools for quantitative assessment of the gasification process, while kinetic models provide physically more realistic picture.
Energy Technology Data Exchange (ETDEWEB)
Izzo, B.; Harrell, C.; Klein, M.T. [Univ. of Delaware, Newark, DE (United States); LaMarca, C. [E.I. du Pont de Nemours & Co., Wilmington, DE (United States)
1996-12-31
The reaction chemistry of acetonitrile and benzonitrile in High Temperature Water (HTW) was investigated. The reaction products were the associated amides and carboxylic acids. A kinetic model incorporating two autocatalytic steps captured the kinetics observed. The optimized rate constants highlighted differences in the reaction chemistry of aliphatic and aromatic nitrites at these reaction conditions. 6 refs., 3 figs., 2 tabs.
Seldam, C.A. ten; Groot, S.R. de
1952-01-01
From Jensen's and Gombás' modification of the statistical Thomas-Fermi atom model, a theory for compressed atoms is developed by changing the boundary conditions. Internal kinetic energy and polarizability of argon are calculated as functions of pressure. At 1000 atm. an internal kinetic energy of a
Acceleration of the KINETICS Integrated Dynamical/Chemical Computational Model Using MPI
Grossman, Max; Willacy, Karen; Allen, Mark
2011-01-01
Understanding the evolution of a planet's atmosphere not only provides a better theoretical understanding of planetary physics and the formation of planets, but also grants useful insight into Earth's own atmosphere. One of the tools used at JPL for the modeling of planetary atmospheres and protostellar disks is KINETICS. KINETICS can simulate years of complex dynamics and chemistry.
DEFF Research Database (Denmark)
Price, Jason Anthony; Nordblad, Mathias; Woodley, John;
2014-01-01
This paper demonstrates the added benefits of using uncertainty and sensitivity analysis in the kinetics of enzymatic biodiesel production. For this study, a kinetic model by Fedosov and co-workers is used. For the uncertainty analysis the Monte Carlo procedure was used to statistically quantify...
International Nuclear Information System (INIS)
Particle-in-cell (PIC) simulation method has been proved to be a good candidate to study the interactions between plasmas and radio-frequency waves. However, for waves in the lower hybrid range of frequencies, a full PIC simulation is not efficient due to its high computational cost. In this work, a gyro-kinetic electron and fully-kinetic ion (GeFi) particle simulation model is applied to study the propagations and mode conversion processes of lower hybrid waves (LHWs) in plasmas. With this method, the computational efficiency of LHW simulations is greatly increased by using a larger grid size and time step. The simulation results in the linear regime are validated by comparison with the linear theory. (magnetically confined plasma)
Kinetic modelling of nitrogen and organics removal in vertical and horizontal flow wetlands.
Saeed, Tanveer; Sun, Guangzhi
2011-05-01
This paper provides a comparative evaluation of the kinetic models that were developed to describe the biodegradation of nitrogen and organics removal in wetland systems. Reaction kinetics that were considered in the model development included first order kinetics, Monod and multiple Monod kinetics; these kinetics were combined with continuous-stirred tank reactor (CSTR) or plug flow pattern to produce equations to link inlet and outlet concentrations of each key pollutants across a single wetland. Using three statistical parameters, a critical evaluation of five potential models was made for vertical and horizontal flow wetlands. The results recommended the models that were developed based on Monod models, for predicting the removal of nitrogen and organics in a vertical and horizontal flow wetland system. No clear correlation was observed between influent BOD/COD values and kinetic coefficients of BOD(5) in VF and HF wetlands, illustrating that the removal of biodegradable organics was insensitive to the nature of organic matter. Higher effluent COD/TN values coincided with greater denitrification kinetic coefficients, signifying the dependency of denitrification on the availability of COD in VF wetland systems. In contrast, the trend was opposite in HF wetlands, indicating that availability of NO(3)-N was the main limiting step for nitrogen removal. Overall, the results suggested the possible application of the developed alternative predictive models, for understanding the complex biodegradation routes of nitrogen and organics removal in VF and HF wetland systems.
Energy Technology Data Exchange (ETDEWEB)
Salloum, Maher N.; Gharagozloo, Patricia E.
2013-10-01
Metal particle beds have recently become a major technique for hydrogen storage. In order to extract hydrogen from such beds, it is crucial to understand the decomposition kinetics of the metal hydride. We are interested in obtaining a a better understanding of the uranium hydride (UH3) decomposition kinetics. We first developed an empirical model by fitting data compiled from different experimental studies in the literature and quantified the uncertainty resulting from the scattered data. We found that the decomposition time range predicted by the obtained kinetics was in a good agreement with published experimental results. Secondly, we developed a physics based mathematical model to simulate the rate of hydrogen diffusion in a hydride particle during the decomposition. We used this model to simulate the decomposition of the particles for temperatures ranging from 300K to 1000K while propagating parametric uncertainty and evaluated the kinetics from the results. We compared the kinetics parameters derived from the empirical and physics based models and found that the uncertainty in the kinetics predicted by the physics based model covers the scattered experimental data. Finally, we used the physics-based kinetics parameters to simulate the effects of boundary resistances and powder morphological changes during decomposition in a continuum level model. We found that the species change within the bed occurring during the decomposition accelerates the hydrogen flow by increasing the bed permeability, while the pressure buildup and the thermal barrier forming at the wall significantly impede the hydrogen extraction.
DEFF Research Database (Denmark)
Malaguerra, Flavio; Chambon, Julie Claire Claudia; Bjerg, Poul Løgstrup;
2011-01-01
A fully kinetic biogeochemical model of sequential reductive dechlorination (SERD) occurring in conjunction with lactate and propionate fermentation, iron reduction, sulfate reduction, and methanogenesis was developed. Production and consumption of molecular hydrogen (H2) by microorganisms have...... been modeled using modified Michaelis–Menten kinetics and has been implemented in the geochemical code PHREEQC. The model have been calibrated using a Shuffled Complex Evolution Metropolis algorithm to observations of chlorinated solvents, organic acids, and H2 concentrations in laboratory batch...
Relations between the kinetic equation and the Langevin models in two-phase flow modelling
International Nuclear Information System (INIS)
The purpose of this paper is to discuss PDF and stochastic models which are used in two-phase flow modelling. The aim of the present analysis is essentially to try to determine relations and consistency between different models. It is first recalled that different approaches actually correspond to PDF models written either in terms of the process trajectories or in terms of the PDF itself. The main difference lies in the choice of the independent variables which are retained. Two particular models are studied, the Kinetic Equation and the Langevin Equation model. The latter uses a Langevin equation to model the fluid velocities seen along particle trajectories. The Langevin model is more general since it contains an additional variable. It is shown that, in certain cases, this variable can be summed up exactly to retrieve the Kinetic Equation model as a marginal PDF. A joint fluid and solid particle PDF which includes the characteristics of both phases is proposed at the end of the paper. (author)
Bordon, Jure; Moskon, Miha; Zimic, Nikolaj; Mraz, Miha
2015-01-01
Quantitative modelling of biological systems has become an indispensable computational approach in the design of novel and analysis of existing biological systems. However, kinetic data that describe the system's dynamics need to be known in order to obtain relevant results with the conventional modelling techniques. These data are often hard or even impossible to obtain. Here, we present a quantitative fuzzy logic modelling approach that is able to cope with unknown kinetic data and thus produce relevant results even though kinetic data are incomplete or only vaguely defined. Moreover, the approach can be used in the combination with the existing state-of-the-art quantitative modelling techniques only in certain parts of the system, i.e., where kinetic data are missing. The case study of the approach proposed here is performed on the model of three-gene repressilator. PMID:26451831
Bordon, Jure; Moskon, Miha; Zimic, Nikolaj; Mraz, Miha
2015-01-01
Quantitative modelling of biological systems has become an indispensable computational approach in the design of novel and analysis of existing biological systems. However, kinetic data that describe the system's dynamics need to be known in order to obtain relevant results with the conventional modelling techniques. These data are often hard or even impossible to obtain. Here, we present a quantitative fuzzy logic modelling approach that is able to cope with unknown kinetic data and thus produce relevant results even though kinetic data are incomplete or only vaguely defined. Moreover, the approach can be used in the combination with the existing state-of-the-art quantitative modelling techniques only in certain parts of the system, i.e., where kinetic data are missing. The case study of the approach proposed here is performed on the model of three-gene repressilator.
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A reduced chemical kinetic model (44 species and 72 reactions) for the homogeneous charge compression ignition (HCCI) combustion of n-heptane was optimized to improve its autoignition predictions under different engine operating conditions. The seven kinetic parameters of the optimized model were determined by using the combination of a micro-genetic algorithm optimization methodology and the SENKIN program of CHEMKIN chemical kinetics software package. The optimization was performed within the range of equivalence ratios 0.2-1.2, initial temperature 310-375 K and initial pressure 0.1-0.3 MPa. The engine simulations show that the optimized model agrees better with the detailed chemical kinetic model (544 species and 2 446 reactions) than the original model does.
Kotasidis, F. A.; Matthews, J. C.; Reader, A. J.; Angelis, G. I.; Zaidi, H.
2014-10-01
Parametric imaging in thoracic and abdominal PET can provide additional parameters more relevant to the pathophysiology of the system under study. However, dynamic data in the body are noisy due to the limiting counting statistics leading to suboptimal kinetic parameter estimates. Direct 4D image reconstruction algorithms can potentially improve kinetic parameter precision and accuracy in dynamic PET body imaging. However, construction of a common kinetic model is not always feasible and in contrast to post-reconstruction kinetic analysis, errors in poorly modelled regions may spatially propagate to regions which are well modelled. To reduce error propagation from erroneous model fits, we implement and evaluate a new approach to direct parameter estimation by incorporating a recently proposed kinetic modelling strategy within a direct 4D image reconstruction framework. The algorithm uses a secondary more general model to allow a less constrained model fit in regions where the kinetic model does not accurately describe the underlying kinetics. A portion of the residuals then is adaptively included back into the image whilst preserving the primary model characteristics in other well modelled regions using a penalty term that trades off the models. Using fully 4D simulations based on dynamic [15O]H2O datasets, we demonstrate reduction in propagation-related bias for all kinetic parameters. Under noisy conditions, reductions in bias due to propagation are obtained at the cost of increased noise, which in turn results in increased bias and variance of the kinetic parameters. This trade-off reflects the challenge of separating the residuals arising from poor kinetic modelling fits from the residuals arising purely from noise. Nonetheless, the overall root mean square error is reduced in most regions and parameters. Using the adaptive 4D image reconstruction improved model fits can be obtained in poorly modelled regions, leading to reduced errors potentially propagating
Modelling anaerobic biomass growth kinetics with a substrate threshold concentration
Ribes, J.; Keesman, K.J.; Spanjers, H.
2004-01-01
Abstract Many bacteria have been observed to stop growing below a certain substrate threshold concentration. In this study, a modification of the Monod kinetics expression has been proposed to take into account this substrate threshold concentration observed in bacterial growth. Besides the threshol
Calcite growth kinetics: Modeling the effect of solution stoichiometry
Wolthers, M.; Nehrke, G.; Gustafsson, J.P.; Van Cappellen, P.
2012-01-01
Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth rat
Isotope exchange kinetics in metal hydrides I : TPLUG model.
Energy Technology Data Exchange (ETDEWEB)
Larson, Rich; James, Scott Carlton; Nilson, Robert H.
2011-05-01
A one-dimensional isobaric reactor model is used to simulate hydrogen isotope exchange processes taking place during flow through a powdered palladium bed. This simple model is designed to serve primarily as a platform for the initial development of detailed chemical mechanisms that can then be refined with the aid of more complex reactor descriptions. The one-dimensional model is based on the Sandia in-house code TPLUG, which solves a transient set of governing equations including an overall mass balance for the gas phase, material balances for all of the gas-phase and surface species, and an ideal gas equation of state. An energy equation can also be solved if thermodynamic properties for all of the species involved are known. The code is coupled with the Chemkin package to facilitate the incorporation of arbitrary multistep reaction mechanisms into the simulations. This capability is used here to test and optimize a basic mechanism describing the surface chemistry at or near the interface between the gas phase and a palladium particle. The mechanism includes reversible dissociative adsorptions of the three gas-phase species on the particle surface as well as atomic migrations between the surface and the bulk. The migration steps are more general than those used previously in that they do not require simultaneous movement of two atoms in opposite directions; this makes possible the creation and destruction of bulk vacancies and thus allows the model to account for variations in the bulk stoichiometry with isotopic composition. The optimization code APPSPACK is used to adjust the mass-action rate constants so as to achieve the best possible fit to a given set of experimental data, subject to a set of rigorous thermodynamic constraints. When data for nearly isothermal and isobaric deuterium-to-hydrogen (D {yields} H) and hydrogen-to-deuterium (H {yields} D) exchanges are fitted simultaneously, results for the former are excellent, while those for the latter show
The models of cosmological inflation in the context of kinetic approximation
Fomin, I.
2016-07-01
In this work the building of models of cosmological inflation with approximate linear dependence of the scalar field kinetic energy on the state parameter is considered. The key parameters of cosmological perturbations are also calculated.
Analysis of Stability for Gas-Kinetic Non-Local Traffic Model
Institute of Scientific and Technical Information of China (English)
SUN Xi-Ming; DONG Yu-Jie
2006-01-01
@@ The gas-kinetic non-local traffic model is improved by taking into account the relative velocity of the correlated vehicles. The stability of different relaxation time modes is analytically investigated with the perturbation method.
Oxygen reduction kinetics on mixed conducting SOFC model cathodes
Energy Technology Data Exchange (ETDEWEB)
Baumann, F.S.
2006-07-01
The kinetics of the oxygen reduction reaction at the surface of mixed conducting solid oxide fuel cell (SOFC) cathodes is one of the main limiting factors to the performance of these promising systems. For ''realistic'' porous electrodes, however, it is usually very difficult to separate the influence of different resistive processes. Therefore, a suitable, geometrically well-defined model system was used in this work to enable an unambiguous distinction of individual electrochemical processes by means of impedance spectroscopy. The electrochemical measurements were performed on dense thin film microelectrodes, prepared by PLD and photolithography, of mixed conducting perovskite-type materials. The first part of the thesis consists of an extensive impedance spectroscopic investigation of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF) microelectrodes. An equivalent circuit was identified that describes the electrochemical properties of the model electrodes appropriately and enables an unambiguous interpretation of the measured impedance spectra. Hence, the dependencies of individual electrochemical processes such as the surface exchange reaction on a wide range of experimental parameters including temperature, dc bias and oxygen partial pressure could be studied. As a result, a comprehensive set of experimental data has been obtained, which was previously not available for a mixed conducting model system. In the course of the experiments on the dc bias dependence of the electrochemical processes a new and surprising effect was discovered: It could be shown that a short but strong dc polarisation of a LSCF microelectrode at high temperature improves its electrochemical performance with respect to the oxygen reduction reaction drastically. The electrochemical resistance associated with the oxygen surface exchange reaction, initially the dominant contribution to the total electrode resistance, can be reduced by two orders of magnitude. This &apos
GE SBWR stability analysis using TRAC-BF1 1-D kinetics model
International Nuclear Information System (INIS)
GE's simplified boiling water reactor, with its unique feature of using natural circulation to remove the heat from the reactor core, is a complicated dynamic system. Previous work by authors using the TRAC-BF1 code and a point kinetics model predicted that an SBWR may experience large amplitude power oscillation under certain low pressure and high power operating conditions. To further confirm the existence of this power oscillation and explore the dynamic spatial reactor power distribution, the TRAC-BF1 1-D kinetics model was used. The results show that an instability exists and the power oscillation starting time and maximum peak power are different from the point kinetics results
A hybrid kinetic-fluid model for solving the gas dynamics Boltzmann-BGK equation
Crouseilles, Nicolas; Degond, Pierre; Lemou, Mohammed
2004-01-01
International audience Our purpose s toderive a hybrid model for particles systems which combines a kinetic description of the fast particles with a fluid description of the thermal ones. Fats particles will be described through a collisional kinetic equation of Boltzmann-BGK type while thermal particles will be modeled by means of a system of a Euler type equations. A conservative numerical scheme is constructed and enables us to validate the approach on various numerical tests.
Bioconversion technologies of crude glycerol to value added industrial products
Directory of Open Access Journals (Sweden)
Vijay Kumar Garlapati
2016-03-01
Full Text Available Crude glycerol that is produced as the by-product from biodiesel, has to be effectively utilized to contribute to the viability of biodiesel. Crude glycerol in large amounts can pose a threat to the environment. Therefore, there is a need to convert this crude glycerol into valued added products using biotechnological processes, which brings new revenue to biodiesel producers. Crude glycerol can serve as a feedstock for biopolymers, poly unsaturated fatty acids, ethanol, hydrogen and n-butanol production and as a raw material for different value added industrial products. Hence, in this review we have presented different bioconversion technologies of glycerol to value added industrial products.
Chemical kinetic modeling of H{sub 2} applications
Energy Technology Data Exchange (ETDEWEB)
Westbrook, C.K.; Marinov, N.; Pitz, W.J.; Curran, H. [Lawrence Livermore National Lab., CA (United States)
1996-10-01
This project is intended to develop detailed and simplified kinetic reaction mechanisms for the combustion of practical systems fueled by hydrogen, and then to use those mechanisms to examine the performance, efficiency, pollutant emissions, and other characteristics of those systems. During the last year, a H2/NOx mechanism has been developed that gives much improved predictions of NOx emissions compared to experimental data. Preliminary chemical kinetic and equilibrium calculations have been performed in support of Br2-H2O experiments to be conducted at NREL. Hydrogen, hydrogen/methane and hydrogen/natural gas mixtures have been investigated in a knock-rating engine to assess their automotive knock characteristics. The authors are currently developing the simplified analog reaction mechanisms that are computationally simple, yet still reproduce many of the macroscopic features of flame propagation.
Institute of Scientific and Technical Information of China (English)
Haozhong HUANG; Wanhua SU
2008-01-01
The micro-genetic algorithm (μGA) as a highly effective optimization method, is applied to calibrate to a newly developed reduced chemical kinetic model (40 species and 62 reactions) for the homogeneous charge compression ignition (HCCI) combustion of n-heptane to improve its autoignition predictions for different engine operating conditions. The seven kinetic parameters of the calibrated model are determined using a combination of the Micro-Genetic Algorithm and the SENKIN program of CHEMKIN chemical kinetics software package. Simulation results show that the autoignition predictions of the calibrated model agree better with those of the detailed chemical kinetic model (544 species and 2 446 reactions) than the original model over the range of equivalence ratios from 0.1-1.3 and temperature from 300-3 000 K. The results of this study have demonstrated that the μGA is an effective tool to facilitate the calibration of a large number of kinetic parameters in a reduced kinetic model.
Experimental and Kinetic Modeling Study of 2-Methyl-2-Butene: Allylic Hydrocarbon Kinetics.
Westbrook, Charles K; Pitz, William J; Mehl, Marco; Glaude, Pierre-Alexandre; Herbinet, Olivier; Bax, Sarah; Battin-Leclerc, Frederique; Mathieu, Olivier; Petersen, Eric L; Bugler, John; Curran, Henry J
2015-07-16
Two experimental studies have been carried out on the oxidation of 2-methyl-2-butene, one measuring ignition delay times behind reflected shock waves in a stainless steel shock tube, and the other measuring fuel, intermediate, and product species mole fractions in a jet-stirred reactor (JSR). The shock tube ignition experiments were carried out at three different pressures, approximately 1.7, 11.2, and 31 atm, and at each pressure, fuel-lean (ϕ = 0.5), stoichiometric (ϕ = 1.0), and fuel-rich (ϕ = 2.0) mixtures were examined, with each fuel/oxygen mixture diluted in 99% Ar, for initial postshock temperatures between 1330 and 1730 K. The JSR experiments were performed at nearly atmospheric pressure (800 Torr), with stoichiometric fuel/oxygen mixtures with 0.01 mole fraction of 2M2B fuel, a residence time in the reactor of 1.5 s, and mole fractions of 36 different chemical species were measured over a temperature range from 600 to 1150 K. These JSR experiments represent the first such study reporting detailed species measurements for an unsaturated, branched hydrocarbon fuel larger than iso-butene. A detailed chemical kinetic reaction mechanism was developed to study the important reaction pathways in these experiments, with particular attention on the role played by allylic C-H bonds and allylic pentenyl radicals. The results show that, at high temperatures, this olefinic fuel reacts rapidly, similar to related alkane fuels, but the pronounced thermal stability of the allylic pentenyl species inhibits low temperature reactivity, so 2M2B does not produce "cool flames" or negative temperature coefficient behavior. The connections between olefin hydrocarbon fuels, resulting allylic fuel radicals, the resulting lack of low-temperature reactivity, and the gasoline engine concept of octane sensitivity are discussed. PMID:25822578
MACROSCOPIC KINETIC MODELS OF GLYCEROL BATCH FERMENTATION WITH OSMOTOLERANT YEAST
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
l introductionGlycerol production by fermentation has beenwidely investigated to meet the great commercialdemand in last decades and osmotolerant yeast wasthe microorganism studied most. To analyze thefermentation process more efficiently, a kinetic modelshould be established but little works about it werereported because of its complicated metabolism ofglycerol [1-3]. Batch fermentation experiment showedthat low glucose concentration in the latterfermentation stage resulted in decrease in both glucoseconsu...
Cell kinetic modelling and the chemotherapy of cancer
Knolle, Helmut
1988-01-01
During the last 30 years, many chemical compounds that are active against tumors have been discovered or developed. At the same time, new methods of testing drugs for cancer therapy have evolved. nefore 1964, drug testing on animal tumors was directed to observation of the incfease in life span of the host after a single dose. A new approach, in which the effects of multiple doses on the proliferation kinetics of the tumor in vivo as well as of cell lines in vitro are investigated, has been outlined by Skipper and his co-workers in a series of papers beginning in 1964 (Skipper, Schabel and Wilcox, 1964 and 1965). They also investigated the influence of the time schedule in the treatment of experimental tumors. Since the publication of those studies, cell population kinetics cannot be left out of any discussion of the rational basis of chemotherapy. When clinical oncologists began to apply cell kinetic concepts in practice about 15 years ago, the theoretical basis was still very poor, in spite of Skipper's pro...
Morin, José A.; Ibarra, Borja; Cao, Francisco J.
2016-05-01
Single-molecule manipulation experiments of molecular motors provide essential information about the rate and conformational changes of the steps of the reaction located along the manipulation coordinate. This information is not always sufficient to define a particular kinetic cycle. Recent single-molecule experiments with optical tweezers showed that the DNA unwinding activity of a Phi29 DNA polymerase mutant presents a complex pause behavior, which includes short and long pauses. Here we show that different kinetic models, considering different connections between the active and the pause states, can explain the experimental pause behavior. Both the two independent pause model and the two connected pause model are able to describe the pause behavior of a mutated Phi29 DNA polymerase observed in an optical tweezers single-molecule experiment. For the two independent pause model all parameters are fixed by the observed data, while for the more general two connected pause model there is a range of values of the parameters compatible with the observed data (which can be expressed in terms of two of the rates and their force dependencies). This general model includes models with indirect entry and exit to the long-pause state, and also models with cycling in both directions. Additionally, assuming that detailed balance is verified, which forbids cycling, this reduces the ranges of the values of the parameters (which can then be expressed in terms of one rate and its force dependency). The resulting model interpolates between the independent pause model and the indirect entry and exit to the long-pause state model
Application of Discrete Lumped Kinetic Modeling on Vacuum Gas Oil Hydrocracking
Institute of Scientific and Technical Information of China (English)
Han Longnian; Fang Xiangchen; Peng Chong; Zhao Tao
2013-01-01
The kinetic model of vacuum gas oil (VGO) hydrocracking based on discrete lumped approach was investigated, and some improvement was put forward at the same time in this article. A parallel reaction scheme to describe the conver-sion of VGO into products (gases, gasoline, and diesel) proposed by Orochko was used. The different experimental data were analyzed statistically and then the product distribution and kinetic parameters were simulated by available data. Fur-thermore, the kinetic parameters were correlated based on the feed property, reaction temperature, and catalyst activity. An optimization code in Matlab 2011b was written to ifne-tune these parameters. The model had a favorable ability to predict the product distribution and there was a good agreement between the model predictions and experiment data. Hence, the ki-netic parameters indeed had something to do with feed properties, reaction temperature and catalyst activity.
Kinetic modelling of tyre pyrolysis in a conical spouted bed reactor
Energy Technology Data Exchange (ETDEWEB)
Olazar, Martin; Lopez, Gartzen; Arabiourrutia, Miriam; Elordi, Gorka; Aguado, Roberto; Bilbao, Javier [University of the Basque Country, Faculty of Science and Technology, Department of Chemical Engineering, P.O. Box 644, E48080 Bilbao (Spain)
2008-01-15
A novel kinetic model has been proposed for the thermal pyrolysis of tyres. The model is based on a reaction scheme that considers an intermediate lump and parallel reactions for the formation of the different product lumps. Seven lumps have been taken, which are gas (C{sub 4}), non-aromatic liquid (C{sub 5}-C), aromatics (C), tar (C{sub 11+}), char (low grade carbon black), intermediate and the original tyre. The kinetic data have been obtained in a pilot plant provided with a conical spouted bed reactor. The inert gas used is nitrogen and the temperature has been varied from 425 to 610 C. Discontinuous runs have been carried out for obtaining the kinetic data, and the product stream has been analysed on-line at different reaction times, thereby monitoring the evolution with time of mass fraction of the different components. The kinetic model gives reasonable predictions for lump yields. (author)
Modelling fuel behaviour in a reactor park using fuel cycle kinetics
International Nuclear Information System (INIS)
In this thesis the theory of fuel cycle kinetics is re-examined. The fuel cycle kinetics theory is a powerful tool to describe the time-dependent fuel behaviour of large populations of nuclear reactors. The fuel cycle kinetics theory is based on the point kinetics theory and the principles of a reactor park. The point kinetics theory is a simplification of the space-, energy-and time-dependent diffusion balance equation to only a time-dependent equation. A reactor park is the description of the interconnections between a population of nuclear reactors with various designs. In the fuel cycle kinetics theory the point kinetics theory is used as a model to simplify space- energy- and time-dependent burn-up equations of the reactors in a reactor park to a set of only time-dependent equations, one for every reactor type. The fuel cycle kinetics theory is verified by means of a number of test cases. In the first test case the same symbiotic system is used as was used by Maudlin. There is no difference between the two obtained results. The second test case is that of only Fast Breeder Reactor, FBR, deployment. Here the result of the fuel cycle kinetics equation is checked against the result obtained from TRITON. TRITON is a module of the SCALE code system that is used for depletion analysis of 3-D reactor models. With the use of the pseudo-initial condition the results of the fuel cycle kinetics and TRITON calculations are almost identical. The pseudo-initial condition is a correction on the initial condition to adjust for neglecting the time dependency of the parameters in the fuel cycle kinetics equations. In the third case a symbiotic system of FBRs and Pressurised Water Reactors, PWRs, is researched. There is only a small difference in the asymptotic growth between the fuel cycle kinetics results and the TRITON results. In the last test case the same system of FBRs and PWRs is used to investigate two demanded asymptotic growths obtained from the upper and lower
Matsui, Yoshihiko; Ando, Naoya; Yoshida, Tomoaki; Kurotobi, Ryuji; Matsushita, Taku; Ohno, Koichi
2011-02-01
The capacity to adsorb natural organic matter (NOM) and polystyrene sulfonates (PSSs) on small particle-size activated carbon (super-powdered activated carbon, SPAC) is higher than that on larger particle-size activated carbon (powdered-activated carbon, PAC). Increased adsorption capacity is likely attributable to the larger external surface area because the NOM and PSS molecules do not completely penetrate the adsorbent particle; they preferentially adsorb near the outer surface of the particle. In this study, we propose a new isotherm equation, the Shell Adsorption Model (SAM), to explain the higher adsorption capacity on smaller adsorbent particles and to describe quantitatively adsorption isotherms of activated carbons of different particle sizes: PAC and SPAC. The SAM was verified with the experimental data of PSS adsorption kinetics as well as equilibrium. SAM successfully characterized PSS adsorption isotherm data for SPACs and PAC simultaneously with the same model parameters. When SAM was incorporated into an adsorption kinetic model, kinetic decay curves for PSSs adsorbing onto activated carbons of different particle sizes could be simultaneously described with a single kinetics parameter value. On the other hand, when SAM was not incorporated into such an adsorption kinetic model and instead isotherms were described by the Freundlich model, the kinetic decay curves were not well described. The success of the SAM further supports the adsorption mechanism of PSSs preferentially adsorbing near the outer surface of activated carbon particles. PMID:21172719
DEFF Research Database (Denmark)
Baty, Florent; Ritz, Christian; van Gestel, Arnoldus;
2016-01-01
BACKGROUND: The six-minute walk test (6MWT) is commonly used to quantify exercise capacity in patients with several cardio-pulmonary diseases. Oxygen uptake ([Formula: see text]O2) kinetics during 6MWT typically follow 3 distinct phases (rest, exercise, recovery) that can be modeled by nonlinear...... regression. Simultaneous modeling of multiple kinetics requires nonlinear mixed models methodology. To the best of our knowledge, no such curve-fitting approach has been used to analyze multiple [Formula: see text]O2 kinetics in both research and clinical practice so far. METHODS: In the present study, we...... describe functionality of the R package medrc that extends the framework of the commonly used packages drc and nlme and allows fitting nonlinear mixed effects models for automated nonlinear regression modeling. The methodology was applied to a data set including 6MWT [Formula: see text]O2 kinetics from 61...
Feisther, Vódice Amoroz; Ulson de Souza, Antônio Augusto; Trigueros, Daniela Estelita Goes; de Mello, Josiane Maria Muneronde; de Oliveira, Déborade; Guelli Ulson de Souza, Selene M A
2015-07-01
The biodegradation kinetics of BTX compounds (benzene, toluene, and xylene) individually and as mixtures was studied using models with different levels of sophistication. To compare the performance of the unstructured models applied in this work we used experimental data obtained here and some results published in the literature. The system description was based on the material balances of key components for batch operations, where the Monod and Andrews models were applied to predict the biodegradation of individual substrates. To simulate the biodegradation kinetics of substrate mixtures, models of substrate inhibition were applied along with the Sum Kinetics with Interaction Parameters (SKIP) models, where for two-component association toluene-xylene SKIP model presented better performance and for tri-component association benzene-toluene-xylene, the uncompetitive inhibition model was better. The kinetic parameters were estimated via a global search method known as Particle Swarm Optimization (PSO). The main result of this study is that the sophisticated biodegradation kinetics of BTX mixtures can be successfully described by applying the SKIP model, with the main advantage being the consideration of the substrate interactions. PMID:25627469
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.
Wang, Weicheng
2013-11-01
A chemical kinetic model has been developed for the transient stage of the continuous countercurrent hydrolysis of triglycerides to free fatty acids and glycerol. Departure functions and group contribution methods were applied to determine the equilibrium constants of the four reversible reactions in the kinetic model. Continuous countercurrent hydrolysis of canola oil in subcritical water was conducted experimentally in a lab-scale reactor over a range of temperatures and the concentrations of all neutral components were quantified. Several of the rate constants in the model were obtained by modeling this experimental data, with the remaining determined from calculated equilibrium constants. Some reactions not included in the present, or previous, hydrolysis modeling efforts were identified from glycerolysis kinetic studies and may explain the slight discrepancy between model and experiment. The rate constants determined in this paper indicate that diglycerides in the feedstock accelerate the transition from "emulsive hydrolysis" to "rapid hydrolysis". © 2013 Elsevier Ltd.
A kinetics modeling study on the inhibition of glucose on cellulosome of Clostridium thermocellum.
Zhang, Pengcheng; Wang, Buyun; Xiao, Qunfang; Wu, Shan
2015-08-01
A simplified kinetics model was built to study the inhibition of glucose on cellulosome of Clostridium thermocellum. Suitable reaction conditions were adopted to evaluate the model. The model was evaluated at different temperatures and further with various activated carbon additions as adsorbent for glucose. Investigation results revealed that the model could describe the hydrolysis kinetics of cellulose by cellulosome quite well. Glucose was found to be an inhibitor for cellulosome based on the kinetics analysis. Inhibition increased with the increase in temperature. Activated carbon as adsorbent could lower the inhibition. Parameters in the model were further discussed based on the experiment. The model might also be used to describe the strong inhibition of cellobiose on cellulosome. Saccharification of cellulose by both cellulosome and C. thermocellum could be enhanced efficiently by activated carbon addition.
Energy Technology Data Exchange (ETDEWEB)
Wang, Quan-De [College of Chemistry, Sichuan University, Chengdu (China); Wang, Jing-Bo; Li, Juan-Qin; Tan, Ning-Xin; Li, Xiang-Yuan [College of Chemical Engineering, Sichuan University, Chengdu (China)
2011-02-15
The initiation mechanisms and kinetics of pyrolysis and combustion of n-dodecane are investigated by using the reactive molecular dynamics (ReaxFF MD) simulation and chemical kinetic modeling. From ReaxFF MD simulations, we find the initiation mechanisms of pyrolysis of n-dodecane are mainly through two pathways, (1) the cleavage of C-C bond to form smaller hydrocarbon radicals, and (2) the dehydrogenation reaction to form an H radical and the corresponding n-C{sub 12}H{sub 25} radical. Another pathway is the H-abstraction reactions by small radicals including H, CH{sub 3}, and C{sub 2}H{sub 5}, which are the products after the initiation reaction of n-dodecane pyrolysis. ReaxFF MD simulations lead to reasonable Arrhenius parameters compared with experimental results based on first-order kinetic analysis of n-dodecane pyrolysis. The density/pressure effects on the pyrolysis of n-dodecane are also analyzed. By appropriate mapping of the length and time from macroscopic kinetic modeling to ReaxFF MD, a simple comparison of the conversion of n-dodecane from ReaxFF MD simulations and that from kinetic modeling is performed. In addition, the oxidation of n-dodecane is studied by ReaxFF MD simulations. We find that formaldehyde molecule is an important intermediate in the oxidation of n-dodecane, which has been confirmed by kinetic modeling, and ReaxFF leads to reasonable reaction pathways for the oxidation of n-dodecane. These results indicate that ReaxFF MD simulations can give an atomistic description of the initiation mechanism and product distributions of pyrolysis and combustion for hydrocarbon fuels, and can be further used to provide molecular based robust kinetic reaction mechanism for chemical kinetic modeling of hydrocarbon fuels. (author)
Evaluation of fungal potentiality for bioconversion of domestic wastewater sludge
Institute of Scientific and Technical Information of China (English)
Md. Zahangir Alam; A. Fakhru'l-Razi; Abul H. Molla
2004-01-01
This study was undertaken to screen the filamentous fungi isolated from its relevant habitats(wastewater, sewage sludge and sludge cake) for the bioconversion of domestic wastewater sludge. A total of 35 fungal strains were tested against wastewater sludge (total suspended solids, TSS 1%-5% w/w) to evaluate its potentiality for enhancing the biodegradability and dewaterability using liquid state bioconversion(LSB) process. The strains were divided into five groups i. e. Penicillium, Aspergillus, Trichoderma, Basidiomycete and Miscellaneous, respectively. The strains WWZP1003, SCahmA103, SCahmT105 and PC-9 among their respective groups of Penicillium,Aspergillus, Trichoderma and Basidiomycete played potential roles in terms of separation (formation of pellets/flocs/filaments ),biodegradation(removal of COD) and filtration(filterability) of treated domestic wastewater sludge. The Miscellaneous group was not considered due to its unsatisfactory results as compared to the other groups. The pH value was also influenced by the microbial treatment during fermentation process. The filterability of treated sludge was improved by fungal treatment, and lowest filtration time was recorded for the strain WWZP1003 and SCahmA103 of Penicillium and Aspergillus groups respectively compared with other strains.
Bioconversion of Birch Wood Hemicellulose Hydrolyzate to Xylitol.
Miura, Masahiro; Shimotori, Yasutaka; Nakatani, Hisayuki; Harada, Akira; Aoyama, Masakazu
2015-06-01
A sugar solution containing 42.9 g l(-1) of xylose was prepared from the wood of Japanese white birch (Betula platyphylla var. japonica) by hydrolysis with 3 % sulfuric acid with a liquor-to-solid ratio of 4 (g g(-1)) at 120 °C for 1 h. During the acid hydrolysis, undesirable by-products were generated, such as acetic acid, furfural, and low-molecular-weight phenols, which inhibit bioconversion of xylose to xylitol. These inhibitors were successfully removed from the hydrolyzate by sorption onto a steam-activated charcoal followed by treatment with an anion exchange resin. Bioconversion of the detoxified hydrolyzate to xylitol by the yeast Candida magnoliae was investigated under the microaerobic conditions. The oxygen transfer rate (OTR) varied from 9.6 to 22.3 mmol O2 l(-1) h(-1). The best fermentative performance of C. magnoliae in the birch wood hydrolyzate (xylitol yield 0.74 g xylitol g xylose(-1); volumetric productivity 1.0 g l(-1) h(-1)) was obtained at the OTR of 12.6 mmol O2 l(-1) h(-1). PMID:25894947
HYGROSCOPIC MOISTURE SORPTION KINETICS MODELING OF CORN STOVER AND ITS FRACTIONS
Energy Technology Data Exchange (ETDEWEB)
Igathinathane, C. [Mississippi State University (MSU); Pordesimo, L. O. [Mississippi State University (MSU); Womac, A.R. [University of Tennessee; Sokhansanj, Shahabaddine [ORNL
2009-01-01
Corn stover, a major crop-based lignocellulosic biomass feedstock, is required to be at an optimum moisture content for efficient bioconversion processes. Environmental conditions surrounding corn stover, as in storage facilities, affect its moisture due to hygroscopic sorption or desorption. The measurement and modeling of sorption characteristics of corn stover and its leaf, husk, and stalk fractions are useful from utilization and storage standpoints, hence investigated in this article. A benchtop low-temperature humidity chamber provided the test environments of 20 C, 30 C, and 40 C at a constant 95% relative humidity. Measured sorption characteristics with three replications for each fraction were obtained from instantaneous sample masses and initial moisture contents. Observed sorption characteristics were fitted using exponential, Page, and Peleg models. Corn stover fractions displayed a rapid initial moisture uptake followed by a slower sorption rates and eventually becoming almost asymptotic after 25 h. Sorption characteristics of all corn stover fractions were significantly different (P < 0.0001) but not the effect of temperature (P > 0.05) on these fractions. The initial 30 min of sorption was found to be critical due to peak rates of sorption from storage, handling, and processing standpoints. The Page and Peleg models had comparable performance fitting the sorption curves (R2 = 0.995), however the exponential model (R2 = 0.91) was not found suitable because of patterned residuals. The Arrhenius type relationship (P < 0.05; R2 = 0.80) explained the temperature variation of the fitted sorption model parameters. The Peleg model fitted constants, among the sorption models studied, had the best fit (R2 = 0.93) with the Arrhenius relationship. A developed method of mass proportion, involving individual corn stover fraction dry matter ratios, predicted the whole corn stover sorption characteristics from that of its individual fractions. Sorption
Kinetic modelling of the demineralization of shrimp exoskeleton using citric acid
Alewo Opuada AMEH; Muhammed Tijani ISA; David ABUTU; Alibaba DANLAMI
2014-01-01
Citric acid was used in the demineralization of shrimp exoskeleton and the kinetics of the demineralization process was studied. Kinetic data was obtained by demineralisation using five acid concentrations (0.1, 0.2, 0.3, 0.4 and 0.5M). The obtained kinetic data were fitted to the shrinking core model for fluid particle reactions. The concentration of calcium was found to decrease with time. For all acid concentrations considered, the best predictive mechanism for the demineralization process...
Kinetics of the iron α -ɛ phase transition at high-strain rates: Experiment and model
Amadou, N.; de Resseguier, T.; Brambrink, E.; Vinci, T.; Benuzzi-Mounaix, A.; Huser, G.; Morard, G.; Guyot, F.; Miyanishi, K.; Ozaki, N.; Kodama, R.; Koenig, M.
2016-06-01
In this article, we investigate the kinetics of the iron α -ɛ transition under laser-driven ramp compression for deformation rates ranging from 3 to 9 ×107s-1 . As in previous work, we observe a plateau in the rear surface velocity profile at the transition. With increasing deformation rate the transition onset pressure raises from 11 to 25 GPa, while the plateau duration decreases. These kinetic effects are well reproduced by an Avrami-type kinetics model of nucleation and growth with a constant, nanosecond scale completion time, which suggests an isokinetic regime over the explored range of strain rates.
KINETIC MODELS STUDY OF HYDRODESULPHURIZATION VACUUM DISTILLATE REACTION
AbdulMunem A. Karim
2013-01-01
This study deals with kinetics of hydrodesulphurization (HDS) reaction of vacuum gas oil (611-833) K which was distillated from Kirkuk crude oil and which was obtained by blending the fractions, light vacuum gas oil (611 - 650) K, medium vacuum gas oil (650-690) K, heavy vacuum gas oil (690-727) K and very heavy vacuum gas oil (727-833) K. The vacuum gas oil was hydrotreated on a commercial cobalt-molybdenum alumina catalyst presulfied at specified conditions in a laboratory trickle bed...
Mean-field-like behavior of the generalized voter-model-class kinetic Ising model
Krause, Sebastian M; Bornholdt, Stefan; 10.1103/PhysRevE.85.031126
2012-01-01
We analyze a kinetic Ising model with suppressed bulk noise which is a prominent representative of the generalized voter model phase transition. On the one hand we discuss the model in the context of social systems, and opinion formation in the presence of a tunable social temperature. On the other hand we characterize the abrupt phase transition. The system shows non-equilibrium dynamics in the presence of absorbing states. We slightly change the system to get a stationary state model variant exhibiting the same kind of phase transition. Using a Fokker-Planck description and comparing to mean field calculations, we investigate the phase transition, finite size effects and the effect of the absorbing states resulting in a dynamic slowing down.
Breit, Marc; Netzer, Michael; Weinberger, Klaus M; Baumgartner, Christian
2015-08-01
The objectives of this work were the classification of dynamic metabolic biomarker candidates and the modeling and characterization of kinetic regulatory mechanisms in human metabolism with response to external perturbations by physical activity. Longitudinal metabolic concentration data of 47 individuals from 4 different groups were examined, obtained from a cycle ergometry cohort study. In total, 110 metabolites (within the classes of acylcarnitines, amino acids, and sugars) were measured through a targeted metabolomics approach, combining tandem mass spectrometry (MS/MS) with the concept of stable isotope dilution (SID) for metabolite quantitation. Biomarker candidates were selected by combined analysis of maximum fold changes (MFCs) in concentrations and P-values resulting from statistical hypothesis testing. Characteristic kinetic signatures were identified through a mathematical modeling approach utilizing polynomial fitting. Modeled kinetic signatures were analyzed for groups with similar behavior by applying hierarchical cluster analysis. Kinetic shape templates were characterized, defining different forms of basic kinetic response patterns, such as sustained, early, late, and other forms, that can be used for metabolite classification. Acetylcarnitine (C2), showing a late response pattern and having the highest values in MFC and statistical significance, was classified as late marker and ranked as strong predictor (MFC = 1.97, P modeling approach demonstrates high potential for dynamic biomarker identification and the investigation of kinetic mechanisms in disease or pharmacodynamics studies using MS data from longitudinal cohort studies.
Institute of Scientific and Technical Information of China (English)
Ping Ao; Lik Wee Lee; Mary E. Lidstrom; Lan Yin; Xiaomei Zhu
2008-01-01
Here we report a systematic method for constructing a large scale kinetic metabolic model and its initial application to the modeling of central metabolism of Methylobacterium extorquens AM1, a methylotrophic and environmental important bacterium. Its central metabolic network includes formaldehyde metabolism, serine cycle, citric acid cycle, pentose phosphate pathway, ghiconeogensis, PHB synthesis and acetyl-CoA conversion pathway, respiration and energy metabolism. Through a systematic and consistent procedure of finding a set of parameters in the physiological range we overcome an outstanding difficulty in large scale kinetic modeling: the requirement for a massive number of enzymatic reaction parameters. We are able to construct the kinetic model based on general biological considerations and incomplete experimental kinetic parameters. Our method consists of the following major steps: 1) using a generic enzymatic rate equation to reduce the number of enzymatic parameters to a minimum set while still preserving their characteristics; 2) using a set of steady state fluxes and metabolite concenwations in the physiological range as the expected output steady state fluxes and metabolite concentrations for the kinetic model to restrict the parametric space of enzymatic reactions; 3) choosing enzyme constants K's and K'eqs optimized for reactions under physiological concentrations, if their experimental values are unknown; 4) for models which do not cover the entire metabolic network of the organisms, designing a dynamical exchange for the coupling between the metabolism represented in the model and the rest not included.
Ignatyev, Yu G
2010-01-01
A complete model of baryon production in an expanding, primordially symmetric hot Universe is constructed in the framework of general-relativistic kinetic theory. In this model specific model for a baryon is calculated and graphs of the value dependence are constructed.
Kinetic limits for pair-interaction driven master equations and biological swarm models
Carlen, Eric; Wennberg, Bernt
2011-01-01
We consider a class of stochastic processes modeling binary interactions in an N-particle system. Examples of such systems can be found in the modeling of biological swarms. They lead to the definition of a class of master equations that we call pair interaction driven master equations. We prove a propagation of chaos result for this class of master equations which generalizes Mark Kac's well know result for the Kac model in kinetic theory. We use this result to study kinetic limits for two biological swarm models. We show that propagation of chaos may be lost at large times and we exhibit an example where the invariant density is not chaotic.
Continuum Kinetic Modeling of the Tokamak Plasma Edge
Dorf, Mikhail
2015-11-01
The problem of edge plasma transport provides substantial challenges for analytical or numerical analysis due to (a) complex magnetic geometry including both open and closed magnetic field lines B, (b) steep radial gradients comparable to ion drift-orbit excursions, and (c) a variation in the collision mean-free path along B from long to short compared to the magnetic connection length. Here, the first 4D continuum drift-kinetic transport simulations that span the magnetic separatrix of a tokamak are presented, motivated in part by the success of continuum kinetic codes for core physics and in part by the potential for high accuracy. The calculations include fully-nonlinear Fokker-Plank collisions and electrostatic potential variations. The problem of intrinsic toroidal rotation driven by ion orbit loss is addressed in detail. The code, COGENT, developed by the Edge Simulation Laboratory collaboration, is distinguished by a fourth-order finite-volume discretization combined with mapped multiblock grid technology to handle the strong anisotropy of plasma transport and the complex magnetic X-point divertor geometry with high accuracy. Previously, successful performance of high-order algorithms has been demonstrated in a simpler closed magnetic-flux-surface geometry for the problems of neoclassical transport and collisionless relaxation of geodesic acoustic modes in a tokamak pedestal, including the effects of a strong radial electric field under H-mode conditions. Work performed for USDOE, at LLNL under contract DE-AC52-07NA27344.
Rahman, Nafisur; Khan, Sumaiya
2014-01-01
Kinetic methods for accurate determination of nortriptyline hydrochloride have been described. The methods are based on the oxidation of nortriptyline hydrochloride with KMnO4 in acidic and basic media. In acidic medium, the decrease in absorbance at 525.5 nm and in basic medium, the increase in absorbance at 608.5 nm were measured as a function of time. The variables affecting the reactions were carefully investigated and optimised. Kinetic models such as initial rate, rate constant, variabl...
International Nuclear Information System (INIS)
D.N. Zubarev's method of non-equilibrium statistical operator is applied to problems of relativistic kinetic theory. Within this method, a generalized relativistic quantum kinetic equation with collision integrals of the first and second orders in the coupling constant is derived. It is shown that this result holds valid in the case of gauge invariant theories as well. An advantage of the developed approach is exemplified by models of relativistic nuclear matter. (orig.)
A model for lignin alteration - Part I: A kinetic reaction-network model
Payne, D.F.; Ortoleva, P.J.
2001-01-01
A new quantitative model is presented which simulates the maturation of lignin-derived sedimentary organic matter under geologic conditions. In this model, compositionally specific reactants evolve to specific intermediate and mobile products through balanced, nth order processes, by way of a network of sequential and parallel reactions. The chemical kinetic approach is based primarily on published observed structural transformations of naturally matured, lignin-derived, sedimentary organic matter. Assuming that Upper Cretaceous Williams Fork coal in the Piceance Basin is primarily lignin-derived, the model is calibrated for the Multi-Well Experiment(MWX) Site in this basin. This kind of approach may be applied to other selectively preserved chemical components of sedimentary organic matter. ?? 2001 Elsevier Science Ltd. All rights reserved.
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.
Explicit equilibria in a kinetic model of gambling
Bassetti, F.; Toscani, G.
2010-06-01
We introduce and discuss a nonlinear kinetic equation of Boltzmann type which describes the evolution of wealth in a pure gambling process, where the entire sum of wealths of two agents is up for gambling, and randomly shared between the agents. For this equation the analytical form of the steady states is found for various realizations of the random fraction of the sum which is shared to the agents. Among others, the exponential distribution appears as steady state in case of a uniformly distributed random fraction, while Gamma distribution appears for a random fraction which is Beta distributed. The case in which the gambling game is only conservative-in-the-mean is shown to lead to an explicit heavy tailed distribution.
Kinetic Modeling of Plasma Methane Conversion Using Gliding Arc
Institute of Scientific and Technical Information of China (English)
Antonius Indarto; Jae-Wook Choi; Hwaung Lee; Hyung Keun Song
2005-01-01
Plasma methane (CH4) conversion in gliding arc discharge was examined. The result data of experiments regarding the performance of gliding arc discharge were presented in this paper. A simulation which is consisted some chemical kinetic mechanisms has been provided to analyze and describe the plasma process. The effect of total gas flow rate and input frequency refers to power consumption have been studied to evaluate the performance of gliding arc plasma system and the reaction mechanism of decomposition.Experiment results indicated that the maximum conversion of CH4 reached 50% at the total gas flow rate of 1 L/min. The plasma reaction was occurred at the atmospheric pressure and the main products were C (solid), hydrogen, and acetylene (C2H2). The plasma reaction of methane conversion was exothermic reaction which increased the product stream temperature around 30-50 ℃.
Kinetic Monte Carlo modelling of neutron irradiation damage in iron
Energy Technology Data Exchange (ETDEWEB)
Gamez, L. [Instituto de Fusion Nuclear, UPM, Madrid (Spain); Departamento de Fisica Aplicada, ETSII, UPM, Madrid (Spain)], E-mail: linarejos.gamez@upm.es; Martinez, E. [Instituto de Fusion Nuclear, UPM, Madrid (Spain); Lawrence Livermore National Laboratory, LLNL, CA 94550 (United States); Perlado, J.M.; Cepas, P. [Instituto de Fusion Nuclear, UPM, Madrid (Spain); Caturla, M.J. [Departamento de Fisica Aplicada, Universidad de Alicante, Alicante (Spain); Victoria, M. [Instituto de Fusion Nuclear, UPM, Madrid (Spain); Marian, J. [Lawrence Livermore National Laboratory, LLNL, CA 94550 (United States); Arevalo, C. [Instituto de Fusion Nuclear, UPM, Madrid (Spain); Hernandez, M.; Gomez, D. [CIEMAT, Madrid (Spain)
2007-10-15
Ferritic steels (FeCr based alloys) are key materials needed to fulfill the requirements expected in future nuclear fusion facilities, both for magnetic and inertial confinement, and advanced fission reactors (GIV) and transmutation systems. Research in such field is actually a critical aspect in the European research program and abroad. Experimental and multiscale simulation methodologies are going hand by hand in increasing the knowledge of materials performance. At DENIM, it is progressing in some specific part of the well-linked simulation methodology both for defects energetics and diffusion, and for dislocation dynamics. In this study, results obtained from kinetic Monte Carlo simulations of neutron irradiated Fe under different conditions are presented, using modified ad hoc parameters. A significant agreement with experimental measurements has been found for some of the parameterization and mechanisms considered. The results of these simulations are discussed and compared with previous calculations.
Energy Technology Data Exchange (ETDEWEB)
Njikam, Eloh, E-mail: ennjikam@alaska.edu [Department of Civil and Environmental Engineering, University of Alaska Fairbanks, P.O. Box 755900, Fairbanks, AK 99775 (United States); Schiewer, Silke, E-mail: sschiewer@alaska.edu [Department of Civil and Environmental Engineering, University of Alaska Fairbanks, P.O. Box 755900, Fairbanks, AK 99775 (United States)
2012-04-30
Graphical abstract: Cadmium was completely and quickly desorbed from grapefruit peels using 0.01 M HNO{sub 3}. The kinetics followed a novel 1st or 2nd order kinetic model, related to the remaining metal bound as the rate-determining reactant concentration. For 0.001 M HNO{sub 3}, desorption was incomplete and the model fit less perfect. Highlights: Black-Right-Pointing-Pointer Metal desorption was over 90% complete within 50 min for most desorbents. Black-Right-Pointing-Pointer Models for biosorbent desorption kinetics were developed. Black-Right-Pointing-Pointer Desorption kinetics best fit a novel first-order model related to remaining metal bound. Black-Right-Pointing-Pointer Cd uptake after desorption by HNO{sub 3} was similar to the original uptake. Black-Right-Pointing-Pointer The optimal desorbent was 0.1 or 0.01 M acid, being fast, efficient and cheap. - Abstract: Citrus peel biosorbents are efficient in removing heavy metals from wastewater. Heavy metal recovery and sorbent regeneration are important for the financial competitiveness of biosorption with other processes. The desorbing agents HNO{sub 3}, NaNO{sub 3}, Ca(NO{sub 3}){sub 2}, EDTA, S, S-EDDS, and Na-Citrate were studied at different concentrations to optimize cadmium elution from orange or grapefruit peels. In most cases, desorption was fast, being over 90% complete within 50 min. However sodium nitrate and 0.001 M nitric acid were less efficient. Several new models for desorption kinetics were developed. While zero-, first- and second-order kinetics are commonly applied for modeling adsorption kinetics, the present study adapts these models to describe desorption kinetics. The proposed models relate to the number of metal-filled binding sites as the rate-determining reactant concentration. A model based on first order kinetics with respect to the remaining metal bound performed best. Cd bound in subsequent adsorption after desorption was similar to the original amount bound for desorption by
Effect of wall growth on the kinetic modeling of nitrite oxidation in a CSTR.
Dokianakis, Spiros N; Kornaros, Michael; Lyberatos, Gerasimos
2006-03-01
A simple kinetic model was developed for describing nitrite oxidation by autotrophic aerobic nitrifiers in a continuous stirred tank reactor (CSTR), in which mixed (suspended and attached) growth conditions prevail. The CSTR system was operated under conditions of constant nitrite feed concentration and varying volumetric flow rates. Experimental data from steady-state conditions in the CSTR system and from batch experiments were used for the determination of the model's kinetic parameters. Model predictions were verified against experimental data obtained under transient operating conditions, when volumetric flow rate and nitrite feed concentration disturbances were imposed on the CSTR. The presented kinetic modeling procedure is quite simple and general and therefore can also be applied to other mixed growth biological systems.
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.
Mathematical Model of Sorption Kinetics of Crude Oil by Rubber Particles from Scrap Tyres
Directory of Open Access Journals (Sweden)
Felix A. AISIEN
2011-06-01
Full Text Available This paper present an insight into how rubber particles from scrap tyres can be utilized to clean up oil spillages as well as how the process of sorption of crude oil by rubber particles can be stimulated based on sorption kinetics. Crude oil sorption tests using recycled rubber particles (a model absorbent were designed for investigating crude oil concentration profiles. The model based on a linear driving force (LDF was developed using a set of experimental data and multiple regression analysis. The crude oil sorption performance tests were conducted under various operating conditions by varying parameters such as rubber particle size and absorption temperature. The predictive capacity of the kinetic model was evaluated under conditions significantly different from those that have already been measured. The experimental results obtained previously were correlated with the first order sorption kinetics model developed. The results showed that the first order kinetics model accurately correlate the experimental data generated. Also, satisfactory results were obtained from simulation of other operating conditions; hence the crude oil sorption kinetics is first order.
Comparison of the kinetics of different Markov models for ligand binding under varying conditions
Martini, Johannes W. R.; Habeck, Michael
2015-03-01
We recently derived a Markov model for macromolecular ligand binding dynamics from few physical assumptions and showed that its stationary distribution is the grand canonical ensemble [J. W. R. Martini, M. Habeck, and M. Schlather, J. Math. Chem. 52, 665 (2014)]. The transition probabilities of the proposed Markov process define a particular Glauber dynamics and have some similarity to the Metropolis-Hastings algorithm. Here, we illustrate that this model is the stochastic analog of (pseudo) rate equations and the corresponding system of differential equations. Moreover, it can be viewed as a limiting case of general stochastic simulations of chemical kinetics. Thus, the model links stochastic and deterministic approaches as well as kinetics and equilibrium described by the grand canonical ensemble. We demonstrate that the family of transition matrices of our model, parameterized by temperature and ligand activity, generates ligand binding kinetics that respond to changes in these parameters in a qualitatively similar way as experimentally observed kinetics. In contrast, neither the Metropolis-Hastings algorithm nor the Glauber heat bath reflects changes in the external conditions correctly. Both converge rapidly to the stationary distribution, which is advantageous when the major interest is in the equilibrium state, but fail to describe the kinetics of ligand binding realistically. To simulate cellular processes that involve the reversible stochastic binding of multiple factors, our pseudo rate equation model should therefore be preferred to the Metropolis-Hastings algorithm and the Glauber heat bath, if the stationary distribution is not of only interest.
A model for precipitation kinetics and hardening in Al-Cu-Mg alloys
I N Khan; Starink, M.J.; Yan, J.L.
2008-01-01
A physically-based numerical model is developed to predict the microstructural evolution and strengthening in Al Cu Mg alloys during isothermal treatments. The modelling of the formation kinetics of the precipitates is based on the Kampmann and Wagner model. The strengthening by the shearable Cu:Mg co clusters is modelled on the basis of modulus strengthening mechanism and the strengthening by the non-shearable S phase precipitates is based on the Orowan looping mechanism. The model predictio...
Mathematical modelling of thermal and kinetic phenomena in electron-beam technologies
Knyazeva, A. G.; Pobol, I. L.; Demidov, V. N.
2016-07-01
The article presents a scheme for constructing models using kinetic laws for additional parameters. The work describes the example of the model of electro-beam treatment of a material with a coating. The study uses the simple kinetic law for powder layer evolution due to shrinkage. The model takes into account the melting of powder layer and substrate. The numerical solution gives the temperature field, evolution of the molten pool, the heat affected zone and the surface relief for different moments of time. The results depend on the treatment rate and electron beam energy.
Kinetic limits for pair-interaction driven master equations and biological swarm models
Carlen, Eric; Degond, Pierre; Wennberg, Bernt
2011-01-01
We consider a class of stochastic processes modeling binary interactions in an N-particle system. Examples of such systems can be found in the modeling of biological swarms. They lead to the definition of a class of master equations that we call pair interaction driven master equations. We prove a propagation of chaos result for this class of master equations which generalizes Mark Kac's well know result for the Kac model in kinetic theory. We use this result to study kinetic limits for two b...
Model-fitting approach to kinetic analysis of non-isothermal oxidation of molybdenite
International Nuclear Information System (INIS)
The kinetics of molybdenite oxidation was studied by non-isothermal TGA-DTA with heating rate 5degC.min-1. The model-fitting kinetic approach applied to TGA data. The Coats-Redfern method used of model fitting. The popular model-fitting gives excellent fit non-isothermal data in chemically controlled regime. The apparent activation energy was determined to be about 34.2 kcalmol-1 With pre-exponential factor about 108 sec-1 for extent of reaction less than 0.5
Kinetic model for torrefaction of wood chips in a pilot-scale continuous reactor
DEFF Research Database (Denmark)
Shang, Lei; Ahrenfeldt, Jesper; Holm, Jens Kai;
2014-01-01
the temperature along the reactor and the biomass feeding rate in combination with the kinetic parameters obtained from the tests in the TGA. Together with results from a laboratory scale, batch torrefaction reactor that was used to determine the higher heating value (HHV) and mass loss (y) of the same material......Torrefaction is a mild thermal treatment (200-300 °C) in an inert atmosphere, known to increase the energy density of biomass by evaporation of water and a proportion of the volatiles. In this work a "two-step reaction in series" model was used to describe the thermal degradation kinetics of pine...... wood. The kinetic parameters were determined using a thermogravimetric analyzer (TGA) and the mass loss during the initial heating period was taken into account when deriving the kinetic parameters. It was shown that the experimental results at different heating rates (10-50 °C min-1) are in good...
Parameter Estimates in Differential Equation Models for Chemical Kinetics
Winkel, Brian
2011-01-01
We discuss the need for devoting time in differential equations courses to modelling and the completion of the modelling process with efforts to estimate the parameters in the models using data. We estimate the parameters present in several differential equation models of chemical reactions of order n, where n = 0, 1, 2, and apply more general…
Systematic identification of crystallization kinetics within a generic modelling framework
DEFF Research Database (Denmark)
Abdul Samad, Noor Asma Fazli Bin; Meisler, Kresten Troelstrup; Gernaey, Krist;
2012-01-01
A systematic development of constitutive models within a generic modelling framework has been developed for use in design, analysis and simulation of crystallization operations. The framework contains a tool for model identification connected with a generic crystallizer modelling tool-box, a tool...
Wang, Dahui; Ju, Xiaomin; Zhang, Gaochuan; Wang, Donghua; Wei, Gongyuan
2016-10-01
The effects of mineral salts on pullulan production by bioconversion using whole cells of Aureobasidium pullulans CCTCC M 2012259 as the catalyst were investigated. Copper sulfate (CuSO4) improved pullulan production by 36.2% and 42.3% when added at the optimum concentration of 0.2mg/L to the bioconversion broth or seed medium, respectively, as compared with controls without CuSO4 addition. Pullulan production was further enhanced when CuSO4 was added to both seed medium and bioconversion broth simultaneously. In order to probe the mechanism of CuSO4 improvement, cell viability, membrane integrity, intracellular adenosine triphosphate (ATP) levels and the activities of key enzymes involved in pullulan biosynthesis were determined. As a result, CuSO4 increased the activities of key biosynthetic enzymes, maintained intracellular ATP at a higher level, and accelerated the rate of pullulan secretion, all of which contributed to improved pullulan production by bioconversion.
Kinetic models for detection of toxicity in a microbial fuel cell based biosensor
Stein, N.E.; Keesman, K.J.; Hamelers, H.V.M.; Straten, van G.
2011-01-01
Currently available models describing microbial fuel cell (MFC) polarization curves, do not describe the effect of the presence of toxic components. A bioelectrochemical model combined with enzyme inhibition kinetics, that describes the polarization curve of an MFC-based biosensor, was modified to d
A kinetic model for iron based mineral matter transformations in coal combustion environment
Energy Technology Data Exchange (ETDEWEB)
Bozic, O.; Leithner, R. [Technische Univ., Braunschweig (Germany). Inst. fuer Waerme und Brennstofftechnik
1997-12-31
It is a preliminary report about the developement of a kinetic model for describing transformations of pyrite, hematite and ironcarbonate in ash particle under conditions of high temperature and oxidizing/reducing environment. The model also includes, in presence of other oxide components as CaO, MgO and Al{sub 2}O{sub 3} in the ash particle and under condition of reducing environment, transformations in calciumferrit, magnesioferrit and hercynit respectively. In this phase of the model development, connections between ironoxide and silicate complex are considered through isolated examples (for ex. fayalite). In the course of transformation of mentioned mineral components different processes occur: chemical reactions (exothermic or endothermic), diffusion (surface-, volume- or Knudsen-diffusion), phase change/transformation (melting, amorph solidification, cristallization, decomposition) which model takes in consideration. The mathematical model includes a system of equations for transformations of 15 solid ash components. Existing literature data on transformations of mineral components into ash were used to establish the basis for this kinetic model. The program determines the process type and kinetic rate and calculates the change of mass of every component as function of time and temperature. The whole process is not stationary and occurs under conditions far from thermochemical equilibrium (with exception of components under extremely fast kinetics). For that reasons the models, which calculate the composition by minimising Gibbs free energy cannot be applied. So, for determining temperature of every particle the heat balance equation with extended definition of source terms was included in the model. (orig.)
A MATHEMATICAL MODEL FOR THE KINETICS OF THE MALE REPRODUCTIVE ENDOCRINE SYSTEM
In this presentation a model for the hormonal regulation of the reproductive endocrine system in the adult male rat will be discussed. The model includes a description of the kinetics of the androgenic hormones testosterone and dihydrotestosterone, as well as the receptor-mediate...
Kinetic Model for Signal Binding to the Quorum Sensing Regulator LasR
DEFF Research Database (Denmark)
Claussen, Anetta; Jakobsen, Tim Holm; Bjarnsholt, Thomas;
2013-01-01
We propose a kinetic model for the activation of the las regulon in the opportunistic pathogen Pseudomonas aeruginosa. The model is based on in vitro data and accounts for the LasR dimerization and consecutive activation by binding of two OdDHL signal molecules. Experimentally, the production of ...
Predicting microbial growth kinetics with the use of genetic circuit models
Koutinas, M.; Kiparissides, A.; Lorenzo, de V.; Martins Dos Santos, V.A.P.; Pistikopoulos, E.N.; Mantalaris, A.
2011-01-01
A novel modeling approach for the description of bioprocesses is proposed, linking microbial growth kinetics to gene regulation. An example is given with the development and experimental validation of a dynamic mathematical model of the TOL plasmid of Pseudomonas putida mt-2, which is used for the m
A new hybrid kinetic electron model for full-f gyrokinetic simulations
Idomura, Y.
2016-05-01
A new hybrid kinetic electron model is developed for electrostatic full-f gyrokinetic simulations of the ion temperature gradient driven trapped electron mode (ITG-TEM) turbulence at the ion scale. In the model, a full kinetic electron model is applied to the full-f gyrokinetic equation, the multi-species linear Fokker-Planck collision operator, and an axisymmetric part of the gyrokinetic Poisson equation, while in a non-axisymmetric part of the gyrokinetic Poisson equation, turbulent fluctuations are determined only by kinetic trapped electrons responses. By using this approach, the so-called ωH mode is avoided with keeping important physics such as the ITG-TEM, the neoclassical transport, the ambipolar condition, and particle trapping and detrapping processes. The model enables full-f gyrokinetic simulations of ITG-TEM turbulence with a reasonable computational cost. Comparisons between flux driven ITG turbulence simulations with kinetic and adiabatic electrons are presented. Although the similar ion temperature gradients with nonlinear upshift from linear critical gradients are sustained in quasi-steady states, parallel flows and radial electric fields are qualitatively different with kinetic electrons.
Application of artificial neural networks to infer subcriticality level through kinetic models - 173
International Nuclear Information System (INIS)
The paper presents some recent advances in the study of the inverse kinetics for subcritical systems. A neural-based approach is adopted to predict the reactivity of the multiplying medium through the analysis of the reactor response to a source pulse. An artificial neural network is designed to infer the subcriticality level through the analysis of power evolution. The training set is computed using an approximate model and its performances are then tested directly on experimental measures, here simulated through a detailed space-energy kinetic model. In order to improve the accuracy of the reactivity estimation, various strategies are proposed and compared, including a multi-transient inversion and the use of different kinetic models for the training. The issue of robustness of the inversion scheme to experimental noise is also addressed (authors)
Enzymatic saccharification of acid pretreated corn stover: Empirical and fractal kinetic modelling.
Wojtusik, Mateusz; Zurita, Mauricio; Villar, Juan C; Ladero, Miguel; Garcia-Ochoa, Felix
2016-11-01
Enzymatic hydrolysis of corn stover was studied at agitation speeds from 50 to 500rpm in a stirred tank bioreactor, at high solid concentrations (20% w/w dry solid/suspension), 50°C and 15.5mgprotein·gglucane(-1). Two empirical kinetic models have been fitted to empirical data, namely: a potential model and a fractal one. For the former case, the global order dramatically decreases from 13 to 2 as agitation speed increases, suggesting an increment in the access of enzymes to cellulose in terms of chemisorption followed by hydrolysis. For its part, the fractal kinetic model fits better to data, showing its kinetic constant a constant augmentation with increasing agitation speed up to a constant value at 250rpm and above, when mass transfer limitations are overcome. In contrast, the fractal exponent decreases with rising agitation speed till circa 0.19, suggesting higher accessibility of enzymes to the substrate. PMID:27566519
Modeling hydrocracking kinetics of atmospheric residue by discrete and continuous lumping
Energy Technology Data Exchange (ETDEWEB)
Alhumaidan, F. [Kuwait Inst. for Scientific Research, Safat (Kuwait). Petroleum Research and Studies Center; Lababidi, H.M.S.; Al-Adwani, H.A. [Kuwait Univ., Safat (Kuwait). Dept. of Chemical Engineering
2004-07-01
A study was conducted to develop a kinetic model for the hydrocracking reactions that occur when atmospheric residue (AR) feedstock undergoes hydrotreatment. The kinetic model was developed using discrete and continuous lumping approaches. The modeling parameters for the developed models were derived from pilot plant experiments that were carried out using hydrodenitrogenation (HDN), hydrodesulphurization (HDS) and HDM catalysts at various residence times and operating temperatures. The study also examined the influence of catalyst type and operating conditions on product quality and yield. Discrete lumping models were found to be in excellent agreement with experimental data. They also accurately predicted the product yields of the proposed lumps. Kerosene and heavy oil were used to evaluate yield prediction performance of the developed models. The discrete lumping models were not very accurate in predicting the yield of the testing lumps. Continuous lumping models were found to be useful in accurately predicting the concentration profile of the complete TBP range.
An optimization approach to kinetic model reduction for combustion chemistry
Lebiedz, Dirk
2013-01-01
Model reduction methods are relevant when the computation time of a full convection-diffusion-reaction simulation based on detailed chemical reaction mechanisms is too large. In this article, we review a model reduction approach based on optimization of trajectories and show its applicability to realistic combustion models. As most model reduction methods, it identifies points on a slow invariant manifold based on time scale separation in the dynamics of the reaction system. The numerical approximation of points on the manifold is achieved by solving a semi-infinite optimization problem, where the dynamics enter the problem as constraints. The proof of existence of a solution for an arbitrarily chosen dimension of the reduced model (slow manifold) is extended to the case of realistic combustion models including thermochemistry by considering the properties of proper maps. The model reduction approach is finally applied to three models based on realistic reaction mechanisms: 1. ozone decomposition as a small t...
Kinetic modelling of runaway electron avalanches in tokamak plasmas
Nilsson, E; Peysson, Y; Granetz, R S; Saint-Laurent, F; Vlainic, M
2015-01-01
Runaway electrons (REs) can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force due to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate REs mainly through knock-on collisions, where enough momentum can be transferred from existing runaways to slow electrons to transport the latter beyond a critical momentum, setting off an avalanche of REs. Since knock-on runaways are usually scattered off with a significant perpendicular component of the momentum with respect to the local magnetic field direction, these particles are highly magnetized. Consequently, the momentum dynamics require a full 3-D kinetic description, since these electrons are highly sensitive to the magnetic non-uniformity of a toroidal configuration. A bounce-averaged knock-on source term is derived. The generation of REs from the combined effect of Dreicer mechanism and knock-on collision process is studied with the code LUKE, a s...
Terpene bioconversion--how does its future look?
Krings, Ulrich; Berger, Ralf Guenter
2010-09-01
The usage of essential oils as such or of volatile fractions thereof is widespread in the flavor and fragrance industry to aromatize perfumery and cosmetic products, foodstuffs, and many household and pharmaceutical products. The increased market share of convenience food together with consumers' request for constant high quality and natural products have established a lasting increase in the demand for natural flavorings that cannot be satisfied by the traditional plant materials. This review summarizes selected work on terpene bioconversion/transformation and focuses on recently published papers dealing with novel strains and products, high product yields, intriguing genetic engineering approaches, and integrated bioprocesses. The future perspectives of an industrial realization of a biotechnological production of terpene-derived natural flavors are critically evaluated. PMID:20923013
Fuzzy Stochastic Petri Nets for Modeling Biological Systems with Uncertain Kinetic Parameters.
Liu, Fei; Heiner, Monika; Yang, Ming
2016-01-01
Stochastic Petri nets (SPNs) have been widely used to model randomness which is an inherent feature of biological systems. However, for many biological systems, some kinetic parameters may be uncertain due to incomplete, vague or missing kinetic data (often called fuzzy uncertainty), or naturally vary, e.g., between different individuals, experimental conditions, etc. (often called variability), which has prevented a wider application of SPNs that require accurate parameters. Considering the strength of fuzzy sets to deal with uncertain information, we apply a specific type of stochastic Petri nets, fuzzy stochastic Petri nets (FSPNs), to model and analyze biological systems with uncertain kinetic parameters. FSPNs combine SPNs and fuzzy sets, thereby taking into account both randomness and fuzziness of biological systems. For a biological system, SPNs model the randomness, while fuzzy sets model kinetic parameters with fuzzy uncertainty or variability by associating each parameter with a fuzzy number instead of a crisp real value. We introduce a simulation-based analysis method for FSPNs to explore the uncertainties of outputs resulting from the uncertainties associated with input parameters, which works equally well for bounded and unbounded models. We illustrate our approach using a yeast polarization model having an infinite state space, which shows the appropriateness of FSPNs in combination with simulation-based analysis for modeling and analyzing biological systems with uncertain information. PMID:26910830
Calibration of Chemical Kinetic Models Using Simulations of Small-Scale Cookoff Experiments
Energy Technology Data Exchange (ETDEWEB)
Wemhoff, A P; Becker, R C; Burnham, A K
2008-02-26
Establishing safe handling limits for explosives in elevated temperature environments is a difficult problem that often requires extensive simulation. The largest influence on predicting thermal cookoff safety lies in the chemical kinetic model used in these simulations, and these kinetic model reaction sequences often contain multiple steps. Several small-scale cookoff experiments, notably Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), One-Dimensional Time-to-Explosion (ODTX), and the Scaled Thermal Explosion (STEX) have been performed on various explosives to aid in cookoff behavior determination. Past work has used a single test from this group to create a cookoff model, which does not guarantee agreement with the other experiments. In this study, we update the kinetic parameters of an existing model for the common explosive 2,4,6-Trinitrotoluene (TNT) using DSC and ODTX experimental data at the same time by minimizing a global Figure of Merit based on hydrodynamic simulated data. We then show that the new kinetic model maintains STEX agreement, reduces DSC agreement, and improves ODTX and TGA agreement when compared to the original model. In addition, we describe a means to use implicit hydrodynamic simulations of DSC experiments to develop a reaction model for TNT melting.
Rodríguez, J; Clemente, G; Sanjuán, N; Bon, J
2014-01-01
The drying kinetics of thyme was analyzed by considering different conditions: air temperature of between 40°C and 70°C , and air velocity of 1 m/s. A theoretical diffusion model and eight different empirical models were fitted to the experimental data. From the theoretical model application, the effective diffusivity per unit area of the thyme was estimated (between 3.68 × 10(-5) and 2.12 × 10 (-4) s(-1)). The temperature dependence of the effective diffusivity was described by the Arrhenius relationship with activation energy of 49.42 kJ/mol. Eight different empirical models were fitted to the experimental data. Additionally, the dependence of the parameters of each model on the drying temperature was determined, obtaining equations that allow estimating the evolution of the moisture content at any temperature in the established range. Furthermore, artificial neural networks were developed and compared with the theoretical and empirical models using the percentage of the relative errors and the explained variance. The artificial neural networks were found to be more accurate predictors of moisture evolution with VAR ≥ 99.3% and ER ≤ 8.7%. PMID:23733820
Numerical Solution of Fractional Neutron Point Kinetics Model in Nuclear Reactor
Nowak Tomasz Karol; Duzinkiewicz Kazimierz; Piotrowski Robert
2014-01-01
This paper presents results concerning solutions of the fractional neutron point kinetics model for a nuclear reactor. Proposed model consists of a bilinear system of fractional and ordinary differential equations. Three methods to solve the model are presented and compared. The first one entails application of discrete Grünwald-Letnikov definition of the fractional derivative in the model. Second involves building an analog scheme in the FOMCON Toolbox in MATLAB environment. Third is the met...
Effects of different per translational kinetics on the dynamics of a core circadian clock model.
Directory of Open Access Journals (Sweden)
Paula S Nieto
Full Text Available Living beings display self-sustained daily rhythms in multiple biological processes, which persist in the absence of external cues since they are generated by endogenous circadian clocks. The period (per gene is a central player within the core molecular mechanism for keeping circadian time in most animals. Recently, the modulation PER translation has been reported, both in mammals and flies, suggesting that translational regulation of clock components is important for the proper clock gene expression and molecular clock performance. Because translational regulation ultimately implies changes in the kinetics of translation and, therefore, in the circadian clock dynamics, we sought to study how and to what extent the molecular clock dynamics is affected by the kinetics of PER translation. With this objective, we used a minimal mathematical model of the molecular circadian clock to qualitatively characterize the dynamical changes derived from kinetically different PER translational mechanisms. We found that the emergence of self-sustained oscillations with characteristic period, amplitude, and phase lag (time delays between per mRNA and protein expression depends on the kinetic parameters related to PER translation. Interestingly, under certain conditions, a PER translation mechanism with saturable kinetics introduces longer time delays than a mechanism ruled by a first-order kinetics. In addition, the kinetic laws of PER translation significantly changed the sensitivity of our model to parameters related to the synthesis and degradation of per mRNA and PER degradation. Lastly, we found a set of parameters, with realistic values, for which our model reproduces some experimental results reported recently for Drosophila melanogaster and we present some predictions derived from our analysis.
Directory of Open Access Journals (Sweden)
W. Lee Childers, PhD, CP
2015-01-01
Full Text Available People with amputation move asymmetrically with regard to kinematics (joint angles and kinetics (joint forces and moments. Clinicians have traditionally sought to minimize kinematic asymmetries, assuming kinetic asymmetries would also be minimized. A cycling model evaluated locomotor asymmetries. Eight individuals with unilateral transtibial amputation pedaled with 172 mm-length crank arms on both sides (control condition and with the crank arm length shortened to 162 mm on the amputated side (CRANK condition. Pedaling kinetics and limb kinematics were recorded. Joint kinetics, joint angles (mean and range of motion [ROM], and pedaling asymmetries were calculated from force pedals and with a motion capture system. A one-way analysis of variance with Tukey post hoc compared kinetics and kinematics across limbs. Statistical significance was set to p kinetic asymmetries as clinically assumed. We propose that future research should concentrate on defining acceptable asymmetry.
Wang, Xu; Ding, Jie; Guo, Wan-Qian; Ren, Nan-Qi
2010-12-01
Investigating how a bioreactor functions is a necessary precursor for successful reactor design and operation. Traditional methods used to investigate flow-field cannot meet this challenge accurately and economically. Hydrodynamics model can solve this problem, but to understand a bioreactor in sufficient depth, it is often insufficient. In this paper, a coupled hydrodynamics-reaction kinetics model was formulated from computational fluid dynamics (CFD) code to simulate a gas-liquid-solid three-phase biotreatment system for the first time. The hydrodynamics model is used to formulate prediction of the flow field and the reaction kinetics model then portrays the reaction conversion process. The coupled model is verified and used to simulate the behavior of an expanded granular sludge bed (EGSB) reactor for biohydrogen production. The flow patterns were visualized and analyzed. The coupled model also demonstrates a qualitative relationship between hydrodynamics and biohydrogen production. The advantages and limitations of applying this coupled model are discussed. PMID:20727741
Energy Technology Data Exchange (ETDEWEB)
Perelson, Alan S [Los Alamos National Laboratory; Shudo, Emi [Los Alamos National Laboratory; Ribeiro, Ruy M [Los Alamos National Laboratory
2008-01-01
Mathematical models have proven helpful in analyzing the virological response to antiviral therapy in hepatitis C virus (HCY) infected subjects. Objective: To summarize the uses and limitations of different models for analyzing HCY kinetic data under pegylated interferon therapy. Methods: We formulate mathematical models and fit them by nonlinear least square regression to patient data in order estimate model parameters. We compare the goodness of fit and parameter values estimated by different models statistically. Results/Conclusion: The best model for parameter estimation depends on the availability and the quality of data as well as the therapy used. We also discuss the mathematical models that will be needed to analyze HCV kinetic data from clinical trials with new antiviral drugs.
Development of chemical kinetic models for lean NOx traps.
Energy Technology Data Exchange (ETDEWEB)
Larson, Richard S.
2010-04-01
Overall project goal: Obtain the fundamental surface chemistry knowledge needed for the design and optimal utilization of NOx trap catalysts, thereby helping to speed the widespread adoption of this technology. Relevance to VT Program goals: Effective, durable advanced aftertreatment systems for lean-burn engines must be available if the fuel economy advantages of these engines are to be realized. Specific current year objective: Identify and correct any deficiencies in the previously developed reaction mechanism describing normal storage/regeneration cycles, and complete development of a supplementary mechanism accounting for the effects of sulfation. A fundamental understanding of LNT chemistry is needed to realize the full potential of this aftertreatment technology, which could lead to greater use of fuel-efficient lean-burn engines. We have used a multi-tiered approach to developing an elementary chemical mechanism benchmarked against experimental data: (1) Simulate a set of steady flow experiments, with storage effects minimized, to infer a tentative mechanism for chemistry on precious metal sites (completed). (2) Simulate a set of long cycle experiments to infer a mechanism for NOx and oxygen storage sites while simultaneously finalizing precious metal chemistry (completed). (3) Simulate a simplified sulfation/desulfation protocol to obtain a supplementary set of reactions involving sulfur on all three kinds of sites (nearly completed). (4) Investigate the potential role of reductants other than CO and H{sub 2}. While simulation of isothermal experiments is the preferred way to extract kinetic parameters, simulation of realistic storage/regeneration cycles requires that exotherms be considered. Our ultimate goal is to facilitate improved designs for LNT-based aftertreatment systems and to assist in the development of improved catalysts.
Franz, Silvio; Gradenigo, Giacomo; Spigler, Stefano
2016-03-01
We study how the thermodynamic properties of the triangular plaquette model (TPM) are influenced by the addition of extra interactions. The thermodynamics of the original TPM is trivial, while its dynamics is glassy, as usual in kinetically constrained models. As soon as we generalize the model to include additional interactions, a thermodynamic phase transition appears in the system. The additional interactions we consider are either short ranged, forming a regular lattice in the plane, or long ranged of the small-world kind. In the case of long-range interactions we call the new model the random-diluted TPM. We provide arguments that the model so modified should undergo a thermodynamic phase transition, and that in the long-range case this is a glass transition of the "random first-order" kind. Finally, we give support to our conjectures studying the finite-temperature phase diagram of the random-diluted TPM in the Bethe approximation. This corresponds to the exact calculation on the random regular graph, where free energy and configurational entropy can be computed by means of the cavity equations.
Semi-gas kinetics model for performance modeling of flowing chemical oxygen-iodine lasers (COIL)
Institute of Scientific and Technical Information of China (English)
GAO Zhi; HU Limin; SHEN Yiqing
2004-01-01
A semi-gas kinetics (SGK) model for performance analyses of flowing chemical oxygen-iodine laser (COIL) is presented. In this model, the oxygen-iodine reaction gas flow is treated as a continuous medium, and the effect of thermal motions of particles of different laser energy levels on the performances of the COIL is included and the velocity distribution function equations are solved by using the double-parameter perturbational method. For a premixed flow, effects of different chemical reaction systems, different gain saturation models and temperature, pressure, yield of excited oxygen, iodine concentration and frequency-shift on the performances of the COIL are computed, and the calculated output power agrees well with the experimental data. The results indicate that the power extraction of the SGK model considering 21 reactions is close to those when only the reversible pumping reaction is considered, while different gain saturation models and adjustable parameters greatly affect the output power, the optimal threshold gain range, and the length of power extraction.
An experimental and kinetic modeling study of combustion of isomers of butanol
Energy Technology Data Exchange (ETDEWEB)
Grana, Roberto; Frassoldati, Alessio; Faravelli, Tiziano; Ranzi, Eliseo [Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, Milano (Italy); Niemann, Ulrich; Seiser, Reinhard; Cattolica, Robert; Seshadri, Kalyanasundaram [Department of Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, CA 92093-0411 (United States)
2010-11-15
A kinetic model is developed to describe combustion of isomers of butanol - n-butanol (n-C{sub 4}H{sub 9}OH), sec-butanol (sec-C{sub 4}H{sub 9}OH), iso-butanol (iso-C{sub 4}H{sub 9}OH), and tert-butanol (tert-C{sub 4}H{sub 9}OH). A hierarchical approach is employed here. This approach was previously found to be useful for developing detailed and semi-detailed mechanism of oxidation of various hydrocarbon fuels. This method starts from lower molecular weight compounds of a family of species and proceeds to higher molecular weight compounds. The pyrolysis and oxidation mechanisms of butanol isomers are similar to those for hydrocarbon fuels. Here, the development of the complete set of the primary propagation reactions for butanol isomers proceeds from the extension of the kinetic parameters for similar reactions already studied and recently revised for ethanol, n-propanol and iso-propanol. A detailed description leading to evaluation of rate constants for initiation reactions, metathesis reactions, decomposition reactions of alkoxy radicals, isomerization reactions, and four-center molecular dehydration reactions are given. Decomposition and oxidation of primary intermediate products are described using a previously developed semi-detailed kinetic model for hydrocarbon fuels. The kinetic mechanism is made up of more than 7000 reactions among 300 species. The model is validated by comparing predictions made using this kinetic model with previous and new experimental data on counterflow non-premixed flames of n-butanol and iso-butanol. The structures of these flames were measured by removing gas samples from the flame and analyzing them using a gas chromatograph. Temperature profiles were measured using coated thermocouples. The flame structures were measured under similar conditions for both fuels to elucidate the similarities and differences in combustion characteristics of the two isomers. The profiles measured include those of butanol, oxygen, carbon dioxide
Modelling kinetics of plant canopy architecture: concepts and applications
Birch, C.J.; Andrieu, B.; Fournier, C.; Vos, J.; Room, P.
2003-01-01
Most crop models simulate the crop canopy as an homogeneous medium. This approach enables modelling of mass and energy transfer through relatively simple equations, and is useful for understanding crop production. However, schematisation of an homogeneous medium cannot address the heterogeneous natu
KINETIC MODELING OF NOX FORMATION AND DESTRUCTION AND COMBUSTIBLES BURNOUT
The report describes a model of the gas-phase chemistry involved in the combustion of simple hydrocarbon fuels and the interconversion of fixed nitrogen species. One focus of the work was on modeling the chemistry involved in reburning and other advanced NOx control strategies. A...
Institute of Scientific and Technical Information of China (English)
Ning Zhengfu; Zhang Shixi; Zhang Qin; Zhen Shuangyi; Chen Guangjin
2007-01-01
The kinetics behavior of methane hydrate formation in the presence of tetrahydrofuran (THF) as promoter was studied. A set of experimental equipment was designed and constructed. A series of kinetics data for the formation of methane hydrate in the presence of THF were measured with the isochoric method. The influences of temperature,pressure and liquid flow rate on the methane consumption rate were studied respectively. Based on the Chen-Guo hydrate formation mechanism,a kinetics model for the formation of methane hydrate in the presence of THF by using the dimensionless Gibbs free energy difference of quasi-chemical reaction of basic hydrate formation,,as the driving force was proposed. The model was used to calculate the rate of methane consumption and it was shown that the calculated results were in good agreement with the experimental results.
Kocadağlı, Tolgahan; Gökmen, Vural
2016-11-15
The study describes the kinetics of the formation and degradation of α-dicarbonyl compounds in glucose/wheat flour system heated under low moisture conditions. Changes in the concentrations of glucose, fructose, individual free amino acids, lysine and arginine residues, glucosone, 1-deoxyglucosone, 3-deoxyglucosone, 3,4-dideoxyglucosone, 5-hydroxymethyl-2-furfural, glyoxal, methylglyoxal and diacetyl concentrations were determined to form a multiresponse kinetic model for isomerisation and degradation reactions of glucose. Degradation of Amadori product mainly produced 1-deoxyglucosone. Formation of 3-deoxyglucosone proceeded directly from glucose and also Amadori product degradation. Glyoxal formation was predominant from glucosone while methylglyoxal and diacetyl originated from 1-deoxyglucosone. Formation of 5-hydroxymethyl-2-furfural from fructose was found to be a key step. Multi-response kinetic modelling of Maillard reaction and caramelisation simultaneously indicated quantitatively predominant parallel and consecutive pathways and rate limiting steps by estimating the reaction rate constants. PMID:27283710
An experimental and kinetic modeling study of premixed nitroethane flames at low pressure
DEFF Research Database (Denmark)
Zhang, Kuiwen; Zhang, Lidong; Xie, Mingfeng;
2013-01-01
An experimental and kinetic modeling study is reported on three premixed nitroethane/oxygen/argon flames at low pressure (4.655kPa) with the equivalence ratios (Φ) of 1.0, 1.5 and 2.0. Over 30 flame species were identified with tunable synchrotron vacuum ultraviolet photoionization mass spectrome......An experimental and kinetic modeling study is reported on three premixed nitroethane/oxygen/argon flames at low pressure (4.655kPa) with the equivalence ratios (Φ) of 1.0, 1.5 and 2.0. Over 30 flame species were identified with tunable synchrotron vacuum ultraviolet photoionization mass...... spectrometry, with their mole fractions quantified as the function of the height above burner. The flame temperature profiles were measured with a Pt–6%Rh/Pt–30%Rh thermocouple. A detailed kinetic mechanism with 115 species and 730 reactions was proposed and validated against experimental results. The computed...
Modeling of Scale-Dependent Bacterial Growth by Chemical Kinetics Approach
Directory of Open Access Journals (Sweden)
Haydee Martínez
2014-01-01
Full Text Available We applied the so-called chemical kinetics approach to complex bacterial growth patterns that were dependent on the liquid-surface-area-to-volume ratio (SA/V of the bacterial cultures. The kinetic modeling was based on current experimental knowledge in terms of autocatalytic bacterial growth, its inhibition by the metabolite CO2, and the relief of inhibition through the physical escape of the inhibitor. The model quantitatively reproduces kinetic data of SA/V-dependent bacterial growth and can discriminate between differences in the growth dynamics of enteropathogenic E. coli, E. coli JM83, and Salmonella typhimurium on one hand and Vibrio cholerae on the other hand. Furthermore, the data fitting procedures allowed predictions about the velocities of the involved key processes and the potential behavior in an open-flow bacterial chemostat, revealing an oscillatory approach to the stationary states.
Personalized Whole-Cell Kinetic Models of Metabolism for Discovery in Genomics and Pharmacodynamics
DEFF Research Database (Denmark)
Bordbar, Aarash; McCloskey, Douglas; Zielinski, Daniel C;
2015-01-01
challenge. Here, we constructed multi-omic, data-driven, personalized whole-cell kinetic models of erythrocyte metabolism for 24 healthy individuals based on fasting-state plasma and erythrocyte metabolomics and whole-genome genotyping. We show that personalized kinetic rate constants, rather than......-induced anemia) and how genetic variation (inosine triphosphatase deficiency) may protect against this side effect. This study demonstrates the feasibility of personalized kinetic models, and we anticipate their use will accelerate discoveries in characterizing individual metabolic variation.......Understanding individual variation is fundamental to personalized medicine. Yet interpreting complex phenotype data, such as multi-compartment metabolomic profiles, in the context of genotype data for an individual is complicated by interactions within and between cells and remains an unresolved...
A Combined Thermodynamic and Kinetic Model for Barite Prediction at Oil Reservoir Conditions
DEFF Research Database (Denmark)
Zhen Wu, Bi Yun
with the experimental values reported in this study and in the literature shows that these values agree within 20% at 0 kinetics via experiments performed in batch reactors in NaCl concentration ranging from 0 to 1.5 mol kg-1...... of this research was to develop a model, based on thermodynamics and kinetics, for predicting barite precipitation rates in saline waters at the pressures and temperatures of oil bearing reservoirs, using the geochemical modelling code PHREEQC. This task is complicated by the conditions where traditional methods...... to 90 C at 1 bar of pressure. Resulting thermodynamic and kinetic parameters were combined and coupled with PHREEQC to predict precipitation scaling rates in three oil production wells, where barite has been observed. Average linear growth rates of 3, 2.5 and 2 mm of barite per year were estimated...
Directory of Open Access Journals (Sweden)
Ali eKhodayari
2015-01-01
Full Text Available Computational strain design prediction accuracy has been the focus for many recent efforts through the selective integration of kinetic information into metabolic models. In general, kinetic model prediction quality is determined by the range and scope of genetic and/or environmental perturbations used during parameterization. In this effort, we apply the k-OptForce procedure on a kinetic model of E. coli core metabolism constructed using the Ensemble Modeling (EM method and parameterized using multiple mutant strains data under aerobic respiration with glucose as the carbon source. Minimal interventions are identified that improve succinate yield under both aerobic and anaerobic conditions to test the fidelity of model predictions under both genetic and environmental perturbations. Under aerobic condition, k-OptForce identifies interventions that match existing experimental strategies pointing at a number of unexplored flux redirections such as routing glyoxylate flux through the glycerate metabolism to improve succinate yield. Many of the identified interventions rely on the kinetic descriptions and would not be discoverable by a purely stoichiometric description. In contrast, under fermentative (anaerobic conditions, k-OptForce fails to identify key interventions including up-regulation of anaplerotic reactions and elimination of competitive fermentative products. This is due to the fact that the pathways activated under anaerobic conditions were not properly parameterized as only aerobic flux data were used in the model construction. This study shed light on the importance of condition-specific model parameterization and provides insight onto how to augment kinetic models so as to correctly respond to multiple environmental perturbations.
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%.
Coupling a CFD code with neutron kinetics and pin thermal models for nuclear reactor safety analyses
International Nuclear Information System (INIS)
Highlights: • A CFD/neutron kinetics coupled code FLUENT/PK for nuclear reactor transient safety was developed. • The mathematical models and coupling methods of FLUENT/PK were described. • The code-to-code validation between FLUENT/PK and SIMMER-III was conducted. - Abstract: Most system codes are based on the one-dimensional lumped-parameter method, which is unsuitable to simulate multi-dimensional thermal-hydraulics problems. CFD method is a good tool to simulate multi-dimensional thermal-hydraulics phenomena in the nuclear reactor, which can increase the accuracy of analysis results. However, since there is no neutron kinetics model and pin thermal model in current CFD codes, the application of the CFD method in the area of nuclear reactor safety analyses is still limited. Coupling a CFD code with the neutron kinetics model (PKM) and the pin thermal model (PTM) is a good way to use CFD code to simulate multi-dimensional thermal-hydraulics problems of nuclear reactors. The motivation for this work is to develop a CFD/neutron kinetics coupled code named FLUENT/PK for nuclear reactor safety analyses by coupling the commercial CFD code named FLUENT with the point kinetics model (PKM) and the pin thermal model (PTM). The mathematical models and the coupling method are described and the unprotected transient overpower (UTOP) accident of a liquid metal cooled fast reactor (LMFR) is chosen as an application case. As a general validation, the calculated results are used to compare with that of another multi-physics coupled code named SIMMER-III and good agreements are achieved for various characteristic parameters
Spectral Problems for the Orientation-Free Discrete Kinetic Models
Institute of Scientific and Technical Information of China (English)
朱光华; 金燕芳; 方竞
2002-01-01
We present computations using orientation-free discrete velocity models for the dispersion relationship of ultrasound propagation in monatomic hard-sphere gases (or a type of gas composed of a system of vortices).Comparisons with previous verified fixed-orientation results for the propagation of the sound mode in rarefied gases show that, if collective excitations are considered, an orientation-free eight-velocity model can capture more physical insights. We also demonstrate the symmetry property of the spectra using the orientation-free eight-velocity model.
A kinetic model of municipal sludge degradation during non-catalytic wet oxidation.
Prince-Pike, Arrian; Wilson, David I; Baroutian, Saeid; Andrews, John; Gapes, Daniel J
2015-12-15
Wet oxidation is a successful process for the treatment of municipal sludge. In addition, the resulting effluent from wet oxidation is a useful carbon source for subsequent biological nutrient removal processes in wastewater treatment. Owing to limitations with current kinetic models, this study produced a kinetic model which predicts the concentrations of key intermediate components during wet oxidation. The model was regressed from lab-scale experiments and then subsequently validated using data from a wet oxidation pilot plant. The model was shown to be accurate in predicting the concentrations of each component, and produced good results when applied to a plant 500 times larger in size. A statistical study was undertaken to investigate the validity of the regressed model parameters. Finally the usefulness of the model was demonstrated by suggesting optimum operating conditions such that volatile fatty acids were maximised. PMID:26426294
Energy Technology Data Exchange (ETDEWEB)
Xiao Yamping; Holappa, L. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Metallurgy
1996-12-31
This article summaries the research work on thermodynamics of chromium slags and kinetic modelling of chromite reduction. The thermodynamic properties of FeCr slag systems were calculated with the regular solution model. The effects of CaO/MgO ratio, Al{sub 2}0{sub 3} amount as well as the slag basicity on the activities of chromium oxides and the oxidation state of chromium were examined. The calculated results were compared to the experimental data in the literature. In the kinetic modelling of the chromite reduction, the reduction possibilities and tendencies of the chromite constitutes with CO were analysed based on the thermodynamic calculation. Two reaction models, a structural grain model and a multi-layers reaction model, were constructed and applied to simulate the chromite pellet reduction and chromite lumpy ore reduction, respectively. The calculated reduction rates were compared with the experimental measurements and the reaction mechanisms were discussed. (orig.) SULA 2 Research Programme; 4 refs.
Directory of Open Access Journals (Sweden)
Marc Breit
2015-08-01
Full Text Available The objectives of this work were the classification of dynamic metabolic biomarker candidates and the modeling and characterization of kinetic regulatory mechanisms in human metabolism with response to external perturbations by physical activity. Longitudinal metabolic concentration data of 47 individuals from 4 different groups were examined, obtained from a cycle ergometry cohort study. In total, 110 metabolites (within the classes of acylcarnitines, amino acids, and sugars were measured through a targeted metabolomics approach, combining tandem mass spectrometry (MS/MS with the concept of stable isotope dilution (SID for metabolite quantitation. Biomarker candidates were selected by combined analysis of maximum fold changes (MFCs in concentrations and P-values resulting from statistical hypothesis testing. Characteristic kinetic signatures were identified through a mathematical modeling approach utilizing polynomial fitting. Modeled kinetic signatures were analyzed for groups with similar behavior by applying hierarchical cluster analysis. Kinetic shape templates were characterized, defining different forms of basic kinetic response patterns, such as sustained, early, late, and other forms, that can be used for metabolite classification. Acetylcarnitine (C2, showing a late response pattern and having the highest values in MFC and statistical significance, was classified as late marker and ranked as strong predictor (MFC = 1.97, P < 0.001. In the class of amino acids, highest values were shown for alanine (MFC = 1.42, P < 0.001, classified as late marker and strong predictor. Glucose yields a delayed response pattern, similar to a hockey stick function, being classified as delayed marker and ranked as moderate predictor (MFC = 1.32, P < 0.001. These findings coincide with existing knowledge on central metabolic pathways affected in exercise physiology, such as β-oxidation of fatty acids, glycolysis, and glycogenolysis. The presented modeling
Kinetic and allometric models for dosimetry using radiopharmaceuticals labeled with lanthanides
International Nuclear Information System (INIS)
This work proposes two models based in compartmental analyses: Animal model and Human model, using images from gamma camera measurements to determinate the kinetic constants of the 177Lu-DOTATATE to three animal species (rat Wistar, Armenian hamster and Syrian hamster) and to the human in biodistribution studies split in two phases: Phase 1 governed by uptake from the blood and Phase 2 governed by the real excretion. The kinetic constants obtained from the animals' data ere used to build allometric scaling to predict radiopharmaceutical biodistribution in the human employing relations by mass, metabolism, by life span and by physiological parameters. These extrapolation results were compared with the PRRT (Peptide receptor radiotherapy) patients kinetic data calculated using the Human model. The kinetic constants obtained from humans were used in dose assessment to PRRT patients considering MIRD 26 organs and tissues. Dosimetry results were in agreement with available results from literature. For the Phase 1 allometric scaling from kinetic data from the blood to the organs straight responsible for the 177Lu-DOTATATE metabolism and excretion - liver, kidneys and urinary bladder -show good correlation in the scaling by mass, metabolism and physiological and parameters. For the Phase 2, only the kinetic data from blood to the liver and to the kidneys show good correlation. Based in the anaesthetics inhibitory action over the renal excretion, there is not empirical basis to allow measurement times over 40 minutes in in vivo studies with small animals. Consequently, the Phase 1 results seem enough to make allometric scaling to assessment dose in PRRT. (author)
Breit, Marc; Netzer, Michael; Weinberger, Klaus M; Baumgartner, Christian
2015-08-01
The objectives of this work were the classification of dynamic metabolic biomarker candidates and the modeling and characterization of kinetic regulatory mechanisms in human metabolism with response to external perturbations by physical activity. Longitudinal metabolic concentration data of 47 individuals from 4 different groups were examined, obtained from a cycle ergometry cohort study. In total, 110 metabolites (within the classes of acylcarnitines, amino acids, and sugars) were measured through a targeted metabolomics approach, combining tandem mass spectrometry (MS/MS) with the concept of stable isotope dilution (SID) for metabolite quantitation. Biomarker candidates were selected by combined analysis of maximum fold changes (MFCs) in concentrations and P-values resulting from statistical hypothesis testing. Characteristic kinetic signatures were identified through a mathematical modeling approach utilizing polynomial fitting. Modeled kinetic signatures were analyzed for groups with similar behavior by applying hierarchical cluster analysis. Kinetic shape templates were characterized, defining different forms of basic kinetic response patterns, such as sustained, early, late, and other forms, that can be used for metabolite classification. Acetylcarnitine (C2), showing a late response pattern and having the highest values in MFC and statistical significance, was classified as late marker and ranked as strong predictor (MFC = 1.97, P hockey stick function, being classified as delayed marker and ranked as moderate predictor (MFC = 1.32, P < 0.001). These findings coincide with existing knowledge on central metabolic pathways affected in exercise physiology, such as β-oxidation of fatty acids, glycolysis, and glycogenolysis. The presented modeling approach demonstrates high potential for dynamic biomarker identification and the investigation of kinetic mechanisms in disease or pharmacodynamics studies using MS data from longitudinal cohort studies. PMID:26317529
Modeling the kinetics of survival of Staphylococcus aureus in regional yogurt from goat's milk.
Bednarko-Młynarczyk, E; Szteyn, J; Białobrzewski, I; Wiszniewska-Łaszczych, A; Liedtke, K
2015-01-01
The aim of this study was to determine the kinetics of the survival of the test strain of Staphylococcus aureus in the product investigated. Yogurt samples were contaminated with S. aure to an initial level of 10(3)-10(4) cfu/g. The samples were then stored at four temperatures: 4, 6, 20, 22°C. During storage, the number of S. aureus forming colonies in a gram of yogurt was determined every two hours. Based on the results of the analysis culture the curves of survival were plotted. Three primary models were selected to describe the kinetics of changes in the count of bacteria: Cole's model, a modified model of Gompertz and the model of Baranyi and Roberts. Analysis of the model fit carried out based on the average values of Pearson's correlation coefficient, between the modeled and measured values, showed that the Cole's model had the worst fit. The modified Gompertz model showed the count of S. aureus as a negative value. These drawbacks were not observed in the model of Baranyi and Roberts. For this reason, this model best reflects the kinetics of changes in the number of staphylococci in yogurt.
Kong, H.; Wang, M.; Venema, K.; Maathuis, A.; Heijden, R. van der; Greef, J. van der; Xu, G.; Hankemeier, T.
2009-01-01
A high-performance liquid chromatography-high resolution Fourier transform ion cyclotron resonance mass spectrometry (HPLC-FTICR-MS) method was developed to investigate the metabolism of ginsenosides in in vitro models of the gastro-intestinal tract. The metabolites were identified by high-resolutio
Kinetic hierarchy and propagation of chaos in biological swarm models
Carlen, Eric; Chatelin, Robin; Degond, Pierre; Wennberg, Bernt
2011-01-01
We consider two models of biological swarm behavior. In these models, pairs of particles interact to adjust their velocities one to each other. In the first process, called 'BDG', they join their average velocity up to some noise. In the second process, called 'CL', one of the two particles tries to join the other one's velocity. This paper establishes the master equations and BBGKY hierarchies of these two processes. It investigates the infinite particle limit of the hierarchies at large tim...
A Nash equilibrium macroscopic closure for kinetic models coupled with Mean-Field Games
Degond, Pierre; Liu, Jian-guo; Ringhofer, Christian
2012-01-01
We introduce a new mean field kinetic model for systems of rational agents interacting in a game theoretical framework. This model is inspired from non-cooperative anonymous games with a continuum of players and Mean-Field Games. The large time behavior of the system is given by a macroscopic closure with a Nash equilibrium serving as the local thermodynamic equilibrium. An application of the presented theory to a social model (herding behavior) is discussed.
Energy Technology Data Exchange (ETDEWEB)
Kittl, J.A. [Texas Instruments Inc., Dallas, TX (United States). Semiconductor Process and Device Center; Aziz, M.J. [Harvard Univ., Cambridge, MA (United States). Div. of Applied Sciences; Brunco, D.P. [Intel Corp., Santa Clara, CA (United States); Thompson, M.O. [Cornell Univ., Ithaca, NY (United States)
1996-12-31
During rapid solidification, deviations from local interfacial equilibrium are manifested by solute trapping and interfacial undercooling. Both the solute trapping function and the interface velocity-temperature function have been measured in the Si:As alloy system following pulsed laser melting, permitting them to test models for nonequilibrium interface kinetics. The results are consistent with the Continuous Growth Model without solute drag of Aziz and Kaplan and are inconsistent with models that incorporate solute drag effects during solidification.
A Linear Diffusion Model of Adsorption Kinetics at Fluid/Fluid Interfaces
Staszak, Maciej
2016-01-01
The paper presents a new model for kinetically controlled adsorption at the fluid/fluid interface. The main purpose of the presented approach is to relate easy to estimate bulk surfactant concentration with Gibbs surface excess. Two adsorption isotherms are involved in the new model development: Frumkin and Szyszkowski isotherms. Additionally the Johannsen time profile of concentration in the adsorption layer is assumed and estimated in the model derivation. The proposed approach assumes the ...
Kinetic model calculations of coloid growth in NaCl
International Nuclear Information System (INIS)
The formation of radiation damage in NaCl has generated interest because of the relevance of this damage to the disposal of radioactive waste in rock salt formations. In order to estimate the long-term behaviour of rock salt under irradiation, an accurate theory describing the major processes of radiation damage in NaCl is required. In 1977, Jain and Lidiard presented a rather simple model which, until now, has served as a means for long-term predictions of near field radiation damage processes in rock salt repositories. Although the model of Jain and Lidiard describes many experimental results on colloid growth in NaCl rather well, it neglects the colloid nucleation stage and the effect of impurities on colloid growth. The model presented in this paper is an extended version of the Jain-Lidiard model; its extensions comprise the effect of impurities and the colloid nucleation stage on the formation of radiation damage. The extended model has been tested against various experimental data obtained from the literature and accounts for several well known aspects of radiation damage in alkali halides which were not covered by the original Jain-Lidiard model. Using this extended model, we have calculated the amounts of NaCl that can be converted into metallic Na and molecular Cl2 for various Dutch concepts for reprocessed high-level radioactive waste (HLW) repositories. The theory predicts that the concentration of these defect aggregates in the rock salt, even very close to the HLW containers will be limited to a few mole %. (orig.)
Derivation and Implementation of Hybrid Fluid/Kinetic Model for Fusion Plasmas
International Nuclear Information System (INIS)
This is a final report for Dr. Eric Held's Junior Faculty in Plasmas Physics grant entitled, ''Derivation and Implementation of Hybrid Fluid/Kinetic Model for Fusion Plasmas''. Progress over the three years and six months of this project included work on analytical and numerical fronts
Synthetic spectral analysis of a kinetic model for slow-magnetosonic waves in solar corona
Ruan, Wenzhi; He, Jiansen; Zhang, Lei; Vocks, Christian; Marsch, Eckart; Tu, Chuanyi; Peter, Hardi; Wang, Linghua
2016-03-01
We propose a kinetic model of slow-magnetosonic waves to explain various observational features associated with the propagating intensity disturbances (PIDs) occurring in the solar corona. The characteristics of slow mode waves, e.g, inphase oscillations of density, velocity, and thermal speed, are reproduced in this kinetic model. Moreover, the red-blue (R-B) asymmetry of the velocity distribution as self-consistently generated in the model is found to be contributed from the beam component, as a result of the competition between Landau resonance and Coulomb collisions. Furthermore, we synthesize the spectral lines and make the spectral analysis, based on the kinetic simulation data of the flux tube plasmas and the hypothesis of the surrounding background plasmas. It is found that the fluctuations of parameters of the synthetic spectral lines are basically consistent with the observations: (1) the line intensity, Doppler shift, and line width are fluctuating in phase; (2) the R-B asymmetry usually oscillate out of phase with the former three parameters; (3) the blueward asymmetry is more evident than the redward asymmetry in the R-B fluctuations. The oscillations of line parameters become weakened for the case with denser surrounding background plasmas. Similar to the observations, there is no doubled-frequency oscillation of the line width for the case with flux-tube plasmas flowing bulkly upward among the static background plasmas. Therefore, we suggest that the "wave + beam flow" kinetic model may be a viable interpretation for the PIDs observed in the solar corona.
Sorption/desorption kinetics of contaminants on mobile particles: Modeling and experimental evidence
Bold, Steffen; Kraft, Siegfried; Grathwohl, Peter; Liedl, Rudolf
2003-12-01
In this study the impact of sorption/desorption kinetics between organic contaminants and mobile particles suspended in subsurface water is analyzed. TCE migration through a granular activated carbon column is investigated at different transport velocities with lignite and activated carbon particles as mobile carriers. The measured breakthrough characteristics of TCE can be reproduced by a reactive transport model simulating sorption/desorption kinetics applying an intraparticle diffusion approach for mobile particles and the packed bed of granular activated carbon. Model predictions are based on independently measured physicochemical parameters, i.e., no calibration of TCE sorption/desorption is required. The close matches of experimental data to predicted data validate the exclusively process-based model assumptions and indicate that this approach has large predictive capabilities. Extending these findings, a sensitivity study is presented in order to specify under which conditions sorption/desorption of contaminants in mobile particles has to be modeled as a kinetic process. It is found that sorption/desorption kinetics are of major importance for Damköhler numbers between 0.01 and 100.
DEFF Research Database (Denmark)
Sayar, N.A.; Chen, B.H.; Lye, G.J.;
2009-01-01
In this paper we have used a proposed mathematical model, describing the carbon-carbon bond format ion reaction between beta-hydroxypyruvate and glycolaldehyde to synthesise L-erythrulose, catalysed by the enzyme transketolase, for the analysis of the sensitivity of the process to its kinetic par....... (C) 2009 Elsevier B.V. All rights reserved....
A kinetic model of the electron-beam-pumped XeCl laser active medium
Energy Technology Data Exchange (ETDEWEB)
Boichenko, A.M.; Derzhiev, V.I.; Zhidkov, A.G.; Iakovlenko, S.I. (Institut Obshchei Fiziki, Moscow (USSR))
1989-02-01
Kinetic models are developed for XeCl laser active media in different buffer gases (helium, neon, and argon) pumped by an electron beam. In the calculations of the generation characteristics, allowance is made for the effect of the cavity field on the photoinduced transitions. The numerical results on the efficiency are in good agreement with experiments on electron beams. 17 refs.
Aspects of Metal-YSZ Electrode Kinetics Studied using Model Electrodes
DEFF Research Database (Denmark)
Graves, Christopher R.; Ebbesen, Sune; Mogensen, Mogens Bjerg
2009-01-01
The electrode kinetics of oxidation and reduction of H2/H2O and CO/CO2 at the metal/yttria stabilized zirconia (YSZ) interface were studied using model metal wire electrodes contacting polished YSZ pellets. The intent was to probe the reaction mechanisms by comparing the same reactions using...
An analytical kinetic model for chemical-vapor deposition of pureB layers from diborane
Mohammadi, V.; De Boer, W.B.; Nanver, L.K.
2012-01-01
In this paper, an analytical model is established to describe the deposition kinetics and the deposition chamber characteristics that determine the deposition rates of pure boron (PureB-) layers grown by chemical-vapor deposition (CVD) from diborane (B2H6) as gas source on a non-rotating silicon waf
The modeling of carbon isotope kinetics and its application to the evaluation of natural gas
Institute of Scientific and Technical Information of China (English)
Xianqing LI; Xianming XIAO; Yongchun TANG; Hui TIAN; Qiang ZHOU; Yunfeng YANG; Peng DONG; Yan WANG; Zhihong SONG
2008-01-01
The modeling of carbon isotope kinetics of natural gas is an issue driving pioneering research in the oil and gas geochemistry in China and internationally.Combined with the sedimentary burial history and basin geothermal history,the modeling of carbon isotope kinetics provides a new and effective means for the determination of the origin and accumulation history of natural gas pools.In this paper,we introduce the modeling of carbon isotope kinetics of natural gas formation and its applications to the assessment of natural gas maturity,the determination of the gas source,the history of gas accumulation,and the oil-gas ratio.It is shown that this approach is of great value for these applications.The carbon isotopic characteristics of natural gas are not only affected by the gas source and maturity of the source rock,but also are related to the accumulation condition and geothermal gradient in a basin.There are obvious differences in the characteristics of carbon isotope ratios between instantaneous gas and cumulative gas.Different basins have different kinetic models of carbon isotope fractionation,which depends on the gas source condition,the accumulation history and the sedimentary-tectonic history.Since the origin of natural gas in the superimposed basin in China is very complicated,and the natural gas pool is characterized by multiphase and variable gas-sources,this paper may provide a new perspective on the study and evaluation of natural gas.
Rodrigues, M.A.M.; Cone, J.W.; Ferreira, L.M.M.; Blok, M.C.; Guedes, C.
2009-01-01
In vitro and in situ studies were conducted to evaluate the influence of different mathematical models, used to fit gas production profiles of 15 feedstuffs, on estimates of nylon bag organic matter (OM) degradation kinetics. The gas production data were fitted to Exponential, Logistic, Gompertz and
Modeling cerebral arteriovenous lactate kinetics after intravenous lactate infusion in the rat
Leegsma-Vogt, G; van der Werf, T; Venema, K; Korf, J
2004-01-01
Venous-arterial lactate differences across the brain during lactate infusion in rats were studied, and the fate of lactate was described with a mathematical model that includes both cerebral and extracerebral kinetics. Ultrafiltration was used to sample continuously and simultaneously arterial and v
Assessment of the kinetic-frictional model for dense granular flow
Institute of Scientific and Technical Information of China (English)
Boon Ho Ng; Yulong Ding; Mojtaba Ghadiri
2008-01-01
This paper aims to quantitatively assess the application of kinetic-frictional model to simulate the motion of dry granular materials in dense condition, in particular, the annular shearing in Couette configuration. The weight of frictional stress was varied to study the contribution of the frictional stress in dense granular flows. The results show that the pure kinetic-theory-based computational fluid dynamics (CFD) model (without frictional stress) over-predicts the dominant solids motion of dense granular flow while adding frictional stress [Schaeffer, D. G. (1987). Instability in the evolution equations describing incompressible granular flow. Journal of Differential Equations, 66(1), 19-50] with the solids pressure of [Lun, C. KTK., Savage, S. B., Jeffrey, D. J., & Chepurniy, N. (1984). Kinetic theories for granular flow: Inelastic particles in Couette flow and slightly inelastic particles in a general flow field. Journal of Fluid Mechanics, 140, 223-256] in the CFD model improves the simulation to better conform available experimental results. The results also suggest that frictional stress transmission plays an important role in dense granular flow and should not be neglected in granular flow simulations. Compatible simulation results to the experimental data are seen by increasing the weight of frictional stress to a factor of 1.25-1.5. These improved simulation results suggest the current constitutive relations (kinetic-frictional model) need to be improved in order to better reflect the real dense granular flow.
Comparison of kinetic and dynamical models of DNA-protein interaction and facilitated diffusion
Florescu, Ana-Maria; 10.1021/jp101151a
2010-01-01
It has long been asserted that proteins like transcription factors may locate their target in DNA sequences at rates that surpass by several orders of magnitude the three-dimensional diffusion limit thank to facilitated diffusion, that is the combination of one-dimensional (sliding along the DNA) and three-dimensional diffusion. This claim has been supported along the years by several mass action kinetic models, while the dynamical model we proposed recently (J. Chem. Phys. 130, 015103 (2009)) suggests that acceleration of targeting due to facilitated diffusion cannot be large. In order to solve this apparent contradiction, we performed additional simulations to compare the results obtained with our model to those obtained with the kinetic model of Klenin et al (Phys. Rev. Letters 96, 018104 (2006)). We show in this paper that the two models actually support each other and agree in predicting a low efficiency for facilitated diffusion. Extrapolation of these results to real systems even indicates that facilit...
Modeling of the reticulation kinetics of alginate/pluronic blends for biomedical applications.
Barba, Anna A; Lamberti, Gaetano; Rabbia, Luca; Grassi, Mario; Larobina, Domenico; Grassi, Gabriele
2014-04-01
In this work, blends of alginate/pluronic (F127) for biomedical applications were investigated. In particular, the kinetics of alginate chain reticulation by bivalent cations was studied by experimental and modeling approaches. Two kinds of sodium alginate were tested to obtain hard gel films. The thicknesses of the reticulated alginate films were measured as function of the exposure time and of the reticulating copper (Cu(2+)) solution concentration. The kinetics was described by a proper model able to reproduce the experimental data. The model parameters, evaluated based on the measurements of thicknesses as function of Cu(2+) concentration and exposure time, were further validated by comparing the prediction of the model with another set of independent measurement; here, the depletion of Cu(2+) ions in the conditioning solution above the reacting gel is measured as function of time. The tuned model could be used in the description of the future applications of the blends. PMID:24582256
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
On the basis of the analysis of the process of treating low concentrations of sulfur dioxide (SO2) gas in a fixed bed reactor, a kinetic model is proposed for this process after taking into consideration the effects of internal diffusion, cell concentration, and production yield of microorganisms but ignoring the effect of external diffusion. The results obtained from the model simulation show that this model can indicate the influence of the process factors, Cin, η, μmax, Cx, A, h, Km, and Q, on the removal of SO2 and that the prediction of the results by this model is also satisfactory. This kinetic model can also provide some very important indications regarding the preparation of immobilized microorganisms, selection and domestication of proper species of microorganisms, as well as the design of bioreactors.
Transperitoneal transport of creatinine. A comparison of kinetic models
DEFF Research Database (Denmark)
Fugleberg, S; Graff, J; Joffe, P;
1994-01-01
and lymphatic convective solute transport. The validation procedure included an assessment of theoretical (a priori) and practical (a posteriori) identifiability, goodness of fit, residual error analysis and plausibility of parameter estimates. The results of the validation procedure demonstrate that the model...
Kinetic Modeling of Food Quality: A Critical Review
Boekel, van T.
2008-01-01
ABSTRACT: This article discusses the possibilities to study relevant quality aspects of food, such as color, nutrient content, and safety, in a quantitative way via mathematical models. These quality parameters are governed by chemical, biochemical, microbial, and physical changes. It is argued that
Three-way catalytic converter modelling. Numerical determination of kinetic data
Energy Technology Data Exchange (ETDEWEB)
Dubien, C.; Schweich, D. [Laboratoire de Genie des Precedes Catalytiques, Villeurbanne cedex (France)
1998-12-31
A numerical approach for obtaining quickly and simply kinetic data from light-off curves is proposed. It is applied to methane oxidation which exhibits light-off at a much higher temperature than the other pollutants. Sensitivity analysis shows that heat loss is secondary and a simple 1-D adiabatic model can be used. Conversions calculated from the estimated kinetic parameters are close to experimental values. Finally, the effects of the apparent activation energy and frequency factor are discussed through a relation that links the rate constants to the light-off temperature. 10 refs.
Jiyuan Zhang; Mun-Wai Cheong; Bin Yu; Philip Curran; Weibiao Zhou
2014-01-01
The application of headspace-solid phase microextraction (HS-SPME) has been widely used in various fields as a simple and versatile method, yet challenging in quantification. In order to improve the reproducibility in quantification, a mathematical model with its root in psychological modeling and chemical reactor modeling was developed, describing the kinetic behavior of aroma active compounds extracted by SPME from two different food model systems, i.e., a semi-solid food and a liquid food....
Acoustic Propagation Modeling for Marine Hydro-Kinetic Applications
Johnson, C. N.; Johnson, E.
2014-12-01
The combination of riverine, tidal, and wave energy have the potential to supply over one third of the United States' annual electricity demand. However, in order to deploy and test prototypes, and commercial installations, marine hydrokinetic (MHK) devices must meet strict regulatory guidelines that determine the maximum amount of noise that can be generated and sets particular thresholds for determining disturbance and injury caused by noise. An accurate model for predicting the propagation of a MHK source in a real-life hydro-acoustic environment has been established. This model will help promote the growth and viability of marine, water, and hydrokinetic energy by confidently assuring federal regulations are meet and harmful impacts to marine fish and wildlife are minimal. Paracousti, a finite difference solution to the acoustic equations, was originally developed for sound propagation in atmospheric environments and has been successfully validated for a number of different geophysical activities. The three-dimensional numerical implementation is advantageous over other acoustic propagation techniques for a MHK application where the domains of interest have complex 3D interactions from the seabed, banks, and other shallow water effects. A number of different cases for hydro-acoustic environments have been validated by both analytical and numerical results from canonical and benchmark problems. This includes a variety of hydrodynamic and physical environments that may be present in a potential MHK application including shallow and deep water, sloping, and canyon type bottoms, with varying sound speed and density profiles. With the model successfully validated for hydro-acoustic environments more complex and realistic MHK sources from turbines and/or arrays can be modeled.
Kinetic modelling of the demineralization of shrimp exoskeleton using citric acid
Directory of Open Access Journals (Sweden)
Alewo Opuada AMEH
2014-11-01
Full Text Available Citric acid was used in the demineralization of shrimp exoskeleton and the kinetics of the demineralization process was studied. Kinetic data was obtained by demineralisation using five acid concentrations (0.1, 0.2, 0.3, 0.4 and 0.5M. The obtained kinetic data were fitted to the shrinking core model for fluid particle reactions. The concentration of calcium was found to decrease with time. For all acid concentrations considered, the best predictive mechanism for the demineralization process was determined to be Ash Layer Diffusion Control Mechanism. This was indicated by the high R2 values obtained (0.965 with 150% excess of citric acid.
A feasible kinetic model for the hydrogen oxidation on ruthenium electrodes
Energy Technology Data Exchange (ETDEWEB)
Rau, M.S.; Gennero de Chialvo, M.R. [Programa de Electroquimica Aplicada e Ingenieria Electroquimica (PRELINE), Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2829, 3000 Santa Fe (Argentina); Chialvo, A.C., E-mail: achialvo@fiq.unl.edu.a [Programa de Electroquimica Aplicada e Ingenieria Electroquimica (PRELINE), Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2829, 3000 Santa Fe (Argentina)
2010-07-01
The hydrogen oxidation reaction (hor) was studied on a polycrystalline ruthenium electrode in H{sub 2}SO{sub 4} solution at different rotation rates ({omega}). 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 {omega}{sup 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.
High-order continuum kinetic method for modeling plasma dynamics in phase space
International Nuclear Information System (INIS)
Continuum methods offer a high-fidelity means of simulating plasma kinetics. While computationally intensive, these methods are advantageous because they can be cast in conservation-law form, are not susceptible to noise, and can be implemented using high-order numerical methods. Advances in continuum method capabilities for modeling kinetic phenomena in plasmas require the development of validation tools in higher dimensional phase space and an ability to handle non-cartesian geometries. To that end, a new benchmark for validating Vlasov-Poisson simulations in 3D (x,vx,vy) is presented. The benchmark is based on the Dory-Guest-Harris instability and is successfully used to validate a continuum finite volume algorithm. To address challenges associated with non-cartesian geometries, unique features of cylindrical phase space coordinates are described. Preliminary results of continuum kinetic simulations in 4D (r,z,vr,vz) phase space are presented
A Minimal Model for Large-scale Epitaxial Growth Kinetics of Graphene
Jiang, Huijun
2015-01-01
Epitaxial growth via chemical vapor deposition is considered to be the most promising way towards synthesizing large area graphene with high quality. However, it remains a big theoretical challenge to reveal growth kinetics with atomically energetic and large-scale spatial information included. Here, we propose a minimal kinetic Monte Carlo model to address such an issue on an active catalyst surface with graphene/substrate lattice mismatch, which facilitates us to perform large scale simulations of the growth kinetics over two dimensional surface with growth fronts of complex shapes. A geometry-determined large-scale growth mechanism is revealed, where the rate-dominating event is found to be $C_{1}$-attachment for concave growth front segments and $C_{5}$-attachment for others. This growth mechanism leads to an interesting time-resolved growth behavior which is well consistent with that observed in a recent scanning tunneling microscopy experiment.
Serdenko, T V; Barabash, Y M; Knox, P P; Seifullina, N Kh
2016-12-01
The present work is related to the investigation of slow kinetics of electron transport in the reaction centers (RCs) of Rhodobacter sphaeroides. Experimental data on the absorption kinetics of aqueous solutions of reaction centers at different modes of photoexcitation are given. It is shown that the kinetics of oxidation and reduction of RCs are well described by the sum of three exponential functions. This allows to suggest a two-level kinetic model for electron transport in the RC as a system of four electron-conformational states which correspond to three balance differential equations combined with state equation. The solution of inverse problem made it possible to obtain the rate constant values in kinetic equations for different times and intensities of exciting light. Analysis of rate constant values in different modes of RC excitation allowed to suggest that two mechanisms of structural changes are involved in RC photo-oxidation. One mechanism leads to the increment of the rate of electron return, another one-to its drop. Structural changes were found out to occur in the RCs under incident light. After light was turned off, the reduction of RCs was determined by the second mechanism. PMID:27271854
New types of experimental data shape the use of enzyme kinetics for dynamic network modeling.
Tummler, Katja; Lubitz, Timo; Schelker, Max; Klipp, Edda
2014-01-01
Since the publication of Leonor Michaelis and Maude Menten's paper on the reaction kinetics of the enzyme invertase in 1913, molecular biology has evolved tremendously. New measurement techniques allow in vivo characterization of the whole genome, proteome or transcriptome of cells, whereas the classical enzyme essay only allows determination of the two Michaelis-Menten parameters V and K(m). Nevertheless, Michaelis-Menten kinetics are still commonly used, not only in the in vitro context of enzyme characterization but also as a rate law for enzymatic reactions in larger biochemical reaction networks. In this review, we give an overview of the historical development of kinetic rate laws originating from Michaelis-Menten kinetics over the past 100 years. Furthermore, we briefly summarize the experimental techniques used for the characterization of enzymes, and discuss web resources that systematically store kinetic parameters and related information. Finally, describe the novel opportunities that arise from using these data in dynamic mathematical modeling. In this framework, traditional in vitro approaches may be combined with modern genome-scale measurements to foster thorough understanding of the underlying complex mechanisms.
Energy Technology Data Exchange (ETDEWEB)
Harikrishna, R., E-mail: r.harikrishna@ncl.res.in [Polymer Science and Engineering Division, National Chemical Laboratory, Pune 411008 (India); Ponrathnam, S. [Polymer Science and Engineering Division, National Chemical Laboratory, Pune 411008 (India); Tambe, S.S. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Pune 411008 (India)
2014-01-01
Highlights: • Photocationic polymerization of alicyclic based diglycidyl ether was carried out. • Kinetic parameters were influenced by gelation and diffusional restrictions. • Applicability of autocatalytic model was established by nonlinear regression. • System showed higher activation energy than cycloaliphatic and aromatic diepoxides. -- Abstract: Photoinitiated cationic polymerization of cycloaliphatic diepoxides had received tremendous attention, while studies with lesser polymerizable diglycidyl ethers are comparatively less reported. The present work deals with the photoinitiated cationic polymerization of cyclohexane dimethanol diglycidyl ether followed by estimation of kinetic parameters. The effects of concentration of photoinitiator and temperature on curing performance were studied using photo differential scanning calorimeter or photo DSC with polychromatic radiation. It was observed that the rate of polymerization as well as ultimate conversion increased with increasing concentration of photoinitiator and temperature. The influences of gelation as well as diffusional restrictions have remarkable effect on cure performance. The kinetic parameters as per autocatalytic kinetic model were studied by Levenberg–Marquardt nonlinear regression method instead of conventional linear method for obtaining more accurate values of apparent rate constant. It was observed that the model fits with data from initial stages to almost towards the end of the reaction. The activation energy was found to be higher than the values reported for more reactive cycloaliphatic diepoxides. The value of pre-exponential factor increased with increase in activation energy showing influence of gelation at early stages of reaction.
Energy Technology Data Exchange (ETDEWEB)
Rial, Diego; Vazquez, Jose Antonio; Murado, Miguel Anxo [Instituto de Investigacions Marinas (CSIC), Vigo (ES). Grupo de Reciclado y Valorizacion de Materiales Residuales (REVAL)
2011-05-15
The effects of three heavy metals (Co, Ni and Cd) on the growth kinetics of five bacterial strains with different characteristics (Pseudomonas sp., Phaeobacter sp. strain 27-4, Listonella anguillarum, Carnobacterium piscicola and Leuconostoc mesenteroides subsp. lysis) were studied in a batch system. A bivariate model, function of time and dose, is proposed to describe simultaneously all the kinetic profiles obtained by incubating a microorganism at increasing concentrations of individual metals. This model combines the logistic equation for describing growth, with a modification of the cumulative Weibull's function for describing the dose-dependent variations of growth parameters. The comprehensive model thus obtained - which minimizes the effects of the experimental error - was statistically significant in all the studied cases, and it raises doubts about toxicological evaluations that are based on a single growth parameter, especially if it is not obtained from a kinetic equation. In lactic acid bacteria cultures (C. piscicola and L. mesenteroides), Cd induced remarkable differences in yield and time course of characteristic metabolites. A global parameter is defined (ED{sub 50,{tau}}: dose of toxic chemical that reduces the biomass of a culture by 50% compared to that produced by the control at the time corresponding to its semi maximum biomass) that allows comparing toxic effects on growth kinetics using a single value. (orig.)
Fluctuating bottleneck model studies on kinetics of DNA escape from α-hemolysin nanopores.
Bian, Yukun; Wang, Zilin; Chen, Anpu; Zhao, Nanrong
2015-11-14
We have proposed a fluctuation bottleneck (FB) model to investigate the non-exponential kinetics of DNA escape from nanometer-scale pores. The basic idea is that the escape rate is proportional to the fluctuating cross-sectional area of DNA escape channel, the radius r of which undergoes a subdiffusion dynamics subjected to fractional Gaussian noise with power-law memory kernel. Such a FB model facilitates us to obtain the analytical result of the averaged survival probability as a function of time, which can be directly compared to experimental results. Particularly, we have applied our theory to address the escape kinetics of DNA through α-hemolysin nanopores. We find that our theoretical framework can reproduce the experimental results very well in the whole time range with quite reasonable estimation for the intrinsic parameters of the kinetics processes. We believe that FB model has caught some key features regarding the long time kinetics of DNA escape through a nanopore and it might provide a sound starting point to study much wider problems involving anomalous dynamics in confined fluctuating channels. PMID:26567685
Heissler, Sarah M; Chinthalapudi, Krishna; Sellers, James R
2015-04-01
Nonmuscle myosin-2 is the primary enzyme complex powering contractility of the F-actin cytoskeleton in the model organism Drosophila. Despite myosin's essential function in fly development and homeostasis, its kinetic features remain elusive. The purpose of this in vitro study is a detailed steady-state and presteady-state kinetic characterization of the Drosophila nonmuscle myosin-2 motor domain. Kinetic features are a slow steady-state ATPase activity, high affinities for F-actin and ADP, and a low duty ratio. Comparative analysis of the overall enzymatic signatures across the nonmuscle myosin-2 complement from model organisms indicates that the Drosophila protein resembles nonmuscle myosin-2s from metazoa rather than protozoa, though modulatory aspects of myosin motor function are distinct. Drosophila nonmuscle myosin-2 is uniquely insensitive toward blebbistatin, a commonly used myosin-2 inhibitor. An in silico modeling approach together with kinetic studies indicate that the nonconsensus amino acid Met466 in the Drosophila nonmuscle myosin-2 active-site loop switch-2 acts as blebbistatin desensitizer. Introduction of the M466I mutation sensitized the protein for blebbistatin, resulting in a half-maximal inhibitory concentration of 36.3 ± 4.1 µM. Together, these data show that Drosophila nonmuscle myosin-2 is a bona fide molecular motor and establish an important link between switch-2 and blebbistatin sensitivity.
Modeling the homogenization kinetics of as-cast U-10wt% Mo alloys
Xu, Zhijie; Joshi, Vineet; Hu, Shenyang; Paxton, Dean; Lavender, Curt; Burkes, Douglas
2016-04-01
Low-enriched U-22at% Mo (U-10Mo) alloy has been considered as an alternative material to replace the highly enriched fuels in research reactors. For the U-10Mo to work effectively and replace the existing fuel material, a thorough understanding of the microstructure development from as-cast to the final formed structure is required. The as-cast microstructure typically resembles an inhomogeneous microstructure with regions containing molybdenum-rich and -lean regions, which may affect the processing and possibly the in-reactor performance. This as-cast structure must be homogenized by thermal treatment to produce a uniform Mo distribution. The development of a modeling capability will improve the understanding of the effect of initial microstructures on the Mo homogenization kinetics. In the current work, we investigated the effect of as-cast microstructure on the homogenization kinetics. The kinetics of the homogenization was modeled based on a rigorous algorithm that relates the line scan data of Mo concentration to the gray scale in energy dispersive spectroscopy images, which was used to generate a reconstructed Mo concentration map. The map was then used as realistic microstructure input for physics-based homogenization models, where the entire homogenization kinetics can be simulated and validated against the available experiment data at different homogenization times and temperatures.
A mechanistic kinetic model for phenol degradation by the Fenton process
International Nuclear Information System (INIS)
The objective of this paper is to develop and validate a mechanistic model for the degradation of phenol by the Fenton process. Experiments were performed in semi-batch operation, in which phenol, catechol and hydroquinone concentrations were measured. Using the methodology described in Pontes and Pinto [R.F.F. Pontes, J.M. Pinto, Analysis of integrated kinetic and flow models for anaerobic digesters, Chemical Engineering Journal 122 (1-2) (2006) 65-80], a stoichiometric model was first developed, with 53 reactions and 26 compounds, followed by the corresponding kinetic model. Sensitivity analysis was performed to determine the most influential kinetic parameters of the model that were estimated with the obtained experimental results. The adjusted model was used to analyze the impact of the initial concentration and flow rate of reactants on the efficiency of the Fenton process to degrade phenol. Moreover, the model was applied to evaluate the treatment cost of wastewater contaminated with phenol in order to meet environmental standards.
DEFF Research Database (Denmark)
Hereu, A.; Dalgaard, Paw; Garriga, M.;
2012-01-01
High pressure (HP) inactivation curves of Listeria monocytogenes CTC1034 (ca. 107CFU/g) on sliced RTE cooked meat products (ham and mortadella) were obtained at pressures from 300 to 800MPa. A clear tail shape was observed at pressures above 450MPa and the log-linear with tail primary model...... provided the best fit to the HP-inactivation kinetics. The relationships between the primary kinetic parameters (log kmax and log Nres) and pressure treatments were described by a polynomial secondary model. To estimate HP-inactivation of L. monocytogenes in log (N/N0) over time, a one-step global fitting...... for predictive purposes, e.g., to set the process criteria required to meet food safety objectives. Industrial relevanceQuantitative mathematical models for predicting inactivation of pathogens by HPP provide useful tools for a process optimization and real time control of a unit operation. The developed models...
Modeling the Emission of CO from Wood Fires using Detailed Chemical Kinetics
DEFF Research Database (Denmark)
Dederichs, Anne
Carbon monoxide is treated as one of the most common and dangerous of gases evolving in fires. Modeling the formation of the toxic gas CO from in fire enclosures using detailed chemical kinetics is the topic of this manuscript. A semi-empirical model is developed to study the formation of CO from...... birch wood using detailed chemical kinetics on the combustion of pyrolysis gas from birch wood. The composition of the pyrolysis gas is taken from the experiment by Zanzi and coworkers. The numerical model applies a counter flow configuration involving 84 chemical species and 804 reactions. Hence......, the model separately treats the process of pyrolysis and combustion. For under ventilated conditions and at high temperatures during pyrolysis it is found that the process of pyrolysation strongly influences the formation of CO in fire. CO2 follows the same trend....
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.
Development of a kinetic metabolic model: application to Catharanthus roseus hairy root
Leduc, M.; Tikhomiroff, C.; Cloutier, M.; Perrier, M.
2006-01-01
A kinetic metabolic model describing Catharanthus roseus hairy root growth and nutrition was developed. The metabolic network includes glycolysis, pentose-phosphate pathway, TCA cycle and the catabolic reactions leading to cell building blocks such as amino acids, organic acids, organic phosphates, lipids and structural hexoses. The central primary metabolic network was taken at pseudo-steady state and metabolic flux analysis technique allowed reducing from 31 metabolic fluxes to 20 independent pathways. Hairy root specific growth rate was described as a function of intracellular concentration in cell building blocks. Intracellular transport and accumulation kinetics for major nutrients were included. The model uses intracellular nutrients as well as energy shuttles to describe metabolic regulation. Model calibration was performed using experimental data obtained from batch and medium exchange liquid cultures of C. roseus hairy root using a minimal medium in Petri dish. The model is efficient in estimating the growth rate. PMID:16453114
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
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...... with reduced numbers of parameters. Whether such simplified models can reproduce dynamic characteristics of the full system is an important question. Results: In this work, we compared the local transient response properties of dynamic models constructed using rate laws with varying levels of approximation...... with measured enzyme parameters yields an excellent approximation of the full system dynamics, while other assumptions cause greater discrepancies in system dynamic behavior. However, iteratively replacing mechanistic rate laws with approximations resulted in a model that retains a high correlation...
Global solution for a kinetic chemotaxis model with internal dynamics and its fast adaptation limit
Liao, Jie
2015-12-01
A nonlinear kinetic chemotaxis model with internal dynamics incorporating signal transduction and adaptation is considered. This paper is concerned with: (i) the global solution for this model, and, (ii) its fast adaptation limit to Othmer-Dunbar-Alt type model. This limit gives some insight to the molecular origin of the chemotaxis behaviour. First, by using the Schauder fixed point theorem, the global existence of weak solution is proved based on detailed a priori estimates, under quite general assumptions. However, the Schauder theorem does not provide uniqueness, so additional analysis is required to be developed for uniqueness. Next, the fast adaptation limit of this model is derived by extracting a weak convergence subsequence in measure space. For this limit, the first difficulty is to show the concentration effect on the internal state. Another difficulty is the strong compactness argument on the chemical potential, which is essential for passing the nonlinear kinetic equation to the weak limit.
STAR 3D nodal kinetics and thermal-hydraulic model for the Pennsylvania State TRIGA reactor
International Nuclear Information System (INIS)
A detailed three-dimensional (3D) time-dependent STAR nodal kinetics model coupled to a one-dimensional (1 D) thermal-hydraulics WIGL model has been developed to describe conservatively the peak power and pulse behavior of the Penn State University (PSU) Breazeale TRIGA reactor. This paper describes how the STAR model and its cross section data input was developed and benchmarked against actual TRIGA pulse experiments. Different core configurations (i.e., different core loading patterns, and with/without the TRIGA core next to the D20 tank) were used for several TRIGA pulse tests with different reactivity insertion worths (1.5$, 2.0$ , 2.5$). This paper shows that the STAR nodal kinetics code adequately simulates TRIGA pulses when group constants are generated from physics codes (i.e., WIMS-D4) that can accurately model the TRIGA uranium-zirconium-hydride fuel. (author)
Modeling and kinetic characterization of wastewater disinfection using chlorine and UV irradiation.
Mounaouer, Brahmi; Abdennaceur, Hassen
2016-10-01
Sewage disinfection has the primary objective of inactivating pathogenic organisms to prevent the dissemination of waterborne diseases. This study analyzed individual disinfection, with chlorine alone, ultraviolet radiation alone, and a combined disinfection process (chlorine-UV radiation). Pseudomonas aeruginosa ATCC 15442, Escherichia coli ATCC 11229, Salmonella typhi ATCC 14028, and Clostridium perfringens were selected to evaluate the efficiency of different disinfection processes. The aim of the present study was to characterize the kinetics of chlorine (as NaHOCl) consumption, to evaluate responses of these bacterial species to the chlorination, the ultraviolet (UV) radiation, and the chlorine/UV disinfection processes in secondary wastewater using a batch laboratory reactor. Another target of this work was to study the modeling of the kinetic of water disinfection by chlorination and/or UV irradiation. Two kinetic models (Chick-Watson and Hom) were tested as to ability to scale disinfection of these bacterial species by different ultraviolet and/or chlorine doses. The results of the kinetics of chlorine consumption showed that monochloramines and trichloramines were the most important forms of residual chlorine as compared to free chlorine and dichloramines. The kinetics of inactivation of all examined bacterial strains showed that the application of the model of Hom in its original form was not representative of this kinetics of inactivation. Modification of this model, considering an initial decline of bacteria during the contact of water with chlorine, improved the results of the model. By the same, results revealed that the involved processes of UV irradiation were too complex to be approached by a simplified formulation, even in the case of specific strains of microorganisms and the use of nearly constant UV radiation intensity. In fact, the results have pointed out that the application of the Chick-Watson law is known to be inadequate to describe
Collective learning modeling based on the kinetic theory of active particles
Burini, D.; De Lillo, S.; Gibelli, L.
2016-03-01
This paper proposes a systems approach to the theory of perception and learning in populations composed of many living entities. Starting from a phenomenological description of these processes, a mathematical structure is derived which is deemed to incorporate their complexity features. The modeling is based on a generalization of kinetic theory methods where interactions are described by theoretical tools of game theory. As an application, the proposed approach is used to model the learning processes that take place in a classroom.
Point kinetic model of the early phase of a spherically symmetric nuclear explosion
Aste, Andreas
2016-01-01
A concise point kinetic model of the explosion of a prompt supercritical sphere driven by a nuclear fission chain reaction is presented. The findings are in good agreement with the data available for Trinity, the first detonation of a nuclear weapon conducted by the United States Army as part of the Manhattan project. Results are presented for an implosion device containing pure plutonium-239, although the model can be easily applied to, e.g., uranium-235. The fizzle probability and correspon...
A hybrid kinetic-fluid model for solving the Vlasov-BGK equation
Crouseilles, Nicolas; Degond, Pierre; Lemou, Mohammed
2005-01-01
International audience Our purpose is to derive a model for charged particles which combines a kinetic description of the fast prticles with a fluid description for the slow ones. This paper generalizes a similar approach where the hybrid approach was applied to gas dynamics. In this work, we consider the effect of a self-consistent electric field together with a more realistic collision operator of BGK type. A numerical scheme is constructed to simulate the hybrid Vlasov-Euler model, and ...
Local stability of perfect alignment for a spatially homogeneous kinetic model
Degond, Pierre; Frouvelle, Amic; Raoul, Gaël
2014-01-01
International audience We prove the nonlinear local stability of Dirac masses for a kinetic model of alignment of particles on the unit sphere, each point of the unit sphere representing a direction. A population concentrated in a Dirac mass then corresponds to the global alignment of all individuals. The main difficulty of this model is the lack of conserved quantities and the absence of an energy that would decrease for any initial condition. We overcome this difficulty thanks to a funct...
Bridging the gap between gene expression and metabolic phenotype via kinetic models
Vital-Lopez, Francisco G; Wallqvist, Anders; Reifman, Jaques
2013-01-01
Background Despite the close association between gene expression and metabolism, experimental evidence shows that gene expression levels alone cannot predict metabolic phenotypes, indicating a knowledge gap in our understanding of how these processes are connected. Here, we present a method that integrates transcriptome, fluxome, and metabolome data using kinetic models to create a mechanistic link between gene expression and metabolism. Results We developed a modeling framework to construct ...
Two-site kinetic modeling of bacteriophages transport through columns of saturated dune sand.
Schijven, Jack F; Hassanizadeh, S Majid; de Bruin, Ria H A M
2002-08-01
Breakthrough curves, on a semi-log scale, from tests in porous media with block-input of viruses, bacteria, protozoa and colloidal particles often exhibit a typical skewness: a rather slowly rising limb and a smooth transition of a declining limb to a very long tail. One-site kinetic models fail to fit the rising and declining limbs together with the tail satisfactorily. Inclusion of an equilibrium adsorption site does not seem to improve simulation results. This was encountered in the simulation of breakthrough curves from a recent field study on the removal of bacteriophages MS2 and PRD1 by passage through dune sand. In the present study, results of laboratory experiments for the study of this issue are presented. Breakthrough curves of salt and bacteriophages MS2, PRDI, and phiX174 in 1 D column experiments have been measured. One- and two-site kinetic models have been applied to fit and predict breakthrough curves from column experiments. The two-site model fitted all breakthrough curves very satisfactorily, accounting for the skewness of the rising limb as well as for the smooth transition of the declining limb to the tail of the breakthrough curve. The one-site model does not follow the curvature of the breakthrough tail, leading to an overestimation of the inactivation rate coefficient for attached viruses. Interaction with kinetic site 1 is characterized by relatively fast attachment and slow detachment, whereas attachment to and detachment from kinetic site 2 is fast. Inactivation of viruses and interaction with kinetic site 2 provide only a minor contribution to removal. Virus removal is mainly determined by the attachment to site 1. Bacteriophage phiX174 attached more than MS2 and PRD1, which can be explained by the greater electrostatic repulsion that MS2 and PRD1 experience compared to the less negatively charged phiX174. PMID:12180812
Branched pore kinetic model analysis of geosmin adsorption on super-powdered activated carbon.
Matsui, Yoshihiko; Ando, Naoya; Sasaki, Hiroshi; Matsushita, Taku; Ohno, Koichi
2009-07-01
Super-powdered activated carbon (S-PAC) is activated carbon of much finer particle size than powdered activated carbon (PAC). Geosmin is a naturally occurring taste and odor compound that impairs aesthetic quality in drinking water. Experiments on geosmin adsorption on S-PAC and PAC were conducted, and the results using adsorption kinetic models were analyzed. PAC pulverization, which produced the S-PAC, did not change geosmin adsorption capacity, and geosmin adsorption capacities did not differ between S-PAC and PAC. Geosmin adsorption kinetics, however, were much higher on S-PAC than on PAC. A solution to the branched pore kinetic model (BPKM) was developed, and experimental adsorption kinetic data were analyzed by BPKM and by a homogeneous surface diffusion model (HSDM). The HSDM describing the adsorption behavior of geosmin required different surface diffusivity values for S-PAC and PAC, which indicated a decrease in surface diffusivity apparently associated with activated carbon particle size. The BPKM, consisting of macropore diffusion followed by mass transfer from macropore to micropore, successfully described the batch adsorption kinetics on S-PAC and PAC with the same set of model parameter values, including surface diffusivity. The BPKM simulation clearly showed geosmin removal was improved as activated carbon particle size decreased. The simulation also implied that the rate-determining step in overall mass transfer shifted from intraparticle radial diffusion in macropores to local mass transfer from macropore to micropore. Sensitivity analysis showed that adsorptive removal of geosmin improved with decrease in activated carbon particle size down to 1microm, but further particle size reduction produced little improvement.
Kinetic Gaussian Model with Long-Range Interactions
Institute of Scientific and Technical Information of China (English)
KONG Xiang-Mu; YANG Zhan-Ru
2004-01-01
In this paper dynamical critical phenomena of the Gaussian model with long-range interactions decaying as 1/rd+δ (δ＞ 0) on d-dimensional hypercubic lattices (d = 1, 2, and 3) are studied. First, the critical points are exactly calculated, and it is found that the critical points depend on the value of δ and the range of interactions. Then the critical dynamics is considered. We calculate the time evolutions of the local magnetizations and the spin-spin correlation functions, and further the dynamic critical exponents are obtained. For one-, two- and three-dimensional lattices, it is found that the dynamic critical exponents are all z = 2 if δ＞ 2, which agrees with the result when only considering nearest neighboring interactions, and that they are all δ if 0 ＜δ＜ 2. It shows that the dynamic critical exponents are independent of the spatial dimensionality but depend on the value of δ.
Kinetic Modeling of Dye Effluent Biodegradation by Pseudomonas Stutzeri
Directory of Open Access Journals (Sweden)
N. Rajamohan
2013-04-01
Full Text Available Dye industry waste water is difficult to treat because of the presence of dyes with complex aromatic structure. In this research study, the biodegradation studies of dye effluent were performed utilizing Pseudomonas stutzeri in a controlled laboratory environment under anoxic conditions. The effects of operational parameters like initial pH of the effluent and initial Chemical Oxygen Demand (COD of the effluent on percentage COD removal were studied. A biokinetic model is established giving the dependence of percentage COD removal on biomass concentration and initial COD of the effluent. The biokinetics of the COD removal was found to be first order with respect to both the microbial concentration and initial COD of the effluent. The optimal pH for better bacterial degradation was found to be 8.The specific degradation rate was found to be 0.1417 l/g Dry Cell Mass (DCM h, at 320 C.
Mechanistic interpretation of glass reaction: Input to kinetic model development
International Nuclear Information System (INIS)
Actinide-doped SRL 165 type glass was reacted in J-13 groundwater at 90 degree C for times up to 278 days. The reaction was characterized by both solution and solid analyses. The glass was seen to react nonstoichiometrically with preferred leaching of alkali metals and boron. High resolution electron microscopy revealed the formation of a complex layer structure which became separated from the underlying glass as the reaction progressed. The formation of the layer and its effect on continued glass reaction are discussed with respect to the current model for glass reaction used in the EQ3/6 computer simulation. It is concluded that the layer formed after 278 days is not protective and may eventually become fractured and generate particulates that may be transported by liquid water. 5 refs., 5 figs. , 3 tabs
Kinetic market models with single commodity having price fluctuations
Chatterjee, A; Chakrabarti, Bikas K.; Chatterjee, Arnab
2006-01-01
We study here numerically the behavior of an ideal gas like model of markets having only one non-consumable commodity. We investigate the behavior of the steady-state distributions of money, commodity and total wealth, as the dynamics of trading or exchange of money and commodity proceeds, with local (in time) fluctuations in the price of the commodity. These distributions are studied in markets with agents having uniform and random saving factors. The self-organizing features in money distribution are similar to the cases without any commodity (or with consumable commodities), the commodity distribution shows an exponential decay. The wealth distribution shows interesting behavior: Gamma like distribution for uniform saving propensity and has the same power-law tail, as that of the money distribution for a market with agents having random saving propensity.
International Nuclear Information System (INIS)
A fully kinetic, reduced-description particle-in-cell (RPIC) model is presented in which deviations from quasineutrality, electron and ion kinetic effects, and nonlinear interactions between low-frequency and high-frequency parametric instabilities are modeled correctly. The model is based on a reduced description where the electromagnetic field is represented by three separate temporal envelopes in order to model parametric instabilities with low-frequency and high-frequency daughter waves. Because temporal envelope approximations are invoked, the simulation can be performed on the electron time scale instead of the time scale of the light waves. The electrons and ions are represented by discrete finite-size particles, permitting electron and ion kinetic effects to be modeled properly. The Poisson equation is utilized to ensure that space-charge effects are included. The RPIC model is fully three dimensional and has been implemented in two dimensions on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. The authors believe this code is the first particle-in-cell code capable of simulating the interaction between low-frequency and high-frequency parametric instabilities in multiple dimensions. Test simulations of stimulated Raman scattering, stimulated Brillouin scattering, and Langmuir decay instability are presented
Mullai, P; Rene, Eldon R; Sridevi, K
2013-01-01
Mangrove sediments host rich assemblages of microorganisms, predominantly mixed bacterial cultures, which can be efficiently used for biohydrogen production through anaerobic dark fermentation. The influence of process parameters such as effect of initial glucose concentration, initial medium pH, and trace metal (Fe(2+)) concentration was investigated in this study. A maximum hydrogen yield of 2.34, 2.3, and 2.6 mol H2 mol(-1) glucose, respectively, was obtained under the following set of optimal conditions: initial substrate concentration-10,000 mg L(-1), initial pH-6.0, and ferrous sulphate concentration-100 mg L(-1), respectively. The addition of trace metal to the medium (100 mg L(-1) FeSO4 ·7H2O) enhanced the biohydrogen yield from 2.3 mol H2 mol(-1) glucose to 2.6 mol H2 mol(-1) glucose. Furthermore, the experimental data was subjected to kinetic analysis and the kinetic constants were estimated with the help of well-known kinetic models available in the literature, namely, Monod model, logistic model and Luedeking-Piret model. The model fitting was found to be in good agreement with the experimental observations, for all the models, with regression coefficient values >0.92. PMID:24319679
Directory of Open Access Journals (Sweden)
P. Mullai
2013-01-01
Full Text Available Mangrove sediments host rich assemblages of microorganisms, predominantly mixed bacterial cultures, which can be efficiently used for biohydrogen production through anaerobic dark fermentation. The influence of process parameters such as effect of initial glucose concentration, initial medium pH, and trace metal (Fe2+ concentration was investigated in this study. A maximum hydrogen yield of 2.34, 2.3, and 2.6 mol H2 mol−1 glucose, respectively, was obtained under the following set of optimal conditions: initial substrate concentration—10,000 mg L−1, initial pH—6.0, and ferrous sulphate concentration—100 mg L−1, respectively. The addition of trace metal to the medium (100 mg L−1 FeSO4·7H2O enhanced the biohydrogen yield from 2.3 mol H2 mol−1 glucose to 2.6 mol H2 mol−1 glucose. Furthermore, the experimental data was subjected to kinetic analysis and the kinetic constants were estimated with the help of well-known kinetic models available in the literature, namely, Monod model, logistic model and Luedeking-Piret model. The model fitting was found to be in good agreement with the experimental observations, for all the models, with regression coefficient values >0.92.
Mullai, P; Rene, Eldon R; Sridevi, K
2013-01-01
Mangrove sediments host rich assemblages of microorganisms, predominantly mixed bacterial cultures, which can be efficiently used for biohydrogen production through anaerobic dark fermentation. The influence of process parameters such as effect of initial glucose concentration, initial medium pH, and trace metal (Fe(2+)) concentration was investigated in this study. A maximum hydrogen yield of 2.34, 2.3, and 2.6 mol H2 mol(-1) glucose, respectively, was obtained under the following set of optimal conditions: initial substrate concentration-10,000 mg L(-1), initial pH-6.0, and ferrous sulphate concentration-100 mg L(-1), respectively. The addition of trace metal to the medium (100 mg L(-1) FeSO4 ·7H2O) enhanced the biohydrogen yield from 2.3 mol H2 mol(-1) glucose to 2.6 mol H2 mol(-1) glucose. Furthermore, the experimental data was subjected to kinetic analysis and the kinetic constants were estimated with the help of well-known kinetic models available in the literature, namely, Monod model, logistic model and Luedeking-Piret model. The model fitting was found to be in good agreement with the experimental observations, for all the models, with regression coefficient values >0.92.
Molecular mechanisms of protein aggregation from global fitting of kinetic models.
Meisl, Georg; Kirkegaard, Julius B; Arosio, Paolo; Michaels, Thomas C T; Vendruscolo, Michele; Dobson, Christopher M; Linse, Sara; Knowles, Tuomas P J
2016-02-01
The elucidation of the molecular mechanisms by which soluble proteins convert into their amyloid forms is a fundamental prerequisite for understanding and controlling disorders that are linked to protein aggregation, such as Alzheimer's and Parkinson's diseases. However, because of the complexity associated with aggregation reaction networks, the analysis of kinetic data of protein aggregation to obtain the underlying mechanisms represents a complex task. Here we describe a framework, using quantitative kinetic assays and global fitting, to determine and to verify a molecular mechanism for aggregation reactions that is compatible with experimental kinetic data. We implement this approach in a web-based software, AmyloFit. Our procedure starts from the results of kinetic experiments that measure the concentration of aggregate mass as a function of time. We illustrate the approach with results from the aggregation of the β-amyloid (Aβ) peptides measured using thioflavin T, but the method is suitable for data from any similar kinetic experiment measuring the accumulation of aggregate mass as a function of time; the input data are in the form of a tab-separated text file. We also outline general experimental strategies and practical considerations for obtaining kinetic data of sufficient quality to draw detailed mechanistic conclusions, and the procedure starts with instructions for extensive data quality control. For the core part of the analysis, we provide an online platform (http://www.amylofit.ch.cam.ac.uk) that enables robust global analysis of kinetic data without the need for extensive programming or detailed mathematical knowledge. The software automates repetitive tasks and guides users through the key steps of kinetic analysis: determination of constraints to be placed on the aggregation mechanism based on the concentration dependence of the aggregation reaction, choosing from several fundamental models describing assembly into linear aggregates and
Multivariate moment closure techniques for stochastic kinetic models
Energy Technology Data Exchange (ETDEWEB)
Lakatos, Eszter, E-mail: e.lakatos13@imperial.ac.uk; Ale, Angelique; Kirk, Paul D. W.; Stumpf, Michael P. H., E-mail: m.stumpf@imperial.ac.uk [Department of Life Sciences, Centre for Integrative Systems Biology and Bioinformatics, Imperial College London, London SW7 2AZ (United Kingdom)
2015-09-07
Stochastic effects dominate many chemical and biochemical processes. Their analysis, however, can be computationally prohibitively expensive and a range of approximation schemes have been proposed to lighten the computational burden. These, notably the increasingly popular linear noise approximation and the more general moment expansion methods, perform well for many dynamical regimes, especially linear systems. At higher levels of nonlinearity, it comes to an interplay between the nonlinearities and the stochastic dynamics, which is much harder to capture correctly by such approximations to the true stochastic processes. Moment-closure approaches promise to address this problem by capturing higher-order terms of the temporally evolving probability distribution. Here, we develop a set of multivariate moment-closures that allows us to describe the stochastic dynamics of nonlinear systems. Multivariate closure captures the way that correlations between different molecular species, induced by the reaction dynamics, interact with stochastic effects. We use multivariate Gaussian, gamma, and lognormal closure and illustrate their use in the context of two models that have proved challenging to the previous attempts at approximating stochastic dynamics: oscillations in p53 and Hes1. In addition, we consider a larger system, Erk-mediated mitogen-activated protein kinases signalling, where conventional stochastic simulation approaches incur unacceptably high computational costs.
Takashima, Keisuke; Yin, Zhiyao; Adamovich, Igor V.
2013-02-01
Nanosecond pulse discharge plasma imaging, coupled pulse energy measurements, and kinetic modeling are used to analyze the mechanism of energy coupling in high repetition rate, spatially uniform, nanosecond pulse discharges in air in plane-to-plane geometry. Under these conditions, coupled pulse energy scales nearly linearly with pressure (number density), with energy coupled per molecule being nearly constant, in good agreement with the kinetic model predictions. In spite of high-peak reduced electric field reached before breakdown, E/N ˜ 500-700 Td, the reduced electric field in the plasma after breakdown is much lower, E/N ˜ 50-100 Td, predicting that a significant fraction of energy coupled to the air plasma, up to 30-40%, is loaded into nitrogen vibrational mode. A self-similar, local ionization kinetic model predicting energy coupling to the plasma in a surface ionization wave discharge produced by a nanosecond voltage pulse has been developed. The model predicts key discharge parameters such as ionization wave speed and propagation distance, electric field, electron density, plasma layer thickness, and pulse energy coupled to the plasma, demonstrating good qualitative agreement with experimental data and two-dimensional kinetic modeling calculations. The model allows an analytic solution and lends itself to incorporation into existing compressible flow codes, at very little computational cost, for in-depth analysis of the nanosecond discharge plasma flow control mechanism. The use of the model would place the main emphasis on coupling of localized thermal perturbations produced by the discharge with the flow via compression waves and would provide quantitative insight into the flow control mechanism on a long time scale.
Modeling the heating and atomic kinetics of a photoionized neon plasma experiment
Lockard, Tom E.
Motivated by gas cell photoionized plasma experiments performed by our group at the Z facility of Sandia National Laboratories, we discuss in this dissertation a modeling study of the heating and ionization of the plasma for conditions characteristic of these experiments. Photoionized plasmas are non-equilibrium systems driven by a broadband x-ray radiation flux. They are commonly found in astrophysics but rarely seen in the laboratory. Several modeling tools have been employed: (1) a view-factor computer code constrained with side x-ray power and gated monochromatic image measurements of the z-pinch radiation, to model the time-history of the photon-energy resolved x-ray flux driving the photoionized plasma, (2) a Boltzmann self-consistent electron and atomic kinetics model to simulate the electron distribution function and configuration-averaged atomic kinetics, (3) a radiation-hydrodynamics code with inline non-equilibrium atomic kinetics to perform a comprehensive numerical simulation of the experiment and plasma heating, and (4) steady-state and time-dependent collisional-radiative atomic kinetics calculations with fine-structure energy level description to assess transient effects in the ionization and charge state distribution of the plasma. The results indicate that the photon-energy resolved x-ray flux impinging on the front window of the gas cell is very well approximated by a linear combination of three geometrically-diluted Planckian distributions. Knowledge of the spectral details of the x-ray drive turned out to be important for the heating and ionization of the plasma. The free electrons in the plasma thermalize quickly relative to the timescales associated with the time-history of the x-ray drive and the plasma atomic kinetics. Hence, electrons are well described by a Maxwellian energy distribution of a single temperature. This finding is important to support the application of a radiation-hydrodynamic model to simulate the experiment. It is found
Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation
Institute of Scientific and Technical Information of China (English)
LI; Zhihui; ZHANG; Hanxin; FU; Song
2005-01-01
The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS.
Experimental study and modeling of the kinetics of refrigerant hydrate formation
International Nuclear Information System (INIS)
Highlights: • The kinetics of the hydrate formation of three refrigerant blends is studied. • The refrigerants include three alternative refrigerants R407C, R410A and R507C. • A kinetic model is developed. • The induction time, apparent rate constant and the rate of hydrate formation are particularly studied. • The effect of sodium dodecyl sulfate (SDS) on the hydrate nucleation rate is investigated. - Abstract: The purpose of this study was to identify compatible hydrate forming-refrigerants suitable for air-conditioning systems. The main challenge in designing an air conditioning system which utilises refrigerant hydrates as a media for storage of cold energy is the rate of formation and dissociation of the refrigerant hydrates. Hence, in this experimental study the kinetics of hydrate formation of three refrigerant blends, viz. R407C, R410A and R507C have been investigated. The induction time for hydrate formation, apparent rate constant of the hydrate reaction, water to hydrate conversion during hydrate growth, storage capacity, and the rate of hydrate formation of these refrigerants at various pressures and temperatures have been obtained using a kinetic model. The effect of sodium dodecyl sulfate (SDS) on the hydrate nucleation rate was also investigated
Modeling the Release Kinetics of Poorly Water-Soluble Drug Molecules from Liposomal Nanocarriers
Directory of Open Access Journals (Sweden)
Stephan Loew
2011-01-01
Full Text Available Liposomes are frequently used as pharmaceutical nanocarriers to deliver poorly water-soluble drugs such as temoporfin, cyclosporine A, amphotericin B, and paclitaxel to their target site. Optimal drug delivery depends on understanding the release kinetics of the drug molecules from the host liposomes during the journey to the target site and at the target site. Transfer of drugs in model systems consisting of donor liposomes and acceptor liposomes is known from experimental work to typically exhibit a first-order kinetics with a simple exponential behavior. In some cases, a fast component in the initial transfer is present, in other cases the transfer is sigmoidal. We present and analyze a theoretical model for the transfer that accounts for two physical mechanisms, collisions between liposomes and diffusion of the drug molecules through the aqueous phase. Starting with the detailed distribution of drug molecules among the individual liposomes, we specify the conditions that lead to an apparent first-order kinetic behavior. We also discuss possible implications on the transfer kinetics of (1 high drug loading of donor liposomes, (2 attractive interactions between drug molecules within the liposomes, and (3 slow transfer of drugs between the inner and outer leaflets of the liposomes.
Kinetics of drug action in disease states: towards physiology-based pharmacodynamic (PBPD) models.
Danhof, Meindert
2015-10-01
Gerhard Levy started his investigations on the "Kinetics of Drug Action in Disease States" in the fall of 1980. The objective of his research was to study inter-individual variation in pharmacodynamics. To this end, theoretical concepts and experimental approaches were introduced, which enabled assessment of the changes in pharmacodynamics per se, while excluding or accounting for the cofounding effects of concomitant changes in pharmacokinetics. These concepts were applied in several studies. The results, which were published in 45 papers in the years 1984-1994, showed considerable variation in pharmacodynamics. These initial studies on kinetics of drug action in disease states triggered further experimental research on the relations between pharmacokinetics and pharmacodynamics. Together with the concepts in Levy's earlier publications "Kinetics of Pharmacologic Effects" (Clin Pharmacol Ther 7(3): 362-372, 1966) and "Kinetics of pharmacologic effects in man: the anticoagulant action of warfarin" (Clin Pharmacol Ther 10(1): 22-35, 1969), they form a significant impulse to the development of physiology-based pharmacodynamic (PBPD) modeling as novel discipline in the pharmaceutical sciences. This paper reviews Levy's research on the "Kinetics of Drug Action in Disease States". Next it addresses the significance of his research for the evolution of PBPD modeling as a scientific discipline. PBPD models contain specific expressions to characterize in a strictly quantitative manner processes on the causal path between exposure (in terms of concentration at the target site) and the drug effect (in terms of the change in biological function). Pertinent processes on the causal path are: (1) target site distribution, (2) target binding and activation and (3) transduction and homeostatic feedback.
Equilibrium models and kinetic for the adsorption of methylene blue on Co-hectorites
International Nuclear Information System (INIS)
The adsorption of methylene blue (MB) onto the surface of cobalt doping hectorite (Co-hectorite) was systematically studied. The physical properties of Co-hectorites were investigated, where characterizations were carried out by X-ray diffraction (XRD) and Electron Diffraction Spectrum (EDS) techniques, and morphology was examined by nitrogen adsorption. The sample with a Co content 5% (m/m) had a higher specific surface area than other Co-hectorites. The pore diameters were distributed between 2.5 and 5.0 nm. The adsorption results revealed that Co-hectorite surfaces possessed effective interactions with MB and bases, and greatest adsorption capacity achieved with Co content 5%, where the best-fit isotherm model was the Langmuir adsorption model. Kinetic studies were fitted to the pseudo-second-order kinetic model. The intraparticle diffusion was not the rate-limiting step for the whole reaction.
Maulidah, Rifa'atul; Purqon, Acep
2016-08-01
Mendong (Fimbristylis globulosa) has a potentially industrial application. We investigate a predictive model for heat and mass transfer in drying kinetics during drying a Mendong. We experimentally dry the Mendong by using a microwave oven. In this study, we analyze three mathematical equations and feed forward neural network (FNN) with back propagation to describe the drying behavior of Mendong. Our results show that the experimental data and the artificial neural network model has a good agreement and better than a mathematical equation approach. The best FNN for the prediction is 3-20-1-1 structure with Levenberg- Marquardt training function. This drying kinetics modeling is potentially applied to determine the optimal parameters during mendong drying and to estimate and control of drying process.
[Effective constituents and kinetic model of microwave drying from shuxiong prescription].
Zhang, Ping; Liao, Zhenggen; Liang, Xinli; Zhao, Guowei; Lai, Jun; Zhu, Jing
2011-03-01
A mathematical model of microwave drying kinetics based on Fick's second diffusion law was established and and the influence of microwave drying on ferulic acid (FA) and hydrosafflower yellow A (HSYA) in Shuxiong prescription was studied. The proposed model has been verified by using experimental data from microwave drying of Shuxiong prescription. By increasing the microwave output power (500-650 W) and the sample amount (15-60 g), the diversion rate of FA and HSYA changed. In order to determine the kinetic parameters, the drying data were fifed to various models based on the ratios of differences between the initial and final moisture contents and equilibrium moisture content versus drying time. The activation energy was calculated using an exponential expression based on Arrhenius equation. The relationship between the drying rate constant and effective moisture diffusivity was also estimated, and it showed linear. PMID:21657072
Empirical modeling the ultrasound-assisted base-catalyzed sunflower oil methanolysis kinetics
Directory of Open Access Journals (Sweden)
Avramović Jelena M.
2012-01-01
Full Text Available The ultrasound-assisted sunflower oil methanolysis catalyzed by KOH was studied to define a simple empirical kinetic model useful for reactor design without complex computation. It was assumed that the neutralization of free fatty acids and the saponification reaction were negligible. The methanolysis process rate was observed to be controlled by the mass transfer limitation in the initial heterogeneous regime and by the chemical reaction in the later pseudo-homogeneous regime. The model involving the irreversible second-order kinetics was established and used for simulation of the triacylglycerol conversion and the fatty acid methyl esters formation in the latter regime. A good agreement between the proposed model and the experimental data in the chemically controlled regime was found.
A new kinetic model of ultrasound-assisted extraction of polysaccharides from Chinese chive.
Zhang, Wei-Nan; Zhang, Hai-Lin; Lu, Chao-Qun; Luo, Jian-Ping; Zha, Xue-Qiang
2016-12-01
Chinese chive, a famous green vegetable, is widely cultivated in the Asia. In the present study, we found that ultrasound caused the degradation of Chinese chive polysaccharides (CCP) in the process of extraction. Since lacking the consideration of polysaccharide degradation, the traditional kinetic models can not reflect the real extraction process of CCP. Therefore, a modified kinetic model was thus established by introducing a parameter of degradation coefficient based on the Fick's second law, suggesting the diffusion and degradation of CCP is highly dependent on the ultrasonic power, extraction temperature and solid-liquid ratio. According to this modified model, the maximum CCP yield was obtained under an optimal extraction condition including extraction temperature 37°C, ultrasonic power 458 w, extraction time 30min and solid-liquid ratio 1:32. The objective polysaccharides responding to ultrasound were shown to be four different fractions, contributing to the increased diffusion and degradation of CCP by ultrasound treatment. PMID:27374533
A capacity fade model for lithium-ion batteries including diffusion and kinetics
International Nuclear Information System (INIS)
A one dimensional model incorporating solvent diffusion and kinetics of solid electrolyte interphase (SEI) formation is developed to study capacity fade in lithium ion batteries. The model assumes that solvent diffuses through the SEI (solid electrolyte interphase) and undergoes a two electron reduction at the carbon SEI interface. The kinetics of the reduction reaction at the SEI–electrolyte interface and the solvent diffusivity are seen to be the most important parameters governing SEI formation. The capacity loss is seen to be a function of the thickness of the SEI layer and is seen to vary linearly over time. The rate constant governing SEI formation and solvent diffusivity are seen to follow Arrhenius type relationships. The model results are compared with and are found to be in good agreement with experimental data.
Rudzinski, Joseph F; Bereau, Tristan
2016-01-01
Molecular simulations can provide microscopic insight into the physical and chemical driving forces of complex molecular processes. Despite continued advancement of simulation methodology, model errors may lead to inconsistencies between simulated and reference (e.g., from experiments or higher-level simulations) observables. To bound the microscopic information generated by computer simulations within reference measurements, we propose a method that reweights the microscopic transitions of the system to improve consistency with a set of coarse kinetic observables. The method employs the well-developed Markov state modeling framework to efficiently link microscopic dynamics with long-time scale constraints, thereby consistently addressing a wide range of time scales. To emphasize the robustness of the method, we consider two distinct coarse-grained models with significant kinetic inconsistencies. When applied to the simulated conformational dynamics of small peptides, the reweighting procedure systematically ...
A KINETIC MODEL FOR H2O2/UV PROCESS IN A COMPLETELY MIXED BATCH REACTOR. (R825370C076)
A dynamic kinetic model for the advanced oxidation process (AOP) using hydrogen peroxide and ultraviolet irradiation (H2O2/UV) in a completely mixed batch reactor (CMBR) is developed. The model includes the known elementary chemical and photochemical reac...
Directory of Open Access Journals (Sweden)
Gizzatkulov Nail M
2010-08-01
Full Text Available Abstract Background Systems biology research and applications require creation, validation, extensive usage of mathematical models and visualization of simulation results by end-users. Our goal is to develop novel method for visualization of simulation results and implement it in simulation software package equipped with the sophisticated mathematical and computational techniques for model development, verification and parameter fitting. Results We present mathematical simulation workbench DBSolve Optimum which is significantly improved and extended successor of well known simulation software DBSolve5. Concept of "dynamic visualization" of simulation results has been developed and implemented in DBSolve Optimum. In framework of the concept graphical objects representing metabolite concentrations and reactions change their volume and shape in accordance to simulation results. This technique is applied to visualize both kinetic response of the model and dependence of its steady state on parameter. The use of the dynamic visualization is illustrated with kinetic model of the Krebs cycle. Conclusion DBSolve Optimum is a user friendly simulation software package that enables to simplify the construction, verification, analysis and visualization of kinetic models. Dynamic visualization tool implemented in the software allows user to animate simulation results and, thereby, present them in more comprehensible mode. DBSolve Optimum and built-in dynamic visualization module is free for both academic and commercial use. It can be downloaded directly from http://www.insysbio.ru.
A generalized cellular automata approach to modeling first order enzyme kinetics
Indian Academy of Sciences (India)
Abhishek Dutta; Saurajyoti Kar; Advait Apte; Ingmar Nopens; Denis Constales
2015-04-01
Biochemical processes occur through intermediate steps which are associated with the formation of reaction complexes. These enzyme-catalyzed biochemical reactions are inhibited in a number of ways such as inhibitors competing for the binding site directly, inhibitors deforming the allosteric site or inhibitors changing the structure of active substrate. Using an in silico approach, the concentration of various reaction agents can be monitored at every single time step, which are otherwise difficult to analyze experimentally. Cell-based models with discrete state variables, such as Cellular Automata (CA) provide an understanding of the organizational principles of interacting cellular systems to link the individual cell (microscopic) dynamics wit a particular collective (macroscopic) phenomenon. In this study, a CA model representing a first order enzyme kinetics with inhibitor activity is formulated. The framework of enzyme reaction rules described in this study is probabilistic. An extended von Neumann neighborhood with periodic boundary condition is implemented on a two-dimensional (2D) lattice framework. The effect of lattice-size variation is studied followed by a sensitivity analysis of the model output to the probabilistic parameters which represent various kinetic reaction constants in the enzyme kinetic model. This provides a deeper insight into the sensitivity of the CA model to these parameters. It is observed that cellular automata can capture the essential features of a discrete real system, consisting of space, time and state, structured with simple local rules without making complex implementations but resulting in complex but explainable patterns.
Development of Kinetic Models for the Liquid Phase Methanol (LPMEOH tm) Process
Energy Technology Data Exchange (ETDEWEB)
Xiang-Dong Peng
2002-06-01
This report covers our recent work on the kinetics of the LPMEOH{trademark} process. The major part of the report concerns the development of more robust kinetic models for the LPMEOH{trademark} reaction system. The development was needed to meet the requirements for more accurate process simulations over a wide range of conditions. To this end, kinetic experiments were designed based on commercial needs and a D-Optimal design package. A database covering 53 different conditions was built. Two new reactions were identified and added to the LPMEOH{trademark} reaction network. New rate models were developed for all 15 reactions in the system. The new rate models are more robust than the original ones, showing better fit to the experimental results over a wide range of conditions. Related to this model development are some new understandings about the sensitivity of rate models and their effects on catalyst life study. The last section of this report covers a separate topic: water injection to the LPMEOH{trademark} reactor and its effects on the LPMEOH{trademark} process. An investigation was made of whether water injection can enhance the reactor productivity and how this enhancement depends on the composition of the major syngas feed. A water injection condition that resulted in 32% enhancement in productivity was observed. A catalyst life test under this water injection condition was conducted and showed no negative effects of water injection on catalyst stability.
Parameter estimation for whole-body kinetic model of FDG metabolism
Institute of Scientific and Technical Information of China (English)
CUI Yunfeng; BAI Jing; CHEN Yingmao; TIAN Jiahe
2006-01-01
Based on the radioactive tracer [18F]2-fluoro-2-deoxy-D-glucose (FDG), positron emission tomography (PET), and compartment model, the tracer kinetic study has become an important method to investigate the glucose metabolic kinetics in human body.In this work, the kinetic parameters of three-compartment and four-parameter model for the FDG metabolism in the tissues of myocardium, lung, liver, stomach, spleen, pancreas, and marrow were estimated through some dynamic FDG-PET experiments. Together with published brain and skeletal muscle parameters, a relatively complete whole-body model was presented. In the liver model, the dual blood supply from the hepatic artery and the portal vein to the liver was considered for parameter estimation, and the more accurate results were obtained using the dual-input rather than the single arterial-input. The established whole-body model provides the functional information of FDG metabolism in human body. It can be used to further investigate the glucose metabolism, and also be used for the simulation and visualization of FDG metabolic process in human body.
Kinetic model of force-free current sheets with non-uniform temperature
Kolotkov, D. Y.; Vasko, I. Y.; Nakariakov, V. M.
2015-11-01
The kinetic model of a one-dimensional force-free current sheet (CS) developed recently by Harrison and Neukirch [Phys. Rev. Lett. 102(13), 135003 (2009)] predicts uniform distributions of the plasma temperature and density across the CS. However, in realistic physical systems, inhomogeneities of these plasma parameters may arise quite naturally due to the boundary conditions or local plasma heating. Moreover, as the CS spatial scale becomes larger than the characteristic kinetic scales (the regime often referred to as the MHD limit), it should be possible to set arbitrary density and temperature profiles. Thus, an advanced model has to allow for inhomogeneities of the macroscopic plasma parameters across the CS, to be consistent with the MHD limit. In this paper, we generalise the kinetic model of a force-free current sheet, taking into account the inhomogeneity of the density and temperature across the CS. In the developed model, the density may either be enhanced or depleted in the CS central region. The temperature profile is prescribed by the density profile, keeping the plasma pressure uniform across the CS. All macroscopic parameters, as well as the distribution functions for the protons and electrons, are determined analytically. Applications of the developed model to current sheets observed in space plasmas are discussed.
Duration of extracorporeal therapy in acute maple syrup urine disease: a kinetic model.
Phan, Véronique; Clermont, Marie-José; Merouani, Aicha; Litalien, Catherine; Tucci, Marisa; Lambert, Marie; Mitchell, Grant; Jouvet, Philippe
2006-05-01
Maple syrup urine disease (MSUD, MIM 248600) can be complicated by metabolic crises necessitating extracorporeal removal therapy (ECRT). Since leucine levels are usually not immediately available during therapy, an accurate kinetic model of leucine plasma levels during removal would be useful to establish the duration of ECRT. Such a kinetic model is available for neonates undergoing continuous ECRT (CECRT) with a leucine clearance>or=35 ml min-1 1.73 m-2. The current study tests the validity of this model in older children. Plasma leucine levels were obtained from eleven ECRT sessions [seven CECRT and four intermittent hemodialysis (HDi) sessions] in seven children aged 1-14 years. No hemodynamic instability or neurological complications were observed during treatment. HDi provided a higher leucine clearance and required shorter sessions than CECRT (5.4+/-0.6 vs. 17.1+/-6.0 h). All patients regained precrisis neurological status except for one patient who had severe neurological damage (severe cerebral edema) at the time of dialysis and subsequently died despite efficient leucine removal. A leucine clearance>or=50 ml min-1 1.73 m-2 is required to obtain a kinetic model similar to that reported in neonates, both with CECRT and HDi. This model should be helpful in predicting the duration of therapy needed to attain desired leucine levels. PMID:16518628
Kinetic model of force-free current sheets with non-uniform temperature
Energy Technology Data Exchange (ETDEWEB)
Kolotkov, D. Y.; Nakariakov, V. M. [Centre for Fusion, Space and Astrophysics, Physics Department, University of Warwick, Coventry (United Kingdom); Vasko, I. Y. [Space Research Institute, RAS, Moscow (Russian Federation)
2015-11-15
The kinetic model of a one-dimensional force-free current sheet (CS) developed recently by Harrison and Neukirch [Phys. Rev. Lett. 102(13), 135003 (2009)] predicts uniform distributions of the plasma temperature and density across the CS. However, in realistic physical systems, inhomogeneities of these plasma parameters may arise quite naturally due to the boundary conditions or local plasma heating. Moreover, as the CS spatial scale becomes larger than the characteristic kinetic scales (the regime often referred to as the MHD limit), it should be possible to set arbitrary density and temperature profiles. Thus, an advanced model has to allow for inhomogeneities of the macroscopic plasma parameters across the CS, to be consistent with the MHD limit. In this paper, we generalise the kinetic model of a force-free current sheet, taking into account the inhomogeneity of the density and temperature across the CS. In the developed model, the density may either be enhanced or depleted in the CS central region. The temperature profile is prescribed by the density profile, keeping the plasma pressure uniform across the CS. All macroscopic parameters, as well as the distribution functions for the protons and electrons, are determined analytically. Applications of the developed model to current sheets observed in space plasmas are discussed.
Bioconversion of natural gas to liquid fuel: opportunities and challenges.
Fei, Qiang; Guarnieri, Michael T; Tao, Ling; Laurens, Lieve M L; Dowe, Nancy; Pienkos, Philip T
2014-01-01
Natural gas is a mixture of low molecular weight hydrocarbon gases that can be generated from either fossil or anthropogenic resources. Although natural gas is used as a transportation fuel, constraints in storage, relatively low energy content (MJ/L), and delivery have limited widespread adoption. Advanced utilization of natural gas has been explored for biofuel production by microorganisms. In recent years, the aerobic bioconversion of natural gas (or primarily the methane content of natural gas) into liquid fuels (Bio-GTL) by biocatalysts (methanotrophs) has gained increasing attention as a promising alternative for drop-in biofuel production. Methanotrophic bacteria are capable of converting methane into microbial lipids, which can in turn be converted into renewable diesel via a hydrotreating process. In this paper, biodiversity, catalytic properties and key enzymes and pathways of these microbes are summarized. Bioprocess technologies are discussed based upon existing literature, including cultivation conditions, fermentation modes, bioreactor design, and lipid extraction and upgrading. This review also outlines the potential of Bio-GTL using methane as an alternative carbon source as well as the major challenges and future research needs of microbial lipid accumulation derived from methane, key performance index, and techno-economic analysis. An analysis of raw material costs suggests that methane-derived diesel fuel has the potential to be competitive with petroleum-derived diesel.
Bioconversion of petroleum hydrocarbons in soil using apple filter cake
Medaura, M. Cecilia; Ércoli, Eduardo C.
2008-01-01
The aim of this study was to investigate the feasibility of using apple filter cake, a fruit-processing waste to enhance the bioremediation of petroleum contaminated soil. A rotating barrel system was used to study the bioconversion of the xenobiotic compound by natural occurring microbial population. The soil had been accidentally polluted with a total petroleum hydrocarbon concentration of 41,000 ppm. Although this global value was maintained during the process, microbial intervention was evidenced through transformation of the petroleum fractions. Thus, fractions that represent a risk for the environment (GRO, Gasoline Range Organics i.e., C6 to C10–12; DRO, Diesel Range Organics i.e., C8–12 to C24–26 and RRO, Residual Range Organics i.e., C25 to C35) were significantly reduced, from 2.95% to 1.39%. On the contrary, heavier weight fraction from C35 plus other organics increased in value from 1.15% to 3.00%. The noticeable diminution of low molecular weight hydrocarbons content and hence environmental risk by the process plus the improvement of the physical characteristics of the soil, are promising results with regard to future application at large scale. PMID:24031241
Bioconversion of natural gas to liquid fuel: Opportunities and challenges
Energy Technology Data Exchange (ETDEWEB)
Fei, Q; Guarnieri, MT; Tao, L; Laurens, LML; Dowe, N; Pienkos, PT
2014-05-01
Natural gas is a mixture of low molecular weight hydrocarbon gases that can be generated from either fossil or anthropogenic resources. Although natural gas is used as a transportation fuel, constraints in storage, relatively low energy content (MJ/L), and delivery have limited widespread adoption. Advanced utilization of natural gas has been explored for biofuel production by microorganisms. In recent years, the aerobic bioconversion of natural gas (or primarily the methane content of natural gas) into liquid fuels (Bio-GTL) by biocatalysts (methanotrophs) has gained increasing attention as a promising alternative for drop-in biofuel production. Methanotrophic bacteria are capable of converting methane into microbial lipids, which can in turn be converted into renewable diesel via a hydrotreating process. In this paper, biodiversity, catalytic properties and key enzymes and pathways of these microbes are summarized. Bioprocess technologies are discussed based upon existing literature, including cultivation conditions, fermentation modes, bioreactor design, and lipid extraction and upgrading. This review also outlines the potential of Bio-GTL using methane as an alternative carbon source as well as the major challenges and future research needs of microbial lipid accumulation derived from methane, key performance index, and techno-economic analysis. An analysis of raw material costs suggests that methane-derived diesel fuel has the potential to be competitive with petroleum-derived diesel. (C) 2014 The Authors. Published by Elsevier Inc.
Bioconversion of Natural Gas to Liquid Fuel. Opportunities and Challenges
Energy Technology Data Exchange (ETDEWEB)
Fei, Qiang [National Renewable Energy Lab. (NREL), Golden, CO (United States); Guarnieri, Michael T. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Tao, Ling [National Renewable Energy Lab. (NREL), Golden, CO (United States); Laurens, Lieve M. L. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Dowe, Nancy [National Renewable Energy Lab. (NREL), Golden, CO (United States); Pienkos, Philip T. [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2014-05-01
Natural gas is a mixture of low molecular weight hydrocarbon gases that can be generated from either fossil or anthropogenic resources. Although natural gas is used as a transportation fuel, constraints in storage, relatively low energy content (MJ/L), and delivery have limited widespread adoption. Advanced utilization of natural gas has been explored for biofuel production by microorganisms. In recent years, the aerobic bioconversion of natural gas (or primarily the methane content of natural gas) into liquid fuels (Bio-GTL) by biocatalysts (methanotrophs) has gained increasing attention as a promising alternative for drop-in biofuel production. Moreover, methanotrophic bacteria are capable of converting methane into microbial lipids, which can in turn be converted into renewable diesel via a hydrotreating process. In this paper, biodiversity, catalytic properties and key enzymes and pathways of these microbes are summarized. Bioprocess technologies are discussed based upon existing literature, including cultivation conditions, fermentation modes, bioreactor design, and lipid extraction and upgrading. Our review also outlines the potential of Bio-GTL using methane as an alternative carbon source as well as the major challenges and future research needs of microbial lipid accumulation derived from methane, key performance index, and techno-economic analysis. An analysis of raw material costs suggests that methane-derived diesel fuel has the potential to be competitive with petroleum-derived diesel.
Numerical Solution of Fractional Neutron Point Kinetics Model in Nuclear Reactor
Directory of Open Access Journals (Sweden)
Nowak Tomasz Karol
2014-06-01
Full Text Available This paper presents results concerning solutions of the fractional neutron point kinetics model for a nuclear reactor. Proposed model consists of a bilinear system of fractional and ordinary differential equations. Three methods to solve the model are presented and compared. The first one entails application of discrete Grünwald-Letnikov definition of the fractional derivative in the model. Second involves building an analog scheme in the FOMCON Toolbox in MATLAB environment. Third is the method proposed by Edwards. The impact of selected parameters on the model’s response was examined. The results for typical input were discussed and compared.
On the Discrete Kinetic Theory for Active Particles. Modelling the Immune Competition
Directory of Open Access Journals (Sweden)
I. Brazzoli
2006-01-01
Full Text Available This paper deals with the application of the mathematical kinetic theory for active particles, with discrete activity states, to the modelling of the immune competition between immune and cancer cells. The first part of the paper deals with the assessment of the mathematical framework suitable for the derivation of the models. Two specific models are derived in the second part, while some simulations visualize the applicability of the model to the description of biological events characterizing the immune competition. A final critical outlines some research perspectives.
Gabardo, Sabrina; Pereira, Gabriela Feix; Rech, Rosane; Ayub, Marco Antônio Záchia
2015-09-01
We investigated the kinetics of whey bioconversion into ethanol by Kluyveromyces marxianus in continuous bioreactors using the "accelerostat technique" (A-stat). Cultivations using free and Ca-alginate immobilized cells were evaluated using two different acceleration rates (a). The kinetic profiles of these systems were modeled using four different unstructured models, differing in the expressions for the specific growth (μ) and substrate consumption rates (r s), taking into account substrate limitation and product inhibition. Experimental data showed that the dilution rate (D) directly affected cell physiology and metabolism. The specific growth rate followed the dilution rate (μ≈D) for the lowest acceleration rate (a = 0.0015 h(-2)), condition in which the highest ethanol yield (0.52 g g(-1)) was obtained. The highest acceleration rate (a = 0.00667 h(-2)) led to a lower ethanol yield (0.40 g g(-1)) in the system where free cells were used, whereas with immobilized cells ethanol yields increased by 23 % (0.49 g g(-1)). Among the evaluated models, Monod and Levenspiel combined with Ghose and Tyagi models were found to be more appropriate for describing the kinetics of whey bioconversion into ethanol. These results may be useful in scaling up the process for ethanol production from whey. PMID:26233317
Gabardo, Sabrina; Pereira, Gabriela Feix; Rech, Rosane; Ayub, Marco Antônio Záchia
2015-09-01
We investigated the kinetics of whey bioconversion into ethanol by Kluyveromyces marxianus in continuous bioreactors using the "accelerostat technique" (A-stat). Cultivations using free and Ca-alginate immobilized cells were evaluated using two different acceleration rates (a). The kinetic profiles of these systems were modeled using four different unstructured models, differing in the expressions for the specific growth (μ) and substrate consumption rates (r s), taking into account substrate limitation and product inhibition. Experimental data showed that the dilution rate (D) directly affected cell physiology and metabolism. The specific growth rate followed the dilution rate (μ≈D) for the lowest acceleration rate (a = 0.0015 h(-2)), condition in which the highest ethanol yield (0.52 g g(-1)) was obtained. The highest acceleration rate (a = 0.00667 h(-2)) led to a lower ethanol yield (0.40 g g(-1)) in the system where free cells were used, whereas with immobilized cells ethanol yields increased by 23 % (0.49 g g(-1)). Among the evaluated models, Monod and Levenspiel combined with Ghose and Tyagi models were found to be more appropriate for describing the kinetics of whey bioconversion into ethanol. These results may be useful in scaling up the process for ethanol production from whey.
Directory of Open Access Journals (Sweden)
Villar-Cociña, E.
2005-06-01
Full Text Available A kinetic-diffusive model proposed by the authors in previous papers to describe pozzolanic reaction kinetics in sugar cane straw-clay ash (SCSCA/calcium hydroxide (CH systems is validated in this study. Two different methods (direct and indirect for determining pozzolanic activity were applied and their effect on pozzolanic reaction rate kinetic constants evaluated. Determined by fitting a model to the data, these constants are used to quantitatively characterize pozzolanic activity. The values of the kinetic constants calculated with the model were similar for the two methods. Classic kinetic models, such as the Jander, modified Jander and Zhuravlev models, were also applied to the system studied and the results were compared to the figures calculated with the model proposed. The kinetic-diffusive approach proposed was found to be valid regardless of the method for determining pozzolanic activity used, and to be the most suitable model for describing pozzolanic reaction kinetics in the SCSCA/lime system.
Se valida la aplicación de un modelo cinético-difusivo propuesto por los autores en trabajos anteriores para describir la cinética de reacción puzolánica en sistemas ceniza de paja de caña-arcilla (CPCAñúdróxido de calcio (CH. Se aplican 2 métodos diferentes de actividad puzolánica (directo e indirecto y se valora el efecto que pudieran tener los mismos sobre las constantes cinéticas de velocidad de reacción de la reacción puzolánica. Estas constantes cinéticas son determinadas en el proceso de ajuste del modelo y permiten caracterizar cuantitativamente la actividad puzolánica. Los resultados muestran la similitud de las constantes cinéticas de velocidad de reacción calculadas, aplicando el modelo a los resultados experimentales obtenidos por ambos métodos. Además, fueron aplicados al sistema estudiado modelos cinéticos el chicos como: modelo de Jander, modelo de Jander Modificado y el modelo de Zhuravlev y
Non-Michaelis-Menten kinetics model for conductance of low-conductance potassium ion channels.
Tolokh, Igor S; Tolokh, Illya I; Cho, Hee Cheol; D'Avanzo, Nazzareno; Backx, Peter H; Goldman, Saul; Gray, C G
2005-02-01
A reduced kinetics model is proposed for ion permeation in low-conductance potassium ion channels with zero net electrical charge in the selectivity filter region. The selectivity filter is assumed to be the only conductance-determining part of the channel. Ion entry and exit rate constants depend on the occupancy of the filter due to ion-ion interactions. The corresponding rates are assumed slow relative to the rates of ion motion between binding sites inside the filter, allowing a reduction of the kinetics model of the filter by averaging the entry and exit rate constants over the states with a particular occupancy number. The reduced kinetics model for low-conductance channels is described by only three states and two sets of effective rate constants characterizing transitions between these states. An explicit expression for the channel conductance as a function of symmetrical external ion concentration is derived under the assumption that the average electrical mobility of ions in the selectivity filter region in a limited range of ion concentrations does not depend on these concentrations. The simplified conductance model is shown to provide a good description of the experimentally observed conductance-concentration curve for the low-conductance potassium channel Kir2.1, and also predicts the mean occupancy of the selectivity filter of this channel. We find that at physiological external ion concentrations this occupancy is much lower than the value of two ions observed for one of the high-conductance potassium channels, KcsA.
Multi-scale modelling and numerical simulation of electronic kinetic transport
International Nuclear Information System (INIS)
This research thesis which is at the interface between numerical analysis, plasma physics and applied mathematics, deals with the kinetic modelling and numerical simulations of the electron energy transport and deposition in laser-produced plasmas, having in view the processes of fuel assembly to temperature and density conditions necessary to ignite fusion reactions. After a brief review of the processes at play in the collisional kinetic theory of plasmas, with a focus on basic models and methods to implement, couple and validate them, the author focuses on the collective aspect related to the free-streaming electron transport equation in the non-relativistic limit as well as in the relativistic regime. He discusses the numerical development and analysis of the scheme for the Vlasov-Maxwell system, and the selection of a validation procedure and numerical tests. Then, he investigates more specific aspects of the collective transport: the multi-specie transport, submitted to phase-space discontinuities. Dealing with the multi-scale physics of electron transport with collision source terms, he validates the accuracy of a fast Monte Carlo multi-grid solver for the Fokker-Planck-Landau electron-electron collision operator. He reports realistic simulations for the kinetic electron transport in the frame of the shock ignition scheme, the development and validation of a reduced electron transport angular model. He finally explores the relative importance of the processes involving electron-electron collisions at high energy by means a multi-scale reduced model with relativistic Boltzmann terms
Directory of Open Access Journals (Sweden)
ROHADIN MORADI-RAD
2015-10-01
Full Text Available The modeling of kinetic and isotherm curves acquired in adsorption of polycyclic aromatic hydrocarbons (PAHs as a model compound (phenanthrene on activated carbons in the organic solvent. All the runs were carried out in a batch system at atmospheric pressure, process temperature of 24±2°C, and using the 100 ml phenanthrene in cyclohexan. This experimental work was mainly focused on the study of how the variables properties such as adsorbent dosage, the initial phenanthrene concentration, contact time and pH of cyclohexane solutions influence the kinetic and isotherm of the adsorption process. The results indicated that pH did not play a key role in the process of phenanthrene adsorption. The considerable adsorption (8.34 mg/g was reached at pH 7, adsorbent dosage of 0.3 g/100 ml and agitation time of 11 h on activated carbons. The impact of adsorbent dose on phenanthrene concentration was not important after 0.3 g/100 ml. The results also showed that adsorption capacity became notably greater with an increase in contact time and initial phenanthrene concentration. Another important finding was that adsorption processes and equilibrium data well fitted by pseudo-second-order kinetic (R2=0.99 and Fraundlich adsorption models (R2=0.99. It can be concluded that there was a significant positive correlation between adsorption processes and the Freundlich isotherm model but Langmuir theory showed only a weak association.
El-Seddik, Mostafa M; Galal, Mona M; Radwan, A G; Abdel-Halim, Hisham S
2016-01-01
This paper addresses a modified kinetic-hydraulic model for up-flow anaerobic sludge blanket (UASB) reactor aimed to treat wastewater of biodegradable organic substrates as acetic acid based on Van der Meer model incorporated with biological granules inclusion. This dynamic model illustrates the biomass kinetic reaction rate for both direct and indirect growth of microorganisms coupled with the amount of biogas produced by methanogenic bacteria in bed and blanket zones of reactor. Moreover, the pH value required for substrate degradation at the peak specific growth rate of bacteria is discussed for Andrews' kinetics. The sensitivity analyses of biomass concentration with respect to fraction of volume of reactor occupied by granules and up-flow velocity are also demonstrated. Furthermore, the modified mass balance equations of reactor are applied during steady state using Newton Raphson technique to obtain a suitable degree of freedom for the modified model matching with the measured results of UASB Sanhour wastewater treatment plant in Fayoum, Egypt. PMID:27054727
El-Seddik, Mostafa M; Galal, Mona M; Radwan, A G; Abdel-Halim, Hisham S
2016-01-01
This paper addresses a modified kinetic-hydraulic model for up-flow anaerobic sludge blanket (UASB) reactor aimed to treat wastewater of biodegradable organic substrates as acetic acid based on Van der Meer model incorporated with biological granules inclusion. This dynamic model illustrates the biomass kinetic reaction rate for both direct and indirect growth of microorganisms coupled with the amount of biogas produced by methanogenic bacteria in bed and blanket zones of reactor. Moreover, the pH value required for substrate degradation at the peak specific growth rate of bacteria is discussed for Andrews' kinetics. The sensitivity analyses of biomass concentration with respect to fraction of volume of reactor occupied by granules and up-flow velocity are also demonstrated. Furthermore, the modified mass balance equations of reactor are applied during steady state using Newton Raphson technique to obtain a suitable degree of freedom for the modified model matching with the measured results of UASB Sanhour wastewater treatment plant in Fayoum, Egypt.
Miller, T L; Currenti, E; Wolin, M J
2000-10-01
A system is described that combines the fermentation of cellulose to acetate, CH4, and CO2 by Ruminococcus albus and Methanobrevibacter smithii with the fermentation of acetate to CH4 and CO2 by Methanosarcina barkeri to convert cellulose to CH4 and CO2. A cellulose-containing medium was pumped into a co-culture of the cellulolytic R. albus and the H2-using methanogen, Mb. smithii. The effluent was fed into a holding reservoir, adjusted to pH 4.5, and then pumped into a culture of Ms. barkeri maintained at constant volume by pumping out culture contents. Fermentation of 1% cellulose to CH4 and CO2 was accomplished during 132 days of operation with retention times (RTs) of the Ms. barkeri culture of 7.5-3.8 days. Rates of acetate utilization were 9.5-17.3 mmol l(-1) day(-1) and increased with decreasing RT. The Ks for acetate utilization was 6-8 mM. The two-stage system can be used as a model system for studying biological and physical parameters that influence the bioconversion process. Our results suggest that manipulating the different phases of cellulose fermentation separately can effectively balance the pH and ionic requirements of the acid-producing phase with the acid-using phase of the overall fermentation. PMID:11092623
Phase field model for strong anisotropy of kinetic and highly anisotropic interfacial energy
Institute of Scientific and Technical Information of China (English)
ZHANG Guo-wei; HOU Hua; CHENG Jun
2006-01-01
A phase-field model was established for simulating pure materials, which was calculated effectively and taken into account the strong anisotropy of kinetic and highly anisotropic interfacial energy. The anisotropy (strong kinetic and highly interfacial energy) of various degrees was simulated with numerical calculation. During a variety of interfacial anisotropy coefficient, equilibrium crystal shape varies from smoothness to corner. There has a critical value during the course of the transformation. When the anisotropy coefficenct is lower than the critical value, the growth velocity v increases monotonically with the increase of it. Whereas the anisotropy coefficent is higher than the critical value, the growth velocity decreases with the increases of it. During a variety of degree of supercooling, the growth velocity is under control from thermal diffusion to kinetics. Under the control of thermal diffusion, the growth velocity increases with the increase of degree of supercooling and tip radius R decreases with the increase of temperature. Under the control of kinetics, with the increase of degree of supercooling both V and R, which can not fit the traditional microcosmic theory.
A look into amyloid formation by transthyretin: aggregation pathway and a novel kinetic model.
Faria, Tiago Q; Almeida, Zaida L; Cruz, Pedro F; Jesus, Catarina S H; Castanheira, Pedro; Brito, Rui M M
2015-03-21
The aggregation of proteins into insoluble amyloid fibrils is the hallmark of many, highly debilitating, human pathologies such as Alzheimer's or Parkinson's disease. Transthyretin (TTR) is a homotetrameric protein implicated in several amyloidoses like Senile Systemic Amyloidosis (SSA), Familial Amyloid Polyneuropathy (FAP), Familial Amyloid Cardiomyopathy (FAC), and the rare Central Nervous System selective Amyloidosis (CNSA). In this work, we have investigated the kinetics of TTR aggregation into amyloid fibrils produced by the addition of NaCl to acid-unfolded TTR monomers and we propose a mathematically simple kinetic mechanism to analyse the aggregation kinetics of TTR. We have conducted circular dichroism, intrinsic tryptophan fluorescence and thioflavin-T emission experiments to follow the conformational changes accompanying amyloid formation at different TTR concentrations. Kinetic traces were adjusted to a two-step model with the first step being second-order and the second being unimolecular. The molecular species present in the pathway of TTR oligomerization were characterized by size exclusion chromatography coupled to multi-angle light scattering and by transmission electron microscopy. The results show the transient accumulation of oligomers composed of 6 to 10 monomers in agreement with reports suggesting that these oligomers may be the causative agent of cell toxicity. The results obtained may prove to be useful in understanding the mode of action of different compounds in preventing fibril formation and, therefore, in designing new drugs against TTR amyloidosis. PMID:25694367
Generalization of the Analytical Exponential Model for Homogeneous Reactor Kinetics Equations
Directory of Open Access Journals (Sweden)
Abdallah A. Nahla
2012-01-01
Full Text Available Mathematical form for two energy groups of three-dimensional homogeneous reactor kinetics equations and average one group of the precursor concentration of delayed neutrons is presented. This mathematical form is called “two energy groups of the point kinetics equations.” We rewrite two energy groups of the point kinetics equations in the matrix form. Generalization of the analytical exponential model (GAEM is developed for solving two energy groups of the point kinetics equations. The GAEM is based on the eigenvalues and the corresponding eigenvectors of the coefficient matrix. The eigenvalues of the coefficient matrix are calculated numerically using visual FORTRAN code, based on Laguerre’s method, to calculate the roots of an algebraic equation with real coefficients. The eigenvectors of the coefficient matrix are calculated analytically. The results of the GAEM are compared with the traditional methods. These comparisons substantiate the accuracy of the results of the GAEM. In addition, the GAEM is faster than the traditional methods.
Zhao, Xuebing; Morikawa, Yuichi; Qi, Feng; Zeng, Jing; Liu, Dehua
2014-01-01
Acetic acid (AcH) pretreatment of sugarcane bagasse with the catalysis of sulfuric acid (SA) could greatly enhance the enzymatic digestibility of cellulose. However, polysaccharide dissolution happened inevitably during the pretreatment. It was found that the simplest model, which assumes that the total polysaccharides were reactive to be dissolved, could not well describe the kinetic behavior of polysaccharide dissolution. A novel pseudo-homogenous kinetic model was thus developed by introducing a parameter termed as "potential dissolution degree" (δ(d)) based on the multilayered structure of cell wall. It was found that solid xylan and glucan dissolutions were a first-order reaction with respect to the dissolvable fraction. Due to the delignification action of AcH, polysaccharide dissolutions were enhanced in AcH media compared with those in aqueous system. Acetylizations of cellulose and sugars were also observed, and AcH concentration showed a significant influence on the degree of acetylization.
Directory of Open Access Journals (Sweden)
Sousa Jr R.
2004-01-01
Full Text Available Partial hydrolysis of whey proteins by enzymes immobilized on an inert support can either change or evidence functional properties of the produced peptides, thereby increasing their applications. The hydrolysis of sweet cheese whey proteins by alcalase, which is multipoint-immobilized on agarose gel, is studied here. A Michaelis-Menten model that takes into account competitive inhibition by the product was fitted to experimental data. The influence of pH on the kinetic parameters in the range 6.0 to 11.0 was assessed, at 50ºC. Initial reaction-rate assays in a pHstat at different concentrations of substrate were used to estimate kinetic and Michaelis-Menten parameters, k and K M. Experimental data from long-term batch assays were used to quantify the inhibition parameter, K I. The fitting of the model to the experimental data was accurate in the entire pH range.
Observational Constraints on Purely Kinetic/c-Essence Dark Energy Models
Institute of Scientific and Technical Information of China (English)
YANG Rong-Jia; GAO Xiang-Ting
2009-01-01
We consider constraints on purely kinetic k-essence models from the latest observational data (including 182 gold SNIa data,the shift parameter,and the acoustic scale).We find the best-fit values of the parameters are Ωm = 0.37 ±0.01 and κo = 0.064 ± 0.013 at 68.3% confidence level.The phase transition from deceleration to acceleration is found to occur at redshift zq=0～0.48-0.52 in 68.3% confidence level limits.By applying modelcomparison statistics (F-test,AICc,and BIC),we find that the purely kinetic k-essence scenario is favored over the A CDM model by the combined data.These results are also confirmed by combined data 307 SNIa + R + la.
Tang, Xian-Zhu; McDevitt, C. J.; Guo, Zehua; Berk, H. L.
2014-03-01
Inertial confinement fusion requires an imploded target in which a central hot spot is surrounded by a cold and dense pusher. The hot spot/pusher interface can take complicated shape in three dimensions due to hydrodynamic mix. It is also a transition region where the Knudsen and inverse Knudsen layer effect can significantly modify the fusion reactivity in comparison with the commonly used value evaluated with background Maxwellians. Here, we describe a hybrid model that couples the kinetic correction of fusion reactivity to global hydrodynamic implosion simulations. The key ingredient is a non-perturbative treatment of the tail ions in the interface region where the Gamow ion Knudsen number approaches or surpasses order unity. The accuracy of the coupling scheme is controlled by the precise criteria for matching the non-perturbative kinetic model to perturbative solutions in both configuration space and velocity space.
Proposal of a risk model for vehicular traffic: A Boltzmann-type kinetic approach
Freguglia, Paolo
2015-01-01
This paper deals with a Boltzmann-type kinetic model describing the interplay between vehicle dynamics and safety aspects in vehicular traffic. Sticking to the idea that the macroscopic characteristics of traffic flow, including the distribution of the driving risk along a road, are ultimately generated by one-to-one interactions among drivers, the model links the personal (i.e., individual) risk to the changes of speeds of single vehicles and implements a probabilistic description of such microscopic interactions in a Boltzmann-type collisional operator. By means of suitable statistical moments of the kinetic distribution function, it is finally possible to recover macroscopic relationships between the average risk and the road congestion, which show an interesting and reasonable correlation with the well-known free and congested phases of the flow of vehicles.
Cortical surface-based analysis reduces bias and variance in kinetic modeling of brain PET data
DEFF Research Database (Denmark)
Greve, Douglas N; Svarer, Claus; Fisher, Patrick M;
2014-01-01
in a ROI making noise management critical to successful exploratory analysis. This work explores how preprocessing choices affect the bias and variability of voxelwise kinetic modeling analysis of brain positron emission tomography (PET) data. These choices include the use of volume- or cortical surface...... radioligand ([(11)C]SB2307145) were collected on sixteen healthy subjects using a Siemens HRRT PET scanner. Kinetic modeling was used to compute maps of non-displaceable binding potential (BPND) after preprocessing. The results showed a complicated interaction between smoothing, PVC, and masking on BPND...... intersubject variance than when volume smoothing was used. This translates into more than 4 times fewer subjects needed in a group analysis to achieve similarly powered statistical tests. Surface-based smoothing has less bias and variance because it respects cortical geometry by smoothing the PET data only...
Turing Systems, Entropy, and Kinetic Models for Self-Healing Surfaces
Directory of Open Access Journals (Sweden)
Eugene Kagan
2010-03-01
Full Text Available The paper addresses the methods of description of friction-induced self-healing at the interface between two solid bodies. A macroscopic description of self-healing is based on a Turing system for the transfer of matter that leads to self-organization at the interface in the case of an unstable state. A microscopic description deals with a kinetic model of the process and entropy production during self-organization. The paper provides a brief overview of the Turing system approach and statistical kinetic models. The relation between these methods and the description of the self-healing surfaces is discussed, as well as results of their application. The analytical considerations are illustrated by numerical simulations.
Kinetic models of collective decision-making in the presence of equality bias
Pareschi, Lorenzo; Zanella, Mattia
2016-01-01
We introduce and discuss kinetic models describing the influence of the competence in the evolution of decisions in a multi-agent system. The original exchange mechanism, which is based on the human tendency to compromise and change opinion through self-thinking, is here modified to include the role of the agents' competence. In particular, we take into account the agents' tendency to behave in the same way as if they were as good, or as bad, as their partner: the so-called equality bias. This occurred in a situation where a wide gap separated the competence of group members. We discuss the main properties of the kinetic models and numerically investigate some examples of collective decision under the influence of the equality bias. The results confirm that the equality bias leads the group to suboptimal decisions.
Energy Technology Data Exchange (ETDEWEB)
Ganusov, Vitaly V [Los Alamos National Laboratory
2008-01-01
Estimation of division and death rates of lymphocytes in different conditions is vital for quantitative understanding of the immune system. Deuterium, in the form of deuterated glucose or heavy water, can be used to measure rates of proliferation and death of lymphocytes in vivo. Inferring these rates from labeling and delabeling curves has been subject to considerable debate with different groups suggesting different mathematical models for that purpose. We show that the three models that are most commonly used are in fact mathematically identical and differ only in their interpretation of the estimated parameters. By extending these previous models, we here propose a more mechanistic approach for the analysis of data from deuterium labeling experiments. We construct a model of 'kinetic heterogeneity' in which the total cell population consists of many sub-populations with different rates of cell turnover. In this model, for a given distribution of the rates of turnover, the predicted fraction of labeled DNA accumulated and lost can be calculated. Our model reproduces several previously made experimental observations, such as a negative correlation between the length of the labeling period and the rate at which labeled DNA is lost after label cessation. We demonstrate the reliability of the new explicit kinetic heterogeneity model by applying it to artificially generated datasets, and illustrate its usefulness by fitting experimental data. In contrast to previous models, the explicit kinetic heterogeneity model (1) provides a mechanistic way of interpreting labeling data; (2) allows for a non-exponential loss of labeled cells during delabeling, and (3) can be used to describe data with variable labeling length.
Directory of Open Access Journals (Sweden)
Vitaly V Ganusov
2010-02-01
Full Text Available Estimation of division and death rates of lymphocytes in different conditions is vital for quantitative understanding of the immune system. Deuterium, in the form of deuterated glucose or heavy water, can be used to measure rates of proliferation and death of lymphocytes in vivo. Inferring these rates from labeling and delabeling curves has been subject to considerable debate with different groups suggesting different mathematical models for that purpose. We show that the three most common models, which are based on quite different biological assumptions, actually predict mathematically identical labeling curves with one parameter for the exponential up and down slope, and one parameter defining the maximum labeling level. By extending these previous models, we here propose a novel approach for the analysis of data from deuterium labeling experiments. We construct a model of "kinetic heterogeneity" in which the total cell population consists of many sub-populations with different rates of cell turnover. In this model, for a given distribution of the rates of turnover, the predicted fraction of labeled DNA accumulated and lost can be calculated. Our model reproduces several previously made experimental observations, such as a negative correlation between the length of the labeling period and the rate at which labeled DNA is lost after label cessation. We demonstrate the reliability of the new explicit kinetic heterogeneity model by applying it to artificially generated datasets, and illustrate its usefulness by fitting experimental data. In contrast to previous models, the explicit kinetic heterogeneity model 1 provides a novel way of interpreting labeling data; 2 allows for a non-exponential loss of labeled cells during delabeling, and 3 can be used to describe data with variable labeling length.
Directory of Open Access Journals (Sweden)
BORZANI W.
1999-01-01
Full Text Available Variation in nitrogen content of Pichia guilliermondii during its batch cultivation on media containing diesel oil as the main carbon source may be explained by means of a kinetic model proposed earlier to interpret the kinetics of nitrogen consumption during the process.
Three species one-dimensional kinetic model for weakly ionized plasmas
Gonzalez, J; Donoso, J. M.; Tierno, S. P.
2016-01-01
A three species one-dimensional kinetic model is presented for a spatially homogeneous weakly ionized plasma subjected to the action of a time varying electric field. Planar geometry is assumed, which means that the plasma dynamics evolves in the privileged direction of the field. The energy transmitted to the charges is be channelized to the neutrals thanks to collisions and impacting the plasma dynamics. Charge-charge interactions have been designed as a one dimensional collision term equiv...
A multi-layer model for turbulent kinetic energy in pipe flows
Chen, Xi; Hussain, Fazle; She, Zhen-Su
2011-01-01
A multi-layer model of an energy length function is developed by employing recent results of the authors. The theory predicts the complete, mean streamwise turbulent kinetic-energy profile (MKP), in good agreement with empirical data for a wide range of Reynolds numbers (Re). In particular, a critical $Re_\\tau$ is predicted, beyond which a scaling anomaly appears and MKP develops a second peak.
Confidence limits of SN, Kinetic Energy and chemical yields in evolutionary synthesis models
Luridiana, V
2001-01-01
When evolutionary synthesis models take into account the stochastic nature of the IMF together with the discrete number of stars in real stellar clusters, typical output turns to dispersion band (where real data can be placed) instead of narrow lines. We present here a qualitative analysis of such dispersion in the SN rate, the kinetic energy and the 14N/12C ratio for different amounts of mass transformed into stars.
Reversible Formation of Nanodomains in Monolayers of DPPC Studied by Kinetic Modeling
M. Stepanova
2009-01-01
Dipalmitoylphosphatidylcholine (DPPC) is the most abundant component in pulmonary surfactants and is believed to be responsible for maintaining low surface tension in alveoli during breathing. In this work, a kinetic model is introduced that describes the phase separation in DPPC films that produces the liquid-condensed (LC) and liquid-expanded (LE) fractions, which differ according to the area density of DPPC. The phase separation in an initially homogeneous film has been investigated numeri...
Sousa Jr R.; Lopes G. P.; Tardioli P. W.; Giordano R.L.C.; Almeida P. I. F.; Giordano R. C.
2004-01-01
Partial hydrolysis of whey proteins by enzymes immobilized on an inert support can either change or evidence functional properties of the produced peptides, thereby increasing their applications. The hydrolysis of sweet cheese whey proteins by alcalase, which is multipoint-immobilized on agarose gel, is studied here. A Michaelis-Menten model that takes into account competitive inhibition by the product was fitted to experimental data. The influence of pH on the kinetic parameters in the range...
FORC Analysis of homogeneous nucleation in the two-dimensional kinetic Ising model
Robb, D. T.; Novotny, M. A.; Rikvold, P. A.
2004-01-01
The first-order reversal curve (FORC) method is applied to the two-dimensional kinetic Ising model. For the system size and magnetic field chosen, the system reverses by the homogeneous nucleation and growth of many droplets. This makes the dynamics of reversal nearly deterministic, in contrast to the strongly disordered systems previously studied by the FORC method. Consequently, the FORC diagrams appear different from those obtained in previous studies. The Kolmogorov-Johnson-Mehl-Avrami (K...
Kinetic Modelling of the Maillard Browning Reaction in Pekmez (Grape Molasses)
Bozkurt, Hüseyin; Göğüş, Fahrettin; Eren, Sami
1998-01-01
The effects of pH, temperature and total solube solids on the Maillard reactions which occurred during the storage of Pekmez were determined using accelerated storage test. The reaction was followed measurement of by the amount of 5-Hydroxymethyl furfural, an intermediate product of the Maillard reaction. The change in the reaction rate was defined with a kinetic model as a function of pH, temperature and the total soluble solids. The reaction rate was correlated with the independen...
A kinetic model for chemical reactions without barriers : transport coefficients and eigenmodes
Alves, Giselle M.; Marques Júnior, Wilson; Soares, A. J.; Kremer, Gilberto M.
2011-01-01
The kinetic model of the Boltzmann equation proposed in the work of Kremer and Soares 2009 for a binary mixture undergoing chemical reactions of symmetric type which occur without activation energy is revisited here, with the aim of investigating in detail the transport properties of the reactive mixture and the influence of the reaction process on the transport coefficients. Accordingly, the non-equilibrium solution of the Boltzmann equation is determined through an expansion in Sonine polyn...
Kinetic modeling of particle dynamics in H− negative ion sources (invited)
International Nuclear Information System (INIS)
Progress in the kinetic modeling of particle dynamics in H− negative ion source plasmas and their comparisons with experiments are reviewed, and discussed with some new results. Main focus is placed on the following two topics, which are important for the research and development of large negative ion sources and high power H− ion beams: (i) Effects of non-equilibrium features of EEDF (electron energy distribution function) on H− production, and (ii) extraction physics of H− ions and beam optics
KINETIC MODELLING AND PERFORMANCE ANALYSIS OF THE FOUR-POST-FRAME LIFTINGMECHANICAL SYSTEM
Institute of Scientific and Technical Information of China (English)
高建华; 杨汝清; 胡洪国
2001-01-01
The kinetic model of the four-post-frame lifting mechanical system was established. The stiffness and damping matrices of differential equations of motion were obtained by using Lagrange's equations. And the dynamic characteristics of system were analyzed by modal analysis method. Based upon this, the modifications of structural parameters which can improve dynamic performance were discussed. The low-level high-speed palletizer MDJ1200L was taken as a real case in the paper.
Marc Breit; Michael Netzer; Weinberger, Klaus M.; Christian Baumgartner
2015-01-01
The objectives of this work were the classification of dynamic metabolic biomarker candidates and the modeling and characterization of kinetic regulatory mechanisms in human metabolism with response to external perturbations by physical activity. Longitudinal metabolic concentration data of 47 individuals from 4 different groups were examined, obtained from a cycle ergometry cohort study. In total, 110 metabolites (within the classes of acylcarnitines, amino acids, and sugars) were measured t...
Stochasticity in Physiologically Based Kinetics Models : implications for cancer risk assessment
Pery, Alexandre; Bois, Frédéric Y.
2009-01-01
International audience In case of low-dose exposure to a substance, its concentration in cells is likely to be stochastic. Assessing the consequences of this stochasticity in toxicological risk assessment requires the coupling of macroscopic dynamics models describing whole-body kinetics with microscopic tools designed to simulate stochasticity. In this article, we propose an approach to approximate stochastic cell concentration of butadiene in the cells of diverse organs. We adapted the d...
Development of a kinetic metabolic model: application to Catharanthus roseus hairy root
Leduc, M.; Tikhomiroff, C.; Cloutier, M.; Perrier, M.; Jolicoeur, M.
2006-01-01
A kinetic metabolic model describing Catharanthus roseus hairy root growth and nutrition was developed. The metabolic network includes glycolysis, pentose-phosphate pathway, TCA cycle and the catabolic reactions leading to cell building blocks such as amino acids, organic acids, organic phosphates, lipids and structural hexoses. The central primary metabolic network was taken at pseudo-steady state and metabolic flux analysis technique allowed reducing from 31 metabolic fluxes to 20 independe...
Muhammad Ali Zulfikar; Henry Setiyanto; Samitha Dewi Djajanti
2013-01-01
The sorption of lignosulfonate onto powdered eggshell under the influence of temperature has been studied. The rate of adsorption onto eggshell was investigated under a variety of adsorbent dosages. The kinetic data from these investigations were correlated to a number of adsorption models in an attempt to elucidate the mechanism of the adsorption processes. Thermodynamic parameter data indicated that the lignosulfonate sorption process was non-spontaneous and endothermic under the experiment...
Extraction of lutein from Marigold flower petals - Experimental kinetics and modelling
Hojnik, Maša; Škerget, Mojca; Knez, Željko
2012-01-01
The extraction kinetics behaviour of lutein from Marigold flower petals and simultaneous alkali hydrolysis has been studied. Extraction was carried out by varying following operating conditions: type of organic solvent, temperature, ratio liquid: material, concentration of alkali solution, and particle size of plant material. Experimental extraction curves were analysed with a mathematical model derived from Fick's second law. The extraction of lutein appeared to be governed by slow and fast ...
New model for colour kinetics of plum under infrared vacuum condition and microwave drying
Directory of Open Access Journals (Sweden)
Reza Amiri Chayjan
2016-06-01
Full Text Available Background. Quality of dried foods is aﬀected by the drying method and physiochemical changes in tissue. The drying method aﬀects properties such as colour. The colour of processed food is one of the most impor- tant quality indices and plays a determinant role in consumer acceptability of food materials and the process- ing method. The colour of food materials can be used as an indirect factor to determine changes in quality, since it is simpler and faster than chemical methods. Material and methods. The study focused on the kinetics of colour changes of plum slices, under infrared vacuum and microwave conditions. Drying the samples was implemented at the absolute pressures of 20 and 60 kPa, drying temperatures of 50 and 60°C and microwave power of 90, 270, 450 and 630 W. Colour changes were quantiﬁed by the tri-stimulus L* (whiteness/darkness, a* (redness/greenness and b* (yellow- ness/blueness model, which is an international standard for color measurement developed by the Commis- sion Internationale d’Eclairage (CIE. These values were also used to calculate total colour change (∆E, chroma, hue angle, and browning index (BI. A new model was used for mathematical modelling of colour change kinetics. Results. The drying process changed the colour parameters of L*, a*, and b*, causing a colour shift toward the darker region. The values of L* and hue angle decreased, whereas the values of a*, b*, ∆E, chroma and browning index increased during exposure to infrared vacuum conditions and microwave drying. Comparing the results obtained using the new model with two conventional models of zero-order and ﬁrst-order kinet- ics indicated that the new model presented more compatibility with the data of colour kinetics for all colour parameters and drying conditions. Conclusion. All kinetic changes in colour parameters can be explained by the new model presented in this study. The hybrid drying system included infrared vacuum conditions and
Lange, Bernd Markus; Rios-Estepa, Rigoberto
2014-01-01
The integration of mathematical modeling with analytical experimentation in an iterative fashion is a powerful approach to advance our understanding of the architecture and regulation of metabolic networks. Ultimately, such knowledge is highly valuable to support efforts aimed at modulating flux through target pathways by molecular breeding and/or metabolic engineering. In this article we describe a kinetic mathematical model of peppermint essential oil biosynthesis, a pathway that has been studied extensively for more than two decades. Modeling assumptions and approximations are described in detail. We provide step-by-step instructions on how to run simulations of dynamic changes in pathway metabolites concentrations. PMID:24218222
Non-thermal plasma destruction of allyl alcohol in waste gas: kinetics and modelling
DeVisscher, A.; Dewulf, J.; Van Durme, J.; Leys, C.; Morent, R.; Van Langenhove, H.
2008-02-01
Non-thermal plasma treatment is a promising technique for the destruction of volatile organic compounds in waste gas. A relatively unexplored technique is the atmospheric negative dc multi-pin-to-plate glow discharge. This paper reports experimental results of allyl alcohol degradation and ozone production in this type of plasma. A new model was developed to describe these processes quantitatively. The model contains a detailed chemical degradation scheme, and describes the physics of the plasma by assuming that the fraction of electrons that takes part in chemical reactions is an exponential function of the reduced field. The model captured the experimental kinetic data to less than 2 ppm standard deviation.
Non-thermal plasma destruction of allyl alcohol in waste gas: kinetics and modelling
International Nuclear Information System (INIS)
Non-thermal plasma treatment is a promising technique for the destruction of volatile organic compounds in waste gas. A relatively unexplored technique is the atmospheric negative dc multi-pin-to-plate glow discharge. This paper reports experimental results of allyl alcohol degradation and ozone production in this type of plasma. A new model was developed to describe these processes quantitatively. The model contains a detailed chemical degradation scheme, and describes the physics of the plasma by assuming that the fraction of electrons that takes part in chemical reactions is an exponential function of the reduced field. The model captured the experimental kinetic data to less than 2 ppm standard deviation
International Nuclear Information System (INIS)
The author has studied the kinetics of heparin and heparin fractions after intravenous administration in humans and in this thesis the results of this study are reported. Basic knowledge about the physico-chemical properties of heparin and its interactions with proteins resulting in anticoagulant and lipolytic effects are discussed in a review (chapter II), which also comprises some clinical aspects of heparin therapy. In chapter III the kinetics of the anticoagulant effect are described after intravenous administration of five commercial heparin preparations. A mathematical model is presented that fits best to these kinetics. The kinetics of the anticoagulant and lipolytic effects after intravenous injection of various 35S-radiolabelled heparin fractions and their relationship with the disappearance of the radiolabel are described in chapter IV. Chapter V gives a description of the kinetics of two radiolabels after injection of in vitro formed complexes consisting of purified, 125I-radiolabelled antithrombin III and various 35S-radiolabelled heparin fractions. (Auth.)
Challenges and pitfalls of P450-dependent (+)-valencene bioconversion by Saccharomyces cerevisiae.
Gavira, Carole; Höfer, René; Lesot, Agnès; Lambert, Fanny; Zucca, Joseph; Werck-Reichhart, Danièle
2013-07-01
Natural nootkatone is a high value ingredient for the flavor and fragrance industry because of its grapefruit flavor/odor, low sensorial threshold and low availability. Valencene conversion into nootkatol and nootkatone is known to be catalyzed by cytochrome P450 enzymes from both prokaryotic and eukaryotic organisms, but so far development of a viable bioconversion process using either native microorganisms or recombinant enzymes was not successful. Using an in silico gene-mining approach, we selected 4 potential candidate P450 enzymes from higher plants and identified two of them that selectively converted (+)-valencene into β-nootkatol with high efficiency when tested using recombinant yeast microsomes in vitro. Recombinant yeast expressing CYP71D51v2 from tobacco and a P450 reductase from arabidopsis was used for optimization of a bioconversion process. Bioconversion assays led to production of β-nootkatol and nootkatone, but with low yields that decreased upon increase of the substrate concentration. The reasons for this low bioconversion efficiency were further investigated and several factors potentially hampering industry-compatible valencene bioconversion were identified. One is the toxicity of the products for yeast at concentrations exceeding 100 mg L⁻¹. The second is the accumulation of β-nootkatol in yeast endomembranes. The third is the inhibition of the CYP71D51v2 hydroxylation reaction by the products. Furthermore, we observed that the formation of nootkatone from β-nootkatol is not P450-dependent but catalyzed by a yeast component. Based on these data, we propose new strategies for implementation of a viable P450-based bioconversion process. PMID:23518241
Ullah, Ghanim; Demuro, Angelo; Parker, Ian; Pearson, John E
2015-01-01
Amyloid beta (Aβ) oligomers associated with Alzheimer's disease (AD) form Ca2+-permeable plasma membrane pores, leading to a disruption of the otherwise well-controlled intracellular calcium (Ca2+) homeostasis. The resultant up-regulation of intracellular Ca2+ concentration has detrimental implications for memory formation and cell survival. The gating kinetics and Ca2+ permeability of Aβ pores are not well understood. We have used computational modeling in conjunction with the ability of optical patch-clamping for massively parallel imaging of Ca2+ flux through thousands of pores in the cell membrane of Xenopus oocytes to elucidate the kinetic properties of Aβ pores. The fluorescence time-series data from individual pores were idealized and used to develop data-driven Markov chain models for the kinetics of the Aβ pore at different stages of its evolution. Our study provides the first demonstration of developing Markov chain models for ion channel gating that are driven by optical-patch clamp data with the advantage of experiments being performed under close to physiological conditions. Towards the end, we demonstrate the up-regulation of gating of various Ca2+ release channels due to Aβ pores and show that the extent and spatial range of such up-regulation increases as Aβ pores with low open probability and Ca2+ permeability transition into those with high open probability and Ca2+ permeability.
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Ghanim Ullah
Full Text Available Amyloid beta (Aβ oligomers associated with Alzheimer's disease (AD form Ca2+-permeable plasma membrane pores, leading to a disruption of the otherwise well-controlled intracellular calcium (Ca2+ homeostasis. The resultant up-regulation of intracellular Ca2+ concentration has detrimental implications for memory formation and cell survival. The gating kinetics and Ca2+ permeability of Aβ pores are not well understood. We have used computational modeling in conjunction with the ability of optical patch-clamping for massively parallel imaging of Ca2+ flux through thousands of pores in the cell membrane of Xenopus oocytes to elucidate the kinetic properties of Aβ pores. The fluorescence time-series data from individual pores were idealized and used to develop data-driven Markov chain models for the kinetics of the Aβ pore at different stages of its evolution. Our study provides the first demonstration of developing Markov chain models for ion channel gating that are driven by optical-patch clamp data with the advantage of experiments being performed under close to physiological conditions. Towards the end, we demonstrate the up-regulation of gating of various Ca2+ release channels due to Aβ pores and show that the extent and spatial range of such up-regulation increases as Aβ pores with low open probability and Ca2+ permeability transition into those with high open probability and Ca2+ permeability.
Mathematical modeling provides kinetic details of the human immune response to vaccination
Directory of Open Access Journals (Sweden)
Dustin eLe
2015-01-01
Full Text Available With major advances in experimental techniques to track antigen-specific immune responses many basic questions on the kinetics of virus-specific immunity in humans remain unanswered. To gain insights into kinetics of T and B cell responses in human volunteers we combine mathematical models and experimental data from recent studies employing vaccines against yellow fever and smallpox. Yellow fever virus-specific CD8 T cell population expanded slowly with the average doubling time of 2 days peaking 2.5 weeks post immunization. Interestingly, we found that the peak of the yellow fever-specific CD8 T cell response is determined by the rate of T cell proliferation and not by the precursor frequency of antigen-specific cells as has been suggested in several studies in mice. We also found that while the frequency of virus-specific T cells increases slowly, the slow increase can still accurately explain clearance of yellow fever virus in the blood. Our additional mathematical model describes well the kinetics of virus-specific antibody-secreting cell and antibody response to vaccinia virus in vaccinated individuals suggesting that most of antibodies in 3 months post immunization are derived from the population of circulating antibody-secreting cells. Taken together, our analysis provides novel insights into mechanisms by which live vaccines induce immunity to viral infections and highlight challenges of applying methods of mathematical modeling to the current, state-of-the-art yet limited immunological data.
Ullah, Ghanim; Demuro, Angelo; Parker, Ian; Pearson, John E
2015-01-01
Amyloid beta (Aβ) oligomers associated with Alzheimer's disease (AD) form Ca2+-permeable plasma membrane pores, leading to a disruption of the otherwise well-controlled intracellular calcium (Ca2+) homeostasis. The resultant up-regulation of intracellular Ca2+ concentration has detrimental implications for memory formation and cell survival. The gating kinetics and Ca2+ permeability of Aβ pores are not well understood. We have used computational modeling in conjunction with the ability of optical patch-clamping for massively parallel imaging of Ca2+ flux through thousands of pores in the cell membrane of Xenopus oocytes to elucidate the kinetic properties of Aβ pores. The fluorescence time-series data from individual pores were idealized and used to develop data-driven Markov chain models for the kinetics of the Aβ pore at different stages of its evolution. Our study provides the first demonstration of developing Markov chain models for ion channel gating that are driven by optical-patch clamp data with the advantage of experiments being performed under close to physiological conditions. Towards the end, we demonstrate the up-regulation of gating of various Ca2+ release channels due to Aβ pores and show that the extent and spatial range of such up-regulation increases as Aβ pores with low open probability and Ca2+ permeability transition into those with high open probability and Ca2+ permeability. PMID:26348728