Kostylev, Maxim; Wilson, David
2014-01-01
Lignocellulosic biomass is a potential source of renewable, low-carbon-footprint liquid fuels. Biomass recalcitrance and enzyme cost are key challenges associated with the large-scale production of cellulosic fuel. Kinetic modeling of enzymatic cellulose digestion has been complicated by the heterogeneous nature of the substrate and by the fact that a true steady state cannot be attained. We present a two-parameter kinetic model based on the Michaelis-Menten scheme (Michaelis L and Menten ML. (1913) Biochem Z 49:333–369), but with a time-dependent activity coefficient analogous to fractal-like kinetics formulated by Kopelman (Kopelman R. (1988) Science 241:1620–1626). We provide a mathematical derivation and experimental support to show that one of the parameters is a total activity coefficient and the other is an intrinsic constant that reflects the ability of the cellulases to overcome substrate recalcitrance. The model is applicable to individual cellulases and their mixtures at low-to-medium enzyme loads. Using biomass degrading enzymes from a cellulolytic bacterium Thermobifida fusca we show that the model can be used for mechanistic studies of enzymatic cellulose digestion. We also demonstrate that it applies to the crude supernatant of the widely studied cellulolytic fungus Trichoderma reesei and can thus be used to compare cellulases from different organisms. The two parameters may serve a similar role to Vmax, KM, and kcat in classical kinetics. A similar approach may be applicable to other enzymes with heterogeneous substrates and where a steady state is not achievable. PMID:23837567
Accurate Stellar Parameters for Exoplanet Host Stars
NASA Astrophysics Data System (ADS)
Brewer, John Michael; Fischer, Debra; Basu, Sarbani; Valenti, Jeff A.
2015-01-01
A large impedement to our understanding of planet formation is obtaining a clear picture of planet radii and densities. Although determining precise ratios between planet and stellar host are relatively easy, determining accurate stellar parameters is still a difficult and costly undertaking. High resolution spectral analysis has traditionally yielded precise values for some stellar parameters but stars in common between catalogs from different authors or analyzed using different techniques often show offsets far in excess of their uncertainties. Most analyses now use some external constraint, when available, to break observed degeneracies between surface gravity, effective temperature, and metallicity which can otherwise lead to correlated errors in results. However, these external constraints are impossible to obtain for all stars and can require more costly observations than the initial high resolution spectra. We demonstrate that these discrepencies can be mitigated by use of a larger line list that has carefully tuned atomic line data. We use an iterative modeling technique that does not require external constraints. We compare the surface gravity obtained with our spectral synthesis modeling to asteroseismically determined values for 42 Kepler stars. Our analysis agrees well with only a 0.048 dex offset and an rms scatter of 0.05 dex. Such accurate stellar gravities can reduce the primary source of uncertainty in radii by almost an order of magnitude over unconstrained spectral analysis.
NASA Astrophysics Data System (ADS)
Ronen, Michal; Rosenberg, Revital; Shraiman, Boris I.; Alon, Uri
2002-08-01
A basic challenge in systems biology is to understand the dynamical behavior of gene regulation networks. Current approaches aim at determining the network structure based on genomic-scale data. However, the network connectivity alone is not sufficient to define its dynamics; one needs to also specify the kinetic parameters for the regulation reactions. Here, we ask whether effective kinetic parameters can be assigned to a transcriptional network based on expression data. We present a combined experimental and theoretical approach based on accurate high temporal-resolution measurement of promoter activities from living cells by using green fluorescent protein (GFP) reporter plasmids. We present algorithms that use these data to assign effective kinetic parameters within a mathematical model of the network. To demonstrate this, we employ a well defined network, the SOS DNA repair system of Escherichia coli. We find a strikingly detailed temporal program of expression that correlates with the functional role of the SOS genes and is driven by a hierarchy of effective kinetic parameter strengths for the various promoters. The calculated parameters can be used to determine the kinetics of all SOS genes given the expression profile of just one representative, allowing a significant reduction in complexity. The concentration profile of the master SOS transcriptional repressor can be calculated, demonstrating that relative protein levels may be determined from purely transcriptional data. This finding opens the possibility of assigning kinetic parameters to transcriptional networks on a genomic scale.
Determination of kinetic parameters for biomass combustion.
Álvarez, A; Pizarro, C; García, R; Bueno, J L; Lavín, A G
2016-09-01
The aim of this work is to provide a wide database of kinetic data for the most common biomass by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). Due to the characteristic parameters of DTG curves, a two-stage reaction model is proposed and the kinetic parameters obtained from model-based methods with energy activation values for first and second stages in the range 1.75·10(4)-1.55·10(5)J/mol and 1.62·10(4)-2.37·10(5)J/mol, respectively. However, it has been found that Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose model-free methods are not suitable to determine the kinetic parameters of biomass combustion since the assumptions of these two methods were not accomplished in the full range of the combustion process.
Determination of kinetic parameters for biomass combustion.
Álvarez, A; Pizarro, C; García, R; Bueno, J L; Lavín, A G
2016-09-01
The aim of this work is to provide a wide database of kinetic data for the most common biomass by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). Due to the characteristic parameters of DTG curves, a two-stage reaction model is proposed and the kinetic parameters obtained from model-based methods with energy activation values for first and second stages in the range 1.75·10(4)-1.55·10(5)J/mol and 1.62·10(4)-2.37·10(5)J/mol, respectively. However, it has been found that Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose model-free methods are not suitable to determine the kinetic parameters of biomass combustion since the assumptions of these two methods were not accomplished in the full range of the combustion process. PMID:27233095
Accurate Parameter Estimation for Unbalanced Three-Phase System
Chen, Yuan
2014-01-01
Smart grid is an intelligent power generation and control console in modern electricity networks, where the unbalanced three-phase power system is the commonly used model. Here, parameter estimation for this system is addressed. After converting the three-phase waveforms into a pair of orthogonal signals via the α β-transformation, the nonlinear least squares (NLS) estimator is developed for accurately finding the frequency, phase, and voltage parameters. The estimator is realized by the Newton-Raphson scheme, whose global convergence is studied in this paper. Computer simulations show that the mean square error performance of NLS method can attain the Cramér-Rao lower bound. Moreover, our proposal provides more accurate frequency estimation when compared with the complex least mean square (CLMS) and augmented CLMS. PMID:25162056
Accurate parameter estimation for unbalanced three-phase system.
Chen, Yuan; So, Hing Cheung
2014-01-01
Smart grid is an intelligent power generation and control console in modern electricity networks, where the unbalanced three-phase power system is the commonly used model. Here, parameter estimation for this system is addressed. After converting the three-phase waveforms into a pair of orthogonal signals via the α β-transformation, the nonlinear least squares (NLS) estimator is developed for accurately finding the frequency, phase, and voltage parameters. The estimator is realized by the Newton-Raphson scheme, whose global convergence is studied in this paper. Computer simulations show that the mean square error performance of NLS method can attain the Cramér-Rao lower bound. Moreover, our proposal provides more accurate frequency estimation when compared with the complex least mean square (CLMS) and augmented CLMS.
A simple and accurate resist parameter extraction method for sub-80-nm DRAM patterns
NASA Astrophysics Data System (ADS)
Lee, Sook; Hwang, Chan; Park, Dong-Woon; Kim, In-Sung; Kim, Ho-Chul; Woo, Sang-Gyun; Cho, Han-Ku; Moon, Joo-Tae
2004-05-01
Due to the polarization effect of high NA lithography, the consideration of resist effect in lithography simulation becomes increasingly important. In spite of the importance of resist simulation, many process engineers are reluctant to consider resist effect in lithography simulation due to time-consuming procedure to extract required resist parameters and the uncertainty of measurement of some parameters. Weiss suggested simplified development model, and this model does not require the complex kinetic parameters. For the device fabrication engineers, there is a simple and accurate parameter extraction and optimizing method using Weiss model. This method needs refractive index, Dill"s parameters and development rate monitoring (DRM) data in parameter extraction. The parameters extracted using referred sequence is not accurate, so that we have to optimize the parameters to fit the critical dimension scanning electron microscopy (CD SEM) data of line and space patterns. Hence, the FiRM of Sigma-C is utilized as a resist parameter-optimizing program. According to our study, the illumination shape, the aberration and the pupil mesh point have a large effect on the accuracy of resist parameter in optimization. To obtain the optimum parameters, we need to find the saturated mesh points in terms of normalized intensity log slope (NILS) prior to an optimization. The simulation results using the optimized parameters by this method shows good agreement with experiments for iso-dense bias, Focus-Exposure Matrix data and sub 80nm device pattern simulation.
Machine learning of parameters for accurate semiempirical quantum chemical calculations
Dral, Pavlo O.; von Lilienfeld, O. Anatole; Thiel, Walter
2015-04-14
We investigate possible improvements in the accuracy of semiempirical quantum chemistry (SQC) methods through the use of machine learning (ML) models for the parameters. For a given class of compounds, ML techniques require sufficiently large training sets to develop ML models that can be used for adapting SQC parameters to reflect changes in molecular composition and geometry. The ML-SQC approach allows the automatic tuning of SQC parameters for individual molecules, thereby improving the accuracy without deteriorating transferability to molecules with molecular descriptors very different from those in the training set. The performance of this approach is demonstrated for the semiempirical OM2 method using a set of 6095 constitutional isomers C_{7}H_{10}O_{2}, for which accurate ab initio atomization enthalpies are available. The ML-OM2 results show improved average accuracy and a much reduced error range compared with those of standard OM2 results, with mean absolute errors in atomization enthalpies dropping from 6.3 to 1.7 kcal/mol. They are also found to be superior to the results from specific OM2 reparameterizations (rOM2) for the same set of isomers. The ML-SQC approach thus holds promise for fast and reasonably accurate high-throughput screening of materials and molecules.
Machine learning of parameters for accurate semiempirical quantum chemical calculations
Dral, Pavlo O.; von Lilienfeld, O. Anatole; Thiel, Walter
2015-04-14
We investigate possible improvements in the accuracy of semiempirical quantum chemistry (SQC) methods through the use of machine learning (ML) models for the parameters. For a given class of compounds, ML techniques require sufficiently large training sets to develop ML models that can be used for adapting SQC parameters to reflect changes in molecular composition and geometry. The ML-SQC approach allows the automatic tuning of SQC parameters for individual molecules, thereby improving the accuracy without deteriorating transferability to molecules with molecular descriptors very different from those in the training set. The performance of this approach is demonstrated for the semiempiricalmore » OM2 method using a set of 6095 constitutional isomers C7H10O2, for which accurate ab initio atomization enthalpies are available. The ML-OM2 results show improved average accuracy and a much reduced error range compared with those of standard OM2 results, with mean absolute errors in atomization enthalpies dropping from 6.3 to 1.7 kcal/mol. They are also found to be superior to the results from specific OM2 reparameterizations (rOM2) for the same set of isomers. The ML-SQC approach thus holds promise for fast and reasonably accurate high-throughput screening of materials and molecules.« less
Construction of feasible and accurate kinetic models of metabolism: A Bayesian approach.
Saa, Pedro A; Nielsen, Lars K
2016-01-01
Kinetic models are essential to quantitatively understand and predict the behaviour of metabolic networks. Detailed and thermodynamically feasible kinetic models of metabolism are inherently difficult to formulate and fit. They have a large number of heterogeneous parameters, are non-linear and have complex interactions. Many powerful fitting strategies are ruled out by the intractability of the likelihood function. Here, we have developed a computational framework capable of fitting feasible and accurate kinetic models using Approximate Bayesian Computation. This framework readily supports advanced modelling features such as model selection and model-based experimental design. We illustrate this approach on the tightly-regulated mammalian methionine cycle. Sampling from the posterior distribution, the proposed framework generated thermodynamically feasible parameter samples that converged on the true values, and displayed remarkable prediction accuracy in several validation tests. Furthermore, a posteriori analysis of the parameter distributions enabled appraisal of the systems properties of the network (e.g., control structure) and key metabolic regulations. Finally, the framework was used to predict missing allosteric interactions. PMID:27417285
Construction of feasible and accurate kinetic models of metabolism: A Bayesian approach
Saa, Pedro A.; Nielsen, Lars K.
2016-01-01
Kinetic models are essential to quantitatively understand and predict the behaviour of metabolic networks. Detailed and thermodynamically feasible kinetic models of metabolism are inherently difficult to formulate and fit. They have a large number of heterogeneous parameters, are non-linear and have complex interactions. Many powerful fitting strategies are ruled out by the intractability of the likelihood function. Here, we have developed a computational framework capable of fitting feasible and accurate kinetic models using Approximate Bayesian Computation. This framework readily supports advanced modelling features such as model selection and model-based experimental design. We illustrate this approach on the tightly-regulated mammalian methionine cycle. Sampling from the posterior distribution, the proposed framework generated thermodynamically feasible parameter samples that converged on the true values, and displayed remarkable prediction accuracy in several validation tests. Furthermore, a posteriori analysis of the parameter distributions enabled appraisal of the systems properties of the network (e.g., control structure) and key metabolic regulations. Finally, the framework was used to predict missing allosteric interactions. PMID:27417285
Direct computation of parameters for accurate polarizable force fields
Verstraelen, Toon Vandenbrande, Steven; Ayers, Paul W.
2014-11-21
We present an improved electronic linear response model to incorporate polarization and charge-transfer effects in polarizable force fields. This model is a generalization of the Atom-Condensed Kohn-Sham Density Functional Theory (DFT), approximated to second order (ACKS2): it can now be defined with any underlying variational theory (next to KS-DFT) and it can include atomic multipoles and off-center basis functions. Parameters in this model are computed efficiently as expectation values of an electronic wavefunction, obviating the need for their calibration, regularization, and manual tuning. In the limit of a complete density and potential basis set in the ACKS2 model, the linear response properties of the underlying theory for a given molecular geometry are reproduced exactly. A numerical validation with a test set of 110 molecules shows that very accurate models can already be obtained with fluctuating charges and dipoles. These features greatly facilitate the development of polarizable force fields.
Accurate label-free reaction kinetics determination using initial rate heat measurements.
Ebrahimi, Kourosh Honarmand; Hagedoorn, Peter-Leon; Jacobs, Denise; Hagen, Wilfred R
2015-01-01
Accurate label-free methods or assays to obtain the initial reaction rates have significant importance in fundamental studies of enzymes and in application-oriented high throughput screening of enzyme activity. Here we introduce a label-free approach for obtaining initial rates of enzyme activity from heat measurements, which we name initial rate calorimetry (IrCal). This approach is based on our new finding that the data recorded by isothermal titration calorimetry for the early stages of a reaction, which have been widely ignored, are correlated to the initial rates. Application of the IrCal approach to various enzymes led to accurate enzyme kinetics parameters as compared to spectroscopic methods and enabled enzyme kinetic studies with natural substrate, e.g. proteases with protein substrates. Because heat is a label-free property of almost all reactions, the IrCal approach holds promise in fundamental studies of various enzymes and in use of calorimetry for high throughput screening of enzyme activity.
Accurate label-free reaction kinetics determination using initial rate heat measurements
Ebrahimi, Kourosh Honarmand; Hagedoorn, Peter-Leon; Jacobs, Denise; Hagen, Wilfred R.
2015-01-01
Accurate label-free methods or assays to obtain the initial reaction rates have significant importance in fundamental studies of enzymes and in application-oriented high throughput screening of enzyme activity. Here we introduce a label-free approach for obtaining initial rates of enzyme activity from heat measurements, which we name initial rate calorimetry (IrCal). This approach is based on our new finding that the data recorded by isothermal titration calorimetry for the early stages of a reaction, which have been widely ignored, are correlated to the initial rates. Application of the IrCal approach to various enzymes led to accurate enzyme kinetics parameters as compared to spectroscopic methods and enabled enzyme kinetic studies with natural substrate, e.g. proteases with protein substrates. Because heat is a label-free property of almost all reactions, the IrCal approach holds promise in fundamental studies of various enzymes and in use of calorimetry for high throughput screening of enzyme activity. PMID:26574737
Towards accurate kinetic modeling of prompt NO formation in hydrocarbon flames via the NCN pathway
Sutton, Jeffrey A.; Fleming, James W.
2008-08-15
A basic kinetic mechanism that can predict the appropriate prompt-NO precursor NCN, as shown by experiment, with relative accuracy while still producing postflame NO results that can be calculated as accurately as or more accurately than through the former HCN pathway is presented for the first time. The basic NCN submechanism should be a starting point for future NCN kinetic and prompt NO formation refinement.
Clinically accurate fetal ECG parameters acquired from maternal abdominal sensors
CLIFFORD, Gari; SAMENI, Reza; WARD, Mr. Jay; ROBINSON, Julian; WOLFBERG, Adam J.
2011-01-01
OBJECTIVE To evaluate the accuracy of a novel system for measuring fetal heart rate and ST-segment changes using non-invasive electrodes on the maternal abdomen. STUDY DESIGN Fetal ECGs were recorded using abdominal sensors from 32 term laboring women who had a fetal scalp electrode (FSE) placed for a clinical indication. RESULTS Good quality data for FHR estimation was available in 91.2% of the FSE segments, and 89.9% of the abdominal electrode segments. The root mean square (RMS) error between the FHR data calculated by both methods over all processed segments was 0.36 beats per minute. ST deviation from the isoelectric point ranged from 0 to 14.2% of R-wave amplitude. The RMS error between the ST change calculated by both methods averaged over all processed segments was 3.2%. CONCLUSION FHR and ST change acquired from the maternal abdomen is highly accurate and on average is clinically indistinguishable from FHR and ST change calculated using FSE data. PMID:21514560
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.
Determining Kinetic Parameters for Isothermal Crystallization of Glasses
NASA Technical Reports Server (NTRS)
Ray, C. S.; Zhang, T.; Reis, S. T.; Brow, R. K.
2006-01-01
Non-isothermal crystallization techniques are frequently used to determine the kinetic parameters for crystallization in glasses. These techniques are experimentally simple and quick compared to the isothermal techniques. However, the analytical models used for non-isothermal data analysis, originally developed for describing isothermal transformation kinetics, are fundamentally flawed. The present paper describes a technique for determining the kinetic parameters for isothermal crystallization in glasses, which eliminates most of the common problems that generally make the studies of isothermal crystallization laborious and time consuming. In this technique, the volume fraction of glass that is crystallized as a function of time during an isothermal hold was determined using differential thermal analysis (DTA). The crystallization parameters for the lithium-disilicate (Li2O.2SiO2) model glass were first determined and compared to the same parameters determined by other techniques to establish the accuracy and usefulness of the present technique. This technique was then used to describe the crystallization kinetics of a complex Ca-Sr-Zn-silicate glass developed for sealing solid oxide fuel cells.
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
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
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.
Evaluation of Anaerobic Biofilm Reactor Kinetic Parameters Using Ant Colony Optimization.
Satya, Eswari Jujjavarapu; Venkateswarlu, Chimmiri
2013-09-01
Fixed bed reactors with naturally attached biofilms are increasingly used for anaerobic treatment of industry wastewaters due their effective treatment performance. The complex nature of biological reactions in biofilm processes often poses difficulty in analyzing them experimentally, and mathematical models could be very useful for their design and analysis. However, effective application of biofilm reactor models to practical problems suffers due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, an inverse modeling approach based on ant colony optimization is proposed and applied to estimate the kinetic and film thickness model parameters of wastewater treatment process in an anaerobic fixed bed biofilm reactor. Experimental data of pharmaceutical industry wastewater treatment process are used to determine the model parameters as a consequence of the solution of the rigorous mathematical models of the process. Results were evaluated for different modeling configurations derived from the combination of mathematical models, kinetic expressions, and optimization algorithms. Analysis of results showed that the two-dimensional mathematical model with Haldane kinetics better represents the pharmaceutical wastewater treatment in the biofilm reactor. The mathematical and kinetic modeling of this work forms a useful basis for the design and optimization of industry wastewater treating biofilm reactors.
Evaluation of Anaerobic Biofilm Reactor Kinetic Parameters Using Ant Colony Optimization
Satya, Eswari Jujjavarapu; Venkateswarlu, Chimmiri
2013-01-01
Abstract Fixed bed reactors with naturally attached biofilms are increasingly used for anaerobic treatment of industry wastewaters due their effective treatment performance. The complex nature of biological reactions in biofilm processes often poses difficulty in analyzing them experimentally, and mathematical models could be very useful for their design and analysis. However, effective application of biofilm reactor models to practical problems suffers due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, an inverse modeling approach based on ant colony optimization is proposed and applied to estimate the kinetic and film thickness model parameters of wastewater treatment process in an anaerobic fixed bed biofilm reactor. Experimental data of pharmaceutical industry wastewater treatment process are used to determine the model parameters as a consequence of the solution of the rigorous mathematical models of the process. Results were evaluated for different modeling configurations derived from the combination of mathematical models, kinetic expressions, and optimization algorithms. Analysis of results showed that the two-dimensional mathematical model with Haldane kinetics better represents the pharmaceutical wastewater treatment in the biofilm reactor. The mathematical and kinetic modeling of this work forms a useful basis for the design and optimization of industry wastewater treating biofilm reactors. PMID:24065871
Bērziņš, Agris; Actiņš, Andris
2014-06-01
The dehydration kinetics of mildronate dihydrate [3-(1,1,1-trimethylhydrazin-1-ium-2-yl)propionate dihydrate] was analyzed in isothermal and nonisothermal modes. The particle size, sample preparation and storage, sample weight, nitrogen flow rate, relative humidity, and sample history were varied in order to evaluate the effect of these factors and to more accurately interpret the data obtained from such analysis. It was determined that comparable kinetic parameters can be obtained in both isothermal and nonisothermal mode. However, dehydration activation energy values obtained in nonisothermal mode showed variation with conversion degree because of different rate-limiting step energy at higher temperature. Moreover, carrying out experiments in this mode required consideration of additional experimental complications. Our study of the different sample and experimental factor effect revealed information about changes of the dehydration rate-limiting step energy, variable contribution from different rate limiting steps, as well as clarified the dehydration mechanism. Procedures for convenient and fast determination of dehydration kinetic parameters were offered.
NASA Astrophysics Data System (ADS)
Nielsen, Jens; d'Avezac, Mayeul; Hetherington, James; Stamatakis, Michail
2013-12-01
Ab initio kinetic Monte Carlo (KMC) simulations have been successfully applied for over two decades to elucidate the underlying physico-chemical phenomena on the surfaces of heterogeneous catalysts. These simulations necessitate detailed knowledge of the kinetics of elementary reactions constituting the reaction mechanism, and the energetics of the species participating in the chemistry. The information about the energetics is encoded in the formation energies of gas and surface-bound species, and the lateral interactions between adsorbates on the catalytic surface, which can be modeled at different levels of detail. The majority of previous works accounted for only pairwise-additive first nearest-neighbor interactions. More recently, cluster-expansion Hamiltonians incorporating long-range interactions and many-body terms have been used for detailed estimations of catalytic rate [C. Wu, D. J. Schmidt, C. Wolverton, and W. F. Schneider, J. Catal. 286, 88 (2012)]. In view of the increasing interest in accurate predictions of catalytic performance, there is a need for general-purpose KMC approaches incorporating detailed cluster expansion models for the adlayer energetics. We have addressed this need by building on the previously introduced graph-theoretical KMC framework, and we have developed Zacros, a FORTRAN2003 KMC package for simulating catalytic chemistries. To tackle the high computational cost in the presence of long-range interactions we introduce parallelization with OpenMP. We further benchmark our framework by simulating a KMC analogue of the NO oxidation system established by Schneider and co-workers [J. Catal. 286, 88 (2012)]. We show that taking into account only first nearest-neighbor interactions may lead to large errors in the prediction of the catalytic rate, whereas for accurate estimates thereof, one needs to include long-range terms in the cluster expansion.
A review of the kinetic detail required for accurate predictions of normal shock waves
NASA Technical Reports Server (NTRS)
Muntz, E. P.; Erwin, Daniel A.; Pham-Van-diep, Gerald C.
1991-01-01
Several aspects of the kinetic models used in the collision phase of Monte Carlo direct simulations have been studied. Accurate molecular velocity distribution function predictions require a significantly increased number of computational cells in one maximum slope shock thickness, compared to predictions of macroscopic properties. The shape of the highly repulsive portion of the interatomic potential for argon is not well modeled by conventional interatomic potentials; this portion of the potential controls high Mach number shock thickness predictions, indicating that the specification of the energetic repulsive portion of interatomic or intermolecular potentials must be chosen with care for correct modeling of nonequilibrium flows at high temperatures. It has been shown for inverse power potentials that the assumption of variable hard sphere scattering provides accurate predictions of the macroscopic properties in shock waves, by comparison with simulations in which differential scattering is employed in the collision phase. On the other hand, velocity distribution functions are not well predicted by the variable hard sphere scattering model for softer potentials at higher Mach numbers.
Emami, Fereshteh; Maeder, Marcel; Abdollahi, Hamid
2015-05-01
Thermodynamic studies of equilibrium chemical reactions linked with kinetic procedures are mostly impossible by traditional approaches. In this work, the new concept of generalized kinetic study of thermodynamic parameters is introduced for dynamic data. The examples of equilibria intertwined with kinetic chemical mechanisms include molecular charge transfer complex formation reactions, pH-dependent degradation of chemical compounds and tautomerization kinetics in micellar solutions. Model-based global analysis with the possibility of calculating and embedding the equilibrium and kinetic parameters into the fitting algorithm has allowed the complete analysis of the complex reaction mechanisms. After the fitting process, the optimal equilibrium and kinetic parameters together with an estimate of their standard deviations have been obtained. This work opens up a promising new avenue for obtaining equilibrium constants through the kinetic data analysis for the kinetic reactions that involve equilibrium processes.
Bayesian parameter estimation of a k-ε model for accurate jet-in-crossflow simulations
Ray, Jaideep; Lefantzi, Sophia; Arunajatesan, Srinivasan; Dechant, Lawrence
2016-05-31
Reynolds-averaged Navier–Stokes models are not very accurate for high-Reynolds-number compressible jet-in-crossflow interactions. The inaccuracy arises from the use of inappropriate model parameters and model-form errors in the Reynolds-averaged Navier–Stokes model. In this study, the hypothesis is pursued that Reynolds-averaged Navier–Stokes predictions can be significantly improved by using parameters inferred from experimental measurements of a supersonic jet interacting with a transonic crossflow.
Zhang, Ying; Xu, Xin; Goddard, William A.
2009-01-01
We develop and validate a density functional, XYG3, based on the adiabatic connection formalism and the Görling–Levy coupling-constant perturbation expansion to the second order (PT2). XYG3 is a doubly hybrid functional, containing 3 mixing parameters. It has a nonlocal orbital-dependent component in the exchange term (exact exchange) plus information about the unoccupied Kohn–Sham orbitals in the correlation part (PT2 double excitation). XYG3 is remarkably accurate for thermochemistry, reaction barrier heights, and nonbond interactions of main group molecules. In addition, the accuracy remains nearly constant with system size. PMID:19276116
Parameter estimation for models of ligninolytic and cellulolytic enzyme kinetics
Wang, Gangsheng; Post, Wilfred M; Mayes, Melanie; Frerichs, Joshua T; Jagadamma, Sindhu
2012-01-01
While soil enzymes have been explicitly included in the soil organic carbon (SOC) decomposition models, there is a serious lack of suitable data for model parameterization. This study provides well-documented enzymatic parameters for application in enzyme-driven SOC decomposition models from a compilation and analysis of published measurements. In particular, we developed appropriate kinetic parameters for five typical ligninolytic and cellulolytic enzymes ( -glucosidase, cellobiohydrolase, endo-glucanase, peroxidase, and phenol oxidase). The kinetic parameters included the maximum specific enzyme activity (Vmax) and half-saturation constant (Km) in the Michaelis-Menten equation. The activation energy (Ea) and the pH optimum and sensitivity (pHopt and pHsen) were also analyzed. pHsen was estimated by fitting an exponential-quadratic function. The Vmax values, often presented in different units under various measurement conditions, were converted into the same units at a reference temperature (20 C) and pHopt. Major conclusions are: (i) Both Vmax and Km were log-normal distributed, with no significant difference in Vmax exhibited between enzymes originating from bacteria or fungi. (ii) No significant difference in Vmax was found between cellulases and ligninases; however, there was significant difference in Km between them. (iii) Ligninases had higher Ea values and lower pHopt than cellulases; average ratio of pHsen to pHopt ranged 0.3 0.4 for the five enzymes, which means that an increase or decrease of 1.1 1.7 pH units from pHopt would reduce Vmax by 50%. (iv) Our analysis indicated that the Vmax values from lab measurements with purified enzymes were 1 2 orders of magnitude higher than those for use in SOC decomposition models under field conditions.
NASA Astrophysics Data System (ADS)
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.
Kinetic Parameters of Binary Iron/Oxidant Pyrolants
NASA Astrophysics Data System (ADS)
Shamsipur, Mojtaba; Mahdi Pourmortazavi, Seied; Fathollahi, Manochehr
2012-04-01
The thermal properties of pyrotechnic mixtures containing iron powder as fuel and KNO3, KClO3, and KClO4 as oxidants are reported. The thermogravimetry-differential thermal analysis results for pure components and corresponding pyrotechnic mixtures revealed that the melting point, decomposition temperature, and rate of oxygen releasing of the oxidants have dominant effects on ignition reaction of the pyrotechnic mixtures. The apparent activation energy and activation parameters for the combustion processes were evaluated from the differential scanning calorimetry experiments. Based on the ignition temperatures obtained and the resulting kinetic data, the thermal reactivity of the pyrotechnic mixtures was found to decrease as in the order Fe + KClO3 > Fe + KNO3 > Fe + KClO4.
NASA Astrophysics Data System (ADS)
Berezovska, Ganna; Prada-Gracia, Diego; Mostarda, Stefano; Rao, Francesco
2012-11-01
Molecular simulations as well as single molecule experiments have been widely analyzed in terms of order parameters, the latter representing candidate probes for the relevant degrees of freedom. Notwithstanding this approach is very intuitive, mounting evidence showed that such descriptions are inaccurate, leading to ambiguous definitions of states and wrong kinetics. To overcome these limitations a framework making use of order parameter fluctuations in conjunction with complex network analysis is investigated. Derived from recent advances in the analysis of single molecule time traces, this approach takes into account the fluctuations around each time point to distinguish between states that have similar values of the order parameter but different dynamics. Snapshots with similar fluctuations are used as nodes of a transition network, the clusterization of which into states provides accurate Markov-state-models of the system under study. Application of the methodology to theoretical models with a noisy order parameter as well as the dynamics of a disordered peptide illustrates the possibility to build accurate descriptions of molecular processes on the sole basis of order parameter time series without using any supplementary information.
Berezovska, Ganna; Prada-Gracia, Diego; Mostarda, Stefano; Rao, Francesco
2012-11-21
Molecular simulations as well as single molecule experiments have been widely analyzed in terms of order parameters, the latter representing candidate probes for the relevant degrees of freedom. Notwithstanding this approach is very intuitive, mounting evidence showed that such descriptions are inaccurate, leading to ambiguous definitions of states and wrong kinetics. To overcome these limitations a framework making use of order parameter fluctuations in conjunction with complex network analysis is investigated. Derived from recent advances in the analysis of single molecule time traces, this approach takes into account the fluctuations around each time point to distinguish between states that have similar values of the order parameter but different dynamics. Snapshots with similar fluctuations are used as nodes of a transition network, the clusterization of which into states provides accurate Markov-state-models of the system under study. Application of the methodology to theoretical models with a noisy order parameter as well as the dynamics of a disordered peptide illustrates the possibility to build accurate descriptions of molecular processes on the sole basis of order parameter time series without using any supplementary information. PMID:23181288
Loewe, Axel; Wilhelms, Mathias; Schmid, Jochen; Krause, Mathias J.; Fischer, Fathima; Thomas, Dierk; Scholz, Eberhard P.; Dössel, Olaf; Seemann, Gunnar
2016-01-01
Computational models of cardiac electrophysiology provided insights into arrhythmogenesis and paved the way toward tailored therapies in the last years. To fully leverage in silico models in future research, these models need to be adapted to reflect pathologies, genetic alterations, or pharmacological effects, however. A common approach is to leave the structure of established models unaltered and estimate the values of a set of parameters. Today’s high-throughput patch clamp data acquisition methods require robust, unsupervised algorithms that estimate parameters both accurately and reliably. In this work, two classes of optimization approaches are evaluated: gradient-based trust-region-reflective and derivative-free particle swarm algorithms. Using synthetic input data and different ion current formulations from the Courtemanche et al. electrophysiological model of human atrial myocytes, we show that neither of the two schemes alone succeeds to meet all requirements. Sequential combination of the two algorithms did improve the performance to some extent but not satisfactorily. Thus, we propose a novel hybrid approach coupling the two algorithms in each iteration. This hybrid approach yielded very accurate estimates with minimal dependency on the initial guess using synthetic input data for which a ground truth parameter set exists. When applied to measured data, the hybrid approach yielded the best fit, again with minimal variation. Using the proposed algorithm, a single run is sufficient to estimate the parameters. The degree of superiority over the other investigated algorithms in terms of accuracy and robustness depended on the type of current. In contrast to the non-hybrid approaches, the proposed method proved to be optimal for data of arbitrary signal to noise ratio. The hybrid algorithm proposed in this work provides an important tool to integrate experimental data into computational models both accurately and robustly allowing to assess the often non
NASA Astrophysics Data System (ADS)
Peng, Liang-You; Gong, Qihuang
2010-12-01
The accurate computations of hydrogenic continuum wave functions are very important in many branches of physics such as electron-atom collisions, cold atom physics, and atomic ionization in strong laser fields, etc. Although there already exist various algorithms and codes, most of them are only reliable in a certain ranges of parameters. In some practical applications, accurate continuum wave functions need to be calculated at extremely low energies, large radial distances and/or large angular momentum number. Here we provide such a code, which can generate accurate hydrogenic continuum wave functions and corresponding Coulomb phase shifts at a wide range of parameters. Without any essential restrict to angular momentum number, the present code is able to give reliable results at the electron energy range [10,10] eV for radial distances of [10,10] a.u. We also find the present code is very efficient, which should find numerous applications in many fields such as strong field physics. Program summaryProgram title: HContinuumGautchi Catalogue identifier: AEHD_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHD_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1233 No. of bytes in distributed program, including test data, etc.: 7405 Distribution format: tar.gz Programming language: Fortran90 in fixed format Computer: AMD Processors Operating system: Linux RAM: 20 MBytes Classification: 2.7, 4.5 Nature of problem: The accurate computation of atomic continuum wave functions is very important in many research fields such as strong field physics and cold atom physics. Although there have already existed various algorithms and codes, most of them can only be applicable and reliable in a certain range of parameters. We present here an accurate FORTRAN program for
Baker, Syed Murtuza; Poskar, C Hart; Junker, Björn H
2011-01-01
In systems biology, experimentally measured parameters are not always available, necessitating the use of computationally based parameter estimation. In order to rely on estimated parameters, it is critical to first determine which parameters can be estimated for a given model and measurement set. This is done with parameter identifiability analysis. A kinetic model of the sucrose accumulation in the sugar cane culm tissue developed by Rohwer et al. was taken as a test case model. What differentiates this approach is the integration of an orthogonal-based local identifiability method into the unscented Kalman filter (UKF), rather than using the more common observability-based method which has inherent limitations. It also introduces a variable step size based on the system uncertainty of the UKF during the sensitivity calculation. This method identified 10 out of 12 parameters as identifiable. These ten parameters were estimated using the UKF, which was run 97 times. Throughout the repetitions the UKF proved to be more consistent than the estimation algorithms used for comparison. PMID:21989173
Guggenheim, James A.; Bargigia, Ilaria; Farina, Andrea; Pifferi, Antonio; Dehghani, Hamid
2016-01-01
A novel straightforward, accessible and efficient approach is presented for performing hyperspectral time-domain diffuse optical spectroscopy to determine the optical properties of samples accurately using geometry specific models. To allow bulk parameter recovery from measured spectra, a set of libraries based on a numerical model of the domain being investigated is developed as opposed to the conventional approach of using an analytical semi-infinite slab approximation, which is known and shown to introduce boundary effects. Results demonstrate that the method improves the accuracy of derived spectrally varying optical properties over the use of the semi-infinite approximation. PMID:27699137
Guggenheim, James A.; Bargigia, Ilaria; Farina, Andrea; Pifferi, Antonio; Dehghani, Hamid
2016-01-01
A novel straightforward, accessible and efficient approach is presented for performing hyperspectral time-domain diffuse optical spectroscopy to determine the optical properties of samples accurately using geometry specific models. To allow bulk parameter recovery from measured spectra, a set of libraries based on a numerical model of the domain being investigated is developed as opposed to the conventional approach of using an analytical semi-infinite slab approximation, which is known and shown to introduce boundary effects. Results demonstrate that the method improves the accuracy of derived spectrally varying optical properties over the use of the semi-infinite approximation.
Kinetic Parameter Extraction of Square Wave Voltammograms from DNA-Modified Gold Electrodes
NASA Astrophysics Data System (ADS)
McWilliams, Marc; Wohlgamuth, Chris; Slinker, Jason
2012-10-01
The field of surface bound electrochemistry is important in a variety of applications specifically sensing. A fundamental understanding of the processes involved could help to improve detection limits, optimize rates of detection and direct changes in device design. Accurate extraction of electrochemical kinetic parameters such as the rate constant k and charge transfer coefficient α from cyclic voltammograms can be challenging when confronted with large background currents and relatively weak signals. The commonly used technique of Laviron analysis is both time consuming and somewhat subjective. Square wave voltammetry (SWV) is therefore an ideal alternative method given that it maximizes signal while minimizing capacitive effects. In this experiment kinetic parameters of DNA-modified gold electrodes are obtained from SWV curves through background subtraction followed by nonlinear least squares fitting using a first order quasi-reversible surface process model. The fitting is accomplished using the Nelder-Mead simplex algorithm with standard parameters and a convergence condition of less than 0.0001%. General agreement with experimental data is shown with varying levels of confidence. Difficulties specific to this experiment are discussed as well as the possible benefits of utilizing the Bayesian statistical approach of nested sampling when confronted with multiple peaks of interest and the background source is well defined.
Electrochemical evaluation of glutathione S-transferase kinetic parameters.
Enache, Teodor Adrian; Oliveira-Brett, Ana Maria
2015-02-01
Glutathione S-transferases (GSTs), are a family of enzymes belonging to the phase II metabolism that catalyse the formation of thioether conjugates between the endogenous tripeptide glutathione and xenobiotic compounds. The voltammetric behaviour of glutathione (GSH), 1-chloro-2,4-dinitrobenzene (CDNB) and glutathione S-transferase (GST), as well as the catalytic conjugation reaction of GSH to CDNB by GST was investigated at room temperature, T=298.15K (25°C), at pH6.5, for low concentration of substrates and enzyme, using differential pulse (DP) voltammetry at a glassy carbon electrode. Only GSH can be oxidized; a sensitivity of 0.14nA/μM and a LOD of 6.4μM were obtained. The GST kinetic parameter electrochemical evaluation, in relation to its substrates, GSH and CDNB, using reciprocal Michaelis-Menten and Lineweaver-Burk double reciprocal plots, was determined. A value of KM~100μM was obtained for either GSH or CDNB, and Vmax varied between 40 and 60μmol/min per mg of GST.
Accurate estimation of motion blur parameters in noisy remote sensing image
NASA Astrophysics Data System (ADS)
Shi, Xueyan; Wang, Lin; Shao, Xiaopeng; Wang, Huilin; Tao, Zhong
2015-05-01
The relative motion between remote sensing satellite sensor and objects is one of the most common reasons for remote sensing image degradation. It seriously weakens image data interpretation and information extraction. In practice, point spread function (PSF) should be estimated firstly for image restoration. Identifying motion blur direction and length accurately is very crucial for PSF and restoring image with precision. In general, the regular light-and-dark stripes in the spectrum can be employed to obtain the parameters by using Radon transform. However, serious noise existing in actual remote sensing images often causes the stripes unobvious. The parameters would be difficult to calculate and the error of the result relatively big. In this paper, an improved motion blur parameter identification method to noisy remote sensing image is proposed to solve this problem. The spectrum characteristic of noisy remote sensing image is analyzed firstly. An interactive image segmentation method based on graph theory called GrabCut is adopted to effectively extract the edge of the light center in the spectrum. Motion blur direction is estimated by applying Radon transform on the segmentation result. In order to reduce random error, a method based on whole column statistics is used during calculating blur length. Finally, Lucy-Richardson algorithm is applied to restore the remote sensing images of the moon after estimating blur parameters. The experimental results verify the effectiveness and robustness of our algorithm.
Graphical estimation of the dual-enzyme kinetic parameters for Cr(VI) reduction.
Hossain, Md Akram
2006-03-01
Chromium(VI) (Cr(VI)) contamination of soil and groundwater is a major environmental concern. Bioreduction of Cr(VI) by Shewanella oneidensis MR-1 (MR-1) can be considered a feasible option to reduce the toxic and mobile Cr(VI) to the less toxic and less mobile chromium(III) (Cr(III)). The reaction rate expression for Cr(VI) reduction is nonlinear and the rate constants are evaluated by employing nonlinear optimization techniques. The outcome of the optimization techniques, in general, depends on the initial estimate of the kinetic parameters which is not always available. A graphical approach based on sound mathematical reasoning has been developed which is accurate, simpler to use, and can provide the best initial estimate for nonlinear optimization.
Exact kinetic energy enables accurate evaluation of weak interactions by the FDE-vdW method
Sinha, Debalina; Pavanello, Michele
2015-08-28
The correlation energy of interaction is an elusive and sought-after interaction between molecular systems. By partitioning the response function of the system into subsystem contributions, the Frozen Density Embedding (FDE)-vdW method provides a computationally amenable nonlocal correlation functional based on the adiabatic connection fluctuation dissipation theorem applied to subsystem density functional theory. In reproducing potential energy surfaces of weakly interacting dimers, we show that FDE-vdW, either employing semilocal or exact nonadditive kinetic energy functionals, is in quantitative agreement with high-accuracy coupled cluster calculations (overall mean unsigned error of 0.5 kcal/mol). When employing the exact kinetic energy (which we term the Kohn-Sham (KS)-vdW method), the binding energies are generally closer to the benchmark, and the energy surfaces are also smoother.
A second-order accurate kinetic-theory-based method for inviscid compressible flows
NASA Technical Reports Server (NTRS)
Deshpande, Suresh M.
1986-01-01
An upwind method for the numerical solution of the Euler equations is presented. This method, called the kinetic numerical method (KNM), is based on the fact that the Euler equations are moments of the Boltzmann equation of the kinetic theory of gases when the distribution function is Maxwellian. The KNM consists of two phases, the convection phase and the collision phase. The method is unconditionally stable and explicit. It is highly vectorizable and can be easily made total variation diminishing for the distribution function by a suitable choice of the interpolation strategy. The method is applied to a one-dimensional shock-propagation problem and to a two-dimensional shock-reflection problem.
Strayer, R F; Tiedje, J M
1978-08-01
The kinetic parameters K(m), V(max), T(t) (turnover time), and v (natural velocity) were determined for H(2) and acetate conversion to methane by Wintergreen Lake sediment, using short-term (a few hours) methods and incubation temperatures of 10 to 14 degrees C. Estimates of the Michaelis-Menten constant, K(m), for both the consumption of hydrogen and the conversion of hydrogen to methane by sediment microflora averaged about 0.024 mumol g of dry sediment. The maximal velocity, V(max), averaged 4.8 mumol of H(2) g h for hydrogen consumption and 0.64 mumol of CH(4) g h for the conversion of hydrogen to methane during the winter. Estimated natural rates of hydrogen consumption and hydrogen conversion to methane could be calculated from the Michaelis-Menten equation and estimates of K(m), V(max), and the in situ dissolved-hydrogen concentration. These results indicate that methane may not be the only fate of hydrogen in the sediment. Among several potential hydrogen donors tested, only formate stimulated the rate of sediment methanogenesis. Formate conversion to methane was so rapid that an accurate estimate of kinetic parameters was not possible. Kinetic experiments using [2-C]acetate and sediments collected in the summer indicated that acetate was being converted to methane at or near the maximal rate. A minimum natural rate of acetate conversion to methane was estimated to be about 110 nmol of CH(4) g h, which was 66% of the V(max) (163 nmol of CH(4) g h). A 15-min preincubation of sediment with 5.0 x 10 atm of hydrogen had a pronounced effect on the kinetic parameters for the conversion of acetate to methane. The acetate pool size, expressed as the term K(m) + S(n) (S(n) is in situ substrate concentration), decreased by 37% and T(t) decreased by 43%. The V(max) remained relatively constant. A preincubation with hydrogen also caused a 37% decrease in the amount of labeled carbon dioxide produced from the metabolism of [U-C]valine by sediment heterotrophs.
NASA Astrophysics Data System (ADS)
Lachaume, Regis; Rabus, Markus; Jordan, Andres
2015-08-01
In stellar interferometry, the assumption that the observables can be seen as Gaussian, independent variables is the norm. In particular, neither the optical interferometry FITS (OIFITS) format nor the most popular fitting software in the field, LITpro, offer means to specify a covariance matrix or non-Gaussian uncertainties. Interferometric observables are correlated by construct, though. Also, the calibration by an instrumental transfer function ensures that the resulting observables are not Gaussian, even if uncalibrated ones happened to be so.While analytic frameworks have been published in the past, they are cumbersome and there is no generic implementation available. We propose here a relatively simple way of dealing with correlated errors without the need to extend the OIFITS specification or making some Gaussian assumptions. By repeatedly picking at random which interferograms, which calibrator stars, and which are the errors on their diameters, and performing the data processing on the bootstrapped data, we derive a sampling of p(O), the multivariate probability density function (PDF) of the observables O. The results can be stored in a normal OIFITS file. Then, given a model m with parameters P predicting observables O = m(P), we can estimate the PDF of the model parameters f(P) = p(m(P)) by using a density estimation of the observables' PDF p.With observations repeated over different baselines, on nights several days apart, and with a significant set of calibrators systematic errors are de facto taken into account. We apply the technique to a precise and accurate assessment of stellar diameters obtained at the Very Large Telescope Interferometer with PIONIER.
Impact of kinetic parameters on heat transfer modeling for a pultrusion process
NASA Astrophysics Data System (ADS)
Gorthala, R.; Roux, J. A.; Vaughan, J. G.; Donti, R. P.; Hassouneh, A.
An examination is conducted of pultrusion heat model predictions for various parameters of resin chemical kinetics; these parameters' values affect model heat-transfer results and model predictions. Attention is given to the applicability of DSC kinetic parameters to resin cure modeling, by comparing the predicted product cure temperature profiles and resin degree-of-cure values with pultrusion experiment results obtained for both carbon and glass reinforcements, different pull speeds and fiber volumes, and various die temperature profiles.
Jeong, Hyunjo; Zhang, Shuzeng; Li, Xiongbing; Barnard, Dan
2015-09-15
The accurate measurement of acoustic nonlinearity parameter β for fluids or solids generally requires making corrections for diffraction effects due to finite size geometry of transmitter and receiver. These effects are well known in linear acoustics, while those for second harmonic waves have not been well addressed and therefore not properly considered in previous studies. In this work, we explicitly define the attenuation and diffraction corrections using the multi-Gaussian beam (MGB) equations which were developed from the quasilinear solutions of the KZK equation. The effects of making these corrections are examined through the simulation of β determination in water. Diffraction corrections are found to have more significant effects than attenuation corrections, and the β values of water can be estimated experimentally with less than 5% errors when the exact second harmonic diffraction corrections are used together with the negligible attenuation correction effects on the basis of linear frequency dependence between attenuation coefficients, α{sub 2} ≃ 2α{sub 1}.
Accurate parameters for HD 209458 and its planet from HST spectrophotometry
NASA Astrophysics Data System (ADS)
del Burgo, C.; Allende Prieto, C.
2016-08-01
We present updated parameters for the star HD 209458 and its transiting giant planet. The stellar angular diameter θ=0.2254±0.0017 mas is obtained from the average ratio between the absolute flux observed with the Hubble Space Telescope and that of the best-fitting Kurucz model atmosphere. This angular diameter represents an improvement in precision of more than four times compared to available interferometric determinations. The stellar radius R⋆=1.20±0.05 R⊙ is ascertained by combining the angular diameter with the Hipparcos trigonometric parallax, which is the main contributor to its uncertainty, and therefore the radius accuracy should be significantly improved with Gaia's measurements. The radius of the exoplanet Rp=1.41±0.06 RJ is derived from the corresponding transit depth in the light curve and our stellar radius. From the model fitting, we accurately determine the effective temperature, Teff=6071±20 K, which is in perfect agreement with the value of 6070±24 K calculated from the angular diameter and the integrated spectral energy distribution. We also find precise values from recent Padova Isochrones, such as R⋆=1.20±0.06 R⊙ and Teff=6099±41 K. We arrive at a consistent picture from these methods and compare the results with those from the literature.
NASA Astrophysics Data System (ADS)
Bruntt, H.; Basu, S.; Smalley, B.; Chaplin, W. J.; Verner, G. A.; Bedding, T. R.; Catala, C.; Gazzano, J.-C.; Molenda-Żakowicz, J.; Thygesen, A. O.; Uytterhoeven, K.; Hekker, S.; Huber, D.; Karoff, C.; Mathur, S.; Mosser, B.; Appourchaux, T.; Campante, T. L.; Elsworth, Y.; García, R. A.; Handberg, R.; Metcalfe, T. S.; Quirion, P.-O.; Régulo, C.; Roxburgh, I. W.; Stello, D.; Christensen-Dalsgaard, J.; Kawaler, S. D.; Kjeldsen, H.; Morris, R. L.; Quintana, E. V.; Sanderfer, D. T.
2012-06-01
We present a detailed spectroscopic study of 93 solar-type stars that are targets of the NASA/Kepler mission and provide detailed chemical composition of each target. We find that the overall metallicity is well represented by Fe lines. Relative abundances of light elements (CNO) and α elements are generally higher for low-metallicity stars. Our spectroscopic analysis benefits from the accurately measured surface gravity from the asteroseismic analysis of the Kepler light curves. The accuracy on the log g parameter is better than 0.03 dex and is held fixed in the analysis. We compare our Teff determination with a recent colour calibration of VT-KS [TYCHO V magnitude minus Two Micron All Sky Survey (2MASS) KS magnitude] and find very good agreement and a scatter of only 80 K, showing that for other nearby Kepler targets, this index can be used. The asteroseismic log g values agree very well with the classical determination using Fe I-Fe II balance, although we find a small systematic offset of 0.08 dex (asteroseismic log g values are lower). The abundance patterns of metals, α elements and the light elements (CNO) show that a simple scaling by [Fe/H] is adequate to represent the metallicity of the stars, except for the stars with metallicity below -0.3, where α-enhancement becomes important. However, this is only important for a very small fraction of the Kepler sample. We therefore recommend that a simple scaling with [Fe/H] be employed in the asteroseismic analyses of large ensembles of solar-type stars.
Ralph, Duncan K.; Matsen, Frederick A.
2016-01-01
VDJ rearrangement and somatic hypermutation work together to produce antibody-coding B cell receptor (BCR) sequences for a remarkable diversity of antigens. It is now possible to sequence these BCRs in high throughput; analysis of these sequences is bringing new insight into how antibodies develop, in particular for broadly-neutralizing antibodies against HIV and influenza. A fundamental step in such sequence analysis is to annotate each base as coming from a specific one of the V, D, or J genes, or from an N-addition (a.k.a. non-templated insertion). Previous work has used simple parametric distributions to model transitions from state to state in a hidden Markov model (HMM) of VDJ recombination, and assumed that mutations occur via the same process across sites. However, codon frame and other effects have been observed to violate these parametric assumptions for such coding sequences, suggesting that a non-parametric approach to modeling the recombination process could be useful. In our paper, we find that indeed large modern data sets suggest a model using parameter-rich per-allele categorical distributions for HMM transition probabilities and per-allele-per-position mutation probabilities, and that using such a model for inference leads to significantly improved results. We present an accurate and efficient BCR sequence annotation software package using a novel HMM “factorization” strategy. This package, called partis (https://github.com/psathyrella/partis/), is built on a new general-purpose HMM compiler that can perform efficient inference given a simple text description of an HMM. PMID:26751373
Ralph, Duncan K; Matsen, Frederick A
2016-01-01
VDJ rearrangement and somatic hypermutation work together to produce antibody-coding B cell receptor (BCR) sequences for a remarkable diversity of antigens. It is now possible to sequence these BCRs in high throughput; analysis of these sequences is bringing new insight into how antibodies develop, in particular for broadly-neutralizing antibodies against HIV and influenza. A fundamental step in such sequence analysis is to annotate each base as coming from a specific one of the V, D, or J genes, or from an N-addition (a.k.a. non-templated insertion). Previous work has used simple parametric distributions to model transitions from state to state in a hidden Markov model (HMM) of VDJ recombination, and assumed that mutations occur via the same process across sites. However, codon frame and other effects have been observed to violate these parametric assumptions for such coding sequences, suggesting that a non-parametric approach to modeling the recombination process could be useful. In our paper, we find that indeed large modern data sets suggest a model using parameter-rich per-allele categorical distributions for HMM transition probabilities and per-allele-per-position mutation probabilities, and that using such a model for inference leads to significantly improved results. We present an accurate and efficient BCR sequence annotation software package using a novel HMM "factorization" strategy. This package, called partis (https://github.com/psathyrella/partis/), is built on a new general-purpose HMM compiler that can perform efficient inference given a simple text description of an HMM. PMID:26751373
Parameter Estimates in Differential Equation Models for Chemical Kinetics
ERIC Educational Resources Information Center
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…
Cui, Yunfeng; Bai, Jing
2005-01-01
Liver kinetic study of [^{18}F]2-fluoro-2-deoxy-D-glucose (FDG) metabolism in human body is an important tool for functional modeling and glucose metabolic rate estimation. In general, the arterial blood time-activity curve (TAC) and the tissue TAC are required as the input and output functions for the kinetic model. For liver study, however, the arterial-input may be not consistent with the actual model input because the liver has a dual blood supply from the hepatic artery (HA) and the portal vein (PV) to the liver. In this study, the result of model parameter estimation using dual-input function is compared with that using arterial-input function. First, a dynamic positron emission tomography (PET) experiment is performed after injection of FDG into the human body. The TACs of aortic blood, PV blood, and five regions of interest (ROIs) in liver are obtained from the PET image. Then, the dual-input curve is generated by calculating weighted sum of both the arterial and PV input curves. Finally, the five liver ROIs' kinetic parameters are estimated with arterial-input and dual-input functions respectively. The results indicate that the two methods provide different parameter estimations and the dual-input function may lead to more accurate parameter estimation.
Parameter Optimization of Nitriding Process Using Chemical Kinetics
NASA Astrophysics Data System (ADS)
Özdemir, İ. Bedii; Akar, Firat; Lippmann, Nils
2016-09-01
Using the dynamics of chemical kinetics, an investigation to search for an optimum condition for a gas nitriding process is performed over the solution space spanned by the initial temperature and gas composition of the furnace. For a two-component furnace atmosphere, the results are presented in temporal variations of gas concentrations and the nitrogen coverage on the surface. It seems that the exploitation of the nitriding kinetics can provide important feedback for setting the model-based control algorithms. The present work shows that when the nitrogen gas concentration is not allowed to exceed 6 pct, the Nad coverage can attain maximum values as high as 0.97. The time evolution of the Nad coverage also reveals that, as long as the temperature is above the value where nitrogen poisoning of the surface due to the low-temperature adsorption of excess nitrogen occurs, the initial ammonia content in the furnace atmosphere is much more important in the nitriding process than is the initial temperature.
Effective Temperatures of Selected Main-Sequence Stars with the Most Accurate Parameters
NASA Astrophysics Data System (ADS)
Soydugan, F.; Eker, Z.; Soydugan, E.; Bilir, S.; Gökçe, E. Y.; Steer, I.; Tüysüz, M.; Šenyüz, T.; Demircan, O.
2015-07-01
In this study we investigate the distributions of the properties of detached double-lined binaries (DBs) in the mass-luminosity, mass-radius, and mass-effective temperature diagrams. We have improved the classical mass-luminosity relation based on the database of DBs by Eker et al. (2014a). Based on the accurate observational data available to us we propose a method for improving the effective temperatures of eclipsing binaries with accurate mass and radius determinations.
k-Cone analysis: determining all candidate values for kinetic parameters on a network scale.
Famili, Iman; Mahadevan, Radhakrishnan; Palsson, Bernhard O
2005-03-01
The absence of comprehensive measured kinetic values and the observed inconsistency in the available in vitro kinetic data has hindered the formulation of network-scale kinetic models of biochemical reaction networks. To meet this challenge we present an approach to construct a convex space, termed the k-cone, which contains all the allowable numerical values of the kinetic constants in large-scale biochemical networks. The definition of the k-cone relies on the incorporation of in vivo concentration data and a simplified approach to represent enzyme kinetics within an established constraint-based modeling approach. The k-cone approach was implemented to define the allowable combination of numerical values for a full kinetic model of human red blood cell metabolism and to study its correlated kinetic parameters. The k-cone approach can be used to determine consistency between in vitro measured kinetic values and in vivo concentration and flux measurements when used in a network-scale kinetic model. k-Cone analysis was successful in determining whether in vitro measured kinetic values used in the reconstruction of a kinetic-based model of Saccharomyces cerevisiae central metabolism could reproduce in vivo measurements. Further, the k-cone can be used to determine which numerical values of in vitro measured parameters are required to be changed in a kinetic model if in vivo measured values are not reproduced. k-Cone analysis could identify what minimum number of in vitro determined kinetic parameters needed to be adjusted in the S. cerevisiae model to be consistent with the in vivo data. Applying the k-cone analysis a priori to kinetic model development may reduce the time and effort involved in model building and parameter adjustment. With the recent developments in high-throughput profiling of metabolite concentrations at a whole-cell scale and advances in metabolomics technologies, the k-cone approach presented here may hold the promise for kinetic
k-Cone Analysis: Determining All Candidate Values for Kinetic Parameters on a Network Scale
Famili, Iman; Mahadevan, Radhakrishnan; Palsson, Bernhard O.
2005-01-01
The absence of comprehensive measured kinetic values and the observed inconsistency in the available in vitro kinetic data has hindered the formulation of network-scale kinetic models of biochemical reaction networks. To meet this challenge we present an approach to construct a convex space, termed the k-cone, which contains all the allowable numerical values of the kinetic constants in large-scale biochemical networks. The definition of the k-cone relies on the incorporation of in vivo concentration data and a simplified approach to represent enzyme kinetics within an established constraint-based modeling approach. The k-cone approach was implemented to define the allowable combination of numerical values for a full kinetic model of human red blood cell metabolism and to study its correlated kinetic parameters. The k-cone approach can be used to determine consistency between in vitro measured kinetic values and in vivo concentration and flux measurements when used in a network-scale kinetic model. k-Cone analysis was successful in determining whether in vitro measured kinetic values used in the reconstruction of a kinetic-based model of Saccharomyces cerevisiae central metabolism could reproduce in vivo measurements. Further, the k-cone can be used to determine which numerical values of in vitro measured parameters are required to be changed in a kinetic model if in vivo measured values are not reproduced. k-Cone analysis could identify what minimum number of in vitro determined kinetic parameters needed to be adjusted in the S. cerevisiae model to be consistent with the in vivo data. Applying the k-cone analysis a priori to kinetic model development may reduce the time and effort involved in model building and parameter adjustment. With the recent developments in high-throughput profiling of metabolite concentrations at a whole-cell scale and advances in metabolomics technologies, the k-cone approach presented here may hold the promise for kinetic
Brito, Paula M.; Antunes, Fernando
2014-01-01
The lack of kinetic data concerning the biological effects of reactive oxygen species is slowing down the development of the field of redox signaling. Herein, we deduced and applied equations to estimate kinetic parameters from typical redox signaling experiments. H2O2-sensing mediated by the oxidation of a protein target and the switch-off of this sensor, by being converted back to its reduced form, are the two processes for which kinetic parameters are determined. The experimental data required to apply the equations deduced is the fraction of the H2O2 sensor protein in the reduced or in the oxidized state measured in intact cells or living tissues after exposure to either endogenous or added H2O2. Either non-linear fittings that do not need transformation of the experimental data or linearized plots in which deviations from the equations are easily observed can be used. The equations were shown to be valid by fitting to them virtual time courses simulated with a kinetic model. The good agreement between the kinetic parameters estimated in these fittings and those used to simulate the virtual time courses supported the accuracy of the kinetic equations deduced. Finally, equations were successfully tested with real data taken from published experiments that describe redox signaling mediated by the oxidation of two protein tyrosine phosphatases, PTP1B and SHP-2, which are two of the few H2O2-sensing proteins with known kinetic parameters. Whereas for PTP1B estimated kinetic parameters fitted in general the present knowledge, for SHP-2 results obtained suggest that reactivity toward H2O2 as well as the rate of SHP-2 regeneration back to its reduced form are higher than previously thought. In conclusion, valuable quantitative kinetic data can be estimated from typical redox signaling experiments, thus improving our understanding about the complex processes that underlie the interplay between oxidative stress and redox signaling responses. PMID:25325054
NASA Astrophysics Data System (ADS)
Brito, Paula; Antunes, Fernando
2014-10-01
The lack of kinetic data concerning the biological effects of reactive oxygen species is slowing down the development of the field of redox signaling. Herein, we deduced and applied equations to estimate kinetic parameters from typical redox signaling experiments. H2O2-sensing mediated by the oxidation of a protein target and the switch-off of this sensor, by being converted back to its reduced form, are the two processes for which kinetic parameters are determined. The experimental data required to apply the equations deduced is the fraction of the H2O2 sensor protein in the reduced or in the oxidized state measured in intact cells or living tissues after exposure to either endogenous or added H2O2. Either non-linear fittings that do not need transformation of the experimental data or linearized plots in which deviations from the equations are easily observed can be used. The equations were shown to be valid by fitting to them virtual time courses simulated with a kinetic model. The good agreement between the kinetic parameters estimated in these fittings and those used to simulate the virtual time courses supported the accuracy of the kinetic equations deduced. Finally, equations were successfully tested with real data taken from published experiments that describe redox signaling mediated by the oxidation of two protein tyrosine phosphatases, PTP1B and SHP-2, which are two of the few H2O2-sensing proteins with known kinetic parameters. Whereas for PTP1B estimated kinetic parameters fitted in general the present knowledge, for SHP-2 results obtained suggest that reactivity towards H2O2 as well as the rate of SHP-2 regeneration back to its reduced form are higher than previously thought. In conclusion, valuable quantitative kinetic data can be estimated from typical redox signaling experiments, thus improving our understanding about the complex processes that underline the interplay between oxidative stress and redox signaling responses.
Brito, Paula M; Antunes, Fernando
2014-01-01
The lack of kinetic data concerning the biological effects of reactive oxygen species is slowing down the development of the field of redox signaling. Herein, we deduced and applied equations to estimate kinetic parameters from typical redox signaling experiments. H2O2-sensing mediated by the oxidation of a protein target and the switch-off of this sensor, by being converted back to its reduced form, are the two processes for which kinetic parameters are determined. The experimental data required to apply the equations deduced is the fraction of the H2O2 sensor protein in the reduced or in the oxidized state measured in intact cells or living tissues after exposure to either endogenous or added H2O2. Either non-linear fittings that do not need transformation of the experimental data or linearized plots in which deviations from the equations are easily observed can be used. The equations were shown to be valid by fitting to them virtual time courses simulated with a kinetic model. The good agreement between the kinetic parameters estimated in these fittings and those used to simulate the virtual time courses supported the accuracy of the kinetic equations deduced. Finally, equations were successfully tested with real data taken from published experiments that describe redox signaling mediated by the oxidation of two protein tyrosine phosphatases, PTP1B and SHP-2, which are two of the few H2O2-sensing proteins with known kinetic parameters. Whereas for PTP1B estimated kinetic parameters fitted in general the present knowledge, for SHP-2 results obtained suggest that reactivity toward H2O2 as well as the rate of SHP-2 regeneration back to its reduced form are higher than previously thought. In conclusion, valuable quantitative kinetic data can be estimated from typical redox signaling experiments, thus improving our understanding about the complex processes that underlie the interplay between oxidative stress and redox signaling responses.
Determining the Kinetic Parameters Characteristic of Microalgal Growth.
ERIC Educational Resources Information Center
Martinez Sancho, Maria Eugenie; And Others
1991-01-01
An activity in which students obtain a growth curve for algae, identify the exponential and linear growth phases, and calculate the parameters which characterize both phases is described. The procedure, a list of required materials, experimental conditions, analytical technique, and a discussion of the interpretations of individual results are…
Validity of repeated initial rise thermoluminescence kinetic parameter determinations
Kierstead, J.A.; Levy, P.W.
1990-01-01
The validity of thermoluminescence (TL) analysis by repeated initial rise measurements has been studied by computer simulation. Thermoluminescence described by 1st Order, 2nd Order, General One Trap and Interactive TL Kinetics was investigated. In the simulation each of the repeated temperature increase and decrease cycles contains a linear temperature increase followed by a decrease appropriate for radiative cooling, i.e. the latter is approximated by a decreasing exponential. The activation energies computed from the simulated emission are readily compared with those used to compute the TL emission. In all cases studied, the repeated initial rise technique provides reliable results only for single peak glow curves or for glow curves containing peaks that do not overlap and, if sufficiently separated, the lowest temperature peak in multipeak curves. Also the temperatures, or temperature cycles corresponding to correct activation energies occur on the low temperature side of the normal glow curve, often well below the peak temperature. A variety of misleading and/or incorrect results an be obtained when the repeated initial rise technique is applied to TL systems that produce overlapping peaks in the usual glow curve. 6 refs., 10 figs.
Hossain, Md Akram; Alam, Mahbub; Yonge, David R
2005-09-01
Hexavalent chromium (Cr (VI)) contamination of soil and groundwater is considered a major environmental concern. Bioreduction of Cr (VI) to trivalent chromium (Cr (III)) can be considered an effective technology in remediating Cr (VI) contaminated sites. Among the Cr (VI) reducing bacteria, Shewanella oneidensis MR-1 (MR-1) is relatively effective. Reduction of Cr (VI) by MR-1 is defined by the dual-enzyme kinetic model. The feasibility of bioreduction of Cr (VI) is usually evaluated by performing batch experiments which may not accurately represent the subsurface environment. The objective of this paper is to present a rational approach to determine the dual-enzyme reaction kinetics of Cr (VI) reduction by MR-1 from continuous flow soil column experiments which more accurately simulate the subsurface environment. Kinetic parameters obtained from soil column data were found to be much smaller than that obtained from batch data. The stable enzyme induced reaction rate was found to be 127th and the average deactivating enzyme induced reaction rate was 117th of the corresponding values obtained from batch reactor data as reported in literature.
NASA Astrophysics Data System (ADS)
Ghezzi, Luan; Dutra-Ferreira, Letícia; Lorenzo-Oliveira, Diego; Porto de Mello, Gustavo F.; Santiago, Basílio X.; De Lee, Nathan; Lee, Brian L.; da Costa, Luiz N.; Maia, Marcio A. G.; Ogando, Ricardo L. C.; Wisniewski, John P.; González Hernández, Jonay I.; Stassun, Keivan G.; Fleming, Scott W.; Schneider, Donald P.; Mahadevan, Suvrath; Cargile, Phillip; Ge, Jian; Pepper, Joshua; Wang, Ji; Paegert, Martin
2014-12-01
Studies of Galactic chemical, and dynamical evolution in the solar neighborhood depend on the availability of precise atmospheric parameters (effective temperature T eff, metallicity [Fe/H], and surface gravity log g) for solar-type stars. Many large-scale spectroscopic surveys operate at low to moderate spectral resolution for efficiency in observing large samples, which makes the stellar characterization difficult due to the high degree of blending of spectral features. Therefore, most surveys employ spectral synthesis, which is a powerful technique, but relies heavily on the completeness and accuracy of atomic line databases and can yield possibly correlated atmospheric parameters. In this work, we use an alternative method based on spectral indices to determine the atmospheric parameters of a sample of nearby FGK dwarfs and subgiants observed by the MARVELS survey at moderate resolving power (R ~ 12,000). To avoid a time-consuming manual analysis, we have developed three codes to automatically normalize the observed spectra, measure the equivalent widths of the indices, and, through a comparison of those with values calculated with predetermined calibrations, estimate the atmospheric parameters of the stars. The calibrations were derived using a sample of 309 stars with precise stellar parameters obtained from the analysis of high-resolution FEROS spectra, permitting the low-resolution equivalent widths to be directly related to the stellar parameters. A validation test of the method was conducted with a sample of 30 MARVELS targets that also have reliable atmospheric parameters derived from the high-resolution spectra and spectroscopic analysis based on the excitation and ionization equilibria method. Our approach was able to recover the parameters within 80 K for T eff, 0.05 dex for [Fe/H], and 0.15 dex for log g, values that are lower than or equal to the typical external uncertainties found between different high-resolution analyses. An additional test was
Ghezzi, Luan; Da Costa, Luiz N.; Maia, Marcio A. G.; Ogando, Ricardo L. C.; Dutra-Ferreira, Letícia; Lorenzo-Oliveira, Diego; Porto de Mello, Gustavo F.; Santiago, Basílio X.; De Lee, Nathan; Lee, Brian L.; Ge, Jian; Wisniewski, John P.; González Hernández, Jonay I.; Stassun, Keivan G.; Cargile, Phillip; Pepper, Joshua; Fleming, Scott W.; Schneider, Donald P.; Mahadevan, Suvrath; Wang, Ji; and others
2014-12-01
Studies of Galactic chemical, and dynamical evolution in the solar neighborhood depend on the availability of precise atmospheric parameters (effective temperature T {sub eff}, metallicity [Fe/H], and surface gravity log g) for solar-type stars. Many large-scale spectroscopic surveys operate at low to moderate spectral resolution for efficiency in observing large samples, which makes the stellar characterization difficult due to the high degree of blending of spectral features. Therefore, most surveys employ spectral synthesis, which is a powerful technique, but relies heavily on the completeness and accuracy of atomic line databases and can yield possibly correlated atmospheric parameters. In this work, we use an alternative method based on spectral indices to determine the atmospheric parameters of a sample of nearby FGK dwarfs and subgiants observed by the MARVELS survey at moderate resolving power (R ∼ 12,000). To avoid a time-consuming manual analysis, we have developed three codes to automatically normalize the observed spectra, measure the equivalent widths of the indices, and, through a comparison of those with values calculated with predetermined calibrations, estimate the atmospheric parameters of the stars. The calibrations were derived using a sample of 309 stars with precise stellar parameters obtained from the analysis of high-resolution FEROS spectra, permitting the low-resolution equivalent widths to be directly related to the stellar parameters. A validation test of the method was conducted with a sample of 30 MARVELS targets that also have reliable atmospheric parameters derived from the high-resolution spectra and spectroscopic analysis based on the excitation and ionization equilibria method. Our approach was able to recover the parameters within 80 K for T {sub eff}, 0.05 dex for [Fe/H], and 0.15 dex for log g, values that are lower than or equal to the typical external uncertainties found between different high-resolution analyses. An
Damon, Bruce M; Heemskerk, Anneriet M; Ding, Zhaohua
2012-06-01
Fiber curvature is a functionally significant muscle structural property, but its estimation from diffusion-tensor magnetic resonance imaging fiber tracking data may be confounded by noise. The purpose of this study was to investigate the use of polynomial fitting of fiber tracts for improving the accuracy and precision of fiber curvature (κ) measurements. Simulated image data sets were created in order to provide data with known values for κ and pennation angle (θ). Simulations were designed to test the effects of increasing inherent fiber curvature (3.8, 7.9, 11.8 and 15.3 m(-1)), signal-to-noise ratio (50, 75, 100 and 150) and voxel geometry (13.8- and 27.0-mm(3) voxel volume with isotropic resolution; 13.5-mm(3) volume with an aspect ratio of 4.0) on κ and θ measurements. In the originally reconstructed tracts, θ was estimated accurately under most curvature and all imaging conditions studied; however, the estimates of κ were imprecise and inaccurate. Fitting the tracts to second-order polynomial functions provided accurate and precise estimates of κ for all conditions except very high curvature (κ=15.3 m(-1)), while preserving the accuracy of the θ estimates. Similarly, polynomial fitting of in vivo fiber tracking data reduced the κ values of fitted tracts from those of unfitted tracts and did not change the θ values. Polynomial fitting of fiber tracts allows accurate estimation of physiologically reasonable values of κ, while preserving the accuracy of θ estimation.
FAST TRACK COMMUNICATION Accurate estimate of α variation and isotope shift parameters in Na and Mg+
NASA Astrophysics Data System (ADS)
Sahoo, B. K.
2010-12-01
We present accurate calculations of fine-structure constant variation coefficients and isotope shifts in Na and Mg+ using the relativistic coupled-cluster method. In our approach, we are able to discover the roles of various correlation effects explicitly to all orders in these calculations. Most of the results, especially for the excited states, are reported for the first time. It is possible to ascertain suitable anchor and probe lines for the studies of possible variation in the fine-structure constant by using the above results in the considered systems.
A robust methodology for kinetic model parameter estimation for biocatalytic reactions.
Al-Haque, Naweed; Santacoloma, Paloma A; Neto, Watson; Tufvesson, Pär; Gani, Rafiqul; Woodley, John M
2012-01-01
Effective estimation of parameters in biocatalytic reaction kinetic expressions are very important when building process models to enable evaluation of process technology options and alternative biocatalysts. The kinetic models used to describe enzyme-catalyzed reactions generally include several parameters, which are strongly correlated with each other. State-of-the-art methodologies such as nonlinear regression (using progress curves) or graphical analysis (using initial rate data, for example, the Lineweaver-Burke plot, Hanes plot or Dixon plot) often incorporate errors in the estimates and rarely lead to globally optimized parameter values. In this article, a robust methodology to estimate parameters for biocatalytic reaction kinetic expressions is proposed. The methodology determines the parameters in a systematic manner by exploiting the best features of several of the current approaches. The parameter estimation problem is decomposed into five hierarchical steps, where the solution of each of the steps becomes the input for the subsequent step to achieve the final model with the corresponding regressed parameters. The model is further used for validating its performance and determining the correlation of the parameters. The final model with the fitted parameters is able to describe both initial rate and dynamic experiments. Application of the methodology is illustrated with a case study using the ω-transaminase catalyzed synthesis of 1-phenylethylamine from acetophenone and 2-propylamine.
Solid State Kinetic Parameters and Chemical Mechanism of the Dehydration of CoCl2.6H2O.
ERIC Educational Resources Information Center
Ribas, Joan; And Others
1988-01-01
Presents an experimental example illustrating the most common methods for the determination of kinetic parameters. Discusses the different theories and equations to be applied and the mechanism derived from the kinetic results. (CW)
Johnson, Kenneth A; Simpson, Zachary B; Blom, Thomas
2009-04-01
Fitting several sets of kinetic data directly to a model based on numerical integration provides the best method to extract kinetic parameters without relying on the simplifying assumptions required to achieve analytical solutions of rate equations. However, modern computer programs make it too easy to enter an overly complex model, and standard error analysis grossly underestimates errors when a system is underconstrained and fails to reveal the full degree to which multiple parameters are linked through the complex relationships common in kinetic data. Here we describe the application of confidence contour analysis obtained by measuring the dependence of the sum square error on each pair of parameters while allowing all remaining parameters to be adjusted in seeking the best fit. The confidence contours reveal complex relationships between parameters and clearly outline the space over which parameters can vary (the "FitSpace"). The utility of the method is illustrated by examples of well-constrained fits to published data on tryptophan synthase and the kinetics of oligonucleotide binding to a ribozyme. In contrast, analysis of alanine racemase clearly refutes claims that global analysis of progress curves can be used to extract the free energy profiles of enzyme-catalyzed reactions.
Accurate nuclear masses from a three parameter Kohn-Sham DFT approach (BCPM)
Baldo, M.; Robledo, L. M.; Schuck, P.; Vinas, X.
2012-10-20
Given the promising features of the recently proposed Barcelona-Catania-Paris (BCP) functional [1], it is the purpose of this work to still improve on it. It is, for instance, shown that the number of open parameters can be reduced from 4-5 to 2-3, i.e. by practically a factor of two without deteriorating the results.
Accurate parameters of the oldest known rocky-exoplanet hosting system: Kepler-10 revisited
Fogtmann-Schulz, Alexandra; Hinrup, Brian; Van Eylen, Vincent; Christensen-Dalsgaard, Jørgen; Kjeldsen, Hans; Silva Aguirre, Víctor; Tingley, Brandon
2014-02-01
Since the discovery of Kepler-10, the system has received considerable interest because it contains a small, rocky planet which orbits the star in less than a day. The system's parameters, announced by the Kepler team and subsequently used in further research, were based on only five months of data. We have reanalyzed this system using the full span of 29 months of Kepler photometric data, and obtained improved information about its star and the planets. A detailed asteroseismic analysis of the extended time series provides a significant improvement on the stellar parameters: not only can we state that Kepler-10 is the oldest known rocky-planet-harboring system at 10.41 ± 1.36 Gyr, but these parameters combined with improved planetary parameters from new transit fits gives us the radius of Kepler-10b to within just 125 km. A new analysis of the full planetary phase curve leads to new estimates on the planetary temperature and albedo, which remain degenerate in the Kepler band. Our modeling suggests that the flux level during the occultation is slightly lower than at the transit wings, which would imply that the nightside of this planet has a non-negligible temperature.
Calibration of Parameters in Beta-Delta HMX Phase Transformation Kinetics Using Computer Simulations
Wemhoff, A P; Burnham, A K
2005-11-17
The kinetics of the beta-delta solid-solid phase transformation of HMX (nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) were modeled in ALE2D using four similar equilibrium-inhibited nucleation-growth models: a reversible set of Arrhenius kinetics following a LANL model, and three sets of kinetics derived based on an autocatalytic model using the bidirectional reaction formalism. The parameters for the bidirectional kinetics models were calibrated using simulations of two experimental setup scenarios where experimental data is available: 165 C XRD and SITI. In this calibration, the transition enthalpy and activation energy values were kept constant, while the frequency factors were iterated to achieve results similar to those provided by the experiments. This process yielded six unique sets of kinetic parameters that describe the phase transformation: a pair of sets for each of the three bidirectional kinetics models. The models calibrated using 165 C XRD data showed good agreement with LX-04 STEX experimental results, while the SITI-based models were in good agreement with the LANL model and PBX-9501 STEX experimental data. These bidirectional models were also shown to require less computational effort than the LANL model.
Burnham, A K
2006-05-17
Chemical kinetic modeling has been used for many years in process optimization, estimating real-time material performance, and lifetime prediction. Chemists have tended towards developing detailed mechanistic models, while engineers have tended towards global or lumped models. Many, if not most, applications use global models by necessity, since it is impractical or impossible to develop a rigorous mechanistic model. Model fitting acquired a bad name in the thermal analysis community after that community realized a decade after other disciplines that deriving kinetic parameters for an assumed model from a single heating rate produced unreliable and sometimes nonsensical results. In its place, advanced isoconversional methods (1), which have their roots in the Friedman (2) and Ozawa-Flynn-Wall (3) methods of the 1960s, have become increasingly popular. In fact, as pointed out by the ICTAC kinetics project in 2000 (4), valid kinetic parameters can be derived by both isoconversional and model fitting methods as long as a diverse set of thermal histories are used to derive the kinetic parameters. The current paper extends the understanding from that project to give a better appreciation of the strengths and weaknesses of isoconversional and model-fitting approaches. Examples are given from a variety of sources, including the former and current ICTAC round-robin exercises, data sets for materials of interest, and simulated data sets.
Andrianaki, Maria; Azariadis, Kalliopi; Kampouri, Errika; Theodoropoulou, Katerina; Lavrentaki, Katerina; Kastrinakis, Stelios; Kampa, Marilena; Agouridakis, Panagiotis; Pirintsos, Stergios; Castanas, Elias
2015-01-01
Severe allergic reactions of unknown etiology,necessitating a hospital visit, have an important impact in the life of affected individuals and impose a major economic burden to societies. The prediction of clinically severe allergic reactions would be of great importance, but current attempts have been limited by the lack of a well-founded applicable methodology and the wide spatiotemporal distribution of allergic reactions. The valid prediction of severe allergies (and especially those needing hospital treatment) in a region, could alert health authorities and implicated individuals to take appropriate preemptive measures. In the present report we have collecterd visits for serious allergic reactions of unknown etiology from two major hospitals in the island of Crete, for two distinct time periods (validation and test sets). We have used the Normalized Difference Vegetation Index (NDVI), a satellite-based, freely available measurement, which is an indicator of live green vegetation at a given geographic area, and a set of meteorological data to develop a model capable of describing and predicting severe allergic reaction frequency. Our analysis has retained NDVI and temperature as accurate identifiers and predictors of increased hospital severe allergic reactions visits. Our approach may contribute towards the development of satellite-based modules, for the prediction of severe allergic reactions in specific, well-defined geographical areas. It could also probably be used for the prediction of other environment related diseases and conditions. PMID:25794106
An Accurate and Generic Testing Approach to Vehicle Stability Parameters Based on GPS and INS
Miao, Zhibin; Zhang, Hongtian; Zhang, Jinzhu
2015-01-01
With the development of the vehicle industry, controlling stability has become more and more important. Techniques of evaluating vehicle stability are in high demand. As a common method, usually GPS sensors and INS sensors are applied to measure vehicle stability parameters by fusing data from the two system sensors. Although prior model parameters should be recognized in a Kalman filter, it is usually used to fuse data from multi-sensors. In this paper, a robust, intelligent and precise method to the measurement of vehicle stability is proposed. First, a fuzzy interpolation method is proposed, along with a four-wheel vehicle dynamic model. Second, a two-stage Kalman filter, which fuses the data from GPS and INS, is established. Next, this approach is applied to a case study vehicle to measure yaw rate and sideslip angle. The results show the advantages of the approach. Finally, a simulation and real experiment is made to verify the advantages of this approach. The experimental results showed the merits of this method for measuring vehicle stability, and the approach can meet the design requirements of a vehicle stability controller. PMID:26690154
Cartwright, Michael S; Dupuis, Janae E; Bargoil, Jessica M; Foster, Dana C
2015-09-01
Mild traumatic brain injury, often referred to as concussion, is a common, potentially debilitating, and costly condition. One of the main challenges in diagnosing and managing concussion is that there is not currently an objective test to determine the presence of a concussion and to guide return-to-play decisions for athletes. Traditional neuroimaging tests, such as brain magnetic resonance imaging, are normal in concussion, and therefore diagnosis and management are guided by reported symptoms. Some athletes will under-report symptoms to accelerate their return-to-play and others will over-report symptoms out of fear of further injury or misinterpretation of underlying conditions, such as migraine headache. Therefore, an objective measure is needed to assist in several facets of concussion management. Limited data in animal and human testing indicates that intracranial pressure increases slightly and cerebrovascular reactivity (the ability of the cerebral arteries to auto-regulate in response to changes in carbon dioxide) decreases slightly following mild traumatic brain injury. We hypothesize that a combination of ultrasonographic measurements (optic nerve sheath diameter and transcranial Doppler assessment of cerebrovascular reactivity) into a single index will allow for an accurate and non-invasive measurement of intracranial pressure and cerebrovascular reactivity, and this index will be clinically relevant and useful for guiding concussion diagnosis and management. Ultrasound is an ideal modality for the evaluation of concussion because it is portable (allowing for evaluation in many settings, such as on the playing field or in a combat zone), radiation-free (making repeat scans safe), and relatively inexpensive (resulting in nearly universal availability). This paper reviews the literature supporting our hypothesis that an ultrasonographic index can assist in the diagnosis and management of concussion, and it also presents limited data regarding the
Cartwright, Michael S; Dupuis, Janae E; Bargoil, Jessica M; Foster, Dana C
2015-09-01
Mild traumatic brain injury, often referred to as concussion, is a common, potentially debilitating, and costly condition. One of the main challenges in diagnosing and managing concussion is that there is not currently an objective test to determine the presence of a concussion and to guide return-to-play decisions for athletes. Traditional neuroimaging tests, such as brain magnetic resonance imaging, are normal in concussion, and therefore diagnosis and management are guided by reported symptoms. Some athletes will under-report symptoms to accelerate their return-to-play and others will over-report symptoms out of fear of further injury or misinterpretation of underlying conditions, such as migraine headache. Therefore, an objective measure is needed to assist in several facets of concussion management. Limited data in animal and human testing indicates that intracranial pressure increases slightly and cerebrovascular reactivity (the ability of the cerebral arteries to auto-regulate in response to changes in carbon dioxide) decreases slightly following mild traumatic brain injury. We hypothesize that a combination of ultrasonographic measurements (optic nerve sheath diameter and transcranial Doppler assessment of cerebrovascular reactivity) into a single index will allow for an accurate and non-invasive measurement of intracranial pressure and cerebrovascular reactivity, and this index will be clinically relevant and useful for guiding concussion diagnosis and management. Ultrasound is an ideal modality for the evaluation of concussion because it is portable (allowing for evaluation in many settings, such as on the playing field or in a combat zone), radiation-free (making repeat scans safe), and relatively inexpensive (resulting in nearly universal availability). This paper reviews the literature supporting our hypothesis that an ultrasonographic index can assist in the diagnosis and management of concussion, and it also presents limited data regarding the
Cartwright, Michael S.; Dupuis, Janae E.; Bargoil, Jessica M.; Foster, Dana C.
2015-01-01
Mild traumatic brain injury, often referred to as concussion, is a common, potentially debilitating, and costly condition. One of the main challenges in diagnosing and managing concussion is that there is not currently an objective test to determine the presence of a concussion and to guide return-to-play decisions for athletes. Traditional neuroimaging tests, such as brain magnetic resonance imaging, are normal in concussion, and therefore diagnosis and management are guided by reported symptoms. Some athletes will under-report symptoms to accelerate their return-to-play and others will over-report symptoms out of fear of further injury or misinterpretation of underlying conditions, such as migraine headache. Therefore, an objective measure is needed to assist in several facets of concussion management. Limited data in animal and human testing indicates that intracranial pressure increases slightly and cerebrovascular reactivity (the ability of the cerebral arteries to auto-regulate in response to changes in carbon dioxide) decreases slightly following mild traumatic brain injury. We hypothesize that a combination of ultrasonographic measurements (optic nerve sheath diameter and transcranial Doppler assessment of cerebrovascular reactivity) into a single index will allow for an accurate and non-invasive measurement of intracranial pressure and cerebrovascular reactivity, and this index will be clinically relevant and useful for guiding concussion diagnosis and management. Ultrasound is an ideal modality for the evaluation of concussion because it is portable (allowing for evaluation in many settings, such as on the playing field or in a combat zone), radiation-free (making repeat scans safe), and relatively inexpensive (resulting in nearly universal availability). This paper reviews the literature supporting our hypothesis that an ultrasonographic index can assist in the diagnosis and management of concussion, and it also presents limited data regarding the
Evaluation of kinetic parameters for water soluble crystals by thermo gravimetric analysis
NASA Astrophysics Data System (ADS)
Rama, S.; Surendra Dilip, C.; Perumal, Rajesh Narayana
2015-01-01
This work elevates the relevance of kinetic parameters of nucleation and thermal decomposition for water soluble crystals. The positive soluble Potassium Dihydrogen Phosphate (KDP) and negative soluble Lithium Sulfate Monohydrate (LSMH) materials were chosen for the kinetic evaluation. The results obtained from the classical nucleation theory are verified with the kinetic parameters which are evaluated from thermo gravimetric analysis. Nucleation parameters of a crystallization process such as interfacial energy (σ), volume free energy (ΔGv), critical energy barrier for nucleation (ΔG*), radius of the critical nucleus (r*) and nucleation rate (J) of the positive (KDP) and negative solubility (LSMH) crystals are determined from the classical nucleation theory of solubility-enthalpy relation. The kinetic parameters viz. the order of reaction, enthalpy, Gibbs free energy of activation, frequency factor, and entropy of activation are obtained from the TG based models viz. Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova. The effect of varying temperature with relative variation on Gibbs free energy for both positive and negative solubility crystals is also discussed. The developed model holds good for both positive and negative solubility crystals.
ERIC Educational Resources Information Center
Hardee, John R.; Delgado, Bryan; Jones, Wray
2011-01-01
The kinetic parameters for the conversion of alpha-D-glucose to beta-D-glucose were measured using a blood glucometer. The reaction order, rate constant, and Arrhenius activation energy are reported for the noncatalyzed reaction and turnover number and Michaelis constant are reported for the reaction catalyzed by porcine kidney mutarotase. The…
Hansen, D Flemming; Westler, William M; Kunze, Micha B A; Markley, John L; Weinhold, Frank; Led, Jens J
2012-03-14
A natural bond orbital (NBO) analysis of unpaired electron spin density in metalloproteins is presented, which allows a fast and robust calculation of paramagnetic NMR parameters. Approximately 90% of the unpaired electron spin density occupies metal-ligand NBOs, allowing the majority of the density to be modeled by only a few NBOs that reflect the chemical bonding environment. We show that the paramagnetic relaxation rate of protons can be calculated accurately using only the metal-ligand NBOs and that these rates are in good agreement with corresponding rates measured experimentally. This holds, in particular, for protons of ligand residues where the point-dipole approximation breaks down. To describe the paramagnetic relaxation of heavy nuclei, also the electron spin density in the local orbitals must be taken into account. Geometric distance restraints for (15)N can be derived from the paramagnetic relaxation enhancement and the Fermi contact shift when local NBOs are included in the analysis. Thus, the NBO approach allows us to include experimental paramagnetic NMR parameters of (15)N nuclei as restraints in a structure optimization protocol. We performed a molecular dynamics simulation and structure determination of oxidized rubredoxin using the experimentally obtained paramagnetic NMR parameters of (15)N. The corresponding structures obtained are in good agreement with the crystal structure of rubredoxin. Thus, the NBO approach allows an accurate description of the geometric structure and the dynamics of metalloproteins, when NMR parameters are available of nuclei in the immediate vicinity of the metal-site.
2012-01-01
A natural bond orbital (NBO) analysis of unpaired electron spin density in metalloproteins is presented, which allows a fast and robust calculation of paramagnetic NMR parameters. Approximately 90% of the unpaired electron spin density occupies metal–ligand NBOs, allowing the majority of the density to be modeled by only a few NBOs that reflect the chemical bonding environment. We show that the paramagnetic relaxation rate of protons can be calculated accurately using only the metal–ligand NBOs and that these rates are in good agreement with corresponding rates measured experimentally. This holds, in particular, for protons of ligand residues where the point-dipole approximation breaks down. To describe the paramagnetic relaxation of heavy nuclei, also the electron spin density in the local orbitals must be taken into account. Geometric distance restraints for 15N can be derived from the paramagnetic relaxation enhancement and the Fermi contact shift when local NBOs are included in the analysis. Thus, the NBO approach allows us to include experimental paramagnetic NMR parameters of 15N nuclei as restraints in a structure optimization protocol. We performed a molecular dynamics simulation and structure determination of oxidized rubredoxin using the experimentally obtained paramagnetic NMR parameters of 15N. The corresponding structures obtained are in good agreement with the crystal structure of rubredoxin. Thus, the NBO approach allows an accurate description of the geometric structure and the dynamics of metalloproteins, when NMR parameters are available of nuclei in the immediate vicinity of the metal-site. PMID:22329704
Sela, Itamar; Ashkenazy, Haim; Katoh, Kazutaka; Pupko, Tal
2015-01-01
Inference of multiple sequence alignments (MSAs) is a critical part of phylogenetic and comparative genomics studies. However, from the same set of sequences different MSAs are often inferred, depending on the methodologies used and the assumed parameters. Much effort has recently been devoted to improving the ability to identify unreliable alignment regions. Detecting such unreliable regions was previously shown to be important for downstream analyses relying on MSAs, such as the detection of positive selection. Here we developed GUIDANCE2, a new integrative methodology that accounts for: (i) uncertainty in the process of indel formation, (ii) uncertainty in the assumed guide tree and (iii) co-optimal solutions in the pairwise alignments, used as building blocks in progressive alignment algorithms. We compared GUIDANCE2 with seven methodologies to detect unreliable MSA regions using extensive simulations and empirical benchmarks. We show that GUIDANCE2 outperforms all previously developed methodologies. Furthermore, GUIDANCE2 also provides a set of alternative MSAs which can be useful for downstream analyses. The novel algorithm is implemented as a web-server, available at: http://guidance.tau.ac.il. PMID:25883146
NASA Astrophysics Data System (ADS)
Lamouroux, Julien; Gamache, Robert R.
2013-06-01
A model for the prediction of the vibrational dependence of CO_2 half-widths and line shifts for several broadeners, based on a modification of the model proposed by Gamache and Hartmann, is presented. This model allows the half-widths and line shifts for a ro-vibrational transition to be expressed in terms of the number of vibrational quanta exchanged in the transition raised to a power p and a reference ro-vibrational transition. Complex Robert-Bonamy calculations were made for 24 bands for lower rotational quantum numbers J'' from 0 to 160 for N_2-, O_2-, air-, and self-collisions with CO_2. In the model a Quantum Coordinate is defined by (c_1 Δν_1 + c_2 Δν_2 + c_3 Δν_3)^p where a linear least-squares fit to the data by the model expression is made. The model allows the determination of the slope and intercept as a function of rotational transition, broadening gas, and temperature. From these fit data, the half-width, line shift, and the temperature dependence of the half-width can be estimated for any ro-vibrational transition, allowing spectroscopic CO_2 databases to have complete information for the line shape parameters. R. R. Gamache, J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transfer. {{83}} (2004), 119. R. R. Gamache, J. Lamouroux, J. Quant. Spectrosc. Radiat. Transfer. {{117}} (2013), 93.
Sela, Itamar; Ashkenazy, Haim; Katoh, Kazutaka; Pupko, Tal
2015-07-01
Inference of multiple sequence alignments (MSAs) is a critical part of phylogenetic and comparative genomics studies. However, from the same set of sequences different MSAs are often inferred, depending on the methodologies used and the assumed parameters. Much effort has recently been devoted to improving the ability to identify unreliable alignment regions. Detecting such unreliable regions was previously shown to be important for downstream analyses relying on MSAs, such as the detection of positive selection. Here we developed GUIDANCE2, a new integrative methodology that accounts for: (i) uncertainty in the process of indel formation, (ii) uncertainty in the assumed guide tree and (iii) co-optimal solutions in the pairwise alignments, used as building blocks in progressive alignment algorithms. We compared GUIDANCE2 with seven methodologies to detect unreliable MSA regions using extensive simulations and empirical benchmarks. We show that GUIDANCE2 outperforms all previously developed methodologies. Furthermore, GUIDANCE2 also provides a set of alternative MSAs which can be useful for downstream analyses. The novel algorithm is implemented as a web-server, available at: http://guidance.tau.ac.il.
NASA Astrophysics Data System (ADS)
Martínez, M. J.; Marco, F. J.; López, J. A.
2009-02-01
The Hipparcos catalog provides a reference frame at optical wavelengths for the new International Celestial Reference System (ICRS). This new reference system was adopted following the resolution agreed at the 23rd IAU General Assembly held in Kyoto in 1997. Differences in the Hipparcos system of proper motions and the previous materialization of the reference frame, the FK5, are expected to be caused only by the combined effects of the motion of the equinox of the FK5 and the precession of the equator and the ecliptic. Several authors have pointed out an inconsistency between the differences in proper motion of the Hipparcos-FK5 and the correction of the precessional values derived from VLBI and lunar laser ranging (LLR) observations. Most of them have claimed that these discrepancies are due to slightly biased proper motions in the FK5 catalog. The different mathematical models that have been employed to explain these errors have not fully accounted for the discrepancies in the correction of the precessional parameters. Our goal here is to offer an explanation for this fact. We propose the use of independent parametric and nonparametric models. The introduction of a nonparametric model, combined with the inner product in the square integrable functions over the unitary sphere, would give us values which do not depend on the possible interdependencies existing in the data set. The evidence shows that zonal studies are needed. This would lead us to introduce a local nonparametric model. All these models will provide independent corrections to the precessional values, which could then be compared in order to study the reliability in each case. Finally, we obtain values for the precession corrections that are very consistent with those that are currently adopted.
NASA Astrophysics Data System (ADS)
Gritsyk, P. A.; Somov, B. V.
2016-08-01
The M7.7 solar flare of July 19, 2012, at 05:58 UT was observed with high spatial, temporal, and spectral resolutions in the hard X-ray and optical ranges. The flare occurred at the solar limb, which allowed us to see the relative positions of the coronal and chromospheric X-ray sources and to determine their spectra. To explain the observations of the coronal source and the chromospheric one unocculted by the solar limb, we apply an accurate analytical model for the kinetic behavior of accelerated electrons in a flare. We interpret the chromospheric hard X-ray source in the thick-target approximation with a reverse current and the coronal one in the thin-target approximation. Our estimates of the slopes of the hard X-ray spectra for both sources are consistent with the observations. However, the calculated intensity of the coronal source is lower than the observed one by several times. Allowance for the acceleration of fast electrons in a collapsing magnetic trap has enabled us to remove this contradiction. As a result of our modeling, we have estimated the flux density of the energy transferred by electrons with energies above 15 keV to be ˜5 × 1010 erg cm-2 s-1, which exceeds the values typical of the thick-target model without a reverse current by a factor of ˜5. To independently test the model, we have calculated the microwave spectrum in the range 1-50 GHz that corresponds to the available radio observations.
Comparison of gasification kinetics parameters of different types of nuclear graphite
El-Genk, M. S.; Tournier, J. M. P.
2012-07-01
A chemical-reaction kinetics model of nuclear graphite gasification has recently been developed and successfully validated with gasification rate measurements for nuclear graphite grades of IG-110, IG-430, NBG-18 and NBG-25. The model employs 4 elementary chemical reactions with applicable parameters, including the values and Gaussian-like distributions of the specific activation energies, the pre-exponential coefficients for adsorption of oxygen and desorption of CO and CO{sub 2} gases, and the surface area of free active sites. These parameters are determined from the reported measurements of the total gasification and transient weight loss using a multi-parameter optimization algorithm. The determined chemical kinetics parameters for IG-100 and NB-25 are nearly the same, but slightly different from those for NBG-18 and IG-430. The initial specific area of free active sites is inversely proportional to the square root of the mass or volume of the graphite specimens used in experiments. The recommended chemical kinetics parameters in this paper for these grades of nuclear graphite should be applicable to future safety analysis of high-temperature gas cooled reactors in the unlikely event of a massive air ingress accident. (authors)
Kinetic parameters for the thermal inactivation of quality-related enzymes in carrots and potatoes.
Anthon, Gordon E; Barrett, Diane M
2002-07-01
Kinetic parameters for the thermal inactivation of several enzymes in carrot and potato homogenates have been determined. In carrots the most heat-resistant activity was polygalacturonase, followed by peroxidase and pectinmethylesterase. In potatoes peroxidase was the most resistant, followed by pectin methylesterase, polyphenol oxidase, and lipoxygenase. There were several notable similarities between the inactivation kinetics in the two vegetables. In both cases peroxidase activity gave simple first-order inactivation kinetics but yielded a curved Arrhenius plot for the temperature dependence. Pectin methylesterase in both commodities consisted of a labile and a resistant form. The relative amounts of the two forms and the temperature dependences for their inactivation were also similar. PMID:12083894
Frias, Moises
2007-07-01
This paper reports on the influence of calcining temperature (800 and 1000 deg. C) on the pozzolanic activation of sugar cane straw (SCS). The reaction kinetics of SCS ash-lime mixtures were inferred from physicochemical characteristics (X-ray diffraction patterns and thermogravimetry analysis. The fitting of a kinetic-diffusive model to the experimental data (fixed lime versus time) allowed the computing of the kinetic parameters (reaction rate constant) of the pozzolanic reaction. Results obtained confirm that the sugar cane straw ash (SCSA) calcined at 800 and 1000 deg. C have properties indicative of very high pozzolanic activity. No influence of calcining temperature on the pozzolanic activity was observed. Also, no crystalline compounds during the pozzolanic reaction were identified up to 90 days of reaction. Environmental durability and strength of the consequential mortars remain to be assessed.
NASA Astrophysics Data System (ADS)
Veličković, D. V.; Dimitrijević, A. S.; Bihelović, F. J.; Jankov, R. M.; Milosavić, N.
2011-12-01
One of the key elements for understanding enzyme reactions is determination of its kinetic parameters. Since transglucosylation is kinetically controlled reaction, besides the reaction of synthesis, very important is the reaction of enzymatic hydrolysis of created product. Therefore, in this study, kinetic parameters for synthesis and secondary hydrolysis of pharmacologically active α isosalicin by baker's yeast maltase were calculated, and it was shown that specifity of maltase for hydrolysis is approximately 150 times higher then for synthesis.
Adsorption of methylene blue onto hazelnut shell: Kinetics, mechanism and activation parameters.
Doğan, Mehmet; Abak, Harun; Alkan, Mahir
2009-05-15
The adsorption kinetics of methylene blue (MB) on the hazelnut shell with respect to the initial dye concentration, pH, ionic strength, particle size and temperature were investigated. The rate and the transport/kinetic processes of MB adsorption were described by applying the first-order Lagergren, the pseudo-second-order, mass transfer coefficient and the intraparticle diffusion models. Kinetic studies showed that the kinetic data were well described by the pseudo-second-order kinetic model. Significant increases in initial adsorption rate were observed with the increase in temperature followed by pH and initial MB concentration. The intraparticle diffusion was found to be the rate-limiting step in the adsorption process. Adsorption activation energy was calculated to be 45.6kJmol(-1). The values of activation parameters such as free energy (DeltaG(*)), enthalpy (DeltaH(*)) and entropy (DeltaS(*)) were also determined as 83.4kJmol(-1), 42.9kJmol(-1) and -133.5Jmol(-1)K(-1), respectively.
Tanaka, Atsushi; Hoshino, Eiichi
2002-01-01
The irreversible thermal inactivation and the thermodynamics of calcium ion binding of Bacillus amyloliquefaciens alpha-amylase in the absence of substrates were studied. The enzyme inactivation on heating was apparently followed by first-order kinetics. The enzyme was stabilized with an increased concentration of calcium ion and thus the inactivation was highly dependent on the state of calcium binding. The activation parameter for the inactivation suggests an unfolding of the enzyme protein upon heating. Values of both the activation enthalpy and entropy were increased with a higher calcium ion concentration. An inactivation kinetic model is based on the assumption of a two-stage unfolding transition in which the bivalent ion dissociation occurs in the first step followed by the secondary structural unfolding. This simple kinetic model provides both a qualitative and quantitative interpretation of calcium ion binding to the enzyme and its effect on the inactivation properties. The specific approximations of the kinetic model were strictly followed in the analysis to calculate the apparent inactivation rate at each calcium ion concentration in terms of the calcium-binding parameters. The enthalpy and entropy changes for the calcium ion binding were calculated to be -149 kJ/mol and -360 J.mol(-1).K(-1) respectively and these values suggest a strong enthalpic affinity for the bivalent ion binding to the enzyme protein. The thermodynamical interpretation attempts to provide clear relations between the terms of an apparent inactivation rate and the calcium binding. PMID:12049626
Wang, Mingyu; Han, Lijuan; Liu, Shasha; Zhao, Xuebing; Yang, Jinghua; Loh, Soh Kheang; Sun, Xiaomin; Zhang, Chenxi; Fang, Xu
2015-09-01
Renewable energy from lignocellulosic biomass has been deemed an alternative to depleting fossil fuels. In order to improve this technology, we aim to develop robust mathematical models for the enzymatic lignocellulose degradation process. By analyzing 96 groups of previously published and newly obtained lignocellulose saccharification results and fitting them to Weibull distribution, we discovered Weibull statistics can accurately predict lignocellulose saccharification data, regardless of the type of substrates, enzymes and saccharification conditions. A mathematical model for enzymatic lignocellulose degradation was subsequently constructed based on Weibull statistics. Further analysis of the mathematical structure of the model and experimental saccharification data showed the significance of the two parameters in this model. In particular, the λ value, defined the characteristic time, represents the overall performance of the saccharification system. This suggestion was further supported by statistical analysis of experimental saccharification data and analysis of the glucose production levels when λ and n values change. In conclusion, the constructed Weibull statistics-based model can accurately predict lignocellulose hydrolysis behavior and we can use the λ parameter to assess the overall performance of enzymatic lignocellulose degradation. Advantages and potential applications of the model and the λ value in saccharification performance assessment were discussed.
Wang, Mingyu; Han, Lijuan; Liu, Shasha; Zhao, Xuebing; Yang, Jinghua; Loh, Soh Kheang; Sun, Xiaomin; Zhang, Chenxi; Fang, Xu
2015-09-01
Renewable energy from lignocellulosic biomass has been deemed an alternative to depleting fossil fuels. In order to improve this technology, we aim to develop robust mathematical models for the enzymatic lignocellulose degradation process. By analyzing 96 groups of previously published and newly obtained lignocellulose saccharification results and fitting them to Weibull distribution, we discovered Weibull statistics can accurately predict lignocellulose saccharification data, regardless of the type of substrates, enzymes and saccharification conditions. A mathematical model for enzymatic lignocellulose degradation was subsequently constructed based on Weibull statistics. Further analysis of the mathematical structure of the model and experimental saccharification data showed the significance of the two parameters in this model. In particular, the λ value, defined the characteristic time, represents the overall performance of the saccharification system. This suggestion was further supported by statistical analysis of experimental saccharification data and analysis of the glucose production levels when λ and n values change. In conclusion, the constructed Weibull statistics-based model can accurately predict lignocellulose hydrolysis behavior and we can use the λ parameter to assess the overall performance of enzymatic lignocellulose degradation. Advantages and potential applications of the model and the λ value in saccharification performance assessment were discussed. PMID:26121186
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. PMID:27001728
Qiu, Xiao-han; Zhang, Yu-jun; Yin, Gao-fang; Shi, Chao-yi; Yu, Xiao-ya; Zhao, Nan-jing; Liu, Wen-qing
2015-08-01
The fast chlorophyll fluorescence induction curve contains rich information of photosynthesis. It can reflect various information of vegetation, such as, the survival status, the pathological condition and the physiology trends under the stress state. Through the acquisition of algae fluorescence and induced optical signal, the fast phase of chlorophyll fluorescence kinetics curve was fitted. Based on least square fitting method, we introduced adaptive minimum error approaching method for fast multivariate nonlinear regression fitting toward chlorophyll fluorescence kinetics curve. We realized Fo (fixedfluorescent), Fm (maximum fluorescence yield), σPSII (PSII functional absorption cross section) details parameters inversion and the photosynthetic parameters inversion of Chlorella pyrenoidosa. And we also studied physiological variation of Chlorella pyrenoidosa under the stress of Cu(2+).
NASA Astrophysics Data System (ADS)
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.
Effects of sonication on the kinetics of orange juice quality parameters.
Tiwari, B K; Muthukumarappan, K; O'Donnell, C P; Cullen, P J
2008-04-01
The effects of sonication on pH, degrees Brix, titratable acidity (TA), cloud, browning index, and color parameters ( L*, a*, and b*) of freshly squeezed orange juice samples were studied. Ultrasonic intensity (UI) levels of 8.61, 9.24, 10.16, 17.17, and 22.79 W/cm2 and treatment times of 0 (control), 2, 4, 6, 8, and 10 min were investigated. No significant changes in pH, degrees Brix, and TA ( p < 0.05) were found. Cloud value, browning index, and color parameters were significantly affected by ultrasonic intensity and treatment time. Changes in cloud value followed first-order kinetics, whereas browning index, L*, a*, and b* values followed zero-order kinetics. Reaction rate constants were linearly correlated ( R2 > 0.90) to ultrasonic intensity. PMID:18321054
Qiu, Xiao-han; Zhang, Yu-jun; Yin, Gao-fang; Shi, Chao-yi; Yu, Xiao-ya; Zhao, Nan-jing; Liu, Wen-qing
2015-08-01
The fast chlorophyll fluorescence induction curve contains rich information of photosynthesis. It can reflect various information of vegetation, such as, the survival status, the pathological condition and the physiology trends under the stress state. Through the acquisition of algae fluorescence and induced optical signal, the fast phase of chlorophyll fluorescence kinetics curve was fitted. Based on least square fitting method, we introduced adaptive minimum error approaching method for fast multivariate nonlinear regression fitting toward chlorophyll fluorescence kinetics curve. We realized Fo (fixedfluorescent), Fm (maximum fluorescence yield), σPSII (PSII functional absorption cross section) details parameters inversion and the photosynthetic parameters inversion of Chlorella pyrenoidosa. And we also studied physiological variation of Chlorella pyrenoidosa under the stress of Cu(2+). PMID:26672292
Kuznetsov, V A; Feofanova, T V; Busol, V A; Nikolaeva, N V
1995-01-01
We analyzed changes in the number of lymphocytes in the blood of cows with chronic lymphoid leukemia using the Gomperts equation of population dynamics. The parameters of this equation were determined. Coefficients beta and gamma proved to be the most variable. The former reflects the delay and the latter characterizes the maximum rate of growth of the lymphocyte population. According to these parameters, three groups of animals were distinguished with different kinetics of leucosis and different correlations between immuno-hematological indices. PMID:7670356
NASA Astrophysics Data System (ADS)
Subramanian, Swetha; Mast, T. Douglas
2015-09-01
Computational finite element models are commonly used for the simulation of radiofrequency ablation (RFA) treatments. However, the accuracy of these simulations is limited by the lack of precise knowledge of tissue parameters. In this technical note, an inverse solver based on the unscented Kalman filter (UKF) is proposed to optimize values for specific heat, thermal conductivity, and electrical conductivity resulting in accurately simulated temperature elevations. A total of 15 RFA treatments were performed on ex vivo bovine liver tissue. For each RFA treatment, 15 finite-element simulations were performed using a set of deterministically chosen tissue parameters to estimate the mean and variance of the resulting tissue ablation. The UKF was implemented as an inverse solver to recover the specific heat, thermal conductivity, and electrical conductivity corresponding to the measured area of the ablated tissue region, as determined from gross tissue histology. These tissue parameters were then employed in the finite element model to simulate the position- and time-dependent tissue temperature. Results show good agreement between simulated and measured temperature.
Subramanian, Swetha; Mast, T Douglas
2015-10-01
Computational finite element models are commonly used for the simulation of radiofrequency ablation (RFA) treatments. However, the accuracy of these simulations is limited by the lack of precise knowledge of tissue parameters. In this technical note, an inverse solver based on the unscented Kalman filter (UKF) is proposed to optimize values for specific heat, thermal conductivity, and electrical conductivity resulting in accurately simulated temperature elevations. A total of 15 RFA treatments were performed on ex vivo bovine liver tissue. For each RFA treatment, 15 finite-element simulations were performed using a set of deterministically chosen tissue parameters to estimate the mean and variance of the resulting tissue ablation. The UKF was implemented as an inverse solver to recover the specific heat, thermal conductivity, and electrical conductivity corresponding to the measured area of the ablated tissue region, as determined from gross tissue histology. These tissue parameters were then employed in the finite element model to simulate the position- and time-dependent tissue temperature. Results show good agreement between simulated and measured temperature. PMID:26352462
Singh, Jasmeet; Ranganathan, Radha; Hajdu, Joseph
2008-12-25
Activity at micellar interfaces of bacterial phospholipase C from Bacillus cereus on phospholipids solubilized in micelles was investigated with the goal of elucidating the role of the interface microstructure and developing further an existing kinetic model. Enzyme kinetics and physicochemical characterization of model substrate aggregates were combined, thus enabling the interpretation of kinetics in the context of the interface. Substrates were diacylphosphatidylcholine of different acyl chain lengths in the form of mixed micelles with dodecyldimethylammoniopropanesulfonate. An early kinetic model, reformulated to reflect the interfacial nature of the kinetics, was applied to the kinetic data. A better method of data treatment is proposed, use of which makes the presence of microstructure effects quite transparent. Models for enzyme-micelle binding and enzyme-lipid binding are developed, and expressions incorporating the microstructural properties are derived for the enzyme-micelle dissociation constant K(s) and the interface Michaelis-Menten constant, K(M). Use of these expressions in the interface kinetic model brings excellent agreement between the kinetic data and the model. Numerical values for the thermodynamic and kinetic parameters are determined. Enzyme-lipid binding is found to be an activated process with an acyl chain length dependent free energy of activation that decreases with micelle lipid molar fraction with a coefficient of about -15RT and correlates with the tightness of molecular packing in the substrate aggregate. Thus, the physical insight obtained includes a model for the kinetic parameters that shows that these parameters depend on the substrate concentration and acyl chain length of the lipid. Enzyme-micelle binding is indicated to be hydrophobic and solvent mediated with a dissociation constant of 1.2 mM.
Thermoluminescence kinetic parameters of different amount La-doped ZnB₂O₄.
Kucuk, Nil; Gozel, Aziz Halit; Yüksel, Mehmet; Dogan, Tamer; Topaksu, Mustafa
2015-10-01
The kinetic parameters of 1%, 2%, 3% and 4% La-doped ZnB2O4 phosphors (i.e. ZnB2O4:0.01La, ZnB2O4:0.02La, ZnB2O4:0.03La and ZnB2O4:0.04La) synthesized by nitric acid method have been calculated. Thermoluminescence (TL) glow curves of ZnB2O4:La phosphors after beta-irradiation showed a very well defined main peak having the maximum temperature at around 200°C and a shoulder peak at around 315°C with a constant heating rate of 5°C/s. The kinetic parameters of ZnB2O4:La phosphors TL glow peaks (i.e. order of kinetics (b), activation energies (Ea) and frequency factors (s)) have been determined and evaluated by Computerized Glow Curve Deconvolution (CGCD), and Peak Shape (PS) methods using the glow curve data. From the results, it can conclude that the values of Ea obtained with these methods for ZnB2O4:La phosphors are consistent with each other, but the s values differ considerably.
Optimization of kinetic parameters for the degradation of plasmid DNA in rat plasma
NASA Astrophysics Data System (ADS)
Chaudhry, Q. A.
2014-12-01
Biotechnology is a rapidly growing area of research work in the field of pharmaceutical sciences. The study of pharmacokinetics of plasmid DNA (pDNA) is an important area of research work. It has been observed that the process of gene delivery faces many troubles on the transport of pDNA towards their target sites. The topoforms of pDNA has been termed as super coiled (S-C), open circular (O-C) and linear (L), the kinetic model of which will be presented in this paper. The kinetic model gives rise to system of ordinary differential equations (ODEs), the exact solution of which has been found. The kinetic parameters, which are responsible for the degradation of super coiled, and the formation of open circular and linear topoforms have a great significance not only in vitro but for modeling of further processes as well, therefore need to be addressed in great detail. For this purpose, global optimization techniques have been adopted, thus finding the optimal results for the said model. The results of the model, while using the optimal parameters, were compared against the measured data, which gives a nice agreement.
Kinetic parameters related to sources and sinks of vibrationally excited OH in the nightglow
McDade, I.C.; Llewellyn, E.J. )
1987-07-01
Kinetic parameters related to vibrational deactivation and chemical removal of vibrationally excited OH radicals in the mesosphere are deduced from ground-based measurements of the mean vibrational distribution of the OH Meinel bands in the nightglow. The derived parameters, which rely on a laboratory measured rate coefficient for the removal of OH(v = 9) by O{sub 2} and a set of relative Meinel band transition probabilities, have been obtained for two limiting Meinel band excitation models that differ in the extent to which single-quantum vibrational deactivation and sudden death' collisional removal processes determine the OH vibrational distribution. It is shown that the OH Meinel band emission can be adequately explained with the deduced parameters and the H + O{sub 3} {yields} OH + O{sub 2} reaction as the only chemical source of vibrationally excited OH. Evidence is presented which suggests that the reaction HO{sub 2} + O {leftrightarrow} HO + O{sub 2} may perhaps be involved as a sink of vibrationally excited OH rather than as a potential source. The deduced kinetic parameters should be particularly useful in future Meinel band studies as they have been obtained from an analysis for which there is no assumption about the very uncertain OH radiative lifetimes.
Wardak, Mirwais; Schiepers, Christiaan; Dahlbom, Magnus; Cloughesy, Timothy; Chen, Wei; Satyamurthy, Nagichettiar; Czernin, Johannes; Phelps, Michael E.; Huang, Sung-Cheng
2011-01-01
Purpose The primary objective of this study was to investigate if changes in 18F-FLT kinetic parameters, taken at an early stage after start of therapy, could predict overall survival (OS) and progression-free survival (PFS) in patients with recurrent malignant glioma undergoing treatment with bevacizumab and irinotecan. Experimental Design High-grade recurrent brain tumors were investigated in 18 patients (8M, 10F), 26-76 yr. Each had 3 dynamic PET studies: at baseline, and after 2 weeks, and 6 weeks from the start of treatment. 2.0 MBq/kg of 18F-FLT was injected intravenously and dynamic PET images acquired for 1 hr. Factor analysis generated factor images from which blood and tumor uptake curves were derived. A 3-compartment, 2-tissue model was applied to estimate the tumor 18F-FLT kinetic rate constants using a metabolite and partial volume corrected input function. Different combinations of predictor variables were exhaustively searched in a discriminant function to accurately classify patients into their known OS and PFS groups. A leave-one-out cross-validation technique was used to assess the generalizability of the model predictions. Results In this study population, changes in single parameters such as standardized uptake value or influx rate constant did not accurately classify patients into their respective OS groups (<1yr and ≥1yr) [hit-ratios ≤ 78%]. However, changes in a set of 18F-FLT kinetic parameters could perfectly separate these two groups of patients [hit-ratio=100%] and were also able to correctly classify patients into their respective PFS groups (<100 days and ≥100 days) [hit-ratio=88%]. Conclusions Discriminant analysis using changes in 18F-FLT kinetic parameters early during treatment appears to be a powerful method for evaluating the efficacy of therapeutic regimens. PMID:21868765
The main objective of this paper is to use Bayesian methods to estimate the kinetic parameters for the inactivation kinetics of Cryptosporidium parvum oocysts with chlorine dioxide or ozone which are characterized by the delayed Chick-Watson model, i.e., a lag phase or shoulder f...
AB-OSEM reconstruction for improved Patlak kinetic parameter estimation: a simulation study
NASA Astrophysics Data System (ADS)
Verhaeghe, Jeroen; Reader, Andrew J.
2010-11-01
The non-negativity constraint inherently present in OSEM reconstruction successfully reduces the standard deviation in cold regions but at the cost of introducing a positive bias, especially at low iteration numbers. For low-count data, as often encountered in short-duration frames in dynamic imaging protocols, it has been shown that it can be advantageous (in terms of bias in the reconstructed image) to remove the non-negativity constraint. In this work two competing algorithms that do not impose non-negativity in the reconstructed image are investigated: NEG-ML and AB-OSEM. It was found that the AB-OSEM reconstruction outperformed the NEG-ML reconstruction. The AB-OSEM algorithm was then further developed to allow a forward model that includes randoms and scatter background terms. In addition to static reconstruction the current analysis was extended to consider the important case of kinetic parameter estimation from dynamic PET data. Simulation studies (comparing OSEM, FBP and AB-OSEM) showed that the positive bias obtained with OSEM reconstruction can be avoided in both static and parametric imaging through use of a negative lower bound in AB-OSEM reconstruction (i.e. by lifting the implicit non-negativity constraint of OSEM). When quantification tasks are considered, the overall error in the estimates (composed of both bias and standard deviation) is often of primary concern. An important finding of this work is that in most cases the activity concentration and the kinetic parameters obtained from images reconstructed using AB-OSEM showed a lower overall root mean squared error compared to the popular choices of either OSEM or FBP reconstruction for both cold and warm regions. As such, AB-OSEM should be preferred instead of the standard OSEM and FBP reconstructions when kinetic parameter estimation is considered. Finally, this work shows example parametric images from the high-resolution research tomograph obtained using the different reconstruction methods.
AB-OSEM reconstruction for improved Patlak kinetic parameter estimation: a simulation study.
Verhaeghe, Jeroen; Reader, Andrew J
2010-11-21
The non-negativity constraint inherently present in OSEM reconstruction successfully reduces the standard deviation in cold regions but at the cost of introducing a positive bias, especially at low iteration numbers. For low-count data, as often encountered in short-duration frames in dynamic imaging protocols, it has been shown that it can be advantageous (in terms of bias in the reconstructed image) to remove the non-negativity constraint. In this work two competing algorithms that do not impose non-negativity in the reconstructed image are investigated: NEG-ML and AB-OSEM. It was found that the AB-OSEM reconstruction outperformed the NEG-ML reconstruction. The AB-OSEM algorithm was then further developed to allow a forward model that includes randoms and scatter background terms. In addition to static reconstruction the current analysis was extended to consider the important case of kinetic parameter estimation from dynamic PET data. Simulation studies (comparing OSEM, FBP and AB-OSEM) showed that the positive bias obtained with OSEM reconstruction can be avoided in both static and parametric imaging through use of a negative lower bound in AB-OSEM reconstruction (i.e. by lifting the implicit non-negativity constraint of OSEM). When quantification tasks are considered, the overall error in the estimates (composed of both bias and standard deviation) is often of primary concern. An important finding of this work is that in most cases the activity concentration and the kinetic parameters obtained from images reconstructed using AB-OSEM showed a lower overall root mean squared error compared to the popular choices of either OSEM or FBP reconstruction for both cold and warm regions. As such, AB-OSEM should be preferred instead of the standard OSEM and FBP reconstructions when kinetic parameter estimation is considered. Finally, this work shows example parametric images from the high-resolution research tomograph obtained using the different reconstruction methods.
Gas phase NMR spectra of N,N-dimethylnitrosamine. Environmental effects on kinetic parameters
NASA Astrophysics Data System (ADS)
Chauvel, J. Paul; Leung, Doris Y.; True, Nancy S.
1984-04-01
Gas phase 1H NMR spectra of N,N-dimethylnitrosamine are consistent with first order chemical exchange rate constants which are ca. 25 times faster than those observed in neat liquids at corresponding temperatures. The associated kinetic parameters: Eact(∞), 20.5(1.1) kcal mol -1, Δ H‡, 19.7(1.0) kcal mol -1 and Δ G‡, 21.1(0.4) kcal mol -1 are approximately 2.5 kcal mol -1 lower than the most recently reported values for the neat liquid. The observed phase dependence is consistent with a process proceeding via a freely rotating transition state.
Effects of metformin on cell kinetic parameters of MCF-7 breast cancer cells in vitro.
Topcul, Mehmet; Cetin, Idil
2015-01-01
In this study, the antiproliferative effects of the metformin was evaluated on MCF-7 Cells (human breast adenocarcinoma cell line). For this purpose cell kinetic parameters including cell proliferation assay, mitotic index and labelling index analysis were used. 30 μM, 65 μM and 130 μM Metformin doses were applied to cells for 24, 48 and 72 hours. The results showed that there was a significant decrease in cell proliferation, mitotic index and labelling index for all experimental groups (p<0.05) for all applications. PMID:25824763
Kinetic parameters for the generation of endothelins-1,-2 and -3 by human cathepsin E.
Robinson, P S; Lees, W E; Kay, J; Cook, N D
1992-01-01
The specific conversion of human endothelin (ET) precursors big ET-1, big ET-2 and big ET-3 into their respective ET by cathepsin E was examined. Comparable pH optima were obtained for ET-1 and ET-2 generation, whereas effective conversion of big ET-3 into ET-3 necessitated a lower pH value. Determination of kinetic parameters (Km, kcat.) for all three conversions indicated that the precursors were efficiently bound by cathepsin E. The significance of the values obtained for the catalytic-centre activities and the effect of a specific inhibitor are discussed. PMID:1599425
1985-02-01
Version 00 TP1 is a transport theory code, developed to determine reactivity effects and kinetic parameters such as effective delayed neutron fractions and mean generation time by applying the usual perturbation formalism for one-dimensional geometry.
1985-02-01
Version 00 TP2 is a transport theory code, developed to determine reactivity effects and kinetic parameters such as effective delayed neutron fractions and mean generation time by applying the usual perturbation formalism for two-dimensional geometry.
Classical nucleation theory of homogeneous freezing of water: thermodynamic and kinetic parameters.
Ickes, Luisa; Welti, André; Hoose, Corinna; Lohmann, Ulrike
2015-02-28
The probability of homogeneous ice nucleation under a set of ambient conditions can be described by nucleation rates using the theoretical framework of Classical Nucleation Theory (CNT). This framework consists of kinetic and thermodynamic parameters, of which three are not well-defined (namely the interfacial tension between ice and water, the activation energy and the prefactor), so that any CNT-based parameterization of homogeneous ice formation is less well-constrained than desired for modeling applications. Different approaches to estimate the thermodynamic and kinetic parameters of CNT are reviewed in this paper and the sensitivity of the calculated nucleation rate to the choice of parameters is investigated. We show that nucleation rates are very sensitive to this choice. The sensitivity is governed by one parameter - the interfacial tension between ice and water, which determines the energetic barrier of the nucleation process. The calculated nucleation rate can differ by more than 25 orders of magnitude depending on the choice of parameterization for this parameter. The second most important parameter is the activation energy of the nucleation process. It can lead to a variation of 16 orders of magnitude. By estimating the nucleation rate from a collection of droplet freezing experiments from the literature, the dependence of these two parameters on temperature is narrowed down. It can be seen that the temperature behavior of these two parameters assumed in the literature does not match with the predicted nucleation rates from the fit in most cases. Moreover a comparison of all possible combinations of theoretical parameterizations of the dominant two free parameters shows that one combination fits the fitted nucleation rates best, which is a description of the interfacial tension coming from a molecular model [Reinhardt and Doye, J. Chem. Phys., 2013, 139, 096102] in combination with the activation energy derived from self-diffusion measurements [Zobrist
Classical nucleation theory of homogeneous freezing of water: thermodynamic and kinetic parameters.
Ickes, Luisa; Welti, André; Hoose, Corinna; Lohmann, Ulrike
2015-02-28
The probability of homogeneous ice nucleation under a set of ambient conditions can be described by nucleation rates using the theoretical framework of Classical Nucleation Theory (CNT). This framework consists of kinetic and thermodynamic parameters, of which three are not well-defined (namely the interfacial tension between ice and water, the activation energy and the prefactor), so that any CNT-based parameterization of homogeneous ice formation is less well-constrained than desired for modeling applications. Different approaches to estimate the thermodynamic and kinetic parameters of CNT are reviewed in this paper and the sensitivity of the calculated nucleation rate to the choice of parameters is investigated. We show that nucleation rates are very sensitive to this choice. The sensitivity is governed by one parameter - the interfacial tension between ice and water, which determines the energetic barrier of the nucleation process. The calculated nucleation rate can differ by more than 25 orders of magnitude depending on the choice of parameterization for this parameter. The second most important parameter is the activation energy of the nucleation process. It can lead to a variation of 16 orders of magnitude. By estimating the nucleation rate from a collection of droplet freezing experiments from the literature, the dependence of these two parameters on temperature is narrowed down. It can be seen that the temperature behavior of these two parameters assumed in the literature does not match with the predicted nucleation rates from the fit in most cases. Moreover a comparison of all possible combinations of theoretical parameterizations of the dominant two free parameters shows that one combination fits the fitted nucleation rates best, which is a description of the interfacial tension coming from a molecular model [Reinhardt and Doye, J. Chem. Phys., 2013, 139, 096102] in combination with the activation energy derived from self-diffusion measurements [Zobrist
Morozova, E A; Bazhulina, N P; Anufrieva, N V; Mamaeva, D V; Tkachev, Y V; Streltsov, S A; Timofeev, V P; Faleev, N G; Demidkina, T V
2010-10-01
Kinetic parameters of Citrobacter freundii methionine γ-lyase were determined with substrates in γ-elimination reactions as well as the inhibition of the enzyme in the γ-elimination of L-methionine by amino acids with different structure. The data indicate an important contribution of the sulfur atom and methylene groups to the efficiency of binding of substrates and inhibitors. The rate constants of the enzyme-catalyzed exchange of C-α- and C-β-protons with deuterium were determined, as well as the kinetic isotope effect of the deuterium label in the C-α-position of inhibitors on the rate of exchange of their β-protons. Neither stereoselectivity in the β-proton exchange nor noticeable α-isotope effect on the exchange rates of β-protons was found. The ionic and tautomeric composition of the external Schiff base of methionine γ-lyase was determined. Spectral characteristics (absorption and circular dichroism spectra) of complexes with substrates and inhibitors were determined. The spectral and kinetic data indicate that deamination of aminocrotonate should be the rate-determining stage of the enzymatic reaction.
Effect of diet-induced obesity on kinetic parameters of amino acid uptake by rat erythrocytes.
Picó, C; Pons, A; Palou, A
1992-11-01
The effects of cafeteria diet-induced obesity upon in vitro uptake of L-Alanine, Glycine, L-Lysine, L-Glutamine, L-Glutamic acid, L-Phenylalanine and L-Leucine by isolated rat erythrocytes have been studied. The total Phe and Leu uptakes followed Michaelis-Menten kinetics. The Glu uptake was fitted to diffusion kinetics. The uptakes of Ala, Gly, Lys and Gln were best explained by a two-component transport: one saturable and one diffusion. Obesity increased the Km value for Ala, Gln and Leu, and the Vmax value for Ala, but decreased the Vmax for Lys. Kinetic parameters of Phe uptake were unaffected by obesity. In addition, the pseudo-first order rate constant (Vmax/Km) for Ala, Gly, Gln, Lys and Leu uptake decreased as a result of cafeteria diet-induced obesity. The Kd value for Ala, Gly, Gln and Glu decreased and that of Lys increased as result of obesity. These adaptations could, at least in part, explain alterations in amino acid distribution between blood cells and plasma related to overfeeding or obesity.
Sparsity Constrained Mixture Modeling for the Estimation of Kinetic Parameters in Dynamic PET
Lin, Yanguang; Haldar, Justin P.; Li, Quanzheng; Conti, Peter S.; Leahy, Richard M.
2013-01-01
The estimation and analysis of kinetic parameters in dynamic PET is frequently confounded by tissue heterogeneity and partial volume effects. We propose a new constrained model of dynamic PET to address these limitations. The proposed formulation incorporates an explicit mixture model in which each image voxel is represented as a mixture of different pure tissue types with distinct temporal dynamics. We use Cramér-Rao lower bounds to demonstrate that the use of prior information is important to stabilize parameter estimation with this model. As a result, we propose a constrained formulation of the estimation problem that we solve using a two-stage algorithm. In the first stage, a sparse signal processing method is applied to estimate the rate parameters for the different tissue compartments from the noisy PET time series. In the second stage, tissue fractions and the linear parameters of different time activity curves are estimated using a combination of spatial-regularity and fractional mixture constraints. A block coordinate descent algorithm is combined with a manifold search to robustly estimate these parameters. The method is evaluated with both simulated and experimental dynamic PET data. PMID:24216681
Determination of the kinetic parameters of BeO using isothermal decay method.
Azorin Nieto, Juan; Vega, Claudia Azorin; Montalvo, Teodoro Rivera; Cabrera, Eugenio Torijano
2016-02-01
Most of the existing methods for obtaining the frequency factors make use of the trap depth (activation energy) making some assumptions about the order of the kinetics. This causes inconsistencies in the reported values of trapping parameters due that the values of the activation energy obtained by different methods differ appreciably among them. Then, it is necessary to use a method independent of the trap depth making use of the isothermal luminescence decay (ILD) method. The trapping parameters associated with the prominent glow peak of BeO (280°C) are reported using ILD method. As a check, the trap parameters are also calculated by glow curve shape (Chen's) method after isolating the prominent glow peak by thermal cleaning technique. Our results show a very good agreement between the trapping parameters calculated by the two methods. ILD method was used for determining the trapping parameters of BeO. Results obtained applying this method are in good agreement with those obtained using other methods, except in the value of the frequency factor.
NASA Astrophysics Data System (ADS)
Zhang, C.-L.; Zhao, F.; Wang, Y.
2012-04-01
Batch adsorption experiments were carried out for the removal of ofloxacin from aqueous solution using modified coal fly ash as adsorbent. The effects of various parameters such as contact time, initial solution concentration and temperature on the adsorption system were investigated. The optimum contact time was found to be 150 min. The adsorption isotherm data fit well with the Langmuir model, and the kinetic data fit well with the pseudo-second order and the intra-particle diffusion model. Intra-particle diffusion analysis demonstrates that ofloxacin diffuses quickly among the particles at the beginning of the adsorption process, and then the diffusion slows down and stabilizes. Thermodynamic parameters such as Δ G, Δ H, and Δ S were also calculated. The negative Gibbs free energy change and the positive enthalpy change indicated the spontaneous and endothermic nature of the adsorption, and the positive entropy change indicated that the adsorption process was aided by increased randomness.
Mohamed, Mohamed M; Saleh, Nawal E; Sherif, Mohsen M
2010-04-01
Dissolved benzene was detected in the shallow unconfined Liwa aquifer (UAE). This aquifer represents the main freshwater source for a nearby residence camp area. A finite element model is used to simulate the fate, transport, and attenuation of the dissolved benzene plume to help decision makers assess natural attenuation as a viable remediation option. Sensitivity of benzene attenuation to uncertainties in the estimation of some of the kinetic and transport parameters is studied. It was found that natural attenuation is more sensitive to microbial growth rate and half saturation coefficients of both benzene and oxygen than initial biomass concentration and dispersivity coefficients. Increasing microbial growth rate by fourfold increased natural attenuation effectiveness after 40 years by 10%; while decreasing it by fourfold decreased natural attenuation effectiveness by 77%. On the other hand, increasing half saturation coefficient by fourfold decreased natural attenuation effectiveness by 46% in 40 years. Decreasing the same parameter fourfold caused natural attenuation effectiveness to increase by 9%.
Local field potentials in primate motor cortex encode grasp kinetic parameters
Milekovic, Tomislav; Truccolo, Wilson; Grün, Sonja; Riehle, Alexa; Brochier, Thomas
2015-01-01
Reach and grasp kinematics are known to be encoded in the spiking activity of neuronal ensembles and in local field potentials (LFPs) recorded from primate motor cortex during movement planning and execution. However, little is known, especially in LFPs, about the encoding of kinetic parameters, such as forces exerted on the object during the same actions. We implanted two monkeys with microelectrode arrays in the motor cortical areas MI and PMd to investigate encoding of grasp-related parameters in motor cortical LFPs during planning and execution of reach-and-grasp movements. We identified three components of the LFP that modulated during grasps corresponding to low (0.3 - 7Hz), intermediate (∼10 - ∼40Hz) and high (∼80 - 250Hz) frequency bands. We show that all three components can be used to classify not only grip types but also object loads during planning and execution of a grasping movement. In addition, we demonstrate that all three components recorded during planning or execution can be used to continuously decode finger pressure forces and hand position related to the grasping movement. Low and high frequency components provide similar classification and decoding accuracies, which were substantially higher than those obtained from the intermediate frequency component. Our results demonstrate that intended reach and grasp kinetic parameters are encoded in multiple LFP bands during both movement planning and execution. These findings also suggest that the LFP is a reliable signal for the control of parameters related to object load and applied pressure forces in brain-machine interfaces. PMID:25869861
NASA Astrophysics Data System (ADS)
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
The role of test parameters on the kinetics and thermodynamics of glass leaching. [None
Jantzen, C M
1988-01-01
The relative durabilities of nuclear waste, natural, and ancient glasses have been assessed by standard laboratory leach tests. Different test conditions result in different glass surface areas (SA), leachant volumes (V), and test durations (t). Leachate concentrations are known to be a parabolic function of the kinetic test parameter SAV/center dot/t. Based on durability experiments of glass monoliths at low (SAV)/center dot/ glass durability has been shown to be a logarithmic function of the thermodynamic hydration free energy, ..delta..G/sub hyd/. The thermodynamic hydration free energy, ..delta..G/sub hyd/, can be calculated from glass composition and solution pH. In the repository environment high effective glass surface areas to solution volume ratios may occur as a result of slow groundwater flow rates. The application of hydration thermodynamics to crushed glass, high (SAV)/center dot/t, durability tests has been demonstrated. The relative contributions of the kinetic test parameters, (SAV)/center dot/t, and the thermodynamic parameter, ..delta..G/sub hyd/, have been shown to define a plane in ..delta..G/sub hyd/-concentration-(SAV)/center dot/t space. At constant test conditions, e.g. constant (SAV/center dot/t, the intersection with this surface indicates that all /delta G//sub hyd/-concentration plots should have similar slopes and predict the same relative durabilities for various glasses as a function of glass composition. Using this approach, the durability of nuclear waste glasses has been interpolated to be -- 10/sup 6/ years and no less than 10/sup 3/ years. 28 refs., 24 figs.
{sup 82}Rb kinetic parameter variability due to depth of anesthesia in the anesthetized canine
Coxson, P.G.; Brennan, K.M.; Yang, L.
1995-05-01
The effect of {open_quotes}depth of anesthesia{close_quotes} on {sup 82}Rb kinetic parameter estimates in the myocardium was tested in a series of replicated studies on six dogs using the Donner 600-Crystal Positron Tomograph. A single lateral slice through the myocardium was imaged following each of four successive injections of {sup 82}Rb. For three of the injections the animals were lightly anesthetized (mean blood pressure about 90 mmHg). For the second injection, the amount of anesthetic was increased until blood pressure dipped to about 70 mHg. The fourth injection was preceded by an infusion of dipyridamole to induce a stress-state. The entire sequence was repeated at least twice with each of the six animals. A two compartment model with parameters k{sub 1} (uptake rate), k{sub 2} (wash-out rate), and f{sub v} (vascular fraction) was fit to the data. There was a consistent finding of a 20% to 30% decrease in k{sub 1} during the deeply anesthetized state compared with the two lightly anesthetized rest states. Analysis of variance showed that the difference observed is significant, though small in comparison with the difference between the rest and stress states (60% to 160% increase). The difference between the two lightly anesthetized states was not significant. Kinetic PET studies using dogs are routinely carried out with the animal anesthetized. Depth of anesthesia has been suspected as as source of variability in parameter estimates, but this conjecture has not previously been systematically investigated. These studies at extremes in the depth of anesthesia show a small but predictable effect on the uptake k{sub 1} of {sup 82}Rb.
AgNOR clusters as a parameter of cell kinetics in chronic lymphocytic leukaemia
Lorand-Metze, Irene; Metze, Konradin
1996-01-01
Aims—To study correlations between the pattern of silver stained nucleolar organiser regions (AgNORs) in chronic lymphocytic leukaemia (CLL) and parameters of tumour kinetics. To investigate whether quantitation of the AgNOR pattern can be used to discriminate between patients with stable and progressive disease. Methods—Peripheral blood smears from 48 patients with CLL, classified as having either stable or progressive disease (Rai stage III or IV; bulky lymph nodes or massive splenomegaly; or peripheral lymphocytes >100 × 109/1), were studied. For each patient, total tumour mass (TTM) and for patients undergoing a period of observation without treatment, the TTM duplication time (DT) and the lymphocyte doubling time (LDT) were calculated. Results—Four cell types could be distinguished according to their AgNOR pattern: (1) cells with a single cluster; (2) cells with a single compact nucleolus; (3) cells with two compact nucleoli; and (4) cells with several scattered dots. The percentage of cells with clusters was the AgNOR parameter which correlated best with TTM and LDT. Correlations were also seen between the proportion of cells with clusters and age and haemoglobin concentration. A significant correlation with DT could be detected only when age was kept constant. Linear discriminant analysis revealed that the percentage of cells with clusters was the most important prognostic factor. This alone classified 94% of the patients correctly (jackknive procedure) as either stable or progressive CLL. Conclusions—The percentage of circulating lymphocytes with clusters of AgNORs can be used as a parameter of tumour kinetics in CLL and helps to discriminate between patients with stable and progressive disease. For practical purposes, a value of more than 13% of cells with clusters is suggestive of progressive disease. Images PMID:16696103
Chemical kinetics parameters and model validation for the gasification of PCEA nuclear graphite
El-Genk, Mohamed S; Tournier, Jean-Michel; Contescu, Cristian I
2014-01-01
A series of gasification experiments, using two right cylinder specimens (~ 12.7 x 25.4 mm and 25.4 x 25.4 mm) of PCEA nuclear graphite in ambient airflow, measured the total gasification flux at weight losses up to 41.5% and temperatures (893-1015 K) characteristics of those for in-pores gasification Mode (a) and in-pores diffusion-limited Mode (b). The chemical kinetics parameters for the gasification of PCEA graphite are determined using a multi-parameters optimization algorithm from the measurements of the total gasification rate and transient weight loss in experiments. These parameters are: (i) the pre-exponential rate coefficients and the Gaussian distributions and values of specific activation energies for adsorption of oxygen and desorption of CO gas; (ii) the specific activation energy and pre-exponential rate coefficient for the breakup of stable un-dissociated C(O2) oxygen radicals to form stable (CO) complexes; (iii) the specific activation energy and pre-exponential coefficient for desorption of CO2 gas and; (iv) the initial surface area of reactive free sites per unit mass. This area is consistently 13.5% higher than that for nuclear graphite grades of NBG-25 and IG-110 and decreases inversely proportional with the square root of the initial mass of the graphite specimens in the experiments. Experimental measurements successfully validate the chemical-reactions kinetics model that calculates continuous Arrhenius curves of the total gasification flux and the production rates of CO and CO2 gases. The model results at different total weight losses agree well with measurements and expand beyond the temperatures in the experiments to the diffusion-limited mode of gasification. Also calculated are the production rates of CO and CO2 gases and their relative contributions to the total gasification rate in the experiments as functions of temperature, for total weight losses of 5% and 10%.
Chemical kinetics parameters and model validation for the gasification of PCEA nuclear graphite
NASA Astrophysics Data System (ADS)
El-Genk, Mohamed S.; Tournier, Jean-Michel P.; Contescu, Cristian I.
2014-01-01
A series of gasification experiments, using two right cylinder specimens (∼12.7 × 25.4 mm and 25.4 × 25.4 mm) of PCEA nuclear graphite in ambient airflow, measured the total gasification flux at weight losses up to 41.5% and temperatures (893-1015 K) characteristics of those for in-pores gasification Mode (a) and in-pores diffusion-limited Mode (b). The chemical kinetics parameters for the gasification of PCEA graphite are determined using a multi-parameters optimization algorithm from the measurements of the total gasification rate and transient weight loss in experiments. These parameters are: (i) the pre-exponential rate coefficients and the Gaussian distributions and values of specific activation energies for adsorption of oxygen and desorption of CO gas; (ii) the specific activation energy and pre-exponential rate coefficient for the breakup of stable un-dissociated C(O2) oxygen radicals to form stable (CO) complexes; (iii) the specific activation energy and pre-exponential coefficient for desorption of CO2 gas and; (iv) the initial surface area of reactive free sites per unit mass. This area is consistently 13.5% higher than that for nuclear graphite grades of NBG-25 and IG-110 and decreases inversely proportional with the square root of the initial mass of the graphite specimens in the experiments. Experimental measurements successfully validate the chemical-reactions kinetics model that calculates continuous Arrhenius curves of the total gasification flux and the production rates of CO and CO2 gases. The model results at different total weight losses agree well with measurements and expand beyond the temperatures in the experiments to the diffusion-limited mode of gasification. Also calculated are the production rates of CO and CO2 gases and their relative contributions to the total gasification rate in the experiments as functions of temperature, for total weight losses of 5% and 10%.
French, Jarrod B; Cen, Yana; Vrablik, Tracy L; Xu, Ping; Allen, Eleanor; Hanna-Rose, Wendy; Sauve, Anthony A
2010-12-14
Nicotinamidases are metabolic enzymes that hydrolyze nicotinamide to nicotinic acid. These enzymes are widely distributed across biology, with examples found encoded in the genomes of Mycobacteria, Archaea, Eubacteria, Protozoa, yeast, and invertebrates, but there are none found in mammals. Although recent structural work has improved our understanding of these enzymes, their catalytic mechanism is still not well understood. Recent data show that nicotinamidases are required for the growth and virulence of several pathogenic microbes. The enzymes of Saccharomyces cerevisiae, Drosophila melanogaster, and Caenorhabditis elegans regulate life span in their respective organisms, consistent with proposed roles in the regulation of NAD(+) metabolism and organismal aging. In this work, the steady state kinetic parameters of nicotinamidase enzymes from C. elegans, Sa. cerevisiae, Streptococcus pneumoniae (a pathogen responsible for human pneumonia), Borrelia burgdorferi (the pathogen that causes Lyme disease), and Plasmodium falciparum (responsible for most human malaria) are reported. Nicotinamidases are generally efficient catalysts with steady state k(cat) values typically exceeding 1 s(-1). The K(m) values for nicotinamide are low and in the range of 2 -110 μM. Nicotinaldehyde was determined to be a potent competitive inhibitor of these enzymes, binding in the low micromolar to low nanomolar range for all nicotinamidases tested. A variety of nicotinaldehyde derivatives were synthesized and evaluated as inhibitors in kinetic assays. Inhibitions are consistent with reaction of the universally conserved catalytic Cys on each enzyme with the aldehyde carbonyl carbon to form a thiohemiacetal complex that is stabilized by a conserved oxyanion hole. The S. pneumoniae nicotinamidase can catalyze exchange of (18)O into the carboxy oxygens of nicotinic acid with H(2)(18)O. The collected data, along with kinetic analysis of several mutants, allowed us to propose a catalytic
Bhuiya, Mohammad W; Sakuraba, Haruhiko; Ohshima, Toshihisa
2002-04-01
The temperature dependence of the steady-state kinetic parameters for a glutamate dehydrogenase from Aeropyrum pernix K1 was investigated. The enzyme showed a biphasic kinetic characteristic for L-glutamate and a monophasic one for NADP at 50-90 degrees C. At low concentrations of L-glutamate the Km decreased from 2.02 to 0.56 mM and the catalytic efficiency (Vmax/Km) markedly increased (4-150 micromol x mg(-1) x mM(-1)) along with the increase of temperature from 50 to 90 degrees C. At high concentrations of the substrate the Km was fairly high and approximately constant (around 225 mM), and the catalytic efficiency was low and its temperature-dependent change was small. The Km (0.039 mM) for NADP did not change with the increase of temperature. In the reductive amination, the Kms for 2-oxoglutarate (1.81 and 9.37 mM at low and high levels of ammonia, respectively) were independent on temperature, but the Kms for ammonia and NADPH rose from 86 to 185 mM and 0.050 to 0.175 mM, respectively.
Does Vibration Warm-up Enhance Kinetic and Temporal Sprint Parameters?
Cochrane, D J; Cronin, M J; Fink, P W
2015-08-01
The aim of this study was to investigate the efficacy of vibration warm-up to enhance sprint performance. 12 males involved in representative team sports performed 4 warm-up conditions in a randomised order performed at least 24 h apart; VbX warm-up (VbX-WU); Neural activation warm-up (Neu-WU); Dynamic warm-up (Dyn-WU) and Control (No VbX). Participants completed 5 m sprint at 30 s, 2:30 min and 5 min post warm-up where sprint time, kinetics, and temporal components were recorded. There was no significant (p>0.05) main effect or interaction effect between the split sprint times of 1 m, 2.5 m, and 5 m. There was a condition effect where vertical mean force was significantly higher (p<0.05) in Dyn-WU and Control compared to Neu-WU. No other significant (p>0.05) main and interaction effects in sprint kinetic and temporal parameters existed. Overall, all 4 warm-up conditions produced comparable results for sprint performance, and there was no detrimental effect on short-duration sprint performance using VbX-WU. Therefore, VbX could be useful for adding variety to the training warm-up or be included into the main warm-up routine as a supplementary modality.
Determination of kinetic parameters of Phlomis bovei de Noé using thermogravimetric analysis.
Yahiaoui, Meriem; Hadoun, Hocine; Toumert, Idir; Hassani, Aicha
2015-11-01
This paper reports the pyrolysis study of Phlomis bovei biomass by thermogravimetric experiments in order to determine the thermal degradation behavior and kinetic parameters. The weight losses were found to occur in three stages. In the DTG thermograms, an increase of the heating rate tended to delay thermal degradation processes towards higher temperatures. The average values of activation energy and pre-exponential factor calculated from Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose and Kissinger methods are 134.83, 134.06, 223.31kJ/mol and 4.1610(13), 1.1810(10), 2.8110(11)/s, respectively. The three-pseudo-component method shows that the activation energy increases with increasing the heating rate for hemicellulose and cellulose while the activation energy of the lignin decreased with an increase of the heating rate. Predicted results and experimental data exhibit similar tendencies and the three pseudo-components model with n different from unity 1 is recommended as the most suitable for prediction of kinetic behavior of Phlomis bovei de Noé.
Ríos, Francisco; Fernández-Arteaga, Alejandro; Lechuga, Manuela; Jurado, Encarnación; Fernández-Serrano, Mercedes
2016-05-01
This paper reports a study of the anaerobic biodegradation of non-ionic surfactants alkyl polyglucosides applying the method by measurement of the biogas production in digested sludge. Three alkyl polyglucosides with different length alkyl chain and degree of polymerization of the glucose units were tested. The influence of their structural parameters was evaluated, and the characteristics parameters of the anaerobic biodegradation were determined. Results show that alkyl polyglucosides, at the standard initial concentration of 100 mgC L(-1), are not completely biodegradable in anaerobic conditions because they inhibit the biogas production. The alkyl polyglucoside having the shortest alkyl chain showed the fastest biodegradability and reached the higher percentage of final mineralization. The anaerobic process was well adjusted to a pseudo first-order equation using the carbon produced as gas during the test; also, kinetics parameters and a global rate constant for all the involved metabolic process were determined. This modeling is helpful to evaluate the biodegradation or the persistence of alkyl polyglucosides under anaerobic conditions in the environment and in the wastewater treatment.
Kinetic parameters of the thermal degradation of the PP and nondegraded and degraded HDPE blends
Albano, C.; Freitas, E.
1996-12-31
We study the thermodegradative behavior of PP, of non-degraded and degraded HDPE and their blends, in order to analyze the thermal stability of such materials. Van-Krevelen (V-K), Coats-Redfern (C-R) and Horowitz-Metzger (H-M) integral methods as well as the Freeman-Carroll (F-C) differential one, were used to determine the kinetic parameters. The activation energy (E{sub a}) obtained for the PP mixed with non-degraded HDPE (5 to 50%) is lower than the E{sub a} correspondent to pure polymers and does not depend on the HDPE concentration. Blends of degraded materials, show an approximate value of E{sub a} of 200 kJ/mol for mixtures with concentrations by weight of HDPE up to 20%, but its value decreases drastically with higher concentrations. 11 refs., 2 tabs.
Aceves, S; Dibble, R; Flowers, D; Smith, J R; Westbrook, C K
1999-07-19
This paper uses the HCT (Hydrodynamics, Chemistry and Transport) chemical kinetics code to analyze natural gas HCCI combustion in an engine. The HCT code has been modified to better represent the conditions existing inside an engine, including a wall heat transfer correlation. Combustion control and low power output per displacement remain as two of the biggest challenges to obtaining satisfactory performance out of an HCCI engine, and these are addressed in this paper. The paper considers the effect of natural gas composition on HCCI combustion, and then explores three control strategies for HCCI engines: DME (dimethyl ether) addition, intake heating and hot EGR addition. The results show that HCCI combustion is sensitive to natural gas composition, and an active control may be required to compensate for possible changes in composition. The three control strategies being considered have a significant effect in changing the combustion parameters for the engine, and should be able to control HCCI combustion.
Determination of μd chemistry kinetic parameters for the MuSun Experiment
NASA Astrophysics Data System (ADS)
Raha, Nandita
2014-09-01
The MuSun experiment at PSI will measure the muon doublet capture rate Λd in ultra pure deuterium gas to 1.5% precision from the measured decay-electron time distribution. This reaction cleanly determines the strength of the two-nucleon weak axial current interaction. The kinetic parameters of the μd chemistry are essential for extracting Λd, which in turn are determined from the process of muon catalyzed fusion in deuterium. This process yields 3 He recoils and 2.45 MeV monoenergetic neutrons from the reaction ddμ -->3 He + n + μ . Encoded in the time dependence of the fusion products are the ddμ molecular formation rates from the F = 1 / 2 , 3 / 2 hyperfine states (λd and λq) and the hyperfine transition rate (λqd) from the higher-energy F = 3 / 2 state to the lower-energy F = 1 / 2 state. This work concentrates on the analysis of the fusion neutrons, which are detected by an array of eight neutron detectors. Pulse shape discrimination was used to distinguish neutrons from background gamma rays. A least squared fit to the time spectrum of the fusion neutrons determines the μd chemistry kinetic parameters λqd and the ratio λq / λd. The MuSun experiment at PSI will measure the muon doublet capture rate Λd in ultra pure deuterium gas to 1.5% precision from the measured decay-electron time distribution. This reaction cleanly determines the strength of the two-nucleon weak axial current interaction. The kinetic parameters of the μd chemistry are essential for extracting Λd, which in turn are determined from the process of muon catalyzed fusion in deuterium. This process yields 3 He recoils and 2.45 MeV monoenergetic neutrons from the reaction ddμ -->3 He + n + μ . Encoded in the time dependence of the fusion products are the ddμ molecular formation rates from the F = 1 / 2 , 3 / 2 hyperfine states (λd and λq) and the hyperfine transition rate (λqd) from the higher-energy F = 3 / 2 state to the lower-energy F = 1 / 2 state. This work concentrates
Kinetics of surface segregation in metallic alloys with first-principles interaction parameters
Wille, L.T. |; Ouannasser, S.; Dreysse, H.
1996-12-31
The authors report the results of Monte Carlo simulations of the kinetics of surface segregation at the (001) face of CuNi and MoW alloys. These two systems were selected because they are based on different lattice structures and show contrasting segregation behavior: CuNi exhibits a monotonic profile, while that of MoW is oscillatory. To describe the energetics they have determined a set of effective cluster interactions (ECI) which govern the ordering or clustering tendencies of these alloys. The ECI were obtained by means of tight-binding electronic structure calculations in which no adjustable or experimentally determined parameters were used. Equilibrium segregation profiles are calculated and a series of quenches are performed. The layer concentrations are studied as a function of time and the existence of metastable phases in the surface region is investigated.
Measuring the kinetic parameters of saltating sand grains using a high-speed digital camera
NASA Astrophysics Data System (ADS)
Zhang, Yang; Wang, Yuan; Jia, Pan
2014-06-01
A high-speed digital camera is used to record the saltation of three sand samples (diameter range: 300-500, 200-300 and 100-125 μm). This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains. The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport. Moreover, the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory, and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air.
NASA Astrophysics Data System (ADS)
Guo, Xingcai; Yates, John T., Jr.
1989-06-01
The effective desorption kinetic parameters of CO on the Pd(111) surface have been studied by thermal desorption spectroscopy. The zero coverage effective desorption activation energy and the preexponential factor were found to be 35.5 kcal/mol and 1013.5 s-1, respectively. As a function of CO coverage, a four-stage correlation between Ed(θ) and the development of stable low-energy electron desorption (LEED) structures was observed for the first time at Tads= 200 K. Ed and ν1 showed a strong compensation effect with Tc=519 K. The adsorption temperature dependence of Ed from Tads=87 to 200 K was observed and interpreted qualitatively by a model involving the production of different domain structures at various adsorption temperatures and the preservation of domain structures at higher coverages during temperature programmed desorption.
NASA Astrophysics Data System (ADS)
Nagaya, Yasunobu
2014-06-01
The methods to calculate the kinetics parameters of βeff and Λ with the differential operator sampling have been reviewed. The comparison of the results obtained with the differential operator sampling and iterated fission probability approaches has been performed. It is shown that the differential operator sampling approach gives the same results as the iterated fission probability approach within the statistical uncertainty. In addition, the prediction accuracy of the evaluated nuclear data library JENDL-4.0 for the measured βeff/Λ and βeff values is also examined. It is shown that JENDL-4.0 gives a good prediction except for the uranium-233 systems. The present results imply the need for revisiting the uranium-233 nuclear data evaluation and performing the detailed sensitivity analysis.
Guo, Shuanbao; Xu, Pengcheng; Yu, Haitao; Cheng, Zhenxing; Li, Xinxin
2015-03-10
A novel method is explored for comprehensive design/optimization of organophosphorus sensing material, which is loaded on mass-type microcantilever sensor. Conventionally, by directly observing the gas sensing response, it is difficult to build quantitative relationship with the intrinsic structure of the material. To break through this difficulty, resonant cantilever is employed as gravimetric tool to implement molecule adsorption experiment. Based on the sensing data, key kinetic/thermodynamic parameters of the material to the molecule, including adsorption heat -ΔH°, adsorption/desorption rate constants Ka and Kd, active-site number per unit mass N' and surface coverage θ, can be quantitatively extracted according to physical-chemistry theories. With gaseous DMMP (simulant of organophosphorus agents) as sensing target, the optimization route for three sensing materials is successfully demonstrated. Firstly, a hyper-branched polymer is evaluated. Though suffering low sensitivity due to insufficient N', the bis(4-hydroxyphenyl)-hexafluoropropane (BHPF) sensing-group exhibits satisfactory reproducibility due to appropriate -ΔH°. To achieve more sensing-sites, KIT-5 mesoporous-silica with higher surface-area is assessed, resulting in good sensitivity but too high -ΔH° that brings poor repeatability. After comprehensive consideration, the confirmed BHPF sensing-group is grafted on the KIT-5 carrier to form an optimized DMMP sensing nanomaterial. Experimental results indicate that, featuring appropriate kinetic/thermodynamic parameters of -ΔH°, Ka, Kd, N' and θ, the BHPF-functionalized KIT-5 mesoporous silica exhibits synergistic improvement among reproducibility, sensitivity and response/recovery speed. The optimized material shows complete signal recovery, 55% sensitivity improvement than the hyper-branched polymer and 2∼3 folds faster response/recovery speed than the KIT-5 mesoporous silica.
Kong, Fansheng; Yu, Shujuan; Bi, Yongguang; Huang, Xiaojun; Huang, Mengqian
2016-01-01
Objective: To optimize and verify the cellulase extraction of polyphenols from honeysuckle and provide a reference for enzymatic extracting polyphenols from honeysuckle. Materials and Methods: The uniform design was used According to Fick's first law and kinetic model, fitting analysis of the dynamic process of enzymatic extracting polyphenols was conducted. Results: The optimum enzymatic extraction parameters for polyphenols from honeysuckle are found to be 80% (v/v) of alcohol, 35:1 (mL/g) of liquid-solid ratio, 80°C of extraction temperature, 8.5 of pH, 6.0 mg of enzyme levels, and 130 min of extraction time. Under the optimal conditions, the extraction rate of polyphenols was 3.03%. The kinetic experiments indicated kinetic equation had a good linear relationship with t even under the conditions of different levels of enzyme and temperature, which means fitting curve tallies well with the experimental values. Conclusion: The results of quantification showed that the results provide a reference for enzymatic extracting polyphenols from honeysuckle. SUMMARY Lonicerae flos (Lonicera japonica Thunb.) is a material of traditional Chinese medicine and healthy drinks, of which active compounds mainly is polyphenols. At present, plant polyphenols are the hotspots centents of food, cosmetic and medicine, because it has strong bioactivity. Several traditional methods are available for the extraction of plant polyphenols including impregnation, solvent extraction, ultrasonic extraction, hot-water extraction, alkaline dilute alcohol or alkaline water extraction, microwave extraction and Supercritical CO2 extraction. But now, an increasing number of research on using cellulase to extract active ingredients from plants. Enzymatic method is widely used for enzyme have excellent properties of high reaction efficiency and specificity, moderate reaction conditions, shorter extraction time and easier to control, less damage to the active ingredient. At present, the enzymatic
Coxson, P.G.; Brennan, K.M.; Huesman, R.H.
1995-02-01
Kinetic analysis of {sup 82}Rb (I) dynamic PET data produces quantitative measures which could be used to evaluate ischemic heart disease. These measures have the potential to generate objective comparisons of different patients or the same patient at different times. To achieve this potential, it is essential to determine the variability and reproducibility of the kinetic parameters. A total of 48 I dynamic PET datasets were acquired from two pure bred beagles. Each animal underwent eight I PET studies with essentially the same protocol for three successive weeks. Data were acquired with the Donner 600-Crystal Positron Tomograph (PET600). In each week, single-slice dynamic I PET datasets were collected with the animal at rest at three different gantry positions separated by 5 mm. Additional dataset were collected after dipyridamole infusion and after administration of aminophylline to induce a return to rest. A two-compartment kinetic model with correction for myocardial vasculature and spillover from the left ventricular blood pool was used to analyze the dynamic datasets. Model parameters for uptake (k{sub 1}), washout (k{sub 2}) and vascular fraction (f{sub v}) were estimated in 11-14 myocardial regions of interest (ROIs) using a weighted least-squares criterion. Statistical fluctuation due to the PET acquisition process was minimized by using a relatively high I dose (about 30 mCi) to take advantage of the high count rate capacity of the PET600. The variation in mean k{sub 1}, where the mean is taken over the myocardial ROIs was 10%-20% (Dog 1) and 15%-50% (Dog 2) among the rest studies conducted on the same data. Similar variation was evident in comparing studies in the same animal for different weeks. Spatial and temporal variation in estimates of the uptake rate (k{sub 1}) of I in the resting myocardium of the anesthetized canine are small in relation to the functional increase in k{sub 1}, following dipyridamole stress. 17 refs., 14 figs.
Tosun, Ismail
2012-03-01
The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.
Tosun, İsmail
2012-01-01
The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R2) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients. PMID:22690177
Aguirre, Juan S; de Fernando, Gonzalo García; Hierro, Eva; Hospital, Xavier F; Ordóñez, Juan A; Fernández, Manuela
2015-06-01
Quantitative microbial risk assessment requires the knowledge of the effect of food preservation technologies on the growth parameters of the survivors of the treatment. This is of special interest in the case of the new non-thermal technologies that are being investigated for minimal processing of foods. This is a study on the effect of pulsed light technology (PL) on the lag phase of Bacillus cereus spores surviving the treatment and the maximum growth rate (μmax) of the survivors after germination. The D value was estimated as 0.35 J/cm(2) and our findings showed that PL affected the kinetic parameters of the microorganism. A log linear relationship was observed between the lag phase and the intensity of the treatment. Increasing the lethality lengthened the mean lag phase and proportionally increased its variability. A polynomial regression was fitted between the μmax of the survivors and the inactivation achieved. The μmax decreased as intensity increased. From these data, and their comparison to published results on the effect of heat and e-beam irradiation on B. cereus spores, it was observed that the shelf-life of PL treated foods would be longer than those treated with heat and similar to irradiated ones. These findings offer information of interest for the implementation of PL for microbial decontamination in the food industry. PMID:25755081
A new methodology to determine kinetic parameters for one- and two-step chemical models
NASA Technical Reports Server (NTRS)
Mantel, T.; Egolfopoulos, F. N.; Bowman, C. T.
1996-01-01
In this paper, a new methodology to determine kinetic parameters for simple chemical models and simple transport properties classically used in DNS of premixed combustion is presented. First, a one-dimensional code is utilized to performed steady unstrained laminar methane-air flame in order to verify intrinsic features of laminar flames such as burning velocity and temperature and concentration profiles. Second, the flame response to steady and unsteady strain in the opposed jet configuration is numerically investigated. It appears that for a well determined set of parameters, one- and two-step mechanisms reproduce the extinction limit of a laminar flame submitted to a steady strain. Computations with the GRI-mech mechanism (177 reactions, 39 species) and multicomponent transport properties are used to validate these simplified models. A sensitivity analysis of the preferential diffusion of heat and reactants when the Lewis number is close to unity indicates that the response of the flame to an oscillating strain is very sensitive to this number. As an application of this methodology, the interaction between a two-dimensional vortex pair and a premixed laminar flame is performed by Direct Numerical Simulation (DNS) using the one- and two-step mechanisms. Comparison with the experimental results of Samaniego et al. (1994) shows a significant improvement in the description of the interaction when the two-step model is used.
Stritzke, P.; Knop, J.; Spielmann, R.P.; Montz, R.; Schneider, C.
1984-01-01
A new method is proposed to determine the locally differing time dependent linear response function h(r,t) of a radioactive tracer injected into a patients blood pool B(t) by mathematical analysis of a dynamic scintigraphic study A(r,t). Transit times, uptake rates and clearance rates of different tracers are calculated from the linear response function at every matrix point by one computer program. The parameters are presented in functional images on a standard computer display. Thus the whole information from a dynamic study can be condensed within a few images. The integral equation A=h+B +c(r)*B (+ means convolution, c(r)*B(t)=nontarget activity) derived from tracer theory is deconvoluted by mathematical methods, which are unsensitive against noise contamination of the input data. The numerical technique is successfully applied in Iodide-123-Hippuran and Tc-99m-DMSA kidney studies, in Tc-99m-MDP and -DPD bone studies, in Tl-201 myocardial studies and in Iodide-123 thyroid studies. Because the regional blood pool-or nontarget activity is calculated and subtracted, the kinetic parameters are considered to be free from nontarget contributions in all dynamic scintigraphic studies. Examples are demonstrated and the usefulness for clinical application is discussed.
Aguirre, Juan S; de Fernando, Gonzalo García; Hierro, Eva; Hospital, Xavier F; Ordóñez, Juan A; Fernández, Manuela
2015-06-01
Quantitative microbial risk assessment requires the knowledge of the effect of food preservation technologies on the growth parameters of the survivors of the treatment. This is of special interest in the case of the new non-thermal technologies that are being investigated for minimal processing of foods. This is a study on the effect of pulsed light technology (PL) on the lag phase of Bacillus cereus spores surviving the treatment and the maximum growth rate (μmax) of the survivors after germination. The D value was estimated as 0.35 J/cm(2) and our findings showed that PL affected the kinetic parameters of the microorganism. A log linear relationship was observed between the lag phase and the intensity of the treatment. Increasing the lethality lengthened the mean lag phase and proportionally increased its variability. A polynomial regression was fitted between the μmax of the survivors and the inactivation achieved. The μmax decreased as intensity increased. From these data, and their comparison to published results on the effect of heat and e-beam irradiation on B. cereus spores, it was observed that the shelf-life of PL treated foods would be longer than those treated with heat and similar to irradiated ones. These findings offer information of interest for the implementation of PL for microbial decontamination in the food industry.
Feitkenhauer, H; Schnicke, S; Müller, R; Märkl, H
2001-12-01
Phenolic compounds are pollutants in many wastewaters, e.g. from crude oil refineries, coal gasification plants or olive oil mills. Phenol removal is a key process for the biodegradation of pollutants at high temperatures because even low concentrations of phenol can inhibit microorganisms severely. Bacillus thermoleovorans sp. A2, a recently isolated thermophilic strain (temperature optimum 65 degrees C), was investigated for its capacity to degrade phenol. The experiments revealed that growth rates were about four times higher than those of mesophilic microorganisms such as Pseudomonas putida. Very high specific growth rates of 2.8 h(-1) were measured at phenol concentrations of 15 mg/l, while at phenol concentrations of 100-500 mg/l growth rates were still in the range of 1 h(-1). The growth kinetics of the thermophilic Bacillus thermoleovorans sp. A2 on phenol as sole carbon and energy source can be described using a three-parameter model developed in enzyme kinetics. The yield coefficient Yx/s of 0.8-1 g cell dry weight/g phenol was considerably higher than cell yields of mesophilic bacteria (Yx/s 0.40-0.52 g cell dry weight/g phenol). The highest growth rate was found at pH 6. Bacillus thermoleovorans sp. A2 was found to be insensitive to hydrodynamic shear stress in stirred bioreactor experiments (despite possible membrane damage caused by phenol) and flourished at an ionic strength of the medium of 0.25(-1) mol/l (equivalent to about 15-60 g NaCl/l). These exceptional properties make Bacillus thermoleovorans sp. A2 an excellent candidate for technical applications.
Alfaro-Cuevas-Villanueva, Ruth; Hidalgo-Vázquez, Aura Roxana; Cortés Penagos, Consuelo de Jesús; Cortés-Martínez, Raúl
2014-01-01
The sorption of cadmium (Cd) and lead (Pb) by calcium alginate beads (CAB) from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4 mg/g and 150.4 mg/g for lead, at 25°C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7. PMID:24587740
NASA Astrophysics Data System (ADS)
Moore, Christopher; Hopkins, Matthew; Moore, Stan; Boerner, Jeremiah; Cartwright, Keith
2015-09-01
Simulation of breakdown is important for understanding and designing a variety of applications such as mitigating undesirable discharge events. Such simulations need to be accurate through early time arc initiation to late time stable arc behavior. Here we examine constraints on the timestep and mesh size required for arc simulations using the particle-in-cell (PIC) method with direct simulation Monte Carlo (DMSC) collisions. Accurate simulation of electron avalanche across a fixed voltage drop and constant neutral density (reduced field of 1000 Td) was found to require a timestep ~ 1/100 of the mean time between collisions and a mesh size ~ 1/25 the mean free path. These constraints are much smaller than the typical PIC-DSMC requirements for timestep and mesh size. Both constraints are related to the fact that charged particles are accelerated by the external field. Thus gradients in the electron energy distribution function can exist at scales smaller than the mean free path and these must be resolved by the mesh size for accurate collision rates. Additionally, the timestep must be small enough that the particle energy change due to the fields be small in order to capture gradients in the cross sections versus energy. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
[Influence of Ca2+ on kinetic parameters of pancreatic acinar mitochondria in situ respiration].
Man'ko, B O; Man'ko, V V
2013-01-01
The dependence of respiration rate of rat permeabilized acinar pancreacytes on oxidative substrates concentration was studied at various [Ca2+] - 10-8-10-6 M. Pancreacytes were permeabilized with 50 microg of digitonin per 1 million cells. Respiration rate was measured polarographically using the Clark electrode at oxidation of succinate or pyruvate either glutamate in the presence of malate. Parameters of Michaelis-Menten equation were calculated by the method of Cornish-Bowden or using Idi-Hofsti coordinates and parameters of Hill equation - using coordinates {v; v/[S]h}. In the studied range of [Ca2+] the kinetic dependence of respiration at pyruvate oxidation is described by the Michaelis-Menten equation, and at oxidation of succinate or glutamate - by Hill equation with h = 1.11-1.43 and 0.50-0.85, respectively. The apparent constant of respiration half-activation (K0.5) did not significantly change in the studied range of [Ca2+] while at 10-7 M Ca2+ it was 0.90 +/- 0.06 mM for succinate, 0.096 +/- 0.007 mM for pyruvate and 0.34 +/- 0.03 mM for glutamate. Maximum respiration rate Vax at pyruvate oxidation increased from 0.077 +/- 0.002 to 0.119 +/- 0.002 and 0.140 +/- 0.002 nmol O2/(s.million cells) due to the increase of [Ca2+] from 10-7 to 5x10-7 or 10-6 M, respectively. At oxidation of succinate or glutamate Ca2+ did not significantly affect Vmax Thus, the increase of [Ca2+] stimulates respiration of mitochondria in situ of acinar pancreacytes at oxidation of exogenous pyruvate (obviously due to pyruvate dehydrogenase activation), but not at succinate or glutamate oxidation.
Chen, Dengyu; Zhou, Jianbin; Zhang, Qisheng
2014-10-01
Effects of heating rate on slow pyrolysis behaviors, kinetic parameters, and products properties of moso bamboo were investigated in this study. Pyrolysis experiments were performed up to 700 °C at heating rates of 5, 10, 20, and 30 °C/min using thermogravimetric analysis (TGA) and a lab-scale fixed bed pyrolysis reactor. The results show that the onset and offset temperatures of the main devolatilization stage of thermogravimetry/derivative thermogravimetry (TG/DTG) curves obviously shift toward the high-temperature range, and the activation energy values increase with increasing heating rate. The heating rate has different effects on the pyrolysis products properties, including biochar (element content, proximate analysis, specific surface area, heating value), bio-oil (water content, chemical composition), and non-condensable gas. The solid yields from the fixed bed pyrolysis reactor are noticeably different from those of TGA mainly because the thermal hysteresis of the sample in the fixed bed pyrolysis reactor is more thorough.
Casoli, P.; Authier, N.; Chapelle, A.
2012-07-01
Several experimental devices are operated by the Criticality and Neutron Science Research Dept. of the CEA Valduc Laboratory. One of these is the Caliban metallic core reactor. The purpose of this study is to develop and perform experiments allowing to determinate some of fundamental kinetic parameters of the reactor. The prompt neutron decay constant and particularly its value at criticality can be measured with reactor noise techniques such as Rossi-{alpha} and Feynman variance-to-mean methods. Subcritical, critical, and even supercritical experiments were performed. Fission chambers detectors were put nearby the core and measurements were analyzed with the Rossi-{alpha} technique. A new value of the prompt neutron decay constant at criticality was determined, which allows, using the Nelson number method, new evaluations of the effective delayed neutron fraction and the in core neutron lifetime. As an introduction of this paper, some motivations of this work are given in part 1. In part 2, principles of the noise measurements experiments performed at the CEA Valduc Laboratory are reminded. The Caliban reactor is described in part 3. Stochastic neutron measurements analysis techniques used in this study are then presented in part 4. Results of fission chamber experiments are summarized in part 5. Part 6 is devoted to the current work, improvement of the experimental device using He 3 neutron detectors and first results obtained with it. Finally, conclusions and perspectives are given in part 7. (authors)
Ghosh, Abir; Bandyopadhyay, Dipankar; Sharma, Ashutosh
2016-09-01
Detachment of a surface from a viscoelastic layer, such as a film of glue, engenders bridges between the surfaces until separation. Such surface instabilities arising during contact and detachment of viscoelastic films with rigid contactors have been theoretically explored by linear stability analysis and nonlinear simulations. The contact instabilities of viscoelastic materials are found to manifest in either a 'critical' or a 'dominant' mode in which the former is preferred when the contactor is slowly brought near the film while the latter manifests when the film is 'hard-pressed' against it. The nonlinear analysis considers the movement of contactor during adhesion-debonding cycle, which uncovers that the kinetic parameters can overshadow the thermodynamically predicted area of contact, average force for pull-off, energy of contactor-film separation, and pathways of debonding. Three distinct pathways of debonding - peeling, catastrophic column collapse, and column coalescence, are found to manifest with the variation in the ratio of the elastic to viscous compliances of the viscoelastic film. The study also reveals that in the dominant mode of instability, a smaller length scale with a larger area contact between the contactor and film can develop patterns having aspect ratio ∼10 times larger than the same obtained from elastic film. PMID:27254253
Kinetic parameters and tissue distribution of 5-oxo-L-prolinase determined by a fluorimetric assay.
Weber, P; Jäger, M; Bangsow, T; Knell, G; Piechaczek, K; Koch, J; Wolf, S
1999-01-13
5-Oxo-L-prolinase (5-OPase) catalyses the hydrolysis of 5-oxo-L-proline to glutamate with concomitant stoichiometric cleavage of ATP to ADP, a reaction which is known to be part of the gamma-glutamyl cycle-an interrelated series of reactions involved in the synthesis and metabolism of glutathione. As recent studies indicate, this cyclic pathway plays a crucial role in the regulation of amino acid transport. Apparently, the intermediate product 5-oxo-L-proline functions as a second messenger molecule that upregulates the activity of certain amino acid transport systems. Thus, the degradation of 5-oxo-L-proline by 5-OPase leads to the downregulation of this stimulus. In this study, a new sensitive fluorimetric assay for 5-OPase activity was established which is based on the derivatization of glutamate with o-phthaldialdehyde in the presence of thiols and subsequent separation of the products by HPLC. The method is suitable for the screening of chromatography fractions as well as for the determination of the kinetic parameters Km and Vmax of purified 5-OPase. Additionally, it can be used for the measurement of enzyme activity in crude cell extracts and evaluation of tissue distribution.
Kleindienst, F I; Michel, K J; Schwarz, J; Krabbe, B
2006-03-01
Based on a higher cardio-pulmonary and cardio-vascular benefit and a promised reduction of mechanical load of the musculoskeletal system Nordic Walking (NW) shows an increased market potential. The present study should investigate whether there are biomechanical differences between the locomotion patterns NW, walking and running. Moreover possible resultant load differences should be determined. Eleven subjects, who were already experienced with the NW-technique, participated in this experiment. The kinematic data were collected using two high-speed camera systems from posterior and from lateral at the same time. Simultaneously the ground reaction forces were recorded. The kinematic and the kinetic data reveal differences between the three analyzed locomotion patterns. For NW as well as walking the mechanical load of the lower extremity is lower compared to running. None of the kinematic parameters suggest a "physiological benefit" of NW compared to walking. Moreover NW shows higher vertical and horizontal forces during landing. Exclusively the lower vertical force peak during push off indicates a lower mechanical load for NW in comparison to walking. Consequently it is questionable is NW -- based on its promised "biomechanical benefits" compared to walking -- should be still recommended for overweight people and for people with existing musculoskeletal problems of the lower limb.
Ferreira, Antonio César Silva; de Pinho, Paula Guedes; Rodrigues, Paula; Hogg, Timothy
2002-10-01
The negative effects of oxygen on white wine quality and the various factors which influence it (including temperature, dissolved oxygen, pH, and free SO(2)) are well documented both at the sensory and compositional levels. What is less defined is the quantitative relationship between these parameters and the kinetics of the development of the negative effects of oxidation. The experiment presented here attempts to generate data which can be used to predictively model the oxidative degradation of white wines. Bottled wines were submitted to extreme conditions (45 degrees C temperature, O(2) saturation) during 3 months witth samples taken every 15 days for both sensorial and chemical analysis (GC-O/FPD/MS, 420 nm). The synergistic effects of increasing temperature and O(2) at lower pH are evident, both on the decrease in levels of terpene alcohols and norisoprenoids (which impart floral aromas), and on the development of off-flavors such as "honey-like", "boiled-potato", and "farm-feed" associated with the presence of phenylacetaldehyde, methional, and 1,1,6-trimethyl-1,2-dihydronaphthalene. PMID:12358460
Hu, Qinghai; Xiao, Zhongjin; Xiong, Xinmei; Zhou, Gongming; Guan, Xiaohong
2015-01-01
Although surface complexation models have been widely used to describe the adsorption of heavy metals, few studies have verified the feasibility of modeling the adsorption kinetics, edge, and isotherm data with one pH-independent parameter. A close inspection of the derivation process of Langmuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model, KS-kinetic, is theoretically equivalent to the adsorption constant in Langmuir isotherm, KS-Langmuir. The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed. The MLK model was employed to simulate the adsorption kinetics of Cu(II), Co(II), Cd(II), Zn(II) and Ni(II) on MnO2 at pH3.2 or 3.3 to get the values of KS-kinetic. The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model), and the values of KS-Langmuir were obtained. The values of KS-kinetic and KS-Langmuir are very close to each other, validating that the constants obtained by these two methods are basically the same. The MMP model with KS-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations. Moreover, the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the KS-kinetic constants.
ERIC Educational Resources Information Center
Salvador, F.; And Others
1984-01-01
Describes a method which adapts itself to the characteristics of the kinetics of a chemical reaction in solution, enabling students to determine the Arrhenius parameters with satisfactory accuracy by means of a single non-isothermic experiment. Both activation energy and the preexponential factor values can be obtained by the method. (JN)
NASA Astrophysics Data System (ADS)
Brawand, Nicholas; Vörös, Márton; Govoni, Marco; Galli, Giulia
The accurate prediction of optoelectronic properties of molecules and solids is a persisting challenge for current density functional theory (DFT) based methods. We propose a hybrid functional where the mixing fraction of exact and local exchange is determined by a non-empirical, system dependent function. This functional yields ionization potentials, fundamental and optical gaps of many, diverse systems in excellent agreement with experiments, including organic and inorganic molecules and nanocrystals. We further demonstrate that the newly defined hybrid functional gives the correct alignment between the energy level of the exemplary TTF-TCNQ donor-acceptor system. DOE-BES: DE-FG02-06ER46262.
Ismail, L F M; Emara, M M; El-Moselhy, M M; Maziad, N A; Hussein, O K
2014-10-15
Silica-coating ZnO nanoparticles were prepared using the hydrothermal method. The prepared nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray Spectroscopy (EDX). It was found that ultrafine core/shell structured silica-coating ZnO nanoparticles were successfully obtained. TEM analysis revealed a continuous and uniform silica coating layer of about 8nm in thickness on the surface of ZnO nanoparticles. The photocatalytic performance of silica-coating ZnO core/shell nanoparticles in methylene blue aqueous solution was investigated. The effects of some operational parameters such as pH value, nanocatalyst loading and initial MB concentration on the degradation efficiency were discussed. Kinetic parameters were experimentally determined and a pseudo-first-order kinetic was observed. Thus, the main advantage of the coating is the stability of the photocatalysts and the better performance in acidic or alkaline solutions. Compared to ZnO the maximum apparent rate constant is obtained at pH 8.5 (pH 11.5 in case of bare ZnO). Moreover, the Langmuir adsorption model was applied to describe the equilibrium isotherm at different MB concentration. The applicability of the Langmuir isotherm suggests monolayer coverage of the MB onto surface of silica-coating ZnO nanoparticles. The kinetics of the adsorption with respect to the initial dye concentration, were also investigated. The pseudo-first-order and second-order kinetic models were used and the rate constants were evaluated. The kinetic studies revealed that the pseudo-second-order kinetic model better represented the adsorption kinetics, suggesting that the adsorption process may be chemisorption.
Sorption of selenate on soils and pure phases: kinetic parameters and stabilisation.
Loffredo, N; Mounier, S; Thiry, Y; Coppin, F
2011-09-01
This study was conducted to identify the principle selenate carrier phases for two selected soils, by comparing their reactivity with selenate to that of pure phases of the solids. Silica, calcium carbonate, aluminium hydroxide, goethite, bentonite and humic acid were selected as the main soil carrier phases. Comparisons were made first on the parameter values obtained with the best fit of a kinetic sorption model which can discriminate instantaneous sorption from kinetically limited sorption. Then comparisons were made of the ability for each solid to stabilise selenate by measuring the ratio of the partition coefficient for sorption (Kd(sorption)) over that of the desorption (Kd(desorption)). Kinetics and stabilisation were used to help elucidate the nature of interactions with the test solid phases for a large range of selenate concentrations. The experiments were conducted over 165 h in batch reactors, the solid being isolated from the solution by dialysis tubing, at two pH (5.4 and 8) and three selenate concentrations (1 × 10(-3), 1 × 10(-6) and 1 × 10(-8) mol L(-1)). The results obtained showed that only aluminium hydroxide can sorb selenate throughout the studied pH range (pH 5.4 to 8.0). The sorption capacity on this mineral was high (Kd(sorption) > 100 to 1 × 10(4) L kg(-1)) and the selenate was mainly stabilized by the formation of inner sphere complexes. The sorption on goethite occurred at pH 5.4 (Kd(sorption) 52 L kg(-1)), mainly as outer sphere complexes, and was null at pH 8. On silica, a weak sorption was observed only at pH 5.4 and at 165 h (Kd(sorption) 4 L kg(-1)). On bentonite, calcium carbonate and humic acid no significant sorption was observed. Concerning the two soils studied, different behaviours were observed for selenate. For soil Ro (pH 5.4), Kd(sorption) was low (8 L kg(-1)) compared to soil Bu (pH 8) (70 L kg(-1)). The sorption behaviour of selenate on soil Ro was mainly due to outer sphere complexes, as for
NASA Astrophysics Data System (ADS)
Choi, Hon-Chit; Wen, Lingfeng; Eberl, Stefan; Feng, Dagan
2006-03-01
Dynamic Single Photon Emission Computed Tomography (SPECT) has the potential to quantitatively estimate physiological parameters by fitting compartment models to the tracer kinetics. The generalized linear least square method (GLLS) is an efficient method to estimate unbiased kinetic parameters and parametric images. However, due to the low sensitivity of SPECT, noisy data can cause voxel-wise parameter estimation by GLLS to fail. Fuzzy C-Mean (FCM) clustering and modified FCM, which also utilizes information from the immediate neighboring voxels, are proposed to improve the voxel-wise parameter estimation of GLLS. Monte Carlo simulations were performed to generate dynamic SPECT data with different noise levels and processed by general and modified FCM clustering. Parametric images were estimated by Logan and Yokoi graphical analysis and GLLS. The influx rate (K I), volume of distribution (V d) were estimated for the cerebellum, thalamus and frontal cortex. Our results show that (1) FCM reduces the bias and improves the reliability of parameter estimates for noisy data, (2) GLLS provides estimates of micro parameters (K I-k 4) as well as macro parameters, such as volume of distribution (Vd) and binding potential (BP I & BP II) and (3) FCM clustering incorporating neighboring voxel information does not improve the parameter estimates, but improves noise in the parametric images. These findings indicated that it is desirable for pre-segmentation with traditional FCM clustering to generate voxel-wise parametric images with GLLS from dynamic SPECT data.
Ozcan, Adnan; Ozcan, A Safa; Tunali, Sibel; Akar, Tamer; Kiran, Ismail
2005-09-30
Adsorption of copper ions onto Capsicum annuum (red pepper) seeds was investigated with the variation in the parameters of pH, contact time, adsorbent and copper(II) concentrations and temperature. The nature of the possible adsorbent and metal ion interactions was examined by the FTIR technique. The copper(II) adsorption equilibrium was attained within 60 min. Adsorption of copper(II) ions onto C. annuum seeds followed by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Maximum adsorption capacity (q(max)) of copper(II) ions onto red pepper seeds was 4.47x10(-4) molg(-1) at 50 degrees C. Three kinetic models including the pseudo-first-order, pseudo-second-order and intraparticle diffusion equations were selected to follow the adsorption process. Kinetic parameters such as rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was indicated that the adsorption of copper(II) ions onto C. annuum seeds could be described by the pseudo-second-order kinetic model and also followed the intraparticle diffusion model up to 60 min, but diffusion is not only the rate controlling step. Thermodynamics parameters such as the change of free energy, enthalpy and entropy were also evaluated for the adsorption of copper(II) ions onto C. annuum seeds.
Ghadermarzi, M; Moosavi-Movahedi, A A
1999-04-12
The effects of cyanide and azide ions (class A), sodium-n-dodecyl sulphate (SDS) and 2-mercaptoethanol (class B), 3-aminotriazole (class C) and NADPH (class D) on the initial activity (ai), inactivation rate constant (ki) and the partition ratio (r) of bovine liver catalase reaction with its suicide substrate, hydrogen peroxide, were studied in 50 mM sodium phosphate buffer, pH 7.0 at 27 degrees C. The above kinetic parameters were determined by processing the progress curve data. In class A, which contains fast and reversible inhibitors of catalase, a proportional decrease in ai and ki was observed by inhibitors, so that the r remained constant. In class B, which contains slow and irreversible inactivators, a decrease in ai and constancy of ki and r were observed when catalase was incubated in the presence of such inactivators for a determined time. In class C, containing effector which can combine with intermediate compound I, ai was relatively unchanged but an increase in ki and a decrease in r were observed. In class D, containing effector which reduces compound I to ferricatalase, ai was not affected significantly but some decrease in ki was detected which was linked with an increase in r. These results demonstrate that different classes of effectors affect the determined kinetic parameters of catalase in various ways. Thus, determination of such parameters by simple kinetic experiments can be carried out for classification of the agents which have an effect on the kinetics of catalase. PMID:10209276
Kinetic parameters for nutrient enhanced crude oil biodegradation in intertidal marine sediments
Singh, Arvind K.; Sherry, Angela; Gray, Neil D.; Jones, D. Martin; Bowler, Bernard F. J.; Head, Ian M.
2014-01-01
Availability of inorganic nutrients, particularly nitrogen and phosphorous, is often a primary control on crude oil hydrocarbon degradation in marine systems. Many studies have empirically determined optimum levels of inorganic N and P for stimulation of hydrocarbon degradation. Nevertheless, there is a paucity of information on fundamental kinetic parameters for nutrient enhanced crude oil biodegradation that can be used to model the fate of crude oil in bioremediation programmes that use inorganic nutrient addition to stimulate oil biodegradation. Here we report fundamental kinetic parameters (Ks and qmax) for nitrate- and phosphate-stimulated crude oil biodegradation under nutrient limited conditions and with respect to crude oil, under conditions where N and P are not limiting. In the marine sediments studied, crude oil degradation was limited by both N and P availability. In sediments treated with 12.5 mg/g of oil but with no addition of N and P, hydrocarbon degradation rates, assessed on the basis of CO2 production, were 1.10 ± 0.03 μmol CO2/g wet sediment/day which were comparable to rates of CO2 production in sediments to which no oil was added (1.05 ± 0.27 μmol CO2/g wet sediment/day). When inorganic nitrogen was added alone maximum rates of CO2 production measured were 4.25 ± 0.91 μmol CO2/g wet sediment/day. However, when the same levels of inorganic nitrogen were added in the presence of 0.5% P w/w of oil (1.6 μmol P/g wet sediment) maximum rates of measured CO2 production increased more than four-fold to 18.40 ± 1.04 μmol CO2/g wet sediment/day. Ks and qmax estimates for inorganic N (in the form of sodium nitrate) when P was not limiting were 1.99 ± 0.86 μmol/g wet sediment and 16.16 ± 1.28 μmol CO2/g wet sediment/day respectively. The corresponding values for P were 63 ± 95 nmol/g wet sediment and 12.05 ± 1.31 μmol CO2/g wet sediment/day. The qmax values with respect to N and P were not significantly different (P < 0.05). When N and P
Petric, Ivan; Helić, Azra; Avdić, Edisa Avdihodžić
2012-08-01
This study aimed to monitor the process parameters and to determine kinetics in composting of organic fraction of municipal solid waste (OFMSW) and poultry manure. The experiments were carried out with three different mixtures. The results showed that the mixture 60% OFMSW, 20% poultry manure, 10% mature compost and 10% sawdust provided the most appropriate conditions for composting process. Using nine kinetic models and nonlinear regression method, kinetic parameters were estimated and the models were analyzed with four statistical indicators. Kinetic models with four measured variables proved to be better than models with less number of measured variables. The number of measured experimental variables influences kinetics more than the number of kinetic parameters. Satisfactory fittings of proposed kinetic model to the experimental data of OM were achieved. The model is more suitable for data obtained from composting of mixtures with much higher percentage of OFMSW than percentage of poultry manure. PMID:22609720
Jiang, Bin; Guo, Hua
2016-08-01
In search for an accurate description of the dissociative chemisorption of water on the Ni(111) surface, we report a new nine-dimensional potential energy surface (PES) based on a large number of density functional theory points using the RPBE functional. Seven-dimensional quantum dynamical calculations have been carried out on the RPBE PES, followed by site averaging and lattice effect corrections, yielding sticking probabilities that are compared with both the previous theoretical results based on a PW91 PES and experiment. It is shown that the RPBE functional increases the reaction barrier, but has otherwise a minor impact on the PES topography. Better agreement with experimental results is obtained with the new PES, but the agreement is still not quantitative. Possible sources of the remaining discrepancies are discussed.
NASA Astrophysics Data System (ADS)
Fonseca, Rodney W.; Pfefferkorn, Lisa L.; Holcombe, James A.
1994-12-01
Three of the methods available for the determination of kinetic parameters for atom formation in ETAAS were compared. In the approach of mcnally and holcombe [ Anal. Chem. 59, 1015 (1987)], Arrhenius-type plots are used to extract activation energy values while an approximation of the order of release is obtained by studying the alignment of the absorption maxima at increasing analyte concentrations. In the method of rojas and olivares [ Spectrochim. Acta47B, 387 (1992)], plots are prepared for different orders of release, with the correct order yielding a longer linear region from whose slope the activation energy is calculated. The method of yan et al. [ Spectrochim. Acta48B, 605 (1993)] uses a single absorption profile for the calculations. Activation energy and the order of release are obtained from the slope and intercept, respectively, on their graph. All three methods assume linear heating rate, constant activation energies, and furnace isothermality. The methods were tested with the same experimental data sets for Cu, Au and Ni using a spatially isothermal cuvette. Since intensive mathematical treatments commonly have deleterious effects on the uncertainty of the final result, the methods were compared using both the original data and a smoothed version of it. In general, the three methods yielded comparable results for the metals studied. However, choosing the most linear plot to determine the correct order of release when using Rojas and Olivares' method was sometimes subjective, and McNally and Holcombe's method provided only estimates for the orders of release that were neither zero nor unity.
[The kinetic parameters of retainment and release of deposited in human tissue structures calcium].
Ermakova, I P; Potanina, T V; Pronchenko, I A; Larina, I M; Sevast'ianov, V I
2014-11-01
The analysis of retainment and release kinetics of deposited in tissue structures calcium was made in the hypercalcemic conditions in 28 healthy volunteers (22 males and 6 females) of the age of 33 ± 6.5 years via drip infusion (Groups 1, 2) and in 9 individuals (3 males and 6 females) in 12 trials via stream infusion (Group 3). By the end of each hour after the termination of calcium infusion the amount of calcium retained in tissues was calculated (Mtis./kg); the parameters of its binding (specific buffer volume--β3 sp, association constant--Ka, number of binding centers--n) were established using the Langmuir and Scetchard coordinates. The Group 1 volunteers (n = = 12) showed a section of positive cooperativity (a direct regression on Sketchard coordinates, Hill coefficient 3.36 ± 1.63) and 2 sections of the consecutive calcium separation from one set of noninteracting centers. 5 volunteers of Group 2 and 8 volunteers of Group 3 demonstrated a slight calcium delivery to tissues after 1 hour of observation which then followed for 2 volunteers of Group 2 and for 2 volunteers of Group 3. Other volunteers of Groups 2 and 3 showed a release of tissue-deposited calcium via the mechanism of the consecutive separation from one set of noninteracting centers with βsp 3 times less and Ka 7 times higher than with the calcium infusion. The excretion of calcium in urine was the highest in Group 1 and the lowest in Group 3. The [Ca2+] and Mtis./kg values were normalized in Groups 1 and 2 the next morning and in Group 3 after 2-3 hours of observation. An assumption was made about the relationship between the tissue and kidney [Ca2+] normalizing mechanisms with hypercalcemia.
Palandri, James L.; Kharaka, Yousif K.
2004-01-01
Geochemical reaction path modeling is useful for rapidly assessing the extent of water-aqueous-gas interactions both in natural systems and in industrial processes. Modeling of some systems, such as those at low temperature with relatively high hydrologic flow rates, or those perturbed by the subsurface injection of industrial waste such as CO2 or H2S, must account for the relatively slow kinetics of mineral-gas-water interactions. We have therefore compiled parameters conforming to a general Arrhenius-type rate equation, for over 70 minerals, including phases from all the major classes of silicates, most carbonates, and many other non-silicates. The compiled dissolution rate constants range from -0.21 log moles m-2 s-1 for halite, to -17.44 log moles m-2 s-1 for kyanite, for conditions far from equilibrium, at 25 ?C, and pH near neutral. These data have been added to a computer code that simulates an infinitely well-stirred batch reactor, allowing computation of mass transfer as a function of time. Actual equilibration rates are expected to be much slower than those predicted by the selected computer code, primarily because actual geochemical processes commonly involve flow through porous or fractured media, wherein the development of concentration gradients in the aqueous phase near mineral surfaces, which results in decreased absolute chemical affinity and slower reaction rates. Further differences between observed and computed reaction rates may occur because of variables beyond the scope of most geochemical simulators, such as variation in grain size, aquifer heterogeneity, preferred fluid flow paths, primary and secondary mineral coatings, and secondary minerals that may lead to decreased porosity and clogged pore throats.
Kinetic parameter estimation in N. europaea biofilms using a 2-D reactive transport model.
Lauchnor, Ellen G; Semprini, Lewis; Wood, Brian D
2015-06-01
Biofilms of the ammonia oxidizing bacterium Nitrosomonas europaea were cultivated to study microbial processes associated with ammonia oxidation in pure culture. We explored the hypothesis that the kinetic parameters of ammonia oxidation in N. europaea biofilms were in the range of those determined with batch suspended cells. Oxygen and pH microelectrodes were used to measure dissolved oxygen (DO) concentrations and pH above and inside biofilms and reactive transport modeling was performed to simulate the measured DO and pH profiles. A two dimensional (2-D) model was used to simulate advection parallel to the biofilm surface and diffusion through the overlying fluid while reaction and diffusion were simulated in the biofilm. Three experimental studies of microsensor measurements were performed with biofilms: i) NH3 concentrations near the Ksn value of 40 μM determined in suspended cell tests ii) Limited buffering capacity which resulted in a pH gradient within the biofilms and iii) NH3 concentrations well below the Ksn value. Very good fits to the DO concentration profiles both in the fluid above and in the biofilms were achieved using the 2-D model. The modeling study revealed that the half-saturation coefficient for NH3 in N. europaea biofilms was close to the value measured in suspended cells. However, the third study of biofilms with low availability of NH3 deviated from the model prediction. The model also predicted shifts in the DO profiles and the gradient in pH that resulted for the case of limited buffering capacity. The results illustrate the importance of incorporating both key transport and chemical processes in a biofilm reactive transport model.
Piron, E. |; Accominotti, M.; Domard, A.
1997-03-19
This work corresponds to the first part of our studies on the interactions between chitosan particles dispersed in water and uranyl ions. The measurements were obtained by ICP, and we considered the role of various physical and physicochemical parameters related to chitosan. We showed that the crystallinity, the particle dimensions, and the swelling in water of chitosan are parameters which are connected together and govern the kinetic laws of metal diffusion and sorption. The molecular mobility of the polymer chains is then essential parameter. 31 refs., 5 figs., 3 tabs.
NASA Astrophysics Data System (ADS)
Marin, Andrew T.; Musselman, Kevin P.; MacManus-Driscoll, Judith L.
2013-04-01
This work shows that when a Schottky barrier is present in a photovoltaic device, such as in a device with an ITO/ZnO contact, equivalent circuit analysis must be performed with admittance spectroscopy to accurately determine the pn junction interface recombination parameters (i.e., capture cross section and density of trap states). Without equivalent circuit analysis, a Schottky barrier can produce an error of ˜4-orders of magnitude in the capture cross section and ˜50% error in the measured density of trap states. Using a solution processed ZnO/Cu2O photovoltaic test system, we apply our analysis to clearly separate the contributions of interface states at the pn junction from the Schottky barrier at the ITO/ZnO contact so that the interface state recombination parameters can be accurately characterized. This work is widely applicable to the multitude of photovoltaic devices, which use ZnO adjacent to ITO.
Investigation of thermoluminescence and kinetic parameters of CaMgB2O5: Dy3+ nanophosphor
NASA Astrophysics Data System (ADS)
Manhas, M.; Kumar, Vinay; Ntwaeaborwa, O. M.; Swart, H. C.
2016-05-01
In this paper, thermoluminescence (TL) properties of Dy3+ (1.5 mol %) doped CaMgB2O5 nanophosphor after being exposed to ultraviolet (UV) radiations (λ=254nm) were investigated. In UV exposed samples, the thermoluminescence glow curve consists of a broad glow peak located at 380 K with a small shoulder at 507 K. A shift in glow peak temperature from 367 K to 380 K after the UV exposure for 80 min was observed, which clearly shows that glow peaks follow the second order kinetics. The TL intensity of the peaks increases with an increase in the exposure time of UV rays (10-180 min). The TL Anal program was used to analyze the glow curve. The kinetic parameters such as activation energy (E), the frequency factor (s) and the order of kinetics (b) were calculated for CaMgB2O5: Dy3+ nanophosphors.
Sheets, Alison L; Corazza, Stefano; Andriacchi, Thomas P
2010-01-01
Accurate subject-specific body segment parameters (BSPs) are necessary to perform kinetic analyses of human movements with large accelerations, or no external contact forces or moments. A new automated topographical image-based method of estimating segment mass, center of mass (CM) position, and moments of inertia is presented. Body geometry and volume were measured using a laser scanner, then an automated pose and shape registration algorithm segmented the scanned body surface, and identified joint center (JC) positions. Assuming the constant segment densities of Dempster, thigh and shank masses, CM locations, and moments of inertia were estimated for four male subjects with body mass indexes (BMIs) of 19.7-38.2. The subject-specific BSP were compared with those determined using Dempster and Clauser regression equations. The influence of BSP and BMI differences on knee and hip net forces and moments during a running swing phase were quantified for the subjects with the smallest and largest BMIs. Subject-specific BSP for 15 body segments were quickly calculated using the image-based method, and total subject masses were overestimated by 1.7-2.9%.When compared with the Dempster and Clauser methods, image-based and regression estimated thigh BSP varied more than the shank parameters. Thigh masses and hip JC to thigh CM distances were consistently larger, and each transverse moment of inertia was smaller using the image-based method. Because the shank had larger linear and angular accelerations than the thigh during the running swing phase, shank BSP differences had a larger effect on calculated intersegmental forces and moments at the knee joint than thigh BSP differences did at the hip. It was the net knee kinetic differences caused by the shank BSP differences that were the largest contributors to the hip variations. Finally, BSP differences produced larger kinetic differences for the subject with larger segment masses, suggesting that parameter accuracy is more
Sheets, Alison L; Corazza, Stefano; Andriacchi, Thomas P
2010-01-01
Accurate subject-specific body segment parameters (BSPs) are necessary to perform kinetic analyses of human movements with large accelerations, or no external contact forces or moments. A new automated topographical image-based method of estimating segment mass, center of mass (CM) position, and moments of inertia is presented. Body geometry and volume were measured using a laser scanner, then an automated pose and shape registration algorithm segmented the scanned body surface, and identified joint center (JC) positions. Assuming the constant segment densities of Dempster, thigh and shank masses, CM locations, and moments of inertia were estimated for four male subjects with body mass indexes (BMIs) of 19.7-38.2. The subject-specific BSP were compared with those determined using Dempster and Clauser regression equations. The influence of BSP and BMI differences on knee and hip net forces and moments during a running swing phase were quantified for the subjects with the smallest and largest BMIs. Subject-specific BSP for 15 body segments were quickly calculated using the image-based method, and total subject masses were overestimated by 1.7-2.9%.When compared with the Dempster and Clauser methods, image-based and regression estimated thigh BSP varied more than the shank parameters. Thigh masses and hip JC to thigh CM distances were consistently larger, and each transverse moment of inertia was smaller using the image-based method. Because the shank had larger linear and angular accelerations than the thigh during the running swing phase, shank BSP differences had a larger effect on calculated intersegmental forces and moments at the knee joint than thigh BSP differences did at the hip. It was the net knee kinetic differences caused by the shank BSP differences that were the largest contributors to the hip variations. Finally, BSP differences produced larger kinetic differences for the subject with larger segment masses, suggesting that parameter accuracy is more
NASA Astrophysics Data System (ADS)
Schiemann, Martin; Geier, Manfred; Shaddix, Christopher R.; Vorobiev, Nikita; Scherer, Viktor
2014-07-01
In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption kinetics. The performance of the specialized systems is compared for two different combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles' burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%-30% are recommended for kinetic rate measurements on 100 μm particles.
Schiemann, Martin; Geier, Manfred; Shaddix, Christopher R; Vorobiev, Nikita; Scherer, Viktor
2014-07-01
In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption kinetics. The performance of the specialized systems is compared for two different combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles' burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%-30% are recommended for kinetic rate measurements on 100 μm particles.
Schiemann, Martin; Geier, Manfred; Shaddix, Christopher R; Vorobiev, Nikita; Scherer, Viktor
2014-07-01
In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption kinetics. The performance of the specialized systems is compared for two different combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles' burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%-30% are recommended for kinetic rate measurements on 100 μm particles. PMID:25085180
NASA Astrophysics Data System (ADS)
Tao, Liang; Xinzhang, Jia; Junfeng, Chen
2009-11-01
Techniques for constructing metamodels of device parameters at BSIM3v3 level accuracy are presented to improve knowledge-based circuit sizing optimization. Based on the analysis of the prediction error of analytical performance expressions, operating point driven (OPD) metamodels of MOSFETs are introduced to capture the circuit's characteristics precisely. In the algorithm of metamodel construction, radial basis functions are adopted to interpolate the scattered multivariate data obtained from a well tailored data sampling scheme designed for MOSFETs. The OPD metamodels can be used to automatically bias the circuit at a specific DC operating point. Analytical-based performance expressions composed by the OPD metamodels show obvious improvement for most small-signal performances compared with simulation-based models. Both operating-point variables and transistor dimensions can be optimized in our nesting-loop optimization formulation to maximize design flexibility. The method is successfully applied to a low-voltage low-power amplifier.
NASA Astrophysics Data System (ADS)
Roy Choudhury, Raja; Roy Choudhury, Arundhati; Kanti Ghose, Mrinal
2013-01-01
A semi-analytical model with three optimizing parameters and a novel non-Gaussian function as the fundamental modal field solution has been proposed to arrive at an accurate solution to predict various propagation parameters of graded-index fibers with less computational burden than numerical methods. In our semi analytical formulation the optimization of core parameter U which is usually uncertain, noisy or even discontinuous, is being calculated by Nelder-Mead method of nonlinear unconstrained minimizations as it is an efficient and compact direct search method and does not need any derivative information. Three optimizing parameters are included in the formulation of fundamental modal field of an optical fiber to make it more flexible and accurate than other available approximations. Employing variational technique, Petermann I and II spot sizes have been evaluated for triangular and trapezoidal-index fibers with the proposed fundamental modal field. It has been demonstrated that, the results of the proposed solution identically match with the numerical results over a wide range of normalized frequencies. This approximation can also be used in the study of doped and nonlinear fiber amplifier.
2012-01-01
Background Compared with static imaging, dynamic emission computed tomographic imaging with compartment modeling can quantify in vivo physiologic processes, providing useful information about molecular disease processes. Dynamic imaging involves estimation of kinetic rate parameters. For multi-compartment models, kinetic parameter estimation can be computationally demanding and problematic with local minima. Methods This paper offers a new perspective to the compartment model fitting problem where Fourier linear system theory is applied to derive closed-form formulas for estimating kinetic parameters for the two-compartment model. The proposed Fourier domain estimation method provides a unique solution, and offers very different noise response as compared to traditional non-linear chi-squared minimization techniques. Results The unique feature of the proposed Fourier domain method is that only low frequency components are used for kinetic parameter estimation, where the DC (i.e., the zero frequency) component in the data is treated as the most important information, and high frequency components that tend to be corrupted by statistical noise are discarded. Computer simulations show that the proposed method is robust without having to specify the initial condition. The resultant solution can be fine tuned using the traditional iterative method. Conclusions The proposed Fourier-domain estimation method has closed-form formulas. The proposed Fourier-domain curve-fitting method does not require an initial condition, it minimizes a quadratic objective function and a closed-form solution can be obtained. The noise is easier to control, simply by discarding the high frequency components, and emphasizing the DC component. PMID:22995548
NASA Astrophysics Data System (ADS)
Ryu, Jaiyoung; Hu, Xiao; Shadden, Shawn C.
2014-11-01
The cerebral circulation is unique in its ability to maintain blood flow to the brain under widely varying physiologic conditions. Incorporating this autoregulatory response is critical to cerebral blood flow modeling, as well as investigations into pathological conditions. We discuss a one-dimensional nonlinear model of blood flow in the cerebral arteries that includes coupling of autoregulatory lumped parameter networks. The model is tested to reproduce a common clinical test to assess autoregulatory function - the carotid artery compression test. The change in the flow velocity at the middle cerebral artery (MCA) during carotid compression and release demonstrated strong agreement with published measurements. The model is then used to investigate vasospasm of the MCA, a common clinical concern following subarachnoid hemorrhage. Vasospasm was modeled by prescribing vessel area reduction in the middle portion of the MCA. Our model showed similar increases in velocity for moderate vasospasms, however, for serious vasospasm (~ 90% area reduction), the blood flow velocity demonstrated decrease due to blood flow rerouting. This demonstrates a potentially important phenomenon, which otherwise would lead to false-negative decisions on clinical vasospasm if not properly anticipated.
Van Wey, A S; Cookson, A L; Roy, N C; McNabb, W C; Soboleva, T K; Shorten, P R
2014-11-17
Microorganisms rarely live in isolation but are most often found in a consortium. This provides the potential for cross-feeding and nutrient competition among the microbial species, which make it challenging to predict the growth kinetics in coculture. In this paper we developed a mathematical model to describe substrate consumption and subsequent microbial growth and metabolite production for bacteria grown in monoculture. The model characterized substrate utilization kinetics of 18 Bifidobacterium strains. Some bifidobacterial strains demonstrated preferential degradation of oligofructose in that sugars with low degree of polymerization (DP) (DP≤3 or 4) were metabolized before sugars of higher DP, or vice versa. Thus, we expanded the model to describe the preferential degradation of oligofructose. In addition, we adapted the model to describe the competition between human colonic bacteria Bacteroides thetaiotaomicron LMG 11262 and Bifidobacterium longum LMG 11047 or Bifidobacterium breve Yakult for inulin as well as cross-feeding of breakdown products from the extracellular hydrolysis of inulin by B. thetaiotaomicron LMG 11262. We found that the coculture growth kinetics could be predicted based on the respective monoculture growth kinetics. Using growth kinetics from monoculture experiments to predict coculture dynamics will reduce the number of in vitro experiments required to parameterize multi-culture models.
Remane, Y; Leopold, C S
2006-01-01
The time of erythema onset may be used as a response parameter for quantification of the cutaneous erythema response induced by methyl nicotinate. The vehicles light mineral oil (LMO; test) and medium chain triglycerides (MCT; standard) were compared with regard to the pharmacodynamic response. Moreover, the influence of penetration enhancers on the time of erythema onset was investigated under zero order penetration kinetics. The enhancers dimethyl sulfoxide, diethylene glycol monoethyl ether and three different glycerides in different concentrations were added to MCT as a standard vehicle. All preparations were applied to the forearms of volunteers under infinite dose conditions at different thermodynamic drug activity levels (0.2-3.2% of the saturation level) and different drug concentrations (0.051-0.816%), respectively. Different penetration kinetics do not influence data of erythema onset, as these data are comparable to those obtained under finite dose conditions (first order penetration kinetics). With regard to the penetration enhancers, a significantly enhanced penetration of methyl nicotinate could be observed only for diethylene glycol monoethyl ether and dimethyl sulfoxide. However, no significant difference between light mineral oil and MCT could be found with regard to penetration enhancement. The time of erythema onset is an easy and efficient parameter for quantification of the pharmacodynamic response caused by nicotinates.
Rüdt, Matthias; Gillet, Florian; Heege, Stefanie; Hitzler, Julian; Kalbfuss, Bernd; Guélat, Bertrand
2015-09-25
Application of model-based design is appealing to support the development of protein chromatography in the biopharmaceutical industry. However, the required efforts for parameter estimation are frequently perceived as time-consuming and expensive. In order to speed-up this work, a new parameter estimation approach for modelling ion-exchange chromatography in linear conditions was developed. It aims at reducing the time and protein demand for the model calibration. The method combines the estimation of kinetic and thermodynamic parameters based on the simultaneous variation of the gradient slope and the residence time in a set of five linear gradient elutions. The parameters are estimated from a Yamamoto plot and a gradient-adjusted Van Deemter plot. The combined approach increases the information extracted per experiment compared to the individual methods. As a proof of concept, the combined approach was successfully applied for a monoclonal antibody on a cation-exchanger and for a Fc-fusion protein on an anion-exchange resin. The individual parameter estimations for the mAb confirmed that the new approach maintained the accuracy of the usual Yamamoto and Van Deemter plots. In the second case, offline size-exclusion chromatography was performed in order to estimate the thermodynamic parameters of an impurity (high molecular weight species) simultaneously with the main product. Finally, the parameters obtained from the combined approach were used in a lumped kinetic model to simulate the chromatography runs. The simulated chromatograms obtained for a wide range of gradient lengths and residence times showed only small deviations compared to the experimental data.
Hermosilla, Laura; Prampolini, Giacomo; Calle, Paloma; García de la Vega, José Manuel; Brancato, Giuseppe; Barone, Vincenzo
2015-01-01
A computational strategy that combines both time-dependent and time-independent approaches is exploited to accurately model molecular dynamics and solvent effects on the isotropic hyperfine coupling constants of the DMPO-H nitroxide. Our recent general force field for nitroxides derived from AMBER ff99SB is further extended to systems involving hydrogen atoms in β-positions with respect to NO. The resulting force-field has been employed in a series of classical molecular dynamics simulations, comparing the computed EPR parameters from selected molecular configurations to the corresponding experimental data in different solvents. The effect of vibrational averaging on the spectroscopic parameters is also taken into account, by second order vibrational perturbation theory involving semi-diagonal third energy derivatives together first and second property derivatives. PMID:26584116
Reaction kinetic parameters for ion transport from steady-state current-voltage curves.
Gradmann, D; Klieber, H G; Hansen, U P
1987-01-01
This study demonstrates possible ways to estimate the rate constants of reaction kinetic models for ion transport from steady-state current-voltage data as measured at various substrate concentrations. This issue is treated theoretically by algebraic reduction and extension of a reaction kinetic four-state model for uniport. Furthermore, an example for application is given; current-voltage data from an open K+ selective channel (Schroeder, J.I., R. Hedrich, and J.M. Fernandez, 1984, Nature (Lond.), 312:361-362) supplemented by some new data have been evaluated. The analysis yields absolute numerical estimates of the 14 rate constants of a six-state model, which is discussed in a wider context. PMID:2437973
Kinetic parameters for plasma. beta. -endorphin in lean and obese Zucker rats
Rodd, D.; Farrell, P.A.; Caston, A.L.; Green, M.H. )
1991-03-01
To determine plasma clearance kinetics for {beta}-endorphin (BE) by empirical compartmental analysis, a bolus of radioactive labeled 125I-BE was rapidly injected into a carotid artery catheter of unanesthetized lean (L) and obese (O) Zucker rats. The plasma disappearance of 125I was followed over a 3-h period. A 3-component exponential equation provided the best fit for plasma data. Plasma transit times were very short (10 s); however, plasma fractional catabolic rate was much slower. Plasma mean residence time was similar for both groups (50 min) as was recycle time (1.3 min). These data suggest that BE plasma disappearance kinetics are similar in L and O rats.
Liu, Hong; Wang, Jie; Xu, Xiangyang; Song, Enmin; Wang, Qian; Jin, Renchao; Hung, Chih-Cheng; Fei, Baowei
2014-11-01
A robust and accurate center-frequency (CF) estimation (RACE) algorithm for improving the performance of the local sine-wave modeling (SinMod) method, which is a good motion estimation method for tagged cardiac magnetic resonance (MR) images, is proposed in this study. The RACE algorithm can automatically, effectively and efficiently produce a very appropriate CF estimate for the SinMod method, under the circumstance that the specified tagging parameters are unknown, on account of the following two key techniques: (1) the well-known mean-shift algorithm, which can provide accurate and rapid CF estimation; and (2) an original two-direction-combination strategy, which can further enhance the accuracy and robustness of CF estimation. Some other available CF estimation algorithms are brought out for comparison. Several validation approaches that can work on the real data without ground truths are specially designed. Experimental results on human body in vivo cardiac data demonstrate the significance of accurate CF estimation for SinMod, and validate the effectiveness of RACE in facilitating the motion estimation performance of SinMod.
A comparison of region-based and pixel-based CEUS kinetics parameters in the assessment of arthritis
NASA Astrophysics Data System (ADS)
Grisan, E.; Raffeiner, B.; Coran, A.; Rizzo, G.; Ciprian, L.; Stramare, R.
2014-03-01
Inflammatory rheumatic diseases are leading causes of disability and constitute a frequent medical disorder, leading to inability to work, high comorbidity and increased mortality. The gold-standard for diagnosing and differentiating arthritis is based on patient conditions and radiographic findings, as joint erosions or decalcification. However, early signs of arthritis are joint effusion, hypervascularization and synovial hypertrophy. In particular, vascularization has been shown to correlate with arthritis' destructive behavior, more than clinical assessment. Contrast Enhanced Ultrasound (CEUS) examination of the small joints is emerging as a sensitive tool for assessing vascularization and disease activity. The evaluation of perfusion pattern rely on subjective semi-quantitative scales, that are able to capture the macroscopic degree of vascularization, but are unable to detect the subtler differences in kinetics perfusion parameters that might lead to a deeper understanding of disease progression and a better management of patients. Quantitative assessment is mostly performed by means of the Qontrast software package, that requires the user to define a region of interest, whose mean intensity curve is fitted with an exponential function. We show that using a more physiologically motivated perfusion curve, and by estimating the kinetics parameters separately pixel per pixel, the quantitative information gathered is able to differentiate more effectively different perfusion patterns. In particular, we will show that a pixel-based analysis is able to provide significant markers differentiating rheumatoid arthritis from simil-rheumatoid psoriatic arthritis, that have non-significant differences in clinical evaluation (DAS28), serological markers, or region-based parameters.
Kosík, Ondřej; Garajová, Soňa; Matulová, Mária; Rehulka, Pavel; Stratilová, Eva; Farkaš, Vladimír
2011-02-01
Fluorescently labeled derivatives of a xyloglucan (XG) nonasaccharide Glc(4)Xyl(3)Gal(2) (XLLG) were used as glycosyl acceptors in assays of xyloglucan endotransglycosylase (XET) from germinated nasturtium (Tropaeolum majus) seeds. We have investigated how the type of the oligosaccharide label influences the kinetic parameters of the reaction. The fluorescent probes used to label XLLG were anthranilic acid (AA), 8-aminonaphtalene-1,3,6-trisulfonic acid (ANTS), fluorescein isothiocyanate (FITC), and sulforhodamine (SR), respectively. The obtained data were compared with those of the reactions where aldose and/or alditol forms of tritium-labeled xyloglucan-derived nonasaccharide served as the respective acceptors. Modification at C-1 of the reducing-end glucose in XLLG by substitution with the fluorophore markedly affected the kinetic parameters of the reaction. The Michaelis constants K(m) for individual acceptors increased in the order [1-(3)H]XLLG
Adadi, Roi; Volkmer, Benjamin; Milo, Ron; Heinemann, Matthias; Shlomi, Tomer
2012-01-01
Identifying the factors that determine microbial growth rate under various environmental and genetic conditions is a major challenge of systems biology. While current genome-scale metabolic modeling approaches enable us to successfully predict a variety of metabolic phenotypes, including maximal biomass yield, the prediction of actual growth rate is a long standing goal. This gap stems from strictly relying on data regarding reaction stoichiometry and directionality, without accounting for enzyme kinetic considerations. Here we present a novel metabolic network-based approach, MetabOlic Modeling with ENzyme kineTics (MOMENT), which predicts metabolic flux rate and growth rate by utilizing prior data on enzyme turnover rates and enzyme molecular weights, without requiring measurements of nutrient uptake rates. The method is based on an identified design principle of metabolism in which enzymes catalyzing high flux reactions across different media tend to be more efficient in terms of having higher turnover numbers. Extending upon previous attempts to utilize kinetic data in genome-scale metabolic modeling, our approach takes into account the requirement for specific enzyme concentrations for catalyzing predicted metabolic flux rates, considering isozymes, protein complexes, and multi-functional enzymes. MOMENT is shown to significantly improve the prediction accuracy of various metabolic phenotypes in E. coli, including intracellular flux rates and changes in gene expression levels under different growth rates. Most importantly, MOMENT is shown to predict growth rates of E. coli under a diverse set of media that are correlated with experimental measurements, markedly improving upon existing state-of-the art stoichiometric modeling approaches. These results support the view that a physiological bound on cellular enzyme concentrations is a key factor that determines microbial growth rate. PMID:22792053
Adadi, Roi; Volkmer, Benjamin; Milo, Ron; Heinemann, Matthias; Shlomi, Tomer
2012-01-01
Identifying the factors that determine microbial growth rate under various environmental and genetic conditions is a major challenge of systems biology. While current genome-scale metabolic modeling approaches enable us to successfully predict a variety of metabolic phenotypes, including maximal biomass yield, the prediction of actual growth rate is a long standing goal. This gap stems from strictly relying on data regarding reaction stoichiometry and directionality, without accounting for enzyme kinetic considerations. Here we present a novel metabolic network-based approach, MetabOlic Modeling with ENzyme kineTics (MOMENT), which predicts metabolic flux rate and growth rate by utilizing prior data on enzyme turnover rates and enzyme molecular weights, without requiring measurements of nutrient uptake rates. The method is based on an identified design principle of metabolism in which enzymes catalyzing high flux reactions across different media tend to be more efficient in terms of having higher turnover numbers. Extending upon previous attempts to utilize kinetic data in genome-scale metabolic modeling, our approach takes into account the requirement for specific enzyme concentrations for catalyzing predicted metabolic flux rates, considering isozymes, protein complexes, and multi-functional enzymes. MOMENT is shown to significantly improve the prediction accuracy of various metabolic phenotypes in E. coli, including intracellular flux rates and changes in gene expression levels under different growth rates. Most importantly, MOMENT is shown to predict growth rates of E. coli under a diverse set of media that are correlated with experimental measurements, markedly improving upon existing state-of-the art stoichiometric modeling approaches. These results support the view that a physiological bound on cellular enzyme concentrations is a key factor that determines microbial growth rate.
Kuznetsov, V A; Zhivoglyadov, V P; Stepanova, L A
1993-01-01
A method is suggested to estimate multi component dynamic systems, which permits, with the help of the computer-calculated kinetic curves, to obtain information about the possible mechanisms of the system component interaction. The method is based on the structural and parametrical identification of mathematical models presented in the form of a system of nonlinear differential equations, using a multi-criterial approach. Using experimental data of studies on growth kinetics and regression of multicellular tumor EMT6 line spheroids in the mouse allogenic system and the immune system cell accumulation in spheroids a mathematical model has been developed of the cellular interaction process in a spheroid. It has been stated that the rate of macrophage and neutrophil accumulation in a spheroid depends on the amount of tumor cells and is determined by the hyperbolic law (as analogous to the Michaelis-Menthen kinetics), while the accumulation of immune lymphocytes in a tumor is determined besides that by the three-cellular cooperation of lymphocytes, macrophages and tumor cells. According to the model, the inhibition of the process of neutrophil and lymphocyte (but not of macrophages) accumulation is realized through the auto-suppression mechanism. The numerical values of the process parameters, which characterise the rates of accumulation, cellular death in a tumor and of local cellular interactions intensity are obtained. PMID:8239905
Shankar, Sini; Agarwal, Madhu; Chaurasia, S P
2013-12-01
Esterification of lauric acid with n-butanol, catalyzed by immobilized Candida antarctica lipase (CAL) in aqueous-organic biphasic solvent system was studied. Effects of various reaction parameters on esterification were investigated, such as type and amount of solvent, amount of buffer, pH, temperature, speed of agitation, amount of enzyme, butanol and lauric acid. The most suitable reaction conditions for esterification were observed at 50 degrees C and pH 7.0 using 5000 micromoles of lauric acid, 7000 pmoles of butanol, 0.25 ml phosphate buffer, 1 ml of isooctane as the solvent and 50 mg of immobilized enzyme in the reaction medium at agitation speed of 150 rpm. Maximum esterification of 96.36% was acheived in 600 min of reaction time at n-butanol to lauric acid molar ratio of 1: 0.7. Kinetic study for the esterification of lauric acid with n-butanol using immobilized CAL was carried out and the kinetic constants were estimated by using non-linear regression method. The estimated value of Michaelis kinetic constants for butanol (KmBt) and acid (KmAc) were 451.56 (M) and 4.7 x 10(-7)(M), respectively and the value of dissociation constant (KBt) of the butanol-lipase complex was 9.41 x 10(7)(M). The estimated constants agreed fairly well with literature data.
Ma, Ying-Shih; Sung, Chi-Fanga; Lin, Jih-Gaw
2010-06-15
To establish an efficient oxidation process for carbofuran degradation, the effects of some operating parameters such as dosages of H(2)O(2), Fe(2+) and initial carbofuran concentrations were observed during carbofuran degradation by the ultrasound process, Fenton process and a combined ultrasound/Fenton process. The degradation kinetics of carbofuran was also examined based on the experimental data. The results show that more than 99% of the carbofuran was degraded by the ultrasound/Fenton process within short reaction time periods. Increased dosages of H(2)O(2) and Fe(2+) enhanced the degradation of carbofuran in the ultrasound and Fenton oxidation processes, but initial carbofuran concentrations decreased carbofuran degradation in both the Fenton and ultrasound/Fenton processes. The degradation kinetics of carbofuran by the three oxidation processes was found to be in accordance with first-order reaction kinetics. The results provide fundamental information about the treatment of carbofuran wastewater and/or other pesticides by the ultrasound/Fenton oxidation process.
Kiernan, D; Walsh, M; O'Sullivan, R; O'Brien, T; Simms, C K
2014-01-01
Inverse Dynamic calculations are routinely used in joint moment and power estimates during gait with anthropometric data often taken from published sources. Many biomechanical analyses have highlighted the need to obtain subject-specific anthropometric data (e.g. Mass, Centre of Mass, Moments of Inertia) yet the types of imaging techniques required to achieve this are not always available in the clinical setting. Differences in anthropometric sets have been shown to affect the reactive force and moment calculations in normal subjects but the effect on a paediatric diplegic cerebral palsy group has not been investigated. The aim of this study was to investigate the effect of using different anthropometric sets on predicted sagittal plane moments during normal and diplegic cerebral palsy gait. Three published anthropometric sets were applied to the reactive force and moment calculations of 14 Cerebral Palsy and 14 Control subjects. Statistically significant differences were found when comparing the different anthropometric sets but variability in the resulting sagittal plane moment calculations between sets was low (0.01-0.07 Nm/kg). In addition, the GDI-Kinetic, used as an outcome variable to assess whether differences were clinically meaningful, indicated no clinically meaningful difference between sets. The results suggest that the effects of using different anthropometric sets on the kinetic profiles of normal and diplegic cerebral palsy subjects are clinically insignificant.
Kinetic parameters of red pepper waste as biomass to solid biofuel.
Maia, Amanda Alves Domingos; de Morais, Leandro Cardoso
2016-03-01
This work aimed to study the kinetic of thermal degradation of red pepper waste as solid biofuel to bioenergy production. The thermal degradation experiments were conducted at three heating rates, 5°C/min, 7.5°C/min and 10°C/min in a thermogravimetric analyzer and oxidative atmosphere. The kinetic analysis was carried out applying the isoconversional model of Ozawa-Flynn-Wall. The activation energy was considerate low and varied 29.49-147.25k J/mol. The enthalpies revealed the energy difference between the reagent and the activated complex agreed with activation energies, the values of the pre-exponential factor indicated empirical first order reactions, Gibbs free energy varied from 71.77 kJ/mol to 207.03 kJ/mol and the changes of entropies had negative values, indicating that the degree of disorder of products formed through bond dissociations was lower than initial reactants. The calorific value was 19.5 MJ/kg, considered a relevant result for bioenergy production.
Kiernan, D; Walsh, M; O'Sullivan, R; O'Brien, T; Simms, C K
2014-01-01
Inverse Dynamic calculations are routinely used in joint moment and power estimates during gait with anthropometric data often taken from published sources. Many biomechanical analyses have highlighted the need to obtain subject-specific anthropometric data (e.g. Mass, Centre of Mass, Moments of Inertia) yet the types of imaging techniques required to achieve this are not always available in the clinical setting. Differences in anthropometric sets have been shown to affect the reactive force and moment calculations in normal subjects but the effect on a paediatric diplegic cerebral palsy group has not been investigated. The aim of this study was to investigate the effect of using different anthropometric sets on predicted sagittal plane moments during normal and diplegic cerebral palsy gait. Three published anthropometric sets were applied to the reactive force and moment calculations of 14 Cerebral Palsy and 14 Control subjects. Statistically significant differences were found when comparing the different anthropometric sets but variability in the resulting sagittal plane moment calculations between sets was low (0.01-0.07 Nm/kg). In addition, the GDI-Kinetic, used as an outcome variable to assess whether differences were clinically meaningful, indicated no clinically meaningful difference between sets. The results suggest that the effects of using different anthropometric sets on the kinetic profiles of normal and diplegic cerebral palsy subjects are clinically insignificant. PMID:24200337
Xu, Qiujian; Zhang, Yinping; Mo, Jinhan; Li, Xinxiao
2011-07-01
Thermal catalytic oxidation (TCO) technology can continuously degrade formaldehyde at room temperature without added energy. However, there is very little knowledge on the TCO kinetic reaction mechanism, which is necessary in developing such air cleaners and in comparison with other air cleaning techniques. This paper addresses the problem of a novel TCO catalyst, Pt/MnO(x)-CeO(2). The experiments measuring the outlet concentrations of formaldehyde and other possible byproducts were conducted at temperatures of 25, 40, 60, 100, and 180 °C and at a series of inlet formaldehyde concentrations (280-3000 ppb). To measure the concentrations precisely and real timely, proton transfer reaction-mass spectrometry (PTR-MS) was used. We found the following from the experimental results: (1) no byproducts were detected; (2) the bimolecular L-H kinetic model best described the catalytic reaction rate; (3) the activation energy of the oxidation was about 25.8 kJ mol(-1); (4) TCO is most energy efficient at room temperature without auxiliary heating; (5) compared with photocatalytic oxidation (PCO) which needs ultraviolet light radiation, the reaction area of TCO can be much larger for a given volume so that TCO can perform much better not only in formaldehyde removal efficiency but also in energy saving.
2014-01-01
Background Accurate estimation of parameters of biochemical models is required to characterize the dynamics of molecular processes. This problem is intimately linked to identifying the most informative experiments for accomplishing such tasks. While significant progress has been made, effective experimental strategies for parameter identification and for distinguishing among alternative network topologies remain unclear. We approached these questions in an unbiased manner using a unique community-based approach in the context of the DREAM initiative (Dialogue for Reverse Engineering Assessment of Methods). We created an in silico test framework under which participants could probe a network with hidden parameters by requesting a range of experimental assays; results of these experiments were simulated according to a model of network dynamics only partially revealed to participants. Results We proposed two challenges; in the first, participants were given the topology and underlying biochemical structure of a 9-gene regulatory network and were asked to determine its parameter values. In the second challenge, participants were given an incomplete topology with 11 genes and asked to find three missing links in the model. In both challenges, a budget was provided to buy experimental data generated in silico with the model and mimicking the features of different common experimental techniques, such as microarrays and fluorescence microscopy. Data could be bought at any stage, allowing participants to implement an iterative loop of experiments and computation. Conclusions A total of 19 teams participated in this competition. The results suggest that the combination of state-of-the-art parameter estimation and a varied set of experimental methods using a few datasets, mostly fluorescence imaging data, can accurately determine parameters of biochemical models of gene regulation. However, the task is considerably more difficult if the gene network topology is not completely
NASA Astrophysics Data System (ADS)
Zubov, V.; Lurie, S.; Solyaev, Y.
2016-04-01
This paper considers the identification algorithm of parameters included in a parabolic law that is often used to predict the time dependence of the thickness of the interfacial layers in the structure of composite materials based on a metal matrix. The incubation period of the process and the speed of reaction and pressure are taken into account. The proposed algorithm of identification is based on the introduction of a minimized objective function of a special kind. The problem of identification of unknown parameters in the parabolic law is formulated in a variational form. The authors of the paper have determined the desired parameters, under which the objective function has a minimum value. It is shown that on the basis of four known experimental values of the interfacial layer thickness, corresponding to different values of temperature, pressure and the time of the interfacial layer growth, it is possible to identified four model parameters. They are the activation energy, a pre-exponential parameter, the delay time of the start of the interfacial layer formation, and the parameter determining the pressure effect on the rate of interfacial layer growth. The stability of the proposed identification algorithm is also studied.
Choi, H W; Kim, Y H; Rim, Y H; Yang, Y S
2013-06-28
The formation of crystalline LiNbO3 (LN) from LN glass has been studied by means of differential scanning calorimetry and in situ synchrotron X-ray diffraction. The LN glass with no glass former was prepared by the polymerized complex method. The isothermal kinetics of the crystallization process is described using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation and the Avrami exponent n is found to be ~2.0, indicating that the crystallization mechanism is diffusion-controlled growth with a decreasing nucleation rate. The effective activation energy of crystallization calculated from isothermal measurements is 6.51 eV. It is found that the LN glass directly transforms into a rhombohedral LN crystal without any intermediate crystalline phase and most crystal grains are confined within the size of ~40 nm irrespective of different isothermal temperatures. Application of JMAK theory to the non-isothermal thermoanalytical study of crystallization of LN glass is discussed.
Xu, Weijie; Yang, Yiqi
2010-03-01
Drug release and its relationship with kinetic and thermodynamic parameters of drug sorption onto starch acetate (SA) fibers have been studied using Diclofenac, 5-Fluorouracil (5-Fu), and Metformin as model drugs. The sorption method is more flexible and can avoid limitations or problems which occur with molten or dissolution methods. To understand drug release of sorption loading, kinetic and apparent thermodynamic parameters, such as diffusion coefficient, activation energy for diffusion, affinity, and sorption enthalpy and entropy, have been investigated. The quantitative relationship between drug release and drug-loading concentration, affinity, and activation energy for diffusion has been established to predict the initial burst and subsequent release of the drugs. Up to 12% of Diclofenac, based on the weight of SA, can be loaded onto fibers using the sorption method. Drugs with higher activation energy for diffusion, lower diffusion coefficients, and higher affinity for SA fiber, such as Diclofenac, are more suitable for sorption loading. It has also been found that elevated temperatures will achieve higher loading capacity and a more constant release rate.
Ostrovskiĭ KuM; Voskoboev, A I; Gorenshtenĭn, B I; Dosta, G A
1979-09-01
The molecula-kinetic parameters (Km, Ki) of three thiamine enzymes, e. g. thiamine pyrophosphokinase (EC 2.7.6.2), pyruvate dehydrogenase (EC 1.2.4.1) and transketolase (EC 2.2.1.1) with respect to the effects of the thiamine antimetabolite hydroxythiamine in the whole animal organism have been compared. It has been shown that only the first two enzymes, which interact competitively with the vitamin, antivitamin or their pyrophosphate ethers, obey the kinetic parameters obtained for the purified enzymes in vitro. The anticoenzymic effect of hydroxythiamine pyrophosphate with respect to transketolase is not observed in vivo at maximal concentration of the anticoenzyme in tissues due to the absence of competitive interactions with thiamine pyrophosphate. The incorporation of the true and false coenzymes into transketolase occurs only during de novo transketolase synthesis (the apoform is absent in tissues, with the exception of erythrocytes) and proceeds slowly with a half-life time equal to 24--30 hrs. After a single injection of hydroxythiamine at a large dose (70--400 mg/kg) the maximal inhibition of the transketolase activity in tissues (liver, heart, kidney, muscle, spleen, lungs adrenal grands) manifests itself by the 48th--72nd hour, when the concentration of free hydroxythiamine and its pyrophosphate is minimal and the whole anticoenzyme is tightly bound to the protein, forming the false holoenzyme. The use of hydroxythiamine for inhibition of pyruvate dehydrogenase or transketolase in animal organism is discussed.
Rizzo, Gaia; Raffeiner, Bernd; Coran, Alessandro; Ciprian, Luca; Fiocco, Ugo; Botsios, Costantino; Stramare, Roberto; Grisan, Enrico
2015-07-01
Inflammatory rheumatic diseases are the leading causes of disability and constitute a frequent medical disorder, leading to inability to work, high comorbidity, and increased mortality. The standard for diagnosing and differentiating arthritis is based on clinical examination, laboratory exams, and imaging findings, such as synovitis, bone edema, or joint erosions. Contrast-enhanced ultrasound (CEUS) examination of the small joints is emerging as a sensitive tool for assessing vascularization and disease activity. Quantitative assessment is mostly performed at the region of interest level, where the mean intensity curve is fitted with an exponential function. We showed that using a more physiologically motivated perfusion curve, and by estimating the kinetic parameters separately pixel by pixel, the quantitative information gathered is able to more effectively characterize the different perfusion patterns. In particular, we demonstrated that a random forest classifier based on pixelwise quantification of the kinetic contrast agent perfusion features can discriminate rheumatoid arthritis from different arthritis forms (psoriatic arthritis, spondyloarthritis, and arthritis in connective tissue disease) with an average accuracy of 97%. On the contrary, clinical evaluation (DAS28), semiquantitative CEUS assessment, serological markers, or region-based parameters do not allow such a high diagnostic accuracy. PMID:27014713
Kinetic Modeling and Parameter Estimation in a Tower Bioreactor for Bioethanol Production
NASA Astrophysics Data System (ADS)
Rivera, Elmer Ccopa; da Costa, Aline Carvalho; Lunelli, Betânia Hoss; Maciel, Maria Regina Wolf; Filho, Rubens Maciel
In this work, a systematic method to support the building of bioprocess models through the use of different optimization techniques is presented. The method was applied to a tower bioreactor for bioethanol production with immobilized cells of Saccharomyces cerevisiae. Specifically, a step-by-step procedure to the estimation problem is proposed. As the first step, the potential of global searching of real-coded genetic algorithm (RGA) was applied for simultaneous estimation of the parameters. Subsequently, the most significant parameters were identified using the Placket-Burman (PB) design. Finally, the quasi-Newton algorithm (QN) was used for optimization of the most significant parameters, near the global optimum region, as the initial values were already determined by the RGA global-searching algorithm. The results have shown that the performance of the estimation procedure applied in a deterministic detailed model to describe the experimental data is improved using the proposed method (RGA-PB-QN) in comparison with a model whose parameters were only optimized by RGA.
Sensitivity analysis of large system of chemical kinetic parameters for engine combustion simulation
Hsieh, H; Sanz-Argent, J; Petitpas, G; Havstad, M; Flowers, D
2012-04-19
In this study, the authors applied the state-of-the art sensitivity methods to downselect system parameters from 4000+ to 8, (23000+ -> 4000+ -> 84 -> 8). This analysis procedure paves the way for future works: (1) calibrate the system response using existed experimental observations, and (2) predict future experiment results, using the calibrated system.
Walsh, Mark S; Waters, Jeff; Kersting, Uwe G
2007-01-01
The purposes of this study were to examine gender differences during drop jumps, to evaluate the effect of a set of simple instructions on kinematic and kinetic parameters during a drop jump, and to determine if there are gender differences in the effects of instruction on those parameters. Twenty-five basketball players, 13 men and 12 women, performed drop jumps from a box (height 30.5 cm) after being asked to perform a land and jump movement as they normally would do when aiming at maximum jump height. The experimental group received a set of instructions designed to make them land softer. The measured parameters were impact force at landing, ground contact time, flight time, frontal plane knee angle, sagittal plane knee angle, and distance between the knees. When the groups were examined by gender, no differences in the parameters were seen in men after instruction, but in women the following significant differences were detected: an increase in contact time, a decrease in landing force, and a decrease in inward movement of the knees after landing. These data indicate that females respond differently to jumping/landing instructions.
Pérez-Gil, J; Martín, J; Acebal, C; Arche, R
1990-01-01
Lysophosphatidylcholine: lysophosphatidylcholine acyltransferase is an enzyme that catalyses two reactions: hydrolysis of lysophosphatidylcholine and transacylation between two molecules of lysophosphatidylcholine to give disaturated phosphatidylcholine. Following the kinetic model previously proposed for this enzyme [Martín, Pérez-Gil, Acebal & Arche (1990) Biochem. J. 266, 47-53], the values of essential pK values in free enzyme and substrate-enzyme complexes have now been determined. The chemical mechanism of catalysis was dependent on the deprotonation of a histidine residue with pK about 5.7. This result was supported by the perturbation of pK values by addition of organic solvent. Very high and exothermic enthalpy of ionization was measured, indicating that a conformational re-arrangement in the enzyme accompanies the ionization of the essential histidine residue. These results, as well as the results from previous studies, enabled the proposal of a chemical mechanism for the enzymic reactions catalysed by lysophosphatidylcholine: lysophosphatidylcholine acyltransferase from rabbit lung. PMID:2241908
Kinetic parameters and relative turnovers of some important catabolic reactions in digesting sludge.
Kaspar, H F; Wuhrmann, K
1978-01-01
The kinetics of propionate degradation, acetate splitting, and hydrogen consumption in digesting sludge were investigated in a lab-scale digester. At natural steady-state conditions, the acetate-splitting systems in well-digested sludge were about half saturated. Propionate-degrading systems were saturated to only 10 to 15%, and hydrogen removal was less than 1% of the maximum possible rate. It was concluded that acetate splitting rather than "methanogenesis from fatty acids" is the rate-limiting reaction in the anaerobic degradation of dissolved organic matter and that a methoanogenic anaerobic ecosystem is stabilized by its large unused capacity of hydrogen consumption which is "buffering" the partial pressure of dissolved hydrogen in the system at sufficiently low values to permit rapid fatty acid oxidation. A tentative scheme of the substrate flow in sludge digestion is presented. It suggests that acid formation coupled with hydrogen formation via pyridine dinucleotide oxidation yields the immediate substrates, namely acetate and hydrogen, for about 54% of the total methanogenesis. PMID:697354
Temperature Effects on Kinetic Parameters and Substrate Affinity of Cel7A Cellobiohydrolases*
Sørensen, Trine Holst; Cruys-Bagger, Nicolaj; Windahl, Michael Skovbo; Badino, Silke Flindt; Borch, Kim; Westh, Peter
2015-01-01
We measured hydrolytic rates of four purified cellulases in small increments of temperature (10–50 °C) and substrate loads (0–100 g/liter) and analyzed the data by a steady state kinetic model that accounts for the processive mechanism. We used wild type cellobiohydrolases (Cel7A) from mesophilic Hypocrea jecorina and thermophilic Rasamsonia emersonii and two variants of these enzymes designed to elucidate the role of the carbohydrate binding module (CBM). We consistently found that the maximal rate increased strongly with temperature, whereas the affinity for the insoluble substrate decreased, and as a result, the effect of temperature depended strongly on the substrate load. Thus, temperature had little or no effect on the hydrolytic rate in dilute substrate suspensions, whereas strong temperature activation (Q10 values up to 2.6) was observed at saturating substrate loads. The CBM had a dual effect on the activity. On one hand, it diminished the tendency of heat-induced desorption, but on the other hand, it had a pronounced negative effect on the maximal rate, which was 2-fold larger in variants without CBM throughout the investigated temperature range. We conclude that although the CBM is beneficial for affinity it slows down the catalytic process. Cel7A from the thermophilic organism was moderately more activated by temperature than the mesophilic analog. This is in accord with general theories on enzyme temperature adaptation and possibly relevant information for the selection of technical cellulases. PMID:26183777
Temperature Effects on Kinetic Parameters and Substrate Affinity of Cel7A Cellobiohydrolases.
Sørensen, Trine Holst; Cruys-Bagger, Nicolaj; Windahl, Michael Skovbo; Badino, Silke Flindt; Borch, Kim; Westh, Peter
2015-09-01
We measured hydrolytic rates of four purified cellulases in small increments of temperature (10-50 °C) and substrate loads (0-100 g/liter) and analyzed the data by a steady state kinetic model that accounts for the processive mechanism. We used wild type cellobiohydrolases (Cel7A) from mesophilic Hypocrea jecorina and thermophilic Rasamsonia emersonii and two variants of these enzymes designed to elucidate the role of the carbohydrate binding module (CBM). We consistently found that the maximal rate increased strongly with temperature, whereas the affinity for the insoluble substrate decreased, and as a result, the effect of temperature depended strongly on the substrate load. Thus, temperature had little or no effect on the hydrolytic rate in dilute substrate suspensions, whereas strong temperature activation (Q10 values up to 2.6) was observed at saturating substrate loads. The CBM had a dual effect on the activity. On one hand, it diminished the tendency of heat-induced desorption, but on the other hand, it had a pronounced negative effect on the maximal rate, which was 2-fold larger in variants without CBM throughout the investigated temperature range. We conclude that although the CBM is beneficial for affinity it slows down the catalytic process. Cel7A from the thermophilic organism was moderately more activated by temperature than the mesophilic analog. This is in accord with general theories on enzyme temperature adaptation and possibly relevant information for the selection of technical cellulases. PMID:26183777
NASA Astrophysics Data System (ADS)
Chaudhari, C. V.; Mondal, R. K.; Dubey, K. A.; Grover, V.; Panicker, L.; Bhardwaj, Y. K.; Varshney, L.
2016-08-01
A transparent, elastomeric, grafted matrix for several potential applications was synthesized by single-step simultaneous radiation grafting of methacrylic acid onto ethylene vinyl acetate (EVA). CuSO4 was found to be the most suitable homo-polymerization inhibitor among different inhibitors tried. The grafting kinetics was found to be a strong function of dose rate (D) and monomer content (M) and an equation relating grafting rate Rg=Kg [M]1.13D0.23 was deduced. Crystallinity of the grafted matrices as assessed from XRD and DSC measurements indicated decrease in crystalline content with increase in grafting yield, suggesting crystalline domain of EVA get disrupted on grafting. Elastic modulus increased linearly with the increase in grafting yield, though elongation at break decreased precipitously from 900% to 30% at even ~9% grafting. Thermo-gravimetric analysis showed three step weight loss of the grafted EVA matrix. The grafting of MAA resulted in increase in surface energy mainly due to enhanced polar component.
Substrate specificity and kinetic parameters of GLUT3 in rat cerebellar granule neurons.
Maher, F; Davies-Hill, T M; Simpson, I A
1996-01-01
This study examines the apparent affinity, catalytic-centre activity ("turnover number') and stereospecificity of the neuronal glucose transporter GLUT3 in primary cultured cerebellar granule neurons. Using a novel variation of the 3-O-[14C]methylglucose transport assay, by measuring zero-trans kinetics at 25 degrees C, GLUT3 was determined to be a high-apparent-affinity, high-activity, glucose transporter with a K(m) of 2.87 +/- 0.23 mM (mean +/- S.E.M.) for 3-O-methylglucose, a Vmax of 18.7 +/- 0.48 nmol/min per 10(6) cells, and cells, and a corresponding catalytic-centre activity of 853 s-1. Transport of 3-O-methylglucose was competed by glucose, mannose, 2-deoxyglucose and galactose, but not by fructose. This methodology is compared with the more common 2-[3H]deoxyglucose methodology and the [U-14C]-glucose transport method. The high affinity and transport activity of the neuronal glucose transporter GLUT3 appears to be an appropriate adaptation to meet the demands of neuronal metabolism at prevailing interstitial brain glucose concentrations (1-2 mM). PMID:8645164
Pitakpoolsil, Wipawan; Hunsom, Mali
2014-01-15
The possibility of using commercial chitosan flakes as an adsorbent for the removal of pollutants from biodiesel wastewater was evaluated. The effect of varying the adsorption time (0.5-5 h), initial wastewater pH (2-8), adsorbent dose (0.5-5.5 g/L) and mixing rate (120-350 rpm) on the efficiency of pollutant removal was explored by univariate analysis. Under the derived optimal conditions, greater than 59.3%, 87.9% and 66.2% of the biological oxygen demand (BOD), chemical oxygen demand (COD) and oil & grease, respectively, was removed by a single adsorption. Nevertheless, the remaining BOD, COD and oil & grease were still higher than the acceptable Thai government limits for discharge into the environment. When the treatment was repeated, a greater than 93.6%, 97.6% and 95.8% removal of the BOD, COD and oil & grease, respectively, was obtained. The reusability of commercial chitosan following NaOH washing (0.05-0.2 M) was not suitable, with less than 40% efficiency after just one recycling and declining rapidly thereafter. The adsorption kinetics of all pollutant types by the commercial chitosan flakes was controlled by a mixed process of diffusion and adsorption of the pollutants during the early treatment period (0-1.5 h) and then solely controlled by adsorption after 2 h.
Pavlovitchev, A.M.
2000-03-08
The present work is a part of Joint U.S./Russian Project with Weapons-Grade Plutonium Disposition in VVER Reactor and presents the neutronics calculations of kinetics parameters of VVER-1000 core with 3 introduced MOX LTAs. MOX LTA design has been studied in [1] for two options of MOX LTA: 100% plutonium and of ''island'' type. As a result, zoning i.e. fissile plutonium enrichments in different plutonium zones, has been defined. VVER-1000 core with 3 introduced MOX LTAs of chosen design has been calculated in [2]. In present work, the neutronics data for transient analysis codes (RELAP [3]) has been obtained using the codes chain of RRC ''Kurchatov Institute'' [5] that is to be used for exploitation neutronics calculations of VVER. Nowadays the 3D assembly-by-assembly code BIPR-7A and 2D pin-by-pin code PERMAK-A, both with the neutronics constants prepared by the cell code TVS-M, are the base elements of this chain. It should be reminded that in [6] TVS-M was used only for the constants calculations of MOX FAs. In current calculations the code TVS-M has been used both for UOX and MOX fuel constants. Besides, the volume of presented information has been increased and additional explications have been included. The results for the reference uranium core [4] are presented in Chapter 2. The results for the core with 3 MOX LTAs are presented in Chapter 3. The conservatism that is connected with neutronics parameters and that must be taken into account during transient analysis calculations, is discussed in Chapter 4. The conservative parameters values are considered to be used in 1-point core kinetics models of accident analysis codes.
Mainz Organics Mechanism (MOM): description and sensitivity to some estimated kinetic parameters
NASA Astrophysics Data System (ADS)
Taraborrelli, Domenico; Cabrera Perez, David; Sander, Rolf; Pozzer, Andrea
2015-04-01
Despite decades of reasearch, global atmospheric chemistry models still have significant biases compared to the estimated distribution and evolution of tropospheric ozone and hydroxyl radical. The gas-phase oxidation of volatile organic compounds (VOC) is acknowledged to play an important role among the processes affecting tropospheric ozone, methane lifetime and aerosol evolution. Thus, chemical mechanisms of very diverse complexity have been developed for the major VOCs. However, all mechanisms present shortcomings such as neglection or lumping of intermediates and estimate of many rate constants and product distributions. Here, we present a VOC oxidation mechanism of intermediate complexity called the Mainz Organics Mechanism (MOM). With about 400 species and 1500 reactions, it represents the oxidation of about 20 primarily emitted VOCs comprising small alkanes and alkenes, isoprene, pinenes and monocyclic aromatic compounds. The development protocol significantly borrows from the Master Chemical Mechanism (MCM). However, MOM distinguishes itself for a number of features. First, the structure activity relationship for estimating the rate constants involving hydroxyl radical is site-specific and dependent on temperature. Second, the alkyl nitrate yields are considered to be dependent on temperature, pressure and molecular structure. RO2 + HO2 reaction kinetics is consistent with the recent direct studies of \\chem{OH}-reformation. Isoprene chemistry includes the latest experimental advancements with respect to OH-recycling and alkyl nitrate chemistry. Pinenes chemistry is largely the one by the MCM but with some modifications according to the work of the Leuven's group. Finally, the chemistry of the aromatics is also borrowed from the MCM but with additional photolysis of ortho-nitrophenols leading to \\chem{HONO} formation. The sensitivity of the model to the temperature and pressure dependence of estimated \\chem{OH} rate constants and alkyl nitrate yields will
Dölken, Lars; Ruzsics, Zsolt; Rädle, Bernd; Friedel, Caroline C; Zimmer, Ralf; Mages, Jörg; Hoffmann, Reinhard; Dickinson, Paul; Forster, Thorsten; Ghazal, Peter; Koszinowski, Ulrich H
2008-09-01
RNA levels in a cell are determined by the relative rates of RNA synthesis and decay. State-of-the-art transcriptional analyses only employ total cellular RNA. Therefore, changes in RNA levels cannot be attributed to RNA synthesis or decay, and temporal resolution is poor. Recently, it was reported that newly transcribed RNA can be biosynthetically labeled for 1-2 h using thiolated nucleosides, purified from total cellular RNA and subjected to microarray analysis. However, in order to study signaling events at molecular level, analysis of changes occurring within minutes is required. We developed an improved approach to separate total cellular RNA into newly transcribed and preexisting RNA following 10-15 min of metabolic labeling. Employing new computational tools for array normalization and half-life determination we simultaneously study short-term RNA synthesis and decay as well as their impact on cellular transcript levels. As an example we studied the response of fibroblasts to type I and II interferons (IFN). Analysis of RNA transcribed within 15-30 min at different times during the first three hours of interferon-receptor activation resulted in a >10-fold increase in microarray sensitivity and provided a comprehensive profile of the kinetics of IFN-mediated changes in gene expression. We identify a previously undisclosed highly connected network of short-lived transcripts selectively down-regulated by IFNgamma in between 30 and 60 min after IFN treatment showing strong associations with cell cycle and apoptosis, indicating novel mechanisms by which IFNgamma affects these pathways.
Blagojević, Slavica M; Anić, Slobodan R; Cupić, Zeljko D; Pejić, Natasa D; Kolar-Anić, Ljiljana Z
2008-11-28
The influence of the initial malonic acid concentration [MA]0 (8.00 x 10(-3) < or = [MA]0 < or = 4.30 x 10(-2) mol dm(-3)) in the presence of bromate (6.20 x 10(-2) mol dm(-3)), bromide (1.50 x 10(-5) mol dm(-3)), sulfuric acid (1.00 mol dm(-3)) and cerium sulfate (2.50 x 10(-3) mol dm(-3)) on the dynamics and the kinetics of the Belousov-Zhabotinsky (BZ) reactions was examined under batch conditions at 30.0 degrees C. The kinetics of the BZ reaction was analyzed by the earlier proposed method convenient for the examinations of the oscillatory reactions. In the defined region of parameters where oscillograms with only large-amplitude relaxation oscillations appeared, the pseudo-first order of the overall malonic acid decomposition with a corresponding rate constant of 2.14 x 10(-2) min(-1) was established. The numerical results on the dynamics and kinetics of the BZ reaction, carried out by the known skeleton model including the Br2O species, were in good agreement with the experimental ones. The already found saddle node infinite period (SNIPER) bifurcation point in transition from a stable quasi-steady state to periodic orbits and vice versa is confirmed by both experimental and numerical investigations of the system under consideration. Namely, the large-amplitude relaxation oscillations with increasing periods between oscillations in approaching the bifurcation points at the beginning and the end of the oscillatory domain, together with excitability of the stable quasi-steady states in their vicinity are obtained.
Schott, Juliane W; Jaeschke, Nico M; Hoffmann, Dirk; Maetzig, Tobias; Ballmaier, Matthias; Godinho, Tamaryin; Cathomen, Toni; Schambach, Axel
2015-05-01
Lentiviral and gammaretroviral vectors are state-of-the-art tools for transgene expression within target cells. The integration of these vectors can be deliberately suppressed to derive a transient gene expression system based on extrachromosomal circular episomes with intact coding regions. These episomes can be used to deliver DNA templates and to express RNA or protein. Importantly, transient gene transfer avoids the genotoxic side effects of integrating vectors. Restricting their applicability, episomes are rapidly lost upon dilution in dividing target cells. Addressing this limitation, we could establish comparably stable percentages of transgene-positive cells over prolonged time periods in proliferating cells by repeated transductions. Flow cytometry was applied for kinetic analyses to decipher the impact of individual parameters on the kinetics of fluoroprotein expression after episomal retransduction and to visualize sequential and simultaneous transfer of heterologous fluoroproteins. Expression windows could be exactly timed by the number of transduction steps. The kinetics of signal loss was affected by the cell proliferation rate. The transfer of genes encoding fluoroproteins with different half-lives revealed a major impact of protein stability on temporal signal distribution and accumulation, determining optimal retransduction intervals. In addition, sequential transductions proved broad applicability in different cell types and using different envelope pseudotypes without receptor overload. Stable percentages of cells coexpressing multiple transgenes could be generated upon repeated coadministration of different episomal vectors. Alternatively, defined patterns of transgene expression could be recapitulated by sequential transductions. Altogether, we established a methodology to control and adjust a temporally defined window of transgene expression using retroviral episomal vectors. Combined with the highly efficient cell entry of these vectors while
ERIC Educational Resources Information Center
Struck, William; Yerrick, Randy
2010-01-01
The effects of two types of two well-established microcomputer-based teaching methods were examined for their effect on teaching high school students kinetics. The use of data acquisition probeware and digital video analysis were studied for their impact on students' conceptions and ability to interpret graphical relationships to real world…
NASA Astrophysics Data System (ADS)
Hageseth, Gaylord T.
1982-02-01
Students under the supervision of a faculty member can collect data and fit the data to the theoretical mathematical model that describes the rate of isothermal seed germination. The best-fit parameters are interpreted as an initial substrate concentration, product concentration, and the autocatalytic reaction rate. The thermodynamic model enables one to calculate the activation energy for the substrate and product, the activation energy for the autocatalytic reaction, and changes in enthalpy, entropy, and the Gibb's free energy. Turnip, lettuce, soybean, and radish seeds have been investigated. All data fit the proposed model.
Patra, Braja N; Majhi, Deola
2015-06-25
Polyaniline was synthesized by the oxidative polymerization method by using ammonium persulfate as an oxidant. The positive charge in the backbone of the polymer was generated by using Potash alum as a dopant. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray fluorescence (XRF), and X-ray diffraction (XRD) techniques were used for characterization of doped polyaniline. The doped polyaniline can be used for selective adsorption of various dyes (selectively sulfonated dyes) from aqueous solution. Adsorption studies regarding the effect of contact time, initial dye concentration, pH, doses of adsorbent, and temperature on adsorption kinetics were investigated. The influence of other anions like Cl(-), NO3(-), and SO4(2-) on the adsorption density of dyes onto doped polyaniline was also explored. Langmuir isotherm and pseudo-second-order kinetics were found to be the most appropriate models to describe the removal of anionic dyes from water through adsorption. Thermodynamic parameters such as free energy (ΔG(0)), enthalpy (ΔH(0)), and entropy (ΔS(0)) changes were also evaluated. The interaction of dyes with doped polyaniline was also investigated by FTIR and UV spectroscopy. PMID:26079693
Patra, Braja N; Majhi, Deola
2015-06-25
Polyaniline was synthesized by the oxidative polymerization method by using ammonium persulfate as an oxidant. The positive charge in the backbone of the polymer was generated by using Potash alum as a dopant. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray fluorescence (XRF), and X-ray diffraction (XRD) techniques were used for characterization of doped polyaniline. The doped polyaniline can be used for selective adsorption of various dyes (selectively sulfonated dyes) from aqueous solution. Adsorption studies regarding the effect of contact time, initial dye concentration, pH, doses of adsorbent, and temperature on adsorption kinetics were investigated. The influence of other anions like Cl(-), NO3(-), and SO4(2-) on the adsorption density of dyes onto doped polyaniline was also explored. Langmuir isotherm and pseudo-second-order kinetics were found to be the most appropriate models to describe the removal of anionic dyes from water through adsorption. Thermodynamic parameters such as free energy (ΔG(0)), enthalpy (ΔH(0)), and entropy (ΔS(0)) changes were also evaluated. The interaction of dyes with doped polyaniline was also investigated by FTIR and UV spectroscopy.
Helbling, Damian E; Johnson, David R; Honti, Mark; Fenner, Kathrin
2012-10-01
The objective of this work was to identify relevant wastewater treatment plant (WWTP) parameters and underlying microbial processes that influence the biotransformation of a diverse set of micropollutants. To do this, we determined biotransformation rate constants for ten organic micropollutants in batch reactors seeded with activated sludge from ten diverse WWTPs. The estimated biotransformation rate constants for each compound ranged between one and four orders of magnitude among the ten WWTPs. The biotransformation rate constants were tested for statistical associations with various WWTP process parameters, amoA transcript abundance, and acetylene-inhibited monooxygenase activity. We determined that (i) ammonia removal associates with oxidative micropollutant biotransformation reaction rates; (ii) archaeal but not bacterial amoA transcripts associate with both ammonia removal and oxidative micropollutant biotransformation reaction rates; and (iii) the activity of acetylene-inhibited monooxygenases (including ammonia monooxygenase) associates with ammonia removal and the biotransformation rate of isoproturon, but does not associate with all oxidative micropollutant biotransformations. In combination, these results lead to the conclusion that ammonia removal and amoA transcript abundance can potentially be predictors of oxidative micropollutant biotransformation reactions, but that the biochemical mechanism is not necessarily linked to ammonia monooxygenase activity. PMID:22938719
Hashim, S; Alajerami, Y S M; Ramli, A T; Ghoshal, S K; Saleh, M A; Abdul Kadir, A B; Saripan, M I; Alzimami, K; Bradley, D A; Mhareb, M H A
2014-09-01
Lithium potassium borate (LKB) glasses co-doped with TiO2 and MgO were prepared using the melt quenching technique. The glasses were cut into transparent chips and exposed to gamma rays of (60)Co to study their thermoluminescence (TL) properties. The TL glow curve of the Ti-doped material featured a single prominent peak at 230 °C. Additional incorporation of MgO as a co-activator enhanced the TL intensity threefold. LKB:Ti,Mg is a low-Z material (Z(eff)=8.89) with slow signal fading. Its radiation sensitivity is 12 times lower that the sensitivity of TLD-100. The dose response is linear at doses up to 10(3) Gy. The trap parameters, such as the kinetics order, activation energy, and frequency factor, which are related to the glow peak, were determined using TolAnal software.
NASA Astrophysics Data System (ADS)
Sahin, Omer; Aslan, Fevzi; Ozdemir, Mustafa; Durgun, Mustafa
2004-10-01
Growth rate of polycrystalline disc of borax compressed at different pressure and rotated at various speed has been measured in a rotating disc crystallizer under well-defined conditions of supersaturation. It was found that the mass transfer coefficient, K, increased while overall growth rate constant, Kg, and surface reaction constant, kr, decreased with increasing smoothness of the disc. It was also determined that kinetic parameters (kr , r , K , g) of crystal growth rate of borax decreased with increasing rotating speed of the polycrystalline disc. The effectiveness factor was calculated from the growth rate data to evaluate the relative magnitude of the steps in series bulk diffusion through the mass transfer boundary layer and the surface integration. At low rotating speed of disc, the crystal growth rate of borax is mainly controlled by integration. However, both diffusion and integration steps affect the growth rate of borax at higher rotating speed of polycrystalline disc.
NASA Astrophysics Data System (ADS)
Gaonkar, Amita; Murudkar, Vrishali; Deshpande, V. D.
2016-05-01
Polyethylene terephthalate (PET) and Nucleated PET/ multi-walled carbon nanotubes (MWCNTs) nanocomposites with different MWCNTs loadings were prepared by melt compounding. The influence of the addition of MWCNTs and precipitated PET (p-PET) on the morphology and thermal properties of the nanocomposites was investigated. From Transmission Electronic Microscopy (TEM) and Wide angle X-Ray diffraction (WAXD) study, it can be clearly seen that nanocomposites with low MWCNTs contents (0.1 wt. %) get better MWCNTs dispersion than higher MWCNT loading. Comparing with PET, nucleated PET nanocomposite with 0.1% MWCNT loading shows higher value of Lauritzen-Hoffman parameters U* and Kg evaluated using the differential isoconversional method. Crystallization regime transition temperature range shifts to higher temperature (208°C - 215°C) for nanocomposites. The presence of p-PET in addition of MWCNT, which act as good nucleating agent, enhanced the crystallization of PET through heterogeneous nucleation.
Liu, Xiaowei; Zhang, Tuqiao; Zhou, Yongchao; Fang, Lei; Shao, Yu
2013-11-01
Photoactivation of peroxymonosulfate (PMS) with UV (254nm) irradiation was used to generate the SO4(-)-based advanced oxidation process, which was adopted to degrade atenolol (ATL) in water. The second-order reaction rate constants of ATL with HO and SO4(-) were determined, and the effects of operational parameters (dose of PMS, solution pH, HCO3(-), humic acids (HA), and N2 bubbling) were evaluated as well. Finally the main transformation intermediates were identified and possible degradation pathways were proposed. The results showed that there was a linear positive correlation between the degradation rate of ATL and specific dose of PMS (1-16M PMS/M ATL). Increasing solution pH from 3 to 9 promoted elimination of ATL due to the pH-dependent effect of PMS photodecomposition, while further pH increase from 9 to 11 caused slowing down of degradation because of apparent conversion of HO to SO4(-). 1-8mM HCO3(-) exerted no more than 5.3% inhibition effect on ATL destruction, suggesting HCO3(-) was a weak inhibitor. Absorption (or complexation) and photosensitized oxidation induced by HA improved ATL degradation during the first minute of degradation process, whereas photon competition and radical scavenging effects became the leading role afterward. Bubbling with nitrogen enhanced the degradation rate due to the stripping of dissolved oxygen. Hydroxylation of aromatic ring, cleavage of ether bond, oxidation of primary and secondary amine moieties, and dimerization were involved in the degradation mechanism of ATL by UV/PMS.
Bunting, Bruce G
2012-10-01
The automotive and engine industries are in a period of very rapid change being driven by new emission standards, new types of after treatment, new combustion strategies, the introduction of new fuels, and drive for increased fuel economy and efficiency. The rapid pace of these changes has put more pressure on the need for modeling of engine combustion and performance, in order to shorten product design and introduction cycles. New combustion strategies include homogeneous charge compression ignition (HCCI), partial-premixed combustion compression ignition (PCCI), and dilute low temperature combustion which are being developed for lower emissions and improved fuel economy. New fuels include bio-fuels such as ethanol or bio-diesel, drop-in bio-derived fuels and those derived from new crude oil sources such as gas-to-liquids, coal-to-liquids, oil sands, oil shale, and wet natural gas. Kinetic modeling of the combustion process for these new combustion regimes and fuels is necessary in order to allow modeling and performance assessment for engine design purposes. In this research covered by this CRADA, ORNL developed and supplied experimental data related to engine performance with new fuels and new combustion strategies along with interpretation and analysis of such data and consulting to Reaction Design, Inc. (RD). RD performed additional analysis of this data in order to extract important parameters and to confirm engine and kinetic models. The data generated was generally published to make it available to the engine and automotive design communities and also to the Reaction Design Model Fuels Consortium (MFC).
Raposo, Maria Monteiro Timóteo, Ana Rita; Ribeiro, Paulo A.; Ferreira, Quirina; Botelho do Rego, Ana Maria
2015-09-21
Photo induced birefringent materials can be used to develop optical and conversion energy devices, and consequently, the study of the variables that influences the creation and relaxation of birefringence should be carefully analyzed. In this work, the parameters of birefringence creation and relaxation kinetics curves obtained on layer-by-layer (LBL) films, prepared from azo-polyectrolyte poly[1-[4-(3-carboxy-4 hydroxyphenylazo) benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) and poly(allylamine hydrochloride)(PAH), are related with the presence of counterions and the degree of ionization of the polyelectrolytes. Those kinetics curves obtained on PAH/PAZO LBL films, prepared from PAH solutions with different pHs and maintaining the pH of PAZO solution constant at pH = 9, were analyzed taking into account the films composition which was characterized by X-ray photoelectron spectroscopy. The creation and relaxation birefringence curves are justified by two processes: one associated to local mobility of the azobenzene with a characteristic time 30 s and intensity constant and other associated with polymeric chains mobility with the characteristic time and intensity decreasing with pH. These results allow us to conclude that the birefringence creation process, associated to local mobility of azobenzenes is independent of the degree of ionization and of number of counterions or co-ions present while the birefringence creation process associated to mobility of chains have its characteristic time and intensity dependent of both degree of ionization and number of counterions. The birefringence relaxation processes are dependent of the degree of ionization. The analysis of the films composition revealed, in addition, the presence of a protonated secondary or tertiary amine revealing that PAZO may have positive charges and consequently a zwitterionic behavior.
NASA Astrophysics Data System (ADS)
Jiao, Jieqing; Salinas, Cristian A.; Searle, Graham E.; Gunn, Roger N.; Schnabel, Julia A.
2012-02-01
Dynamic Positron Emission Tomography is a powerful tool for quantitative imaging of in vivo biological processes. The long scan durations necessitate motion correction, to maintain the validity of the dynamic measurements, which can be particularly challenging due to the low signal-to-noise ratio (SNR) and spatial resolution, as well as the complex tracer behaviour in the dynamic PET data. In this paper we develop a novel automated expectation-maximisation image registration framework that incorporates temporal tracer kinetic information to correct for inter-frame subject motion during dynamic PET scans. We employ the Zubal human brain phantom to simulate dynamic PET data using SORTEO (a Monte Carlo-based simulator), in order to validate the proposed method for its ability to recover imposed rigid motion. We have conducted a range of simulations using different noise levels, and corrupted the data with a range of rigid motion artefacts. The performance of our motion correction method is compared with pairwise registration using normalised mutual information as a voxel similarity measure (an approach conventionally used to correct for dynamic PET inter-frame motion based solely on intensity information). To quantify registration accuracy, we calculate the target registration error across the images. The results show that our new dynamic image registration method based on tracer kinetics yields better realignment of the simulated datasets, halving the target registration error when compared to the conventional method at small motion levels, as well as yielding smaller residuals in translation and rotation parameters. We also show that our new method is less affected by the low signal in the first few frames, which the conventional method based on normalised mutual information fails to realign.
La Fontaine, M; Bradshaw, T; Kubicek, L; Forrest, L; Jeraj, R
2014-06-15
Purpose: Regions of poor perfusion within tumors may be associated with higher hypoxic levels. This study aimed to test this hypothesis by comparing measurements of hypoxia from Cu-ATSM PET to vasculature kinetic parameters from DCE-CT kinetic analysis. Methods: Ten canine patients with sinonasal tumors received one Cu-ATSM PET/CT scan and three DCE-CT scans prior to treatment. Cu-ATSM PET/CT and DCE-CT scans were registered and resampled to matching voxel dimensions. Kinetic analysis was performed on DCE-CT scans and for each patient, the resulting kinetic parameter values from the three DCE-CT scans were averaged together. Cu-ATSM SUVs were spatially correlated (r{sub spatial}) on a voxel-to-voxel basis against the following DCE-CT kinetic parameters: transit time (t{sub 1}), blood flow (F), vasculature fraction (v{sub 1}), and permeability (PS). In addition, whole-tumor comparisons were performed by correlating (r{sub ROI}) the mean Cu-ATSM SUV (SUV{sub mean}) with median kinetic parameter values. Results: The spatial correlations (r{sub spatial}) were poor and ranged from -0.04 to 0.21 for all kinetic parameters. These low spatial correlations may be due to high variability in the DCE-CT kinetic parameter voxel values between scans. In our hypothesis, t{sub 1} was expected to have a positive correlation, while F was expected to have a negative correlation to hypoxia. However, in wholetumor analysis the opposite was found for both t{sub 1} (r{sub ROI} = -0.25) and F (r{sub ROI} = 0.56). PS and v{sub 1} may depict angiogenic responses to hypoxia and found positive correlations to Cu-ATSM SUV for PS (r{sub ROI} = 0.41), and v{sub 1} (r{sub ROI} = 0.57). Conclusion: Low spatial correlations were found between Cu-ATSM uptake and DCE-CT vasculature parameters, implying that poor perfusion is not associated with higher hypoxic regions. Across patients, the most hypoxic tumors tended to have higher blood flow values, which is contrary to our initial hypothesis. Funding
Wiltner, A.; Linsmeier, Ch.; Jacob, T.
2008-08-28
This paper investigates the reactivity of elemental carbon films deposited from the vapor phase with Fe and Ni substrates at room temperature. X-ray photoelectron spectroscopy (XPS) measurements are presented as a method for evaluating kinetic reaction data. Carbon films are deposited on different surface orientations representing geometries from a dense atom packing as in fcc (111) to an open surface structure as in fcc (100). During annealing experiments several reactions are observed (carbon subsurface diffusion, carbide formation, carbide decomposition, and graphite ordering). These reactions and the respective kinetic parameters are analyzed and quantified by XPS measurements performed while annealing at elevated temperatures (620-820 K). The resulting activation barriers for carbon subsurface diffusion are compared with calculated values using the density functional theory. The determined kinetic parameters are used to reproduce the thermal behavior of carbon films on nickel surfaces.
Jussier, Delphine; Dubé Morneau, Amélie; Mira de Orduña, Ramón
2006-01-01
Inoculating grape musts with wine yeast and lactic acid bacteria (LAB) concurrently in order to induce simultaneous alcoholic fermentation (AF) and malolactic fermentation (MLF) can be an efficient alternative to overcome potential inhibition of LAB in wines because of high ethanol concentrations and reduced nutrient content. In this study, the simultaneous inoculation of yeast and LAB into must was compared with a traditional vinification protocol, where MLF was induced after completion of AF. For this, two suitable commercial yeast-bacterium combinations were tested in cool-climate Chardonnay must. The time courses of glucose and fructose, acetaldehyde, several organic acids, and nitrogenous compounds were measured along with the final values of other key wine parameters. Sensory evaluation was done after 12 months of storage. The current study could not confirm a negative impact of simultaneous AF/MLF on fermentation success and kinetics or on final wine parameters. While acetic acid concentrations were slightly increased in wines after simultaneous AF/MLF, the differences were of neither practical nor legal significance. No statistically significant differences were found with regard to the final values of pH or total acidity and the concentrations of ethanol, acetaldehyde, glycerol, citric and lactic acids, and the nitrogen compounds arginine, ammonia, urea, citrulline, and ornithine. Sensory evaluation by a semiexpert panel confirmed the similarity of the wines. However, simultaneous inoculation led to considerable reductions in overall fermentation durations. Furthermore, differences of physiological and microbiological relevance were found. Specifically, we report the vinification of “super-dry” wines devoid of glucose and fructose after simultaneous inoculation of yeast and bacteria. PMID:16391046
De Luis, R; Pérez, M D; Sánchez, L; Lavilla, M; Calvo, M
2008-08-01
The effect of heat treatment on the denaturation of Cry1A(b) protein expressed in transgenic maize was studied over a temperature range of 69 to 77 degrees C. Denaturation of Cry1A(b) protein was measured by the loss of reactivity with its specific antibodies using a sandwich ELISA. The process of denaturation was studied by analyzing the values of inmunoreactive protein after each heat treatment by kinetic analysis. Denaturation of Cry1A(b) protein was best described assuming a reaction order of 1.5. D-values calculated were 4338, 2350, 1272, 734, and 601 s at 69, 71, 73, 75, and 77 degrees C, respectively. Z-value was estimated to be 9.0 degrees C and the activation energy value was 266.15 kJ/mol. Thermodynamic parameters for the process of denaturation of Cry1A(b) protein were also calculated. The high values of the enthalpy of activation and the positive values of the entropy of activation obtained for Cry1A(b) protein are typical of a reaction in which the denaturation of the protein is the rate-determining process that predominates over an aggregation process during heating.
Comparison of dual-echo DSC-MRI- and DCE-MRI-derived contrast agent kinetic parameters.
Quarles, C Chad; Gore, John C; Xu, Lei; Yankeelov, Thomas E
2012-09-01
The application of dynamic susceptibility contrast (DSC) MRI methods to assess brain tumors is often confounded by the extravasation of contrast agent (CA). Disruption of the blood-brain barrier allows CA to leak out of the vasculature leading to additional T(1), T(2) and T(2) relaxation effects in the extravascular space, thereby affecting the signal intensity time course in a complex manner. The goal of this study was to validate a dual-echo DSC-MRI approach that separates and quantifies the T(1) and T(2) contributions to the acquired signal and enables the estimation of the volume transfer constant, K(trans), and the volume fraction of the extravascular extracellular space, v(e). To test the validity of this approach, DSC-MRI- and dynamic contrast enhanced (DCE) MRI-derived K(trans) and v(e) estimates were spatially compared in both 9L and C6 rat brain tumor models. A high degree of correlation (concordance correlation coefficients >0.83, Pearson's r>0.84) and agreement was found between the DSC-MRI- and DCE-MRI-derived measurements. These results indicate that dual-echo DSC-MRI can be used to simultaneously extract reliable DCE-MRI kinetic parameters in brain tumors in addition to conventional blood volume and blood flow metrics.
Thomas, Divya; Rasheed, Zafna; Jagan, Jesny Siri; Kumar, Krishnapillai Girish
2015-10-01
Electrochemical behavior of artificial antioxidant, butylated hydroxyanisole (BHA), was investigated at a glassy carbon electrode modified with poly L- cysteine [poly (L- Cys/GCE)]. BHA exhibits a pair of well - defined redox peak on L- cysteine modified GCE with Epa = 69 mV and Epc = 4 mV. The modified electrode showed good electrocatalytic activity towards the oxidation of BHA under optimal conditions and exhibited a linear response in the range from 1.0 × 10(-5) to 1.0 × 10(-6) M with a correlation coefficient of 0.998. The limit of detection was found to be 4.1 × 10(-7) M. The kinetics parameters of the proposed sensor such as heterogeneous electron transfer rate, k s , and charge transfer coefficient,α, was calculated and found to be 1.20 s(-1) and 0.575 respectively. The average surface concentration of BHA on the surface of poly (L- Cys/GCE) was calculated to be 3.18 × 10(-4) mol cm(-2). The analytical utility of the proposed sensor was evaluated by the successful determination of BHA in coconut oil and sesame oil samples. PMID:26396421
Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.
2013-03-01
Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. An advanced type of storage bed has been proposed that utilizes oxidation of uranium hydride to heat and decompose the hydride, releasing the hydrogen. To reduce the cost and time required to develop these systems experimentally, a valid computational model is required that simulates the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. This SAND report discusses the advancements made in FY12 (since our last SAND report SAND2011-6939) to the model developed as a part of an ASC-P&EM project to address the shortcomings of the previous model. The model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion are accounted for. These expansions result in mechanical stresses that lead to bed deformation. To describe this, a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation is developed. By using this solid mechanics model, the agreement between our reacting bed model and the experimental data is improved. Additionally, more accurate uranium hydride oxidation kinetics parameters are obtained by fitting the experimental results from a pure uranium hydride oxidation measurement to the ones obtained from the coupled transport-solid mechanics model. Finally, the coupled transport-solid mechanics model governing equations and boundary conditions are summarized and recommendations are made for further development of ARIA and other Sandia codes in order for them to sufficiently implement the model.
NASA Technical Reports Server (NTRS)
Green, Sheldon; Boissoles, J.; Boulet, C.
1988-01-01
The first accurate theoretical values for off-diagonal (i.e., line-coupling) pressure-broadening cross sections are presented. Calculations were done for CO perturbed by He at thermal collision energies using an accurate ab initio potential energy surface. Converged close coupling, i.e., numerically exact values, were obtained for coupling to the R(0) and R(2) lines. These were used to test the coupled states (CS) and infinite order sudden (IOS) approximate scattering methods. CS was found to be of quantitative accuracy (a few percent) and has been used to obtain coupling values for lines to R(10). IOS values are less accurate, but, owing to their simplicity, may nonetheless prove useful as has been recently demonstrated.
Navarro, F; Harouna, S; Calvo, M; Pérez, M D; Sánchez, L
2015-07-01
Lactoferrin is a protein with important biological functions that can be obtained from milk and by-products derived from the dairy industry, such as whey. Although bovine lactoferrin has been extensively studied, ovine lactoferrin is not quite as well known. In the present study, the effect of several heat treatments in 3 different media, over a temperature range from 66 to 75°C, has been studied on lactoferrin isolated from sheep milk. Denaturation of lactoferrin was determined by measuring its immunoreactivity with specific polyclonal antibodies. Kinetic and thermodynamic parameters obtained indicate that lactoferrin denatures by heat more rapidly in whey than in phosphate buffer or milk. The value of activation energy found for the denaturation process of lactoferrin when treated in whey is higher (390kJ/mol) than that obtained in milk (194kJ/mol) or phosphate buffer (179kJ/mol). This indicates that a great amount of energy is necessary to start denaturation of ovine lactoferrin, probably due to the interaction of this protein with other whey proteins. The changes in the hydrophobicity of lactoferrin after heat treatments were determined by fluorescence measurement using acrylamide. The decrease in the hydrophobicity constant was very small for the treatments from 66 to 75°C, up to 20min, which indicates that lactoferrin conformation did not experienced a great change. The results obtained in this study permit the prediction of behavior of ovine lactoferrin under several heat treatments and show that high-temperature, short-time pasteurization (72°C, 15 s) does not cause loss of its immunoreactivity and, consequently, would not affect its conformation and biological activity. PMID:25958286
Manukhov, I V; Mamaeva, D V; Morozova, E A; Rastorguev, S M; Faleev, N G; Demidkina, T V; Zavilgelsky, G B
2006-04-01
It is shown for the first time for the Enterobacteriaceae family that a gene encoding L-methionine gamma-lyase (MGL) is present in the genome of Citrobacter freundii. Homogeneous enzyme has been purified from C. freundii cells and its N-terminal sequence has been determined. The hybrid plasmid pUCmgl obtained from the C. freundii genomic library contains an EcoRI insert of about 3000 bp, which ensures the appearance of MGL activity when expressed in Escherichia coli TG1 cells. The nucleotide sequence of the EcoRI fragment contains two open reading frames. The first frame (the megL gene) encodes a protein of 398 amino acid residues that has sequence homology with MGLs from different sources. The second frame encodes a protein with sequence homology with proteins belonging to the family of permeases. To overexpress the megL gene it was cloned into pET-15b vector. Recombinant enzyme has been purified and its kinetic parameters have been determined. It is demonstrated that a presence of a hybrid plasmid pUCmgl, containing the megL gene in the E. coli K12 cells, leads to a decrease in efficiency of EcoKI-restriction. It seems likely that decomposition of L-methionine under the action of MGL leads to a decrease in the intracellular content of S-adenosylmethionine. Expression of the megL gene in the C. freundii genome occurs only upon induction by a significant amount of L-methionine.
Navarro, F; Harouna, S; Calvo, M; Pérez, M D; Sánchez, L
2015-07-01
Lactoferrin is a protein with important biological functions that can be obtained from milk and by-products derived from the dairy industry, such as whey. Although bovine lactoferrin has been extensively studied, ovine lactoferrin is not quite as well known. In the present study, the effect of several heat treatments in 3 different media, over a temperature range from 66 to 75°C, has been studied on lactoferrin isolated from sheep milk. Denaturation of lactoferrin was determined by measuring its immunoreactivity with specific polyclonal antibodies. Kinetic and thermodynamic parameters obtained indicate that lactoferrin denatures by heat more rapidly in whey than in phosphate buffer or milk. The value of activation energy found for the denaturation process of lactoferrin when treated in whey is higher (390kJ/mol) than that obtained in milk (194kJ/mol) or phosphate buffer (179kJ/mol). This indicates that a great amount of energy is necessary to start denaturation of ovine lactoferrin, probably due to the interaction of this protein with other whey proteins. The changes in the hydrophobicity of lactoferrin after heat treatments were determined by fluorescence measurement using acrylamide. The decrease in the hydrophobicity constant was very small for the treatments from 66 to 75°C, up to 20min, which indicates that lactoferrin conformation did not experienced a great change. The results obtained in this study permit the prediction of behavior of ovine lactoferrin under several heat treatments and show that high-temperature, short-time pasteurization (72°C, 15 s) does not cause loss of its immunoreactivity and, consequently, would not affect its conformation and biological activity.
Taschenberger, Holger; Scheuss, Volker; Neher, Erwin
2005-10-15
We have characterized developmental changes in the kinetics and quantal parameters of action potential (AP)-evoked neurotransmitter release during maturation of the calyx of Held synapse. Quantal size (q) and peak amplitudes of evoked EPSCs increased moderately, whereas the fraction of vesicles released by single APs decreased. During synaptic depression induced in postnatal day (P) 5-7 synapses by 10-100 Hz stimulation, q declined rapidly to 40-12% of its initial value. The decrease in q was generally smaller in more mature synapses (P12-14), but quite severe for frequencies > or = 300 Hz. The stronger decline of q in immature synapses resulted from a slower recovery from desensitization, presumably due to delayed glutamate clearance. Recovery from this desensitization followed an exponential time course with a time constant of approximately 480 ms in P5-7 synapses, and sped up > 20-fold during maturation. Deconvolution analysis of EPSCs revealed a significant acceleration of the release time course during development, which was accompanied by a 2-fold increase of the peak release rate. During long 100 Hz trains, more mature synapses were able to sustain average rates of 8-10 quanta s(-1) per active zone for phasic release. The rates of asynchronous vesicle release increased transiently > 35-fold immediately after such stimuli and decayed rapidly with an exponential time constant of approximately 50 ms to low resting levels of spontaneous release. However, even following extended periods of 100 Hz stimulation, the amount of asynchronous release was relatively minor with peak rates of less than 5% of the average rate of synchronous release measured at steady state during the tetani. Therefore, a multitude of mechanisms seems to converge on the generation of fast, temporally precise and reliable high-frequency transmission at the mature calyx of Held synapse.
Al Mardini, Fadi; Legube, Bernard
2009-10-30
The application of several monosolute equilibrium models has previously shown that Bromacil adsorption on SA-UF (Norit) powdered activated carbon (PAC) is probably effective on two types of sites. High reactivity sites were found to be 10-20 less present in a carbon surface than lower reactivity sites, according to the q(m) values calculated by isotherm models. The aims of this work were trying, primarily, to identify the kinetic-determinant stage of the sorption of Bromacil at a wide range of initial pesticide concentrations (approximately 5 to approximately 500 microg L(-1) at pH 7.8), and secondly, to specify the rate constants and other useful design parameters for the application in water treatment. It was therefore not possible to specify a priori whether the diffusion or surface reaction is the key step. It shows that many of the tested models which describe the stage of distribution or the surface reaction are correctly applied. However, the diffusivity values (D and D(0)) were found to be constant only constants for some specific experimental concentrations. The HSDM model of surface diffusion in pores was also applied but the values of the diffusion coefficient of surface (D(s)) were widely scattered and reduce significantly with the initial concentration or the equilibrium concentration in Bromacil. The model of surface reaction of pseudo-second order fitted particularly well and led to constant values which are independent of the equilibrium concentration, except for the low concentrations where the constants become significantly more important. This last observation confirms perfectly the hypothesis based on two types of sites as concluded by the equilibrium data (part 1).
Photon kinetic modeling of laser pulse propagation in underdense plasma
Reitsma, A. J. W.; Trines, R. M. G. M.; Bingham, R.; Cairns, R. A.; Mendonca, J. T.; Jaroszynski, D. A.
2006-11-15
This paper discusses photon kinetic theory, which is a description of the electromagnetic field in terms of classical particles in coordinate and wave number phase space. Photon kinetic theory is applied to the interaction of laser pulses with underdense plasma and the transfer of energy and momentum between the laser pulse and the plasma is described in photon kinetic terms. A comparison is made between a one-dimensional full wave and a photon kinetic code for the same laser and plasma parameters. This shows that the photon kinetic simulations accurately reproduce the pulse envelope evolution for photon frequencies down to the plasma frequency.
Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.
2015-07-01
Object kinetic Monte Carlo (OKMC) simulations have been performed to investigate various aspects of cascade aging in bulk tungsten and to determine the sensitivity of the results to the kinetic parameters. The primary focus is on how the kinetic parameters affect the initial recombination of defects in the first few ns of a simulation. The simulations were carried out using the object kinetic Monte Carlo (OKMC) code KSOME (kinetic simulations of microstructure evolution), using a database of cascades obtained from results of molecular dynamics (MD) simulations at various primary knock-on atom (PKA) energies and directions at temperatures of 300, 1025 and 2050 K. The OKMC model was parameterized using defect migration barriers and binding energies from ab initio calculations. Results indicate that, due to the disparate mobilities of SIA and vacancy clusters in tungsten, annealing is dominated by SIA migration even at temperatures as high as 2050 K. For 100 keV cascades initiated at 300 K recombination is dominated by annihilation of large defect clusters. But for all other PKA energies and temperatures most of the recombination is due to the migration and rotation of small SIA clusters, while all the large SIA clusters escape the cubic simulation cell. The inverse U-shape behavior exhibited by the annealing efficiency as a function of temperature curve, especially for cascades of large PKA energies, is due to asymmetry in SIA and vacancy clustering assisted by the large difference in mobilities of SIAs and vacancies. This annealing behavior is unaffected by the dimensionality of SIA migration persists over a broad range of relative mobilities of SIAs and vacancies.
Boller, A J; Thomas, P J; Cavanaugh, C M; Scott, K M
2015-01-01
The cosmopolitan, bloom-forming diatom, Skeletonema costatum, is a prominent primary producer in coastal oceans, fixing CO2 with ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) that is phylogenetically distinct from terrestrial plant RubisCO. RubisCOs are subdivided into groups based on sequence similarity of their large subunits (IA-ID, II, and III). ID is present in several major oceanic primary producers, including diatoms such as S. costatum, coccolithophores, and some dinoflagellates, and differs substantially in amino acid sequence from the well-studied IB enzymes present in most cyanobacteria and in green algae and plants. Despite this sequence divergence, and differences in isotopic discrimination apparent in other RubisCO enzymes, stable carbon isotope compositions of diatoms and other marine phytoplankton are generally interpreted assuming enzymatic isotopic discrimination similar to spinach RubisCO (IB). To interpret phytoplankton δ(13) C values, S. costatum RubisCO was characterized via sequence analysis, and measurement of its KCO2 and Vmax , and degree of isotopic discrimination. The sequence of this enzyme placed it among other diatom ID RubisCOs. Michaelis-Menten parameters were similar to other ID enzymes (KCO2 = 48.9 ± 2.8 μm; Vmax = 165.1 ± 6.3 nmol min(-1 ) mg(-1) ). However, isotopic discrimination (ε = [(12) k/(13) k - 1] × 1000) was low (18.5‰; 17.0-19.9, 95% CI) when compared to IA and IB RubisCOs (22-29‰), though not as low as ID from coccolithophore, Emiliania huxleyi (11.1‰). Variability in ε-values among RubisCOs from primary producers is likely reflected in δ(13) C values of oceanic biomass. Currently, δ(13) C variability is ascribed to physical or chemical factors (e.g. illumination, nutrient availability) and physiological responses to these factors (e.g. carbon-concentrating mechanisms). Estimating the importance of these factors from δ(13) C measurements requires an accurate ε-value, and a mass
Boller, A J; Thomas, P J; Cavanaugh, C M; Scott, K M
2015-01-01
The cosmopolitan, bloom-forming diatom, Skeletonema costatum, is a prominent primary producer in coastal oceans, fixing CO2 with ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) that is phylogenetically distinct from terrestrial plant RubisCO. RubisCOs are subdivided into groups based on sequence similarity of their large subunits (IA-ID, II, and III). ID is present in several major oceanic primary producers, including diatoms such as S. costatum, coccolithophores, and some dinoflagellates, and differs substantially in amino acid sequence from the well-studied IB enzymes present in most cyanobacteria and in green algae and plants. Despite this sequence divergence, and differences in isotopic discrimination apparent in other RubisCO enzymes, stable carbon isotope compositions of diatoms and other marine phytoplankton are generally interpreted assuming enzymatic isotopic discrimination similar to spinach RubisCO (IB). To interpret phytoplankton δ(13) C values, S. costatum RubisCO was characterized via sequence analysis, and measurement of its KCO2 and Vmax , and degree of isotopic discrimination. The sequence of this enzyme placed it among other diatom ID RubisCOs. Michaelis-Menten parameters were similar to other ID enzymes (KCO2 = 48.9 ± 2.8 μm; Vmax = 165.1 ± 6.3 nmol min(-1 ) mg(-1) ). However, isotopic discrimination (ε = [(12) k/(13) k - 1] × 1000) was low (18.5‰; 17.0-19.9, 95% CI) when compared to IA and IB RubisCOs (22-29‰), though not as low as ID from coccolithophore, Emiliania huxleyi (11.1‰). Variability in ε-values among RubisCOs from primary producers is likely reflected in δ(13) C values of oceanic biomass. Currently, δ(13) C variability is ascribed to physical or chemical factors (e.g. illumination, nutrient availability) and physiological responses to these factors (e.g. carbon-concentrating mechanisms). Estimating the importance of these factors from δ(13) C measurements requires an accurate ε-value, and a mass
NASA Astrophysics Data System (ADS)
Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.
2015-07-01
A study has been performed using object kinetic Monte Carlo (OKMC) simulations to investigate various aspects of cascade aging in bulk tungsten (W) and to determine its sensitivity to the kinetic parameters. The primary focus is on how the kinetic parameters affect the intracascade recombination of defects. Results indicate that, due to the disparate mobilities of SIA and vacancy clusters, annealing is dominated by SIA migration even at 2050 K. It was found that for 100 keV cascades initiated at 300 K, recombination is dominated by the annihilation of large defect clusters, while for all the other primary knock-on atom (PKA) energies and temperatures, recombination is primarily due to the migration and rotation of small SIA clusters, while the large SIA clusters escape the simulation cell. The annealing efficiency exhibits an inverse U-shaped curve behavior with increasing temperature, especially at large PKA energies, caused by the asymmetry in SIA and vacancy clustering assisted by the large differences in their mobilities. This behavior is unaffected by the dimensionality of SIA migration, and it persists over a broad range of relative mobilities of SIAs and vacancies.
Aghilinategh, Nahid; Rafiee, Shahin; Gholikhani, Abolfazl; Hosseinpur, Soleiman; Omid, Mahmoud; Mohtasebi, Seyed S; Maleki, Neda
2015-11-01
In the study, the effectiveness of intermittent (IMWD) and continuous (CMWD) microwave drying and hot air drying (HAD) treatments on apple slices were compared in terms of drying kinetics (moisture diffusivity and activation energy) and critical physicochemical quality attributes (color change, rehydration ratio, bulk density, and total phenol content (TPC) of the final dried product. The temperature, microwave power, air velocity, and pulse ratio (PR) applied in the experiments were 40-80°C, 200-600 W, 0.5-2 m/s, and 2-6, respectively. Results showed that IMWD and CMWD more effective than HAD in kinetic parameters and physicochemical quality attributes. Also, results indicated CMWD had the lowest and highest drying time and effective diffusivity. The exponential model for estimating IMWD activation energy, considering absolute power (1/P) and pulse ratio were also represented. The color change in apple slices dried by HAD showed the highest change. PMID:26788293
Mellado, Maria Candida M; Mena, Jimmy A; Lopes, António; Ramírez, Octavio T; Carrondo, Manuel J T; Palomares, Laura A; Alves, Paula M
2009-11-01
Virus-like particles constitute potentially relevant vaccine candidates. Nevertheless, their behavior in vitro and assembly process needs to be understood in order to improve their yield and quality. In this study we aimed at addressing these issues and for that purpose triple- and double-layered rotavirus-like particles (TLP 2/6/7 and DLP 2/6, respectively) size and zeta potential were measured using dynamic light scattering at different physicochemical conditions, namely pH, ionic strength, and temperature. Both TLP and DLP were stable within a pH range of 3-7 and at 5-25 degrees C. Aggregation occurred at 35-45 degrees C and their disassembly became evident at 65 degrees C. The isoelectric points of TLP and DLP were 3.0 and 3.8, respectively. In vitro kinetics of TLP disassembly was monitored. Ionic strength, temperature, and the chelating agent employed determined disassembly kinetics. Glycerol (10%) stabilized TLP by preventing its disassembly. Disassembled TLP was able to reassemble by dialysis at high calcium conditions. VP7 monomers were added to DLP in the presence of calcium to follow in vitro TLP assembly kinetics; its assembly rate being mostly affected by pH. Finally, DLP and TLP were found to coexist under certain conditions as determined from all reaction products analyzed by capillary electrophoresis. Overall, these results contribute to the design of new strategies for the improvement of TLP yield and quality by reducing the VP7 detachment from TLP.
NASA Astrophysics Data System (ADS)
Suchomska, K.; Graczyk, D.; Smolec, R.; Pietrzyński, G.; Gieren, W.; Stȩpień, K.; Konorski, P.; Pilecki, B.; Villanova, S.; Thompson, I. B.; Górski, M.; Karczmarek, P.; Wielgórski, P.; Anderson, R. I.
2015-07-01
We have analyzed the double-lined eclipsing binary system ASAS J180057-2333.8 from the All Sky Automated Survey (ASAS) catalogue. We measure absolute physical and orbital parameters for this system based on archival V-band and I-band ASAS photometry, as well as on high-resolution spectroscopic data obtained with ESO 3.6 m/HARPS and CORALIE spectrographs. The physical and orbital parameters of the system were derived with an accuracy of about 0.5-3 per cent. The system is a very rare configuration of two bright well-detached giants of spectral types K1 and K4 and luminosity class II. The radii of the stars are R1 = 52.12 ± 1.38 and R2 = 67.63 ± 1.40 R⊙ and their masses are M1 = 4.914 ± 0.021 and M2 = 4.875 ± 0.021 M⊙. The exquisite accuracy of 0.5 per cent obtained for the masses of the components is one of the best mass determinations for giants. We derived a precise distance to the system of 2.14 ± 0.06 kpc (stat.) ± 0.05 (syst.) which places the star in the Sagittarius-Carina arm. The Galactic rotational velocity of the star is Θs = 258 ± 26 km s-1 assuming Θ0 = 238 km s-1. A comparison with PARSEC isochrones places the system at the early phase of core helium burning with an age of slightly larger than 100 million years. The effect of overshooting on stellar evolutionary tracks was explored using the MESA star code.
Badran, Yasser Ali; Abdelaziz, Alsayed Saad; Shehab, Mohamed Ahmed; Mohamed, Hazem Abdelsabour Dief; Emara, Absel-Aziz Ali; Elnabtity, Ali Mohamed Ali; Ghanem, Maged Mohammed; ELHelaly, Hesham Abdel Azim
2016-01-01
Objective: The objective was to determine the predicting success of shock wave lithotripsy (SWL) using a combination of computed tomography based metric parameters to improve the treatment plan. Patients and Methods: Consecutive 180 patients with symptomatic upper urinary tract calculi 20 mm or less were enrolled in our study underwent extracorporeal SWL were divided into two main groups, according to the stone size, Group A (92 patients with stone ≤10 mm) and Group B (88 patients with stone >10 mm). Both groups were evaluated, according to the skin to stone distance (SSD) and Hounsfield units (≤500, 500–1000 and >1000 HU). Results: Both groups were comparable in baseline data and stone characteristics. About 92.3% of Group A rendered stone-free, whereas 77.2% were stone-free in Group B (P = 0.001). Furthermore, in both group SWL success rates was a significantly higher for stones with lower attenuation <830 HU than with stones >830 HU (P < 0.034). SSD were statistically differences in SWL outcome (P < 0.02). Simultaneous consideration of three parameters stone size, stone attenuation value, and SSD; we found that stone-free rate (SFR) was 100% for stone attenuation value <830 HU for stone <10 mm or >10 mm but total number SWL sessions and shock waves required for the larger stone group were higher than in the smaller group (P < 0.01). Furthermore, SFR was 83.3% and 37.5% for stone <10 mm, mean HU >830, SSD 90 mm and SSD >120 mm, respectively. On the other hand, SFR was 52.6% and 28.57% for stone >10 mm, mean HU >830, SSD <90 mm and SSD >120 mm, respectively. Conclusion: Stone size, stone density (HU), and SSD is simple to calculate and can be reported by radiologists to applying combined score help to augment predictive power of SWL, reduce cost, and improving of treatment strategies. PMID:27141192
Dominguez, H.; Nunez, M.J.; Lema, J.M. ); Chamy, R. )
1993-05-01
A quick technique for determination of kinetic parameters of fermentation processes is proposed and applied to the transformation of D-xylose into ethanol by Pichi stipitis. The commonly used method to evaluate these parameters is based on achieving several steady states. In the proposed procedure, [mu][sub m] and K[sub S] can be determined from only one steady state, by provoking a disturbance over it, after allowing the system to return to the original conditions. The main difference between the steady and unsteady state methods is the required fermentation time; while the former method lasted 350 h, the latter required a period 25 times lower. Kinetic and stoichiometric parameters were determined with both methods under anoxic and limited oxygen concentration conditions. Results from the two methods were compared, giving only 2% and 4.5% differences in the values of K[sub S] and [mu][sub m], respectively, under anoxic conditions; 12.5% for K[sub S] and a little over 4% for [mu][sub m] were the deviations under the latter ones.
Owhondah, Raymond O; Walker, Mark; Ma, Lin; Nimmo, Bill; Ingham, Derek B; Poggio, Davide; Pourkashanian, Mohamed
2016-06-01
Biochemical reactions occurring during anaerobic digestion have been modelled using reaction kinetic equations such as first-order, Contois and Monod which are then combined to form mechanistic models. This work considers models which include between one and three biochemical reactions to investigate if the choice of the reaction rate equation, complexity of the model structure as well as the inclusion of inhibition plays a key role in the ability of the model to describe the methane production from the semi-continuous anaerobic digestion of green waste (GW) and food waste (FW). A parameter estimation method was used to investigate the most important phenomena influencing the biogas production process. Experimental data were used to numerically estimate the model parameters and the quality of fit was quantified. Results obtained reveal that the model structure (i.e. number of reactions, inhibition) has a much stronger influence on the quality of fit compared with the choice of kinetic rate equations. In the case of GW there was only a marginal improvement when moving from a one to two reaction model, and none with inclusion of inhibition or three reactions. However, the behaviour of FW digestion was more complex and required either a two or three reaction model with inhibition functions for both ammonia and volatile fatty acids. Parameter values for the best fitting models are given for use by other authors.
NASA Astrophysics Data System (ADS)
Rubin, Yoram; Cushey, Mark A.; Wilson, Amy
1997-11-01
This paper presents a concise methodology for estimating the moments of the breakthrough curves for tracers and reactive solutes in heterogeneous aquifers. Under some conditions these are also the temporal or travel time moments between a source and a given destination downstream. The temporal moments of tracers as well as instantaneously or kinetically sorbing solutes, characterized by linear isotherms, are expressed in terms of a few parameters which characterize the chemical reactions and the spatial distribution and correlation structure of the hydraulic conductivity. The chemical reaction parameters are assumed to be homogeneous. The estimated moments can also be made conditional to field measurements. Applications for the case of uniform mean flow are presented, but the general approach can be applied for other flow regimes such as injection-pumping well doublets. Physical and chemical nonequilibrium processes are represented by mobile-immobile domains and two-site models, respectively. The estimated temporal moments can be used for both predictive purposes as well as for interpretation of field experiments. These two objectives are pursued in this paper. A significant advantage of the solution is that it does not require the assumptions of Gaussianity or log Gaussianity of the travel times. Throughout the discussion the combined and relative effects of the mass transfer and kinetic parameters and the spatial variability of the conductivity on the travel time moments are evaluated.
Barbero, N; Cauteruccio, S; Thakare, P; Licandro, E; Viscardi, G; Visentin, S
2016-10-01
Peptide nucleic acids (PNAs) are among the most interesting and versatile artificial structural mimics of nucleic acids and exhibit peculiar and important properties (i.e. high chemical stability, and a high resistance to cellular enzymes and nucleases). Despite their unnatural structure, they are able to recognize and bind DNA and RNA in a very high, specific and selective manner. One of the most popular, easy and reliable method to measure the stability of PNA-DNA hybrid systems is the melting temperature but the thermodynamic data are obtained using a big quantity of materials failing to provide information on the kinetics of the interaction. In the present work, the PNA decamer 6, with the TCACTAGATG sequence of nucleobases, and the corresponding fluorescent PNA-FITU (fluorescein isothiourea) decamer 8 were synthesized with standard manual Boc-based chemistry. The interaction of the PNA-FITU with parallel and antiparallel DNA has been studied by stopped-flow fluorescence, which is proposed as an alternative technique to obtain the kinetic parameters of the binding. The great advantage of using the stopped-flow technique is the possibility of studying the kinetics of the PNA-DNA duplex formation in a physiological environment. In particular, fluorescence stopped-flow technique has been exploited to compare the affinity of two PNA-DNA duplexes since it can discriminate between parallel and antiparallel DNA binding.
Barbero, N; Cauteruccio, S; Thakare, P; Licandro, E; Viscardi, G; Visentin, S
2016-10-01
Peptide nucleic acids (PNAs) are among the most interesting and versatile artificial structural mimics of nucleic acids and exhibit peculiar and important properties (i.e. high chemical stability, and a high resistance to cellular enzymes and nucleases). Despite their unnatural structure, they are able to recognize and bind DNA and RNA in a very high, specific and selective manner. One of the most popular, easy and reliable method to measure the stability of PNA-DNA hybrid systems is the melting temperature but the thermodynamic data are obtained using a big quantity of materials failing to provide information on the kinetics of the interaction. In the present work, the PNA decamer 6, with the TCACTAGATG sequence of nucleobases, and the corresponding fluorescent PNA-FITU (fluorescein isothiourea) decamer 8 were synthesized with standard manual Boc-based chemistry. The interaction of the PNA-FITU with parallel and antiparallel DNA has been studied by stopped-flow fluorescence, which is proposed as an alternative technique to obtain the kinetic parameters of the binding. The great advantage of using the stopped-flow technique is the possibility of studying the kinetics of the PNA-DNA duplex formation in a physiological environment. In particular, fluorescence stopped-flow technique has been exploited to compare the affinity of two PNA-DNA duplexes since it can discriminate between parallel and antiparallel DNA binding. PMID:27611452
Mann, U.; Selim, S.; Jih, J.
1982-06-01
The thermal decomposition of lignite in the absence of oxygen (pyrolysis) is important as a part of processes for converting lignite to more desirable fuels or for recovery of energy from deep basin lignite. The pyrolysis reaction kinetics of San Miguel (Texas) lignite has been experimentally studied in the temperature range 650 to 800/sup 0/C at atmospheric pressure. Gas and tar produced were collected and measured, and weight change as a function of time was measured. Lignite decomposition into gas, tar, and char can be described by three parallel first order reactions. In the temperature range investigated, the rates of pyrolysis are controlled by intraparticle transport phenomena. A simplified kinetic-transport model was used to estimate the individual reaction rate constants and activation energies. The gas produced was found to consist primarily of carbon dioxide, carbon monoxide, and hydrogen, with some methane, ethane, ethylene, and a trace C/sub 3/ compounds. Sample temperature increases and theoretical calculations indicate that oxygen from the lignite structure may be oxidizing lignite or pyrolysis products. It is recommended that, after suitable equipment modifications, the investigation be extended to study combined oxidation and pyrolysis of lignite.
Bhagavatula, Abhijit; Huffman, Gerald; Shah, Naresh; Honaker, Rick
2014-01-01
The thermal evolution profiles and kinetic parameters for the pyrolysis of two Montana coals (DECS-38 subbituminous coal and DECS-25 lignite coal), one biomass sample (corn stover), and their blends (10%, 20%, and 30% by weight of corn stover) have been investigated at a heating rate of 5°C/min in an inert nitrogen atmosphere, using thermogravimetric analysis. The thermal evolution profiles of subbituminous coal and lignite coal display only one major peak over a wide temperature distribution, ~152–814°C and ~175–818°C, respectively, whereas the thermal decomposition profile for corn stover falls in a much narrower band than that of the coals, ~226–608°C. Themore » nonlinearity in the evolution of volatile matter with increasing percentage of corn stover in the blends verifies the possibility of synergistic behavior in the blends with subbituminous coal where deviations from the predicted yield ranging between 2% and 7% were observed whereas very little deviations (1%–3%) from predicted yield were observed in blends with lignite indicating no significant interactions with corn stover. In addition, a single first-order reaction model using the Coats-Redfern approximation was utilized to predict the kinetic parameters of the pyrolysis reaction. The kinetic analysis indicated that each thermal evolution profile may be represented as a single first-order reaction. Three temperature regimes were identified for each of the coals while corn stover and the blends were analyzed using two and four temperature regimes, respectively.« less
NASA Technical Reports Server (NTRS)
Garcia-Comas, Maya; Lopez-Puertas, M.; Funke, B.; Bermejo-Pantaleon, D.; Marshall, Benjamin T.; Mertens, Christopher J.; Remsberg, Ellis E.; Mlynczak, Martin G.; Gordley, L. L.; Russell, James M.
2008-01-01
The vast set of near global and continuous atmospheric measurements made by the SABER instrument since 2002, including daytime and nighttime kinetic temperature (T(sub k)) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 micron CO2 limb emission. This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO2 vibrational state non-LTE populations in the retrieval algorithm above 70 km. Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known. We consider current uncertainties in the rates of quenching of CO2 (v2 ) by N2 , O2 and O, and the CO2 (v2 ) vibrational-vibrational exchange to estimate their impact on SABER T(sub k) for different atmospheric conditions. The T(sub k) is more sensitive to the uncertainty in the latter two and their effects depend on altitude. The T(sub k) combined systematic error due to non-LTE kinetic parameters does not exceed +/- 1.5 K below 95 km and +/- 4-5 K at 100 km for most latitudes and seasons (except for polar summer) if the Tk profile does not have pronounced vertical structure. The error is +/- 3 K at 80 km, +/- 6 K at 84 km and +/- 18 K at 100 km under the less favourable polar summer conditions. For strong temperature inversion layers, the errors reach +/- 3 K at 82 km and +/- 8 K at 90 km. This particularly affects tide amplitude estimates, with errors of up to +/- 3 K.
Fouchard, Swanny; Pruvost, Jérémy; Degrenne, Benoit; Titica, Mariana; Legrand, Jack
2009-01-01
Chlamydomonas reinhardtii is a green microalga capable of turning its metabolism towards H2 production under specific conditions. However this H2 production, narrowly linked to the photosynthetic process, results from complex metabolic reactions highly dependent on the environmental conditions of the cells. A kinetic model has been developed to relate culture evolution from standard photosynthetic growth to H2 producing cells. It represents transition in sulfur-deprived conditions, known to lead to H2 production in Chlamydomonas reinhardtii, and the two main processes then induced which are an over-accumulation of intracellular starch and a progressive reduction of PSII activity for anoxia achievement. Because these phenomena are directly linked to the photosynthetic growth, two kinetic models were associated, the first (one) introducing light dependency (Haldane type model associated to a radiative light transfer model), the second (one) making growth a function of available sulfur amount under extracellular and intracellular forms (Droop formulation). The model parameters identification was realized from experimental data obtained with especially designed experiments and a sensitivity analysis of the model to its parameters was also conducted. Model behavior was finally studied showing interdependency between light transfer conditions, photosynthetic growth, sulfate uptake, photosynthetic activity and O2 release, during transition from oxygenic growth to anoxic H2 production conditions.
Dill, Eric D.; Folmer, Jacob C.W.; Martin, James D.
2013-12-05
A series of simulations was performed to enable interpretation of the material and physical significance of the parameters defined in the Kolmogorov, Johnson and Mehl, and Avrami (KJMA) rate expression commonly used to describe phase boundary controlled reactions of condensed matter. The parameters k, n, and t_{0} are shown to be highly correlated, which if unaccounted for seriously challenge mechanistic interpretation. It is demonstrated that rate measurements exhibit an intrinsic uncertainty without precise knowledge of the location and orientation of nucleation with respect to the free volume into which it grows. More significantly, it is demonstrated that the KJMA rate constant k is highly dependent on sample size. However, under the simulated conditions of slow nucleation relative to crystal growth, sample volume and sample anisotropy correction affords a means to eliminate the experimental condition dependence of the KJMA rate constant, k, producing the material-specific parameter, the velocity of the phase boundary, v_{pb}.
Wong, Wilson W; Liao, James C
2009-11-01
Understanding how growth rates changes under different perturbations is fundamental to many aspect of microbial physiology. In this work, we experimentally showed that maximal specific growth rate is a square-root function of the biomass yield, the substrate turnover number, and the maximum synthesis rate of the substrate transporter under that condition. We used Escherichia coli cultures in lactose minimal medium as a model system by introducing genetic modifications, in vitro evolution, and ethanol stress to the cell. Deletion of crr affected all three parameters in different directions while deletion of ptsG decreased only the biomass yield. Ethanol stress negatively impacted all three parameters, while anaerobicity decreased biomass yield and transporter synthesis rate. In addition, laboratory evolution increased the growth rate in lactose mostly through enhancing the expression rate of the lac operon. Despite all these changes, the growth rate of the perturbed strain was successfully related to the three parameters by the square-root equation. Thus, this square-root relationship provides insight into how growth rate is altered by different physiological parameters. PMID:19712746
NASA Astrophysics Data System (ADS)
Wang, Yong; Goh, Wang Ling; Chai, Kevin T.-C.; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu
2016-04-01
The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators.
Wang, Yong; Goh, Wang Ling; Chai, Kevin T-C; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu
2016-04-01
The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators. PMID:27131699
Gritti, Fabrice; Guiochon, Georges A
2010-01-01
Band broadening in chromatography results from the combination of the dispersive effects that are associated with the different steps involved in the migration of compound bands along the column. These steps include longitudinal diffusion, trans-particle mass transfer, external film mass transfer, overall eddy diffusion, including trans-column, short-range inter-channel, trans-channel eddy diffusion, and the possible, additional mass transfer contributions arising from heat friction and the thermal heterogeneity of the column. We describe a series of experiments that provide the data needed to determine the coefficients of the contributions to band broadening of each one of these individual mass transfer steps. This specifically designed protocol can provide key information regarding the kinetic performance of columns used in liquid chromatography and explain why different columns behave so differently. The limitations, accuracy and precision of these methods are discussed. Further avenues of research that could improve the characterization of the mass transfer mechanisms in chromatographic columns, possibly contributing to the development of better columns, are suggested.
NASA Astrophysics Data System (ADS)
Efremenko, V. G.; Chabak, Yu. G.; Brykov, M. N.
2013-05-01
This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white cast iron during the destabilization heat treatment. The as-cast iron was heat treated at temperatures in the range of 800-1100 °C with soaking up to 6 h. Investigation was carried out by optical and electron microscopy, dilatometric analysis, Ms temperature measurement, and bulk hardness evaluation. TTT-curve of precipitation process of secondary carbides (M7C3, M23C6, M3C2) has been constructed in this study. It was determined that the precipitation occurs at the maximum rate at 950 °C where the process is started after 10 s and completed within 160 min further. The precipitation leads to significant increase of Ms temperature and bulk hardness; large soaking times at destabilization temperatures cause coarsening of secondary carbides and decrease in particles number, followed by decrease in hardness. The results obtained are discussed in terms of solubility of carbon in the austenite and diffusion activation of Cr atoms. The precipitation was found to consist of two stages with activation energies of 196.5 kJ/g-mole at the first stage and 47.1 kJ/g-mole at the second stage.
NASA Astrophysics Data System (ADS)
Denis, A. B.; Viana, R. B.; Plepis, A. M. G.
2012-06-01
This paper evaluates the photopolymerization kinetics and degree of conversion of different commercial dental composites when photoactivated by a LED curing unit using two different modes (standard and soft-start mode). The investigation was performed on with RelyX ARC (dual-cured), Filtek Z-350 (Nanocomposite), Filtek Z-250 (Hybrid), and Filtek Z-350flow (Flowable) resin composites. The analysis used was attenuated total reflection with a Fourier transform infrared (ATR-FTIR). The RelyX ARC resin demonstrated the highest degree of conversion with both LED photoactivation modes. For this resin a 28% decrease in maximum rate was observed and the time to reach its highest rate was almost 2.3 times higher than when the soft-start photoactivation light curing was used. Z-350flow resin recorder a higher maximum rate using the soft-start mode rather than the standard mode. In contrast, the Z-250 showed a higher value using the standard mode. Although Z-250 and Z-350 showed a higher total degree of conversion effectiveness using the soft-start mode, RelyX and Z-350flow achieved a higher value using the standard mode.
NASA Astrophysics Data System (ADS)
Mann, R. F.; Thurgood, C. P.
2011-05-01
Modelling of PEM fuel cells has long been an active research area to improve understanding of cell and stack operation, facilitate design improvements and support simulation studies. The prediction of activation polarization in most PEM models has concentrated on the cathode losses since anode losses are commonly much smaller and tend to be ignored. Further development of the anode activation polarization term is being undertaken to broaden the application and usefulness of PEM models in general. Published work on the kinetics of the hydrogen oxidation reaction (HOR) using Pt(h k l) electrodes in dilute H2SO4 has been recently reassessed and published. Correlations for diffusion-free exchange current densities were developed and empirical predictive equations for the anode activation polarization were proposed for the experimental conditions of the previously published work: Pt(1 0 0), Pt(1 1 0) and Pt(1 1 1) electrodes, pH2 of 1 atm, and temperatures of 1, 30 and 60 °C. It was concluded that the HOR on Pt(1 1 0) electrodes followed a Tafel-Volmer reaction sequence. The aim of the present paper is to generalize these Tafel-Volmer correlations, apply them to published data for Pt(1 1 0) electrodes and further develop the modelling of anode activation polarization over the range of operating conditions found in PEMFC operation.
Investigation of the skin effect in plasmas with the use of a two-parameter kinetic equation
NASA Astrophysics Data System (ADS)
Latyshev, A. V.; Tereshina, T. V.; Yushkanov, A. A.
2011-01-01
An analytic solution taking into account the effect of electron-electron collisions has been obtained for the problem on the skin effect in a nondegenerate electron plasma. The impedance was analyzed in relation to a parameter b, which describes the ratio of the frequency of electron-electron collisions to the total frequency of electron scattering. For b→0 the results obtained become the classical ones for weakly ionized plasma.
Wibowo, Scheling; Grauwet, Tara; Santiago, Jihan Santanina; Tomic, Jovana; Vervoort, Liesbeth; Hendrickx, Marc; Van Loey, Ann
2015-11-15
In view of understanding colour instability of pasteurised orange juice during storage, to the best of our knowledge, this study reports for the first time in a systematic and quantitative way on a range of changes in specific quality parameters as a function of time and as well as temperature (20-42 °C). A zero-order (°Brix, fructose, glucose), a first-order (vitamin C), a second-order (sucrose) and a fractional conversion model (oxygen) were selected to model the evolution of the parameters between parentheses. Activation energies ranged from 22 to 136 kJ mol(-1), HMF formation being the most temperature sensitive. High correlations were found between sugars, ascorbic acid, their degradation products (furfural and HMF) and total colour difference (ΔE(∗)). Based on PLS regression, the importance of the quality parameters for colour degradation was ranked relatively among each other: the acid-catalysed degradation of sugars and ascorbic acid degradation reactions appeared to be important for browning development in pasteurised orange juice during ambient storage. PMID:25977009
Wibowo, Scheling; Grauwet, Tara; Santiago, Jihan Santanina; Tomic, Jovana; Vervoort, Liesbeth; Hendrickx, Marc; Van Loey, Ann
2015-11-15
In view of understanding colour instability of pasteurised orange juice during storage, to the best of our knowledge, this study reports for the first time in a systematic and quantitative way on a range of changes in specific quality parameters as a function of time and as well as temperature (20-42 °C). A zero-order (°Brix, fructose, glucose), a first-order (vitamin C), a second-order (sucrose) and a fractional conversion model (oxygen) were selected to model the evolution of the parameters between parentheses. Activation energies ranged from 22 to 136 kJ mol(-1), HMF formation being the most temperature sensitive. High correlations were found between sugars, ascorbic acid, their degradation products (furfural and HMF) and total colour difference (ΔE(∗)). Based on PLS regression, the importance of the quality parameters for colour degradation was ranked relatively among each other: the acid-catalysed degradation of sugars and ascorbic acid degradation reactions appeared to be important for browning development in pasteurised orange juice during ambient storage.
NASA Astrophysics Data System (ADS)
Jayasudha, S.; Madhukumar, K.; Nair, C. M. K.; Nair, Resmi G.; Anandakumar, V. M.; Elias, Thayal Singh
2016-02-01
Nanostructured SrSO4:Eu phosphors with high thermoluminescence (TL) emission temperatures have been synthesized through a controlled chemical precipitation method. Structural analysis and TL studies under both γ-ray and X-ray excitations were done. The phosphors were characterized using Powder X-ray diffraction, X-ray photoelectron spectroscopy, SEM, TEM, thermogravimetry, UV-VIS and photoluminescence studies. The average crystallite size estimated using PXRD data is found to be around 40 nm. XPS and PL studies reveal that Eu2 + ions are the luminescence emission centres in the phosphor. The phosphor is found to be highly TL sensitive to both γ-rays and X-rays with very high emission temperature which is not reported so far. The emission behaviour is suitable for environmental radiation dosimetry applications. The TL glow curve shows well-defined isolated high temperature emission peak at 312 °C under 2 Gy γ-excitation and 284 °C for low energy diagnostic X-ray irradiation and 271 °C for high energy therapeutic X-rays. Chen's peak shape method is applied to obtain the kinetic parameters behind the TL emission. The TL mechanism is found to follow second order kinetics, suggesting the probability of re-trapping of charge carriers.
Jayasudha, S; Madhukumar, K; Nair, C M K; Nair, Resmi G; Anandakumar, V M; Elias, Thayal Singh
2016-02-15
Nanostructured SrSO4:Eu phosphors with high thermoluminescence (TL) emission temperatures have been synthesized through a controlled chemical precipitation method. Structural analysis and TL studies under both γ-ray and X-ray excitations were done. The phosphors were characterized using Powder X-ray diffraction, X-ray photoelectron spectroscopy, SEM, TEM, thermogravimetry, UV-VIS and photoluminescence studies. The average crystallite size estimated using PXRD data is found to be around 40nm. XPS and PL studies reveal that Eu(2+) ions are the luminescence emission centres in the phosphor. The phosphor is found to be highly TL sensitive to both γ-rays and X-rays with very high emission temperature which is not reported so far. The emission behaviour is suitable for environmental radiation dosimetry applications. The TL glow curve shows well-defined isolated high temperature emission peak at 312°C under 2Gy γ-excitation and 284°C for low energy diagnostic X-ray irradiation and 271°C for high energy therapeutic X-rays. Chen's peak shape method is applied to obtain the kinetic parameters behind the TL emission. The TL mechanism is found to follow second order kinetics, suggesting the probability of re-trapping of charge carriers. PMID:26562181
Jayasudha, S; Madhukumar, K; Nair, C M K; Nair, Resmi G; Anandakumar, V M; Elias, Thayal Singh
2016-02-15
Nanostructured SrSO4:Eu phosphors with high thermoluminescence (TL) emission temperatures have been synthesized through a controlled chemical precipitation method. Structural analysis and TL studies under both γ-ray and X-ray excitations were done. The phosphors were characterized using Powder X-ray diffraction, X-ray photoelectron spectroscopy, SEM, TEM, thermogravimetry, UV-VIS and photoluminescence studies. The average crystallite size estimated using PXRD data is found to be around 40nm. XPS and PL studies reveal that Eu(2+) ions are the luminescence emission centres in the phosphor. The phosphor is found to be highly TL sensitive to both γ-rays and X-rays with very high emission temperature which is not reported so far. The emission behaviour is suitable for environmental radiation dosimetry applications. The TL glow curve shows well-defined isolated high temperature emission peak at 312°C under 2Gy γ-excitation and 284°C for low energy diagnostic X-ray irradiation and 271°C for high energy therapeutic X-rays. Chen's peak shape method is applied to obtain the kinetic parameters behind the TL emission. The TL mechanism is found to follow second order kinetics, suggesting the probability of re-trapping of charge carriers.
Chidambaram, Ramalingam
2015-01-01
Biosorption is a promising alternative method to replace the existing conventional technique for Cr(VI) removal from the industrial effluent. In the present experimental design, the removal of Cr(VI) from the aqueous solution was studied by Aspergillus niger MSR4 under different environmental conditions in the batch systems. The optimum conditions of biosorption were determined by investigating pH (2.0) and temperature (27°C). The effects of parameters such as biomass dosage (g/L), initial Cr(VI) concentration (mg/L) and contact time (min) on Cr(VI) biosorption were analyzed using a three parameter Box–Behnken design (BBD). The experimental data well fitted to the Langmuir isotherm, in comparison to the other isotherm models tested. The results of the D-R isotherm model suggested that a chemical ion-exchange mechanism was involved in the biosorption process. The biosorption process followed the pseudo-second-order kinetic model, which indicates that the rate limiting step is chemisorption process. Fourier transform infrared (FT-IR) spectroscopic studies revealed the possible involvement of functional groups, such as hydroxyl, carboxyl, amino and carbonyl group in the biosorption process. The thermodynamic parameters for Cr(VI) biosorption were also calculated, and the negative ∆Gº values indicated the spontaneous nature of biosorption process. PMID:25786227
Cai, Junmeng; Li, Tao; Liu, Ronghou
2011-02-01
Using some theoretically simulated data constructed from known sets of the activation energy distribution f(E) (assumed to follow the Gaussian distribution [Formula in text] where E is the activation energy, E(0) is the mean value of the activation energy distribution, and σ is the standard deviation of the activation energy distribution) and the frequency factor k(0), a critical study of the use of the Miura-Maki integral method for the estimation of the kinetic parameters of the distributed activation energy model has been performed from three cases. For all cases, the use of the Miura-Maki integral method leads to important errors in the estimation of k(0). There are some differences between the assumed and calculated activation energy distributions and the differences decrease with increasing the assumed k(0) values (for Case 1), with increasing the assumed σ values (for Case 2), and with decreasing the b values (for Case 3).
Mulquiney, P J; Kuchel, P W
1999-01-01
Over the last 25 years, several mathematical models of erythrocyte metabolism have been developed. Although these models have identified the key features in the regulation and control of erythrocyte metabolism, many important aspects remain unexplained. In particular, none of these models have satisfactorily accounted for 2,3-bisphosphoglycerate (2,3-BPG) metabolism. 2,3-BPG is an important modulator of haemoglobin oxygen affinity, and hence an understanding of the regulation of 2,3-BPG concentration is important for understanding blood oxygen transport. A detailed, comprehensive, and hence realistic mathematical model of erythrocyte metabolism is presented that can explain the regulation and control of 2,3-BPG concentration and turnover. The model is restricted to the core metabolic pathways, namely glycolysis, the 2,3-BPG shunt and the pentose phosphate pathway (PPP), and includes membrane transport of metabolites, the binding of metabolites to haemoglobin and Mg(2+), as well as pH effects on key enzymic reactions and binding processes. The model is necessarily complex, since it is intended to describe the regulation and control of 2,3-BPG metabolism under a wide variety of physiological and experimental conditions. In addition, since H(+) and blood oxygen tension are important external effectors of 2,3-BPG concentration, it was important that the model take into account the large array of kinetic and binding phenomena that result from changes in these effectors. Through an iterative loop of experimental and simulation analysis many values of enzyme-kinetic parameters of the model were refined to yield close conformity between model simulations and 'real' experimental data. This iterative process enabled a single set of parameters to be found which described well the metabolic behaviour of the erythrocyte under a wide variety of conditions. PMID:10477269
Fontes, R; Ribeiro, J M; Sillero, A
2000-01-01
A combined analysis of enzyme inhibition and activation is presented, based on a rapid equilibrium model assumption in which one molecule of enzyme binds one molecule of substrate (S) and/or one molecule of a modifier X. The modifier acts as activator (essential or non-essential), as inhibitor (total or partial), or has no effect on the reaction rate (v), depending on the values of the equilibrium constants, the rate constants of the limiting velocity steps, and the concentration of substrate ([S]). Different possibilities have been analyzed from an equation written to emphasize that v = f([X]) is, in general and at a fixed [S], a hyperbolic function. Formulas for Su (the value of [S], different from zero, at which v is unaffected by the modifier) and v(su) (v at that particular [S]) were deduced. In Lineweaver-Burk plots, the straight lines related to different [X] generally cross in a point (P) with coordinates (Su, v(su)). In certain cases, point P is located in the first quadrant which implies that X acts as activator, as inhibitor, or has no effect, depending on [S]. Furthermore, we discuss: (1) the apparent Vmax and Km displayed by the enzyme in different situations; (2) the degree of effect (inhibition or activation) observed at different concentrations of substrate and modifier; (3) the concept of Ke, a parameter that depends on the concentration of substrate and helps to evaluate the effect of the modifier: it equals the value of [X] at which the increase or decrease in the reaction rate is half of that achieved at saturating [X]. Equations were deduced for the general case and for particular situations, and used to obtain computer-drawn graphs that are presented and discussed. Formulas for apparent Vmax, Km and Ke have been written in a way making it evident that these parameters can be expressed as pondered means.
NASA Astrophysics Data System (ADS)
Pöschl, U.; Rudich, Y.; Ammann, M.
2005-04-01
Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It allows to describe mass transport and chemical reactions at the gas-particle interface and to link aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion correction, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependencies; flexible inclusion/omission of chemical species and physicochemical processes; flexible convolution/deconvolution of species and processes; and full compatibility with traditional resistor model
Fleming, Donald G; Arseneau, Donald J; Sukhorukov, Oleksandr; Brewer, Jess H; Mielke, Steven L; Truhlar, Donald G; Schatz, George C; Garrett, Bruce C; Peterson, Kirk A
2011-11-14
The neutral muonic helium atom (4)Heμ, in which one of the electrons of He is replaced by a negative muon, may be effectively regarded as the heaviest isotope of the hydrogen atom, with a mass of 4.115 amu. We report details of the first muon spin rotation (μSR) measurements of the chemical reaction rate constant of (4)Heμ with molecular hydrogen, (4)Heμ + H(2) → (4)HeμH + H, at temperatures of 295.5, 405, and 500 K, as well as a μSR measurement of the hyperfine coupling constant of muonic He at high pressures. The experimental rate constants, k(Heμ), are compared with the predictions of accurate quantum mechanical (QM) dynamics calculations carried out on a well converged Born-Huang (BH) potential energy surface, based on complete configuration interaction calculations and including a Born-Oppenheimer diagonal correction. At the two highest measured temperatures the agreement between the quantum theory and experiment is good to excellent, well within experimental uncertainties that include an estimate of possible systematic error, but at 295.5 K the quantum calculations for k(Heμ) are below the experimental value by 2.1 times the experimental uncertainty estimates. Possible reasons for this discrepancy are discussed. Variational transition state theory calculations with multidimensional tunneling have also been carried out for k(Heμ) on the BH surface, and they agree with the accurate QM rate constants to within 30% over a wider temperature range of 200-1000 K. Comparisons between theory and experiment are also presented for the rate constants for both the D + H(2) and Mu + H(2) reactions in a novel study of kinetic isotope effects for the H + H(2) reactions over a factor of 36.1 in isotopic mass of the atomic reactant.
Lai, K P K; Dolan, K D; Ng, P K W
2009-06-01
Thermal and moisture effects on grape anthocyanin degradation were investigated using solid media to simulate processing at temperatures above 100 degrees C. Grape pomace (anthocyanin source) mixed with wheat pastry flour (1: 3, w/w dry basis) was used in both isothermal and nonisothermal experiments by heating the same mixture at 43% (db) initial moisture in steel cells in an oil bath at 80, 105, and 145 degrees C. To determine the effect of moisture on anthocyanin degradation, the grape pomace-wheat flour mixture was heated isothermally at 80 degrees C at constant moisture contents of 10%, 20%, and 43% (db). Anthocyanin degradation followed a pseudo first-order reaction with moisture. Anthocyanins degraded more rapidly with increasing temperature and moisture. The effects of temperature and moisture on the rate constant were modeled according to the Arrhenius and an exponential relationship, respectively. The nonisothermal reaction rate constant and activation energy (mean +/- standard error) were k(80 degrees C, 43% (db) moisture) = 2.81 x 10(-4)+/- 1.1 x 10(-6) s(-1) and DeltaE = 75273 +/- 197 J/g mol, respectively. The moisture parameter for the exponential model was 4.28 (dry basis moisture content)(-1). One possible application of this study is as a tool to predict the loss of anthocyanins in nutraceutical products containing grape pomace. For example, if the process temperature history and moisture history in an extruded snack fortified with grape pomace is known, the percentage anthocyanin loss can be predicted. PMID:19646039
Locher, Kathrin; Borghardt, Jens M; Frank, Kerstin J; Kloft, Charlotte; Wagner, Karl G
2016-08-01
Biphasic dissolution models are proposed to have good predictive power for the in vivo absorption. The aim of this study was to improve our previously introduced mini-scale dissolution model to mimic in vivo situations more realistically and to increase the robustness of the experimental model. Six dissolved APIs (BCS II) were tested applying the improved mini-scale biphasic dissolution model (miBIdi-pH-II). The influence of experimental model parameters including various excipients, API concentrations, dual paddle and its rotation speed was investigated. The kinetics in the biphasic model was described applying a one- and four-compartment pharmacokinetic (PK) model. The improved biphasic dissolution model was robust related to differing APIs and excipient concentrations. The dual paddle guaranteed homogenous mixing in both phases; the optimal rotation speed was 25 and 75rpm for the aqueous and the octanol phase, respectively. A one-compartment PK model adequately characterised the data of fully dissolved APIs. A four-compartment PK model best quantified dissolution, precipitation, and partitioning also of undissolved amounts due to realistic pH profiles. The improved dissolution model is a powerful tool for investigating the interplay between dissolution, precipitation and partitioning of various poorly soluble APIs (BCS II). In vivo-relevant PK parameters could be estimated applying respective PK models.
Locher, Kathrin; Borghardt, Jens M; Frank, Kerstin J; Kloft, Charlotte; Wagner, Karl G
2016-08-01
Biphasic dissolution models are proposed to have good predictive power for the in vivo absorption. The aim of this study was to improve our previously introduced mini-scale dissolution model to mimic in vivo situations more realistically and to increase the robustness of the experimental model. Six dissolved APIs (BCS II) were tested applying the improved mini-scale biphasic dissolution model (miBIdi-pH-II). The influence of experimental model parameters including various excipients, API concentrations, dual paddle and its rotation speed was investigated. The kinetics in the biphasic model was described applying a one- and four-compartment pharmacokinetic (PK) model. The improved biphasic dissolution model was robust related to differing APIs and excipient concentrations. The dual paddle guaranteed homogenous mixing in both phases; the optimal rotation speed was 25 and 75rpm for the aqueous and the octanol phase, respectively. A one-compartment PK model adequately characterised the data of fully dissolved APIs. A four-compartment PK model best quantified dissolution, precipitation, and partitioning also of undissolved amounts due to realistic pH profiles. The improved dissolution model is a powerful tool for investigating the interplay between dissolution, precipitation and partitioning of various poorly soluble APIs (BCS II). In vivo-relevant PK parameters could be estimated applying respective PK models. PMID:27297570
Braxton, B L; Mullins, L S; Raushel, F M; Reinhart, G D
1992-03-01
The effects of the allosteric ligands UMP, IMP, and ornithine on the partial reactions catalyzed by Escherichia coli carbamyl phosphate synthetase have been examined. Both of these reactions, a HCO3(-)-dependent ATP synthesis reaction and a carbamyl phosphate-dependent ATP synthesis reaction, follow bimolecular ordered sequential kinetic mechanisms. In the ATPase reaction, MgATP binds before HCO3- as established previously for the overall reaction catalyzed by carbamyl phosphate synthetase [Raushel, F. M., Anderson, P. M., & Villafranca, J. J. (1978) Biochemistry 17, 5587-5591]. The initial velocity kinetics for the ATP synthesis reaction indicate that MgADP binds before carbamyl phosphate in an equilibrium ordered mechanism except in the presence of ornithine. Determination of true thermodynamic linked-function parameters describing the impact of allosteric ligands on the binding interactions of the first substrate to bind in an ordered mechanism requires experiments to be performed in which both substrates are varied even if only one is apparently affected by the allosteric ligands. In so doing, we have found that IMP has little effect on the overall reaction of either of these two partial reactions. UMP and ornithine, which have a pronounced effect on the apparent Km for MgATP in the overall reaction, both substantially change the thermodynamic dissociation constant for MgADP from the binary E-MgADP complex, Kia, in the ATP synthesis reaction, with UMP increasing Kia 15-fold and ornithine decreasing Kia by 18-fold. By contrast, only UMP substantially affects the Kia for MgATP in the ATPase reaction, increasing it by 5-fold.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1531767
Ratelle, Mylène; Coté, Jonathan; Bouchard, Michèle
2015-12-01
Biomonitoring of pyrethroid exposure is largely conducted but human toxicokinetics has not been fully documented. This is essential for a proper interpretation of biomonitoring data. Time profiles and toxicokinetic parameters of key biomarkers of exposure to cypermethrin in orally exposed volunteers have been documented and compared with previously available kinetic data following permethrin dosing. Six volunteers ingested 0.1 mg kg(-1) bodyweight of cypermethrin acutely. The same volunteers were exposed to permethrin earlier. Blood samples were taken over 72 h after treatment and complete timed urine voids were collected over 84 h postdosing. Cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acids (trans- and cis-DCCA) and 3-phenoxybenzoic acid (3-PBA) metabolites, common to both cypermethrin and permethrin, were quantified. Blood and urinary time courses of all three metabolites were similar following cypermethrin and permethrin exposure. Plasma levels of metabolites reached peak values on average ≈ 5-7 h post-dosing; the elimination phase showed mean apparent half-lives (t½ ) for trans-DCCA, cis-DCCA and 3-PBA of 5.1, 6.9 and 9.2 h, respectively, following cypermethrin treatment as compared to 7.1, 6.2 and 6.5 h after permethrin dosing. Corresponding mean values obtained from urinary rate time courses were peak values at ≈ 9 h post-dosing and apparent elimination t½ of 6.3, 6.4 and 6.4 h for trans-DCCA, cis-DCCA and 3-PBA, respectively, following cypermethrin treatment as compared to 5.4, 4.5 and 5.7 h after permethrin dosing. These data confirm that the kinetics of cypermethrin is similar to that of permethrin in humans and that their common biomarkers of exposure may be used for an overall assessment of exposure.
NASA Astrophysics Data System (ADS)
Bisetti, Fabrizio; El Morsli, Mbark
2014-01-01
The effects of an electric field on the collision rates, energy exchanges and transport properties of electrons in premixed flames are investigated via solutions to the Boltzmann kinetic equation. The case of high electric field strength, which results in high-energy, non-thermal electrons, is analysed in detail at sub-breakdown conditions. The rates of inelastic collisions and the energy exchange between electrons and neutrals in the reaction zone of the flame are characterised quantitatively. The analysis includes attachment, ionisation, impact dissociation, and vibrational and electronic excitation processes. Our results suggest that Townsend breakdown occurs for E/N = 140 Td. Vibrational excitation is the dominant process up to breakdown, despite important rates of electronic excitation of CO, CO2 and N2 as well as impact dissociation of O2 being apparent from 50 Td onwards. Ohmic heating in the reaction zone is found to be negligible (less than 2% of peak heat release rate) up to breakdown field strengths for realistic electron densities equal to 1010 cm-3. The observed trends are largely independent of equivalence ratio. In the non-thermal regime, electron transport coefficients are insensitive to mixture composition and approximately constant across the flame, but are highly dependent on the electric field strength. In the thermal limit, kinetic parameters and transport coefficients vary substantially across the flame due to the spatially inhomogeneous concentration of water vapour. A practical approach for identifying the plasma regime (thermal versus non-thermal) in studies of electric field effects on flames is proposed.
NASA Astrophysics Data System (ADS)
Pöschl, U.; Rudich, Y.; Ammann, M.
2007-12-01
Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It enables a detailed description of mass transport and chemical reactions at the gas-particle interface, and it allows linking aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined and consistent rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependences (transient and steady-state conditions); flexible addition of unlimited numbers of chemical species and physicochemical processes; optional aggregation or resolution
Lauquin, G; Lunardi, J; Vignais, P V
1976-01-01
1. Ghe kinetic and binding parameters of adenine-nucleotide transport have been studied in mitochondria isolated from yeast cells in which the mitochondrial protein-synthetizing system had been inhibited by growth in the presence of erythromycin. These parameters have also been studied in promitochondria isolated from yeast grown in anaerobiosis aesence of ethidium bromide results in a loss of cytochromes b, alpha and alpha 3, but it does not affect the rate constant of ADP transport in isolated mitochondria, nor the number of binding sites for atractyloside, bongkrekic acid and ADP. 3. Promitochondria from S. cerevisiae grown in anaerobiosis, mitochondria from a qo mutant (qo mitochondria) and mitochondria from S. cerevisiae grown in the presence of erythromycin (ERY-mitochondria) are able to transport ADP by the same exchange-diffusion mechanism, sensitive to carboxy-atractyloside, and with the same rate constant as the wild type mitochondria. Promitochondria, qo mitochondria and ERY-mitochondria bind atractyloside, bongkrekic acid and ADP with the same high affinity as the wild type mitochondria. They only differ from the wild type mitochondria by a lower number of binding sites for ADP and for specific inhibitors of ADP transport. 4. Mitochondria isolated from the nuclear mutant p9 of S. cerevisae, called also op1, are characterized by a much lower affinity for bongkrekic acid than mitochondria from the wild type (20 times less). 5. Manipulation of the fatty acid composition of the mitochondrial membranes in the desaturase auxotroph mutant KD115 does not modify the number of sites, no their affinity of bongkrekic acid. 6. The above results are interpreted to mean that the structure and function of the mitochondrial adN translocator are not affected by any change in the mitochondrial protein synthetizing system. PMID:795470
Sato, H.; Sugiyama, Y.; Sawada, Y.; Iga, T.; Sakamoto, S.; Fuwa, T.; Hanano, M. )
1988-11-01
Hepatic elimination of epidermal growth factor (EGF) via receptor-mediated endocytosis was studied by a multiple-indicator dilution method in the isolated perfused rat liver, in which cell polarity and spatial organization are maintained. In this method EGF was given with inulin, an extracellular reference, as a bolus into the portal vein, and dilution curves of both compounds in the hepatic vein effluent were analyzed. Analysis of the dilution curve for EGF, compared with that for somatostatin, which showed no specific binding to isolated liver plasma membranes, resulted as follows: (i) both extraction ratio and distribution volume of {sup 125}I-labeled EGF decreased as the injected amount of unlabeled EGF increased; (ii) the ratio plot of the dilution curve for EGF exhibited an upward straight line initially for a short period of time, whereas the ratio plot of somatostatin gradually decreased. The multiple-indicator dilution method was used for other peptides also. Insulin and glucagon, known to have hepatocyte receptors, behaved similarly to EGF in shape of their ratio plots. The kinetic parameters calculated by this analysis were comparable with reported values obtained by in vitro direct binding measurements at equilibrium using liver homogenates. They conclude that the multiple-indicator dilution method is a good tool for analyzing the dynamics of peptide hormones-cell-surface receptor interaction under a condition in which spatial architecture of the liver is maintained.
Morozova, E A; Kulikova, V V; Yashin, D V; Anufrieva, N V; Anisimova, N Y; Revtovich, S V; Kotlov, M I; Belyi, Y F; Pokrovsky, V S; Demidkina, T V
2013-07-01
The steady-state kinetic parameters of pyridoxal 5'-phosphate-dependent recombinant methionine γ -lyase from three pathogenic bacteria, Clostridium tetani, Clostridium sporogenes, and Porphyromonas gingivalis, were determined in β- and γ-elimination reactions. The enzyme from C. sporogenes is characterized by the highest catalytic efficiency in the γ-elimination reaction of L-methionine. It was demonstrated that the enzyme from these three sources exists as a tetramer. The N-terminal poly-histidine fragment of three recombinant enzymes influences their catalytic activity and facilitates the aggregation of monomers to yield dimeric forms under denaturing conditions. The cytotoxicity of methionine γ-lyase from C. sporogenes and C. tetani in comparison with Citrobacter freundii was evaluated using K562, PC-3, LnCap, MCF7, SKOV-3, and L5178y tumor cell lines. K562 (IC50=0.4-1.3 U/ml), PC-3 (IC50=0.1-0.4 U/ml), and MCF7 (IC50=0.04-3.2 U/ml) turned out to be the most sensitive cell lines.
Beloglazova, N G; Mironova, N L; Konevets, D A; Petiuk, V A; Sil'nikov, V N; Vlasov, V V; Zenkova, M A
2002-01-01
Kinetic parameters of cleavage of CpA and UpA sequences in an oligoribonucleotide under the action of artificial ribonuclease ABL3C1 were measured. The compounds were built of RNA-binding domain B, catalytic fragment C, linker L3 comprising 3 methylene groups, and aliphatic fragment A. The rate of cleavage of phosphodiester bonds in CpA sequence within decaribonucleotide UUCAUGUAAA was shown to be 3.4 +/- 0.2 times higher than in UpA sequence. The rate of cleavage of phosphodiester bonds were found to depend on substrate length: a thousandfold increase in cleavage rate constant was observed for CpA sequence in decaribonucleotide as compared with diribonucleotide monophosphate CpA. A slight decrease in the cleavage rates was observed for the reactions proceeding in different buffers at pH 7.0: imidazole > HEPES > phosphate > cacodylate. At the same time, the ratio of cleavage rates for CpA and UpA sequences remained constant.
Salwiński, Aleksander; Delépée, Raphaël; Maunit, Benoît
2011-12-15
A mass spectrometry (MS)-based methodology for enzymatic assay in equilibrium conditions was designed and evaluated. This on-line assay involves the introduction of a continuous-flow step gradient (CFSG) of a substrate solution in the column containing immobilized enzyme and the simultaneous tracking of the product formation. We showed that the constant concentration of substrate in the entire bioreactor for an appropriate duration ensures the equilibration of the studied enzyme (mushroom tyrosinase). Under these conditions, it was demonstrated also that the kinetic and enzymatic parameters (Michaelis-Menten constant, K(M) , the maximal specific activity, SA(max)) are independent of the flow rate of the mobile phase. The feasibility of the mentioned approach for inhibitory tests was also investigated. The coupling of the mass spectrometer to the bio-reactor allows the selective monitoring of the enzymatic reaction products and increases their detection level. Very high sensitivity, 500 pmol/min/column, and selective monitoring of the products of the enzymatic reaction are allowed by MS detection. The methodology developed here constitutes a sensitive analytical tool to study enzymes requiring long equilibration times.
Huang, Limao; Liu, Jingyong; He, Yao; Sun, Shuiyu; Chen, Jiacong; Sun, Jian; Chang, KenLin; Kuo, Jiahong; Ning, Xun'an
2016-10-01
Thermodynamics and kinetics of sewage sludge (SS) and water hyacinth (WH) co-combustion as a blend fuel (SW) for bioenergy production were studied through thermogravimetric analysis. In CO2/O2 atmosphere, the combustion performance of SS added with 10-40wt.% WH was improved 1-1.97 times as revealed by the comprehensive combustion characteristic index (CCI). The conversion of SW in different atmospheres was identified and their thermodynamic parameters (ΔH,ΔS,ΔG) were obtained. As the oxygen concentration increased from 20% to 70%, the ignition temperature of SW decreased from 243.1°C to 240.3°C, and the maximum weight loss rate and CCI increased from 5.70%·min(-1) to 7.26%·min(-1) and from 4.913%(2)·K(-3)·min(-2) to 6.327%(2)·K(-3)·min(-2), respectively, which corresponded to the variation in ΔS and ΔG. The lowest activation energy (Ea) of SW was obtained in CO2/O2=7/3 atmosphere.
Becker, P; Abu-Reesh, I; Markossian, S; Antranikian, G; Märkl, H
1997-08-01
A thermostable lipase was produced in continuous cultivation of a newly isolated thermophilic Bacillus sp. strain IHI-91 growing optimally at 65 degrees C. Lipase activity decreased with increasing dilution rate while lipase productivity showed a maximum of 340 U l-1 h-1 at a condition rate of 0.4 h-1. Lipase productivity was increased by 50% compared to data from batch fermentations. Up to 70% of the total lipase activity measured was associated to cells and by-products or residual substrate. Kinetic and stoichiometric parameters for the utilisation of olive oil were determined. The maximal biomass output method led to a saturation constant Ks of 0.88 g/l. Both batch growth data and a washout experiment yielded a maximal specific growth rate, mu max, of 1.0 h-1. Oxygen uptake rates of up to 2.9 g l-1 h-1 were calculated and the yield coefficient, Y X/O, was determined to be 0.29 g dry cell weight/g O2. From an overall material balance the yield coefficient, Y X/S, was estimated to be 0.60 g dry cell weight/g olive oil.
Kitahama, Yasutaka; Sakaguchi, Yoshio
2008-01-17
We investigated the quantum beats, the oscillation between singlet and triplet states of radical pairs induced by the microwave field resonant to one of the component radicals. They were observed as the alternation of the yields of the component radicals by a nanosecond time-resolved optical absorption with the X-band (9.15 GHz) resonant microwave pulse. This technique was applied to the photochemical reaction of benzophenone, benzophenone-d(10), and benzophenone-carbonyl-(13)C in a sodium dodecylsulfate micellar solution with a step-by-step increase of the resonant microwave pulse width. The yields of the component radicals showed alternation with an increase of the microwave pulse width. This indicates that the radical pair retains spin coherence in the micellar solution. The magnetic isotope effect on the amplitude of the quantum beat was observed. The MW effect on the quantum beat of BP-(13)C decreases from 80% to 60% of that of BP by irradiation of the pi-pulse MW due to spin-locking. The kinetic parameters were also determined using the X- or Ku-band (17.44 GHz) region. They are almost similar to each other except for the intersystem recombination rate in the system of BP-(13)C, which may be slightly higher than those in other systems.
Huang, Limao; Liu, Jingyong; He, Yao; Sun, Shuiyu; Chen, Jiacong; Sun, Jian; Chang, KenLin; Kuo, Jiahong; Ning, Xun'an
2016-10-01
Thermodynamics and kinetics of sewage sludge (SS) and water hyacinth (WH) co-combustion as a blend fuel (SW) for bioenergy production were studied through thermogravimetric analysis. In CO2/O2 atmosphere, the combustion performance of SS added with 10-40wt.% WH was improved 1-1.97 times as revealed by the comprehensive combustion characteristic index (CCI). The conversion of SW in different atmospheres was identified and their thermodynamic parameters (ΔH,ΔS,ΔG) were obtained. As the oxygen concentration increased from 20% to 70%, the ignition temperature of SW decreased from 243.1°C to 240.3°C, and the maximum weight loss rate and CCI increased from 5.70%·min(-1) to 7.26%·min(-1) and from 4.913%(2)·K(-3)·min(-2) to 6.327%(2)·K(-3)·min(-2), respectively, which corresponded to the variation in ΔS and ΔG. The lowest activation energy (Ea) of SW was obtained in CO2/O2=7/3 atmosphere. PMID:27416513
NASA Astrophysics Data System (ADS)
Tan, R. P.; Carrey, J.; Respaud, M.
2014-12-01
Understanding the influence of dipolar interactions in magnetic hyperthermia experiments is of crucial importance for fine optimization of nanoparticle (NP) heating power. In this study we use a kinetic Monte Carlo algorithm to calculate hysteresis loops that correctly account for both time and temperature. This algorithm is shown to correctly reproduce the high-frequency hysteresis loop of both superparamagnetic and ferromagnetic NPs without any ad hoc or artificial parameters. The algorithm is easily parallelizable with a good speed-up behavior, which considerably decreases the calculation time on several processors and enables the study of assemblies of several thousands of NPs. The specific absorption rate (SAR) of magnetic NPs dispersed inside spherical lysosomes is studied as a function of several key parameters: volume concentration, applied magnetic field, lysosome size, NP diameter, and anisotropy. The influence of these parameters is illustrated and comprehensively explained. In summary, magnetic interactions increase the coercive field, saturation field, and hysteresis area of major loops. However, for small amplitude magnetic fields such as those used in magnetic hyperthermia, the heating power as a function of concentration can increase, decrease, or display a bell shape, depending on the relationship between the applied magnetic field and the coercive/saturation fields of the NPs. The hysteresis area is found to be well correlated with the parallel or antiparallel nature of the dipolar field acting on each particle. The heating power of a given NP is strongly influenced by a local concentration involving approximately 20 neighbors. Because this local concentration strongly decreases upon approaching the surface, the heating power increases or decreases in the vicinity of the lysosome membrane. The amplitude of variation reaches more than one order of magnitude in certain conditions. This transition occurs on a thickness corresponding to approximately
Kinetic investigation of wood pyrolysis
Thurner, F.; Mann, U.; Beck, S. R.
1980-06-01
The objective of this investigation was to determine the kinetics of the primary reactions of wood pyrolysis. A new experimental method was developed which enabled us to measure the rate of gas, tar, and char production while taking into account the temperature variations during the wood heating up. The experimental method developed did not require any sophisticated instruments. It facilitated the collection of gas, tar and residue (unreacted wood and char) as well as accurate measurement of the temperature inside the wood sample. Expressions relating the kinetic parameters to the measured variables were derived. The pyrolysis kinetics was investigated in the range of 300 to 400/sup 0/C at atmospheric pressure and under nitrogen atmosphere. Reaction temperature and mass fractions of gas, tar, and residue were measured as a function of time. Assuming first-order reactions, the kinetic parameters were determined using differential method. The measured activation energies of wood pyrolysis to gas, tar, and char were 88.6, 112.7, and 106.5 kJ/mole, respectively. These kinetic data were then used to predict the yield of the various pyrolysis products. It was found that the best prediction was obtained when an integral-mean temperature obtained from the temperature-time curve was used as reaction temperature. The pyrolysis products were analyzed to investigate the influence of the pyrolysis conditions on the composition. The gas consisted mainly of carbon dioxide, carbon monoxide, oxygen, and C/sub 3//sup +/-compounds. The gas composition depended on reaction time as well as reactor temperature. The tar analysis indicated that the tar consisted of about seven compounds. Its major compound was believed to be levoglucosan. Elemental analysis for the char showed that the carbon content increased with increasing temperature.
Ramalingam, Chidambaram
2015-01-01
This study is focused on the possible use of Ceratocystis paradoxa MSR2 native biomass for Cr(VI) biosorption. The influence of experimental parameters such as initial pH, temperature, biomass dosage, initial Cr(VI) concentration and contact time were optimized using batch systems as well as response surface methodology (RSM). Maximum Cr(VI) removal of 68.72% was achieved, at an optimal condition of biomass dosage 2g L−1, initial Cr(VI) concentration of 62.5 mg L−1 and contact time of 60 min. The closeness of the experimental and the predicted values exhibit the success of RSM. The biosorption mechanism of MSR2 biosorbent was well described by Langmuir isotherm and a pseudo second order kinetic model, with a high regression coefficient. The thermodynamic study also revealed the spontaneity and exothermic nature of the process. The surface characterization using FT-IR analysis revealed the involvement of amine, carbonyl and carboxyl groups in the biosorption process. Additionally, desorption efficiency of 92% was found with 0.1 M HNO3. The Cr(VI) removal efficiency, increased with increase in metal ion concentration, biomass concentration, temperature but with a decrease in pH. The size of the MSR2 biosorbent material was found to be 80 μm using particle size analyzer. Atomic force microscopy (AFM) visualizes the distribution of Cr(VI) on the biosorbent binding sites with alterations in the MSR2 surface structure. The SEM-EDAX analysis was also used to evaluate the binding characteristics of MSR2 strain with Cr(VI) metals. The mechanism of Cr(VI) removal of MSR2 biomass has also been proposed. PMID:25822726
Negri-Cesi, P; Celotti, F; Martini, L
1989-01-01
It has been demonstrated that exposure of the hamster to a short photoperiod (light on less than 12 h/day) induces an increased sensitivity of the hypothalamic-pituitary axis to the feedback effect of testosterone. It was consequently felt of interest to investigate whether the photoperiod might act by increasing the formation of estrogens in the CNS and/or in the anterior pituitary. The aromatase activity was studied utilizing a sensitive in vitro assay that measures the amount of 3H2O formed during the conversion of [1 beta-3H]androstenedione to estrone. First of all it has been investigated whether the aromatizing enzymes, previously found in the hypothalamus, were present also in the cerebral cortex and in the anterior pituitary; secondly, the kinetic parameters of the enzyme were determined; finally, the possible variation of the central aromatase activity in hamsters exposed to a long or to a short photoperiod was investigated. The results obtained indicate that both in the hypothalamus and in the cerebral cortex the aromatization of androstenedione is linear with respect to time of incubation and tissue concentration; moreover, in the two structures, the enzyme demonstrated a similar Michaelis-Menten constant (0.03 and 0.08 microM respectively). From a quantitative point of view, the hypothalamus seems to possess an aromatizing activity higher than that of the cerebral cortex. Exposure of the hamsters to a short photostimulation for 60 days resulted in a significant regression of the reproductive system (decreased testicular weight and serum LH levels) and in a decrease of the aromatase activity of the hypothalamus. There was no effect of the photoperiod on the aromatase of the cerebral cortex. Since androgens are known to stimulate the aromatase, the present data might be tentatively interpreted by suggesting that the variation in the formation of estrogens during the short photoperiod might be the consequence of the decreased serum testosterone levels
Garcia-Peña, E I; Canul-Chan, M; Chairez, I; Salgado-Manjarez, E; Aranda-Barradas, J
2013-09-01
Hydrogen (H2) production from the organic fraction of solid waste such as fruit and vegetable waste (FVW) is a novel and feasible energy technology. Continuous application of this process would allow for the simultaneous treatment of organic residues and energy production. In this study, batch experiments were conducted using glucose as substrate, and data of H2 production obtained were successfully adjusted by a logistic model. The kinetic parameters (μ max = 0.101 h(-1), K s = 2.56 g/L) of an H2-producing microbial culture determined by the Monod and Haldane-Andrews growth models were used to establish the continuous culture conditions. This strategy led to a productive steady state in continuous culture. Once the steady state was reached in the continuous reactor, a maximum H2 production of 700 mL was attained. The feasibility of producing H2 from the FVW obtained from a local market in Mexico City was also evaluated using batch conditions. The effect of the initial FVW concentration on the H2 production and waste organic material degradation was determined. The highest H2 production rate (1.7 mmol/day), the highest cumulative H2 volume (310 mL), and 25 % chemical oxygen demand (COD) removal were obtained with an initial substrate (FVW) concentration of 37 g COD/L. The lowest H2 production rates were obtained with relatively low initial substrate concentrations of 5 and 11 g COD/L. The H2 production rates with FVW were also characterized by the logistic model. Similar cumulative H2 production was obtained when glucose and FVW were used as substrates.
NASA Astrophysics Data System (ADS)
Huerta, E. A.; Gair, Jonathan R.; Brown, Duncan A.
2012-03-01
-4, and 10-1, respectively. LISA should also be able to determine the location of the source in the sky and the SMBH spin orientation to within ˜10-4 steradians. Furthermore, we show that by including conservative corrections up to 2.5PN order, systematic errors no longer dominate over statistical errors. This shows that search templates that include small body spin effects in the equations of motion up to 2.5PN order should allow us to perform accurate parameter extraction for IMRIs with typical signal-to-noise ratio ˜1000.
de Andrade, Rafael Ramos; Maugeri Filho, Francisco; Maciel Filho, Rubens; da Costa, Aline Carvalho
2013-02-01
In this work, a kinetic model for ethanol fermentation from sugarcane bagasse enzymatic hydrolysate concentrated with molasses was developed. A model previously developed for fermentation of pure molasses was modified by the inclusion of a new term for acetic acid inhibition on microorganism growth rate and the kinetic parameters were estimated as functions of temperature. The influence of the hydrolysate on the kinetic parameters is analyzed by comparing with the parameters from fermentation of pure molasses. The impact of cells recycling in the kinetic parameters is also evaluated, as well as on the ethanol yield and productivity. The model developed described accurately most of the fermentations performed in several successive batches for temperatures from 30 to 38°C.
NASA Astrophysics Data System (ADS)
Kalenchuk, A. N.; Bogorodskii, S. E.; Bogdan, V. I.
2016-10-01
Comparative studies on the temperature dependence of the dehydrogenation of cis- and trans-isomers of perhydro- m-terphenyl are performed in a flow catalytic reactor. Rate constants and equilibrium constants of all elementary acts of this reaction are calculated on basis of experimental data using the KINET 0.8 program for the mathematical modeling of the kinetics of complex reactions. The resulting data indicate that perhydro- m-terphenyl cis- and trans-isomers structural differences have no appreciable effect on dehydrogenation.
Metastable Solution Thermodynamic Properties and Crystal Growth Kinetics
NASA Technical Reports Server (NTRS)
Kim, Soojin; Myerson, Allan S.
1996-01-01
The crystal growth rates of NH4H2PO4, KH2PO4, (NH4)2SO4, KAl(SO4)2 central dot 12H2O, NaCl, and glycine and the nucleation rates of KBr, KCl, NaBr central dot 2H2O, (NH4)2Cl, and (NH4)2SO4 were expressed in terms of the fundamental driving force of crystallization calculated from the activity of supersaturated solutions. The kinetic parameters were compared with those from the commonly used kinetic expression based on the concentration difference. From the viewpoint of thermodynamics, rate expressions based on the chemical potential difference provide accurate kinetic representation over a broad range of supersaturation. The rates estimated using the expression based on the concentration difference coincide with the true rates of crystallization only in the concentration range of low supersaturation and deviate from the true kinetics as the supersaturation increases.
Measurement of the Kinetic Energy of a Body by Means of a Deformation.
ERIC Educational Resources Information Center
Perez, Pedro J.; And Others
1996-01-01
Describes a technique that measures the deformation produced in a plastic material by a falling ball in order to compute the ball's kinetic energy. Varying the parameters produces accurate results and gives students a good understanding of the measurement of energy. Combines various mechanical concepts that students have learned separately in…
Erbium hydride thermal desorption : controlling kinetics.
Ferrizz, Robert Matthew
2007-08-01
Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report show that hydride film processing parameters directly impact thermal stability. Issues to be addressed include desorption kinetics for dihydrides and trihydrides, and the effect of film growth parameters, loading parameters, and substrate selection on desorption kinetics.
Romero-González, Jaime; Peralta-Videa, José R.; Rodríguez, Elena
2005-01-01
This investigation reveals the capability of Agave lechuguilla for trivalent and hexavalent chromium removal from aqueous solutions. Experimentation included pH profile, time dependence, adsorption capacity (KF and QL), adsorption intensity (n and RL) and saturation capacity (q s) studies. Batch experiments were conducted at 22∘C to characterize and model the adsorption equilibrium as well as biomass adsorption rates. pH 4 was the optimum for Cr(III) binding, while Cr(VI) optimum binding was at pH 2. Time profile experiments indicated that the adsorption of Cr(VI) by lechuguilla biomass was time-dependent and that of Cr(III) was not. Kinetic models demonstrated that a pseudo-second order reaction model best described the kinetic data for Cr(VI). The adsorption isotherms showed that the binding pattern for Cr(VI) followed the Freundlich isotherm model, while that for Cr(III) followed the Langmuir isotherm. PMID:18365089
Reynolds, J.G.; Murray, A.
1991-01-01
The Pyromat 2 micropyrolyzer can routinely measure kinetics on standard shales and source rocks. However, when examining samples which have high native bitumen contents, samples with high TOC and native bitumen contents, asphaltenes, tar sands, and other non-kerogen type materials, the pyrolysis profiles sometimes deviate from normal expected behavior. Some of the deviant features are: (1) evolution before the maximum assigned to kerogen breakdown, (2) broadening of the maximum assigned to kerogen breakdown and shifting in T{sub max} with increasing sample size, and (3) artifacts in activation energy distributions derived in kinetic analyses. This report examines these features in more detail and offers potential experimental solutions to circumvent problems created by these features. 9 refs., 9 figs., 5 tabs.
NASA Astrophysics Data System (ADS)
Watanabe, Yoshiki; Mowbray, Ryan W.; Rice, Katherine P.; Stoykovich, Mark P.
2014-10-01
The oxidation of colloidal metal nanocrystals to form hollow shells via the nanoscale Kirkendall effect has been investigated using a combined theoretical and experimental approach. A generalized kinetic model for the formation of hollow nanoparticles describes the phenomenon and, unlike prior models, is applicable to any material system and accounts for the effect of surface energies. Phase diagrams of the ultimate oxidized nanoparticle morphology and the time to achieve complete oxidation are calculated, and are found to depend significantly upon consideration of surface energy effects that destabilize the initial formation of small voids. For the oxidation of Cu nanocrystals to Cu2O nanoparticles, we find that the diffusion coefficients dictate the morphological outcomes: the ratio of ? to ? controls the void size, ? determines the time of oxidation and ? is largely irrelevant in the kinetics of oxidation. The kinetic model was used to fit experimental measurements of 11 nm diameter Cu nanocrystals oxidized in air from which temperature-dependent diffusivities of ? and ? for 100 ≤ T ≤ 200 °C were determined. In contrast to previous interpretations of the nanoscale Kirkendall effect in the Cu/Cu2O system, these results are obtained without any a priori assumptions about the relative magnitudes of ? and ?. The theoretical and experimental approaches presented here are broadly applicable to any nanoparticle system undergoing oxidation, and can be used to precisely control the final nanoparticle morphology for applications in catalysis or optical materials.
Song, Chengjie; Wang, Liping; Ren, Jie; Lv, Bo; Sun, Zhonghao; Yan, Jing; Li, Xinying; Liu, Jingjing
2016-02-01
The photodegradation of diethyl phthalate (DEP) by UV/H2O2 and UV/TiO2 is studied. The DEP degradation kinetics and multiple crucial factors effecting the clearance of DEP are investigated, including initial DEP concentration ([DEP]0), initial pH values (pH0), UV light intensity, anions (Cl(-), NO(3-), SO4 (2-), HCO3 (-), and CO3 (2-)), cations (Mg(2+), Ca(2+), Mn(2+), and Fe(3+)), and humic acid (HA). Total organic carbon (TOC) removal is tested by two treatments. And, cytotoxicity evolution of DEP degradation intermediates is detected. The relationship between molar ratio ([H2O2]/[DEP] or [TiO2]/[DEP]) and degradation kinetic constant (K) is also studied. And, the cytotoxicity tests of DEP and its degradation intermediates in UV/H2O2 and UV/TiO2 treatments are researched. The DEP removal efficiency of UV/H2O2 treatment is higher than UV/TiO2 treatment. The DEP degradation fitted a pseudo-first-order kinetic pattern under experimental conditions. The K linearly related with molar ratio in UV/H2O2 treatment while nature exponential relationship is observed in the case of UV/TiO2. However, K fitted corresponding trends better in H2O2 treatment than in TiO2 treatment. The Cl(-) is in favor of the DEP degradation in UV/H2O2 treatment; in contrast, it is disadvantageous to the DEP degradation in UV/TiO2 treatment. Other anions are all disadvantageous to the DEP degradation in two treatments. Fe(3+) promotes the degradation rates significantly. And, all other cations in question inhibit the degradation of DEP. HA hinders DEP degradation in two treatments. The intermediates of DEP degradation in UV/TiO2 treatment are less toxic to biological cell than that in UV/H2O2 treatment.
Romero-González, Jaime; Gardea-Torresdey, Jorge L; Peralta-Videa, José R; Rodríguez, Elena
2005-01-01
This investigation reveals the capability of Agave lechuguilla for trivalent and hexavalent chromium removal from aqueous solutions. Experimentation included pH profile, time dependence, adsorption capacity (K(F) and Q(L)), adsorption intensity (n and R(L)) and saturation capacity (q(s)) studies. Batch experiments were conducted at 22( composite function)C to characterize and model the adsorption equilibrium as well as biomass adsorption rates. pH 4 was the optimum for Cr(III) binding, while Cr(VI) optimum binding was at pH 2. Time profile experiments indicated that the adsorption of Cr(VI) by lechuguilla biomass was time-dependent and that of Cr(III) was not. Kinetic models demonstrated that a pseudo-second order reaction model best described the kinetic data for Cr(VI). The adsorption isotherms showed that the binding pattern for Cr(VI) followed the Freundlich isotherm model, while that for Cr(III) followed the Langmuir isotherm. PMID:18365089
KINETICS OF SLURRY PHASE FISCHER-TROPSCH SYNTHESIS
Dragomir B. Bukur; Gilbert F. Froment; Tomasz Olewski
2006-09-29
This report covers the fourth year of a research project conducted under the University Coal Research Program. The overall objective of this project is to develop a comprehensive kinetic model for slurry-phase Fischer-Tropsch synthesis (FTS) employing iron-based catalysts. This model will be validated with experimental data obtained in a stirred-tank slurry reactor (STSR) over a wide range of process conditions. The model will be able to predict molar flow rates and concentrations of all reactants and major product species (water, carbon dioxide, linear 1- and 2-olefins, and linear paraffins) as a function of reaction conditions in the STSR. During the fourth year of the project, an analysis of experimental data collected during the second year of this project was performed. Kinetic parameters were estimated utilizing product distributions from 27 mass balances. During the reporting period two kinetic models were employed: a comprehensive kinetic model of Dr. Li and co-workers (Yang et al., 2003) and a hydrocarbon selectivity model of Van der Laan and Beenackers (1998, 1999) The kinetic model of Yang et al. (2003) has 24 parameters (20 parameters for hydrocarbon formation, and 4 parameters for the water-gas-shift (WGS) reaction). Kinetic parameters for the WGS reaction and FTS synthesis were estimated first separately, and then simultaneously. The estimation of these kinetic parameters employed the Levenberg-Marquardt (LM) method and the trust-region reflective Newton large-scale (LS) method. A genetic algorithm (GA) was incorporated into estimation of parameters for FTS reaction to provide initial estimates of model parameters. All reaction rate constants and activation energies were found to be positive, but at the 95% confidence level the intervals were large. Agreement between predicted and experimental reaction rates has been fair to good. Light hydrocarbons are predicted fairly accurately, whereas the model underpredicts values of higher molecular weight
Accurate monotone cubic interpolation
NASA Technical Reports Server (NTRS)
Huynh, Hung T.
1991-01-01
Monotone piecewise cubic interpolants are simple and effective. They are generally third-order accurate, except near strict local extrema where accuracy degenerates to second-order due to the monotonicity constraint. Algorithms for piecewise cubic interpolants, which preserve monotonicity as well as uniform third and fourth-order accuracy are presented. The gain of accuracy is obtained by relaxing the monotonicity constraint in a geometric framework in which the median function plays a crucial role.
Accurate Finite Difference Algorithms
NASA Technical Reports Server (NTRS)
Goodrich, John W.
1996-01-01
Two families of finite difference algorithms for computational aeroacoustics are presented and compared. All of the algorithms are single step explicit methods, they have the same order of accuracy in both space and time, with examples up to eleventh order, and they have multidimensional extensions. One of the algorithm families has spectral like high resolution. Propagation with high order and high resolution algorithms can produce accurate results after O(10(exp 6)) periods of propagation with eight grid points per wavelength.
Arslan-Alaton, Idil; Olmez-Hanci, Tugba; Genç, Bora; Dursun, Duygu
2013-01-01
This study explored the potential use of a sulfate radical (SO·−4)-based photochemical oxidation process to treat the commercial nonionic surfactant octylphenol polyethoxylate (OPPE) Triton™ X-45. For this purpose, the effect of initial S2O2−8 (0–5.0 mM) and OPPE (10–100 mg/L) concentrations on OPPE and its organic carbon content (TOC) removal were investigated at an initial reaction pH of 6.5. Results indicated that very fast OPPE degradation (100%) accompanied with high TOC abatement rates (90%) could be achieved for 10 and 20 mg/L aqueous OPPE at elevated S2O2−8 concentrations (≥2.5 mM). S2O2−8/UV-C treatment was still capable of complete OPPE removal up to an initial concentration of 40 mg/L in the presence of 2.5 mM S2O2−8. On the other hand, TOC removal efficiencies dropped down to only 40% under the same reaction conditions. S2O2−8/UV-C oxidation of OPPE was also compared with the relatively well-known and established H2O2/UV-C oxidation process. Treatment results showed that the performance of S2O2−8/UV-C was comparable to that of H2O2/UV-C oxidation for the degradation and mineralization of OPPE. In order to elucidate the relative reactivity and selectivity of SO·−4 and HO·, bimolecular reaction rate coefficients of OPPE with SO·−4 and HO· were determined by employing competition kinetics with aqueous phenol (47 μM) selected as the reference compound. The pseudo-first-order abatement rate coefficient obtained for OPPE during S2O2−8/UV-C oxidation (0.044 min−1) was found to be significantly lower than that calculated for phenol (0.397 min−1). In the case of H2O2/UV-C oxidation however, similar pseudo-first-order abatement rate coefficients were obtained for both OPPE (0.087 min−1) and phenol (0.140 min−1). From the kinetic study, second-order reaction rate coefficients for OPPE with SO·−4 and HO· were determined as 9.8 × 108 M−1 s−1 and 4.1 × 109 M−1 s−1, respectively. The kinetic study also revealed
Hafke, Jens B.; Höll, Sabina-Roxana; Kühn, Christina; van Bel, Aart J. E.
2013-01-01
Apart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fully-expanded leaf, half-way along the stem, in the transition zone between the autotrophic and heterotrophic part of the stem, and in the root axis. A top-to-bottom membrane potential gradient of sieve elements was observed along the stem (−130 mV to −110 mV), while the membrane potential of the phloem parenchyma cells was stable (approx. −100 mV). In roots, the membrane potential of sieve elements dropped abruptly to −55 mV. Bathing solutions having various sucrose concentrations were administered and sucrose/H+-induced depolarizations were recorded. Data analysis by non-linear least-square data fittings as well as by linear Eadie–Hofstee (EH) -transformations pointed at biphasic Michaelis–Menten kinetics (2 MM, EH: Km1 1.2–1.8 mM, Km2 6.6–9.0 mM) of sucrose uptake by sieve elements. However, Akaike's Information Criterion (AIC) favored single MM kinetics. Using single MM as the best-fitting model, Km values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher Km values (EH: Km1 10 mM, Km2 70 mM) as compared to sieve elements were found. In preliminary patch-clamp experiments with sieve-element protoplasts, small sucrose-coupled proton currents (−0.1 to −0.3 pA/pF) were detected in the whole-cell mode. In conclusion (a) Km values for sucrose uptake measured by electrophysiology are similar to those obtained with heterologous systems, (b) electrophysiology provides a useful tool for in situ determination of Km values, (c) As yet, it remains unclear if one or two uptake systems are involved
Cong, Jiawei; Yun, Binfeng; Cui, Yiping
2013-08-26
By introducing the frequency tuning sensitivity, an analytical model based on equivalent LC circuit is developed for the relative frequency tuning range of THz semiconductor split-ring resonator (SRR). And the model reveals that the relative tuning range is determined by the ratio of the kinetic inductance to the geometric inductance (RKG). The results show that under the same carrier density variation, a larger RKG results in a larger relative tuning range. Based on this model, a stacked SRR-dimer structure with larger RKG compared to the single SRR due to the inductive coupling is proposed, which improves the relative tuning range effectively. And the results obtained by the simple analytical model agree well with the numerical FDTD results. The presented analytical model is robust and can be used to analyze the relative frequency tuning of other tunable THz devices.
Shuaibov, A. K.; Grabovaya, I. A.; Minya, A. I.; Homoki, Z. T.; Kalyuzhnaya, A. G.; Shchedrin, A. I.
2011-03-15
A kinetic model of the processes occurring in the plasma of a high-power low-pressure gas-discharge lamp is presented, and the output characteristics of the lamp are described. The lamp is excited by a longitudinal glow discharge and emits the I{sub 2}(D Prime -A Prime ) 342-nm and XeI(B-X) 253-nm bands and the 206.2-nm spectral line of atomic iodine. When the emitter operates in a sealed-off mode on the p(He): p(Xe): p(I{sub 2}) = 400: 120: (100-200) Pa mixture, the fractions of the UV radiation power of iodine atoms, exciplex molecules of xenon iodide, and iodine molecules comprise 55, 10, and 35%, respectively. At the optimal partial pressure, the maximum total radiation power of the lamp reaches 37 W, the energy efficiency being about 15%.
ERIC Educational Resources Information Center
Wilson, David B.
1981-01-01
Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)
ERIC Educational Resources Information Center
Moe, Owen; Cornelius, Richard
1988-01-01
Conveys an appreciation of enzyme kinetic analysis by using a practical and intuitive approach. Discusses enzyme assays, kinetic models and rate laws, the kinetic constants (V, velocity, and Km, Michaels constant), evaluation of V and Km from experimental data, and enzyme inhibition. (CW)
NASA Astrophysics Data System (ADS)
Truskinovsky, Lev; Vainchtein, Anna
2010-09-01
We introduce the concept of kinetic or rate equations for moving defects representing a natural extension of the more conventional notion of a kinetic relation. Algebraic kinetic relations, widely used to model dynamics of dislocations, cracks and phase boundaries, link the instantaneous value of the velocity of a defect with an instantaneous value of the driving force. The new approach generalizes kinetic relations by implying a relation between the velocity and the driving force which is nonlocal in time. To make this relation explicit one may need to integrate a system of kinetic equations. We illustrate the difference between kinetic relation and kinetic equations by working out in full detail a prototypical model of an overdamped defect in a one-dimensional discrete lattice. We show that the minimal nonlocal kinetic description, containing now an internal time scale, is furnished by a system of two ordinary differential equations coupling the spatial location of defect with another internal parameter that describes configuration of the core region.
Accurately Predicting Complex Reaction Kinetics from First Principles
NASA Astrophysics Data System (ADS)
Green, William
Many important systems contain a multitude of reactive chemical species, some of which react on a timescale faster than collisional thermalization, i.e. they never achieve a Boltzmann energy distribution. Usually it is impossible to fully elucidate the processes by experiments alone. Here we report recent progress toward predicting the time-evolving composition of these systems a priori: how unexpected reactions can be discovered on the computer, how reaction rates are computed from first principles, and how the many individual reactions are efficiently combined into a predictive simulation for the whole system. Some experimental tests of the a priori predictions are also presented.
Can accurate kinetic laws be created to describe chemical weathering?
NASA Astrophysics Data System (ADS)
Schott, Jacques; Oelkers, Eric H.; Bénézeth, Pascale; Goddéris, Yves; François, Louis
2012-11-01
Knowledge of the mechanisms and rates of mineral dissolution and growth, especially close to equilibrium, is essential for describing the temporal and spatial evolution of natural processes like weathering and its impact on CO2 budget and climate. The Surface Complexation approach (SC) combined with Transition State Theory (TST) provides an efficient framework for describing mineral dissolution over wide ranges of solution composition, chemical affinity, and temperature. There has been a large debate for several years, however, about the comparative merits of SC/TS versus classical growth theories for describing mineral dissolution and growth at near-to-equilibrium conditions. This study considers recent results obtained in our laboratory on oxides, hydroxides, silicates, and carbonates on near-equilibrium dissolution and growth via the combination of complementary microscopic and macroscopic techniques including hydrothermal atomic force microscopy, hydrogen-electrode concentration cell, mixed flow and batch reactors. Results show that the dissolution and precipitation of hydroxides, kaolinite, and hydromagnesite powders of relatively high BET surface area closely follow SC/TST rate laws with a linear dependence of both dissolution and growth rates on fluid saturation state (Ω) even at very close to equilibrium conditions (|ΔG| < 500 J/mol). This occurs because sufficient reactive sites (e.g. at kink, steps, and edges) are available at the exposed faces for dissolution and/or growth, allowing reactions to proceed via the direct and reversible detachment/attachment of reactants at the surface. In contrast, for magnesite and quartz, which have low surface areas, fewer active sites are available for growth and dissolution. Such minerals exhibit rates dependencies on Ω at near equilibrium conditions ranging from linear to highly non-linear functions of Ω, depending on the treatment of the crystals before the reaction. It follows that the form of the f(ΔG) function describing the growth and dissolution of minerals with low surface areas depends on the availability of reactive sites at the exposed faces and thus on the history of the mineral-fluid interaction and the hydrodynamic conditions under which the crystals are reacted. It is advocated that the crystal surface roughness could serve as a proxy of the density of reactive sites. The consequences of the different rate laws on the quantification of loess weathering along the Mississippi valley for the next one hundred years are examined.
Garrido, Nuno M; Jorge, Miguel; Queimada, António J; Gomes, José R B; Economou, Ioannis G; Macedo, Eugénia A
2011-10-14
The Gibbs energy of hydration is an important quantity to understand the molecular behavior in aqueous systems at constant temperature and pressure. In this work we review the performance of some popular force fields, namely TraPPE, OPLS-AA and Gromos, in reproducing the experimental Gibbs energies of hydration of several alkyl-aromatic compounds--benzene, mono-, di- and tri-substituted alkylbenzenes--using molecular simulation techniques. In the second part of the paper, we report a new model that is able to improve such hydration energy predictions, based on Lennard Jones parameters from the recent TraPPE-EH force field and atomic partial charges obtained from natural population analysis of density functional theory calculations. We apply a scaling factor determined by fitting the experimental hydration energy of only two solutes, and then present a simple rule to generate atomic partial charges for different substituted alkyl-aromatics. This rule has the added advantages of eliminating the unnecessary assumption of fixed charge on every substituted carbon atom and providing a simple guideline for extrapolating the charge assignment to any multi-substituted alkyl-aromatic molecule. The point charges derived here yield excellent predictions of experimental Gibbs energies of hydration, with an overall absolute average deviation of less than 0.6 kJ mol(-1). This new parameter set can also give good predictive performance for other thermodynamic properties and liquid structural information.
Cappuyns, Astrid M; Bernaerts, Kristel; Smets, Ilse Y; Ona, Ositadinma; Prinsen, Els; Vanderleyden, Jos; Van Impe, Jan F
2007-01-01
In this paper the problem of reliable and accurate parameter estimation for unstructured models is considered. It is illustrated how a theoretically optimal design can be successfully translated into a practically feasible, robust, and informative experiment. The well-known parameter estimation problem of Monod kinetic parameters is used as a vehicle to illustrate our approach. As known for a long time, noisy batch measurements do not allow for unique and accurate estimation of the kinetic parameters of the Monod model. Techniques of optimal experiment design are, therefore, exploited to design informative experiments and to improve the parameter estimation accuracy. During the design process, practical feasibility has to be kept in mind. The designed experiments are easy to implement in practice and do not require additional monitoring equipment. Both design and experimental validation of informative fed batch experiments are illustrated with a case study, namely, the growth of the nitrogen-fixing bacteria Azospirillum brasilense.
Laumer, Bernhard; Schuster, Fabian; Stutzmann, Martin; Bergmaier, Andreas; Dollinger, Guenther; Eickhoff, Martin
2013-06-21
Zn{sub 1-x}Mg{sub x}O epitaxial films with Mg concentrations 0{<=}x{<=}0.3 were grown by plasma-assisted molecular beam epitaxy on a-plane sapphire substrates. Precise determination of the Mg concentration x was performed by elastic recoil detection analysis. The bandgap energy was extracted from absorption measurements with high accuracy taking electron-hole interaction and exciton-phonon complexes into account. From these results a linear relationship between bandgap energy and Mg concentration is established for x{<=}0.3. Due to alloy disorder, the increase of the photoluminescence emission energy with Mg concentration is less pronounced. An analysis of the lattice parameters reveals that the epitaxial films grow biaxially strained on a-plane sapphire.
Zhang, Jiayi; Shao, Xiongjun; Townsend, Oliver V; Lynd, Lee R
2009-12-01
A kinetic model was developed to predict batch simultaneous saccharification and co-fermentation (SSCF) of paper sludge by the xylose-utilizing yeast Saccharomyces cerevisiae RWB222 and the commercial cellulase preparation Spezyme CP. The model accounts for cellulose and xylan enzymatic hydrolysis and competitive uptake of glucose and xylose. Experimental results show that glucan and xylan enzymatic hydrolysis are highly correlated, and that the low concentrations of xylose encountered during SSCF do not have a significant inhibitory effect on enzymatic hydrolysis. Ethanol is found to not only inhibit the specific growth rate, but also to accelerate cell death. Glucose and xylose uptake rates were found to be competitively inhibitory, but this did not have a large impact during SSCF because the sugar concentrations are low. The model was used to evaluate which constants had the greatest impact on ethanol titer for a fixed substrate loading, enzyme loading, and fermentation time. The cellulose adsorption capacity and cellulose hydrolysis rate constants were found to have the greatest impact among enzymatic hydrolysis related constants, and ethanol yield and maximum ethanol tolerance had the greatest impact among fermentation related constants.
Cusnir, Ruslan; Jaccard, Maud; Bailat, Claude; Christl, Marcus; Steinmann, Philipp; Haldimann, Max; Bochud, François; Froidevaux, Pascal
2016-05-17
The interaction of trace metals with naturally occurring organic matter (NOM) is a key process of the speciation of trace elements in aquatic environments. The rate of dissociation of metal-NOM complexes will impact the amount of free metal available for biouptake. Assessing the bioavailability of plutonium (Pu) helps to predict its toxic effects on aquatic biota. However, the rate of dissociation of Pu-NOM complexes in natural freshwaters is currently unknown. Here, we used the technique of diffusive gradients in thin films (DGT) with several diffusive layer thicknesses to provide new insights into the dissociation kinetics of Pu-NOM complexes. Results show that Pu complexes with NOM (mainly fulvic acid) are somewhat labile (0.2 ≤ ξ ≤ 0.4), with kd = 7.5 × 10(-3) s(-1). DGT measurements of environmental Pu in organic-rich natural water confirm these findings. In addition, we determined the effective diffusion coefficients of Pu(V) in polyacrylamide (PAM) gel in the presence of humic acid using a diffusion cell (D = 1.70 ± 0.25 × 10(-6) cm(2) s(-1)). These results show that Pu(V) is a more mobile species than Pu(IV). PMID:27064997
Nieuwenhuizen, W; Voskuilen, M; Vermond, A; Hoegee-de Nobel, B; Traas, D W
1988-05-16
In the present work we have determined Km,app and kcat,app values for tissue-type plasminogen-activator-catalyzed activation of Glu-plasminogen, Lys-plasminogen and mini-plasminogen in the absence and in the presence of fibrinogen-derived fragments. These were CNBr fragment 2, the A alpha chain remnant of CNBr fragment 2 (A alpha 148-207) and plasmin-generated fragment D-EGTA. The time course of plasmin formation from the various types of plasminogen (plg) was measured spectrophotometrically in a coupled assay system where D-valyl-L-leucyl-L-lysine p-nitroanilide served as a plasmin substrate. The kinetic constants are summarized as follows. (Values in parentheses are concentrations at which the minimum Km,app and maximum kcat,app value is reached.) (Table: see text). In conclusion our results show that CNBr fragment 2, A alpha 148-207 and to some extent D-EGTA mimic the accelerating effect of fibrin. The first two of these fragments did not accelerate activation of mini-plasminogen, lacking the kringle structures I-IV. This suggests that the stimulating effects of these two fragments were dependent on the presence of kringles I-IV of the plasminogen molecule. PMID:3131143
Accurate quantum chemical calculations
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.
1989-01-01
An important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.
NASA Astrophysics Data System (ADS)
Bisdas, Sotirios; Konstantinou, George N.; Sherng Lee, Puor; Thng, Choon Hua; Wagenblast, Jens; Baghi, Mehran; San Koh, Tong
2007-10-01
The objective of this work was to evaluate the feasibility of a two-compartment distributed-parameter (DP) tracer kinetic model to generate functional images of several physiologic parameters from dynamic contrast-enhanced CT data obtained of patients with extracranial head and neck tumors and to compare the DP functional images to those obtained by deconvolution-based DCE-CT data analysis. We performed post-processing of DCE-CT studies, obtained from 15 patients with benign and malignant head and neck cancer. We introduced a DP model of the impulse residue function for a capillary-tissue exchange unit, which accounts for the processes of convective transport and capillary-tissue exchange. The calculated parametric maps represented blood flow (F), intravascular blood volume (v1), extravascular extracellular blood volume (v2), vascular transit time (t1), permeability-surface area product (PS), transfer ratios k12 and k21, and the fraction of extracted tracer (E). Based on the same regions of interest (ROI) analysis, we calculated the tumor blood flow (BF), blood volume (BV) and mean transit time (MTT) by using a modified deconvolution-based analysis taking into account the extravasation of the contrast agent for PS imaging. We compared the corresponding values by using Bland-Altman plot analysis. We outlined 73 ROIs including tumor sites, lymph nodes and normal tissue. The Bland-Altman plot analysis revealed that the two methods showed an accepted degree of agreement for blood flow, and, thus, can be used interchangeably for measuring this parameter. Slightly worse agreement was observed between v1 in the DP model and BV but even here the two tracer kinetic analyses can be used interchangeably. Under consideration of whether both techniques may be used interchangeably was the case of t1 and MTT, as well as for measurements of the PS values. The application of the proposed DP model is feasible in the clinical routine and it can be used interchangeably for measuring
Bergin, Ingrid L; Wilding, Laura A; Morishita, Masako; Walacavage, Kim; Ault, Andrew P; Axson, Jessica L; Stark, Diana I; Hashway, Sara A; Capracotta, Sonja S; Leroueil, Pascale R; Maynard, Andrew D; Philbert, Martin A
2016-01-01
Consumer exposure to silver nanoparticles (AgNP) via ingestion can occur due to incorporation of AgNP into products such as food containers and dietary supplements. AgNP variations in size and coating may affect toxicity, elimination kinetics or tissue distribution. Here, we directly compared acute administration of AgNP of two differing coatings and sizes to mice, using doses of 0.1, 1 and 10 mg/kg body weight/day administered by oral gavage for 3 days. The maximal dose is equivalent to 2000× the EPA oral reference dose. Silver acetate at the same doses was used as ionic silver control. We found no toxicity and no significant tissue accumulation. Additionally, no toxicity was seen when AgNP were dosed concurrently with a broad-spectrum antibiotic. Between 70.5% and 98.6% of the administered silver dose was recovered in feces and particle size and coating differences did not significantly influence fecal silver. Peak fecal silver was detected between 6- and 9-h post-administration and <0.5% of the administered dose was cumulatively detected in liver, spleen, intestines or urine at 48 h. Although particle size and coating did not affect tissue accumulation, silver was detected in liver, spleen and kidney of mice administered ionic silver at marginally higher levels than those administered AgNP, suggesting that silver ion may be more bioavailable. Our results suggest that, irrespective of particle size and coating, acute oral exposure to AgNP at doses relevant to potential human exposure is associated with predominantly fecal elimination and is not associated with accumulation in tissue or toxicity. PMID:26305411
Nanduri, Bindu; Eoff, Robert L.; Tackett, Alan J.; Raney, Kevin D.
2001-01-01
Measurement of steady-state rates of unwinding of double-stranded oligonucleotides by helicases is hampered due to rapid reannealing of the single-stranded DNA products. Including an oligonucleotide in the reaction mixture which can hybridize with one of the single strands can prevent reannealing. However, helicases bind to single-stranded DNA, therefore the additional oligonucleotide can sequester the enzyme, leading to slower observed rates for unwinding. To circumvent this problem, the oligonucleotide that serves as a trap was replaced with a strand of peptide nucleic acid (PNA). Fluorescence polarization was used to determine that a 15mer PNA strand does not bind to the bacteriophage T4 Dda helicase. Steady-state kinetic parameters of unwinding catalyzed by Dda were determined by using PNA as a trapping strand. The substrate consisted of a partial duplex with 15 nt of single-stranded DNA and 15 bp. In the presence of 250 nM substrate and 1 nM Dda, the rate of unwinding in the presence of the DNA trapping strand was 0.30 nM s–1 whereas the rate was 1.34 nM s–1 in the presence of the PNA trapping strand. PNA prevents reannealing of single-stranded DNA products, but does not sequester the helicase. This assay will prove useful in defining the complete kinetic mechanism for unwinding of oligonucleotide substrates by this helicase. PMID:11433029
Poggio, D; Walker, M; Nimmo, W; Ma, L; Pourkashanian, M
2016-07-01
This work proposes a novel and rigorous substrate characterisation methodology to be used with ADM1 to simulate the anaerobic digestion of solid organic waste. The proposed method uses data from both direct substrate analysis and the methane production from laboratory scale anaerobic digestion experiments and involves assessment of four substrate fractionation models. The models partition the organic matter into a mixture of particulate and soluble fractions with the decision on the most suitable model being made on quality of fit between experimental and simulated data and the uncertainty of the calibrated parameters. The method was tested using samples of domestic green and food waste and using experimental data from both short batch tests and longer semi-continuous trials. The results showed that in general an increased fractionation model complexity led to better fit but with increased uncertainty. When using batch test data the most suitable model for green waste included one particulate and one soluble fraction, whereas for food waste two particulate fractions were needed. With richer semi-continuous datasets, the parameter estimation resulted in less uncertainty therefore allowing the description of the substrate with a more complex model. The resulting substrate characterisations and fractionation models obtained from batch test data, for both waste samples, were used to validate the method using semi-continuous experimental data and showed good prediction of methane production, biogas composition, total and volatile solids, ammonia and alkalinity.
Poggio, D; Walker, M; Nimmo, W; Ma, L; Pourkashanian, M
2016-07-01
This work proposes a novel and rigorous substrate characterisation methodology to be used with ADM1 to simulate the anaerobic digestion of solid organic waste. The proposed method uses data from both direct substrate analysis and the methane production from laboratory scale anaerobic digestion experiments and involves assessment of four substrate fractionation models. The models partition the organic matter into a mixture of particulate and soluble fractions with the decision on the most suitable model being made on quality of fit between experimental and simulated data and the uncertainty of the calibrated parameters. The method was tested using samples of domestic green and food waste and using experimental data from both short batch tests and longer semi-continuous trials. The results showed that in general an increased fractionation model complexity led to better fit but with increased uncertainty. When using batch test data the most suitable model for green waste included one particulate and one soluble fraction, whereas for food waste two particulate fractions were needed. With richer semi-continuous datasets, the parameter estimation resulted in less uncertainty therefore allowing the description of the substrate with a more complex model. The resulting substrate characterisations and fractionation models obtained from batch test data, for both waste samples, were used to validate the method using semi-continuous experimental data and showed good prediction of methane production, biogas composition, total and volatile solids, ammonia and alkalinity. PMID:27156366
Sun, Zhigang Yu, Dequan; Xie, Wenbo; Hou, Jiayi; Dawes, Richard; Guo, Hua
2015-05-07
The O + O{sub 2} isotope exchange reactions play an important role in determining the oxygen isotopic composition of a number of trace gases in the atmosphere, and their temperature dependence and kinetic isotope effects (KIEs) provide important constraints on our understanding of the origin and mechanism of these and other unusual oxygen KIEs important in the atmosphere. This work reports a quantum dynamics study of the title reactions on the newly constructed Dawes-Lolur-Li-Jiang-Guo (DLLJG) potential energy surface (PES). The thermal reaction rate coefficients of both the {sup 18}O + {sup 32}O{sub 2} and {sup 16}O + {sup 36}O{sub 2} reactions obtained using the DLLJG PES exhibit a clear negative temperature dependence, in sharp contrast with the positive temperature dependence obtained using the earlier modified Siebert-Schinke-Bittererova (mSSB) PES. In addition, the calculated KIE shows an improved agreement with the experiment. These results strongly support the absence of the “reef” structure in the entrance/exit channels of the DLLJG PES, which is present in the mSSB PES. The quantum dynamics results on both PESs attribute the marked KIE to strong near-threshold reactive resonances, presumably stemming from the mass differences and/or zero point energy difference between the diatomic reactant and product. The accurate characterization of the reactivity for these near-thermoneutral reactions immediately above the reaction threshold is important for correct characterization of the thermal reaction rate coefficients.
NASA Astrophysics Data System (ADS)
Ege, A. Turkler; Tekin, E. Ekdal; Karali, T.; Can, N.; Prokić, M.
2009-05-01
We appreciate the opportunity to respond to comments regarding the paper published by Ege et al (2007 Effect of heating rate on kinetic parameters of β-irradiated Li2B4O7:Cu,Ag,P in TSL measurements Meas. Sci. Technol. 18 889). We would like to thank the authors for taking the time to tell us about their opinion, but unfortunately we do not agree with them completely. In the article presented by Kumar and Chourasiya some comment is advanced to the analysis of the glow curves measured with different heating rates, presented in our recent study. According to our study, the area under the glow curve decreases with increasing heating rate in TL-temperature plots due to the quenching effects. Contrary to this, Kumar and Chourasiya suggest that this decrease is due to the normalization process. Here we hope to clarify any confusion regarding our published study.
NASA Astrophysics Data System (ADS)
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
NASA Astrophysics Data System (ADS)
Mikhailovskaya, A. V.; Golovin, I. S.; Zaitseva, A. A.; Portnoi, V. K.; Dröttboom, P.; Cifre, J.
2013-03-01
Methods of microstructural analysis, measurements of hardness, and temperature and time dependences of internal friction (TDIF and TDIF(iso), respectively) have been used to study recrystallization in cold-rolled alloys and grain-boundary relaxation in annealed alloys. A complex analysis of the effect of additions of transition metals (Mn, Cr) on the magnitude of the activation energy of the background of the internal friction in deformed and annealed states and on the activation parameters of grain-boundary relaxation has been performed. Methods of amplitude dependences of internal friction (ADIF) have been used to determine the critical amplitude that corresponds to the beginning of microplastic deformation in the alloys at different temperatures.
Accurate Optical Reference Catalogs
NASA Astrophysics Data System (ADS)
Zacharias, N.
2006-08-01
Current and near future all-sky astrometric catalogs on the ICRF are reviewed with the emphasis on reference star data at optical wavelengths for user applications. The standard error of a Hipparcos Catalogue star position is now about 15 mas per coordinate. For the Tycho-2 data it is typically 20 to 100 mas, depending on magnitude. The USNO CCD Astrograph Catalog (UCAC) observing program was completed in 2004 and reductions toward the final UCAC3 release are in progress. This all-sky reference catalogue will have positional errors of 15 to 70 mas for stars in the 10 to 16 mag range, with a high degree of completeness. Proper motions for the about 60 million UCAC stars will be derived by combining UCAC astrometry with available early epoch data, including yet unpublished scans of the complete set of AGK2, Hamburg Zone astrograph and USNO Black Birch programs. Accurate positional and proper motion data are combined in the Naval Observatory Merged Astrometric Dataset (NOMAD) which includes Hipparcos, Tycho-2, UCAC2, USNO-B1, NPM+SPM plate scan data for astrometry, and is supplemented by multi-band optical photometry as well as 2MASS near infrared photometry. The Milli-Arcsecond Pathfinder Survey (MAPS) mission is currently being planned at USNO. This is a micro-satellite to obtain 1 mas positions, parallaxes, and 1 mas/yr proper motions for all bright stars down to about 15th magnitude. This program will be supplemented by a ground-based program to reach 18th magnitude on the 5 mas level.
Estimation of Temperature Dependent Parameters of a Batch Alcoholic Fermentation Process
NASA Astrophysics Data System (ADS)
de Andrade, Rafael Ramos; Rivera, Elmer Ccopa; Costa, Aline C.; Atala, Daniel I. P.; Filho, Francisco Maugeri; Filho, Rubens Maciel
In this work, a procedure was established to develop a mathematical model considering the effect of temperature on reaction kinetics. Experiments were performed in batch mode in temperatures from 30 to 38°C. The microorganism used was Saccharomyces cerevisiae and the culture media, sugarcane molasses. The objective is to assess the difficulty in updating the kinetic parameters when there are changes in fermentation conditions. We conclude that, although the re-estimation is a time-consuming task, it is possible to accurately describe the process when there are changes in raw material composition if a re-estimation of parameters is performed.
NASA Astrophysics Data System (ADS)
Vranová, V.; Formánek, P.; Rejšek, K.; Kisza, L.
2009-03-01
The aim of this study was to find out the effect of intensity of thinning (FD-dense stand = 2044 trees/ha; FS-open stand = 1652 trees/ha) performed in young forest stands (99% spruce, 1% fir) in Moravian-Silesian Beskids Mts. (908 m a.s.l.; 49°30'10″ N, 18°32'20″ E) on V DS (C mineralization rate immediately after drying and re-wetting of soil), V BR (basal soil respiration at 60% w/w soil water content measured 5th day after rewetting of dry soil), V MAX (maximum respiration rate after glucose addition measured from 6th day after rewetting of dry soil), V DS/ V MAX (heterotrophic respiratory potential) and ACDS/ACBR (the potential flush of biologically available C) in Ae horizon of Haplic and Entic Podzols. The ACDS/ACBR was calculated from three 24-hour respirations of 7-day incubation according to the equation ACDS/ACBR= V DS V MAX/(2 V BR( V MAX- V DS)). The aim of the work was also to find the effect of circa 11-year abandonment of a mountain meadow in the locality (825-860 m a.s.l.; 49°30'17″ N, 18°32'28″ E) on the same parameters in Ah horizon of Gleyic Luvisol. The studied parameters were measured in the course of the vegetation season 2004 (May-September) at 30-day intervals. The higher intensity of thinning caused alternately higher or lower or very similar values of V DS, V BR, V MAX, V DS/ V MAX and ACDS/ACBR in the course of the season. The abandonment of the meadow increased V DS, V BR, V MAX throughout the whole experiment. V DS/ V MAX increased due to the abandonment except for the last sampling in September. Alternately higher or lower or very similar values of ACDS/ACBR in course of the season appeared on abandoned or moderately mown meadows. The lower intensity of thinning or abandonment of the meadow were connected with increasing number of significant ( P < 0.05) correlations between the studied properties.
NASA Astrophysics Data System (ADS)
Zikic, Darko; Sourbron, Steven; Feng, Xinxing; Michaely, Henrik J.; Khamene, Ali; Navab, Nassir
2008-03-01
Tracer kinetic modeling with dynamic contrast enhanced MRI (DCE-MRI) and the quantification of the kinetic parameters are active fields of research which have the potential to improve the measurement of renal function. However, the strong coronal motion of the kidney in the time series inhibits an accurate assessment of the kinetic parameters. Automatic motion correction is challenging due to the large movement of the kidney and the strong intensity changes caused by the injected bolus. In this work, we improve the quantification results by a template matching motion correction method using a gradient-based similarity measure. Thus, a tedious manual motion correction is replaced by an automatic procedure. The only remaining user interaction is reduced to a selection of a reference slice and a coarse manual segmentation of the kidney in this slice. These steps do not present an overhead to the interaction needed for the assessment of the kinetic parameters. In order to achieve reliable and fast results, we constrain the degrees of freedom for the correction method as far as possible. Furthermore, we compare our method to deformable registration using the same similarity measure. In all our tests, the presented template matching correction was superior to the deformable approach in terms of reliability, leading to more accurate parameter quantification. The evaluation on 10 patient data series with 180-230 images each demonstrate that the quantitative analysis by a two-compartment model can be improved by our method.
Developing Accurate Spatial Maps of Cotton Fiber Quality Parameters
Technology Transfer Automated Retrieval System (TEKTRAN)
Awareness of the importance of cotton fiber quality (Gossypium, L. sps.) has increased as advances in spinning technology require better quality cotton fiber. Recent advances in geospatial information sciences allow an improved ability to study the extent and causes of spatial variability in fiber p...
A novel cost function to estimate parameters of oscillatory biochemical systems
2012-01-01
Oscillatory pathways are among the most important classes of biochemical systems with examples ranging from circadian rhythms and cell cycle maintenance. Mathematical modeling of these highly interconnected biochemical networks is needed to meet numerous objectives such as investigating, predicting and controlling the dynamics of these systems. Identifying the kinetic rate parameters is essential for fully modeling these and other biological processes. These kinetic parameters, however, are not usually available from measurements and most of them have to be estimated by parameter fitting techniques. One of the issues with estimating kinetic parameters in oscillatory systems is the irregularities in the least square (LS) cost function surface used to estimate these parameters, which is caused by the periodicity of the measurements. These irregularities result in numerous local minima, which limit the performance of even some of the most robust global optimization algorithms. We proposed a parameter estimation framework to address these issues that integrates temporal information with periodic information embedded in the measurements used to estimate these parameters. This periodic information is used to build a proposed cost function with better surface properties leading to fewer local minima and better performance of global optimization algorithms. We verified for three oscillatory biochemical systems that our proposed cost function results in an increased ability to estimate accurate kinetic parameters as compared to the traditional LS cost function. We combine this cost function with an improved noise removal approach that leverages periodic characteristics embedded in the measurements to effectively reduce noise. The results provide strong evidence on the efficacy of this noise removal approach over the previous commonly used wavelet hard-thresholding noise removal methods. This proposed optimization framework results in more accurate kinetic parameters that
Dash, C; Phadtare, S; Deshpande, V; Rao, M
2001-09-25
We present here the first report of a hydrophilic peptidic inhibitor, ATBI, from an extremophilic Bacillus sp. exhibiting a two-step inhibition mechanism against the aspartic proteases, pepsin and F-prot from Aspergillus saitoi. Kinetic analysis shows that these proteases are competitively inhibited by ATBI. The progress curves are time-dependent and consistent with slow-tight binding inhibition: E + I right arrow over left arrow (k(3), k(4)) EI right arrow over left arrow (k(5), k(6)) EI. The K(i) values for the first reversible complex (EI) of ATBI with pepsin and F-prot were (17 +/- 0.5) x 10(-9) M and (3.2 +/- 0.6) x 10(-6) M, whereas the overall inhibition constant K(i) values were (55 +/- 0.5) x 10(-12) M and (5.2 +/- 0.6) x 10(-8) M, respectively. The rate constant k(5) revealed a faster isomerization of EI for F-prot [(2.3 +/- 0.4) x 10(-3) s(-1)] than pepsin [(7.7 +/- 0.3) x 10(-4) s(-1)]. However, ATBI dissociated from the tight enzyme-inhibitor complex (EI) of F-prot faster [(3.8 +/- 0.5) x 10(-5) s(-1)] than pepsin [(2.5 +/- 0.4) x 10(-6) s(-1)]. Comparative analysis of the kinetic parameters with pepstatin, the known inhibitor of pepsin, revealed a higher value of k(5)/k(6) for ATBI. The binding of the inhibitor with the aspartic proteases and the subsequent conformational changes induced were monitored by exploiting the intrinsic tryptophanyl fluorescence. The rate constants derived from the fluorescence data were in agreement with those obtained from the kinetic analysis; therefore, the induced conformational changes were correlated to the isomerization of EI to EI. Chemical modification of the Asp or Glu by WRK and Lys residues by TNBS abolished the antiproteolytic activity and revealed the involvement of two carboxyl groups and one amine group of ATBI in the enzymatic inactivation.
NASA Astrophysics Data System (ADS)
Widayatno, Tri
2015-12-01
Electrodeposition of nickel onto copper in a system of low Ni2+ concentration and at a narrow interelectrode gap has been carried out. This electrochemical system was required for maskless pattern transfer through electroplating (Enface technique). Kinetics of Electrochemical reaction of Nickel is relatively slow, where such electrochemical system has never been used in this technology. Study on the kinetics of the electrochemical reaction of nickel in such system is essential due to the fact that the quality of an electrodeposited nickel is affected by kinetics. Analytical and graphical methods were utilised to determine kinetic parameters. The kinetic model was approximated by Butler-Volmer and j-η equation. Kinetic parameters such as exchange current density (j0) and charge transfer coefficient (α) were also graphically determined using the plot of η vs. log|j| known as Tafel plot. The polarisation data for an unstirred 0.19 M nickel sulfamate solution at 0.5 mV/s scan rate and RDE system was used. The results indicate that both methods are fairly accurate. For the analytical, the Tafel slope, the exchange current density, and charge transfer coefficient were found to be 149 mV/dec, 1.60 × 10-4 mA/cm2, and 0.39 respectively, whilst for the graphical method were 159 mV/dec, 3.16 × 10-4 mA/cm2, and 0.37. The kinetics parameters in this current study were also compared to those in literature. Significant differences were observed which might be due to the effect of composition and concentration of the electrolytes, operating temperature, and pH leading to the different reaction mechanism. However, the results obtained in this work are in the range of acceptable values. These kinetic parameters will then be used in further study of nickel deposition by modelling and simulation
NASA Astrophysics Data System (ADS)
Kim, B. K.; Jackman, A. P.; Triska, F. J.
1990-03-01
An existing transport model including storage zones was combined with a submodel describing biotic retention of nutrient based on Michaelis-Menten kinetics. This transport/retention model was used to simulate the results of an experiment in which the inflows to flumes containing nitrate-limited natural stream periphyton on artificial substrates were amended with chloride and nitrate. Hydrodynamic parameters were determined by fitting the model to the chloride data. The Michaelis-Menten maximum uptake rate parameter was determined by fitting the model to the nitrate data. The transport/retention model accurately simulated the responses of the flumes to the amendments. Independent batch experiments to determine Michaelis-Menten parameters were performed on periphyton from a control flume. The maximum uptake rate parameters from the two experiments are in good agreement. Both experiments indicate possible inadequacies of the Michaelis-Menten kinetic model for describing nutrient uptake in a complex field community.
2000-03-20
Given the space-independent, one energy group reactor kinetics equations and the initial conditions, this prgram determines the time variation of reactivity required to produce the given input of flux-time data.
Erbium hydride decomposition kinetics.
Ferrizz, Robert Matthew
2006-11-01
Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.
Computer-Aided Construction of Chemical Kinetic Models
Green, William H.
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.
Calculation of Kinetics Parameters for the NBSR
Hanson A. L.; Diamond D.
2012-03-06
The delayed neutron fraction and prompt neutron lifetime have been calculated at different times in the fuel cycle for the NBSR when fueled with both high-enriched uranium (HEU) and low-enriched uranium (LEU) fuel. The best-estimate values for both the delayed neutron fraction and the prompt neutron lifetime are the result of calculations using MCNP5-1.60 with the most recent ENDFB-VII evaluations. The best-estimate values for the total delayed neutron fraction from fission products are 0.00665 and 0.00661 for the HEU fueled core at startup and end-of-cycle, respectively. For the LEU fuel the best estimate values are 0.00650 and 0.00648 at startup and end-of-cycle, respectively. The present recommendations for the delayed neutron fractions from fission products are smaller than the value reported previously of 0.00726 for the HEU fuel. The best-estimate values for the contribution from photoneutrons will remain as 0.000316, independent of the fuel or time in the cycle.The values of the prompt neutron lifetime as calculated with MCNP5-1.60 are compared to values calculated with two other independent methods and the results are in reasonable agreement with each other. The recommended, conservative values of the neutron lifetime for the HEU fuel are 650 {micro}s and 750 {micro}s for the startup and end-of-cycle conditions, respectively. For LEU fuel the recommended, conservative values are 600 {micro}s and 700 {micro}s for the startup and end-of-cycle conditions, respectively. In all three calculations, the prompt neutron lifetime was determined to be longer for the end-of-cycle equilibrium condition when compared to the startup condition. The results of the three analyses were in agreement that the LEU fuel will exhibit a shorter prompt neutron lifetime when compared to the HEU fuel.
NASA Astrophysics Data System (ADS)
Patel, Ketan S.; Patel, Jiten C.; Dholariya, Hitesh R.; Patel, Kanuprasad D.
2012-10-01
Series of new Cu(II) complexes were synthesized by classical thermal technique. The biologically potent ligands (L) were prepared by refluxing 6-brom 3-acetyl coumarin with aldehydes in the presence of piperidine in ethanol. The Cu(II) complexes have been synthesized by mixing an aqueous solution of Cu(NO3)2 in 1:1 molar ratios with ethanolic bidentate ligands and Clioquinol. The structures of the ligands and their copper complexes were investigated and confirmed by the elemental analysis, FT-IR, 1H NMR, 13C NMR, mass spectral and powder X-ray diffraction studies respectively. Thermal behaviour of newly synthesized mixed ligand Cu(II) complexes were investigated by means of thermogravimetry, differential thermogravimetry, differential scanning calorimetry, electronic spectra and magnetic measurements. Dynamic scan of DSC experiments for Cu(II) complexes were taken at different heating rates (2.5-20 °C min-1). Kinetic parameters for second step degradation of all complexes obtained by Kissinger's and Ozawa's methods were in good agreement. On the basis of these studies it is clear that ligands coordinated to metal atom in a monobasic bidentate mode, by Osbnd O and Osbnd N donor system. Thus, suitable octahedral geometry for hexa-coordinated state has been suggested for the metal complexes. Both the ligands as well as its complexes have been screened for their in vitro antioxidant, anti-tubercular and antimicrobial activities. All were found to be significant potent compared to parent ligands employed for complexation.
Patel, Ketan S; Patel, Jiten C; Dholariya, Hitesh R; Patel, Kanuprasad D
2012-10-01
Series of new Cu(II) complexes were synthesized by classical thermal technique. The biologically potent ligands (L) were prepared by refluxing 6-brom 3-acetyl coumarin with aldehydes in the presence of piperidine in ethanol. The Cu(II) complexes have been synthesized by mixing an aqueous solution of Cu(NO(3))(2) in 1:1 molar ratios with ethanolic bidentate ligands and Clioquinol. The structures of the ligands and their copper complexes were investigated and confirmed by the elemental analysis, FT-IR, (1)H NMR, (13)C NMR, mass spectral and powder X-ray diffraction studies respectively. Thermal behaviour of newly synthesized mixed ligand Cu(II) complexes were investigated by means of thermogravimetry, differential thermogravimetry, differential scanning calorimetry, electronic spectra and magnetic measurements. Dynamic scan of DSC experiments for Cu(II) complexes were taken at different heating rates (2.5-20 °C min(-1)). Kinetic parameters for second step degradation of all complexes obtained by Kissinger's and Ozawa's methods were in good agreement. On the basis of these studies it is clear that ligands coordinated to metal atom in a monobasic bidentate mode, by OO and ON donor system. Thus, suitable octahedral geometry for hexa-coordinated state has been suggested for the metal complexes. Both the ligands as well as its complexes have been screened for their in vitro antioxidant, anti-tubercular and antimicrobial activities. All were found to be significant potent compared to parent ligands employed for complexation.
Behnajady, Mohammad A; Amirmohammadi-Sorkhabi, Sadegh; Modirshahla, Nasser; Shokri, Mohammad
2011-01-01
In this study, to investigate the application of heterogeneous photocatalysis in the removal of organic contaminants from aqueous media a novel tubular continuous-flow photoreactor with supported TiO2-P25 on glass plates was designed and constructed. The photoreactor comprises six quartz tubes and a UV lamp which was placed in the center of the quartz tubes. 4-nitrophenol (4-NP) as a most refractory pollutant was chosen as a probe pollutant to examine the photoreactor efficiency for environmental cleaning applications. Results of experiments show that the removal efficiency of 4-NP in this photoreactor is a function of photoreactor length, gas and liquid flow rates and 4-NP initial concentration. Kinetics analysis indicates that degradation of 4-NP in continuous-mode can be modeled with the Langmuir-Hinshelwood (L-H) model (k(L-H) = 1.5 mg L(-1) min(-1), K(ads) = 0.11 mg(-1) L). A design equation was obtained with a combination of L-H modified equation and tubular reactor design equation. This equation can be used for estimation of 4-NP concentration in different photoreactor lengths under various operational parameters. Mineralization study was followed through total organic carbon (TOC) analysis and measurement of nitrite and nitrate as final degradation products. PMID:22053458
High Frequency QRS ECG Accurately Detects Cardiomyopathy
NASA Technical Reports Server (NTRS)
Schlegel, Todd T.; Arenare, Brian; Poulin, Gregory; Moser, Daniel R.; Delgado, Reynolds
2005-01-01
High frequency (HF, 150-250 Hz) analysis over the entire QRS interval of the ECG is more sensitive than conventional ECG for detecting myocardial ischemia. However, the accuracy of HF QRS ECG for detecting cardiomyopathy is unknown. We obtained simultaneous resting conventional and HF QRS 12-lead ECGs in 66 patients with cardiomyopathy (EF = 23.2 plus or minus 6.l%, mean plus or minus SD) and in 66 age- and gender-matched healthy controls using PC-based ECG software recently developed at NASA. The single most accurate ECG parameter for detecting cardiomyopathy was an HF QRS morphological score that takes into consideration the total number and severity of reduced amplitude zones (RAZs) present plus the clustering of RAZs together in contiguous leads. This RAZ score had an area under the receiver operator curve (ROC) of 0.91, and was 88% sensitive, 82% specific and 85% accurate for identifying cardiomyopathy at optimum score cut-off of 140 points. Although conventional ECG parameters such as the QRS and QTc intervals were also significantly longer in patients than controls (P less than 0.001, BBBs excluded), these conventional parameters were less accurate (area under the ROC = 0.77 and 0.77, respectively) than HF QRS morphological parameters for identifying underlying cardiomyopathy. The total amplitude of the HF QRS complexes, as measured by summed root mean square voltages (RMSVs), also differed between patients and controls (33.8 plus or minus 11.5 vs. 41.5 plus or minus 13.6 mV, respectively, P less than 0.003), but this parameter was even less accurate in distinguishing the two groups (area under ROC = 0.67) than the HF QRS morphologic and conventional ECG parameters. Diagnostic accuracy was optimal (86%) when the RAZ score from the HF QRS ECG and the QTc interval from the conventional ECG were used simultaneously with cut-offs of greater than or equal to 40 points and greater than or equal to 445 ms, respectively. In conclusion 12-lead HF QRS ECG employing
Parameter estimation in complex flows with chemical reactions
NASA Astrophysics Data System (ADS)
Robinson, Daniel J.
The estimation of unknown parameters in engineering and scientific models continues to be of great importance in order to validate them to available experimental data. These parameters of concern cannot be known beforehand, but must be measured experimentally, variables such as chemical species concentrations, pressures, or temperatures as examples. Particularly, in chemically reacting flows, the estimation of kinetic rate parameters from experimentally determined values is in great demand and not well understood. New parameter optimization algorithms have been developed from a Gauss-Newton formulation for the estimation of reaction rate parameters in several different complex flow applications. A zero-dimensional parameter estimation methodology was used in conjunction with a parameter sensitivity study and then applied to three-dimensional flow models. This new parameter estimation technique was applied to three-dimensional models for chemical vapor deposition of silicon carbide and gallium arsenide semiconductor materials. The parameter estimation for silicon carbide for several different operating points was in close agreement to experiment. The parameter estimation for gallium arsenide proved to be very accurate, being within four percent of the experimental data. New parameter estimation algorithms were likewise created for a three-dimensional multiphase model for methanol spray combustion. The kinetic rate parameters delivered results in close agreement to experiment for profiles of combustion species products. In addition, a new parameter estimation method for the determination of spray droplet sizes and velocities is presented. The results for methanol combustion chemical species profiles are in good agreement to experiment for several different droplet sizes. Lastly, the parameter estimation method was extended to a bio-kinetic application, namely mitochondrial cells, that are cardiac or respiratory cells found in animals and humans. The results for the
Kuby, S A; Roy, R N
1976-05-01
A systematic study has been made of the pH- and temperature-dependency of the steady-state kinetic parameters of the stabilized two-subunit enzyme species of glucose-6-phosphate dehydrogenase, in the absence of superimposed association-dissociation reactions. The Vmax(app) data obtained in several buffers between pH 5 and 10 and at 18-32 degrees C lead to the postulate that at least two sets of protonic equilibria may govern the catalysis (one near pH 5.7 AT 25 DEGREES C and another near pH 9.2); furthermore, two pathways for product formation (i.e., two Vmax's) appear to be required to explain the biphasic nature of the log Vmax(app) vs. pH curves, with Vmax(basic) greater than Vmax(acidic + neutral). Of the several buffers explored, either a uniform degree of interaction or a minimal degree of buffer species interaction could be assessed from the enthalpy changes associated with the derived values for ionization constants attributed to the protonic equilibria in the enzyme-substrates ternary complexes for the case of Tris-acetate-EDTA buffers, at constant ionic strength. With the selection of this buffer at 0.1 (T/2) and at 25 and 32 degrees C, a self-consistent kinetic mechanism has emerged which allows for the random binding of the two fully ionized substrates to the enzyme via two major pathways, and product formation by both E-A--B- and HE-A--B-. As before (Kuby et al. Arch. Biochem, Biophys. 165, 153-178, 1974), a quasi-equilibrium is presumed, with rate-limiting steps (k + 5 and k + 5') at the interconversion of the ternary complexes. Values for the two sets of protonic equilibria defined by this mechanism (viz., pKk, pKH2 for the first ionizations, and pKk', pKH' for the second) could then be estimated. From their numerical values (e.g., at 25 degrees C: pKK = 5.7 PKH2 = 5.2; and pKK' = 9.1, PKH' = 8.2) and from the values for delta H degrees ioniz (e.g., delta H degrees pKK APPROXIMATELY 5.1 KCAL/MOL; DELTA H degrees pKK' APPROXIMATELY 11 KCAL/MOL), A
Towards cleaner combustion engines through groundbreaking detailed chemical kinetic models
Battin-Leclerc, Frédérique; Blurock, Edward; Bounaceur, Roda; Fournet, René; Glaude, Pierre-Alexandre; Herbinet, Olivier; Sirjean, Baptiste; Warth, V.
2013-01-01
In the context of limiting the environmental impact of transportation, this paper reviews new directions which are being followed in the development of more predictive and more accurate detailed chemical kinetic models for the combustion of fuels. In the first part, the performance of current models, especially in terms of the prediction of pollutant formation, is evaluated. In the next parts, recent methods and ways to improve these models are described. An emphasis is given on the development of detailed models based on elementary reactions, on the production of the related thermochemical and kinetic parameters, and on the experimental techniques available to produce the data necessary to evaluate model predictions under well defined conditions. PMID:21597604
NNLOPS accurate associated HW production
NASA Astrophysics Data System (ADS)
Astill, William; Bizon, Wojciech; Re, Emanuele; Zanderighi, Giulia
2016-06-01
We present a next-to-next-to-leading order accurate description of associated HW production consistently matched to a parton shower. The method is based on reweighting events obtained with the HW plus one jet NLO accurate calculation implemented in POWHEG, extended with the MiNLO procedure, to reproduce NNLO accurate Born distributions. Since the Born kinematics is more complex than the cases treated before, we use a parametrization of the Collins-Soper angles to reduce the number of variables required for the reweighting. We present phenomenological results at 13 TeV, with cuts suggested by the Higgs Cross section Working Group.
Accurate Molecular Polarizabilities Based on Continuum Electrostatics
Truchon, Jean-François; Nicholls, Anthony; Iftimie, Radu I.; Roux, Benoît; Bayly, Christopher I.
2013-01-01
A novel approach for representing the intramolecular polarizability as a continuum dielectric is introduced to account for molecular electronic polarization. It is shown, using a finite-difference solution to the Poisson equation, that the Electronic Polarization from Internal Continuum (EPIC) model yields accurate gas-phase molecular polarizability tensors for a test set of 98 challenging molecules composed of heteroaromatics, alkanes and diatomics. The electronic polarization originates from a high intramolecular dielectric that produces polarizabilities consistent with B3LYP/aug-cc-pVTZ and experimental values when surrounded by vacuum dielectric. In contrast to other approaches to model electronic polarization, this simple model avoids the polarizability catastrophe and accurately calculates molecular anisotropy with the use of very few fitted parameters and without resorting to auxiliary sites or anisotropic atomic centers. On average, the unsigned error in the average polarizability and anisotropy compared to B3LYP are 2% and 5%, respectively. The correlation between the polarizability components from B3LYP and this approach lead to a R2 of 0.990 and a slope of 0.999. Even the F2 anisotropy, shown to be a difficult case for existing polarizability models, can be reproduced within 2% error. In addition to providing new parameters for a rapid method directly applicable to the calculation of polarizabilities, this work extends the widely used Poisson equation to areas where accurate molecular polarizabilities matter. PMID:23646034
Su, Min; Sun, Hua; Zhao, Yingying; Lu, Aidang; Cao, Xiaohui; Wang, Jingkang
2016-01-01
In an effort to promote sustainability and to reduce manufacturing costs, the traditional production process for 6-aminopenicillanic acid (6-APA) has been modified to include less processing units. The objectives of this study are to investigate the degradation kinetics of 6-APA, to propose a reasonable degradation mechanism, and to optimize the manufacturing conditions within this new process. A series of degradation kinetic studies were conducted in the presence of impurities, as well as at various chemical and physical conditions. The concentrations of 6-APA were determined by high-performance liquid chromatography. An Arrhenius-type kinetic model was established to give a more accurate prediction on the degradation rates of 6-APA. A hydrolysis degradation mechanism is shown to be the major pathway for 6-APA. The degradation mechanisms and the kinetic models for 6-APA in the new system enable the design of a good manufacturing process with optimized parameters. PMID:26852849
Removal of water and iodine by solid sorbents: adsorption isotherms and kinetics
Lin, R.; Tavlarides, L.L.
2013-07-01
Tritium and iodine-129 are two major radioactive elements that are present in off-gases from spent fuel reprocessing plants. Adsorption by solid sorbents is the state-of-the-art technique for removal of these species from off-gases. Modeling and simulating adsorption processes require accurate adsorption equilibrium and kinetic data to permit reasonable estimates of process parameters. We have developed a continuous flow single-pellet adsorption system to gather accurate adsorption equilibrium and kinetic data for adsorption of water by molecular sieve 3A and for adsorption of iodine by silver exchanged mordenite. In this paper, the design of the water and iodine adsorption experimental systems are briefly described and results of water adsorption experiments are presented and discussed. Water uptake curves are fitted with the linear-driving force (LDF) model and the shrinking-core model to determine kinetic parameters. It is shown that the kinetics of water adsorption on zeolite 3A under current experimental conditions is controlled by both the external film resistance and the macro-pore diffusion and can be predicted by both the LDF model and the shrinking-core model with the former one performing slightly better. Preliminary results from iodine adsorption experiments will be presented in the conference.
Accurate basis set truncation for wavefunction embedding
NASA Astrophysics Data System (ADS)
Barnes, Taylor A.; Goodpaster, Jason D.; Manby, Frederick R.; Miller, Thomas F.
2013-07-01
Density functional theory (DFT) provides a formally exact framework for performing embedded subsystem electronic structure calculations, including DFT-in-DFT and wavefunction theory-in-DFT descriptions. In the interest of efficiency, it is desirable to truncate the atomic orbital basis set in which the subsystem calculation is performed, thus avoiding high-order scaling with respect to the size of the MO virtual space. In this study, we extend a recently introduced projection-based embedding method [F. R. Manby, M. Stella, J. D. Goodpaster, and T. F. Miller III, J. Chem. Theory Comput. 8, 2564 (2012)], 10.1021/ct300544e to allow for the systematic and accurate truncation of the embedded subsystem basis set. The approach is applied to both covalently and non-covalently bound test cases, including water clusters and polypeptide chains, and it is demonstrated that errors associated with basis set truncation are controllable to well within chemical accuracy. Furthermore, we show that this approach allows for switching between accurate projection-based embedding and DFT embedding with approximate kinetic energy (KE) functionals; in this sense, the approach provides a means of systematically improving upon the use of approximate KE functionals in DFT embedding.
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
Two highly accurate methods for pitch calibration
NASA Astrophysics Data System (ADS)
Kniel, K.; Härtig, F.; Osawa, S.; Sato, O.
2009-11-01
Among profiles, helix and tooth thickness pitch is one of the most important parameters of an involute gear measurement evaluation. In principle, coordinate measuring machines (CMM) and CNC-controlled gear measuring machines as a variant of a CMM are suited for these kinds of gear measurements. Now the Japan National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) and the German national metrology institute the Physikalisch-Technische Bundesanstalt (PTB) have each developed independently highly accurate pitch calibration methods applicable to CMM or gear measuring machines. Both calibration methods are based on the so-called closure technique which allows the separation of the systematic errors of the measurement device and the errors of the gear. For the verification of both calibration methods, NMIJ/AIST and PTB performed measurements on a specially designed pitch artifact. The comparison of the results shows that both methods can be used for highly accurate calibrations of pitch standards.
Nonphotochemical hole burning and dispersive kinetics in amorphous solids
Kenney, M.J.
1990-09-21
Results covering burn intensities in the nW to {mu}W/cm{sup 2} range, of dispersive hole growth kinetics are reported for Oxazine 720 in glycerol glasses and polyvinyl alcohol polymer films and their deuterated analogues. A theoretical model which employs a distribution function for the hole burning rate constant based upon a Gaussian distribution for the tunnel parameter is shown to accurately describe the kinetic data. This model incorporates the linear electron-phonon coupling. A method for calculating the nonphotochemical quantum yield is presented which utilizes the Gaussian distribution of tunnel parameters. The quantum yield calculation can be extended to determine a quantum yield as a function of hole depth. The effect of spontaneous hole filling is shown to be insignificant over the burn intensity range studied. Average relaxation rates for hole burning are {approximately}8 orders of magnitude greater than for hole filling. The dispersive kinetics of hole burning are observed to be independent over the temperature range of these experiments, 1.6 to 7.0 K. 6 refs., 20 figs., 1 tab.
Kinetic distance and kinetic maps from molecular dynamics simulation.
Noé, Frank; Clementi, Cecilia
2015-10-13
Characterizing macromolecular kinetics from molecular dynamics (MD) simulations requires a distance metric that can distinguish slowly interconverting states. Here, we build upon diffusion map theory and define a kinetic distance metric for irreducible Markov processes that quantifies how slowly molecular conformations interconvert. The kinetic distance can be computed given a model that approximates the eigenvalues and eigenvectors (reaction coordinates) of the MD Markov operator. Here, we employ the time-lagged independent component analysis (TICA). The TICA components can be scaled to provide a kinetic map in which the Euclidean distance corresponds to the kinetic distance. As a result, the question of how many TICA dimensions should be kept in a dimensionality reduction approach becomes obsolete, and one parameter less needs to be specified in the kinetic model construction. We demonstrate the approach using TICA and Markov state model (MSM) analyses for illustrative models, protein conformation dynamics in bovine pancreatic trypsin inhibitor and protein-inhibitor association in trypsin and benzamidine. We find that the total kinetic variance (TKV) is an excellent indicator of model quality and can be used to rank different input feature sets.
Studies of Reaction Kinetics of Methane Hydrate Dissocation in Porous Media
Moridis, George J.; Seol, Yongkoo; Kneafsey, Timothy J.
2005-03-10
The objective of this study is the description of the kinetic dissociation of CH4-hydrates in porous media, and the determination of the corresponding kinetic parameters. Knowledge of the kinetic dissociation behavior of hydrates can play a critical role in the evaluation of gas production potential of gas hydrate accumulations in geologic media. We analyzed data from a sequence of tests of CH4-hydrate dissociation by means of thermal stimulation. These tests had been conducted on sand cores partially saturated with water, hydrate and CH4 gas, and contained in an x-ray-transparent aluminum pressure vessel. The pressure, volume of released gas, and temperature (at several locations within the cores) were measured. To avoid misinterpreting local changes as global processes, x-ray computed tomography scans provided accurate images of the location and movement of the reaction interface during the course of the experiments. Analysis of the data by means of inverse modeling (history matching ) provided estimates of the thermal properties and of the kinetic parameters of the hydration reaction in porous media. Comparison of the results from the hydrate-bearing porous media cores to those from pure CH4-hydrate samples provided a measure of the effect of the porous medium on the kinetic reaction. A tentative model of composite thermal conductivity of hydrate-bearing media was also developed.
Kinetics of Slurry Phase Fischer-Tropsch Synthesis
Dragomir B. Bukur; Gilbert F. Froment; Tomasz Olewski; Lech Nowicki; Madhav Nayapati
2006-12-31
be used only to fit product distribution of total olefins and n-paraffins. The kinetic model of Van der Laan and Beenackers was extended to account separately for formation of 1- and 2-olefins, as well as n-paraffins. A simplified form of the kinetic model of Lox and Froment (1993b) has only five parameters at isothermal conditions. Because of its relative simplicity, this model is well suited for initial studies where the main goal is to learn techniques for parameter estimation and statistical analysis of estimated values of model parameters. The same techniques and computer codes were used in the analysis of other kinetic models. The Levenberg-Marquardt (LM) method was employed for minimization of the objective function and kinetic parameter estimation. Predicted reaction rates of inorganic and hydrocarbon species were not in good agreement with experimental data. All reaction rate constants and activation energies (24 parameters) of the Yang et al. (2003) model were found to be positive, but the corresponding 95% confidence intervals were large. Agreement between predicted and experimental reaction rates has been fair to good. Light hydrocarbons were predicted fairly accurately, whereas the model predictions of higher molecular weight hydrocarbons values were lower than the experimental ones. The Van der Laan and Beenackers kinetic model (known as olefin readsorption product distribution model = ORPDM) provided a very good fit of the experimental data for hydrocarbons (total olefins and n-paraffins) up to about C{sub 20} (with the exception of experimental data that showed higher paraffin formation rates in C{sub 12}-C{sub 25} region, due to hydrocracking or other secondary reactions). Estimated values of all model parameters (true and pseudo-kinetic parameters) had high statistical significance after combining parameters related to olefin termination and readsorption into one (total of 7 model parameters). The original ORPDM was extended to account separately
Chemical kinetics of geminal recombination
Levin, P.P.; Khudyakov, I.V.; Brin, E.F.; Kuz'min, V.A.
1988-09-01
The kinetics of geminal recombination of triplet radical pairs formed in photoreduction of benzophenone by p-cresol in glycerin solution was studied by pulsed laser photolysis. The experiments were conducted at several temperatures and in a constant magnetic field of H = 0.34 T. The parameters in six kinetic equations describing geminal recombination were determined with a computer. The values of the sums of the squares of the residual deviations of the approximation were obtained. It was found that the kinetics are best described by the functions proposed by Noyes and Shushin. It was shown that it is necessary to use the mutual diffusion coefficient of the radicals, which is significantly smaller than the sum of the estimations of the experimental values of the radical diffusion coefficients, for describing the kinetics due to the correlations of the molecular motions of the radicals in the cage.
Enhanced von Weizsäcker Wang-Govind-Carter kinetic energy density functional for semiconductors
NASA Astrophysics Data System (ADS)
Shin, Ilgyou; Carter, Emily A.
2014-05-01
We propose a new form of orbital-free (OF) kinetic energy density functional (KEDF) for semiconductors that is based on the Wang-Govind-Carter (WGC99) nonlocal KEDF. We enhance within the latter the semi-local von Weizsäcker KEDF term, which is exact for a single orbital. The enhancement factor we introduce is related to the extent to which the electron density is localized. The accuracy of the new KEDF is benchmarked against Kohn-Sham density functional theory (KSDFT) by comparing predicted energy differences between phases, equilibrium volumes, and bulk moduli for various semiconductors, along with metal-insulator phase transition pressures. We also compare point defect and (100) surface energies in silicon for a broad test of its applicability. This new KEDF accurately reproduces the exact non-interacting kinetic energy of KSDFT with only one additional adjustable parameter beyond the three parameters in the WGC99 KEDF; it exhibits good transferability between semiconducting to metallic silicon phases and between various III-V semiconductors without parameter adjustment. Overall, this KEDF is more accurate than previously proposed OF KEDFs (e.g., the Huang-Carter (HC) KEDF) for semiconductors, while the computational efficiency remains at the level of the WGC99 KEDF (several hundred times faster than the HC KEDF). This accurate, fast, and transferable new KEDF holds considerable promise for large-scale OFDFT simulations of metallic through semiconducting materials.
Westbrook, C.K.; Pitz, W.J.
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.
Kinetic characterisation of primer mismatches in allele-specific PCR: a quantitative assessment.
Waterfall, Christy M; Eisenthal, Robert; Cobb, Benjamin D
2002-12-20
A novel method of estimating the kinetic parameters of Taq DNA polymerase during rapid cycle PCR is presented. A model was constructed using a simplified sigmoid function to represent substrate accumulation during PCR in combination with the general equation describing high substrate inhibition for Michaelis-Menten enzymes. The PCR progress curve was viewed as a series of independent reactions where initial rates were accurately measured for each cycle. Kinetic parameters were obtained for allele-specific PCR (AS-PCR) amplification to examine the effect of mismatches on amplification. A high degree of correlation was obtained providing evidence of substrate inhibition as a major cause of the plateau phase that occurs in the later cycles of PCR. PMID:12470637
Kinetic characterisation of primer mismatches in allele-specific PCR: a quantitative assessment.
Waterfall, Christy M; Eisenthal, Robert; Cobb, Benjamin D
2002-12-20
A novel method of estimating the kinetic parameters of Taq DNA polymerase during rapid cycle PCR is presented. A model was constructed using a simplified sigmoid function to represent substrate accumulation during PCR in combination with the general equation describing high substrate inhibition for Michaelis-Menten enzymes. The PCR progress curve was viewed as a series of independent reactions where initial rates were accurately measured for each cycle. Kinetic parameters were obtained for allele-specific PCR (AS-PCR) amplification to examine the effect of mismatches on amplification. A high degree of correlation was obtained providing evidence of substrate inhibition as a major cause of the plateau phase that occurs in the later cycles of PCR.
Profitable capitation requires accurate costing.
West, D A; Hicks, L L; Balas, E A; West, T D
1996-01-01
In the name of costing accuracy, nurses are asked to track inventory use on per treatment basis when more significant costs, such as general overhead and nursing salaries, are usually allocated to patients or treatments on an average cost basis. Accurate treatment costing and financial viability require analysis of all resources actually consumed in treatment delivery, including nursing services and inventory. More precise costing information enables more profitable decisions as is demonstrated by comparing the ratio-of-cost-to-treatment method (aggregate costing) with alternative activity-based costing methods (ABC). Nurses must participate in this costing process to assure that capitation bids are based upon accurate costs rather than simple averages. PMID:8788799
Kinetic study on biomass gasification
Bingyan, X.; Chuangzhi, W.; Zhengfen, L.; Guang, Z.X. )
1992-09-01
An experimental apparatus, with the features of fast heating rate and continuous record of reaction parameters, was developed to study kinetics of fast pyrolysis. The temperature effects, at a range of 400 C to 900 C, on pyrolysis rate, products profile, gas quality and quantity, and so on, were studied and the results are listed and analyzed. The effect of secondary reaction of gas phase at 700 C was tested and the regression result is expressed in an experimental formula. Based on the experimental results, the three-stage-reaction mechanism module is suggested. The kinetic expression to calculate gas formation rate is concluded as: d{alpha}/dt = A exp({minus}E/RT)(1 {minus} {alpha}){sup n}. The kinetic parameters of A, E, and n at different temperatures are given in the paper.
Kinetic modeling of pH-dependent antimony (V) sorption and transport in iron oxide-coated sand.
Cai, Yongbing; Li, Lulu; Zhang, Hua
2015-11-01
Understanding the mechanisms and kinetics controlling the retention and transport of antimony (Sb) is prerequisite for evaluating the risk of groundwater contamination by the toxic element. In this study, kinetic batch and saturated miscible displacement experiments were performed to investigate effects of protonation-deprotonation reactions on sorption-desorption and transport of Sb(V) in iron oxide-coated sand (IOCS). Results clearly demonstrated that Sb(V) sorption was highly nonlinear and time dependent, where both sorption capacity and kinetic rates decreased with increasing solution pH. Breakthrough curves (BTCs) obtained at different solution pH exhibited that mobility of Sb(V) were higher under neutral to alkaline condition than under acidic condition. Because of the nonlinear and non-equilibrium nature of Sb(V) retention and transport, multi-reaction models (MRM) with equilibrium and kinetic sorption expressions were utilized successfully to simulate the experiment data. Equilibrium distribution coefficient (Ke) and reversible kinetic retention parameters (k1 and k2) of both kinetic sorption and transport experiment showed marked decrease as pH increased from 4.0 to 7.5. Surface complexation is suggested as the dominant mechanism for the observed pH-dependent phenomena, which need to be incorporated into the kinetic models to accurately simulate the reactive transport of Sb(V) in vadose zone and aquifers.
A Comprehensive Enzyme Kinetic Exercise for Biochemistry
ERIC Educational Resources Information Center
Barton, Janice S.
2011-01-01
This article describes a comprehensive treatment of experimental enzyme kinetics strongly coupled to electronic data acquisition and use of spreadsheets to organize data and perform linear and nonlinear least-squares analyses, all in a manner that promotes development of important reasoning skills. Kinetic parameters are obtained for the stable…
Alibrandi, Giuseppe; Fabbrizzi, Luigi; Licchelli, Maurizio; Puglisi, Antonio
2015-01-12
This paper proposes a new type of molecular device that is able to act as an inverse proton sponge to slowly decrease the pH inside a reaction vessel. This makes the automatic monitoring of the concentration of pH-sensitive systems possible. The device is a composite formed of an alkyl chloride, which kinetically produces acidity, and a buffer that thermodynamically modulates the variation in pH value. Profiles of pH versus time (pH-t plots) have been generated under various experimental conditions by computer simulation, and the device has been tested by carrying out automatic spectrophotometric titrations, without using an autoburette. To underline the wide variety of possible applications, this new system has been used to realize and monitor HCl uptake by a di-copper(II) bistren complex in a single run, in a completely automatic experiment.
The moisture outgassing kinetics of a silica reinforced polydimethylsiloxane
NASA Astrophysics Data System (ADS)
Sharma, H. N.; McLean, W.; Maxwell, R. S.; Dinh, L. N.
2016-09-01
A silica-filled polydimethylsiloxane (PDMS) composite M9787 was investigated for potential outgassing in a vacuum/dry environment with the temperature programmed desorption/reaction method. The outgassing kinetics of 463 K vacuum heat-treated samples, vacuum heat-treated samples which were subsequently re-exposed to moisture, and untreated samples were extracted using the isoconversional and constrained iterative regression methods in a complementary fashion. Density functional theory (DFT) calculations of water interactions with a silica surface were also performed to provide insight into the structural motifs leading to the obtained kinetic parameters. Kinetic analysis/model revealed that no outgassing occurs from the vacuum heat-treated samples in subsequent vacuum/dry environment applications at room temperature (˜300 K). The main effect of re-exposure of the vacuum heat-treated samples to a glove box condition (˜30 ppm by volume of H2O) for even a couple of days was the formation, on the silica surface fillers, of ˜60 ppm by weight of physisorbed and loosely bonded moisture, which subsequently outgasses at room temperature in a vacuum/dry environment in a time span of 10 yr. However, without any vacuum heat treatment and even after 1 h of vacuum pump down, about 300 ppm by weight of H2O would be released from the PDMS in the next few hours. Thereafter the outgassing rate slows down substantially. The presented methodology of using the isoconversional kinetic analysis results and some appropriate nature of the reaction as the constraints for more accurate iterative regression analysis/deconvolution of complex kinetic spectra, and of checking the so-obtained results with first principle calculations such as DFT can serve as a template for treating other complex physical/chemical processes as well.
Global parameter estimation methods for stochastic biochemical systems
2010-01-01
described in this work have provided an effective and practical approach in the estimation of kinetic parameters of stochastic systems from either sparse or dense cell population data. Nevertheless, similar to kinetic parameter estimation in other modelling frameworks, not all parameters can be estimated accurately, which is a common problem arising from the lack of complete parameter identifiability from the available data. PMID:20691037
Kinetics of HMX and Phase Transitions: Effects of Grain Size at Elevated Temperature
Saw, C K
2002-06-13
To date a global kinetic rate law has not been written to accurately describe solid-solid phase transformations of HMX and TATB where contributions from grain size effects, binder contents, and impurity levels are explicitly defined. Our recent work presented at the 2001 SCCM topical APS meeting, Atlanta, GA, demonstrated one can not confidently use the second harmonic generation (SHG) diagnostic to study energetic material phase transitions where non-uniform grain size distributions are present. For example, in HMX, the early arrival of SHG before the XRD in the SHG/XRD simultaneous high temperature experiment clearly indicates the partial molecular conversion from centrosymmetric to non-centrosymmetric without any structural changes as exhibit by the XRD pattern. This conversion is attributed to the changes of the surface molecules due to the differences in potential between the surface and the bulk. The present paper reports on accurate XRD measurements following changes of {beta}-HMX to {delta}-HMX at elevated temperature. The results are compared for sample with 2 different grain sizes for HMX. We report accurate temperature dependent lattice parameters and hence volume and linear thermal expansion coefficients along each crystallographic axis. We have also conducted kinetic studies of the behavior of 2 grain-sizes of HMX and concluded that their kinetics, are drastically different.
Accurate documentation and wound measurement.
Hampton, Sylvie
This article, part 4 in a series on wound management, addresses the sometimes routine yet crucial task of documentation. Clear and accurate records of a wound enable its progress to be determined so the appropriate treatment can be applied. Thorough records mean any practitioner picking up a patient's notes will know when the wound was last checked, how it looked and what dressing and/or treatment was applied, ensuring continuity of care. Documenting every assessment also has legal implications, demonstrating due consideration and care of the patient and the rationale for any treatment carried out. Part 5 in the series discusses wound dressing characteristics and selection.
Modeling of hydrogen production methods: Single particle model and kinetics assessment
Miller, R.S.; Bellan, J.
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.
Toward Accurate and Quantitative Comparative Metagenomics.
Nayfach, Stephen; Pollard, Katherine S
2016-08-25
Shotgun metagenomics and computational analysis are used to compare the taxonomic and functional profiles of microbial communities. Leveraging this approach to understand roles of microbes in human biology and other environments requires quantitative data summaries whose values are comparable across samples and studies. Comparability is currently hampered by the use of abundance statistics that do not estimate a meaningful parameter of the microbial community and biases introduced by experimental protocols and data-cleaning approaches. Addressing these challenges, along with improving study design, data access, metadata standardization, and analysis tools, will enable accurate comparative metagenomics. We envision a future in which microbiome studies are replicable and new metagenomes are easily and rapidly integrated with existing data. Only then can the potential of metagenomics for predictive ecological modeling, well-powered association studies, and effective microbiome medicine be fully realized. PMID:27565341
Toward Accurate and Quantitative Comparative Metagenomics
Nayfach, Stephen; Pollard, Katherine S.
2016-01-01
Shotgun metagenomics and computational analysis are used to compare the taxonomic and functional profiles of microbial communities. Leveraging this approach to understand roles of microbes in human biology and other environments requires quantitative data summaries whose values are comparable across samples and studies. Comparability is currently hampered by the use of abundance statistics that do not estimate a meaningful parameter of the microbial community and biases introduced by experimental protocols and data-cleaning approaches. Addressing these challenges, along with improving study design, data access, metadata standardization, and analysis tools, will enable accurate comparative metagenomics. We envision a future in which microbiome studies are replicable and new metagenomes are easily and rapidly integrated with existing data. Only then can the potential of metagenomics for predictive ecological modeling, well-powered association studies, and effective microbiome medicine be fully realized. PMID:27565341
How Accurately can we Calculate Thermal Systems?
Cullen, D; Blomquist, R N; Dean, C; Heinrichs, D; Kalugin, M A; Lee, M; Lee, Y; MacFarlan, R; Nagaya, Y; Trkov, A
2004-04-20
I would like to determine how accurately a variety of neutron transport code packages (code and cross section libraries) can calculate simple integral parameters, such as K{sub eff}, for systems that are sensitive to thermal neutron scattering. Since we will only consider theoretical systems, we cannot really determine absolute accuracy compared to any real system. Therefore rather than accuracy, it would be more precise to say that I would like to determine the spread in answers that we obtain from a variety of code packages. This spread should serve as an excellent indicator of how accurately we can really model and calculate such systems today. Hopefully, eventually this will lead to improvements in both our codes and the thermal scattering models that they use in the future. In order to accomplish this I propose a number of extremely simple systems that involve thermal neutron scattering that can be easily modeled and calculated by a variety of neutron transport codes. These are theoretical systems designed to emphasize the effects of thermal scattering, since that is what we are interested in studying. I have attempted to keep these systems very simple, and yet at the same time they include most, if not all, of the important thermal scattering effects encountered in a large, water-moderated, uranium fueled thermal system, i.e., our typical thermal reactors.
SPLASH: Accurate OH maser positions
NASA Astrophysics Data System (ADS)
Walsh, Andrew; Gomez, Jose F.; Jones, Paul; Cunningham, Maria; Green, James; Dawson, Joanne; Ellingsen, Simon; Breen, Shari; Imai, Hiroshi; Lowe, Vicki; Jones, Courtney
2013-10-01
The hydroxyl (OH) 18 cm lines are powerful and versatile probes of diffuse molecular gas, that may trace a largely unstudied component of the Galactic ISM. SPLASH (the Southern Parkes Large Area Survey in Hydroxyl) is a large, unbiased and fully-sampled survey of OH emission, absorption and masers in the Galactic Plane that will achieve sensitivities an order of magnitude better than previous work. In this proposal, we request ATCA time to follow up OH maser candidates. This will give us accurate (~10") positions of the masers, which can be compared to other maser positions from HOPS, MMB and MALT-45 and will provide full polarisation measurements towards a sample of OH masers that have not been observed in MAGMO.
Accurate thickness measurement of graphene
NASA Astrophysics Data System (ADS)
Shearer, Cameron J.; Slattery, Ashley D.; Stapleton, Andrew J.; Shapter, Joseph G.; Gibson, Christopher T.
2016-03-01
Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.
Accurate thickness measurement of graphene.
Shearer, Cameron J; Slattery, Ashley D; Stapleton, Andrew J; Shapter, Joseph G; Gibson, Christopher T
2016-03-29
Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.
YOST, FREDERICK G.
1999-09-09
The importance of interfacial processes in materials joining has a long history. A significant amount of work has suggested that processes collateral to wetting can affect the extent of wetting and moderate or retard wetting rate. Even very small additions of a constituent, known to react with the substrate, cause pronounced improvement in wetting and are exploited in braze alloys, especially those used for joining to ceramics. The wide diversity of processes, such as diffusion, chemical reaction, and fluxing, and their possible combinations suggest that various rate laws should be expected for wetting kinetics depending on the controlling processes. These rate laws are expected to differ crucially from the standard fluid controlled wetting models found in the literature. Voitovitch et al. and Mortensen et al. have shown data that suggests diffusion control for some systems and reaction control for others. They also presented a model of wetting kinetics controlled by the diffusion of a constituent contained by the wetting fluid. In the following a model will be constructed for the wetting kinetics of a small droplet of metal containing a constituent that diffuses to the wetting line and chemically reacts with a flat, smooth substrate. The model is similar to that of Voitovitch et al. and Mortensen et al. but incorporates chemical reaction kinetics such that the result contains both diffusion and reaction kinetics. The model is constructed in the circular cylinder coordinate system, satisfies the diffusion equation under conditions of slow flow, and considers diffusion and reaction at the wetting line to be processes in series. This is done by solving the diffusion equation with proper initial and boundary conditions, computing the diffusive flux at the wetting line and equating this to both the convective flux and reaction flux. This procedure is similar to equating the current flowing in components of a series circuit. The wetting rate will be computed versus time
Comparisons of kinetic ablation models for the capillary discharge
Li Rui; Li Xingwen; Jia Shenli; Murphy, Anthony B.
2010-07-15
The properties of kinetic ablation models are considered in this paper. The widely used kinetic ablation model (model-K) only considers monatomic vapor. A revised model (model-Z) was introduced by taking into account the polyatomic vapor's internal degrees of freedom, as well as the temperature dependence of the average particle mass. In this work, both temperature and pressure dependence of average particle mass and the specific heat ratio {gamma} are taken into account, producing an improved version of model-Z (denoted model-Z{sup *}). Ablation data calculated by model-K and model-Z* for two typical capillary materials are presented. Compared to model-K, model-Z* predicts an increased ablation rate at lower plasma temperature and higher plasma density, and a decreased rate for the opposite conditions. Finally, based on the plasma parameters in a typical discharge cycle, all three models are used to calculate the time-dependent ablation rate and the integrated ablated mass. It is found that the main difference between their results arises because of the different average particle masses near the wall surface, and model-Z* is the most accurate for the discharge cycle considered. Further, it is found that the ablation parameters are highly sensitive to the pressure, in particular, through the pressure dependence of average particle mass.
Yost, F.G.
2000-04-14
The importance of interfacial processes in materials joining has a long history. A significant amount of work has suggested that processes collateral to wetting can affect the extent of wetting and moderate or retard wetting rate. Even very small additions of a constituent, known to react with the substrate, cause pronounced improvement in wetting and are exploited in braze alloys, especially those used for joining to ceramics. In the following a model will be constructed for the wetting kinetics of a small droplet of metal containing a constituent that diffuses to the wetting line and chemically reacts with a flat, smooth substrate. The model is similar to that of Voitovitch et al. and Mortensen et al. but incorporates chemical reaction kinetics such that the result contains both diffusion and reaction kinetics. The model is constructed in the circular cylinder coordinate system, satisfies the diffusion equation under conditions of slow flow, and considers diffusion and reaction at the wetting line to be processes in series. This is done by solving the diffusion equation with proper initial and boundary conditions, computing the diffusive flux at the wetting line, and equating this to both the convective flux and reaction flux. This procedure is similar to equating the current flowing in components of a series circuit. The wetting rate will be computed versus time for a variety of diffusion and reaction conditions. A transition is observed from nonlinear (diffusive) to linear (reactive) behavior as the control parameters (such as the diffusion coefficient) are modified. This is in agreement with experimental observations. The adequacy of the slow flow condition, used in this type of analysis, is discussed and an amended procedure is suggested.
Saffman-Taylor fingers with kinetic undercooling
NASA Astrophysics Data System (ADS)
Gardiner, Bennett P. J.; McCue, Scott W.; Dallaston, Michael C.; Moroney, Timothy J.
2015-02-01
The mathematical model of a steadily propagating Saffman-Taylor finger in a Hele-Shaw channel has applications to two-dimensional interacting streamer discharges which are aligned in a periodic array. In the streamer context, the relevant regularization on the interface is not provided by surface tension but instead has been postulated to involve a mechanism equivalent to kinetic undercooling, which acts to penalize high velocities and prevent blow-up of the unregularized solution. Previous asymptotic results for the Hele-Shaw finger problem with kinetic undercooling suggest that for a given value of the kinetic undercooling parameter, there is a discrete set of possible finger shapes, each analytic at the nose and occupying a different fraction of the channel width. In the limit in which the kinetic undercooling parameter vanishes, the fraction for each family approaches 1 /2 , suggesting that this "selection" of 1 /2 by kinetic undercooling is qualitatively similar to the well-known analog with surface tension. We treat the numerical problem of computing these Saffman-Taylor fingers with kinetic undercooling, which turns out to be more subtle than the analog with surface tension, since kinetic undercooling permits finger shapes which are corner-free but not analytic. We provide numerical evidence for the selection mechanism by setting up a problem with both kinetic undercooling and surface tension and numerically taking the limit that the surface tension vanishes.
Kinetic MHD simulation of large 'circ; tearing mode
NASA Astrophysics Data System (ADS)
Cheng, Jianhua; Chen, Yang; Parker, Scott; Uzdensky, Dmitri
2012-03-01
We have developed a second-order accurate semi-implicit δ method for kinetic MHD simulation with Lorentz force ions and fluid electrons. The model has been used to study the resistive tearing mode instability, which involves multiple spatial scales. In small 'circ; cases, the linear growth rate and eigenmode structure are consistent with resistive MHD analysis. The Rutherford stage and saturation are demonstrated, but the simulation exhibits different saturation island widths compared with previous MHD simulations. In large 'circ; cases, nonlinear simulations show multiple islands forming, followed by the islands coalescing at later times. The competition between these two processes strongly influences the reconnection rates and eventually leads to a steady state reconnection. We will present various parameter studies and show that our hybrid results agree with fluid analysis in certain limits (e.g., relatively large resisitivities).
α-Phase transformation kinetics of U - 8 wt% Mo established by in situ neutron diffraction
NASA Astrophysics Data System (ADS)
Steiner, M. A.; Calhoun, C. A.; Klein, R. W.; An, K.; Garlea, E.; Agnew, S. R.
2016-08-01
The α-phase transformation kinetics of as-cast U - 8 wt% Mo below the eutectoid temperature have been established by in situ neutron diffraction. α-phase weight fraction data acquired through Rietveld refinement at five different isothermal hold temperatures can be modeled accurately utilizing a simple Johnson-Mehl-Avrami-Kolmogorov impingement-based theory, and the results are validated by a corresponding evolution in the γ-phase lattice parameter during transformation that follows Vegard's law. Neutron diffraction data is used to produce a detailed Time-Temperature-Transformation diagram that improves upon inconsistencies in the current literature, exhibiting a minimum transformation start time of 40 min at temperatures between 500 °C and 510 °C. The transformation kinetics of U - 8 wt% Mo can vary significantly from as-cast conditions after extensive heat treatments, due to homogenization of the typical dendritic microstructure which possesses non-negligible solute segregation.
A Kinetic and Mass Transfer Model for Glycerol Hydrogenolysis in a Trickle-Bed Reactor
Xi, Yaoyan; Holladay, Johnathan E.; Frye, John G.; Oberg, Aaron A.; Jackson, James E.; Miller, Dennis J.
2010-11-15
A detailed model of glycerol hydrogenolysis in a trickle-bed reactor is presented that includes a mechanistically based kinetic rate expression, energy transport, mass transport across the gas-liquid and liquid-solid interfaces, intraparticle catalyst mass transfer, and partial wetting of the bed. Optimal kinetic parameters for the glycerol hydrogenolysis rate expression were determined via nonlinear regression analysis on the basis of experiments conducted in a laboratory-scale trickle-bed reactor over a broad range of operating conditions. Model predictions agree well with experimental data and accurately predict trends in reactor performance with liquid flow rate, temperature, hydrogen pressure, and base promoter concentration. The model is thus a useful tool for predicting laboratory reactor performance and for design of commercial-scale trickle-bed systems.
Kinetics of phenol degradation in an anaerobic fixed-biofilm process
Lin, Y.H.; Lee, K.K.
2006-06-15
A mathematical model was developed to describe phenol degradation in an anaerobic fixed-biofilm process. The model incorporates the mechanisms of diffusive mass transport and Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A pilot-scale column reactor was used to verify the model. Batch kinetic tests were conducted independently to determine the biokinetic parameters used in the model, while shear loss and initial thickness of biofilm were assumed so that the model simulated the substrate concentration results well. The removal efficiency for phenol was approximately 98.5% at a steady-state condition. The model accurately described the effluent substrate concentrations and the sequence of biodegradation in the reactor. The model simulations are in agreement with the experimental results. The approaches presented in this paper could be used to design full-scale anaerobic fixed-biofilm reactor systems for the biodegradation of phenolic substrates.
Kinetic pinning and biological antifreezes.
Sander, Leonard M; Tkachenko, Alexei V
2004-09-17
Biological antifreezes protect cold-water organisms from freezing. An example is the antifreeze proteins (AFP's) that attach to the surface of ice crystals and arrest growth. The mechanism for growth arrest has not been heretofore understood in a quantitative way. We present a complete theory based on a kinetic model. We use the "stones on a pillow" picture. Our theory of the suppression of the freezing point as a function of the concentration of the AFP is quantitatively accurate. It gives a correct description of the dependence of the freezing point suppression on the geometry of the protein, and might lead to advances in design of synthetic AFP's.
Determining anaerobic degradation kinetics from batch tests.
Moreda, Iván López
2016-01-01
Data obtained from a biomethane potential (BMP) test were used in order to obtain the parameters of a kinetic model of solid wastes anaerobic degradation. The proposed model considers a hydrolysis step with a first order kinetic, a Monod kinetic for the soluble organic substrate degradation and a first order decay of microorganisms. The instantaneous release of methane was assumed. The parameters of the model are determined following a direct search optimization procedure. A 'multiple-shooting' technique was used as a first step of the optimization process. The confidence interval of the parameters was determined by using Monte Carlo simulations. Also, the distribution functions of the parameters were determined. Only the hydrolysis first order constant shows a normal distribution. PMID:27191569
Kovalyuk, T. T. Maistruk, E. V.; Maryanchuk, P. D.
2014-12-15
The results of studies of the kinetic properties of Hg{sub 1−x−y}Cd{sub x}Eu{sub y}Se semiconductor crystals in the ranges of temperatures T = 77–300 K and magnetic fields H = 0.5–5 kOe before and after heat treatment of the samples in Se vapors are reported. It is established that annealing of the samples in Se vapors induces a decrease in the electron concentration. From the concentration dependence of the electron effective mass at the Fermi level, the band gap, the matrix element of interband interaction, and the electron effective mass at the bottom of the conduction band are determined.
A general moment expansion method for stochastic kinetic models
NASA Astrophysics Data System (ADS)
Ale, Angelique; Kirk, Paul; Stumpf, Michael P. H.
2013-05-01
Moment approximation methods are gaining increasing attention for their use in the approximation of the stochastic kinetics of chemical reaction systems. In this paper we derive a general moment expansion method for any type of propensities and which allows expansion up to any number of moments. For some chemical reaction systems, more than two moments are necessary to describe the dynamic properties of the system, which the linear noise approximation is unable to provide. Moreover, also for systems for which the mean does not have a strong dependence on higher order moments, moment approximation methods give information about higher order moments of the underlying probability distribution. We demonstrate the method using a dimerisation reaction, Michaelis-Menten kinetics and a model of an oscillating p53 system. We show that for the dimerisation reaction and Michaelis-Menten enzyme kinetics system higher order moments have limited influence on the estimation of the mean, while for the p53 system, the solution for the mean can require several moments to converge to the average obtained from many stochastic simulations. We also find that agreement between lower order moments does not guarantee that higher moments will agree. Compared to stochastic simulations, our approach is numerically highly efficient at capturing the behaviour of stochastic systems in terms of the average and higher moments, and we provide expressions for the computational cost for different system sizes and orders of approximation. We show how the moment expansion method can be employed to efficiently quantify parameter sensitivity. Finally we investigate the effects of using too few moments on parameter estimation, and provide guidance on how to estimate if the distribution can be accurately approximated using only a few moments.
Dash, Chandravanu; Vathipadiekal, Vinod; George, Sudeep P; Rao, Mala
2002-05-17
The first report of slow-tight inhibition of xylanase by a bifunctional inhibitor alkalo-thermophilic Bacillus inhibitor (ATBI), from an extremophilic Bacillus sp. is described. ATBI inhibits aspartic protease (Dash, C., and Rao, M. (2001) J. Biol. Chem., 276, 2487-2493) and xylanase (Xyl I) from a Thermomonospora sp. The steady-state kinetics revealed time-dependent competitive inhibition of Xyl I by ATBI, consistent with two-step inhibition mechanism. The inhibition followed a rapid equilibrium step to form a reversible enzyme-inhibitor complex (EI), which isomerizes to the second enzyme-inhibitor complex (EI*), which dissociated at a very slow rate. The rate constants determined for the isomerization of EI to EI*, and the dissociation of EI* were 13 +/- 1 x 10(-6) s(-1) and 5 +/- 0.5 x 10(-8) s(-1), respectively. The K(i) value for the formation of EI complex was 2.5 +/- 0.5 microm, whereas the overall inhibition constant K(i)* was 7 +/- 1 nm. The conformational changes induced in Xyl I by ATBI were monitored by fluorescence spectroscopy and the rate constants derived were in agreement with the kinetic data. Thus, the conformational alterations were correlated to the isomerization of EI to EI*. ATBI binds to the active site of the enzyme and disturbs the native interaction between the histidine and lysine, as demonstrated by the abolished isoindole fluorescence of o-phthalaldehyde (OPTA)-labeled Xyl I. Our results revealed that the inactivation of Xyl I is due to the disruption of the hydrogen-bonding network between the essential histidine and other residues involved in catalysis and a model depicting the probable interaction between ATBI or OPTA with Xyl I has been proposed.
Chemical and Biological Kinetics
NASA Astrophysics Data System (ADS)
Emanuel', N. M.
1981-10-01
Examples of the application of the methods and ideas of chemical kinetics in various branches of chemistry and biology are considered and the results of studies on the kinetics and mechanisms of autoxidation and inhibited and catalysed oxidation of organic substances in the liquid phase are surveyed. Problems of the kinetics of the ageing of polymers and the principles of their stabilisation are discussed and certain trends in biological kinetics (kinetics of tumour growth, kinetic criteria of the effectiveness of chemotherapy, problems of gerontology, etc.) are considered. The bibliography includes 281 references.
Temperature-Dependent Kinetic Model for Nitrogen-Limited Wine Fermentations▿
Coleman, Matthew C.; Fish, Russell; Block, David E.
2007-01-01
A physical and mathematical model for wine fermentation kinetics was adapted to include the influence of temperature, perhaps the most critical factor influencing fermentation kinetics. The model was based on flask-scale white wine fermentations at different temperatures (11 to 35°C) and different initial concentrations of sugar (265 to 300 g/liter) and nitrogen (70 to 350 mg N/liter). The results show that fermentation temperature and inadequate levels of nitrogen will cause stuck or sluggish fermentations. Model parameters representing cell growth rate, sugar utilization rate, and the inactivation rate of cells in the presence of ethanol are highly temperature dependent. All other variables (yield coefficient of cell mass to utilized nitrogen, yield coefficient of ethanol to utilized sugar, Monod constant for nitrogen-limited growth, and Michaelis-Menten-type constant for sugar transport) were determined to vary insignificantly with temperature. The resulting mathematical model accurately predicts the observed wine fermentation kinetics with respect to different temperatures and different initial conditions, including data from fermentations not used for model development. This is the first wine fermentation model that accurately predicts a transition from sluggish to normal to stuck fermentations as temperature increases from 11 to 35°C. Furthermore, this comprehensive model provides insight into combined effects of time, temperature, and ethanol concentration on yeast (Saccharomyces cerevisiae) activity and physiology. PMID:17616615
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
Cesium removal and kinetics equilibrium: Precipitation kinetics
Barnes, M.J.
1999-12-17
This task consisted of both non-radioactive and radioactive (tracer) tests examining the influence of potentially significant variables on cesium tetraphenylborate precipitation kinetics. The work investigated the time required to reach cesium decontamination and the conditions that affect the cesium precipitation kinetics.
Ozone mass transfer and kinetics experiments
Bollyky, L.J.; Beary, M.M.
1981-12-01
Experiments were conducted at the Hanford Site to determine the most efficient pH and temperature levels for the destruction of complexants in Hanford high-level defense waste. These complexants enhance migration of radionuclides in the soil and inhibit the growth of crystals in the evaporator-crystallizer. Ozone mass transfer and kinetics tests have been outlined for the determination of critical mass transfer and kinetics parameters of the ozone-complexant reaction.
Accurate SHAPE-directed RNA structure determination
Deigan, Katherine E.; Li, Tian W.; Mathews, David H.; Weeks, Kevin M.
2009-01-01
Almost all RNAs can fold to form extensive base-paired secondary structures. Many of these structures then modulate numerous fundamental elements of gene expression. Deducing these structure–function relationships requires that it be possible to predict RNA secondary structures accurately. However, RNA secondary structure prediction for large RNAs, such that a single predicted structure for a single sequence reliably represents the correct structure, has remained an unsolved problem. Here, we demonstrate that quantitative, nucleotide-resolution information from a SHAPE experiment can be interpreted as a pseudo-free energy change term and used to determine RNA secondary structure with high accuracy. Free energy minimization, by using SHAPE pseudo-free energies, in conjunction with nearest neighbor parameters, predicts the secondary structure of deproteinized Escherichia coli 16S rRNA (>1,300 nt) and a set of smaller RNAs (75–155 nt) with accuracies of up to 96–100%, which are comparable to the best accuracies achievable by comparative sequence analysis. PMID:19109441
Kinetics of hydrogen consumption by rumen fluid, anaerobic digestor sludge, and sediment.
Robinson, J A; Tiedje, J M
1982-12-01
Michaelis-Menten kinetic parameters for H(2) consumption by three methanogenic habitats were determined from progress curve and initial velocity experiments. The influences of mass transfer resistance, endogenous H(2) production, and growth on apparent parameter estimates were also investigated. Kinetic parameters could not be determined for undiluted rumen fluid and some digestor sludge from gas-phase measurements of H(2), since mass transfer of H(2) across the gas-liquid interface was rate limiting. However, accurate values were obtained once the samples were diluted. H(2) consumption by digestor sludge with a long retention time and by hypereutrophic lake sediment was not phase transfer limited. The K(m) values for H(2) uptake by these habitats were similar, with means of 5.8, 6.0, and 7.1 muM for rumen fluid, digestor sludge, and sediment, respectively. V(max) estimates suggested a ratio of activity of approximately 100 (rumen fluid):10 (sludge):1 (sediment); their ranges were as follows: rumen fluid, 14 to 28 mM h; Holt sludge, 0.7 to 4.3 mM h; and Wintergreen sediment, 0.13 to 0.49 mM h. The principles of phase transfer limitation, studied here for H(2), are the same for all gaseous substrates and products. The limitations and errors associated with gas phase determination of kinetic parameters were evaluated with a mathematical model that combined mass transport and Michaelis-Menten kinetics. Three criteria are described which can be used to evaluate the possibility that a phase transfer limitation exists. If it does not exist, (i) substrate consumption curves are Michaelis-Menten and not first order, (ii) the K(m) is independent of initial substrate concentration, and (iii) the K(m) is independent of biomass (V(max)) and remains constant with dilution of sample. Errors in the Michaelis-Menten kinetic parameters are caused by endogenously produced H(2), but they were <15% for rumen fluid and 10% for lake sediment and digestor sludge. Increases in V
NASA Astrophysics Data System (ADS)
Rahman, Anis; Rahman, Aunik; Mentzer, Mark A.
2014-05-01
Terahertz dynamic scanning reflectometry (TDSR) was used for measuring layered materials' deformation kinetics spectra. Multi-layered materials are used for protective devices such as helmet and body armor. An in-situ measurement of deformation profile and other dynamic characteristics is important when such material is subjected to ballistic impacts. Current instrumentation is limited in their abilities to provide sub-surface information in a non-destructive fashion. A high sensitivity TDSR has been used to measure dynamic surface deformation characteristics in real-time (in-situ) and also at post deformation (ex-situ). Real-time ballistic deformation kinetics was captured with a high speed measurement system. The kinetics spectra was used to compute a number of crucial parameters such as deformation length and its propagation profile, the relaxation position, and the macroscopic vibration profile. In addition, the loss of mass due to impact was quantified for accurate determination of the trauma causing energy. For non-metallic substrates, a transmitted beam was used to calibrate mass loss, a priori, of the laminate layers due to impact. Deformation kinetics information may then be used to formulate trauma diagnosis conditions from blunt hit via the Sturdivan criterion [1]. The basic difference in the proposed approach is that here diagnostic criteria are inferred by measuring the helmet itself; no need to draw blood or any biopsy from the patient.
Ueda, Hiroshi; Ida, Yasuo; Kadota, Kazunori; Tozuka, Yuichi
2014-02-28
The feasibility of Raman mapping for understanding the crystallization mechanism of an amorphous drug was investigated using described images. The crystallization tendency of amorphous indomethacin under dry condition at 30 °C was kinetically evaluated by means of Raman mapping and X-ray powder diffraction (XRPD) with change in the calculated crystallinities. Raman images directly revealed the occurrence of particle size-dependent non-uniform crystallization; slow crystallization of large particles, but fast crystallization of small particles. Kinetic analysis by fitting to the Kolmogorov-Johnson-Mehl-Avrami equation was performed for the crystallization profiles of both Raman mapping and XRPD data. For the Raman mapping data, the distribution of large particles was characterized and examined. The kinetic parameters calculated from the whole Raman image area agreed well with those of XRPD, suggesting accurate prediction of both techniques for the entire crystallization. Raman images revealed the change in the crystallization mechanism for the focused area; the large particles showed a reduced crystallization rate constant and an increase in the dimensional crystal growth exponent. Raman mapping is an attractive tool for quantitative and kinetic investigation of the crystallization mechanism with distributional images.
Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid
NASA Astrophysics Data System (ADS)
Yadav, Vishnu P.; Mukherjee, Rudra Palash; Bantraj, Kandi; Maity, Sunil K.
2010-10-01
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.
Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid
Yadav, Vishnu P.; Maity, Sunil K.; Mukherjee, Rudra Palash; Bantraj, Kandi
2010-10-26
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.
Mohamed, Samah Y; Cai, Liming; Khaled, Fethi; Banyon, Colin; Wang, Zhandong; Al Rashidi, Mariam J; Pitsch, Heinz; Curran, Henry J; Farooq, Aamir; Sarathy, S Mani
2016-04-14
Accurate chemical kinetic combustion models of lightly branched alkanes (e.g., 2-methylalkanes) are important to investigate the combustion behavior of real fuels. Improving the fidelity of existing kinetic models is a necessity, as new experiments and advanced theories show inaccuracies in certain portions of the models. This study focuses on updating thermodynamic data and the kinetic reaction mechanism for a gasoline surrogate component, 2-methylhexane, based on recently published thermodynamic group values and rate rules derived from quantum calculations and experiments. Alternative pathways for the isomerization of peroxy-alkylhydroperoxide (OOQOOH) radicals are also investigated. The effects of these updates are compared against new high-pressure shock tube and rapid compression machine ignition delay measurements. It is shown that rate constant modifications are required to improve agreement between kinetic modeling simulations and experimental data. We further demonstrate the ability to optimize the kinetic model using both manual and automated techniques for rate parameter tunings to improve agreement with the measured ignition delay time data. Finally, additional low temperature chain branching reaction pathways are shown to improve the model's performance. The present approach to model development provides better performance across extended operating conditions while also strengthening the fundamental basis of the model.
Effect of kinetics on residue curve maps for reactive distillation
Venimadhavan, G.; Buzad, G.; Doherty, M.F.; Malone, M.F. . Dept. of Chemical Engineering)
1994-11-01
A class of models is derived for studying the effects of chemical kinetics on residue curve maps for reactive distillation. Activity-based rate and phase equilibrium expressions provide an accurate and thermodynamically consistent description of composition changes in nonideal, reacting vapor-liquid mixtures. For certain strategies of operation, which dictate the rate of product removal, the model equations are nonautonomous, leading to unusual dynamic behavior. However, for a certain special product removal policy, the effects of kinetics can be described by a single parameter, the Damkoehler number, which measures the rate of reaction relative to product removal. For small values of the Damkoehler number, the nonreactive simple distillation residue curve map is recovered and the singular points are the pure components and azeotropes in the nonreactive mixture. A bifurcation analysis shows the deformation and, in some cases, the disappearance of these singular points as the Damkoehler number is increased until the equilibrium reactive residue curve map is recovered at large values. A model problem for the reactive distillation of methyl tert-butyl ether from isobutene and methanol is solved.
Blais, AR; Dekaban, M; Lee, T-Y
2014-08-15
Quantitative analysis of dynamic positron emission tomography (PET) data usually involves minimizing a cost function with nonlinear regression, wherein the choice of starting parameter values and the presence of local minima affect the bias and variability of the estimated kinetic parameters. These nonlinear methods can also require lengthy computation time, making them unsuitable for use in clinical settings. Kinetic modeling of PET aims to estimate the rate parameter k{sub 3}, which is the binding affinity of the tracer to a biological process of interest and is highly susceptible to noise inherent in PET image acquisition. We have developed linearized kinetic models for kinetic analysis of dynamic contrast enhanced computed tomography (DCE-CT)/PET imaging, including a 2-compartment model for DCE-CT and a 3-compartment model for PET. Use of kinetic parameters estimated from DCE-CT can stabilize the kinetic analysis of dynamic PET data, allowing for more robust estimation of k{sub 3}. Furthermore, these linearized models are solved with a non-negative least squares algorithm and together they provide other advantages including: 1) only one possible solution and they do not require a choice of starting parameter values, 2) parameter estimates are comparable in accuracy to those from nonlinear models, 3) significantly reduced computational time. Our simulated data show that when blood volume and permeability are estimated with DCE-CT, the bias of k{sub 3} estimation with our linearized model is 1.97 ± 38.5% for 1,000 runs with a signal-to-noise ratio of 10. In summary, we have developed a computationally efficient technique for accurate estimation of k{sub 3} from noisy dynamic PET data.
Hazrati, Hossein; Shayegan, Jalal; Seyedi, Seyed Mojtaba
2015-01-01
This study examined biodegradation kinetics of styrene and ethylbenzene as representatives of alkenylbenzenes and mono-alkylbenzenes, respectively. The compounds were studied independently and as binary mixtures using a series of aerobic batch degradation experiments introduced by acclimatized mix culture. Initial concentration of styrene and ethylbenzene in the liquid phase vacillated from 0 to 220 mg/l. The Andrew model was applied for the biodegradation of individual substrates and the estimated constants of the equation for styrene and ethylbenzene were μmax = 0.1581, 0.2090 (1/h), KS =25.91, 37.77 (mg/L), KI =13.15, 62.62 (mg/L), respectively. The accomplished parameters from single substrate degradation tests were used to predict possible interaction factors achieved from dual substrate experiments. The Sum Kinetics with Interaction Parameters (SKIP) model and the purely competitive enzyme kinetics model were employed to evaluate any interactions. The SKIP model was found to accurately describe these interactions. Moreover, it was revealed that ethylbenzene plays an influential role on styrene consumption (e.g. IE,S = 1.64) compared to styrene which has insignificant inhibitory effect on ethylbenzene usage (e.g. IS,E =0.4) . The active site differences for styrene and ethylbenzene biodegradation and the pathway variations for biodegradation are among the major potential reasons for failure of the estimation that occurred in purely competitive kinetics model. This study is the first to calculate the interactions between styrene and ethylbenzene.
Stephenson, Ned A; Bell, Alexis T
2005-06-22
A study has been conducted of the mechanism and kinetics of cyclooctene epoxidation by hydrogen peroxide catalyzed by iron(III) tetrakispentafluorophenyl [F(20)TPPFe(III)] porphyrin. The formation of cyclooctene oxide, the only product, was determined by gas chromatography, and the consumption of hydrogen peroxide was determined by (1)H NMR. UV-visible spectroscopy was used to identify the state of the porphyrin as a function of solvent composition and reaction conditions and to follow the kinetics of porphyrin degradation. F(20)TPPFe(III) was found to be inactive in the chloride-ligated form, but became active when the chloride ligand was replaced by a methoxide ligand. The methoxide-ligated form of F(20)TPPFe(III) reacts with hydrogen peroxide to form an iron(III) hydroperoxide species, which then undergoes both heterolytic and homolytic cleavage to form iron(IV) pi-radical cations and iron(IV) oxo species, respectively. The iron(IV) pi-radical cations are responsible for the epoxidation of cyclooctene, whereas the iron(IV) oxo species are responsible for hydrogen peroxide decomposition. The kinetics of cyclooctene epoxidation and hydrogen peroxide decomposition developed from the proposed mechanism describe the experimentally observed kinetics accurately. The rate parameters derived from a fit of the model to the experimental data are consistent with previous estimates of the magnitude of these parameters.
Markin, Craig J; Spyracopoulos, Leo
2012-12-01
NMR-monitored chemical shift titrations for the study of weak protein-ligand interactions represent a rich source of information regarding thermodynamic parameters such as dissociation constants (K ( D )) in the micro- to millimolar range, populations for the free and ligand-bound states, and the kinetics of interconversion between states, which are typically within the fast exchange regime on the NMR timescale. We recently developed two chemical shift titration methods wherein co-variation of the total protein and ligand concentrations gives increased precision for the K ( D ) value of a 1:1 protein-ligand interaction (Markin and Spyracopoulos in J Biomol NMR 53: 125-138, 2012). In this study, we demonstrate that classical line shape analysis applied to a single set of (1)H-(15)N 2D HSQC NMR spectra acquired using precise protein-ligand chemical shift titration methods we developed, produces accurate and precise kinetic parameters such as the off-rate (k ( off )). For experimentally determined kinetics in the fast exchange regime on the NMR timescale, k ( off ) ~ 3,000 s(-1) in this work, the accuracy of classical line shape analysis was determined to be better than 5 % by conducting quantum mechanical NMR simulations of the chemical shift titration methods with the magnetic resonance toolkit GAMMA. Using Monte Carlo simulations, the experimental precision for k ( off ) from line shape analysis of NMR spectra was determined to be 13 %, in agreement with the theoretical precision of 12 % from line shape analysis of the GAMMA simulations in the presence of noise and protein concentration errors. In addition, GAMMA simulations were employed to demonstrate that line shape analysis has the potential to provide reasonably accurate and precise k ( off ) values over a wide range, from 100 to 15,000 s(-1). The validity of line shape analysis for k ( off ) values approaching intermediate exchange (~100 s(-1)), may be facilitated by more accurate K ( D ) measurements
LSENS - GENERAL CHEMICAL KINETICS AND SENSITIVITY ANALYSIS CODE
NASA Technical Reports Server (NTRS)
Bittker, D. A.
1994-01-01
LSENS has been developed for solving complex, homogeneous, gas-phase, chemical kinetics problems. The motivation for the development of this program is the continuing interest in developing detailed chemical reaction mechanisms for complex reactions such as the combustion of fuels and pollutant formation and destruction. A reaction mechanism is the set of all elementary chemical reactions that are required to describe the process of interest. Mathematical descriptions of chemical kinetics problems constitute sets of coupled, nonlinear, first-order ordinary differential equations (ODEs). The number of ODEs can be very large because of the numerous chemical species involved in the reaction mechanism. Further complicating the situation are the many simultaneous reactions needed to describe the chemical kinetics of practical fuels. For example, the mechanism describing the oxidation of the simplest hydrocarbon fuel, methane, involves over 25 species participating in nearly 100 elementary reaction steps. Validating a chemical reaction mechanism requires repetitive solutions of the governing ODEs for a variety of reaction conditions. Analytical solutions to the systems of ODEs describing chemistry are not possible, except for the simplest cases, which are of little or no practical value. Consequently, there is a need for fast and reliable numerical solution techniques for chemical kinetics problems. In addition to solving the ODEs describing chemical kinetics, it is often necessary to know what effects variations in either initial condition values or chemical reaction mechanism parameters have on the solution. Such a need arises in the development of reaction mechanisms from experimental data. The rate coefficients are often not known with great precision and in general, the experimental data are not sufficiently detailed to accurately estimate the rate coefficient parameters. The development of a reaction mechanism is facilitated by a systematic sensitivity analysis
On fast reactor kinetics studies
Seleznev, E. F.; Belov, A. A.; Matveenko, I. P.; Zhukov, A. M.; Raskach, K. F.
2012-07-01
The results and the program of fast reactor core time and space kinetics experiments performed and planned to be performed at the IPPE critical facility is presented. The TIMER code was taken as computation support of the experimental work, which allows transient equations to be solved in 3-D geometry with multi-group diffusion approximation. The number of delayed neutron groups varies from 6 to 8. The code implements the solution of both transient neutron transfer problems: a direct one, where neutron flux density and its derivatives, such as reactor power, etc, are determined at each time step, and an inverse one for the point kinetics equation form, where such a parameter as reactivity is determined with a well-known reactor power time variation function. (authors)
Accurate method of modeling cluster scaling relations in modified gravity
NASA Astrophysics Data System (ADS)
He, Jian-hua; Li, Baojiu
2016-06-01
We propose a new method to model cluster scaling relations in modified gravity. Using a suite of nonradiative hydrodynamical simulations, we show that the scaling relations of accumulated gas quantities, such as the Sunyaev-Zel'dovich effect (Compton-y parameter) and the x-ray Compton-y parameter, can be accurately predicted using the known results in the Λ CDM model with a precision of ˜3 % . This method provides a reliable way to analyze the gas physics in modified gravity using the less demanding and much more efficient pure cold dark matter simulations. Our results therefore have important theoretical and practical implications in constraining gravity using cluster surveys.
Communication: An accurate global potential energy surface for the ground electronic state of ozone
Dawes, Richard E-mail: hguo@unm.edu; Lolur, Phalgun; Li, Anyang; Jiang, Bin; Guo, Hua E-mail: hguo@unm.edu
2013-11-28
We report a new full-dimensional and global potential energy surface (PES) for the O + O{sub 2} → O{sub 3} ozone forming reaction based on explicitly correlated multireference configuration interaction (MRCI-F12) data. It extends our previous [R. Dawes, P. Lolur, J. Ma, and H. Guo, J. Chem. Phys. 135, 081102 (2011)] dynamically weighted multistate MRCI calculations of the asymptotic region which showed the widely found submerged reef along the minimum energy path to be the spurious result of an avoided crossing with an excited state. A spin-orbit correction was added and the PES tends asymptotically to the recently developed long-range electrostatic model of Lepers et al. [J. Chem. Phys. 137, 234305 (2012)]. This PES features: (1) excellent equilibrium structural parameters, (2) good agreement with experimental vibrational levels, (3) accurate dissociation energy, and (4) most-notably, a transition region without a spurious reef. The new PES is expected to allow insight into the still unresolved issues surrounding the kinetics, dynamics, and isotope signature of ozone.
Cosgrove, M S; Gover, S; Naylor, C E; Vandeputte-Rutten, L; Adams, M J; Levy, H R
2000-12-12
The role of Asp-177 in the His-Asp catalytic dyad of glucose 6-phosphate dehydrogenase from Leuconostoc mesenteroides has been investigated by a structural and functional characterization of the D177N mutant enzyme. Its three-dimensional structure has been determined by X-ray cryocrystallography in the presence of NAD(+) and in the presence of glucose 6-phosphate plus NADPH. The structure of a glucose 6-phosphate complex of a mutant (Q365C) with normal enzyme activity has also been determined and substrate binding compared. To understand the effect of Asp-177 on the ionization properties of the catalytic base His-240, the pH dependence of kinetic parameters has been determined for the D177N mutant and compared to that of the wild-type enzyme. The structures give details of glucose 6-phosphate binding and show that replacement of the Asp-177 of the catalytic dyad with asparagine does not affect the overall structure of glucose 6-phosphate dehydrogenase. Additionally, the evidence suggests that the productive tautomer of His-240 in the D177N mutant enzyme is stabilized by a hydrogen bond with Asn-177; hence, the mutation does not affect tautomer stabilization. We conclude, therefore, that the absence of a negatively charged aspartate at 177 accounts for the decrease in catalytic activity at pH 7.8. Structural analysis suggests that the pH dependence of the kinetic parameters of D177N glucose 6-phosphate dehydrogenase results from an ionized water molecule replacing the missing negative charge of the mutated Asp-177 at high pH. Glucose 6-phosphate binding orders and orients His-178 in the D177N-glucose 6-phosphate-NADPH ternary complex and appears to be necessary to form this water-binding site.
NASA Astrophysics Data System (ADS)
Yogurtcu, Osman N.; Johnson, Margaret E.
2015-08-01
The dynamics of association between diffusing and reacting molecular species are routinely quantified using simple rate-equation kinetics that assume both well-mixed concentrations of species and a single rate constant for parameterizing the binding rate. In two-dimensions (2D), however, even when systems are well-mixed, the assumption of a single characteristic rate constant for describing association is not generally accurate, due to the properties of diffusional searching in dimensions d ≤ 2. Establishing rigorous bounds for discriminating between 2D reactive systems that will be accurately described by rate equations with a single rate constant, and those that will not, is critical for both modeling and experimentally parameterizing binding reactions restricted to surfaces such as cellular membranes. We show here that in regimes of intrinsic reaction rate (ka) and diffusion (D) parameters ka/D > 0.05, a single rate constant cannot be fit to the dynamics of concentrations of associating species independently of the initial conditions. Instead, a more sophisticated multi-parametric description than rate-equations is necessary to robustly characterize bimolecular reactions from experiment. Our quantitative bounds derive from our new analysis of 2D rate-behavior predicted from Smoluchowski theory. Using a recently developed single particle reaction-diffusion algorithm we extend here to 2D, we are able to test and validate the predictions of Smoluchowski theory and several other theories of reversible reaction dynamics in 2D for the first time. Finally, our results also mean that simulations of reactive systems in 2D using rate equations must be undertaken with caution when reactions have ka/D > 0.05, regardless of the simulation volume. We introduce here a simple formula for an adaptive concentration dependent rate constant for these chemical kinetics simulations which improves on existing formulas to better capture non-equilibrium reaction dynamics from dilute
Baghel, Shrawan; Cathcart, Helen; Redington, Wynette; O'Reilly, Niall J
2016-07-01
Amorphous drug formulations have great potential to enhance solubility and thus bioavailability of BCS class II drugs. However, the higher free energy and molecular mobility of the amorphous form drive them towards the crystalline state which makes them unstable. Accurate determination of the crystallization tendency/kinetics is the key to the successful design and development of such systems. In this study, dipyridamole (DPM) and cinnarizine (CNZ) have been selected as model compounds. Thermodynamic fragility (mT) was measured from the heat capacity change at the glass transition temperature (Tg) whereas dynamic fragility (mD) was evaluated using methods based on extrapolation of configurational entropy to zero [Formula: see text] , and heating rate dependence of Tg [Formula: see text] . The mean relaxation time of amorphous drugs was calculated from the Vogel-Tammann-Fulcher (VTF) equation. Furthermore, the correlation between fragility and glass forming ability (GFA) of the model drugs has been established and the relevance of these parameters to crystallization of amorphous drugs is also assessed. Moreover, the crystallization kinetics of model drugs under isothermal conditions has been studied using Johnson-Mehl-Avrami (JMA) approach to determine the Avrami constant 'n' which provides an insight into the mechanism of crystallization. To further probe into the crystallization mechanism, the non-isothermal crystallization kinetics of model systems were also analysed by statistically fitting the crystallization data to 15 different kinetic models and the relevance of model-free kinetic approach has been established. The crystallization mechanism for DPM and CNZ at each extent of transformation has been predicted. The calculated fragility, glass forming ability (GFA) and crystallization kinetics are found to be in good correlation with the stability prediction of amorphous solid dispersions. Thus, this research work involves a multidisciplinary approach to
Kinetic analysis of nonisothermal crystallization
Kelton, K.F.
1996-12-31
A realistic computer model for polymorphic crystallization under isothermal and nonisothermal conditions, which takes proper account of time-dependent nucleation behavior and cluster-size-dependent growth, is presented. A new correction to the standard Johnson-Mehl-Avrami-Kolmogorov (JMAK) statistical analysis that takes account of finite sample size is incorporated to simulate data taken from fine particles and nano-structured materials. Model predictions compare well with experimental data obtained from calorimetric studies of the polymorphic crystallization of lithium disilicate glass. The computer model is employed to evaluate commonly used methods of analysis for calorimetric data and to suggest new approaches for extracting kinetic parameters.
GEOMETRY, HEAT REMOVAL AND KINETICS SCOPING MODELS FOR HYDROGEN STORAGE SYSTEMS
Hardy, B
2007-11-16
It is recognized that detailed models of proposed hydrogen storage systems are essential to gain insight into the complex processes occurring during the charging and discharging processes. Such insight is an invaluable asset for both assessing the viability of a particular system and/or for improving its design. The detailed models, however, require time to develop and run. Clearly, it is much more efficient to begin a modeling effort with a good system design and to progress from that point. To facilitate this approach, it is useful to have simplified models that can quickly estimate optimal loading and discharge kinetics, effective hydrogen capacities, system dimensions and heat removal requirements. Parameters obtained from these models can then be input to the detailed models to obtain an accurate assessment of system performance that includes more complete integration of the physical processes. This report describes three scoping models that assess preliminary system design prior to invoking a more detailed finite element analysis. The three models address the kinetics, the scaling and heat removal parameters of the system, respectively. The kinetics model is used to evaluate the effect of temperature and hydrogen pressure on the loading and discharge kinetics. As part of the kinetics calculations, the model also determines the mass of stored hydrogen per mass of hydride (in a particular reference form). As such, the model can determine the optimal loading and discharge rates for a particular hydride and the maximum achievable loading (over an infinite period of time). The kinetics model developed with the Mathcad{reg_sign} solver, runs in a mater of seconds and can quickly be used to identify the optimal temperature and pressure for either the loading or discharge processes. The geometry scoping model is used to calculate the size of the system, the optimal placement of heat transfer elements, and the gravimetric and volumetric capacities for a particular
NASA Astrophysics Data System (ADS)
Elmer, Sidney P.; Pande, Vijay S.
2005-03-01
Using simulation to study the folding kinetics of 20-mer poly-phenylacetylene (pPA) oligomers, we find a long time scale trapped kinetic phase in the cumulative folding time distribution. This is demonstrated using molecular dynamics to simulate an ensemble of over 100 folding trajectories. The simulation data are fit to a four-state kinetic model which includes the typical folded and unfolded states, along with an intermediate state, and most surprisingly, a kinetically trapped state. Topologically diverse conformations reminiscent of α helices, β turns, and sheets in proteins are observed, along with unique structures in the form of knots. The nonhelical conformations are implicated, on the basis of structural correlations to kinetic parameters, to contribute to the trapped kinetic behavior. The strong solvophobic forces which mediate the folding process and produce a stable helical folded state also serve to overstabilize the nonhelical conformations, ultimately trapping them. From our simulations, the folding time is predicted to be on the order of 2.5-12.5 μs in the presence of the trapped kinetic phase. The folding mechanism for these 20-mer chains is compared with the previously reported folding mechanism for the pPA 12-mer chains. A linear scaling relationship between the chain length and the mean first passage time is predicted in the absence of the trapped kinetic phase. We discuss the major implications of this discovery in the design of self-assembling nanostructures.
Sánchez, Ana; Vázquez, José A; Quinteiro, Javier; Sotelo, Carmen G
2013-04-10
Real-time PCR is the most sensitive method for detection and precise quantification of specific DNA sequences, but it is not usually applied as a quantitative method in seafood. In general, benchmark techniques, mainly cycle threshold (Ct), are the routine method for quantitative estimations, but they are not the most precise approaches for a standard assay. In the present work, amplification data from European hake (Merluccius merluccius) DNA samples were accurately modeled by three sigmoid reparametrized equations, where the lag phase parameter (λc) from the Richards equation with four parameters was demonstrated to be the perfect substitute for Ct for PCR quantification. The concentrations of primers and probes were subsequently optimized by means of that selected kinetic parameter. Finally, the linear correlation among DNA concentration and λc was also confirmed.
Mill profiler machines soft materials accurately
NASA Technical Reports Server (NTRS)
Rauschl, J. A.
1966-01-01
Mill profiler machines bevels, slots, and grooves in soft materials, such as styrofoam phenolic-filled cores, to any desired thickness. A single operator can accurately control cutting depths in contour or straight line work.
Effect of Perturbing a Simulated Motion on Knee and Anterior Cruciate Ligament Kinetics
Herfat, Safa T.; Boguszewski, Daniel V.; Nesbitt, Rebecca J.
2013-01-01
Current surgical treatments for common knee injuries do not restore the normal biomechanics. Among other factors, the abnormal biomechanics increases the susceptibility to the early onset of osteoarthritis. In pursuit of improving long term outcome, investigators must understand normal knee kinematics and corresponding joint and anterior cruciate ligament (ACL) kinetics during the activities of daily living. Our long term research goal is to measure in vivo joint motions for the ovine stifle model and later simulate these motions with a 6 degree of freedom (DOF) robot to measure the corresponding 3D kinetics of the knee and ACL-only joint. Unfortunately, the motion measurement and motion simulation technologies used for our project have associated errors. The objective of this study was to determine how motion measurement and motion recreation error affect knee and ACL-only joint kinetics by perturbing a simulated in vivo motion in each DOF and measuring the corresponding intact knee and ACL-only joint forces and moments. The normal starting position for the motion was perturbed in each degree of freedom by four levels (−0.50, −0.25, 0.25, and 0.50 mm or degrees). Only translational perturbations significantly affected the intact knee and ACL-only joint kinetics. The compression-distraction perturbation had the largest effect on intact knee forces and the anterior-posterior perturbation had the largest effect on the ACL forces. Small translational perturbations can significantly alter intact knee and ACL-only joint forces. Thus, translational motion measurement errors must be reduced to provide a more accurate representation of the intact knee and ACL kinetics. To account for the remaining motion measurement and recreation errors, an envelope of forces and moments should be reported. These force and moment ranges will provide valuable functional tissue engineering parameters (FTEPs) that can be used to design more effective ACL treatments. PMID:23083204
An articulated statistical shape model for accurate hip joint segmentation.
Kainmueller, Dagmar; Lamecker, Hans; Zachow, Stefan; Hege, Hans-Christian
2009-01-01
In this paper we propose a framework for fully automatic, robust and accurate segmentation of the human pelvis and proximal femur in CT data. We propose a composite statistical shape model of femur and pelvis with a flexible hip joint, for which we extend the common definition of statistical shape models as well as the common strategy for their adaptation. We do not analyze the joint flexibility statistically, but model it explicitly by rotational parameters describing the bent in a ball-and-socket joint. A leave-one-out evaluation on 50 CT volumes shows that image driven adaptation of our composite shape model robustly produces accurate segmentations of both proximal femur and pelvis. As a second contribution, we evaluate a fine grain multi-object segmentation method based on graph optimization. It relies on accurate initializations of femur and pelvis, which our composite shape model can generate. Simultaneous optimization of both femur and pelvis yields more accurate results than separate optimizations of each structure. Shape model adaptation and graph based optimization are embedded in a fully automatic framework. PMID:19964159
Simplification of the unified gas kinetic scheme.
Chen, Songze; Guo, Zhaoli; Xu, Kun
2016-08-01
The unified gas kinetic scheme (UGKS) is an asymptotic preserving (AP) scheme for kinetic equations. It is superior for transition flow simulation and has been validated in the past years. However, compared to the well-known discrete ordinate method (DOM), which is a classical numerical method solving the kinetic equations, the UGKS needs more computational resources. In this study, we propose a simplification of the unified gas kinetic scheme. It allows almost identical numerical cost as the DOM, but predicts numerical results as accurate as the UGKS. In the simplified scheme, the numerical flux for the velocity distribution function and the numerical flux for the macroscopic conservative quantities are evaluated separately. The equilibrium part of the UGKS flux is calculated by analytical solution instead of the numerical quadrature in velocity space. The simplification is equivalent to a flux hybridization of the gas kinetic scheme for the Navier-Stokes (NS) equations and the conventional discrete ordinate method. Several simplification strategies are tested, through which we can identify the key ingredient of the Navier-Stokes asymptotic preserving property. Numerical tests show that, as long as the collision effect is built into the macroscopic numerical flux, the numerical scheme is Navier-Stokes asymptotic preserving, regardless the accuracy of the microscopic numerical flux for the velocity distribution function. PMID:27627418
Simplification of the unified gas kinetic scheme
NASA Astrophysics Data System (ADS)
Chen, Songze; Guo, Zhaoli; Xu, Kun
2016-08-01
The unified gas kinetic scheme (UGKS) is an asymptotic preserving (AP) scheme for kinetic equations. It is superior for transition flow simulation and has been validated in the past years. However, compared to the well-known discrete ordinate method (DOM), which is a classical numerical method solving the kinetic equations, the UGKS needs more computational resources. In this study, we propose a simplification of the unified gas kinetic scheme. It allows almost identical numerical cost as the DOM, but predicts numerical results as accurate as the UGKS. In the simplified scheme, the numerical flux for the velocity distribution function and the numerical flux for the macroscopic conservative quantities are evaluated separately. The equilibrium part of the UGKS flux is calculated by analytical solution instead of the numerical quadrature in velocity space. The simplification is equivalent to a flux hybridization of the gas kinetic scheme for the Navier-Stokes (NS) equations and the conventional discrete ordinate method. Several simplification strategies are tested, through which we can identify the key ingredient of the Navier-Stokes asymptotic preserving property. Numerical tests show that, as long as the collision effect is built into the macroscopic numerical flux, the numerical scheme is Navier-Stokes asymptotic preserving, regardless the accuracy of the microscopic numerical flux for the velocity distribution function.
Kumar, V.T.
1992-01-01
Simultaneous evaluation of electron transfer rate constant, k[sup 0], following chemical reaction rate constant, k[sub f], electron transfer coefficient, [alpha] and standard potential, E[sup 0][prime] for an electrochemical reaction following the EC mechanism is described. A mathematical model for the current response to a potential step is developed, starting with the Butler-Volmer equation for electrode kinetics and concentration expressions for the redox couple. The resulting integral equations are solved numerically via the Step Function method. Current-potential and current-time curves are simulated and tested under limiting conditions. The four parameters of the system are evaluated by fitting simulated current-voltage-time (i-E-t) surface to the theoretical equation. The method is applied to study an important biological molecule, viz., methyl cobalamin, in DMSO. Included in the discussion part is the use of kinetic zone diagrams to depict chronoamperometric current response as a function of dimensionless rate constants for the EC reaction scheme. This compact display of the influence of the two rate constants on current in all time windows can be used to select the best data for analysis. Theoretical limits of measurable rate constants can be estimated from the zone diagram. The development of a dropping mercury electrode detector for High Performance Liquid Chromatography (HPLC) and its application to analysis of B[sub 12] and other vitamins is described. This EC detector is able to achieve high levels of sensitivity by exploiting the catalytic hydrogen evolution undergone by many nitrogenous organic molecules. Vitamin B[sub 12], thiamine, riboflavin and niacinamide were analyzed individually and in mixtures on reverse phase C18 column. Preliminary results from the analysis of commercial multivitamin preparations are also discussed.
Adaptation of the microdosimetric kinetic model to hypoxia
NASA Astrophysics Data System (ADS)
Bopp, C.; Hirayama, R.; Inaniwa, T.; Kitagawa, A.; Matsufuji, N.; Noda, K.
2016-11-01
Ion beams present a potential advantage in terms of treatment of lesions with hypoxic regions. In order to use this potential, it is important to accurately model the cell survival of oxic as well as hypoxic cells. In this work, an adaptation of the microdosimetric kinetic (MK) model making it possible to account for cell hypoxia is presented. The adaptation relies on the modification of damage quantity (double strand breaks and more complex lesions) due to the radiation. Model parameters such as domain size and nucleus size are then adapted through a fitting procedure. We applied this approach to two cell lines, HSG and V79 for helium, carbon and neon ions. A similar behaviour of the parameters was found for the two cell lines, namely a reduction of the domain size and an increase in the sensitive nuclear volume of hypoxic cells compared to those of oxic cells. In terms of oxygen enhancement ratio (OER), the experimental data behaviour can be reproduced, including dependence on particle type at the same linear energy transfer (LET). Errors on the cell survival prediction are of the same order of magnitude than for the original MK model. Our adaptation makes it possible to account for hypoxia without modelling the OER as a function of the LET of the particles, but directly accounting for hypoxic cell survival data.
Oxidation kinetics of aluminum diboride
NASA Astrophysics Data System (ADS)
Whittaker, Michael L.; Sohn, H. Y.; Cutler, Raymond A.
2013-11-01
The oxidation characteristics of aluminum diboride (AlB2) and a physical mixture of its constituent elements (Al+2B) were studied in dry air and pure oxygen using thermal gravimetric analysis to obtain non-mechanistic kinetic parameters. Heating in air at a constant linear heating rate of 10 °C/min showed a marked difference between Al+2B and AlB2 in the onset of oxidation and final conversion fraction, with AlB2 beginning to oxidize at higher temperatures but reaching nearly complete conversion by 1500 °C. Kinetic parameters were obtained in both air and oxygen using a model-free isothermal method at temperatures between 500 and 1000 °C. Activation energies were found to decrease, in general, with increasing conversion for AlB2 and Al+2B in both air and oxygen. AlB2 exhibited O2-pressure-independent oxidation behavior at low conversions, while the activation energies of Al+2B were higher in O2 than in air. Differences in the composition and morphology between oxidized Al+2B and AlB2 suggested that Al2O3-B2O3 interactions slowed Al+2B oxidation by converting Al2O3 on aluminum particles into a Al4B2O9 shell, while the same Al4B2O9 developed a needle-like morphology in AlB2 that reduced oxygen diffusion distances and increased conversion. The model-free kinetic analysis was critical for interpreting the complex, multistep oxidation behavior for which a single mechanism could not be assigned. At low temperatures, moisture increased the oxidation rate of Al+2B and AlB2, but both appear to be resistant to oxidation in cool, dry environments.
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.
Kinetics of Propargyl Radical Dissociation.
Klippenstein, Stephen J; Miller, James A; Jasper, Ahren W
2015-07-16
Due to the prominent role of the propargyl radical for hydrocarbon growth within combustion environments, it is important to understand the kinetics of its formation and loss. The ab initio transition state theory-based master equation method is used to obtain theoretical kinetic predictions for the temperature and pressure dependence of the thermal decomposition of propargyl, which may be its primary loss channel under some conditions. The potential energy surface for the decomposition of propargyl is first mapped at a high level of theory with a combination of coupled cluster and multireference perturbation calculations. Variational transition state theory is then used to predict the microcanonical rate coefficients, which are subsequently implemented within the multiple-well multiple-channel master equation. A variety of energy transfer parameters are considered, and the sensitivity of the thermal rate predictions to these parameters is explored. The predictions for the thermal decomposition rate coefficient are found to be in good agreement with the limited experimental data. Modified Arrhenius representations of the rate constants are reported for utility in combustion modeling. PMID:25871530
Kinetics of Propargyl Radical Dissociation.
Klippenstein, Stephen J; Miller, James A; Jasper, Ahren W
2015-07-16
Due to the prominent role of the propargyl radical for hydrocarbon growth within combustion environments, it is important to understand the kinetics of its formation and loss. The ab initio transition state theory-based master equation method is used to obtain theoretical kinetic predictions for the temperature and pressure dependence of the thermal decomposition of propargyl, which may be its primary loss channel under some conditions. The potential energy surface for the decomposition of propargyl is first mapped at a high level of theory with a combination of coupled cluster and multireference perturbation calculations. Variational transition state theory is then used to predict the microcanonical rate coefficients, which are subsequently implemented within the multiple-well multiple-channel master equation. A variety of energy transfer parameters are considered, and the sensitivity of the thermal rate predictions to these parameters is explored. The predictions for the thermal decomposition rate coefficient are found to be in good agreement with the limited experimental data. Modified Arrhenius representations of the rate constants are reported for utility in combustion modeling.
Modelling heart rate kinetics.
Zakynthinaki, Maria S
2015-01-01
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).
Zakynthinaki, Maria S.
2015-01-01
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). PMID:25876164
Selişteanu, Dan; Șendrescu, Dorin; Georgeanu, Vlad
2015-01-01
Monoclonal antibodies (mAbs) are at present one of the fastest growing products of pharmaceutical industry, with widespread applications in biochemistry, biology, and medicine. The operation of mAbs production processes is predominantly based on empirical knowledge, the improvements being achieved by using trial-and-error experiments and precedent practices. The nonlinearity of these processes and the absence of suitable instrumentation require an enhanced modelling effort and modern kinetic parameter estimation strategies. The present work is dedicated to nonlinear dynamic modelling and parameter estimation for a mammalian cell culture process used for mAb production. By using a dynamical model of such kind of processes, an optimization-based technique for estimation of kinetic parameters in the model of mammalian cell culture process is developed. The estimation is achieved as a result of minimizing an error function by a particle swarm optimization (PSO) algorithm. The proposed estimation approach is analyzed in this work by using a particular model of mammalian cell culture, as a case study, but is generic for this class of bioprocesses. The presented case study shows that the proposed parameter estimation technique provides a more accurate simulation of the experimentally observed process behaviour than reported in previous studies. PMID:25685797
Selişteanu, Dan; Șendrescu, Dorin; Georgeanu, Vlad; Roman, Monica
2015-01-01
Monoclonal antibodies (mAbs) are at present one of the fastest growing products of pharmaceutical industry, with widespread applications in biochemistry, biology, and medicine. The operation of mAbs production processes is predominantly based on empirical knowledge, the improvements being achieved by using trial-and-error experiments and precedent practices. The nonlinearity of these processes and the absence of suitable instrumentation require an enhanced modelling effort and modern kinetic parameter estimation strategies. The present work is dedicated to nonlinear dynamic modelling and parameter estimation for a mammalian cell culture process used for mAb production. By using a dynamical model of such kind of processes, an optimization-based technique for estimation of kinetic parameters in the model of mammalian cell culture process is developed. The estimation is achieved as a result of minimizing an error function by a particle swarm optimization (PSO) algorithm. The proposed estimation approach is analyzed in this work by using a particular model of mammalian cell culture, as a case study, but is generic for this class of bioprocesses. The presented case study shows that the proposed parameter estimation technique provides a more accurate simulation of the experimentally observed process behaviour than reported in previous studies. PMID:25685797
Parameter identification of robot manipulators: a heuristic particle swarm search approach.
Yan, Danping; Lu, Yongzhong; Levy, David
2015-01-01
Parameter identification of robot manipulators is an indispensable pivotal process of achieving accurate dynamic robot models. Since these kinetic models are highly nonlinear, it is not easy to tackle the matter of identifying their parameters. To solve the difficulty effectively, we herewith present an intelligent approach, namely, a heuristic particle swarm optimization (PSO) algorithm, which we call the elitist learning strategy (ELS) and proportional integral derivative (PID) controller hybridized PSO approach (ELPIDSO). A specified PID controller is designed to improve particles' local and global positions information together with ELS. Parameter identification of robot manipulators is conducted for performance evaluation of our proposed approach. Experimental results clearly indicate the following findings: Compared with standard PSO (SPSO) algorithm, ELPIDSO has improved a lot. It not only enhances the diversity of the swarm, but also features better search effectiveness and efficiency in solving practical optimization problems. Accordingly, ELPIDSO is superior to least squares (LS) method, genetic algorithm (GA), and SPSO algorithm in estimating the parameters of the kinetic models of robot manipulators. PMID:26039090
Parameter Identification of Robot Manipulators: A Heuristic Particle Swarm Search Approach
Yan, Danping; Lu, Yongzhong; Levy, David
2015-01-01
Parameter identification of robot manipulators is an indispensable pivotal process of achieving accurate dynamic robot models. Since these kinetic models are highly nonlinear, it is not easy to tackle the matter of identifying their parameters. To solve the difficulty effectively, we herewith present an intelligent approach, namely, a heuristic particle swarm optimization (PSO) algorithm, which we call the elitist learning strategy (ELS) and proportional integral derivative (PID) controller hybridized PSO approach (ELPIDSO). A specified PID controller is designed to improve particles’ local and global positions information together with ELS. Parameter identification of robot manipulators is conducted for performance evaluation of our proposed approach. Experimental results clearly indicate the following findings: Compared with standard PSO (SPSO) algorithm, ELPIDSO has improved a lot. It not only enhances the diversity of the swarm, but also features better search effectiveness and efficiency in solving practical optimization problems. Accordingly, ELPIDSO is superior to least squares (LS) method, genetic algorithm (GA), and SPSO algorithm in estimating the parameters of the kinetic models of robot manipulators. PMID:26039090
Selişteanu, Dan; Șendrescu, Dorin; Georgeanu, Vlad; Roman, Monica
2015-01-01
Monoclonal antibodies (mAbs) are at present one of the fastest growing products of pharmaceutical industry, with widespread applications in biochemistry, biology, and medicine. The operation of mAbs production processes is predominantly based on empirical knowledge, the improvements being achieved by using trial-and-error experiments and precedent practices. The nonlinearity of these processes and the absence of suitable instrumentation require an enhanced modelling effort and modern kinetic parameter estimation strategies. The present work is dedicated to nonlinear dynamic modelling and parameter estimation for a mammalian cell culture process used for mAb production. By using a dynamical model of such kind of processes, an optimization-based technique for estimation of kinetic parameters in the model of mammalian cell culture process is developed. The estimation is achieved as a result of minimizing an error function by a particle swarm optimization (PSO) algorithm. The proposed estimation approach is analyzed in this work by using a particular model of mammalian cell culture, as a case study, but is generic for this class of bioprocesses. The presented case study shows that the proposed parameter estimation technique provides a more accurate simulation of the experimentally observed process behaviour than reported in previous studies.
Parameter identification of robot manipulators: a heuristic particle swarm search approach.
Yan, Danping; Lu, Yongzhong; Levy, David
2015-01-01
Parameter identification of robot manipulators is an indispensable pivotal process of achieving accurate dynamic robot models. Since these kinetic models are highly nonlinear, it is not easy to tackle the matter of identifying their parameters. To solve the difficulty effectively, we herewith present an intelligent approach, namely, a heuristic particle swarm optimization (PSO) algorithm, which we call the elitist learning strategy (ELS) and proportional integral derivative (PID) controller hybridized PSO approach (ELPIDSO). A specified PID controller is designed to improve particles' local and global positions information together with ELS. Parameter identification of robot manipulators is conducted for performance evaluation of our proposed approach. Experimental results clearly indicate the following findings: Compared with standard PSO (SPSO) algorithm, ELPIDSO has improved a lot. It not only enhances the diversity of the swarm, but also features better search effectiveness and efficiency in solving practical optimization problems. Accordingly, ELPIDSO is superior to least squares (LS) method, genetic algorithm (GA), and SPSO algorithm in estimating the parameters of the kinetic models of robot manipulators.
More-Accurate Model of Flows in Rocket Injectors
NASA Technical Reports Server (NTRS)
Hosangadi, Ashvin; Chenoweth, James; Brinckman, Kevin; Dash, Sanford
2011-01-01
An improved computational model for simulating flows in liquid-propellant injectors in rocket engines has been developed. Models like this one are needed for predicting fluxes of heat in, and performances of, the engines. An important part of predicting performance is predicting fluctuations of temperature, fluctuations of concentrations of chemical species, and effects of turbulence on diffusion of heat and chemical species. Customarily, diffusion effects are represented by parameters known in the art as the Prandtl and Schmidt numbers. Prior formulations include ad hoc assumptions of constant values of these parameters, but these assumptions and, hence, the formulations, are inaccurate for complex flows. In the improved model, these parameters are neither constant nor specified in advance: instead, they are variables obtained as part of the solution. Consequently, this model represents the effects of turbulence on diffusion of heat and chemical species more accurately than prior formulations do, and may enable more-accurate prediction of mixing and flows of heat in rocket-engine combustion chambers. The model has been implemented within CRUNCH CFD, a proprietary computational fluid dynamics (CFD) computer program, and has been tested within that program. The model could also be implemented within other CFD programs.
Kinetic and mechanistic studies of free-radical reactions in combustion
Tully, F.P.
1993-12-01
Combustion is driven by energy-releasing chemical reactions. Free radicals that participate in chain reactions carry the combustion process from reactants to products. Research in chemical kinetics enables us to understand the microscopic mechanisms involved in individual chemical reactions as well as to determine the rates at which they proceed. Both types of information are required for an understanding of how flames burn, why engines knock, how to minimize the production of pollutants, and many other important questions in combustion. In this program the authors emphasize accurate measurements over wide temperature ranges of the rates at which ubiquitous free radicals react with stable molecules. The authors investigate a variety of OH, CN, and CH + stable molecule reactions important to fuel conversion, emphasizing application of the extraordinarily precise technique of laser photolysis/continuous-wave laser-induced fluorescence (LP/cwLIF). This precision enables kinetic measurements to serve as mechanistic probes. Since considerable effort is required to study each individual reaction, prudent selection is critical. Two factors encourage selection of a specific reaction: (1) the rates and mechanisms of the subject reaction are required input to a combustion model; and (2) the reaction is a chemical prototype which, upon characterization, will provide fundamental insight into chemical reactivity, facilitate estimation of kinetic parameters for similar reactions, and constrain and test the computational limits of reaction-rate theory. Most studies performed in this project satisfy both conditions.
Mollica, Luca; Theret, Isabelle; Antoine, Mathias; Perron-Sierra, Françoise; Charton, Yves; Fourquez, Jean-Marie; Wierzbicki, Michel; Boutin, Jean A; Ferry, Gilles; Decherchi, Sergio; Bottegoni, Giovanni; Ducrot, Pierre; Cavalli, Andrea
2016-08-11
Ligand-target residence time is emerging as a key drug discovery parameter because it can reliably predict drug efficacy in vivo. Experimental approaches to binding and unbinding kinetics are nowadays available, but we still lack reliable computational tools for predicting kinetics and residence time. Most attempts have been based on brute-force molecular dynamics (MD) simulations, which are CPU-demanding and not yet particularly accurate. We recently reported a new scaled-MD-based protocol, which showed potential for residence time prediction in drug discovery. Here, we further challenged our procedure's predictive ability by applying our methodology to a series of glucokinase activators that could be useful for treating type 2 diabetes mellitus. We combined scaled MD with experimental kinetics measurements and X-ray crystallography, promptly checking the protocol's reliability by directly comparing computational predictions and experimental measures. The good agreement highlights the potential of our scaled-MD-based approach as an innovative method for computationally estimating and predicting drug residence times. PMID:27391254
Measurement of intracellular ice formation kinetics by high-speed video cryomicroscopy.
Karlsson, Jens O M
2015-01-01
Quantitative information about the kinetics and cumulative probability of intracellular ice formation is necessary to develop minimally damaging freezing procedures for the cryopreservation of cells and tissue. Conventional cryomicroscopic assays, which rely on indirect evidence of intracellular freezing (e.g., opacity changes in the cell cytoplasm), can yield significant errors in the estimated kinetics. In contrast, the formation and growth of intracellular ice crystals can be accurately detected using temporally resolved imaging methods (i.e., video recording at sub-millisecond resolution). Here, detailed methods for the setup and operation of a high-speed video cryomicroscope system are described, including protocols for imaging of intracellular ice crystallization events, and stochastic analysis of the ice formation kinetics in a cell population. Recommendations are provided for temperature profile design, sample preparation, and configuration of the video acquisition parameters. Throughout this chapter, the protocols incorporate best practices that have been drawn from over a decade of experience with high-speed video cryomicroscopy in our laboratory.
2012-01-01
Bioaccumulation and biotransformation are key toxicokinetic processes that modify toxicity of chemicals and sensitivity of organisms. Bioaccumulation kinetics vary greatly among organisms and chemicals; thus, we investigated the influence of biotransformation kinetics on bioaccumulation in a model aquatic invertebrate using fifteen 14C-labeled organic xenobiotics from diverse chemical classes and physicochemical properties (1,2,3-trichlorobenzene, imidacloprid, 4,6-dinitro-o-cresol, ethylacrylate, malathion, chlorpyrifos, aldicarb, carbofuran, carbaryl, 2,4-dichlorophenol, 2,4,5-trichlorophenol, pentachlorophenol, 4-nitrobenzyl-chloride, 2,4-dichloroaniline, and sea-nine (4,5-dichloro-2-octyl-3-isothiazolone)). We detected and identified metabolites using HPLC with UV and radio-detection as well as high resolution mass spectrometry (LTQ-Orbitrap). Kinetics of uptake, biotransformation, and elimination of parent compounds and metabolites were modeled with a first-order one-compartment model. Bioaccumulation factors were calculated for parent compounds and metabolite enrichment factors for metabolites. Out of 19 detected metabolites, we identified seven by standards or accurate mass measurements and two via pathway analysis and analogies to other compounds. 1,2,3-Trichlorobenzene, imidacloprid, and 4,6-dinitro-o-cresol were not biotransformed. Dietary uptake contributed little to overall uptake. Differentiation between parent and metabolites increased accuracy of bioaccumulation parameters compared to total 14C measurements. Biotransformation dominated toxicokinetics and strongly affected internal concentrations of parent compounds and metabolites. Many metabolites reached higher internal concentrations than their parents, characterized by large metabolite enrichment factors. PMID:22321051
NASA Technical Reports Server (NTRS)
Bittker, David A.; Radhakrishnan, Krishnan
1994-01-01
LSENS, the Lewis General Chemical Kinetics and Sensitivity Analysis Code, has been developed for solving complex, homogeneous, gas-phase chemical kinetics problems and contains sensitivity analysis for a variety of problems, including nonisothermal situations. This report is part 3 of a series of three reference publications that describe LSENS, provide a detailed guide to its usage, and present many example problems. Part 3 explains the kinetics and kinetics-plus-sensitivity analysis problems supplied with LSENS and presents sample results. These problems illustrate the various capabilities of, and reaction models that can be solved by, the code and may provide a convenient starting point for the user to construct the problem data file required to execute LSENS. LSENS is a flexible, convenient, accurate, and efficient solver for chemical reaction problems such as static system; steady, one-dimensional, inviscid flow; reaction behind incident shock wave, including boundary layer correction; and perfectly stirred (highly backmixed) reactor. In addition, the chemical equilibrium state can be computed for the following assigned states: temperature and pressure, enthalpy and pressure, temperature and volume, and internal energy and volume. For static problems the code computes the sensitivity coefficients of the dependent variables and their temporal derivatives with respect to the initial values of the dependent variables and/or the three rate coefficient parameters of the chemical reactions.
Adsorption kinetics of methyl violet onto perlite.
Doğan, Mehmet; Alkan, Mahir
2003-01-01
This study examines adsorption kinetics and activation parameters of methyl violet on perlite. The effect of process parameters like contact time, concentration of dye, temperature and pH on the extent of methyl violet adsorption from solution has been investigated. Results of the kinetic studies show that the adsorption reaction is first order with respect to dye solution concentration with activation energy of 13.2 kJ mol(-1). This low activation energy value indicates that the adsorption reaction is diffusion controlled. The activation parameters using Arrhenius and Eyring equations have been calculated. Adsorption increases with increase of variables such as contact time, initial dye concentration, temperature and pH.
Oxidation and hydrolysis kinetic studies on UN
NASA Astrophysics Data System (ADS)
Rao, G. A. Rama; Mukerjee, S. K.; Vaidya, V. N.; Venugopal, V.; Sood, D. D.
1991-11-01
The reaction of oxygen and water vapour with UN microspheres containing 0.78 and 10.9 mol% UO 2 as impurity was studied under non-isothermal heating conditions in a thermobalance under different partial pressures of oxygen, a fixed pressure of water vapour in argon, and in air. Uranium mononitride was ultimately converted to U 3O 8, with the formation of UO 2 and U 2N 3 as intermediates. The end product of pyrohydrolysis was UO 2. The kinetic parameters were evaluated and the mechanism of the reaction was suggested. Different kinetic models were used to explain the oxidation behaviour of UN.
Leveraging Two Kinect Sensors for Accurate Full-Body Motion Capture.
Gao, Zhiquan; Yu, Yao; Zhou, Yu; Du, Sidan
2015-09-22
Accurate motion capture plays an important role in sports analysis, the medical field and virtual reality. Current methods for motion capture often suffer from occlusions, which limits the accuracy of their pose estimation. In this paper, we propose a complete system to measure the pose parameters of the human body accurately. Different from previous monocular depth camera systems, we leverage two Kinect sensors to acquire more information about human movements, which ensures that we can still get an accurate estimation even when significant occlusion occurs. Because human motion is temporally constant, we adopt a learning analysis to mine the temporal information across the posture variations. Using this information, we estimate human pose parameters accurately, regardless of rapid movement. Our experimental results show that our system can perform an accurate pose estimation of the human body with the constraint of information from the temporal domain.
Leveraging Two Kinect Sensors for Accurate Full-Body Motion Capture
Gao, Zhiquan; Yu, Yao; Zhou, Yu; Du, Sidan
2015-01-01
Accurate motion capture plays an important role in sports analysis, the medical field and virtual reality. Current methods for motion capture often suffer from occlusions, which limits the accuracy of their pose estimation. In this paper, we propose a complete system to measure the pose parameters of the human body accurately. Different from previous monocular depth camera systems, we leverage two Kinect sensors to acquire more information about human movements, which ensures that we can still get an accurate estimation even when significant occlusion occurs. Because human motion is temporally constant, we adopt a learning analysis to mine the temporal information across the posture variations. Using this information, we estimate human pose parameters accurately, regardless of rapid movement. Our experimental results show that our system can perform an accurate pose estimation of the human body with the constraint of information from the temporal domain. PMID:26402681
Exploring Kinetics of Phenol Biodegradation by Cupriavidus taiwanesis 187
Wei, Yu-Hong; Chen, Wei-Chuan; Chang, Shan-Ming; Chen, Bor-Yann
2010-01-01
Phenol biodegradation in batch systems using Cupriavidus taiwanesis 187 has been experimentally studied. To determine the various parameters of a kinetic model, combinations of rearranged equations have been evaluated using inverse polynomial techniques for parameter estimation. The correlations between lag phase and phase concentration suggest that considering phenol inhibition in kinetic analysis is helpful for characterizing phenol degradation. This study proposes a novel method to determine multiplicity of steady states in continuous stirred tank reactors (CSTRs) in order to identify the most appropriate kinetics to characterize the dynamics of phenol biodegradation. PMID:21614192
Modified chemiluminescent NO analyzer accurately measures NOX
NASA Technical Reports Server (NTRS)
Summers, R. L.
1978-01-01
Installation of molybdenum nitric oxide (NO)-to-higher oxides of nitrogen (NOx) converter in chemiluminescent gas analyzer and use of air purge allow accurate measurements of NOx in exhaust gases containing as much as thirty percent carbon monoxide (CO). Measurements using conventional analyzer are highly inaccurate for NOx if as little as five percent CO is present. In modified analyzer, molybdenum has high tolerance to CO, and air purge substantially quenches NOx destruction. In test, modified chemiluminescent analyzer accurately measured NO and NOx concentrations for over 4 months with no denegration in performance.
Cluster kinetics model for mixtures of glassformers
NASA Astrophysics Data System (ADS)
Brenskelle, Lisa A.; McCoy, Benjamin J.
2007-10-01
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.
Berendsen, W R; Gendrot, G; Freund, A; Reuss, M
2006-12-01
Lipase-catalyzed kinetic resolution of racemates is a popular method for synthesis of chiral synthons. Most of these resolutions are reversible equilibrium limited reactions. For the first time, an extensive kinetic model is proposed for kinetic resolution reactions, which takes into account the full reversibility of the reaction, substrate inhibition by an acyl donor and an acyl acceptor as well as alternative substrate inhibition by each enantiomer. For this purpose, the reversible enantioselective transesterification of (R/S)-1-methoxy-2-propanol with ethyl acetate catalyzed by Candida antarctica lipase B (CAL-B) is investigated. The detailed model presented here is valid for a wide range of substrate and product concentrations. Following model discrimination and the application of Haldane equations to reduce the degree of freedom in parameter estimation, the 11 free parameters are successfully identified. All parameters are fitted to the complete data set simultaneously. Six types of independent initial rate studies provide a solid data basis for the model. The effect of changes in substrate and product concentration on reaction kinetics is discussed. The developed model is used for simulations to study the behavior of reaction kinetics in a fixed bed reactor. The typical plot of enantiomeric excess versus conversion of substrate and product is evaluated at various initial substrate mixtures. The model is validated by comparison with experimental results obtained with a fixed bed reactor, which is part of a fully automated state-of-the-art miniplant.
National Institute of Standards and Technology Data Gateway
SRD 17 NIST Chemical Kinetics Database (Web, free access) The NIST Chemical Kinetics Database includes essentially all reported kinetics results for thermal gas-phase chemical reactions. The database is designed to be searched for kinetics data based on the specific reactants involved, for reactions resulting in specified products, for all the reactions of a particular species, or for various combinations of these. In addition, the bibliography can be searched by author name or combination of names. The database contains in excess of 38,000 separate reaction records for over 11,700 distinct reactant pairs. These data have been abstracted from over 12,000 papers with literature coverage through early 2000.
A "Stationery" Kinetics Experiment.
ERIC Educational Resources Information Center
Hall, L.; Goberdhansingh, A.
1988-01-01
Describes a simple redox reaction that occurs between potassium permanganate and oxalic acid that can be used to prepare an interesting disappearing ink for demonstrating kinetics for introductory chemistry. Discusses laboratory procedures and factors that influence disappearance times. (CW)
Parameter estimation in food science.
Dolan, Kirk D; Mishra, Dharmendra K
2013-01-01
Modeling includes two distinct parts, the forward problem and the inverse problem. The forward problem-computing y(t) given known parameters-has received much attention, especially with the explosion of commercial simulation software. What is rarely made clear is that the forward results can be no better than the accuracy of the parameters. Therefore, the inverse problem-estimation of parameters given measured y(t)-is at least as important as the forward problem. However, in the food science literature there has been little attention paid to the accuracy of parameters. The purpose of this article is to summarize the state of the art of parameter estimation in food science, to review some of the common food science models used for parameter estimation (for microbial inactivation and growth, thermal properties, and kinetics), and to suggest a generic method to standardize parameter estimation, thereby making research results more useful. Scaled sensitivity coefficients are introduced and shown to be important in parameter identifiability. Sequential estimation and optimal experimental design are also reviewed as powerful parameter estimation methods that are beginning to be used in the food science literature.
FIRST ORDER KINETIC GAS GENERATION MODEL PARAMETERS FOR WET LANDFILLS
Landfill gas is produced as a result of a sequence of physical, chemical, and biological processes occurring within an anaerobic landfill. Landfill operators, energy recovery project owners, regulators, and energy users need to be able to project the volume of gas produced and re...
Can Appraisers Rate Work Performance Accurately?
ERIC Educational Resources Information Center
Hedge, Jerry W.; Laue, Frances J.
The ability of individuals to make accurate judgments about others is examined and literature on this subject is reviewed. A wide variety of situational factors affects the appraisal of performance. It is generally accepted that the purpose of the appraisal influences the accuracy of the appraiser. The instrumentation, or tools, available to the…
Accurate pointing of tungsten welding electrodes
NASA Technical Reports Server (NTRS)
Ziegelmeier, P.
1971-01-01
Thoriated-tungsten is pointed accurately and quickly by using sodium nitrite. Point produced is smooth and no effort is necessary to hold the tungsten rod concentric. The chemically produced point can be used several times longer than ground points. This method reduces time and cost of preparing tungsten electrodes.
Laricchia, S; Fabiano, E; Constantin, L A; Della Sala, F
2011-08-01
We present a new class of noninteracting kinetic energy (KE) functionals, derived from the semiclassical-atom theory. These functionals are constructed using the link between exchange and kinetic energies and employ a generalized gradient approximation (GGA) for the enhancement factor, namely, the Perdew-Burke-Ernzerhof (PBE) one. Two of them, named APBEK and revAPBEK, recover in the slowly varying density limit the modified second-order gradient (MGE2) expansion of the KE, which is valid for a neutral atom with a large number of electrons. APBEK contains no empirical parameters, while revAPBEK has one empirical parameter derived from exchange energies, which leads to a higher degree of nonlocality. The other two functionals, APBEKint and revAPBEKint, modify the APBEK and revAPBEK enhancement factors, respectively, to recover the second-order gradient expansion (GE2) of the homogeneous electron gas. We first benchmarked the total KE of atoms/ions and jellium spheres/surfaces: we found that functionals based on the MGE2 are as accurate as the current state-of-the-art KE functionals, containing several empirical parameters. Then, we verified the accuracy of these new functionals in the context of the frozen density embedding (FDE) theory. We benchmarked 20 systems with nonbonded interactions, and we considered embedding errors in the energy and density. We found that all of the PBE-like functionals give accurate and similar embedded densities, but the revAPBEK and revAPBEKint functionals have a significant superior accuracy for the embedded energy, outperforming the current state-of-the-art GGA approaches. While the revAPBEK functional is more accurate than revAPBEKint, APBEKint is better than APBEK. To rationalize this performance, we introduce the reduced-gradient decomposition of the nonadditive kinetic energy, and we discuss how systems with different interactions can be described with the same functional form.
Helbling, Damian E; Hammes, Frederik; Egli, Thomas; Kohler, Hans-Peter E
2014-02-01
The fundamentals of growth-linked biodegradation occurring at low substrate concentrations are poorly understood. Substrate utilization kinetics and microbial growth yields are two critically important process parameters that can be influenced by low substrate concentrations. Standard biodegradation tests aimed at measuring these parameters generally ignore the ubiquitous occurrence of assimilable organic carbon (AOC) in experimental systems which can be present at concentrations exceeding the concentration of the target substrate. The occurrence of AOC effectively makes biodegradation assays conducted at low substrate concentrations mixed-substrate assays, which can have profound effects on observed substrate utilization kinetics