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1

Estimation of yield, maintenance, and product formation kinetic parameters in anaerobic fermentations  

SciTech Connect

In many anaerobic processes, high energy bonds in adenosine triphosphate (ATP) are produced when available electrons are converted from organic substrate into extracellular organic products such as ethanol. The true growth yield and maintenance parameters are directly related to the product formation kinetic parameters for these anaerobic processes. Methods are presented which allow all of the experimental measurements to be used simultaneously to estimate these parameters. Results are presented for several different anaerobic fermentations. 36 references.

Oner, M.D.; Erickson, L.E.; Yang, S.S.

1984-12-01

2

Kinetic parameters from thermogravimetric analysis  

NASA Technical Reports Server (NTRS)

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

Kiefer, Richard L.

1993-01-01

3

Simulating labeling to estimate kinetic parameters for flux control analysis.  

PubMed

An important aspect of kinetic modeling is the ability to provide predictive information on network control and dynamic responses to genetic or environmental perturbations based on innate enzyme kinetics. In a top-down approach to model assembly, unknown kinetic parameters are calculated using experimental data such as metabolite pool concentrations and transient labeling patterns after supply of an isotopically labeled substrate. These kinetic parameters can then be used to calculate flux control coefficients for every reaction in a network, which aids in the identification of enzymatic reactions that exert the most control over the network as a whole. This chapter describes a modeling approach to estimate kinetic parameters which are then used to perform metabolic control analysis. An example is provided for the benzenoid network of Petunia hybrida; however, the methodologies can be applied to any small segment of metabolism. PMID:24222418

Marshall-Colon, Amy; Sengupta, Neelanjan; Rhodes, David; Morgan, John A

2014-01-01

4

Interpretation of microbial bioassays using kinetic parameters.  

PubMed

A method analogous to that used for enzyme kinetics was applied to estimate maximum growth rates and oxygen depletion rates as measures of microbial toxicity. Selected toxicants including phenol, formalin and CuSO4 were tested against an axenic culture of E. coli and a mixed culture derived from soil to determine reproducibility of the test procedures. Optical density was used as a measure of growth over time. Oxygen uptake over a short term (less than 20 min.) and over extended time (greater than 4 hrs.) was also monitored. Microbial growth rate constants (g) and oxygen depletion rate constants (k) were calculated and the EC50 values for toxicity were taken as one half the maximum growth rate or oxygen depletion rates, respectively. The method proved a reasonable and reliable measure of toxicity. PMID:3042851

Anderson, A C; Abdelghani, A A; Tchounwou, P; Monkiedje, A

1988-06-01

5

Parameter Balancing in Kinetic Models of Cell Metabolism†  

PubMed Central

Kinetic modeling of metabolic pathways has become a major field of systems biology. It combines structural information about metabolic pathways with quantitative enzymatic rate laws. Some of the kinetic constants needed for a model could be collected from ever-growing literature and public web resources, but they are often incomplete, incompatible, or simply not available. We address this lack of information by parameter balancing, a method to complete given sets of kinetic constants. Based on Bayesian parameter estimation, it exploits the thermodynamic dependencies among different biochemical quantities to guess realistic model parameters from available kinetic data. Our algorithm accounts for varying measurement conditions in the input data (pH value and temperature). It can process kinetic constants and state-dependent quantities such as metabolite concentrations or chemical potentials, and uses prior distributions and data augmentation to keep the estimated quantities within plausible ranges. An online service and free software for parameter balancing with models provided in SBML format (Systems Biology Markup Language) is accessible at www.semanticsbml.org. We demonstrate its practical use with a small model of the phosphofructokinase reaction and discuss its possible applications and limitations. In the future, parameter balancing could become an important routine step in the kinetic modeling of large metabolic networks.

2010-01-01

6

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

PubMed Central

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

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

2012-01-01

7

Kinetic limit of the ethane and ethylene yield in the gas phase condensation of methane  

SciTech Connect

A kinetic simulation of the initiated oxidative condensation of methane in the gas phase showed that the additional generation of methyl radicals via the reaction CH{sub 4} + O{sub 2} {yields} CH{sub 3} + HO{sub 2} causes a nearly tenfold increase in the C{sub 2} hydrocarbon yield. However, a kinetic limit of the yield exists that is close to that determined in experiments on the catalytic oxidative condensation of methane.

Vedeneev, V.I.; Arutyunov, V.S.; Basevich, V.Ya. [N.N. Semenov Institute of Chemical Physics, Moscow (Russian Federation)

1995-08-01

8

Physical meaning of kinetics parameter “lifetime” used in the new multi-point reactor kinetics equations derived using Green's function  

Microsoft Academic Search

The reactor kinetics parameter l which is used in the new multi-point reactor kinetics equations derived using Green's function is shown to have a physical meaning of neutron production time which can be calculated by the Monte Carlo method, although the corresponding reactor kinetics parameter used in the conventional one-point reactor kinetics equations derived using an adjoint function as a

Keisuke Kobayashi

1996-01-01

9

Breakdown parameter for kinetic modeling of multiscale gas flows  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

10

Determining Kinetic Parameters for Isothermal Crystallization of Glasses  

NASA Technical Reports Server (NTRS)

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.

Ray, C. S.; Zhang, T.; Reis, S. T.; Brow, R. K.

2006-01-01

11

Kinetic parameter estimation from SPECT cone-beam projection measurements.  

PubMed

Kinetic parameters are commonly estimated from dynamically acquired nuclear medicine data by first reconstructing a dynamic sequence of images and subsequently fitting the parameters to time-activity curves generated from regions of interest overlaid upon the image sequence. Biased estimates can result from images reconstructed using inconsistent projections of a time-varying distribution of radiopharmaceutical acquired by a rotating SPECT system. If the SPECT data are acquired using cone-beam collimators wherein the gantry rotates so that the focal point of the collimators always remains in a plane, additional biases can arise from images reconstructed using insufficient, as well as truncated, projection samples. To overcome these problems we have investigated the estimation of kinetic parameters directly from SPECT cone-beam projection data by modelling the data acquisition process. To accomplish this it was necessary to parametrize the spatial and temporal distribution of the radiopharmaceutical within the SPECT field of view. In a simulated chest image volume, kinetic parameters were estimated for simple one-compartment models for four myocardial regions of interest. Myocardial uptake and washout parameters estimated by conventional analysis of noiseless simulated cone-beam data had biases ranging between 3-26% and 0-28%, respectively. Parameters estimated directly from the noiseless projection data were unbiased as expected, since the model used for fitting was faithful to the simulation. Statistical uncertainties of parameter estimates for 10,000,000 events ranged between 0.2-9% for the uptake parameters and between 0.3-6% for the washout parameters. PMID:9572520

Huesman, R H; Reutter, B W; Zeng, G L; Gullberg, G T

1998-04-01

12

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

NASA Astrophysics Data System (ADS)

The space exposure of LDEF for 5.75 years, forming a host target in low earth orbit (LEO) orbit to a wide distribution of hypervelocity particulates of varying dimensions and different impact velocities, has yielded a multiplicity of impact features. Although the projectile parameters are generally unknown and, in fact not identical for any two impacts on a target, the great number of impacts provides statistically meaningful basis for the valid comparison of the response of different targets. Given sufficient impacts for example, a comparison of impact features (even without knowledge of the project parameters) is possible between: (1) differing material types (for the same incident projectile distribution); (2) differing target configurations (e.g., thick and thin targets for the same material projectiles; and (3) different velocities (using LDEF's different faces). A comparison between different materials is presented for infinite targets of aluminum, Teflon, and brass in the same pointing direction; the maximum finite-target penetration (ballistic limit) is also compared to that of the penetration of similar materials comprising of a semi-infinite target. For comparison of impacts on similar materials at different velocities, use is made of the pointing direction relative to LDEF's orbital motion. First, however, care must be exercised to separate the effect of spatial flux anisotropies from those resulting from the spacecraft velocity through a geocentrically referenced dust distribution. Data comprising thick and thin target impacts, impacts on different materials, and in different pointing directions is presented; hypervelocity impact parameters are derived. Results are also shown for flux modeling codes developed to decode the relative fluxes of Earth orbital and unbound interplanetary components intercepting LDEF. Modeling shows the west and space pointing faces are dominated by interplanetary particles and yields a mean velocity of 23.5 km/s at LDEF, corresponding to a V(infinity) Earth approach velocity = 20.9 km/s. Normally resolved average impact velocities on LDEF's cardinal point faces are shown. As 'excess' flux on the east, north, and south faces is observed, compatible with an Earth orbital component below some 5 microns in particle diameter.

McDonnell, J. A. M.

1992-06-01

13

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

NASA Technical Reports Server (NTRS)

The space exposure of LDEF for 5.75 years, forming a host target in low earth orbit (LEO) orbit to a wide distribution of hypervelocity particulates of varying dimensions and different impact velocities, has yielded a multiplicity of impact features. Although the projectile parameters are generally unknown and, in fact not identical for any two impacts on a target, the great number of impacts provides statistically meaningful basis for the valid comparison of the response of different targets. Given sufficient impacts for example, a comparison of impact features (even without knowledge of the project parameters) is possible between: (1) differing material types (for the same incident projectile distribution); (2) differing target configurations (e.g., thick and thin targets for the same material projectiles; and (3) different velocities (using LDEF's different faces). A comparison between different materials is presented for infinite targets of aluminum, Teflon, and brass in the same pointing direction; the maximum finite-target penetration (ballistic limit) is also compared to that of the penetration of similar materials comprising of a semi-infinite target. For comparison of impacts on similar materials at different velocities, use is made of the pointing direction relative to LDEF's orbital motion. First, however, care must be exercised to separate the effect of spatial flux anisotropies from those resulting from the spacecraft velocity through a geocentrically referenced dust distribution. Data comprising thick and thin target impacts, impacts on different materials, and in different pointing directions is presented; hypervelocity impact parameters are derived. Results are also shown for flux modeling codes developed to decode the relative fluxes of Earth orbital and unbound interplanetary components intercepting LDEF. Modeling shows the west and space pointing faces are dominated by interplanetary particles and yields a mean velocity of 23.5 km/s at LDEF, corresponding to a V(infinity) Earth approach velocity = 20.9 km/s. Normally resolved average impact velocities on LDEF's cardinal point faces are shown. As 'excess' flux on the east, north, and south faces is observed, compatible with an Earth orbital component below some 5 microns in particle diameter.

Mcdonnell, J. A. M.

1992-01-01

14

Reconstruction of linear kinetic parameters directly from projection PET data  

NASA Astrophysics Data System (ADS)

Dynamic Positron Emission Tomography (PET) data provide functional information. Usually, this is measured in the form of pharmacokinetic parameters derived from the temporal response of each region. Recent trends have shown that when pharmacokinetic parameters are estimated directly from the projection data, they are less affected by noise. This work investigates an existing parametric maximum likelihood expectation maximization algorithm applied to [18F]DOPA data using reference-tissue input function. The study reveals how direct reconstruction of pharmacokinetic parameters from the measured data can be performed optimally. It explains how to optimize the speed of the standard iterative algorithm and it compares the results with the existing FBP method. The improvement of the quality of the parametric images preserving quantification suggests the usefulness of direct estimation of the kinetic parameters. This algorithm is freely available within the open-source library STIR 2.1.

Angelis, G. I.; Tziortzi, A. C.; Tsoumpas, C.

2011-09-01

15

Kinetics and yields of pesticide biodegradation at low substrate concentrations and under conditions restricting assimilable organic carbon.  

PubMed

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

Helbling, Damian E; Hammes, Frederik; Egli, Thomas; Kohler, Hans-Peter E

2014-02-01

16

Parameter estimation for models of ligninolytic and cellulolytic enzyme kinetics  

SciTech Connect

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

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

2012-01-01

17

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

NASA Astrophysics Data System (ADS)

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

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

1982-09-01

18

A comparison between shaker and bioreactor performance based on the kinetic parameters of xanthan gum production.  

PubMed

Xanthan gum production was studied using sugarcane broth as the raw material and batch fermentation by Xanthomonas campestris pv. campestris NRRL B-1459. The purpose of this study was to optimize the variables of sucrose, yeast extract, and ammonium nitrate concentrations and to determine the kinetic parameters of this bioreaction under optimized conditions. The effects of yeast extract and ammonium nitrate concentrations for a given sucrose concentration (12.1-37.8 g L(-1)) were evaluated by central composite design to maximize the conversion efficiency. In a bioreactor, the maximum conversion efficiency was achieved using 27.0 g L(-1) sucrose, 2.7 g L(-1) yeast extract, and 0.9 g L(-1) NH(4)NO(3). This point was assayed in a shaker and in a bioreactor to compare bioreaction parameters. These parameters were estimated by the unstructured kinetic model of Weiss and Ollis (Biotechnol Bioeng 22:859-873, 1980) to determinate the yields (Y (P/S)), the maximum growth specific rate (mu (max)), and the saturation cellular concentration (X*). The parameters of the model (mu (max), X*, m, lambda, alpha, and beta) were obtained by nonlinear regression. For production of xanthan gum in a shaker, the values of mu (max) and Y (P/S) obtained were 0.119 h(-1) and 0.34 g g(-1), respectively, while in a bioreactor, they were 0.411 h(-1) and 0.63 g g(-1), respectively. PMID:19130306

Faria, S; Vieira, P A; Resende, M M; França, F P; Cardoso, V L

2009-05-01

19

Sintering kinetics and alumina yield in lime-soda sinter process for alumina from coal wastes  

Microsoft Academic Search

An investigation of the application of the lime-soda sinter process to alumina extraction from coal wastes has been carried\\u000a out. In the sintering stage, the optimal operating conditions have been obtained for the highest yield of alumina. The kinetics\\u000a of sodium aluminate formation have also been studied in the sintering stage. The sinter mixes have been fired isothermally\\u000a in air

R. Padilla; H. Y. Sohn

1985-01-01

20

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

SciTech Connect

Acid rain occurs in the midwest. Studies to date have suggested minimal yield response of field corn to acid rain. However, small but significant reductions in yield have been shown for some cultivars under extreme conditions. To define further these yield changes the study examined the effect of simulated acid rain on parameters associated with corn yield. Cultivars B73 x Mo17 and Pioneer 3377 were shielded from ambient rain by two movable rain exclusion shelters. Six simulated rain treatments were applied biweekly within these shelters through the use of a nozzle distribution system. For the most part, growth and yield parameters were unaffected by simulated rain treatment. While the only significant yield reduction was a contrast of pH 3.0 and the average of all other treatments for B73 x Mo17, the reduction appears to be the result both of slightly fewer ears and slightly less successful ear fill.

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

1988-01-01

21

Estimating Biophysical and Biochemical Parameters and Yield of Winter Wheat Based on Landsat TM Images  

Microsoft Academic Search

Contents of crop biophysical and biochemical components influence its yield and seed quality. If farmers can know crop biophysical and biochemical information, they may implement exact field management. This advanced agriculture cultivation method not only increases crop yield and improves seed quality, but also utilizes fertilizer and water more effectively. Therefore, monitoring crop biophysical and biochemical parameters is very important

Yansong Bao; Liangyun Liu; Jihua Wang

2008-01-01

22

The investigation of the degradation mechanism from the kinetic parameters of dehydrochlorinated polyvinyl chloride decomposition  

NASA Astrophysics Data System (ADS)

Kinetic theory in regards to the basic understanding of reaction order as it relates to polymer degradation is discussed. The theory is then tested by determining the kinetic parameters for dehydrochlorinated polyvinyl chloride using thermogravimetric analysis. Four different mechanisms of degradation were deduced from four sets of kinetic parameters. The calculated kinetic parameters were apparent reaction order, apparent activation energy, and apparent frequency factor as determined by the original Freeman and Carroll model. A method for obtaining the optimal heating rate from a set of heating rates is also discussed. The product distributions for polyvinyl chloride, polyethylene, polypropylene, and polystyrene are also discussed. When the product distributions are separated into two divisions (volatile and non-volatile) two different modes of degradation are observed for each polymer. The non-volatile product distribution is characterized by random chain scission kinetics while the volatile product distribution is either controlled by some other kinetic phenomenon, thermodynamically controlled, or a combination of the two.

Jordan, Kelly Joel

23

Impact of kinetic parameters on heat transfer modeling for a pultrusion process  

NASA Astrophysics Data System (ADS)

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.

Gorthala, R.; Roux, J. A.; Vaughan, J. G.; Donti, R. P.; Hassouneh, A.

24

Montelukast photodegradation: Elucidation of ?-order kinetics, determination of quantum yields and application to actinometry.  

PubMed

A recently developed ?-order semi-emperical integrated rate-law for photoreversible AB(2?) reactions has been successfully applied to investigate Montelukast sodium (Monte) photodegradation kinetics in ethanol. The model equations also served to propose a new stepwise kinetic elucidation method valid for any AB(2?) system and its application to the determination of Monte's forward ( [Formula: see text] ) and reverse ( [Formula: see text] ) quantum yields at various irradiation wavelengths. It has been found that [Formula: see text] undergoes a 15-fold increase with wavelength between 220 and 360nm, with the spectral section 250-360nm representing Monte effective photodegradation causative range. The reverse quantum yield values were generally between 12 and 54% lower than those recorded for [Formula: see text] , with the trans-isomer (Monte) converting almost completely to its cis-counterpart at high irradiation wavelengths. Furthermore, the potential use of Monte as an actinometer has been investigated, and an actinometric method was proposed. This study demonstrated the usefulness of Monte for monochromatic light actinometry for the dynamic range 258-380nm. PMID:24835854

Maafi, Mounir; Maafi, Wassila

2014-08-25

25

Relationship between latex yield of Hevea brasiliensis and antecedent environmental parameters  

NASA Astrophysics Data System (ADS)

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

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

2005-01-01

26

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

PubMed

Polyhydroxybutyrate or PHB is a biodegradable and biocompatible thermoplastic with many interesting applications in medicine, food packaging, and tissue engineering materials. The present study deals with the enhanced production of PHB by Azohydromonas australica using sucrose and the estimation of fundamental kinetic parameters of PHB fermentation process. The preliminary culture growth inhibition studies were followed by statistical optimization of medium recipe using response surface methodology to increase the PHB production. Later on batch cultivation in a 7-L bioreactor was attempted using optimum concentration of medium components (process variables) obtained from statistical design to identify the batch growth and product kinetics parameters of PHB fermentation. A. australica exhibited a maximum biomass and PHB concentration of 8.71 and 6.24 g/L, respectively in bioreactor with an overall PHB production rate of 0.75 g/h. Bioreactor cultivation studies demonstrated that the specific biomass and PHB yield on sucrose was 0.37 and 0.29 g/g, respectively. The kinetic parameters obtained in the present investigation would be used in the development of a batch kinetic mathematical model for PHB production which will serve as launching pad for further process optimization studies, e.g., design of several bioreactor cultivation strategies to further enhance the biopolymer production. PMID:22915234

Gahlawat, Geeta; Srivastava, Ashok K

2012-11-01

27

Production of potato minitubers by repeated harvesting: Effects of crop husbandry on yield parameters  

Microsoft Academic Search

Summary  Minitubers can be produced in large quantities by repeated harvesting of tubers from in vitro propagated plantlets at 4, 7\\u000a and 10 weeks after transplanting to the glasshouse at high plant densities. Yield parameters of minitubers can be manipulated\\u000a by crop husbandry.\\u000a \\u000a By supplying nutrients or using a square plant arrangement, minituber yield increased. Effects on numbers of tubers were

W. J. M. Lommen; P. C. Struik

1992-01-01

28

KINETIC PARAMETER ESTIMATION BY STANDARD OPTIMIZATION METHODS IN CATALYTIC CONVERTER MODELING  

Microsoft Academic Search

The application of mathematical models to the prediction of the performance of automotive catalytic converters is gaining increasing interest, both for gasoline and diesel engined-vehicles. This article addresses converter modeling in the transient state under realistic experimental conditions. The model employed in this study relies on Langmuir-Hinshelwood kinetics, and a number of apparent kinetic parameters must be tuned to match

G. PONTIKAKIS; C. PAPADIMITRIOU; A. STAMATELOS

2004-01-01

29

Kinetic simulations of a deuterium-tritium z pinch with >10^16 neutron yield  

NASA Astrophysics Data System (ADS)

Fully kinetic, collisional, and electromagnetic simulations of the time evolution of an imploding z-pinch plasma have been performed as first reported in D. R. Welch, et al. [Phys. Rev. Lett. 103, 255002 (2009)]. Using the implicit particle-in-cell (PIC) code Lsp, multi-dimensional (1-3D) simulations of deuterium and deuterium-tritium z-pinches provide insight into the mechanisms of neutron production. The PIC code allows non-Maxwellian particle distributions, simulates finite mean-free-path effects, performs self-consistent calculations of anomalous resistivity, and permits charge separation. At pinch current I < 7 MA, neutron production is dominated by high energy ions driven by instabilities. The instabilities produce a power-law ion-energy distribution function in the distribution tail. At higher currents, roughly half of the neutrons are thermonuclear in origin and follow a I ^4 neutron yield scaling. High-current, multi-dimension simulations (> 40 MA with > 10^16 neutron yield) suggest that the fraction of thermonuclear neutrons is not sensitive to I, and the strong dependence of neutron yield on current will continue at still higher currents. Scenarios for fusion breakeven and possible ignition will be discussed.

Welch, Dale

2010-11-01

30

Parameter Estimates in Differential Equation Models for Chemical Kinetics  

ERIC Educational Resources Information Center

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

Winkel, Brian

2011-01-01

31

Arabidopsis HOG1 gene and its petunia homolog PETCBP act as key regulators of yield parameters  

Microsoft Academic Search

Plant hormones influence the key parameters that contribute to crop yield, including biomass, branching and seed number. We\\u000a tested manipulation of cytokinin signaling as an avenue for influencing these growth parameters. Here we report a full-length\\u000a cDNA coding for a cytokinin binding protein, Petunia cytokinin binding protein (PETCBP) from Petunia hybrida cv. Mitchell. PETCBP encodes for a protein that exhibits high sequence

Mandar R. Godge; Dhinoth Kumar; Prakash P. Kumar

2008-01-01

32

Bacterial bioluminescence: equilibrium association measurements, quantum yields, reaction kinetics, and overall reaction scheme.  

PubMed

The characteristics of the bioluminescence reactions with bacterial luciferase from two different cell types, Photobacterium fischeri and Beneckea harveyi, are reported. The reduced flavine mononucleotide (FMNH2)-luciferase association constant, directly measured by equilibrium dialysis and gel filtration is the same for both luciferases, 3 times 10(-4) Mminus1 at romm temperature, and is significantly different from the kinetic reciprocal Michaelis-Menten constant. The luciferase bioluminescence quantum yield for the highest activity preparations is the same as for the aldehyde. Rapid stopped-flow observations show that the oxidation of FMNH2 in the presence of sufficient luciferase to outcompete autoxidation, is bimodal. A long-lived intermediate, formed before reaction with aldehyde, has an activation energy for decay of 35 kcal mol-1, much greater than for the light reaction, 14 kcal mol-1. The ratio of bioluminescence quantum yields with respect to aldehyde and FMNH2 is independent of temperature, however, and also of aldehyde chain lenght longer than octanal, pH (6.5-8), and type of luciferase and its specific activity. Even when the aldehyde concentration limits the rate of the light reaction, the quantum yield of the long-lived intermediate is unchanged, and together these data mean that, under the optimal conditions chosen for quantum yield measurements, no dark side reactions effectively compete with the main reaction leading to light emission. A series of reactions involving one-electron steps and the sequential oxidation of two FMNH2 molecules is postulated for the formation of the long-lived intermediate. PMID:807236

Lee, J; Murphy, C L

1975-05-20

33

Engineering topology and kinetics of sucrose metabolism in Saccharomyces cerevisiae for improved ethanol yield.  

PubMed

Sucrose is a major carbon source for industrial bioethanol production by Saccharomyces cerevisiae. In yeasts, two modes of sucrose metabolism occur: (i) extracellular hydrolysis by invertase, followed by uptake and metabolism of glucose and fructose, and (ii) uptake via sucrose-proton symport followed by intracellular hydrolysis and metabolism. Although alternative start codons in the SUC2 gene enable synthesis of extracellular and intracellular invertase isoforms, sucrose hydrolysis in S. cerevisiae predominantly occurs extracellularly. In anaerobic cultures, intracellular hydrolysis theoretically enables a 9% higher ethanol yield than extracellular hydrolysis, due to energy costs of sucrose-proton symport. This prediction was tested by engineering the promoter and 5' coding sequences of SUC2, resulting in predominant (94%) cytosolic localization of invertase. In anaerobic sucrose-limited chemostats, this iSUC2-strain showed an only 4% increased ethanol yield and high residual sucrose concentrations indicated suboptimal sucrose-transport kinetics. To improve sucrose-uptake affinity, it was subjected to 90 generations of laboratory evolution in anaerobic, sucrose-limited chemostat cultivation, resulting in a 20-fold decrease of residual sucrose concentrations and a 10-fold increase of the sucrose-transport capacity. A single-cell isolate showed an 11% higher ethanol yield on sucrose in chemostat cultures than an isogenic SUC2 reference strain, while transcriptome analysis revealed elevated expression of AGT1, encoding a disaccharide-proton symporter, and other maltose-related genes. After deletion of both copies of the duplicated AGT1, growth characteristics reverted to that of the unevolved SUC2 and iSUC2 strains. This study demonstrates that engineering the topology of sucrose metabolism is an attractive strategy to improve ethanol yields in industrial processes. PMID:21963484

Basso, Thiago O; de Kok, Stefan; Dario, Marcelo; do Espirito-Santo, Júlio Cézar A; Müller, Gabriela; Schlölg, Paulo S; Silva, Carlos P; Tonso, Aldo; Daran, Jean-Marc; Gombert, Andreas K; van Maris, Antonius J A; Pronk, Jack T; Stambuk, Boris U

2011-11-01

34

Kinematic and kinetic parameters associated with running in different shoes.  

PubMed Central

The characteristics of the midsole were examined in four pairs of running shoes by a materials test. The variables of interest were the peak acceleration, time to peak acceleration and the kinetic energy absorbed. Ten subjects then ran at a recreational jogging pace (3.5 ms-1) barefoot and in the shoes. An accelerometer secured to the lower tibia was used to measure the peak acceleration and time to peak acceleration associated with footstrike. Subjects were also videoed and a kinematic analysis was undertaken at the knee and ankle joints. The results from the materials test showed that the shoes differed in their midsole characteristics, however, no significant differences (P > 0.05) were observed in the peak acceleration and time to peak acceleration during running in shoes. These variables were significantly greater in the barefoot running condition (P < 0.05), as compared with running in shoes. Small and subtle kinematic differences were observed between the barefoot and shoe conditions. It appears that the differences observed between the shoes in the materials test were not sufficient to elicit the kinematic changes observed between the barefoot and shoe conditions. It is suggested that runners operate within a 'kinetic bandwidth' when responding to impact stresses.

McNair, P J; Marshall, R N

1994-01-01

35

Correlation between yield and biochemical parameters in the mulberry silkworm, Bombyx mori L  

Microsoft Academic Search

A detailed study was carried out on six biochemical parameters and four yield attributes using multiple regression analysis to investigate their relationship in the mulberry silkworm,Bombyx mori. The study generated new information on the importance of digestive amylase activity for the survival of the silkworm and revealed the inability of other enzymes to affect this relationship. Data also substantiate the

S. N. Chatterjee; C. G. P. Rao; G. K. Chatterjee; S. K. Ashwath; A. K. Patnaik

1993-01-01

36

Radiative Corrections to Asymmetry Parameter in the {Omega}{sup -{yields}{Lambda}}+K{sup -} Decay  

SciTech Connect

We compute the radiative corrections, to first order in the fine structure constant {alpha}, to the asymmetry parameter {alpha}{sub {Omega}}of the {Omega}{sup -{yields}{Lambda}}+K{sup -} decay. We use previous results where Sirlin's procedure is used to separate the radiative corrections into two parts, one independent model contribution and a model dependent one.

Queijeiro, A. [Departamento de Fisica, Esc. Sup. de Fisica y Matematicas Instituto Politecnico Nacional, U.P. Adolfo Lopez Mateos, Mexico D.F. 07738 (Mexico)

2010-07-29

37

Determining the Kinetic Parameters Characteristic of Microalgal Growth.  

ERIC Educational Resources Information Center

An activity in which students obtain a growth curve for algae, identify the exponential and linear growth phases, and calculate the parameters which characterize both phases is described. The procedure, a list of required materials, experimental conditions, analytical technique, and a discussion of the interpretations of individual results are…

Martinez Sancho, Maria Eugenie; And Others

1991-01-01

38

Steam pressure disruption of municipal solid waste enhances anaerobic digestion kinetics and biogas yield.  

PubMed

Biomass waste, including municipal solid waste (MSW), contains lignocellulosic-containing fiber components that are not readily available as substrates for anaerobic digestion due to the physical shielding of cellulose imparted by the nondigestible lignin. Consequently, a substantial portion of the potentially available carbon is not converted to methane and the incompletely digested residues from anaerobic digestion generally require additional processing prior to their return to the environment. We investigated and developed steam pressure disruption as a treatment step to render lignocellulosic-rich biomass more digestible and as a means for increasing methane energy recovery. The rapid depressurization after steam heating (240 degrees C, 5 min.) of the nondigested residues following a 30-day primary digestion of MSW caused a visible disruption of fibers and release of soluble organic components. The disrupted material, after reinoculation, provided a rapid burst in methane production at rates double those observed in the initial digestion. This secondary digestion proceeded without a lag phase in gas production, provided approximately 40% additional methane yields, and was accompanied by a approximately 40% increase in volatile solids reduction. The secondary digestate was found to be enriched in lignin and significantly depleted in cellulose and hemi-cellulose components when compared to primary digestate. Thus, steam pressure disruption treatment rendered lignocellulosic substrates readily accessible to anaerobic digestion bacteria and improved both the kinetics of biogas production and the overall methane yield from MSW. Steam pressure disruption is central to a new anaerobic digestion process approach including sequential digestion stages and integrated energy recovery, to improve process yields, provide cogenerated energy for process needs, and to provide effective reuse and recycling of waste biomass materials. PMID:11753918

Liu, H W; Walter, H K; Vogt, G M; Vogt, H S; Holbein, B E

2002-01-20

39

Minimal model assessment of hepatic insulin extraction during an oral test from standard insulin kinetic parameters  

PubMed Central

In this article, a first aim was to develop a minimal modeling approach to noninvasively assess hepatic insulin extraction in 204 healthy subjects studied with a standard meal by coupling the already available meal C-peptide minimal model with a new insulin model. The ingredients of this model are posthepatic IDR, which in turn is described in terms of pancreatic ISR and hepatic insulin extraction HE, and a linear monocompartmental model of insulin kinetics. Even if ISR is provided by the C-peptide minimal model, the simultaneous assessment of HE and insulin kinetics is critical, since compensations may arise between parameters describing these two processes. Therefore, as a second aim of this study, a method was developed to predict standard values of insulin kinetic parameters in an individual on the basis of the individual's anthropometric characteristics. The statistical analysis, based on linear regression of insulin kinetic parameters estimated from IM-IVGTT data performed on the same subjects, demonstrated that insulin kinetic parameters can be accurately predicted from age and body surface area. Once kinetic parameters of the new insulin model were fixed to these values, HE profile and indexes during a meal were reliably estimated in each individual, indicating a significant suppression during the meal since the overall index of HE, equal to 60 ± 1% in the basal state, is reduced to 40 ± 1% during a meal. However, standard parameters provide an approximation of the individual one; thus, the third aim was to define the impact on estimated indexes of using standard instead of individually estimated values. Our results showed that the 25% uncertainty affecting as an average insulin kinetic parameters of an individual, when they are predicted from age and body surface area, translates into a similar relative uncertainty in the individual's hepatic insulin extraction indexes.

Campioni, M.; Toffolo, G.; Basu, R.; Rizza, R. A.

2009-01-01

40

Validity of repeated initial rise thermoluminescence kinetic parameter determinations  

SciTech Connect

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

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

1990-01-01

41

Effect of lactation length adjustment procedures on genetic parameter estimates for buffalo milk yield  

PubMed Central

The objectives of this study were to estimate the genetic parameters for milk yield unadjusted and adjusted for days in milk and, subsequently, to assess the influence of adjusting for days in milk on sire rank. Complete lactations from 90 or 150 days of lactation to 270 or 350 days in milk were considered in these analyses. Milk yield was adjusted for days in milk by multiplicative correction factors, or by including lactation length as a covariable in the model. Milk yields adjusted by different procedures were considered as different traits. Heritability estimates varied from 0.17 to 0.28. Genetic correlation estimates between milk yields unadjusted and adjusted for days in milk were greater than 0.82. Adjusting for days in milk affected the parameter estimates. Multiplicative correction factors produced the highest heritability estimates. More reliable breeding value estimates can be expected by including short length lactation records in the analyses and adjusting the milk yields for days in milk, regardless of the method used for the adjustment. High selection intensity coupled to the inclusion of short length lactations and adjustment with multiplicative factors can change the sire rank..

Baldi, Fernando; Laureano, Monyka Marianna Massolini; Gordo, Daniel Gustavo Mansan; Bignardi, Annaiza Braga; Borquis, Rusbel Raul Aspilcueta; de Albuquerque, Lucia Galvao; Tonhati, Humberto

2011-01-01

42

State-dependent fluorescence yields through the core-valence Coulomb exchange parameter  

NASA Astrophysics Data System (ADS)

Total and partial fluorescence yield (PFY) L-edge x-ray absorption spectra differ from the transmission x-ray absorption spectra (XAS) through state-dependent fluorescence yield across the XAS. For 3d1 to 3d9 in octahedral symmetry we apply simulations of PFY and XAS and show how the atomic 2p3d Coulomb exchange parameter Gpd governs the differences in the L3/(L2+L3) branching ratio between PFY and XAS. Gpd orders the XAS final states following Hund's rules creating a strong state-dependent fluorescence decay strength variation across the XAS leading to the differences between PFY and XAS.

Miedema, Piter S.; Wernet, Philippe; Föhlisch, Alexander

2014-05-01

43

Estimating kinetic and thermodynamic parameters from single molecule enzyme-inhibitor interactions.  

PubMed

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

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

2008-10-21

44

Genetic parameters for milk, fat and protein yields in Murrah buffaloes (Bubalus bubalis Artiodactyla, Bovidae)  

PubMed Central

The objective of the present study was to estimate genetic parameters for test-day milk, fat and protein yields and 305-day-yields in Murrah buffaloes. 4,757 complete lactations of Murrah buffaloes were analyzed. Co-variance components were estimated by the restricted maximum likelihood method. The models included additive direct genetic and permanent environmental effects as random effects, and the fixed effects of contemporary group, milking number and age of the cow at calving as linear and quadratic covariables. Contemporary groups were defined by herd-year-month of test for test-day yields and by herd-year-season of calving for 305-day yields. The heritability estimates obtained by two-trait analysis ranged from 0.15 to 0.24 for milk, 0.16 to 0.23 for protein and 0.13 to 0.22 for fat, yields. Genetic and phenotypic correlations were all positive. The observed population additive genetic variation indicated that selection might be an effective tool in changing population means in milk, fat and protein yields.

2010-01-01

45

Theory of kinetic arrest, elasticity, and yielding in dense binary mixtures of rods and spheres.  

PubMed

We extend the quiescent and stressed versions of naïve mode coupling theory to treat the dynamical arrest, shear modulus, and absolute yielding of particle mixtures where one or more species is a nonrotating nonspherical object. The theory is applied in detail to dense isotropic "chemically matched" mixtures of variable aspect ratio rods and spheres that interact via repulsive and short range attractive site-site pair potentials. A remarkably rich ideal kinetic arrest behavior is predicted with up to eight "dynamical phases" emerging: an ergodic fluid, partially localized states where the spheres remain fluid but the rods can be a gel, repulsive glass or attractive glass, doubly localized glasses and gels, a porous rod gel plus sphere glass, and a narrow window where a type of rod glass and gel localization coexist. Dynamical complexity increases with rod length and the introduction of attractive forces between all species which both enhance gel network formation. Multiple dynamic reentrant features and triple points are predicted, and each dynamic phase has unique particle localization characteristics and mechanical properties. Orders of magnitude variation of the linear shear modulus and absolute yield stress are found as rod length, mixture composition and the detailed nature of interparticle attractions are varied. The interplay of total (high) mixture packing fraction and composition at fixed temperature is also briefly studied. The present work provides a foundation to study more complex rod-sphere mixtures of both biological and synthetic interest that include physical features such as interaction site size asymmetry, rod-sphere specific attractions, and/or Coulomb repulsion. PMID:23367954

Jadrich, Ryan; Schweizer, Kenneth S

2012-12-01

46

Theory of kinetic arrest, elasticity, and yielding in dense binary mixtures of rods and spheres  

NASA Astrophysics Data System (ADS)

We extend the quiescent and stressed versions of naïve mode coupling theory to treat the dynamical arrest, shear modulus, and absolute yielding of particle mixtures where one or more species is a nonrotating nonspherical object. The theory is applied in detail to dense isotropic “chemically matched” mixtures of variable aspect ratio rods and spheres that interact via repulsive and short range attractive site-site pair potentials. A remarkably rich ideal kinetic arrest behavior is predicted with up to eight “dynamical phases” emerging: an ergodic fluid, partially localized states where the spheres remain fluid but the rods can be a gel, repulsive glass or attractive glass, doubly localized glasses and gels, a porous rod gel plus sphere glass, and a narrow window where a type of rod glass and gel localization coexist. Dynamical complexity increases with rod length and the introduction of attractive forces between all species which both enhance gel network formation. Multiple dynamic reentrant features and triple points are predicted, and each dynamic phase has unique particle localization characteristics and mechanical properties. Orders of magnitude variation of the linear shear modulus and absolute yield stress are found as rod length, mixture composition and the detailed nature of interparticle attractions are varied. The interplay of total (high) mixture packing fraction and composition at fixed temperature is also briefly studied. The present work provides a foundation to study more complex rod-sphere mixtures of both biological and synthetic interest that include physical features such as interaction site size asymmetry, rod-sphere specific attractions, and/or Coulomb repulsion.

Jadrich, Ryan; Schweizer, Kenneth S.

2012-12-01

47

Multi-Parameter Yield Zone Model for Predicting Spectrum Crack Growth  

NASA Technical Reports Server (NTRS)

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

Johnson, W. S.

1980-01-01

48

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

NASA Astrophysics Data System (ADS)

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

Minnema, Douglas Martin

49

Solid State Kinetic Parameters and Chemical Mechanism of the Dehydration of CoCl2.6H2O.  

ERIC Educational Resources Information Center

Presents an experimental example illustrating the most common methods for the determination of kinetic parameters. Discusses the different theories and equations to be applied and the mechanism derived from the kinetic results. (CW)

Ribas, Joan; And Others

1988-01-01

50

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

PubMed

The dehydration kinetics of mildronate dihydrate [3-(1,1,1-trimethylhydrazin-1-ium-2-yl)propionate dihydrate] was analyzed in isothermal and nonisothermal modes. The particle size, sample preparation and storage, sample weight, nitrogen flow rate, relative humidity, and sample history were varied in order to evaluate the effect of these factors and to more accurately interpret the data obtained from such analysis. It was determined that comparable kinetic parameters can be obtained in both isothermal and nonisothermal mode. However, dehydration activation energy values obtained in nonisothermal mode showed variation with conversion degree because of different rate-limiting step energy at higher temperature. Moreover, carrying out experiments in this mode required consideration of additional experimental complications. Our study of the different sample and experimental factor effect revealed information about changes of the dehydration rate-limiting step energy, variable contribution from different rate limiting steps, as well as clarified the dehydration mechanism. Procedures for convenient and fast determination of dehydration kinetic parameters were offered. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci. PMID:24729295

B?rzi?š, Agris; Acti?š, Andris

2014-06-01

51

Interstitial insulin kinetic parameters for a 2-compartment insulin model with saturable clearance.  

PubMed

Glucose-insulin system models are commonly used for identifying insulin sensitivity. With physiological, 2-compartment insulin kinetics models, accurate kinetic parameter values are required for reliable estimates of insulin sensitivity. This study uses data from 6 published microdialysis studies to determine the most appropriate parameter values for the transcapillary diffusion rate (n(I)) and cellular insulin clearance rate (n(C)). The 6 studies (12 data sets) used microdialysis techniques to simultaneously obtain interstitial and plasma insulin concentrations. The reported plasma insulin concentrations were used as input and interstitial insulin concentrations were simulated with the interstitial insulin kinetics sub-model. These simulated results were then compared to the reported interstitial measurements and the most appropriate set of parameter values was determined across the 12 data sets by combining the results. Interstitial insulin kinetic parameters values n(I)=n(C)=0.0060 min?¹ were shown to be the most appropriate. These parameter values are associated with an effective, interstitial insulin half-life, t(½)=58 min, within the range of 25-130 min reported by others. PMID:24548900

Pretty, Christopher G; Le Compte, Aaron; Penning, Sophie; Fisk, Liam; Shaw, Geoffrey M; Desaive, Thomas; Chase, J Geoffrey

2014-05-01

52

Determination of kinetic parameters of enzyme-catalyzed reactions with a minimum number of velocity measurements.  

PubMed

Duggleby [Duggleby, R.G., 1979. Experimental designs for estimating kinetic parameters for enzyme-catalyzed reactions. J. Theor. Biol. 81, 672-684] discussed the "design of several replicate measurements of the velocity at as many experimental conditions as there are parameters to be estimated." He discussed the application of this method to A-->products, without and with competitive inhibition, and commented briefly on A+B-->products. The availability of computer applications that can solve large sets of simultaneous equations makes it possible to use this method to calculate kinetic parameters for more complicated enzyme mechanisms. This article is concerned with rapid-equilibrium rate equations, but this method can also be used with steady-state rate equations. Computer programs are provided for the calculation of the three kinetic parameters for ordered A+B-->products from three velocity measurements and for the calculation of the four kinetic parameters for random A+B-->products from four velocity measurements. Computer programs are also provided for competitive inhibition, uncompetitive inhibition, and mixed inhibition of ordered A+B-->products. PMID:18582902

Alberty, Robert A

2008-09-01

53

Determination of adsorption and kinetic parameters for methyl acetate esterification and hydrolysis reaction catalyzed by Amberlyst 15  

Microsoft Academic Search

In this paper, the adsorption equilibrium constants, dispersion coefficients, and kinetic parameters were obtained for the liquid phase reversible reaction of methanol with acetic acid catalyzed by Amberlyst 15. The adsorption and kinetic parameters are determined corresponding to two different mobile phases, methanol and water. Such parameters are required for three different applications of the model reaction: namely, synthesis of

Weifang Yu; K. Hidajat; Ajay K. Ray

2004-01-01

54

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

55

On the influence of the yield parameters identification procedure in cylindrical cups earing prediction  

NASA Astrophysics Data System (ADS)

This work presents a study concerning the deep drawing process of a cylindrical cup, following the process conditions defined on the BENCHMARK 1 - Earing Evolution During Drawing and Ironing Processes, of NUMISHEET 2011 [1]. The deep drawing operation is analyzed for an AA5042 aluminum alloy, which orthotropic behavior is described using the Cazacu and Barlat, 2001 yield criterion [2]. The constitutive parameters were determined based on the experimental data obtained from tensile tests, with different orientations to the rolling direction, disk compression test and the equibiaxial tension test, using DD3MAT in-house code. An analytical approach that relates the earing profile with the ones of both r -values and yield stresses [3,4] is used to understand the influence of the identification procedure on the analytically and numerically predicted earing profile. The numerical simulations of the forming process were performed using DD3IMP in-house code. The analysis shows that, although earing is generally assumed as being coupled to the r -values profile, it is also important that the yield criterion captures the relative differences of the yield stress profile.

Barros, Pedro D.; Simões, Vasco M.; Neto, Diogo M.; Oliveira, Marta C.; Alves, José L.; Menezes, Luís F.

2013-12-01

56

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

PubMed

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

Tan, W K; Tan, G Y

1980-07-01

57

Kinetic parameters of the dissociation of ? during oxidation determined by Mössbauer spectrometry  

NASA Astrophysics Data System (ADS)

Powdered Nd - Fe - B permanent magnets were sieved to different particle sizes and oxidized in an ambient air furnace in the 0953-8984/8/49/056/img2 temperature range for different times. Transmission Mössbauer spectrometry was used to determine the dissociation kinetics of the 0953-8984/8/49/056/img3 phase. The experimental curves were fitted according to the Ginstling - Brounshtein model, taking into account the real distribution of particle size. The kinetic parameters, namely the activation energy 0953-8984/8/49/056/img4 and the diffusivity pre-exponential factor 0953-8984/8/49/056/img5 were determined to be 0953-8984/8/49/056/img6 and 0953-8984/8/49/056/img7 respectively, It appeared that the kinetics parameters could be determined as well by considering a simple theoretical single-particle analysis model. The influence of the particle size was studied in the case of this simple model.

Steyaert, S.; LeBreton, J. M.; Teillet, J.

1996-12-01

58

Estimation of kinetic parameters when modifiers are bound in enzyme-catalyzed reactions.  

PubMed

Modifiers of enzyme-catalyzed reactions can have various types of effects on the velocity, but the most important effect is that they provide multiple pathways to products. The rapid-equilibrium kinetic effects of modifiers are explored for the enzyme-catalyzed reaction A --> products. When a single molecule of modifier X is bound, the mechanism involves three independent equilibrium expressions and two rate constants. But when two molecules of X are bound are bound in two reactions, there are five independent equilibria and three paths to products. The advantages of using a computer to derive rapid-equilibrium rate equations are that more complicated rate equations can be derived and the kinetic parameters can be estimated using the minimum number of velocity measurements. The mechanism with three paths to products is of special interest because the effects of cooperativity can be studied. Thermodynamic cycles can be used to estimate additional kinetic parameters. PMID:20055362

Alberty, Robert A

2010-02-01

59

Variability in kinetic parameter estimates: A review of possible causes and a proposed terminology  

Microsoft Academic Search

The measured kinetics of a bacterial culture degrading a single organic compound as sole carbon source in a batch reactor depend on the history of the culture, the identifiability of the parameters, and the manner in which the experiment to measure them is run. The initial substrate to biomass ratio used in the experiment is particularly important because it influences

C. P. Leslie Grady; Barth F. Smets; Daniel S. Barbeau

1996-01-01

60

The determination of the kinetic parameters of electrochemical reaction in chemical power sources: A critical review  

Microsoft Academic Search

The derivation and proposal of major electrochemical techniques used to determine and calculate the electrochemical kinetic parameters is basically based on the electrochemical reaction taking place at liquid\\/solid or liquid\\/liquid interface in which all the reactants and products are soluble in liquid aqueous solution or liquid mercury electrode, or are volatile gas. Such electrochemical reaction system is classical and traditional

Yanhui Xu; Ying Chen; Jun Wu; Decheng Li; Hua Ju; Junwei Zheng

2010-01-01

61

Trapping parameters and kinetics in Gd 2O 2S: Tb phosphor  

NASA Astrophysics Data System (ADS)

Thermoluminescence (TL) of gadolinium oxysulfide activated with Tb (Gd 2O 2S: Tb) is investigated. The TL spectrum recorded in the temperature range 93 to 500 K with a heating rate of 0.52 K s -1 shows five glow peaks. An analysis of the trapping parameters and order of kinetics for all of the prominent glow peaks has been done.

Chatterjee, S.; Shanker, V.; Ghosh, P. K.

1991-12-01

62

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

Microsoft Academic Search

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

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

2010-01-01

63

Application of an optimization algorithm for estimating intrinsic kinetic parameters of immobilized enzymes  

Microsoft Academic Search

A simple optimization methodology is applied to estimate the intrinsic kinetic parameters for both reversible and irreversible unireactant immobilized enzyme systems that follow the Michaelis-Menten mechanism. The method utilizes a direct-search optimization algorithm along with the numerical solution of the governing differential equations. The usefulness and validity of the method is demonstrated by comparing the predicted values of the intrinsic

Farhad Khorasheh; Azadeh Kheirolomoom; Seyedalireza Mireshghi

2002-01-01

64

Identification of regulatory structure and kinetic parameters of biochemical networks via mixed-integer dynamic optimization  

PubMed Central

Background Recovering the network topology and associated kinetic parameter values from time-series data are central topics in systems biology. Nevertheless, methods that simultaneously do both are few and lack generality. Results Here, we present a rigorous approach for simultaneously estimating the parameters and regulatory topology of biochemical networks from time-series data. The parameter estimation task is formulated as a mixed-integer dynamic optimization problem with: (i) binary variables, used to model the existence of regulatory interactions and kinetic effects of metabolites in the network processes; and (ii) continuous variables, denoting metabolites concentrations and kinetic parameters values. The approach simultaneously optimizes the Akaike criterion, which captures the trade-off between complexity (measured by the number of parameters), and accuracy of the fitting. This simultaneous optimization mitigates a possible overfitting that could result from addition of spurious regulatory interactions. Conclusion The capabilities of our approach were tested in one benchmark problem. Our algorithm is able to identify a set of plausible network topologies with their associated parameters.

2013-01-01

65

Multi-parameter yield zone model for predicting spectrum crack growth  

NASA Technical Reports Server (NTRS)

A phenomenological load interaction model referred to as the Multi-Parameter Yield Zone model is presented which accounts for crack growth retardation caused by previous overloads, acceleration due to current overloads, and underload effects. In the present model, load interaction effects are calculated utilizing a residual stress intensity concept. Crack growth retardation and acceleration are accounted for by decreasing or increasing, respectively, the effective stress ratio used in a modified Forman's (1967) crack growth equation. Results of spectrum crack growth predictions for 2219-T851 aluminum are presented.

Johnson, W. S.

1981-01-01

66

Estimating maize grain yield from crop biophysical parameters using remote sensing  

NASA Astrophysics Data System (ADS)

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

Guindin-Garcia, Noemi

67

Steady state kinetic parameters of bulk V 2O 5 for ethane and propane oxidation reactions  

Microsoft Academic Search

The kinetics of ethane and propane oxidation reactions over bulk V2O5 suggests that the sum of the pre-exponential factors for alkene formation and direct alkane oxidation to CO2 is closely related to the alkane oxidation activity. Furthermore, the activation energy for ethene formation is found to be greater. The alkene yield at iso-conversion is explained in terms of two lumped

T. V. Malleswara Rao; Goutam Deo

2007-01-01

68

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

PubMed

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

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

2007-03-01

69

Variability of kinetic parameters due to biomass acclimation: Case of para-nitrophenol biodegradation  

Microsoft Academic Search

The study regards para-nitrophenol (p-NP) removal by a mixed culture in a batch reactor under aerobic conditions performed at low ratio substrate (p-NP) to p-NP degrading microorganisms (0.09kinetic including Haldane formalism. The purpose was to examine the effect of operating conditions of acclimation phases in the kinetic parameters estimated by

Fériel Rezouga; Moktar Hamdi; Mathieu Sperandio

2009-01-01

70

Kinetic parameters of overall gas-phase reactions for propellants based on ammonium perchlorate and polybutadiene binder  

Microsoft Academic Search

A technique is described for calculating the thermal kinetic parameters of an overall reaction v1A1+v2A2?v3A3+v4P which approximates a multistage kinetic mechanism. The stoichiometric coefficients vi, the rate constant and order of the reaction, and the thermodynamic parameters of the reagents Ai and final reaction product P are obtained at pressures p=10–100 atm using the heat release functions based on kinetic

N. E. Ermolin

1993-01-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

72

Sensitivity of Bayes estimators to hyper-parameters with an application to maximum yield from fisheries.  

PubMed

Priors are seldom unequivocal and an important component of Bayesian modeling is assessment of the sensitivity of the posterior to the specified prior distribution. This is especially true in fisheries science where the Bayesian approach has been promoted as a rigorous method for including existing information from previous surveys and from related stocks or species. These informative priors may be highly contested by various interest groups. Here, formulae for the first and second derivatives of Bayes estimators with respect to hyper-parameters of the joint prior density are given. The formula for the second derivative provides a correction to a previously published result. The formulae are shown to reduce to very convenient and easily implemented forms when the hyper-parameters are for exponential family marginal priors. For model parameters with such priors it is shown that the ratio of posterior variance to prior variance can be interpreted as the sensitivity of the posterior mean to the prior mean. This methodology is applied to a nonlinear state-space model for the biomass of South Atlantic albacore tuna and sensitivity of the maximum sustainable yield to the prior specification is examined. PMID:15180682

Millar, Russell B

2004-06-01

73

Thermoluminescence systems with two or more glow peaks described by anomalous kinetic parameters  

SciTech Connect

The usual first and second order TL kinetic expressions are based on a number of assumptions, including the usually unstated assumption that charges released from one type of trap, giving rise to one glow peak, are not retrapped on other types of traps, associated with other glow peaks. Equations have been developed describing TL systems in which charges released from one type of trap may be retrapped in other types of traps. Called interactive kinetic equations, they are quite simple but have been studied by numerical methods. In particular, glow curves computed from the interactive kinetic equations have been regarded as data and analyzed by fitting them to the usual first and second order kinetic expressions. All of the anomalous features described above are reproduced. For example, usually the computed glow peaks are well fitted by the first and second order expressions over their upper 60 to 80% but not in the wings. This explains why the usual analysis methods, especially those utilizing peak temperature, full width, etc. appear to describe such peaks. Often unrealistic kinetic parameters are often obtained. Furthermore, the computed glow curves often reproduce the observed dependence on dose.

Levy, P.W.

1983-01-01

74

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

PubMed

A methodology for modeling photocatalytic reactors for their application in indoor air pollution control is carried out. The methodology implies, firstly, the determination of intrinsic reaction kinetics for the removal of formaldehyde. This is achieved by means of a simple geometry, continuous reactor operating under kinetic control regime and steady state. The kinetic parameters were estimated from experimental data by means of a nonlinear optimization algorithm. The second step was the application of the obtained kinetic parameters to a very different photoreactor configuration. In this case, the reactor is a corrugated wall type using nanosize TiO(2) as catalyst irradiated by UV lamps that provided a spatially uniform radiation field. The radiative transfer within the reactor was modeled through a superficial emission model for the lamps, the ray tracing method and the computation of view factors. The velocity and concentration fields were evaluated by means of a commercial CFD tool (Fluent 12) where the radiation model was introduced externally. The results of the model were compared experimentally in a corrugated wall, bench scale reactor constructed in the laboratory. The overall pollutant conversion showed good agreement between model predictions and experiments, with a root mean square error less than 4%. PMID:22030272

Passalía, Claudio; Alfano, Orlando M; Brandi, Rodolfo J

2012-04-15

75

Calcium-binding parameter of Bacillus amyloliquefaciens alpha-amylase determined by inactivation kinetics.  

PubMed Central

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.

Tanaka, Atsushi; Hoshino, Eiichi

2002-01-01

76

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

PubMed

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

Robinson, J A; Tiedje, J M

1983-05-01

77

An investigation on the catalytic capacity of dolomite in transesterification and the calculation of kinetic parameters.  

PubMed

The catalytic capacity of dolomite in transesterification was investigated and the kinetic parameters were calculated. The activated dolomites as transesterification catalyst were characterized by X-ray diffraction, nitrogen adsorption and desorption and Hammett indicator method, where the original dolomite was analyzed by thermogravimetric and X-ray fluorescence in advance. Its potential catalytic capacity was validated from aspects of the activated temperature and the reused property, where the reliability of the experimental system was also examined. Then, influences of the catalyst added amount, the mole ratio of methanol to oil, the transesterification temperature and the transesterification time on the catalytic capacity were investigated. Finally, kinetic parameters of the transesterification catalyzed by the activated dolomite were calculated. PMID:24583217

Niu, Sheng-Li; Huo, Meng-Jia; Lu, Chun-Mei; Liu, Meng-Qi; Li, Hui

2014-04-01

78

Errors in evaluation of the kinetic parameters in temperature programmed reduction  

Microsoft Academic Search

The possibility to determine the kinetic parameters for temperature programmed reduction of Cu\\/Fe3O4 using only one TPR profile is analyzed. The same data are analyzed both by Friedman’s iso-conversional method and another\\u000a one previously derived and published by the authors. One shows that taking into account the experimental restrictions of Monti\\u000a and Baiker, the Friedman’s method, although gives values of

G. Munteanu; C. Miclea; E. Segal

2008-01-01

79

Estimating Kinetic Parameter Maps from Dynamic Contrast-Enhanced MRI using Spatial Prior Knowledge  

Microsoft Academic Search

Dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging can be used to study microvascular struc- ture in vivo by monitoring the abundance of an injected dif- fusible contrast agent over time. The resulting spatially resolved intensity-time curves are usually interpreted in terms of kinetic parameters obtained by fitting a pharmacokinetic model to th e observed data. Least squares estimates of the highly

Bernd Michael Kelm; Bjoern H. Menze; Oliver Nix; Christian M. Zechmann; Fred A. Hamprecht

2009-01-01

80

A new multi-wavelength model-based method for determination of enzyme kinetic parameters  

Microsoft Academic Search

Lineweaver-Burk plot analysis is the most widely used method to determine enzyme kinetic parameters. In the spectrophotometric\\u000a determination of enzyme activity using the Lineweaver-Burk plot, it is necessary to find a wavelength at which only the substrate\\u000a or the product has absorbance without any spectroscopic interference of the other reaction components. Moreover, in this method,\\u000a different initial concentrations of the

Mohammad-Hossein Sorouraddin; Kaveh Amini; Abdolhossein Naseri; Javad Vallipour; Jalal Hanaee; Mohammad-Reza Rashidi

2010-01-01

81

A longitudinal, five year survey of urea kinetic parameters in CAPD patients  

Microsoft Academic Search

A longitudinal, five year survey of urea kinetic parameters in CAPD patients. This study reports on the five years' evolution of the KT\\/V urea index and protein catabolic rate (PCR) in 16 CAPD patients who were treated with a constant daily dialysis dose. Total KT\\/V urea index decreased with time from a value of 0.96 ± 0.06 at the start

Norbert H Lameire; Raymond Vanholder; Denise Veyt; Marie-Christine Lambert; Severin Ringoir

1992-01-01

82

The dynamics of local kinetic parameters of glutamate dehydrogenase in rat liver  

Microsoft Academic Search

Kinetic parameters of glutamate dehydrogenase (GDH, EC 1.4.1.2) for glutamate were determined in periportal and pericentral\\u000a zones of adult male and female rat liver lobules under normal fed conditions and after starvation for 24 h. GDH activity was\\u000a measured as formazan production over time against a range of glutamate concentrations in serial cryostat sections using image\\u000a analysis. Captured gray value

Ard Jonker; Willie J. C. Geerts; Rob Charles; Wouter H. Lamers; Cornelis J. F. Van Noorden

1996-01-01

83

The effect of process parameters on kinetics and mechanisms of Co removal by bone char  

Microsoft Academic Search

Bone char powder, composed mainly of poorly crystalline hydroxyapatite (Ca10(PO4)6(OH)2), carbon and CaCO3, has potential applicability in the removal of Co ions from contaminated effluents. In the present study, the influence of process parameters: particle size, agitation speed, initial pH and initial sorbate concentration, onto kinetics and mechanism of Cosorption was studied and discussed. In order to describe and compare

Slavko D. Dimovi?; Ivana D. Smi?iklas; Marija Z. Šljivi?-Ivanovi?; Ilija B. Ple?aš; Latinka Slavkovi?-Beškoski

2011-01-01

84

Kinetic parameters of a material test research reactor fueled with various low enriched uranium dispersion fuels  

Microsoft Academic Search

The effects of using different low enriched uranium fuels, having same uranium density, on the kinetic parameters of a material test research reactor were studied. For this purpose, the original aluminide fuel (UAlx–Al) containing 4.40gU\\/cm3 of an MTR was replaced with silicide (U3Si–Al and U3Si2–Al) and oxide (U3O8–Al) dispersion fuels having the same uranium density as of the original fuel.

Farhan Muhammad; Asad Majid

2009-01-01

85

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

PubMed

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

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

2013-08-01

86

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

PubMed Central

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

2014-01-01

87

Application of lab derived kinetic biodegradation parameters at the field scale  

NASA Astrophysics Data System (ADS)

Estimating the intrinsic remediation potential of an aquifer typically requires the accurate assessment of the biodegradation kinetics, the level of available electron acceptors and the flow field. Zero- and first-order degradation rates derived at the laboratory scale generally overpredict the rate of biodegradation when applied to the field scale, because limited electron acceptor availability and microbial growth are typically not considered. On the other hand, field estimated zero- and first-order rates are often not suitable to forecast plume development because they may be an oversimplification of the processes at the field scale and ignore several key processes, phenomena and characteristics of the aquifer. This study uses the numerical model BIO3D to link the laboratory and field scale by applying laboratory derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at Canadian Forces Base (CFB) Borden. All additional input parameters were derived from laboratory and field measurements or taken from the literature. The simulated results match the experimental results reasonably well without having to calibrate the model. An extensive sensitivity analysis was performed to estimate the influence of the most uncertain input parameters and to define the key controlling factors at the field scale. It is shown that the most uncertain input parameters have only a minor influence on the simulation results. Furthermore it is shown that the flow field, the amount of electron acceptor (oxygen) available and the Monod kinetic parameters have a significant influence on the simulated results. Under the field conditions modelled and the assumptions made for the simulations, it can be concluded that laboratory derived Monod kinetic parameters can adequately describe field scale degradation processes, if all controlling factors are incorporated in the field scale modelling that are not necessarily observed at the lab scale. In this way, there are no scale relationships to be found that link the laboratory and the field scale, accurately incorporating the additional processes, phenomena and characteristics, such as a) advective and dispersive transport of one or more contaminants, b) advective and dispersive transport and availability of electron acceptors, c) mass transfer limitations and d) spatial heterogeneities, at the larger scale and applying well defined lab scale parameters should accurately describe field scale processes.

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

2003-04-01

88

Determination of Kinetic Parameters of Enzyme-Catalyzed Reaction A + B + C -> Products with the Minimum Number of Velocity Measurements  

PubMed Central

Rapid-equilibrium rate equations are derived for the five different mechanisms for the enzymatic catalysis of A + B + C ? products using a computer. These rate equations are used to determine the minimum number of velocities required to estimate the values of the kinetic parameters. The rate equation for the completely ordered mechanism involves four kinetic parameters, and the rate equation for the completely random mechanism involves eight kinetic parameters. Therefore, the four to eight kinetic parameters can be estimated by determining four to eight velocities and solving four to eight simultaneous equations. General recommendations are made as to the choices of triplets of substrate concentrations {[A], [B], [C]} to be used to determine the velocities. The effects of 5% errors in the measured velocities, one at a time, are calculated and are summarized in tables. Calculations of effects of experimental errors are useful in choosing the triplets of substrate concentrations to be used to obtain the most accurate values of the kinetic parameters. When the kinetic parameters for A + B + C ? products are to be determined for the first time, it is recommended that the program for the completely random mechanism be used because it can identify the mechanism and determine the kinetic parameters in one operation.

2009-01-01

89

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

PubMed Central

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

2014-01-01

90

Four-Parameter Hybrid-Bishop-Hill Model Applied to OFE Copper for the Evaluation of Elastic/Yield Limit  

NASA Astrophysics Data System (ADS)

This study employs a novel stress-based Hybrid-Bishop-Hill yield model approach to evaluate the yield surface of oxygen-free electronic copper samples. The local yield surface is determined from three parameters of crystal orientation and one parameter of geometrically necessary dislocation (GND). All four local state variables can be rapidly determined by analysis of measured electron backscatter diffraction patterns. Estimates for the polycrystalline yield surface are obtained by standard averaging procedures. The shape of the yield surface is most influenced by the texture of the material, while the volume of the envelope scales with the average GND density. However, correlations between crystal orientation and GND content modify the yield surface shape and size. While correlations between GND density and crystal orientation are not strong for most copper samples, there are sufficient dependencies to demonstrate the benefits of the detailed four-parameter model. The four-parameter approach has potential for improving estimates of elastic-yield limit in all polycrystalline materials.

Takahashi, Ribeka; Fullwood, David T.; Adams, Brent L.

2014-06-01

91

Enhanced heat stability and kinetic parameters of maize endosperm ADPglucose pyrophosphorylase by alteration of phylogenetically identified amino acids.  

PubMed

ADP-glucose pyrophosphorylase (AGPase) controls the rate-limiting step in starch biosynthesis and is regulated at various levels. Cereal endosperm enzymes, in contrast to other plant AGPases, are particularly heat labile and transgenic studies highlight the importance of temperature for cereal yield. Previously, a phylogenetic approach identified Type II and positively selected amino acid positions in the large subunit of maize endosperm AGPase. Glycogen content, kinetic parameters and heat stability were measured in AGPases having mutations in these sites and interesting differences were observed. This study expands on our earlier evolutionary work by determining how all Type II and positively selected sites affect kinetic constants, heat stability and catalytic rates at increased temperatures. Variants with enhanced properties were identified and combined into one gene, designated Sh2-E. Enhanced properties include: heat stability, enhanced activity at 37 °C, activity at 55 °C, reduced Ka and activity in the absence of activator. The resulting enzyme exhibited all improved properties of the various individual changes. Additionally, Sh2-E was expressed with a small subunit variant with enhanced enzyme properties resulting in an enzyme that has exceptional heat stability, a high catalytic rate at increased temperatures and significantly decreased Km values for both substrates in the absence of the activator. PMID:24378757

Boehlein, Susan K; Shaw, Janine R; Georgelis, Nikolaos; Hannah, L Curtis

2014-02-01

92

Parameter inference for discretely observed stochastic kinetic models using stochastic gradient descent  

PubMed Central

Background Stochastic effects can be important for the behavior of processes involving small population numbers, so the study of stochastic models has become an important topic in the burgeoning field of computational systems biology. However analysis techniques for stochastic models have tended to lag behind their deterministic cousins due to the heavier computational demands of the statistical approaches for fitting the models to experimental data. There is a continuing need for more effective and efficient algorithms. In this article we focus on the parameter inference problem for stochastic kinetic models of biochemical reactions given discrete time-course observations of either some or all of the molecular species. Results We propose an algorithm for inference of kinetic rate parameters based upon maximum likelihood using stochastic gradient descent (SGD). We derive a general formula for the gradient of the likelihood function given discrete time-course observations. The formula applies to any explicit functional form of the kinetic rate laws such as mass-action, Michaelis-Menten, etc. Our algorithm estimates the gradient of the likelihood function by reversible jump Markov chain Monte Carlo sampling (RJMCMC), and then gradient descent method is employed to obtain the maximum likelihood estimation of parameter values. Furthermore, we utilize flux balance analysis and show how to automatically construct reversible jump samplers for arbitrary biochemical reaction models. We provide RJMCMC sampling algorithms for both fully observed and partially observed time-course observation data. Our methods are illustrated with two examples: a birth-death model and an auto-regulatory gene network. We find good agreement of the inferred parameters with the actual parameters in both models. Conclusions The SGD method proposed in the paper presents a general framework of inferring parameters for stochastic kinetic models. The method is computationally efficient and is effective for both partially and fully observed systems. Automatic construction of reversible jump samplers and general formulation of the likelihood gradient function makes our method applicable to a wide range of stochastic models. Furthermore our derivations can be useful for other purposes such as using the gradient information for parametric sensitivity analysis or using the reversible jump samplers for full Bayesian inference. The software implementing the algorithms is publicly available at http://cbcl.ics.uci.edu/sgd

2010-01-01

93

Quantitative structure-activity relationships for kinetic parameters of polycyclic aromatic hydrocarbon biotransformation.  

PubMed

Quantitative structure-activity relationships (QSARs) were developed for three Monod-type parameters--qmax, Ks, and qmax/Ks--that express the kinetics of polycyclic aromatic hydrocarbon (PAH) biotransformation by Sphingomonas paucimobilis strain EPA505. The training sets contained high-quality experimental values of the kinetic parameters for 20 unsubstituted and methylated PAHs as well as values of 41 meaningful molecular descriptors. A genetic function approximation algorithm was used to develop the QSARs. Statistical evaluation of the developed QSARs showed that the relationships are statistically significant and satisfy the assumptions of linear-regression analysis. The Organization for Economic Co-operation and Development principles for (Q)SAR validation were followed to evaluate the developed QSARs, which showed that the QSARs are valid. The QSARs contain spatial, spatial and electronic, topological, and thermodynamic molecular descriptors. Whereas spatial descriptors were essential in explaining biotransformation kinetics, electronic descriptors were not. Mechanistic interpretation of the QSARs resulted in evidence that is consistent with the hypothesis of membrane transport as being the rate-limiting process in PAH biotransformation by strain EPA505. The present study demonstrates the value of QSAR not only as a predictive tool but also as a framework for understanding the mechanisms governing biodegradation at the molecular level. PMID:18366261

Dimitriou-Christidis, Petros; Autenrieth, Robin L; Abraham, Michael H

2008-07-01

94

Influence of introduction devices on crystallisation kinetic parameters in a supercritical antisolvent process  

NASA Astrophysics Data System (ADS)

Supercritical CO2 antisolvent processes developed in this work are based on two different introduction devices: the Concentric Tube Antisolvent Reactor (a capillary centred in a larger tube) and the Impinging Jet Technology (organic solution and supercritical CO2 impinging face to face). Griseofulvin pharmaceutical compound is chosen to test those two processes. The different experimental results indicate the same trends as classical supercritical antisolvent process for the evolution of particle size and particle size distribution with process parameters (mainly concentrations and flow rates). The second and main part is dedicated to the use of these experimental results for deriving modelling evaluation. Concerning this part, it is first shown that, in a first approximation, these processes can be represented by a continuous, mixed suspension and mixed product removal crystallizer. This allows modelling the mass particle size distribution. It also allows giving some numerical data on kinetics parameters (nucleation and growth). Secondly, general kinetic laws are derived for each process. In particular in the case of the impinging jet technology, the energy dissipated in the medium by the flow rates must be included in the crystallisation kinetic law.

Boutin, Olivier

2012-03-01

95

Kinetics of Bacterial Phospholipase C Activity at Micellar Interfaces: Effect of Substrate Aggregate Microstructure and a Model for the Kinetic Parameters  

PubMed Central

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 KS and the interface Michaelis-Menten constant, KM. 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 ?15 RT 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.

Singh, Jasmeet; Ranganathan, Radha; Hajdu, Joseph

2009-01-01

96

Study of the reaction of OH with HNO/sub 3/: kinetics and NO/sub 3/ yield  

SciTech Connect

The kinetics of the reaction OH + HNO/sub 3/ ..-->.. products (k/sub 2/) were investigated at 298 and 251 K. OH was produced by 248-nm laser photolysis of HNO/sub 3/. The temporal profile of N0/sub 3/, a reaction product, was monitored by using long-path laser absorption at 662 nm. The value of k/sub 2/ obtained agrees well with our previous measurements. The yield of NO/sub 3/ in reaction 2 was directly measured to be near unity at both 298 and 251 K.

Ravishankara, A.R.; Eisele, F.L.; Wine, P.H.

1982-05-13

97

Study of kinetic parameters in a mechanistic model for enzymatic hydrolysis of sugarcane bagasse subjected to different pretreatments.  

PubMed

The goal of this work is to evaluate the influence of different pretreatments in the kinetics of enzymatic hydrolysis of sugarcane bagasse and to propose a reliable methodology to easily perform sensitivity analysis and updating kinetic parameters whenever necessary. A kinetic model was modified to represent the experimental data of the batch enzymatic hydrolysis of sugarcane bagasse pretreated with alkaline hydrogen peroxide. The simultaneous estimation of kinetic parameters of the mathematical model was performed using the Pikaia genetic algorithm using batch hydrolysis experimental data obtained with different enzymatic loads. Subsequently, Plackett-Burman designs were used to identify the kinetic parameters with the higher influence on the dynamic behavior of the process variables, which were re-estimated to describe experimental data of the hydrolysis of bagasse pretreated with phosphoric acid + sodium hydroxide. The methodology was accurate and straightforward and can be used whenever there are changes in pretreatment conditions and/or fluctuations in biomass composition in different harvests. PMID:23474967

Neto, João Moreira; Dos Reis Garcia, Daniella; Rueda, Sandra Marcela Gómez; da Costa, Aline Carvalho

2013-11-01

98

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

EPA Science Inventory

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

99

Use of the Covariance Matrix in Directly Fitting Kinetic Parameters: Application to GABAA Receptors  

PubMed Central

A new method of analysis is described that begins to explore the relationship between the phases of ion channel desensitization and the underlying states of the channel. The method, referred to as covariance fitting (CVF), couples Q-matrix calculations with a maximum likelihood algorithm to fit macroscopic desensitization data directly to kinetic models. Unlike conventional sum-of-squares minimization, CVF fits both the magnitude of the recorded current and the strength of the correlations between different time points. When applied to simulated data generated using various kinetic models with up to 11 free parameters, CVF leads to reasonable parameter estimates. Coupled with the likelihood ratio test, it accurately discriminates between models with different numbers of states, discriminates between most models with the same number but a different arrangement of states, and extracts meaningful information on the relationship between the desensitized states and the phases of macroscopic desensitization. When applied to GABAA receptor traces (outside out patches, ?1?2?2S, 1 mM GABA, >2.5 s), a model with two open states and three desensitized states is favored. When applied to simulated data generated using a consensus model, CVF leads to reasonable parameter estimates and accurately discriminates between this and other models.

Celentano, James J.; Hawkes, Alan G.

2004-01-01

100

Prediction of biogas yield and its kinetics in reed canary grass using near infrared reflectance spectroscopy and chemometrics.  

PubMed

A rapid method is needed to assess biogas and methane yield potential of various kinds of substrate prior to anaerobic digestion. This study reports near infrared reflectance spectroscopy (NIRS) as a rapid alternative method to the conventional batch methods for prediction of specific biogas yield (SBY), specific methane yield (SMY) and kinetics of biogas yield (k-SBY) of reed canary grass (RCG) biomass. Dried and powdered RCG biomass with different level of maturity was used for biochemical composition analysis, batch assays and NIRS analysis. Calibration models were developed using partial least square (PLS) regression from NIRS spectra. The calibration models for SBY (R(2)=0.68, RPD=1.83) and k-SBY (R(2)=0.71, RPD=1.75) were better than the model for SMY (R(2)=0.53, RPD=1.49). Although the PLS model for SMY was less successful, the model performance was better compared to the models based on chemical composition. PMID:23941712

Kandel, Tanka P; Gislum, René; Jørgensen, Uffe; Lærke, Poul E

2013-10-01

101

Efficient estimation of dynamic cardiac SPECT kinetic parameters using singular value decomposition reconstruction  

SciTech Connect

Error estimates of time activity curves are necessary to obtain efficient estimates of dynamic of dynamic cardiac SPECT kinetic parameters which are determined using weighted least squares fitting that incorporates these error estimates. In cardiac SPECT, iterative algorithms are used to obtain attenuation corrected reconstructions, and the use of an iterative algorithm makes it difficult to estimate the errors of the estimated reconstruction. An alternate approach is to estimate the reconstruction by solving the system of normal equations using singular value decomposition. This method was applied to dynamic data acquired from a canine study. A canine was injected with 25 mCi of Tc-99m-teboroxime and was imaged using a three-detector SPECT system (Picker PRISM 3000). Sequential 5 sec tomographic acquisitions were acquired for 15 min, allowing both the wash-in and wash-out of teboroxime to be measured. The projection data were reconstructed into 64x64 transaxial slices for each 5 sec acquisition using singular value decomposition to calculate the reconstructed estimate, the variance of the estimate, and the covariance between tissue and blood regions-of-interest. One 4096x4096 singular value decomposition was obtained in 71 hours using a 40 mHz Supper SPARC processor. Tissue and blood time-activity curves were generated from the attenuation corrected transaxial reconstructions. The blood activity curve was generated from a region drawn inside the left ventricle. A two-compartment model was fit to the blood and tissue activity curves to give weighted least squares estimates of blood volume fraction and wash-in and wash-out rate constants specifying teboroxime kinetics for regions of the left ventricular myocardium. As expected the weighted least squares estimates of the kinetic parameters had smaller variances than the unweighted estimates, thus demonstrating more efficient parameter estimation.

Gulberg, G.T.; Huesman, R.H.; Zeng, G.L. [Lawrence Berkeley Lab., CA (United States)]|[Univ. of Utah, Salt Lake City, UT (United States)] [and others

1994-05-01

102

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

NASA Astrophysics Data System (ADS)

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

Zhang, Yang; Wang, Yuan; Jia, Pan

2014-06-01

103

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

NASA Astrophysics Data System (ADS)

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

Zhang, Yang; Wang, Yuan; Jia, Pan

2014-04-01

104

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

Microsoft Academic Search

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

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

2008-01-01

105

Kinetic and spectral parameters of interaction of Citrobacter freundii methionine ?-lyase with amino acids.  

PubMed

Kinetic parameters of Citrobacter freundii methionine ?-lyase were determined with substrates in ?-elimination reactions as well as the inhibition of the enzyme in the ?-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-?- and C-?-protons with deuterium were determined, as well as the kinetic isotope effect of the deuterium label in the C-?-position of inhibitors on the rate of exchange of their ?-protons. Neither stereoselectivity in the ?-proton exchange nor noticeable ?-isotope effect on the exchange rates of ?-protons was found. The ionic and tautomeric composition of the external Schiff base of methionine ?-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. PMID:21166645

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

106

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

107

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

PubMed

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

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

2010-04-01

108

Optimized experimental design for the estimation of enzyme kinetic parameters: an experimental evaluation.  

PubMed

A set of compounds (n = 30), including traditional cytochrome P450 substrates and compounds from AstraZeneca's compound library, was used in an experimental evaluation of an optimal design approach (ODA) for the estimation of enzyme kinetic parameters (CL(int), V(max), and K(m)). A depletion method previously shown to provide reliable results, the multiple depletion curves method (MDCM), was used as reference. Experiments were conducted with human liver microsomes, and samples were analyzed using liquid chromatography-tandem mass spectrometry. CL(int) estimated with the ODA were in >90% of the cases within a 2-fold difference compared with MDCM estimates. In addition, good agreement was generally seen for V(max) and K(m) estimates between the two methods as >80% of the estimates were within or almost within a 2-fold difference. The variability in V(max) and K(m) estimates were generally higher than for CL(int) estimates. In addition, decreased substrate turnover considerably increased the variability in V(max) and K(m) estimates, whereas only a modest increase was observed for CL(int) estimates. The experimental design of using multiple starting concentrations for the estimation of enzyme kinetics was shown to be appropriate even when there was a limitation to the number of samples. The method allowed for good estimates of CL(int) and also for V(max) and K(m) in many cases. Hence, this approach is a good alternative for the estimation of enzyme kinetic parameters, especially if enzyme saturation and an assessment of a potential risk for nonlinear metabolism are of interest. PMID:22942316

Sjögren, Erik; Svanberg, Petter; Kanebratt, Kajsa P

2012-12-01

109

Kinetic and thermodynamic parameters for heat denaturation of human recombinant lactoferrin from rice.  

PubMed

Heat denaturation of recombinant human lactoferrin (rhLf) from rice with 3 different iron-saturation degrees, holo rhLf (iron-saturated), AsIs rhLf (60% iron saturation), and apo rhLf (iron-depleted), was studied. The 3 forms of rhLf were subjected to heat treatment, and the kinetic and thermodynamic parameters of the denaturation process were determined. Thermal denaturation of rhLf was assessed by measuring the loss of reactivity against specific antibodies. D(t) values (time to reduce 90% of immunoreactivity) decreased with increasing temperature of treatment for apo and holo rhLf, those values being higher for the iron-saturated form, which indicates that iron confers thermal stability to rhLf. However, AsIs rhLf showed a different behaviour with an increase in resistance to heat between 79 °C and 84 °C, so that the kinetic parameters could not be calculated. The heat denaturation process for apo and holo rhLf was best described assuming a reaction order of 1.5. The activation energy of the denaturation process was 648.20 kJ/mol for holo rhLf and 406.94 kJ/mol for apo rhLf, confirming that iron-depleted rhLf is more sensitive to heat treatment than iron-saturated rhLf. PMID:22332867

Castillo, Eduardo; Pérez, María Dolores; Franco, Indira; Calvo, Miguel; Sánchez, Lourdes

2012-06-01

110

Dengue in Travelers: Kinetics of Viremia and NS1 Antigenemia and Their Associations with Clinical Parameters  

PubMed Central

Despite the increasing numbers of travel-acquired dengue, few studies have assessed virologic markers of the disease in non-endemic populations. We examined the kinetics of diagnostic markers and their associations with clinical parameters in 93 patients with travel-acquired dengue fever. Kinetics analyses suggested a longer average duration for viremia (9 days, CI95%: 8–10) and non-structural protein 1 (NS1) antigenemia (15 days, CI95%: 12–20) than reported in endemic populations. While none of the tests sufficed alone, the best diagnostic coverage was achieved by combining antibody detection with RNA or NS1 testing. Studied by regression models, early relative levels of viremia and NS1 antigenemia proved to be significantly associated with several clinical parameters: high viremia predicted greater likelihood and increased length of hospitalization, the degree of NS1 antigenemia correlated positively with hematocrit and liver transaminases, and both viremia and NS1 antigenemia levels negatively with platelet counts in follow-up. Levels of viremia and NS1 antigenemia may serve as predictors of the clinical manifestations in travel-acquired dengue.

Huhtamo, Eili; Vapalahti, Olli; Kantele, Anu

2013-01-01

111

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

PubMed Central

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

Kareem, KT; Taiwo, MA

2007-01-01

112

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

113

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

SciTech Connect

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

El-Genk, Mohamed S [University of New Mexico, Albuquerque] [University of New Mexico, Albuquerque; Tournier, Jean-Michel [University of New Mexico, Albuquerque] [University of New Mexico, Albuquerque; Contescu, Cristian I [ORNL] [ORNL

2014-01-01

114

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

SciTech Connect

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

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

1995-05-01

115

Effects of dry plasma releasing process parameters and induced in-plane stress on MEMS devices yield  

NASA Astrophysics Data System (ADS)

An investigation into the effects of dry plasma etching release process parameters, local wafer position and induced inplane stress on the yield of MEMS devices is presented. Several identical wafer quarters, each subjected to different releasing process conditions, are studied. Yield is evaluated by observational measurements of the stiction of MEMS nanocantilevers fabricated alongside with bent beam strain sensors. Results show that lower yield is found for larger processing times as well as higher releasing temperatures. On the other hand, yield improves when thicker nanocantilevers are released using the same processing parameters. The distribution of process-induced in-plane stress of PECVD silicon nitride films is shown to change widely from compressive to tensile based on the local wafer position, whereas no clear correlation between stiction and stress distribution is found. Viability of determining MEMS yield at the wafer-level based on process-induced residual stress is discussed. Other possible root causes of yield in MEMS due to dry plasma release etching are also briefly touched.

Nieva, Patricia M.; Godin, Jeremy R.; Norris, Ryan C.; Najafi Sohi, Ali; Leung, Timothy

2012-02-01

116

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

Microsoft Academic Search

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

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

2009-01-01

117

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

PubMed

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

Willeman; Hanefeld; Straathof; Heijnen

2000-09-01

118

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

PubMed

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

Kareem, K T; Taiwo, M A

2007-01-01

119

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

SciTech Connect

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

Joung, J.J.; Akin, C.

1983-01-01

120

A new multi-wavelength model-based method for determination of enzyme kinetic parameters.  

PubMed

Lineweaver-Burk plot analysis is the most widely used method to determine enzyme kinetic parameters. In the spectrophotometric determination of enzyme activity using the Lineweaver-Burk plot, it is necessary to find a wavelength at which only the substrate or the product has absorbance without any spectroscopic interference of the other reaction components. Moreover, in this method, different initial concentrations of the substrate should be used to obtain the initial velocities required for Lineweaver-Burk plot analysis. In the present work, a multi-wavelength model-based method has been developed and validated to determine Michaelis-Menten constants for some enzyme reactions. In this method, a selective wavelength region and several experiments with different initial concentrations of the substrate are not required. The absorbance data of the kinetic assays are fitted by non-linear regression coupled to the numeric integration of the related differential equation. To indicate the applicability of the proposed method, the Michaelis-Menten constants for the oxidation of phenanthridine, 6-deoxypenciclovir and xanthine by molybdenum hydroxylases were determined using only a single initial concentration of the substrate, regardless of any spectral overlap. PMID:20826949

Sorouraddin, Mohammad-Hossein; Amini, Kaveh; Naseri, Abdolhossein; Vallipour, Javad; Hanaee, Jalal; Rashidi, Mohammad-Reza

2010-09-01

121

Kinetic parameters for thermal decomposition of supramolecular polymers derived from diclofenac-meglumine supramolecular adducts.  

PubMed

Meglumine is an aminocarbohydrate able to form supramolecular adducts with organic acids. The recognition is based on hydrogen bonds and the structures resulting from the complexation have high solubility in water. This property has been exploited by the pharmaceutical industry in the improvement of existing drugs, and the successful example of this approach involves the poorly soluble non-steroidal anti-inflammatory drugs (NSAIDs). Investigation of the thermal behavior of adduct obtained from meglumine and the NSAID diclofenac revealed that a polymer-like material is formed from the self-assembly of diclofenac-meglumine adducts in the melt. This polymer showed a high molecular weight around 2.0×10(5)kDa. The kinetic parameters for the thermal decomposition step of the polymer were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and heating rates of 5, 10, 15 and 20°Cmin(-1), the E(?) and B(?) terms could be determined, and consequently the pre-exponential factor, A(?), as well as the kinetic model, g(?). PMID:22561058

Cassimiro, Douglas L; Ferreira, Leonardo M B; Capela, Jorge M V; Crespi, Marisa S; Ribeiro, Clóvis A

2013-01-25

122

Effect of cell mechanics on instantaneous molecular bond force and measured kinetic parameters  

NASA Astrophysics Data System (ADS)

Receptor-ligand interactions that mediate cellular adhesion are subjected to forces that regulate their dissociation via modulating off-rates. One should be able to determine off-rates from either dissociation force measurements. The correct knowledge of the transient molecular force history is essential for accurate estimation of kinetics parameters through force spectroscopy. Currently, it is assumed that the molecular force is instantaneously equal to the externally applied force. In this work we predict via analytical models and simulation that cell mechanics and hydrodynamics modulates the externally applied force such that the instantaneous bond force is not equivalent. Various mechanical models (solid, elastic, viscoelastic) of cells and microvillus are considered over relevant ranges of loading rates (10^2-10^6 pN/s). Specifically it is demonstrated that microvillus extension and tether formation decrease the pulling force imposed on the adhesive bonds leading to a prolonged bond lifetime. It is demonstrated that modulation of molecular force leads to inaccurate estimation of kinetic off-rate even when the cell and microvillus are modeled as solid materials.

Gupta, Vijay; Eggleton, Charles

2010-03-01

123

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

NASA Astrophysics Data System (ADS)

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

Nagaya, Yasunobu

2014-06-01

124

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

PubMed

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

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

2013-07-01

125

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

PubMed Central

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

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

2013-01-01

126

Hot-air drying characteristics of Aloe vera ( Aloe barbadensis Miller) and influence of temperature on kinetic parameters  

Microsoft Academic Search

The aim of this research was to study and model the kinetics of the hot-air drying of Aloe vera (Aloe barbadensis Miller) and to evaluate the influence of temperature on the kinetic parameters for the proposed models. A convective dryer was used at 50, 60, 70, 80 and 90°C with an air flow of 2.0±0.2m\\/s. The sorption isotherm of the

Antonio Vega; Elsa Uribe; Roberto Lemus; Margarita Miranda

2007-01-01

127

A relative-least-squares technique to determine unique Monod kinetic parameters of BTEX compounds using batch experiments  

Microsoft Academic Search

An analysis of aerobic m-xylene biodegradation kinetics was performed on the results of laboratory batch microcosms. A modified version of the computer model BIO3D was used to determine the Monod kinetic parameters, kmax (maximum utilization rate) and KS (half-utilization constant), as well as the Haldane inhibition concentration, KI, for pristine Borden aquifer material. The proposed method allows for substrate degradation

Mario Schirmer; Barbara J. Butler; James W. Roy; Emil O. Frind; James F. Barker

1999-01-01

128

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

NASA Astrophysics Data System (ADS)

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

Necmeddin Yazici, A.

2003-06-01

129

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

NASA Astrophysics Data System (ADS)

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

Dohare, C.; Mehta, N.

2014-02-01

130

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

NASA Astrophysics Data System (ADS)

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

Khalil, Iftikhar Hussain; At-Ur-Rahman, Hiday; Khan, Imran

2008-01-01

131

Effects of parameters on yield for sub-critical R134a extraction of palm oil  

Microsoft Academic Search

Extraction of palm oil from its palm mesocarp using sub-critical 1,1,1,2-tetrafluoroethane (R134a) as an alternative solvent to supercritical CO2 was studied. The effects of pressure, temperature, flowrate and sample pre-treatment method on extraction yield were examined. Dynamic method was used to determine palm oil solubility at flowrate between 0.5 and 5.0ml\\/min. Extraction was performed at pressures between 45 and 100bar

A. N. Mustapa; Z. A. Manan; C. Y. Mohd Azizi; N. A. Nik Norulaini; A. K. Mohd Omar

2009-01-01

132

Functional imaging of kinetic parameters from the time dependent linear response function by dynamic scintigraphy  

SciTech Connect

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.

Stritzke, P.; Knop, J.; Spielmann, R.P.; Montz, R.; Schneider, C.

1984-01-01

133

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

134

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

NASA Technical Reports Server (NTRS)

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

Ioup, George E.; Ioup, Juliette W.

1991-01-01

135

Genetic parameter estimates for buffalo milk yield, milk quality and mozzarella production and Bayesian inference analysis of their relationships.  

PubMed

Buffalo milk has excellent physical and chemical qualities as a consequence of the high percentage of constituents. This milk property is desirable for the dairy industry because it facilitates manufacture of mozzarella cheese. We estimated genetic parameters for milk yield, milk fat and protein and their effects on mozzarella cheese production using Bayesian inference. Using information from 4907 lactation records of buffaloes, genetic and non-genetic parameters were estimated for accumulated 305-day milk yield (MY), milk fat (%F) and protein (%P) percentages and mozzarella production per lactation (MP). The (co)variance components were obtained by Bayesian inference using a multiple trait model, which included as fixed effects contemporary group, milking number and buffalo age at calving as covariables (linear and quadratic), along with the additive genetic, permanent environmental and residual random effects. Mean a posteriori heritability distributions for MY, %F, %P, and MP were 0.25, 0.30, 0.38, and 0.23, respectively. The genetic correlation estimates between MY with %P and %F were negative and moderate. Positive genetic correlation estimates varying from 0.19 (%P/MP) to 0.95 (MY/MP) were obtained among the traits. Milk yield, milk components, and mozzarella production in Murrah buffaloes have enough genetic variation for selection purposes. We conclude that selection to increase milk yield would be effective in improving mozzarella production. PMID:20799160

Aspilcueta-Borquis, R R; Di Palo, R; Araujo Neto, F R; Baldi, F; de Camargo, G M F; de Albuquerque, L G; Zicarelli, L; Tonhati, H

2010-01-01

136

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

NASA Astrophysics Data System (ADS)

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

Kim, Ki-Bum; Hong, Duk-Geun

2014-10-01

137

Genetic parameters for lean meat yield, meat quality, reproduction and feed efficiency traits for Australian pigs  

Microsoft Academic Search

Genetic parameters were obtained using REML procedures applied to a multiple trait animal model for number born alive (NBA), litter birth weight (LBW), average piglet weight at birth (ABW) recorded in the first, second and third parity (NBA1,2,3, LBW1,2,3, ABW1,2,3) and 21-day litter weight (LW211) for 6050 Large White and Landrace sows. Heritability estimates ranged from 0.06 to 0.22 for

S. Hermesch; B. G. Luxford; H.-U. Graser

2000-01-01

138

Determination of rapid-equilibrium kinetic parameters of ordered and random enzyme-catalyzed reaction A+B=P+Q.  

PubMed

This article deals with the rapid-equilibrium kinetics of the forward and reverse reactions together for the ordered and random enzyme-catalyzed A+B=P+Q and emphasizes the importance of reporting the values of the full set of equilibrium constants. Equilibrium constants that are not in the rate equation can be calculated for random mechanisms using thermodynamic cycles. This treatment is based on the use of a computer to derive rate equations for three mechanisms and to estimate the kinetic parameters with the minimum number of velocity measurements. The most general of these three programs is the one to use first when the mechanism for A+B=P+Q is studied for the first time. This article shows the effects of experimental errors in velocity measurements on the values of the kinetic parameters and on the apparent equilibrium constant calculated using the Haldane relation. PMID:19558174

Alberty, Robert A

2009-07-23

139

Determination of Rapid-Equilibrium Kinetic Parameters of Ordered and Random Enzyme-Catalyzed Reaction A + B = P + Q  

PubMed Central

This article deals with the rapid-equilibrium kinetics of the forward and reverse reactions together for the ordered and random enzyme-catalyzed A + B = P + Q and emphasizes the importance of reporting the values of the full set of equilibrium constants. Equilibrium constants that are not in the rate equation can be calculated for random mechanisms using thermodynamic cycles. This treatment is based on the use of a computer to derive rate equations for three mechanisms and to estimate the kinetic parameters with the minimum number of velocity measurements. The most general of these three programs is the one to use first when the mechanism for A + B = P + Q is studied for the first time. This article shows the effects of experimental errors in velocity measurements on the values of the kinetic parameters and on the apparent equilibrium constant calculated using the Haldane relation.

2009-01-01

140

Phase-transition kinetics with the formation of topological defects in superconductors with a multicomponent order parameter  

Microsoft Academic Search

This paper discusses the kinetics of phase transitions to superconductivity with a multicomponent order parameter in zero\\u000a external field. It is shown that as it approaches equilibrium the superconductor passes through an intermediate vortex-like\\u000a state containing domain walls, single-quantum, and multiquantum axially nonsymmetric vortices and antivortices. The energy\\u000a and other parameters of the domain walls are derived. Rigid superconducting bubbles

A. S. Zel’tser; A. V. Radievskii; A. É. Filippov

1997-01-01

141

Study of kinetic parameters in the RA4 reactor by means of computational modeling and neutron noise measurements  

Microsoft Academic Search

It was carried out a study of the kinetic parameters of the reactor RA-4 (SUR-100 type reactor) by means of a simulation with calculation codes and a measurement with the neutron noise technique. For the simulation the WIMS (cell calculation) and PUMA (3D diffusion code to model a complete reactor) codes were used to estimate the ‘effective delayed neutron fraction’

Guillermo Quinteiro

2001-01-01

142

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

ERIC Educational Resources Information Center

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

Salvador, F.; And Others

1984-01-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2004-01-01

144

Kinetics of immunological parameters in patients with malignant melanoma treated with hyperthermic isolated limb perfusion.  

PubMed

Kinetics of immunological parameters such as natural killer (NK) cell activity and tritium-thymidine uptake rate of T lymphocytes by phytohemagglutinin stimulation were investigated using peripheral leukocyte fractions of melanoma patients treated with hyperthermic isolated limb perfusion (HILP). Also, serum concentrations of soluble intercellular adhesion molecule-1 (sICAM-1) were quantified during and after HILP. It was found that NK cell activity was augmented during HILP, and T lymphocyte function was stimulated 24 h and 1 week after HILP with statistical significance. NK cell activities in the cells isolated from perfused and non-perfused circulations were equally augmented during HILP in two patients examined. Serum concentrations of sICAM-1 in the patients who received HILP also increased 24 h or even 1 week after HILP. The stimulation of these immune competent cells and upregulation of sICAM-1 by HILP were independent of the stages of melanoma patients at the time of HILP or the doses of agents which were used for the infusion during HILP. The origin of cells which shed sICAM-1 into the serum of the patients who received HILP remains to be further investigated. PMID:9186806

Nakayama, J; Nakao, T; Mashino, T; Nagae, S; Hori, Y; Mayumi, H; Tominaga, R; Yasui, H; Matsuda, K; Takahashi, S

1997-05-01

145

Determination of the kinetic parameters of the CALIBAN metallic core reactor from stochastic neutron measurements  

SciTech Connect

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)

Casoli, P.; Authier, N.; Chapelle, A. [Commissariat a l'Energie Atomique et Aux Energies Alternatives, CEA, DAM, F-21120 Is sur Tille (France)

2012-07-01

146

Evaluation of reactor kinetic parameters without the need for perturbation codes.  

SciTech Connect

The analysis of research reactor transients depends on the effective delayed neutron fraction (k{sub eff}), its family-dependent components ({beta}{sub eff,i}), the prompt neutron lifetime (l{sub p}), and the decay constants ({lambda}{sub i}) for each delayed neutron family. Beginning with ENDF/B-V data, methods are presented for accurately calculating these kinetic parameters within the framework of diffusion theory but without the need for a perturbation code. For heavy water systems these methods can be extended to include the delayed photoneutron component of {beta}{sub eff}. However, a separate calculation is needed to estimate the fractional loss of fission product gamma rays, energetic enough to dissociate the deuteron, from leakage, energy degradation and absorption in fuel and structural materials. These methods are illustrated for a light-water Oak Ridge Research Reactor (ORR) LEU core and for a heavy-water Georgia Tech Research Reactor (GTRR) HEU core where calculated and measured values of the prompt neutron decay constant ({beta}{sub eff}/l{sub p}) are compared.

Bretscher, M. M.

1998-01-14

147

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

PubMed Central

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

Lizama, Hector M.; Suzuki, Isamu

1989-01-01

148

Stochasticity in single gene expression with both intrinsic noise and fluctuation in kinetic parameters.  

PubMed

Stochasticity is one of the most important properties in gene expression. Noise originates from two sources: thermal fluctuation inherent in the system (intrinsic noise) and variabilities in factors external to the system that usually result to the fluctuation in the kinetic parameters (extrinsic noise). This paper studies analytically the stationary fluctuation of the number of protein molecules through a mathematical model involving both sources of noises. The results in this paper show that the two sources of noises interlock to each other to generate total fluctuation in protein numbers. In particular, the extrinsic noises effect the total fluctuation in multiple ways, including the extrinsic fluctuation, the correlation with intrinsic noise, the alternation of the time averaging of transcription and translation, and the amplification of the total fluctuation by an impact factor. The impact factor is pronounced when the fluctuations in the degradation rates of mRNA or protein are large. Moreover, the extrinsic noise to the translational rate generates large fluctuation when the translational efficiency is too low, which is contrast to the translational bursting in high translational efficiency because of intrinsic noise. These results suggest that it is important to control the mRNA and protein degradation rate as well as the translational efficiency in order to attenuate the fluctuation in gene expression in the present of both intrinsic and extrinsic noises. PMID:19056400

Lei, Jinzhi

2009-02-21

149

[Comparison of kinematic and kinetic parameters between the locomotion patterns in nordic walking, walking and running].  

PubMed

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. PMID:16544213

Kleindienst, F I; Michel, K J; Schwarz, J; Krabbe, B

2006-03-01

150

EMF signals and ion\\/ligand binding kinetics: prediction of bioeffective waveform parameters  

Microsoft Academic Search

The kinetics of an electromagnetic field (EMF) target pathway are used to estimate frequency windows for EMF bioeffects. Ion\\/ligand binding is characterized via first order kinetics from which a specific electrical impedance can be derived. The resistance\\/capacitance properties of the binding pathway impedance, determined by the kinetics of the rate-determining step, define the frequency range over which the target pathway

A. A Pilla; D. J Muehsam; M. S Markov; B. F Sisken

1999-01-01

151

Kinetics  

NSDL National Science Digital Library

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

Nurrenbern, Susan C.; Robinson, William R.

2008-02-27

152

Nonlinear electrophoretic response yields a unique parameter for separation of biomolecules  

PubMed Central

We demonstrate a unique parameter for biomolecule separation that results from the nonlinear response of long, charged polymers to electrophoretic fields and apply it to extraction and concentration of nucleic acids from samples that perform poorly under conventional methods. Our method is based on superposition of synchronous, time-varying electrophoretic fields, which can generate net drift of charged molecules even when the time-averaged molecule displacement generated by each field individually is zero. Such drift can only occur for molecules, such as DNA, whose motive response to electrophoretic fields is nonlinear. Consequently, we are able to concentrate DNA while rejecting high concentrations of contaminants. We demonstrate one application of this method by extracting DNA from challenging samples originating in the Athabasca oil sands.

Pel, Joel; Broemeling, David; Mai, Laura; Poon, Hau-Ling; Tropini, Giorgia; Warren, Rene L.; Holt, Robert A.; Marziali, Andre

2009-01-01

153

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

PubMed

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

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

2010-07-15

154

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

PubMed

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. PMID:24830629

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

2014-10-15

155

Genetic parameters of total milk yield and factors describing the shape of lactation curve in dairy buffaloes.  

PubMed

The objective of this study was to apply factor analysis to describe lactation curves in dairy buffaloes in order to estimate the phenotypic and genetic association between common latent factors and cumulative milk yield. A total of 31 257 monthly test-day milk yield records from buffaloes belonging to herds located in the state of São Paulo were used to estimate two common latent factors, which were then analysed in a multi-trait animal model for estimating genetic parameters. Estimates of (co)variance components for the two common latent factors and cumulated 270-d milk yield were obtained by Bayesian inference using a multiple trait animal model. Contemporary group, number of milkings per day (two levels) and age of buffalo cow at calving (linear and quadratic) as covariate were included in the model as fixed effects. The additive genetic, permanent environmental and residual effects were included as random effects. The first common latent factor (F1) was associated with persistency of lactation and the second common latent factor (F2) with the level of production in early lactation. Heritability estimates for F1 and F2 were 0·12 and 0·07, respectively. Genetic correlation estimates between F1 and F2 with cumulative milk yield were positive and moderate (0·63 and 0·52). Multivariate statistics employing factor analysis allowed the extraction of two variables (latent factors) that described the shape of the lactation curve. It is expected that the response to selection to increase lactation persistency is higher than the response obtained from selecting animals to increase lactation peak. Selection for higher total milk yield would result in a favourable correlated response to increase the level of production in early lactation and the lactation persistency. PMID:22054225

Aspilcueta-Borquis, Rúsbel R; Baldi, Fernando; Araujo Neto, Francisco R; Albuquerque, Lucia G; Muñoz-Berrocal, Milthon; Tonhati, Humberto

2012-02-01

156

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

PubMed

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

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

2014-01-01

157

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

PubMed Central

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

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

2014-01-01

158

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

USGS Publications Warehouse

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

Palandri, James L.; Kharaka, Yousif K.

2004-01-01

159

Facilitated diffusion of monosaccharides in Saccharomyces cerevisiae: experimental investigation of kinetic parameters without the assumptions of symmetry.  

PubMed

Until the question of symmetry or asymmetry in the facilitated diffusion of monosaccharides by Saccharomyces cerevisiae is resolved, attempts to study the transport process cannot be based on assumptions of symmetry, such as equal concentrations at equilibrium or kinetic parameters that are equal in opposite directions. The assumptions of symmetry may be circumvented by measuring efflux against water and against various external concentrations of sugar. The measurement of efflux against water eliminates any involvement of influx, and the separate determinations of influx and efflux parameters do not require that the parameters be equal. Furthermore, the use of relative internal concentrations eliminates any necessity of assuming that the equilibrium concentrations are equal. Since the influx and efflux parameters are to be compared, the measurement of influx on effluxing cells allows both sets of parameters to be determined on cells which are physiologically the same. This procedure has been tested by obtaining the kinetic parameters of l-sorbose transport. The validity of these parameters was demonstrated by using them to generate theoretical efflux curves that fit the experimental data and by showing that they give the best fit curve to the relationship of velocity and permeant concentration. Although the question of symmetry remains unanswered, this procedure has opened the way for experimental evaluation of the situation and further investigation of the transport process in yeast. PMID:4570600

Kalsow, C M; Doyle, R J

1973-02-01

160

Development and demonstration of an explicit lumped-parameter biofilter model and design equation incorporating monod kinetics.  

PubMed

Biofiltration is an economical air pollution control (APC) technology, particularly suitable for the treatment of air-streams having high flow rates and low concentrations of volatile organic compounds (VOCs). This technology utilizes enzymatic catalysis at ambient conditions to mineralize such pollutants to CO2, H2O, and salts. A pilot-scale study conducted for more than 4 years investigated the development of a new biofiltration technology employing trickle bed air biofilters (TBABs). Following the completion of this experimental study, additional data analysis was performed to develop a simple lumped-parameter biofilter model, assuming first-order kinetics. This model related the observed biofilter performance to the principle independent physical, thermodynamic, and biochemical parameters. The initial model has subsequently been expanded to incorporate Monod kinetics. In this paper, the development and use of the final explicit lumped-parameter biofilter model and design equation, incorporating Monod kinetics, are presented. To facilitate the application of this model, practical procedures are also presented for the determination of VOC solubility, VOC biokinetic Monod parameters, and the maximum practical biofilter inlet VOC concentration. PMID:15143796

Smith, Francis L; Sorial, George A; Suidan, Makram T; Biswas, Pratim; Brenner, Richard C

2002-02-01

161

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

PubMed

Genetic parameters were estimated with restricted maximum likelihood for individual test-day milk, fat, and protein yields and somatic cell scores with a random regression cubic spline model. Test-day records of Holstein cows that calved from 1994 through early 1999 were obtained from Dairy Records Management Systems in Raleigh, North Carolina, for the analysis. Estimates of heritability for individual test-days and estimates of genetic and phenotypic correlations between test-days were obtained from estimates of variances and covariances from the cubic spline analysis. Estimates were calculated of genetic parameters for the averages of the test days within each of the ten 30-day test intervals. The model included herd test-day, age at first calving, and bovine somatropin treatment as fixed factors. Cubic splines were fitted for the overall lactation curve and for random additive genetic and permanent environmental effects, with five predetermined knots or four intervals between days 0, 50, 135, 220, and 305. Estimates of heritability for lactation one ranged from 0.10 to 0.15, 0.06 to 0.10, 0.09 to 0.15, and 0.02 to 0.06 for test-day one to test-day 10 for milk, fat, and protein yields and somatic cell scores, respectively. Estimates of heritability were greater in lactations two and three. Estimates of heritability increased over the course of the lactation. Estimates of genetic and phenotypic correlations were smaller for test-days further apart. PMID:17952867

DeGroot, B J; Keown, J F; Van Vleck, L D; Kachman, S D

2007-01-01

162

Genetic parameters of different measures of cheese yield and milk nutrient recovery from an individual model cheese-manufacturing process.  

PubMed

Cheese yield (CY) is an important technological trait in the dairy industry, and the objective of this study was to estimate the genetic parameters of cheese yield in a dairy cattle population using an individual model-cheese production procedure. A total of 1,167 Brown Swiss cows belonging to 85 herds were sampled once (a maximum of 15 cows were sampled per herd on a single test day, 1 or 2 herds per week). From each cow, 1,500 mL of milk was processed according to the following steps: milk sampling and heating, culture addition, rennet addition, gelation-time recording, curd cutting, whey draining and sampling, wheel formation, pressing, salting in brine, weighing, and cheese sampling. The compositions of individual milk, whey, and curd samples were determined. Three measures of percentage cheese yield (%CY) were calculated: %CY(CURD), %CY(SOLIDS), and %CY(WATER), which represented the ratios between the weight of fresh curd, the total solids of the curd, and the water content of the curd, respectively, and the weight of the milk processed. In addition, 3 measures of daily cheese yield (dCY, kg/d) were defined, considering the daily milk yield. Three measures of nutrient recovery (REC) were computed: REC(FAT), REC(PROTEIN), and REC(SOLIDS), which represented the ratio between the weights of the fat, protein, and total solids in the curd, respectively, and the corresponding nutrient in the milk. Energy recovery, REC(ENERGY), represented the energy content of the cheese versus that in the milk. For statistical analysis, a Bayesian animal model was implemented via Gibbs sampling. The effects of parity (1 to ?4), days in milk (6 classes), and laboratory vat (15 vats) were assigned flat priors; those of herd-test-date, animal, and residual were given Gaussian prior distributions. Intra-herd heritability estimates of %CY(CURD), %CY(SOLIDS), and %CY(WATER) ranged from 0.224 to 0.267; these were larger than the estimates obtained for milk yield (0.182) and milk fat content (0.122), and similar to that for protein content (0.275). Daily cheese yields showed heritability estimates similar to those of daily milk yield. The trait %CY(WATER) showed a highly positive genetic correlation with %CY(SOLIDS) (0.87), whereas their phenotypic correlation was moderate (0.37), and the fat and protein contents of milk showed high genetic correlations with %CY traits. The heritability estimates of REC(PROTEIN) and REC(FAT) were larger (0.490 and 0.208, respectively) than those obtained for the protein and fat contents of milk, and the genetic relationships between REC(PROTEIN) and REC(FAT) with milk protein and fat content were low or moderate; REC(PROTEIN) and REC(FAT) were moderately correlated with the %CY traits and highly correlated with REC(SOLIDS) and REC(ENERGY). Both REC(SOLIDS) and REC(ENERGY) were heritable (0.274 and 0.232), and showed high correlations with each other (0.96) and with the %CY traits (0.83 to 0.97). Together, these findings demonstrate the existence of economically important, genetically determined variability in cheese yield that does not depend solely upon the fat and protein contents of milk, but also relies on the ability of the coagulum to retain the highest possible proportions of the available protein, fat, and water. Exploitation of this interesting genetic variation does not seem to be feasible through direct measurement of the phenotype in cows at the population level. Instead, further research is warranted to examine possible means for indirect prediction, such as through assessing the mid-infrared spectra of milk samples. PMID:24094539

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

2013-12-01

163

Solar Fenton and solar TiO2 catalytic treatment of ofloxacin in secondary treated effluents: evaluation of operational and kinetic parameters.  

PubMed

Two different technical approaches based on advanced oxidation processes (AOPs), solar Fenton homogeneous photocatalysis (hv/Fe(2+)/H(2)O(2)) and heterogeneous photocatalysis with titanium dioxide (TiO(2)) suspensions were studied for the chemical degradation of the fluoroquinolone ofloxacin in secondary treated effluents. A bench-scale solar simulator in combination with an appropriate photochemical batch reactor was used to evaluate and select the optimal oxidation conditions of ofloxacin spiked in secondary treated domestic effluents. The concentration profile of the examined substrate during degradation was determined by UV/Vis spectrophotometry. Mineralization was monitored by measuring the dissolved organic carbon (DOC). The concentrations of Fe(2+) and H(2)O(2) were the key factors for the solar Fenton process, while the most important parameter of the heterogeneous photocatalysis was proved to be the catalyst loading. Kinetic analyses indicated that the photodegradation of ofloxacin can be described by a pseudo-first-order reaction. The rate constant (k) for the solar Fenton process was determined at different Fe(2+) and H(2)O(2) concentrations whereas the Langmuir-Hinshelwood (LH) kinetic expression was used to assess the kinetics of the heterogeneous photocatalytic process. The conversion of ofloxacin depends on several parameters based on the various experimental conditions, which were investigated. A Daphnia magna bioassay was used to evaluate the potential toxicity of the parent compound and its photo-oxidation by-products in different stages of oxidation. In the present study solar Fenton has been demonstrated to be more effective than the solar TiO(2) process, yielding complete degradation of the examined substrate and DOC reduction of about 50% in 30 min of the photocatalytic treatment. PMID:20667580

Michael, I; Hapeshi, E; Michael, C; Fatta-Kassinos, D

2010-10-01

164

Optimization of process parameters by response surface methodology and kinetic modeling for batch production of canthaxanthin by Dietzia maris NIT-D (accession number: HM151403).  

PubMed

Dietzia maris NIT-D, a canthaxanthin producer, was isolated during routine screening of pigment-producing bacteria. Response surface methodology was applied for statistical designing of process parameters for biomass and canthaxanthin production. The effects of four process parameters (considered as independent variables), namely temperature (10-30 °C), pH (4.75-5.75), shaker speed (75-135 rpm) and percentage inoculum (0.5-2.5 %) on the biomass and canthaxanthin yield (considered as dependent variables) were studied. As much as 122 mg L(-1) of canthaxanthin was obtained when Dietzia maris NIT-D was incubated for 120 h at 25 °C and 120 rpm, initial pH and percentage inoculum being 5.5 and 2 % respectively. The pigment yield is the highest reported till date, with Dietzia maris as the test organism. The maximum biomass yield was 7.39 g L(-1) under optimized process parameters. The predicted values were also verified by validation experiments in 5-day fermentation. Different mathematical models were used to describe growth and production, considering the effect of glucose in batch mode. The kinetic constants were calculated by fitting the experimental data to the models. Cell growth was inhibited beyond a glucose concentration of 15 g L(-1). Andrews' model gave the best fit with a R (2) value of 0.9993. During the exponential growth phase, the specific growth rate was found to remain fairly constant with respect to time. There was no inhibitory effect due to intracellular product accumulation for all concentrations of glucose. This observation is the first of its kind, as previous studies have reported that increasing accumulation of intracellular carotenoid exerts greater degree of inhibition on growth. PMID:22451081

Goswami, Gargi; Chakraborty, Samarprit; Chaudhuri, Surabhi; Dutta, Debjani

2012-10-01

165

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

PubMed Central

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

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

2013-01-01

166

The parameters of plasma and the kinetics of generation and loss of active particles in chlorine-nitrogen mixtures  

Microsoft Academic Search

An investigation is performed of the effect of the initial composition of Cl2\\/N2 mixture on the electrophysical and kinetic parameters of plasma of a dc glow discharge. It is found that the dilution of\\u000a chlorine with nitrogen causes a variation of the electron energy distribution function (EEDF), which is accompanied by an\\u000a increase in the average electron energy and in

A. M. Efremov; D. V. Sitanov; V. I. Svettsov

2008-01-01

167

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

Microsoft Academic Search

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

Pavlovitchev

2000-01-01

168

Kinetic parameters of dehydrogenase in the assessment of the response of soil to vermicompost and inorganic fertilisers  

Microsoft Academic Search

Kinetic parameters (V\\u000a max and K\\u000a m) of dehydrogenase activity were determined in order to assess the metabolic response of a soil about 1?year after organic\\u000a and mineral treatments. The soil was planted with maize (Zea mays) and treated with the following fertilisers: organic (vermicompost; VC), mineral (ammonium phosphate and urea), and an organo-mineral\\u000a mixture. V\\u000a max, which represents a

G. Masciandaro; B. Ceccanti; V. Ronchi; C. Bauer

2000-01-01

169

Antioxidative effects of melatonin on kinetics, microscopic and oxidative parameters of cryopreserved bull spermatozoa.  

PubMed

Reactive oxygen species generated during the freeze-thawing process may reduce sperm quality. This study evaluates the effects of melatonin supplementation as an antioxidant in the semen extender on post-thaw parameters of bull spermatozoa. Melatonin was added to the citrate-egg yolk extender to yield six different final concentrations: 0, 0.1, 1, 2, 3 and 4mM. Ejaculates were collected from six proven Holstein bulls. Semen was diluted in the extender packaged in straws, which was frozen with liquid nitrogen. The semen extender supplemented with various doses of melatonin increased (p<0.05) total motility, progressive motility, linearity, sperm track straightness, lateral head displacement, viability, integrity of the sperm membrane and total normal morphology of sperm after the freeze-thawing process. The most effective concentration of melatonin in microscopic evaluations of the bull sperm freezing extender was 2mM. The highest (p<0.05) value of total antioxidant capacity (48.9±2.7) and the lowest value of lipid peroxidation (2.7±0.8) were achieved by inclusion of 3mM concentration of melatonin in the semen extender and the highest activity of catalase (0.7±0.1) was obtained by 2mM melatonin. Four millimolar concentration of melatonin were reduced (p<0.05) the progressive motility and straight linear velocity. In conclusion, supplementation of 2 or 3mM concentration of melatonin in the semen extender improved the quality of post-thawed semen, which may associate with a reduction in lipid peroxidation as well as an increase in the total antioxidant capacity and antioxidant enzyme activity. PMID:23664651

Ashrafi, Iraj; Kohram, Hamid; Ardabili, Farhad Farrokhi

2013-06-01

170

Environmental and Kinetic Parameters for Cr(VI) Bioreduction by a Bacterial Monoculture Purified from Cr(VI)Resistant Consortium  

Microsoft Academic Search

Hexavalent chromium, Cr(VI), is toxic to living systems. Widespread contamination of water and soil by Cr(VI) present a serious\\u000a public health problem. Chromium-resistant bacteria can reduce and detoxify Cr(VI). Twelve bacteria resistant to high concentrations\\u000a of Cr(VI) were isolated from soil enrichment cultures. Environmental parameters and kinetic parameters of Cr(VI) bioreduction\\u000a by one monoculture isolate, identified by 16S rRNA gene

Benedict C. Okeke; Jeffery Laymon; Shakena Crenshaw; Charles Oji

2008-01-01

171

Multiple-trait random regression models for the estimation of genetic parameters for milk, fat, and protein yield in buffaloes.  

PubMed

In this study, genetic parameters for test-day milk, fat, and protein yield were estimated for the first lactation. The data analyzed consisted of 1,433 first lactations of Murrah buffaloes, daughters of 113 sires from 12 herds in the state of São Paulo, Brazil, with calvings from 1985 to 2007. Ten-month classes of lactation days were considered for the test-day yields. The (co)variance components for the 3 traits were estimated using the regression analyses by Bayesian inference applying an animal model by Gibbs sampling. The contemporary groups were defined as herd-year-month of the test day. In the model, the random effects were additive genetic, permanent environment, and residual. The fixed effects were contemporary group and number of milkings (1 or 2), the linear and quadratic effects of the covariable age of the buffalo at calving, as well as the mean lactation curve of the population, which was modeled by orthogonal Legendre polynomials of fourth order. The random effects for the traits studied were modeled by Legendre polynomials of third and fourth order for additive genetic and permanent environment, respectively, the residual variances were modeled considering 4 residual classes. The heritability estimates for the traits were moderate (from 0.21-0.38), with higher estimates in the intermediate lactation phase. The genetic correlation estimates within and among the traits varied from 0.05 to 0.99. The results indicate that the selection for any trait test day will result in an indirect genetic gain for milk, fat, and protein yield in all periods of the lactation curve. The accuracy associated with estimated breeding values obtained using multi-trait random regression was slightly higher (around 8%) compared with single-trait random regression. This difference may be because to the greater amount of information available per animal. PMID:23831097

Borquis, Rusbel Raul Aspilcueta; Neto, Francisco Ribeiro de Araujo; Baldi, Fernando; Hurtado-Lugo, Naudin; de Camargo, Gregório M F; Muñoz-Berrocal, Milthon; Tonhati, Humberto

2013-09-01

172

Identification of quantitative trait loci for resistance to Verticillium wilt and yield parameters in hop (Humulus lupulus L.).  

PubMed

Verticillium wilt (VW) can cause substantial yield loss in hop particularly with the outbreaks of the lethal strain of Verticillium albo-atrum. To elucidate genetic control of VW resistance in hop, an F1 mapping population derived from a cross of cultivar Wye Target, with the predicted genetic basis of resistance, and susceptible male breeding line BL2/1 was developed to assess wilting symptoms and to perform QTL mapping. The genetic linkage map, constructed with 203 markers of various types using a pseudo-testcross strategy, formed ten major linkage groups (LG) of the maternal and paternal maps, covering 552.98 and 441.1 cM, respectively. A significant QTL for VW resistance was detected at LOD 7 on a single chromosomal region on LG03 of both parental maps, accounting for 24.2-26.0 % of the phenotypic variance. QTL analysis for alpha-acid content and yield parameters was also performed on this map. QTLs for these traits were also detected and confirmed our previously detected QTLs in a different pedigree and environment. The work provides the basis for exploration of QTL flanking markers for possible use in marker-assisted selection. PMID:23423654

Jakse, Jernej; Cerenak, Andreja; Radisek, Sebastjan; Satovic, Zlatko; Luthar, Zlata; Javornik, Branka

2013-06-01

173

Kinetic parameters for the elimination reaction catalyzed by triosephosphate isomerase and an estimation of the reaction's physiological significance.  

PubMed

Kinetic parameters for triosephosphate isomerase catalysis of the elimination reaction of an equilibrium mixture of dihydroxyacetone phosphate (DHAP) and D-glyceraldehyde-3-phosphate (DGAP) to form methylglyoxal and phosphate ion are reported for the enzyme from rabbit muscle. Pseudo-first-order rate constants for the disappearance of substrate (kelim) were determined for reactions at [Enzyme] much greater than [Substrate]. The second-order rate constant kEnz = 10.1 M-1 s-1 was determined from a plot of kelim against enzyme concentration. The kinetic parameters, determined from a steady-state kinetic analysis at [Substrate] much greater than [Enzyme], are kcat = 0.011 s-1, Km = 0.76 mM, and kcat/Km = 14 M-1 s-1. The estimated rate-constant ratio for partitioning of the enzyme-bound intermediate between protonation at carbon 2 and elimination, 1,000,000, is much larger than the ratio of 6.5 determined for the reaction of the enediolate phosphate in a loose complex with quinuclidinonium cation, a small buffer catalyst. There is a 10(5)-10(8)-fold decrease in the rate constant for the elimination reaction of the enediolate phosphate when this species binds to triosephosphate isomerase. The kinetic parameters for the elimination reaction catalyzed by the native triosephosphate isomerase and for the reaction catalyzed by a mutant form of the enzyme, which is missing a segment that forms hydrogen bonds with the phosphate group of substrate [Pompliano, D. L., Peyman, A., & Knowles, J. R. (1990) Biochemistry 29, 3186-3194] are similar.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2021650

Richard, J P

1991-05-01

174

Kinetic Parameters for OH Nightglow Modeling Consistent with Recent Laboratory Measurements.  

National Technical Information Service (NTIS)

An improved kinetic model for the Meinel bands of OH has been constructed from rate constants and Einstein A coefficients derived in recent laboratory experiments. Using a semiempirical parameterization of the state-to- state rate constants for OH(v) quen...

S. Adler-Golden

1997-01-01

175

Calibration of Parameters in Beta-Delta HMX Phase Transformation Kinetics Using Computer Simulations.  

National Technical Information Service (NTIS)

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 kin...

A. K. Burnham A. P. Wemhoff

2006-01-01

176

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

Microsoft Academic Search

This dissertation develops a method to allow the determination of the SPR III fast burst reactor's kinetic behavior based on pre-pulse measurements. The purpose is to reduce the vulnerability of pulse operations to human errors, and to improve understanding of the reactor's interactions with experiments. First, the operational history of SPR III over a wide range of experimental conditions was

Douglas Martin Minnema

1999-01-01

177

Dry mechanochemical synthesis of hydroxyapatites from DCPD and CaO: influence of instrumental parameters on the reaction kinetics.  

PubMed

Mechanochemistry is a possible route to synthesize calcium deficient hydroxyapatite (CDHA) with an expected molar calcium-to-phosphate (Ca/P) ratio +/-0.01. To optimize the experimental conditions of CDHA preparation from dicalcium phosphate dihydrate (DCPD) and calcium oxide by dry mechanosynthesis reaction, we performed the kinetic study varying some experimental parameters. This kinetic study was carried out with two different planetary ball mills (Retsch or Fritsch Instuments). Results obtained with the two mills led to the same conclusions although the values of the rate constants of DCPD disappearance and times for complete reaction were very different. Certainly, the origin of these differences was from the mills used, thus we investigated the influence of instrumental parameters such as the mass and the surface area of the balls or the rotation velocity on the mechanochemical reaction kinetics of DCPD with CaO. Results show that the DCPD reaction rate constant and the inverse of the time for complete disappearance of CaO both vary linearly with (i) the square of the rotation velocity, (ii) the square of eccentricity of the vial on the rotating disc and (iii) the product of the mass by the surface area of the balls. These observations comply with theoretical models developed for mechanical alloying. The consideration of these four parameters allows the transposition of experimental conditions from one mill to another or the comparison between results obtained with different planetary ball mills. These instrumental parameters have to be well described in papers concerning mechanochemistry or when grinding is an important stage in a process. PMID:14643588

Mochales, Carolina; El Briak-BenAbdeslam, Hassane; Ginebra, Maria Pau; Terol, Alain; Planell, Josep A; Boudeville, Philippe

2004-01-01

178

Determination of Kinetic Parameters in Laminar Flow Reactors. II. Experimental Aspects  

Microsoft Academic Search

In the present contribution laser spectroscopic studies are described in which the chemical kinetics of benchmark elementary\\u000a reaction steps in different laminar flow reactors were experimentally investigated along with detailed numerical modeling\\u000a calculations (see the article Carraro\\/Heuveline\\/Rannacher [5] in this vol-ume). Coherent anti-Stokes Raman spectroscopy (CARS) was utilized to study the collisional relaxation and vibrational\\u000a energy transfer of vibrationally excited

A. Hanf; H.-R. Volpp; J. Wolfrum

179

Kinetic parameters and mode of action of the cellobiohydrolases produced by Talaromyces emersonii  

Microsoft Academic Search

Three forms of cellobiohydrolase (EC 3.2.1.91), CBH IA, CBH IB and CBH II, were isolated to apparent homogeneity from culture filtrates of the aerobic fungus Talaromyces emersonii. The three enzymes are single sub-unit glycoproteins, and unlike most other fungal cellobiohydrolases are characterised by noteworthy thermostability. The kinetic properties and mode of action of each enzyme against polymeric and small soluble

Maria G Tuohy; Daniel J Walsh; Patrick G Murray; Marc Claeyssens; Michelle M Cuffe; Angela V Savage; Michael P Coughlan

2002-01-01

180

Impact of accurate motion-corrected statistical reconstruction on dynamic PET kinetic parameter estimation  

Microsoft Academic Search

With continuing improvements in spatial resolution of PET scanners, small subject movements become a significant source of resolution degradation. This work assesses the impact of an accurate motion correction (MC) method, modeling the 'motion-induced' interaction of lines-of-response (LORs) inside and outside the field-of-view, on the task of kinetic parametric estimation in high resolution dynamic PET. Following extensive prior phantom and

A. Rahmim; K. Dinelle; J. C. Cheng; G. Topping; H. A. Vajihollahi; D. F. Wong; V. Sossi

2007-01-01

181

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

Microsoft Academic Search

Blue (F 450) and green (F 530) leaf fluorescence were studied together with the red chlorophyll fluorescence (emission maxima F 690 and F 735) during light-induced chlorophyll fluorescence induction kinetics (Kautsky effect) in predarkened leaves of wheat (Triticum aestivum L.) and soybean (Glycine max L.). The intensity of the red chlorophyll fluorescence decreased from maximum fluorescence Fm to steady-state fluorescence

F. Stober; H. K. Lichtenthaler

1993-01-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

183

Uncertainties in Kinetic and Photochemical Parameters of Ozone Depleting Substances and the Impact on Atmospheric Lifetime Calculations  

NASA Astrophysics Data System (ADS)

The SPARC (Stratospheric Processes And their Role in Climate) initiative "Reevaluation of the Lifetimes of Dominant Stratospheric Ozone-Depleting Substances (ODSs)" is aimed toward providing a critical evaluation of atmospheric lifetimes for a number of key compounds. The atmospheric lifetimes of ODSs and greenhouse gases play a key role in the evaluation of ozone loss/recovery and climate change. Therefore, it is critically important to have accurate estimates of lifetimes as well as their uncertainty. The initiative has identified 26 key compounds to be included in this study. The compounds were chosen primarily due to their contribution to ozone depletion, their use as ODS replacements, and their contribution as climate forcing agents. Model calculated atmospheric lifetimes rely on kinetic and photochemical input parameters that are obtained from laboratory studies. Important gas-phase loss processes include reaction with OH, O(1D), and Cl atoms as well as EUV (Lyman-?) and UV photolysis where the relative importance of these processes depends on the properties of the individual compound. As part of the initiative, an evaluation of the model kinetic input parameters and their uncertainties was performed. Here, an assessment of the atmospheric loss processes and associated uncertainties for the target compounds will be presented. Two-dimensional (2D) atmospheric model calculations are used to characterize the globally/annually averaged vertical profiles of the target compounds, loss processes and uncertainties, and their atmospheric lifetimes. The 2D model results are used to highlight the limitations of atmospheric lifetime calculations due to uncertainties in the kinetic and photochemical input parameters, which in some cases are substantial. This component of the initiative also identifies areas where more accurate laboratory studies are needed in order to reduce uncertainties in calculated atmospheric lifetimes for these key species.

Burkholder, J. B.; Kurylo, M. J.; Wallington, T.; Fleming, E. L.; Jackman, C. H.

2011-12-01

184

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

NASA Technical Reports Server (NTRS)

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

Anderson, J. G.; Kaufman, F.

1973-01-01

185

Determinazione dei Parametri Cinetici del Cristallo Termoluminescente CAF2 (TM) (Determination of the Kinetic Parameters of the Thermoluminescent CaF2 (TM) Crystal).  

National Technical Information Service (NTIS)

The kinetic parameters are determined following different procedures, based on the thermoluminescent light emission characteristics curve. The methods include the initial gradient method, the numerical fitting of the glow curve, and the peak shape method....

P. Bernardini C. Bini M. Crisafulli D. Moraldi S. Orlando

1988-01-01

186

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

Microsoft Academic Search

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

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

1991-01-01

187

Analysis of kinetics and trapping parameters of LiF : Mg, Ti thermoluminescent dosimeters by general order model  

NASA Astrophysics Data System (ADS)

Kinetics and trapping parameters of glow peaks 2-5 of LiF : Mg, Ti thermoluminescent dosimeters (TLD-100) were determined by using variable heating rate (VHR), isothermal decay (ID) and initial rise (IR) methods using general-order (GO) kinetics. For peaks 2-5, the order of kinetics was found to be 1.3, 1.15, 1.3 and 1.25, respectively. The mean activation energy ( E) and mean frequency factor ( s) for peaks 2-5 were determined for the three methods to be, respectively, 1.14 eV and 3.2×10 14 s -1 for peak 2; 1.29 eV and 2.5×10 15 s -1 for peak 3; 1.57 eV and 7.0×10 17 s -1 for peak 4; and 1.95 eV and 1.8×10 21 s -1 for peak 5. The results match well with the reported values within the discrepancies usually expected for such studies. The results are presented and discussed.

Sohrabi, M.; Jafarizadeh, M.; Zahedifar, M.

188

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

Microsoft Academic Search

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

D. L. Allara; Robert Shaw

1980-01-01

189

Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile/buffer mobile phases  

SciTech Connect

The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at 25 {+-} 2 C. The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this distribution, the adsorption data were modeled using a tri-Langmuir isotherm equation and the best estimates of the isotherm parameters were determined. The intraparticle mass transfer parameters were derived by comparing the profiles of experimental overloaded bands and the profiles calculated using the isotherm model and the lumped pore diffusion (POR) model of chromatography. These results showed that different adsorption and mass transfer mechanisms exist in mobile phases made of acetonitrile/aqueous buffer and of acetonitrile/acetic acid solutions.

Kim, Hyunjung [University of Tennessee, Knoxville (UTK); Kaczmarski, Krzysztof [University of Tennessee and Rzeszow University of Technology, Poland; Guiochon, Georges A [ORNL

2006-03-01

190

A Kinetic Model for Calcium Dynamics in RAW 264.7 Cells: 1. Mechanisms, Parameters, and Subpopulational Variability  

PubMed Central

Calcium (Ca2+) is an important second messenger and has been the subject of numerous experimental measurements and mechanistic studies in intracellular signaling. Calcium profile can also serve as a useful cellular phenotype. Kinetic models of calcium dynamics provide quantitative insights into the calcium signaling networks. We report here the development of a complex kinetic model for calcium dynamics in RAW 264.7 cells stimulated by the C5a ligand. The model is developed using the vast number of measurements of in vivo calcium dynamics carried out in the Alliance for Cellular Signaling (AfCS) Laboratories. Ligand binding, phospholipase C-? (PLC-?) activation, inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) dynamics, and calcium exchange with mitochondria and extracellular matrix have all been incorporated into the model. The experimental data include data from both native and knockdown cell lines. Subpopulational variability in measurements is addressed by allowing nonkinetic parameters to vary across datasets. The model predicts temporal response of Ca2+ concentration for various doses of C5a under different initial conditions. The optimized parameters for IP3R dynamics are in agreement with the legacy data. Further, the half-maximal effect concentration of C5a and the predicted dose response are comparable to those seen in AfCS measurements. Sensitivity analysis shows that the model is robust to parametric perturbations.

Maurya, Mano Ram; Subramaniam, Shankar

2007-01-01

191

Crystallization kinetics of lithium niobate glass: determination of the Johnson-Mehl-Avrami-Kolmogorov parameters.  

PubMed

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. PMID:23677338

Choi, H W; Kim, Y H; Rim, Y H; Yang, Y S

2013-06-28

192

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

193

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

PubMed Central

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

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

2014-01-01

194

Estimates of genetic parameters for total milk yield over multiple ages in Brazilian Murrah buffaloes using different models.  

PubMed

The objective of this study was to estimate variance components and genetic parameters for accumulated 305-day milk yield (MY305) over multiple ages, from 24 to 120 months of age, applying random regression (RRM), repeatability (REP) and multi-trait (MT) models. A total of 4472 lactation records from 1882 buffaloes of the Murrah breed were utilized. The contemporary group (herd-year-calving season) and number of milkings (two levels) were considered as fixed effects in all models. For REP and RRM, additive genetic, permanent environmental and residual effects were included as random effects. MT considered the same random effects as did REP and RRM with the exception of permanent environmental effect. Residual variances were modeled by a step function with 1, 4, and 6 classes. The heritabilities estimated with RRM increased with age, ranging from 0.19 to 0.34, and were slightly higher than that obtained with the REP model. For the MT model, heritability estimates ranged from 0.20 (37 months of age) to 0.32 (94 months of age). The genetic correlation estimates for MY305 obtained by RRM (L23.res4) and MT models were very similar, and varied from 0.77 to 0.99 and from 0.77 to 0.99, respectively. The rank correlation between breeding values for MY305 at different ages predicted by REP, MT, and RRM were high. It seems that a linear and quadratic Legendre polynomial to model the additive genetic and animal permanent environmental effects, respectively, may be sufficient to explain more parsimoniously the changes in MY305 genetic variation with age. PMID:24782092

Sesana, R C; Baldi, F; Borquis, R R A; Bignardi, A B; Hurtado-Lugo, N A; El Faro, L; Albuquerque, L G; Tonhati, H

2014-01-01

195

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

NASA Astrophysics Data System (ADS)

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

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

196

JOINT ESTIMATION OF STATE VARIABLES AND KINETICS PARAMETERS OF A DENITRIFICATION PROCESS  

Microsoft Academic Search

This work was a contribution to the attempts aiming to solve the problems of estimation in biotechnological processes. These problems are related to the difficulty of on-line measurements of biological variables and to the fact that bioreactors are nonlinear time-varying processes with parameters uncertainties. For overcoming measurement difficulties, we proposed an adaptive estimation algorithm. This estimator is a combination of

KARIM DAHECH; TARAK DAMAK; AHMED TOUMI

197

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

SciTech Connect

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.

Pavlovitchev, A.M.

2000-03-08

198

Dependence of tar, nicotine and carbon monoxide yields on physical parameters: implications for exposure, emissions control and monitoring  

Microsoft Academic Search

Objective: To estimate the extent to which tar, nicotine and carbon monoxide (TNCO) yields are dependent on cigarette design features such as burn rate, filter ventilation and paper porosity, and to consider the implications for human exposure and the regulation of TNCO emissions. A related aim is to determine whether accurate prediction of TNCO yields is possible using only simple

W E Stephens

2007-01-01

199

Mild hydrocracking of bitumen-derived coker and hydrocracker heavy gas oils; Kinetics, product yields, and product properties  

SciTech Connect

The authors describe bitumen-derived coker and hydrocracker heavy gas oils hydrotreated at 350-400{sup 0}C, 7-11 MPa, 0.7-1.5h/sup -1/ LHSV, and 600 S m/sup 3/ of H/sub 2//m/sup 3/ of feed in a pilot-scale trickle-bed reactor, over presulfided commercial NiMo/Al/sub 2/O/sub 3/ catalysts. The conversion of HGO materials (343+ {sup 0}C) in feed to naphtha (195- {sup 0}C) and LGO (195/343 {sup 0}C) was determined by gas chromatographic simulated distillation. The degree of conversion was analyzed with modified first-order kinetics, which incorporate power terms for LHSV and hydrogen partial pressure. The equations were based on three cracking schemes; parallel, consecutive, and combined parallel-consecutive conversion.

Yui, S.M.; Sanford, E.C. (Research Dept., Syncrude Canada Ltd., PO Box 5790, Edmonton, Alberta (CA))

1989-09-01

200

User Manual Parameter Estimation for a Compartmental Tracer Kinetic Model Applied to PET data  

Microsoft Academic Search

Abstract This manual describes the functionality of an application developed with R ?MATLAB’s, graphical interface for the following analyses: † FDG pixel-wise parameter estimation, such as k1 ¡ k6 where { k1 is the transport rate from the blood to the extra-vascular space { k2 is the transport rate back from the extra-vascular space to the blood { k3 is

Guadalupe Ayala; Christina Negoita; Rosemary A. Renaut

201

3 Tesla Dynamic Contrast Enhanced Magnetic Resonance Imaging of the Breast: Pharmacokinetic Parameters versus Conventional Kinetic Curve Analysis  

PubMed Central

Purpose To evaluate the incremental value of pharmacokinetic analysis of dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI) compared to conventional breast MRI (morphology plus kinetic curve type analysis) in characterizing breast lesions as malignant or benign. Patients and Methods The study was approved by our institutional review board. Patients underwent 3D high resolution T1 (3DT1) contrast enhanced MRI and dynamic contrast enhancement (DCE) MRI at 3T, and had pathology proven diagnosis (95%) or more than 2 years follow up confirming lesion stability (5%). Lesions were identified using the high-spatial resolution post-contrast MRI. Morphologic features (margin, enhancement pattern) and conventional DCE-MRI results (kinetic curve types I, II or III) or pharmacokinetic parameters (wash-in rate Ktrans, washout rate Kep, and leakage space volume Ve), were included in multivariate models for prediction of benign versus malignant diagnosis. Results 95 patients with 101 lesions were included: 52% of patients were pre-menopausal and 48% post-menopausal. Sixty eight lesions (67.3%) were malignant and 33 (32.7%) were benign. There was a significant association between Ktrans and Kep and the diagnosis of benign versus malignant (p<0.001). The AUC for morphologic features (lesion margin and enhancement pattern) was 0.85, while inclusion of Ktrans or Kep in the model showed similar modest improvement in performance (AUC, 0.88–0.89). Conclusion The use of kinetic curve type assessment or pharmacokinetic modeling in conjunction with high resolution 3D breast MRI appears to offer similar improvement in diagnostic performance..

El Khouli, Riham H.; Macura, Katarzyna J.; Kamel, Ihab R.; Jacobs, Michael A.; Bluemke, David A.

2012-01-01

202

Effect of soil parameters on the kinetics of the displacement of Fe from FeEDDHA chelates by Cu.  

PubMed

In soil application, o,o-FeEDDHA (iron (3+) ethylene diamine-N,N'-bis(2-hydroxy phenyl acetic acid) complex) is the active ingredient of FeEDDHA chelate-based Fe fertilizers. The effectiveness of o,o-FeEDDHA is potentially compromised by the displacement of Fe from FeEDDHA by Cu. The actual impact of Cu competition is codetermined by the kinetics of the displacement reaction. In this study, the influence of soil parameters on the displacement kinetics has been examined in goethite suspensions. The displacement reaction predominantly takes place on the reactive surface rather than in solution. The rate at which the o,o-FeEDDHA concentration declined depended on the available reactive surface area, the Cu loading, and the FeEDDHA loading. Soil factors reducing FeEDDHA adsorption (high ionic strength, humic acid adsorption onto the goethite surface, and monovalent instead of divalent cations in the electrolyte) decreased the displacement rate. For meso o,o-FeEDDHA, the displacement rate equation was derived, which is first order in FeEDDHA loading and half order in Cu loading. For soil conditions, the equation can be simplified to an exponential decay function in meso o,o-FeEDDHA solution concentration. PMID:22656725

Schenkeveld, Walter D C; Reichwein, Arjen M; Temminghoff, Erwin J M; van Riemsdijk, Willem H

2012-06-28

203

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

NASA Astrophysics Data System (ADS)

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

Hageseth, Gaylord T.

1982-02-01

204

Modeling and Estimation of Kinetic Parameters and Replicative Fitness of HIV-1 from Flow-Cytometry-Based Growth Competition Experiments  

PubMed Central

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

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

2014-01-01

205

Influence of acidic exopolysaccharide of Xanthomonas campestris IBPM 124 on the kinetic parameters of extracellular bacteriolytic enzymes.  

PubMed

Interactions of a negatively charged exopolysaccharide of Xanthomonas campestris IBPM 124 with its extracellular enzymes (muramidase, endopeptidase, and neutral phosphatase) and also with egg lysozyme, lysostaphin, muramidase of Streptomyces globisporus, and a bacteriolytic enzyme complex of Streptomyces albus were studied. All these enzymes were positively charged under the conditions of their maximal activity. It was shown that interaction of the acidic exopolysaccharide from X. campestris with these enzymes changed their kinetic parameters. The change was either positive (increase in reaction rate) or negative (decrease in reaction rate) and depended on the enzyme and type of substrate cleaved. Due to such interactions, the acidic exopolysaccharide secreted by X. campestris into the environment not only retained and transported positively charged exoenzymes into the near-cellular space, but also regulated their activity. PMID:11421816

Stepnaya, O A; Ryazanova, L P; Krupyanko, V I; Kulaev, I S

2001-06-01

206

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

PubMed

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

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

2014-09-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

208

Estimation of transport and degradation parameters for naphthalene and anthracene: influence of mass transfer on kinetics.  

PubMed

The method of temporal moment solutions (MOM) for one-dimensional convective-dispersive solute transport involving linear equilibrium sorption and first-order degradation for time pulse sources has been applied to analyze experimental data from a soil microcosm reactor. Estimation of the pore water velocity V for a nonreactive solute was aided by the use of only the first normalized moment while the dispersion coefficient D, first-order degradation rate constant lambda, and the retardation factor R were estimated using both first and second normalized moments. These transport and degradation parameters were compared to those obtained by a transport model using a nonlinear least square curve-fitting program CXTFIT (version 2.0). Results obtained showed that the MOM fits the breakthrough curve with tailing better than the CXTFIT. The initial estimates of these parameters aided the reduction of the dimensionality of the search process of the non- steady-state model. A residual concentration of 1.12E-5 and 1.48 mg/l for naphthalene and 7.67E-4 and 1.61 mg/l for anthracene, in the axial and radial directions, respectively, suggests the preference of naphthalene during the biodegradation process. The surface concentration as depicted using three-dimensional plots showed that there is occlusion of the aromatics (naphthalene and anthracene) within the soil micropores, thereby limiting their bioavailability and in the long run increasing their toxicity. PMID:19911293

Owabor, Chiedu N; Ogbeide, Samuel E; Susu, Alfred A

2010-10-01

209

Relationship of exo-beta-D-galactofuranosidase kinetic parameters to the number of phosphodiesters in Penicillium fellutanum peptidophosphogalactomannan: enzyme purification and kinetics of glycopeptide and galactofuran chain hydrolysis.  

PubMed

Extracellular Penicillium fellutanum exo-beta-D-galactofuranosidase, with a mass of 70 kDa, was purified to apparent homogeneity. The enzyme was used to investigate the influence of phosphodiesters of the peptidophosphogalactomannans pP(2)GM(ii) and pP(25)GM(ii) (containing 2 and 25 phosphodiester residues, respectively, per mol of polymer) on the kinetic parameters of galactofuranosyl hydrolysis of these two polymers, of 1-O-methyl-beta-D-galactofuranoside, and of two galactofuranooligosaccharides. The enzyme did not hydrolyze phosphorylated galactose residues of pP(2)GM(ii) or pP(25)GM(ii). The k(cat)/K(m) value for pP(25)GM(ii) is 1.7 x 10(3) M(-1) s(-1), that for 1-O-methyl-beta-D-galactofuranoside is 1.1 x 10(4) M(-1) s(-1), that for pP(2)GM(ii) is 1.7 x 10 (4) M(-1) s(-1), and those for 5-O-beta-D-galactofuranooligosaccharides with degrees of polymerization of 3.4 and 5.5 are 1.7 x 10(5) and 4.1 x 10(5) M(-1) s(-1), respectively. Variability in the k(cat)/K(m) values is due primarily to differences in K(m) values; the k(-1)/k(1) ratio likely provides the most influence on K(m). k(cat) increases as the degree of polymerization of galactofuranosyl residues increases. Most of the galactofuranosyl and phosphocholine residues were removed by day 8 in vivo from pP(x)GM(ii) added to day 3 cultures initiated in medium containing 2 mM phosphate but not from those initially containing 20 mM phosphate. The filtrates from day 9 cultures initiated in 2 mM inorganic phosphate in modified Raulin-Thom medium contained 0.2 mM inorganic phosphate and 2.2 U of galactofuranosidase ml(-1)h(-1). No galactofuranosidase activity but 15 mM inorganic phosphate was found in filtrates from day 9 cultures initiated in 20 mM phosphate. In vivo the rate of galactofuranosyl hydrolysis of pP(x)GM(ii) and of related polymers is proportional to the k(cat)/K(m) value of each polymer. The kinetic data show that the k(cat)/K(m) value increases as the number of phosphodiesters of pP(x)GM(ii) decreases, also resulting in an increase in the activity of exo-beta-D-galactofuranosidase. PMID:11571168

Tuekam, B A; Park, Y I; Unkefer, C J; Gander, J E

2001-10-01

210

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

National Technical Information Service (NTIS)

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

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

1991-01-01

211

Degradation of atenolol by UV/peroxymonosulfate: kinetics, effect of operational parameters and mechanism.  

PubMed

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. PMID:24083900

Liu, Xiaowei; Zhang, Tuqiao; Zhou, Yongchao; Fang, Lei; Shao, Yu

2013-11-01

212

Computer-based gait analysis of dogs: evaluation of kinetic and kinematic parameters after cemented and cementless total hip replacement.  

PubMed

To date it is unclear whether cementless total hip replacement (THR) in dogs is of clinical advantage in comparison to cemented THR with regard to lameness improvement. Thus the aim of this study was to compare objectively the development of the gait pattern after cemented and cementless THR in dogs. For this purpose, 18 adult dogs with hip dysplasia underwent computer-based gait analysis on an instrumented treadmill prior to unilateral THR and then again ten days, four weeks and four months after surgery. Analysed kinetic parameters were symmetry indices (SI) of vertical ground reaction forces (GRF), which included peak vertical forces (PFz), mean vertical forces (MFz), vertical impulse (IFz), and vertical ground reaction forces of the arthroplasty limbs only. Analysed kinematic parameters were range-of-motion and the flexion and extension angles of hip, stifle and hock joints. The symmetry indice for PVF, MFz and IFz decreased to a value less than six in both THR groups four months after surgery, which is defined as not lame. Improvement in lameness of the arthroplasty limbs during the examination period of four months was not significantly different between the cemented and cementless groups. The results suggest that within a short-term observation period of four months after surgery, neither cementless nor cemented THR have a greater advantage with regard to lameness improvement. Additional studies with larger pools of subjects and longer time periods for follow-up examinations are necessary to verify these findings. PMID:22828804

Drüen, S; Böddeker, J; Meyer-Lindenberg, A; Fehr, M; Nolte, I; Wefstaedt, P

2012-01-01

213

Balancing yield, kinetics and cost for three external carbon sources used for suspended growth post-denitrification.  

PubMed

Facilities across North America are designing plants to meet stringent limit of technology (LOT) treatment for nitrogen removal. In the Mid-Atlantic region of the United States, this is in response to the Chesapeake Bay Agreement, which limit effluent total nitrogen discharges from wastewater treatment plants to between 3-5 mg/L. Since denitrification is crucial for the removal of nitrogen, maximizing this process step will result in a decrease in nutrient load to the receiving waters. Of particular interest is the use of an alternate external carbon source to replace the most commonly used carbon, methanol. Three external carbon sources were evaluated in this study including: methanol, ethanol and acetate at 13 degrees C. The aim of this study was to evaluate the relative benefits and constraints for using these three carbon types. Laboratory scale Sequencing Batch Reactors (SBRs) were set up to grow and acclimate carbon free biomass to the specified substrate while in-situ Specific Denitrification Rates (SDNRs) were conducted concurrently. The results suggest that the SDNRs for acetate (31.0 + or - 4.6 mgNO(3)-N/gVSS/hr) and ethanol (29.6 + or - 5.6 mgNO(3)-N/gVSS/hr) are higher than that for methanol (10.1 + or - 2.5 mgNO(3)-N/gVSS/hr). The yield coefficients in g COD/g COD were observed to follow a similar trend with values of 0.45 + or - 0.05 for methanol, 0.53 + or - 0.06 for ethanol and 0.66 + or - 0.06 for acetate. PMID:19923753

Mokhayeri, Y; Riffat, R; Murthy, S; Bailey, W; Takacs, I; Bott, C

2009-01-01

214

Genetic parameters for test-day yield of milk, fat and protein in buffaloes estimated by random regression models.  

PubMed

The test-day yields of milk, fat and protein were analysed from 1433 first lactations of buffaloes of the Murrah breed, daughters of 113 sires from 12 herds in the state of São Paulo, Brazil, born between 1985 and 2007. For the test-day yields, 10 monthly classes of lactation days were considered. The contemporary groups were defined as the herd-year-month of the test day. Random additive genetic, permanent environmental and residual effects were included in the model. The fixed effects considered were the contemporary group, number of milkings (1 or 2 milkings), linear and quadratic effects of the covariable cow age at calving and the mean lactation curve of the population (modelled by third-order Legendre orthogonal polynomials). The random additive genetic and permanent environmental effects were estimated by means of regression on third- to sixth-order Legendre orthogonal polynomials. The residual variances were modelled with a homogenous structure and various heterogeneous classes. According to the likelihood-ratio test, the best model for milk and fat production was that with four residual variance classes, while a third-order Legendre polynomial was best for the additive genetic effect for milk and fat yield, a fourth-order polynomial was best for the permanent environmental effect for milk production and a fifth-order polynomial was best for fat production. For protein yield, the best model was that with three residual variance classes and third- and fourth-order Legendre polynomials were best for the additive genetic and permanent environmental effects, respectively. The heritability estimates for the characteristics analysed were moderate, varying from 0·16±0·05 to 0·29±0·05 for milk yield, 0·20±0·05 to 0·30±0·08 for fat yield and 0·18±0·06 to 0·27±0·08 for protein yield. The estimates of the genetic correlations between the tests varied from 0·18±0·120 to 0·99±0·002; from 0·44±0·080 to 0·99±0·004; and from 0·41±0·080 to 0·99±0·004, for milk, fat and protein production, respectively, indicating that whatever the selection criterion used, indirect genetic gains can be expected throughout the lactation curve. PMID:22444071

Aspilcueta-Borquis, Rúsbel R; Araujo Neto, Francisco R; Baldi, Fernando; Santos, Daniel J A; Albuquerque, Lucia G; Tonhati, Humberto

2012-08-01

215

Determination of creatine kinase kinetic parameters in rat brain by NMR magnetization transfer. Correlation with brain function.  

PubMed

The pseudo first-order rate constant kf of the creatine kinase (CK) forward reaction as well as the CK forward flux FCK,f have been shown to correlate better with cardiac performance than the steady-state levels of ATP and PCr (Bittl, J. A., and Ingwall, J. S. (1985) J. Biol. Chem. 260, 3512-3517). In order to elucidate the relationship between the CK kinetic parameters and brain activity, we have determined, using the non-invasive NMR technique of magnetization transfer, kf and FCK,f in rats, in which brain activity was experimentally varied by administration of either thiopental sodium or bicuculline to decrease or increase electro-encephalogram (EEG) intensity, respectively. The steady-state levels of ATP and PCr, as well as the accumulation of deoxyglucose 6-phosphate (DG-6P) in brain following intraperitoneal administration of deoxyglucose, were determined simultaneously by the NMR technique, whereas the cortical EEG was recorded in a separate experiment. The EEG intensity (range, 1-20 Hz), taken as a measure for brain performance, as well as the amount of DG-6P formed in brain, reflecting the synthesis rate of high energy phosphates (ATP and PCr), linearly correlated with kf. Despite large changes in both EEG intensity (50-250%) and kf (0.12-0.69 s-1) between thiopental sodium- and bicuculline-treated rats, the ATP levels remained constant, whereas the PCr levels decreased with high EEG activity. In contrast to the expectation based on model calculations of CK kinetics, the PCr levels did not increase above control values at reduced EEG intensity (50% of controls). At EEG intensities exceeding control values (bicuculline-treated rats) FCK,f increased as predicted by CK equilibrium. In conclusion, we have shown that in the rat brain, like in the heart, the CK forward rate constant kf, in contrast to ATP and PCr levels, is a sensitive reliable indicator of both increased and reduced function. PMID:8514755

Sauter, A; Rudin, M

1993-06-25

216

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

PubMed Central

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

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

2012-01-01

217

Final Report for NFE-07-00912: Development of Model Fuels Experimental Engine Data Base & Kinetic Modeling Parameter Sets  

SciTech Connect

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).

Bunting, Bruce G [ORNL

2012-10-01

218

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

219

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

PubMed Central

Winter wheat has a central role in ensuring the food security and welfare of 1.3 billion people in China. Extensive previous studies have concluded that winter wheat yields would decrease with higher temperatures, owing to warming-induced soil drying or shortening of phenophase. Temperature in China is predicted to increase by 1–5°C by 2100, which may greatly impact plant production and cause other negative effects. We performed a manipulative field experiment, creating diverse growth regimes for wheat by infrared radiation (IR) warming day and night, including IR warming only (DW), IR warming + delayed sowing dates (DS), IR warming + increased irrigation (IW), and a control (CK). The results show that IR warming increased daily average wheat canopy and soil temperatures by 2.0°C and 2.3°C, respectively. DW was associated with an advanced maturity of 10 days and yield reduction of 8.2%. IR-warming effects on the photosynthetic apparatus of wheat varied with season as well as significant differences were found in the booting stage. DS represented a worsened situation, lowering yield per plant by 16.4%, with a significant decline in aboveground biomass and functional leaf area. Wheat under DS showed double-peak patterns of diurnal gas exchange during booting stages and, consequently, lower photosynthetic capacity with high transpiration for cooling. Significantly lower actual water use efficiency and intrinsic water use efficiency from jointing to anthesis stages were also found under DS. However, IW had no significant difference from CK, irrespective of yield and photosynthesis. Therefore, we concluded that delayed sowing date may not be a good choice for winter wheat, whereas a thoroughly-watered wheat agroecosystem should be promoted in the context of global warming.

Fang, Shibo; Su, Hua; Liu, Wei; Tan, Kaiyan; Ren, Sanxue

2013-01-01

220

The influence of arbuscular mycorrhizal colonisation on key growth parameters and fruit yield of pepper plants grown at high salinity  

Microsoft Academic Search

This study investigated the effects of arbuscular mycorrhizal (AM) colonisation by Glomus clarum on growth and fruit yield of pepper (Capsicum annum cv. 11B 14) grown at high salinity. The experiment was conducted in pots containing a mixture of perlite and sand (1:1, v\\/v) under glasshouse conditions. Treatments were: (1) no added NaCl without arbuscular mycorrhizae (NS-AM), (2) no added

Cengiz Kaya; Muhammed Ashraf; Osman Sonmez; Salih Aydemir; Atilla Levent Tuna; Mehmet Ali Cullu

2009-01-01

221

Genetic Parameters of Dairy Character, Protein Yield, Clinical Mastitis, and Other Diseases in the Danish Holstein Cattle  

Microsoft Academic Search

The primary aim of this study was to estimate ge- netic correlations between dairy character, protein yield, clinical mastitis, and other diseases. Data con- sisted of first lactation records of Danish Holstein cows calving from 1990 to 1999. After editing, the data in- cluded records on 934,639 cows, of which 101,853 were assessed for dairy character, 472,421 for diseases, and

M. Hansen; M. S. Lund; M. K. Sørensen; L. G. Christensen

2002-01-01

222

Improved yield parameters in catalytic steam gasification of forestry residue; optimizing biomass feed rate and catalyst type  

Microsoft Academic Search

The catalytic gasification (900 °C) of forestry industry residue (Eucalyptussaligna) was laboratory-studied. Biomass feed rate and type and amount of catalyst were assayed for their effect on the gasified product composition and the overall energy yield of the gasification reaction. The use of a calcined dolomite catalyst resulted in a combustible gas mixture of adequate calorific power (10.65 MJ m?3) for use as

Andrea Corujo; Luis Yermán; Beatríz Arizaga; Mariana Brusoni; Jorge Castiglioni

2010-01-01

223

Infrared warming reduced winter wheat yields and some physiological parameters, which were mitigated by irrigation and worsened by delayed sowing.  

PubMed

Winter wheat has a central role in ensuring the food security and welfare of 1.3 billion people in China. Extensive previous studies have concluded that winter wheat yields would decrease with higher temperatures, owing to warming-induced soil drying or shortening of phenophase. Temperature in China is predicted to increase by 1-5°C by 2100, which may greatly impact plant production and cause other negative effects. We performed a manipulative field experiment, creating diverse growth regimes for wheat by infrared radiation (IR) warming day and night, including IR warming only (DW), IR warming + delayed sowing dates (DS), IR warming + increased irrigation (IW), and a control (CK). The results show that IR warming increased daily average wheat canopy and soil temperatures by 2.0°C and 2.3°C, respectively. DW was associated with an advanced maturity of 10 days and yield reduction of 8.2%. IR-warming effects on the photosynthetic apparatus of wheat varied with season as well as significant differences were found in the booting stage. DS represented a worsened situation, lowering yield per plant by 16.4%, with a significant decline in aboveground biomass and functional leaf area. Wheat under DS showed double-peak patterns of diurnal gas exchange during booting stages and, consequently, lower photosynthetic capacity with high transpiration for cooling. Significantly lower actual water use efficiency and intrinsic water use efficiency from jointing to anthesis stages were also found under DS. However, IW had no significant difference from CK, irrespective of yield and photosynthesis. Therefore, we concluded that delayed sowing date may not be a good choice for winter wheat, whereas a thoroughly-watered wheat agroecosystem should be promoted in the context of global warming. PMID:23874424

Fang, Shibo; Su, Hua; Liu, Wei; Tan, Kaiyan; Ren, Sanxue

2013-01-01

224

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

PubMed

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

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

2011-07-01

225

Carbon reaction and diffusion on Ni(111), Ni(100), and Fe(110): Kinetic parameters from x-ray photoelectron spectroscopy and density functional theory analysis.  

PubMed

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. PMID:19044838

Wiltner, A; Linsmeier, Ch; Jacob, T

2008-08-28

226

Utilization of the Phaseolus vulgaris L. Waste biomass for decolorization of the textile dye Acid Red 57: determination of equilibrium, kinetic and thermodynamic parameters  

Microsoft Academic Search

In the present study, biosorption of Acid Red 57 (AR57) onto a waste biomass of Phaseolus vulgaris L. was investigated by varying pH, contact time, biosorbent concentration and temperature, to determine the equilibrium, thermodynamic and kinetic parameters. The AR57 biosorption was fast, and equilibrium was attained within 20 min. Biosorption equilibrium data fit the Langmuir isotherm model well with high

Sibel Tunali; Adnan Ozcan; Zerrin Kaynak; A. Safa Ozcan; Tamer Akar

2007-01-01

227

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

PubMed

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

Sevi; Taibi; Albenzio; Muscio; Annicchiarico

2000-07-01

228

Effect of Simultaneous Inoculation with Yeast and Bacteria on Fermentation Kinetics and Key Wine Parameters of Cool-Climate Chardonnay  

PubMed Central

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.

Jussier, Delphine; Dube Morneau, Amelie; Mira de Orduna, Ramon

2006-01-01

229

A means to estimate thermal and kinetic parameters of coal dust layer from hot surface ignition tests.  

PubMed

A method to estimate thermal and kinetic parameters of Pittsburgh seam coal subject to thermal runaway is presented using the standard ASTM E 2021 hot surface ignition test apparatus. Parameters include thermal conductivity (k), activation energy (E), coupled term (QA) of heat of reaction (Q) and pre-exponential factor (A) which are required, but rarely known input values to determine the thermal runaway propensity of a dust material. Four different dust layer thicknesses: 6.4, 12.7, 19.1 and 25.4mm, are tested, and among them, a single steady state dust layer temperature profile of 12.7 mm thick dust layer is used to estimate k, E and QA. k is calculated by equating heat flux from the hot surface layer and heat loss rate on the boundary assuming negligible heat generation in the coal dust layer at a low hot surface temperature. E and QA are calculated by optimizing a numerically estimated steady state dust layer temperature distribution to the experimentally obtained temperature profile of a 12.7 mm thick dust layer. Two unknowns, E and QA, are reduced to one from the correlation of E and QA obtained at criticality of thermal runaway. The estimated k is 0.1 W/mK matching the previously reported value. E ranges from 61.7 to 83.1 kJ/mol, and the corresponding QA ranges from 1.7 x 10(9) to 4.8 x 10(11)J/kg s. The mean values of E (72.4 kJ/mol) and QA (2.8 x 10(10)J/kg s) are used to predict the critical hot surface temperatures for other thicknesses, and good agreement is observed between measured and experimental values. Also, the estimated E and QA ranges match the corresponding ranges calculated from the multiple tests method and values reported in previous research. PMID:19307057

Park, Haejun; Rangwala, Ali S; Dembsey, Nicholas A

2009-08-30

230

Photooxidation of benzene-structured compounds: influence of substituent type on degradation kinetic and sum water parameters.  

PubMed

The combined influence of substituent type and UV/H(2)O(2) process parameters on the degradation of four aromatic water pollutants was investigated using modified 3(3) full factorial design and response surface methodology. Degradation kinetics was described by the quadratic polynomial model. According to the applied ANOVA, besides pH and [H(2)O(2)], model terms related with the pollutant structure are found to be significant. Different optimal operating conditions and values of observed degradation rate constants were determined for each of the pollutants indicating that the type of substituent influences the overall process effectiveness over structurally defined degradation pathway. Biodegradability (BOD(5)/COD) and toxicity (TU) were evaluated prior to the treatment and at the reference time intervals t(1/2)(P), t(3/4)(P), t(1/4)(OC) and t(1/2)(OC) corresponding to the real time required to reduce the concentration of parent pollutant and organic content for 1/2, 3/4, 1/4 and 1/2 of initial amount. The observed differences are correlated to the structural differences of studied aromatics. PMID:22463859

Juretic, Daria; Kusic, Hrvoje; Koprivanac, Natalija; Loncaric Bozic, Ana

2012-06-01

231

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

PubMed Central

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

Ramon, F; Castillon, M; De La Mata, I; Acebal, C

1998-01-01

232

Comparison of dual-echo DSC-MRI- and DCE-MRI-derived contrast agent kinetic parameters  

PubMed Central

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 T1, T2 and T2? relaxation effects in the extravascular space, thereby affecting the signal intensity time course in a complex manner. The goal of this study is to validate a dual-echo DSC-MRI approach that separates and quantifies the T1 and T2? contributions to the acquired signal and enables the estimation of the volume transfer constant, Ktrans, and the volume fraction of the extravascular extracellular space, ?e. To test the validity of this approach, DSC-MRI- and dynamic contrast enhanced (DCE) MRI-derived Ktrans and ?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.

Quarles, C. Chad; Gore, John C.; Xu, Lei; Yankeelov, Thomas E.

2012-01-01

233

Influence of process parameters on yield and composition of gluten fractions obtained in a laboratory scale dough batter procedure  

Microsoft Academic Search

The influence of process parameters during the dough formation step on wheat flour gluten agglomeration and composition in a laboratory scale gluten–starch separation process was studied. In the process, in which a dough was transformed into a batter then poured over a set of vibrating sieves (400, 250 and 125 ?m), increasing water contents, mixing times and speeds during dough

S. A Frederix; C. M Courtin; J. A Delcour

2004-01-01

234

The Effects of Dietary Inclusion of Probiotic Protexin on Egg Yield Parameters of Japanese Quails (Coturnix coturnix Japonica)  

Microsoft Academic Search

The present study was conducted to investigate the effects of grower diets, dietary three different levels of probiotic (protexin) in grower diet on egg production parameters and egg shell quality of Japanese quail (Coturnix coturnix Japonica). In this study, 225 female Japanese quails were used. The experimental quails were divided into three dietary groups of similar mean weight comprising 75

2006-01-01

235

n-alkanes on Pt(111) and on C(0001)/Pt(111): Chain Length Dependence of Kinetic Desorption Parameters  

SciTech Connect

We have measured the desorption of seven small n-alkanes (CNH2N+2, N = 1-4, 6, 8, 10) from the Pt(111) and C(0001) surfaces by temperature programmed desorption. We compare these results to our recent study of the desorption kinetics of these molecules on MgO(100) [J. Chem. Phys. 122, 164708 (2005)]. There we showed an increase in the desorption pre-exponential factor by several orders of magnitude with increasing n-alkane chain length and a linear desorption energy scaling with a small y-intercept value. We suggest that the significant increase in desorption prefactor with chain length is not particular to the MgO(100) surface, but is a general effect for desorption of the small n-alkanes. This argument is supported by statistical mechanical arguments for the increase in the entropy gain of the molecules upon desorption. In this work, we demonstrate that this hypothesis holds true on both a metal surface and a graphite surface. We observe an increase in prefactor by five orders of magnitude over the range of n-alkane chain lengths studied here. On each surface, the desorption energies of the n-alkanes are found to increase linearly with the molecule chain length and have a small y-intercept value. Prior results of other groups have yielded a linear desorption energy scaling with chain length that has unphysically large y-intercept values. We demonstrate that by allowing the prefactor to increase according to our model, a reanalysis of their data resolves this y-intercept problem to some degree.

Tait, Steven L.; Dohnalek, Zdenek; Campbell, Charles T.; Kay, Bruce D.

2006-12-21

236

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

PubMed Central

Background and Aims Prediction of phenotypic traits from new genotypes under untested environmental conditions is crucial to build simulations of breeding strategies to improve target traits. Although the plant response to environmental stresses is characterized by both architectural and functional plasticity, recent attempts to integrate biological knowledge into genetics models have mainly concerned specific physiological processes or crop models without architecture, and thus may prove limited when studying genotype × environment interactions. Consequently, this paper presents a simulation study introducing genetics into a functional–structural growth model, which gives access to more fundamental traits for quantitative trait loci (QTL) detection and thus to promising tools for yield optimization. Methods The GREENLAB model was selected as a reasonable choice to link growth model parameters to QTL. Virtual genes and virtual chromosomes were defined to build a simple genetic model that drove the settings of the species-specific parameters of the model. The QTL Cartographer software was used to study QTL detection of simulated plant traits. A genetic algorithm was implemented to define the ideotype for yield maximization based on the model parameters and the associated allelic combination. Key Results and Conclusions By keeping the environmental factors constant and using a virtual population with a large number of individuals generated by a Mendelian genetic model, results for an ideal case could be simulated. Virtual QTL detection was compared in the case of phenotypic traits – such as cob weight – and when traits were model parameters, and was found to be more accurate in the latter case. The practical interest of this approach is illustrated by calculating the parameters (and the corresponding genotype) associated with yield optimization of a GREENLAB maize model. The paper discusses the potentials of GREENLAB to represent environment × genotype interactions, in particular through its main state variable, the ratio of biomass supply over demand.

Letort, Veronique; Mahe, Paul; Cournede, Paul-Henry; de Reffye, Philippe; Courtois, Brigitte

2008-01-01

237

Quantitative evaluation of dual-flip-angle T1 mapping on DCE-MRI kinetic parameter estimation in head and neck  

PubMed Central

Purpose To quantitatively evaluate the kinetic parameter estimation for head and neck (HN) dynamic contrast-enhanced (DCE) MRI with dual-flip-angle (DFA) T1 mapping. Materials and methods Clinical DCE-MRI datasets of 23 patients with HN tumors were included in this study. T1 maps were generated based on multiple-flip-angle (MFA) method and different DFA combinations. Tofts model parameter maps of kep, Ktrans and vp based on MFA and DFAs were calculated and compared. Fitted parameter by MFA and DFAs were quantitatively evaluated in primary tumor, salivary gland and muscle. Results T1 mapping deviations by DFAs produced remarkable kinetic parameter estimation deviations in head and neck tissues. In particular, the DFA of [2º, 7º] overestimated, while [7º, 12º] and [7º, 15º] underestimated Ktrans and vp, significantly (P<0.01). [2º, 15º] achieved the smallest but still statistically significant overestimation for Ktrans and vp in primary tumors, 32.1% and 16.2% respectively. kep fitting results by DFAs were relatively close to the MFA reference compared to Ktrans and vp. Conclusions T1 deviations induced by DFA could result in significant errors in kinetic parameter estimation, particularly Ktrans and vp, through Tofts model fitting. MFA method should be more reliable and robust for accurate quantitative pharmacokinetic analysis in head and neck.

Chow, Steven Kwok Keung; Yeung, David Ka Wai; Ahuja, Anil T; King, Ann D

2012-01-01

238

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

239

Kinetic study of the reaction CH (X 2Pi) + H2 yields CH2 (X 3B1) + H in the temperature range 372 to 675 K  

NASA Technical Reports Server (NTRS)

The kinetics of the reversible reaction CH (X 2Pi) + H2 yields CH2 (X 3B1) + H at 372-675 K and total pressure 100 torr (mainly Ar) is investigated experimentally. The ground-state CH radicals are produced by photolysis of CHBr3 using 10-mJ 266-nm laser pulses (repetition rate 10 Hz) and monitored by measuring the fluorescence induced by a 429.8-nm dye laser, in the apparatus described by Berman et al. (1982) and Berman and Lin (1984). The results are presented in tables and graphs and characterized. The absolute rate constants for the forward and reverse reactions are determined, and their temperature dependence is given by Arrhenius expressions and formulas obtained in transition-state-theory calculations. The heat of formation of CH2 at 0 K is estimated (assuming that the recombination reaction CH2 + H has zero activation energy) as 92.6 + or - 0.5 kcal/mol.

Zabarnick, S.; Fleming, J. W.; Lin, M. C.

1986-01-01

240

Determination of the equilibrium, kinetic and thermodynamic parameters of the batch biosorption of nickel(II) ions onto Chlorella vulgaris  

Microsoft Academic Search

Although the search for new and innovative treatment technologies has focused attention on the metal binding capacities of various microorganisms, the kinetics of the metal uptake process and the description of the thermal properties of biosorption remain essentially unknown. Biosorption equilibrium, kinetics and thermodynamics of nickel(II) ions to Chlorella vulgaris were studied in a batch system with respect to temperature

Z. Aksu

2002-01-01

241

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

NASA Astrophysics Data System (ADS)

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

Witte, M.

2004-11-01

242

Quantitative Production of Compound I from a Cytochrome P450 Enzyme at Low Temperatures. Kinetics, Activation Parameters, and Kinetic Isotope Effects for Oxidation of Benzyl Alcohol  

PubMed Central

Cytochrome P450 enzymes are commonly thought to oxidize substrates via an iron(IV)-oxo porphyrin radical cation transient termed Compound I, but kinetic studies of P450 Compounds I are essentially non-existent. We report production of Compound I from cytochrome P450 119 (CYP119) in high conversion from the corresponding Compound II species at low temperatures in buffer mixtures containing 50% glycerol by photolysis with 365 nm light from a pulsed lamp. Compound I was studied as a reagent in oxidations of benzyl alcohol and its benzylic mono- and dideuterio isotopomers. Pseudo-first-order rate constants obtained at ?50 °C with concentrations of substrates between 1.0 and 6.0 mM displayed saturation kinetics that gave binding constants for the substrate in the Compound I species (Kbind) and first-order rate constants for the oxidation reactions (kox). Representative results are Kbind = 214 M?1 and kox = 0.48 s?1 for oxidation of benzyl alcohol. For the dideuterated substrate C6H5CD2OH, kinetics were studied between ?50 °C and ?25 °C, and a van't Hoff plot for complexation and an Arrhenius plot for the oxidation reaction were constructed. The H/D kinetic isotope effects (KIEs) at ?50 °C were resolved into a large primary KIE (P = 11.9) and a small, inverse secondary KIE (S = 0.96). Comparison of values extrapolated to 22 °C of both the rate constant for oxidation of C6H5CD2OH and the KIE for the non-deuterated and dideuterated substrates to values obtained previously in laser flash photolysis experiments suggested that tunneling could be a significant component of the total rate constant at ?50 °C.

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

2009-01-01

243

Effect of farming systems on the yield, quality parameters and sensory properties of conventionally and organically grown potato (Solanum tuberosum L.) tubers.  

PubMed

The objectives of this two-year research were to study the impact of two different farming types, conventional and organic, on the yield and sensory properties of five Lithuanian varieties of potato tuber. The parameters and properties examined were: phenolic acids; dry matter and starch content; and the spread and intensity of Phytophthora infestans growth. It was determined that potato yield fluctuates with the variety, but for conventional farming it is significantly (p<0.05) higher than that obtained by organic farming. The farming type has no significant effect (p>0.05) on the content of phenolic acids. No significant effect (p>0.05) of farming type on dry matter and starch content, or sensory properties was found. No significant relation (p>0.05) was found between the content of phenolic acids and P. infestans spread. The spread of P. infestans was faster and infection was heavier in organically grown potatoes. PMID:24128562

Brazinskiene, V; Asakaviciute, R; Miezeliene, A; Alencikiene, G; Ivanauskas, L; Jakstas, V; Viskelis, P; Razukas, A

2014-02-15

244

Erbium hydride decomposition kinetics.  

SciTech Connect

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

Ferrizz, Robert Matthew

2006-11-01

245

Effect of Tannin-Binding Agents (Polyethylene Glycol and Polyvinylpyrrolidone) Supplementation on In Vitro Gas Production Kinetics of Some Grape Yield Byproducts  

PubMed Central

The effects of polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) on in vitro gas production characteristics, organic matter digestibility (OMD), and metabolizable energy (ME) contents of some grape yield byproducts were investigated. The gas production was recorded after 2, 4, 6, 8, 12, 16, 24, 36, and 48?h of incubation. The gas production profiles in triplicate fitted with equation Y = A (1 – e?ct). The data was analyzed using completely randomized design. Total phenol (TP) and total tannin (TT) contents were highest for raisin waste (RW). The TP content (g/kg DM) ranged from 30.1 in grape pomace (GP) to 96.3 in RW, which also had the higher TT (72.1?g/kg DM). The potential gas production (a + b) of DGB, GP, and RW were 239.43, 263.49, and 208.22?mL/g DM, respectively. In the absence of PEG and PVP, rate constant of gas production (c) for GP was highest among the feedstuffs (0.1073?mL/h), but in presence of PEG or PVP, RW had highest fraction (c) among the feedstuffs. Addition of PEG and PVP inactivated effects of tannins and increased gas production, ME, NE1, OMD, and VFA in grape yield byproducts. Addition of PEG and PVP could overcome adverse effects of tannins on nutrient availability as indicated by gas production parameters.

Besharati, Maghsoud; Taghizadeh, Akbar

2011-01-01

246

Systematics of Fission-Product Yields  

SciTech Connect

Empirical equations representing systematics of fission-product yields have been derived from experimental data. The systematics give some insight into nuclear-structure effects on yields, and the equations allow estimation of yields from fission of any nuclide with atomic number Z{sub F} = 90 thru 98, mass number A{sub F} = 230 thru 252, and precursor excitation energy (projectile kinetic plus binding energies) PE = 0 thru {approx}200 MeV--the ranges of these quantities for the fissioning nuclei investigated. Calculations can be made with the computer program CYFP. Estimates of uncertainties in the yield estimates are given by equations, also in CYFP, and range from {approx} 15% for the highest yield values to several orders of magnitude for very small yield values. A summation method is used to calculate weighted average parameter values for fast-neutron ({approx} fission spectrum) induced fission reactions.

A.C. Wahl

2002-05-01

247

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

PubMed Central

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

Schodel, R; Hillmann, F; Schrotter, T; Voigt, J; Irrgang, K D; Renger, G

1996-01-01

248

Effect of molecular and processing parameters on the flow-induced crystallization of poly-1-butene. Part 1: Kinetics and morphology  

Microsoft Academic Search

In this work the effect of molecular parameters (molecular weight (MW), molecular weight distribution (MWD)) and processing conditions (crystallization temperature, flow conditions) on the isothermal crystallization behavior of three isotactic poly-1-butene (iPB) samples is investigated by means of rheo-optical techniques. The emphasis in this paper will be on the kinetics and the resulting morphology.Turbidity measurements show a strong effect of

Jimmy Baert; Peter Van Puyvelde

2006-01-01

249

Kinetics Modeling of Mass Transfer Using Peleg’s Equation During Osmotic Dehydration of Seedless Guava ( Psidium guajava L.): Effect of Process Parameters  

Microsoft Academic Search

Peleg’s equation was used to study the effect of process parameters on kinetics of mass transfer in terms of solids gain and\\u000a water loss during osmotic dehydration using 30–50% (w\\/w) sucrose solution at 30, 40 and 50 °C. The experimental data were successfully fitted employing Peleg’s equation with the\\u000a coefficient of determination (R\\u000a 2) higher than 0.88, the root mean square

Ali Ganjloo; Russly Abdul Rahman; Jamilah Bakar; Azizah Osman; Mandana Bimakr

250

Determination of kinetic parameters for the water–gas shift reaction on copper catalysts under realistic conditions for fuel cell applications  

Microsoft Academic Search

The kinetic parameters for water–gas shift reaction on Cu-based catalysts were measured under fuel reformer conditions for fuel cell applications (7% CO, 8.5% CO2, 22% H2O, 37% H2, and 25% Ar) at 1 atm total pressure and temperature in the range of 200°C. The rate per unit of Cu surface area at the stated concentrations was 0.8×10?6 molm?2s?1 at 200°C.

N. A. Koryabkina; A. A. Phatak; W. F. Ruettinger; R. J. Farrauto; F. H. Ribeiro

2003-01-01

251

Ranking the Potential Yield of Salinity and Selenium from Subbasins in the Lower Gunnison River Basin Using Seasonal, Multi-parameter Regression Models  

NASA Astrophysics Data System (ADS)

Elevated levels of salinity and dissolved selenium can detrimentally effect the quality of water where anthropogenic and natural uses are concerned. In areas, such as the lower Gunnison Basin of western Colorado, salinity and selenium are such a concern that control projects are implemented to limit their mobilization. To prioritize the locations in which control projects are implemented, multi-parameter regression models were developed to identify subbasins in the lower Gunnison River Basin that were most likely to have elevated salinity and dissolved selenium levels. The drainage area is about 5,900 mi2 and is underlain by Cretaceous marine shale, which is the most common source of salinity and dissolved selenium. To characterize the complex hydrologic and chemical processes governing constituent mobilization, geospatial variables representing 70 different environmental characteristics were correlated to mean seasonal (irrigation and nonirrigation seasons) salinity and selenium yields estimated at 154 sampling sites. The variables generally represented characteristics of the physical basin, precipitation, soil, geology, land use, and irrigation water delivery systems. Irrigation and nonirrigation seasons were selected due to documented effects of irrigation on constituent mobilization. Following a stepwise approach, combinations of the geospatial variables were used to develop four multi-parameter regression models. These models predicted salinity and selenium yield, within a 95 percent confidence range, at individual points in the Lower Gunnison Basin for irrigation and non-irrigation seasons. The corresponding subbasins were ranked according to their potential to yield salinity and selenium and rankings were used to prioritize areas that would most benefit from control projects.

Linard, J.; Leib, K.; Colorado Water Science Center

2010-12-01

252

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

PubMed

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

Afolabi, Afolawemi; Akinlabi, Olakemi; Bilgili, Ecevit

2014-01-23

253

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

254

Pattern formation during phase transitions: kinetics of partially conserved order parameters and the role of gradient energies  

Microsoft Academic Search

The formation of kinetic, transient microstructures in structural phase transitions is analysed within the framework of time-dependent Landau-Ginzburg theories. The mesoscopic rate equation is delta phi \\/ delta t= phi - phi 3+ delta 2 phi \\/ delta x2- gamma delta 2 phi \\/ delta x4+ delta delta 6 phi \\/ delta x6. A front of a stable state phi

I. Tsatskis; E. K. H. Salje; V. Heine

1994-01-01

255

Kinetic parameters for the removal of lead and chromium from wastewater using activated carbon developed from fertilizer waste material  

Microsoft Academic Search

The waste slurry generated in fertilizer plants in India has been converted into a cheap carbonaceous adsorbent material. The prepared adsorbent has been characterised and used for the removal of lead and chromium metals. The kinetics of adsorption and the extent of adsorption at equilibrium are dependent on the physical and chemical characteristics of the adsorbate, adsorbent and experimental system.

S. K. Srivastava; V. K. Gupta; Dinesh Mohan

1996-01-01

256

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

Microsoft Academic Search

Cardiac 82rubidium dynamic PET studies allow quantifying absolute myocardial perfusion by using tracer kinetic modeling. Here, the accurate measurement of the input function, i.e. the tracer concentration in blood plasma, is a major challenge. This measurement is deteriorated by inappropriate temporal sampling, spillover, etc. Such effects may influence the measured input peak value and the measured blood pool clearance. The

Carsten Meyer; Dragos-Nicolae Peligrad; Martin Weibrecht

2007-01-01

257

Kinetics of hydrogen abstraction O({sup 3}P) + alkane {yields} OH + alkyl reaction class: An application of the reaction class transition state theory  

SciTech Connect

This paper presents an application of the reaction class transition state theory (RC-TST) for prediction of thermal rate constants of the O({sup 3}P) + alkane {yields} OH + alkyl reaction class. Parameters of the RC-TST were derived from first principles from a set of 19 reactions representing hydrogen abstractions from primary, secondary, and tertiary carbon atoms so that rate constants of any reaction in this class can be estimated without any further information or with its reaction energy calculated either at the density functional theory BH and HLYP/cc-pVDZ level or the semiempirical AM1 level. Detailed error analyses show that when compared to explicit theoretical calculations, the systematic errors in the calculated rate constants arising from the use of analytical expressions to approximate different reaction class factors in the RC-TST method are less than 40% on the average over the temperature range from 300 to 3000 K. In addition, we found that the rate constants estimated using either approach are in good agreement with available data in the literature. (author)

Huynh, Lam K.; Truong, Thanh N. [Department of Chemistry, University of Utah, Salt Lake City, UT 84112 (United States); Zhang, Shaowen [Beijing Institute of Technology, Beijing (China)

2008-01-15

258

The dehydrogenation of 2-butanol over copper-based catalysts: optimising catalyst composition and determining kinetic parameters  

Microsoft Academic Search

This work examines the dehydrogenation of 2-butanol over copper-based catalyst. The effects of support type (MgO and SiO2) and copper loading on methyl ethyl ketone (MEK) yield were studied. The effects of reaction temperature, 2-butanol feed flow rate and catalyst particle size were also investigated. The highest MEK yields were obtained with a 15wt.% copper on silica catalyst. The optimum

J. N. Keuler; L. Lorenzen; S. Miachon

2001-01-01

259

Study of the decomposition of phase stabilized ammonium nitrate (PSAN) by simultaneous thermal analysis: determination of kinetic parameters  

Microsoft Academic Search

Ammonium nitrate (AN) has been extensively used both in explosive and propellant formulations. Unlike AN, there is a lack of information about the thermal decomposition and related kinetic analysis of phase stabilized ammonium nitrate (PSAN). Simultaneous thermal analysis (DSC-TG) has been used in the thermal characterisation of a specific type of PSAN containing 1.0% of NiO (stabilizing agent) and 0.5%

P. N. Simões; L. M. Pedroso; A. A. Portugal; J. L. Campos

1998-01-01

260

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

Microsoft Academic Search

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

D. Kavitha; C. Namasivayam

2008-01-01

261

Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile\\/buffer mobile phases  

Microsoft Academic Search

The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile\\/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at 25±2?C. The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this

Hyunjung Kim; Krzysztof Kaczmarski; Georges A Guiochon

2006-01-01

262

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

PubMed Central

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

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

2009-01-01

263

The comparison of the estimation of enzyme kinetic parameters by fitting reaction curve to the integrated Michaelis–Menten rate equations of different predictor variables  

Microsoft Academic Search

The estimation of enzyme kinetic parameters by nonlinear fitting reaction curve to the integrated Michaelis–Menten rate equation ln(S0\\/S)+(S0?S)\\/Km=(Vm\\/Km)×twas investigated and compared to that by fitting to (S0?S)\\/t=Vm?Km×[ln(S0\\/S)\\/t] (Atkins GL, Nimmo IA. The reliability of Michaelis-Menten constants and maximum velocities estimated by using the integrated Michaelis-Menten equation. Biochem J 1973;135:779-84) with uricase as the model. Uricase reaction curve was simulated with

Fei Liao; Xiao-Yun Zhu; Yong-Mei Wang; Yu-Ping Zuo

2005-01-01

264

On the design of optimal dynamic experiments for parameter estimation of a Ratkowsky-type growth kinetics at suboptimal temperatures  

Microsoft Academic Search

It is generally known that accurate model building, i.e., proper model structure selection and reliable parameter estimation, constitutes an essential matter in the field of predictive microbiology, in particular, when integrating these predictive models in food safety systems. In this context, Versyck et al. (1999) have introduced the methodology of optimal experimental design techniques for parameter estimation within the field.

Kristel Bernaerts; Karina J. Versyck; Jan F. Van Impe

2000-01-01

265

Cob(I)alamin for trapping butadiene epoxides in metabolism with rat S9 and for determining associated kinetic parameters.  

PubMed

The reduced state of vitamin B(12), cob(I)alamin, acts as a supernucleophile that reacts ca. 10(5) times faster than standard nucleophiles, for example, thiols. Methods have been developed for trapping electrophilically reactive compounds by exploiting this property of cob(I)alamin. 1,3-Butadiene (BD) has recently been classified as a group 1 human carcinogen by the International Agency for Research on Cancer (IARC). The carcinogenicity of BD is considered to be dependent on the activation or deactivation of the reactive metabolites of BD, that is, the epoxides (oxiranes) 1,2-epoxy-3-butene (EB), 1,2:3,4-diepoxybutane (DEB), and 1,2-epoxy-3,4-butanediol (EBdiol). Cytochrome P450 (P450) isozymes are involved in oxidation of BD to EB and further activation to DEB. EB and DEB are hydrolyzed by epoxide hydrolases (EH) to 3,4-dihydroxy-1-butene (BDdiol) and EBdiol, respectively. EBdiol can also be formed by oxidation of BDdiol. In the present study, cob(I)alamin was used for instant trapping of the BD epoxide metabolites generated in in vitro metabolism to study enzyme kinetics. The substrates EB, DEB, and BDdiol were incubated with rat S9 liver fraction, and apparent K(m) and apparent V(max), were determined. The ratio of conversion of EB to DEB (by P450) to the rate of deactivation of DEB by EH was 1.09. Formation of EBdiol from hydrolysis of DEB was ca. 10 times faster than that from oxidation of BDdiol. It was also found that the oxidation of EB to DEB was much faster than that of BDdiol to EBdiol. The study offers comparative enzyme kinetic data of different BD metabolic steps, which is useful for quantitative interspecies comparison. Furthermore, a new application of cob(I)alamin was demonstrated for the measurement of enzyme kinetics of compounds that form electophilically reactive metabolites. PMID:19764821

Motwani, Hitesh V; Fred, Charlotta; Haglund, Johanna; Golding, Bernard T; Törnqvist, Margareta

2009-09-01

266

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

267

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

PubMed Central

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

2014-01-01

268

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

269

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

270

Do organic solvents affect the catalytic properties of lipase? Intrinsic kinetic parameters of lipases in ester hydrolysis and formation in various organic solvents  

SciTech Connect

When it is assumed that organic solvents do not interfere with the binding process nor with the catalytic mechanism, the contribution of substrate-solvent interactions to enzyme kinetics can be accounted for by just replacing substrate concentrations in the equations by thermodynamic activities. It appears from the transformation that only the affinity parameters (K{sub m},k{sub sp}) are affected by this. Thus, in theory, the values of these corrected, intrinsic parameters (K{sub m}{sup int}, k{sub sp}{sup int}) and the maximal rate (V{sub 1}) should be equal for all media. This was tested for hydrolysis, transesterification, and esterification reactions catalyzed by pig pancreas lipase and Pseudomonas cepacia lipase in various organic solvents. Correction was carried out via experimentally determined activity coefficients for the substrates in these solvents or, if not feasible, from values in data bases. However, although the kinetic performances of each enzyme in the solvents became much more similar after correction, differences still remained. Analysis of the enzyme suspensions revealed massive particles, which explains the low activity of enzymes in organic solvents. However, no correlation was found between estimates of the amount of catalytically available enzyme (present at the surface of suspended particles or immobilized on beads) and the maximal rates observed. Moreover, the solvents had similar effects on the intrinsic parameters of suspended and immobilized enzyme. The possible causes for the effects of the solvents on the catalytic performance of the enzymes, remaining after correction for solvent-substrate interactions and the amount of participating enzyme, are discussed with respect to the premises on which the correction method is based.

Tol, J.B.A. van; Stevens, R.M.M.; Veldhuizen, W.J.; Jongejan, J.A.; Duine, J.A. [Delft Univ. of Technology (Netherlands)

1995-07-05

271

Non-Isothermal Kinetics.  

ERIC Educational Resources Information Center

Discusses the principle of nonisothermal kinetics and some of the factors involved in such reactions, especially when considering the reliability of the kinetic parameters, compared to those of isothermal conditions. (GA)

Brown, M. E.; Phillpotts, C. A. R.

1978-01-01

272

Structure-kinetic relationships--an overlooked parameter in hit-to-lead optimization: a case of cyclopentylamines as chemokine receptor 2 antagonists.  

PubMed

Preclinical models of inflammatory diseases (e.g., neuropathic pain, rheumatoid arthritis, and multiple sclerosis) have pointed to a critical role of the chemokine receptor 2 (CCR2) and chemokine ligand 2 (CCL2). However, one of the biggest problems of high-affinity inhibitors of CCR2 is their lack of efficacy in clinical trials. We report a new approach for the design of high-affinity and long-residence-time CCR2 antagonists. We developed a new competition association assay for CCR2, which allows us to investigate the relation of the structure of the ligand and its receptor residence time [i.e., structure-kinetic relationship (SKR)] next to a traditional structure-affinity relationship (SAR). By applying combined knowledge of SAR and SKR, we were able to re-evaluate the hit-to-lead process of cyclopentylamines as CCR2 antagonists. Affinity-based optimization yielded compound 1 with good binding (Ki = 6.8 nM) but very short residence time (2.4 min). However, when the optimization was also based on residence time, the hit-to-lead process yielded compound 22a, a new high-affinity CCR2 antagonist (3.6 nM), with a residence time of 135 min. PMID:24028535

Vilums, Maris; Zweemer, Annelien J M; Yu, Zhiyi; de Vries, Henk; Hillger, Julia M; Wapenaar, Hannah; Bollen, Ilse A E; Barmare, Farhana; Gross, Raymond; Clemens, Jeremy; Krenitsky, Paul; Brussee, Johannes; Stamos, Dean; Saunders, John; Heitman, Laura H; Ijzerman, Adriaan P

2013-10-10

273

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

SciTech Connect

A glucosyltransferase, forming a predominantly al-6 linked glucan, was partially purified from the culture filtrate of S. mutans GS-5. The kinetic properties of the enzyme, assessed using the transfer of /sup 14/C glucose from sucrose into total glucan, were studied at pH values from pH 3.5 to 6.5. From the dependence of km on pH, a group with pKa = 5.5 must be protonated to maximize substrate binding. From plots of V/sub max/ vs pH two groups, with pKa's of 4.5 and 5.5 were indicated. The results suggest the involvement of either two carboxyl groups (one protonated, one unprotonated in the native enzyme) or a carboxyl group (unprotonated) and some other protonated group such as histidine, cysteine. Chemical modification studies showed that Diethylyrocarbonate (histidine specific) had no effect on enzyme activity while modification with p-phydroxy-mercuribenzoate or iodoacetic acid (sulfhydryl reactive) and carbodimide reagents (carboxyl specific) resulted in almost complete inactivation. Activity loss was dependent upon time of incubation and reagent concentration. The disaccharide lylose, (shown to be an inhibitor of the enzyme with similar affinity to sucrose) offers no protection against modification by the sulfhydryl reactive reagents.

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

1986-05-01

274

Rationalization and prediction of in vivo metabolite exposures: The role of metabolite kinetics, clearance predictions and in vitro parameters  

PubMed Central

Importance of the field Due to growing concerns over toxic or active metabolites, significant efforts have been focused on qualitative identification of potential in vivo metabolites from in vitro data. However, limited tools are available to quantitatively predict their human exposures. Areas covered in this review Theory of clearance predictions and metabolite kinetics is reviewed together with supporting experimental data. In vitro and in vivo data of known circulating metabolites and their parent drugs was collected and the predictions of in vivo exposures of the metabolites were evaluated. What the reader will gain The theory and data reviewed will be useful in early identification of human metabolites that will circulate at significant levels in vivo and help in designing in vivo studies that focus on characterization of metabolites. It will also assist in rationalization of metabolite-to-parent ratios used as markers of specific enzyme activity. Take home message The relative importance of a metabolite in comparison to the parent compound as well as other metabolites in vivo can only be predicted using the metabolites in vitro formation and elimination clearances, and the in vivo disposition of a metabolite can only be rationalized when the elimination pathways of that metabolite are known.

Lutz, Justin D.; Fujioka, Yasushi; Isoherranen, Nina

2010-01-01

275

Kinetic Parameters of Secondary Carbide Precipitation in High-Cr White Iron Alloyed by Mn-Ni-Mo-V Complex  

NASA Astrophysics Data System (ADS)

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.

Efremenko, V. G.; Chabak, Yu. G.; Brykov, M. N.

2013-05-01

276

A protocol for the measurement of all the parameters of the mass transfer kinetics in columns used in liquid chromatography  

SciTech Connect

Band broadening in chromatography results from the combination of the dispersive effects that are associated with the different steps involved in the migration of compound bands along the column. These steps include longitudinal diffusion, trans-particle mass transfer, external film mass transfer, overall eddy diffusion, including trans-column, short-range inter-channel, trans-channel eddy diffusion, and the possible, additional mass transfer contributions arising from heat friction and the thermal heterogeneity of the column. We describe a series of experiments that provide the data needed to determine the coefficients of the contributions to band broadening of each one of these individual mass transfer steps. This specifically designed protocol can provide key information regarding the kinetic performance of columns used in liquid chromatography and explain why different columns behave so differently. The limitations, accuracy and precision of these methods are discussed. Further avenues of research that could improve the characterization of the mass transfer mechanisms in chromatographic columns, possibly contributing to the development of better columns, are suggested.

Gritti, Fabrice [University of Tennessee, Knoxville (UTK); Guiochon, Georges A [ORNL

2010-01-01

277

In vitro characterization of rosiglitazone metabolites and determination of the kinetic parameters employing rat liver microsomal fraction.  

PubMed

Rosiglitazone (RSG), a thiazolidinedione antidiabetic drug, is metabolized by CYP450 enzymes into two main metabolites: N-desmethyl rosiglitazone (N-Dm-R) and ?-hydroxy rosiglitazone (?-OH-R). In humans, CYP2C8 appears to have a major role in RSG metabolism. On the other hand, the in vitro metabolism of RSG in animals has not been described in literature yet. Based on these concerns, the kinetic metabolism study of RSG using rat liver microsomal fraction is described for the first time. Maximum velocity (V (max)) values of 87.29 and 51.09 nmol/min/mg protein were observed for N-Dm-R and ?-OH-R, respectively. Michaelis-Menten constant (K(m)) values were of 58.12 and 78.52 ?M for N-Dm-R and ?-OH-R, respectively. Therefore, these results demonstrated that this in vitro metabolism model presents the capacity of forming higher levels of N-Dm-R than of ?-OH-R, which also happens in humans. Three other metabolites were identified employing mass spectrometry detection under positive electrospray ionization: ortho-hydroxy-rosiglitazone (?-OH-R) and two isomers of N-desmethyl hydroxy-rosiglitazone. These metabolites have also been observed in humans. The results observed in this study indicate that rats could be a satisfactory model for RSG metabolism. PMID:21499911

Calixto, Leandro Augusto; de Oliveira, Anderson Rodrigo Moraes; Jabor, Valquíria Aparecida Polisel; Bonato, Pierina Sueli

2011-09-01

278

Regulators of calcium homeostasis identified by inference of kinetic model parameters from live single cells perturbed by siRNA.  

PubMed

Assigning molecular functions and revealing dynamic connections between large numbers of partially characterized proteins in regulatory networks are challenges in systems biology. We showed that functions of signaling proteins can be discovered with a differential equations model of the underlying signaling process to extract specific molecular parameter values from single-cell, time-course measurements. By analyzing the effects of 250 small interfering RNAs on Ca(2+) signals in single cells over time, we identified parameters that were specifically altered in the Ca(2+) regulatory system. Analysis of the screen confirmed known functions of the Ca(2+) sensors STIM1 (stromal interaction molecule 1) and calmodulin and of Ca(2+) channels and pumps localized in the endoplasmic reticulum (ER) or plasma membrane. Furthermore, we showed that the Alzheimer's disease-linked protein presenilin-2 and the channel protein ORAI2 prevented overload of ER Ca(2+) and that feedback from Ca(2+) to phosphatidylinositol 4-kinase and PLC? (phospholipase C?) may regulate the abundance of the plasma membrane lipid PI(4,5)P2 (phosphatidylinositol 4,5-bisphosphate) to control Ca(2+) extrusion. Thus, functions of signaling proteins and dynamic regulatory connections can be identified by extracting molecular parameter values from single-cell, time-course data. PMID:23838183

Bandara, Samuel; Malmersjö, Seth; Meyer, Tobias

2013-07-01

279

Photooxidation processes for an azo dye in aqueous media: modeling of degradation kinetic and ecological parameters evaluation.  

PubMed

Three photooxidation processes, UV/H(2)O(2), UV/S(2)O(8)(2-) and UV/O(3) were applied to the treatment of model wastewater containing non-biodegradable organic pollutant, azo dye Acid Orange 7 (AO7). Dye degradation was monitored using UV/VIS and total organic carbon (TOC) analysis, determining decolorization, the degradation/formation of naphthalene and benzene structured AO7 by-products, and the mineralization of model wastewater. The water quality during the treatment was evaluated on the bases of ecological parameters: chemical (COD) and biochemical (BOD(5)) oxygen demand and toxicity on Vibrio fischeri determining the EC(50) value. The main goals of the study were to develop an appropriate mathematic model (MM) predicting the behavior of the systems under investigation, and to evaluate the toxicity and biodegradability of the model wastewater during treatments. MM developed showed a high accuracy in predicting the degradation of AO7 when considering the following observed parameters: decolorization, formation/degradation of by-products and mineralization. Good agreement of the data predicted and the empirically obtained was confirmed by calculated standard deviations. The biodegradability of model wastewater was significantly improved by three processes after mineralizing a half of the initially present organic content. The toxicity AO7 model wastewater was decreased as well. The differences in monitored ecological parameters during the treatment indicated the formation of different by-products of dye degradation regarding the oxidant type applied. PMID:21093983

Kusic, Hrvoje; Juretic, Daria; Koprivanac, Natalija; Marin, Vedrana; Boži?, Ana Lon?ari?

2011-01-30

280

The Effects of Crown Removal, Short Days and Polyethylene Mulch Color on Fruit Yield Parameters and Quality Compounds, in Tunnel-Grown ‘Korona’ Strawberry (Fragaria × ananassa Duch.)  

Microsoft Academic Search

The effects of exposing strawberry plants to a short-day treatment (10 h day-1) from August 10 to September 17, and reducing the crown number per plant in the following spring were examined on fruit yield and quality in Haygrow® (UK) tunnel-grown strawberries. Reducing the number of crowns per plant increased °Brix level and reduced fruit yield. The yield reduction was

Rolf Nestby; Mikko Anttonen; Michel Verheul; Reijo Karjalainen

2007-01-01

281

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

PubMed

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

Nikolakakis, Ioannis; Malamataris, Stavros

2014-05-01

282

Determination of kinetic and thermodynamic parameters of surface confined species through ac voltammetry and a nonstationary signal processing technique: the Hilbert transform.  

PubMed

Data analysis of voltammetric responses has usually been done through application of the fast Fourier transform although it is widely accepted that electrochemical signals are intrinsically nonlinear and nonstationary. In this work, we present a time-series analysis based on the Hilbert transform (HT), a nonstationary signal processing technique, as an alternative tool that can overcome many of the difficulties associated with Fourier techniques. We use the HT to study the behavior of thin-film processes when the excitation perturbation is ac voltammetry. From the analysis of simulated data, we propose simple relations that enable species-specific kinetic and thermodynamic parameters to be estimated, without prior utilization of baseline subtraction even when double layer capacitance significantly influences the current response. We also propose a method to determine whether the characteristics of the applied voltage perturbation are adequate for the accurate estimation of these parameters. The methodology developed here will be applied to previously published experimental time series data (Guo, S. X.; Zhang, J.; Elton, D. M.; Bond, A. M. Anal. Chem. 2004, 76, 166-177.) obtained with ac voltammetry to show how a number of physical parameters can be directly extracted from the processed data. PMID:15889929

Anastassiou, Costas A; Parker, Kim H; O'Hare, Danny

2005-05-15

283

Comparison of static and dynamic respirometry for the determination of stoichiometric and kinetic parameters of a nitrifying process.  

PubMed

Respirometry consists in the measurement of the biological oxygen consumption rate under well-defined conditions and has been used for the characterization of countless biological processes. In the field of biotechnology and applied microbiology, several respirometry methods are commonly used for the determination of process parameters. Dynamic and static respirometry, which are based on oxygen measurements with or without continuous aeration, respectively, are the methods most commonly used. Additionally to several respirometry methods, different methods have also been developed to retrieve process parameters from respirometric data. Among them, methods based on model fitting and methods based on the injection of substrate pulse at increasing concentration are commonly used. An important question is then; what respirometry and data interpretation methods should be preferably used? So far, and despite a growing interest for respirometry, relatively little attention has been paid on the comparison between the different methods available. In this work, both static and dynamic respirometry methods and both interpretation methods; model fitting and pulses of increasing concentration, were compared to characterize an autotrophic nitrification process. A total of 60 respirometry experiments were done and exhaustively analysed, including sensitivity and error analyses. According to the results obtained, the substrate affinity constant (K S ) was better determined by static respirometry with pulses of increasing concentration and the maximum oxygen uptake rate (OUR ex.max ) was better determined by dynamic respirometry coupled to fitting procedure. The best method for combined K S and OUR ex.max determination was static respirometry with pulses of increasing concentration. PMID:23255019

Ramirez-Vargas, R; Ordaz, A; Carrión, M; Hernández-Paniagua, I Y; Thalasso, F

2013-09-01

284

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

PubMed

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

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

2014-02-01

285

Kinetic model for the oxidative chlorination of ethane yielding vinyl chloride. III. Formation and transformation of 1,1-dichloroethane and 1,1,2-trichloroethane  

SciTech Connect

A study was carried out on the oxidative chlorination of 1,1-dichloroethane at 350-450/sup 0/C and of 1,1,2-trichloroethane at 375-450/sup 0/C on an aged CuCl/sub 2/-KCl catalyst. The rates of transformation of both these chloroethanes is proportional to their partial pressures. In addition, the rate of transformation of 1,1,2-trichloroethane depends on the partial pressure of chlorine to the 0.5 power. Vinyl chloride is formed in the oxidative chlorination of ethane from 1,1- and 1,2-dichloroethanes. The single pathway for the reaction of vinyl chloride is its additive chlorination to yield 1,1,2-trichloroethane. The results obtained were used to describe the transformations of ethyl chloride to yield ethylene and dichloroethanes. 3 figures, 4 tables.

Gel'perin, E.I.; Bakshi, Yu.M.; Avetisov, A.K.; Gel'bshtein, A.I.

1983-05-01

286

Toward full-chip prediction of yield-limiting contact patterning failure: correlation of simulated image parameters to advanced contact metrology metrics  

NASA Astrophysics Data System (ADS)

Electrical failure due to incomplete contacts or vias has arisen as one of the primary modes of yield loss for 130 nm and below designs in manufacturing. Such failures are generally understood to arise from both random and systematic sources. The addition of redundant vias, where possible, has long been an accepted DFM practice for mitigating the impact of random defects. Incomplete vias are often characterized by having a diameter near the target dimension but a depth of less than 100% of target. As such, it is a difficult problem to diagnose and debug in-line, since bright and dark field optical inspection systems cannot typically distinguish between a closed, partially open and fully open contact. Advanced metrology systems have emerged in recent years to meet this challenge, but no perfect manufacturing solution has yet been identified for full field verification of all contacts. Voltage Contrast (VC) SEM metrology biases the wafer to directly measure electrical conductivity after fill / polish, and can therefore easily discern a lack of electrical connection to the underlying conductor caused by incomplete photo, etch, or fill processing. While an entire wafer can in principal be VC scanned, throughput limitations dictate very sparse sampling in manufacturing. SEM profile grading (PG) leverages the rich content of the secondary electron waveform to decipher information about the bottom of the contact. Several authors have demonstrated an excellent response of the Profile Grade to intentional defocus vectors. However, the SEM can only target discreet or single digit groupings of contacts, and therefore requires intelligent guidance to identify those contacts which are most prone to failure, enabling protection of the fab WIP. An a-priori knowledge of which specific contacts in a layout are most likely to fail would prove very useful for proactive inspection in manufacturing. Model based pre-manufacturing verification allows for such knowledge to be communicated to manufacturing. This paper will focus on 130 nm node contact patterning, and will correlate SEM Profile Grade output to the extensive suite of model-based image tags from the Calibre TM opc-verification engine. With an understanding of which image parameters are most highly correlated to the occurrence of incomplete contact formation for a given process, the process model can be used to automatically direct inspection metrology to those layout instances that pose the highest risk of patterning failure through the lithographic process window. Such an approach maximizes the value content of in-line metrology.

Sturtevant, John L.; Chou, Dyiann

2006-04-01

287

Characterization of sialidase from an influenza A (H3N2) virus strain: kinetic parameters and substrate specificity.  

PubMed

Neuraminidase (NA) of influenza A (H3N2) viruses was characterized after purification by gel filtration and proteolytic treatment, using the X-31 variant strain that is a reassortment between the influenza A/Victoria/3/75 (responsible for the 1975 pandemic) and the influenza A/PR/8/34 virus samples, as a model. In the purification process, NA heads, that is the spike responsible for the virus sialidase activity, were purified by filtration through a Bio-Gel polyacrylamide column. The enzyme activity was determined by periodic acid/thiobarbituric acid assay and high-performance thin-layer chromatography. The sialidase showed preference for the alpha-2,3-linkage over the alpha-2,6-linkage of sialyllactoses (K(m) of 1.8 and 5.2 x 10(-4)M, respectively) at pH 5.2. The enzyme acted on natural and synthetic substrates at different hydrolysis rates, as well as on human erythrocytes (A group, Rh+) and yeast (CANDIDA ALBICANS) cells. The active NA produced by gel filtration was characterized by different parameters of its sialidase activity, also showing to be a suitable tool for the identification of natural sialocompounds and for the screening of antisialidase drugs to treat influenza virus infections. PMID:12931027

França de Barros, José; Sales Alviano, Daniela; da Silva, Maria Helena; Dutra Wigg, Marcia; Sales Alviano, Celuta; Schauer, Roland; dos Santos Silva Couceiro, José Nelson

2003-01-01

288

Analysis of Kinetic and Operational Parameters in a Structured Model for Acrylic Acid Production through Experimental Design  

NASA Astrophysics Data System (ADS)

In biotechnological processes, a great number of factors can influence the income productivity and conversion. Normally, it is not evident which of these factors are the most important and how they interact. In this work, multivariate analysis techniques are used as experimental design coupled to a detailed deterministic model to identify the parameters with the most significant impact on the model to represent well the acrylic acid production process. It is proposed as an alternative process, having sugarcane as feedstock, to the petrochemical-based ones that have significant environmental impacts for their production. To increase the competitiveness of renewable acrylic-acid-based process, it is necessary to find out working conditions near the optimal region, which is not an easy task, as the process is multivariable and non-linear. The mapping of the dynamics of the developed process is made using techniques of factorial design together with the methodology of Plackett-Burman. It is shown that it is possible to increase the process performance by choosing optimized conditions for the reactor operation.

Lunelli, B. H.; Rivera, E. C.; Vasco de Toledo, E. C.; Maciel, M. R. Wolf; Filho, R. Maciel

289

Analysis of kinetic and operational parameters in a structured model for acrylic acid production through experimental design.  

PubMed

In biotechnological processes, a great number of factors can influence the income productivity and conversion. Normally, it is not evident which of these factors are the most important and how they interact. In this work, multivariate analysis techniques are used as experimental design coupled to a detailed deterministic model to identify the parameters with the most significant impact on the model to represent well the acrylic acid production process. It is proposed as an alternative process, having sugarcane as feedstock, to the petrochemical-based ones that have significant environmental impacts for their production. To increase the competitiveness of renewable acrylic-acid-based process, it is necessary to find out working conditions near the optimal region, which is not an easy task, as the process is multivariable and non-linear. The mapping of the dynamics of the developed process is made using techniques of factorial design together with the methodology of Plackett-Burman. It is shown that it is possible to increase the process performance by choosing optimized conditions for the reactor operation. PMID:18418750

Lunelli, B H; Rivera, E C; Vasco de Toledo, E C; Wolf Maciel, M R; Maciel Filho, R

2008-03-01

290

Proteolysis of prothrombin by thrombin. Determination of kinetic parameters, and demonstration and characterization of an unusual inhibition by Ca2+ ions.  

PubMed

A discontinuous assay to measure the proteolysis of tritiated prothrombin to fragment 1 and prethrombin 1 by thrombin has been devised, based empirically on extracting the radiolabeled fragment 1 into 4% p-toluenesulfonic acid. The assay is shown to be valid for the measurement of the initial rate of reaction in simple mixtures and has been used to determine the Michaelis-Menten parameters. The Km, 127 microgram of prothrombin per ml, and the kcat, 6.9 s(-1), indicate that, in the absence of other controls, attack of thrombin on prothrombin would be overwhelming during coagulation in plasma and that the prothrombin concentration would be rate-limiting. However, Ca2+ ions at concentrations around 1 mM reduce the rate of proteolysis by at least 20-fold. This inhibition is rapidly reversible by the addition of chelating agents. Measurement of initial rates at Ca2+ concentrations up to 1.5 mM shows that the inhibition is multisite and perhaps involves cooperative binding of the metal ions. The effect of Ca2+ on the kinetic parameters has also been investigated. kcat could not be measured because thrombin could not be saturated with prothrombin under conditions amenable to assay, but the Km is increased, showing that the inhibition by Ca2+ is at least partially competitive. An independent qualitative demonstration that Ca2+ is inhibitory in the reaction of native prothrombin with thrombin has been obtained by measurement of intrinsic fluorescence. PMID:758328

Silverberg, S A

1979-01-10

291

Measurement of the slope parameter {alpha} for the {eta}{yields}3{pi}{sup 0} decay with the Crystal Ball detector at the Mainz Microtron (MAMI-C)  

SciTech Connect

The dynamics of the {eta}{yields}3{pi}{sup 0} decay have been studied with the Crystal Ball multiphoton spectrometer and the TAPS calorimeter. Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz microtron MAMI-C and tagged by the Glasgow photon spectrometer were used for {eta}-meson production. The analysis of 3x10{sup 6} {gamma}p{yields}{eta}p{yields}3{pi}{sup 0}p{yields}6{gamma}p events yields the value {alpha}=-0.032{+-}0.003 for the {eta}{yields}3{pi}{sup 0} slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The {pi}{sup 0}{pi}{sup 0} invariant-mass spectrum was investigated for the occurrence of a cusplike structure in the vicinity of the {pi}{sup +}{pi}{sup -} threshold. The observed effect is small and does not affect our measured value for the slope parameter.

Prakhov, S.; Nefkens, B. M. K.; Brudvik, J.; Starostin, A.; Suarez, I. M. [University of California Los Angeles, Los Angeles, California 90095-1547 (United States); Aguar-Bartolome, P.; Akasoy, L. K.; Arends, H. J.; Jahn, O.; Krambrich, D.; Martinez, M.; Ostrick, M.; Otte, P. B.; Rost, M.; Thomas, A. [Institute fuer Kernphysik, University of Mainz, D-55099 Mainz (Germany); Annand, J. R. M.; Codling, R. F. B.; Kellie, J. D.; Livingston, K.; MacGregor, I. J. D. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)] (and others)

2009-03-15

292

The effect of temperature on the kinetics of ethanol production by strains of Zymomonas mobilis  

Microsoft Academic Search

Two strains of Z. mobilis were evaluated for temperature sensitivity between 25°C and 40°C. At higher temperatures the cell viability, biomass yield, ethanol yield and final ethanol concentration decreased, and there was evidence of increased ethanol inhibition. However the kinetic parameters µ, qs and qp were largely unaffected by temperature over this range.

K. J. Lee; M. L. Skotnicki; D. E. Tribe; P. L. Rogers

1981-01-01

293

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

PubMed

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

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

2014-04-21

294

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

295

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

SciTech Connect

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

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

2005-05-01

296

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

PubMed

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

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

2012-08-01

297

/sup 15/N tracer kinetic studies on the validity of various /sup 15/N tracer substances for determining whole-body protein parameters in very small preterm infants  

SciTech Connect

Reliable /sup 15/N tracer substances for tracer kinetic determination of whole-body protein parameters in very small preterm infants are still a matter of intensive research, especially after some doubts have been raised about the validity of (/sup 15/N)glycine, a commonly used /sup 15/N tracer. Protein turnover, synthesis, breakdown, and further protein metabolism data were determined by a paired comparison in four preterm infants. Their post-conceptual age was 32.2 +/- 0.8 weeks, and their body weight was 1670 +/- 181 g. Tracer substances applied in this study were a (/sup 15/N)amino acid mixture (Ia) and (/sup 15/N)glycine (Ib). In a second group of three infants with a post conceptual age of /sup 15/N-labeled 32.0 +/- 1.0 weeks and a body weight of 1,907 +/- 137 g, yeast protein hydrolysate (II) was used as a tracer substance. A three-pool model was employed for the analysis of the data. This model takes into account renal and fecal /sup 15/N losses after a single /sup 15/N pulse. Protein turnovers were as follows: 11.9 +/- 3.1 g kg-1 d-1 (Ia), 16.2 +/- 2.5 g kg-1 d-1 (Ib), and 10.8 +/- 3.0 g kg-1 d-1 (II). We were able to demonstrate an overestimation of the protein turnover when Ib was used. There was an expected correspondence in the results obtained from Ia and II. The /sup 15/N-labeled yeast protein hydrolysate is a relatively cheap tracer that allows reliable determination of whole-body protein parameters in very small preterm infants.

Plath, C.; Heine, W.; Wutzke, K.D.; Krienke, L.; Toewe, J.M.; Massute, G.; Windischmann, C.

1987-05-01

298

Kinetic and safety parameters analysis for 1,1,-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane in isothermal and non-isothermal conditions.  

PubMed

Over the past 30 years, the field of thermal analysis of organic peroxides has become an important issue in chemical engineering departments, safety departments, and in companies working with polymerization, petrifaction process, and so on. The contributions of thermal analysis to the evaluation and prediction of the runaway reactions have been important for decreasing or preventing a hazard, such as fire or explosion accident. This study was carried out using differential scanning calorimetry (DSC) to evaluate the kinetic and safety parameters in isothermal and non-isothermal conditions, for instance, temperature of no return (T(NR)), self accelerating decomposition temperature (SADT), time to maximum rate (TMR), activation energy (E(a)), frequency factor (A), reaction order (n), and reaction heat (?H), in terms of the hazardous material of 1,1,-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane (TMCH) 88 mass%. On the basis of this study, we demonstrated that TMCH 88 mass% must be well controlled in the manufacturing process due to the unstable structure of O-O, which releases a great quantity of heat, higher than 1300 J/g under decomposition. Results of this study could contribute to the relevant plants adopting TMCH 88mass% in a process, in order to prevent a fire or explosion accident from happening. PMID:21784576

Tseng, Jo-Ming; Lin, Chun-Ping; Huang, Sheng-Tien; Hsu, Johnson

2011-09-15

299

The effect 3,5,3'-triiodo-L-thyronine on the kinetic parameters of sugar transport in cultured chick embryo heart cells.  

PubMed

The effect of 3,5,3'-triiodo-L-thyronine (T3; 10(-8)M) on sugar transport was studied in cultured chick embryo heart cells. T3 did not increase the uptake of L-glucose, a sugar which enters the cell by simple diffusion. The effect of T3 on the kinetic parameters of the uptake of both 3-0-methyl-D-glucose (3-OMET) and 2-deoxy-D-glucose (2-DOG) was studied after 6 and 24 h exposure to T3. T3 had no effect on the Km for either sugar. T3 increased the Vmax for the first 6 h or exposure for 3-OMET, a sugar which is only transported, and increased the Vmax after 6 and 24 h for 2-DOG, a sugar both transported and phosphorylated. T3 also increased the relative phosphorylation of 2-DOG within the cells in the period between 6 and 24 h. The data show a biphasic effect of T3 on sugar accumulation, an early effect on transport along and a later effect on phosphorylation as well. PMID:562257

Segal, J; Gordon, A

1977-11-01

300

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

PubMed

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

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

2008-06-01

301

[Kinetic parameters of hydrolysis of CpA and UpA sequences in an oligoribonucleotide by compounds functionally mimicking ribonuclease A].  

PubMed

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. PMID:12500546

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

302

n-Alkanes on MgO(100). II. Chain Length Dependence of Kinetic Desorption Parameters for Small n-Alkanes  

SciTech Connect

Coverage-dependent desorption kinetics parameters are obtained from high quality temperature programmed desorption (TPD) data for seven small n-alkane molecules on MgO(100). The molecules, CNH2N+2 (N = 1-4, 6, 8, 10), were each studied for a set of 29 initial coverages at a heating ramp rate of 0.6 K/s as well as at a set of nine ramp rates in the range 0.3 to 10.0 K/s. The inversion analysis method with its least-squares prefactor optimization discussed in the accompanying article is applied to these data. This method allows for accurate determination of prefactors and coverage-dependent desorption energies. The pre-exponential factor for desorption increases dramatically with chain length from 1013.1 to 1019.1 s-1 over the range N = 1-10. We show that this increase can be physically justified by considering the increase in rotational entropy available to the molecules in the gas-like transition state for desorption. The desorption energy increases with chain length as Ed(N) = 6.5 + 7.1 N, which implies an incremental increase of 7.1?0.2 kJ/mol per CH2.

Tait, Steven L.; Dohnalek, Zdenek; Campbell, C T.; Kay, Bruce D.

2005-04-22

303

Grease Yields.  

National Technical Information Service (NTIS)

The invention is directed to lubricating grease compositions, more particularly to the use of certain agents to improve the yield of calcium base greases. The yields of grease compositions are increased by incorporating therein an oil-soluble polyglycol p...

D. W. Criddle

1965-01-01

304

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

PubMed Central

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 125I-labeled EGF decreased as the injected amount of unlabeled EGF increased; (ii) the ratio plot [ln (inulin/EGF) versus time] of the dilution curve for EGF exhibited an upward straight line initially for a short period of time (approximately equal to 10 sec), whereas the ratio plot [ln (inulin/somatostatin) versus time] 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. Thus, analysis of dilution curves can reveal whether or not the cell surface has receptors for certain peptides. In addition, the dilution curves for EGF at various doses (tracer approximately equal to 30 micrograms) were analyzed simultaneously based on a kinetic model incorporating the perfusion rate, the association rate constant of EGF to surface receptors (kappa on), the dissociation rate constant of EGF from the EGF-receptor complex (kappa off), and the sequestration rate constant of the complex. The kinetic parameters [the dissociation constant (Kd = kappa off/kappa on) and the number of surface receptors] calculated by this analysis were comparable with reported values obtained by in vitro direct binding measurements at equilibrium using liver homogenates. We conclude that the multiple-indicator dilution method is a good tool for analyzing the dynamics of peptide hormones--cell-surface receptor interaction under a condition in which spatial architecture of the liver is maintained.

Sato, H; Sugiyama, Y; Sawada, Y; Iga, T; Sakamoto, S; Fuwa, T; Hanano, M

1988-01-01

305

Sediment Loads and Yield, and Selected Water-Quality Parameters in Clear Creek, Carson City and Douglas County, Nevada, Water Years 2004-07  

USGS Publications Warehouse

Some reaches of Clear Creek above U.S. Highway 395 have experienced severe erosion as a result of fires, extreme precipitation events, and past and current human activities in the basin. Previous evaluations of erosion in the basin have concluded that most of the sediment produced and transported in the basin was associated with U.S. Highway 50, a four-lane highway that roughly parallels Clear Creek through much of the basin. During this study (water years 2004-07), construction of roads and a large residential area and golf course in the area began and are likely to affect water quality and sediment transport in the basin. Sediment data were collected between October 2003 and September 2007 (water years 2004-07) from three sites along Clear Creek. Annual suspended-sediment load was estimated to range from 1,456 tons in water year 2006 to only 100 tons in water year 2004, which corresponds to suspended-sediment yields of 93.9 tons per square mile per year in 2006 to 6.4 tons per square mile per year in 2004. In water year 2006, the suspended-sediment load on December 31, 2005, alone exceeded the combined annual load for water years 2004, 2005, and 2007. Bedload sediment was estimated to comprise 73 percent of total sediment load in the creek. Mean annual suspended-sediment yield in Clear Creek basin was much greater than yields in the Logan House, Edgewood, and Glenbrook Creek basins in the adjacent Lake Tahoe basin. Comparison of data collected during this study with data collected by university researchers in the 1970s is inconclusive as to whether fundamental changes in basin sediment characteristics have occurred during the 30-year period because different methods and sampling locations were used in the earlier studies.

Seiler, Ralph L.; Wood, James L.

2009-01-01

306

Complete steady-state rate equation for DNA ligase and its use for measuring product kinetic parameters of NAD+-dependent DNA ligase from Haemophilus influenzae  

PubMed Central

Background DNA ligase seals the nicks in the phosphodiester backbone between Okazaki fragments during DNA replication. DNA ligase has an unusual Bi Ter Ping Pong kinetic mechanism. Its substrates in eubacteria are NAD+ and nicked DNA (nDNA). Its products are nicotinamide mononucleotide (NMN), adenosine 5?-monophosphate (AMP), and sealed DNA. Investigation of the kinetic mechanism and measurement of the kinetic constants of DNA ligase using steady-state kinetics would benefit from the availability of the complete steady-state rate equation, including terms for product concentrations and product-related kinetic constants, which has not previously been published. Results The rate equations for two possible Bi Ter kinetic mechanisms for DNA ligase, including products, are reported. The mechanisms differ according to whether the last two products, AMP and sealed DNA, are released in an ordered or rapid-equilibrium random (RER) manner. Steady-state kinetic studies of product inhibition by NMN and AMP were performed with Haemophilus influenzae NAD+-dependent DNA ligase. The complete rate equation enabled measurement of dissociation constants for NAD+, NMN, and AMP and eliminated one of 3 possible product release mechanisms. Conclusions Steady-state kinetic product inhibition experiments and complete steady-state kinetic rate equations were used to measure dissociation constants of NAD+, NMN, and AMP and eliminate the possibility that AMP is the second product released in an ordered mechanism. Determining by steady-state kinetics whether the release of sealed DNA and AMP products goes by an ordered (AMP last off) or RER mechanism was shown to require a product inhibition study using sealed DNA.

2014-01-01

307

A study of the spray injection Reynolds number effects on gasoline yields of an FCC riser reactor  

SciTech Connect

A computational analysis of the combined effects of feed oil injection parameters in a commercial-scale fluidized catalytic cracking riser reactor was performed using a three-phase, multiple species kinetic cracking computer code. The analysis showed that the injection operating parameters (droplet diameter and injection velocity) had strong impacts on the gasoline yields of the FCC unit. A spray injection Reynolds number combining the two parameters was defined. A correlation between the spray injection Reynolds number and the gasoline product yields for various feed injection conditions was developed. A range of spray injection Reynolds number for the maximum gasoline yield was identified.

Bowman, B. J.; Zhou, C. Q.; Chang, S. L.; Lottes, S. A.

2000-04-03

308

Effect of the cold-rolling parameters and the yield strength of the strip material on the friction stresses in a deformation zone  

NASA Astrophysics Data System (ADS)

The reliability of the methods of determining the friction coefficient is analyzed, since the friction stresses in the deformation zone during cold rolling significantly affect the quality of cold-rolled sheets and the energy consumption. The well-known experimental data and empirical dependences are shown to contradict each other, and the statistical assurance of these dependences is absent. A database on the interrelated technological and energy-force parameters of a five-stand cold-rolling mill, which includes a wide range of steel grades and strip sizes and shapes, is analyzed. Regression analysis is used to obtain a statistically reliable regression dependence of the friction coefficient in the deformation zone on the most significant technological parameters. The application of this dependence decreases the error of energy-force calculations by more than two times.

Garber, E. A.; Yagudin, I. V.; Ermilov, V. V.; Traino, A. I.

2009-10-01

309

Chlorophyll Fluorescence Parameters: The Definitions, Photosynthetic Meaning, and Mutual Relationships  

Microsoft Academic Search

Chlorophyll fluorescence parameters (Chl FPs) derived from the slow (long-term) induction kinetics of modulated Chl a fluorescence are reviewed and analysed with respect to their application in photosynthesis research. Only four mutually independent Chl FPs, calculated from values of five essential Chl fluorescence (ChlF) yields, are distinguished as the basic ones. These are: the maximum quantum yield of PS2 photochemistry

K. Rohá?ek

2002-01-01

310

Kinetic investigation of wood pyrolysis  

SciTech Connect

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.

Thurner, F.; Mann, U.; Beck, S. R.

1980-06-01

311

Kinetics of ethanol production from sugarcane bagasse enzymatic hydrolysate concentrated with molasses under cell recycle.  

PubMed

In this work, a kinetic model for ethanol fermentation from sugarcane bagasse enzymatic hydrolysate concentrated with molasses was developed. A model previously developed for fermentation of pure molasses was modified by the inclusion of a new term for acetic acid inhibition on microorganism growth rate and the kinetic parameters were estimated as functions of temperature. The influence of the hydrolysate on the kinetic parameters is analyzed by comparing with the parameters from fermentation of pure molasses. The impact of cells recycling in the kinetic parameters is also evaluated, as well as on the ethanol yield and productivity. The model developed described accurately most of the fermentations performed in several successive batches for temperatures from 30 to 38°C. PMID:23313680

de Andrade, Rafael Ramos; Maugeri Filho, Francisco; Maciel Filho, Rubens; da Costa, Aline Carvalho

2013-02-01

312

Measurement of D{sup 0}-D{sup 0} Mixing Parameters Using D{sup 0}{yields}K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and D{sup 0}{yields}K{sub S}{sup 0}K{sup +}K{sup -} Decays  

SciTech Connect

We report a direct measurement of D{sup 0}-D{sup 0} mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D{sup 0}{yields}K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and, for the first time, D{sup 0}{yields}K{sub S}{sup 0}K{sup +}K{sup -} decays. The low-momentum pion {pi}{sub s}{sup +} in the decay D{sup *+{yields}}D{sup 0{pi}}{sub s}{sup +} identifies the flavor of the neutral D meson at its production. Using 468.5 fb{sup -1} of e{sup +}e{sup -} colliding-beam data recorded near {radical}(s)=10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x=[1.6{+-}2.3(stat){+-}1.2(syst){+-}0.8(model)]x10{sup -3}, and y=[5.7{+-}2.0(stat){+-}1.3(syst){+-}0.7(model)]x10{sup -3}. These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing.

Amo Sanchez, P. del; Lees, J. P.; Poireau, V.; Prencipe, E.; Tisserand, V. [Laboratoire d'Annecy-le-Vieux de Physique des Particules (LAPP), Universite de Savoie, CNRS/IN2P3, F-74941 Annecy-Le-Vieux (France); Garra Tico, J.; Grauges, E. [Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona (Spain); Martinelli, M.; Palano, A.; Pappagallo, M. [INFN Sezione di Bari, I-70126 Bari (Italy); Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); Eigen, G.; Stugu, B.; Sun, L. [University of Bergen, Institute of Physics, N-5007 Bergen (Norway); Battaglia, M.; Brown, D. N.; Hooberman, B.; Kerth, L. T.; Kolomensky, Yu. G.; Lynch, G.; Osipenkov, I. L. [Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720 (United States)

2010-08-20

313

Measuring Epoxy-Curing Kinetics  

NASA Technical Reports Server (NTRS)

Key reaction parameters estimated from single run. Single DSC Curve used to construct linearized plot from which kinetic reaction parameters are obtained: vertical axis intercept proportional to activation energy, while slope equals reaction order. DSC methods show promise for rapid screening and estimation of cure kinetic parameters of epoxy resins.

Cizmecioglu, M.

1983-01-01

314

Growth kinetics of thermophilic Methanosarcina spp. isolated from full-scale biogas plants treating animal manures  

Microsoft Academic Search

This study determines the growth kinetics of thermophilic strains of Methanosarcina spp. from full-scale thermophilic biogas plants. The complete set of kinetic parameters, including maximum specific growth rate ?max, half saturation constant KS, acetate threshold concentration and cell growth yield YX\\/S, were determined for six Methanosarcina strains newly isolated from full-scale reactors and the type strain Methanosarcina thermophila TM-1T. The

Zuzana Mladenovska; Birgitte Kiær Ahring

2000-01-01

315

Cell Biology: Cell Kinetics.  

National Technical Information Service (NTIS)

Within the purview of cell kinetics are all studies relating to the characterization and measurement of cell cycle parameters, particularly for in vivo studies of normal and tumor cells, and in vitro studies of derived cell lines. Methodologies for measur...

1979-01-01

316

Cell Biology: Cell Kinetics.  

National Technical Information Service (NTIS)

Within the purview of cell kinetics are all studies relating to the characterization and measurement of cell cycle parameters, particularly for in vivo studies of normal and tumor cells, and in vitro studies of derived cell lines. Methodologies for measur...

1984-01-01

317

Cell Biology: Cell Kinetics.  

National Technical Information Service (NTIS)

Within the purview of cell kinetics are all studies relating to the characterization and measurement of cell cycle parameters, particularly for in vivo studies of normal and tumor cells, and in vitro studies of derived cell lines. Methodologies for measur...

1982-01-01

318

Cell Biology: Cell Kinetics.  

National Technical Information Service (NTIS)

Within the purview of cell kinetics are all studies relating to the characterization and measurement of cell cycle parameters, particularly for in vivo studies of normal and tumor cells, and in vitro studies of derived cell lines. Methodologies for measur...

1980-01-01

319

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

PubMed

Pulsed ArF excimer laser (193 nm)-CW infrared (IR) tunable diode laser Herriott type absorption spectroscopic technique has been made for the detection of product hydrochloric acid HCl. Absorption spectroscopic technique is used in the reaction chlorine atoms with methyl iodide (Cl+CH3I) to the study of kinetics on reaction Cl+CH3I and the yield of (HCl). The reaction of Cl+CH3I has been studied with the support of the reaction Cl+C4H10 (100% HCl) at temperature 298 K. In the reaction Cl+CH3I, the total pressure of He between 20 and 125 Torr at the constant concentration of [CH3I] 7.0×10(14) molecule cm(-3). In the present work, we estimated adduct formation is very important in the reaction Cl+CH3I and reversible processes as well and CH3I molecule photo-dissociated in the methyl [CH3] radical. The secondary chemistry has been studied as CH3+CH3ICl = product, and CH3I+CH3ICl = product2. The system has been modeled theoretically for secondary chemistry in the present work. The calculated and experimentally HCl yield nearly 65% at the concentration 1.00×10(14) molecule cm(-3) of [CH3I] and 24% at the concentration 4.0×10(15) molecule cm(-3) of [CH3I], at constant concentration 4.85×10(12) molecule cm(-3) of [CH3], and at 7.3×10(12) molecule cm(-3) of [Cl]. The pressure dependent also studied product of HCl at the constant [CH3], [Cl] and [CH3I]. The experimental results are also very good matching with the modelling work at the reaction CH3+CH3ICl = product (k = (2.75±0.35)×10(-10) s(-1)) and CH3I+CH3ICl = product2 (k = 1.90±0.15)×10(-12) s(-1). The rate coefficients of the reaction CH3+CH3ICl and CH3I+CH3ICl has been made in the present work. The experimental results has been studied by two method (1) phase locked and (2) burst mode. PMID:24667422

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

2014-07-15

320

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

321

Kinetics of acrylamide formation and elimination during heating of an asparagine-sugar model system.  

PubMed

The kinetics of acrylamide (AA) was analyzed by heating a simple model system consisting of asparagine and glucose, fructose, or sucrose (0.01 M, pH 6) at temperatures between 140 and 200 degrees C. The AA concentration appeared to be the net result of simultaneous formation and elimination. A general kinetic model describing the AA yield was identified, and kinetic parameters were obtained by nonlinear regression on the nonisothermally derived data. On the basis of kinetic parameters, the AA formation appeared to proceed faster and to be more temperature sensitive in the asparagine-glucose than in the asparagine-fructose model system. The AA elimination kinetics, on the other hand, was similar. Significantly less AA was formed in the asparagine-sucrose model system as compared to the model systems with glucose or fructose. PMID:16366686

Claeys, Wendie L; De Vleeschouwer, Kristel; Hendrickx, Marc E

2005-12-28

322

Measurement of Time-Dependent CP-Violating Parameters in B{sup 0}{yields}K{sub S}{sup 0}K{sub S}{sup 0} Decays  

SciTech Connect

We report a measurement of the CP-violating parameters in B{sup 0}{yields}K{sub S}{sup 0}K{sub S}{sup 0} decays based on a data sample of 657x10{sup 6} BB pairs collected at the {upsilon}(4S) resonance with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. In this Letter, one neutral B meson is fully reconstructed in the B{sup 0}{yields}K{sub S}{sup 0}K{sub S}{sup 0} decay mode, and the flavor of the accompanying B meson is identified by its decay products. The CP-violating parameters are measured from the asymmetry in the distributions of the proper-time interval between the two B decays: S{sub K{sub S}{sup 0}}{sub K{sub S}{sup 0}}=-0.38{sub -0.77}{sup +0.69}(stat){+-}0.09(syst) and A{sub K{sub S}{sup 0}}{sub K{sub S}{sup 0}}=-0.38{+-}0.38(stat){+-}0.05(syst)

Nakahama, Y.; Aihara, H.; Iwasaki, M. [Department of Physics, University of Tokyo, Tokyo (Japan); Sumisawa, K.; Adachi, I.; Haba, J.; Hazumi, M.; Itoh, R.; Iwasaki, Y.; Katayama, N.; Kichimi, H.; Krokovny, P.; Nakao, M.; Nishida, S.; Nozaki, T.; Ozaki, H.; Sakai, Y.; Tajima, O.; Takasaki, F.; Tanaka, M. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (and others)

2008-03-28

323

Kinetic and electromagnetic effects in technical plasmas  

NASA Astrophysics Data System (ADS)

There is an accumulating body of evidence that kinetic effects play a significant role in practically all kinds of technical plasmas. Such plasmas often exhibit several groups of electrons with disparate energies, where electrons from different groups exchange energy only through weak processes. The intrinsically non-Maxwellian charachter of the electron distribution function in this case invalidates the fluid-based approaches for description of the technical plasmas. Rather, a self-consistent kinetic treatment is frequently needed for capturing all the important physics features, whereas fluid models under such conditions can yield quantitatively or even qualitatively erroneous results. Despite this, the fluid-based numerical codes remain a popular tool for investigation of the technical plasmas due to the low computational cost of such codes compared to that of the kinetic ones. The proper description of technical plasmas becomes further complicated if in addition to the kinetic treatment one needs to consider electromagnetic effects, which gain in significance as the electrode size and driving frequency increase, which continues to be the tendency in many CCP industrial plasmas usually described under the electrostatic approximation. In this talk we discuss modern techniques of parallelization of self-consistent kinetic particle-in-cell/Monte-Carlo (PIC/MCC) numerical codes on graphics cards (GPUs), which make kinetic simulations a routine numerical tool for investigation of technical plasmas. Then, we will demonstrate for the plasmas spanning broad parameter range examples of simulations made with such codes, where kinetic effects are important and thus the fluid description is inadequate. Finally, we argue that in many situations the electromagnetic effects relevant to the technical plasmas can be described in the framework of Darwin (magneto-inductive) approximation, which can be implemented as a natural modification in an electrostatic PIC/MCC code, as all the field equations are elliptic. We give the examples of kinetic simulations with electromagnetic effects obtained with such Darwin code.

Eremin, Denis

2012-10-01

324

Erbium hydride thermal desorption : controlling kinetics.  

SciTech Connect

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

Ferrizz, Robert Matthew

2007-08-01

325

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

SciTech Connect

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

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

2007-09-28

326

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

SciTech Connect

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

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

2009-02-15

327

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

328

Modelling and dynamic simulation of a pilot-scale moving bed bioreactor for the treatment of municipal wastewater: model concepts and the use of respirometry for the estimation of kinetic parameters.  

PubMed

A model for the simulation of a moving bed bioreactor (MBBR) used for the treatment of municipal wastewater is proposed. The model includes attachment of particulates to the biofilm and detachment of biofilm into the bulk liquid. The growth kinetics are modelled with the activated sludge model no. 1 (ASM1). Respirometry was used for the estimation of kinetic parameters. The resulting respirograms featured the typical endogenous and exogenous respiration phases and the respirogram shapes were as expected from analogous respirometry with activated sludge. The estimated parameter set was used for modelling and simulation of the pilot-scale MBBR. The main proportion of biomass in the MBBR was found to be attached as biofilm on the carrier elements (4.1 -4.6 g dm-3) and only a small amount was suspended in the bulk liquid (0.15gdm(-3)). Attachment and detachment rates were estimated to be 4.8-7.5g m(-2) d(-1) 1for attachment and 6.5-7.5g m(-2) d(-1) for detachment. The biofilm age was estimated to be 1.8-2.7d. The model was used to predict effluent quality parameters and a good fit of the simulated data to the measured data originating from a four-days-long measurement campaign was obtained. PMID:17547000

Plattes, M; Fiorelli, D; Gillé, S; Girard, C; Henry, E; Minette, F; O'Nagy, O; Schosseler, P M

2007-01-01

329

Kinetics of Phosphate Ions Induced Invertase Synthesis by Saccharomyces cerevisiae  

Microsoft Academic Search

Invertase (?-fructofuranosidase) is a high cost enzyme. Aim of present study was to develop an economically feasible synthetic fermentation medium with appropriate supplemented nutrients. Saccharomyces cerevisiae GCB-K5 was used for investigation. Phosphate ions in fermentation medium greatly influence the invertase secretion capacity of yeast cells. By comparing the kinetic parameters, namely product yield coefficient (Yp\\/x, Yp\\/s in Amount of enzyme

KIRAN SHAFIQ; SIKANDER ALI

330

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

PubMed

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

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

2014-02-01

331

Evaluation and modeling of thermal kinetic degradation for PVA doped PbS quantum dot  

SciTech Connect

Highlights: {yields} Synthesis of PVA doped PbS quantum dots. {yields} Data fitting using integral and differential thermal kinetic models for calculating activation energy. {yields} Prediction of thermal degradation using iso-conversion model. -- Abstract: The kinetic analysis of the thermogravimetric curves for the thermal decomposition processes of PVA/PbS was performed. The samples were heated in nitrogen, with three different heating rates: 10, 20 and 30 {sup o}C min{sup -1}. Various forms of non-isothermal methods of analysis for determining the kinetic parameters were used. The differential and integral models were used to calculate the activation energies. Comparing with pure PVA, the results showed that the maximum activation energy of thermal degradation is achieved for PVA/PbS nanocomposite. Isoconversion model is used for predicting the thermal degradation acceleration. The results showed that the acceleration of thermal degradation for pure PVA was faster than PVA/PbS nanocomposite.

Mahmoud, Waleed E., E-mail: w_e_mahmoud@yahoo.com [King Abdul Aziz University, Faculty of Science, Physics Department, Jeddah (Saudi Arabia); Al-Heniti, S.H. [King Abdul Aziz University, Faculty of Science, Physics Department, Jeddah (Saudi Arabia)] [King Abdul Aziz University, Faculty of Science, Physics Department, Jeddah (Saudi Arabia)

2011-09-15

332

Advanced oxidation of the commercial nonionic surfactant octylphenol polyethoxylate Triton(TM) X-45 by the persulfate/UV-C process: effect of operating parameters and kinetic evaluation  

PubMed Central

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 ?M) 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 that the selectivity of SO·?4 was found to be significantly higher than that of HO·.

Arslan-Alaton, Idil; Olmez-Hanci, Tugba; Genc, Bora; Dursun, Duygu

2013-01-01

333

Advanced oxidation of the commercial nonionic surfactant octylphenol polyethoxylate Triton™ X-45 by the persulfate/UV-C process: effect of operating parameters and kinetic evaluation.  

PubMed

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 S2O(2-) 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 S2O(2-) 8 concentrations (?2.5 mM). S2O(2-) 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 S2O(2-) 8. On the other hand, TOC removal efficiencies dropped down to only 40% under the same reaction conditions. S2O(2-) 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 S2O(2-) 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 ?M) selected as the reference compound. The pseudo-first-order abatement rate coefficient obtained for OPPE during S2O(2-) 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 × 10(8) M(-1) s(-1) and 4.1 × 10(9) M(-1) s(-1), respectively. The kinetic study also revealed that the selectivity of SO(·-) 4 was found to be significantly higher than that of HO(·). PMID:24790933

Arslan-Alaton, Idil; Olmez-Hanci, Tugba; Genç, Bora; Dursun, Duygu

2013-01-01

334

Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants  

PubMed Central

Apart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fully-expanded leaf, half-way along the stem, in the transition zone between the autotrophic and heterotrophic part of the stem, and in the root axis. A top-to-bottom membrane potential gradient of sieve elements was observed along the stem (?130 mV to ?110 mV), while the membrane potential of the phloem parenchyma cells was stable (approx. ?100 mV). In roots, the membrane potential of sieve elements dropped abruptly to ?55 mV. Bathing solutions having various sucrose concentrations were administered and sucrose/H+-induced depolarizations were recorded. Data analysis by non-linear least-square data fittings as well as by linear Eadie–Hofstee (EH) -transformations pointed at biphasic Michaelis–Menten kinetics (2 MM, EH: Km1 1.2–1.8 mM, Km2 6.6–9.0 mM) of sucrose uptake by sieve elements. However, Akaike's Information Criterion (AIC) favored single MM kinetics. Using single MM as the best-fitting model, Km values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher Km values (EH: Km1 10 mM, Km2 70 mM) as compared to sieve elements were found. In preliminary patch-clamp experiments with sieve-element protoplasts, small sucrose-coupled proton currents (?0.1 to ?0.3 pA/pF) were detected in the whole-cell mode. In conclusion (a) Km values for sucrose uptake measured by electrophysiology are similar to those obtained with heterologous systems, (b) electrophysiology provides a useful tool for in situ determination of Km values, (c) As yet, it remains unclear if one or two uptake systems are involved in sucrose uptake by sieve elements, (d) Affinity for sucrose uptake by sieve elements exceeds by far that by phloem parenchyma cells, (e) Patch-clamp studies provide a feasible basis for quantification of sucrose uptake by single cells. The consequences of the findings for whole-plant carbohydrate partitioning are discussed.

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

2013-01-01

335

The ratio of the kinetic inductance to the geometric inductance: a key parameter for the frequency tuning of the THz semiconductor split-ring resonator.  

PubMed

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. PMID:24105581

Cong, Jiawei; Yun, Binfeng; Cui, Yiping

2013-08-26

336

Kinetics of the processes, plasma parameters, and output characteristics of a UV emitter operating on XeI molecules and iodine molecules and atoms  

SciTech Connect

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%.

Shuaibov, A. K.; Grabovaya, I. A.; Minya, A. I.; Homoki, Z. T. [Uzhgorod National University (Ukraine); Kalyuzhnaya, A. G.; Shchedrin, A. I. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine)

2011-03-15

337

Kinetic and Chemical Mechanism of Malate Synthase from Mycobacterium tuberculosis  

PubMed Central

Malate synthase catalyzes the Claisen-like condensation of acetyl-coenzyme A and glyoxylate in the glyoxylate shunt of the citric acid cycle. The Mycobacterium tuberculosis malate synthase G gene, glcB, was cloned, and the N-terminal His6 tagged 80 kDa protein was expressed in soluble form and purified by metal affinity chromatography. A chromogenic 4,4?-dithiodipyridine assay did not yield linear kinetics, but the generation of an active site directed mutant, C619S, gave an active enzyme and linear kinetics. The resulting mutant exhibited comparable kinetics to wild type and was used for the full kinetic analysis. Initial velocity studies were intersecting suggesting a sequential mechanism, which was confirmed by product and dead-end inhibition. The inhibition studies delineated the ordered binding of glyoxylate followed by AcCoA and the ordered release of CoA followed by malate. The pH dependence of kcat and kcat/Kgly are both bell-shaped and catalysis depends on a general base (pK 5.3) and a general acid (pK 9.2). Primary kinetic isotope effects determined using [C2H3-methyl] acetyl-CoA suggested that proton removal and carbon-carbon bond formation were partially rate-limiting. Solvent kinetic isotope effects on kcat suggested the hydrolysis of the malyl-CoA intermediate was also partially rate-limiting. Multiple kinetic isotope effects, utilizing D2O and [C2H3-methyl] acetyl-CoA, confirmed a stepwise mechanism in which the step exhibiting primary kinetic isotope effects precedes the step exhibiting the solvent isotope effects. The kinetic data and the pH dependence of the kinetic parameters were combined with existing structural and mutagenesis data to propose a chemical mechanism for malate synthase from Mycobacterium tuberculosis.

Quartararo, Christine E.; Blanchard, John S.

2011-01-01

338

Good relationship between saliva cotinine kinetics and plasma cotinine kinetics after smoking one cigarette.  

PubMed

This study investigated the relationship between plasma and saliva cotinine kinetics after smoking one cigarette and the relationship between cotinine kinetics and estimated nicotine intake, which was calculated as mouth level exposure (MLE) of nicotine, from smoking two test cigarettes with different nicotine yields. This study was conducted in 16 healthy adult Japanese smokers, who did not have null nor reduced-activity alleles of CYP2A6, with a quasi-randomized crossover design of smoking a low-tar cigarette or a high-tar cigarette. Saliva cotinine showed similar concentration profiles to plasma cotinine, and all of the calculated pharmacokinetic parameters of cotinine showed the same values in plasma and saliva. The Cmax and AUC of cotinine showed almost the same dose-responsiveness to the estimated MLE of nicotine between plasma and saliva, but the tmax and t1/2 of cotinine were not affected by the estimated MLE of nicotine in either plasma or saliva. The results show that saliva cotinine kinetics reflects plasma cotinine kinetics, and measurement of saliva cotinine concentration gives the same information as plasma cotinine on the nicotine intake. Thus, saliva cotinine would be a good and less-invasive exposure marker of cigarette smoke, reflecting the plasma cotinine concentration and kinetics. PMID:23933006

Yuki, Dai; Kikuchi, Akira; Miura, Naoki; Kakehi, Aoi; Onozawa, Masahiro

2013-11-01

339

Kinetic Atom.  

ERIC Educational Resources Information Center

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

Wilson, David B.

1981-01-01

340

Kinetic Demonstration.  

ERIC Educational Resources Information Center

Presents a unit on chemical reaction kinetics that consists of a predemonstration activity, the demonstration, and a set of postdemonstration activities that help students transfer the concepts to actual chemical reactions. Simulates various aspects of chemical reaction kinetics. (JRH)

Burgardt, Erik D.; Ryan, Hank

1996-01-01

341

SABIO Reaction Kinetics Database (Homepage)  

NSDL National Science Digital Library

The SABIO-RK (System for the Analysis of Biochemical Pathways - Reaction Kinetics) is a web-based application based on the SABIO relational database that contains information about biochemical reactions, their kinetic equations with their parameters, and the experimental conditions under which these parameters were measured. It aims to support modellers in the setting-up of models of biochemical networks, but it is also useful for experimentalists or researchers with interest in biochemical reactions and their kinetics. Information about reactions and their kinetics can be exported in SBML (Systems Biology Mark-Up Language) format.

Scientific Databases And Visualization Group At The Eml Research In Heidelberg, Germany

342

Evaluation of kinetics parameters in the X-irradiated TSL studies of RE3+-doped (RE=Eu, Tb) ZnO nanorods for dosimetric applications  

NASA Astrophysics Data System (ADS)

This paper reports the detail description of the structural and thermoluminescence of the RE3+-doped (RE=Eu, Tb) ZnO nanorods prepared by adopting co-precipitation method. Formation of as synthesized ZnO nanorods were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD pattern showed monophasic nature of the as prepared ZnO doped with Eu3+ and Tb3+ ions. The SEM image elaborates the nanorod morphology of RE3+ doped ZnO with diameter ranging between 60-90 nm and length between 600-900 nm. The thermoluminescence spectra of the X-ray irradiated ZnO:Eu3+ and ZnO:Tb3+ show the prominent peak for the broad glow curve peaked at 365 °C and 350 °C, respectively, which have been generated via the recombination of the released electrons from the traps upon thermal stimulation. The peaks are found to obey first order kinetics and the activation energy for the ZnO:Eu3+ and ZnO:Tb3+ samples, estimated via isothermal luminescence glow peak decay method, are found to be 0.8 eV and 0.9 eV respectively. Furthermore, the TL dose response and reproducibility were also studied in details, which could be very useful to establish the potentiality of the present phosphors in the field of radiation dosimetry.

Pal, Partha P.; Manam, J.

2013-07-01

343

Characterization of the atrazine sorption process on Andisol and Ultisol volcanic ash-derived soils: kinetic parameters and the contribution of humic fractions.  

PubMed

Atrazine sorption was studied in six Andisol and Ultisol soils. Humic and fulvic acids and humin contributions were established. Sorption on soils was well described by the Freundlich model. Kf values ranged from 2.2-15.6 ?g(1-1/n)mL(1/n)g?¹. The relevance of humic acid and humin was deduced from isotherm and kinetics experiments. KOC values varied between 221 and 679 mLg?¹ for these fractions. Fulvic acid presented low binding capacity. Sorption was controlled by instantaneous equilibrium followed by a time-dependent phase. The Elovich equation, intraparticle diffusion model, and a two-site nonequilibrium model allowed us to conclude that (i) there are two rate-limited phases in Andisols related to intrasorbent diffusion in organic matter and retarded intraparticle diffusion in the organo-mineral complex and that (ii) there is one rate-limited phase in Ultisols attributed to the mineral composition. The lower organic matter content of Ultisols and the slower sorption rate and mechanisms involved must be considered to assess the leaching behavior of atrazine. PMID:23711282

Báez, María E; Fuentes, Edwar; Espinoza, Jeannette

2013-07-01

344

Study of kinetic parameters related to the decolourization and mineralization of reactive dyes from textile dyeing using Fenton and photo-Fenton processes  

Microsoft Academic Search

The decolourization and mineralization of two reactive azo dyes, Procion Red H-E7B (CI Reactive Red 141) and Cibacron Red FN-R (CI Reactive Red 238), under Fenton's and photo-Fenton's conditions have been investigated. Some parameters, like temperature, initial concentrations of Fe(II) and H2O2 and the use of natural or artificial light were evaluated aiming to find the optimal conditions to promote

Lluís Núñez; José Antonio García-Hortal; Francesc Torrades

2007-01-01

345

Prediction of optimum process parameters to achieve eco-friendly desizing of organic cotton fabrics with indigenously produced alpha-amylase and their enzyme kinetics  

Microsoft Academic Search

An attempt has been made to study the desizing of polyvinyl alcohol (PVA) starch-based organic cotton fabric using alpha-amylase enzyme with various process parameters such as enzyme concentration, temperature and reaction time. These process variables are selected based on the Box–Behnken design of experiment and the output of experiment resulted in weight loss of the fabric and their results are

C. Vigneswaran; N. Anbumani; M. Ananthasubramanian; R. Rajendran

2012-01-01

346

Prediction of optimum process parameters to achieve eco-friendly desizing of organic cotton fabrics with indigenously produced alpha-amylase and their enzyme kinetics  

Microsoft Academic Search

An attempt has been made to study the desizing of polyvinyl alcohol (PVA) starch-based organic cotton fabric using alpha-amylase enzyme with various process parameters such as enzyme concentration, temperature and reaction time. These process variables are selected based on the Box–Behnken design of experiment and the output of experiment resulted in weight loss of the fabric and their results are

C. Vigneswaran; N. Anbumani; M. Ananthasubramanian; R. Rajendran

2011-01-01

347

Nonphotochemical hole burning and dispersive kinetics in amorphous solids  

SciTech Connect

Results covering burn intensities in the nW to {mu}W/cm{sup 2} range, of dispersive hole growth kinetics are reported for Oxazine 720 in glycerol glasses and polyvinyl alcohol polymer films and their deuterated analogues. A theoretical model which employs a distribution function for the hole burning rate constant based upon a Gaussian distribution for the tunnel parameter is shown to accurately describe the kinetic data. This model incorporates the linear electron-phonon coupling. A method for calculating the nonphotochemical quantum yield is presented which utilizes the Gaussian distribution of tunnel parameters. The quantum yield calculation can be extended to determine a quantum yield as a function of hole depth. The effect of spontaneous hole filling is shown to be insignificant over the burn intensity range studied. Average relaxation rates for hole burning are {approximately}8 orders of magnitude greater than for hole filling. The dispersive kinetics of hole burning are observed to be independent over the temperature range of these experiments, 1.6 to 7.0 K. 6 refs., 20 figs., 1 tab.

Kenney, M.J.

1990-09-21

348

Kinetics of Adsorption from Liquid Phase on Activated Carbon.  

National Technical Information Service (NTIS)

The kinetics of adsorption in activated carbon are investigated and single solute kinetic parameters are used to describe (predict) multisolute kinetics. This is achieved by studying the overall rate of adsorption of several organic compounds from dilute ...

M. S. Kouyoumdjiev

1992-01-01

349

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

PubMed

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

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

2013-11-01

350

General solutions for the oxidation kinetics of polymers  

SciTech Connect

The simplest general kinetic schemes applicable to the oxidation of polymers are presented, discussed and analyzed in terms of the underlying kinetic assumptions. For the classic basic autoxidation scheme (BAS), which involves three bimolecular termination steps and is applicable mainly to unstabilized polymers, typical assumptions used singly or in groups include (1) long kinetic chain length, (2) a specific ratio of the termination rate constants and (3) insensitivity to the oxygen concentration (e.g., domination by a single termination step). Steady-state solutions for the rate of oxidation are given in terms of one, two, three, or four parameters, corresponding respectively to three, two, one, or zero kinetic assumptions. The recently derived four-parameter solution predicts conditions yielding unusual dependencies of the oxidation rate on oxygen concentration and on initiation rate, as well as conditions leading to some unusual diffusion-limited oxidation profile shapes. For stabilized polymers, unimolecular termination schemes are typically more appropriate than bimolecular. Kinetics incorporating unimolecular termination reactions are shown to result in very simple oxidation expressions which have been experimentally verified for both radiation-initiated oxidation of an EPDM and thermoxidative degradation of nitrile and chloroprene elastomers.

Gillen, K.T.; Clough, R.L.; Wise, J.

1996-08-01

351

Comparative kinetic analysis of raw and cleaned coals  

Microsoft Academic Search

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

K. E. Ozbas; M. V. Kök; C. Hicyilmaz

2002-01-01

352

Kinetic modeling of ethanol production by Scheffersomyces stipitis from xylose.  

PubMed

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

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

2014-01-01

353

Selected kinetic parameters of soil microbial respiration in the A horizon of differently managed mountain forests and meadows of Moravian-Silesian Beskids Mts.  

NASA Astrophysics Data System (ADS)

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.

Vranová, V.; Formánek, P.; Rejšek, K.; Kisza, L.

2009-03-01

354

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

PubMed

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

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

2014-02-01

355

Reaction kinetics, geospeedometry, and relaxation theory  

Microsoft Academic Search

This paper explores the application of homogeneous reaction kinetics to geospeedometry and to structural relaxation theory. Numerical simulations of reaction kinetics during cooling for some first- and second-order elementary reactions have been carried out to systematically examine the effects of kinetic parameters and cooling histories on the final speciation. An analytical solution for a special case of first-order reaction A

Youxue Zhang

1994-01-01

356

Enzyme Kinetics  

NSDL National Science Digital Library

This resrouce provides detailed protocols for performing a laboratory exercise in enzyme kinetics. The activity of enzymes are characterized both by reaction rates and the effect of different concentrations of substrates.

Carl Stiefbold (University of Oregon;); Karen Sprague (University of Oregon;); Will Goodwin (University of Oregon;); Sam Donovan (University of Oregon;); Vicki Chandler (University of Oregon;)

1998-01-01

357

Interactions between SH2 domains and tyrosine-phosphorylated platelet-derived growth factor beta-receptor sequences: analysis of kinetic parameters by a novel biosensor-based approach.  

PubMed Central

The interaction between SH2 domains and phosphotyrosine-containing sequences was examined by real-time measurements of kinetic parameters. The SH2 domains of the p85 subunit of the phosphatidylinositol 3-kinase as well as of other signaling molecules were expressed in bacteria as glutathione S-transferase fusion proteins. Phosphotyrosine-containing peptides, corresponding to two autophosphorylation sites on the human platelet-derived growth factor beta-receptor that are responsible for phosphatidylinositol 3-kinase binding, were synthesized and used as capturing molecules, immobilized on a biosensor surface. The association and dissociation rate constants for binding to both sites were determined for intact p85 and the recombinant SH2 domains. High association rates were found to be coupled to very fast dissociation rates for all interactions studied. A binding specificity was observed for the two SH2 domains of p85, with the N-terminal SH2 binding with high affinity to the Tyr-751 site but not to the Tyr-740 site, and the C-terminal SH2 interacting strongly with both sites. This approach should be generally applicable to the study of the specificity inherent in the assembly of signaling complexes by activated protein-tyrosine kinase receptors.

Panayotou, G; Gish, G; End, P; Truong, O; Gout, I; Dhand, R; Fry, M J; Hiles, I; Pawson, T; Waterfield, M D

1993-01-01

358

Multiple heating rate kinetic parameters, thermal, X-ray diffraction studies of newly synthesized octahedral copper complexes based on bromo-coumarins along with their antioxidant, anti-tubercular and antimicrobial activity evaluation  

NASA Astrophysics Data System (ADS)

Series of new Cu(II) complexes were synthesized by classical thermal technique. The biologically potent ligands (L) were prepared by refluxing 6-brom 3-acetyl coumarin with aldehydes in the presence of piperidine in ethanol. The Cu(II) complexes have been synthesized by mixing an aqueous solution of Cu(NO3)2 in 1:1 molar ratios with ethanolic bidentate ligands and Clioquinol. The structures of the ligands and their copper complexes were investigated and confirmed by the elemental analysis, FT-IR, 1H NMR, 13C NMR, mass spectral and powder X-ray diffraction studies respectively. Thermal behaviour of newly synthesized mixed ligand Cu(II) complexes were investigated by means of thermogravimetry, differential thermogravimetry, differential scanning calorimetry, electronic spectra and magnetic measurements. Dynamic scan of DSC experiments for Cu(II) complexes were taken at different heating rates (2.5-20 °C min-1). Kinetic parameters for second step degradation of all complexes obtained by Kissinger's and Ozawa's methods were in good agreement. On the basis of these studies it is clear that ligands coordinated to metal atom in a monobasic bidentate mode, by Osbnd O and Osbnd N donor system. Thus, suitable octahedral geometry for hexa-coordinated state has been suggested for the metal complexes. Both the ligands as well as its complexes have been screened for their in vitro antioxidant, anti-tubercular and antimicrobial activities. All were found to be significant potent compared to parent ligands employed for complexation.

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

2012-10-01

359

Multiple heating rate kinetic parameters, thermal, X-ray diffraction studies of newly synthesized octahedral copper complexes based on bromo-coumarins along with their antioxidant, anti-tubercular and antimicrobial activity evaluation.  

PubMed

Series of new Cu(II) complexes were synthesized by classical thermal technique. The biologically potent ligands (L) were prepared by refluxing 6-brom 3-acetyl coumarin with aldehydes in the presence of piperidine in ethanol. The Cu(II) complexes have been synthesized by mixing an aqueous solution of Cu(NO(3))(2) in 1:1 molar ratios with ethanolic bidentate ligands and Clioquinol. The structures of the ligands and their copper complexes were investigated and confirmed by the elemental analysis, FT-IR, (1)H NMR, (13)C NMR, mass spectral and powder X-ray diffraction studies respectively. Thermal behaviour of newly synthesized mixed ligand Cu(II) complexes were investigated by means of thermogravimetry, differential thermogravimetry, differential scanning calorimetry, electronic spectra and magnetic measurements. Dynamic scan of DSC experiments for Cu(II) complexes were taken at different heating rates (2.5-20 °C min(-1)). Kinetic parameters for second step degradation of all complexes obtained by Kissinger's and Ozawa's methods were in good agreement. On the basis of these studies it is clear that ligands coordinated to metal atom in a monobasic bidentate mode, by OO and ON donor system. Thus, suitable octahedral geometry for hexa-coordinated state has been suggested for the metal complexes. Both the ligands as well as its complexes have been screened for their in vitro antioxidant, anti-tubercular and antimicrobial activities. All were found to be significant potent compared to parent ligands employed for complexation. PMID:22728283

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

2012-10-01

360

Calculation of Kinetics Parameters for the NBSR  

SciTech Connect

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.

Hanson A. L.; Diamond D.

2012-03-06

361

Model-free and model-fitting approaches to kinetic analysis of isothermal and nonisothermal data  

Microsoft Academic Search

The model-free and model-fitting kinetic approaches have been applied to data for nonisothermal and isothermal thermal decompositions of HMX and ammonium dinitramide. The popular model-fitting approach gives excellent fits for both isothermal and nonisothermal data but yields highly uncertain values of the Arrhenius parameters when applied to nonisothermal data. These values cannot be meaningfully compared with the values derived from

Sergey Vyazovkin; Charles A Wight

1999-01-01

362

Polymerization of 4-methylpentene-1 using homogeneous Ziegler–Natta type catalysts: a kinetic study  

Microsoft Academic Search

The kinetics of the polymerization of 4-methylpentene-1 (4MP1) with soluble, homogeneous Ziegler–Natta type catalyst systems, M(acac)3–AlEt2Br (M=Cr, Mn, Fe and Co) at 40°C in benzene medium was studied. The effect of various parameters such as Al\\/M ratio, reaction time, ageing time, temperature, catalyst and monomer concentrations on the rate of polymerization and yield were examined. The rate of polymerization increased

R. Balaji; H. Kothandaraman; D. Rajarathnam

2002-01-01

363

Adsorption kinetics of methyl violet onto perlite  

Microsoft Academic Search

This study examines adsorption kinetics and activation parameters of methyl violet on perlite. The effect of process parameters like contact time, concentration of dye, temperature and pH on the extent of methyl violet adsorption from solution has been investigated. Results of the kinetic studies show that the adsorption reaction is first order with respect to dye solution concentration with activation

Mehmet Do?an; Mahir Alkan

2003-01-01

364

Multiaxial yield behaviour of polypropylene  

NASA Astrophysics Data System (ADS)

In order to characterize the yield behavior of polypropylene as a function of pressure and to verify the applicability of the Drucker-Prager yield function, various tests were conducted to cover a wide range of stress states from uniaxial tension and compression to multiaxial tension and confined compression. Tests were performed below and above the glass transition temperature, to study the combined effect of pressure and temperature. The pressure sensitivity coefficient as an intrinsic material parameter was determined as a function of temperature. Increasing pressure sensitivity values were found with increasing temperature, which can be related to the change in the free volume and thus, to the enhanced molecular mobility. A best-fit Drucker-Prager yield function was applied to the experimental yield stresses and an average error between the predictions and the measurements of 7 % was obtained.

Jerabek, M.; Tscharnuter, D.; Major, Z.; Ravi-Chandar, K.; Lang, R.

2010-06-01

365

Vacuum pyrolysis of PVC I. Kinetic study  

Microsoft Academic Search

Vacuum pyrolysis of PVC has been studied emphasizing two aspects: the kinetics of PVC pyrolysis reactions and the yields of pyrolysis products. The purpose of the kinetic study is to identify each apparent reaction involved in PVC pyrolysis. Three stages of weight loss have been evidenced by TG analysis during PVC decomposition both under vacuum and in nitrogen atmosphere, while

Rosa Miranda; Jin Yang; Christian Roy; Cornelia Vasile

1999-01-01

366

Representation of the Kinetics of Leaching of Galena by Ferric Chloride in Concentrated Sodium Chloride Solutions by a Modified Mixed Kinetics Model  

NASA Astrophysics Data System (ADS)

Galena (PbS) is leached by a solution concentrated in NaCl and containing ferrous and ferric chloride. The ferric ion concentration is kept constant by adding KMnO4 or the potential is kept constant by adding a concentrated ferric chloride solution. The ferrous concentration of the solution has no effect upon the kinetics, the temperature and the chloride concentration have only a weak effect, whereas the radius of solid particles and the concentration of the ferric ion have the major influences. The kinetics are represented by a shrinking core model for up to 99 pet of ore dissolved. Both the aqueous diffusion of ferric ion in the pores of the sulfur layer and the chemical reaction at the surface are involved in the kinetic model. Taking into account the self blockage improves the representation of the end of reaction and yields a more consistent set of parameters.

Morin, D.; Gaunand, A.; Renon, H.

1985-12-01

367

Kinetics of batch fermentations for ethanol production with Zymomonas mobilis growing on Jerusalem artichoke juice  

SciTech Connect

A flocculent strain of Zymomonas mobilis was used for ethanol production from Jerusalem artichoke juice containing 113-245 g/l sugar in batch fermentation. The kinetic and yields parameters are calculated using a new method based on polynomial equations for the variation of biomass, ethanol, and sugar concentrations with time. The results show that Z. mobilis can convert rapidly and efficiently Jerusalem artichoke juice to ethanol. When a sugar concentraton of 248 g/l was used, 100g/l ethanol was formed with an ethanol yield based on sugar utilized of 0.47 g/g (92% of theoretical). 27 references.

Favela-Torres, E.; Allais, J.J.; Baratti, J.

1986-06-01

368

Kinetics of biomass catalytic pyrolysis  

Microsoft Academic Search

The Coats–Redfern method was used to analyze the kinetic characteristics of biomass catalytic pyrolysis, indicating that it can be described by multi-step reactions, rather than as a simple first-order reaction. Friedman model-free calculations were used to describe the starting reaction types and the corresponding initial kinetic parameters. Finally, nonlinear regression of biomass catalytic pyrolysis showed that the reaction mechanism of

Changbo Lu; Wenli Song; Weigang Lin

2009-01-01

369

Kinetics of heterotrophic biomass and storage mechanism in wetland cores measured by respirometry.  

PubMed

Although oxygen uptake rate has been widely used in activated sludge for measuring kinetic and stoichiometric parameters or for wastewater characterization, its application in constructed wetlands (CWs) cores has been recently proposed. The aim of this research is to estimate the kinetic and stoichiometric parameters of the heterotrophic biomass in CW cores. Respirometric tests were carried out with pure carbonaceous substrate and real wastewater. Endogenous respiration was about 2 gO2 m(-3) h(-1) (per unit of bed volume), while the kinetic parameters obtained for COD oxidation were very high (maximum rate per unit of bed volume of 10.7-26.8 gCOD m(-3) h(-1)) which indicates high biodegradation potential in fully aerobic environment. Regarding to stoichiometric parameter, the maximum growth yield, Y(H), was 0.56-0.59 mgCOD/mgCOD, while the storage yield, Y(STO), was 0.75-0.77 mgCOD/mgCOD. The storage mechanism was observed in CW cores during COD oxidation, which leads to the transformation of the external soluble substrate in internal storage products, probably as response to intermittent loads applied in CW systems, transient concentrations of readily biodegradable substrate and alternance of feast/famine periods. PMID:22097015

Ortigara, A R C; Foladori, P; Andreottola, G

2011-01-01

370

Kinetic Energy  

NSDL National Science Digital Library

Part of a comprehensive physics tutorial for high school students, this page describes kinetic energy conceptually and mathematically, provides examples enhanced by illustrations, and problems for practice with drop down boxes for your answers and feedback. In the left navigation bar, click on Potential Energy to get parallel information on potential energy.

2010-01-01

371

Kinetic modeling of kraft delignification of Eucalyptus globulus  

SciTech Connect

A kinetic model for the kraft pulping delignification of Eucalyptus globulus is proposed. This model is discriminated among some kinetic expressions often used in the literature, and the kinetic parameters are determined by fitting of experimental results. A total of 25 isothermal experiments at liquor-to-wood ratios of 50 and 5 L/kg have been carried out. Initial, bulk, and residual delignification stages have been observed during the lignin removal, the transitions being, referring to the lignin initial content, about 82 and 3%. Carbohydrate removal and effective alkali-metal and hydrosulfide consumption have been related with the lignin removal by means of effective stoichiometric coefficients for each stage, coefficients also being calculated by fitting of the experimental data. The kinetic model chosen has been used to simulate typical kraft pulping experiments carried out at nonisothermal conditions, using a temperature ramp. The model yields simulated values close to those obtained experimentally for the wood studied and also ably reproduces the trends of the literature data.

Santos, A.; Rodriguez, F.; Gilarranz, M.A.; Moreno, D.; Garcia-Ochoa, F. [Univ. Complutense, Madrid (Spain). Dept. de Ingenieria Quimica] [Univ. Complutense, Madrid (Spain). Dept. de Ingenieria Quimica

1997-10-01

372

New kinetic model for thermal decomposition of heterogeneous materials  

SciTech Connect

In the kinetic studies of thermal decomposition of lignocellulosic materials using dynamic TG, relationships between the biomass fraction ``w`` and the time ``t`` of the form dw/dt = {minus}k(w {minus} w{sub {infinity}}){sup n} are usually admitted, and the residue fraction at infinite time (w{sub {infinity}}) is considered constant. However, in heterogeneous solids such as lignocellulosic materials, the different polymers decompose at different temperatures, and so the value of w{sub {infinity}} is not constant, Therefore, the previous equation must be considered approximate. To illustrate this feature, experiments with kraft lignin, which decomposes in an interval of temperatures between 150 and 750 C, have been carried out. A kinetic model is proposed, bearing in mind that there is a maximum pyrolyzable fraction at each temperature. This model considers that the thermal decomposition of a heterogeneous material occurs through a great number of reactions and that at a given temperature only some fractions can decompose. The kinetic parameters (activation energy and preexponential factor) can change during the decomposition process as function of the reactions taking place. Under some assumptions, it is deduced that this model is equivalent to assume the kinetic law dw/dt = {minus}k(w{minus}w{sub {infinity}}) for first-order reaction, where the residue yield w{sub {infinity}} is a function of the temperature.

Caballero, J.A.; Font, R.; Marcilla, A.; Conesa, J.A. [Univ. de Alicante (Spain). Dept. de Ingenieria Quimica

1995-03-01

373

Kinetics of Fullerene Formation in a Contact Arc Generator  

Microsoft Academic Search

A kinetic model of the fullerene growth process in a contact arc generator is developed. On the basis of the kinetic model, the yield of the magic fullerenes C60 and C70 is calculated. The fullerene yield is determined by the temperature gradient in the fullerene formation zone, the carbon vapor concentration and the helium jet velocity in the interelectrode space.

Z. M. Markovi?; B. M. Todorovi?-Markovi?; T. Lj. Joki?; P. Pavlovi?; P. Stefanovi?; J. Blanuša; T. Nenadovi?

1998-01-01

374

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

NASA Astrophysics Data System (ADS)

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

Dohare, C.; Mehta, N.

2013-08-01

375

Sensitivity Analysis for Reactor Period Induced by Positive Reactivity Using One-point Adjoint Kinetic Equation  

NASA Astrophysics Data System (ADS)

In order to better predict a kinetic behavior of a nuclear fission reactor, an improvement of the delayed neutron parameters is essential. The present paper specifies important nuclear data for a reactor kinetics: Fission yield and decay constant data of 86Ge, some bromine isotopes, 94Rb, 98mY and some iodine isotopes. Their importance is quantified as sensitivities with a help of the adjoint kinetic equation, and it is found that they are dependent on an inserted reactivity (or a reactor period). Moreover, dependence of sensitivities on nuclear data files is also quantified using the latest files. Even though the currently evaluated data are used, there are large differences among different data files from a view point of the delayed neutrons.

Chiba, G.; Tsuji, M.; Narabayashi, T.

2014-04-01

376

Kinetic City  

NSDL National Science Digital Library

Kinetic City is an after-school standards-based science program in which kids complete activities in conjunction with a dynamic website. It includes science experiments, games, activities, challenges and more. It provides kids in grades three through five a fun, entertaining way to learn standards-based science. It is the ideal combination of technology and hands-on collaboration. A free log-in is required for some of the content on the site. An additional section for educators or parents is featured. This provides guidance on how to best implement some of the resources. Overall, this is a nice collection for more general resources on these topics.

2009-07-02

377

Crystallization kinetics  

NASA Astrophysics Data System (ADS)

Avrami's treatment of nucleation and growth kinetics considers that active nucleation sites are randomly distributed throughout the volume and that grains may impinge upon grains grown from other sites, causing growth to cease on the common interface. This treatment resulted in the well-known Avrami equation. As a result of the reassessment of these basic assumptions, an integral equation is proposed for the time-dependence evaluation of the transformed phase volume fraction in crystallization processes, instead of the Avrami equation. The proposed model fits very well the whole range of experimental data for NiZr2 and Te92Pb8 amorphous to crystalline transformation.

Erukhimovitch, V.; Baram, J.

1994-09-01

378

Determining Enzyme Kinetics for Systems Biology with Nuclear Magnetic Resonance Spectroscopy  

PubMed Central

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

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

2012-01-01

379

Reinvestigation of the elementary chemical kinetics of the reaction C2H5(•) + HBr (HI) ? C2H6 + Br(•) (I(•)) in the range 293-623 K and its implication on the thermochemical parameters of C2H5(•) free radical.  

PubMed

A reinvestigation of the absolute rate constants of the metathesis reactions C2H5• + HBr ? C2H6 + Br• (R1) and C2H5• + HI ? C2H6 + I• (R2) has been performed and led to the following Arrhenius expressions: k1 = 3.69(±0.95) × 10–11 exp(?10.62(±0.66)/RT), k2 = 1.20(±0.38) × 10–11 exp(?7.12(±1.059)/RT) in the temperature range 293–623 K (A/cm3 molecule–1 s–1, Ea/kJ mol–1). The study has been performed using a Knudsen reactor coupled to single-photon (VUV) photoionization mass spectrometer (SPIMS). Hydrocarbon free radicals have been generated externally before admission into the Knudsen reactor according to two different chemical schemes, enabling the generation of thermalized C2H5• free radicals. A minor correction to k1 and k2 for the wall loss of C2H5• (kw) has been applied throughout the temperature range. The obtained results are consistent regarding both the disappearance of C2H5• and the formation of closed shell products (n-C4H10, C2H4, C2H6), indicating that the chemical mechanism is largely understood and complete. Thermochemical parameters for C2H5• free radical resulting from the present kinetic measurements are discussed and point toward a slightly lower value for the standard heat of formation ?fH298°(C2H5•) compared to some presently recommended values. On the basis of the present results and suitable data on the reverse reaction taken from the literature, we recommend ?fH298°(C2H5•) = 117.3 ± 3.1 kJ/mol resulting from an average of “third law” evaluations using S298°(C2H5•) = 242.9 ± 4.6 J/K mol. The present work yields a standard heat of formation in satisfactory agreement with the results obtained by W. Tsang (?fH298°(C2H5•) = 119 ± 2 kJ/mol) despite using two very different experimental techniques. PMID:24134055

Leplat, N; Wokaun, A; Rossi, M J

2013-11-14

380

A Comprehensive Enzyme Kinetic Exercise for Biochemistry  

ERIC Educational Resources Information Center

This article describes a comprehensive treatment of experimental enzyme kinetics strongly coupled to electronic data acquisition and use of spreadsheets to organize data and perform linear and nonlinear least-squares analyses, all in a manner that promotes development of important reasoning skills. Kinetic parameters are obtained for the stable…

Barton, Janice S.

2011-01-01

381

Urea Kinetics and When to Commence Dialysis  

Microsoft Academic Search

Blood urea and serum creatinine levels are important factors in deciding when to start dialysis. Recently, in the assessment of dialysis adequacy, emphasis has shifted from reliance on these parameters to use of kinetic methods. We therefore applied urea kinetic modelling (UKM) to 63 consecutive chronic renal failure (CRF) patients at the time dialysis commenced and compared the results to

James Tattersall; Roger Greenwood; Ken Farrington

1995-01-01

382

Biodeterioration of polymeric materials: generalized kinetic data  

Microsoft Academic Search

The process of biodegradation of polymers has been investigated, and is defined by adhesion of cells of microorganisms with further growth of biomass, extracting aggressive media. Macro-kinetic parameters for adhesion, biomass accumulation and biodegradation have been obtained. The possibility of the description of biodegradation by generalized kinetic curves is demonstrated.

K. Z. Gumargalieva; G. E. Zaikov

1995-01-01

383

Kinetics of Thermal Dissociation of Hydrazine Nitrate.  

National Technical Information Service (NTIS)

On a micro-calorimeter in intervals of 194-254C the kinetic reaction of thermal dissociation of hydrazine nitrate has been investigated. The reaction accelerates whereupon the amount of acceleration depends upon m/V. The kinetic parameters of the reaction...

Y. I. Rubtsov G. B. Manelis

1975-01-01

384

Kinetics of nonisothermal recrystallization  

NASA Astrophysics Data System (ADS)

The kinetics of recrystallization from nonisothermal cycles is modeled using an extension of the Arrhenius relationship. This model is used to predict the annealing response for both isothermal and nonisothermal annealing cycles. A nondimensional parameter called the “annealing index” is based on time and temperature and is related to the extent of anneal through physical properties. The effect of heating and cooling rate also can be quantified because the entire thermal cycle is evaluated. Nonisothermal anneals with heating rates of 10 and 100 °C/s were evaluated (along with isothermal anneals) for colddrawn ETP copper wire. A numerical solution is set forth to evaluate nonisothermal cycles.

Kraft, F. F.; Wright, R. N.; Jensen, M. K.

1996-04-01

385

Distribution of Independent Fission-Product Yields to Isomeric States.  

National Technical Information Service (NTIS)

A simple one-parameter model is presented for calculating the distribution of independent yield strength between ground and isomeric states of primary fission products formed by neutron-induced fission of actinide nuclei. Yield branching ratios are calcul...

D. G. Madland T. R. England

1976-01-01

386

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

PubMed

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

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

2014-06-12

387

Tolrestat kinetics  

SciTech Connect

The kinetics of tolrestat, a potent inhibitor of aldose reductase, were examined. Serum concentrations of tolrestat and of total /sup 14/C were measured after dosing normal subjects and subjects with diabetes with /sup 14/C-labeled tolrestat. In normal subjects, tolrestat was rapidly absorbed and disappearance from serum was biphasic. Distribution and elimination t 1/2s were approximately 2 and 10 to 12 hr, respectively, after single and multiple doses. Unchanged tolrestat accounted for the major portion of /sup 14/C in serum. Radioactivity was rapidly and completely excreted in urine and feces in an approximate ratio of 2:1. Findings were much the same in subjects with diabetes. In normal subjects, the kinetics of oral tolrestat were independent of dose in the 10 to 800 mg range. Repetitive dosing did not result in unexpected cumulation. Tolrestat was more than 99% bound to serum protein; it did not compete with warfarin for binding sites but was displaced to some extent by high concentrations of tolbutamide or salicylate.

Hicks, D.R.; Kraml, M.; Cayen, M.N.; Dubuc, J.; Ryder, S.; Dvornik, D.

1984-10-01

388

Kinetics of coal pyrolysis and devolatilization  

SciTech Connect

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

Not Available

1986-01-01

389

Yield Improvement in Steel Casting (Yield II)  

SciTech Connect

This report presents work conducted on the following main projects tasks undertaken in the Yield Improvement in Steel Casting research program: Improvement of Conventional Feeding and Risering Methods, Use of Unconventional Yield Improvement Techniques, and Case Studies in Yield Improvement. Casting trials were conducted and then simulated using the precise casting conditions as recorded by the participating SFSA foundries. These results present a statistically meaningful set of experimental data on soundness versus feeding length. Comparisons between these casting trials and casting trials performed more than forty years ago by Pellini and the SFSA are quite good and appear reasonable. Comparisons between the current SFSA feeding rules and feeding rules based on the minimum Niyama criterion reveal that the Niyama-based rules are generally less conservative. The niyama-based rules also agree better with both the trials presented here, and the casting trails performed by Pellini an d the SFSA years ago. Furthermore, the use of the Niyama criterion to predict centerline shrinkage for horizontally fed plate sections has a theoretical basis according to the casting literature reviewed here. These results strongly support the use of improved feeding rules for horizontal plate sections based on the Niyama criterion, which can be tailored to the casting conditions for a given alloy and to a desired level of soundness. The reliability and repeatability of ASTM shrinkage x-ray ratings was investigated in a statistical study performed on 128 x-rays, each of which were rated seven different times. A manual ''Feeding and Risering Guidelines for Steel Castings' is given in this final report. Results of casting trials performed to test unconventional techniques for improving casting yield are presented. These use a stacked arrangement of castings and riser pressurization to increase the casting yield. Riser pressurization was demonstrated to feed a casting up to four time s the distance of a non-pressurized riser, and can increase casting yield by decreasing the required number of risers. All case studies for this projects were completed and compiled into an SFSA Technical Report that is submitted part of this Final Report

Richard A. Hardin; Christoph Beckermann; Tim Hays

2002-02-18

390

Reckoning wheat yield trends  

NASA Astrophysics Data System (ADS)

Wheat yields have increased approximately linearly since the mid-twentieth century across the globe, but stagnation of these trends has now been suggested for several nations. We present a new statistical test for whether a yield time series has leveled off and apply it to wheat yield data from 47 different regions to show that nearly half of the production within our sample has transitioned to level trajectories. With the major exception of India, the majority of leveling in wheat yields occurs within developed nations—including the United Kingdom, France and Germany—whose policies appear to have disincentivized yield increases relative to other objectives. The effects of climate change and of yields nearing their maximum potential may also be important.

Lin, M.; Huybers, P.

2012-06-01

391

A Fuzzy Neural Network Approach for Die Yield Prediction of Wafer Fabrication Line  

Microsoft Academic Search

To improve prediction accuracy of die yield, a novel fuzzy neural networks (FNN) based yield prediction approach is proposed. The yield prediction model is built, in which the impact factors of yield, including physical parameters, electrical test parameters and wafer defect parameters are considered simultaneously and are taken as independent variables. A back-propagation algorithm is used to train and adjust

Lihui Wu; Jie Zhang; Gong Zhang

2009-01-01

392

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

NASA Technical Reports Server (NTRS)

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

Simsic, P. L.

1974-01-01

393

Reconstructing kinetic pathways from single-molecule FRET experiments using Bayesian inference  

NASA Astrophysics Data System (ADS)

Single-molecule FRET studies have enabled observation of conformational transitions in individual molecules, allowing targeted investigations into the mechanistic function of molecular machines. Like in many single-molecule platforms, sm-FRET studies yield observations of hundreds of noisy time series, which report on the same underlying conformational steps, but exhibit significant variations in photophysical properties and kinetic rates. Reconstruction of a consensus kinetic pathway from such noisy measurements is statistically challenging. Hidden Markov Models are widely used to identify states and estimate the associated kinetic rates. Existing techniques perform inference on one time series at a time, yielding variable parameter estimates that must now be `averaged' using ad-hoc experiment specific post-processing steps. Here, we propose a technique known as Empirical Bayes estimation, which performs simultaneous analysis on a collection of trajectories in an experiment. This results in a single estimate for a consensus kinetic model, as well as a significantly reduced estimation error. By comparing models with different constraints, we show how these methods may be used to test detailed mechanistic hypotheses in a statistically principled, adaptable manner.

van de Meent, Jan-Willem; Gonzalez, Ruben L., Jr.; Wiggins, Chris H.

2013-03-01

394

Isothermal and non-isothermal pyrolysis kinetics of Kapton ® polyimide  

Microsoft Academic Search

The kinetics involved in the thermal decomposition of Kapton® polyimide 100HN under nitrogen atmosphere were studied by applying various fitting techniques to the isothermal and non-isothermal gravimetric data. The correlation of the reaction mechanism fitting, the analytical model fitting and the isoconversional method to these data was examined in relation to the kinetic parameters and the kinetic predictions. The mechanisms

Aik Chong Lua; Jincai Su

2006-01-01

395

Novel laccase redox mediators: spectral, electrochemical, and kinetic properties.  

PubMed

The screening of potential redox mediators for laccase was performed using homogeneous enzyme preparations from Coriolus hirsutus and Coriolus zonatus. It was discovered that derivatives of 1-phenyl-3-methyl-pyrazolones were efficient substrates for the laccases. The characterization of two representatives of the 1-phenyl-pyrazolone class, sodium 1-phenyl-3-methyl-4- methylamino-pyrazolone-5-N(4)-methanesulfonate and 1-(3'-sulfophenyl)-3- methylpyrazolone-5, in the reaction catalyzed by laccase was carried out using spectral, electrochemical, and enzyme kinetics methods. The kinetic parameters for the oxidation of the newly discovered substrates were comparable with those for 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) oxidation by laccase. Electrochemical experiments demonstrated that oxidation of these compounds yielded two high-potential intermediates capable of oxidizing veratryl alcohol, which was used as a lignin model substrate, to the corresponding aldehyde and acid. 1-(3'-Sulfophenyl)-3- methylpyrazolone-5 was about 30-40% as effective in degrading veratryl alcohol compared to ABTS as judged from high-performance liquid chromatography kinetic studies. 1-Phenyl-3-methyl-pyrazolones may be of commercial interest for oxidoreductase-catalyzed biodegradation of organic compounds. PMID:14665736

Shleev, S V; Khan, I Gvon; Gazaryan, I G; Morozova, O V; Yaropolov, A I

2003-12-01

396

Kinetics of acid base catalyzed transesterification of Jatropha curcas oil.  

PubMed

Out of various non-edible oil resources, Jatropha curcas oil (JCO) is considered as future feedstock for biodiesel production in India. Limited work is reported on the kinetics of transesterification of high free fatty acids containing oil. The present study reports the results of kinetic study of two-step acid base catalyzed transesterification process carried out at an optimum temperature of 65 °C and 50 °C for esterification and transesterification respectively under the optimum methanol to oil ratio of 3:7 (v/v), catalyst concentration 1% (w/w) for H?SO? and NaOH. The yield of methyl ester (ME) has been used to study the effect of different parameters. The results indicate that both esterification and transesterification reaction are of first order with reaction rate constant of 0.0031 min?¹ and 0.008 min?¹ respectively. The maximum yield of 21.2% of ME during esterification and 90.1% from transesterification of pretreated JCO has been obtained. PMID:20570507

Jain, Siddharth; Sharma, M P

2010-10-01

397

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

NASA Astrophysics Data System (ADS)

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

Chevrot, Guillaume; Sollier, Arnaud; Pineau, Nicolas

2012-02-01

398

Analysis of volatile species kinetics during typical medical waste materials pyrolysis using a distributed activation energy model.  

PubMed

The complex reactions of typical medical waste materials pyrolysis and the evolution of different volatile species can be well represented by a Distributed Activation Energy Model (DAEM). In this study, A thermogravimetric analyser (TGA), coupled with Fourier transform infrared analysis of evolving products (TG-FTIR), were used to perform kinetic analysis of typical medical waste materials pyrolysis. A simple direct search method was used for the determination of DAEM kinetic parameters and the yield of individual pyrolysis products under any given heating condition. The agreement between the model prediction and the experimental data was generally good. The results can be used as inputs to a pyrolysis model based on first-order kinetic expression with a Gaussian Distribution of Activation Energies as a sub-model to CFD code. PMID:18579296

Yan, J H; Zhu, H M; Jiang, X G; Chi, Y; Cen, K F

2009-03-15

399

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

400

High Yield Neutron Source.  

National Technical Information Service (NTIS)

A high yield neutron source comprising a plasma focus device in combination with a structured target is described. The plasma focus device generates a plasma sheath which focuses on a structured target in a predetermined focal region. The structured targe...

H. L. Sahlin J. H. Brownell B. L. Freeman

1978-01-01