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1

Prediction of microbial growth rate versus biomass yield by a metabolic network with kinetic parameters.  

PubMed

Identifying the factors that determine microbial growth rate under various environmental and genetic conditions is a major challenge of systems biology. While current genome-scale metabolic modeling approaches enable us to successfully predict a variety of metabolic phenotypes, including maximal biomass yield, the prediction of actual growth rate is a long standing goal. This gap stems from strictly relying on data regarding reaction stoichiometry and directionality, without accounting for enzyme kinetic considerations. Here we present a novel metabolic network-based approach, MetabOlic Modeling with ENzyme kineTics (MOMENT), which predicts metabolic flux rate and growth rate by utilizing prior data on enzyme turnover rates and enzyme molecular weights, without requiring measurements of nutrient uptake rates. The method is based on an identified design principle of metabolism in which enzymes catalyzing high flux reactions across different media tend to be more efficient in terms of having higher turnover numbers. Extending upon previous attempts to utilize kinetic data in genome-scale metabolic modeling, our approach takes into account the requirement for specific enzyme concentrations for catalyzing predicted metabolic flux rates, considering isozymes, protein complexes, and multi-functional enzymes. MOMENT is shown to significantly improve the prediction accuracy of various metabolic phenotypes in E. coli, including intracellular flux rates and changes in gene expression levels under different growth rates. Most importantly, MOMENT is shown to predict growth rates of E. coli under a diverse set of media that are correlated with experimental measurements, markedly improving upon existing state-of-the art stoichiometric modeling approaches. These results support the view that a physiological bound on cellular enzyme concentrations is a key factor that determines microbial growth rate. PMID:22792053

Adadi, Roi; Volkmer, Benjamin; Milo, Ron; Heinemann, Matthias; Shlomi, Tomer

2012-01-01

2

Obtaining and Estimating Kinetic Parameters from the Literature  

NSDL National Science Digital Library

This Teaching Resource provides lecture notes, slides, and a student assignment for a lecture on strategies for the development of mathematical models. Many biological processes can be represented mathematically as systems of ordinary differential equations (ODEs). Simulations with these mathematical models can provide mechanistic insight into the underlying biology of the system. A prerequisite for running simulations, however, is the identification of kinetic parameters that correspond closely with the biological reality. This lecture presents an overview of the steps required for the development of kinetic ODE models and describes experimental methods that can yield kinetic parameters and concentrations of reactants, which are essential for the development of kinetic models. Strategies are provided to extract necessary parameters from published data. The homework assignment requires students to find parameters appropriate for a well-studied biological regulatory system, convert these parameters into appropriate units, and interpret how different values of these parameters may lead to different biological behaviors.

Susana R. Neves (New York; Mount Sinai School of Medicine REV)

2011-09-20

3

Methanol bioconversion by butyribacterium methylotrophicum - batch fermentation yield and kinetics  

SciTech Connect

Butyribacterium methylotrophicum is an anaerobic bacterium that can convert methanol to butyrate. This ability to produce longer- chain carbon compounds from C1 substrates could be of commercial significance. The fermentation rates and product formation depend on the methanol/bicarbonate ratios during fermentation. The kinetics of batch fermentation fit the Luedeking-Piret model with growth and maintenance associated product formation. Butyrate yield of 0.256 mol/mol methanol (ca. 85% of theoretical yield) has been obtained in batch fermentation. (Refs. 9).

Datta, R.; Ogeltree, J.

1983-04-01

4

On the Derivation of Polyurethane Kinetic Parameters Using Genetic Algorithms   

E-print Network

There is a lack of quantification for the kinetics mechanism of polyurethane thermal decomposition. The objective of this work is to derive a set of parameters for the kinetics of polyurethane valid for numerical models, with an emphasis...

Rein, Guillermo; Herren, Jaime; Fernandez-Pello, Carlos; Urban, David

5

New approach for kinetic parameters determination for hydrothermal oxidation reaction  

E-print Network

1 New approach for kinetic parameters determination for hydrothermal oxidation reaction David different methods, namely pseudo first order kinetics, multiple linear regression and Runge-Kutta algorithm for industrial or agricultural applications. In order to scale up reactors for HOT of industrial wastewaters

Paris-Sud XI, Université de

6

New post-yield fracture toughness parameters for engineering materials  

SciTech Connect

Micromechanics approach is employed to investigate the constraint effect on post-yield fracture toughness. Relationships between the conventional post-yield fracture toughness values, J{sub lc} and {delta}{sub c}, and crack tip constraint characterized by the crack tip stress triaxiality are derived on the basis of an improved micromechanics criterion for ductile fracture. Then, new crack tip parameters J{sub mc} and {delta}{sub mc} (and associated new criteria for ductile fracture) are proposed, in which the effects of crack tip deformation and constraint are taken into account. Experiments show that both J{sub mc} and {delta}{sub mc} are material constant independent of stress state or specimen geometry. They can serve as new post-yield fracture toughness parameters to differentiate the fracture toughness of engineering materials, which provide new approaches for fracture assessments of engineering structures.

Wang, T.J.; Kuang, Z.B. [Xi`an Jiaotong Univ. (China). Dept. of Engineering Mechanics

1995-11-01

7

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

PubMed Central

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

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

2012-01-01

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.  

PubMed

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. PMID:25019910

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

2014-06-01

10

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

SciTech Connect

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

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

2006-07-20

11

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

12

User Manual Parameter Estimation for a Compartmental Tracer Kinetic  

E-print Network

User Manual Parameter Estimation for a Compartmental Tracer Kinetic Model Applied to PET data, NIH grant EB 2553301, NSF grant CMG-02223 and the Underrepresented Graduate Enrichment Match (UGEM's Disease studies is provided. Appropriate references to the standard literature give background

Renaut, Rosemary

13

Mechanistic analysis of multi-omics datasets to generate kinetic parameters for constraint-based metabolic models  

PubMed Central

Background Constraint-based modeling uses mass balances, flux capacity, and reaction directionality constraints to predict fluxes through metabolism. Although transcriptional regulation and thermodynamic constraints have been integrated into constraint-based modeling, kinetic rate laws have not been extensively used. Results In this study, an in vivo kinetic parameter estimation problem was formulated and solved using multi-omic data sets for Escherichia coli. To narrow the confidence intervals for kinetic parameters, a series of kinetic model simplifications were made, resulting in fewer kinetic parameters than the full kinetic model. These new parameter values are able to account for flux and concentration data from 20 different experimental conditions used in our training dataset. Concentration estimates from the simplified kinetic model were within one standard deviation for 92.7% of the 790 experimental measurements in the training set. Gibbs free energy changes of reaction were calculated to identify reactions that were often operating close to or far from equilibrium. In addition, enzymes whose activities were positively or negatively influenced by metabolite concentrations were also identified. The kinetic model was then used to calculate the maximum and minimum possible flux values for individual reactions from independent metabolite and enzyme concentration data that were not used to estimate parameter values. Incorporating these kinetically-derived flux limits into the constraint-based metabolic model improved predictions for uptake and secretion rates and intracellular fluxes in constraint-based models of central metabolism. Conclusions This study has produced a method for in vivo kinetic parameter estimation and identified strategies and outcomes of kinetic model simplification. We also have illustrated how kinetic constraints can be used to improve constraint-based model predictions for intracellular fluxes and biomass yield and identify potential metabolic limitations through the integrated analysis of multi-omics datasets. PMID:23360254

2013-01-01

14

Evaluation of true kinetic parameters for reversible immobilized enzyme reactions  

SciTech Connect

For a reversible one-substrate reaction system that follows the Haldane reaction mechanism, a new and effective method has been proposed to extract true or intrinsic kinetic parameters of immobilized enzymes from diffusion limited rate data. The method utilizes the effectiveness factors correlated in terms of the general modulus defined by Aris and Bischoff, and a new modulus defined in the present study. It requires a trial-and-error calculation, but only a few data points. Furthermore, it provides a saving of materials such as substrates and enzymes, and takes less time for experiments compared to the initial rate methods. The usefulness of the method is demonstrated by determining the kinetic parameters for membrane bound fumarase which catalyzes the reaction of the conversion of fumarate to L-malate, for which the equilibrium constant is circa 4. (Refs. 20).

Ishikawa, H.; Tanaka, T.; Kurose, K.; Hikita, H.

1987-06-01

15

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

PubMed Central

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

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

2014-01-01

16

Evolutionary optimization of enzyme kinetic parameters; effect of constraints.  

PubMed

The distribution of the kinetic parameters of enzymic reactions is theoretically studied, on the assumption that, during evolution, the increase of reaction rates was an important target of natural selection. In extension of previous work on the optimization of enzyme kinetic parameters, the influence of constraints concerning upper limits of the individual rate constants is analyzed. The concept of "evolutionary effort" is applied to derive an expression for the cost function, leading to an overall upper limit for the values of the rate constants. The resulting optimization problem is solved for ordered mechanisms involving different numbers of elementary steps. It is shown that the optimum for the enzyme kinetic parameters strongly depends on the concentrations of the reactants. Low reactant concentrations lead generally to a tight binding of the reactants, while high concentrations result in a weak binding, favouring the rate constants of the other steps. In particular, states of maximum activity are not always characterized by maximal values of second-order rate constants. The results support the hypothesis that there is a mutual adaptation of Michaelis constants and reactant concentrations in an evolutionary timescale. In the limit of infinite values of the exponent of the cost function the results of the present "overall limit model" turn into the results of a model which takes into account individual upper limits for rate constants ("separate limit model"). The distributions of optimal rate constants are discussed in terms of free-energy profiles. The model is applied to the interpretation of the kinetic data of triosephosphate isomerase and inorganic pyrophosphatase. PMID:7869733

Klipp, E; Heinrich, R

1994-12-01

17

Model-based analysis of coupled equilibrium-kinetic processes: indirect kinetic studies of thermodynamic parameters using the dynamic data.  

PubMed

Thermodynamic studies of equilibrium chemical reactions linked with kinetic procedures are mostly impossible by traditional approaches. In this work, the new concept of generalized kinetic study of thermodynamic parameters is introduced for dynamic data. The examples of equilibria intertwined with kinetic chemical mechanisms include molecular charge transfer complex formation reactions, pH-dependent degradation of chemical compounds and tautomerization kinetics in micellar solutions. Model-based global analysis with the possibility of calculating and embedding the equilibrium and kinetic parameters into the fitting algorithm has allowed the complete analysis of the complex reaction mechanisms. After the fitting process, the optimal equilibrium and kinetic parameters together with an estimate of their standard deviations have been obtained. This work opens up a promising new avenue for obtaining equilibrium constants through the kinetic data analysis for the kinetic reactions that involve equilibrium processes. PMID:25723920

Emami, Fereshteh; Maeder, Marcel; Abdollahi, Hamid

2015-05-01

18

Albite [yields] jadeite + quartz transformation in rock: Mechanism and kinetics  

SciTech Connect

Recent work on the calcite [yields] aragonite transformation using fully dense marble revealed significant differences from earlier experiments on powders and single-crystals. The reaction rate is retarded by a factor of > 1,000 and reaction mechanisms and resultant textures are considerably more complex. Stimulated by this, the authors conducted a study of the albite [yields] jadeite + quartz/coesite transformation in a fully dense albitite. Again the results are in marked contrast with previous powder-based studies of this archetypal metamorphic reaction. Solid cores of albitite were held at temperatures of 500-1,200 C and at pressure oversteps of 500 MPa into the jadeite + quartz stability field for 1--8 days in piston-cylinder apparatus. Samples that were dried in vacuum transformed appreciably only at temperatures in excess of 1,000 C. At all grain boundaries there is subequal transformation to micron-scale intergrowths of jadeite + quartz. Samples that were vacuum-impregnated with 1 wt% water contain jadeite + quartz to temperatures as low as 600 C. In contrast to the dried samples, transformation is much less homogeneous. The jadeite + quartz intergrowths do not form rows of subparallel crystals on grain boundaries, but rather are flower-shaped clusters that radiate outward from single nucleation sites at 3-grain edges and 4-grain corners. Compared to powders, pressure oversteps a factor of 10 greater are necessary to induce equivalent reaction in albitite. The sluggishness of this reaction has important implications for the evolution of the lower continental crust and subducting oceanic crust in terms of their (1) seismic velocity profiles, (2) petrological evolution, and (3) buoyancy forces, stresses and vertical crustal movements connected with densification and dilatational reactions.

Bohlen, S.R.; Kirby, S.H. (Geological Survey, Menlo Park, CA (United States)); Hacker, B.R.

1992-01-01

19

Mass Yields and Kinetic Energies from Symmetric Fission of 236U* and 240PU*  

NASA Astrophysics Data System (ADS)

We have precisely measured mass yields and kinetic-energy distributions of fission fragments from the thermal-neutron-induced fission of 235U and 239Pu, in the symmetry region, with the Lohengrin mass separator at the Institut Laue-Langevin (Grenoble). The dip in the kinetic energy between asymmetric and symmetric fission regions amounts to 28 MeV for 235U and 23 MeV for 239Pu, which agrees with other experimental findings. A pronounced asymmetry in the yields was found for masses from A=119 to A=125. For the 235U case, this asymmetry is at variance with the data given by libraries. An attempt has been made to explain this asymmetry in the mass distribution as resulting from neutron evaporation. The presence of a five-mass structure found in the mass yields (235U nucleus) tentatively indicates the presence of a proton odd-even effect in the isotopic yields.

Tsekhanovich, I.; Simpson, G.; Orlandi, R.; Scherillo, A.; Rochman, D.; Sokolov, V.

2004-02-01

20

[Determination of kinetic parameters of activated sludge in an MBR wastewater treatment plant].  

PubMed

One of the main problems in application of MBR technology is lack of reliable kinetic parameters for process design. The activated sludge in the aerobic tank of an MBR municipal wastewater treatment plant was investigated therefore. Using oxygen utilization rate method, following kinetic parameters were measured: heterotrophic yield coefficient YH = 0.693, autotrophic yield coefficient Y(A) = 0.263, heterotrophic decay coefficient KdH, = 0.108 d(-1), autotrophic yield coefficient KdA = 0.089 d(-1), specific maximum COD removal rate v(mS), = 1.94 mg x (mg x d)(-1), half saturation constant for COD removal K(S) = 34.6 mg x L(-1), specific maximum ammonia removal rate vmN = 0.18 mg x (mg x d)(-1), half saturation constant for ammonia removal K(N) = 1.06 mg x L(-1). Compared with the normal reported data of conventional activated sludge process (CAS), Y(H), KdH obtained are higher and vmS, vmN are lower. The high sludge concentration condition of MBR process may account for those differences. PMID:21717743

Xue, Tao; Yu, Kai-Chang; Guan, Jing; Huang, Xia; Wen, Xiang-Hua; Miao, Xue-Na; Cui, Zhi-Guang

2011-04-01

21

Effect of flow parameters of rumen digesta on effective degradability and microbial yield in sheep.  

PubMed

The aim of this experiment was to examine the effect of rumen digesta flow parameters on effective degradability (EDG) and microbial nitrogen (MBN) yield in sheep fed diets of identical provision of both metabolizable energy and rumen degradable nitrogen (RDN). Ruminal degradation parameters of early-harvested perennial ryegrass hay (EH), late-harvested perennial ryegrasses hay (LH) and winter sown barley straw (BS) were determined by a nylon bag technique. Subsequently, three experimental diets (EHD, LHD and BSD) were formulated using the tested forages, sucrose and urea as supplements. An in vivo feeding study was conducted using four rumen cannulated sheep in a partial Latin square design. Digestibility, rate constants of rumen particle breakdown and passage, ruminal fermentation parameters and MBN supply to the small intestine were determined. Animals thoroughly consumed the forages fed at a restricted level. Digestion coefficients were greater for EHD than for LHD and were lowest for BSD (P < 0.05). The rate constant of large particle breakdown was 4.3, 5.9 and 6.7 %/h, respectively, and small particle passage was 5.3, 4.7 and 6.3 %/h for EHD, LHD and BSD, respectively. The estimates differed (P < 0.05) between the diets. The overall passage rate constant of total rumen particles was estimated to be higher for BSD than that for EHD or LHD (P < 0.05). Ruminal fermentation parameters were unaffected by dietary treatments (P > 0.05). Intake levels of rumen degradable organic matter (RDOM) and RDN were estimated to be greater for LHD than that for EHD or BSD (P < 0.05). Although dietary arrangements were made to give identical microbial efficiency, the estimated value was higher for EHD than that for LHD or BSD (P < 0.05); and the MBN yield for BSD was estimated to be lower than that for EHD or LHD (P < 0.05). Rumen kinetic parameters of degradation and particle flow of forage affected EDG values and MBN yield from forage-related RDN intake, although those had little effect on the efficiency of MBN yield from forage-related RDOM intake. PMID:20163598

Ichinohe, Toshiyoshi; Fujihara, Tsutomu

2009-08-01

22

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

23

Spectral and kinetic parameters of phosphorescence of triplet chlorophyll a in the photosynthetic apparatus of plants.  

PubMed

Spectral and kinetic parameters and quantum yield of IR phosphorescence accompanying radiative deactivation of the chlorophyll a (Chl a) triplet state were compared in pigment solutions, greening and mature plant leaves, isolated chloroplasts, and thalluses of macrophytic marine algae. On the early stages of greening just after the Shibata shift, phosphorescence is determined by the bulk Chl a molecules. According to phosphorescence measurement, the quantum yield of triplet state formation is not less than 25%. Further greening leads to a strong decrease in the phosphorescence yield. In mature leaves developing under normal irradiation conditions, the phosphorescence yield declined 1000-fold. This parameter is stable in leaves of different plant species. Three spectral forms of phosphorescence-emitting chlorophyll were revealed in the mature photosynthetic apparatus with the main emission maxima at 955, 975, and 995 nm and lifetimes ~1.9, ~1.5, and 1.1-1.3 ms. In the excitation spectra of chlorophyll phosphorescence measured in thalluses of macrophytic green and red algae, the absorption bands of Chl a and accessory pigments - carotenoids, Chl b, and phycobilins - were observed. These data suggest that phosphorescence is emitted by triplet chlorophyll molecules that are not quenched by carotenoids and correspond to short wavelength forms of Chl a coupled to the normal light harvesting pigment complex. The concentration of the phosphorescence-emitting chlorophyll molecules in chloroplasts and the contribution of these molecules to chlorophyll fluorescence were estimated. Spectral and kinetic parameters of the phosphorescence corresponding to the long wavelength fluorescence band at 737 nm were evaluated. The data indicate that phosphorescence provides unique information on the photophysics of pigment molecules, molecular organization of the photosynthetic apparatus, and mechanisms and efficiency of photodynamic stress in plants. PMID:24910208

Krasnovsky, A A; Kovalev, Yu V

2014-04-01

24

Use of fermentative metabolites for heterotrophic microalgae growth: Yields and kinetics.  

PubMed

The growth of two lipid-producing Chlorella species on fermentative end-products acetate, butyrate and lactate, was investigated using a kinetic modeling approach. Chlorella sorokiniana and Auxenochlorella protothecoides were grown on synthetic media with various (acetate:butyrate:lactate) ratios. Both species assimilated efficiently acetate and butyrate with yields between 0.4 and 0.5g carbon of biomass/g carbon of substrate, but did not use lactate. The highest growth rate on acetate, 2.23d(-1), was observed for C. sorokiniana, and on butyrate, 0.22d(-1), for A. protothecoides. Butyrate removal started after complete acetate exhaustion (diauxic effect). However, butyrate consumption may be favored by the increase of biomass concentration induced by the initial use of acetate. A model combining Monod and Haldane functions was then built and fitted the experimental data well for both species. Butyrate concentration and (acetate:butyrate) ratios were identified as key parameters for heterotrophic growth of microalgae on fermentative metabolites. PMID:25459841

Turon, V; Baroukh, C; Trably, E; Latrille, E; Fouilland, E; Steyer, J-P

2014-10-29

25

Impact of sustaining a controlled residual growth on polyhydroxybutyrate yield and production kinetics in Cupriavidus necator.  

PubMed

In this study a complementary modeling and experimental approach was used to explore how growth controls the NADPH generation and availability, and the resulting impact on PHB (polyhydroxybutyrate) yields and kinetics. The results show that the anabolic demand allowed the NADPH production through the Entner-Doudoroff (ED) pathway, leading to a high maximal theoretical PHB production yield of 0.89 C mole C mole(-1); whereas without biomass production, NADPH regeneration is only possible via the isocitrate dehydrogenase leading to a theoretical yield of 0.67 C mole C mole(-1). Furthermore, the maximum specific rate of NADPH produced at maximal growth rate (to fulfil biomass requirement) was found to be the maximum set in every conditions, which by consequence determines the maximal PHB production rate. These results imply that sustaining a controlled residual growth improves the PHB specific production rate without altering production yield. PMID:24035890

Grousseau, Estelle; Blanchet, Elise; Déléris, Stéphane; Albuquerque, Maria G E; Paul, Etienne; Uribelarrea, Jean-Louis

2013-11-01

26

Crop yield estimation model for Iowa using remote sensing and surface parameters  

E-print Network

Crop yield estimation model for Iowa using remote sensing and surface parameters Anup K. Prasad, surface temperature and rainfall data of Iowa state, US, for 19 years for crop yield assessment-variate optimization method is utilized, which reasonably minimizes inconsistency and errors in yield prediction

Singh, Ramesh P.

27

Optimum Designs for the Equality of Parameters in Enzyme Inhibition Kinetic  

E-print Network

Optimum Designs for the Equality of Parameters in Enzyme Inhibition Kinetic Models Anthony C Abstract A general model for enzyme kinetics with inhibition, the "mixed" inhibi- tion model, simplifies Establishing the equality of parameters is important in the building of the non- linear models used for enzyme

28

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

PubMed

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

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

2011-11-01

29

Measurement of the asymmetry parameter for the decay {Lambda}{yields}p{pi}{sup +}  

SciTech Connect

Based on a sample of 58x10{sup 6}J/{psi} decays collected with the BESII detector at the BEPC, the {Lambda} decay parameter {alpha}{sub {Lambda}}for {Lambda}{yields}p{pi}{sup +} is measured using about 9000 J/{psi}{yields}{Lambda}{Lambda}{yields}pp{pi}{sup +{pi}-} decays. A fit to the joint angular distributions yields {alpha}{sub {Lambda}({Lambda}{yields}p{pi}{sup +})}=-0.755{+-}0.083{+-}0.063, where the first error is statistical, and the second systematic.

Ablikim, M.; Bai, J. Z.; Bai, Y.; Cai, X.; Chen, H. S.; Chen, H. X.; Chen, J. C.; Chen, Jin; Chen, Y. B.; Chu, Y. P.; Deng, Z. Y.; Du, S. X.; Fang, J.; Fu, C. D.; Gao, C. S.; Gu, S. D.; Guo, Y. N.; He, K. L.; Heng, Y. K.; Hu, H. M. [Institute of High Energy Physics, Beijing 100049 (China)

2010-01-01

30

High-yield hydrogen production from biomass by in vitro metabolic engineering: Mixed sugars coutilization and kinetic modeling.  

PubMed

The use of hydrogen (H2) as a fuel offers enhanced energy conversion efficiency and tremendous potential to decrease greenhouse gas emissions, but producing it in a distributed, carbon-neutral, low-cost manner requires new technologies. Herein we demonstrate the complete conversion of glucose and xylose from plant biomass to H2 and CO2 based on an in vitro synthetic enzymatic pathway. Glucose and xylose were simultaneously converted to H2 with a yield of two H2 per carbon, the maximum possible yield. Parameters of a nonlinear kinetic model were fitted with experimental data using a genetic algorithm, and a global sensitivity analysis was used to identify the enzymes that have the greatest impact on reaction rate and yield. After optimizing enzyme loadings using this model, volumetric H2 productivity was increased 3-fold to 32 mmol H2?L(-1)?h(-1). The productivity was further enhanced to 54 mmol H2?L(-1)?h(-1) by increasing reaction temperature, substrate, and enzyme concentrations-an increase of 67-fold compared with the initial studies using this method. The production of hydrogen from locally produced biomass is a promising means to achieve global green energy production. PMID:25848015

Rollin, Joseph A; Martin Del Campo, Julia; Myung, Suwan; Sun, Fangfang; You, Chun; Bakovic, Allison; Castro, Roberto; Chandrayan, Sanjeev K; Wu, Chang-Hao; Adams, Michael W W; Senger, Ryan S; Zhang, Y-H Percival

2015-04-21

31

Kinetic simulations of a deuterium-tritium Z pinch with >10{sup 16} neutron yield  

SciTech Connect

Fully kinetic, collisional, and electromagnetic simulations of the time evolution of an imploding and burning Z pinch plasma have been performed. Using the implicit particle-in-cell (PIC) code, multidimensional (1D and 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 low pinch current, 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 with deuterium-tritium fuel, the vast majority of the neutrons is thermonuclear in origin and neutron yield follows an I{sup 4} neutron yield scaling with current. High-current, multidimension simulations (up to 40 MA with > 10{sup 16} neutron yield) suggest that the fraction of thermonuclear neutrons increases with current and the strong dependence of neutron yield with current will continue at still higher currents. Scenarios for fusion breakeven and possible ignition in the 40-80 MA regime are discussed.

Welch, D. R.; Rose, D. V.; Thoma, C.; Clark, R. E.; Mostrom, C. B. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); Stygar, W. A.; Leeper, R. J. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1196 (United States)

2011-05-15

32

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 (?(?(irr))(A-->B)) and reverse (?(?(irr))(B-->A)) quantum yields at various irradiation wavelengths. It has been found that ?(?(irr))(A-->B) undergoes a 15-fold increase with wavelength between 220 and 360 nm, with the spectral section 250-360 nm representing Monte effective photodegradation causative range. The reverse quantum yield values were generally between 12 and 54% lower than those recorded for ?(?(irr))(A-->B), 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 258-380 nm. PMID:24835854

Maafi, Mounir; Maafi, Wassila

2014-08-25

33

Chemical-kinetic prediction of critical parameters in gaseous detonations  

SciTech Connect

A theoretical model including a detailed chemical kinetic reaction mechanism for hydrogen and hydrocarbon oxidation is used to examine the effects of variations in initial pressure and temperature on the detonation properties of gaseous fuel-oxidizer mixtures. Fuels considered include hydrogen, methane, ethane, ethylene, and acetylene. Induction lengths are computed for initial pressures between 0.1 and 10.0 atmospheres and initial temperatures between 200K and 500K. These induction lengths are then compared with available experimental data for critical energy and critical tube diameter for initiation of spherical detonation, as well as detonation limits in linear tubes. Combined with earlier studies concerning variations in fuel-oxidizer equivalence ratio and degree of dilution with N/sub 2/, the model provides a unified treatment of fuel oxidation kinetics in detonations. 4 figures, 1 table.

Westbrook, C.K.; Urtiew, P.A.

1982-01-12

34

Parameter Optimization for Enhancement of Ethanol Yield by Atmospheric Pressure DBD-Treated Saccharomyces cerevisiae  

NASA Astrophysics Data System (ADS)

In this study, Saccharomyces cerevisiae (S. cerevisiae) was exposed to dielectric barrier discharge plasma (DBD) to improve its ethanol production capacity during fermentation. Response surface methodology (RSM) was used to optimize the discharge-associated parameters of DBD for the purpose of maximizing the ethanol yield achieved by DBD-treated S. cerevisiae. According to single factor experiments, a mathematical model was established using Box-Behnken central composite experiment design, with plasma exposure time, power supply voltage, and exposed-sample volume as impact factors and ethanol yield as the response. This was followed by response surface analysis. Optimal experimental parameters for plasma discharge-induced enhancement in ethanol yield were plasma exposure time of 1 min, power voltage of 26 V, and an exposed sample volume of 9 mL. Under these conditions, the resulting yield of ethanol was 0.48 g/g, representing an increase of 33% over control.

Dong, Xiaoyu; Yuan, Yulian; Tang, Qian; Dou, Shaohua; Di, Lanbo; Zhang, Xiuling

2014-01-01

35

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

36

[Analysis of hydrodynamics parameters of runoff erosion and sediment-yielding on unpaved road].  

PubMed

By the method of field runoff washout experiment, a simulation study was conducted on the relationships between the soil detachment rate and the hydrodynamic parameters on unpaved road, and the related quantitative formulas were established. Under the conditions of different flow discharges and road gradients, the averaged soil detachment rate increased with increasing flow discharge and road gradient, and the relationships between them could be described by a power function. As compared with road gradient, flow discharge had greater effects on the soil detachment rate. The soil detachment rate had a power relation with water flow velocity and runoff kinetic energy, and the runoff kinetic energy was of importance to the soil detachment rate. The soil detachment rate was linearly correlated with the unit runoff kinetic energy. The averaged soil erodibility was 0.120 g m-1.J-F-1, and the averaged critical unit runoff kinetic energy was 2.875 g.m-1.J-1. Flow discharge, road gradient, and unit runoff kinetic energy could be used to accurately describe the soil erosion process and calculate the soil erosion rate on unpaved road. PMID:23705397

Huang, Peng-Fei; Wang, Wen-Long; Luo, Ting; Wang, Zhen; Wang, Zheng-Li; Li, Ren

2013-02-01

37

Estimation of kinetic parameters related to biochemical interactions between hydrogen peroxide and signal transduction proteins  

PubMed Central

The lack of kinetic data concerning the biological effects of reactive oxygen species is slowing down the development of the field of redox signaling. Herein, we deduced and applied equations to estimate kinetic parameters from typical redox signaling experiments. H2O2-sensing mediated by the oxidation of a protein target and the switch-off of this sensor, by being converted back to its reduced form, are the two processes for which kinetic parameters are determined. The experimental data required to apply the equations deduced is the fraction of the H2O2 sensor protein in the reduced or in the oxidized state measured in intact cells or living tissues after exposure to either endogenous or added H2O2. Either non-linear fittings that do not need transformation of the experimental data or linearized plots in which deviations from the equations are easily observed can be used. The equations were shown to be valid by fitting to them virtual time courses simulated with a kinetic model. The good agreement between the kinetic parameters estimated in these fittings and those used to simulate the virtual time courses supported the accuracy of the kinetic equations deduced. Finally, equations were successfully tested with real data taken from published experiments that describe redox signaling mediated by the oxidation of two protein tyrosine phosphatases, PTP1B and SHP-2, which are two of the few H2O2-sensing proteins with known kinetic parameters. Whereas for PTP1B estimated kinetic parameters fitted in general the present knowledge, for SHP-2 results obtained suggest that reactivity toward H2O2 as well as the rate of SHP-2 regeneration back to its reduced form are higher than previously thought. In conclusion, valuable quantitative kinetic data can be estimated from typical redox signaling experiments, thus improving our understanding about the complex processes that underlie the interplay between oxidative stress and redox signaling responses. PMID:25325054

Brito, Paula M.; Antunes, Fernando

2014-01-01

38

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

39

Alcoholysis catalyzed by Candida antarctica lipase B in a gas/solid system : effects of water on kinetic parameters  

E-print Network

the influence of water on enzyme kinetic behavior is to perform a full kinetic description based on properly on kinetic parameters Marianne Graber, Marie-Pierre Bousquet-Dubouch, Sylvain Lamare and Marie- Dominique from Candida antarctica ­ kinetics ­ transesterification ­ water ­ solid/gas biocatalysis - hydration

Paris-Sud XI, Université de

40

Reduced parameter set determinable from geminate kinetics Noam Agmon *  

E-print Network

the Smoluchowski theory [6,7] to fluorescence quenching data. In this case it is possible to recover all concentrations, so there is no distance scale outside the microscopic parameters that one hopes to determine from with a relative diffusion constant, D, or (re)associate with a rate constant ka following their collision

Agmon, Noam

41

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

42

Nuclide yields of light fission products from thermal-neutron induced fission of 233U at different kinetic energies  

Microsoft Academic Search

The yields of light fission products from thermal-neutron induced fission of 233U are measured as a function of their mass A, their nuclear charge Z, their kinetic energy E and their ionic charge state q at the recoil spectrometer Lohengrin of the Institut Laue-Langevin in Grenoble. The mass yields are determined by intercepting the fragments with an ionization chamber of

U. Quade; K. Rudolph; S. Skorka; P. Armbruster; H.-G. Clerc; W. Lang; M. Mutterer; C. Schmitt; J. P. Theobald; F. Gönnenwein; J. Pannicke; H. Schrader; G. Siegert; D. Engelhardt

1988-01-01

43

Identification of Material Parameters in Yield Functions and Flow Rules for WeaklyTextured Sheets of Cubic Metals  

E-print Network

Identification of Material Parameters in Yield Functions and Flow Rules for Weakly­Textured Sheets in uniaxial tensile tests. As far as possible, we determine the material parameters in the yield functions of aluminum (see also Barlat [4]). Since then, many phenomenological non­quadratic yield functions and plastic

Kentucky, University of

44

Effects of heating rate on slow pyrolysis behavior, kinetic parameters and products properties of moso bamboo.  

PubMed

Effects of heating rate on slow pyrolysis behaviors, kinetic parameters, and products properties of moso bamboo were investigated in this study. Pyrolysis experiments were performed up to 700 °C at heating rates of 5, 10, 20, and 30 °C/min using thermogravimetric analysis (TGA) and a lab-scale fixed bed pyrolysis reactor. The results show that the onset and offset temperatures of the main devolatilization stage of thermogravimetry/derivative thermogravimetry (TG/DTG) curves obviously shift toward the high-temperature range, and the activation energy values increase with increasing heating rate. The heating rate has different effects on the pyrolysis products properties, including biochar (element content, proximate analysis, specific surface area, heating value), bio-oil (water content, chemical composition), and non-condensable gas. The solid yields from the fixed bed pyrolysis reactor are noticeably different from those of TGA mainly because the thermal hysteresis of the sample in the fixed bed pyrolysis reactor is more thorough. PMID:25063973

Chen, Dengyu; Zhou, Jianbin; Zhang, Qisheng

2014-10-01

45

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.. PMID:21637545

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

2011-01-01

46

Statistical estimation of physical quantities in thermal- and fast-neutron-induced fission. [Fission product mass yields, fragment kinetic energies, numbers of prompt neutrons  

Microsoft Academic Search

Making use of a model based on the statistical theory in which the scission-point distance is treated as an adjustable parameter, calculations were performed to obtain the mass yields of fission products, the kinetic energies of fission fragments and the numbers of prompt neutrons from neutron-induced fission of ²³²Th, ²³¹Pa, ²³³U, ²³⁵U, ²³⁸U, ²³⁷Np, ²³⁹Pu and ²⁴¹Pu for incident-neutron energies

T. Yamamoto; K. Sugiyama

1975-01-01

47

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. PMID:21637608

2010-01-01

48

Charge recombination reactions in photosystem II. I. Yields, recombination pathways, and kinetics of the primary pair.  

PubMed

Recombination reactions of the primary radical pair in photosystem II (PS II) have been studied in the nanosecond to millisecond time scales by flash absorption spectroscopy. Samples in which the first quinone acceptor (QA) was in the semiquinone form (QA-) or in the doubly reduced state (presumably QAH2) were used. The redox state of QA and the long-lived triplet state of the primary electron donor chlorophyll (3P680) were monitored by EPR. The following results were obtained at cryogenic temperatures (around 20 K). (1) the primary radical pair, P680+Pheo-, is formed with a high yield irrespective of the redox state of QA. (2) The decay of the primary pair is faster with QA- than with QAH2 and could be described biexponentially with t1/2 approximately 20 ns (approximately 65%)/150 ns (approximately 35%) and t1/2 approximately 60 ns (approximately 35%)/250 ns (approximately 65%), respectively. The different kinetics may be due to electrostatic and/or magnetic effects of QA- on charge recombination or due to conformational changes caused by the double reduction treatment. (3) The yield of the triplet state 3P680 was high both with QA- and QAH2. (4) The triplet decay was much faster with QA- [t1/2 approximately 2 microseconds (approximately 50%)/20 microseconds (approximately 50%)] than with QAH2 [t1/2 approximately 1 ms (approximately 65%)/3 ms (approximately 35%)]. The short lifetime of the triplet with QA- explains why it was not detected earlier. The mechanism of triplet quenching in the presence of QA- is not understood; however it may represent a protective process in PS II. (5) Almost identical data were obtained for PS II-enriched membranes from spinach and PS II core preparations from Synechococcus. Room temperature optical studies were performed on the Synechococcus preparation. In samples containing sodium dithionite to form QA- in the dark, EPR controls showed that multiple excitation flashes given at room temperature led to a decrease of the QA-Fe2+ signal, indicating double reduction of QA. During the first few flashes, QA- was still present in the large majority of the centers. In this case, the yield of the primary pair at room temperature was around 50%, and its decay could be described monoexponentially with t1/2 approximately 8 ns (a slightly better fit was obtained with two exponentials: t1/2 approximately 4 ns (approximately 80%)/25 ns (approximately 20%).(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7718587

van Mieghem, F; Brettel, K; Hillmann, B; Kamlowski, A; Rutherford, A W; Schlodder, E

1995-04-11

49

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. PMID:24729295

B?rzi?š, Agris; Acti?š, Andris

2014-06-01

50

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

51

Effects of secondary yield parameter variation on predicted equilibrium potential of an object in a charging environment. [for spacecraft  

NASA Technical Reports Server (NTRS)

A study is presented in which the sensitivity of predicted equilibrium potential to changes in secondary electron yield parameters is investigated using MATCHG, a simple charging code which incorporates the NASCAP material property formulations. It is found that equilibrium potential is a sensitive function of one of the two parameters specifying secondary electron yield due to proton impact and of essentially all the parameters specifying yield due to electron impact. In addition, it is found that information on the electron generated secondary yield parameters can be obtained from monoenergetic beam charging data if charging rates as well as equilibrium potentials are accurately recorded.

Purvis, C. K.

1979-01-01

52

Evaluation of Anaerobic Biofilm Reactor Kinetic Parameters Using Ant Colony Optimization  

PubMed Central

Abstract Fixed bed reactors with naturally attached biofilms are increasingly used for anaerobic treatment of industry wastewaters due their effective treatment performance. The complex nature of biological reactions in biofilm processes often poses difficulty in analyzing them experimentally, and mathematical models could be very useful for their design and analysis. However, effective application of biofilm reactor models to practical problems suffers due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, an inverse modeling approach based on ant colony optimization is proposed and applied to estimate the kinetic and film thickness model parameters of wastewater treatment process in an anaerobic fixed bed biofilm reactor. Experimental data of pharmaceutical industry wastewater treatment process are used to determine the model parameters as a consequence of the solution of the rigorous mathematical models of the process. Results were evaluated for different modeling configurations derived from the combination of mathematical models, kinetic expressions, and optimization algorithms. Analysis of results showed that the two-dimensional mathematical model with Haldane kinetics better represents the pharmaceutical wastewater treatment in the biofilm reactor. The mathematical and kinetic modeling of this work forms a useful basis for the design and optimization of industry wastewater treating biofilm reactors. PMID:24065871

Satya, Eswari Jujjavarapu; Venkateswarlu, Chimmiri

2013-01-01

53

Thermodynamic Characterization of Five Key Kinetic Parameters that Define Neuronal Nitric Oxide Synthase Catalysis  

PubMed Central

NO synthase (NOS) enzymes convert L-arginine to NO in two sequential reactions whose rates (kcat1 and kcat2) are both limited by the rate of ferric heme reduction (kr). An enzyme ferric heme-NO complex forms as an immediate product complex and then undergoes either dissociation (at a rate that we denote as kd) to release NO in a productive manner, or reduction (kr) to form a ferrous heme-NO complex (FeIINO) that must react with O2 (at a rate that we denote as kox) in a NO dioxygenase reaction that regenerates the ferric enzyme. The interplay of these five kinetic parameters (kcat1, kcat2, kr, kd, and kox) determine NOS specific activity, O2 concentration response, and pulsatile versus steady-state NO generation. Here we utilized stopped-flow spectroscopy and single catalytic turnover methods to characterize the individual temperature dependencies of the five kinetic parameters of rat neuronal NOS (nNOS). We then incorporated the measured kinetic values into computer simulations of the nNOS reaction using a global kinetic model to comprehensively model its temperature-dependent catalytic behaviors. Our results provide new mechanistic insights and also reveal that the different temperature dependencies of the five kinetic parameters significantly alter nNOS catalytic behaviors and NO release efficiency as a function of temperature. PMID:23789902

Haque, Mohammad Mahfuzul; Tejero, Jesús; Bayachou, Mekki; Wang, Zhi-Qiang; Fadlalla, Mohammed; Stuehr, Dennis J.

2013-01-01

54

Nuclide yields of light fission products from thermal-neutron induced fission of 233U at different kinetic energies  

NASA Astrophysics Data System (ADS)

The yields of light fission products from thermal-neutron induced fission of 233U are measured as a function of their mass A, their nuclear charge Z, their kinetic energy E and their ionic charge state q at the recoil spectrometer Lohengrin of the Institut Laue-Langevin in Grenoble. The mass yields are determined by intercepting the fragments with an ionization chamber of high energy resolution positioned at the focal plane of the spectrometer. The nuclear charges and their yields are determined with the same ionization chamber by measuring the residual energy of fission products, selected monoenergetically by Lohengrin, behind a passive absorber made of parylene-C. The nuclear charge resolution enabled by this detector device is considerably improved to Z/d Z = 58. The nuclear charge and mass distributions summed over all ionic charge states are listed within the mass range 79 ? A ? 106 at 6 energies: E = 85.34, 90.41, 95.46, 100.50, 105.55 and 110.55 MeV. The energy-integrated nuclear charge and mass yields are also given. The isotonic and isotopic yields are shown. An odd-even effect in the yields is found for the protons as well as for the neutrons at all kinetic energies. The yield weighted total odd-even effect for the protons is found to be (22.1 ± 2.1)%, for the neutrons (5.4 ± 1.7)%. An odd-even effect for the protons in the mean kinetic energy is also observed. The displacement of the mean isobaric nuclear charges from the unchanged charge-density values and the variances of the isobaric nuclear-charge distributions reveal fine structures in their mass dependences.

Quade, U.; Rudolph, K.; Skorka, S.; Armbruster, P.; Clerc, H.-G.; Lang, W.; Mutterer, M.; Schmitt, C.; Theobald, J. P.; Gönnenwein, F.; Pannicke, J.; Schrader, H.; Siegert, G.; Engelhardt, D.

1988-10-01

55

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

PubMed

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

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

2014-03-01

56

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

57

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

E-print Network

Compost mixture influence of interactive physical parameters on microbial kinetics and substrate 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 Composting is a feasible by selecting an initial compost recipe with physical properties that enhance microbial activity. The present

Paris-Sud XI, Université de

58

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

ERIC Educational Resources Information Center

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

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

2011-01-01

59

The kinetic parameters and safe operating conditions of nitroglycerine manufacture in the CSTR of Biazzi process  

Microsoft Academic Search

Nitroglycerine has been widely used as an ingredient of explosives and propellants for a long time. It is produced by the glycerine nitration reaction. Many fire and explosion incidents have occurred during its manufacturing process owing to its severe thermal instability in both the nitration reaction and the purification processes. The kinetic parameters of this reaction and the criteria for

Kai-Tai Lu; Kuo-Ming Luo; Tsao-Fa Yeh; Peng-Chu Lin

2008-01-01

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

Kinetic parameters of association and dissociation between single molecules measured by single-molecule force spectroscopy  

Microsoft Academic Search

This presentation is focused on development of experimental scanning probe microscopy (SPM) approaches to quantify kinetic parameters of association and dissociation between receptor--ligand pairs. The potential of mean force (pmf) between interacting molecules is quantified by single molecule force spectroscopy (SMFS) approach. In SMFS molecules are allowed to interact and form molecular bond. Consequent measurements of rupture forces are used

Boris Akhremitchev

2009-01-01

62

Heterogeneity of kinetic parameters of enzymes in situ in rat liver lobules  

Microsoft Academic Search

In the present review, metabolic compartmentation in liver lobules is discussed as being dynamic and more complex than thus far assumed on the basis of numbers of mRNA or protein molecules or the capacity (zero-order activity) of enzymes. Isoenzyme distribution patterns and local kinetic parameters of enzymes may vary over the different zones of liver lobules. As a consequence, metabolic

C. J. F. Van Noorden; G. N. Jonges

1995-01-01

63

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

64

A genetic algorithm with decimal coding for the estimation of kinetic and energetic parameters  

Microsoft Academic Search

A hybrid estimation method is proposed to estimate simultaneously the kinetic and energetic parameters of chemical models. This method combines a genetic algorithm with a local convergence method, the former generating initialisation points for the latter. The method is applied to a real complex chemical system: the saponification of ethyl acetate at a concentration of 1 mol l?1. The reaction

L. Balland; L. Estel; J.-M. Cosmao; N. Mouhab

2000-01-01

65

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

PubMed

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

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

2013-09-01

66

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

PubMed

Plant hormones influence the key parameters that contribute to crop yield, including biomass, branching and seed number. We tested manipulation of cytokinin signaling as an avenue for influencing these growth parameters. Here we report a full-length 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 similarity to S-adenosyl-L-homocysteine hydrolase (SAHH). Transgenic petunia plants expressing this gene in antisense orientation displayed profuse branching, delayed flowering and delayed shoot bud induction from leaf explants in vitro. Homologs were also isolated from Arabidopsis thaliana homology-dependent gene silencing 1 (HOG1) and Orzya sativa (OsCBP). Arabidopsis HOG1 showed high affinity cytokinin binding activity and modified plant architecture similar to PETCBP. Transgenic Arabidopsis plants overexpressing HOG1 showed early flowering with a significantly reduced plant biomass and number of leaves. In contrast, profuse branching, delayed flowering, increased leaf size and higher seed yield were the major phenotypes observed in the antisense suppression lines. These results suggest that genetic manipulation of this cytokinin binding protein or its orthologs could be used for improving crop biomass and seed yield. PMID:18592247

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

2008-09-01

67

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

68

Fission yields at different fission-product kinetic energies for thermal-neutron-induced fission of 239Pu  

NASA Astrophysics Data System (ADS)

At the recoil spectrometer "Lohengrin" of the Institut Laue-Langevin in Grenoble, the yields of the light fission products from the thermal-neutron-induced fission of 239Pu were measured as a function of A, Z, the kinetic energy E and the ionic charge states q. The nuclear charge and mass distributions summed over all ionic charge states were determined for different light fissionproduct kinetic energies between 93 and 112 MeV. The proton odd-even effect which was measured to be (11.6 ± 0.6)% causes considerable fine structure in the yields. The average kinetic energy of even- Z elements in the light fission-product group is 0.3 ± 0.1 MeV larger than for odd- Z elements. The neutron odd-even effect is (6.5 ± 0.7)%. The comparison with previously published data 1) for thermal-neutron-induced fission of 235U reveals a correlation between the proton odd-even effect in the yield and in the kinetic energy of the elements. The dependence of the proton odd-even effect on the fragmentation is very similar for 235U and 239Pu when it is considered as a function of the nuclear charge of the heavy fission products. The isobaric variances ?z2. for thermal-neutron fission of 235U and 239Pu coincide at all kinetic energies if the influence of the proton odd-even effect is averaged out. This supports the hypothesis that the magnitude of ?z2 is determined only by quantum-mechanical zero-point fluctuations. The influence of the spherical shells Z = 50 and N = 82 on the fragmentation is discussed.

Schmitt, C.; Guessous, A.; Bocquet, J. P.; Clerc, H.-G.; Brissot, R.; Engelhardt, D.; Faust, H. R.; Gönnenwein, F.; Mutterer, M.; Nifenecker, H.; Pannicke, J.; Ristori, CH.; Theobald, J. P.

1984-11-01

69

Identi cation of Material Parameters in Yield Functions and Flow Rules for Weakly-Textured Sheets of Cubic Metals  

E-print Network

Identi cation of Material Parameters in Yield Functions and Flow Rules for Weakly-Textured Sheets tests. As far as possible, we determine the material parameters in the yield functions which would are notably inadequate for modelling the plastic behavior of aluminum (see also Barlat 4]). Since then, many

Kentucky, University of

70

Fission yields at different fission-product kinetic energies for thermal-neutron-induced fission of 239Pu  

Microsoft Academic Search

At the recoil spectrometer ``Lohengrin'' of the Institut Laue-Langevin in Grenoble, the yields of the light fission products from the thermal-neutron-induced fission of 239Pu were measured as a function of A, Z, the kinetic energy E and the ionic charge states q. The nuclear charge and mass distributions summed over all ionic charge states were determined for different light fissionproduct

C. Schmitt; A. Guessous; J. P. Bocquet; H.-G. Clerc; R. Brissot; D. Engelhardt; H. R. Faust; F. Gönnenwein; M. Mutterer; H. Nifenecker; J. Pannicke; Ch. Ristori; J. P. Theobald

1984-01-01

71

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

72

Constraints on effective field theory parameters for the {Lambda}N{yields}NN transition  

SciTech Connect

The relation between the low-energy constants appearing in the effective field theory description of the {Lambda}N{yields}NN transition potential and the parameters of the one-meson-exchange model previously developed is obtained. We extract the relative importance of the different exchange mechanisms included in the meson picture by means of a comparison to the corresponding operational structures appearing in the effective approach. The ability of this procedure to obtain the weak baryon-baryon-meson couplings for a possible scalar exchange is also discussed.

Perez-Obiol, Axel; Parreno, Assumpta [Departament d'Estructura i Constituents de la Materia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona, Marti i Franques 1, E-08028 (Spain); Julia-Diaz, Bruno [Departament d'Estructura i Constituents de la Materia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona, Marti i Franques 1, E-08028 (Spain); Institut de Ciencies Fotoniques (ICFO), Parc Mediterrani de la Tecnologia, E-08860 Castelldefels (Barcelona) (Spain)

2011-08-15

73

Impact of initial conditions on extant microbial kinetic parameter estimates: application to chlorinated ethene dehalorespiration.  

PubMed

Monod kinetics are the foundation of mathematical models of many environmentally important biological processes, including the dehalorespiration of chlorinated ethene groundwater contaminants. The Monod parameters--qmax, the maximum specific substrate utilization rate, and KS, the half-saturation constant--are typically estimated in batch assays, which are superficially simple to prepare and maintain. However, if initial conditions in batch assays are not chosen carefully, it is unlikely that the estimated parameter values will be meaningful because they do not reflect microbial activity in the environmental system of interest, and/or they are not mathematically identifiable. The estimation of qmax and KS values that are highly correlated undoubtedly contributes significantly to the wide range in reported parameter values and may undermine efforts to use mathematical models to demonstrate the occurrence of natural attenuation or predict the performance of engineered bioremediation approaches. In this study, a series of experimental and theoretical batch kinetic assays were conducted using the tetrachloroethene-respirer Desulfuromonas michiganensis to systematically evaluate the effects of initial batch assay conditions, expressed as the initial substrate (S0)-to-initial biomass concentration (X0) ratio (S0/X0) and the S0/KS ratio on parameter correlation. An iterative approach to obtain meaningful Monod parameter estimates was developed and validated using three different strains and can be broadly applied to a range of other substrates and populations. While the S0/X0 ratio is critical to obtaining kinetic parameter estimates that reflect in situ microbial activity, this study shows that optimization of the S0/KS ratio is key to minimizing Monod parameter correlation. PMID:23963272

Huang, Deyang; Lai, Yenjung; Becker, Jennifer G

2014-03-01

74

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

75

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

PubMed Central

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

Robinson, J A; Tiedje, J M

1983-01-01

76

Estimation of genetic parameters for milk yield in Murrah buffaloes by Bayesian inference.  

PubMed

Random regression models were used to estimate genetic parameters for test-day milk yield in Murrah buffaloes using Bayesian inference. Data comprised 17,935 test-day milk records from 1,433 buffaloes. Twelve models were tested using different combinations of third-, fourth-, fifth-, sixth-, and seventh-order orthogonal polynomials of weeks of lactation for additive genetic and permanent environmental effects. All models included the fixed effects of contemporary group, number of daily milkings and age of cow at calving as covariate (linear and quadratic effect). In addition, residual variances were considered to be heterogeneous with 6 classes of variance. Models were selected based on the residual mean square error, weighted average of residual variance estimates, and estimates of variance components, heritabilities, correlations, eigenvalues, and eigenfunctions. Results indicated that changes in the order of fit for additive genetic and permanent environmental random effects influenced the estimation of genetic parameters. Heritability estimates ranged from 0.19 to 0.31. Genetic correlation estimates were close to unity between adjacent test-day records, but decreased gradually as the interval between test-days increased. Results from mean squared error and weighted averages of residual variance estimates suggested that a model considering sixth- and seventh-order Legendre polynomials for additive and permanent environmental effects, respectively, and 6 classes for residual variances, provided the best fit. Nevertheless, this model presented the largest degree of complexity. A more parsimonious model, with fourth- and sixth-order polynomials, respectively, for these same effects, yielded very similar genetic parameter estimates. Therefore, this last model is recommended for routine applications. PMID:20105550

Breda, F C; Albuquerque, L G; Euclydes, R F; Bignardi, A B; Baldi, F; Torres, R A; Barbosa, L; Tonhati, H

2010-02-01

77

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

78

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

NASA Astrophysics Data System (ADS)

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

Zhou, Yang; Yang, Daiwen

2014-12-01

79

The secondary electron emission yield of muscovite mica: Charging kinetics and current density effects  

E-print Network

insulation properties, combined with good mechanical and thermal properties.1,2 It is a highly reliable yield curve 0 (E), representing the variation of the yield of the uncharged material with the energy E is obtained at high current density in the energy range (EI ,EII ) where the material is normally positively

Paris-Sud 11, Université de

80

Reliability of spatiotemporal and kinetic gait parameters determined by a new instrumented treadmill system  

PubMed Central

Background Despite the emerging use of treadmills integrated with pressure platforms as outcome tools in both clinical and research settings, published evidence regarding the measurement properties of these new systems is limited. This study evaluated the within– and between–day repeatability of spatial, temporal and vertical ground reaction force parameters measured by a treadmill system instrumented with a capacitance–based pressure platform. Methods Thirty three healthy adults (mean age, 21.5?±?2.8 years; height, 168.4?±?9.9 cm; and mass, 67.8?±?18.6 kg), walked barefoot on a treadmill system (FDM–THM–S, Zebris Medical GmbH) on three separate occasions. For each testing session, participants set their preferred pace but were blinded to treadmill speed. Spatial (foot rotation, step width, stride and step length), temporal (stride and step times, duration of stance, swing and single and double support) and peak vertical ground reaction force variables were collected over a 30–second capture period, equating to an average of 52?±?5 steps of steady–state walking. Testing was repeated one week following the initial trial and again, for a third time, 20 minutes later. Repeated measures ANOVAs within a generalized linear modelling framework were used to assess between–session differences in gait parameters. Agreement between gait parameters measured within the same day (session 2 and 3) and between days (session 1 and 2; 1 and 3) were evaluated using the 95% repeatability coefficient. Results There were statistically significant differences in the majority (14/16) of temporal, spatial and kinetic gait parameters over the three test sessions (P?parameters, 14% and 33% for spatial parameters, and 4% and 20% for kinetic parameters between days. Within–day repeatability was similar to that observed between days. Temporal and kinetic gait parameters were typically more consistent than spatial parameters. The 95% repeatability coefficient for vertical force peaks ranged between?±?53 and?±?63 N. Conclusions The limits of agreement in spatial parameters and ground reaction forces for the treadmill system encompass previously reported changes with neuromuscular pathology and footwear interventions. These findings provide clinicians and researchers with an indication of the repeatability and sensitivity of the Zebris treadmill system to detect changes in common spatiotemporal gait parameters and vertical ground reaction forces. PMID:23964707

2013-01-01

81

Cotton-Basil Intercropping: Effects on Pests, Yields and Economical Parameters in an Organic Field in Fayoum, Egypt  

Microsoft Academic Search

In many countries, cotton is traditionally intercropped with other plants in order to increase yields and to control pests. The effects of intercropping cotton (Gossypium barbcidense L.) and basil (Ocimum basilicum L.) were tested during one field season on pest infestation, yields and economical parameters in the Governorate of Fayoum, Egypt. Basil, which is known for its repellent effect on

Christian Schader; Johann G. Zaller; Ulrich Köpke

2005-01-01

82

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

E-print Network

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

California at Riverside, University of

83

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

84

Determination of thermoluminescence kinetic parameters of terbium-doped zirconium oxide  

NASA Astrophysics Data System (ADS)

In recent years considerable importance has been attached to zirconium oxide doped with rare earth (ZrO 2 : RE) thin films due to their desirable characteristics for use in UV dosimetry. In our laboratories we have developed a method to prepare ZrO 2 : RE thin films. Dosimetric characteristics of these materials have been reported previously (Azorin et al., Radiat. Meas. 29 (1998) 315; Radiat. Prot. Dosim. 85 (1999) 317) and results of these have stimulated continued development and analysis of the thermoluminescence mechanism. Two important parameters to be determined in TL studies are the activation energy ( E) and the frequency factor ( s). This paper presents the results of determining kinetic parameters of terbium-doped zirconium oxide (ZrO 2 : Tb) thin films, exposed to 260 nm UV light, using the Lushchik (Sov. Phys. JETF 3 (1956) 390) and Chen (J. Appl. Phys. 40 (1969) 570; J. Electrochem. Soc. 166 (1969) 1254) methods. Kinetic analysis of the glow curve shows second order kinetics for both the first and second glow peaks.

Rivera, T.; Azorín, J.; Falcony, C.; Martínez, E.; García, M.

2001-06-01

85

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

86

Emerging Parameter Space Map of Magnetic Reconnection in Collisional and Kinetic Regimes  

NASA Astrophysics Data System (ADS)

In large-scale systems of interest to solar physics, there is growing evidence that magnetic reconnection involves the formation of extended current sheets which are unstable to plasmoids (secondary magnetic islands). Recent results suggest that plasmoids may play a critical role in the evolution of reconnection, and have raised fundamental questions regarding the applicability of resistive MHD to various regimes. In collisional plasmas, where the thickness of all resistive layers remain larger than the ion gyroradius, simulations results indicate that plasmoids permit reconnection to proceed much faster than the slow Sweet-Parker scaling. However, it appears these rates are still a factor of ˜10× slower than observed in kinetic regimes, where the diffusion region current sheet falls below the ion gyroradius and additional physics beyond MHD becomes crucially important. Over a broad range of interesting parameters, the formation of plasmoids may naturally induce a transition into these kinetic regimes. New insights into this scenario have emerged in recent years based on a combination of linear theory, fluid simulations and fully kinetic simulations which retain a Fokker-Planck collision operator to allow a rigorous treatment of Coulomb collisions as the reconnection electric field exceeds the runaway limit. Here, we present some new results from this approach for guide field reconnection. Based upon these results, a parameter space map is constructed that summarizes the present understanding of how reconnection proceeds in various regimes.

Daughton, William; Roytershteyn, Vadim

2012-11-01

87

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

NASA Astrophysics Data System (ADS)

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

Chaudhry, Q. A.

2014-12-01

88

Importance of cholinesterase kinetic parameters in environmental monitoring using estuarine fish.  

PubMed

The aim of the present study was to determine the kinetic parameters and cholinesterase (ChE) activity in two teleost fish, the white mouth croaker Micropogonias furnieri (Scianidae) and the Madamango sea catfish Cathorops spixii (Ariidae), to verify their suitability as sentinel species of aquatic pollution by anticholinergic compounds. Individuals of each species were captured in one reference and one polluted site in the Southern Brazilian coast. Brain tissue was used as enzyme source. Inhibition kinetic parameters indicated that ChE from C. spixii collected at the reference site showed more affinity (Ka) for eserine that from those collected at the polluted site. The opposite was observed for the carbamylation constants (Kc). Thus, similar inhibition constants (Ki) were observed. M. furnieri brain showed an extremely low sensitivity to in vitro inhibition by eserine, indicating that it is not a suitable biomarker to be employed in environmental monitoring of anticholinergic compounds. Results from the present study also point to the need for considering kinetic analysis when cholinesterase activity is employed as a biomarker. PMID:16643981

Tortelli, V; Colares, E P; Robaldo, R B; Nery, L E M; Pinho, G L L; Bianchini, A; Monserrat, J M

2006-10-01

89

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 PMID:20663171

2010-01-01

90

Alternative bio-based solvents for extraction of fat and oils: solubility prediction, global yield, extraction kinetics, chemical composition and cost of manufacturing.  

PubMed

The present study was designed to evaluate the performance of alternative bio-based solvents, more especially 2-methyltetrahydrofuran, obtained from crop's byproducts for the substitution of petroleum solvents such as hexane in the extraction of fat and oils for food (edible oil) and non-food (bio fuel) applications. First a solvent selection as well as an evaluation of the performance was made with Hansen Solubility Parameters and the COnductor-like Screening MOdel for Realistic Solvation (COSMO-RS) simulations. Experiments were performed on rapeseed oil extraction at laboratory and pilot plant scale for the determination of lipid yields, extraction kinetics, diffusion modeling, and complete lipid composition in term of fatty acids and micronutrients (sterols, tocopherols and tocotrienols). Finally, economic and energetic evaluations of the process were conducted to estimate the cost of manufacturing using 2-methyltetrahydrofuran (MeTHF) as alternative solvent compared to hexane as petroleum solvent. PMID:25884332

Sicaire, Anne-Gaëlle; Vian, Maryline; Fine, Frédéric; Joffre, Florent; Carré, Patrick; Tostain, Sylvain; Chemat, Farid

2015-01-01

91

Measurement of Kinetic Energy Distributions, Mass and Isotopic Yields in the Heavy Fission Products Region at Lohengrin  

NASA Astrophysics Data System (ADS)

Mass yields and kinetic energy distribution functions for heavy mass fission products from thermal neutron induced fission of 235U and 239Pu have been measured at the spectrometer Lohengrin at the high flux reactor of the Institut Laue-Langevin in Grenoble. In addition to these measurements where an ionization chamber was used for the mass identification, we also performed gamma spectrometry to quantify the isotopic and isomeric yields. This setup using Ge-detectors has been commissioned with the system 241Pu(nth,f). In order to extend the data to less abundant fission products, a proportional counter for beta detection has been constructed, allowing to reduce the background by beta-gamma coincidences.

Bail, A.; Serot, O.; Litaize, O.; Faust, H. R.; Köster, U.; Materna, T.; Letourneau, A.; Dupont, E.

2008-04-01

92

Joint estimation of subject motion and tracer kinetic parameters of dynamic PET data in an EM framework  

NASA Astrophysics Data System (ADS)

Dynamic Positron Emission Tomography is a powerful tool for quantitative imaging of in vivo biological processes. The long scan durations necessitate motion correction, to maintain the validity of the dynamic measurements, which can be particularly challenging due to the low signal-to-noise ratio (SNR) and spatial resolution, as well as the complex tracer behaviour in the dynamic PET data. In this paper we develop a novel automated expectation-maximisation image registration framework that incorporates temporal tracer kinetic information to correct for inter-frame subject motion during dynamic PET scans. We employ the Zubal human brain phantom to simulate dynamic PET data using SORTEO (a Monte Carlo-based simulator), in order to validate the proposed method for its ability to recover imposed rigid motion. We have conducted a range of simulations using different noise levels, and corrupted the data with a range of rigid motion artefacts. The performance of our motion correction method is compared with pairwise registration using normalised mutual information as a voxel similarity measure (an approach conventionally used to correct for dynamic PET inter-frame motion based solely on intensity information). To quantify registration accuracy, we calculate the target registration error across the images. The results show that our new dynamic image registration method based on tracer kinetics yields better realignment of the simulated datasets, halving the target registration error when compared to the conventional method at small motion levels, as well as yielding smaller residuals in translation and rotation parameters. We also show that our new method is less affected by the low signal in the first few frames, which the conventional method based on normalised mutual information fails to realign.

Jiao, Jieqing; Salinas, Cristian A.; Searle, Graham E.; Gunn, Roger N.; Schnabel, Julia A.

2012-02-01

93

Accounting for the kinetics in order parameter analysis: lessons from theoretical models and a disordered peptide  

E-print Network

Molecular simulations as well as single molecule experiments have been widely analyzed in terms order parameters, the latter representing candidate probes for the relevant degrees of freedom. Notwithstanding this approach is very intuitive, mounting evidence showed that such description is not accurate, leading to ambiguous definitions of states and wrong kinetics. To overcome these limitations a framework making use of order parameter fluctuations in conjunction with complex network analysis is investigated. Derived from recent advances in the analysis of single molecule time traces, this approach takes into account of the fluctuations around each time point to distinguish between states that have similar values of the order parameter but different dynamics. Snapshots with similar fluctuations are used as nodes of a transition network, the clusterization of which into states provides accurate Markov-State-Models of the system under study. Application of the methodology to theoretical models with a noisy orde...

Berezovska, Ganna; Mostarda, Stefano; Rao, Francesco

2012-01-01

94

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...

95

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

96

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

PubMed Central

Background Most traits targeted in the genetic improvement of hop are quantitative in nature. Improvement based on selection of these traits requires a comprehensive understanding of their inheritance. This study estimated quantitative genetic parameters for 20 traits related to three key objectives for the genetic improvement of hop: cone chemistry, cone yield and agronomic characteristics. Results Significant heritable genetic variation was identified for ?-acid and ?-acid, as well as their components and relative proportions. Estimates of narrow-sense heritability for these traits (h 2 ?=?0.15 to 0.29) were lower than those reported in previous hop studies, but were based on a broader suite of families (108 from European, North American and hybrid origins). Narrow-sense heritabilities are reported for hop growth traits for the first time (h 2 ?=?0.04 to 0.20), relating to important agronomic characteristics such as emergence, height and lateral morphology. Cone chemistry and growth traits were significantly genetically correlated, such that families with more vigorous vegetative growth were associated with lower ?-acid and ?-acid levels. This trend may reflect the underlying population structure of founder genotypes (European and North American origins) as well as past selection in the Australian environment. Although male and female hop plants are thought to be indistinguishable until flowering, sex was found to influence variation in many growth traits, with male and female plants displaying differences in vegetative morphology from emergence to cone maturity. Conclusions This study reveals important insights into the genetic control of quantitative hop traits. The information gained will provide hop breeders with a greater understanding of the additive genetic factors which affect selection of cone chemistry, yield and agronomic characteristics in hop, aiding in the future development of improved cultivars. PMID:24524684

2014-01-01

97

Kinetic Parameter Extraction of Square Wave Voltammograms from DNA-Modified Gold Electrodes  

NASA Astrophysics Data System (ADS)

The field of surface bound electrochemistry is important in a variety of applications specifically sensing. A fundamental understanding of the processes involved could help to improve detection limits, optimize rates of detection and direct changes in device design. Accurate extraction of electrochemical kinetic parameters such as the rate constant k and charge transfer coefficient ? from cyclic voltammograms can be challenging when confronted with large background currents and relatively weak signals. The commonly used technique of Laviron analysis is both time consuming and somewhat subjective. Square wave voltammetry (SWV) is therefore an ideal alternative method given that it maximizes signal while minimizing capacitive effects. In this experiment kinetic parameters of DNA-modified gold electrodes are obtained from SWV curves through background subtraction followed by nonlinear least squares fitting using a first order quasi-reversible surface process model. The fitting is accomplished using the Nelder-Mead simplex algorithm with standard parameters and a convergence condition of less than 0.0001%. General agreement with experimental data is shown with varying levels of confidence. Difficulties specific to this experiment are discussed as well as the possible benefits of utilizing the Bayesian statistical approach of nested sampling when confronted with multiple peaks of interest and the background source is well defined.

McWilliams, Marc; Wohlgamuth, Chris; Slinker, Jason

2012-10-01

98

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

PubMed Central

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

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

2011-01-01

99

A parametric modeling of ionic channel current fluctuations using third-order statistics and its application to estimation of the kinetic parameters of single ionic channels.  

PubMed

A parametric modeling of stationary ionic-channel current fluctuations (SICF's) using third-order cumulants is presented and its application to estimation of the kinetic parameters of single ionic channels is discussed. We consider the case where third-order cumulants of SICF's are nonzero, and where SICF's are corrupted by an unobservable additive colored Gaussian noise that is independent of SICF's. First, we construct a virtual synthesizer that yields an output whose third-order cumulants are equivalent to those of SICF's on a specific slice. The synthesizer output is expressed by the sum of N5 - 1 first-order differential equation systems, where N8 denotes the number of states of single ionic channels. Next, discretizing the synthesizer output, we derive a discrete autoregressive (AR(N8 - 1)) process driven by the sum of N8 - 1 moving average (MA(N9 - 2)) processes. Then the AR coefficients are explicitly related to the kinetic parameters of single ionic channels, implying that the kinetic parameters can be estimated by identifying the ARMA coefficients using the third-order cumulants. In order to assess the validity of the proposed modeling and the accuracy of parameter estimates, Monte Carlo simulation is carried out in which the closed-open and closed-open-blocked schemes are treated as specific examples. PMID:7507087

Mino, H

1993-09-01

100

Rod outer segment structure influences the apparent kinetic parameters of cyclic GMP phosphodiesterase  

PubMed Central

Cyclic GMP hydrolysis by the phosphodiesterase (PDE) of retinal rod outer segments (ROS) is a key amplification step in phototransduction. Definitive estimates of the turnover number, kcat, and of the Km are crucial to quantifying the amplification contributed by the PDE. Published estimates for these kinetic parameters vary widely; moreover, light-dependent changes in the Km of PDE have been reported. The experiments and analyses reported here account for most observed variations in apparent Km, and they lead to definitive estimates of the intrinsic kinetic parameters in amphibian rods. We first obtained a new and highly accurate estimate of the ratio of holo-PDE to rhodopsin in the amphibian ROS, 1:270. We then estimated the apparent kinetic parameters of light-activated PDE of suspensions of disrupted frog ROS whose structural integrity was systematically varied. In the most severely disrupted ROS preparation, we found Km = 95 microM and kcat = 4,400 cGMP.s-1. In suspensions of disc-stack fragments of greater integrity, the apparent Km increased to approximately 600 microM, though kcat remained unchanged. In contrast, the Km for cAMP was not shifted in the disc stack preparations. A theoretical analysis shows that the elevated apparent Km of suspensions of disc stacks can be explained as a consequence of diffusion with hydrolysis in the disc stack, which causes active PDEs nearer the center of the stack to be exposed to a lower concentration of cyclic GMP than PDEs at the disc stack rim. The analysis predicts our observation that the apparent Km for cGMP is elevated with no accompanying decrease in kcat. The analysis also predicts the lack of a Km shift for cAMP and the previously reported light dependence of the apparent Km for cGMP. We conclude that the intrinsic kinetic parameters of the PDE do not vary with light or structural integrity, and are those of the most severely disrupted disc stacks. PMID:7931138

1994-01-01

101

Calculating kinetics parameters and reactivity changes with continuous-energy Monte Carlo  

SciTech Connect

The iterated fission probability interpretation of the adjoint flux forms the basis for a method to perform adjoint weighting of tally scores in continuous-energy Monte Carlo k-eigenvalue calculations. Applying this approach, adjoint-weighted tallies are developed for two applications: calculating point reactor kinetics parameters and estimating changes in reactivity from perturbations. Calculations are performed in the widely-used production code, MCNP, and the results of both applications are compared with discrete ordinates calculations, experimental measurements, and other Monte Carlo calculations.

Kiedrowski, Brian C [Los Alamos National Laboratory; Brown, Forrest B [Los Alamos National Laboratory; Wilson, Paul [UNIV. WISCONSIN

2009-01-01

102

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

PubMed

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

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

2015-02-10

103

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

SciTech Connect

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

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

1999-02-01

104

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

PubMed

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

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

2015-04-01

105

Hydrolysis of a lipid membrane by single enzyme molecules: accurate determination of kinetic parameters.  

PubMed

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

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

2015-01-12

106

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

PubMed

Olive mill wastewater (OMW) with total phenol (TP) concentration range of 300-1200 mg/L was treated with alginate-immobilized Rhodotorula glutinis cells in batch system. The effects of pellet properties (diameter, alginate concentration and cell loading (CL)) and operational parameters (initial TP concentration, agitation rate and reusability of pellets) on dephenolization of OMW were studied. Up to 87% dephenolization was obtained after 120 h biodegradations. The utilization number of pellets increased with the addition of calcium ions into the biodegradation medium. The overall effectiveness factors calculated for different conditions showed that diffusional limitations arising from pellet size and pellet composition could be neglected. Mass transfer limitations appeared to be more effective at high substrate concentrations and low agitation rates. The parameters of logistic model for growth kinetics of R. glutinis in OMW were estimated at different initial phenol concentrations of OMW by curve-fitting of experimental data with the model. PMID:25244135

Bozkoyunlu, Gaye; Takaç, Serpil

2014-01-01

107

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

NASA Astrophysics Data System (ADS)

Key kinetic parameters governing the partitioning of chlorine species in the Antarctic polar stratosphere were retrieved from 28 days of chlorine monoxide (ClO) microwave radiometer measurements made during the late winter/early spring of 2005 at Scott Base (77.85° S, 166.75° E). During day-time the loss of the ClO dimer chlorine peroxide (ClOOCl) occurs mainly by photolysis. Some time after sunrise, a photochemical equilibrium is established and the ClO/ClOOCl partitioning is determined by the ratio of the photolysis frequency, J, and the dimer formation rate, kf. The values of J and kf from laboratory studies remain uncertain to a considerable extent, and as a complement to these ongoing studies, the goal of this work is to provide a constraint on that uncertainty based on observations of ClO profiles in the Antarctic. First an optimal estimation technique was used to derive J/kf ratios for a range of Keq values. The optimal estimation forward model was a photochemical box model that takes J, kf, and Keq as inputs, together with a priori profiles of activated chlorine (ClOx = ClO+2×ClOOCl), profiles of ozone, temperature, and pressure. JPL06 kinetics are used as a priori in the optimal estimation and for all other chemistry in the forward model. Using the more recent JPL09 kinetics results in insignificant differences in the retrieved value of J/kf. A complementary approach was used to derive the optimal kinetic parameters; the full parameter space of J, kf, Keq and ClOx was sampled to find the minimum in differences between measured and modelled ClO profiles. Furthermore, values of Keq up to 2.0 times larger than recommended by JPL06 were explored to test the sensitivity of the J/kf ratio to changes in Keq. The results show that the retrieved J/kf ratios bracket the range of 1.23 to 1.97 times the J/kf value recommended by JPL06 over the range of Keq values considered. The retrieved J/kf ratios lie in the lower half of the large uncertainty range of J/kf recommended by JPL06 and towards the upper portion of the smaller uncertainty range recommended by JPL09.

Kremser, S.; Schofield, R.; Bodeker, G. E.; Connor, B. J.; Rex, M.; Barret, J.; Mooney, T.; Salawitch, R. J.; Canty, T.; Frieler, K.; Chipperfield, M. P.; Langematz, U.; Feng, W.

2011-06-01

108

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

NASA Astrophysics Data System (ADS)

Key kinetics parameters governing the partitioning of chlorine species in the Antarctic polar stratosphere were retrieved from 28 days of chlorine monoxide (ClO) microwave radiometer measurements made during the late-winter/early spring of 2005 at Scott Base (77.85° S, 166.75° E). During day-time the ratio of the photolysis rate, J, and the dimer formation rate, kf, determines the partitioning of ClO and its dimer, chlorine peroxide (ClOOCl). This ratio J/kf remains uncertain and, as a complement to ongoing laboratory studies, the goal of this work is to provide a constraint on that uncertainty based on observations of ClO profiles in the Antarctic. First an optimal estimation technique was used to derive J/kf ratios for a range of Keq values. The optimal estimation forward model was a photochemical box model that takes J, kf, and Keq as inputs, together with a priori of activated chlorine (ClOx=ClO+2×ClOOCl), ozone, temperature and pressure profiles. JPL06 kinetics are used as a priori in the optimal estimation and for all other chemistry in the forward model. Using the more recent JPL09 kinetics results in insignificant differences in the retrieved value of J/kf. A complementary approach was used to derive the optimal kinetic parameters; the full parameter space of J, kf, Keq and ClOx was sampled to find the minimum in differences between measured and modelled ClO profiles. Furthermore, values of Keq up to 2.0 times larger than recommended by JPL06 were explored to test the sensitivity of the J/kf ratio to changes in Keq. The results show that the retrieved J/kf ratios bracket the range of 1.97 to 1.23×(J/kf)JPL06 over the range of Keq values considered. The retrieved J/kf ratios lie in the lower half of the large uncertainty range of J/kf recommended by JPL06 and towards the upper portion of the smaller uncertainty range recommended by JPL09.

Kremser, S.; Schofield, R.; Bodeker, G. E.; Connor, B. J.; Rex, M.; Barret, J.; Mooney, T.; Salawitch, R. J.; Canty, T.; Frieler, K.; Chipperfield, M. P.; Langematz, U.; Feng, W.

2010-11-01

109

Optimization of glycerol fed-batch fermentation in different reactor states: a variable kinetic parameter approach.  

PubMed

To optimize the fed-batch processes of glycerol fermentation in different reactor states, typical bioreactors including 500-mL shaking flask, 600-mL and 15-L airlift loop reactor, and 5-L stirred vessel were investigated. It was found that by reestimating the values of only two variable kinetic parameters associated with physical transport phenomena in a reactor, the macrokinetic model of glycerol fermentation proposed in previous work could describe well the batch processes in different reactor states. This variable kinetic parameter (VKP) approach was further applied to model-based optimization of discrete-pulse feed (DPF) strategies of both glucose and corn steep slurry for glycerol fed-batch fermentation. The experimental results showed that, compared with the feed strategies determined just by limited experimental optimization in previous work, the DPF strategies with VKPs adjusted could improve glycerol productivity at least by 27% in the scale-down and scale-up reactor states. The approach proposed appeared promising for further modeling and optimization of glycerol fermentation or the similar bioprocesses in larger scales. PMID:12049203

Xie, Dongming; Liu, Dehua; Zhu, Haoli; Zhang, Jianan

2002-05-01

110

Kinetically Stable Lanthanide Complexes Displaying Exceptionally High Quantum Yields upon Long-Wavelength Excitation: Synthesis, Photophysical Properties, and Solution Speciation.  

PubMed

We demonstrate how highly emissive, kinetically stable complexes can be prepared using the macrocyclic scaffold of DO3A bearing coordinating aryl ketones as highly effective sensitizing chromophores. In the europium complexes, high quantum yields (up to 18% in water) can be combined with long-wavelength excitation (370 nm). The behavior in solution upon variation of pH, studied by means of UV-vis absorption, emission, and NMR spectroscopies, reveals that the nature of the chromophore can give rise to pH-dependent behavior as a consequence of deprotonation adjacent to the carbonyl group. Knowledge of the molecular speciation in solution is therefore critical when assessing the luminescence properties of such complexes. PMID:25751278

Routledge, Jack D; Jones, Michael W; Faulkner, Stephen; Tropiano, Manuel

2015-04-01

111

Seasonal variation of the canopy structure parameters and its correlation with yield-related traits in sugarcane.  

PubMed

Population structure determines sugarcane yield, of which canopy structure is a key component. To fully understand the relations between sugarcane yield and parameters of the canopy structure, 17 sugarcane varieties were investigated at five growth stages. The results indicated that there were significant differences between characterized parameters among sugarcane populations at different growth stages. During sugarcane growth after planting, leaf area index (LAI) and leaf distribution (LD) increased, while transmission coefficient for diffuse radiation (TD), mean foliage inclination angle (MFIA), transmission coefficient for solar beam radiation penetration (TR), and extinction coefficient (K) decreased. Significant negative correlations were found between sugarcane yield and MFIA, TD, TR, and K at the early elongation stage, while a significant positive correlation between sugarcane yield and LD was found at the same stage. A regression for sugarcane yield, with relative error of yield fitting less than 10%, was successfully established: sugarcane yield = 2380.12 + 46.25 × LD - 491.82 × LAI + 1.36 × MFIA + 614.91 × TD - 1908.05 × TR - 182.53 × K + 1281.75 × LD - 1.35 × MFIA + 831.2 × TR - 407.8 × K + 8.21 × MFIA - 834.50 × TD - 1695.49 × K (R (2) = 0.94**). PMID:24453909

Luo, Jun; Que, Youxiong; Zhang, Hua; Xu, Liping

2013-01-01

112

Seasonal Variation of the Canopy Structure Parameters and Its Correlation with Yield-Related Traits in Sugarcane  

PubMed Central

Population structure determines sugarcane yield, of which canopy structure is a key component. To fully understand the relations between sugarcane yield and parameters of the canopy structure, 17 sugarcane varieties were investigated at five growth stages. The results indicated that there were significant differences between characterized parameters among sugarcane populations at different growth stages. During sugarcane growth after planting, leaf area index (LAI) and leaf distribution (LD) increased, while transmission coefficient for diffuse radiation (TD), mean foliage inclination angle (MFIA), transmission coefficient for solar beam radiation penetration (TR), and extinction coefficient (K) decreased. Significant negative correlations were found between sugarcane yield and MFIA, TD, TR, and K at the early elongation stage, while a significant positive correlation between sugarcane yield and LD was found at the same stage. A regression for sugarcane yield, with relative error of yield fitting less than 10%, was successfully established: sugarcane yield = 2380.12 + 46.25 × LD ? 491.82 × LAI + 1.36 × MFIA + 614.91 × TD ? 1908.05 × TR ? 182.53 ×??K + 1281.75 × LD ? 1.35 × MFIA + 831.2 × TR ? 407.8 ×??K + 8.21 × MFIA ? 834.50 × TD ? 1695.49 ×??K??(R2 = 0.94**). PMID:24453909

Luo, Jun; Que, Youxiong; Zhang, Hua; Xu, Liping

2013-01-01

113

Mass and nuclear charge yields for 237Np(2n th,f) at different fission fragment kinetic energies  

NASA Astrophysics Data System (ADS)

The recoil mass separator LOHENGRIN of the Laue-Langevin Institute Grenoble has been used to measure for the first time, the yields of light fission fragments from the fissioning system: 23993Np; this odd-Z nucleus is formed after double thermal neutron capture in a 23993Np target. The mass distributions were measured for different kinetic energies between 92 and 115.5 MeV, but the nuclear charge distributions were determined only up to 112 MeV. These distributions are compared to the distributions obtained for the even-even system 24094Pu. At high kinetic energy, the mass distribution shows a prominent peak around mass number AL = 106. These cold fragmentations are discussed in terms of a calculation based on a scission point model extrapolated to the cold fission case. As expected for an odd- Z fissioning nucleus, the nuclear charge distributions do not reveal any odd-even effect. The global neutron odd-even effect is found to be (8.1 ± 1.5)%. A simple model has been used to show that most of the neutron odd-even effect results from prompt neutron evaporation from the fragments.

Martinez, G.; Barreau, G.; Sicre, A.; Doan, T. P.; Audouard, P.; Leroux, B.; Arafa, W.; Brissot, R.; Bocquet, J. P.; Faust, H.; Koczon, P.; Mutterer, M.; Gönnenwein, F.; Asghar, M.; Quade, U.; Rudolph, K.; Engelhardt, D.; Piasecki, E.

1990-09-01

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

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

SciTech Connect

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

Jantzen, C M

1988-01-01

116

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

117

Associations of fiber quality parameters and lint yield components in six diverse cotton genotypes  

E-print Network

(SBOLL) , f ibers per seed (FS), lint yield per seed (LYS), fibers per unit seed surface area (FSA) , and lint yield per unit seed surface area (LYSA) . Parents and Fi I s from a diallel mating scheme, excluding reciprocals, were space planted in 1989...

Golladay, Gwendolyn Kay

1993-01-01

118

Breath-by-breath pulmonary O2 uptake kinetics: effect of data processing on confidence in estimating model parameters.  

PubMed

To improve the signal-to-noise ratio of breath-by-breath pulmonary O2 uptake (V?O2p) data, it is common practice to perform multiple step transitions, which are subsequently processed to yield an ensemble-averaged profile. The effect of different data-processing techniques on phase II V?O2p kinetic parameter estimates (V?O2p amplitude, time delay and phase II time constant (?V?O2p)] and model confidence [95% confidence interval (CI95)] was examined. Young (n = 9) and older men (n = 9) performed four step transitions from a 20 W baseline to a work rate corresponding to 90% of their estimated lactate threshold on a cycle ergometer. Breath-by-breath V?O2p was measured using mass spectrometry and volume turbine. Mono-exponential kinetic modelling of phase II V?O2p data was performed on data processed using the following techniques: (A) raw data (trials time aligned, breaths of all trials combined and sorted in time); (B) raw data plus interpolation (trials time aligned, combined, sorted and linearly interpolated to second by second); (C) raw data plus interpolation plus 5 s bin averaged; (D) individual trial interpolation plus ensemble averaged [trials time aligned, linearly interpolated to second by second (technique 1; points joined by straight-line segments), ensemble averaged]; (E) 'D' plus 5 s bin averaged; (F) individual trial interpolation plus ensemble averaged [trials time aligned, linearly interpolated to second by second (technique 2; points copied until subsequent point appears), ensemble averaged]; and (G) 'F' plus 5 s bin averaged. All of the model parameters were unaffected by data-processing technique; however, the CI95 for ?V?O2p in condition 'D' (4 s) was lower (P < 0.05) than the CI95 reported for all other conditions (5-10 s). Data-processing technique had no effect on parameter estimates of the phase II V?O2p response. However, the narrowest interval for CI95 occurred when individual trials were linearly interpolated and ensemble averaged. PMID:25063837

Keir, Daniel A; Murias, Juan M; Paterson, Donald H; Kowalchuk, John M

2014-11-01

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

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

121

Kinetic parameter estimation and fluctuation analysis of CO at SnO2 single nanowires.  

PubMed

In this work, we present calculated numerical values for the kinetic parameters governing adsorption/desorption processes of carbon monoxide at tin dioxide single-nanowire gas sensors. The response of such sensors to pulses of 50?ppm carbon monoxide in nitrogen is investigated at different temperatures to extract the desired information. A rate-equation approach is used to model the reaction kinetics, which results in the problem of determining coefficients in a coupled system of nonlinear ordinary differential equations. The numerical values are computed by inverse-modeling techniques and are then used to simulate the sensor response. With our model, the dynamic response of the sensor due to the gas-surface interaction can be studied in order to find the optimal setup for detection, which is an important step towards selectivity of these devices. We additionally investigate the noise in the current through the nanowire and its changes due to the presence of carbon monoxide in the sensor environment. Here, we propose the use of a wavelet transform to decompose the signal and analyze the noise in the experimental data. This method indicates that some fluctuations are specific for the gas species investigated here. PMID:23851634

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

2013-08-01

122

Kinetics and activation parameters of the reaction of organoarsenic(V) compounds with glutathione.  

PubMed

In this work the kinetics of the reaction of glutathione (GSH) with the organoarsenic(V) compounds phenylarsonic acid (PAA), 4-hydroxy-3-nitrophenylarsonic acid (HNPAA), p-aminophenylarsonic acid (p-APAA) and o-aminophenylarsonic acid (o-APAA) as well as monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) is investigated. The reaction progress is monitored in real time by (1)H NMR, allowing the determination of rate coefficients and half-lives as well as activation parameters. The reaction consists of two steps: redox reaction and conjugation. In all investigated systems the conjugation is fast compared to the redox reaction and, therefore, rate determining. All investigated phenylarsonic acids follow the same rate law, showing overall reaction orders of 3 and half-lives between 47.7 ± 0.2 and 71.0 ± 3.6 min. The methylated compounds react slower, showing half-lives of 76.6 ± 0.4 and 444 ± 10 min for DMAA and MMAA, respectively. Enthalpies of activation range from 20 to 36 (± 2) kJ mol(-1) and the entropies of activation are within -154 and -97(± 7)J mol(-1)K(-1). The results reveal a correlation of the toxicity of the arsenic compound and the reaction rate with GSH. This may pave the way for the estimation of the toxicity of such compounds by simple kinetic studies. PMID:25238190

Kretzschmar, Jerome; Brendler, Erica; Wagler, Jörg; Schmidt, Anne-Christine

2014-09-15

123

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

124

Kinetic parameters of the thermal degradation of the PP and nondegraded and degraded HDPE blends  

SciTech Connect

We study the thermodegradative behavior of PP, of non-degraded and degraded HDPE and their blends, in order to analyze the thermal stability of such materials. Van-Krevelen (V-K), Coats-Redfern (C-R) and Horowitz-Metzger (H-M) integral methods as well as the Freeman-Carroll (F-C) differential one, were used to determine the kinetic parameters. The activation energy (E{sub a}) obtained for the PP mixed with non-degraded HDPE (5 to 50%) is lower than the E{sub a} correspondent to pure polymers and does not depend on the HDPE concentration. Blends of degraded materials, show an approximate value of E{sub a} of 200 kJ/mol for mixtures with concentrations by weight of HDPE up to 20%, but its value decreases drastically with higher concentrations. 11 refs., 2 tabs.

Albano, C.; Freitas, E. [Universidad Central de Venezuela, Caracas (Venezuela)

1996-12-31

125

Determination Of Kinetic Parameters Of Combustion Processes Using Optical Detection Techniques  

NASA Astrophysics Data System (ADS)

The increased use of dirty fuels such as coal and oil shale in station-ary combustors has increased the necessity for controlling NOx emissions. A potential method to accomplish this goal is the thermal deN0x process, where ammonia added to the combustion exhaust gas chemically converts nitric oxide to harmless products (N2 and H20). A complete understanding of the chemical processes occurring has been hampered by a lack of detailed high-temperature kinetic data. Using a high-temperature fast flow reactor equipped with a variety of optical detection devices, key rate parameters and product channels are determined for this process, and, in conjunction with computer modeling, a consistent comprehensive model is developed which describes the features of the NHi/NOx chemical system.

Silver, Joel A.

1981-08-01

126

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

127

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

128

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

Microsoft Academic Search

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

Saibal Mukhopadhyay; Hamid Mahmoodi-Meimand; Kaushik Roy

2004-01-01

129

Effect of combined nitrogen and sulphur fertilization on yield and qualitative parameters of Camelina sativa [L.] Crtz. (false flax)  

Microsoft Academic Search

Camelina (Camelina sativa (L.) Crtz., false flax) is described as a species requiring fewer inputs than other oilseed crops thus making it an interesting alternative in sustainable cropping systems. As information on the combined effects of nitrogen and sulphur on camelina yield and quality parameters is meagre, a pot fertilization experiment was carried out with nitrogen applied as NH4NO3 at

Tomas Lošák; Jaroslav Hlusek; Jiri Martinec; Johann Vollmann; Jiri Peterka; Radek Filipcik; Ladislav Varga; Ladislav Ducsay; Anna Martensson

2011-01-01

130

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

131

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

132

Aqueous oxidation of green leaf volatiles by hydroxyl radical as a source of SOA: Kinetics and SOA yields  

NASA Astrophysics Data System (ADS)

Green leaf volatiles (GLVs) are a class of oxygenated hydrocarbons released from vegetation, especially during mechanical stress or damage. The potential for GLVs to form secondary organic aerosol (SOA) via aqueous-phase reactions is not known. Fog events over vegetation will lead to the uptake of GLVs into water droplets, followed by aqueous-phase reactions with photooxidants such as the hydroxyl radical (OH). In order to determine if the aqueous oxidation of GLVs by OH can be a significant source of secondary organic aerosol, we studied the partitioning and reaction of five GLVs: cis-3-hexen-1-ol, cis-3-hexenyl acetate, methyl salicylate, methyl jasmonate, and 2-methyl-3-butene-2-ol. For each GLV we measured the kinetics of aqueous oxidation by OH, and the corresponding SOA mass yield. The second-order rate constants for GLVs with OH were all near diffusion controlled, (5.4-8.6) × 109 M-1 s-1 at 298 K, and showed a small temperature dependence, with an average activation energy of 9.3 kJ mol-1 Aqueous-phase SOA mass yields ranged from 10 to 88%, although some of the smaller values were not statistically different from zero. Methyl jasmonate was the most effective aqueous-phase SOA precursor due to its larger Henry's law constant and high SOA mass yield (68 ± 8%). While we calculate that the aqueous-phase SOA formation from the five GLVs is a minor source of aqueous-phase SOA, the availability of other GLVs, other oxidants, and interfacial reactions suggest that GLVs overall might be a significant source of SOA via aqueous reactions.

Richards-Henderson, Nicole K.; Hansel, Amie K.; Valsaraj, Kalliat T.; Anastasio, Cort

2014-10-01

133

Ammonium Removal from Aqueous Solutions by Clinoptilolite: Determination of Isotherm and Thermodynamic Parameters and Comparison of Kinetics by the Double Exponential Model and Conventional Kinetic Models  

PubMed Central

The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R2) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (?G°), enthalpy (?H°) and entropy (?S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients. PMID:22690177

Tosun, ?smail

2012-01-01

134

Estimation of the growth kinetic parameters of Bacillus cereus spores as affected by pulsed light treatment.  

PubMed

Quantitative microbial risk assessment requires the knowledge of the effect of food preservation technologies on the growth parameters of the survivors of the treatment. This is of special interest in the case of the new non-thermal technologies that are being investigated for minimal processing of foods. This is a study on the effect of pulsed light technology (PL) on the lag phase of Bacillus cereus spores surviving the treatment and the maximum growth rate (?max) of the survivors after germination. The D value was estimated as 0.35J/cm(2) and our findings showed that PL affected the kinetic parameters of the microorganism. A log linear relationship was observed between the lag phase and the intensity of the treatment. Increasing the lethality lengthened the mean lag phase and proportionally increased its variability. A polynomial regression was fitted between the ?max of the survivors and the inactivation achieved. The ?max decreased as intensity increased. From these data, and their comparison to published results on the effect of heat and e-beam irradiation on B. cereus spores, it was observed that the shelf-life of PL treated foods would be longer than those treated with heat and similar to irradiated ones. These findings offer information of interest for the implementation of PL for microbial decontamination in the food industry. PMID:25755081

Aguirre, Juan S; de Fernando, Gonzalo García; Hierro, Eva; Hospital, Xavier F; Ordóñez, Juan A; Fernández, Manuela

2015-06-01

135

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

136

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

137

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

PubMed Central

The sorption of cadmium (Cd) and lead (Pb) by calcium alginate beads (CAB) from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4?mg/g and 150.4?mg/g for lead, at 25°C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7. PMID:24587740

Alfaro-Cuevas-Villanueva, Ruth; Hidalgo-Vázquez, Aura Roxana; Cortés Penagos, Consuelo de Jesús; Cortés-Martínez, Raúl

2014-01-01

138

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.

139

Derivation of hydrous pyrolysis kinetic parameters from open-system pyrolysis  

NASA Astrophysics Data System (ADS)

Kinetic information is essential to predict the temperature, timing or depth of hydrocarbon generation within a hydrocarbon system. The most common experiments for deriving kinetic parameters are mainly by open-system pyrolysis. However, it has been shown that the conditions of open-system pyrolysis are deviant from nature by its low near-ambient pressure and high temperatures. Also, the extrapolation of heating rates in open-system pyrolysis to geological conditions may be questionable. Recent study of Lewan and Ruble shows hydrous-pyrolysis conditions can simulate the natural conditions better and its applications are supported by two case studies with natural thermal-burial histories. Nevertheless, performing hydrous pyrolysis experiment is really tedious and requires large amount of sample, while open-system pyrolysis is rather convenient and efficient. Therefore, the present study aims at the derivation of convincing distributed hydrous pyrolysis Ea with only routine open-system Rock-Eval data. Our results unveil that there is a good correlation between open-system Rock-Eval parameter Tmax and the activation energy (Ea) derived from hydrous pyrolysis. The hydrous pyrolysis single Ea can be predicted from Tmax based on the correlation, while the frequency factor (A0) is estimated based on the linear relationship between single Ea and log A0. Because the Ea distribution is more rational than single Ea, we modify the predicted single hydrous pyrolysis Ea into distributed Ea by shifting the pattern of Ea distribution from open-system pyrolysis until the weight mean Ea distribution equals to the single hydrous pyrolysis Ea. Moreover, it has been shown that the shape of the Ea distribution is very much alike the shape of Tmax curve. Thus, in case of the absence of open-system Ea distribution, we may use the shape of Tmax curve to get the distributed hydrous pyrolysis Ea. The study offers a new approach as a simple method for obtaining distributed hydrous pyrolysis Ea with only routine open-system Rock-Eval data, which will allow for better estimating hydrocarbon generation.

Tseng, Yu-Hsin; Huang, Wuu-Liang

2010-05-01

140

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

141

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

Microsoft Academic Search

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

T Khursheed; MYK Ansari; D Shahab

142

Modelling Escherichia coli concentration in a wastewater reservoir using an operational parameter MRT%FE and first order kinetics  

Microsoft Academic Search

The operational parameter MRT%FE, representing the mean residence time of different ages fractions of effluent within a completely mixed reactor, was evaluated and integrated with first order kinetics. The parameter was used to model Escherichia coli concentrations in a municipal wastewater reservoir managed under different operating conditions (continuous and discontinuous).The study was conducted during 2004–2005 in a reservoir receiving effluents

Giuseppe Luigi Cirelli; Simona Consoli; Marcelo Juanicó

2009-01-01

143

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

144

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

145

Re-examination of safety parameters using kinetic theory of nano-granular flows  

NASA Astrophysics Data System (ADS)

The origin of the kinetic theory of granular flow was originally credited to Bagnold [1]. By using a very primitive expression of the particle collision frequency, he derived an expression for the repulsive pressure of the particles in uniform shear flows. His repulsive pressure was proportional to the square of the velocity gradient and the particle diameter and directly proportional to the particle density. This theory was later extended by Savage [2] and Gidaspow [3]. Such theories provide insight on the dependence of the viscosity, and various moduli (elastic, non elastic, viscous...) in terms of the granular temperature and the associated shear-rates. Until recently, such parameters were difficult to measure because of the lack of specifically designed equipment. This challenge was successfully taken up and resolved by P. Marchal of ENSIC who designed a new rheometer for powders (figure 1). This equipment can put in evidence the importance of the granular temperature on the elastic and viscous behaviors of the granular flows. Such rheological behavior is important in risk analysis for nanopowders, because as the nanopowder may be subjected to process shear rates and stresses, its structural and topological changes, in terms of the transformation of agglomerates into primary nanoparticles, have strong impacts on emission factors of nanosized particles that can be released in the environment or into a workplace from such dense-phase nanopowder processes. Such transformation can be analyzed by studying the nano-granular rheological signature of the system. Such risk assessment approach using these new fundamental rheological safety parameters is described in this paper.

Bouillard, Jacques Xavier; Marchal, Philippe; Henry, François; Vignes, Alexis; Dufaud, Olivier; Perrin, Laurent; Plasari, Edouard

2011-07-01

146

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

PubMed Central

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

Lizama, Hector M.; Suzuki, Isamu

1989-01-01

147

A study of line widths and kinetic parameters of ions in the solar corona  

NASA Astrophysics Data System (ADS)

Solar extreme-ultraviolet (EUV) lines emitted by highly charged ions have been extensively studied to discuss the issue of coronal heating and solar wind acceleration. Based on observations of the polar corona by the SUMER/SOHO spectrometer, this paper investigates the relation between the line widths and kinetic parameters of ions. It is shown that there exists a strongly linear correlation between two variables ( ?/ ?)2 and M -1, where ?, ? and M are the half-width of the observed line profile at , the wavelength and the ion mass, respectively. The Pearson product-moment correlation coefficients exceed 0.9. This finding tends to suggest that the ions from a given height of polar corona have a common temperature and a common non-thermal velocity in terms of existing equation. The temperature and non-thermal velocity are obtained by linear least-square fit. The temperature is around 2.8 MK at heights of 57? and 102?. The non-thermal velocity is typical 21.6 km s-1 at height of 57? and 25.2 km s-1 at height of 102?.

Zhao, G. Q.; Wu, D. J.; Wang, C. B.

2014-10-01

148

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

149

Comprehensive method based on model free method and IKP method for evaluating kinetic parameters of solid state reactions.  

PubMed

This article presents, firstly, a short review of methods for evaluating kinetic parameters of solid state reactions and a critical analysis of the isoconversional principle of model free methods. It shows theoretically that the activation energy for complex reactions is not only a function of the reaction degree but also of heating programs, and points out that any method that attempts to extract the dependences of activation energy on conversion degree without considering the dependences of heating programs is problematic. Then an analysis is given of the invariant kinetic parameters (IKP) method and recommends an incremental version of it. Based on the incremental IKP method and model free method, a comprehensive method is proposed that predicts the degree of the dependences of activation energy on heating programs, selects reliable values of activation energy and extracts the values of variable pre-exponential factor. This comprehensive method is tested using both simulation data and experimental data, the results of which show it can not only give reliable values of kinetic parameters but also be helpful in explaining inconsistencies of kinetic results in solid state reactions. PMID:22926734

Han, Yunqing; Li, Tianxiang; Saito, Kozo

2012-12-01

150

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

SciTech Connect

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

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

1997-03-19

151

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

152

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

PubMed Central

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

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

2014-01-01

153

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

154

The effects of process parameters on yield and properties of iron nanoparticles from ferrocene in a low-pressure plasma  

NASA Astrophysics Data System (ADS)

The effects of process parameters on iron nanoparticle formation and properties while using ferrocene as a precursor in a low-pressure capacitively coupled plasma are investigated. The L18 array of the Taguchi method, followed by the L4 array, is used with the notional objective of increasing the yield of nanoparticles. A study of the size, shape and composition of the particles (using transmission electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, x-ray diffraction, CHON and inductively coupled plasma-atomic emission spectroscopy analysis) gives an insight into the role played by various process parameters. Pressure is the most critical parameter in increasing nanoparticle yield, whereas hydrogen flow plays a key role in determining the nanoparticle size and composition. Atomic hydrogen helps in removing amorphous carbon and reducing the nanoparticle size. RF power plays an important role in the dissociation of ferrocene thus also affecting the composition. Nanoparticles obtained using optimized conditions are a mixture of Fe3O4 and Fe2O3 with cluster size 25-40 nm in diameter that are further made up of 2-4 nm crystallites. Magnetic property measurements indicate that the nanoparticles are super-paramagnetic in nature.

Panchal, V.; Lahoti, G.; Bhandarkar, U.; Neergat, M.

2011-08-01

155

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. PMID:19706437

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

2009-01-01

156

Determination of char combustion kinetics parameters: Comparison of point detector and imaging-based particle-sizing pyrometry  

NASA Astrophysics Data System (ADS)

In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption kinetics. The performance of the specialized systems is compared for two different combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles' burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%-30% are recommended for kinetic rate measurements on 100 ?m particles.

Schiemann, Martin; Geier, Manfred; Shaddix, Christopher R.; Vorobiev, Nikita; Scherer, Viktor

2014-07-01

157

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

158

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

PubMed Central

This white paper provides a critical analysis of methods for estimating transporter kinetics and recommendations on proper parameter calculation in various experimental systems. Rational interpretation of transporter-knockout animal findings and application of static and dynamic physiologically based modeling approaches for prediction of human transporter-mediated pharmacokinetics and drug–drug interactions (DDIs) are presented. The objective is to provide appropriate guidance for the use of in vitro, in vivo, and modeling tools in translational transporter science. PMID:23588311

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

2013-01-01

159

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

NASA Astrophysics Data System (ADS)

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 aim of our study is to evaluate the effect of input function distortions on the myocardial perfusion as estimated by the model. To this end, we simulate noise-free myocardium time activity curves (TACs) with a two-compartment kinetic model. The input function to the model is a generic analytical function. Distortions of this function have been introduced by varying its parameters. Using the distorted input function, the compartment model has been fitted to the simulated myocardium TAC. This analysis has been performed for various sets of model parameters covering a physiologically relevant range. The evaluation shows that ±10% error in the input peak value can easily lead to ±10-25% error in the model parameter K1, which relates to myocardial perfusion. Variations in the input function tail are generally less relevant. We conclude that an accurate estimation especially of the plasma input peak is crucial for a reliable kinetic analysis and blood flow estimation.

Meyer, Carsten; Peligrad, Drago?-Nicolae; Weibrecht, Martin

2007-02-01

160

A Gurson-type criterion for porous ductile solids containing arbitrary ellipsoidal voids—II: Determination of yield criterion parameters  

NASA Astrophysics Data System (ADS)

The aim of this paper is to fully determine the parameters of the approximate homogenized yield criterion for porous ductile solids containing arbitrary ellipsoidal cavities proposed in Part I. This is done through improvements of the limit-analysis of some representative hollow cell presented there. The improvements are of two kinds. For hydrostatic loadings, the limit-analysis is refined by performing micromechanical finite element computations in a number of significant cases, so as to replace Leblond and Gologanu (2008)'s trial velocity field representing the expansion of the void by the exact, numerically determined one. For deviatoric loadings, limit-analysis is dropped and direct use is made of some general rigorous results for nonlinear composites derived by Ponte-Castaneda (1991), Willis (1991) and Michel and Suquet (1992) using the earlier work of Willis (1977) and the concept of "linear comparison material". This hybrid approach is thought to lead to the best possible expressions of the yield criterion parameters. The criterion proposed reduces to (variants of) classical approximate criteria proposed by Gurson (1977) and Gologanu et al. (1993, 1994, 1997) in the specific cases of spherical or spheroidal, prolate or oblate cavities. An overview of the validation of this criterion through micromechanical finite element computations is finally presented.

Madou, Komlanvi; Leblond, Jean-Baptiste

2012-05-01

161

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

PubMed

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

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

2014-11-17

162

Maximum likelihood estimation of protein kinetic parameters under weak assumptions from unfolding force spectroscopy experiments  

Microsoft Academic Search

Single molecule force spectroscopy (SMFS) is extensively used to characterize the mechanical unfolding behavior of individual protein domains under applied force by pulling chimeric polyproteins consisting of identical tandem repeats. Constant velocity unfolding SMFS data can be employed to reconstruct the protein unfolding energy landscape and kinetics. The methods applied so far require the specification of a single stretching force

Daniel Aioanei; Bruno Samorì; Marco Brucale

2009-01-01

163

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

164

The anomalous expansion of lattice parameter as a function of temperature for an Fe-24Mn alloy during {gamma}{yields}{epsilon} martensitic transformation  

SciTech Connect

In the present letter, the authors will report their experiment on an Fe-24Mn alloy using high temperature XRD and dilation. A relation between the lattice parameter of austenite and temperature during {gamma}{yields}{epsilon} martensitic transformation was determined. It is expected to be helpful in the understanding of {gamma}{yields}{epsilon} martensitic transformation in Fe-Mn based alloys.

Lu, X.; Qin, Z.; Zhang, Y.; Ding, B.; Hu, Z.

2000-02-14

165

Kinetics of the {beta} {yields} {delta} Solid-Solid Transition of HMX, Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine  

SciTech Connect

We apply Differential Scanning Calorimetry, DSC, to measure the kinetics of the {beta} {yields} {delta} solid-solid phase transition of Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocinet HMX. Integration of the DSC signal gives a direct measurement of degree of conversion. We apply 1st order kinetics, the Ozawa method, and isoconversional analysis to show that the phase transition is not a simple one-step reaction, but instead is a complex combination of steps. The range of activation energies found in this work, centering around 500 kJ/mol, is higher than previously reported values. We discuss possible reasons for the higher activation energies measured here.

Weese, R K; Maienschein, J L; Perrino, C T

2001-09-05

166

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

NASA Astrophysics Data System (ADS)

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

Gubchenko, Vladimir

167

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

SciTech Connect

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

Rodd, D.; Farrell, P.A.; Caston, A.L.; Green, M.H. (Department of Exercise and Sport Science, Pennsylvania State University, University Park (USA))

1991-03-01

168

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

169

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

170

Model of 2,3-bisphosphoglycerate metabolism in the human erythrocyte based on detailed enzyme kinetic equations: equations and parameter refinement.  

PubMed Central

Over the last 25 years, several mathematical models of erythrocyte metabolism have been developed. Although these models have identified the key features in the regulation and control of erythrocyte metabolism, many important aspects remain unexplained. In particular, none of these models have satisfactorily accounted for 2,3-bisphosphoglycerate (2,3-BPG) metabolism. 2,3-BPG is an important modulator of haemoglobin oxygen affinity, and hence an understanding of the regulation of 2,3-BPG concentration is important for understanding blood oxygen transport. A detailed, comprehensive, and hence realistic mathematical model of erythrocyte metabolism is presented that can explain the regulation and control of 2,3-BPG concentration and turnover. The model is restricted to the core metabolic pathways, namely glycolysis, the 2,3-BPG shunt and the pentose phosphate pathway (PPP), and includes membrane transport of metabolites, the binding of metabolites to haemoglobin and Mg(2+), as well as pH effects on key enzymic reactions and binding processes. The model is necessarily complex, since it is intended to describe the regulation and control of 2,3-BPG metabolism under a wide variety of physiological and experimental conditions. In addition, since H(+) and blood oxygen tension are important external effectors of 2,3-BPG concentration, it was important that the model take into account the large array of kinetic and binding phenomena that result from changes in these effectors. Through an iterative loop of experimental and simulation analysis many values of enzyme-kinetic parameters of the model were refined to yield close conformity between model simulations and 'real' experimental data. This iterative process enabled a single set of parameters to be found which described well the metabolic behaviour of the erythrocyte under a wide variety of conditions. PMID:10477269

Mulquiney, P J; Kuchel, P W

1999-01-01

171

Effect of the label of oligosaccharide acceptors on the kinetic parameters of nasturtium seed xyloglucan endotransglycosylase (XET).  

PubMed

Fluorescently labeled derivatives of a xyloglucan (XG) nonasaccharide Glc(4)Xyl(3)Gal(2) (XLLG) were used as glycosyl acceptors in assays of xyloglucan endotransglycosylase (XET) from germinated nasturtium (Tropaeolum majus) seeds. We have investigated how the type of the oligosaccharide label influences the kinetic parameters of the reaction. The fluorescent probes used to label XLLG were anthranilic acid (AA), 8-aminonaphtalene-1,3,6-trisulfonic acid (ANTS), fluorescein isothiocyanate (FITC), and sulforhodamine (SR), respectively. The obtained data were compared with those of the reactions where aldose and/or alditol forms of tritium-labeled xyloglucan-derived nonasaccharide served as the respective acceptors. Modification at C-1 of the reducing-end glucose in XLLG by substitution with the fluorophore markedly affected the kinetic parameters of the reaction. The Michaelis constants K(m) for individual acceptors increased in the order [1-(3)H]XLLGXLLG-SR>XLLG-ANTS>[1-(3)H]XLLGol>[1-(3)H]XLLG>XLLG-AA. Catalytic efficiency (expressed as k(cat)/K(m)) with XLLG labeled with SR or FITC was 15 and 28 times, respectively, higher than with the tritium-labeled natural substrate [1-(3)H]XLLG. Comparison of the kinetic parameters found with acceptors labeled with different types of labels enables to select the most effective substrates for the high-throughput assays of XET. PMID:21146161

Kosík, Ond?ej; Garajová, So?a; Matulová, Mária; Rehulka, Pavel; Stratilová, Eva; Farkaš, Vladimír

2011-02-01

172

Yield, kinetic energy, pairing effect, and shell effect of light fission products for thermal-neutron fission of uranium 233  

Microsoft Academic Search

The mass spectrometer HIAWATHA in conjunction with a thin-windowed gridded ionization chamber was used to determine the yields of light fission products for thermal-neutron fission of U-233. HIAWATHA has an energy resolution of 0.3%, a mass resolution of 0.5 amu, and an atomic-number resolving power of 38. The yields were measured as a function of mass number, atomic number, and

1983-01-01

173

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

174

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

SciTech Connect

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

Keszenman, D.J.; Sutherland, B. M.

2010-08-01

175

Kinetic parameters of radical reactions of 2-mercaptobenzothiazole with quinone imines  

NASA Astrophysics Data System (ADS)

The chain reaction of N, N'-diphenyl-1,4-benzoquinone diimine with 2-mercaptobenzothiazole was studied by two methods developed earlier for the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole. In the methods used, the kinetic scheme of the reaction is simplified by creating conditions under which the rates of all stages except radical generation and decay can be neglected. One of the methods was updated. For the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole, both methods gave close results; for the chain reaction of N, N'-diphenyl-1,4-phenylenediamine with 2-mercaptobenzothiazole, the results differed by approximately one order of magnitude.

Varlamov, V. T.; Gadomska, A. V.

2014-09-01

176

A novel bacterial expression method with optimized parameters for very high yield production of triple-labeled proteins.  

PubMed

The Gram-negative bacterium Escherichia coli offer a means for rapid, high-yield, and economical production of recombinant proteins. However, when preparing protein samples for NMR, high-level production of functional isotopically labeled proteins can be quite challenging. This is especially true for the preparation of triple-labeled protein samples in D(2)O ((2)H/(13)C/(15)N). The large expense and time-consuming nature of triple-labeled protein production for NMR led us to revisit the current bacterial protein expression protocols. Our goal was to develop an efficient bacterial expression method for very high-level production of triple-labeled proteins that could be routinely utilized in every NMR lab without changing expression vectors or requiring fermentation. We developed a novel high cell-density IPTG-induction bacterial expression method that combines tightly controlled traditional IPTG-induction expression with the high cell-density of auto-induction expression. In addition, we optimize several key experimental protocols and parameters to ensure that our new high cell-density bacterial expression method routinely produces 14-25 mg of triple-labeled proteins and 15-35 mg of unlabeled proteins from 50-mL bacterial cell cultures. PMID:22167665

Murray, Victoria; Huang, Yuefei; Chen, Jianglei; Wang, Jianjun; Li, Qianqian

2012-01-01

177

Tank cultivation of the red alga Palmaria palmata: Effects of intermittent light on growth rate, yield and growth kinetics  

Microsoft Academic Search

Tank cultivation of marine macroalgaeinvolves air-agitation of the algal biomassand intermittent light conditions,i.e.periodic, short light exposure of thethalli in the range of 10 s at the watersurface followed by plunging to low lightor darkness at the tank bottom andrecirculation back to the surface in therange of 1–2 min. Open questions relate toeffects of surface irradiance on growthrate and yield in

Shaojun Pang; Klaus Lüning

2004-01-01

178

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

SciTech Connect

In this study, the authors applied the state-of-the art sensitivity methods to downselect system parameters from 4000+ to 8, (23000+ -> 4000+ -> 84 -> 8). This analysis procedure paves the way for future works: (1) calibrate the system response using existed experimental observations, and (2) predict future experiment results, using the calibrated system.

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

2012-04-19

179

Kinetic parameters of oxidation of bituminous coals from heat-release rate measurements  

Microsoft Academic Search

Arrhenius parameters of oxidation of two Scottish bituminous coals were determined from heat-release rate measurements at laboratory oven temperatures. When the heat release rate expression so obtained was applied at stockpiling temperatures (?300 K), one coal was shown to have a significantly greater propensity to spontaneous combustion than the other.

J. C. Jones; P. S. Chiz; R. Koh; J. Matthew

1996-01-01

180

Kinetics study of the Cl/2P/ + Cl2O yields Cl2 + ClO reaction at 298 K  

NASA Technical Reports Server (NTRS)

The kinetics of the Cl + Cl2O reaction, a possible source of ClO(2 Pi) radicals for atmospheric photochemical studies, are investigated at 298 K. The discharge flow/mass spectrometry and discharge flow/resonance fluorescence techniques were used to monitor the decay of C12O in the presence of excess concentrations of atomic chlorine and chlorine monoxide, respectively. The pseudo-first order rate constants obtained from both experiments are found to be in excellent agreement, averaging 9.8 + or - 0.8 x 10 to the -11th cu cm/molecule per sec. Results are consistent with the lower limit obtained by Edgecombe et al. (1957) but differ by a factor of 150 from those of Basco and Dogra (1971). The present value is also noted to be consistent with a lower value for the rate constant of the reaction of oxygen atoms with Cl2O.

Ray, G. W.; Keyser, L. F.; Watson, R. T.

1980-01-01

181

Immobilization of denatured DNA to macroporous supports: II. Steric and kinetic parameters of heterogeneous hybridization reactions.  

PubMed Central

The accessibility of immobilized DNA has been shown to depend more crucially on the method of immobilization than on the type of support used for fixation. When sonicated denatured DNA is coupled via diazotization or via cyanogen bromide reaction to solid Sephadex G-25 and Cellex 410 or to macroporous Sephacryl S-500 and Sepharose C1-6B its accessibility varies from 100 to 24 percent. Generally the loss of accessibility is linked to a depression of the melting temperature of DNA helices formed on the support. This correlation shows a characteristic course for a particular coupling method. DNA coupled under denaturing conditions may become totally inaccessible when only 3 percent of its bases are involved in the covalent linkage. Kinetic experiments with sonicated E.coli DNA have shown that the rate constants for renaturation or hybridization reactions are very similar for DNA immobilized by different methods to solid or macroporous supports. Generally the second order rate constant for a heterogeneous reaction (between mobile and immobilized DNA) is about one order of magnitude smaller than that of the analogous homogeneous reaction (in solution). PMID:6185922

Bünemann, H

1982-01-01

182

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

PubMed Central

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

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

2012-01-01

183

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

184

Application of artificial neural networks and DFT-based parameters for prediction of reaction kinetics of ethylbenzene dehydrogenase.  

PubMed

Artificial neural networks (ANNs) are used for classification and prediction of enzymatic activity of ethylbenzene dehydrogenase from EbN1 Azoarcus sp. bacterium. Ethylbenzene dehydrogenase (EBDH) catalyzes stereo-specific oxidation of ethylbenzene and its derivates to alcohols, which find its application as building blocks in pharmaceutical industry. ANN systems are trained based on theoretical variables derived from Density Functional Theory (DFT) modeling, topological descriptors, and kinetic parameters measured with developed spectrophotometric assay. Obtained models exhibit high degree of accuracy (100% of correct classifications, correlation between predicted and experimental values of reaction rates on the 0.97 level). The applicability of ANNs is demonstrated as useful tool for the prediction of biochemical enzyme activity of new substrates basing only on quantum chemical calculations and simple structural characteristics. Multi Linear Regression and Molecular Field Analysis (MFA) are used in order to compare robustness of ANN and both classical and 3D-quantitative structure-activity relationship (QSAR) approaches. PMID:16779618

Szaleniec, Maciej; Witko, Ma?gorzata; Tadeusiewicz, Ryszard; Goclon, Jakub

2006-03-01

185

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

PubMed

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

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

2014-09-01

186

Influence of ultrasound on the kinetic parameters of electrochemical redox reactions.  

PubMed

The aim of this work is to determine the Tafel parameters with and without ultrasound. The total overvoltage has been corrected for diffusion by using rotating disk technique and potentiostatic extrapolation to infinite rotating speed. Three well known redox systems have been selected regardless to their different electrochemical behaviour: the quinone-hydroquinone, the Fe(II)Fe(III) chlorides and Fe(II)-Fe(III) cyanide systems. This work shows that the reversibility is higher with ultrasound only in the case of the quinone-hydroquinone system. PMID:11237025

Jung, C G; Chapelle, F; Fontana, A

1997-04-01

187

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

188

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

PubMed

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

Huang, Lihan

2015-02-16

189

Estimation of single channel kinetic parameters from data subject to limited time resolution.  

PubMed

The limited responsiveness of single-channel recording systems results in some brief events not being detected, and if this is ignored parameter estimation from the observed data will be biased. Statistical methods of correcting for this limited time resolution in a two-state Markov model have been proposed by Neher (1983. J. Physiol. (Lond.). 339:663-678) and by Colquhoun and Sigworth (1983. Single Channel Recording. 191-263). However, a numerical study by Blatz and Magleby (1986. Biophys. J. 49:967-980) indicated differences of 3-40% in the corrected values given by the two techniques. Here we explain why Neher's method produces biased results and the Colquhoun and Sigworth approach, which is no more difficult, provides reasonably accurate estimates. PMID:2470426

Milne, R K; Yeo, G F; Madsen, B W; Edeson, R O

1989-04-01

190

Estimation of kinetic parameters for glucose transport in human brain cortex  

SciTech Connect

3-O-C-11-methyl-D-glucose (CMG), F-18-3-deoxy-3-fluoro D-glucose (3FDG), and dynamic positron-emission-tomography (dPET) were used to measure the rate constants for glucose transport across the blood brain barrier (BBB) in human cortex. The assay takes advantage of CMG or 3FDG being practically not metabolized in brain and being transported back from the tissue into the circulation. The simultaneous registration of tracer concentration in blood and tissue by dPET at 1 min intervals for 40 min yields time activity curves, which permit the in vivo determination of the rate constants for CMG or 3FDG transport across the BBB. In the present study, 4 healthy volunteers and 10 patients suffering from a single-sided ischemic brain disease were examined. In all cases the CMG/3FDG measurements were carried out at two different glucose plasma concentrations i.e. at normoglycemia and hyperglycemia after i.v. application of 10 g glucose. The determination of glucose plasma concentration was performed just before and immediately after the CMG/3FDG study. Using these data and a new mathematical model the Michaelis-Menten constant (K/sub M/) and maximal velocity (V/sub M/) for CMG, 3FDG and glucose transport across the BBB in normal and non-affected human cortex were determined. K/sub M CMG/ was 7.21 ..mu..mol/g; K/sub M 3FDG/ was 3.93 ..mu..mol/g and K/sub M gluc/ was 6.31 ..mu..mol/g. V/sub M/ was found in all cases to be 2.1 ..mu..mol/min g. The data obtained suggest that the CMG/3FDG method might provide a powerful tool for studying the mechanisms involved in the pathological alterations of glucose carrier system.

Vyska, K.; Machulla, H.J.; Mehdorn, H.M.; Notohamiprodjo, G.; Knapp, W.H.; Feinendegen, L.E.

1985-05-01

191

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

Microsoft Academic Search

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

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

1999-01-01

192

The effect of sustained static kneeling on kinetic and kinematic knee joint gait parameters.  

PubMed

Despite epidemiological evidence for kneeling as an occupational risk factor for knee osteoarthritis, biomechanical evidence is lacking. Gait knee joint mechanics, a common measure used to study knee osteoarthritis initiation, were used in the present study to investigate the effect of sustained static kneeling on the knee. Ten healthy male subjects (24.1 years ± 3.5) performed ten baseline walking trials, followed by a 30-min kneeling protocol and a second set of walking trials. Knee joint moments and angles were calculated during the stance phase. Within-subject root mean squared differences were compared within and between the pre- and post-kneeling gait trials. Differences were observed between the pre-kneeling and post-kneeling walking trails for flexion and adduction knee moments (0.12 Nm/kg ± 0.03, 0.07 Nm/kg ± 0.02) and angles (3.18° ± 1.22 and 1.64° ± 1.15), indicating that sustained static deep-knee flexion kneeling does acutely alter knee joint gait parameters. PMID:25172306

Kajaks, Tara; Costigan, Patrick

2015-01-01

193

A general method for determining chemical kinetic parameters during ignition of coal char particles  

SciTech Connect

In this paper a viewpoint is presented that the activation energy, E, is independent of coal type and only varies with the temperature of particle, but the frequency factor of coal char, k{sub O, ch}, varies with coal type. The authors determined the E = 152 kJ/mol (36.3 kcal/mol), which is a constant in oxidation of any kind of coal char in air during ignition. The relationship between k{sub O, ch} and coal type, which is also applicable to any kind of coal, is presented. These are different from the previous references in which E and k{sub O, ch} all vary with coal type, but no general rules have been found. A new dimensionless number, Fz, which is used to indicate the ignition characteristics of coal char, is also presented. Fz depends only on the proximate analysis of coal and reflects the ignition property in a combined way, so that Fz is called the ignition index of coal. It is a very useful parameter for engineers and operators to use in predicting the ignition characteristics of different types of coals.

Fu, W.B.; Zeng, T.F. (Dept. of Engineering Mechanics, Tsinghua Univ., Beijing (CN))

1992-03-01

194

Kinetics of the reaction OH + HO2 yields H2O + O2 from 254 to 382 K  

NASA Technical Reports Server (NTRS)

The discharge-flow resonance fluorescence technique has been used to determine the absolute rate constant for the reaction OH + HO2 yields H2O + O2 from 254 to 382 K at a total pressure of 1 Torr. Pseudo-=first-order conditions were used with HO2 in large excess over OH. The rate constant was obtained directly from observed decays of OH and measured concentrations of HO2. Since the observed rate constant was found to be very sensitive to small background concentrations of O and H atoms, NO2 was used to remove both atom species from the system. With added NO2 the result at 299 K is (1.1 + or - 0.3) x 10 to the -10th cu cm/molecule where the error limits are one standard deviation and include an estimate of overall experimental uncertainty. The temperature dependence expressed in Arrhenius form is (4.8 + or - 0.8) x 10 to the -11th exp (250 + or - 50)/T. The results are independent of the type of reactor surface and the precursor used to produce OH and HO2. The present results agree well with earlier measurements near 1-atm total pressure and suggest that this rate constant exhibits little or no pressure dependence between 1 and 1000 Torr.

Keyser, Leon F.

1988-01-01

195

Measurements of fluorescence yield of electrons in air under atmospheric conditions: A key parameter for energy of cosmic rays  

NASA Astrophysics Data System (ADS)

The measurement of the fluorescence yield and its dependence on atmospheric properties such as pressure, temperature or pollutants, are essential to obtain a reliable measurement of the primary energy of cosmic rays. A new type of absolute measurement of the nitrogen fluorescence yield in the air will be performed at LAL using 3 items which will yield an unprecedented precision in all conditions of pressure, temperature, and pollutants. A 5 MeV electron beam will be provided by the new electron accelerator PHIL at LAL(Laboratoire de l'Accélérateur Linéaire, Univ Paris-Sud, CNRS/IN2P3, Orsay). This source will induce florescence yield inside an integrating sphere. The sphere will be surrounded by a spherical envelope to create a temperature controlled chamber (a Dewar). With this setup it will be possible to vary the temperature from -60 C to +40 C and the pressure from 1 to 0.01 atm. An output device on this sphere will be equipped with a set of optical fibers driving the fluorescence light to a Jobin-Yvon spectrometer equipped with an LN_{2} cooled CCD. The fluorescence spectrum in the 300-430 nm range will be accurately measured in steps of 0.1 nm resolution. A PMT equipped with a BG3 filter (the same as on JEM-EUSO) will be set on the sphere to measure the integrated yield. The expected precision of the yield should be better than 5%.

Monnier Ragaigne, D.; Gorodetzky, P.; Blacksley, C.; Wicek, F.; Monard, H.; Dagoret-Campagne, S.

2012-12-01

196

Kinetics and product yields of the acetyl peroxy + HO2 radical reaction studied by photoionization mass spectrometry  

NASA Astrophysics Data System (ADS)

The acetyl peroxy radical (CH3C(O)O2) is a key intermediate in the oxidation of carbonyl-containing hydrocarbons in the troposphere. Reaction of acetyl peroxy radicals with HO2 has been suggested as a source of OH radicals in low-NOx environments. Previous work on this reaction observed only two product channels forming (1) peracetic acid and (2) acetic acid. Recent experiments have shown that there is a third channel that generates the radicals OH and acetoxy: CH3C(O)O2 + HO2 ? (1) CH3C(O)OOH + O2 (2) CH3C(O)OH + O3 (3) CH3C(O)O + O2 + OH This last pathway to OH formation would then contribute to the apparent isoprene OH recycling suggested by discrepancies between atmospheric models and field observations of OH. There have, however, been significant disagreements among experiments on the yield of OH from reaction of acetyl peroxy radicals with HO2. We report our preliminary studies of acetyl peroxy self-reaction and its reaction with HO2 at 298 K and 8 Torr. Experiments were conducted at the Advanced Light Source synchrotron at the Lawerence Berkeley National Laboratory using tunable VUV ionizing radiation coupled to the Sandia National Laboratory pulsed-laser-photolysis multiplexed photoionization mass spectrometer to detect the time- and isomer-resolved formation of radical intermediates and products. From these results, we report new branching fractions of the three product channels in the acetyl peroxy + HO2 radical reaction.

Dodson, L. G.; Shen, L.; Savee, J. D.; Eddingsaas, N. C.; Welz, O.; Taatjes, C. A.; Osborn, D. L.; Sander, S. P.; Okumura, M.

2013-12-01

197

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

PubMed Central

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

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

2012-01-01

198

Use of extant kinetic parameters to predict effluent concentrations of specific organic compounds at full-scale facilities.  

PubMed

To use the results of kinetic tests to predict effluent concentrations of specific contaminants in activated sludge systems, the fraction of the biomass that has an ability to degrade the test compound (i.e., competent biomass) must be estimated. A calibration procedure was developed to assess the competent biomass concentration because the chemical oxygen demand (COD) fraction tended to underestimate the degrading fraction for three of the four test compounds. Acetone, for instance, had a measured influent COD fraction of 0.08%, and the actual competent fraction was estimated to be 2.3%, based on the model calibration. Once the competent biomass fraction in the mixed liquor was determined, the extant kinetic parameters were subsequently used to predict activated sludge system performance. Predicted effluent concentrations were within 2, 5, and 16% of the average measured concentrations for acetone, linear alkylbenzene sulfonate, and furfural, respectively. Day-to-day predictions for these compounds were less accurate, possibly because of the non-steady-state nature of the activated sludge systems studied. The difference between the fraction of the influent COD contributed by the target compounds and the competent biomass fraction in the mixed liquor was found to be more significant when the target compound contributed less than 1% of the influent organic matter. The chemical structure of the target compound and chemical composition of the influent likely had an effect on the resulting competent biomass concentration. The total maximum growth rate, microX, was observed to be independent of the influent concentration of acetone and furfural, thus suggesting that the competent biomass concentration for these compounds was not affected by the changes in their influent concentrations. Consequently, a majority of competent biomass growth resulted from the degradation of other substrates, resulting in a competent biomass concentration significantly higher than predicted based on the influent COD fraction contributed by the test compound. PMID:15523790

Ellis, Timothy G; Eliosov, Boris

2004-01-01

199

Chromium(VI) biosorption by dried Rhizopus arrhizus: effect of salt (NaCl) concentration on equilibrium and kinetic parameters.  

PubMed

Some industrial wastewaters contain high quantities of salts besides heavy metal ions. The presence of salt ions leads to high ionic strength, which may significantly affect the performance of the biosorption process so the effect of salts on the biosorption of heavy metal ions should be investigated. In this study the biosorption of chromium(VI) from saline solutions on dried Rhizopus arrhizus was studied as a function of pH, initial chromium(VI) and salt (NaCl) concentrations in a batch system. The biosorption capacity of R. arrhizus strongly depended on solution pH and maximum chromium(VI) sorption capacity of sorbent was obtained at pH 2.0 both in the absence and in the presence of increasing concentrations of salt. Chromium(VI)-salt biosorption studies were performed at this pH value. Equilibrium uptakes of chromium(VI) increased with increasing chromium(VI) concentration up to 250mgl(-1) and decreased considerably by the presence of increasing concentrations of salt. At 100mgl(-1), initial chromium(VI) concentration, dried R. arrhizus biosorbed 78.0mgg(-1) of chromium(VI) in 72h without salt medium. When salt concentration was raised to 50gl(-1), this value dropped to 64.0mgg(-1) of chromium(VI) at the same conditions resulting in 17.9% decrease of biosorption capacity. The equilibrium sorption data were analysed by using Freundlich, Langmuir, Redlich-Peterson and Langmuir-Freundlich (Sips), the two and three parameters adsorption models, using non-linear regression technique and isotherm constants were evaluated depending on salt concentration. The Langmuir-Freundlich (Sips) was the best suitable adsorption model for describing the biosorption of chromium(VI) individually and in salt-containing medium. Pseudo-first-order, pseudo-second-order and saturation type kinetic models described the biosorption kinetics accurately at all chromium(VI) concentrations in the absence and in the presence of changing concentrations of salt. Isotherm and saturation type kinetic constants varied due to the level of salt were expressed as a function of initial salt concentration. PMID:17188810

Aksu, Z; Balibek, E

2007-06-25

200

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

201

Estimates of Genetic Parameters for a Test Day Model with Random Regressions for Yield Traits of First Lactation Holsteins  

Microsoft Academic Search

A model that contains both fixed and random linear regressions is described for analyzing test day records of dairy cows. Estimation of the variances and covariances for this model was achieved by Bayesian methods utilizing the Gibbs sampler to generate sam- ples from the marginal posterior distributions. A single-trait model was applied to yields of milk, fat, and protein of

J. Jamrozik; L. R. Schaeffer

1997-01-01

202

Polyacrylamide gels as support for enzyme immobilization by entrapment. Effect of polyelectrolyte carrier, pH and temperature on enzyme action and kinetics parameters  

Microsoft Academic Search

This study investigates the main interactions which occur among enzymes and the polymeric support in which they are immobilized, when charges are created within the support as a result of the effect of external variables. The electrostatic field generated by the charges has a major impact on the enzymatic activity and kinetic parameters. In the most extreme conditions for the

J. M. González-Sáiz; C. Pizarro

2001-01-01

203

Photoactive yellow protein from the purple phototrophic bacterium, Ectothiorhodospira halophila. Quantum yield of photobleaching and effects of temperature, alcohols, glycerol, and sucrose on kinetics of photobleaching and recovery.  

PubMed Central

A water-soluble yellow protein from E. halophila was previously shown to be photoactive (Meyer, T. E., E. Yakali, M. A. Cusanovich, and G. Tollin. 1987. Biochemistry. 26:418-423). Pulsed laser excitation in the protein visible absorption band (maximum at 445 nm) causes a rapid bleach of color (k = 7.5 x 10(3) s-1) followed by a slower dark recovery (k = 2.6 s-1). This is analogous to the photocycle of sensory rhodopsin II from Halobacterium (which also has k = 2.6 s-1 for recovery). We have now determined the quantum yield of the photobleaching process to be 0.64, which is comparable with that of bacteriorhodopsin (0.25), and is thus large enough to be biologically significant. Although the photoreactions of yellow protein were previously shown to be relatively insensitive to pH, ionic strength and the osmoregulator betaine, the present experiments demonstrate that temperature, glycerol, sucrose, and various alcohol-water mixtures strongly influence the kinetics of photobleaching and recovery. The effect of temperature follows normal Arrhenius behavior for the bleach reaction (Ea = 15.5 kcal/mol). The rate constant for the recovery reaction increases with temperature between 5 degrees C and 35 degrees C, but decreases above 35 degrees C indicating alternate conformations with differing kinetics. There is an order of magnitude decrease in the rate constant for photobleaching in both glycerol and sucrose solutions that can be correlated with the changes in viscosity. We conclude from this that the protein undergoes a conformational change as a consequence of the photoinduced bleach. Recovery kinetics are affected by glycerol and sucrose to a much smaller extent and in a more complicated manner. Aliphatic, monofunctional alcohol-water solutions increase the rate constant for the bleach reaction and decrease the rate constant for the recovery reaction, each by an order of magnitude. These effects do not correlate with dielectric constant, indicating that the photocycle probably does not involve separation or recombination of charge accessible to the protein surface. However, the effects on both bleaching and recovery correlate well with the relative hydrophobicity(as measured by partition coefficients in detergent/water mixtures), in the order of increasing effectiveness:methanol < ethanol < iso-propanol

Meyer, T. E.; Tollin, G.; Hazzard, J. H.; Cusanovich, M. A.

1989-01-01

204

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. PMID:16391046

Jussier, Delphine; Dubé Morneau, Amélie; Mira de Orduña, Ramón

2006-01-01

205

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

206

Estimation of genetic parameters for daily milk yield of primiparous Ayrshire cows by random regression test-day models  

Microsoft Academic Search

Test-day data comprising of 63,331 test-day milk records of 6310 primiparous Finnish Ayrshire cows were used to estimate genetic parameters for daily milk production. Two alternative random regression (RR) sub-models were used to describe breeding values for the shape of lactation curves of individual cows: a five parameter logarithmic polynomial (ASM) or a normalised third order orthogonal polynomial. Permanent environment

Anne Kettunen; Esa A. Mäntysaari; Jukka Pösö

2000-01-01

207

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

208

Olive oil pilot-production assisted by pulsed electric field: impact on extraction yield, chemical parameters and sensory properties.  

PubMed

The impact of the use of pulsed electric field (PEF) technology on Arroniz olive oil production in terms of extraction yield and chemical and sensory quality has been studied at pilot scale in an industrial oil mill. The application of a PEF treatment (2 kV/cm; 11.25 kJ/kg) to the olive paste significantly increased the extraction yield by 13.3%, with respect to a control. Furthermore, olive oil obtained by PEF showed total phenolic content, total phytosterols and total tocopherols significantly higher than control (11.5%, 9.9% and 15.0%, respectively). The use of PEF had no negative effects on general chemical and sensory characteristics of the olive oil, maintaining the highest quality according to EU legal standards (EVOO; extra virgin olive oil). Therefore, PEF could be an appropriate technology to improve olive oil yield and produce EVOO enriched in human-health-related compounds, such as polyphenols, phytosterols and tocopherols. PMID:25149017

Puértolas, Eduardo; Martínez de Marañón, Iñigo

2015-01-15

209

Genetic parameters and correlations of collar rot resistance with important biochemical and yield traits in opium poppy (Papaver somniferum L.).  

PubMed

Collar rot, caused by Rhizoctonia solani Kühn, is one of the most severe fungal diseases of opium poppy. In this study, heritability, genetic advance and correlation for 10 agronomic, 1 physiological, 3 biochemical and 1 chemical traits with disease severity index (DSI) for collar rot were assessed in 35 accessions of opium poppy. Most of the economically important characters, like seed and capsule straw yield per plant, oil and protein content of seeds, peroxidase activity in leaves, morphine content of capsule straw and DSI for collar rot showed high heritability as well as genetic advance. Highly significant negative correlation between DSI and seed yield clearly shows that as the disease progresses in plants, seed yield declines, chiefly due to premature death of infected plants as well as low seed and capsule setting in the survived population of susceptible plants. Similarly, a highly significant negative correlation between peroxidase activity and DSI indicated that marker-assisted selection of disease-resistant plants based on high peroxidase activity would be effective and survived susceptible plants could be removed from the population to stop further spread. PMID:16424606

Trivedi, Mala; Tiwari, Rajesh K; Dhawan, Om P

2006-01-01

210

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

211

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

212

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

213

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. PMID:17766844

Letort, Véronique; Mahe, Paul; Cournède, Paul-Henry; de Reffye, Philippe; Courtois, Brigitte

2008-01-01

214

Influence of Different Parameters on a Dual-Fractal Analysis for Antigen-Antibody Binding Kinetics for Biosensor Applications  

PubMed

The diffusion-limited binding kinetics of antigen (or antibody) in solution to antibody (or antigen) immobilized on a biosensor surface is analyzed within a fractal framework. The fit obtained by a dual-fractal analysis is compared with that obtained from a single-fractal analysis. In some cases, the dual-fractal analysis provides an improved fit when compared with a single-fractal analysis. This was indicated by the regression analysis provided by Sigmaplot (46). It is of interest to note that the state of disorder (or the fractal dimension) and the binding rate coefficient both increase as the reaction progresses on the biosensor surface. For example, for the binding of HIV-1 p24 in solution to monoclonal antibody (MAb) 18 covalently attached to a biosensor surface (49), an increase in the fractal dimension by 59% from a value of Df1 equal to 1.91 to Df2 equal to 2.95 leads to an increase in the binding rate coefficient by a factor of 15 from k1 equal to 21.1 to k2 equal to 339. Also, the binding of MAb 6301 and 6303 in solution to insulin growth factor binding protein-1 (IGFBP-1) covalently attached to the sensor surface is adequately described by a single-fractal analysis (48). The binding of MAb 6302 to IGFBP-1, however, requires dual fractals. This indicates a difference in the binding mechanisms of these MAbs. The different examples analyzed and presented together provide a means by which the antigen-antibody reactions may be better controlled by noting the magnitude of the changes in the fractal dimension and in the binding rate coefficient as the reaction progresses on the biosensor surface. Also, the magnitude of the changes in the binding rate coefficients (k1 and k2) and in the fractal dimensions (Df1 and Df2) as different parameters are changed for the different biosensor applications are of particular value. PMID:9245322

Milum; Sadana

1997-03-01

215

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

216

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

217

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

E-print Network

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 ...

Alberty, Robert A.

218

Kinetic Parameters of Cleavage of CpA and UpA Sequences in an Oligoribonucleotide by Compounds Functionally Mimicking Ribonuclease A  

Microsoft Academic Search

Kinetic parameters of cleavage of CpA and UpA sites 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 the CpA site within decaribonucleotide UUCAUGUAAA was shown to be

N. G. Beloglazova; N. L. Mironova; D. A. Konevets; V. A. Petyuk; V. N. Sil'nikov; V. V. Vlasov; M. A. Zenkova

2002-01-01

219

Kinetic Parameter ? eff\\/? Measurement on Low Enriched Uranyl Nitrate Solution with Single Unit Cores (600?, 280T, 800? )o f STACY  

Microsoft Academic Search

The kinetic parameter ?eff\\/? of low enriched (10% EU) uranyl nitrate solution was measured by the pulsed neutron source (PNS) method in STACY. This measurement was repeated systematically over several uranium concentrations from about 195 gU\\/l to about 430 gU\\/l. Used core tanks were two cylindrical tanks whose diameters are 600 mm and 800 mm and one slab tank which

Kotaro TONOIKE; Yoshinori MIYOSHI; Tsukasa KIKUCHI; Toshihiro YAMAMOTO

220

Measurement of minimum substrate concentration (Smin) in a recycling fermentor and its prediction from the kinetic parameters of Pseudomonas strain B13 from batch and chemostat cultures.  

PubMed Central

The minimum substrate concentration required for growth, Smin, was measured for Pseudomonas sp. strain B13 with 3-chlorobenzoate (3CB) and acetate in a recycling fermentor. The substrates were provided alone or in a mixture. Smin values predicted with kinetic parameters from resting-cell batches and chemostat cultures differed clearly from the values measured in the recycling fermentor. When 3CB and acetate were fed as single substrates, the measured Smin values were higher than the individual Smin values in the mixture. The Smin in the mixture reflected the relative energy contributions of the two substrates in the fermentor feed. The energy-based maintenance coefficients during zero growth in the recycling fermentor were comparable for all influent compositions (mean +/- standard deviation, 0.34 +/- 0.07 J mg [dry weight]-1 h-1). Maintenance coefficient values for acetate were significantly higher in chemostat experiments than in recycling-fermentor experiments. 3CB maintenance coefficients were comparable in both experimental systems. The parameters for 3CB consumption kinetics varied remarkably with the experimental growth conditions in batch, chemostat, and recycling-fermentor environments. The results demonstrate that the determination of kinetic parameters in the laboratory for prediction of microbial activity in complex natural systems should be done under conditions which best mimic the system under consideration. PMID:8967775

Tros, M E; Bosma, T N; Schraa, G; Zehnder, A J

1996-01-01

221

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

222

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

223

Effect of changes in diet energy density on feed intake, milk yield and metabolic parameters in dairy cows in early lactation.  

PubMed

The purpose of this experiment was to investigate how early lactating cows adjust their metabolism and production to acute, but moderate changes in the energy density of the diet. Sixty dairy cows were randomly assigned to one of four treatments: two change-over groups (HNH and NHN) and two control groups (HHH and NNN), where H and N refer to a high and normal energy density in the total mixed ration (TMR), respectively. The experimental period covered the first 9 weeks post calving, which was split up in three 3-week periods. Thus, cows assigned to HNH or NHN shifted TMR in weeks 4 and 7 after calving while cows assigned to HHH or NNN were fed the same TMR for all 9 weeks. Results from cows on treatment HNH were compared with group HHH while cows on treatment NHN were compared with group NNN. When the diet changed from N to H and H to N, cows increased and decreased their dry-matter intake (DMI), respectively compared with control groups. Cows adjusted milk yield accordingly to changes in DMI, although not always significantly. Energy-corrected milk yield was not significantly affected by any of the changes in the energy density of the diet but generally showed same tendencies as milk yield. Non-esterified fatty acids (NEFA), beta-hydroxybutyrate in blood and milk and triacylglycerol and glycogen content in the liver were not significantly affected by changes in the energy density of the diet, except from NEFA at one change. Glucose increased more when the diet changed from N to H and increased less when the diet changed from H to N, compared with control groups, although not always significantly. Collectively, these results suggest that cows adjust their DMI and partly milk yield according to the energy density of the diet and therefore only limited effects were observed in physiological parameters. PMID:22444331

Nielsen, N I; Friggens, N C; Larsen, T; Andersen, J B; Nielsen, M O; Ingvartsen, K L

2007-03-01

224

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

225

Modeling sugarcane 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, 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 sugarcane 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 sugarcane cultivation in Australia and Brazil. The 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 different climate-mediated sensitivities of modeled sugarcane 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.; Caubel, A.; Huth, N.; Marin, F.; Martiné, J.-F.

2014-06-01

226

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

227

Sorption of SO(2) and NO from simulated flue gas over rice husk ash (RHA)/CaO/CeO(2) sorbent: evaluation of deactivation kinetic parameters.  

PubMed

In this study, the kinetic parameters of rice husk ash (RHA)/CaO/CeO(2) sorbent for SO(2) and NO sorptions were investigated in a laboratory-scale stainless steel fixed-bed reactor. Data experiments were obtained from our previous results and additional independent experiments were carried out at different conditions. The initial sorption rate constant (k(0)) and deactivation rate constant (k(d)) for SO(2)/NO sorptions were obtained from the nonlinear regression analysis of the experimental breakthrough data using deactivation kinetic model. Both the initial sorption rate constants and deactivation rate constants increased with increasing temperature, except at operating temperature of 170 °C. The activation energy and frequency factor for the SO(2) sorption were found to be 18.0 kJ/mol and 7.37 × 10(5)cm(3)/(g min), respectively. Whereas the activation energy and frequency factor for the NO sorption, were estimated to be 5.64 kJ/mol and 2.19 × 10(4)cm(3)/(g min), respectively. The deactivation kinetic model was found to give a very good agreement with the experimental data of the SO(2)/NO sorptions. PMID:21071143

Dahlan, Irvan; Lee, Keat Teong; Kamaruddin, Azlina Harun; Mohamed, Abdul Rahman

2011-01-30

228

Exact relativistic kinetic theory of an electron beam-plasma system: hierarchy of the competing modes in the system parameter space  

E-print Network

Besides being one of the most fundamental basic issues of plasma physics, the stability analysis of an electron beam-plasma system is of critical relevance in many areas of physics. Surprisingly, decades of extensive investigation had not yet resulted in a realistic unified picture of the multidimensional unstable spectrum within a fully relativistic and kinetic framework. All attempts made so far in this direction were indeed restricted to simplistic distribution functions and/or did not aim at a complete mapping of the beam-plasma parameter space. The present paper comprehensively tackles this problem by implementing an exact linear model. We show that three kinds of modes compete in the linear phase, which can be classified according to the direction of their wavenumber with respect to the beam. We then determine their respective domain of preponderance in a three-dimensional parameter space. All these results are supported by multidimensional particle-in-cell simulations.

A. Bret; L. Gremillet; D. Benisti; E. Lefebvre

2008-05-07

229

Degradation\\/decoloration of concentrated solutions of Orange II. Kinetics and quantum yield for sunlight induced reactions via Fenton type reagents  

Microsoft Academic Search

Light and thermal processes involving Fenton reagent are shown to be effective in the mineralization\\/decoloration of concentrated Orange II solutions. Light activation accelerates the observed degradation and the UV component of natural sunlight is sufficient to promote the reaction leading to the azo-dye abatement. The degradation involves dark and light steps. Kinetic information on these steps is reported. The results

J. Bandara; C. Morrison; J. Kiwi; C. Pulgarin; P. Peringer

1996-01-01

230

Kinetics of lipogenic genes expression in milk purified mammary epithelial cells (MEC) across lactation and their correlation with milk and fat yield in buffalo.  

PubMed

Expression patterns of lipogenic genes (LPL, ABCG2, ACSS2, ACACA, SCD, BDH, LIPIN1, SREBF1, PPAR? and PPAR?) were studied in milk purified MEC across different stages of lactation (15, 30, 45, 60, 90, 120 and 240 days relative to parturition) in buffalo. PPAR? was the most abundant gene while ABCG2 and ACSS2 had moderate level of expression; whereas expression of SREBF and PPAR? was very low. The expression patterns of some genes (BDH1, ACSS2, and LIPIN1) across lactation were positively correlated with milk yield while negatively correlated with fat yield. SCD also showed weak correlation with milk yield (p, 0.53) and fat yield (p, -0.47). On the other hand, expression pattern of ACACA was negatively correlated with milk yield (p, -0.88) and positively correlated with fat yield (p, 0.62). Strong correlation was observed between genes involved in de novo milk fat synthesis (BDH1, ACSS2, LIPIN2 and SCD) and milk yield. PMID:25660400

Yadav, Poonam; Kumar, Parveen; Mukesh, Manishi; Kataria, R S; Yadav, Anita; Mohanty, A K; Mishra, B P

2015-04-01

231

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

232

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

PubMed

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 correlation coefficients. According to Langmuir isotherm model the maximum biosorption capacity of Phaseolus vulgaris L. for AR57 dye was determined as 4.09 x 10(- 4) mol g(- 1) or 215.13 mg g(- 1) at 20 degrees C. The thermodynamic parameters (Gibbs free energy, enthalpy and entropy) for the biosorption of AR57 were indicated that the biosorption was spontaneous and exothermic in nature. The pseudo-second-order kinetic model agrees well with the dynamic behavior of the biosorption of AR57 onto P. vulgaris L., under various temperatures. The removal efficiency of the biomass was also examined in real textile wastewater. PMID:17454366

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

2007-04-01

233

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

234

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

PubMed Central

Background Accurate estimation of parameters of biochemical models is required to characterize the dynamics of molecular processes. This problem is intimately linked to identifying the most informative experiments for accomplishing such tasks. While significant progress has been made, effective experimental strategies for parameter identification and for distinguishing among alternative network topologies remain unclear. We approached these questions in an unbiased manner using a unique community-based approach in the context of the DREAM initiative (Dialogue for Reverse Engineering Assessment of Methods). We created an in silico test framework under which participants could probe a network with hidden parameters by requesting a range of experimental assays; results of these experiments were simulated according to a model of network dynamics only partially revealed to participants. Results We proposed two challenges; in the first, participants were given the topology and underlying biochemical structure of a 9-gene regulatory network and were asked to determine its parameter values. In the second challenge, participants were given an incomplete topology with 11 genes and asked to find three missing links in the model. In both challenges, a budget was provided to buy experimental data generated in silico with the model and mimicking the features of different common experimental techniques, such as microarrays and fluorescence microscopy. Data could be bought at any stage, allowing participants to implement an iterative loop of experiments and computation. Conclusions A total of 19 teams participated in this competition. The results suggest that the combination of state-of-the-art parameter estimation and a varied set of experimental methods using a few datasets, mostly fluorescence imaging data, can accurately determine parameters of biochemical models of gene regulation. However, the task is considerably more difficult if the gene network topology is not completely defined, as in challenge 2. Importantly, we found that aggregating independent parameter predictions and network topology across submissions creates a solution that can be better than the one from the best-performing submission. PMID:24507381

2014-01-01

235

Mechanism of adenylate kinase. What can be learned from a mutant enzyme with minor perturbation in kinetic parameters?  

PubMed

The structural and functional roles of threonine-23 in the chicken muscle adenylate kinase (AK) were investigated by site-directed mutagenesis coupled with proton nuclear magnetic resonance (NMR) and phosphorus stereochemistry. The residue is potentially important because it is conserved among all types of AK and is part of the consensus P-loop sequence, 15GXPGXGKGT23. A mutant enzyme T23A (replacing threonine-23 with alanine) was constructed. Analyses of conformational stability and proton NMR indicate that the side chain of this residue contributes little to the structure of AK, which suggests that the side chain of Thr-23 does not play a structural role. The steady-state kinetic data of the mutant enzyme T23A showed no change in kcat and only 5-7-fold increases in Km and dissociation constants. Such minor changes in kinetic data are insufficient to suggest a functional role of Thr-23. However, two-dimensional NMR analyses of WT.MgAP5A and T23A.MgAP5A complexes indicated that the side chain of Thr-23 is in proximity to the adenine ring of the ATP moiety in the WT.MgAP5A complex in solution. In addition, T23A showed a significant perturbation in the stereospecificity toward the diastereomers of (Rp)- and (Sp)-adenosine 5'-(1-thiotriphosphate) (ATP alpha S), with the Rp/Sp ratio increased from < 0.02 in wild-type to 0.37 in T23A. Detailed 31P NMR analysis indicated that the stereospecificity at the AMP site was not perturbed. These results suggest that the side chain of Thr-23 is involved in catalysis, most likely via a hydrogen bonding interaction Thr-OH...O-P alpha(ATP).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8518288

Shi, Z; Byeon, I J; Jiang, R T; Tsai, M D

1993-06-29

236

The effect of marine algae in the ration of high-yielding dairy cows during transition on metabolic parameters in serum and follicular fluid around parturition.  

PubMed

Sixteen Holstein cows were assigned to 2 groups to evaluate the caloric and metabolic effect of feeding marine algae (ALG) from 3 wk prepartum until 12 wk postpartum. Milk production characteristics and the profiles of hormones and metabolites in the serum were monitored from -7 to 46 d in milk (DIM) and in follicular fluid (FF) from 14 to 46 DIM. All cows received a corn- and grass silage-based partially mixed ration supplemented with concentrate and protein supplement. In the diet of the ALG group, 2 kg of the concentrate was replaced by a concentrate containing ALG (44 g/d of docosahexaenoic acid). Diets were isocaloric (net energy basis) and equal in intestinal digestible protein. The ALG diet increased milk yield (41.2 vs. 38.2 kg/d) and decreased milk fat yield (1.181 vs. 1.493 kg/d) and milk fat content (31.6 vs. 40.7 g/kg). Protein yield (1.336 vs. 1.301 kg/d) was not affected but a tendency toward decreased milk protein content (32.8 vs. 34.7 g/kg) was observed. Marine algae supplementation increased the ?-hydroxybutyric acid (BHBA) concentration in FF of the ALG cows compared with that in the controls (0.992 vs. 0.718 mmol/L). The total protein concentration in FF was decreased in ALG (62.9 vs. 67.6 g/L). Plasma and serum metabolites did not significantly differ between treatments except for a tendency toward a lower concentration of urea in the serum of the control compared with ALG (4.69 vs. 5.13 mmol/L). Based on metabolizable energy calculations, a daily energy-sparing effect of 3.48 Mcal was obtained due to milk fat depression (MFD). The concomitant increase in milk yield suggests that at least part of this spared energy is used to stimulate milk production. Theoretically, 3.48 Mcal of ME could lead to an increase in milk yield of 7.43 kg/d, which is higher than the observed 3 kg/d. However, when evaluating nutrient requirements during MFD in early lactation, we calculated that increased milk production is caused by a propionate-saving effect of 2.71 mol in the udder when milk fat is depressed. Concurrent increased BHBA concentrations in FF in the ALG group cannot be attributed to a worsened energy status of the animals because all other indicators contradict any change in energy balance, indicating that BHBA might not be an appropriate metabolic parameter to estimate the energy balance in early lactating dairy cows during MFD. PMID:21854933

Hostens, M; Fievez, V; Vlaeminck, B; Buyse, J; Leroy, J; Piepers, S; De Vliegher, S; Opsomer, G

2011-09-01

237

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

238

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

239

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

Microsoft Academic Search

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

Z. Aksu; T. Kutsal

1998-01-01

240

Calculation of reactivities using ionization chamber currents with different sets of kinetic parameters for reduced scram system efficiency in the VVER-1000 of the third unit of the Kalinin nuclear power plant at the stage of physical start-up  

SciTech Connect

The effectiveness of the VVER-1000 reactor scram system is analyzed using ionization chamber currents with different sets of kinetic parameters with allowance for the isotopic composition in the calculation of these parameters. The most 'correct, aesthetically acceptable' results are obtained using the eight-group constants of the ROSFOND (BNAB-RF) library. The difference between the maximum and minimum values of the scram system effectiveness calculated with different sets of kinetic parameters slightly exceeds 2{beta}. The problems of introducing corrections due to spatial effects are not considered in this study.

Zizin, M. N., E-mail: zizin@adis.vver.kiae.ru [Russian Research Centre Kurchatov Institute (Russian Federation); Zizina, S. N.; Kryakvin, L. V.; Pitilimov, V. A.; Tereshonok, V. A. [JSC VNIIAES (Russian Federation)

2011-12-15

241

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

242

Photooxidative degradation of Malachite Green (MG) by UV\\/H 2O 2: Influence of operational parameters and kinetic modeling  

Microsoft Academic Search

The decolorization of Malachite Oxalate Green (MG), a dye containing three groups of aryls was investigated using UV radiation in the presence of H2O2 in a batch photoreactor at different light intensities. H2O2 and UV-light showed negligible effect when they were used independently. Removal efficiency of MG was sensitive to the operational parameters such as initial concentrations of H2O2, MG

N. Modirshahla; M. A. Behnajady

2006-01-01

243

UV\\/H 2O 2 treatment of Rhodamine B in aqueous solution: Influence of operational parameters and kinetic modeling  

Microsoft Academic Search

The decolorization and degradation of Rhodamine B (RB) were investigated using UV radiation in the presence of H2O2 in a batch photoreactor at different light intensities. H2O2 and UV light have a negligible effect when they were used on their own. Removal efficiency of RB was sensitive to the operational parameters such as initial concentrations of H2O2 and RB, initial

N. Daneshvar; M. A. Behnajady; M. Khayyat Ali Mohammadi; M. S. Seyed Dorraji

2008-01-01

244

Isotherm Modelling, Kinetic Study and Optimization of Batch Parameters Using Response Surface Methodology for Effective Removal of Cr(VI) Using Fungal Biomass  

PubMed Central

Biosorption is a promising alternative method to replace the existing conventional technique for Cr(VI) removal from the industrial effluent. In the present experimental design, the removal of Cr(VI) from the aqueous solution was studied by Aspergillus niger MSR4 under different environmental conditions in the batch systems. The optimum conditions of biosorption were determined by investigating pH (2.0) and temperature (27°C). The effects of parameters such as biomass dosage (g/L), initial Cr(VI) concentration (mg/L) and contact time (min) on Cr(VI) biosorption were analyzed using a three parameter Box–Behnken design (BBD). The experimental data well fitted to the Langmuir isotherm, in comparison to the other isotherm models tested. The results of the D-R isotherm model suggested that a chemical ion-exchange mechanism was involved in the biosorption process. The biosorption process followed the pseudo-second-order kinetic model, which indicates that the rate limiting step is chemisorption process. Fourier transform infrared (FT-IR) spectroscopic studies revealed the possible involvement of functional groups, such as hydroxyl, carboxyl, amino and carbonyl group in the biosorption process. The thermodynamic parameters for Cr(VI) biosorption were also calculated, and the negative ?Gº values indicated the spontaneous nature of biosorption process. PMID:25786227

Chidambaram, Ramalingam

2015-01-01

245

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

246

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

NASA Astrophysics Data System (ADS)

Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It allows to describe mass transport and chemical reactions at the gas-particle interface and to link aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion correction, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependencies; flexible inclusion/omission of chemical species and physicochemical processes; flexible convolution/deconvolution of species and processes; and full compatibility with traditional resistor model formulations. Exemplary practical applications and model calculations illustrating the relevance of the above aspects will be presented in a companion paper (Ammann and Pöschl, 2005). We expect that the presented model framework will serve as a useful tool and basis for experimental and theoretical studies investigating and describing atmospheric aerosol and cloud surface chemistry and gas-particle interactions. In particular, it is meant to support the planning and design of laboratory experiments for the elucidation and determination of kinetic parameters; the establishment, evaluation, and quality assurance of comprehensive and self-consistent collections of rate parameters; and the development of detailed master mechanisms for process models and the derivation of simplified but yet realistic parameterizations for atmospheric and climate models.

Pöschl, U.; Rudich, Y.; Ammann, M.

2005-04-01

247

Inhibition and activation of enzymes. The effect of a modifier on the reaction rate and on kinetic parameters.  

PubMed

A combined analysis of enzyme inhibition and activation is presented, based on a rapid equilibrium model assumption in which one molecule of enzyme binds one molecule of substrate (S) and/or one molecule of a modifier X. The modifier acts as activator (essential or non-essential), as inhibitor (total or partial), or has no effect on the reaction rate (v), depending on the values of the equilibrium constants, the rate constants of the limiting velocity steps, and the concentration of substrate ([S]). Different possibilities have been analyzed from an equation written to emphasize that v = f([X]) is, in general and at a fixed [S], a hyperbolic function. Formulas for Su (the value of [S], different from zero, at which v is unaffected by the modifier) and v(su) (v at that particular [S]) were deduced. In Lineweaver-Burk plots, the straight lines related to different [X] generally cross in a point (P) with coordinates (Su, v(su)). In certain cases, point P is located in the first quadrant which implies that X acts as activator, as inhibitor, or has no effect, depending on [S]. Furthermore, we discuss: (1) the apparent Vmax and Km displayed by the enzyme in different situations; (2) the degree of effect (inhibition or activation) observed at different concentrations of substrate and modifier; (3) the concept of Ke, a parameter that depends on the concentration of substrate and helps to evaluate the effect of the modifier: it equals the value of [X] at which the increase or decrease in the reaction rate is half of that achieved at saturating [X]. Equations were deduced for the general case and for particular situations, and used to obtain computer-drawn graphs that are presented and discussed. Formulas for apparent Vmax, Km and Ke have been written in a way making it evident that these parameters can be expressed as pondered means. PMID:10961698

Fontes, R; Ribeiro, J M; Sillero, A

2000-01-01

248

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

PubMed

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

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

2015-03-01

249

Processing parameters and kinetics of bromination and chlorination in the YBa2Cu3O(6+x) system  

NASA Astrophysics Data System (ADS)

The introduction of halogens such as Cl2 and Br2 can restore 90-K superconductivity to oxygen deficient YBa2Cu3O(6+x). This is potentially important for applications to thin-film devices due to the low processing temperatures required relative to reprocessing with oxygen. Low-temperature (260 C) and short-time (above 5 min) bromination has been shown to convert initially insulating YBa2Cu3O6.2 powder to a high-temperature superconductor with properties similar to the standard O7 material. This process has now been extended to single crystals as well, but with somewhat different processing parameters. Thermal gravimetric analysis (TGA) coupled with mass spectrometry indicated that the Br becomes strongly bonded with no release of Br observed in taking powder samples to 1000 C in flowing forming gas (2 percent H2/98 percent N2). The reaction has also been found to be highly exothermic for both Br and Cl treatments, which is consistent with the strong bonding of the bromine.

Radousky, H. B.; Glass, R. S.; Back, D.; Chin, A. H.; Fluss, M. J.

1991-03-01

250

Analysis of the kinetics and yields of OH radical production from the CH3OCH2 + O2 reaction in the temperature range 195-650 K: an experimental and computational study.  

PubMed

The methoxymethyl radical, CH3OCH2, is an important intermediate in the low temperature combustion of dimethyl ether. The kinetics and yields of OH from the reaction of the methoxymethyl radical with O2 have been measured over the temperature and pressure ranges of 195-650 K and 5-500 Torr by detecting the hydroxyl radical using laser-induced fluorescence following the excimer laser photolysis (248 nm) of CH3OCH2Br. The reaction proceeds via the formation of an energized CH3OCH2O2 adduct, which either dissociates to OH + 2 H2CO or is collisionally stabilized by the buffer gas. At temperatures above 550 K, a secondary source of OH was observed consistent with thermal decomposition of stabilized CH3OCH2O2 radicals. In order to quantify OH production from the CH3OCH2 + O2 reaction, extensive relative and absolute OH yield measurements were performed over the same (T, P) conditions as the kinetic experiments. The reaction was studied at sufficiently low radical concentrations (?10(11) cm(-3)) that secondary (radical + radical) reactions were unimportant and the rate coefficients could be extracted from simple bi- or triexponential analysis. Ab initio (CBS-GB3)/master equation calculations (using the program MESMER) of the CH3OCH2 + O2 system were also performed to better understand this combustion-related reaction as well as be able to extrapolate experimental results to higher temperatures and pressures. To obtain agreement with experimental results (both kinetics and yield data), energies of the key transition states were substantially reduced (by 20-40 kJ mol(-1)) from their ab initio values and the effect of hindered rotations in the CH3OCH2 and CH3OCH2OO intermediates were taken into account. The optimized master equation model was used to generate a set of pressure and temperature dependent rate coefficients for the component nine phenomenological reactions that describe the CH3OCH2 + O2 system, including four well-skipping reactions. The rate coefficients were fitted to Chebyshev polynomials over the temperature and density ranges 200 to 1000 K and 1 × 10(17) to 1 × 10(23) molecules cm(-3) respectively for both N2 and He bath gases. Comparisons with an existing autoignition mechanism show that the well-skipping reactions are important at a pressure of 1 bar but are not significant at 10 bar. The main differences derive from the calculated rate coefficient for the CH3OCH2OO ? CH2OCH2OOH reaction, which leads to a faster rate of formation of O2CH2OCH2OOH. PMID:25069059

Eskola, A J; Carr, S A; Shannon, R J; Wang, B; Blitz, M A; Pilling, M J; Seakins, P W; Robertson, S H

2014-08-28

251

Kinetic characteristics of SnO2 thin-film gas sensors for environmental monitoring  

NASA Astrophysics Data System (ADS)

In this report we presented results of gas sensitivity' kinetics analysis for undoped SnO2 thin films, deposited by spray pyrolysis method, using SnCl4x5H2O alcohol solution. The comparison of gas sensitivity's kinetics in measurement cycles air yields {air+(0.08 - 1.7%)CO} yields air and air yields (N2 + 0.5%O2} yields air for different thickness of SnO2 films (d equals 40 - 200 nm) and operating temperature (T equals 150 - 400 degree(s)C) was carried out. We have determined the kinetic parameters ((tau) and Eact) and made a conclusion that kinetics of gas sensitivity is limited by the rate of SnO2 surface refilling by oxygen.

Korotchenkov, Ghennadii S.; Brynzari, Vladimir I.; Dmitriev, Sergei V.

1998-12-01

252

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

253

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

2006-03-01

254

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

255

Kinetics and activation parameter analyses of hydrolysis and interconversion of 2',5'- and 3',5'-linked dinucleoside monophosphate at extremely high temperatures.  

PubMed

Kinetic analysis of hydrolytic stability of 2',5'- and 3',5'-linked dinucleoside monophosphate (N(2)'pN and N(3)'pN) was successfully performed in aqueous solution at 175-240 degrees C using a new real-time monitoring method for rapid hydrothermal reactions. The half-lives of NpN were in the range 2-8 s at 240 degrees C and apparent activation energy decreases in the order U(2)'pU>A(2)'pA>G(2)'pG>U(3)pU approximately C(3)'pC>A(3)pA. The stability of phosphodiester bond was dependent on the types of base moiety and phosphodiester linkages, but no systematic correlation was found between the structure and stability. The interconversion of 2',5'-adenylyladenosine monophosphate (A(2)'pA) and 3',5'-adenylyladenosine monophosphate (A(3)'pA) was enhanced in the presence of D- or L-histidine. The rate constants of degradation of NpN were dissected into the rate constants of hydrolysis and interconversion between N(2)'pN and N(3)'pN using a computer program SIMFIT. Kinetic analysis supports the mechanism that imidazolium ion and imidazole catalyze interconversion and hydrolysis even under hydrothermal environments. The activation parameters for the hydrolysis and interconversion of NpN were systematically determined for the first time from the temperature dependence of the rate constants, where both DeltaH(app)( not equal ) and DeltaS(app)( not equal ) for 2',5'-linked NpN are larger than those for 3',5'-linked NpN. These parameters support the pseudorotation mechanism through pentacoordinate intermediate from 2',5'- and 3',5'-linked NpN, where the average value of DeltaH( not equal ) (pseudorotation) was estimated to be 30+/-18 kJ mol(-1) at 175-240 degrees C. PMID:12595090

Kawamura, Kunio

2003-03-17

256

[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

257

n-alkanes on MgO(100). II. Chain length dependence of kinetic desorption parameters for small n-alkanes.  

PubMed

Coverage-dependent desorption-kinetics parameters are obtained from high-quality temperature-programmed desorption 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 of 0.3-10.0 K/s. The inversion analysis method with its least-squares preexponential factor (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 prefactor for desorption increases dramatically with chain length from 10(13.1) to 10(19.1) s(-1) over the range of 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 gaslike transition state for desorption. The desorption energy increases with chain length as Ed(N)=6.5+7.1N, which implies an incremental increase of 7.1+/-0.2 kJ/mol per CH2. PMID:15945700

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

2005-04-22

258

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

259

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

260

Yield-SAFE: A parameter-sparse, process-based dynamic model for predicting resource capture, growth, and production in agroforestry systems  

Microsoft Academic Search

1.Silvoarable agroforestry (SAF) is the cultivation of trees and arable crops on the same parcel of land. SAF may contribute to modern diversified land use objectives in Europe, such as enhanced biodiversity and productivity, reduced leaching of nitrogen, protection against flooding and erosion, and attractiveness of the landscape. Long-term yield predictions are needed to assess long-term economic profitability of SAF.2.A

Wopke van der Werf; Karel Keesman; Paul Burgess; Anil Graves; David Pilbeam; L. D. Incoll; Klaas Metselaar; Martina Mayus; Roel Stappers; Herman van Keulen; João Palma; Christian Dupraz

2007-01-01

261

The Effects of Restraint Using Self-Locking Stanchions on Dairy Cows in Relation to Behavior, Feed Intake, Physiological Parameters, Health, and Milk Yield1,2  

Microsoft Academic Search

Holstein cows (n = 64) ranging from peak to end lactation were restrained in self-locking stanchions (i.e., head locks) for approximately 4 h\\/d for four periods in a modified switchback design. Milk yield, milk fat percentage, somatic cell count, and dry mat- ter intake and dry matter intake were unaffected by restraint. Milk protein percentage was significantly lower for cows

D. J. BOLINGER; J. L. ALBRIGHT; J. MORROW-TESCH; S. J. KENYON; M. D. CUNNINGHAM

262

Subcritical hydrothermal liquefaction of cattle manure to bio-oil: Effects of conversion parameters on bio-oil yield and characterization of bio-oil.  

PubMed

In this study, cattle manure was converted to bio-oil by subcritical hydrothermal liquefaction in the presence of NaOH. The effects of conversion temperature, process gas, initial conversion pressure, residence time and mass ratio of cattle manure to water on the bio-oil yield were studied. The bio-oil was characterized in terms of elemental composition, higher heating value, ultraviolet-visible (UV/Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Results showed that the bio-oil yield depended on the conversion temperature and the process gas. Higher initial conversion pressure, longer residence time and larger mass ratio of cattle manure to water, however, had negative impacts on the bio-oil yield. The higher heating value of bio-oil was 35.53MJ/kg on average. The major non-polar components of bio-oil were toluene, ethyl benzene and xylene, which are components of crude oil, gasoline and diesel. PMID:20083403

Yin, Sudong; Dolan, Ryan; Harris, Matt; Tan, Zhongchao

2010-05-01

263

Biosorption of Cr(VI) by Ceratocystis paradoxa MSR2 Using Isotherm Modelling, Kinetic Study and Optimization of Batch Parameters Using Response Surface Methodology.  

PubMed

This study is focused on the possible use of Ceratocystis paradoxa MSR2 native biomass for Cr(VI) biosorption. The influence of experimental parameters such as initial pH, temperature, biomass dosage, initial Cr(VI) concentration and contact time were optimized using batch systems as well as response surface methodology (RSM). Maximum Cr(VI) removal of 68.72% was achieved, at an optimal condition of biomass dosage 2g L-1, initial Cr(VI) concentration of 62.5 mg L-1 and contact time of 60 min. The closeness of the experimental and the predicted values exhibit the success of RSM. The biosorption mechanism of MSR2 biosorbent was well described by Langmuir isotherm and a pseudo second order kinetic model, with a high regression coefficient. The thermodynamic study also revealed the spontaneity and exothermic nature of the process. The surface characterization using FT-IR analysis revealed the involvement of amine, carbonyl and carboxyl groups in the biosorption process. Additionally, desorption efficiency of 92% was found with 0.1 M HNO3. The Cr(VI) removal efficiency, increased with increase in metal ion concentration, biomass concentration, temperature but with a decrease in pH. The size of the MSR2 biosorbent material was found to be 80 ?m using particle size analyzer. Atomic force microscopy (AFM) visualizes the distribution of Cr(VI) on the biosorbent binding sites with alterations in the MSR2 surface structure. The SEM-EDAX analysis was also used to evaluate the binding characteristics of MSR2 strain with Cr(VI) metals. The mechanism of Cr(VI) removal of MSR2 biomass has also been proposed. PMID:25822726

Samuel, Melvin S; E A Abigail, M; Ramalingam, Chidambaram

2015-01-01

264

Biosorption of Cr(VI) by Ceratocystis paradoxa MSR2 Using Isotherm Modelling, Kinetic Study and Optimization of Batch Parameters Using Response Surface Methodology  

PubMed Central

This study is focused on the possible use of Ceratocystis paradoxa MSR2 native biomass for Cr(VI) biosorption. The influence of experimental parameters such as initial pH, temperature, biomass dosage, initial Cr(VI) concentration and contact time were optimized using batch systems as well as response surface methodology (RSM). Maximum Cr(VI) removal of 68.72% was achieved, at an optimal condition of biomass dosage 2g L?1, initial Cr(VI) concentration of 62.5 mg L?1 and contact time of 60 min. The closeness of the experimental and the predicted values exhibit the success of RSM. The biosorption mechanism of MSR2 biosorbent was well described by Langmuir isotherm and a pseudo second order kinetic model, with a high regression coefficient. The thermodynamic study also revealed the spontaneity and exothermic nature of the process. The surface characterization using FT-IR analysis revealed the involvement of amine, carbonyl and carboxyl groups in the biosorption process. Additionally, desorption efficiency of 92% was found with 0.1 M HNO3. The Cr(VI) removal efficiency, increased with increase in metal ion concentration, biomass concentration, temperature but with a decrease in pH. The size of the MSR2 biosorbent material was found to be 80 ?m using particle size analyzer. Atomic force microscopy (AFM) visualizes the distribution of Cr(VI) on the biosorbent binding sites with alterations in the MSR2 surface structure. The SEM-EDAX analysis was also used to evaluate the binding characteristics of MSR2 strain with Cr(VI) metals. The mechanism of Cr(VI) removal of MSR2 biomass has also been proposed. PMID:25822726

Ramalingam, Chidambaram

2015-01-01

265

A coupled transport and solid mechanics formulation with improved reaction kinetics parameters for modeling oxidation and decomposition in a uranium hydride bed.  

SciTech Connect

Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. An advanced type of storage bed has been proposed that utilizes oxidation of uranium hydride to heat and decompose the hydride, releasing the hydrogen. To reduce the cost and time required to develop these systems experimentally, a valid computational model is required that simulates the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. This SAND report discusses the advancements made in FY12 (since our last SAND report SAND2011-6939) to the model developed as a part of an ASC-P&EM project to address the shortcomings of the previous model. The model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion are accounted for. These expansions result in mechanical stresses that lead to bed deformation. To describe this, a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation is developed. By using this solid mechanics model, the agreement between our reacting bed model and the experimental data is improved. Additionally, more accurate uranium hydride oxidation kinetics parameters are obtained by fitting the experimental results from a pure uranium hydride oxidation measurement to the ones obtained from the coupled transport-solid mechanics model. Finally, the coupled transport-solid mechanics model governing equations and boundary conditions are summarized and recommendations are made for further development of ARIA and other Sandia codes in order for them to sufficiently implement the model.

Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.

2013-03-01

266

A spatially distributed analysis of erosion susceptibility and sediment yield in a river basin by means of geomorphic parameters and regression relationships  

Microsoft Academic Search

In the present work, an application of statistical regression relationships utilising geomorphic parameters is attempted in a spatially distributed mode, in order to predict the amount of river sediment supply at varying sections of the drainage network. Simple and multiple regression relationships utilising drainage density Dd and hierarchical anomaly index Deltaa as independent variables were applied to the Calvano watershed

S. Grauso; G. Fattoruso; C. Crocetti; A. Montanari

2007-01-01

267

Kinetic simulation of living carbocationic polymerizations. II. Simulation of living isobutylene polymerization using a mechanistic model  

Microsoft Academic Search

This paper discusses the kinetic simulation of TiCl4––coinitiated living carbocationic isobutylene (IB) polymerizations governed by dormant-active equilibria, using a mechanistic model. Two kinetic models were constructed from the same underlying mechanism: one using a commercial simulation software package (Predici®), and the other using the method of moments. Parameter estimation from experimental batch reactor data with Predici yielded a rate constant

Judit E. Puskas; Sohel Shaikh; Kevin Z. Yao; Kim B. McAuley; Gabor Kaszas

2005-01-01

268

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

269

Increasing Yield  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

270

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

NASA Astrophysics Data System (ADS)

Particles count rates at given Earth location and altitude result from the convolution of (i) the interstellar (IS) cosmic-ray fluxes outside the solar cavity, (ii) the time-dependent modulation of IS into Top-of-Atmosphere (TOA) fluxes, (iii) the rigidity cut-off (or geomagnetic transmission function) and grammage at the counter location, (iv) the atmosphere response to incoming TOA cosmic rays (shower development), and (v) the counter response to the various particles/energies in the shower. Count rates from neutron monitors or muon counters are therefore a proxy to solar activity. In this paper, we review all ingredients, discuss how their uncertainties impact count rate calculations, and how they translate into variation/uncertainties on the level of solar modulation ? (in the simple Force-Field approximation). The main uncertainty for neutron monitors is related to the yield function. However, many other effects have a significant impact, at the 5-10% level on ? values. We find no clear ranking of the dominant effects, as some depend on the station position and/or the weather and/or the season. An abacus to translate any variation of count rates (for neutron and ? detectors) to a variation of the solar modulation ? is provided.

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

2015-01-01

271

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

E-print Network

Particles count rates at given Earth location and altitude result from the convolution of (i) the interstellar (IS) cosmic-ray fluxes outside the solar cavity, (ii) the time-dependent modulation of IS into Top-of-Atmosphere (TOA) fluxes, (iii) the rigidity cut-off (or geomagnetic transmission function) and grammage at the counter location, (iv) the atmosphere response to incoming TOA cosmic rays (shower development), and (v) the counter response to the various particles/energies in the shower. Count rates from neutron monitors or muon counters are therefore a proxy to solar activity. In this paper, we review all ingredients, discuss how their uncertainties impact count rate calculations, and how they translate into variation/uncertainties on the level of solar modulation $\\varphi$ (in the simple Force-Field approximation). The main uncertainty for neutron monitors is related to the yield function. However, many other effects have a significant impact, at the 5-10\\% level on $\\varphi$ values. We find no clear ranking of the dominant effects, as some depend on the station position and/or the weather and/or the season. An abacus to translate any variation of count rates (for neutron and $\\mu$ detectors) to a variation of the solar modulation $\\varphi$ is provided.

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

2014-07-01

272

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

273

Effects of Operation Conditions on Removal Rate Constant and Quantum Yield of Gaseous Chlorobenzene Degradation in a Photochemical Reactor  

Microsoft Academic Search

A photochemical reactor with a low-pressure mercury ultraviolet (UV) lamp was established to treat waste gas containing chlorobenzene. Operation conditions such as light intensity, gas humidity, and inlet chlorobenzene concentration were varied. Two significant parameters, the removal rate constant and the quantum yield (relating to removal kinetic and light energy utilization), were investigated under each set of conditions. The experimental

Can Wang; Jin-Ying Xi; Hong-Ying Hu; Mohammad Arhami; Andrea Polidori; Ralph Delfino; Thomas Tjoa; Constantinos Sioutas; Adriano Pacheco; Maria Freitas; Gregory Pratt; Mary Dymond; Judi Krzyzanowski; Huan-Lin Luo; Wei-Che Chang; Deng-Fong Lin; Kelly Pennell; Ozgur Bozkurt; Eric Suuberg; Vlad Isakov; Jawad Touma; Janet Burke; Danelle Lobdell; Ted Palma; Arlene Rosenbaum; Frederick Lipfert; Ronald Wyzga; Jack Baty; J. Miller; Richard Mohan; Giovanni Leonardi; Alan Robins; Stephan Jefferis; Joanne Coy; Jeremy Wight; Virginia Murray

2009-01-01

274

Parsimonious Modeling of Yield Curves  

Microsoft Academic Search

This paper introduces a parametrically parsimonious model for yield curves that has the ability to represent the shapes generally associated with yield curves: monotonic, humped, and S-shaped. The authors find that the model explains 96 percent of the variation in bill yields across maturities during the period 1981-83. The movement of the parameters through time reflects and confirms a change

Charles R. Nelson; Andrew F. Siegel

1987-01-01

275

Kinetics calculation of cascade in K p and K d atoms by Monte-Carlo method  

Microsoft Academic Search

method. The x-ray yields due to the radiative transitions during the cascade processes are calculated. The evolution of the kinetic energy distribution during the atomic cascade is very important, because many collisional processes are energy dependence(2). we have taken into account the energy dependence of collisional processes and we have not used any tuning parameters in the Coulomb transition and

S. Z. Kalantari; M. G. Raeisi

276

Multifactorial analysis of acetaldehyde kinetics during alcoholic fermentation by Saccharomyces cerevisiae  

Microsoft Academic Search

Acetaldehyde is the terminal electron acceptor in the alcoholic fermentation by Saccharomyces cerevisiae. Quantitatively the most important carbonyl by-product, it has relevance for ethanol production yields as well as product stabilization and toxicology. The aim of this study was to investigate the effect of various enological parameters on acetaldehyde kinetics during alcoholic fermentations. Two commercial yeast strains were tested in

J. N. Jackowetz; S. Dierschke; R. Mira de Orduña

2011-01-01

277

Measurement of the CP-violation parameter of B{sup 0} mixing and decay with pp{yields}{mu}{mu}X data  

SciTech Connect

We measure the dimuon charge asymmetry A in pp collisions at a center of mass energy {radical}(s)=1960 GeV. The data was recorded with the D0 detector and corresponds to an integrated luminosity of approximately 1.0 fb{sup -1}. Assuming that the asymmetry A is due to asymmetric B{sup 0}{r_reversible}B{sup 0} mixing and decay, we extract the CP-violation parameter of B{sup 0} mixing and decay: ((Re({epsilon}{sub B{sup 0}})/1+ vertical bar {epsilon}{sub B{sup 0}} vertical bar{sup 2})=(A{sub B{sup 0}}/4)-0.0023{+-}0.0011(stat){+-}0.0008(syst).A{sub B{sup 0}} is the dimuon charge asymmetry from decays of B{sup 0}B{sup 0} pairs. The general case, with CP violation in both B{sup 0} and B{sub s}{sup 0} systems, is also considered. Finally we obtain the forward-backward asymmetry that quantifies the tendency of {mu}{sup +} to go in the proton direction and {mu}{sup -} to go in the antiproton direction. The results are consistent with the standard model and constrain new physics.

Abazov, V. M.; Alexeev, G. D.; Kalinin, A. M.; Kharzheev, Y. M.; Malyshev, V. L.; Tokmenin, V. V.; Vertogradov, L. S.; Yatsunenko, Y. A. [Joint Institute for Nuclear Research, Dubna, Russia (Russian Federation); Abbott, B.; Gutierrez, P.; Hall, I.; Jain, S.; Kopal, M.; Pompos, A.; Severini, H.; Skubic, P.; Strauss, M. [University of Oklahoma, Norman, Oklahoma 73019 (United States); Abolins, M.; Benitez, J. A.; Brock, R. [Michigan State University, East Lansing, Michigan 48824 (United States)] (and others)

2006-11-01

278

Pulse Radiolysis of Gases H atom yields, OH reactions,  

E-print Network

mechanisms: 1) The hydrogen atom yield in the pulse radiolysis of H2 was measured by four independentRisø-R-480 Pulse Radiolysis of Gases H atom yields, OH reactions, and kinetics of H2O systems Ole PULSE RADIOLYSIS OP GASES H atom yields, OH reactions, and kinetics of H2S systems Ole John Nielsen

279

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

280

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

E-print Network

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

Kumar, Ashutosh; Dua, Arti

2015-01-01

281

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

282

EVALUATION OF CHEMICAL REACTION MECHANISMS FOR PHOTOCHEMICAL SMOG. PART 3. SENSITIVITY OF EKMA (EMPIRICAL KINETIC MODELING APPROACH) TO CHEMICAL MECHANISM AND INPUT PARAMETERS  

EPA Science Inventory

Six chemical reaction mechanisms for photochemical smog were used to study the effect of input parameters on volatile organic compound (VOC) control requirements needed to reduce ozone. The parameters studied were initial VOC composition, dilution rate, post 8-A.M. emissions, bas...

283

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

284

The clinical application of DNA content and kinetic parameters in the treatment of patients with squamous cell carcinomas of the head and neck.  

PubMed

Patients with squamous cell cancers of the head and neck (SCCHN) vary tremendously in their natural history and treatment outcome even amongst subgroups where the clinical and morphological parameters are similar. The ability to pretherapeutically identify individual patients and patient subgroups that differ in these regards would greatly facilitate clinical and basic science cancer research in this tumor. DNA content parameters are simple and accurate intermediate markers of a tumor's biology and reflect the fundamental process associated with the development of malignancy, chromosomal aneuploidy. In patients with SCCHN, DNA content parameters have been shown to be highly predictive of the natural history of the tumor and treatment outcome. They are also useful as intermediate markers for the study of the underlying molecular-genetic properties and processes responsible for the biological differences seen in these cancers. DNA content parameters therefore serve as fundamental 'translational' bridges in clinical and laboratory research in patients with SCCHN. PMID:8842484

Ensley, J F

1996-03-01

285

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

286

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

287

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

288

Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants.  

PubMed

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: K m1 1.2-1.8 mM, K m2 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, K m values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher K m values (EH: K m1 10 mM, K m2 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) K m 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 K m 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. PMID:23914194

Hafke, Jens B; Höll, Sabina-Roxana; Kühn, Christina; van Bel, Aart J E

2013-01-01

289

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. PMID:23914194

Hafke, Jens B.; Höll, Sabina-Roxana; Kühn, Christina; van Bel, Aart J. E.

2013-01-01

290

Enzyme Kinetics.  

ERIC Educational Resources Information Center

Conveys an appreciation of enzyme kinetic analysis by using a practical and intuitive approach. Discusses enzyme assays, kinetic models and rate laws, the kinetic constants (V, velocity, and Km, Michaels constant), evaluation of V and Km from experimental data, and enzyme inhibition. (CW)

Moe, Owen; Cornelius, Richard

1988-01-01

291

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

292

Study on degradation kinetics of sulforaphane in broccoli extract.  

PubMed

The objective of this study was to investigate the thermal degradation kinetics of sulforaphane (SF) in broccoli extract at selected temperatures (60, 75, 82 and 100°C) and pH values (2.2, 3.0, 4.0, 5.0 and 6.0). The results indicated that SF is unstable at high temperatures, but is more heat-stable when present in acidic food products. The degradation rate constants of SF in broccoli extract were lower than those obtained in purified SF. The thermal degradation of SF followed first-order reaction kinetics, and the rate constant increased with increase of temperature and pH values. The rate constant vs temperature relationships, which yield linear Arrhenius plots, were described by a simpler exponential equation, and a mathematical model was developed, using the steady-state kinetic parameters obtained to predict the retentions of SF at various pH values, heating times and temperatures. PMID:24594180

Wu, Yuanfeng; Mao, Jianwei; You, Yuru; Liu, Shiwang

2014-07-15

293

Rainfall Energy as Related to Sediment Yield  

Microsoft Academic Search

Two mixed-cover agricultural watersheds yielded data for an evaluation of the relationship of the kinetic energy of a rainstorm to suspended sediment yields. The relation is developed on the hypothesis that the cultivated acres are the only source of sediment. This statistical analysis is extended to cover the interaction effects of rainfall energy as a function of factors such as

Frank J. Dragoun

1962-01-01

294

Advanced oxidation of the commercial nonionic surfactant octylphenol polyethoxylate TritonTM X-45 by the persulfate/UV-C process: effect of operating parameters and kinetic evaluation  

NASA Astrophysics Data System (ADS)

This study explored the potential use of a sulfate radical (SO4?-)-based photochemical oxidation process to treat the commercial nonionic surfactant octylphenol polyethoxylate (OPPE) TritonTMX-45. For this purpose, the effect of initial S2O82- (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 S2O82- concentrations (>2.5 mM). S2O82-/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 S2O82-. On the other hand, TOC removal efficiencies dropped down to only 40% under the same reaction conditions. S2O82-/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 S2O82-/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 SO4?- and HO?, bimolecular reaction rate coefficients of OPPE with SO4?- and HO? were determined by employing competition kinetics with aqueous phenol (47 ?M) selected as the reference compound. The first-order abatement rate coefficient obtained for OPPE during S2O82-/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 first-order abatement rate coefficients were obtained for both OPPE (0.087 min-1) and phenol (0.140 min-1). Second-order reaction rate coefficients for OPPE with SO4?- and HO? were determined as 9.8?108 M-1s-1 and 4.1?109 M-1s-1, respectively. The kinetic study also revealed that the selectivity of SO4?- was found to be significantly higher than that of HO?.

Arslan-Alaton, Idil; Olmez-Hanci, Tugba; Genc, Bora; Dursun, Duygu

2013-03-01

295

Density functional theory investigation of competitive free-radical processes during the thermal cracking of methylated polyaromatics: estimation of kinetic parameters.  

PubMed

Density functional B3LYP and BH&HLYP calculations with the 6-31G** basis set have been performed to investigate elementary reactions playing an important role in the pyrolysis of 1-methylnaphthalene. The pathways describing the destiny of the main radicals, H, methyl, hydromethylnaphthyl and methylnaphthyl, have been studied. At low temperature, addition of H atoms on the aromatic ring is favored over hydrogen abstraction. Except at low temperature (below 400 K), the hydromethylnaphthyl radical undergoes preferentially a loss of hydrogen rather than a bimolecular hydrogen transfer with methylnaphthalene or addition reaction on methylnaphthalene forming a hydrogenated dimer. In the range 400-750 K, the formation of methane by hydrogen abstraction of methyl radical on methylnaphthalene is predominant compared to the formation of hydrodimethylnaphthalenes by addition reaction. Rate constants of reactions describing the formation of heavy products like methyldinaphthylmethanes or dimethylbinaphthalenes have been calculated and discussed. They are also compared to recombination reactions from the literature. Rate constants of these reactions have been computed using transition state theory and can be integrated in kinetic radical schemes of methylated polyaromatic compounds pyrolysis from geological to laboratory conditions. PMID:17394290

Leininger, J-Philippe; Minot, Christian; Lorant, François; Behar, Françoise

2007-04-26

296

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

297

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

298

Crystallization kinetics of gehlenite glass  

Microsoft Academic Search

Isothermal and non-isothermal kinetics of gehlenite glass devitrification have been studied. A Johnson—Mehl—Avrami rate equation was assumed. The values of kinetic parameters obtained from XRD patterns and DTA curves are in a good agreement. The crystallization process is thought to proceed by a rod-like growth controlled by diffusion from a fixed number of nuclei.

A. Marotta; A. Buri; G. L. Valenti

1978-01-01

299

Kinetic Turbulence  

E-print Network

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

Howes, Gregory G

2015-01-01

300

Kinetic Turbulence  

NASA Astrophysics Data System (ADS)

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

Howes, Gregory G.

301

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

PubMed Central

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

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

2012-01-01

302

Oxygen consumption rate of cells in 3D culture: the use of experiment and simulation to measure kinetic parameters and optimise culture conditions.  

PubMed

Understanding the basal O(2) and nutrient requirements of cells is paramount when culturing cells in 3D tissue models. Any scaffold design will need to take such parameters into consideration, especially as the addition of cells introduces gradients of consumption of such molecules from the surface to the core of scaffolds. We have cultured two cell types in 3D native collagen type I scaffolds, and measured the O(2) tension at specific locations within the scaffold. By changing the density of cells, we have established O(2) consumption gradients within these scaffolds and using mathematical modeling have derived rates of consumption for O(2). For human dermal fibroblasts the average rate constant was 1.19 × 10(-17) mol cell(-1) s(-1), and for human bone marrow derived stromal cells the average rate constant was 7.91 × 10(-18) mol cell(-1) s(-1). These values are lower than previously published rates for similar cells cultured in 2D, but the values established in this current study are more representative of rates of consumption measured in vivo. These values will dictate 3D culture parameters, including maximum cell-seeding density and maximum size of the constructs, for long-term viability of tissue models. PMID:21804989

Streeter, Ian; Cheema, Umber

2011-10-01

303

Determination of kinetic parameters in the biosorption of Cr (VI) on immobilized Bacillus cereus M(1)(16) in a continuous packed bed column reactor.  

PubMed

Due to technological advancement, environment suffers from untreated toxic heavy metal bearing effluent coming from different industries. Chromium (VI) is one of those heavy metals having adverse impact on ecological balance, human, and plant health because of its carcinogenic properties. Biosorption is presented as an alternative to traditional technologies which are costly and inefficient for treatment of industrial wastes containing low amount of heavy metals. In this study, bioremediation of Cr (VI) ions by immobilized Bacillus cereus M(1) (16) was investigated in a laboratory scale packed bed up-flow column reactor. The effect of important parameters, such as the inlet flow rate, influent concentration, and effective bed height, has been studied. External mass transfer, surface adsorption, and intrabead mass transfer were also studied to conclude the rate limiting step for removal of Cr (VI) and to determine the process parameters which are important for biosorption optimization. The external mass transfer coefficient was calculated at different flow rates (6.51 x 10(-2) to 7.58 x 10(-2) cm/min). Using the model, the surface adsorption rate constant (k(ad)) and the intrabead mass transfer coefficient (k (i)) were predicted as 0.0267 x 10(-3) and 0.7465 x 10(-3) l/g/min, respectively. Both are much lower than the external mass transfer coefficient (k(e)). The surface adsorption phenomenon is acting as the rate-limiting step due to its high resistance for removal of Cr (VI). PMID:19333567

Maiti, Soumen K; Bera, Debabrata; Chattopadhyay, Parimal; Ray, Lalitagauri

2009-11-01

304

Crystallization kinetics of amorphous ferroelectric films  

Microsoft Academic Search

The kinetic parameters characterizing the crystallite growth during annealing of PZT and PGO amorphous films were determined by proposed mathematical treatment of in situ elastic light scattering data.

V. Ya. Shur; S. A. Negashev; A. L. Subbotin; E. A. Borisova

1997-01-01

305

Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State  

PubMed Central

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

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

2012-01-01

306

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

307

Kinetic models of opinion formation  

E-print Network

We introduce and discuss certain kinetic models of (continuous) opinion formation involving both exchange of opinion between individual agents and diffusion of information. We show conditions which ensure that the kinetic model reaches non trivial stationary states in case of lack of diffusion in correspondence of some opinion point. Analytical results are then obtained by considering a suitable asymptotic limit of the model yielding a Fokker-Planck equation for the distribution of opinion among individuals.

G. Toscani

2006-05-17

308

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

PubMed

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

Samsudin, Mohd Dinie Muhaimin; Mat Don, Mashitah

2014-10-30

309

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

Microsoft Academic Search

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

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

2008-01-01

310

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; )

1998-01-01

311

Kinetic and stoichiometric characterization of a fixed biofilm reactor by pulse respirometry.  

PubMed

An in situ respirometric technique was applied to a sequential biofilm batch reactor treating a synthetic wastewater containing acetate. In this reactor, inoculated with mixed liquor from a wastewater plant, unglazed ceramic tiles were used as support media while maintaining complete mixing regime. A total of 8 kinetic and stoichiometric parameters were determined by in situ pulse respirometry; namely substrate oxidation yield, biomass growth yield, storage yield, storage growth yield, substrate affinity constant, storage affinity constant, storage kinetic constant and maximum oxygen uptake rate. Additionally, biofilm growth was determined from support media sampling showing that the colonization process occurred during the first 40 days, reaching an apparent steady-state afterward. Similarly, most of the stoichiometric and kinetic parameters were changing over time but reached steady values after day 40. During the experiment, the respirometric method allowed to quantify the amount of substrate directed to storage, which was significant, especially at substrate concentration superior to 30mg CODL(-1). The Activated Sludge Model 3 (ASM3), which is a model that takes into account substrate storage mechanisms, fitted well experimental data and allowed confirming that feast and famine cycles in SBR favor storage. These results also show that in situ pulse respirometry can be used for fixed-bed reactors characterization. PMID:22100265

Ordaz, Alberto; Oliveira, Catarina S; Quijano, Guillermo; Ferreira, Eugenio C; Alves, Madalena; Thalasso, Frédéric

2012-01-01

312

Detailed chemical kinetic modeling of butylbenzene pyrolysis  

Microsoft Academic Search

The gas phase pyrolysis of butylbenzene is modeled using a detailed chemical kinetic approach. A 60-reaction, free radical mechanism is used. The thermodynamics of the chemical species and the kinetic rate parameters for the reactions are taken from the literature or estimated from closely related species or reactions. There was no fitting of these parameters to better match the butylbenzene

H. Freund; W. N. Olmstead

1988-01-01

313

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

314

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

315

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

316

Simple model relating recombination rates and non-proportional light yield in scintillators  

SciTech Connect

We present a phenomenological approach to derive an approximate expression for the local light yield along a track as a function of the rate constants of different kinetic orders of radiative and quenching processes for excitons and electron-hole pairs excited by an incident {gamma}-ray in a scintillating crystal. For excitons, the radiative and quenching processes considered are linear and binary, and for electron-hole pairs a ternary (Auger type) quenching process is also taken into account. The local light yield (Y{sub L}) in photons per MeV is plotted as a function of the deposited energy, -dE/dx (keV/cm) at any point x along the track length. This model formulation achieves a certain simplicity by using two coupled rate equations. We discuss the approximations that are involved. There are a sufficient number of parameters in this model to fit local light yield profiles needed for qualitative comparison with experiment.

Moses, William W.; Bizarri, Gregory; Singh, Jai; Vasil'ev, Andrey N.; Williams, Richard T.

2008-09-24

317

Carbon monoxide activation by organoactinides: a comparative synthetic, thermodynamic, kinetic, and mechanistic investigation of migratory CO insertion into actinide-carbon and actinide-hydrogen bonds to yield eta/sup 2/-acyls and eta/sup 2/-formyls  

SciTech Connect

Reported are results of the synthesis, characterization, and carbon monoxide chemistry of a series of sterically hindered thorium alkyls and hydrides of the type Cp'/sub 2/ Th(R)(X) (Cp' = eta/sup 5/-C/sub 5/Me/sub 5/) where R = H, D, methyl, eta-butyl, and CH /sub 2/-t-Bu and X = OCH-t-Bu/sub 2/, OC/sub 6/H/sub 3/-2,6-t-Bu/sub 2/, and O-t-Bu. In addition, improved syntheses of the known complexes (Cp'/sub 2/Th(..mu..-H)(H))/sub 2/, Cp'/sub 2/Th(O-t-Bu)(Cl) and Cp'/sub 2/Th(CH/sub 2/-t-Bu)(Cl) are presented. The alkyl complexes undergo facile, irreversible carbonylation to yield eta/sup 2/-acyls that were characterized by a variety of methods. Infrared Ir and /sup 13/C NMR spectra of these complexes demonstrate that strong meta-(acyl)oxygen bonding takes place, fostering a pronounced carbene-like character. Thus, these complexes are characterized by low C-O Ir infrared stretching frequencies (nu/sub CO/ = 1450-1480 cm/sup -1/) and low-field /sup 13/C NMR chemical shifts (delta/sub /sup 13/C/ 355-370). The hydrides undergo a rapid, reversible, migratory CO insertion to yield formyls that have been characterized spectroscopically at low temperature. Infrared Ir and /sup 13/C NMR spectra of these species are similar to the corresponding acyls, suggesting an analogous eta/sup 2/ structure. Variable-temperature equilibrium data show that the insertion of CO into thorium-hydrogen bonds is exothermic by ca. 5 kcal/mol, and this value is compared to that for the analogous alkyls. The equilibrium was also found to exhibit a distinct equilibrium isotope effect upon deuterium substitution, K/sub H//K/sub D/ = 0.31 at -78/sup 0/C. The carbonylation of the complex Cp'/sub 2/Th(n-Bu)(OCH-t-Bu/sub 2/) was found to obey a second-order rate law where rate = kP/sub CO/ (complex). The insertion of CO into the Th-H bond of Cp'/sub 2/Th(H)(OCH-t-Bu/sub 2/) was found by NMR methods to be first order in metal hydride. 55 references, 3 figures, 6 tables.

Moloy, K.G.; Marks, T.J.

1984-11-14

318

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

319

MAIZE YIELD POTENTIAL: CRITICAL PROCESSES AND SIMULATION MODELING IN A HIGH-YIELDING ENVIRONMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Accurate parameters describing processes of maize (Zea mays L.) growth and grain yield production in high-yielding, irrigated conditions provide a system for studying grain yield potential in different environments. In this study we measured maize leaf area index (LAI), the light extinction coeffic...

320

Kinetic Sculpture  

NSDL National Science Digital Library

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

WGBH

2010-01-01

321

Yield Factors Lithography-  

E-print Network

Yield Factors Parametric Lithography- based Defect Density 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.35 micron 0.25 micron 0.18 micron 0.13 micron 0.09 micron Process Technology NominalYields Defect Density Lithography-based Parametric Yield Yield-Aware Cache Architectures Serkan Ozdemir Debjit

Zhou, Hai

322

Yield Advances in Peanut  

Technology Transfer Automated Retrieval System (TEKTRAN)

Average yields of peanut in the U.S. set an all time record of 4,695 kg ha-1 in 2012. This far exceeded the previous record yield of 3,837 kg ha-1 in 2008. Favorable weather conditions undoubtedly contributed to the record yields in 2012; however, these record yields would not have been achievable...

323

Kinetic City  

NSDL National Science Digital Library

Developed by the American Association for the Advancement of Science, this website offers an assortment of science experiments, games, activities, and projects. In the Shape it Up game, students can learn about land formations and processes. Users can learn the basic interactions of mixing different chemicals in the Slush Rush link. Educators can find Leader packets and information on how to start a Kinetic City club. Besides the games educating users about topics in the physical sciences, the website also offers a variety of biology-related activities. After filling out the free sign-up form, the website saves individual's power points and results.

324

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

325

Chemical kinetics modeling  

SciTech Connect

This project emphasizes numerical modeling of chemical kinetics of combustion, including applications in both practical combustion systems and in controlled laboratory experiments. Elementary reaction rate parameters are combined into mechanisms which then describe the overall reaction of the fuels being studied. Detailed sensitivity analyses are used to identify those reaction rates and product species distributions to which the results are most sensitive and therefore warrant the greatest attention from other experimental and theoretical research programs. Experimental data from a variety of environments are combined together to validate the reaction mechanisms, including results from laminar flames, shock tubes, flow systems, detonations, and even internal combustion engines.

Westbrook, C.K.; Pitz, W.J. [Lawrence Livermore National Laboratory, CA (United States)

1993-12-01

326

Application of Genetic Algorithms and Thermogravimetry to Determine the Kinetics of Polyurethane Foam in Smoldering Combustion   

E-print Network

In this work, the kinetic parameters governing the thermal and oxidative degradation of flexible polyurethane foam are determined using thermogravimetric data and a genetic algorithm. These kinetic parameters are needed ...

Rein, Guillermo; Lautenberger, Chris; Fernandez-Pello, Carlos; Torero, Jose L; Urban, David

327

Kinetics of tetrataenite disordering  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

328

Crystallization kinetics of palm oil  

Microsoft Academic Search

The quality and yield of oils obtained by fractionation processes depend mainly on the separation efficiency of fat crystals\\u000a from the mother liquor; this process is, to a large extent, determined by crystal-size distributions. The size of the crystals\\u000a is influenced by the crystallization conditions applied, and the quantitative data on crystallization kinetics are a useful\\u000a tool to optimize and

K. P. A. M. van Putte; B. H. Bakker

1987-01-01

329

The yield stress myth?  

Microsoft Academic Search

New experimental data obtained from constant stress rheometers are used to show that the yield stress concept is an idealization, and that, given accurate measurements, no yield stress exists. The simple Cross model is shown to be a useful empiricism for many non-Newtonian fluids, including those which have hitherto been thought to possess a yield stress.

H. A. Barnes; K. Walters

1985-01-01

330

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

331

The kinetic study of hydrogen bacteria and methanotrophs in pure and defined mixed cultures  

SciTech Connect

The kinetics of pure and mixed cultures of Alcaligenes eutrophus H 16 and Methylobacterium organophilum CRL 26 under double substrate limited conditions were studied. In pure culture growth kinetics, a non-interactive model was found to fit the experimental data best. The yield of biomass on limiting substrate was found to vary with the dilution rate. The variation in the biomass yield may be attributed to the change in metabolic pathways resulting from a shift in the limiting substrates. Both species exhibited wall growth in the chemostat under dark conditions. However, under illuminated conditions, there was significant reduction in wall growth. Poly-{beta}-hydroxybutyric acid was synthesized by both species under ammonia and oxygen limiting conditions. The feed gas mixture was optimized to achieve the steady-state coexistence of these two species in a chemostate for the first time. In mixed cultures, the biomass species assays were differentiated on the basis of their selective growth on particular compounds: Sarcosine and D-arabinose were selected for hydrogen bacteria and methylotrophs, respectively. The kinetics parameters estimated from pure cultures were used to predict the growth kinetics of these species in defined mixed cultures.

Arora, D.K.

1989-01-01

332

Kinetic and stoichiometric characterization for efficient enhanced biological phosphorus removal (EBPR) process at high temperatures.  

PubMed

A recently reported stable and efficient EBPR system at high temperatures around 30 °C has led to characterization of kinetic and stoichiometric parameters of the Activated Sludge Model no. 2d (ASM2d). Firstly, suitable model parameters were selected by identifiability analysis. Next, the model was calibrated and validated. ASM2d was found to represent the processes well at 28 and 32 °C except in polyhyroxyalkanoate (PHA) accumulation of the latter. The values of the kinetic parameters for PHA storage (q PHA), polyphosphate storage (q PP) and growth (? PAO) of polyphosphate-accumulating organisms (PAOs) at 28 and 32 °C were found to be much higher than those reported by previous studies. Besides, the value of the stoichiometric parameter for the requirement of polyphosphate for PHA storage (Y PO4) was found to decrease as temperature rose from 28 to 32 °C. Values of two other stoichiometric parameters, i.e. the growth yield of heterotrophic organisms (Y H) and PAOs (Y PAO), were high at both temperatures. These calibrated parameters imply that the extremely active PAOs of the study were able to store PHA, store polyphosphate and even utilize PHA for cell growth. Besides, the parameters do not follow the Arrhenius correlation due to the previously reported unique microbial clade at 28 and 32 °C, which actively performs EBPR at high temperatures. PMID:25381606

Liau, Kee Fui; Shoji, Tadashi; Ong, Ying Hui; Chua, Adeline Seak May; Yeoh, Hak Koon; Ho, Pei Yee

2015-04-01

333

Glucose reversion reaction kinetics.  

PubMed

The reversion reactions of glucose in mildly acidic aqueous solutions have been studied, and the kinetics of conversion to disaccharides has been modeled. The experiments demonstrate that, at high sugar loadings, up to 12 wt % of the glucose can be converted into reversion products. The reversion products observed are primarily disaccharides; no larger oligosaccharides were observed. Only disaccharides linked to the C1 carbon of one of the glucose residues were observed. The formation of 1,6-linked disaccharides was favored, and alpha-linked disaccharides were formed at higher concentrations than beta-linked disaccharides. This observation can be rationalized on the basis of steric effects. At temperatures >140 degrees C, the disaccharides reach equilibrium with glucose and the reversion reaction competes with dehydration reactions to form 5-hydroxymethylfurfural. As a result, disaccharide formation reaches a maximum at reaction times <10 min and decreases with time. At temperatures <130 degrees C, disaccharide formation reaches a maximum at reaction times >30 min. As expected, disaccharide formation exhibits a second-order dependence upon glucose concentration. Levoglucosan formation is also observed; because it shows a first-order dependence upon glucose concentration, its formation is more significant at low concentrations (10 mg mL(-1)), whereas disaccharide formation dominates at high concentrations (200 mg mL(-1)). Experiments conducted using glucose and its disaccharides were calibrated with readily available standards. The kinetic parameters for hydrolysis of some glucodisaccharides could be compared to published literature values. From these experiments, the kinetics and activation energies for the reversion reactions have been calculated. The rate parameters can be used to model the formation of the disaccharides as a function of reaction time and temperature. A new and detailed picture of the molecular mechanism of these industrially important reversion reactions has been developed. PMID:20429509

Pilath, Heidi M; Nimlos, Mark R; Mittal, Ashutosh; Himmel, Michael E; Johnson, David K

2010-05-26

334

Measurement of B{sub s}{sup 0} Mixing Parameters from the Flavor-Tagged Decay B{sub s}{sup 0}{yields}J/{psi}{phi}  

SciTech Connect

From an analysis of the flavor-tagged decay B{sub s}{sup 0}{yields}J/{psi}{phi} we obtain the width difference between the B{sub s}{sup 0} light and heavy mass eigenstates, {delta}{gamma}{sub s}=0.19{+-}0.07(stat){sub -0.01}{sup +0.02}(syst) ps{sup -1}, and the CP-violating phase, {phi}{sub s}=-0.57{sub -0.30}{sup +0.24}(stat){sub -0.02}{sup +0.08}(syst). The allowed 90% CL intervals of {delta}{gamma}{sub s} and {phi}{sub s} are 0.06<{delta}{gamma}{sub s}<0.30 ps{sup -1} and -1.20<{phi}{sub s}<0.06, respectively. The data sample corresponds to an integrated luminosity of 2.8 fb{sup -1} accumulated with the D0 detector at the Fermilab Tevatron collider.

Abazov, V. M.; Alexeev, G. D.; Kalinin, A. M.; Kharzheev, Y. M.; Malyshev, V. L.; Tokmenin, V. V.; Vertogradov, L. S.; Yatsunenko, Y. A. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Abbott, B.; Gutierrez, P.; Hossain, S.; Jain, S.; Rominsky, M.; Severini, H.; Skubic, P.; Strauss, M. [University of Oklahoma, Norman, Oklahoma 73019 (United States); Abolins, M.; Benitez, J. A.; Brock, R.; Dyer, J. [Michigan State University, East Lansing, Michigan 48824 (United States)] (and others)

2008-12-12

335

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

336

Parameter estimation for mathematical models of NKCC2 cotransporter isoforms  

PubMed Central

An optimization problem, formulated using a nonlinear least-squares approach, was used to estimate parameters for kinetic models of the three isoforms of the kidney-specific Na-K-2Cl (NKCC2) cotransporter. Specifically, the optimization problem estimates the magnitude of model parameters (i.e., off-binding and translocation rate constants) by minimizing the distance between model unidirectional fluxes and published unidirectional 86Rb+ uptake curves for the A, B, and F isoforms of the NKCC2 cotransporter obtained in transfected Xenopus oocytes. By using different symmetry assumptions, NKCC2 models with five, six, seven, or eight parameters were evaluated. The optimization method identified parameter sets that yielded computed unidirectional fluxes consistent with the uptake data. However, the parameter values were not unique, in that systematic exploration of the parameter space revealed alternative parameter sets that fit the data with similar accuracy. Finally, we demonstrate that the optimization method can identify parameter sets for the three transporter isoforms that differ only in ion binding affinities, a result that is consistent with a published mutagenesis analysis of the molecular and structural bases for the differences in 86Rb+ uptake among the A, B, and F isoforms. These NKCC2 cotransporter models will facilitate the development of larger scale models of ion transport by thick ascending limb cells. PMID:19036850

Marcano, Mariano; Yang, Hun-Mo; Nieves-González, Aniel; Clausen, Chris; Moore, Leon C.

2009-01-01

337

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

338

Atmospheric Nitrogen Fluorescence Yield  

NASA Technical Reports Server (NTRS)

Several existing and planned experiments estimate the energies of ultra-high energy cosmic rays from air showers using the atmospheric nitrogen fluorescence. The nitrogen fluorescence yield from air shower electrons depends on the atmospheric composition. We will discuss the uncertainties in the fluorescence yield form electrons in the real atmosphere and describe a concept for a small balloon payload to measure the atmospheric fluorescence yield as a function of attitude.

Adams, J. H., Jr.; Christl, M. J.; Fountain, W. F.; Gregory, J. C.; Martens, K. U.; Sokolsky, Pierre; Whitaker, Ann F. (Technical Monitor)

2001-01-01

339

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

340

Kinetics of thermal decomposition of surrogate solid wastes  

SciTech Connect

Decomposition behavior of different materials in a controlled environment at different heating rates are presented. The surrogate materials used are cellulose, polyethylene, polystyrene, polypropylene, nylon and bisphenol-A-polycarbonate. A series of tests were performed using a Perkin-Elmer 7 series thermal analysis system. Two heating rates of 10 C/minute and 100 C/minute were used. The temperature dependence and mass load characteristics of materials was obtained and used to obtain Arrhenius kinetic parameters and therefore the decomposition rates under defined conditions of pressure, temperature, environment, heating rate and waste composition. This information is helpful in characterizing and understanding the thermal decomposition properties of these materials during their thermal destruction. The decomposition rates are affected by the heating rate. The higher the heating rate the faster the decomposition. The results show that an increase in heating rate shifted thermal decomposition to higher temperatures and that the temperature at which maximum devolatilization began and ended was affected by heating rate. The kinetic parameters were calculated and the char yield from the different samples was less than 2% by weight except for polycarbonate which was around 5%. The remaining char in nylon and polycarbonate is attributed to the inert impurities in these materials. The thermal decomposition of the materials studied here could be related to their composition. It was found that polyethylene, polypropylene and polycarbonate have comparable decomposition rates over the same temperature range. Cellulose has the lowest decomposition rate and polystyrene has the highest.

Missoum, A.; Gupta, A.K.; Chen, J. [Univ. of Maryland, College Park, MD (United States); Keating, E.L. [Naval Surface Warfare Center, Annapolis, MD (United States)

1996-12-31

341

Kinetica; An Excel program to Stimulate or Analyze Kinetic Data  

NSDL National Science Digital Library

The Excel spreadsheet Kinetica both simulates and analyzes kinetic data for simple rate equations of the form: - d[A]/dt = k [A]^n Instructors or students can generate simulated kinetic data using parameters they specify, or using parameters randomized by Kinetica. The data set that is generated may then be exported for use in exercises, homework, and exams, or may be analyzed directly within Kinetica. A kinetics data set may also be imported from an external source into Kinetica for analysis.

342

Negative Kinetic Energy Between Past and Future State Vectors  

E-print Network

An analysis of errors in measurement yields new insight into classically forbidden quantum processes. In addition to "physical" values, a realistic measurement can yield "unphysical" values; we show that in {\\it sequences} of measurements, the "unphysical" values can form a consistent pattern. An experiment to isolate a particle in a classically forbidden region obtains a negative value for its kinetic energy. It is the {\\it weak value} of kinetic energy between past and future state vectors.

Daniel Rohrlich; Yakir Aharonov; Sandu Popescu; Lev Vaidman

1994-06-29

343

Reaction kinetics of cellulose hydrolysis in subcritical and supercritical water  

NASA Astrophysics Data System (ADS)

The uncertainties in the continuous supply of fossil fuels from the crisis-ridden oil-rich region of the world is fast shifting focus on the need to utilize cellulosic biomass and develop more efficient technologies for its conversion to fuels and chemicals. One such technology is the rapid degradation of cellulose in supercritical water without the need for an enzyme or inorganic catalyst such as acid. This project focused on the study of reaction kinetics of cellulose hydrolysis in subcritical and supercritical water. Cellulose reactions at hydrothermal conditions can proceed via the homogeneous route involving dissolution and hydrolysis or the heterogeneous path of surface hydrolysis. The work is divided into three main parts. First, the detailed kinetic analysis of cellulose reactions in micro- and tubular reactors was conducted. Reaction kinetics models were applied, and kinetics parameters at both subcritical and supercritical conditions were evaluated. The second major task was the evaluation of yields of water soluble hydrolysates obtained from the hydrolysis of cellulose and starch in hydrothermal reactors. Lastly, changes in molecular weight distribution due to hydrothermolytic degradation of cellulose were investigated. These changes were also simulated based on different modes of scission, and the pattern generated from simulation was compared with the distribution pattern from experiments. For a better understanding of the reaction kinetics of cellulose in subcritical and supercritical water, a series of reactions was conducted in the microreactor. Hydrolysis of cellulose was performed at subcritical temperatures ranging from 270 to 340 °C (tau = 0.40--0.88 s). For the dissolution of cellulose, the reaction was conducted at supercritical temperatures ranging from 375 to 395 °C (tau = 0.27--0.44 s). The operating pressure for the reactions at both subcritical and supercritical conditions was 5000 psig. The results show that the rate-limiting step in converting cellulose to fermentable sugars in subcritical and supercritical water differs because of the difference in their activation energies. Cellulose and starch were both hydrolyzed in micro- and tubular reactors and at subcritical and supercritical conditions. Due to the difficulty involved in generating an aqueous based dissolved cellulose and having it reacted in subcritical water, dissolved starch was used instead. Better yield of water soluble hydrolysates, especially fermentable sugars, were observed from the hydrolysis of cellulose and dissolved starch in subcritical water than at supercritical conditions. The concluding phase of this project focuses on establishing the mode of scission of cellulose chains in the hydrothermal reactor. This was achieved by using the simulated degradation pattern generated based on different scission modes to fingerprint the degradation pattern obtained from experiment.

Olanrewaju, Kazeem Bode

344

A comparison of the rate equations, kinetic parameters, and activation energies for the initial uptake of l -lysine, l -valine, ?-aminobutyric acid, and ?-aminoisobutyric acid by mouse brain slices  

Microsoft Academic Search

Summary  At substrate concentrations, in medium, of 0.2 to 20mm and at temperatures of 25 and 37°C, the initial concentrative influx of the amino acidsl-lysine (30 and 37°C),l-valine, and -aminobutyric acid into incubated mouse-cerebrum slices follows the rate equation for the initial influx of -aminoisobutyric acid (Cohen,J. Physiol.\\u000a228:105, 1973),v=V\\u000amax\\/(1+K\\u000at\\/S)+k\\u000au\\u000aS. Kinetic constants at 37°C are:V\\u000amax=0.089 moles\\/g

Stephen R. Cohen

1975-01-01

345

Simple kinetic models of petroleum formation. Part I: oil and gas generation from kerogen  

Microsoft Academic Search

Modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks. The global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age; this is useful in areas of low geochemical knowledge, including exploration frontiers. Five kerogen kinetic organofacies, each characterized by a specific organic matter input and early

Andrew S. Pepper; Peter J. Corvi

1995-01-01

346

Kinetics of Bose-Einstein condensation in a dimple potential  

NASA Astrophysics Data System (ADS)

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

Dutta, Shovan; Mueller, Erich J.

2015-01-01

347

Preignition volatile yield as related to coal characteristics. Quarterly report, October-December 1980  

SciTech Connect

The computer model for the study of pulverized fuel processing is being modified to reflect the effect of variations in preignition volatile yields on the burning of coal in a conventional swirl burner. Two important criteria which define the performance of suspension burning of a solid fuel in a swirl burner are: (1) flame stability; and (2) combustion efficiency. Both of these parameters depend strongly on the ratio of kinetic or combustion time scales of the fuel to the residence time available in the vicinity of the recirculation zone of the swirl burner. Enhanced pyrolysis yield at high heating rate may function in three ways in boiler combustion: (1) enhanced mixture ignitability, resulting in a heat release closer to the input structure; (2) enhanced combustion rate, allowing easier overall stabilization of the flame; and (3) ehanced fuel burnout both in the vicinity of the recirculation stabilization region and downstream of it. The existing combustion model, previously developed at AERL, Inc., for general modeling of pulverized fuel processing, is being modified to investigate these effects in a semi-quantitative manner. The flow, mixing and radiative environment of a swirl are simulated, while the combustion history of the fuel is predicted as a function of such fuel-related parameters as size distribution, volatile yield and char reactivity. Ten different coals have been selected and the test reactor has been modified to improve operability and the precision of the results. (LTN)

None

1981-01-01

348

Argentina corn yield model  

NASA Technical Reports Server (NTRS)

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

Callis, S. L.; Sakamoto, C.

1984-01-01

349

Argentina soybean yield model  

NASA Technical Reports Server (NTRS)

A model based on multiple regression was developed to estimate soybean yields for the country of Argentina. A meteorological data set was obtained for the country by averaging data for stations within the soybean growing area. Predictor variables for the model were derived from monthly total precipitation and monthly average temperature. A trend variable was included for the years 1969 to 1978 since an increasing trend in yields due to technology was observed between these years.

Callis, S. L.; Sakamoto, C.

1984-01-01

350

Kinetic model for supercritical water gasification of algae.  

PubMed

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

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

2012-03-01

351

Cellular senescence: ex vivo p53-dependent asymmetric cell kinetics  

PubMed Central

Although senescence is a defining property of euploid mammalian cells, its physiologic basis remains obscure. Previously, cell kinetics properties of normal tissue cells have not been considered in models for senescence. We now provide evidence that senescence is in fact the natural consequence of normal in vivo somatic stem cell kinetics extended in culture. This concept of senescence is based on our discovery that cells engineered to conditionally express the well-recognized tumor suppressor protein and senescence factor, p53, exhibit asymmetric cell kinetics. In vivo, asymmetric cell kinetics are essential for maintenance of somatic stem cells; ex vivo, the same cell kinetics yield senescence as a simple kinetic endpoint. This new “asymmetric cell kinetics model” for senescence suggests novel strategies for the isolation and propagation of somatic tissue stem cells in culture. PMID:12488624

2001-01-01

352

Reaction {pi}N {yields} {pi}{pi}N near threshold  

SciTech Connect

The LAMPF E1179 experiment used the {pi}{sup 0} spectrometer and an array of charged particle range counters to detect and record {pi}{sup +}{pi}{sup 0}, {pi}{sup 0}p, and {pi}{sup +}{pi}{sup 0}p coincidences following the reaction {pi}{sup +}p {yields} {pi}{sup 0}{pi}{sup +}p near threshold. The total cross sections for single pion production were measured at the incident pion kinetic energies 190, 200, 220, 240, and 260 MeV. Absolute normalizations were fixed by measuring {pi}{sup +}p elastic scattering at 260 MeV. A detailed analysis of the {pi}{sup 0} detection efficiency was performed using cosmic ray calibrations and pion single charge exchange measurements with a 30 MeV {pi}{sup {minus}} beam. All published data on {pi}N {yields} {pi}{pi}N, including our results, are simultaneously fitted to yield a common chiral symmetry breaking parameter {xi} ={minus}0.25{plus_minus}0.10. The threshold matrix element {vert_bar}{alpha}{sub 0}({pi}{sup 0}{pi}{sup +}p){vert_bar} determined by linear extrapolation yields the value of the s-wave isospin-2 {pi}{pi} scattering length {alpha}{sub 0}{sup 2}({pi}{pi}) = {minus}0.041{plus_minus}0.003 m{sub {pi}}{sup {minus}1}, within the framework of soft-pion theory.

Frlez, E.

1993-11-01

353

Physisorption kinetics  

NASA Astrophysics Data System (ADS)

A quantum statistical theory of phonon-mediated physisorption has been developed by setting up the initial value problem within nonequilibrium statistical mechanics and calculating the desorption times appropriate for the various experimental procedures, i.e. virgin adsorption, isothermal desorption and flash desorption. We calculate desorption times for various gas-solid systems like helium-constantan, He-LiF, He-graphite, He-Ar, Xe-W, etc. which compare favorably with experiments. We are able to delimit the temperature range over which the Arrhenius-Frenkel parameterization of the desorption time td = t0dexp(Q/kBT) is acceptable. We can correlate isothermal and flash desorption times and suggest the temperature range where differences in these times can be detected. A complete fourth-order calculation enables us to delineate the range of validity of the one-phonon (second-order) theory and of the relaxation time approach to desorption. Desorption via phonon cascades is calculated. Our theory, which is essentially parameter-free, produces prefactors t0d in the whole experimental range of physisorption from 10-7 s to 10-14 s.

Kreuzer, H. J.

1981-03-01

354

Temperature-Dependent Kinetic Model for Nitrogen-Limited Wine Fermentations?  

PubMed Central

A physical and mathematical model for wine fermentation kinetics was adapted to include the influence of temperature, perhaps the most critical factor influencing fermentation kinetics. The model was based on flask-scale white wine fermentations at different temperatures (11 to 35°C) and different initial concentrations of sugar (265 to 300 g/liter) and nitrogen (70 to 350 mg N/liter). The results show that fermentation temperature and inadequate levels of nitrogen will cause stuck or sluggish fermentations. Model parameters representing cell growth rate, sugar utilization rate, and the inactivation rate of cells in the presence of ethanol are highly temperature dependent. All other variables (yield coefficient of cell mass to utilized nitrogen, yield coefficient of ethanol to utilized sugar, Monod constant for nitrogen-limited growth, and Michaelis-Menten-type constant for sugar transport) were determined to vary insignificantly with temperature. The resulting mathematical model accurately predicts the observed wine fermentation kinetics with respect to different temperatures and different initial conditions, including data from fermentations not used for model development. This is the first wine fermentation model that accurately predicts a transition from sluggish to normal to stuck fermentations as temperature increases from 11 to 35°C. Furthermore, this comprehensive model provides insight into combined effects of time, temperature, and ethanol concentration on yeast (Saccharomyces cerevisiae) activity and physiology. PMID:17616615

Coleman, Matthew C.; Fish, Russell; Block, David E.

2007-01-01

355

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

SciTech Connect

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

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

2014-12-15

356

Yield gaps and yield relationships in US soybean production systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

The magnitude of yield gaps (YG) (potential yield – farmer yield) provides some indication of the prospects for increasing crop yield to meet the food demands of future populations. Quantile regression analysis was applied to county soybean [Glycine max (L.) Merrill] yields (1971 – 2011) from Kentuc...

357

Growth kinetics and energetics of a deep-sea hyperthermophilic methanogen under varying  

E-print Network

on defining growth kinetics, cell yields and growth energy demand (GE) across a range of conditionsGrowth kinetics and energetics of a deep-sea hyperthermophilic methanogen under varyingHs, and chlorinities, its growth rates and cell yields co-varied while GE remained uniform at 1.69 ¥ 10-11 J cell-1 s-1

Holden, James F.

358

Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid  

SciTech Connect

The reaction kinetics of the esterification of ethylene glycol with acetic acid in the presence of cation exchange resin has been studied and kinetic models based on empirical and Langmuir approach has been developed. The Langmuir based model involving eight kinetic parameters fits experimental data much better compared to empirical model involving four kinetic parameters. The effect of temperature and catalyst loading on the reaction system has been analyzed. Further, the activation energy and frequency factor of the rate constants for Langmuir based model has been estimated.

Yadav, Vishnu P.; Maity, Sunil K. [Department of Chemical Engineering, Indian Institute of Technology, Hyderabad, Ordnance Factory Estate, Yeddumailiram-502205, Andhra Pradesh (India); Mukherjee, Rudra Palash [Department of Chemical Engineering, National Institute of Technology, Durgapur, Mahatma Gandhi Avenue, Durgapur-713209, West Bengal (India); Bantraj, Kandi [Department of Chemical Engineering, National Institute of Technology, Rourkela-769008, Orissa (India)

2010-10-26

359

Ecosystem Viable Yields  

E-print Network

The World Summit on Sustainable Development (Johannesburg, 2002) encouraged the application of the ecosystem approach by 2010. However, at the same Summit, the signatory States undertook to restore and exploit their stocks at maximum sustainable yield (MSY), a concept and practice without ecosystemic dimension, since MSY is computed species by species, on the basis of a monospecific model. Acknowledging this gap, we propose a definition of "ecosystem viable yields" (EVY) as yields compatible i) with biological viability levels for all time and ii) with an ecosystem dynamics. To the difference of MSY, this notion is not based on equilibrium, but on viability theory, which offers advantages for robustness. For a generic class of multispecies models with harvesting, we provide explicit expressions for the EVY. We apply our approach to the anchovy--hake couple in the Peruvian upwelling ecosystem between the years 1971 and 1981.

De Lara, Michel; Oliveros-Ramos, Ricardo; Tam, Jorge

2011-01-01

360

Super-AGB yields  

NASA Astrophysics Data System (ADS)

We present the first simulations of the full evolution of super-AGB stars through the entire thermally pulsing AGB phase. We analyse their structural and evolutionary properties and determine the first SAGB yields. Owing to their massive oxygen-neon core, SAGB stars suffer weak thermal pulses, have very short interpulse periods and develop very high temperatures at the base of their convective envelope leading to very efficient hot bottom burning. SAGB stars are consequently heavy manufacturers of 4He, 13C and 14N. They are also able to inject significant amounts of 7Li, 17O, 25Mg and 26,27Al in the interstellar medium. The 3DUP mainly affects the CNO yields, especially at low metallicity. This study also reveals that changes in the temperature at the base of the convective envelope have a dramatic impact on the yields and represents another major source of uncertainty.

Siess, Lionel

361

Kinetics of uranium(VI) desorption from contaminated sediments: effect of geochemical conditions and model evaluation.  

PubMed

Stirred-flow cell experiments were performed to investigate the kinetics of uranyl [U(VI)] desorption from a contaminated sedimentcollected from the Hanford 300 Area at the U.S. Department of Energy Hanford Site, Washington. Three influent solutions of variable pH, Ca and carbonate concentrations that affected U(VI) aqueous and surface speciation were used under dynamic flow conditions to evaluate the effect of geochemical conditions on the rate of U(Vl) desorption. The measured rate of U(VI) desorption varied with solution chemical composition that evolved as a result of thermodynamic and kinetic interactions between the solutions and sediment The solution chemical composition that led to a larger disequilibrium between adsorbed U(VI) and equilibrium adsorption state yielded a faster desorption rate. The experimental results were used to evaluate a multirate, surface complexation model (SCM) that has been proposed to describe U(VI) desorption kinetics in the Hanford sedimentthat contained complex adsorbed U(VI) in mass transfer limited domains (Lui et al. Water Resour. Res. 2008, 44, W08413). The model was modified and supplemented by including multirate, ion exchange reactions to describe the geochemical interactions between the solutions and sediment With the same setof model parameters, the modified model reasonably well described the evolution of major ions and the rates of U(VI) desorption under variable geochemical and flow conditions, implying that the multirate SCM is an effective way to describe U(VI) desorption kinetics in subsurface sediments. PMID:19764217

Liu, Chongxuan; Shi, Zhenqing; Zachara, John M

2009-09-01

362

NISt Chemical Kinetics Database  

NSDL National Science Digital Library

The NIST Chemical Kinetics Database includes essentially all reported kinetics results for thermal gas-phase chemical reactions. The database is designed to be searched for kinetics data based on the specific reactants involved, for reactions resulting in specified products, for all the reactions of a particular species, or for various combinations of these.

363

Development of Quantitative FRET Technology for SENP Enzyme Kinetics Determinations and High-Sensitive High-Throughput Screening Assay for Protease Inhibitor Discovery  

E-print Network

to cancers . Kinetic analysis of enzyme-catalyzed reactionsan enzyme is best characterized by the ratio of the kineticand kinetic parameters determination Michaelis–Menten kinetics is one of the simplest and best-known models of enzyme

Liu, Yan

2012-01-01

364

Drying of tomato slices: changes in drying kinetics, mineral contents, antioxidant activity and color parameters Secado de rodajas de tomate: cambios en cinéticos del secado, contenido en minerales, actividad antioxidante y parámetros de color  

Microsoft Academic Search

The sun, oven (50?°C and 70?°C) and microwave oven (210 and 700 W) drying behaviors of tomato slices were investigated. Effects of these drying methods in terms of mineral content, antioxidant activity and color parameters of tomato slices were also studied. “Page, Modified Page and Midilli and Küçük” models exhibited generally high coefficient of determination (R ) values ranging between

D. Arslan; M. M. Özcan

2011-01-01

365

Compartment modeling of dynamic brain PET—The impact of scatter corrections on parameter errors  

SciTech Connect

Purpose: The aim of this study was to investigate the effect of scatter and its correction on kinetic parameters in dynamic brain positron emission tomography (PET) tumor imaging. The 2-tissue compartment model was used, and two different reconstruction methods and two scatter correction (SC) schemes were investigated. Methods: The GATE Monte Carlo (MC) software was used to perform 2 × 15 full PET scan simulations of a voxelized head phantom with inserted tumor regions. The two sets of kinetic parameters of all tissues were chosen to represent the 2-tissue compartment model for the tracer 3?-deoxy-3?-({sup 18}F)fluorothymidine (FLT), and were denoted FLT{sub 1} and FLT{sub 2}. PET data were reconstructed with both 3D filtered back-projection with reprojection (3DRP) and 3D ordered-subset expectation maximization (OSEM). Images including true coincidences with attenuation correction (AC) and true+scattered coincidences with AC and with and without one of two applied SC schemes were reconstructed. Kinetic parameters were estimated by weighted nonlinear least squares fitting of image derived time–activity curves. Calculated parameters were compared to the true input to the MC simulations. Results: The relative parameter biases for scatter-eliminated data were 15%, 16%, 4%, 30%, 9%, and 7% (FLT{sub 1}) and 13%, 6%, 1%, 46%, 12%, and 8% (FLT{sub 2}) for K{sub 1}, k{sub 2}, k{sub 3}, k{sub 4}, V{sub a}, and K{sub i}, respectively. As expected, SC was essential for most parameters since omitting it increased biases by 10 percentage points on average. SC was not found necessary for the estimation of K{sub i} and k{sub 3}, however. There was no significant difference in parameter biases between the two investigated SC schemes or from parameter biases from scatter-eliminated PET data. Furthermore, neither 3DRP nor OSEM yielded the smallest parameter biases consistently although there was a slight favor for 3DRP which produced less biased k{sub 3} and K{sub i} estimates while OSEM resulted in a less biased V{sub a}. The uncertainty in OSEM parameters was about 26% (FLT{sub 1}) and 12% (FLT{sub 2}) larger than for 3DRP although identical postfilters were applied. Conclusions: SC was important for good parameter estimations. Both investigated SC schemes performed equally well on average and properly corrected for the scattered radiation, without introducing further bias. Furthermore, 3DRP was slightly favorable over OSEM in terms of kinetic parameter biases and SDs.

Häggström, Ida, E-mail: ida.haggstrom@radfys.umu.se; Karlsson, Mikael; Larsson, Anne [Department of Radiation Sciences, Umeå University, Umeå 90187 (Sweden); Schmidtlein, C. Ross [Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York 10065 (United States)

2014-11-01

366

Biotechnology of Forest Yield  

Microsoft Academic Search

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

Peter Farnum; Roger Timmis; J. Laurence Kulp

1983-01-01

367

Retorting of oil shale followed by solvent extraction of spent shale: Experiment and kinetic analysis  

SciTech Connect

Samples of El-Lajjun oil shale were thermally decomposed in a laboratory retort system under a slow heating rate (0.07 K/s) up to a maximum temperature of 698--773 K. After decomposition, 0.02 kg of spent shale was extracted by chloroform in a Soxhlet extraction unit for 2 h to investigate the ultimate amount of shale oil that could be produced. The retorting results indicate an increase in the oil yields from 3.24% to 9.77% of oil shale feed with retorting temperature, while the extraction results show a decrease in oil yields from 8.10% to 3.32% of spent shale. The analysis of the data according to the global first-order model for isothermal and nonisothermal conditions shows kinetic parameters close to those reported in literature.

Khraisha, Y.H.

2000-05-01

368

Resolution, Line-Edge Roughness, Sensitivity Tradeoff, and Quantum Yield of High Photo Acid Generator Resists for Extreme Ultraviolet Lithography  

NASA Astrophysics Data System (ADS)

Ultrahigh loadings of photoacid generators (PAGs) in phenolic extreme ultraviolet (EUV) resists have generated the highest known film quantum yields (FQYs). We evaluate the performance of these resists in terms of resolution, line-edge roughness (LER), and sensitivity and collectively evaluate these three parameters (known as RLS) in terms of KLUP and Z-Parameter figures of merit. An analytical model describing the kinetics of photodecomposition was developed to explain the relationship between film quantum yield and PAG concentration. Resists were prepared using a broad range of concentrations of iodonium (DTBPI-PFBS), sulfonium (TPS-PFBS), and non-ionic (NDI-PFBS) PAGs. The model fits the experimental data (correlation coefficient R2 = 0.998, 0.994, and 0.995) and compares the rate at which electrons react with PAGs or recombine with holes. Resists prepared with 15-20 wt % of iodonium nonaflate PAG exhibit both high quantum yields and the best RLS performance as determined using both KLUP and Z-Parameter methodologies. The improvement in RLS performance correlates with the increase in FQY at higher PAG concentrations.

Higgins, Craig D.; Szmanda, Charles R.; Antohe, Alin; Denbeaux, Greg; Georger, Jacque; Brainard, Robert L.

2011-03-01

369

A kinetic-based approach to understanding heterologous mevalonate pathway function in E. coli.  

PubMed

To aid in debugging efforts to increase yield, titer, and productivity of engineered metabolic pathways, computational models are increasingly needed to predict how changes in experimentally manipulable variables such as enzyme expression map to changes in pathway flux. Here, an ordinary differential equation model is developed for a heterologous mevalonate pathway in E. coli using kinetic parameters culled from literature and enzyme concentrations derived from Selective Reaction Monitoring Mass Spectrometry (SRM-MS). To identify parameters most important to further experimental investigation, a global sensitivity analysis was performed, which pointed to amorphadiene synthase activity as the main limiting factor for amorphadiene production. Furthermore, the model predicted that in this local enzyme expression regime, the overall pathway flux is insensitive to farnesyl pyrophosphate (FPP)-mediated inhibition of mevalonate kinase, not supporting a hypothesis that had previously been posited to be limiting amorphadiene production. To test these predictions experimentally, two strains were constructed: (1) a strain containing a homologous mevalonate kinase with weaker feedback inhibition, and (2) a strain with greater amorphadiene synthase expression. The experimental results validate the qualitative model hypotheses and accurately match the predicted productivities for the two strains, particularly when an in vivo-derived kcat for amorphadiene synthase was substituted for the literature value. These results demonstrate the utility of using kinetic representations of engineered metabolic pathways parameterized with experimentally derived protein concentrations and enzyme kinetic constants to predict productivities and test hypotheses about engineering strategies. PMID:24981116

Weaver, Lane J; Sousa, Mirta M L; Wang, George; Baidoo, Edward; Petzold, Christopher J; Keasling, Jay D

2015-01-01

370

Combustion kinetics and reaction pathways  

SciTech Connect

This project is focused on the fundamental chemistry of combustion. The overall objectives are to determine rate constants for elementary reactions and to elucidate the pathways of multichannel reactions. A multitechnique approach that features three independent experiments provides unique capabilities in performing reliable kinetic measurements over an exceptionally wide range in temperature, 300 to 2500 K. Recent kinetic work has focused on experimental studies and theoretical calculations of the methane dissociation system (CH{sub 4} + Ar {yields} CH{sub 3} + H + Ar and H + CH{sub 4} {yields} CH{sub 3} + H{sub 2}). Additionally, a discharge flow-photoionization mass spectrometer (DF-PIMS) experiment is used to determine branching fractions for multichannel reactions and to measure ionization thresholds of free radicals. Thus, these photoionization experiments generate data that are relevant to both reaction pathways studies (reaction dynamics) and fundamental thermochemical research. Two distinct advantages of performing PIMS with high intensity, tunable vacuum ultraviolet light at the National Synchrotron Light Source are high detection sensitivity and exceptional selectivity in monitoring radical species.

Klemm, R.B.; Sutherland, J.W. [Brookhaven National Laboratory, Upton, NY (United States)

1993-12-01

371

Continuous growth kinetics of Candida utilis in pineapple cannery effluent  

SciTech Connect

Candida utilis was grown on a pineapple cannery effluent as the sole carbon and energy source in a chemostat at dilution rates between 0.10 and 0.62 h/sup -1/ to determine the growth kinetics. The principal sugars in the effluent were sucrose, glucose, and fructose. The cell yield coefficient on carbohydrate varied with dilution rate and a maximum value of 0.63 was observed at a dilution rate of 0.33 h/sup -1/. The steady-state concentrations of carbohydrate, reducing sugar, and chemical oxygen demand (COD) appeared to follow Monod saturation kinetics with increasing dilution rate, although none of the measured parameters represented a pure substrate. The maximum specific growth rate and reducing sugar saturation constant were 0.64 h/sup -1/ and 0.060 g/L, respectively. A maximum cell mass productivity of 2.3 g/L h was observed at a dilution rate of 0.51 h/sup -1/. At this dilution rate, only 68% of the COD was removed. A 95% COD removal was attained at a dilution rate of 0.10 h/sup -1/. Optimal yeast productivity and COD reduction occurred at a dilution rate of 0.33 h/sup -1/.

Prior, B.A.

1984-01-01

372

On fast reactor kinetics studies  

SciTech Connect

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

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

2012-07-01

373

Kinetic studies and model development for the formation of galacto-oligosaccharides from lactose using synthesized thermo-responsive bioconjugate.  

PubMed

In an earlier study by us [47], thermo-responsive bioconjugate (poly-N-isopropylacrylamide-?-galactosidase) was synthesized and characterized. This study utilizes the prowess of such smart bioconjugate for the enzymatic synthesis of galacto-oligosaccharides (GOS) from lactose at various initial lactose concentrations (ILC), enzyme concentrations, and temperatures, while maintaining a constant pH of 6. A maximum GOS yield of 35% (on dry basis) was observed at 100g/L ILC and 0.275mg/mL (0.055U/mL) conjugated protein. The GOS yield remained approximately the same for 50 and 100g/L ILC, beyond which, it decreased. As the enzyme concentration increased, the equilibrium formation of GOS increased and eventually attained a plateau when the concentration of conjugated protein exceeded 0.275mg/mL (0.055U/mL). GOS yield increased on raising the temperature from 30 to 40°C, and declined thereafter. The apparent kinetic parameters were estimated from a five-step, nine-parameter kinetic model, which was then simulated using the COPASI package. The simulated results demonstrated an excellent match with the experimental data. PMID:25659631

Palai, Tapas; Kumar, Ashok; Bhattacharya, Prashant K

2015-03-01

374

Influence of the experimental parameters on the TPR profiles  

Microsoft Academic Search

Some corrections are introduced into relations used both to compute TPR curves and to determine kinetic parameters. New experimental parameters which have an influence on the TPR curve profiles are described.

G. Munteanu; M. Craiu

1993-01-01

375

Yielding elastic tethers stabilize robust cell adhesion.  

PubMed

Many bacteria and eukaryotic cells express adhesive proteins at the end of tethers that elongate reversibly at constant or near constant force, which we refer to as yielding elasticity. Here we address the function of yielding elastic adhesive tethers with Escherichia coli bacteria as a model for cell adhesion, using a combination of experiments and simulations. The adhesive bond kinetics and tether elasticity was modeled in the simulations with realistic biophysical models that were fit to new and previously published single molecule force spectroscopy data. The simulations were validated by comparison to experiments measuring the adhesive behavior of E. coli in flowing fluid. Analysis of the simulations demonstrated that yielding elasticity is required for the bacteria to remain bound in high and variable flow conditions, because it allows the force to be distributed evenly between multiple bonds. In contrast, strain-hardening and linear elastic tethers concentrate force on the most vulnerable bonds, which leads to failure of the entire adhesive contact. Load distribution is especially important to noncovalent receptor-ligand bonds, because they become exponentially shorter lived at higher force above a critical force, even if they form catch bonds. The advantage of yielding is likely to extend to any blood cells or pathogens adhering in flow, or to any situation where bonds are stretched unequally due to surface roughness, unequal native bond lengths, or conditions that act to unzip the bonds. PMID:25473833

Whitfield, Matt J; Luo, Jonathon P; Thomas, Wendy E

2014-12-01

376

Yielding Elastic Tethers Stabilize Robust Cell Adhesion  

PubMed Central

Many bacteria and eukaryotic cells express adhesive proteins at the end of tethers that elongate reversibly at constant or near constant force, which we refer to as yielding elasticity. Here we address the function of yielding elastic adhesive tethers with Escherichia coli bacteria as a model for cell adhesion, using a combination of experiments and simulations. The adhesive bond kinetics and tether elasticity was modeled in the simulations with realistic biophysical models that were fit to new and previously published single molecule force spectroscopy data. The simulations were validated by comparison to experiments measuring the adhesive behavior of E. coli in flowing fluid. Analysis of the simulations demonstrated that yielding elasticity is required for the bacteria to remain bound in high and variable flow conditions, because it allows the force to be distributed evenly between multiple bonds. In contrast, strain-hardening and linear elastic tethers concentrate force on the most vulnerable bonds, which leads to failure of the entire adhesive contact. Load distribution is especially important to noncovalent receptor-ligand bonds, because they become exponentially shorter lived at higher force above a critical force, even if they form catch bonds. The advantage of yielding is likely to extend to any blood cells or pathogens adhering in flow, or to any situation where bonds are stretched unequally due to surface roughness, unequal native bond lengths, or conditions that act to unzip the bonds. PMID:25473833

Whitfield, Matt J.; Luo, Jonathon P.; Thomas, Wendy E.

2014-01-01

377

Atmospheric Fluorescence Yield  

NASA Technical Reports Server (NTRS)

Several existing and planned experiments estimate the energies of ultra-high energy cosmic rays from air showers using the atmospheric fluorescence from these showers. Accurate knowledge of the conversion from atmospheric fluorescence to energy loss by ionizing particles in the atmosphere is key to this technique. In this paper we discuss a small balloon-borne instrument to make the first in situ measurements versus altitude of the atmospheric fluorescence yield. The instrument can also be used in the lab to investigate the dependence of the fluorescence yield in air on temperature, pressure and the concentrations of other gases that present in the atmosphere. The results can be used to explore environmental effects on and improve the accuracy of cosmic ray energy measurements for existing ground-based experiments and future space-based experiments.

Adams, James H., Jr.; Christl, M. J.; Fountain, W. F.; Gregory, J. C.; Martens, K.; Sokolsky, P.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

378

Mechanisms and kinetics of coal hydrogenation  

SciTech Connect

Colorado School of Mines is engaged in an experimental program to develop comprehensive models for the effects of coal composition upon the kinetics and mechanisms of coal hydrogenation, for the effects of mineral matter additives (disposable catalysts) upon kinetics and mechanisms of coal hydrogenation, and for the kinetics and mechanisms of the hydrogenation of coal derived products such as preasphaltenes, and asphaltenes. Experimental work was completed on a suite of bituminous coals, thus completing the initial phase of the coal reactivity study. Eleven of the 14 coals of the suite were successfully run in duplicate. Conversion to THF solubles was correlated well by pseudo-second order kinetics. The resulting kinetic rate constants correlated with H/C ratio, mean-max vitrinite reflectance, and a specially-defined fraction of reactive macerals. The data did not correlate well with O/C ratios of the parent coals. Computer-derived statistical fits of various kinetic models were limited in their effectiveness at fitting the experimental data. Experimental work on the first phase of the disposal catalyst studies was completed. Statistical significance testing of the experimental data showed: fractional conversion and yield of light hydrocarbon products increased with time; and mineral properties of the additives were more significant in increasing overall conversion than the additive surface areas. The relative effects of the additives are given.

Baldwin, R M; Furlong, M W

1981-05-01

379

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

SciTech Connect

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

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

1994-11-01

380

UNCONVENTIONAL METHODS FOR YIELD IMPROVEMENT  

E-print Network

/average casting weight (yield decreases with its increase). VARIABLES IMPACTING YIELD IN STEEL CASTING of Iowa researchers are conducting a casting yield survey to deter- mine the average metal yield in steel techniques for decreasing the size and number of risers re- quired to produce quality castings

Beckermann, Christoph

381

Some Formal Approaches to the Analysis of Kinetic Data in Terms of Linear Compartmental Systems  

PubMed Central

A formal approach to the routine analysis of kinetic data in terms of linear compartmental systems is presented. The methods of analysis are general in that they include much of the theory in common use, such as direct solution of differential equations, integral equations, transfer functions, fitting of data to sums of exponentials, matrix solutions, etc. The key to the formalism presented lies in the fact that a basic operational unit—called “compartment”—has been defined, in terms of which physical and mathematical models as well as input and output functions can be expressed. Additional features for calculating linear combinations of functions and for setting linear dependence relations between parameters add to the versatility of this method. The actual computations for the values of model parameters to yield a least squares fit of the data are performed on a digital computer. A general computer program was developed that permits the routine fitting of data and the evolution of models. PMID:13867976

Berman, Mones; Shahn, Ezra; Weiss, Marjory F.

1962-01-01

382

Inactivation Kinetics of Yeast Cells during Infrared Drying  

Microsoft Academic Search

In this study, aqueous yeast suspensions were used to investigate the effects of drying (in an infrared heating environment) on the survival of yeast. The processes were modeled mathematically using a range of kinetics rate equations. The model parameters for each kinetic rate expression were obtained using a Matlab optimization procedure and the more suitable models describing the inactivation processes

Hui Huang; Marianne Su-Ling Brooks; Hua-Jiang Huang; Xiao Dong Chen

2009-01-01

383

Detailed chemical kinetic mechanisms for combustion of oxygenated fuels  

Microsoft Academic Search

Thermodynamic properties and detailed chemical kinetic models have been developed for the combustion of two oxygenates: methyl butanoate, a model compound for biodiesel fuels, and methyl formate, a related simpler molecule. Bond additivity methods and rules for estimating kinetic parameters were adopted from hydrocarbon combustion and extended. The resulting mechanisms have been tested against the limited combustion data available in

E. M. Fisher; W. J. Pitz; H. J. Curran; C. K. Westbrook

2000-01-01

384

GAS–LIQUID REACTION KINETICS: A REVIEW OF DETERMINATION METHODS  

Microsoft Academic Search

The aim of this article is to provide comprehensive insight into the determination and interpretation of reaction kinetics of two-phase (gas–liquid) systems. Various aspects of the methodologies used for the measurements of kinetic parameters (such as equipment design, corresponding theoretical background, main steps, advantages, and limitations) are discussed in detail. In addition, an illustrating example is provided based on an

Prakash D. Vaidya; Eugeny Y. Kenig

2007-01-01

385

Comparative pyrolysis and combustion kinetics of oil shales  

Microsoft Academic Search

In this research, thermal characteristics and kinetic parameters of eight Turkish oil shale samples were determined by thermogravimetry (TG\\/DTG) at non-isothermal heating conditions both for pyrolysis and combustion processes. A general computer program was developed and the methods are compared with regard to their accuracy and the ease of interpretation of the kinetics of thermal decomposition. Activation energies of the

Mustafa Versan Kök; M. Reha Pamir

2000-01-01

386

Kinetics of boehmite precipitation from supersaturated sodium aluminate solutions  

Microsoft Academic Search

This work presents the effect of the most important parameters, the precipitation temperature, the sodium hydroxide concentration and the initial seed ratio (SR) in the solution, on the boehmite precipitation from supersaturated sodium aluminate solutions. A kinetic model that describes the experimental data was developed. According to that model, boehmite precipitation follows second order reaction kinetics and has activation energy

C. Skoufadis; D. Panias; I. Paspaliaris

2003-01-01

387

Kinetic Investigations by Techniques of Thermal Analysis  

Microsoft Academic Search

Thermoanalytical techniques offer attractive ways of determining kinetic parameters. There are obvious convenience and economy in making a single set of measurements in a few hours and performing extensive computations while the equipment is generating data on another material. This apparent gain in efficiency has led to considerable effort in planning computations which lead to easy extraction of the activation

P. D. Garn; S. F. Hulber

1972-01-01

388

Parametric and Kinetic Minimum Spanning Trees  

Microsoft Academic Search

We consider the parametric minimum spanning tree problem, in which we are given a graph with edge weights that are linear functions of a parameter‚ and wish to com- pute the sequence of minimum spanning trees generated as‚ varies. We also consider the kinetic minimum spanning tree problem, in which‚ represents time and the graph is subject in addition to

Pankaj K. Agarwal; David Eppstein; Leonidas J. Guibas; Monika Rauch Henzinger

1998-01-01

389

Kinetic model for designing a cancer therapy  

Microsoft Academic Search

A kinetic model has been developed to study cancer growth. Cancer growth has been considered as interaction between various independent but interacting compartments. The model considers cell growth and metastasis resulting in the formation of new tumor masses. Using certain representative parameter values, cell growth has been modeled in the absence and the presence of various cancer therapies. Based on

Siddhartha Jain

2002-01-01

390

Evaluated Kinetic Data for Combustion Modelling  

Microsoft Academic Search

This compilation contains critically evaluated kinetic data on elementary homogeneous gas phase chemical reactions for use in modelling combustion processes. Data sheets are presented for some 196 reactions. Each data sheet sets out relevant thermodynamic data, rate coefficient measurements, an assessment of the reliability of the data, references, and recommended rate parameters. Tables summarizing the preferred rate data are also

D. L. Baulch; C. J. Cobos; R. A. Cox; C. Esser; P. Frank; Th. Just; J. A. Kerr; M. J. Pilling; J. Troe; R. W. Walker; J. Warnatz

1992-01-01

391

Kinetics of hexamine crystallization in industrial scale  

Microsoft Academic Search

The values of kinetic parameters for hexamine crystallization from aqueous solution, necessary for control of industrial crystallizers were calculated in this study. Hexamine is an intermediate chemical mainly used in pharmaceutical and resin industries. In Meissner process, the major industrial method of hexamine production, formaldehyde and ammonia in gaseous states are introduced into the reaction vessel, and crystalline hexamine is

A. Alamdari; F. Tabkhi

2004-01-01

392

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

PubMed Central

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

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

2014-01-01

393

Accurate argon cluster-ion sputter yields: Measured yields and effect of the sputter threshold in practical depth-profiling by x-ray photoelectron spectroscopy and secondary ion mass spectrometry  

SciTech Connect

Argon Gas Cluster-Ion Beam sources are likely to become widely used on x-ray photoelectron spectroscopy and secondary ion mass spectrometry instruments in the next few years. At typical energies used for sputter depth profiling the average argon atom in the cluster has a kinetic energy comparable with the sputter threshold, meaning that for the first time in practical surface analysis a quantitative model of sputter yields near threshold is needed. We develop a simple equation based on a very simple model. Though greatly simplified it is likely to have realistic limiting behaviour and can be made useful for estimating sputter yields by fitting its three parameters to experimental data. We measure argon cluster-ion sputter yield using a quartz crystal microbalance close to the sputter threshold, for silicon dioxide, poly(methyl methacrylate), and polystyrene and (along with data for gold from the existing literature) perform least-squares fits of our new sputter yield equation to this data. The equation performs well, with smaller residuals than for earlier empirical models, but more importantly it is very easy to use in the design and quantification of sputter depth-profiling experiments.

Cumpson, Peter J.; Portoles, Jose F.; Barlow, Anders J.; Sano, Naoko [National EPSRC XPS User's Service (NEXUS), School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom)] [National EPSRC XPS User's Service (NEXUS), School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom)

2013-09-28

394

Accurate argon cluster-ion sputter yields: Measured yields and effect of the sputter threshold in practical depth-profiling by x-ray photoelectron spectroscopy and secondary ion mass spectrometry  

NASA Astrophysics Data System (ADS)

Argon Gas Cluster-Ion Beam sources are likely to become widely used on x-ray photoelectron spectroscopy and secondary ion mass spectrometry instruments in the next few years. At typical energies used for sputter depth profiling the average argon atom in the cluster has a kinetic energy comparable with the sputter threshold, meaning that for the first time in practical surface analysis a quantitative model of sputter yields near threshold is needed. We develop a simple equation based on a very simple model. Though greatly simplified it is likely to have realistic limiting behaviour and can be made useful for estimating sputter yields by fitting its three parameters to experimental data. We measure argon cluster-ion sputter yield using a quartz crystal microbalance close to the sputter threshold, for silicon dioxide, poly(methyl methacrylate), and polystyrene and (along with data for gold from the existing literature) perform least-squares fits of our new sputter yield equation to this data. The equation performs well, with smaller residuals than for earlier empirical models, but more importantly it is very easy to use in the design and quantification of sputter depth-profiling experiments.

Cumpson, Peter J.; Portoles, Jose F.; Barlow, Anders J.; Sano, Naoko

2013-09-01

395

Maximum yield of foreign lipase in Escherichia coli HB101 limited by duration of protein expression  

Microsoft Academic Search

When a microbial lipase was overexpressed in Escherichia coli HB101, the expression kinetics as represented by the expression rate, duration, and maximum yield of lipase were studied. Lipase synthesis, controlled by the tac promoter, continued for about 4h after IPTG induction. The duration of the expression phase was similar, irrespective of expression rate and yield, which were manipulated by using

Dae Hyun Hahm; Soo Hyoung Kim; Jaegu Pan; Joon Shick Rhee

1995-01-01

396

Dimension scaling effects on the yield sensitivity of HEMT digital circuits  

NASA Technical Reports Server (NTRS)

In our previous works, using a graphical tool, yield factor histograms, we studied the yield sensitivity of High Electron Mobility Transistors (HEMT) and HEMT circuit performance with the variation of process parameters. This work studies the scaling effects of process parameters on yield sensitivity of HEMT digital circuits. The results from two HEMT circuits are presented.

Sarker, Jogendra C.; Purviance, John E.

1992-01-01

397

Oxidation kinetics of aluminum diboride  

SciTech Connect

The oxidation characteristics of aluminum diboride (AlB{sub 2}) and a physical mixture of its constituent elements (Al+2B) were studied in dry air and pure oxygen using thermal gravimetric analysis to obtain non-mechanistic kinetic parameters. Heating in air at a constant linear heating rate of 10 °C/min showed a marked difference between Al+2B and AlB{sub 2} in the onset of oxidation and final conversion fraction, with AlB{sub 2} beginning to oxidize at higher temperatures but reaching nearly complete conversion by 1500 °C. Kinetic parameters were obtained in both air and oxygen using a model-free isothermal method at temperatures between 500 and 1000 °C. Activation energies were found to decrease, in general, with increasing conversion for AlB{sub 2} and Al+2B in both air and oxygen. AlB{sub 2} exhibited O{sub 2}-pressure-independent oxidation behavior at low conversions, while the activation energies of Al+2B were higher in O{sub 2} than in air. Differences in the composition and morphology between oxidized Al+2B and AlB{sub 2} suggested that Al{sub 2}O{sub 3}–B{sub 2}O{sub 3} interactions slowed Al+2B oxidation by converting Al{sub 2}O{sub 3} on aluminum particles into a Al{sub 4}B{sub 2}O{sub 9} shell, while the same Al{sub 4}B{sub 2}O{sub 9} developed a needle-like morphology in AlB{sub 2} that reduced oxygen diffusion distances and increased conversion. The model-free kinetic analysis was critical for interpreting the complex, multistep oxidation behavior for which a single mechanism could not be assigned. At low temperatures, moisture increased the oxidation rate of Al+2B and AlB{sub 2}, but both appear to be resistant to oxidation in cool, dry environments. - Graphical abstract: Isothermal kinetic data for AlB{sub 2} in air, showing a constantly decreasing activation energy with increasing conversion. Model-free analysis allowed for the calculation of global kinetic parameters despite many simultaneous mechanisms occurring concurrently. (a) Time–temperature plots, (b) conversion as a function of time, (c) Arrhenius plots used to calculate activation energies, and (d) activation energy as a function of conversion. Display Omitted - Highlights: • First reported kinetic parameters for AlB{sub 2} and Al+2B oxidation in air and O{sub 2}. • Possible mechanism of enhanced boron combustion presented. • Moisture sensitivity shown to be problematic for AlB{sub 2}, less for Al+2B.

Whittaker, Michael L., E-mail: michaelwhittaker2016@u.northwestern.edu [Department of Materials Science and Engineering, University of Utah, 122S. Central Campus Drive, Salt Lake City, UT 84112 (United States); Sohn, H.Y. [Department of Metallurgical Engineering, University of Utah, 135S 1460 E, Rm 00412, Salt Lake City, UT 84112 (United States); Cutler, Raymond A. [Ceramatec, Inc., 2425S. 900W., Salt Lake City, UT 84119 (United States)

2013-11-15

398

Timescales in creep and yielding of attractive gels.  

PubMed

The stress-induced yielding scenario of colloidal gels is investigated under rough boundary conditions by means of rheometry coupled with local velocity measurements. Under an applied shear stress ?, the fluidization of gels made of attractive carbon black particles dispersed in a mineral oil is shown to involve a previously unreported shear rate response ? dot above(t) characterized by two well-defined and separated timescales ?c and ?f. First ? dot above decreases as a weak power law strongly reminiscent of the primary creep observed in numerous crystalline and amorphous solids, coined the "Andrade creep". We show that the bulk deformation remains homogeneous at the micron scale, which demonstrates that whether plastic events take place or whether any shear transformation zone exists, such phenomena occur at a smaller scale. As a key result of this paper, the duration ?c of this creep regime decreases as a power law of the viscous stress, defined as the difference between the applied stress and the yield stress ?c, i.e. ?c ? (? - ?c)(-?), with ? = 2-3 depending on the gel concentration. The end of this first regime is marked by a jump of the shear rate by several orders of magnitude, while the gel slowly slides as a solid block experiencing strong wall slip at both walls, despite rough boundary conditions. Finally, a second sudden increase of the shear rate is concomitant with the full fluidization of the material which ends up being homogeneously sheared. The corresponding fluidization time ?f robustly follows an exponential decay with the applied shear stress, i.e. ?f = ?0?exp(-?/?0), as already reported for smooth boundary conditions. Varying the gel concentration C in a systematic fashion shows that the parameter ?0 and the yield stress ?c exhibit similar power-law dependences with C. Finally, we highlight a few features that are common to attractive colloidal gels and to solid materials by discussing our results in the framework of theoretical approaches of solid rupture (kinetic, fiber bundle, and transient network models). PMID:24651869

Grenard, Vincent; Divoux, Thibaut; Taberlet, Nicolas; Manneville, Sébastien

2014-03-14

399

Kinetics of chlorination of metallic sodium at low temperatures  

Microsoft Academic Search

Using ultra-high vacuum methods and a photometric technique, the kinetics of the chlorination of vacuum-deposited sodium films have been determined in the temperature range 228–298° K. The functional form of the kinetics is shown to be in accord with the Mott-Cabrera model applied to film growth by cation vacancy migration. Fitting the experimental data to this model yields a value

W. Y. Shiu; D. J. Young; M. J. Dignam

1973-01-01

400

Thermodynamic and kinetic analyses for understanding sequence-specific DNA recognition  

Microsoft Academic Search

Thermodynamic and kinetic analyses of biomolecular interactions reveal details of the energetic and dynamic features of molecular recognition processes, and complement structural analyses of the free and complexed conformations. The recent improvements in both isothermal titration calorimetry and surface plasmon resonance sensoring provide powerful tools for analysing biomolecular interactions in thermodynamic and kinetic approaches. The thermodynamic and kinetic parameters obtained

Masayuki Oda; Haruki Nakamura

2000-01-01

401

Kinetic and Structural Analysis of -D-Glucose-1-phosphate Cytidylyltransferase from Salmonella typhi*S  

E-print Network

. The kinetic and x-ray crystallographic data presented here support a mech- anism for this enzyme reports es- tablished the kinetic parameters of the enzyme and were in general agreement despiteKinetic and Structural Analysis of -D-Glucose-1-phosphate Cytidylyltransferase from Salmonella

Holden, Hazel

402

Temperature-rate profiles by polarimetric variable-temperature kinetic experiments to study racemization reactions  

Microsoft Academic Search

The racemization of (?)-adrenaline was followed by polarimetric variable-temperature kinetic experiments obtaining activation parameters and kobs(T) profile in one tenth of the time usually spent for traditional kinetic runs. A polarimeter connected to a computer for the acquisition and processing of the analytical data was used. The kinetic profiles were processed by both an integral method and a differential method.

Giuseppe Alibrandi; Salvatore Coppolino; Santi D'Aliberti; Paola Ficarra; Norberto Micali; Antonino Villari

2002-01-01

403

Medicinal Chemistry and Enzyme Kinetics  

E-print Network

Medicinal Chemistry and Enzyme Kinetics Elizabeth Amin and C. R. Wagner, Medicinal Chemistry Jiali Stankovich, Jiali Gao, and Donald G. Truhlar, University of Minnesota February 2007 Enzyme Kinetics Kinetic isotope effects Variational transition state theory Multidimensional tunneling Ensemble averaging

Truhlar, Donald G

404

Yield inception of a soft coating on a flat substrate indented by a rigid sphere  

E-print Network

Yield inception of a soft coating on a flat substrate indented by a rigid sphere Wenping Song a indentation Soft coating Yield inception The yield inception of a deformable half space covered by a soft parameter, which controls the yield behavior of this problem, is defined. Dimensionless empirical

Fainman, Yeshaiahu

405

Secondary electron yield of Cu technical surfaces: Dependence on electron irradiation  

NASA Astrophysics Data System (ADS)

The secondary emission yield (SEY) properties of colaminated Cu samples for LHC beam screens are correlated to the surface chemical composition determined by x-ray photoelectron spectroscopy. The surface of the as-received samples is characterized by the presence of significant quantities of contaminating adsorbates and by the maximum of the SEY curve (?max?) being as high as 2.1. After extended electron scrubbing at kinetic energy of 10 and 500 eV, the ?max? value drops to the ultimate values of 1.35 and 1.1, respectively. In both cases the surface oxidized phases are significantly reduced, whereas only in the sample scrubbed at 500 eV the formation of a graphitic-like C layer is observed. We find that the electron scrubbing of technical Cu surfaces can be described as occurring in two steps: the first step consists in the electron-induced desorption of weakly bound contaminants that occurs indifferently at 10 and at 500 eV and corresponds to a partial decrease of ?max?; the second step, activated by more energetic electrons and becoming evident at high doses, increases the number of graphitic-like C-C bonds via the dissociation of adsorbates already contaminating the as-received surface or accumulating on this surface during irradiation. Our results demonstrate how the kinetic energy of impinging electrons is a crucial parameter when conditioning the surfaces of Cu and other metals by means of electron-induced chemical processing.

Larciprete, R.; Grosso, D. R.; Commisso, M.; Flammini, R.; Cimino, R.

2013-01-01

406

Substrate Recognition of Anthrax Lethal Factor Examined by Combinatorial and Pre-steady-state Kinetic Approaches*  

PubMed Central

Lethal factor (LF), a zinc-dependent protease of high specificity produced by Bacillus anthracis, is the effector component of the binary toxin that causes death in anthrax. New therapeutics targeting the toxin are required to reduce systemic anthrax-related fatalities. In particular, new insights into the LF catalytic mechanism will be useful for the development of LF inhibitors. We evaluated the minimal length required for formation of bona fide LF substrates using substrate phage display. Phage-based selection yielded a substrate that is cleaved seven times more efficiently by LF than the peptide targeted in the protein kinase MKK6. Site-directed mutagenesis within the metal-binding site in the LF active center and within phage-selected substrates revealed a complex pattern of LF-substrate interactions. The elementary steps of LF-mediated proteolysis were resolved by the stopped-flow technique. Pre-steady-state kinetics of LF proteolysis followed a four-step mechanism as follows: initial substrate binding, rearrangement of the enzyme-substrate complex, a rate-limiting cleavage step, and product release. Examination of LF interactions with metal ions revealed an unexpected activation of the protease by Ca2+ and Mn2+. Based on the available structural and kinetic data, we propose a model for LF-substrate interaction. Resolution of the kinetic and structural parameters governing LF activity may be exploited to design new LF inhibitors. PMID:19359249

Zakharova, Maria Yu.; Kuznetsov, Nikita A.; Dubiley, Svetlana A.; Kozyr, Arina V.; Fedorova, Olga S.; Chudakov, Dmitry M.; Knorre, Dmitry G.; Shemyakin, Igor G.; Gabibov, Alexander G.; Kolesnikov, Alexander V.

2009-01-01

407

Fully kinetic simulations of megajoule-scale dense plasma focus  

SciTech Connect

Dense plasma focus (DPF) Z-pinch devices are sources of copious high energy electrons and ions, x-rays, and neutrons. Megajoule-scale DPFs can generate 10{sup 12} neutrons per pulse in deuterium gas through a combination of thermonuclear and beam-target fusion. However, the details of the neutron production are not fully understood and past optimization efforts of these devices have been largely empirical. Previously, we reported on the first fully kinetic simulations of a kilojoule-scale DPF and demonstrated that both kinetic ions and kinetic electrons are needed to reproduce experimentally observed features, such as charged-particle beam formation and anomalous resistivity. Here, we present the first fully kinetic simulation of a MegaJoule DPF, with predicted ion and neutron spectra, neutron anisotropy, neutron spot size, and time history of neutron production. The total yield predicted by the simulation is in agreement with measured values, validating the kinetic model in a second energy regime.

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

2014-10-15

408

Kinetic analysis of nitroxide radical formation under oxygenated photolysis: toward quantitative singlet oxygen topology.  

PubMed

Reaction kinetics for two sterically hindered secondary amines with singlet oxygen have been studied in detail. A water soluble porphyrin sensitizer, 5,10,15,20-tetrakis-(4-sulfunatophenyl)-21,23H-porphyrin (TPPS), was irradiated in oxygenated aqueous solutions containing either 2,2,6,6-tetramethylpiperidin-4-one (TMPD) or 4-[N,N,N-trimethyl-ammonium]-2,2,6,6-tetramethylpiperidinyl chloride (N-TMPCl). The resulting sensitization reaction produced singlet oxygen in high yield, ultimately leading to the formation of the corresponding nitroxide free radicals (R2NO) which were detected using steady-state electron paramagnetic resonance (EPR) spectroscopy. Careful actinometry and EPR calibration curves, coupled with a detailed kinetic analysis, led to a simple and compact expression relating the nitroxide quantum yield ?R2NO (from the doubly-integrated EPR signal intensity) to the initial amine concentration [R2NH]i. With all other parameters held constant, a plot of ?R2NOvs. [R2NH]i gave a straight line with a slope proportional to the rate constant for nitroxide formation, kR2NO. This establishment of a rigorous quantitative relationship between the EPR signal and the rate constant provides a mechanism for quantifying singlet oxygen production as a function of its topology in heterogeneous media. Implications for in vivo assessment of singlet oxygen topology are briefly discussed. PMID:25369860

Zigler, David F; Ding, Eva Chuheng; Jarocha, Lauren E; Khatmullin, Renat R; DiPasquale, Vanessa M; Sykes, R Brendan; Tarasov, Valery F; Forbes, Malcolm D E

2014-12-01

409

Optimization and kinetic studies on algal oil extraction from marine macroalgae Ulva lactuca.  

PubMed

In this present investigation, kinetic studies on oil extraction were performed in marine macroalgae Ulva lactuca. The algal biomass was characterized by scanning electron microscopy and Fourier Transform-Infra Red Spectroscopy. Six different pre-treatment methods were carried out to evaluate the best method for maximum oil extraction. Optimization of extraction parameters were performed and high oil yield was obtained at 5% moisture content, 0.12 mm particle size, 500 rpm stirrer speed, 55°C temperature, 140 min time and solvent-to-solid ratio as 6:1 with 1% diethyl-ether and 10% methylene chloride in n-hexane solvent mixture. After optimization, 10.88% (g/g) of oil extraction yield was achieved from 30 g of algal biomass. The rate constant was obtained for the first order kinetic study by differential method. The activation energy (Ea) was calculated as 63.031 kJ/mol. From the results obtained in the investigation, U. lactuca biomass was proved to be a suitable source for the biodiesel production. PMID:22209436

Suganya, Tamilarasan; Renganathan, Sahadevan

2012-03-01

410

A cellular automata model of enzyme kinetics.  

PubMed

We have developed a cellular automata model of an enzyme reaction with a substrate in water. The model produces Michaelis-Menten kinetics with good Lineweaver-Burk plots. The variation in affinity parameters predicts that, in general, hydrophobic substrates are more reactive with enzymes, this attribute being more important than the relationship between enzyme and substrate. The ease of generation and the illustrative value of the model lead us to believe that cellular automata models have a useful role in the study of dynamic phenomena such as enzyme kinetics. PMID:9076636

Kier, L B; Cheng, C K; Testa, B; Carrupt, P A

1996-08-01

411

Nonergodic activated kinetics in polar media  

SciTech Connect

A theoretical formulation is developed for the activated kinetics when some subset of nuclear modes of the thermal bath is slower than the reaction and ergodicity of the thermal bath is not maintained. Nonergodic free energy profiles along the reaction coordinate are constructed by using restricted canonical ensembles with the phase space available to the system found by solving a self-consistent kinetic equation. The resulting activation barrier incorporates not only thermodynamic parameters but also dynamical information from the time autocorrelation function of the solute-solvent interaction energy. The theory is applied to the reactions of solvolysis and charge transfer in polar media.

Matyushov, Dmitry V. [Center for Biological Physics, Arizona State University, P.O. Box 871504, Tempe, Arizona 85287-1504 (United States)

2009-04-28

412

Modelling Heart Rate Kinetics  

PubMed Central

The objective of the present study was to formulate a simple and at the same time effective mathematical model of heart rate kinetics in response to movement (exercise). Based on an existing model, a system of two coupled differential equations which give the rate of change of heart rate and the rate of change of exercise intensity is used. The modifications introduced to the existing model are justified and discussed in detail, while models of blood lactate accumulation in respect to time and exercise intensity are also presented. The main modification is that the proposed model has now only one parameter which reflects the overall cardiovascular condition of the individual. The time elapsed after the beginning of the exercise, the intensity of the exercise, as well as blood lactate are also taken into account. Application of the model provides information regarding the individual’s cardiovascular condition and is able to detect possible changes in it, across the data recording periods. To demonstrate examples of successful numerical fit of the model, constant intensity experimental heart rate data sets of two individuals have been selected and numerical optimization was implemented. In addition, numerical simulations provided predictions for various exercise intensities and various cardiovascular condition levels. The proposed model can serve as a powerful tool for a complete means of heart rate analysis, not only in exercise physiology (for efficiently designing training sessions for healthy subjects) but also in the areas of cardiovascular health and rehabilitation (including application in population groups for which direct heart rate recordings at intense exercises are not possible or not allowed, such as elderly or pregnant women). PMID:25876164

Zakynthinaki, Maria S.

2015-01-01