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1

Second order hydrodynamic coefficients from kinetic theory  

SciTech Connect

In a relativistic setting, hydrodynamic calculations which include shear viscosity (which is first order in an expansion in gradients of the flow velocity) are unstable and acausal unless they also include terms to second order in gradients. To date such terms have only been computed in supersymmetric N=4 super-Yang-Mills theory at infinite coupling. Here we compute these second-order hydrodynamic coefficients in weakly coupled QCD, perturbatively to leading order in the QCD coupling, using kinetic theory. We also compute them in QED and scalar {lambda}{phi}{sup 4} theory.

York, Mark Abraao; Moore, Guy D. [McGill University, Department of Physics, 3600 rue University, Montreal QC H3A 2T8 (Canada)

2009-03-01

2

ALTERNATIVE RBC (ROTATING BIOLOGICAL CONTACTOR) DESIGN - SECOND ORDER KINETICS  

EPA Science Inventory

This paper presents an alternative method for designing rotating biological contactors (RBC) for use as a secondary treatment operation. The method uses a combination of chemical kinetics, good engineering practice, operational simplicity, and cost effectiveness to design a RBC s...

3

Efficient Bisimilarities from Second-Order Reaction Semantics for ?-Calculus  

NASA Astrophysics Data System (ADS)

We investigate Leifer and Milner RPO approach for deriving efficient (finitely branching) LTS's and bisimilarities for ?-calculus. To this aim, we work in a category of second-order term contexts and we apply a general pruning technique, which allows to simplify the set of transitions in the LTS obtained from the original RPO approach. The resulting LTS and bisimilarity provide an alternative presentation of symbolic LTS and Sangiorgi's open bisimilarity.

di Gianantonio, Pietro; Jakši?, Svetlana; Lenisa, Marina

4

Second-order radio frequency kinetic theory revisited: Resolving inconsistency with conventional fluid theory  

NASA Astrophysics Data System (ADS)

The second-order velocity distribution function was calculated from the second-order rf kinetic theory [Jaeger et al., Phys. Plasmas 7, 641 (2000)]. However, the nonresonant ponderomotive force in the radial direction derived from the theory is inconsistent with that from the fluid theory. The inconsistency arises from that the multiple-timescale-separation assumption fails when the second-order Vlasov equation is directly integrated along unperturbed particle orbits. A slowly ramped wave field including an adiabatic turn-on process is applied in the modified kinetic theory in this paper. Since this modification leads only to additional reactive/nonresonant response relevant with the secular resonant response from the previous kinetic theory, the correct nonresonant ponderomotive force can be obtained while all the resonant moments remain unchanged.

Chen, Jiale; Gao, Zhe

2013-08-01

5

Iron chelation by polyamidoamine dendrimers: a second-order kinetic model for metal-amine complexation.  

PubMed

This study presents a kinetic model of the chelation of iron ions by generation 4 hydroxyl-terminated polyamidoamine (PAMAM) with ethylenediamine core (G4-OH). The coordination processes of iron ions from ferric chloride, FeCl(3), and ferrous bromide, FeBr(2), to G4-OH dendrimers were analyzed using ultraviolet-visible (UV-vis) spectroscopy, proton nuclear magnetic resonance ((1)H NMR) spectroscopy, and liquid chromatography-mass spectrometry (LC-MS). In the visible region, a charge-transfer was observed when the dendrimer was added to a ferric chloride solution. This phenomenon is a ligand-to-metal charge-transfer (LMCT) between the free electron group of the dendrimer's internal amines and the dehalogenated iron ion that takes 2 h to complete at room temperature. Analysis of potential rate laws and diffusion effects led to a second-order kinetic model for this reaction. By measuring the rate coefficients as a function of temperature (22-37 °C), an apparent activation energy of 41.5 kJ/mol was obtained using the Arrhenius method. The results of this study will fuel research of PAMAM dendrimers for environmental, pharmaceutical, and materials applications. PMID:21995617

Mankbadi, Michael R; Barakat, Mohamed A; Ramadan, Mohamed H; Woodcock, H Lee; Kuhn, John N

2011-10-28

6

Temporal Frequency Modulates Reaction Time Responses to First-Order and Second-Order Motion  

ERIC Educational Resources Information Center

|This study investigated the effect of temporal frequency and modulation depth on reaction times for discriminating the direction of first-order (luminance-defined) and second-order (contrast-defined) motion, equated for visibility using equal multiples of direction-discrimination threshold. Results showed that reaction times were heavily…

Hutchinson, Claire V.; Ledgeway, Tim

2010-01-01

7

Integrated rate equations for irreversible enzyme-catalysed first-order and second-order reactions.  

PubMed Central

Integrated rate equations are presented that describe irreversible enzyme-catalysed first-order and second-order reactions. The equations are independent of the detailed mechanism of the reaction, requiring only that it be hyperbolic and unbranched. The results should be directly applicable in the laboratory.

Boeker, E A

1985-01-01

8

Kinetics and mechanism of N-Boc cleavage: evidence of a second-order dependence upon acid concentration.  

PubMed

The kinetics of the HCl-catalyzed deprotection of the Boc-protected amine, thioester 2 to liberate AZD3409 1 have been studied in a mixture of toluene and propan-2-ol. The reaction rate was found to exhibit a second-order dependence upon the HCl concentration. This behavior was found to have a degree of generality as the deprotection of a second Boc-protected amine, tosylate 3 to yield amine 4 using HCl, sulfuric acid, and methane sulfonic acid showed the same kinetic dependence. In contrast the deprotection of tosylate 3 with trifluoroacetic acid required a large excess of acid to obtain a reasonable rate of reaction and showed an inverse kinetic dependence upon the trifluoroacetate concentration. These observations are rationalized mechanistically in terms of a general acid-catalyzed separation of a reversibly formed ion-molecule pair arising from the fragmentation of the protonated tert-butyl carbamate. PMID:21067172

Ashworth, Ian W; Cox, Brian G; Meyrick, Brian

2010-11-10

9

Implementing the Second-Order Fermi Process in a Kinetic Monte-Carlo Simulation  

NASA Astrophysics Data System (ADS)

Kinetic Monte-Carlo test-particle simulations require a way to simulate the effects of turbulence on particles. One way to do this is to prescribe a phenomenological scattering mechanism based on an empirical and/or qualitative description of turbulent scattering. Previous incarnations of the simulation presented here parameterize a scattering mean free path proportional to some power of the particle’s momentum in agreement with observational evidence from many sources. The scattering itself was done by scattering of the particle’s local fluid frame velocity onto a sphere of radius |v| via either large of small angle scattering. However, in real plasmas the scattering centers (turbulent plasma waves) are not stationary in the local fluid frame and particle velocities should, instead, be randomized in the frame of the moving scattering centers (which presumably move with the Alfvén speed) to more accurately represent the effects of turbulence on particles. Allowing scattering centers to move introduces heating as particles now diffuse in momentum as well as space (receiving a random kick of order the Alfvén speed at each scattering event). In 1965, Eugene Parker considered this effect (then called fermi acceleration) for cosmic ray particles and (correctly) concluded that it was negligible for those highly energetic particles because the particle speed was so much larger than the Alfvén speed kick which it received. However, doing the same calculation for thermal particles embedded in the solar wind (for whom a single kick of an Alfvén speed is significant) yields a very different result and it becomes clear that this process, now called second-order Fermi acceleration, must be included to get an accurate picture of particle acceleration in the heliosphere. This presentation will highlight the theoretical argument for the importance of second-order fermi acceleration in both the solar wind and shock environs as well as problems in heliophysics to which it may be applicable and problems it creates for the conventional picture of first-order fermi shock acceleration. It will also discuss results from the kinetic Monte-Carlo simulation described above (including second-order fermi) in the vicinity of shocks.

Summerlin, E. J.

2010-12-01

10

Applying constraints on model-based methods: estimation of rate constants in a second order consecutive reaction.  

PubMed

This paper describes estimation of reaction rate constants and pure ultraviolet/visible (UV-vis) spectra of the component involved in a second order consecutive reaction between Ortho-Amino benzoeic acid (o-ABA) and Diazoniom ions (DIAZO), with one intermediate. In the described system, o-ABA was not absorbing in the visible region of interest and thus, closure rank deficiency problem did not exist. Concentration profiles were determined by solving differential equations of the corresponding kinetic model. In that sense, three types of model-based procedures were applied to estimate the rate constants of the kinetic system, according to Levenberg/Marquardt (NGL/M) algorithm. Original data-based, Score-based and concentration-based objective functions were included in these nonlinear fitting procedures. Results showed that when there is error in initial concentrations, accuracy of estimated rate constants strongly depends on the type of applied objective function in fitting procedure. Moreover, flexibility in application of different constraints and optimization of the initial concentrations estimation during the fitting procedure were investigated. Results showed a considerable decrease in ambiguity of obtained parameters by applying appropriate constraints and adjustable initial concentrations of reagents. PMID:23220674

Kompany-Zareh, Mohsen; Khoshkam, Maryam

2012-11-01

11

Positronium formation as a three-body reaction. II. The second-order nuclear amplitudes  

SciTech Connect

We derive an exact analytic form for the second-order nuclear amplitudes, under the Faddeev three-body approach, which is applicable to the nonrelativistic high energy impact interaction where positronium is formed in the collision of a positron with an atom.

Shojaei, F.; Bolorizadeh, M. A. [Physics Department, Shahid Bahonar University of Kerman, Kerman, 76169, Iran and ICST, Mahan, 76315 (Iran, Islamic Republic of); Ghanbari-Adivi, E. [Physics Department and Isfahan Quantum Optics Group, University of Isfahan, Isfahan, 81746 (Iran, Islamic Republic of); Brunger, M. J. [Centre for Antimatter-Matter Studies, School of Chemistry, Physics and Earth Sciences, Flinders University, Adelaide South Australia, 5042 (Australia)

2009-01-15

12

Comparative Analysis of Linear and Nonlinear Methods of Estimating the Pseudo-Second-Order Kinetic Parameters for Sorption of Malachite Green onto Pretreated Rice Husk  

Microsoft Academic Search

Batch sorption experiments were carried out for removal of malachite green from aqueous solution using pretreated rice husk. The equilibrium kinetic data were analyzed using pseudo-second-order kinetic model. A comparison between linear and nonlinear methods of estimating the kinetic parameters was carried out. Four pseudo-second-order kinetic linear equations were discussed. The coefficient of determination (r ) and chi-square (?) test

Shamik Chowdhury; Papita Das Saha

2011-01-01

13

Choice reaction times for identifying the direction of first-order motion and different varieties of second-order motion  

Microsoft Academic Search

This study sought to quantify the temporal properties of the human visual system by measuring forced-choice reaction times for discriminating the drift direction of first-order motion (luminance-modulated noise) and a variety of second-order motion patterns (modulations of either the contrast, polarity, orientation or spatial length of a noise carrier) over a range of stimulus modulation depths. In general, reaction times

Tim Ledgeway; Claire V. Hutchinson

2008-01-01

14

Reaction kinetics, geospeedometry, and relaxation theory  

Microsoft Academic Search

This paper explores the application of homogeneous reaction kinetics to geospeedometry and to structural relaxation theory. Numerical simulations of reaction kinetics during cooling for some first- and second-order elementary reactions have been carried out to systematically examine the effects of kinetic parameters and cooling histories on the final speciation. An analytical solution for a special case of first-order reaction A

Youxue Zhang

1994-01-01

15

Integrated rate equations for enzyme-catalysed first-order and second-order reactions.  

PubMed Central

Generalized rate equations covering all mechanisms giving hyperbolic initial-rate kinetics with stoichiometry A in equilibrium P, A in equilibrium P + Q, A + B in equilibrium P and A + B in equilibrium P + Q were integrated. The results are regular and reasonably economical.

Boeker, E A

1984-01-01

16

The relation between reaction rate and shock strength-A possible second order improvement to the crest reactive burn model  

NASA Astrophysics Data System (ADS)

Analysis of particle-velocity gauge results in explosives undergoing a shock to detonation transition showed that at the same shock strength the particle velocity histories scaled. It was concluded that, at least to first order, reaction rate is a function of shock strength and time since the shock passed. The success of the CREST reactive burn model in calculating many shock initiation and detonation phenomena demonstrates the power of this conclusion. However, from a theoretical assessment of the implications of the scaling phenomena, this paper suggests that the CREST reaction rate should also probably contain a second order factor dependent on the evolution of the flow.

Lambourn, Brian D.; James, Hugh R.

2012-03-01

17

A finite difference method for estimating second order parameter sensitivities of discrete stochastic chemical reaction networks  

NASA Astrophysics Data System (ADS)

We present an efficient finite difference method for the approximation of second derivatives, with respect to system parameters, of expectations for a class of discrete stochastic chemical reaction networks. The method uses a coupling of the perturbed processes that yields a much lower variance than existing methods, thereby drastically lowering the computational complexity required to solve a given problem. Further, the method is simple to implement and will also prove useful in any setting in which continuous time Markov chains are used to model dynamics, such as population processes. We expect the new method to be useful in the context of optimization algorithms that require knowledge of the Hessian.

Wolf, Elizabeth Skubak; Anderson, David F.

2012-12-01

18

Reaction path determination for quantum mechanical\\/molecular mechanical modeling of enzyme reactions by combining first order and second order ``chain-of-replicas'' methods  

Microsoft Academic Search

A two-step procedure for the determination of reaction paths in enzyme systems is presented. This procedure combines two chain-of-states methods: a quantum mechanical\\/molecular mechanical (QM\\/MM) implementation of the nudged elastic band (NEB) method and a second order parallel path optimizer method both recently developed in our laboratory. In the first step, a reaction path determination is performed with the NEB

G. Andrés Cisneros; Haiyan Liu; Zhenyu Lu; Weitao Yang

2005-01-01

19

Contact time optimization of two-stage batch adsorber design using second-order kinetic model for the adsorption of phosphate onto alunite.  

PubMed

The adsorption of phosphate onto alunite in a batch adsorber has been studied. Four kinetic models including pseudo first- and second-order equation, intraparticle diffusion equation and the Elovich equation were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of phosphate onto alunite could be described by the pseudo second-order equation. Adsorption of phosphate onto alunite followed the Langmuir isotherm. A model has been used for the design of a two-stage batch adsorber based on pseudo second-order adsorption kinetics. The model has been optimized with respect to operating time in order to minimize total operating time to achieve a specified amount of phosphate removal using a fixed mass of adsorbent. The results of two-stage batch adsorber design studies showed that the required times for specified amounts of phosphate removal significantly decreased. It is particularly suitable for low-cost adsorbents/adsorption systems when minimising operating time is a major operational and design criterion, such as, for highly congested industrial sites in which significant volume of effluent need to be treated in the minimum amount of time. PMID:16530939

Ozacar, Mahmut

2006-03-13

20

Evaluation of the prediction of trace organic compound removal during ozonation of secondary effluents using tracer substances and second order rate kinetics.  

PubMed

The application of the RCT-concept for predicting the removal of trace organic compounds (TrOCs) in organic rich WWTP effluents is often problematic due to the fast ozone depletion with instantaneous ozone demand in the range of typically applied ozone dosages. In this study, the determination of OH-radical and ozone exposure from second order rate kinetics with two internal tracer substances was evaluated as alternative approach for these waters. Results from batch and semi-batch experiments showed a linear correlation of OH-radical exposure with ozone consumption, characterized by its slope indicating the formation efficiency of OH-radicals and a lag ozone consumption without significant formation of OH-radicals. Evaluation of data from the project PILOTOX on ozonation of secondary effluent confirmed reasonable prediction of ozone resistant compound removal from relative residual concentration of an internal tracer substance. In contrast, predicting the reduction of TrOCs by direct reactions with ozone from internal tracers was not feasible. Similar removal efficiencies for fast reacting compounds with different rate constants from kO3 = 10(4) M(-1) s(-1) to kO3 = 10(6) M(-1) s(-1) were observed indicating a limitation of the reaction by mass transfer. This effect was observed at low ozone dosages in semi-batch and pilot experiments as well as in batch experiments, where mass transfer from gas to liquid phase is not limiting. It is assumed that consumption of low ozone dosages is faster than sample homogenization in the batch reactors used. Thus, prediction of compound removal by direct reaction with ozone always needs to consider reactor design and geometry. PMID:24050684

Hübner, U; Keller, S; Jekel, M

2013-09-04

21

Kinetics of solute adsorption at solid/solution interfaces: a theoretical development of the empirical pseudo-first and pseudo-second order kinetic rate equations, based on applying the statistical rate theory of interfacial transport.  

PubMed

For practical applications of solid/solution adsorption processes, the kinetics of these processes is at least as much essential as their features at equilibrium. Meanwhile, the general understanding of this kinetics and its corresponding theoretical description are far behind the understanding and the level of theoretical interpretation of adsorption equilibria in these systems. The Lagergren empirical equation proposed at the end of 19th century to describe the kinetics of solute sorption at the solid/solution interfaces has been the most widely used kinetic equation until now. This equation has also been called the pseudo-first order kinetic equation because it was intuitively associated with the model of one-site occupancy adsorption kinetics governed by the rate of surface reaction. More recently, its generalization for the two-sites-occupancy adsorption was proposed and called the pseudo-second-order kinetic equation. However, the general use and the wide applicability of these empirical equations during more than one century have not resulted in a corresponding fundamental search for their theoretical origin. Here the first theoretical development of these equations is proposed, based on applying the new fundamental approach to kinetics of interfacial transport called the Statistical Rate Theory. It is shown that these empirical equations are simplified forms of a more general equation developed here, for the case when the adsorption kinetics is governed by the rate of surface reactions. The features of that general equation are shown by presenting exhaustive model investigations, and the applicability of that equation is tested by presenting a quantitative analysis of some experimental data reported in the literature. PMID:16913785

Rudzinski, Wladyslaw; Plazinski, Wojciech

2006-08-24

22

Steady state voltammetry at microelectrodes for the hydrogen evolution from strong and weak acids under pseudo-first and second order kinetic conditions  

Microsoft Academic Search

The reaction of hydrogen evolution involving discharge of protons arising from strong and weak acids, namely perchloric, nitric, acetic, ethylenediaminetetra-acetic and dihydrogen phosphoric acids, was investigated in the concentration range 0.1–10 mM by steady state voltammetry at inlaid platinum micro-disc electrodes (of 10–12.5 ?m radius). The second-order CE mechanism for the weak acids was rationalised by digital simulation, demonstrating the

Salvatore Daniele; Irma Lavagnini; M. Antonietta Baldo; Franco Magno

1996-01-01

23

A simple method for analysis of consecutive reactions with a second order formation and a first order decay of an intermediate  

Microsoft Academic Search

A simple method is developed to evaluate rate constants from absorbance-time traces for a pair of consecutive reactions consisting\\u000a of a second order formation and a first order decay of an intermediate. Initially, a first order profile is simulated utilizing\\u000a the data near the end of the reaction. The difference between this simulated and observed profiles provides the absorbance-time\\u000a data

N. J. Matuska; R. N. Bose

1997-01-01

24

Second-order elections  

Microsoft Academic Search

The composition of the directly elected European Parliament does not precisely reflect the ‘real’ balance of political forces in the European Community. As long as the national political systems decide most of what there is to be decided politically, and everything really important, European elections are additional national second-order elections. They are determined more by the domestic political cleavages than

Karlheinz Reif; Hermann Schmitt

1997-01-01

25

Second-order motions contribute to vection  

Microsoft Academic Search

First- and second-order motions differ in their ability to induce motion aftereffects (MAEs) and the kinetic depth effect (KDE). To test whether second-order stimuli support computations relating to motion-in-depth we examined the vection illusion (illusory self motion induced by image flow) using a vection stimulus (V, expanding concentric rings) that depicted a linear path through a circular tunnel. The set

Rick Gurnsey; David Fleet; Cindy Potechin

1998-01-01

26

Cycloaddition reactions of polyenic donor-?-acceptor systems with an electron-rich alkyne: access to new chromophores with second-order optical nonlinearities.  

PubMed

The formal [2 + 2] cycloaddition-cycloreversion (CA-CR) between 4-ethynyl-N,N-dimethylaniline and polyenic Donor-?-Acceptor (D-?-A) systems takes place to yield compounds bearing two donors and one acceptor. Structural, linear and second-order nonlinear optical (NLO) properties of the new molecules reveal the stronger polarization of these systems when compared to analogous merocyanines lacking the dimethylaminophenyl (DMA) ring. PMID:23034533

Galán, Elena; Andreu, Raquel; Garín, Javier; Orduna, Jesús; Villacampa, Belén; Diosdado, Beatriz E

2012-11-21

27

Second-Order Motions Contribute Vection  

Microsoft Academic Search

First- and second-order motions differ in their ability to induce motionaftereffects (MAEs) and the kinetic depth effect (KDE). To test whether second-orderstimuli support computations relating to motion-in-depth we examined the vectionillusion (illusory self motion induced by image flow) using a vection stimulus (V,expanding concentric rings) that depicted a linear path through a circular tunnel.The set of vection stimuli contained differing

Rick Gurnsey; David Fleet; Cindy Potechin

2001-01-01

28

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

29

Second-order modeling of arsenite transport in soils  

NASA Astrophysics Data System (ADS)

Rate limited processes including kinetic adsorption-desorption can greatly impact the fate and behavior of toxic arsenic compounds in heterogeneous soils. In this study, miscible displacement column experiments were carried out to investigate the extent of reactivity during transport of arsenite in soils. Arsenite breakthrough curves (BTCs) of Olivier and Windsor soils exhibited strong retardation with diffusive effluent fronts followed by slow release or tailing during leaching. Such behavior is indicative of the dominance of kinetic retention reactions for arsenite transport in the soil columns. Sharp decrease or increase in arsenite concentration in response to flow interruptions (stop-flow) further verified that non-equilibrium conditions are dominant. After some 40-60 pore volumes of continued leaching, 30-70% of the applied arsenite was retained by the soil in the columns. Furthermore, continued arsenite slow release for months was evident by the high levels of residual arsenite concentrations observed during leaching. In contrast, arsenite transport in a reference sand material exhibited no retention where complete mass recovery in the effluent solution was attained. A second-order model (SOM) which accounts for equilibrium, reversible, and irreversible retention mechanisms was utilized to describe arsenite transport results from the soil columns. Based on inverse and predictive modeling results, the SOM model successfully depicted arsenite BTCs from several soil columns. Based on inverse and predictive modeling results, a second-order model which accounts for kinetic reversible and irreversible reactions is recommended for describing arsenite transport in soils.

Zhang, Hua; Magdi Selim, H.

2011-11-01

30

Second-order modeling of arsenite transport in soils.  

PubMed

Rate limited processes including kinetic adsorption-desorption can greatly impact the fate and behavior of toxic arsenic compounds in heterogeneous soils. In this study, miscible displacement column experiments were carried out to investigate the extent of reactivity during transport of arsenite in soils. Arsenite breakthrough curves (BTCs) of Olivier and Windsor soils exhibited strong retardation with diffusive effluent fronts followed by slow release or tailing during leaching. Such behavior is indicative of the dominance of kinetic retention reactions for arsenite transport in the soil columns. Sharp decrease or increase in arsenite concentration in response to flow interruptions (stop-flow) further verified that non-equilibrium conditions are dominant. After some 40-60 pore volumes of continued leaching, 30-70% of the applied arsenite was retained by the soil in the columns. Furthermore, continued arsenite slow release for months was evident by the high levels of residual arsenite concentrations observed during leaching. In contrast, arsenite transport in a reference sand material exhibited no retention where complete mass recovery in the effluent solution was attained. A second-order model (SOM) which accounts for equilibrium, reversible, and irreversible retention mechanisms was utilized to describe arsenite transport results from the soil columns. Based on inverse and predictive modeling results, the SOM model successfully depicted arsenite BTCs from several soil columns. Based on inverse and predictive modeling results, a second-order model which accounts for kinetic reversible and irreversible reactions is recommended for describing arsenite transport in soils. PMID:22115079

Zhang, Hua; Magdi Selim, H

2011-08-27

31

Kinetics of the reaction between oxygen and haemoglobin bound to haptoglobin (Short Communication)  

PubMed Central

The kinetics of the reaction between O2 and haemoglobin bound to haptoglobin 1–1 were investigated by the stopped-flow and temperature-jump techniques. The reaction, which follows second-order kinetics in the lower concentration range, becomes independent of O2 concentration above about 150?m-O2.

Chiancone, Emilia; Antonini, Eraldo; Brunori, Maurizio; Alfsen, Annette; Lavialle, Francoise

1973-01-01

32

Kinetics of actinide complexation reactions.  

National Technical Information Service (NTIS)

Though the literature records extensive compilations of the thermodynamics of actinide complexation reactions, the kinetics of complex formation and dissociation reactions of actinide ions in aqueous solutions have not been extensively investigated. In li...

K. L. Nash J. C. Sullivan

1997-01-01

33

Virtual Instrument for Determining Rate Constant of Second-Order Reaction by pX Based on LabVIEW 8.0.  

PubMed

The virtual instrument system based on LabVIEW 8.0 for ion analyzer which can measure and analyze ion concentrations in solution is developed and comprises homemade conditioning circuit, data acquiring board, and computer. It can calibrate slope, temperature, and positioning automatically. When applied to determine the reaction rate constant by pX, it achieved live acquiring, real-time displaying, automatical processing of testing data, generating the report of results; and other functions. This method simplifies the experimental operation greatly, avoids complicated procedures of manual processing data and personal error, and improves veracity and repeatability of the experiment results. PMID:19730752

Meng, Hu; Li, Jiang-Yuan; Tang, Yong-Huai

2009-08-31

34

Virtual Instrument for Determining Rate Constant of Second-Order Reaction by pX Based on LabVIEW 8.0  

PubMed Central

The virtual instrument system based on LabVIEW 8.0 for ion analyzer which can measure and analyze ion concentrations in solution is developed and comprises homemade conditioning circuit, data acquiring board, and computer. It can calibrate slope, temperature, and positioning automatically. When applied to determine the reaction rate constant by pX, it achieved live acquiring, real-time displaying, automatical processing of testing data, generating the report of results; and other functions. This method simplifies the experimental operation greatly, avoids complicated procedures of manual processing data and personal error, and improves veracity and repeatability of the experiment results.

Meng, Hu; Li, Jiang-Yuan; Tang, Yong-Huai

2009-01-01

35

Ametryn degradation by aqueous chlorine: kinetics and reaction influences.  

PubMed

The chemical oxidation of the herbicide ametryn was investigated by aqueous chlorination between pH 4 and 10 at a temperature of 25 degrees C. Ametryn was found to react very rapidly with aqueous chlorine. The reaction kinetics can be well described by a second-order kinetic model. The apparent second-order rate constants are greater than 5 x 10(2)M(-1)s(-1) under acidic and neutral conditions. The reaction proceeds much more slowly under alkaline conditions. The predominant reactions were found to be the reactions of HOCl with neutral ametryn and the charged ametryn, with rate constants equal to 7.22 x 10(2) and 1.58 x 10(3)M(-1)s(-1), respectively. The ametryn degradation rate increases with addition of bromide and decreases with addition of ammonia during the chlorination process. Based on elementary chemical reactions, a kinetic model of ametryn degradation by chlorination in the presence of bromide or ammonia ion was also developed. By employing this model, we estimate that the rate constants for the reactions of HOBr with neutral ametryn and charged ametryn were 9.07 x 10(3) and 3.54 x 10(6)M(-1)s(-1), respectively. These values are 10- to 10(3)-fold higher than those of HOCl, suggesting that the presence of bromine species during chlorination could significantly accelerate ametryn degradation. PMID:19423216

Xu, Bin; Gao, Nai-yun; Cheng, Hefa; Hu, Chen-yan; Xia, Sheng-ji; Sun, Xiao-feng; Wang, Xuejiao; Yang, Shaogui

2009-04-07

36

SECOND ORDER OPTIMALITY CONDITIONS BASED ON PARABOLIC SECOND ORDER TANGENT SETS  

Microsoft Academic Search

In this paper we discuss second order optimality conditions in optimization problems subject to abstract constraints. Our analysis is based on various concepts of second order tangent sets and parametric duality. We introduce a condition, called second order regularity, under which there is no gap between the corresponding second order necessary and second order sucient conditions. We show that the

J. FR ED ERIC; ALEXANDER SHAPIROx

37

Second order geodesic corrections to cosmic shear  

SciTech Connect

We consider the impact of second order corrections to the geodesic equation governing gravitational lensing. We start from the full second order metric, including scalar, vector, and tensor perturbations, and retain all relevant contributions to the cosmic shear corrections that are second order in the gravitational potential. The relevant terms are: the nonlinear evolution of the scalar gravitational potential, the Born correction, and lens-lens coupling. No other second order terms contribute appreciably to the lensing signal. Since ray-tracing algorithms currently include these three effects, this derivation serves as rigorous justification for the numerical predictions.

Dodelson, Scott [Particle Astrophysics Center Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637-1433 (United States); Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States); Kolb, Edward W. [Particle Astrophysics Center Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637-1433 (United States); Matarrese, S. [Dipartimento di Fisica 'G. Galilei', Universita di Padova (Italy); INFN, Sezione di Padova, via Marzolo 8, I-35131 (Italy); Riotto, A. [Dipartimento di Fisica 'G. Galilei', Universita di Padova (Italy); Zhang Pengjie [Particle Astrophysics Center Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 (United States)

2005-11-15

38

Chiral second-order nonlinear optics  

Microsoft Academic Search

Organic second-order nonlinear optical (NLO) materials can be efficiently utilized in photonics devices for optical telecommunications and signal processing due to their high nonlinear response, processability, and low cost. Media with polar order are usually used to ensure the absence of the inversion symmetry required in second-order NLO. This study presents a method that results in creation of efficient chiral

Victor P. Ostroverkhov

2001-01-01

39

Second-order optic flow processing.  

PubMed

Optic flow-large-field rotational and radial motion-is processed as efficiently as translational motion for first-order (luminance-defined) stimuli. However, it has been suggested recently that the same pattern does not hold for second-order (e.g. contrast-defined) stimuli. We used random dot kinematogram (RDK) stimuli to determine whether global processing of optic flow is as efficient as processing of global translational motion for both first- and second-order stimuli. For first-order stimuli, we found that coherence thresholds for radial and rotational motion were equivalent to thresholds for translational motion, supporting previous findings. For second-order stimuli we found, firstly, that given sufficient contrast, second-order optic flow can be processed as efficiently as first-order optic flow and, secondly, that rotational and translational second-order motion are processed with equal efficiency. This contradicts the suggestion that there is a loss of efficiency between integration of second-order global motion and second-order optic flow. The third interesting finding was that the processing of radial second-order motion appears to suffer from a deficit that is dependent upon both the contrast and spatial extent of the stimulus. Further experiments discounted the possibility that the observed deficit is caused by a centrifugal or centripetal bias, but demonstrated that a longer temporal integration period for radial second-order motion is responsible for the observed difference. For durations of approximately 850ms, all three types of motion are processed with equal efficiency. PMID:17462696

Aaen-Stockdale, Craig; Ledgeway, Tim; Hess, Robert F

2007-04-25

40

Second-order gravitational self-force.  

PubMed

Using a rigorous method of matched asymptotic expansions, I derive the equation of motion of a small, compact body in an external vacuum spacetime through second order in the body's mass (neglecting effects of internal structure). The motion is found to be geodesic in a certain locally defined regular geometry satisfying Einstein's equation at second order. I outline a method of numerically obtaining both the metric of that regular geometry and the complete second-order metric perturbation produced by the body. PMID:23006161

Pound, Adam

2012-07-31

41

Second-Order Gravitational Self-Force  

NASA Astrophysics Data System (ADS)

Using a rigorous method of matched asymptotic expansions, I derive the equation of motion of a small, compact body in an external vacuum spacetime through second order in the body’s mass (neglecting effects of internal structure). The motion is found to be geodesic in a certain locally defined regular geometry satisfying Einstein’s equation at second order. I outline a method of numerically obtaining both the metric of that regular geometry and the complete second-order metric perturbation produced by the body.

Pound, Adam

2012-08-01

42

Visualizing Second Order Tensor Fields with Hyperstreamlines.  

National Technical Information Service (NTIS)

Hyperstreamlines are a generalization to second order tensor fields of the conventional streamlines used in vector field visualization. As opposed to point icons commonly used in visualizing tensor fields, hyperstreamlines form a continuous representation...

T. Delmarcelle L. Hesselink

1993-01-01

43

Tensorial Calibration. 2. Second Order Tensorial Calibration.  

National Technical Information Service (NTIS)

Tensorial calibration provides a useful approach to calibration in general. For calibration of instruments that produce two dimensional (second order) data arrays of data per sample, tensorial concepts are a natural way of solving the calibration problems...

E. Sanchez B. R. Kowalski

1987-01-01

44

Second-order dust acoustic wave theory  

NASA Astrophysics Data System (ADS)

A second-order perturbation theory for non-dispersive, undamped dust acoustic waves is presented. The analysis leads to a second-order wave equation with source terms consisting of (nonlinear) products of first-order terms. The nonlinear effects included in this analysis might be useful in explaining the non-sinusoidal waveforms that are observed with large-amplitude, self-excited dust acoustic waves.

Merlino, Robert L.

2012-03-01

45

Contact Geometry of Second Order I  

Microsoft Academic Search

Classical theory for systems of the first order partial differential equations for a scalar function can be rephrased as the\\u000a submanifold theory of contact manifolds (geometric first order jet spaces). In the same spirit, we will develop the geometric\\u000a theory of systems of partial differential equations of second order for a scalar function as the Contact Geometry of Second Order,

Keizo Yamaguchi

46

Second-Order Algebraic Theories - (Extended Abstract)  

Microsoft Academic Search

\\u000a Fiore and Hur [10] recently introduced a conservative extension of universal algebra and equational logic from first to second\\u000a order. Second-order universal algebra and second-order equational logic respectively provide a model theory and a formal deductive\\u000a system for languages with variable binding and parameterised metavariables. This work completes the foundations of the subject\\u000a from the viewpoint of categorical algebra. Specifically,

Marcelo P. Fiore; Ola Mahmoud

2010-01-01

47

Kinetics of the reaction of N -2,6-trichlorobenzoquinonimine with sodium thiosulphate  

Microsoft Academic Search

The reaction ofN-2,6-trichlorobenzoquinonimine with sodium thiosulphate has been studied in aqueous solutions. The reaction follows second-order kinetics atpH 4.62.Ea, ?G and ?S being 6.2, 21.4 kcal\\/mol (26,90 kJ\\/mol) and -53.0 eu, respectively. The rate is acid catalyzed. The results are discussed in terms of nucleophilic addition of the thiosulphate ion.

A. A. Harfoush; A. Zagloul; F. M. Abdel Halim

1982-01-01

48

Kinetics of reactions occurring during polyurethane synthesis  

NASA Astrophysics Data System (ADS)

We have used Fourier transform IR spectroscopy to study the kinetics of reaction between phenylisocyanate and oligomeric polyols at room temperature. We have determined the degree of conversion and the reaction rate constants for urethane formation.

Volkova, E. R.; Tereshatov, V. V.; Karmanov, V. I.

2010-11-01

49

Second-Order Conditioning in "Drosophila"  

ERIC Educational Resources Information Center

|Associative conditioning in "Drosophila melanogaster" has been well documented for several decades. However, most studies report only simple associations of conditioned stimuli (CS, e.g., odor) with unconditioned stimuli (US, e.g., electric shock) to measure learning or establish memory. Here we describe a straightforward second-order

Tabone, Christopher J.; de Belle, J. Steven

2011-01-01

50

The Second-Order Rytov Approximation.  

National Technical Information Service (NTIS)

An explicit and useful formulation of the solution for the second-order Rytov approximation is given. From this solution a condition of validity for the Rytov solution is obtained. It is concluded that, in general, both the Born and Rytov approximations h...

H. T. Yura

1969-01-01

51

Second-order eikonal exchange amplitudes  

SciTech Connect

The analytic expressions of the second-order eikonal exchange amplitudes are derived for electron-hydrogen scattering in both post and prior forms. In the case of the Glauber exchange amplitude, these expressions are shown to be reducible to closed forms. The results are applied to the calculation of elastic e-H(1s) scattering. Useful conclusions are drawn.

Gien, T.T.

1986-11-01

52

Nine Practices of Second Order Schools  

ERIC Educational Resources Information Center

|Many schools are in some stage of implementing differentiated instruction, with some already in what Carol Tomlinson describes in "The Differentiated School" as "second order change," where the entire school practices differentiation. In high-performing schools, differentiation has proved to be an effective instructional strategy; in classroom…

Brown, Bill; Tucker, Patrick; Williams, Thomas L.

2012-01-01

53

A second order model for cylindrical data  

Microsoft Academic Search

Modeling cylindrical data, comprised of a linear component and a directional component, can be done using Fourier series expansions if we consider the conditional distribution of the linear component given the angular component. This paper presents the second order model which is a natural extension of the Mardia and Sutton (1978) first order model. This model can be parameterized either

Christine M. Anderson-Cook

2000-01-01

54

Witnessing entanglement with second-order interference  

SciTech Connect

Second-order interference and Hanbury-Brown and Twiss-type experiments can provide an operational framework for the construction of witness operators that can test classical and nonclassical properties of a Gaussian squeezed state, and provide entanglement witness operators to study the separability properties of correlated Gaussian squeezed sates.

Stobinska, Magdalena; Wodkiewicz, Krzysztof [Instytut Fizyki Teoretycznej, Uniwersytet Warszawski, Warsaw 00-681 (Poland); Instytut Fizyki Teoretycznej, Uniwersytet Warszawski, Warsaw 00-681 (Poland); Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131-1156 (United States)

2005-03-01

55

Second-Order Invariants and Holography  

NASA Astrophysics Data System (ADS)

Motivated by recent works on the role of the holographic principle in cosmology, we relate a class of second-order Ricci invariants to the IR cutoff characterizing the holographic dark energy density. The choice of second-order invariants provides an invariant way to account the problem of causality for the correct cosmological cutoff, since the presence of event horizons is not an a priori assumption. We find that these models work fairly well, by fitting the observational data, through a combined cosmological test with the use of SNeIa, BAO and CMB. This class of models is also able to overcome the fine-tuning and coincidence problems. Finally, to make a comparison with other recent models, we adopt the statistical tests AIC and BIC.

Luongo, Orlando; Bonanno, Luca; Iannone, Gerardo

2012-11-01

56

Second order Pseudo-gaussian shaper  

SciTech Connect

The purpose of this document is to provide a calculus spreadsheet for the design of second-order pseudo-gaussian shapers. A very interesting reference is given by C.H. Mosher ''Pseudo-Gaussian Transfer Functions with Superlative Recovery'', IEEE TNS Volume 23, p. 226-228 (1976). Fred Goulding and Don Landis have studied the structure of those filters and their implementation and this document will outline the calculation leading to the relation between the coefficients of the filter. The general equation of the second order pseudo-gaussian filter is: f(t) = P{sub 0} {center_dot} e{sup -3kt} {center_dot} sin{sup 2}(kt). The parameter k is a normalization factor.

Beche, Jean-Francois

2002-11-22

57

Spacetime encodings. III. Second order Killing tensors  

NASA Astrophysics Data System (ADS)

This paper explores the Petrov type D, stationary axisymmetric vacuum (SAV) spacetimes that were found by Carter to have separable Hamilton-Jacobi equations, and thus admit a second-order Killing tensor. The derivation of the spacetimes presented in this paper borrows from ideas about dynamical systems, and illustrates concepts that can be generalized to higher-order Killing tensors. The relationship between the components of the Killing equations and metric functions are given explicitly. The origin of the four separable coordinate systems found by Carter is explained and classified in terms of the analytic structure associated with the Killing equations. A geometric picture of what the orbital invariants may represent is built. Requiring that a SAV spacetime admits a second-order Killing tensor is very restrictive, selecting very few candidates from the group of all possible SAV spacetimes. This restriction arises due to the fact that the consistency conditions associated with the Killing equations require that the field variables obey a second-order differential equation, as opposed to a fourth-order differential equation that imposes the weaker condition that the spacetime be SAV. This paper introduces ideas that could lead to the explicit computation of more general orbital invariants in the form of higher-order Killing tensors.

Brink, Jeandrew

2010-01-01

58

Chemical Kinetics: Rate of Reaction  

NSDL National Science Digital Library

This site offers an interactive tutorial that emphasizes graphical interpretation of chemical kinetics. The stoichiometric coefficients for a chemical equation are determined by comparing the slopes of concentration-time plots for the reactants and products. This tutorial is coupled to others to further guide the student to a better understanding of chemical kinetics.

Blauch, David N.

59

The kinetics of the recombination reaction between apomyoglobin and alkaline haematin.  

PubMed Central

Apomyoglobin was prepared by an extremely mild modification of the acid/butanone technique, and the kinetics of the recombination reaction between this preparation and alkaline haematin were studied. The recombination has been shown to be precisely second-order and mono-phasic. Rate constants obtained from the study are in good agreement with values obtained previously by an indirect technique not involving separation of haem and apoprotein.

Adams, P A

1977-01-01

60

Implementation of fitted second order ODE integrators  

SciTech Connect

The fixed step size integration of a system of second-order ODES without first derivatives can most efficiently be implemented using backward differences (if variable step sizes are needed, modified backward differences appear to be the most efficient(2)). This note indicates how to modify these methods so that they are exact for solutions of the form e/sup /lambda/t/ for specified values of /lambda/. These appear to be particularly promising for the equations of planetary motion in which /lambda/ = i/omega/, where /omega//2/pi/ is the rotational frequency. 3 refs.

Gear, C.W.

1988-07-01

61

The Kinetics of Isotopic Exchange Reactions.  

ERIC Educational Resources Information Center

|Discussed are the kinetic interactions of these chemical processes and the determination of the actual order of such reactions. Included are multiple exchange, catalytic exchange with deuterium, and depletion of the original substrate. (CW)|

Logan, S. R.

1990-01-01

62

Synchronization from Second Order Network Connectivity Statistics  

PubMed Central

We investigate how network structure can influence the tendency for a neuronal network to synchronize, or its synchronizability, independent of the dynamical model for each neuron. The synchrony analysis takes advantage of the framework of second order networks, which defines four second order connectivity statistics based on the relative frequency of two-connection network motifs. The analysis identifies two of these statistics, convergent connections, and chain connections, as highly influencing the synchrony. Simulations verify that synchrony decreases with the frequency of convergent connections and increases with the frequency of chain connections. These trends persist with simulations of multiple models for the neuron dynamics and for different types of networks. Surprisingly, divergent connections, which determine the fraction of shared inputs, do not strongly influence the synchrony. The critical role of chains, rather than divergent connections, in influencing synchrony can be explained by their increasing the effective coupling strength. The decrease of synchrony with convergent connections is primarily due to the resulting heterogeneity in firing rates.

Zhao, Liqiong; Beverlin, Bryce; Netoff, Theoden; Nykamp, Duane Q.

2011-01-01

63

First- and second-order Poisson spots  

NASA Astrophysics Data System (ADS)

Although Thomas Young is generally given credit for being the first to provide evidence against Newton's corpuscular theory of light, it was Augustin Fresnel who first stated the modern theory of diffraction. We review the history surrounding Fresnel's 1818 paper and the role of the Poisson spot in the associated controversy. We next discuss the boundary-diffraction-wave approach to calculating diffraction effects and show how it can reduce the complexity of calculating diffraction patterns. We briefly discuss a generalization of this approach that reduces the dimensionality of integrals needed to calculate the complete diffraction pattern of any order diffraction effect. We repeat earlier demonstrations of the conventional Poisson spot and discuss an experimental setup for demonstrating an analogous phenomenon that we call a ``second-order Poisson spot.'' Several features of the diffraction pattern can be explained simply by considering the path lengths of singly and doubly bent paths and distinguishing between first- and second-order diffraction effects related to such paths, respectively.

Kelly, William R.; Shirley, Eric L.; Migdall, Alan L.; Polyakov, Sergey V.; Hendrix, Kurt

2009-08-01

64

Kinetics of Chemical Reactions in Foods  

Microsoft Academic Search

Chemical reactions occur in foods during processing and storage. Some reactions result in a quality loss and must be minimized,\\u000a whereas others result in the formation of a desired flavor or color and must be optimized to obtain the best product quality.\\u000a Kinetics is a science that involves the study of chemical reaction rates and mechanisms. An understanding of reaction

Romeo T. Toledo

65

Slowly rotating scalar field wormholes: The second order approximation  

SciTech Connect

We discuss rotating wormholes in general relativity with a scalar field with negative kinetic energy. To solve the problem, we use the assumption about slow rotation. The role of a small dimensionless parameter plays the ratio of the linear velocity of rotation of the wormhole's throat and the velocity of light. We construct the rotating wormhole solution in the second-order approximation with respect to the small parameter. The analysis shows that the asymptotical mass of the rotating wormhole is greater than that of the nonrotating one, and the null energy condition violation in the rotating wormhole spacetime is weaker than that in the nonrotating one.

Kashargin, P. E. [Department of General Relativity and Gravitation, Kazan State University, Kremlevskaya str. 18, Kazan 420008 (Russian Federation); Sushkov, S. V. [Department of General Relativity and Gravitation, Kazan State University, Kremlevskaya str. 18, Kazan 420008 (Russian Federation); Department of Mathematics, Tatar State University of Humanities and Education, Tatarstan str. 2, Kazan 420021 (Russian Federation)

2008-09-15

66

Second-order superintegrable quantum systems  

SciTech Connect

A classical (or quantum) superintegrable system on an n-dimensional Riemannian manifold is an integrable Hamiltonian system with potential that admits 2n - 1 functionally independent constants of the motion that are polynomial in the momenta, the maximum number possible. If these constants of the motion are all quadratic, then the system is second-order superintegrable, the most tractable case and the one we study here. Such systems have remarkable properties: multi-integrability and separability, a quadratic algebra of symmetries whose representation theory yields spectral information about the Schroedinger operator, and deep connections with expansion formulas relating classes of special functions. For n = 2 and for conformally flat spaces when n = 3, we have worked out the structure of the classical systems and shown that the quadratic algebra always closes at order 6. Here, we describe the quantum analogs of these results. We show that, for nondegenerate potentials, each classical system has a unique quantum extension.

Miller, W. [University of Minnesota, School of Mathematics (United States); Kalnins, E. G. [University of Waikato, Department of Mathematics and Statistics (New Zealand); Kress, J. M. [The University of New South Wales, School of Mathematics (Australia)], E-mail: j.kress@unsw.edu.au

2007-03-15

67

Kinetics of Metal Atom Oxidation Reactions.  

National Technical Information Service (NTIS)

The tubular fast-flow reactor, previously used for reaction kinetic measurements at temperatures up to only 1000K, has been adapted to reach temperatures up to 2000K and has been applied to studies of gas phase reactions of metal atoms with O2. The most e...

A. Fontijn S. C. Kurzius J. J. Houghton

1972-01-01

68

Random channel kinetics for reaction-diffusion systems  

NASA Astrophysics Data System (ADS)

A random channel approach is developed for reaction-diffusion processes in disordered systems. Although the starting point of our research is the kinetic study of the decay and preservation of marine organic carbon, our approach can be used for describing other disordered kinetic catalytic processes with random pathways. We consider a generic catalytic mechanism with two species: (a) a catalyst, which is continuously produced by a variable number of independent sources randomly distributed in space; this catalyst diffuses from the sources and is degrading according to a first order kinetic law; the generation, the degradation and the diffusion of the catalyst balance each other out and a stationary concentration field is generated; (b) an active species, which decays according to a second order kinetic law; the decay rate is proportional to the product of the concentrations of the catalyst and the concentration of the active species. We show that the catalyst concentration field can be represented by the sum of a random number of Yukawa-like potentials. The average value of the survival function of the active species can be expressed as a grand canonical average of a nonlinear functional of the catalyst field and can be evaluated exactly. We show that a good approximation is given by a nearest neighbor approach, where only the contribution of the closest source is taken into account for the computation of the random concentration field of the catalyst. We discuss the application of the model to the problem of decay and preservation of marine organic carbon. With minor adaptation the model can be applied to other problems of disordered kinetics, such as spatially distributed heterogeneous catalytic processes.

Vlad, Marcel O.; Rothman, Daniel H.; Ross, John

2010-06-01

69

Chiral second-order nonlinear optics  

NASA Astrophysics Data System (ADS)

Organic second-order nonlinear optical (NLO) materials can be efficiently utilized in photonics devices for optical telecommunications and signal processing due to their high nonlinear response, processability, and low cost. Media with polar order are usually used to ensure the absence of the inversion symmetry required in second-order NLO. This study presents a method that results in creation of efficient chiral non-polar axially aligned NLO media. The stages of design and optimization include molecular engineering, quantum-mechanical theory of the molecular hyperpolarizability, chromophore characterization by means of Kleinman-disallowed hyper-Rayleigh scattering (KD-HRS), and analysis of the macroscopic alignment of the NLO chromophores in the bulk. Chiral systems belonging to non-polar symmetry groups Dinfinity and D2 with high nonlinear response can be easily fabricated in a number of polymeric and liquid-crystalline materials. The NLO susceptibility chi(2) of such media are defined by the Kleinman-disallowed irreducible component of the hyperpolarizability tensor beta that transforms as a traceless symmetric second-rank tensor. Using KD-HRS, one can determine the figures of merit of all irreducible components of beta including the second-rank part, which is relevant in chiral non-polar media. It is shown that conjugated ?-shaped chromophores containing one electron acceptor and two donors (or vice versa) can have large second-rank component of beta. Quantum-mechanically, this can be attributed to existence of low lying electronic states of B-symmetry, that is those that change sign upon rotation around the ?'s two fold axis. A propeller-like molecule Crystal Violet is also shown to have large second-rank response and is believed to be similar in this sense to a ?-molecule. The analysis of alignment schemes for ?-shaped and propeller-like chromophores shows that the optimized configuration can be achieved in uniaxially and biaxially stretched chiral polymers and in noncentrosymmetric liquid crystal phases. Potential applications for such media in photonics devices are discussed.

Ostroverkhov, Victor P.

70

Kinetics and the Mechanism of Certain Reactions of Concentrated Ozone.  

National Technical Information Service (NTIS)

The state of knowledge of the kinetics and mechanism of reactions of concentrated ozone is reviewed under the following headings: (1) kinetics and mechanism of ozone decomposition in the gas phase; (2) kinetic stability of gaseous ozone; (3) kinetic stabi...

G. I. Emelyanova B. V. Strakhov

1969-01-01

71

Kinetics and mechanisms of homogeneous catalytic reactions  

Microsoft Academic Search

A kinetic study of the homogeneous hydroformylation of 1-hexene to the corresponding aldehydes (heptanal and 2-methyl-hexanal) was carried out using a rhodium catalyst formed by addition of 1equiv. of 1,2-bis(diphenylphosphino)ethane (dppe) to Rh(acac)(CO)2 under mild reaction conditions (80°C, 1–7atm H2 and 1–7atm CO) in toluene; in all cases linear to branched ratios were close to 2. The reaction rate is

Merlin Rosales; Angel González; YusbeIi Guerrero; Inés Pacheco; Roberto A. Sánchez-Delgado

2007-01-01

72

Manganese peroxidase from the lignin-degrading basidiomycete Phanerochaete chrysosporium: Transient state kinetics and reaction mechanism  

SciTech Connect

Stopped-flow techniques were used to investigate the kinetics of the formation of manganese peroxidase compound I (MnPI) and of the reactions of MnPI and manganese peroxidase compound II (MnPII) with p-cresol and Mn{sup II}. All of the rate data were obtained from single turnover experiments under pseudo-first order conditions. In the presence of H{sub 2}O{sub 2} the formation of MnPI is independent of pH over the range 3.12-8.29 with a second-order rate constant of (2.0{+-}0.1) {times} 10{sup 6} M{sup {minus}1} s{sup {minus}1}. The activation energy for MnPI formation is 20 kJ mol{sup {minus}1}. MnPI formation also occurs with organic peroxides such as peracetic acid, m-chloroperoxybenzoic acid, and p-nitroperoxybenzoic acid with second-order rate constants of 9.7 x 10{sup 5}, 9.5 {times} 10{sup 4}, and 5.9 {times} 10{sup 4} M{sup {minus}1} s{sup {minus}1}, respectively. The reactions of MnPI and MnPII with p-cresol strictly obeyed second-order kinetics. The second-order rate constant for the reaction of MnPII with p-cresol is extremely low, (9.5{+-}0.5) m{sup {minus}1} s{sup {minus}1}. Kinetic analysis of the reaction of Mn{sup II} with MnPI and MnPII showed a binding interaction with the oxidized enzymes which led to saturation kinetics. The first-order dissociation rate constants for the reaction of Mn{sup II} with MnPI and MnPII are (0.7{+-}0.1) and (0.14{+-}0.01) s{sup {minus}1}, respectively, when the reaction is conducted in lactate buffer. Rate constants are considerably lower when the reactions are conducted in succinate buffer. Single turnover experiments confirmed that Mn{sup II} serves as an obligatory substrate for MnPII and that both oxidized forms of the enzyme form productive complexes with Mn{sup II}. Finally, these results suggest the {alpha}-hydroxy acids such as lactate facilitate the dissociation of Mn{sup II} from the enzyme.

Wariishi, Hiroyuki; Gold, M.H. (Oregon Graduate Center, Beaverton (United States)); Dunford, H.B.; MacDonald, I.D. (Univ. of Alberta, Edmonton (Canada))

1989-02-25

73

COS-forming reaction between CO and sulfur: A high-temperature intrinsic kinetics study  

SciTech Connect

Carbonyl sulfide is formed in the front end (i.e., the reaction furnace and the waste heat boiler) of Claus plants which are commonly used to recover sulfur from acid gases. Moreover, COS along with CS{sub 2}, are recognized as the problematic sulfur compounds that contribute significantly to plant sulfur emissions. Further, there is limited kinetic information on the important reaction for the formation of these two compounds. Now, it is well-known that one of the important COS-forming reactions is that between CO and sulfur. In this laboratory, the authors conducted an experimental study to measure the intrinsic kinetics of this homogeneous gas-phase reaction in the temperature range of 600--1150 C and over a residence time of 0.5--2.0 s. The overall reaction was found to be second order with a reaction rate constant k{sub f} = (3.18 {+-} 0.36) {times} 10{sup 5} exp[{minus}(6700 {+-} 108 K)/T] m{sup 3}/(kmol{center_dot}s). In addition, a kinetic model was developed to account for both the COS formation and the COS decomposition reactions. And, finally, for the reverse reaction, the COS decomposition reaction rate constant (k{sub r}) was regressed to match the equilibrium data of experiments at high temperatures giving a second-order reaction rate constant as k{sub r} = (2.18 {+-} 1.12) {times} 10{sup 9} exp[{minus}(21630 {+-} 160 K)/T] m{sup 3}/(kmol{center_dot}s).

Karan, K.; Mehrotra, A.K.; Behie, L.A. [Univ. of Calgary, Alberta (Canada). Dept. of Chemical and Petroleum Engineering

1998-12-01

74

Real second order freeness and Haar orthogonal matrices  

NASA Astrophysics Data System (ADS)

We demonstrate the asymptotic real second order freeness of Haar distributed orthogonal matrices and an independent ensemble of random matrices. Our main result states that if we have two independent ensembles of random matrices with a real second order limit distribution and one of them is invariant under conjugation by an orthogonal matrix, then the two ensembles are asymptotically real second order free. This captures the known examples of asymptotic real second order freeness introduced by Redelmeier.

Mingo, James A.; Popa, Mihai

2013-05-01

75

Kinetics of coupling reactions that generate monothiophosphate disulfides: implications for modification of RNAs.  

PubMed

The inclusion of guanosine-5'-monothiophosphate (GMPS) in an in vitro transcription reaction facilitates enzymatic synthesis of an RNA transcript with a monothiophosphate group at the 5' end. A kinetic study of the modification reactions that generate monothiophosphate disulfide linkages with either 5'-GMPS alone or 5'-GMPS-primed RNA as the substrate revealed that the second-order rate constants increased as the pH was decreased. For example, when the reaction pH was lowered from 8 to 4, the k2 value for the coupling reaction between N-(6-[biotinamido]hexyl)-3'-(2'-pyridyldithio)propionamide (biotin-HPDP) and GMPS increased 67-fold from 1.84 to 123 M(-1) x s(-1). In addition to discussing a possible mechanism for coupling reactions that involve GMPS and disulfides, we also indicate conditions that are likely to be optimal for modification of the nucleophilic sulfur in 5'-GMPS-primed RNAs. PMID:11716671

Wu, C W; Eder, P S; Gopalan, V; Behrman, E J

76

Kinetics of autocatalytic reactions involving solids  

SciTech Connect

The authors construct a mathematical model depicting autocatalytic reactions between gases and solids in two reaction scenarios. These are the oxidation of copper iodide and the thermal decomposition of barium azide. The model assumes that, in the case of processes of thermal decomposition which take place without diffusion inhibition, the rate of these processes is determined by the number of active sites whose role is played by nuclei of the solid phase and the amount of unreacted initial solid phase. It is further hypothesized that the rate of formation of active sites is directly proportional to the degree of transformation of the solid phase. These assumptions are mathematically reduced to kinetic equations.

Filippov, G.G.; Shevyreva, L.I.; Gorbunov, A.I.

1987-06-01

77

Assessment of closure schemes in second-order conditional moment closure against DNS with extinction and ignition  

SciTech Connect

The performance of second-order conditional moment closure (CMC) depends on models to evaluate conditional variances and covariances of temperature and species mass fractions. In this paper the closure schemes based on the steady laminar flamelet model (SLFM) are validated against direct numerical simulation (DNS) involving extinction and ignition. Scaling is performed to reproduce proper absolute magnitudes, irrespective of the origin of mismatch between local flamelet structures and scalar dissipation rates. DNS based on the pseudospectral method is carried out to study hydrogen-air combustion with a detailed kinetic mechanism, in homogeneous, isotropic, and decaying turbulent media. Lewis numbers are set equal to unity to avoid complication of differential diffusion. The SLFM-based closures for correlations among fluctuations of reaction rate, scalar dissipation rate, and species mass fractions show good comparison with DNS. The variance parameter in lognormal PDF and the constants in the dissipation term have been estimated from DNS results. Comparison is made for the resulting conditional profiles from DNS, first-order CMC, and second-order CMC with correction to the most critical reaction step according to sensitivity analysis. Overall good agreement ensures validity of the SLFM-based closures for modeling conditional variances and covariances in second-order CMC.

Sreedhara, S.; Huh, Kang Y. [Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784 (Korea, Republic of)

2005-12-01

78

Mechanisms and Kinetics of Catalytic Reactions.  

National Technical Information Service (NTIS)

Second order rate constants, KIBA have been determined for unsubstituted and 4-alkyl substituted o-iodosobenzoate catalyzed hydrolysis of the simulant p-nitrophenyl-diphenyl phosphate in microemulsions containing surfactants: cetyltrimethyl-ammonium bromi...

S. M. Garlick

1990-01-01

79

Kinetics of rouleau formation. II. Reversible reactions.  

PubMed Central

Red blood cells aggregate face-to-face to form long, cylindrical, straight chains and sometimes branched structures called rouleaux. Here we extend a kinetic model developed by R. W. Samsel and A. S. Perelson (1982, Biophys. J. 37:493-514) to include both the formation and dissociation of rouleaux. We examine thermodynamic constraints on the rate constants of the model imposed by the principle of detailed balance. Incorporation of reverse reactions allows us to compute mean sizes of rouleaux and straight chain segments within rouleaux, as functions of time and at equilibrium. Using the Flory - Stockmayer method from polymer chemistry, we obtain a closed-form solution for the size distribution of straight chain segments within rouleaux at any point in the evolution of the reaction. The predictions of our theory compare favorably with data collected by D. Kernick , A.W.L. Jay , S. Rowlands , and L. Skibo (1973, Can. J. Physiol. Pharmacol. 51:690-699) on the kinetics of rouleau formation. When rouleaux grow large, they may contain rings or loops and take on the appearance of a network. We demonstrate the importance of including the kinetics of ring closure in the development of realistic models of rouleaux formation. Images FIGURE 1 FIGURE 13

Samsel, R W; Perelson, A S

1984-01-01

80

Reaction Dynamics Through Kinetic Transition States  

NASA Astrophysics Data System (ADS)

The transformation of a system from one state to another is often mediated by a bottleneck in the system’s phase space. In chemistry, these bottlenecks are known as transition states through which the system has to pass in order to evolve from reactants to products. The chemical reactions are usually associated with configurational changes where the reactants and products states correspond, e.g., to two different isomers or the undissociated and dissociated state of a molecule or cluster. In this Letter, we report on a new type of bottleneck which mediates kinetic rather than configurational changes. The phase space structures associated with such kinetic transition states and their dynamical implications are discussed for the rotational vibrational motion of a triatomic molecule. An outline of more general related phase space structures with important dynamical implications is given.

Çiftçi, Ünver; Waalkens, Holger

2013-06-01

81

Bose-Einstein or HBT Correlation Signals of a Second Order QCD Phase Transition  

SciTech Connect

For particles emerging from a second order QCD phase transition, we show that a recently introduced shape parameter of the Bose-Einstein correlation function, the Levy index of stability equals to the correlation exponent -- one of the critical exponents that characterize the behaviour of the matter in the vicinity of the second order phase transition point. Hence the shape of the Bose-Einstein / HBT correlation functions, when measured as a function of bombarding energy and centrality in various heavy ion reactions, can be utilized to locate experimentally the second order phase transition and the critical end point of the first order phase transition line in QCD.

Csoergo, T.; Hegyi, S. [MTA KFKI RMKI, H - 1525 Budapest 114, P.O.Box 49 (Hungary); Novak, T. [University of Nijmegen, NL - 6525 ED Nijmegen, Toernooiveld 1 (Netherlands); Zajc, W. A. [Department of Physics, Columbia University, 538 W 120th Street, New York, NY 10027 (United States)

2006-04-11

82

Kinetics of elementary atom and radical reactions  

SciTech Connect

During the past three years we have been working on four problems in the general area of gas phase kinetics and energy transfer of small molecules. These are: (1) measurements of the fine structure populations of ground state oxygen atoms produced in photodissociation reactions; (2) quenching of the Rydberg B ({sup 1}{Sigma}{sup {plus}}) state of CO; (3) vibrational relaxation of highly excited molecules; and (4) kinetics of hydrogen molecules. The first two topics, which involve transitions between different electronic states of the parent molecule, are a departure from our previous research interests. In the accompanying renewal proposal we discuss plans to pursue these new topics vigorously during the coming year. The third topic is a continuation of our long interest in the energy dependence of the rates laws governing vibrational-to-translational energy transfer of molecules having large initial amounts of vibrational excitation. The final topic is a continuation of our studies of the reaction of O({sup 3}P) + H{sub 2}. In this work we measured the rate constant for the reaction O({sup 3}P) with deuterium and also analyzed spectroscopically different sources of vibrationally excited hydrogen for possible future work. We discuss each of these four studies in the following sections.

Gordon, R.J.

1990-06-01

83

OSCILLATION AND NONOSCILLATION OF FORCED SECOND ORDER DYNAMIC EQUATIONS  

Microsoft Academic Search

Oscillation and nonoscillation properties of second order Sturm{Liouville dynamic equations on time scales attracted much interest. These equations include, as special cases, second order self-adjoint dierential equations as well as second order Sturm{Liouville dierence equations. In this paper we con- sider a given (homogeneous) equation and a corresponding equation with forcing term. We give new conditions implying that the inhomogeneous

MARTIN BOHNER; CHRISTOPHER C TISDELL

2005-01-01

84

Second-Order Global Optimality Conditions for Optimization Problems  

Microsoft Academic Search

Second-order optimality conditions are studied for the constrained optimization problem where the objective function and the\\u000a constraints are compositions of convex functions and twice strictly differentiable functions. A second-order sufficient condition\\u000a of a global minimizer is obtained by introducing a generalized representation condition. Second-order minimizer characterizations\\u000a for a convex program and a linear fractional program are derived using the generalized

X. Q. Yang

2004-01-01

85

Second-Order Nonsmooth Analysis in Nonlinear Programming  

Microsoft Academic Search

Problems of nonlinear programming are placed in a broader framework of com- posite optimization. This allows second-order smoothness in the data structure to be utilized despite apparent nonsmoothness in the objective. Second-order epi-derivatives are shown to exist as expressions of such underlying smooth- ness, and their connection with several kinds of second-order approximation is examined. Expansions of the Moreau envelope

Rene Poliquin; Terry Rockafellar

86

Second-Order Conditioning during a Compound Extinction Treatment  

ERIC Educational Resources Information Center

|Two conditioned taste aversion experiments with rats were conducted to establish if a target taste that had received a prior pairing with illness could be subject to second-order conditioning during extinction treatment in compound with a flavor that also received prior conditioning. In these experiments, the occurrence of second-order

Pineno, Oskar; Zilski, Jessica M.; Schachtman, Todd R.

2007-01-01

87

Estimation Of Nonlinearities In A Second Order System  

Microsoft Academic Search

In this paper we report on a method to estimate the nonlinear stiffness and the nonlintear damping characteristics of a second order system with one degree of freedom and governed by a second order differential equation. Use is made of the Volterra functional series to represent the output of a weakly nonlinear system. The linear impulse response is evaluated from

K. Govender; D. C. Levy

1990-01-01

88

Second Order Modeling of Boundary-Free Turbulent Shear Flows.  

National Technical Information Service (NTIS)

A set of realizable second order models for boundary-free turbulent flows is presented. The constraints on second order models based on the realizability principle are re-examined. The rapid terms in the pressure correlations for both the Reynolds stress ...

T. Shih Y. Chen J. L. Lumley

1991-01-01

89

Ionosphere layer shape from second-order ATS 6 measurements  

Microsoft Academic Search

electron content value. The second-order component of phase path is primarily due to a truncation of the expansion for refractive index when the satellite is within about 45 ø of zenith, but it is dominated by ray path bending when the satellite is outside that zone. The second-order value is used to derive scale height at the peak of the

M. L. Heron

1981-01-01

90

Second Order Moments in Linear Smart Material Composites  

Microsoft Academic Search

Homogenization is a mean field approach for the determination of the effective properties of heterogeneous materials. It can provide the average fields per phase but also some information about the field distribution such as second order moments. The use of second order moments of fields can notably improve the estimates of the macroscopic behavior in the nonlinear case. This has

Romain Corcolle; Valentin Preault; Laurent Daniel

2012-01-01

91

The second order adjoint analysis: Theory and applications  

Microsoft Academic Search

Summary The adjoint method application in variational data assimilation provides a way of obtaining the exact gradient of the cost functionj with respect to the control variables. Additional information may be obtained by using second order information. This paper presents a second order adjoint model (SOA) for a shallow-water equation model on a limited-area domain. One integration of such a

Zhi Wang; I. M. Navon; F. X. Le Dimet; X. Zou

1992-01-01

92

Second order Poincaré inequalities and CLTs on Wiener space  

Microsoft Academic Search

We prove infinite-dimensional second order Poincaré inequalities on Wiener space, thus closing a circle of ideas linking limit theorems for functionals of Gaussian fields, Stein's method and Malliavin calculus. We provide two applications: (i) to a new “second order” characterization of CLTs on a fixed Wiener chaos, and (ii) to linear functionals of Gaussian-subordinated fields.

Ivan Nourdin; Giovanni Peccati; Gesine Reinert

2009-01-01

93

Some Steady MHD Flows of the Second Order Fluid  

Microsoft Academic Search

The exact analytic solutions of two problems of a second order fluid in presence of a uniform transverse magnetic field are investigated. The governing equation is of fourth order ordinary differential equation and is solved using perturbation method. In the first problem we discuss the flow of a second order fluid due to non-coaxial rotations of a porous disk and

T. Hayat; M. I. Hameed; S. Asghar; A. M. Siddiqui

2004-01-01

94

Hyperbolic field electron energy analyzer with second order focusing  

Microsoft Academic Search

Second order focusing is a desirable property of dispersion type electron energy analyzers because it allows a greater angular acceptance or, alternatively, higher energy resolution. We derive the second order focusing conditions for the hyperbolic field analyzer, which also allows a large range of energies to be collected in parallel, making it suitable for surface analysis techniques such as Auger

M. Jacka; A. Kale; N. Traitler

2003-01-01

95

At what energies are second order effects important?  

NASA Astrophysics Data System (ADS)

Over 20 years ago, Byron et al (J. Phys. B (1980) 13, L673) demonstrated that second order effects were important for impact energies as large as 250 eV. In that work, the projectile was treated as a plane wave and the closure approximation was used to perform the sum over intermediate states in the second order term. We have developed a second order distorted wave theory for atomic ionization which does not use closure but instead sums over all intermediate states. We have examined electron impact ionization of hydrogen and helium from the ground state, and found that second order effects are important for impact energies as high as 600 eV and that second order dominates the higher order effects (at least for smaller projectile deflection angles) down to about 100 eV impact energy.

Chen, Zhangjin; Madison, Don H.; Whelan, Colm T.; Walters, H. R. J.

2004-05-01

96

Anaerobic corrosion reaction kinetics of nanosized iron.  

PubMed

Nanosized Fe0 exhibits markedly different anaerobic corrosion rates in water compared to that disseminated in moist quartz sand. In water, hydrogen production from corrosion exhibits an autocatalytic style, attaining a maximum rate of 1.9 mol kg(-1) d(-1) within 2 d of reaction. The rate then drops sharply over the next 20 d and enters a period of uniformly decreasing rate, represented equally well by first-order or diffusion-controlled kinetic expressions. In quartz sand, hydrogen production exhibits a double maximum over the first 20 d, similar to the hydration reaction of Portland cement, and the highest rate attained is less than 0.5 mol kg(-1) d(-1). We ascribe this difference in early time corrosion behavior to the ability of the released hydrogen gas to convect both water and iron particles in an iron/water system and to its inability to do so when the iron particles are disseminated in sand. By 30 d, the hydrogen production rate of iron in quartz sand exhibits a uniform decrease as in the iron/water system, which also can be described by first-order or diffusion-controlled kinetic expressions. However, the corrosion resistance of the iron in moist sand is 4 times greater than in pure water (viz. t1/2 of 365 d vs 78 d, respectively). The lower rate for iron in sand is likely due to the effect of dissolved silica sorbing onto iron reaction sites and acting as an anodic inhibitor, which reduces the iron's susceptibility to oxidation by water. This study indicates that short-term laboratory corrosion tests of nanosized Fe0/water slurries will substantially underestimate both the material's longevity as an electron source and its potential as a long-term source of hydrogen gas in groundwater remediation applications. PMID:18504975

Reardon, Eric J; Fagan, Randal; Vogan, John L; Przepiora, Andrzej

2008-04-01

97

Kinetic modelling of the Maillard reaction between proteins and sugars  

Microsoft Academic Search

Keywords: Maillard reaction, sugar isomerisation, kinetics, multiresponse modelling, brown colour formation, lysine damage, mutagenicity, casein, monosaccharides, disaccharides, aldoses, ketosesThe aim of this thesis was to determine the kinetics of the Maillard reaction between proteins and sugars, taking into account other simultaneously occurring sugar reactions. Model systems of foods, consisting of the protein casein and various sugars in a buffered solution,

C. M. J. Brands

2002-01-01

98

'DO SECOND-ORDER ELECTIONS MAKE FOR SECOND-ORDER MEPS ? MEP RECRUITMENT IN BELGIUM 1979-99  

Microsoft Academic Search

The dominant paradigm has been to treat elections to the European Parliament as second - order national elections. Although patterns of candidate recruitment rather than the electorate's choice determine the composition of the EP, second-order elections arguably have an effect on the supply side. In analogy to Gresham, bad parliaments could be said to drive out good politicians. Prior research

Sam Depauw

99

A Numerical Method for Differential Equations of Second Order  

NASA Astrophysics Data System (ADS)

A new algorithm of order five is presented for the solution of the initial value problem where the system of ordinary differential equations is of second order and does not contain the first derivative.

Cui, Douxing; Huang, Tian-Yi

1993-04-01

100

First and second-order Raman scattering in nanocrystalline silicon  

Microsoft Academic Search

Confinement effects on first-order and second-order Raman scattering in nanocrystalline silicon are presented. The average dimension of the nanocrystals has been determined by an analysis of the first-order Raman spectra using the phenomenological phonon confinement model. The second-order acoustic bands 2LA and 2TA do not seem to be influenced by confinement effects and are similar to those in the bulk.

Puspashree Mishra; K. P. Jain

2001-01-01

101

Quantifier Elimination in Second-Order Predicate Logic  

Microsoft Academic Search

An algorithm is presented which eliminates second{order quantiers over predicate vari- ables in formulae of type 9P1; ... ;Pn where is an arbitrary formula of rst{order pred- icate logic. The resulting formula is equiva- lent to the original formula { if the algorithm terminates. The algorithm can for example be applied to do interpolation, to eliminate the second{order quantiers in

Dov M. Gabbay; Hans Jürgen Ohlbach

1992-01-01

102

Universality of second order transport in Gauss-Bonnet gravity  

NASA Astrophysics Data System (ADS)

We compute all the second order transport coefficients of a hydrodynamic theory with a gravity dual which includes a Gauss-Bonnet term. We find that a particular linear combination of the second order transport coefficients, which was found to vanish in generic two derivative gravity theories with matter, remains zero even in the presence of the Gauss-Bonnet term. We contrast this behavior with the shear viscosity to entropy density ratio.

Shaverin, Evgeny; Yarom, Amos

2013-04-01

103

Children’s Understanding of Second-Order Mental States  

Microsoft Academic Search

The most popular topic in theory-of-mind research has been first-order false belief: the realization that it is possible to hold false beliefs about events in the world. A more advanced development is second-order false belief: the realization that it is possible to hold a false belief about someone else’s belief. This article reviews research directed to second-order false belief and

Scott A. Miller

2009-01-01

104

Second order modeling of boundary-free turbulent shear flows  

Microsoft Academic Search

A set of realizable second order models for boundary-free turbulent flows is presented. The constraints on second order models based on the realizability principle are re-examined. The rapid terms in the pressure correlations for both the Reynolds stress and the passive scalar flux equations are constructed to exactly satisfy the joint realizability. All other model terms (return-to-isotropy, third moments, and

T.-H. Shih; Y.-Y. Chen; J. L. Lumley

1991-01-01

105

Relaxations in Second Order Nonlinear Optical Polymeric Systems  

Microsoft Academic Search

Second order nonlinear optical (NLO) materials are important for applications such as optical switching, frequency conversion, and electro-optic modulation. Polarized infrared reflection-absorption spectroscopy is employed as an approach to study the relaxation of the poled order in second order NLO materials using new characterization techniques. Both guest\\/host and photo-crosslinkable systems are investigated. This simple and common tool is used to

Jeng-I. Chen

1993-01-01

106

Second-order generalised beam theory for arbitrary orthotropic materials  

Microsoft Academic Search

The paper presents the formulation of a second-order Generalised Beam Theory (GBT) developed to analyse the buckling behaviour of composite thin-walled members made of laminated plates and displaying arbitrary orthotropy. The derived second-order GBT equations are compared with the Vlassov-type ones obtained by Bauld and Tzeng and a few remarks are made concerning the cross-section mechanical properties appearing in the

N. Silvestre; D. Camotim

2002-01-01

107

The Monadic Second-Order Logic of Graphs XII  

Microsoft Academic Search

We prove that we can specify by formulas of monadic second-order logic the unique planar embedding of a 3-connected planar graph. If the planar graph is not 3-connected but given with a linear order of its set of edges, we can also define a planar embedding by monadic second-order formulas. We cannot do so in general without the ordering, even

Bruno Courcelle

108

Second-Order Epi-Derivatives of Composite Functionals  

Microsoft Academic Search

We compute two-sided second-order epi-derivatives for certain composite functionals f=g?F where F is a C1 mapping between two Banach spaces X and Y, and g is a convex extended real-valued function on Y. These functionals include most essential objectives associated with smooth constrained minimization problems on Banach spaces. Our proof relies on our development of a formula for the second-order

A. B. Levy

2001-01-01

109

Second-order global optimality conditions for convex composite optimization  

Microsoft Academic Search

In recent years second-order sufficient conditions of an isolated local minimizer for convex composite optimization problems have been established. In this paper, second-order optimality conditions are obtained of aglobal minimizer for convex composite problems with a non-finite valued convex function and a twice strictly differentiable function by introducing a generalized representation condition. This result is applied to a minimization problem

Xiaoqi Yang

1998-01-01

110

On differential geometric formalization of chemical reaction kinetics statical aspects  

Microsoft Academic Search

In this article the basic mathematical structure of chemical reaction kinetics is investigated. For this purpose the methods of modern differential geometry are used. Using this approach the various aspects of species, reactions and stoichiometry can be separately treated.

L. Ropolyi; P. Réti

1984-01-01

111

Bimolecular kinetic studies with high-temperature gas-phase 19F NMR: cycloaddition reactions of fluoroolefins.  

PubMed

A gas-phase NMR kinetic technique has been used for the first time to obtain accurate measurements of rate constants of some bimolecular, second-order cycloaddition reactions. As a test of the potential use of this technique for the study of second-order reactions, the rate constants and the activation parameters for the cyclodimerization reactions of chlorotrifluoroethylene (CTFE) and tetrafluoroethylene (TFE) were determined in the temperature range 240-340 degrees C, using a commercial high-temperature NMR probe. Obtaining excellent agreement of the results with published data, the technique was then applied to the reaction of 1,1-difluoroallene with 1,3-butadiene, the results of which indicate that the use of gas-phase NMR for reaction kinetics is particularly valuable when a reagent is available only in small amounts and in cases where there are several competing processes occurring simultaneously. The major processes observed in this reaction are regioselective [2+2] and [2+4] cycloadditions, whose rates and activation parameters were determined [k2 = 9.3 x 10(6) exp(-20.1 kcal x mol(-1)/RT) L/mol(-1) x s(-1) and k3 = 1.2 x 10(6) exp(-18.4 kcal x mol(-1)/RT) L/mol(-1) x s(-)(1), respectively] in the temperature range 130-210 degrees C. PMID:11592874

Shtarov, A B; Krusic, P J; Smart, B E; Dolbier, W R

2001-10-17

112

Understanding Chemical Reaction Kinetics and Equilibrium with Interlocking Building Blocks  

ERIC Educational Resources Information Center

|Chemical reaction kinetics and equilibrium are essential core concepts of chemistry but are challenging topics for many students, both at the high school and undergraduate university level. Visualization at the molecular level is valuable to aid understanding of reaction kinetics and equilibrium. This activity provides a discovery-based method to…

Cloonan, Carrie A.; Nichol, Carolyn A.; Hutchinson, John S.

2011-01-01

113

Extension of second-order Stokes theory to variable bathymetry  

NASA Astrophysics Data System (ADS)

In the present work second-order Stokes theory has been extended to the case of a generally shaped bottom profile connecting two half-strips of constant (but possibly different) depths, initiating a method for generalizing the Stokes hierarchy of second- and higher-order wave theory, without the assumption of spatial periodicity. In modelling the wave bottom interaction three partial problems arise: the first order, the unsteady second order and the steady second order. The three problems are solved by using appropriate extensions of the consistent coupled-mode theory developed by the present authors for the linearized problem. Apart from the Stokes small-amplitude expansibility assumption, no additional asymptotic assumptions have been introduced. Thus, bottom slope and curvature may be arbitrary, provided that the resulting wave dynamics is Stokes-compatible. Accordingly, the present theory can be used for the study of various wave phenomena (propagation, reflection, diffraction) arising from the interaction of weakly nonlinear waves with a general bottom topography, in intermediate water depth. An interesting phenomenon, that is also very naturally resolved, is the net mass flux induced by the depth variation, which is consistently calculated by means of the steady second-order potential. The present method has been validated against experimental results and fully nonlinear numerical solutions. It has been found that it correctly predicts the second-order harmonic generation, the amplitude nonlinearity, and the amplitude variation due to non-resonant first-and-second harmonic interaction, up to the point where the energy transfer to the third and higher harmonics can no longer be neglected. Under the restriction of weak nonlinearity, the present model can be extended to treat obliquely incident waves and the resulting second-order refraction patterns, and to study bichromatic and/or bidirectional wave wave interactions, with application to the transformation of second-order random seas in variable bathymetry regions.

Belibassakis, K. A.; Athanassoulis, G. A.

2002-08-01

114

A joint experimental and theoretical investigation of kinetics and mechanistic study in a synthesis reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of benzhydrazide.  

PubMed

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine (TPP) and dialkyl acetylenedicarboxylates, in the presence of NH-acids, such as benzhydrazide. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometery. The second order fits were automatically drawn and the values of the second order rate constant (k(2)) were calculated using standard equations within the program. At the temperature range studied the dependence of the second order rate constant (Ln k(2)) on reciprocal temperature was compatible with Arrhenius equation. This provided the relevant plots to calculate the activation energy of all reactions. Furthermore, useful information were obtained from studies of the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates) and also concentration of reactants on the rate of reactions. On the basis of experimental data the proposed mechanism was confirmed according to the obtained results and a steady state approximation and the first step (k(2)) and third (k(3)) steps of the reactions were recognized as the rate determining steps, respectively. In addition, three speculative proposed mechanisms were theoretically investigated using quantum mechanical calculation. The results, arising from the second and third speculative mechanisms, were far from the experimental data. Nevertheless, there was a good agreement between the theoretical kinetic data, emerge from the first speculative mechanism, and experimental kinetic data of proposed mechanism. PMID:22752542

Kazemian, Mohammad Amin; Habibi-Khorassani, Sayyed Mostafa; Ebrahimi, Ali; Maghsoodlou, Malek Taher; Jahani, Peyman Mohammadzadeh; Ghahramaninezhad, Mahbobeh

2012-07-03

115

Current issues in sol-gel reaction kinetics  

SciTech Connect

This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative features of the reaction kinetics can depend on catalyst concentration. At very high acid-catalyst concentrations, reverse are significant for TMOS sol-gels, while for moderate acid-catalyst concentrations, reverse reactions are substantially reduced. The reaction kinetics are substantially reduced. The reaction kinetics of two similar tetraalkoxysilanes: tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), can be markedly different under identical reaction conditions. Under acid-catalyzed reaction conditions, a TMOS sol-gel undergoes both water-and alcohol-producing condensation reactions while a TEOS sol-gel undergoes only water-producing condensation. The early time hydrolysis and condensation reactions of a TMOS sol-gel are statistical in nature and can be quantitatively described by a few simple reaction rate constants while the reaction behavior of a TEOS sol-gel is markedly nonstatistical. A comprehensive theory of sol-gel kinetics must address diverse experimental findings. 9 refs., 3 figs., 1 tab.

Assink, R.A.; Kay, B.D.

1990-01-01

116

Children's understanding of second-order mental states.  

PubMed

The most popular topic in theory-of-mind research has been first-order false belief: the realization that it is possible to hold false beliefs about events in the world. A more advanced development is second-order false belief: the realization that it is possible to hold a false belief about someone else's belief. This article reviews research directed to second-order false belief and other forms of higher order, recursive mentalistic reasoning. Three general issues are considered. Research directed to developmental changes indicates that preschoolers typically fail second-order tasks and that success emerges at about age 5 or 6, although results vary some with method of assessment. Research directed to the consequences of second-order competence has revealed positive relations with a number of other aspects of children's development. Finally, measures of both language and executive function relate positively to performance on second-order tasks; the causal bases for the correlations, however, remain to be established. This article concludes with suggestions for future research. PMID:19702381

Miller, Scott A

2009-09-01

117

Second-Order Olfactory-Mediated Fear-Potentiated Startle  

PubMed Central

Recently, we reported that discrete (4-sec) olfactory cues paired with footshock serve as effective conditioned stimuli (CSs) for potentiating the acoustic startle response in rats using the fear-potentiated startle paradigm. Because odors are such salient cues for the rat, and because of the robust olfactory conditioning observed previously, the current studies investigated second-order fear conditioning using olfactory and visual cues. In Experiments 1 and 2, we used a small number of first-order and second-order training trials on separate days to investigate second-order fear-potentiated startle. Significant potentiated startle was observed in animals receiving Paired/Paired training in both studies, but surprisingly, control animals in the Unpaired/Paired group (Exp. 1) also showed significant potentiated startle to a light S2 at testing. These findings are addressed in the Discussion. Overall, the results of both experiments suggest that olfactory cues serve as efficient S1 and S2 stimuli in second-order fear-potentiated startle paradigms when only a small number of first and second-order training trials are presented.

Paschall, Gayla Y.; Davis, Michael

2002-01-01

118

Second-order quasinormal mode of the Schwarzschild black hole  

SciTech Connect

We formulate and calculate the second-order quasinormal modes (QNMs) of a Schwarzschild black hole (BH). Gravitational waves (GW) from a distorted BH, the so-called ringdowns, are well understood as QNMs in general relativity. Since QNMs from binary BH mergers will be detected with a high signal-to-noise ratio by GW detectors, it is also possible to detect the second perturbative order of QNMs, generated by nonlinear gravitational interaction near the BH. In the BH perturbation approach, we derive the master Zerilli equation for the metric perturbation to second order and explicitly regularize it at the horizon and spatial infinity. We numerically solve the second-order Zerilli equation by implementing the modified Leaver continued fraction method. The second-order QNM frequencies are found to be twice the first-order ones, and the GW amplitude is up to {approx}10% that of the first order for the binary BH mergers. Since the second-order QNMs always exist, we can use their detections (i) to test the nonlinearity of general relativity, in particular, the no-hair theorem, (ii) to remove fake events in the data analysis of QNM GWs, and (iii) to measure the distance to the BH.

Nakano, Hiroyuki [Center for Computational Relativity and Gravitation, School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York 14623 (United States); Ioka, Kunihito [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)

2007-10-15

119

Development of a Second Order Closure Model for Computation of Turbulent Diffusion Flames.  

National Technical Information Service (NTIS)

A typical eddy box model for the second-order closure of turbulent, multispecies, reacting flows developed. The model structure was quite general and was valid for an arbitrary number of species. For the case of a reaction involving three species, the nin...

A. K. Varma C. D. Donaldson

1974-01-01

120

Second-order nonlinear silicon-organic hybrid waveguides.  

PubMed

We describe a concept for second-order nonlinear optical processes in silicon photonics. A silicon-organic hybrid (SOH) double slot waveguide is dispersion-engineered for mode phase-matching (MPM). The proposed waveguide enables highly efficient nonlinear processes in the mid-IR range. With a cladding nonlinearity of ?(2) = 230 pm/V and 20 dBm pump power at a CW wavelength of 1550 nm, we predict a gain of 14.7 dB/cm for a 3100 nm signal. The suggested structure enables for the first time efficient second-order nonlinear optical mixing in silicon photonics with standard technology. PMID:23037098

Alloatti, L; Korn, D; Weimann, C; Koos, C; Freude, W; Leuthold, J

2012-08-27

121

Second-order coupling between excited atoms and surface polaritons  

NASA Astrophysics Data System (ADS)

Casimir-Polder interactions between an atom and a macroscopic body are typically regarded as being due to the exchange of virtual photons. This is strictly true only at zero temperature. At finite temperatures, real-photon exchange can provide a significant contribution to the overall dispersion interaction. Here, we describe a resonant two-photon process between an atom and a planar interface. We derive a second-order effective Hamiltonian to explain how atoms can couple resonantly to the surface polariton modes of the dielectric medium. This leads to second-order energy exchanges which we compare with the standard nonresonant Casimir-Polder energy.

Ribeiro, Sofia; Buhmann, Stefan Y.; Scheel, Stefan

2013-04-01

122

Second order flavor perturbation theory for the baryons  

SciTech Connect

In this paper, the authors argue that second order flavor perturbation theory may still have some interesting things to say about low energy QCD Application is made to the technical, but important, question of cleanly extracting the quark mass difference ratio R = [m[sub s][minus](m[sub d] + m[sub u])/2]/(m[sub d][minus]m[sub u]) from the experimental baryon masses. The authors also give a group theoretical decomposition of the second order contributions according to the SU(3) representation of the intermediate states. This is used to provide constraints on quantum mechanics type models of the nucleon.

Schechter, J.; Subbaraman, A. (Syracuse Univ., NY (United States). Dept. of Physics)

1992-11-10

123

Second Order “FLAVOR” Perturbation Theory for the Baryons  

NASA Astrophysics Data System (ADS)

We argue that second order flavor perturbation theory may still have some interesting things to say about low energy QCD. Application is made to the technical, but important, question of cleanly extracting the quark mass difference ratio R= [ms-(md+mu)/2]/(md-mu) from the experimental baryon masses. We also give a group theoretical decomposition of the second order contributions according to the SU(3) representation of the intermediate states. This is used to provide constraints on quantum mechanics type models of the nucleon.

Schechter, J.; Subbaraman, A.

124

Second order secular planetary theory for the four major planets  

NASA Astrophysics Data System (ADS)

In the present generalization of the Kamel and Bakry (1982) results for a second-order Jupiter-Saturn planetary theory, so that they may be applied to the Jupiter, Saturn, Uranus and Neptune four-planet system, the Von Zeipel method is used. Powers higher than the third with respect to the eccentricities and sines of the inclinations in the present expansions are neglected, and only the critical terms are considered as periodic. Attention is given to second-order secular terms arising from the indirect part of the disturbing function, as well as the secular part arising from the principal part of the disturbing function.

Kamel, O. M.; Bakry, A. A.

1984-10-01

125

Elasto-plastic model with second order defect density tensor  

NASA Astrophysics Data System (ADS)

The paper deals with a second order finite elasto-plastic model, which involves the defect density tensor, as a measure of the extra material defects existing in the damaged microstructure. The material behaviour is described with respect to an anholonomic configuration, which is introduced through the second order plastic deformation, consisting in plastic distortion and plastic connection. The defect density tensor enters the expression of the plastic connection through its gradient and represents a measure of non-metricity. The constitutive and evolution equations are derived to be compatible with the free energy imbalance. The evolution equation for the defect density tensor is non-local and coupled with the plastic distortion.

Cleja-?igoiu, Sanda

2011-05-01

126

Second-order Talbot effect with entangled photon pairs  

SciTech Connect

The second-order Talbot effect is analyzed for a periodic object illuminated by entangled photon pairs in both the quantum imaging and quantum lithography configurations. The Klyshko picture is applied to describe the quantum imaging scheme, in which self-images of the object that may or may not be magnified can be observed nonlocally in the photon coincidences but not in the singles count rate. In the quantum lithography setup, we find that the second-order Talbot length is half that of the classical first-order case, thus the resolution may be improved by a factor of 2.

Luo Kaihong; Chen Xihao; Liu Qian; Wu Lingan [Laboratory of Optical Physics, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wen Jianming; Xiao Min [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

2009-10-15

127

Chemical kinetics of the gas-phase reaction between uranium hexafluoride and hydrogen  

SciTech Connect

A study was made of the chemical kinetics of the homogeneous gas-phase reaction between uranium hexafluoride and hydrogen by measuring the rate of disappearance of UF/sub 6/. It has been concluded that the rate-limiting step for which the kinetics have been measured is UF/sub 6/ + HF + H (2). The reaction has been studied in a steady-state flow system over a temperature range of approx.625 to 825 K. Various surface-to-volume ratios were employed to aid in distinguishing gas-phase reactions from surface reactions. The steady-state concentration of the UF/sub 6/ after reaction with H/sub 2/ was monitored in a special multipass infrared spectrophotometer at the 626-cm/sup -1/ absorption band of UF/sub 6/. The principal problems were corrosion, plugging, surface intrusion, and the deleterious effects of minute traces of water; these problems have greatly slowed progress in this field. Several series of measurements involving different initial species concentrations and residence times, with each series at constant temperature, show that the rate is first order in UF/sub 6/. Our measurements yield a dependable Arrhenius curve in terms of a second-order expression for k, the bimolecular specific reaction rate constant for the disappearance of UF/sub 6/. It is believed that this overall rate of the disappearance of UF/sub 6/ is somewhat less than twice that of the critical reaction step 2, indicated above, so that the specific reaction rate constant k/sub 2/ is approx.8.7 c 10/sup 14/ exp(-34550 kcal/RT) cm/sup 3/ mol/sup -1/ s/sup -1/. Conclusions have been reached concerning the relative importance of the various elementary reaction steps involved in the chemical mechanism.

Myerson, A.L. (Mote Marine Lab., Sarasota, FL); Chludzinski, J.J. Jr.

1981-12-10

128

A general model of reaction kinetics in biological systems.  

PubMed

Dynamic mathematical models in biotechnology require, besides the information about the stoichiometry of the biological reaction system, knowledge about the reaction kinetics. Modulation phenomena like limitation, inhibition and activation occur in different forms of competition with the key enzymes responsible for the respective metabolic reaction steps. The identification of a priori unknown reaction kinetics is often a critical task due to the non-linearity and (over-) parameterization of the model equations introduced to account for all the possible modulation phenomena. The contribution of this paper is to propose a general formulation of reaction kinetics, as an extension of the Michaelis-Menten kinetics, which allows limitation/activation and inhibition effects to be described with a reduced number of parameters. The versatility of the new model structure is demonstrated with application examples. PMID:15986214

Haag, J E; Vande Wouwer, A; Remy, M

2005-06-29

129

High Temperature Reaction Kinetics of Boron Oxides.  

National Technical Information Service (NTIS)

Kinetics experiments performed under this contract show a much larger rate of H+OH recombination at high temperature (1500-2500K ) when phosphine combustion products are present in the gas mixture. A kinetic mechanism has been developed for phosphorus spe...

A. J. Twarowski

1994-01-01

130

Wolfe type second-order symmetric duality in nondifferentiable programming  

NASA Astrophysics Data System (ADS)

A pair of Wolfe type second-order symmetric dual programs involving nondifferentiable functions is considered and appropriate duality theorems are established under [eta]1-bonvexity/[eta]2-boncavity. Several known results including that of Mond and Gulati et al. are obtained as special cases.

Gulati, T. R.; Gupta, Shiv Kumar

2005-10-01

131

Comparing Conditional Quantile Estimators: First and Second Order Considerations  

Microsoft Academic Search

In this paper, we examine first and second order asymptotic theory for two estimatorsin a linear quantile model in the case where the response is observed multiple timesat fixed covariate vectors x 1; \\\\Delta \\\\Delta \\\\Delta ; x k . The first estimator is the regression quantile estimatorintroduced by Koenker and Bassett (1978) while the second estimator is a leastsquares

Keith Knight

132

Linear second-order divergence equations in Lipschitz domains  

NASA Astrophysics Data System (ADS)

In this paper we generalize gradient estimates in Lp spaces to Orlicz spaces for weak solutions of second-order divergence elliptic equations with small BMO coefficients in Lipschitz domains. Our results improve the known results for such equations using the harmonic analysis method.

Yao, Fengping; Zhou, Shulin

2008-08-01

133

The topology of symmetric, second-order tensor fields  

Microsoft Academic Search

We study the topology of symmetric, second-order tensor fields. The goal is to represent their complex structure by a simple set of carefully chosen points and lines analogous to vector field topology. We extract topological skeletons of the eigenvector fields, and we track their evolution over time. We study tensor topological transitions and correlate tensor and vector data.The basic constituents

Thierry Delmarcelle; Lambertus Hesselink

1994-01-01

134

Motion of Ellipsoids in a Second Order Fluid.  

National Technical Information Service (NTIS)

The rigid body motion of an ellipsoid in a second order fluid (SOF) under the action of specified (time independent) external forces and torques have been obtained to first order in the Weissenberg number by inverting the resistance relations for the forc...

S. Kim

1985-01-01

135

Second-Order Conditioning of Human Causal Learning  

ERIC Educational Resources Information Center

|This article provides the first demonstration of a reliable second-order conditioning (SOC) effect in human causal learning tasks. It demonstrates the human ability to infer relationships between a cause and an effect that were never paired together during training. Experiments 1a and 1b showed a clear and reliable SOC effect, while Experiments…

Jara, Elvia; Vila, Javier; Maldonado, Antonio

2006-01-01

136

Noise Performance of Second-Order Bidirectional Associative Memory  

Microsoft Academic Search

SUMMARY This paper describes the error probability of the second order BAM estimated by a computer simulation and an analytical calculation method. The computer simulation suggests that the iterations to retrieve a library pattern almost converge within four times and the difference between once and twice is much larger than that between twice and four times. The error probability at

Yutaka KAWABATA; Yoshimasa DAIDO; Shimmi HATTORI

1999-01-01

137

Modeling Ability Differentiation in the Second-Order Factor Model  

ERIC Educational Resources Information Center

In this article we present factor models to test for ability differentiation. Ability differentiation predicts that the size of IQ subtest correlations decreases as a function of the general intelligence factor. In the Schmid-Leiman decomposition of the second-order factor model, we model differentiation by introducing heteroscedastic residuals,…

Molenaar, Dylan; Dolan, Conor V.; van der Maas, Han L. J.

2011-01-01

138

PREDICTIONS OF HIGHWAY EMISSIONS BY A SECOND ORDER CLOSURE MODEL  

EPA Science Inventory

The dispersion of sulfur hexafluoride tracer and sulfate from automobile emissions in the immediate vicinity of a highway were estimated for conditions similar to those existing during the General Motors sulfate dispersion experiment conducted at a GM test track. A second-order c...

139

Solving Second-Order Differential Equations with Variable Coefficients  

ERIC Educational Resources Information Center

|A method is developed in which an analytical solution is obtained for certain classes of second-order differential equations with variable coefficients. By the use of transformations and by repeated iterated integration, a desired solution is obtained. This alternative method represents a different way to acquire a solution from classic power…

Wilmer, A., III; Costa, G. B.

2008-01-01

140

Second-order accurate difference schemes on highly irregular meshes  

SciTech Connect

In this paper compact-as-possible second-order accurate difference schemes will be constructed for boundary-value problems of arbitrary order on highly irregular meshes. It will be shown that for equations of order (K) these schemes will have truncation error of order (3/endash/K). This phenomena is known as supraconvergence. 7 refs.

Manteuffel, T.A.; White, A.B. Jr.

1988-01-01

141

Composite plasticity based on matrix average second order stress moment  

Microsoft Academic Search

An effective stress of a ductile matrix is defined directly from the average second order stress moment. It is evaluated exactly provided that an estimation of the composite effective moduli is given. On the basis of this effective stress and the secant moduli concept originally proposed by Berveiller and Zaoui (Berveiller, M. and Zaoui, A. (1979). An extension of the

Gengkai Hu

1997-01-01

142

Stochastic groundwater flow modeling using the second-order method  

Microsoft Academic Search

Stochastic groundwater flow modeling by means of a second-order uncertainty analysis technique is discussed. This technique is based on a Taylor series expansion of the state variables of interest (hydraulic heads and Darcian velocities) about the expected values of the model parameters. The method has been incorporated into the computer code PORSTAT, which solves the two-dimensional stochastic groundwater flow equation

B. Sagar; P. M. Clifton

1984-01-01

143

Forward and Backward Second-Order Pavlovian Conditioning in Honeybees  

ERIC Educational Resources Information Center

|Second-order conditioning (SOC) is the association of a neutral stimulus with another stimulus that had previously been combined with an unconditioned stimulus (US). We used classical conditioning of the proboscis extension response (PER) in honeybees ("Apis mellifera") with odors (CS) and sugar (US). Previous SOC experiments in bees were…

Hussaini, Syed Abid; Komischke, Bernhard; Menzel, Randolf; Lachnit, Harald

2007-01-01

144

A uniformly second order fast sweeping method for eikonal equations  

NASA Astrophysics Data System (ADS)

A uniformly second order method with a local solver based on the piecewise linear discontinuous Galerkin formulation is introduced to solve the eikonal equation with Dirichlet boundary conditions. The method utilizes an interesting phenomenon, referred as the superconvergence phenomenon, that the numerical solution of monotone upwind schemes for the eikonal equation is first order accurate on both its value and gradient when the solution is smooth. This phenomenon greatly simplifies the local solver based on the discontinuous Galerkin formulation by reducing its local degrees of freedom from two (1-D) (or three (2-D), or four (3-D)) to one with the information of the gradient frozen. When considering the eikonal equation with point-source conditions, we further utilize a factorization approach to resolve the source singularities of the eikonal by decomposing it into two parts, either multiplicatively or additively. One part is known and captures the source singularities; the other part serves as a correction term that is differentiable at the sources and satisfies the factored eikonal equations. We extend the second order method to solve the factored eikonal equations to compute the correction term with second order accuracy, then recover the eikonal with second order accuracy. Numerical examples are presented to demonstrate the performance of the method.

Luo, Songting

2013-05-01

145

STATISTICAL INFERENCES BASED ON A SECOND-ORDER POSSIBILITY DISTRIBUTION  

Microsoft Academic Search

A new, general method of statistical inference is proposed. It encompasses all the coherent forms of statistical inference that can be derived from a Bayesian prior distribution, Bayesian sensitivity analysis or upper and lower prior probabilities. The method is to model prior uncertainty about statistical parameters in terms of a second-order possibility distribution (a special type of upper probability) which

PETER WALLEY

1997-01-01

146

Center Points in Second—Order Response Surface Designs  

Microsoft Academic Search

Previous approaches for selecting the number of center points in a second-order response surface design are explained, and an integrated variance criterion is offered. Calculations extending results in the literature are made for various composite and Box-Behnken designs for 2 ? k ? 8. The results are compared and discussed and indicate that fewer center points than initially recommended are

Norman R. Draper

1982-01-01

147

Modeling Ability Differentiation in the Second-Order Factor Model  

ERIC Educational Resources Information Center

|In this article we present factor models to test for ability differentiation. Ability differentiation predicts that the size of IQ subtest correlations decreases as a function of the general intelligence factor. In the Schmid-Leiman decomposition of the second-order factor model, we model differentiation by introducing heteroscedastic residuals,…

Molenaar, Dylan; Dolan, Conor V.; van der Maas, Han L. J.

2011-01-01

148

Second-order complex random vectors and normal distributions  

Microsoft Academic Search

Complex random vectors are usually described by their covariance matrix. This is insufficient for a complete description of second-order statistics, and another matrix called the relation matrix is necessary. Some of its properties are analyzed and used to express the probability density function of normal complex vectors. Various consequences are presented

B. Picinbono

1996-01-01

149

Second Order Necessary Conditions for Optimal Impulsive Control Problems  

Microsoft Academic Search

First and second order necessary conditions of optimality for an impulsive control problem are presented and derived. One of the main features of these results is that no a priori normality assumptions are required and they are informative for abnormal control processes as well. This feature follows from the fact that the conditions are derived from an extremal principle, which

A. Arutyunov; V. Ja?imovi?; F. Pereira

2003-01-01

150

SECOND{ORDER CONDITIONS IN EXTREMAL PROBLEMS. THE ABNORMAL POINTS  

Microsoft Academic Search

In this paper we study a minimization problem with constraints and obtain rst- and second-order necessary conditions for a minimum. Those conditions { as opposed to the known ones { are also informative in the ab- normal case. We have introduced the class of 2-normal constraints and shown that for them the \\\\gap\\

A. V. ARUTYUNOV

151

SECOND ORDER NECESSARY CONDITIONS FOR OPTIMAL IMPULSIVE CONTROL PROBLEMS  

Microsoft Academic Search

Abstract. First and second order necessary conditions of optimali- ty for an impulsive control problem are presented and derived. One of the main features of these results is that no a priori normality assumptions are required and they are informative for abnormal con- trol processes as well. This feature follows fromthe fact that the conditions are derived froman extremal principle,

A. Arutyunov; V. Ja Cimovic; F. Pereira

2003-01-01

152

The Expressiveness of Simple and Second-Order Type Structures  

Microsoft Academic Search

Typed lambda (?`-) calculi provtde convement mathematical settings in which to investigate the effects of type structure on the function definmon mechamsm m programming languages. Lambda expressaons mtm~c programs that do not use while loops or carcular function definitions. Two typed ?`-calculi are investigated, the sunply typed ?`-calculus, whose types are similar to Pascal types, and the second-order typed ?,-calculus,

Steven Fortune; Daniel Leivant; Michael O'Donnell

1983-01-01

153

Low Power Thermal Tuning of Second-order Microring Resonators  

Microsoft Academic Search

Efficient thermal tuning of 36 pm\\/K and 60 muW\\/GHz is shown for high-index-contrast silicon nitride second-order filters. Their compact size, large free-spectral range, low tuning power, and silicon compatibility make these resonators attractive for photonic integration.

R. Amatya; C. W. Holzwarth; M. A. Popovic; F. Gan; H. I. Smith; F. Kartner; R. J. Ram

2007-01-01

154

Second-order sloshing over an arbitrary bed  

Microsoft Academic Search

The two-dimensional problem of the free sloshing of an inviscid fluid in a vertically walled tank with an arbitrary bed shape is solved at both first and second order in the Stokes expansion of the velocity potential. The approach employed at both orders uses Green's functions for a flat bed in conjunction with the Cauchy-Riemann equations to derive integral equations

G. J. D. Chapman; R. Porter

2005-01-01

155

A second order multiconfiguration SCF procedure with optimum convergence  

Microsoft Academic Search

An MCSCF procedure is described which is based on the direct minimization of an approximate energy expression which is periodic and correct to second order in the changes in the orthonormal orbitals. Within this approximation, the CI coefficients are fully optimized, thereby accounting for the coupling between orbital rotations and CI coefficients to higher order than in previous treatments. Additional

Hans-Joachim Werner; Peter J. Knowles

1985-01-01

156

Remarks on the second-order Seiberg-Witten maps  

SciTech Connect

In this brief report, we discuss the Seiberg-Witten maps up to the second order in the noncommutative parameter {theta}. They add to the recently published solutions in [A. Alboteanu, T. Ohl, and R. Rueckl, Phys. Rev. D 76, 105018 (2007).]. Expressions for the vector, fermion, and Higgs fields are given explicitly.

Trampetic, Josip [Theoretical Physics Division, Rudjer Boskovic Institute, Zagreb (Croatia); Wohlgenannt, Michael [Erwin Schroedinger International Institute for Mathematical Physics, Boltzmanngasse 9, 1090 Vienna (Austria)

2007-12-15

157

Artificial Second Order Non-Linearity in Photonic Crystals.  

National Technical Information Service (NTIS)

We describe a technique for obtaining effective second order non- linearity X(sup 2) in non-centro-symmetric Photonic Crystal made from centro- symmetric materials (e.g., glass, Ge or Si). The effect is based on the electric quadrupole transition, strong ...

A. Feigel B. Sfez Z. Kotler

2002-01-01

158

Kinetics and mechanism of reactions of the drug tiopronin with platinum(IV) complexes.  

PubMed

Tiopronin, a synthetic thiol-containing drug being used in treatments of cystinuria and certain types of rare arthritis, is also a hepatoprotective and a detoxifying agent. Many analytical methods have been developed based on its redox chemistry with metal ions/complexes, but the kinetic and mechanistic aspects are poorly understood. In this work, the oxidation of tiopronin by cisplatin prodrug and a model compound, cis-[Pt(NH3)2Cl4] and trans-[PtCl2(CN)4](2-), was investigated. The oxidation kinetics was followed by a stopped-flow spectrophotometer over a wide pH range under the pseudo first-order conditions of [Tiopronin]?[Pt(IV)]. Time-resolved spectra were also recorded for both Pt(IV) complexes, enabling to establish an overall second-order rate law: -d[Pt(IV)]/dt=k'[Tiopronin][Pt(IV)], where k' pertains to observed second-order rate constants. Under the kinetic conditions, tiopronin was oxidized to form the tiopronin-disulfide exclusively as identified by mass spectrometry. A reaction mechanism was proposed, involving parallel reductions of the Pt(IV) complexes by the three protolytic tiopronin species as rate-determining steps. The rate constants for the rate-determining steps were derived. The fully deprotonated tiopronin is about 4×10(4) more reactive than its corresponding thiol form for both Pt(IV) complexes; the huge reactivity difference orchestrates closely with the fact that the nucleophilicity of thiolate is much higher than the corresponding thiol. Hence, the attack of the sulfur atom in thiol/thiolate of tiopronin on the axially-coordinated chloride in the Pt(IV) complexes is nucleophilic in nature in the rate-determining steps, resulting in a bridge formation and a subsequent bridged electron-transfer. PMID:23665090

Huo, Shuying; Shi, Hongmei; Liu, Dongzhi; Shen, Shigang; Zhang, Jiong; Song, Changying; Shi, Tiesheng

2013-04-19

159

Current issues in sol-gel reaction kinetics.  

National Technical Information Service (NTIS)

This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative f...

R. A. Assink B. D. Kay

1990-01-01

160

Kinetic Study of the Heck Reaction: An Interdisciplinary Experiment  

ERIC Educational Resources Information Center

|The aim of this experiment is to study and calculate the kinetic constant of a Heck reaction: the arylation of but-3-en-2-ol by iodobenzene catalyzed by palladium acetate in presence of triethylamine in DMF. The reaction leads to a mixture of two ketones. Students use GC analysis to quantify reagents and products of reaction. They control the…

Gozzi, Christel; Bouzidi, Naoual

2008-01-01

161

Kinetic and theoretical study of the reaction of Cl atoms with a series of linear thiols  

SciTech Connect

The reactions of Cl with a series of linear thiols: 1-propanethiol (k{sub 1}), 1-butanethiol (k{sub 2}), and 1-pentanethiol (k{sub 3}) were investigated as a function of temperature (in the range of 268-379 K) and pressure (in the range of 50-200 Torr) by laser photolysis-resonance fluorescence. Only 1-propanethiol has previously been studied, but at 1 Torr of total pressure. The derived Arrhenius expressions obtained using our kinetic data were as follows: k{sub 1}=(3.97{+-}0.44)x10{sup -11} exp[(410{+-}36)/T], k{sub 2}=(1.01{+-}0.16)x10{sup -10} exp[(146{+-}23)/T], and k{sub 3}=(1.28{+-}0.10)x10{sup -10} exp[(129{+-}25)/T] (in units of cm{sup 3} molecule{sup -1} s{sup -1}). Moreover, a theoretical insight into mechanisms of these reactions has also been pursued through ab initio Moeller-Plesset second-order perturbation treatment calculations with 6-311G** basis set. Optimized geometries have been obtained for transition states and molecular complexes appearing along the different reaction pathways. Furthermore, molecular energies have been calculated at QCISD(T) level in order to get an estimation of the activation energies. Finally, the nature of the molecular complexes and transitions states is analyzed by using kinetic-potential and natural bond orbital total energy decomposition schemes.

Garzon, Andres; Albaladejo, Jose [Departamento de Quimica Fisica, Facultad de CC. Quimicas, Universidad de Castilla La Mancha, Avenida Camilo Jose Cela, s/n, 13071 Ciudad Real (Spain); Notario, Alberto [Departamento de Quimica Fisica, Instituto de Tecnologias Quimica y Medioambiental (ITQUIMA), Universidad de Castilla La Mancha, Avenida Camilo Jose Cela, s/n, 13071 Ciudad Real (Spain); Pena-Ruiz, Tomas; Fernandez-Gomez, Manuel [Departamento de Quimica Fisica y Analitica, Facultad de CC. Experimentales, Universidad de Jaen, Paraje las Lagunillas, s/n, 23071 Jaen (Spain)

2008-11-21

162

Laboratory Kinetics of Chemical Reactions occurring in Astrophysical Environments  

Microsoft Academic Search

To model the dynamics and molecular evolution of interstellar clouds, a great deal of information on chemical kinetics is required, preferably under the appropriate conditions of kinetic temperature and internal excitation. This kinetics includes (i) gas phase ionic (ion-molecule and electron-ion) and (ii) neutral-neutral reactions and (iii) heterogeneous surface catalysis, all from simple species to those as complex as polyaromatic

N. G. Adams; L. M. Babcock

2005-01-01

163

Second-Order Arguments for Second-Order Elections? Measuring “Election Stakes” in a Multilevel Context: The Case of Norway  

Microsoft Academic Search

Low turnout and the prevalence of national arena motivation in sub- and supranational elections are claimed to be due to voters perceiving that less is “at stake” in second-order national elections. The article asks whether voters' differential assessments of election stakes when confronted with elections to different representative institutions are evidence of electoral sophistication. In the context of Norwegian elections

Bjørn Ervik

2012-01-01

164

Reaction Kinetics: An Experiment for Biochemistry and Organic Chemistry Laboratories.  

ERIC Educational Resources Information Center

Describes an experiment to examine the kinetics of carbamate decomposition and the effect of buffer catalysis on the reaction. Includes background information, laboratory procedures, evaluation of data, and teaching suggestions. (Author/JN)

Ewing, Sheila

1982-01-01

165

Kinetics of Acid Reactions: Making Sense of Associated Concepts  

ERIC Educational Resources Information Center

In chemical kinetics, in addition to the concepts related to kinetics, stoichiometry, chemical equilibrium and the characteristics of the reactants are often involved when comparing the rates of different reactions, making such comparisons very challenging for students at all levels, as well as for pre-service science teachers. Consequently, four…

Tan, Kim Chwee Daniel; Treagust, David F.; Chandrasegaran, A. L.; Mocerino, Mauro

2010-01-01

166

Kinetics of Acid Reactions: Making Sense of Associated Concepts  

ERIC Educational Resources Information Center

|In chemical kinetics, in addition to the concepts related to kinetics, stoichiometry, chemical equilibrium and the characteristics of the reactants are often involved when comparing the rates of different reactions, making such comparisons very challenging for students at all levels, as well as for pre-service science teachers. Consequently, four…

Tan, Kim Chwee Daniel; Treagust, David F.; Chandrasegaran, A. L.; Mocerino, Mauro

2010-01-01

167

Gel-free experiments of reaction-diffusion front kinetics  

NASA Astrophysics Data System (ADS)

We present a gel-free experimental system to study the kinetics of the reaction front in the A+B-->C reaction-diffusion system with initially-separated reactants. The experimental setup consists of a CCD camera monitoring the kinetics of the front formed in the reaction-diffusion process Cu2++ tetra [disodium ethyl bis(5-tetrazolylazo) acetate trihydrate] -->1:1 complex, in aqueous, gel-free solution, taking place inside a 150 ?m gap between two flat microscope slides. The experimental results agree with the theoretical predictions for the time dependence of the front's width, height, and location, as well as the global reaction rate.

Park, Sung Hyun; Parus, Stephen; Kopelman, Raoul; Taitelbaum, Haim

2001-11-01

168

Second-order refraction and diffraction of surface water waves  

NASA Astrophysics Data System (ADS)

The mild-slope equation is an effective approximation for treating the combined effects of refraction and diffraction of infinitesimal water waves, for it reduces the spatial dimension of the linear boundary-value problem from three to two. We extend this approximation to nonlinear waves up to the second order in wave steepness, in order to simplify the inherently three-dimensional task. Assuming that the geometrical complexity is restricted to a finite, though large, horizontal domain, the hybrid-element method designed earlier for linearized problems is modified for the two-dimensional elliptic boundary-value problems at the second order. In the special case of a semi-circular peninsula (or a vertical cylinder on a cliff) in a sea of constant depth, the solution is analytical. Effects of the angle of incidence are examined for the free-surface height along the cylinder. For a cylinder standing on a shoal of radially varying depth, numerical results are discussed.

Chen, Meng-Yi; Mei, Chiang C.

2006-04-01

169

Inefficient visual search for second-order motion.  

PubMed

Visual search rate was used to assess attentional resources required for detection of opposing motions defined either by luminance or by modulations of texture contrast, flicker, or size. Though luminance-based targets were detected quickly, search through second-order motion was slow. Control experiments ruled out stimuli visibility, complexity, eccentricity sensitivity, and attributes of the carrier as possible accounts. Results suggest separate processing of the two types of stimuli: Luminance-based motion is detected by spatiotemporal filters, whereas second-order motion is likely processed by a capacity-limited, later stage. Rate-reducing effects of increased contrast and speed mirrored previous research suggesting that effortful feature tracking may be the mechanism. PMID:11551060

Ashida, H; Seiffert, A E; Osaka, N

2001-09-01

170

First- and second-order charged particle optics  

SciTech Connect

Since the invention of the alternating gradient principle there has been a rapid evolution of the mathematics and physics techniques applicable to charged particle optics. In this publication we derive a differential equation and a matrix algebra formalism valid to second-order to present the basic principles governing the design of charged particle beam transport systems. A notation first introduced by John Streib is used to convey the essential principles dictating the design of such beam transport systems. For example the momentum dispersion, the momentum resolution, and all second-order aberrations are expressed as simple integrals of the first-order trajectories (matrix elements) and of the magnetic field parameters (multipole components) characterizing the system. 16 references, 30 figures.

Brown, K.L.; Servranckx, R.V.

1984-07-01

171

Second-order amplitudes in loop quantum gravity  

NASA Astrophysics Data System (ADS)

We explore some second-order amplitudes in loop quantum gravity. In particular, we compute some second-order contributions to diagonal components of the graviton propagator in the large distance limit, using the old version of the Barrett-Crane vertex amplitude. We illustrate the geometry associated with these terms. We find some peculiar phenomena in the large distance behavior of these amplitudes, related to the geometry of the generalized triangulations dual to the Feynman graphs of the corresponding group field theory. In particular, we point out a possible further difficulty with the old Barrett-Crane vertex: it appears to lead to flatness instead of Ricci flatness, at least in some situations. The observation raises the question whether this difficulty remains with the new version of the vertex.

Mamone, Davide; Rovelli, Carlo

2009-12-01

172

Second-order statistical properties of quantum chaotic beams  

SciTech Connect

We consider the situation in which the field of quantum particles such as photons (bosons) or electrons (fermions) undergoes a significant attenuation during the detection process. We characterize the second-order statistical properties of the field by the bunching for bosons and the antibunching for fermions. Bunching and antibunching effects are derived from the time intervals distributions of the random point process of detection instead of the moments of the number of particles registered in a given time interval. Fields of both beams are supposed to be in chaotic states and have second-order time correlation functions of exponential profile and of arbitrary correlation time. A test is proposed for nonclassical states: the behavior of the antibunching function is a nondecreasing function near the origin of the time axis.

Bendjaballah, C.; Pourmir, M. [Laboratoire des Signaux et Systemes, CNRS and Ecole Superieure d'Electricite, 3 rue Joliot-Curie, 91192 Gif-sur-Yvette (France); Departement des Telecommunications, Ecole Superieure d'Electricite, 3 rue Joliot-Curie, 91192 Gif-sur-Yvette (France)

2009-05-15

173

A Second-Order Achromat Design Based on FODO Cell  

SciTech Connect

Two dipole doglegs are widely used to translate the beam axis horizontally or vertically. Quadrupoles are placed between the two consecutive dipoles to match first order dispersion and provide betatron focusing. Similarly a four dipole chicane is usually employed to form a bypass region, where the beam axis is transversely shifted first, then translated back to the original axis. In order to generate an isochronous section, quadrupoles are again needed to tune the first order transfer matrix element R{sub 56} equaling zero. Usually sextupoles are needed to correct second order dispersion in the bending plane, for both the dogleg optics and the chicane (with quad) optics. In this paper, an alternative optics design is introduced, which is based on a simple FODO cell and does not need sextupoles assistance to form a second-order achromat. It may provide a similar function of either a dogleg or a bypass, by using 2 or 4 of such combined supercells.

Sun, Yipeng; /SLAC

2011-08-19

174

Second-order acceleration models for an MMAE target tracker  

NASA Astrophysics Data System (ADS)

The performance of a multiple model adaptive estimator (MMAE) for an enhanced correlator/forward-looking-infrared tracker for airborne targets is analyzed in order to improve its performance. Performance evaluation is based on elemental filter selection and MMAE estimation error sizes and trends. The elemental filters are based on either first or second-order acceleration models. Improved filter selection is achieved by using acceleration models that separate the frequency content of acceleration power spectral densities into non-overlapping regions with second-order models versus the more traditional overlapping regions with first-order models. A revised tuning method is presented. The maximum a posteriori (MAP) versus the Bayesian MMAE is investigated. The calculation of the hypothesis probability calculation is altered to see how performance is affected. The impact of the ad hoc selection of a lower bound on the elemental filter probability calculation to prevent filter lockout is evaluated. Parameter space discretization is investigated.

Wheaton, Barbara J.; Maybeck, Peter S.

1995-01-01

175

Reaction mechanism, kinetics and high temperature transformations of geopolymers  

Microsoft Academic Search

The reaction kinetics and mechanism of geopolymers are studied. The dissolved silicate concentration decreases from the beginning\\u000a of the reaction. A characteristic time ‘t\\u000a 0,vit’ for the setting of the reaction mixture is derived from isothermal Dynamic Mechanical Analysis experiments. ‘t\\u000a 0,vit’ increases with SiO2\\/R2O but goes through a minimum for increasing water content. The reaction is slower for K

H. Rahier; J. Wastiels; M. Biesemans; R. Willlem; G. Van Assche; B. Van Mele

2007-01-01

176

Formalizing Forcing Arguments in Subsystems of Second-Order Arithmetic  

Microsoft Academic Search

We show that certain model-theoretic forcing arguments involving sub- systems of second-order arithmetic can be formalized in the base the- ory, thereby converting them to eective proof-theoretic arguments. We use this method to sharpen conservation theorems of Harrington and Brown-Simpson, giving an eective proof that WKL+0 is conservative over RCA0 with no significant increase in the lengths of proofs.

Jeremy Avigad

1996-01-01

177

Comparison theorems for second order nonlinear difference equations  

Microsoft Academic Search

New oscillation results are obtained for the second order nonlinear difference equation ?(rnf(?xn?1))+g(n,xn)=0, and its functional form ?(rnf(?xn?1))+g(n,x?n)=0. The role played by the argument ?n on the oscillation of the functional equation is explored. In particular, we characterize a class of sequences {?n} which have a harmless effect on the oscillation of this type of equations. Some of our results

H ELMORSHEDY; S.R. Grace

2005-01-01

178

Second-order DOA estimation from digitally modulated signals  

Microsoft Academic Search

The paper deals with the problem of estimating the direction-of-arrival (DOA) of multiple digitally-modulated sources. This problem arises naturally when studying positioning applications in the context of cellular systems. The formulation of the optimal second-order tracker is found to depend on the transmitted symbols distribution for medium-to-high signal-to-noise ratios (SNR). Simulations show that the common Gaussian assumption yields significant losses

Javier Villares; G. Vazquez

2003-01-01

179

Efficient iterations for Gauss methods on second-order problems  

NASA Astrophysics Data System (ADS)

We consider some important aspects about the implementation of high order implicit formulas (specially the Gauss methods) for solving second-order differential systems having high frequencies and small amplitudes superimposed. The choice of an appropriate iterative scheme is discussed in detail. Important topics about the predictors (initial guesses) are analyzed and a variable order strategy to select the best predictor at each integration step is supplied. A few numerical experiments on some standard test problems confirm the theory presented.

Gonzalez-Pinto, S.; Perez-Rodriguez, S.; Rojas-Bello, R.

2006-05-01

180

Superquadric Glyphs for Symmetric Second-Order Tensors  

Microsoft Academic Search

Symmetric second-order tensor fields play a central role in scientific and biomedical studies as well as in image analysis and feature-extraction methods. The utility of displaying tensor field samples has driven the development of visualization techniques that encode the tensor shape and orientation into the geometry of a tensor glyph. With some exceptions, these methods work only for positive-definite tensors

Thomas Schultz; Gordon L. Kindlmann

2010-01-01

181

The Second Order Local-Image-Structure Solid  

Microsoft Academic Search

Characterization of second order local image structure by a 6D vector (or jet) of Gaussian derivative measurements is considered. We consider the affect on jets of a group of transformations—affine intensity-scaling, image rotation and reflection, and their compositions—that preserve intrinsic image structure. We show how this group stratifies the jet space into a system of orbits. Considering individual orbits as

Lewis D. Griffin

2007-01-01

182

Time Series Modeling by a Second-Order Hammerstein System  

Microsoft Academic Search

In this paper, we discuss the modeling of an observed time series as the output of a second-order Hammerstein model driven by an independent and identically distributed (i.i.d.) Gaussian noise. The modeling is discussed from the point of view of the hypothesis testing (HT) of statistical indexes derived from higher order statistics (HOS). Three points of view can be adopted

Jean-marc Le Caillec

2008-01-01

183

Smoothing Functions for Second-Order-Cone Complementarity Problems  

Microsoft Academic Search

Smoothing functions have been much studied in the solution of optimization and complementarityproblems with nonnegativity constraints. In this paper, we extend smoothing functions to problemswhere the nonnegative orthant is replaced by the direct product of second-order cones. Thesesmoothing functions include the Chen-Mangasarian class and the smoothed Fischer-Burmeisterfunction. We study the Lipschitzian and dierential properties of these functions and, in particular,we

Masao Fukushima; Zhi-Quan Luo; Paul Tseng

2002-01-01

184

Mixed hyperbolic-second-order-parabolic formulations of general relativity  

SciTech Connect

Two new formulations of general relativity are introduced. The first one is a parabolization of the Arnowitt-Deser-Misner formulation and is derived by the addition of combinations of the constraints and their derivatives to the right-hand side of the Arnowitt-Deser-Misner evolution equations. The desirable property of this modification is that it turns the surface of constraints into a local attractor because the constraint propagation equations become second-order parabolic independently of the gauge conditions employed. This system may be classified as mixed hyperbolic--second-order parabolic. The second formulation is a parabolization of the Kidder-Scheel-Teukolsky formulation and is a manifestly mixed strongly hyperbolic--second-order-parabolic set of equations, bearing thus resemblance to the compressible Navier-Stokes equations. As a first test, a stability analysis of flat space is carried out and it is shown that the first modification exponentially damps and smoothes all constraint-violating modes. These systems provide a new basis for constructing schemes for long-term and stable numerical integration of the Einstein field equations.

Paschalidis, Vasileios [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago Illinois 60637 (United States)

2008-07-15

185

Kinetic mechanism for modeling of electrochemical reactions  

NASA Astrophysics Data System (ADS)

We propose a kinetic mechanism of electrochemical interactions. We assume fast formation and recombination of electron donors D- and acceptors A+ on electrode surfaces. These mediators are continuously formed in the electrode matter by thermal fluctuations. The mediators D- and A+, chemically equivalent to the electrode metal, enter electrochemical interactions on the electrode surfaces. Electrochemical dynamics and current-voltage characteristics of a selected electrochemical system are studied. Our results are in good qualitative agreement with those given by the classical Butler-Volmer kinetics. The proposed model can be used to study fast electrochemical processes in microsystems and nanosystems that are often out of the thermal equilibrium. Moreover, the kinetic mechanism operates only with the surface concentrations of chemical reactants and local electric potentials, which facilitates the study of electrochemical systems with indefinable bulk.

?ervenka, Petr; Hrdli?ka, Ji?í; P?ibyl, Michal; Šnita, Dalimil

2012-04-01

186

Time-resolved gas-phase kinetic studies of the reaction of dimethylsilylene with triethylsilane-1-d: kinetic isotope effect for the Si-H insertion process.  

PubMed

Time-resolved kinetic studies of the reaction of dimethylsilylene, SiMe2, generated by laser flash photolysis of 1,1-dimethyl-1-silacyclopent-3-ene, have been carried out to obtain rate coefficients for its bimolecular reactions with trimethylsilane-1-d, Me3SiD. The reaction was studied in the gas phase at five temperatures in the range 292-605 K. The rate coefficients showed no pressure dependence in the presence of up to 13 kPa of SF6. The second order rate coefficients obtained at 0.7 kPa fitted the Arrhenius equation: log(k/cm(3) molecule(-1) s(-1)) = (-13.53 ± 0.19) + (11.29 ± 1.46) kJ mol(-1)/RT ln 10. By comparison with rate coefficients obtained previously for the reaction of SiMe2 with Me3SiH, a set of kinetic isotope effects, kH/kD, of value ca. 1.2 showing very little temperature dependence was obtained. Theoretical support for these values has been obtained by means of quantum chemical calculations used in conjunction with transition state theory. This study provides the first comprehensive set of kinetic isotope effects for the Si-H(D) insertion process of a silylene in the gas phase. PMID:23455034

Becerra, Rosa; Cannady, J Pat; Walsh, Robin

2013-04-21

187

Desulfurization of fuel oil by oxidation and extraction. Part 2; Kinetic modeling of oxidation reaction  

SciTech Connect

The oxidation of Arabian atmospheric gas oil (AGO) with nitric acid to remove sulfur from the oil is similar to the gradual processes involved in the storage instability of petroleum distillates and synfuels, except that in this process the instability process is accelerated by adding a strong oxidizing agent, nitric acid. The elemental composition of these sediments is compared. A mathematical kinetic model is presented to describe the kinetics of sulfur removal in the oxidation of AGO using a CSTR. This model employs lumping of the sulfur compounds in the oil into four groups according to their retention times (hence, boiling points) in the gas chromatograph, and residue (R) containing some of the other three sulfur groups. The first group had a very fast reaction rate. The second group reacts with second-order kinetics with a rate constant of 17 g of oil/(g of S2 {center dot} min) at 25{degrees}C. The third group was not present in the unoxidized oil, and as it was formed, it equilibrated between the oil and the residue phases.

Tan, P.S.; Eldridge, J.W. (Massachusetts Univ., Amherst, MA (USA). Dept. of Chemical Engineering); Kittrell, J.R. (KSE, Inc., Amherst, MA (US))

1990-03-01

188

Reaction kinetics of hydrothermal carbonization of loblolly pine.  

PubMed

Hydrothermal carbonization (HTC) is a pretreatment process to convert diverse feedstocks to homogeneous energy-dense solid fuels. Understanding of reaction kinetics is necessary for reactor design and optimization. In this study, the reaction kinetics and effects of particle size on HTC were investigated. Experiments were conducted in a novel two-chamber reactor maintaining isothermal conditions for 15s to 30 min reaction times. Loblolly pine was treated at 200, 230, and 260°C. During the first few minutes of reaction, the solid-product mass yield decreases rapidly while the calorific value increases rapidly. A simple reaction mechanism is proposed and validated, in which both hemicellulose and cellulose degrade in parallel first-order reactions. Activation energy of hemicellulose and cellulose degradation were determined to be 30 and 73 kJ/mol, respectively. For short HTC times, both reaction and diffusion effects were observed. PMID:23651600

Reza, M Toufiq; Yan, Wei; Uddin, M Helal; Lynam, Joan G; Hoekman, S Kent; Coronella, Charles J; Vásquez, Victor R

2013-04-15

189

Evaluated Chemical Kinetic Rate Constants for Various Gas Phase Reactions  

Microsoft Academic Search

The available information, up to mid-1972, for the rate constants of a series of gas phase chemical reactions has been evaluated critically. For each reaction, relevant thermodynamic data are presented and values for the equilibrium constant expressed in mathematical form. Kinetic data are presented in tabular and graphical form together with a discussion of the pertinent details. Recommended rate constant

Keith Schofield

1973-01-01

190

The Reaction of a Food Colorant with Sodium Hypochlorite: A Student-Designed Kinetics Experiment  

NASA Astrophysics Data System (ADS)

The kinetics of the reaction of the food colorant FD&C Blue #1 with sodium hypochlorite (Clorox) is described in a student-designed experimental format. In this format, students are guided- by means of questions- to make decisions regarding concentration of reagents, choice of equipment, and actual laboratory procedures to be followed. This format provides an opportunity for students to apply the concepts and skills learned in class and in previous laboratory sessions to a new problem. We have found that this experience helps students gain depth of understanding of all concepts involved. The reaction (with a large excess of NaOCl) is followed with a Spectronic 20 at the Blue #1 colorant lmax of 630 nm. The %T is measured over time and three graphs: A vs time, ln A vs time and 1/A vs time are plotted to find that the second one is linear and thus first order with respect to the Blue #1. When the concentration of NaOCl is reduced to one-half the original value, it is found that the rate is reduced by one-half, indicating that the reaction is first order with respect to NaOCl and second order overall. The rate constant of the reaction is determined from the slope of the curve and the mean obtained by our students is 17 M-1 min-1 at room temperature (about 28° C).

Arce, Josefina; Betancourt, Rosa; Rivera, Yamil; Pijem, Joan

1998-09-01

191

Kinetic Analysis of Sequential Multi-step Reactions  

PubMed Central

Many processes in biology and chemistry involve multi-step reactions or transitions. The kinetic data associated with these reactions are manifested by superpositions of exponential decays that are often difficult to dissect. Two major challenges have hampered the kinetic analysis of multi-step chemical reactions: (1) Reliable and unbiased determination of the number of reaction steps, (2) Stable reconstruction of the distribution of kinetic rate constants. Here, we introduce two numerically stable integral transformations to solve these two challenges. The first transformation enables us to deduce the number of rate-limiting steps from kinetic measurements, even when each step has arbitrarily distributed rate constants. The second transformation allows us to reconstruct the distribution of rate constants in the multi-step reaction using the phase function approach, without fitting the data. We demonstrate the stability of the two integral transformations by both analytic proofs and numerical tests. These new methods will help providing robust and unbiased kinetic analysis for many complex chemical and biochemical reactions.

Zhou, Yajun; Zhuang, Xiaowei

2009-01-01

192

Fluid flow and chemical reaction kinetics in metamorphic systems  

SciTech Connect

The treatment and effects of chemical reaction kinetics during metamorphism are developed along with the incorporation of fluid flow, diffusion, and thermal evolution. The interplay of fluid flow and surface reaction rates, the distinction between steady state and equilibrium, and the possible overstepping of metamorphic reactions are discussed using a simple analytic model. This model serves as an introduction to the second part of the paper, which develops a reaction model that solves the coupled temperature-fluid flow-chemical composition differential equations relevant to metamorphic processes. Consideration of stable isotopic evidence requires that such a kinetic model be considered for the chemical evolution of a metamorphic aureole. A general numerical scheme is discussed to handle the solution of the model. The results of this kinetic model allow us to reach several important conclusions regarding the factors controlling the chemical evolution of mineral assemblages during a metamorphic event. 41 refs., 19 figs., 5 tabs.

Lasaga, A.C.; Rye, D.M. (Yale Univ., New Haven, CT (United States))

1993-05-01

193

Superquadric glyphs for symmetric second-order tensors.  

PubMed

Symmetric second-order tensor fields play a central role in scientific and biomedical studies as well as in image analysis and feature-extraction methods. The utility of displaying tensor field samples has driven the development of visualization techniques that encode the tensor shape and orientation into the geometry of a tensor glyph. With some exceptions, these methods work only for positive-definite tensors (i.e. having positive eigenvalues, such as diffusion tensors). We expand the scope of tensor glyphs to all symmetric second-order tensors in two and three dimensions, gracefully and unambiguously depicting any combination of positive and negative eigenvalues. We generalize a previous method of superquadric glyphs for positive-definite tensors by drawing upon a larger portion of the superquadric shape space, supplemented with a coloring that indicates the quadratic form (including eigenvalue sign). We show that encoding arbitrary eigenvalue magnitudes requires design choices that differ fundamentally from those in previous work on traceless tensors that arise in the study of liquid crystals. Our method starts with a design of 2-D tensor glyphs guided by principles of scale-preservation and symmetry, and creates 3-D glyphs that include the 2-D glyphs in their axis-aligned cross-sections. A key ingredient of our method is a novel way of mapping from the shape space of three-dimensional symmetric second-order tensors to the unit square. We apply our new glyphs to stress tensors from mechanics, geometry tensors and Hessians from image analysis, and rate-of-deformation tensors in computational fluid dynamics. PMID:20975202

Schultz, Thomas; Kindlmann, Gordon L

194

Second order distorted wave calculations for electron impact ionization processes  

NASA Astrophysics Data System (ADS)

Electron impact ionization of atoms provides a fundamental test of the current understanding of atomic structure as well as our understanding of the three body problem. Triple differential cross sections (TDCS), measured in the coincidence experiment, provide the most sensitive test of the theory of electron impact ionization processes. It was found two decades ago that second-order effects were crucial in explaining both the positions and magnitudes of the binary and recoil peaks in the TDCS. However, the existing theoretical calculations of second-order amplitudes typically resort to simplifying approximations, such as the closure approximation or neglecting the real part of the Green's function, to make the calculation tractable. In this work, we have developed a second-order distorted wave (DWB2) theory for atomic ionization which does not make these approximations. The DWB2 theory has been used to calculate the TDCS for electron impact ionization of hydrogen. It is found that the DWB2 results are in good agreement with absolute experimental measurements for incident energy greater than 100 eV. We have also performed DWB2 calculations for electron impact ionization of helium with the residual ion left in the n=1 and 2 states at intermediate energies in coplanar asymmetric geometry. Both the neutral and ionic distorting potentials are employed for the projectile in the final state. It has been found that the DWB2 results with the ionic distorting potential are in better agreement with experiment for the case in which the residual ion is left in the excited states. We have also performed the calculations to check the validity of the closure approximation and the simplified Green's function approximation and found that these approximations are not accurate for non-coplanar geometry and low incident energies.

Chen, Zhangjin

195

Comparison theorems for second order nonlinear difference equations  

Microsoft Academic Search

New oscillation results are obtained for the second order nonlinear difference equation [Delta](rnf([Delta]xn-1))+g(n,xn)=0, and its functional form [Delta](rnf([Delta]xn-1))+g(n,x[tau]n)=0. The role played by the argument [tau]n on the oscillation of the functional equation is explored. In particular, we characterize a class of sequences {[tau]n} which have a harmless effect on the oscillation of this type of equations. Some of our results

Hassan A. El-Morshedy; S. R. Grace

2005-01-01

196

Second order contributions to the absorption of massive particles  

SciTech Connect

Recently, in analogy with multiphoton ionization, it has been suggested that multiparticle ionization can also be induced by massive systems. We explore in this paper the possibility that multiparticle absorption processes can also take place for massive particles. To study it we consider, in a perturbative way, a model of absorption which illustrates the analogies with Glauber's scheme for photons and previous analysis on matter-waves coherence. A major advantage of this approach is that the dependence of the absorption rates on the wavefunction of the incident system can be analyzed in an explicit way. The calculations confirm the form of the second order (two particle) contributions.

Sancho, Pedro [GPV de Valladolid, Centro Zonal en Castilla y Leon, Orion 1, 47014, Valladolid (Spain)], E-mail: psancho@inm.es

2008-05-15

197

Second-order electromagnetic eigenfrequencies of a triaxial ellipsoid  

NASA Astrophysics Data System (ADS)

The dependence of the eigenvalues of the TM1n and TE1n electromagnetic triplet modes on the shape of a triaxial ellipsoid cavity resonator is investigated. For an ellipsoid with semi-axes proportional to 1 : (1 + epsilon1) : (1 + epsilon2) the fractional perturbations of the triplet components are found to second order in epsilon1 and epsilon2. The formulae are derived from the results of Kokkorakis and Roumeliotis (1997 J. Electromagn. Waves Appl. 11 279-92) for prolate and oblate spheroids. Finite-element calculations were carried out to confirm the accuracy of the formulae and to determine the next correction terms.

Mehl, James B.

2009-10-01

198

Forced oscillation of second order differential equations with mixed nonlinearities  

Microsoft Academic Search

This article is concerned with the oscillation of the forced second order differential equation with mixed nonlinearities(a(t)(x?(t))?)?+po(t)x?(go(t))+?i=1npi(t)|x(gi(t))|?isgnx(gi(t))=e(t) where ? is a quotient of odd positive integers, ?i > 0, i = 1, 2, …, n, a, e, andpi?C([0,?),?),a(t)>o,gi:??? are positive continuous functions on ? withlimt??gi(t)=?,i=0,1,…,n Our results generalize and improve the results in a recent article by Sun and Wong

Taher S. Hassan; Lynn Erbe; Allan Peterson

2011-01-01

199

Second-order MBPT results for the carbon isoelectronic sequence  

NASA Astrophysics Data System (ADS)

The electric quadrupole (E2) and magnetic dipole (M1) transitions between the levels of the 1s22s22p2, 1s22s2p3 and 1s22p4 configurations have been investigated in the carbon isoelectronic sequence. The stationary second-order many-body perturbation theory (MBPT) was used to account for electron correlations. Relativistic corrections were included within the Breit-Pauli approximation. The E2 and M1 transition energies, line strengths and transition probabilities obtained in various approximations are compared with experimental values as well as with results of other theoretical calculations.

Vilkas, M. J.; Martinson, I.; Merkelis, G.; Gaigalas, G.; Kisielius, R.

1996-09-01

200

P-stable boundary value methods for second order IVPs  

NASA Astrophysics Data System (ADS)

We introduce a family of Linear Multistep Methods used as Boundary Value Methods for the numerical solution of initial value problems for second order ordinary differential equations of special type. The aim is to obtain P-stable methods with arbitrary order of accuracy. This result allows to overcome the order barrier established by Lambert and Watson which limited to p = 2 the maximum order of a P-stable Linear Multistep Method. In addition, an extension of the methods in the Exponential Fitting framework is also considered.

Aceto, Lidia; Ghelardoni, Paolo; Magherini, Cecilia

2012-09-01

201

Second-order neutral impulsive stochastic evolution equations with delay  

NASA Astrophysics Data System (ADS)

In this paper, we study the second-order neutral stochastic evolution equations with impulsive effect and delay (SNSEEIDs). We establish the existence and uniqueness of mild solutions to SNSEEIDs under non-Lipschitz condition with Lipschitz condition being considered as a special case by the successive approximation. Furthermore, we give the continuous dependence of solutions on the initial data by means of corollary of the Bihari inequality. An application to the stochastic nonlinear wave equation with impulsive effect and delay is given to illustrate the theory.

Ren, Yong; Sun, Dandan

2009-10-01

202

Generalized modified gravity with the second-order acceleration equation  

NASA Astrophysics Data System (ADS)

In the theories of generalized modified gravity, the acceleration equation is generally fourth order. So, it is hard to analyze the evolution of the Universe. In this paper, we present a class of generalized modified gravity theories which have the acceleration equation of a second-order derivative. Then both the cosmic evolution and the weak-field limit of the theories are easily investigated. We find that, not only the big bang singularity problem, but also that the current cosmic acceleration problem could be easily dealt with.

Gao, Changjun

2012-11-01

203

Kinetics of reactions between aqueous sulfates and sulfides in hydrothermal systems  

Microsoft Academic Search

The rates of chemical reactions between aqueous sulfates and sulfides are essentially identical to sulfur isotopic exchange rates between them, because both the chemical and isotopic reactions involve simultaneous oxidation of sulfide-sulfur atoms and reduction of sulfate-sulfur. The rate of reaction can be expressed as a second order rate law: R = k ·[ SO 4 2- ]·[ S 2-

Hiroshi Ohmoto; Antonio C. Lasaga

1982-01-01

204

Adsorption Isotherms and Surface Reaction Kinetics  

ERIC Educational Resources Information Center

|Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)|

Lobo, L. S.; Bernardo, C. A.

1974-01-01

205

Low temperature kinetics of unstable radical reactions.  

PubMed

Recent advances in Earth and satellite based observations of molecules in interstellar environments and in planetary atmospheres have highlighted the lack of information regarding many important gas-phase formation mechanisms involving neutral species at low temperatures. Whilst significant progress has been made towards a better understanding of radical-molecule reactions in these regions, the inherent difficulties involved in the investigation of reactions between two unstable radical species have hindered progress in this area. This perspective article provides a brief review of the most common techniques applied to study radical-radical reactions below room temperature, before outlining the developments in our laboratory that have allowed us to extend such measurements to temperatures relevant to astrochemical environments. These developments will be discussed with particular emphasis on our recent investigations of the reactions of atomic nitrogen with diatomic radicals. PMID:22864404

Hickson, Kevin M; Bergeat, Astrid

2012-08-03

206

The Kinetic Rate Law for Autocatalytic Reactions.  

ERIC Educational Resources Information Center

Presented is a method of obtaining accurate rate constants for autocatalytic reactions. The autocatalytic oxidation of dimethylamine by permanganate ion in aqueous solution is used as an example. (RH)

Mata-Perez, Fernando; Perez-Benito, Joaquin F.

1987-01-01

207

From small-molecule reactions to protein folding: studying biochemical kinetics by stopped-flow electrospray mass spectrometry.  

PubMed

This work introduces stopped-flow electrospray ionization (ESI) mass spectrometry (MS) as a method for studying fast biochemical reaction kinetics. After initiating a reaction by rapid mixing of two solutions, the mixture is transferred to a reaction vessel and a steady liquid flow to the ESI source of the mass spectrometer is established. The kinetics are studied in real time by monitoring selected ion intensities as a function of time. In order to characterize the performance of this setup the acid-induced demetallation of chlorophyll a was studied. It was found that the reaction is second order in acid concentration and that pseudo-first-order rate constants of up to roughly 7 s(-1) can be measured reliably. Stopped-flow ESI MS was also applied to study the acid-induced denaturation of myoglobin. The data presented here confirm the occurrence of a short-lived unfolding intermediate during this reaction. Stopped-flow ESI MS can provide information that is not accessible by optical rapid-mixing experiments. Therefore it appears that this novel technique has the potential to become a standard tool for kinetic studies in a number of different fields. PMID:11319824

Kolakowski, B M; Konermann, L

2001-05-01

208

NMR Imaging Using Second Order Quadrupole Broadened Resonances.  

PubMed

Theoretical and experimental results for NMR imaging measurements of powdered materials using the +(1/2) to -(1/2) transition of (1/2)-integerspin nuclei in the presence of a very large second-order electric quadrupolar broadening are presented. An "effective spin-(1/2)" formalism is developed to account for additional effects due to the presence of quadrupolar interactions comparable in size to the Zeeman interaction. A large (7.9 mT/cm-A, with a maximum current of approximately 20 A), rapid ( approximately 30 µs) pulsed linear gradient field is used with echoes and phase encoding techniques to obtain images in the limit gammaH1 is much narrower than the NMR linewidth. A one-dimensional projection of the second-order quadrupolar perturbed, 4-MHz-wide, +(1/2) left and right arrow -(1/2) transition for 63Cu in Cu2O powder is presented as an example. An experimental one-dimensional projection of a sample containing Cu2O and YBa2Cu3O6.7 is also presented. Copyright 1998 Academic Press. PMID:9632553

Swaminathan; Suits

1998-06-01

209

Stochastic evaluation of second-order Dyson self-energies.  

PubMed

A stochastic method is proposed that evaluates the second-order perturbation corrections to the Dyson self-energies of a molecule (i.e., quasiparticle energies or correlated ionization potentials and electron affinities) directly and not as small differences between two large, noisy quantities. With the aid of a Laplace transform, the usual sum-of-integral expressions of the second-order self-energy in many-body Green's function theory are rewritten into a sum of just four 13-dimensional integrals, 12-dimensional parts of which are evaluated by Monte Carlo integration. Efficient importance sampling is achieved with the Metropolis algorithm and a 12-dimensional weight function that is analytically integrable, is positive everywhere, and cancels all the singularities in the integrands exactly and analytically. The quasiparticle energies of small molecules have been reproduced within a few mEh of the correct values with 10(8) Monte Carlo steps. Linear-to-quadratic scaling of the size dependence of computational cost is demonstrated even for these small molecules. PMID:23635115

Willow, Soohaeng Yoo; Kim, Kwang S; Hirata, So

2013-04-28

210

Stochastic evaluation of second-order Dyson self-energies  

NASA Astrophysics Data System (ADS)

A stochastic method is proposed that evaluates the second-order perturbation corrections to the Dyson self-energies of a molecule (i.e., quasiparticle energies or correlated ionization potentials and electron affinities) directly and not as small differences between two large, noisy quantities. With the aid of a Laplace transform, the usual sum-of-integral expressions of the second-order self-energy in many-body Green's function theory are rewritten into a sum of just four 13-dimensional integrals, 12-dimensional parts of which are evaluated by Monte Carlo integration. Efficient importance sampling is achieved with the Metropolis algorithm and a 12-dimensional weight function that is analytically integrable, is positive everywhere, and cancels all the singularities in the integrands exactly and analytically. The quasiparticle energies of small molecules have been reproduced within a few mEh of the correct values with 108 Monte Carlo steps. Linear-to-quadratic scaling of the size dependence of computational cost is demonstrated even for these small molecules.

Willow, Soohaeng Yoo; Kim, Kwang S.; Hirata, So

2013-04-01

211

Ozonation Kinetics Of o-phenylphenol in Aqueous Solutions  

Microsoft Academic Search

This study investigated the oxidation and reaction kinetics of biocide o-phenylphenol (o-PP) during ozonation. The second-order rate constants for direct reaction of molecular ozone with o-PP were determined in homogenous system using classical and competition kinetics. Obtained values of the second-order rate at pH 2 are equal to (3.79 ± 0.23)?×?10 M s and (4.42 ± 0.64)?×?10 M s, for

Magdalena Olak-Kucharczyk; Jacek S. Miller; Stanis?aw Ledakowicz

2012-01-01

212

Kinetic analysis of the fluorescence reaction of histamine with orthophthalaldehyde.  

PubMed

Histamine reacts with orthophthalaldehyde (OPA) in an alkaline medium to form an unstable fluorescent adduct (Fbase). Acidification of the solution gives a stable adduct (Facid). In order to elucidate the mechanism of this fluorescence reaction, a kinetic study of this reaction was carried out. Although Fbase was believed to be the precursor of Facid, it was shown not to be the precursor of Facid owing to the effects of the reaction time in an alkaline medium and OPA concentration on the yields of Fbase and Facid. The kinetic analysis of the formation and degradation of Fbase revealed the pathway of the fluorescence reaction. On the basis of the results obtained in this study, the mechanism of the fluorescence reaction is proposed. PMID:3674363

Yoshimura, T; Kaneuchi, T; Miura, T; Kimura, M

1987-07-01

213

Kinetic analysis of protein modification reactions at equilibrium.  

PubMed Central

A kinetic analysis is presented of reactions of protein modification, and/or of modification-induced enzyme inactivation, which can formally be described by a single exponential function, or by a summation of two exponential functions, of reaction time plus a constant term. The reaction schemes compatible with the kinetic formalism of these cases are given, and a simple kinetic criterion is described whereby the identification of one of these cases, strong negative protein modification co-operativity, may be carried out. The treatment outlined in this paper is applied to a case from the literature, the inactivation of glyceraldehyde-3-phosphate dehydrogenase by butane-2,3-dione [Asriyants, Benkevich & Nagradova (1983) Biokhimiya (Engl. Transl.) 48, 164-171].

Rakitzis, E T

1989-01-01

214

Programmable calculator and kinetics of chemical reactions  

Microsoft Academic Search

This paper suggests the use of simulation techniques using a programmable calculator in the study of chemical reactions.† This article does not deal with the use of programmable calculations for producing ‘experimental’ data (i.e. as a substitute for the laboratory). Readers interested in that direction may refer to [1]. Also, I would like to thank E. W. Jenkins of the

Amos Ehrlich

1980-01-01

215

Insights into the "free state" enzyme reaction kinetics in nanoconfinement.  

PubMed

The investigation of enzyme reaction kinetics in nanoconfined spaces mimicking the conditions in living systems is of great significance. Here, a nanofluidics chip integrated with an electrochemical detector has been designed for studying "free state" enzyme reaction kinetics in nanoconfinement. The nanofluidics chip is fabricated using the UV-ablation technique developed in our group. The enzyme and substrate solutions are simultaneously supplied from two single streams into a nanochannel through a Y-shaped junction. The laminar flow forms in the front of the nanochannel, then the two liquids fully mix at their downstream where a homogeneous enzyme reaction occurs. The "free state" enzyme reaction kinetics in nanoconfinement can thus be investigated in this laminar flow based nanofluidics device. For demonstration, glucose oxidase (GOx) is chosen as the model enzyme, which catalyzes the oxidation of beta-d-glucose. The reaction product hydrogen peroxide (H2O2) can be electrochemically detected by a microelectrode aligning to the end of nanochannel. The steady-state electrochemical current responding to various glucose concentrations is used to evaluate the activity of the "free state" GOx under nanoconfinement conditions. The effect of liquid flow rate, enzyme concentration, and nanoconfinement on reaction kinetics has been studied in detail. Results show that the "free state" GOx activity increases significantly compared to the immobilized enzyme and bath system, and the GOx reaction rate in the nanochannel is two-fold faster than that in bulk solution, demonstrating the importance of "free state" and spatial confinement for the enzyme reaction kinetics. The present approach provides an effective method for exploiting the "free state" enzyme activity in nanospatial confinement. PMID:23429726

Wang, Chen; Ye, De-Kai; Wang, Yun-Yi; Lu, Tao; Xia, Xing-Hua

2013-04-21

216

The Kinetics of the Hydrogen, Fluorine Reaction. II. The Oxygen-Inhibited Reaction.  

National Technical Information Service (NTIS)

The kinetics of the thermal, gaseous hydrogen-fluorine reaction were investigated by a colorimetric technique. The reaction was found to be inhibited by oxygen and the inhibited reaction was studied mainly at 132C, but also from 122 to 162C. The experimen...

J. B. Levy B. K. W. Copeland

1964-01-01

217

Communication: Explicitly correlated four-component relativistic second-order Møller-Plesset perturbation theory  

NASA Astrophysics Data System (ADS)

We propose explicitly correlated Ansatz for four-component relativistic methods within the framework of the no-pair approximation. Kinetically balanced geminal basis is derived to satisfy the cusp conditions in the non-relativistic limit based on the Lévy-Leblend-like equation. Relativistic variants of strong-orthogonality projection operator (Ansätze 2? and 2?) suitable for practical calculations are introduced by exploiting the orthogonal complement of the large-component basis. A pilot implementation is performed for the second order Møller-Plesset perturbation theory.

Ten-no, Seiichiro; Yamaki, Daisuke

2012-10-01

218

Reaction of silylene with sulfur dioxide: some gas-phase kinetic and theoretical studies.  

PubMed

Time-resolved kinetic studies of the reaction of silylene, SiH2, with SO2 have been carried out in the gas phase over the temperature range 297-609 K, using laser flash photolysis to generate and monitor SiH2. The second order rate coefficients at 1.3 kPa (SF6 bath gas) fitted the Arrhenius equation: log(k/cm(3) molecule(-1) s(-1)) = (-10.10 ± 0.06) + (3.46 ± 0.45 kJ mol(-1))/RT?ln?10 where the uncertainties are single standard deviations. The collisional efficiency is 71% at 298 K, and in kinetic terms the reaction most resembles those of SiH2 with CH3CHO and (CH3)2CO. Quantum chemical calculations at the G3 level suggest a mechanism occurring via addition of SiH2 to one of the S[double bond, length as m-dash]O double bonds leading to formation of the three-membered ring, thione-siloxirane which has a low energy barrier to ring expansion to yield the four-membered ring, 3-thia-2,4-dioxasiletane, the lowest energy adduct found on the potential energy (PE) surface. RRKM calculations, however, show that, if formed, this molecule would only be partially stabilised under the reaction conditions and the rate coefficients would be pressure dependent, in contrast with experimental findings. The G3 calculations reveal the complexity of possible intermediates and end products and taken together with the RRKM calculations indicate the most likely end products to be H2SiO + SO ((3)?(-)). The reaction is compared and contrasted with that of SiH2 + CO2. PMID:23903751

Becerra, Rosa; Cannady, J Pat; Goldberg, Nicola; Walsh, Robin

2013-08-14

219

Comparison of the Biological Health of two Second Order Streams  

NASA Astrophysics Data System (ADS)

Similarly to other towns, Columbia, Missouri is experiencing growth through the development of its outlying land. The future development of 500 acres of land that span two second order stream's watersheds produces the possibility of significant altering of the biological structure of these streams. In order to show this change, benthic macroinvertebrates were collected in order to determine the current ecological structure of the stream. The streams have both similar topography and stream bed composition, allowing for straightforward comparison. Four sample sites on each stream were chosen and samples from each stream taken in November, January, and March of 2004-2005. This paper attempts to compare the biological health of these streams using the benthic macroinvertebrate ecological structure found through the sampling.

Knobbe, N. J.; Weaver, D.

2005-05-01

220

Communications: Ab initio second-order nonlinear optics in solids.  

PubMed

We present a first-principles theory for the calculation of the macroscopic second-order susceptibility chi((2)), based on the time-dependent density-functional theory approach. Our method allows to include straightforwardly the many-body effects, such as crystal local fields and excitons. We apply the theory to the computation of the second-harmonic generation spectroscopy. In order to demonstrate the accuracy of this approach we present spectra for the cubic semiconductor GaAs for which we obtain a very good agreement with the experimental results. We point out that crystal local fields are not sufficient to reproduce the experimental results. Only when we account for the excitonic effects we obtain a very good agreement with the experimental second-harmonic generation spectrum. PMID:20590173

Luppi, Eleonora; Hübener, Hannes; Véniard, Valérie

2010-06-28

221

Optical Pulse Deformation in Second Order Nonlinear Media  

NASA Astrophysics Data System (ADS)

The deformation of optical pulses in one dimensional lossless second order nonlinear media is considered. Using a KdV-type of equation, with dispersion determined by the material properties, the deformation of a bichromatic initial signal is studied. An explicit expression for a third order approximation is used and the maximal temporal amplitude MTA is investigated. This MTA is obtained by looking at the maximum over time of the amplitude at each position. It is shown that modulations of the carrier waves and of the envelopes of the bound and free third order terms determine respectively the oscillations and the recurrence of the MTA curve. We will illustrate the explicit formula with numerical displays for the characteristic cases.

Andonowati; van Groesen, E.

222

Switched-capacitor second-order noise-shaping coder  

NASA Astrophysics Data System (ADS)

The tests of the feasibility of a switched-capacitor second-order noise-shaping coder (SCSONSC) for high resolution conversion are reported along with its application to PCM coders. The general principles and the switched capacitor realization of the coder are described. The SCSONSC can be used in conjunction with a digital signal processor in order to eliminate the outband noise before subsampling, and with two digital processors for the realization of a digital PCM coder with filters. By using the switch capacitor technique, the coder sensitivity can be reduced to variations in the internal clock generators. It is noted that the SCSONSC does not require any trimming of components, and that the performances achieved using a one-bit noise coder were as good as those obtained using a conventional 13-bit coder.

Lainey, G.; Saintlaurens, R.; Senn, P.

1983-02-01

223

Second-Order Analysis of Semiparametric Recurrent Event Processes  

PubMed Central

Summary A typical recurrent event dataset consists of an often large number of recurrent event processes, each of which contains multiple event times observed from an individual during a followup period. Such data have become increasingly available in medical and epidemiological studies. In this paper, we introduce novel procedures to conduct second-order analysis for a flexible class of semiparametric recurrent event processes. Such an analysis can provide useful information regarding the dependence structure within each recurrent event process. Specifically, we will use the proposed procedures to test whether the individual recurrent event processes are all Poisson processes and to suggest sensible alternative models for them if they are not. We apply these procedures to a well-known recurrent event dataset on chronic granulomatous disease and an epidemiological dataset on Meningococcal disease cases in Merseyside, UK to illustrate their practical value.

Guan, Yongtao

2011-01-01

224

Weak Galerkin methods for second order elliptic interface problems  

NASA Astrophysics Data System (ADS)

Weak Galerkin methods refer to general finite element methods for partial differential equations (PDEs) in which differential operators are approximated by their weak forms as distributions. Such weak forms give rise to desirable flexibilities in enforcing boundary and interface conditions. A weak Galerkin finite element method (WG-FEM) is developed in this paper for solving elliptic PDEs with discontinuous coefficients and interfaces. Theoretically, it is proved that high order numerical schemes can be designed by using the WG-FEM with polynomials of high order on each element. Extensive numerical experiments have been carried out to validate the WG-FEM for solving second order elliptic interface problems. High order of convergence is numerically confirmed in both L2 and L? norms for the piecewise linear WG-FEM. Special attention is paid to solve many interface problems, in which the solution possesses a certain singularity due to the nonsmoothness of the interface. A challenge in research is to design nearly second order numerical methods that work well for problems with low regularity in the solution. The best known numerical scheme in the literature is of order O(h) to O(h1.5) for the solution itself in L? norm. It is demonstrated that the WG-FEM of the lowest order, i.e., the piecewise constant WG-FEM, is capable of delivering numerical approximations that are of order O(h1.75) to O(h2) in the L? norm for C1 or Lipschitz continuous interfaces associated with a C1 or H2 continuous solution.

Mu, Lin; Wang, Junping; Wei, Guowei; Ye, Xiu; Zhao, Shan

2013-10-01

225

Kinetics and mechanism of the hypochlorous Acid-trithionate reaction.  

PubMed

The trithionate-hypochlorous acid reaction has been studied by the stopped-flow technique and conventional spectrophotometry between pH = 6.59-12.2 monitoring absorbance-time profiles at 285 and 225 nm. We showed that the formal kinetic order of Cl(I) is nearly 2; however, those of hydrogen ion and trithionate are significantly lower than unity, suggesting complex kinetics. It was also demonstrated that both forms of Cl(I) are kinetically active within the concentration range studied. Simultaneous evaluation of the kinetic curves revealed that the reaction was initiated by a formal Cl(+) transfer to the partially negatively charged ?-sulfur of trithionate. S3O6Cl(-) formed in the first step was also found to be equilibrating with S3O6OH(-) via a simple chlorine-OH exchange reaction followed by their subsequent oxidation of hypochlorite and hypochlorous acid, respectively. A six-step kinetic model is proposed and discussed with having four fitted and four fixed parameters. PMID:24000830

Csek?, György; Rauscher, Evelin; Horváth, Attila K

2013-09-03

226

Lignin peroxidase compounds II and III. Spectral and kinetic characterization of reactions with peroxides.  

PubMed

Stopped-flow techniques were used to investigate the kinetics of the reaction of lignin peroxidase compounds II and III (LiPII and LiPIII) with peroxides. Rate data were obtained from single-turnover experiments under pseudo-first-order conditions. LiPII reacts with H2O2 or peracetic acid (AcOOH) to form a modified LiPIII, designated as LiPIII*, via a biphasic reaction. During the first phase, LiPIII is formed as an intermediate. Kinetic analysis also indicates a LiPII-peroxide complex. The first-order dissociation rate constants for the reaction of LiPII with H2O2 and AcOOH are 7.9 +/- 0.5 and 4.9 +/- 0.6 s-1, respectively. The rate of the H2O2 reaction is approximately 500 times the rate of the comparable reaction with horseradish peroxidase, suggesting it is physiologically significant. The activation energy for the formation of LiPIII is 23 kJ mol-1. During the second phase, the intermediate LiPIII is converted to LiPIII*, confirmed by analyzing the reaction of exogenously prepared LiPIII with peroxides. The second-order rate constants for the reaction of LiPIII with H2O2 and AcOOH are (3.7 +/- 0.2) x 10(2) M-1 s-1 and (2.9 +/- 0.2) x 10(2) M-1 s-1, respectively. The conversion of LiPIII to LiPIII* is reversible; the first-order rate constant for the reverse reaction is approximately (6.6 +/- 0.6) x 10(-2) s-1. The rates of both LiPIII and LiPIII* formation decrease markedly above pH 4.0. The pH dependence of these reactions is controlled by a heme-linked ionizable group of pK alpha congruent to 4.2. PMID:2162833

Wariishi, H; Marquez, L; Dunford, H B; Gold, M H

1990-07-01

227

SABIO-RK--database for biochemical reaction kinetics  

PubMed Central

SABIO-RK (http://sabio.h-its.org/) is a web-accessible database storing comprehensive information about biochemical reactions and their kinetic properties. SABIO-RK offers standardized data manually extracted from the literature and data directly submitted from lab experiments. The database content includes kinetic parameters in relation to biochemical reactions and their biological sources with no restriction on any particular set of organisms. Additionally, kinetic rate laws and corresponding equations as well as experimental conditions are represented. All the data are manually curated and annotated by biological experts, supported by automated consistency checks. SABIO-RK can be accessed via web-based user interfaces or automatically via web services that allow direct data access by other tools. Both interfaces support the export of the data together with its annotations in SBML (Systems Biology Markup Language), e.g. for import in modelling tools.

Wittig, Ulrike; Kania, Renate; Golebiewski, Martin; Rey, Maja; Shi, Lei; Jong, Lenneke; Algaa, Enkhjargal; Weidemann, Andreas; Sauer-Danzwith, Heidrun; Mir, Saqib; Krebs, Olga; Bittkowski, Meik; Wetsch, Elina; Rojas, Isabel; Muller, Wolfgang

2012-01-01

228

Penicillin Hydrolysis: A Kinetic Study of a Multistep, Multiproduct Reaction.  

ERIC Educational Resources Information Center

|Background, procedures used, and typical results are provided for an experiment in which students carry out the necessary measurements on the acid-catalysis of penicillin in two hours. By applying kinetic theory to the data obtained, the reaction pathways for the hydrolysis of potassium benzyl penicillin are elucidated. (JN)|

McCarrick, Thomas A.; McLafferty, Fred W.

1984-01-01

229

Some aspects of the kinetics of heterogeneous catalytic reactions  

SciTech Connect

An approach to developing a chemical kinetic model for heterogeneous catalytic reactions was elaborated for the case when in the course of the catalytic interaction of various gases, the adsorption of one of them (an electron donor) is promoted under the action of the other (an electron acceptor). This phenomenon is referred to as the effect of stimulating induced surface heterogeneity.

Golodets, G.I.; Il`chenko, N.I.; Dolgikh, L.Yu. [Pisarzhevskii Institute of Physical Chemistry, Kiev (Ukraine)

1995-01-01

230

Reaction Kinetics in Food Extrusion: Methods and Results  

Microsoft Academic Search

Extrusion cooking is a highly efficient food processing technology. During the extrusion process, there are many desirable and undesirable reactions which will determine final product quality. While being heated and sheared simultaneously, food raw materials experience a non-isothermal process and their residence time in the extruder is distributed. All these factors contribute to the difficulties in determining the kinetic parameters

Xuewei Zhao; Yimin Wei; Zhangcun Wang; Fengliang Chen; Anthony Okhonlaye Ojokoh

2011-01-01

231

Reaction Kinetics in Food Extrusion-Methods and Results  

Microsoft Academic Search

Extrusion cooking is a highly efficient food processing technology. During extrusion process, there are many desirable and undesirable reactions which will determine final product quality. While being heated and sheared simultaneously, food raw materials experience a non-isothermal process and their residence time in extruder is distributed. All these factors contribute to the difficulties in determining the kinetic parameters for those

Xuewei Zhao; Yimin Wei; Zhangcun Wang; Fengliang Chen; Anthony Okhonlaye Ojokoh

2011-01-01

232

Cr stable isotope fractionation and reaction kinetics in aqueous milieu  

Microsoft Academic Search

Mass-dependent stable Cr isotope variations show great potential to monitor the natural attenuation of anthropogenic chromate pollution as well as to investigate changes in environmental conditions in the present and the past. However, accurate interpretation of mass-dependent Cr isotope variations requires profound knowledge of the Cr isotope fractionation behaviour during redox transitions and the isotope exchange kinetics of the reactions

S. Zink; R. Schoenberg; M. Staubwasser

2009-01-01

233

Penicillin Hydrolysis: A Kinetic Study of a Multistep, Multiproduct Reaction.  

ERIC Educational Resources Information Center

Background, procedures used, and typical results are provided for an experiment in which students carry out the necessary measurements on the acid-catalysis of penicillin in two hours. By applying kinetic theory to the data obtained, the reaction pathways for the hydrolysis of potassium benzyl penicillin are elucidated. (JN)

McCarrick, Thomas A.; McLafferty, Fred W.

1984-01-01

234

Kinetics of the aqueous-phase reaction between ozone and 2,4,6-trichlorophenol  

SciTech Connect

Treatment of industrial and municipal wastewater containing organic pollutants is of primary concern. Ozonation of these wastewaters has been effective in oxidizing organic pollutants into harmless compounds (CO{sub 2} and H{sub 2}O) as well as breaking up refractory compounds into different compounds that are more easily treated with cheaper, more conventional methods such as biodegradation, ion exchange, and filtration. In order to effectively treat wastewater with ozone and design appropriate treatment processes, reaction kinetics and reaction products must be determined. In addition, ozone solubilities and diffusivities must be known in order to model the diffusion/reaction process in this gas-liquid system. A wetted-sphere absorber was used to measure absorption rates of ozone into aqueous-buffered solutions of 2,4,6-trichlorophenol (TCP). Gas consisting of approximately 2.5% ozone in oxygen was contacted with aqueous-buffered TCP solution flowing over a sphere in a laminar liquid film. Absorption data were obtained by measuring the change in the liquid-phase concentration of TCP from the inlet to the outlet of the absorber. A rigorous numerical model for this diffusion/reaction process was used to analyze the absorption data to determine the second-order rate constant of the reaction between ozone and TCP at 15--35 C and pH 2 and 7. The kinetic data indicate that the rate-limiting step for the reaction of aqueous TCP with ozone is the same at pH 2 and 7. Four reaction products that occur early in the reaction of ozone with aqueous TCP were identified by GCMS, including: 2,3,4,6-tetrachlorophenol (TRCP), 4,6-dichlorocatechol (DCC), 2,6-dichlorohydroquinone (DCHQ), and 2,6-dichloroquinone (DCQ). Only DCHQ and CDQ occurred in significant concentrations. Over the pH range of 2 to 5, both DCHQ and DCQ were detected in the reacted solutions, while for pH 6 and 7 only DCHQ was detected. Carbon-13 NMR analysis shows that over longer ozone exposure times short-chain carboxylic acids are the dominant species in the reacted TCP solutions.

Rinker, E.B.; Ashour, S.S.; Johnson, M.C.; Kott, G.J.; Rinker, R.G.; Sandall, O.C. [Univ. of California, Santa Barbara, CA (United States). Dept. of Chemical Engineering

1999-08-01

235

Second-order spatial analysis of epidermal nerve fibers.  

PubMed

Breakthroughs in imaging of skin tissue reveal new details on the distribution of nerve fibers in the epidermis. Preliminary neurologic studies indicate qualitative differences in the spatial patterns of nerve fibers based on pathophysiologic conditions in the subjects. Of particular interest is the evolution of spatial patterns observed in the progression of diabetic neuropathy. It appears that the spatial distribution of nerve fibers becomes more 'clustered' as neuropathy advances, suggesting the possibility of diagnostic prediction based on patterns observed in skin biopsies. We consider two approaches to establish statistical inference relating to this observation. First, we view the set of locations where the nerves enter the epidermis from the dermis as a realization of a spatial point process. Secondly, we treat the set of fibers as a realization of a planar fiber process. In both cases, we use estimated second-order properties of the observed data patterns to describe the degree and scale of clustering observed in the microscope images of blister biopsies. We illustrate the methods using confocal microscopy blister images taken from the thigh of one normal (disease-free) individual and two images each taken from the thighs of subjects with mild, moderate, and severe diabetes and report measurable differences in the spatial patterns of nerve entry points/fibers associated with disease status. PMID:21823143

Waller, Lance A; Särkkä, Aila; Olsbo, Viktor; Myllymäki, Mari; Panoutsopoulou, Ioanna G; Kennedy, William R; Wendelschafer-Crabb, Gwen

2011-08-08

236

Holographic dark matter and dark energy with second order invariants  

NASA Astrophysics Data System (ADS)

One of the main goals of modern cosmology remains to summon up a self-consistent policy, able to explain, in the framework of Einstein’s theory, the cosmic speedup and the presence of dark matter in the Universe. According to the holographic principle, which postulates the existence of a minimal size of a physical region, we argue, in this paper, that if this size exists for the Universe and it is accrued from the independent geometrical second order invariants, it would be possible to ensure a surprising source for dark matter and a viable candidate for explaining the late acceleration of the Universe. We develop low redshift tests, such as supernovae Ia and kinematical analysis, compiled by the use of cosmography, and we compare the outcomes with higher redshift tests, such as the CMB peak and anisotropy of the cosmic power spectrum. All the results indicate that the models presented here can be interpreted as unified models that are capable of describing both dark matter and dark energy.

Aviles, Alejandro; Bonanno, Luca; Luongo, Orlando; Quevedo, Hernando

2011-11-01

237

Second-order structure function in fully developed turbulence  

NASA Astrophysics Data System (ADS)

We relate the second-order structure function of a time series with the power spectrum of the original variable, taking an assumption of statistical stationarity. With this approach, we find that the structure function is strongly influenced by the large scales. The large-scale contribution and the contribution range are, respectively, 79% and 1.4 decades for a Kolmogorov -5/3 power spectrum. We show numerically that a single scale influence range, over smaller scales is about 2 decades. We argue that the structure function is not a good method to extract the scaling exponents when the data possess large energetic scales. An alternative methodology, the arbitrary order Hilbert spectral analysis which may constrain this influence within 0.3 decade, is proposed to characterize the scaling property directly in an amplitude-frequency space. An analysis of passive scalar (temperature) turbulence time series is presented to show the influence of large-scale structures in real turbulence and the efficiency of the Hilbert-based methodology. The corresponding scaling exponents ??(q) provided by the Hilbert-based approach indicate that the passive scalar turbulence field may be less intermittent than what was previously believed.

Huang, Y. X.; Schmitt, F. G.; Lu, Z. M.; Fougairolles, P.; Gagne, Y.; Liu, Y. L.

2010-08-01

238

Kinetics of reactions of Câ olefins on HY zeolite  

Microsoft Academic Search

Reactions of two Câ olefins (n-octene and 2,4,4-trimethylpentene) have been studied on HY at 300°C. Skeletal isomerization is the dominant reaction of n-octene (initial selectivity 0.98), while cracking is the dominant reaction of 2,4,4-trimethylpentene (initial selectivity 0.80). Conversion rates of both olefins can be fitted by a kinetic expression previously applied to the cracking of n-paraffins on HY at 400°C.

J. Abbot; B. W. Wojciechowski

1987-01-01

239

Second order nonlinear spatial stability analysis of compressible mixing layers  

NASA Astrophysics Data System (ADS)

Second order nonlinear spatial stability to three-dimensional perturbation waves is analyzed for compressible mixing layers by expanding the perturbations into amplitude-dependent harmonic waves and truncating the Landau equation to the second term. This leads to a system of nonlinear ordinary differential equations for the harmonics. The two constants in Landau equation are calculated, wherein the independent variable, time t, is replaced by the streamwise coordinate direction x. The basic procedure in this paper is similar to that by Liu for compressible laminar wakes [Phys. Fluids 12, 1763 (1969)]. However, unlike this reference, which does not provide any results for their analysis, the present paper obtained many interesting results. The linear results from the present work compare very favorably with those reported by Day, Reynolds, and Mansour [Phys. Fluids 10, 993 (1998)], who employed a different procedure and limited their analysis to the linear regime. In the present studies, both the linear and nonlinear problems were analyzed in exactly the same manner, with the implication that the nonlinear results are probably accurate. These results include the convergence of the amplitude to an equilibrium value that depends on the two constants in the amplitude equation from Landau's procedure. The present analysis is restricted to exponentially decaying linear solutions at the boundaries and hence to region one in the phase speed-Mach number diagram. However, we have observed that nonlinear effects could introduce constant, decaying, or outgoing wave solutions at the boundaries, depending on the velocity and density ratios and the Mach number of the fast stream. Other effects of these parameters are reported.

Ladeinde, F.; Wu, J.

2002-09-01

240

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

241

Reactions of hydrogen on silicon:??Kinetics and dynamics  

NASA Astrophysics Data System (ADS)

Hydrogen molecules desorbing from silicon exhibit very low translational heating in spite of a high adsorption barrier. This “barrier puzzle” can be explained in terms of a strong phonon coupling leading to a strong energy transfer to phonons in desorption and, vice versa, to a strong phonon-assisted sticking. Recent kinetic and scanning tunneling microscopy data at higher coverages indicate the existence of a new barrierless reaction path which is supposed to dominate the high coverage reaction dynamics. However, recent data on translational and earlier results on vibrational heating at higher coverage indicate the presence of a high adsorption barrier well in accordance with low-coverage data on vibrationally and translationally assisted sticking. For the solution of this barrier puzzle we present kinetic and dynamic model calculations. We use nonequilibrium thermodynamics to formulate the coupled adsorption-desorption kinetics allowing for different weights for the 2H and 4H processes. We perform four-dimensional coupled channel calculations to treat the dependence of phonons, molecular vibrations and corrugation on these two reaction mechanisms. These calculations indicate that dramatic changes in the vibrational and translational dynamics due to the new barrierless reaction path may occur only near monolayer coverage.

Brenig, W.; Kreuzer, H. J.; Payne, S. H.

2003-05-01

242

Kinetics of the monomer-monomer surface reaction model  

SciTech Connect

The two-dimensional monomer-monomer ([ital AB]) surface reaction model without diffusion is considered for infinitesimal, finite, and infinite reaction rates [ital k]. For equal reactant adsorption rates, in all cases, simulations reveal the same form of slow poisoning, associated with clustering of reactants. This behavior is also the same as that found in simulations of the two-dimensional [ital voter] [ital model] studied in interacting-particle systems theory. The voter model can also be obtained from the dimer-dimer or monomer-dimer surface reaction models with infinitesimal reaction rate. We provide a detailed elucidation of the slow poisoning kinetics via an analytic treatment for the [ital k]=0[sup +] [ital AB] reaction and the voter models. This analysis is extended to incorporate the effects of place-exchange diffusion which slows, but does not prevent poisoning. We also show that the [ital k]=0[sup +] [ital AB] reaction with no diffusion is equivalent to the voter model with diffusion at rate 1/2. Identical behavior of the monomer-monomer reaction and the voter model is also found in an epidemic'' analysis, where one considers the evolution of a surface poisoned by one species, except for a small patch. Finally, we apply our findings to elucidate the behavior of the monomer-dimer surface reaction model for small reaction rates.

Evans, J.W.; Ray, T.R. (Ames Laboratory and Department of Mathematics, Iowa State University, Ames, Iowa 50011 (United States))

1993-02-01

243

Kinetics of sulfur and nitrogen reactions in combustion systems  

SciTech Connect

This volume is the second of a three volume set. Specifically, the activities reported herein cover investigations of the reactivity of sorbent materials toward SO{sub 2}. For the most part this focuses on the furnace injection of calcium-based sorbents, although some work also considers post-furnace injection and the use of alternative sorbents. Work is described in the following sections. Reactivity kinetics of calcium-based sorbents for SO{sub x}: this task provides experimental data on improving the reactivity of calcium-based sorbents to sulfur dioxide. It is designed to identify what limits calcium utilization and how to avoid these limitations. The focus is on the influence of sorbent structure on sulfation. Sorbent sulfation: the goal is to define the sulfation rate processes and sulfation mechanism for calcium-based sorbents under furnace conditions. The focus is on the reaction kinetics of sulfation. Alternative sorbents: the objective is to provide detailed kinetics of SO{sub x} absorption by minerals (other than calcium based) which have application in a dry sorbent SO{sub 2} process. This study also includes a modeling element for SO{sub 2} capture by calcium-based materials. Physical/chemical modeling of sulfur/sorbent reaction: this project utilized the kinetic and mechanistic data from the experimental studies to develop and apply a detailed process model of the sulfur gas and sorbent solid reactions. Low temperature capture of SO{sub 2}: this experimental study supplies kinetic and mechanistic information of the capture of SO{sub 2} by calcium-based sorbents under post-air heater conditions (e.g., in the flue gas duct, at or below 300{degree}F). 36 refs., 95 figs., 7 tabs.

Kramlich, J.C.; Seeker, W.R. (Energy and Environmental Research Corp., Irvine, CA (USA)); Sarofim, A.F.; Longwell, J.T. (Massachusetts Inst. of Tech., Cambridge, MA (USA)); Ham, D.; Simons, G.A. (Physical Sciences, Inc., Woburn, MA (USA))

1989-09-01

244

Kinetics of the Hydrogen-Oxygen Difluoride Reaction in Monel.  

National Technical Information Service (NTIS)

The kinetics of the H2-OF2 reaction were studied in the temperature range of 110-220C at 1 atm total pressure in a monel, stirred-flow reactor. Initial reactant concentration ranges were 0.5 to 2.0 mole % OF2, 0.5 to 5.0 mole % H2 with 0 to 5.0 mole % O2 ...

T. J. Houser T. W. Asmus

1971-01-01

245

Kinetics and transport processes in aqueous polysulfide-electrode reactions  

Microsoft Academic Search

The objectives of this research are to obtain information on the electrochemical and chemical reactions of the aqueous sulfide\\/polysulfide redox couple and to use that information to design a stable and efficient redox electrode. The kinetics of the aqueous polysulfide redox couple were investigated using a transient potential step technique in a solution 1M in S° and 1.3M in total

Lessner

1986-01-01

246

Kinetics of hydrogen evolution reaction on a stainless steel electrode  

Microsoft Academic Search

The kinetic parameters for the hydrogen evolution reaction on a stainless steel substrate have been obtained from a study\\u000a of the steady-state polarization curves as well as the galvanostatic transients. The high Tafel slope obtained in the steady-state\\u000a polarization measurements was ascribed to the presence of an oxide film present on the surface of the stainless steel electrode.

P. Radhakrishnamurthy; S. Sathyanarayana; A. K. N. Reddy

1977-01-01

247

Monoclonal antibody refolding and assembly: Protein disulfide isomerase reaction kinetics  

Microsoft Academic Search

The protein disulfide isomerase (PDI) reaction kinetics has been studied to evaluate its effect on the monoclonal antibody\\u000a (MAb) refolding and assembly which accompanies disulfide bond formation. The MAbin vitro assembly experiments showed that the assembly rate of heavy and light chains can be greatly enhanced in the presence of PDI\\u000a as compared to the rate of assembly obtained by

Dewey D. Y. Ryu

1996-01-01

248

Portable centrifugal analyzer for the determination of rapid reaction kinetics  

SciTech Connect

A portable centrifugal analyzer prototype is capable of rapidly initiating reactions and monitoring 17 optical channels as they rotate past a stationary photodetector. An advanced rotor drive permits transfer of discretely loaded sample and reagent into a cuvette within 60 ms. Various rotor designs have been employed to ensure effieicnt mixing concurrent with solution transfer, thus permitting absorbance or luminescence measurements to be made almost immediately after solution contract. Dye-dillution studies have been used to investigate transfer and mixing efficiencies. Rotor designs with parallel access for sample and reagent into the cuvette were found to promote efficient mixing during liquid transfer. The hypochlorite-luminol chemiluminescent reaction served to demonstrate the utility of the system for performing rapid kinetic analyses. Appropriate adjustment of reaction conditions allows first-order reaction half-lives as short as 0.04 s to be measured. 13 figures, 3 tables.

Bostick, W.D.; Bauer, M.L.; McCracken, R.; Mrochek, J.E.

1980-02-01

249

Polynuclear aromatic hydrocarbons hydrogenation. 1: Experimental reaction pathways and kinetics  

SciTech Connect

The relationship between molecular structure and hydrogenation reactivity in heavy oil hydroprocessing was sought via the elucidation of the controlling reaction pathways and kinetics of one-, two-, three-, and four-fused ring compounds. Hydrogenation reactions of o-xylene, tetralin, naphthalene, phenanthrene, anthracene, pyrene, and chrysene and their multicomponent mixtures were studied in cyclohexane solvent using a presulfided CoMo/Al[sub 2]O[sub 3] catalyst in a 1-liter batch autoclave at P[sub H[sub 2

Korre, S.C.; Klein, M.T. (Univ. of Delaware, Newark, DE (United States). Dept. of Chemical Engineering); Quann, R.J. (Mobil Research and Development Corp., Paulsboro, NJ (United States). Paulsboro Research Lab.)

1995-01-01

250

Bayesian experts in exploring reaction kinetics of transcription circuits  

PubMed Central

Motivation Biochemical reactions in cells are made of several types of biological circuits. In current systems biology, making differential equation (DE) models simulatable in silico has been an appealing, general approach to uncover a complex world of biochemical reaction dynamics. Despite of a need for simulation-aided studies, our research field has yet provided no clear answers: how to specify kinetic values in models that are difficult to measure from experimental/theoretical analyses on biochemical kinetics. Results: We present a novel non-parametric Bayesian approach to this problem. The key idea lies in the development of a Dirichlet process (DP) prior distribution, called Bayesian experts, which reflects substantive knowledge on reaction mechanisms inherent in given models and experimentally observable kinetic evidences to the subsequent parameter search. The DP prior identifies significant local regions of unknown parameter space before proceeding to the posterior analyses. This article reports that a Bayesian expert-inducing stochastic search can effectively explore unknown parameters of in silico transcription circuits such that solutions of DEs reproduce transcriptomic time course profiles. Availability: A sample source code is available at the URL http://daweb.ism.ac.jp/?yoshidar/lisdas/ Contact: yoshidar@ism.ac.jp

Yoshida, Ryo; Saito, Masaya M.; Nagao, Hiromichi; Higuchi, Tomoyuki

2010-01-01

251

Kinetics and mechanism of the chlorine dioxide-trithionate reaction.  

PubMed

The trithionate-chlorine dioxide reaction has been studied spectrophotometrically in a slightly acidic medium at 25.0 ± 0.1 °C in acetate/acetic acid buffer monitoring the decay of chlorine dioxide at constant ionic strength (I = 0.5 M) adjusted by sodium perchlorate. We found that under our experimental conditions two limiting stoichiometries exist and the pH, the concentration of the reactants, and even the concentration of chloride ion affects the actual stoichiometry of the reaction that can be augmented by an appropriate linear combination of these limiting processes. It is also shown that although the formal kinetic order of trithionate is strictly one that of chlorine dioxide varies between 1 and 2, depending on the actual chlorine dioxide excess and the pH. Moreover, the otherwise sluggish chloride ion, which is also a product of the reaction, slightly accelerates the initial rate of chlorine dioxide consumption and may therefore act as an autocatalyst. In addition to that, overshoot-undershoot behavior is also observed in the [(·)ClO(2)]-time curves in the presence of chloride ion at chlorine dioxide excess. On the basis of the experiments, a 13-step kinetic model with 6 fitted kinetic parameter is proposed by nonlinear parameter estimation. PMID:22404742

Cseko, György; Horváth, Attila K

2012-03-09

252

Reaction kinetics of the addition of atomic sulfur to nitric oxide  

SciTech Connect

The reaction of S({sup 3}P{sub J}) with NO ({sup 2}{pi}) in an Ar bath gas has been studied by the laser photolysis-resonance fluorescence technique over 300-810 K at pressures from 60 to 800 mbar. The observed second-order rate constants are close to the low-pressure limit. Fitting of Troe's formalism to experiment, with an estimated F{sub cent}=0.78 exp(-T/7445) and k{sub {infinity}} given subsequently, yields k{sub 0}=(6.2{+-}0.6)x10{sup -33} exp(+(940{+-}40)/T) cm{sup 6} molecule{sup -2} s{sup -1}. Error limits are {+-}25%. A theoretical analysis of this value suggests that the average energy transferred during collisions between Ar and the excited intermediate is <{delta}E>=-360{sub -160}{sup +90} cm{sup -1}. Over 300-800 K, the high-pressure limit is predicted to be k{sub {infinity}}=2.2x10{sup -10} (T/300){sup 0.24} cm{sup 3} molecule{sup -1} s{sup -1}. Doublet and quartet adducts between S and NO were characterized via CBS-QB3 theory. The kinetic data can be rationalized with SNO ({sup 2}A{sup '}) as the major product, and an ab initio estimate of {delta}{sub f}H{sub 298} for SNO is 176{+-}8 kJ mol-1.

Goumri, A.; Shao, Diane D.; Marshall, Paul [Department of Chemistry, University of North Texas, Denton, Texas 76203-5070 (United States)

2004-11-22

253

Theoretical Analysis of Kinetic Isotope Effects on Proton Transfer Reactions between Substituted ?-Methoxystyrenes and Substituted Acetic Acids  

PubMed Central

Primary kinetic isotope effects (KIEs) on a series of carboxylic acid-catalyzed protonation reactions of aryl-substituted ?-methoxystyrenes (X-1) to form oxocarbenium ions have been computed using the Kleinert variational second-order perturbation theory (KP2) in the framework of Feynman path integrals (PI) along with the potential energy surface obtained at the B3LYP/6-31+G(d,p) level. Good agreement with the experimental data was obtained, demonstrating that this novel computational approach for computing KIEs of organic reactions is a viable alternative to the traditional method employing Bigeleisen equation and harmonic vibrational frequencies. Although tunneling makes relative small contributions to the lowering of the free energy barriers for the carboxylic acid catalyzed protonation reaction, it is necessary to include tunneling contributions to obtain quantitative estimates of the KIEs. Consideration of anharmonicity can further improve the calculated KIEs for the protonation of substituted ?-methoxystyrenes by chloroacetic acid, but for the reactions of the parent and 4-NO2 substituted ?-methoxystyrene with substituted carboxylic acids, the correction of anharmonicity overestimates the computed KIEs for strong acid catalysts. In agreement with experimental findings, the largest KIEs are found in nearly ergoneutral reactions, ?Go ? 0, where the transition structures are nearly symmetric and the reaction barriers are relatively low. Furthermore, the optimized transition structures are strongly dependent on the free energy for the formation of the carbocation intermediate, i.e., the driving force ?Go, along with a good correlation of Hammond shift in the transition state structure.

Wong, Kin Yiu; Richard, John P.; Gao, Jiali

2009-01-01

254

Reaction Path Optimization with Holonomic Constraints and Kinetic Energy Potentials  

SciTech Connect

Two methods are developed to enhance the stability, efficiency, and robustness of reaction path optimization using a chain of replicas. First, distances between replicas are kept equal during path optimization via holonomic constraints. Finding a reaction path is, thus, transformed into a constrained optimization problem. This approach avoids force projections for finding minimum energy paths (MEPs), and fast-converging schemes such as quasi-Newton methods can be readily applied. Second, we define a new objective function - the total Hamiltonian - for reaction path optimization, by combining the kinetic energy potential of each replica with its potential energy function. Minimizing the total Hamiltonian of a chain determines a minimum Hamiltonian path (MHP). If the distances between replicas are kept equal and a consistent force constant is used, then the kinetic energy potentials of all replicas have the same value. The MHP in this case is the most probable isokinetic path. Our results indicate that low-temperature kinetic energy potentials (<5 K) can be used to prevent the development of kinks during path optimization and can significantly reduce the required steps of minimization by 2-3 times without causing noticeable differences between a MHP and MEP. These methods are applied to three test cases, the C?eq-to-Cax isomerization of an alanine dipeptide, the ?C?- to-¹C? transition of an ?-D-glucopyranose, and the helix-to-sheet transition of a GNNQQNY heptapeptide. By applying the methods developed in this work, convergence of reaction path optimization can be achieved for these complex transitions, involving full atomic details and a large number of replicas (>100). For the case of helix-to-sheet transition, we identify pathways whose energy barriers are consistent with experimental measurements. Further, we develop a method based on the work energy theorem to quantify the accuracy of reaction paths and to determine whether the atoms used to define a path are enough to provide quantitative estimation of energy barriers.

Brokaw, Jason B.; Haas, Kevin R.; Chu, Jhih-wei

2009-08-11

255

Further development and testing of a second-order bulk boundary layer model. Master's thesis  

SciTech Connect

A one-layer bulk boundary layer model is developed. The model predicts the mixed layer values of the potential temperature, mixing ratio, and u- and v-momentum. The model also predicts the depth of the boundary layer and the vertically integrated turbulence kinetic energy (TKE). The TKE is determined using a second-order closure that relates the rate of dissipation to the TKE. The fractional area covered by rising motion sigma and the entrainment rate (E) are diagnostically determined. The model is used to study the clear convective boundary layer (CBL) using data from the Wangara, Australia boundary layer experiment. The Wangara data is also used as an observation base to validate model results. A further study is accomplished by simulating the planetary boundary layer (PBL) over an ocean surface. This study is designed to find the steady-state solutions of the prognostic variable.

Krasner, R.D.

1993-05-03

256

Influence of Chemical Kinetics on Postcolumn Reaction in a Capillary Taylor Reactor with Catechol Analytes and Photoluminescence Following Electron Transfer  

PubMed Central

Postcolumn derivatization reactions can enhance detector sensitivity and selectivity, but their successful combination with capillary liquid chromatography has been limited because of the small peak volumes in capillary chromatography. A capillary Taylor reactor (CTR), developed in our laboratory, provides simple and effective mixing and reaction in a 25-?m-radius postcolumn capillary. Homogenization of reactant streams occurs by radial diffusion, and a chemical reaction follows. Three characteristic times for a given reaction process can be predicted using simple physical and chemical parameters. Two of these times are the homogenization time, which governs how long it takes the molecules in the analyte and reagent streams to mix, and the reaction time, which governs how long the molecules in a homogeneous solution take to react. The third characteristic time is an adjustment to the reaction time called the start time, which represents an estimate of the average time the analyte stream spends without exposure to reagent. In this study, laser-induced fluorescence monitored the extent of the postcolumn reaction (reduction of Os(bpy)33+ by analyte to the photoluminescent Os(bpy)32+) in a CTR. The reaction time depends on the reaction rates. Analysis of product versus time data yielded second-order reaction rate constants between the PFET reagent, tris(2,2?-bipyridine)osmium, and standards ((ferrocenylmethyl)trimethylammonium cation and p-hydroquinone) or catechols (dopamine, epinephrine, norepinephrine, 3, 4-dihydroxyphenylacetic acid. The extent of the reactions in a CTR were then predicted from initial reaction conditions and compared to experimental results. Both the theory and experimental results suggested the reactions of catechols were generally kinetically controlled, while those of the standards were controlled by mixing time (1–2 s). Thus, the extent of homogenization can be monitored in a CTR using the relatively fast reaction of the reagent and p-hydroquinone. Kinetically controlled reactions of catechols, however, could be also completed in a reasonable time at increased reagent concentration. A satisfactory reactor, operating at 1.7 cm/s (2 ?L/min) velocity with solutes having diffusion coefficients in the 5 × 10?6 cm2/s range, can be constructed from 8.0 cm of 25-?m-radius capillary. Slower reactions require longer reaction times, but theoretical calculations expect that a CTR does not broaden a chromatographic peak (N = 14 000) from a 100-?m-capillary chromatography column by 10% if the pseudo-first-order rate constant is larger than 0.1 s?1.

Jung, Moon Chul; Weber, Stephen G.

2006-01-01

257

Renormalized second-order perturbation theory for the electron correlation energy: Concept, implementation, and benchmarks  

NASA Astrophysics Data System (ADS)

We present a renormalized second-order perturbation theory (rPT2), based on a Kohn-Sham (KS) reference state, for the electron correlation energy that includes the random-phase approximation (RPA), second-order screened exchange (SOSEX), and renormalized single excitations (rSE). These three terms all involve a summation of certain types of diagrams to infinite order, and can be viewed as ``renormalization'' of the second-order direct, exchange, and single-excitation (SE) terms of Rayleigh-Schrödinger perturbation theory based on a KS reference. In this work, we establish the concept of rPT2 and present the numerical details of our SOSEX and rSE implementations. A preliminary version of rPT2, in which the renormalized SE (rSE) contribution was treated approximately, has already been benchmarked for molecular atomization energies and chemical reaction barrier heights and shows a well-balanced performance [J. Paier , New J. Phys.1367-263010.1088/1367-2630/14/4/043002 14, 043002 (2012)]. In this work, we present a refined version of rPT2, in which we evaluate the rSE series of diagrams rigorously. We then extend the benchmark studies to noncovalent interactions, including the rare-gas dimers, and the S22 and S66 test sets, as well as the cohesive energy of small copper clusters, and the equilibrium geometry of 10 diatomic molecules. Despite some remaining shortcomings, we conclude that rPT2 gives an overall satisfactory performance across different electronic situations, and is a promising step towards a generally applicable electronic-structure approach.

Ren, Xinguo; Rinke, Patrick; Scuseria, Gustavo E.; Scheffler, Matthias

2013-07-01

258

NO sub x -char reactions: Kinetics and transport aspects  

SciTech Connect

The present project is motivated by the need to reduce NO{sub x} emissions from combustors, especially coal combustors. Reactions with carbon are known to be effective at reducing No to N{sub 2}, and remain interesting candidates in a wide variety of possible applications. These reactions are known to be important in reducing NO{sub x} emissions from fluidized bed coal combustors, in which the coal char itself serves as the reducing agent. The principal goal of this project is to develop a mechanistic understanding of the processes by which carbons reduce NO to N{sub 2}. The carbon was a char derived from phenol-formaldehyde resin. This material has been noted to be a reasonable model for coal chars in most respects, expect that its gasification behavior is not complicated by catalytic processes due to minerals. In the first phases of the project, the global kinetics of the process were established. In more recent work, attention has been turned to the individual steps in the mechanism. Recent quarterly reports have detailed the role of both chemisorption and desorption processes in determining the course and kinetics of the process. This report continues the reporting of results obtained along these lines, and draws an important new conclusion concerning the number of separate processes involved in determining the kinetics. 40 refs., 3 figs., 2 tabs.

Calo, J.M.; Suuberg, E.M.

1990-01-01

259

Time-resolved gas-phase kinetic, quantum chemical, and RRKM studies of reactions of silylene with alcohols.  

PubMed

Time-resolved kinetic studies of silylene, SiH(2), generated by laser flash photolysis of 1-silacyclopent-3-ene and phenylsilane, have been carried out to obtain rate constants for its bimolecular reactions with methanol, ethanol, 1-propanol, 1-butanol, and 2-methyl-1-butanol. The reactions were studied in the gas phase over the pressure range 1-100 Torr in SF(6) bath gas, at room temperature. In the study with methanol several buffer gases were used. All five reactions showed pressure dependences characteristic of third body assisted association reactions. The rate constant pressure dependences were modeled using RRKM theory, based on E(0) values of the association complexes obtained by ab initio calculation (G3 level). Transition state models were adjusted to fit experimental fall-off curves and extrapolated to obtain k(?) values in the range (1.9-4.5) × 10(-10) cm(3) molecule(-1) s(-1). These numbers, corresponding to the true bimolecular rate constants, indicate efficiencies of between 16% and 67% of the collision rates for these reactions. In the reaction of SiH(2) + MeOH there is a small kinetic component to the rate which is second order in MeOH (at low total pressures). This suggests an additional catalyzed reaction pathway, which is supported by the ab initio calculations. These calculations have been used to define specific MeOH-for-H(2)O substitution effects on this catalytic pathway. Where possible our experimental and theoretical results are compared with those of previous studies. PMID:21469721

Becerra, Rosa; Cannady, J Pat; Walsh, Robin

2011-04-06

260

LETTER TO THE EDITOR: Evolution of second-order cosmological perturbations  

NASA Astrophysics Data System (ADS)

We present a method for constructing gauge-invariant cosmological perturbations which are gauge-invariant up to second order. As an example, we give the gauge-invariant definition of the second-order curvature perturbation on uniform density hypersurfaces. Using only the energy conservation equation, we show that this curvature perturbation is conserved at second order on large scales for adiabatic perturbations.

Malik, Karim A.; Wands, David

2004-06-01

261

A Comprehensive Kinetic Model of the Exocytotic Process: Evaluation of the Reaction Mechanism  

Microsoft Academic Search

This study presents a comprehensive, quantitative description of the exocytotic process that has both analytic and predictive\\u000a powers. The model utilizes strict chemical formalism and is based on a set of equilibria between the various SNARE proteins,\\u000a their complexes and the reaction which free Ca2?+? ions. All these reactions are linked by first and second order rate constants. With the

Aviv Mezer; Eran Bosis; Uri Ashery; Esther Nachliel; Menachem Gutman

2005-01-01

262

Methane generation from coal during open system pyrolysis investigated by isotope specific, Gaussian distributed reaction kinetics  

Microsoft Academic Search

A reaction kinetic model is presented to differentiate individual complexes of reactions of the thermal decomposition of sedimentary organic matter during pyrolysis experiments. This model is applied to methane generation from coal during open system pyrolysis experiments with linear heating. The reaction kinetic model is based on the concept of a certain number of reaction complexes contributing to the generation

Bernhard Cramer

2004-01-01

263

Mechanistic study of the Soai autocatalytic reaction informed by kinetic analysis  

Microsoft Academic Search

Detailed kinetic studies of the Soai reaction affirm the basic mechanistic picture previously developed in kinetic, spectroscopic and molecular modelling studies, and also suggest that refinements to the proposed elementary reaction steps must be considered. The alkanol reaction product is driven strongly and without bias towards the formation of homochiral and heterochiral dimers. The reaction is catalyzed by only the

Donna G. Blackmond

2006-01-01

264

An application of second-order UV-derivative spectrophotometry for study of solvolysis of a novel fluocinolone acetonide ester.  

PubMed

A novel topical corticosteroid FA-21-PhP, 2-phenoxypropionate ester of fluocinolone acetonide, has been synthesized in order to investigate the possibility of decreasing systemic side effects. In this study model system for in vitro solvolytic reaction of FA-21-PhP has been analyzed in ethanol/water (90:10, v/v) with excess of sodium hydrogen carbonate. The selected conditions have been used as in vitro model for activation of corticosteroid C-21 ester prodrug. The second-order derivative spectrophotometric method (DS) using zero-crossing technique was developed for monitoring ternary mixture of solvolysis. Fluocinolone acetonide (FA) as a solvolyte was determined in the mixture in the concentration range 0.062-0.312 mM using amplitude (2)D(274.96). Experimentally determined LOD value was 0.0295 mM. The accuracy of proposed DS method was confirmed with HPLC referent method. Peak area of parent ester FA-21-PhP was used for solvolysis monitoring to ensure the initial stage of changes. Linear relationship in HPLC assay for parent ester was obtained in the concentration range 0.054-0.54 mM, with experimentally determined LOD value of 0.0041 mM. Investigated solvolytic reaction in the presence of excess of NaHCO(3) proceeded via a pseudo-first-order kinetic with significant correlation coefficients 0.9891 and 0.9997 for DS and HPLC, respectively. The values of solvolysis rate constant calculated according to DS and HPLC methods are in good accordance 0.038 and 0.043 h(-1), respectively. PMID:20044302

Markovic, Bojan; Vladimirov, Sote; Cudina, Olivera; Savic, Vladimir; Karljikovic-Rajic, Katarina

2009-12-16

265

Kinetic modeling of interesterification reactions catalyzed by immobilized lipase.  

PubMed

Kinetic data for lipase-catalyzed interesterification reactions between free fatty acids and triglycerides were collected and the dynamics of the interesterification reactions were successfully modeled using tow rate experssions requiring a total of five adjustable parameters. One rate expression describes the disappearance of the free fatty acid (octanoic or linolenic acid), and the second describes the rate of release of fatty acid residues from the triglycerides (olive oil or milkfat). This model is able to account for the effects of the concentration of all chemical species participating in interesterification throughout the entire reaction. When the data for both milkfat and olive oil were subjected to nonlinear regression analyses using the same mathematical model, the parameter estimates for both systems were comparable. In addition to reproducing the tendencies observed experimentally, simulations of the interesterification system under a variety of initial conditions provided insight into the effects of several reaction variables which could not be examined experimentally. Among the most significant findings of the simulation work are (1) there is a limit beyond which increasing the initial concentration of water produces no further increase in the initial rate of the interesterification reaction; (2) an increase in the initial concentration of lower glycerides produces a concomitant increase in the rate of the interesterification reaction; (3) the free fatty acids inhibit the rate of hydrolysis of the fatty acid residues of the triglycerides; (4) there is a limit beyond which increasing the initial concentration of triglycerides produces no significant increase in the rate of either the hydrolysis reaction or the interesterification reaction. PMID:18615612

Reyes, H R; Hill, C G

1994-01-20

266

Python framework for kinetic modeling of electronically excited reaction pathways  

NASA Astrophysics Data System (ADS)

The use of plasma energy to enhance and control the chemical reactions during combustion, a technology referred to as ``plasma assisted combustion'' (PAC), can result in a variety of beneficial effects: e.g. stable lean operation, pollution reduction, and wider range of p-T operating conditions. While experimental evidence abounds, theoretical understanding of PAC is at best incomplete, and numerical tools still lack in reliable predictive capabilities. In the context of a joint experimental-numerical effort at Michigan State University, we present here an open-source modular Python framework dedicated to the dynamic optimization of non-equilibrium PAC systems. Multiple sources of experimental reaction data, e.g. reaction rates, cross-sections and oscillator strengths, are used in order to quantify the effect of data uncertainty and limiting assumptions. A collisional-radiative model (CRM) is implemented to organize reactions by importance and as a potential means of measuring a non-Maxwellian electron energy distribution function (EEDF), when coupled to optical emission spectroscopy data. Finally, we explore scaling laws in PAC parameter space using a kinetic global model (KGM) accelerated with CRM optimized reaction sequences and sparse stiff integrators.

Verboncoeur, John; Parsey, Guy; Guclu, Yaman; Christlieb, Andrew

2012-10-01

267

SECOND-ORDER SOLUTIONS OF COSMOLOGICAL PERTURBATION IN THE MATTER-DOMINATED ERA  

SciTech Connect

We present the growing mode solutions of cosmological perturbations to the second order in the matter-dominated era. We also present several gauge-invariant combinations of perturbation variables to the second order in the most general fluid context. Based on these solutions, we study the Newtonian correspondence of relativistic perturbations to the second order. In addition to the previously known exact relativistic/Newtonian correspondence of density and velocity perturbations to the second order in the comoving gauge, here we show that in the sub-horizon limit we have the correspondences for density, velocity, and potential perturbations in the zero-shear gauge and in the uniform-expansion gauge to the second order. Density perturbation in the uniform-curvature gauge also shows the correspondence to the second order in the sub-horizon scale. We also identify the relativistic gravitational potential that shows exact correspondence to the Newtonian one to the second order.

Hwang, Jai-chan [Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Noh, Hyerim [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Gong, Jinn-Ouk [Theory Division, CERN, CH-1211 Geneve 23 (Switzerland)

2012-06-10

268

Kinetic analysis for optimization of DNA ligation reactions.  

PubMed Central

Kinetic equations describing ligation of DNA to circular recombinant forms were developed and solved for four types of reactions: (a) a homogeneous population of singly restricted DNA fragments, (b) insertion of singly restricted insert into vector, (c) forced directional insertion of doubly restricted insert into vector, and (d) insertion of singly restricted insert into phosphatased vector. The effects of varying vector and insert sizes, starting concentrations, and phosphatase treatment on the yield of circular 1:1 recombinants were analyzed. Selected theoretical predictions were experimentally tested and verified. Our suggestions on optimizing ligation reactions in several cases are at variance with common practice. For example, optimum conditions in case (b) and (d) ligations are best specified as individual insert and vector concentrations rather than as insert/vector molar ratios, except in case (d) ligations involving very small insert size. In case (c) ligations, highest efficiencies are obtained when both vector and insert are at relatively low concentration. Images

Revie, D; Smith, D W; Yee, T W

1988-01-01

269

Anomalous kinetics of attractive A + B-->0 reactions.  

PubMed

We investigate the kinetics of the A + B-->0 reaction with the attractive interaction between opposite species in one spatial dimension. The attractive interaction leads to isotropic diffusions inside segregated single species domains, and accelerates the reactions of opposite species at the domain boundaries. At equal initial densities of and , we analytically and numerically show that the density of particles (rho), the size of domains (l), the distance between the closest neighbor of same species (lAA), and the distance between adjacent opposite species (lAB) scale in time as rho approximately t(-1/3), lAA approximately t(1/3), and l approximately lAB approximately lAB(2/3), respectively. These dynamical exponents define critical behavior distinguished from the class of uniformly driven systems of hard-core particles. PMID:16605379

Kwon, Sungchul; Yoon, S Y; Kim, Yup

2006-02-06

270

Optimal automatic reaction and species elimination in kinetic mechanisms  

SciTech Connect

A known challenge for the simulation of reacting flow systems is that detailed chemical mechanisms contain hundreds to thousands of species and thousands of reactions, leading to high CPU requirements despite the use of state-of-the-art solvers. For specific conditions of interest (temperature, pressure, and composition), smaller mechanisms can predict the chemistry relatively accurately. One possibility for obtaining such mechanisms is species elimination from a detailed mechanism. Here, an automatic method for kinetic model reduction by simultaneous reaction and species elimination is proposed, based on an integer linear program (ILP) formulation. The solution of the ILP is an optimally reduced kinetic mechanism that reproduces the predictions of a reference mechanism within prespecified tolerances for finitely many reference points in the state space. The method is applied to generate optimally reduced models for isobaric, adiabatic homogeneous combustion. Case studies are presented for the combustion of n-heptane. Comparisons between the full and reduced models are shown and the tradeoff between species and reaction elimination is discussed. Tolerances in the ILP formulation control the error introduced by the model reduction. For increasing acceptable error, more species and/or reactions are eliminated. A method of quantifying this tradeoff between approximation error and reduction achieved is proposed, based on multiobjective optimization, and demonstrated in a case study. The effect of variable initial conditions is investigated. The mechanisms generated achieve significant reduction in the CPU requirement and can accurately predict the trajectories of the state variables (species mass fractions and temperature), as well as other metrics of interest, such as ignition time delay. (author)

Mitsos, A. [RES Group/Numerica Technology, Cambridge, MA 02142 (United States); Oxberry, G.M.; Barton, P.I.; Green, W.H. [Massachusetts Institute of Technology/Department of Chemical Engineering, Cambridge, MA 02139 (United States)

2008-10-15

271

Study of enzyme adsorption and reaction kinetics for cellulose hydrolysis  

SciTech Connect

Enzymatic hydrolysis of cellulose occurs due to the combined catalytic action of two types of cellulase components commonly referred to as C/sub 1/ and C/sub x/. However, before the hydrolysis reaction can begin, it is necessary for these enzymes to first adsorb onto the accessible surfaces of the insoluble cellulose substrate. The objective of the study was to gain a better understanding of the relationships between the adsorption of these enzyme components, the hydrolysis kinetics, the cellulosic surface area accessible to the enzymes, and the cellulose crystallinity. These relationships were investigated by passing a Trichoderma viride cellulase solution through columns of cellulose powder having different accessibility and crystallinity, and then analyzing the quantities of the different enzyme components and the hydrolysis product in the effluent. The amounts of the different cellulase components were analyzed using high-performance anion-exchange chromatography. Additional adsorption and hydrolysis experiments were done using columns of cellulose beads specially developed to provide amodel substrate for this analysis. A mathematical model has been formulated to describe the kinetics of enzyme adsorption and the resultant, initial hydrolysis rate in cellulose column. The analytical solutions obtained have been linearized into a convenient form so that the kinetic parameters of the model can be readily determined from experimental breakthrough curves.

Gilbert, I.G.

1982-01-01

272

A Generic Length-scale Equation For Second-order Turbulence Models of Oceanic Boundary Layers  

NASA Astrophysics Data System (ADS)

A generic transport equation for a generalized length-scale in second-order turbulence closure models for geophysical boundary layers is suggested. This variable consists of the products of powers of the turbulent kinetic energy, k, and the integral length-scale, l. The new approach generalizes traditional second-order models used in geophysical boundary layer modelling, e.g. the Mellor-Yamada model and the k- model, which, however, can be recovered as special cases. It is demonstrated how this new model can be calibrated with measurements in some typical geophysical boundary layer flows. As an example, the generic model is applied to the uppermost oceanic boundary layer directly influenced by the effects of breaking surface waves. Recent measurements show that in this layer the classical law of the wall is invalid, since there turbulence is dominated by turbulent transport of TKE from above, and not by shear-production. A widely accepted approach to describe the wave-affected layer with a one-equation turbulence model was suggested by Craig and Banner (1994). Here, some deficien- cies of their solutions are pointed out and a generalization of their ideas for the case of two-equation models is suggested. Direct comparison with very recently obtained measurements of the dissipation rate, , in the wave-affected boundary layer with com- puted results clearly demonstrate that only the generic two-equation model yields cor- rect predictions for the profiles of and the turbulent length scale, l. Also, the pre- dicted velocity profiles in the wave-affected layer, important e.g. for the interpretation of surface drifter experiments, are reproduced correctly only by the generic model. Implementation and computational costs of the generic model are comparable with traditonal two-equation models.

Umlauf, L.; Burchard, H.

273

Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles  

NASA Astrophysics Data System (ADS)

Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

Liechty, Derek S.; Lewis, Mark J.

2011-05-01

274

UV-induced reaction kinetics of dilinoleoylphosphatidylethanolamine monolayers.  

PubMed

The UV-induced reactivity of dilinoleoylphosphatidylethanolamine (DLiPE) Langmuir and Langmuir-Blodgett films has been studied by in situ measurements of the changes in the mean molecular area, UV-vis and Fourier transform infrared spectroscopy, and atomic force microscopy (AFM). Optimum orientation and packing density of the DLiPE molecules in the monolayer were achieved by adding uranyl acetate to the subphase. A first-order reaction kinetic model was successfully fitted to the experimental reaction kinetics data obtained at a surface pressure of 30 mN/m. Topographical studies of LB films by AFM were performed on bilayer structures as a function of subphase composition and UV irradiation time. The orientational effect of the uranyl ions on the monolayer molecules was observed as an enhanced homogeneity of the freshly prepared monomeric LB films. However, the long-term stability of these films proved to be bad; clear reorganization and loss of a true monolayer structure were evidenced by the AFM images. This instability was inhibited for the UV-irradiated films, indicating that the UV irradiation gave rise to a cross-linked structure. PMID:10233096

Viitala, T; Peltonen, J

1999-05-01

275

UV-induced reaction kinetics of dilinoleoylphosphatidylethanolamine monolayers.  

PubMed Central

The UV-induced reactivity of dilinoleoylphosphatidylethanolamine (DLiPE) Langmuir and Langmuir-Blodgett films has been studied by in situ measurements of the changes in the mean molecular area, UV-vis and Fourier transform infrared spectroscopy, and atomic force microscopy (AFM). Optimum orientation and packing density of the DLiPE molecules in the monolayer were achieved by adding uranyl acetate to the subphase. A first-order reaction kinetic model was successfully fitted to the experimental reaction kinetics data obtained at a surface pressure of 30 mN/m. Topographical studies of LB films by AFM were performed on bilayer structures as a function of subphase composition and UV irradiation time. The orientational effect of the uranyl ions on the monolayer molecules was observed as an enhanced homogeneity of the freshly prepared monomeric LB films. However, the long-term stability of these films proved to be bad; clear reorganization and loss of a true monolayer structure were evidenced by the AFM images. This instability was inhibited for the UV-irradiated films, indicating that the UV irradiation gave rise to a cross-linked structure.

Viitala, T; Peltonen, J

1999-01-01

276

Oxidation of fluoroquinolone antibiotics and structurally related amines by chlorine dioxide: Reaction kinetics, product and pathway evaluation.  

PubMed

Fluoroquinolones (FQs) are a group of widely prescribed antibiotics and have been frequently detected in the aquatic environment. The reaction kinetics and transformation of seven FQs (ciprofloxacin (CIP), enrofloxacin (ENR), norfloxacin (NOR), ofloxacin (OFL), lomefloxacin (LOM), pipemidic acid (PIP) and flumequine (FLU)) and three structurally related amines (1-phenylpiperazine (PP), N-phenylmorpholine (PM) and 4-phenylpiperidine (PD)) toward chlorine dioxide (ClO(2)) were investigated to elucidate the behavior of FQs during ClO(2) disinfection processes. The reaction kinetics are highly pH-dependent, can be well described by a second-order kinetic model incorporating speciation of FQs, and follow the trend of OFL > ENR > CIP ? NOR ? LOM > > PIP in reactivity. Comparison among FQs and related amines and product characterization indicate that FQs' piperazine ring is the primary reactive center toward ClO(2). ClO(2) likely attacks FQ's piperazinyl N4 atom followed by concerted fragmentation involving piperazinyl N1 atom, leading to dealkylation, hydroxylation and intramolecular ring closure at the piperazine moiety. While FQs with tertiary N4 react faster with ClO(2) than FQs with secondary N4, the overall reactivity of the piperazine moiety also depends strongly on the quinolone ring through electronic effects. The reaction rate constants obtained in clean water matrix can be used to model the decay of CIP by ClO(2) in surface water samples, but overestimate the decay in wastewater samples. Overall, transformation of FQs, particularly for those with tertiary N4 amines, could be expected under typical ClO(2) disinfection conditions. However, the transformation may not eliminate antibacterial activity because of little destruction at the quinolone ring. PMID:20708211

Wang, Pei; He, Yi-Liang; Huang, Ching-Hua

2010-07-27

277

Violation of the rate-window concept in the charge deep-level transient spectroscopy using second-order filtering  

NASA Astrophysics Data System (ADS)

When applying the thermal-scan charge deep-level transient spectroscopy (Q-DLTS) utilizing second-order filtering to diamond- or GaAs-based Schottky-like diodes, we found correlated Q-DLTS signals which increased monotonically with temperature and did not depend on the rate window set at t1-1. In accordance with the hyperbolic kinetics of the transient current in diamond films, the related transient charge Q(t) (integrated current), when correlated, is invariant for the rate window. Thermal activation energy of the transient current is easily deduced from the Q-DLTS experiment. Possible consequences for feedback-charge capacitance-voltage measurements, which may also be classified as second-order filtering in the time domain, are pointed out. One of them might be a sign reversal of the excess capacitance at short times of observation.

Thurzo, I.; Zahn, D. R. T.; Dua, A. K.

2002-05-01

278

First principle kinetic studies of zeolite-catalyzed methylation reactions.  

PubMed

Methylations of ethene, propene, and butene by methanol over the acidic microporous H-ZSM-5 catalyst are studied by means of state of the art computational techniques, to derive Arrhenius plots and rate constants from first principles that can directly be compared with the experimental data. For these key elementary reactions in the methanol to hydrocarbons (MTH) process, direct kinetic data became available only recently [J. Catal.2005, 224, 115-123; J. Catal.2005, 234, 385-400]. At 350 °C, apparent activation energies of 103, 69, and 45 kJ/mol and rate constants of 2.6 × 10(-4), 4.5 × 10(-3), and 1.3 × 10(-2) mol/(g h mbar) for ethene, propene, and butene were derived, giving following relative ratios for methylation k(ethene)/k(propene)/k(butene) = 1:17:50. In this work, rate constants including pre-exponential factors are calculated which give very good agreement with the experimental data: apparent activation energies of 94, 62, and 37 kJ/mol for ethene, propene, and butene are found, and relative ratios of methylation k(ethene)/k(propene)/k(butene) = 1:23:763. The entropies of gas phase alkenes are underestimated in the harmonic oscillator approximation due to the occurrence of internal rotations. These low vibrational modes were substituted by manually constructed partition functions. Overall, the absolute reaction rates can be calculated with near chemical accuracy, and qualitative trends are very well reproduced. In addition, the proposed scheme is computationally very efficient and constitutes significant progress in kinetic modeling of reactions in heterogeneous catalysis. PMID:21182253

Van Speybroeck, Veronique; Van der Mynsbrugge, Jeroen; Vandichel, Matthias; Hemelsoet, Karen; Lesthaeghe, David; Ghysels, An; Marin, Guy B; Waroquier, Michel

2010-12-23

279

Circadian rhythm in the kinetics of acid denaturation of cell membranes of Euglena gracilis  

Microsoft Academic Search

The denaturation of Euglena gracilis in aggressive acids has been investigated by means of the chlorophyll oxidation. A comparative study in different halogen acetic acids revealed that the reaction kinetics are determined by a reaction between the acid anion and the outer membrane. The denaturation of cell membranes in trichloracetic acid obeys clear second-order kinetics with respect to the overall

Klaus Brinkmann

1976-01-01

280

Spectator Ions ARE Important! A Kinetic Study of the Copper-Aluminum Displacement Reaction  

ERIC Educational Resources Information Center

|Surprisingly, spectator ions are responsible for unexpected kinetics in the biphasic copper(II)-aluminum displacement reaction, with the rate of reaction dependent on the identity of the otherwise ignored spectator ions. Application of a published kinetic analysis developed for a reaction between a rotating Al disk and a Cu(II) ion solution to…

Sobel, Sabrina G.; Cohen, Skyler

2010-01-01

281

Spectator Ions ARE Important! A Kinetic Study of the Copper-Aluminum Displacement Reaction  

ERIC Educational Resources Information Center

Surprisingly, spectator ions are responsible for unexpected kinetics in the biphasic copper(II)-aluminum displacement reaction, with the rate of reaction dependent on the identity of the otherwise ignored spectator ions. Application of a published kinetic analysis developed for a reaction between a rotating Al disk and a Cu(II) ion solution to the…

Sobel, Sabrina G.; Cohen, Skyler

2010-01-01

282

Characterisation of micromixing efficiency by the iodide–iodate reaction system. Part II: kinetic study  

Microsoft Academic Search

In a previous paper (Part I), the operating conditions of the iodide–iodate reaction system used to quantify micromixing phenomena in chemical reactors and mixers has been presented. In order to determine the micromixing time through models, the complete kinetics of the reactions must be known. This paper presents the kinetics of the Dushman reaction obtained in operating conditions close to

Pierrette Guichardon; Laurent Falk; Jacques Villermaux

2000-01-01

283

Effect of ADP on Na+-Na+ Exchange Reaction Kinetics of Na,K-ATPase  

PubMed Central

The whole-cell voltage-clamp technique was used in rat cardiac myocytes to investigate the kinetics of ADP binding to phosphorylated states of Na,K-ATPase and its effects on presteady-state Na+-dependent charge movements by this enzyme. Ouabain-sensitive transient currents generated by Na,K-ATPase functioning in electroneutral Na+-Na+ exchange mode were measured at 23°C with pipette ADP concentrations ([ADP]) of up to 4.3 mM and extracellular Na+ concentrations ([Na]o) between 36 and 145 mM at membrane potentials (VM) from ?160 to +80 mV. Analysis of charge-VM curves showed that the midpoint potential of charge distribution was shifted toward more positive VM both by increasing [ADP] at constant Na+o and by increasing [Na]o at constant ADP. The total quantity of mobile charge, on the other hand, was found to be independent of changes in [ADP] or [Na]o. The presence of ADP increased the apparent rate constant for current relaxation at hyperpolarizing VM but decreased it at depolarizing VM as compared to control (no added ADP), an indication that ADP binding facilitates backward reaction steps during Na+-Na+ exchange while slowing forward reactions. Data analysis using a pseudo three-state model yielded an apparent Kd of ?6 mM for ADP binding to and release from the Na,K-ATPase phosphoenzyme; a value of 130 s?1 for k2, a rate constant that groups Na+ deocclusion/release and the enzyme conformational transition E1?P ? E2-P; a value of 162 s?1M?1 for k?2, a lumped second-order VM-independent rate constant describing the reverse reactions; and a Hill coefficient of ?1 for Na+o binding to E2-P. The results are consistent with electroneutral release of ADP before Na+ is deoccluded and released through an ion well. The same approach can be used to study additional charge-moving reactions and associated electrically silent steps of the Na,K-pump and other transporters.

Peluffo, R. Daniel

2004-01-01

284

Radical Recombination Kinetics: An Experiment in Physical Organic Chemistry.  

ERIC Educational Resources Information Center

|Describes a student kinetic experiment involving second order kinetics as well as displaying photochromism using a wide variety of techniques from both physical and organic chemistry. Describes measurement of (1) the rate of the recombination reaction; (2) the extinction coefficient; and (3) the ESR spectrometer signal. (Author/JN)|

Pickering, Miles

1980-01-01

285

Kinetics and mechanism of ligand-exchange reactions of Cd(II) chelates  

SciTech Connect

Tetrahedral Cd(II) bis(5-thio(or seleno)pyrazole-4-carboxaldiminates) of types II and III have been synthesized for the first time. The kinetics of the degenerate ligand exchange and enantiomerization of the complexes obtained have been studied by dynamic /sup 111/Cd, /sup 77/Se, and /sup 1/H (s = 1/2) NMR. The rate of intramolecular enantiomerization (k = 1/tau) is more than an order of magnitude greater than the corresponding values for processes of degenerate ligand exchange (a second-order reaction) determined from the dynamics of the averaging of the /sup 111/Cd-/sup 77/Se and /sup 111/Cd-N=CH spin-spin coupling constants. The cleavage and formation processes of the Cd-Se and Cd-N bonds are isoenergetic (..delta.. G/sub 298//sup not equal to/ = 14.4 kcal/mole for chelate II with X = Se and R = CH/sub 2/C/sub 6/H/sub 5/). The free energies of activation of degenerate ligand exchange determined form the dynamics of the averaging of the /sup 111/Cd N=CH spin-spin coupling constant increase from 12.7 to 17.9 kcal/mole along the following series for R: C/sub 2/H/sub 5/ < Ar < CH/sub 2/C/sub 6/H/sub 5/ < t-C/sub 4/H/sub 9/ < cyclo-C/sub 6/H/sub 11/. Replacement of the sulfur atom in the chelate ring by selenium results in increases in the rates of ligand exchange. A mechanism of degenerate ligand exchange has been proposed.

Nivorozhkin, L.E.; Kalabin, G.A.; Nivorozhkin, A.L.; Valeev, R.B.; Minkin, V.I.

1987-03-01

286

Second order scheme for Maxwell's equations with discontinuous dielectric permittivity on structured meshes  

NASA Astrophysics Data System (ADS)

A second order finite volume scheme for numerical solution of Maxwell's equations with discontinuous dielectric permittivity on structured meshes is suggested. The scheme is based on approaches of Godunov, Lax-Wendroff and Van Leer. The distinctive feature of the suggested scheme is calculation and limitation of derivatives that ensures second order of approximation even in the cells adjacent to dielectric permittivity discontinuity. Numerical tests for problems with linear and curvilinear dielectric permittivity discontinuities confirm second order of approximation.

Ismagilov, Timur Z.

2013-10-01

287

Oscillation criteria for second order forced elliptic differential equations with mixed nonlinearities  

Microsoft Academic Search

In the case of oscillatory potentials, we establish some oscillation criteria for the second order forced elliptic differential equation with mixed nonlinearities div(A(x)?y)+?b(x),?y?+C(x,y)=e(x). When N=1, our results extend those of Kong [Q. Kong, Interval criteria for oscillation of second order linear ordinary differential equations, J. Math. Anal. Appl. 229 (1999) 258–270] for certain second order linear ordinary differential equations, Sun

Zhiting Xu

2008-01-01

288

Stability-Controllable Second-order Difference scheme for convection term  

Microsoft Academic Search

A new finite difference scheme-SCSD scheme has been proposed based on CD (Central Difference) scheme and SUD (Second-order\\u000a Upwind Difference) scheme. Its basic feature is controllable convective stability and always second-order accuracy (Stability-Controllable\\u000a Second-order Difference). It has been proven that this scheme is convective-stable if the grid Peclet number |P?|?2\\/?(0???1). The advantage of this new scheme has been discussed based

Ming-Jiu Ni; Wen-Quan Tao; Shang-Jin Wang

1998-01-01

289

Optimal Central Composite Designs for Fitting Second Order Response Surface Linear Regression Models  

Microsoft Academic Search

The central composite design (CCD) is a design widely used for estimating second order response surfaces. It is perhaps the\\u000a most popular class of second order designs. Since introduced by Box and Wilson (1951), the CCD has been studied and used by\\u000a many researchers.\\u000a \\u000a This paper deals with optimal CCDs under several design criteria for fitting second order response surface

Sung Hyun Park; Hyuk Joo Kim; Jae-Il Cho

290

Nonsingularity in second-order cone programming via the smoothing metric projector  

Microsoft Academic Search

Based on the differential properties of the smoothing metric projector onto the second-order cone, we prove that, for a locally\\u000a optimal solution to a nonlinear second-order cone programming problem, the nonsingularity of the Clarke’s generalized Jacobian\\u000a of the smoothing Karush-Kuhn-Tucker system, constructed by the smoothing metric projector, is equivalent to the strong second-order\\u000a sufficient condition and constraint nondegeneracy, which is

Yun Wang; Liwei Zhang

2010-01-01

291

Second-order subdifferential calculus with applications to tilt stability in optimization  

Microsoft Academic Search

The paper concerns the second-order generalized differentiation theory of variational analysis and new applications of this theory to some problems of constrained optimization in finitedimensional spaces. The main attention is paid to the so-called (full and partial) second-order subdifferentials of extended-real-valued functions, which are dual-type constructions generated by coderivatives of frst-order subdifferential mappings. We develop an extended second-order subdifferential calculus

B. S. Mordukhovich; R. T. Rockafellar

2011-01-01

292

SEMI-ANALYTICAL FORMULATION FOR SECOND-ORDER DIFFRACTION BY A VERTICAL CYLINDER IN BICHROMATIC WAVES  

Microsoft Academic Search

This paper extends the exact theory for second-order wave diffraction by a vertical cylinder in monochromatic waves to the case of bichromatic incident waves. On the basis of the usual assumption of an irrotational flow, the wave-diffraction problems at second-order sum-frequencies and difference-frequencies are considered. The corresponding second-order diffraction potentials are decomposed into three parts; these are associated with the

R. Eatock Taylor; J. B. Huang

1997-01-01

293

Kinetics of the reactions of allylsilanes, allylgermanes, and allylstannanes with carbenium ions  

Microsoft Academic Search

AbsbPct Second-order rate constants for the reactions of para-substituted diarylmrbenium ions (ArAr'CH' = 1) with allylsilanes 2, allylgermanes 3, and allylstannanes 4 have been determined in CH2C12 solution at -70 to -30 OC. Generally, the attack of ArAr'CH+ at the CC double bond of the allylelement compounds 2-4 is rate-determining and leads to the formation of the j3-element-stabilized carbenium ions

Gisela Hagen; Herbert Mayr

1991-01-01

294

Inferring Genetic Interactions via a Data-Driven Second Order Model  

PubMed Central

Genetic/transcriptional regulatory interactions are shown to predict partial components of signaling pathways, which have been recognized as vital to complex human diseases. Both activator (A) and repressor (R) are known to coregulate their common target gene (T). Xu et al. (2002) proposed to model this coregulation by a fixed second order response surface (called the RS algorithm), in which T is a function of A, R, and AR. Unfortunately, the RS algorithm did not result in a sufficient number of genetic interactions (GIs) when it was applied to a group of 51 yeast genes in a pilot study. Thus, we propose a data-driven second order model (DDSOM), an approximation to the non-linear transcriptional interactions, to infer genetic and transcriptional regulatory interactions. For each triplet of genes of interest (A, R, and T), we regress the expression of T at time t?+?1 on the expression of A, R, and AR at time t. Next, these well-fitted regression models (viewed as points in R3) are collected, and the center of these points is used to identify triples of genes having the A-R-T relationship or GIs. The DDSOM and RS algorithms are first compared on inferring transcriptional compensation interactions of a group of yeast genes in DNA synthesis and DNA repair using microarray gene expression data; the DDSOM algorithm results in higher modified true positive rate (about 75%) than that of the RS algorithm, checked against quantitative RT-polymerase chain reaction results. These validated GIs are reported, among which some coincide with certain interactions in DNA repair and genome instability pathways in yeast. This suggests that the DDSOM algorithm has potential to predict pathway components. Further, both algorithms are applied to predict transcriptional regulatory interactions of 63 yeast genes. Checked against the known transcriptional regulatory interactions queried from TRANSFAC, the proposed also performs better than the RS algorithm.

Jiang, Ci-Ren; Hung, Ying-Chao; Chen, Chung-Ming; Shieh, Grace S.

2012-01-01

295

Simulation of hydrodynamics using large eddy simulation-second-order moment model in circulating fluidized beds  

NASA Astrophysics Data System (ADS)

Flow behavior of gas and particles is predicted by the large eddy simulation of gas-second order moment of solid model (LES-SOM model) in the simulation of flow behavior in CFB. This study shows that the simulated solid volume fractions along height using a two-dimensional model are in agreement with experiments. The velocity, volume fraction and second-order moments of particles are computed. The second-order moments of clusters are calculated. The solid volume fraction, velocity and second order moments are compared at the three different model constants.

Juhui, Chen; Yanjia, Tang; Dan, Li; Pengfei, Xu; Huilin, Lu

2013-07-01

296

Reaction kinetics of the hydrothermal treatment of lignin.  

PubMed

Lignins derived from abundant and renewable resources are nontoxic and extremely versatile in performance, qualities that have made them increasingly important in many industrial applications. We have shown recently that liquefaction of lignin extracted from aspen wood resulted in a 90% yield of liquid. In this paper, the hydrothermal treatment of five types of lignin and biomass residues was studied: Kraft pine lignin provided by MeadWestvaco, Kraft pine lignin from Sigma-Aldrich, organosolv lignin extracted from oat hull, the residues of mixed southern hardwoods, and switchgrass after hydrolysis. The yields were found dependent on the composition or structure of the raw materials, which may result from different pretreatment processes. We propose a kinetic model to describe the hydrothermal treatment of Kraft pine lignin and compare it with another model from the literature. The kinetic parameters of the presented model were estimated, including the reaction constants, the pre-exponential factor, and the activation energy of the Arrhenius equations. Results show that the presented model is well in agreement with the experiments. PMID:18401758

Zhang, Bo; Huang, Hua-Jiang; Ramaswamy, Shri

2007-10-23

297

Kinetic study of the reactions between chloramine disinfectants and hydrogen peroxide: temperature dependence and reaction mechanism.  

PubMed

The temperature-dependent kinetics for the reaction between hydrogen peroxide and chloramine water disinfectants (NH2Cl, NHCl2, and NCl3) have been determined using stopped flow-UV/Vis spectrophotometry. Rate constants for the mono- and dichloramine-peroxide reaction were on the order of 10(-2)M(-1)s(-1) and 10(-5)M(-1)s(-1), respectively. The reaction of trichloramine with peroxide was negligibly slow compared to its thermal and photolytically-induced decomposition. Arrhenius expressions of ln(kH2O2-NH2Cl)=(17.3±1.5)-(51500±3700)/RT and ln(kH2O2-NHCl2)=(18.2±1.9)-(75800±5100)/RT were obtained for the mono- and dichloramine peroxide reaction over the temperature ranges 11.4-37.9 and 35.0-55.0°C, respectively. Both monochloramine and hydrogen peroxide were first-order in the rate-limiting kinetic step and concomitant measurements made using a chloride ion selective electrode showed that the chloride was produced quantitatively. These data will aid water utilities in predicting chloramine concentrations (and thus disinfection potential) throughout the water distribution system. PMID:23601896

McKay, Garrett; Sjelin, Brittney; Chagnon, Matthew; Ishida, Kenneth P; Mezyk, Stephen P

2013-04-17

298

Kinetic study of hydrated lime reaction with HCl.  

PubMed

Hydrochloride (HCl) is an acidic pollutant present in the flue gas of most municipal or hazardous waste incinerators. Hydrated lime (Ca(OH)2) is often used as a dry sorbent for injection in a spray reactor to remove HCI. However, due to the short residence time encountered, this control method has generally been found to have low conversion efficiencies which results in the high lime usage and generates large amount of fly ash as solid wastes. A fundamental study was carried outto investigate the kinetics of HCl-lime reaction under simulated flue gas conditions in order to better understand the process thereby providing a basis for an optimized lime usage and reduced fly ash production. The initial reaction rate and conversion of three limes were studied using a thermogravimetric analyzer by varying the gas flow rate, temperature (170-400 degrees C), and HCI concentrations (600-1200 mg/m3) as well as the associated particle size and surface area of the limes. The initial lime conversions were found to rely mostly on the residence time, while the ultimate lime conversions were strongly influenced by temperature and the reaction products. CaOHCI was found to be the primary product in most cases, while for one specific lime, CaCl2 was the ultimate conversion product after an extended time period. The true utilization of lime in flue gas cleanup is thus higher when CaOHCl is considered as the final product than those based on CaCl2 as the final product, which has been commonly used in previous studies. The initial reaction was controlled by diffusion of HCl in gas phase and the subsequent reaction by gaseous diffusion through the developing product layer. Increasing the HCI concentration raised the initial rate as well as conversion. However, overloading the lime with excessive HCI caused clogging at its surface and a drop in the ultimate conversion. Limes with smaller particle diameters and higher surface areas were found to be more reactive. The effect of gas-phase mass transfer was minimized when an optimum flow rate was chosen, and in the absence of internal diffusion the reaction was found to be first order with respect to HCI concentration. PMID:12831043

Yan, Rong; Chin, Terence; Liang, David Tee; Laursen, Karin; Ong, Wan Yean; Yao, Kaiwen; Tay, Joo Hwa

2003-06-01

299

Theoretical analysis of kinetic isotope effects on proton transfer reactions between substituted alpha-methoxystyrenes and substituted acetic acids.  

PubMed

Primary kinetic isotope effects (KIEs) on a series of carboxylic acid-catalyzed protonation reactions of aryl-substituted alpha-methoxystyrenes (X-1) to form oxocarbenium ions have been computed using the second-order Kleinert variational perturbation theory (KP2) in the framework of Feynman path integrals (PI) along with the potential energy surface obtained at the B3LYP/6-31+G(d,p) level. Good agreement with the experimental data was obtained, demonstrating that this novel computational approach for computing KIEs of organic reactions is a viable alternative to the traditional method employing Bigeleisen equation and harmonic vibrational frequencies. Although tunneling makes relatively small contributions to the lowering of the free energy barriers for the carboxylic acid catalyzed protonation reaction, it is necessary to include tunneling contributions to obtain quantitative estimates of the KIEs. Consideration of anharmonicity can further improve the calculated KIEs for the protonation of substituted alpha-methoxystyrenes by chloroacetic acid, but for the reactions of the parent and 4-NO(2) substituted alpha-methoxystyrene with substituted carboxylic acids, the correction of anharmonicity overestimates the computed KIEs for strong acid catalysts. In agreement with experimental findings, the largest KIEs are found in nearly ergoneutral reactions, DeltaG(o) approximately 0, where the transition structures are nearly symmetric and the reaction barriers are relatively low. Furthermore, the optimized transition structures are strongly dependent on the free energy for the formation of the carbocation intermediate, that is, the driving force DeltaG(o), along with a good correlation of Hammond shift in the transition state structure. PMID:19754046

Wong, Kin-Yiu; Richard, John P; Gao, Jiali

2009-10-01

300

Quantitative assessment of trihalomethane formation using simulations of reaction kinetics.  

PubMed

A modelling procedure with a time discretisation of 1 min is developed in order to study and simulate the kinetics of formation of total trihalomethanes (TTHM) in water treatment plants. This methodology was applied on two significant processing units of Athens (Galatsi Treatment Plant-GTP, Menidi Treatment Plant-MTP). The fundamental concept of the model was based on the representation of the water treatment plant as a mixed flow reactor, where the formation of TTHM was predicated on a generalised reaction of total halogens with an organic precursor. Differential rates of reactants and products were expressed in terms of the reaction stoichiometry. Volatilisation, flocculation, coagulation and sedimentation processes were also incorporated in the model in order to assess their distinct role. The most appropriate coefficient set was sought and it was found that a stoichiometric ratio of 0.5 for total halogen, 0.6 for organic substrate and 0.2 for TTHM (or 2.5:3:1) resulted in the best fit between simulated and experimental data. The present modelling approach should be considered as a promising methodological basis towards the realistic reproduction of the dynamics of water treatment plants and the development of reliable numerical tools for the accurate prediction of THM formation. PMID:12146874

Golfinopoulos, Spyros K; Arhonditsis, George B

2002-06-01

301

Predicting perfect adaptation motifs in reaction kinetic networks.  

PubMed

Adaptation and compensation mechanisms are important to keep organisms fit in a changing environment. "Perfect adaptation" describes an organism's response to an external stepwise perturbation by resetting some of its variables precisely to their original preperturbation values. Examples of perfect adaptation are found in bacterial chemotaxis, photoreceptor responses, or MAP kinase activities. Two concepts have evolved for how perfect adaptation may be understood. In one approach, so-called "robust perfect adaptation", the adaptation is a network property (due to integral feedback control), which is independent of rate constant values. In the other approach, which we have termed "nonrobust perfect adaptation", a fine-tuning of rate constant values is needed to show perfect adaptation. Although integral feedback describes robust perfect adaptation in general terms, it does not directly show where in a network perfect adaptation may be observed. Using control theoretic methods, we are able to predict robust perfect adaptation sites within reaction kinetic networks and show that a prerequisite for robust perfect adaptation is that the network is open and irreversible. We applied the method on various reaction schemes and found that new (robust) perfect adaptation motifs emerge when considering suggested models of bacterial and eukaryotic chemotaxis. PMID:19367864

Drengstig, Tormod; Ueda, Hiroki R; Ruoff, Peter

2008-12-25

302

Kinetic analysis of the genome packaging reaction in bacteriophage lambda.  

PubMed

Bacteriophage lambda is a double-stranded DNA virus that infects the Escherichia coli bacterium. lambda genomic DNA is replicated via rolling circle replication, resulting in multiple genomes linked head to tail at the cos site. To insert a single lambda genome into the viral capsid, the lambda terminase enzyme introduces symmetric nicks, 12 bp apart, at the cos site, and then promotes a strand separation reaction, releasing the tail end of the previous genome and leaving a binary complex consisting of lambda terminase bound to the head end of the adjacent genome. Next, the genome is translocated into the interior of the capsid particle, in a process that requires ATP hydrolysis by lambda terminase. Even though DNA packaging has been studied extensively, currently no bulk assays are available that have been optimized to report directly on DNA translocation. Rather, these assays are sensitive to assembly steps reflecting formation of the active, DNA packaging machine. In this work, we have modified the DNase protection assay commonly used to study DNA packaging in several bacteriophage systems, such that it reports directly on the kinetics of the DNA packaging reaction. We have analyzed our DNA packaging data according to an N-step sequential minimal kinetic model and have estimated an overall packaging rate of 119 +/- 8 bp/s, at 4 degrees C and 1 mM ATP. Furthermore, we have measured an apparent step size for the this reaction (m(obs)) of 410 +/- 150 bp. The magnitude of this value indicates that our assay is most likely sensitive to both mechanical steps associated with DNA insertion as well as occasional slow steps that are repeated every >410 bp. These slow steps may be reflective of the pausing events observed in recent single-molecule studies of DNA packaging in bacteriophage lambda [Fuller, D. N., et al. (2007) J. Mol. Biol. 373, 1113-1122]. Finally, we show that either ATP or ADP is required for terminase cutting at cos, to generate the active, DNA packaging complex. PMID:19788336

Yang, Qin; Catalano, Carlos E; Maluf, Nasib Karl

2009-11-17

303

Reaction Kinetics and Transport in Relaxing Gases Reaktionskinetik und Transport in Relaxierenden Gasen.  

National Technical Information Service (NTIS)

Kinetic theory is applied in order to calculate the influence of internal excitations, chemical reactions, and nonequilibrium effects on rate constants and transport coefficients in gases. Dissociative reactions and three-body recombinations are taken int...

K. Baerwinkel H. Wolters

1975-01-01

304

Detailed Chemical Kinetic Reaction Mechanisms for Incineration of Organophosphorus and Fluoro-Organophosphorus Compounds.  

National Technical Information Service (NTIS)

A detailed chemical kinetic reaction mechanism is developed to describe incineration of the chemical warfare nerve agent sarin (GB), based on commonly used principles of bond additivity and hierarchical reaction mechanisms. The mechanism is based on previ...

P. A. Glaude C. Melius W. J. Pitz C. K. Westbrook

2001-01-01

305

New oscillation criteria for second order linear difference equations with positive and negative coefficients  

Microsoft Academic Search

The oscillation of second order neutral difference equations with positive and negative coefficients of the form ?2(xn+?anxn??)+pnxn???qnxn??=0,?=±1 is investigated. We obtain many new results using the comparison between both first order and second order difference equations. An example is given to show the strength of the obtained results.

Hassan A. El-Morshedy

2009-01-01

306

Post processing with first- and second-order hidden Markov models  

NASA Astrophysics Data System (ADS)

In this paper, we present the implementation and evaluation of first order and second order Hidden Markov Models to identify and correct OCR errors in the post processing of books. Our experiments show that the first order model approximately corrects 10% of the errors with 100% precision, while the second order model corrects a higher percentage of errors with much lower precision.

Taghva, Kazem; Poudel, Srijana; Malreddy, Spandana

2013-01-01

307

The support vector machine learning using the second order cone programming  

Microsoft Academic Search

We propose a data dependent learning method for the support vector machine. This method is based on the technique of second order cone programming. We reformulate the SVM quadratic problem into the second order cone problem. The proposed method requires decomposing the kernel matrix of SVM optimization problem. In this paper we apply Cholesky decomposition method. Since the kernel matrix

Rameswar Debnath; Masakazu Muramatsu; Haruhisa Takahashi

2004-01-01

308

Stability and statistical properties of second-order bidirectional associative memory  

Microsoft Academic Search

In this paper, a bidirectional associative memory (BAM) model with second-order connections, namely second-order bidirectional associative memory (SOBAM), is first reviewed. The stability and statistical properties of the SOBAM are then examined. We use an example to illustrate that the stability of the SOBAM is not guaranteed. For this result, we cannot use the conventional energy approach to estimate its

Chi-Sing Leung; Lai-Wan Chan; E. M. K. Lai

1997-01-01

309

Application of Second Order TVD and WENO Schemes in Internal Aerodynamics  

Microsoft Academic Search

We deal with the comparison of several finite volume TVD schemes and finite difference ENO schemes and we describe a second order finite volume WENO scheme which was developed for the case of general unstructured meshes. The proposed second order WENO reconstruction is much simpler than the original ENO scheme introduced in [Harten and Chakravarthy 1991]. Moreover, the proposed WENO

Jirí Fürst; Karel Kozel

2002-01-01

310

Exact second-order estimates for the effective mechanical properties of nonlinear composite materials  

Microsoft Academic Search

Motivated by previous small-contrast perturbation estimates, this paper proposes a new method for estimating the effective behavior of nonlinear composite materials with arbitrary phase contrast. The key idea is to write down a second-order Taylor expansion for the phase potentials, about appropriately defined phase average strains. The resulting estimates, which are exact to second order in the contrast, involve the

P. Ponte Castañeda

1996-01-01

311

Second-order space focusing in two-field time-of-flight mass spectrometers  

Microsoft Academic Search

Design equations are given for second-order space focusing in two-field time-of-flight mass spectrometers. Simulations and experimental tests confirm that, for diffuse sources and high-energy fragments, second-order designs give superior resolution and linearity of flight time deviations to initial ion velocities.

J. H. D. Eland

1993-01-01

312

Find Intelligent Knowledge by Second-Order Mining: Three Cases from China  

Microsoft Academic Search

This paper discusses the second-order mining of the results of data mining. There is still gap between the knowledge which can direct the operation of company and the knowledge got from data mining. We take the knowledge from data mining as primary knowledge and the knowledge from second-order data mining as intelligent knowledge. We discuss the importance of intelligent knowledge

Guangli Nie; Lingling Zhang; Yuejin Zhang; Wei Deng; Yong Shi

2010-01-01

313

A frequency domain analysis of a second order iterative learning control algorithm  

Microsoft Academic Search

A frequency domain analysis method of a second order iterative learning control (ILC) algorithm is considered. Using the notion of iterative systems bounds for stability are presented in the frequency domain for the second order term. The bounds are found using a geometrical approach based on the special structure of the transfer matrix in the iterative system. Two examples are

M. Norrlof; S. Gunnarsson

1999-01-01

314

Identification of Hemorphins from Bovine Hemoglobin Hydrolysate: Application of UV Second Order Derivative Spectroscopy  

Microsoft Academic Search

Aromatic amino acids have very informative second order derivative spectra. Whereas they exhibit overlapping maxima between 250 and 300nm in the zero order spectra, thin minima are obtained in their second order derivative spectra. This feature allowed to develop a method to identify aromatic amino acids, but also to calculate the ratio between these amino acids in peptides and proteins.

Q. Zhao; I. Garreau; F. Sannier; J. M. Piot

1995-01-01

315

Unified interpretation for second-order subwavelength interference based on Feynman's path-integral theory  

SciTech Connect

The second-order spatial subwavelength interference pattern is observed in a modified Michelson interferometer with single-mode continuous-wave laser beams. By analyzing our subwavelength interference experiment based on Feynman's path integral theory, a unified interpretation for all the second-order subwavelength interference is suggested.

Liu Jianbin; Zhang Guoquan [MOE Key Laboratory of Weak Light Nonlinear Photonics, Nankai University, Tianjin 300457 (China) and Photonics Center, School of Physics, Nankai University, Tianjin 300071 (China)

2010-07-15

316

Asymptotic approximations for second-order linear difference equations in Banach algebras, I  

NASA Astrophysics Data System (ADS)

An asymptotic approximation theory is developed for some classes of linear second-order difference equations in Banach algebras, subject to "finite moments perturbations." The special case of linear matrix difference equations (or, equivalently, of second-order systems) is included. Rigorous and explicitly computable bounds for the error terms are obtained.

Soldà, Tania; Spigler, Renato; Vianello, Marco

2008-01-01

317

Superelectrophilicity of the nitroolefinic fragment of 4-nitrobenzodifuroxan in Michael-type reactions with indoles: a kinetic study in acetonitrile.  

PubMed

The kinetics of the coupling of 4-nitrobenzodifuroxan (NBDF) with a series of indoles 8 a-e to give the expected Michael-type adducts 9 a-e have been investigated in acetonitrile solution. No significant influence of the nature of the isotopic substitution at C-3 of the indole ring has been found, indicating that the NBDF addition step is the rate limiting step of the SEAr substitution of the indole moiety. This implies that the measured second-order rate constants (k) for the reactions are identical to the second order rate constants (k1NBDF) associated to the C--C coupling step. By using the known N and s parameters characterizing the nucleophilicity of indoles, the k1NBDF rate constants are found to fit nicely to the three parameters equation logk1=s(N+E) introduced by Mayr to describe the feasibility of nucleophilic-electrophilic combinations. Based on this, the electrophilicity parameter E of NBDF could be determined as E=-6.15. This corresponds to a positioning of the reactivity of the nitroactivated double bond of NBDF in the domain of superelectrophilicity previously defined for nitrobenzofuroxans, in accord with the finding that the rates of coupling of 8 a-e with NBDF are only one order of magnitude lower than those for the coupling of these indoles with 4,6-dinitrobenzofuroxan (DNBF). The theoretical scale of electrophilicity introduced by Domingo et al. on the basis of the global electrophilicity index omega defined by Parr is also a very useful tool to discuss the relative reactivities of NBDF, DNBF, and a number of differently activated C==C double bonds. PMID:17642071

Lakhdar, Sami; Goumont, Régis; Berionni, Guillaume; Boubaker, Taoufik; Kurbatov, Sergey; Terrier, François

2007-01-01

318

Second-order random internal and surface waves in a two-fluid system  

NASA Astrophysics Data System (ADS)

Second-order solutions for internal and surface waves in a two-fluid system are derived using a perturbation technique. As expected, solutions of the second order are composed of the products of the first-order components. Super- and subharmonic transfer functions describing the relation between the first- and second-order wave amplitudes are introduced. For the self interaction of the first-order waves with a fixed wavenumber, there exist three combinations of linear waves. The associated superharmonic transfer function and the effects of second-order waves on wave profiles are examined. Furthermore, taking the density of the upper layer to be zero, present results include most existing theories for second-order surface waves as special cases.

Liu, Chi-Min

2006-03-01

319

Second order gravitational effects on CMB temperature anisotropy in {lambda} dominated flat universes  

SciTech Connect

We study second order gravitational effects of local inhomogeneities on the cosmic microwave background radiation in flat universes with matter and a cosmological constant {lambda}. We find that the general relativistic correction to the Newtonian approximation is negligible at second order provided that the size of the inhomogeneous region is sufficiently smaller than the horizon scale. For a spherically symmetric top-hat type quasilinear perturbation, the first order temperature fluctuation corresponding to the linear integrated Sachs-Wolfe effect is enhanced (suppressed) by the second order one for a compensated void (lump). As a function of redshift of the local inhomogeneity, the second order temperature fluctuations due to evolution of the gravitational potential have a peak before the matter-{lambda} equality epoch for a fixed comoving size and a density contrast. The second order gravitational effects from local quasilinear inhomogeneities at a redshift z{approx}1 may significantly affect the cosmic microwave background.

Tomita, Kenji; Inoue, Kaiki Taro [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Department of Science and Engineering, Kinki University, Higashi-Osaka, 577-8502 (Japan)

2008-05-15

320

Data-based symbolic simplification of kinetic mechanisms for surface reaction networks  

Microsoft Academic Search

Detailed kinetic surface reaction mechanisms are used in kinetic models for automotive catalysis applications. Therefore, these models are complex and often numerically stiff. For simulation, optimization and control purposes it is desirable to employ models of lower complexity that are accurate in specific operating regimes. In this contribution, a number of data-based kinetic mechanism reduction methods are combined in order

K. M. Nauta

2006-01-01

321

Kinetic Modelling of GlmU Reactions - Prioritization of Reaction for Therapeutic Application  

PubMed Central

Mycobacterium tuberculosis(Mtu), a successful pathogen, has developed resistance against the existing anti-tubercular drugs necessitating discovery of drugs with novel action. Enzymes involved in peptidoglycan biosynthesis are attractive targets for antibacterial drug discovery. The bifunctional enzyme mycobacterial GlmU (Glucosamine 1-phosphate N-acetyltransferase/ N-acetylglucosamine-1-phosphate uridyltransferase) has been a target enzyme for drug discovery. Its C- and N- terminal domains catalyze acetyltransferase (rxn-1) and uridyltransferase (rxn-2) activities respectively and the final product is involved in peptidoglycan synthesis. However, the bifunctional nature of GlmU poses difficulty in deciding which function to be intervened for therapeutic advantage. Genetic analysis showed this as an essential gene but it is still unclear whether any one or both of the activities are critical for cell survival. Often enzymatic activity with suitable high-throughput assay is chosen for random screening, which may not be the appropriate biological function inhibited for maximal effect. Prediction of rate-limiting function by dynamic network analysis of reactions could be an option to identify the appropriate function. With a view to provide insights into biochemical assays with appropriate activity for inhibitor screening, kinetic modelling studies on GlmU were undertaken. Kinetic model of Mtu GlmU-catalyzed reactions was built based on the available kinetic data on Mtu and deduction from Escherichia coli data. Several model variants were constructed including coupled/decoupled, varying metabolite concentrations and presence/absence of product inhibitions. This study demonstrates that in coupled model at low metabolite concentrations, inhibition of either of the GlmU reactions cause significant decrement in the overall GlmU rate. However at higher metabolite concentrations, rxn-2 showed higher decrement. Moreover, with available intracellular concentration of the metabolites and in vivo variant of model, uncompetitive inhibition of rxn-2 caused highest decrement. Thus, at physiologically relevant metabolite concentrations, targeting uridyltranferase activity of Mtu GlmU would be a better choice for therapeutic intervention.

Singh, Vivek K.; Das, Kaveri; Seshadri, Kothandaraman

2012-01-01

322

Kinetic rotating droplet electrochemistry: a simple and versatile method for reaction progress kinetic analysis in microliter volumes.  

PubMed

Here, we demonstrate a new generic, affordable, simple, versatile, sensitive, and easy-to-implement electrochemical kinetic method for monitoring, in real time, the progress of a chemical or biological reaction in a microdrop of a few tens of microliters, with a kinetic time resolution of ca. 1 s. The methodology is based on a fast injection and mixing of a reactant solution (1-10 ?L) in a reaction droplet (15-50 ?L) rapidly rotated over the surface of a nonmoving working electrode and on the recording of the ensuing transient faradaic current associated with the transformation of one of the components. Rapid rotation of the droplet was ensured mechanically by a rotating rod brought in contact atop the droplet. This simple setup makes it possible to mix reactants efficiently and rotate the droplet at a high spin rate, hence generating a well-defined hydrodynamic steady-state convection layer at the underlying stationary electrode. The features afforded by this new kinetic method were investigated for three different reaction schemes: (i) the chemical oxidative deprotection of a boronic ester by H2O2, (ii) a biomolecular binding recognition between a small target and an aptamer, and (iii) the inhibition of the redox-mediated catalytic cycle of horseradish peroxidase (HRP) by its substrate H2O2. For the small target/aptamer binding reaction, the kinetic and thermodynamic parameters were recovered from rational analysis of the kinetic plots, whereas for the HRP catalytic/inhibition reaction, the experimental amperometric kinetic plots were reproduced from numerical simulations. From the best fits of simulations to the experimental data, the kinetics rate constants primarily associated with the inactivation/reactivation pathways of the enzyme were retrieved. The ability to perform kinetics in microliter-size samples makes this methodology particularly attractive for reactions involving low-abundance or expensive reagents. PMID:23985016

Challier, Lylian; Miranda-Castro, Rebeca; Marchal, Damien; Noël, Vincent; Mavré, François; Limoges, Benoît

2013-09-17

323

Kinetic energies and reactions of trapped ions in a Fourier transform ion cyclotron resonance mass spectrometer  

Microsoft Academic Search

Three independent investigations to ascertain the kinetic energies of trapped ions in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer were performed. Two of these studies were accomplished with the observation of ion-molecule reactions. The quantification of ion-molecule reaction rate constants as well as equilibrium constants was employed for ion kinetic energy determinations. The third inquiry relied on ion

Bruce

1992-01-01

324

Evaluating the interfacial reaction kinetics of the bipolar membrane interface in the bipolar membrane fuel cell.  

PubMed

A reaction kinetic model of the bipolar membrane interface in the bipolar membrane fuel cell (BPMFC) was proposed based on the p-n junction theory and chemical reaction kinetics. It verified the self-humidification feasibility of the BPMFC successfully. PMID:23744271

Peng, Sikan; Lu, Shanfu; Zhang, Jin; Sui, Pang-Chieh; Xiang, Yan

2013-06-06

325

Kinetics of Ethyl Acetate Synthesis Catalyzed by Acidic Resins  

ERIC Educational Resources Information Center

|A low-cost experiment to carry out the second-order reversible reaction of acetic acid esterification with ethanol to produce ethyl acetate is presented to illustrate concepts of kinetics and reactor modeling. The reaction is performed in a batch reactor, and the acetic acid concentration is measured by acid-base titration versus time. The…

Antunes, Bruno M.; Cardoso, Simao P.; Silva, Carlos M.; Portugal, Ines

2011-01-01

326

Electrochemical Study of the Reaction of Zinc Diisooctyldithiophosphate with Cumylhydroperoxide  

Microsoft Academic Search

Kinetics of a chemical reaction of cumylhydroperoxide with zinc diisooctyldithiophosphate (ZD) in dimethylformamide is studied by voltammetric techniques and a potentiometric method with a glass electrode. In the course of reaction, the activity of hydrogen ions first increases by two orders of magnitude and then decreases. The decomposition of cumylhydroperoxide during the second period is a second-order reaction, while the

E. A. Stezeryanskii

2005-01-01

327

Kinetics and Mechanism of Iodide Oxidation by Iron(III): A Clock Reaction Approach  

ERIC Educational Resources Information Center

|A simple method for studying the kinetics of a chemical reaction is described and the significance of reaction orders in deducing reaction mechanisms is demonstrated. In this student laboratory experiment, oxidation of iodide by iron(III) ions in an acidic medium is transformed into a clock reaction. By means of the initial rates method, it is…

Bauer, Jurica; Tomisic, Vladislav; Vrkljan, Petar B. A.

2008-01-01

328

Kinetics of the thermal reaction of H atoms with propyne.  

PubMed

The reaction of hydrogen atoms with propyne (CH[triple bond]CCH(3)) was investigated in a heated single pulse-shock tube at temperatures of 874-1196 K and pressures of 1.6-7.6 bar. Stable products from various reaction channels (terminal and nonterminal H addition, and by inference H abstraction) were identified and quantified by gas chromatography and mass spectrometry. The rate constant for the channel involving the displacement of methyl radical from propyne (nonterminal H addition) was determined relative to the methyl displacement from 1,3,5-trimethylbenzene (135-TMB), with k (H + 135-TMB --> m-xylene + CH(3)) = 6.70 x 10(13) exp(-3255/T[K]) cm(3)/mol x s, k(H+propyne-->CH[triple bond]CH+CH3))=6.26 x 10(13) exp(-2267/T[K]) cm3/mole x s. Our results show that the acetylene to allene yield is approximately 2 at 900 K, and decreases with increasing temperature. The rate expression is: k(H+propyne-->CH2=C=CH2+H))=2.07 x 10(14) exp(-3759/T[K]) cm3/mole x s. This is a lower limit for terminal addition. Kinetic information for abstraction of the propargylic hydrogen by H was determined via mass balance. The rate expression is approximately k(H+CH3C[triple bond]CH-->CH[triple bond]C-CH2+H2))=1.20 x 10(14) exp(-4940/T[K])cm3 /mole x s and is only 10% of the rate constant for acetylene formation. All channels from H atom attack on propyne at combustion temperatures have now been determined. Comparisons are made with results of recent ab initio calculations and conclusions are drawn on the quantitative accuracy of such estimates. PMID:20394350

Rosado-Reyes, Claudette M; Manion, Jeffrey A; Tsang, Wing

2010-05-13

329

Determination of nitric oxide using horseradish peroxidase by UV second-order derivative spectrometry.  

PubMed

Based on the reaction of horseradish peroxidase (HRP) with nitric oxide (NO), a novel detection method of NO has been developed. The method uses second-order derivative spectrometry in an anaerobic phosphate buffer solution. The effects of pH and HRP concentration on the determination of NO in HRP system were investigated, and the conditions for the measurements were optimized. Some possible coexisting substances, such as nitrite, nitrate and hydrogen peroxide, were tested. The linear regression equation of standard curve was found to be h = 8.89 x 10(-2)c(NO)-1.56 x 10(-3) with the relevant coefficient of 0.9966 (n = 5) in the NO concentration range of 0.085-1.3 microM. The relative standard deviations were less than 3%. Based on the standard deviation of 5 blank measurements and a signal-to-noise ratio of 3, the detection limit for NO was 0.032 microM. The proposed method was successfully applied to the determination of NO levels in serum samples. PMID:20009336

Qiang, Li; Zhou, Jie

2009-12-01

330

Soil solid materials affect the kinetics of extracellular enzymatic reactions  

NASA Astrophysics Data System (ADS)

INTRODUCTION Soil solid materials affect the degradation processes of many organic compounds by decreasing the bioavailability of substrates and by interacting with degraders. The magnitude of this effect in the environment is shown by the fact that xenobiotics which are readily metabolized in aquatic environments can have long residence times in soil. Extracellular enzymatic hydrolysis of cellobiose (enzyme: beta-glucosidase from Aspergillus niger) was chosen as model degradation process since it is easier to control and more reproducible than a whole cell processes. Furthermore extracellular enzymes play an important role in the environment since they are responsible for the first steps in the degradation of organic macromolecules; beta-glucosidase is key enzyme in the degradation of cellulose and therefore it is fundamental in the carbon cycle and for soil in general. The aims of the project are: 1) quantification of solid material effect on degradation, 2) separation of the effects of minerals on enzyme (adsorption ?change in activity) and substrate (adsorption ?change in bioavailability). Our hypothesis is that a rate reduction in the enzymatic reaction in the presence of a solid phase results from the sum of decreased bioavailability of the substrate and decreased activity of enzyme molecules. The relative contribution of the two terms to the overall effect can vary widely depending on the chemical nature of the substrate, the properties of the enzyme and on the surface properties of the solid materials. Furthermore we hypothesize that by immobilizing the enzyme in an appropriate carrier the adsorption of enzymes to soil materials can be eliminated and that therefore immobilization can increase the overall reaction rate (activity loss caused by immobilization < activity loss caused by adsorption to soil minerals). MATERIALS AND METHODS Enzymatic kinetic experiments are carried out in homogeneous liquid systems and in heterogeneous systems where solid materials (bentonite, kaolinite, goethite, activated charcoal) are suspended in a mixed liquid (standard experimental conditions: 66 mM phosphate buffer, pH 5, 25°C, 20 mg solid/ml buffer). The enzyme in an immobilized form (covalent bonding to oxirane groups on the surfaces of macroporous Eupergit® C particles) is used to exclude a direct effect of soil solid materials on the enzyme without excluding their effect on the availability of the substrate.The progress of the reactions is determined by measuring the accumulation of the product (i.e. glucose) in the systems at different times (after destroying enzymatic activity by boiling the samples) with a coupled enzymatic assay and an automatic microplate spectrophotometer. A regression analysis on the data points is performed to calculate the initial reaction rates, which is the parameter that allows to compare the different systems. RESULTS AND DISCUSSION The results show that, under the standard experimental conditions, cellobiose is not adsorbed by the clay minerals bentonite and kaolinite and by the iron oxyhydroxide goethite. In the case of activated charcoal a rapid adsorption phase in the first 20' is followed by a much slower process; after 4h 30' approximately 98% of cellobiose was adsorbed. The results from the adsorption experiments of beta-glucosidase to bentonite, kaolinite, goethite and activated charcoal show that, under the standard experimental conditions, the adsorption process is rapid in all cases (more than 80% of the adsorption takes place in the first 20 minutes). After 1h 20min the following fractions of enzyme were adsorbed: 30 % to bentonite, 60% to kaolinite, 67% to goethite, 100% to activated charcoal. The effect of kaolinite on the reaction rate was quantified: under the standard experimental conditions the initial reaction rate in presence of the mineral was 22% less then in the control. The fraction of enzyme molecules which are adsorbed to kaolinite (60%) loses 37% of its activity. CONCLUSIONS The results from the adsorption experiments lead to the conclusion that, among the sol

Lammirato, C.; Miltner, A.; Kästner, M.

2009-04-01

331

Conditional second-order short-crested water waves applied to extreme wave episodes  

NASA Astrophysics Data System (ADS)

A derivation of the mean second-order short-crested wave pattern and associated wave kinematics, conditional on a given magnitude of the wave crest, is presented. The analysis is based on the second-order Sharma and Dean finite-water wave theory. A comparison with a measured extreme wave profile, the Draupner New Year Wave, shows a good agreement in the mean, indicating that this second-order wave can be a good identifier of the shape and occurrence of extreme wave events. A discussion on its use as an initial condition for a fully nonlinear three-dimensional surface wave analysis is given.

Juncher Jensen, Jørgen

2005-12-01

332

Optical suppression of second-order stimulated Brillouin scattering in a simple focused beam cell  

NASA Astrophysics Data System (ADS)

It has been investigated experimentally that the output energy and pulse-durational profile of first-order Stokes depend on the effective gain length due to the presence of the second-order SBS. The experimental results indicate that when the energy of an incident pump laser is strong enough and the effective gain length is relatively long, the self-accumulation of energy of first-order Stokes is enough to adequately reach a high peak power point to activate the second-order. The second-order SBS restrains the output energy of first-order to a great extent and plays an optical suppression role.

Shi, J.; He, X.; Liu, J.; Chen, W.; Mo, X.; Liu, D.; Yang, K.

2012-05-01

333

Ab initio study of the kinetics of hydrogen abstraction reactions on toluene and tetralin  

SciTech Connect

Hydrogen abstraction reactions play a key role in many thermal and catalytic processes involved in the production of fuels and chemicals. In this paper, the reaction barriers and rate constants for the hydrogen abstraction reactions on toluene and tetralin by the benzyl radical are calculated by ab initio methods. These reactions are representatives of similar reactions occurring in the thermolysis of lignin model compounds containing the phenethyl phenyl ether (PPE) structural moiety. Thermolysis of PPE occurs by a free radical chain mechanism in which the product selectivity arises from competitive hydrogen abstraction at the benzylic and nonbenzylic methylen sites by chain carrying benzyl and phenoxyl radicals. The title reactions serve to calibrate the theoretical methods to be used in the study of PPE through comparison of the rate constants and the reaction enthalpies with reliable experimental values. In this study, we used two different hybrid density functionals (BHandHLYP, B3LYP) and second-order perturbation theory to obtain equilibrium and transition state geometries. Multiple transition states were found for both reactions. BHandHLYP underestimates and second-order perturbation theory overestimates the reaction barriers; B3LYP energy barriers agree well with experiment. Absolute and relative rate constants were calculated using transition state theory. We found that the relative rate constant using the B3LYP functional agrees within a factor of 2.0 with experiment at the experimental temperature of 333 K, indicating that the B3LYP functional will be successful in predicting relative rate constants for hydrogen abstraction reactions participating in the pyrolysis of PPE.

Beste, Ariana [ORNL; Britt, Phillip F [ORNL; Buchanan III, A C [ORNL; Harrison, Robert J [ORNL; Hathorn, Bryan C [ORNL

2008-01-01

334

Kinetics and mechanism of the reaction of ozone with aromatic hydrocarbons  

Microsoft Academic Search

1.The kinetics of the reaction of a number of aromatic compounds with ozone was investigated and the rate constants and other kinetic parameters of the reaction were determined.2.An increase in the reaction rate is observed with decreasing energy of conjugation in the aromatic system. An empirical equation relating the activation energy and the energy of conjugation was obtained.3.Ozonides of aromatic

S. D. Razumovskii; G. E. Zaikov

1971-01-01

335

Probability-Weighted Dynamic Monte Carlo Method for Reaction Kinetics Simulations  

SciTech Connect

The reaction kinetics underlying the dynamic features of physical systems can be investigated by using various approaches such as the Dynamic Monte Carlo (DMC) method. The usefulness of the DMC method to study reaction kinetics has been limited to systems where the underlying reactions occur with similar frequencies, i.e., similar rate constraints. We have developed a probability-weighted DMC method by incorporating the weighted sampling algorithm of equilibrium molecular simulations.

Resat, Haluk; Wiley, H S.; Dixon, David A.

2001-07-01

336

Second Order Tensor Invariants in Continuum Mechanics Using the Lagrangian Formulations.  

National Technical Information Service (NTIS)

The paper presents for second order tensors a simple account of invariant theory from the point of view of its application to continuum mechanics. It is demonstrated that working with the tensors themselves instead of working with their components exclusi...

J. C. Grossetie

1984-01-01

337

Variational Methods and Almost Periodic Solutions of Second Order Functional Differential Equations with Infinite Delay  

Microsoft Academic Search

By means of variational methods, we study the existence and uniqueness of almost\\u000aperiodic solutions for a class of second order neutral functional differential\\u000aequations with infinite delay.

Moez Ayachi

2010-01-01

338

Experimental demonstration of second-order processes in photonic crystal microcavities at submilliwatt excitation powers  

NASA Astrophysics Data System (ADS)

The far-field second-order radiation pattern from a wavelength-scale, InP-based photonic crystal microcavity that confines light in three dimensions is measured when excited on resonance by 300?W of continuous-wave power from a laser diode. The measurements are accurately simulated using the finite-difference time-domain method, showing that both absorption and scattering play significant roles in determining the pattern of the radiation. The results show that the bulk second-order nonlinear susceptibility mediates the nonlinear process. In a separate set of experiments, a short-pulse laser is used to simultaneously populate two distinct modes of a similar microcavity. The detected second-order spectra show features due to the second harmonic generated by each mode, as well as the sum-frequency generation due to nonlinear intermode mixing. The key phenomena that determine the second-order response of these fundamentally small optical cavities are identified.

McCutcheon, Murray W.; Young, Jeff F.; Rieger, Georg W.; Dalacu, Dan; Frédérick, Simon; Poole, Philip J.; Williams, Robin L.

2007-12-01

339

Sensitivity to first- and second-order drifting gratings in 3-month-old infants  

PubMed Central

In two experiments, we investigated 3-month-old infants' sensitivity to first- and second-order drifting gratings. In Experiment 1 we used forced-choice preferential looking with drifting versus stationary gratings to estimate depth modulation thresholds for 3-month-old infants and a similar task for a comparison group of adults. Thresholds for infants were more adult-like for second-order than first-order gratings. In Experiment 2, 3-month-olds dishabituated to a change in first-order orientation, but not to a change in direction of first- or second-order motion. Hence, results from Experiment 1 were likely driven by the perception of flicker rather than motion. Thus, infants' sensitivity to uniform motion is slow to develop and appears to be driven initially by flicker-sensitive mechanisms. The underlying mechanisms have more mature tuning for second-order than for first-order information.

Armstrong, Vickie; Maurer, Daphne; Ellemberg, Dave; Lewis, Terri L

2011-01-01

340

Calculation of Hypersonic Non-Equilibrium Viscous Flow Using Second Order Boundary Layer Theory.  

National Technical Information Service (NTIS)

A method is presented for the calculation of hypersonic boundary layers in chemical nonequilibrium. The second order boundary layer equations are solved using a finite difference space marching method. The flow and the chemistry are solved simultaneously ...

C. Mundt F. Monnoyer

1990-01-01

341

Second-order theory for nonlinear dielectric composites incorporating field fluctuations  

Microsoft Academic Search

This paper deals with the development of an improved second-order theory for estimating the effective behavior of nonlinear composite dielectrics. The theory makes use of the field fluctuations in the phases of the relevant \\

Pedro Ponte-Castañeda

2001-01-01

342

Stable Second Order Nonlinear Optical Polyimide/Inorganic Composite. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

The second order nonlinear optical (NLO) properties of polymeric materials have been attracting a lot of attention, especially for such potential applications as fast waveguide electrooptic modulation and frequency-doubling devices. The ultimate applicabi...

R. J. Jeng Y. M. Chen A. K. Jain J. Kumar S. K. Tripathy

1992-01-01

343

SMITE - A Second Order Eulerian Code for Hydrodynamic and Elastic-Plastic Problems.  

National Technical Information Service (NTIS)

A computer code for hydrodynamic and elastic-perfectly plastic problems is described. The model uses a second order finite difference method based upon a Eulerian formulation of the basic differential equations. The algorithm uses an individual grid for e...

S. Z. Burstein H. S. Schechter E. L. Turkel

1975-01-01

344

Thermally driven acoustic oscillations, part III: Second-order heat flux  

Microsoft Academic Search

Summary The second-order heat flux in thermally driven oscillations of gas columns is calculated and given in a form suitable for numerical evaluation. Order-of-magnitude estimates are made in the case of steep temperature gradients.

Nikolaus Rott

1975-01-01

345

A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions  

NASA Astrophysics Data System (ADS)

This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.

Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C.; Brooks, Scott C.; Pace, Molly N.; Kim, Young-Jin; Jardine, Philip M.; Watson, David B.

2007-06-01

346

Laboratory studies of stratospheric bromine chemistry: Kinetics of the reactions of bromine monoxide with nitrogen dioxide and atomic oxygen  

SciTech Connect

A laser flash photolysis - long path absorption - technique has been employed to study the kinetics of the reaction BrO+NO2+M(k[sub 16]) yields products as a function of temperature (248-346 K), pressure (16-800 Torr), and buffer gas identity (N2, CF4). 351 nm photolysis of NO2/Br2/N2 mixtures generated BrO. The BrO decay in the presence of excess NO2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k[sub 16](P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k[sub 16](P,T) for use in modeling stratospheric BrO(x) chemistry. The kinetics of the important stratospheric reaction BrO+O(P-3)(k[sub 14]) yields Br+O2 in N2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25-150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of Br2/O3/N2 mixtures produces O atoms in excess over Br2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolysis a small fraction of the O3 to generate O(P-3). The decay of O(P-3) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resoved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k[sub 14](T) is k[sub 14](T) = 1.64 x 10(exp -11) exp(263/T) cm(exp 3) molecule(exp-1)s(exp -1). The absolute accuracy of k[sub 14](T) at any temperature within the range studied is estimated to be +/- 25%.

Thorn, R.P.

1993-01-01

347

On the global attractivity and oscillations in a class of second order difference equations from macroeconomics  

Microsoft Academic Search

New global attractivity criteria are obtained for the second order difference equation \\\\[ x_{n+1}=cx_{n}+f(x_{n}-x_{n-1}),\\\\quad n=1, 2, ... \\\\] via a Lyapunov-like method. Some of these results are sharp and support recent related conjectures. Also, a necessary and sufficient condition for the oscillation of this equation is obtained using comparison with a second order linear difference equation with positive coefficients.

Hassan A. El-Morshedy

2010-01-01

348

A nonconstructive proof of Gentzen's Hauptsatz for second order predicate logic  

Microsoft Academic Search

Takeuti (3) showed that the consistency of analysis (i.e. second order number theory) is finitisticall y implied by the Hauptsatz for second order logic» i.e. by the proposition that every theorem of this system is derivable without cut.1 We will prove that, conversely, the Hauptsatz for this system follows from a certain generalization of the consistency of analysis; namely from:

W. W. Tait

1966-01-01

349

Algorithms and design for a second-order automatic differentiation module  

SciTech Connect

This article describes approaches to computing second-order derivatives with automatic differentiation (AD) based on the forward mode and the propagation of univariate Taylor series. Performance results are given that show the speedup possible with these techniques relative to existing approaches. The authors also describe a new source transformation AD module for computing second-order derivatives of C and Fortran codes and the underlying infrastructure used to create a language-independent translation tool.

Abate, J. [Univ. of Texas, Austin, TX (United States). Texas Inst. for Computational and Applied Mathematics; Bischof, C.; Roh, L. [Argonne National Lab., IL (United States). Mathematics and Computer Science Div.; Carle, A. [Rice Univ., Houston, TX (United States). Center for Research on Parallel Computation

1997-07-01

350

Stability, capacity, and statistical dynamics of second-order bidirectional associative memory  

Microsoft Academic Search

The stability, capacity and statistical dynamics of second-order bidirectional associative memory (BAM) are presented here. We first use an example to illustrate that the state of second-order BAR I may converge to limited cycles. When error in the retrieved pairs is not allowed, a lower bound of memory capacity is derived. That is O(min(n 2\\/(log n),p2\\/(log p))) where n and

Chi-Sing Leung; Lai-Wan Chan; Edmund Lai

1995-01-01

351

Second Order Magnetic Phase Transition in TbCo2-xFex  

NASA Astrophysics Data System (ADS)

We have investigated the nature of magnetic phase transition in TbCo2-xFex laves phase compounds. There is a structural phase transition coupled with a magnetic phase transition but the nature of the magnetic phase transition is of second order in TbCo2. On Fe substation, we find that the magnetic phase transition remains second order in nature, however, the transition spreads over a wide temperature range.

Halder, Madhumita; Yusuf, S. M.

2011-06-01

352

Velocity Control of Permanent Magnet Synchronous Motor Based on Second-Order Sliding-Mode Technology  

Microsoft Academic Search

A scheme for the speed control of permanent-magnet synchronous motor (PMSM), based on second order sliding-mode-control (SO-SMC) algorithm using proportional-plus-integral (PI) sliding plane, is presented in this paper. The model of the PMSM, based on field-oriented, is given and both of second-order sliding mode control law and PI sliding plan are discussed also. Some experiments of simulations have been made

Bitao Zhang; Youguo Pi

2010-01-01

353

The second-order post-newtonian orbit equation of light  

Microsoft Academic Search

The photon's orbital equation is often used to discuss the movement of man-made satellite, small planet and photon in the solar system. It is also applied to the studies of astronomical measure such as VLBI, GPS and XNAV etc. In this paper, based on the second-order post-Newtonian approximation under the DSX scheme of GTR, it is educed that the second-order

Y. Xiao; B. J. Fei; W. J. Sun; C. X. Ji

2008-01-01

354

A high-Tc second-order gradiometer for use in an unshielded environment  

Microsoft Academic Search

We have developed a highly balanced five-channel planar high-Tc second-order SQUID gradiometer. The gradiometer incorporates two long-baseline, first-order single-layer SQUID gradiometers and three orthogonal flux-gate magnetometers used as reference sensors. The outputs of the five channels are combined synthetically on a computer to form a fully balanced second-order gradiometer. We have investigated the use of both time-domain and frequency-domain balancing.

P. P. Broussov; E. J. Romans; C. Carr; G. B. Donaldson; C. M. Pegrum

2003-01-01

355

Explicit One-Step P-Stable Methods for Second Order Periodic Initial Value Problems  

Microsoft Academic Search

In this paper, we present an explicit one-step method for solving periodic initial value problems of second order ordinary differential equations. The method is P-stable, and of first algebraic order and high phase-lag order. To improve the algebraic order, we give a composition second order scheme with the proposed method and its adjoint. We report some numerical results to illustrate

Qinghong Li; Yongzhong Song

356

Photorefractive composite materials with bi-functional charge transporting second-order nonlinear optical chromophores  

Microsoft Academic Search

Two bi-functional chromophores have been developed which possess second-order nonlinear optical and charge transporting properties. The second-order nonlinearity arises from conjugated structures terminated by donor and acceptor groups and the charge transporting property results from a triphenylamine moiety. The bi-functionality of the chromophores is confirmed by the large electro-optic coefficients and high photoconductivities of composites containing these chromophores. These chromophores

Yue Zhang; Saswati Ghosal; Martin K. Casstevens; Ryszard Burzynski

1996-01-01

357

Composition dependence of photoinduced second-order nonlinearity of germanosilicate glasses  

Microsoft Academic Search

The dependence of the photoinduced second-order nonlinearity of germanosilicate glasses on the GeO2-SiO2 composition was investigated using photoinduced second-harmonic generation (SHG). The photoinduced SHG was encoded by coherent superposition of the 800-nm fundamental and the 400-nm second-harmonic light of a femtosecond laser. Experimental results showed that the photoinduced second-order optical nonlinearity increased with increasing concentrations of GeO2 in the glasses,

Jinhai Si; Shingo Kanehira; Kiyotaka Miura; Kazuyuki Hirao

2006-01-01

358

Parameterization of a two-stage mass spectrometer performing second-order space focusing  

Microsoft Academic Search

High mass resolution can be achieved with a time-of-flight mass spectrometer performing first-order space focusing in combination with supersonic molecular beams. The introduction of a second-order correction of the space focus allows an enhancement of the resolution. We present a general parameterization for designing a two-stage mass spectrometer performing second-order space focusing. This formalism is well suited for the design

P. Piseri; S. Iannotta; P. Milani

1996-01-01

359

Linearization of Second-Order Ordinary Differential Equations by Generalized Sundman Transformations  

NASA Astrophysics Data System (ADS)

The linearization problem of a second-order ordinary differential equation by the generalized Sundman transformation was considered earlier by Duarte, Moreira and Santos using the Laguerre form. The results obtained in the present paper demonstrate that their solution of the linearization problem for a second-order ordinary differential equation via the generalized Sundman transformation is not complete. We also give examples which show that the Laguerre form is not sufficient for the linearization problem via the generalized Sundman transformation.

Nakpim, Warisa; Meleshko, Sergey V.

2010-06-01

360

Equivalence of second order optimality conditions for bang–bang control problems. Part 1: Main results  

Microsoft Academic Search

Abstract: Second order optimality conditions have been derived in the literature in two different forms. Osmolovskii (1988a, 1995, 2000, 2004) obtained second order necessary and sufficient conditions requiring that a certain quadratic form be positive (semi)-definite on a critical cone. Agrachev, Stefani, Zezza (2002) first reduced the bang-bang control problem to finite-dimensional optimization and then show that well-known sufficient optimality

N. p. Osmolovskii; H. Maurer

361

Applications of the second-order achromat concept to the design of particle accelerators  

SciTech Connect

A property of the second-order achromat, whereby dipole and sextupole families may be inserted into a lattice for chromatic corrections without introducing second-order geometrical (on momentum) optical distortions, has been incorporated in several new particle accelerator designs. These include the SLC at SLAC, LEP at CERN, the EROS pulse stretcher ring at Saskatoon, the CEBAF ring at SURA, and the MIT ring.

Brown, K.L.; Servranckx, R.V.

1985-05-01

362

Proving and Applying Program Transformations Expressed with Second-Order Patterns  

Microsoft Academic Search

We propose a program transformation method based on rewriting-rules composed of second-order schemas. A complete second-order matching algorithm is presented that allows effective use of these rules. We show how to formally prove the correctness of the rules using a denotational semantics for the programming language. We establish the correctness of the transformation method itself, and give techniques pertaining to

Gérard P. Huet; Bernard Lang

1978-01-01

363

The complexity of first-order and monadic second-order logic revisited  

Microsoft Academic Search

The model-checking problem for a logic L on a class C of structures asks whether a given L-sentence holds in a given structure in C. In this paper, we give super-exponential lower bounds for fixed-parameter tractable model-checking problems for first-order and monadic second-order logic.We show that unless PTIME=NP, the model-checking problem for monadic second-order logic on finite words is not

Markus Frick; Martin Grohe

2004-01-01

364

The Complexity of First-Order and Monadic Second-Order Logic Revisited  

Microsoft Academic Search

The model-checking problem for a logic L on a class C of structures asks whether a given L-sentence holds in a given structure in C. In this paper, we give super-exponential lower bounds for fixed-parameter tractable model-checking problems for first-order and monadic second-order logic. We show that unless PTIME = NP, the model-checking problem for monadic second-order logic on finite

Markus Frick; Martin Grohe

2002-01-01

365

Second order hold and taylor series based discretization of SISO input time-delay systems  

Microsoft Academic Search

Second order hold is a method that enables the discretization of input-driven nonlinear systems to be carried out with high\\u000a precision. A new discretization scheme combining second order hold with the Taylor-series is proposed. The sampled-data representation\\u000a and mathematical structure are explored. Both exact and approximate sampled-data representations are described in detail.\\u000a The performance of the proposed algorithm is evaluated

Zheng Zhang; Kil To Chong

2009-01-01

366

Second Order Hold Based Discretization Method of Input Time-Delay Systems  

Microsoft Academic Search

Second order hold is a method can provide a high precision for discretization of input-driven nonlinear systems. A new discretization scheme combined second order hold with Taylor-series is proposed. The sampled-data representation and the mathematical structure of the new discretization scheme are explored. Both exact sampled-data representation and approximate sampled-data representation are described in detail. The performance of the proposed

Zheng Zhang; Kil To Chong

2007-01-01

367

Second-order focusing parallel electron energy magnetic sector analyzer designs  

Microsoft Academic Search

This paper presents parallel magnetic sector analyzer designs that are predicted to have second-order or better focusing properties. Simulation results indicate that by reducing the gap between excitation plates in a compact parallel energy magnetic sector box design, second-order focusing regions in the detected energy spectrum can be obtained. A method for combining a first-order focusing magnetic box sector unit

Anjam Khursheed

2011-01-01

368

A Second-Order Dual X-\\/Ka-Band Frequency Selective Surface  

Microsoft Academic Search

In this letter, a new technique for designing dual-band frequency selective surfaces with arbitrary bands of operation, with second-order band-pass responses at each band of operation, is presented and experimentally verified. The technique is based on utilizing a particular topology of a second-order band-pass microwave filter and synthesizing its constituting elements using periodic structures with inductive, capacitive, or resonant type

Mohsen Salehi; Nader Behdad

2008-01-01

369

Asymptotic approximations for second-order linear difference equations in Banach algebras, II  

NASA Astrophysics Data System (ADS)

A Liouville-Green (WKB) asymptotic approximation theory is developed for some classes of linear second-order difference equations in Banach algebras. The special case of linear matrix difference equations (or, equivalently, of second-order systems) is emphasized. Rigorous and explicitly computable bounds for the error terms are obtained, and this when both, the sequence index and some parameter that may enter the coefficients, go to infinity. A simple application is made to orthogonal matrix polynomials in the Nevai class.

Soldà, Tania; Spigler, Renato; Vianello, Marco

2008-04-01

370

Self-forced gravitational waveforms for intermediate mass ratio inspirals: estimating second order effects  

NASA Astrophysics Data System (ADS)

We present the orbit-integrated self force effects on the gravitational waveform for an IMRI source. We consider the quasi-circular motion of a particle in the spacetime of a Schwarzschild black hole and study the dependence of the dephasing of the corresponding gravitational waveforms due to ignoring the conservative piece of the self force or the second order dissipative piece of the self force. First order self forces are modeled by the fully relativistic Barack--Sago self force. Second order effects are approximated by their post Newtonian expressions. This hybrid approach allows us to gain insight into the quantitative aspects of second order self-force effects, although the post Newtonian approximation of the second order effect does not allow us to quantitatively determine the observable quantities of interest. However, when fully relativistic second order effects become known, out method will allow us to refine our analysis by including them. We calculate the cumulative dephasing of the waveforms and their overlap integral, and discuss the importance of the conservative piece of the self force vis-à-vis the second order dissipative effect in detection and parameter estimation. We then study the effects for the parameter space of the problem.

Burko, Lior M.

2013-04-01

371

A literature review of reactions and kinetics of lithium hydride hydrolysis  

NASA Astrophysics Data System (ADS)

Studies of lithium hydride (LiH) reactions with H2O are reviewed in this paper. We discuss reaction products that are formed and the reaction kinetics involved. For discussion purposes, the studies are roughly categorized as reactions between LiH and H2O in low and higher concentration regimes, as well as reactions between LiH hydrolysis products. Both LiH and H2O can exist in many structural or phase variations and can contain various impurities, all of which may affect products and kinetics.

Haertling, C.; Hanrahan, R. J.; Smith, R.

2006-02-01

372

A Pore Scale Evaluation of the Kinetics of Mineral Dissolution and Precipitation Reactions (EMSI)  

SciTech Connect

The chief goals for CEKA are to (1) collect and synthesize molecular-level kinetic data into a coherent framework that can be used to predict time evolution of environmental processes over a range of temporal and spatial scales; (2) train a cohort of talented and diverse students to work on kinetic problems at multiple scales; (3) develop and promote the use of new experimental techniques in environmental kinetics; (4) develop and promote the use of new modeling tools to conceptualize reaction kinetics in environmental systems; and (5) communicate our understanding of issues related to environmental kinetics and issues of scale to the broader scientific community and to the public.

Steefel, Carl I.

2006-06-01

373

Kinetics  

NSDL National Science Digital Library

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

Nurrenbern, Susan C.; Robinson, William R.

2008-02-27

374

A non-isothermal, non-equimolar transient kinetic model for gas-solid reactions  

Microsoft Academic Search

A numerical model is presented, designed to simulate the kinetic and thermal behaviour of a porous pellet in which any gas-solid reaction is taking place. Its novelty consists in the fact that it can deal with reactions whether they are exothermic or endothermic, whether they are equimolar or not, whether they are reversible or irreversible and further reactions in the

Fabrice Patisson; Magda Galant François; Denis Ablitzer

1998-01-01

375

Molecular Beam and Surface Science Studies of Heterogeneous Reaction Kinetics Including Combustion Dynamics. Final Technical Report  

Microsoft Academic Search

This research program examined the heterogeneous reaction kinetics and reaction dynamics of surface chemical processes which are of direct relevance to efficient energy production, condensed phase reactions, and mateials growth including nanoscience objectives. We have had several notable scientific and technical successes. Illustrative highlights include: (1) a thorough study of how one can efficiently produce synthesis gas (SynGas) at relatively

Sibener

2006-01-01

376

Kinetics of Phthalate Reactions with Ammonium Hydroxide in Aqueous Matrix  

Microsoft Academic Search

Common phthalate pollutants, such as dimethyl phthalate and diethyl phthalate found in aqueous environmental matrices react with ammonium hydroxide at ordinary temperatures exhibiting an overall reaction order in the range 1.3–1.4. While the reaction is of first order with respect to the phthalate, the order of reaction is fractional in ammonium hydroxide. The rate constants for the reactions of these

Pradyot Patnaik; Min Yang; Evelyn Powers

2001-01-01

377

Reaction Kinetics in Micro/Nanofluidic Devices: Effect of Confinement and AC Voltage  

NASA Astrophysics Data System (ADS)

Owing to limited sample consumption, electrokinetic control of convective transport and rapid dissipation of heat, nanofluidic devices are currently being investigated extensively in the field of chemical reactions. The reactants are typically transported into the nanochannel by using external DC electric fields. In this study, a novel technique to increase the rate of catalytic reactions inside nanofluidic devices is presented. Specifically, the effect of combined AC and DC electric fields on different reaction kinetics was numerically investigated and it was found to enhance the rate of formation of desired species in reaction limited kinetics (when the Damköhler number (Da) <= 1). We investigate the role of AC frequency, amplitude, channel height and surface charge density on reaction kinetics. We develop analytical expressions for fluid transport under combined AC and DC fields and also develop expressions to identify optimal frequencies. Several examples are considered to illustrate the effect of AC fields on chemical reactions in nanochannels.

Nandigana, Vishal V. R.; Aluru, Narayana R.

2010-11-01

378

Molecular Beam Study of the Kinetics of the Fluorine--Uranium Dioxide Reaction.  

National Technical Information Service (NTIS)

The kinetics of uranium dioxide fluorination were studied using an experimental system in which a molecular beam of fluorine was directed at a heated uranium dioxide single crystal wafer maintained in high vacuum. Gaseous reaction products desorbed from t...

A. J. Machiels

1976-01-01

379

Detailed Chemical Kinetic Reaction Mechanisms for Incineration of Organophosphorus and Fluoro-Organophosphorus Compounds  

SciTech Connect

A detailed chemical kinetic reaction mechanism is developed to describe incineration of the chemical warfare nerve agent sarin (GB), based on commonly used principles of bond additivity and hierarchical reaction mechanisms. The mechanism is based on previous kinetic models of organophosphorus compounds such as TMP, DMMP and DIMP that are often used as surrogates to predict incineration of GB. Kinetic models of the three surrogates and GB are then used to predict their consumption in a perfectly stirred reactor fueled by natural gas to simulate incineration of these chemicals. Computed results indicate that DIMP is the only one of these surrogates that adequately describes combustion of GB under comparable conditions. The kinetic pathways responsible for these differences in reactivity are identified and discussed. The most important reaction in GB and DIMP that makes them more reactive than TMP or DMMP is found to be a six-center molecular elimination reaction producing propene.

Glaude, P A; Melius, C; Pitz, W J; Westbrook, C K

2001-12-13

380

Detailed Chemical Kinetic Reaction Mechanism for Oxidation of Four Small Alkyl Esters in Laminar Premixed Flames.  

National Technical Information Service (NTIS)

A detailed chemical kinetic reaction mechanism has been developed for a group of four small alkyl ester fuels, consisting of methyl formate, methyl acetate, ethyl formate and ethyl acetate. This mechanism is validated by comparisons between computed resul...

C. K. Westbrook F. L. Dryer M. Chaos P. R. Westmoreland W. J. Pitz

2008-01-01

381

Kinetics of Free Radical Metathetical and Addition Reactions in Silane Solutions.  

National Technical Information Service (NTIS)

In this work radiolytic technique was employed for the initiation of free radical chain reactions in silane solution. The kinetic analysis of the chain mechanism in various solutions enabled the determination of the Arrhenius parameters for metathesis, ad...

R. Aloni

1976-01-01

382

Utilization of the Recycle Reactor in Determining Kinetics of Gas-Solid Catalytic Reactions.  

ERIC Educational Resources Information Center

|Describes a laboratory scale reactor that determines the kinetics of a gas-solid catalytic reaction. The external recycle reactor construction is detailed with accompanying diagrams. Experimental details, application of the reactor to CO oxidation kinetics, interphase gradients, and intraphase gradients are discussed. (CS)|

Paspek, Stephen C.; And Others

1980-01-01

383

Kinetic phase transitions in a surface-reaction model: Mean-field theory  

Microsoft Academic Search

A kinetic model for irreversible surface reactions, recently proposed by Ziff, Gulari, and Barshad, is studied in the site and pair approximations. The latter approach predicts the phase diagram correctly, and yields quantitative predictions which are in very close agreement with simulation, in the vicinity of the first-order kinetic transition.

Ronald Dickman

1986-01-01

384

Utilization of the Recycle Reactor in Determining Kinetics of Gas-Solid Catalytic Reactions.  

ERIC Educational Resources Information Center

Describes a laboratory scale reactor that determines the kinetics of a gas-solid catalytic reaction. The external recycle reactor construction is detailed with accompanying diagrams. Experimental details, application of the reactor to CO oxidation kinetics, interphase gradients, and intraphase gradients are discussed. (CS)

Paspek, Stephen C.; And Others

1980-01-01

385

A diffusion-reaction kinetic model for the removal of aqueous 4-chlorophenol with immobilized peroxidase  

Microsoft Academic Search

A diffusion-reaction kinetic model is presented for the kinetic analysis of the removal process of phenolic compounds using hydrogen peroxide and immobilized peroxidase. The good results obtained in the fitting of the experimental data to the model confirm its validity, in the experimental range considered, as well as the one of the extended version of the Dunford mechanism proposed in

J. L. Gómez Carrasco; E. Gomez Gomez; M. F. Máximo; M. Gomez Gomez; M. D. Murcia; S. Ortega Requena

2011-01-01

386

Equilibrium and kinetic modeling of char reduction reactions in a downdraft biomass gasifier: A comparison  

Microsoft Academic Search

The thermodynamic and kinetic modeling of char reduction reactions in a downdraft (biomass) gasifier has been presented. Mass and energy balance are coupled with equilibrium relations or kinetic rate parameters (using varying char reactivity factor) in order to predict status of un-converted char in addition to gas composition, calorific value, conversion efficiency, exit gas temperature, endothermic heat absorption rate and

Avdhesh Kr. Sharma

2008-01-01

387

Recent advances in the fundamentals of the kinetics of steelmaking reactions  

Microsoft Academic Search

G.R. Belton was the leader in developing our understanding of the kinetics of metallurgical reactions. Selected recent kinetic\\u000a studies, based on this understanding and the application of the results to actual processes, are presented in this article.\\u000a In particular, the rates of reaction of carbon and carbon in iron with CO2 and H2O gases and FeO in slag are reviewed

R. J. Fruehan; D. Goldstein; B. Sarma; S. R. Story; P. C. Glaws; H. U. Pasewicz

2000-01-01

388

Determination of Reaction Kinetics for a Two-Part Epoxy Adhesive  

NSDL National Science Digital Library

In this exercise, you will use Fourier transform infrared spectroscopy (FTIR) to determine the reaction kinetics for a two-part polymer system. After in-class presentation, completion of hands-on laboratory experiment and review of the information provided, you should: ⢠Be able to communicate effectively about the synthesis and mechanism for condensation polymerizations. ⢠Be familiar with FTIR methods for determining the reaction kinetics for a 2-part polymer.

Derosa, Rebecca L.

2008-09-26

389

Kinetics of Some Aqueous-Phase Reactions of Peroxyacetyl Nitrate.  

National Technical Information Service (NTIS)

The contribution to cloudwater acidification by reactions of peroxyacetyl nitrate (PAN) with various atmospheric species reported in this work. Clearly, at representative concentration of PAN (less than or equal to 5 x 10 exp -9 atm), the reactions which ...

Y. N. Lee

1984-01-01

390

Effects of ventral striatal lesions on first- and second-order appetitive conditioning.  

PubMed

Rats with bilateral lesions of the ventral striatal nucleus accumbens failed to acquire Pavlovian second-order conditioning to auditory stimuli paired with visual stimuli that had previously received first-order pairings with food. This deficit in second-order conditioning was specific to learning driven by incentive properties of the first-order cues, and was observed whether the first-order training had occurred prior to or after lesion surgery. Lesions also produced deficits in the display of conditioned responses to the first-order conditioned stimulus, but only when they were made after first-order training. These results suggest a specific role for the ventral striatum in acquiring and expressing incentive properties of conditioned stimuli through second-order conditioning, as well as a more general role in expressing previously acquired Pavlovian conditioned responses. PMID:23691939

McDannald, Michael A; Setlow, Barry; Holland, Peter C

2013-05-20

391

Use of the particle swarm optimization algorithm for second order design of levelling networks  

NASA Astrophysics Data System (ADS)

The weight problem in geodetic networks can be dealt with as an optimization procedure. This classic problem of geodetic network optimization is also known as second-order design. The basic principles of geodetic network optimization are reviewed. Then the particle swarm optimization (PSO) algorithm is applied to a geodetic levelling network in order to solve the second-order design problem. PSO, which is an iterative-stochastic search algorithm in swarm intelligence, emulates the collective behaviour of bird flocking, fish schooling or bee swarming, to converge probabilistically to the global optimum. Furthermore, it is a powerful method because it is easy to implement and computationally efficient. Second-order design of a geodetic levelling network using PSO yields a practically realizable solution. It is also suitable for non-linear matrix functions that are very often encountered in geodetic network optimization. The fundamentals of the method and a numeric example are given.

Yetkin, Mevlut; Inal, Cevat; Yigit, Cemal Ozer

2009-08-01

392

a Two-Level Second-Order Finite Difference Scheme for the Single Term Structure Equation  

NASA Astrophysics Data System (ADS)

In the paper [6] the classical single factor term structure equation for models that predict non-negative interest rates is numerically studied. For these models the authors proposed a second order accurate three-level finite difference scheme (FDs) using the appropriate boundary conditions at zero. For the same problem we propose a two-level second-order accurate FDs. We also propose an effective algorithm for solving the difference schemes, for which also follows the positivity of the numerical solution. The flexibility of our FDs makes it easy to change the drift and diffusion terms in the model. The numerical experiments confirm the second-order of accuracy of the scheme and the positivity-convexity property.

Chernogorova, T.; Valkov, R.

2011-12-01

393

Consistency of Equations in the Second-Order Gauge-Invariant Cosmological Perturbation Theory  

NASA Astrophysics Data System (ADS)

Along the general framework of the gauge-invariant perturbation theory developed in the papers [K.~Nakamura, Prog.~Theor.~Phys. 110 (2003), 723; Prog.~Theor.~Phys. 113 (2005), 481], we rederive the second-order Einstein equation on four-dimensional homogeneous isotropic background universe in a gauge-invariant manner without ignoring any mode of perturbations. We consider the perturbations both in the universe dominated by the single perfect fluid and in that dominated by the single scalar field. We also confirmed the consistency of all the equations of the second-order Einstein equation and the equations of motion for matter fields, which are derived in the paper [K.~Nakamura, arXiv:0804.3840]. This confirmation implies that all the derived equations of the second order are self-consistent and these equations are correct in this sense.

Nakamura, K.

2009-06-01

394

A Quasi-Lie Schemes Approach to Second-Order Gambier Equations  

NASA Astrophysics Data System (ADS)

A quasi-Lie scheme is a geometric structure that provides t-dependent changes of variables transforming members of an associated family of systems of first-order differential equations into members of the same family. In this note we introduce two quasi-Lie schemes for studying second-order Gambier equations in a geometric way. This allows us to study the transformation of these equations into simpler canonical forms, which solves a gap in the previous literature, and other relevant differential equations, which leads to derive new constants of motion for families of second-order Gambier equations. Additionally, we describe general solutions of certain second-order Gambier equations in terms of particular solutions of Riccati equations, linear systems, and t-dependent frequency harmonic oscillators.

Cariñena, José F.; Guha, Partha; de Lucas, Javier

2013-03-01

395

Second-Order Belief Attribution in Williams Syndrome: Intact or Impaired?  

PubMed Central

Second-order mental state attribution in a group of children with Williams syndrome was investigated. The children were compared to age, IQ, and language-matched groups of children with Prader-Willi syndrome or nonspecific mental retardation. Participants were given two trials of a second-order reasoning task. No significant differences between the Williams syndrome and Prader-WiIli or mentally retarded groups on any of the test questions were found. Results contrast with the view that individuals with Williams syndrome have an intact theory of mind and suggest that in their attributions of second-order mental states, children with Williams syndrome perform no better than do other groups of children with mental retardation.

Sullivan, Kate; Tager-Flusberg, Helen

2005-01-01

396

Shot-Noise Seeded Microbunching Instability: Second-Order Correction to the Gain Function  

SciTech Connect

We determine the second-order correction to the gain function of the microbunching instability in single-pass systems of interest for the next generation of light sources. The calculation applies to the case where the instability is seeded by shot noise. We examine an analytically treatable model of beam dynamics where collective forces are active only in non-dispersive sections of the linac. We find that the second order term can augment the linear gain significantly while affecting the spectrum of the overall gain only marginally. The weight of the second-order correction relative to the linear gain is found to scale quadratically with respect to R56. The qualitative behavior predicted by the model is consistent with exact numerical solutions of the Vlasov equations for realistic lattices.

Venturini, Marco

2008-06-30

397

A second order analytical atmospheric drag theory based on the TD88 thermospheric density model  

NASA Astrophysics Data System (ADS)

A second order atmospheric drag theory based on the usage of TD88 model is constructed. It is developed to the second order in terms of TD88 small parameters K n, j . The short periodic perturbations, of all orbital elements, are evaluated. The secular perturbations of the semi-major axis and of the eccentricity are obtained. The theory is applied to determine the lifetime of the satellites ROHINI (1980 62A), and to predict the lifetime of the microsatellite MIMOSA. The secular perturbations of the nodal longitude and of the argument of perigee due to the Earth’s gravity are taken into account up to the second order in Earth’s oblateness.

El-Salam, F. A. Abd.; Sehnal, L.

2004-11-01

398

Second-order nonlinear Schrödinger equation breather solutions in the degenerate and rogue wave limits  

NASA Astrophysics Data System (ADS)

We present an explicit analytic form for the two-breather solution of the nonlinear Schrödinger equation with imaginary eigenvalues. It describes various nonlinear combinations of Akhmediev breathers and Kuznetsov-Ma solitons. The degenerate case, when the two eigenvalues coincide, is quite involved. The standard inverse scattering technique does not generally provide an answer to this scenario. We show here that the solution can still be found as a special limit of the general second-order expression and appears as a mixture of polynomials with trigonometric and hyperbolic functions. A further restriction of this particular case, where the two eigenvalues are equal to i, produces the second-order rogue wave with two free parameters considered as differential shifts. The illustrations reveal a precarious dependence of wave profile on the degenerate eigenvalues and differential shifts. Thus we establish a hierarchy of second-order solutions, revealing the interrelated nature of the general case, the rogue wave, and the degenerate breathers.

Kedziora, David J.; Ankiewicz, Adrian; Akhmediev, Nail

2012-06-01

399

Second-order all-fiber comb filter based on polarization-diversity loop configuration.  

PubMed

By concatenating three birefringence loops in series, a second-order all-fiber comb filter based on a polarization-diversity loop configuration is newly proposed. The proposed filter consists of one polarization beam splitter, polarization-maintaining fibers, and two halfwave plates. The effect of a second-order structure of polarization-maintaining fiber loops on a bandwidth of the filter passband was theoretically analyzed and experimentally demonstrated. Transmission output of the second-order filter (flat-top and narrow-band transmission spectra) could be obtained by adjusting two half-wave plates. 1 and 3 dB bandwidths of the proposed filter in flat-top and narrow-band operations were greater by approximately 102.9 and 44.3 % and smaller by approximately 47.9 and 47.1 % than those of a conventional Sagnac birefringence filter, respectively. PMID:18542484

Lee, Yong Wook; Kim, Hyun-Tak; Lee, Yong Wan

2008-03-17

400

Kinetic Mechanism of Reaction between TT-Phase Niobium Oxide and Carbon Tetrachloride (CCl 4)  

Microsoft Academic Search

The kinetic mechanism of reaction between TT-phase niobium oxide and carbon tetrachloride (CCl4) at low (453 K) and high (above 573 K) temperatures was investigated. The reaction of the TT-phase niobium oxide with CCl4 at 453 K was controlled by the diffusion of CCl4 through the outer layer of the reaction product, NbOCl3, formed around the surface. For the reaction

Kohki Ebitani; Yoshiaki Hirano; Akira Morikawa

1995-01-01

401

Test of the second order asymptotic theory with low degree solar gravity modes  

SciTech Connect

Further testing of first and second order asymptotic theory predictions for solar gravity modes is possible with the work of gu and Hill in which the number of classified low-degree gravity mode multiplets was increased from 31 to 53. In an extension of the work where the properties of 31 multiplets were analyzed in the framework of first order asymptotic theory, a new analysis has been performed using the properties of the 53 classified multiplets. The result of this analysis again shows the inadequacy of first order asymptotic theory for describing the eigenfrequency spectrum and clearly demonstrates the necessity of using second order asymptotic theory. 30 refs.

Barry, C.T.; Rosenwald, R.D.; Gu, Y.; Hill, H.A

1988-01-01

402

On the global attractivity and oscillations in a class of second order difference equations from macroeconomics  

Microsoft Academic Search

New global attractivity criteria are obtained for the second order difference\\u000aequation \\\\[ x_{n+1}=cx_{n}+f(x_{n}-x_{n-1}),\\\\quad n=1, 2, ... \\\\] via a\\u000aLyapunov-like method. Some of these results are sharp and support recent\\u000arelated conjectures. Also, a necessary and sufficient condition for the\\u000aoscillation of this equation is obtained using comparison with a second order\\u000alinear difference equation with positive coefficients.

Hassan A. El-Morshedy

2010-01-01

403

Spectral stability analysis for special solutions of second order in time PDEs: The higher dimensional case  

NASA Astrophysics Data System (ADS)

We develop a general theory to treat the linear stability of certain special solutions of second order in time evolutionary PDE. We apply these results to standing waves of the following problems: the Klein-Gordon equation, for which we consider both ground states and certain excited states, the Klein-Gordon-Zakharov system and the beam equation. We also discuss applications to excited states for the Klein-Gordon model as well as multidimensional traveling waves (not necessarily homoclinic to zero) for general second order equations of this type. In all cases, our abstract results provide a complete characterization of the linear stability of such solutions.

Stanislavova, Milena; Stefanov, Atanas

2013-11-01

404

Imaging of biological tissues with pixel-level analysis of second-order susceptibility  

NASA Astrophysics Data System (ADS)

We discuss the recent advances in the development and applications of second-order susceptibility as a contrast mechanism in optical microscopy for biological tissues. We review nonlinear optical methods and approaches for differentiation of tissue structures and discrimination of normal and pathological skin tissues, which have been demonstrated for the potential use in clinical diagnosis. In addition, the potential of second-order susceptibility imaging, encompassing applications in differentiating various types of collagen molecules for clinical diagnosis, is demonstrated. Finally, we discuss future development and application of this technique.

Hu, Po-Sheng; Ghazaryan, Ara; Hovhannisyan, Vladimir; Chen, Shean-Jen; Chen, Yang-Fang; Kim, Chang-Seok; Tsai, Tsung-Hua; Dong, Chen-Yuan

2013-03-01

405

Integrable dissipative nonlinear second order differential equations via factorizations and Abel equations  

NASA Astrophysics Data System (ADS)

We emphasize two connections, one well known and another less known, between the dissipative nonlinear second order differential equations and the Abel equations which in their first-kind form have only cubic and quadratic terms. Then, employing an old integrability criterion due to Chiellini, we introduce the corresponding integrable dissipative equations. For illustration, we present the cases of some integrable dissipative Fisher, nonlinear pendulum, and Burgers-Huxley type equations which are obtained in this way and can be of interest in applications. We also show how to obtain Abel solutions directly from the factorization of second order nonlinear equations.

Mancas, Stefan C.; Rosu, Haret C.

2013-09-01

406

Interpair electron correlation by second-order perturbative corrections to PNOF5  

NASA Astrophysics Data System (ADS)

An antisymmetrized product of strongly orthogonal geminals with the expansion coefficients explicitly expressed by the occupation numbers is used to generate the Piris natural orbital functional 5 (PNOF5). Second-order corrections to PNOF5 are derived and implemented using the multiconfigurational perturbation theory size consistent at second-order (SC2-MCPT). A modified version of the SC2-MCPT including only doubly excited determinants from different geminals is proposed to describe the dispersion interaction in the helium dimer, and to avoid the breakdown of curves in homolytic dissociations of FH, CO, and N2. Comparisons of calculated properties to experimental data are included to verify the accuracy of the formulation.

Piris, M.

2013-08-01

407

Incorporation of aqueous reaction and sorption kinetics andbiodegradation into TOUGHREACT  

SciTech Connect

The needs for considering aqueous and sorption kinetics and microbiological processes arises in many subsurface problems, such as environmental and acid mine remediation. A general rate expression has been implemented into TOUGHREACT, which considers multiple mechanisms(pathways) and includes multiple product, Monod, and inhibition terms. In this paper, the formulation for incorporating kinetic rates among primary species into the mass balance equations is presented. A batch sulfide oxidation problem is simulated. The resulting concentrations are consistent with simple hand calculations. A 1-D reactive transport problem with kinetic biodegradation and sorption was investigated, which models the processes when a pulse of water containing NTA (nitrylotriacetate) and cobalt is injected into a column. The problem has several interacting chemical processes that are common to many environmental problems: biologically-mediated degradation of an organic substrate, bacterial cell growth and decay, metal sorption and aqueous speciation including metal-ligand complexation. The TOUGHREACT simulation results agree very well with those obtained with other simulators.

Xu, Tianfu

2006-04-17

408

Determination of nicotine in tobacco with second-order spectra data of charge-transfer complex in ethanol-water binary solvents processed by parallel factor analysis  

NASA Astrophysics Data System (ADS)

A new spectrophotometric method for the determination of nicotine in mixtures without pre-separation has been proposed. Nicotine could react with 2,4-dinitrophenol through a charge-transfer reaction to form a colored complex. The second-order data from the visible absorption spectra of the complex in a series of ethanol-water binary solvents with various water volume fractions could be expressed as the combination of two bilinear data matrices. With the bilinear model, the second-order spectra data of mixtures containing nicotine and other interferents could be analysed by using second-order calibration algorithms, and the determination of nicotine in the mixtures could be achieved. The algorithm used here was parallel factor analysis. The method has been successfully used to determine nicotine in tobacco samples with satisfactory results.

Gao, Shuqin; Liao, Lifu; Xiao, Xilin; Zhao, Zhiyuan; Du, Nan; Du, Jiangfeng

2010-05-01

409

Synthetic semiconductor diamond electrodes: kinetics of some redox reactions  

Microsoft Academic Search

Linear-sweep voltammograms were recorded on boron-doped diamond thin-film electrodes in K3Fe(CN)6, K4Fe(CN)6, quinone, and hydroquinone solutions; transfer coefficients and rate constants for anodic and cathodic reactions were determined. The reaction rates were compared to the diamond samples' electrical characteristics measured by the impedance spectroscopy techniques. The polarization (faradaic) resistance of a redox reaction at its equilibrium potential was shown to

A. D. Modestov; Yu. E. Evstefeeva; Yu. V. Pleskov; V. M. Mazin; V. P. Varnin; I. G. Teremetskaya

1997-01-01

410

Aquatic plant augmented TNT degradation ? Analysis of reaction kinetics  

Microsoft Academic Search

The purpose of this paper is to evaluate and analyze the kinetic data from both the laboratory and the field, and relate it to the Trinitrotoluene transport and biotransformation in the overall bioremediation process. Laboratory batch experiment results indicate that TNT dissolution mass transfer coefficients from TNT nuggets is 4.13 cm\\/h. The TNT desorption mass transfer coefficient from soil is

K. M. Qaisi; L. J. Thibodeaux; D. Adrian

1996-01-01

411

Cellulosic Insulation Material I. Overall Degradation Kinetics and Reaction Heats  

Microsoft Academic Search

Kinetic studies on the thermal and oxidative decomposition of untreated cellulosic insulation have been carried out with thermal analytical techniques (TGA and DSC) to provide input parameters for smoldering studies of this material. In dry nitrogen, the weight loss proceeds in one overall step that follows a diffusion-controlled rate law with parameters: A = 1.1 × 10 min and E

F. E. ROGERS; T. J. OHLEMILLER

1980-01-01

412

Citation review of Lagergren kinetic rate equation on adsorption reactions  

Microsoft Academic Search

This study presents a literature review concerning the preciseness of over 170 publications citing the original Lagergren's paper in kinetics equation for solute adsorption on various adsorbents. This equation applies to a range of solid-liquid systems such as metal ions, dyestuffs and several organic substances in aqueous systems onto various adsorbents. The main objectives are to manifest different forms of

Yuh-shan Ho

2004-01-01

413

Kinetics of Reactions of Monomeric Nitrosomethane Induced by Flash Photolysis.  

ERIC Educational Resources Information Center

|Describes an experiment in which the kinetics of dimerization of nitrosamine induced by a flash of light is measured. The experiment can be performed with a commercial ultraviolet-VIS spetrophotometer with easy to make modifications. The experiment demonstrates a flash photolysis system not always available in university chemistry laboratories.…

Kozubek, H.; And Others

1984-01-01

414

Probability-Weighted Dynamic Monte Carlo Method for Reaction Kinetics Simulations  

SciTech Connect

The reaction kinetics underlying the dynamic features of physical systems can be investigated using various approaches such as the dynamic Monte Carlo (DMC) method. Up to now, the usefulness of the DMC method to study reaction kinetics has been limited to systems where the underlying reactions occur with similar frequencies, i.e., similar rate constants. However, many interesting physical phenomena involve sets of reactions with a wide range of rate constants leading to a broad range of relevant time scales. Widely varying reaction rates result in a highly skewed reaction occurrence probability distribution. When the reaction occurrence probability distribution has a wide spectrum, the reactions with faster rates dominate the computations making the reliable statistical sampling cumbersome. We have developed a probability weighted DMC method by incorporating the preferential sampling algorithm of equilibrium molecular simulations. This new algorithm samples the slow reactions very efficiently and makes it possible to simulate the reaction kinetics of physical systems in which the rates of reactions vary by several orders of magnitude in a computationally efficient manner. We validate the probability weighted DMC algorithm by applying it to a model of vesicular trafficking in living cells.

Resat, Haluk (BATTELLE (PACIFIC NW LAB)); Wiley, H S. (Battelle (Pacific NW Lab)); Dixon, David A. (BATTELLE (PACIFIC NW LAB))

2000-11-01

415

Older Adults' Configural Processing of Faces: Role of Second-Order Information  

Microsoft Academic Search

Problems with face recognition are frequent in older adults. However, the mechanisms involved have only been partially discovered. In particular, it is unknown to what extent these problems may be related to changes in configural face processing. Here, we investigated the face inversion effect (FIE) together with the ability to detect modifications in the vertical or horizontal second-order relations between

Laurence Chaby; Pauline Narme; Nathalie George

2011-01-01

416

Multidimensional first and second order symmetric strang splitting for hyperbolic systems  

SciTech Connect

We propose an algebraic basis for symmetric Strang splitting for first and second order accurate schemes for hyperbolic systems in N dimensions. Examples are given for two and three dimensions. Optimal stability is shown for symmetric systems. Lack of strong stability is shown for a non-symmetric example. Some numerical examples are presented for some Euler-like constant coefficient problems.

Kucharik, Milan [Los Alamos National Laboratory; Wendroff, Burton [Los Alamos National Laboratory

2008-01-01

417

Anharmonic vibrational properties by a fully automated second-order perturbative approach.  

PubMed

This paper describes the implementation of a fully automated code for the building of anharmonic force constants and their use in a second-order perturbative evaluation of vibrorotational parameters. Next, a number of test applications are discussed, which show the strengths and limits of various computational levels. PMID:15638643

Barone, Vincenzo

2005-01-01

418

Lie symmetries of systems of second-order linear ordinary differential equations with constant coefficients.  

PubMed

Lie symmetries of systems of second-order linear ordinary differential equations with constant coefficients are exhaustively described over both the complex and real fields. The exact lower and upper bounds for the dimensions of the maximal Lie invariance algebras possessed by such systems are obtained using an effective algebraic approach. PMID:23564972

Boyko, Vyacheslav M; Popovych, Roman O; Shapoval, Nataliya M

2013-01-01

419

Second-order residual stresses in Armco iron deformed in an ultrasonic field  

Microsoft Academic Search

1.The effect of ultrasonic vibrations on a sample of Armco iron during deformation is to change the distribution of second-order residual stresses along the height of the sample. The highest residual stresses are found in the area of the contact surfaces and the lowest in the central part of the sample. But after deformation without ultrasonic vibrations the highest residual

V. P. Severdenko; V. V. Klubovich; M. V. Kharitonovich

1966-01-01

420

Maximally confined high-speed second-order silicon microdisk switches.  

SciTech Connect

We demonstrate the first high-speed second-order silicon microdisk bandpass switch. The switch, constructed of a pair of 3 {micro}m radii active microdisks possesses {approx}40GHz flat-top passbands, a 4.2THz free-spectral-range, and a 2.4ns switching time.

Young, Ralph Watson; Trotter, Douglas Chandler; Watts, Michael R.

2008-03-01

421

Critical Comparison of Second Order Closures with Direct Numerical Simulation of Homogeneous Turbulence.  

National Technical Information Service (NTIS)

Recently, several second order closure models have been proposed for closing the second moment equations, in which the velocity-pressure gradient (and scalar-pressure gradient) tensor and the dissipation rate tensor are two of the most important terms. In...

T. Shih J. L. Lumley

1991-01-01

422

Oscillation and Nonoscillation Criteria for Half-linear Second Order Difference Equations  

Microsoft Academic Search

New oscillation and nonoscillation criteria are established for the second order half- linear dierence equation ( rn( xn)) + qn( xn+1) = 0; ( x) = jxjp 2x; p > 1; via the Riccati technique. Some known results are also improved including the discrete version of the Hille-Wintner comparison theorem. AMS (MOS) Subject Classication. 39A10.

HASSAN A. EL-MORSHEDY

2006-01-01

423

The role of multipole contributions to the second-order response of gold nanoparticles  

Microsoft Academic Search

Great progress has been achieved in fabricating arbitrary metal nanoparticle shapes and geometries in order to control their linear optical properties. However, their nonlinear optical properties, particularly their second-order response, are frequently overlooked. Exploiting the nonlinear responses of metal nanoparticles opens another exciting avenue for developing nanoscale photonics applications. Second-harmonic generation (SHG) from metal nanoparticles is typically attributed to electric

Brian Canfield; Sami Kujala; Konstantins Jefimovs; Yuri Svirko; Jari Turunen; Martti Kauranen

2006-01-01

424

Keep Your Distance! Using Second-Order Ordinary Differential Equations to Model Traffic Flow  

ERIC Educational Resources Information Center

|A simple mathematical model for how vehicles follow each other along a stretch of road is presented. The resulting linear second-order differential equation with constant coefficients is solved and interpreted. The model can be used as an application of solution techniques taught at first-year undergraduate level and as a motivator to encourage…

McCartney, Mark

2004-01-01

425

Computer Simulation for Calculating the Second-Order Correlation Function of Classical and Quantum Light  

ERIC Educational Resources Information Center

|We propose an undergraduate numerical project for simulating the results of the second-order correlation function as obtained by an intensity interference experiment for two kinds of light, namely bunched light with Gaussian or Lorentzian power density spectrum and antibunched light obtained from single-photon sources. While the algorithm for…

Facao, M.; Lopes, A.; Silva, A. L.; Silva, P.

2011-01-01

426

Second-Order Selection for Evolvability in a Large Escherichia coli Population  

Microsoft Academic Search

In theory, competition between asexual lineages can lead to second-order selection for greater evolutionary potential. To test this hypothesis, we revived a frozen population of Escherichia coli from a long-term evolution experiment and compared the fitness and ultimate fates of four genetically distinct clones. Surprisingly, two clones with beneficial mutations that would eventually take over the population had significantly lower

Robert J. Woods; Jeffrey E. Barrick; Tim F. Cooper; Utpala Shrestha; Mark R. Kauth; Richard E. Lenski

2011-01-01

427

Digital second order sliding mode control for a synchronous reluctance motor  

Microsoft Academic Search

Investigating the performance of a synchronous reluctance drive speed control system using second order sliding mode control (SOSMC) is presented in this paper. In this paper based on the theory of SOSMC, a controller for vector control of synchronous reluctance motor (SRM) is first derived and the performance of the controller is verified by simulation results. The proposed SOSMC shows

M. Mohamadian; M. M. Pedram; F. Ashrafzadeh

2004-01-01

428

Contact and non-contact type Hamiltonian systems generated by second-order Lagrangians  

Microsoft Academic Search

We showthatsomeverynaturallyoccurringenergymanifoldsthatareinducedby second-order Lagrangians L = L(u, u? ,u ?? ) are not, in general, of contact type in (R4 ,? ). We also comment on the more general question whether there exist any contact forms on these energy manifolds for which the associated Reeb vector field coincides with the Hamiltonian vector field.

S. B. ANGENENT; J. B. VAN DEN BERG; R. C. A. M. VANDERVORST

2007-01-01

429

Contact Analysis of Cable Networks by Using Second-Order Cone Programming  

Microsoft Academic Search

A method based on mathematical programming is proposed for large deformation and contact analysis of cable networks. By explicitly considering these nonsmooth behaviors, we formulate the linear complementarity problems over symmetric cones under some practically accept- able assumptions. We also present the equivalent second-order cone programming (SOCP) problems, which can be regarded as the minimization problem of total potential energy

Yoshihiro Kanno; Makoto Ohsaki

2006-01-01

430

Learning and Extracting Finite State Automata with Second-Order Recurrent Neural Networks  

Microsoft Academic Search

We show that a recurrent, second-order neural network using a real-time, forward training algorithm readily learns to infer small regular grammars from positive and negative string training samples. We present simulations that show the effect of initial conditions, training set size and order, and neural network architecture. All simulations were performed with random initial weight strengths and usually converge after

C. Lee Giles; Clifford B. Miller; D. Chen; H. H. Chen; Guo-zheng Sun; Y. C. Lee

1992-01-01

431

Pleistocene Extinctions - Counterintuitive Results of Combining Hypotheses (Overkill, Second Order Predation, and Environmental Degradation)  

Microsoft Academic Search

There are two popular hypotheses to explain extinctions at the end of the last ice age, Climate Change and Overkill (humans hunting herbivores to extinction); each has significant problems. Some have suggested that the two hypotheses in combination would yield a stronger explanation. The Pleistocene Extinction Model (PEM)(Whitney-Smith, 1991, 2003) was originally developed to test a third hypothesis, Second Order

Elin Whitney-Smith

432

Thermal poling with alternating voltage: a way to increase the second order nonlinearity  

NASA Astrophysics Data System (ADS)

We present experimental results of thermal polings performed on Suprasil I samples (Heraeus) under square alternative voltages at various frequencies. We report a large increase (×5 compared to a continuous voltage poling) of the second order non-linear coefficient within a sample poled at 1mHz.

Martinelli, Gilbert; Quiquempois, Yves; Kudlinski, Alexandre; Bailleux, Stephane; Zeghlache, Hassina

2003-04-01

433

Capacity of second-ordered bidirectional associative memory in the presence of noise bits  

Microsoft Academic Search

This paper describes error probability of the second-ordered BAM in the presence of noise bits in initial input. A calculation method is proposed to estimate the error probability at the second iteration to retrieve a library pair. Theoretical estimation suggests that the BAM with a larger number of neurons are more robust for the noise bits: the error probability of

Yutaka Kawabata; Yoshimasa Daido; Shimmi Hattori

1999-01-01

434

Sample Sizes for Two-Group Second-Order Latent Growth Curve Models  

ERIC Educational Resources Information Center

|Second-order latent growth curve models (S. C. Duncan & Duncan, 1996; McArdle, 1988) can be used to study group differences in change in latent constructs. We give exact formulas for the covariance matrix of the parameter estimates and an algebraic expression for the estimation of slope differences. Formulas for calculations of the required…

Wanstrom, Linda

2009-01-01

435

Test of the Second Order Asymptotic Theory with Low Degree Solar Gravity Modes.  

National Technical Information Service (NTIS)

Further testing of first and second order asymptotic theory predictions for solar gravity modes is possible with the work of gu and Hill in which the number of classified low-degree gravity mode multiplets was increased from 31 to 53. In an extension of t...

C. T. Barry R. D. Rosenwald Y. Gu H. A Hill

1988-01-01

436

Oscillation criteria for second order forced ordinary differential equations with mixed nonlinearities  

NASA Astrophysics Data System (ADS)

We present new oscillation criteria for the second order forced ordinary differential equation with mixed nonlinearities: where , p(t) is positive and differentiable, [alpha]1>...>[alpha]m>1>[alpha]m+1>...>[alpha]n. No restriction is imposed on the forcing term e(t) to be the second derivative of an oscillatory function. When n=1, our results reduce to those of El-Sayed [M.A. El-Sayed, An oscillation criterion for a forced second order linear differential equation, Proc. Amer. Math. Soc. 118 (1993) 813-817], Wong [J.S.W. Wong, Oscillation criteria for a forced second linear differential equations, J. Math. Anal. Appl. 231 (1999) 235-240], Sun, Ou and Wong [Y.G. Sun, C.H. Ou, J.S.W. Wong, Interval oscillation theorems for a linear second order differential equation, Comput. Math. Appl. 48 (2004) 1693-1699] for the linear equation, Nazr [A.H. Nazr, Sufficient conditions for the oscillation of forced super-linear second order differential equations with oscillatory potential, Proc. Amer. Math. Soc. 126 (1998) 123-125] for the superlinear equation, and Sun and Wong [Y.G. Sun, J.S.W. Wong, Note on forced oscillation of nth-order sublinear differential equations, JE Math. Anal. Appl. 298 (2004) 114-119] for the sublinear equation.

Sun, Yuan Gong; Wong, James S. W.

2007-10-01

437

Employment of Second Order Ruled Surfaces in Design of Sheet Beam Guns  

SciTech Connect

A novel 3D method of sheet beam gun design has recently been developed. Second order ruled surfaces (SORS) can be used to define the geometry of the gun electrodes. The gun design process is made simpler if SORS are derived from analytical formulas. A proposed method is discussed and illustrated.

Krasnykh, Anatoly; /SLAC

2007-03-05

438

A parallel second-order adaptive mesh algorithm for incompressible flow in porous media  

Microsoft Academic Search

In this paper we present a second-order accurate adaptive algorithm for solving multiphase, incompressible ow in porous media. We assume a multiphase form of Darcy's law with relative permeabilities given as a function of the phase saturation. The remaining equations express conservation of mass for the uid constituents. In this setting the total velocity, dened to be the sum of

George S. H. Pau; Ann S. Almgren; John B. Bell

2009-01-01

439

A Parallel Second-Order Adaptive Mesh Algorithm for Incompressible Flow in Porous Media  

Microsoft Academic Search

In this paper we present a second-order accurate adaptive algorithm for solving multiphase, incompressible flows in porous media. We assume a multiphase form of Darcy's law with relative permeabilities given as a function of the phase saturation. The remaining equations express conservation of mass for the fluid constituents. In this setting the total velocity, defined to be the sum of

George Shu Heng Pau; Ann S. Almgren; John B. Bell; Michael J. Lijewski

2008-01-01

440

Stochastic Models of Intermediate State Interaction in Second Order Optical Processes Stationary Response. II---  

Microsoft Academic Search

The stochastic theory of intermediate state interaction developed in a preceding paper is applied to more realistic models to discuss the correlation between the incident and the scattered photons in more detail. Through these model calculations it is confirmed that the spectral characteristics of the second order optical process are determined by a few physical parameters of the radiative damping

Toshihide Takagahara; Eiichi Hanamura; Ryogo Kubo

1977-01-01

441

The Second-Order Aberrations in the Interferometric Measurement of Concentration Gradients  

Microsoft Academic Search

The second-order aberrations in interferograms of cells with a continuously varying refractive index have been computed for those interferometric methods where an optical image of the cell is produced. The aberrations have been given in terms of four parameters, the cell thickness a, the cell position parameter r, the convergence parameter k, and the angular off-axis position rhoof the centre

Harry Svensson

1954-01-01

442

Second-order cascaded frequency shifting and signal amplification in organic and inorganic crystals  

Microsoft Academic Search

We report wavelength shifting (generation of a pulse at the wavelength (lambda) p - (Delta) (lambda) from a signal at (lambda) p + (Delta) (lambda) under the action of a pump at (lambda) p) and parametric amplification through a cascaded second order process in a periodically poled lithium niobate crystal and also in an organic crystal N-(4-nitrophenyl)-L- prolinol (NPP). NPP

Gian P. Banfi; P. K. Datta; Ilaria Cristiani; D. Fortusini; Vittorio Degiorgio; John N. Sherwood

1999-01-01

443

Sample Sizes for Two-Group Second-Order Latent Growth Curve Models  

Microsoft Academic Search

Second-order latent growth curve models (S. C. Duncan & Duncan, 1996; McArdle, 1988) can be used to study group differences in change in latent constructs. We give exact formulas for the covariance matrix of the parameter estimates and an algebraic expression for the estimation of slope differences. Formulas for calculations of the required sample size are presented, illustrated, and discussed.

Linda Wänström

2009-01-01

444

Working Set Selection Using Second Order Information for Training Support Vector Machines  

Microsoft Academic Search

Working set selection is an important step in decomposition methods for training support vector machines (SVMs). This paper develops a new technique for working set selection in SMO-type decomposition methods. It uses second order information to achieve fast con- vergence. Theoretical properties such as linear convergence are established. Experiments demonstrate that the proposed method is faster than existing selection methods

Rong-en Fan; Pai-hsuen Chen; Chih-jen Lin

2005-01-01

445

Validity of the Quality of School Life Scale: A Primary and Second-Order Factor Analysis  

Microsoft Academic Search

A primary and second-order principal components analysis was performed on the Quality of School Life Scale (QSL), a popular measure of elementary school climate. The scale was administered to 141 fourth-, fifth-, and sixth-grade students in an elementary school in the Southwestern United States. The findings of this study, like the information reported in the Administration and Technical Manual for

William L. Johnson; Annabel M. Johnson

1993-01-01

446

A working mechanical model for first- and second-order phase transitions and the cusp catastrophe  

NASA Astrophysics Data System (ADS)

We have modified a toy to demonstrate first- and second-order phase transitions. The toy consists of a ball constrained to move on a rotating hoop. Analysis of the equilibrium positions of the ball as a function of the angular velocity and location of the axis of rotation shows that this system contains a cusp catastrophe.

Mancuso, Richard V.

2000-03-01

447

Plasmonic electromagnetically-induced transparency in metamaterial based on second-order plasmonic resonance  

NASA Astrophysics Data System (ADS)

Using only two gold strips, we propose a scheme for generation of the plasmonic analogue of electromagnetically-induced transparency (EIT) in stacked optical metamaterials by utilizing the second-order plasmon resonance. In addition, we show that the plasmonic EIT can be achieved with asymmetric structure, since the asymmetric structure allows the excitation of the dark mode.

Jin, Xing-Ri; Lu, Yuehui; Zheng, Haiyu; Lee, Youngpak; Rhee, Joo Yull; Kim, Ki Won; Jang, Won Ho

2011-09-01

448

Fish Species Composition in Two Second-Order Headwater Streams in the North Central Appalachians Ecoregion  

Microsoft Academic Search

Fish species composition was determined for two second-order headwater streams within the North Central Appalachians ecoregion in northern Pennsylvania. The two streams were widely spaced geographically (over 193 km apart) and occurred in different drainage systems. Streams were sampled in the spring and fall over two years (1996–98) yielding similar fish assemblages. A total of five species was collected. Mottled

Martin N. DiLauro; Randy M. Bennett

2001-01-01

449

Extension of Central Composite Design for Second-Order Response Surface Model Building  

Microsoft Academic Search

The central composite design (CCD) is perhaps the most popular class of second-order response surface designs. Even though the CCDs are popular for response surface designs, this class of design has some limitations such as it does not sometimes possess good statistical properties, and it does not fit complicated models well. In this article, we propose extended central composite designs

Hee J. Park; Sung H. Park

2010-01-01

450

Second-order conditional modeling of turbulent nonpremixed flames with a composite PDF  

Microsoft Academic Search

A second-order conditional model for turbulent nonpremixed flames with a composite probability density function (pdf) is presented. The composite pdf represents three parts of the scalar field: a fully turbulent part, a surrounding nonturbulent part, and a superlayer part. The conditional equations are derived using Favre averaging (density weighting) with the interfacial interaction therms appearing in explicitly separate groups. These

1987-01-01

451

Cubic Lack of Fit for Three-Level Second Order Response Surface Designs.  

National Technical Information Service (NTIS)

A recent paper by Box and Draper (1982) discussed the detection of cubic lack of fit in second order composite design experiments, and its possible removal by the use of power transformations in the predictor variables. The designs examined were five-leve...

N. R. Draper

1982-01-01

452

Composite second-order performance improvement in optical fibre CATV transmission system using chirped fibre grating  

Microsoft Academic Search

Theoretically, we analyse the dispersion compensation characteristics of the chirped fibre grating (CFG) in an optical fibre cable television (CATV) system and obtain the analytic expression of the composite second-order (CSO) distortion using the time-domain form of the field envelope wave equation. The obtained result is in good agreement with the numerical simulation result. Experimentally, we verify the result by

Qing Ye; Feng Liu; Hai-Wen Cai; Rong-Hui Qu; Zu-Jie Fang

2005-01-01

453

Polyimide/Inorganic Composite - Interpenetrating Polymer Network for Stable Second-Order Nonlinear Optics.  

National Technical Information Service (NTIS)

A new class of IPN system has been prepared and investigated. This IPN system combines the polybismaleinimide network and the NLO-active phenoxysilicon network. The second-order NLO coefficients, d33, values of the samples range from 2.5 to 6.7 pm/V depen...

S. Marturunkakul J. I . Chen L. Li X. L. Jiang R. J. Jeng

1993-01-01

454

Sol-gel-processed inorganic oxides: organic polymer composites for second-order nonlinear optical applications  

Microsoft Academic Search

A new class of promising composite materials consisting of sol-gel processed inorganic oxides and organic polymers has been developed over the last several years. These materials have been shown to be homogeneous, mechanically stable and have excellent optical properties. Second-order nonlinear optical properties are dependent upon the active chromophore being aligned within the structure. We report here the studies on

Jaroslaw W. Zieba; Yue Zhang; Paras N. Prasad; Martin K. Casstevens; Ryszard Burzynski

1992-01-01

455

Choice of second-order response surface designs for logistic and Poisson regression models  

Microsoft Academic Search

Response surface methodology is widely used for process development and optimisation, product design, and as part of the modern framework for robust parameter design. For normally distributed responses, the standard second-order designs such as the central composite design and the Box-Behnken design have relatively high D and G efficiencies. In situations where these designs are inappropriate, standard computer software can

Rachel T. Johnson; Douglas C. Montgomery

2009-01-01

456

Analysis of internal structures of composite materials by second-order property of mosaic patterns  

Microsoft Academic Search

Properties of composite materials depend on their internal structures which in most cases are highly random. Therefore, high-order information is often required for quantitative characterization of morphological features in spatial distributions of the constituent phases. The present study develops a general expression for a second-order moment, that is, autocorrelation function Rx?, of multiphase heterogeneous composites. The obtained Rx? depends on

Yunping Xi

1996-01-01

457

Second-order homogenization estimates for nonlinear composites incorporating field fluctuations: I—theory  

Microsoft Academic Search

This paper is concerned with the development of an improved second-order homogenization method incorporating field fluctuations for nonlinear composite materials. The idea is to combine the desirable features of two different, earlier methods making use of “linear comparison composites”, the properties of which are chosen optimally from suitably designed variational principles. The first method (Ponte Castañeda, J. Mech. Phys. Solids

Pedro Ponte Castañeda

2002-01-01

458

Second-order conditional modeling of turbulent nonpremixed flames with a composite pdf  

Microsoft Academic Search

A second-order conditional model for turbulent nonpremixed flames with a composite probability density function (pdf) is presented. The composite pdf represents three parts of the scalar field: a fully turbulent part, a surrounding nonturbulent part, and a superlayer part. The conditional equations are derived using Favre averaging (density weighting) with the interfacial interaction terms appearing in explicitly separate groups. These

1987-01-01

459

Effects of measuring instrument errors on the properties of second-order plans  

Microsoft Academic Search

The paper discusses the effects of various instrumental errors on features of composite second-order plans for two and three\\u000a variables that are related to the accuracy in predicting the response by means of the model.

G. G. Bakradze; I. G. Zedginidze; N. O. Beraya

2006-01-01

460

Central composite designs for estimating the optimum conditions for a second-order model  

Microsoft Academic Search

Central composite designs which maximize both the precision and the accuracy of estimates of the extremal point of a second-order response surface for fixed values of the model parameters are constructed. Two optimality criteria are developed, the one relating to precision and based on the sum of the first-order approximations to the asymptotic variances and the other to accuracy and

R. L. J. Coetzer; L. M. Haines; L. P. Fatti

2011-01-01

461

Determination of 55-155-155-1in second order QCD from hadronic Z decays  

Microsoft Academic Search

Distributions of event shape variables obtained from 120600 hadronicZ decays measured with the DELPHI detector are compared to the predictions of QCD based event generators. Values of the strong coupling constant as are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions. The final result, as(MZ), is based on second order perturbation theory

P. Abreu; W. Adam; F. Adami; T. Adye; T. Akesson; G. D. Alekseev; P. Allen; S. Almehed; S. J. Alvsvaag; U. Amaldi; E. Anassontzis; P. Antilogus; W.-D. Apel; R. J. Apsimon; B. Åsman; J. E. Augustin; A. Augustinus; P. Baillon; P. Bambade; F. Barao; R. Barate; G. Barbiellini; D. Y. Bardin; A. Baroncelli; O. Barring; W. Bartl; M. J. Bates; M. Battaglia; M. Baubillier; K. H. Becks; C. J. Beeston; M. Begalli; P. Beilliere; Yu. Belokopytov; P. Beltran; D. Benedic; J. M. Benlloch; M. Berggren; D. Bertrand; F. Bianchi; M. S. Bilenky; P. Billoir; J. Bjarne; D. Bloch; S. Blyth; V. Bocci; P. N. Bogolubov; T. Bolognese; M. Bonapart; M. Bonesini; W. Bonivento; P. S. L. Booth; P. Borgeaud; G. Borisov; H. Borner; C. Bosio; B. Bostjancic; O. Botner; B. Bouquet; C. Bourdarios; M. Bozzo; S. Braibant; P. Branchini; K. D. Brand; R. A. Brenner; H. Briand; C. Bricman; R. C. A. Brown; N. Brummer; J. M. Brunet; L. Bugge; T. Buran; H. Burmeister; J. A. M. A. Buytaert; M. Caccia; M. Calvi; A. J. Camacho Rozas; A. Campion; T. Camporesi; V. Canale; F. Cao; F. Carena; L. Carroll; C. Caso; E. Castelli; M. V. Castillo Gimenez; A. Cattai; F. R. Cavallo; L. Cerrito; A. Chan; M. Chapkin; P. Charpentier; L. Chaussard; J. Chauveau; P. Checchia; G. A. Chelkov; L. Chevalier; P. Chliapnikov; V. Chorowicz; R. Cirio; M. P. Clara; P. Collins; J. L. Contreras; R. Contri; G. Cosme; F. Couchot; H. B. Crawley; D. Crennell; G. Crosetti; M. Crozon; J. Cuevas Maestro; S. Czellar; S. Dagoret; E. Dahl-Jensen; B. Dalmagne; M. Dam; G. Damgaard; G. Darbo; E. Daubie; P. D. Dauncey; M. Davenport; P. David; W. Da Silva; C. Defoix; D. Delikaris; S. Delorme; P. Delpierre; N. Demaria; A. De Angelis; M. De Beer; H. De Boeck; W. De Boer; C. De Clercq; M. D. M. De Fez Laso; N. De Groot; C. De La Vaissiere; B. De Lotto; A. De Min; H. Dijkstra; L. Di Ciaccio; F. Djama; J. Dolbeau; O. Doll; M. Donszelmann; K. Doroba; M. Dracos; J. Drees; M. Dris; Y. Dufour; W. Dulinski; L. O. Eek; P. A.-M. Eerola; T. Ekelof; G. Ekspong; A. Elliot Peisert; J.-P. Engel; D. Fassouliotis; M. Feindt; A. Fenyuk; M. Fernandez Alonso; A. Ferrer; T. A. Filippas; A. Firestone; H. Foeth; E. Fokitis; P. Folegati; F. Fontanelli; K. A. J. Forbes; B. Franek; P. Frenkiel; D. C. Fries; A. G. Frodesen; R. Fruhwirth; F. Fulda-Quenzer; K. Furnival; H. Furstenau; J. Fuster; G. Galeazzi; D. Gamba; C. Garcia; J. Garcia; C. Gaspar; U. Gasparini; P. Gavillet; E. N. Gazis; J. P. Gerber; P. Giacomelli; R. Gokieli; V. M. Golovatyuk; J. J. Gomez Y Cadenas; A. Goobar; G. Gopal; M. Gorski; V. Gracco; A. Grant; F. Grard; E. Graziani; G. Grosdidier; E. Gross; P. Grosse-Wiesmann; B. Grossetete; J. Guy; F. Hahn; M. Hahn; S. Haider; Z. Hajduk; A. Hakansson; A. Hallgren; K. Hamacher; G. Hamel De Monchenault; F. J. Harris; B. W. Heck; T. Henkes; J. J. Hernandez; P. Herquet; H. Herr; I. Hietanen; C. O. Higgins; E. Higon; H. J. Hilke; S. D. Hodgson; T. Hofmokl; R. Holmes; S. O. Holmgren; D. Holthuizen; P. F. Honore; J. E. Hooper; M. Houlden; J. Hrubec; P. O. Hulth; K. Hultqvist; D. Husson; P. Ioannou; D. Isenhower; P. S. Iversen; J. N. Jackson; P. Jalocha; G. Jarlskog; P. Jarry; B. Jean-Marie; E. K. Johansson; D. Johnson; M. Jonker; L. Jonsson; P. Juillot; G. Kalkanis; G. Kalmus; F. Kapusta; M. Karlsson; S. Katsanevas; E. C. Katsoufis; R. Keranen; J. Kesteman; B. A. Khomenko; N. N. Khovanski; B. King; N. J. Kjaer; H. Klein; W. Klempt; A. Klovning; P. Kluit; A. Koch-Mehrin; J. H. Koehne; B. Koene; P. Kokkinias; M. Kopf; M. Koratzinos; K. Korcyl; A. V. Korytov; V. Kostiukhin; C. Kourkoumelis; P. H. Kramer; T. Kreuzberger; J. Krolikowski; I. Kronkvist; J. Krstic; U. Krüner-Marquis; W. Krupinski; W. Kucewicz; K. Kurvinen; C. Lacasta; C. Lambropoulos; J. W. Lamsa; L. Lanceri; V. Lapin; J. P. Laugier; R. Lauhakangas; G. Leder; F. Ledroit; R. Leitner; Y. Lemoigne; J. Lemonne; G. Lenzen; V. Lepeltier; A. Letessier-Selvon; E. Lieb; D. Liko; E. Lillethun; J. Lindgren; R. Lindner; A. Lipniacka; I. Lippi; R. Llosa; B. Loerstad; M. Lokajicek; J. G. Loken; A. Lopez-Fernandez; M. A. Lopez Aguera; M. Los; D. Loukas; A. Lounis; J. J. Lozano; P. Lutz; L. Lyons; G. Maehlum; N. Magnussen; J. Maillard; A. Maltezos; F. Mandl; J. Marco; M. Margoni; J. C. Marin; A. Markou; T. Maron; S. Marti; L. Mathis; F. Matorras; C. Matteuzzi; G. Matthiae; M. Mazzucato; M. McCubbin; R. McKay; R. McNulty; G. Meola; C. Meroni; W. T. Meyer; M. Michelotto; W. A. Mitaroff; G. V. Mitselmakher; U. Mjoernmark; T. Moa; R. Moeller; K. Mönig; M. R. Monge; P. Morettini; H. Mueller; W. J. Murray; B. Muryn; G. Myatt; F. Naraghi; F. L. Navarria; P. Negri; B. S. Nielsen; B. Nijjhar; V. Nikolaenko; V. Obraztsov; K. Oesterberg; A. G. Olshevski; R. Orava; A. Ostankov; A. Ouraou; M. Paganoni; R. Pain; H. Palka; T. Papadopoulou; L. Pape; A. Passeri; M. Pegoraro; J. Pennanen; V. Perevozchikov; M. Pernicka; A. Perrotta

1992-01-01

462

Second-Order Schedules of Token Reinforcement with Pigeons: Implications for Unit Price  

ERIC Educational Resources Information Center

|Four pigeons were exposed to second-order schedules of token reinforcement, with stimulus lights serving as token reinforcers. Tokens were earned according to a fixed-ratio (token-production) schedule, with the opportunity to exchange tokens for food (exchange period) occurring after a fixed number had been produced (exchange-production ratio).…

Bullock, Christopher E.; Hackenberg, Timothy D.

2006-01-01

463

LOCAL VOLUME-AVERAGED EQUATIONS OF MOTION FOR SUSPENSIONS IN SECOND-ORDER FLUIDS  

Microsoft Academic Search

The local volume averages of the equations of motion as well as the appropriate boundary conditions are developed for a flowing suspension of non-neutrally buoyant, uniform spheres in an incompressible, weak, second-order fluid under conditions such that inertial effects can be neglected. These equations do not represent an asymptotic theory with respect to the volume fraction of solids. Higher order

ALFRED C. Li; JOHN C. SLATTERY

1989-01-01

464

A Posteriori Error Estimates for a Discontinuous Galerkin Approximation of Second-Order Elliptic Problems  

Microsoft Academic Search

Several a posteriori error estimators are introduced and analyzed for a discontin- uous Galerkin formulation of a model second-order elliptic problem. In addition to residual-type estimators, we introduce some estimators that are couched in the ideas and techniques of domain decomposition. Results of numerical experiments are presented.

Ohannes A. Karakashian; Frédéric Pascal

2003-01-01

465

Ultra-fast digital holography of the femto-second order  

Microsoft Academic Search

We report on pulsed digital micro holographic systems recording ultra-fast process of the femto-second order, by spatially angular division multiplexing (SADM) and wavelength division multiplexing (WDM), respectively. Both intensity and phase images of the digitally reconstructed images are obtained through Fourier transformation and digital filtering, which show clearly the plasma forming and propagating dynamic process of laser induced ionization of

Hongchen Zhai; Xiaolei Wang; Guoguang Mu

2007-01-01

466

Dynamic second-order sliding mode control of the hovercraft vessel  

Microsoft Academic Search

A suitable combination of the differential flatness property and the second-order sliding mode controller design technique is proposed for the specification of a robust dynamic feedback multivariable controller accomplishing prescribed trajectory tracking tasks for the earth coordinate position variables of a hovercraft vessel model.

Hebertt Sira-Ramírez

2002-01-01

467

Second-Order Signature: A Tool for Specifying Data Models, Query Processing, and Optimization  

Microsoft Academic Search

We propose a framework for the specification of extensible database systems. A particu- lar goal is to implement a software component for parsing and rule-based optimization that can be used with widely varying data models and query languages as well as representation and query pro- cessing systems. The key idea is to use second-order signature (and algebra), a system of

Ralf Hartmut Güting

1993-01-01

468

Interior h 1 -estimates for second order elliptic equations with vanishing LMO coefficients  

Microsoft Academic Search

An a priori interior h1-estimate in a bounded domain for a second order elliptic operator with vanishing LMO coefficients is proved via a corresponding estimate for the commutator of a singular integral with an LMO function. The preceding estimate is of independent interest in harmonic analysis.

Yongzhong Sun; Weiyi Su

2006-01-01

469

New Guest-Host System: Towards Stable Second-Order Optical Nonlinearity.  

National Technical Information Service (NTIS)

A new guest-host system based on the azo dye disperse red 1 and phenyl siloxane polymer has been investigated. The second order susceptibility of the polymer cured at 220 deg C was found to be stable at room temperature and decays to 60 % of its original ...

R. J. Jeng Y. M. Chen A. K. Jain S. K. Tripathy J. Kumar

1992-01-01

470

Asymptotic iteration technique for second-order dynamic equations on time scales  

NASA Astrophysics Data System (ADS)

An asymptotic iteration method for solving second-order homogeneous linear dynamic equation of the form y?? = a0(t)y? + b0(t)y is introduced. Where a0(t) and b0(t) are Crdm(T) functions and the positive integer m depends on the differentiability of a0(t), b0(t) and iteration steps.

Misir, Adil; Ogrekci, Suleyman

2011-04-01

471

Disconjugacy of a second order linear differential equation and periodic solutions  

Microsoft Academic Search

The present paper is devoted to a new criterion for disconjugacy of a second order linear differential equation. Unlike most of the classical sufficient conditions for disconjugacy, our criterion does not involve assumptions on the smallness of the coefficients of the equation. We compare our criterion with several known criteria for disconjugacy, for which we provide detailed proofs, and discuss

V. Ya. Derr

2010-01-01

472

Steepest-descents integral representations for dominant solutions of linear second-order differential equations  

Microsoft Academic Search

It is shown that for certain linear second-order differential equations, there are solutions (usually referred to as recessive solutions) which have integral representations of Stieltjes transform type. It also is shown that there are special dominant solutions (the solution Bi of Airy's equation is an archetype) which have integral representations of one-sided Hilbert transform type. The differential equations we consider

William G. C. Boyd

1996-01-01

473

Independence of First- and Second-Order Memories in Newborn Rabbits  

ERIC Educational Resources Information Center

|The mammary pheromone promotes the acquisition of novel odorants (CS1) in newborn rabbits. Here, experiments pinpoint that CS1 becomes able to support neonatal learning of other odorants (CS2). We therefore evaluated whether these first- and second-order memories remained dependent after reactivation. Amnesia induced after CS2 recall selectively…

Coureaud, Gerard; Languille, Solene; Joly, Virginie; Schaal, Benoist; Hars, Bernard

2011-01-01

474

Determination of the second order doppler shift of iron in myoglobin by Mössbauer spectroscopy  

Microsoft Academic Search

We have performed Mössbauer absorption experiments on a sample of deoxygenated myoglobin crystals from 5 K to 280 K. With two series of measurements, one with the source and sample at the same temperature and the other with the source always at 298 K, we are able to extract information from the second-order Doppler effect in the sample. Simple models

L. Reinisch; J. Heidemeier; F. Parak

1985-01-01

475

Generalized solutions of initial-boundary value problems for second-order hyperbolic systems  

Microsoft Academic Search

The method of boundary integral equations is developed as applied to initial-boundary value problems for strictly hyperbolic systems of second-order equations characteristic of anisotropic media dynamics. Based on the theory of distributions (generalized functions), solutions are constructed in the space of generalized functions followed by passing to integral representations and classical solutions. Solutions are considered in the class of singular

L. A. Alexeyeva; G. K. Zakir'yanova

2011-01-01

476

Discrete Time Analyses of Nonuniform Sampling First and Second-Order Digital Phase Lock Loops  

Microsoft Academic Search

The present paper considers discrete time analyses of firstand second-order digital phase lock loops. These loops are characterized by the fact that they track the zero crossings of the incoming signal; consequently, the sampling intervals are nonuniform. The firstorder loop is analyzed for phase step and frequency step inputs; mean time to skip cycle is also considered. For phase step

A. Weinberg; B. Liu

1974-01-01

477

Estimate of the second order electron self energy corrections in highly charged heavy ions  

Microsoft Academic Search

An estimate for the last unknown gauge-invariant set of QED corrections of order ?2, the second-order self-energy correction, is presented utilizing the so-called sign approximation. This is able to reduce\\u000a the present uncertainties in Lamb-shift predictions considerably.

I. Goidenko; L. Labzowsky; A. Nefiodov; G. Plunien; G. Soff; S. Zschocke

2000-01-01

478

First- and Second-Order Factor Analyses of the Behavior Problem Checklist with Behaviorally Disordered Pupils.  

ERIC Educational Resources Information Center

Teacher completed Behavior Problem Checklists on 730 behaviorally disordered pupils were subjected to first- and second-order factor analyses. Four narrow band factors and two broad band factors were identified suggesting two general patterns of psychopathology among children. (Author/DB)

Luebke, Jerry; And Others

1987-01-01

479

Second-order conditions in extremal problems with finite-dimensional range. 2-normal maps  

Microsoft Academic Search

A minimization problem with constraints that includes problems for which the constraints are of equality and inequality type is considered. First- and second-order necessary conditions in the Lagrangian form are obtained for this problem. The main difference between these conditions and most of the previously known ones is the fact that they also remain meaningful for abnormal problems, in both

A. V. Arutyunov

1996-01-01

480

Second-Order Approximations to the Density, Mean and Variance of Brownian First-Exit Times  

Microsoft Academic Search

This paper presents correction terms to the tangent approximation for the first-exit density of Brownian motion at distant boundaries. These lead to second-order approximations to the first-exit distribution. Asymptotic formulas for the mean and variance of the first-exit time are derived. Numerical comparisons show the accuracy of the approximations.

Christel Jennen

1985-01-01

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