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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

ROTATING BIOLOGICAL CONTACTORS - SECOND ORDER KINETICS  

EPA Science Inventory

Rotating biological contactors (RBC) have been employed for treating municipal wastewaters within the United States since 1970. The RBC process lends itself to kinetic interpretation because of the sequential stages employed in the operation. This mode of operation enables the su...

3

Gravitational radiation reaction and second-order perturbation theory  

NASA Astrophysics Data System (ADS)

A point particle of small mass m moves in free fall through a background vacuum spacetime metric gab0 and creates a first-order metric perturbation hab1ret that diverges at the particle. Elementary expressions are known for the singular m/r part of hab1ret and for its tidal distortion determined by the Riemann tensor in a neighborhood of m. Subtracting this singular part hab1S from hab1ret leaves a regular remainder hab1R. The self-force on the particle from its own gravitational field adjusts the world line at O(m) to be a geodesic of gab0+hab1R. The generalization of this description to second-order perturbations is developed and results in a wave equation governing the second-order hab2ret with a source that has an O(m2) contribution from the stress-energy tensor of m added to a term quadratic in hab1ret. Second-order self-force analysis is similar to that at first order: The second-order singular field hab2S subtracted from hab2ret yields the regular remainder hab2R, and the second-order self-force is then revealed as geodesic motion of m in the metric gab0+h1R+h2R.

Detweiler, Steven

2012-02-01

4

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...

5

A weak second order tau-leaping method for chemical kinetic systems  

NASA Astrophysics Data System (ADS)

Recently Anderson and Mattingly [Comm. Math. Sci. 9, 301 (2011)] proposed a method which can solve chemical Langevin equations with weak second order accuracy. We extend their work to the discrete chemical jump processes. With slight modification, the method can also solve discrete chemical kinetic systems with weak second order accuracy in the large volume scaling. Especially, this method achieves higher order accuracy than both the Euler ?-leaping and mid-point ?-leaping methods in the sense that the local truncation error for the covariance is of order ?3V-1 when ? = V-? (0 < ? < 1) and the system size V --> ?. We present the convergence analysis, numerical stability analysis, and numerical examples. Overall, in the authors' opinion, the new method is easy to be implemented and good in performance, which is a good candidate among the highly accurate ?-leaping type schemes for discrete chemical reaction systems.

Hu, Yucheng; Li, Tiejun; Min, Bin

2011-07-01

6

A weak second order tau-leaping method for chemical kinetic systems  

Microsoft Academic Search

Recently Anderson and Mattingly [Comm. Math. Sci. 9, 301 (2011)] proposed a method which can solve chemical Langevin equations with weak second order accuracy. We extend their work to the discrete chemical jump processes. With slight modification, the method can also solve discrete chemical kinetic systems with weak second order accuracy in the large volume scaling. Especially, this method achieves

Yucheng Hu; Tiejun Li; Bin Min

2011-01-01

7

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

SciTech Connect

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 [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China) [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Center for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei (China); Gao, Zhe [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China) [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Center for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei (China)

2013-08-15

8

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

2011-11-24

9

REMOVAL OF LEAD(II) FROM EFFLUENTS BY SORPTION ON PEAT USING SECOND-ORDER KINETICS  

Microsoft Academic Search

The sorption of lead ions from aqueous solution onto peat has been studied. The kinetics of sorption of lead ion are described by a pseudo-second-order model modified with a new parameter, t0, included to account for an initial resistance due to the film boundary layer. Analysis of this model has been carried out at various experimental conditions to study the

Y. S. Ho; J. C. Y. Ng; G. McKay

2001-01-01

10

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

11

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

2010-12-01

12

DECAY OF DISSOLVED SUBSTANCES BY SECOND-ORDER REACTION: PROBLEM DESCRIPTION AND BATCH-REACTOR SOLUTIONS  

EPA Science Inventory

The mass transport (advection-dispersion) equations allowing coupled second-order reaction (i.e. Omega sub 1, C sub 1) + (omega sub 2, C sub 2) (R sub 12) -> Re) between two constituents are derived and result in a set of coupled nonlinear partial differential equations. Neglecti...

13

First-Order or Second-Order Kinetics? A Monte Carlo Answer  

NASA Astrophysics Data System (ADS)

In chemical kinetics, data for the concentration [A] as a function of time can be analyzed by least-squares fitting to the appropriate expression for the integrated rate law. The problem of discriminating between first and second order in such analyses is examined through Monte Carlo computational experiments in which synthetic data are fitted to both the direct expressions for [A]( t ) and to their linearized versions. For 11 data points spanning two half-lives, with 10% random error, a simple comparison of the sum of weighted squared residuals picks the correct order ˜90% of the time, which is better than implied in earlier discussions of this problem. The discriminating ability improves markedly with increasing numbers of data points and reduced experimental error. The article includes a description of procedures that permit students to explore the role of random noise in kinetics data, using the representative data analysis program KaleidaGraph.

Tellinghuisen, Joel

2005-11-01

14

Implicit Second Order Weak Taylor Tau-Leaping Methods for the Stochastic Simulation of Chemical Kinetics  

Microsoft Academic Search

For biochemical systems, when some chemical species are represented by small numbers of molecules, discrete and stochastic approaches are more appropriate than continuous and deterministic approaches. The stochastic simulation algorithm (SSA), proposed by Gillespie, is a cardinal simulation method for the chemical kinetics. Because the SSA simulates every reaction event, the amount of the computational time is huge when models

T.-H. Ahn; A. Sandu

2011-01-01

15

An Activation Energy Experiment for a Second-Order Reaction in a Single Laboratory Period.  

ERIC Educational Resources Information Center

Describes modification of a chemical reaction to a single 4 1/2-hour laboratory period. Reaction kinetics between 2, 4-initrochlorobenzene and piperidine to form 2, 4-dinitrophenyl-piperidine and piperidinium hydrochloride are followed conductometrically at three temperatures to obtain data to calculate activation parameters. (Author/JN)

Barile, Raymond C.; Michiels, Leo P.

1983-01-01

16

A kinetic energy fitting metric for resolution of the identity second-order Møller-Plesset perturbation theory.  

PubMed

A kinetic-energy-based fitting metric for application in the context of resolution of the identity second-order Møller-Plesset perturbation theory is presented, which is derived from the Poisson equation. Preliminary tests of the applicability include the evaluation of the error in the correlation energy, compared to standard Møller-Plesset perturbation theory, with respect to the auxiliary basis set employed. We comment on the potential merits of this fitting metric, compared to standard resolution of the identity second-order Møller-Plesset perturbation theory, and discuss its scaling behavior in the limit of large molecules. PMID:21391690

Lambrecht, Daniel S; Brandhorst, Kai; Miller, William H; McCurdy, C William; Head-Gordon, Martin

2011-04-01

17

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

NASA Astrophysics Data System (ADS)

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.

Kompany-Zareh, Mohsen; Khoshkam, Maryam

2013-02-01

18

Poling kinetics and second order NLO properties of DCNP doped PMMA based thin film  

NASA Astrophysics Data System (ADS)

Results of DC field poling and second harmonic generation experiments on a thin film of polymethyl methacrylate (PMMA) polymer doped with the dye molecule (3-(1,1-dicyanothenyl)-1-phenyl-4, 5-dihydro-1H-pryazole) (DCNP) are reported. The temporal variation of SHG signal upon application of static (DC) electric field at the temperature close to the glass transition Tg of PMMA establishes rapidly, within 66 s. A large value of second order NLO susceptibility dpp(-2?;?,?) of 52 ± 8 pm/V at 1064.2 nm fundamental wavelength was observed. Its possible origin is proposed and discussed.

Manea, Ana-Maria; Rau, Ileana; Tane, Alexandrina; Kajzar, Francois; Sznitko, Lech; Miniewicz, Andrzej

2013-11-01

19

A second-order accurate kinetic-theory-based method for inviscid compressible flows  

NASA Technical Reports Server (NTRS)

An upwind method for the numerical solution of the Euler equations is presented. This method, called the kinetic numerical method (KNM), is based on the fact that the Euler equations are moments of the Boltzmann equation of the kinetic theory of gases when the distribution function is Maxwellian. The KNM consists of two phases, the convection phase and the collision phase. The method is unconditionally stable and explicit. It is highly vectorizable and can be easily made total variation diminishing for the distribution function by a suitable choice of the interpolation strategy. The method is applied to a one-dimensional shock-propagation problem and to a two-dimensional shock-reflection problem.

Deshpande, Suresh M.

1986-01-01

20

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

21

Reaction Kinetics  

NASA Astrophysics Data System (ADS)

Detonation, which is the result of a reacting high explosive, is not a simple chemical reaction. Instead it is a complex process of rapid chemical changes that give rise to equally rapid mechanical and physical changes. Initially, as the explosive is initiated or Subscriptjected to a stimulus such as a shock wave, energy is transferred to the material causing mechanical deformation and heating. The transferred energy and heating produce chemically excited species, leading to initial bond-breaking or reaction initiation. These processes are thought to occur in a Hot-Molecule Zone (HMZ). Once reaction is initiated, sequences of chemical reactions follow resulting in the liberation of chemical energy and the production of gaseous reaction products.

Peiris, Suhithi M.

22

Second order cross-correlation between kinetic Sunyaev-Zel'dovich effect and 21-cm fluctuations from the epoch of reionization  

NASA Astrophysics Data System (ADS)

The measurement of the brightness temperature fluctuations of neutral hydrogen 21-cm lines from the epoch of reionization (EoR) is expected to be a powerful tool for revealing the reionization process. We study the 21-cm cross-correlation with cosmic microwave background (CMB) temperature anisotropies, focusing on the effect of the patchy reionization. We calculate, up to second order, the angular power spectrum of the cross-correlation between 21-cm fluctuations and the CMB kinetic Sunyaev-Zel'dovich effect (kSZ) from the EoR, using an analytical reionization model. We show that the kSZ and the 21-cm fluctuations are anti-correlated on the scale corresponding to the typical size of an ionized bubble at the observed redshift of the 21-cm fluctuations. The amplitude of the angular power spectrum of the cross-correlation depends on the fluctuations of the ionized fraction. Especially, in a highly inhomogeneous reionization model, the amplitude reaches the order of 100 ? K2 at ?˜ 3000. We also show that second-order terms may help in distinguishing between reionization histories.

Tashiro, Hiroyuki; Aghanim, Nabila; Langer, Mathieu; Douspis, Marian; Zaroubi, Saleem; Jeli?, Vibor

2011-07-01

23

Kinetic study of neutral lead cluster reactions  

Microsoft Academic Search

Kinetic studies of the reactions of neutral lead clusters with NO2, NO and O2 were performed at 300 K. Reaction with NO2 is rapid, with the observed second-order rate constants for most clusters being between 0.2 and 5 × 10-11 cm3\\/s. There is a general trend of increasing rate with cluster size, although a few clusters display unusually high or

R. W. Farley; P. J. Ziemann; R. G. Keesee; A. W. Castleman Jr.

1993-01-01

24

Second order symmetry operators  

NASA Astrophysics Data System (ADS)

Using systematic calculations in spinor language, we obtain simple descriptions of the second order symmetry operators for the conformal wave equation, the Dirac–Weyl equation and the Maxwell equation on a curved four-dimensional Lorentzian manifold. The conditions for existence of symmetry operators for the different equations are seen to be related. Computer algebra tools have been developed and used to systematically reduce the equations to a form which allows geometrical interpretation.

Andersson, Lars; Bäckdahl, Thomas; Blue, Pieter

2014-07-01

25

Second-Order Algebraic Theories  

NASA Astrophysics Data System (ADS)

Fiore and Hur [10] recently introduced a conservative extension of universal algebra and equational logic from first to second order. Second-order universal algebra and second-order equational logic respectively provide a model theory and a formal deductive system for languages with variable binding and parameterised metavariables. This work completes the foundations of the subject from the viewpoint of categorical algebra. Specifically, the paper introduces the notion of second-order algebraic theory and develops its basic theory. Two categorical equivalences are established: at the syntactic level, that of second-order equational presentations and second-order algebraic theories; at the semantic level, that of second-order algebras and second-order functorial models. Our development includes a mathematical definition of syntactic translation between second-order equational presentations. This gives the first formalisation of notions such as encodings and transforms in the context of languages with variable binding.

Fiore, Marcelo; Mahmoud, Ola

26

Non-autonomous second order Hamiltonian systems  

NASA Astrophysics Data System (ADS)

We study the existence of periodic solutions for a second order non-autonomous dynamical system containing variable kinetic energy terms. Our assumptions balance the interaction between the kinetic energy and the potential energy with neither one dominating the other. We study sublinear problems and the existence of non-constant solutions.

Pipan, John; Schechter, Martin

2014-07-01

27

Kinetic studies of hydralazine reaction with acetaldehyde.  

PubMed

In vitro kinetic studies of the reaction of hydralazine with acetaldehyde at physiological concentrations and pH were conducted. This reaction, which leads to the formation of 3-methyl-S-triazolo[3,4-a]phthalazine, may occur in the plasma and may represent an alternative pathway for hydralazine metabolism. The reaction of hydralazine with acetaldehyde followed second-order kinetics with an activation energy of 16.9 kcal/mole. At 37 degrees, the half-life of the reaction for a colution containing 2.3 microgram of acetaldehyde/ml and 1 microgram of hydralazine/ml was 4.5 hr. The rate increased with increasing acetaldehyde concentrations. PMID:512856

O'Donnell, J P; Proveaux, W J; Ma, J K

1979-10-01

28

Application of a second order kinetic model for the preliminary design of an adsorption bed system using ammonium molybdophosphate–polyacrylonitrile for the removal of 137Cs from acidic nuclear waste solutions  

Microsoft Academic Search

Ammonium molybdophosphate (AMP) immobilized on polyacrylonitrile (PAN) is an engineered form of cesium selective sorbent material developed at the Czech Technical University in Prague. A form of a second order kinetic model is applied to experimental AMP–PAN breakthrough data. A system utilizing three fixed beds in series is described that allows for continuous nuclear waste processing at approximately 890 l\\/h.

T. J. Tranter; R. S. Herbst; T. A. Todd; A. L. Olson; H. B. Eldredge

2003-01-01

29

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

30

Relation of Turbojet and Ramjet Combustion Efficiency to Second-Order Reaction Kinetics and Fundamental Flame Speed  

NASA Technical Reports Server (NTRS)

Theoretical studies of the turbojet and ramjet combustion process are summarized and the resulting equations are applied to experimental data obtained from various combustor tests. The theoretical treatment assumes that one step in the over-all chain of processes which constitute jet-engine combustion is sufficiently slow to be the rate-controlling step that determines combustion efficiency.

Childs, J Howard; Reynolds, Thaine W; Graves, Charles C

1957-01-01

31

Second order transport from anomalies  

NASA Astrophysics Data System (ADS)

We study parity odd transport at second order in derivative expansion for a non-conformal charged fluid. We see that there are 27 parity odd transport coefficients, of which 12 are non-vanishing in equilibrium. We use the equilibrium partition function method to express 7 of these in terms of the anomaly, shear viscosity, charge diffusivity and thermodynamic functions. The remaining 5 are constrained by 3 relations which also involve the anomaly. We derive Kubo formulae for 2 of the transport coefficients and show these agree with that derived from the equilibrium partition function.

Bhattacharyya, Sayantani; David, Justin R.; Thakur, Somyadip

2014-01-01

32

Reaction Kinetics of C60 Fullerene Ozonation  

Microsoft Academic Search

It has been verified that the reaction between O3 and C60 follows the general second order reaction rate which is valid for all the reactions between ozone and unsaturated olefinic bonds: v = k[C?C][O3]. The reaction rate constant k has been measured ?(1.5 ± 0.3) × 10 L mol s. The value of this rate constant has the same order of magnitude of the rate constant measured for instance

Metodi P. Anachkov; Franco Cataldo; Slavtcho K. Rakovsky

2003-01-01

33

Kinetics of resid hydrodesulfurization reactions  

SciTech Connect

In this article the authors examine the results obtained in hydrodesulfurizing an atmospheric resis from Bai-Hassan crude on Ni-Mo/Al/sub 2/O/sub 3/ catalyst at 320-420/sup 0/C, feedstock space velocity 0.37-2.6 h/sup -1/, pressure 6.1 MPa, and hydrogen/feed ratio 300 liters/liter, in a single-pass downflow reactor with a stationary bed of catalyst. Also, they give certain thermodynamic characteristics for desulfurization, demetalization, and deasphalting of this resid. The kinetic model describing most accurately the kinetics of the different reactions will be examined.

Mohammed, A.H.A.K.; Abbas, A.A.A.; Al'-Maiya, A.S.K.

1987-07-01

34

Kinetics of Polymer Interfacial Reaction  

NASA Astrophysics Data System (ADS)

Germanium crystals modified with high quality azide functional monolayers are used to directly monitor in situ the kinetics of interfacial ``click'' reactions with complementary alkyne end-functional poly(n-butyl acrylate) (PnBA) and polystyrene (PS) by attenuated total reflectance infrared spectroscopy (ATR-IR). In the presence of copper (I), the azide-modified Ge substrates react quantitatively with PnBA and PS via a 1,3-dipolar cycloaddition reaction. Time-resolved ATR-IR measurements show two regimes of kinetic behavior, as predicted by theory. In the first regime the rate is rapid and is controlled by diffusion of the polymer through the solvent, scaling with the square root of time. The rate slows considerably in the second regime, limited by penetration of the reacting polymer through the covalently bound polymer brush layer, scaling with the natural logarithm of time. The influence of polymer size and solvent quality are reported.

Zhang, Shuo; Koberstein, Jeffrey

2012-02-01

35

Second-order mathematical theory of computation  

Microsoft Academic Search

In this work we show that it is possible to formalize all properties regularly observed in (deterministic and non-deterministic) algorithms in second-order predicate calculus. Moreover, we show that for any given algorithm it suffices to know how to formalize its 'partial correctness' by a second-order formula in order to formalize all other properties by second-order formulas. This result is of

Zohar Manna

1970-01-01

36

Communication: Electronic UV-Vis transient spectra of the .OH reaction products of uracil, thymine, cytosine, and 5,6-dihydrouracil by using the complete active space self-consistent field second-order perturbation (CASPT2//CASSCF) theory  

NASA Astrophysics Data System (ADS)

Addition of .OH radicals to pyrimidine nucleobases is a common reaction in DNA/RNA damage by reactive oxygen species. Among several experimental techniques, transient absorption spectroscopy has been during the last decades used to characterize such compounds. Discrepancies have however appeared in the assignment of the adduct or adducts responsible for the reported transient absorption UV-Vis spectra. In order to get an accurate assignment of the transient spectra and a unified description of the absorption properties of the .OH reaction products of pyrimidines, a systematic complete active space self-consistent field second-order perturbation (CASPT2//CASSCF) theory study has been carried out on the uracil, thymine, and cytosine .OH addition adducts, as well as on the 5,6-dihydrouracil hydrogen abstraction products. With the obtained findings, the C5OH contributions to the lowest-energy band can be finally discarded. Instead, a bright 2(?2) state of the C6OH adducts is determined to be the main responsible in all compounds for the absorption band in the Vis range.

Francés-Monerris, Antonio; Merchán, Manuela; Roca-Sanjuán, Daniel

2013-08-01

37

Using of "pseudo-second-order model" in adsorption.  

PubMed

A research paper's contribution exists not only in its originality and creativity but also in its continuity and development for research that follows. However, the author easily ignores it. Citation error and quotation error occurred very frequently in a scientific paper. Numerous researchers use secondary references without knowing the original idea from authors. Sulaymon et al. (Environ Sci Pollut Res 20:3011-3023, 2013) and Spiridon et al. (Environ Sci Pollut Res 20:6367-6381, 2013) presented wrong pseudo-second-order models in Environmental Science and Pollution Research, vol. 20. This comment pointed the errors of the kinetic models and offered information for citing original idea of pseudo-second-order kinetic expression. In order to stop the proliferation of the mistake, it is suggested to cite the original paper for the kinetic model which provided greater accuracy and more details about the kinetic expression. PMID:24132523

Ho, Yuh-Shan

2014-06-01

38

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

2012-08-01

39

Applications of Second-Order Cone Programming  

Microsoft Academic Search

In a second-Order cone program (SOCP) a linear function is minimized over the inter- section of an affine set and the product of second-Order (quadratic) cones. SOCPs are nonlinear convex Problems that include linear and (convex) quadratic programs as spe- cial cases, but are less general than semidefinite programs (SDPs). Several efficient pri- maldual interior-Point methods for SOCP have been

Miguel Sousa Lobo; Lieven Vandenberghe; Stephen Boyd; Hervé Lebret

1998-01-01

40

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

41

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

42

Reaction Kinetics of Nanostructured Silicon Carbide  

Microsoft Academic Search

Nanostructured silicon carbide (SiC) is of interest particularly for use in nanocomposites that demonstrate high hardness as well as for use in semiconductor applications. Reaction kinetics studies of solid-solid reactions are relatively recent and present a method of determining the reaction mechanism and activation energy by measuring reaction rates. We have used induction heating to heat quickly, thus reducing the

Kendra Wallis; T. W. Zerda

2006-01-01

43

Reaction kinetics and transformation of antipyrine chlorination with free chlorine.  

PubMed

Chlorine has been documented that it can effectively remove some pharmaceuticals. Recently, new active oxidants chlorine monoxide and molecular chlorine, which exist as free active chlorine in solution, were reported during pharmaceuticals chlorination. In this study, reaction kinetics, active oxidants, and transformation products during antipyrine chlorination were investigated with batch experiments. The reaction orders in [chlorine] were determined at various pH (6.53-7.62) and ranged from 1.13 ± 0.15 to 1.59 ± 0.08, which indicated that antipyrine chlorination is the concurrent existence of reactions appearing first-order and second-order in [chlorine]. The results by varying solution conditions (solution pH, chloride, ionic strength, and buffer concentration) show that chlorine monoxide and molecular chlorine play significant roles during the process of antipyrine chlorination. With kinetics modeling, the second-order rate constants for hypochlorous acid, chlorine monoxide, and molecular chlorine were obtained at 25 ± 2 °C (units: M(-1) s(-1)): kHOCl = 3.23 × 10(3), kCL2 = 2.86 × 10(7), kCL2O= 8.38 × 10(9) (R(2) = 0.9801). At pH 7, hypochlorous acid and chlorine monoxide are the main contributors to the degradation of antipyrine, about 80% and 20%, respectively (calculated by kHOCl, kCL2 and kCL2O. By applying these rate constants to predict the antipyrine elimination in real water matrixes (surface water, ground water), a good agreement was obtained, particularly in ground water. Moreover, liquid chromatography-tandems mass spectrometry (LC-MS/MS) and gas chromatograph-mass spectrometry (GC-MS) were used for products identification. Two main intermediate products and three stable products were observed during the process of antipyrine chlorination. The possible routes for antipyrine chlorination were proposed, which mainly consisted of halogenations, dealkylations and hydroxylations. PMID:23521978

Cai, Mei-Quan; Feng, Li; Jiang, Jin; Qi, Fei; Zhang, Li-Qiu

2013-05-15

44

Comparison of second-order impact line shifts  

NASA Astrophysics Data System (ADS)

The second-order impact shifts in hydrogen obtained from the Baranger formalism are compared with those from a kinetic theory approach. The resulting ?n=0 contributions to the shift from the two theories are shown to be identical, except for the neglect of electron-electron correlations in the Baranger formalism. It is also shown that some care is required in taking the classical limit for the perturbing electrons, or else the shift from ?n=0 interactions vanishes.

Griem, H. R.; Iglesias, C. A.; Boercker, D. B.

1991-10-01

45

Urban Principals' Second Order Change Leadership  

ERIC Educational Resources Information Center

Urban school leaders have challenges in continually improving student achievement and making change as quickly as needed. To address this problem 37 non-Title I principals completed an on-line survey, Principal's Actions Survey (PAS), based on the seven responsibilities for second order change identified by Marzano, Waters, and McNulty (2005).…

Taylor, Rosemarye T.; La Cava, Gonzalo S.

2011-01-01

46

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 conditioning…

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

2011-01-01

47

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

48

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

49

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.

50

Second-order gravitational self-force  

SciTech Connect

We derive an expression for the second-order gravitational self-force that acts on a self-gravitating compact object moving in a curved background spacetime. First we develop a new method of derivation and apply it to the derivation of the first-order gravitational self-force. Here we find that our result conforms with the previously derived expression. Next we generalize our method and derive a new expression for the second-order gravitational self-force. This study also has a practical motivation: The data analysis for the planned gravitational wave detector LISA requires construction of waveform templates for the expected gravitational waves. Calculation of the two leading orders of the gravitational self-force will enable one to construct highly accurate waveform templates, which are needed for the data analysis of gravitational waves that are emitted from extreme mass-ratio binaries.

Rosenthal, Eran [Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1 (Canada)

2006-10-15

51

Calculating Second-Order Effects in MOSFET's  

NASA Technical Reports Server (NTRS)

Collection of mathematical models includes second-order effects in n-channel, enhancement-mode, metal-oxide-semiconductor field-effect transistors (MOSFET's). When dimensions of circuit elements relatively large, effects neglected safely. However, as very-large-scale integration of microelectronic circuits leads to MOSFET's shorter or narrower than 2 micrometer, effects become significant in design and operation. Such computer programs as widely-used "Simulation Program With Integrated Circuit Emphasis, Version 2" (SPICE 2) include many of these effects. In second-order models of n-channel, enhancement-mode MOSFET, first-order gate-depletion region diminished by triangular-cross-section deletions on end and augmented by circular-wedge-cross-section bulges on sides.

Benumof, Reuben; Zoutendyk, John A.; Coss, James R.

1990-01-01

52

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

53

Kinetic study on the reaction of cisplatin with metallothionein.  

PubMed

The binding of cisplatin to metallothionein (MT) was investigated at 37 degrees C in 10 mM Tris-NO3 (pH approximately 7.4) and 4.62 mM NaCl. The conditions were chosen to mimic passage of clinical concentrations of cisplatin through the cytosol. The reactions were monitored by high-performance liquid chromatography (HPLC), atomic absorption spectroscopy, and ultraviolet (UV) absorption spectroscopy. The UV data showed that several reactions occur, the first of which does not affect the absorbance (no Pt-sulfur bond formation). They also suggested that if [cisplatin] is large compared with [MT], the rate of subsequent reaction is between first and second order in [cisplatin] and between zeroth and first order in [MT]. HPLC eluates with 24 < retention time (tR) < 27 min contained undialyzable Pt, which increased with reaction time and corresponded to Pt-thionein product. Eluates with 3 < tR < 7 min corresponded to unbound cisplatin and allowed determination of second-order rate constants (k), using the second-order rate equation. The k value for cisplatin reacting with apo-MT was approximately 0.14 M-1 s-1, Cd/Zn-MT approximately 0.75 M-1 s-1, Cd7-MT approximately 0.53 M-1 s-1, and Zn7-MT approximately 0.65 M-1 s-1. Thus, cisplatin displaced Cd and Zn equally well. Leukocyte MT concentration was approximately 1.0 mM, so that the kinetics of cisplatin binding to cellular MT is pseudo-first order (pseudo-first-order rate constant, approximately 0.63 x 10-3 s-1; half-life, approximately 18 min). With [cisplatin] = 10 microM, the rate of cisplatin reaction with MT is approximately 6.3 micromol s-1 cm-3. We conclude that cellular MT can trap significant amounts of cisplatin and may efficiently contribute to cisplatin resistance. PMID:12814969

Hagrman, Douglas; Goodisman, Jerry; Dabrowiak, James C; Souid, Abdul-Kader

2003-07-01

54

Rapid biocatalytic polytransesterification: Reaction kinetics in an exothermic reaction  

SciTech Connect

Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. The authors have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization. Rate of polymerization increases with the concentration of monomers. This is also reflected by the increase in the temperature of the reaction mixture. Using time-temperature-conversion contours, a differential method of kinetic analysis was used to calculate the energy of activation ({approximately} 15.1 Kcal/mol).

Chaudhary, A.K.; Beckman, E.J.; Russell, A.J. [Univ. of Pittsburgh, PA (United States)] [Univ. of Pittsburgh, PA (United States)

1998-08-20

55

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

56

Quinoline hydrodenitrogenation kinetics and reaction inhibition  

Microsoft Academic Search

Quinoline hydrodenitrogenation kinetics and reaction inhibition are studied in a unique high-pressure liquid-phase flow microreactor and in a batch autoclave at 350°C and 34 atm over presulfided commercial nickel-molybdenum\\/..gamma..-alumina catalysts. Hydrodenitrogenation of quinoline and its methyl-substituted derivatives involved hydrogenation of the nitrogen-containing ring followed by carbon-nitrogen bond scission. Methyl substitution had only secondary effects on the hydrodenitrogenation kinetics. Quinoline inhibited

Bhinde

1979-01-01

57

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

58

Bulk photogalvanic effects beyond second order  

NASA Astrophysics Data System (ADS)

Examining the bulk photogalvanic effect (BPE) at nonperturbative laser fields, it is shown that illuminating a thin noncentrosymmetric crystal, quasicrystal, or nanotube the point group of which is Dn>2, C(3,5,…)h, or D(3,5,…)h with a monochromatic linearly polarized field, at practically any orientation, induces a nonvanishing directed current component jz along its polar axis. This is in contrast to the vanishing jz predicted by the commonly employed photogalvanic tensor. Similarly, we discuss the appearance of an angular-dependent jz, already for C(n>2)v and Cn>2, and circular dichroism in the BPE that are not resolved in second order. We suggest the possible observation of these currents in, e.g., thin ?-quartz and LiNbO3:Fe crystals and single-walled chiral carbon nanotubes.

Alon, Ofir E.

2003-03-01

59

The hydrothermal reaction kinetics of aspartic acid  

NASA Astrophysics Data System (ADS)

Experimental data on the hydrothermal reaction kinetics of aspartic acid were acquired using a custom-built spectrophotometric reaction cell which permits in situ observation under hydrothermal conditions. The results of this study indicate that the reaction kinetics of dilute aspartic acid solutions are significantly different depending on the presence or absence of catalytic surfaces such as standard metal alloys. The spectroscopic data presented here represent the first direct observations, in situ and in real time, of an amino acid reacting in a hydrothermal solution. Quantitative kinetic information, including rate constants, concentration versus time profiles, and calculations of the individual component spectra, was obtained from the data using a chemometric approach based on factor analysis/principle component analysis which treats the rate expressions simultaneously as a system of differential algebraic equations (DAE) of index 1. Identification of the products was confirmed where possible by high pressure anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The reaction kinetics of aspartic acid under hydrothermal conditions was observed to be highly complex, in contrast to previous studies which indicated almost exclusively deamination. At lower temperatures (120-170 °C), several different reaction pathways were observed, including decarboxylation and polymerization, and the catalytic effects of reactor surfaces on the aspartic acid system were clearly demonstrated. At higher temperatures (above 170 °C), aspartic acid exhibited highly complex behaviour, with evidence indicating that it can simultaneously dimerize and cyclize, deaminate (by up to two pathways), and decarboxylate (by up to two pathways). These higher temperature kinetics were not fully resolvable in a quantitative manner due to the complexity of the system and the constraints of UV spectroscopy. The results of this study provide strong evidence that the reaction kinetics of aspartic acid are very sensitive to parameters such as temperature, reactor materials (i.e., reactive surfaces), and additives, and that previous observations on aspartic acid were specific to the choice of experimental conditions.

Cox, Jenny S.; Seward, Terry M.

2007-02-01

60

Kinetics of the Reverse Deacon Reaction.  

National Technical Information Service (NTIS)

The reverse Deacon reaction Cl sub 2 + H sub 2 O implies 2HCl + 1/2 O sub 2 is considered one of the most important steps in thermochemical water-splitting processes, for production of hydrogen from water. An investigation was made of the kinetics of the ...

A. K. Nanda

1981-01-01

61

Theories and Measurements on Nonisothermal Reaction Kinetics.  

National Technical Information Service (NTIS)

In connection with the thermal decomposition of calcium carbonate and calcium oxalate, the validity of equations derived from different non-isothermal reaction kinetics theories based upon the analysis of DTA and TG as well as of TG and DTG plots were inv...

L. Hodany

1981-01-01

62

Second-order continuum traffic flow model  

NASA Astrophysics Data System (ADS)

A second-order traffic flow model is derived from microscopic equations and is compared to existing models. In order to build in different driver characteristics on the microscopic level, we exploit the idea of an additional phase-space variable, called the desired velocity originally introduced by Paveri-Fontana [Trans. Res. 9, 225 (1975)]. By taking the moments of Paveri-Fontana's Boltzmann-like ansatz, a hierachy of evolution equations is found. This hierarchy is closed by neglecting cumulants of third and higher order in the cumulant expansion of the distribution function, thus leading to Euler-like traffic equations. As a consequence of the desired velocity, we find dynamical quantities, which are the mean desired velocity, the variance of the desired velocity, and the covariance of actual and desired velocity. Through these quantities an alternative explanation for the onset of traffic clusters can be given, i.e., a spatial variation of the variance of the desired velocity can cause the formation of a traffic jam. Furthermore, by taking into account the finite car length, Paveri-Fontana's equation is generalized to the high-density regime eventually producing corrections to the macroscopic equations. The relevance of the present dynamic quantities is demonstrated by numerical simulations.

Wagner, C.; Hoffmann, C.; Sollacher, R.; Wagenhuber, J.; Schürmann, B.

1996-11-01

63

Effects of second order photobleaching on recovered diffusion parameters from fluorescence photobleaching recovery  

PubMed Central

In the original theoretical development of fluorescence photobleaching recovery with circular or Gaussian laser intensity profiles (Axelrod et al., 1976, Biophys. J.) the bleaching process is assumed to obey first order kinetics in the fluorescent probe. While this is reasonable in most cases where oxygen participates in the photolysis reaction, some processes may obey second order kinetics in the fluorophore concentration due to dimerization. Accordingly, we present here an analysis of the fluorescence recovery when the photobleaching process is taken to be second order in the probe. Analytical solutions for small bleaching levels indicate that the fluorescence recovery curve is very similar to that measured following a bleaching process first order in the probe. Numerical solutions for moderate bleaching levels show that the recovery is qualitatively similar, but quantitatively different. Because the shape of the recovery curve provides no evidence as to the order of photobleaching, we recommend continued use of the previous theoretical analysis. However, it must be borne in mind that the diffusion coefficient is increasingly underestimated as the extent of photobleaching is increased. The true diffusion coefficient is obtained in the limit of small levels of photobleaching. Estimates of the fractional recovery are not affected by this approach.

Bjarneson, D. W.; Petersen, N. O.

1991-01-01

64

Diffusion and Heterogeneous Reaction X. Kinetic Considerations of Surface Reactions.  

National Technical Information Service (NTIS)

A theoretical analysis is presented of the influence of the kinetic order of the heterogeneous surface reaction on the diffusive mass transport of the reactant through a cylinder with catalytic walls and catalytic end plate. Because of the relevance to ex...

C. M. Ablow H. Wise

1967-01-01

65

Second-Order Nonlinear Optical Imaging of Chiral Crystals  

PubMed Central

Second-order nonlinear optical imaging of chiral crystals (SONICC) is an emerging technique for crystal imaging and characterization. We provide a brief overview of the origin of second harmonic generation signals in SONICC and discuss recent studies using SONICC for biological applications. Given that they provide near-complete suppression of any background, SONICC images can be used to determine the presence or absence of protein crystals through both manual inspection and automated analysis. Because SONICC creates high-resolution images, nucleation and growth kinetics can also be observed. SONICC can detect metastable, homochiral crystalline forms of amino acids crystallizing from racemic solutions, which confirms Ostwald’s rule of stages for crystal growth. SONICC’s selectivity, based on order, and sensitivity, based on background suppression, make it a promising technique for numerous fields concerned with chiral crystal formation.

Kissick, David J.; Wanapun, Debbie; Simpson, Garth J.

2012-01-01

66

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

67

Oxidation of bisphenol A by permanganate: reaction kinetics and removal of estrogenic activity.  

PubMed

The kinetics for reaction between bisphenol A (BPA) and permanganate was examined over pH range of 5.0-9.9 and the estrogenic activity of aqueous BPA solution after oxidation was assessed by yeast two-hybrid assay. Reaction kinetics follows the second-order rate law, with the apparent second-order rate constant of 15.1 ± 1.1 M(-1)s(-1) at pH 6.0 and 25°C and the activation energy of 48.7 kJ/mol. The kinetics exhibits pH dependency and the specific rate constants related to speciation of BPA are 50 ± 28 M(-1)s(-1), 9.6 (±0.6) × 10(3) M(-1)s(-1) and 1.4 (±0.1) × 10(4) M(-1)s(-1) for BPA, BPA(-) and BPA(2-), respectively. The results of the estrogenic/antiestrogenic activity test show that there is a hysteresis for the removal of estrogenic activity of aqueous BPA solution at pH 7.3. Removal of BPA is completed in 10 min, but complete removal of estrogenic activity requires a further 20 min. PMID:23579844

Yang, Jingjing; Wen, Gang; Zhao, Ji; Shao, Xiaoling; Ma, Jun

2013-01-01

68

Spectroscopy and reaction kinetics of HCO  

SciTech Connect

The high-resolution infrared spectrum of the C-H stretching fundamental of HCO has been studied by means of infrared flash kinetic spectroscopy. HCO was generated by flash photolysis of acetaldehyde or formaldehyde using a 308 nm (XeCl) excimer laser. The transient absorption was probed with an infrared difference frequency laser system. The high resolution spectra obtained were assigned and fitted with rotational, spin-rotational, and centrifugal distortion constants. The ..nu../sub 1/ band origin is 2434.48 cm/sup /minus/1/. New ground state constants have been derived from a least-squares fit combining the ..nu../sub 1/ data with previous microwave and FIR LMR measurements. A new set of spectroscopic constants for the (1, 0, 0) state, the equilibrium rotational constants, and the orientation of the transition dipole moment are also reported. The kinetics and product branching ratios of the HCO + NO/sub 2/ reaction have been studied using visible and infrared laser flash kinetic spectroscopy. The rate constant for the disappearance of HCO radical at 296 K is (5.7 +- 0.9) /times/ 10/sup /minus/11/ cm/sup 3/ molec/sup /minus/1/ sec/sup /minus/1/, and it is independent of the pressure of SF/sub 6/ buffer gas up to 700 torr. Less than 10% of the reaction goes through the most exothermic product channel, HNO + CO/sub 2/. The product channel, H + CO/sub 2/ + NO, is responsible for 52% of the reaction. HONO has been observed, though not quantitatively, as a reaction product corresponding to the HONO + CO channel. 51 refs., 21 figs., 8 tabs.

Guo, Yili

1989-01-01

69

Reactions in microemulsions: Effect of thermal fluctuations on reaction kinetics  

NASA Astrophysics Data System (ADS)

In this paper we address the generic effects arising from the interplay of thermal fluctuations and reactions. This is accomplished by considering specifically the kinetics of reactions effected in microemulsion media. In the first part of this paper we consider the kinetics of the reaction A+B-->Ø in bicontinuous microemulsion media, wherein the solutes A and B are assumed to be preferentially attracted to water and oil, respectively, and Ø constitutes an inert product. We formulate the diffusion and reaction of these solutes in a field-theoretical framework within which the fluctuations of the background microemulsion are embedded. We then employ mean-field arguments and a perturbative Wilson-type renormalization group (RG) approach to discern the relevance, at long length scales, of the background fluctuations. Our analysis indicates that the dynamic fluctuations of the microemulsion prove irrelevant in impacting the asymptotic kinetics of the reaction. In view of the fact that our field-theoretic approach enables us to probe only the long time characteristics, moreover, only in the weak-coupling limit, in the second part of this paper we analyze similar issues in the context of the droplet phase of microemulsions. This enables us to surmount some of the restrictions placed upon the results of the first part of this paper. In the second part, our analysis focuses upon a simpler reaction, viz., A-->Ø, wherein the solute A which is present only in the water phase is anhiliated upon contact with the fluctuating interfaces of the droplets. We employ a standard diffusion equation framework to formulate the transport and reaction of A. The fluctuations of the microemulsion are manifest in the boundary condition positing the vanishing concentration of A. We then employ a perturbation scheme to the solution of the diffusion equation, and thereby discern the explicit effects of the fluctuations of the sinks. Our formulation enables, in a sequentially improvable asymptotic manner, the explicit computation of the time-dependent and the steady state fluctuation contributions to the reaction rate.

Ganesan, Venkat; Fredrickson, Glenn H.

2000-08-01

70

Reaction rate kinetics for in situ combustion retorting of Michigan Antrim oil shale  

USGS Publications Warehouse

The intrinsic reaction rate kinetics for the pyrolysis of Michigan Antrim oil shale and the oxidation of the carbonaceous residue of this shale have been determined using a thermogravimetric analysis method. The kinetics of the pyrolysis reaction were evaluated from both isothermal and nonisothermal rate data. The reaction was found to be second-order with an activation energy of 252.2 kJ/mole, and with a frequency factor of 9.25 ?? 1015 sec-1. Pyrolysis kinetics were not affected by heating rates between 0.01 to 0.67??K/s. No evidence of any reactions among the oil shale mineral constituents was observed at temperatures below 1173??K. However, it was found that the presence of pyrite in oil shale reduces the primary devolatilization rate of kerogen and increases the amount of residual char in the spent shale. Carbonaceous residues which were prepared by heating the oil shale at a rate of 0.166??K/s to temperatures between 923??K and 1073??K, had the highest reactivities when oxidized at 0.166??K/s in a gas having 21 volume percent oxygen. Oxygen chemisorption was found to be the initial precursor to the oxidation process. The kinetics governing oxygen chemisorption is (Equation Presented) where X is the fractional coverage. The oxidation of the carbonaceous residue was found also to be second-order. The activation energy and the frequency factor determined from isothermal experiments were 147 kJ/mole and 9.18??107 sec-1 respectively, while the values of these parameters obtained from a nonisothermal experiment were 212 kJ/mole and 1.5??1013 sec-1. The variation in the rate constants is attributed to the fact that isothermal and nonisothermal analyses represent two different aspects of the combustion process.

Rostam-Abadi, M.; Mickelson, R. W.

1984-01-01

71

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

72

Second-Order Model to Predict Microbial Degradation of Organic Compounds in Natural Waters  

PubMed Central

The reliability of second-order rate constants for assessing microbial degradation kinetics in natural waters was examined by using three compounds that undergo hydrolytic degradation. The butoxyethyl ester of 2,4-dichlorophenoxyacetic acid was studied in water samples from 31 sites, malathion was examined in water from 14 sites, and chlorpropham was studied in samples from 11 sites. The coefficient of variation for rate constants for each compound was less than 65% over all sites. Additional studies indicated that the rate conformed to second-order kinetics; that is, the rate was proportional to both bacterial and xenobiotic concentrations.

Paris, Doris F.; Steen, William C.; Baughman, George L.; Barnett, John T.

1981-01-01

73

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

PubMed

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

Richard, J P

1991-05-01

74

[Kinetics modeling and reaction mechanism of ferrate(VI) oxidation of triclosan].  

PubMed

Triclosan (TCS) is a broad-spectrum antibacterial agent widely used in many personal care products. We investigated oxidation of TCS by aqueous ferrate Fe(VI) to determine reaction kinetics, interpreted the reaction mechanism by a linear free-energy relationship, and evaluated the degradation efficiency. Second-order reaction kinetics was used to model Fe (VI) oxidation of TCS, with the apparent second-order rate constant (k(app)) being 531.9 L x (mol x s)(-1) at pH 8.5 and (24 +/- 1) degrees C. The half life (t1/2) is 25.8 s for an Fe( VI) concentration of 10 mg x L(-1). The rate constants of the reaction decrease with increasing pH values. These pH-dependent variations in k(app) could be distributed by considering species-specific reactions between Fe(VI) species and acid-base species of an ionizable TCS. Species-specific second-order reaction rate constants, k, were determined for reaction of HFeO4(-) with each of TCS's acid-base species. The value of k determined for neutral TCS was (4.1 +/- 3.5) x 10(2) L x (mol x s)(-1), while that measured for anionic TCS was (1.8 +/- 0.1) x 10(4) L x (mol x s)(-1). The reaction between HFeO4(-) and the dissociated TCS controls the overall reaction. A linear free-energy relationship illustrated the electrophilic oxidation mechanism. Fe (VI) reacts initially with TCS by electrophilic attack at the latter's phenol moiety. At a n[Fe(VI)]: n(TCS) > 7: 1, complete removal of TCS was achieved. And lower concentration of the humic acid could enhance the k(app) of Fe( VI) with TCS. In conclusion, Fe(VI) oxidation technology appears to be a promising tool for applications of WWTPs effluents and other decontamination processes. PMID:22165218

Yang, Bin; Ying, Guang-Guo; Zhao, Jian-Liang

2011-09-01

75

Second-order shallow flow equation for anisotropic aquifers  

NASA Astrophysics Data System (ADS)

Transient unconfined ground-water flow is described using the well-known Boussinesq equation, in which the Dupuit assumptions are implicit. When these assumptions fail, one must recur to the next level of approximation, which is the second-order theory for shallow flow in porous media, developed by Dagan (1967) for isotropic aquifers. When the soil is highly anisotropic Dagan's second-order theory can become invalid. Here we present the generalized second order theory that account for anisotropy. An analytical solution for the second-order theory with anisotropy is presented for the linearized equation that is used to illustrate this effect on the bank storage problem.

Castro-Orgaz, O.; Giraldez, J. V.; Mateos, L.

2013-09-01

76

Kinetic analysis of free-radical reactions in the low-temperature autoxidation of triglycerides  

SciTech Connect

The kinetics of the low-temperature autoxidation of triglycerides has been investigated by electron spin resonance spectroscopy. After initial radical production, four reaction stages are found in the overall autoxidation of unsaturated lipids: (1) formation of peroxyl radicals by addition of molecular oxygen to the initial carbon radicals, (2) consumption of oxygen in the autoxidation cycle, (3) decay of the lipid peroxyl radical into allylic and pentadienyl radicals, and (4) recombination of the carbon-centered radicals. Peroxyl radical decay in saturated lipids follows second-order kinetics with an apparent activation energy of ca. 50 kJ/mol. The authors find that, for polyunsaturated lipids, even at quite low temperatures (120 K), the autoxidation process occurs readily and must be considered in the storage of biological samples.

Zhu, Jingmin; Sevilla, M.D. (Oakland Univ., Rochester, MI (USA))

1990-02-22

77

A robust second order sliding mode controller for Buck converter  

Microsoft Academic Search

A robust second order sliding mode control is used for Buck converter. After building the model of Buck circuit, the Twisting Algorithm is designed, which is based on relative degree of sliding mode control. The second order sliding mode not only reserves advantages of traditional sliding mode: robustness, but also eliminates the chattering problem. By comparing PID control with second

Huangfu Yigeng; Ma Ruiqing; Xie En; Abdellatif Miraoui

2010-01-01

78

Second-Order Factor Analysis: Methods and Interpretation.  

ERIC Educational Resources Information Center

This paper presents the methodology for performing and interpreting second-order factor analysis. Procedures for extracting and rotating solutions are presented. Critical issues of interpretation, such as interpreting second-order factors are discussed. Two methods for accomplishing this are explained, including multiplying the first- and…

Arnau, Randolph C.

79

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

80

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

81

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

82

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

83

Approximate Calculation Method for Second Order Sensitivity Coefficient  

Microsoft Academic Search

A simple method has been developed for calculating the second order sensitivity coefficient of static and burnup-dependent core performance parameters. The method is applied to a small and a large fast breeder reactors. Changes in core performance parameters due to 10% cross section changes are compared with that predicted by the first and the second order sensitivity analyses. Numerical results

Kazuhisa MATSUMOTO; Toshikazu TAKEDA; Tomoaki MASUDA

1994-01-01

84

Multivariate curve resolution applied to second order data  

Microsoft Academic Search

Application of multivariate curve resolution to second order data from hyphenated liquid chromatography with spectrometric diode array detection is shown. Chromatographic analysis of samples giving unresolved mixtures produces different data structures depending on the reproducibility of the elution process: (a) second order data where elution peaks of the same component in the different chromatographic runs have the same shape and

Roma Tauler

1995-01-01

85

An improved non-isothermal kinetic model for prediction of extent of transesterification reaction and degree of randomness in PET\\/PEN blends  

Microsoft Academic Search

An improved non-isothermal kinetic model was developed based on mass balance and Arrhenius laws using a second-order reversible reaction capable of predicting the extent of transesterification reaction (X) and the degree of randomness (RD) in poly(ethylene tereph-thalate) (PET)\\/poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) blends prepared by a twin screw micro-compounder over a full composition range under different processing conditions. The experimental values of

Mahdi Golriz; Hossein Ali Khonakdar; Seyed Hassan Jafari; Abdolrasoul Oromiehie; Hossein Abedini

2008-01-01

86

SECOND-ORDER MODEL TO PREDICT MICROBIAL DEGRADATION OF ORGANIC COMPOUNDS IN NATURAL WATERS  

EPA Science Inventory

The reliability of second-order rate constants for assessing microbial degradation kinetics in natural waters was examined by using three compounds that undergo hydrolytic degradation. The butoxyethyl ester of 2,4-diclorophenoxyacetic acid was studied in water samples from 31 sit...

87

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

88

A Case Study in Chemical Kinetics: The OH + CO Reaction.  

ERIC Educational Resources Information Center

Reviews some important properties of the bimolecular reaction between the hydroxyl radical and carbon monoxide. Investigates the kinetics of the reaction, the temperature and pressure dependence of the rate constant, the state-to-state dynamics of the reaction, and the reverse reaction. (MVL)

Weston, Ralph E., Jr.

1988-01-01

89

Second order guiding-center Vlasov-Maxwell equations  

SciTech Connect

Second order gyrogauge invariant guiding-center coordinates with strong ExB-flow are derived using the Lie transformation method. The corresponding Poisson bracket structure and equations of motion are obtained. From a variational principle the explicit Vlasov-Maxwell equations are derived including second order terms. The second order contributions contain the lowest order finite-Larmor-radius corrections to the electromagnetic field. Therefore, the model is capable of describing situations where strong ExB-flows and finite-Larmor-radius effects are mutually important.

Madsen, Jens [Association EURATOM-Risoe DTU, Technical University of Denmark, DK-4000 Roskilde (Denmark)

2010-08-15

90

Canonical description of a second-order achromat  

SciTech Connect

Charged particle motion in second-order magnetic optical achromat is described using a canonical perturbation theory. Necessary and sufficient conditions for the existence of such a device are presented. Given these conditions, the second-order matrix elements at the end of the achromat are found explicity. It is shown that all geometric matrix elements are equal to zero and all chromatic matrix elements are either also equal to zero or proportional to the corresponding chromaticity. Thus all second-order matrix elements vanish simultaneously when the two chromaticities are made to be equal to zero 13 refs., 1 tab.

Kheifets, S.A.; Fieguth, T.H.; Ruth, R.D.

1988-03-01

91

Observation of a Second-Order Spin-Depolarizing Resonance  

SciTech Connect

A recent experiment using a 160 MeV stored spin-polarized proton beam found clear evidence for a second-order intrinsic depolarizing resonance. With a 20% partial Siberian snake, we studied a first-order intrinsic depolarizing resonance; we then discovered and studied the second-order depolarizing resonance by changing both the horizontal and vertical betatron tunes. As expected, this second-order resonance is much weaker than the first-order resonance; it is probably due to sextupole fields plus coupling between the horizontal and vertical betatron oscillations caused by the 20% snake.

Ohmori, C.; Sato, H. [KEK, National Laboratory for High Energy Physics, Tsukuba, Ibaraki 305 (Japan)] [KEK, National Laboratory for High Energy Physics, Tsukuba, Ibaraki 305 (Japan); Alexeeva, L.V.; Anferov, V.A.; Caussyn, D.D.; Chu, C.M.; Crandell, D.A.; Gladycheva, S.E.; Hu, S.; Krisch, A.D.; Phelps, R.A.; Varzar, S.M.; Wong, V.K. [Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120 (United States)] [Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120 (United States); Lee, S.Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; Stephenson, E.J.; von Przewoski, B. [Indiana University Cyclotron Facility, Bloomington, Indiana 47408-0768 (United States)] [Indiana University Cyclotron Facility, Bloomington, Indiana 47408-0768 (United States); Baiod, R.; Russell, A.D. [Fermilab, Batavia, Illinois 60510 (United States)] [Fermilab, Batavia, Illinois 60510 (United States)

1995-09-04

92

A second-order theory for transverse ion heating and momentum coupling due to electrostatic ion cyclotron waves  

NASA Technical Reports Server (NTRS)

A second-order theory for electrostatic instabilities driven by counterstreaming ion beams is developed which describes momentum coupling and heating of the plasma via wave-particle interactions. Exchange rates between the waves and particles are derived, which are suitable for the fluid equations simulating microscopic effects on macroscopic scales. Using a fully kinetic simulation, the electrostatic ion cyclotron instability due to counterstreaming H(+) beams has been simulated. A power spectrum from the kinetic simulation is used to evaluate second-order exchange rates. The calculated heating and momentum loss from second-order theory is compared to the numerical simulation.

Miller, Ronald H.; Winske, Dan; Gary, S. P.

1992-01-01

93

Kinetics of the reaction between carbon dioxide and tertiary amines  

SciTech Connect

The reaction between carbon dioxide and amines is of great technical importance and has been the subject of many investigations. The authors have shown that the reaction for secondary amines in anhydrous ethanol and in aqueous solution is exclusively second-order in amine and that the zwitterion intermediate postulated by Danckwerts is probably of negligible significance in the mechanism. The reaction with tertiary amines has also been studied, but the data are less controversial. In order to complete their studies of the reactions of carbon dioxide with amines, using their conductimetric stopped-flow apparatus, they have studied this reaction for MDEA (methyldiethanolamine, IUPAC name N-methyl-2,2{prime}-iminodiethanol) and TEA (triethanolamine, IUPAC name 2,2{prime},2{double prime}-nitrilotris(ethanol)).

Crooks, J.E.; Donnellan, J.P. (King's Coll., London (England))

1990-02-16

94

Wave Propagation in Second-order Nonlinear Piezoelectric Media.  

National Technical Information Service (NTIS)

Computational results for the response of piezoelectric materials to various excitations are presented. The governing equations are based on a second-order theory of piezoelectricity, which is specialized for the 6mm crystal class. The equations are formu...

D. A. Hopkins G. A. Gazonas

2011-01-01

95

Photocross-Linked Second Order Nonlinear Optical Polymers.  

National Technical Information Service (NTIS)

We report a novel method to obtain stable second order nonlinear optical (NLO) properties in polymeric thin films. Photocross-linking between the NLO active molecules and a photoreactive polymer is achieved by ultraviolet irradiation subsequent to poling....

Y. M. Chen B. K. Mandal J. Y. Lee P. Miller J. Kumar

1991-01-01

96

Nonoscillation criteria for quasilinear second order differential equations  

NASA Astrophysics Data System (ADS)

Some nonoscillation criteria for quasilinear second order differential equations are obtained. These results generalize the classical results of Hille, Wintner and Opial and recent results of Elbert, Yan, Del Pino as well as Takasi and Yoshida.

Yang, Xiaojing; Lo, Kueiming

2007-07-01

97

Second-order model selection in mixture experiments  

SciTech Connect

Full second-order models for q-component mixture experiments contain q(q+l)/2 terms, which increases rapidly as q increases. Fitting full second-order models for larger q may involve problems with ill-conditioning and overfitting. These problems can be remedied by transforming the mixture components and/or fitting reduced forms of the full second-order mixture model. Various component transformation and model reduction approaches are discussed. Data from a 10-component nuclear waste glass study are used to illustrate ill-conditioning and overfitting problems that can be encountered when fitting a full second-order mixture model. Component transformation, model term selection, and model evaluation/validation techniques are discussed and illustrated for the waste glass example.

Redgate, P.E.; Piepel, G.F.; Hrma, P.R.

1992-07-01

98

A generalized kinetic model for heterogeneous gas-solid reactions.  

PubMed

We present a generalized kinetic model for gas-solid heterogeneous reactions taking place at the interface between two phases. The model studies the reaction kinetics by taking into account the reactions at the interface, as well as the transport process within the product layer. The standard unreacted shrinking core model relies on the assumption of quasi-static diffusion that results in a steady-state concentration profile of gas reactant in the product layer. By relaxing this assumption and resolving the entire problem, general solutions can be obtained for reaction kinetics, including the reaction front velocity and the conversion (volume fraction of reacted solid). The unreacted shrinking core model is shown to be accurate and in agreement with the generalized model for slow reaction (or fast diffusion), low concentration of gas reactant, and small solid size. Otherwise, a generalized kinetic model should be used. PMID:22920132

Xu, Zhijie; Sun, Xin; Khaleel, Mohammad A

2012-08-21

99

A generalized kinetic model for heterogeneous gas-solid reactions  

NASA Astrophysics Data System (ADS)

We present a generalized kinetic model for gas-solid heterogeneous reactions taking place at the interface between two phases. The model studies the reaction kinetics by taking into account the reactions at the interface, as well as the transport process within the product layer. The standard unreacted shrinking core model relies on the assumption of quasi-static diffusion that results in a steady-state concentration profile of gas reactant in the product layer. By relaxing this assumption and resolving the entire problem, general solutions can be obtained for reaction kinetics, including the reaction front velocity and the conversion (volume fraction of reacted solid). The unreacted shrinking core model is shown to be accurate and in agreement with the generalized model for slow reaction (or fast diffusion), low concentration of gas reactant, and small solid size. Otherwise, a generalized kinetic model should be used.

Xu, Zhijie; Sun, Xin; Khaleel, Mohammad A.

2012-08-01

100

L -functions of second-order cusp forms  

Microsoft Academic Search

We discuss equivalent definitions of holomorphic second-order cusp forms and prove bounds on their Fourier coefficients. We\\u000a also introduce their associated L-functions, prove functional equations for twisted versions of these L-functions and establish a criterion for a Dirichlet series to originate from a second order form. In the last section we\\u000a investigate the effect of adding an assumption of periodicity

N. Diamantis; M. Knopp; G. Mason; C. O’Sullivan

2006-01-01

101

Numerical Methods for Second-Order Stochastic Differential Equations  

Microsoft Academic Search

We seek numerical methods for second-order stochastic differential equations that reproduce the stationary density accurately for all values of damping. A complete analysis is possible for scalar linear second-order equations (damped harmonic oscillators with additive noise), where the statistics are Gaussian and can be calculated exactly in the continuous-time and discrete-time cases. A matrix equation is given for the stationary

Kevin Burrage; Ian Lenane; Grant Lythe

2007-01-01

102

Ambient reaction kinetics of atmospheric oxygenated organics with the OH radical: a computational methodology study.  

PubMed

The gas phase hydrogen abstraction reaction kinetics of short chained oxygenated hydrocarbons of atmospheric relevance has been studied using density functional theory, basis set extrapolation procedures, Møller-Plesset second order perturbation theory and Coupled-Cluster Singles Doubles. The rate constants for the reaction of the OH radical with nine different oxygenated compounds: CH3OH, CH3CH2OH, H2CO, CH3CHO, CH3COCH3, CH3OCH3, HCOOH, CH3COOH, HCOOCH3 with a total of 18 individual hydrogen abstraction reactions have been computationally determined and compared to experimental data. The performance of DFT in predicting the imaginary vibrational frequency of the nuclear motion at the transition state has been evaluated to assess tunnelling effects using Wigner, Bell and Eckart tunnelling corrections. Several different hybrid methodologies utilizing DFT/MP2 structures, vibrational frequencies and explicitly correlated Coupled Cluster single point energy corrections have been investigated to identify an approach for obtaining reliable reaction kinetics. Our investigation shows that CCSD(T)-F12a/VTZ-F12//BH&HLYP/aug-cc-pVTZ using a Bell or Eckart tunnelling correction yields rate constants within a factor of ~3 of experimental data and branching ratios within experimental uncertainty for the test set of short chained oxygenated compounds of atmospheric relevance. PMID:23674114

Elm, Jonas; Jørgensen, Solvejg; Bilde, Merete; Mikkelsen, Kurt V

2013-06-28

103

Reaction kinetics in confined geometries: Lonely adatoms in space  

NASA Astrophysics Data System (ADS)

There is a close relation between the problems of second-layer nucleation in epitaxial crystal growth and chemical surface reactions, such as hydrogen recombination, on interstellar dust grains. In both cases, standard rate equation analysis has been found to fail because the process takes place in a confined geometry, and under typical conditions the mean number of reactant particles on the surface is small compared to unity (the lonely adatom regime). Using scaling arguments developed in the context of second-layer nucleation, I present a simple derivation of the hydrogen recombination rate for small and large grains. I clarify the reasons for the failure of rate equations for small grains, and point out a logarithmic correction to the reaction rate when the reaction is limited by the desorption of hydrogen atoms (the second-order reaction regime).

Krug, Joachim

2003-06-01

104

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

105

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

106

Second-order perturbations of the Friedmann world model  

NASA Astrophysics Data System (ADS)

We consider the instability of the Friedmann world model to second order in perturbations. We present the perturbed set of equations up to second order in the Friedmann background world model with a general spatial curvature and cosmological constant. We consider systems with completely general imperfect fluids, minimally coupled scalar fields, an electromagnetic field, and generalized gravity theories. We also present the case of null geodesic equations, and one based on the relativistic Boltzmann equation. In due time, a decomposition is made for scalar-, vector-, and tensor-type perturbations which couple with each other to second order. A gauge issue is resolved to each order. The basic equations are presented without imposing any gauge condition, and thus in a gauge-ready form so that we can take full advantage of having gauge freedom in analyzing the problems. As an application we show that to second order in perturbation the relativistic pressureless ideal fluid of the scalar type reproduces exactly the known Newtonian result. As another application we rederive the large-scale conserved quantities (of the pure scalar and tensor perturbations) to second order, first shown by Salopek and Bond, now from the exact equations. Several other applications are shown as well.

Noh, Hyerim; Hwang, Jai-Chan

2004-05-01

107

Kinetic investigation of a solvent-free, chemoenzymatic reaction sequence towards enantioselective synthesis of a ?-amino acid ester.  

PubMed

A solvent-free, chemoenzymatic reaction sequence for the enantioselective synthesis of ?-amino acid esters has been kinetically and thermodynamically characterized. The coupled sequence comprises a thermal aza-Michael addition of cheap starting materials and a lipase catalyzed aminolysis for the kinetic resolution of the racemic ester. Excellent ee values of >99% were obtained for the ?-amino acid ester at 60% conversion. Kinetic constants for the aza-Michael addition were obtained by straightforward numerical integration of second-order rate equations and nonlinear fitting of the progress curves. A different strategy had to be devised for the biocatalytic reaction. Initially, a simplified Michaelis-Menten model including product inhibition was developed for the reaction running in THF as an organic solvent. Activity based parameters were used instead of concentrations in order to facilitate the transfer of the kinetic model to the solvent-free system. Observed solvent effects not accounted for by the use of thermodynamic activities were incorporated into the kinetic model. Enzyme deactivation was observed to depend on the ratio of the applied substrates and also included in the kinetic model. The developed simple model is in very good agreement with the experimental data and allows the simulation and optimization of the solvent-free process. PMID:22275046

Strompen, Simon; Weiss, Markus; Ingram, Thomas; Smirnova, Irina; Gröger, Harald; Hilterhaus, Lutz; Liese, Andreas

2012-06-01

108

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

2013-08-01

109

Semiempirical hybrid density functional with perturbative second-order correlation  

NASA Astrophysics Data System (ADS)

A new hybrid density functional for general chemistry applications is proposed. It is based on a mixing of standard generalized gradient approximations (GGAs) for exchange by Becke (B) and for correlation by Lee, Yang, and Parr (LYP) with Hartree-Fock (HF) exchange and a perturbative second-order correlation part (PT2) that is obtained from the Kohn-Sham (GGA) orbitals and eigenvalues. This virtual orbital-dependent functional contains only two global parameters that describe the mixture of HF and GGA exchange (ax) and of the PT2 and GGA correlation (c), respectively. The parameters are obtained in a least-squares-fit procedure to the G2/97 set of heat of formations. Opposed to conventional hybrid functionals, the optimum ax is found to be quite large (53% with c=27%) which at least in part explains the success for many problematic molecular systems compared to conventional approaches. The performance of the new functional termed B2-PLYP is assessed by the G2/97 standard benchmark set, a second test suite of atoms, molecules, and reactions that are considered as electronically very difficult (including transition-metal compounds, weakly bonded complexes, and reaction barriers) and comparisons with other hybrid functionals of GGA and meta-GGA types. According to many realistic tests, B2-PLYP can be regarded as the best general purpose density functional for molecules (e.g., a mean absolute deviation for the two test sets of only 1.8 and 3.2 kcal/mol compared to about 3 and 5 kcal/mol, respectively, for the best other density functionals). Very importantly, also the maximum and minium errors (outliers) are strongly reduced (by about 10-20 kcal/mol). Furthermore, very good results are obtained for transition state barriers but unlike previous attempts at such a good description, this definitely comes not at the expense of equilibrium properties. Preliminary calculations of the equilibrium bond lengths and harmonic vibrational frequencies for diatomic molecules and transition-metal complexes also show very promising results. The uniformity with which B2-PLYP improves for a wide range of chemical systems emphasizes the need of (virtual) orbital-dependent terms that describe nonlocal electron correlation in accurate exchange-correlation functionals. From a practical point of view, the new functional seems to be very robust and it is thus suggested as an efficient quantum chemical method of general purpose.

Grimme, Stefan

2006-01-01

110

Second-order closure models for rotating turbulent flows  

NASA Technical Reports Server (NTRS)

The physical properties of the commonly used second-order closure models are examined theoretically for rotating turbulent flows. Comparisons are made with results which are a rigorous consequence of the Navier-Stokes equations for the problem of a fully-developed turbulent channel flow in a rapidly rotating framework. It is demonstrated that all existing second-order closures yield spurious physical results for this test problem of rotating channel flow. In fact, the results obtained are shown to be substantially more unphysical than those obtained from the simpler K-epsilon and K-l models. Modifications in the basic structure of these second-order closure models are proposed which can alleviate this problem.

Speziale, C. G.

1985-01-01

111

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

112

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

113

Second-order Talbot self-imaging with pseudothermal light  

SciTech Connect

The second-order Talbot effect with thermal light is both theoretically and experimentally investigated. Three kinds of experimental schemes are performed, one of which reproduces the classical Talbot self-imaging and the others show plentiful self-imaging effects, in which an object with a periodic structure can be enlarged or diminished. The theoretical analysis, in good agreement with the experimental results, testifies that the specificity in the second-order Talbot effect refers to the joint diffraction of two correlated beams.

Song Xinbing; Xiong Jun; Zhang Xiangdong; Wang Kaige [Department of Physics, Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875 (China)

2010-09-15

114

Second Order Integrability Conditions for Difference Equations: An Integrable Equation  

NASA Astrophysics Data System (ADS)

Integrability conditions for difference equations admitting a second order formal recursion operator are presented and the derivation of symmetries and canonical conservation laws are discussed. In a generic case, some of these conditions yield nonlocal conservation laws. A new integrable equation satisfying the second order integrability conditions is presented and its integrability is established by the construction of symmetries, conservation laws and a 3 × 3 Lax representation. Finally, via the relation of the symmetries of this equation to the Bogoyavlensky lattice, an integrable asymmetric quad equation and a consistent pair of difference equations are derived.

Mikhailov, Alexandre V.; Xenitidis, Pavlos

2014-04-01

115

Second-order Talbot self-imaging with pseudothermal light  

NASA Astrophysics Data System (ADS)

The second-order Talbot effect with thermal light is both theoretically and experimentally investigated. Three kinds of experimental schemes are performed, one of which reproduces the classical Talbot self-imaging and the others show plentiful self-imaging effects, in which an object with a periodic structure can be enlarged or diminished. The theoretical analysis, in good agreement with the experimental results, testifies that the specificity in the second-order Talbot effect refers to the joint diffraction of two correlated beams.

Song, Xin-Bing; Xiong, Jun; Zhang, Xiangdong; Wang, Kaige

2010-09-01

116

Static second-order polarizabilities of aminobenzophenones and nitrobenzophenones  

NASA Technical Reports Server (NTRS)

Static-field theoretical studies on molecular second-order polarizabilities (beta) of benzophenone derivatives were performed. Calculations were based on the use of shaped electric fields and semiempirical Hamiltonians. Either an electron-donating (amine) or an electron-withdrawing (nitro) substituent was incorporated into a phenyl ring of benzophenone; the phenyl rings of benzophenone were oriented either coplanar or perpendicular to the carbonyl. The change in charge transfer with respect to the electrophilic character of the carbonyl group was monitored to determine its effect on the molecular second-order polarizability. Calculations were performed for all constitutional isomers of the two benzophenone derivatives.

Moore, Craig E.; Cardelino, Beatriz H.

1991-01-01

117

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

118

Controlling flexible structures with second order actuator dynamics  

NASA Technical Reports Server (NTRS)

The control of flexible structures for those systems with actuators that are modeled by second order dynamics is examined. Two modeling approaches are investigated. First a stability and performance analysis is performed using a low order finite dimensional model of the structure. Secondly, a continuum model of the flexible structure to be controlled, coupled with lumped parameter second order dynamic models of the actuators performing the control is used. This model is appropriate in the modeling of the control of a flexible panel by proof-mass actuators as well as other beam, plate and shell like structural numbers. The model is verified with experimental measurements.

Inman, Daniel J.; Umland, Jeffrey W.; Bellos, John

1989-01-01

119

Unexpected second-order nonlinear optical effects in conjugated polymers  

NASA Astrophysics Data System (ADS)

Conjugated polymers do not only attract great attention due to their suitability in organic transistors, light emitting diodes and solar cells, moreover, they posses unexpected record-high second-order nonlinear optical responses. Nonlinear optical polymers have been reported as attractive materials for space applications such as electro-optic modulation and optical power limiting. In this work, we report on a new approach for increased second-order nonlinear properties demonstrated in a series of poly(thiophene) derivatives and poly(phenanthrene)s.

Asselberghs, Inge; Clays, Koen; Verbiest, Thierry; Koeckelberghs, Guy

2011-09-01

120

Polycrystals under applied loads: Second-order grain statistics  

NASA Astrophysics Data System (ADS)

The authors report results for the second-order statistics of the effective elastic moduli of polycrystals as a function of applied stress. These results are indicative of scattering behavior that occurs in such materials at ultrasonic frequencies. Numerical examples are given for materials of general interest with cubic symmetry subject to an applied uniaxial stress. The results suggest that the second-order statistics (scattering) may be more significantly affected than the first-order statistics (wave speed) with application of load for some materials. This work may be useful for development of techniques for monitoring changes in stress of loaded structures.

Turner, Joseph A.; Ghoshal, Goutam

2010-07-01

121

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

122

Second-Order Raman Spectra of Thorium Dioxide  

NASA Astrophysics Data System (ADS)

The second-order Raman spectra of the thorium dioxide crystal have been investigated. The results are interpreted in terms of the phonon energies near the Brillouin zone boundaries and the zone center, which have been calculated by using Born-von Karman force model. A nearly complete interpretation of the spectra is given. The observed polarization of Raman spectra is in good agreement with the calculated selection rules for the second-order Raman process at the symmetric points \\varGamma, M and L.

Ishigame, Mareo; Kojima, Masahisa

1976-07-01

123

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

124

A second-order moment method of dense gas–solid flow for bubbling fluidization  

Microsoft Academic Search

A gas–solid two-fluid model with the second-order moment method is presented to close the set of equations applied to fluidization. With the kinetic theory of granular flow, transport equations for the velocity moments are derived for the particle phase. Closure equations for the third-order moments of velocity and for the fluid–particle velocity correlation are presented. The former is based on

Sun Dan; Wang Shuyan; Lu Huilin; Shen Zhiheng; Li Xiang; Wang Shuai; Zhao Yunhua; Wei Lixin

2009-01-01

125

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

126

A Second-Order Growth Mixture Model for Developmental Research  

Microsoft Academic Search

Growth mixture modeling, a combination of growth modeling and finite mixture modeling, is a flexible, exploratory method for identifying and describing between-person heterogeneity in change. In this article we introduce a second-order growth mixture model that combines a longitudinal common factor model, measurement invariance constraints, latent growth model, and mixture model. This approach capitalizes on the benefits of multivariate measurement

Kevin J. Grimm; Nilam Ram

2009-01-01

127

USE OF SECOND-ORDER ELECTROSEISMIC EFFECTS IN ELECTRIC PROSPECTING  

Microsoft Academic Search

The second-order electroseismic effects described may be divided into three classes: electroseismic, electromagnetic, and piezoelectric. Application of these effects to prospecting for certain types of geological features such as quartz veins and pegmatites indicates new methods of subsurface exploration. A brief review of methods and procedures is discussed with results of testing over a pegmatite which is not exposed at

N. N. Neyshtadt

1962-01-01

128

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 2a…

Jara, Elvia; Vila, Javier; Maldonado, Antonio

2006-01-01

129

Second-order accurate nonoscillatory schemes for scalar conservation laws  

NASA Technical Reports Server (NTRS)

Explicit finite difference schemes for the computation of weak solutions of nonlinear scalar conservation laws is presented and analyzed. These schemes are uniformly second-order accurate and nonoscillatory in the sense that the number of extrema of the discrete solution is not increasing in time.

Huynh, Hung T.

1989-01-01

130

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...

131

Mass Spectrometer Image Displacements due to Second-Order Aberrations  

Microsoft Academic Search

Second-order aberrations in mass spectrometers give rise to image broadening which is generally unsymmetrical about the optic axis, resulting in a net displacement of the image center from the optic axis. The net displacement depends on the properties of the mass resolving system and on the velocity and angular distribution in the ion beam. In the event different ionic species

Charles F. Robinson

1958-01-01

132

Mass Spectrometer Image Displacements due to Second-Order Aberrations  

Microsoft Academic Search

Second-order aberrations in mass spectrometers give rise to image ; broadening which is generally unsymmetrical about the optic axis, resulting in a ; net displacement of the image center from the optic axis. The net displacement ; depends on the properties of the mass resolving system and on the velocity and ; angular distribution in the ion beam. In the

Charles F. Robinson

1958-01-01

133

Second-Order Raman Spectra of Thorium Dioxide  

Microsoft Academic Search

The second-order Raman spectra of the thorium dioxide crystal have been investigated. The results are interpreted in terms of the phonon energies near the Brillouin zone boundaries and the zone center, which have been calculated by using Born-von Karman force model. A nearly complete interpretation of the spectra is given. The observed polarization of Raman spectra is in good agreement

Mareo Ishigame; Masahisa Kojima

1976-01-01

134

Static second-order polarizability calculations for large molecular systems  

NASA Technical Reports Server (NTRS)

A procedure to calculate all second-order polarizability tensor elements in static fields has been developed. The calculations are based on semiempirical Hamiltonians (MNDO) that include shaped electric fields. The technique has been applied to mono-, di-, and trisubstituted benzenes incorporating nitro, methyl, and primary and secondary amino groups.

Cardelino, Beatriz H.; Stickel, Robert E.; Moore, Craig E.

1991-01-01

135

Coordinated Ramp Metering Via Second Order Sliding Mode Control  

Microsoft Academic Search

In this paper, we develop a coordinated ramp control strategy based on second order sliding mode control. As in the well known ALINEA procedure, the developed feedback control law uses as control objective the desired density downstream the ramp. The ramp metering controller is developed on the basis of a first order traffic flow model. The effectiveness of the approach

Salim Mammar; Sai. Mammar; M. Netto

2006-01-01

136

Ab initio correlation functionals from second-order perturbation theory.  

PubMed

Orbital-dependent exchange-correlation functionals are not limited by the explicit dependence on the density and present an attractive alternative to conventional functionals. With the successful implementation of the exact orbital-dependent exchange functional, the challenge lies in developing orbital-dependent approximations for the correlation functional. Ab initio many-body methods can provide such approximations. In particular, perturbation theory with the Kohn-Sham model as the reference [Görling and Levy, Phys. Rev. A 50, 196 (1994)] defines the exact correlation functional via an infinite perturbation series. The second-order term of these series gives the lowest-order approximation to the correlation functional. However, it has been suggested [Bartlett et al., J. Chem. Phys. 122, 034104 (2005)] that the Kohn-Sham Hamiltonian is not the optimal choice for the perturbation expansion and a different reference Hamiltonian may lead to an improved perturbation series and more accurate second-order approximation. Here, we demonstrate explicitly that the modified series can be used to define superior functional and potential. We present results of atomic and molecular calculations with both second-order functionals. Our results demonstrate that the modified functional offers a significantly improved description of the correlation effects as it does not suffer from convergence problems and results in energies and densities that are more accurate than those obtained with second-order Møller-Plesset perturbation theory or generalized-gradient approximation functionals. PMID:16999516

Schweigert, Igor V; Lotrich, Victor F; Bartlett, Rodney J

2006-09-14

137

A New Factorisation of a General Second Order Differential Equation  

ERIC Educational Resources Information Center

A factorisation of a general second order ordinary differential equation is introduced from which the full solution to the equation can be obtained by performing two integrations. The method is compared with traditional methods for solving these type of equations. It is shown how the Green's function can be derived directly from the factorisation…

Clegg, Janet

2006-01-01

138

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

139

Second-order bounds for linear recurrences with negative coefficients  

NASA Astrophysics Data System (ADS)

This paper introduces a generalization of Fibonacci and Pell polynomials in order to obtain optimal second-order bounds for general linear recurrences with negative coefficients. An important aspect of the derived bounds is that they are applicable and easily computable. The results imply bounds on all entries in inverses of triangular matrices as well as on coefficients of reciprocals of power series.

Berenhaut, Kenneth S.; Morton, Daniel C.

2006-02-01

140

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

141

A Second-Order Markov Gravity Anomaly Model  

Microsoft Academic Search

A second-order Markov process is proposed as a statistical model for gravity anomalies in a local region. The method is applied to the analysis of errors in an inertial navigation system caused by unknown gravity phenomena. Statistical models of vertical deflection obtained from the anomaly model by means of the Vening Meinesz equations yield predictions of rms position and velocity

Joseph F. Kasper

1971-01-01

142

Blind channel identification based on second order cyclostationary statistics  

Microsoft Academic Search

For finite impulse response (FIR), channels with uncorrelated input sequences, L. Tong et al. (1991, 1992) have proposed an identification method under the special rank condition. The relationship is established between the rank condition and identifiability of FIR channels using second-order cyclostationary statistics. The method is generalized to the FIR channels with correlated input sequences. For general autoregressive moving average

Y. Li; Z. Ding

1993-01-01

143

Observer or self-observer in second-order cybernetics?  

Microsoft Academic Search

The distinction between “observed” and “observing” systems that legitimizes the rise of second-order cybernetics also raises a number of methodological and epistemological issues. These can be generically classified into two broad groups: first, adherence to the model approach and its overemphasis on cognition, at the expense of conation and other factors responsible for the initiation of action; second, an inadequate

Pere Julià

2000-01-01

144

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

145

Second-order moment analysis of dispersion-managed solitons  

Microsoft Academic Search

This paper shows how a second-order moment analysis can be used to derive explicit approximate expressions for the evolution of the root-mean-square (rms) width and chirp parameters of a dispersion-managed soliton within one period of the dispersion map. The energy enhancement factor can also be estimated with a good accuracy

P.-A. Belanger; C. Pare

1999-01-01

146

Second-order elliptic equations with variably partially VMO coefficients  

Microsoft Academic Search

The solvability in Wp2(Rd) spaces is proved for second-order elliptic equations with coefficients which are measurable in one direction and VMO in the orthogonal directions in each small ball with the direction depending on the ball. This generalizes to a very large extent the case of equations with continuous or VMO coefficients.

N. V. Krylov

2009-01-01

147

On oscillation of nonlinear second order differential equations  

NASA Astrophysics Data System (ADS)

The oscillatory behavior of solutions of second order nonlinear differential equations is studied and some new sufficient conditions are obtained by using the refined integral averaging. Some well known results in the literature are extended. Moreover, some examples are given to illustrate the theoretical analysis.

Salhin, Ambarka Abdalla; Din, Ummul Khair Salma; Ahmad, Rokiah Rozita; Noorani, Mohd Salmi Md

2014-06-01

148

Kinetics of the reactions of hydrogen fluoride with calcium oxide  

SciTech Connect

This paper studies the kinetics of interaction of gaseous hydrogen fluoride with calcium oxide at temperatures 300-700 degrees. The experiments were conducted in a laboratory adsorption apparatus modified and adapted for work with corrosive hydrogen fluoride. Calcium oxide samples in granulated form and deposited on gamma-alumina were used in the experiments. Kinetic curves representing variations of the degree of conversion of the solid samples with time are shown. The influence of retardation dure to diffusion was observed in the experiments. The influence of diffusion control on the reaction rate was also observed in a study of the reaction kinetics on supported layers of calcium oxide.

Kossaya, A.M.; Belyakov, B.P.; Kuchma, Z.V.; Sandrozd, M.K.; Vasil'eva, V.G.

1986-08-01

149

A study of the Sabatier-methanation reaction kinetics  

NASA Technical Reports Server (NTRS)

The kinetics of the Sabatier methanation reaction, the reduction of carbon dioxide with hydrogen to methane and water, was investigated for 58 percent nickel on kieselguhr catalyst and 20 percent ruthenium on alumina catalyst. Differential rate data from an experimental program were correlated with a power function rate equation both for forward and reverse reactions. The kinetic parameters of activation energy, frequency rate constant and reaction order were determined for the rate equation. The values of these parameters were obtained from an Arrhenius plot of the experimental differential rate data. Also the carbon monoxide side reaction effect was measured and included in the correlation of parameters. The reaction was found to fit the rate equation experimentally within the temperature range 421 K, where the reaction effectively begins, the 800 K where the reaction rate drops and departs from the rate equation form.

Verostko, C. E.; Forsythe, R. K.

1974-01-01

150

Kinetics of Exchange Reactions in a Cation-Exchange Resin  

Microsoft Academic Search

The kinetics of the exchange reactions of several cations from aqueous solution by protons from a sulfonated polystyrene resin have been studied in detail. The reaction rate is first-order with respect to both the resin and the cation concentrations and increases with the stirring velocity. The activation parameters for the exchange of Mg, Cu, Cr, and Fe ions have been

Fernando Mata-perez; Felix A. Castro; Joaquin F. Perez-benito

1987-01-01

151

A kinetic mechanism inducing oscillations in simple chemical reactions networks.  

PubMed

It is known that a kinetic reaction network in which one or more secondary substrates are acting as cofactors may exhibit an oscillatory behavior. The aim of this work is to provide a description of the functional form of such a cofactor action guaranteeing the onset of oscillations in sufficiently simple reaction networks. PMID:20462291

Coatleven, Julien; Altafini, Claudio

2010-04-01

152

The steady-state kinetics of a catalytic reaction sequence  

Microsoft Academic Search

With the growth in the use of DFT for predicting elementary catalytic reaction step kinetics, it is desirable to develop approaches that provide the overall reaction (OR) rate in terms of these. Deriving an explicit rate expression for a sequence with three or more steps by solving the quasi-steady-state (QSS) equations, however, is tedious, or infeasible, and the resulting expressions

Saurabh A. Vilekar; Ilie Fishtik; Ravindra Datta

2009-01-01

153

Chemical kinetics computer program for static and flow reactions  

NASA Technical Reports Server (NTRS)

General chemical kinetics computer program for complex gas mixtures has been developed. Program can be used for any homogeneous reaction in either one dimensional flow or static system. It is flexible, accurate, and easy to use. It can be used for any chemical system for which species thermodynamic data and reaction rate constant data are known.

Bittker, D. A.; Scullin, V. J.

1972-01-01

154

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

155

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

156

Kinetic and mechanistic studies of blue tetrazolium reaction with phenylhydrazines.  

PubMed

The reaction kinetics of blue tetrazolium with selected arylhydrazines were investigated under pseudo-first-order conditions. The reaction rate constants were obtained at various temperatures, and the enthalpy (8.4-11.2 kcal/mole) and entropy (-38--45 eu) of activations were calculated. A Hammett plot yielded a straight line with a slope of 0.52. The reaction was inhibited by atmospheric oxygen and iodine. A free radical mechanism is presented. PMID:660510

Biehl, E R; Wooten, R; Kenner, C T; Graham, R E

1978-07-01

157

Non-isothermal reaction kinetics of lithium cobalt oxide  

Microsoft Academic Search

The reaction kinetics of the formation of LiCoO2 during solid-state reaction was investigated using a non-isothermal approach at constant heating rates. The conversion ratios of the starting material of LiCoO2 were calculated from thermogravimetric measurements. Analysis based on the differential method revealed that two diffusion-controlled models described the probable reaction mechanisms. The utilized integral method corroborated the fact that the

Chung-Hsin Lu; Po-Ying Yeh; Wei-Tse Hsu

2009-01-01

158

Kinetics and mechanisms of some atomic oxygen reactions  

NASA Technical Reports Server (NTRS)

Mechanisms and kinetics of some reactions of the ground state of oxygen atoms, O(3P), are briefly summarized. Attention is given to reactions of oxygen atoms with several different types of organic and inorganic compounds such as alkanes, alkenes, alkynes, aromatics, and some oxygen, nitrogen, halogen and sulfur derivatives of these compounds. References to some recent compilations and critical evaluations of reaction rate constants are given.

Cvetanovic, R. J.

1987-01-01

159

Kinetics of Chemical Reactions in Flames  

NASA Technical Reports Server (NTRS)

In part I of the paper the theory of flame propagation is developed along the lines followed by Frank-Kamenetsky and one of the writers. The development of chain processes in flames is considered. A basis is given for the application of the method of stationary concentrations to reactions in flames; reactions with branching chains are analyzed. The case of a diffusion coefficient different from the coefficient of temperature conductivity is considered.

Zeldovich, Y.; Semenov, N.

1946-01-01

160

Synthesis of ?,?-dimethoxyfluoropolyethers: reaction mechanism and kinetics  

Microsoft Academic Search

A new class of hydrofluoropolyethers, the ?,?-dimethoxyfluoropolyethers (DM-FPEs), characterized by the copolymeric structure CH3O(CF2CF2O)n(CF2O)mCH3 has been recently developed. The synthesis of DM-FPEs here described, has been carried out via a new synthetic route which consists of the reaction of a perfluoropolyether diacyl fluoride with methyl fluoroformate in the presence of a metal fluoride. The reaction products are DM-FPEs and carbon

M. Avataneo; U. De Patto; M. Galimberti; G. Marchionni

2005-01-01

161

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

162

On second-order, divergence-free tensors  

NASA Astrophysics Data System (ADS)

The aim of this paper is to describe the vector spaces of those second-order tensors on a pseudo-Riemannian manifold (i.e., tensors whose local expressions only involve second derivatives of the metric) that are divergence-free. The main result establishes isomorphisms between these spaces and certain spaces of tensors (at a point) that are invariant under the action of an orthogonal group. This result is valid for tensors with an arbitrary number of indices and symmetries among them and, in certain cases, it allows to explicitly compute basis, using the classical theory of invariants of the orthogonal group. In the particular case of tensors with two indices, we prove the Lovelock tensors are a basis for the vector space of second-order, divergence-free 2-tensors. This statement generalizes to arbitrary dimension a result established by Lovelock in the case of four-dimensional manifolds.

Navarro, José

2014-06-01

163

Periodic orbits from second order perturbation via rational trigonometric integrals  

NASA Astrophysics Data System (ADS)

The second order Poincaré-Pontryagin-Melnikov perturbation theory is used in this paper to study the number of bifurcated periodic orbits from certain centers. This approach also allows us to give the shape and the period up to the first order. We address these problems for some classes of Abel differential equations and quadratic isochronous vector fields in the plane. We prove that two is the maximum number of hyperbolic periodic orbits bifurcating from the isochronous quadratic centers with a birational linearization under quadratic perturbations of second order. In particular the configurations (2,0) and (1,1) are realizable when two centers are perturbed simultaneously. The required computations show that all the considered families share the same iterated rational trigonometric integrals.

Prohens, R.; Torregrosa, J.

2014-07-01

164

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

165

Asteroid long-periodic perturbations - The second order Hamiltonian  

NASA Astrophysics Data System (ADS)

The Hamiltonian of the second order with respect to the disturbing mass, as defined in the higher order-higher degree theory of asteroid secular perturbations by Yuasa (1973), is expressed in the heliocentric, ecliptic coordinate system. Errors found in the original paper with terms coming from the principal part of the disturbing function are removed, and corrected values of the coefficients are computed. The importance of second-order perturbations and the improvement ih the accuracy of proper element determination, achieved by using the newly-obtained coefficients, are demonstrated. Finally, a table of the secular frequencies as functions of the semimajor axis is given, and compared with the analogous one by Kozai (1979).

Knezevic, Zoran

1989-06-01

166

Second order modeling of boundary-free turbulent shear flows  

NASA Technical Reports Server (NTRS)

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 terms in the dissipation equations) already satisfy realizability. To correct the spreading rate of the axisymmetric jet, an extra term is added to the dissipation equation which accounts for the effect of mean vortex stretching on dissipation. The test flows used in this study are the mixing shear layer, plane jet, axisymmetric jet, and plane wake. The numerical solutions show that the unified model equations predict all these flows reasonably. It is expected that these models would be suitable for more complex and critical flows.

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

1991-01-01

167

Bioethics as public discourse and second-order discipline.  

PubMed

Bioethics is best viewed as both a second-order discipline and also part of public discourse. Since their goals differ, some bioethical activities are more usefully viewed as advancing public discourse than academic disciplines. For example, the "Universal Declaration on Bioethics and Human Rights" sponsored by the United Nations Educational, Scientific, and Cultural Organization seeks to promote ethical guidance on bioethical issues. From the vantage of philosophical ethics, it fails to rank or specify its stated principles, justify controversial principles, clarify key terms, or say what is meant by calling potentially conflicting norms "foundational." From the vantage of improving the public discourse about bioethical problems and seeking ethical solutions in the public arena, however, this document may have an important role. The goals and relations between bioethics as a second-order discipline and public discourse are explored. PMID:19387001

Kopelman, Loretta M

2009-06-01

168

DC current induced second order optical nonlinearity in graphene.  

PubMed

We calculate the dc current induced second harmonic generation in doped graphene using the semiconductor Bloch equations under relaxation time approximations. We find that the maximum value of the effective second order susceptibility appears when the fundamental photon energy matches the chemical potential. For a surface current density 1.1 × 103 A/m and a relaxation time at optical frequencies of 13 fs, the effective second order susceptibility ?eff(2);xxx can be as large as 10-7m/V for h?? = 0.2 eV or 10-8 m/V for h?? = 0.53 eV. PMID:24977842

Cheng, J L; Vermeulen, N; Sipe, J E

2014-06-30

169

Second-order closure models for supersonic turbulent flows  

NASA Technical Reports Server (NTRS)

Recent work on the development of a second-order closure model for high-speed compressible flows is reviewed. This turbulent closure is based on the solution of modeled transport equations for the Favre-averaged Reynolds stress tensor and the solenoidal part of the turbulent dissipation rate. A new model for the compressible dissipation is used along with traditional gradient transport models for the Reynolds heat flux and mass flux terms. Consistent with simple asymptotic analyses, the deviatoric part of the remaining higher-order correlations in the Reynolds stress transport equations are modeled by a variable density extension of the newest incompressible models. The resulting second-order closure model is tested in a variety of compressible turbulent flows which include the decay of isotropic turbulence, homogeneous shear flow, the supersonic mixing layer, and the supersonic flat-plate turbulent boundary layer. Comparisons between the model predictions and the results of physical and numerical experiments are quite encouraging.

Speziale, Charles G.; Sarkar, Sutanu

1991-01-01

170

Proving trust in systems of second-order processes  

Microsoft Academic Search

We consider the problem of proving correctness properties for concurrent systems with features such as higher-order communication and dynamic resource generation. As examples we consider operational models of security and authentication protocols based on the higher-order ?-calculus. Key features such as nonces\\/time stamps, encryption\\/decryption, and key generation are modelled using channel name generation and second-order process communication. A temporal logic

M. Dam

1998-01-01

171

Splitting methods for second?order initial value problems  

Microsoft Academic Search

We consider implicit integration methods for the solution of stiff initial value problems for second-order differential equations\\u000a of the special form y'' = f(y). In implicit methods, we are faced with the problem of solving systems of implicit relations. This paper focuses on the construction\\u000a and analysis of iterative solution methods which are effective in cases where the Jacobian of

P. J. van der Houwen; E. Messina

1998-01-01

172

Oblique derivative problems for linear mixed equations of second order  

Microsoft Academic Search

Oblique derivative boundary value problems for the linear mixed (elliptic-hyperbolic) equation of the second order, i.e. the\\u000a generalized Lavrent’ev-Bitsadze equation with weak conditions are discussed. The representation of solutions for the above\\u000a boundary value problem is given, the uniqueness and existence of solutions of the above problem are proved, and a priori estimates\\u000a of the solutions of the above problem

Guochun Wen

1998-01-01

173

Second-order electron mass dispersion relation at finite temperature  

SciTech Connect

Using the real-time finite-temperature methods the result of a detailed and explicit calculation of the renormalized electron mass to second order in {alpha} in QED is presented. The calculation is in the low-temperature approximation {ital T}{much lt}{ital m}{sub {ital e}} (electron mass) and demonstrates the consistency of the finite-temperature renormalization scheme.

Qader, M.; Masood, S.S.; Ahmed, K. (Department of Physics, Quaid-e-Azam University, Islamabad (Pakistan))

1991-11-15

174

Straightening the characteristics of a quasilinear second-order equation  

SciTech Connect

An invertible transformation that preserves the class of quasilinear second-order equations is proposed. Necessary and sufficient conditions are found under which this transformation carries a quasilinear equation into an equation with straight characteristics. For one quasilinear equation the general solution is found by means of the transformation. Examples of Lagrangians of the form L(u,u/sub x/u/sub y/) possessing conservation laws of high order are given.

Mukminov, F.Kh.

1988-10-01

175

Extensions and applications of a second-order landsurface parameterization  

NASA Technical Reports Server (NTRS)

Extensions and applications of a second order land surface parameterization, proposed by Andreou and Eagleson are developed. Procedures for evaluating the near surface storage depth used in one cell land surface parameterizations are suggested and tested by using the model. Sensitivity analysis to the key soil parameters is performed. A case study involving comparison with an "exact" numerical model and another simplified parameterization, under very dry climatic conditions and for two different soil types, is also incorporated.

Andreou, S. A.; Eagleson, P. S.

1983-01-01

176

Second-Order Linear Homogeneous Differential Equations with Constant Coefficients  

NSDL National Science Digital Library

Created by Lang Moore and David Smith for the Connected Curriculum Project, the purpose of this module is to investigate the qualitative behavior of the solutions of initial value problems for second-order constant coefficient differential equations. In particular, to determine how solutions depend on the signs and magnitudes of the coefficients and on the initial conditions. This is part of a larger group of learning modules hosted by Duke University.

Moore, Lang; Smith, David

2010-07-12

177

Second order perturbations of relativistic membranes in curved spacetime  

NASA Astrophysics Data System (ADS)

A manifestly covariant equation is derived to describe the second-order perturbations in topological defects and membranes on arbitrary curved background spacetimes. This, on one hand, generalizes work on macroscopic strings in Minkowski spacetime and introduces a framework for studying in a precise manner membrane behavior near the black hole horizon and on the other hand introduces a more general framework for examining the stability of topological defects in curved spacetimes.

Kiosses, V.; Nicolaidis, A.

2014-06-01

178

Second-order dispersion interactions in pi-conjugated polymers  

Microsoft Academic Search

We calculate the ground state and excited state second-order dispersion interactions between parallel pi-conjugated polymers. The unperturbed eigenstates and energies are calculated from the Pariser-Parr-Pople model using CI-singles theory. Based on large-scale calculations using the molecular structure of trans-polyacetylene as a model system and by exploiting dimensional analysis, we find that: (1) For inter-chain separations, R, greater than a few

William Barford; Nattapong Paiboonvorachat; David Yaron

2011-01-01

179

An explicit second order spectral element method for acoustic waves  

Microsoft Academic Search

The acoustic wave equation is here discretized by conforming spectral elements in space and by the second order leap-frog\\u000a method in time. For simplicity, homogeneous boundary conditions are considered. A stability analysis of the resulting method\\u000a is presented, providing an upper bound for the allowed time step that is proportional to the size of the elements and inversely\\u000a proportional to

Elena Zampieri; Luca F. Pavarino

2006-01-01

180

Similarity solutions of boundary layer equations for second order fluids  

NASA Astrophysics Data System (ADS)

An isovector derived via exterior calculus for the boundary layers of second-order fluids is presently used to ascertain the ordinary differential equations that lead to the similarity solutions. Taking the problem as an initial-value problem, an effort is made to find the arbitrary condition by resort to the shooting method. The shear stress of the similarity solution is calculated, together with the profile corresponding to the solution.

Pakdemirli, M.; Suhubi, E. S.

1992-05-01

181

Oxidation of carbamazepine by Mn(VII) and Fe(VI): reaction kinetics and mechanism.  

PubMed

Experimental studies were conducted to examine the oxidation of carbamazepine, an anticonvulsant drug widely detected in surface waters and sewage treatment effluent, by potassium salts of permanganate (Mn(VII); KMnO4) and ferrate (Fe(VI); K2FeO4). Results show that both Mn(VII) and Fe(VI) rapidly oxidize carbamazepine by electrophilic attack at an olefinic group in the central heterocyclic ring, leading to ring-opening and a series of organic oxidation products. Reaction kinetics follow a generalized second-order rate law, with apparent rate constants at pH 7.0 and 25 degrees C of 3.0 (+/-0.3) x 10(2) M(-1) s(-1) for Mn(VII) and 70(+/-3) M(-1) s(-1) for Fe(VI). Mn(VII) reaction rates exhibit no pH dependence, whereas Fe(VI) reaction rates increase dramatically with decreasing pH, due to changing acid-base speciation of Fe(VI). Further studies with Mn(VII) show that most common nontarget water constituents, including natural organic matter, have no significant effect on rates of carbamazepine oxidation; reduced metals and (bi)sulfide exert a stoichiometric Mn(VII) demand that can be incorporated into the kinetic model. The removal of carbamazepine in two utility source waters treated with KMnO4 agrees closely with predictions from the kinetic model that was parametrized using experiments conducted in deionized water at much higher reagent concentrations. PMID:19238987

Hu, Lanhua; Martin, Heather M; Arce-Bulted, Osmarily; Sugihara, Matthew N; Keating, Kelly A; Strathmann, Timothy I

2009-01-15

182

New chromophores and polymers for second-order nonlinear optics  

NASA Astrophysics Data System (ADS)

Linear conjugated, fluorine-containing chromophores are differing from conventional chromophores like disperse red one by a reduced linear refractive index. Second order nonlinear optical susceptibilities of asymmetrically substituted fluorine-containing dyes reach, however, values as high as those of DR I or of similar chromophores. This can be concluded from measurements of solvatochromy of absorption and fluorescence spectra, electroabsorption measurements, and from quantum chemical calculations carried out for a series of azomethine and azo dyes. The chemical constitution of the conjugated part of investigate chromophores has an important influence both on linear and non nonlinear optical properties. So azomethine dyes show a blue shifted absorption in comparison to the absorption of azo chromophores. This goes along with lower off-resonant second order susceptibility. Introduction of fluorine into the acceptor part of the molecule by attaching a CF3- group does not lead to a significantly lower second order susceptibly in comparison to non-fluorinated chromophores. Perfluorination of the acceptor part result in case of the investigated molecules in an increased second order susceptibility as compared to the non-fluorinated chromophore. Polymers which contain these chromophores are either prepared by physical doping or by covalent bonding of the dyes to the polymeric main chain.In case of physically doped polymers the classes of thermally stable allylic polymers and of polyphenyl quinoxalines (PPQs) were used as matrix material. These polymers show miscibility with the investigated chromophores up to high concentrations and are haracterized by glass transition temperatures between 140 degrees C and 180 degrees C or 180 degrees C and 350 degrees C (PPQs) dependent on chemical structure and on dye concentration. Polymers which contain the active chromophores in side chains were prepared on basis of maleic acid anhydride or as novolak epoxy amine aduct polymer. The former can be utilized for preparation of waveguides by means of Langmuir-Blodgett technique while the later provide films of excellent quality by spin-coating and subsequent corona poling. Second order susceptibilities of the polymer films as determined by second harmonic generation reach values between 5 and 27 pm/V dependent on chromophore concentration and preparation conditions.

Schrader, Sigurd K.; Prescher, Dietrich; Zauls, Vismants

1998-10-01

183

Kinetics and Thermochemistry of the Cl((sup 2)P(sub J)) + C2Cl4 Association Reaction  

NASA Technical Reports Server (NTRS)

A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Cl(sup 2)P(sub j) + C2Cl4 association reaction as a function of temperature (231-390 K) and pressure (3-700 Torr) in nitrogen buffer gas. The reaction is found to be in the falloff regime between third and second order over the range of conditions investigated, although the second-order limit is approached at the highest pressures and lowest temperatures. At temperatures below 300 K, the association reaction is found to be irreversible on the experimental time scale of approximately 20 m-s. The kinetic data at T is less than 300 K have been employed to obtain falloff parameters in a convenient format for atmospheric modeling. At temperatures above 330 K, reversible addition is observed, thus allowing equilibrium constants for C2Cl5 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the association reaction: Delta-H(298) = -18.1 +/- 1.3 kcal/mol, Delta-H(0) = -17.6 +/- 1.3 kcal/mol, and Delta-S(298) = -27.7 +/- 3.0 cal/mol.K. In conjunction with the well-known heats of formation of Cl((sup 2)P(sub j)) and C2Cl4 the above Delta-H values lead to the following heats of formation for C2Cl5, at 298 and 0 K: Delta-H(f,298) = 8.0 +/- 1.3 kcal/mol and Delta-H(f,0) = 8.1 +/- 1.5 kcal/mol. The kinetic and thermochemical parameters reported above are compared with other reported values, and the significance of reported association rate coefficients for understanding tropospheric chlorine chemistry is discussed.

Nicovich, J. M.; Wang, S.; Mckee, M. L.; Wine, P. H.

1997-01-01

184

Exercises in the Geochemical Kinetics of Mineral-Water Reactions  

NSDL National Science Digital Library

This module consists of a laboratory exercise and related homework problems on geochemical kinetics of mineral-solution reactions for undergraduate mineralogy. Students measure the grain sizes of equant halite crystals, and the time for complete dissolution of each grain. From these data, students retrieve a rate law, from several possible. Additional homework problems allow various chemical and physical transport processes in mineral-fluid systems to be evaluated. The lab and homework illustrate several basic principles of chemical kinetics directly relevant to geology, including rate laws of reactions, diffusion, advective transport, and the relationship between rate-limiting mechanisms and crystal-surface morphology.

185

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=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

2013-09-21

186

Non-Gaussianity from the second-order cosmological perturbation  

SciTech Connect

Several conserved and/or gauge-invariant quantities described as the second-order curvature perturbation have been given in the literature. We revisit various scenarios for the generation of second-order non-Gaussianity in the primordial curvature perturbation {zeta}, employing for the first time a unified notation and focusing on the normalization f{sub NL} of the bispectrum. When {zeta} first appears a few Hubble times after horizon exit, |f{sub NL}| is much less than 1 and is, therefore, negligible. Thereafter {zeta} (and hence f{sub NL}) is conserved as long as the pressure is a unique function of energy density (adiabatic pressure). Nonadiabatic pressure comes presumably only from the effect of fields, other than the one pointing along the inflationary trajectory, which are light during inflation ('light noninflaton fields'). During single-component inflation f{sub NL} is constant, but multicomponent inflation might generate vertical bar f{sub NL} vertical bar {approx}1 or bigger. Preheating can affect f{sub NL} only in atypical scenarios where it involves light noninflaton fields. The simplest curvaton scenario typically gives f{sub NL}<<-1 or f{sub NL}=+5/4. The inhomogeneous reheating scenario can give a wide range of values for f{sub NL}. Unless there is a detection, observation can eventually provide a limit vertical bar f{sub NL} vertical bar or approx. 1, at which level it will be crucial to calculate the precise observational limit using second-order theory.

Lyth, David H. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Rodriguez, Yeinzon [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Centro de Investigaciones, Universidad Antonio Narino, Cll 58A no. 37-94, Bogota D.C. (Colombia)

2005-06-15

187

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

2010-01-01

188

Second-order schedules: discrimination of components1  

PubMed Central

Pigeons were exposed to a series of second-order schedules in which the completion of a fixed number of fixed-interval components produced food. In Experiment 1, brief (2 sec) stimulus presentations occurred as each fixed-interval component was completed. During the brief-stimulus presentation terminating the last fixed-interval component, a response was required on a second key, the brief-stimulus key, to produce food. Responses on the brief-stimulus key before the last brief-stimulus presentation had no scheduled consequences, but served as a measure of the extent to which the final component was discriminated from preceding components. Whether there were one, two, four, or eight fixed-interval components, responses on the brief-stimulus key occurred during virtually every brief-stimulus presentation. In Experiment 2, an attempt was made to punish unnecessary responses on the brief-stimulus key, i.e., responses on the brief-stimulus key that occurred before the last component. None of the pigeons learned to withhold these responses, even though they produced a 15-sec timeout and loss of primary reinforcement. In Experiment 3, different key colors were associated with each component of a second-order schedule (a chain schedule). In contrast to Experiment 1, brief-stimulus key responses were confined to the last component. It was concluded that pigeons do not discriminate well between components of second-order schedules unless a unique exteroceptive cue is provided for each component. The relative discriminability of the components may account for the observed differences in initial-component response rates between comparable brief-stimulus, tandem, and chain schedules.

Squires, Nancy; Norborg, James; Fantino, Edmund

1975-01-01

189

Grignard reaction with chlorosilanes in THF: a kinetic study.  

PubMed

Kinetics of the reactions of phenylmagnesium chloride and bromide and diphenylmagnesium with chlorosilanes were investigated in tetrahydrofurane (THF) and in THF-hydrocarbon mixtures. The reaction in THF is much faster than that in diethyl ether. Assuming coordination of magnesium halides with three molecules of THF, concentrations of all the species involved in Schlenk equilibrium were calculated. In the Grignard reaction, species R(2)Mg and RMgX react competitively accompanied by additional reaction paths involving electrophilic catalysis by magnesium halide. This conclusion also proved to be valid for the Grignard reaction with a ketone and probably can be expanded to any Grignard reaction. When Schlenk equilibrium is shifted far to the RMgX species, the catalytic pathways are insignificant. Substituents at the silicon center control the rate of the reaction through their inductive and steric effects. PMID:15255738

Tuulmets, Ants; Nguyen, Binh T; Panov, Dmitri

2004-07-23

190

Linear programming based optimal power flow using second order sensitivities  

SciTech Connect

For the electric railway traction in Sweden, a system of 130 kV transmission lines connected parallel to the contact lines is being built. Within this system, the generation costs differs only slightly between different nodes with power injections. In order to optimize the power flow in the system, an extended optimal power flow algorithm based on successive linear programming, has been developed. To improve the convergence, a method based on a second order sensitivity approximation of the active power losses of the total system is applied. Numerical examples are given to show the enhanced convergence properties.

Olofsson, M.; Andersson, G.; Soeder, L. [Royal Inst. of Tech., Stockholm (Sweden). Electric Power Systems] [Royal Inst. of Tech., Stockholm (Sweden). Electric Power Systems

1995-08-01

191

Efficient second order remapping on arbitrary two dimensional meshes  

SciTech Connect

The authors have developed an efficient method of remapping physical variables from one unstructured grid composed of arbitrary polygons to another, based on the work of Ramshaw and Dukowicz. Eulerian cycles are used to convert the mesh into a single chain of connected edge,s which eliminates grid searching. The error is second order in the zone size. The algorithm handles degenerate meshes well. Computational effort to perform a remap scales linearly with the number of zones in the two grids, which is an improvement over typical N log N methods.

Miller, D.S.; Burton, D.E.; Oliviera, J.S.

1996-03-18

192

Second-order SMO improves SVM online and active learning.  

PubMed

Iterative learning algorithms that approximate the solution of support vector machines (SVMs) have two potential advantages. First, they allow online and active learning. Second, for large data sets, computing the exact SVM solution may be too time-consuming, and an efficient approximation can be preferable. The powerful LASVM iteratively approaches the exact SVM solution using sequential minimal optimization (SMO). It allows efficient online and active learning. Here, this algorithm is considerably improved in speed and accuracy by replacing the working set selection in the SMO steps. A second-order working set selection strategy, which greedily aims at maximizing the progress in each single step, is incorporated. PMID:18045012

Glasmachers, Tobias; Igel, Christian

2008-02-01

193

Second-order nonlinear optical crystal susceptibility: computational approach  

NASA Astrophysics Data System (ADS)

A computer program has been developed to calculate crystal susceptibility tensor components. In addition to previous considerations where molecular polarization tensors have been treated as 1D or 2D, the present program allows the use of the 3D case that appears necessary for non-planar molecules. Calculation of crystal susceptibility is based on the approximation of relatively weak intermolecular forces in relation to intramolecular ones. Local field corrections have been estimated using simple Lorentz form. To provide molecular second-order polarizability, a semiempirical quantum chemical calculation has been carried out using the finite field method incorporated in the MOPAC program.

Timofeeva, Tatiana V.; Suponitsky, Kirill Y.; Cardelino, Beatriz H.; Clark, Ronald D.

1999-10-01

194

Oscillation theory for linear second-order differential systems  

SciTech Connect

This article is concerned with the oscillatory behavior at infinity of the solution y:(a,infinity) ..-->.. R/sup n/ of a system of second-order differential equations, y''(t) + Q(t)y(t) = 0, t epsilon(a,infinity); Q is a continuous function on (a,infinity), whose values are real symmetric matrices of order n. It is shown that the solution is oscillatory at infinity if the largest eigenvalue of the matrix ..integral../sub a/ Q(t) dt is sufficiently large on a sufficiently large set of t-values. 11 refs.

Kaper, H.G.; Kwong, Man Kam

1987-01-01

195

Random walk theory of reaction kinetics in zeolites  

Microsoft Academic Search

We discuss application of the continuous-time random walk (CTRW) model to studying the kinetics of pseudo-first-order reactions in zeolites. The model includes distance-dependent reaction mechanism, details of the zeolite structure, and dynamics of migration of guest molecules between adsorption sites. Diffuse-reflectance transient-absorption study of triplet anthracene quenching by azulene in NaY zeolite shows that quenching can occur when reactants are

A. V. Barzykin; S. Hashimoto

2000-01-01

196

Interfacial kinetics of a model epoxy-amine addition reaction.  

PubMed

The kinetics of the addition reaction at a solid interface for a model epoxy-amine system composed of monofunctionalized phenyl glycidyl ether and hexylamine was examined. The chemical character for the reaction of this system at the interface was the same as that in the bulk, while the physical nature was significantly different. Slowing down of the diffusion for the reactants in close proximity to the solid interface was also addressed by interfacial selective spectroscopy. PMID:22968718

Hirai, Tomoyasu; Kawasaki, Kaoru; Tanaka, Keiji

2012-10-21

197

The chemistry of peroxynitrite. Reaction mechanisms and kinetics  

NASA Astrophysics Data System (ADS)

Methods for the preparation of peroxynitrite and its physical and chemical properties are considered. The pathways, mechanisms and kinetics of the decomposition and best-studied reactions with hydrocarbons, dimethyl sulfoxide and other substrates are analysed. The emphasis is placed on the nature of reactive species in peroxynitrite reactions and on the reasons for its high and polyfunctional reactivity. The biochemical role of this important inorganic oxidant formed in vivo is outlined.

Lobachev, Vladimir L.; Rudakov, Elisei S.

2006-05-01

198

Kinetics of self-decomposition and hydrogen atom transfer reactions of substituted phthalimide N-oxyl radicals in acetic acid.  

PubMed

Kinetic data have been obtained for three distinct types of reactions of phthalimide N-oxyl radicals (PINO(.)) and N-hydroxyphthalimide (NHPI) derivatives. The first is the self-decomposition of PINO(.) which was found to follow second-order kinetics. In the self-decomposition of 4-methyl-N-hydroxyphthalimide (4-Me-NHPI), H-atom abstraction competes with self-decomposition in the presence of excess 4-Me-NHPI. The second set of reactions studied is hydrogen atom transfer from NHPI to PINO(.), e.g., PINO(.) + 4-Me-NHPI <=> NHPI + 4-Me-PINO(.). The substantial KIE, k(H)/k(D) = 11 for both forward and reverse reactions, supports the assignment of H-atom transfer rather than stepwise electron-proton transfer. These data were correlated with the Marcus cross relation for hydrogen-atom transfer, and good agreement between the experimental and the calculated rate constants was obtained. The third reaction studied is hydrogen abstraction by PINO(.) from p-xylene and toluene. The reaction becomes regularly slower as the ring substituent on PINO(.) is more electron donating. Analysis by the Hammett equation gave rho = 1.1 and 1.8 for the reactions of PINO(.) with p-xylene and toluene, respectively. PMID:15624928

Cai, Yang; Koshino, Nobuyoshi; Saha, Basudeb; Espenson, James H

2005-01-01

199

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

2013-09-12

200

Second-order near-wall turbulence closures - A review  

NASA Astrophysics Data System (ADS)

Advances in second-order near-wall turbulence closures are summarized. All closures under consideration are based on high-Reynolds-number models. Most near-wall closures proposed to date attempt to modify the high-Reynolds-number models for the dissipation function and the pressure redistribution term so that the resultant models are applicable all the way to the wall. The asymptotic behavior of the near-wall closures is examined and compared with the proper near-wall behavior of the exact Reynolds-stress equations. It is found that three second-order near-wall closures give the best correlations with simulated turbulence statistics. However, their predictions of near-wall Reynolds-stress budgets are considered to be incorrect. A proposed modification to the dissipitation-rate equation remedies part of those predictions. It is concluded that further improvements are required if a complete replication of all the turbulence properties and Reynolds-stress budgets by a statistical model of turbulence is desirable.

So, R. M. C.; Lai, Y. G.; Zhang, H. S.; Hwang, B. C.

1991-11-01

201

Second-order near-wall turbulence closures - A review  

NASA Technical Reports Server (NTRS)

Advances in second-order near-wall turbulence closures are summarized. All closures under consideration are based on high-Reynolds-number models. Most near-wall closures proposed to date attempt to modify the high-Reynolds-number models for the dissipation function and the pressure redistribution term so that the resultant models are applicable all the way to the wall. The asymptotic behavior of the near-wall closures is examined and compared with the proper near-wall behavior of the exact Reynolds-stress equations. It is found that three second-order near-wall closures give the best correlations with simulated turbulence statistics. However, their predictions of near-wall Reynolds-stress budgets are considered to be incorrect. A proposed modification to the dissipitation-rate equation remedies part of those predictions. It is concluded that further improvements are required if a complete replication of all the turbulence properties and Reynolds-stress budgets by a statistical model of turbulence is desirable.

So, R. M. C.; Lai, Y. G.; Zhang, H. S.; Hwang, B. C.

1991-01-01

202

Second-order closure models for supersonic turbulent flows  

NASA Technical Reports Server (NTRS)

Recent work by the authors on the development of a second-order closure model for high-speed compressible flows is reviewed. This turbulence closure is based on the solution of modeled transport equations for the Favre-averaged Reynolds stress tensor and the solenoidal part of the turbulent dissipation rate. A new model for the compressible dissipation is used along with traditional gradient transport models for the Reynolds heat flux and mass flux terms. Consistent with simple asymptotic analyses, the deviatoric part of the remaining higher-order correlations in the Reynolds stress transport equation are modeled by a variable density extension of the newest incompressible models. The resulting second-order closure model is tested in a variety of compressible turbulent flows which include the decay of isotropic turbulence, homogeneous shear flow, the supersonic mixing layer, and the supersonic flat-plate turbulent boundary layer. Comparisons between the model predictions and the results of physical and numerical experiments are quite encouraging.

Speziale, Charles G.; Sarkar, Sutanu

1991-01-01

203

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

204

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

205

Kinetics of Solid State Reactions With Fractal Reagent  

Microsoft Academic Search

In the present research we theoretically studied the kinetics of nucleation-limited solid state reactions as influenced by the fractal properties of solid reagent. We consider the model of equal-sized primary particles assembled in fractal cluster. The geometry of such an object is assumed to be described solely by its fractal dimension D and by upper (Rmax) and lower (Rmin) cutoffs

S. V. Kalinin; A. A. Vertegel; N. N. Oleynikov; Yu. D. Tretyakov

1998-01-01

206

Kinetics of Liquid Lithium Reaction with Oxygen-Nitrogen Mixtures.  

National Technical Information Service (NTIS)

A series of experiments have been conducted in order to characterize the kinetics of lithium chemical reaction with a mixture of oxygen and nitrogen. Three mixed gas compositions were used; 80% N sub 2 and 20% O sub 2 , 90% N sub 2 and 10% O sub 2 , and 9...

T. K. Gil M. S. Kazimi

1986-01-01

207

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

208

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

209

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

210

Kinetics of the BrO + NO2 Association Reaction. Temperature and Pressure Dependence in the Falloff Regime  

NASA Technical Reports Server (NTRS)

A laser flash photolysis-long path absorption technique has been employed to study the kinetics of the reaction BrO + NO2 + M yields (k1) products as a function of temperature (248-346 K), pressure (16-800 torr), and buffer gas identity (N2,CF4) The reaction is found to be 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 k1(P,T) have been reported at pressures greater than 12 torr; hence, our results help constrain choices of k1(P,T) for use in models of lower stratospheric BrO(x) chemistry. Approximate falloff parameters in a convenient form for atmospheric modeling are derived.

Thron, R. P.; Daykin, E. P.; Wine, P.H.

1997-01-01

211

Bispectrum of cosmological density perturbations in the most general second-order scalar-tensor theory  

NASA Astrophysics Data System (ADS)

We study the bispectrum of matter density perturbations induced by the large-scale structure formation in the most general second-order scalar-tensor theory that may possess the Vainshtein mechanism as a screening mechanism. On the basis of the standard perturbation theory, we derive the bispectrum being expressed by a kernel of the second-order density perturbations. We find that the leading-order kernel is characterized by one parameter, which is determined by the solutions of the linear density perturbations, the Hubble parameter, and the other function specifying nonlinear interactions. This is because our model, which may be equipped with the Vainshtein mechanism, includes only one simple function that describes mode couplings of the nonlinear interactions. This feature does not allow for varied behavior in the bispectrum of the matter density perturbations in the most general second-order scalar-tensor theory equipped with the Vainshtein mechanism. We exemplify the typical behavior of the bispectrum in a kinetic gravity braiding model.

Takushima, Yuichiro; Terukina, Ayumu; Yamamoto, Kazuhiro

2014-05-01

212

Magnetic Compensation for Second-Order Doppler Shift in LITS  

NASA Technical Reports Server (NTRS)

The uncertainty in the frequency of a linear-ion-trap frequency standard (LITS) can be reduced substantially by use of a very small magnetic inhomogeneity tailored to compensate for the residual second-order Doppler shift. An effect associated with the relativistic time dilatation, one cause of the second-order Doppler shift, is ion motion that is attributable to the trapping radio-frequency (RF)electromagnetic field used to trap ions. The second-order Doppler shift is reduced by using a multi-pole trap; however it is still the largest source of systematic frequency shift in the latest generation of LITSs, which are among the most stable clocks in the world. The present compensation scheme reduces the frequency instability of the affected LITS to about a tenth of its previous value. The basic principles of prior generation LITSs were discussed in several prior NASA Tech Briefs articles. Below are recapitulated only those items of basic information necessary to place the present development in context. A LITS includes a microwave local oscillator, the frequency of which is stabilized by comparison with the frequency of the ground state hyperfine transition of 199Hg+ ions. The comparison involves a combination of optical and microwave excitation and interrogation of the ions in a linear ion trap in the presence of a nominally uniform magnetic field. In the current version of the LITS, there are two connected traps (see figure): (1) a quadrupole trap wherein the optical excitation and measurement take place and (2) a 12-pole trap (denoted the resonance trap), wherein the microwave interrogation takes place. The ions are initially loaded into the quadrupole trap and are thereafter shuttled between the two traps. Shuttling ions into the resonance trap allows sensitive microwave interrogation to take place well away from loading interference. The axial magnetic field for the resonance trap is generated by an electric current in a finely wound wire coil surrounded by magnetic shields. In the quadrupole and 12-pole traps, the potentials are produced by RF voltages applied to even numbers (4 and 12, respectively) of parallel rods equally spaced around a circle. The polarity of the voltage on each rod is opposite that of the voltage on the adjacent rod. As a result, the amplitude of the RF trapping field is zero along the centerline and increases, with radius, to a maximum value near the rods.

Burt, Eric; Tjoelker, Robert

2008-01-01

213

Chemical Kinetics: half-life  

NSDL National Science Digital Library

This site offers an interactive tutorial that emphasizes graphical interpretation of chemical kinetics. The half-life is measured for various initial concentrations for zero-, first-, and second-order reactions. The data is analyzed graphically to determine the relationship between the half-life and reactant concentration for each order reaction and to determine the rate constant for each reaction. This tutorial is coupled to others to further guide the student to a better understanding of chemical kinetics.

Blauch, David N.

214

The second order hyperpolarizability of cis azobenzene isomer  

NASA Astrophysics Data System (ADS)

The second order hyperpolarizability of cis azobenzene isomer ( ? c) was obtained by measuring the third harmonic generation (THG) variation of an azobenzene doped polymer film when the film was optically pumped to create a large amount of cis isomers via photoisomerization. A steady state theory was developed to treat the THG intensity variation by considering the optical pump induced redistribution and reorientation of azobenzene in the polymer film and the contribution of cis isomer to the THG signal. The ratio of ? of cis and trans molecule, ( ? c/ ? t), was found to be 0.51. After the ? t was obtained from the time-resolved optical Kerr effect (OKE) measurement, ? c was deduced to be 5.6 × 10 -33 esu. The result shows that the optical nonlinearity of cis isomer is clearly not negligible.

Shan, Jiong; Yang, Pei; Liu, Liying; Xu, Lei

2009-08-01

215

Regularized orbital-optimized second-order perturbation theory.  

PubMed

Orbital-optimized second-order perturbation theory (OOMP2) optimizes the zeroth order wave function in the presence of correlations, removing the dependence of the method on Hartree-Fock orbitals. This is particularly important for systems where mean field orbitals spin contaminate to artificially lower the zeroth order energy such as open shell molecules, highly conjugated systems, and organometallic compounds. Unfortunately, the promise of OOMP2 is hampered by the possibility of solutions being drawn into divergences, which can occur during the optimization procedure if HOMO and LUMO energies approach degeneracy. In this work, we regularize these divergences through the simple addition of a level shift parameter to the denominator of the MP2 amplitudes. We find that a large level shift parameter of 400 mEh removes divergent behavior while also improving the overall accuracy of the method for atomization energies, barrier heights, intermolecular interactions, radical stabilization energies, and metal binding energies. PMID:24387359

Stück, David; Head-Gordon, Martin

2013-12-28

216

Regularized orbital-optimized second-order perturbation theory  

NASA Astrophysics Data System (ADS)

Orbital-optimized second-order perturbation theory (OOMP2) optimizes the zeroth order wave function in the presence of correlations, removing the dependence of the method on Hartree-Fock orbitals. This is particularly important for systems where mean field orbitals spin contaminate to artificially lower the zeroth order energy such as open shell molecules, highly conjugated systems, and organometallic compounds. Unfortunately, the promise of OOMP2 is hampered by the possibility of solutions being drawn into divergences, which can occur during the optimization procedure if HOMO and LUMO energies approach degeneracy. In this work, we regularize these divergences through the simple addition of a level shift parameter to the denominator of the MP2 amplitudes. We find that a large level shift parameter of 400 mEh removes divergent behavior while also improving the overall accuracy of the method for atomization energies, barrier heights, intermolecular interactions, radical stabilization energies, and metal binding energies.

Stück, David; Head-Gordon, Martin

2013-12-01

217

Simple expressions for second order density perturbations in standard cosmology  

NASA Astrophysics Data System (ADS)

In this paper we present four simple expressions for the relativistic first and second order fractional density perturbations for ?CDM cosmologies in different gauges: the Poisson, uniform curvature, total matter and synchronous gauges. A distinctive feature of our approach is the use of a canonical set of quadratic differential expressions involving an arbitrary spatial function, the so-called comoving curvature perturbation, to describe the spatial dependence, which enables us to unify, simplify and extend previous seemingly disparate results. The simple structure of the expressions makes the evolution of the density perturbations completely transparent and clearly displays the effect of the cosmological constant on the dynamics, namely that it stabilizes the perturbations. We expect that the results will be useful in applications, for example, studying the effects of primordial non-Gaussianity on the large scale structure of the universe.

Uggla, Claes; Wainwright, John

2014-05-01

218

Analysis of implicit second-order upwind-biased stencils  

NASA Technical Reports Server (NTRS)

Truncation error and stability properties of several implicit upwind schemes for the two-dimensional Euler equations are examined. The schemes use linear data reconstruction methods to achieve second-order flux integrations where the implicit Jacobian operators are first order. The stability properties of the schemes are examined by a Von Neumann analysis of the linearized, constant-coefficient Euler equations. The choice of the data reconstruction method used to evaluate the flux integral has a dramatic effect on the convergence properties of the implicit solution method. In particular, the typical one-dimensional data reconstruction methods used with structured grids exhibit poor convergence properties compared to the unstructured grid method considered. Of the schemes examined, the one with the superior convergence properties is well-suited for both unstructured and structured grids, which has important implications for the design of implicit methods.

Roberts, Thomas W.; Warren, Gary P.

1993-01-01

219

Vainshtein mechanism in second-order scalar-tensor theories  

NASA Astrophysics Data System (ADS)

In second-order scalar-tensor theories we study how the Vainshtein mechanism works in a spherically symmetric background with a matter source. In the presence of the field coupling F(?)=e-2Q? with the Ricci scalar R we generally derive the Vainshtein radius within which the general relativistic behavior is recovered even for the coupling Q of the order of unity. Our analysis covers the models such as the extended Galileon and Brans-Dicke theories with a dilatonic field self-interaction. We show that, if these models are responsible for the cosmic acceleration today, the corrections to gravitational potentials are generally small enough to be compatible with local gravity constraints.

de Felice, Antonio; Kase, Ryotaro; Tsujikawa, Shinji

2012-02-01

220

A second-order closure analysis of turbulent diffusion flames. [combustion physics  

NASA Technical Reports Server (NTRS)

A complete second-order closure computer program for the investigation of compressible, turbulent, reacting shear layers was developed. The equations for the means and the second order correlations were derived from the time-averaged Navier-Stokes equations and contain third order and higher order correlations, which have to be modeled in terms of the lower-order correlations to close the system of equations. In addition to fluid mechanical turbulence models and parameters used in previous studies of a variety of incompressible and compressible shear flows, a number of additional scalar correlations were modeled for chemically reacting flows, and a typical eddy model developed for the joint probability density function for all the scalars. The program which is capable of handling multi-species, multistep chemical reactions, was used to calculate nonreacting and reacting flows in a hydrogen-air diffusion flame.

Varma, A. K.; Fishburne, E. S.; Beddini, R. A.

1977-01-01

221

Explicitly correlated second-order Møller-Plesset perturbation theory employing pseudospectral numerical quadratures  

NASA Astrophysics Data System (ADS)

We implemented explicitly correlated second-order Møller-Plesset perturbation theory with numerical quadratures using pseudospectral construction of grids. Introduction of pseudospectral approach for the calculation of many-electron integrals gives a possibility to use coarse grids without significant loss of precision in correlation energies, while the number of points in the grid is reduced about nine times. The use of complementary auxiliary basis sets as the sets of dealiasing functions is justified at both theoretical and computational levels. Benchmark calculations for a set of 16 molecules have shown the possibility to keep an error of second-order correlation energies within 1 milihartree (mH) with respect to MP2-F12 method with dense grids. Numerical tests for a set of 13 isogyric reactions are also performed.

Bokhan, Denis; Trubnikov, Dmitrii N.

2012-05-01

222

Explicitly correlated second-order Møller-Plesset perturbation theory employing pseudospectral numerical quadratures.  

PubMed

We implemented explicitly correlated second-order Møller-Plesset perturbation theory with numerical quadratures using pseudospectral construction of grids. Introduction of pseudospectral approach for the calculation of many-electron integrals gives a possibility to use coarse grids without significant loss of precision in correlation energies, while the number of points in the grid is reduced about nine times. The use of complementary auxiliary basis sets as the sets of dealiasing functions is justified at both theoretical and computational levels. Benchmark calculations for a set of 16 molecules have shown the possibility to keep an error of second-order correlation energies within 1 milihartree (mH) with respect to MP2-F12 method with dense grids. Numerical tests for a set of 13 isogyric reactions are also performed. PMID:22667543

Bokhan, Denis; Trubnikov, Dmitrii N

2012-05-28

223

Oxidation of triclosan by ferrate: reaction kinetics, products identification and toxicity evaluation.  

PubMed

The oxidation of triclosan by commercial grade aqueous ferrate (Fe(VI)) was investigated and the reaction kinetics as a function of pH (7.0-10.0) were experimentally determined. Intermediate products of the oxidation process were characterized using both GC-MS and RRLC-MS/MS techniques. Changes in toxicity during the oxidation process of triclosan using Fe(VI) were investigated using Pseudokirchneriella subcapitata growth inhibition tests. The results show that triclosan reacted rapidly with Fe(VI), with the apparent second-order rate constant, k(app), being 754.7 M(-1) s(-1) at pH 7. At a stoichiometric ratio of 10:1 (Fe(VI):triclosan), complete removal of triclosan was achieved. Species-specific rate constants, k, were determined for reaction of Fe(VI) with both the protonated and deprotonated triclosan species. The value of k determined for neutral triclosan was 6.7(±1.9)×10(2) M(-1) s(-1), while that measured for anionic triclosan was 7.6(±0.6)×10(3) M(-1) s(-1). The proposed mechanism for the oxidation of triclosan by the Fe(VI) involves the scission of ether bond and phenoxy radical addition reaction. Coupling reaction may also occur during Fe(VI) degradation of triclosan. Overall, the degradation processes of triclosan resulted in a significant decrease in algal toxicity. The toxicity tests showed that Fe(VI) itself dosed in the reaction did not inhibit green algae growth. PMID:21093982

Yang, Bin; Ying, Guang-Guo; Zhao, Jian-Liang; Zhang, Li-Juan; Fang, Yi-Xiang; Nghiem, Long Duc

2011-02-15

224

Kinetic studies of Np(VI) reduction reactions with kojic acid and tropolone  

SciTech Connect

To study the problems of potential migration of radionuclides from a nuclear waste repository, the Np(VI) reduction reactions with kojic acid and with tropolone were investigated at tracer level concentration of Np(VI). From results on the kinetic studies of these reactions, the NpO/sub 2//sup + +/ is reduced to the NpO/sub 2//sup +/ in a one-electron transfer process with no structural change of the dioxo neptunium species. The rates for both reactions are directly proportional to the total concentrations of Np(VI) ion and of oxidizing organic compounds: i.e., kojic acid or tropolone. However, the hydrogen ion dependence on the rate is inverse first-order for kojic acid and inverse second-order for tropolone. The Np(VI) reduction proceeds from the precursor complex via an activated complex and results in oxidation products from radicals formed in the rate-limiting step. The rate for the formation of Np(V) by kojic acid (k/sub 1/ = 6.06 +/- 0.30 sec/sup -1/) is faster than by tropolone (k/sub 1/ = 2.49 +/- 0.10 sec/sup -1/). The rate of reduction increases with the pK/sub a/ values (basicity) of the hydroxyl group in oxidizing organic compounds. The activation parameters for the Np(VI) reduction with kojic acid and tropolone have the same values within the uncertainties: i.e., ..delta..H/sup not equal to/ = 82.7 +/- 3.4 KJ/mol, ..delta..S/sup not equal to/ = 15 +/- 12 J/mol/deg for tropolone. Therefore, the Np(VI) reduction reaction occurs through the same mechanism in both reactions.

Kim, W.

1987-01-01

225

Stochastic Lindemann kinetics for unimolecular gas-phase reactions.  

PubMed

Lindemann, almost a century ago, proposed a schematic mechanism for unimolecular gas-phase reactions. Here, we present a new semiempirical method to calculate the effective rate constant in unimolecular gas-phase kinetics through a stochastic reformulation of Lindemann kinetics. Considering the rate constants for excitation and de-excitation steps in the Lindemann mechanism as temperature dependent empirical parameters, we construct and solve a chemical master equation for unimolecular gas-phase kinetics. The effective rate constant thus obtained shows excellent agreement with experimental data in the entire concentration range in which it is reported. The extrapolated values of the effective rate constant for very low and very high concentrations of inert gas molecules are in close agreement with values obtained using the Troe semiempirical method. Stochastic Lindemann kinetics, thus, provides a simple method to construct the full falloff curves and can be used as an alternative to the Troe semiempirical method of kinetic data analysis for unimolecular gas-phase reactions. PMID:23879409

Saha, Soma; Dua, Arti

2013-08-22

226

Computation of kinetic isotope effects for enzymatic reactions  

PubMed Central

We describe a computational approach, incorporating quantum mechanics into enzyme kinetics modeling with a special emphasis on computation of kinetic isotope effects. Two aspects are highlighted: (1) the potential energy surface is represented by a combined quantum mechanical and molecular mechanical (QM/MM) potential in which the bond forming and breaking processes are modeled by electronic structure theory, and (2) a free energy perturbation method in path integral simulation is used to determine both kinetic isotope effects (KIEs). In this approach, which is called the PI-FEP/UM method, a light (heavy) isotope is mutated into a heavy (light) counterpart in centroid path integral simulations. The method is illustrated in the study of primary and secondary KIEs in two enzyme systems. In the case of nitroalkane oxidase, the enzymatic reaction exhibits enhanced quantum tunneling over that of the uncatalyzed process in water. In the dopa delarboxylase reaction, there appears to be distinguishable primary carbon-13 and secondary deuterium KIEs when the internal proton tautomerism is in the N-protonated or in the O-protonated positions. These examples show that the incorporation of quantum mechanical effects in enzyme kinetics modeling offers an opportunity to accurately and reliably model the mechanisms and free energies of enzymatic reactions.

GAO, JiaLi

2013-01-01

227

A unifying kinetic framework for modeling oxidoreductase-catalyzed reactions  

PubMed Central

Motivation: Oxidoreductases are a fundamental class of enzymes responsible for the catalysis of oxidation–reduction reactions, crucial in most bioenergetic metabolic pathways. From their common root in the ancient prebiotic environment, oxidoreductases have evolved into diverse and elaborate protein structures with specific kinetic properties and mechanisms adapted to their individual functional roles and environmental conditions. While accurate kinetic modeling of oxidoreductases is thus important, current models suffer from limitations to the steady-state domain, lack empirical validation or are too specialized to a single system or set of conditions. Results: To address these limitations, we introduce a novel unifying modeling framework for kinetic descriptions of oxidoreductases. The framework is based on a set of seven elementary reactions that (i) form the basis for 69 pairs of enzyme state transitions for encoding various specific microscopic intra-enzyme reaction networks (micro-models), and (ii) lead to various specific macroscopic steady-state kinetic equations (macro-models) via thermodynamic assumptions. Thus, a synergistic bridge between the micro and macro kinetics can be achieved, enabling us to extract unitary rate constants, simulate reaction variance and validate the micro-models using steady-state empirical data. To help facilitate the application of this framework, we make available RedoxMech: a Mathematica™ software package that automates the generation and customization of micro-models. Availability: The Mathematica™ source code for RedoxMech, the documentation and the experimental datasets are all available from: http://www.igb.uci.edu/tools/sb/metabolic-modeling. Contact: pfbaldi@ics.uci.edu Supplementary information: Supplementary data are available at Bioinformatics online.

Chang, Ivan; Baldi, Pierre

2013-01-01

228

Model-order reduction of large-scale second-order MIMO dynamical systems via a block second-order Arnoldi method  

Microsoft Academic Search

In this paper, we present a structure-preserving model-order reduction method for solving large-scale second-order MIMO dynamical systems. It is a projection method based on a block second-order Krylov subspace. We use the block second-order Arnoldi (BSOAR) method to generate an orthonormal basis of the projection subspace. The reduced system preserves the second-order structure of the original system. Some theoretical results

Yiqin Lin; Liang Bao; Yimin Wei

2007-01-01

229

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

230

Determination of thermodynamics and kinetics of RNA reactions by force  

PubMed Central

Single-molecule methods have made it possible to apply force to an individual RNA molecule. Two beads are attached to the RNA; one is on a micropipette, the other is in a laser trap. The force on the RNA and the distance between the beads are measured. Force can change the equilibrium and the rate of any reaction in which the product has a different extension from the reactant. This review describes use of laser tweezers to measure thermodynamics and kinetics of unfolding/refolding RNA. For a reversible reaction the work directly provides the free energy; for irreversible reactions the free energy is obtained from the distribution of work values. The rate constants for the folding and unfolding reactions can be measured by several methods. The effect of pulling rate on the distribution of force-unfolding values leads to rate constants for unfolding. Hopping of the RNA between folded and unfolded states at constant force provides both unfolding and folding rates. Force-jumps and force-drops, similar to the temperature jump method, provide direct measurement of reaction rates over a wide range of forces. The advantages of applying force and using single-molecule methods are discussed. These methods, for example, allow reactions to be studied in non-denaturing solvents at physiological temperatures; they also simplify analysis of kinetic mechanisms because only one intermediate at a time is present. Unfolding of RNA in biological cells by helicases, or ribosomes, has similarities to unfolding by force.

Tinoco, Ignacio; Li, Pan T. X.; Bustamante, Carlos

2008-01-01

231

Second-Order Modeling of Low-Reynolds-Number Turbulence Near Walls  

NASA Technical Reports Server (NTRS)

This paper presents a set of second-order closure models for low-Reynolds-number turbulence near the wall. Existing closure models for the Reynolds-stress equations were modified to show proper near-wall behavior. A dissipation-rate equation for the turbulent kinetic energy is also reformulated. The proposed models satisfy realizability and will not produce unphysical behavior. Fully developed channel flows are used for model testing. The equations are solved for the mean velocity, the Reynolds stresses, and the dissipation rate of the turbulent kinetic energy. The calculations are compared with both direct numerical simulations and with measurements. It is shown that the present models perform well in predicting the behavior of the turbulence near a wall. Significant improvements over previous models in predicting the components of the Reynolds stress tensor are obtained in the present models.

Shih, T.-H.; Mansour, N. N.

1989-01-01

232

Kinetics of ozone reactions with 1-naphthalene, 1,5-naphthalene and 3-nitrobenzene sulphonic acids in aqueous solutions.  

PubMed

This paper describes the ozone oxidation kinetics of 1-naphthalene (1 NS), 1,5-naphthalene (1,5NDS), and 3-nitrobenzene (3NBS) sulphonic acid. The presence of hydroxyl radicals and their effect on the overall rate of reaction was studied. Second order kinetic constants of direct reactions were estimated at around 252 M(-1) s(-1), 41 M(-1) s(-1) and 22 M(-1) s(-1), for 1NS, 1,5NDS, and 3NBS sulphonic acids, respectively. At pH 3, the indirect reaction accounted for 2%, 15% and 4% of total primary oxidation of 1 NS, 1,5NBS, and 3NBS sulphonic acids, respectively. At pH 9, indirect reaction contribution increased to 73%, 84% and 48%, respectively. C4 compounds (maleic and fumaric acids), C2 (oxalic), C1 (formic) and sulphate were identified as oxidation by-products in all cases. TOC slowly decreased throughout ozonation, reaching around 40-60% and 60-70% reduction over 90 minutes at pH 7 and 3, respectively. PMID:11695486

Calderara, V; Jekel, M; Zaror, C

2001-01-01

233

PHD filters of second order in target number  

NASA Astrophysics Data System (ADS)

The multitarget recursive Bayes nonlinear filter is the theoretically optimal approach to multisensor-multitarget detection, tracking, and identification. For applications in which this filter is appropriate, it is likely to be tractable for only a small number of targets. In earlier papers we derived closed-form equations for an approximation of this filter based on propagation of a first-order multitarget moment called the probability hypothesis density (PHD). In a recent paper, Erdinc, Willett, and Bar-Shalom argued for the need for a PHD-type filter which remains first-order in the states of individual targets, but which is higher-order in target number. In an earlier paper at this conference we derived a closed-form cardinalized PHD CPHD), filter, which propagates not only the PHD but also the entire probability distribution on target number. Since the CPHD filter has computational complexity O(m 3) in the number m of measurements, additional approximation is desirable. In this paper we discuss a second-order approximation called the "binomial filter."

Mahler, Ronald

2006-06-01

234

Movable algebraic singularities of second-order ordinary differential equations  

NASA Astrophysics Data System (ADS)

Any nonlinear equation of the form y''=?n=0Nan(z)yn has a solution with leading behavior proportional to (z-z0)-2/(N-1) about a point z0, where the coefficients an are analytic at z0 and aN(z0)?0. Equations are considered for which each possible leading term of this form extends to a Laurent series solution in fractional powers of z-z0. For these equations we show that the only movable singularities that can be reached by analytic continuation along finite-length curves are of the algebraic type just described. This generalizes results of Shimomura [``On second order nonlinear differential equations with the quasi-Painlevé property II,'' RIMS Kokyuroku 1424, 177 (2005)]. The possibility that these algebraic singularities could accumulate along infinitely long paths ending at a finite point is considered. Smith [``On the singularities in the complex plane of the solutions of y''+y'f(y)+g(y)=P(x),'' Proc. Lond. Math. Soc. 3, 498 (1953)] showed that such singularities do occur in solutions of a simple equation outside this class.

Filipuk, G.; Halburd, R. G.

2009-02-01

235

Second-order hyperbolic Fuchsian systems and applications  

NASA Astrophysics Data System (ADS)

We introduce a new class of singular partial differential equations, referred to as the second-order hyperbolic Fuchsian systems, and we investigate the associated initial value problem when data are imposed on the singularity. First, we establish a general existence theory of solutions with asymptotic behavior prescribed on the singularity, which relies on a new approximation scheme, suitable also for numerical purposes. Second, this theory is applied to the (vacuum) Einstein equations for Gowdy spacetimes, and allows us to recover, by more direct arguments, well-posedness results established earlier by Rendall and collaborators. Another main contribution in this paper is the proposed approximation scheme, which we refer to as the Fuchsian numerical algorithm and is shown to provide highly accurate numerical approximations to the singular initial value problem. For the class of Gowdy spacetimes, the numerical experiments presented here show the interest and efficiency of the proposed method and demonstrate the existence of a class of Gowdy spacetimes containing a smooth, incomplete and non-compact Cauchy horizon.

Beyer, Florian; LeFloch, Philippe G.

2010-12-01

236

Covariance kernel representations of multidimensional second-order stochastic processes  

SciTech Connect

The dynamics of stationary stochastic processes in space is not exactly analogous to that of stationary stochastic processes in the time domain. This is due to the unilateral nature of the time series that is only influenced by past values as opposed to the dependence in all directions of the spatial process. In this work, we unfold the connection that exits between the covariance kernel of a multi-dimensional second-order autoregressive random process and its underlying discrete random dynamical system. Starting from a discrete random dynamical system, we show that the random process satisfying that system is governed by the modified Helmholtz equation in the continuous limit. We establish the dependence of the correlation constant on the grid size of the discretization. We also show that the random forcing term in the continuous case turns out to be a white noise process. A number of covariance functions are worked out for simple and more complex geometrical domains with various boundary conditions in multi-dimensions. We use both the discrete and the continuous systems in our computations.

Su, C.H. [Center for Fluid Mechanics, Turbulence and Computation, Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States); Lucor, Didier [Laboratoire de Modelisation en Mecanique, Universite Pierre et Marie Curie, 4 Place Jussieu, Case 162, 75252 Paris (France)]. E-mail: lucor@lmm.jussieu.fr

2006-09-01

237

Correction of the Chromaticity up to Second Order for MEIC  

SciTech Connect

The proposed electron collider lattice exhibits low ?- functions at the Interaction Point (IP) (?x?100mm ? ?y? 20 mm) and rather large equilibrium momentum spread of the collider ring (?p/p = 0.00158). Both features make the chromatic corrections of paramount importance. Here the chromatic effects of the final focus quadruples are cor- rected both locally and globally. Local correction features symmetric sextupole families around the IP, the betatron phase advances from the IP to the sextupoles are chosen to eliminate the second order chromatic aberration. Global interleaved families of sextupoles are placed in the figure-8 arc sections, and non-interleaved families at straight sec- tion making use of the freely propagated dispersion wave from the arcs. This strategy minimizes the required sex- tupole strength and eventually leads to larger dynamic aper- ture of the collider. The resulting spherical aberrations induced by the sextupoles are mitigated by design; the straight and arc sections optics features an inverse identity transformation between sextupoles in each pair.

H. K. Sayed, S.A. Bogacz, P. Chevtsov

2010-03-01

238

Second order statistics target-specified virtual dimensionality  

NASA Astrophysics Data System (ADS)

Virtual dimensionality (VD) has received considerable interest in its use of specifying the number of spectrally distinct signatures. So far all techniques are decomposition approaches which use eigenvalues, eigenvectors or singular vectors to estimate the virtual dimensionality. However, when eigenvalues are used to estimate VD such as Harsanyi-Farrand- Chang's method or hyperspectral signal subspace identification by minimum error (HySime), there will be no way to find what the spectrally distinct signatures are. On the other hand, if eigenvectors/singular vectors are used to estimate VD such as maximal orthogonal complement algorithm (MOCA), eigenvectors/singular vectors do not represent real signal sources. In this paper we introduce a new concept, referred to as target-specified VD (TSVD), which operates on the signal sources themselves to both determine the number of distinct sources and identify their signature. The underlying idea of TSVD was derived from that used to develop high-order statistics (HOS) VD where its applicability to second order statistics (2OS) was not explored. In this paper we investigate a 2OS-based target finding algorithm, called automatic target generation process (ATGP) to determine VD. Experiments are conducted in comparison with well-known and widely used eigen-based approaches.

Paylor, Drew; Chang, Chein-I.

2013-05-01

239

Maximum Probability Reaction Sequences in Stochastic Chemical Kinetic Systems  

PubMed Central

The detailed behavior of many molecular processes in the cell, such as protein folding, protein complex assembly, and gene regulation, transcription and translation, can often be accurately captured by stochastic chemical kinetic models. We investigate a novel computational problem involving these models – that of finding the most-probable sequence of reactions that connects two or more states of the system observed at different times. We describe an efficient method for computing the probability of a given reaction sequence, but argue that computing most-probable reaction sequences is EXPSPACE-hard. We develop exact (exhaustive) and approximate algorithms for finding most-probable reaction sequences. We evaluate these methods on test problems relating to a recently-proposed stochastic model of folding of the Trp-cage peptide. Our results provide new computational tools for analyzing stochastic chemical models, and demonstrate their utility in illuminating the behavior of real-world systems.

Salehi, Maryam; Perkins, Theodore J.

2010-01-01

240

Mechanisms and kinetics of reaction-bonded aluminium oxide ceramics  

Microsoft Academic Search

Reaction-bonded Al[sub 2]O[sub 3] (RBAO) ceramics were fabricated starting from mechanically alloyed Al[sub 2]O[sub 3]\\/Al, Al[sub 2]O[sub 3]\\/Al\\/ZrO[sub 2], and Al[sub 2]O[sub 3]\\/Al\\/ZrO[sub 2]\\/Zr mixtures. Isopressed compacts were heat-treated in air up to 1,550 C. Reaction-bonding mechanisms, kinetics, and the influence of ZrO[sub 2] and Zr additions are investigated. Independent of additive, oxidation of Al proceeds both as solid\\/gas and

Suxing Wu; Dietmar Holz; Nils Claussen

1993-01-01

241

High temperature heterogeneous reaction kinetics and mechanisms of tungsten oxidation  

NASA Astrophysics Data System (ADS)

Tungsten, which is a material used in many high temperature applications, is limited by its susceptibility to oxidation at elevated temperatures. Although tungsten has the highest melting temperature of any metal, at much lower temperatures volatile oxides are formed during oxidation with oxygen containing species. This differs from many heterogeneous oxidation reactions involving metals since most reactions form very stable oxides that have higher melting or boiling points than the pure metal (e.g., aluminum, iron). Understanding heterogeneous oxidation and vaporization processes may allow for the expansion and improvement of high temperature tungsten applications. In order to increase understanding of the oxidation processes of tungsten, there is a need to develop reaction mechanisms and kinetics for oxidation processes involving oxidizers and environmental conditions of interest. Tungsten oxidation was thoroughly studied in the past, and today there is a good phenomenological understanding of these processes. However, as the design of large scale systems increasingly relies on computer modeling there becomes a need for improved descriptions of chemical reactions. With the increase in computing power over the last several decades, and the development of quantum chemistry and physics theories, heterogeneous systems can be modeled in detail at the molecular level. Thermochemical parameters that may not be measured experimentally may now be determined theoretically, a tool that was previously unavailable to scientists and engineers. Additionally, chemical kinetic modeling software is now available for both homogeneous and heterogeneous reactions. This study takes advantage of these new theoretical tools, as well as a thermogravimetric (TG) flow reactor developed as part of this study to learn about mechanisms and kinetics of tungsten oxidation. Oxidizers of interest are oxygen (O2), carbon dioxide (CO 2), water (H2O), and other oxidizers present in combustion and energy systems. The primary application for this research topic is the migration of erosion processes in solid rocket motor nozzles. Since oxidation is the primary erosion mechanism of tungsten based nozzles, mitigation of this process through improved comprehension of the chemical mechanisms will increase performance of future rocket systems. In this dissertation, results of the high temperature reaction rates of bulk tungsten are studied using TG analysis in oxidizing atmospheres of O2, CO2, and H2O using helium (He) as an inert carrier gas. Isothermal reaction rates were determined at temperatures up to 1970 K, and oxidizing species partial pressures up to 64.6 torr. Kinetic parameters such as activation energies, frequency factors, and pressure exponents were determined for each reactive system. An important contribution of this work was quantifying the effects of carbon monoxide (CO) on the CO2 reaction, and hydrogen (H2) on the H2O reaction. In both cases the non-oxidizing species significantly reduced oxidation rates. Results have led to new interpretations and thought processes for limiting nozzle erosion in rocket motors. Combined with the TG analysis, as well as recent theoretical interpretations of reaction thermodynamics and kinetics, a new mechanism for tungsten and O2 oxidation has been developed using a one-dimensional numerical model of the TG flow reactor. Important chemical processes and species are also identified for reaction systems involving H2O and CO2. In the future, additional studies are needed to improve our understanding of these chemical species and processes so that more advanced kinetic mechanisms may be developed. In addition to a detailed analysis of high temperature tungsten corrosion processes, synthetic graphite corrosion processes are studied in detail as well. Details of these studies are presented in an attached appendix of this dissertation. These studies considered not only oxidation processes, but decomposition of synthetic graphite in the presence of reducing and inert gas environments.

Sabourin, Justin L.

242

Shock tube kinetics in homogeneous and heterogeneous reaction systems  

Microsoft Academic Search

The shock tube used as a high-temperature wave reactor has dominated high-temperature kinetics for more than 45 years. The nearly instantaneous heating to high temperatures, the accessible wide temperature and pressure ranges, and the diffusion-free reaction conditions are the main advantages of this technique for measuring rate co-efficients at high temperatures. In this paper some applications of the shock tube

Paul Roth

1995-01-01

243

Reaction kinetics and pathways of MoSe2  

Microsoft Academic Search

Molybdenum is widely used as a back contact for CIGS solar cells due to its low cost and proven electrical and morphological compatibility with CIGS. Furthermore, it is believed that MoSe2 forms during the absorber synthesis step to yield ohmic contacts with good adhesion. In this study the reaction kinetics of MoSe2 formation are investigated by reacting Mo films on

R. Krishnan; E. A. Payzant; R. Kacnyzki; U. Schoop; J. Britt; R. Noufi; T. J. Anderson

2010-01-01

244

Modeling Investigation of Volume Variation Kinetics of Fast Response Hydrogels  

Microsoft Academic Search

Fast response hydrogels have attracted great attention recently. Three kinds of models with different complexity are available in the literature to investigate their volume variation kinetics. A phenomenal model based on second?order reaction kinetics provides a simple method to correlate the experimental kinetic data. A power law model can be employed to evaluate different volume variation mechanisms according to the

Shunnian Wu; Hua Li; J. Paul Chen

2004-01-01

245

Diffusion in Natural Melts: Kinetics and Mechanisms of Redox Reactions  

NASA Astrophysics Data System (ADS)

Diffusion in silicate melts plays a fundamental role in all magmatic processes in nature as well as in the glass industry. The diffusivity contrast that occurs between the so-called network-former (e.g., Si, Al) and network- modifier (e.g., alkali and alkaline-earth) cations is of particular importance. Whereas the diffusivities of all these cations tend to converge at the high-temperature limit, a strong decoupling is observed at glass transition temperatures. The diffusivity of oxygen and network-former cations becomes much lower than that of network- modifier cations. This decoupling exerts an influence on the kinetics and mechanisms of redox reactions. In redox reactions, diffusion of oxygen is the rate-limiting factor only at superliquidus temperatures whereas at lower temperatures, the kinetics of these reactions is controlled instead by diffusion of alkaline-earth or alkaline cations coupled to a flux of electron holes. For iron redox reactions, we have investigated these effects quantitatively from the glass transition up to 2100 K by in situ high temperature X-ray Absorption Near Edge Structure (XANES) experiments at the iron K-edge. To compare in a simple way the observations made, we have introduced the concept of redox diffusivity from the time required to achieve redox equilibrium at a given temperature. Comparisons of these redox diffusivities with the diffusivities of oxygen, network-forming and network-modifying cations then allow one to distinguish the temperature range where a given redox mechanism predominates. The results obtained in this way for a variety of natural iron lavas will be presented. In particular we will discuss the kinetics of iron redox reactions obtained on depolymerized melt such as basalt and komatiite or on polymerized melt such as phonolite and rhyolite.

Cochain, B.; Neuville, D. R.; de Ligny, D.; Roux, J.; Richet, P.

2009-05-01

246

Second order multidimensional sign-preserving remapping for ALE methods  

SciTech Connect

A second-order conservative sign-preserving remapping scheme for Arbitrary Lagrangian-Eulerian (ALE) methods is developed utilising concepts of the Multidimensional Positive Definite Advection Transport Algorithm (MPDATA). The algorithm is inherently multidimensional, and so does not introduce splitting errors. The remapping is implemented in a two-dimensional, finite element ALE solver employing staggered quadrilateral meshes. The MPDATA remapping uses a finite volume discretization developed for volume coordinates. It is applied for the remapping of density and internal energy arranged as cell centered, and velocity as nodal, dependent variables. In the paper, the advection of scalar fields is examined first for test cases with prescribed mesh movement. A direct comparison of MPDATA with the performance of the van Leer MUSCL scheme indicates advantages of a multidimensional approach. Furthermore, distinctly different performance between basic MPDATA and the infinite gauge option is illustrated using benchmarks involving transport of a sign changing velocity field. Further development extends the application of MPDATA remapping to the full ALE solver with a staggered mesh arrangement for density, internal energy and momentum using volume coordinates. At present, two options of the algorithm - basic and infinite gauge - are implemented. To ensure a meaningful assessment, an identical Lagrangian solver and computational mesh update routines are used with either MPDATA or van Leer MUSCL remapping. The evaluation places particular focus on the abilities of both schemes to accurately model multidimensional problems. Theoretical considerations are supported with numerical examples. In addition to the prescribed mesh movement cases for advection of scalars, the demonstrations include two-dimensional Eulerian and ALE flow simulations on quadrilateral meshes with both fixed and variable timestep control. The key comparisons include the standard test cases of Sod and Noh for single material problems. The results demonstrate that the MPDATA gauge option is suitable for providing accurate ALE remapping and preserves the multidimensionality and sign of both scalar and vector fields.

Hill, Ryan N [Los Alamos National Laboratory; Szmelter, J. [LOUGHBOROUGH UNIV.

2010-12-15

247

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

248

Modeling Large Zinc Isotope Fractionations Associated with Reaction Kinetics  

NASA Astrophysics Data System (ADS)

Often multiple processes govern isotope fractionation during a chemical reaction, such as the mass-transport, equilibrium and reaction kinetics between reactants and products. Here we use experimental electrochemical techniques to control the mass-transport and reaction kinetics of the electrodeposition reaction: Zn2+ + 2e- = Zn(s); and model the isotopic fractionation measured to resolve the underlying mechanisms of fractionation. Zn was plated on a rotating disc electrode at various applied overpotentials, rotation rates and temperatures. Electroplated Zn was recovered in acid for analysis of the stable isotope composition by multi-collector ICP-MS. The isotopic composition (66Zn/64Zn) of plated metal is reported relative to the stock solution. A large range of ?66Znsample-stock is observed, with increasing fractionation at higher rotation rates (Fig. 1A), and lower overpotentials (Fig. 1B). Models of electrochemical kinetics, show that these variables control the relative rates of precipitation and diffusion, as defined by the Koutecky-Levich equation [Bard and Faulkner (2001), Electrochemical Methods, John Wiley & Sons]. Using this equation to interpret our data shows that all the data fall along a systematic trend (Fig. 1C) with smaller fractionations in the mass-transport limited regime and larger fractionations produced under electrochemical kinetic control. We extend the Koutecky-Levich model to predict isotope fractionation during electrochemical processes as a function of mass-dependent diffusion (Fig. 2A); standard rate constant (Fig. 2B); and transfer coefficient, describing reaction barrier symmetry (Fig. 2C). A comparison of the model and our data shows that diffusive and equilibrium fractionation alone (Fig. 2A-B) cannot reproduce the trends in our data, but a mass-dependence in ? can explain our observations. However, the predicted fractionation is very sensitive to the magnitude of k0 (Fig. 2C). This model predicts how isotope fractionation varies over a wide range of reaction rates, showing that the largest fractionations arise in a regime away from equilibrium and yet without mass-transport limitations. Fig 1. Zn isotope fractionation during electrodeposition Fig 2. Modeling Zn isotope fractionation at 25°C. A) diffusive control; B) equilibrium control; C) combined diffusion, equilibrium and electrochemical control.

Black, J. R.; John, S.; Kavner, A.

2009-12-01

249

Influence of chemical kinetics on postcolumn reaction in a capillary Taylor reactor with catechol analytes and photoluminescence following electron transfer.  

PubMed

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-microm-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)3(3+) by analyte to the photoluminescent Os(bpy)3(2+)) 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 microL/min) velocity with solutes having diffusion coefficients in the 5 x 10(-6) cm2/s range, can be constructed from 8.0 cm of 25-microm-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-microm-capillary chromatography column by 10% if the pseudo-first-order rate constant is larger than 0.1 s(-1). PMID:15858975

Jung, Moon Chul; Weber, Stephen G

2005-02-15

250

Ulraviolet spectrum and reaction kinetics of the formyl radical  

SciTech Connect

A transient ultraviolet absorption attributed to the formyl radical, HCO, was produced by the flash photolysis of water vapor in the presence of CO. For CO saturated with H/sub 2/O at a total pressure of 1 atm, the formation of HCO is complete within approx. 60 ..mu..s, after which it undergoes second-order decay, with k/epsilon(230 nm) = 1.5 +- 0.2) x 10/sup 7/ cm s/sup -1/. During the relatively slow formation reaction (H + CO(+M) ..-->.. HCO), the competing reaction H + HCO ..-->.. H/sub 2/ + CO is significant. By employing the H/sub 2/O + CH/sub 4/ system as an actinometer to determine the amount of H/sub 2/O dissociated by the flash (discussed elsewhere) and by computer modeling the observed formation and decay of HCO as a function of CO pressure, the following absolute rate constants were obtained: k/sub 3/(H + CO(+M) ..-->.. HCO) = (3.6 +- 0.9) x 10/sup 7/ M/sup -2/ s/sup -1/ for M = CO, (5.8 +- 0.6) x 10/sup 7/ M/sup -2/ s/sup -1/ for M = CH/sub 4/, and (3.8 +- 0.4) x 10/sup 7/ M/sup -2/ s/sup -1/ for M = H/sub 2/, k/sub 4/(HCO + HCO ..-->.. products) = (1.4 +- 0.3) x 10/sup 10/ M/sup -1/ s/sup -1/, and k/sub 5/(H +- HCO ..-->.. products) = (6.9 +- 1.7) x 10/sup 10/ M/sup -1/ s/sup -1/. The molar extinction coefficient epsilon(HCO, 230 nm) = 941 +- 171 M/sup -1/ cm/sup -1/.

Hochanadel, C.J.; Sworski, T.J.; Ogren, P.J.

1980-02-07

251

A kinetic study of platinum-mercury contact reaction  

NASA Astrophysics Data System (ADS)

The reaction between solid Pt and liquid Hg, at temperatures varying from 20 to 153 °C, has been investigated using a combination of gravimetric, x ray, and radioactive tracer techniques in an effort to evaluate the suitability of Pt-Hg contacts for Josephson device packages. The reaction product was identified as Hg4Pt with a lattice parameter of 6.2047 A?+/-0.02%. No penetration of Hg into Pt lattice or grain boundaries has been detected. The kinetic law governing the amalgam formation has been found to be X (cm)=4.48×10-3t exp(-0.52 eV/kT) where X is Pt thickness consumed in the amalgam, t is time in sec, k is Boltzmann constant, and T is temperature. The results indicate that the rate of amalgam formation is controlled by reaction at the Pt-amalgam interface.

Lahiri, S. K.; Gupta, D.

1980-10-01

252

Kinetics and toxicity of direct reaction between ozone and 1,2-dihydrobenzene in dilute aqueous solution.  

PubMed

The presence of toxic aromatic organic compounds in industrial wastewater affects the efficiency of conventional biological treatment. The oxidizing power of ozone represents an interesting pretreatment to reduce toxicity and increase biodegradability. At low pH, ozone is known to attack electron-rich structures by direct electrophilic reactions which open aromatic rings, and generate smaller oxidized compounds. This paper reports experimental results on kinetic and toxicity aspects of ozone direct reactions with 1,2-dihydrobenzene. This toxic compound is frequently found in cellulose bleaching effluents. Although the reaction pathway is rather complex, 4-carbon compounds, such as maleic acid, are readily formed during the first stage of ozonation. These 4-carbon compounds are further oxidized to form smaller molecules (mostly 2-carbon, such as oxalic acid). The apparent kinetics of 1,2-dihydrobenzene follows a second order law, with a rate constant around 0.36 (dm3 mmol-1s-1), at pH 2 and 20 degrees C. Results show that the BOD:COD ratio increase five-fold as ozonation progresses. Furthermore, the mutagenicity of 1,2-dihydrobenzene totally disappears as the aromatic compound is destroyed by ozonation. PMID:11380197

Zaror, C; Carrasco, V; Perez, L; Soto, G; Mondaca, M A; Mansilla, H

2001-01-01

253

Second-order dispersion interactions in ?-conjugated polymers  

NASA Astrophysics Data System (ADS)

We calculate the ground state and excited state second-order dispersion interactions between parallel ?-conjugated polymers. The unperturbed eigenstates and energies are calculated from the Pariser-Parr-Pople model using CI-singles theory. Based on large-scale calculations using the molecular structure of trans-polyacetylene as a model system and by exploiting dimensional analysis, we find that: (1) For inter-chain separations, R, greater than a few lattice spacings, the ground-state dispersion interaction, ?EGS, satisfies, ?EGS~L2/R6 for L << R and ?EGS~L/R5 for R << L, where L is the chain length. The former is the London fluctuating dipole-dipole interaction while the latter is a fluctuating line dipole-line dipole interaction. (2) The excited state screening interaction exhibits a crossover from fluctuating monopole-line dipole interactions to either fluctuating dipole-dipole or fluctuating line dipole-line dipole interactions when R exceeds a threshold Rc, where Rc is related to the root-mean-square separation of the electron-hole excitation. Specifically, the excited state screening interaction, ?En, satisfies, ?En ~ L/R6 for Rc < L << R and ?En ~ L0/R5 for Rc < R << L. For R < Rc < L, ?En ~ R-?, where ? ~= 3. We also investigate the relative screening of the primary excited states in conjugated polymers, namely the n = 1, 2, and 3 excitons. We find that a larger value of n corresponds to a larger value of ?En. For example, for poly(para-phenylene), ?En = 1 ~= 0.1 eV, ?En = 2 ~= 0.6 eV, and ?En = 3 ~= 1.2 eV (where n = 1 is the 11B1 state, n = 2 is the m1A state, and n = 3 is the n1B1 state). Finally, we find that the strong dependence of ?En on inter-chain separation implies a strong dependency of ?En on density fluctuations. In particular, a 10% density fluctuation implies a fluctuation of 13 meV, 66 meV, and 120 meV for the 11B1, m1A state, and n1B1 states of poly(para-phenylene), respectively. Our results for the ground-state dispersion are applicable to all types of conjugated polymers. However, our excited state results are only applicable to conjugated polymers, such as the phenyl-based class of light emitting polymers, in which the primary excitations are particle-hole (or ionic) states.

Barford, William; Paiboonvorachat, Nattapong; Yaron, David

2011-06-01

254

Optimally-reduced kinetic models: reaction elimination in large-scale kinetic mechanisms  

Microsoft Academic Search

A new optimization-based approach to kinetic model reduction is presented. The reaction-elimination problem is formulated as a linear integer program which can be solved to guaranteed global optimality. This formulation ensures that the solution to the integer program is the smallest possible reduced model consistent with the user-set tolerances. The method is applied to generate optimally-reduced models for isobaric, adiabatic

Binita Bhattacharjee; Douglas A. Schwer; Paul I. Barton; William H. Green

2003-01-01

255

Local kinetics and thermodynamics of rapid electrochemical reactions.  

PubMed

We introduce and discuss a local kinetic mechanism for an n-electron electrochemical reaction at the interface formed by an electrode and diluted electrolyte. We show that the suggested mechanism is in agreement with the Nernst equation in the thermal equilibrium. We also qualitatively characterize the structure of a flat electrode-diluted electrolyte boundary in the meaning of the spatial distribution of electrochemical reactants and electric potential. As the suggested kinetic mechanism is not limited by the duration of relaxation processes in electric double layers, it is suitable for the understanding and simulation of fast transient processes that appear in modern applications such as nanocolloid dielectrophoresis, AC electrospray, AC electroosmosis, or nanopore biosensing. PMID:24827256

P?ibyl, Michal; Šnita, Dalimil

2014-04-01

256

Local kinetics and thermodynamics of rapid electrochemical reactions  

NASA Astrophysics Data System (ADS)

We introduce and discuss a local kinetic mechanism for an n-electron electrochemical reaction at the interface formed by an electrode and diluted electrolyte. We show that the suggested mechanism is in agreement with the Nernst equation in the thermal equilibrium. We also qualitatively characterize the structure of a flat electrode-diluted electrolyte boundary in the meaning of the spatial distribution of electrochemical reactants and electric potential. As the suggested kinetic mechanism is not limited by the duration of relaxation processes in electric double layers, it is suitable for the understanding and simulation of fast transient processes that appear in modern applications such as nanocolloid dielectrophoresis, AC electrospray, AC electroosmosis, or nanopore biosensing.

P?ibyl, Michal; Šnita, Dalimil

2014-04-01

257

Two alternative descriptions of second order phase transitions: Landau theory and the self-consistent approach  

NASA Astrophysics Data System (ADS)

Two alternative descriptions of second order phase transitions are considered, Landau theory and the self-consistent approach. The temperature dependence of the heat capacity in these two descriptions is considered. The Landau theory gives only a jump in the heat capacity. It is not defined by the Gibbs-Boltzmann entropy, which is equal to zero in the Landau approach, but by the thermal thermodynamical force. The self-consistent approach gives not only this jump, but also the peak in the temperature dependence of the heat capacity near the ?-point. The latter is defined by the Gibbs-Boltzmann entropy. On the basis of the S-theorem the relative degree of order of the states above and below the ?-point is defined. It is shown that the state below the ?-point is more ordered. Thus, the transition from the more symmetrical state to the less symmetrical one corresponds to self-organization. The possibility of a kinetic description of second order phase transitions is considered.

Klimontovich, Yu. L.

1996-02-01

258

Evaluation of Turbulent Transport and Dissipation Closures in Second-Order Modeling.  

NASA Astrophysics Data System (ADS)

We show that the turbulence statistics from our (96)3 large-eddy-simulation (LES) studies of a convective boundary layer are in excellent agreement with those from the Deardorff-Willis laboratory convection tank. Using these LES data, we evaluate contemporary parameterizations for turbulent transport and dissipation in second-order closure models of the convective boundary layer. The gradient-diffusion parameterization for turbulent transport fares poorly, due in large part to the direct influence of buoyancy. This leads to poor predictions of the vertical profiles of some turbulence statistics. We also find that the characteristic length scales for the mechanical and thermal dissipation rates typically used in second-order closure models are a factor of 2-3 too small; this leads to underpredictions of turbulence kinetic energy levels. Finally, we find that the flux and variance budgets for conservative scalars are substantially different in top-down and bottom-up diffusion. In order to reproduce these differences accurately, it seems necessary to model the turbulent transport, pressure covariance, and molecular destruction terms differently in top-down and bottom-up diffusion.

Moeng, Chin-Hoh; Wyngaard, John C.

1989-07-01

259

A study of switchgrass pyrolysis: Product variability and reaction kinetics  

NASA Astrophysics Data System (ADS)

Samples of the same cultivar of cave-in-rock switchgrass were harvested from plots in Frankenmuth, Roger City, Cass County, and Grand Valley, Michigan. It was determined that variation exists, between locations, among the pyrolytic compounds which can lead to variability in bio-oil and increased processing costs at bio-refineries to make hydrocarbon fuels. Washed and extractives-free switchgrass samples, which contain a lower alkali and alkaline earth metals content than untreated samples, were shown to produce lower amounts of acids, esters, furans, ketones, phenolics, and saccharides and also larger amounts of aldehydes upon pyrolysis. Although the minerals catalyzed pyrolytic reactions, there was no evidence indicating their effect on reducing the production of anhydrosugars, specifically levoglucosan. To further link minerals present in the biomass to a catalytic pathway, mathematic models were employed to determine the kinetic parameters of the switchgrass. While the calculated activation energies of switchgrass, using the FWO and KAS methods, were 227.7 and 217.8 kJ/mol, correspondingly, it was concluded that the activation energies for the switchgrass hemicellulose and cellulose peaks were 115.5 and 158.2 kJ/mol, respectively, using a modified model-fitting method. The minerals that effect the production of small molecules and levoglucosan also have an observable catalytic effect on switchgrass reaction rate, which may be quantifiable through the use of reaction kinetics so as to determine activation energy.

Bovee, Jonathan Matthew

260

The kinetics of cyclization reactions on polyaromatics from first principles.  

PubMed

Ab initio density functional theory calculations are presented on cyclization reactions of polyaromatics involved in coke formation during the thermal cracking of hydrocarbons. During coke formation, cyclization can take place at various sites, differing from each other by the local polyaromatic structure. This local structure also determines the minimum number of carbon atoms that must be added to allow the formation of a new ring. Kinetic parameters are calculated for the various ring-closure reactions by means of transition state theory. The activation energy is largely affected by the local structure of the polycyclic aromatic hydrocarbon, whereas the frequency factor varies significantly in terms of the length of the attached alkyl chain. The calculations, as presented, give a microscopic insight into the mechanisms that contribute to barrier formation and to the value of the frequency factor. The relative importance of cyclization at different sites, under conditions typical for an industrial cracking unit is studied on the basis of the calculated rate constants at various temperatures. The results suggest that the nature of coke formation is autocatalytic: the larger the macroradicals, the faster the subsequent reactions that lead to further growth of the polyaramatic surface. This type of calculation is the first step towards the development of structural relations for the kinetic parameters in terms of the local structure of the coke matrix. PMID:12465185

Van Speybroeck, Veronique; Reyniers, Marie-Françoise; Marin, Guy B; Waroquier, Michel

2002-10-18

261

An asymptotic initial value method for boundary value problems for a system of singularly perturbed second order ordinary differential equations  

Microsoft Academic Search

In this paper a numerical method is suggested to solve a class of boundary value problems for a weakly coupled system of singularly perturbed second order ordinary differential equations of reaction-diffusion type. First, in this method, an asymptotic expansion approximation of the solution of the boundary value problem is constructed using the basic ideas of the well known perturbation method.

T. Valanarasu; N. Ramanujam

2004-01-01

262

Second-order dispersion interactions in ?-conjugated polymers.  

PubMed

We calculate the ground state and excited state second-order dispersion interactions between parallel ?-conjugated polymers. The unperturbed eigenstates and energies are calculated from the Pariser-Parr-Pople model using CI-singles theory. Based on large-scale calculations using the molecular structure of trans-polyacetylene as a model system and by exploiting dimensional analysis, we find that: (1) For inter-chain separations, R, greater than a few lattice spacings, the ground-state dispersion interaction, ?E(GS), satisfies, ?E(GS)?L(2)/R(6) for L ? R and ?E(GS)?L/R(5) for R ? L, where L is the chain length. The former is the London fluctuating dipole-dipole interaction while the latter is a fluctuating line dipole-line dipole interaction. (2) The excited state screening interaction exhibits a crossover from fluctuating monopole-line dipole interactions to either fluctuating dipole-dipole or fluctuating line dipole-line dipole interactions when R exceeds a threshold R(c), where R(c) is related to the root-mean-square separation of the electron-hole excitation. Specifically, the excited state screening interaction, ?E(n), satisfies, ?E(n) ? L?R(6) for R(c) < L ? R and ?E(n) ? L(0)?R(5) for R(c) < R ? L. For R < R(c) < L, ?E(n) ? R(-?), where ? ? 3. We also investigate the relative screening of the primary excited states in conjugated polymers, namely the n = 1, 2, and 3 excitons. We find that a larger value of n corresponds to a larger value of ?E(n). For example, for poly(para-phenylene), ?E(n = 1) ? 0.1 eV, ?E(n = 2) ? 0.6 eV, and ?E(n = 3) ? 1.2 eV (where n = 1 is the 1(1)B(1) state, n = 2 is the m(1)A state, and n = 3 is the n(1)B(1) state). Finally, we find that the strong dependence of ?E(n) on inter-chain separation implies a strong dependency of ?E(n) on density fluctuations. In particular, a 10% density fluctuation implies a fluctuation of 13 meV, 66 meV, and 120 meV for the 1(1)B(1), m(1)A state, and n(1)B(1) states of poly(para-phenylene), respectively. Our results for the ground-state dispersion are applicable to all types of conjugated polymers. However, our excited state results are only applicable to conjugated polymers, such as the phenyl-based class of light emitting polymers, in which the primary excitations are particle-hole (or ionic) states. PMID:21702545

Barford, William; Paiboonvorachat, Nattapong; Yaron, David

2011-06-21

263

Kinetic Study of the Austempering Reactions in Ductile Irons  

NASA Astrophysics Data System (ADS)

Kinetics of the reaction that occur during the austempering heat treatment in unalloyed and alloyed ductile irons with 1Cu-0.25Mo, 1Ni-0.25Mo, and 0.7Cu-1Ni-0.25Mo, was studied. The austenitization and austempering cycles were achieved by isothermal dilatometry in cylindrical samples of 2 mm in diameter and 12 mm in length. The specimens were austenitized at 870 °C for 120 min, followed by isothermal holding for 300 min at temperatures between 270 and 420 °C. Kinetic parameters such as the order of reaction " n" and the rate of reaction " k" were calculated using the Johnson-Mehl equation while the empirical activation energy was calculated by means of the Arrhenius equation. It was found that the values of " k" decreased with the addition of Cu, Ni, and Mo as well as with the reduction of the isothermal temperature. The activation energy changes with the austempering temperature, in the range 30,348-58,250 J/mol when the heat treatment was carried out between 370 and 420 °C and 10,336-26,683 J/mol when the temperature varied from 270 to 350 °C. The microstructures in samples austempered at 370 and 315 °C were observed by transmission electron microscopy. No carbides precipitation was observed on samples heat treated at 370 °C for less than 120 min, while at 315 °C carbides of hexagonal structure ?(Fe2.4C) were found from the beginning of the transformation. The smallest value of activation energy and a slower kinetic transformation seem to be related with the presence of a carbide phase. Additionally, the time results obtained for transformation fractions of 0.05 and 0.95 by the dilatometry analysis were used to build the temperature-time-transformation diagrams for the irons.

Pérez, M. J.; Cisneros, M. M.; Almanza, E.; Haro, S.

2012-11-01

264

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

265

Reaction Kinetics and Mechanism of Magnetic Field Effects in Cryptochrome  

PubMed Central

Creatures as varied as mammals, fish, insects, reptiles, and birds have an intriguing ‘sixth’ sense that allows them to orient themselves in the Earth's magnetic field. Despite decades of study, the physical basis of this magnetic sense remains elusive. A likely mechanism is furnished by magnetically sensitive radical pair reactions occurring in the retina, the light-sensitive part of animal eyes. A photoreceptor, cryptochrome, has been suggested to endow birds with magnetoreceptive abilities as the protein has been shown to exhibit the biophysical properties required for an animal magnetoreceptor to operate properly. Here, we propose a theoretical analysis method for identifying cryptochrome's signaling reactions involving comparison of measured and calculated reaction kinetics in cryptochrome. Application of the method yields an exemplary light-driven reaction cycle, supported through transient absorption and electron-spin-resonance observations together with known facts on avian magnetoreception. The reaction cycle permits one to predict magnetic field effects on cryptochrome activation and deactivation. The suggested analysis method gives insight into structural and dynamic design features required for optimal detection of the geomagnetic field by cryptochrome and suggests further experimental and theoretical studies.

2012-01-01

266

Kinetics of Cl atom reactions with butadienes including isoprene  

NASA Astrophysics Data System (ADS)

The laser photolysis-resonance fluorescence technique was used to determine the rate constants for the reactions of Cl atoms with 1,3-butadiene, 2-methyl-1,3 butadiene (isoprene) and 2,3-dimethyl-1,3-butadiene in the pressure range 15-60 Torr and T=(298±2) K. The obtained rate constants (in units of 10 -10 cm 3 molecule -1 s -1) were as follows: 1,3-butadiene (3.48±0.10), isoprene (3.61±0.10) and 2,3-dimethyl-1,3-butadiene (3.63±0.14). These kinetic data are discussed.

Notario, Alberto; Le Bras, Georges; Mellouki, Abdelwahid

1997-12-01

267

Single-molecule chemical reaction reveals molecular reaction kinetics and dynamics.  

PubMed

Understanding the microscopic elementary process of chemical reactions, especially in condensed phase, is highly desirable for improvement of efficiencies in industrial chemical processes. Here we show an approach to gaining new insights into elementary reactions in condensed phase by combining quantum chemical calculations with a single-molecule analysis. Elementary chemical reactions in liquid-phase, revealed from quantum chemical calculations, are studied by tracking the fluorescence of single dye molecules undergoing a reversible redox process. Statistical analyses of single-molecule trajectories reveal molecular reaction kinetics and dynamics of elementary reactions. The reactivity dynamic fluctuations of single molecules are evidenced and probably arise from either or both of the low-frequency approach of the molecule to the internal surface of the SiO2 nanosphere or the molecule diffusion-induced memory effect. This new approach could be applied to other chemical reactions in liquid phase to gain more insight into their molecular reaction kinetics and the dynamics of elementary steps. PMID:24963600

Zhang, Yuwei; Song, Ping; Fu, Qiang; Ruan, Mingbo; Xu, Weilin

2014-01-01

268

Second-Order Self-Organization in Coordination-Driven Self-Assembly: Exploring the Limits of Self-Selection  

PubMed Central

Self-organization during the self-assembly of a series of functionalized bispyridyl organic donors with complementary di-Pt(II) acceptors into supramolecular rhomboids and rectangles is explored. The connectivity and location of functional groups on the organic donors ensures that they do not interfere sterically or electronically with their respective binding sites. Carefully controlled reaction conditions are employed so that the only means of self-organization during self-assembly is through “second-order” effects arising from the distal functional groups themselves. With the selection of functionalized systems studied the extent of second-order self-organization varies from essentially zero to quite pronounced.

Northrop, Brian H.; Yang, Hai-Bo; Stang, Peter J.

2009-01-01

269

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

NASA Technical Reports Server (NTRS)

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.

2010-01-01

270

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

271

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

Microsoft Academic Search

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

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

2001-01-01

272

Uptake and reaction kinetics of acetone, 2-butanone, 2,4-pentanedione, and acetaldehyde in sulfuric acid solutions.  

PubMed

This work presents a study of the uptake of acetone, 2-butanone (methyl ethyl ketone), 2,4-pentanedione, and acetaldehyde by sulfuric acid solutions with an aim at understanding the reactivity of carbonyl compounds present in the atmosphere toward acidic aerosols. Experiments were performed in a rotating wetted-wall reactor coupled to a mass spectrometer at room temperature (298 +/- 3 K) with 0-96 wt % H(2)SO(4) solutions. For all compounds, a reactive uptake was observed at high acidity (>or=64 wt % H(2)SO(4)). The corresponding reactions were found to follow a second-order kinetics, and their rate constants, k (M(-1) s(-1)) were found to increase exponentially with acidity. These rate constants and their variations with acid concentration were in good agreement with the kinetic behavior of acid-catalyzed aldol condensation reported in the organic chemical literature, except for 2,4-pentanedione. The results of this work suggest that aldol condensation should be too slow to account for the enhanced organic aerosol mass observed in smog chamber studies and should have an even smaller contribution under atmospheric conditions. The rate constants of other compounds, such as large aldehydes, remain however to be measured. However, in order to contribute significantly to organic aerosol formation, a liquid phase reaction would have to result in an uptake coefficient of the order of 10(-2). PMID:16331936

Esteve, Williams; Nozière, Barbara

2005-12-01

273

Factorizations and Representations of Second Order Linear Recurrences with Indices in Arithmetic Progressions.  

National Technical Information Service (NTIS)

In this paper we consider second order recurrences (Vk) and (Un) We give second order linear recurrences for the sequences (V +/- kn) and (U +/- kn). Using these recurrence relations, we derive relationships between the determinants of certain matrices an...

E. Kilic P. Stanica

2009-01-01

274

Kinetics of reaction of sulfide with thiosulfate in aqueous solution  

SciTech Connect

The kinetics of the reaction 2H{sub 2}S(aq) + S{sub 2}O{sub 3}{sup 2{minus}} + 2H{sup +} {r_arrow} 1/2S{sub 8}(s) + 3H{sub 2}O has been investigated at 0--40 C in the pH interval from 5 to 7. The rate law was found to be r = {minus}d[S{sub 2}O{sub 3}{sup 2{minus}}]/dt = {kappa}[H{sub 2}S][S{sub 2}O{sub 3}{sup 2{minus}}], where {kappa} = 8 {times} 10{sup 11} exp({minus}74,300/RT) M{sup {minus}1} s{sup {minus}1}. Thermodynamic calculation shows that the reaction is unfavorable at pH {ge} 8, which is confirmed by the experimental observation. The ionic strength effect on the reaction also has been studied. The mechanism postulated to account for the observed rate law involves the formation and subsequent reactions of an intermediate H{sub 2}S{sub 3}O{sub 3}{sup 2{minus}}.

Siu, T.; Jia, C.Q. [Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry] [Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry

1999-04-01

275

Kinetics of soybean lipoxygenase reaction in hydrated reversed micelles.  

PubMed

The rate of linoleic acid peroxidation catalysed by soybean lipoxygenase I was studied as a function of the hydration degree of aerosol OT (bis(2-ethylhexyl) sulfosuccinate sodium salt) reversed micelles in octane. Lipoxygenase reaction parameters for the micelle-bound substrate were spectrophotometrically determined. The linoleic acid distribution between the micelles and octane was detected by the sedimentation method, with the concentration of linoleic acid in supernatant after settling of micelles (i.e. the concentration of free linoleic acid) being estimated by the enzymatic method. The apparent constant of linoleic acid distribution (the ratio of the bound and free substrate concentrations) was enhanced with increasing hydration of reversed micelles. The dependence of the enzymatic reaction rate on the bound substrate concentration obeyed the empiric Hill equation. The Hill coefficient remained practically constant (h = 1.34) as the hydration degree changed. Parameters of the lipoxygenase reaction, enzyme reaction limiting rate V and semi-saturation substrate concentration [S]0.5 increased with increasing degree of hydration and reached the optimum at [H2O]/[AOT] approximately 30, where dimensions of the micellar internal cavity coincided with those of the enzyme molecule. Some aspects of kinetic behavior of membrane-bound enzymes participating in chemical transformation of non-polar compounds dispersed in lipid phase are discussed. PMID:2474334

Kurganov, B I; Shkarina, T N; Malakhova, E A; Davydov, D R; Chebotareva, N A

1989-04-01

276

Deformation measurements by digital image correlation: Implementation of a second-order displacement gradient  

Microsoft Academic Search

This paper outlines the procedure for refining the digital image correlation (DIC) method by implementing a second-order approximation\\u000a of the displacement gradients. The second-order approximation allows the DIC method to directly measure both the first- and\\u000a second-order displacement gradients resulting from nonlinear deformation. Thirteen unknown parameters, consisting of the components\\u000a of displacement, the first- and second-order displacement gradients and the

H. Lu; P. D. Cary

2000-01-01

277

Effects of Deception on Children's Understanding of Second-Order False Belief  

ERIC Educational Resources Information Center

This research examined two questions: effects of deception on children's understanding of second-order false belief, and possible effects of number of siblings on second-order performance. Kindergarten children responded to 3 second-order problems that varied in the presence and the nature of deception. Performance was better on the problems…

Miller, Scott A.

2013-01-01

278

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

NASA Astrophysics Data System (ADS)

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 2D 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.

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

2010-02-01

279

Reaction of enzymes with starch granules: kinetics and products of the reaction with glucoamylase  

Microsoft Academic Search

The reaction of glucoamylase with starch granules from seven botanical sources (waxy maize, maize, barley, tapioca, amylomaize-7, shoti, and potato) and with four potato starches modified with acid in four types of alcohols (methanol, ethanol, 2-propanol, and 1-butanol) were studied using three concentrations of enzyme (2, 20, and 200 units mL?1). The kinetics of the formation of d-glucose were followed

Atsuo Kimura; John F. Robyt

1995-01-01

280

Atmospheric reactions Cl+CH3-(CH2)n-OH (n=0-4): A kinetic and theoretical study  

NASA Astrophysics Data System (ADS)

The reactions of Cl with a series of linear alcohols: methanol (k1), ethanol (k2), 1-propanol (k3), 1-butanol (k4), and 1-pentanol (k5) were investigated as a function of temperature in the range of 264-382 K by laser photolysis-resonance fluorescence. The obtained kinetic data were used to derive the following Arrhenius expressions: k1=(3.55+/-0.22)×10-10 exp[-(559+/-40)/T], k2=(5.25+/-0.52)×10-11 exp[(190+/-68)/T], k3=(2.63+/-0.21)×10-11 exp[(525+/-51)/T], k4=(3.12+/-0.31)×10-11 exp[(548+/-65)/T], and k5=(3.97+/-0.48)×10-11 exp[(533+/-77)/T] (in units of cm3 molecule-1 s-1). To our knowledge, these are the first absolute kinetic data reported for 1-butanol and 1-pentanol and also the first kinetic study as a function of temperature for these two compounds. Results, mechanism, and tropospheric implications are discussed and compared with the reported reactivity with OH radicals. Moreover, a theoretical insight into the mechanisms of these reactions has also been pursued through ab initio Möller-Plesset second-order perturbation treatment calculations with 6-311G** basis sets. Optimized geometries and vibrational frequencies have been obtained for transition states and molecular complexes appearing along the different reaction pathways. Furthermore, molecular energies have been calculated at quadratic configuration interaction with single, double, and triple excitations level in order to get an estimation of the activation energies.

Garzón, Andrés; Cuevas, Carlos A.; Ceacero, Antonio A.; Notario, Alberto; Albaladejo, José; Fernández-Gómez, Manuel

2006-09-01

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

Kinetics of diamond-silicon reaction under high pressure-high temperature conditions  

Microsoft Academic Search

In this dissertation work, the kinetics of the reaction between diamond and silicon at high pressure-high temperature conditions was investigated. This study was motivated by the extremely limited amount of information related to the kinetics of the reaction in diamond-silicon carbide composites formation. It was found that the reaction between diamond and melted silicon and the subsequent silicon carbide formation

Cristian Pantea

2004-01-01

283

Stepwise kinetic equilibrium models of quantitative polymerase chain reaction  

PubMed Central

Background Numerous models for use in interpreting quantitative PCR (qPCR) data are present in recent literature. The most commonly used models assume the amplification in qPCR is exponential and fit an exponential model with a constant rate of increase to a select part of the curve. Kinetic theory may be used to model the annealing phase and does not assume constant efficiency of amplification. Mechanistic models describing the annealing phase with kinetic theory offer the most potential for accurate interpretation of qPCR data. Even so, they have not been thoroughly investigated and are rarely used for interpretation of qPCR data. New results for kinetic modeling of qPCR are presented. Results Two models are presented in which the efficiency of amplification is based on equilibrium solutions for the annealing phase of the qPCR process. Model 1 assumes annealing of complementary targets strands and annealing of target and primers are both reversible reactions and reach a dynamic equilibrium. Model 2 assumes all annealing reactions are nonreversible and equilibrium is static. Both models include the effect of primer concentration during the annealing phase. Analytic formulae are given for the equilibrium values of all single and double stranded molecules at the end of the annealing step. The equilibrium values are then used in a stepwise method to describe the whole qPCR process. Rate constants of kinetic models are the same for solutions that are identical except for possibly having different initial target concentrations. Analysis of qPCR curves from such solutions are thus analyzed by simultaneous non-linear curve fitting with the same rate constant values applying to all curves and each curve having a unique value for initial target concentration. The models were fit to two data sets for which the true initial target concentrations are known. Both models give better fit to observed qPCR data than other kinetic models present in the literature. They also give better estimates of initial target concentration. Model 1 was found to be slightly more robust than model 2 giving better estimates of initial target concentration when estimation of parameters was done for qPCR curves with very different initial target concentration. Both models may be used to estimate the initial absolute concentration of target sequence when a standard curve is not available. Conclusions It is argued that the kinetic approach to modeling and interpreting quantitative PCR data has the potential to give more precise estimates of the true initial target concentrations than other methods currently used for analysis of qPCR data. The two models presented here give a unified model of the qPCR process in that they explain the shape of the qPCR curve for a wide variety of initial target concentrations.

2012-01-01

284

Second Order Catalytic Quasispecies Yields Discontinuous Mean Fitness at Error Threshold  

NASA Astrophysics Data System (ADS)

The quasispecies model describes processes related to the origin of life and viral evolutionary dynamics. We discuss how the error catastrophe that reflects the transition from localized to delocalized quasispecies population is affected by catalytic replication of different reaction orders. Specifically, we find that second order mechanisms lead to a discontinuity in the mean fitness of the population at the error threshold. This is in contrast to the behavior of the first order, autocatalytic replication mechanism considered in the standard quasispecies model. This suggests that quasispecies models with higher order replication mechanisms produce discontinuities in the mean fitness, and hence the viable population fraction as well, at the error threshold, while lower order replication mechanisms yield a continuous mean fitness function. We discuss potential implications for understanding replication in the RNA world and in virology.

Wagner, Nathaniel; Tannenbaum, Emmanuel; Ashkenasy, Gonen

2010-05-01

285

First- and second-order Fermi acceleration in thick relativistic shocks  

NASA Astrophysics Data System (ADS)

Shocks in relativistic jets are regions where cosmic ray acceleration takes place mainly via two kinds of Fermi acceleration mechanism: The first-order and the second-order Fermi acceleration. Moreover, the back-reaction of accelerated particles in astrophysical shock fronts leads to the formation of a precursor (thick) shock with a length scale which can correspond to the diffusive scale of the energetic particles. Our scope here is to investigate the properties of particle shock acceleration, using test-particle simulation studies, assuming stochastic and diffusive acceleration mechanisms, in thick parallel and perpendicular relativistic shocks. The role of the above parameters in the acceleration efficiency and generated cosmic ray spectra, is important to understanding further the favourable subject of the cosmic ray shock acceleration in relativistic astrophysical environments.

Meli, A.

2012-12-01

286

Remarks on the construction of a second-order closure description of turbulent reacting flows  

NASA Technical Reports Server (NTRS)

In this paper an attempt is made to illustrate how second-order closure techniques might be used to make detailed calculations of turbulent diffusion flames. Two of the problems of closure that are peculiar to turbulent chemically reacting flows are discussed in some detail. These are the problem of computing in a consistent way all the correlations of fluctuations in scalar quantities needed for closure and the problem of the generation of turbulence by chemical reactions. Tentative closure models are put forward for both of these problems. Although the closure model for fluctuations in scalar quantities can, to a certain extent, be checked against idealized numerical examples for which exact solutions are known, the validity of both the closure models proposed here must, in the end, be determined by detailed comparison of computed results with experimental data.

DONALDSON C. DUP.; Varma, A. K.

1976-01-01

287

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

2013-09-01

288

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

289

Biogeochemical Reaction Kinetics Associated With Uranium Bioremediation at Multiple Scales  

NASA Astrophysics Data System (ADS)

Effective bioremediation requires understanding and quantification of biogeochemical reaction kinetics in natural porous media. Although the intrinsic rates of biogeochemical reactions have been measured in well-mixed laboratory systems, extrapolation of those rates to natural porous media remains challenging, partly due to the fact that natural systems are rarely well-mixed. In this work, we examine the reaction kinetics of iron and sulfate reductions involved in a bioremediation field experiment at the Old Rifle UMTRA site in Western Colorado where acetate as an electron donor was injected into the subsurface to reduce mobile U(VI) to relatively immobile U(IV). We examine at multiple spatial scales how the biogeochemical reaction rates are affected by the extent of mixing and how this in turn affects the efficiency of bioremediation and the evolution of physical and chemical properties of bioremediation sites over the long term. The rates of iron and sulfate reduction were examined at the pore scale and the field scale. At the pore scale (tens to thousands of microns), numerical experiments show that transport processes are fast enough to homogenize the concentration and that the intrinsic rate measured under well-mixed conditions can be directly used. However, at the field scale (tens of meters), dispersion/diffusion processes are not fast enough to homogenize the concentration and the local reaction rates depend on local, spatially variable concentrations. As such, the overall reaction rates at the field scale depend largely on the extent of mixing, which is controlled in large part by the physical and chemical heterogeneities present in the subsurface. Focusing on dissimilatory Fe reduction and assuming the same average flow velocity and the same average total solid iron content, we compare three different cases: 1) a homogeneous permeability distribution with a homogeneous Fe distribution; 2) a heterogeneous permeability distribution, determined from the inverse modeling of field-scale tracer breakthrough data, with a homogeneous Fe distribution; and 3) the same heterogeneous permeability distribution as in the second case, but with a heterogeneous Fe distribution based on an assumed negative correlation between permeability and iron content. Reactive transport modeling results were compared to field data to determine the overall volume-averaged reaction rates. The first case represents the largest extent of mixing and therefore leads to the largest overall Fe reduction rates, while the second and third cases, respectively, represent progressively lower extents of mixing and therefore lead to slower reduction rates. Differences in the overall Fe reduction rates result in different amounts and spatial patterns of precipitated secondary minerals. In the homogeneous case, secondary minerals precipitate evenly across the transverse distance, while in the heterogeneous cases, secondary minerals precipitate primarily where the contact between the electron donor acetate and solid iron is greatest. As such, both physical and chemical heterogeneity may dramatically affect reductions in permeability over the long term.

Li, L.; Steefel, C. I.; Kowalsky, M. B.

2007-12-01

290

Kinetics of boehmite precipitation from supersaturated sodium aluminate solutions  

Microsoft Academic Search

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

C. Skoufadis; D. Panias; I. Paspaliaris

2003-01-01

291

Reaction sequence and kinetics of uranium nitride decomposition.  

PubMed

The reaction mechanism and kinetics of the thermal decomposition of uranium dinitride/uranium sesquinitride to uranium mononitride under inert atmosphere at elevated temperature were studied. An increase in the lattice parameter of the UN(2)/alpha-U(2)N(3) phase was observed as the reaction temperature increased, corresponding to a continuous removal of nitrogen. Electron density calculations for these two compounds using XRD powder patterns of the samples utilizing charge-flipping technique were performed for the first time to visualize the decrease in nitrogen level as a function of temperature. Complete decomposition of UN(2) into alpha-U(2)N(3) at 675 degrees C and the UN formation after a partial decomposition of alpha-U(2)N(3) at 975 degrees C were also identified in this study. The activation energy for the decomposition of the UN(2)/alpha-U(2)N(3) phase into UN, 423.8 +/- 0.3 kJ/mol (101.3 kcal/mol), was determined under an inert argon atmosphere and is reported here experimentally for the first time. PMID:19845318

Silva, G W Chinthaka; Yeamans, Charles B; Sattelberger, Alfred P; Hartmann, Thomas; Cerefice, Gary S; Czerwinski, Kenneth R

2009-11-16

292

Control of DNA replication by anomalous reaction-diffusion kinetics  

NASA Astrophysics Data System (ADS)

DNA replication requires two distinct processes: the initiation of pre-licensed replication origins and the propagation of replication forks away from the fired origins. Experiments indicate that these origins are triggered over the whole genome at a rate I(t) (the number of initiations per unreplicated length per time) that increases throughout most of the synthesis (S) phase, before rapidly decreasing to zero at the end of the replication process. We propose a simple model for the control of DNA replication in which the rate of initiation of replication origins is controlled by the interaction with a population of rate-limiting proteins. We find the time set by reaction-diffusion kinetics for such proteins to find, bind to, and trigger a potential origin. Analyzing data from Xenopus frog embryos, we find that the initiation rate is reaction limited until nearly the end of replication, when it becomes diffusion limited. Initiation of origins and hence I(t) is suppressed when the diffusion-limited search time dominates. We find that, in order to fit the experimental data, the interaction between DNA and the rate-limiting protein must be subdiffusive.

Gauthier, Michel; Bechhoefer, John

2009-05-01

293

Stereochemical lability of azatitanacyclopropanes: dynamic kinetic resolution in reductive cross-coupling reactions with allylic alcohols.  

PubMed

Azatitanacyclopropanes (titanaziridines) are shown to be stereochemically labile under reaction conditions for reductive cross-coupling. This fundamental property has been employed to realize highly selective asymmetric coupling reactions with allylic alcohols that proceed by dynamic kinetic resolution. PMID:23963189

Yang, Dexi; Micalizio, Glenn C

2013-10-01

294

Iteration Scheme for Implicit Calculations of Kinetic and Equilibrium Chemical Reactions in Fluid Dynamics  

NASA Astrophysics Data System (ADS)

An iteration scheme for the implicit treatment of equilibrium chemical reactions in partial equilibrium flow has previously been described (J. D. Ramshaw and A. A. Amsden, J. Comput. Phys.59, 484 (1985); 71 , 224 (1987)). Here we generalize this scheme to kinetic reactions as well as equilibrium reactions. This extends the applicability of the scheme to problems with kinetic reactions that are fast in some regions of the flow field but slow in others. The resulting scheme thereby provides a single unified framework for the implicit treatment of an arbitrary number of coupled equilibrium and kinetic reactions in chemically reacting fluid flow.

Ramshaw, J. D.; Chang, C. H.

1995-02-01

295

Iteration scheme for implicit calculations of kinetic and equilibrium chemical reactions in fluid dynamics  

SciTech Connect

An iteration scheme for the implicit treatment of equilibrium chemical reactions in partial equilibrium flow has previously been described. Here we generalize this scheme to kinetic reactions as well as equilibrium reactions. This extends the applicability of the scheme to problems with kinetic reactions that are fast in regions of the flow field but slow in others. The resulting scheme thereby provides a single unified framework for the implicit treatment of an arbitrary number of coupled equilibrium and kinetic reactions in chemically reacting fluid flow. 10 refs., 2 figs.

Ramshaw, J.D.; Chang, C.H. [Idaho National Engineering Lab., ID (United States)] [Idaho National Engineering Lab., ID (United States)

1995-02-01

296

Thin film reaction kinetics of niobium/aluminum multilayers  

SciTech Connect

Phase formation kinetics in Nb/Al multilayered thin films having overall compositions of 25, 33, 50, and 75 at. % Al have been investigated using scanning calorimetry, x-ray diffraction, and cross-sectional transmission electron microscopy. The first phase to form upon annealing the Nb/Al layered structure of all samples is the NbAl{sub 3} intermetallic. Calorimetry clearly identifies the NbAl{sub 3} formation to be a two-stage process. The first stage is the formation of a planar layer by nucleation and growth to coalescence while the second stage is the thickening of the planar layer. The large amount of heat released (and hence large volume fraction of NbAl{sub 3} formed) during the first reaction stage is consistent with heterogeneous nucleation at well-isolated sites in the Nb/Al interface. This is surprising in light of the large thermodynamic driving force expected for nucleation and suggests that the local nonequilibrium nature of the Nb/Al interface greatly reduces the driving force for nucleation. The next phase observed in samples of 25 and 33 at. % Al is the A15 superconducting phase, Nb{sub 3}Al. The Nb{sub 3}Al growth completes a first reaction stage similar to the NbAl{sub 3}, but the subsequent thickening reaction stage is not observed without simultaneous Nb{sub 2}Al growth. The high interface velocities derived from the calorimetry for formation of both NbAl{sub 3} and the A15 Nb{sub 3}Al indicate that atomic transport must be by grain boundary diffusion.

Coffey, K.R. (IBM, Storage Systems Product Division, 5600 Cottle Road, San Jose, California 95193 (United States)); Barmak, K. (IBM, General Technology Division, East Fishkill Facility, Hopewell Junction, New York 12533 (United States)); Rudman, D.A. (National Institute of Science and Technology, 325 Broadway, Boulder, Colorado 80303 (United States)); Foner, S. (Francis Bitter National Magnet Laboratory and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States))

1992-08-15

297

General chemical kinetics computer program for static and flow reactions, with application to combustion and shock-tube kinetics  

NASA Technical Reports Server (NTRS)

A general chemical kinetics program is described for complex, homogeneous ideal-gas reactions in any chemical system. Its main features are flexibility and convenience in treating many different reaction conditions. The program solves numerically the differential equations describing complex reaction in either a static system or one-dimensional inviscid flow. Applications include ignition and combustion, shock wave reactions, and general reactions in a flowing or static system. An implicit numerical solution method is used which works efficiently for the extreme conditions of a very slow or a very fast reaction. The theory is described, and the computer program and users' manual are included.

Bittker, D. A.; Scullin, V. J.

1972-01-01

298

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

299

ASYMPTOTIC STABILITY FOR SECOND-ORDER DIFFERENTIAL EQUATIONS WITH COMPLEX COEFFICIENTS  

Microsoft Academic Search

We prove asymptotical stability and instability results for a gen- eral second-order dierential equations with complex-valued functions as coef- ficients. To prove asymptotic stability of linear second-order dierential equa- tions, we use the technique of asymptotic representations of solutions and error estimates. For nonlinear second-order dierential equations, we extend the as- ymptotic stability theorem of Pucci and Serrin to the

GRO R. HOVHANNISYAN

2004-01-01

300

Linearizability criteria for systems of two second-order differential equations by complex methods  

Microsoft Academic Search

Lie’s linearizability criteria for scalar second-order ordinary differential equations had been extended to systems of second-order ordinary differential equations by using geometric methods. These methods not only yield the linearizing transformations but also the solutions of the nonlinear equations. Here, complex methods for a scalar ordinary differential equation are used for linearizing systems of two second-order ordinary and partial differential

S. Ali; F. M. Mahomed; Asghar Qadir

2011-01-01

301

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

302

Kinetics for coarsening co-controlled by diffusion and a reversible interface reaction  

Microsoft Academic Search

The kinetics for coarsening co-controlled by diffusion and a reversible interface reaction were investigated theoretically. Equations for the particle size distributions and particle growth were deduced, through which the effects of the competition, in terms of the rate-controlling strength, between diffusion and the interface reaction on the kinetics behaviors were revealed. When the coarsening was mainly controlled by the interface

Weian Sun

2007-01-01

303

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

304

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

PubMed

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

Lee, J; Murphy, C L

1975-05-20

305

Kinetic studies of sulfation reactions of mineral materials in the coal ash  

Microsoft Academic Search

The sulfation reaction kinetics are studied for CaO, MgO, CaO-FeâOâ, CaO-NaâSOâ, CaO-KâSOâ, and CaO-MgO. It is determined that only iron ions have a catalysis effect on the calcium sulfation reaction. The collected kinetic data are correlated for this catalysis effect of FeâOâ. The correlated kinetics are then applied in two mathematical models, to predict the sulfur retention rate in the

Yeh

1986-01-01

306

CHLORINE DEMAND AND TTHM FORMATION KINETICS: A SECOND-ORDER MODEL  

EPA Science Inventory

Much effort has been expended in attempting to develop mathematical models for chlorine demand in water and wastewater. Most of these efforts have centered around the use of first-order functions or modifications of first-order functions. Recently there has also been interest i...

307

Constraining kinetic rates of mineral reactions using reactive transport models  

NASA Astrophysics Data System (ADS)

We use a reactive transport model to better understand results of experiments to obtain kinetic rates of mineral reactions in closed systems. Closed system experiments pose special challenges in that secondary minerals may form that modify the fluid composition evolution and may grow on the dissolving minerals thus armoring the surface. Even so, such closed system experiments provide critical data for what minerals would actually form in field applications and how coupled dissolution and precipitation mineral reactions are strongly linked. Comparing to experimental observations can test the reactive transport model, and the experimental observations can be better understood by comparing the results to the modeling. We apply a 0D end member of the model to understand the dissolution of single crystals of forsterite in a variety of settings (low pH, high pH, or NaHCO3 initial fluids, at 100 C and 1 bar, or 200 C and 150 bar). Depending on the initial conditions, we observe the precipitation of talc, brucite, amorphous silica, chrysotile, or magnesite, in various combinations. We compare simulation results to fluid compositions and the presence of secondary minerals experimentally sampled at various times. Insight from the simulations helped create an inverse model to extract the rates of forsterite dissolution and to create a simple forward model useful for exploring the influence of system size, secondary mineral surface areas, etc. Our reactive transport model allows secondary minerals to armor the forsterite surface, which can strongly decrease the dissolution rate as the system evolves. Tuning our model with experimentally derived rates and assuring relevant processes are included so as to reproduce experimental observations is necessary before upscaling to heterogeneous field conditions. The reactive transport model will be used for field-scale sequestration simulations and coupled with a geomechanical model that includes the influence of deformation.

Bolton, E. W.; Wang, Z.; Ague, J.; Bercovici, D.; Cai, Z.; Karato, S.; Oristaglio, M. L.; Qiu, L.

2012-12-01

308

Reaction kinetics of stover liquefaction in recycled stover polyol.  

PubMed

The purpose of this research was to study the kinetics of liquefaction of crop residues. The liquefaction of corn stover in the presence of ethylene glycol and ethylene carbonate using sulfuric acid as a catalyst was studied. It was found that the liquefaction yield was a function of ratio of solvent to corn stover, temperature, residence time, and amount of catalyst. Liquefaction of corn stover was conducted over a range of conditions encompassing residence times of 0-2.5 h, temperatures of 150-170 degrees C, sulfuric acid concentrations of 2-4% (w/w), and liquefaction reagent/corn stover ratio of 1-3. The liquefaction rate constants for individual sets of conditions were examined using a first-order reaction model. Rate constant increased with the increasing of liquefaction temperature, catalyst content, and liquefaction reagent/corn stover ratio. Reuse of liquefied biomass as liquefying agent was also evaluated. When using recycled liquefied biomass instead of fresh liquefaction reagent, the conversion is reduced. It appeared that 82% of liquefaction yield was achieved after two times of reuse. PMID:16915669

Yu, Fei; Ruan, Roger; Lin, Xiangyang; Liu, Yuhuan; Fu, Rong; Li, Yuhong; Chen, Paul; Gao, Yinyu

2006-01-01

309

Reaction of Phenyl Radical with O2: Thermodynamic Properties, Important Reaction Paths and Kinetics  

SciTech Connect

The Phenyl + O{sub 2} association results in a chemically activated phenyl-peroxy radical which can dissociate to phenoxy radical + O, undergo intramolecular addition of the peroxy radical to several unsaturated carbon sites or react back to phenyl + O{sub 2}. The intramolecular addition channels further react through several paths to ring opening (unsaturated + carbonyl moieties) as well as cyclopentadieny radical + CO{sub 2}. Enthalpy ({Delta}H{sub f(298)}{sup o}), Entropy (S{sub 298}), and heat capacities Cp(T) for species in the decomposition of the ring are evaluated using density functional and ab initio calculations and by comparisons to vinyl + O{sub 2} data of Mebel et al, and phenyl + O{sub 2} data of Hadad et al. Isodesmic reaction analysis is used to estimate enthalpy values of the intermediates and well depths of the adducts. High Pressure limit kinetic parameters are obtained from the calculation results using canonical Transition State Theory. Quantum RRK analysis is utilized to obtain k(E) and modified strong collision or master equation analysis is used for evaluation of pressure fall-off in this complex bimolecular, chemical activation, reaction system. Uncertainty in key barriers is discussed, resulting variations in important reaction product ratios are illustrated, and changes in these branching ratios are evaluated with a detailed reaction mechanism.

Bozzelli, J; Sebbar, N; Pitz, W; Bockhorn, H

2001-04-12

310

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

311

Operator Factorization and the Solution of Second-Order Linear Ordinary Differential Equations  

ERIC Educational Resources Information Center

The theory and application of second-order linear ordinary differential equations is reviewed from the standpoint of the operator factorization approach to the solution of ordinary differential equations (ODE). Using the operator factorization approach, the general second-order linear ODE is solved, exactly, in quadratures and the resulting…

Robin, W.

2007-01-01

312

Kantor's second-order Doppler-effect experiment treated by the absolute space-time theory  

Microsoft Academic Search

It is shown that the second-order Doppler-effect experiment proposed recently by Kantor must give the same result within an accuracy of second order in nu\\/c, when treated by the nonrelativistic and relativistic mathematical apparatus, in contradiction to Kantor's conclusions.

S. Marinov

1973-01-01

313

Teacher's Corner: Testing Measurement Invariance of Second-Order Factor Models  

ERIC Educational Resources Information Center

We illustrate testing measurement invariance in a second-order factor model using a quality of life dataset (n = 924). Measurement invariance was tested across 2 groups at a set of hierarchically structured levels: (a) configural invariance, (b) first-order factor loadings, (c) second-order factor loadings, (d) intercepts of measured variables,…

Chen, Fang Fang; Sousa, Karen H.; West, Stephen G.

2005-01-01

314

Second-order perturbation energy corrections for the optimized effective potential for atoms  

SciTech Connect

The second-order perturbation corrections to the energy computed using the optimized effective potential (OEP) arising from single-particle excitations are computed explicitly for a number of closed-shell atoms. It is found that almost all of the difference between the Hartree-Fock energy and the OEP energy is recovered in second order.

Talman, James D. [Department of Applied Mathematics and Centre for Chemical Physics, University of Western Ontario, London, Ontario, N6A 5B7 (Canada)

2005-10-15

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

Simplifying Second-Order Belief Attribution: What Facilitates Children's Performance on Measures of Conceptual Understanding?  

ERIC Educational Resources Information Center

This study investigated how 4- to 7-year-old children's second-order belief attribution might be facilitated by either reducing information processing or varying the sequence of task questions. In Experiment 1, compared with Perner and Wimmer's (1985) original second-order false-belief task, a new task with reduced information-processing demands…

Coull, Greig J.; Leekam, Susan R.; Bennett, Mark

2006-01-01

317

Oscillations of a class of second-order nonlinear delay differential equations with variable sign coefficients  

Microsoft Academic Search

In this paper, we study the oscillations of a kind of second-order nonlinear delay differential equations with variable sign oscillation factors. Three sufficient conditions about the equation are obtained, which generalize the present oscillation results of second-order nonlinear differential equations and delay differential equations with invariable sign coefficients.

Jietao Zou; Jianguo Zhang; Xiaoyou Han; Hongxia Zhu

2007-01-01

318

Explanation of Second-Order Asymptotic Theory Via Information Spectrum Method  

NASA Astrophysics Data System (ADS)

We explain second-order asymptotic theory via the information spectrum method. From a unified viewpoint based on the generality of the information spectrum method, we consider second-order asymptotic theory for use in fixed-length data compression, uniform random number generation, and channel coding. Additionally, we discuss its application to quantum cryptography, folklore in source coding, and security analysis.

Hayashi, Masahito

319

A New Second Order Mimetic Finite Difference Scheme to Tackle Boundary Layers-Like Problems  

Microsoft Academic Search

As part of an effort to create a discrete analog of vector and tensor calculus, that could be used to accurately discretize continuum models of physical and engineering problems, we'll be presenting a new second order conservative finite difference discretization scheme which attains second order accuracy in the whole computational domain, including the boundaries. Though the scheme could be derived

S. Rojas; J. M. Guevara-Jordan

2009-01-01

320

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

321

Kinetics of the reaction of CO2 with aqueous potassium salt of taurine and glycine  

Microsoft Academic Search

The kinetics of the reaction between CO2 and aqueous potassium salts of taurine and glycine was measured at 295 K in a stirred-cell reactor with a flat gas-liquid interface. For aqueous potassium taurate solutions, the temperature effect on the reaction kinetics was measured at 285 and 305 K. Unlike aqueous primary alkanolamines, the partial reaction order in amino acid salt

P. S. Kumar; J. A. Hogendoorn; G. F. Versteeg; P. H. M. Feron

2003-01-01

322

Effect of second-order exchange in electron-hydrogen scattering  

NASA Astrophysics Data System (ADS)

The electron-hydrogen scattering problem has been a nemesis to theoretical atomic physicists due to the fact that even the most sophisticated of theoretical calculations, both perturbative and nonperturbative, do not agree with experiment. The current opinion is that the perturbative approach cannot be used for this problem since recent second-order calculations are not in agreement with the experimental data and higher-order calculations are deemed impractical. However, these second-order calculations neglected second-order exchange. We have now added exchange to the second-order calculation and have found that the primary source of disagreement between experiment and theory for intermediate energies is attributable not to higher-order terms but to second-order exchange.

Madison, D. H.; Bray, I.; McCarthy, I.

1990-05-01

323

A Comprehensive Chemical Kinetic Reaction Mechanism for Oxidation and Pyrolysis of Propane and Propene  

Microsoft Academic Search

Abstract—A detailed chemical kinetic reaction mechanism is developed to describe the oxidation and pyrolysis of propane and propene. The mechanism consists of 163 elementary reactions among 4l chemical species. New rate expressions are developed for a number of reactions of propane, propene, and intermediate hydrocarbon species with radicals including H, 0, and OH. The mechanism is tested by comparisons between

CHARLES K. WESTBROOK; WILLIAM J. PITZ

1984-01-01

324

Kinetic study of coal char hydrogasification: rapid initial reaction  

Microsoft Academic Search

The coal char hydrogasification reaction may be regarded as two simultaneous reactions differing considerably in their rates. The rate of coal hydrogasification, particularly that for the initial rapid reaction, was studied. The initial reaction rates in semiflow tests were analyzed and found to be proportional to the amount of unreacted carbon remaining in the particles as well as the effective

C. Y. Wen; Jack Huebler

1965-01-01

325

Oxidation of microcystins by permanganate: reaction kinetics and implications for water treatment.  

PubMed

A few genera of cyanobacteria produce toxins which contaminate drinking water resources. Microcystins (MC), widely reported cyanotoxins, cause acute and chronic toxicity effects in living beings including humans and warrant removal from drinking water. In the present study, unknown second-order rate constants for the reactions of microcystin-LR (MC-LR), -RR and -YR with potassium permanganate were determined at pH 6.2-8.2 and temperature 10-25 degrees C. The reaction of permanganate with MCs is second-order overall and first-order with respect to both permanganate and toxin. The second-order rate constant for the reaction of MC-LR with permanganate at pH 7 and 20 degrees C was 357.2+/-17.5M(-1)s(-1). The influence of pH on the oxidation process was not appreciable and the activation energy was 28.8 kJ mol(-1). Slightly higher reactivity with permanganate was found for MC-RR (418.0M(-1)s(-1)) and MC-YR (405.9M(-1)s(-1)). According to the results obtained, permanganate likely attacks the Adda moiety of the MC molecule. The oxidation of MCs in a natural surface water was also investigated. A permanganate dose of 1-1.25mgL(-1) was enough to reduce MCs concentration below the guideline value of 1microgL(-1). Permanganate oxidation is therefore a feasible option for microcystin removal during preoxidation processes. However, the oxidant dose must be carefully optimized in order to remove extracellular MCs without causing cell lysis (due to chemical stress) and further release of MCs. PMID:17097716

Rodríguez, Eva; Majado, María E; Meriluoto, Jussi; Acero, Juan L

2007-01-01

326

Second-order solution for determining density and velocity fields of galaxies  

NASA Technical Reports Server (NTRS)

In this Letter, I use second-order Lagrangian perturbation theory to calculate an analytical expression relating density to velocity in a gravitating system. This solution can be used to compare peculiar velocity field measurements with observations of large-scale structure. The predictions of both linear theory and second-order theory are compared with the results of N-body simulations. While linear theory systematically overestimates the velocity flows in high-density regions, the second-order corrections calculated herein remove this systematic error.

Gramann, Mirt

1993-01-01

327

Constraints on the second order transport coefficients of an uncharged fluid  

NASA Astrophysics Data System (ADS)

In this note we have tried to determine how the existence of a local entropy current with non-negative divergence constrains the second order transport coefficients of an uncharged fluid, following the procedure described in [1]. Just on symmetry ground the stress tensor of an uncharged fluid can have 15 transport coefficients at second order in derivative expansion. The condition of entropy-increase gives five relations among these 15 coefficients. So finally the relativistic stress tensor of an uncharged fluid can have 10 independent transport coefficients at second order.

Bhattacharyya, Sayantani

2012-07-01

328

First and second order approximations to stage numbers in multicomponent enrichment cascades  

SciTech Connect

This paper describes closed form, Taylor series approximations to the number product stages in a multicomponent enrichment cascade. Such closed form approximations are required when a symbolic, rather than a numeric, algorithm is used to compute the optimal cascade state. Both first and second order approximations were implemented. The first order solution was found to be grossly incorrect, having the wrong functional form over the entire domain. On the other hand, the second order solution shows excellent agreement with the 'true' solution over the domain of interest. An implementation of the symbolic, second order solver is available in the free and open source PyNE library. (authors)

Scopatz, A. [University of Chicago, 5754 S. Ellis Ave, Chicago, IL, 60637 (United States)] [University of Chicago, 5754 S. Ellis Ave, Chicago, IL, 60637 (United States)

2013-07-01

329

Orientation-selective adaptation to first- and second-order patterns in human visual cortex  

PubMed Central

Second-order textures – patterns that cannot be detected by mechanisms sensitive only to luminance changes – are ubiquitous in visual scenes, but the neuronal mechanisms mediating perception of such stimuli are not well understood. We used an adaptation protocol to measure neural activity in the human brain selective for the orientation of second-order textures. FMRI responses were measured in three subjects to presentations of first- and second-order probe gratings after adapting to a high-contrast first- or second-order grating that was either parallel or orthogonal to the probe gratings. First-order (LM) stimuli were generated by modulating the stimulus luminance. Second-order stimuli were generated by modulating the contrast (CM) or orientation (OM) of a first-order carrier. We used four combinations of adapter and probe stimuli: LM:LM, CM:CM, OM:OM, and LM:OM. The fourth condition tested for cross-modal adaptation with first-order adapter and second-order probe stimuli. Attention was diverted from the stimulus by a demanding task at fixation. Both first- and second-order stimuli elicited orientation-selective adaptation in multiple cortical visual areas, including V1, V2, V3, V3A/B, a newly identified visual area anterior to dorsal V3 which we have termed LO1, hV4, and VO1. For first-order stimuli (condition LM:LM), the adaptation was no larger in extrastriate areas than in V1, implying that the orientation-selective first-order (luminance) adaptation originated in V1. For second-order stimuli (conditions CM:CM and OM:OM), the magnitude of adaptation, relative to the absolute response magnitude, was significantly larger in VO1 (and for condition CM:CM, also in V3A/B and LO1) than in V1, suggesting that second-order stimulus orientation was extracted by additional processing after V1. There was little difference in the amplitude of adaptation between the second-order conditions. No consistent effect of adaptation was found in the cross-modal condition LM:OM, in agreement with psychophysical evidence for weak interactions between first- and second-order stimuli and computational models of separate mechanisms for first- and second-order visual processing.

Larsson, Jonas; Landy, Michael S.; Heeger, David J.

2006-01-01

330

Systematic study of exact solutions in second-order conformal hydrodynamics  

NASA Astrophysics Data System (ADS)

In this paper we present the details of our previous work on exact solutions in second-order conformal hydrodynamics together with a number of new solutions found by mapping Minkowski space onto various curved space-times, such as anti-de Sitter space and hyperbolic space. We analytically show how the solutions of ideal hydrodynamics are modified by the second-order effects including vorticity. We also find novel boost-invariant exact solutions which exist only in second-order hydrodynamics and have an unusual dependence on the proper time.

Hatta, Yoshitaka; Noronha, Jorge; Xiao, Bo-Wen

2014-06-01

331

The Primal-Dual Second-Order Cone Approximations Algorithm for Symmetric Cone Programming  

Microsoft Academic Search

Given any open convex cone K, a logarithmically homogeneous, self-concordant barrier for K, and any positive real number r\\u000a \\u000a \\u000a , a second-order cone \\u000a \\u000a containing K. We show that K is the interior of the intersection of the second-order cones \\u000a \\u000a , as x ranges over all directions in K. Using these second-order cones as approximations to cones of symmetric, positive definite

Chek Beng Chua

2007-01-01

332

Observation of a second order intrinsic depolarizing resonance with a partial Siberian snake  

SciTech Connect

A recent experiment at the Indiana University Cyclotron Facility (IUCF) Cooler Ring found a second order intrinsic depolarizing resonance. The authors injected a spin-polarized beam at 160 MeV and studied both first and second order intrinsic resonances. With a 20% partial Siberian snake they observed clear evidence of a second order depolarizing resonance. This resonance, as expected, is much weaker than the first order intrinsic resonance also studied. Similar experiments with 0% and 10% partial Siberian snakes did not find this resonance.

Crandell, D.A.; Alexeeva, L.V.; Anferov, V.A. [Univ. of Michigan, Ann Arbor, MI (United States)] [and others

1995-04-01

333

Second-order focusing parallel electron energy magnetic sector analyzer designs  

NASA Astrophysics Data System (ADS)

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 with a larger magnet sector unit is also presented in which, the field strength varies relatively slowly. Simulations predict that using a combination of such magnetic sector units, focusing properties better than second order can be achieved for most of the detected energy range.

Khursheed, Anjam

2011-07-01

334

First and Second Order Necessary Conditions for Stochastic Optimal Control Problems  

SciTech Connect

In this work we consider a stochastic optimal control problem with either convex control constraints or finitely many equality and inequality constraints over the final state. Using the variational approach, we are able to obtain first and second order expansions for the state and cost function, around a local minimum. This fact allows us to prove general first order necessary condition and, under a geometrical assumption over the constraint set, second order necessary conditions are also established. We end by giving second order optimality conditions for problems with constraints on expectations of the final state.

Bonnans, J. Frederic, E-mail: Frederic.Bonnans@inria.fr [Ecole Polytechnique, INRIA-Saclay and CMAP (France); Silva, Francisco J., E-mail: fsilva@mat.uniroma1.it [Dipartimento di Matematica Guido Castelnuovo (Italy)

2012-06-15

335

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

336

Linear free energy relationship and deuterium kinetic isotope effect observed on phospho and thiophosphoryl transfer reactions in some organophosphorous compounds  

NASA Astrophysics Data System (ADS)

Tetracoordinated organophosphorous compounds were synthesized, characterized and nucleophilic substitution reaction were investigated by varying substituents around phosphorous centre or in nucleophile considering its utility in biological and environmental system. The reactivity is expressed in terms of second-order rate constant, k2 and measured conductometrically. Linear Free Energy Relationship (LFER) tools mainly Hammett (?), Brönsted (?) LFER coefficients and deuterium kinetic isotope effects (KIEs) being determined for the pyridinolysis of 4 – chlorophenyl 4 – methoxy phenyl chlorophosphate, 1 in acetonitrile at 5.0 °C. The experimental data's were compared with those of structurally similar organophosphorous compounds reported earlier in quest for the mechanistic information. Nice linear correlation being found for Hammett (logk2 vs ?x), having negative value of the ?X = ?5.85 and Brönsted (logk2 vs pKa(x)) plots having large positive value for ?X = 1.18 for 1 can be interpreted as SN2 process with greater extent of bond formation in transition state (TS) of 1. The observed kH/kD values of 1 is 1.00 ± 0.05 and net KIE, 1.32 suggests the primary KIE and indicates frontside nucleophilic attack through the partial deprotonation of pyridine occurs by the hydrogen bonding in the rate-determining step.

Lumbiny, B. J.; Hui, Z.; Islam, M. A.; Quader, M. A.; Rahman, M.

2014-04-01

337

Submesoscale process studies using a new variant of second order closure  

NASA Astrophysics Data System (ADS)

Ageostrophic baroclinic instabilities of lateral density gradients in the mixed layer evolve into eddies of O(1-10km) horizontal scale, characterized by O(1) Rossby number and O(1) Richardson number. This work focuses on submesoscale process studies using a new variant of second order closure for vertical mixing. This new approach suggested by Venayagamoorthy and Stretch (2010) uses the original k-epsilon model for the turbulent viscosity, but poses a turbulent Prandtl number model in an irreversible mixing framework to derive the diffusivity, providing a less heuristic parameterization compared to previous models. This new variant agrees well with previous closure models for idealized studies of entrainment mixing with and without a diurnal cycle. Tests of this model with observational datasets show high near-inertial shear below the mixed-layer and absence of shear within the mixed-layer, in agreement with earlier studies. This variant has subsequently been implemented in a three-dimensional submesoscale resolving process model. Model simulations initialized with an idealized wind forced frontal domain show the evolution of submesoscale eddies, restratifying buoyancy flux and enhanced dissipation at the front. Zonally averaged eddy kinetic energy budget at the frontal region shows a balance between the ageostrophic shear produced by wind forcing, and subgrid dissipation. The magnitude of near-surface subgrid dissipation is consistent with Monin-Obukhov scaling, as with a previous anisotropic Smagorinsky model. In June 2011 a large set of observations were made as part of the Directed Research Initiative of Scalable Lateral Mixing and Coherent Turbulence - LATMIX 2011, funded primarily by the office of Naval Research. We report on tracer simulations inspired by the LATMIX 2011 observations to help understand the mechanisms for lateral and vertical mixing.

Mukherjee, S.; Tandon, A.; Mahadevan, A.

2012-12-01

338

The making of an Alfvenic fluctuation: The resolution of a second-order analysis  

NASA Technical Reports Server (NTRS)

Ulysses observations of the high speed polar streams show that they are largely occupied by very large amplitude Alfvenic fluctuations accompanied by many rotational discontinuities. These fluctuations have a nearly constant magnetic intensity or amplitude, and the magnetic field direction per wave cycle sweeps only through a limited arc, much as a car wiperblade would do. Barnes and Hollweg (JGR, 79, 2302, 1974) suggested that this unusual waveform could arise from an obliquely propagating and linearly polarized Alfven wave of finite amplitude. From a second-order analysis, they showed that the existence of a particular solution with a constant amplitude but could not resolve the outcome of the homogeneous solution which consisted of fast waves. They suggested that Landau damping of these fast waves may be needed to get the observed waveform. We present a 1 1/2 D hybrid simulation which is fully nonlinear and correctly describes the ion kinetics for an initially monochromatic and linearly polarized Alfven wave propagating obliquely to the background magnetic field. The wave has a large amplitude and a wavelength so long that it can be considered dispersionless for simulation times. At early times, the second harmonic in density and in magnetic field transverse to the initial wave magnetic field are generated and have more power than other harmonics. Steepening is observed with a weak fast shock emerging, but no rotational discontinuity is left behind, and instead a constant amplitude and an arc-shaped waveform is made. The compressional component which develops after the shocks have dissipated is to zeroth order better described as a pure acoustic wave than as a fast wave. This might be explained by the relaxing of the Alfven wave to a state where its ponderomotive force vanishes so that the compressional component can travel almost independently of it.

Vasquez, Bernard J.; Hollweg, Joseph V.

1995-01-01

339

Hydroxyl Radical Kinetics by Kinetic Spectroscopy. V. Reactions with H2 and CO in the Range 300–500°K  

Microsoft Academic Search

The reactions of OH with H2 and CO were studied by the flash-photolysis–kinetic-spectroscopy technique over the temperature range 300–500°K. At both ends of this range it was verified that the reactions are first order in [OH] and [H2] or [CO]. The Arrhenius parameters and their 95% confidence limits, as determined from least-squares fits of the data, follow: For H2+OH?H+H2O, E

N. R. Greiner

1969-01-01

340

Exam Question Exchange: A Popular Approach to Reaction Kinetics.  

ERIC Educational Resources Information Center

Presents an undergraduate physical chemistry question and its acceptable solution. This question, presented to share exam questions with other teachers, shows the analogy between molecular kinetics and population dynamics. (HM)

Collins, Michael P. S.; Alexander, John J., Ed.

1979-01-01

341

Kinetics of Halogen Gas/Solid Reactions at Elevated Temperatures.  

National Technical Information Service (NTIS)

Using transonic continuum flow filament reactors adapted for use with dissociated fluorine the authors have successfully studied the high temperature heterogeneous kinetics of a number of important prototype fluorine/metal, semi-metal and insulator gasifi...

D. E. Rosner P. C. Nordine

1975-01-01

342

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

343

Second-Order Nonlinearity in Triangular Lattice Perforated Gold Film due to Surface Plasmas Resonance  

PubMed Central

We have studied the excitation second-order nonlinearity through a triangular lattice perforated gold film instead of square lattice in many papers. Under the excitation of surface plasmas resonance effect, the second order nonlinearity exists in the noncentrosymmetric split-ring resonators arrays. Reflection of fundamental frequency wave through a triangular lattice perforated gold film is obtained. We also described the second harmonic conversion efficiencies in the second order nonlinear optical process with the spectra. Moreover, the electric field distributions of fundamental frequency above the gold film region are calculated. The light propagation through the holes results in the enhancement of the second order nonlinearity including second harmonic generation as well as the sum (difference) frequency generation.

Chen, Xiaoshuang; Xiao, Yingyi; Zhou, Bingju; Wu, Lingxi; Liu, Xiaojuan; Gao, Yongyi; Zhan, Jie

2014-01-01

344

The Principal Eigenvalue for Linear Second Order Elliptic Equations with Natural Boundary Conditions.  

National Technical Information Service (NTIS)

This paper presents recent work on the characterization of the principal eigenvalue. A new characterization was derived of the principal eigenvalue for second order linear elliptic partial differential equations, not necessarily self-adjoint, with both na...

C. J. Holland

1978-01-01

345

Multiple Positive Solutions in the Second Order Autonomous Nonlinear Boundary Value Problems  

NASA Astrophysics Data System (ADS)

We construct the second order autonomous equations with arbitrarily large number of positive solutions satisfying homogeneous Dirichlet boundary conditions. Phase plane approach and bifurcation of solutions are the main tools.

Atslega, Svetlana; Sadyrbaev, Felix

2009-09-01

346

Effects of the Orientational Pair Correlation on Second Order Nonlinear Optical Coefficients.  

National Technical Information Service (NTIS)

The orientational order parameter associated with the second order nonlinear optical (NLO) coefficient is calculated by using a statistical mechanics method that includes the angular dependent intermolecular interaction potential. It is shown that in addi...

C. H. Wang

1992-01-01

347

Wavemaker 2.0: Simulation and Identification of Second-Order Random Waves.  

National Technical Information Service (NTIS)

WAVEMAKER is a FORTRAN subroutine to simulate random non-Gaussian ocean wave histories. It generates a first-order (Gaussian) wave process with an arbitrary power spectrum, and applies nonlinear corrections based on second- order hydrodynamics. Inputs to ...

A. K. Jha S. R. Winterstein

1996-01-01

348

Variational iteration method for solving a nonlinear system of second-order boundary value problems  

Microsoft Academic Search

The variational iteration method is introduced to solve a nonlinear system of second-order boundary value problems. Numerical results demonstrate that this method is promising and readily implemented.

Junfeng Lu

2007-01-01

349

Relationship of the Second Order Nonlinear Optical Coefficient to Bandgap in Inorganic Non-Centrosymmetric Crystals.  

National Technical Information Service (NTIS)

Second order nonlinear optical coefficient data and band gap data collected from the literature have been classified and are organized by plotting their respective values. The two dimensional plots indicate that both large bandgap - and small X(2), and sm...

A. G. Jackson M. Ohmer S. R. Leclair

1995-01-01

350

Kinetics of the carbon-oxygen reaction in molten iron  

Microsoft Academic Search

The kinetics of carbon monoxide absorption by stagnant liquid iron has been investigated over the first 10 min or so of gas-liquid\\u000a metal contact. On the basis of experiments conducted at temperatures ranging between 1580? and 1700?C (PCO= 1 atm) and carbon monoxide pressures ranging between 0.1 and 1.5 atm (at 1600†C), it was concluded that the absorption\\u000a kinetics of

M. Y. Solar; R. I. L. Guthrie

1972-01-01

351

Kinetics of elementary atom and radical reactions. Progress report, December 1, 1981-November 30, 1982  

SciTech Connect

Research projects discussed include: the branching ratio for abstraction vs. exchange in the reaction D + HCl; kinetics of O + H/sub 2/; energy storage in polyatomic molecules; and optoacoustic measurements of ir absorption and relaxation in large molecules. (GHT)

Gordon, R J

1982-08-02

352

Kinetics and thermodynamics of chemical reactions in Li/SOCl2 cells  

NASA Technical Reports Server (NTRS)

Work is described that was designed to determine the kinetic constants necessary to extrapolate kinetic data on Li/SOCl2 cells over the temperature range from 25 to 75 C. A second objective was to characterize as far as possible the chemical reactions that occur in the cells since these reactions may be important in understanding the potential hazards of these cells. The kinetics of the corrosion processes in undischarged Li/SOCl2 cells were determined and separated according to their occurrence at the anode and cathode; the effects that switching the current on and off has on the corrosion reactions was determined; and the effects of discharge state on the kinetics of the corrosion process were found. A thermodynamic analysis of the current-producing reactions in the cell was done and is included.

Hansen, Lee D.; Frank, Harvey

1987-01-01

353

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

354

Asymmetric transfer of the dynamic motion aftereffect between first- and second-order cues and among different second-order cues.  

PubMed

Recent work on motion processing has suggested a distinction between first-order cues (such as luminance modulation [LM]) and second-order cues (such as local contrast modulation [CM]). We studied interactions between moving LM, CM, and orientation modulation (OM) first comparing their spatial- and temporal-frequency sensitivity. We then tested for the transfer of the dynamic motion aftereffect (dMAE) between the three cues, matched for visibility. Observers adapted to moving, 0.5-c/deg horizontal modulations for 2 min (with 10 s top-ups). Relatively strong dMAEs were found when the adaptation and test patterns were defined by the same cue (i.e., both LM, both CM, or both OM); these effects were tuned for spatial frequency in the case of LM and CM. There was a partial transfer of the dMAE from LM to CM and OM; this transferred effect seemed to lose its tuning. The aftereffect transferred well from CM to OM and retained its tuning. There was little or no transfer from CM to LM or from OM to CM or LM. This asymmetric transfer of the dMAE between first- and second-order cues and between the second-order cues suggests some degree of separation between the mechanisms that process them. PMID:17685808

Schofield, Andrew J; Ledgeway, Timothy; Hutchinson, Claire V

2007-01-01

355

Second-order solution for determining density and velocity fields of galaxies  

Microsoft Academic Search

In this Letter, I use second-order Lagrangian perturbation theory to calculate an analytical expression relating density to velocity in a gravitating system. This solution can be used to compare peculiar velocity field measurements with observations of large-scale structure. The predictions of both linear theory and second-order theory are compared with the results of N-body simulations. While linear theory systematically overestimates

Mirt Gramann

1993-01-01

356

A New Technique for Design of Low-Profile, Second-Order, Bandpass Frequency Selective Surfaces  

Microsoft Academic Search

In this study, a new method for designing low profile frequency selective surfaces (FSS) with second-order bandpass responses is presented. The FSSs designed using this technique utilize non-resonant subwavelength constituting unit cells with unit cell dimensions and periodicities in the order of 0.15lambda0. It is demonstrated that using the proposed technique, second-order FSSs with an overall thickness of lambda0\\/30 can

Mudar Al-Joumayly; Nader Behdad

2009-01-01

357

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

358

Stable second-order finite-difference methods for linear initial-boundary-value problems  

Microsoft Academic Search

Finite-difference methods of second order at the boundary points are presented for problems with one-dimensional second-order hyperbolic and parabolic equations with mixed boundary conditions. These methods do not require information at points outside the region of consideration. The linear stability of the algorithms developed is investigated. Numerical experiments are given for illustrating the accuracy and stability of the methods. Though

K. George; Edward H. Twizell

2006-01-01

359

Investigating local network interactions underlying first- and second-order processing  

Microsoft Academic Search

We compared the spatial lateral interactions for first-order cues to those for second-order cues, and investigated spatial inter- actions between these two types of cues. We measured the apparent modulation depth of a target Gabor at fixation, in the presence and the absence of horizontally flanking Gabors. The Gabors' gratings were either added to (first-order) or multiplied with (second- order)

Dave Ellemberg; Harriet A. Allen; Robert F. Hess

2004-01-01

360

Noise reduction in Digital IIR Filters by finding optimum arrangement of second-order sections  

Microsoft Academic Search

This paper proposed a new method to obtain an optimum arrangement of the second-order sections in digital IIR filters in order to reduce the steady-state output noise variance when the model of filter is considered as the cascade connections of second-order sections. The proposed method is based on minimizing the external normalization coefficients in each section. According to the computational

M. Lankarany; H. Marvi

2008-01-01

361

Attention mechanisms for multi-location first- and second-order motion perception  

Microsoft Academic Search

We applied the external noise plus attention paradigm to study attention mechanisms involved in concurrent first-order and second-order motion perception at two spatial locations. Cued to attend to one of the locations, the observer was instructed to independently judge direction of motion of either first-order (Experiment 1) or second-order (Experiment 2) motion stimuli at both locations in every trial. Across

Zhong-Lin Lu; Christine Qi Liu; Barbara Anne Dosher

362

Second-order negative-curvature methods for box-constrained and general constrained optimization  

Microsoft Academic Search

A Nonlinear Programming algorithm that converges to second-order stationary points is introduced in this paper. The main tool\\u000a is a second-order negative-curvature method for box-constrained minimization of a certain class of functions that do not possess\\u000a continuous second derivatives. This method is used to define an Augmented Lagrangian algorithm of PHR (Powell-Hestenes-Rockafellar)\\u000a type. Convergence proofs under weak constraint qualifications are

R. Andreani; E. G. Birgin; J. M. Martínez; M. L. Schuverdt

2010-01-01

363

Consensus of second-order multi-agent dynamic systems with quantized data  

NASA Astrophysics Data System (ADS)

The consensus problem of second-order multi-agent systems with quantized link is investigated in this Letter. Some conditions are derived for the quantized consensus of the second-order multi-agent systems by the stability theory. Moreover, a result characterizing the relationship between the eigenvalues of the Laplacians matrix and the quantized consensus is obtained. Examples are given to illustrate the theoretical analysis.

Guan, Zhi-Hong; Meng, Cheng; Liao, Rui-Quan; Zhang, Ding-Xue

2012-01-01

364

Dynamical Consensus Algorithm for Second-Order Multi-Agent Systems Subjected to Communication Delay  

NASA Astrophysics Data System (ADS)

To solve the dynamical consensus problem of second-order multi-agent systems with communication delay, delay-dependent compensations are added into the normal asynchronously-coupled consensus algorithm so as to make the agents achieve a dynamical consensus. Based on frequency-domain analysis, sufficient conditions are gained for second-order multi-agent systems with communication delay under leaderless and leader-following consensus algorithms respectively. Simulation illustrates the correctness of the results.

Liu, Cheng-Lin; Liu, Fei

2013-06-01

365

Triple-Frequency Methods for Correcting Second-Order Ionospheric Delay Error in COMPASS System  

Microsoft Academic Search

A advanced triple-frequency methods for correcting higher order ionospheric refraction error were discussed in this paper since COMPASS system provides three carrier frequencies. Based on the analysis of ionospheric delay error model, the triple-frequency corrected model using COMPASS pseudo-range measurements is presented. The second-order ionospheric effect can be eliminated efficiently, and the instance illustrates the advantages and necessity of second-order

Yaqin Zhao; Xiao Fu

2010-01-01

366

Analysis of a smoothing Newton method for second-order cone complementarity problem  

Microsoft Academic Search

In this paper, we consider the second-order cone complementarity problem with P\\u000a 0-property. By introducing a smoothing parameter into the Fischer-Burmeister function, we present a smoothing Newton method\\u000a for the second-order cone complementarity problem. The proposed algorithm solves only a linear system of equations and performs\\u000a only one line search at each iteration. At the same time, the algorithm does

Xiangsong Zhang; Sanyang Liu; Zhenhua Liu

2009-01-01

367

A one-step smoothing Newton method for second-order cone programming  

Microsoft Academic Search

A new smoothing function for the second-order cone programming is given by smoothing the symmetric perturbed Fischer–Burmeister function. Based on this new function, a one-step smoothing Newton method is presented for solving the second-order cone programming. The proposed algorithm solves only one linear system of equations and performs only one line search at each iteration. This algorithm does not have

Xiaoni Chi; Sanyang Liu

2009-01-01

368

First and second-order Raman scattering from finite-size crystals of graphite  

Microsoft Academic Search

First- and second-order Raman scattering from graphite has been studied. The second-order spectra of single crystals and of highly oriented pyrolytic graphite are continuous and exhibit several well-defined bands which can be attributed to features in the density of vibrational states as determined from current lattice-dynamics models. The density of states deduced from the lattice-dynamics model of Nicklow, Wakabayashi, and

R. J. Nemanich; S. A. Solin

1979-01-01

369

B-spline method for solving linear system of second-order boundary value problems  

Microsoft Academic Search

The B-spline method is used for the numerical solution of a linear system of second-order boundary value problems. Two examples are considered for the numerical illustration and the method is also compared with the method proposed by J. Lu [J. Lu, Variational iteration method for solving a nonlinear system of second-order boundary value problems, Comput. Math. Appl. 54 (2007) 1133–1138].

Nazan Caglar; Hikmet Caglar

2009-01-01

370

Three-dimensional direct femtosecond laser writing of second-order nonlinearities in glass.  

PubMed

We demonstrate that direct femtosecond laser writing in silver-containing zinc and gallium phosphate glass enables generation of three-dimensional (3D) optical second-order nonlinear microstructures having an ?(2) value about 2.5 times that of quartz. The proposed physical model involves photo-reduction, photo-dissociation, and migration of silver species within the glass matrix. 3D laser-written second-order nonlinear structures could become a new class of nonlinear optical components. PMID:22446213

Choi, Jiyeon; Bellec, Matthieu; Royon, Arnaud; Bourhis, Kevin; Papon, Gautier; Cardinal, Thierry; Canioni, Lionel; Richardson, Martin

2012-03-15

371

Second-Order Motion Stimuli: A New Handle to Visual Motion Processing  

Microsoft Academic Search

\\u000a This chapter addresses three different aspects related to visual motion processing by means of second-order motion stimuli.\\u000a The first question discussed is whether there is a need for separate mechanisms underlying the execution of action and perception\\u000a elicited by these motion stimuli. Second, light is shed on the neuronal responses to second-order motion stimuli recorded\\u000a from the middle temporal (MT)

Uwe J. Ilg; Jan Churan

372

Second-order contributions to relativistic time delay in the parametrized post-Newtonian formalism  

SciTech Connect

Using a parametrized expansion of the solar metric to second order in the Newtonian potential, we calculate the relativistic delay in the round-trip travel time of a radar signal reflected from a nearby planet. We find that one second-order contribution to the delay is on the order of ten nanoseconds, which is comparable to the uncertainties in present-day experiments involving the Viking spacecraft.

Richter, G.W.; Matzner, R.A.

1983-12-15

373

Simplified second-order rezoning algorithm for generalized two-dimensional meshes  

SciTech Connect

A second-order conservative rezoning algorithm for generalized two-dimensional meshes has recently been described by Dukowicz and Kodis (SIAM J. Sci. Statist. Comput., in press). Here it is shown that this algorithm can be simplified by a different and more symmetrical choice of the flux vector F whose divergence is the cell density. The resulting formulation is the natural second-order generalizaton of the simplified first-order algorithm described earlier (J. Comput. Phys. 59, 193 (1985)).

Ramshaw, J.D.

1986-11-01

374

Second-order divided difference filter with application to ballistic target tracking  

Microsoft Academic Search

In this paper, we propose a second-order divided difference (DD2) filter for ballistic target tracking in the re-entry phase. The DD2 filter linearizes the nonlinear dynamic and measurement functions by using a second-order interpolation formula to approximate the derivatives of nonlinear functions. We compare the new method, extended Kalman filter (EKF) and unscented Kalman filter (UKF) using a Monte Carlo

Chunling Wu; Chongzhao Han

2008-01-01

375

A second look at second-order belief attribution in autism  

Microsoft Academic Search

Compared the performance of autistic and mentally retarded subjects, all of whom had passed a standard first-order test of false belief, on a new second-order belief task 12 autistic and 12 mentally retarded subjects, matched on verbal mental age (assessed by PPVT and a sentence comprehension subtest of the CELF) and full-scale IQ were given two trials of a second-order

Helen Tager-Flusberg; Kate Sullivan

1994-01-01

376

An alternative assessment of second-order closure models in turbulent shear flows  

NASA Technical Reports Server (NTRS)

The performance of three recently proposed second-order closure models is tested in benchmark turbulent shear flows. Both homogeneous shear flow and the log-layer of an equilibrium turbulent boundary layer are considered for this purpose. An objective analysis of the results leads to an assessment of these models that stands in contrast to that recently published by other authors. A variety of pitfalls in the formulation and testing of second-order closure models are uncovered by this analysis.

Speziale, Charles G.; Gatski, Thomas B.

1994-01-01

377

Second Order Nonlinear Evolution Inclusions II: Structure of the Solution Set  

Microsoft Academic Search

We continue the work initiated in [1] (Second order nonlinear evolution inclusions I: Existence and relaxation results. Acta Mathematics Science, English Series, 21(5), 977-966 (2005)) and study the structural properties of the solution\\u000a set of second order evolution inclusions which are defined in the analytic framework of the evolution\\u000a triple. For the convex problem we show that the solution set

Nikolaos S. Papageorgiou; Nikolaos Yannakakis

2006-01-01

378

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

379

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

380

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

381

Bench-scale Kinetics Study of Mercury Reactions in FGD Liquors  

Microsoft Academic Search

This document is the final report for Cooperative Agreement DE-FC26-04NT42314, 'Kinetics Study of Mercury Reactions in FGD Liquors'. The project was co-funded by the U.S. DOE National Energy Technology Laboratory and EPRI. The objective of the project has been to determine the mechanisms and kinetics of the aqueous reactions of mercury absorbed by wet flue gas desulfurization (FGD) systems, and

Gary M. Blythe; John Currie; David DeBerry

2008-01-01

382

A second-order modelling of a stably stratified sheared turbulence submitted to a non-vertical shear  

NASA Astrophysics Data System (ADS)

In this work, the evolution of homogeneous stably stratified turbulence submitted to a non-vertical shear is studied using second-order closure models. Two cases of turbulent flows are considered. Firstly, the case of a purely horizontal shear is considered. In this case, the evolution of the turbulence is studied according to the Richardson number Ri which is varied from 0.2 to 2.0 when other parameters are kept constant. In the second case, two components of shear are present. The turbulence is submitted to a vertical component Sv = partU1/partx3 = S cos(thgr) and a horizontal component Sh = partU1/partx2 = S sin(thgr). In this case, we study the influence of shear inclination angle thgr on the evolution of turbulence. In both cases, we are referred respectively to the recent direct numerical simulations of Jacobitz (2002 J. Turbulence 3 055) and Jacobitz and Sarkar (1998 Phys. Fluids 10 1158-68) which are, to our knowledge, the most recent results of the above-mentioned flows. Transport equations of second-order moments \\overline{u_{i} u_{j}} , \\overline{u_{i} \\rho } , \\overline{\\rho^{2}} are derived. The Shih-Lumley (SL) (Shih T H 1996 Turbulence Transition and Modeling ed H D S Henningson, A V Johansson and P H Alfredsson (Dordrecht: Kluwer); Shih and Lumley J L 1989 27th Aerospace Meeting 9-12 January, Center of Turbulent Research, Nevada) and the Craft-Launder (CL) (Craft T J and Launder B E 1989 Turbulent Shear Flow Stanford University, USA, pp 12-1-12-6 Launder B E 1996 Turbulence Transition and Modeling ed H D S Henningson, A V Johansson and P H Alfredsson (Dordrecht: Kluwer)) second-order models are retained for the pressure-strain correlation phgrij and the pressure-scalar gradient correlation phgrirgr. The corresponding models are also retained for the dissipation egr of the turbulent kinetic energy and an algebraic model is retained for the dissipation egrrgrrgr of the variance of the scalar. A fourth-order Runge-Kutta method is used for the numerical integration of the closed systems of non-linear dimensionless differential equations. A good agreement between the predictions of second-order models and values of direct numerical simulation of Jacobitz has been generally observed for the principal component of anisotropy b12. A qualitative agreement has been observed for the ratios K/E and Krgr/E of the kinetic and potential energies to the total energy E.

Bouzaiane, Mounir; Ben Abdallah, Hichem; Lili, Taieb

2004-09-01

383

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

384

Kinetically influenced terms for solute transport affected by heterogeneous and homogeneous classical reactions  

USGS Publications Warehouse

This paper extends a four-step derivation procedure, previously presented for cases of transport affected by surface reactions, to transport problems involving homogeneous reactions. Derivations for these classes of reactions are used to illustrate the manner in which mathematical differences between reaction classes are reflected in the mathematical derivation procedures required to identify kinetically influenced terms. Simulation results for a case of transport affected by a single solution phase complexation reaction and for a case of transport affected by a precipitation-dissolution reaction are used to demonstrate the nature of departures from equilibrium-controlled transport as well as the use of kinetically influenced terms in determining criteria for the applicability of the local equilibrium assumption. A final derivation for a multireaction problem demonstrates the application of the generalized procedure to a case of transport affected by reactions of several classes. -from Author

Bahr, J. M.

1990-01-01

385

Hyperspherical analysis of kinetic paths for elementary chemical reactions and their angular momentum dependence  

NASA Astrophysics Data System (ADS)

Exploiting the hyperspherical mapping of potential energy surfaces, the evolutions of minima (valley bottoms) and saddles (ridges) as a function of the kinetic radius are identified as kinetic paths for studying reaction mechanisms and dynamics. The effect of angular momentum is investigated quantum-mechanically in a hyperspherical harmonic basis and a lower bound to adiabatic evolution is established. By a classical stability analysis, the dependence of angular momentum effects on configuration is studied. Some features of kinetic paths (such as the occurrence of symmetry degeneracies and bifurcations related to elementary catastrophes) are briefly illustrated for kinetic paths on surfaces for H 3 and H 3+.

Aquilanti, Vincenzo; Cavalli, Simonetta

1987-11-01

386

High temperature chemical kinetic study of the H2-CO-CO2-NO reaction system  

NASA Technical Reports Server (NTRS)

An experimental study of the kinetics of the H2-CO-CO2-NO reaction system was made behind incident shock waves at temperatures of 2460 and 2950 K. The overall rate of the reaction was measured by monitoring radiation from the CO + O yields CO2 + h upoilon reaction. Correlation of these data with a detailed reaction mechanism showed that the high-temperature rate of the reaction N + OH yields NO + H can be described by the low-temperature (320 K) rate coefficient. Catalytic dissociation of molecular hydrogen was an important reaction under the tests conditions.

Jachimowski, C. J.

1975-01-01

387

Transport Properties of a Kinetic Model for Chemical Reactions without Barriers  

SciTech Connect

A kinetic model of the Boltzmann equation for chemical reactions without energy barrier is considered here with the aim of evaluating the reaction rate and characterizing the transport coefficient of shear viscosity for the reactive system. The Chapman-Enskog solution of the Boltzmann equation is used to compute the chemical reaction effects, in a flow regime for which the reaction process is close to the final equilibrium state. Some numerical results are provided illustrating that the considered chemical reaction without energy barrier can induce an appreciable influence on the reaction rate and on the transport coefficient of shear viscosity.

Alves, Giselle M. [Escola Tecnica, Universidade Federal do Parana, Curitiba (Brazil); Kremer, Gilberto M. [Departamento de Fisica, Universidade Federal do Parana, Curitiba (Brazil); Soares, Ana Jacinta [Departamento de Matematica, Universidade do Minho, Braga (Portugal)

2011-05-20

388

Kinetics of gas-Grain Reactions in the Solar Nebula  

Microsoft Academic Search

Thermochemical equilibrium calculations predict gas phase, gas-grain, and solid phase reactions as a function of pressure\\u000a and temperature in the solar nebula. However, chemical reactions proceed at different rates, which generally decrease exponentially\\u000a with decreasing temperature. At sufficiently low temperatures (which vary depending on the specific reaction) there may not\\u000a have been enough time for the predicted equilibrium chemistry to

Bruce Fegley Jr.

2000-01-01

389

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

390

Kinetics of liquid-solid reactions in naphthenic acid conversion and Kraft pulping  

NASA Astrophysics Data System (ADS)

Two liquid-solid reactions, in which the morphology of the solid changes as the reactions proceeds, were examined. One is the NA conversion in oil by decarboxylation on metal oxides and carbonates, and the other is the Kraft pulping in which lignin removal by delignification reaction. In the study of the NA conversion, CaO was chosen as the catalyst for the kinetic study from the tested catalysts based on NA conversion. Two reaction mixtures, carrier oil plus commercial naphthenic acids and heavy vacuum gas oil (HVGO) from Athabasca bitumen, were applied in the kinetic study. The influence of TAN, temperature, and catalyst loading on the NA conversion and decarboxylation were studied systematically. The results showed that the removal rate of TAN and the decarboxylation of NA were both independent of the concentration of NA over the range studied, and significantly dependent on reaction temperature. The data from analyzing the spent catalyst demonstrated that calcium naphthenate was an intermediate of the decarboxylation reaction of NA, and the decomposition of calcium naphthenate was a rate-determining step. In the study on the delignification of the Kraft pulping, a new mechanism was proposed for the heterogeneous delignification reaction during the Kraft pulping process. In particular, the chemical reaction mechanism took into account the heterogeneous nature of Kraft pulping. Lignin reacted in parallel with sodium hydroxide and sodium sulfide. The mechanism consists of three key kinetic steps: (1) adsorption of hydroxide and hydrosulfide ions on lignin; (2) surface reaction on the solid surface to produce degraded lignin products; and (3) desorption of degradation products from the solid surface. The most important step for the delignification process is the surface reaction, rather than the reactions occurring in the liquid phase. A kinetic model has, thus, been developed based on the proposed mechanism. The derived kinetic model showed that the mechanism could be employed to predict the pulping behavior under a variety of conditions with good accuracy.

Yang, Ling

391

Reaction of 2,3-Dimethylmercaptopropionic Acid with Methylene Blue as an Indicator Reaction for the Kinetic Determination of Selenium  

Microsoft Academic Search

A new indicator reaction between 2,3-dimethylmercaptopropionic acid and Methyl Blue was proposed for the kinetic determination of selenium. The optimal reaction conditions were found. A linear relationship was observed between the induction period and the Se(IV) concentration in the range between 0.9 and 9.6 ng\\/mL Se. Masking with EDTA and solvent extraction with diethyldithiophosphoric acid can be used for the

D. F. Gainutdinova; N. V. Shirshova; V. F. Toropova; G. K. Budnikov; A. R. Garifzyanov

2001-01-01

392

Kinetic energy release in thermal ion–molecule reactions: The Nb2+–(benzene) single charge–transfer reaction  

Microsoft Academic Search

We have adapted the techniques originally developed to measure ion kinetic energies in ion cyclotron resonance (ICR) spectrometry to study the single charge–transfer reaction of Nb2+ with benzene under thermal conditions in a Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS). The partitioning of reaction exothermicity among the internal and translational modes available is consistent with a long-distance electron-transfer mechanism,

James R. Gorda; Ben S. Freiser; Steven W. Buckner

1991-01-01

393

Kinetic energy release in thermal ion-molecule reactions: The Nb2 + -(benzene) single charge-transfer reaction  

Microsoft Academic Search

We have adapted the techniques originally developed to measure ion kinetic energies in ion cyclotron resonance (ICR) spectrometry to study the single charge--transfer reaction of Nb{sup 2+} with benzene under thermal conditions in a Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS). The partitioning of reaction exothermicity among the internal and translational modes available is consistent with a long-distance electron-transfer

James R. Gord; Ben S. Freiser; Steven W. Buckner

1991-01-01

394

Reaction Kinetics of Fuel Formation for In-Situ Combustion  

Microsoft Academic Search

Chemical reactions believed to cause fuel formation for in-situ combustion have been studied and modeled. A thin, packed bed of sand\\/oil mixture is heated under nitrogen flow at linearly increasing temperatures, simulating the approach of a combustion front. Analysis of gases produced from the reaction cell revealed that pyrolysis of crude oil in porous media goes through three overlapping stages:

Sidqi Abu-Khamsin; William Brigham; Henry Ramey Jr.

1988-01-01

395

High temperature heterogeneous reaction kinetics and mechanisms of tungsten oxidation  

Microsoft Academic Search

Tungsten, which is a material used in many high temperature applications, is limited by its susceptibility to oxidation at elevated temperatures. Although tungsten has the highest melting temperature of any metal, at much lower temperatures volatile oxides are formed during oxidation with oxygen containing species. This differs from many heterogeneous oxidation reactions involving metals since most reactions form very stable

Justin L. Sabourin

2010-01-01

396

Laser threshold analysis of first- and second-order organic solid state distributed feedback laser  

NASA Astrophysics Data System (ADS)

Optically pumped organic semiconductor thin-films have been processed on first and second order distributed feedback gratings. The organic thin-films were made by co-evaporation of tris-(8-hydroxy quinoline)aluminium (Alq3) and the laser dye 4-(Dicyanomethylene)-2-methyl-6-(julolidin-4-yl-vinyl)-4H-pyran (DCM2). The DFB laser wavelength varied depending on the grating period between 647.8 nm and 668.6 nm for first order operation and between 626.7 nm and 640.1 nm for second order operation. By evaporating the same organic film on both resonator designs we could compare first and second order laser parameters. We measured laser output characteristics and determined threshold energy values for different wavelengths and for first and second order of the Bragg grating. The laser threshold energy of the first order organic DFB laser was reduced by a factor 8 compared to the second order laser. Minimum threshold energy density was measured for a first order sample with 13.8 ?J/cm2. Reducing the laser threshold value is especially important for future applications like electrically driven organic solid-state lasers, where it will be more difficult to reach the laser threshold excitation.

Schneider, Daniel; Hartmann, Soeren; Dobbertin, Thomas; Benstem, Torsten; Metzdorf, Dirk; Becker, Eike; Kammoun, Anis; Schildknecht, Christian; Krautwald, Henning; Johannes, Hans-Hermann; Riedl, Thomas; Kowalsky, Wolfgang

2004-02-01

397

Lateralization based on interaural differences in the second-order amplitude modulator.  

PubMed

Second-order amplitude modulation is a relatively slow variation of the modulation depth of a first-order amplitude modulation with higher frequency. In contrast to first-order modulation, which appears as a physical component in the stimulus spectrum after half-wave rectification, second-order modulation is not necessarily demodulated by the auditory periphery. For binaural processing of second-order amplitude modulated stimuli it is unknown whether interaural time differences (ITDs) in the second-order modulation result in a lateralized percept. Thus, second-order modulation can serve as a tool to investigate whether demodulation of interaurally delayed components is a prerequisite for lateralization. In most of the psychoacoustic experiments presented here, a 25 Hz sinusoidally amplitude-modulated (SAM) 160 Hz tone was either transposed to 4 kHz by half-wave rectifying this SAM waveform before multiplication with a 4 kHz tone (TSAM), or by adding an offset before multiplication (SAMAM). The experiments revealed an inability to lateralize the SAMAM based on ITDs in the 25 Hz component, whereas subjects could lateralize the TSAM. Given that only the TSAM results in a demodulated 25 Hz component after peripheral auditory processing, this result supports the hypothesis that demodulation is a prerequisite for lateralization, which has consequences for temporal modulation processing in models of binaural interaction. PMID:22280601

Dietz, Mathias; Ewert, Stephan D; Hohmann, Volker

2012-01-01

398

Looking at faces: first-order and second-order features as determinants of facial appearance.  

PubMed

The encoding and relative importance of first-order (discrete) and second-order (configural) features in mental representations of unfamiliar faces have been investigated. Nonmetric multidimensional scaling (KYST) was carried out on similarity judgments of forty-one photographs of faces (homogeneous with respect to sex, race, facial expression, and, to a lesser extent, age). A large set of ratings, measurements, and ratios of measurements of the faces was regressed against the three-dimensional KYST solution in order to determine the first-order and second-order features used to judge similarity. Parameters characterizing both first-order and second-order features emerged as important determinants of facial similarity. First-order feature parameters characterizing the appearance of the eyes, eyebrows, and mouth, and second-order feature parameters characterizing the position of the eyes, spatial relations between the internal features, and chin shape correlated with the dimensions of the KYST solution. There was little difference in the extent to which first-order and second-order features were encoded. Two higher-level parameters, age and weight, were also used to judge similarity. The implications of these results for mental representations of faces are discussed. PMID:24601031

Rhodes, Gillian

2013-01-01

399

First estimates of the second-order ionospheric effect on radio occultation observations  

NASA Astrophysics Data System (ADS)

This study examines the impact of the second-order ionospheric effect on radio occultation (RO) data products. We propose a new linear combination between dual frequency GPS observables, which retrieves slant total electron content free from the second-order ionospheric effect. Our STEC values differ from those obtained by independent techniques by a maximum of 3 total electron content units (TECU), depending on the geographic location and geomagnetic activity. Additionally, we suggest an alternative method of computing the second-order ionospheric delay in RO experiments, which does not require the use of geomagnetic and ionospheric models. First estimates show that the second-order ionospheric delay for the RO experiments falls within the range [-10, -8] mm, which is of the same order of magnitude with second-order ionospheric delay estimates from ground-based experiments. Finally, as a by-product of our model, we retrieve weighted mean geomagnetic field values, which we compare with theoretical estimates computed by the International Geomagnetic Reference Field-10 (IGRF-10) model. Our estimations agree with the IGRF-10 model between 0.23% and 7.0%.

Vergados, Panagiotis; Pagiatakis, Spiros D.

2010-07-01

400

Physicochemical Studies of PMR Resins. I: Reaction Mechanism and Kinetics at Room Temperature  

Microsoft Academic Search

The reaction mechanism and kinetics of PMR 15 resin (polymerization of monomeric reactants) were studied at low and room temperature using models thoroughly characterized by nuclear magnetic resonance (1H, 13C liquid and solid state) and liquid chromatography. The results indicate a difference in reactvity of the esters at room temperature and competing reactions that lead to large variations in resin

Marie-Florence Grenier-Loustalot; Philippe Grenier

1991-01-01

401

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

Microsoft Academic Search

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

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

2010-01-01

402

Mathematical model for kinetics of alkali–silica reaction in concrete  

Microsoft Academic Search

Vast though the literature on the chemistry of the alkali–silica reaction (ASR) in concrete has become, a comprehensive mathematical model allowing quantitative predictions seems lacking. The present study attempts a step toward this goal. While two distinct problems must be dealt with, namely, (1) the kinetics of the chemical reaction with the associated diffusion processes and (2) fracture mechanics of

Alexander Steffens

2000-01-01

403

Laboratory Support for in Situ Gasification Reaction Kinetics. Quarterly Report, January--March 1977.  

National Technical Information Service (NTIS)

This work is directed toward support studies for the national endeavor on in-situ coal gasification. The objective is to determine the reaction-controlling variables and reaction kinetics for gasification of chars resulting when coal is pyrolyzed in under...

J. Fischer J. E. Young J. E. Johnson D. C. Bowyer A. A. Jonke

1977-01-01

404

Comparison of kinetic and equilibrium reaction models insimulating the behavior of porous media  

SciTech Connect

In this study we compare the use of kinetic and equilibriumreaction models in the simulation of gas (methane) hydrate behavior inporous media. Our objective is to evaluate through numerical simulationthe importance of employing kinetic versus equilibrium reaction modelsfor predicting the response of hydrate-bearing systems to externalstimuli, such as changes in pressure and temperature. Specifically, we(1) analyze and compare the responses simulated using both reactionmodels for natural gas production from hydrates in various settings andfor the case of depressurization in a hydrate-bearing core duringextraction; and (2) examine the sensitivity to factors such as initialhydrate saturation, hydrate reaction surface area, and numericaldiscretization. We find that for large-scale systems undergoing thermalstimulation and depressurization, the calculated responses for bothreaction models are remarkably similar, though some differences areobserved at early times. However, for modeling short-term processes, suchas the rapid recovery of a hydrate-bearing core, kinetic limitations canbe important, and neglecting them may lead to significantunder-prediction of recoverable hydrate. Assuming validity of the mostaccurate kinetic reaction model that is currently available, the use ofthe equilibrium reaction model often appears to be justified andpreferred for simulating the behavior of gas hydrates, given that thecomputational demands for the kinetic reaction model far exceed those forthe equilibrium reaction model.

Kowalsky, Michael B.; Moridis, George J.

2006-11-29

405

Theory of relaxation phenomena in a spin-3/2 Ising system near the second-order phase transition temperature  

NASA Astrophysics Data System (ADS)

The relaxation behavior of the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic interactions near the second-order phase transition temperature or critical temperature is studied by means of the Onsager's theory of irreversible thermodynamics or the Onsager reciprocity theorem (ORT). First, we give the equilibrium case briefly within the molecular-field approximation in order to study the relaxation behavior by using the ORT. Then, the ORT is applied to the model and the kinetic equations are obtained. By solving these equations, three relaxation times are calculated and examined for temperatures near the second-order phase transition temperature. It is found that one of the relaxation times goes to infinity near the critical temperature on either side, the second relaxation time makes a cusp at the critical temperature and third one behaves very differently in which it terminates at the critical temperature while approaching it, then showing a “flatness” property and then decreases. We also study the influences of the Onsager rate coefficients on the relaxation times. The behavior of these relaxation times is discussed and compared with the spin-1/2 and spin-1 Ising systems.

Keskin, Mustafa; Canko, Osman

2005-12-01

406

General theory of multistage geminate reactions of isolated pairs of reactants. I. Kinetic equations  

NASA Astrophysics Data System (ADS)

General matrix approach to the consideration of multistage geminate reactions of isolated pairs of reactants depending on reactant mobility is formulated on the basis of the concept of "effective" particles. Various elementary reactions (stages of multistage reaction including physicochemical processes of internal quantum state changes) proceeding with the participation of isolated pairs of reactants (or isolated reactants) are taken into account. Investigation has been made in terms of kinetic approach implying the derivation of general (matrix) kinetic equations for local and mean probabilities of finding any of the reaction species in the sample under study (or for local and mean concentrations). The recipes for the calculation of kinetic coefficients of the equations for mean quantities in terms of relative coordinates of reactants have been formulated in the general case of inhomogeneous reacting systems. Important specific case of homogeneous reacting systems is considered.

Doktorov, Alexander B.; Kipriyanov, Alexey A.

2014-05-01

407

Kinetic Monte Carlo Studies of The Reaction Kinetics of Crystal Defects That Diffuse One-Dimensionally With Occasional Transverse Migration  

SciTech Connect

The reaction kinetics of the various species of mobile defects in irradiated materials are crucially dependent on the dimensionality of their diffusion processes. Sink strengths for one-dimensionally (1D) gliding interstitial loops undergoing occasional direction changes have been described analytically and confirmed by kinetic Monte Carlo (KMC) simulations. Here we report on KMC simulations investigating the transition from 1D to 3D diffusion for 1D gliding loops whose 1D migration is interrupted by occasional 2D migration due to conservative climb by dislocation core diffusion within a plane transverse to their 1D glide direction. Their transition from 1D to 3D kinetics is significantly different from that due to direction changes. The KMC results are compared to an analytical description of this diffusion mode in the form of a master curve relating the 1D normalized sink strength to the frequency of disturbance of 1D migration.

Heinisch, Howard L.; Trinkaus, Helmut; Singh, Bachu N.

2007-03-19

408

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

409

Sum Frequency Vibrational Spectroscopy: The Molecular Origins of the Optical Second-Order Nonlinearity of Collagen  

PubMed Central

The molecular origins of second-order nonlinear effects in type I collagen fibrils have been identified with sum-frequency generation vibrational spectroscopy. The dominant contributing molecular groups are: 1), the methylene groups associated with a Fermi resonance between the fundamental symmetric stretch and the bending overtone of methylene; and 2), the carbonyl and peptide groups associated with the amide I band. The noncentrosymmetrically aligned methylene groups are characterized by a distinctive tilt relative to the axis perpendicular to the main axis of the collagen fiber, a conformation producing a strong achiral contribution to the second-order nonlinear effect. In contrast, the stretching vibration of the carbonyl groups associated with the amide I band results in a strong chiral contribution to the optical second-order nonlinear effect. The length scale of these chiral effects ranges from the molecular to the supramolecular.

Rocha-Mendoza, Israel; Yankelevich, Diego R.; Wang, Mingshi; Reiser, Karen M.; Frank, Curt W.; Knoesen, Andre

2007-01-01

410

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

411

Observable ??* at LHC and second-order QED matrix element in Z/?*?l+l- decays  

NASA Astrophysics Data System (ADS)

In a recent publication by ATLAS Collaboration a new observable, the so-called ??* angle, was used for precise measurement of transverse Z momentum. One of the dominant systematic errors for this measurement originates from the theoretical control of QED final-state bremsstrahlung. At present, it is estimated at the 0.3% level for the shape of the ??* distribution. In this Letter we discuss the possible effects of the second-order QED matrix element for that quantity. For that purpose, results from simulations based on the Yennie-Frautchi-Suura (YFS) exponentiation and featuring the second-order matrix elements are used and compared with the case when the matrix element is restricted to the first-order. From this study we conclude that in order to reach the precision below 0.3% for the ??* distribution at the LHC, inclusion of the second-order QED matrix element in a respective Monte Carlo event generator is necessary.

Doan, T. K. O.; P?aczek, W.; Wa¸s, Z.

2013-08-01

412

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

413

Second-Order Interactions with the Treatment Groups in Controlled Clinical Trials  

PubMed Central

Abstract Summary The occurrence of significant second-order interactions for group characteristics was examined using real data in a randomized controlled trial (RCT). The interactions exist in all RCTs; they could be easily overlooked when using the simple randomization or stratification methods, but could become more obvious when minimization methods are used. Using real data from an RCT, the minimization method enabled balancing the distributions of the four selected stratified factors. Analyses for 3-way second-order interactions including 6 additional potential confounding variables (for a total of 10 variables) presented 8 significant second-order interactions with the treatment groups. Interaction effects need to be evaluated when treatment effects are examined to maximize the power of the treatment effects in any RCTs. A stepwise regression method with piecewise linear functions would be useful to select the significant variables with interaction effects affecting the treatment outcomes in RCTs. Additional ways to handle interaction effects in RCTs are presented in this paper.

Shiao, Shyang-Yun Pamela K.; Ahn, Chul W.; Akazawa, Kouhei

2007-01-01

414

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

415

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

416

Part A: Nonprincipal-plane scattering from flat plates: Second-order and corner diffractions  

NASA Technical Reports Server (NTRS)

Two models of a flat plate for nonprincipal-plane scattering are explored. The first is a revised version of the Physical Optics/Physical Theory of Diffraction (PO/PTD) model with second-order PTD equivalent currents included to account for second-order interactions among the plate edges. The second model uses a heurisitcally derived corner diffraction coefficient to account for the corner scattering mechanism. The patterns obtained using the newer models were compared to the data of previously reported models, the Moment Method (MM), and experimental results. Near normal incidence, all the models agreed; however, near grazing incidence a need for higher-order and corner diffraction mechanisms was noted. In many instances the second-order and corner-scattered fields which were formulated improved the results.

Balanis, Constantine A.; Polka, Lesley A.

1989-01-01

417

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

418

Broadband cascading of second-order nonlinearity in randomized nonlinear photonic crystal  

NASA Astrophysics Data System (ADS)

We study both experimentally and theoretically optical parametric process in one-dimensional nonlinear photonic crystal with random variation to the sign of the second-order nonlinear coefficient. We demonstrate that the structure randomness enables broadband third-harmonic generation via cascading of two second-order nonlinear parametric wave interactions with the overall conversion efficiency higher than previously recorded in fully disordered media such as the as-grown strontium barium niobate crystal. Furthermore, thanks to the one-dimensional modulation of the second-order nonlinearity, the emitted broadband harmonics preserve well the spatial intensity profile of the incident fundamental light beam, a feature critical for applications of optical frequency conversion but unavailable in two-dimensional fully random media due to the beam divergence caused by the simultaneous emission of noncollinear harmonic.

Sheng, Yan; Ma, Dongli; Ren, Mingliang; Chen, Baoqin; Roppo, Vito; Li, Zhiyuan; Koynov, Kaloian; Krolikowski, Wieslaw

2012-09-01

419

Poly (cyanophenylene sulfide) as new host materials of second order nonlinear optical polymers  

NASA Astrophysics Data System (ADS)

Here, we will propose poly (cyano phenylene sulfide) as novel host materials of nonlinear optical (NLO) polymers. Our experimental results proved that NLO chromophore-doped PCPS thin films deposited on the metal layers exhibited second order NLO susceptibilities just by annealing at the temperatures higher than a glass transition point even without conventional poling procedures. We determined the optimized annealing temperatures and the film thickness for the nonelectrical poling procedure. The nonelectrical poling procedure was applicable for the films as thick as a few ?m. The second order nonlinear coefficient of was 0.5 pm/V for the PCPS doped with 10w% of 4-[Ethyl(2- hydroxyethyl)amino]-4'-nitroazobenzene. Taking advantage of the unique polarization self-organization procedure, we may prepare one- or two-dimensionally periodically poled structures in these materials for the second-order NLO active photonic crystals pretty easily.

Sugita, A.; Tamaki, Y.; Mase, N.; Kawata, Y.; Tasaka, S.

2012-02-01

420

A Damped Gauss-Newton Method for the Second-Order Cone Complementarity Problem  

SciTech Connect

We investigate some properties related to the generalized Newton method for the Fischer-Burmeister (FB) function over second-order cones, which allows us to reformulate the second-order cone complementarity problem (SOCCP) as a semismooth system of equations. Specifically, we characterize the B-subdifferential of the FB function at a general point and study the condition for every element of the B-subdifferential at a solution being nonsingular. In addition, for the induced FB merit function, we establish its coerciveness and provide a weaker condition than Chen and Tseng (Math. Program. 104:293-327, 2005) for each stationary point to be a solution, under suitable Cartesian P-properties of the involved mapping. By this, a damped Gauss-Newton method is proposed, and the global and superlinear convergence results are obtained. Numerical results are reported for the second-order cone programs from the DIMACS library, which verify the good theoretical properties of the method.

Pan Shaohua [South China University of Technology, School of Mathematical Sciences (China)], E-mail: shhpan@scut.edu.cn; Chen, J.-S. [National Taiwan Normal University, Department of Mathematics (China)], E-mail: jschen@math.ntnu.edu.tw

2009-06-15

421

Optical control of ?3-frequency conversion by the second-order modulation instability  

NASA Astrophysics Data System (ADS)

A numerical study showing the excitation and control of second-order modulation instability (MI) dynamics in nonlinear optical fibers via two optical seed fields located under the MI gain spectrum is presented. The phase dependence of the two weak input seed fields on the temporal and spectral second-order MI dynamics, i.e., on the frequency generation process, is investigated. The considered approach allows the generation and control of asymmetric MI spectra, modifiable via the phase relation of the initial seed fields with considerably small amplitudes. An optimal frequency relation of the seed fields for the highest possible influence could be identified. Furthermore, the phase-dependent effect of second-order MI is discussed for a pulsed excitation and higher-order perturbative effects, such as higher-order dispersion, Raman scattering, and self-steepening.

Kues, Michael; Brinkmann, Maximilian; Fallnich, Carsten

2014-03-01

422

Second-order Born calculation of coplanar symmetric (e, 2e) process on Mg  

NASA Astrophysics Data System (ADS)

The second-order distorted wave Born approximation (DWBA) method is employed to investigate the triple differential cross sections (TDCS) of coplanar doubly symmetric (e, 2e) collisions for magnesium at excess energies of 6 eV–20 eV. Comparing with the standard first-order DWBA calculations, the inclusion of the second-order Born term in the scattering amplitude improves the degree of agreement with experiments, especially for backward scattering region of TDCS. This indicates that the present second-order Born term is capable to give a reasonable correction to DWBA model in studying coplanar symmetric (e, 2e) problems of two-valence-electron target in low energy range.

Zhang, Yong-Zhi; Wang, Yang; Zhou, Ya-Jun

2014-06-01

423

First- and Second-Order Full-Differential in Edge Analysis of Images  

PubMed Central

Two concepts of first- and second-order differential of images are presented to deal with the changes of pixels. These are the basic ideas in mathematics. We propose and reformulate them with a uniform definition framework. Based on our observation and analysis with the difference, we propose an algorithm to detect the edge from image. Experiments on Corel5K and PASCAL VOC 2007 are done to show the difference between the first order and the second order. After comparison with Canny operator and the proposed first-order differential, the main result is that the second-order differential has the better performance in analysis of changes of the context of images with good selection of control parameter.

Pu, Dong-Mei; Yuan, Yu-Bo

2014-01-01

424

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

425

Perfectly matched layer on curvilinear grid for the second-order seismic acoustic wave equation  

NASA Astrophysics Data System (ADS)

A curvilinear-grid perfectly matched layer (PML) absorbing boundary condition for the second-order seismic acoustic wave equation is presented in this paper. The rectangular grids are transformed into curvilinear grids by using a mathematical mapping to fit the curvilinear boundary, and the original wave equation is reformulated under the curvilinear coordinate system. Based on the reformulated wave equation, theoretical expressions and analysis of the curvilinear-grid PML are given. Furthermore, PML model 1 with symmetric form and PML model 2 with asymmetric form are derived from the same acoustic wave equation. By combination with the finite difference (FD) method, these two models are applied to seismic wave modelling with surface topography. The results show that the absorption effect of these two models discretised by the same second-order time difference and second-order space difference are different, and the symmetric-form PML yields better modelling results than the asymmetric-form.

Yuan, Sanyi 1Wang, Shangxu 14Sun, Wenju 1Miao, Lina 2Li, Zhenhua

2014-03-01

426

The evaluation of various kinetic models for base-catalyzed ethanolysis of palm oil.  

PubMed

In this paper, the kinetics of palm oil ethanolysis with various models have been investigated in a temperature range of 25-55 °C. The highest yield was achieved when the conversion to ethyl ester was 97.5±0.5% in the stated temperature range, using ethanol:oil molar ratio of 12:1, and 1.0 wt.% sodium ethoxide. The level of conformity of the reaction with reversible second order, irreversible second order and first order kinetic models were evaluated by means of the R(2) values of the linear curves. The ethanolysis showed the best conformity with irreversible second order kinetic model with 92-98% level of confidence. The reaction rate constants were within 0.018-0.088 dm(3)/mol min and the activation energy of the reaction was 42.36 kJ/mol. PMID:22154586

Shahla, Sanaz; Ngoh, Gek Cheng; Yusoff, Rozita

2012-01-01

427

Explaining the Atypical Reaction Profiles of Heme Enzymes with a Novel Mechanistic Hypothesis and Kinetic Treatment  

PubMed Central

Many heme enzymes show remarkable versatility and atypical kinetics. The fungal extracellular enzyme chloroperoxidase (CPO) characterizes a variety of one and two electron redox reactions in the presence of hydroperoxides. A structural counterpart, found in mammalian microsomal cytochrome P450 (CYP), uses molecular oxygen plus NADPH for the oxidative metabolism (predominantly hydroxylation) of substrate in conjunction with a redox partner enzyme, cytochrome P450 reductase. In this study, we employ the two above-mentioned heme-thiolate proteins to probe the reaction kinetics and mechanism of heme enzymes. Hitherto, a substrate inhibition model based upon non-productive binding of substrate (two-site model) was used to account for the inhibition of reaction at higher substrate concentrations for the CYP reaction systems. Herein, the observation of substrate inhibition is shown for both peroxide and final substrate in CPO catalyzed peroxidations. Further, analogy is drawn in the “steady state kinetics” of CPO and CYP reaction systems. New experimental observations and analyses indicate that a scheme of competing reactions (involving primary product with enzyme or other reaction components/intermediates) is relevant in such complex reaction mixtures. The presence of non-selective reactive intermediate(s) affords alternate reaction routes at various substrate/product concentrations, thereby leading to a lowered detectable concentration of “the product of interest” in the reaction milieu. Occam's razor favors the new hypothesis. With the new hypothesis as foundation, a new biphasic treatment to analyze the kinetics is put forth. We also introduce a key concept of “substrate concentration at maximum observed rate”. The new treatment affords a more acceptable fit for observable experimental kinetic data of heme redox enzymes.

Manoj, Kelath Murali; Baburaj, Arun; Ephraim, Binoy; Pappachan, Febin; Maviliparambathu, Pravitha Parapurathu; Vijayan, Umesh K.; Narayanan, Sivaprasad Valiyaveettil; Periasamy, Kalaiselvi; George, Ebi Ashley; Mathew, Lazar T.

2010-01-01

428

Density Functional Theory and Reaction Kinetics Studies of the Water–Gas Shift Reaction on Pt–Re Catalysts  

SciTech Connect

Periodic, self-consistent density functional theory calculations (DFT-GGA-PW91) on Pt(111) and Pt3Re(111) surfaces, reaction kinetics measurements, and microkinetic modeling are employed to study the mechanism of the water–gas shift (WGS) reaction over Pt and Pt–Re catalysts. The values of the reaction rates and reaction orders predicted by the model are in agreement with the ones experimentally determined; the calculated apparent activation energies are matched to within 6% of the experimental values. The primary reaction pathway is predicted to take place through adsorbed carboxyl (COOH) species, whereas formate (HCOO) is predicted to be a spectator species. We conclude that the clean Pt(111) is a good representation of the active site for the WGS reaction on Pt catalysts, whereas the active sites on the Pt–Re alloy catalyst likely contain partially oxidized metal ensembles.

Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos

2013-12-01

429

Mechanistic interpretation of glass reaction: Input to kinetic model development  

SciTech Connect

Actinide-doped SRL 165 type glass was reacted in J-13 groundwater at 90{degree}C for times up to 278 days. The reaction was characterized by both solution and solid analyses. The glass was seen to react nonstoichiometrically with preferred leaching of alkali metals and boron. High resolution electron microscopy revealed the formation of a complex layer structure which became separated from the underlying glass as the reaction progressed. The formation of the layer and its effect on continued glass reaction are discussed with respect to the current model for glass reaction used in the EQ3/6 computer simulation. It is concluded that the layer formed after 278 days is not protective and may eventually become fractured and generate particulates that may be transported by liquid water. 5 refs., 5 figs. , 3 tabs.

Bates, J.K.; Ebert, W.L. [Argonne National Lab., IL (USA); Bradley, J.P. [McCrone Associates, Inc., Westmont, IL (USA); Bourcier, W.L. [Lawrence Livermore National Lab., CA (USA)

1991-05-01

430

Kinetics and Transport Processes in Aqueous Polysulfide Electrode Reactions.  

National Technical Information Service (NTIS)

Fundamental and applied research on the aqueous sulfide/polysulfide redox couple has been carried out, motivated by its possible use in photoelectrochemical cells (PECs) and redox batteries. Recent work on PECs has concentrated on the reactions at photoel...

P. M. Lessner F. R. McLarnon E. J. Cairns

1986-01-01

431

Kinetics of Hydration-Dehydration Reactions Considered as Solid Transformations.  

National Technical Information Service (NTIS)

A mechanism is proposed for the dehydration-rehydration process in solid inorganic salts and model rate equations are derived and applied to the observed behavior of potassium carbonate. Quantitative expressions for the effect of pressure on the reaction ...

M. A. Stanish D. D. Perlmutter

1982-01-01

432

Heterogeneous reaction mechanisms and kinetics relevant to the CVD of semiconductor materials  

SciTech Connect

This report documents the state of the art in experimental and theoretical techniques for determining reaction mechanisms and chemical kinetics of heterogeneous reactions relevant to the chemical vapor deposition of semiconductor materials. It summarizes the most common ultra-high vacuum experimental techniques that are used and the types of rate information available from each. Several case studies of specific chemical systems relevant to the microelectronics industry are described. Theoretical methods for calculating heterogeneous reaction rate constants are also summarized.

Creighton, J.R.; Coltrin, M.E.

1994-03-01

433

Partial oxidation of methane, methanol, formaldehyde, and carbon monoxide over silica: global reaction kinetics  

Microsoft Academic Search

Oxidation of methane (848–898K), methanol (648–748K), formaldehyde (623–673K), and carbon monoxide (673–833K) over a precipitated silica catalyst has been examined over a range of reactant and oxygen partial pressures. Conversion–selectivity relationships are used to assess the reaction network and differential reactor experiments are employed to determine the global reaction kinetics. All reactions exhibited a positive-order dependence on oxygen, partial pressure

Robert L. McCormick; Mohammad B. Al-Sahali; Gokhan O. Alptekin

2002-01-01

434

Kinetic Modeling of Large?Scale Reaction Systems  

Microsoft Academic Search

This review gives a brief account of basic ideas underlying approaches to analysis and modeling of large?scale reaction systems. The emphasis is on model simplification and mechanism\\/dimension reduction via heuristic concepts and formal mathematical techniques. Among the key topics discussed are: top?down and bottom?up modeling approaches, graph\\/matrix representation of chemical reactions, mechanistic vs. pathways models, quantitative structure?reactivity relationships, mathematical reduction

Teh C. Ho

2008-01-01

435

Independence of first- and second-order memories in newborn rabbits.  

PubMed

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 blocked this memory, when recall and amnesia of CS1 left the souvenir of CS2 safe; this finding partially differed from results obtained in adult mammals. Thus, in this model of neonatal appetitive odor learning, second-order memory seems to depend on first-order memory for its formation but not for its maintenance. PMID:21602320

Coureaud, Gérard; Languille, Solène; Joly, Virginie; Schaal, Benoist; Hars, Bernard

2011-06-01

436

On Sturm-Liouville boundary value problems for second-order nonlinear functional finite difference equations  

NASA Astrophysics Data System (ADS)

Motivated by the interesting paper [I. Karaca, Discrete third-order three-point boundary value problem, J. Comput. Appl. Math. 205 (2007) 458-468], this paper is concerned with a class of boundary value problems for second-order functional difference equations. Sufficient conditions for the existence of at least one solution of a Sturm-Liouville boundary value problem for second-order nonlinear functional difference equations are established. We allow f to be at most linear, superlinear or sublinear in obtained results.

Liu, Yuji

2008-07-01

437

Stabilizing Second-Order Linear Dynamic Systems Via Hybrid Output Feedback Controls  

Microsoft Academic Search

\\u000a This paper considers the open problem whether there exists a finite-state hybrid output feedback control to asymptotically\\u000a stabilize a second-order linear dynamic system. More precisely, for second-order linear time-invariant systems which are not\\u000a stabilizable via a single static output feedback, we find two different output feedback gains and a switching law orchestrating\\u000a the feedback gains such that the closed-loop system

Liguo Zhang; Yangzhou Chen; Pingyuan Cui

2006-01-01

438

Robust controller designs for second-order dynamic systems - A virtual passive approach  

NASA Technical Reports Server (NTRS)

A robust controller design is presented for second-order dynamic systems. The controller is model-independent and itself is a virtual second-order dynamic system. Conditions on actuator and sensor placements are identified for controller designs that guarantee overall closed-loop stability. The dynamic controller can be viewed as a virtual passive damping system that serves to stabilize the actual dynamic system. The control gians are interpreted as virtual mass, spring, and dashpot elements that play the same roles as actual physical elements in stability analysis. Position, velocity, and acceleration feedback are considered. Simple examples are provided to illustrate the physical meaning of this controller design.

Juang, Jer-Nan; Phan, Minh

1991-01-01

439

Spin dependence of critical point behavior for first and second order phase transitions in nuclei  

SciTech Connect

A study of first and second order nuclear shape phase transitional behavior in yrast states of even-even nuclei in the context of the Interacting Boson Model-1 is presented. Finite boson number effects are identified using calculations with up to 150 bosons, and the role of the rotational degree of freedom of observables in first and second order quantum phase transitional nuclei is discussed. We aim to provide a first investigation of the angular momentum dependence of experimentally accessible phase transitional signatures in finite-sized quantum nuclear systems.

Williams, E.; Casperson, R. J.; Werner, V. [A.W. Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520 (United States)

2008-06-15

440

Mild solutions of second-order differential equations on the line  

NASA Astrophysics Data System (ADS)

A necessary condition for the existence and uniqueness of mild solutions of first- and second-order differential equations on the real line is given. It is known that the first-order problem is related to the operator equation AX [minus sign] XD = [minus sign][delta]0. Here, it is shown how the second-order problem on the real line is connected to the operator equation AX [minus sign] XD2 = [minus sign][delta]0 and also to some other operator equations.

Schweiker, Sibylle

2000-07-01

441

Robust controller designs for second-order dynamic system: A virtual passive approach  

NASA Technical Reports Server (NTRS)

A robust controller design is presented for second-order dynamic systems. The controller is model-independent and itself is a virtual second-order dynamic system. Conditions on actuator and sensor placements are identified for controller designs that guarantee overall closed-loop stability. The dynamic controller can be viewed as a virtual passive damping system that serves to stabilize the actual dynamic system. The control gains are interpreted as virtual mass, spring, and dashpot elements that play the same roles as actual physical elements in stability analysis. Position, velocity, and acceleration feedback are considered. Simple examples are provided to illustrate the physical meaning of this controller design.

Juang, Jer-Nan; Phan, Minh

1990-01-01

442

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

443

Approximate Controllability of Second-Order Stochastic Differential Equations with Impulsive Effects  

NASA Astrophysics Data System (ADS)

Many practical systems in physical and biological sciences have impulsive dynamical behaviors during the evolution process which can be modeled by impulsive differential equations. In this paper, the approximate controllability of nonlinear second-order stochastic infinite-dimensional dynamical systems with impulsive effects is considered. By using the Holder's inequality, stochastic analysis and fixed point strategy, a new set of necessary and sufficient conditions are formulated which guarantees the approximate controllability of the nonlinear second-order stochastic system. The results are obtained under the assumption that the associated linear system is approximately controllable.

Sakthivel, Rathinasamy; Ren, Yong; Mahmudov, N. I.

444

Second-order discrete Kalman filtering equations for control-structure interaction simulations  

NASA Technical Reports Server (NTRS)

A general form for the first-order representation of the continuous, second-order linear structural dynamics equations is introduced in order to derive a corresponding form of first-order Kalman filtering equations (KFE). Time integration of the resulting first-order KFE is carried out via a set of linear multistep integration formulas. It is shown that a judicious combined selection of computational paths and the undetermined matrices introduced in the general form of the first-order linear structural systems leads to a class of second-order discrete KFE involving only symmetric, N x N solution matrix.

Park, K. C.; Belvin, W. Keith; Alvin, Kenneth F.

1991-01-01

445

Effective second-order susceptibility in photonic crystals mode of centrosymmetric materials  

NASA Astrophysics Data System (ADS)

A technique for obtaining efficient bulk second-order susceptibility in noncentrosymmetric photonic crystals (PC) made of centrosymmetric materials is discussed. The effect is based on the electric quadrupole effect, strong electromagnetic mode deformation, and nonhomogeneous contribution to volume polarization from different parts of the PC. The required symmetry breaking is introduced on the macroscale of the PC unit cell. The obtained structural ?(2)str is comparable with the second-order susceptibility of ordinary nonlinear materials. Phase matching can be achieved by introducing symmetry modulation (quasi-phase-matching) during fabrication of the PC.

Feigel, A.; Kotler, Z.; Sfez, B.

2002-02-01

446

Unifying intensity noise and second-order coherence properties of amplified spontaneous emission sources.  

PubMed

We present joint investigations of relative intensity noise (RIN) and second-order coherence properties of amplified spontaneous emission (ASE) generated by a superluminescent diode. We introduce a generalized intensity noise description for ASE sources that contains the shot noise contribution but also accounts for first- and second-order coherence properties reflecting the process of light generation. We find excellent agreement between pump-current-dependent RIN values and this new description, with the perspective of particular interesting consequences for the realization of low-noise broadband emitters. PMID:21886242

Blazek, Martin; Hartmann, Sébastien; Molitor, Andreas; Elsaesser, Wolfgang

2011-09-01

447

Kinetics and mechanism of the IO + IO reaction  

SciTech Connect

The flash photolysis-absorption technique has been used to measure the rate constant for the reaction IO + IO ..-->.. products (1) over the temperature range 250-373 K and pressure range 20-700 torr of N/sub 2/. The rate constant for the overall reaction was found to be independent of pressure and equal to 1.73 x 10/sup -12/ exp(1020 +/- 200)/T) cm/sup 3/ molecule/sup -1/ s/sup -1/ where k/sub 1/ is defined by the relation -d(IO)/dt = 2k/sub 1/(IO)/sup 2/. Branching ratios for the reaction channels forming 2I + O/sub 2/ (1a), I/sub 2/ + O/sub 2/ (1b), and I/sub 2/O/sub 2/ (1c) were found to be pressure dependent with the I/sub 2/ channel accounting for less than 5% of the total reaction over the observed pressure range. A stable reaction product was observed between 230 and 300 nm which was formed on a long time scale compared to IO disappearance. The rate constant for the reaction I + O/sub 3/ ..-->.. IO + O/sub 2/ was measured at 298 K and found to be (9.5 +/- 1.5) x 10/sup -13/ cm/sup 3/ molecule/sup -1/ s/sup -1/. 31 references, 6 figures, 3 tables.

Sander, S.P.

1986-05-08

448

Theoretical analysis of reaction kinetics with singlet oxygen molecules.  

PubMed

A comparative analysis of predictive ability of three approaches to estimate the rate constants of reactions of H(2), H, H(2)O and CH(4) with electronically excited O(2)(a(1)?(g)) and O(2)(b(1)?(g)(+)) molecules is conducted. The first approach is based on a detailed ab initio study of potential energy surfaces. The second one is known as the "bond energy-bond order" method, and the third approach is a modification of the updated method of vibronic terms that makes it possible to evaluate the activation energy of reactions involving electronically excited species. The comparison showed that the estimates of the energy barrier by the updated method of vibronic terms for some reactions can be in good agreement with ab initio calculations and available experimental data. It was revealed that reactions of O(2)(b(1)?(g)(+)) molecules with H(2), H(2)O and CH(4) molecules and with the H atom result in the formation of electronically excited species. The reactivity of O(2)(b(1)?(g)(+)) molecules is smaller than that of O(2)(a(1)?(g)) ones, but much higher as compared to the reactivity of ground state O(2) molecules. For each reaction under study involving oxygen molecules in the excited electronic states O(2)(a(1)?(g)) and O(2)(b(1)?(g)(+)) the recommended temperature-dependent rate constants are presented. PMID:21845271

Starik, Alexander; Sharipov, Alexander

2011-09-28

449

Anomalous Kinetic Roughening by Chemical Reaction-Limited Aggregation  

NASA Astrophysics Data System (ADS)

The evolution of rough fronts in the early growth stage of poly(chloro-p-xylylene) films on Si/SiO2 substrates was measured using atomic force microscopy, and analyzed in detail according to the dynamic scaling theories of kinetic roughening. While the growth of the interface width and the correlation length were reduced as the system entered into the three-dimensional growth mode, both the global and the local roughness exponents remained at ?=1.39 and ?loc=0.74. The scaling behavior, ?=?s\

Lee, InJae; Park, Euldoo

2011-12-01

450

Modeling the aqueous reaction kinetics of estriol with ferrate  

Microsoft Academic Search

In this study the aqueous oxidation kinetics of estriol (E3) by potassium ferrate (K2FeO4), a chemical for its strong oxidizing power and for producing a coagulant from its reduced state (i.e. Fe(III)), was evaluated\\u000a in the range of pH 8–12 with different molar ratios of the reactants. As the degree of Fe(VI) protonation varies with the\\u000a solution pH, it was

Cong Li; Naiyun Gao

2009-01-01

451

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

452

Ab initio chemical kinetics for the HCCO + OH reaction  

NASA Astrophysics Data System (ADS)

The mechanism for the reaction of HCCO and OH has been investigated at different high-levels of theory. The reaction was found to occur on singlet and triplet potential energy surfaces with multiple accessible paths. Rate constants predicted by variational RRKM/ME calculations show that the reaction on both surfaces occurs primarily by barrierless OH attack at both C atoms producing excited intermediates which fragment to produce predominantly CO and 1,3HCOH with kS = 3.12 × 10-8T-0.59exp[-73.0/T] and kT = 6.29 × 10-11T0.13exp[108/T] cm3 molecule-1 s-1 at T = 300-2000 K, independent of pressure at P < 76 000 Torr.

Mai, Tam V.-T.; Raghunath, P.; Le, Xuan T.; Huynh, Lam K.; Nam, Pham-Cam; Lin, M. C.

2014-01-01

453

Oxygen Diffusion and Reaction Kinetics in Continuous Fiber Ceramic Matrix Composites  

NASA Technical Reports Server (NTRS)

Previous stressed oxidation tests of C/SiC composites at elevated temperatures (350 C to 1500 C) and sustained stresses (69 MPa and 172 MPa) have led to the development of a finite difference cracked matrix model. The times to failure in the samples suggest oxidation occurred in two kinetic regimes defined by the rate controlling mechanisms (i.e. diffusion controlled and reaction controlled kinetics). Microstructural analysis revealed preferential oxidation along as-fabricated, matrix microcracks and also suggested two regimes of oxidation kinetics dependent on the oxidation temperature. Based on experimental results, observation, and theory, a finite difference model was developed. The model simulates the diffusion of oxygen into a matrix crack bridged by carbon fibers. The model facilitates the study of the relative importance of temperature, the reaction rate constant, and the diffusion coefficient on the overall oxidation kinetics.

Halbig, Michael C.; Eckel, Andrew J.; Cawley, James D.

1999-01-01

454

A class of continuous methods for general second order initial value problems in ordinary differential equations  

Microsoft Academic Search

In this paper we propose a class of continuous methods for the solution of initial value problems of general second order ordinary differential equations . The procedure which yields a solution matrix equation for different stepnumber k?2 is based on collocation of the differential systems at the grid points. For n=2, three discrete schemes of order four for k=2 and

D. O. Awoyemi

1999-01-01

455

Separating bias and state estimates in a recursive second-order filter  

Microsoft Academic Search

When recursively estimating the state of a nonlinear process using a second-order filter to process data from many sensors, the method of augmenting the state vector with those sensor systematic errors for which estimates are desired can result in a new vector of extremely large dimension. To avoid the computational problems arising from operations with large dimension matrices it is

E. Shreve; W. Hedrick

1974-01-01

456

Anisotropy-induced transformation of a phase transition from first to second order [rapid communication  

NASA Astrophysics Data System (ADS)

Fluctuation-induced first order phase transitions are known to exist in rotation-invariant systems with coupled order parameters. Using exact calculations, it is shown that when a uniform uniaxial anisotropy is added, critical behavior corresponding to second order transitions is restored.

Nicolaides, Demetris

2005-09-01

457

Impulsive consensus problem of second-order multi-agent systems with switching topologies  

NASA Astrophysics Data System (ADS)

The paper proposes an impulsive consensus protocol to solve the consensus problem of the second-order multi-agent systems with fixed and switching topologies. Some sufficient conditions are obtained for the states of follower agents converging to the state of leader asymptotically. Two numerical simulations are also given to verify the effectiveness of the theoretical analysis.

Zhang, Qing; Chen, Shihua; Yu, Changchun

2012-01-01

458

On the Scatterers' Mobility and Second Order Statistics of Narrowband Fixed Outdoor Wireless Channels  

Microsoft Academic Search

In this paper, we study the temporal behavior of narrowband fixed outdoor wireless channels by modeling the impact of scatterers' mobility on the second order statistics of such channels. We show that the Nakagami-m, gamma, Weibull and lognormal probability density functions (PDFs) can adequately approximate the scatterers' mobility at outdoor environments by comparing the theoretically derived autocorrelation functions (ACFs) with

Petros Karadimas; Efstathios D. Vagenas; Stavros A. Kotsopoulos

2010-01-01

459

Study of a Family of Singular Second-Order Ordinary Differential Equations.  

National Technical Information Service (NTIS)

The following family of second order ODEs is considered: d/dx(x exp 2 d phi/dx) = lambda (phi - g(x)), where g(x) is a given function, and lambda is a real constant. We require that phi(x) be continuous for x greater than or equal to 0 with phi(0) = 0. An...

A. C. Hindmarsh

1981-01-01

460

An Immersed Boundary Method with Formal Second-Order Accuracy and Reduced Numerical Viscosity  

Microsoft Academic Search

A formally second-order accurate immersed boundary method is presented and tested in this paper. We apply this new scheme to simulate the flow past a circular cylinder and study the effect of numerical viscosity on the accuracy of the computation by comparing the numerical results with those of a first-order method. The numerical evidence shows that the new scheme has

Ming-Chih Lai; Charles S. Peskin

2000-01-01

461

user's guide to viscosity solutions of second order partial differential equations  

Microsoft Academic Search

The notion of viscosity solutions of scalar fully nonlinear partial differential equations of second order provides a framework in which startling comparison and uniqueness theorems, existence theorems, and theorems about continuous dependence may now be proved by very efficient and striking arguments. The range of important applications of these results is enormous. This article is a self-contained exposition of the

Michael G. Crandall; Hitoshi Ishii; Pierre-Louis Lions

1992-01-01

462

Asymptotic expansions and L ? -error estimates for mixed finite element methods for second order elliptic problems  

Microsoft Academic Search

Summary Asymptotic expansions for mixed finite element approximations of the second order elliptic problem are derived and Richardson extrapolation can be applied to increase the accuracy of the approximations. A new procedure, which is called the ‘error corrected method’, is presented as a further application of the asymptotic error expansion for the first order BDM approximation of the scalar field.

Junping Wang

1989-01-01