ERIC Educational Resources Information Center
Silvestri, Michael G.; Dills, Charles E.
1989-01-01
Describes an organic chemistry experiment for teaching the basic concepts of chemical kinetics. Provides background information about first- and second-order reactions, experimental procedures of the Diels-Alder reaction between cyclopentadiene and dimethyl fumarate, and the experimental results. (YP)
Sun, Hongyan; Zhang, Peng; Law, Chung K
2012-05-31
The gas-phase kinetics of H-abstraction reactions of monomethylhydrazine (MMH) by OH radical was investigated by second-order multireference perturbation theory and two-transition-state kinetic model. It was found that the abstractions of the central and terminal amine H atoms by the OH radical proceed through the formation of two hydrogen bonded preactivated complexes with energies of 6.16 and 5.90 kcal mol(-1) lower than that of the reactants, whereas the abstraction of methyl H atom is direct. Due to the multireference characters of the transition states, the geometries and ro-vibrational frequencies of the reactant, transition states, reactant complexes, and product complexes were optimized by the multireference CASPT2/aug-cc-pVTZ method, and the energies of the stationary points of the potential energy surface were refined at the QCISD(T)/CBS level via extrapolation of the QCISD(T)/cc-pVTZ and QCISD(T)/cc-pVQZ energies. It was found that the abstraction reactions of the central and two terminal amine H atoms of MMH have the submerged energy barriers with energies of 2.95, 2.12, and 1.24 kcal mol(-1) lower than that that of the reactants respectively, and the abstraction of methyl H atom has a real energy barrier of 3.09 kcal mol(-1). Furthermore, four MMH radical-H(2)O complexes were found to connect with product channels and the corresponding transition states. Consequently, the rate coefficients of MMH + OH for the H-abstraction of the amine H atoms were determined on the basis of a two-transition-state model, with the total energy E and angular momentum J conserved between the two transition-state regions. In units of cm(3) molecule(-1) s(-1), the rate coefficient was found to be k(1) = 3.37 × 10(-16)T(1.295) exp(1126.17/T) for the abstraction of the central amine H to form the CH(3)N(•)NH(2) radical, k(2) = 2.34 × 10(-17)T(1.907) exp(1052.26/T) for the abstraction of the terminal amine H to form the trans-CH(3)NHN(•)H radical, k(3) = 7.41 × 10(-20)T(2.428) exp(1343.20/T) for the abstraction of the terminal amine H to form the cis-CH(3)NHN(•)H radical, and k(4) = 9.13 × 10(-21)T(2.964) exp(-114.09/T) for the abstraction of the methyl H atom to form the C(•)H(2)NHNH(2) radical, respectively. Assuming that the rate coefficients are additive, the total rate coefficient of these theoretical predictions quantitatively agrees with the measured rate constant at temperatures of 200-650 K, with no adjustable parameters. PMID:22545789
Epidemic analysis of the second-order transition in the Ziff-Gulari-Barshad surface-reaction model
Voigt, Chris
Epidemic analysis of the second-order transition in the Ziff-Gulari-Barshad surface-reaction model-Gulari-Barshad irreversible surface-reaction model around its kinetic second-order phase transition, using both epidemic, including directed percolation DP 1,2 , the contact process 3 , and various surface-reaction or catalysis
A weak second order tau-leaping method for chemical kinetic systems
NASA Astrophysics Data System (ADS)
Hu, Yucheng; Li, Tiejun; Min, Bin
2011-07-01
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.
ALTERNATIVE RBC (ROTATING BIOLOGICAL CONTACTOR) DESIGN - SECOND ORDER KINETICS
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...
A weak second order tau-leaping method for chemical kinetic systems
Yucheng Hu; Tiejun Li; Bin Min
2011-01-01
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
An Example of Following Second-Order Kinetics by Simple Laboratory Means
ERIC Educational Resources Information Center
Schreiber, Gisela
1976-01-01
Describes a procedure for studying the kinetics of the second-order hydrolysis of ethylene bromohydrine in alkaline medium by incorporating a substance that changes color as one of the reacting components is depleted. (MLH)
NASA Astrophysics Data System (ADS)
Chen, Jiale; Gao, Zhe
2013-08-01
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.
From Langmuir kinetics to first- and second-order rate equations for adsorption.
Liu, Yu; Shen, Liang
2008-10-21
So far, the first- and second-order kinetic equations have been most frequently employed to interpret adsorption data obtained under various conditions, whereas the theoretical origins of these two equations still remain unknown. Using the Langmuir kinetics as a theoretical basis, this study showed that the Langmuir kinetics can be transformed to a polynomial expression of dtheta t /d t = k 1(theta e - theta t ) + k 2(theta e - theta t ) (2), a varying-order rate equation. The sufficient and necessary conditions for simplification of the Langmuir kinetics to the first- and second-order rate equations were put forward, which suggested that the relative magnitude of theta e over k 1/ k 2 governs the simplification of the Langmuir kinetics. In cases where k 1/ k 2 is greater than theta e or k 1/ k 2 is very close to theta e, adsorption kinetics would be reasonably described by the first-order rate equation, whereas the Langmuir kinetics would be reduced to the second-order equation only at k 1/ k 2 < theta e. It was further demonstrated that both theta e and k 1/ k 2 are the function of initial adsorbate concentration ( C 0) at a given dosage of adsorbent, indicating that simplification of the Langmuir kinetics indeed is determined by C 0. Detailed C 0-depedent boundary conditions for simplifying the Langmuir kinetics were also established and were verified by experimental data. PMID:18788769
REMOVAL OF LEAD(II) FROM EFFLUENTS BY SORPTION ON PEAT USING SECOND-ORDER KINETICS
Y. S. Ho; J. C. Y. Ng; G. McKay
2001-01-01
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
First-Order or Second-Order Kinetics? A Monte Carlo Answer
ERIC Educational Resources Information Center
Tellinghuisen, Joel
2005-01-01
Monte Carlo computational experiments reveal that the ability to discriminate between first- and second-order kinetics from least-squares analysis of time-dependent concentration data is better than implied in earlier discussions of the problem. The problem is rendered as simple as possible by assuming that the order must be either 1 or 2 and that…
Second-order fluid dynamics for the unitary Fermi gas from kinetic theory
NASA Astrophysics Data System (ADS)
Schäfer, Thomas
2014-10-01
We compute second-order transport coefficients of the dilute Fermi gas at unitarity. The calculation is based on kinetic theory and the Boltzmann equation at second order in the Knudsen expansion. The second-order transport coefficients describe the shear stress relaxation time, nonlinear terms in the strain-stress relation, and nonlinear couplings between vorticity and strain. An exact calculation in the dilute limit gives ?R=? /P , where ?R is the shear stress relaxation time, ? is the shear viscosity, and P is pressure. This relation is identical to the result obtained using the Bhatnagar-Gross-Krook approximation to the collision term, but other transport coefficients are sensitive to the exact collision integral.
Li, Tiejun
2011-01-01
THE JOURNAL OF CHEMICAL PHYSICS 135, 024113 (2011) A weak second order tau-leaping method with weak second order accuracy. We extend their work to the discrete chemical jump processes. With slight modification, the method can also solve dis- crete chemical kinetic systems with weak second order accuracy
Ashworth, Ian W; Cox, Brian G; Meyrick, Brian
2010-12-01
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
Temporal Frequency Modulates Reaction Time Responses to First-Order and Second-Order Motion
ERIC Educational Resources Information Center
Hutchinson, Claire V.; Ledgeway, Tim
2010-01-01
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…
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...
Implementing the Second-Order Fermi Process in a Kinetic Monte-Carlo Simulation
NASA Astrophysics Data System (ADS)
Summerlin, E. J.
2010-12-01
Kinetic Monte-Carlo test-particle simulations require a way to simulate the effects of turbulence on particles. One way to do this is to prescribe a phenomenological scattering mechanism based on an empirical and/or qualitative description of turbulent scattering. Previous incarnations of the simulation presented here parameterize a scattering mean free path proportional to some power of the particle’s momentum in agreement with observational evidence from many sources. The scattering itself was done by scattering of the particle’s local fluid frame velocity onto a sphere of radius |v| via either large of small angle scattering. However, in real plasmas the scattering centers (turbulent plasma waves) are not stationary in the local fluid frame and particle velocities should, instead, be randomized in the frame of the moving scattering centers (which presumably move with the Alfvén speed) to more accurately represent the effects of turbulence on particles. Allowing scattering centers to move introduces heating as particles now diffuse in momentum as well as space (receiving a random kick of order the Alfvén speed at each scattering event). In 1965, Eugene Parker considered this effect (then called fermi acceleration) for cosmic ray particles and (correctly) concluded that it was negligible for those highly energetic particles because the particle speed was so much larger than the Alfvén speed kick which it received. However, doing the same calculation for thermal particles embedded in the solar wind (for whom a single kick of an Alfvén speed is significant) yields a very different result and it becomes clear that this process, now called second-order Fermi acceleration, must be included to get an accurate picture of particle acceleration in the heliosphere. This presentation will highlight the theoretical argument for the importance of second-order fermi acceleration in both the solar wind and shock environs as well as problems in heliophysics to which it may be applicable and problems it creates for the conventional picture of first-order fermi shock acceleration. It will also discuss results from the kinetic Monte-Carlo simulation described above (including second-order fermi) in the vicinity of shocks.
T.-H. Ahn; A. Sandu
2011-01-01
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
An Activation Energy Experiment for a Second-Order Reaction in a Single Laboratory Period.
ERIC Educational Resources Information Center
Barile, Raymond C.; Michiels, Leo P.
1983-01-01
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)
Lambrecht, Daniel S; Brandhorst, Kai; Miller, William H; McCurdy, C William; Head-Gordon, Martin
2011-04-01
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
Radiation-Reaction Force on a Small Charged Body to Second Order
NASA Astrophysics Data System (ADS)
Moxon, Jordan; Flanagan, Eanna
2015-04-01
In classical electrodynamics, an accelerating charge emits radiation and experiences a corresponding radiation reaction force, or self force. We extend to greater precision (higher order in perturbation theory) a previous rigorous derivation of the electromagnetic self force in flat spacetime by Gralla, Harte, and Wald. The method introduced by Gralla, Harte, and Wald computes the self-force from the Maxwell field equations and conservation of stress-energy, and does not require regularization of a singular point charge, as has been necessary in prior computations. For our higher order compuation, it becomes necessary to adopt an adjusted definition of the mass of the body to avoid including self-energy from the electromagnetic field sourced during the history of the body. We derive the evolution equations for the mass, spin, and center of mass position of an extended body through second order using our adjusted formalism. The final equations give an acceleration dependent evolution of the spin (self-torque), as well as a mixing between the extended body effects and the acceleration dependent effects on the overall body motion.
Shamik Chowdhury; Papita Saha
2010-01-01
In this study, the sorption of methylene blue, a basic dye, onto tamarind fruit shell was studied by performing batch kinetic sorption experiments. The equilibrium kinetic data were analyzed using the pseudo-second-order kinetic model. A comparison between linear least squares method and nonlinear regression method of estimating the kinetic parameters was examined. Four pseudo-second-order kinetic linear equations were discussed. The
Yuh-Shan Ho
2006-01-01
A comparison was made of the linear least-squares method and a trial-and-error non-linear method of the widely used pseudo-second-order kinetic model for the sorption of cadmium onto ground-up tree fern. Four pseudo-second-order kinetic linear equations are discussed. Kinetic parameters obtained from the four kinetic linear equations using the linear method differed but they were the same when using the non-linear
Positronium formation as a three-body reaction. II. The second-order nuclear amplitudes
Shojaei, F.; Bolorizadeh, M. A. [Physics Department, Shahid Bahonar University of Kerman, Kerman, 76169, Iran and ICST, Mahan, 76315 (Iran, Islamic Republic of); Ghanbari-Adivi, E. [Physics Department and Isfahan Quantum Optics Group, University of Isfahan, Isfahan, 81746 (Iran, Islamic Republic of); Brunger, M. J. [Centre for Antimatter-Matter Studies, School of Chemistry, Physics and Earth Sciences, Flinders University, Adelaide South Australia, 5042 (Australia)
2009-01-15
We derive an exact analytic form for the second-order nuclear amplitudes, under the Faddeev three-body approach, which is applicable to the nonrelativistic high energy impact interaction where positronium is formed in the collision of a positron with an atom.
Gh Juncu
2002-01-01
Conjugate mass transfer between a drop and a surrounding fluid flow with second-order (inclusive the particular case – pseudo-first-order), irreversible chemical reaction in the dispersed phase has been analyzed. The dispersed phase reactant is insoluble in the continuous phase and its complete depletion is allowed. Two sphere models were considered: the rigid sphere and the fluid sphere with internal circulation.
Glucose reversion reaction kinetics.
Pilath, Heidi M; Nimlos, Mark R; Mittal, Ashutosh; Himmel, Michael E; Johnson, David K
2010-05-26
The reversion reactions of glucose in mildly acidic aqueous solutions have been studied, and the kinetics of conversion to disaccharides has been modeled. The experiments demonstrate that, at high sugar loadings, up to 12 wt % of the glucose can be converted into reversion products. The reversion products observed are primarily disaccharides; no larger oligosaccharides were observed. Only disaccharides linked to the C1 carbon of one of the glucose residues were observed. The formation of 1,6-linked disaccharides was favored, and alpha-linked disaccharides were formed at higher concentrations than beta-linked disaccharides. This observation can be rationalized on the basis of steric effects. At temperatures >140 degrees C, the disaccharides reach equilibrium with glucose and the reversion reaction competes with dehydration reactions to form 5-hydroxymethylfurfural. As a result, disaccharide formation reaches a maximum at reaction times <10 min and decreases with time. At temperatures <130 degrees C, disaccharide formation reaches a maximum at reaction times >30 min. As expected, disaccharide formation exhibits a second-order dependence upon glucose concentration. Levoglucosan formation is also observed; because it shows a first-order dependence upon glucose concentration, its formation is more significant at low concentrations (10 mg mL(-1)), whereas disaccharide formation dominates at high concentrations (200 mg mL(-1)). Experiments conducted using glucose and its disaccharides were calibrated with readily available standards. The kinetic parameters for hydrolysis of some glucodisaccharides could be compared to published literature values. From these experiments, the kinetics and activation energies for the reversion reactions have been calculated. The rate parameters can be used to model the formation of the disaccharides as a function of reaction time and temperature. A new and detailed picture of the molecular mechanism of these industrially important reversion reactions has been developed. PMID:20429509
Alejandro García-Reiriz; Patricia C. Damiani; Alejandro C. Olivieri
2007-01-01
The kinetic evolution of UV–visible absorption spectra of amoxicillin in the presence of copper(II) ions has been processed by the second-order multivariate methods parallel factor analysis (PARAFAC) and also by a novel approach based on partial least-squares with residual bilinearization (PLS\\/RBL). The latter one is employed for the first time to evaluate kinetic–spectral information. The mechanism of the analyte metal-catalyzed
Kinetic phase transitions in an irreversible surface-reaction model
Robert M. Ziff; Erdagon Gulari; Yoav Barshad
1986-01-01
An irreversible kinetic surface-reaction model, based upon the reaction of carbon monoxide and oxygen on a catalyst surface, is presented. It is found by computer simulation that the adsorbed molecules on the surface undergo both first- and second-order kinetic phase transitions. These transitions correspond to the ``poisoning'' phenomenon seen on catalysts. Interesting transient and periodic behavior is also seen.
NASA Astrophysics Data System (ADS)
Kopelman, Raoul
1988-09-01
Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal ``memories.'' The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of ``fractal-like kinetics'' are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds. Diffusion-controlled reactions with geometrical constraints, as found in heterogeneous kinetics, may be described by reactions on fractal domains. The hallmarks of ``fractal-like'' reactions are anomalous reaction orders and time-dependent reaction rate ``constants.'' These anomalies stem from the nonrandomness of the reactant distributions in low dimensions. For homo-bimolecular reactions (A + A --> Pr) the distribution is partially ordered, for example, quasi-periodic. However, for hetero-bimolecular reactions (A + B --> Pr) the reactants segregate. Theory, simulations, and experiments are interrelated through the formalism of fractal reaction kinetics (42).
Kopelman, R
1988-09-23
Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal "memories." The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of "fractal-like kinetics" are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds. PMID:17820893
NASA Astrophysics Data System (ADS)
Espin, Johnny; Krasnov, Kirill
2015-06-01
It is known, though not commonly, that one can describe fermions using a second order in derivatives Lagrangian instead of the first order Dirac one. In this description the propagator is scalar, and the complexity is shifted to the vertex, which contains a derivative operator. In this paper we rewrite the Lagrangian of the fermionic sector of the Standard Model in such second order form. The new Lagrangian is extremely compact, and is obtained from the usual first order Lagrangian by integrating out all primed (or dotted) 2-component spinors. It thus contains just half of the 2-component spinors that appear in the usual Lagrangian, which suggests a new perspective on unification. We sketch a natural in this framework SU (2) × SU (4) ? SO (9) unified theory.
D. I. Aleksiev; S. Ivanova; Tashkova Kr
1993-01-01
Addition of unsubstituted and substituted benzenesulfinic acids to ?-nitrostyrene has been studied kinetically by means of ultraviolet spectrophotometry. The reaction follows the second-order kinetics: v=k. [?-nitrostyrene][sulfinic acid]. The dependence of rate constants on the temperature and influence of ?-substituents on the kinetic parameters have been investigated. The activating energy and the enthalpy of activation are calculated in the temperature range
Kinetics of the reaction of ozone with 2,4,6-trichlorophenol
Richard A. Davis; Robert G. Rinker; Orville C. Sandall
1995-01-01
The kinetics of the aqueous phase reaction between ozone and 2,4,6-trichlorophenol was studied in this work using a wetted-sphere absorber. Ozone absorption rates into an aqueous solution of trichlorophenol were interpreted to give an expression for the second-order kinetic rate constant as k2 = 8.19 × 1021 exp(?11630\\/T) l\\/g mol s. Stoichiometry experiments showed that one mole of ozone reacts
NASA Astrophysics Data System (ADS)
Lukes, P.; Dolezalova, E.; Sisrova, I.; Clupek, M.
2014-02-01
The formation of transient species (OH·, NO2·, NO radicals) and long-lived chemical products (O3, H2O2, NO_{3}^{-} , NO_{2}^{-} ) produced by a gas discharge plasma at the gas-liquid interface and directly in the liquid was measured in dependence on the gas atmosphere (20% oxygen mixtures with nitrogen or with argon) and pH of plasma-treated water (controlled by buffers at pH 3.3, 6.9 or 10.1). The aqueous-phase chemistry and specific contributions of these species to the chemical and biocidal effects of air discharge plasma in water were evaluated using phenol as a chemical probe and bacteria Escherichia coli. The nitrated and nitrosylated products of phenol (4-nitrophenol, 2-nitrophenol, 4-nitrocatechol, 4-nitrosophenol) in addition to the hydroxylated products (catechol, hydroquinone, 1,4-benzoquinone, hydroxy-1,4-benzoquinone) evidenced formation of NO2·, NO· and OH· radicals and NO+ ions directly by the air plasma at the gas-liquid interface and through post-discharge processes in plasma-activated water (PAW) mediated by peroxynitrite (ONOOH). Kinetic study of post-discharge evolution of H2O2 and NO_{2}^{-} in PAW has demonstrated excellent fit with the pseudo-second-order reaction between H2O2 and NO_{2}^{-} . The third-order rate constant k = 1.1 × 103 M-2 s-1 for the reaction NO_{2}^{-} +H_{2}O_{2}+H^{+}\\to ONOOH+H_{2}O was determined in PAW at pH 3.3 with the rate of ONOOH formation in the range 10-8-10-9 M s-1. Peroxynitrite chemistry was shown to significantly participate in the antibacterial properties of PAW. Ozone presence in PAW was proved indirectly by pH-dependent degradation of phenol and detection of cis,cis-muconic acid, but contribution of ozone to the inactivation of bacteria by the air plasma was negligible.
S. Ivanova; D. I. Aleksiev
2002-01-01
The addition of unsubstituted and substituted benzenesulfinic acids to 2-nitro-1-phenyl-1-phenylsulfonylethene was studied kinetically by means of LC. The reaction follows the second-order kinetics: v = k[2-nitro-1-phenyl-1-phenylsulfonylethene] ·; [sulfinic acid]. The dependance of the rate constants on the temperature, and the influence of the p-substituents on the kinetic parameters were studied. The activation energy and the enthalpy of activation were calculated
Kinetics of NCO + hydrocarbon reactions
NASA Astrophysics Data System (ADS)
Park, Joonbum; Hershberger, John F.
1994-02-01
The kinetics of NCO reactions with hydrocarbon molecules were investigated using time-resolved infrared diode laser absorption spectroscopy. NCO was probed at 1905.6 cm -1, and HNCO reaction products were probed at 2280.1 cm -1. Rate constants at 296 K were measured to be < 1.0 × 10 -14, (7.04 ± 1.20) × 10 -14, (2.29 ± 0.13) × 10 -13, (6.13 ± 0.32) × 10 -13, (8.78 ± 0.42) × 10 -13, (7.47 ± 0.8) × 10 -14, and (2.85 ± 0.22) × 10 -12 cm 3 molecule -1 s -1, for CH 4, C 2H 6, C 3H 8, n-C 4H 10, n-C 5H 12, C 2H 2, and C 2H 4, respectively. Hydrogen abstraction to form HNCO was observed to be a major product channel for reactions with alkanes and for C 2H 2. For C 2H 2, HNCO is formed in negligible yield, indicating that addition—elimination is the primary mechanism active.
The kinetics of the esterification reaction between castor oil and oleic acid
A. T. Erciyes; L. Dandik; O. S. Kabasakal
1991-01-01
In this study, esterification of castor oil with oleic acid was investigated in view of the reaction kinetics under various\\u000a conditions. Potassium hydroxide,p-toluenesulfonic acid and tin chloride (SnCl22H2O) were used as catalysts. Reaction was carried out at 200C, 225C and 250 C by using equivalent proportions of the reactants.\\u000a For tin chloride, experimental data fitted the second-order rate equation, while
NASA Astrophysics Data System (ADS)
Isegawa, Miho; Liu, Fengyi; Maeda, Satoshi; Morokuma, Keiji
2014-10-01
We report reaction paths starting from N(2D) + H2O for doublet spin states, D0 and D1. The potential energy surfaces are explored in an automated fashion using the global reaction route mapping strategy. The critical points and reaction paths have been fully optimized at the complete active space second order perturbation theory level taking all valence electrons in the active space. In addition to direct dissociation pathways that would be dominant, three roaming processes, two roaming dissociation, and one roaming isomerization: (1) H2ON ? H-O(H)N ? H-HON ? NO(2?) + H2, (2) cis-HNOH ? HNO-H ? H-HNO ? NO + H2, (3) H2NO ? H-HNO ? HNO-H ? trans-HNOH, are confirmed on the D0 surface.
Isegawa, Miho; Liu, Fengyi; Maeda, Satoshi; Morokuma, Keiji
2014-10-21
We report reaction paths starting from N((2)D) + H2O for doublet spin states, D0 and D1. The potential energy surfaces are explored in an automated fashion using the global reaction route mapping strategy. The critical points and reaction paths have been fully optimized at the complete active space second order perturbation theory level taking all valence electrons in the active space. In addition to direct dissociation pathways that would be dominant, three roaming processes, two roaming dissociation, and one roaming isomerization: (1) H2ON ? H-O(H)N ? H-HON ? NO((2)?) + H2, (2) cis-HNOH ? HNO-H ? H-HNO ? NO + H2, (3) H2NO ? H-HNO ? HNO-H ? trans-HNOH, are confirmed on the D0 surface. PMID:25338892
The Kinetics of Isotopic Exchange Reactions.
ERIC Educational Resources Information Center
Logan, S. R.
1990-01-01
Discussed are the kinetic interactions of these chemical processes and the determination of the actual order of such reactions. Included are multiple exchange, catalytic exchange with deuterium, and depletion of the original substrate. (CW)
Ammonia, oxidation leaching of chalcopyrite —reaction kinetics
L. W. Beckstead; J. D. Miller
1977-01-01
The reaction for the ammonia, oxidation leaching of chalcopyrite, CuFeS2 + 4NH3 + 17\\/4 O2 + 2 OH- ? Cu(NH3)+2\\u000a 42 + l\\/2Fe2O3 + 2 SO4 + H2O was studied using monosize particles in an intensely stirred reactor under moderate pressures to determine the important\\u000a chemical factors which govern the kinetic response of the system. The reaction kinetics were studied
Thermodynamically Feasible Kinetic Models of Reaction Networks
Ederer, Michael; Gilles, Ernst Dieter
2007-01-01
The dynamics of biological reaction networks are strongly constrained by thermodynamics. An holistic understanding of their behavior and regulation requires mathematical models that observe these constraints. However, kinetic models may easily violate the constraints imposed by the principle of detailed balance, if no special care is taken. Detailed balance demands that in thermodynamic equilibrium all fluxes vanish. We introduce a thermodynamic-kinetic modeling (TKM) formalism that adapts the concepts of potentials and forces from irreversible thermodynamics to kinetic modeling. In the proposed formalism, the thermokinetic potential of a compound is proportional to its concentration. The proportionality factor is a compound-specific parameter called capacity. The thermokinetic force of a reaction is a function of the potentials. Every reaction has a resistance that is the ratio of thermokinetic force and reaction rate. For mass-action type kinetics, the resistances are constant. Since it relies on the thermodynamic concept of potentials and forces, the TKM formalism structurally observes detailed balance for all values of capacities and resistances. Thus, it provides an easy way to formulate physically feasible, kinetic models of biological reaction networks. The TKM formalism is useful for modeling large biological networks that are subject to many detailed balance relations. PMID:17208985
Fujimoto, Takahiro; Furuta, Nao; Mizutani, Tadashi
2015-03-21
Porphyrins carrying either a primary alcohol, a tertiary alcohol or a primary bromide linker group were allowed to react with the surface silanol groups on silicate glass thermally at 80-240 °C to obtain a monolayer film. The kinetics of the reaction was analysed based on the pseudo-second order equation. The tertiary alcohol and the primary bromide reacted much slower than the primary alcohol. Arrhenius plots indicated that higher activation energies can account for the slower reaction of both tertiary alcohol and primary bromide linkers. The introduction of six dodecyl chains into hydroxyporphyrin accelerated the anchoring reaction by a factor of 50 owing to the larger frequency factor of the reaction, demonstrating that the dynamics of the interface is one of the dominant factors regulating the reaction kinetics. PMID:25658579
NASA Astrophysics Data System (ADS)
Francés-Monerris, Antonio; Merchán, Manuela; Roca-Sanjuán, Daniel
2013-08-01
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.
Non-Markovian polymer reaction kinetics
NASA Astrophysics Data System (ADS)
Guérin, T.; Bénichou, O.; Voituriez, R.
2012-07-01
Describing the kinetics of polymer reactions, such as the formation of loops and hairpins in nucleic acids or polypeptides, is complicated by the structural dynamics of their chains. Although both intramolecular reactions, such as cyclization, and intermolecular reactions have been studied extensively, both experimentally and theoretically, there is to date no exact explicit analytical treatment of transport-limited polymer reaction kinetics, even in the case of the simplest (Rouse) model of monomers connected by linear springs. We introduce a new analytical approach to calculate the mean reaction time of polymer reactions that encompasses the non-Markovian dynamics of monomer motion. This requires that the conformational statistics of the polymer at the very instant of reaction be determined, which provides, as a by-product, new information on the reaction path. We show that the typical reactive conformation of the polymer is more extended than the equilibrium conformation, which leads to reaction times significantly shorter than predicted by the existing classical Markovian theory.
Kinetics of Heterogeneous Chemical Reactions, II*
Lin, S. H.; Eyring, H.
1970-01-01
The first-order and zero-order kinetics of heterogeneous reactions coupled with the diffusion process are studied. The differential equations of these reaction systems are solved for the cases in which the fluid is not stirred and the fluid is well stirred. It is shown that both the rate constants and the diffusion coefficient can be determined in various ways depending on the experimental conditions. PMID:5263761
Transient Kinetics of Slag Metal Reactions
G. A. Brooks; M. A. Rhamdhani; K. S. Coley; Subagyo; Y. Pan
2009-01-01
The kinetics of slag metal reactions are complex and often transient, in the sense that interfacial area, the equilibrium driving force, temperature gradients, and fluid properties are changing with time. This highly transient behavior is challenging to model using simple ordinary differential equations, and new theoretical approaches must be developed to deal with the complexity associated with these systems. Three
Wariishi, Hiroyuki; Gold, M.H. (Oregon Graduate Center, Beaverton (United States)); Dunford, H.B.; MacDonald, I.D. (Univ. of Alberta, Edmonton (Canada))
1989-02-25
Stopped-flow techniques were used to investigate the kinetics of the formation of manganese peroxidase compound I (MnPI) and of the reactions of MnPI and manganese peroxidase compound II (MnPII) with p-cresol and Mn{sup II}. All of the rate data were obtained from single turnover experiments under pseudo-first order conditions. In the presence of H{sub 2}O{sub 2} the formation of MnPI is independent of pH over the range 3.12-8.29 with a second-order rate constant of (2.0{+-}0.1) {times} 10{sup 6} M{sup {minus}1} s{sup {minus}1}. The activation energy for MnPI formation is 20 kJ mol{sup {minus}1}. MnPI formation also occurs with organic peroxides such as peracetic acid, m-chloroperoxybenzoic acid, and p-nitroperoxybenzoic acid with second-order rate constants of 9.7 x 10{sup 5}, 9.5 {times} 10{sup 4}, and 5.9 {times} 10{sup 4} M{sup {minus}1} s{sup {minus}1}, respectively. The reactions of MnPI and MnPII with p-cresol strictly obeyed second-order kinetics. The second-order rate constant for the reaction of MnPII with p-cresol is extremely low, (9.5{+-}0.5) m{sup {minus}1} s{sup {minus}1}. Kinetic analysis of the reaction of Mn{sup II} with MnPI and MnPII showed a binding interaction with the oxidized enzymes which led to saturation kinetics. The first-order dissociation rate constants for the reaction of Mn{sup II} with MnPI and MnPII are (0.7{+-}0.1) and (0.14{+-}0.01) s{sup {minus}1}, respectively, when the reaction is conducted in lactate buffer. Rate constants are considerably lower when the reactions are conducted in succinate buffer. Single turnover experiments confirmed that Mn{sup II} serves as an obligatory substrate for MnPII and that both oxidized forms of the enzyme form productive complexes with Mn{sup II}. Finally, these results suggest the {alpha}-hydroxy acids such as lactate facilitate the dissociation of Mn{sup II} from the enzyme.
Second-order statistics of complex signals
Bernard Picinbono; Pascal Bondon
1997-01-01
The second-order statistical properties of complex signals are usually characterized by the covariance function. However, this is not sufficient for a complete second-order description, and it is necessary to introduce another moment called the relation function. Its properties, and especially the conditions that it must satisfy, are analyzed both for stationary and nonstationary signals. This leads to a new perspective
Paper # XXX Topic: Reaction Kinetics Eastern State Fall Technical Meeting
Knyazev, Vadim D.
Paper # XXX Topic: Reaction Kinetics 1 Eastern State Fall Technical Meeting Chemical & Physical 1017 s-1 #12;Paper # XXX Topic: Reaction Kinetics 2 and activation energy values close to the C-C bond
Wu, C W; Eder, P S; Gopalan, V; Behrman, E J
2001-01-01
The inclusion of guanosine-5'-monothiophosphate (GMPS) in an in vitro transcription reaction facilitates enzymatic synthesis of an RNA transcript with a monothiophosphate group at the 5' end. A kinetic study of the modification reactions that generate monothiophosphate disulfide linkages with either 5'-GMPS alone or 5'-GMPS-primed RNA as the substrate revealed that the second-order rate constants increased as the pH was decreased. For example, when the reaction pH was lowered from 8 to 4, the k2 value for the coupling reaction between N-(6-[biotinamido]hexyl)-3'-(2'-pyridyldithio)propionamide (biotin-HPDP) and GMPS increased 67-fold from 1.84 to 123 M(-1) x s(-1). In addition to discussing a possible mechanism for coupling reactions that involve GMPS and disulfides, we also indicate conditions that are likely to be optimal for modification of the nucleophilic sulfur in 5'-GMPS-primed RNAs. PMID:11716671
Transient Kinetics of Slag Metal Reactions
NASA Astrophysics Data System (ADS)
Brooks, G. A.; Rhamdhani, M. A.; Coley, K. S.; Subagyo; Pan, Y.
2009-06-01
The kinetics of slag metal reactions are complex and often transient, in the sense that interfacial area, the equilibrium driving force, temperature gradients, and fluid properties are changing with time. This highly transient behavior is challenging to model using simple ordinary differential equations, and new theoretical approaches must be developed to deal with the complexity associated with these systems. Three examples from recent studies are described to illustrate methods of analyzing transient behavior. The first is desulfurization of steel in ladle metallurgy where the equilibrium driving force is changing with time, and the second is the case of reacting droplets in oxygen steelmaking where “bloating” of the droplet has a dramatic effect on the kinetics. The third is in the case of reactions between an alloy droplet and slag that result in large changes in interfacial area due to surface tension driven flows.
Transient Kinetics of Slag Metal Reactions
G. A. Brooks; M. A. Rhamdhani; K. S. Coley; Subagyo; Y. Pan
2009-01-01
The kinetics of slag metal reactions are complex and often transient, in the sense that interfacial area, the equilibrium\\u000a driving force, temperature gradients, and fluid properties are changing with time. This highly transient behavior is challenging\\u000a to model using simple ordinary differential equations, and new theoretical approaches must be developed to deal with the complexity\\u000a associated with these systems. Three
Numerical calculation of second order perturbations
Huston, Ian; Malik, Karim A., E-mail: i.huston@qmul.ac.uk, E-mail: k.malik@qmul.ac.uk [Astronomy Unit, School of Mathematical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS (United Kingdom)
2009-09-01
We numerically solve the Klein-Gordon equation at second order in cosmological perturbation theory in closed form for a single scalar field, describing the method employed in detail. We use the slow-roll version of the second order source term and argue that our method is extendable to the full equation. We consider two standard single field models and find that the results agree with previous calculations using analytic methods, where comparison is possible. Our procedure allows the evolution of second order perturbations in general and the calculation of the non-linearity parameter f{sub NL} to be examined in cases where there is no analytical solution available.
ON SECOND ORDER THOM-BOARDMAN SINGULARITIES
O M. FEH
In this paper we derive closed formulas for the Thom polynomials of two families of second order Thom-Boardman singularities §i;j. The formulas are given as linear combinations of Schur polynomials, and all coecients are nonneg- ative.
Contact Geometry of Second Order I
Keizo Yamaguchi
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,
A kinetic mechanism inducing oscillations in simple chemical reactions networks
Altafini, Claudio
A kinetic mechanism inducing oscillations in simple chemical reactions networks J. Coatl´even and C of oscillations in sufficiently simple reaction networks. Keywords: chemical reaction networks, oscillations, Hopf. Altafini September 10, 2009 Abstract It is known that a kinetic reaction network in which one or more
Oxidation of bisphenol A by permanganate: reaction kinetics and removal of estrogenic activity.
Yang, Jingjing; Wen, Gang; Zhao, Ji; Shao, Xiaoling; Ma, Jun
2013-01-01
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
A novel approach to modeling the reaction kinetics of tetracycline antibiotics with aqueous ozone.
Hopkins, Zachary R; Blaney, Lee
2014-01-15
Tetracycline antibiotics represent one of the most successful classes of pharmaceuticals and are extensively used around the world for human and veterinary health. Ozone-based processes have emerged as a selective water treatment process for many pharmaceuticals. The primary objective of this study was to determine the reaction kinetics for transformation of five tetracycline antibiotics (i.e., chlortetracycline, doxycycline, oxytetracycline, rolitetracycline, and tetracycline) by ozone across the pH2 to 9 range. The apparent second-order rate constant for tetracycline was on the order of 1-6 × 10(4) M(-1) s(-1) at low pH, and 0.6-2.0 × 10(6) M(-1) s(-1) at near neutral pH. The apparent second-order rate constants did not fit a conventional pKa-based model, presumably due to the complex acid/base speciation of tetracycline antibiotics. A model that considers the net charge on tetracycline molecules in solution provided a nice fit to experimental data for all five tetracyclines. The five tetracycline antibiotics demonstrated similar reaction kinetics with ozone, and a cumulative analysis of all kinetics data provides a baseline model for other tetracycline compounds. The ozone exposure required for complete transformation of tetracycline antibiotics (10(-5) M-s) is well below that achieved during ozone disinfection processes (10(-3) M-s), indicating that ozone is an effective treatment for tetracycline antibiotics. PMID:24041601
Spectroscopy and reaction kinetics of HCO
Guo, Yili
1989-01-01
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.
Kinetics of rouleau formation. II. Reversible reactions.
Samsel, R W; Perelson, A S
1984-01-01
Red blood cells aggregate face-to-face to form long, cylindrical, straight chains and sometimes branched structures called rouleaux. Here we extend a kinetic model developed by R. W. Samsel and A. S. Perelson (1982, Biophys. J. 37:493-514) to include both the formation and dissociation of rouleaux. We examine thermodynamic constraints on the rate constants of the model imposed by the principle of detailed balance. Incorporation of reverse reactions allows us to compute mean sizes of rouleaux and straight chain segments within rouleaux, as functions of time and at equilibrium. Using the Flory - Stockmayer method from polymer chemistry, we obtain a closed-form solution for the size distribution of straight chain segments within rouleaux at any point in the evolution of the reaction. The predictions of our theory compare favorably with data collected by D. Kernick , A.W.L. Jay , S. Rowlands , and L. Skibo (1973, Can. J. Physiol. Pharmacol. 51:690-699) on the kinetics of rouleau formation. When rouleaux grow large, they may contain rings or loops and take on the appearance of a network. We demonstrate the importance of including the kinetics of ring closure in the development of realistic models of rouleaux formation. Images FIGURE 1 FIGURE 13 PMID:6426540
Understanding Arsenate Reaction Kinetics with Ferric Hydroxides
Farrell, James; Chaudhary, Binod K.
2015-01-01
Understanding arsenic reactions with ferric hydroxides is important in understanding arsenic transport in the environment and in designing systems for removing arsenic from potable water. Many experimental studies have shown that the kinetics of arsenic adsorption on ferric hydroxides is biphasic, where a fraction of the arsenic adsorption occurs on a time scale of seconds while full equilibrium may require weeks to attain. This research employed density functional theory modeling in order to understand the mechanisms contributing to biphasic arsenic adsorption kinetics. The reaction energies and activation barriers for three modes of arsenate adsorption to ferric hydroxides were calculated. Gibbs free energies of reaction depended on the net charge of the complexes, which is a function of the system pH value. Physical adsorption of arsenate to ferric hydroxide proceeded with no activation barrier, with Gibbs free energies of reaction ranging from ?21 to ?58 kJ/mol. The highest Gibbs free energies of reaction for physical adsorption resulted from negative charge assisted hydrogen bonding between H atoms on the ferric hydroxide and O atoms in arsenate. The conversion of physically adsorbed arsenate into monodentate surface complexes had Gibbs free energies of activation ranging from 62 to 73 kJ/mol, and Gibbs free energies of reaction ranging from ?23 to ?38 kJ/mol. The conversion of monodentate surface complexes to bidentate, binuclear complexes had Gibbs free energies of activation ranging from 79 to 112 kJ/mol, and Gibbs free energies of reaction ranging from ?11 to ?55 kJ/mol. For release of arsenate from uncharged bidentate complexes, energies of activation as high as 167 kJ/mol were encountered. Increasingly negative charges on the complexes lowered the activation barriers for desorption of arsenate, and in complexes with ?2 charges, the highest activation barrier was 65 kJ/mol. This study shows that the slow kinetics associated with arsenic adsorption and desorption can be attributed to the high Gibbs free energies of activation for forming and breaking bonds with the ferric hydroxide. PMID:23806140
Reaction rate kinetics for in situ combustion retorting of Michigan Antrim oil shale
Rostam-Abadi, M.; Mickelson, R.W.
1984-01-01
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.
Reaction rates for mesoscopic reaction-diffusion kinetics
Stefan Hellander; Andreas Hellander; Linda Petzold
2015-01-28
The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework, frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a mixed boundary condition at the reaction radius of two molecules. We also establish fundamental limits for the range of mesh resolutions for which this approach yields accurate results, and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics.
Urban Principals' Second Order Change Leadership
ERIC Educational Resources Information Center
Taylor, Rosemarye T.; La Cava, Gonzalo S.
2011-01-01
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).…
Second-order eikonal exchange amplitudes
Gien, T.T.
1986-11-01
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.
Properties of second-order geometrical aberrations
NASA Astrophysics Data System (ADS)
Grammatin, A. P.
1994-08-01
This paper analyzes the properties of second-order aberrations that arise in centered optical systems that contain an aspherical surface whose sagittal equation contains a term proportional to the cube of the distance from a surface point to the optical axis. It is shown that the second-order spherical aberration decreases from the center of the field to its edge. No astigmatism appears in wide, oblique beams in the central part of the field. Coma increases linearly from zero at the center of the field to a value equal to the spherical aberration, and then remains constant over the field. A proof is given of the possibility of correcting the image curvature by using an aspherical surface of the type described above.
Second-order gravitational self-force
Eran Rosenthal
2006-09-18
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 waveforms 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.
Attentive processing of second-order motion?
Hiroshi Ashida
How we detect second-order motion, i.e., motion defined by higher-order properties like texture contrast, has been a matter of controversies. Models of early-level detection have been proposed, but recent psychophysical results suggest higher-level processing based on feature tracking. Here I review recent studies including our visual search experiments to discuss the role of feature tracking and\\/or attention, and to find
Visualizing second order tensor fields with hyperstreamlines
NASA Technical Reports Server (NTRS)
Delmarcelle, Thierry; Hesselink, Lambertus
1993-01-01
Hyperstreamlines are a generalization to second order tensor fields of the conventional streamlines used in vector field visualization. As opposed to point icons commonly used in visualizing tensor fields, hyperstreamlines form a continuous representation of the complete tensor information along a three-dimensional path. This technique is useful in visulaizing both symmetric and unsymmetric three-dimensional tensor data. Several examples of tensor field visualization in solid materials and fluid flows are provided.
Spacetime Encodings III - Second Order Killing Tensors
Jeandrew Brink
2009-11-09
This paper explores the Petrov type D, stationary axisymmetric vacuum (SAV) spacetimes that were found by Carter to have separable Hamilton-Jacobi equations, and thus admit a second-order Killing tensor. The derivation of the spacetimes presented in this paper borrows from ideas about dynamical systems, and illustrates concepts that can be generalized to higher- order Killing tensors. The relationship between the components of the Killing equations and metric functions are given explicitly. The origin of the four separable coordinate systems found by Carter is explained and classified in terms of the analytic structure associated with the Killing equations. A geometric picture of what the orbital invariants may represent is built. Requiring that a SAV spacetime admits a second-order Killing tensor is very restrictive, selecting very few candidates from the group of all possible SAV spacetimes. This restriction arises due to the fact that the consistency conditions associated with the Killing equations require that the field variables obey a second-order differential equation, as opposed to a fourth-order differential equation that imposes the weaker condition that the spacetime be SAV. This paper introduces ideas that could lead to the explicit computation of more general orbital invariants in the form of higher-order Killing Tensors.
Shtarov, A B; Krusic, P J; Smart, B E; Dolbier, W R
2001-10-17
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
Current issues in sol-gel reaction kinetics
Assink, R.A.; Kay, B.D.
1990-01-01
This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative features of the reaction kinetics can depend on catalyst concentration. At very high acid-catalyst concentrations, reverse are significant for TMOS sol-gels, while for moderate acid-catalyst concentrations, reverse reactions are substantially reduced. The reaction kinetics are substantially reduced. The reaction kinetics of two similar tetraalkoxysilanes: tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), can be markedly different under identical reaction conditions. Under acid-catalyzed reaction conditions, a TMOS sol-gel undergoes both water-and alcohol-producing condensation reactions while a TEOS sol-gel undergoes only water-producing condensation. The early time hydrolysis and condensation reactions of a TMOS sol-gel are statistical in nature and can be quantitatively described by a few simple reaction rate constants while the reaction behavior of a TEOS sol-gel is markedly nonstatistical. A comprehensive theory of sol-gel kinetics must address diverse experimental findings. 9 refs., 3 figs., 1 tab.
Higher Derivative versus Second Order Field Equations
NASA Astrophysics Data System (ADS)
Müller-Hoissen, F.
The first part of this work reviews problems of (particle and field) theories with higher than second time derivatives. The second part gives an overview about the known results concerning the structure of bosonic field theories with at most second order equations.Translated AbstractFeldgleichungen höherer versus zweiter OrdnungDie erste Hälfte dieser Arbeit faßt die bekannten Probleme von (Teilchenund Feld-)Gleichungen mit höheren als zweiten Zeitableitungen zusammen. In der zweiten Hälfte wird eine Übersicht über die Struktur der komplementären Klasse von Feldgleichungen mit höchstens zweiten Zeitableitungen für bosonische Felder gegeben.
Second-order conditioning in Drosophila
Tabone, Christopher J.; de Belle, J. Steven
2011-01-01
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 (SOC) protocol that further demonstrates the flexibility of fly behavior. In SOC, a previously conditioned stimulus (CS1) is used as reinforcement for a second conditioned stimulus (CS2) in associative learning. This higher-order context presents an opportunity for reassessing the roles of known learning and memory genes and neuronal networks in a new behavioral paradigm. PMID:21441302
A Generalized Kinetic Model for Heterogeneous Gas-Solid Reactions
Xu, Zhijie; Sun, Xin; Khaleel, Mohammad A.
2012-08-15
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.
Second order thermal corrections to electron wavefunction
NASA Astrophysics Data System (ADS)
Haseeb, Mahnaz Q.; Masood, Samina S.
2011-10-01
Second order perturbative corrections to electron wavefunction are calculated here, for the first time, at generalized temperature. Calculations of electron self energy are important for the renormalizability of electron mass and wavefunction in QED through order by order cancellation of singularities up to order ?. Cancellation of temperature dependent singularities is demonstrated by incorporating the results of both orders of integration between cold and hot loops. For finite terms, we have rewritten second order thermal corrections as well, in a concise form, to calculate wavefunction renormalization constant. Our results are in a form that includes intermediate temperatures T?m (where m is electron mass) while limits of high temperature T?m and low temperature T?m are also retrievable from them. A comparison with the existing results is included as well. The renormalized mass and wavefunction are used to calculate particle processes in extremely hot systems such as stellar cores and primordial nucleosynthesis during very early universe. An application to the latter case is also discussed.
Robust stability of second-order systems
NASA Technical Reports Server (NTRS)
Chuang, C.-H.
1995-01-01
It has been shown recently how virtual passive controllers can be designed for second-order dynamic systems to achieve robust stability. The virtual controllers were visualized as systems made up of spring, mass and damping elements. In this paper, a new approach emphasizing on the notion of positive realness to the same second-order dynamic systems is used. Necessary and sufficient conditions for positive realness are presented for scalar spring-mass-dashpot systems. For multi-input multi-output systems, we show how a mass-spring-dashpot system can be made positive real by properly choosing its output variables. In particular, sufficient conditions are shown for the system without output velocity. Furthermore, if velocity cannot be measured then the system parameters must be precise to keep the system positive real. In practice, system parameters are not always constant and cannot be measured precisely. Therefore, in order to be useful positive real systems must be robust to some degrees. This can be achieved with the design presented in this paper.
Second-order splitting schemes for a class of reactive systems
NASA Astrophysics Data System (ADS)
Ren, Zhuyin; Pope, Stephen B.
2008-09-01
We consider the numerical time integration of a class of reaction-transport systems that are described by a set of ordinary differential equations for primary variables. In the governing equations, the terms involved may require the knowledge of secondary variables, which are functions of the primary variables. Specifically, we consider the case where, given the primary variables, the evaluation of the secondary variables is computationally expensive. To solve this class of reaction-transport equations, we develop and demonstrate several computationally efficient splitting schemes, wherein the portions of the governing equations containing chemical reaction terms are separated from those parts containing the transport terms. A computationally efficient solution to the transport sub-step is achieved through the use of linearization or predictor-corrector methods. The splitting schemes are applied to the reactive flow in a continuously stirred tank reactor (CSTR) with the Davis-Skodjie reaction model, to the CO+H oxidation in a CSTR with detailed chemical kinetics, and to a reaction-diffusion system with an extension of the Oregonator model of the Belousov-Zhabotinsky reaction. As demonstrated in the test problems, the proposed splitting schemes, which yield efficient solutions to the transport sub-step, achieve second-order accuracy in time.
Second-order superintegrable quantum systems
Miller, W. [University of Minnesota, School of Mathematics (United States); Kalnins, E. G. [University of Waikato, Department of Mathematics and Statistics (New Zealand); Kress, J. M. [The University of New South Wales, School of Mathematics (Australia)], E-mail: j.kress@unsw.edu.au
2007-03-15
A classical (or quantum) superintegrable system on an n-dimensional Riemannian manifold is an integrable Hamiltonian system with potential that admits 2n - 1 functionally independent constants of the motion that are polynomial in the momenta, the maximum number possible. If these constants of the motion are all quadratic, then the system is second-order superintegrable, the most tractable case and the one we study here. Such systems have remarkable properties: multi-integrability and separability, a quadratic algebra of symmetries whose representation theory yields spectral information about the Schroedinger operator, and deep connections with expansion formulas relating classes of special functions. For n = 2 and for conformally flat spaces when n = 3, we have worked out the structure of the classical systems and shown that the quadratic algebra always closes at order 6. Here, we describe the quantum analogs of these results. We show that, for nondegenerate potentials, each classical system has a unique quantum extension.
Second-order temporal modulation transfer functions.
Lorenzi, C; Soares, C; Vonner, T
2001-08-01
Detection thresholds were measured for a sinusoidal modulation applied to the modulation depth of a sinusoidally amplitude-modulated (SAM) white noise carrier as a function of the frequency of the modulation applied to the modulation depth (referred to as f'm). The SAM noise acted therefore as a "carrier" stimulus of frequency fm, and sinusoidal modulation of the SAM-noise modulation depth generated two additional components in the modulation spectrum: fm-f'm and fm+f'm. The tracking variable was the modulation depth of the sinusoidal variation applied to the "carrier" modulation depth. The resulting "second-order" temporal modulation transfer functions (TMTFs) measured on four listeners for "carrier" modulation frequencies fm of 16, 64, and 256 Hz display a low-pass segment followed by a plateau. This indicates that sensitivity to fluctuations in the strength of amplitude modulation is best for fluctuation rates f'm below about 2-4 Hz when using broadband noise carriers. Measurements of masked modulation detection thresholds for the lower and upper modulation sideband suggest that this capacity is possibly related to the detection of a beat in the sound's temporal envelope. The results appear qualitatively consistent with the predictions of an envelope detector model consisting of a low-pass filtering stage followed by a decision stage. Unlike listeners' performance, a modulation filterbank model using Q values > or = 2 should predict that second-order modulation detection thresholds should decrease at high values of f'm due to the spectral resolution of the modulation sidebands (in the modulation domain). This suggests that, if such modulation filters do exist, their selectivity is poor. In the latter case, the Q value of modulation filters would have to be less than 2. This estimate of modulation filter selectivity is consistent with the results of a previous study using a modulation-masking paradigm [S. D. Ewert and T. Dau, J. Acoust. Soc. Am. 108, 1181-1196 (2000)]. PMID:11519571
Kinetic studies on the reaction between Trametes villosa laccase and dioxygen.
Bukh, Christian; Lund, Martin; Bjerrum, Morten J
2006-09-01
A laccase from the fungus Trametes villosa (TviL) was investigated in order to elucidate the reaction mechanism of the reduction of dioxygen to water performed by this blue multi-copper oxidase. The ability of TviL to activate dioxygen was studied by stopped-flow experiments and under steady-state conditions. In the stopped-flow experiments TviL was reduced with a small excess of 4-hydroxyphenylacetic acid and afterwards the re-oxidation process was monitored by stopped-flow techniques by mixing with excess dioxygen. The reaction between reduced TviL and dioxygen was studied in the temperature range 10-35 degrees Celsius and with the concentration of dioxygen between 30 and 240microM. The observed rate constant k(obs) is found to be linear dependent on the dioxygen concentration and the observed second-order rate constant for the re-oxidation of reduced TviL is, at 25 degrees Celsius, determined to be 1.14x10(6)M(-1)s(-1). The activation energy, E(a), is from the same data determined to be 22kJmol(-1). Oxidation of different phenols (4-hydroxyphenylacetic acid, 4-hydroxybenzoic acid, guaiacolsulfonic acid and hydroquinone) under steady state conditions was investigated at concentrations of dioxygen ranging from 60 to 250microM. This line of experiments showed that TviL follows a ping-pong mechanism, and an observed second-order rate constant for the reaction with dioxygen of 7.1x10(5)M(-1)s(-1) at 25 degrees Celsius was found with 4-hydroxyphenylacetic acid as reducing substrate. The two kinetic methods resulted in observed rate constants of equal magnitudes for the reaction with dioxygen, which suggests that the rate limiting step(s) is (are) included in both the reactions studied by the two different techniques. PMID:16828870
Karlesa, Anggita; De Vera, Glen Andrew D; Dodd, Michael C; Park, Jihye; Espino, Maria Pythias B; Lee, Yunho
2014-09-01
Oxidation of ?-lactam antibiotics by aqueous ferrate(VI) was investigated to determine reaction kinetics, reaction sites, antibacterial activity changes, and transformation products. Apparent second-order rate constants (kapp) were determined in the pH range 6.0-9.5 for the reaction of ferrate(VI) with penicillins (amoxicillin, ampicillin, cloxacillin, and penicillin G), a cephalosporin (cephalexin), and several model compounds. Ferrate(VI) shows an appreciable reactivity toward the selected ?-lactams (kapp for pH 7 = 110-770 M(-1) s(-1)). The pH-dependent kapp could be well explained by considering species-specific reactions between ferrate(VI) and the ?-lactams (with reactions occurring at thioether, amine, and/or phenol groups). On the basis of the kinetic results, the thioether is the main reaction site for cloxacillin and penicillin G. In addition to the thioether, the amine is a reaction site for ampicillin and cephalexin, and amine and phenol are reaction sites for amoxicillin. HPLC/MS analysis showed that the thioether of ?-lactams was transformed to stereoisomeric (R)- and (S)-sulfoxides and then to a sulfone. Quantitative microbiological assay of ferrate(VI)-treated ?-lactam solutions indicated that transformation products resulting from the oxidation of cephalexin exhibited diminished, but non-negligible residual activity (i.e., ?24% as potent as the parent compound). For the other ?-lactams, the transformation products showed much lower (<5%) antibacterial potencies compared to the parent compounds. Overall, ferrate(VI) oxidation appears to be effective as a means of lowering the antibacterial activities of ?-lactams, although alternative approaches may be necessary to achieve complete elimination of cephalosporin activities. PMID:25073066
Kinetic studies of isoprene reactions with hydroxyl and chlorine radicals
Suh, Inseon
2000-01-01
Kinetic studies of the isoprene oxidation reactions initiated by the hydroxyl radical OH and the chlorine atom Cl have been investigated using a fast-flow reactor in conjunction with chemical ionization mass spectrometry (CIMS) and using laser...
Kinetics of Acid Reactions: Making Sense of Associated Concepts
ERIC Educational Resources Information Center
Tan, Kim Chwee Daniel; Treagust, David F.; Chandrasegaran, A. L.; Mocerino, Mauro
2010-01-01
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…
Kinetic and theoretical study of the reaction of Cl atoms with a series of linear thiols
Garzon, Andres; Albaladejo, Jose [Departamento de Quimica Fisica, Facultad de CC. Quimicas, Universidad de Castilla La Mancha, Avenida Camilo Jose Cela, s/n, 13071 Ciudad Real (Spain); Notario, Alberto [Departamento de Quimica Fisica, Instituto de Tecnologias Quimica y Medioambiental (ITQUIMA), Universidad de Castilla La Mancha, Avenida Camilo Jose Cela, s/n, 13071 Ciudad Real (Spain); Pena-Ruiz, Tomas; Fernandez-Gomez, Manuel [Departamento de Quimica Fisica y Analitica, Facultad de CC. Experimentales, Universidad de Jaen, Paraje las Lagunillas, s/n, 23071 Jaen (Spain)
2008-11-21
The reactions of Cl with a series of linear thiols: 1-propanethiol (k{sub 1}), 1-butanethiol (k{sub 2}), and 1-pentanethiol (k{sub 3}) were investigated as a function of temperature (in the range of 268-379 K) and pressure (in the range of 50-200 Torr) by laser photolysis-resonance fluorescence. Only 1-propanethiol has previously been studied, but at 1 Torr of total pressure. The derived Arrhenius expressions obtained using our kinetic data were as follows: k{sub 1}=(3.97{+-}0.44)x10{sup -11} exp[(410{+-}36)/T], k{sub 2}=(1.01{+-}0.16)x10{sup -10} exp[(146{+-}23)/T], and k{sub 3}=(1.28{+-}0.10)x10{sup -10} exp[(129{+-}25)/T] (in units of cm{sup 3} molecule{sup -1} s{sup -1}). Moreover, a theoretical insight into mechanisms of these reactions has also been pursued through ab initio Moeller-Plesset second-order perturbation treatment calculations with 6-311G** basis set. Optimized geometries have been obtained for transition states and molecular complexes appearing along the different reaction pathways. Furthermore, molecular energies have been calculated at QCISD(T) level in order to get an estimation of the activation energies. Finally, the nature of the molecular complexes and transitions states is analyzed by using kinetic-potential and natural bond orbital total energy decomposition schemes.
de Almeida, Natália E C; de Aguiar, Inara; de Zawadzki, Andressa; Cardoso, Daniel R
2014-12-11
Hydroxyalkyl radicals have been reported to induce lipid oxidation as the key aspect of the pathogenesis of alcoholic fatty liver disease and are responsible for the alkylation and cleavage of DNA during the metabolism of a wide range of genotoxic compounds. However, relevant kinetic data for the oxidation of unsaturated lipids by 1-hydroxyethyl radical (HER) has not been reported. In this study, the rate constants for the reaction of unsaturated fatty acid methyl esters and sterols with HER have been determined using a competitive kinetic approach employing the spin-trap ?-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) as the competitive substrate. Polyunsaturated fatty acid methyl ester is shown to react with HER with an apparent second-order rate constant ranging from (3.7 ± 0.1) × 10(6) L mol(-1) s(-1) for methyl linoleate to (2.7 ± 0.2) × 10(7) L mol(-1) s(-1) for methyl docosahexanoate at 25.0 ± 0.2 °C in ethanol. The apparent second-order rate constant for polyunsaturated fatty acid methyl ester oxidation by HER is dependent on the number of bisallylic hydrogen atoms rather than on the bond dissociation energy value for the weakest C-H bond as determined by ab initio density functional theory calculations. Sterols displayed higher reactivity compared to unsaturated fatty acid methyl esters with apparent second-order rate constants of (2.7 ± 0.1) × 10(6) and (5.2 ± 0.1) × 10(7) L mol(-1) s(-1) at 25.0 ± 0.2 °C in ethanol for cholesterol and ergosterol, respectively. Similar experiments with prenylflavonoids as potential herbal chemopreventive agents for preventing alcoholic liver diseases yield apparent second-order rate constants close to the diffusion control with kapp values of (1.5 ± 0.2) and (3.6 ± 0.1) × 10(9) L mol(-1)s(-1) for 6-prenylnarigerin and xanthohumol at 25.0 ± 0.2 °C in ethanol solution, respectively. Polyunsaturated lipids were revealed to be highly reactive oxidizable substrates toward HER-induced oxidation in biological systems leading to damage of membranes and sensitive structures. PMID:25409421
Second-order continuum traffic flow model
NASA Astrophysics Data System (ADS)
Wagner, C.; Hoffmann, C.; Sollacher, R.; Wagenhuber, J.; Schürmann, B.
1996-11-01
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.
Reaction kinetics of hydrothermal carbonization of loblolly pine.
Reza, M Toufiq; Yan, Wei; Uddin, M Helal; Lynam, Joan G; Hoekman, S Kent; Coronella, Charles J; Vásquez, Victor R
2013-07-01
Hydrothermal carbonization (HTC) is a pretreatment process to convert diverse feedstocks to homogeneous energy-dense solid fuels. Understanding of reaction kinetics is necessary for reactor design and optimization. In this study, the reaction kinetics and effects of particle size on HTC were investigated. Experiments were conducted in a novel two-chamber reactor maintaining isothermal conditions for 15s to 30 min reaction times. Loblolly pine was treated at 200, 230, and 260°C. During the first few minutes of reaction, the solid-product mass yield decreases rapidly while the calorific value increases rapidly. A simple reaction mechanism is proposed and validated, in which both hemicellulose and cellulose degrade in parallel first-order reactions. Activation energy of hemicellulose and cellulose degradation were determined to be 30 and 73 kJ/mol, respectively. For short HTC times, both reaction and diffusion effects were observed. PMID:23651600
Second-Order Nonlinear Optical Imaging of Chiral Crystals
Kissick, David J.; Wanapun, Debbie; Simpson, Garth J.
2012-01-01
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. PMID:21469954
Kinetics of enzymatic reactions in lipid membranes containing domains.
Zhdanov, Vladimir P; Höök, Fredrik
2015-04-01
An appreciable part of enzymes operating in vivo is associated with lipid membranes. The function of such enzymes can be influenced by the presence of domains containing proteins and/or composed of different lipids. The corresponding experimental model-system studies can be performed under well controlled conditions, e.g., on a planar supported lipid bilayer or surface-immobilized vesicles. To clarify what may happen in such systems, we propose general kinetic equations describing the enzyme-catalyzed substrate conversion occurring via the Michaelis-Menten (MM) mechanism on a membrane with domains which do not directly participate in reaction. For two generic situations when a relatively slow reaction takes place primarily in or outside domains, we take substrate saturation and lateral substrate-substrate interactions at domains into account and scrutinize the dependence of the reaction rate on the average substrate coverage. With increasing coverage, depending on the details, the reaction rate reaches saturation via an inflection point or monotonously as in the conventional MM case. In addition, we show analytically the types of reaction kinetics occurring primarily at domain boundaries. In the physically interesting situation when the domain growth is fast on the reaction time scale, the latter kinetics are far from conventional. The opposite situation when the reaction is fast and controlled by diffusion has been studied by using the Monte Carlo technique. The corresponding results indicate that the dependence of the reaction kinetics on the domain size may be weak. PMID:25743228
Denicola, A; Freeman, B A; Trujillo, M; Radi, R
1996-09-01
Peroxynitrite is a strong oxidant produced in vivo as the reaction product of superoxide anion and nitric oxide (k approximately 5 x 10(9) M-1 s-1) and can be formed and mediate reactions in the extracellular environment. It has recently been reported that peroxynitrite and carbon dioxide react in a second-order process (S. V. Lymar and K. Hurst (1995) J. Am. Chem. Soc. 117, 8867-8868). Since one of the most abundant constituents of the extracellular milieu is bicarbonate anion (25 mM in plasma) which is in equilibrium with carbon dioxide (1.3 mM in plasma) we have further studied the kinetics of the reaction between peroxynitrite and carbon dioxide/ bicarbonate and the effect of bicarbonate on different peroxynitrite-mediated oxidations. The apparent second-order rate constant for the reaction is (2.3 +/- 0.1) x 10(3) M-1 s-1 at 37 degrees C and pH 7.4 and a pH-independent second-order rate constant of (5.8 +/- 0.2) x 10(4) M-1 s-1 at 37 degrees C was obtained considering peroxynitrite anion and carbon dioxide as the reacting species. The enthalpy and entropy of activation are delta H* = +10.7 +/- 0.8 kcal mol-1 and delta S* = -6.5 +/- 0.5 cal mol-1 K-1, respectively. The presence of bicarbonate had variable influence on peroxynitrite-mediated oxidations. While bicarbonate significantly enhanced peroxynitrite-mediated nitration of aromatics, it partially inhibited the oxidation of thiols, dimethylsulfoxide, oxyhemoglobin, and cytochrome c+2 and totally inhibited the hydroxylation of benzoate. Spontaneous chemiluminescence studies suggest the formation of bicarbonate radicals during the interactions of peroxynitrite with carbon dioxide/ bicarbonate. Our results support that peroxynitrite anion rapidly reacts with carbon dioxide to yield an adduct (ONOOCO2-) which can participate in oxidation and nitration processes, thus redirecting the primary reactivity of peroxynitrite. PMID:8806753
Second-Order Accurate Method for Solving Radiation-Hydrodynamics
Edwards, Jarrod Douglas
2013-11-12
Second-order discretization for radiation-hydrodynamics is currently an area of great interest. Second-order methods used to solve the respective single-physics problems often differ fundamentally, making it difficult to combine them in a second...
Kinetics and mechanisms of some atomic oxygen reactions
NASA Technical Reports Server (NTRS)
Cvetanovic, R. J.
1987-01-01
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.
Reaction-diffusion systems with stochastic time delay in kinetics
NASA Astrophysics Data System (ADS)
Sen, Shrabani; Ghosh, Pushpita; Ray, Deb Shankar
2010-05-01
Time delay is an important dynamical issue in a multistep chemical reaction. We present a theoretical scheme for delayed reaction-diffusion systems where the time delay in kinetics is stochastic in nature. It has been shown that a small but finite strength of delay may result in generic change in the nature of spatiotemporal instability in the dynamics. Our theoretical analysis has been corroborated by numerical simulations on two reaction-diffusion systems.
The Reaction of a Food Colorant with Sodium Hypochlorite: A Student-Designed Kinetics Experiment
NASA Astrophysics Data System (ADS)
Arce, Josefina; Betancourt, Rosa; Rivera, Yamil; Pijem, Joan
1998-09-01
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).
Iuga, Cristina; Alvarez-Idaboy, J Raul; Vivier-Bunge, Annik
2011-05-26
In this work, we have revisited the mechanism of the formic acid + OH radical reaction assisted by a single water molecule. Density functional methods are employed in conjunction with large basis sets to explore the potential energy surface of this radical-molecule reaction. Computational kinetics calculations in a pseudo-second-order mechanism have been performed, taking into account average atmospheric water concentrations and temperatures. We have used this method recently to study the single water molecule assisted H-abstraction by OH radicals (Iuga, C.; Alvarez-Idaboy, J. R.; Reyes, L.; Vivier-Bunge, A. J. Phys. Chem. Lett. 2010, 1, 3112; Iuga, C.; Alvarez-Idaboy, J. R.; Vivier-Bunge, A. Chem. Phys. Lett. 2010, 501, 11; Iuga, C.; Alvarez-Idaboy, J. R.; Vivier-Bunge, A. Theor. Chem. Acc. 2011, 129, 209), and we showed that the initial water complexation step is essential in the rate constant calculation. In the formic acid reaction with OH radicals, we find that the water-acid complex concentration is small but relevant under atmospheric conditions, and it could in principle be large enough to produce a measurable increase in the overall rate constant. However, the water-assisted process occurs according to a formyl hydrogen abstraction, rather than abstraction of carboxylic hydrogen as in the water-free case. As a result, the overall reaction rate constant is considerably smaller. Products are different in the water-free and water-assisted processes. PMID:21528871
Kinetics of reactions between aqueous sulfates and sulfides in hydrothermal systems
Hiroshi Ohmoto; Antonio C. Lasaga
1982-01-01
The rates of chemical reactions between aqueous sulfates and sulfides are essentially identical to sulfur isotopic exchange rates between them, because both the chemical and isotopic reactions involve simultaneous oxidation of sulfide-sulfur atoms and reduction of sulfate-sulfur. The rate of reaction can be expressed as a second order rate law: R = k ·[ SO 4 2- ]·[ S 2-
Adsorption Isotherms and Surface Reaction Kinetics
ERIC Educational Resources Information Center
Lobo, L. S.; Bernardo, C. A.
1974-01-01
Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)
Chemical kinetic reaction mechanism for the combustion of propane
NASA Technical Reports Server (NTRS)
Jachimowski, C. J.
1984-01-01
A detailed chemical kinetic reaction mechanism for the combustion of propane is presented and discussed. The mechanism consists of 27 chemical species and 83 elementary chemical reactions. Ignition and combustion data as determined in shock tube studies were used to evaluate the mechanism. Numerical simulation of the shock tube experiments showed that the kinetic behavior predicted by the mechanism for stoichiometric mixtures is in good agrement with the experimental results over the entire temperature range examined (1150-2600K). Sensitivity and theoretical studies carried out using the mechanism revealed that hydrocarbon reactions which are involved in the formation of the HO2 radical and the H2O2 molecule are very important in the mechanism and that the observed nonlinear behavior of ignition delay time with decreasing temperature can be interpreted in terms of the increased importance of the HO2 and H2O2 reactions at the lower temperatures.
Reaction kinetics of Ca-based sorbents with HC1
B. K. Gulett; W. Jozewicz; L. A. Stefanski
1992-01-01
The paper gives results of an investigation of the kinetics of the reaction between CaO and HCl under conditions that minimize bulk mass transfer and pore diffusion limitations. Reactivity data from 0.2 to 1 s exposure to 5000 ppm HCl in a fixed-bed reactor were analyzed by a shrinking core model of diffusion and chemical reaction control, either singly or
Kinetics and Mechanisms of Calcite Reactions with Saline Waters
Chapman, Piers; *Morse, John W. (*/deceased)
2010-11-15
1. Objective The general objective of this research was to determine the kinetics and mechanisms of calcite reactions with saline waters over a wide range of saline water composition, carbon dioxide partial pressure (pCO2), and modest ranges of T and P. This would be done by studying both reaction rates and solubility from changes in solution chemistry. Also, nanoscale observations of calcite surface morphology and composition would be made to provide an understanding of rate controlling mechanisms.
Basics of Chemical Kinetics -1 Rate of reaction = rate of disappearance of A =
Albert, RÃ©ka
Basics of Chemical Kinetics - 1 Rate of reaction = rate of disappearance of A = # of moles of Chemical Kinetics - 3 Elementary Reaction: Reaction order of each species is identical reactions: Forward Reaction Backward Reaction CBA + 2 CBA + 2 CBA + 2 CBA + 2 #12;Basics of Chemical
Reaction Kinetics in Food Extrusion-Methods and Results
Xuewei Zhao; Yimin Wei; Zhangcun Wang; Fengliang Chen; Anthony Okhonlaye Ojokoh
2011-01-01
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
REACTION KINETICS OF CA-BASED SORBENTS WITH HC1
The paper gives results of an investigation of the kinetics of the reaction between CaO and HC1 under conditions that minimize bulk mass transfer and pore diffusion limitations. eactivity data from 0.2 to 1 s exposure to 5000 ppm HC1 in a fixed-bed reactor were analyzed by a shri...
REACTION KINETICS OF CA-BASED SORBENTS WITH HC1
The kinetics of the reaction between CaO and HCl were investigated under conditions that minimize bulk mass transfer and pore diffusion limitations. Reactivity data from 0.2- to 1-s exposure to 5000 ppm HCl in a fixed bed reactor were analyzed by a shrinking core model of diffusi...
NASA Technical Reports Server (NTRS)
Miller, Ronald H.; Winske, Dan; Gary, S. P.
1992-01-01
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.
Pulsed ion beam investigation of the kinetics of surface reactions
NASA Technical Reports Server (NTRS)
Horton, C. C.; Eck, T. G.; Hoffman, R. W.
1989-01-01
Pulsed ion beam measurements of the kinetics of surface reactions are discussed for the case where the width of the ion pulse is comparable to the measured reaction time, but short compared to the time between successive pulses. Theoretical expressions are derived for the time dependence of the ion-induced signals for linear surface reactions. Results are presented for CO emission from surface carbon and CF emission from Teflon induced by oxygen ion bombardment. The strengths and limitations of this technique are described.
Kinetics of the aqueous-phase reaction between ozone and 2,4,6-trichlorophenol
Rinker, E.B.; Ashour, S.S.; Johnson, M.C.; Kott, G.J.; Rinker, R.G.; Sandall, O.C. [Univ. of California, Santa Barbara, CA (United States). Dept. of Chemical Engineering] [Univ. of California, Santa Barbara, CA (United States). Dept. of Chemical Engineering
1999-08-01
Treatment of industrial and municipal wastewater containing organic pollutants is of primary concern. Ozonation of these wastewaters has been effective in oxidizing organic pollutants into harmless compounds (CO{sub 2} and H{sub 2}O) as well as breaking up refractory compounds into different compounds that are more easily treated with cheaper, more conventional methods such as biodegradation, ion exchange, and filtration. In order to effectively treat wastewater with ozone and design appropriate treatment processes, reaction kinetics and reaction products must be determined. In addition, ozone solubilities and diffusivities must be known in order to model the diffusion/reaction process in this gas-liquid system. A wetted-sphere absorber was used to measure absorption rates of ozone into aqueous-buffered solutions of 2,4,6-trichlorophenol (TCP). Gas consisting of approximately 2.5% ozone in oxygen was contacted with aqueous-buffered TCP solution flowing over a sphere in a laminar liquid film. Absorption data were obtained by measuring the change in the liquid-phase concentration of TCP from the inlet to the outlet of the absorber. A rigorous numerical model for this diffusion/reaction process was used to analyze the absorption data to determine the second-order rate constant of the reaction between ozone and TCP at 15--35 C and pH 2 and 7. The kinetic data indicate that the rate-limiting step for the reaction of aqueous TCP with ozone is the same at pH 2 and 7. Four reaction products that occur early in the reaction of ozone with aqueous TCP were identified by GCMS, including: 2,3,4,6-tetrachlorophenol (TRCP), 4,6-dichlorocatechol (DCC), 2,6-dichlorohydroquinone (DCHQ), and 2,6-dichloroquinone (DCQ). Only DCHQ and CDQ occurred in significant concentrations. Over the pH range of 2 to 5, both DCHQ and DCQ were detected in the reacted solutions, while for pH 6 and 7 only DCHQ was detected. Carbon-13 NMR analysis shows that over longer ozone exposure times short-chain carboxylic acids are the dominant species in the reacted TCP solutions.
Cheng, Hanyang; Song, Dean; Liu, Huijuan; Qu, Jiuhui
2015-10-01
In this work, the fate of diclofenac (DCF) during permanganate (Mn(VII)) oxidation was investigated at environmentally relevant pH conditions (from 5 to 9). The batch experiments showed that the kinetics of the Mn(VII)/DCF reaction follows a second-order rate law with an apparent rate constant of 1.57±0.02M(-1)s(-1) at pH 7 and 20°C. The half-value of DCF was calculated to be 37.5min, when the concentration of Mn(VII) (0.4mM) was 20-fold excess of DCF. The pH-dependence of the reaction kinetics was investigated, and the DCF reactivity with Mn(VII) was found to decrease with increasing pH. The second-order rate constants were then quantitatively described by incorporating the species distribution of DCF. A lower reactivity of the anionic DCF (DCF(-)) in comparison with its neutral counterpart (DCF(0)) was most likely attributable to the interaction between the ionized carboxylate group and amine nitrogen position, which can reduce the nucleophilicity of amine nitrogen by inductive and resonance effects. Moreover, a range of degradation products and the corresponding structures were proposed on the basis of the LC-Q-TOF-MS analysis. A detailed ring-opening reaction mechanism was proposed as follows: Mn(VII) acts as an electrophile to attack the amine moiety, leading to the formation of the primary intermediate products 2,6-dichloroaniline and 5-hydroxy-diclofenac, which can be further transformed. The further degradation proceeded through a multistep process including ring-opening, decarboxylation, hydroxylation, and cyclation reactions. PMID:25522850
Injectivity of chemical reaction networks with mass action kinetics revisited
Feliu, Elisenda
2011-01-01
In this work we extend the characterization of injectivity via the Jacobian criterion first developed by Craciun and Feinberg for chemical reaction networks with outflow reactions to arbitrary chemical reaction networks taken with mass action kinetics. Injective chemical reaction networks do not have the capacity to admit multiple positive steady states for any rate constants and within each stoichiometric class. It is shown that a network is injective if and only if the determinant of the Jacobian of the system of ordinary differential equations associated to the network never vanishes. The determinant is a polynomial on the species concentrations and the rate constants, and its coefficients are fully determined. Previous works apply to chemical reaction networks whose stoichiometric space has maximal dimension. Here we present a direct route, independent of the dimension of the stoichiometric space which precludes at the same time the existence of degenerate steady states.
A Simple Second Order Cartesian Scheme for Compressible Flows
Paris-Sud XI, Université de
A Simple Second Order Cartesian Scheme for Compressible Flows Y. Gorsse, A. Iollo and L. Weynans Abstract A simple second order scheme for compressible inviscid flows on carte- sian meshes is presented to the simulation of a Ringleb flow is presented to demonstrate the accuracy of the method. Key words: compressible
Second order image statistics in computer graphics Erik Reinhard
Reinhard, Erik
Second order image statistics in computer graphics Erik Reinhard University of Central Florida order image statistics as well as their implications for computer graphics. We show of rendering parameters. As a result, second order image statistics are useful for modeling applications, which
SECOND ORDER CORRECTNESS OF THE BLOCKWISE BOOTSTRAP FOR
Bielefeld, University of
SECOND ORDER CORRECTNESS OF THE BLOCKWISE BOOTSTRAP FOR STATIONARY OBSERVATIONS F. G¨otze Fakult¨ur Statistik ETH Z¨urich CH8092 Z¨urich, Switzerland Abstract We show that the blockwise bootstrap 62M10; secondary 62G15, 62E20. Running head. Second order correctness. 1 #12; 1 Introduction Efron
Second-Order Conditioning during a Compound Extinction Treatment
ERIC Educational Resources Information Center
Pineno, Oskar; Zilski, Jessica M.; Schachtman, Todd R.
2007-01-01
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…
Jester-Weinstein, Jack (Jack L.)
2013-01-01
The design process for an experimental platform measuring reaction kinetics in a chemical looping combustion (CLC) process is documented and justified. To enable an experiment designed to characterize the reaction kinetics ...
Kinetic analysis of ligand-induced autocatalytic reactions.
Liu, Jiang-Hong; Wang, Zhi-Xin
2004-01-01
Protein phosphorylation and limited proteolysis are two most common regulatory mechanisms involving the energy-dependent covalent modification of regulatory enzymes. In addition to modifying other proteins, many protein kinases and proteases catalyse automodification reactions (i.e. reactions in which the kinase or zymogen serves as its own substrate), and their activities are frequently regulated by other regulatory ligands. In the present study, a kinetic analysis of autocatalytic reaction modulated by regulatory ligands is presented. On the basis of the kinetic equation, a novel procedure is developed to evaluate the kinetic parameters of the reaction. As an example of an application of this method, the effects of calcium ions on the autoacatalytic activation of trypsinogen by trypsin is re-examined. The results indicate that the binding affinity for Ca2+-bound trypsinogen to trypsin is at least two orders of magnitude higher than that for Ca2+-free trypsinogen, and therefore that the effect of Ca2+ ions on K(m*) values for trypsinogen is very much greater than that for the model peptides. Based on the experimental results, one possible molecular mechanism has been proposed. PMID:14705964
The kinetics study of the S + S2 ? S3 reaction by the chaperone mechanism.
Du, Shiyu; Germann, Timothy C; Francisco, Joseph S; Peterson, Kirk A; Yu, Hua-Gen; Lyons, James R
2011-04-21
The recombination of S atoms has been found to be stepwise from the smallest unit, the elemental S atom, to the most abundant molecule S(8). The reaction between S + S(2) ? S(3) has not been reported either experimentally or by theory, but may be a key intermediate step in the formation of sulfur aerosols in low-O(2) atmospheres. In this work, the kinetics of this reaction is reported with Ar gas used as the chaperone molecule in the production of S(3) via two complex intermediates: SAr + S(2) and S(2)Ar + S. Quasi-classical and classical trajectory methods are used. The rate constant of the S + S(2) + Ar ? S(3) + Ar reaction is determined to be 2.66 × 10(-33) cm(6)? mol(-1)?s(-1) at 298.15 K. The temperature dependence of the reaction is found to be 2.67 × 10(-33) exp[143.56(1?T-1?298.15)]. The second-order rate constant of S + S(2) ? S(3) is 6.47 × 10(-14) cm(3)?molecule(-1)?s(-1) at 298.15 K and the Arrhenius-type rate constant is calculated to be 6.25 × 10(-14) exp[450.15(1?T-1?298.15)] cm(3)?molecule(-1)?s(-1). This work provides a rate coefficient for a key intermediate species in studies of sulfur formation in the modern Venus atmosphere and the primitive Earth atmosphere, for which assumed model rate coefficients have spanned nearly 4 orders of magnitude. Although a symmetry-induced mass-independent isotope effect is not expected for a chaperone mechanism, the present work is an important step toward evaluating whether mass-independence is expected for thiozone formation as is observed for ozone formation. PMID:21513396
Alternative nonlinear model for estimating second-order rate coefficients for biodegradation.
Suflita, J M; Smolenski, W J; Robinson, J A
1987-01-01
A modification of the second-order model for biodegradation was derived, applied to an example data set, and shown to be superior for describing the anaerobic biodegradation of p-cresol by an enriched bacterial consortium. The modified model circumvents the no-growth assumption implicit in the use of the second-order rate equation, but still requires the assumption of first-order kinetics over the course of substrate depletion. Violation of the no-growth assumption is particularly important since overestimates of the pseudo-first-order rate coefficient lead to underestimates of the time required for the removal of a xenobiotic chemical from a contaminated environment. Our calculations show that the errors introduced into the pseudo-first-order rate coefficient (and the resulting estimates of the second-order rate coefficient) approach 100% if one doubling occurs in activity over the course of substrate depletion. For an exemplary data set, use of a first-order model resulted in a 100% overestimate of the first-order decay coefficient, which would in turn lead to a corresponding overestimate of the second-order rate coefficient. The modified model we describe is a potential alternative to the pseudo-first-order model for the routine estimation of second-order rate coefficients. PMID:3606091
Optimal second order sliding mode control for nonlinear uncertain systems.
Das, Madhulika; Mahanta, Chitralekha
2014-07-01
In this paper, a chattering free optimal second order sliding mode control (OSOSMC) method is proposed to stabilize nonlinear systems affected by uncertainties. The nonlinear optimal control strategy is based on the control Lyapunov function (CLF). For ensuring robustness of the optimal controller in the presence of parametric uncertainty and external disturbances, a sliding mode control scheme is realized by combining an integral and a terminal sliding surface. The resulting second order sliding mode can effectively reduce chattering in the control input. Simulation results confirm the supremacy of the proposed optimal second order sliding mode control over some existing sliding mode controllers in controlling nonlinear systems affected by uncertainty. PMID:24780159
Second-order Raman scattering in CuO.
Litvinchuk, A P; Möller, A; Debbichi, L; Krüger, P; Iliev, M N; Gospodinov, M M
2013-03-13
Polarized second-order Raman scattering spectra of CuO single crystals are reported. It is shown that for some scattering geometries the second-order processes dominate the inelastic light scattering spectra. Group-theoretical symmetry analysis of the selection rules for the first- and second-order scattering processes is performed and phonon dispersion relations are calculated within density functional theory. The main spectral features of the two-phonon spectra are assigned to overtones of the vibrational branches at various special points across the Brillouin zone. PMID:23388624
CMB anisotropies at second-order II: analytical approach
NASA Astrophysics Data System (ADS)
Bartolo, Nicola; Matarrese, Sabino; Riotto, Antonio
2007-01-01
We provide an analytical approach to the second-order cosmic microwave background (CMB) anisotropies generated by the non-linear dynamics taking place at last scattering. We study the acoustic oscillations of the photon baryon fluid in the tight coupling limit and we extend at second order the Meszaros effect. We allow for a generic set of initial conditions due to primordial non-Gaussianity and we compute all of the additional contributions arising at recombination. Our results are useful to provide the full second-order radiation transfer function at all scales necessary for establishing the level of non-Gaussianity in the CMB.
CMB Anisotropies at Second-Order II: Analytical Approach
Nicola Bartolo; Sabino Matarrese; Antonio Riotto
2007-01-30
We provide an analytical approach to the second-order Cosmic Microwave Background (CMB) anisotropies generated by the non-linear dynamics taking place at last scattering. We study the acoustic oscillations of the photon-baryon fluid in the tight coupling limit and we extend at second-order the Meszaros effect. We allow for a generic set of initial conditions due to primordial non-Gaussianity and we compute all the additional contributions arising at recombination. Our results are useful to provide the full second-order radiation transfer function at all scales necessary for establishing the level of non-Gaussianity in the CMB.
Superposition rules and second-order differential equations
J. F. Cariñena; J. de Lucas
2011-07-14
The main purpose of this work is to introduce and analyse some generalizations of diverse superposition rules for first-order differential equations to the setting of second-order differential equations. As a result, we find a way to apply the theories of Lie and quasi-Lie systems to analyse second-order differential equations. In order to illustrate our results, several second-order differential equations appearing in the physics and mathematical literature are analysed and some superposition rules for these equations are derived by means of our methods.
Jung, Moon Chul; Weber, Stephen G.
2006-01-01
Postcolumn derivatization reactions can enhance detector sensitivity and selectivity, but their successful combination with capillary liquid chromatography has been limited because of the small peak volumes in capillary chromatography. A capillary Taylor reactor (CTR), developed in our laboratory, provides simple and effective mixing and reaction in a 25-?m-radius postcolumn capillary. Homogenization of reactant streams occurs by radial diffusion, and a chemical reaction follows. Three characteristic times for a given reaction process can be predicted using simple physical and chemical parameters. Two of these times are the homogenization time, which governs how long it takes the molecules in the analyte and reagent streams to mix, and the reaction time, which governs how long the molecules in a homogeneous solution take to react. The third characteristic time is an adjustment to the reaction time called the start time, which represents an estimate of the average time the analyte stream spends without exposure to reagent. In this study, laser-induced fluorescence monitored the extent of the postcolumn reaction (reduction of Os(bpy)33+ by analyte to the photoluminescent Os(bpy)32+) in a CTR. The reaction time depends on the reaction rates. Analysis of product versus time data yielded second-order reaction rate constants between the PFET reagent, tris(2,2?-bipyridine)osmium, and standards ((ferrocenylmethyl)trimethylammonium cation and p-hydroquinone) or catechols (dopamine, epinephrine, norepinephrine, 3, 4-dihydroxyphenylacetic acid. The extent of the reactions in a CTR were then predicted from initial reaction conditions and compared to experimental results. Both the theory and experimental results suggested the reactions of catechols were generally kinetically controlled, while those of the standards were controlled by mixing time (1–2 s). Thus, the extent of homogenization can be monitored in a CTR using the relatively fast reaction of the reagent and p-hydroquinone. Kinetically controlled reactions of catechols, however, could be also completed in a reasonable time at increased reagent concentration. A satisfactory reactor, operating at 1.7 cm/s (2 ?L/min) velocity with solutes having diffusion coefficients in the 5 × 10?6 cm2/s range, can be constructed from 8.0 cm of 25-?m-radius capillary. Slower reactions require longer reaction times, but theoretical calculations expect that a CTR does not broaden a chromatographic peak (N = 14 000) from a 100-?m-capillary chromatography column by 10% if the pseudo-first-order rate constant is larger than 0.1 s?1. PMID:15858975
Microdroplet fusion mass spectrometry for fast reaction kinetics.
Lee, Jae Kyoo; Kim, Samuel; Nam, Hong Gil; Zare, Richard N
2015-03-31
We investigated the fusion of high-speed liquid droplets as a way to record the kinetics of liquid-phase chemical reactions on the order of microseconds. Two streams of micrometer-size droplets collide with one another. The droplets that fused (13 ?m in diameter) at the intersection of the two streams entered the heated capillary inlet of a mass spectrometer. The mass spectrum was recorded as a function of the distance x between the mass spectrometer inlet and the droplet fusion center. Fused droplet trajectories were imaged with a high-speed camera, revealing that the droplet fusion occurred approximately within a 500-?m radius from the droplet fusion center and both the size and the speed of the fused droplets remained relatively constant as they traveled from the droplet fusion center to the mass spectrometer inlet. Evidence is presented that the reaction effectively stops upon entering the heated inlet of the mass spectrometer. Thus, the reaction time was proportional to x and could be measured and manipulated by controlling the distance x. Kinetic studies were carried out in fused water droplets for acid-induced unfolding of cytochrome c and hydrogen-deuterium exchange in bradykinin. The kinetics of the former revealed the slowing of the unfolding rates at the early stage of the reaction within 50 ?s. The hydrogen-deuterium exchange revealed the existence of two distinct populations with fast and slow exchange rates. These studies demonstrated the power of this technique to detect reaction intermediates in fused liquid droplets with microsecond temporal resolution. PMID:25775573
S. Ivanova; D. I. Aleksiev
2006-01-01
The addition of unsubstituted and substituted benzenesulfinic acids to 1-aryl-1-arylsulfonyl-2-nitroethenes has been studied kinetically by means of LC. The rection follows the second-order kinetics v = k [1-aryl-1-arylsulfonyl-2-nitroethene].[sulfinic acid]. The dependence of rate constants on the temperature and the influence of p-substituents on the kinetic parameters have been investigated. The activation energy and the enthalpy of the activation are calculated
Second-order aberrations of an aspherical surface of rotation.
NASA Astrophysics Data System (ADS)
Grammatin, A. P.; Marchuk, S. M.
1990-06-01
Formulas are derived relating the meridional and sagittal components of second-order lateral aberration of an aspherical surface of rotation to the coordinates of the intersection of the extrameridional ray with the object plane and the entrance pupil plane.
Variational Principles for multisymplectic second-order classical field theories
Pedro Daniel Prieto-Martínez; Narciso Román-Roy
2015-03-31
We state a unified geometrical version of the variational principles for second-order classical field theories. The standard Lagrangian and Hamiltonian variational principles and the corresponding field equations are recovered from this unified framework.
Reaction kinetics of the addition of atomic sulfur to nitric oxide
Goumri, A.; Shao, Diane D.; Marshall, Paul [Department of Chemistry, University of North Texas, Denton, Texas 76203-5070 (United States)
2004-11-22
The reaction of S({sup 3}P{sub J}) with NO ({sup 2}{pi}) in an Ar bath gas has been studied by the laser photolysis-resonance fluorescence technique over 300-810 K at pressures from 60 to 800 mbar. The observed second-order rate constants are close to the low-pressure limit. Fitting of Troe's formalism to experiment, with an estimated F{sub cent}=0.78 exp(-T/7445) and k{sub {infinity}} given subsequently, yields k{sub 0}=(6.2{+-}0.6)x10{sup -33} exp(+(940{+-}40)/T) cm{sup 6} molecule{sup -2} s{sup -1}. Error limits are {+-}25%. A theoretical analysis of this value suggests that the average energy transferred during collisions between Ar and the excited intermediate is <{delta}E>=-360{sub -160}{sup +90} cm{sup -1}. Over 300-800 K, the high-pressure limit is predicted to be k{sub {infinity}}=2.2x10{sup -10} (T/300){sup 0.24} cm{sup 3} molecule{sup -1} s{sup -1}. Doublet and quartet adducts between S and NO were characterized via CBS-QB3 theory. The kinetic data can be rationalized with SNO ({sup 2}A{sup '}) as the major product, and an ab initio estimate of {delta}{sub f}H{sub 298} for SNO is 176{+-}8 kJ mol-1.
Second-Order Accurate FDTD Equations at Magnetic Media Interfaces
Qing Xin Chu; Hai Ding
2006-01-01
The rigorous second-order accurate finite-difference time-domain (FDTD) equations at magnetic media interfaces are straightforwardly derived through the discretization of the integral forms of Maxwell's curl equations on the nonuniform Yee's lattice and Taylor series extending of continuous field components over finite volumes including the interfaces. It is shown that in order to obtain second-order accuracy, we not only require to
Quantifier Elimination in Second-Order Predicate Logic
Dov M. Gabbay; Hans Jürgen Ohlbach
1992-01-01
An algorithm is presented which eliminates second{order quantiers over predicate vari- ables in formulae of type 9P1; ... ;Pn where is an arbitrary formula of rst{order pred- icate logic. The resulting formula is equiva- lent to the original formula { if the algorithm terminates. The algorithm can for example be applied to do interpolation, to eliminate the second{order quantiers in
First and second-order Raman scattering in nanocrystalline silicon
Puspashree Mishra; K. P. Jain
2001-01-01
Confinement effects on first-order and second-order Raman scattering in nanocrystalline silicon are presented. The average dimension of the nanocrystals has been determined by an analysis of the first-order Raman spectra using the phenomenological phonon confinement model. The second-order acoustic bands 2LA and 2TA do not seem to be influenced by confinement effects and are similar to those in the bulk.
Kinetic Studies on the Reaction between Dicyanocobinamide and Hypochlorous Acid
Maitra, Dhiman; Ali, Iyad; Abdulridha, Rasha M.; Shaeib, Faten; Khan, Sana N.; Saed, Ghassan M.; Pennathur, Subramaniam; Abu-Soud, Husam M.
2014-01-01
Hypochlorous acid (HOCl) is a potent oxidant generated by myeloperoxidase (MPO), which is an abundant enzyme used for defense against microbes. We examined the potential role of HOCl in corrin ring destruction and subsequent formation of cyanogen chloride (CNCl) from dicyanocobinamide ((CN)2-Cbi). Stopped-flow analysis revealed that the reaction consists of at least three observable steps, including at least two sequential transient intermediates prior to corrin ring destruction. The first two steps were attributed to sequential replacement of the two cyanide ligands with hypochlorite, while the third step was the destruction of the corrin ring. The formation of (OCl)(CN)-Cbi and its conversion to (OCl)2-Cbi was fitted to a first order rate equation with second order rate constants of 0.002 and 0.0002 µM?1s?1, respectively. The significantly lower rate of the second step compared to the first suggests that the replacement of the first cyanide molecule by hypochlorite causes an alteration in the ligand trans effects changing the affinity and/or accessibility of Co toward hypochlorite. Plots of the apparent rate constants as a function of HOCl concentration for all the three steps were linear with Y-intercepts close to zero, indicating that HOCl binds in an irreversible one-step mechanism. Collectively, these results illustrate functional differences in the corrin ring environments toward binding of diatomic ligands. PMID:25375773
A. K. Yatsimirskii; A. D. Ryabov; I. V. Berezin
1977-01-01
1.The interaction between Pd(OAc)2 anda-methylstyrene in acetic acid at 50–90°C leads to the formation of 2,5-diphenyl-2,4-hexadiene andp-(a-methylstyryl)palladium acetate.2.The kinetics of diene formation follow a second-order rate equation with the rate ofp-complex formation approaching a limiting value as the concentration of thea-methylstyrene is increased. Rate constants and activation parameters have been calculated for the reaction.3.Possible mechanisms for diene andp-complex formation are
Surface Reaction Kinetics of Ga 1x In x P Growth During Pulsed Chemical Beam Epitaxy
Surface Reaction Kinetics of Ga 1x In x P Growth During Pulsed Chemical Beam Epitaxy N. Dietz 1 growth has been a slow process because little is known about chemical reaction properties and reaction into the surface reaction kinetics during an organometallic deposition process. These insights will allow us
Giménez, Domingo
Using hyperheuristics to improve the determination of the kinetic constants of a chemical reaction constants of a chemical reaction Kinetic parameters of a chemical reaction are determined with metaheuristic of a chemical reaction that occurs in heterogeneous phase involves the simulation of the processes occurring
Second-order gauge-invariant perturbations during inflation
Finelli, F.; Marozzi, G.; Vacca, G. P.; Venturi, G. [INAF/IASF-BO, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna Istituto Nazionale di Astrofisica Via Gobetti 101, I-40129 Bologna (Italy) and INAF/OAB, Osservatorio Astronomico di Bologna Istituto Nazionale di Astrofisica Via Ranzani 1, I-40127 Bologna (Italy) and INFN, Sezione di Bologna, Via Irnerio 46, I-40126 Bologna (Italy); Dipartimento di Fisica, Universita degli Studi di Bologna and INFN, via Irnerio 46, I-40126 Bologna (Italy)
2006-10-15
The evolution of gauge invariant second-order scalar perturbations in a general single field inflationary scenario are presented. Different second-order gauge-invariant expressions for the curvature are considered. We evaluate perturbatively one of these second order curvature fluctuations and a second-order gauge-invariant scalar field fluctuation during the slow-roll stage of a massive chaotic inflationary scenario, taking into account the deviation from a pure de Sitter evolution and considering only the contribution of super-Hubble perturbations in mode-mode coupling. The spectra resulting from their contribution to the second order quantum correlation function are nearly scale-invariant, with additional logarithmic corrections with respect to the first order spectrum. For all scales of interest the amplitude of these spectra depends on the total number of e-folds. We find, on comparing first and second order perturbation results, an upper limit to the total number of e-folds beyond which the two orders are comparable.
Correction for instrument time constant in determination of reaction kinetics.
Chilton, Marie (Brigham Young University, Provo, UT); Clark, Jared (Brigham Young University, Provo, UT); Thomas, Nathan (Brigham Young University, Provo, UT); Nicholson, Allen (Brigham Young University, Provo, UT); Hansen, Lee D. (Brigham Young University, Provo, UT); Hansen, Clifford W.; Hansen, Jaron (Brigham Young University, Provo, UT)
2010-02-01
Rates of reactions can be expressed as dn/dt = kcf(n) where n is moles of reaction, k is a rate constant, c is a proportionality constant, and f(n) is a function of the properties of the sample. When the instrument time constant, ?, and k are sufficiently comparable that measured rates are significantly affected by instrument response, correction for instrument response must be done to obtain accurate reaction kinetics. Correction for instrument response has previously been done by truncating early data or by use of the Tian equation. Both methods can lead to significant errors. We describe a method for simultaneous determination of ?, k, and c by fitting equations describing the combined instrument response and rate law to rates observed as a function of time. The method was tested with data on the heat rate from acid-catalyzed hydrolysis of sucrose.
NO sub x -char reactions: Kinetics and transport aspects
Calo, J.M.; Suuberg, E.M.
1990-01-01
The present project is motivated by the need to reduce NO{sub x} emissions from combustors, especially coal combustors. Reactions with carbon are known to be effective at reducing No to N{sub 2}, and remain interesting candidates in a wide variety of possible applications. These reactions are known to be important in reducing NO{sub x} emissions from fluidized bed coal combustors, in which the coal char itself serves as the reducing agent. The principal goal of this project is to develop a mechanistic understanding of the processes by which carbons reduce NO to N{sub 2}. The carbon was a char derived from phenol-formaldehyde resin. This material has been noted to be a reasonable model for coal chars in most respects, expect that its gasification behavior is not complicated by catalytic processes due to minerals. In the first phases of the project, the global kinetics of the process were established. In more recent work, attention has been turned to the individual steps in the mechanism. Recent quarterly reports have detailed the role of both chemisorption and desorption processes in determining the course and kinetics of the process. This report continues the reporting of results obtained along these lines, and draws an important new conclusion concerning the number of separate processes involved in determining the kinetics. 40 refs., 3 figs., 2 tabs.
A second-order moment method of dense gas–solid flow for bubbling fluidization
Sun Dan; Wang Shuyan; Lu Huilin; Shen Zhiheng; Li Xiang; Wang Shuai; Zhao Yunhua; Wei Lixin
2009-01-01
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
Simulation of the kinetics of precipitation reactions in ferritic steels
Schneider, A. [Department of Materials Technology, Max-Planck-Institut fuer Eisenforschung GmbH, Max-Planck Strasse 1, 40237 Duesseldorf (Germany)]. E-mail: schneider@mpie.de; Inden, G. [Department of Materials Technology, Max-Planck-Institut fuer Eisenforschung GmbH, Max-Planck Strasse 1, 40237 Duesseldorf (Germany)
2005-01-10
Computer simulations of diffusion-controlled phase transformations in model alloys of Fe-Cr-C, Fe-Cr-W-C, Fe-Cr-Si-C, and Fe-Cr-Co-V-C are presented. The compositions considered are typical for ferritic steels. The simulations are performed using the software DICTRA and the thermodynamic calculations of phase equilibria are performed using Thermo-Calc. The thermodynamic driving forces and the kinetics of diffusion-controlled precipitation reactions of M{sub 23}C{sub 6}, M{sub 7}C{sub 3}, cementite and Laves-phase (Fe, Cr){sub 2}W are discussed. The simultaneous growth of stable and metastable phases is treated in a multi-cell approach. The results show remarkable effects on the growth kinetics due to the competition during simultaneous growth.
NASA Technical Reports Server (NTRS)
Liechty, Derek S.; Lewis, Mark J.
2010-01-01
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.
Reaction of OH with CINO: kinetics and mechanisms
Finlayson-Pitts, B.J.; Ezell, M.J.; Wang, S.Z.; Grant, C.E.
1987-04-23
The kinetics and products of the gas-phase reaction of OH with CINO have been studied in a fast flow discharge system using the reaction of hydrogen atoms with NO/sub 2/ as the source of OH. The decay of OH in excess CINO at a total pressure of 1.05 +/- 0.05 Torr in He was followed by resonance fluorescence at 309.5 nm at temperatures from 262 to 373K. The stable products observed by mass spectrometry from 276 to 353 K and from 0.2 to 0.8 Torr total pressure were HOCl, HONO, and Cl/sub 2/. Molecular Cl/sub 2/ results from the reaction of Cl atoms with the excess CINO present. The ratio of the products HOCl/Cl/sub 2/ did not change significantly with temperature or total pressure. The Arrhenius expression for the rate constant k/sub 1/ (= k/sub 1a/ + k/sub 1b/) for the reaction of Oh with CINO is k/sub 1/ = (1.5/sub -0.1//sup +0.1/ x 10/sup -12/) exp(-(458 +/- 27)/T) cm/sup 3/ molecule/sup -1/ s/sup -1/, with k/sub 1/ = (3.2 +/- 0.5) x 10/sup -13/ cm/sup 3/ molecule/sup -1/ cm/sup 3/ molecule/sup -1/ s/sup -1/ at 298 K, where all errors are two standard deviations. From these kinetic data, a typical tropospheric lifetime of CINO with respect to reaction with Oh is calculated to be approx.36 days, too slow to compete with CINO photolysis.
Kinetic Study of the Austempering Reactions in Ductile Irons
NASA Astrophysics Data System (ADS)
Pérez, M. J.; Cisneros, M. M.; Almanza, E.; Haro, S.
2012-11-01
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.
Kinetics and mechanisms of reactions involving small aromatic reactive intermediates
Lin, M.C. [Emory Univ., Atlanta, GA (United States)
1993-12-01
Small aromatic radicals such as C{sub 6}H{sub 5}, C{sub 6}H{sub 5}O and C{sub 6}H{sub 4} are key prototype species of their homologs. C{sub 6}H{sub 5} and its oxidation product, C{sub 6}H{sub 5}O are believed to be important intermediates which play a pivotal role in hydrocarbon combustion, particularly with regard to soot formation. Despite their fundamental importance, experimental data on the reaction mechanisms and reactivities of these species are very limited. For C{sub 6}H{sub 5}, most kinetic data except its reactions with NO and NO{sub 2}, were obtained by relative rate measurements. For C{sub 6}H{sub 5}O, the authors have earlier measured its fragmentation reaction producing C{sub 5}H{sub 5} + CO in shock waves. For C{sub 6}H{sub 4}, the only rate constant measured in the gas phase is its recombination rate at room temperature. The authors have proposed to investigate systematically the kinetics and mechanisms of this important class of molecules using two parallel laser diagnostic techniques--laser resonance absorption (LRA) and resonance enhanced multiphoton ionization mass spectrometry (REMPI/MS). In the past two years, study has been focused on the development of a new multipass adsorption technique--the {open_quotes}cavity-ring-down{close_quotes} technique for kinetic applications. The preliminary results of this study appear to be quite good and the sensitivity of the technique is at least comparable to that of the laser-induced fluorescence method.
Thermochemical kinetics for multireference systems: addition reactions of ozone.
Zhao, Yan; Tishchenko, Oksana; Gour, Jeffrey R; Li, Wei; Lutz, Jesse J; Piecuch, Piotr; Truhlar, Donald G
2009-05-14
The 1,3-dipolar cycloadditions of ozone to ethyne and ethene provide extreme examples of multireference singlet-state chemistry, and they are examined here to test the applicability of several approaches to thermochemical kinetics of systems with large static correlation. Four different multireference diagnostics are applied to measure the multireference characters of the reactants, products, and transition states; all diagnostics indicate significant multireference character in the reactant portion of the potential energy surfaces. We make a more complete estimation of the effect of quadruple excitations than was previously available, and we use this with CCSDT/CBS estimation of Wheeler et al. (Wheeler, S. E.; Ess, D. H.; Houk, K. N. J. Phys. Chem. A 2008, 112, 1798.) to make new best estimates of the van der Waals association energy, the barrier height, and the reaction energy to form the cycloadduct for both reactions. Comparing with these best estimates, we present comprehensive mean unsigned errors for a variety of coupled cluster, multilevel, and density functional methods. Several computational aspects of multireference reactions are considered: (i) the applicability of multilevel theory, (ii) the convergence of coupled cluster theory for reaction barrier heights, (iii) the applicability of completely renormalized coupled cluster methods to multireference systems, (iv) the treatment by density functional theory, (v) the multireference perturbation theory for multireference reactions, and (vi) the relative accuracy of scaling-type multilevel methods as compared with additive ones. It is found that scaling-type multilevel methods do not perform better than the additive-type multilevel methods. Among the 48 tested density functionals, only M05 reproduces the best estimates within their uncertainty. Multireference perturbation theory based on the complete-active-space reference wave functions constructed using a small number of reaction-specific active orbitals gives accurate forward barrier heights; however, it significantly underestimates reaction energies. PMID:19374412
Kinetics of the reaction of hydroxyl radicals with nitric acid
NASA Technical Reports Server (NTRS)
Margitan, J. J.; Watson, R. T.
1982-01-01
An extensive study was made of the reaction of hydroxyl radicals with nitric acid in a laser photolysis-resonance fluorescence system. A 266 nm laser was used to photolyze HNO3 in the temperature range 225-415 K at pressures of 20-300 torr. A temperature dependence was detected below room temperature, with a leveling off at 298 K and a wide spread in the rate constants. A pressure dependence was observed over the entire range and was more pronounced at lower temperatures. The results are noted to be in agreement with those of previous investigations. However, the wide range of rate constants are suggested to be a problem for stratospheric HO(x) modeling for anthropogenic effects. No explanation could be given of the varying results obtained by other investigators regarding the kinetics of the reactions.
Second-order wave effects on TLP tendon tension responses
Xue, H.; Mercier, R.S. [Shell E and P Technology Co., Houston, TX (United States). Offshore Structures
1996-12-31
This paper presents a general procedure for analyzing the second-order wave effects on the tendon tension responses of a TLP. The approach solves both first- and second-order equation of motions for a TLP system in frequency domain. Viscous effects are included in the form of statistically linearized damping coefficients. An efficient algorithm has been devised for reducing the burden of second-order wave diffraction analysis, which selects the interacting frequency pairs according to springing frequency of interest to minimize the cost of computing quadratic transfer functions (QTFs) and allow accurate interpolation of QTFs. Moment statistics of the tension process are computed through an eigenvalue analysis. The developed method is applied to analyze the tendon tension responses of a TLP design in water depth of 3,000 ft.
Second order perturbations during inflation beyond slow-roll
Huston, Ian; Malik, Karim A., E-mail: i.huston@qmul.ac.uk, E-mail: k.malik@qmul.ac.uk [Queen Mary University of London, Astronomy Unit, School of Physics and Astronomy, Mile End Road, London E1 4NS (United Kingdom)
2011-10-01
We numerically calculate the evolution of second order cosmological perturbations for an inflationary scalar field without resorting to the slow-roll approximation or assuming large scales. In contrast to previous approaches we therefore use the full non-slow-roll source term for the second order Klein-Gordon equation which is valid on all scales. The numerical results are consistent with the ones obtained previously where slow-roll is a good approximation. We investigate the effect of localised features in the scalar field potential which break slow-roll for some portion of the evolution. The numerical package solving the second order Klein-Gordon equation has been released under an open source license and is available for download.
First- and second-order Raman scattering in nanocrystalline silicon
Mishra, Puspashree; Jain, K. P.
2001-08-15
Confinement effects on first-order and second-order Raman scattering in nanocrystalline silicon are presented. The average dimension of the nanocrystals has been determined by an analysis of the first-order Raman spectra using the phenomenological phonon confinement model. The second-order acoustic bands 2LA and 2TA do not seem to be influenced by confinement effects and are similar to those in the bulk. The second-order optic bands are broadened and shifted in comparison to those in the bulk. The ratio of the integrated intensities I(2TO){sub int}/I(TO){sub int} depends upon the nanocrystal size and varies between the crystalline and amorphous limits.
Skyrme interaction to second order in nuclear matter
N. Kaiser
2015-05-26
Based on the phenomenological Skyrme interaction various density-dependent nuclear matter quantities are calculated up to second order in many-body perturbation theory. The spin-orbit term as well as two tensor terms contribute at second order to the energy per particle. The simultaneous calculation of the isotropic Fermi-liquid parameters provides a rigorous check through the validity of the Landau relations. It is found that published results for these second order contributions are incorrect in most cases. In particular, interference terms between $s$-wave and $p$-wave components of the interaction can contribute only to (isospin or spin) asymmetry energies. Even with nine adjustable parameters, one does not obtain a good description of the empirical nuclear matter saturation curve in the low density region $0Skyrme framework.
Spacecraft attitude determination using a second-order nonlinear filter
NASA Technical Reports Server (NTRS)
Vathsal, S.
1987-01-01
The stringent attitude determination accuracy and faster slew maneuver requirements demanded by present-day spacecraft control systems motivate the development of recursive nonlinear filters for attitude estimation. This paper presents the second-order filter development for the estimation of attitude quaternion using three-axis gyro and star tracker measurement data. Performance comparisons have been made by computer simulation of system models and filter mechanization. It is shown that the second-order filter consistently performs better than the extended Kalman filter when the performance index of the root sum square estimation error of the quaternion vector is compared. The second-order filter identifies the gyro drift rates faster than the extended Kalman filter. The uniqueness of this algorithm is the online generation of the time-varying process and measurement noise covariance matrices, derived as a function or the process and measurement nonlinearity, respectively.
TÃ³th, JÃ¡nos
OF CHEMICAL REACTIONS BY DIGITAL COMPUTER, H. APPLICATIONS T. Sipos1, J.TSth 2 and P. ~.rdi1 1. Danube Oil chemical reactions (especially those of biological interest, e.g. reactions exhibiting oscillationReaction Kinetics and Catalysis Letters, Vol. 1, No. 2/1974/209-213 STOCHASTIC SIMULATION
Kubo Formulas for Second-Order Hydrodynamic Coefficients
Moore, Guy D.; Sohrabi, Kiyoumars A. [Department of Physics, McGill University, 3600 rue University, Montreal, Quebec H3A 2T8 (Canada)
2011-03-25
At second order in gradients, conformal relativistic hydrodynamics depends on the viscosity {eta} and on five additional ''second-order'' hydrodynamical coefficients {tau}{sub {Pi}}, {kappa}, {lambda}{sub 1}, {lambda}{sub 2}, and {lambda}{sub 3}. We derive Kubo relations for these coefficients, relating them to equilibrium, fully retarded three-point correlation functions of the stress tensor. We show that the coefficient {lambda}{sub 3} can be evaluated directly by Euclidean means and does not in general vanish.
Second-order coupling between excited atoms and surface polaritons
NASA Astrophysics Data System (ADS)
Ribeiro, Sofia; Buhmann, Stefan Y.; Scheel, Stefan
2013-04-01
Casimir-Polder interactions between an atom and a macroscopic body are typically regarded as being due to the exchange of virtual photons. This is strictly true only at zero temperature. At finite temperatures, real-photon exchange can provide a significant contribution to the overall dispersion interaction. Here, we describe a resonant two-photon process between an atom and a planar interface. We derive a second-order effective Hamiltonian to explain how atoms can couple resonantly to the surface polariton modes of the dielectric medium. This leads to second-order energy exchanges which we compare with the standard nonresonant Casimir-Polder energy.
Static second-order polarizabilities of aminobenzophenones and nitrobenzophenones
NASA Technical Reports Server (NTRS)
Moore, Craig E.; Cardelino, Beatriz H.
1991-01-01
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.
Second-order subsonic airfoil theory including edge effects
NASA Technical Reports Server (NTRS)
Van Dyke, Milton D
1956-01-01
Several recent advances in plane subsonic flow theory are combined into a unified second-order theory for airfoil sections of arbitrary shape. The solution is reached in three steps: the incompressible result is found by integration, it is converted into the corresponding subsonic compressible result by means of the second-order compressibility rule, and it is rendered uniformly valid near stagnation points by further rules. Solutions for a number of airfoils are given and are compared with the results of other theories and of experiment. A straight-forward computing scheme is outlined for calculating the surface velocities and pressures on any airfoil at any angle of attack
The Poisson equation at second order in relativistic cosmology
Hidalgo, J.C. [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Christopherson, Adam J. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Malik, Karim A., E-mail: juan.hidalgo@port.ac.uk, E-mail: Adam.Christopherson@nottingham.ac.uk, E-mail: k.malik@qmul.ac.uk [Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS (United Kingdom)
2013-08-01
We calculate the relativistic constraint equation which relates the curvature perturbation to the matter density contrast at second order in cosmological perturbation theory. This relativistic ''second order Poisson equation'' is presented in a gauge where the hydrodynamical inhomogeneities coincide with their Newtonian counterparts exactly for a perfect fluid with constant equation of state. We use this constraint to introduce primordial non-Gaussianity in the density contrast in the framework of General Relativity. We then derive expressions that can be used as the initial conditions of N-body codes for structure formation which probe the observable signature of primordial non-Gaussianity in the statistics of the evolved matter density field.
Controlling flexible structures with second order actuator dynamics
NASA Technical Reports Server (NTRS)
Inman, Daniel J.; Umland, Jeffrey W.; Bellos, John
1989-01-01
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.
KINETICS OF IRON - SODIUM DISILICATE REACTIONS AND WETTING
Tomsia, Antoni P.; Pask, Joseph A.
1980-01-01
Thermogravimetric and sessile drop measurements were used to study kinetics of redox reactions between sodium disilicate glass and iron. Two redox reaction sequences were identified; both introduced ferrous oxide into the glass at the interface. One consists of formation of ferrous oxide at the interface by reduction of sodium ions in the glass; this is primarily dependent on the a(FeO) in the metal being less than one. The second consists of oxidation of ferrous ions in the glass by the reduction of sodium ions to form ferric ions which subsequently react with the iron to form ferrous oxide. The reaction rates were shown to be sensitive to temperature, time, total ambient pressure, partial pressure of sodium and oxygen in the atmosphere, and the a(FeO) in the iron. Decrease of contact angles and spreading occur with the redox reaction in which the metal plays an active role, i.e. whose a(FeO) is less than one and whose composition undergoes a change.
Kinetic study of the OH radical reaction with phenylacetylene.
Abhinavam Kailasanathan, Ranjith Kumar; Thapa, Juddha; Goulay, Fabien
2014-09-11
The reaction of the OH radical with phenylacetylene is studied over the 298-423 K temperature range and 1-7.5 Torr pressure range in a quasi-static reaction cell. The OH radical is generated by 266 nm photolysis of hydrogen peroxide (H2O2) or 355 nm photolysis of nitrous acid (HONO), and its concentration monitored using laser-induced fluorescence. The measured reaction rates are found to strongly depend on laser fluence at 266 nm. The 266 nm absorption cross-section of phenylacetylene is measured to be 1.29 (±0.71) × 10(-17) cm(2), prohibiting any accurate kinetic measurements at this wavelength. The rates are independent of laser fluence at 355 nm with an average value of 8.75 (±0.73) × 10(-11) cm(3) s(-1). The reaction exhibits no pressure or temperature dependence over the studied experimental conditions and is much faster than the estimated values presently used in combustion models. These results are consistent with the formation of a short lifetime intermediate that stabilizes by collisional quenching with the buffer gas. The structures of the most likely formed products are discussed based on both the computed energies for the OH-addition intermediates and previous theoretical investigations on similar chemical systems. PMID:25111848
Hydroxymethylfurfural and furosine reaction kinetics in tomato products.
Hidalgo, A; Pompei, C
2000-01-01
The reaction kinetics of two heat damage indices, HMF and furosine, were examined in four tomato products with different dry matter contents (10.2, 25.5, 28.6, and 34.5%) over a temperature-time range of 80-120 degrees C and 0-255 min. The reactions followed pseudo-zero order kinetics. E(a) and z-value were, respectively, 139. 9 kJ/mol and 19.2 degrees C for HMF, and 93.9 kJ/mol and 28.4 degrees C for furosine. The analyses of both indices in several samples of commercial and industrial tomato products showed very low levels of HMF (from 1 to 42 ppm) and a lack of correlation between HMF and furosine mainly because of the different evolution of the two indices during storage. The HMF level of a tomato paste sample stored at 25 degrees C decreased from 609 to 17 ppm after 98 days, while furosine increased from 458 to 550 mg/100 g of protein. PMID:10637055
Spectator Ions ARE Important! A Kinetic Study of the Copper-Aluminum Displacement Reaction
ERIC Educational Resources Information Center
Sobel, Sabrina G.; Cohen, Skyler
2010-01-01
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…
Grad's distribution functions in the kinetic equations for a chemical reaction
Spiga, Giampiero
Grad's distribution functions in the kinetic equations for a chemical reaction Marzia Bisi, Maria of four species undergoing a bimolecular reversible chemical reaction, along with all possible elastic] and Prigogine-Xhrouet [2], kinetic approaches to chemical reactions in a gas have gained interest and importance
Parnis, J.M.; Mitchell, S.A.; Hackett, P.A. (National Research Council of Canada, Ottawa, Ontario (Canada))
1990-10-18
The kinetics of gas-phase reactions of ground-state ({sup 7}S{sub 3}) chromium atoms with O{sub 2}, NO, N{sub 2}O, and CCl{sub 4} have been examined over the buffer gas pressure range of 1-700 Torr and between 298 and 348 K. Ground-state ({sup 7}S{sub 3}) Cr atoms were produced in a static pressure cell by laser multiphoton dissociation(MPD) of Cr(CO){sub 6} at 559 nm and probed by laser-induced fluorescence at 425.43 nm (z{sup 7}P{degree}{sub 4} {yields} a{sup 7}S{sub 3}) or 357.87 nm (h{sup 7}P{degree}{sub 4} {yields} a{sup 7}S{sub 3}). Relaxation of excited states of Cr produced in the MPD process was monitored and found to be complete within 2 {mu}s. Pseudo-second-order rate constants for the reaction of Cr with O{sub 2} exhibited strong buffer gas pressure dependence, which is interpreted as arising from formation of CrO{sub 2} in a termolecular association reaction.
A simple second order cartesian scheme for compressible Euler flows
Paris-Sud XI, Université de
A simple second order cartesian scheme for compressible Euler flows Yannick Gorsse1 , Angelo Iollo1 Turin, Italy. Abstract We present a finite-volume scheme for compressible Euler flows where the grid to this class, and was mainly developed for compressible flows, see for example [31], [42], [25], [11], [18
Optimization Online - Second order forward-backward dynamical ...
Radu Ioan Bot
2015-03-16
Mar 16, 2015 ... ... Cauchy-Lipschitz-Picard Theorem and prove weak convergence for ... a convex closed set by means of second order dynamical systems. ... the function value along the ergodic trajectory to its minimum value. ... Category 1: Nonlinear Optimization (Systems governed by Differential Equations Optimization ).
A second-order sequential optimality condition for nonlinear ...
2015-04-29
Apr 29, 2015 ... criteria are usually based on the approximate fulfillment of a ... In practice, it is usually impossible to find a point that conforms exactly to the ... There is also strong evidence that even simple second-order methods will fail to.
Correcting second-order contamination in low-resolution spectra
V. Stanishev
2007-05-23
An empirical method for correcting low-resolution astronomical spectra for second-order contamination is presented. The method was developed for correcting spectra obtained with grism #4 of the ALFOSC spectrograph at the Nordic Optical Telescope and the performance is demonstrated on spectra of two nearby bright Type Ia supernovae.
Modeling Ability Differentiation in the Second-Order Factor Model
ERIC Educational Resources Information Center
Molenaar, Dylan; Dolan, Conor V.; van der Maas, Han L. J.
2011-01-01
In this article we present factor models to test for ability differentiation. Ability differentiation predicts that the size of IQ subtest correlations decreases as a function of the general intelligence factor. In the Schmid-Leiman decomposition of the second-order factor model, we model differentiation by introducing heteroscedastic residuals,…
Computer-assisted reduction of second order linear differential equations
P. Midy
1992-01-01
So as to explore the possibilities of representing its solutions in terms of special functions, and using factorization techniques, a process is defined to decide whether a second order linear differential equation with polynomial coefficients can be brought to the hypergeometric or the confluent hypergeometric equation by a rational change of variable. In the first case, an upper bound has
HOW TO REPAIR A SECOND-ORDER SURFACE FOR COMPUTER
Paris-Sud XI, Université de
1 HOW TO REPAIR A SECOND-ORDER SURFACE FOR COMPUTER EXPERIMENTS BY KRIGING Astrid JOURDAN and analysis of computer experiments have been widely investigated in the past decade. Two approaches seem describes and compares them briefly in order to present a methodology for computer experiments based
Second order bibliometric operators in the Astrophysics Data System
M. J. Kurtz; Guenther Eichhorn; Alberto Accomazzi; C. S. Grant; Stephen S. Murray
2002-01-01
Second order relational operators are functions which take lists which have been generated by a database query, and from those lists form sets of other lists, which can then be merged and sorted on the basis of one or more of the attributes of the items in the lists. The NASA Astrophysics Data System is unique among bibliometric information retrieval
A uniformly second order fast sweeping method for eikonal equations
NASA Astrophysics Data System (ADS)
Luo, Songting
2013-05-01
A uniformly second order method with a local solver based on the piecewise linear discontinuous Galerkin formulation is introduced to solve the eikonal equation with Dirichlet boundary conditions. The method utilizes an interesting phenomenon, referred as the superconvergence phenomenon, that the numerical solution of monotone upwind schemes for the eikonal equation is first order accurate on both its value and gradient when the solution is smooth. This phenomenon greatly simplifies the local solver based on the discontinuous Galerkin formulation by reducing its local degrees of freedom from two (1-D) (or three (2-D), or four (3-D)) to one with the information of the gradient frozen. When considering the eikonal equation with point-source conditions, we further utilize a factorization approach to resolve the source singularities of the eikonal by decomposing it into two parts, either multiplicatively or additively. One part is known and captures the source singularities; the other part serves as a correction term that is differentiable at the sources and satisfies the factored eikonal equations. We extend the second order method to solve the factored eikonal equations to compute the correction term with second order accuracy, then recover the eikonal with second order accuracy. Numerical examples are presented to demonstrate the performance of the method.
Textural segmentation, second-order statistics, and textural elements
Jacob Beck
1983-01-01
Beck (1972, 1973) hypothesized that textural segmentation occurs strongly on the basis of simple properties such as brightness, color, size, and the slopes of contours and lines of the elemental descriptors of a texture or textural elements. The experiment reported supports the hypothesis that specific stimulus features, rather than second-order statistics, account for textural segmentation. The results agree with Julesz
Channel Capacity and Second-Order Statistics in Weibull Fading
Nikos C. Sagias; Dimitris A. Zogas; George K. Karagiannidis; George S. Tombras
2004-01-01
The second-order statistics and the channel capacity of the Weibull fading channel are studied. Exact closed-form expressions are derived for the average level crossing rate, the average fade duration, as well as the average Shannon's channel capacity of the Weibull fading process. Numerical results are presented to illustrate the proposed mathematical analysis and to examine the effects of the fading
Blind source-separation using second-order cyclostationary statistics
Karim Abed-Meraim; Yong Xiang; Jonathan H. Manton; Yingbo Hua
2001-01-01
This paper studies the blind source separation (BSS) problem with the assumption that the source signals are cyclostationary. Identifiability and separability criteria based on second-order cyclostationary statistics (SOCS) alone are derived. The identifiability condition is used to define an appropriate contrast function. An iterative algorithm (ATH2) is derived to minimize this contrast function. This algorithm separates the sources even when
TOWARDS A BAYESIAN THEORY OF SECOND-ORDER UNCERTAINTY
Hosni, Hykel
TOWARDS A BAYESIAN THEORY OF SECOND-ORDER UNCERTAINTY: LESSONS FROM NON-STANDARD LOGICS HYKEL HOSNI that subjective probability, and more generally Bayesian theory, are ill- suited to represent a number What is the right measure of uncertainty? Now I suppose the vast majority of uncertain reasoners would
A stable second order method for training back propagation networks
NASA Technical Reports Server (NTRS)
Nachtsheim, Philip R.
1993-01-01
A simple method for improving the learning rate of the back-propagation algorithm is described. The basis of the method is that approximate second order corrections can be incorporated in the output units. The extended method leads to significant improvements in the convergence rate.
Second Order Motion Compensation for Squinted Spotlight Synthetic Aperture Radar
Second Order Motion Compensation for Squinted Spotlight Synthetic Aperture Radar Minh Phuong Nguyen motion com- pensation (MoCom) algorithm for squinted spotlight synthetic aperture radar (SAR). A preciseCom accomplishes a phase error compensation considered for every position in the spot. For pulsed SAR with a squint
ARMA system identification based on second-order cyclostationarity
Geoffrey Ye Li; Zhi Ding
1994-01-01
Previous work has presented novel techniques that exploit cyclostationarity for channel identification in data communication systems. The present authors investigate the identifiability of linear time-invariant (LTI) ARMA systems based on second-order cyclic statistics. They present a parametric and a nonparametric method. The parametric method directly identifies the zeros and poles of ARMA channels with a mixed phase. The nonparametric method
Second-Order Conditioning of Human Causal Learning
ERIC Educational Resources Information Center
Jara, Elvia; Vila, Javier; Maldonado, Antonio
2006-01-01
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…
OPTIMAL MAGNETIC SHIELD DESIGN WITH SECOND-ORDER CONE PROGRAMMING
Tsuchiya, Takashi
OPTIMAL MAGNETIC SHIELD DESIGN WITH SECOND-ORDER CONE PROGRAMMING TAKASHI SASAKAWA AND TAKASHI-dual interior-point algorithms have been developed recently. An optimal magnetic shielding design problem efficiency and stability, we further apply the algorithm to robust design of the magnetic shielding. Key
Overcompressive versus compressive shock solutions in second order
Coquel, Frédéric
propagative phenomena with finite speed while the right hand side (a second order operator) repre- sents and shock waves. By shock wave we mean a viscous shock 1 O.N.E.R.A., B.P. 72, 29 Avenue de la Division, it differs from the first one in the existence of two new families of waves, propagating in between
Skyrme interaction to second order in nuclear matter
Kaiser, N
2015-01-01
Based on the phenomenological Skyrme interaction various density-dependent nuclear matter quantities are calculated up to second order in many-body perturbation theory. The spin-orbit term as well as two tensor terms contribute at second order to the energy per particle. The simultaneous calculation of the isotropic Fermi-liquid parameters provides a rigorous check through the validity of the Landau relations. It is found that published results for these second order contributions are incorrect in most cases. In particular, interference terms between $s$-wave and $p$-wave components of the interaction can contribute only to (isospin or spin) asymmetry energies. Even with nine adjustable parameters, one does not obtain a good description of the empirical nuclear matter saturation curve in the low density region $0<\\rho<2\\rho_0$. The reason for this feature is the too strong density-dependence $\\rho^{8/3}$ of several second-order contributions. The inclusion of the density-dependent term ${1\\over 6}t_3 \\r...
Second-order Self-similar Identities and Multifractal Decompositions
Lau, Ka Sing
ABSTRACT. Motivated by the study of convolutions of the Cantor measure, we set up a framework for computingSecond-order Self-similar Identities and Multifractal Decompositions KA-SING LAU & SZE-MAN NGAI the mul- tifractal Lq -spectrum (q), q > 0, for certain overlapping self- similar measures which satisfy
Symmetric second order edge elements for triangles and tetrahedra
Akihisa Kameari
1999-01-01
A new type of second order edge elements for simplexes (triangles and tetrahedra) is proposed. The element is geometrically symmetric and the shape functions are orthogonal to each other in the integrals of the tangential components on edges. The number of nodes and edges are 14 and 24 in a tetrahedral element. The proposed elements are validated by eigenmode calculations
Kinetics of enol formation from reaction of OH with propene.
Huynh, Lam K; Zhang, Hongzhi R; Zhang, Shaowen; Eddings, Eric; Sarofim, Adel; Law, Matthew E; Westmoreland, Phillip R; Truong, Thanh N
2009-04-01
Kinetics of enol generation from propene has been predicted in an effort to understand the presence of enols in flames. A potential energy surface for reaction of OH with propene was computed by CCSD(T)/cc-pVDZ//B3LYP/cc-pVTZ calculations. Rate constants of different product channels and branching ratios were then calculated using the Master Equation formulation (J. Phys. Chem. A 2006, 110, 10528). Of the two enol products, ethenol is dominant over propenol, and its pathway is also the dominant pathway for the OH + propene addition reactions to form bimolecular products. In the temperature range considered, hydrogen abstraction dominated propene + OH consumption by a branching ratio of more than 90%. Calculated rate constants of enol formation were included in the Utah Surrogate Mechanism to model the enol profile in a cyclohexane premixed flame. The extended model shows consistency with experimental data and gives 5% contribution of ethenol formation from OH + propene reaction, the rest coming from ethene + OH. PMID:19271758
Doktorov, Alexander B; Kipriyanov, Alexander A; Kipriyanov, Alexey A
2010-05-28
Using an modern many-particle method for the derivation of non-Markovian binary kinetic equations, we have treated theoretically the applicability of the encounter theory (ET) (the prototype of the collision theory) concepts to the widely known diffusion assisted irreversible bulk reaction A+A-->product (for example, radical reaction) in dilute solutions. The method shows that the agreement with the ET is observed when the familiar integral ET is employed which in this method is just a step in the derivation of kinetic equations. It allows for two-particle correlations only, but fails to take account of correlation of reactant simultaneously with the partner of the encounter and the reactant in the bulk. However, the next step leading to the modified ET under transformation of equations to the regular form both extends the time range of the applicability of ET rate equation (as it was for reactions proceeding with one of the reactants in excess), and gives the equation of the generalized ET. In full agreement with physical considerations, this theory reveals macroscopic correlations induced by the encounters in the reservoir of free walks. This means that the encounters of reactants in solution are correlated on a rather large time interval of the reaction. Though any nonstationary (non-Markovian) effects manifest themselves rather weakly in the kinetics of the bimolecular reaction in question, just the existence of the revealed macroscopic correlations in the binary theory is of primary importance. In particular, it means that the well-known phenomena which are generally considered to be associated solely with correlation of particles on the encounter (for example, chemically induced dynamic nuclear polarization) may be induced by correlation in the reservoir of free random walks of radicals in solution. PMID:20515095
Yang, Dexi; Micalizio, Glenn C
2013-10-01
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
CHAPTER 9. CHEMICAL KINETICS In the following chapters we will present various chemical reaction
Jacob, Daniel J.
AND CHEMICAL EQUILIBRIA Reactions are re155 CHAPTER 9. CHEMICAL KINETICS In the following chapters we will present various chemical reaction mechanisms controlling the abundance of stratospheric ozone, the oxidizing power of the atmosphere
The reaction kinetics of lithium salt with water vapor
NASA Astrophysics Data System (ADS)
Balooch, M.; Dinh, L. N.; Calef, D. F.
2002-06-01
The interaction of lithium salt (LiH and/or LiD) with water vapor in the partial pressure range of 10 -5-2657 Pa has been investigated. The reaction probability of water with LiH cleaved in an ultra high vacuum environment was obtained using the modulated molecular beam technique. This probability was 0.11 and independent of LiH surface temperature, suggesting a negligible activation energy for the reaction in agreement with quantum chemical calculations. The value gradually reduced, however, to 0.007 as the surface concentration of oxygen containing product approached full coverage. As the film grew beyond a monolayer, the phase lag of hydrogen product increased from 0 °C to 20 °C and the reaction probability reduced further until it approached our detection limit (˜10 -4). This phase lag was attributed to a diffusion-limited process in this regime. For micrometer thick hydroxide films grown in high moisture concentration environment on LiD and LiH, the reaction probability reduced to ˜4×10 -7 and was independent of exposure time. In this regime of thick hydroxide films (LiOH and/or LiOD), microcracks generated in the films to release stress provided easier pathways for moisture to reach the interface. A modified microscope, capable of both atomic force microscopy and nanoindentation, was also employed to investigate the surface morphology of hydroxide monohydrate (LiOH · H 2O and/or LiOD · H 2O) grown on hydroxide at high water vapor partial pressures and the kinetics of this growth.
Kinetics and mechanism of ligand-exchange reactions of Cd(II) chelates
Nivorozhkin, L.E.; Kalabin, G.A.; Nivorozhkin, A.L.; Valeev, R.B.; Minkin, V.I.
1987-03-01
Tetrahedral Cd(II) bis(5-thio(or seleno)pyrazole-4-carboxaldiminates) of types II and III have been synthesized for the first time. The kinetics of the degenerate ligand exchange and enantiomerization of the complexes obtained have been studied by dynamic /sup 111/Cd, /sup 77/Se, and /sup 1/H (s = 1/2) NMR. The rate of intramolecular enantiomerization (k = 1/tau) is more than an order of magnitude greater than the corresponding values for processes of degenerate ligand exchange (a second-order reaction) determined from the dynamics of the averaging of the /sup 111/Cd-/sup 77/Se and /sup 111/Cd-N=CH spin-spin coupling constants. The cleavage and formation processes of the Cd-Se and Cd-N bonds are isoenergetic (..delta.. G/sub 298//sup not equal to/ = 14.4 kcal/mole for chelate II with X = Se and R = CH/sub 2/C/sub 6/H/sub 5/). The free energies of activation of degenerate ligand exchange determined form the dynamics of the averaging of the /sup 111/Cd N=CH spin-spin coupling constant increase from 12.7 to 17.9 kcal/mole along the following series for R: C/sub 2/H/sub 5/ < Ar < CH/sub 2/C/sub 6/H/sub 5/ < t-C/sub 4/H/sub 9/ < cyclo-C/sub 6/H/sub 11/. Replacement of the sulfur atom in the chelate ring by selenium results in increases in the rates of ligand exchange. A mechanism of degenerate ligand exchange has been proposed.
Optimal second order sliding mode control for linear uncertain systems.
Das, Madhulika; Mahanta, Chitralekha
2014-11-01
In this paper an optimal second order sliding mode controller (OSOSMC) is proposed to track a linear uncertain system. The optimal controller based on the linear quadratic regulator method is designed for the nominal system. An integral sliding mode controller is combined with the optimal controller to ensure robustness of the linear system which is affected by parametric uncertainties and external disturbances. To achieve finite time convergence of the sliding mode, a nonsingular terminal sliding surface is added with the integral sliding surface giving rise to a second order sliding mode controller. The main advantage of the proposed OSOSMC is that the control input is substantially reduced and it becomes chattering free. Simulation results confirm superiority of the proposed OSOSMC over some existing. PMID:25249166
Symmetries of second-order PDEs and conformal Killing vectors
NASA Astrophysics Data System (ADS)
Tsamparlis, Michael; Paliathanasis, Andronikos
2015-06-01
We study the Lie point symmetries of a general class of partial differential equations (PDE) of second order. An equation from this class naturally defines a second-order symmetric tensor (metric). In the case the PDE is linear on the first derivatives we show that the Lie point symmetries are given by the conformal algebra of the metric modulo a constraint involving the linear part of the PDE. Important elements in this class are the Klein-Gordon equation and the Laplace equation. We apply the general results and determine the Lie point symmetries of these equations in various general classes of Riemannian spaces. Finally we study the type II hidden symmetries of the wave equation in a Riemannian space with a Lorenzian metric.
Symmetries of second-order PDEs and conformal Killing vectors
Tsamparlis, Michael
2015-01-01
We study the Lie point symmetries of a general class of partial differential equations (PDE) of second order. An equation from this class naturally defines a second-order symmetric tensor (metric). In the case the PDE is linear on the first derivatives we show that the Lie point symmetries are given by the conformal algebra of the metric modulo a constraint involving the linear part of the PDE. Important elements in this class are the Klein--Gordon equation and the Laplace equation. We apply the general results and determine the Lie point symmetries of these equations in various general classes of Riemannian spaces. Finally we study the type II\\ hidden symmetries of the wave equation in a Riemannian space with a Lorenzian metric.
First and second order convex approximation strategies in structural optimization
NASA Technical Reports Server (NTRS)
Fleury, C.
1989-01-01
In this paper, various methods based on convex approximation schemes are discussed that have demonstrated strong potential for efficient solution of structural optimization problems. First, the convex linearization method (Conlin) is briefly described, as well as one of its recent generalizations, the method of moving asymptotes (MMA). Both Conlin and MMA can be interpreted as first-order convex approximation methods that attempt to estimate the curvature of the problem functions on the basis of semiempirical rules. Attention is next directed toward methods that use diagonal second derivatives in order to provide a sound basis for building up high-quality explicit approximations of the behavior constraints. In particular, it is shown how second-order information can be effectively used without demanding a prohibitive computational cost. Various first-order and second-order approaches are compared by applying them to simple problems that have a closed form solution.
Evaluation of Supersingular Integrals: Second-Order Boundary Derivatives
Moore, Matthew N [ORNL; Gray, Leonard J [ORNL; Kaplan, Ted [ORNL
2007-01-01
The boundary integral representation of second-order derivatives of the primary function involves second-order (hypersingular) and third-order (supersingular) derivatives of the Green's function. By defining these highly singular integrals as a difference of boundary limits, interior minus exterior, the limiting values are shown to exist. With a Galerkin formulation, coincident and edge-adjacent supersingular integrals are separately divergent, but the sum is finite, while the individual hypersingular integrals are finite. Moreover, the cancellation of the supersingular divergent terms only requires a continuous interpolation of the surface potential, and there is no continuity requirement on the surface flux. The algorithm is efficient, the nonsingular integrals vanish and the singular integrals are computed entirely analytically, and accurate values are obtained for smooth surfaces. However, it is shown that a (continuous) linear interpolation is not appropriate for evaluation at boundary corners.
Second-order nonlinear optical metamaterials: ABC-type nanolaminates
Alloatti, Luca; Froelich, Andreas; Lauermann, Matthias; Frenzel, Tobias; Koehnle, Kira; Freude, Wolfgang; Leuthold, Juerg; Wegener, Martin; Koos, Christian
2015-01-01
Structuring optical materials on a nanometer scale can lead to artificial effective media, or metamaterials, with strongly altered optical behavior. Metamaterials can provide a wide range of linear optical properties such as negative refractive index, hyperbolic dispersion, or magnetic behavior at optical frequencies. Nonlinear optical properties, however, have only been demonstrated for patterned metallic films which suffer from high optical losses. Here we show that second-order nonlinear metamaterials can also be obtained from non-metallic centrosymmetric constituents with inherently low optical absorption. In our proof-of-principle experiments, we have iterated atomic-layer deposition (ALD) of three different constituents, A = Al$_2$O$_3$, B = TiO$_2$ and C = HfO$_2$. The centrosymmetry of the resulting ABC stack is broken since the ABC and the inverted CBA sequences are not equivalent - a necessary condition for non-zero second-order nonlinearity. To the best of our knowledge, this is the first realizati...
First- and second-order charged particle optics
Brown, K.L.; Servranckx, R.V.
1984-07-01
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.
Second-order centrality correlation in scale-free networks
NASA Astrophysics Data System (ADS)
Lv, Meilei; Guo, Xinling; Chen, Jiaquan; Lu, Zhe-Ming; Nie, Tingyuan
2015-02-01
Scale-free networks in which the degree displays a power-law distribution can be classified into assortative, disassortative, and neutral networks according to their degree-degree correlation. The second-order centrality proposed in a distributed computation manner is quick-calculated and accurate to identify critical nodes. We explore the second-order centrality correlation (SOC) for each type of the scale-free networks. The SOC-SOC correlation in assortative network and neutral network behaves similarly to the degree-degree correlation, while it behaves an apparent difference in disassortative networks. Experiments show that the invulnerability of most of scale-free networks behaves similarly under the node removal ordering by SOC centrality and degree centrality, respectively. The netscience network and the Yeast network behave a little differently because they are native disconnecting networks.
A Second-Order Achromat Design Based on FODO Cell
Sun, Yipeng; /SLAC
2011-08-19
Two dipole doglegs are widely used to translate the beam axis horizontally or vertically. Quadrupoles are placed between the two consecutive dipoles to match first order dispersion and provide betatron focusing. Similarly a four dipole chicane is usually employed to form a bypass region, where the beam axis is transversely shifted first, then translated back to the original axis. In order to generate an isochronous section, quadrupoles are again needed to tune the first order transfer matrix element R{sub 56} equaling zero. Usually sextupoles are needed to correct second order dispersion in the bending plane, for both the dogleg optics and the chicane (with quad) optics. In this paper, an alternative optics design is introduced, which is based on a simple FODO cell and does not need sextupoles assistance to form a second-order achromat. It may provide a similar function of either a dogleg or a bypass, by using 2 or 4 of such combined supercells.
Biogeochemical Reaction Kinetics Associated With Uranium Bioremediation at Multiple Scales
NASA Astrophysics Data System (ADS)
Li, L.; Steefel, C. I.; Kowalsky, M. B.
2007-12-01
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.
Solving second order linear differential equations with Klein's theorem
Mark van Hoeij; Jacques-Arthur Weil
2005-01-01
Given a second order linear differential equations with coefficients in a field k=C(x), the Kovacic algorithm finds all Liouvillian solutions, that is, solutions that one can write in terms of exponentials, logarithms, integration symbols, algebraic extensions, and combinations thereof. A theorem of Klein states that, in the most interesting cases of the Kovacic algorithm (i.e when the projective differential Galois
Smoothing Functions for Second-Order-Cone Complementarity Problems
Masao Fukushima; Zhi-Quan Luo; Paul Tseng
2002-01-01
Smoothing functions have been much studied in the solution of optimization and complementarityproblems with nonnegativity constraints. In this paper, we extend smoothing functions to problemswhere the nonnegative orthant is replaced by the direct product of second-order cones. Thesesmoothing functions include the Chen-Mangasarian class and the smoothed Fischer-Burmeisterfunction. We study the Lipschitzian and dierential properties of these functions and, in particular,we
On Second-Order Optimality Conditions for Vector Optimization
María C. Maciel; Sandra A. Santos; Graciela N. Sottosanto
2011-01-01
In this article, two second-order constraint qualifications for the vector optimization problem are introduced, that come\\u000a from first-order constraint qualifications, originally devised for the scalar case. The first is based on the classical feasible\\u000a arc constraint qualification, proposed by Kuhn and Tucker (Proceedings of the Second Berkeley Symposium on Mathematical Statistics\\u000a and Probability, vol. 1, pp. 481–492, University of California Press, California,
Second order filter response with series coupled silica microresonators
NASA Technical Reports Server (NTRS)
Savchenkov, A.; Iitchenko, V. S.; Handley, T.; Maleki, L.
2002-01-01
We have demonstrated an approach for fabricating a photonic filter with second order response function. The filter consists of two germania-doped silica microtoroidal or microspherical resonators cascaded in series. We use UV irradiation to tune the mode of one microcavity to bring it close to the mode of the second microcavity. This approach produces a filter function with much sharper rolloff than can be obtained with the individual microresonators.
Second-Order Linear Homogeneous Differential Equations with Constant Coefficients
NSDL National Science Digital Library
Moore, Lang
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.
Second-Order Linear Homogeneous Differential Equations with Constant Coefficients
NSDL National Science Digital Library
Moore, Lang
Created by Lang Moore and David Smith for the Connected Curriculum Project, the purpose of this module is to investigate the qualitative behavior of second-order constant coefficient differential equations and corresponding initial value problems. In particular, to determine how solutions depend on the signs and magnitudes of the coefficients and on the initial conditions. This is one of a much larger set of learning modules hosted by Duke University.
Second-Order Accurate Method for Solving Radiation-Hydrodynamics
Edwards, Jarrod Douglas
2013-11-12
IMEX Implicit/Explicit ISP Isothermal Sonic Point CN Crank-Nicholson vi TABLE OF CONTENTS Page ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii DEDICATION... the radiation diffusion equation in time is the Crank-Nicholson method, also known as the Trapezoid Rule. This is a well-known, implicit method that is second-order accurate; however, its principal drawback is that it can become highly oscillatory for stiff...
Combined first and second order Fermi acceleration at comets
T. I. Gombosi; K. Lorencz; J. R. Jokipii
1989-01-01
Two-dimensional, time-dependent model calculations indicate that an interplay between velocity and spatial diffusion may be responsible for the acceleration of implanted heavy ions in the cometary preshock region. Velocity diffusion (second order Fermi acceleration) accelerates the pickup ions to moderate energies thus creating a seed population for the more efficient diffusive-compressive shock acceleration. Solar wind convection limits the time available
Second-order output statistics of the adaptive line enhancer
J. Rickard; J. Zeidler
1979-01-01
The adaptive line enhancer (ALE) is an adaptive digital filter designed to suppress uncorrelated components of its input, while passing any narrow-band components with little attenuation. The purpose of this paper is to analyze the second-order output statistics of the ALE in steady-state operation, for input samples consisting of weak narrow-band signals in white Gaussian noise. The ALE output is
Gravitational waves from global second order phase transitions
Jr, John T. Giblin [Department of Physics, Kenyon College, 201 North College Rd, Gambier, OH 43022 (United States); Price, Larry R.; Siemens, Xavier; Vlcek, Brian, E-mail: giblinj@kenyon.edu, E-mail: larryp@caltech.edu, E-mail: siemens@gravity.phys.uwm.edu, E-mail: bvlcek@uwm.edu [Center for Gravitation and Cosmology, Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States)
2012-11-01
Global second-order phase transitions are expected to produce scale-invariant gravitational wave spectra. In this manuscript we explore the dynamics of a symmetry-breaking phase transition using lattice simulations. We explicitly calculate the stochastic gravitational wave background produced during the transition and subsequent self-ordering phase. We comment on this signal as it compares to the scale-invariant spectrum produced during inflation.
A short note on the curvature perturbation at second order
Adam J. Christopherson; Ellie Nalson; Karim A. Malik
2015-02-28
Working with perturbations about an FLRW spacetime, we compute the gauge-invariant curvature perturbation to second order solely in terms of scalar field fluctuations. Using the curvature perturbation on uniform density hypersurfaces as our starting point, we give our results in terms of field fluctuations in the flat gauge, incorporating both large and small scale behaviour. For ease of future numerical implementation we give our result in terms of the scalar field fluctuations and their time derivatives.
Second-order resonance of sloshing in a tank
G. X. Wu
2007-01-01
Sloshing in a two-dimensional rectangular tank in horizontal motion is analysed based on the velocity potential theory. It is found that even when the first-order excitation is away from all the natural frequencies of the tank, second-order resonance can still occur when the sum-frequency or the difference-frequency is equal to one of the natural frequencies corresponding to the even mode.
Extensions and applications of a second-order landsurface parameterization
NASA Technical Reports Server (NTRS)
Andreou, S. A.; Eagleson, P. S.
1983-01-01
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.
Asymptotic stability of second-order neutral stochastic differential equations
NASA Astrophysics Data System (ADS)
Sakthivel, R.; Ren, Yong; Kim, Hyunsoo
2010-05-01
In this paper, we study the existence and asymptotic stability in pth moment of mild solutions to second-order nonlinear neutral stochastic differential equations. Further, this result is extended to establish stability criterion for stochastic equations with impulsive effects. With the help of fixed point strategy, stochastic analysis technique, and semigroup theory, a set of novel sufficient conditions are derived for achieving the required result. Finally, an example is provided to illustrate the obtained result.
Local conservation laws of second-order evolution equations
Roman O. Popovych; Anatoly M. Samoilenko
2008-08-06
Generalizing results by Bryant and Griffiths [Duke Math. J., 1995, V.78, 531-676], we completely describe local conservation laws of second-order (1+1)-dimensional evolution equations up to contact equivalence. The possible dimensions of spaces of conservation laws prove to be 0, 1, 2 and infinity. The canonical forms of equations with respect to contact equivalence are found for all nonzero dimensions of spaces of conservation laws.
Wavelet Based Transistor Parameter Estimation Using Second Order Volterra Model
Sudipta Majumdar; Harish Parthasarathy
In this paper, we present a wavelet based parameter estimation technique to estimate the transistor parameter in a common\\u000a emitter amplifier circuit. The method uses the closed form expression of the second order Volterra model of a common emitter\\u000a amplifier circuit derived using perturbation technique and the Ebers–Moll model. Simulations show that the proposed method\\u000a gives more accurate parameter estimation
Oscillation Criteria for Second Order Linear Differential Equations
H. J. Li
1995-01-01
Some oscillation criteria are given for the second order linear differential equation [r(t)u?(t)]? + c(t)u(t) = 0, where r(t) ? C1([t0, ?); (0, ?)) and c(t) ? C([t0, ?); R). These results improve oscillation criteria of Wintner, Hartman, Kamenev, Yan, and Philos by using a generalized Riccati transformation ?(t) = a(t)r(t){u?(t)\\/u(t) + f(t)}, where f ? C1 is a given
Pattern masking investigations of the second-order visual mechanisms
NASA Astrophysics Data System (ADS)
Huang, Pi-Chun; Chen, Chien-Chung
2009-02-01
Human visual system is sensitive to both the first-order and the second-order variations in an image. The latter one is especially important for the digital image processing as it allows human observers to perceive the envelope of the pixel intensities as smooth surface instead of the discrete pixels. Here we used pattern masking paradigm to measure the detection threshold of contrast modulated (CM) stimuli, which comprise the modulation of the contrast of horizontal gratings by a vertical Gabor function, under different modulation depth of the CM stimuli. The threshold function showed a typical dipper shape: the threshold decreased with modulation depth (facilitation) at low pedestal depth modulations and then increased (suppression) at high pedestal modulation. The data was well explained by a modified divisive inhibition model that operated both on depth modulation and carrier contrast in the input images. Hence the divisive inhibition, determined by both the first- and the second-order information in the stimuli, is necessary to explain the discrimination between two second-order stimuli.
A Biological Interpretation of Transient Anomalous Subdiffusion. II. Reaction Kinetics?
Saxton, Michael J.
2008-01-01
Abstract Reaction kinetics in a cell or cell membrane is modeled in terms of the first passage time for a random walker at a random initial position to reach an immobile target site in the presence of a hierarchy of nonreactive binding sites. Monte Carlo calculations are carried out for the triangular, square, and cubic lattices. The mean capture time is expressed as the product of three factors: the analytical expression of Montroll for the capture time in a system with a single target and no binding sites; an exact expression for the mean escape time from the set of lattice points; and a correction factor for the number of targets present. The correction factor, obtained from Monte Carlo calculations, is between one and two. Trapping may contribute significantly to noise in reaction rates. The statistical distribution of capture times is obtained from Monte Carlo calculations and shows a crossover from power-law to exponential behavior. The distribution is analyzed using probability generating functions; this analysis resolves the contributions of the different sources of randomness to the distribution of capture times. This analysis predicts the distribution function for a lattice with perfect mixing; deviations reflect imperfect mixing in an ordinary random walk. PMID:17905849
Transport coefficients in second-order non-conformal viscous hydrodynamics
NASA Astrophysics Data System (ADS)
Ryblewski, Radoslaw
2015-05-01
Based on the exact solution of Boltzmann kinetic equation in the relaxation-time approximation, the precision of the two most recent formulations of relativistic second-order non-conformal viscous hydrodynamics (14-moment approximation and causal Chapman-Enskog method), standard Israel-Stewart theory, and anisotropic hydrodynamics framework, in the simple case of one-dimensional Bjorken expansion, is tested. It is demonstrated that the failure of Israel-Stewart theory in reproducing exact solutions of the Boltzmann kinetic equation occurs due to neglecting and/or choosing wrong forms of some of the second-order transport coefficients. In particular, the importance of shear-bulk couplings in the evolution equations for dissipative quantities is shown. One finds that, in the case of the bulk viscous pressure correction, such coupling terms are as important as the corresponding first-order Navier-Stokes term and must be included in order to obtain, at least qualitative, overall agreement with the kinetic theory.
"Kinetics of Chemical Reactions in Environmental Systems: Research Needs and Challenges"
Sparks, Donald L.
"Kinetics of Chemical Reactions in Environmental Systems: Research Needs and Challenges" Donald(oid)s, nutrients, radionuclides, and organic chemicals have shown that reaction rates are initially rapid followed by a slow approach to a steady state. The rapid reaction has been ascribed to chemical reactions and film
Kinetics and Mechanism of Iodide Oxidation by Iron(III): A Clock Reaction Approach
ERIC Educational Resources Information Center
Bauer, Jurica; Tomisic, Vladislav; Vrkljan, Petar B. A.
2008-01-01
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…
Roegner, Matthias
Kinetics and mechanism of electron transfer in intact photosystem II and in the isolated reaction center: Pheophytin is the primary electron acceptor A. R. Holzwarth , M. G. Mu¨ ller , M. Reus , M and kinetics of electron transfer in isolated D1 D2-cytb559 photosystem (PS) II reaction centers (RCs
Chen, Peng
Single-Molecule Kinetics Reveals a Hidden Surface Reaction Intermediate in Single polydispersion in reaction kinetics. Here we use single-molecule fluorescence microscopy to study two.3 nm pseudospherical Au nanoparticlesat the single-particle, single- turnover resolution in catalyzing
Non-meanfield deterministic limits in chemical reaction kinetics R. E. Lee DeVille
Van Den Eijnden, Eric
Non-meanfield deterministic limits in chemical reaction kinetics R. E. Lee DeVille Courant is demonstrated for the kinetic Monte Carlo version of the Schnakenberg reaction where we identified a scaling, and it is at the very heart of the majority of macroscopic models of physical, chemical, and biological systems
NASA Astrophysics Data System (ADS)
Takushima, Yuichiro; Terukina, Ayumu; Yamamoto, Kazuhiro
2014-05-01
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.
Kinetic Electrode Reactions in Silver Electrodeposition Using a Multipulse Current Measurement
M. Saitouz
Silver and silver alloy deposition in various electrolytes 1-5 have attracted scientific and technological interest. However, there have been very few reports on the kinetics of electrode reactions in silver electrodeposition. In particular, the kinetic constant, the ex- change current density, and the double-layer capacitance in the ferrocyanide-thiocyanate electrolytes, which characterize the kinet- ics of the electrode reactions in silver
Inhibition of the Reaction Kinetics of the Enzyme o-Diphenol Oxidase
Kieran Fergus LIM
Chemical kinetics is a fundamental component of chemistry: traditional chemistry-laboratory exercises have concentrated on the study of non- biological organic or inorganic reaction kinetics. Many students feel that such studies bear little relationship to the world outside the chemistry laboratory. The aim of this experiment is to investigate the kinetics of a reaction catalysed by the enzyme o-diphenol oxidase (oDPO
Experimental and theoretical methods in kinetic studies of heterogeneously catalyzed reactions.
Reyniers, Marie-Françoise; Marin, Guy B
2014-01-01
This review aims to illustrate the potential of kinetic analysis in general and microkinetic modeling in particular for rational catalyst design. Both ab initio calculations and experiments providing intrinsic kinetic data allow us to assess the effects of catalytic properties and reaction conditions on the activity and selectivity of the targeted reactions. Three complementary approaches for kinetic analysis of complex reaction networks are illustrated, using select examples of acid zeolite-catalyzed reactions from the authors' recent work. Challenges for future research aimed at defining targets for synthesis strategies that enable us to tune zeolite properties are identified. PMID:24910922
Kinetics of Ethyl Acetate Synthesis Catalyzed by Acidic Resins
ERIC Educational Resources Information Center
Antunes, Bruno M.; Cardoso, Simao P.; Silva, Carlos M.; Portugal, Ines
2011-01-01
A low-cost experiment to carry out the second-order reversible reaction of acetic acid esterification with ethanol to produce ethyl acetate is presented to illustrate concepts of kinetics and reactor modeling. The reaction is performed in a batch reactor, and the acetic acid concentration is measured by acid-base titration versus time. The…
Second-Order Corrections to QED Coupling at Low Temperature
NASA Astrophysics Data System (ADS)
Masood, Samina S.; Haseeb, Mahnaz
We calculate the second-order corrections to vacuum polarization tensor of photons at low temperatures, i.e. T ? 1010 K (T ? me). The thermal contributions to the QED coupling constant are evaluated at temperatures below the electron mass that is T < me. Renormalization of QED at these temperatures has explicitly been checked. The electromagnetic properties of such a thermal medium are modified. Parameters like electric permittivity and magnetic permeability of such a medium are no more constant and become functions of temperature.
Supersonic second order analysis and optimization program user's manual
NASA Technical Reports Server (NTRS)
Clever, W. C.
1984-01-01
Approximate nonlinear inviscid theoretical techniques for predicting aerodynamic characteristics and surface pressures for relatively slender vehicles at supersonic and moderate hypersonic speeds were developed. Emphasis was placed on approaches that would be responsive to conceptual configuration design level of effort. Second order small disturbance theory was utilized to meet this objective. Numerical codes were developed for analysis and design of relatively general three dimensional geometries. Results from the computations indicate good agreement with experimental results for a variety of wing, body, and wing-body shapes. Case computational time of one minute on a CDC 176 are typical for practical aircraft arrangement.
Second-order susceptibility from a tight-binding Hamiltonian
Dumitrica, T.; Graves, JS; Allen, Roland E.
1998-01-01
e is the charge of the electron and A is the vector potential, is equivalent to the replacement Second-order susceptibility fro T. Dumitrica?, J. S. Graves Department of Physics, Texas A&M University ~Received 1 Using a new formalism... by P. E. A. Turchi, A. Gonis, and L. Colombo ~Materials Research Society, Warrendale, PA, 1998!. 10 W. A. Harrison, Electronic Structure and the Properties of Solids ~Dover, New York, 1989!. 11 J. S. Graves and R. E. Allen, in Tight-Binding Approach...
Soil solid materials affect the kinetics of extracellular enzymatic reactions
NASA Astrophysics Data System (ADS)
Lammirato, C.; Miltner, A.; Kästner, M.
2009-04-01
INTRODUCTION Soil solid materials affect the degradation processes of many organic compounds by decreasing the bioavailability of substrates and by interacting with degraders. The magnitude of this effect in the environment is shown by the fact that xenobiotics which are readily metabolized in aquatic environments can have long residence times in soil. Extracellular enzymatic hydrolysis of cellobiose (enzyme: beta-glucosidase from Aspergillus niger) was chosen as model degradation process since it is easier to control and more reproducible than a whole cell processes. Furthermore extracellular enzymes play an important role in the environment since they are responsible for the first steps in the degradation of organic macromolecules; beta-glucosidase is key enzyme in the degradation of cellulose and therefore it is fundamental in the carbon cycle and for soil in general. The aims of the project are: 1) quantification of solid material effect on degradation, 2) separation of the effects of minerals on enzyme (adsorption ?change in activity) and substrate (adsorption ?change in bioavailability). Our hypothesis is that a rate reduction in the enzymatic reaction in the presence of a solid phase results from the sum of decreased bioavailability of the substrate and decreased activity of enzyme molecules. The relative contribution of the two terms to the overall effect can vary widely depending on the chemical nature of the substrate, the properties of the enzyme and on the surface properties of the solid materials. Furthermore we hypothesize that by immobilizing the enzyme in an appropriate carrier the adsorption of enzymes to soil materials can be eliminated and that therefore immobilization can increase the overall reaction rate (activity loss caused by immobilization < activity loss caused by adsorption to soil minerals). MATERIALS AND METHODS Enzymatic kinetic experiments are carried out in homogeneous liquid systems and in heterogeneous systems where solid materials (bentonite, kaolinite, goethite, activated charcoal) are suspended in a mixed liquid (standard experimental conditions: 66 mM phosphate buffer, pH 5, 25°C, 20 mg solid/ml buffer). The enzyme in an immobilized form (covalent bonding to oxirane groups on the surfaces of macroporous Eupergit® C particles) is used to exclude a direct effect of soil solid materials on the enzyme without excluding their effect on the availability of the substrate.The progress of the reactions is determined by measuring the accumulation of the product (i.e. glucose) in the systems at different times (after destroying enzymatic activity by boiling the samples) with a coupled enzymatic assay and an automatic microplate spectrophotometer. A regression analysis on the data points is performed to calculate the initial reaction rates, which is the parameter that allows to compare the different systems. RESULTS AND DISCUSSION The results show that, under the standard experimental conditions, cellobiose is not adsorbed by the clay minerals bentonite and kaolinite and by the iron oxyhydroxide goethite. In the case of activated charcoal a rapid adsorption phase in the first 20' is followed by a much slower process; after 4h 30' approximately 98% of cellobiose was adsorbed. The results from the adsorption experiments of beta-glucosidase to bentonite, kaolinite, goethite and activated charcoal show that, under the standard experimental conditions, the adsorption process is rapid in all cases (more than 80% of the adsorption takes place in the first 20 minutes). After 1h 20min the following fractions of enzyme were adsorbed: 30 % to bentonite, 60% to kaolinite, 67% to goethite, 100% to activated charcoal. The effect of kaolinite on the reaction rate was quantified: under the standard experimental conditions the initial reaction rate in presence of the mineral was 22% less then in the control. The fraction of enzyme molecules which are adsorbed to kaolinite (60%) loses 37% of its activity. CONCLUSIONS The results from the adsorption experiments lead to the conclusion that, among the sol
A-posteriori error estimation for second order mechanical systems
NASA Astrophysics Data System (ADS)
Ruiner, Thomas; Fehr, Jörg; Haasdonk, Bernard; Eberhard, Peter
2012-06-01
One important issue for the simulation of flexible multibody systems is the reduction of the flexible bodies degrees of freedom. As far as safety questions are concerned knowledge about the error introduced by the reduction of the flexible degrees of freedom is helpful and very important. In this work, an a-posteriori error estimator for linear first order systems is extended for error estimation of mechanical second order systems. Due to the special second order structure of mechanical systems, an improvement of the a-posteriori error estimator is achieved. A major advantage of the a-posteriori error estimator is that the estimator is independent of the used reduction technique. Therefore, it can be used for moment-matching based, Gramian matrices based or modal based model reduction techniques. The capability of the proposed technique is demonstrated by the a-posteriori error estimation of a mechanical system, and a sensitivity analysis of the parameters involved in the error estimation process is conducted.
On the universal identity in second order hydrodynamics
NASA Astrophysics Data System (ADS)
Grozdanov, S.; Starinets, A. O.
2015-03-01
We compute the 't Hooft coupling correction to the infinite coupling expression for the second order transport coefficient ? 2 in SU( N c ) supersymmetric Yang-Mills theory at finite temperature in the limit of infinite N c , which originates from the R 4 terms in the low energy effective action of the dual type IIB string theory. Using this result, we show that the identity involving the three second order transport coefficients, 2 ?? ? - 4 ? 1 - ? 2 = 0, previously shown by Haack and Yarom to hold universally in relativistic conformal field theories with string dual descriptions to leading order in supergravity approximation, holds also at next to leading order in this theory. We also compute corrections to transport coefficients in a (hypothetical) strongly interacting conformal fluid arising from the generic curvature squared terms in the corresponding dual gravity action (in particular, Gauss-Bonnet action), and show that the identity holds to linear order in the higher-derivative couplings. We discuss potential implications of these results for the near-equilibrium entropy production rate at strong coupling.
Stochastic evaluation of second-order Dyson self-energies.
Willow, Soohaeng Yoo; Kim, Kwang S; Hirata, So
2013-04-28
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
Ab initio study of the kinetics of hydrogen abstraction reactions on toluene and tetralin
Beste, Ariana [ORNL; Britt, Phillip F [ORNL; Buchanan III, A C [ORNL; Harrison, Robert J [ORNL; Hathorn, Bryan C [ORNL
2008-01-01
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.
Anunciacion Espinosa-Mansilla; Isabel Durán Merás; Francisco Salinas López
1996-01-01
For the first time a fluorimetric-kinetic method for the determination of malonaldehyde (MLD) is proposed. The fluorescence emission of the thiobarbituric acid (TBA)-MLD reaction product has been monitored at 553 nm (excitation wavelength 515 nm), and the instrumental and experimental variables have been studied. A selective and fast kinetic-fluorimetric determination of malonaldehyde is proposed. The sensitivity of the method is
Pseudo-second order model for sorption processes
Y. S Ho; G McKay
1999-01-01
A literature review of the use of sorbents and biosorbents to treat polluted aqueous effluents containing dyes\\/organics or metal ions has been conducted. Over 70 systems have been reported since 1984 and over 43 of these reported the mechanism as being a pseudo-first order kinetic mechanism. Three sorption kinetic models are presented in this paper and have been used to
Sontag, Eduardo
On persistence of chemical reaction networks with time-dependent kinetics and no global for persistence of chemical reaction networks are proposed, which extend those obtained by the authors in previous. Interpreted for chemical reactions and population models, this translates into a "non-extinction property
Disorder-induced anomalous kinetics in the A+A-->0 reaction
NASA Astrophysics Data System (ADS)
Park, Jeong-Man; Deem, Michael W.
1998-03-01
We address the two-dimensional bimolecular annihilation reaction A+A-->0 in the presence of random impurities. Impurities with sufficiently long-ranged interactions are known to lead to anomalous diffusion,
Kinetic modelling of GlmU reactions - prioritization of reaction for therapeutic application.
Singh, Vivek K; Das, Kaveri; Seshadri, Kothandaraman
2012-01-01
Mycobacterium tuberculosis(Mtu), a successful pathogen, has developed resistance against the existing anti-tubercular drugs necessitating discovery of drugs with novel action. Enzymes involved in peptidoglycan biosynthesis are attractive targets for antibacterial drug discovery. The bifunctional enzyme mycobacterial GlmU (Glucosamine 1-phosphate N-acetyltransferase/ N-acetylglucosamine-1-phosphate uridyltransferase) has been a target enzyme for drug discovery. Its C- and N- terminal domains catalyze acetyltransferase (rxn-1) and uridyltransferase (rxn-2) activities respectively and the final product is involved in peptidoglycan synthesis. However, the bifunctional nature of GlmU poses difficulty in deciding which function to be intervened for therapeutic advantage. Genetic analysis showed this as an essential gene but it is still unclear whether any one or both of the activities are critical for cell survival. Often enzymatic activity with suitable high-throughput assay is chosen for random screening, which may not be the appropriate biological function inhibited for maximal effect. Prediction of rate-limiting function by dynamic network analysis of reactions could be an option to identify the appropriate function. With a view to provide insights into biochemical assays with appropriate activity for inhibitor screening, kinetic modelling studies on GlmU were undertaken. Kinetic model of Mtu GlmU-catalyzed reactions was built based on the available kinetic data on Mtu and deduction from Escherichia coli data. Several model variants were constructed including coupled/decoupled, varying metabolite concentrations and presence/absence of product inhibitions. This study demonstrates that in coupled model at low metabolite concentrations, inhibition of either of the GlmU reactions cause significant decrement in the overall GlmU rate. However at higher metabolite concentrations, rxn-2 showed higher decrement. Moreover, with available intracellular concentration of the metabolites and in vivo variant of model, uncompetitive inhibition of rxn-2 caused highest decrement. Thus, at physiologically relevant metabolite concentrations, targeting uridyltranferase activity of Mtu GlmU would be a better choice for therapeutic intervention. PMID:22952829
A conditional mean second-order wave theory
Jensen, J.J.; Baatrup, J. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Ocean Engineering; Mansour, A.E. [Univ. of California, Berkeley, CA (United States). Dept. of Naval Architecture and Offshore Engineering
1995-12-31
In the design of bottom supported offshore structures for oil exploration and oil production the wave loading is often determined by subjecting the structure to a periodic wave with prescribed wave height and period. The advantage of this procedure is that a non-linear wave theory, for instance Stokes` fifth-order, can be applied to predict the instantaneous submerged parts of the structure and the wave kinematics up to the free water surface. In a stationary stochastic sea state the mean wave profile and associated wave kinematics conditioned on a given wave elevation at a specified point in space or time are derived. The results are based on the second-order, unidirectional, deep water Stoke`s wave theory, but can easily be extended to other moderate non-linear wave formulations. The application of the proposed wave theory as a design wave is discussed together with methods to overcome convergence problems associated with wideband wave spectra.
Invariant classification of second-order conformally flat superintegrable systems
Joshua Capel; Jonathan Kress
2014-06-12
In this paper we continue the work of Kalnins et al in classifying all second-order conformally-superintegrable (Laplace-type) systems over conformally flat spaces, using tools from algebraic geometry and classical invariant theory. The results obtained show, through Staeckel equivalence, that the list of known nondegenerate superintegrable systems over three-dimensional conformally flat spaces is complete. In particular, a 7-dimensional manifold is determined such that each point corresponds to a conformal class of superintegrable systems. This manifold is foliated by the nonlinear action of the conformal group in three-dimensions. Two systems lie in the same conformal class if and only if they lie in the same leaf of the foliation. This foliation is explicitly described using algebraic varieties formed from representations of the conformal group. The proof of these results rely heavily on Groebner basis calculations using the computer algebra software packages Maple and Singular.
Relativistic quantum transport coefficients for second-order viscous hydrodynamics
NASA Astrophysics Data System (ADS)
Florkowski, Wojciech; Jaiswal, Amaresh; Maksymiuk, Ewa; Ryblewski, Radoslaw; Strickland, Michael
2015-05-01
We express the transport coefficients appearing in the second-order evolution equations for bulk viscous pressure and shear stress tensor using Bose-Einstein, Boltzmann, and Fermi-Dirac statistics for the equilibrium distribution function and Grad's 14-moment approximation as well as the method of Chapman-Enskog expansion for the nonequilibrium part. Focusing on the case of transversally homogeneous and boost-invariant longitudinal expansion of the viscous medium, we compare the results obtained using the above methods with those obtained from the exact solution of the massive 0+1 d relativistic Boltzmann equation in the relaxation-time approximation. We show that compared to the 14-moment approximation, the hydrodynamic transport coefficients obtained by employing the Chapman-Enskog method lead to better agreement with the exact solution of the relativistic Boltzmann equation.
Invariant classification of second-order conformally flat superintegrable systems
NASA Astrophysics Data System (ADS)
Capel, J. J.; Kress, J. M.
2014-12-01
In this paper we continue the work of Kalnins et al in classifying all second-order conformally-superintegrable (Laplace-type) systems over conformally flat spaces, using tools from algebraic geometry and classical invariant theory. The results obtained show, through Stäckel equivalence, that the list of known nondegenerate superintegrable systems over three-dimensional conformally flat spaces is complete. In particular, a seven-dimensional manifold is determined such that each point corresponds to a conformal class of superintegrable systems. This manifold is foliated by the nonlinear action of the conformal group in three dimensions. Two systems lie in the same conformal class if and only if they lie in the same leaf of the foliation. This foliation is explicitly described using algebraic varieties formed from representations of the conformal group. The proof of these results rely heavily on Gröbner basis calculations using the computer algebra software packages Maple and Singular.
Regularized orbital-optimized second-order perturbation theory
Stück, David; Head-Gordon, Martin [Department of Chemistry, University of California, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California, Berkeley, California 94720 (United States)
2013-12-28
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 mE{sub h} 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.
Second-order phase transitions, L. Landau and his successors
Y. Mnyukh
2011-02-05
There are only two ways for solid-state phase transitions to be compliant with thermodynamics: emerging of infinitesimal quantity of the new phase, or infinitesimal "qualitative" change occurring uniformly throughout the bulk at a time. The suggested theories of phase transitions are checked here for that compliance and in historical perspective. While introducing the theory of "continuous" second-order phase transitions, L. Landau claimed that they "may also exist" along with the majority of first order phase transitions, the latter being "discontinuous", displaying "jumps" of their physical properties; the fundamental differences between the two types were specified. But his theoretical successors disregarded these irreconcilable differences, incorrectly presenting all phase transitions as a cooperative phenomenon treatable by statistical mechanics. In the meantime, evidence has been mounted that all phase transitions have a nucleation-and-growth mechanism, thus making the above classification unneeded.
Noise calculations within the second-order von Neumann approach
NASA Astrophysics Data System (ADS)
Zedler, Philipp; Emary, Clive; Brandes, Tobias; Novotný, Tomáš
2011-12-01
We extend the second-order von Neumann approach within the generalized master equation formalism for quantum electronic transport to include the counting field. The resulting non-Markovian evolution equation for the reduced density matrix of the system resolved with respect to the number of transported charges enables the evaluation of the noise and higher-order cumulants of the full counting statistics. We apply this formalism to an analytically solvable model of a single-level quantum dot coupled to highly biased leads with Lorentzian energy-dependent tunnel coupling and demonstrate that, although reproducing exactly the mean current, the resonant tunneling approximation is not exact for the noise and higher-order cumulants. Even if it may fail in the regime of strongly non-Markovian dynamics, this approach generically improves results of lower-order and/or Markovian approaches.
Second-order mixtures in relativistic Schrödinger theory
NASA Astrophysics Data System (ADS)
Mattes, M.; Sorg, M.
1999-01-01
In relativistic Schrödinger theory the mixtures and pure states can be treated from a unified point of view such that a pure state merely emerges as a special case of a mixture. Here the concept of mixture is of purely local nature and therefore the mixture character (degree of order) can change over space and time. Although the general dynamics does not forbid the transitions from mixtures to pure states (and vice versa), the considered models do admit these transitions only in an asymptotic sense. The general concepts and results are demonstrated by considering the four-component Dirac theory for spinning matter over the Robertson-Walker universes. A detailed study is made for a specific subclass of second-order mixtures sharing many of their properties with the pure states (i.e., wave functions).
Twist and Turn: Weak Lensing Image Distortions to Second Order
David J. Bacon; Bjoern Malte Schaefer
2009-04-17
We account for all the image distortions relevant to weak gravitational lensing to second order. Besides the familiar shear, convergence, rotation and flexions, we find a new image distortion with two distinct descriptions, the twist and the turn. Like rotation, this distortion is not activated gravitationally to first order, but will be activated by systematic effects. We examine the rotational properties of twist and turn, and their effect on images in real and shapelet space. We construct estimators for the new distortion, taking into account the centroid shift which it generates. We then use these estimators to make first constraints on twist using the STAGES HST survey; we find that the mean twist estimator is consistent with zero. We measure correlation functions for our twist estimator on the survey, again finding no evidence of systematic effects.
A simplified structure for the second order cosmological perturbation equations
NASA Astrophysics Data System (ADS)
Uggla, Claes; Wainwright, John
2013-03-01
Increasingly accurate observations of the cosmic microwave background and the large scale distribution of galaxies necessitate the study of nonlinear perturbations of Friedmann-Lemaitre cosmologies, whose equations are notoriously complicated. In this paper we present a new derivation of the governing equations for second order perturbations within the framework of the metric-based approach that is minimal, as regards amount of calculation and length of expressions, and flexible, as regards choice of gauge and stress-energy tensor. Because of their generality and the simplicity of their structure our equations provide a convenient starting point for determining the behaviour of nonlinear perturbations of FL cosmologies with any given stress-energy content, using either the Poisson gauge or the uniform curvature gauge.
Second order closure modeling of turbulent buoyant wall plumes
NASA Technical Reports Server (NTRS)
Zhu, Gang; Lai, Ming-Chia; Shih, Tsan-Hsing
1992-01-01
Non-intrusive measurements of scalar and momentum transport in turbulent wall plumes, using a combined technique of laser Doppler anemometry and laser-induced fluorescence, has shown some interesting features not present in the free jet or plumes. First, buoyancy-generation of turbulence is shown to be important throughout the flow field. Combined with low-Reynolds-number turbulence and near-wall effect, this may raise the anisotropic turbulence structure beyond the prediction of eddy-viscosity models. Second, the transverse scalar fluxes do not correspond only to the mean scalar gradients, as would be expected from gradient-diffusion modeling. Third, higher-order velocity-scalar correlations which describe turbulent transport phenomena could not be predicted using simple turbulence models. A second-order closure simulation of turbulent adiabatic wall plumes, taking into account the recent progress in scalar transport, near-wall effect and buoyancy, is reported in the current study to compare with the non-intrusive measurements. In spite of the small velocity scale of the wall plumes, the results showed that low-Reynolds-number correction is not critically important to predict the adiabatic cases tested and cannot be applied beyond the maximum velocity location. The mean and turbulent velocity profiles are very closely predicted by the second-order closure models. but the scalar field is less satisfactory, with the scalar fluctuation level underpredicted. Strong intermittency of the low-Reynolds-number flow field is suspected of these discrepancies. The trends in second- and third-order velocity-scalar correlations, which describe turbulent transport phenomena, are also predicted in general, with the cross-streamwise correlations better than the streamwise one. Buoyancy terms modeling the pressure-correlation are shown to improve the prediction slightly. The effects of equilibrium time-scale ratio and boundary condition are also discussed.
Lam K. Huynh; Thanh N. Truong
2008-01-01
The kinetics of the hydrogen abstraction at alkanes by formyl radicals is investigated using the reaction class transition\\u000a state theory (RC-TST) approach combined with the linear energy relationship (LER) or the barrier height grouping (BHG). The\\u000a rate constants of a reaction in this class can be estimated through those of the reference reaction, CHO + C2H6, which are obtained from
Naik, C; Westbrook, C K; Herbinet, O; Pitz, W J; Mehl, M
2010-01-22
New chemical kinetic reaction mechanisms are developed for two of the five major components of biodiesel fuel, methyl stearate and methyl oleate. The mechanisms are produced using existing reaction classes and rules for reaction rates, with additional reaction classes to describe other reactions unique to methyl ester species. Mechanism capabilities were examined by computing fuel/air autoignition delay times and comparing the results with more conventional hydrocarbon fuels for which experimental results are available. Additional comparisons were carried out with measured results taken from jet-stirred reactor experiments for rapeseed methyl ester fuels. In both sets of computational tests, methyl oleate was found to be slightly less reactive than methyl stearate, and an explanation of this observation is made showing that the double bond in methyl oleate inhibits certain low temperature chain branching reaction pathways important in methyl stearate. The resulting detailed chemical kinetic reaction mechanism includes more approximately 3500 chemical species and more than 17,000 chemical reactions.
Gordon, R J
1982-08-02
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)
Kinetics and thermodynamics of chemical reactions in Li/SOCl2 cells
NASA Technical Reports Server (NTRS)
Hansen, Lee D.; Frank, Harvey
1987-01-01
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.
Kinetic phase transitions in a surface-reaction model: Mean-field theory
Ronald Dickman
1986-01-01
A kinetic model for irreversible surface reactions, recently proposed by Ziff, Gulari, and Barshad, is studied in the site and pair approximations. The latter approach predicts the phase diagram correctly, and yields quantitative predictions which are in very close agreement with simulation, in the vicinity of the first-order kinetic transition.
ERIC Educational Resources Information Center
Koga, Nobuyoshi; Goshi, Yuri; Yoshikawa, Masahiro; Tatsuoka, Tomoyuki
2014-01-01
An undergraduate kinetic experiment of the thermal decomposition of solids by microscopic observation and thermal analysis was developed by investigating a suitable reaction, applicable techniques of thermal analysis and microscopic observation, and a reliable kinetic calculation method. The thermal decomposition of sodium hydrogen carbonate is…
Minnesota, University of
Solvent Polarization and Kinetic Isotope Effects in Nitroethane Deprotonation and Implications to the Nitroalkane Oxidase Reaction Dan T. Major,* Darrin M. York, and Jiali Gao* Department of Chemistry and the deuterium kinetic isotope effects (KIEs) were found to be 9.2 in the enzyme and 7.8 in water. The similarity
Kinetic measurements on elementary fossil fuel combustion reactions over wide temperature ranges
Fontijn, A.
1991-01-01
The goals of this work are to provide accurate data on the temperature dependence of the kinetics of elementary combustion reactions (i) for use by combustion modelers, and (ii) to gain a better fundamental understanding of, and hence predictive ability for, the chemistry involved. In this reporting period our work on the O + Hcl reaction was published, experimental work on the O + benzene and O + 1-butene reactions was completed, and measurements on the O + isobutene reaction were initiated.
The Saunders-Bell Analysis of Tunnel Effects in Reactions with Kinetic Isotope Effects
Vladimir Leskovac; Svetlana Trivic ´; Draginja Peric?in; Julijan Kandra?
2004-01-01
Summary. The primary kinetic isotope effects of deuterium were investigated in 22 hydrogen and deuterium transfer reactions, including enzymatic and nonenzymatic hydride transfer reactions, elimination reactions, and reactions catalyzed by enzymes lipooxygenase, amine dehydrogenase, and methylmalonyl-CoA mutase. In each case, the Saunders-Bell analysis was applied to calculate the tunnel effects and the corresponding thermodynamic parameters. The Saunders-Bell analysis was effective
Determination of Reaction Kinetics for a Two-Part Epoxy Adhesive
NSDL National Science Digital Library
DeRosa, Rebecca L.
2008-09-26
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.
Correction of the Chromaticity up to Second Order for MEIC
H. K. Sayed, S.A. Bogacz, P. Chevtsov
2010-03-01
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.
The motion of ellipsoids in a second order fluid
NASA Astrophysics Data System (ADS)
Kim, S.
1985-09-01
The rigid body motion of an ellipsoid in a second order fluid (SOF) under the action of specified (time independent) external forces and torques have been obtained to first order in the Weissenberg number by inverting the resistance relations for the force an torque under specified rigid body motions. The reciprocal theorem of Lorentz was used to bypass the calculation of the O(W) velocity field. The results agree with known analytic solutions for SOF with the secondary to primary normal stress ratio of -1/2. The solution procedure was also tested by computing the torque on a translating prolate spheroid with aspect ratios ranging from slender bodies to near-spheres. One result is that for a SOF with zero secondary normal stress (Weissenberg fluid), previous asymptotic results for near-spheres were found to be accurate even at fairly large aspect ratios. New results of nondegenerate ellipsoids suggest that the orientation (as monitored by Euler angles) and trajectory of sedimenting, nonaxisymmetric particles such as ellipsoids provide useful information on the rheology of the suspending fluid.
Second order closure for stratified convection: bulk region and overshooting
NASA Astrophysics Data System (ADS)
Biferale, L.; Mantovani, F.; Pivanti, M.; Pozzati, F.; Sbragaglia, M.; Scagliarini, A.; Schifano, S. F.; Toschi, F.; Tripiccione, R.
2011-12-01
The parameterization of small-scale turbulent fluctuations in convective systems and in the presence of strong stratification is important for many applied problems in oceanography, atmospheric science and planetology. In the presence of stratification, both bulk turbulent fluctuations and inversion regions, where temperature, density -or both- develop highly nonlinear mean profiles, are crucial. We present a second order closure able to reproduce simultaneously both bulk and boundary layer regions. We test it using high-resolution state-of-the-art 2D numerical simulations in a Rayleigh-Taylor convective and stratified belt for values of the Rayleigh number, up to Ra ~ 109. The system is confined by the existence of an adiabatic gradient. Our numerical simulations are performed using a thermal Lattice Boltzmann Method (Sbragaglia et al, 2009) able to reproduce the Navier-Stokes equations for momentum, density and internal energy (see also (Biferale et al, 2011b) for an extension to a case with forcing on internal energy). Validation of the method can be found in (Biferale et al, 2010; Scagliarini et al, 2010). Here we present numerical simulations up to 4096 × 10000 grid points obtained on the QPACE supercomputer (Goldrian et al, 2008).
Second order sliding mode control for a quadrotor UAV.
Zheng, En-Hui; Xiong, Jing-Jing; Luo, Ji-Liang
2014-07-01
A method based on second order sliding mode control (2-SMC) is proposed to design controllers for a small quadrotor UAV. For the switching sliding manifold design, the selection of the coefficients of the switching sliding manifold is in general a sophisticated issue because the coefficients are nonlinear. In this work, in order to perform the position and attitude tracking control of the quadrotor perfectly, the dynamical model of the quadrotor is divided into two subsystems, i.e., a fully actuated subsystem and an underactuated subsystem. For the former, a sliding manifold is defined by combining the position and velocity tracking errors of one state variable, i.e., the sliding manifold has two coefficients. For the latter, a sliding manifold is constructed via a linear combination of position and velocity tracking errors of two state variables, i.e., the sliding manifold has four coefficients. In order to further obtain the nonlinear coefficients of the sliding manifold, Hurwitz stability analysis is used to the solving process. In addition, the flight controllers are derived by using Lyapunov theory, which guarantees that all system state trajectories reach and stay on the sliding surfaces. Extensive simulation results are given to illustrate the effectiveness of the proposed control method. PMID:24751475
A visual field dependent architecture for second order motion processing.
Meso, Andrew Isaac; Hess, Robert F
2011-10-01
The visual system exploits a cortical hierarchy to process complex inputs such as those defined by modulations of motion and/or texture. One class of visual stimuli, composed of alternate stripes of opposing motion requires at least 2 separate stages of computation within this cortical hierarchy, thought to involve cortical area V1 and extra-striate regions like global motion area MT respectively. Using a psychophysical task, we characterise sensitivity to such stimuli containing periodic spatial modulations of motion gradients as a function of the ratio of the spatial parameters at the two processing levels by manipulating the spatial properties of the carrier and modulator. We find band-passed functions for foveal stimulus presentations showing an optimum sensitivity at ratios in the range of r?10, informative of the coupling relationship between frequency channels at the carrier and modulator levels. An annulus stimulus (excluding the fovea) with a radius of 15.5° exhibited optima of sensitivity at r>15. This difference in the optimal coupling between filtering stages reflects a processing architecture that changes with eccentricity, consistent with the previously observed smaller differences between mean receptive field sizes in striate and extra-striate filtering stages in the fovea compared to the periphery. This is also important for visual psychophysics when comparing sensitivity for first and second order stimuli across retinal eccentricity. PMID:21843594
On computing first and second order derivative spectra
NASA Astrophysics Data System (ADS)
Roy, Indrajit G.
2015-08-01
Enhancing resolution in spectral response and an ability to differentiate spectral mixing in delineating the endmembers from the spectral response are central to the spectral data analysis. First and higher order derivatives analysis of absorbance and reflectance spectral data is commonly used techniques in differentiating the spectral mixing. But high sensitivity of derivative to the noise in data is a major problem in the robust estimation of derivative of spectral data. An algorithm of robust estimation of first and second order derivative spectra from evenly spaced noisy normal spectral data is proposed. The algorithm is formalized in the framework of an inverse problem, where based on the fundamental theorem of calculus a matrix equation is formed using a Volterra type integral equation of first kind. A regularization technique, where the balancing principle is used in selecting a posteriori optimal regularization parameter is designed to solve the inverse problem for robust estimation of first order derivative spectra. The higher order derivative spectra are obtained while using the algorithm in sequel. The algorithm is tested successfully with synthetically generated spectral data contaminated with additive white Gaussian noise, and also with real absorbance and reflectance spectral data for fresh and sea water respectively.
Second order semiclassics with self-generated magnetic fields
Laszlo Erdos; Soren Fournais; Jan Philip Solovej
2011-09-25
We consider the semiclassical asymptotics of the sum of negative eigenvalues of the three-dimensional Pauli operator with an external potential and a self-generated magnetic field $B$. We also add the field energy $\\beta \\int B^2$ and we minimize over all magnetic fields. The parameter $\\beta$ effectively determines the strength of the field. We consider the weak field regime with $\\beta h^{2}\\ge {const}>0$, where $h$ is the semiclassical parameter. For smooth potentials we prove that the semiclassical asymptotics of the total energy is given by the non-magnetic Weyl term to leading order with an error bound that is smaller by a factor $h^{1+\\e}$, i.e. the subleading term vanishes. However, for potentials with a Coulomb singularity the subleading term does not vanish due to the non-semiclassical effect of the singularity. Combined with a multiscale technique, this refined estimate is used in the companion paper \\cite{EFS3} to prove the second order Scott correction to the ground state energy of large atoms and molecules.
A planar second-order DC SQUID gradiometer.
Carelli, P; Chiaventi, L; Leoni, R; Pullano, M; Schirripa Spagnolo, G
1991-01-01
In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localisation capability is similar to that one usually achieves with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundreds of pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be the combination of four square holes of 500 microns side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor 10) the gradiometer will have a sensitivity of 10(-11) T m-2 Hz-1/2 and a field sensitivity of about 2 fT Hz-1/2. Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO chi-PbAuIn Josephson tunnel junctions. Some possible improvements will also be described. PMID:1807874
Exam Question Exchange: A Popular Approach to Reaction Kinetics.
ERIC Educational Resources Information Center
Collins, Michael P. S.; Alexander, John J., Ed.
1979-01-01
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)
High temperature chemical kinetic study of the H2-CO-CO2-NO reaction system
NASA Technical Reports Server (NTRS)
Jachimowski, C. J.
1975-01-01
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.
Transport Properties of a Kinetic Model for Chemical Reactions without Barriers
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
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.
NASA Astrophysics Data System (ADS)
Markovic, Bojan; Vladimirov, Sote; Cudina, Olivera; Savic, Vladimir; Karljikovic-Rajic, Katarina
2010-02-01
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.
Kinetics of FeS precipitation: Part 1. Competing reaction mechanisms
NASA Astrophysics Data System (ADS)
Rickard, David
1995-11-01
The kinetics of the fast precipitation reaction between aqueous iron (II) and dissolved sulfide at 25°C can be interpreted in terms of two competing reactions. The first may be represented by Fe 2+ + H2S ? FeS(s) + 2 H+ This can be described by an observed rate law - d[aH 2S]/dt = k11[aH 2S] where k' 1, is the observed first order rate constant with a value of 90 ± 10 s -1, [ cH 2S] is the concentration of dissolved H 2S in moles per liter, and t is time in seconds. The rate law is consistent with an Eigen-Wilkins model of the process in which the rate is described by d[FeS]/dt = - d[ aH2S]/dt = k1[ aFe2+][aH 2S], where aH 2S and aFe 2+ are the formally dimensionless hydrogen sulfide and Fe(II) activities which are represented on a moles·liter -1 scale for experimental and practical convenience. The logarithm of k1, the theoretical Eigen-Wilkins reaction rate constant, has a value of 7 ± 1 liters·mole -1·s -1. The second reaction may be represented by Fe 2 + 2HS - ? Fe(HS) 2(s) The rate of this reaction may be described by an observed rate law of the form - d[aHS -]/ dt = k21[aHS -] 2 where [ aHS -] is the formally dimensionless bisulfide activity which is represented on a moles·liter -1 scale for experimental convenience. The observed second order rate constant, k' 2, has a value of 1.3 × 10 7 liters·mole -1·s -1 at 25°C. The result is consistent with an Eigen-Wilkins model of the process in which k21[aFe 2+][aHS -] 2 where aFe 2+ is the dissolved Fe(II) activity and the logarithm of k2, the Eigen-Wilkins reaction rate constant, has a value of 12.5 ± 1 liters 2·mole -2·s -1. The theoretical interpretation of both reactions suggests that the rates are direct functions of the ion activity products of the iron sulfide precipitates. The second stage of the reaction involves the condensation of Fe(SH) 2 to FeS with the release of dissolved sulfide back to solution: Fe(SH) 2( s)?FeS( s)+H 2S This reaction is relatively slow and results in a sinusoidal form superimposed on the Stage 1 concentration-time curve. Overall, the rate of removal of total dissolved sulfide from solution by these processes can be empirically modeled by - d[ ?S]/ dt= ko[ ?S] and [ ?S] - [ ?S] o = e- ko1 where [?S] is the concentration of total dissolved sulfide at any time, [?S] 0 is the concentration of total dissolved sulfide at t = 0, and k0 is a pseudo first order rate constant of 15 s -1 where [?Fe 2+], the total dissolved iron(II) concentration, is between 10 -3 and 10 -4 M. Theoretically, the rates of both reactions are directly proportional to [ aFe 2+]. A good approximation for the rate of removal of total dissolved sulfide by the iron(II) (bi)sulfide precipitation processes in most environments can, therefore, be obtained by using a value for k 0of15 × 10 -4/[ ?Fe2+] . Application of the rate laws to natural systems suggests that the relative dominance of the two competing pathways is pH and ?S dependent and independent of ?Fe 2+. In environments with ppm or greater ?S concentrations (?10 -3 M), the rate of sulfide removal is two magnitudes greater in neutral to alkaline systems than in systems with pH < 7. The bisulfide pathway resulting in the formation of Fe(SH) 2 dominates and the H 2S pathway only dominates in acidic environments. The results suggest that, in these relatively sulfide-rich environments, a standing concentration of Fe(SH) 2 will be present and may constitute an important component in further reactions, such as pyrite formation. In contrast, in sulfide-poor systems with ?S concentrations at the sub-ppm (<10 -3 M) level, the rate is greater in neutral to acidic conditions and the H 2S pathway, involving the direct formation of FeS, dominates in all environments with pH < 8.
Simultaneous determination of kinetic and diffusion parameters for the water-gas shift reaction
T. Salmi; Abo Akademi
1990-01-01
The water-gas shift reaction was studied at 563–638 K over an industrial ferrochrome catalyst. The reaction rate data could be described by first order kinetics coupled to a diffusional resistance model for isothermal pellets. The model parameters were determined by simultaneous nonlinear regression.
Kinetics of thermal regeneration reaction of activated carbons used in waste water treatment
Kenji Hashimoto; Kouichi Miura; Tsuneo Watanabe
1982-01-01
The kinetics of the thermal regeneration of activated carbons used in the waste water treatment was analyzed on the basis of a model that the regeneration reaction consists of a set of many first-order reactions each of which has different activation energy and frequency factor. The frequency factors were correlated approximately by a function of the activation energy. The difference
Paper Number 15736-PA Title Reaction Kinetics of Fuel Formation for In-Situ Combustion
Abu-Khamsin, Sidqi
Paper Number 15736-PA Title Reaction Kinetics of Fuel Formation for In-Situ Combustion Authors Abu believed to cause fuel formation for in-situ combustion have been studied and modeled. A thin, packed bed the approach of a combustion front. Analysis of gases produced from the reaction cell revealed that pyrolysis
Kinetics of Radical-Radical Reactions of Hydrocarbon-Based Radicals Vadim D. Knyazev,*
Knyazev, Vadim D.
1 Kinetics of Radical-Radical Reactions of Hydrocarbon-Based Radicals Vadim D. Knyazev,* Irene R of Chemistry The Catholic University of America, Washington, DC 20064, USA, E-mail: knyazev@cua.edu Radical-radical as chain termination pathways. In addition, radical-radical reactions represent pathways of molecular mass
Muhammad Abdul Hamid; Ejaz Ur Rehman; Muhammad Fuzail; Riffat Naheed; Amin-Uddin Ahmed
1995-01-01
The oxidation-reduction reaction between U(VI) and Ti(III) in HCl solution was studied spectrophotometrically. The reaction is second-order at all concentrations of reactants, HCl, ferrous chloride and mannitol used in this work. In 5M HCl the rate constantk increases with increasing Ti(III) concentration, whereas it decreases with increasing U(VI) concentration, with increasing HCl concentration from 1.00M to 7.17M and increases thereafter
Comparison of kinetic and equilibrium reaction models insimulating the behavior of porous media
Kowalsky, Michael B.; Moridis, George J.
2006-11-29
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.
Incorporation of aqueous reaction and sorption kinetics andbiodegradation into TOUGHREACT
Xu, Tianfu
2006-04-17
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.
Brown, L.F.; Robinson, B.A.
1986-01-01
The technique of temperature-programmed reaction (TPR) is shown to be a practical experimental method for determining reaction-rate expressions and kinetics parameters for reactions in dilute aqueous solutions under high ambient pressure. By sampling and measuring the extent of reaction during a rise in temperature, information normally obtained from a series of isothermal batch kinetics experiments can be found in a single TPR test. The use of nonlinear least-squares regression eliminates the need to achieve a constant rate of temperature rise, simplifies the experimental requirements for TPR results, and gives more accurate answers than does a linear analysis of TPR results. Numerical simulations of TPR tests in the presence of random concentration-measurement error is used to assess the accuracy of the technique and to identify the best values of crucial operating parameters. The results of two TPR experiments measuring the alkaline hydrolysis of ethyl acetate demonstrate the applicability of the technique to reactions in dilute aqueous solutions at high pressure. These preliminary experimental results, along with numerical simulations, allow us to chart a course for future TPR kinetics experiments on a large number of similar reactions. 16 refs., 6 figs., 8 tabs.
Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos
2013-12-01
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.
Kinetic studies of isoprene reactions with hydroxyl and chlorine radicals
Suh, Inseon
2000-01-01
photolysis/laser induced fluorescence (LP/LIF) detection. Both the CIMS and LP/LIF techniques were employed to investigate the reaction of isoprene with OH. The rate constants for the OH-isoprene reaction were measured in a pressure range of 70 to 112 Torr...
Coherent chemical kinetics as quantum walks I: Reaction operators for radical pairs
A. Chia; A. Gorecka; K. C. Tan; L. Pawela; P. Kurzynski; T. Paterek; D. Kaszlikowski
2015-06-13
Classical chemical kinetics use rate-equation models to describe how a reaction proceeds in time. Such models are sufficient for describing state transitions in a reaction where coherences between different states do not arise, or in other words, a reaction which contain only incoherent transitions. A prominent example reaction containing coherent transitions is the radical-pair model. The kinetics of such reactions is defined by the so-called reaction operator which determines the radical-pair state as a function of intermediate transition rates. We argue that the well-known concept of quantum walks from quantum information theory is a natural and apt framework for describing multisite chemical reactions. By composing Kraus maps that act only on two sites at a time, we show how the quantum-walk formalism can be applied to derive a reaction operator for the standard avian radical-pair reaction. Our reaction operator predicts a recombination dephasing rate consistent with recent experiments [J. Chem. Phys. {\\bf 139}, 234309 (2013)], in contrast to previous work by Jones and Hore [Chem. Phys. Lett. {\\bf 488}, 90 (2010)]. The standard radical-pair reaction has conventionally been described by either a normalised density operator incorporating both the radical pair and reaction products, or by a trace-decreasing density operator that considers only the radical pair. We demonstrate a density operator that is both normalised and refers only to radical-pair states. Generalisations to include additional dephasing processes and an arbitrary number of sites are also discussed.
Citation review of Lagergren kinetic rate equation on adsorption reactions
Yuh-shan Ho
2004-01-01
This study presents a literature review concerning the preciseness of over 170 publications citing the original Lagergren's paper in kinetics equation for solute adsorption on various adsorbents. This equation applies to a range of solid-liquid systems such as metal ions, dyestuffs and several organic substances in aqueous systems onto various adsorbents. The main objectives are to manifest different forms of
Cellulosic Insulation Material I. Overall Degradation Kinetics and Reaction Heats
F. E. ROGERS; T. J. OHLEMILLER
1980-01-01
Kinetic studies on the thermal and oxidative decomposition of untreated cellulosic insulation have been carried out with thermal analytical techniques (TGA and DSC) to provide input parameters for smoldering studies of this material. In dry nitrogen, the weight loss proceeds in one overall step that follows a diffusion-controlled rate law with parameters: A = 1.1 × 10 min and E
Kinetics of Reactions of Monomeric Nitrosomethane Induced by Flash Photolysis.
ERIC Educational Resources Information Center
Kozubek, H.; And Others
1984-01-01
Describes an experiment in which the kinetics of dimerization of nitrosamine induced by a flash of light is measured. The experiment can be performed with a commercial ultraviolet-VIS spetrophotometer with easy to make modifications. The experiment demonstrates a flash photolysis system not always available in university chemistry laboratories.…
Davies, D M; Jones, P; Mantle, D
1976-01-01
1. The kinetics of formation of horseradish peroxidase Compound I were studied by using peroxobenzoic acid and ten substituted peroxobenzoic acids as substrates. Kinetic data for the formation of Compound I with H2O2 and for the reaction of deuteroferrihaem with H2O2 and peroxobenzoic acids, to form a peroxidatically active intermediate, are included for comparison. 2. The observed second-order rate constants for the formation of Compound I with peroxobenzoic acids decrease with increasing pH, in the range pH 5-10, in contrast with pH-independence of the reaction with H2O2. The results imply that the formation of Compound I involves a reaction between the enzyme and un-ionized hydroperoxide molecules. 3. The maximal rate constants for Compound I formation with unhindered peroxobenzoic acids exceed that for H2O2. Peroxobenzoic acids with bulky ortho substituents show marked adverse steric effects. The pattern of substituent effects does not agree with expectations for an electrophilic oxidation of the enzyme by peroxoacid molecules in aqueous solution, but is in agreement with that expected for a reaction involving nucleophilic attack by peroxo anions. 4. Possible reaction mechanisms are considered by which the apparent conflict between the pH-effect and substituent-effect data may be resolved. A model in which it is postulated that a negatively charged 'electrostatic gate' controls access of substrate to the active site and may also activate substrate within the active site, provides the most satisfactory explanation for both the present results and data from the literature. PMID:9067
Second-Order Statistical Property of Partially Developed Speckle and its Applications to Speckle-Communications, Japan; 2 Risoe National Laboratory, Denmark weiwang@ice.uec.ac.jp, Some second-order statistics indicate the field after a displacement has been introduced. To provide a complete second-order statistical
GRAVITY ERROR COMPENSATION USING SECOND-ORDER GAUSS-MARKOV PROCESSES
Born, George
AAS 11-502 GRAVITY ERROR COMPENSATION USING SECOND-ORDER GAUSS-MARKOV PROCESSES Jason M. Leonard the use of a second-order Gauss-Markov process to compensate for higher order spherical harmonic gravity an improvement in POD through the use of a second-order Gauss-Markov process (GMP2) for modeling J3 gravity
Mechanistic interpretation of glass reaction: Input to kinetic model development
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
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.
NO-char reactions: Kinetics and transport aspects
Suuberg, E.M.; Calo, J.M.; Teng, Hsisheng; Lilly, W.D.
1991-07-01
The reaction chemistry of NO with carbons is quite complex. This study details many different aspects of this chemistry. The choice was made to study the reaction chemistry using carbons derived from phenolic resins. These chars are microporous and have porosity characteristics similar to those of coal chars, but have the advantage that they are relatively free of potentially catalytic impurities. The results have been noted to be quite similar to results obtained on a variety of very different carbons, as reported in the literature. The reaction behavior was studied over a range of NO pressures up to 10.1kPa, and at temperatures between 323K and 1073K. The reaction behavior is an extremely sensitive function of temperature. 87 refs., 51 figs., 26 tabs. (VC)
Kinetics of chlorine atom reactions with molecules of atmospheric interest
NASA Astrophysics Data System (ADS)
Goliff, Wendy Suzanne
1997-07-01
The major factor in determining whether chlorine atom (Cl) reactions are important sinks in the stratosphere for hydrogen-containing species is the relative rate constants for attack by Cl versus attack by hydroxyl (HO). Although the rates of HO with methyl bromide (CH3Br), HFC-32 (CH2F2), HFC-125 (CHF2CF3), HFC-152a (CH3CHF2), HCFC-123 (CHCl2CF3) and HCFC-124 (CHClFCF3) are well-known, few data are available for their rate constants with Cl. The thermal reaction rate constants of hydrogen abstraction by Cl with CH3Br, CH2F2,/ CHF2CF3,/ CH3CHF2,/ CHCl2CF3/ and/ CHClFCF3 in the gas phase have been measured at 298K and 4,000 torr. 38Cl was reacted with each species against the common competitor, bromotrifluoroethylene (CF2=CFBr). The decomposition product of the competitor reaction, 38-chlorotrifluoroethylene (CF2[=]CF38Cl), was measured by radiogas chromatography. The relative rate constants were converted to an absolute scale by comparison to the well- known rate constant of Cl with methane (CH4). The gas phase substitution reactions of thermal atomic chlorine with methyl iodide and methyl bromide to form methyl chloride have been Cl+CH3X/to CH3Cl+X/ (X=Br,I)investigated at two pressures (4,000 torr & 760 torr) and three temperatures (273K, 295K, 343K), using radioactive 38Cl from the thermal neutron induced 37Cl(n,/gamma)38Cl nuclear reaction. The initially energetic 38Cl atoms are thermalized by inelastic collisions with inert CClF3 prior to reaction with the methyl halide. The yields of CH338Cl were analyzed by radiogas chromatography. The yields of CH338Cl from thermal chlorine atom reactions at 295K are 8.6% from methyl iodide, and 0.5% from methyl bromide. The corresponding reaction rate constant for thermal chlorine attack to form CH3Cl at 295K is (1.7/pm0.2)×10-15/ cm3 molecule- 1/sec-1 with CH3Br. The substitution reaction with methyl iodide is pressure-independent over the 1-5 atmosphere range. The yields of CH338Cl increase with decreasing temperature for both CH3I and CH3Br, indicating a lower energy barrier for the substitution reaction than for the competitive reaction of hydrogen abstraction by atomic chlorine.
The Gaseous Explosive Reaction : A Study of the Kinetics of Composite Fuels
NASA Technical Reports Server (NTRS)
Stevens, F W
1929-01-01
This report deals with the results of a series of studies of the kinetics of gaseous explosive reactions where the fuel under observation, instead of being a simple gas, is a known mixture of simple gases. In the practical application of the gaseous explosive reaction as a source of power in the gas engine, the fuels employed are composite, with characteristics that are apt to be due to the characteristics of their components and hence may be somewhat complex. The simplest problem that could be proposed in an investigation either of the thermodynamics or kinetics of the gaseous explosive reaction of a composite fuel would seem to be a separate study of the reaction characteristics of each component of the fuel and then a study of the reaction characteristics of the various known mixtures of those components forming composite fuels more and more complex. (author)
Mechanism and kinetics of phase transitions and other reactions in solids
Yuri Mnyukh
2011-10-07
The work is presented, leading to the universal contact molecular mechanism of phase transitions and other reactions in solid state. The two components of the mechanism - nucleation and interface propagation - are investigated in detail and their role in the kinetics is specified. They were shown to be peculiar: nucleation is "pre-coded", rather than resulted from a successful fluctuation, and the interface propagates by molecular filling of thin layers in the transverse direction. The structure of the nucleation sites is determined. The inherent instability and irreproducibility of the kinetics in question is revealed. A linear kinetics, as opposed to the bulk kinetics, is introduced and shown to be in accord with the contact mechanism. Ferromagnetic phase transition and magnetization are added to the list of solid-state reactions; neither occurs without structural rearrangement.
NASA Astrophysics Data System (ADS)
Nagaraj, Karuppiah; Senthil Murugan, Krishnan; Thangamuniyandi, Pilavadi; Sakthinathan, Subramanian
2015-05-01
The kinetics of outer sphere electron transfer reaction of surfactant cobalt(III) complex ions, cis-[Co(en)2(C12H25NH2)2]3+ (1), cis-[Co(dp)2(C12H25NH2)2]3+ (2), cis-[Co(trien)(C12H25NH2)2]3+ (3), cis-[Co(bpy)2(C12H25NH2)2]3+ (4) and cis-[Co(phen)2(C12H25NH2)2]3+ (5) (en: ethylenediamine, dp: diaminopropane, trien : triethylenetetramine, bpy: 2,2?-bipyridyl, phen: 1,10-phenanthroline and C12H25NH2 : dodecylamine) have been interrogated by Fe2+ ion in ionic liquid (1-butyl-3-methylimidazoliumbromide) medium at different temperatures (298, 303, 308, 313, 318 and 323 K) by the spectrophotometry method under pseudo first order conditions using an excess of the reductant. Experimentally the reactions were found to be of second order and the electron transfer as outer sphere. The second order rate constant for the electron transfer reaction in ionic liquids was found to increase with increase in the concentration of all these surfactant cobalt(III) complexes. Among these complexes (from en to phen ligand), complex containing the phenanthroline ligand rate is higher compared to other complexes. By assuming the outer sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of ionic liquids formed by the surfactant cobalt(III) complexes in the reaction medium. The activation parameters (enthalpy of activation ?H‡ and entropy of activation ?S‡) of the reaction have been calculated which substantiate the kinetics of the reaction.
Second Order Catalytic Quasispecies Yields Discontinuous Mean Fitness at Error Threshold
NASA Astrophysics Data System (ADS)
Wagner, Nathaniel; Tannenbaum, Emmanuel; Ashkenasy, Gonen
2010-05-01
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.
Kinetics of gas-Grain Reactions in the Solar Nebula
NASA Astrophysics Data System (ADS)
Fegley, Bruce, Jr.
2000-04-01
Thermochemical equilibrium calculations predict gas phase, gas-grain, and solid phase reactions as a function of pressure and temperature in the solar nebula. However, chemical reactions proceed at different rates, which generally decrease exponentially with decreasing temperature. At sufficiently low temperatures (which vary depending on the specific reaction) there may not have been enough time for the predicted equilibrium chemistry to have taken place before the local environment cooled significantly or before the gaseous solar nebula was dispersed. As a consequence, some of the high temperature chemistry established in sufficiently hot regions of the solar nebula may be quenched or frozen in without the production of predicted low temperature phases. Experimental studies and theoretical models of three exemplary low temperature reactions, the formation of troilite (FeS), magnetite (Fe3O4), and hydrous silicates, have been done to quantify these ideas. A comparison of the chemical reaction rates with the estimated nebular lifetime of 0.1-10 million years indicates that troilite formation proceeded to completion in the solar nebula. Magnetite formation was much slower and only thin magnetite rims could have formed on metal grains. Hydrous silicate formation is predicted to be even slower, and hydrous silicates in meteorites and interplanetary dust particles probably formed later on the parent bodies of these objects, instead of in the solar nebula.
Kinetics of OCN- formation from the HNCO + NH3 solid-state thermal reaction
NASA Astrophysics Data System (ADS)
Mispelaer, F.; Theule, P.; Duvernay, F.; Roubin, P.; Chiavassa, T.
2012-04-01
Context. Solid-state features in infrared astronomical spectra can provide useful information on interstellar ices within different astrophysical environments. Solid OCN- has an absorption feature at 4.62 ?m, which is observed in star formation regions only with a large source-to-source abundance variation. Aims: We aim to investigate the thermal formation mechanism of solid OCN- from HNCO on the basis of kinetic arguments. Methods: We experimentally studied the kinetics of the low-temperature OCN- formation from the purely thermal reaction between HNCO and NH3 in interstellar ice analogs using Fourier transform infrared spectroscopy. We used a rate equation approach, a kinetic Monte Carlo approach and a gamma probability distribution approach to derive kinetic parameters from experimental data. Results: The kinetics can de divided into two-processes, a fast process corresponding to the chemical reaction, and a slow process that we interpret as the spatial orientation of the two reactants within the ice. The three approaches give the same results. The HNCO + NH3 ? OCN- + NH4+ reaction rate follows an Arrhenius law with an activation energy of 0.4 ± 0.1 kJ mol-1 (48 ± 12 K) and a pre-exponential factor of 0.0035 ± 0.0015 s-1. Conclusions: The present experiment has the important implication that the HNCO + NH3 reaction can account for the observed abundances of solid OCN- and the HNCO non detection in young stellar objects.
Duirk, Stephen E; Bridenstine, David R; Leslie, Daniel C
2013-02-01
The transformation of two benzophenone UV filters (Oxybenzone and Dioxybenzone) was examined over the pH range 6-11 in the presence of excess aqueous chlorine. Under these conditions, both UV filters were rapidly transformed by aqueous chlorine just above circumneutral pH while transformation rates were significantly lower near the extremes of the pH range investigated. Observed first-order rate coefficients (k(obs)) were obtained at each pH for aqueous chlorine concentrations ranging from 10 to 75 ?M. The k(obs) were used to determine the apparent second-order rate coefficient (k(app)) at each pH investigated as well as determine the reaction order of aqueous chlorine with each UV filter. The reaction of aqueous chlorine with either UV filter was found to be an overall second-order reaction, first-order with respect to each reactant. Assuming elemental stoichiometry described the reaction between aqueous chlorine and each UV filter, models were developed to determine intrinsic rate coefficients (k(int)) from the k(app) as a function of pH for both UV filters. The rate coefficients for the reaction of HOCl with 3-methoxyphenol moieties of oxybenzone (OXY) and dioxybenzone (DiOXY) were k(1,OxY) = 306 ± 81 M?¹s?¹ and k(1,DiOxY) = 154 ± 76 M?¹s?¹, respectively. The k(int) for the reaction of aqueous chlorine with the 3-methoxyphenolate forms were orders of magnitude greater than the un-ionized species, k(2,OxY) = 1.03(±0.52) × 10? M?¹s?¹ and k(2_1,DiOxY) = 4.14(±0.68) × 10? M?¹s?¹. Also, k(int) for the reaction of aqueous chlorine with the DiOXY ortho-substituted phenolate moiety was k(2_2,DiOxY) = 2.17(±0.30) × 10³ M?¹s?¹. Finally, chloroform formation potential for OXY and DiOXY was assessed over the pH range 6-10. While chloroform formation decreased as pH increased for OXY, chloroform formation increased as pH increased from 6 to 10 for DiOXY. Ultimate molar yields of chloroform per mole of UV filter were pH dependent; however, chloroform to UV filter molar yields at pH 8 were 0.221 CHCl?/OXY and 0.212 CHCl?/DiOXY. PMID:23168312
Ceramic Thin-Film Reactions: Nucleation and Kinetics
Paul Gabriel Kotula
1995-01-01
The initial stages of the solid-state reaction between thin-films of nickel oxide (NiO) and single-crystals of aluminum oxide (alpha-Al _2O_3) have been investigated with two distinctly different geometries. In the first, epitactic NiO films were grown on (0001) alpha -Al_2O_3. The films in this case consisted of two twin-related variants. Upon reaction, nickel-aluminate spinel (NiAl_2O_4) was found to form first
Kinetics and mechanisms of nonmetal redox reactions of oxyhalogens
Kara Elizabeth Huff Hartz
2002-01-01
The mechanisms of several oxidation\\/reduction reactions of oxyhalogen species are presented. Bromine chloride (BrCl) catalyzes the decomposition of hypochlorous acid\\/hypobromous acid (HOCl\\/HOBr) mixtures. BrCl reacts with hypochlorite ion (OCl?) to form BrOCl, which hydrolyzes to chlorite (ClO2?) and bromide (Br ?) ions. Bromite ion (BrO2?) is formed via HOBr disproportionation. Rapid reactions of HOCl\\/BrO2 ? and HOBr\\/ClO2? produce bromate (BrO3?)
Fang, Liling; Demee, Michael; Sierra, Teresa; Kshirsagar, Tushar; Celebi, Azim A; Yan, Bing
2002-01-01
The kinetics of cleavage reactions of seven resin-bound thiophenol esters with three amines has been studied by single-bead FTIR. The reactivity of these seven thiophenol esters was dependent on their structures and could be summarized as follows: 5-benzimidazolecarboxylic thiophenol ester > alkyl thiophenol ester > aromatic thiophenol ester. The reactivity of three amines was summarized as follows: n-butylamine > 3,4-dimethoxyphenethylamine > 1-piperonylpiperazine. The rate of the cleavage reaction increased 2-fold per 10 degrees C rise in reaction temperature. Oxidation of the thiophenol linker increased the rate of the cleavage reaction by 580-fold. PMID:12099855
KINETICS: A computer program to analyze chemical reaction data. Revision 2
Braun, R.L.; Burnham, A.K.
1994-09-01
KINETICS (Version 3.2) is a copyrighted, user-friendly kinetics analysis computer program designed for reactions such-as kerogen or polymer decomposition. It can fit rate parameters to chemical reaction data (rate or cumulative reacted) measured at a series of constant temperatures, constant heating rates, or arbitrary thermal histories. The program uses two models with conversion-dependent Azrhenius parameters and two models with activation energy distributions. The discrete distribution model fits an average frequency factor and relative fractions and activation energies for up to 25 parallel, fast-order reactions. The Gaussian distribution model fits a frequency factor, activation energy, Gaussian distribution parameter, and reaction order for up to 3 parallel reactions. For both distribution models, if the experiments are at a series of constant heating rates, the program uses a very fast approximate fitting procedure to determine possible initial parameter-estimates for the subsequent nonlinear regression analysis. This increases the probability that the regression analysis will properly. converge with a minimum of computer time. Once convergence is reached by the discrete model, the parameter space is further systematically searched to achieve global convergence. With the Gaussian model, the calculated rates or integrals can be convoluted with an experimental tracer signal during the nonlinear regression to account for dispersion effects often found in real chemical reaction data. KINETICS can also be used in an application mode to calculate reaction rates and integrals for previously determined Gaussian or discrete, parameters, using an arbitrary thermal history. Four additional models have been incorporated for the kinetics analysis of polymers and other materials, including some kerogens, which have a reaction-rate profile that is narrower than that for a single first-order reaction.
Vivekanand, P A; Wang, Maw-Ling
2011-09-01
In the current study, kinetics of synthesis of 2-phenylvaleronitrile (PVN) was successfully carried out by selective C-alkylation of benzyl cyanide (BC) with n-bromopropane (BP) using aqueous KOH and catalyzed by TBAB under ultrasonic (300W) assisted organic solvent-free conditions. Selective monoalkylation of benzyl cyanide has been achieved by controlling the reaction conditions and has been followed using gas chromatogram. The effects of various parameters such as agitation speed, catalyst concentration, KOH concentration, benzyl cyanide concentration, volume of water, ultrasonic frequency and temperature were studied systematically to understand their influence on the rate of the reaction. The experimental observations are consistent with an interfacial-type process. Further the kinetic results demonstrate clearly, that ultrasonic assisted phase-transfer catalysis significantly increased the reaction rate when compared to silent reactions. PMID:21377400
NASA Astrophysics Data System (ADS)
Montero, María A.; Gennero de Chialvo, María R.; Chialvo, Abel C.
2015-06-01
The hydrogen oxidation reaction was studied on a nanostructured rhodium electrode at different rotation rates in alkaline solution. The electrode was prepared via sputtering on a glassy carbon disc support and it was characterized by atomic force microscopy and cyclic voltammetry. The real surface area was evaluated by CO stripping voltammetry. Experimental current density (j) - overpotential (?) curves of the hydrogen oxidation reaction were obtained in the range -0.015 ? ?/V ? 0.40 at different rotation rates (900 ? ?/rpm ? 4900). The resulting curves were correlated by kinetic expressions derived from the Tafel-Heyrovsky-Volmer mechanism with a Frumkin type adsorption of the reaction intermediate and the kinetic parameters were evaluated. It was verified that over this overpotential region the reaction in alkaline solution proceeds mainly through the Tafel-Volmer route. These results were compared with those previously obtained in acid solutions.
A DSC Study on Cure Kinetics of HTPB-IPDI Urethane Reaction
K. B. Catherine; K. Krishnan; K. N. Ninan
2000-01-01
The kinetics of theurethane-forming cure reaction of hydroxyl terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI) in presence of ferric tris (acetyl acetonate) (FeAA) catalyst was investigated using differential scanning calorimetry (DSC). The Arrhenius activation parameters, viz., activation energy E and pre-exponential factor A were evaluated using the non-isothermal integral Coats-Redfern equation. The cure reaction was catalysed by ferric acetyl acetonate
The kinetics of the nitrogen reaction with liquid iron-Sulfur alloys
P. C. Glaws; R. J. Fruehan
1985-01-01
An experimental apparatus was designed and constructed which permits utilization of both the modified Sieverts' technique\\u000a and the isotope exchange technique for study of the kinetics of ni-trogen reaction with liquid iron alloys. Experimental results\\u000a from the two techniques are used in con-junction with the current knowledge in the field to readdress several persisting questions\\u000a dealing with the nitrogen reaction.
Kinetics of simultaneous reactions between liquid iron-carbon alloys and slags containing MnO
Etsuro Shibata; Haiping Sun; Katsumi Mori
1999-01-01
The oxidation rates of carbon, phosphorus, and silicon; the desulfurization rate of liquid iron; and the simultaneous reduction\\u000a rate of MnO from slag were examined at 1450 C to 1550 C by using high carbon iron alloys and CaO-SiO2-CaF2 slags containing MnO and FeO. The reaction rates were well reproduced by a kinetic model describing the reaction between\\u000a the slag
Fei Liao; Kao-Cong Tian; Xiao Yang; Qi-Xin Zhou; Zhao-Chun Zeng; Yu-Ping Zuo
2003-01-01
The reliability of kinetic substrate quantification by nonlinear fitting of the enzyme reaction curve to the integrated Michaelis-Menten equation was investigated by both simulation and preliminary experimentation. For simulation, product absorptivity k was 3.00 mmolу L cmу and Km was 0.10 mmol Lу, and uniform absorbance error † was randomly inserted into the error-free reaction curve of product absorbance Ai
The reaction kinetics of lithium salt with water vapor
M. Balooch; L. N. Dinh; D. F. Calef
2002-01-01
The interaction of lithium salt (LiH and\\/or LiD) with water vapor in the partial pressure range of 10?5–2657 Pa has been investigated. The reaction probability of water with LiH cleaved in an ultra high vacuum environment was obtained using the modulated molecular beam technique. This probability was 0.11 and independent of LiH surface temperature, suggesting a negligible activation energy for
Kinetics of surface grafting on polyisoprene latexes by reaction calorimetry
Wiyong Kangwansupamonkon; Christopher M. Fellows; David J. Lamb; Robert G. Gilbert; Suda Kiatkamjornwong
2004-01-01
The two-component redox-initiation system, cumene hydroperoxide (CHP) and tetraethylene pentamine (TEPA), was used to polymerize dimethylaminoethyl methacrylate (DMAEMA) in the presence of synthetic polyisoprene latexes. The modified latex particles are postulated to possess a ‘hairy layer’ of surface-grafted poly(DMAEMA) chains formed via an abstraction reaction between cumyloxy radicals and the isoprene moieties present in the seed polymer. The modified latexes
Kinetic of antigent-antibody reactions with scattering method
NASA Astrophysics Data System (ADS)
Bilyi, Olexander I.; Kiselyov, Yevgen M.; Novikov, Volodymyr P.
2001-07-01
The immune reactions of interaction antigen-antibody represent specific effect of an antigene with an antibody, which outcome are the complex immune aggregates forming precipitate in case of a soluble antigene, or agglutinate in case of a corpuscular antigene. Immunological methods which uses in the quality of carrier protein latex's polymeric microspheresis, gained name and method latex agglutination. Polymeric microspheresis have the array of advantages before biological carries, which consist in the opportunity of the variation of attributes surface and size microspheresis in the broad band of meanings with the preservation of narrow distribution particles behind measurements, the putting of functional groups, necessary for bunch with ligand on stage their synthesis, in ragidity at storage. The quantitative evaluation of parameters of a response of interaction antigen-antibody in immunology is possible by optical methods on a measurement of a modification of intensity of a light stream of a solution in an outcome of a course of a reaction. Concentration of immune complexes determine both on slacking a taking place stream of light, and on a modification of intensity of a stream of light scattering suspended particles in a solution. The process light scattering by colloidal aggregates are formed from suspension microspheresis with adsorbed on their surface protein is described. In report the physics principle of registration immune reaction by light scattering methods is concerned. The results of the effectiveness latex's preparation created on basis of the polymeric carries is described.
Low Temperature Kinetics of the CH3OH + OH Reaction
Martín, J. C. Gómez; Caravan, R. L.; Blitz, M. A.; Heard, D. E.; Plane, J. M. C.
2014-01-01
The rate constant of the reaction between methanol and the hydroxyl radical has been studied in the temperature range 56-202 K by pulsed laser photolysis-laser induced fluorescence in two separate experiments using either a low temperature flow tube coupled to a time of flight mass spectrometer or a pulsed Laval nozzle apparatus. The two independent techniques yield rate constants which are in mutual agreement and consistent with the results reported previously below 82 K [Shannon et al., Nature Chemistry, 2013, 5, 745-749] and above 210 K [Dillon et al., Phys. Chem. Chem. 2005, 7, 349-355], showing a very sharp increase with decreasing temperature with an onset around 180 K. This onset is also signalled by strong chemiluminescence tentatively assigned to formaldehyde, which is consistent with the formation of the methoxy radical at low temperature by quantum tunnelling, and its subsequent reaction with H and OH. Our results add confidence to the previous low temperature rate constant measurements and consolidate the experimental reference dataset for further theoretical work required to describe quantitatively the tunnelling mechanism operating in this reaction. An additional measurement of the rate constant at 56 K yielded a value of (4.9 ± 0.8) × 10?11 cm3 molecule?1 s?1 (2?), showing that the rate constant is increasing less rapidly at temperatures below 70 K. PMID:24669816
Studies of Reaction Kinetics of Methane Hydrate Dissocation in Porous Media
Moridis, George J.; Seol, Yongkoo; Kneafsey, Timothy J.
2005-03-10
The objective of this study is the description of the kinetic dissociation of CH4-hydrates in porous media, and the determination of the corresponding kinetic parameters. Knowledge of the kinetic dissociation behavior of hydrates can play a critical role in the evaluation of gas production potential of gas hydrate accumulations in geologic media. We analyzed data from a sequence of tests of CH4-hydrate dissociation by means of thermal stimulation. These tests had been conducted on sand cores partially saturated with water, hydrate and CH4 gas, and contained in an x-ray-transparent aluminum pressure vessel. The pressure, volume of released gas, and temperature (at several locations within the cores) were measured. To avoid misinterpreting local changes as global processes, x-ray computed tomography scans provided accurate images of the location and movement of the reaction interface during the course of the experiments. Analysis of the data by means of inverse modeling (history matching ) provided estimates of the thermal properties and of the kinetic parameters of the hydration reaction in porous media. Comparison of the results from the hydrate-bearing porous media cores to those from pure CH4-hydrate samples provided a measure of the effect of the porous medium on the kinetic reaction. A tentative model of composite thermal conductivity of hydrate-bearing media was also developed.
Modulation of the Bulk Structure and Second-Order Statistical Properties of Ekman Layers by Buoyancy
NASA Astrophysics Data System (ADS)
Shah, Stimit
Parameterization of turbulence in the atmospheric boundary layers (ABL), where buoyant forces enhance or destroy turbulent kinetic energy (TKE), remains a challenging and very important problem in geophysical fluid dynamics. In order to understand the difficulties associated with understanding and modeling ABL turbulence, especially under stable conditions, this dissertation presents an in-depth analysis of changes in the bulk structure and second order statistical properties due to buoyancy, using new-generation numerical techniques for solving the fundamental equations that include direct and large-eddy simulations. Using direct numerical simulations, changes in the mean profiles and second-order statistics due to variation in imposed surface temperature are examined. The mechanisms through which buoyancy affects turbulence and the flow are identified as primarily being related to the damping of turbulence production, rather than to direct destruction by buoyancy. Budget analyses that are crucial for researchers aiming to understand stably-stratified shear flows, and to develop higher-order closure models are performed. The results obtained shed light on what terms in the budgets are negligible and how to model the remaining important terms. Very strong stability is shown to result in global intermittency in the turbulence fields. Although this intermittency lacks simple mechanistic explanation, a method for parameterization of the duration over which these intermittent patches are seen is proposed using simple dynamical systems analysis. Subsequently, large-eddy simulations are used to explore buoyancy modulation of large scale structures that carry TKE and fluxes in the ABL. The largest eddies are found to consist of streamwise rolls with similarities to the very large scale structures reported in wind tunnel studies. These rolls however are strongly modulated by buoyancy: they are intensified under unstable conditions and weakened, sometimes completely damped, by stable conditions. Finally, simulations with heterogeneities in surface properties affecting the real world ABL dynamics are carried out with a special emphasis on the implications for the 1.5-order turbulence closures in coarse atmospheric models. Advection is shown to become a critical term in the turbulence kinetic energy budget, and unexpected impacts on the bulk flow are identified.
Young, J.E.; Wong, S.H.; Johnson, J.E.; Sikand, N.; Jonke, A.A.
1980-02-01
This work is directed toward support studies for the national program for the development and demonstration of in situ coal gasification processes. The objective of this work is to determine the reaction-controlling variables and reaction kinetics for the gasification of chars obtained by pyrolyzing coal in simulated underground gasification conditions. The reactions being studied and to be studied include steam-char, CO/sub 2/-char, H/sub 2/-char, the water-gas shift reaction, and the methanation reaction. In this report are presented data regarding the kinetics of the reaction of steam with chars prepared from Pittsburgh seam high-volatile bituminous coal. In addition, a reaction model is described correlating the steam-char reaction rates measured earlier for Hanna subbituminous coal with operating conditions including temperature, partial pressures of steam and hydrogen, and extent of carbon gasification. Partial results are presented and discussed for an investigation of structural parameters of Hanna char as a function of pyrolysis conditions and extent of carbon gasified.
Andujar-De Sanctis, Ivonne L.
2012-01-01
Intramolecular 13C kinetic isotope effects were determined for the dimerization of methacrolein. Trajectory studies accurately predict the isotope effects and support an origin in Newton’s second law of motion, with no involvement of zero-point energy or transition state recrossing. Atomic motion reaction coordinate diagrams are introduced as a way to qualitatively understand the selectivity. PMID:23025278
Detailed chemical kinetic reaction mechanisms for soy and rapeseed biodiesel fuels
Paris-Sud XI, Université de
Detailed chemical kinetic reaction mechanisms for soy and rapeseed biodiesel fuels C.K. Westbrooka and rapeseed biodiesel fuels. These components, methyl stearate, methyl oleate, methyl linoleate, methyl properties between the two biodiesel fuels, derived from soy and rapeseed oils, are traced to the differences
Pulsed laser photolysis kinetics study of the O(3P) + ClO reaction
NASA Technical Reports Server (NTRS)
Nicovich, J. M.; Wine, P. H.; Ravishankara, A. R.
1988-01-01
A pulsed laser photolysis technique was used to investigate the kinetics of the important stratospheric reaction O + ClO yields Cl + O2 in buffer gas over the temperature and pressure ranges of 231-367 K and 25-500 torr. The results indicate a lack of pressure dependence at 298 K over the 25-500 torr range.
Shaozeng Sun; Juwei Zhang; Xidong Hu; Shaohua Wu; Jiancheng Yang; Yang Wang; Yukun Qin [Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Institute
2009-01-15
Four coal chars were prepared in a flat flame flow reactor (FFR), which can simulate the temperature and gas composition of a real pulverized coal combustion environment. The pore structure of chars was measured by mercury porosimetry and nitrogen adsorption, and the Hg and Brunauer-Emmett-Teller (BET) surface areas were obtained. The kinetics of NO-char was studied in a drop-tube furnace (DTF) and thermogravimetric analyzer (TGA). In the TGA experiments, the random pore model (RPM) was applied to describe the NO-char reactions and obtain the intrinsic kinetics. By presenting the data of DTF and TGA experiments on the same Arrhenius plot, it can be concluded that TGA is an available tool to study the kinetics of a high-temperature NO-char reaction. With respect to the DTF experiments, in comparison to the BET surface area, the Hg surface area is a better basis for normalizing the reactivity of different coal chars because of less scatter in the measured values, better agreement with TGA experimental data, and more stable values during the process of reaction. Moreover, by comparing the Hg surface area of chars before and after reactions, it is believed that the Hg surface area basis is more appropriate for high-rank coal chars. The determined kinetic rate constants are in good agreement with other data in the literature, and a new rate constant expression is proposed. 30 refs., 8 figs., 7 tabs.
Wenlin Zhang; M. P. Sridhar Kumar; Arnaldo Visintin; Supramaniam Srinivasan; Harry J. Ploehn
1996-01-01
A microcalorimetric technique was used to study the thermodynamics and kinetics of the hydriding-dehydriding reactions of some AB5-type alloys. The effects of Ce, Co and Sn substitution were analyzed. Co and Sn substitution increase the stability of the hydride state, while Ce substitution has the opposite effect. These observations are rationalized on the basis of the rule of reversed stability
Reaction kinetics and transport in soil: Compatibility and differences between some simple models
Sjoerd E. A. T. M. van der Zee
1991-01-01
Non-equilibrium between the composition of the soil solution and of the sorption sites on the solid matrix of soil may be due to mass transfer resistances and to slow chemical kinetics of elementary or complex reactions. Different mechanistic models have been used to describe the rate of change of the soil solution composition due to sorption, using a good description
Interfacial reaction kinetics of coated SiC fibers with various titanium alloys
NASA Technical Reports Server (NTRS)
Gundel, D. B.; Wawner, F. E.
1991-01-01
The kinetics of the reaction between the silicon carbide fibers and the titanium-based alloy matrix was investigated at temperatures from 800 to 1000 C for several titanium-based alloys (including Ti-1100 alloy and BETA 21S) and unalloyed Ti, reinforced with coated silicon carbide fiber SCS-6. The reaction zone growth kinetics was studied by exposing vacuum encapsulated samples to temperatures from 700 to 1000 C for times up to 150 hrs, followed by SAM observations of samples which were polished perpendicular to the fiber axis and etched. It was found that the reaction zone growth kinetics of the alpha (hcp) and beta (bcc) phases of unalloyed titanium reacting with SCS-6 fibers exhibited different values of the apparent activation energy and of the preexponential factor. Additions of other metals to Ti was found to slow down the reaction kinetics. Among the alloys studied, the Ti-1100 was the slowest reacting conventional alloy and the Ti-14Al-21Nb (in wt pct) was the slowest overall.
Dynamics calculations of kinetic isotope effects for the reactions of muonium atoms with Fâ and Clâ
Rozeanne Steckler; Donald G. Truhlar; Bruce C. Garrett
1986-01-01
Variational-transition-state theory with semiclassical ground-state transmission coefficients is applied to calculate reaction rate constants, activation energies, and kinetic isotope effects for the protium (H) and muonium (Mu) cases of H + Fâ to HF + F and H + Clâ to HCl + Cl. The authors examine four potential energy surfaces for H + Fâ and two for H +
ERIC Educational Resources Information Center
Abdel-Kader, M. H.; Steiner, U.
1983-01-01
Three experiments using merocyanine M suitable as an integrated laboratory experience for undergraduates are described. Experiments demonstrate: complete molecular cycle composed of photochemical, thermal, and protolytic reaction steps; kinetics of cis-trans isomerization of the dye; and mechanism of base catalysis for thermal isomerization of the…
Characterization of reaction kinetics in a porous electrode
NASA Technical Reports Server (NTRS)
Fedkiw, Peter S.
1990-01-01
A continuum-model approach, analogous to porous electrode theory, was applied to a thin-layer cell of rectangular and cylindrical geometry. A reversible redox couple is assumed, and the local reaction current density is related to the potential through the formula of Hubbard and Anson for a uniformily accessible thin-layer cell. The placement of the reference electrode is also accounted for in the analysis. Primary emphasis is placed on the effect of the solution-phase ohmic potential drop on the voltammogram characteristics. Correlation equations for the peak-potential displacement from E(sup 0 prime) and the peak current are presented in terms of two dimensionless parameters.
Goddard III, William A.
First-Principles-Based Reaction Kinetics for Decomposition of Hot, Dense Liquid TNT from Reax Supporting Information ABSTRACT: The reaction kinetics of the thermal decomposition of hot, dense liquid TNT), whereas dimer formation and decomposition to TNT derivatives and smaller gaseous fragments prevails
Bench-scale Kinetics Study of Mercury Reactions in FGD Liquors
Gary Blythe; John Currie; David DeBerry
2008-03-31
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 develop a kinetics model to predict mercury reactions in wet FGD systems. The model may be used to determine optimum wet FGD design and operating conditions to maximize mercury capture in wet FGD systems. Initially, a series of bench-top, liquid-phase reactor tests were conducted and mercury species concentrations were measured by UV/visible light spectroscopy to determine reactant and byproduct concentrations over time. Other measurement methods, such as atomic absorption, were used to measure concentrations of vapor-phase elemental mercury, that cannot be measured by UV/visible light spectroscopy. Next, a series of bench-scale wet FGD simulation tests were conducted. Because of the significant effects of sulfite concentration on mercury re-emission rates, new methods were developed for operating and controlling the bench-scale FGD experiments. Approximately 140 bench-scale wet FGD tests were conducted and several unusual and pertinent effects of process chemistry on mercury re-emissions were identified and characterized. These data have been used to develop an empirically adjusted, theoretically based kinetics model to predict mercury species reactions in wet FGD systems. The model has been verified in tests conducted with the bench-scale wet FGD system, where both gas-phase and liquid-phase mercury concentrations were measured to determine if the model accurately predicts the tendency for mercury re-emissions. This report presents and discusses results from the initial laboratory kinetics measurements, the bench-scale wet FGD tests, and the kinetics modeling efforts.
NASA Astrophysics Data System (ADS)
Nayak, Rajesh Kumar
Nucleic acid hairpins play pivotal roles in biological and cellular processes. The functions of the DNA and RNA hairpins depend upon the conformational changes they adopt during the biological process. Therefore, a clear understanding of their conformational dynamics such as folding and unfolding kinetics, reaction mechanism as well as thermodynamic stability is essential to understand their biological functions. This dissertation describes folding kinetics, reaction mechanism and thermodynamic stability of stem-loop nucleic acid hairpins by using rapid-mixing stopped-flow kinetics and other spectroscopic techniques. Firstly, the folding kinetics and reaction mechanism of a five base-paired stem and twenty one polythymidine loop DNA hairpin as a function of varying monovalent counter ion concentrations have been discussed. The important observation of this investigation is that the DNA hairpin folding is not simply a two-state process, and based on our experiments and kinetic modeling, we proposed a three-state reaction mechanism, wherein, the intermediate formation occurs on microsecond time scale and the complete hairpin formation occurs on millisecond time scale. Secondly, the loop length and counter ion dependent thermodynamic stability and folding of DNA hairpins have been described. This investigation provides a detailed understanding of how the stability and folding changes as a function of loop length and counter ion concentrations. The most important conclusion of this part of the investigation is that the thermodynamic stability of tetraloop hairpins depend upon counter ion concentration regimes and we explained the exceptional stability of a tetraloop hairpin in the higher concentration regime, compared to longer loop length hairpins on the basis of base-stacking effect. Finally, the folding and unfolding kinetics of RNA hairpins with identical four base-paired stem but different nucleotide loop sequence is discussed. Here we observed that the RNA hairpin folding and unfolding can be much more complex than previously thought and also RNA hairpin folding process can be different than DNA hairpin folding process.
Towards the ultimate conservative difference scheme. V - A second-order sequel to Godunov's method
B. van Leer
1979-01-01
A method of second-order accuracy is described for integrating the equations of ideal compressible flow. The method is based on the integral conservation laws and is dissipative, so that it can be used across shocks. The heart of the method is a one-dimensional Lagrangean scheme that may be regarded as a second-order sequel to Godunov's method. The second-order accuracy is
The effects of wood species and treatment retention on kinetics of CCA-C fixation reactions
Suzana Radivojevic; Paul A. Cooper
2010-01-01
Reaction kinetics of fixation of CCA-C (chromated copper arsenate type C) preservative was studied at 30°C in ground wood\\u000a of trembling aspen, red pine, and red maple at treatment retentions of 4.0, 6.4, 9.6, and 30 kg\\/m3, and red maple pre-extracted with hot water at retentions of 6.4 and 30 kg\\/m3. Reaction orders of cumulative Cr, Cu, and As reactions decreased gradually
Lin, S. H.; Sahai, R.; Eyring, H.
1971-01-01
A theoretical model for the accumulation of pesticides in soil has been proposed and discussed from the viewpoint of heterogeneous reaction kinetics with a basic aim to understand the complex nature of soil processes relating to the environmental pollution. In the bulk of soil, the pesticide disappears by diffusion and a chemical reaction; the rate processes considered on the surface of soil are diffusion, chemical reaction, vaporization, and regular pesticide application. The differential equations involved have been solved analytically by the Laplace-transform method. PMID:5279519
NASA Astrophysics Data System (ADS)
Juhui, Chen; Yanjia, Tang; Dan, Li; Pengfei, Xu; Huilin, Lu
2013-07-01
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.
Use of Fiber Optic Technology to Measure the Effects of Anesthesia on Luciferase Reaction Kinetics
Semprini, Sabrina; Saunter, Christopher D; Ludwig, Mike; Girkin, John M; Mullins, John J
2012-01-01
In vivo bioluminescent imaging (BLI) is a sensitive and reliable technique for studying gene expression, although experiments must be controlled tightly to obtain reproducible and quantitative measurements. The luciferase reaction depends on the availability of the reaction substrate, oxygen, and ATP, the distribution of which can vary markedly in different tissues. Here we used in vivo fiber optic technology, combined with stereotaxis-assisted surgery, to assess luciferase reaction kinetics in response to 2 anesthetic regimens, isoflurane and ketamine–xylazine. Transgenic rats that expressed luciferase under the control of the human prolactin promoter were used as a model organism. Anesthesia had a marked effect on luciferase reaction kinetics. The rise time to peak emission differed by 20 min between isoflurane and ketamine–xylazine. Optical imaging using a charge-coupled–device camera confirmed this delay. These results demonstrate that different anesthetics can have substantial effects on luciferase reaction kinetics and suggest that the timing of image acquisition after substrate injection should be optimized in regard to experimental conditions and the tissues of interest. PMID:23294890
V. Franklin; M. Paramasivam; S. Valarmathi; J. J. H. Miller
2010-08-14
A singularly perturbed linear system of second order partial differential equations of parabolic reaction-diffusion type with given initial and boundary conditions is considered. The leading term of each equation is multiplied by a small positive parameter. These singular perturbation parameters are assumed to be distinct. The components of the solution exhibit overlapping layers. Shishkin piecewise-uniform meshes are introduced, which are used in conjunction with a classical finite difference discretisation, to construct a numerical method for solving this problem. It is proved that the numerical approximations obtained with this method are first order convergent in time and essentially second order convergent in the space variable uniformly with respect to all of the parameters.
Kinetics of the Br2-CH3CHO Photochemical Chain Reaction
NASA Technical Reports Server (NTRS)
Nicovich, J. M.; Shackelford, C. J.; Wine, P. H.
1997-01-01
Time-resolved resonance fluorescence spectroscopy was employed in conjunction with laser flash photolysis of Br2 to study the kinetics of the two elementary steps in the photochemical chain reaction nBr2 + nCH3CHO + hv yields nCH3CBrO + nHBr. In the temperature range 255-400 K, the rate coefficient for the reaction Br((sup 2)P(sub 3/2)) + CH3CHO yields CH3CO + HBr is given by the Arrhenius expression k(sub 6)(T) = (1.51 +/- 0.20) x 10(exp -11) exp(-(364 +/- 41)/T)cu cm/(molecule.s). At 298 K, the reaction CH3CO + Br2 yields CH3CBrO + Br proceeds at a near gas kinetic rate, k(sub 7)(298 K) = (1.08 +/- 0.38) x 10(exp -10)cu cm/(molecule.s).
Implementing the Second-Order Fermi Process in a Kinetic Monte-Carlo Simulation
NASA Technical Reports Server (NTRS)
Summerlin, Errol J.
2010-01-01
Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials
CHLORINE DEMAND AND TTHM FORMATION KINETICS: A SECOND-ORDER MODEL
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...
Chemical Kinetics of Reaction Systems Carbon Monoxide + Hydroxy Radical and Methyl Radical + Oxygen
NASA Astrophysics Data System (ADS)
Yu, Ching-Len
Experimental and modeling studies were carried out on kinetics and mechanism of two key reactions of natural gas combustion. Five mixtures of hydrogen, oxygen, and carbon dioxide diluted in argon were studied behind reflected -shock waves in the temperature range from 1420 to 2640 K. The production of CO molecules and OH radicals was measured in-situ by laser absorption. The rate coefficient of reaction CO + OH --> CO_2 + H was derived by detailed kinetic modeling, expressed as 4.76 times 10 ^7T^{1.228}{rm e} ^{-35/T}{rm cm}^3 {rm mol}^{-1}{rm s}^{-1}. Theoretical analysis of the CO + OH reaction was performed by using Rice-Ramsperger -Kassel-Marcus (RRKM) theory and the master equation approach by fitting the experimental rate coefficient. The resulting entrance and exit barrier heights, relative to the CO + OH energy level, are 0.92 and 0.72 kcal/mol, respectively. Oxidation of methyl radicals by molecular oxygen were studied by using four shock-heated fuel-lean methane -oxygen-argon mixtures at temperatures from 1550 to 2200 K. The reaction progress was monitored by laser absorption of OH radicals and CO molecules. The rate coefficients of the CH_3+O_2 reactions were determined via kinetic modeling and the RRKM-master equation approach: 2.87 times 10^ {13}{rm e}^{-15340/T } for reaction CH_3+O _2 --> CH_3O + O and 1.85 times 10^{12 }{rm e}^{-10224/T} for reaction CH_3+O_2 --> CH_2O + OH, in the units of cm^3mol^ {-1}s^{-1}. The former was found to be in agreement with that computed based on the canonical variational transition state theory. The derived reaction model was shown to be consistent with essentially all available experimental data. The discrepancy among literature studies results from data interpretation and experimental design.
ACKS2: Atom-condensed Kohn-Sham DFT approximated to second order
NASA Astrophysics Data System (ADS)
Verstraelen, T.; Ayers, P. W.; Van Speybroeck, V.; Waroquier, M.
2013-02-01
A new polarizable force field (PFF), namely atom-condensed Kohn-Sham density functional theory approximated to second order (ACKS2), is proposed for the efficient computation of atomic charges and linear response properties of extended molecular systems. It is derived from Kohn-Sham density functional theory (KS-DFT), making use of two novel ingredients in the context of PFFs: (i) constrained atomic populations and (ii) the Legendre transform of the Kohn-Sham kinetic energy. ACKS2 is essentially an extension of the Electronegativity Equalization Method (EEM) [W. J. Mortier, S. K. Ghosh, and S. Shankar, J. Am. Chem. Soc. 108, 4315 (1986)], 10.1021/ja00275a013 in which two major EEM shortcomings are fixed: ACKS2 predicts a linear size-dependence of the dipole polarizability in the macroscopic limit and correctly describes the charge distribution when a molecule dissociates. All ACKS2 parameters are defined as atoms-in-molecules expectation values. The implementation of ACKS2 is very similar to that of EEM, with only a small increase in computational cost.
Kinetics of the oxidation of hexacyanoferrate(III) with pyrolusite
NASA Astrophysics Data System (ADS)
Chirkst, D. E.; Cheremisina, O. V.; Sulimova, M. A.
2013-06-01
It is established that the oxidation of potassium ferricyanide at pH 7-11 proceeds as a pseudo-second-order reaction with rate constants of 2.93, 4.19, 6.16, 8.66, and 9.22 L/(mol min) at 313, 323, 333, 343, and 353 K, respectively. The activation energy of the reaction is found to be 27.82 kJ/mol. The second order of the reaction, as along with the non-dependence of the rate constant on the liquid-phase volume: solidphase weight ratio, and on the rotation speed of the mixer, allow us to assume that the reaction proceeds in the kinetic region with a transition to the diffusion-kinetic mode at 353 K.
Generic modeling of surface reaction kinetics in plasma etching systems
NASA Astrophysics Data System (ADS)
Bray, Raymond Paul
The complexity of both the bulk plasma phase physics and the substrate surface reaction chemistry indicate the need for simplified phenomenological modeling of etching systems. Simplified models are useful for design, analysis and control, within a reasonable time after data collection, and at modest cost. A current typical method in industry is a response surface model (an empirical polynomial), which has no predictive properties outside the range of fitted data, is completely arbitrary, and offers little physical understanding of the system. A set of generic etch rate expressions based on simplified representations of physical phenomena are presented in this dissertation. The model parameter values are regressed from data with a constrained, nonlinear optimization routine. Also presented are a statistical method for discriminating which model best represents the phenomenon of a particular etching system and a statistical model validation procedure. The benefits of this approach are a predictive, statistically validated model; the small number of model parameters may reduce the number of data points required for regression; and there is no need to re-derive a polynomial fit for each new data set. The method will be demonstrated on experimental data for chlorine plasma etching of polysilicon; tetrafluoromethane/oxygen plasma etching of polysilicon and silicon dioxide; and oxygen plasma ashing of photoresist.
Thermodynamics and kinetics of reactions in protective coating systems
NASA Technical Reports Server (NTRS)
Gupta, B.; Sarkhel, A.; Sivakumar, R.; Seigle, L.
1974-01-01
Investigations of fluoride activated packs with Al:Ni ratios greater than 50 a/o prove that the specimen surface is not in equilibrium with the pack at high Al:Ni ratios but that an activity gradient exists between pack and specimen. Therefore, gaseous diffusion and possibly surface reactions play a role in determining the overall rate of Al deposition in such packs. Noticeable differences in coating behavior have been obtained in packs activated with chloride and iodide, and it appears that poorest results are obtained with iodides, better with chlorides, and best with fluorides. A numerical method has been perfected for calculating rates of solid-state diffusion controlled coating formation, allowing for the variation of diffusivity with composition in the NiAl phase. Layer growth rates can now be accurately predicted from a knowledge of the surface and substrate compositions. Furthermore, the correct diffusion profiles are obtained by this method. These differ substantially from the profile obtained when the diffusivity is assumed constant.
Bond energies, reaction volumes, and kinetics for ?- and ?-complexes of MoCO5L.
Gittermann, Shannon M; Letterman, Roger G; Jiao, Tianjie; Leu, Ging-Long; DeYonker, Nathan J; Webster, Charles Edwin; Burkey, Theodore J
2011-08-18
The photosubstitution reactions of molybdenum hexacarbonyl with ? and ? donor ligands were investigated using photoacoustic calorimetry and computational methods in a series of linear alkane solvents (pentane, hexane, heptane, octane, decane, and dodecane). The results show that reaction volumes make a significant contribution to the photoacoustic signal and must be considered during thermodynamic calculations based on photoacoustic measurements. The enthalpies of CO substitution by an alkane solvent and subsequent substitution by each Lewis base were determined. Corresponding Mo-L bond energies (kcal mol(-1)) were calculated: L = linear alkanes (13), triethylsilane (26), 1-hexyne (27), 1-hexene (27), and benzene (17). The relative energies are in agreement with computational results. The experimental reaction volume for CO substitution by alkane was positive (15 mL mol(-1)) and negative or close to zero for alkane substitution by a Lewis base (for example, -11 mL mol(-1) for triethylsilane and 3.6 mL mol(-1) for benzene). The errors in the experimental and computational reaction volumes are large and often comparable to the reaction volumes. An improved calibration of the methods as well as a better understanding of the underlying physics involved is needed. For the Lewis bases reported in this study, the second-order rate constants for the displacement of a coordinated alkane are less than diffusion control (5 × 10(6)-4 × 10(7) M(-1) s(-1)) and decrease monotonically with the alkane chain length. The rate constants correlate better with steric effects than with bond energies. An interchange mechanism is consistent with the results. PMID:21780751
Using Single-Turnover Kinetics with Osmotic Stress to Characterize the EcoRV Cleavage Reaction
Ferrandino, Rocco; Sidorova, Nina; Rau, Donald
2014-01-01
Type II restriction endonucleases require metal ions to specifically cleave DNA at canonical sites. Despite the wealth of structural and biochemical information, the number of Mg2+ ions used for cleavage by EcoRV, in particular, at physiological divalent ion concentrations is still not established. In this work we employ a single-turnover technique that uses osmotic stress in order to probe reaction kinetics between an initial specific EcoRV-DNA complex formed in the absence of Mg2+ and the final cleavage step. With osmotic stress, complex dissociation before cleavage is minimized and the reaction rates are slowed to a convenient timescale of minutes to hours. We find that cleavage occurs by a two-step mechanism that can be characterized by two rate constants. The dependence of these rate constants on Mg2+ concentration and osmotic pressure gives the number of Mg2+ ions and water molecules coupled to each kinetic step of the EcoRV cleavage reaction. Each kinetic step is coupled to the binding 1.5 – 2.5 Mg2+ ions, the uptake of ~30 water molecules, and the cleavage of a DNA single strand. We suggest that each kinetic step reflects an independent, rate limiting conformational change of each monomer of the dimeric enzyme that allows Mg2+ ion binding. This modified single turnover protocol has general applicability for metalloenzymes. PMID:24328115
Kowalsky, Michael B.; Moridis, George J.
2006-11-29
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. The use of the equilibriumreaction model often appears to be justified and preferred for simulatingthe behavior of gas hydrates, given that the computational demands forthe kinetic reaction model far exceed those for the equilibrium reactionmodel.
Kinetic and thermochemical studies of the ClO + ClO + M ? Cl2O2 + M reaction
NASA Astrophysics Data System (ADS)
Ferracci, V.; Rowley, D. M.
2009-12-01
Chlorine monoxide (ClO) radicals play a crucial role in polar ozone destruction events and the ClO dimer cycle has been identified as one of the most effective ozone-depleting catalytic cycles operating in the polar winter. A recent paper by von Hobe et al.1 highlighted significant inconsistencies between laboratory results, theoretical calculations and field observations concerning the ClO dimer ozone destruction cycle. This work has investigated the temperature dependence of the equilibrium constant of one of the key reactions in this cycle, ClO + ClO + M ? Cl2O2 + M (1, -1), by means of laser flash photolysis coupled with time-resolved UV absorption spectroscopy. ClO radicals were generated via laser flash photolysis of Cl2/Cl2O mixtures in synthetic air. The concentration of radicals was monitored via UV absorption spectroscopy: the use of a Charge Coupled Device (CCD) detector allowed time resolution over a broad range of wavelengths. The equilibrium constant Keq was determined as the ratio of the rate constants of the forward and reverse reaction (1, -1) over the T range 256 - 312 K. Second Law and Third Law analytical methods were employed to determine the standard enthalpy and entropy changes of reaction 1, ?rH° and ?rS°, from the measured equilibrium constants. The values obtained from the Second Law analysis (?rH° = - 80.8 ± 2.2 kJ mol-1; ?rS° = - 168.4 ± 7.9 J K-1 mol-1) are in good agreement with previous work 2 but greater in magnitude than current NASA recommendations 3. It was also found that, under typical laboratory conditions employed in this work, [ClO] decay exhibits pure second order kinetics at T ? 250 K. A higher rate constant for the ClO recombination reaction (1) was also observed in this work (compared to the NASA evaluation 3), implying a higher Keq and a different partitioning between ClO and Cl2O2, shifting towards the dimer. 1. M. Von Hobe, R. J. Salawitch, T. Canty, H. Keller-Rudek, G. K. Moortgat, J.-U. Grooss, R. Müller, F. Stroh, Atmospheric Chemistry and Physics, 2007, 7, 3055 2. S. L. Nickolaisen, R. R. Friedl, S. P. Sander, Journal of Physical Chemistry, 1994, 98, 155 3. S. P. Sander, R. R. Friedl, D. M. Golden, M. J. Kurylo, R. E. Huie, V. L. Orkin, G. K. Moortgat, A. R. Ravishankara, C. E. Kolb, M. J. Molina, B. J. Finlayson-Pitts, Chemical Kinetics and Photochemical Data for use in Atmospheric Studies, Evaluation No. 14, JPL Publication 02-25, NASA Jet Propulsion Laboratory, Pasadena CA, 2003
Sensitivity of Polar Stratospheric Ozone Loss to Uncertainties in Chemical Reaction Kinetics
NASA Astrophysics Data System (ADS)
Kawa, S. R.; Rex, M.; Stolarski, R. S.; Douglass, A. R.; Newman, P. A.; Frieler, K.
2008-12-01
Several recent observational and laboratory studies of processes involved in polar stratospheric ozone loss have prompted a reexamination of aspects of our understanding for this key indicator of global change. To a large extent, our confidence in understanding and projecting changes in polar and global ozone is based on our ability to simulate these processes in numerical models of chemistry and transport. The fidelity of the models is assessed in comparison with a wide range of observations. These models depend on laboratory- measured kinetic reaction rates and photolysis cross sections to simulate molecular interactions. The rates of all of these reactions are subject to uncertainty, some substantial. Given the complexity of the models, however, it is difficult to quantify uncertainties in many aspects of system. In this study we use trajectory box- model simulations for Antarctic and Arctic ozone to estimate the uncertainty in loss attributable to known reaction kinetic uncertainties. Following the method of earlier work, rates and uncertainties from the latest laboratory evaluations are applied in random combinations. We determine the key reactions and rates contributing the largest potential errors and compare the results with observations to evaluate which combinations are consistent with atmospheric data. Comparisons with ozone sonde and MLS data in the Antarctic and MATCH observations in the Arctic present a consistent picture of seasonal ozone loss and chlorine partitioning vis-a-vis the kinetic rates and their uncertainties. Implications for our theoretical and practical understanding of polar ozone loss will be assessed.
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
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.
A Simplification of the Agrachev-Gamkrelidze Second-Order Variation for Bang-Bang Controls
Margaliot, Michael
A Simplification of the Agrachev-Gamkrelidze Second-Order Variation for Bang-Bang Controls Irad (SOV) of bang-bang controls derived by Agrachev and Gamkre- lidze. The SOV plays an important role in both necessary and sufficient secondorder optimality conditions for bang-bang controls
Second Order Sufficient Optimality Conditions for a Control Problem with Continuous and Bang-Bang
Maurer, Helmut
Second Order Sufficient Optimality Conditions for a Control Problem with Continuous and Bang-Bang@math.uni-muenster.de Abstract Second order sufficient optimality conditions for bang-bang con- trol problems in a very general: a continuous unconstrained control appear- ing nonlinearly and a bang-bang control appearing linearly
A second-order system for polytime reasoning based on Gradel's Stephen Cook and Antonina Kolokolova
Penn, Gerald
A second-order system for polytime reasoning based on Gradel's theorem Stephen Cook and Antonina-order system V 1 -Horn of bounded arithmetic formalizing polynomial- time reasoning, based on Gradel's [11] second-order Horn characterization of P. Our system has comprehension over P predicates (de#12;ned by Gradel
Operator Factorization and the Solution of Second-Order Linear Ordinary Differential Equations
ERIC Educational Resources Information Center
Robin, W.
2007-01-01
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…
Modulation frequency and orientation tuning of second-order texture mechanisms
Kingdom, Frederick A. A.
Modulation frequency and orientation tuning of second-order texture mechanisms A. Serge Arsenault October 15, 1998 Modulation frequency and orientation tuning of second-order mechanisms underlying. Thresholds were determined for spatial-frequency modulated test patterns (0.2 and 0.8 cpd) with fixed
An expansion for some second-order probability distributions and its application to noise problems
J. Barrett; D. Lampard
1955-01-01
In this paper it is shown that, in general, second-order probability distributions may be expanded in a certain double series involving orthogonal polynomials associated with the corresponding first-order probability distributions. Attention is restricted to those second-order probability distributions which lead to a \\
Soatto, Stefano
stable second order accurate projection method for the in- compressible Navier-Stokes equations on fullyA Second Order Accurate Projection Method for the Incompressible Navier-Stokes Equations on Fully in the L1 and L norms. 1 Introduction The incompressible Navier-Stokes equations describe the motion of uid
SECOND{ORDER AND HIGHER{ORDER PERTURBATIONS OF TRAVEL TIME IN ISOTROPIC AND ANISOTROPIC MEDIA
Cerveny, Vlastislav
SECOND{ORDER AND HIGHER{ORDER PERTURBATIONS OF TRAVEL TIME IN ISOTROPIC AND ANISOTROPIC MEDIA Lud derivatives of travel time with respect to model parameters are re- ferred to as perturbations. Explicit equations for the second{order and higher{order perturbations of travel time in both isotropic
Grid travel{time tracing: second{order method for the rst arrivals in smooth media *
Cerveny, Vlastislav
Grid travel{time tracing: second{order method for the #12;rst arrivals in smooth media * Lud#20;ek the #12;rst{arrival travel times on a rectangular grid of points is proposed. Whereas the former "#12;nite is of the second{order accu- racy. It means that the relative propagation{velocity error of calculated travel time
P. Ponte Castañeda
1996-01-01
Motivated by previous small-contrast perturbation estimates, this paper proposes a new method for estimating the effective behavior of nonlinear composite materials with arbitrary phase contrast. The key idea is to write down a second-order Taylor expansion for the phase potentials, about appropriately defined phase average strains. The resulting estimates, which are exact to second order in the contrast, involve the
Adaptation of Log Domain Second Order Filters Implemented by Floating Gate MOSFETs
Maryland at College Park, University of
Adaptation of Log Domain Second Order Filters Implemented by Floating Gate MOSFETs Yiming Zhai, MD 20742, USA ymzhai, pabshire@umd.edu Abstract--We describe an adaptive log domain second order transistors to realize on-line learning of quality factor and time constant. We use adaptive dynamical system
On the Second-Order Statistics of the Sample Information Processing Center
Xu, Zhengyuan "Daniel"
On the Second-Order Statistics of the Sample Covariance Nenghai Yu Information Processing Center@ee.ucr.edu Abstract-- The second-order statistics of the sample covariance are encountered in many covariance based and fourth-order statistics of the channel noise and inputs. They can be directly applied to study
A SECOND-ORDER GRADIENT-LIKE DISSIPATIVE DYNAMICAL SYSTEM with HESSIAN DRIVEN DAMPING.
Alvarez, Felipe
A SECOND-ORDER GRADIENT-LIKE DISSIPATIVE DYNAMICAL SYSTEM with HESSIAN DRIVEN DAMPING. Application of ), mechanics (non-elastic shocks), control theory (asymptotic stabilization of oscillators) and PDE theory (damped wave equation). The terminology reflects the fact that (DIN) is a second order in time dynamical
A SECOND-ORDER DIFFERENTIAL SYSTEM WITH HESSIAN-DRIVEN DAMPING;
Boyer, Edmond
A SECOND-ORDER DIFFERENTIAL SYSTEM WITH HESSIAN-DRIVEN DAMPING; APPLICATION TO NON-ELASTIC SHOCK of his 60th birthday Abstract. We consider the second-order differential system with Hessian-driven damp framework, we introduce a nonlinear hyperbolic PDE describing a damped oscillating system with obsta- cle
Second-order Kohn-Sham perturbation theory: Correlation potential for atoms in a cavity
Engel, Eberhard
Second-order Kohn-Sham perturbation theory: Correlation potential for atoms in a cavity Hong Jiang online 12 December 2005 Second-order perturbation theory based on the Kohn-Sham Hamiltonian leads occupied and unoccupied Kohn-Sham single-particle orbitals and energies. The corresponding correlation
Engel, Eberhard
Kohn-Sham perturbation theory: Simple solution to variational instability of second order resulting from second order Kohn-Sham perturbation theory leads to atomic correlation potentials we examine the simplest resummation of the Kohn-Sham perturbation series which has the potential
Properties of second-order spatial frequency channels Michael S. Landy *, _IIpek Oruc
Landy, Michael S.
Properties of second-order spatial frequency channels Michael S. Landy *, _IIpek Orucß Department response), and finally subsequent (``second-order'') linear spatial filters (to provide a strong response flat over a five-octave range of spatial frequency, but was bandpass when stated as efficiency
Towards Ecient Second-Order Power Analysis Jason Waddle and David Wagner
Wagner, David
Towards EÆcient Second-Order Power Analysis Jason Waddle and David Wagner University of California at Berkeley Abstract. Viable cryptosystem designs must address power analysis attacks, and masking variants of second- order di#11;erential power analysis: Zero-O#11;set 2DPA and FFT 2DPA. 1 Introduction
Beyond second-order statistics for learning: A pairwise interaction model for entropy estimation
Deniz Erdogmus; José Carlos Príncipe; Kenneth E. Hild II
2002-01-01
Second order statistics have formed the basis of learning and adaptation due to its appeal and analytical simplicity. On the other hand, in many realistic engineering problems requiring adaptive solutions, it is not sufficient to consider only the second order statistics of the underlying distributions. Entropy, being the average information content of a distribution, is a better-suited criterion for adaptation
J. Li; D. J. W. Geldart; Petr Chylek
1995-01-01
A second order perturbation expansion solution is obtained for solar radiative transfer in a medium with a horizontally arbitrary periodic variation of extinction coefficient. The calculations show that the perturbation solution series is convergent. The cloud albedo changes from the unperturbed value when the second order perturbation correction is applied. The change of albedo can be negative as well as
Paris-Sud XI, Université de
Uniqueness Results for Second Order Bellman-Isaacs Equations under Quadratic Growth Assumptions semicontinuous viscosity sub and supersolu- tions growing at most quadratically of second-order degenerate parabolic Hamilton-Jacobi-Bellman and Isaacs equations. As an application, we characterize the value
STABILITY OF SECOND-ORDER ASYMMETRIC LINEAR MECHANICAL SYSTEMS WITH APPLICATION TO ROBOT GRASPING
Shapiro, Amir
is concerned with the stability of second-order linear systems that have an asymmetric stiffness matrix. Our that the symmetric part of the stiffness matrix, ´Kpµs 1 2 ´Kp · KT p µ, is positive definite. This assumption hasSTABILITY OF SECOND-ORDER ASYMMETRIC LINEAR MECHANICAL SYSTEMS WITH APPLICATION TO ROBOT GRASPING
Phys. Fluids. Two spheres in a free stream of a second-order fluid
Joseph, Daniel D.
Phys. Fluids. Two spheres in a free stream of a second-order fluid A. M. Ardekani1 , R. H. Rangel1 are investigated. When 1 + 2 = 0, where 1 and 2 are fluid parameters related to the first and second normal stress coefficients, the velocity field for a second-order fluid is the same as the one predicted by the Stokes
The similarity rules for second-order subsonic and supersonic flow
NASA Technical Reports Server (NTRS)
Van Dyke, Milton D
1958-01-01
The similarity rules for linearized compressible flow theory (Gothert's rule and its supersonic counterpart) are extended to second order. It is shown that any second-order subsonic flow can be related to "nearly incompressible" flow past the same body, which can be calculated by the Janzen-Rayleigh method.
Xiaobing Feng; Michael Neilan
2007-01-01
This paper concerns with numerical approximations of solutions of second order fully nonlinear partial differential equations (PDEs). A new notion of weak solutions, called moment solutions, is introduced for second order fully nonlinear PDEs. Unlike viscosity solutions, moment solutions are defined by a constructive method, called vanishing moment method, hence, they can be readily computed by existing numerical methods such
Confining Domains Lead to Reaction Bursts: Reaction Kinetics in the Plasma Membrane
Kalay, Ziya; Fujiwara, Takahiro K.; Kusumi, Akihiro
2012-01-01
Confinement of molecules in specific small volumes and areas within a cell is likely to be a general strategy that is developed during evolution for regulating the interactions and functions of biomolecules. The cellular plasma membrane, which is the outermost membrane that surrounds the entire cell, was considered to be a continuous two-dimensional liquid, but it is becoming clear that it consists of numerous nano-meso-scale domains with various lifetimes, such as raft domains and cytoskeleton-induced compartments, and membrane molecules are dynamically trapped in these domains. In this article, we give a theoretical account on the effects of molecular confinement on reversible bimolecular reactions in a partitioned surface such as the plasma membrane. By performing simulations based on a lattice-based model of diffusion and reaction, we found that in the presence of membrane partitioning, bimolecular reactions that occur in each compartment proceed in bursts during which the reaction rate is sharply and briefly increased even though the asymptotic reaction rate remains the same. We characterized the time between reaction bursts and the burst amplitude as a function of the model parameters, and discussed the biological significance of the reaction bursts in the presence of strong inhibitor activity. PMID:22479350
The effects of second-order hydrodynamics on a semisubmersible floating offshore wind turbine
NASA Astrophysics Data System (ADS)
Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.
2014-06-01
The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of a floating system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the Maritime Research Institute Netherlands (MARIN) offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method was applied to the Offshore Code Comparison Collaboration Continuation OC4-DeepCwind semisubmersible platform, supporting the National Renewable Energy Laboratory's 5-MW baseline wind turbine. In this paper, the loads and response of the system caused by the second-order hydrodynamics are analysed and compared to the first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second-order loads and induced response data are compared to the loads and motions induced by aerodynamic loading as solved by FAST.
Effects of Second-Order Hydrodynamics on a Semisubmersible Floating Offshore Wind Turbine: Preprint
Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.
2014-07-01
The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of the system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the MARIN offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST in the future. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method has been applied to the OC4-DeepCwind semisubmersible platform, supporting the NREL 5-MW baseline wind turbine. The loads and response of the system due to the second-order hydrodynamics are analysed and compared to first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second-order loads and induced response data are compared to the loads and motions induced by aerodynamic loading as solved by FAST.
Mendes, Jorge; Zhou, Chong-Wen; Curran, Henry J
2013-06-01
This work presents an ab initio and chemical kinetic study of the reaction mechanisms of hydrogen atom abstraction by the HO2 radical on five ketones: dimethyl, ethyl methyl, n-propyl methyl, iso-propyl methyl, and iso-butyl methyl ketones. The Møller-Plesset method using the 6-311G(d,p) basis set has been used in the geometry optimization and the frequency calculation for all the species involved in the reactions, as well as the hindrance potential description for reactants and transition states. Intrinsic reaction coordinate calculations were carried out to validate all the connections between transition states and local minima. Energies are reported at the CCSD(T)/cc-pVTZ//MP2/6-311G(d,p) level of theory. The CCSD(T)/cc-pVXZ method (X = D, T, Q) was used for the reaction mechanism of dimethyl ketone + HO2 radical in order to benchmark the computationally less expensive method of CCSD(T)/cc-pVTZ//MP2/6-311G(d,p). High-pressure limit rate constants have been calculated for all the reaction channels by conventional transition state theory with asymmetric Eckart tunneling corrections and 1-D hindered rotor approximations in the temperature range 500-2000 K. PMID:23590552
Wang Haifeng [Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853 (United States)], E-mail: hw98@cornell.edu; Popov, Pavel P.; Pope, Stephen B. [Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853 (United States)
2010-03-01
We study a class of methods for the numerical solution of the system of stochastic differential equations (SDEs) that arises in the modeling of turbulent combustion, specifically in the Monte Carlo particle method for the solution of the model equations for the composition probability density function (PDF) and the filtered density function (FDF). This system consists of an SDE for particle position and a random differential equation for particle composition. The numerical methods considered advance the solution in time with (weak) second-order accuracy with respect to the time step size. The four primary contributions of the paper are: (i) establishing that the coefficients in the particle equations can be frozen at the mid-time (while preserving second-order accuracy), (ii) examining the performance of three existing schemes for integrating the SDEs, (iii) developing and evaluating different splitting schemes (which treat particle motion, reaction and mixing on different sub-steps), and (iv) developing the method of manufactured solutions (MMS) to assess the convergence of Monte Carlo particle methods. Tests using MMS confirm the second-order accuracy of the schemes. In general, the use of frozen coefficients reduces the numerical errors. Otherwise no significant differences are observed in the performance of the different SDE schemes and splitting schemes.
Kinetics and dynamics of oxidation reactions involving an adsorbed CO species
Harold, M.P.; Conner, C.W.
1992-07-01
Objectives were to formulate kinetic models/mechanistic sequences, and to develop bifunctional catalysts for selective oxidation of hdyrocarbons. Efforts are reported this year on 3 items: development of Fourier transform infrared emission spectroscopy to monitor near infrared (ir) under reaction conditions (ethylene oxidation on V{sub 2}O{sub 5}); kinetics study of methanol oxidation on supported Pt catalysts (methanol-rich feed the CO{sub 2} yield exhibits a maximum at an intermediate temperature); and comparative kinetics study of CO oxidation on Pt, Pd, and Rh. The ir spectra of V{sub 2}O{sub 5} show a correlation between the ir features and the degree of surface oxidation. 4 figs. (DLC)
Ben O'Shaughnessy; Dimitrios Vavylonis
1998-12-21
We study reactions between end-functionalized chains at a polymer-polymer interface. For small chemical reactivities (the typical case) the number of diblocks formed, $R_t$, obeys 2nd order chemically controlled kinetics, $R_t \\sim t$, until interfacial saturation. For high reactivities (e.g. radicals) a transition occurs at short times to 2nd order diffusion-controlled kinetics, with $R_t \\sim t/\\ln t$ for unentangled chains while $t/\\ln t$ and $t^{1/2}$ regimes occur for entangled chains. Long time kinetics are 1st order and controlled by diffusion of the more dilute species to the interface: $R_t \\sim t^{1/4}$ for unentangled cases, while $R_t \\sim t^{1/4}$ and $t^{1/8}$ regimes arise for entangled systems. The final 1st order regime is governed by center of gravity diffusion, $R_t \\sim t^{1/2}$.
Reaction kinetics of Cl atoms with limonene: An experimental and theoretical study
NASA Astrophysics Data System (ADS)
Dash, Manas Ranjan; Rajakumar, B.
2014-12-01
Rate coefficients for the reaction of Cl atoms with limonene (C10H16) were measured between 278-350 K and 800 Torr of N2, using the relative rate technique, with 1,3-butadiene (C4H6), n-nonane (C9H20), and 1-pentene (C5H10) as reference compounds. Cl atoms were generated by UV photolysis of oxalyl chloride ((COCl)2) at 254 nm. A gas chromatograph equipped with a flame ionization detector (GC-FID) was used for quantitative analysis of the organics. The rate coefficient for the reaction of Cl atoms with limonene at 298 K was measured to be (8.65 ± 2.44) × 10-10 cm3 molecule-1 s-1. The rate coefficient is an average value of the measurements, with two standard deviations as the quoted error, including uncertainties in the reference rate coefficients. The kinetic data obtained over the temperature range of 278-350 K were used to derive the following Arrhenius expression: k(T) = (9.75 ± 4.1) × 10-11 exp[(655 ± 133)/T] cm3 molecule-1 s-1. Theoretical kinetic calculations were also performed for the title reaction using conventional transition state theory (CTST) in combination with G3(MP2) theory between 275 and 400 K. The kinetic data obtained over the temperature range of 275-400 K were used to derive an Arrhenius expression: k(T) = (7.92 ± 0.82) × 10-13 exp[(2310 ± 34)/T] cm3 molecule-1 s-1. The addition channels contributes maximum to the total reaction and H-abstraction channels can be neglected in the range of studied pressures. The Atmospheric lifetime (?) of limonene due to its reaction with Cl atoms was estimated and concluded that the reaction with chlorine atoms can be an effective tropospheric loss pathway in the marine boundary layer and in coastal urban areas.
Kinetics of the reaction between Pu(III) and Fe(III) in nitric acid solution
Koltunov, V.S.; Zhuravleva, G.I.
1988-01-01
The kinetics of the reaction between Pu/sup (III)/ and Fe/sup (III)/ in an aqueous nitric acid solution in the presence of persulfate ions at a constant ionic strength of the solution was studied spectrophotometrically. It was shown that the reaction is first order with respect to the reagents; its rate is practically independent of the concentration of the H/sup +/ and S/sub 2/O/sub 8//sup 2 -/ ions and with increase in the analytical HNO/sub 3/ concentration at variable ionic strength, it first increases, and then decreases. The temperature dependence of the reaction was determined, and its thermodynamic activation parameters were calculated. A possible mechanism for the reaction between Pu/sup (III)/ and Fe/sup (III)/ was proposed.
Stoichiometry and kinetics of the reaction of nitrite with free chlorine in aqueous solutions
Diyamandoglu, V.; Marinas, B.J.; Selleck, R.E. (Univ. of California, Berkeley (USA))
1990-11-01
The reaction of nitrite with free chlorine in dilute aqueous solution (3.4 < pH < 11.5) was studied under continuous-flow mixing conditions. Chlorine, chloride, nitrite, and nitrate were all measured analytically. Stoichiometric balances demonstrated that nitrate was oxidized to nitrate, and chlorine was reduced to chloride, without the significant production of any other chemical species. The kinetic studies demonstrated that the reaction is very fast at neutral or acidic pH with the rate decreasing with increasing pH. The reaction was strictly bimolecular in the pH range of 9.5-11.6, whereas it was sufficiently slow to be followed with time. The reaction appears to proceed between nitrous and hypochlorous acid molecules, or HNO{sub 2} + HOCl {yields} 2H{sup +} + NO{sub 3}{sup {minus}} + Cl{sup {minus}}.
ERIC Educational Resources Information Center
Lombardo, Anthony
1982-01-01
Described is an advanced undergraduate kinetics experiment using buffer dilutions to determine spontaneous rate, catalyzed rate, and reaction order. The reaction utilized is hydrolysis of p-nitro-phenyl acetate in presence of imidazole, which has been shown to enhance rate of the reaction. (Author/JN)
ERIC Educational Resources Information Center
Sattsangi, Prem D.
2011-01-01
A microscale laboratory for teaching chemical kinetics utilizing the iodine clock reaction is described. Plastic pipets, 3 mL volume, are used to store and deliver precise drops of reagents and the reaction is run in a 24 well plastic tray using a total 60 drops of reagents. With this procedure, students determine the rate of reaction and the…
Modeling of reaction kinetics for reactor selection in the case of L-erythrulose synthesis.
Vasic-Racki, D; Bongs, J; Schörken, U; Sprenger, G A; Liese, A
2003-03-01
To choose the most effective process design in enzyme process development it is important to find the most effective reactor mode of operation. This goal is achieved by modeling of the reaction kinetics as a tool of enzyme reaction engineering. With the example of the transketolase catalyzed L-erythrulose synthesis we demonstrate how the most effective reactor mode can be determined by kinetic simulations. This is of major importance if the biocatalyst deactivation is caused by one of the substrates as in this case by glycolaldehyde. The cascade of two membrane reactors in series with soluble enzyme is proposed as a solution for the enzyme deactivation by one of the substrates. PMID:14505172
Kinetics of the Reaction of O((sup 3)P) with CF3NO
NASA Technical Reports Server (NTRS)
Thorn, R. P.; Nicovich, J. M.; Cronkhite, J. M.; Wine, P. H.
1997-01-01
A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reaction of O((sup 3)P) with CF3NO (k(2)) as a function of temperature. Our results are described by the Arrhenius expression k(2)(T) = (4.54 +/- 0.70) x 10(exp -l2)exp[(-560 +/- 46)/T] cu cm/molecule.s (243 K is less than or equal to T is less than or equal to 424 K); errors are 2 sigma and represent precision only. The O((sup 3)P) + CF3NO reaction is sufficiently rapid that CF3NO cannot be employed as a selective quencher for O2(alpha(1) Delta-g) in laboratory systems where O((sup 3)P) and O2(alpha 1 Delta g) coexist, and where O((sup 3)P) kinetics are being investigated.
Investigation of reaction kinetics and interfacial phase formation in Ti3Al + Nb composites
NASA Technical Reports Server (NTRS)
Wawner, F. E.; Gundel, D. B.
1992-01-01
Titanium aluminide metal matrix composites are prominent materials systems being considered for high temperature aerospace applications. One of the major problems with this material is the reactivity between existing reinforcements and the matrix after prolonged thermal exposure. This paper presents results from an investigation of reaction kinetics between Ti-14Al-21Nb (wt pct) and SCS-6 fibers and SiC fibers with surface coatings of TiB2, TiC, TiN, W, and Si. Microstructural evaluation of the reaction layers as well as matrix regions around the fibers is presented.
Kinetics of the reactions of alkyl radicals with HBr and DBr
NASA Technical Reports Server (NTRS)
Nicovich, J. M.; Van Dijk, C. A.; Kreutter, K. D.; Wine, P. H.
1991-01-01
The kinetics of the reactions CH3 + HBr, CD3 + HBr, CH3 + DBr, C2H5 + HBr, C2H5 + DBr, t-C4H9 + HBr, and t-C4H9 + DBr is studied as a function of temperature (257-430 K) and pressure (10-300 Torr of N2). Time-resolved resonance fluorescence detection of Br atom appearance following laser flash photolysis of RI was used in the experiments. Results show that the rates of all reactions increased as the temperature decreased.
Xie, Hong-Bin; Li, Chao; He, Ning; Wang, Cheng; Zhang, Shaowen; Chen, Jingwen
2014-02-01
Monoethanolamine (MEA) is a benchmark and widely utilized solvent in amine-based postcombustion CO2 capture (PCCC), a leading technology for reducing CO2 emission from fossil fuel power plants. The large-scale implementation of PCCC would lead to inevitable discharges of amines to the atmosphere. Therefore, understanding the kinetics and mechanisms of the transformation of representative amine MEA in the atmosphere is of great significance for risk assessment of the amine-based PCCC. In this study, the H-abstraction reaction of MEA with ·OH, and ensuing reactions of produced MEA-radicals, including isomerization, dissociation, and bimolecular reaction MEA-radicals+O2, were investigated by quantum chemical calculation [M06-2X/aug-cc-pVTZ//M06-2X/6-311++G(d,p)] and kinetic modeling. The calculated overall rate constant [(7.27 × 10(-11)) cm(3) molecule(-1) s(-1)] for H-abstraction is in excellent agreement with the experimental value [(7.02 ± 0.46) × 10(-11) cm(3) molecule(-1) s(-1)]. The results show that the product branching ratio of NH2CH2 · CHOH (MEA-?) (43%) is higher than that of NH2 · CHCH2OH (MEA-?) (39%), clarifying that MEA-? is not an exclusive product. On the basis of the unveiled reaction mechanisms of MEA-radicals + O2, the proton transfer reaction mass spectrometry signal (m/z 60.044), not recognized in the experiment, was identified. PMID:24438015
Sankaran, R.; Grout, R.
2012-01-01
Combustion of hydrocarbon fuels has been a very challenging scientific and engineering problem due to the complexity of turbulent flows and hydrocarbon reaction kinetics. There is an urgent need to develop an efficient modeling capability to accurately predict the combustion of complex fuels. Detailed chemical kinetic models for the surrogates of fuels such as gasoline, diesel and JP-8 consist of thousands of chemical species and Arrhenius reaction steps. Oxygenated fuels such as bio-fuels and heavier hydrocarbons, such as from newer fossil fuel sources, are expected to have a much more complex chemistry requiring increasingly larger chemical kinetic models. Such models are beyond current computational capability, except for homogeneous or partially stirred reactor type calculations. The advent of highly parallel multi-core processors and graphical processing units (GPUs) promises a steep increase in computational performance in the coming years. This paper will present a software framework that translates the detailed chemical kinetic models to high-performance code targeted for GPU accelerators.
Kinetics of the reaction of peracetic acid with naphthalene and anisol
A. A. Akhrem; P. A. Kiselev; D. E. Metelitza
1975-01-01
The kinetics of the bimolecular reaction of peracetic acid with naphthalene (58–75 °C) and anisol (37.5–50.5 °C) have been studied in 2?1 dichlorethane-acetic acid. The rate constans for naphthalene and anisol are Knapht=2.0×109 exp (?21000\\/RT) 1 mol?1 sec?1, Kanis=6.3×108 exp (?17000\\/RT) 1 mol?1 sec?1.
Computation of the tunneling H-transfer reaction kinetics in the fluorene molecular crystal
Mikhail V. Basilevsky; Viacheslav A. Tikhomirov
2008-01-01
The semi-empirical computation of the rate constant is fully performed for the photochemical bimolecular hydrogen atom transfer reaction in condensed phase, proceeding in the deep tunneling regime. For the system considered (fluorene + acridine in its first triplet state, inside the fluorene molecular crystal) the kinetics have been thoroughly investigated experimentally over wide temperature range (http:\\/\\/bernd-prass.de). In the present theoretical
Oxydehydrogenation of propane over Mg-V-Sb-oxide catalysts. II. Reaction kinetics and mechanism
James N. Michaels; David L. Stern; Robert K. Grasselli
1996-01-01
Recently we reported that Mg4V2Sb2Ox is selective for propane andn-butane Oxydehydrogenation at low hydrocarbon conversion, and that propane is oxidized in parallel reactions to propylene and COx. We report now on the kinetics of propane and propylene oxidations over this catalyst. The partial oxidations of propane and propylene and zero-order in oxygen, whereas deep oxidations of both hydrocarbons are half-order.
Chemical Kinetic Reaction Mechanisms for Combustion of Hydrocarbon and Other Types of Chemical Fuels
Reaction mechanisms have been tested and validated extensively through comparisons between computed results and measured data from laboratory experiments (e.g., shock tubes, laminar flames, rapid compression machines, flow reactors, stirred reactors) and from practical systems (e.g., diesel engines, spark-ignition engines, homogeneous charge, compression ignition (HCCI) engines). These kinetic models are used to examine a wide range of combustion systems.
Non-meanfield deterministic limits in chemical reaction kinetics far from equilibrium
R. E. Lee DeVille; Cyrill B. Muratov; Eric Vanden-Eijnden
2005-12-25
A general mechanism is proposed by which small intrinsic fluctuations in a system far from equilibrium can result in nearly deterministic dynamical behaviors which are markedly distinct from those realized in the meanfield limit. The mechanism is demonstrated for the kinetic Monte-Carlo version of the Schnakenberg reaction where we identified a scaling limit in which the global deterministic bifurcation picture is fundamentally altered by fluctuations. Numerical simulations of the model are found to be in quantitative agreement with theoretical predictions.
Phenolic resins: 2. Influence of catalyst type on reaction mechanisms and kinetics
Didier Bedel
1996-01-01
We have investigated the influence of the type of basic catalyst on the mechanisms and kinetics of phenolformaldehyde reactions in perfectly controlled conditions of synthesis (temperature, stoichiometry and pH). The results obtained using liquid-state physicochemical analysis techniques, such as high performance liquid chromatography, 13C nuclear magnetic resonance spectroscopy and chemical assays, indicate that the nature of the basic catalyst affects
D. L Green; S Jayasundara; Yui-Fai Lam; M. T Harris
2003-01-01
29Si-NMR and 13C-NMR were used in methanol and ethanol to monitor the intermediates or hydrolyzed monomers that lead to the formation of the first primary particles as detected by small angle X-ray scattering. This identification was facilitated by using initial NH3 and H2O levels at the lower end of those experienced in Stober synthesis to slow the reaction kinetics. We
NASA Astrophysics Data System (ADS)
Le, Nam T. P.; Roohi, Ehsan
2014-12-01
In the literature, the combination of the second order slip and the second order jump conditions was mostly employed with the Burnett and BGK Burnett equations for hypersonic gas flows. In this paper, we will investigate both the first order and the second order slip/jump conditions, in which the combination of the second order slip and the second order jump conditions is implemented to work with the Navier-Stokes-Fourier equations for low speed nano/micro-scale and hypersonic rarefied gas flows such as the pressure driven backward facing step and 90-degree bend nano/micro-channels, the lid-driven micro-cavity, and hypersonic gas flow over the flat plate. The simulation results show that the combination of the second order slip condition and the second order jump condition predicts better surface pressure and gas temperature than those of the first order slip and jump conditions in all cases studied in comparing with experimental and DSMC data.
Chhantyal-Pun, Rabi; Davey, Anthony; Shallcross, Dudley E; Percival, Carl J; Orr-Ewing, Andrew J
2015-02-01
Criegee intermediates are important species formed during the ozonolysis of alkenes. Reaction of stabilized Criegee intermediates with various species like SO2 and NO2 may contribute significantly to tropospheric chemistry. In the laboratory, self-reaction can be an important loss pathway for Criegee intermediates and thus needs to be characterized to obtain accurate bimolecular reaction rate coefficients. Cavity ring-down spectroscopy was used to perform kinetic measurements for various reactions of CH2OO at 293 K and under low pressure (7 to 30 Torr) conditions. For the reaction CH2OO + CH2OO (8), a rate coefficient k8 = (7.35 ± 0.63) × 10(-11) cm(3) molecule(-1) s(-1) was derived from the measured CH2OO decay rates, using an absorption cross section value reported previously. A rate coefficient of k4 = (3.80 ± 0.04) × 10(-11) cm(3) molecule(-1) s(-1) was obtained for the CH2OO + SO2 (4) reaction. An upper limit for the unimolecular CH2OO loss rate coefficient of 11.6 ± 8.0 s(-1) was deduced from studies of reaction (4). SO2 catalysed CH2OO isomerization or intersystem crossing is proposed to occur with a rate coefficient of (3.53 ± 0.32) × 10(-11) cm(3) molecule(-1) s(-1). PMID:25553776
NASA Astrophysics Data System (ADS)
Babey, T.; Ginn, T. R.; De Dreuzy, J. R.
2014-12-01
Solute transport in porous media may be structured at various scales by geological features, from connectivity patterns of pores to fracture networks. This structure impacts solute repartition and consequently reactivity. Here we study numerically the influence of the organization of porous volumes within diffusive porosity zones on different reactions. We couple a mobile-immobile transport model where an advective zone exchanges with diffusive zones of variable structure to the geochemical modeling software PHREEQC. We focus on two kinetically-controlled reactions, a linear sorption and a nonlinear dissolution of a mineral. We show that in both cases the structure of the immobile zones has an important impact on the overall reaction rates. Through the Multi-Rate Mass Transfer (MRMT) framework, we show that this impact is very well captured by residence times-based models for the kinetic linear sorption, as it is mathematically equivalent to a modification of the initial diffusive structure; Consequently, the overall reaction rate could be easily extrapolated from a conservative tracer experiment. The MRMT models however struggle to reproduce the non-linearity and the threshold effects associated with the kinetic dissolution. A slower reaction, by allowing more time for diffusion to smooth out the concentration gradients, tends to increase their relevance. Figure: Left: Representation of a mobile-immobile model with a complex immobile architecture. The mobile zone is indicated by an arrow. Right: Total remaining mass of mineral in mobile-immobile models and in their equivalent MRMT models during a flush by a highly under-saturated solution. The models only differ by the organization of their immobile porous volumes.
Second-order Born effect in coplanar doubly symmetric (e,2e) collisions for sodium
NASA Astrophysics Data System (ADS)
Wang, Yang; Jiao, Liguang; Zhou, Yajun
2012-06-01
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 alkali target sodium at excess energies of 6-60 eV. Comparing with the first-order DWBA calculations, the inclusion of second-order Born term in the scattering amplitude improves the degree of agreement with experiments, especially for backward scattering region of TDCS. This indicates the present second-order Born term is capable to give a reasonable correction to DWBA model in studying coplanar symmetric (e,2e) problems in low and intermediate energy range.
Second-Order Born Effect in Single Ionization of Argon by Electron Impact
NASA Astrophysics Data System (ADS)
Wang, Yang; Zhou, Ya-Jun; Jiao, Li-Guang
2012-01-01
We extend the standard distorted wave Born approximation (DWBA) to include the second-order Born amplitude in order to describe the multiple interactions between a projectile and an atomic target. Both the first- and second- order DWBA models are used to calculate triply differential cross sections (TDCS) of coplanar (e, 2e) on atomic argon with the scattered electron energy fixed at 500 eV, the scattering angle at 6° and the ejected electron energies at 37, 74 and 205 eV. Overall agreements with experimental measurements have been obtained in shape, and the second-order DWBA model improves the calculations as expected, especially for recoil peak of TDCS.
Constructing set-valued fundamental diagrams from jamiton solutions in second order traffic models
Seibold, Benjamin; Kasimov, Aslan R; Rosales, Rodolfo Ruben
2012-01-01
Fundamental diagrams of vehicular traffic flow are generally multi-valued in the congested flow regime. We show that such set-valued fundamental diagrams can be constructed systematically from simple second order macroscopic traffic models, such as the classical Payne-Whitham model or the inhomogeneous Aw-Rascle-Zhang model. These second order models possess nonlinear traveling wave solutions, called jamitons, and the multi-valued parts in the fundamental diagram correspond precisely to jamiton-dominated solutions. This study shows that transitions from function-valued to set-valued parts in a fundamental diagram arise naturally as intrinsic properties of well-known second order models.
Luo, T.; Khursheed, A. [Electrical and Computer Engineering Department, National University of Singapore, co4 Engineering Drive 3, Singapore 117576 (Singapore)
2006-04-15
At present transmission electron energy loss spectrum (EELS) analysis is only carried out in dedicated research instruments such as transmission electron microscopes (TEMs) or scanning transmission electron microscopes. This article presents a new design of second-order geometric aberration corrected EELS spectrometer attachment using split plates, which enables conventional scanning electron microscopes (SEMs) to provide TEM-like EELS spectra. Correction to a third-order dominant geometric aberration pattern has been achieved, which indicates that most of the second-order geometric aberration component is eliminated. This second-order aberration corrected spectrometer attachment design can enable SEMs to provide transmission EELS spectrums.
Chen, Mingmin; Cao, Hongxia; Peng, Huasong; Hu, Hongbo; Wang, Wei; Zhang, Xuehong
2014-01-01
The phenazine derivative 2-hydroxyphenazine (2-OH-PHZ) plays an important role in the biocontrol of plant diseases, and exhibits stronger bacteriostatic and fungistatic activity than phenazine-1-carboxylic acid (PCA) toward some pathogens. PhzO has been shown to be responsible for the conversion of PCA to 2-OH-PHZ, however the kinetics of the reaction have not been systematically studied. Further, the yield of 2-OH-PHZ in fermentation culture is quite low and enhancement in our understanding of the reaction kinetics may contribute to improvements in large-scale, high-yield production of 2-OH-PHZ for biological control and other applications. In this study we confirmed previous reports that free PCA is converted to 2-hydroxy-phenazine-1-carboxylic acid (2-OH-PCA) by the action of a single enzyme PhzO, and particularly demonstrate that this reaction is dependent on NADP(H) and Fe3+. Fe3+ enhanced the conversion from PCA to 2-OH-PHZ and 28°C was a optimum temperature for the conversion. However, PCA added in excess to the culture inhibited the production of 2-OH-PHZ. 2-OH-PCA was extracted and purified from the broth, and it was confirmed that the decarboxylation of 2-OH-PCA could occur without the involvement of any enzyme. A kinetic analysis of the conversion of 2-OH-PCA to 2-OH-PHZ in the absence of enzyme and under different temperatures and pHs in vitro, revealed that the conversion followed first-order reaction kinetics. In the fermentation, the concentration of 2-OH-PCA increased to about 90 mg/L within a red precipitate fraction, as compared to 37 mg/L within the supernatant. The results of this study elucidate the reaction kinetics involved in the biosynthesis of 2-OH-PHZ and provide insights into in vitro methods to enhance yields of 2-OH-PHZ. PMID:24905009
Kirsch, J.F.; Julin, D.A.; McLeish, M.; Wiesinger, H.
1986-05-01
The intermediates, aldimine (A), quinonoid (Q) and ketimine (K), along the transaminase reaction coordinate were probed by isotope transfer and solvent exchange kinetics. Less than 0.003% of /sup 3/H is transferred from C/sub ..cap alpha../(/sup 3/H)-aspartate to pyridoxamine phosphate in the cytoplasmic aspartate aminotransferase (cAATase) reaction implying either that Q does not exist as a kinetically competent intermediate or that there is a rapid exchange of isotope with solvent. The ratio of the rate constants for C/sub ..cap alpha../ hydrogen exchange vs keto acid product formation (k/sub exge//k/sub prod/) are 2.5 and 0.5 for the reactions of cAATase with C/sub ..cap alpha../ (/sup 2/H)-aspartate and mitochondrial (m) AATase with C/sub ..cap alpha../(/sup 2/H)-glutamate respectively. The latter reaction was also probed from the ..cap alpha..-keto-glutarate side with carbonyl 0-18 enriched keto acid. This experiment gave k/sub exge//k/sub prod/ = 1.0 for oxygen-18 exchange in ..cap alpha..-ketoglutarate versus amino acid formation. The two exchange experiments with mAATase are interpreted in terms of a model in which the rate constant for diffusion of water from the active site is comparable with those for product forming steps.
A constant-time kinetic Monte Carlo algorithm for simulation of large biochemical reaction networks.
Slepoy, Alexander; Thompson, Aidan P; Plimpton, Steven J
2008-05-28
The time evolution of species concentrations in biochemical reaction networks is often modeled using the stochastic simulation algorithm (SSA) [Gillespie, J. Phys. Chem. 81, 2340 (1977)]. The computational cost of the original SSA scaled linearly with the number of reactions in the network. Gibson and Bruck developed a logarithmic scaling version of the SSA which uses a priority queue or binary tree for more efficient reaction selection [Gibson and Bruck, J. Phys. Chem. A 104, 1876 (2000)]. More generally, this problem is one of dynamic discrete random variate generation which finds many uses in kinetic Monte Carlo and discrete event simulation. We present here a constant-time algorithm, whose cost is independent of the number of reactions, enabled by a slightly more complex underlying data structure. While applicable to kinetic Monte Carlo simulations in general, we describe the algorithm in the context of biochemical simulations and demonstrate its competitive performance on small- and medium-size networks, as well as its superior constant-time performance on very large networks, which are becoming necessary to represent the increasing complexity of biochemical data for pathways that mediate cell function. PMID:18513044
A First-Passage Kinetic Monte Carlo method for reaction–drift–diffusion processes
Mauro, Ava J., E-mail: avamauro@bu.edu [Department of Mathematics and Statistics, Boston University, 111 Cummington Mall, Boston, MA 02215 (United States); Sigurdsson, Jon Karl; Shrake, Justin [Department of Mathematics, University of California, Santa Barbara (United States)] [Department of Mathematics, University of California, Santa Barbara (United States); Atzberger, Paul J., E-mail: atzberg@math.ucsb.edu [6712 South Hall, Department of Mathematics, University of California, Santa Barbara, CA 93106 (United States); Isaacson, Samuel A., E-mail: isaacson@math.bu.edu [Department of Mathematics and Statistics, Boston University, 111 Cummington Mall, Boston, MA 02215 (United States)
2014-02-15
Stochastic reaction–diffusion models are now a popular tool for studying physical systems in which both the explicit diffusion of molecules and noise in the chemical reaction process play important roles. The Smoluchowski diffusion-limited reaction model (SDLR) is one of several that have been used to study biological systems. Exact realizations of the underlying stochastic processes described by the SDLR model can be generated by the recently proposed First-Passage Kinetic Monte Carlo (FPKMC) method. This exactness relies on sampling analytical solutions to one and two-body diffusion equations in simplified protective domains. In this work we extend the FPKMC to allow for drift arising from fixed, background potentials. As the corresponding Fokker–Planck equations that describe the motion of each molecule can no longer be solved analytically, we develop a hybrid method that discretizes the protective domains. The discretization is chosen so that the drift–diffusion of each molecule within its protective domain is approximated by a continuous-time random walk on a lattice. New lattices are defined dynamically as the protective domains are updated, hence we will refer to our method as Dynamic Lattice FPKMC or DL-FPKMC. We focus primarily on the one-dimensional case in this manuscript, and demonstrate the numerical convergence and accuracy of our method in this case for both smooth and discontinuous potentials. We also present applications of our method, which illustrate the impact of drift on reaction kinetics.
Kinetic study of the reaction of chlorine atoms with hydroxyacetone in gas-phase
NASA Astrophysics Data System (ADS)
Stoeffler, Clara; Joly, Lilian; Durry, Georges; Cousin, Julien; Dumelié, Nicolas; Bruyant, Aurélien; Roth, Estelle; Chakir, Abdelkhaleq
2013-12-01
In this letter the kinetics of the reaction of hydroxyacetone CH3C(O)CH2OH with Cl atoms is investigated using the relative rate technique. Experiments are carried out in a 65 L multipass photoreactor in the temperature range of 281-350 K. A mid-infrared spectrometer based on a quantum cascade laser in external cavity emitting at 9.5 ?m is used to analyze the reactants. The determined rate coefficient for the investigated reaction is (1.7 ± 0.3) × 10-11exp(381.5 ± 57.3/T). The results are presented and discussed in terms of precision and compared with those obtained previously. The impact of Cl atoms on the atmospheric life time of hydroxyacetone is also discussed. Developing analytical techniques to quantify this compound in the atmosphere. Several methods of measurement have been used including the technique of proton transfer mass spectrometry (PTR-MS) [2] and derivatization with a chemical agent such as dinitrophenylhydrazine (DNPH) [3,4] followed by GC/MS or HPLC analyses. The HA amount in the troposphere was found to be in the order of a few hundred parts per trillion by volume [4], Performing laboratory experiments in order to study the HA reactivity with atmospheric oxidants. The first study on the kinetic of the reaction between OH radicals and HA was made by Dagault et al. [5] whose work was performed at room temperature by flash photolysis-resonance fluorescence. The determined rate constant implies a lifetime of a few days for HA relative to oxidation by OH radicals. Orlando et al. performed mechanistic and kinetics studies of the reaction of HA with OH radicals and Cl atoms at room temperature using a relative method [6]. Products detection was performed using FTIR spectroscopy. Moreover, these authors studied the photolysis of HA to determine its quantum yield and UV absorption spectrum. These studies showed that HA is principally removed from the atmosphere by reaction with OH radicals. Kinetic studies of the reaction of OH radicals with HA as a function of temperature (233-298 K) were performed by Dillon et al. [7]. An experimental (laser photolysis/FIL) and theoretical approach (quantum calculation) were realized. This study showed that the oxidation of HA by OH-radicals has a negative temperature coefficient which is explained by an intermediate complex formation. Another study as a function of temperature was conducted by Butkovskaya et al. using the technique of a turbulent flow reactor coupled with a mass spectrometer chemical ionization [8]. This work was purely mechanistic and it shows that the mechanism of this reaction changes with temperature: a temperature increase favors the production yields of methanoic and ethanoic acids and reduces the formation yield of methylglyoxal [8]. Our work is motivated by the fact that the kinetic studies of the reaction of HA with chlorine radicals are rare in comparison with the kinetic studies of the reaction of HA with OH radicals. So far, only one such kinetic study is reported in the literature. It has been carried out by Orlando et al. at 294 K [6]. To the best of our knowledge, this reaction has not yet been studied as a function of temperature. Therefore, to enrich kinetic data concerning this compound, the study of HA with Cl atoms reaction as a function of temperature has been undertaken. Experiments are carried out using the relative technique in a simulation chamber coupled with an infrared Fourier transform (FTIR) spectrometer and a quantum cascade laser in external cavity (ECQCL) at 1 bar with the temperature ranging 277-350 K. Using both FTIR and ECQCL techniques allows comparing the measurements sensitivity and improving the kinetic precision determination. The FTIR spectroscopy is widely used to perform kinetic measurements whereas the ECQCL spectrometer is quite original in kinetic studies. Laser spectrometry indeed presents advantages such as high sensitivity, high resolution, and fast acquisition time compared to the FTIR spectrometer. The ECQCL principle is based on a quantum cascade laser coupled with an external cavity that includes a d
la O’, G. J.
Oxygen reduction reaction (ORR) kinetics was investigated on dense La?.?Sr?.?MnO? microelectrodes as a function of temperature and microelectrode thickness using electrochemical impedance spectroscopy. The surface oxygen ...
NASA Astrophysics Data System (ADS)
Azaroual, M. M.; Parmentier, M.; Andre, L.; Croiset, N.; Pettenati, M.; Kremer, S.
2010-12-01
Microbial processes interact closely with abiotic geochemical reactions and mineralogical transformations in several hydrogeochemical systems. Reactive transport models are aimed to analyze these complex mechanisms integrating as well as the degradation of organic matter as the redox reactions involving successive terminal electron acceptors (TEAPs) mediated by microbes through the continuum of unsaturated zone (soil) - saturated zone (aquifer). The involvement of microbial processes in reactive transport in soil and subsurface geologic greatly complicates the mastery of the major mechanisms and the numerical modelling of these systems. The introduction of kinetic constraints of redox reactions in aqueous phase requires the decoupling of equilibrium reactions and the redefinition of mass balance of chemical elements including the concept of basis species and secondary species of thermodynamic databases used in geochemical modelling tools. An integrated methodology for modelling the reactive transport has been developed and implemented to simulate the transfer of arsenic, denitrification processes and the role of metastable aqueous sulfur species with pyrite and organic matter as electron donors entities. A mechanistic rate law of microbial respiration in various geochemical environments was used to simulate reactive transport of arsenic, nitrate and organic matter combined to the generalized rate law of mineral dissolution - precipitation reactions derived from the transition state theory was used for dissolution - precipitation of silica, aluminosilicate, carbonate, oxyhydroxide, and sulphide minerals. The kinetic parameters are compiled from the literature measurements based on laboratory constrained experiments and field observations. Numerical simulations, using the geochemical software PHREEQC, were performed aiming to identify the key reactions mediated by microbes in the framework of in the first hand the concept of the unsaturated - saturated zones of an artificial recharge of deep aquifers system and in a second hand an acid mine drainage system. A large amount of data is available on the old mine site of Cheni (France). This field data on acid mine drainage are compared to a thermokinetic model including biological kinetics, precipitation-dissolution kinetics and surface complexation on ferrihydrite. The kinetic parameters are from literature and from a fitting on batch biological experiments. The integrated approach combining reaction kinetics and biogeochemical thermodynamic constraints is successfully applied to denitrification experiments in the presence of acetate and pyrite conducted in the laboratory for batch and column systems. The powerful of this coupled approach allows a fine description of the different transition species from nitrate to nitrogen. The fitted kinetic parameters established for modelling these laboratory results are thus extended to simulate the denitrification processes in a field case where organic matter and pyrite FeS2 are the electron donors and O2, NO3, Fe(OH)3, SO4 are the electron acceptors in the framework of a continuum UZ - SZ aiming to identify the stabilized redox zones of acid mine drainage. The detailed results obtained on two actual case studies will be presented.
Meskhidze, Nicholas
The kinetics and mechanism of an aqueous phase isoprene reaction with hydroxy radical D. Huang, X space in the 2.1 L reactor. Fig.S2. Experiments 1 and 2 (green and blue) for the kinetics of aqueous OH
Hammes-Schiffer, Sharon
, and Kinetic Isotope Effects He´le`ne Decornez and Sharon Hammes-Schiffer* Department of Chemistry, 152 Da isotope effects for proton-coupled electron transfer (PCET) reactions. These studies are based region. The kinetic isotope effects are predicted to increase as the probability of the EPT mechanism
Setaka, Wataru; Ohmizu, Soichiro; Kira, Mitsuo
2014-02-01
Macrocage molecules with a bridged rotor have been synthesized as molecular gyroscopes. The kinetics of the oxidation reaction of the thiophene-bridged molecular gyroscope, whose thiophene ring was bridged inside a silaalkane cage, was investigated. A remarkable kinetic stabilization against the oxidation of the thiophene moiety induced by the molecular cage framework was observed. PMID:24317303
[Determination of trace amounts of nitrite and its chemical reaction kinetics].
Luo, Zhi-yong; Zheng, Huai-li
2014-06-01
A catalytic kinetic spectrophotometric method for the determination of nitrite, NO2(-)-S2O8(2-)-MR, was developed. It is based on the fading reaction of methyl red (MR) oxidized by potassium persulfate which can be catalyzed by NO2- in the medium of dilute HCl. The optimum experimental conditions were gained by combining single factor experiments with orthogonal experiments. Calibration curve, detection limit, precision, and anti-interference under the optimum experimental conditions were researched. Its kinetics principles and parameters were discussed. Its quantitative principle was investigated. The results show that the optimum experimental conditions of this method should be as follows: 1.0 mL 0.3 mol x L(-1) HCl, 1.0 mL 0.01 mol x L(-1) K2S2O8, 0.6 mL 0.2 g x L(-1) MR, reaction temperature 80 degrees C and reaction time 9 min. The principles for the quantitative determination of trace nitrite is that variation of MR concentration at the maximum absorption wavelength of 518 nm, ln(A0/A), shows a good linear relationship with the concentration of NO2- under the optimum experimental conditions. Its determination range is 0.01-0.80 mg x L(-1) and its detection limit is 0.007 mg x L(-1). The kinetic characteristics are that the reaction order in NO2- is 1 and the fading reaction is a pseudo first order reaction. Its apparent activation energy is 85.04 kJ x mol(-1). Its apparent rate constant is 0.021 4 min(-1), and the half-life is 32.39 min at 80 degrees C. The kinetic principle is that the variation of MR concentration is directly proportional to the concentration of NO2-, ln(A0/A) = kc(NO2-). This new method for the determination of trace nitrite has never previously been reported in the published literature so far. It is highly sensitive and selective. Most of the common ions don't interfere with the determination of nitrite. This method has the advantages of convenient operation and the regents used are cheap and nontoxic. It was applied to the determination of trace nitrite in food and water samples with satisfactory results. PMID:25358175
Uniformly convex subsets of the Hilbert space with modulus of convexity of the second order
Balashov, Maxim V; 10.1016/j.jmaa.2010.11.046
2011-01-01
We prove that in the Hilbert space every uniformly convex set with modulus of convexity of the second order at zero is an intersection of closed balls of fixed radius. We also obtain an estimate of this radius.
Eleven-channel second-order silicon microring-resonator filterbank with tunable channel spacing
Dahlem, Marcus Vinicius Sobral
A wide-band, eleven-channel second-order filterbank fabricated on an SOI platform is demonstrated with tunable channel spacing and a 20 GHz single-channel bandwidth. The tuning efficiency is ~28 ?W/GHz/ring.
Second-order conditioning of the pigeon's key-peck using an autoshaping procedure.
Green, L; Schweitzer, L
1980-03-01
Second-order conditioning of the pigeon's key-peck was established using an autoshaping procedure. In the first experiment, pigeons came to peck a response key, the second-order conditioned stimulus (CS2), when it was paired with another key (CS1) that had previously been paired with food delivery. In the second experiment, pigeons again came to peck a key (CS2) when it was followed by a clicker (CS1) which had been paired with food delivery, even though the clicker itself had not evoked pecking. Responses to a second-order stimulus, therefore, need not resemble responses to the first-order CS. Furthermore, in both experiments, extinction of the first-order IS led to reduction in pecking CS2. These results were discussed in terms of the nature of the associations being formed during second-order conditioning. PMID:7396046
Integration of second order ordinary differential equations not possessing Lie point symmetries
NASA Astrophysics Data System (ADS)
Abraham-Shrauner, B.; Govinder, K. S.; Leach, P. G. L.
1995-02-01
A class of integrable second order ordinary differential equations not possessing Lie point symmetries is shown to be rich in nonlocal symmetries which provide one route for integration and to have general solutions which are uniform functions.
Constructing set-valued fundamental diagrams from Jamiton solutions in second order traffic models
Rosales, Rodolfo R.
Fundamental diagrams of vehicular traffic flow are generally multi-valued in the congested flow regime. We show that such set-valued fundamental diagrams can be constructed systematically from simple second order macroscopic ...
Unitary eikonal approximation including second-order phase function for particle-atom collisions
Rosendorff, S.
1981-02-01
A scattering amplitude for particle-atom collisions is developed in the eikonal approximation, taking into consideration the second-order term in the phase function of the S matrix. A finite value of the average excitation energy of the atom in its intermediate states is retained in each order (except the first) of the perturbation series. For zero excitation energy the second-order phase function reduces to twice the second-order Wentzel-Kramers-Brillouin phase shift for a static potential. Our amplitude becomes the modified Glauber amplitude by putting the second-order phase function equal to zero. The new amplitude satisfies the unitarity theorem to all orders of the coupling constant. It is free of all the shortcomings of the conventional Glauber theory.
Kinetics and Thermochemistry of the Br((sup 2)P3/2) + NO2 Association Reaction
NASA Technical Reports Server (NTRS)
Kreutter, K. D.; Nicovich, J. M.; Wine, P. H.
1997-01-01
A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Br((sup 2)P3/2) + NO2 association reaction as a function of temperature (259-432 K) pressure (12.5 - 700 Torr), and buffer gas identity (He, Ar, H2, N2, CO2, CF4, SF6). The reaction is found to be in the falloff regime between third and second order over the entire range of conditions investigated. At temperatures below 350 K, the association reaction is found to be irreversible on the time scale of the experiment (approximately 30 ms). At higher temperatures reversible addition is observed, allowing equilibrium constants for BrNO2 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data are in only fair agreement and lead to the following thermochemical parameters for the association reaction: Delta-H(298) = 19.6 +/- 1.7 kcal/mol, Delta-H(0) = -18.6 +/- 2.0 kcal/mol, Delta-S(298) = 29.3 +/- 4.2 cal/mol/K, Delta-H(sub f)(sub 298)(BrNO2) = 17.0 +/-1.8 kcal/mol(uncertainties are 2 sigma estimates of absolute accuracy). The value for Delta-H(0) determined in this study has been employed to calculate k(sub 0)(sup SC), the low-pressure third-order rate coefficient in the strong collision limit, by using the method of Troe; calculated values of k(sub 0)(sup SC) are inconsistent with experimental results unless Delta-H(0) is assigned a value near the lower limit derived from analysis of the high-temperature approach to equilibrium data, i.e. delta-H(0) approximately equals -16.6 kcal/mol. A potential source of systematic error in the calculation of both k(sub 0)(sup SC) and the absolute entropy of BrNO2 results from the complete lack of knowledge of the energies and degeneracies of the electronic states of BrNO3. The procedure developed by Troe and co-workers has been employed to extrapolate experimental falloff curves to the low- and high-pressure limits. Derived values for k(sub 0)(M,298K) in units of 10(exp -31) cm(exp 6)/sq molecule/s range from 2.75 for M = He to 6.54 for M = CO2; 2 sigma uncertainties are estimated to be +/- 20%. Values for k(sub 0)(N2,T) in units of 10(exp -31) cm(exp 6)/sq molecule/s are 5.73 at 259 K, 4.61 at 298 K, and 3.21 at 346 K; the observed temperature dependence for k(sub 0)(N2,T) is consistent with the theoretical temperature dependence for Beta(sub c)k(sub 0)(sup SC). Values for k(sub infinity)(T) in units of 10(exp -11) cu cm/molecule/s are 2.86 at 259 K, 3.22 at 298 K, and 3.73 at 346 K; 2 sigma uncertainties are estimated to be a factor of 2. Approximate falloff parameters in a convenient format for atmospheric modeling are also derived.
Kinetic study of model reactions in the gas phase at the early stage of coke formation
Nohara, D.; Sakai, T. (Dept. of Chemical Reaction Engineering, Faculty of Pharmaceutical Sciences, Nagoya City Univ., Mizuho-ku, Nagoya 467 (JP))
1992-01-01
This paper reports that the most probable gas-phase reactions at the early stage of coke formation were elucidated by kinetic study on the model reactions adopted for formation of cyclic compounds and growth of ring. It was revealed that the formation and growth of ring proceeded mainly through cycloaddition of butadiene or allyl radicals to unsaturated hydrocarbons at relatively low temperatures ({approximately}600{degrees}C), i.e., through a Diels-Alder type reaction. On the other hand, such growth of ring as formation of biphenyl accompanying dehydrogenation from benzene can proceed only at the higher temperatures. It was also revealed that in the growth of the ring, cycloaddition of butadiene favors a cyclic olefin molecule that possesses a nonconjugated double bond and a nearly planar structure.
Surfkin: A program to solve transient and steady state heterogeneous reaction kinetics
COLTRIN,MICHAEL E.; WIXOM,RYAN R.; DANDY,DAVID S.
2000-05-01
Heterogeneous chemical reactions occurring at a gas/surface interface are fundamental in a variety of important applications, such as combustion, catalysis, chemical vapor deposition and plasma processing. Detailed simulation of these processes may involve complex, coupled fluid flow, heat transfer, gas-phase chemistry, in addition to heterogeneous reaction chemistry. This report documents the Surfkin program, which simulates the kinetics of heterogeneous chemical reactions. The program is designed for use with the Chemkin and Surface Chemkin (heterogeneous chemistry) programs. It calculates time-dependent or steady state surface site fractions and bulk-species production/destruction rates. The surface temperature may be specified as a function of time to simulate a temperature-programmed desorption experiment, for example. This report serves as a user's manual for the program, explaining the required input and format of the output. Two detailed example problems are included to further illustrate the use of this program.
A variable-complexity approach to second-order reliability-based optimization
S. A. Burton; P. Hajela
2003-01-01
This paper outlines a new methodology for second-order reliability-based optimization (RBO). A variable-complexity (VC) approach is used to implement a computationally efficient VCRBO algorithm, which reduces the number of costly second-order reliability analyses by using a lower fidelity, scaled mean-value technique during the majority of the constraint assessments. Two numerical examples are presented, which provide a comparison of several standard
Second-order statistical properties of the WSS Jakes' fading channel simulator
Chengshan Xiao; Yahong R. Zheng; Norman C. Beaulieu
2002-01-01
An improved Jakes' (1994) fading channel simulator was proposed by Pop and Beaulieu (see ibid., vol.49, p.699-708, Apr. 2001) to eliminate the stationarity problem occurring in Jakes' original design. In this paper, second-order statistical properties of the improved Jakes' simulator are analyzed. Consistent with Pop and Beaulieu's caution about high-order statistics of the simulator, it is proved that some second-order
Applications of the second-order achromat concept to the design of particle accelerators
Brown, K.L.; Servranckx, R.V.
1985-05-01
A property of the second-order achromat, whereby dipole and sextupole families may be inserted into a lattice for chromatic corrections without introducing second-order geometrical (on momentum) optical distortions, has been incorporated in several new particle accelerator designs. These include the SLC at SLAC, LEP at CERN, the EROS pulse stretcher ring at Saskatoon, the CEBAF ring at SURA, and the MIT ring.
V. V. Kludzin; V. V. Slavinskaya; D. V. Tigin
2005-01-01
We offer a design procedure of characteristics of acousto-optical deflector, which uses the regime of an anisotropic mode in any cut of a crystal TeO2 with taking into account consideration of second-order diffraction. We determine the conditions, allowing to avoid influence of second-order diffraction and to receive the frequency characteristic with the required non-uniformity in an acceptable frequency range.
Using Second-Order Power Analysis to Attack DPA Resistant Software
Thomas S. Messerges
2000-01-01
Under a simple power leakage model based on Hamming weight, a software implementation of a data-whitening routine is shown to be vulnerable to a first-order Differential Power Analysis (DPA) attack. This routine is modified to resist the first-order DPA attack, but is subsequently shown to be vulnerable to a second-order DPA attack. A second-order DPA attack that is optimal under
Second Order Post Newtonian Equations of Light Propagation in Multiple Systems
Chongming Xu; Yanxiang Gong; Xuejun Wu; MichaelSoffel; Sergei Klioner
2005-01-01
The first order post Newtonian scheme in multiple systems presented by Damour-Soffel-Xu is extended to the second order one for light propagation without changing the advantage of the scheme on the linear partial differential equations of potential and vector potential. The spatial components of the metric tensor are extended to the second order level both in the global coordinates ($q_{ij}\\/c^4$
Xiaobing Feng; Michael Neilan
2009-01-01
This paper concerns with numerical approximations of solutions of fully nonlinear second order partial differential equations\\u000a (PDEs). A new notion of weak solutions, called moment solutions, is introduced for fully nonlinear second order PDEs. Unlike\\u000a viscosity solutions, moment solutions are defined by a constructive method, called the vanishing moment method, and hence,\\u000a they can be readily computed by existing numerical
NASA Astrophysics Data System (ADS)
Basilevsky, M. V.; Odinokov, A. V.; Titov, S. V.; Mitina, E. A.
2013-12-01
The algorithm for a theoretical calculation of transfer reaction rates for light quantum particles (i.e., the electron and H-atom transfers) in non-polar solid matrices is formulated and justified. The mechanism postulated involves a local mode (an either intra- or inter-molecular one) serving as a mediator which accomplishes the energy exchange between the reacting high-frequency quantum mode and the phonon modes belonging to the environment. This approach uses as a background the Fermi golden rule beyond the usually applied spin-boson approximation. The dynamical treatment rests on the one-dimensional version of the standard quantum relaxation equation for the reduced density matrix, which describes the frequency fluctuation spectrum for the local mode under consideration. The temperature dependence of a reaction rate is controlled by the dimensionless parameter ?0 = ??0/kBT where ?0 is the frequency of the local mode and T is the temperature. The realization of the computational scheme is different for the high/intermediate (?0 < 1 - 3) and for low (?0 ? 1) temperature ranges. For the first (quasi-classical) kinetic regime, the Redfield approximation to the solution of the relaxation equation proved to be sufficient and efficient in practical applications. The study of the essentially quantum-mechanical low-temperature kinetic regime in its asymptotic limit requires the implementation of the exact relaxation equation. The coherent mechanism providing a non-vanishing reaction rate has been revealed when T ? 0. An accurate computational methodology for the cross-over kinetic regime needs a further elaboration. The original model of the hopping mechanism for electronic conduction in photosensitive organic materials is considered, based on the above techniques. The electron transfer (ET) in active centers of such systems proceeds via local intra- and intermolecular modes. The active modes, as a rule, operate beyond the kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode/medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.
Basilevsky, M. V.; Mitina, E. A. [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation)] [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation); Odinokov, A. V. [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation) [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation); National Research Nuclear University “MEPhI,” 31, Kashirskoye shosse, Moscow (Russian Federation); Titov, S. V. [Karpov Institute of Physical Chemistry, 3-1/12, Building 6, Obuha pereulok, Moscow (Russian Federation)] [Karpov Institute of Physical Chemistry, 3-1/12, Building 6, Obuha pereulok, Moscow (Russian Federation)
2013-12-21
The algorithm for a theoretical calculation of transfer reaction rates for light quantum particles (i.e., the electron and H-atom transfers) in non-polar solid matrices is formulated and justified. The mechanism postulated involves a local mode (an either intra- or inter-molecular one) serving as a mediator which accomplishes the energy exchange between the reacting high-frequency quantum mode and the phonon modes belonging to the environment. This approach uses as a background the Fermi golden rule beyond the usually applied spin-boson approximation. The dynamical treatment rests on the one-dimensional version of the standard quantum relaxation equation for the reduced density matrix, which describes the frequency fluctuation spectrum for the local mode under consideration. The temperature dependence of a reaction rate is controlled by the dimensionless parameter ?{sub 0}=??{sub 0}/k{sub B}T where ?{sub 0} is the frequency of the local mode and T is the temperature. The realization of the computational scheme is different for the high/intermediate (?{sub 0} < 1 ? 3) and for low (?{sub 0}? 1) temperature ranges. For the first (quasi-classical) kinetic regime, the Redfield approximation to the solution of the relaxation equation proved to be sufficient and efficient in practical applications. The study of the essentially quantum-mechanical low-temperature kinetic regime in its asymptotic limit requires the implementation of the exact relaxation equation. The coherent mechanism providing a non-vanishing reaction rate has been revealed when T? 0. An accurate computational methodology for the cross-over kinetic regime needs a further elaboration. The original model of the hopping mechanism for electronic conduction in photosensitive organic materials is considered, based on the above techniques. The electron transfer (ET) in active centers of such systems proceeds via local intra- and intermolecular modes. The active modes, as a rule, operate beyond the kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode/medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.
Experimental study of the reactions of limonene with OH and OD radicals: kinetics and products.
Braure, Tristan; Bedjanian, Yuri; Romanias, Manolis N; Morin, Julien; Riffault, Véronique; Tomas, Alexandre; Coddeville, Patrice
2014-10-01
The kinetics of the reactions of limonene with OH and OD radicals has been studied using a low-pressure flow tube reactor coupled with a quadrupole mass spectrometer: OH + C10H16 ? products (1), OD + C10H16 ? products (2). The rate constants of the title reactions were determined using four different approaches: either monitoring the kinetics of OH (OD) radicals or limonene consumption in excess of limonene or of the radicals, respectively (absolute method), and by the relative rate method using either the reaction OH (OD) + Br2 or OH (OD) + DMDS (dimethyl disulfide) as the reference one and following HOBr (DOBr) formation or DMDS and limonene consumption, respectively. As a result of the absolute and relative measurements, the overall rate coefficients, k1 = (3.0 ± 0.5) × 10(-11) exp((515 ± 50)/T) and k2 = (2.5 ± 0.6) × 10(-11) exp((575 ± 60)/T) cm(3) molecule(-1) s(-1), were determined at a pressure of 1 Torr of helium over the temperature ranges 220-360 and 233-353 K, respectively. k1 was found to be pressure independent over the range 0.5-5 Torr. There are two possible pathways for the reaction between OH (OD) and limonene: addition of the radical to one of the limonene double bonds (reactions 1a and 2a ) and abstraction of a hydrogen atom (reactions 1b and 2b ), resulting in the formation of H2O (HOD). Measurements of the HOD yield as a function of temperature led to the following branching ratio of the H atom abstraction channel: k2b/k2 = (0.07 ± 0.03) × exp((460 ± 140)/T) for T = (253-355) K. PMID:25211148
Low-temperature Kinetic Studies of OH Radical Reactions Relevant to Planetary Atmospheres
NASA Astrophysics Data System (ADS)
Townsend, T. M.; Antiñolo, M.; Ballesteros, B.; Jimenez, E.; Canosa, A.
2011-05-01
In the solar system, the temperature (T) of the atmosphere of giant planets or their satellites is only several tens of Kelvin (K). The temperature of the tropopause of Titan (satellite of Saturn) and the surface of Mars is 70 K and 210 K, respectively. In the Earth's atmosphere, T decreases from 298 K (surface) to 210 K close to the T-inversion region (tropopause). The principal oxidants in the Earth's lower atmosphere are ozone, the hydroxyl (OH) radical and hydrogen peroxide. A number of critical atmospheric chemical problems depend on the Earth's oxidising capacity, which is essentially the global burden of these oxidants. In the interstellar clouds and circumstellar envelopes, OH radicals have also been detected. As the chemistry of atmospheres is highly influenced by temperature, the knowledge of the T-dependence of the rate coefficients for OH-reactions (k) is the key to understanding the underlying molecular mechanisms. In general, these reactions take place on a short temporal scale. Therefore, a detection technique with high temporal resolution is required. Measurements of k at low temperatures can be achieved by maintaining a thermalised environment using either cryogenic cooling (T>200 K) or supersonic gas expansion with a Laval nozzle (several tens of K). The pulsed laser photolysis technique coupled with laser induced fluorescence detection has been widely used in our laboratory to determine the rate coefficients of OH-reactions with different volatile organic compounds, such as alcohols (1), saturated and unsaturated aliphatic aldehydes (2), linear ketones (3), as a function of temperature (260 350 K). An experimental system based on the CRESU (Cinetique de Reaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow) technique is currently under construction. This technique will allow the performance of kinetic studies of OH-reactions of astrophysical interest at temperatures lower than 200 K.
Szundi, Istvan; Kittredge, Clive; Choi, Sylvia K; McDonald, William; Ray, Jayashree; Gennis, Robert B; Einarsdóttir, Ólöf
2014-08-26
Cytochrome bo? ubiquinol oxidase from Escherichia coli catalyzes the reduction of O? to water by ubiquinol. The reaction mechanism and the role of ubiquinol continue to be a subject of discussion. In this study, we report a detailed kinetic scheme of the reaction of cytochrome bo? with O? with steps specific to ubiquinol. The reaction was investigated using the CO flow-flash method, and time-resolved optical absorption difference spectra were collected from 1 ?s to 20 ms after photolysis. Singular value decomposition-based global exponential fitting resolved five apparent lifetimes, 22 ?s, 30 ?s, 42 ?s, 470 ?s, and 2.0 ms. The reaction mechanism was derived by an algebraic kinetic analysis method using frequency-shifted spectra of known bovine states to identify the bo3 intermediates. It shows 42 ?s O? binding (3.8 × 10(7) M(-1) s(-1)), producing compound A, followed by faster (22 ?s) heme b oxidation, yielding a mixture of PR and F, and rapid heme b rereduction by ubiquinol (30 ?s), producing the F intermediate and semiquinone. In the 470 ?s step, the o? F state is converted into the o?(3+) oxidized state, presumably by semiquinone/ubiquinol, without the concomitant oxidation of heme b. The final 2 ms step shows heme b reoxidation and the partial rereduction of the binuclear center and, following O? binding, the formation of a mixture of P and F during a second turnover cycle. The results show that ubiquinol/semiquinone plays a complex role in the mechanism of O? reduction by bo?, displaying kinetic steps that have no analogy in the CuA-containing heme-copper oxidases. PMID:25076393
NASA Astrophysics Data System (ADS)
Abdelhamid, A.; Addala, R.; Vizenor, N.; Scruggs, A.; Tyndall, G. S.; Orlando, J. J.; Le, T.; Cardenas, E.; Maitra, S.; Hasson, A. S.
2013-12-01
Isoprene nitrates are formed in the troposphere from the reactions of isoprene with OH in the presence of NOx during the day and with NO3 during the night. Depending on their subsequent reactions, these compounds may be reservoirs or sinks for NOx, and may contribute to secondary organic aerosol formation. In this work, two isoprene hydroxynitrates (CH2=CHC(ONO2)(CH3)CH2OH, 1,2-IHN and CH2OHCH(ONO2)C(CH3)=CH2, 4,3-IHN ) and one isoprene carbonyl nitrate (CH2=CHC(ONO2)(CH3)CHO, ICN)) were synthesized. The kinetics and product yields from their reaction with O3, OH, NO3 and Cl were then investigated in a photochemical reactor using a combination of long-path Fourier transform infra-red spectroscopy, proton transfer reaction mass spectrometry and gas chromatography with flame ionization detection. Measured rate coefficients are consistent with reaction with OH and NO3 as the major chemical sinks for these compounds. Measured product yields imply that NOx is not released from these compounds in their reactions with atmospheric oxidants.
Tao, W.C.; Tarver, C.M.; Ornellas, D.L.
1991-12-06
Using Fabry-Perot interferometry techniques, we have determined that early time rate of energy release from detonating PETN and TNT explosives filled with 5 and 10 wt % of either 5 {mu}m of 18 {mu}m spherical aluminum (Al) particles. From the measured particle velocity data, we are able to infer the reaction rate of aluminum with the detonation products, and calculate the extent of reaction 1--3 {mu}s after the detonation. We observed that a substantional portion of the aluminum metal in all of the PETN and TNE formulations reacted within the timeframe of the one-dimensional experiment. In the PETN formulation filed with 5 wt % of 5 {mu}m aluminum, all of the metal reacted within 1.5 {mu}s, resulting in an increase of 22% in energy compared to pure PETN. A reactive-flow hydrodynamic model based on the Zeldovich-von Neumann-Doring (ZND) description of the reaction zone and subsequent reaction produce expansion (Taylor wave) is used to interpret the reaction rate of the aluminum particles with detonation product gases. The diffusion-controlled reaction mechanism for aluminum and the global kinetic parameters used in the model have been found to be consistent for all the PETN and TNT formulations.
Nuclear spin dependence of the reaction of H3+ with H2. I. Kinetics and modeling
NASA Astrophysics Data System (ADS)
Crabtree, Kyle N.; Tom, Brian A.; McCall, Benjamin J.
2011-05-01
The chemical reaction H_3^+ + H2 ? H2 + H_3^+ is the simplest bimolecular reaction involving a polyatomic, yet is complex enough that exact quantum mechanical calculations to adequately model its dynamics are still unfeasible. In particular, the branching fractions for the "identity," "proton hop," and "hydrogen exchange" reaction pathways are unknown, and to date, experimental measurements of this process have been limited. In this work, the nuclear-spin-dependent steady-state kinetics of the H_3^+ + H2 reaction is examined in detail, and employed to generate models of the ortho:para ratio of H_3^+ formed in plasmas of varying ortho:para H2 ratios. One model is based entirely on nuclear spin statistics, and is appropriate for temperatures high enough to populate a large number of H_3^+ rotational states. Efforts are made to include the influence of three-body collisions in this model by deriving nuclear spin product branching fractions for the H_5^+ + H2 reaction. Another model, based on rate coefficients calculated using a microcanonical statistical approach, is appropriate for lower-temperature plasmas in which energetic considerations begin to compete with the nuclear spin branching fractions. These models serve as a theoretical framework for interpreting the results of laboratory studies on the reaction of H_3^+ with H2.
NASA Astrophysics Data System (ADS)
Harikrishna, R.; Ponrathnam, S.; Tambe, S. S.
2014-01-01
Photoinitiated cationic polymerization of cycloaliphatic diepoxides had received tremendous attention, while studies with lesser polymerizable diglycidyl ethers are comparatively less reported. The present work deals with the photoinitiated cationic polymerization of cyclohexane dimethanol diglycidyl ether followed by estimation of kinetic parameters. The effects of concentration of photoinitiator and temperature on curing performance were studied using photo differential scanning calorimeter or photo DSC with polychromatic radiation. It was observed that the rate of polymerization as well as ultimate conversion increased with increasing concentration of photoinitiator and temperature. The influences of gelation as well as diffusional restrictions have remarkable effect on cure performance. The kinetic parameters as per autocatalytic kinetic model were studied by Levenberg-Marquardt nonlinear regression method instead of conventional linear method for obtaining more accurate values of apparent rate constant. It was observed that the model fits with data from initial stages to almost towards the end of the reaction. The activation energy was found to be higher than the values reported for more reactive cycloaliphatic diepoxides. The value of pre-exponential factor increased with increase in activation energy showing influence of gelation at early stages of reaction.
TICIANELLI,E.A.; MUKERJEE,S.; MCBREEN,J.; ADZIC,G.D.; JOHNSON,J.R.; REILLY,J.J.
1998-11-01
This was a study of electrode degradation mechanisms and the reaction kinetics of LaNi{sub 4.7}Sn{sub 0.3}, La{sub (1{minus}x)}, (x = 0.1, 0.2, and 0.3) and La{sub 0.7}Y{sub 0.3}Ni{sub 4.6}Sn{sub 0.3}Co{sub 0.1} metal hydride electrodes. Alloy characterization included x-ray diffraction (XRD), x-ray absorption (XAS), hydrogen absorption in a Sieverts apparatus, and electrochemical cycling of alloy electrodes. The atomic volume of H was determined for two of the alloys. Electrochemical kinetic measurements were made using steady state galvanostatic measurements, galvanodynamic sweep, and electrochemical impedance techniques. XAS was used to examine the degree of corrosion of the alloys with cycling. Alloying with Y decreased the corrosion rate. The results are consistent with corrosion inhibition by a Y containing passive film. The increase in the kinetics of the hydrogen oxidation reaction (HOR) with increasing depth of discharge was much greater on the Y containing alloys. This may be due to the dehydriding of the catalytic species on the surface of the metal hydride particles.
Ticianelli, E.A.; Mukerjee, S.; McBreen, J.; Adzic, G.D.; Johnson, J.R.; Reilly, J.J. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science
1998-12-31
This was a study of electrode degradation mechanisms and the reaction kinetics of LaNi{sub 4.7}Sn{sub 0.3}, La{sub (1{minus}x)} Y{sub x}Ni{sub 4.7}Sn{sub 0.3} (x = 0.1, 0.2, and 0.3) and La{sub 0.7}Y{sub 0.3}Ni{sub 4.6}Sn{sub 0.3}Co{sub 0.1} metal hydride electrodes. Alloy characterization included x-ray diffraction (XRD), x-ray absorption (XAS), hydrogen absorption in a Sieverts apparatus, and electrochemical cycling of alloy electrodes. The atomic volume of H was determined for two of the alloys. Electrochemical kinetic measurements were made using steady state galvanostatic measurements, galvanodynamic sweep, and electrochemical impedance techniques. XAS was used to examine the degree of corrosion of the alloys with cycling. Alloying with Y decreased the corrosion rate. The results are consistent with corrosion inhibition by a Y containing passive film. The increase in the kinetics of the hydrogen oxidation reaction (HOR) with increasing depth of discharge was much greater on the Y containing alloys. This may be due to the dehydriding of the catalytic species on the surface of the metal hydride particles.
Kinetic study of the complexation of gallic acid with Fe(II)
NASA Astrophysics Data System (ADS)
Lu, Li-li; Li, Ying-hua; Lu, Xiu-yang
2009-10-01
Kinetic study on the complexation of gallic acid with ferrous sulfate was performed using UV-Vis absorption spectroscopy. Under the experimental conditions, the stoichiometric composition of the formed complex is 1:1. The complexation reaction was found to be a second-order one. The influences of temperature, ionic strength and solvents on the complexation reaction were investigated. According to the Arrhenius equation, the apparent activation energy of the complexation reaction was evaluated to be 71.64 kJ × mol -1. A three-step reaction mechanism was proposed, which can well explain the kinetic results obtained.
NASA Astrophysics Data System (ADS)
Gao, Shuqin; Liao, Lifu; Xiao, Xilin; Zhao, Zhiyuan; Du, Nan; Du, Jiangfeng
2010-05-01
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.
Chongfu Zhou; Jinghong Ma; Lihua Pan; Borun Liang
2002-01-01
The transesterification kinetics of poly(ethylene terephthalate) (PET)\\/copoly(oxybenzoate-p-terephthalate) (liquid crystalline polymer, LCP) (70\\/30 by weight) in the presence of small amount of bis(2-oxazoline) (BOZ) as chain extender was studied by using 1H nuclear magnetic resonance. The kinetic data was treated as a second-order reversible reaction, and it was found that the rate constants of transesterification at 270, 280 and 290 °C
NASA Technical Reports Server (NTRS)
Hynes, A. J.; Wine, P. H.
1997-01-01
The pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to determine absolute rate coefficients for the reaction OH + CH3CN (1) and its isotopic variants, OH + CD3CN (2), OD + CH3CN (3), and OD + CD3CN (4). Reactions 1 and 2 were studied as a function of pressure and temperature in N2, N2/O2, and He buffer gases. In the absence of O2 all four reactions displayed well-behaved kinetics with exponential OH decays and pseudo-first rate constants which were proportional to substrate concentration. Data obtained in N2 over the range 50-700 Torr at 298 K are consistent with k(sub 1), showing a small pressure dependence. The Arrhenius expression obtained by averaging data at all pressures in k(sub 1)(T) = (1.1(sup +0.5)/(sub -0.3)) x 10(exp -12) exp[(-1130 +/- 90)/T] cu cm /(molecule s). The kinetics of reaction 2 are found to be pressure dependent with k(sub 2) (298 K) increasing from (1.21 +/- 0.12) x 10(exp -14) to (2.16 +/- 0.11) x 10(exp -14) cm(exp 3)/ (molecule s) over the pressure range 50-700 Torr of N2 at 298 K. Data at pressures greater than 600 Torr give k(sub 2)(T) = (9.4((sup +13.4)(sub -5.0))) x 10(exp -13) exp[(-1180 +/- 250)/T] cu cm/(molecule s). The rates of reactions 3 and 4 are found to be independent of pressure over the range 50-700 Torr of N2 with 298 K rate coefficient given by k(sub 3) =(3.18 +/- 0.40) x 10(exp -14) cu cm/(molecule s) and k(sub 4) = (2.25 +/-0.28) x 10(exp -14) cu cm/(molecule s). In the presence of O2 each reaction shows complex (non-pseudo-first-order) kinetic behavior and/or an apparent decrease in the observed rate constant with increasing [O2], indicating the presence of significant OH or OD regeneration. Observation of regeneration of OH in (2) and OD in (3) is indicative of a reaction channel which proceeds via addition followed by reaction of the adduct, or one of its decomposition products, with O2. The observed OH and OD decay profiles have been modeled by using a simple mechanistic scheme to extract kinetic information about the adduct reations with O2 and branching ratios for OH regeneration. A plausible mechanism for OH regeneration in (2) involves OH addition to the nitrogen atom followed by O2 addition to the cyano carbon atom, isomeriazation and decomposition to D2CO + DOCN + OH. Our results suggest that the OH + CH3CN reaction occurs via a complex mechanism involving both bimolecular and termolecular pathways, analogous to the mechanisms for the the important atmospheric reactions of OH with CO and HNO3.
Numerical modeling of surface reaction kinetics in electrokinetically actuated microfluidic devices.
Sadeghi, Arman; Amini, Younes; Saidi, Mohammad Hassan; Chakraborty, Suman
2014-08-01
We outline a comprehensive numerical procedure for modeling of species transport and surface reaction kinetics in electrokinetically actuated microfluidic devices of rectangular cross section. Our results confirm the findings of previous simplified approaches that a concentration wave is created for sufficiently long microreactors. An analytical solution, developed for the wave propagation speed, shows that, when normalizing with the fluid mean velocity, it becomes a function of three parameters comprising the channel aspect ratio, the relative adsorption capacity, and the kinetic equilibrium constant. Our studies also reveal that the reactor geometry idealized as a slit, instead of a rectangular shape, gives rise to the underestimation of the saturation time. The extent of this underestimation increases by increasing the Damkohler number or decreasing the dimensionless Debye-Hückel parameter. Moreover, increasing the values of the Damkohler number, the dimensionless Debye-Hückel parameter, the relative adsorption capacity, and the velocity scale ratio results in lower saturation times. PMID:25064245
Kinetic studies of overlapping pyrolysis reactions in industrial waste activated sludge.
Yang, Xiaoyi; Jiang, Zhenpeng
2009-07-01
A sludge pyrolytic kinetics model was established in this study. Two types of sewage sludge from different industrial wastewater treatment plant produced different DTG (Derivative Thermogravimetry) shapes with an overlapping pattern. The multi-heating rate method was conducted to evaluate the kinetics for obtaining reasonable pyrolysis mechanisms and DTG curves were divided into several peaks using the Lorentz fitting method based on the composition of the sludge and the desire for precision. The peaks formed corresponded to the pyrolysis reactions of volatile matter, microbe cells, proteins, inorganic substances and char respectively, which can be reasonably explained based on the results from the flue gas analyzer and the chemical analysis. Two types of sewage sludge were found to have similar pyrolysis mechanisms. Reasonable reasons were also given to explain the distortion and lag observed in the DTG curves and pyrolysis mechanism. PMID:19342231
Kinetic Isotope Effects for the Reactions of Muonic Helium and Muonium with H2
Fleming, Donald G.; Arseneau, Donald J.; Sukhorukov, Oleksandr; Brewer, Jess H.; Mielke, Steven L.; Schatz, George C.; Garrett, Bruce C.; Peterson, Kirk A.; Truhlar, Donald G.
2011-01-28
The neutral muonic helium atom may be regarded as the heaviest isotope of the hydrogen atom, with a mass of ~4.1 amu (4.1H), because the negative muon screens one proton charge. We report the reaction rate of 4.1H with 1H2 to produce 4.1H1H + 1H at 295 to 500 K. The experimental rate constants are compared with the predictions of accurate quantum mechanical dynamics calculations carried out on an accurate Born-Huang potential energy surface and with previously measured rate constants of 0.11H (where 0.11H is shorthand for muonium). Kinetic isotope effects can be compared for the unprecedentedly large mass ratio of 36. The agreement with accurate quantum dynamics is quantitative at 500 K, and variational transition state theory is used to interpret the extremely low (large inverse) kinetic isotope effects in the 10-4 to 10-2 range.
Reaction kinetics, P-T-t paths and rates of tectonic processes
Bohlen, S.R.; Hankins, W.B.; Eckert, J.O. Jr.; Kirby, S.H.; Liu, J. (Geological Survey, Menlo Park, CA (United States)); Hacker, B.R.; Mosenfelder, J.L. (Stanford Univ., Stanford, CA (United States). Dept. of Geology)
1992-01-01
The interpretation of portions of P-T-time (t) paths in metamorphic rocks assumes that continuous and discontinuous reactions record local equilibrium as P-T conditions change, implying that the kinetics of many reactions are rapid relative to dT/dt and dP/dt. Occurrence of eclogite veins in granulites from Bergen, Norway as well as occurrences of coesite and diamond in crustal rocks imply that, under certain conditions, this assumption is wrong. Knowledge of the kinetics of important reactions under appropriate conditions would provide limits on the duration of relatively narrowly defined P-T conditions, allow inference of the rates of exhumation of rocks containing high-pressure phases, and allow the calculation of the time required for the conversion of gabbro to eclogite in the lower crust as a function of P-T-t. The authors are currently assessing the rates of key phase transformations: calcite to aragonite, albite to jadeite + quartz, coesite to quartz, opx[sub Fs[sup 80
Reaction Kinetics of CO2 Carbonation with Mg-Rich Minerals
Kwon, Dr. Soonchul [Georgia Institute of Technology; Fan, Maohong [University of Wyoming, Laramie; DaCosta, Dr. Herbert F.M. [Chem-Innovations Inc; Russell, Dr. Armistead [Georgia Institute of Technology; Tsouris, Costas [ORNL
2011-01-01
Due to their low price, wide availability, and stability of the resulting carbonates, Mg-rich minerals are promising materials for carbonating CO{sub 2}. Direct carbonation of CO{sub 2} with Mg-rich minerals reported in this research for the first time could be considerably superior to conventional liquid extraction processes from an energy consumption perspective due to its avoidance of the use of a large amount of water with high specific heat capacity and latent heat of vaporization. Kinetic models of the reactions of the direct CO{sub 2} carbonation with Mg-rich minerals and within simulated flue gas environments are important to the scale-up of reactor designs. Unfortunately, such models have not been made available thus far. This research was initiated to fill that gap. Magnesium silicate (Mg{sub 2}SiO{sub 4}), a representative compound in Mg-rich minerals, was used to study CO{sub 2} carbonation reaction kinetics under given simulated flue gas conditions. It was found that the chosen sorbent deactivation model fits well the experimental data collected under given conditions. A reaction order of 1 with respect to CO{sub 2} is obtained from experimental data. The Arrhenius form of CO{sub 2} carbonation with Mg{sub 2}SiO{sub 4} is established based on changes in the rate constants of the chosen deactivation model as a function of temperature.
Kinetics of thermal reaction HOCl ? H(2 S) + OCl( X 2? i ) in gas phase
NASA Astrophysics Data System (ADS)
Begovi?, N.; Markovi?, Z.; Ani?, S.
2011-12-01
The kinetics of gas reaction HOCl\\underset{{k_r }}{overset{{k_f }}{longleftrightarrow}}H(^2 S) + OCl(X^2 Pi _i ) was analyzed by the MP4 method. In the temperature range of 100-373 K the rate constants k f and k r and equilibrium constant K were changed from 1.10 × 10-220 to 1.17 × 10-52 s-1, from 2.89 × 10-16 to 1.68 × 10-5s-1 and from 3.80 × 10-205 to 6.96 × 10-48 respectively. In the above temperature range, the activation energy of the forward reaction ( E f) is 105.05 kcal/mol. In the same temperature interval there are two kinetic domains for the reverse reaction with activation energies ( E r1 = 5.53 kcal/mol when T is 100-273 K and E r2 = 14.50 kcal/mol when T is 273-373 K, respectively.
Reactions of the CN Radical with Benzene and Toluene: Product Detection and Low-Temperature Kinetics
Trevitt, Adam J.; Goulay, Fabien; Taatjes, Craig A.; Osborn, David L.; Leone, Stephen R.
2009-12-23
Low temperature rate coefficients are measured for the CN + benzene and CN + toluene reactions using the pulsed Laval nozzle expansion technique coupled with laser-induced fluorescence detection. The CN + benzene reaction rate coefficient at 105, 165 and 295 K is found to be relatively constant over this temperature range, 3.9 - 4.9 x 10-10 cm3 molecule-1 s-1. These rapid kinetics, along with the observed negligible temperature dependence, are consistent with a barrierless reaction entrance channel and reaction efficiencies approaching unity. The CN + toluene reaction is measured to have a slower rate coefficient of 1.3 x 10-10 cm3 molecule-1 s-1 at 105 K. At room temperature, non-exponential decay profiles are observed for this reaction that may suggest significant back-dissociation of intermediate complexes. In separate experiments, the products of these reactions are probed at room temperature using synchrotron VUV photoionization mass spectrometry. For CN + benzene, cyanobenzene (C6H5CN) is the only product recorded with no detectable evidence for a C6H5 + HCN product channel. In the case of CN + toluene, cyanotoluene (NCC6H4CH3) constitutes the only detected product. It is not possible to differentiate among the ortho, meta and para isomers of cyanotoluene because of their similar ionization energies and the ~;; 40 meV photon energy resolution of the experiment. There is no significant detection of benzyl radicals (C6H5CH2) that would suggest a H-abstraction or a HCN elimination channel is prominent at these conditions. As both reactions are measured to be rapid at 105 K, appearing to have barrierless entrance channels, it follows that they will proceed efficiently at the temperatures of Saturn?s moon Titan (~;;100 K) and are also likely to proceed at the temperature of interstellar clouds (10-20 K).
The hexacyanomanganate(IV)-hydrogen peroxide reaction. Kinetic determination of vanadium.
Angulo, R; López-Cueto, G; Ubide, C
1998-05-01
The reaction between hexacyanomanganate(IV) and hydrogen peroxide in acidic medium is strongly catalysed by vanadium. The stoichiometry has been proved to be Delta[Mn(IV)]/Delta[H(2)O(2)]=1. S-shaped absorbance-time curves are obtained for a wide range of conditions, which seems to be due to the transient formation of hydroperoxyl radicals, HO(2).; therefore, the reaction is autoinduced. The reaction kinetics is first order on the hexacyanomanganate(IV) concentration. Complex dependence of the initial rate on the H(2)O(2) as well as H(+) concentrations are observed both for the uncatalysed and for the catalysed reactions, but the rate laws are given and reaction mechanisms are proposed. The catalytic effect of vanadium has been used to determine traces of vanadium (the (IV) and (V) oxidation states are determined together). By applying the initial rate method a detection limit of 0.9 ng ml(-1) (18 nM), and a linear range up to 50 ng ml(-1) were found. The relative standard deviations for the 4 and 25.5 ng ml(-1) levels were 5.2 and 2.5% respectively. Positive kinetic interferences from Cr(VI), Hg(I) and Ag(I) have been observed; other interferences are less severe and Cr(IIl), Fe(II) and Fe(III), among many others, do not interfere. The Mn(IV) solution must be prepared daily and its conservation needs some care (0 degrees C) but the proposed method has been applied to the determination of vanadium in a phosphate rock (reference material, BCR No. 32) without previous separations. Recovery experiments have also been performed; excellent results were obtained in both cases. PMID:18967128
Human primary visual cortex (V1) is selective for second-order spatial frequency
Landy, Michael S.; Heeger, David J.
2011-01-01
A variety of cues can differentiate objects from their surrounds. These include “first-order” cues such as luminance modulations and “second-order” cues involving modulations of orientation and contrast. Human sensitivity to first-order modulations is well described by a computational model involving spatially localized filters that are selective for orientation and spatial frequency (SF). It is widely held that first-order modulations are represented by the firing rates of simple and complex cells (“first-order” neurons) in primary visual cortex (V1) that, likewise, have spatially localized receptive fields that are selective for orientation- and SF. Human sensitivity to second-order modulations is well described by a filter-rectify-filter (FRF) model, with first- and second-order filters selective for orientation and SF. However, little is known about how neuronal activity in visual cortex represents second-order modulations. We tested the FRF model by using an functional (f)MRI-adaptation protocol to characterize the selectivity of activity in visual cortex to second-order, orientation-defined gratings of two different SFs. fMRI responses throughout early visual cortex exhibited selective adaptation to these stimuli. The low-SF grating was a more effective adapter than the high-SF grating, incompatible with the FRF model. To explain the results, we extended the FRF model by incorporating normalization, yielding a filter-rectify-normalize-filter model, in which normalization enhances selectivity for second-order SF but only for low spatial frequencies. We conclude that neurons in human visual cortex are selective for second-order SF, that normalization (surround suppression) contributes to this selectivity, and that the selectivity in higher visual areas is simply fed forward from V1. PMID:21346207
Garin, F.; Keller, V.; Muller, A. [CNRS, Strasbourg (France)] [and others] [CNRS, Strasbourg (France); and others
1997-03-01
This paper describes in close molecular detail the complex reactions which occur when a variety of hydrocarbons are adsorbed on fresh or oxygen-modified bulk tungsten carbide catalysts. On fresh tungsten carbide without oxygen, cracking reactions are the only reaction processes occurring; the results have been interpreted with a kinetic treatment which assumes successive carbon-carbon bond ruptures. The conditions under which the bulk tungsten carbide powders are treated with oxygen have a determinantal influence on their catalytic properties. If air is introduced at moderate temperature (350{degrees}C), an acidic character of the catalyst is observed which leads to a bifunctional mechanism. Cracking reactions are the most important processes, and corresponding mechanisms have been interpreted using the presence of OH surface groups leading to alkoxy species as intermediates. If air is introduced in flowing hydrogen at high temperature (700{degrees}C), the metallic character of the material is observed, leading to cracking and isomerization reactions explained via classical metallacyclobutane and {sigma}-alkyl species, respectively. 28 refs., 3 figs.
Po-Huang Liang; Julian Lewis; Karen S. Anderson; Amnon Kohen; Francis Wallace D'Souza; Yaakov Benenson; Timor Baasov
1998-01-01
The mechanistic pathway for the reaction catalyzed by Kdo8P synthase has been investigated, and the cyclic bisphosphate 2 has been examined as a putative reaction intermediate. Two parallel approaches were used: (1) chemical synthesis of 2 and evaluation as an alternate substrate for the enzyme and (2) transient kinetic studies using rapid chemical quench methodology to provide direct observation and
Fontijn, A.
1983-12-01
A High-Temperature Photochemistry (HTP) reactor facility, designed and constructed this year, is described and discussed. It is suitable for kinetics measurements on isolated elementary hydrocarbon oxidation reactions in the 300 to 1800 K temperature range. Plans for its use in the study of the reaction between oxygen atoms and ethylene are summarized. 8 references, 1 figure.
van Stokkum, Ivo
that absorption of a blue photon leads to cisCCtrans isomerization of the 4-hydroxy-cinnamyl chromophore of PYP Abstract We have studied the kinetics of the blue light-induced branching reaction in the photocycle/Vis spectroscopy. As compared to the parallel dark recovery reaction of the presumed blue-shifted signaling state p
The kinetics of the reactions between iodide and hydrogen peroxide in seawater
George T. F. Wong; Ling-Su Zhang
2008-01-01
The kinetics of the reactions between H2O2 and I? were studied in artificial seawater as a function of temperature (10–30 °C), salinity (0–36), pH (7–9) and the concentrations of molybdate (0–480 ?M) at a range of concentrations of H2O2 (5 to 40 mM) and I? (0.1 to 30 mM) by following the changes in the concentrations of the two reactants with time. While the
Kinetic resolution of acids in acylation reactions in the presence of chiral tertiary amines
Potapov, V.M.; Dem'yanovich, V.M.; Khlebnikov, V.A.
1988-07-10
Asymmetric synthesis has now become an important method for the production of optically active compounds, and its most attractive form is asymmetric catalysis. This work was devoted to an investigation into asymmetric catalysis with chiral tertiary amines in acylation reactions. During the acylation of alcohols and amines by the action of racemic 2-phenylpropionic and 2-methyl-3-phenylpropionic acids in the presence of S-nicotine the initial acids are resolved kinetically. The (R)-2-phenylpropionic acid obtained in this way had an optical purity of 0.5-1.5%.
Kinetics of the benzyl + O(3P) reaction: a quantum chemical/statistical reaction rate theory study.
da Silva, Gabriel; Bozzelli, Joseph W
2012-12-14
The resonance stabilized benzyl radical is an important intermediate in the combustion of aromatic hydrocarbons and in polycyclic aromatic hydrocarbon (PAH) formation in flames. Despite being a free radical, benzyl is relatively stable in thermal, oxidizing environments, and is predominantly removed through bimolecular reactions with open-shell species other than O(2). In this study the reaction of benzyl with ground-state atomic oxygen, O((3)P), is examined using quantum chemistry and statistical reaction rate theory. C(7)H(7)O energy surfaces are generated at the G3SX level, and include several novel pathways. Transition state theory is used to describe elementary reaction kinetics, with canonical variational transition state theory applied for barrierless O atom association with benzyl. Apparent rate constants and branching ratios to different product sets are obtained as a function of temperature and pressure from solving the time-dependent master equation, with RRKM theory for microcanonical k(E). These simulations indicate that the benzyl + O reaction predominantly forms the phenyl radical (C(6)H(5)) plus formaldehyde (HCHO), with lesser quantities of the C(7)H(6)O products benzaldehyde, ortho-quinone methide, and para-quinone methide (+H), along with minor amounts of the formyl radical (HCO) + benzene. Addition of O((3)P) to the methylene site in benzyl produces a highly vibrationally excited C(7)H(7)O* adduct, the benzoxyl radical, which can ?-scission to benzaldehyde + H and phenyl + HCHO. In order to account for the experimental observation of benzene as the major reaction product, a roaming radical mechanism is proposed that converts the nascent products phenyl and HCHO to benzene + HCO. Oxygen atom addition at the ortho and para ring sites in benzyl, which has not been previously considered, is shown to lead to the quinone methides + H; these species are less-stable isomers of benzaldehyde that are proposed as important combustion intermediates, but are yet to be identified experimentally. Franck-Condon simulations of the benzaldehyde, o-quinone methide, and p-quinone methide photoelectron spectra suggest that these C(7)H(6)O isomers could be distinguished using tunable VUV photoionization mass spectrometry. PMID:23108328
Kinetics of the Gas-Phase Reaction of OH with Chlorobenzene
Bryukov, Mikhail G.; Knyazev, Vadim D.; Gehling, William M.; Dellinger, Barry
2009-01-01
The kinetics of the reaction of hydroxyl radicals with chlorobenzene was studied experimentally using a pulsed laser photolysis/pulsed laser induced fluorescence technique over a wide range of temperatures, 298-670 K, and at pressures between 13.33 and 39.92 kPa. The bimolecular rate constants demonstrate different behavior at low and high temperatures. At room temperature, T = 298.8±1.5 K, the rate constant is equal to (6.02 ± 0.34)×10-13 cm3 molecule-1 s-1; at high temperatures (474 - 670 K), the rate constant values are significantly lower and have a positive temperature dependence that can be described by an Arrhenius expression k1(T ) = (1.01 ± 0.35)×10-11 exp[(-2490 ± 170 K)/T] cm3 molecule-1 s-1. This behavior is consistent with the low-temperature reaction being dominated by reversible addition and the high-temperature reaction representing abstraction and addition-elimination channels. The potential energy surface of the reaction was studied using quantum chemical methods and a transition state theory model was developed for all reaction channels. The temperature dependences of the high-temperature rate constants obtained in calculations using the method of isodesmic reactions for transition states (IRTS) and the CBS-QB3 method are in very good agreement with experiment, with deviations smaller than the estimated experimental uncertainties. The G3//B3LYP-based calculated rate constants are in disagreement with the experimental values. The IRTS-based model was used to provide modified Arrhenius expressions for the temperature dependences of the rate constant for the abstraction and addition-elimination (Cl replacement) channels of the reaction. PMID:19728723
Rashed, Mohammed Abouelleil
2015-04-01
The centenary of Karl Jaspers' General Psychopathology was recognised in 2013 with the publication of a volume of essays dedicated to his work (edited by Stanghellini and Fuchs). Leading phenomenological-psychopathologists and philosophers of psychiatry examined Jaspers notion of empathic understanding and his declaration that certain schizophrenic phenomena are 'un-understandable'. The consensus reached by the authors was that Jaspers operated with a narrow conception of phenomenology and empathy and that schizophrenic phenomena can be understood through what they variously called second-order and radical empathy. This article offers a critical examination of the second-order empathic stance along phenomenological and ethical lines. It asks: (1) Is second-order empathy (phenomenologically) possible? (2) Is the second-order empathic stance an ethically acceptable attitude towards persons diagnosed with schizophrenia? I argue that second-order empathy is an incoherent method that cannot be realised. Further, the attitude promoted by this method is ethically problematic insofar as the emphasis placed on radical otherness disinvests persons diagnosed with schizophrenia from a fair chance to participate in the public construction of their identity and, hence, to redress traditional symbolic injustices. PMID:25820144
Hilbe, Christian; Traulsen, Arne; Röhl, Torsten; Milinski, Manfred
2014-01-14
Individuals usually punish free riders but refuse to sanction those who cooperate but do not punish. This missing second-order peer punishment is a fundamental problem for the stabilization of cooperation. To solve this problem, most societies today have implemented central authorities that punish free riders and tax evaders alike, such that second-order punishment is fully established. The emergence of such stable authorities from individual decisions, however, creates a new paradox: it seems absurd to expect individuals who do not engage in second-order punishment to strive for an authority that does. Herein, we provide a mathematical model and experimental results from a public goods game where subjects can choose between a community with and without second-order punishment in two different ways. When subjects can migrate continuously to either community, we identify a bias toward institutions that do not punish tax evaders. When subjects have to vote once for all rounds of the game and have to accept the decision of the majority, they prefer a society with second-order punishment. These findings uncover the existence of a democracy premium. The majority-voting rule allows subjects to commit themselves and to implement institutions that eventually lead to a higher welfare for all. PMID:24367116
Hilbe, Christian; Traulsen, Arne; Röhl, Torsten; Milinski, Manfred
2014-01-01
Individuals usually punish free riders but refuse to sanction those who cooperate but do not punish. This missing second-order peer punishment is a fundamental problem for the stabilization of cooperation. To solve this problem, most societies today have implemented central authorities that punish free riders and tax evaders alike, such that second-order punishment is fully established. The emergence of such stable authorities from individual decisions, however, creates a new paradox: it seems absurd to expect individuals who do not engage in second-order punishment to strive for an authority that does. Herein, we provide a mathematical model and experimental results from a public goods game where subjects can choose between a community with and without second-order punishment in two different ways. When subjects can migrate continuously to either community, we identify a bias toward institutions that do not punish tax evaders. When subjects have to vote once for all rounds of the game and have to accept the decision of the majority, they prefer a society with second-order punishment. These findings uncover the existence of a democracy premium. The majority-voting rule allows subjects to commit themselves and to implement institutions that eventually lead to a higher welfare for all. PMID:24367116
Pollock, Ciara L; Fox, Kevin J; Lacroix, Sophie D; McDonagh, James; Marr, Patricia C; Nethercott, Alanna M; Pennycook, Annie; Qian, Shimeng; Robinson, Linda; Saunders, Graham C; Marr, Andrew C
2012-11-21
Chemoenzymatic dynamic kinetic resolution (DKR) of rac-1-phenyl ethanol into R-1-phenylethanol acetate was investigated with emphasis on the minimization of side reactions. The organometallic hydrogen transfer (racemization) catalyst was varied, and this was observed to alter the rate and extent of oxidation of the alcohol to form ketone side products. The performance of highly active catalyst [(pentamethylcyclopentadienyl)IrCl(2)(1-benzyl,3-methyl-imidazol-2-ylidene)] was found to depend on the batch of lipase B used. The interaction between the bio- and chemo-catalysts was reduced by employing physical entrapment of the enzyme in silica using a sol-gel process. The nature of the gelation method was found to be important, with an alkaline method preferred, as an acidic method was found to initiate a further side reaction, the acid catalyzed dehydration of the secondary alcohol. The acidic gel was found to be a heterogeneous solid acid. PMID:23007791
Flavonoid B-ring chemistry and antioxidant activity: fast reaction kinetics.
Sekher Pannala, A; Chan, T S; O'Brien, P J; Rice-Evans, C A
2001-04-20
Rapid scavenging of the model stable radical cation, ABTS(*+), has been applied to screen for the antioxidant activity of flavonoids. The reaction follows two distinct phases. For compounds with a monophenolic B-ring there is a rapid initial phase of reduction of ABTS(*+) within 0.1 s with no further change in the subsequent 2.9 s. In contrast, compounds with a catechol-containing B ring follow a fast initial scavenging phase with a slow secondary phase. Flavonoids with an unsubstituted B ring do not react within this time scale. The findings suggest that the structure of the B ring is the primary determinant of the antioxidant activity of flavonoids when studied through fast reaction kinetics. PMID:11302737
Chemical Kinetic Data Base for Propellant Combustion. II. Reactions Involving CN, NCO, and HNCO
NASA Astrophysics Data System (ADS)
Tsang, Wing
1992-07-01
This paper contains evaluated chemical kinetic data on single step elementary reactions involving small polyatomic molecules which are of importance in propellant combustion. The work consists of the collection and evaluation of mechanistic and rate information and the use of various methods for the extrapolation and estimation of rate data where information does not exist. The conditions covered range from 500-2500 K and 1017-1022 particles cm-3. The results of the second year's effort add to the existing data base reactions involving CN, NCO, and HNCO with each other and the following species: H, H2, H2O, O, OH, HCHO, CHO, CO, NO, NO2, HNO, HNO2, HCN, and N2O.
On the Upscaling of Reaction-Transport Processes in Porous Media with Fast Kinetics
Kechagi, P.; Tsimpanogiannis, I.; Yortsos, Y.C.; Lichtner, P.
2001-01-09
This report is organized as follows: Provide a brief review of the upscaling constraints of the type (2) for a typical diffusion-reaction system. In this an analogy with two-phase flow in porous media was drawn. Then, using the methodology of QW a problem at the unit cell for the computation of the effective mass transfer coefficient, in processes where local thermodynamic equilibrium applies was derived. This problem is found to be different than in QW, as it depends on the gradients of the macroscale variable, and can be cast in terms of an eigenvalue problem. Two simple, examples, one involving advection-dissolution and another involving drying in a pore network, was presented to illustrate the coupling between scales and to show the quantitative effect in case this coupling was neglected. Finally, similar ideas and an illustrative example was applied to reaction-diffusion systems with fast kinetics, where an equilibrium state is approached.
High-temperature kinetics of the nickel-oxygen reaction by ceramic electrolyte cells
Gozzi, D.; De Maria, G.
1986-08-01
A multiple-electrode cell with yttria-stabilized zirconia electrolyte is used to oxidize selected regions of an Ni-laminated disk by applying galvanostatic steps. Reaction kinetics is studied by examining the chronopotentiometric curve associated to a given current step. Oxidation rate and rate constant data are given in the temperature range between 870 and 1100/sup 0/C as well as the diffusion coefficient of Ni in NiO and electrical conductivity values of the growing oxide scale. Activation enthalpy for the oxidation reaction is given as a function of the oxygen partial pressure and the activation enthalpies for the conductivity, and the diffusion processes are also reported. Some morphologies of the oxidized samples are shown as obtained by SEM.
Kinetics and Thermochemistry of ClCO Formation from the Cl + CO Association Reaction
NASA Technical Reports Server (NTRS)
Nicovich, J. M.; Kreutter, K. D.; Wine, P. H.
1997-01-01
Laser flash photolysis of Cl2/CO/M mixtures (M = N2, CO, Ar, CO2) has been employed in conjunction with Cl((sup 2)P(sub J)) detection by time-resolved resonance fluorescence spectroscopy to investigate equilibration kinetics in the reactions Cl((sup 2)P(sub J)) + CO ClCO as a function of temperature (185-260 K) and pressure (14-200 Torr). The association and dissociation reactions are found to be in the low-pressure limit over the range of experimental conditions investigated. In N2 and/or CO buffer gases, the temperature dependences of the ClCO formation and dissociation reaction rate constants are described by the Arrhenius expressions k(sub 1) = (1.05 +/- 0.36) x 10(exp -34) exp[(810 +/- 70)/T] cm(exp 6)/molecules(exp 2).s and k(sub -1) = (4.1 +/- 3.1) x 10(exp -10) exp[(-2960 +/- 60)/T]cu cm/(molecule.s) (errors are 2 sigma). Second- and third-law analyses of the temperature dependence of the equilbrium constant (k/k-1) lead to the following thermodynamic parameters for the association reaction: Delta-H(sub 298) = -7.7 +/- 0.6 kcal/mol, Delta-H(sub 0) = -6.9 +/- 0.7 kcal/mol, Delta-S(sub 298) = -23.8 +/- 2.0 cal/mole.K, Delta-H(sub f,298)(ClCO) = 5.2 +/- 0.6 kcal/mol (errors are 2 sigma). The results repported in this study significantly reduce the uncertainties in all reported kinetic and thermodynamic parameters.
A kinetic investigation on the gas-phase reaction of ozone with four sesquiterpenes
NASA Astrophysics Data System (ADS)
Richters, Stefanie; Herrmann, Hartmut; Berndt, Torsten
2014-05-01
Sesquiterpenes (C15H24, SQT) are emitted by plants with a global emission rate of about 15 Tg per year (Seinfeld and Pankow, 2003). They are possibly an important source of secondary organic aerosol (SOA) but their oxidation processes are scarcely examined. This study focusses on the kinetics of the reaction of ozone with four atmospherically relevant SQT: ?-caryophyllene, ?-humulene, ?-cedrene and isolongifolene. Up to now there are only two studies available in the literature describing kinetic measurements of the ozonolysis of a series of SQT, (Shu and Atkinson, 1994; Ghalaieny et al., 2012). As a result of these studies the rate coefficients of the ozone reaction with ?-caryophyllene and ?-humulene differ by three orders of magnitude making a reinvestigation necessary. Both literature studies were carried out in a reaction chamber with long reaction times. Shu and Atkinson (1994) used high concentrations of [SQT] = 2.4 • 1013 molecules cm-3 and [O3] = 2.5 • 1012 molecules cm-3 making particle formation and consecutive reactions relevant. The latter study of Ghalaieny et al. (2012) investigated the reaction at even higher concentrations ([SQT] = (2.1 - 3.5) • 1014 molecules cm-3, [O3] > 2.1 • 1015 molecules cm-3) at elevated temperatures (366 K) to avoid particle formation. Our study was carried out with very low SQT concentrations ((1 - 2) • 1010 molecules cm-3), [O3] = (1 - 15) • 1011 molecules cm-3, in a flow tube at atmospheric pressure and room temperature. The relative rate coefficients were investigated by means of an online GC-MS technique allowing measuring SQT concentrations down to 109 molecules cm-3. Particle formation was detected using an ultrafine condensed particle counter (TSI-3025 with a 50% cut-off size of 2.5 - 3 nm) and was found to be negligible under the chosen reaction conditions. Our study supports the rate coefficients as given by Shu and Atkinson (1994). References: J. H. Seinfeld and J. F. Pankow, Annu. Rev. Phys. Chem., 54:121-140, 2003. Y. Shu and R. Atkinson, Int. J. of Chem.Kin., 26:1193-1205, 1994. M. Ghalaieny, A. Bacak, M. McGillen, D. Martin, A. V. Knights, S. O'Doherty, D. E. Shallcross, and C. J. Percival, Phys. Chem. Chem. Phys, 14:6596-6602, 2012.
McAuliffe, J.J. (Univ. of Cincinnati College of Medicine, OH (United States)); Perry, S.B. (Childrens Hospital, Boston, MA (United States)); Brooks, E.E. (Univ. of Cincinnati, OH (United States)); Ingwall, J.S. (Brigham and Women's Hospital, Boston, MA (United States) Harvard Medical School, Boston, MA (United States))
1991-03-12
Here the authors define the kinetics of the creatine kinase (CK) reaction in an intact mammalian heart containing the full rnage of CK isoenzymes. Previously derived kinetic constants were refit for the reaction occurring at 37C. Steady-state metabolite concentrations from {sup 31}P NMR and standard biochemical techniques were determined. {sup 31}P magnetization transfer data were obtained to determine unidirectional creatine kinase fluxes in hearts with differing total creatine contents and differing mitochondrial CK activities during KCl arrest and isovolumic work for both the forward reaction (MgATP synthesis) and reverse reaction (phosphocreatine synthesis). The NMR kinetic data and substrate concentrations data were used in conjunction with a kinetic model based on MM-CK in solution to determine the applicability of the solution-based kinetic models to the CK kinetics of the intact heart. The results indicated that no single set of rate equation constants could describe both the KCl-arrested and working hearts. Analysis of the results indicated that the CK reaction is rate limited in the direction of ATP synthesis, the size of the guanidino substrate pool drives the measured CK flux in the intact heart, and during isovolumic work, the CK reaction operates under saturating conditions; that is, the substrate concentrations are at least 2-fold greater than the K{sub m} or K{sub im} for each substrate. However, during KCl arrest the reaction does not operate under saturating conditions and the CK reaction velocity is strongly influenced by the guanidino substrate pool size.
Second-order all-fiber comb filter based on polarization-diversity loop configuration.
Lee, Yong Wook; Kim, Hyun-Tak; Lee, Yong Wan
2008-03-17
By concatenating three birefringence loops in series, a second-order all-fiber comb filter based on a polarization-diversity loop configuration is newly proposed. The proposed filter consists of one polarization beam splitter, polarization-maintaining fibers, and two halfwave plates. The effect of a second-order structure of polarization-maintaining fiber loops on a bandwidth of the filter passband was theoretically analyzed and experimentally demonstrated. Transmission output of the second-order filter (flat-top and narrow-band transmission spectra) could be obtained by adjusting two half-wave plates. 1 and 3 dB bandwidths of the proposed filter in flat-top and narrow-band operations were greater by approximately 102.9 and 44.3 % and smaller by approximately 47.9 and 47.1 % than those of a conventional Sagnac birefringence filter, respectively. PMID:18542484
Second order QCD corrections to the forward-backward asymmetry in e+e--collisions
NASA Astrophysics Data System (ADS)
Ravindran, V.; van Neerven, W. L.
1998-12-01
We will present the result of an analytical calculation of the second order contribution to the forward-backward asymmetry AFBH and the shape constant aH for heavy flavour production in e+e--collisions. The calculation has been carried out by assuming that the quark mass is equal to zero. This is a reasonable approximation for the exact second order correction for charm and bottom quark production at LEP energies but not for top production at future linear colliders. Our result for AFBH is a factor 2.6 (charm) and 4.7 (bottom) larger than obtained by a numerical calculation performed earlier in the literature. We study the effect of the second order corrections on the above parameters including their dependence on the renormalization scale. Further we make a comparison between the fixed pole mass and the running mass approach.
The second-order interference of two independent single-mode He-Ne lasers
Jianbin Liu; Minglan Le; Bin Bai; Wentao Wang; Hui Chen; Yu Zhou; Fu-Li Li; Zhuo Xu
2014-10-08
The second-order spatial and temporal interference patterns with two independent single-mode He-Ne lasers are observed in a Hong-Ou-Mandel interferometer. Two-photon interference in Feynman's path integral theory is employed to interpret the experimental results. The conditions to observe the second-order interference pattern with two independent single-mode continuous wave lasers are discussed. It is concluded that two-photon interference exists for not only identical photons, but also photons with different spectrums if the detection system can not distinguish them in principle. The second-order temporal beating with two independent lasers can be employed to measure the coherence time and frequency of one laser if the properties of the other laser were known.
First- and second-order full-differential in edge analysis of images.
Pu, Dong-Mei; Yuan, Yu-Bo
2014-01-01
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. PMID:25054162
Second-order Born calculation of coplanar symmetric (e, 2e) process on Mg
NASA Astrophysics Data System (ADS)
Zhang, Yong-Zhi; Wang, Yang; Zhou, Ya-Jun
2014-06-01
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.
Shot-Noise Seeded Microbunching Instability: Second-Order Correction to the Gain Function
Venturini, Marco
2008-06-30
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.
Beneke, M.; Fidler, C. [Institut fuer Theoretische Teilchenphysik und Kosmologie, RWTH Aachen University, D-52056 Aachen (Germany)
2010-09-15
Non-Gaussianity and B-mode polarization are particularly interesting features of the cosmic microwave background, as--at least in the standard model of cosmology--their only sources to first order in cosmological perturbation theory are primordial, possibly generated during inflation. If the primordial sources are small, the question arises how large is the non-Gaussianity and B-mode background induced in second order from the initially Gaussian and scalar perturbations. In this paper we derive the Boltzmann hierarchy for the microwave background photon phase-space distributions at second order in cosmological perturbation theory including the complete polarization information, providing the basis for further numerical studies. As an aside we note that the second-order collision term contains new sources of B-mode polarization and that no polarization persists in the tight-coupling limit.
A Damped Gauss-Newton Method for the Second-Order Cone Complementarity Problem
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
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.
Consistency of Equations in the Second-Order Gauge-Invariant Cosmological Perturbation Theory
NASA Astrophysics Data System (ADS)
Nakamura, K.
2009-06-01
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.
Effect of temperature and pressure on the kinetics of the oxygen reduction reaction.
Tse, Edmund C M; Gewirth, Andrew A
2015-02-26
Fundamental understanding of the oxygen reduction reaction in aqueous medium at temperatures above 100 °C is lacking due to the practical limitations related to the harsh experimental conditions. In this work, the challenge to suppress water from boiling was overcome by conducting the electrochemical investigation under pressurized conditions. A striking improvement in the kinetics of the electrocatalytic reduction of O2 by about 150 fold relative to room temperature and pressure was recorded under an O2 pressure of 3.4 MPa at 200 °C in basic aqueous environment. To deconvolute the combined effect of temperature and pressure, the underlying variables that dictate the observed O2 reduction kinetics of Pt and carbon electrodes were examined individually. O2 availability at the electrode-solution interface was controlled by the interplay between the diffusion coefficient and concentration of O2. Accurate knowledge of the temperature and pressure dependence of O2 availability at the electrode surface, the Tafel slope, the transfer coefficient, and the electrochemical active surface area was required to correctly account for the enhanced O2 reduction kinetics. PMID:25636087
Kinetics of thermochemical gas-solid reactions important in the Venus sulfur cycle
NASA Technical Reports Server (NTRS)
Fegley, Bruce, Jr.
1988-01-01
The thermochemical net reaction CaCO3 + SO2 yields CaSO4 + CO is predicted to be an important sink for incorporation of SO2 into the Venus crust. The reaction rate law was established to understand the dependence of rate on experimental variables such as temperature and partial pressure of SO2, CO2, and O2. The experimental approach was a variant of the thermogravimetric method often employed to study the kinetics of thermochemical gas-solid reactions. Clear calcite crystals were heated at constant temperature in SO2-bearing gas streams for varying time periods. Reaction rate was determined by three independent methods. A weighted linear least squares fit to all rate data yielded a rate equation. Based on the Venera 13, 14 and Vega 2 observations of CaO content of the Venus atmosphere, SO2 at the calculated rate would be removed from the Venus atmosphere in about 1,900,00 years. The most plausible endogenic source of the sulfur needed to replenish atmospheric SO2 is volcanism. The annual amount of erupted material needed for the replenishment depends on sulfur content; three ratios are used to calculate rates ranging from 0.4 to 11 cu km/year. This geochemically derived volcanism rate can be used to test if geophysically derived rates are correct. The work also suggests that Venus is less volcanically active than the Earth.
NASA Astrophysics Data System (ADS)
Smith, Jeremy George; Jain, Prashant
2014-06-01
The realization of common materials transformations in nanocrystalline systems is fostering the development of novel nanostructures and allowing a deep look into the atomistic mechanisms involved. Galvanic corrosion is one such transformation. We studied galvanic replacement within individual metal nanoparticles by using plasmonic spectroscopy. This proved to be a powerful approach to studying materials transformations in the absence of ensemble averaging. Individual nanoscale units act as domains that can be interrogated optically in isolation, whereas the averaging of all such domains provides a bulk reaction trajectory. Single-nanoparticle reaction trajectories showed that a Ag nanoparticle exposed to Au3+ makes an abrupt transition into a nanocage structure. The transition is limited by a critical structural event, which we identified by electron microscopy to comprise the formation of a nanosized void, similar to the pitting process commonly observed in the corrosion of metals. Trajectories also revealed a surprisingly strong nonlinearity of the reaction kinetics, which we explain by a model involving the critical coalescence of vacancies into a growing void. The critical void size for galvanic exchange to spontaneously proceed was found to be 20 atomic vacancies. In the future we hope to extend this approach to examine a wide variety of materials transformations and chemical reactions.
Kinetic measurements on elementary fossil fuel combustion reactions over wide temperatures ranges
Fontijin, A.
1992-01-01
The goals of this work are to provide accurate data on the temperature dependence of the kinetics of elementary combustion reactions (i) for use by combustion modelers, and (ii) to gain a better fundamental understanding of, and hence predictive ability for, the chemistry involved. Experimental measurements are made using the pseudo-static HTP (high-temperature photochemistry) technique. This approach allows observations on single reactions in the 300 to 1800 K temperature range to be made. Typical total (bath gas) pressures are in the 100 to 1000 mbar range. Ground-state O and H atoms are produced by flash or excimer laser photolysis of suitable precursors (O{sub 2}, CO{sub 2}, SO{sub 2}, NH{sub 3}). The relative atom concentrations are monitored by resonance fluorescence pumped by a cw microwave discharge flow lamp. The molecular reactant-in-excess is introduced through a cooled inlet. Adequate time for mixing, 0.1 to 10 s, between this inlet and the photolysis/observation zone is achieved by using slow flows (typically less than 20 cm s{sup {minus}1}). Results are reported for: O-Atom Reactions with the Four Isomeric Butenes, H + HCl {yields} H{sub 2} + Cl, and the O-atom 1,3-butadiene reaction.
Water gas shift reaction kinetics and reactor modeling for fuel cell grade hydrogen
NASA Astrophysics Data System (ADS)
Choi, Yongtaek; Stenger, Harvey G.
The kinetics of the water gas shift reaction was studied to evaluate existing reaction mechanisms, test various rate expressions and simulate the performance in a methanol fuel processor for fuel cell applications. The reaction was carried out in a micro reactor testing unit using a commercial Sud-Chemie Cu/ZnO/Al 2O 3 catalyst between 120 and 250 °C with a range of feed rates and compositions. Using non-linear least squares optimization, the parameters in five rate expressions were fit to the experimental data. Based on a review of published work on the WGS reaction mechanism, our study found that a rate expression derived from a regenerative mechanism and another rate expression derived from adsorptive mechanism fit the experimental data equally well. Numerical integration of a one-dimensional PFR model was used for this parameter fitting. An empirical rate expression, rCO= kPCOPH 2O (1- ?) with activation energy of 47.4 kJ/mol was also obtained from the experimental data. Reactor performance was simulated to determine catalyst loadings required to achieve specific CO conversions as a function of temperature and water feed rate. These results are useful in studying the design trade offs available to reformer systems.
Kinetics of the Reactions of IO Radicals with NO and NO2
NASA Technical Reports Server (NTRS)
Daykin, E. P.; Wine, P. H.
1997-01-01
A laser flash photolysis-long path absorption technique has been employed to study the kinetics of the reactions of IO radicals with NO and NO2 as a function of temperature and pressure. The IO and NO rate coefficient is independent of pressure over the range 40-200 Torr of N2, and its temperature dependence over the range 242-359 K is adequately described by the Arrhenius expression k(sub 1) = (6.9 +/- 1.7) x 10(exp -12) exp[(328 +/- 71)/T] cu cm/(molecule.s) (errors are 2 sigma, precision only). These Arrhenius parameters are similar to those determined previously for the ClO + NO and BrO + NO reactions. The IO and NO2 association reaction is found to be in the falloff regime over the temperature and pressure ranges investigated (254-354 K and 40-750 Torr of N2). Assuming F(sub c) = 0.4 independent of temperature, a physically reasonable set of falloff parameters which adequately describe the data are k(sub 0) = 7.7 x 10(exp -31)(T/300)(exp -5.0) cm(exp 6)/(molecule(exp 2).s) and k(sub infinity) = 1.55 x 10(exp -11)cu cm/(molecule.s) independent of temperature. The IO + NO2 rate coefficients determined in this study are about a factor of 2 faster than those reported in the only previous study of this reaction.