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)
ROTATING BIOLOGICAL CONTACTORS - SECOND ORDER KINETICS
Rotating biological contactors (RBC) have been employed for treating municipal wastewaters within the United States since 1970. The RBC process lends itself to kinetic interpretation because of the sequential stages employed in the operation. This mode of operation enables the su...
TRANSPORT OF DISSOLVED SUBSTANCES WITH SECOND-ORDER REACTION
A mass transport equation which allows coupled second-order reaction between two chemical components in groundwater systems is described. everal analytical solutions to the system of nonlinear equations for advective flow systems have been found, and the features of the solution ...
Second order dissipative fluid dynamics from kinetic theory
Betz, B; Koide, T; Molnar, E; Niemi, H; Rischke, D H
2010-01-01
We derive the equations of second order dissipative fluid dynamics from the relativistic Boltzmann equation following the method by W. Israel and J. M. Stewart. We present a frame independent calculation of all first and second order terms and their coefficients using a linearised collision integral. Therefore, we restore all terms that were previously neglected in the original papers by W. Israel and J. M. Stewart.
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...
Chen, Jiale [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China) [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Center for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei (China); Gao, Zhe [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China) [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Center for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei (China)
2013-08-15
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.
Theory of Ostwald ripening due to a second-order reaction
L. Ratke; D. Uffelmann; W. Bender; P. W. Voorhees
1995-01-01
The theoretical analysis of Ostwald ripening for coarsening of a dispersion of particles by a second-order interfacial reaction at the particle-matrix interface revealed: in the case of a simple second-order interfacial reaction the mean particle size increases as t13, the same as that for a diffusion controlled coarsening process. However, the stationary normalized particle size distribution has a large cut-off
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.
Second order fluid dynamics for the unitary Fermi gas from kinetic theory
Thomas Schaefer
2014-10-15
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, non-linear terms in the strain-stress relation, and non-linear couplings between vorticity and strain. An exact calculation in the dilute limit gives $\\tau_R=\\eta/P$, where $\\tau_R$ is the shear stress relaxation time, $\\eta$ is the shear viscosity, and $P$ is pressure. This relation is identical to the result obtained using the Bhatnagar-Gross-Krook (BGK) approximation to the collision term, but other transport coefficients are sensitive to the exact collision integral.
Temporal Frequency Modulates Reaction Time Responses to First-Order and Second-Order Motion
Nottingham, University of
Temporal Frequency Modulates Reaction Time Responses to First-Order and Second-Order Motion Claire the effect of temporal frequency and modulation depth on reaction times for discriminating the direction using equal multiples of direction-discrimination threshold. Results showed that reaction times were
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…
Li, Tiejun
2011-01-01
THE JOURNAL OF CHEMICAL PHYSICS 135, 024113 (2011) A weak second order tau-leaping method for chemical kinetic systems Yucheng Hu,a) Tiejun Li,b) and Bin Minc) Laboratory of Mathematics and Applied and Mattingly [Comm. Math. Sci. 9, 301 (2011)] proposed a method which can solve chemical Langevin equations
Nottingham, University of
Choice reaction times for identifying the direction of first-order motion and different varieties of the human visual system by measuring forced-choice reaction times for dis- criminating the drift direction of stimulus modulation depths. In general, reaction times for all types of second-order motion were slower
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.
Positronium formation as a three-body reaction. II. The second-order nuclear amplitudes
Shojaei, F.; Bolorizadeh, M. A.; Ghanbari-Adivi, E.; Brunger, M. J.
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.
Jaeger, E. F. [P.O. Box 2009, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States)] [P.O. Box 2009, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States); Berry, L. A. [P.O. Box 2009, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States)] [P.O. Box 2009, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States); Batchelor, D. B. [P.O. Box 2009, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States)] [P.O. Box 2009, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States)
2000-02-01
A comprehensive kinetic theory is developed to treat radio frequency (rf) driven plasma flow in one-dimensional geometry. The kinetic equation is expanded to second order in the perturbing rf electric field. No assumption is made regarding the smallness of the ion Larmor radius relative to wavelength. Moments of the second-order distribution function give time-averaged expressions for the rf-driven particle transport, forces, and heating, including the wave kinetic flux. On the transport time scale, the rf force in the poloidal direction is balanced by neoclassical viscosity, and the force in the radial direction is balanced by ambipolar electric fields. Comparison is made with previous theories which have relied on incompressible fluid approximations and a Reynolds stress model for the rf pressure. Substantial differences are seen in situations involving the ion Bernstein wave, which is compressional in nature. Linear electron Landau damping and magnetic pumping, by themselves, do not lead to significant poloidal flow. But ion cyclotron damping of either fast magnetosonic waves or ion Bernstein waves can drive significant flow at power levels typical of plasma heating experiments. (c)
A second-order accurate kinetic-theory-based method for inviscid compressible flows
NASA Technical Reports Server (NTRS)
Deshpande, Suresh M.
1986-01-01
An upwind method for the numerical solution of the Euler equations is presented. This method, called the kinetic numerical method (KNM), is based on the fact that the Euler equations are moments of the Boltzmann equation of the kinetic theory of gases when the distribution function is Maxwellian. The KNM consists of two phases, the convection phase and the collision phase. The method is unconditionally stable and explicit. It is highly vectorizable and can be easily made total variation diminishing for the distribution function by a suitable choice of the interpolation strategy. The method is applied to a one-dimensional shock-propagation problem and to a two-dimensional shock-reflection problem.
NASA Astrophysics Data System (ADS)
Mazur, O. Yu.; Stefanovich, L. I.; Yurchenko, V. M.
2015-07-01
The effect of hydrostatic pressure on the kinetics of the formation of electrical domains in ferroelectric materials that undergo second-order phase transitions has been considered. It has been shown using the example of triglycine sulfate ferroelectric crystals undergoing an order-disorder phase transition that the applied pressure increases the ordering temperature and thus accelerates the ordering process. It has been found that, by increasing the hydrostatic pressure applied to the sample after quenching, it is possible to obtain a single-domain state, instead of the multi-domain type of ordering. The evolution curves for the average value of the order parameter and its dispersion have been obtained by numerical integration. These curves indicate that quasi-stationary multi-domain structures of the asymmetric type can be formed at specially selected pressures. It has been established that the kinetics of the formation of electrical domains in ferroelectrics depends significantly on the initial relaxation conditions, which are determined by the technological prehistory of the quenching.
Maurer, Daphne M.
Longer VEP latencies and slower reaction times to the onset of second-order motion than to the onset of first-order motion D. Ellemberg a,b , K. Lavoie a , T.L. Lewis b , D. Maurer b , F. Lepore times to the onset of first- and second-order motion. The stimuli consisted of luminance
Hübner, U; Keller, S; Jekel, M
2013-11-01
The application of the R(CT)-concept for predicting the removal of trace organic compounds (TrOCs) in organic rich WWTP effluents is often problematic due to the fast ozone depletion with instantaneous ozone demand in the range of typically applied ozone dosages. In this study, the determination of OH-radical and ozone exposure from second order rate kinetics with two internal tracer substances was evaluated as alternative approach for these waters. Results from batch and semi-batch experiments showed a linear correlation of OH-radical exposure with ozone consumption, characterized by its slope indicating the formation efficiency of OH-radicals and a lag ozone consumption without significant formation of OH-radicals. Evaluation of data from the project PILOTOX on ozonation of secondary effluent confirmed reasonable prediction of ozone resistant compound removal from relative residual concentration of an internal tracer substance. In contrast, predicting the reduction of TrOCs by direct reactions with ozone from internal tracers was not feasible. Similar removal efficiencies for fast reacting compounds with different rate constants from k(O3) = 10(4) M(-1) s(-1) to k(O3) = 10(6) M(-1) s(-1) were observed indicating a limitation of the reaction by mass transfer. This effect was observed at low ozone dosages in semi-batch and pilot experiments as well as in batch experiments, where mass transfer from gas to liquid phase is not limiting. It is assumed that consumption of low ozone dosages is faster than sample homogenization in the batch reactors used. Thus, prediction of compound removal by direct reaction with ozone always needs to consider reactor design and geometry. PMID:24050684
NASA Astrophysics Data System (ADS)
Bolorizadeh, M. A.; Brunger, M. J.; Maddern, T.; Ghanbari Adivi, E.
2007-03-01
We derive the exact analytic form for the second-order positron-electron interaction term in the Faddeev three-body approach which is applicable in the nonrelativistic high energy region. Although there is no nonintegrable singularity in the six-dimensional integral form of this amplitude, here the basic difficulty arises from the presence of complex nonintegral exponents in the components included in the integrand. Consequently, three brunch cuts must be handled simultaneously. However, by using an integral representation of the gamma function, these brunch cuts are removed from the integrand. Expanding the radial parts of the initial and final wave functions further reduces the second-order positron-electron interaction term to a one-variable integral in terms of Bessel functions of the third kind. The different final closed expressions are ultimately derived in terms of the generalized hypergeometric functions for different regions of the scattering angle.
Cieslar, J H; Dobson, G P
2000-03-01
The relationship between free cytosolic [ADP] (and [P(i)]) and steady-state aerobic muscle work in rat gastrocnemius muscle in vivo using (31)P NMR was investigated. Anesthetized rats were ventilated and placed in a custom-built cradle fitted with a force transducer that could be placed into a 7-tesla NMR magnet. Muscle work was induced by supramaximal sciatic nerve stimulation that activated all fibers. Muscles were stimulated at 0.1, 0.2, 0.3, 0.4, 0.5, 0.8, 1.0, and 2.0 Hz until twitch force, phosphocreatine, and P(i) were unchanged between two consecutive spectra acquired in 4-min blocks (8-12 min). Parallel bench experiments were performed to measure total tissue glycogen, lactate, total creatine, and pyruvate in freeze-clamped muscles after 10 min of stimulation at each frequency. Up to 0.5 Hz, there was no significant change in muscle glycogen, lactate, and the lactate/pyruvate ratios between 8-12 min. At 0.8 Hz, there was a 17% fall in glycogen and a 65% rise in the muscle lactate with a concomitant fall in pH. Above this frequency, glycogen fell rapidly, lactate continued to rise, and ATP and pH declined. On the basis of these force and metabolic measurements, we estimated the maximal mitochondrial capacity (V(max)) to be 0.8 Hz. Free [ADP] was then calculated at each submaximal workload from measuring all the reactants of the creatine kinase equilibrium after adjusting the K'(CK) to the muscle temp (30 degrees C), pH, and pMg. We show that ADP (and P(i)) and tension-time integral follow a Hill relationship with at least a second order function. The K(0.5) values for free [ADP] and [P(i)] were 48 microM and 9 mM, respectively. Our data did not fit any form of the Michaelis-Menten equation. We therefore conclude that free cytosolic [ADP] and [P(i)] could potentially control steady-state oxidative phosphorylation in skeletal muscle in vivo. PMID:10692403
COMMUNICATIONS Kinetics of Coupling Reactions That Generate Monothiophosphate
Gopalan, Venkat
COMMUNICATIONS Kinetics of Coupling Reactions That Generate Monothiophosphate Disulfides 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
NASA Astrophysics Data System (ADS)
Tashiro, Hiroyuki; Aghanim, Nabila; Langer, Mathieu; Douspis, Marian; Zaroubi, Saleem; Jeli?, Vibor
2011-07-01
The measurement of the brightness temperature fluctuations of neutral hydrogen 21-cm lines from the epoch of reionization (EoR) is expected to be a powerful tool for revealing the reionization process. We study the 21-cm cross-correlation with cosmic microwave background (CMB) temperature anisotropies, focusing on the effect of the patchy reionization. We calculate, up to second order, the angular power spectrum of the cross-correlation between 21-cm fluctuations and the CMB kinetic Sunyaev-Zel'dovich effect (kSZ) from the EoR, using an analytical reionization model. We show that the kSZ and the 21-cm fluctuations are anti-correlated on the scale corresponding to the typical size of an ionized bubble at the observed redshift of the 21-cm fluctuations. The amplitude of the angular power spectrum of the cross-correlation depends on the fluctuations of the ionized fraction. Especially, in a highly inhomogeneous reionization model, the amplitude reaches the order of 100 ? K2 at ?˜ 3000. We also show that second-order terms may help in distinguishing between reionization histories.
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.
Johnny Espin
2015-09-19
It has been proposed several times in the past that one can obtain an equivalent, but in many aspects simpler description of fermions by first reformulating their first-order (Dirac) Lagrangian in terms of two-component spinors, and then integrating out the spinors of one chirality ($e.g.$ primed or dotted). The resulting new Lagrangian is second-order in derivatives, and contains two-component spinors of only one chirality. The new second-order formulation simplifies the fermion Feynman rules of the theory considerably, $e.g.$ the propagator becomes a multiple of an identity matrix in the field space. The aim of this thesis is to work out the details of this formulation for theories such as Quantum Electrodynamics, and the Standard Model of elementary particles. After having developed the tools necessary to establish the second-order formalism as an equivalent approach to spinor field theories, we proceed with some important consistency checks that the new formulation is required to pass, namely the presence or absence of anomalies in their perturbative and non-perturbative description, and the unitarity of the S-Matrix derived from their Lagrangian. Another aspect which is studied is unification, where we seek novel gauge-groups that can be used to embed all of the Standard Model content: forces and fermionic representations. Finally, we will explore the possibility to unify gravity and the Standard Model when the former is seen as a diffeomorphism invariant gauge-theory.
Espin, Johnny
2015-01-01
It has been proposed several times in the past that one can obtain an equivalent, but in many aspects simpler description of fermions by first reformulating their first-order (Dirac) Lagrangian in terms of two-component spinors, and then integrating out the spinors of one chirality ($e.g.$ primed or dotted). The resulting new Lagrangian is second-order in derivatives, and contains two-component spinors of only one chirality. The new second-order formulation simplifies the fermion Feynman rules of the theory considerably, $e.g.$ the propagator becomes a multiple of an identity matrix in the field space. The aim of this thesis is to work out the details of this formulation for theories such as Quantum Electrodynamics, and the Standard Model of elementary particles. After having developed the tools necessary to establish the second-order formalism as an equivalent approach to spinor field theories, we proceed with some important consistency checks that the new formulation is required to pass, namely the presence...
Blitz, M A; Green, N J B; Shannon, R J; Pilling, M J; Seakins, P W; Western, C M; Robertson, S H
2015-07-16
Rate coefficients for the CH3 + CH3 reaction, over the temperature range 300-900 K, have been corrected for errors in the absorption coefficients used in the original publication ( Slagle et al., J. Phys. Chem. 1988 , 92 , 2455 - 2462 ). These corrections necessitated the development of a detailed model of the B?(2)A1' (3s)-X?(2)A2? transition in CH3 and its validation against both low temperature and high temperature experimental absorption cross sections. A master equation (ME) model was developed, using a local linearization of the second-order decay, which allows the use of standard matrix diagonalization methods for the determination of the rate coefficients for CH3 + CH3. The ME model utilized inverse Laplace transformation to link the microcanonical rate constants for dissociation of C2H6 to the limiting high pressure rate coefficient for association, k?(T); it was used to fit the experimental rate coefficients using the Levenberg-Marquardt algorithm to minimize ?(2) calculated from the differences between experimental and calculated rate coefficients. Parameters for both k?(T) and for energy transfer ??E?down(T) were varied and optimized in the fitting procedure. A wide range of experimental data were fitted, covering the temperature range 300-2000 K. A high pressure limit of k?(T) = 5.76 × 10(-11)(T/298 K)(-0.34) cm(3) molecule(-1) s(-1) was obtained, which agrees well with the best available theoretical expression. PMID:25992467
NASA Astrophysics Data System (ADS)
Watanabe, T.; Sakai, Y.; Nagata, K.; Ito, Y.; Hayase, T.
2014-10-01
The reactive scalar field near the turbulent/non-turbulent (T/NT) interface is analyzed using a direct numerical simulation (DNS) of a planar jet with an isothermal second-order chemical reaction A + B ? P. Reactants A and B are supplied from the jet and ambient flows, respectively. The DNS of the reactive jet is performed for Damköhler numbers Da = 0.1, 1, and 10. A visualization of the T/NT interface shows that most of the product P is contained in the turbulent region. The conditional mean concentrations of the reactive species change sharply near the T/NT interface. The width of the jump in the conditional mean concentration is almost independent of the chemical species and the Damköhler number. For the slow reaction (Da = 0.1), the conditional average of the chemical production rate gradually increases from the non-turbulent region toward the turbulent region. In contrast, the conditional average of the production rate for Da = 1 and 10 has a large peak value slightly inside the T/NT interface. The chemical reaction near the T/NT interface strongly depends on the interface orientation. The reactant A is deficient near the T/NT interface. The production rate is large near the interface toward which the deficient reactant A is frequently transported by the velocity fields. The transport due to the velocity relative to the interface movement strongly depends on the relationship between the interface geometry and the mean flow field. The dependence of the chemical reaction on the interface orientation becomes strong as Da increases. When the interface propagates toward the non-turbulent region, the reactant A and product P are contained in the turbulent region although the molecular diffusion and reaction contribute to the increase in the concentrations of A (non-reactive case) and P in the non-turbulent region. In contrast, the interface propagation toward the turbulent region leaves the fluids containing A and P in the non-turbulent region.
Rapid reaction kinetic techniques.
Toseland, Christopher P; Geeves, Michael A
2014-01-01
Most biochemical processes occur on sub-second time scales. Relaxation and rapid mixing methods allow reactions from microsecond time scales onwards to be monitored in real time. This chapter describes the instrumentation for these techniques and it discusses general topics of sample excitation and signal detection. PMID:25095990
Lifeng Xu; Chi Li; K. Y. Simon Ng
2000-01-01
The effects of RF fields on the reaction kinetics of urethane formation in the presence of a catalyst, ionic compounds or polar solvents were studied using in situ Raman spectroscopy. Kinetics simulations based on a simple second-order reaction model were used to verify the reaction mechanism. A maximum reaction rate of about 10% per second for urethane formation with 100
Kinetics of actinide complexation reactions
Nash, K.L.; Sullivan, J.C.
1997-09-01
Though the literature records extensive compilations of the thermodynamics of actinide complexation reactions, the kinetics of complex formation and dissociation reactions of actinide ions in aqueous solutions have not been extensively investigated. In light of the central role played by such reactions in actinide process and environmental chemistry, this situation is somewhat surprising. The authors report herein a summary of what is known about actinide complexation kinetics. The systems include actinide ions in the four principal oxidation states (III, IV, V, and VI) and complex formation and dissociation rates with both simple and complex ligands. Most of the work reported was conducted in acidic media, but a few address reactions in neutral and alkaline solutions. Complex formation reactions tend in general to be rapid, accessible only to rapid-scan and equilibrium perturbation techniques. Complex dissociation reactions exhibit a wider range of rates and are generally more accessible using standard analytical methods. Literature results are described and correlated with the known properties of the individual ions.
NASA Astrophysics Data System (ADS)
Medien, H. A. A.
1998-02-01
A spectrophotometric method is described for the determination of amino acids. The method is based on the reaction between amino acids and syringaldehyde at pH 9.0, by which a color is developed with maximum absorption at 420 nm in aqueous methyl alcohol. The absorption of the product obeys Beer's law within the concentration range of 0.025-0.5 mM of original amino acid. The kinetics of the reaction follows overall second order kinetics, first order in each of the reactants. The rates of the reaction were investigated as a function of pH of the reaction medium and structure of the amino compounds. Logarithms of the second-order rate constants increased with amino acid anion concentration as the pH was increased. The mechanisms of the reaction have been discussed.
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.
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.
Meng, Hu; Li, Jiang-Yuan; Tang, Yong-Huai
2009-01-01
The virtual instrument system based on LabVIEW 8.0 for ion analyzer which can measure and analyze ion concentrations in solution is developed and comprises homemade conditioning circuit, data acquiring board, and computer. It can calibrate slope, temperature, and positioning automatically. When applied to determine the reaction rate constant by pX, it achieved live acquiring, real-time displaying, automatical processing of testing data, generating the report of results; and other functions. This method simplifies the experimental operation greatly, avoids complicated procedures of manual processing data and personal error, and improves veracity and repeatability of the experiment results. PMID:19730752
Laxson, William W; Finke, Richard G
2014-12-17
Nucleation initiates phase changes across nature. A fundamentally important, presently unanswered question is if nucleation begins as classical nucleation theory (CNT) postulates, with n equivalents of monomer A forming a "critical nucleus", A(n), in a thermodynamic (equilibrium) process. Alternatively, is a smaller nucleus formed at a kinetically limited rate? Herein, nucleation kinetics are studied starting with the nanoparticle catalyst precursor, [A] = [(Bu4N)5Na3(1,5-COD)Ir(I)·P2W15Nb3O62], forming soluble/dispersible, B = Ir(0)(?300) nanoparticles stabilized by the P2W15Nb3O62(9-) polyoxoanion. The resulting sigmoidal kinetic curves are analyzed using the 1997 Finke-Watzky (hereafter FW) two-step mechanism of (i) slow continuous nucleation (A ? B, rate constant k(1obs)), then (ii) fast autocatalytic surface growth (A + B ? 2B, rate constant k(2obs)). Relatively precise homogeneous nucleation rate constants, k(1obs), examined as a function of the amount of precatalyst, A, reveal that k(1obs) has an added dependence on the concentration of the precursor, k(1obs) = k(1obs(bimolecular))[A]. This in turn implies that the nucleation step of the FW two-step mechanism actually consists of a second-order homogeneous nucleation step, A + A ? 2B (rate constant, k(1obs(bimol))). The results are significant and of broad interest as an experimental disproof of the applicability of the "critical nucleus" of CNT to nanocluster formation systems such as the Ir(0)n one studied herein. The results suggest, instead, the experimentally-based concepts of (i) a kinetically effective nucleus and (ii) the concept of a first-observable cluster, that is, the first particle size detectable by whatever physical methods one is currently employing. The 17 most important findings, associated concepts, and conclusions from this work are provided as a summary. PMID:25479070
Factors Affecting Reaction Kinetics of Glucose Oxidase
NASA Astrophysics Data System (ADS)
Johnson, Kristin A.
2002-01-01
Basic principles of enzyme kinetics are demonstrated using the enzyme glucose oxidase. The glucose oxidase enzymatic reaction is coupled to horseradish peroxidase, which in turn catalyzes the oxidation of a dye to a bright blue-green color. The appearance of the blue-green dye is used to monitor the course of the reaction and is quite visible in a classroom setting. A series of reactions are arranged that vary the enzyme concentration, substrate concentration, temperature, and the substrate used in the reaction. By monitoring the rate of the color change in each beaker, the reaction kinetics of glucose oxidase in each series is observed.
Second-Order Fermions and the Standard Model
Johnny Espin
2015-01-31
We present a construction of a non-hermitian fermionic Lagrangian which has a second-order kinetic term. Despite the non-hermicity of the latter, the theory is unitary and the perturbation theory that can be derived is equivalent to the usual one derived from a first-order formalism. Having this in mind, the construction of a second-order Standard Model allows a more compact description of the theory. This work is based on [1, 2] and citations therein.
Second-Order Fermions and the Standard Model
Espin, Johnny
2015-01-01
We present a construction of a non-hermitian fermionic Lagrangian which has a second-order kinetic term. Despite the non-hermicity of the latter, the theory is unitary and the perturbation theory that can be derived is equivalent to the usual one derived from a first-order formalism. Having this in mind, the construction of a second-order Standard Model allows a more compact description of the theory. This work is based on [1, 2] and citations therein.
Rapid biocatalytic polytransesterification: Reaction kinetics in an exothermic reaction
Chaudhary, A.K.; Beckman, E.J.; Russell, A.J.
1998-08-20
Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. The authors have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization. Rate of polymerization increases with the concentration of monomers. This is also reflected by the increase in the temperature of the reaction mixture. Using time-temperature-conversion contours, a differential method of kinetic analysis was used to calculate the energy of activation ({approximately} 15.1 Kcal/mol).
Basic Chemical Principles 1: Reaction Kinetics
Schofield, Jeremy
#15; Orbitals come from quantum mechanics: electron has spin states #6;1=2 (spin up, spin down) #15Basic Chemical Principles 1: Reaction Kinetics Mechanism of a reaction is a sequence of basic; Pauli principle: If electrons have same spin, cannot be paired in same orbital #15; Electronic ground
Kinetic studies of atmospheric reactions
NASA Astrophysics Data System (ADS)
Hall, I. W.
Experiments to measure the rate coefficients for some reactions of atmospherically important radicals are described. The discharge flow technique couples with resonance fluorescence detection of OH was used to measure the rate constants for the reactions of OH radicals with molecular chlorine and bromine in the following reactions: (1) OH + Cl2 yields HOCl + Cl; and (2) OH + Br2 yields HOBr + Br. Rate constants were obtained at room temperature that were in agreement with previous results. The temperature dependence of the first reaction was found to be described by an Arrhenius expression, and for the second reaction, the results show greater scatter, so that the error limits associated with the Arrhenius parameters are large. Calculation of the collision frequency factor for the reaction of OH and Br2 allows more realisitc estimates of E(sub A) and A to be made. The discharge flow/resonance fluorescence technique was also used to determine the temperature dependences of OH + alkyne reactions. A possible pressure dependence of the interaction of OH with propyne was investigated with the constraints imposed by the use of a fast-flow apparatus; no variation of the rate constant with pressure was observed over the range 1.7 to 6.4 mmHg. The relative reactivity of the alkynes is discussed with both OH and NO3, and similar behavior is found in the reactions of the alkenes with OH, O, and NO3. Molecular modulation spectroscopy was used to measure the rate constant for the reaction HO2 + NO3 yields products. The temperature dependence of this reaction was studied. The absorption cross section of the nitrate radical is an important parameter in atmospheric monitoring and modeling, and in experimental measurements of NO3 concentration. Experiments performed using the molecular modulation apparatus in single-shot mode gave a value which agrees with the majority of published results. Other results from the investigation are presented.
Kinetic Studies of Atmospheric Reactions.
NASA Astrophysics Data System (ADS)
Hall, I. W.
Available from UMI in association with The British Library. Requires signed TDF. This thesis describes experiments to measure the rate coefficients for some reactions of atmospherically important radicals. The discharge flow technique coupled with resonance fluorescence detection of OH was used to measure the rate constants for the reactions of OH radicals with molecular chlorine and bromine. Rate constants were obtained at room temperature that were in agreement with previous results. For the reaction(UNFORMATTED TABLE OR EQUATION FOLLOWS)eqalign{rm OH + Cl_2&to rm HOCl + Cl,cr k _{rm A.1}rm(293 K) = (6.8 +/- 1.7)× 10^{-14} rm cm^3molecule^{-1}s ^{-1},cr}eqno{rm (A.1)}(TABLE/EQUATION ENDS)and for (UNFORMATTED TABLE OR EQUATION FOLLOWS) eqalign{rm OH + Br_2&to rm HOBr + Br,cr k_{rm A.2}rm(293 K) = (3.4+/- 1.5)× 10^{ -11} rm cm^3molecule^{ -1}s^{-1}.cr}eqno {rm (A.2)}(TABLE/EQUATION ENDS)The temperature dependence of reaction A.1 was found to be described by an Arrhenius expression of the form k_{rm A.1}(T)=(1.7_sp {-1.2}{+4.4})times10^{ -12} exp (-(914 +/- 373)/T) cm^3molecule ^{-1}s^ {-1}. For reaction A.2, the results show greater scatter, so that the error limits associated with the Arrhenius parameters are large. Calculation of the collision frequency factor for the reaction of OH with Br_2 allows more realistic estimates of E_{rm A} and A to be made:(UNFORMATTED TABLE OR EQUATION FOLLOWS)eqalign{&qquad qquadqquadrm 0<{it E} _{it A}/kJ mol^{ -1} < 5.5cr&rm 2.8 times 10^ {-11} < {it A}/cm^3molecule ^{-1}s^{-1} < 3.1 times 10^{-10}.cr}(TABLE/EQUATION ENDS)The discharge flow/resonance fluorescence technique was also used to determine the temperature dependences of OH + alkyne reactions. A possible pressure dependence of the interaction of OH with propyne was investigated within the constraints imposed by the use of a fast-flow apparatus; no variation of the rate constant with pressure was observed over the range 1.7-6.4 mmHg (227-853 Pa). The relative reactivity of the alkynes is discussed, both with OH and NO_3, and similar behaviour is found in the reactions of the alkenes with OH, O, and NO_3. Molecular modulation spectroscopy was used to measure the rate constant for the reaction rm HO_2 + NO_3to products.eqno {rm (A.3)}The temperature dependence of this reaction was studied. A small negative activation energy of (-1.4 +/- 2.2) kJ mol^{-1} is indicated by the results of computer fitting to the observed HO_2 and NO_3 waveforms over the temperature range 263-343 K, but the large error limits also allow for the possibility that the reaction is temperature independent. In that case, the average rate constant is ca. 4 times 10^{-12} cm ^3molecule^{-1} s^{-1}, in good agreement with the only other published value. The absorption cross section of the nitrate radical is an important parameter in atmospheric monitoring and modelling, and in experimental measurements of (NO _3). Experiments performed using the molecular modulation apparatus in single-shot mode gave sigma_{662}=(1.84+/-0.15)times10 ^{-17} cm^2molecule ^{-1}, a value which agrees with the majority of published results.
Reaction yields in intramolecular dissipative kinetics
NASA Astrophysics Data System (ADS)
Agmon, Noam; Levine, R. D.
1993-04-01
Intramolecular dissipation has recently been invoked by Schlag, Grotemeyer and Levine to interpret dynamical processes in highly excited large molecules. In such problems there is diffusive motion in the presence of a potential. In addition, there are two (or more) reaction processes which proceed at a finite rate. We present the solution of the Smoluchowski equation for the yields (branching fractions) of the reactions and consider its various limiting forms. When reaction is much faster than diffusion, the result of Schlag is recovered. In the opposite limit the reaction yield corresponds to that obtained from a simple kinetic scheme. The two limiting forms also correspond to "kinetic control" and "thermodynamic control" of physical organic chemistry. The derivation is equally valid if the source of dissipation is intermolecular.
Modeling the Enzyme Kinetic Reaction.
Atangana, Abdon
2015-09-01
The Enzymatic control reactions model was presented within the scope of fractional calculus. In order to accommodate the usual initial conditions, the fractional derivative used is in Caputo sense. The methodologies of the three analytical methods were used to derive approximate solution of the fractional nonlinear system of differential equations. Two methods use integral operator and the other one uses just an integral. Numerical results obtained exhibit biological behavior of real world problem. PMID:25930963
Yeung, Man-Chung
KINETICS, CATALYSIS, AND REACTION ENGINEERING Nonthermal Plasma Reactions of Dilute Nitrogen Oxide technical potential, the nonthermal plasma reactions and their kinetics are poorly understood the rate of the electron collision reactions, which de- pends on the electron energy distribution.4
Using of "pseudo-second-order model" in adsorption.
Ho, Yuh-Shan
2014-01-01
A research paper's contribution exists not only in its originality and creativity but also in its continuity and development for research that follows. However, the author easily ignores it. Citation error and quotation error occurred very frequently in a scientific paper. Numerous researchers use secondary references without knowing the original idea from authors. Sulaymon et al. (Environ Sci Pollut Res 20:3011-3023, 2013) and Spiridon et al. (Environ Sci Pollut Res 20:6367-6381, 2013) presented wrong pseudo-second-order models in Environmental Science and Pollution Research, vol. 20. This comment pointed the errors of the kinetic models and offered information for citing original idea of pseudo-second-order kinetic expression. In order to stop the proliferation of the mistake, it is suggested to cite the original paper for the kinetic model which provided greater accuracy and more details about the kinetic expression. PMID:24132523
Source of second order chromaticity in RHIC
Luo, Y.; Gu, X.; Fischer, W.; Trbojevic, D.
2011-01-01
In this note we will answer the following questions: (1) what is the source of second order chromaticities in RHIC? (2) what is the dependence of second order chromaticity on the on-momentum {beta}-beat? (3) what is the dependence of second order chromaticity on {beta}* at IP6 and IP8? To answer these questions, we use the perturbation theory to numerically calculate the contributions of each quadrupole and sextupole to the first, second, and third order chromaticities.
Second Order Vector Perturbations on Bouncing Universes
NASA Astrophysics Data System (ADS)
Mena, F. C.
Considering inflationary, ekpyrotic and “dust-like” models we have shown that second order vector perturbations provide new distinguishing observational features between those early univese scenarios.
Tóth, János
1976-01-01
Reaction Kinetics and Catalysis Letters, Vol, 4, No. 1, 81-85 (1976) STOCHASTIC REACTION KINETICS the deterministic and stochastic models of a complex chemical reaction are presented. Indications are given about the possible development of a quasi-thermodynamic theory of reaction kinetics by the aid of stochastic
NASA Astrophysics Data System (ADS)
Medien, H. A. A.
1996-11-01
A new and sensitive spectrophotometric method is described for the determination of p-benzoquinone, p-chloranil and 1.4-naphthoquinone. The method is based on the reaction between quinones and barbituric acid, by which a color is developed with maximum absorption between 485 and 555 nm in 50% methyl alcohol-water mixture. The absorption of the product obeys Beer's law within the concentration range 0.025-05 mM of orginal quinone. The kinetics of the reaction between p-benzoquinone and barbituric acid was studied in a range of methyl alcohol-water mixtures. The reaction follows overall second order kinetics, first order in each of the reactants. The rate increases with increasing dielectric constant. The method was applied for determination of barbituric acid with p-benzoquinone in the concentration range of 0.025-0.345 mM. Other barbiturates do not interfere.
The second-order gravitational red shift
NASA Technical Reports Server (NTRS)
Jaffe, J.
1973-01-01
The direct measurement of the nonlinear term of the gravitational field equations by using very stable clocks is discussed along with measuring the perhelion advance of a planet or satellite. These are considered measurements of the second-order gravitational red shift. The exact expression for the frequency shift of light in a gravitational field is derived. Other topics discussed include: The Doppler-cancelling technique; the second-order red shift in a spherically symmetric gravitational field; finite signal transit time; and the reality and interpretation of coordinates in the second-order red shift experiment.
Second-order gravitational self-force.
Pound, Adam
2012-08-01
Using a rigorous method of matched asymptotic expansions, I derive the equation of motion of a small, compact body in an external vacuum spacetime through second order in the body's mass (neglecting effects of internal structure). The motion is found to be geodesic in a certain locally defined regular geometry satisfying Einstein's equation at second order. I outline a method of numerically obtaining both the metric of that regular geometry and the complete second-order metric perturbation produced by the body. PMID:23006161
Second-Order-Potential Analysis and Optimization
NASA Technical Reports Server (NTRS)
Clever, W. C.
1986-01-01
Optimum camber designed for supersonic and hypersonic vehicles. Second Order Potential Analysis and Optimization (SOPA) package set of computer programs used to predict aerodynamic characteristics and design optimum camber for both supersonic and hypersonic vehicles. Analysis program incorporates second-order-potential, small-disturbance theory for analysis of wing/body configurations. Optimization program uses analysis results to generate optimum camber, twist, or flap deflections by minimizing zero suction drag. SOPA written in FORTRAN V for batch execution.
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 COCO2 reaction with iron oxide containing slags
Mansoor Barati Sedeh
2006-01-01
The reaction between CO-CO2 gases and metallurgical slags is one of the most crucial reactions in metal production and refining processes. However, a full understanding of the reaction kinetics has not been achieved due to the complex effect of different variables. The aim of the present study was to obtain a consistent and comprehensive picture of the reaction kinetics. ^
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 Dynamics Through Kinetic Transition States
NASA Astrophysics Data System (ADS)
Çiftçi, Ünver; Waalkens, Holger
2013-06-01
The transformation of a system from one state to another is often mediated by a bottleneck in the system’s phase space. In chemistry, these bottlenecks are known as transition states through which the system has to pass in order to evolve from reactants to products. The chemical reactions are usually associated with configurational changes where the reactants and products states correspond, e.g., to two different isomers or the undissociated and dissociated state of a molecule or cluster. In this Letter, we report on a new type of bottleneck which mediates kinetic rather than configurational changes. The phase space structures associated with such kinetic transition states and their dynamical implications are discussed for the rotational vibrational motion of a triatomic molecule. An outline of more general related phase space structures with important dynamical implications is given.
Reaction kinetics of dolomite rim growth
NASA Astrophysics Data System (ADS)
Helpa, V.; Rybacki, E.; Abart, R.; Morales, L. F. G.; Rhede, D.; Je?ábek, P.; Dresen, G.
2014-04-01
Reaction rims of dolomite (CaMg[CO3]2) were produced by solid-state reactions at the contacts of oriented calcite (CaCO3) and magnesite (MgCO3) single crystals at 400 MPa pressure, 750-850 °C temperature, and 3-146 h annealing time to determine the reaction kinetics. The dolomite reaction rims show two different microstructural domains. Elongated palisades of dolomite grew perpendicular into the MgCO3 interface with length ranging from about 6 to 41 µm. At the same time, a 5-71 µm wide rim of equiaxed granular dolomite grew at the contact with CaCO3. Platinum markers showed that the original interface is located at the boundary between the granular and palisade-forming dolomite. In addition to dolomite, a 12-80 µm thick magnesio-calcite layer formed between the dolomite reaction rims and the calcite single crystals. All reaction products show at least an axiotactic crystallographic relationship with respect to calcite reactant, while full topotaxy to calcite prevails within the granular dolomite and magnesio-calcite. Dolomite grains frequently exhibit growth twins characterized by a rotation of 180° around one of the equivalent axis. From mass balance considerations, it is inferred that the reaction rim of dolomite grew by counter diffusion of MgO and CaO. Assuming an Arrhenius-type temperature dependence, activation energies for diffusion of CaO and MgO are E a (CaO) = 192 ± 54 kJ/mol and E a (MgO) = 198 ± 44 kJ/mol, respectively.
Reaction rates for mesoscopic reaction-diffusion kinetics
NASA Astrophysics Data System (ADS)
Hellander, Stefan; Hellander, Andreas; Petzold, Linda
2015-02-01
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 scale-dependent 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 Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on 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. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.
Reaction rates for mesoscopic reaction-diffusion kinetics.
Hellander, Stefan; Hellander, Andreas; Petzold, Linda
2015-02-01
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 scale-dependent 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 Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on 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. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results. PMID:25768640
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.
Nine Practices of Second Order Schools
ERIC Educational Resources Information Center
Brown, Bill; Tucker, Patrick; Williams, Thomas L.
2012-01-01
Many schools are in some stage of implementing differentiated instruction, with some already in what Carol Tomlinson describes in "The Differentiated School" as "second order change," where the entire school practices differentiation. In high-performing schools, differentiation has proved to be an effective instructional strategy; in classroom…
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 Conditioning in "Drosophila"
ERIC Educational Resources Information Center
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…
Challenges for an enzymatic reaction kinetics database.
Wittig, Ulrike; Rey, Maja; Kania, Renate; Bittkowski, Meik; Shi, Lei; Golebiewski, Martin; Weidemann, Andreas; Müller, Wolfgang; Rojas, Isabel
2014-01-01
The scientific literature contains a tremendous amount of kinetic data describing the dynamic behaviour of biochemical reactions over time. These data are needed for computational modelling to create models of biochemical reaction networks and to obtain a better understanding of the processes in living cells. To extract the knowledge from the literature, biocurators are required to understand a paper and interpret the data. For modellers, as well as experimentalists, this process is very time consuming because the information is distributed across the publication and, in most cases, is insufficiently structured and often described without standard terminology. In recent years, biological databases for different data types have been developed. The advantages of these databases lie in their unified structure, searchability and the potential for augmented analysis by software, which supports the modelling process. We have developed the SABIO-RK database for biochemical reaction kinetics. In the present review, we describe the challenges for database developers and curators, beginning with an analysis of relevant publications up to the export of database information in a standardized format. The aim of the present review is to draw the experimentalist's attention to the problem (from a data integration point of view) of incompletely and imprecisely written publications. We describe how to lower the barrier to curators and improve this situation. At the same time, we are aware that curating experimental data takes time. There is a community concerned with making the task of publishing data with the proper structure and annotation to ontologies much easier. In this respect, we highlight some useful initiatives and tools. PMID:24165050
Anaerobic corrosion reaction kinetics of nanosized iron.
Reardon, Eric J; Fagan, Randal; Vogan, John L; Przepiora, Andrzej
2008-04-01
Nanosized Fe0 exhibits markedly different anaerobic corrosion rates in water compared to that disseminated in moist quartz sand. In water, hydrogen production from corrosion exhibits an autocatalytic style, attaining a maximum rate of 1.9 mol kg(-1) d(-1) within 2 d of reaction. The rate then drops sharply over the next 20 d and enters a period of uniformly decreasing rate, represented equally well by first-order or diffusion-controlled kinetic expressions. In quartz sand, hydrogen production exhibits a double maximum over the first 20 d, similar to the hydration reaction of Portland cement, and the highest rate attained is less than 0.5 mol kg(-1) d(-1). We ascribe this difference in early time corrosion behavior to the ability of the released hydrogen gas to convect both water and iron particles in an iron/water system and to its inability to do so when the iron particles are disseminated in sand. By 30 d, the hydrogen production rate of iron in quartz sand exhibits a uniform decrease as in the iron/water system, which also can be described by first-order or diffusion-controlled kinetic expressions. However, the corrosion resistance of the iron in moist sand is 4 times greater than in pure water (viz. t1/2 of 365 d vs 78 d, respectively). The lower rate for iron in sand is likely due to the effect of dissolved silica sorbing onto iron reaction sites and acting as an anodic inhibitor, which reduces the iron's susceptibility to oxidation by water. This study indicates that short-term laboratory corrosion tests of nanosized Fe0/water slurries will substantially underestimate both the material's longevity as an electron source and its potential as a long-term source of hydrogen gas in groundwater remediation applications. PMID:18504975
[Kinetics modeling and reaction mechanism of ferrate(VI) oxidation of triclosan].
Yang, Bin; Ying, Guang-Guo; Zhao, Jian-Liang
2011-09-01
Triclosan (TCS) is a broad-spectrum antibacterial agent widely used in many personal care products. We investigated oxidation of TCS by aqueous ferrate Fe(VI) to determine reaction kinetics, interpreted the reaction mechanism by a linear free-energy relationship, and evaluated the degradation efficiency. Second-order reaction kinetics was used to model Fe (VI) oxidation of TCS, with the apparent second-order rate constant (k(app)) being 531.9 L x (mol x s)(-1) at pH 8.5 and (24 +/- 1) degrees C. The half life (t1/2) is 25.8 s for an Fe( VI) concentration of 10 mg x L(-1). The rate constants of the reaction decrease with increasing pH values. These pH-dependent variations in k(app) could be distributed by considering species-specific reactions between Fe(VI) species and acid-base species of an ionizable TCS. Species-specific second-order reaction rate constants, k, were determined for reaction of HFeO4(-) with each of TCS's acid-base species. The value of k determined for neutral TCS was (4.1 +/- 3.5) x 10(2) L x (mol x s)(-1), while that measured for anionic TCS was (1.8 +/- 0.1) x 10(4) L x (mol x s)(-1). The reaction between HFeO4(-) and the dissociated TCS controls the overall reaction. A linear free-energy relationship illustrated the electrophilic oxidation mechanism. Fe (VI) reacts initially with TCS by electrophilic attack at the latter's phenol moiety. At a n[Fe(VI)]: n(TCS) > 7: 1, complete removal of TCS was achieved. And lower concentration of the humic acid could enhance the k(app) of Fe( VI) with TCS. In conclusion, Fe(VI) oxidation technology appears to be a promising tool for applications of WWTPs effluents and other decontamination processes. PMID:22165218
Kinetics investigations of atmospheric chemical reactions
Hills, A.J.
1987-01-01
Two separate gas-phase kinetics investigations were performed using a low-pressure fast-flow system with mass spectrometer detection. The first part of this research was a study of the atmospheric reactivity of diatomic sulfur, S/sub 2/. Rates of the reactions of sulfur with O, O/sub 2/, O/sub 3/, N/sub 2/O, NO, and NO/sub 2/ were investigated at 409 K and low pressure (0.89-3.0 Torr) in a discharge-flow system with mass spectrometric detection. The second investigation involves a study of the synergistic coupling of atmospheric bromine and chlorine chemistry. Recent measurements of ozone in the stratosphere over Antarctica have shown that the springtime ozone column decreased by 40% from 1960 to 1985. Both dynamical and chemical theories have been advanced to explain the formation of the Antarctic ozone hole. Prominent among these theories is that a synergistic interaction between gas-phase BrO and ClO radicals may be responsible for springtime ozone loss. The overall rate constant for the reaction, BrO + ClO ..-->.. Br + OClO ..-->.. Br + Cl + O/sub 2/ ..-->.. BrCl + O/sub 2/, has been measured over the temperature range 241-408 K. The rate constant for the overall reaction equals (8.2 +/- 1.0) 10/sup -12/ cm/sup 3//molecule s, independent of temperature.
Calculating Second-Order Effects in MOSFET's
NASA Technical Reports Server (NTRS)
Benumof, Reuben; Zoutendyk, John A.; Coss, James R.
1990-01-01
Collection of mathematical models includes second-order effects in n-channel, enhancement-mode, metal-oxide-semiconductor field-effect transistors (MOSFET's). When dimensions of circuit elements relatively large, effects neglected safely. However, as very-large-scale integration of microelectronic circuits leads to MOSFET's shorter or narrower than 2 micrometer, effects become significant in design and operation. Such computer programs as widely-used "Simulation Program With Integrated Circuit Emphasis, Version 2" (SPICE 2) include many of these effects. In second-order models of n-channel, enhancement-mode MOSFET, first-order gate-depletion region diminished by triangular-cross-section deletions on end and augmented by circular-wedge-cross-section bulges on sides.
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.
Second-Order Invariants and Holography
NASA Astrophysics Data System (ADS)
Luongo, Orlando; Bonanno, Luca; Iannone, Gerardo
2012-12-01
Motivated by recent works on the role of the holographic principle in cosmology, we relate a class of second-order Ricci invariants to the IR cutoff characterizing the holographic dark energy density. The choice of second-order invariants provides an invariant way to account the problem of causality for the correct cosmological cutoff, since the presence of event horizons is not an a priori assumption. We find that these models work fairly well, by fitting the observational data, through a combined cosmological test with the use of SNeIa, BAO and CMB. This class of models is also able to overcome the fine-tuning and coincidence problems. Finally, to make a comparison with other recent models, we adopt the statistical tests AIC and BIC.
Spacetime encodings. III. Second order Killing tensors
Brink, Jeandrew [Theoretical Astrophysics, California Institute of Technology, Pasadena, California 91103 (United States)
2010-01-15
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.
Reaction kinetics of paddy husk thermal decomposition
Jain, A.K.; Sharma, S.K.; Singh, D. [Panjab Univ., Chandigarh (India). Energy Research Center
1996-12-31
Paddy husk production in world is estimated to be around 80 million tons. It has a calorific value of 15 MJ/kg and thus has a tremendous potential as a renewable energy source. Its current uses are: cattle feed, raw material for paper and board, furfural production and silica industries. A large quantity of paddy husk is used in husk fired boiler furnaces at a very low efficiency. For efficient design of husk fired furnaces, reliable data on thermal characteristics of rice husk is essential which is lacking in the literature. In the present study, paddy husk was subjected to Thermogravimetric Analysis at heating rates of 10 and 100 C/min. in a thermal analyzer. The analysis was carried out in air and mixture of oxygen and nitrogen (5:95%) atmosphere. Reaction kinetic parameters such as activation energy, frequency factor and order of reaction have been evaluated and reported. These are relevant to the design of paddy husk fired gasifiers, furnaces and other thermochemical conversion equipment. The results of the thermochemical studies and their potential applications are presented in the paper.
Modeling the Kinetics of Bimolecular Reactions Antonio Fernandez-Ramos
Truhlar, Donald G
-Phase Thermal Reactions 4518 2.1. Thermodynamics: Enthalpies and Free Energies of Reaction 4518 2.2. Kinetics diffusion control and equilibrium and nonequilib- rium solvation. 2. Gas-Phase Thermal Reactions 2.1. Thermodynamics: Enthalpies and Free Energies of Reaction The rate constant (or, equivalently, rate coefficient
A Case Study in Chemical Kinetics: The OH + CO Reaction.
ERIC Educational Resources Information Center
Weston, Ralph E., Jr.
1988-01-01
Reviews some important properties of the bimolecular reaction between the hydroxyl radical and carbon monoxide. Investigates the kinetics of the reaction, the temperature and pressure dependence of the rate constant, the state-to-state dynamics of the reaction, and the reverse reaction. (MVL)
Slowly rotating scalar field wormholes: The second order approximation
Kashargin, P. E.; Sushkov, S. V.
2008-09-15
We discuss rotating wormholes in general relativity with a scalar field with negative kinetic energy. To solve the problem, we use the assumption about slow rotation. The role of a small dimensionless parameter plays the ratio of the linear velocity of rotation of the wormhole's throat and the velocity of light. We construct the rotating wormhole solution in the second-order approximation with respect to the small parameter. The analysis shows that the asymptotical mass of the rotating wormhole is greater than that of the nonrotating one, and the null energy condition violation in the rotating wormhole spacetime is weaker than that in the nonrotating one.
Understanding Chemical Reaction Kinetics and Equilibrium with Interlocking Building Blocks
ERIC Educational Resources Information Center
Cloonan, Carrie A.; Nichol, Carolyn A.; Hutchinson, John S.
2011-01-01
Chemical reaction kinetics and equilibrium are essential core concepts of chemistry but are challenging topics for many students, both at the high school and undergraduate university level. Visualization at the molecular level is valuable to aid understanding of reaction kinetics and equilibrium. This activity provides a discovery-based method to…
Second-order (2 +1 ) -dimensional anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Bazow, Dennis; Heinz, Ulrich; Strickland, Michael
2014-11-01
We present a complete formulation of second-order (2 +1 ) -dimensional anisotropic hydrodynamics. The resulting framework generalizes leading-order anisotropic hydrodynamics by allowing for deviations of the one-particle distribution function from the spheroidal form assumed at leading order. We derive complete second-order equations of motion for the additional terms in the macroscopic currents generated by these deviations from their kinetic definition using a Grad-Israel-Stewart 14-moment ansatz. The result is a set of coupled partial differential equations for the momentum-space anisotropy parameter, effective temperature, the transverse components of the fluid four-velocity, and the viscous tensor components generated by deviations of the distribution from spheroidal form. We then perform a quantitative test of our approach by applying it to the case of one-dimensional boost-invariant expansion in the relaxation time approximation (RTA) in which case it is possible to numerically solve the Boltzmann equation exactly. We demonstrate that the second-order anisotropic hydrodynamics approach provides an excellent approximation to the exact (0+1)-dimensional RTA solution for both small and large values of the shear viscosity.
Second-order (2+1)-dimensional anisotropic hydrodynamics
Dennis Bazow; Ulrich W. Heinz; Michael Strickland
2014-09-19
We present a complete formulation of second-order (2+1)-dimensional anisotropic hydrodynamics. The resulting framework generalizes leading-order anisotropic hydrodynamics by allowing for deviations of the one-particle distribution function from the spheroidal form assumed at leading order. We derive complete second-order equations of motion for the additional terms in the macroscopic currents generated by these deviations from their kinetic definition using a Grad-Israel-Stewart 14-moment ansatz. The result is a set of coupled partial differential equations for the momentum-space anisotropy parameter, effective temperature, the transverse components of the fluid four-velocity, and the viscous tensor components generated by deviations of the distribution from spheroidal form. We then perform a quantitative test of our approach by applying it to the case of one-dimensional boost-invariant expansion in the relaxation time approximation (RTA) in which case it is possible to numerically solve the Boltzmann equation exactly. We demonstrate that the second-order anisotropic hydrodynamics approach provides an excellent approximation to the exact (0+1)-dimensional RTA solution for both small and large values of the shear viscosity.
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
Robust stability of second-order systems
NASA Technical Reports Server (NTRS)
Chuang, C. H.
1993-01-01
This report presents a robust control design using strictly positive realness for second-order dynamic systems. The robust strictly positive real controller allows the system to be stabilized with only acceleration measurements. An important property of this design is that stabilization of the system is independent of the system parameters. The control design connects a virtual system to the given plant. The combined system is positive real regardless of system parameter uncertainty. Then any strictly positive real controllers can be used to achieve robust stability. A spring-mass system example and its computer simulations are presented to demonstrate this controller design.
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
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{sub 2} 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.
Kinetic Study of the Heck Reaction: An Interdisciplinary Experiment
ERIC Educational Resources Information Center
Gozzi, Christel; Bouzidi, Naoual
2008-01-01
The aim of this experiment is to study and calculate the kinetic constant of a Heck reaction: the arylation of but-3-en-2-ol by iodobenzene catalyzed by palladium acetate in presence of triethylamine in DMF. The reaction leads to a mixture of two ketones. Students use GC analysis to quantify reagents and products of reaction. They control the…
Second order cosmological perturbations: a minimal approach
Uggla, Claes
2012-01-01
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. Our goal in this paper is to derive the governing equations for second order perturbations of Friedmann-Lemaitre cosmologies in gauge-invariant form in a way that is minimal, as regards amount of calculation and length of expressions, and flexible, as regards choice of gauge and stress-energy tensor. We specialize our general equations to two gauges, the Poisson gauge and the uniform curvature gauge, obtaining equations that are significantly simpler than those in the literature when comparisons can be made, due firstly to our choice of variables, and secondly to our use of differential operators and mode extraction operators.
Second order formalism in Poincare gauge theory
M. Leclerc
2006-09-26
Changing the set of independent variables of Poincare gauge theory and considering, in a manner similar to the second order formalism of general relativity, the Riemannian part of the Lorentz connection as function of the tetrad field, we construct theories that do not contain second or higher order derivatives in the field variables, possess a full general relativity limit in the absence of spinning matter fields, and allow for propagating torsion fields in the general case. A concrete model is discussed and the field equations are reduced by means of a Yasskin type ansatz to a conventional Einstein-Proca system. Approximate solutions describing the exterior of a spin polarized neutron star are prsented and the possibility of an experimental detection of the torsion fields is briefly discussed.
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
The surface reaction kinetics of salicylate on alumina
Wang, Z.; Ainsworth, C.C.; Friedrich, D.M.; Joly, A.G.; Gassman, P.L. [Pacific Northwest National Lab., Richland, WA (United States)
1997-12-31
The kinetics of reaction of salicylate with colloidal alumina in aqueous suspension and with Al(III) in homogeneous aqueous solution were studied by stopped-flow laser fluorescence spectroscopy. The emission spectra confirmed the formation of both monodentate complexes and more stable bidentate chelates. Temporal evolution of the spectra indicated that the reaction was fast (within first few minutes) for both the homogeneous and heterogeneous reactions but slowed down afterwards for the latter. Reactions completed within 10 minutes in homogeneous phase at pH 3.3 but took more than 12 hours in alumina suspension. Analysis of the fluorescence intensity within first four minutes showed that in homogeneous phase the reaction followed a single pseudo-first-order kinetics. In alumina suspension log plots were nonlinear and characteristic of multiple heterogeneous reaction paths. The kinetics are interpreted in terms of the simultaneous formation of multiple species as well as subsequent conversion between species.
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...
Reaction Kinetics: An Experiment for Biochemistry and Organic Chemistry Laboratories.
ERIC Educational Resources Information Center
Ewing, Sheila
1982-01-01
Describes an experiment to examine the kinetics of carbamate decomposition and the effect of buffer catalysis on the reaction. Includes background information, laboratory procedures, evaluation of data, and teaching suggestions. (Author/JN)
Quantitative evaluation of biological reaction kinetics in confined nanospaces.
Yu, Jiachao; Luo, Peicheng; Xin, Chuanxian; Cao, Xiaodong; Zhang, Yuanjian; Liu, Songqin
2014-08-19
Evaluating the kinetics of biological reaction occurring in confined nanospaces is of great significance in studying the molecular biological processes in vivo. Herein, we developed a nanochannel-based electrochemical reactor and a kinetic model to investigate the immunological reaction in confined nanochannels simply by the electrochemical method. As a result, except for the reaction kinetic constant that was previously studied, more insightful kinetic information such as the moving speed of the antibody and the immunological reaction progress in nanochannels were successfully revealed in a quantitative way for the first time. This study would not only pave the investigation of molecular biological processes in confined nanospaces but also be promising to extend to other fields such as biological detection and clinical diagnosis. PMID:25034149
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 modeling of electro-Fenton reaction in aqueous solution
H. Liu; X. Z. Li; Y. J. Leng; C. Wang
2007-01-01
To well describe the electro-Fenton (E-Fenton) reaction in aqueous solution, a new kinetic model was established according to the generally accepted mechanism of E-Fenton reaction. The model has special consideration on the rates of hydrogen peroxide (H2O2) generation and consumption in the reaction solution. The model also embraces three key operating factors affecting the organic degradation in the E-Fenton reaction,
Sreedhara, S.; Huh, Kang Y.
2005-12-01
The performance of second-order conditional moment closure (CMC) depends on models to evaluate conditional variances and covariances of temperature and species mass fractions. In this paper the closure schemes based on the steady laminar flamelet model (SLFM) are validated against direct numerical simulation (DNS) involving extinction and ignition. Scaling is performed to reproduce proper absolute magnitudes, irrespective of the origin of mismatch between local flamelet structures and scalar dissipation rates. DNS based on the pseudospectral method is carried out to study hydrogen-air combustion with a detailed kinetic mechanism, in homogeneous, isotropic, and decaying turbulent media. Lewis numbers are set equal to unity to avoid complication of differential diffusion. The SLFM-based closures for correlations among fluctuations of reaction rate, scalar dissipation rate, and species mass fractions show good comparison with DNS. The variance parameter in lognormal PDF and the constants in the dissipation term have been estimated from DNS results. Comparison is made for the resulting conditional profiles from DNS, first-order CMC, and second-order CMC with correction to the most critical reaction step according to sensitivity analysis. Overall good agreement ensures validity of the SLFM-based closures for modeling conditional variances and covariances in second-order CMC.
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.
A study of the Sabatier-methanation reaction kinetics
NASA Technical Reports Server (NTRS)
Verostko, C. E.; Forsythe, R. K.
1974-01-01
The kinetics of the Sabatier methanation reaction, the reduction of carbon dioxide with hydrogen to methane and water, was investigated for 58 percent nickel on kieselguhr catalyst and 20 percent ruthenium on alumina catalyst. Differential rate data from an experimental program were correlated with a power function rate equation both for forward and reverse reactions. The kinetic parameters of activation energy, frequency rate constant and reaction order were determined for the rate equation. The values of these parameters were obtained from an Arrhenius plot of the experimental differential rate data. Also the carbon monoxide side reaction effect was measured and included in the correlation of parameters. The reaction was found to fit the rate equation experimentally within the temperature range 421 K, where the reaction effectively begins, the 800 K where the reaction rate drops and departs from the rate equation form.
Implementation of high throughput experimentation techniques for kinetic reaction testing.
Nagy, Anton J
2012-02-01
Successful implementation of High throughput Experimentation (EE) tools has resulted in their increased acceptance as essential tools in chemical, petrochemical and polymer R&D laboratories. This article provides a number of concrete examples of EE systems, which have been designed and successfully implemented in studies, which focus on deriving reaction kinetic data. The implementation of high throughput EE tools for performing kinetic studies of both catalytic and non-catalytic systems results in a significantly faster acquisition of high-quality kinetic modeling data, required to quantitatively predict the behavior of complex, multistep reactions. PMID:21902639
Chemical kinetics computer program for static and flow reactions
NASA Technical Reports Server (NTRS)
Bittker, D. A.; Scullin, V. J.
1972-01-01
General chemical kinetics computer program for complex gas mixtures has been developed. Program can be used for any homogeneous reaction in either one dimensional flow or static system. It is flexible, accurate, and easy to use. It can be used for any chemical system for which species thermodynamic data and reaction rate constant data are known.
Kinetics Feasibility Study of Alcohol Sulfate Esterification Reactions in
Elrod, Matthew J.
, 2008. Revised manuscript received March 25, 2008. Accepted March 25, 2008. Sulfate esters have recently and sulfuric acid to form sulfate esters in aerosol particles is explored. Nuclear magnetic resonance methods were used to monitor the bulk reaction kinetics of sulfate esterification reactions for a number
Kinetic mechanism for modeling of electrochemical reactions
NASA Astrophysics Data System (ADS)
?ervenka, Petr; Hrdli?ka, Ji?í; P?ibyl, Michal; Šnita, Dalimil
2012-04-01
We propose a kinetic mechanism of electrochemical interactions. We assume fast formation and recombination of electron donors D- and acceptors A+ on electrode surfaces. These mediators are continuously formed in the electrode matter by thermal fluctuations. The mediators D- and A+, chemically equivalent to the electrode metal, enter electrochemical interactions on the electrode surfaces. Electrochemical dynamics and current-voltage characteristics of a selected electrochemical system are studied. Our results are in good qualitative agreement with those given by the classical Butler-Volmer kinetics. The proposed model can be used to study fast electrochemical processes in microsystems and nanosystems that are often out of the thermal equilibrium. Moreover, the kinetic mechanism operates only with the surface concentrations of chemical reactants and local electric potentials, which facilitates the study of electrochemical systems with indefinable bulk.
Fluid flow and chemical reaction kinetics in metamorphic systems
Lasaga, A.C.; Rye, D.M. )
1993-05-01
The treatment and effects of chemical reaction kinetics during metamorphism are developed along with the incorporation of fluid flow, diffusion, and thermal evolution. The interplay of fluid flow and surface reaction rates, the distinction between steady state and equilibrium, and the possible overstepping of metamorphic reactions are discussed using a simple analytic model. This model serves as an introduction to the second part of the paper, which develops a reaction model that solves the coupled temperature-fluid flow-chemical composition differential equations relevant to metamorphic processes. Consideration of stable isotopic evidence requires that such a kinetic model be considered for the chemical evolution of a metamorphic aureole. A general numerical scheme is discussed to handle the solution of the model. The results of this kinetic model allow us to reach several important conclusions regarding the factors controlling the chemical evolution of mineral assemblages during a metamorphic event. 41 refs., 19 figs., 5 tabs.
Reaction kinetics in a tight spot.
Biham, Ofer; Krug, Joachim; Lipshtat, Azi; Michely, Thomas
2005-05-01
The standard analysis of reaction networks based on deterministic rate equations fails in confined geometries, commonly encountered in fields such as astrochemistry, thin-film growth and cell biology. In these systems the small reactant population implies anomalous behavior of reaction rates, which can be accounted for only by following the full distribution of reactant numbers. PMID:17193475
Calcite Reaction Kinetics in Saline Waters
Finneran, David
2012-02-14
and oversaturated conditions. First order kinetics were found sufficient to describe the dissolution rate data. Dissolution rates decreased with increasing I and were faster in KCl than NaCl solutions at the same I indicating that Na^ interacts more strongly...
Oxidation of diclofenac by potassium ferrate (VI): reaction kinetics and toxicity evaluation.
Wang, Yingling; Liu, Haijin; Liu, Guoguang; Xie, Youhai; Gao, Shuyan
2015-02-15
The reaction kinetics and toxicity of diclofenac (DCF) oxidation by ferrate (VI) under simulated water disinfection conditions were investigated. Experimental results indicated that the reaction between DCF and Fe(VI) followed first-order kinetics with respect to each reactant. Furthermore, the effects of pH and temperature on DCF oxidation by Fe(VI) were elucidated using a systematic examination. The apparent second-order rate constants (kapp) increased significantly from 2.54 to 11.6M(-1)s(-1), as the pH of the solution decreased from 11.0 to 7.0, and the acid-base equilibriums of Fe(VI) and DCF were proposed to explain the pH dependence of kapp. The acute toxicity of DCF solution during Fe(VI) oxidation was evaluated using a Microtox bioassay. Overall, the DCF degradation process resulted in a rapid increase of the inhibition rate of luminescent bacteria. These toxicity tests suggest that the formation of enhanced toxic intermediates during the Fe(VI) disinfection process may pose potential health risk to consumers. PMID:25460958
Oscillation criteria for a forced second order nonlinear dynamic equation
Logan, David
Oscillation criteria for a forced second order nonlinear dynamic equation L. Erbe, A. Peterson, we will establish some new interval oscillation cri- teria for forced second-order nonlinear dynamic with oscillation of the second-order 1 #12;2 ERBE, PETERSON, AND SAKER nonlinear dynamic equation of Emden
The Kinetic Rate Law for Autocatalytic Reactions.
ERIC Educational Resources Information Center
Mata-Perez, Fernando; Perez-Benito, Joaquin F.
1987-01-01
Presented is a method of obtaining accurate rate constants for autocatalytic reactions. The autocatalytic oxidation of dimethylamine by permanganate ion in aqueous solution is used as an example. (RH)
Kinetics of Chemical Reactions in Flames
NASA Technical Reports Server (NTRS)
Zeldovich, Y.; Semenov, N.
1946-01-01
In part I of the paper the theory of flame propagation is developed along the lines followed by Frank-Kamenetsky and one of the writers. The development of chain processes in flames is considered. A basis is given for the application of the method of stationary concentrations to reactions in flames; reactions with branching chains are analyzed. The case of a diffusion coefficient different from the coefficient of temperature conductivity is considered.
Bose-Einstein or HBT correlation signature of a second order QCD phase transition
T. Csorgo; S. Hegyi; T. Novak; W. A. Zajc
2005-12-15
For particles emerging from a second order QCD phase transition, we show that a recently introduced shape parameter of the Bose-Einstein correlation function, the Levy index of stability equals to the correlation exponent - one of the critical exponents that characterize the behavior of the matter in the vicinity of the second order phase transition point. Hence the shape of the Bose-Einstein / HBT correlation functions, when measured as a function of bombarding energy and centrality in various heavy ion reactions, can be utilized to locate experimentally the second order phase transition and the critical end point of the first order phase transition line in QCD.
Deng, Bo
(t) and (t), L[c] = cL, (5) and L[ + ] = L + L. (6) 5. Proposition: If u1(t) and u2(t) satisfy (4Second-Order, Linear Equations 1 1. A second-order, linear ordinary differential equation is one a second-order, linear differential operator. Using operator notation, we can write the linear
Whitney, David
Second-order motion without awareness: Passive adaptation to second-order motion produces a motion-order motion may be detected by early and automatic mechanisms, some models suggest that perceiving second- order motion requires higher-order processes, such as feature or attentive tracking. These types
ENGI 2422 Second Order Linear ODEs Page 4-01 4. Second Order Linear Ordinary Differential Equations
George, Glyn
Newton's second law of motion: ( ) d d F mv m dt ENGI 2422 Second Order Linear ODEs Page 4-01 4. Second Order Linear Ordinary Differential Equations The general second order linear ordinary differential equation is of the form ( ) ( ) ( ) 2 2 d y dy P x Q x y
Kinetics and Thermochemistry of the Cl((sup 2)P(sub J)) + C2Cl4 Association Reaction
NASA Technical Reports Server (NTRS)
Nicovich, J. M.; Wang, S.; Mckee, M. L.; Wine, P. H.
1997-01-01
A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Cl(sup 2)P(sub j) + C2Cl4 association reaction as a function of temperature (231-390 K) and pressure (3-700 Torr) in nitrogen buffer gas. The reaction is found to be in the falloff regime between third and second order over the range of conditions investigated, although the second-order limit is approached at the highest pressures and lowest temperatures. At temperatures below 300 K, the association reaction is found to be irreversible on the experimental time scale of approximately 20 m-s. The kinetic data at T is less than 300 K have been employed to obtain falloff parameters in a convenient format for atmospheric modeling. At temperatures above 330 K, reversible addition is observed, thus allowing equilibrium constants for C2Cl5 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the association reaction: Delta-H(298) = -18.1 +/- 1.3 kcal/mol, Delta-H(0) = -17.6 +/- 1.3 kcal/mol, and Delta-S(298) = -27.7 +/- 3.0 cal/mol.K. In conjunction with the well-known heats of formation of Cl((sup 2)P(sub j)) and C2Cl4 the above Delta-H values lead to the following heats of formation for C2Cl5, at 298 and 0 K: Delta-H(f,298) = 8.0 +/- 1.3 kcal/mol and Delta-H(f,0) = 8.1 +/- 1.5 kcal/mol. The kinetic and thermochemical parameters reported above are compared with other reported values, and the significance of reported association rate coefficients for understanding tropospheric chlorine chemistry is discussed.
Reaction kinetics of paddy husk thermal decomposition
Jain, A.K. [Punjab Agricultural Univ., Ludhiana (India). School of Energy Studies for Agriculture; Sharma, S.K.; Singh, D. [Panjab Univ., Chandigarh (India)
1999-02-01
The physical characteristics, proximate analysis, elemental analysis and chemical analysis of paddy husk, an important renewable source of energy, are reported in this paper. The kinetic parameters for the thermal degradation of paddy husk at heating rates of 10 and 100 C min{sup {minus}1} and under atmospheres of air and oxygen-nitrogen mixture (5:95) have been evaluated from experimentally obtained TGA data. The limitations of the existing TGA models are discussed, and a modified model has been used for correlation of the data.
kinetics of the reaction NO + O 2 ? BO 2 + O
NASA Astrophysics Data System (ADS)
Llewellyn, Ian P.; Fontijn, Arthur; Clyne, Michael A. A.
1981-12-01
The reaction of BCl 3 + N + O was used to produce BO X 2 ? + radicals for study in a fast-flow reactor. Laser-induced flu- orescence was used to follow the BO X 2 ? + radicals. The feasibility of kinetic studies on these radicals was demonstrated through a kinetic study of the BO + O 2 reaction, giving a rate coefficient k1 equal to (4.4 -3.2+4.7) × XXX -12 cm 3 molecule -1 s -1 at 295 K.
Exercises in the Geochemical Kinetics of Mineral-Water Reactions
NSDL National Science Digital Library
This module consists of a laboratory exercise and related homework problems on geochemical kinetics of mineral-solution reactions for undergraduate mineralogy. Students measure the grain sizes of equant halite crystals, and the time for complete dissolution of each grain. From these data, students retrieve a rate law, from several possible. Additional homework problems allow various chemical and physical transport processes in mineral-fluid systems to be evaluated. The lab and homework illustrate several basic principles of chemical kinetics directly relevant to geology, including rate laws of reactions, diffusion, advective transport, and the relationship between rate-limiting mechanisms and crystal-surface morphology.
Reaction kinetics and diagnostics for oil-shale retorting
NASA Astrophysics Data System (ADS)
Burnham, A. K.
1981-10-01
The advances in pyrolysis chemistry and kinetics and the resulting diagnostic methods based on effluent products for determining retort performance were reviewed. Kerogen pyrolysis kinetics and stoichiometry were generalized by further measurements on a larger number of samples. Analysis by capillary colunn gas chromatography of shale oil samples produced under a variety of field and laboratory conditions resulted in a method for determining the oil yield from a combustion retort. Measurement of sulfur products under a variety of conditions led to an understanding sulfur reactions both those of processing and environmental importance. Equations for estimating the heat of combustion of spent shale were developed by understanding oil shale composition and reactions.
Reaction of silylene with sulfur dioxide: some gas-phase kinetic and theoretical studies.
Becerra, Rosa; Cannady, J Pat; Goldberg, Nicola; Walsh, Robin
2013-09-21
Time-resolved kinetic studies of the reaction of silylene, SiH2, with SO2 have been carried out in the gas phase over the temperature range 297-609 K, using laser flash photolysis to generate and monitor SiH2. The second order rate coefficients at 1.3 kPa (SF6 bath gas) fitted the Arrhenius equation: log(k/cm(3) molecule(-1) s(-1)) = (-10.10 ± 0.06) + (3.46 ± 0.45 kJ mol(-1))/RT ln 10 where the uncertainties are single standard deviations. The collisional efficiency is 71% at 298 K, and in kinetic terms the reaction most resembles those of SiH2 with CH3CHO and (CH3)2CO. Quantum chemical calculations at the G3 level suggest a mechanism occurring via addition of SiH2 to one of the S=O double bonds leading to formation of the three-membered ring, thione-siloxirane which has a low energy barrier to ring expansion to yield the four-membered ring, 3-thia-2,4-dioxasiletane, the lowest energy adduct found on the potential energy (PE) surface. RRKM calculations, however, show that, if formed, this molecule would only be partially stabilised under the reaction conditions and the rate coefficients would be pressure dependent, in contrast with experimental findings. The G3 calculations reveal the complexity of possible intermediates and end products and taken together with the RRKM calculations indicate the most likely end products to be H2SiO + SO ((3)?(-)). The reaction is compared and contrasted with that of SiH2 + CO2. PMID:23903751
Chemistry 231 Fall 2013 Chemistry 231, Chemical Kinetics and Molecular Reaction Dynamics
Continetti, Robert E.
Chemistry 231 Fall 2013 Chemistry 231, Chemical Kinetics and Molecular Reaction Dynamics Dept chemical kinetics, the connection between chemical kinetics and molecular reaction dynamics as well as some and Hase, Prentice Hall (1999) 4. Chemical Kinetics, K.J. Laidler, McGraw Hill (1965) 5. Gas Phase Reaction
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.
Light-off curve of catalytic reaction and kinetics
Françoise Duprat
2002-01-01
The light-off curve is the conversion-temperature plot of a catalytic reaction; it is usually used in catalyst development. The possibility to deduce kinetic information such as the apparent reaction order or mass transfer limitation from the shape of the curve is examined here. The light-off plots obtained by numerical simulation with several different rate equations are compared between themselves and
Penicillin Hydrolysis: A Kinetic Study of a Multistep, Multiproduct Reaction.
ERIC Educational Resources Information Center
McCarrick, Thomas A.; McLafferty, Fred W.
1984-01-01
Background, procedures used, and typical results are provided for an experiment in which students carry out the necessary measurements on the acid-catalysis of penicillin in two hours. By applying kinetic theory to the data obtained, the reaction pathways for the hydrolysis of potassium benzyl penicillin are elucidated. (JN)
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...
Microdroplet fusion mass spectrometry for fast reaction kinetics
Zare, Richard N.
94305; b Center for Plant Aging Research, Institute for Basic Science, Daegu 711-873, Republic of Korea investigated the fusion of high-speed liquid droplets as a way to record the kinetics of liquid-phase chemical is presented that the reaction effectively stops upon en- tering the heated inlet of the mass spectrometer
Nonlinear kinetics and new approaches to complex reaction mechanisms.
Ross, J; Vlad, M O
1999-01-01
This paper reviews recent developments in the field of nonlinear chemical kinetics. Five topics are dealt with: (a) new approaches to complex reaction mechanisms, stoichiometric network analysis, classification of chemical oscillators and formulation of their mechanisms by deduction from experiments, and correlation metric construction of reaction pathways from measurements; (b) thermodynamic and stochastic theory of nonequilibrium processes, the eikonal approximation, the evaluation of stochastic potentials, experimental tests of the thermodynamic and stochastic theory of relative stability, and fluctuation-dissipation relations in nonequilibrium chemical systems; (c) chemical kinetics and cellular automata and lattice gas automata; (d) theoretical approaches and experimental studies of stochastic resonance in chemical kinetics; and (e) rate processes in disordered systems, stochastic Liouville equations, stretched exponential relaxation in disordered systems, and universality classes for rate processes in systems with static or dynamic disorder. PMID:15012406
SABIO-RK—database for biochemical reaction kinetics
Wittig, Ulrike; Kania, Renate; Golebiewski, Martin; Rey, Maja; Shi, Lei; Jong, Lenneke; Algaa, Enkhjargal; Weidemann, Andreas; Sauer-Danzwith, Heidrun; Mir, Saqib; Krebs, Olga; Bittkowski, Meik; Wetsch, Elina; Rojas, Isabel; Müller, Wolfgang
2012-01-01
SABIO-RK (http://sabio.h-its.org/) is a web-accessible database storing comprehensive information about biochemical reactions and their kinetic properties. SABIO-RK offers standardized data manually extracted from the literature and data directly submitted from lab experiments. The database content includes kinetic parameters in relation to biochemical reactions and their biological sources with no restriction on any particular set of organisms. Additionally, kinetic rate laws and corresponding equations as well as experimental conditions are represented. All the data are manually curated and annotated by biological experts, supported by automated consistency checks. SABIO-RK can be accessed via web-based user interfaces or automatically via web services that allow direct data access by other tools. Both interfaces support the export of the data together with its annotations in SBML (Systems Biology Markup Language), e.g. for import in modelling tools. PMID:22102587
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
Second order factors in the California Psychological Inventory.
Burger, G K; Pickett, L; Goldman, M
1977-02-01
In order to further specify the structure of the California Psychological Inventory (CPI), correlations among the first order factors of the CPI were factor analyzed, yielding two second order factors. These factors were described, and were named General Adjustment and Social Sensitivity, respectively. The second order configuration of CPI scales appeared to be consistent with other research done on the scales. It was suggested that, like the 16PF, second order factor scores for the CPI could have some utility. PMID:845778
Galaxy bias and gauges at second order in general relativity
NASA Astrophysics Data System (ADS)
Bertacca, Daniele; Bartolo, Nicola; Bruni, Marco; Koyama, Kazuya; Maartens, Roy; Matarrese, Sabino; Sasaki, Misao; Wands, David
2015-09-01
We discuss the question of gauge choice when analysing relativistic density perturbations at second order. We compare Newtonian and general relativistic approaches. Some misconceptions in the recent literature are addressed. We show that the comoving-synchronous gauge is the unique gauge in general relativity that corresponds to the Lagrangian frame and is entirely appropriate to describe the matter overdensity at second order. The comoving-synchronous gauge is the simplest gauge in which to describe Lagrangian bias at second order.
Kinetics of combined heterogeneous catalytic reactions with a common reagent
Pyatnitskii, Yu.I. [Pisarzhevskii Institute of Physical Chemistry, Kiev (Ukraine)
1995-01-01
The kinetics of combined catalytic reactions with a common reagent (competitive reactions) is analyzed assuming that no changes in the reaction mechanisms occur under their conjugation. A simplified approach is advanced for determining the relative rates of competitive reactions characterized by a similar mechanism of the initial stage for the interaction between the competitive reactants and catalyst. This includes the complex reactions, in which one of the reaction product serves as a competitive agent. The effects of nontrivial mutual influence of the competitive catalytic reactions are discussed. One type of this mutual influence manifests itself as a drastic inhibition of one reaction by another; this is not due to the catalyst surface blocking. This effect is inherent to the reactions involving the reversible dissociation of a heteroatomic reagent. The other type of the mutual influence is revealed in the promotion of one reaction by another when at least one of the reaction follows the Langmuir-Hinshelwood mechanism and the adsorption of a common reagent is far from the equilibrium.
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.
NASA Technical Reports Server (NTRS)
Thron, R. P.; 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 reaction BrO + NO2 + M yields (k1) products as a function of temperature (248-346 K), pressure (16-800 torr), and buffer gas identity (N2,CF4) The reaction is found to be in the falloff regime between third and second-order over the entire range of conditions investigated This is the first study where temperature-dependent measurements of k1(P,T) have been reported at pressures greater than 12 torr; hence, our results help constrain choices of k1(P,T) for use in models of lower stratospheric BrO(x) chemistry. Approximate falloff parameters in a convenient form for atmospheric modeling are derived.
Minnesota, University of
-limiting. The second-order rate constant is enhanced by a factor of 109 over the uncatalyzed reaction in water,5, and acetate ion, plus a sodium ion and 898 water molecules in a box of ca. 30 × 30 × 30 Å3. This gives to the Nitroalkane Oxidase Reaction Dan T. Major,* Darrin M. York, and Jiali Gao* Department of Chemistry
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
Yang, Bin; Ying, Guang-Guo; Zhao, Jian-Liang; Zhang, Li-Juan; Fang, Yi-Xiang; Nghiem, Long Duc
2011-02-15
The oxidation of triclosan by commercial grade aqueous ferrate (Fe(VI)) was investigated and the reaction kinetics as a function of pH (7.0-10.0) were experimentally determined. Intermediate products of the oxidation process were characterized using both GC-MS and RRLC-MS/MS techniques. Changes in toxicity during the oxidation process of triclosan using Fe(VI) were investigated using Pseudokirchneriella subcapitata growth inhibition tests. The results show that triclosan reacted rapidly with Fe(VI), with the apparent second-order rate constant, k(app), being 754.7 M(-1) s(-1) at pH 7. At a stoichiometric ratio of 10:1 (Fe(VI):triclosan), complete removal of triclosan was achieved. Species-specific rate constants, k, were determined for reaction of Fe(VI) with both the protonated and deprotonated triclosan species. The value of k determined for neutral triclosan was 6.7(±1.9)×10(2) M(-1) s(-1), while that measured for anionic triclosan was 7.6(±0.6)×10(3) M(-1) s(-1). The proposed mechanism for the oxidation of triclosan by the Fe(VI) involves the scission of ether bond and phenoxy radical addition reaction. Coupling reaction may also occur during Fe(VI) degradation of triclosan. Overall, the degradation processes of triclosan resulted in a significant decrease in algal toxicity. The toxicity tests showed that Fe(VI) itself dosed in the reaction did not inhibit green algae growth. PMID:21093982
A kinetics investigation of several reactions involving chlorine containing compounds
NASA Technical Reports Server (NTRS)
Davis, D. D.
1978-01-01
The technique of flash photolysis-resonance fluorescence was utilized to study nine reactions of stratospheric importance. The tropospheric degradation reactions of seven halogenated hydrocarbons were studied to assess their possible influx into the stratosphere. There are reactions of either Cl, OH, or O(3P) species with hydrogenated species, O3 or chlorinated compounds. Apart from the kinetic measurements, the quantum yield for the production of O(1D) from O3 in the crucial wavelength region of 293 to 316.5 nm was studied by utilizing a narrow wavelength laser as the photolysis source. The product formation was monitored by measuring the fluorescence of NO2 formed through O(1D) reaction with N2O followed by NO reaction with O3 to give NO2.
Computation of kinetic isotope effects for enzymatic reactions
GAO, JiaLi
2013-01-01
We describe a computational approach, incorporating quantum mechanics into enzyme kinetics modeling with a special emphasis on computation of kinetic isotope effects. Two aspects are highlighted: (1) the potential energy surface is represented by a combined quantum mechanical and molecular mechanical (QM/MM) potential in which the bond forming and breaking processes are modeled by electronic structure theory, and (2) a free energy perturbation method in path integral simulation is used to determine both kinetic isotope effects (KIEs). In this approach, which is called the PI-FEP/UM method, a light (heavy) isotope is mutated into a heavy (light) counterpart in centroid path integral simulations. The method is illustrated in the study of primary and secondary KIEs in two enzyme systems. In the case of nitroalkane oxidase, the enzymatic reaction exhibits enhanced quantum tunneling over that of the uncatalyzed process in water. In the dopa delarboxylase reaction, there appears to be distinguishable primary carbon-13 and secondary deuterium KIEs when the internal proton tautomerism is in the N-protonated or in the O-protonated positions. These examples show that the incorporation of quantum mechanical effects in enzyme kinetics modeling offers an opportunity to accurately and reliably model the mechanisms and free energies of enzymatic reactions. PMID:23976893
Reaction kinetics of some important site-specific endonucleases.
Hinsch, B; Kula, M R
1981-01-01
Reaction kinetics of the site-specific endonucleases BamHI, BgIII, C1aI, EcoRI, HpaII, PstI, SaII, SmaI, and XorII were investigated employing some frequently used substrates. Six of these enzymes could be analyzed under steady-state conditions. Kinetic data were obtained from progress curves applying an integrated Michaelis-Menten equation. KM ranged from 4 x 10(-9) M to 4 x 10(-11) M. Activities also spanned two orders of magnitude. In the case of C1aI the analysis of the pre-steady-state kinetics ("burst reaction") allowed the assessment of several rate constants. The rate-limiting step is the very slow dissociation of the enzyme-product complex (0.22 min(-1)). This complex is formed from the enzyme-bound nicked intermediate at a rate of 1.7 min(-1). The introduction of the first cut is again faster by a factor of about 6. SmaI and XorII resembled C1aI in their kinetics. The burst reaction can be used for the easy and unambiguous determination of molar concentrations of site-specific endonucleases in any preparation, which is free of non-specific DNases. PMID:6269074
Reaction kinetics of cellulose hydrolysis in subcritical and supercritical water
NASA Astrophysics Data System (ADS)
Olanrewaju, Kazeem Bode
The uncertainties in the continuous supply of fossil fuels from the crisis-ridden oil-rich region of the world is fast shifting focus on the need to utilize cellulosic biomass and develop more efficient technologies for its conversion to fuels and chemicals. One such technology is the rapid degradation of cellulose in supercritical water without the need for an enzyme or inorganic catalyst such as acid. This project focused on the study of reaction kinetics of cellulose hydrolysis in subcritical and supercritical water. Cellulose reactions at hydrothermal conditions can proceed via the homogeneous route involving dissolution and hydrolysis or the heterogeneous path of surface hydrolysis. The work is divided into three main parts. First, the detailed kinetic analysis of cellulose reactions in micro- and tubular reactors was conducted. Reaction kinetics models were applied, and kinetics parameters at both subcritical and supercritical conditions were evaluated. The second major task was the evaluation of yields of water soluble hydrolysates obtained from the hydrolysis of cellulose and starch in hydrothermal reactors. Lastly, changes in molecular weight distribution due to hydrothermolytic degradation of cellulose were investigated. These changes were also simulated based on different modes of scission, and the pattern generated from simulation was compared with the distribution pattern from experiments. For a better understanding of the reaction kinetics of cellulose in subcritical and supercritical water, a series of reactions was conducted in the microreactor. Hydrolysis of cellulose was performed at subcritical temperatures ranging from 270 to 340 °C (tau = 0.40--0.88 s). For the dissolution of cellulose, the reaction was conducted at supercritical temperatures ranging from 375 to 395 °C (tau = 0.27--0.44 s). The operating pressure for the reactions at both subcritical and supercritical conditions was 5000 psig. The results show that the rate-limiting step in converting cellulose to fermentable sugars in subcritical and supercritical water differs because of the difference in their activation energies. Cellulose and starch were both hydrolyzed in micro- and tubular reactors and at subcritical and supercritical conditions. Due to the difficulty involved in generating an aqueous based dissolved cellulose and having it reacted in subcritical water, dissolved starch was used instead. Better yield of water soluble hydrolysates, especially fermentable sugars, were observed from the hydrolysis of cellulose and dissolved starch in subcritical water than at supercritical conditions. The concluding phase of this project focuses on establishing the mode of scission of cellulose chains in the hydrothermal reactor. This was achieved by using the simulated degradation pattern generated based on different scission modes to fingerprint the degradation pattern obtained from experiment.
Second-order logic and foundations of mathematics
Jouko A. Väänänen
2001-01-01
We discuss the dierences between first-order set theory and second- order logic as a foundation for mathematics. We analyse these lan- guages in terms of two levels of formalization. The analysis shows that if second-order logic is understood in its full semantics capable of characterizing categorically central mathematical concepts, it re- lies entirely on informal reasoning. On the other hand,
Weak lensing induced by second-order vector mode
NASA Astrophysics Data System (ADS)
Saga, Shohei; Yamauchi, Daisuke; Ichiki, Kiyotomo
2015-09-01
The vector mode of cosmological perturbation theory imprints characteristic signals on the weak lensing signals such as curl and B modes which are never imprinted by the scalar mode. However, the vector mode is neglected in the standard first-order cosmological perturbation theory since it only has a decaying mode. This situation changes if the cosmological perturbation theory is expanded up to second order. The second-order vector and tensor modes are inevitably induced by the product of the first-order scalar modes. We study the effect of the second-order vector mode on the weak lensing curl and B modes. We find that the curl mode induced by the second-order vector mode is comparable to that induced by the primordial gravitational waves with the tensor-to-scalar ratio r =0.1 at ??200 . In this case, the curl mode induced by the second-order vector mode dominates at ?>200 . Furthermore, the B-mode cosmic shear induced by the second-order vector mode dominates on almost all scales. However, we find that the observational signatures of the second-order vector and tensor modes cannot exceed the expected noise of ongoing and upcoming weak lensing measurements. We conclude that the curl and B modes induced by the second-order vector and tensor modes are unlikely to be detected in future experiments.
Controllability of second order linear systems Josep Clotet
PolitÃ¨cnica de Catalunya, Universitat
Controllability of second order linear systems Josep Clotet 1 , M a Â¯ Isabel Garc linearization process we study the controllability of second order linear systems. We obtain sufficient-Words: - Two-order linear systems, linearization, feedback, controllability. 1 Introduction The study of second
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…
Weak lensing induced by second-order vector mode
Shohei Saga; Daisuke Yamauchi; Kiyotomo Ichiki
2015-05-11
Vector mode of cosmological perturbation theory imprints characteristic signals on the weak lensing signals such as curl- and B-modes which are never imprinted by the scalar mode. However, the vector mode is neglected in the standard first-order cosmological perturbation theory since it only has a decaying mode. This situation changes if the cosmological perturbation theory is expanded up to second order. The second-order vector and tensor modes are inevitably induced by the product of the first-order scalar modes. We study the effect of the second-order vector mode on the weak lensing curl- and B-modes. The curl-mode induced by the second-order vector mode dominates instead of the primordial gravitational waves when the tensor-to-scalar ratio is $r = 0.1$ and the second-order tensor mode at $\\ell \\geq 200$. Furthermore, the B-mode cosmic shear induced by the second-order vector mode dominates on almost all scales. However, we find that the observational signatures of the second-order vector and tensor modes cannot exceed the expected noise of ongoing and upcoming weak lensing measurements. We conclude that the curl- and B-modes induced by the second-order vector and tensor modes are unlikely to be detected in future experiments.
Solving Second Order Linear Differential Equations with Klein's Theorem
Weil, Jacques-Arthur
of the differential Galois group instead of semi-invariants. 1. INTRODUCTION The Kovacic algorithm [18] computes closed form (Liouvil- lian) solutions of second order linear differential equations over k = C(x). SinceSolving Second Order Linear Differential Equations with Klein's Theorem M. van Hoeij & J.-A. Weil
Induction is not derivable in second order dependent type theory
Geuvers, Herman
Induction is not derivable in second order dependent type theory Herman Geuvers ? Department-derivability of induction in second order dependent type theory (#21;P 2). This is done by providing a model construction extensional combinatory algebra. We give counter-models in which the induction principle over natural num
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 ...
Visualization of second order tensor fields and matrix data
NASA Technical Reports Server (NTRS)
Delmarcelle, Thierry; Hesselink, Lambertus
1992-01-01
We present a study of the visualization of 3-D second order tensor fields and matrix data. The general problem of visualizing unsymmetric real or complex Hermitian second order tensor fields can be reduced to the simultaneous visualization of a real and symmetric second order tensor field and a real vector field. As opposed to the discrete iconic techniques commonly used in multivariate data visualization, the emphasis is on exploiting the mathematical properties of tensor fields in order to facilitate their visualization and to produce a continuous representation of the data. We focus on interactively sensing and exploring real and symmetric second order tensor data by generalizing the vector notion of streamline to the tensor concept of hyperstreamline. We stress the importance of a structural analysis of the data field analogous to the techniques of vector field topology extraction in order to obtain a unique and objective representation of second order tensor fields.
V. Burdyuzha; Yu. Ponomarev; O. Lalaculich; G. Vereshkov
1996-04-22
We propose that the Universe was created from "Nothing" with a relatively small particles number and it very quick relaxed to quasiequilibrium state at the Planck parameters. The classic cosmological solution for this Universe, with the calculation of its ability to be undergo to the second order relativistic phase transition (RPT), has two branches divided by gap. On one from these branches near to "Nothing" state the second order RPT isn't possible at the GUT scale. Other branch is thermodynamically instable. The quantum process of tunneling between the cosmological solution branches and kinetics of the second order RPT after tunneling are investigated by numerical methods. Other quantum geometrodynamics process (the bounce from singularity) is taken into consideration also. It is shown that discussed phenomenon with the calculation of all RPT from the GUT scale to the Salam-Weinberg scale gives the new cosmological scenarios of the macroscopic Universe origin with observable particles number.
Portable centrifugal analyzer for the determination of rapid reaction kinetics
Bostick, W.D.; Bauer, M.L.; McCracken, R.; Mrochek, J.E.
1980-02-01
A portable centrifugal analyzer prototype is capable of rapidly initiating reactions and monitoring 17 optical channels as they rotate past a stationary photodetector. An advanced rotor drive permits transfer of discretely loaded sample and reagent into a cuvette within 60 ms. Various rotor designs have been employed to ensure effieicnt mixing concurrent with solution transfer, thus permitting absorbance or luminescence measurements to be made almost immediately after solution contract. Dye-dillution studies have been used to investigate transfer and mixing efficiencies. Rotor designs with parallel access for sample and reagent into the cuvette were found to promote efficient mixing during liquid transfer. The hypochlorite-luminol chemiluminescent reaction served to demonstrate the utility of the system for performing rapid kinetic analyses. Appropriate adjustment of reaction conditions allows first-order reaction half-lives as short as 0.04 s to be measured. 13 figures, 3 tables.
Characterization of hot hydrogen-atom reactions by kinetic spectrography.
NASA Technical Reports Server (NTRS)
Tomalesky, R. E.; Sturm, J. E.
1971-01-01
The flash photolysis of hydrogen iodide in the presence of nitrous oxide, carbon dioxide, and water has been investigated by kinetic spectroscopy. Although the fraction of hydrogen iodide dissociated was very large, the only observable intermediate was imidogen. It was demonstrated that the rapid removal of imidogen and the apparent absence of hydroxyl radicals in each case is a result of the following two reactions, respectively: (1) NH + HI yields NH2 + I; and (2) OH + HI yields H2O + I.
A study of second-order supersonic flow theory
NASA Technical Reports Server (NTRS)
Van Dyke, Milton D
1952-01-01
Second-order solutions of supersonic-flow problems are sought by iteration, using the linearized solution as the first step. For plane and axially symmetric flows, particular solutions of the iteration equation are discovered which reduce the second-order problem to an equivalent linearized problem. Comparison of second-order solutions with exact and numerical results shows great improvement over linearized theory. For full three-dimensional flow, only a partial particular solution is found. The inclined cone is solved, and the possibility of treating more general problems is considered.
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
Method to render second order beam optics programs symplectic
Douglas, D.; Servranckx, R.V.
1984-10-01
We present evidence that second order matrix-based beam optics programs violate the symplectic condition. A simple method to avoid this difficulty, based on a generating function approach to evaluating transfer maps, is described. A simple example illustrating the non-symplectricity of second order matrix methods, and the effectiveness of our solution to the problem, is provided. We conclude that it is in fact possible to bring second order matrix optics methods to a canonical form. The procedure for doing so has been implemented in the program DIMAT, and could be implemented in programs such as TRANSPORT and TURTLE, making them useful in multiturn applications. 15 refs.
Second-order upwind differencing in a recirculating flow
NASA Technical Reports Server (NTRS)
Vanka, S. P.
1987-01-01
The accuracy and stability of the second order upwind differencing scheme was investigated. The solution algorithm employed is based on a coupled solution of the nonlinear finite difference equations by the multigrid technique. Calculations have been made of the driven cavity flow for several Reynolds numbers and finite difference grids. In comparison with the hybrid differencing, the second order upwind differencing is somewhat more accurate but it is not monotonically accurate with mesh refinement. Also, the convergence of the solution algorithm deteriorates with the use of the second order upwind differencing.
Study of second order upwind differencing in a recirculating flow
NASA Technical Reports Server (NTRS)
Vanka, S. P.
1985-01-01
The accuracy and stability of the second order upwind differencing scheme was investigated. The solution algorithm employed is based on a coupled solution of the nonlinear finite difference equations by the multigrid technique. Calculations have been made of the driven cavity flow for several Reynolds numbers and finite difference grids. In comparison with the hybrid differencing, the second order upwind differencing is somewhat more accurate but it is not monotonically accurate with mesh refinement. Also, the convergence of the solution algorithm deteriorates with the use of the second order upwind differencing.
Exciton microscopy and reaction kinetics in restricted spaces.
Kopelman, R
1991-01-01
We describe the development of a new biologically non-invasive ultraresolution light microscopy, based on combining the energy transfer "spectral ruler" method with the micro-movement technology employed in scanning tunneling microscopy (STM). We use near-field scanning optical microscopy, with micropipettes containing crystals of energy packaging donor molecules in the tips that can have apertures below 5 nm. The excitation of these tips extends near field microscopy well beyond the 50 nm limit. The theoretical resolution limit for this spectrally sensitive light microscopy is well below 1 nm. Exciton microscopy is ideally suited for kinetic studies that are spatially resolved on the molecular scale, i.e., at a single molecule site. Moreover, the successful operation of the scanning exciton tip depends on an understanding of reaction kinetics in restricted spaces. In contrast to the many recent reviews on scanning tip microscopies, there is no adequate review of the recent revolutionary developments in the area of reaction kinetics in confined geometries. We thus attempt such a review in this paper. Reactions in restricted spaces rarely get stirred vigorously by convection and are thus often controlled by diffusion. Furthermore, the compactness of the Brownian motion leads to both anomalous diffusion and anomalous reaction kinetics. Elementary binary reactions of the type A + A----Products, A + B----Products and A + C----C + Products are discussed theoretically for both batch and steady-state conditions. The anomalous reaction orders and time exponents (for the rate coefficients) are discussed for various situations. Global and local rate laws are related to particle distribution functions. Only Poissonian distributions guarantee the classical rate laws. Reactant self-organization leads to interesting new phenomena. These are demonstrated by theory, simulations, and experiments. The correlation length of reactant production affects the self-ordering length-scale. These effects are demonstrated experimentally, including the stability of reactant segregation observed in chemical reactions in one-dimensional spaces, e.g., capillaries and microcapillaries. The gap between the reactant A (cation) and B (anion) actually increases in time, and extends over millimeters. Excellent agreement is found among theory, simulation, and experiment for the various scaling exponents. PMID:1811482
Microdroplet fusion mass spectrometry for fast reaction kinetics
Lee, Jae Kyoo; Kim, Samuel; Nam, Hong Gil; Zare, Richard N.
2015-01-01
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
Reaction Path Optimization with Holonomic Constraints and Kinetic Energy Potentials
Brokaw, Jason B.; Haas, Kevin R.; Chu, Jhih-wei
2009-08-11
Two methods are developed to enhance the stability, efficiency, and robustness of reaction path optimization using a chain of replicas. First, distances between replicas are kept equal during path optimization via holonomic constraints. Finding a reaction path is, thus, transformed into a constrained optimization problem. This approach avoids force projections for finding minimum energy paths (MEPs), and fast-converging schemes such as quasi-Newton methods can be readily applied. Second, we define a new objective function - the total Hamiltonian - for reaction path optimization, by combining the kinetic energy potential of each replica with its potential energy function. Minimizing the total Hamiltonian of a chain determines a minimum Hamiltonian path (MHP). If the distances between replicas are kept equal and a consistent force constant is used, then the kinetic energy potentials of all replicas have the same value. The MHP in this case is the most probable isokinetic path. Our results indicate that low-temperature kinetic energy potentials (<5 K) can be used to prevent the development of kinks during path optimization and can significantly reduce the required steps of minimization by 2-3 times without causing noticeable differences between a MHP and MEP. These methods are applied to three test cases, the C?eq-to-Cax isomerization of an alanine dipeptide, the ?C?- to-¹C? transition of an ?-D-glucopyranose, and the helix-to-sheet transition of a GNNQQNY heptapeptide. By applying the methods developed in this work, convergence of reaction path optimization can be achieved for these complex transitions, involving full atomic details and a large number of replicas (>100). For the case of helix-to-sheet transition, we identify pathways whose energy barriers are consistent with experimental measurements. Further, we develop a method based on the work energy theorem to quantify the accuracy of reaction paths and to determine whether the atoms used to define a path are enough to provide quantitative estimation of energy barriers.
Wong, Kin Yiu; Richard, John P.; Gao, Jiali
2009-01-01
Primary kinetic isotope effects (KIEs) on a series of carboxylic acid-catalyzed protonation reactions of aryl-substituted ?-methoxystyrenes (X-1) to form oxocarbenium ions have been computed using the Kleinert variational second-order perturbation theory (KP2) in the framework of Feynman path integrals (PI) along with the potential energy surface obtained at the B3LYP/6-31+G(d,p) level. Good agreement with the experimental data was obtained, demonstrating that this novel computational approach for computing KIEs of organic reactions is a viable alternative to the traditional method employing Bigeleisen equation and harmonic vibrational frequencies. Although tunneling makes relative small contributions to the lowering of the free energy barriers for the carboxylic acid catalyzed protonation reaction, it is necessary to include tunneling contributions to obtain quantitative estimates of the KIEs. Consideration of anharmonicity can further improve the calculated KIEs for the protonation of substituted ?-methoxystyrenes by chloroacetic acid, but for the reactions of the parent and 4-NO2 substituted ?-methoxystyrene with substituted carboxylic acids, the correction of anharmonicity overestimates the computed KIEs for strong acid catalysts. In agreement with experimental findings, the largest KIEs are found in nearly ergoneutral reactions, ?Go ? 0, where the transition structures are nearly symmetric and the reaction barriers are relatively low. Furthermore, the optimized transition structures are strongly dependent on the free energy for the formation of the carbocation intermediate, i.e., the driving force ?Go, along with a good correlation of Hammond shift in the transition state structure. PMID:19754046
Second order critical point in QCD phase diagram
Assawasunthonnet, Wathid
2009-01-01
In this thesis I explore the theoretical model based on Asakawa and Nonaka's idea[l]. I start by arguing that the critical point of the QCD phase diagram is second order and belongs to the three dimensional Ising model ...
Best constants in a borderline case of second order
Tarsi, Cristina
Best constants in a borderline case of second order Moser type inequalities Daniele Cassani a borderline case of D.R. Adams' [1] generalization of Trudinger-Moser type inequalities to the case of higher
Some nonlinear second order equation modelling rocket motion
Dorota Bors; Robert Sta?czy
2012-12-23
In this paper, we consider a nonlinear second order equation modelling rocket motion in the gravitational field obstructed by the drag force. The proofs of the main results are based on topological fixed point approach.
Orthogonal canonical forms for second-order systems
NASA Technical Reports Server (NTRS)
Williams, Trevor; Laub, Alan
1989-01-01
The authors prove that a linear second-order system with arbitrary damping cannot be reduced to Hessenberg-triangular form by means of orthogonal transformations, while this reduction is always possible for the modal damping commonly assumed for models of flexible structures. The type of canonical form obtainable by means of orthogonal transformations acting on a second-order system is heavily dependent on the type of damping considered. If the damping matrix is merely positive semi-definite symmetric, it is generally not possible to obtain a reduction to Hessenberg-triangular form, while this reduction is trivial for zero or Rayleigh damping. If damping is modal, however, as is commonly assumed in structural models, the reduction exists and is nontrivial. Furthermore, reduction to triangular second-order Schur form is always possible for such damping: this canonical form appears likely to have applications to second-order system theory.
second-order convex splitting schemes for gradient flows with ...
2011-11-08
unconditional stability, second order scheme, convex-concave decomposition, .... point out that efficient first, second and third order in time accurate schemes have been ...... islands and 3D mounds, Surface Science Reports 61 (2006) 1-128.
On the state estimation of structures with second order observers
NASA Technical Reports Server (NTRS)
Belvin, W. Keith; Park, K. C.
1989-01-01
The use of Linear Quadratic Regulator (LQR) control synthesis techniques implies the availability of full state feedback. For vibration control of structures, usually only a limited number of states are measured from which an observer model reconstructs the full state. It is shown that using second order observers is a viable technique for reconstructing the unmeasured states of structures under mildly restrictive conditions. Moreover, the computational advantages of the second order observer as compared to a first order observer indicate that significantly larger observer models may be utilized. Numerical examples are used to demonstrate the performance of second order observers. The implications of second order observers in the development of Controls-Structures Interaction (CSI) technology is discussed.
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 $0density-dependence $\\rho^{8/3}$ of several second-order contributions. The inclusion of the density-dependent term ${1\\over 6}t_3 \\r...
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
Second-order nonlinear optical activity vs. chromophore content in simple organic glass/PMMA system
NASA Astrophysics Data System (ADS)
Lee, Seung Mook; Jahng, Woong Sang; Lee, Jin Hyun; Rhee, Bum Ku; Park, Ki Hong
2005-08-01
A simple organic glass with a connection of two nonlinear optical (NLO) moieties was synthesized by condensation reaction of alkyl-substituted dibenzaldehyde with barbituric acid. This organic glass with Tg of 81 °C was formed to be optically transparent films without any phase separation even at the highest chromophore content (100 wt% loading without host matrix). The second-order NLO properties with various organic glass/PMMA composition systems were systematically studied by Maker fringe method at a wavelength of 1064 nm. We demonstrate that second-order optical nonlinearity of this organic glass/PMMA system can be progressively enlarged with increasing chromophore loading from 0 to 100 wt%.
Redner, Sidney
Chapter 8 REACTION KINETICS In this chapter, we will discuss the time evolution of simple reactions-controlled limit. In contrast, in the reaction-controlled limit, reactants must meet many times before a reaction in reduced spatial dimension. Diffusion- limited reactions have played an important role in the development
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
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
Local kinetics and thermodynamics of rapid electrochemical reactions
NASA Astrophysics Data System (ADS)
P?ibyl, Michal; Šnita, Dalimil
2014-04-01
We introduce and discuss a local kinetic mechanism for an n-electron electrochemical reaction at the interface formed by an electrode and diluted electrolyte. We show that the suggested mechanism is in agreement with the Nernst equation in the thermal equilibrium. We also qualitatively characterize the structure of a flat electrode-diluted electrolyte boundary in the meaning of the spatial distribution of electrochemical reactants and electric potential. As the suggested kinetic mechanism is not limited by the duration of relaxation processes in electric double layers, it is suitable for the understanding and simulation of fast transient processes that appear in modern applications such as nanocolloid dielectrophoresis, AC electrospray, AC electroosmosis, or nanopore biosensing.
A study of switchgrass pyrolysis: Product variability and reaction kinetics
NASA Astrophysics Data System (ADS)
Bovee, Jonathan Matthew
Samples of the same cultivar of cave-in-rock switchgrass were harvested from plots in Frankenmuth, Roger City, Cass County, and Grand Valley, Michigan. It was determined that variation exists, between locations, among the pyrolytic compounds which can lead to variability in bio-oil and increased processing costs at bio-refineries to make hydrocarbon fuels. Washed and extractives-free switchgrass samples, which contain a lower alkali and alkaline earth metals content than untreated samples, were shown to produce lower amounts of acids, esters, furans, ketones, phenolics, and saccharides and also larger amounts of aldehydes upon pyrolysis. Although the minerals catalyzed pyrolytic reactions, there was no evidence indicating their effect on reducing the production of anhydrosugars, specifically levoglucosan. To further link minerals present in the biomass to a catalytic pathway, mathematic models were employed to determine the kinetic parameters of the switchgrass. While the calculated activation energies of switchgrass, using the FWO and KAS methods, were 227.7 and 217.8 kJ/mol, correspondingly, it was concluded that the activation energies for the switchgrass hemicellulose and cellulose peaks were 115.5 and 158.2 kJ/mol, respectively, using a modified model-fitting method. The minerals that effect the production of small molecules and levoglucosan also have an observable catalytic effect on switchgrass reaction rate, which may be quantifiable through the use of reaction kinetics so as to determine activation energy.
Beaupre, Brett A; Hoag, Matthew R; Carmichael, Brenton R; Moran, Graham R
2013-12-10
Renalase is a recently discovered flavoprotein that has been reported to be a hormone produced by the kidney to down-modulate blood pressure and heart rate. The consensus belief has been that renalase oxidizes circulating catecholamine neurotransmitters thereby attenuating vascular tone. However, a convincing in vitro demonstration of this activity has not been made. We have recently discovered that renalase has ?-NAD(P)H oxidase/anomerase activity. Unlike most naturally occurring nucleotides, NAD(P)H can accumulate small amounts of the ?-anomers that once oxidized are configurationally stable and unable to participate in cellular activity. Thus, anomerization of NAD(P)H would result in a continual loss of cellular redox currency. As such, it appears that the root purpose of renalase is to return ?-anomers of nicotinamide dinucleotides to the ?-anomer pool. In this article, we measure the kinetics and equilibria of renalase in turnover with ?-NADPH. Renalase is selective for the ?-anomer, which binds with a dissociation constant of ?20±3 ?M. This association precedes monophasic two-electron reduction of the FAD cofactor with a rate constant of 40.2±1.3 s(-1). The reduced enzyme then delivers both electrons to dioxygen in a second-order reaction with a rate constant of ?2900 M(-1) s(-1). Renalase has modest affinity for its ?-NADP+ product (Kd=2.2 mM), and the FAD cofactor has a reduction potential of -155 mV that is unaltered by saturating ?-NADP+. Together these data suggest that the products are formed and released in a kinetically ordered sequence (?-NADP+ then H2O2), however, the reoxidation of renalase is not contingent on the dissociation of ?-NADP+. Neither the oxidized nor the reduced form of renalase is able to catalyze anomerization, implying that the redox and anomerization chemistries are inextricably linked through a common intermediate. PMID:24266457
Classic reaction kinetics can explain complex patterns of antibiotic action
zur Wiesch, P. Abel; Abel, S.; Gkotzis, S.; Ocampo, P.; Engelstädter, J.; Hinkley, T.; Magnus, C.; Waldor, M. K.; Udekwu, K.; Cohen, T.
2015-01-01
Finding optimal dosing strategies for treating bacterial infections is extremely difficult, and improving therapy requires costly and time-intensive experiments. To date, an incomplete mechanistic understanding of drug effects has limited our ability to make accurate quantitative predictions of drug-mediated bacterial killing and impeded the rational design of antibiotic treatment strategies. Three poorly understood phenomena complicate predictions of antibiotic activity: post-antibiotic growth suppression, density-dependent antibiotic effects, and persister cell formation. Here, we show that chemical binding kinetics alone are sufficient to explain these three phenomena, using single cell data and time-kill curves of Escherichia coli and Vibrio cholerae exposed to a variety of antibiotics in combination with a theoretical model that links chemical reaction kinetics to bacterial population biology. Our model reproduces existing observations, has a high predictive power across different experimental setups (R2= 0.86), and makes several testable predictions, which we verified in new experiments and by analysing published data from a clinical trial on tuberculosis therapy. While a variety of biological mechanisms have previously been invoked to explain post-antibiotic growth suppression, density-dependent antibiotic effects, and especially persister cell formation, our findings reveal that a simple model which considers only binding kinetics provides a parsimonious and unifying explanation for these three complex, phenotypically distinct behaviours. Current antibiotic and other chemotherapeutic regimens are often based on trial-and-error or expert opinion. Our ‘chemical reaction kinetics’-based approach may inform new strategies, that are based on rational design. PMID:25972005
Classic reaction kinetics can explain complex patterns of antibiotic action.
Abel Zur Wiesch, Pia; Abel, Sören; Gkotzis, Spyridon; Ocampo, Paolo; Engelstädter, Jan; Hinkley, Trevor; Magnus, Carsten; Waldor, Matthew K; Udekwu, Klas; Cohen, Ted
2015-05-13
Finding optimal dosing strategies for treating bacterial infections is extremely difficult, and improving therapy requires costly and time-intensive experiments. To date, an incomplete mechanistic understanding of drug effects has limited our ability to make accurate quantitative predictions of drug-mediated bacterial killing and impeded the rational design of antibiotic treatment strategies. Three poorly understood phenomena complicate predictions of antibiotic activity: post-antibiotic growth suppression, density-dependent antibiotic effects, and persister cell formation. We show that chemical binding kinetics alone are sufficient to explain these three phenomena, using single-cell data and time-kill curves of Escherichia coli and Vibrio cholerae exposed to a variety of antibiotics in combination with a theoretical model that links chemical reaction kinetics to bacterial population biology. Our model reproduces existing observations, has a high predictive power across different experimental setups (R(2) = 0.86), and makes several testable predictions, which we verified in new experiments and by analyzing published data from a clinical trial on tuberculosis therapy. Although a variety of biological mechanisms have previously been invoked to explain post-antibiotic growth suppression, density-dependent antibiotic effects, and especially persister cell formation, our findings reveal that a simple model that considers only binding kinetics provides a parsimonious and unifying explanation for these three complex, phenotypically distinct behaviours. Current antibiotic and other chemotherapeutic regimens are often based on trial and error or expert opinion. Our "chemical reaction kinetics"-based approach may inform new strategies, which are based on rational design. PMID:25972005
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.
Python framework for kinetic modeling of electronically excited reaction pathways
NASA Astrophysics Data System (ADS)
Verboncoeur, John; Parsey, Guy; Guclu, Yaman; Christlieb, Andrew
2012-10-01
The use of plasma energy to enhance and control the chemical reactions during combustion, a technology referred to as ``plasma assisted combustion'' (PAC), can result in a variety of beneficial effects: e.g. stable lean operation, pollution reduction, and wider range of p-T operating conditions. While experimental evidence abounds, theoretical understanding of PAC is at best incomplete, and numerical tools still lack in reliable predictive capabilities. In the context of a joint experimental-numerical effort at Michigan State University, we present here an open-source modular Python framework dedicated to the dynamic optimization of non-equilibrium PAC systems. Multiple sources of experimental reaction data, e.g. reaction rates, cross-sections and oscillator strengths, are used in order to quantify the effect of data uncertainty and limiting assumptions. A collisional-radiative model (CRM) is implemented to organize reactions by importance and as a potential means of measuring a non-Maxwellian electron energy distribution function (EEDF), when coupled to optical emission spectroscopy data. Finally, we explore scaling laws in PAC parameter space using a kinetic global model (KGM) accelerated with CRM optimized reaction sequences and sparse stiff integrators.
Understanding intramembrane proteolysis: from protein dynamics to reaction kinetics.
Langosch, D; Scharnagl, C; Steiner, H; Lemberg, M K
2015-06-01
Intramembrane proteolysis - cleavage of proteins within the plane of a membrane - is a widespread phenomenon that can contribute to the functional activation of substrates and is involved in several diseases. Although different families of intramembrane proteases have been discovered and characterized, we currently do not know how these enzymes discriminate between substrates and non-substrates, how site-specific cleavage is achieved, or which factors determine the rate of proteolysis. Focusing on ?-secretase and rhomboid proteases, we argue that answers to these questions may emerge from connecting experimental readouts, such as reaction kinetics and the determination of cleavage sites, to the structures and the conformational dynamics of substrates and enzymes. PMID:25941170
Probing the Reaction Kinetics of the Charge Reactions of Nonaqueous Li-O2 Batteries.
Lu, Yi-Chun; Shao-Horn, Yang
2013-01-01
Understanding the reaction mechanism of nonaqueous oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is key to increase the low round-trip efficiency and power capability of rechargeable Li-air batteries. Here we show that the ORR kinetics are much faster than OER kinetics and OER occurs in two distinct stages upon Li-air battery charging. The first OER stage occurs at low overpotentials (<400 mV) with a slopping voltage profile, whose kinetics are relatively insensitive to charge rates and catalysts. This OER stage could be attributed to the delithiation of the outer part of Li2O2 forming lithium-deficient Li2-xO2, which is chemically disproportionate to evolve O2. The second stage takes place at high overpotentials (400-1200 mV), whose kinetics are sensitive to discharge/charge rates and catalysts, which can be attributed to the oxidation of bulk Li2O2 particles. Our study provides insights into bridging current two schools of thought on the OER mechanism. PMID:26291218
Second-order quasinormal mode of the Schwarzschild black hole
NASA Astrophysics Data System (ADS)
Nakano, Hiroyuki; Ioka, Kunihito
2007-10-01
We formulate and calculate the second-order quasinormal modes (QNMs) of a Schwarzschild black hole (BH). Gravitational waves (GW) from a distorted BH, the so-called ringdowns, are well understood as QNMs in general relativity. Since QNMs from binary BH mergers will be detected with a high signal-to-noise ratio by GW detectors, it is also possible to detect the second perturbative order of QNMs, generated by nonlinear gravitational interaction near the BH. In the BH perturbation approach, we derive the master Zerilli equation for the metric perturbation to second order and explicitly regularize it at the horizon and spatial infinity. We numerically solve the second-order Zerilli equation by implementing the modified Leaver continued fraction method. The second-order QNM frequencies are found to be twice the first-order ones, and the GW amplitude is up to ˜10% that of the first order for the binary BH mergers. Since the second-order QNMs always exist, we can use their detections (i) to test the nonlinearity of general relativity, in particular, the no-hair theorem, (ii) to remove fake events in the data analysis of QNM GWs, and (iii) to measure the distance to the BH.
Second-order quasinormal mode of the Schwarzschild black hole
Nakano, Hiroyuki; Ioka, Kunihito
2007-10-15
We formulate and calculate the second-order quasinormal modes (QNMs) of a Schwarzschild black hole (BH). Gravitational waves (GW) from a distorted BH, the so-called ringdowns, are well understood as QNMs in general relativity. Since QNMs from binary BH mergers will be detected with a high signal-to-noise ratio by GW detectors, it is also possible to detect the second perturbative order of QNMs, generated by nonlinear gravitational interaction near the BH. In the BH perturbation approach, we derive the master Zerilli equation for the metric perturbation to second order and explicitly regularize it at the horizon and spatial infinity. We numerically solve the second-order Zerilli equation by implementing the modified Leaver continued fraction method. The second-order QNM frequencies are found to be twice the first-order ones, and the GW amplitude is up to {approx}10% that of the first order for the binary BH mergers. Since the second-order QNMs always exist, we can use their detections (i) to test the nonlinearity of general relativity, in particular, the no-hair theorem, (ii) to remove fake events in the data analysis of QNM GWs, and (iii) to measure the distance to the BH.
Diffusion Controlled Reactions, Fluctuation Dominated Kinetics, and Living Cell Biochemistry
Konkoli, Zoran
2009-01-01
In recent years considerable portion of the computer science community has focused its attention on understanding living cell biochemistry and efforts to understand such complication reaction environment have spread over wide front, ranging from systems biology approaches, through network analysis (motif identification) towards developing language and simulators for low level biochemical processes. Apart from simulation work, much of the efforts are directed to using mean field equations (equivalent to the equations of classical chemical kinetics) to address various problems (stability, robustness, sensitivity analysis, etc.). Rarely is the use of mean field equations questioned. This review will provide a brief overview of the situations when mean field equations fail and should not be used. These equations can be derived from the theory of diffusion controlled reactions, and emerge when assumption of perfect mixing is used.
Deflection of light to second order in conformal Weyl gravity
NASA Astrophysics Data System (ADS)
Sultana, Joseph
2013-04-01
We reexamine the deflection of light in conformal Weyl gravity obtained in Sultana and Kazanas (2010), by extending the calculation based on the procedure by Rindler and Ishak, for the bending angle by a centrally concentrated spherically symmetric matter distribution, to second order in M/R, where M is the mass of the source and R is the impact parameter. It has recently been reported in Bhattacharya et al. (JCAP 09 (2010) 004; JCAP 02 (2011) 028), that when this calculation is done to second order, the term ?r in the Mannheim-Kazanas metric, yields again the paradoxical contribution ?R (where the bending angle is proportional to the impact parameter) obtained by standard formalisms appropriate to asymptotically flat spacetimes. We show that no such contribution is obtained for a second order calculation and the effects of the term ?r in the metric are again insignificant as reported in our earlier work.
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.
Second order ODEs under area-preserving maps
NASA Astrophysics Data System (ADS)
Wone, Oumar
2015-03-01
We study the geometry of real analytic second order ODEs under the local real analytic diffeomorphism of which are area preserving, through the method of Cartan. We obtain a subdivision into three "parts". The first one is the most symmetric case. It is characterized by the vanishing of an area-preserving relative invariant namely . In this situation we associate a local affine normal Cartan connection on the first jet space whose curvature contains all the area-preserving relative differential invariants, to any second order ODE under study. The second case which includes all the Painlevé transcendents is given by the ODEs for which . In the latter case we give all necessary steps in order to obtain an -structure on for a generic second order ODE equation of that type. Finally we give the method to reduce to an -structure on when.
Carborane tuning on iridium complexes: redox-switchable second-order NLO responses.
Wang, Jiao; Wang, Wen-Yong; Fang, Xin-Yan; Qiu, Yong-Qing
2015-04-01
Much effort has been devoted to investigating the molecular geometries, electronic structures, redox properties and nonlinear optical (NLO) properties of Ir complexes involving o-, m- or p-carborane groups by density functional theory (DFT) methods. Switchable second-order NLO properties were induced by redox processes involving these complexes, and it was found that mainly the coordination bonds of Ir complexes changed during the oxidation process. Our calculations revealed that oxidation reactions have a significant influence on the second-order NLO response owing to the change in charge transfer pattern. The ? tot values of oxidized species are at least ?9 times larger for set I and ?5 times larger for set II than those of the corresponding parent complexes. Introduction of carborane groups into ppy (phenylpyridine) ligands can enhance the second-order NLO response by 1.2-?1.6 times by a metal-to-ligand charge transfer (MLCT) transition between the Ir atom and carborane. The ? tot of complex 2 [(ppy)2Ir(phen)](+) (phen?=?phenanthroline) is 3.3 times larger than that of complex 1 (ppy)2Ir(acce) (acce?=?acetylacetonate), which is caused by ligand-to-ligand charge transfer (LLCT) between ppy ligands and the ancillary ligand. Therefore, it can be concluded that the second-order NLO response can be effectively enhanced by oxidation reactions. PMID:25791353
Gilli, L.; Lathouwers, D.; Kloosterman, J. L.; Van Der Hagen, T. H. J. J.
2012-07-01
In this paper a second-order perturbation technique for nonlinear time-dependent problems is presented and applied to a simplified multi-physics model. This method is developed by using the properties of the adjoint problem which allows calculating the set of first and second order coefficients by solving a number of linear systems. As an illustrative example the adjoint procedure is applied to a reference transient problem, represented by a coupled point-kinetic/lumped-parameters model, and used to calculate the sensitivity coefficients of a safety related response with respect to a set of input parameters. The results obtained are compared with the values given by a direct sampling of the forward nonlinear problem. A way to reduce the number of calculations required for the application of second order adjoint techniques is also discussed. Our first results show that the procedure provides good estimations in presence of higher order perturbation components, being able to reconstruct the responses of interest even in presence of non-Gaussian probability density functions. Furthermore, the use of reduced second order information decreases the computational requirements of the method, making it appealing for possible large scale applications. (authors)
Tóth, János
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
Kinetics of reaction of sulfide with thiosulfate in aqueous solution
Siu, T.; Jia, C.Q. [Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry] [Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry
1999-04-01
The kinetics of the reaction 2H{sub 2}S(aq) + S{sub 2}O{sub 3}{sup 2{minus}} + 2H{sup +} {r_arrow} 1/2S{sub 8}(s) + 3H{sub 2}O has been investigated at 0--40 C in the pH interval from 5 to 7. The rate law was found to be r = {minus}d[S{sub 2}O{sub 3}{sup 2{minus}}]/dt = {kappa}[H{sub 2}S][S{sub 2}O{sub 3}{sup 2{minus}}], where {kappa} = 8 {times} 10{sup 11} exp({minus}74,300/RT) M{sup {minus}1} s{sup {minus}1}. Thermodynamic calculation shows that the reaction is unfavorable at pH {ge} 8, which is confirmed by the experimental observation. The ionic strength effect on the reaction also has been studied. The mechanism postulated to account for the observed rate law involves the formation and subsequent reactions of an intermediate H{sub 2}S{sub 3}O{sub 3}{sup 2{minus}}.
Kinetics of catalytic reaction between methanol and hydrogen sulfide
Mashkin, V.Yu.; Kudenkov, V.M.; Mashkina, A.V. [Pr. Akademika Lavrentieva, Novosibirsk (Russian Federation). Boreskov Inst. of Catalysis
1995-09-01
Methanol reaction with H{sub 2}S on tungsten- and potassium-promoted alumina was studied in the absence of any diffusional restrictions. The authors have found that on both W/Al{sub 2}O{sub 3} and KW/Al{sub 2}O{sub 3} catalysts methanol reacts with H{sub 2}S to produce methyl mercaptan, which may convert to dimethyl sulfide through either interaction with the second molecule of methanol or disproportionation. Methanol dehydration yields dimethyl ether. For KW/Al{sub 2}O{sub 3} catalyst, the generation of methyl mercaptan dominates. Adsorption data permitted the authors to suggest a mechanism of methanol reaction with H{sub 2}S. According to this mechanism reaction proceeds via the rapid methoxylation of catalyst surface and further interaction of CH{sub 3}O groups with the activated H{sub 2}S, CH{sub 3}SH, and CH{sub 3}OH. The kinetic equations obtained describe fairly well the reaction on the inhomogeneous catalyst surface.
UV-induced reaction kinetics of dilinoleoylphosphatidylethanolamine monolayers.
Viitala, T; Peltonen, J
1999-01-01
The UV-induced reactivity of dilinoleoylphosphatidylethanolamine (DLiPE) Langmuir and Langmuir-Blodgett films has been studied by in situ measurements of the changes in the mean molecular area, UV-vis and Fourier transform infrared spectroscopy, and atomic force microscopy (AFM). Optimum orientation and packing density of the DLiPE molecules in the monolayer were achieved by adding uranyl acetate to the subphase. A first-order reaction kinetic model was successfully fitted to the experimental reaction kinetics data obtained at a surface pressure of 30 mN/m. Topographical studies of LB films by AFM were performed on bilayer structures as a function of subphase composition and UV irradiation time. The orientational effect of the uranyl ions on the monolayer molecules was observed as an enhanced homogeneity of the freshly prepared monomeric LB films. However, the long-term stability of these films proved to be bad; clear reorganization and loss of a true monolayer structure were evidenced by the AFM images. This instability was inhibited for the UV-irradiated films, indicating that the UV irradiation gave rise to a cross-linked structure. PMID:10233096
Second order coupling between excited atoms and surface polaritons
Sofia Ribeiro; Stefan Y. Buhmann; Stefan Scheel
2012-12-20
Casimir-Polder interactions between an atom and a macroscopic body are typically regarded as due to the exchange of virtual photons. This is strictly true only at zero temperature. At finite temperature, real-photon exchange can provide a significant contribution to the overall dispersion interaction. Here we describe a new 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.
Notes 02. Dynamic response of second order mechanical systems
San Andres, Luis
2008-01-01
: Handout 2a ? Luis San Andr?s (2008) 2-1 Handout #2a (pp. 1-39) Dynamic Response of Second Order Mechanical Systems with Viscous Dissipation forces 2 () 2 ext t dX dX MDKXF dt dt ++= Free Response to initial conditions and F (t) = 0..., Underdamped, Critically Damped and Overdamped Systems Free Response for system with Coulomb (Dry) friction Forced Response for Step Loading F (t) = F o MEEN 617 Notes: Handout 2a ? Luis San Andr?s (2008) 2-2 Second Order Mechanical...
Elasto-plastic model with second order defect density tensor
NASA Astrophysics Data System (ADS)
Cleja-?igoiu, Sanda
2011-05-01
The paper deals with a second order finite elasto-plastic model, which involves the defect density tensor, as a measure of the extra material defects existing in the damaged microstructure. The material behaviour is described with respect to an anholonomic configuration, which is introduced through the second order plastic deformation, consisting in plastic distortion and plastic connection. The defect density tensor enters the expression of the plastic connection through its gradient and represents a measure of non-metricity. The constitutive and evolution equations are derived to be compatible with the free energy imbalance. The evolution equation for the defect density tensor is non-local and coupled with the plastic distortion.
The Poisson equation at second order in relativistic cosmology
Hidalgo, J.C.; Christopherson, Adam J.; Malik, Karim A. E-mail: Adam.Christopherson@nottingham.ac.uk
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.
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…
Kinetics of sulfur and nitrogen reactions in combustion systems
Kramlich, J.C.; Seeker, W.R. ); Lester, T.W. ); Wendt, J.O.L. )
1989-10-01
This volume is the last of a three volume set. Specifically, the activities reported herein cover investigations on the problem of determining NO yields from pulverized coal flames. Work also focused on several approaches to reducing NO in combustion products. The work is described in the following sections. Homogenous Kinetics: This task seeks to improve and update a model describing homogenous fuel nitrogen reactions. The specific focus is reburning, although all fuel chemistry (through C{sub 2} hydrocarbons) is considered. Nitrogen species include HCN, N{sub 2}O, NH{sub 3}, NO{sub x}, and all the relevant intermediates. Heterogenous Reduction: This project was designed to measure the rate of NO reduction on soot so that the importance of the heterogenous pathway could be quantitatively determined. Fuel-Nitrogen Reactions in Pulverized Coal Combustion: This project is designed to provide a bridge between the more fundamental elements of the program. The goal is to develop global data against which the more fundamental models can be compared. Nitrous Oxide Behavior: This section describes the development of an analytical method for measuring nitrous oxide in flue gases. It also describes the discovery of a major sampling artifact in which N{sub 2}O is produced with containers that are commonly used for grab samples. Post-Flame NO{sub x} Reduction Agents: This project focused on the detailed kinetics of the reduction of NO by cyanuric acid. The study also focused on the promotion of the reaction by CO. 3 refs., 34 figs., 4 tabs.
A New Factorisation of a General Second Order Differential Equation
ERIC Educational Resources Information Center
Clegg, Janet
2006-01-01
A factorisation of a general second order ordinary differential equation is introduced from which the full solution to the equation can be obtained by performing two integrations. The method is compared with traditional methods for solving these type of equations. It is shown how the Green's function can be derived directly from the factorisation…
Solving Second-Order Differential Equations with Variable Coefficients
ERIC Educational Resources Information Center
Wilmer, A., III; Costa, G. B.
2008-01-01
A method is developed in which an analytical solution is obtained for certain classes of second-order differential equations with variable coefficients. By the use of transformations and by repeated iterated integration, a desired solution is obtained. This alternative method represents a different way to acquire a solution from classic power…
PREDICTIONS OF HIGHWAY EMISSIONS BY A SECOND ORDER CLOSURE MODEL
The dispersion of sulfur hexafluoride tracer and sulfate from automobile emissions in the immediate vicinity of a highway were estimated for conditions similar to those existing during the General Motors sulfate dispersion experiment conducted at a GM test track. A second-order c...
SECOND-ORDER METHODS FOR THE OPTIMIZATION OF MOLECULAR POTENTIAL
Helgaker, Trygve
-9784 USA The optimization of ab initio Born-Oppenheimer potential energy surfaces is an important subject of the molecular potential energy surface are an essential tool in studies of molecular structure and reactivitySECOND-ORDER METHODS FOR THE OPTIMIZATION OF MOLECULAR POTENTIAL ENERGY SURFACES 1 Introduction
Optimal Magnetic Shield Design with Second--Order Cone Programming
Tsuchiya, Takashi
car is equipped with several superconducting magnet units which generate the magnetic field. Passengers inside the car need to be shielded from the magnetic field outside. The optimal design problemOptimal Magnetic Shield Design with Second--Order Cone Programming Takashi Sasakawa # Takashi
Optimal Magnetic Shield Design with SecondOrder Cone Programming
Tsuchiya, Takashi
. Each car is equipped with several super-conducting magnet units which generate the magnetic field. Passengers inside the car need to be shielded from the magnetic field outside. The optimal design problemOptimal Magnetic Shield Design with SecondOrder Cone Programming Takashi Sasakawa Takashi Tsuchiya
Oscillation Criteria for Second-Order Nonlinear Dynamic Equations
Logan, David
Oscillation Criteria for Second-Order Nonlinear Dynamic Equations on Time Scales Lynn Erbe1 , Allan and generalized exponential functions, we give some oscillation criteria for the nonlinear dynamic equation (p(t)x (t)) + q(t)(f x ) = 0, on time scales. We also apply our results to linear and nonlinear dynamic
Second Order Backward Stochastic Differential Equations with Quadratic Growth
Dylan, Possamai
2012-01-01
We prove the existence and uniqueness of a solution for one-dimensionnal second order backward stochastic differential equations introduced by Soner, Touzi and Zhang (2010), with a bounded terminal condition and a generator which is continuous with quadratic growth in z. We also prove a Feyman-Kac formula and a probabilistic representation for fully nonlinear PDEs in this setting.
Static second-order polarizability calculations for large molecular systems
NASA Technical Reports Server (NTRS)
Cardelino, Beatriz H.; Stickel, Robert E.; Moore, Craig E.
1991-01-01
A procedure to calculate all second-order polarizability tensor elements in static fields has been developed. The calculations are based on semiempirical Hamiltonians (MNDO) that include shaped electric fields. The technique has been applied to mono-, di-, and trisubstituted benzenes incorporating nitro, methyl, and primary and secondary amino groups.
Algebraic Multigrid for Discrete Elliptic SecondOrder Problems
Algebraic Multigrid for Discrete Elliptic SecondOrder Problems Ferdinand Kickinger Institute of Algebraic MultiGrid (AMG) methods, which are especially suited for the solution of large sparse systemsscales, where the generation of a ''coarse mesh'' with a few number of grid points might not be feasible. One
Second-order adaptive infinite impulse response filter
Ahmed, N.; Hush, D.; Elliott, G.R.; Fogler, R.J.
1983-01-01
A simple second-order infinite impulse response (IIR) filter is introduced. An efficient algorithm to use it as a line enhancer and tracker is presented. The related experimental results demonstrate that it can be used very effectively to enhance and track a single or dominant sinusoid in broadband noise.
FIRST-ORDER SYSTEM LEAST SQUARES FOR SECOND-ORDER ...
1997-03-07
second-order uniformly elliptic partial differential equations in n = 2 or 3 ... elliptic in the H(div) × H1 norm and to yield optimal convergence for finite ... [11], is the solution of elliptic equations (including convection–diffusion and Helmholtz ...... a constant; their difference would yield a nonzero function of the form (2.37) that.
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.
FIRST AND SECOND-ORDER ADAPTIVE DIFFERENTIAL MICROPHONE ARRAYS
Heinz Teutsch; Gary W. Elko
2001-01-01
Whenever undesired noise sources are spatially non- stationary, conventional directional microphone technology has its limits in terms of interference suppression. Adap- tive differential microphone arrays (ADMAs) with their null steering capabilities promise better performance. This con- tribution introduces and examines first- and second-order ADMAs based on fullband as well as on subband algo- rithms. A real-time implementation that demonstrates its
Forward and backward second-order Pavlovian conditioning in honeybees
Menzel, Randolf - Institut für Biologie
, associative learning can be in- direct or of second-order, as in the case of Pavlov's dog (Pavlov 1927). A dog, when put into a dark room and given food (primary reinforcer, US) just before switching on the light to CR). Then, in a separate event, the dog was presented with the tone of a bell (neutral stimulus, NS
Second-order accurate monotone finite volume scheme for ...
Oleksandr Misiats
2013-02-28
Oct 16, 2012 ... The uniqueness of u?t; x? is proved using the same idea. ... positive for evaporation and negative for infiltration. ..... The experimental convergence rate indicates that the scheme is of the second order of accuracy; ..... [20] L. Richards, Capillary conduction of liquids through porous mediums, Physics 1 (5) ...
Second-order accurate nonoscillatory schemes for scalar conservation laws
NASA Technical Reports Server (NTRS)
Huynh, Hung T.
1989-01-01
Explicit finite difference schemes for the computation of weak solutions of nonlinear scalar conservation laws is presented and analyzed. These schemes are uniformly second-order accurate and nonoscillatory in the sense that the number of extrema of the discrete solution is not increasing in time.
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…
Maximum-principle-satisfying second order discontinuous Galerkin ...
2014-05-05
We propose second order accurate discontinuous Galerkin (DG) schemes ... Keywords: discontinuous Galerkin method; maximum principle; positivity preserving; .... to the time level and j denotes the spatial cell, and uj is the numerical ... To extend the idea above to convection-diffusion equations (1.1) or (
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 $0density-dependence $\\rho^{8/3}$ of several second-order contributions. The inclusion of the density-dependent term ${1\\over 6}t_3 \\rho^{1/6}$ is therefore indispensable for a realistic description of nuclear matter in the Skyrme framework.
Skyrme interaction to second order in nuclear matter
NASA Astrophysics Data System (ADS)
Kaiser, N.
2015-09-01
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\\lt ? \\lt 2{? }0. The reason for this feature is the too strong density-dependence {? }8/3 of several second-order contributions. The inclusion of the density-dependent term \\frac{1}{6}{t}3{? }1/6 is therefore indispensable for a realistic description of nuclear matter in the Skyrme framework.
Second Order Surface Analysis Using Hybrid Symbolic and Numeric Operators
for the creation of tool paths for NC (Numerically Con- trolled) code generation for freeform surfaces are usuallySecond Order Surface Analysis Using Hybrid Symbolic and Numeric Operators Gershon Elbery and Elaine the curvature of a surface can be used to improve the implementation, e ciency, and e ectiveness
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,…
Forward and Backward Second-Order Pavlovian Conditioning in Honeybees
ERIC Educational Resources Information Center
Hussaini, Syed Abid; Komischke, Bernhard; Menzel, Randolf; Lachnit, Harald
2007-01-01
Second-order conditioning (SOC) is the association of a neutral stimulus with another stimulus that had previously been combined with an unconditioned stimulus (US). We used classical conditioning of the proboscis extension response (PER) in honeybees ("Apis mellifera") with odors (CS) and sugar (US). Previous SOC experiments in bees were…
Wang, Pei; He, Yi-Liang; Huang, Ching-Hua
2010-12-01
Fluoroquinolones (FQs) are a group of widely prescribed antibiotics and have been frequently detected in the aquatic environment. The reaction kinetics and transformation of seven FQs (ciprofloxacin (CIP), enrofloxacin (ENR), norfloxacin (NOR), ofloxacin (OFL), lomefloxacin (LOM), pipemidic acid (PIP) and flumequine (FLU)) and three structurally related amines (1-phenylpiperazine (PP), N-phenylmorpholine (PM) and 4-phenylpiperidine (PD)) toward chlorine dioxide (ClO(2)) were investigated to elucidate the behavior of FQs during ClO(2) disinfection processes. The reaction kinetics are highly pH-dependent, can be well described by a second-order kinetic model incorporating speciation of FQs, and follow the trend of OFL > ENR > CIP ? NOR ? LOM > > PIP in reactivity. Comparison among FQs and related amines and product characterization indicate that FQs' piperazine ring is the primary reactive center toward ClO(2). ClO(2) likely attacks FQ's piperazinyl N4 atom followed by concerted fragmentation involving piperazinyl N1 atom, leading to dealkylation, hydroxylation and intramolecular ring closure at the piperazine moiety. While FQs with tertiary N4 react faster with ClO(2) than FQs with secondary N4, the overall reactivity of the piperazine moiety also depends strongly on the quinolone ring through electronic effects. The reaction rate constants obtained in clean water matrix can be used to model the decay of CIP by ClO(2) in surface water samples, but overestimate the decay in wastewater samples. Overall, transformation of FQs, particularly for those with tertiary N4 amines, could be expected under typical ClO(2) disinfection conditions. However, the transformation may not eliminate antibacterial activity because of little destruction at the quinolone ring. PMID:20708211
Atmospheric reactions Cl+CH3-(CH2)n-OH (n=0-4): A kinetic and theoretical study
NASA Astrophysics Data System (ADS)
Garzón, Andrés; Cuevas, Carlos A.; Ceacero, Antonio A.; Notario, Alberto; Albaladejo, José; Fernández-Gómez, Manuel
2006-09-01
The reactions of Cl with a series of linear alcohols: methanol (k1), ethanol (k2), 1-propanol (k3), 1-butanol (k4), and 1-pentanol (k5) were investigated as a function of temperature in the range of 264-382K by laser photolysis-resonance fluorescence. The obtained kinetic data were used to derive the following Arrhenius expressions: k1=(3.55±0.22)×10-10exp[-(559±40)/T], k2=(5.25±0.52)×10-11exp[(190±68)/T], k3=(2.63±0.21)×10-11exp[(525±51)/T], k4=(3.12±0.31)×10-11exp[(548±65)/T], and k5=(3.97±0.48)×10-11exp[(533±77)/T] (in units of cm3molecule-1s-1). To our knowledge, these are the first absolute kinetic data reported for 1-butanol and 1-pentanol and also the first kinetic study as a function of temperature for these two compounds. Results, mechanism, and tropospheric implications are discussed and compared with the reported reactivity with OH radicals. Moreover, a theoretical insight into the mechanisms of these reactions has also been pursued through ab initio Möller-Plesset second-order perturbation treatment calculations with 6-311G** basis sets. Optimized geometries and vibrational frequencies have been obtained for transition states and molecular complexes appearing along the different reaction pathways. Furthermore, molecular energies have been calculated at quadratic configuration interaction with single, double, and triple excitations level in order to get an estimation of the activation energies.
Kinetics of the Self Reaction of Cyclopentadienyl Radicals.
Knyazev, Vadim D; Popov, Konstantin V
2015-07-16
The kinetics of the self-reaction of cyclopentadienyl radicals (c-C5H5) was studied by laser photolysis/photoionization mass spectroscopy. Overall rate constants were obtained in direct real-time experiments in the temperature region 304-600 K and at bath gas densities of (3.00-12.0) × 10(16) molecules cm(-3). The room-temperature value of the rate constant, (3.98 ± 0.41) × 10(-10) cm(3) molecule(-1) s(-1), is significantly higher than the rate constants for most hydrocarbon radical-radical reactions and coincides with the estimated collision rate. The observed overall c-C5H5 + c-C5H5 rate constant demonstrates an unprecedented strong negative temperature dependence: k1 = 2.9 × 10(-12) exp(+1489 K/T) cm(3) molecule(-1) s(-1), with estimated uncertainty increasing with temperature, from 13% at 304 to 32% at 600 K. Formation of C10H10 as the primary product of cyclopentadienyl self-reaction was observed. In additional experiments performed at the temperature of 800 K, formation of C10H10, C10H9, and C10H8 was observed. Final product analysis by gas chromatography/mass spectrometry detected two isomers of C10H8 at 800 K: naphthalene (major) and azulene (minor). PMID:25760686
McKay, Garrett; Sjelin, Brittney; Chagnon, Matthew; Ishida, Kenneth P; Mezyk, Stephen P
2013-09-01
The temperature-dependent kinetics for the reaction between hydrogen peroxide and chloramine water disinfectants (NH2Cl, NHCl2, and NCl3) have been determined using stopped flow-UV/Vis spectrophotometry. Rate constants for the mono- and dichloramine-peroxide reaction were on the order of 10(-2)M(-1)s(-1) and 10(-5)M(-1)s(-1), respectively. The reaction of trichloramine with peroxide was negligibly slow compared to its thermal and photolytically-induced decomposition. Arrhenius expressions of ln(kH2O2-NH2Cl)=(17.3±1.5)-(51500±3700)/RT and ln(kH2O2-NHCl2)=(18.2±1.9)-(75800±5100)/RT were obtained for the mono- and dichloramine peroxide reaction over the temperature ranges 11.4-37.9 and 35.0-55.0°C, respectively. Both monochloramine and hydrogen peroxide were first-order in the rate-limiting kinetic step and concomitant measurements made using a chloride ion selective electrode showed that the chloride was produced quantitatively. These data will aid water utilities in predicting chloramine concentrations (and thus disinfection potential) throughout the water distribution system. PMID:23601896
Kinetics and stereospecificity of the lysyl oxidase reaction.
Shah, M A; Scaman, C H; Palcic, M M; Kagan, H M
1993-06-01
The structural specificity of amine oxidation by lysyl oxidase was investigated using kinetic and NMR spectroscopic analyses. Substrate efficiency increased with increasing molecular distance from the alpha-carbon of the aromatic moiety substituted on the aliphatic chains of a series of primary amines. The p-hydroxyl substituent of p-hydroxybenzylamine significantly increased kcat over that of benzylamine, whereas this was not the case when tyramine and phenethylamine were compared. Direct spectrophotometric measurement of p-hydroxybenzaldehyde formation yielded burst kinetics, the second, slower phase of which was eliminated under anaerobic conditions. Thus, enzyme reoxidation is the more rate-limiting of the two half-reactions catalyzed with this substrate by this ping-pong enzyme. 1H NMR spectroscopy of the alcohol reductively derived from the aldehyde product of the lysyl oxidase-catalyzed oxidation of deuterated tyramine indicated that the pro-S but not the pro-R alpha-deuteron was catalytically abstracted. Moreover, lysyl oxidase catalyzed solvent exchange of protons at the C-2 position. Such stereospecificity and proton exchange uniquely differentiates lysyl oxidase from all but an aortic semicarbazide-sensitive amine oxidase among the pro-S-specific copper-dependent amine oxidases analyzed thus far. PMID:8099354
Nuclear quantum effects and kinetic isotope effects in enzyme reactions.
Vardi-Kilshtain, Alexandra; Nitoker, Neta; Major, Dan Thomas
2015-09-15
Enzymes are extraordinarily effective catalysts evolved to perform well-defined and highly specific chemical transformations. Studying the nature of rate enhancements and the mechanistic strategies in enzymes is very important, both from a basic scientific point of view, as well as in order to improve rational design of biomimetics. Kinetic isotope effect (KIE) is a very important tool in the study of chemical reactions and has been used extensively in the field of enzymology. Theoretically, the prediction of KIEs in condensed phase environments such as enzymes is challenging due to the need to include nuclear quantum effects (NQEs). Herein we describe recent progress in our group in the development of multi-scale simulation methods for the calculation of NQEs and accurate computation of KIEs. We also describe their application to several enzyme systems. In particular we describe the use of combined quantum mechanics/molecular mechanics (QM/MM) methods in classical and quantum simulations. The development of various novel path-integral methods is reviewed. These methods are tailor suited to enzyme systems, where only a few degrees of freedom involved in the chemistry need to be quantized. The application of the hybrid QM/MM quantum-classical simulation approach to three case studies is presented. The first case involves the proton transfer in alanine racemase. The second case presented involves orotidine 5'-monophosphate decarboxylase where multidimensional free energy simulations together with kinetic isotope effects are combined in the study of the reaction mechanism. Finally, we discuss the proton transfer in nitroalkane oxidase, where the enzyme employs tunneling as a catalytic fine-tuning tool. PMID:25769515
Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes
Sheng, Wenchao
The kinetics of the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) on polycrystalline platinum [Pt(pc)] and high surface area carbon-supported platinum nanoparticles (Pt/C) were studied in 0.1 M ...
Kinetic study of hydrated lime reaction with HCl.
Yan, Rong; Chin, Terence; Liang, David Tee; Laursen, Karin; Ong, Wan Yean; Yao, Kaiwen; Tay, Joo Hwa
2003-06-01
Hydrochloride (HCl) is an acidic pollutant present in the flue gas of most municipal or hazardous waste incinerators. Hydrated lime (Ca(OH)2) is often used as a dry sorbent for injection in a spray reactor to remove HCI. However, due to the short residence time encountered, this control method has generally been found to have low conversion efficiencies which results in the high lime usage and generates large amount of fly ash as solid wastes. A fundamental study was carried outto investigate the kinetics of HCl-lime reaction under simulated flue gas conditions in order to better understand the process thereby providing a basis for an optimized lime usage and reduced fly ash production. The initial reaction rate and conversion of three limes were studied using a thermogravimetric analyzer by varying the gas flow rate, temperature (170-400 degrees C), and HCI concentrations (600-1200 mg/m3) as well as the associated particle size and surface area of the limes. The initial lime conversions were found to rely mostly on the residence time, while the ultimate lime conversions were strongly influenced by temperature and the reaction products. CaOHCI was found to be the primary product in most cases, while for one specific lime, CaCl2 was the ultimate conversion product after an extended time period. The true utilization of lime in flue gas cleanup is thus higher when CaOHCl is considered as the final product than those based on CaCl2 as the final product, which has been commonly used in previous studies. The initial reaction was controlled by diffusion of HCl in gas phase and the subsequent reaction by gaseous diffusion through the developing product layer. Increasing the HCI concentration raised the initial rate as well as conversion. However, overloading the lime with excessive HCI caused clogging at its surface and a drop in the ultimate conversion. Limes with smaller particle diameters and higher surface areas were found to be more reactive. The effect of gas-phase mass transfer was minimized when an optimum flow rate was chosen, and in the absence of internal diffusion the reaction was found to be first order with respect to HCI concentration. PMID:12831043
Bounded solutions of a second order evolution equation and applications
NASA Astrophysics Data System (ADS)
Leiva, Hugo
2001-02-01
In this paper we study the following abstract second order differential equation with dissipation in a Hilbert space H: u?+cu'+dA u+kG(u)=P(t), u?H, t?R, where c, d and k are positive constants, G:H?H is a Lipschitzian function and P:R?H is a continuous and bounded function. A:D(A)?H?H is an unbounded linear operator which is self-adjoint, positive definite and has compact resolvent. Under these conditions we prove that for some values of d, c and k this system has a bounded solution which is exponentially asymptotically stable. Moreover; if P(t) is almost periodic, then this bounded solution is also almost periodic. These results are applied to a very well known second order system partial differential equations; such as the sine-Gordon equation, The suspension bridge equation proposed by Lazer and McKenna, etc.
Cosmological perturbations at second order and recombination perturbed
Senatore, Leonardo [School of Natural Sciences, Institute for Advanced Study, Olden Lane, Princeton, NJ 08540 (United States); Tassev, Svetlin [Center for Astrophysics, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States); Zaldarriaga, Matias, E-mail: senatore@ias.edu, E-mail: stassev@cfa.harvard.edu, E-mail: matiasz@ias.edu [Jefferson Physical Laboratory, Harvard University, 17 Oxford Street, Cambridge, MA 02138 (United States)
2009-08-01
We derive the full set of second-order equations governing the evolution of cosmological perturbations, including the effects of the first-order electron number density perturbations, ?{sub e}. We provide a detailed analysis of the perturbations to the recombination history of the universe and show that a perturbed version of the Peebles effective 3-level atom is sufficient for obtaining the evolution of ?{sub e} for comoving wavenumbers smaller than 1 Mpc{sup ?1}. We calculate rigorously the perturbations to the Ly? escape probability and show that to a good approximation it is governed by the local baryon velocity divergence. For modes longer than the photon diffusion scale, we find that ?{sub e} is enhanced during recombination by a factor of roughly 5 relative to other first-order quantities sourcing the CMB anisotropies at second order. Using these results, in a companion paper we calculate the CMB bispectrum generated during recombination.
Linear second-order differential equations for barotropic FRW cosmologies
H. C. Rosu; O. Cornejo; M. Reyes; D. Jimenez
2002-12-15
Simple linear second-order differential equations have been written down for FRW cosmologies with barotropic fluids by Faraoni. His results have been extended by Rosu, who employed techniques belonging to nonrelativistic supersymmetry to obtain time-dependent adiabatic indices. Further extensions are presented here using the known connection between the linear second-order differential equations and Dirac-like equations in the same supersymmetric context. These extensions are equivalent to adding an imaginary part to the adiabatic index which is proportional to the mass parameter of the Dirac spinor. The natural physical interpretation of the imaginary part is related to the particular dissipation and instabilities of the barotropic FRW hydrodynamics that are introduced by means of this supersymmetric scheme
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.
Quantum degradation of a second-order phase transition
NASA Astrophysics Data System (ADS)
Stishov, S. M.; Petrova, A. E.; Gavrilkin, S. Yu.; Klinkova, L. A.
2015-04-01
The specific heat, magnetization, and thermal expansion of single crystals of the antiferromagnetic insulator EuTe, measured at temperatures down to 2 K and in magnetic fields up to 90 kOe, demonstrate nontrivial properties. The Néel temperature, being ˜9.8 at H =0 , decreases with magnetic field and tends to zero at ˜76 kOe , therefore forming a quantum critical point. The heat capacity and thermal expansion coefficient reveal ? -type anomalies at the second order magnetic phase transition at low magnetic fields, evolving into simple jumps at high magnetic fields and low temperatures; these are well described in a fluctuation-free mean-field theory. The experimental data and the corresponding analysis favor the quantum concept of an effective increase in spatial dimensionality at low temperatures that suppresses a fluctuation-driven divergence at a second-order phase transition.
Second-order nonlinear optical devices in poled polymers
Singer, K.D.; Holland, W.R.; Kuzyk, M.G.; Wolk, G.L.; Katz, H.E.; Schilling, M.L.; Cahill, P.A.
1989-01-01
Guest-host poled polymer films have become an active area of research as potential candidates for second-order nonlinear optical and electro-optic devices. This interest derives mainly from their large nonlinear optical coefficients, ease of fabrication, and high optical quality. Progress has been rapid in producing stable, efficient materials, and in building demonstration devices. The second-order nonlinear optical properties arise from the orientational order induced in a collection of highly nonlinear molecules incorporated in a glassy polymer matrix. After reviewing the alignment physics, we present results of nonlinear optical measurements on a methacrylate polymer functionalized with a dicyanovinyl terminated azo dye. Device issues concerning nonlinear optical devices are described with particular attention to phase-matching. We present data on the demonstration of anomalous-dispersion phase matched second harmonic generation in dye solutions. We also present results on electro-optic modulators. 13 refs., 9 figs., 2 tabs.
Enzyme Kinetics: The study of reaction rates. For the 1st-order reaction S P the Velocity (V) is
O'Neil, Joe
litre · moles litre = moles litre·sec k-1 k1 A + B C ! #12;9/25/13 2 Factors affecting Enzyme9/25/13 1 Enzyme Kinetics: The study of reaction rates. For the 1st-order reaction S P-Catalysed Reactions: 1. Enzyme Concentration Usually, [E
Kinetics of boehmite precipitation from supersaturated sodium aluminate solutions
C. Skoufadis; D. Panias; I. Paspaliaris
2003-01-01
This work presents the effect of the most important parameters, the precipitation temperature, the sodium hydroxide concentration and the initial seed ratio (SR) in the solution, on the boehmite precipitation from supersaturated sodium aluminate solutions. A kinetic model that describes the experimental data was developed. According to that model, boehmite precipitation follows second order reaction kinetics and has activation energy
Radical Recombination Kinetics: An Experiment in Physical Organic Chemistry.
ERIC Educational Resources Information Center
Pickering, Miles
1980-01-01
Describes a student kinetic experiment involving second order kinetics as well as displaying photochromism using a wide variety of techniques from both physical and organic chemistry. Describes measurement of (1) the rate of the recombination reaction; (2) the extinction coefficient; and (3) the ESR spectrometer signal. (Author/JN)
Modified Gravity Models Admitting Second Order Equations of Motion
Colléaux, Aimeric
2015-01-01
The aim of this paper is to find higher order geometrical corrections to the Einstein-Hilbert action that can lead to only second order equations of motion. The metric formalism is used, and static spherically symmetric and Friedmann-Lema\\^itre space-times are considered, in four dimensions. The FKWC-basis are introduced in order to consider all the possible invariant scalars, and both polynomial and non-polynomial gravities are investigated.
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.
Gravitational Waves from Global Second Order Phase Transitions
John T. Giblin Jr; Larry R. Price; Xavier Siemens; Brian Vlcek
2011-11-17
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.
On an Interpretation of Second Order Quanti cation in
Pitts, Andrew
Andrew.Pitts@cl.cam.ac.uki Abstract We prove the following surprising property of Heyting's intuitionistic propositional calculus, IpC be modelled in IpC, and there is an interpretation of the second order propositional calculus, IpC2, in IpC is the strengthening of the usual Interpolation Theorem for IpC to the statement that there are least and greatest in
Different approaches to the second order Klein-Gordon equation
Malik, Karim A; Ananda, Kishore N
2007-01-01
We derive the Klein--Gordon equation for a single scalar field coupled to gravity at second order in perturbation theory and leading order in slow-roll. This is done in two ways: we derive the Klein--Gordon equation first using the Einstein field equations, and then directly from the action after integrating out the constraint equations. We also point out an unexpected result regarding the treatment of the field equations.
Different approaches to the second order Klein-Gordon equation
Karim A. Malik; David Seery; Kishore N. Ananda
2007-12-11
We derive the Klein--Gordon equation for a single scalar field coupled to gravity at second order in perturbation theory and leading order in slow-roll. This is done in two ways: we derive the Klein--Gordon equation first using the Einstein field equations, and then directly from the action after integrating out the constraint equations. We also point out an unexpected result regarding the treatment of the field equations.
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,
Asymptotic analysis of perturbed dust cosmologies to second order
NASA Astrophysics Data System (ADS)
Uggla, Claes; Wainwright, John
2013-08-01
Nonlinear perturbations of Friedmann-Lemaitre cosmologies with dust and a cosmological constant ? >0 have recently attracted considerable attention. In this paper our first goal is to compare the evolution of the first and second order perturbations by determining their asymptotic behaviour at late times in ever-expanding models. We show that in the presence of spatial curvature K or a cosmological constant, the density perturbation approaches a finite limit both to first and second order, but the rate of approach depends on the model, being power law in the scale factor if ? >0 but logarithmic if ? =0 and K<0. Scalar perturbations in general contain a growing and a decaying mode. We find, somewhat surprisingly, that if ? >0 the decaying mode does not die away, i.e. it contributes on an equal footing as the growing mode to the asymptotic expression for the density perturbation. On the other hand, the future asymptotic regime of the Einstein-de Sitter universe (K=? =0) is completely different, as exemplified by the density perturbation which diverges; moreover, the second order perturbation diverges faster than the first order perturbation, which suggests that the Einstein-de Sitter universe is unstable to perturbations, and that the perturbation series do not converge towards the future. We conclude that the presence of spatial curvature or a cosmological constant stabilizes the perturbations. Our second goal is to derive an explicit expression for the second order density perturbation that can be used to study the effects of including a cosmological constant and spatial curvature.
NASA Technical Reports Server (NTRS)
Bittker, D. A.; Scullin, V. J.
1972-01-01
A general chemical kinetics program is described for complex, homogeneous ideal-gas reactions in any chemical system. Its main features are flexibility and convenience in treating many different reaction conditions. The program solves numerically the differential equations describing complex reaction in either a static system or one-dimensional inviscid flow. Applications include ignition and combustion, shock wave reactions, and general reactions in a flowing or static system. An implicit numerical solution method is used which works efficiently for the extreme conditions of a very slow or a very fast reaction. The theory is described, and the computer program and users' manual are included.
Second-order reconstruction of the inflationary potential
NASA Technical Reports Server (NTRS)
Liddle, Andrew R.; Turner, Michael S.
1994-01-01
To first order in the deviation from scale invariance the inflationary potential and its first two derivatives can be expressed in terms of the spectral indices of the scalar and tensor perturbations, n and n(sub T), and their contributions to the variance of the quadrupole CBR temperature anisotropy, S and T. In addition, there is a 'consistency relation' between these quantities: n(sub T) = (-1/ 7)(T/S). We derive the second-order expressions for the inflationary potential and its first two derivatives and the first-order expression for its third derivative, in terms, of n, n(sub T), S, T, and dn/d ln gamma. We also obtain the second-order consistency relation, n(sub T) = (-1/7)(T/S)(1 + 0.11(T/S) + 0.15(n-1)). As an example we consider the exponential potential, the only known case where exact analytic solutions for the perturbation spectra exist. We reconstruct the potential via Taylor expansion (with coefficients calculated at both first and second order), and introduce the Pade approximate as a greatly improved alternative.
Mixed hyperbolic-second-order-parabolic formulations of general relativity
Paschalidis, Vasileios [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago Illinois 60637 (United States)
2008-07-15
Two new formulations of general relativity are introduced. The first one is a parabolization of the Arnowitt-Deser-Misner formulation and is derived by the addition of combinations of the constraints and their derivatives to the right-hand side of the Arnowitt-Deser-Misner evolution equations. The desirable property of this modification is that it turns the surface of constraints into a local attractor because the constraint propagation equations become second-order parabolic independently of the gauge conditions employed. This system may be classified as mixed hyperbolic--second-order parabolic. The second formulation is a parabolization of the Kidder-Scheel-Teukolsky formulation and is a manifestly mixed strongly hyperbolic--second-order-parabolic set of equations, bearing thus resemblance to the compressible Navier-Stokes equations. As a first test, a stability analysis of flat space is carried out and it is shown that the first modification exponentially damps and smoothes all constraint-violating modes. These systems provide a new basis for constructing schemes for long-term and stable numerical integration of the Einstein field equations.
Properties of second-order spatial frequency channels.
Landy, Michael S; Oruç, Ipek
2002-09-01
The segregation of texture patterns may be carried out by a set of linear spatial filters (to enhance one of the constituent textures), a nonlinearity (to convert the higher contrast of response to that constituent to a higher mean response), and finally subsequent ("second-order") linear spatial filters (to provide a strong response to the texture-defined edge itself). In this paper, the properties of such second-order filters are characterized. Observers were required to detect or discriminate textures that were modulated between predominantly horizontally oriented and predominantly vertically oriented noise patterns. Spatial summation for these patterns reached asymptote for a stimulus size of 15 x 15 deg. Modulation contrast sensitivity was nearly flat over a five-octave range of spatial frequency, but was bandpass when stated as efficiency (relative to an idealized observer confronted with the same task). Increment threshold showed the improved performance with a sub-threshold pedestal seen in the "dipper effect", but the typical Weber's law behavior at higher pedestal contrasts was not observed at the highest pedestal modulation contrasts achievable with our stimuli. Sub-threshold summation experiments indicate that second-order filters have a moderate bandwidth. PMID:12220586
Noise masking reveals channels for second-order letters
Oruç, ?pek; Landy, Michael S.; Pelli, Denis G.
2009-01-01
We investigate the channels underlying identification of second-order letters using a critical-band masking paradigm. We find that observers use a single 1–1.5 octave-wide channel for this task. This channel’s best spatial frequency (c/letter) did not change across different noise conditions (indicating the inability of observers to switch channels to improve signal-to-noise ratio) or across different letter sizes (indicating scale invariance), for a fixed carrier frequency (c/letter). However, the channel’s best spatial frequency does change with stimulus carrier frequency (both in c/letter); one is proportional to the other. Following Majaj et al. (Majaj, N. J., Pelli, D. G., Kurshan, P., & Palomares, M. (2002). The role of spatial frequency channels in letter identification. Vision Research, 42, 1165–1184), we define “stroke frequency” as the line frequency (strokes/deg) in the luminance image. That is, for luminance-defined letters, stroke frequency is the number of lines (strokes) across each letter divided by letter width. For second-order letters, letter texture stroke frequency is the number of carrier cycles (luminance lines) within the letter ink area divided by the letter width. Unlike the nonlinear dependence found for first-order letters (implying scale-dependent processing), for second-order letters the channel frequency is half the letter texture stroke frequency (suggesting scale-invariant processing). PMID:16203023
Reaction sequence and kinetics of uranium nitride decomposition.
Silva, G W Chinthaka; Yeamans, Charles B; Sattelberger, Alfred P; Hartmann, Thomas; Cerefice, Gary S; Czerwinski, Kenneth R
2009-11-16
The reaction mechanism and kinetics of the thermal decomposition of uranium dinitride/uranium sesquinitride to uranium mononitride under inert atmosphere at elevated temperature were studied. An increase in the lattice parameter of the UN(2)/alpha-U(2)N(3) phase was observed as the reaction temperature increased, corresponding to a continuous removal of nitrogen. Electron density calculations for these two compounds using XRD powder patterns of the samples utilizing charge-flipping technique were performed for the first time to visualize the decrease in nitrogen level as a function of temperature. Complete decomposition of UN(2) into alpha-U(2)N(3) at 675 degrees C and the UN formation after a partial decomposition of alpha-U(2)N(3) at 975 degrees C were also identified in this study. The activation energy for the decomposition of the UN(2)/alpha-U(2)N(3) phase into UN, 423.8 +/- 0.3 kJ/mol (101.3 kcal/mol), was determined under an inert argon atmosphere and is reported here experimentally for the first time. PMID:19845318
Wong, Kin-Yiu; Richard, John P; Gao, Jiali
2009-10-01
Primary kinetic isotope effects (KIEs) on a series of carboxylic acid-catalyzed protonation reactions of aryl-substituted alpha-methoxystyrenes (X-1) to form oxocarbenium ions have been computed using the second-order Kleinert variational perturbation theory (KP2) in the framework of Feynman path integrals (PI) along with the potential energy surface obtained at the B3LYP/6-31+G(d,p) level. Good agreement with the experimental data was obtained, demonstrating that this novel computational approach for computing KIEs of organic reactions is a viable alternative to the traditional method employing Bigeleisen equation and harmonic vibrational frequencies. Although tunneling makes relatively small contributions to the lowering of the free energy barriers for the carboxylic acid catalyzed protonation reaction, it is necessary to include tunneling contributions to obtain quantitative estimates of the KIEs. Consideration of anharmonicity can further improve the calculated KIEs for the protonation of substituted alpha-methoxystyrenes by chloroacetic acid, but for the reactions of the parent and 4-NO(2) substituted alpha-methoxystyrene with substituted carboxylic acids, the correction of anharmonicity overestimates the computed KIEs for strong acid catalysts. In agreement with experimental findings, the largest KIEs are found in nearly ergoneutral reactions, DeltaG(o) approximately 0, where the transition structures are nearly symmetric and the reaction barriers are relatively low. Furthermore, the optimized transition structures are strongly dependent on the free energy for the formation of the carbocation intermediate, that is, the driving force DeltaG(o), along with a good correlation of Hammond shift in the transition state structure. PMID:19754046
Electrochemical Kinetics in Dense, Reactive and Wet Gels. Biomimicking Reactions and Devices
T. F. Otero; J. Arias-Pardilla; M. I. Roca; J. G. Martínez
2012-01-01
Both p-doping and n-doping processes kinetics were studied by potential steps using different polymers from initial states having different conformational compaction degree. At the chronoamperometric maxima exist, in both cases, a chemical kinetic control. The kinetic coefficient, k, and the reaction order related to the active sites in the polymer chains, ?, decrease for increasing packed conformations of the initial
Transport coefficients in second-order non-conformal viscous hydrodynamics
Radoslaw Ryblewski
2014-11-26
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…
Kinetics of the reaction of olefin synthesis from methanol and dimethyl ether
E. V. Pisarenko; V. N. Pisarenko
2008-01-01
The kinetics of the reaction of olefin synthesis from dimethyl ether and methanol is studied. A kinetic model of the nine-route\\u000a reaction under study is constructed. The constants of the model are estimated using experimental data. The adequacy of the\\u000a model to the results of experiments is shown
Effect of spatial concentration fluctuations on effective kinetics in diffusion-reaction systems
Bolster, Diogo
Effect of spatial concentration fluctuations on effective kinetics in diffusion-reaction systems A scaling in the asymptotic regime (d is the dimensionality of the problem). Here we study the effect (2012), Effect of spatial concentration fluctuations on effective kinetics in diffusion-reaction systems
ERROR ANALYSIS OF DIFFUSION APPROXIMATION METHODS FOR MULTISCALE SYSTEMS IN REACTION KINETICS
Erban, Radek
ERROR ANALYSIS OF DIFFUSION APPROXIMATION METHODS FOR MULTISCALE SYSTEMS IN REACTION KINETICS SIMON in a container of volume V is described, at time t, by its N-dimensional state vector X(t) [X1(t), X2(t] of the algorithm in Table 1.1 requires to specify propensity functions which are, for mass-action reaction kinetics
Constraints on general second-order scalar-tensor models from gravitational Cherenkov radiation
Kimura, Rampei; Yamamoto, Kazuhiro E-mail: kazuhiro@hiroshima-u.ac.jp
2012-07-01
We demonstrate that the general second-order scalar-tensor theories, which have attracted attention as possible modified gravity models to explain the late time cosmic acceleration, could be strongly constrained from the argument of the gravitational Cherenkov radiation. To this end, we consider the purely kinetic coupled gravity and the extended galileon model on a cosmological background. In these models, the propagation speed of tensor mode could be less than the speed of light, which puts very strong constraints from the gravitational Cherenkov radiation.
Effect of molecular mobility on kinetics of an electrochemical Langmuir-Hinshelwood reaction
A. V. Petukhov
1997-01-01
A simple model to study the kinetics of a Langmuir-Hinshelwood surface reaction is developed and applied to the oxidation of a complete monolayer of CO molecules at a metal\\/electrolyte interface in a potential-step experiment. A dramatic influence of the molecular mobility on the reaction kinetics is found. The present model is able to connect the simple Langmuir-Hinshelwood kinetics to that
Pereira, José Clayston Melo; Iretskii, Alexei V; Han, Rui-Min; Ford, Peter C
2015-01-14
Kinetics studies provide mechanistic insight regarding the formation of dinitrosyl iron complexes (DNICs) now viewed as playing important roles in the mammalian chemical biology of the ubiquitous bioregulator nitric oxide (NO). Reactions in deaerated aqueous solutions containing FeSO4, cysteine (CysSH), and NO demonstrate that both the rates and the outcomes are markedly pH dependent. The dinuclear DNIC Fe2(?-CysS)2(NO)4, a Roussin's red salt ester (Cys-RSE), is formed at pH 5.0 as well as at lower concentrations of cysteine in neutral pH solutions. The mononuclear DNIC Fe(NO)2(CysS)2(-) (Cys-DNIC) is produced from the same three components at pH 10.0 and at higher cysteine concentrations at neutral pH. The kinetics studies suggest that both Cys-RSE and Cys-DNIC are formed via a common intermediate Fe(NO)(CysS)2(-). Cys-DNIC and Cys-RSE interconvert, and the rates of this process depend on the cysteine concentration and on the pH. Flash photolysis of the Cys-RSE formed from Fe(II)/NO/cysteine mixtures in anaerobic pH 5.0 solution led to reversible NO dissociation and a rapid, second-order back reaction with a rate constant kNO = 6.9 × 10(7) M(-1) s(-1). In contrast, photolysis of the mononuclear-DNIC species Cys-DNIC formed from Fe(II)/NO/cysteine mixtures in anaerobic pH 10.0 solution did not labilize NO but instead apparently led to release of the CysS(•) radical. These studies illustrate the complicated reaction dynamics interconnecting the DNIC species and offer a mechanistic model for the key steps leading to these non-heme iron nitrosyl complexes. PMID:25479566
A novel spectral framework for second-order homogenization theories
NASA Astrophysics Data System (ADS)
Binci, Massimiliano
Composite systems are emerging as materials of choice in many engineering applications. Their increasing popularity is predicated on the capacity of these materials to tailor their proprieties by varying their internal structure. Composites exhibit unique combinations of anisotropic properties that are not achievable by traditional materials. Recently, we have developed a novel mathematical framework, called the Microstructure Sensitive Design (MSD), to represent efficiently the microstructure-property relationships of composites using second-order homogenization theories. The latter are a formidable advancement over the elementary first-order theories that account only for the volume fraction information of the constituents. Second-order theories account for the morphological details of the microstructure in capturing the anisotropic properties of materials. The spectral framework of MSD results in simplified structure-property linkages and identifies the microstructure hull, i.e. the space of all theoretically possible microstructural realizations of a given material system. With this new framework, we have successfully established macroscopic elastic properties of composites and delineated second-order property closures for the first time. We also predicted local properties of composites by casting relevant scale-bridging relations in the spectral framework of MSD. These linkages describe the fourth-rank localization tensors connecting the microscopic stresses or strains to the macroscopic loading conditions. The spectral formulations for the localization tensors result in algebraic expressions whose coefficients do not depend on the microstructural details. These coefficients are called the influence coefficients. We have performed numerical integrations and finite element calibrations to evaluate these influence coefficients. These have resulted in very accurate descriptions of the local elastic stress (or strain) fields in a broad range of composite microstructures.
Second order distorted wave calculations for electron impact ionization processes
NASA Astrophysics Data System (ADS)
Chen, Zhangjin
Electron impact ionization of atoms provides a fundamental test of the current understanding of atomic structure as well as our understanding of the three body problem. Triple differential cross sections (TDCS), measured in the coincidence experiment, provide the most sensitive test of the theory of electron impact ionization processes. It was found two decades ago that second-order effects were crucial in explaining both the positions and magnitudes of the binary and recoil peaks in the TDCS. However, the existing theoretical calculations of second-order amplitudes typically resort to simplifying approximations, such as the closure approximation or neglecting the real part of the Green's function, to make the calculation tractable. In this work, we have developed a second-order distorted wave (DWB2) theory for atomic ionization which does not make these approximations. The DWB2 theory has been used to calculate the TDCS for electron impact ionization of hydrogen. It is found that the DWB2 results are in good agreement with absolute experimental measurements for incident energy greater than 100 eV. We have also performed DWB2 calculations for electron impact ionization of helium with the residual ion left in the n=1 and 2 states at intermediate energies in coplanar asymmetric geometry. Both the neutral and ionic distorting potentials are employed for the projectile in the final state. It has been found that the DWB2 results with the ionic distorting potential are in better agreement with experiment for the case in which the residual ion is left in the excited states. We have also performed the calculations to check the validity of the closure approximation and the simplified Green's function approximation and found that these approximations are not accurate for non-coplanar geometry and low incident energies.
Determination of robust stability margin for second-order systems
NASA Technical Reports Server (NTRS)
Chuang, C.-H.; Kau, C.-T.; Juang, Jer-Nan
1992-01-01
Robust stabilization of uncertain systems has been extensively investigated and the stability test for the whole set of uncertain parameters has been reduced to a finite number of test points, four points for the characteristic polynomial with independent coefficients. As a result the robust stability margin can be determined using a reasonable amount of computation. It is impossible to apply the results of the test to a practical system as the coefficients of the characteristic polynomial for a physical system are usually functions of uncertain parameters. However, many physical systems may be represented by a second-order mass-spring-damper system with a special multilinear form in its characteristic polynomial. This paper investigates second-order mass-spring-damper systems and the reduction of the number of test points. It is shown that such a system with arbritrary compensators always has a multilinear characteristic polynomial. It is also shown that a line in the two-dimensional parameter space forms the boundary after the mapping of a multilinear characteristic polynomial and this interior extreme line forms a conic curve in the complex plane. The boundary of uncertain domain for a multilinear polynomial with two uncertainty parameters can be determined analytically using this curve, and the four sides image of a square of the uncertain parameter. Therefore, the stability margin may be determined by checking the intersections of the boundary with the zero point. A similar procedure can be used for second-order systems with more than two uncertainty parameters when parameter optimization is used in determining the boundary.
Finite difference schemes for second order systems describing black holes
Motamed, Mohammad; Kreiss, H-O. [NADA, Royal Institute of Technology, 10044 Stockholm (Sweden); Albert Einstein Institute, Max Planck Gesellschaft, Am Muehlenberg 1, D-14476 Golm (Germany); Babiuc, M.; Winicour, J. [Albert Einstein Institute, Max Planck Gesellschaft, Am Muehlenberg 1, D-14476 Golm (Germany); Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Szilagyi, B. [Albert Einstein Institute, Max Planck Gesellschaft, Am Muehlenberg 1, D-14476 Golm (Germany)
2006-06-15
In the harmonic description of general relativity, the principal part of Einstein's equations reduces to 10 curved space wave equations for the components of the space-time metric. We present theorems regarding the stability of several evolution-boundary algorithms for such equations when treated in second order differential form. The theorems apply to a model black hole space-time consisting of a spacelike inner boundary excising the singularity, a timelike outer boundary and a horizon in between. These algorithms are implemented as stable, convergent numerical codes and their performance is compared in a 2-dimensional excision problem.
Galaxy number counts to second order and their bispectrum
Dio, Enea Di; Durrer, Ruth; Marozzi, Giovanni; Montanari, Francesco, E-mail: Enea.DiDio@unige.ch, E-mail: Ruth.Durrer@unige.ch, E-mail: Giovanni.Marozzi@unige.ch, E-mail: Francesco.Montanari@unige.ch [Université de Genève, Département de Physique Théorique and CAP, 24 quai Ernest-Ansermet, CH-1211 Genève 4 (Switzerland)
2014-12-01
We determine the number counts to second order in cosmological perturbation theory in the Poisson gauge and allowing for anisotropic stress. The calculation is performed using an innovative approach based on the recently proposed ''geodesic light-cone'' gauge. This allows us to determine the number counts in a purely geometric way, without using Einstein's equation. The result is valid for general dark energy models and (most) modified gravity models. We then evaluate numerically some relevant contributions to the number counts bispectrum. In particular we consider the terms involving the density, redshift space distortion and lensing.
Second-order susceptibility from a tight-binding Hamiltonian
Dumitrica, T.; Graves, JS; Allen, Roland E.
1998-01-01
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 that modifies a tight-bindin dependent... 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...
Linear programming based optimal power flow using second order sensitivities
Olofsson, M.; Andersson, G.; Soeder, L.
1995-08-01
For the electric railway traction in Sweden, a system of 130 kV transmission lines connected parallel to the contact lines is being built. Within this system, the generation costs differs only slightly between different nodes with power injections. In order to optimize the power flow in the system, an extended optimal power flow algorithm based on successive linear programming, has been developed. To improve the convergence, a method based on a second order sensitivity approximation of the active power losses of the total system is applied. Numerical examples are given to show the enhanced convergence properties.
Second order contributions to the absorption of massive particles
Sancho, Pedro [GPV de Valladolid, Centro Zonal en Castilla y Leon, Orion 1, 47014, Valladolid (Spain)], E-mail: psancho@inm.es
2008-05-15
Recently, in analogy with multiphoton ionization, it has been suggested that multiparticle ionization can also be induced by massive systems. We explore in this paper the possibility that multiparticle absorption processes can also take place for massive particles. To study it we consider, in a perturbative way, a model of absorption which illustrates the analogies with Glauber's scheme for photons and previous analysis on matter-waves coherence. A major advantage of this approach is that the dependence of the absorption rates on the wavefunction of the incident system can be analyzed in an explicit way. The calculations confirm the form of the second order (two particle) contributions.
New implicitly solvable potential produced by second order shape invariance
NASA Astrophysics Data System (ADS)
Cannata, F.; Ioffe, M. V.; Kolevatova, E. V.; Nishnianidze, D. N.
2015-05-01
The procedure proposed recently by Bougie et al. (2010) to study the general form of shape invariant potentials in one-dimensional Supersymmetric Quantum Mechanics (SUSY QM) is generalized to the case of Higher Order SUSY QM with supercharges of second order in momentum. A new shape invariant potential is constructed by this method. It is singular at the origin, it grows at infinity, and its spectrum depends on the choice of connection conditions in the singular point. The corresponding Schrödinger equation is solved explicitly: the wave functions are constructed analytically, and the energy spectrum is defined implicitly via the transcendental equation which involves Confluent Hypergeometric functions.
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 electromagnetic eigenfrequencies of a triaxial ellipsoid
NASA Astrophysics Data System (ADS)
Mehl, James B.
2009-10-01
The dependence of the eigenvalues of the TM1n and TE1n electromagnetic triplet modes on the shape of a triaxial ellipsoid cavity resonator is investigated. For an ellipsoid with semi-axes proportional to 1 : (1 + epsilon1) : (1 + epsilon2) the fractional perturbations of the triplet components are found to second order in epsilon1 and epsilon2. The formulae are derived from the results of Kokkorakis and Roumeliotis (1997 J. Electromagn. Waves Appl. 11 279-92) for prolate and oblate spheroids. Finite-element calculations were carried out to confirm the accuracy of the formulae and to determine the next correction terms.
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
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…
Kinetic Studies of the Solvolysis of Two Organic Halides
ERIC Educational Resources Information Center
Duncan, J. A.; Pasto, D. J.
1975-01-01
Describes an undergraduate organic chemistry laboratory experiment which utilizes the solvolysis of organic halides to demonstrate first and second order reaction kinetics. The experiment also investigates the effect of a change of solvent polarity on reaction rate, common-ion and noncommon-ion salt effects, and the activation parameters of a…
On the universal identity in second order hydrodynamics
Sašo Grozdanov; Andrei O. Starinets
2014-12-29
We compute the 't Hooft coupling correction to the infinite coupling expression for the second order transport coefficient $\\lambda_2$ in ${\\cal N}=4$ $SU(N_c)$ 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, $2 \\eta \\tau_\\Pi - 4 \\lambda_1 - \\lambda_2 =0$, 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.
Second-order near-wall turbulence closures - A review
NASA Technical Reports Server (NTRS)
So, R. M. C.; Lai, Y. G.; Zhang, H. S.; Hwang, B. C.
1991-01-01
Advances in second-order near-wall turbulence closures are summarized. All closures under consideration are based on high-Reynolds-number models. Most near-wall closures proposed to date attempt to modify the high-Reynolds-number models for the dissipation function and the pressure redistribution term so that the resultant models are applicable all the way to the wall. The asymptotic behavior of the near-wall closures is examined and compared with the proper near-wall behavior of the exact Reynolds-stress equations. It is found that three second-order near-wall closures give the best correlations with simulated turbulence statistics. However, their predictions of near-wall Reynolds-stress budgets are considered to be incorrect. A proposed modification to the dissipitation-rate equation remedies part of those predictions. It is concluded that further improvements are required if a complete replication of all the turbulence properties and Reynolds-stress budgets by a statistical model of turbulence is desirable.
Studies of anomalous dispersion in the SLC second order achromat
Fieguth, T.; Kheifets, S.; Murray, J.J.
1987-03-01
Certain causes of anomalous dispersion in the second order achromats of the SLC arcs are investigated. For matched dispersion, transverse displacements of combined function magnets do not introduce anomalous dispersion. This is shown by deriving a non-dispersive condition connecting the average of the matched dispersion function with the quadrupole and sextupole components of the field. In the SLC Arcs, however, the achromats are rolled producing a dispersion mismatch. In this case, the horizontal (vertical) dispersion is affected linearly by vertical (horizontal) displacement of magnets. The integral condition connecting the dipole and quadrupole fields and the matched dispersion is also derived. Combining this with the non-dispersive condition and the analytic expression of the matched dispersion gives two simple relationships for the fields of second order achromats constructed of combined function magnets. The effects of the dispersion mismatch in the SLC Arcs is investigated using computer simulations. The results show that this mismatch will increase the sensitivity to transverse errors. We report the effects of certain systematic errors.
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
Second-order analytic solutions for re-entry trajectories
NASA Astrophysics Data System (ADS)
Kim, Eun-Kyou
1993-01-01
With the development of aeroassist technology, either for near-earth orbital transfer with or without a plane change or for planetary aerocapture, it is of interest to have accurate analytic solutions for reentry trajectories in an explicit form. Starting with the equations of motion of a non-thrusting aerodynamic vehicle entering a non-rotating spherical planetary atmosphere, a normalization technique is used to transform the equations into a form suitable for an analytic integration. Then, depending on the type of planar entry modes with a constant angle-of-attack, namely, ballistic fly-through, lifting skip, and equilibrium glide trajectories, the first-order solutions are obtained with the appropriate simplification. By analytic continuation, the second-order solutions for the altitude, speed, and flight path angle are derived. The closed form solutions lead to explicit forms for the physical quantities of interest, such as the deceleration and aerodynamic heating rates. The analytic solutions for the planar case are extended to three-dimensional skip trajectories with a constant bank angle. The approximate solutions for the heading and latitude are developed to the second order. In each type of trajectory examined, explicit relations among the principal variables are in a form suitable for guidance and navigation purposes. The analytic solutions have excellent agreement with the numerical integrations. They also provide some new results which were not reported in the existing classical theory.
Kinetics of sunflower oil methanolysis at low temperatures.
Stamenkovi?, Olivera S; Todorovi?, Zoran B; Lazi?, Miodrag L; Veljkovi?, Vlada B; Skala, Dejan U
2008-03-01
The kinetics of the sunflower oil methanolysis process was studied at lower temperatures (10-30 degrees C). The sigmoidal kinetics of the process was explained by the mass transfer controlled region in the initial heterogenous regime, followed by the chemical reaction controlled region in the pseudo-homogenous regime. A simple kinetic model, which did not require complex computation of the kinetic constants, was used for simulation of the TG conversion and the FAME formation in the latter regime: the fast irreversible second-order reaction was followed by the slow reversible second-order reaction close to the completion of the methanolysis reaction. The mass transfer was related to the drop size of the dispersed (methanol) phase, which reduced rapidly with the progress of the methanolysis reaction. This was attributed to the formation of the emulsifying agents stabilizing the emulsion of methanol drops into the oil. PMID:17434728
Kinetics of exciplex formation/dissipation in reaction following Weller Scheme II
Fedorenko, S. G.; Burshtein, A. I.
2014-09-21
Creation of exciplexes from the charged products of photoionization is considered by means of Integral Encounter Theory. The general kinetic equations of such a reaction following the Weller scheme II are developed. The special attention is given to the particular case of irreversible remote ionization of primary excited electron donor. Kinetics of exciplex formation is considered at fast biexponential geminate transformation of exciplexes in cage that gives way to subsequent bulk reaction of equilibrated reaction products controlled by power law recombination of ions. It is shown that the initial geminate stage of exciplex kinetics is observed only in diffusion controlled regime of the reaction and disappears with increasing mobility of ions in passing to kinetic regime. The quantum yield of exciplexes is studied along with their kinetics.
Klein, R.L.
1984-01-01
The kinetics of the platinum catalyzed reaction between NO and CO has been studied under conditions chosen to approximate those observed during operation of catalysts in automotive exhaust gas treatment applications. The catalysts were polycrystalline platinum foils and wires. The reaction was studied over a range of reactant partial pressures of 10 V Torr to 1 Torr and catalyst temperatures of 500 to 1500K. The steady-state kinetics results could not be fit by a simple Langmuir-Hinshelwood kinetic model over all experimental conditions studied. The kinetics at high coverage were most consistent with Langmuir-Hinshelwood kinetics assuming a bimolecular reaction between NO and CO as the rate-limiting step. At high temperature, the Langmuir-Hinshelwood assumption of fast adsorption-desorption equilibrium relative to the surface reaction rate was no longer appropriate and the mechanism of adsorption of NO had to be considered explicitly.
Magnetic Compensation for Second-Order Doppler Shift in LITS
NASA Technical Reports Server (NTRS)
Burt, Eric; Tjoelker, Robert
2008-01-01
The uncertainty in the frequency of a linear-ion-trap frequency standard (LITS) can be reduced substantially by use of a very small magnetic inhomogeneity tailored to compensate for the residual second-order Doppler shift. An effect associated with the relativistic time dilatation, one cause of the second-order Doppler shift, is ion motion that is attributable to the trapping radio-frequency (RF)electromagnetic field used to trap ions. The second-order Doppler shift is reduced by using a multi-pole trap; however it is still the largest source of systematic frequency shift in the latest generation of LITSs, which are among the most stable clocks in the world. The present compensation scheme reduces the frequency instability of the affected LITS to about a tenth of its previous value. The basic principles of prior generation LITSs were discussed in several prior NASA Tech Briefs articles. Below are recapitulated only those items of basic information necessary to place the present development in context. A LITS includes a microwave local oscillator, the frequency of which is stabilized by comparison with the frequency of the ground state hyperfine transition of 199Hg+ ions. The comparison involves a combination of optical and microwave excitation and interrogation of the ions in a linear ion trap in the presence of a nominally uniform magnetic field. In the current version of the LITS, there are two connected traps (see figure): (1) a quadrupole trap wherein the optical excitation and measurement take place and (2) a 12-pole trap (denoted the resonance trap), wherein the microwave interrogation takes place. The ions are initially loaded into the quadrupole trap and are thereafter shuttled between the two traps. Shuttling ions into the resonance trap allows sensitive microwave interrogation to take place well away from loading interference. The axial magnetic field for the resonance trap is generated by an electric current in a finely wound wire coil surrounded by magnetic shields. In the quadrupole and 12-pole traps, the potentials are produced by RF voltages applied to even numbers (4 and 12, respectively) of parallel rods equally spaced around a circle. The polarity of the voltage on each rod is opposite that of the voltage on the adjacent rod. As a result, the amplitude of the RF trapping field is zero along the centerline and increases, with radius, to a maximum value near the rods.
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
A constant-time kinetic Monte Carlo algorithm for simulation of large biochemical reaction networks
Li, Tiejun
A constant-time kinetic Monte Carlo algorithm for simulation of large biochemical reaction networks The time evolution of species concentrations in biochemical reaction networks is often modeled using simulation. We present here a constant-time algorithm, whose cost is independent of the number of reactions
Substrate effects on the fractal kinetics of a simple surface reaction
F. Moiny; Martine Dumont
2001-01-01
The reversible monomer-monomer model occurring without diffusion on irregular substrates (probabilistic supports and Sierpinski carpets) is investigated by means of Monte Carlo simulations. The strong influence of the catalyst surface structure on the kinetics of the reaction and its fractal like features such as noninteger reaction rate orders is investigated for steady-state regimes controlled by the reaction. We succeed in
Catalysis Today 54 (1999) 495505 The bifunctional reaction pathway and dual kinetic regimes
Regalbuto, John R.
1999-01-01
Catalysis Today 54 (1999) 495505 The bifunctional reaction pathway and dual kinetic regimes in NOx the rates of the individual reactions (NO oxidation, CH4 oxidation, NO2 reduction) with that of the combined reaction (NO + O2 + CH4). Co(+2) was exchanged into H-MOR and Na-MOR to give catalysts with different metal
Thorn, R.P.
1993-01-01
A laser flash photolysis - long path absorption - technique has been employed to study the kinetics of the reaction BrO+NO2+M(k[sub 16]) yields products as a function of temperature (248-346 K), pressure (16-800 Torr), and buffer gas identity (N2, CF4). 351 nm photolysis of NO2/Br2/N2 mixtures generated BrO. The BrO decay in the presence of excess NO2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k[sub 16](P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k[sub 16](P,T) for use in modeling stratospheric BrO(x) chemistry. The kinetics of the important stratospheric reaction BrO+O(P-3)(k[sub 14]) yields Br+O2 in N2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25-150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of Br2/O3/N2 mixtures produces O atoms in excess over Br2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolysis a small fraction of the O3 to generate O(P-3). The decay of O(P-3) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resoved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k[sub 14](T) is k[sub 14](T) = 1.64 x 10(exp -11) exp(263/T) cm(exp 3) molecule(exp-1)s(exp -1). The absolute accuracy of k[sub 14](T) at any temperature within the range studied is estimated to be +/- 25%.
Reaction instabilities in Co/Al nanolaminates due to chemical kinetics variation over micron-scales
NASA Astrophysics Data System (ADS)
Reeves, Robert V.; Adams, David P.
2014-01-01
The reaction front dynamics of Co/Al reactive nanolaminates were studied as a function of the initial temperature of the unreacted material. Sample geometries that exhibit stable reaction fronts as well as geometries that present "spinning" reaction front instabilities were investigated at initial temperatures ranging from room temperature to 200 °C. It was found that reactions in samples with small reactant periodicities (<66.4 nm) were stable at all temperatures, reaction in large periodicity samples (?100 nm) were unstable at all temperatures, and reactions in samples with intermediate periodicities transitioned from unstable behavior to stable behavior with increasing initial temperature. The results suggest that behaviors typical of two types of reaction kinetics are present in unstable reaction fronts: slow, diffusion-limited kinetics in the regions between transverse reaction bands, and a faster mechanism at the leading edge of the transverse bands.
New Implicitly Solvable Potential Produced by Second Order Shape Invariance
F. Cannata; M. V. Ioffe; E. V. Kolevatova; D. N. Nishnianidze
2015-04-11
The procedure proposed recently by J.Bougie, A.Gangopadhyaya and J.V.Mallow to study the general form of shape invariant potentials in one-dimensional Supersymmetric Quantum Mechanics (SUSY QM) is generalized to the case of Higher Order SUSY QM with supercharges of second order in momentum. A new shape invariant potential is constructed by this method. It is singular at the origin, it grows at infinity, and its spectrum depends on the choice of connection conditions in the singular point. The corresponding Schr\\"odinger equation is solved explicitly: the wave functions are constructed analytically, and the energy spectrum is defined implicitly via the transcendental equation which involves Confluent Hypergeometric functions.
Quadratically consistent nodal integration for second order meshfree Galerkin methods
NASA Astrophysics Data System (ADS)
Duan, Qinglin; Wang, Bingbing; Gao, Xin; Li, Xikui
2014-08-01
Robust and efficient integration of the Galerkin weak form only at the approximation nodes for second order meshfree Galerkin methods is proposed. The starting point of the method is the Hu-Washizu variational principle. The orthogonality condition between stress and strain difference is satisfied by correcting nodal derivatives. The corrected nodal derivatives are essentially linear functions which can exactly reproduce linear strain fields. With the known area moments, the stiffness matrix resulting from these corrected nodal derivatives can be exactly evaluated using only the nodes as quadrature points. The proposed method can exactly pass the quadratic patch test and therefore is named as quadratically consistent nodal integration. In contrast, the stabilized conforming nodal integration (SCNI) which prevails in the nodal integrations for meshfree Galerkin methods fails to pass the quadratic patch test. Better accuracy, convergence, efficiency and stability than SCNI are demonstrated by several elastostatic and elastodynamic examples.
Relativistic second-order dissipative hydrodynamics at finite chemical potential
Amaresh Jaiswal; Bengt Friman; Krzysztof Redlich
2015-07-22
Starting from the Boltzmann equation in the relaxation time approximation and employing Chapman-Enskog like expansion for the distribution function close to equilibrium, we derive second-order evolution equations for shear stress tensor and dissipative charge current for a system of massless quarks and gluons. The transport coefficients are obtained exactly using quantum statistics for the phase space distribution functions at non-zero chemical potential. We show that, within the relaxation time approximation, the evolution equations for shear stress tensor and dissipative charge current could be decoupled. We find that, for large values of the ratio of chemical potential to temperature, the charge conductivity is small compared to the coefficient of shear viscosity. We also show that in the relaxation-time approximation, the limiting behaviour of the heat conductivity to shear viscosity ratio is the same as that obtained for a strongly coupled plasma.
Relativistic quantum transport coefficients for second-order viscous hydrodynamics
Wojciech Florkowski; Amaresh Jaiswal; Ewa Maksymiuk; Radoslaw Ryblewski; Michael Strickland
2015-05-19
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 non-equilibrium part. Specializing to 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+1d 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 leads to better agreement with the exact solution of the relativistic Boltzmann equation.
Relativistic second-order dissipative hydrodynamics at finite chemical potential
Jaiswal, Amaresh; Redlich, Krzysztof
2015-01-01
Starting from the Boltzmann equation in the relaxation time approximation and employing Chapman-Enskog like expansion for the distribution function close to equilibrium, we derive second-order evolution equations for shear stress tensor and dissipative charge current for a system of massless quarks and gluons. The transport coefficients are obtained exactly using quantum statistics for the phase space distribution functions at non-zero chemical potential. We show that, within the relaxation time approximation, the evolution equations for shear stress tensor and dissipative charge current could be decoupled. We find that, for large values of the ratio of chemical potential to temperature, the charge conductivity is small compared to the coefficient of shear viscosity.
Organic Polymer Films For Second Order Nonlinear Applications
NASA Astrophysics Data System (ADS)
Hill, Julian R.; Pantelis, Philip; Dunn, Peter L.; Davies, Graham J.
1990-01-01
A large and highly stable internal electric field has been measured in thin films of corona poled copoly(vinylidene fluoride - trifluoroethylene) by analysis of the alignment of coloured organic compounds (chromophores) dissolved as guests at low concentration in the host polymer. These chromophores were designed to have both large electric dipole moments and high microscopic second order optical nonlinearities so that, when aligned in the internal field, they contributed to the small intrinsic nonlinearity of the poled host polymer. The second harmonic coefficient of the mixture was found to be linear with the guest concentration and at 10% by weight to have a value of 2.6x10-12 m/V at 1.064?m.. The coefficient of the films was found to be stable with time unless precipitation of the guest occured owing to an insufficient solubilty at the selected concentration. This system is compared with thermopoled polymeric systems which have no stable internal electric field.
K-inflationary power spectra at second order
Martin, Jérôme; Vennin, Vincent; Ringeval, Christophe E-mail: christophe.ringeval@uclouvain.be
2013-06-01
Within the class of inflationary models, k-inflation represents the most general single field framework that can be associated with an effective quadratic action for the curvature perturbations and a varying speed of sound. The incoming flow of high-precision cosmological data, such as those from the Planck satellite and small scale Cosmic Microwave Background (CMB) experiments, calls for greater accuracy in the inflationary predictions. In this work, we calculate for the first time the next-to-next-to-leading order scalar and tensor primordial power spectra in k-inflation needed in order to obtain robust constraints on the inflationary theory. The method used is the uniform approximation together with a second order expansion in the Hubble and sound flow functions. Our result is checked in various limits in which it reduces to already known situations.
Second Order Optical Nonlinearities in Thermally Poled Phosphate Glasses
Thamboon, P; Krol, D
2001-12-14
Second order optical nonlinearities were induced in commercial phosphate glasses (Schott, IOG-1) by the thermal poling technique. The induced {chi}{sup (2)} was measured via second harmonic generation using a fundamental beam from a 1064 nm mode-locked Nd:YAG laser. The nonlinear regions were characterized using the Maker-Fringe technique, in which the second harmonic signals were observed as a function of incident angle of the fundamental beam. The results show that the {chi}{sup (2)} profile has contributions from two distinct regions: a near-anodic surface region and a bulk. We have modeled the induced profile to fit our experimental results. The dependence of the induced nonlinearity on applied poling fields, temperatures and poling time is discussed.
Reconstructing the inflaton potential: Perturbative reconstruction to second order
Copeland, Edmund J.; Kolb, Edward W.; Liddle, Andrew R.; Lidsey, James E.
1993-08-01
One method to reconstruct the scalar field potential of inflation is a perturbative approach, where the values of the potential and its derivatives are calculated as an expansion in departures from the slow-roll approximation. They can then be expressed in terms of observable quantities, such as the square of the ratio of the gravitational wave amplitude to the density perturbation amplitude, the deviation of the spectral index from the Harrison--Zel'dovich value, etc. Here, we calculate complete expressions for the second-order contributions to the coefficients of the expansion by including for the first time corrections to the standard expressions for the perturbation spectra. As well as offering an improved result, these corrections indicate the expected accuracy of the reconstruction. Typically the corrections are only a few percent.
Second-order phase transitions, L. Landau and his successors
Mnyukh, Y
2011-01-01
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.
New Implicitly Solvable Potential Produced by Second Order Shape Invariance
Cannata, F; Kolevatova, E V; Nishnianidze, D N
2015-01-01
The procedure proposed recently by J.Bougie, A.Gangopadhyaya and J.V.Mallow to study the general form of shape invariant potentials in one-dimensional Supersymmetric Quantum Mechanics (SUSY QM) is generalized to the case of Higher Order SUSY QM with supercharges of second order in momentum. A new shape invariant potential is constructed by this method. It is singular at the origin, it grows at infinity, and its spectrum depends on the choice of connection conditions in the singular point. The corresponding Schr\\"odinger equation is solved explicitly: the wave functions are constructed analytically, and the energy spectrum is defined implicitly via the transcendental equation which involves Confluent Hypergeometric functions.
Digital second-order phase-locked loop
NASA Technical Reports Server (NTRS)
Holes, J. K.; Carl, C.; Tegnelia, C. R. (inventors)
1973-01-01
A digital second-order phase-locked loop is disclosed in which a counter driven by a stable clock pulse source is used to generate a reference waveform of the same frequency as an incoming waveform, and to sample the incoming waveform at zero-crossover points. The samples are converted to digital form and accumulated over M cycles, reversing the sign of every second sample. After every M cycles, the accumulated value of samples is hard limited to a value SGN = + or - 1 and multiplied by a value delta sub 1 equal to a number of n sub 1 of fractions of a cycle. An error signal is used to advance or retard the counter according to the sign of the sum by an amount equal to the sum.
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.
Perfectly matched layers for Maxwell's equations in second order formulation
Sjogreen, B; Petersson, A
2004-07-26
We consider the two-dimensional Maxwell's equations in domains external to perfectly conducting objects of complex shape. The equations are discretized using a node-centered finite-difference scheme on a Cartesian grid and the boundary condition are discretized to second order accuracy employing an embedded technique which does not suffer from a ''small-cell'' time-step restriction in the explicit time-integration method. The computational domain is truncated by a perfectly matched layer (PML). We derive estimates for both the error due to reflections at the outer boundary of the PML, and due to discretizing the continuous PML equations. Using these estimates, we show how the parameters of the PML can be chosen to make the discrete solution of the PML equations converge to the solution of Maxwell's equations on the unbounded domain, as the grid size goes to zero. Several numerical examples are given.
Absorbing boundary conditions for second-order hyperbolic equations
NASA Technical Reports Server (NTRS)
Jiang, Hong; Wong, Yau Shu
1989-01-01
A uniform approach to construct absorbing artificial boundary conditions for second-order linear hyperbolic equations is proposed. The nonlocal boundary condition is given by a pseudodifferential operator that annihilates travelling waves. It is obtained through the dispersion relation of the differential equation by requiring that the initial-boundary value problem admits the wave solutions travelling in one direction only. Local approximation of this global boundary condition yields an nth-order differential operator. It is shown that the best approximations must be in the canonical forms which can be factorized into first-order operators. These boundary conditions are perfectly absorbing for wave packets propagating at certain group velocities. A hierarchy of absorbing boundary conditions is derived for transonic small perturbation equations of unsteady flows. These examples illustrate that the absorbing boundary conditions are easy to derive, and the effectiveness is demonstrated by the numerical experiments.
A Pore Scale Evaluation of the Kinetics of Mineral Dissolution and Precipitation Reactions (EMSI)
Steefel, Carl I.
2006-06-01
The chief goals for CEKA are to (1) collect and synthesize molecular-level kinetic data into a coherent framework that can be used to predict time evolution of environmental processes over a range of temporal and spatial scales; (2) train a cohort of talented and diverse students to work on kinetic problems at multiple scales; (3) develop and promote the use of new experimental techniques in environmental kinetics; (4) develop and promote the use of new modeling tools to conceptualize reaction kinetics in environmental systems; and (5) communicate our understanding of issues related to environmental kinetics and issues of scale to the broader scientific community and to the public.
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.
NASA Astrophysics Data System (ADS)
Caruso, U.; Casalboni, M.; Fort, A.; Fusco, M.; Panunzi, B.; Quatela, A.; Roviello, A.; Sarcinelli, F.
2005-12-01
Six new side-chain polyurethanes with large molecular hyperpolarizabilities were synthesized by reaction of ethylenic and/or azo bridged push-pull chromophoric monomers with tolylene 2,4-diisocyanate. The NLO-phores show different conjugation pathway but analogous donor/withdrawing substituents. The chemical and thermal properties of the chromophores and of the polymers were examined. Evaluation of the second order NLO properties was performed by EFISH determination of ?? on the monomers, and by SHG measurements on some amorphous thin films obtained from polymers through spin-coating technique.
Analytic energy gradients for the orbital-optimized second-order Møller-Plesset perturbation theory
NASA Astrophysics Data System (ADS)
Bozkaya, U?ur; Sherrill, C. David
2013-05-01
Analytic energy gradients for the orbital-optimized second-order Møller-Plesset perturbation theory (OMP2) are presented. The OMP2 method is applied to difficult chemical systems, including those where spatial or spin symmetry-breaking instabilities are observed. The performance of the OMP2 method is compared with that of second-order Møller-Plesset perturbation theory (MP2) for investigating geometries and vibrational frequencies of the cis-HOOH+, trans-HOOH+, LiO2, C3+, and NO2 molecules. For harmonic vibrational frequencies, the OMP2 method eliminates the singularities arising from the abnormal response contributions observed for MP2 in case of symmetry-breaking problems, and provides significantly improved vibrational frequencies for the above molecules. We also consider the hydrogen transfer reactions between several free radicals, for which MP2 provides poor reaction energies. The OMP2 method again exhibits a considerably better performance than MP2, providing a mean absolute error of 2.3 kcal mol-1, which is more than 5 times lower than that of MP2 (13.2 kcal mol-1). Overall, the OMP2 method seems quite helpful for electronically challenging chemical systems such as symmetry-breaking molecules, hydrogen transfer reactions, or other cases where standard MP2 proves unreliable. For such systems, we recommend using OMP2 instead of MP2 as a more robust method with the same computational scaling.
Bahr, Jean M.; Rubin, Jacob
1987-01-01
Modeling transport of reacting solutes in porous media often requires a choice between models based on the local equilibrium assumption (LEA) and models involving reaction kinetics. Direct comparison of the mathematical formulations for these two types of transport models can aid in this choice. For cases of transport affected by surface reaction, such a comparison is made possible by a new derivation procedure. This procedure yields a kinetics-based formulation that is the sum of the LEA formulation and one or more kinetically influenced terms. The dimensionless form of the new kinetics-based formulation facilitates identification of critical parameter groupings which control the approach to transport behavior consistent with LEA model predictions. Results of numerical experiments demonstrate that criteria for LEA applicability can be expressed conveniently in terms of these parameter groupings. The derivation procedure is demonstrated for examples of surface reactions including first-order reversible sorption, Langmuir-type kinetics and binary, homovalent ion exchange.
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.
Glaude, P A; Melius, C; Pitz, W J; Westbrook, C K
2001-12-13
A detailed chemical kinetic reaction mechanism is developed to describe incineration of the chemical warfare nerve agent sarin (GB), based on commonly used principles of bond additivity and hierarchical reaction mechanisms. The mechanism is based on previous kinetic models of organophosphorus compounds such as TMP, DMMP and DIMP that are often used as surrogates to predict incineration of GB. Kinetic models of the three surrogates and GB are then used to predict their consumption in a perfectly stirred reactor fueled by natural gas to simulate incineration of these chemicals. Computed results indicate that DIMP is the only one of these surrogates that adequately describes combustion of GB under comparable conditions. The kinetic pathways responsible for these differences in reactivity are identified and discussed. The most important reaction in GB and DIMP that makes them more reactive than TMP or DMMP is found to be a six-center molecular elimination reaction producing propene.
Hirschi, Jennifer Sue
2009-05-15
A variety of biological and organic reaction mechanisms are studied using powerful tools from experimental and theoretical chemistry. These tools include the precise measurement of kinetic isotope effects (KIEs) and the ...
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)
Zhuang, Xiaowei
Dissecting the multistep reaction pathway of an RNA enzyme by single-molecule kinetic and undocked forms of the enzyme display distinct FRET values, the cleaved and ligated forms do not by a distinct kinetic fingerprint at the single-molecule level. This method allowed us to unambiguously
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…
Kinetics and mechanism of the photochemical reactions of radicals in polyvinylene carbonate
Mikhailik, O.M.; Mel'nikov, M.Ya.; Fok, N.V.
1982-04-01
A study of the kinetics and mechanism of the photodegradation of polyvinylene carbonate is presented in this paper. The photodecomposition of the middle macroradicals in PVCA results in cleavage of the backbone of the macromolecules and a decrease in the molecular weight. Kinetic inequivalence of the middle macroradicals in PVCA in their photodecomposition reactions has been discovered.
Effects of Ionization on the Reaction Behavior and Kinetics of Acrylic Acid Polymerizations
Peppas, Nicholas A.
Effects of Ionization on the Reaction Behavior and Kinetics of Acrylic Acid Polymerizations Kristi, 1996X ABSTRACT: The kinetics of acrylic acid (AA) solution polymerization was investigated of partially neutralized acrylic acid (AA) using a variety of methods, as described by Buchholz.6 Although
Utilization of the Recycle Reactor in Determining Kinetics of Gas-Solid Catalytic Reactions.
ERIC Educational Resources Information Center
Paspek, Stephen C.; And Others
1980-01-01
Describes a laboratory scale reactor that determines the kinetics of a gas-solid catalytic reaction. The external recycle reactor construction is detailed with accompanying diagrams. Experimental details, application of the reactor to CO oxidation kinetics, interphase gradients, and intraphase gradients are discussed. (CS)
Kyoung-Su Ha; Yun-Jo Lee; Jong Wook Bae; Ye Won Kim; Min Hee Woo; Hyo-Sik Kim; Myung-June Park; Ki-Won Jun
2011-01-01
Kinetics of the methanol (MeOH) dehydration has been investigated using two kinds of alkali metal-modified ZSM-5 (mZSM-5) catalysts, which were developed for the purpose of preparing dimethyl ether (DME) from water-containing MeOH. Two intrinsic kinetic mechanisms have been suggested and rigorous reaction rate equations were derived based on a series of reaction experiments in the presence and in the absence
John M. Haschke; Thomas H. Allen; Jerry L. Stakebake
1996-01-01
Kinetic measurements for the reactions of unalloyed plutonium with water vapor and oxygen in the 35 to 400°C range show that moisture enhancement of the corrosion rate is confined to a temperature regime below 200°C. In combination with kinetic data from literature sources and measurements with air at 25°C, the data define a rate-temperature envelope in which the corrosion reaction
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)
Neural basis for stereopsis from second-order contrast cues.
Tanaka, Hiroki; Ohzawa, Izumi
2006-04-19
Humans and animals use visual cues such as brightness and color boundaries to identify objects and navigate through environments. However, even when these cues are not available, we can effortlessly perform these tasks by using second-order cues such as contrast variation (envelope) of patterns on surfaces. Previously, numerous psychophysical studies examined properties of binocular depth processing based on the contrast-envelope cues and suggested the existence of a stereo system that uses these cues. However, its physiological substrate has not been identified yet. Here, we show that a subset of cortical neurons in cat area 18 show binocular interactions for the contrast-envelope stimuli. These neurons are capable of representing a variety of depths in the three-dimensional space based on the information available from contrast cues alone. Furthermore, these neurons show similar disparity-tuning curves for borders defined by both luminance and contrast cues. This cue-invariant tuning is consistent with a linear binocular convergence model for monocular luminance and contrast-envelope processing pathways. PMID:16624957
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.
a Second Order Model of a Swirling Turbulent Jet
NASA Astrophysics Data System (ADS)
Ettestad, David Jorgen
This work attempts to model turbulence in swirling flows. Equations for the second moments of the turbulent fluctuations are derived and the various unknown terms in the equation are modeled. Invariance and physical realizability are used as constraints on the model. The rapid part of the pressure correlations is modeled to second order in the anisotropy tensor, leaving three adjustable constants. Improvements are made in the models of Lumley (1978) for the pressure transport and dissipation transport terms. The third order moments are modeled by a rough approximation of the terms in the third order moment equation. The model is then put on computer and a numerical simulation of a swirling turbulent jet is performed. Several of the constants in the model are adjusted separately and the effects on the model are shown and analyzed. The constants are then adjusted to best fit the experimental data of Rose, using Morse's data as an additional guide. The model fits the experimental data for a nonswirling jet very well. It does fairly well on the swirling jet except it doesn't spread fast enough for the first few diameters. Explanations are offered for this slow spreading rate. Finally, a correction term to take into account the effects of swirl on dissipation is given which dramatically improves the swirling jet results for the first few diameters.
Second order statistics target-specified virtual dimensionality
NASA Astrophysics Data System (ADS)
Paylor, Drew; Chang, Chein-I.
2013-05-01
Virtual dimensionality (VD) has received considerable interest in its use of specifying the number of spectrally distinct signatures. So far all techniques are decomposition approaches which use eigenvalues, eigenvectors or singular vectors to estimate the virtual dimensionality. However, when eigenvalues are used to estimate VD such as Harsanyi-Farrand- Chang's method or hyperspectral signal subspace identification by minimum error (HySime), there will be no way to find what the spectrally distinct signatures are. On the other hand, if eigenvectors/singular vectors are used to estimate VD such as maximal orthogonal complement algorithm (MOCA), eigenvectors/singular vectors do not represent real signal sources. In this paper we introduce a new concept, referred to as target-specified VD (TSVD), which operates on the signal sources themselves to both determine the number of distinct sources and identify their signature. The underlying idea of TSVD was derived from that used to develop high-order statistics (HOS) VD where its applicability to second order statistics (2OS) was not explored. In this paper we investigate a 2OS-based target finding algorithm, called automatic target generation process (ATGP) to determine VD. Experiments are conducted in comparison with well-known and widely used eigen-based approaches.
Holographic dark matter and dark energy with second order invariants
NASA Astrophysics Data System (ADS)
Aviles, Alejandro; Bonanno, Luca; Luongo, Orlando; Quevedo, Hernando
2011-11-01
One of the main goals of modern cosmology remains to summon up a self-consistent policy, able to explain, in the framework of Einstein’s theory, the cosmic speedup and the presence of dark matter in the Universe. According to the holographic principle, which postulates the existence of a minimal size of a physical region, we argue, in this paper, that if this size exists for the Universe and it is accrued from the independent geometrical second order invariants, it would be possible to ensure a surprising source for dark matter and a viable candidate for explaining the late acceleration of the Universe. We develop low redshift tests, such as supernovae Ia and kinematical analysis, compiled by the use of cosmography, and we compare the outcomes with higher redshift tests, such as the CMB peak and anisotropy of the cosmic power spectrum. All the results indicate that the models presented here can be interpreted as unified models that are capable of describing both dark matter and dark energy.
Second-order electromagnetic eigenfrequencies of a triaxial ellipsoid II
NASA Astrophysics Data System (ADS)
Mehl, James B.
2015-10-01
Finite-element calculations of electromagnetic eigenvalues are known to converge to the exact solutions in the limit of vanishing element sizes. In an extension of previous work (Mehl 2009 Metrologia 46 554–9) the eigenfrequencies of the TM1n and TE1n (n??=??1, 2, ··· 6) modes of triaxial ellipsoids were calculated as a function of mesh size. Higher-accuracy eigenvalues were obtained through a limiting process as the mesh size was reduced; the extrapolation was based on the theoretical convergence rate. The difference between the finite-element eigenfrequencies and the eigenfrequencies predicted by shape perturbation theory is found to be proportional to the cube of the fractional deformation parameter ? for all investigated modes. For ellipsoids with axes proportional to 1?:?1.0005?:?1.0010, the cubic term represents a fractional perturbation of the average TM16 eigenvalue k2 by???0.16??× 10?????6 and the average TE16 eigenvalue by???0.22??× 10?????6. This work adds support to the correctness of the analytic second-order formula derived in the previous work, and also demonstrates the usefulness of finite-element methods for investigating the quasi-spherical resonators (QSRs) used in measurements of the Boltzmann constant. In principle, the method can be extended to QSRs whose shape differs from triaxial ellipsoids.
Kinetics of the carbon-oxygen reaction in molten iron
M. Y. Solar; R. I. L. Guthrie
1972-01-01
The kinetics of carbon monoxide absorption by stagnant liquid iron has been investigated over the first 10 min or so of gas-liquid\\u000a metal contact. On the basis of experiments conducted at temperatures ranging between 1580? and 1700?C (PCO= 1 atm) and carbon monoxide pressures ranging between 0.1 and 1.5 atm (at 1600†C), it was concluded that the absorption\\u000a kinetics of
Probing Aluminum Reactions in Combustion and Explosion Via the Kinetic Isotope Effect
NASA Astrophysics Data System (ADS)
Tappan, Bryce
2015-06-01
The mechanism that controls the reaction speed of aluminum in explosion and combustion is poorly understood, and experimentally difficult to measure. Recently, work in our laboratory has demonstrated that during the combustion of nanoparticulate aluminum with H2O or D2O, different reaction rates due to the kinetic isotope effect are observed. This result is the first-ever observed kinetic isotope effect in a metal combustion reaction and verifies that chemical reaction kinetics play a major role in determining the global burning rate. During or shortly after a detonation, however, the reaction rates are dramatically faster and the physical mechanism controlling Al reaction is likely different than during combustion events. To utilize the kinetic isotope effect to probe Al reactions in detonation, formulations were produced that contain powdered Al in deuterated high explosives and high-fidelity detonation velocity were determined along with PDV measurements to observe early wall velocity expansion measurements. The JWL equation of state was solved to determine temperature, pressure and energies at specific time periods, in addition of Gurney energies, which enables the elucidation of Al reaction extent. By comparison of the Al oxidation with LiF, data indicate that Al oxidation occurs on an extremely fast time scale and isotope effects in both the HE detonation and post-detonation Al reactions are discussed.
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.
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.
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.
Kinetics of chemical reactions on solid surfaces: deviations from conventional theory.
Zaera, Francisco
2002-02-01
Isothermal kinetic measurements on elementary steps between species adsorbed on solid surfaces have highlighted significant deviations from conventional kinetic theories. In particular, it has been found that neighboring adsorbates modify the energetics of surface reaction in ways not explained by macroscopic kinetic models. The free energy barriers associated with transition state theory can be expanded to include coverage-dependent terms, but that does not account for local effects due to surface islanding. Changes in surface concentrations also lead to changes in adsorption geometries, and even to different adsorbate-surface bonding. Future Monte Carlo simulations and other theoretical approaches to describe surface kinetics need to include these factors. PMID:11851391
Further development and testing of a second-order bulk boundary layer model. Master's thesis
Krasner, R.D.
1993-05-03
A one-layer bulk boundary layer model is developed. The model predicts the mixed layer values of the potential temperature, mixing ratio, and u- and v-momentum. The model also predicts the depth of the boundary layer and the vertically integrated turbulence kinetic energy (TKE). The TKE is determined using a second-order closure that relates the rate of dissipation to the TKE. The fractional area covered by rising motion sigma and the entrainment rate (E) are diagnostically determined. The model is used to study the clear convective boundary layer (CBL) using data from the Wangara, Australia boundary layer experiment. The Wangara data is also used as an observation base to validate model results. A further study is accomplished by simulating the planetary boundary layer (PBL) over an ocean surface. This study is designed to find the steady-state solutions of the prognostic variable.
Second order multidimensional sign-preserving remapping for ALE methods
Hill, Ryan N; Szmelter, J.
2010-12-15
A second-order conservative sign-preserving remapping scheme for Arbitrary Lagrangian-Eulerian (ALE) methods is developed utilising concepts of the Multidimensional Positive Definite Advection Transport Algorithm (MPDATA). The algorithm is inherently multidimensional, and so does not introduce splitting errors. The remapping is implemented in a two-dimensional, finite element ALE solver employing staggered quadrilateral meshes. The MPDATA remapping uses a finite volume discretization developed for volume coordinates. It is applied for the remapping of density and internal energy arranged as cell centered, and velocity as nodal, dependent variables. In the paper, the advection of scalar fields is examined first for test cases with prescribed mesh movement. A direct comparison of MPDATA with the performance of the van Leer MUSCL scheme indicates advantages of a multidimensional approach. Furthermore, distinctly different performance between basic MPDATA and the infinite gauge option is illustrated using benchmarks involving transport of a sign changing velocity field. Further development extends the application of MPDATA remapping to the full ALE solver with a staggered mesh arrangement for density, internal energy and momentum using volume coordinates. At present, two options of the algorithm - basic and infinite gauge - are implemented. To ensure a meaningful assessment, an identical Lagrangian solver and computational mesh update routines are used with either MPDATA or van Leer MUSCL remapping. The evaluation places particular focus on the abilities of both schemes to accurately model multidimensional problems. Theoretical considerations are supported with numerical examples. In addition to the prescribed mesh movement cases for advection of scalars, the demonstrations include two-dimensional Eulerian and ALE flow simulations on quadrilateral meshes with both fixed and variable timestep control. The key comparisons include the standard test cases of Sod and Noh for single material problems. The results demonstrate that the MPDATA gauge option is suitable for providing accurate ALE remapping and preserves the multidimensionality and sign of both scalar and vector fields.
Isotopic Effect on the Kinetics of the Belousov-Zhabotinsky Reaction
Rossi, Federico; Rustici, Mauro; Rossi, Claudio; Tiezzi, Enzo
2007-01-01
In this work we present results about the deuterium isotope effect on the global kinetics of a Belousov-Zhabotinsky reaction in batch conditions. A nonlinear dependence of the Induction Period upon the percentage of deuterated reactants was found. The isotopic effect on the bromination reaction of malonic acid was evaluated.
Accelerated Search Kinetics Mediated by Redox Reactions of DNA Repair Enzymes
Levine, Alex J.
Accelerated Search Kinetics Mediated by Redox Reactions of DNA Repair Enzymes Pak-Wing Fok and Tom to explain the localization of base excision repair (BER) enzymes to lesions on DNA. The CT mechanism relies on redox reactions of iron-sulfur cofactors that modify the enzyme's binding affinity. These redox
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 hydrocarbons and substituted hydrocarbons. Usually, although not without exceptions, these reactions serve and polyaromatic hydrocarbons (PAH), which leads, in turn, to production of soot in combustion systems. In spite
Kinetic calculations and mechanism definition for reactions in an ammonium perchlorate flame
Ermolin, N.E.; Fomin, V.M.; Korobeinichev, O.P.; Tereshchenko, A.G.
1982-09-01
This article reports on detailed calculations on the reaction kinetics in APC flames on the basis of a wide set of possible reactions and experimental data on the initial composition of the gas mixture (gasification products from APC). The purpose is to select the most important reactions in this system by comparing the calculations on the kinetics with experimental data on the concentration profiles in APC flames. Discusses kinetic equations; rate constants as the reaction mechanism; results from kinetic calculations; and identification of major stages. A laminar flame such as that provided by ammonium perchlorate is described in general form by a system of differential equations that incorporate the transport of heat and matter in the presence of chemical reactions. APC is a system consisting of 4 elements (N,H,Cl and O). Points out that the scheme enables one to determine which reactions are responsible for producing the final products. Suggests that in the future one will be able to analyze experimental data on the reaction-rate profiles for stable components in order to determine either the atom and radical concentrations or the rate constants of the reactions involving them.
1984-01-01
The kinetics of the platinum catalyzed reaction between NO and CO has been studied under conditions chosen to approximate those observed during operation of catalysts in automotive exhaust gas treatment applications. The catalysts were polycrystalline platinum foils and wires. The reaction was studied over a range of reactant partial pressures of 10 V Torr to 1 Torr and catalyst temperatures
Effects of nonproductive binding on the kinetics of enzymatic reactions with patterned substrates
Dinner, Aaron
Effects of nonproductive binding on the kinetics of enzymatic reactions with patterned substrates of substrate molecules immobilized on a surface. The simulations reveal a crossover in the overall reaction rates for randomly distributed and clustered substrate molecules as the enzyme unbinding rate is varied
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.
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.
Power law kinetics in reversible enzyme-catalyzed reaction due to diffusion
NASA Astrophysics Data System (ADS)
Paul, Sujata; Gangopadhyay, Gautam
2003-08-01
The effect of diffusion on the reversible enzyme-catalyzed reaction is investigated. The kinetic scheme of the enzyme-catalyzed reaction is considered with a little generalization of Michaelis-Menten mechanism where the last step is taken as reversible. By using a fluctuation theory approach we have considered the relaxation mechanism where the quadratic nonlinearity of the equation of fluctuation around the equilibrium acts as a small perturbation. In three dimensions, the effect of diffusion is reflected through the relaxation kinetics of the reaction as a power law asymptotics, t-3/2, when the system approaches equilibrium.
NASA Astrophysics Data System (ADS)
Gray, Patrick J.; Olesik, John W.
2015-03-01
Reaction gas flow rate dependent Ar2+ and Ar+ signals are correlated to fundamental kinetic rate coefficients. A simple calculation, assuming that gas exits the reaction cell due only to effusion, is described to estimate the gas pressure in the reaction cell. The value of the product of the kinetic rate constant and the ion residence time in the reaction cell can be determined from experimental measurement of the decrease in an ion signal as a function of reaction gas flow rate. New kinetic rate constants are determined for the reaction of CH3F with Ar+ and Ar2+.
General theory of multistage geminate reactions of isolated pairs of reactants. I. Kinetic equations
Doktorov, Alexander B.; Kipriyanov, Alexey A.
2014-05-14
General matrix approach to the consideration of multistage geminate reactions of isolated pairs of reactants depending on reactant mobility is formulated on the basis of the concept of “effective” particles. Various elementary reactions (stages of multistage reaction including physicochemical processes of internal quantum state changes) proceeding with the participation of isolated pairs of reactants (or isolated reactants) are taken into account. Investigation has been made in terms of kinetic approach implying the derivation of general (matrix) kinetic equations for local and mean probabilities of finding any of the reaction species in the sample under study (or for local and mean concentrations). The recipes for the calculation of kinetic coefficients of the equations for mean quantities in terms of relative coordinates of reactants have been formulated in the general case of inhomogeneous reacting systems. Important specific case of homogeneous reacting systems is considered.
Doktorov, Alexander B; Kipriyanov, Alexey A
2014-05-14
General matrix approach to the consideration of multistage geminate reactions of isolated pairs of reactants depending on reactant mobility is formulated on the basis of the concept of "effective" particles. Various elementary reactions (stages of multistage reaction including physicochemical processes of internal quantum state changes) proceeding with the participation of isolated pairs of reactants (or isolated reactants) are taken into account. Investigation has been made in terms of kinetic approach implying the derivation of general (matrix) kinetic equations for local and mean probabilities of finding any of the reaction species in the sample under study (or for local and mean concentrations). The recipes for the calculation of kinetic coefficients of the equations for mean quantities in terms of relative coordinates of reactants have been formulated in the general case of inhomogeneous reacting systems. Important specific case of homogeneous reacting systems is considered. PMID:24832250
General theory of multistage geminate reactions of isolated pairs of reactants. I. Kinetic equations
NASA Astrophysics Data System (ADS)
Doktorov, Alexander B.; Kipriyanov, Alexey A.
2014-05-01
General matrix approach to the consideration of multistage geminate reactions of isolated pairs of reactants depending on reactant mobility is formulated on the basis of the concept of "effective" particles. Various elementary reactions (stages of multistage reaction including physicochemical processes of internal quantum state changes) proceeding with the participation of isolated pairs of reactants (or isolated reactants) are taken into account. Investigation has been made in terms of kinetic approach implying the derivation of general (matrix) kinetic equations for local and mean probabilities of finding any of the reaction species in the sample under study (or for local and mean concentrations). The recipes for the calculation of kinetic coefficients of the equations for mean quantities in terms of relative coordinates of reactants have been formulated in the general case of inhomogeneous reacting systems. Important specific case of homogeneous reacting systems is considered.
Redner, Sidney
Chapter 8 REACTION KINETICS In this chapter, we will discuss the time evolution of simple reactions#usionÂcontrolled limit. In contrast, in the reactionÂcontrolled limit, reactants must meet many times before a reaction in reduced spatial dimension. Di#usionÂ limited reactions have played an important role in the development
High temperature heterogeneous reaction kinetics and mechanisms of tungsten oxidation
Justin L. Sabourin
2010-01-01
Tungsten, which is a material used in many high temperature applications, is limited by its susceptibility to oxidation at elevated temperatures. Although tungsten has the highest melting temperature of any metal, at much lower temperatures volatile oxides are formed during oxidation with oxygen containing species. This differs from many heterogeneous oxidation reactions involving metals since most reactions form very stable
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.
Systematic study of the reaction kinetics for HMX.
Long, Yao; Chen, Jun
2015-05-01
The reaction process of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in wide temperature and pressure ranges is simulated by molecular dynamics. A set of postprocessing programs is written to evaluate the intermediate molecules and chemical reactions. On the basis of these evaluations, the reaction rates, reactive Hugoniot curves, and detonation wave profile are calculated. The detonation velocity and detonation pressure are determined as 9984 m/s and 38.3349 GPa, in agreement with the experimental results, 9110 m/s and 39.5 GPa. The width of the reaction zone is 10 ?m, and the main products are N2, H2O, and CO2. We find some molecules play an important role in intermediate reactions but are not exhibited in final products, such as N2O2, N2O5, and C3H3N3. PMID:25866915
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
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.…
Chemistry 722 Spring 2003 Reaction Kinetics and Dynamics Ian Harrison
Zhigilei, Leonid V.
Reversibility and Detailed Balancing Potential Energy Surfaces: Ab Initio and Semi-Empirical (LEPS) Dynamics-Entropy Postulate Surprisal Analysis and Synthesis 3) Selected Applications Microcanonical unimolecular rate theory to dissociative adsorption on metals Gas-phase protein kinetics in ICR mass spectrometers (e.g., JACS 118, 10640
Kinetic studies of the infrared-induced reaction between atomic chlorine and solid parahydrogen
NASA Astrophysics Data System (ADS)
Raston, Paul L.; Kettwich, Sharon C.; Anderson, David T.
2015-04-01
We present Fourier-transform infrared (FTIR) spectroscopic studies of the IR-induced Cl + H2(v = 1) ? HCl + H reaction in a parahydrogen (pH2) matrix aimed at distinguishing between two proposed reactions mechanisms; direct-IR and vibron-mediated. The Cl atom reactants are produced via 355 nm in situ photolysis of a Cl2 doped pH2 matrix. After photolysis is complete, a long-pass IR filter in the FTIR beam is removed and we measure the ensuing IR-induced reaction kinetics using rapid scan FTIR spectroscopy. We follow both the decay of the Cl atom reactant and growth of the HCl product using the Cl spin-orbit (SO) + Q1(0) and HCl R1(0) transitions, respectively. We show the IR-induced reaction mechanism depends on the spectral profile of the IR radiation; for IR spectral profiles that have significant IR intensities between 4000 and 5000 cm-1 we observe first-order kinetics that are assigned to a vibron-mediated mechanism and for spectral profiles that have significant IR intensities that include the Cl SO + Q1(0) transition near 5094 cm-1 we observe bi-exponential kinetics that are dominated by the direct-IR mechanism at early reaction times. We can distinguish between the two mechanisms using the observed kinetics. We investigate the reaction kinetics for different FTIR optical setups, for a range of sample conditions, and start and stop the IR-induced reaction to investigate the importance of secondary H atom reactions. We also study the IR-induced reaction in Br/Cl co-doped pH2 samples and show the presence of the Br atom quenches the vibron-mediated reaction kinetics presumably because the Br-atoms serve as efficient vibron traps. This paper indicates that in a highly enriched pH2 matrix the H atoms that are produced by the IR-induced Cl atom reaction likely do not play a significant role in the measured reaction kinetics which implies these secondary H atom reactions are highly selective.
Thermal analysis of paddy husk. Part 2: Order of reaction and other kinetic parameters
Jain, A.K.; Sharma, S.K.; Singh, D. [Panjab Univ., Chandigarh (India)
1997-12-31
This paper presents experimental data on the thermal degradation of paddy husk and cellulose in air, argon and a mixture of nitrogen and oxygen (95:5) at different linear heating rates. The data is used for the determination of kinetic parameters using different orders of reaction and an optimum order of reaction identified. The often used assumption of unity order of reaction under all circumstances is shown to have a limited validity.
Heterogeneous reaction mechanisms and kinetics relevant to the CVD of semiconductor materials
Creighton, J.R.; Coltrin, M.E.
1994-03-01
This report documents the state of the art in experimental and theoretical techniques for determining reaction mechanisms and chemical kinetics of heterogeneous reactions relevant to the chemical vapor deposition of semiconductor materials. It summarizes the most common ultra-high vacuum experimental techniques that are used and the types of rate information available from each. Several case studies of specific chemical systems relevant to the microelectronics industry are described. Theoretical methods for calculating heterogeneous reaction rate constants are also summarized.
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
2015-08-20
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.
Ren, Rong; Li, Kexun; Zhang, Chong; Liu, Dongfang; Sun, Jie
2011-02-01
The biosorption of tetradecyl benzyl dimethyl ammonium chloride (C(14)BDMA) onto activated sludge was examined in aqueous solution with respect to the contact time, temperature and particle size. Equilibrium reached in about 2h contact time. An decrease in the temperature increases of biosorption capacity of C(14)BDMA onto activated sludge, which also increases with decreasing particle size. The experimental data fit the pseudo-second-order kinetics model well. The Langmuir and Freundlich models were applied to describe equilibrium isotherms, and the equilibrium partitioning data was described well by both models. Thermodynamic data showed that C(14)BDMA biosorption onto activated sludge was feasible, spontaneous and exothermic. The Fourier transform infrared (FT-IR) spectrophotometry results show that both physisorption and chemisorption were involved. The measured zeta potential values and the enhanced cation concentration indicate the presence of electrostatic interactions, hydrophobic interactions and ion exchange. PMID:21195609
Low energy ion-molecule reaction dynamics and chemiionization kinetics
NASA Astrophysics Data System (ADS)
Farrar, J. M.
Low energy crossed ion beam neutral beam studies of a wide spectrum of elementary chemical reactions were performed. The reactive scattering work embodies crossed beam studies of simple chemical processes under single collision conditions which elucidate reaction dynamics by measuring product branching ratios, translational energy distributions and scattering angle distributions. The studies have emphasized the proton transfer reactions of the important flame cations HCO(+) and H3O(+) with a number of neutral molecules present in flames, including H2O, CH3OH, CH3CH2OH, and (CH3)2CO, and a wide variety of reactions of the ground state carbon cation, C(+)((2)P), with neutrals, illustrating the important reactions of insertion into C-H, O-H, N-H, and C-C bonds, as well as condensation reactions in which new C-C bonds are formed, yielding significant increases in the molecular weight of the charged product. These studies represent the first crossed beam studies in which information more detailed than rate constants and energy dependent total cross sections was inferred about the reaction dynamics.
Graves-Woodward, K; Pratt, R F
1998-01-01
The kinetics of reaction of solubilized penicillin-binding protein 2a (sPBP2a) of methicillin-resistant Staphylococcus aureus with a variety of beta-lactams and acyclic species was studied in homogeneous aqueous solution at 37 degreesC in 25 mM Hepes buffer, pH7.0, containing 1 M NaCl. Under these conditions, but not at lower salt concentrations, protein precipitation did not occur either during or after the reaction. The reactions of beta-lactams in general could be monitored by competition with a chromophoric beta-lactam, nitrocefin, or directly in certain cases by protein fluorescence. Rate constants for reaction of a wide variety of beta-lactams are reported. The interactions are characterized by a slow second-order acylation reaction followed by a slower deacylation. For example, the rate constants for benzylpenicillin were 12 M-1.s-1 and 3x10(-5) s-1 respectively. The acylation is slow in comparison with those of normal non-resistant high-molecular-mass penicillin-binding proteins. sPBP2a also seemed to catalyse the slow hydrolysis of a variety of acyclic depsipeptides but not that of a d-Ala-d-Ala peptide. The reactions with certain depsipeptides also led to protein precipitation. These reactions were, however, not affected by prior blockage of the beta-lactam-binding site by benzylpenicillin and thus might take place elsewhere on the enzyme. Two classes of potential transition- state analogue inhibitors, phosphonate monoesters and boronates, seemed to have little effect on the rate of reaction of sPBP2a with nitrocefin and therefore seem to have little affinity for the beta-lactam-binding/D,D-peptidase site. PMID:9620879
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
Surface reactions kinetics between nanocrystalline magnetite and uranyl.
Missana, Tiziana; Maffiotte, César; García-Gutiérrez, Miguel
2003-05-01
Magnetite is the most important end member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Nanocrystalline magnetite was synthesized in the laboratory and its physicochemical properties were analyzed in detail. The kinetics of the adsorption of U(VI) and the kinetics of the actinide reduction to a lower oxidation state, in presence of the oxide, were studied by means of batch sorption techniques and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the uranium sorption and reduction processes on the magnetite surface have very fast kinetics (hours), the reduction process being triggered by sorption. XPS measurements showed that the speciation of uranium at the surface does not show significant changes with time (from 1 day to 3 months), as well as the quantity of uranium detected at the surface. The surface speciation depended on the initial pH of the contact solution. Considering that the Eh of equilibrium between magnetite and the solution, under our experimental conditions, is slightly positive (50-100 mV), the uranium reduction would also be thermodynamically possible within the liquid phase. However, the kinetics of reduction in the liquid occur at a much slower rate which, in turn, has to depend on the attainment of the magnetite/solution equilibrium. The decrease of uranium in solution, observed after the uranyl adsorption stage, and particularly at acidic pH, is most probably due to the precipitation of U(IV) formed in the solution. PMID:12725835
NASA Technical Reports Server (NTRS)
Radhakrishnan, Krishnan; Bittker, David A.
1993-01-01
A general chemical kinetics and sensitivity analysis code for complex, homogeneous, gas-phase reactions is described. The main features of the code, LSENS, are its flexibility, efficiency and convenience in treating many different chemical reaction models. The models include static system, steady, one-dimensional, inviscid flow, shock initiated reaction, and a perfectly stirred reactor. In addition, equilibrium computations can be performed for several assigned states. An implicit numerical integration method, which works efficiently for the extremes of very fast and very slow reaction, is used for solving the 'stiff' differential equation systems that arise in chemical kinetics. For static reactions, sensitivity coefficients of all dependent variables and their temporal derivatives with respect to the initial values of dependent variables and/or the rate coefficient parameters can be computed. This paper presents descriptions of the code and its usage, and includes several illustrative example problems.
Kinetics of the reaction of hydrogen sulfide and sulfur dioxide in organic solvents
Neumann, D.W.; Lynn, S.
1986-01-01
Calorimetry was used to study the kinetics of the irreversible reaction between hydrogen sulfide and sulfur dioxide in mixtures of N,N-dimethylaniline (DMA) and diethylene glycol monomethyl ether (DGM) and of DMA and triethylene glycol dimethyl ether (triglyne). The reaction was found to be first order in both H/sub 2/S and SO/sub 2/ in the presence of DMA. The approximate heat of reaction is 28 kcal/mol of sulfur dioxide. The addition of DMA accelerates the reaction by an order of magnitude over that obtained in the glycol ethers alone. Rate constants are in the range of 1-20 L/(mol s). Hydroxylated species such as water, methanol, and other alcohols increase the rate still more dramatically when added to the DMA/ether mixtures. The results of these experiments show some of the effects of solvent composition on the kinetics of the reaction.
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)
Gargano, Immacolata; Olivieri, Giuseppe; Spasiano, Danilo; Andreozzi, Roberto; Pollio, Antonino; Marotta, Raffaele; D'Ambrosio, Nicola; Marzocchella, Antonio
2015-10-20
The kinetic characterization of the photosynthetic activity in autotrophic microalgae plays a key role in the design of optimized photobioreactors. This paper presents a procedure to assess kinetic parameters of a three-state photosynthetic reaction centres model. Four kinetic parameters of the model were assessed by processing the time-series measurements of pulse-amplitude modulation fluorimetry. The kinetic parameters were assessed for several microalgal strains (Stichococcus bacillaris, Scenedesmus vacuolatus, Chlamydomonas reinhardtii, Chlorella vulgaris) growth in vertical and inclined bubble columns and irradiated by white-light or red/blue light. The procedure was successfully applied to the investigated strains. The assessed parameters allow identifying the irradiance range under which: the photochemical process is controlled by the photons capture; the photoinhibition competes with the photochemical quenching. The analysis of the time-scale of the photosynthetic reaction centres as a function of the irradiance allows interpreting the performances of photobioreactors characterized by non-homogeneous irradiance. PMID:26216180
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.
Oxygen Diffusion and Reaction Kinetics in Continuous Fiber Ceramic Matrix Composites
NASA Technical Reports Server (NTRS)
Halbig, Michael C.; Eckel, Andrew J.; Cawley, James D.
1999-01-01
Previous stressed oxidation tests of C/SiC composites at elevated temperatures (350 C to 1500 C) and sustained stresses (69 MPa and 172 MPa) have led to the development of a finite difference cracked matrix model. The times to failure in the samples suggest oxidation occurred in two kinetic regimes defined by the rate controlling mechanisms (i.e. diffusion controlled and reaction controlled kinetics). Microstructural analysis revealed preferential oxidation along as-fabricated, matrix microcracks and also suggested two regimes of oxidation kinetics dependent on the oxidation temperature. Based on experimental results, observation, and theory, a finite difference model was developed. The model simulates the diffusion of oxygen into a matrix crack bridged by carbon fibers. The model facilitates the study of the relative importance of temperature, the reaction rate constant, and the diffusion coefficient on the overall oxidation kinetics.
Second-order polarizability of p-substituted cinnamic acids
NASA Astrophysics Data System (ADS)
Chandra Ray, Paresh
1996-01-01
First-order hyperpolarizabilities (?) of a series of p-substituted cinnamic acids have been measured using the hyper-Rayleigh scattering technique and compared with those of p-substituted benzoic acids. ? in these acids increases as a function of the donor strength. It increases twice with the increase in the effective chain length. Semi-empirical calculations also support this enhancement. Solvents effects are dealt with at the ab initio level within the self-consistent reaction field approach.
Second-order analytic solutions for re-entry trajectories
NASA Astrophysics Data System (ADS)
Vinh, Nguyen X.; Kim, Eun-Kyou; Greenwood, Donald T.
With the development of aeroassist technology, either for near-earth operations or for planetary aero-capture, it is of interest to have accurate analytic solutions for the speed, flight path angle and altitude during the atmospheric passage. For a future aerospace plane which uses the accumulated kinetic energy to glide for a long range, explicit relations among the main state variables are also useful for guidance purposes. In this paper we have used normalization to put the equations of motion for planar entry around a non-rotating planet into a form which is suitable for an analytic integration. Explicit and accurate solutions are then obtained for ballistic fly-through trajectories, lifting skip trajectories and equilibrium glide trajectories.
Non-linear reduction for kinetic models of metabolic reaction networks
Ziomara P. Gerdtzen; Prodromos Daoutidis; Wei-Shou Hu
2004-01-01
Kinetic models of metabolic networks are essential for predicting and optimizing the transient behavior of cells in culture. However, such models are inherently high dimensional and stiff due to the large number of species and reactions involved and to kinetic rate constants of widely different orders of magnitude. In this paper we address the problem of deriving non-stiff, reduced-order non-linear
On the potential failure of reduced reaction kinetics
NASA Astrophysics Data System (ADS)
Powers, Joseph; Paolucci, Samuel
2013-11-01
Severe stiffness of equations modeling advection, reaction, and diffusion in combustion systems has motivated many efforts to filter the primary mechanism inducing the stiffness: the simultaneous presence of fast and slow reaction dynamics. Here, it is demonstrated that a common filtering technique for construction of low dimensional reaction manifolds, connection of equilibria by heteroclinic orbits, can fail. While the method is guaranteed to generate an invariant manifold, the local dynamics far from equilibrium may be such that nearby trajectories are in fact carried away from the identified invariant manifold, thus rendering it to be of limited utility in capturing slow dynamics far from equilibrium. An eigenvalue-based method is described to characterize the local behavior of such invariant manifolds. The method provides a diagnostic tool for evaluating whether a candidate manifold has the desirable properties of being both slow and attractive. A simple model system and a realistic hydrogen-air system are examined; method success and failure are demonstrated.
Kinetics of the reactions of Cl atoms with several ethers.
Giri, Binod R; Roscoe, John M
2010-08-19
The reactions of Cl with tetrahydrofuran, tetrahydropyran, and dimethyl ether have been studied as a function of temperature, pressure, and O(2) concentration. The temperature was varied from approximately 280 to 360 K, the mole fraction of O(2) ranged from zero to approximately 0.6, and the experiments were made in a bath of argon at total pressures ranging from approximately 300 to 760 Torr. The rate coefficients were measured using the relative rate method with gas chromatographic analysis. The reaction of Cl with isobutane was the reference reaction, the rate coefficients for which were calibrated against the reaction of propane with chlorine atoms as a function of temperature. The rate coefficients were unaffected by the concentration of O(2) or by variation in pressure. The rate coefficient for the reaction of Cl with isobutane increased slightly with decreasing temperature. This weak temperature dependence of the rate coefficient was in satisfactory agreement with information in the literature and is represented in Arrhenius form by k(T) = (1.02(-0.25)(+0.32)) x 10(-10) exp(99 +/- 88/T) cm(3) molecule(-1) s(-1), where the uncertainties represent two standard deviations. The rate coefficients for the reactions of Cl with the ethers did not show a statistically significant dependence on temperature. Their average values over our range of temperature are: for Cl + tetrahydrofuran, k = (2.71 +/- 0.34) x 10(-10) cm(3) molecule(-1) s(-1); for Cl + tetrahydropyran, k = (2.03 +/- 0.82) x 10(-10) cm(3) molecule(-1) s(-1); and for Cl + dimethyl ether, k = (1.73 +/- 0.22) x 10(-10) cm(3) molecule(-1) s(-1), in which the uncertainties are again two standard deviations. PMID:20701344
Nagaraj, Karuppiah; Senthil Murugan, Krishnan; Thangamuniyandi, Pilavadi; Sakthinathan, Subramanian
2015-05-15
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 Fe(2+) ion in ionic liquid (1-butyl-3-methylimidazoliumbromide) medium at different temperatures (298, 303, 308, 313, 318 and 323K) 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. PMID:25721780
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.
Non-linear surface reaction kinetics in GaAs selective area MOVPE
NASA Astrophysics Data System (ADS)
Song, Haizheng; Wang, Yunpeng; Sugiyama, Masakazu; Nakano, Yoshiaki; Shimogaki, Yukihiro
2008-11-01
Two-dimensional numerical simulation on growth rate non-uniformity of selective area growth (SAG) in metal-organic vapor phase epitaxy (MOVPE) is an effective method to examine the surface reaction kinetics, which is difficult to be investigated in mass-transport limited growth regime. Non-linear kinetic analysis based on the Langmuir-Hinshelwood mechanism is revealing the intrinsic process in MOVPE. Two important kinetic parameters, surface reaction rate constant ( ksn) and adsorption equilibrium coefficient ( K), were successfully extracted from GaAs SAG-MOVPE on (1 0 0) exact and 2° off misoriented substrates in the temperature range of 520-600 °C. The activation energy is 126-127 kJ/mol for ksn, and -53 to -59 kJ/mol for K. The surface coverage of Ga-species during the GaAs growth can be estimated from these kinetic parameters as 0.05-0.60. There is a critical temperature ( Tc) for the conversion of GaAs surface reaction mode. When growth temperature is higher than Tc, non-linear kinetic can be simplified as linear kinetic mode which is easier in calculation. Tc was found to be 600 °C for (1 0 0) exact GaAs substrate and 650 °C for 2° off substrate.
Kinetics and mechanism of atmospheric reactions of partially fluorinated alcohols
E. S. Vasil’ev; I. I. Morozov; W. Hack; K.-H. Hoyermann; M. Hold
2006-01-01
Gas-phase reactions typical of the Earth’s atmosphere have been studied for a number of partially fluorinated alcohols (PFAs).\\u000a The rate constants of the reactions of CF3CH2OH, CH2FCH2OH, and CHF2CH2OH with fluorine atoms have been determined by the relative measurement method. The rate constant for CF3CH2OH has been measured in the temperature range 258–358 K (k = (3.4 ± 2.0) ×
Nonlocal Kinetic Equation and Simulations of Heavy Ion Reactions
Klaus Morawetz; Pavel Lipavský; Václav Špi?ka
1998-11-25
A kinetic equation which combines the quasiparticle drift of Landau's equation with a dissipation governed by a nonlocal and noninstantaneous scattering integral in the spirit of Enskog corrections is discussed. Numerical values of the off-shell contribution to the Wigner distribution, of the collision duration and of the collision nonlocality are presented for different realistic potentials. On preliminary results we show that simulations of quantum molecular dynamics extended by the nonlocal treatment of collisions leads to a broader proton distribution bringing the theoretical spectra closer towards the experimental values than the local approach.
Enhanced in situ continuous-flow MAS NMR for reaction kinetics in the nanocages.
Xu, Shutao; Zhang, Weiping; Liu, Xianchun; Han, Xiuwen; Bao, Xinhe
2009-09-30
A new approach of in situ continuous-flow laser-hyperpolarized (129)Xe MAS NMR together with (13)C MAS NMR is designed and applied successfully to study the adsorption and reaction kinetics in the nanospace. Methanol conversion in CHA nanocages has been investigated in detail for proof of principle demonstrating the prospect of in situ NMR of reaction kinetics. Our findings well elucidates that the reaction intermediate can be identified by (13)C MAS NMR spectroscopy, meanwhile the kinetic and dynamic processes of methanol adsorption and reaction in CHA nanocages can be monitored by one- and two-dimensional hyperpolarized (129)Xe MAS NMR spectroscopy under the continuous-flow condition close to the real heterogeneous catalysis. The kinetic curves and apparent activation energy of the nanocages involving the active site are obtained quantitatively. The advantages of hyperpolarized (129)Xe with much higher sensitivity and shorter acquisition time allow the kinetics to be probed in a confined geometry under real working conditions. PMID:19736983
Jarvis, Michael J Y; Blagojevic, Voislav; Koyanagi, Gregory K; Bohme, Diethard K
2013-02-14
Experimental results are reported for the gas-phase room-temperature kinetics of chemical reactions between nitrogen dioxide (NO(2)) and 46 atomic main-group and transition metal cations (M(+)). Measurements were taken with an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer in helium buffer gas at a pressure of 0.35 ± 0.01 Torr and at 295 ± 2 K. The atomic cations were produced at ca. 5500 K in an ICP source and allowed to decay radiatively and to thermalize to room temperature by collisions with Ar and He atoms prior to reaction with NO(2). Measured apparent bimolecular rate coefficients and primary reaction product distributions are reported for all 46 atomic metal cations and these provide an overview of trends across and down the periodic table. Three main types of reactions were observed: O-atom transfer to form either MO(+) or NO(+), electron transfer to form NO(2)(+), and addition to form MNO(2)(+). Bimolecular O-atom transfer was observed to predominate. Correlations are presented between reaction efficiency and the O-atom affinity of the metal cation and between the prevalence of NO(+) product formation and the electron recombination energy of the product metal oxide cation. Some second-order reactions are evident with metal cations that react inefficiently. Most interesting of these is the formation of the MNO(+) cation with Rh(+) and Pd(+). The higher-order chemistry with NO(2) is very diverse and includes the formation of numerous NO(2) ion clusters and a number of tri- and tetraoxide metal cations. Group 2 metal dioxide cations (CaO(2)(+), SrO(2)(+), BaO(2)(+)) exhibit a unique reaction with NO(2) to form MO(NO)(+) ions perhaps by NO transfer from NO(2) concurrent with O(2) formation by recombination of a NO(2) and an oxide oxygen. PMID:22894764
SECOND-ORDER SOLUTIONS OF COSMOLOGICAL PERTURBATION IN THE MATTER-DOMINATED ERA
Hwang, Jai-chan; Noh, Hyerim; Gong, Jinn-Ouk
2012-06-10
We present the growing mode solutions of cosmological perturbations to the second order in the matter-dominated era. We also present several gauge-invariant combinations of perturbation variables to the second order in the most general fluid context. Based on these solutions, we study the Newtonian correspondence of relativistic perturbations to the second order. In addition to the previously known exact relativistic/Newtonian correspondence of density and velocity perturbations to the second order in the comoving gauge, here we show that in the sub-horizon limit we have the correspondences for density, velocity, and potential perturbations in the zero-shear gauge and in the uniform-expansion gauge to the second order. Density perturbation in the uniform-curvature gauge also shows the correspondence to the second order in the sub-horizon scale. We also identify the relativistic gravitational potential that shows exact correspondence to the Newtonian one to the second order.
Chang, M. H.; Cho, S.; Lee, E. S.; Ahn, M. Y.; Kim, D. H.; Jung, J. J. [National Fusion Research Inst., 52 Eoeun-dong, Yuseong-gu, Daejeon, 305-333 (Korea, Republic of); Chung, H.; Shim, M. [Korea Atomic Energy Research Inst., P.O.Box 105, Yuseong-gu, Daejeon, 305-353 (Korea, Republic of); Song, K. M. [Korea Electric Power Research Inst., 103-16 Munji-Dong, Yuseong-gu, Daejeon, 305-380 (Korea, Republic of); Kim, D. [KOCEN Consulting and Services, Inc., Jungwon-gu, Seongnam-si, 462-819 (Korea, Republic of); Yoshida, H. [Tritium Plant Consultant (Japan)
2008-07-15
The de-hydriding reaction between ZrCo and hydrogen is the most important role of delivering hydrogen isotopes for fusion energies. Many researchers experimented in various conditions and estimated the relationship between ZrCo and hydrogen. In this study the kinetic approaches are performed using numerical simulations between ZrCo and hydrogen. Two kinds of parameter estimations are performed for the equilibrium pressure and the kinetics modeling and those are validated by the good agreement between predicted and experimental data. Based on the numerical simulation with obtained parameters, more rapid rates of de-hydriding reaction can be achieved with lower pressure and higher temperature. (authors)
Free convection in an electrochemical system with nonlinear reaction kinetics
NASA Astrophysics Data System (ADS)
Bark, Fritz H.; Alavyoon, Farid
1995-05-01
Unsteady electrolysis of a dilute solution of a metal salt made up of two ions in a system with vertical electrodes is considered for large values of the Rayleigh and Schmidt numbers. The mass transfer at the electrodes is assumed to be related to the local charge transfer potential and concentration by a nonlinear Butler-Volmer law. Free convection of the electrolyte appears owing to the variation of the concentration field. After a short initial period, the electrolyte becomes strongly stratified and the motion takes place in boundary layers at the solid boundaries. An approximate model equation for the evolution of the stratification is derived by using perturbation theory. Predictions from the simplified model are found to be in good agreement with numerical solutions of the complete problem. Significant differences compared with earlier studies for linear kinetics, i.e. cases in which the electric current density at the electrodes is constant, are found. Among other things, for large values of the difference Delta V in electric potential between the electrodes, most of the dissolved salt eventually collects near the bottom of the cell. The concentration in the bulk of the electrolyte is, for large values of Delta V, approximately given by a ninth-order polynomial to be compared with a linear behavior for linear kinetics.
Brocklehurst, K; Dixon, H B
1977-01-01
1. Reactions of enzymes with site-specific reagents may involve intermediate adsorptive complexes formed by parallel reactions in several protonic states. Accordingly, a profile of the apparent second-order rate constant for the modification reaction (Kobs., the observed rate constant under conditions where the reagent concentration is low enough for the reaction to be first-order in reagent) against pH can, in general, reflect free-reactant-state molecular pKa values only if a quasi-equilibrium condition exists around the reactive protonic state (EHR) of the adsorptive complex. 2. Usually the condition for quasi-equilibrium is expressed in terms of the rate constants around EHR: (formula: see text) i.e. k mod. less than k-2. This often cannot be assessed directly, particularly if it is not possible to determine kmod. 3. It is shown that kmod. must be much less than k-2, however, if kobs. (the pH-independent value of kobs.) less than k+2. 4. Since probable values of k+2 greater than 10(6)M-1.S-1 and since values of kobs. for many modification reactions less than 10(6)M-1.S-1, the equilibrium assumption should be valid, and kinetic study of such reactions should provide reactant-state pKa values. 5. This may not apply to catalyses, because for them the value of kcat./Km may exceed 5 X 10(5)M-1.S-1. 6. The conditions under which the formation of an intermediate complex by parallel pathways may come to quasi-equilibrium are discussed in the Appendix. PMID:23769
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.
In situ study of reaction kinetics using compressed sensing NMR
Wu, Yuting; D’Agostino, Carmine; Holland, Daniel J.; Gladden, Lynn F.
2014-10-02
unsaturated carbonyl compounds upon dehydration. If these routes are followed, at least two intermediate species might be expected.14 Such con- densation reactions may occur between the same carbonyl species (i.e., self aldol condensation) but also between two... , which may dehydrate to mesityl oxide; self aldol condensation of propionaldehyde may lead to the for- mation 3-hydroxy-2-methylpentanal, and the unsaturated dehy- dration product 2-methylpentenal.15 Cross aldol condensation between propionaldehyde...
Reaction Mechanism and Kinetics of Enargite Oxidation at Roasting Temperatures
NASA Astrophysics Data System (ADS)
Padilla, Rafael; Aracena, Alvaro; Ruiz, Maria C.
2012-10-01
Roasting of enargite (Cu3AsS4) in the temperature range of 648 K to 898 K (375 °C to 625 °C) in atmospheres containing variable amounts of oxygen has been studied by thermogravimetric methods. From the experimental results of weight loss/gain data and X-ray diffraction (XRD) analysis of partially reacted samples, the reaction mechanism of the enargite oxidation was determined, which occurred in three sequential stages:
Reaction kinetics of resveratrol with tert-butoxyl radicals
NASA Astrophysics Data System (ADS)
Džeba, Iva; Pedzinski, Tomasz; Mihaljevi?, Branka
2012-09-01
The rate constant for the reaction of t-butoxyl radicals with resveratrol was studied under pseudo-first order conditions. The rate constant was determined by measuring the phenoxyl radical formation rate at 390 nm as function of resveratrol concentration in acetonitrile. The rate constant was determined to be 6.5×108 M-1s-1. This high value indicates the high reactivity consistent with the strong antioxidant activity of resveratrol.
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.
Kinetics of Thermochemical Reactions Important in the Venus Atmospheric Sulfur Cycle
NASA Technical Reports Server (NTRS)
Fegley, Bruce, Jr.
1997-01-01
The purpose of this project was to experimentally measure the rates of several thermochemical gas-solid reactions between sulfur gases in the Venus atmosphere and reactive minerals on the hot Venus surface. Despite the great importance of these reactions for the maintenance of significant amounts of sulfur gases (and thus for the maintenance of the global cloud cover) in the atmosphere of Venus, essentially no kinetic data are currently available for them.
Kinetics of the displacement reaction between iron and Cu 2 O
Gregory J. Yurek; Robert A. Rapp; John P. Hirth
1973-01-01
The displacement reaction between iron and Cu2O at 1000?C results in the lamellar modifi-cation of the aggregate product morphology. According to a model presented for\\u000a the growth kinetics, the reaction rate depends on two parameters: the oxygen activity at the growth front of the product-oxide\\u000a lamellae and the volume fraction of oxide in the product zone. Two mathematical expressions for
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
Kinetics of the displacement reaction between iron and Cu2O
Gregory J. Yurek; Robert A. Rapp; John P. Hirth
1973-01-01
The displacement reaction between iron and Cu2O at 1000°C results in the lamellar modifi-cation of the aggregate product morphology. According to a model presented for the growth kinetics, the reaction rate depends on two parameters: the oxygen activity at the growth front of the product-oxide lamellae and the volume fraction of oxide in the product zone. Two mathematical expressions for
Reaction kinetics of toluene diisocynate and propanol by in situ FTIR
Z. H. Gao; J. Y. Gu; X. D. Bai
2007-01-01
Purpose – To evaluate the effect of the concentrations of isocyanate group and hydroxyl group and hydroxyl group species on the rate constants of isocyanate-propanol reaction, and to reveal the kinetics of isocyanate-hydroxyl reaction. Design\\/methodology\\/approach – The in situ FTIR technique was employed to measure the group concentration evolutions, by which the rate constants were determined. Besides, the FTIR was
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
Yancey, Benjamin; Vyazovkin, Sergey
2015-04-21
This study highlights the effect of the aggregate state of a reactant on the reaction kinetics under the conditions of nanoconfinement. Our previous work (Phys. Chem. Chem. Phys., 2014, 16, 11409) has demonstrated considerable deceleration of the solid state trimerization of sodium dicyanamide in organically modified silica nanopores. In the present study we use FTIR, NMR, pXRD, TGA and DSC to analyze the kinetics and mechanism of the liquid state trimerization of potassium and rubidium dicyanamide under similar conditions of nanoconfinement. It is found that nanoconfinement accelerates dramatically the kinetics of the liquid state trimerization, whereas it does not appear to affect the reaction mechanism. Kinetic analysis indicates that the acceleration is associated with an increase in the preexponential factor. Although nanoconfinement has the opposite effects on the respective kinetics of solid and liquid state trimerization, both effects are linked to a change in the preexponential factor. The results obtained are consistent with our hypothesis that the effects differ because nanoconfinement may promote disordering of the solid and ordering of the liquid reaction media. PMID:25796991
Kinetics of Single-Enzyme Reactions on Vesicles: Role of Substrate Aggregation
NASA Astrophysics Data System (ADS)
Zhdanov, Vladimir P.
2015-03-01
Enzymatic reactions occurring in vivo on lipid membranes can be influenced by various factors including macromolecular crowding in general and substrate aggregation in particular. In academic studies, the role of these factors can experimentally be clarified by tracking single-enzyme kinetics occurring on individual lipid vesicles. To extend the conceptual basis for such experiments, we analyze herein the corresponding kinetics mathematically with emphasis on the role of substrate aggregation. In general, the aggregation may occur on different length scales. Small aggregates may e.g. contain a few proteins or peptides while large aggregates may be mesoscopic as in the case of lipid domains which can be formed in the membranes composed of different lipids. We present a kinetic model describing comprehensively the effect of aggregation of the former type on the dependence of the reaction rate on substrate membrane concentration. The results obtained with physically reasonable parameters indicate that the aggregation-related deviations from the conventional Michaelis-Menten kinetics may be appreciable. Special Issue Comments: This theoretical article is focused on single-enzyme reactions occurring in parallel with substrate aggregation on individual vesicles. This subject is related to a few Special Issue articles concerning enzyme dynamics6,7 and function8 and mathematical aspects of stochastic kinetics.9
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.
Kinetics of the BrO + BrO reaction
Turnipseed, A.A.; Birks, J.W. ); Calvert, J.G. )
1990-09-20
Discharge flow/mass spectrometry has been used to measure the rate coefficient for the disproportionation reaction of BrO radicals, BrO + BrO {yields} products, at 2-Torr total pressure and over the temperature range 253-400 K. This is the first direct study of the temperature dependence of the BrO/BrO system that does not rely on the measurement of the absorption cross section of BrO and is in good agreement with previous studies using flash photolysis.
Kinetics of collision-induced reactions between hard-sphere reactants
NASA Astrophysics Data System (ADS)
Kim, Ji-Hyun; Lee, Sangyun; Lee, Jinuk; Lee, Sangyoub
2009-10-01
We investigate the reaction kinetics of hard-sphere reactants that undergo reaction upon collision. When the reaction probability at a given collision is unity, the Noyes rate theory provides an exact expression of the rate coefficient. For the general case with the reaction probability less than unity, Noyes assumed that successive recollision times between a tagged pair of reactants are decorrelated. We show that with this renewal assumption, the rate theory of Wilemski and Fixman yields the same rate coefficient expression as the Noyes theory. To evaluate the validity of the renewal assumption, we carry out molecular dynamics simulations. Contrary to the usual expectation, we find that the renewal assumption works better at higher particle densities. The present study shows that the rate coefficient for collision-induced hard-sphere reactions can be estimated with great accuracy by using the first recollision time distribution alone, regardless of the magnitude of the reaction probability at a given collision.
SurfKin: an ab initio kinetic code for modeling surface reactions.
Le, Thong Nguyen-Minh; Liu, Bin; Huynh, Lam K
2014-10-01
In this article, we describe a C/C++ program called SurfKin (Surface Kinetics) to construct microkinetic mechanisms for modeling gas-surface reactions. Thermodynamic properties of reaction species are estimated based on density functional theory calculations and statistical mechanics. Rate constants for elementary steps (including adsorption, desorption, and chemical reactions on surfaces) are calculated using the classical collision theory and transition state theory. Methane decomposition and water-gas shift reaction on Ni(111) surface were chosen as test cases to validate the code implementations. The good agreement with literature data suggests this is a powerful tool to facilitate the analysis of complex reactions on surfaces, and thus it helps to effectively construct detailed microkinetic mechanisms for such surface reactions. SurfKin also opens a possibility for designing nanoscale model catalysts. PMID:25111729
Control of Mass Transport and Chemical Reaction Kinetics in Ultrasmall Volumes
NASA Astrophysics Data System (ADS)
Collier, Charles
2012-02-01
This talk will describe means for triggering chemical reactions for studying reaction kinetics under extreme confinement with sub-millisecond temporal resolution, including on-demand generation and fusion of femtoliter (10-15 L) volume water-in-oil droplets, and triggering reactions in femtoliter chambers microfabricated in poly(dimethylsiloxane) (PDMS). We demonstrated a reversible chemical toggle switch, which lays the groundwork for exploring more complex chemical and biochemical reaction sequences triggered and monitored in real time in discrete ultrasmall reactors, such as sequential and coupled enzymatic reactions. We are also developing methods to vary confinement and macromolecular crowding in ultrasmall, water-in-oil droplets and chambers micromolded in PDMS as biomimetic reaction vessels containing minimal synthetic gene circuits, in order to better understand how confinement, reduced dimensionality and macromolecular crowding affect molecular mechanisms involved in the operation and regulation of genetic circuits in living cells.
M. A. H. Hegazy; J. F. Fowler
1973-01-01
The kinetics of cellular proliferation in plucked and unplucked dorsal ; skin of mice after local x-irradiation are described, in relation to the time ; course of the gross desquamation reaction in skin of the dorsum and or the foot. ; Radiation was with 250 kV x rays at a dose rate of 325 rads\\/min to soft tissue ; over
An Inexpensive Kinetic Study: The Reaction of FD&C Red #3 (Erythrosin B) with Hypochlorite
ERIC Educational Resources Information Center
Henary, Maher M.; Russell, Arlene A.
2007-01-01
Kinetics constitutes a core topic in both the lecture and laboratory components of lower- level chemistry courses. While textbook examples can ignore issues of time, temperature and safety, the laboratory can not. Reactions must occur slowly enough to be detected by students, occur rapidly enough for data collection in the few hours assigned to a…
Marcus Theory: Thermodynamics CAN Control the Kinetics of Electron Transfer Reactions
ERIC Educational Resources Information Center
Silverstein, Todd P.
2012-01-01
Although it is generally true that thermodynamics do not influence kinetics, this is NOT the case for electron transfer reactions in solution. Marcus Theory explains why this is so, using straightforward physical chemical principles such as transition state theory, Arrhenius' Law, and the Franck-Condon Principle. Here the background and…
Kinetics of the reaction of diethylene glycol bis-chloroformate with allyl alcohol
Alekseev, N.N.; Shtoda, N.F.; Dzumedzei, N.V.
1988-10-01
The kinetics of diethylene glycol bis-chloroformate solvolysis by excess allyl alcohol in toluene and carbon tetrachloride has been studied. Under conditions of a pseudofirst order reaction with respect to diethylene glycol bis-chloroformate the activation parameters confirm an addition-detachment mechanism.
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.
Employing Magnetic Levitation to Monitor Reaction Kinetics and Measure Activation Energy
ERIC Educational Resources Information Center
Benz, Lauren; Cesafsky, Karen E.; Le, Tran; Park, Aileen; Malicky, David
2012-01-01
This article describes a simple and inexpensive undergraduate-level kinetics experiment that uses magnetic levitation to monitor the progress and determine the activation energy of a condensation reaction on a polymeric solid support. The method employs a cuvette filled with a paramagnetic solution positioned between two strong magnets. The…
Kinetics of intrachain reactions of supercoiled DNA: Theory and numerical modeling
Langowski, JÃ¶rg
Kinetics of intrachain reactions of supercoiled DNA: Theory and numerical modeling Konstantin V to the productive collisions is the quasione-dimensional reptation of the strands forming the superhelix. The mean of DNA strands was simulated by the repton model, in which a superhelix branch is approximated
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…
Fundamental Kinetic Modeling: ab initio rate constant calculations of elementary reactions
Jenks, Richard Lee
1998-01-01
Fundamental Kinetic Model' provides an alternative method for collecting rate constant data of elementary reactions when experimental observation is unavailable. A standard procedure of PMP4/6-3 IG*//UHF/6-3 IG* ab initio calculations of reactants...
Reaction kinetics of iodine and cesium in steam\\/hydrogen mixtures
A. W. Cronenberg; D. J. Osetek
1988-01-01
The chemical reaction kinetics of fission product iodine and cesium released from fuel to a steam\\/hydrogen atmosphere are investigated at conditions associated with severe core damage accidents. The results are used to assess the time to establish equilibrium and the ultimate chemical form of iodine and cesium as a function of gas mixture concentration and temperature conditions. Illustrative calculations are
Andujar-De Sanctis, Ivonne L; Singleton, Daniel A
2012-10-19
Intramolecular (13)C 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
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.
Macroscopic Kinetic Effect of Cell-to-Cell Variation in Biochemical Reactions
Kim, Pan-Jun
2009-01-01
Genetically identical cells under the same environmental conditions can show strong variations in protein copy numbers due to inherently stochastic events in individual cells. We here develop a theoretical framework to address how variations in enzyme abundance affect the collective kinetics of metabolic reactions observed within a population of cells. Kinetic parameters measured at the cell population level are shown to be systematically deviated from those of single cells, even within populations of homogeneous parameters. Due to these considerations, Michaelis-Menten kinetics can even be inappropriate to apply at the population level. Our findings elucidate a novel origin of discrepancy between in vivo and in vitro kinetics, and offer potential utility for analysis of single-cell metabolomic data.
A Gas-Kinetic Scheme for Multimaterial Flows and Its Application in Chemical Reaction
NASA Technical Reports Server (NTRS)
Lian, Yongsheng; Xu, Kun
1999-01-01
This paper concerns the extension of the multicomponent gas-kinetic BGK-type scheme to multidimensional chemical reactive flow calculations. In the kinetic model, each component satisfies its individual gas-kinetic BGK equation and the equilibrium states of both components are coupled in space and time due to the momentum and energy exchange in the course of particle collisions. At the same time, according to the chemical reaction rule one component can be changed into another component with the release of energy, where the reactant and product could have different gamma. Many numerical test cases are included in this paper, which show the robustness and accuracy of kinetic approach in the description of multicomponent reactive flows.
Bolster, Diogo
2011-01-01
kinetics related to segregation in the one-dimensional reaction- diffusion system A + B C. It is wellTHE JOURNAL OF CHEMICAL PHYSICS 135, 174104 (2011) Anomalous kinetics in diffusion limited the mean-field t-1 to the anomalous t-1/4 behavior. Using a stochastic modeling approach, the reaction
ERIC Educational Resources Information Center
Lundberg, Dan; Stjerndahl, Maria
2011-01-01
The effects of self-assembly on the hydrolysis kinetics of surfactants that contain ester bonds are discussed. A number of examples on how reaction rates and apparent reaction orders can be modulated by changes in the conditions, including an instance of apparent zero-order kinetics, are presented. Furthermore, it is shown that the examples on…
Reaction kinetics of dye decomposition processes monitored inside a photocatalytic microreactor.
Tsuchiya, Naomi; Kuwabara, Kenta; Hidaka, Asuna; Oda, Kazuyo; Katayama, Kenji
2012-04-14
The photocatalytic decomposition processes of several kinds of dyes were monitored in real-time, in a TiO(2)-immobilized microcapillary. Their fluorescence spectra were measured directly from the UV-irradiated area. The photocatalytic reactions proceeded two orders of magnitude faster in the microcapillary than in a bulk reaction, and intermediate species were easily observed, due to their high concentrations compared with those of the reactants. Even for molecules that were not originally fluorescent, fluorescence was detected for the reactants or intermediate species of all the molecules studied. Photocatalytic reactions are typically analyzed in terms of pseudo-first-order or Langmuir-Hinshelwood reaction mechanisms, but it was ascertained that all of the dyes investigated in this study decomposed via a multi-step reaction such as a simple multi-step reaction, a self-catalytic reaction, and further, a more complicated reaction, depending on the molecular structure. These reactions were simulated using models based on the reaction kinetics, and reaction mechanisms were assigned to each type of dye. The fact that intermediate species (which are difficult to observe using conventional analytical methods) were successfully detected meant that mechanisms for different dyes could be further clarified. PMID:22307739
On kinetic phase transition of the dimer-monomer reaction model
NASA Astrophysics Data System (ADS)
Hou, Zhonghuai; Yang, Lingfa; Xin, Houwen
1997-12-01
A detailed mean field theory (MFT) based on pair approximation (PA) is constructed to illustrate the kinetic phase transition behavior of the dimer-monomer surface reaction model A+1/2B 2?AB and its variants which take into account diffusion and desorption of both adsorbed species, Eley-Rideal reaction step, finite reaction probability and "endon mechanism" for B 2 adsorption. We find that the PA-MFT can reproduce well the phase diagrams and yield quite good predictions of the effects of diffusion, desorption etc., which indicates that PA-MFT may be suitable for the description of the steady state behavior of this model.
NASA Astrophysics Data System (ADS)
Wang, Quan-De; Wang, Xing-Jian; Liu, Zi-Wu; Kang, Guo-Jun
2014-11-01
Ab initio and chemical kinetic study of the hydrogen abstraction reactions by the hydrogen radical on ethyl formate, ethyl acetate, ethyl propanoate, and ethyl butanoate have been performed at the CCSD(T)/CBS//B3LYP/6-311G(d, p) level of theory. High-pressure limit rate constants at temperatures from 300 to 2500 K have been calculated for all of the reaction channels using transition state theory with Eckart tunneling corrections, and the data are fitted to the modified three parameters Arrhenius expression using least-squares regression. A branching ratio analysis for each reaction site has also been investigated for all of the ethyl esters.
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
Second-order polarization mode dispersion: impact on analog and digital transmissions
Philippe Ciprut; B. Gisin; Nicolas Gisin; Rogerio Passy; P. Von Der Weld; F. Prieto; C. W. Zimmer
1998-01-01
Second-order polarization mode dispersion (PMD) is a major limitation to the transmission capabilities of analog systems and of high bit rate digital systems. Basically, the effect of second-order PMD is the same as that of chromatic dispersion. However, like all polarization effects in standard single-mode fibers, the effects of second-order PMD are stochastic, due to the random polarization mode coupling
Kinetics of CH3S(-) reaction with in situ ferrate(VI) in aqueous alkaline solution.
Ding, Ling; Li, Xiang-Zhong; Lee, Shun-Cheng
2013-08-01
This study introduced a new treatment process named "in situ ferrate(VI) oxidation (IFO)" in which odorous compounds such as CH3S(-) can be quickly degraded by in situ freshly generated ferrate(VI) through electrolysis in aqueous alkaline solution. Two kinetic models to describe the in situ ferrate(VI) generation and its reaction with CH3S(-) were established mathematically by considering three main reaction mechanisms of ferrate(VI) electrochemical generation, ferrate(VI) self-decomposition and CH3S(-) degradation in aqueous strong alkaline solution. The effects of three key factors: (i) NaOH concentration, (ii) applied current density, and (iii) initial CH3S(-) concentration on the performance of the IFO process were investigated by conducting three sets of experiments and the kinetic models were validated by fitting the experimental data. The goodness of the fittings demonstrated that the new models could well describe both the kinetics of ferrate(VI) generation reaction and CH3S(-) degradation reaction. The experimental results confirmed that the higher NaOH concentration and current density applied would be beneficial to the electrochemical generation of ferrate(VI) and also elimination of its self-decomposition, but the experiments also demonstrated an optimum NaOH concentration at 10M to achieve the best performance of CH3S(-) degradation reaction in such an IFO system. PMID:23725753
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).
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.
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
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.
Mukai, Kazuo; Ouchi, Aya; Nakano, Masahiko
2011-03-01
A kinetic study of the quenching reaction of singlet oxygen ((1)O(2)) with pyrroloquinolinequinol (PQQH(2), a reduced form of pyrroloquinolinequinone (PQQ)), PQQNa(2) (disodium salt of PQQ), and seven kinds of natural antioxidants (vitamin C (Vit C), uric acid (UA), epicatechin (EC), epigallocatechin (EGC), ?-tocopherol (?-Toc), ubiquinol-10 (UQ(10)H(2)), and ?-carotene (?-Car)) has been performed. The second-order rate constants k(Q) (k(Q) = k(q) + k(r), physical quenching and chemical reaction) for the reaction of (1)O(2) with PQQH(2), PQQNa(2), and seven kinds of antioxidants were measured in 5.0 wt % Triton X-100 micellar solution (pH 7.4), using UV-visible spectrophotometry. The k(Q) values decreased in the order of ?-Car > PQQH(2) > ?-Toc > UA > UQ(10)H(2) > Vit C ? EGC > EC ? PQQNa(2). PQQH(2) is a water-soluble antioxidant. The singlet oxygen-quenching activity of PQQH(2) was found to be 6.3, 2.2, 6.1, and 22 times as large as the corresponding those of water-soluble antioxidants (Vit C, UA, EGC, and EC). Further, the activity of PQQH(2) was found to be 2.2 and 3.1 times as large as the corresponding activity of lipid-soluble antioxidants (?-Toc and UQ(10)H(2)). On the other hand, the activity of PQQH(2) is 6.4 times as small as that of ?-Car. It was observed that the chemical reaction (k(r)) is almost negligible in the quenching reaction of (1)O(2) by PQQH(2). The result suggests that PQQH(2) may contribute to the protection of oxidative damage in biological systems, by quenching (1)O(2). PMID:21309575
Fit of second order thermoluminescence glow peaks using the logistic distribution function.
Pagonis, V; Kitis, G
2001-01-01
A new thermoluminescence glow curve deconvolution (GCD) function is introduced which accurately describes second order thermoluminescence (TL) curves. The logistic asymmetric (LA) statistical probability function is used with the function variables being the maximum peak intensity (Im), the temperature of the maximum peak intensity (Tm) and the LA width parameter a2. An analytical expression is derived from which the activation energy E can be calculated as a function of Tm and the LA width parameter a2 with an accuracy of 2% or better. The accuracy of the fit was tested for E values ranging from 0.7 to 2.5 eV, for s values between 10(5) and 10(25) s(-1), and for trap occupation numbers no/N between 1 and 10(-6). The goodness of fit of the logistic asymmetric function is described by the Figure of Merit (FOM) which is found to be of the order of 10(-2). Preliminary results show that the GCD described here can easily be extended to the description of general order TL glow curves by varying the asymmetry parameter of the logistic asymmetric function. It is concluded that the TL kinetic analysis of first, second and general order TL glow curves can be performed with high accuracy and speed by using commercially available statistical packages that incorporate the Weibull and logistic asymmetric functions. PMID:11605796
Kinetic parameters of radical reactions of 2-mercaptobenzothiazole with quinone imines
NASA Astrophysics Data System (ADS)
Varlamov, V. T.; Gadomska, A. V.
2014-09-01
The chain reaction of N, N'-diphenyl-1,4-benzoquinone diimine with 2-mercaptobenzothiazole was studied by two methods developed earlier for the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole. In the methods used, the kinetic scheme of the reaction is simplified by creating conditions under which the rates of all stages except radical generation and decay can be neglected. One of the methods was updated. For the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole, both methods gave close results; for the chain reaction of N, N'-diphenyl-1,4-phenylenediamine with 2-mercaptobenzothiazole, the results differed by approximately one order of magnitude.
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.
Determination of reaction kinetics of rice husks in air using thermogravimetric analysis
Mansaray, K.G.; Ghaly, A.E.
1999-12-01
Rice husk is produced in large quantities as a by-product of rice milling in rice-producing countries and has posed disposal problems in these countries. Disposal of or energy recovery from rice husk can be accomplished by thermochemical conversion processes (pyrolysis, combustion, and gasification). However, it appears that the kinetics of rice husk, which can contribute to the accurate modeling and design of thermochemical conversion processes, have not been studied extensively. In this paper the technique of thermogravimetric analysis (TGA) was used to study the thermochemical behavior of four varieties of rice husk (Lemont LG, ROK 14, CP 4, and Pa Potho). The thermal degradation of rice husk was studied in an air atmosphere (21% oxygen and 79% nitrogen) from ambient temperature to 700 C at the heating rate of 20 C/min. The thermograms showed two distinct reaction zones. The kinetic parameters (activation energy, preexponential factor, and order of reaction) were determined for the two reaction zones by applying thermoanalytical techniques to the reaction kinetics. Higher thermal degradation rates were observed in the first reaction zone due to rapid release of volatiles as compared to those in the second reaction zone. In the first reaction zone the activation energies ranged from 37.0 to 54.7 kJ/mol. Relatively lower activation energies (18.0--21.0 kJ/mol) were obtained in the second reaction zone. The preexponential factors were in the range of 4.3 x 10{sup 4} to 6.4 x 10{sup 6} min{sup {minus}1} in the first reaction zone and 4.5 x 10{sup 2} to 1.5 x 10{sup 3} min{sup {minus}1} in the second reaction zone. The orders of reaction were in the range of 1.2--1.6 and 0.4--0.5 for the first and second reaction zones, respectively. The predicted thermal degradations were in good agreement with the experimental data in both the first and second reaction zones.
Dynamics of a lamellar system with diffusion and reaction: Scaling analysis and global kinetics
NASA Astrophysics Data System (ADS)
Muzzio, F. J.; Ottino, J. M.
1989-12-01
The evolution of a one-dimensional array of reactive lamellae with distributed striation thickness is studied by means of simulations, scaling analysis, and space-averaged kinetics. An infinitely fast, diffusion-controlled reaction A+B-->2P occurs at the interfaces between striations. As time increases, thin striations are eaten by thicker neighbors resulting in a modification of the striation thickness distribution (STD). Scaling analysis suggests that the STD evolves into a universal form and that the behavior of the system at short and long times is characterized by two different kinetic regimes. These predictions are confirmed by means of a novel numerical algorithm.
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
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
Genome-scale Metabolic Reaction Modeling: a New Approach to Geomicrobial Kinetics
NASA Astrophysics Data System (ADS)
McKernan, S. E.; Shapiro, B.; Jin, Q.
2014-12-01
Geomicrobial rates, rates of microbial metabolism in natural environments, are a key parameter of theoretical and practical problems in geobiology and biogeochemistry. Both laboratory- and field-based approaches have been applied to study rates of geomicrobial processes. Laboratory-based approaches analyze geomicrobial kinetics by incubating environmental samples under controlled laboratory conditions. Field methods quantify geomicrobial rates by observing the progress of geomicrobial processes. To take advantage of recent development in biogeochemical modeling and genome-scale metabolic modeling, we suggest that geomicrobial rates can also be predicted by simulating metabolic reaction networks of microbes. To predict geomicrobial rates, we developed a genome-scale metabolic model that describes enzyme reaction networks of microbial metabolism, and simulated the network model by accounting for the kinetics and thermodynamics of enzyme reactions. The model is simulated numerically to solve cellular enzyme abundance and hence metabolic rates under the constraints of cellular physiology. The new modeling approach differs from flux balance analysis of system biology in that it accounts for the thermodynamics and kinetics of enzymatic reactions. It builds on subcellular metabolic reaction networks, and hence also differs from classical biogeochemical reaction modeling. We applied the new approach to Methanosarcina acetivorans, an anaerobic, marine methanogen capable of disproportionating acetate to carbon dioxide and methane. The input of the new model includes (1) enzyme reaction network of acetoclastic methanogenesis, and (2) representative geochemical conditions of freshwater sedimentary environments. The output of the simulation includes the proteomics, metabolomics, and energy and matter fluxes of M. acetivorans. Our simulation results demonstrate the predictive power of the new modeling approach. Specifically, the results illustrate how methanogenesis rates vary with acetate concentrations and the energy available in the environment, and how M. acetivorans regulate the enzymes of methanogenesis under different biogeochemical conditions.
Sensitivity of Polar Stratospheric Ozone Loss to Uncertainties in Chemical Reaction Kinetics
NASA Technical Reports Server (NTRS)
Kawa, S. Randolph; Stolarksi, Richard S.; Douglass, Anne R.; Newman, Paul A.
2008-01-01
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. A typical stratospheric chemistry mechanism has on the order of 50- 100 species undergoing over a hundred intermolecular reactions and several tens of photolysis reactions. 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 a simple box-model scenario for Antarctic 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 to observations to evaluate which combinations are consistent with atmospheric data. Implications for our theoretical and practical understanding of polar ozone loss will be assessed.
Chemical kinetic analysis of hydrogen-air ignition and reaction times
NASA Technical Reports Server (NTRS)
Rogers, R. C.; Schexnayder, C. J., Jr.
1981-01-01
An anaytical study of hydrogen air kinetics was performed. Calculations were made over a range of pressure from 0.2 to 4.0 atm, temperatures from 850 to 2000 K, and mixture equivalence ratios from 0.2 to 2.0. The finite rate chemistry model included 60 reactions in 20 species of the H2-O2-N2 system. The calculations also included an assessment of how small amounts of the chemicals H2O, NOx, H2O2, and O3 in the initial mixture affect ignition and reaction times, and how the variation of the third body efficiency of H2O relative of N2 in certain key reactions may affect reaction time. The results indicate that for mixture equivalence ratios between 0.5 and 1.7, ignition times are nearly constant; however, the presence of H2O and NO can have significant effects on ignition times, depending on the mixture temperature. Reaction time is dominantly influenced by pressure but is nearly independent of initial temperature, equivalence ratio, and the addition of chemicals. Effects of kinetics on reaction at supersonic combustor conditions are discussed.
A kinetic analysis of coal char gasification reactions at high pressures
D.G. Roberts; D.J. Harris [CSIRO Division of Energy Technology, Kenmore, Qld. (Australia). Cooperative Research Centre for Coal in Sustainable Development
2006-12-15
A Langmuir-Hinshelwood (LH) rate equation is often used for the incorporation of gasification reaction kinetics data into gasification models, as it is applicable over a wider range of conditions than the nth-order rate equation. The use of a LH rate equation at high reactant partial pressures has been questioned, however, with some authors recommending extra terms based on additional reaction steps. Unfortunately, the lack of agreement on the details of these additional steps makes the incorporation of high-pressure gasification reactivity data into gasification models potentially a difficult task. This paper presents further analysis of previously published reactivity data for the reaction of reference chars with 0.1-3.0 MPa of CO{sub 2} and, separately, H{sub 2}O. This analysis is done using LH-style rate equations well-established for use with up to 0.1 MPa of the reactant. It is shown that, in the absence of product gases, these established LH rate formulations can describe the measured high-pressure char-gas reaction kinetics. Furthermore, theoretical predictions of surface coverage phenomena made using these equations agree with experimental measurements of the relative amount of reaction intermediates present on the char surface as the reactant pressure increases. The effects of char surface area, and how reaction at high-pressure develops this surface, are highlighted as an area of investigation requiring more work. 30 refs., 6 figs., 2 tabs.
Dai, B; Butler, R J; Garrett, W E; Queen, R M
2014-12-01
Asymmetries in sagittal plane knee kinetics have been identified as a risk factor for anterior cruciate ligament (ACL) re-injury. Clinical tools are needed to identify the asymmetries. This study examined the relationships between knee kinetic asymmetries and ground reaction force (GRF) asymmetries during athletic tasks in adolescent patients following ACL reconstruction (ACL-R). Kinematic and GRF data were collected during a stop-jump task and a side-cutting task for 23 patients. Asymmetry indices between the surgical and non-surgical limbs were calculated for GRF and knee kinetic variables. For the stop-jump task, knee kinetics asymmetry indices were correlated with all GRF asymmetry indices (P?kinetic asymmetry indices were correlated with the peak propulsion vertical GRF and vertical GRF impulse asymmetry indices (P?kinetic asymmetries and therefore may assist in optimizing rehabilitation outcomes and minimizing re-injury rates. PMID:24118495
Espinosa-García, J; Nyman, G; Corchado, J C
2009-05-14
On a new potential energy surface (PES-2008) developed by our group (preceding paper), we performed an extensive kinetics study using variational transition-state theory with semiclassical transmission coefficients over a wide temperature range of 250-2000 K and a dynamics study using quasiclassical trajectory (QCT) and quantum-mechanical (QM) calculations at collision energies between 0.7 and 2.0 eV for the title reaction and isotopically substituted versions. Kinetically, the H + CH(4) forward and reverse thermal rate constants reproduce the available experimental data, with a small curvature of the Arrhenius plot indicating the role of tunneling in this hydrogen abstraction reaction. Five sets of kinetic isotope effects are also calculated. In general, they reproduce the experimental information. Dynamically, we focused on the H + CD(4) reaction because there are more experimental studies for comparison. Most of the available energy appears as product translational energy (55%-68%), with the HD product being vibrationally cold (v(')=0,1) in agreement with experiment, although rotationally hotter than experiment. The reaction cross section is practically negligible at 0.7 eV and still small at 1.5 eV, reproducing the experimental evidence, although our values are smaller. The product angular distribution is analyzed using QCT and QM methods. While at low energies (0.7 eV) both the QCT and the QM calculations yield forward scattered CD(3) product, i.e., a rebound mechanism, at high energy (1.2 eV) only the QM calculations reproduce the experiment. The agreement with this wide variety of kinetic and dynamic experimental data (always qualitative and in some cases quantitative) shows the capacity of the PES-2008 surface to describe the reaction system. PMID:19449929
Moxley, Michael A; Becker, Donald F
2012-01-10
The multifunctional proline utilization A (PutA) flavoenzyme from Escherichia coli catalyzes the oxidation of proline to glutamate in two reaction steps using separate proline dehydrogenase (PRODH) and ?(1)-pyrroline-5-carboxylate (P5C) dehydrogenase domains. Here, the kinetic mechanism of PRODH in PutA is studied by stopped-flow kinetics to determine microscopic rate constants for the proline:ubiquinone oxidoreductase mechanism. Stopped-flow data for proline reduction of the flavin cofactor (reductive half-reaction) and oxidation of reduced flavin by CoQ(1) (oxidative half-reaction) were best-fit by a double exponential from which maximum observable rate constants and apparent equilibrium dissociation constants were determined. Flavin semiquinone was not observed in the reductive or oxidative reactions. Microscopic rate constants for steps in the reductive and oxidative half-reactions were obtained by globally fitting the stopped-flow data to a simulated mechanism that includes a chemical step followed by an isomerization event. A microscopic rate constant of 27.5 s(-1) was determined for proline reduction of the flavin cofactor followed by an isomerization step of 2.2 s(-1). The isomerization step is proposed to report on a previously identified flavin-dependent conformational change [Zhang, W. et al. (2007) Biochemistry 46, 483-491] that is important for PutA functional switching but is not kinetically relevant to the in vitro mechanism. Using CoQ(1), a soluble analogue of ubiquinone, a rate constant of 5.4 s(-1) was obtained for the oxidation of flavin, thus indicating that this oxidative step is rate-limiting for k(cat) during catalytic turnover. Steady-state kinetic constants calculated from the microscopic rate constants agree with the experimental k(cat) and k(cat)/K(m) parameters. PMID:22148640
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 was modulated about an aver- age value of 4.7 cycles per degree (cpd) according to a sinusoidal function
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
International Association for Cryptologic Research (IACR)
Gold functions Ruchi Gode and Sugata Gangopadhyay Department of Mathematics Indian Institute are concatenations of quadratic Gold functions. A lower bound of second-order nonlinearities of these functions Gold functions. A lower bound of second-order nonlinearities of these functions is obtained. This bound
TEMPORAL SECOND-ORDER ACCURACY OF SIMPLE-TYPE METHODS FOR INCOMPRESSIBLE
Abdou, Mohamed
TEMPORAL SECOND-ORDER ACCURACY OF SIMPLE-TYPE METHODS FOR INCOMPRESSIBLE UNSTEADY FLOWS Ming-Jiu Ni are employed to obtain second-order-temporal-accuracy SIMPLE methods. An example is simulated using SIMPLE-type and Mohamed A. Abdou UCLA MAE Department, Engineering IV, Los Angeles, California, USA SIMPLE-type methods
On group classification of normal systems of linear second-order ordinary differential equations
NASA Astrophysics Data System (ADS)
Meleshko, S. V.; Moyo, S.
2015-05-01
In this paper we study the general group classification of systems of linear second-order ordinary differential equations inspired from earlier works and recent results on the group classification of such systems. Some interesting results and subsequent theorem arising from this particular study are discussed here. This paper considers the study of irreducible systems of second-order ordinary differential equations.
Sensitivity to spatial and temporal modulations of first-order and second-order motion
Nottingham, University of
Sensitivity to spatial and temporal modulations of first-order and second-order motion Claire V) and three varieties of second-order motion (contrast-modulated, polarity-modulated and spatial length-modulated of shape and sensitivity. However, sensitivity to modulations of spatial length was extremely poor and more
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…
Bremer, James
differential equations, fast algorithms, phase functions, special functions, Bessel's equation 1. Introduction Second order linear differential equations of the form y2 ptq ` 2 qptqyptq " 0 for all a t b (1On the numerical solution of second order ordinary differential equations in the high
Classical mapping for second-order quantized Hamiltonian dynamics Oleg V. Prezhdoa)
ARTICLES Classical mapping for second-order quantized Hamiltonian dynamics Oleg V. Prezhdoa; accepted 23 May 2002 Second-order quantized Hamiltonian dynamics QHD-2 is mapped onto classical mechanics by doubling the dimensionality. The mapping establishes the classical canonical structure for QHD-2
Goal Directed Adaptive Behavior in Second-Order Neural Networks: The MAXSON family of architectures
Crabbe, Frederick
Goal Directed Adaptive Behavior in Second-Order Neural Networks: The MAXSON family of architectures architecture (MAXSON) based on second-order connections that can learn a multiple goal approach/avoid task tasks much faster than traditional Q-learning, as well as learn goal directed behavior, increasing
Positive solutions to semi-positone second-order three-point problems on time scales
Anderson, Douglas R.
Positive solutions to semi-positone second-order three-point problems on time scales Douglas R and compression we establish the existence of at least two positive solutions for the nonlinear semi-positone will be concerned with proving the existence of positive solutions to the semi-positone second-order three-point non
Spontaneously generated coherence induced second-order susceptibility in atomic gases
Yueping Niu; Shangqing Gong
2006-03-12
The second-order susceptibility which vanishes in the electric-dipole approximation for an atom is induced by the spontaneously generated coherence. The spontaneously generated coherence considered in a lambda-type atomic system causes an indirect coupling between the lower two levels which acts equivalently as a DC-field and therefore makes possible the existence of second-order susceptibility.
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{arrival travel times on a rectan- gular grid of points is proposed. The new proposed method is of second{order accuracy. This means that the error of the calculated travel time is proportional to the second power
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
Nonlinear Multigrid Methods for Second Order Differential Operators with Nonlinear Diffusion
Jimack, Peter
for a general second order nonlinear operator. The comparison is based upon a detailed analysis of their costsNonlinear Multigrid Methods for Second Order Differential Operators with Nonlinear Diffusion, Nottingham, NG7 2RD Abstract Nonlinear multigrid methods such as the Full Approximation Scheme (FAS
Fang, Guo-Dong; Dionysiou, Dionysios D; Wang, Yu; Al-Abed, Souhail R; Zhou, Dong-Mei
2012-08-15
Advanced oxidation processes (AOPs) based on sulfate radical (SO(4)(·-)) have been recently used for soil and groundwater remediation. The presence of chloride ion in natural or wastewater decreases the reactivity of sulfate radical system, but explanations for this behavior were inconsistent, and the mechanisms are poorly understood. Therefore, in this paper we investigated the effect of chloride ion on the degradation of 2,4,4'-CB (PCB28) and biphenyl (BP) by persulfate, based on the produced SO(4)(·-). The results showed that the presence of chloride ion greatly inhibited the transformation of PCB28 and BP. Transformation intermediates of BP were monitored, suggesting that the chloride ion can react with SO(4)(·-) to produce chlorine radical, which reacts with BP to generate chlorinated compounds. To better understand the underlying mechanisms of these processes, a kinetic model was developed for predicting the effect of chloride ion on the types of radical species and their distributions. The results showed that chloride ion could influence the selectivity of radical species and their distribution, and increase the concentration of the sum of radical species. In addition, the second-order rate constants of sulfate radical with PCBs were determined, and quantum-chemical descriptors were introduced to predict the rate constants of other PCBs based on our experimental data. PMID:22683213
The kinetics and mechanisms of aromatic nucleophilic substitution reactions in liquid ammonia.
Ji, Pengju; Atherton, John H; Page, Michael I
2011-05-01
The rates of aromatic nucleophilic substitution reactions in liquid ammonia are much faster than those in protic solvents indicating that liquid ammonia behaves like a typical dipolar aprotic solvent in its solvent effects on organic reactions. Nitrofluorobenzenes (NFBs) readily undergo solvolysis in liquid ammonia and 2-nitrofluorobenzene is about 30 times more reactive than the 4-substituted isomer. Oxygen nucleophiles, such as alkoxide and phenoxide ions, readily displace fluorine of 4-NFB in liquid ammonia to give the corresponding substitution product with little or no competing solvolysis product. Using the pK(a) of the substituted phenols in liquid ammonia, the Brønsted ?(nuc) for the reaction of 4-NFB with para-substituted phenoxides is 0.91, indicative of the removal of most of the negative charge on the oxygen anion and complete bond formation in the transition state and therefore suggests that the decomposition of the Meisenheimer ?-intermediate is rate limiting. The aminolysis of 4-NFB occurs without general base catalysis by the amine and the second-order rate constants generate a Brønsted ?(nuc) of 0.36 using either the pK(a) of aminium ion in acetonitrile or in water, which is also interpreted in terms of rate limiting breakdown of the Meisenheimer ?-intermediate. Nitrobenzene and diazene are formed as unusual products from the reaction between sodium azide and 4-NFB, which may be due to the initially formed 4-nitroazidobenzene decomposing to give a nitrene intermediate, which may then give diazene or be trapped by ammonia to give the unstable hydrazine which then yields nitrobenzene. PMID:21417418
Second-order diffraction forces on an array of vertical cylinders in bichromatic bidirectional waves
Vazquez, J.H.; Williams, A.N.
1995-02-01
A complete second-order solution is presented for the hydrodynamic forces due to the action of bichromatic, bidirectional waves on an array of bottom-mounted, surface-piercing cylinders of arbitrary cross section in water of uniform finite depth. Based on the constant structural cross section, the first-order problem is solved utilizing a two-dimensional Green function approach, while an assisting radiation potential approach is used to obtain the hydrodynamic loads due to the second-order potential. Results are presented which illustrate the influence of wave directionality on the second-order sum and difference frequency hydrodynamic forces on a two-cylinder array. It is found that wave directionality may have a significant influence on the second-order hydrodynamic forces on these arrays and that the assumption of unidirectional waves does not always lead to conservative estimates of the second-order loading.
Optimality Conditions in Differentiable Vector Optimization via Second-Order Tangent Sets
Jimenez, Bienvenido [Departamento de Economia e Historia Economica, Facultad de Economia y Empresa, Universidad deSalamanca, Campus Miguel de Unamuno, s/n, 37007 Salamanca (Spain)], E-mail: bjimen1@encina.pntic.mec.es; Novo, Vicente [Departamento de Matematica Aplicada, E.T.S.I. Industriales, UNED, c/ Juan del Rosal 12, Apartado 60149, 28080 Madrid (Spain)], E-mail: vnovo@ind.uned.es
2004-03-15
We provide second-order necessary and sufficient conditions for a point to be an efficient element of a set with respect to a cone in a normed space, so that there is only a small gap between necessary and sufficient conditions. To this aim, we use the common second-order tangent set and the asymptotic second-order cone utilized by Penot. As an application we establish second-order necessary conditions for a point to be a solution of a vector optimization problem with an arbitrary feasible set and a twice Frechet differentiable objective function between two normed spaces. We also establish second-order sufficient conditions when the initial space is finite-dimensional so that there is no gap with necessary conditions. Lagrange multiplier rules are also given.
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.
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.
Weese, R K; Burnham, A K; Fontes, A T
2005-03-23
The properties of pentaamine (5-cyano-2H-tetrazolato-N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook-off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear heating rates, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 10,000 psi and analyzed over a dynamic temperature range of -20 C to 70 C. Using differential scanning calorimetry, DSC, CP was decomposed at linear heating rates of 1, 3, and 7 C/min and the kinetic triplet calculated using the LLNL code Kinetics05. Values are also reported for spark, friction, and impact sensitivity.
Kinetics of trans-cis isomerization in azobenzene dimers at an air-water interface
Kumar, Bharat [Raman Research Institute, Sadashivanagar, Bangalore 560 080 (India); Suresh, K. A. [Centre for Liquid Crystal Research, P.B. No. 1329, Jalahalli, Bangalore 560 013 (India)
2009-08-15
We have studied the kinetics of trans to cis isomerization under the illumination of ultraviolet light, in the Langmuir monolayer of mesogenic azobenzene dimer, bis-[5-(4{sup '}-n-dodecyloxy benzoyloxy)-2-(4{sup ''}-methylphenylazo)phenyl] adipate, at an air-water interface. We find that the trans to cis isomerization reaction of the molecules in the monolayer shows deviation from the first-order kinetics unlike those reported on Langmuir monolayers of azobenzene molecules. We attribute the deviation from first-order kinetics to the simultaneous photoisomerization of trans isomers to form cis isomers and the reverse thermal isomerization of cis isomers to form trans isomers. Our analysis of the rate of change of mole fraction of trans isomers to form cis isomers indicates a first-order kinetics for trans to cis photoisomerization reaction and a second-order kinetics for cis to trans thermal isomerization reaction. This second-order kinetics mechanism is similar to the Lindemann-Hinshelwood mechanism for the unimolecular reactions at low concentration of reactants. The formation of the activated cis isomer by collisions is a slow process as compared to the decay of the activated cis isomer to trans isomer in the liquid expanded phase. This results in the second-order kinetics for the thermal isomerization of cis isomers.
Mesoscopic modeling of stochastic reaction-diffusion kinetics in the subdiffusive regime
Emilie Blanc; Stefan Engblom; Andreas Hellander; Per Lötstedt
2015-03-24
Subdiffusion has been proposed as an explanation of various kinetic phenomena inside living cells. In order to fascilitate large-scale computational studies of subdiffusive chemical processes, we extend a recently suggested mesoscopic model of subdiffusion into an accurate and consistent reaction-subdiffusion computational framework. Two different possible models of chemical reaction are revealed and some basic dynamic properties are derived. In certain cases those mesoscopic models have a direct interpretation at the macroscopic level as fractional partial differential equations in a bounded time interval. Through analysis and numerical experiments we estimate the macroscopic effects of reactions under subdiffusive mixing. The models display properties observed also in experiments: for a short time interval the behavior of the diffusion and the reaction is ordinary, in an intermediate interval the behavior is anomalous, and at long times the behavior is ordinary again.
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.
Morphological impact on the reaction kinetics of size-selected cobalt oxide nanoparticles
NASA Astrophysics Data System (ADS)
Bartling, Stephan; Pohl, Marga-Martina; Meiwes-Broer, Karl-Heinz; Barke, Ingo
2015-09-01
Apart from large surface areas, low activation energies are essential for efficient reactions, particularly in heterogeneous catalysis. Here, we show that not only the size of nanoparticles but also their detailed morphology can crucially affect reaction kinetics, as demonstrated for mass-selected, soft-landed, and oxidized cobalt clusters in a 6 nm to 18 nm size range. The method of reflection high-energy electron diffraction is extended to the quantitative determination of particle activation energies which is applied for repeated oxidation and reduction cycles at the same particles. We find unexpectedly small activation barriers for the reduction reaction of the largest particles studied, despite generally increasing barriers for growing sizes. We attribute these observations to the interplay of reaction-specific material transport with a size-dependent inner particle morphology.
de Anna, Pietro; Dentz, Marco; Tartakovsky, Alexandre M.; Le Borgne, Tanguy
2014-07-08
We investigate the effective kinetics of a reaction front for mixing limited bimolecular reaction $A+B\\rightarrow C$ in a porous medium. While Fickian diffusion predicts a scaling of the cumulative mass produced as $M_C \\propto t^{1/2}$, we observe two time regimes in which the total product mass evolves faster then $t^{1/2}$. At early times the invading solute is organized in fingers of high velocity. Reactions take place only at the fingers boundaries whose surface grows linearly in time. We show that this configuration leads to a mass scaling $M_C \\propto t^2$. When diffusion mixes reactants and destroy these finger structures, the effective reaction rate slows down and we relate it to the longitudinal advective spreading providing $M_C \\propto \\sigma_x$. The transition time between these two regimes is characterized by the diffusion time over the transverse fingers cross section.
Kamil, Ruzaimah Nik Mohamad; Yusup, Suzana
2010-08-01
A mathematical model describing chemical kinetics of transesterification of palm-based methyl esters with trimethylolpropane has been developed. The model was developed by utilizing nonlinear regression method, which is an efficient and powerful way to determine rate constants for both forward and reverse reactions. A comparison with previous study which excludes the reverse reactions was made. The model was based on the reverse mechanism of transesterification reactions and describes concentration changes of trimethylolpropane, monoesters and diesters production. The developed model was validated against data from the literature. The reaction rate constants were determined using MATLAB version 7.2 and the ratios of rate constants obtained were well in agreement with those reported in the literature. A good correlation between model simulations and experimental data was observed. It was proven that both methods were able to predict the rate constants with plausible accuracy. PMID:20304636
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.
Sahoo, Chittaranjan; Gupta, Ashok K; Pillai, Indu M Sasidharan
2012-01-01
Real textile wastewater collected from the cotton dyeing bath of a fabric dyeing and finishing plant was subjected to heterogeneous photocatalysis using Ag(+) doped TiO(2) under UV irradiation in a batch reactor. The photocatalysts were characterized by FESEM, XRD, EDS, FTIR, DRS and BET analyses. The kinetics of the reaction was also evaluated. Colour removal was more than 88%, 94% and 99%, respectively for undiluted, 2 times diluted and 5 times diluted wastewater with Ag(+) doped TiO(2) (2.5 g/L) after UV irradiation for 360 minutes. The COD removal for undiluted, 2 times diluted and 5 times diluted wastewater was 47%, 70% and 92%, respectively under similar conditions. The reaction followed Langmuir-Hinshelwood pseudo first order kinetic model and the data fitted well to polynomial regression analysis. PMID:22871009
Fundamental kinetics and mechanistic pathways for oxidation reactions in supercritical water
NASA Technical Reports Server (NTRS)
Webley, Paul A.; Tester, Jefferson W.
1988-01-01
Oxidation of the products of human metabolism in supercritical water has been shown to be an efficient way to accomplish the on-board water/waste recycling in future long-term space flights. Studies of the oxidation kinetics of methane to carbon dioxide in supercritical water are presented in this paper in order to enhance the fundamental understanding of the oxidation of human waste compounds in supercritical water. It is concluded that, although the elementary reaction models remain the best hope for simulating oxidation in supercritical water, several modifications to existing mechanisms need to be made to account for the role of water in the reaction mechanism.
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.
Monte Carlo modeling of a simple catalytic reaction mechanism: Comparison with Langmuir kinetics
Lutsevich, L.V.; Usov, A.G. (Computer Center, Novosibirsk (Russian Federation)); Elokhin, V.I. (Inst. of Catalysis, Novosibirsk (Russian Federation)); Myshlyavtsev, A.V.; Yablonskii, A.G. (Touvinian Complex Dept., Kyzyl (Russian Federation))
1991-12-01
Using a Monte Carlo (MC) simulation technique, the authors have investigated the model of a simple catalytic reaction (the Langmuir-Hinshelwood mechanism) under varying intensities of surface diffusion. Having compared the results of the MC simulation with those obtained previously in the model based on the kinetic equations (formulated under the assumption of ideal adsorbed layer, the IAL model), they found the conditions under which both models give identical results. The difference between the results obtained with the IAL and those obtained with the MC model is associated with clustering of the adsorbed substances on the surface. The paper uses the CO oxidation reaction to illustrate the modeling.
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…
Study of the Reaction Stages and Kinetics of the Europium Oxide Carbochlorination
NASA Astrophysics Data System (ADS)
Pomiro, Federico J.; Fouga, Gastón G.; Gaviría, Juan P.; Bohé, Ana E.
2015-02-01
The europium oxide (Eu2O3(s)) chlorination reaction with sucrose carbon was studied by thermogravimetry between room temperature and 1223 K (950 °C). The nonisothermal thermogravimetry showed that the reaction consists of three stages, and their stoichiometries were studied. The product of the first stage was europium oxychloride, and it showed independence of the reaction kinetics with the carbon content. Subsequently, in the second stage, the EuOCl(s) was carbochlorinated with formation of EuCl3(l) and its evaporation is observed in the third stage. The analysis by Fourier transform infrared spectroscopy of gaseous species showed that the reaction at second stage occurs with the formation of CO2(g) and CO(g). Both reactants and products were analyzed by X-ray diffraction, scanning electron microscopy and wavelength-dispersive X-ray fluorescence spectroscopy. The influence of carbon content, total flow rate, sample initial mass, chlorine partial pressure, and temperature were evaluated. The second stage kinetics was analyzed, which showed an anomalous behavior caused by generation of chlorine radicals during interaction of Cl2(g) and carbon. It was found that the reaction rate at 933 K (660 °C) was proportional to a potential function of the chlorine partial pressure whose exponent is 0.56. The conversion curves were analyzed with the Avrami-Erofeev model and it was obtained an activation energy of 154 ± 5 kJ mol-1.
Construction of Hydrazine and NTO Kinetic Reaction Model for Bipropellant Thruster Simulation
NASA Astrophysics Data System (ADS)
Ohminami, Kaori; Ogawa, Hiroyuki; Hayashi, A. Koichi
Hydrazine (N2H4) and NTO (dinitrogen tetroxide: N2O4) mixtures are used in spacecraft bipropellant systems, having the advantage, for sampling missions, of having no carbon composition. However, no reasonable hydrazine and NTO combustion model has been developed. To construct a hydrazine and NTO combustion model that is useful for bipropellant thruster CFD simulation, we extracted efficient elementary reactions from detailed kinetic reaction model proposed by Ohminami and Ogawa in 2007. The reduced hydrazine and NTO combustion model was composed of 61 extracted reactions with 23 chemical species and was coincident with the original detailed kinetic reaction model in terms of combustion gas temperatures and ignition delay times over O/F(oxidizer and fuel mass ration) =0.82-1.84. Also the simulated combustion gas temperatures were good agreed with the adiabatic flame temperatures, and the simulated ignition delay time at O/F=1.2 was consistent with the literature value. Chemical reaction paths before and after ignition were showed, and could explain hydrazine and NTO combustion network mechanism change.
Reactions of plutonium and uranium with water: Kinetics and potential hazards
Haschke, J.M.
1995-12-01
The chemistry and kinetics of reactions between water and the metals and hydrides of plutonium and uranium are described in an effort to consolidate information for assessing potential hazards associated with handling and storage. New experimental results and data from literature sources are presented. Kinetic dependencies on pH, salt concentration, temperature and other parameters are reviewed. Corrosion reactions of the metals in near-neutral solutions produce a fine hydridic powder plus hydrogen. The corrosion rate for plutonium in sea water is a thousand-fold faster than for the metal in distilled water and more than a thousand-fold faster than for uranium in sea water. Reaction rates for immersed hydrides of plutonium and uranium are comparable and slower than the corrosion rates for the respective metals. However, uranium trihydride is reported to react violently if a quantity greater than twenty-five grams is rapidly immersed in water. The possibility of a similar autothermic reaction for large quantities of plutonium hydride cannot be excluded. In addition to producing hydrogen, corrosion reactions convert the massive metals into material forms that are readily suspended in water and that are aerosolizable and potentially pyrophoric when dry. Potential hazards associated with criticality, environmental dispersal, spontaneous ignition and explosive gas mixtures are outlined.
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 lime/bentonite pozzolanic reactions at 20 and 50 °C: Batch tests and modeling
De Windt, Laurent, E-mail: laurent.dewindt@mines-paristech.fr [Mines-ParisTech (Ecole des Mines de Paris), Centre de Géosciences, 35 Rue St-Honoré, 77305 Fontainebleau Cedex (France); Deneele, Dimitri [LUNAM, IFSTTAR, Institut Français des Sciences et des Technologies des Transports, de l'Aménagement et des Réseaux, BP 4129, route de Bouaye, 44332 Bouguenais (France); Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France); Maubec, Nicolas [LUNAM, IFSTTAR, Institut Français des Sciences et des Technologies des Transports, de l'Aménagement et des Réseaux, BP 4129, route de Bouaye, 44332 Bouguenais (France)
2014-05-01
The effects of duration (1–100 days) and temperature (20 and 50 °C) were assessed from batch tests for Ca-bentonite mixed with 10 wt.% lime. The pozzolanic processes were monitored over time by {sup 29}Si NMR (Cement Concr. Res. 42, 2012), TGA-DTA, XRD and chemical analysis. Modeling considered kinetics and thermodynamics of mineralogical transformations and cation exchange. Kinetic laws were dependent on pH and temperature (Arrhenius energy). Lime hydration occurs within hours, modifying the bentonite exchangeable population and increasing the pH. These alkaline conditions initiate the pozzolanic reactions in a second stage. The rate-limiting step is the dissolution kinetics of the bentonite minerals, i.e. a relatively fast and total consumption of cristobalite in parallel to a long-term slower dissolution of montmorillonite. First C–S–H and then C–A–S–H are formed consequently. Temperature speeds up the pozzolanic reaction kinetics by a factor 5 from 20 to 50 °C, corresponding to an apparent activation energy of 40–50 kJ/mol.
Grout, Ray W [ORNL
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.
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.
Influence of Zn and gypsum on the changes in reaction kinetics of salt affected soil
D. K. Das; Tanmoy Karak; Debtanu Maiti
Chelated zinc in the form of Zn-EDTA is a free flowing crystalline powder salt. On an equivalent Zn-basis, chelated Zn is at least five times more effective than inorganic Zn salts although chelated Zn is most costly. This investigation was undertaken to study the reaction kinetics of chelated Zn (Zn-EDTA) in a salt-affected soils of West Bengal (Kakdwip series) influenced