Quantum dynamics of fast chemical reactions

Energy Technology Data Exchange (ETDEWEB)

Light, J.C. [Univ. of Chicago, IL (United States)

1993-12-01

The aims of this research are to explore, develop, and apply theoretical methods for the evaluation of the dynamics of gas phase collision processes, primarily chemical reactions. The primary theoretical tools developed for this work have been quantum scattering theory, both in time dependent and time independent forms. Over the past several years, the authors have developed and applied methods for the direct quantum evaluation of thermal rate constants, applying these to the evaluation of the hydrogen isotopic exchange reactions, applied wave packet propagation techniques to the dissociation of Rydberg H{sub 3}, incorporated optical potentials into the evaluation of thermal rate constants, evaluated the use of optical potentials for state-to-state reaction probability evaluations, and, most recently, have developed quantum approaches for electronically non-adiabatic reactions which may be applied to simplify calculations of reactive, but electronically adiabatic systems. Evaluation of the thermal rate constants and the dissociation of H{sub 3} were reported last year, and have now been published.

Development of tight-binding, chemical-reaction-dynamics simulator for combinatorial computational chemistry

International Nuclear Information System (INIS)

Kubo, Momoji; Ando, Minako; Sakahara, Satoshi; Jung, Changho; Seki, Kotaro; Kusagaya, Tomonori; Endou, Akira; Takami, Seiichi; Imamura, Akira; Miyamoto, Akira

2004-01-01

Recently, we have proposed a new concept called 'combinatorial computational chemistry' to realize a theoretical, high-throughput screening of catalysts and materials. We have already applied our combinatorial, computational-chemistry approach, mainly based on static first-principles calculations, to various catalysts and materials systems and its applicability to the catalysts and materials design was strongly confirmed. In order to realize more effective and efficient combinatorial, computational-chemistry screening, a high-speed, chemical-reaction-dynamics simulator based on quantum-chemical, molecular-dynamics method is essential. However, to the best of our knowledge, there is no chemical-reaction-dynamics simulator, which has an enough high-speed ability to perform a high-throughput screening. In the present study, we have succeeded in the development of a chemical-reaction-dynamics simulator based on our original, tight-binding, quantum-chemical, molecular-dynamics method, which is more than 5000 times faster than the regular first-principles, molecular-dynamics method. Moreover, its applicability and effectiveness to the atomistic clarification of the methanol-synthesis dynamics at reaction temperature were demonstrated

Crossed molecular beam studies of unimolecular reaction dynamics

International Nuclear Information System (INIS)

Buss, R.J.

1979-04-01

The study of seven radical-molecule reactions using the crossed molecular beam technique with supersonic nozzle beams is reported. Product angular and velocity distributions were obtained and compared with statistical calculations in order to identify dynamical features of the reactions. In the reaction of chlorine and fluorine atoms with vinyl bromide, the product energy distributions are found to deviate from predictions of the statistical model. A similar effect is observed in the reaction of chlorine atoms with 1, 2 and 3-bromopropene. The reaction of oxygen atoms with ICl and CF 3 I has been used to obtain an improved value of the IO bond energy, 55.0 +- 2.0 kcal mol -1 . In all reactions studied, the product energy and angular distributions are found to be coupled, and this is attributed to a kinematic effect of the conservation of angular momentum

Effective dynamics along given reaction coordinates, and reaction rate theory.

Science.gov (United States)

Zhang, Wei; Hartmann, Carsten; Schütte, Christof

2016-12-22

In molecular dynamics and related fields one considers dynamical descriptions of complex systems in full (atomic) detail. In order to reduce the overwhelming complexity of realistic systems (high dimension, large timescale spread, limited computational resources) the projection of the full dynamics onto some reaction coordinates is examined in order to extract statistical information like free energies or reaction rates. In this context, the effective dynamics that is induced by the full dynamics on the reaction coordinate space has attracted considerable attention in the literature. In this article, we contribute to this discussion: we first show that if we start with an ergodic diffusion process whose invariant measure is unique then these properties are inherited by the effective dynamics. Then, we give equations for the effective dynamics, discuss whether the dominant timescales and reaction rates inferred from the effective dynamics are accurate approximations of such quantities for the full dynamics, and compare our findings to results from approaches like Mori-Zwanzig, averaging, or homogenization. Finally, by discussing the algorithmic realization of the effective dynamics, we demonstrate that recent algorithmic techniques like the "equation-free" approach and the "heterogeneous multiscale method" can be seen as special cases of our approach.

Reaction cross section calculation of some alkaline earth elements

Science.gov (United States)

Tel, Eyyup; Kavun, Yusuf; Sarpün, Ismail Hakki

2017-09-01

Reaction cross section knowledge is crucial to application nuclear physics such as medical imaging, radiation shielding and material evaluations. Nuclear reaction codes can be used if the experimental data are unavailable or are improbably to be produced because of the experimental trouble. In this study, there action cross sections of some target alkaline earth elements have been calculated by using pre-equilibrium and equilibrium nuclear reaction models for nucleon induced reactions. While these calculations, the Hybrid Model, the Geometry Dependent Hybrid Model, the Full Exciton Model, the Cascade Exciton Model for pre-equilibrium reactions and the Weisskopf-Ewing Model for equilibrium reactions have been used. The calculated cross sections have been discussed and compared with the experimental data taken from Experimental Nuclear Reaction Data library.

Chemical dynamics in the gas phase: Time-dependent quantum mechanics of chemical reactions

Energy Technology Data Exchange (ETDEWEB)

Gray, S.K. [Argonne National Laboratory, IL (United States)

1993-12-01

A major goal of this research is to obtain an understanding of the molecular reaction dynamics of three and four atom chemical reactions using numerically accurate quantum dynamics. This work involves: (i) the development and/or improvement of accurate quantum mechanical methods for the calculation and analysis of the properties of chemical reactions (e.g., rate constants and product distributions), and (ii) the determination of accurate dynamical results for selected chemical systems, which allow one to compare directly with experiment, determine the reliability of the underlying potential energy surfaces, and test the validity of approximate theories. This research emphasizes the use of recently developed time-dependent quantum mechanical methods, i.e. wave packet methods.

Chemical Reaction Rates from Ring Polymer Molecular Dynamics: Zero Point Energy Conservation in Mu + H2 → MuH + H.

Science.gov (United States)

Pérez de Tudela, Ricardo; Aoiz, F J; Suleimanov, Yury V; Manolopoulos, David E

2012-02-16

A fundamental issue in the field of reaction dynamics is the inclusion of the quantum mechanical (QM) effects such as zero point energy (ZPE) and tunneling in molecular dynamics simulations, and in particular in the calculation of chemical reaction rates. In this work we study the chemical reaction between a muonium atom and a hydrogen molecule. The recently developed ring polymer molecular dynamics (RPMD) technique is used, and the results are compared with those of other methods. For this reaction, the thermal rate coefficients calculated with RPMD are found to be in excellent agreement with the results of an accurate QM calculation. The very minor discrepancies are within the convergence error even at very low temperatures. This exceptionally good agreement can be attributed to the dominant role of ZPE in the reaction, which is accounted for extremely well by RPMD. Tunneling only plays a minor role in the reaction.

Reaction cross section calculation of some alkaline earth elements

Directory of Open Access Journals (Sweden)

Tel Eyyup

2017-01-01

Full Text Available Reaction cross section knowledge is crucial to application nuclear physics such as medical imaging, radiation shielding and material evaluations. Nuclear reaction codes can be used if the experimental data are unavailable or are improbably to be produced because of the experimental trouble. In this study, there action cross sections of some target alkaline earth elements have been calculated by using pre-equilibrium and equilibrium nuclear reaction models for nucleon induced reactions. While these calculations, the Hybrid Model, the Geometry Dependent Hybrid Model, the Full Exciton Model, the Cascade Exciton Model for pre-equilibrium reactions and the Weisskopf-Ewing Model for equilibrium reactions have been used. The calculated cross sections have been discussed and compared with the experimental data taken from Experimental Nuclear Reaction Data library.

Improved techniques for outgoing wave variational principle calculations of converged state-to-state transition probabilities for chemical reactions

Science.gov (United States)

Mielke, Steven L.; Truhlar, Donald G.; Schwenke, David W.

1991-01-01

Improved techniques and well-optimized basis sets are presented for application of the outgoing wave variational principle to calculate converged quantum mechanical reaction probabilities. They are illustrated with calculations for the reactions D + H2 yields HD + H with total angular momentum J = 3 and F + H2 yields HF + H with J = 0 and 3. The optimization involves the choice of distortion potential, the grid for calculating half-integrated Green's functions, the placement, width, and number of primitive distributed Gaussians, and the computationally most efficient partition between dynamically adapted and primitive basis functions. Benchmark calculations with 224-1064 channels are presented.

Trajectory calculation of a trapped particle in electro-dynamic balance for study of chemical reaction of aerosol particles

International Nuclear Information System (INIS)

Okuma, Miho; Itou, Takahiro; Harano, Azuchi; Takarada, Takayuki; James, Davis E

2013-01-01

Electrodynamic balance (EDB) is a powerful tool for investigating the chemical reactions between a fine particle and gaseous species. But the EDB device alone is inadequate to match the rapid weight change of a fine particle caused by chemical reactions, because it takes a few seconds to set a fine particle at null point. The particle trajectory calculation for the trapped particle added to the EDB is thus a very useful tool for the measurement of the transient response of a particle weight change with no need to adjust the applied DC voltage to set the null point. The purpose of this study is to develop the trajectory calculation method to track the particle oscillation pattern in the EDB and examine the possibility for kinetic studies on the reaction of a single aerosol particle with gaseous species. The results demonstrated the feasibility of applying particle trajectory calculation to realize the research purpose.

Photochemical reaction dynamics

Energy Technology Data Exchange (ETDEWEB)

Moore, B.C. [Lawrence Berkeley Laboratory, Livermore, CA (United States)

1993-12-01

The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.

Classical molecular dynamics simulation of weakly-bound projectile heavy-ion reactions

Directory of Open Access Journals (Sweden)

Morker Mitul R.

2015-01-01

Full Text Available A 3-body classical molecular dynamics approach for heavy-ion reactions involving weakly bound projectiles is developed. In this approach a weakly bound projectile is constructed as a two-body cluster of the constituent tightly bound nuclei in a configuration corresponding to the observed breakup energy. This 3-body system with their individual nucleon configuration in their ground state is dynamically evolved for given initial conditions using the three-stage classical molecular dynamics approach (3S-CMD. Various levels of rigidbody constraints on the projectile constituents and the target are considered at appropriate stages. This 3-dimensional approach explicitly takes into account not only the long range Coulomb reorientation of the deformed collision partner but internal excitations and breakup probabilities at distances close to the barrier also. Dynamical simulations of 6Li+209Bi show all the possible reaction mechanism like complete fusion, incomplete fusion, scattering and breakup scattering. Complete fusion cross sections of 6Li+209Bi and 7Li+209Bi reactions are calculated in this approach with systematic relaxations of the rigid-body constraints on one or more constituent nuclei.

Time-Dependent Wave Packet Dynamics Calculations of Cross Sections for Ultracold Scattering of Molecules

Science.gov (United States)

Huang, Jiayu; Liu, Shu; Zhang, Dong H.; Krems, Roman V.

2018-04-01

Because the de Broglie wavelength of ultracold molecules is very large, the cross sections for collisions of molecules at ultracold temperatures are always computed by the time-independent quantum scattering approach. Here, we report the first accurate time-dependent wave packet dynamics calculation for reactive scattering of ultracold molecules. Wave packet dynamics calculations can be applied to molecular systems with more dimensions and provide real-time information on the process of bond rearrangement and/or energy exchange in molecular collisions. Our work thus makes possible the extension of rigorous quantum calculations of ultracold reaction properties to polyatomic molecules and adds a new powerful tool for the study of ultracold chemistry.

Recent developments in nuclear reaction theories and calculations

International Nuclear Information System (INIS)

Gardner, D.G.

1980-01-01

A brief review is given of some recent developments in the fields of optical model potentials; level densities; and statistical model, precompound, and direct reaction codes and calculations. Significant developments have occurred in all of these fields since the 1977 Conference on Neutron Cross Sections, which will greatly enhance the ability to calculate high-energy neutron-induced reaction cross sections in the next few years. 11 figures, 3 tables

Ab Initio Calculations Of Nuclear Reactions And Exotic Nuclei

Energy Technology Data Exchange (ETDEWEB)

Quaglioni, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2014-05-05

Our ultimate goal is to develop a fundamental theory and efficient computational tools to describe dynamic processes between nuclei and to use such tools toward supporting several DOE milestones by: 1) performing predictive calculations of difficult-to-measure landmark reactions for nuclear astrophysics, such as those driving the neutrino signature of our sun; 2) improving our understanding of the structure of nuclei near the neutron drip line, which will be the focus of the DOE’s Facility for Rare Isotope Beams (FRIB) being constructed at Michigan State University; but also 3) helping to reveal the true nature of the nuclear force. Furthermore, these theoretical developments will support plasma diagnostic efforts at facilities dedicated to the development of terrestrial fusion energy.

Comparison of dynamical aspects of nonadiabatic electron, proton, and proton-coupled electron transfer reactions

International Nuclear Information System (INIS)

Hatcher, Elizabeth; Soudackov, Alexander; Hammes-Schiffer, Sharon

2005-01-01

The dynamical aspects of a model proton-coupled electron transfer (PCET) reaction in solution are analyzed with molecular dynamics simulations. The rate for nonadiabatic PCET is expressed in terms of a time-dependent probability flux correlation function. The impact of the proton donor-acceptor and solvent dynamics on the probability flux is examined. The dynamical behavior of the probability flux correlation function is dominated by a solvent damping term that depends on the energy gap correlation function. The proton donor-acceptor motion does not impact the dynamical behavior of the probability flux correlation function but does influence the magnitude of the rate. The approximations previously invoked for the calculation of PCET rates are tested. The effects of solvent damping on the proton donor-acceptor vibrational motion are found to be negligible, and the short-time solvent approximation, in which only equilibrium fluctuations of the solvent are considered, is determined to be valid for these types of reactions. The analysis of PCET reactions is compared to previous analyses of single electron and proton transfer reactions. The dynamical behavior is qualitatively similar for all three types of reactions, but the time scale of the decay of the probability flux correlation function is significantly longer for single proton transfer than for PCET and single electron transfer due to a smaller solvent reorganization energy for proton transfer

A molecular dynamics study of intramolecular proton transfer reaction of malonaldehyde in solution based upon a mixed quantum-classical approximation. II. Proton transfer reaction in non-polar solvent

Science.gov (United States)

Kojima, H.; Yamada, A.; Okazaki, S.

2015-05-01

The intramolecular proton transfer reaction of malonaldehyde in neon solvent has been investigated by mixed quantum-classical molecular dynamics (QCMD) calculations and fully classical molecular dynamics (FCMD) calculations. Comparing these calculated results with those for malonaldehyde in water reported in Part I [A. Yamada, H. Kojima, and S. Okazaki, J. Chem. Phys. 141, 084509 (2014)], the solvent dependence of the reaction rate, the reaction mechanism involved, and the quantum effect therein have been investigated. With FCMD, the reaction rate in weakly interacting neon is lower than that in strongly interacting water. However, with QCMD, the order of the reaction rates is reversed. To investigate the mechanisms in detail, the reactions were categorized into three mechanisms: tunneling, thermal activation, and barrier vanishing. Then, the quantum and solvent effects were analyzed from the viewpoint of the reaction mechanism focusing on the shape of potential energy curve and its fluctuations. The higher reaction rate that was found for neon in QCMD compared with that found for water solvent arises from the tunneling reactions because of the nearly symmetric double-well shape of the potential curve in neon. The thermal activation and barrier vanishing reactions were also accelerated by the zero-point energy. The number of reactions based on these two mechanisms in water was greater than that in neon in both QCMD and FCMD because these reactions are dominated by the strength of solute-solvent interactions.

Nuclear structure effects on calculated fast neutron reaction cross sections

International Nuclear Information System (INIS)

Avrigeanu, V.

1992-01-01

The importance of accurate low-lying level schemes for reaction cross section calculation and need for microscopically calculated levels are proved with reference to fast neutron induced reactions in the A = 50 atomic mass range. The uses of the discrete levels both for normalization of phenomenological level density approaches and within Hauser-Feshbach calculations are discussed in this respect. (Author)

APUAMA: a software tool for reaction rate calculations.

Science.gov (United States)

Euclides, Henrique O; P Barreto, Patricia R

2017-06-01

APUAMA is a free software designed to determine the reaction rate and thermodynamic properties of chemical species of a reagent system. With data from electronic structure calculations, the APUAMA determine the rate constant with tunneling correction, such as Wigner, Eckart and small curvature, and also, include the rovibrational level of diatomic molecules. The results are presented in the form of Arrhenius-Kooij form, for the reaction rate, and the thermodynamic properties are written down in the polynomial form. The word APUAMA means "fast" in Tupi-Guarani Brazilian language, then the code calculates the reaction rate on a simple and intuitive graphic interface, the form fast and practical. As program output, there are several ASCII files with tabulated information for rate constant, rovibrational levels, energy barriers and enthalpy of reaction, Arrhenius-Kooij coefficient, and also, the option to the User save all graphics in BMP format.

PTOLEMY, a program for heavy-ion direction-reaction calculations

International Nuclear Information System (INIS)

Gloeckner, D.H.; Macfarlane, M.H.; Pieper, S.C.

1976-03-01

Ptolemy is an IBM/360 program for the computation of nuclear elastic and direct-reaction cross sections. It carries out both optical-model fits to elastic-scattering data at one or more energies, and DWBA calculations for nucleon-transfer reactions. Ptolemy has been specifically designed for heavy-ion calculations. It is fast and does not require large amounts of core. The input is exceptionally flexible and easy to use. This report outlines the types of calculation that Ptolemy can carry out, summarizes the formulas used, and gives a detailed description of its input

The Reaction Mechanism of Claisen Rearrangement Obtained by Transition State Spectroscopy and Single Direct-Dynamics Trajectory

Directory of Open Access Journals (Sweden)

Takayoshi Kobayashi

2013-02-01

Full Text Available Chemical bond breaking and formation during chemical reactions can be observed using “transition state spectroscopy”. Comparing the measurement result of the transition state spectroscopy with the simulation result of single direct-dynamics trajectory, we have elucidated the reaction dynamics of Claisen rearrangement of allyl vinyl ether. Observed the reaction of the neat sample liquid, we have estimated the time constants of transformation from straight-chain structure to aromatic-like six-membered ring structure forming the C1-C6 bond. The result clarifies that the reaction proceeds via three steps taking longer time than expected from the gas phase calculation. This finding provides new hypothesis and discussions, helping the development of the field of reaction mechanism analysis.

Reactive scattering of H2 from Cu(100): comparison of dynamics calculations based on the specific reaction parameter approach to density functional theory with experiment.

Science.gov (United States)

Sementa, L; Wijzenbroek, M; van Kolck, B J; Somers, M F; Al-Halabi, A; Busnengo, H F; Olsen, R A; Kroes, G J; Rutkowski, M; Thewes, C; Kleimeier, N F; Zacharias, H

2013-01-28

We present new experimental and theoretical results for reactive scattering of dihydrogen from Cu(100). In the new experiments, the associative desorption of H(2) is studied in a velocity resolved and final rovibrational state selected manner, using time-of-flight techniques in combination with resonance-enhanced multi-photon ionization laser detection. Average desorption energies and rotational quadrupole alignment parameters were obtained in this way for a number of (v = 0, 1) rotational states, v being the vibrational quantum number. Results of quantum dynamics calculations based on a potential energy surface computed with a specific reaction parameter (SRP) density functional, which was derived earlier for dihydrogen interacting with Cu(111), are compared with the results of the new experiments and with the results of previous molecular beam experiments on sticking of H(2) and on rovibrationally elastic and inelastic scattering of H(2) and D(2) from Cu(100). The calculations use the Born-Oppenheimer and static surface approximations. With the functional derived semi-empirically for dihydrogen + Cu(111), a chemically accurate description is obtained of the molecular beam experiments on sticking of H(2) on Cu(100), and a highly accurate description is obtained of rovibrationally elastic and inelastic scattering of D(2) from Cu(100) and of the orientational dependence of the reaction of (v = 1, j = 2 - 4) H(2) on Cu(100). This suggests that a SRP density functional derived for H(2) interacting with a specific low index face of a metal will yield accurate results for H(2) reactively scattering from another low index face of the same metal, and that it may also yield accurate results for H(2) interacting with a defected (e.g., stepped) surface of that same metal, in a system of catalytic interest. However, the description that was obtained of the average desorption energies, of rovibrationally elastic and inelastic scattering of H(2) from Cu(100), and of the

Theoretical calculations of the reaction cross-sections for proton-induced reactions on natural copper using ALICE-IPPE code

International Nuclear Information System (INIS)

Alharbi, A.A.; Azzam, A.

2012-01-01

A theoretical study of the nuclear-reaction cross sections for proton-induced reactions on 63 Cu and 65 Cu was performed in the proton energy range from threshold values up to 50 MeV. The produced nuclei were different isotopes of Zn, Cu, Ni, Co and Mn, some of which have important applications. The reaction cross-section calculations were performed using the ALICE-IPPE code, which depends on the pre-equilibrium compound nucleus model. This code is suitable for the studied energy and isotopic mass ranges. Approximately 14 excitation functions for the different reactions have been constructed from the calculated cross-section values. The excitation function curves for the proton reactions with natural copper targets have been constructed from those for enriched targets using the natural abundance of the copper isotopes. Comparisons between the calculated excitation functions with those previously experimentally measured are given whenever the experimental values were available. Some statistical parameters were introduced to control the quality of the fitting between both the experimental and the theoretical calculated cross-section values. - Highlights: ► We performed reaction cross section calculations using ALICE-IPPE code. ► We constructed 14 excitation functions for nat Cu(p,xn)Zn,Cu,Ni,Co,Mn reactions. ► The available experimental data were fitted to the performed ALICE-IPPE calculations. ► Statistical parameters were introduced to control the quality of the fitting. ► The code failed to fit the experimental data for reactions with large nucleon emissions.

Ptolemy: a program for heavy-ion direct-reaction calculations

International Nuclear Information System (INIS)

Macfarlane, M.H.; Pieper, S.C.

1978-04-01

Ptolemy is an IBM/360 program for the computation of nuclear elastic and direct-reaction cross sections. It carries out optical-model fits to elastic-scattering data at one or more energies and for one or more combinations of projectile and target, collective model DWBA calculations of excitation processes, and finite-range DWBA calculations of nucleon-transfer reactions. It is fast and does not require large amounts of core. The input is exceptionally flexible and easy to use. The types of calculations that Ptolemy can carry out are outlined, the formulas used are summarized, and a detailed description of its input is given

A network dynamics approach to chemical reaction networks

NARCIS (Netherlands)

van der Schaft, Abraham; Rao, S.; Jayawardhana, B.

2016-01-01

A treatment of chemical reaction network theory is given from the perspective of nonlinear network dynamics, in particular of consensus dynamics. By starting from the complex-balanced assumption the reaction dynamics governed by mass action kinetics can be rewritten into a form which allows for a

Markovian dynamics on complex reaction networks

Energy Technology Data Exchange (ETDEWEB)

Goutsias, J., E-mail: goutsias@jhu.edu; Jenkinson, G., E-mail: jenkinson@jhu.edu

2013-08-10

Complex networks, comprised of individual elements that interact with each other through reaction channels, are ubiquitous across many scientific and engineering disciplines. Examples include biochemical, pharmacokinetic, epidemiological, ecological, social, neural, and multi-agent networks. A common approach to modeling such networks is by a master equation that governs the dynamic evolution of the joint probability mass function of the underlying population process and naturally leads to Markovian dynamics for such process. Due however to the nonlinear nature of most reactions and the large size of the underlying state-spaces, computation and analysis of the resulting stochastic population dynamics is a difficult task. This review article provides a coherent and comprehensive coverage of recently developed approaches and methods to tackle this problem. After reviewing a general framework for modeling Markovian reaction networks and giving specific examples, the authors present numerical and computational techniques capable of evaluating or approximating the solution of the master equation, discuss a recently developed approach for studying the stationary behavior of Markovian reaction networks using a potential energy landscape perspective, and provide an introduction to the emerging theory of thermodynamic analysis of such networks. Three representative problems of opinion formation, transcription regulation, and neural network dynamics are used as illustrative examples.

Markovian dynamics on complex reaction networks

International Nuclear Information System (INIS)

Goutsias, J.; Jenkinson, G.

2013-01-01

Complex networks, comprised of individual elements that interact with each other through reaction channels, are ubiquitous across many scientific and engineering disciplines. Examples include biochemical, pharmacokinetic, epidemiological, ecological, social, neural, and multi-agent networks. A common approach to modeling such networks is by a master equation that governs the dynamic evolution of the joint probability mass function of the underlying population process and naturally leads to Markovian dynamics for such process. Due however to the nonlinear nature of most reactions and the large size of the underlying state-spaces, computation and analysis of the resulting stochastic population dynamics is a difficult task. This review article provides a coherent and comprehensive coverage of recently developed approaches and methods to tackle this problem. After reviewing a general framework for modeling Markovian reaction networks and giving specific examples, the authors present numerical and computational techniques capable of evaluating or approximating the solution of the master equation, discuss a recently developed approach for studying the stationary behavior of Markovian reaction networks using a potential energy landscape perspective, and provide an introduction to the emerging theory of thermodynamic analysis of such networks. Three representative problems of opinion formation, transcription regulation, and neural network dynamics are used as illustrative examples

Exciton model and quantum molecular dynamics in inclusive nucleon-induced reactions

International Nuclear Information System (INIS)

Bevilacqua, Riccardo; Pomp, Stephan; Watanabe, Yukinobu

2011-01-01

We compared inclusive nucleon-induced reactions with two-component exciton model calculations and Kalbach systematics; these successfully describe the production of protons, whereas fail to reproduce the emission of composite particles, generally overestimating it. We show that the Kalbach phenomenological model needs to be revised for energies above 90 MeV; agreement improves introducing a new energy dependence for direct-like mechanisms described by the Kalbach model. Our revised model calculations suggest multiple preequilibrium emission of light charged particles. We have also compared recent neutron-induced data with quantum molecular dynamics (QMD) calculations complemented by the surface coalescence model (SCM); we observed that the SCM improves the predictive power of QMD. (author)

Photoinduced reactions of both 2-formyl-2H-azirine and isoxazole: A theoretical study based on electronic structure calculations and nonadiabatic dynamics simulations

International Nuclear Information System (INIS)

Cao, Jun

2015-01-01

In the present work, the combined electronic structure calculations and dynamics simulations have been performed to explore photocleavages of 2-formyl-2H-azirine and isoxazole in the gas phase and the subsequent rearrangement reactions. The carbonyl n → π * transition induces a cleavage of the C—N single bond of 2-formyl-2H-azirine to yield β-formylvinylnitrene in open-shell singlet state. However, the n → π * excitation of the imine chromophore results in a cleavage of the C—C single bond, producing a nitrile ylide intermediate through an internal conversion to the ground state. β-formylvinylnitrene and nitrile ylide with the carbonyl group are easily transformed into 2-formyl-2H-azirine and oxazole, respectively. The N—O bond cleavages on both S 1 ( 1 ππ * ) and S 2 ( 1 n N π * ) of isoxazole are ultrafast processes, and they give products of 2-formyl-2H-azirine, 3-formylketenimine, HCN + CHCHO, and HCO + CHCHN. Both 2H-azirines and ketenimines were suggested to be formed from the triplet vinylnitrenes by intersystem crossing in the previous studies. However, our calculations show that the singlet β-formylvinylnitrene is responsible for the formation of 2-formyl-2H-azirine and 3-formylketenimine, and the singlet vinylnitrenes can play a key role in the photoinduced reactions of both 2H-azirines and isoxazoles

Photoinduced reactions of both 2-formyl-2H-azirine and isoxazole: A theoretical study based on electronic structure calculations and nonadiabatic dynamics simulations

Science.gov (United States)

Cao, Jun

2015-06-01

In the present work, the combined electronic structure calculations and dynamics simulations have been performed to explore photocleavages of 2-formyl-2H-azirine and isoxazole in the gas phase and the subsequent rearrangement reactions. The carbonyl n → π* transition induces a cleavage of the C—N single bond of 2-formyl-2H-azirine to yield β-formylvinylnitrene in open-shell singlet state. However, the n → π* excitation of the imine chromophore results in a cleavage of the C—C single bond, producing a nitrile ylide intermediate through an internal conversion to the ground state. β-formylvinylnitrene and nitrile ylide with the carbonyl group are easily transformed into 2-formyl-2H-azirine and oxazole, respectively. The N—O bond cleavages on both S1(1ππ*) and S2(1nNπ*) of isoxazole are ultrafast processes, and they give products of 2-formyl-2H-azirine, 3-formylketenimine, HCN + CHCHO, and HCO + CHCHN. Both 2H-azirines and ketenimines were suggested to be formed from the triplet vinylnitrenes by intersystem crossing in the previous studies. However, our calculations show that the singlet β-formylvinylnitrene is responsible for the formation of 2-formyl-2H-azirine and 3-formylketenimine, and the singlet vinylnitrenes can play a key role in the photoinduced reactions of both 2H-azirines and isoxazoles.

Reactor dynamics calculations

International Nuclear Information System (INIS)

Devooght, J.; Lefvert, T.; Stankiewiez, J.

1981-01-01

This chapter deals with the work done in reactor dynamics within the Coordinated Research Program on Transport Theory and Advanced Reactor Calculations by three groups in Belgium, Poland, Sweden and Italy. Discretization methods in diffusion theory, collision probability methods in time-dependent neutron transport and singular perturbation method are represented in this paper

Computing the Free Energy along a Reaction Coordinate Using Rigid Body Dynamics.

Science.gov (United States)

Tao, Peng; Sodt, Alexander J; Shao, Yihan; König, Gerhard; Brooks, Bernard R

2014-10-14

The calculations of potential of mean force along complex chemical reactions or rare events pathways are of great interest because of their importance for many areas in chemistry, molecular biology, and material science. The major difficulty for free energy calculations comes from the great computational cost for adequate sampling of the system in high-energy regions, especially close to the reaction transition state. Here, we present a method, called FEG-RBD, in which the free energy gradients were obtained from rigid body dynamics simulations. Then the free energy gradients were integrated along a reference reaction pathway to calculate free energy profiles. In a given system, the reaction coordinates defining a subset of atoms (e.g., a solute, or the quantum mechanics (QM) region of a quantum mechanics/molecular mechanics simulation) are selected to form a rigid body during the simulation. The first-order derivatives (gradients) of the free energy with respect to the reaction coordinates are obtained through the integration of constraint forces within the rigid body. Each structure along the reference reaction path is separately subjected to such a rigid body simulation. The individual free energy gradients are integrated along the reference pathway to obtain the free energy profile. Test cases provided demonstrate both the strengths and weaknesses of the FEG-RBD method. The most significant benefit of this method comes from the fast convergence rate of the free energy gradient using rigid-body constraints instead of restraints. A correction to the free energy due to approximate relaxation of the rigid-body constraint is estimated and discussed. A comparison with umbrella sampling using a simple test case revealed the improved sampling efficiency of FEG-RBD by a factor of 4 on average. The enhanced efficiency makes this method effective for calculating the free energy of complex chemical reactions when the reaction coordinate can be unambiguously defined by a

A network dynamics approach to chemical reaction networks

Science.gov (United States)

van der Schaft, A. J.; Rao, S.; Jayawardhana, B.

2016-04-01

A treatment of a chemical reaction network theory is given from the perspective of nonlinear network dynamics, in particular of consensus dynamics. By starting from the complex-balanced assumption, the reaction dynamics governed by mass action kinetics can be rewritten into a form which allows for a very simple derivation of a number of key results in the chemical reaction network theory, and which directly relates to the thermodynamics and port-Hamiltonian formulation of the system. Central in this formulation is the definition of a balanced Laplacian matrix on the graph of chemical complexes together with a resulting fundamental inequality. This immediately leads to the characterisation of the set of equilibria and their stability. Furthermore, the assumption of complex balancedness is revisited from the point of view of Kirchhoff's matrix tree theorem. Both the form of the dynamics and the deduced behaviour are very similar to consensus dynamics, and provide additional perspectives to the latter. Finally, using the classical idea of extending the graph of chemical complexes by a 'zero' complex, a complete steady-state stability analysis of mass action kinetics reaction networks with constant inflows and mass action kinetics outflows is given, and a unified framework is provided for structure-preserving model reduction of this important class of open reaction networks.

The quantum dynamics of electronically nonadiabatic chemical reactions

Science.gov (United States)

Truhlar, Donald G.

1993-01-01

Considerable progress was achieved on the quantum mechanical treatment of electronically nonadiabatic collisions involving energy transfer and chemical reaction in the collision of an electronically excited atom with a molecule. In the first step, a new diabatic representation for the coupled potential energy surfaces was created. A two-state diabatic representation was developed which was designed to realistically reproduce the two lowest adiabatic states of the valence bond model and also to have the following three desirable features: (1) it is more economical to evaluate; (2) it is more portable; and (3) all spline fits are replaced by analytic functions. The new representation consists of a set of two coupled diabatic potential energy surfaces plus a coupling surface. It is suitable for dynamics calculations on both the electronic quenching and reaction processes in collisions of Na(3p2p) with H2. The new two-state representation was obtained by a three-step process from a modified eight-state diatomics-in-molecules (DIM) representation of Blais. The second step required the development of new dynamical methods. A formalism was developed for treating reactions with very general basis functions including electronically excited states. Our formalism is based on the generalized Newton, scattered wave, and outgoing wave variational principles that were used previously for reactive collisions on a single potential energy surface, and it incorporates three new features: (1) the basis functions include electronic degrees of freedom, as required to treat reactions involving electronic excitation and two or more coupled potential energy surfaces; (2) the primitive electronic basis is assumed to be diabatic, and it is not assumed that it diagonalizes the electronic Hamiltonian even asymptotically; and (3) contracted basis functions for vibrational-rotational-orbital degrees of freedom are included in a very general way, similar to previous prescriptions for locally

Calculation of the energetics of chemical reactions

Energy Technology Data Exchange (ETDEWEB)

Dunning, T.H. Jr.; Harding, L.B.; Shepard, R.L.; Harrison, R.J.

1988-01-01

To calculate the energetics of chemical reactions we must solve the electronic Schroedinger equation for the molecular conformations of importance for the reactive encounter. Substantial changes occur in the electronic structure of a molecular system as the reaction progresses from reactants through the transition state to products. To describe these changes, our approach includes the following three elements: the use of multiconfiguration self-consistent field wave functions to provide a consistent zero-order description of the electronic structure of the reactants, transition state, and products; the use of configuration interaction techniques to describe electron correlation effects needed to provide quantitative predictions of the reaction energetics; and the use of large, optimized basis sets to provide the flexibility needed to describe the variations in the electronic distributions. With this approach we are able to study reactions involving as many as 5--6 atoms with errors of just a few kcal/mol in the predicted reaction energetics. Predictions to chemical accuracy, i.e., to 1 kcal/mol or less, are not yet feasible, although continuing improvements in both the theoretical methodology and computer technology suggest that this will soon be possible, at least for reactions involving small polyatomic species. 4 figs.

Benchmark calculations of thermal reaction rates. I - Quantal scattering theory

Science.gov (United States)

Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.

1991-01-01

The thermal rate coefficient for the prototype reaction H + H2 yields H2 + H with zero total angular momentum is calculated by summing, averaging, and numerically integrating state-to-state reaction probabilities calculated by time-independent quantum-mechanical scattering theory. The results are very carefully converged with respect to all numerical parameters in order to provide high-precision benchmark results for confirming the accuracy of new methods and testing their efficiency.

Modeling non-adiabatic photoexcited reaction dynamics in condensed phases

International Nuclear Information System (INIS)

Coker, D.F.

2003-01-01

Reactions of photoexcited molecules, ions, and radicals in condensed phase environments involve non-adiabatic dynamics over coupled electronic surfaces. We focus on how local environmental symmetries can effect non-adiabatic coupling between excited electronic states and thus influence, in a possibly controllable way, the outcome of photo-excited reactions. Semi-classical and mixed quantum-classical non-adiabatic molecular dynamics methods, together with semi-empirical excited state potentials are used to probe the dynamical mixing of electronic states in different environments from molecular clusters, to simple liquids and solids, and photo-excited reactions in complex reaction environments such as zeolites

Molecular beam studies of reaction dynamics

International Nuclear Information System (INIS)

Lee, Yuan T.

1991-03-01

The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation

Molecular beam studies of reaction dynamics

Energy Technology Data Exchange (ETDEWEB)

Lee, Y.T. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

Photoinduced reactions of both 2-formyl-2H-azirine and isoxazole: A theoretical study based on electronic structure calculations and nonadiabatic dynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Cao, Jun, E-mail: caojunbnu@mail.bnu.edu.cn [Guizhou Provincial Key Laboratory of Computational Nano-Material Sciences, Guizhou Normal College, Guiyang, Guizhou 550018, China and Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875 (China)

2015-06-28

In the present work, the combined electronic structure calculations and dynamics simulations have been performed to explore photocleavages of 2-formyl-2H-azirine and isoxazole in the gas phase and the subsequent rearrangement reactions. The carbonyl n → π{sup *} transition induces a cleavage of the C—N single bond of 2-formyl-2H-azirine to yield β-formylvinylnitrene in open-shell singlet state. However, the n → π{sup *} excitation of the imine chromophore results in a cleavage of the C—C single bond, producing a nitrile ylide intermediate through an internal conversion to the ground state. β-formylvinylnitrene and nitrile ylide with the carbonyl group are easily transformed into 2-formyl-2H-azirine and oxazole, respectively. The N—O bond cleavages on both S{sub 1}({sup 1}ππ{sup *}) and S{sub 2}({sup 1}n{sub N}π{sup *}) of isoxazole are ultrafast processes, and they give products of 2-formyl-2H-azirine, 3-formylketenimine, HCN + CHCHO, and HCO + CHCHN. Both 2H-azirines and ketenimines were suggested to be formed from the triplet vinylnitrenes by intersystem crossing in the previous studies. However, our calculations show that the singlet β-formylvinylnitrene is responsible for the formation of 2-formyl-2H-azirine and 3-formylketenimine, and the singlet vinylnitrenes can play a key role in the photoinduced reactions of both 2H-azirines and isoxazoles.

Combining molecular dynamics with mesoscopic Green’s function reaction dynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Vijaykumar, Adithya, E-mail: vijaykumar@amolf.nl [FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam (Netherlands); van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam (Netherlands); Bolhuis, Peter G. [van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam (Netherlands); Rein ten Wolde, Pieter, E-mail: p.t.wolde@amolf.nl [FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam (Netherlands)

2015-12-07

In many reaction-diffusion processes, ranging from biochemical networks, catalysis, to complex self-assembly, the spatial distribution of the reactants and the stochastic character of their interactions are crucial for the macroscopic behavior. The recently developed mesoscopic Green’s Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. We propose a novel approach that combines GFRD for simulating the system at the mesoscopic scale where particles are far apart, with a microscopic technique such as Langevin dynamics or Molecular Dynamics (MD), for simulating the system at the microscopic scale where reactants are in close proximity. This scheme defines the regions where the particles are close together and simulated with high microscopic resolution and those where they are far apart and simulated with lower mesoscopic resolution, adaptively on the fly. The new multi-scale scheme, called MD-GFRD, is generic and can be used to efficiently simulate reaction-diffusion systems at the particle level.

Combining molecular dynamics with mesoscopic Green’s function reaction dynamics simulations

International Nuclear Information System (INIS)

Vijaykumar, Adithya; Bolhuis, Peter G.; Rein ten Wolde, Pieter

2015-01-01

In many reaction-diffusion processes, ranging from biochemical networks, catalysis, to complex self-assembly, the spatial distribution of the reactants and the stochastic character of their interactions are crucial for the macroscopic behavior. The recently developed mesoscopic Green’s Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. We propose a novel approach that combines GFRD for simulating the system at the mesoscopic scale where particles are far apart, with a microscopic technique such as Langevin dynamics or Molecular Dynamics (MD), for simulating the system at the microscopic scale where reactants are in close proximity. This scheme defines the regions where the particles are close together and simulated with high microscopic resolution and those where they are far apart and simulated with lower mesoscopic resolution, adaptively on the fly. The new multi-scale scheme, called MD-GFRD, is generic and can be used to efficiently simulate reaction-diffusion systems at the particle level

Cold and ultracold dynamics of the barrierless D{sup +} + H{sub 2} reaction: Quantum reactive calculations for ∼R{sup −4} long range interaction potentials

Energy Technology Data Exchange (ETDEWEB)

Lara, Manuel, E-mail: manuel.lara@uam.es [Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Jambrina, P. G.; Aoiz, F. J. [Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid (Spain); Launay, J.-M. [Institut de Physique de Rennes, UMR CNRS 6251, Université de Rennes I, F-35042 Rennes (France)

2015-11-28

Quantum reactive and elastic cross sections and rate coefficients have been calculated for D{sup +} + H{sub 2} (v = 0, j = 0) collisions in the energy range from 10{sup −8} K (deep ultracold regime), where only one partial wave is open, to 150 K (Langevin regime) where many of them contribute. In systems involving ions, the ∼R{sup −4} behavior extends the interaction up to extremely long distances, requiring a special treatment. To this purpose, we have used a modified version of the hyperspherical quantum reactive scattering method, which allows the propagations up to distances of 10{sup 5} a{sub 0} needed to converge the elastic cross sections. Interpolation procedures are also proposed which may reduce the cost of exact dynamical calculations at such low energies. Calculations have been carried out on the PES by Velilla et al. [J. Chem. Phys. 129, 084307 (2008)] which accurately reproduces the long range interactions. Results on its prequel, the PES by Aguado et al. [J. Chem. Phys. 112, 1240 (2000)], are also shown in order to emphasize the significance of the inclusion of the long range interactions. The calculated reaction rate coefficient changes less than one order of magnitude in a collision energy range of ten orders of magnitude, and it is found in very good agreement with the available experimental data in the region where they exist (10-100 K). State-to-state reaction probabilities are also provided which show that for each partial wave, the distribution of HD final states remains essentially constant below 1 K.

Unimolecular reaction dynamics of free radicals

International Nuclear Information System (INIS)

Terry A. Miller

2006-01-01

Free radical reactions are of crucial importance in combustion and in atmospheric chemistry. Reliable theoretical models for predicting the rates and products of these reactions are required for modeling combustion and atmospheric chemistry systems. Unimolecular reactions frequently play a crucial role in determining final products. The dissociations of vinyl, CH2= CH, and methoxy, CH3O, have low barriers, about 13,000 cm-1 and 8,000 cm-1, respectively. Since barriers of this magnitude are typical of free radicals these molecules should serve as benchmarks for this important class of reactions. To achieve this goal, a detailed understanding of the vinyl and methoxy radicals is required. Results for dissociation dynamics of vinyl and selectively deuterated vinyl radical are reported. Significantly, H-atom scrambling is shown not to occur in this reaction. A large number of spectroscopic experiments for CH3O and CHD2O have been performed. Spectra recorded include laser induced fluorescence (LIF), laser excited dispersed fluorescence (LEDF), fluorescence dip infrared (FDIR) and stimulated emission pumping (SEP). Such results are critical for implementing dynamics experiments involving the dissociation of methoxy

Cross-section calculations for neutron-induced reactions up to 50 MeV

International Nuclear Information System (INIS)

Yamamuro, Nobuhiro.

1996-01-01

In the field of accelerator development, medium-energy reaction cross-section data for structural materials of accelerator and shielding components are required, especially for radiation protection purposes. For a d + Li stripping reaction neutron source used in materials research, neutron reaction cross sections up to 50 MeV are necessary for the design study of neutron irradiation facilities. The current version of SINCROS-II is able to calculate neutron and proton-induced reaction cross sections up to ∼ 50 MeV with some modifications and extensions of the cross-section calculation code. The production of isotopes when structural materials and other materials are bombarded with neutrons or protons is calculated using a revised code in the SINCROS-II system. The parameters used in the cross-section calculations are mainly examined with proton-induced reactions because the experimental data for neutrons above 20 MeV are rare. The status of medium mass nuclide evaluations for aluminum, silicon, chromium, manganese, and copper is presented. These data are useful to estimate the radiation and transmutation of nuclei in the materials

Heavy ion collision dynamics of 10,11B+10,11B reactions

Directory of Open Access Journals (Sweden)

Singh BirBikram

2015-01-01

Full Text Available The dynamical cluster-decay model (DCM of Gupta and collaborators has been applied successfully to the decay of very-light (A ∼ 30, light (A ∼ 40−80, medium, heavy and super-heavy mass compound nuclei for their decay to light particles (evaporation residues, ER, fusion-fission (ff, and quasi-fission (qf depending on the reaction conditions. We intend to extend here the application of DCM to study the extreme case of decay of very-light nuclear systems 20,21,22Ne∗ formed in 10,11B+10,11B reactions, for which experimental data is available for their binary symmetric decay (BSD cross sections, i.e., σBSD. For the systems under study, the calculations are presented for the σBSD in terms of their preformation and barrier penetration probabilities P0 and P. Interesting results are that in the decay of such lighter systems there is a competing reaction mechanism (specifically, the deep inelastic orbiting of non-compound nucleus (nCN origin together with ff. We have emipirically estimated the contribution of σnCN. Moreover, the important role of nuclear structure characteristics via P0 as well as angular momentum ℓ in the reaction dynamics are explored in the study.

Raman spectroscopic study of reaction dynamics

Science.gov (United States)

MacPhail, R. A.

1990-12-01

The Raman spectra of reacting molecules in liquids can yield information about various aspects of the reaction dynamics. The author discusses the analysis of Raman spectra for three prototypical unimolecular reactions, the rotational isomerization of n-butane and 1,2-difluoroethane, and the barrierless exchange of axial and equatorial hydrogens in cyclopentane via pseudorotation. In the first two cases the spectra are sensitive to torsional oscillations of the gauche conformer, and yield estimates of the torsional solvent friction. In the case of cyclopentane, the spectra can be used to discriminate between different stochastic models of the pseudorotation dynamics, and to determine the relevant friction coefficients.

A new global analytical potential energy surface of NaH2+ system and dynamical calculation for H(2S) + NaH+(X2Σ+) → Na+(1S) + H2(X1Σg+) reaction

Science.gov (United States)

Yuan, Meiling; Li, Wentao; Yuan, Jiuchuang

2018-05-01

A new global potential energy surface (PES) of the NaH2+ system is constructed by fitting 27,621 ab initio energy points with the neural network method. The root mean square error of the new PES is only 4.1609 × 10-4 eV. Based on the new PES, dynamical calculations have been performed using the time-dependent quantum wave packet method. These results are then compared with the H(2S) + LiH+(X2Σ+) → Li+(1S) + H2(X1Σg+) reaction. The direct abstract mechanism is found to play an important role in the reaction because only forward scattering signals on the differential cross section results for all calculated collision energies.

Calculation of astrophysical S-factor and reaction rate in 12C(p, γ)13N reaction

Science.gov (United States)

Moghadasi, A.; Sadeghi, H.; Pourimani, R.

2018-02-01

The 12C(p, γ)13N reaction is the first process in the CNO cycle. Also it is a source of low-energy solar neutrinos in various neutrino experiments. Therefore, it is of high interest to gain data of the astrophysical S-factor in low energies. By applying Faddeev's method, we calculated wave functions for the bound state of 13N. Then the cross sections for resonance and non-resonance were calculated through using Breit-Wigner and direct capture cross section formulae, respectively. After that, we calculated the total S-factor and compared it with previous experimental data, revealing a good agreement altogether. Then, we extrapolated the S-factor in zero energy and the result was 1.32 ± 0.19 (keV.b). In the end, we calculated reaction rate and compared it with NACRE data.

Bayesian inversion analysis of nonlinear dynamics in surface heterogeneous reactions.

Science.gov (United States)

Omori, Toshiaki; Kuwatani, Tatsu; Okamoto, Atsushi; Hukushima, Koji

2016-09-01

It is essential to extract nonlinear dynamics from time-series data as an inverse problem in natural sciences. We propose a Bayesian statistical framework for extracting nonlinear dynamics of surface heterogeneous reactions from sparse and noisy observable data. Surface heterogeneous reactions are chemical reactions with conjugation of multiple phases, and they have the intrinsic nonlinearity of their dynamics caused by the effect of surface-area between different phases. We adapt a belief propagation method and an expectation-maximization (EM) algorithm to partial observation problem, in order to simultaneously estimate the time course of hidden variables and the kinetic parameters underlying dynamics. The proposed belief propagation method is performed by using sequential Monte Carlo algorithm in order to estimate nonlinear dynamical system. Using our proposed method, we show that the rate constants of dissolution and precipitation reactions, which are typical examples of surface heterogeneous reactions, as well as the temporal changes of solid reactants and products, were successfully estimated only from the observable temporal changes in the concentration of the dissolved intermediate product.

Reaction dynamics of the four-centered elimination CH2OH + --> CHO + +H2: Measurement of kinetic energy release distribution and classical trajectory calculation

Science.gov (United States)

Lee, Tae Geol; Park, Seung C.; Kim, Myung Soo

1996-03-01

Mass-analyzed ion kinetic energy (MIKE) spectrum of CHO+ generated in the unimolecular dissociation of CH2OH+ was measured. Kinetic energy release distribution (KERD) was evaluated by analyzing the spectrum according to the algorithm developed previously. The average kinetic energy release evaluated from the distribution was extraordinarily large, 1.63 eV, corresponding to 75% of the reverse barrier of the reaction. A global analytical potential energy surface was constructed such that the experimental energetics was represented and that various features in the ab initio potential energy surface were closely reproduced. Classical trajectory calculation was carried out with the global analytical potential energy surface to investigate the causes for the extraordinarily large kinetic energy release. Based on the detailed dynamical calculations, it was found that the strained bending forces at the transition state and strengthening of the CO bond from double to triple bond character were mainly responsible for such a significant kinetic energy release. In addition, the dissociation products H2 and CHO+ ion were found to be rotationally excited in the trajectory calculations. This was attributed to the asymmetry of the transition state and the release of asymmetric bending forces. Also, the bending vibrational modes of CHO+ and the H2 stretching mode, which are coupled with the bending coordinates, were found to be moderately excited.

Molecular dynamics simulation of a chemical reaction

International Nuclear Information System (INIS)

Gorecki, J.; Gryko, J.

1988-06-01

Molecular dynamics is used to study the chemical reaction A+A→B+B. It is shown that the reaction rate constant follows the Arrhenius law both for Lennard-Jones and hard sphere interaction potentials between substrate particles. A. For the denser systems the reaction rate is proportional to the value of the radial distribution function at the contact point of two hard spheres. 10 refs, 4 figs

Ab initio molecular dynamics of the reaction of quercetin with superoxide radical

International Nuclear Information System (INIS)

Lespade, Laure

2016-01-01

Highlights: • Ab initio molecular dynamics is performed to describe the reaction of quercetin and superoxide. • The reaction occurs near the sites 4′ and 7 when the system contains sufficiently water molecules. • The difference of reactivity of superoxide compared to commonly used radicals as DPPH · or ABTS ·+ is explained. - Abstract: Superoxide plays an important role in biology but in unregulated concentrations it is implicated in a lot of diseases such as cancer or atherosclerosis. Antioxidants like flavonoids are abundant in plant and are good scavengers of superoxide radical. The modeling of superoxide scavenging by flavonoids from the diet still remains a challenge. In this study, ab initio molecular dynamics of the reaction of the flavonoid quercetin toward superoxide radical has been carried out using Car–Parrinello density functional theory. The study has proven different reactant solvation by modifying the number of water molecules surrounding superoxide. The reaction consists in the gift of a hydrogen atom of one of the hydroxyl groups of quercetin to the radical. When it occurs, it is relatively fast, lower than 100 fs. Calculations show that it depends largely on the environment of the hydroxyl group giving its hydrogen atom, the geometry of the first water layer and the presence of a certain number of water molecules in the second layer, indicating a great influence of the solvent on the reactivity.

Probing reaction dynamics with GDR decay

International Nuclear Information System (INIS)

Beene, J.R.

1994-01-01

The giant dipole resonance (GDR) has been a prolific source of information on the physics of the nucleus. Mostly it has taught us about nuclear structure, but recently experiments have utilized the GDR as a probe of nuclear reaction dynamics. In this report two examples of such investigations are discussed involving very different reactions and probing time scales that differ by a factor of ∼10 3

Three-dimensional TDHF calculation for reactions of unstable nuclei

Energy Technology Data Exchange (ETDEWEB)

Kim, Ka-Hae; Otsuka, Takaharu [Tokyo Univ. (Japan). Dept. of Physics; Bonche, P.

1998-07-01

The fusion is studied for reactions between a stable and an unstable nuclei with neutron skin. The reactions {sup 16,28}O+{sup 40}Ca and {sup 16}O+{sup 16,28}O are taken as examples, and the three-dimensional time-dependent Hartree-Fock method with the full Skyrme interaction is used. It is confirmed that the fusion cross section in low-energy region is sensitive to the interaction used in the calculation. (author)

Model calculations of excitation functions of neutron-induced reactions on Rh

International Nuclear Information System (INIS)

Strohmaier, Brigitte

1995-01-01

Cross sections of neutron-induced reactions on 103 Rh have been calculated by means of the statistical model and the coupled-channels optical model for incident-neutron energies up to 30 MeV. The incentive for this study was a new measurement of the 103 Rh(n, n') 103m Rh cross section which will - together with the present calculations -enter into a dosimetry-reaction evaluation. The validation of the model parameters relied on nuclear-structure data as far as possible. (author)

Dynamics of nuclear fission and heavy-ion reactions

International Nuclear Information System (INIS)

Nix, J.R.; Sierk, A.J.

1979-01-01

Large-amplitude collective motion in fission and heavy-ion reactions is studied by solving classical equations of motion for the time evolution of the nuclear shape. In the nuclear potential energy of deformation, the generalized surface energy was calculated by means of a double volume integral of a Yukawa-plus-exponential function, which was obtained by requiring that two semi-infinite slabs of constant-density nuclear matter have minimum energy at zero separation. The collective kinetic energy is calculated for nuclear flow that is a superposition of incompressible, nearly irrotational collective-shape motion and rigid-body rotation. Nuclear dissipation is included by means of the Rayleigh dissipation function, which depends upon the physical mechanism that converts collective energy into internal energy. For both ordinary two-body viscosity and a combined wall and window one-body dissipation, fission-fragment kinetic energies are calculated for the fission of nuclei throughout the periodic table and compare with experimental results. Finally, the one-body dynamics of nucleons inside a cylinder colliding with a moving piston is explicitly studied by solving exactly the collisionless Boltzmann equation for the distribution function. By examining the relative phases of the pressure at the piston and the piston's velocity, a dissipative force and an elastic restoring force can be separately identified. 9 references

Recent experimental results on level densities for compound reaction calculations

International Nuclear Information System (INIS)

Voinov, A.V.

2012-01-01

There is a problem related to the choice of the level density input for Hauser-Feshbach model calculations. Modern computer codes have several options to choose from but it is not clear which of them has to be used in some particular cases. Availability of many options helps to describe existing experimental data but it creates problems when it comes to predictions. Traditionally, different level density systematics are based on experimental data from neutron resonance spacing which are available for a limited spin interval and one parity only. On the other hand reaction cross section calculations use the total level density. This can create large uncertainties when converting the neutron resonance spacing to the total level density that results in sizable uncertainties in cross section calculations. It is clear now that total level densities need to be studied experimentally in a systematic manner. Such information can be obtained only from spectra of compound nuclear reactions. The question is does level densities obtained from compound nuclear reactions keep the same regularities as level densities obtained from neutron resonances- Are they consistent- We measured level densities of 59-64 Ni isotopes from proton evaporation spectra of 6,7 Li induced reactions. Experimental data are presented. Conclusions of how level density depends on the neutron number and on the degree of proximity to the closed shell ( 56 Ni) are drawn. The level density parameters have been compared with parameters obtained from the analysis of neutron resonances and from model predictions

Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

International Nuclear Information System (INIS)

Bradforth, S.E.

1992-11-01

The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound → bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN - , NCO - and NCS - . Transition state photoelectron spectra are presented for the following systems Br + HI, Cl + HI, F + HI, F + CH 3 0H,F + C 2 H 5 OH,F + OH and F + H 2 . A time dependent framework for the simulation and interpretation of the bound → free transition state photoelectron spectra is subsequently developed and applied to the hydrogen transfer reactions Br + HI, F + OH → O( 3 P, 1 D) + HF and F + H 2 . The theoretical approach for the simulations is a fully quantum-mechanical wave packet propagation on a collinear model reaction potential surface. The connection between the wavepacket time evolution and the photoelectron spectrum is given by the time autocorrelation function. For the benchmark F + H 2 system, comparisons with three-dimensional quantum calculations are made

Ab initio molecular dynamics of the reaction of quercetin with superoxide radical

Energy Technology Data Exchange (ETDEWEB)

Lespade, Laure, E-mail: l.lespade@ism.u-bordeaux1.fr

2016-08-22

Highlights: • Ab initio molecular dynamics is performed to describe the reaction of quercetin and superoxide. • The reaction occurs near the sites 4′ and 7 when the system contains sufficiently water molecules. • The difference of reactivity of superoxide compared to commonly used radicals as DPPH{sup ·} or ABTS{sup ·+} is explained. - Abstract: Superoxide plays an important role in biology but in unregulated concentrations it is implicated in a lot of diseases such as cancer or atherosclerosis. Antioxidants like flavonoids are abundant in plant and are good scavengers of superoxide radical. The modeling of superoxide scavenging by flavonoids from the diet still remains a challenge. In this study, ab initio molecular dynamics of the reaction of the flavonoid quercetin toward superoxide radical has been carried out using Car–Parrinello density functional theory. The study has proven different reactant solvation by modifying the number of water molecules surrounding superoxide. The reaction consists in the gift of a hydrogen atom of one of the hydroxyl groups of quercetin to the radical. When it occurs, it is relatively fast, lower than 100 fs. Calculations show that it depends largely on the environment of the hydroxyl group giving its hydrogen atom, the geometry of the first water layer and the presence of a certain number of water molecules in the second layer, indicating a great influence of the solvent on the reactivity.

Use of nuclear reaction models in cross section calculations

International Nuclear Information System (INIS)

Grimes, S.M.

1975-03-01

The design of fusion reactors will require information about a large number of neutron cross sections in the MeV region. Because of the obvious experimental difficulties, it is probable that not all of the cross sections of interest will be measured. Current direct and pre-equilibrium models can be used to calculate non-statistical contributions to neutron cross sections from information available from charged particle reaction studies; these are added to the calculated statistical contribution. Estimates of the reliability of such calculations can be derived from comparisons with the available data. (3 tables, 12 figures) (U.S.)

Semiclassical methods in chemical reaction dynamics

Energy Technology Data Exchange (ETDEWEB)

Keshavamurthy, Srihari [Univ. of California, Berkeley, CA (United States)

1994-12-01

Semiclassical approximations, simple as well as rigorous, are formulated in order to be able to describe gas phase chemical reactions in large systems. We formulate a simple but accurate semiclassical model for incorporating multidimensional tunneling in classical trajectory simulations. This model is based on the existence of locally conserved actions around the saddle point region on a multidimensional potential energy surface. Using classical perturbation theory and monitoring the imaginary action as a function of time along a classical trajectory we calculate state-specific unimolecular decay rates for a model two dimensional potential with coupling. Results are in good comparison with exact quantum results for the potential over a wide range of coupling constants. We propose a new semiclassical hybrid method to calculate state-to-state S-matrix elements for bimolecular reactive scattering. The accuracy of the Van Vleck-Gutzwiller propagator and the short time dynamics of the system make this method self-consistent and accurate. We also go beyond the stationary phase approximation by doing the resulting integrals exactly (numerically). As a result, classically forbidden probabilties are calculated with purely real time classical trajectories within this approach. Application to the one dimensional Eckart barrier demonstrates the accuracy of this approach. Successful application of the semiclassical hybrid approach to collinear reactive scattering is prevented by the phenomenon of chaotic scattering. The modified Filinov approach to evaluating the integrals is discussed, but application to collinear systems requires a more careful analysis. In three and higher dimensional scattering systems, chaotic scattering is suppressed and hence the accuracy and usefulness of the semiclassical method should be tested for such systems.

Semiclassical methods in chemical reaction dynamics

International Nuclear Information System (INIS)

Keshavamurthy, S.

1994-12-01

Semiclassical approximations, simple as well as rigorous, are formulated in order to be able to describe gas phase chemical reactions in large systems. We formulate a simple but accurate semiclassical model for incorporating multidimensional tunneling in classical trajectory simulations. This model is based on the existence of locally conserved actions around the saddle point region on a multidimensional potential energy surface. Using classical perturbation theory and monitoring the imaginary action as a function of time along a classical trajectory we calculate state-specific unimolecular decay rates for a model two dimensional potential with coupling. Results are in good comparison with exact quantum results for the potential over a wide range of coupling constants. We propose a new semiclassical hybrid method to calculate state-to-state S-matrix elements for bimolecular reactive scattering. The accuracy of the Van Vleck-Gutzwiller propagator and the short time dynamics of the system make this method self-consistent and accurate. We also go beyond the stationary phase approximation by doing the resulting integrals exactly (numerically). As a result, classically forbidden probabilties are calculated with purely real time classical trajectories within this approach. Application to the one dimensional Eckart barrier demonstrates the accuracy of this approach. Successful application of the semiclassical hybrid approach to collinear reactive scattering is prevented by the phenomenon of chaotic scattering. The modified Filinov approach to evaluating the integrals is discussed, but application to collinear systems requires a more careful analysis. In three and higher dimensional scattering systems, chaotic scattering is suppressed and hence the accuracy and usefulness of the semiclassical method should be tested for such systems

X particle effect for 6Li reaction rates calculations

International Nuclear Information System (INIS)

Kocak, G.; Balantekin, A. B.

2009-01-01

The inferred primordial 6 L i-7 L i abundances are different from standard big bang nucleosynthesis results, 6 L i is 1000 times larger and 7 L i is 3 times smaller than the big bang prediction. In big bang nucleosynthesis, negatively charged massive X particles a possible solution to explain this primordial Li abundances problem [1]. In this study, we consider only X particle effect for nuclear reactions to obtain S-factor and reaction rates for Li. All S-factors calculated within the Optical Model framework for d(α,γ)6 L i system. We showed that the enhancement effect of massive negatively charged X particle for 6 L i system reaction rate.(author)

Dynamics of synchrotron VUV-induced intracluster reactions

Energy Technology Data Exchange (ETDEWEB)

Grover, J.R. [Brookhaven National Laboratory, Upton, NY (United States)

1993-12-01

Photoionization mass spectrometry (PIMS) using the tunable vacuum ultraviolet radiation available at the National Synchrotron Light Source is being exploited to study photoionization-induced reactions in small van der Waals mixed complexes. The information gained includes the observation and classification of reaction paths, the measurement of onsets, and the determination of relative yields of competing reactions. Additional information is obtained by comparison of the properties of different reacting systems. Special attention is given to finding unexpected features, and most of the reactions investigated to date display such features. However, understanding these reactions demands dynamical information, in addition to what is provided by PIMS. Therefore the program has been expanded to include the measurement of kinetic energy release distributions.

Nuclear reaction studies

International Nuclear Information System (INIS)

Alexander, J.M.; Lacey, R.A.

1994-01-01

Research focused on the statistical and dynamical properties of ''hot'' nuclei formed in symmetric heavy-ion reactions. Theses included ''flow'' measurements and the mechanism for multifragment disassembly. Model calculations are being performed for the reactions C+C, Ne+Al, Ar+Sc, Kr+Nb, and Xe+La. It is planned to study 40 Ar reactions from 27 to 115 MeV/nucleon. 2 figs., 41 refs

Multiscale simulations of anisotropic particles combining molecular dynamics and Green's function reaction dynamics

NARCIS (Netherlands)

Vijaykumar, A.; Ouldridge, T.E.; ten Wolde, P.R.; Bolhuis, P.G.

2017-01-01

The modeling of complex reaction-diffusion processes in, for instance, cellular biochemical networks or self-assembling soft matter can be tremendously sped up by employing a multiscale algorithm which combines the mesoscopic Green's Function Reaction Dynamics (GFRD) method with explicit stochastic

Theoretical studies of chemical reaction dynamics

Energy Technology Data Exchange (ETDEWEB)

Schatz, G.C. [Argonne National Laboratory, IL (United States)

1993-12-01

This collaborative program with the Theoretical Chemistry Group at Argonne involves theoretical studies of gas phase chemical reactions and related energy transfer and photodissociation processes. Many of the reactions studied are of direct relevance to combustion; others are selected they provide important examples of special dynamical processes, or are of relevance to experimental measurements. Both classical trajectory and quantum reactive scattering methods are used for these studies, and the types of information determined range from thermal rate constants to state to state differential cross sections.

Multiscale simulations of anisotropic particles combining molecular dynamics and Green's function reaction dynamics

Science.gov (United States)

Vijaykumar, Adithya; Ouldridge, Thomas E.; ten Wolde, Pieter Rein; Bolhuis, Peter G.

2017-03-01

The modeling of complex reaction-diffusion processes in, for instance, cellular biochemical networks or self-assembling soft matter can be tremendously sped up by employing a multiscale algorithm which combines the mesoscopic Green's Function Reaction Dynamics (GFRD) method with explicit stochastic Brownian, Langevin, or deterministic molecular dynamics to treat reactants at the microscopic scale [A. Vijaykumar, P. G. Bolhuis, and P. R. ten Wolde, J. Chem. Phys. 143, 214102 (2015)]. Here we extend this multiscale MD-GFRD approach to include the orientational dynamics that is crucial to describe the anisotropic interactions often prevalent in biomolecular systems. We present the novel algorithm focusing on Brownian dynamics only, although the methodology is generic. We illustrate the novel algorithm using a simple patchy particle model. After validation of the algorithm, we discuss its performance. The rotational Brownian dynamics MD-GFRD multiscale method will open up the possibility for large scale simulations of protein signalling networks.

Use of shell model calculations in R-matrix studies of neutron-induced reactions

International Nuclear Information System (INIS)

Knox, H.D.

1986-01-01

R-matrix analyses of neutron-induced reactions for many of the lightest p-shell nuclei are difficult due to a lack of distinct resonance structure in the reaction cross sections. Initial values for the required R-matrix parameters, E,sub(lambda) and γsub(lambdac) for states in the compound system, can be obtained from shell model calculations. In the present work, the results of recent shell model calculations for the lithium isotopes have been used in R-matrix analyses of 6 Li+n and 7 Li+n reactions for E sub(n) 7 Li and 8 Li on the 6 Li+n and 7 Li+n reaction mechanisms and cross sections are discussed. (author)

A ring polymer molecular dynamics study of the isotopologues of the H + H2 reaction.

Science.gov (United States)

Suleimanov, Yury V; de Tudela, Ricardo Pérez; Jambrina, Pablo G; Castillo, Jesús F; Sáez-Rábanos, Vicente; Manolopoulos, David E; Aoiz, F Javier

2013-03-14

The inclusion of Quantum Mechanical (QM) effects such as zero point energy (ZPE) and tunneling in simulations of chemical reactions, especially in the case of light atom transfer, is an important problem in computational chemistry. In this respect, the hydrogen exchange reaction and its isotopic variants constitute an excellent benchmark for the assessment of approximate QM methods. In particular, the recently developed ring polymer molecular dynamics (RPMD) technique has been demonstrated to give very good results for bimolecular chemical reactions in the gas phase. In this work, we have performed a detailed RPMD study of the H + H(2) reaction and its isotopologues Mu + H(2), D + H(2) and Heμ + H(2), at temperatures ranging from 200 to 1000 K. Thermal rate coefficients and kinetic isotope effects have been computed and compared with exact QM calculations as well as with quasiclassical trajectories and experiment. The agreement with the QM results is good for the heaviest isotopologues, with errors ranging from 15% to 45%, and excellent for Mu + H(2), with errors below 15%. We have seen that RPMD is able to capture the ZPE effect very accurately, a desirable feature of any method based on molecular dynamics. We have also verified Richardson and Althorpe's prediction [J. O. Richardson and S. C. Althorpe, J. Chem. Phys., 2009, 131, 214106] that RPMD will overestimate thermal rates for asymmetric reactions and underestimate them for symmetric reactions in the deep tunneling regime. The ZPE effect along the reaction coordinate must be taken into account when assigning the reaction symmetry in the multidimensional case.

Multi-body simulation of a canine hind limb: model development, experimental validation and calculation of ground reaction forces

Directory of Open Access Journals (Sweden)

Wefstaedt Patrick

2009-11-01

Full Text Available Abstract Background Among other causes the long-term result of hip prostheses in dogs is determined by aseptic loosening. A prevention of prosthesis complications can be achieved by an optimization of the tribological system which finally results in improved implant duration. In this context a computerized model for the calculation of hip joint loadings during different motions would be of benefit. In a first step in the development of such an inverse dynamic multi-body simulation (MBS- model we here present the setup of a canine hind limb model applicable for the calculation of ground reaction forces. Methods The anatomical geometries of the MBS-model have been established using computer tomography- (CT- and magnetic resonance imaging- (MRI- data. The CT-data were collected from the pelvis, femora, tibiae and pads of a mixed-breed adult dog. Geometric information about 22 muscles of the pelvic extremity of 4 mixed-breed adult dogs was determined using MRI. Kinematic and kinetic data obtained by motion analysis of a clinically healthy dog during a gait cycle (1 m/s on an instrumented treadmill were used to drive the model in the multi-body simulation. Results and Discussion As a result the vertical ground reaction forces (z-direction calculated by the MBS-system show a maximum deviation of 1.75%BW for the left and 4.65%BW for the right hind limb from the treadmill measurements. The calculated peak ground reaction forces in z- and y-direction were found to be comparable to the treadmill measurements, whereas the curve characteristics of the forces in y-direction were not in complete alignment. Conclusion In conclusion, it could be demonstrated that the developed MBS-model is suitable for simulating ground reaction forces of dogs during walking. In forthcoming investigations the model will be developed further for the calculation of forces and moments acting on the hip joint during different movements, which can be of help in context with the in

Ab Initio Calculations Of Light-Ion Reactions

International Nuclear Information System (INIS)

Navratil, P.; Quaglioni, S.; Roth, R.; Horiuchi, W.

2012-01-01

The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of nuclear forces, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD employing Hamiltonians constructed within chiral effective field theory. In this contribution, we present one of such promising techniques capable of describing simultaneously both bound and scattering states in light nuclei. By combining the resonating-group method (RGM) with the ab initio no-core shell model (NCSM), we complement a microscopic cluster approach with the use of realistic interactions and a microscopic and consistent description of the clusters. We discuss applications to light nuclei scattering, radiative capture and fusion reactions.

Statistical model calculation of fission isomer excitation functions in (n,n') and (n,γ) reactions

International Nuclear Information System (INIS)

Chatterjee, A.; Athougies, A.L.; Mehta, M.K.

1977-01-01

A statistical model developed by Britt and others (1971, 1973) to analyze isomer excitation functions in spallation type reactions like (α,2n) has been adopted in fission isomer calculations for (n,n') and (n,γ) reactions. Calculations done for 235 U(n,n')sup(238m)U and 235 U(n,γ)sup(236m)U reactions have been compared with experimental measurements. A listing of the computer program ISOMER using FORTRAN IV to calculate the isomer to prompt ratios is given. (M.G.B.)

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

International Nuclear Information System (INIS)

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

1995-01-01

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

The dynamics of the H(+) + D(2) reaction: a comparison of quantum mechanical wavepacket, quasi-classical and statistical-quasi-classical results.

Science.gov (United States)

Jambrina, P G; Aoiz, F J; Bulut, N; Smith, Sean C; Balint-Kurti, G G; Hankel, M

2010-02-07

A detailed study of the proton exchange reaction H(+) + D(2)(v = 0, j = 0) --> HD + D(+) on its ground 1(1)A' potential energy surface has been carried out using 'exact' close-coupled quantum mechanical wavepacket (WP-EQM), quasi-classical trajectory (QCT), and statistical quasi-classical trajectory (SQCT) calculations for a range of collision energies starting from the reaction threshold to 1.3 eV. The WP-EQM calculations include all total angular momenta up to J(max) = 50, and therefore the various dynamical observables are converged up to 0.6 eV. It has been found that it is necessary to include all Coriolis couplings to obtain reliable converged results. Reaction probabilities obtained using the different methods are thoroughly compared as a function of the total energy for a series of J values. Comparisons are also made of total reaction cross sections as function of the collision energy, and rate constants. In addition, opacity functions, integral cross sections (ICS) and differential cross sections (DCS) are presented at 102 meV, 201.3 meV and 524.6 meV collision energy. The agreement between the three sets of results is only qualitative. The QCT calculations fail to describe the overall reactivity and most of the dynamical observables correctly. At low collision energies, the QCT method is plagued by the lack of conservation of zero point energy, whilst at higher collision energies and/or total angular momenta, the appearance of an effective repulsive potential associated with the centrifugal motion "over" the well causes a substantial decrease of the reactivity. In turn, the statistical models overestimate the reactivity over the whole range of collision energies as compared with the WP-EQM method. Specifically, at sufficiently high collision energies the reaction cannot be deemed to be statistical and important dynamical effects seem to be present. In general the WP-EQM results lie in between those obtained using the QCT and SQCT methods. One of the main

Multiscale simulations of patchy particle systems combining Molecular Dynamics, Path Sampling and Green's Function Reaction Dynamics

Science.gov (United States)

Bolhuis, Peter

Important reaction-diffusion processes, such as biochemical networks in living cells, or self-assembling soft matter, span many orders in length and time scales. In these systems, the reactants' spatial dynamics at mesoscopic length and time scales of microns and seconds is coupled to the reactions between the molecules at microscopic length and time scales of nanometers and milliseconds. This wide range of length and time scales makes these systems notoriously difficult to simulate. While mean-field rate equations cannot describe such processes, the mesoscopic Green's Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. The recently developed multiscale Molecular Dynamics Green's Function Reaction Dynamics (MD-GFRD) approach combines GFRD for simulating the system at the mesocopic scale where particles are far apart, with microscopic Molecular (or Brownian) Dynamics, for simulating the system at the microscopic scale where reactants are in close proximity. The association and dissociation of particles are treated with rare event path sampling techniques. I will illustrate the efficiency of this method for patchy particle systems. Replacing the microscopic regime with a Markov State Model avoids the microscopic regime completely. The MSM is then pre-computed using advanced path-sampling techniques such as multistate transition interface sampling. I illustrate this approach on patchy particle systems that show multiple modes of binding. MD-GFRD is generic, and can be used to efficiently simulate reaction-diffusion systems at the particle level, including the orientational dynamics, opening up the possibility for large-scale simulations of e.g. protein signaling networks.

NATO Advanced Study Institute on Advances in Chemical Reaction Dynamics

CERN Document Server

Capellos, Christos

1986-01-01

This book contains the formal lectures and contributed papers presented at the NATO Advanced Study Institute on. the Advances in Chemical Reaction Dynamics. The meeting convened at the city of Iraklion, Crete, Greece on 25 August 1985 and continued to 7 September 1985. The material presented describes the fundamental and recent advances in experimental and theoretical aspects of, reaction dynamics. A large section is devoted to electronically excited states, ionic species, and free radicals, relevant to chemical sys­ tems. In addition recent advances in gas phase polymerization, formation of clusters, and energy release processes in energetic materials were presented. Selected papers deal with topics such as the dynamics of electric field effects in low polar solutions, high electric field perturbations and relaxation of dipole equilibria, correlation in picosecond/laser pulse scattering, and applications to fast reaction dynamics. Picosecond transient Raman spectroscopy which has been used for the elucidati...

Study of dynamics of glucose-glucose oxidase-ferricyanide reaction

Science.gov (United States)

Nováková, A.; Schreiberová, L.; Schreiber, I.

2011-12-01

This work is focused on dynamics of the glucose-glucose oxidase-ferricyanide enzymatic reaction with or without sodium hydroxide in a continuous-flow stirred tank reactor (CSTR) and in a batch reactor. This reaction exhibits pH-variations having autocatalytic character and is reported to provide nonlinear dynamic behavior (bistability, excitability). The dynamical behavior of the reaction was examined within a wide range of inlet parameters. The main inlet parameters were the ratio of concentrations of sodium hydroxide and ferricyanide and the flow rate. In a batch reactor we observed an autocatalytic drop of pH from slightly basic to medium acidic values. In a CSTR our aim was to find bistability in the presence of sodium hydroxide. However, only a basic steady state was found. In order to reach an acidic steady state, we investigated the system in the absence of sodium hydroxide. Under these conditions the transition from the basic to the acidic steady state was observed when inlet glucose concentration was increased.

The Dynamics of Chemical Reactions: Atomistic Visualizations of Organic Reactions, and Homage to van 't Hoff.

Science.gov (United States)

Yang, Zhongyue; Houk, K N

2018-03-15

Jacobus Henricus van 't Hoff was the first Nobel Laureate in Chemistry. He pioneered in the study of chemical dynamics, which referred at that time to chemical kinetics and thermodynamics. The term has evolved in modern times to refer to the exploration of chemical transformations in a time-resolved fashion. Chemical dynamics has been driven by the development of molecular dynamics trajectory simulations, which provide atomic visualization of chemical processes and illuminate how dynamic effects influence chemical reactivity and selectivity. In homage to the legend of van 't Hoff, we review the development of the chemical dynamics of organic reactions, our area of research. We then discuss our trajectory simulations of pericyclic reactions, and our development of dynamic criteria for concerted and stepwise reaction mechanisms. We also describe a method that we call environment-perturbed transition state sampling, which enables trajectory simulations in condensed-media using quantum mechanics and molecular mechanics (QM/MM). We apply the method to reactions in solvent and in enzyme. Jacobus Henricus van 't Hoff (1852, Rotterdam-1911, Berlin) received the Nobel Prize for Chemistry in 1901 "in recognition of the extraordinary services he has rendered by the discovery of the laws of chemical dynamics and osmotic pressure in solutions". van 't Hoff was born the Netherlands, and earned his doctorate in Utrecht in 1874. In 1896 he moved to Berlin, where he was offered a position with more research and less teaching. van 't Hoff is considered one of the founders of physical chemistry. A key step in establishing this new field was the start of Zeitschrift für Physikalische Chemie in 1887. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mode specific dynamics of the H2 + CH3 → H + CH4 reaction studied using quasi-classical trajectory and eight-dimensional quantum dynamics methods

International Nuclear Information System (INIS)

Wang, Yan; Li, Jun; Guo, Hua; Chen, Liuyang; Yang, Minghui; Lu, Yunpeng

2015-01-01

An eight-dimensional quantum dynamical model is proposed and applied to the title reaction. The reaction probabilities and integral cross sections have been determined for both the ground and excited vibrational states of the two reactants. The results indicate that the H 2 stretching and CH 3 umbrella modes, along with the translational energy, strongly promote the reactivity, while the CH 3 symmetric stretching mode has a negligible effect. The observed mode specificity is confirmed by full-dimensional quasi-classical trajectory calculations. The mode specificity can be interpreted by the recently proposed sudden vector projection model, which attributes the enhancement effects of the reactant modes to their strong couplings with the reaction coordinate at the transition state

Temperature dependent dynamic susceptibility calculations for itinerant ferromagnets

Energy Technology Data Exchange (ETDEWEB)

Cooke, J. F.

1980-10-01

Inelastic neutron scattering experiments have revealed a variety of interesting and unusual phenomena associated with the spin dynamics of the 3-d transition metal ferromagnets nickel and iron. An extensive series of calculations based on the itinerant electron formalism has demonstrated that the itinerant model does provide an excellent quantitative as well as qualitative description of the measured spin dynamics of both nickel and iron at low temperatures. Recent angular photo emission experiments have indicated that there is a rather strong temperature dependence of the electronic spin-splitting which, from relatively crude arguments, appears to be inconsistent with neutron scattering results. In order to investigate this point and also the origin of spin-wave renormalization, a series of calculations of the dynamic susceptibility of nickel and iron has been undertaken. The results of these calculations indicate that a discrepancy exists between the interpretations of neutron and photoemission experimental results regarding the temperature dependence of the spin-splitting of the electronic energy bands.

Linear cascade calculations of matrix due to neutron-induced nuclear reactions

International Nuclear Information System (INIS)

Avila, Ricardo E

2000-01-01

A method is developed to calculate the total number of displacements created by energetic particles resulting from neutron-induced nuclear reactions. The method is specifically conceived to calculate the damage in lithium ceramics by the 6L i(n, α)T reaction. The damage created by any particle is related to that caused by atoms from the matrix recoiling after collision with the primary particle. An integral equation for that self-damage is solved by interactions, using the magic stopping powers of Ziegler, Biersack and Littmark. A projectile-substrate dependent Kinchin-Pease model is proposed, giving and analytic approximation to the total damage as a function of the initial particle energy (au)

Electromagnetic Reactions and Few-Nucleon Dynamics

Directory of Open Access Journals (Sweden)

Bacca Sonia

2014-03-01

Full Text Available We present an update on recent theoretical studies of electromagnetic reactions obtained by using the Lorentz integral transform method. The 4He nucleus will be the main focus of this report: results for the photo-disintegration and the electro-disintegration processes will be shown, as well as a recent calculation of polarizability effects in muonic atoms. We also discuss the exciting possibility to investigate inelastic reactions for mediummass nuclei in coupled-cluster theory, highlighted by the recent application to the 16O photo-nuclear cross section.

Dynamic Load Balancing of Parallel Monte Carlo Transport Calculations

International Nuclear Information System (INIS)

O'Brien, M; Taylor, J; Procassini, R

2004-01-01

The performance of parallel Monte Carlo transport calculations which use both spatial and particle parallelism is increased by dynamically assigning processors to the most worked domains. Since the particle work load varies over the course of the simulation, this algorithm determines each cycle if dynamic load balancing would speed up the calculation. If load balancing is required, a small number of particle communications are initiated in order to achieve load balance. This method has decreased the parallel run time by more than a factor of three for certain criticality calculations

Mass formula dependence of calculated spallation reaction product distributions

International Nuclear Information System (INIS)

Nishida, Takahiko; Nakahara, Yasuaki

1990-01-01

A new version of the spallation reaction simulation code NUCLEUS was developed by incorporating Uno and Yamada's mass formula. This version was used to calculate the distribution of products from the spallation of uranium nuclei by high-energy protons. The dependence of the distributions on the mass formula was examined by comparing the results with those from the original version, which is based on Cameron's mass formula and the mass table compiled by Wapstra et al. As regards the fission component of spallation products, the new version reproduces the reaction product data obtained from thin foil experiments much better, especially on the neutron excess side. (orig.) [de

Chemical dynamics simulations of X- + CH3Y → XCH3 + Y- gas-phase S(N)2 nucleophilic substitution reactions. Nonstatistical dynamics and nontraditional reaction mechanisms.

Science.gov (United States)

Manikandan, Paranjothy; Zhang, Jiaxu; Hase, William L

2012-03-29

Extensive classical chemical dynamics simulations of gas-phase X(-) + CH(3)Y → XCH(3) + Y(-) S(N)2 nucleophilic substitution reactions are reviewed and discussed and compared with experimental measurements and predictions of theoretical models. The primary emphasis is on reactions for which X and Y are halogen atoms. Both reactions with the traditional potential energy surface (PES), which include pre- and postreaction potential energy minima and a central barrier, and reactions with nontraditional PESs are considered. These S(N)2 reactions exhibit important nonstatistical atomic-level dynamics. The X(-) + CH(3)Y → X(-)---CH(3)Y association rate constant is less than the capture model as a result of inefficient energy transfer from X(-)+ CH(3)Y relative translation to CH(3)Y rotation and vibration. There is weak coupling between the low-frequency intermolecular modes of the X(-)---CH(3)Y complex and higher frequency CH(3)Y intramolecular modes, resulting in non-RRKM kinetics for X(-)---CH(3)Y unimolecular decomposition. Recrossings of the [X--CH(3)--Y](-) central barrier is important. As a result of the above dynamics, the relative translational energy and temperature dependencies of the S(N)2 rate constants are not accurately given by statistical theory. The nonstatistical dynamics results in nonstatistical partitioning of the available energy to XCH(3) +Y(-) reaction products. Besides the indirect, complex forming atomic-level mechanism for the S(N)2 reaction, direct mechanisms promoted by X(-) + CH(3)Y relative translational or CH(3)Y vibrational excitation are possible, e.g., the roundabout mechanism.

Computer code PRECIP-II for the calculation of Zr-steam reaction

International Nuclear Information System (INIS)

Suzuki, Motoye; Kawasaki, Satoru; Furuta, Teruo

1978-06-01

The computer code PRECIP-II developed, a modification of S.Malang's SIMTRAN-I, is to calculate Zr-Steam reaction under LOCA conditions. Improved are the following: 1. treatment of boundary conditions at alpha/beta phase interface during temperature decrease. 2. method of time-mesh control. 3. number of input-controllable parameters, and output format. These improvements made possible physically reasonable calculations for an increased number of temperature history patterns, including the cladding temperature excursion assumed during LOCA. Calculations were made along various transient temperature histories, with the parameters so modified as to enable fitting of numerical results of weight gain, oxide thickness and alpha phase thickness in isothermal reactions to the experimental data. Then the computed results were compared with the corresponding experimental values, which revealed that most of the differences lie within +-10%. Slow cooling effect on ductility change of Zircaloy-4 was investigated with some of the oxidized specimens by a ring compression test; the effect is only slight. (auth.)

Dynamical calculations for RHEED intensity oscillations

Science.gov (United States)

Daniluk, Andrzej

2005-03-01

A practical computing algorithm working in real time has been developed for calculating the reflection high-energy electron diffraction from the molecular beam epitaxy growing surface. The calculations are based on the use of a dynamical diffraction theory in which the electrons are taken to be diffracted by a potential, which is periodic in the dimension perpendicular to the surface. The results of the calculations are presented in the form of rocking curves to illustrate how the diffracted beam intensities depend on the glancing angle of the incident beam. Program summaryTitle of program: RHEED Catalogue identifier:ADUY Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUY Program obtainable from:CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: Pentium-based PC Operating systems or monitors under which the program has been tested: Windows 9x, XP, NT, Linux Programming language used: Borland C++ Memory required to execute with typical data: more than 1 MB Number of bits in a word: 64 bits Number of processors used: 1 Distribution format:tar.gz Number of lines in distributed program, including test data, etc.:982 Number of bytes in distributed program, including test data, etc.: 126 051 Nature of physical problem: Reflection high-energy electron diffraction (RHEED) is a very useful technique for studying growth and surface analysis of thin epitaxial structures prepared by the molecular beam epitaxy (MBE). Nowadays, RHEED is used in many laboratories all over the world where researchers deal with the growth of materials by MBE. The RHEED technique can reveal, almost instantaneously, changes either in the coverage of the sample surface by adsorbates or in the surface structure of a thin film. In most cases the interpretation of experimental results is based on the use of dynamical diffraction approaches. Such approaches are said to be quite useful in qualitative and

Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

Energy Technology Data Exchange (ETDEWEB)

Bradforth, Stephen Edmund [Univ. of California, Berkeley, CA (United States)

1992-11-01

The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound {yields} bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN^-, NCO^- and NCS^-. Transition state photoelectron spectra are presented for the following systems Br + HI, Cl + HI, F + HI, F + CH₃0H,F + C₂H₅OH,F + OH and F + H₂. A time dependent framework for the simulation and interpretation of the bound → free transition state photoelectron spectra is subsequently developed and applied to the hydrogen transfer reactions Br + HI, F + OH → O(³P, ¹D) + HF and F + H₂. The theoretical approach for the simulations is a fully quantum-mechanical wave packet propagation on a collinear model reaction potential surface. The connection between the wavepacket time evolution and the photoelectron spectrum is given by the time autocorrelation function. For the benchmark F + H₂ system, comparisons with three-dimensional quantum calculations are made.

Dependence of ICF reaction dynamics on target structure

International Nuclear Information System (INIS)

Kumar, Kamal; Dutt, Sunil; GulI, Muntazir; Ahmad, Tauseef; Rizvi, I.A.; Ali, Sabir; Agarwal, Avinash; Kumar, R.; Chaubey, A.K.

2016-01-01

The projectile structure is also found responsible for the ICF reaction processes. It is found that projectile having bigger alpha cluster is more unstable towards break up. In this context, a comparative study of 12 C and 16 O ion-beams induced reactions with different targets has been done. The deduced ICF contributions for different systems have been plotted against the target charge of different targets. It is observed that target properties may also be responsible for the interplay between CF and ICF reaction dynamics

The correlation schemes in calculations of the rate constants of some radiation chemical reactions

International Nuclear Information System (INIS)

Zagorets, P.A.; Shostenko, A.G.; Kim, V.

1983-01-01

The various correlation relationships of the evaluation of the rate constants of radiation chemical reactions of addition, abstraction and isomerization were considered. It was shown that neglection of the influence of solvent can result in errors in calculations of rate constants equalling two orders in magnitude. Several examples of isokinetic relationship are given. The methods of calculation of transmission coefficient of reaction addition have been discussed. (author)

Theoretical study and rate constant calculation for the reactions of SH (SD) with Cl2, Br2, and BrCl.

Science.gov (United States)

Wang, Li; Liu, Jing-Yao; Li, Ze-Sheng; Sun, Chia-Chung

2005-01-30

The mechanisms of the SH (SD) radicals with Cl2 (R1), Br2 (R2), and BrCl (R3) are investigated theoretically, and the rate constants are calculated using a dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MP2/6-311G(d,p) and MPW1K/6-311G(d,p) levels. Higher-level energies are obtained at the approximate QCISD(T)/6-311++G(3df, 2pd) level using the MP2 geometries as well as by the multicoefficient correlation method based on QCISD (MC-QCISD) using the MPW1K geometries. Complexes with energies less than those of the reactants or products are located at the entrance or the exit channels of these reactions, which indicate that the reactions may proceed via an indirect mechanism. The enthalpies of formation for the species XSH/XSD (X = Cl and Br) are evaluated using hydrogenation working reactions method. By canonical variational transition-state theory (CVT), the rate constants of SH and SD radicals with Cl2, Br2, and BrCl are calculated over a wide temperature range of 200-2000 K at the a-QCISD(T)/6-311++G(3df, 2pd)//MP2/6-311G(d, p) level. Good agreement between the calculated and experimental rate constants is obtained in the measured temperature range. Our calculations show that for SH (SD) + BrCl reaction bromine abstraction (R3a or R3a') leading to the formation of BrSH (BrSD) + Cl in a barrierless process dominants the reaction with the branching ratios for channels 3a and 3a' of 99% at 298 K, which is quite different from the experimental result of k3a'/k3' = 54 +/- 10%. Negative activation energies are found at the higher level for the SH + Br2 and SH + BrCl (Br-abstraction) reactions; as a result, the rate constants show a slightly negative temperature dependence, which is consistent with the determination in the literature. The kinetic isotope effects for the three reactions are "inverse". The values of kH/kD are 0.88, 0.91, and 0.69 at room temperature, respectively, and they increase

Switching dynamics in reaction networks induced by molecular discreteness

International Nuclear Information System (INIS)

Togashi, Yuichi; Kaneko, Kunihiko

2007-01-01

To study the fluctuations and dynamics in chemical reaction processes, stochastic differential equations based on the rate equation involving chemical concentrations are often adopted. When the number of molecules is very small, however, the discreteness in the number of molecules cannot be neglected since the number of molecules must be an integer. This discreteness can be important in biochemical reactions, where the total number of molecules is not significantly larger than the number of chemical species. To elucidate the effects of such discreteness, we study autocatalytic reaction systems comprising several chemical species through stochastic particle simulations. The generation of novel states is observed; it is caused by the extinction of some molecular species due to the discreteness in their number. We demonstrate that the reaction dynamics are switched by a single molecule, which leads to the reconstruction of the acting network structure. We also show the strong dependence of the chemical concentrations on the system size, which is caused by transitions to discreteness-induced novel states

Empire-3.2 Malta. Modular System for Nuclear Reaction Calculations and Nuclear Data Evaluation. User's Manual

International Nuclear Information System (INIS)

Herman, M.; Capote, R.; Sin, M.

2013-08-01

EMPIRE is a modular system of nuclear reaction codes, comprising various nuclear models, and designed for calculations over a broad range of energies and incident particles. The system can be used for theoretical investigations of nuclear reactions as well as for nuclear data evaluation work. Photons, nucleons, deuterons, tritons, helions ( 3 He), α's, and light or heavy ions can be selected as projectiles. The energy range starts just above the resonance region in the case of a neutron projectile, and extends up to few hundred MeV for heavy ion induced reactions. The code accounts for the major nuclear reaction models, such as optical model, Coupled Channels and DWBA (ECIS06 and OPTMAN), Multi-step Direct (ORION + TRISTAN), NVWY Multi-step Compound, exciton model (PCROSS), hybrid Monte Carlo simulation (DDHMS), and the full featured Hauser-Feshbach model including width fluctuations and the optical model for fission. Heavy ion fusion cross section can be calculated within the simplified coupled channels approach (CCFUS). A comprehensive library of input parameters based on the RIPL-3 library covers nuclear masses, optical model parameters, ground state deformations, discrete levels and decay schemes, level densities, fission barriers, and γ-ray strength functions. Effects of the dynamic deformation of a fast rotating nucleus can be taken into account in the calculations (BARFIT, MOMFIT). The results can be converted into the ENDF-6 format using the accompanying EMPEND code. Modules of the ENDF Utility Codes and the ENDF Pre-Processing codes are applied for ENDF file verification. The package contains the full EXFOR library of experimental data in computational format C4 that are automatically retrieved during the calculations. EMPIRE contains the resonance module that retrieves data from the electronic version of the Atlas of Neutron Resonances by Mughabghab (not provided with the EMPIRE distribution), to produce resonance section and related covariances for the

Dynamics of anion-molecule reactions at low energy

International Nuclear Information System (INIS)

Mikosch, J.

2007-11-01

Anion-molecule reactions must find their way through deeply bound entrance and exit channel complexes separated by a central barrier. This results in low reaction rates and rich dynamics since direct pathways compete with the formation of transient intermediates. In this thesis we examine the probability of proton transfer to a small anion and transient lifetimes of a thermoneutral bimolecular nucleophilic substitution (S N 2) reaction at well defined variable temperature down to 8 Kelvin in a multipole trap. The observed strong inverse temperature dependence is attributed to the deficit of available quantum states in the entrance channel at decreasing temperature. Furthermore we investigate scattering dynamics of S N 2 reactions at defined relative energy between 0.4 and 10 eV by crossed beam slice imaging. A weakly exothermic reaction with high central barrier proceeds via an indirect, complex-mediated mechanism at low relative energies featuring high internal product excitation in excellent quantitative agreement with a statistical model. In contrast, direct backward scattering prevails for higher energies with product velocities close to the kinematical cutoff. For a strongly exothermic reaction, competing S N 2-, dihalide- and proton transfer-channels are explored which proceed by complex mediation for low energy and various rebound-, grazing- and collision induced bond rupture-mechanisms at higher energy. From our data and a collaboration with theory we identify a new indirect roundabout S N 2 mechanism involving CH 3 -rotation. (orig.)

Dynamics of anion-molecule reactions at low energy

Energy Technology Data Exchange (ETDEWEB)

Mikosch, J.

2007-11-15

Anion-molecule reactions must find their way through deeply bound entrance and exit channel complexes separated by a central barrier. This results in low reaction rates and rich dynamics since direct pathways compete with the formation of transient intermediates. In this thesis we examine the probability of proton transfer to a small anion and transient lifetimes of a thermoneutral bimolecular nucleophilic substitution (S{sub N}2) reaction at well defined variable temperature down to 8 Kelvin in a multipole trap. The observed strong inverse temperature dependence is attributed to the deficit of available quantum states in the entrance channel at decreasing temperature. Furthermore we investigate scattering dynamics of S{sub N}2 reactions at defined relative energy between 0.4 and 10 eV by crossed beam slice imaging. A weakly exothermic reaction with high central barrier proceeds via an indirect, complex-mediated mechanism at low relative energies featuring high internal product excitation in excellent quantitative agreement with a statistical model. In contrast, direct backward scattering prevails for higher energies with product velocities close to the kinematical cutoff. For a strongly exothermic reaction, competing S{sub N}2-, dihalide- and proton transfer-channels are explored which proceed by complex mediation for low energy and various rebound-, grazing- and collision induced bond rupture-mechanisms at higher energy. From our data and a collaboration with theory we identify a new indirect roundabout S{sub N}2 mechanism involving CH{sub 3}-rotation. (orig.)

Calculation of thermodynamic equilibrium for reactions of plutonium with air

International Nuclear Information System (INIS)

Zou Lexi; Sun Ying; Luo Deli; Xue Weidong; Zhu Zhenghe; Wang Rong

2000-01-01

There are six independent component with 4 chemical elements, i.e. PuH 2.7 (s), PuN(s), Pu 2 O 3 (s), N 2 (g) and H 2 (g), therefore, the system described involves of 2 independent reactions, both ΔG degree << O. The mass balances calculated for gas and solid phases are in good agreement with those of experimental, indicating the chemical equilibrium is nearly approached. So, it is believed that the reaction ratio of plutonium hydride with air is extremely rapid. The results are meaningful to the storage of plutonium

Communication: Rate coefficients from quasiclassical trajectory calculations from the reverse reaction: The Mu + H2 reaction re-visited

Science.gov (United States)

Homayoon, Zahra; Jambrina, Pablo G.; Aoiz, F. Javier; Bowman, Joel M.

2012-07-01

In a previous paper [P. G. Jambrina et al., J. Chem. Phys. 135, 034310 (2011), 10.1063/1.3611400] various calculations of the rate coefficient for the Mu + H2 → MuH + H reaction were presented and compared to experiment. The widely used standard quasiclassical trajectory (QCT) method was shown to overestimate the rate coefficients by several orders of magnitude over the temperature range 200-1000 K. This was attributed to a major failure of that method to describe the correct threshold for the reaction owing to the large difference in zero-point energies (ZPE) of the reactant H2 and product MuH (˜0.32 eV). In this Communication we show that by performing standard QCT calculations for the reverse reaction and then applying detailed balance, the resulting rate coefficient is in very good agreement with the other computational results that respect the ZPE, (as well as with the experiment) but which are more demanding computationally.

Calculation of the Reaction Cross Section for Several Actinides

International Nuclear Information System (INIS)

Hambsch, Franz-Josef; Oberstedt, Stephan; Vladuca, Gheorghita; Tudora, Anabella; Filipescu, Dan

2005-01-01

New, self-consistent, neutron-induced reaction cross-section calculations for 235,238U, 237Np, and 231,232,233Pa have been performed. The statistical model code STATIS was extended to take into account the multi-modality of the fission process. The three most dominant fission modes, the two asymmetric standard I (S1) and standard II (S2) modes, and the symmetric superlong (SL) mode have been taken into account. De-convoluted fission cross sections for these modes in 235,238U(n,f) and 237Np(n,f) based on experimental branching ratios, were calculated for the first time up to the second chance fission threshold. For 235U(n,f) and 233Pa(n,f), the calculations being made up to 50 MeV and 20 MeV incident neutron energy, respectively, higher fission chances have been considered. This implied the need for additional calculations for the neighbouring isotopes.As a side product also mass yield distributions could be calculated at energies hitherto not accessible by experiment. Experimental validation of the predictions is being envisaged

Ultrafast infrared studies of chemical reaction dynamics in room-temperature liquids

Energy Technology Data Exchange (ETDEWEB)

Yang, Haw [Univ. of California, Berkeley, CA (United States)

1999-11-01

Femtosecond infrared spectroscopy provides sufficient spectral and temporal resolution to support a detailed investigation of the early events of a photochemical reaction. Previously unreported transient species that arise as intermediates during the course of a reaction may have lifetimes that are too short for conventional characterization. For these species, quantum-mechanical (density functional theoretical and ab initio) electronic structure calculations provide invaluable insight into chemical properties including molecular structure and energetic. With the combination of experimental and theoretical results, it is possible to assemble a comprehensive picture of the reaction dynamics of a system that is intricately influenced by the surrounding solvent molecules. The mechanisms of several important organometallic reactions, such as alkane C– H bond activation by η³-Tp*Rh(CO), silane Si–H bond activation by η⁵-CpMn(CO)₂ and η⁵-CpRe(CO)₂, as well as chlorinated methane C–Cl bond cleavage by the Re(CO)₅ radical are elucidated. The results demonstrate the importance of molecular morphology change (C–H and Si–H act ivat ion), solvent rearrangement (Si–H activation), intersystem crossing (Si–H activation), and solvent caging (C–Cl cleavage) in understanding the reactivity of the organometallic species, The nature of the apparent free-energy barrier for C–H, Si–H, and C–Cl bond activation reaction is found to be- cleavage of an alkane C–H bond, rearrangement of a silane molecule HSiR₃ (R = alkyl group) from a nonreactive alkyl site to the reactive Si–H bond, and Cl atom transfer from a chlorinated methane molecule to Re(CO)₅, respectively. These results support previous d initio calculations for C–H and Si–H bond activation reaction profiles which suggest that cleavage of an alkane C–H bond by a transition metal center, unlike that of a silane

Reaction dynamics in polyatomic molecular systems

Energy Technology Data Exchange (ETDEWEB)

Miller, W.H. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

The goal of this program is the development of theoretical methods and models for describing the dynamics of chemical reactions, with specific interest for application to polyatomic molecular systems of special interest and relevance. There is interest in developing the most rigorous possible theoretical approaches and also in more approximate treatments that are more readily applicable to complex systems.

Stochastic modeling and simulation of reaction-diffusion system with Hill function dynamics.

Science.gov (United States)

Chen, Minghan; Li, Fei; Wang, Shuo; Cao, Young

2017-03-14

Stochastic simulation of reaction-diffusion systems presents great challenges for spatiotemporal biological modeling and simulation. One widely used framework for stochastic simulation of reaction-diffusion systems is reaction diffusion master equation (RDME). Previous studies have discovered that for the RDME, when discretization size approaches zero, reaction time for bimolecular reactions in high dimensional domains tends to infinity. In this paper, we demonstrate that in the 1D domain, highly nonlinear reaction dynamics given by Hill function may also have dramatic change when discretization size is smaller than a critical value. Moreover, we discuss methods to avoid this problem: smoothing over space, fixed length smoothing over space and a hybrid method. Our analysis reveals that the switch-like Hill dynamics reduces to a linear function of discretization size when the discretization size is small enough. The three proposed methods could correctly (under certain precision) simulate Hill function dynamics in the microscopic RDME system.

Analysis of Brownian Dynamics Simulations of Reversible Bimolecular Reactions

KAUST Repository

Lipková, Jana

2011-01-01

A class of Brownian dynamics algorithms for stochastic reaction-diffusion models which include reversible bimolecular reactions is presented and analyzed. The method is a generalization of the λ-bcȳ model for irreversible bimolecular reactions which was introduced in [R. Erban and S. J. Chapman, Phys. Biol., 6(2009), 046001]. The formulae relating the experimentally measurable quantities (reaction rate constants and diffusion constants) with the algorithm parameters are derived. The probability of geminate recombination is also investigated. © 2011 Society for Industrial and Applied Mathematics.

To address surface reaction network complexity using scaling relations machine learning and DFT calculations

International Nuclear Information System (INIS)

Ulissi, Zachary W.; Medford, Andrew J.; Bligaard, Thomas; Nørskov, Jens K.

2017-01-01

Surface reaction networks involving hydrocarbons exhibit enormous complexity with thousands of species and reactions for all but the very simplest of chemistries. We present a framework for optimization under uncertainty for heterogeneous catalysis reaction networks using surrogate models that are trained on the fly. The surrogate model is constructed by teaching a Gaussian process adsorption energies based on group additivity fingerprints, combined with transition-state scaling relations and a simple classifier for determining the rate-limiting step. The surrogate model is iteratively used to predict the most important reaction step to be calculated explicitly with computationally demanding electronic structure theory. Applying these methods to the reaction of syngas on rhodium(111), we identify the most likely reaction mechanism. Lastly, propagating uncertainty throughout this process yields the likelihood that the final mechanism is complete given measurements on only a subset of the entire network and uncertainty in the underlying density functional theory calculations.

Carrying out thermodynamic calculations and definition of the main reactions of decomposition of vapours of ethyl alcohol

International Nuclear Information System (INIS)

Sechin, A I; Kyrmakova, O S; Ivanova, T A

2015-01-01

Thermodynamic opportunities of course of chemical reactions of decomposition of the vapors of ethyl alcohol necessary at development of devices where these reactions will take place are considered. The entalpiyny method of calculation of constants of balance of probable chemical reactions is given in the Excel editor. Independent reactions of process of oxidation are defined. By result of thermodynamic calculation of each reaction schedules of dependence of a constant of balance on environment temperature from which follows are constructed that one reactions proceed until the end of aside formation of the final products, and others are improbable or impossible. The analysis of the received results shows that reactions of oxidation will successfully proceed in the established directions, and for an intensification of process of decomposition it is necessary to provide a supply of some energy which quantity will be sufficient for oxidation of vapors of ethyl alcohol. Results of calculations showed good convergence with programs of thermodynamic calculations like 'Aster - 4' and 'TERRA'. (paper)

Nuclear Research Center IRT reactor dynamics calculation

International Nuclear Information System (INIS)

Aleman Fernandez, J.R.

1990-01-01

The main features of the code DIRT, for dynamical calculations are described in the paper. With the results obtained by the program, an analysis of the dynamic behaviour of the Research Reactor IRT of the Nuclear Research Center (CIN) is performed. Different transitories were considered such as variation of the system reactivity, coolant inlet temperature variation and also variations of the coolant velocity through the reactor core. 3 refs

Theoretical calculation of n + {sup 59}Co reaction in energy region up to 100 MeV

Energy Technology Data Exchange (ETDEWEB)

Qingbiao, Shen; Baosheng, Yu; Dunjiu, Cai [Chinese Nuclear Data Center, Beijing, BJ (China)

1996-06-01

A set of neutron optical potential parameters for {sup 59}Co in energy region of 2{approx}100 MeV was obtained based on concerned experimental data. Various cross sections of n + {sup 59}Co reactions were calculated and predicted. The calculated results show that the activation products {sup 58,57}Co, {sup 59}Fe and {sup 56}Mn are main neutron monitor reaction products for n + {sup 59}Co reaction in energy range up to 100 MeV. {sup 54}Mn production reaction can be a promising neutron monitor reaction in the energy region from 30 to 100 MeV. (6 figs.).

The Paterno-Buchi reaction

DEFF Research Database (Denmark)

Brogaard, Rasmus Yding; Schalk, Oliver; Boguslavskiy, Andrey E.

2012-01-01

The Paternò-Büchi (PB) reaction between an excited carbonyl compound and an alkene has been widely studied, but so far little is known about the excited-state dynamics of the reaction. In this investigation, we used a compound in which a formyl and a vinyl group are attached to a [2.......2]paracyclophane in order to obtain a model system in pre-reactive conformation for the PB reaction. We studied the excited-state dynamics of the isolated molecule in a molecular beam using femtosecond time-resolved photoelectron spectroscopy and ab initio calculations. The results show that inter-system crossing...... within two picoseconds competes efficiently with the reaction in the singlet manifold. Thus, the PB reaction in this model system takes place in the triplet state on a time scale of nanoseconds. This result stresses the importance of triplet states in the excited-state pathway of the PB reaction...

molecular dynamics simulations and quantum chemical calculations

African Journals Online (AJOL)

ABSTRACT. The molecular dynamic (MD) simulation and quantum chemical calculations for the adsorption of [2-(2-Henicos-10- .... electronic properties of molecule clusters, surfaces and ... The local reactivity was analyzed by determining the.

Soft tissue deformation modelling through neural dynamics-based reaction-diffusion mechanics.

Science.gov (United States)

Zhang, Jinao; Zhong, Yongmin; Gu, Chengfan

2018-05-30

Soft tissue deformation modelling forms the basis of development of surgical simulation, surgical planning and robotic-assisted minimally invasive surgery. This paper presents a new methodology for modelling of soft tissue deformation based on reaction-diffusion mechanics via neural dynamics. The potential energy stored in soft tissues due to a mechanical load to deform tissues away from their rest state is treated as the equivalent transmembrane potential energy, and it is distributed in the tissue masses in the manner of reaction-diffusion propagation of nonlinear electrical waves. The reaction-diffusion propagation of mechanical potential energy and nonrigid mechanics of motion are combined to model soft tissue deformation and its dynamics, both of which are further formulated as the dynamics of cellular neural networks to achieve real-time computational performance. The proposed methodology is implemented with a haptic device for interactive soft tissue deformation with force feedback. Experimental results demonstrate that the proposed methodology exhibits nonlinear force-displacement relationship for nonlinear soft tissue deformation. Homogeneous, anisotropic and heterogeneous soft tissue material properties can be modelled through the inherent physical properties of mass points. Graphical abstract Soft tissue deformation modelling with haptic feedback via neural dynamics-based reaction-diffusion mechanics.

TDHF calculations for heavy-ion collisions

International Nuclear Information System (INIS)

Dhar, A.K.

1981-01-01

In considering the TDHF theory for heavy-ion reaction calculations it is shown that this parameter-free approach spans a wide range of nuclear phenomena ranging from elastic scattering to fusion, including dissipative and collective processes, in a unified manner. The subject is considered under the headings: (1) TDHF equations, conservation laws, effective hamiltonian and initial conditions. (2) Symmetries and filling approximation. (3) Qualitative features of TDHF dynamics. (4) Comparison with experiment (fusion results, deep-inelastic reaction studies, particle emission from TDHF calculations). (U.K.)

Fast fission phenomenon, deep inelastic reactions and compound nucleus formation described within a dynamical macroscopic model

International Nuclear Information System (INIS)

Gregoire, C.; Ngo, C.; Remaud, B.

1982-01-01

We present a dynamical model to describe dissipative heavy ion reactions. It treats explicitly the relative motion of the two ions, the mass asymmetry of the system and the projection of the isospin of each ion. The deformations, which are induced during the collision, are simulated with a time-dependent interaction potential. This is done by a time-dependent transition between a sudden interaction potential in the entrance channel and an adiabatic potential in the exit channel. The model allows us to compute the compound-nucleus cross section and multidifferential cross-sections for deep inelastic reactions. In addition, for some systems, and under certain conditions which are discussed in detail, a new dissipative heavy ion collision appears: fast-fission phenomenon which has intermediate properties between deep inelastic and compound nucleus reactions. The calculated properties concerning fast fission are compared with experimental results and reproduce some of those which could not be understood as belonging to deep inelastic or compound-nucleus reactions. (orig.)

Reaction matrix calculation of 4He including Δ degrees of freedom

International Nuclear Information System (INIS)

Wakamatsu, Masashi.

1979-06-01

The effects of the Δ(3-3 resonance) components on the binding energy of 4 He are studied within the framework of the reaction matrix theory. In this approach, the Δ configurations in 4 He are introduced in terms of the NΔ transition potential by solving the reaction matrix equation and thus it goes beyond perturbation theory with the NΔ transition potential. Not only the two-body cluster energy but also the three-body cluster energy containing Δ configurations are calculated. (author)

Cross Sections Calculations of ( d, t) Nuclear Reactions up to 50 MeV

Science.gov (United States)

Tel, E.; Yiğit, M.; Tanır, G.

2013-04-01

In nuclear fusion reactions two light atomic nuclei fuse together to form a heavier nucleus. Fusion power is the power generated by nuclear fusion processes. In contrast with fission power, the fusion reaction processes does not produce radioactive nuclides. The fusion will not produce CO2 or SO2. So the fusion energy will not contribute to environmental problems such as particulate pollution and excessive CO2 in the atmosphere. Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production is still believed to be unlikely before 2050. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. In the fusion reactor, tritium self-sufficiency must be maintained for a commercial power plant. Therefore, for self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of ( d, t) nuclear reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. Since the experimental data of charged particle induced reactions are scarce, self-consistent calculation and analyses using nuclear theoretical models are very important. In this study, ( d, t) cross sections for target nuclei 19F, 50Cr, 54Fe, 58Ni, 75As, 89Y, 90Zr, 107Ag, 127I, 197Au and 238U have been investigated up to 50 MeV deuteron energy. The excitation functions for ( d, t) reactions have been calculated by pre-equilibrium reaction mechanism. Calculation results have been also compared with the available measurements in

Dynamically biased statistical model for the ortho/para conversion in the H2 + H3+ → H3+ + H2 reaction

OpenAIRE

Gómez-Carrasco, Susana; González-Sánchez, Lola; Aguado, Alfredo; Sanz-Sanz, Cristina; Zanchet, Alexandre; Roncero, Octavio

2012-01-01

In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)10.1063/1.2430711]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constrain...

Calculation of astrophysical S-factor in reaction ^{13}C(p,γ )^{14}N for first resonance levels

Science.gov (United States)

Moghadasi, A.; Sadeghi, H.; Pourimani, R.

2018-01-01

The ^{13}C(p,γ )^{14}N reaction is one of the important reactions in the CNO cycle, which is a key process in nucleosynthesis. We first calculated wave functions for the bound state of ^{14}N with Faddeev's method. In this method, the considered reaction components are ^{12}C+n+p. Then, by using direct capture cross section and Breit-Wigner formulae, the non-resonant and resonant cross sections were calculated, respectively. In the next step, we calculated the total S-factor and compared it with experimental data, which showed good agreement between them. Next, we extrapolated the S-factor for the transition to the ground state at zero energy and obtained S(0)=5.8 ± 0.7 (keV b) and then calculate reaction rate. These ones are in agreement with previous reported results.

Imaging the reactions of molecular dications: a new probe of dicationic reaction dynamics and energetics

International Nuclear Information System (INIS)

Wan-Ping Hu, S.; Harper, S.M.; Price, S.D.

2002-01-01

Experiments which generated angularly resolved data to prove the dynamics of dication chemical reactions were performed using a position sensitive coincidence (PSCO) apparatus, to detect in coincidence both of the charged products from such reaction. It consists of a ion source, a hemispherical energy analyser, and a time-of-flight mass spectrometer. Initial experiments to test the apparatus performance were runned on the atomic electron transfer reaction: Ne 2+ + Ar → Ne + + Ar + . Angular distributions, translational and internal energies of the product ions were extracted, as well as the scattering diagram among other data. (nevyjel)

The reaction rate for dissociative adsorption of N-2 on stepped Ru(0001): Six-dimensional quantum calculations

DEFF Research Database (Denmark)

van Harrevelt, Rob; Honkala, Johanna Karoliina; Nørskov, Jens Kehlet

2005-01-01

Quantum-mechanical calculations of the reaction rate for dissociative adsorption of N-2 on stepped Ru(0001) are presented. Converged six-dimensional quantum calculations for this heavy-atom reaction have been performed using the multiconfiguration time-dependent Hartree method. A potential...

Fusion-fission dynamics

International Nuclear Information System (INIS)

Blocki, J.; Planeta, R.; Brzychczyk, J.; Grotowski, K.

1991-04-01

Classical dynamical calculations of the heavy ion induced fission process for the reactions 40 Ar+ 141 Pr, 20 Ne+ 165 Ho and 12 C+ 175 Lu leading to the iridium like nucleus have been performed. As a result prescission lifetimes were obtained and compared with the experimental values. The agreement between the calculated and experimental lifetimes indicates that the one-body dissipation picture is much more relevant in describing the fusion-fission dynamics than the two-body one. Somewhat bigger calculated times than the experimental ones in case of the C+Lu reaction at 16 MeV/nucleon may be a signal on the energy range applicability of the one-body dissipation model. (author)

Study of the intermediate-energy nucleon-nucleus reactions in terms of the quantum molecular dynamics

International Nuclear Information System (INIS)

Chiba, Satoshi; Niita, Koji; Maruyama, Toshiki; Fukahori, Tokio; Takada, Hiroshi; Iwamoto, Akira

1995-01-01

The double-differential (p,xp') and (p,xn) reaction cross sections of 58 Ni and 90 Zr in the energy range from 120 to 200 MeV have been studied in terms of the Quantum Molecular Dynamics. It was found that the present calculation could give a quantitative explanation of experimentally observed values of both channels simultaneously without adjusting any parameter, showing the usefulness of the QMD approach to study the pre-equilibrium process in this energy region. Comparisons were also made with prediction of other theories such as Antisymmetrized Molecular Dynamics (AMD) and semiclassical distorted wave theory. Effect of the anti-symmetrization, which is in AMD but not in QMD, was found surprisingly small, being the result of QMD even slightly better. At the same time, it was found that the present calculation does not give the quasi-free peak of the 1-step cross sections similar to the semiclassical model, due probably to different treatment of the refraction and acceleration effects caused by the mean field. (author)

Quantum chemical and conventional TST calculations of rate constants for the OH + alkane reaction

International Nuclear Information System (INIS)

Bravo-Perez, Graciela; Alvarez-Idaboy, J. Raul; Jimenez, Annia Galano; Cruz-Torres, Armando

2005-01-01

Reactions of OH with methane, ethane, propane, i-butane, and n-butane have been modeled using ab initio (MP2) and hybrid DFT (BHandHLYP) methods, and the 6-311G(d,p) basis set. Furthermore, single-point calculations at the CCSD(T) level were carried out at the optimized geometries. The rate constants have been calculated using the conventional transition-state theory (CTST). Arrhenius equations are proposed in the temperature range of 250-650 K. Hindered Internal Rotation partition functions calculations were explicitly carried out and included in the total partition functions. These corrections showed to be relevant in the determination of the pre-exponential parameters, although not so important as in the NO 3 + alkane reactions [G. Bravo-Perez, J.R. Alvarez-Idaboy, A. Cruz-Torres, M.E. Ruiz, J. Phys. Chem. A 106 (2002) 4645]. The explicit participation of the tunnel effect has been taken into account. The calculated rate coefficients provide a very good agreement with the experimental data. The best agreement for the overall alkane + OH reactions seemed to occur when the BHandHLYP geometries and partition functions are used. For propane and i-butane, in addition to the respective secondary and tertiary H-abstraction channels, the primary one has been considered. These pathways are confirmed to be significant in spite of the large differences in activation energies between primary and secondary or primary and tertiary channels, respectively of propane and i-butane reactions and should not be disregarded

Quantum wave packet study of D+OF reaction

International Nuclear Information System (INIS)

Kurban, M.; Karabulut, E.; Tutuk, R.; Goektas, F.

2010-01-01

The quantum dynamics of the D+OF reaction on the adiabatic potential energy surface of the ground 1 3 A ' state has been studied by using a time-dependent quantum real wave packet method. The state-to-state and state-to-all reaction probabilities for total angular momentum J = 0 have been calculated. The probabilities for J > 0 have been calculated by J-shifting the J = 0 results by means of capture model. Then, the integral cross sections and initial state selected rate constants have been calculated. The initial state-selected reaction probabilities and reaction cross section show threshold but not manifest any resonances and the initial state selected rate constants are sensitive to the temperature.

Automated Discovery of New Chemical Reactions and Accurate Calculation of Their Rates

Science.gov (United States)

2015-06-02

chemistry calculations are run. The product matrices P are obtained and converted to block structure by simple linear algebra operations...in the system, i.e. 0 , =∑ ji ija Usually in elementary reactions |aij|ɛ since the change by two implies a significant chemical process, for...instance, formation or rupture of a double bond in a single elementary step. After applying the reaction matrix A, the product matrix P can then be

Stability and dynamics of reactors with heterogeneously catalyzed reactions

Energy Technology Data Exchange (ETDEWEB)

Eigenberger, G [BASF A.G., Ludwigshafen am Rhein (Germany, F.R.)

1978-12-01

Our knowledge of causes and consequences of problems arising from instability and dynamic effects in reactors with heterogeneously catalyzed reactions has increased remarkably in recent years. Especially thermal effects, caused by the self-acceleration of an exothermic reaction in combination with heat and mass transport, are now well understood. In addition, kinetic effects, i.e. phenomena which have to be explained by the kinetic peculiarities of surface reactions, have attracted increasing interest. For both cases the state of the art will be reviewed, highlighting the physical and chemical causes of the observed phenomena.

Mechanistic Insights into Radical-Mediated Oxidation of Tryptophan from ab Initio Quantum Chemistry Calculations and QM/MM Molecular Dynamics Simulations.

Science.gov (United States)

Wood, Geoffrey P F; Sreedhara, Alavattam; Moore, Jamie M; Wang, John; Trout, Bernhardt L

2016-05-12

An assessment of the mechanisms of (•)OH and (•)OOH radical-mediated oxidation of tryptophan was performed using density functional theory calculations and ab initio plane-wave Quantum Mechanics/Molecular Mechanics (QM/MM) molecular dynamics simulations. For the (•)OH reactions, addition to the pyrrole ring at position 2 is the most favored site with a barrierless reaction in the gas phase. The subsequent degradation of this adduct through a H atom transfer to water was intermittently observed in aqueous-phase molecular dynamics simulations. For the (•)OOH reactions, addition to the pyrrole ring at position 2 is the most favored pathway, in contrast to the situation in the model system ethylene, where concerted addition to the double bond is preferred. From the (•)OOH position 2 adduct QM/MM simulations show that formation of oxy-3-indolanaline occurs readily in an aqueous environment. The observed transformation starts from an initial rupture of the O-O bond followed by a H atom transfer with the accompanying loss of an (•)OH radical to solution. Finally, classical molecular dynamics simulations were performed to equate observed differential oxidation rates of various tryptophan residues in monoclonal antibody fragments. It was found that simple parameters derived from simulation correlate well with the experimental data.

Fe IX CALCULATIONS FOR THE SOLAR DYNAMICS OBSERVATORY

International Nuclear Information System (INIS)

Foster, Adam R.; Testa, Paola

2011-01-01

New calculations of the energy levels, radiative transition rates, and collisional excitation rates of Fe IX have been carried out using the Flexible Atomic Code, paying close attention to experimentally identified levels and extending existing calculations to higher energy levels. For lower levels, R-matrix collisional excitation rates from earlier work have been used. Significant emission is predicted by these calculations in the 5f-3d transitions, which will impact analysis of Solar Dynamics Observatory Atmospheric Imaging Assembly observations using the 94 A filter.

Ab initio molecular dynamics study of thermite reaction at Al and CuO nano-interfaces at different temperatures

Science.gov (United States)

Tang, Cui-Ming; Chen, Xiao-Xu; Cheng, Xin-Lu; Zhang, Chao-Yang; Lu, Zhi-Peng

2018-05-01

The thermite reaction at Al/CuO nano-interfaces is investigated with ab initio molecular dynamics calculations in canonical ensemble at 500 K, 800 K, 1200 K and 1500 K, respectively. The reaction process and reaction products are analyzed in terms of chemical bonds, average charge, time constants and total potential energy. The activity of the reactants enhances with increasing temperature, which induces a faster thermite reaction. The alloy reaction obviously expands outward at Cu-rich interface of Al/CuO system, and the reaction between Al and O atoms obviously expands outward at O-rich interface as temperature increases. Different reaction products are found at the outermost layer of different interfaces in the Al/CuO system. In generally, the average charge of the outer layer aluminum atoms (i.e., Al1, Al2, Al5 and Al6) increases with temperature. The potential energy of Al/CuO system decreases significantly, which indicates that drastic exothermic reaction occurs at the Al/CuO system. This research enhances fundamental understanding in temperature effect on the thermite reaction at atomic level, which can potentially open new possibilities for its industrial application.

Reaction theories for N* excitations in πN and γN reactions

International Nuclear Information System (INIS)

Lee, T.S.H.

1996-01-01

The importance of developing reaction theories for investigating N* physics is illustrated in an analysis of pion photoproduction on the nucleon. It is shown that the γN ↔ Δ transition amplitudes predicted by the constituent quark model are in agreement with the values extracted from the γN → πN data only when the contributions from the reaction mechanisms calculated using a dynamical approach are taken into account in the analysis

Variational Flooding Study of a SN2 Reaction.

Science.gov (United States)

Piccini, GiovanniMaria; McCarty, James J; Valsson, Omar; Parrinello, Michele

2017-02-02

We have studied the reaction dynamics of a prototypical organic reaction using a variationally optimized truncated bias to accelerate transitions between educt and product reactant states. The asymmetric S N 2 nucleophilic substitution reaction of fluoromethane and chloromethane CH 3 F + Cl - ⇌ CH 3 Cl + F - is considered, and many independent biased molecular dynamics simulations have been performed at 600, 900, and 1200 K, collecting several hundred transitions at each temperature. The transition times and relative rate constants have been obtained for both reaction directions. The activation energies extracted from an Arrhenius plot compare well with standard static calculations.

Molecular Interactions and Reaction Dynamics in Supercritical Water Oxidation

National Research Council Canada - National Science Library

Johnston, K

1998-01-01

.... From UV-vis spectroscopic measurements and molecular dynamics simulation of chemical equilibria, we have shown that density effects on broad classes of reactions may be explained in terms of changes...

Atom-radical reaction dynamics of O(3P)+C3H5→C3H4+OH: Nascent rovibrational state distributions of product OH

Science.gov (United States)

Park, Jong-Ho; Lee, Hohjai; Kwon, Han-Cheol; Kim, Hee-Kyung; Choi, Young-Sang; Choi, Jong-Ho

2002-08-01

The reaction dynamics of ground-state atomic oxygen [O(3P)] with allyl radicals (C3H5) has been investigated by applying a combination of crossed beams and laser induced fluorescence techniques. The reactants O(3P) and C3H5 were produced by the photodissociation of NO2 and the supersonic flash pyrolysis of precursor allyl iodide, respectively. A new exothermic channel of O(3P)+C3H5→C3H4+OH was observed and the nascent internal state distributions of the product OH (X 2Π:υ″=0,1) showed substantial bimodal internal excitations of the low- and high-N″ components without Λ-doublet and spin-orbit propensities in the ground and first excited vibrational states. With the aid of the CBS-QB3 level of ab initio theory and Rice-Ramsperger-Kassel-Marcus calculations, it is predicted that on the lowest doublet potential energy surface the major reaction channel of O(3P) with C3H5 is the formation of acrolein (CH2CHCHO)+H, which is consistent with the previous bulk kinetic experiments performed by Gutman et al. [J. Phys. Chem. 94, 3652 (1990)]. The counterpart C3H4 of the probed OH product in the title reaction is calculated to be allene after taking into account the factors of reaction enthalpy, barrier height and the number of intermediates involved along the reaction pathway. On the basis of population analyses and comparison with prior calculations, the statistical picture is not suitable to describe the reactive atom-radical scattering processes, and the dynamics of the title reaction is believed to proceed through two competing dynamical pathways. The major low N″-components with significant vibrational excitation may be described by the direct abstraction process, while the minor but extraordinarily hot rotational distribution of high N″-components implies that some fraction of reactants is sampled to proceed through the indirect short-lived addition-complex forming process.

Wang-Landau Reaction Ensemble Method: Simulation of Weak Polyelectrolytes and General Acid-Base Reactions.

Science.gov (United States)

Landsgesell, Jonas; Holm, Christian; Smiatek, Jens

2017-02-14

We present a novel method for the study of weak polyelectrolytes and general acid-base reactions in molecular dynamics and Monte Carlo simulations. The approach combines the advantages of the reaction ensemble and the Wang-Landau sampling method. Deprotonation and protonation reactions are simulated explicitly with the help of the reaction ensemble method, while the accurate sampling of the corresponding phase space is achieved by the Wang-Landau approach. The combination of both techniques provides a sufficient statistical accuracy such that meaningful estimates for the density of states and the partition sum can be obtained. With regard to these estimates, several thermodynamic observables like the heat capacity or reaction free energies can be calculated. We demonstrate that the computation times for the calculation of titration curves with a high statistical accuracy can be significantly decreased when compared to the original reaction ensemble method. The applicability of our approach is validated by the study of weak polyelectrolytes and their thermodynamic properties.

Dual-level direct dynamics studies for the hydrogen abstraction reaction of 1,1-difluoroethane with O( 3P)

Science.gov (United States)

Liu, Jing-yao; Li, Ze-sheng; Dai, Zhen-wen; Zhang, Gang; Sun, Chia-chung

2004-01-01

We present dual-level direct dynamics calculations for the CH 3CHF 2 + O( 3P) hydrogen abstraction reaction in a wide temperature range, based on canonical variational transition-state theory including small curvature tunneling corrections. For this reaction, three distinct transition states, one for α-abstraction and two for β-abstraction, have been located. The potential energy surface information is obtained at the MP2(full)/6-311G(d,p) level of theory, and higher-level single-point calculations for the stationary points are preformed at several levels, namely QCISD(T)/6-311+G(3df,3pd), G2, and G3 using the MP2 geometries, as well as at the G3//MP4SDQ/6-311G(d,p) level. The energy profiles are further refined with the interpolated single-point energies method at the G3//MP2(full)/6-311G(d,p) level. The total rate constants match the experimental data reasonable well in the measured temperature range 1110-1340 K. It is shown that at low temperature α-abstraction may be the major reaction channel, while β-abstraction will have more contribution to the whole reaction rate as the temperature increases.

Probing the role of Skyrme interactions on the fission dynamics of the {sup 6}Li + {sup 238}U reaction

Energy Technology Data Exchange (ETDEWEB)

Sharma, Ishita; Kumar, Raj; Sharma, Manoj K. [Thapar University, School of Physics and Materials Science, Patiala (India)

2017-06-15

The performance of selected five Skyrme forces (out of a set of 240), tested by Dutra et al., is analyzed in view of fusion-fission dynamics. These forces are assumed to perform better for neutron-rich systems, so the choice of the reaction is accordingly made by opting for a neutron-rich target in {sup 6}Li + {sup 238}U reaction. This reaction is diagnosed further in reference to fusion hindrance within the dynamical approach of the cluster-decay model (DCM). In order to reduce the computational time, three Skyrme forces are figured out with the criteria that these forces cover the barrier characteristics of the remaining two forces as well. The fission cross-sections are successfully addressed at low energies for the {sup 6}Li + {sup 238}U reaction. However, at relatively higher energies, the excitation functions show theoretical suppression with respect to experimental data, which may be associated with the possible existence of incomplete fusion (ICF). For ICF, we have considered that the {sup 6}Li broke into {sup 4}He + {sup 2}H, as mentioned in the experimental work. The calculations of ICF are carried out for the {sup 4}He + {sup 238}U reaction with the selected Skyrme forces at E{sub c.m.} = 26.20 and 27.51 MeV. These forces address the data nicely for the compound nucleus (CN) as well as ICF processes. Here, the NRAPR force seems to require lesser barrier modification as compared to the other forces, therefore it can be used as an alternate choice for calculating the interaction potential. Additionally, the prediction of cross-sections at lower energies has been done with DCM using the NRAPR force. The l-dependent % barrier modification of the Skyrme forces undertaken is also worked out in reference to fusion hindrance at below barrier energies. (orig.)

High energy nuclear reactions ('Spallation') and their application in calculation of the Acceleration Driven Systems (ADS)

International Nuclear Information System (INIS)

Rossi, Pedro Carlos Russo

2011-01-01

This work presents a study of high energy nuclear reactions which are fundamental to dene the source term in accelerator driven systems. These nuclear reactions, also known as spallation, consist in the interaction of high energetic hadrons with nucleons in the atomic nucleus. The phenomenology of these reactions consist in two step. In the rst, the proton interacts through multiple scattering in a process called intra-nuclear cascade. It is followed by a step in which the excited nucleus, coming from the intranuclear cascade, could either, evaporates particles to achieve a moderate energy state or fission. This process is known as competition between evaporation and fission. In this work the main nuclear models, Bertini and Cugnon are reviewed, since these models are fundamental for design purposes of the source term in ADS, due to lack of evaluated nuclear data for these reactions. The implementation and validation of the calculation methods for the design of the source is carried out to implement the methodology of source design using the program MCNPX (Monte Carlo N-Particle eXtended), devoted to calculation of transport of these particles and the validation performed by an international cooperation together with a Coordinated Research Project (CRP) of the International Atomic Energy Agency and available jobs, in order to qualify the calculations on nuclear reactions and the de-excitation channels involved, providing a state of the art of design and methodology for calculating external sources of spallation for source driven systems. The CRISP, is a brazilian code for the phenomenological description of the reactions involved and the models implemented in the code were reviewed and improved to continue the qualification process. Due to failure of the main models in describing the production of light nuclides, the multifragmentation reaction model was studied. Because the discrepancies in the calculations of production of these nuclides are attributes to the

ReaDDy--a software for particle-based reaction-diffusion dynamics in crowded cellular environments.

Directory of Open Access Journals (Sweden)

Johannes Schöneberg

Full Text Available We introduce the software package ReaDDy for simulation of detailed spatiotemporal mechanisms of dynamical processes in the cell, based on reaction-diffusion dynamics with particle resolution. In contrast to other particle-based reaction kinetics programs, ReaDDy supports particle interaction potentials. This permits effects such as space exclusion, molecular crowding and aggregation to be modeled. The biomolecules simulated can be represented as a sphere, or as a more complex geometry such as a domain structure or polymer chain. ReaDDy bridges the gap between small-scale but highly detailed molecular dynamics or Brownian dynamics simulations and large-scale but little-detailed reaction kinetics simulations. ReaDDy has a modular design that enables the exchange of the computing core by efficient platform-specific implementations or dynamical models that are different from Brownian dynamics.

DCHAIN: A user-friendly computer program for radioactive decay and reaction chain calculations

International Nuclear Information System (INIS)

East, L.V.

1994-05-01

A computer program for calculating the time-dependent daughter populations in radioactive decay and nuclear reaction chains is described. Chain members can have non-zero initial populations and be produced from the preceding chain member as the result of radioactive decay, a nuclear reaction, or both. As presently implemented, chains can contain up to 15 members. Program input can be supplied interactively or read from ASCII data files. Time units for half-lives, etc. can be specified during data entry. Input values are verified and can be modified if necessary, before used in calculations. Output results can be saved in ASCII files in a format suitable for including in reports or other documents. The calculational method, described in some detail, utilizes a generalized form of the Bateman equations. The program is written in the C language in conformance with current ANSI standards and can be used on multiple hardware platforms

Fusion dynamics in 40Ca induced reactions

International Nuclear Information System (INIS)

Prasad, E.; Hinde, D.J.; Williams, E.

2017-01-01

Synthesis of superheavy elements (SHEs) and investigation of their properties are among the most challenging research topics in modern science. A non-compound nuclear process called quasi fission is partly responsible for the very low production cross sections of SHEs. The formation and survival probabilities of the compound nucleus (CN) strongly depend on the competition between fusion and quasi fission. A clear understanding of these processes and their dynamics is required to make reliable predictions of the best reactions to synthesise new SHEs. All elements beyond Nh are produced using hot fusion reactions and beams of 48 Ca were used in most of these experiments. In this context a series of fission measurements have been carried out at the Australian National University (ANU) using 40;48 Ca beams on various targets ranging from 142 Nd to 249 Cf. Some of the 40 Ca reactions will be discussed in this symposium

Microscopic study on dynamic barrier in fusion reactions

International Nuclear Information System (INIS)

Wu Xizhen; Tian Junlong; Zhao Kai; Li Zhuxia; Wang Ning

2004-01-01

The authors briefly review the fusion process of very heavy nuclear systems and some theoretical models. The authors propose a microscopic transport dynamic model, i.e. the Improved Quantum Molecular Dynamic model, for describing fusion reactions of heavy systems, in which the dynamical behavior of the fusion barrier in heavy fusion systems has been studied firstly. The authors find that with the incident energy decreasing the lowest dynamic barrier is obtained which approaches to the adiabatic static barrier and with increase of the incident energy the dynamic barrier goes up to the diabatic static barrier. The authors also indicate that how the dynamical fusion barrier is correlated with the development of the configuration of fusion partners along the fusion path. Associating the single-particle potentials obtained at different stages of fusion with the Two Center Shell Model, authors can study the time evolution of the single particle states of fusion system in configuration space of single particle orbits along the fusion path. (author)

A computer program incorporating Pitzer's equations for calculation of geochemical reactions in brines

Science.gov (United States)

Plummer, Niel; Parkhurst, D.L.; Fleming, G.W.; Dunkle, S.A.

1988-01-01

The program named PHRQPITZ is a computer code capable of making geochemical calculations in brines and other electrolyte solutions to high concentrations using the Pitzer virial-coefficient approach for activity-coefficient corrections. Reaction-modeling capabilities include calculation of (1) aqueous speciation and mineral-saturation index, (2) mineral solubility, (3) mixing and titration of aqueous solutions, (4) irreversible reactions and mineral water mass transfer, and (5) reaction path. The computed results for each aqueous solution include the osmotic coefficient, water activity , mineral saturation indices, mean activity coefficients, total activity coefficients, and scale-dependent values of pH, individual-ion activities and individual-ion activity coeffients , and scale-dependent values of pH, individual-ion activities and individual-ion activity coefficients. A data base of Pitzer interaction parameters is provided at 25 C for the system: Na-K-Mg-Ca-H-Cl-SO4-OH-HCO3-CO3-CO2-H2O, and extended to include largely untested literature data for Fe(II), Mn(II), Sr, Ba, Li, and Br with provision for calculations at temperatures other than 25C. An extensive literature review of published Pitzer interaction parameters for many inorganic salts is given. Also described is an interactive input code for PHRQPITZ called PITZINPT. (USGS)

Dynamic Modelling and Identification of Precipitation Reactions in Full-Scale WWTP

DEFF Research Database (Denmark)

Mbamba, Christian Kazadi; Tait, Stephan; Flores-Alsina, Xavier

, this paper evaluates plant-wide modelling of precipitation reactions using a generic approach integrated within activated sludge and anaerobic models. Preliminary results of anaerobic digester sludge in batch system suggest that the model is able to simulate the dynamics of precipitation reactions. Kinetic...

Investigation of Coal-biomass Catalytic Gasification using Experiments, Reaction Kinetics and Computational Fluid Dynamics

Energy Technology Data Exchange (ETDEWEB)

Battaglia, Francine [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Agblevor, Foster [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Klein, Michael [Univ. of Delaware, Newark, DE (United States); Sheikhi, Reza [Northeastern Univ., Boston, MA (United States)

2015-12-31

A collaborative effort involving experiments, kinetic modeling, and computational fluid dynamics (CFD) was used to understand co-gasification of coal-biomass mixtures. The overall goal of the work was to determine the key reactive properties for coal-biomass mixed fuels. Sub-bituminous coal was mixed with biomass feedstocks to determine the fluidization and gasification characteristics of hybrid poplar wood, switchgrass and corn stover. It was found that corn stover and poplar wood were the best feedstocks to use with coal. The novel approach of this project was the use of a red mud catalyst to improve gasification and lower gasification temperatures. An important results was the reduction of agglomeration of the biomass using the catalyst. An outcome of this work was the characterization of the chemical kinetics and reaction mechanisms of the co-gasification fuels, and the development of a set of models that can be integrated into other modeling environments. The multiphase flow code, MFIX, was used to simulate and predict the hydrodynamics and co-gasification, and results were validated with the experiments. The reaction kinetics modeling was used to develop a smaller set of reactions for tractable CFD calculations that represented the experiments. Finally, an efficient tool was developed, MCHARS, and coupled with MFIX to efficiently simulate the complex reaction kinetics.

Time-resolved imaging of purely valence-electron dynamics during a chemical reaction

DEFF Research Database (Denmark)

Hockett, Paul; Bisgaard, Christer Z.; Clarkin, Owen J.

2011-01-01

Chemical reactions are manifestations of the dynamics of molecular valence electrons and their couplings to atomic motions. Emerging methods in attosecond science can probe purely electronic dynamics in atomic and molecular systems(1-6). By contrast, time-resolved structural-dynamics methods...... such as electron(7-10) or X-ray diffraction(11) and X-ray absorption(12) yield complementary information about the atomic motions. Time-resolved methods that are directly sensitive to both valence-electron dynamics and atomic motions include photoelectron spectroscopy(13-15) and high-harmonic generation(16......,17): in both cases, this sensitivity derives from the ionization-matrix element(18,19). Here we demonstrate a time-resolved molecular-frame photoelectron-angular-distribution (TRMFPAD) method for imaging the purely valence-electron dynamics during a chemical reaction. Specifically, the TRMFPADs measured during...

Nonlinear electromechanical modelling and dynamical behavior analysis of a satellite reaction wheel

Science.gov (United States)

Aghalari, Alireza; Shahravi, Morteza

2017-12-01

The present research addresses the satellite reaction wheel (RW) nonlinear electromechanical coupling dynamics including dynamic eccentricity of brushless dc (BLDC) motor and gyroscopic effects, as well as dry friction of shaft-bearing joints (relative small slip) and bearing friction. In contrast to other studies, the rotational velocity of the flywheel is considered to be controllable, so it is possible to study the reaction wheel dynamical behavior in acceleration stages. The RW is modeled as a three-phases BLDC motor as well as flywheel with unbalances on a rigid shaft and flexible bearings. Improved Lagrangian dynamics for electromechanical systems is used to obtain the mathematical model of the system. The developed model can properly describe electromechanical nonlinear coupled dynamical behavior of the satellite RW. Numerical simulations show the effectiveness of the presented approach.

Transverse flow reactor studies of the dynamics of radical reactions

Energy Technology Data Exchange (ETDEWEB)

Macdonald, R.G. [Argonne National Laboratory, IL (United States)

1993-12-01

Radical reactions are in important in combustion chemistry; however, little state-specific information is available for these reactions. A new apparatus has been constructed to measure the dynamics of radical reactions. The unique feature of this apparatus is a transverse flow reactor in which an atom or radical of known concentration will be produced by pulsed laser photolysis of an appropriate precursor molecule. The time dependence of individual quantum states or products and/or reactants will be followed by rapid infrared laser absorption spectroscopy. The reaction H + O{sub 2} {yields} OH + O will be studied.

Calculation of neutron monitor reaction cross sections of {sup 90}Zr in energy region up to 100 MeV

Energy Technology Data Exchange (ETDEWEB)

Qingbiao, Shen; Baosheng, Yu; Dunjiu, Cai [Chinese Nuclear Data Center, Beijing, BJ (China)

1996-06-01

Many nuclear data for n + {sup 90}Zr reaction were calculated by using optical model evaporation model and exciton model. The program SPEC, including the first to the sixth particle emission processes, was used in our calculations. The calculated results show that the activation products {sup 89,88}Zr and {sup 88,87}Y are important neutron monitor reaction products for n + {sup 90}Zr reaction in energy range up to 100 MeV. (4 figs.).

Calculation of reaction forces in the boiler supports using the method of equivalent stiffness of membrane wall.

Science.gov (United States)

Sertić, Josip; Kozak, Dražan; Samardžić, Ivan

2014-01-01

The values of reaction forces in the boiler supports are the basis for the dimensioning of bearing steel structure of steam boiler. In this paper, the application of the method of equivalent stiffness of membrane wall is proposed for the calculation of reaction forces. The method of equalizing displacement, as the method of homogenization of membrane wall stiffness, was applied. On the example of "Milano" boiler, using the finite element method, the calculation of reactions in the supports for the real geometry discretized by the shell finite element was made. The second calculation was performed with the assumption of ideal stiffness of membrane walls and the third using the method of equivalent stiffness of membrane wall. In the third case, the membrane walls are approximated by the equivalent orthotropic plate. The approximation of membrane wall stiffness is achieved using the elasticity matrix of equivalent orthotropic plate at the level of finite element. The obtained results were compared, and the advantages of using the method of equivalent stiffness of membrane wall for the calculation of reactions in the boiler supports were emphasized.

Nuclear dynamics in heavy ion induced fusion-fission reactions

International Nuclear Information System (INIS)

Kapoor, S.S.

1992-01-01

Heavy ion induced fission and fission-like reactions evolve through a complex nuclear dynamics encountered in the medium energy nucleus-nucleus collisions. In the recent years, measurements of the fragment-neutron and fragment-charged particle angular correlations in heavy ion induced fusion-fission reactions, have provided new information on the dynamical times of nuclear deformations of the initial dinuclear complex to the fission saddle point and the scission point. From the studies of fragment angular distributions in heavy ion induced fission it has been possible to infer the relaxation times of the dinuclear complex in the K-degree of freedom and our recent measurements on the entrance channel dependence of fragment anisotropies have provided an experimental signature of the presence of fissions before K-equilibration. This paper reviews recent experimental and theoretical status of the above studies with particular regard to the questions relating to dynamical times, nuclear dissipation and the effect of nuclear dissipation on the K-distributions at the fission saddle in completely equilibrated compound nucleus. (author). 19 refs., 9 figs

Dynamic transition in the structure of an energetic crystal during chemical reactions at shock front prior to detonation.

Science.gov (United States)

Nomura, Ken-Ichi; Kalia, Rajiv K; Nakano, Aiichiro; Vashishta, Priya; van Duin, Adri C T; Goddard, William A

2007-10-05

Mechanical stimuli in energetic materials initiate chemical reactions at shock fronts prior to detonation. Shock sensitivity measurements provide widely varying results, and quantum-mechanical calculations are unable to handle systems large enough to describe shock structure. Recent developments in reactive force-field molecular dynamics (ReaxFF-MD) combined with advances in parallel computing have paved the way to accurately simulate reaction pathways along with the structure of shock fronts. Our multimillion-atom ReaxFF-MD simulations of l,3,5-trinitro-l,3,5-triazine (RDX) reveal that detonation is preceded by a transition from a diffuse shock front with well-ordered molecular dipoles behind it to a disordered dipole distribution behind a sharp front.

Direct Dynamics Simulation of the Thermal 3CH2 + 3O2 Reaction. Rate Constant and Product Branching Ratios.

Science.gov (United States)

Lakshmanan, Sandhiya; Pratihar, Subha; Machado, Francisco Bolivar Correto; Hase, William Louis

2018-04-26

The reaction of 3CH2 with 3O2 is of fundamental importance in combustion and the reaction is complex as a result of multiple extremely exothermic product channels. In the present study, direct dynamics simulations were performed to study the reaction on both the singlet and triplet potential energy surfaces (PESs). The simulations were performed at the UM06/6-311++G(d,p) level of theory. Trajectories were calculated at a temperature of 300 K and all reactive trajectories proceeded through the carbonyl oxide Criegee intermediate, CH2OO, on both the singlet and triplet PESs. The triplet surface leads to only one product channel, H2CO + O(3P), while the singlet surface leads to 8 product channels with their relative importance as: CO + H2O > CO + OH + H ~ H2CO + O(1D) > HCO + OH ~ CO2 + H2 ~ CO + H2 + O(1D) > CO2 + H + H > HCO + O(1D) + H. Reaction on the singlet PES is barrierless, consistent with experiment and the total rate constant on the singlet surface is 0.93 ± 0.22 x 10-12 cm3molecule-1s-1 in comparison to the recommended experimental rate constant of 3.3 x 10-12 cm3molecule-1s-1. The simulation product yields for the singlet PES are compared with experiment and the most significant differences are for H, CO2, and H2O. Reaction on the triplet surface is also barrierless, inconsistent with experiment. A discussion is given of the need for future calculations to address the: (1) barrier on the triplet PES for 3CH2 + 3O2 → 3CH2OO; (2) temperature dependence of the 3CH2 + 3O2 reaction rate constant and product branching ratios; and (3) possible non-RRKM dynamics of the 1CH2OO Criegee intermediate.

Time Analysis of Building Dynamic Response Under Seismic Action. Part 2: Example of Calculation

Science.gov (United States)

Ufimtcev, E. M.

2017-11-01

The second part of the article illustrates the use of the time analysis method (TAM) by the example of the calculation of a 3-storey building, the design dynamic model (DDM) of which is adopted in the form of a flat vertical cantilever rod with 3 horizontal degrees of freedom associated with floor and coverage levels. The parameters of natural oscillations (frequencies and modes) and the results of the calculation of the elastic forced oscillations of the building’s DDM - oscillograms of the reaction parameters on the time interval t ∈ [0; 131,25] sec. The obtained results are analyzed on the basis of the computed values of the discrepancy of the DDS motion equation and the comparison of the results calculated on the basis of the numerical approach (FEM) and the normative method set out in SP 14.13330.2014 “Construction in Seismic Regions”. The data of the analysis testify to the accuracy of the construction of the computational model as well as the high accuracy of the results obtained. In conclusion, it is revealed that the use of the TAM will improve the strength of buildings and structures subject to seismic influences when designing them.

KAPSIES: A program for the calculation of multi-step direct reaction cross sections

International Nuclear Information System (INIS)

Koning, A.J.; Akkermans, J.M.

1994-09-01

We present a program for the calculation of continuum cross sections, sepctra, angular distributions and analyzing powers according to various quantum-mechanical theories for statistical multi-step direct nuclear reactions. (orig.)

Proton transfers in the Strecker reaction revealed by DFT calculations

Directory of Open Access Journals (Sweden)

Shinichi Yamabe

2014-08-01

Full Text Available The Strecker reaction of acetaldehyde, NH3, and HCN to afford alanine was studied by DFT calculations for the first time, which involves two reaction stages. In the first reaction stage, the aminonitrile was formed. The rate-determining step is the deprotonation of the NH3+ group in MeCH(OH-NH3+ to form 1-aminoethanol, which occurs with an activation energy barrier (ΔE≠ of 9.6 kcal/mol. The stereochemistry (R or S of the aminonitrile product is determined at the NH3 addition step to the carbonyl carbon of the aldehyde. While the addition of CN− to the carbon atom of the protonated imine 7 appears to scramble the stereochemistry, the water cluster above the imine plane reinforces the CN− to attack the imine group below the plane. The enforcement hinders the scrambling. In the second stage, the aminonitrile transforms to alanine, where an amide Me-CH(NH2-C(=O-NH2 is the key intermediate. The rate-determining step is the hydrolysis of the cyano group of N(amino-protonated aminonitrile which occurs with an ΔE≠ value of 34.7 kcal/mol. In the Strecker reaction, the proton transfer along the hydrogen bonds plays a crucial role.

Dynamic disorder in single-molecule Michaelis-Menten kinetics: The reaction-diffusion formalism in the Wilemski-Fixman approximation

Science.gov (United States)

Chaudhury, Srabanti; Cherayil, Binny J.

2007-09-01

Single-molecule equations for the Michaelis-Menten [Biochem. Z. 49, 333 (1913)] mechanism of enzyme action are analyzed within the Wilemski-Fixman [J. Chem. Phys. 58, 4009 (1973); 60, 866 (1974)] approximation after the effects of dynamic disorder—modeled by the anomalous diffusion of a particle in a harmonic well—are incorporated into the catalytic step of the reaction. The solution of the Michaelis-Menten equations is used to calculate the distribution of waiting times between successive catalytic turnovers in the enzyme β-galactosidase. The calculated distribution is found to agree qualitatively with experimental results on this enzyme obtained at four different substrate concentrations. The calculations are also consistent with measurements of correlations in the fluctuations of the fluorescent light emitted during the course of catalysis, and with measurements of the concentration dependence of the randomness parameter.

Calculation of the dynamic air flow resistivity of fibre materials

DEFF Research Database (Denmark)

Tarnow, Viggo

1997-01-01

The acoustic attenuation of acoustic fiber materials is mainly determined by the dynamic resistivity to an oscillating air flow. The dynamic resistance is calculated for a model with geometry close to the geometry of real fibre material. The model constists of parallel cylinders placed randomly.......The second procedure is an extension to oscillating air flow of the Brinkman self-consistent procedure for dc flow. The procedures are valid for volume concentrations of cylinders less than 0.1. The calculations show that for the density of fibers of interest for acoustic fibre materials the simple self...

Chemical reaction dynamics of Rydberg atoms with neutral molecules: A comparison of molecular-beam and classical trajectory results for the H(n)+D2→HD+D(n') reaction

International Nuclear Information System (INIS)

Song Hui; Dai Dongxu; Wu Guorong; Wang, C.-C.; Harich, Steven A.; Hayes, Michael Y.; Wang Xiuyan; Gerlich, Dieter; Yang Xueming; Skodje, Rex T.

2005-01-01

Recent molecular-beam experiments have probed the dynamics of the Rydberg-atom reaction, H(n)+D 2 →HD+D(n) at low collision energies. It was discovered that the rotationally resolved product distribution was remarkably similar to a much more limited data set obtained at a single scattering angle for the ion-molecule reaction H + +D 2 →D + +HD. The equivalence of these two problems would be consistent with the Fermi-independent-collider model (electron acting as a spectator) and would provide an important new avenue for the study of ion-molecule reactions. In this work, we employ a classical trajectory calculation on the ion-molecule reaction to facilitate a more extensive comparison between the two systems. The trajectory simulations tend to confirm the equivalence of the ion+molecule dynamics to that for the Rydberg-atom+molecule system. The theory reproduces the close relationship of the two experimental observations made previously. However, some differences between the Rydberg-atom experiments and the trajectory simulations are seen when comparisons are made to a broader data set. In particular, the angular distribution of the differential cross section exhibits more asymmetry in the experiment than in the theory. The potential breakdown of the classical model is discussed. The role of the 'spectator' Rydberg electron is addressed and several crucial issues for future theoretical work are brought out

Cellular reprogramming dynamics follow a simple 1D reaction coordinate

Science.gov (United States)

Teja Pusuluri, Sai; Lang, Alex H.; Mehta, Pankaj; Castillo, Horacio E.

2018-01-01

Cellular reprogramming, the conversion of one cell type to another, induces global changes in gene expression involving thousands of genes, and understanding how cells globally alter their gene expression profile during reprogramming is an ongoing problem. Here we reanalyze time-course data on cellular reprogramming from differentiated cell types to induced pluripotent stem cells (iPSCs) and show that gene expression dynamics during reprogramming follow a simple 1D reaction coordinate. This reaction coordinate is independent of both the time it takes to reach the iPSC state as well as the details of the experimental protocol used. Using Monte-Carlo simulations, we show that such a reaction coordinate emerges from epigenetic landscape models where cellular reprogramming is viewed as a ‘barrier-crossing’ process between cell fates. Overall, our analysis and model suggest that gene expression dynamics during reprogramming follow a canonical trajectory consistent with the idea of an ‘optimal path’ in gene expression space for reprogramming.

Analysis of the nucleon-nucleus reactions by the quantum molecular dynamics

International Nuclear Information System (INIS)

Chiba, Satoshi; Niita, Koji; Maruyama, Toshiki; Fukahori, Tokio; Takada, Hiroshi; Iwamoto, Akira

1995-01-01

The quantum molecular dynamics + statistical decay model has been applied to analyze the nucleon-induced nuclear reactions in the energy range from 50 to 3 GeV in order to verify its applicability to light-ion induced nuclear reactions. It was found that the present approach could give a quantitative description of various cross sections such as (p,p'), (p,n), (n,p) reactions from a wide range of targets and also target-like isotope production cross sections from p+Fe reaction, showing its basic ability as a tool for the study of intermediate energy nuclear reactions and nuclear data evaluation. (author)

Theoretical studies of combustion dynamics

International Nuclear Information System (INIS)

Bowman, J.M.

1986-01-01

The reactions of O( 3 P)+H 2 , D 2 , and HD are the focus of this research. Their approximate three-dimensional quantum calculations of the rate constant for both the ground and first excited vibrational states of the above reactions were completed last year. Comparisons of the calculated rate constants, isotope effects and branching ratios have been made with available experimental work and also with the variational transition state theory calculations. The main conclusion of that paper is that tunneling plays a major role in the reaction dynamics at room temperature and below

Calculating evolutionary dynamics in structured populations.

Directory of Open Access Journals (Sweden)

Charles G Nathanson

2009-12-01

Full Text Available Evolution is shaping the world around us. At the core of every evolutionary process is a population of reproducing individuals. The outcome of an evolutionary process depends on population structure. Here we provide a general formula for calculating evolutionary dynamics in a wide class of structured populations. This class includes the recently introduced "games in phenotype space" and "evolutionary set theory." There can be local interactions for determining the relative fitness of individuals, but we require global updating, which means all individuals compete uniformly for reproduction. We study the competition of two strategies in the context of an evolutionary game and determine which strategy is favored in the limit of weak selection. We derive an intuitive formula for the structure coefficient, sigma, and provide a method for efficient numerical calculation.

Abnormal reactions in a evaporator in a fuel reprocessing plant

International Nuclear Information System (INIS)

Kida, Takashi; Umeda, Miki; Sugikawa, Susumu

2003-01-01

In order to evaluate a self-accelerated reaction in an evaporator in a fuel reprocessing plant due to organic-nitric acid reactions, a development of a calculation code is under way. Mock-up tests were performed to investigate the fluid dynamic behavior of the organic solvent in the evaporator. Based on these results, the model of the calculation code was constructed. This report describes the results of mock-up tests and the model of the calculation code. (author)

Calculation and evaluation of the activation cross sections for 187Re(n,2n)186m,gRe reactions

International Nuclear Information System (INIS)

Huang Xiaolong; Lu Hanlin; Zhou Chunmei

1998-01-01

The activation cross sections for 187 Re(n,2n) 186m,g Re reactions are calculated using UNF code. The calculations are in good agreement with the re-evaluated measured data. Finally the excitation function for 187 Re(n,2n) 186m,g Re reactions are evaluated and recommended based on present calculations and evaluated decay data

Nonmonotonic Temperature Dependence of the Pressure-Dependent Reaction Rate Constant and Kinetic Isotope Effect of Hydrogen Radical Reaction with Benzene Calculated by Variational Transition-State Theory.

Science.gov (United States)

Zhang, Hui; Zhang, Xin; Truhlar, Donald G; Xu, Xuefei

2017-11-30

The reaction between H and benzene is a prototype for reactions of radicals with aromatic hydrocarbons. Here we report calculations of the reaction rate constants and the branching ratios of the two channels of the reaction (H addition and H abstraction) over a wide temperature and pressure range. Our calculations, obtained with an accurate potential energy surface, are based on variational transition-state theory for the high-pressure limit of the addition reaction and for the abstraction reaction and on system-specific quantum Rice-Ramsperger-Kassel theory calibrated by variational transition-state theory for pressure effects on the addition reaction. The latter is a very convenient way to include variational effects, corner-cutting tunneling, and anharmonicity in falloff calculations. Our results are in very good agreement with the limited experimental data and show the importance of including pressure effects in the temperature interval where the mechanism changes from addition to abstraction. We found a negative temperature effect of the total reaction rate constants at 1 atm pressure in the temperature region where experimental data are missing and accurate theoretical data were previously missing as well. We also calculated the H + C 6 H 6 /C 6 D 6 and D + C 6 H 6 /C 6 D 6 kinetic isotope effects, and we compared our H + C 6 H 6 results to previous theoretical data for H + toluene. We report a very novel nonmonotonic dependence of the kinetic isotope effect on temperature. A particularly striking effect is the prediction of a negative temperature dependence of the total rate constant over 300-500 K wide temperature ranges, depending on the pressure but generally in the range from 600 to 1700 K, which includes the temperature range of ignition in gasoline engines, which is important because aromatics are important components of common fuels.

Nuclear structure calculations in the dynamic-interaction propagator approach

International Nuclear Information System (INIS)

Engelbrecht, C.A.; Hahne, F.J.W.; Heiss, W.D.

1978-01-01

The dynamic-interaction propagator approach provides a natural method for the handling of energy-dependent effective two-body interactions induced by collective excitations of a many-body system. In this work this technique is applied to the calculation of energy spectra and two-particle strengths in mass-18 nuclei. The energy dependence is induced by the dynamic exchange of the lowest 3 - octupole phonon in O 16 , which is described within a normal static particle-hole RPA. This leads to poles in the two-body self-energy, which can be calculated if other fermion lines are restricted to particle states. The two-body interaction parameters are chosen to provide the correct phonon energy and reasonable negative-parity mass-17 and positive-parity mass-18 spectra. The fermion lines must be dressed consistently with the same exchange phonon to avoid redundant solutions or ghosts. The negative-parity states are then calculated in a parameter-free way which gives good agreement with the observed spectra [af

Calculation of Reaction Forces in the Boiler Supports Using the Method of Equivalent Stiffness of Membrane Wall

Directory of Open Access Journals (Sweden)

Josip Sertić

2014-01-01

Full Text Available The values of reaction forces in the boiler supports are the basis for the dimensioning of bearing steel structure of steam boiler. In this paper, the application of the method of equivalent stiffness of membrane wall is proposed for the calculation of reaction forces. The method of equalizing displacement, as the method of homogenization of membrane wall stiffness, was applied. On the example of “Milano” boiler, using the finite element method, the calculation of reactions in the supports for the real geometry discretized by the shell finite element was made. The second calculation was performed with the assumption of ideal stiffness of membrane walls and the third using the method of equivalent stiffness of membrane wall. In the third case, the membrane walls are approximated by the equivalent orthotropic plate. The approximation of membrane wall stiffness is achieved using the elasticity matrix of equivalent orthotropic plate at the level of finite element. The obtained results were compared, and the advantages of using the method of equivalent stiffness of membrane wall for the calculation of reactions in the boiler supports were emphasized.

Direct single-molecule dynamic detection of chemical reactions.

Science.gov (United States)

Guan, Jianxin; Jia, Chuancheng; Li, Yanwei; Liu, Zitong; Wang, Jinying; Yang, Zhongyue; Gu, Chunhui; Su, Dingkai; Houk, Kendall N; Zhang, Deqing; Guo, Xuefeng

2018-02-01

Single-molecule detection can reveal time trajectories and reaction pathways of individual intermediates/transition states in chemical reactions and biological processes, which is of fundamental importance to elucidate their intrinsic mechanisms. We present a reliable, label-free single-molecule approach that allows us to directly explore the dynamic process of basic chemical reactions at the single-event level by using stable graphene-molecule single-molecule junctions. These junctions are constructed by covalently connecting a single molecule with a 9-fluorenone center to nanogapped graphene electrodes. For the first time, real-time single-molecule electrical measurements unambiguously show reproducible large-amplitude two-level fluctuations that are highly dependent on solvent environments in a nucleophilic addition reaction of hydroxylamine to a carbonyl group. Both theoretical simulations and ensemble experiments prove that this observation originates from the reversible transition between the reactant and a new intermediate state within a time scale of a few microseconds. These investigations open up a new route that is able to be immediately applied to probe fast single-molecule physics or biophysics with high time resolution, making an important contribution to broad fields beyond reaction chemistry.

Calculation of the 5th AER dynamic benchmark with APROS

International Nuclear Information System (INIS)

Puska, E.K.; Kontio, H.

1998-01-01

The model used for calculation of the 5th AER dynamic benchmark with APROS code is presented. In the calculation of the 5th AER dynamic benchmark the three-dimensional neutronics model of APROS was used. The core was divided axially into 20 nodes according to the specifications of the benchmark and each six identical fuel assemblies were placed into one one-dimensional thermal hydraulic channel. The five-equation thermal hydraulic model was used in the benchmark. The plant process and automation was described with a generic VVER-440 plant model created by IVO PE. (author)

Fractal sets generated by chemical reactions discrete chaotic dynamics

International Nuclear Information System (INIS)

Gontar, V.; Grechko, O.

2007-01-01

Fractal sets composed by the parameters values of difference equations derived from chemical reactions discrete chaotic dynamics (DCD) and corresponding to the sequences of symmetrical patterns were obtained in this work. Examples of fractal sets with the corresponding symmetrical patterns have been presented

Resonances and reactions from mean-field dynamics

Directory of Open Access Journals (Sweden)

Stevenson P. D.

2016-01-01

Full Text Available The time-dependent version of nuclear density functional theory, using functionals derived from Skyrme interactions, is able to approximately describe nuclear dynamics. We present time-dependent results of calculations of dipole resonances, concentrating on excitations of valence neutrons against a proton plus neutron core in the neutron-rich doubly-magic 132Sn nucleus, and results of collision dynamics, highlighting potential routes to ternary fusion, with the example of a collision of 48Ca+48Ca+208Pb resulting in a compound nucleus of element 120 stable against immediate fission.

Calculation code MIXSET for Purex process

International Nuclear Information System (INIS)

Gonda, Kozo; Fukuda, Shoji.

1977-09-01

MIXSET is a FORTRAN IV calculation code for Purex process that simulate the dynamic behavior of solvent extraction processes in mixer-settlers. Two options permit terminating dynamic phase by time or by achieving steady state. These options also permit continuing calculation successively using new inputs from a arbitrary phase. A third option permits artificial rapid close to steady state and a fourth option permits searching optimum input to satisfy both of specification and recovery rate of product. MIXSET handles maximum chemical system of eight components with or without mutual dependence of the distribution of the components. The chemical system in MIXSET includes chemical reactions and/or decaying reaction. Distribution data can be supplied by third-power polynominal equations or tables, and kinetic data by tables or given constants. The fluctuation of the interfacial level height in settler is converted into the flow rate changes of organic and aqueous stream to follow dynamic behavior of extraction process in detail. MIXSET can be applied to flowsheet study, start up and/or shut down procedure study and real time process management in countercurrent solvent extraction processes. (auth.)

Calculation of rate coefficients of some proton-transfer ion-molecule reactions in weakly ionized gases

International Nuclear Information System (INIS)

Stiller, W.

1985-01-01

A classical collision theory is used to describe thermal bimolecular rate coefficeints for reaction between positive and negative ions and polar molecules in a carrier gas. Special attention is paid to ion-molecule reaction in which proton transfer occurs. These reactions play an important role in terrestrial plasma devices, in ionosphere, in planetary atmospheres and in interstellar matter. The equilibrium rate coefficients of the reactions are calculated based on a microscopic reactive cross section derived from a long distance polar molecule-ion potential. The results are compared with experimental values of afterglow measurements. (D.Gy.)

Reaction dynamics of inflammation proteins and T lymphocytes during radon balneotherapy

International Nuclear Information System (INIS)

Peter, A.; Vulpe, B.

1989-01-01

During a three-week radon treatment with daily administration of baths a periodical course of reaction with antidromic dynamics of inflammation proteins and T lymphocytes could be shown. A conspicuous reaction of the organism (moment of the treatment reaction) is to be observed one week after the beginning of the treatment. At the end of the cure a decrease of the activity of inflammation as well as of individual acute-phase proteins and immunoglobulins it to be proved. (author)

Construction of global ab initio potential energy surfaces for the HNS system and quantum dynamics calculations for the S({sup 3}P) + NH(X{sup 3}Σ) → NS(X{sup 2}Π) + H({sup 2}S) and N({sup 4}S) + SH(X{sup 2}Π) → NS(X{sup 2}Π) + H({sup 2}S) reactions

Energy Technology Data Exchange (ETDEWEB)

Sato, Kazuma; Takayanagi, Toshiyuki, E-mail: tako@mail.saitama-u.ac.jp

2014-08-17

Highlights: • Low-lying three potential energy surfaces for the HNS/HSN system are developed. • Quantum scattering calculations are performed for S + NH and N + SH reactions. • NS production mechanisms from S + NH and N + SH reactions are discussed. - Abstract: The lowest three adiabatic potential energy surfaces (1{sup 1}A′, 1{sup 1}A″ and 1{sup 3}A″) of the HNS molecular system have been developed using ab initio MRCI + Q-level electronic structure calculations with a complete-basis-set approach in order to understand the NS production mechanisms from the S({sup 3}P) + NH(X{sup 3}Σ) → NS(X{sup 2}Π) + H({sup 2}S) and N({sup 4}S) + SH(X{sup 2}Π) → NS(X{sup 2}Π) + H({sup 2}S) reactions. The results of time-independent quantum reactive scattering calculations show that the reactions proceed with the contribution of both direct and HNS/HSN complex-forming mechanisms on all the three potential energy surfaces. It is found that the reaction dynamics is not entirely statistical and cannot be described with a simple capture theory despite that the reactions are barrierless with large exoergicity.

Studies of the Three-Nucleon System Dynamics in the Deuteron-Proton Breakup Reaction

Science.gov (United States)

Ciepał, I.; Kłos, B.; Stephan, E.; Kistryn, St.; Biegun, A.; Bodek, K.; Deltuva, A.; Epelbaum, E.; Eslami-Kalantari, M.; Fonseca, A. C.; Golak, J.; Jha, V.; Kalantar-Nayestanaki, N.; Kamada, H.; Khatri, G.; Kirillov, Da.; Kirillov, Di.; Kliczewski, St.; Kozela, A.; Kravcikova, M.; Machner, H.; Magiera, A.; Martinska, G.; Messchendorp, J.; Nogga, A.; Parol, W.; Ramazani-Moghaddam-Arani, A.; Roy, B. J.; Sakai, H.; Sekiguchi, K.; Sitnik, I.; Siudak, R.; Skibiński, R.; Sworst, R.; Urban, J.; Witała, H.; Zejma, J.

2014-03-01

One of the most important goals of modern nuclear physics is to contruct nuclear force model which properly describes the experimental data. To develop and test predictions of current models the breakup 1H(overrightarrow d, pp)n reaction was investigated experimentally at 100 and 130 MeV deuteron beam energies. Rich set of data for cross section, vector and tensor analyzing powers was obtained with the use of the SALAD and BINA detectors at KVI and Germanium Wall setup at FZ-Jülich. Results are compared with various theoretical approaches which describe the three-nucleon (3N) system dynamics. For correct description of the cross section data both, three-nucleon force (3NF) and Coulomb force, have to be included into calculations and influence of those ingredients is seizable at specific parts of the phase space. In case of the vector analyzing powers very low sensitivity to any effects beyond nucleon-nucleon interaction was found. At 130 MeV, the Axy data are not correctly described when 3NF models are included into calculations.

Eight-dimensional quantum reaction rate calculations for the H+CH4 and H2+CH3 reactions on recent potential energy surfaces.

Science.gov (United States)

Zhou, Yong; Zhang, Dong H

2014-11-21

Eight-dimensional (8D) transition-state wave packet simulations have been performed on two latest potential energy surfaces (PES), the Zhou-Fu-Wang-Collins-Zhang (ZFWCZ) PES [Y. Zhou, B. Fu, C. Wang, M. A. Collins, and D. H. Zhang, J. Chem. Phys. 134, 064323 (2011)] and the Xu-Chen-Zhang (XCZ)-neural networks (NN) PES [X. Xu, J. Chen, and D. H. Zhang, Chin. J. Chem. Phys. 27, 373 (2014)]. Reaction rate constants for both the H+CH4 reaction and the H2+CH3 reaction are calculated. Simulations of the H+CH4 reaction based on the XCZ-NN PES show that the ZFWCZ PES predicts rate constants with reasonable high accuracy for low temperatures while leads to slightly lower results for high temperatures, in line with the distribution of interpolation error associated with the ZFWCZ PES. The 8D H+CH4 rate constants derived on the ZFWCZ PES compare well with full-dimensional 12D results based on the equivalent m-ZFWCZ PES, with a maximum relative difference of no more than 20%. Additionally, very good agreement is shown by comparing the 8D XCZ-NN rate constants with the 12D results obtained on the ZFWCZ-WM PES, after considering the difference in static barrier height between these two PESs. The reaction rate constants calculated for the H2+CH3 reaction are found to be in good consistency with experimental observations.

Reaction Cross Section Calculations in Neutron Induced Reactions and GEANT4 Simulation of Hadronic Interactions for the Reactor Moderator Material BeO

Directory of Open Access Journals (Sweden)

Veli ÇAPALI

2016-05-01

Full Text Available BeO is one of the most common moderator material for neutron moderation; due to its high density, neutron capture cross section and physical-chemical properties that provides usage at elevated temperatures. As it’s known, for various applications in the field of reactor design and neutron capture, reaction cross–section data are required. The cross–sections of (n,α, (n,2n, (n,t, (n,EL and (n,TOT reactions for 9Be and 16O nuclei have been calculated by using TALYS 1.6 Two Component Exciton model and EMPIRE 3.2 Exciton model in this study. Hadronic interactions of low energetic neutrons and generated isotopes–particles have been investigated for a situation in which BeO was used as a neutron moderator by using GEANT4, which is a powerful simulation software. In addition, energy deposition along BeO material has been obtained. Results from performed calculations were compared with the experimental nuclear reaction data exist in EXFOR.

Calculation of nuclear reaction parameters with the generator co-ordinate method and their interpretation

International Nuclear Information System (INIS)

Beck, R.; Mihailovic, M.V.; Poljsak, M.

1980-05-01

Collisions between complex nuclei are described variationally in terms of the GCM with the aim to provide an evidence that it is a manageable calculational procedure. The variational principle of Kohn and Kato is used to derive the expression for the K matrix. The space of scattering states is spanned entirely by antisymmetrized products of shell model wave functions describing separate clusters; the generator coordinate is the separation between the two shell model potentials. Scattering boundary conditions are enforced by solving an integral equation for the channel GC amplitude in each open channel separately. The main part of evaluation of collision parameters is performed by calculating double integrals of a form factor between channel GC amplitudes. A theorem about a property of the form factors is proved which allows reduction of the amount of work needed to calculate double integrals. The application of the method to the elastic 3 H to 4 He scattering has shown the feasibility of the calculation. It is shown how an analysis of calculated scattering parameters and corresponding scattering states in terms of quasibound states enables one to make a consistent comparison with experiment and to extract some knowledge of the reaction mechanism. Finally a comparative list of the calculational procedures of the GCM and RGM for reactions is made. (author)

Chemical reaction dynamics using the Advanced Light Source

International Nuclear Information System (INIS)

Yang, X.; Blank, D.A.; Heimann, P.A.; Lee, Y.T.; Suits, A.G.; Lin, J.; Wodtke, A.M.

1995-01-01

The recently commissioned Advanced Light Source (ALS) at Berkeley provides a high brightness, tunable VUV light source for chemical dynamics studies. A dedicated chemical dynamics beamline has been built at the ALS for studies of fundamental chemical processes. High flux (10(sup 16) photon/s with 2% bandwidth) VUV synchrotron radiation from 5 to 30 eV can be obtained from the beamline, whose source is the U8/10 undulator. Three endstations will be in operation for studies ranging from crossed beam reaction dynamics and photodissociation to high resolution photoionization dynamics and spectroscopy. A rotatable source crossed molecular beam apparatus (endstation one) has been established for unimolecular and bimolecular reactive scattering studies. Photodissociation of methylamine and ozone were carried out using VUV synchrotron radiation as the ionization detection technique at this endstation. Results show the advantages of the new endstation using VUV ionization as the detection scheme over similar machines using electron bombardment as the ionization source

Chemical reaction dynamics using the Advanced Light Source

International Nuclear Information System (INIS)

Yang, X.; Blank, D.A.; Heimann, P.A.; Lee, Y.T.; Suits, A.G.; Lin, J.; Wodtke, A.M.

1995-09-01

The recently commissioned Advanced Light Source (ALS) at Berkeley provides a high brightness, tunable VUV light source for chemical dynamics studies. A dedicated chemical dynamics beamline has been built at the ALS for studies of fundamental chemical processes. High flux (10 16 photon/s with 2% bandwidth) VUV synchrotron radiation from 5 to 30 eV can be obtained from the beamline, whose source is the U8/10 undulator. Three endstations will be in operation for studies ranging from crossed beam reaction dynamics and photodissociation to high resolution photoionization dynamics and spectroscopy. A rotatable source crossed molecular beam apparatus (endstation one) has been established for unimolecular and bimolecular reactive scattering studies. Photodissociation of methylamine and ozone were carried out using VUV synchrotron radiation as the ionization detection technique at this endstation. Results show the advantages of the new endstation using VUV ionization as the detection scheme over similar machines using electron bombardment as the ionization source

Inclusive charged-current neutrino-nucleus reactions calculated with the relativistic quasiparticle random-phase approximation

International Nuclear Information System (INIS)

Paar, N.; Vretenar, D.; Marketin, T.; Ring, P.

2008-01-01

Inclusive neutrino-nucleus cross sections are calculated using a consistent relativistic mean-field theoretical framework. The weak lepton-hadron interaction is expressed in the standard current-current form, the nuclear ground state is described with the relativistic Hartree-Bogoliubov model, and the relevant transitions to excited nuclear states are calculated in the relativistic quasiparticle random-phase approximation. Illustrative test calculations are performed for charged-current neutrino reactions on 12 C, 16 O, 56 Fe, and 208 Pb, and results compared with previous studies and available data. Through the use of the experimental neutrino fluxes, the averaged cross sections are evaluated for nuclei of interest for neutrino detectors. We analyze the total neutrino-nucleus cross sections and the evolution of the contribution of the different multipole excitations as a function of neutrino energy. The cross sections for reactions of supernova neutrinos on 16 O and 208 Pb target nuclei are analyzed as functions of the temperature and chemical potential

Application of evaporation model to the calculation of energy spectrum and angular distribution of recoil nuclei from neutron induced reaction

Energy Technology Data Exchange (ETDEWEB)

Takeda, Y; Sugimoto, M; Sugiyama, K [Tohoku Univ., Sendai (Japan). Faculty of Engineering

1978-12-01

Calculated angular distributions and energy spectra from 14.8 MeV neutron induced (n,2n) reactions based on a simple evaporation model were obtained by means of the Monte Carlo method. It was ascertained that the effects on the spectra of the method of determining the nuclear temperature and the value of the level density parameter are much smaller than those of the reaction Q-value and the nuclear mass. As a check on the calculational procedure, results of similar calculations were compared with the experimental recoil escape efficiency for /sup 27/Al(n,..cap alpha..)/sup 24/Na reaction. Distortions of the energy spectra in thick target materials were also obtained. These results suggest that this model is fully applicable to the calculation of primary knock-on atoms distributions from various nuclear reactions.

The photodissociation and reaction dynamics of vibrationally excited molecules

Energy Technology Data Exchange (ETDEWEB)

Crim, F.F. [Univ. of Wisconsin, Madison (United States)

1993-12-01

This research determines the nature of highly vibrationally excited molecules, their unimolecular reactions, and their photodissociation dynamics. The goal is to characterize vibrationally excited molecules and to exploit that understanding to discover and control their chemical pathways. Most recently the author has used a combination of vibrational overtone excitation and laser induced fluorescence both to characterize vibrationally excited molecules and to study their photodissociation dynamics. The author has also begun laser induced grating spectroscopy experiments designed to obtain the electronic absorption spectra of highly vibrationally excited molecules.

Molecular dynamics and Monte Carlo calculations in statistical mechanics

International Nuclear Information System (INIS)

Wood, W.W.; Erpenbeck, J.J.

1976-01-01

Monte Carlo and molecular dynamics calculations on statistical mechanical systems is reviewed giving some of the more significant recent developments. It is noted that the term molecular dynamics refers to the time-averaging technique for hard-core and square-well interactions and for continuous force-law interactions. Ergodic questions, methodology, quantum mechanical, Lorentz, and one-dimensional, hard-core, and square and triangular-well systems, short-range soft potentials, and other systems are included. 268 references

Molecular dynamics calculation of shear viscosity for molten salt

International Nuclear Information System (INIS)

Okamoto, Yoshihiro; Yokokawa, Mitsuo; Ogawa, Toru

1993-12-01

A computer program of molecular dynamics simulation has been made to calculate shear viscosity of molten salt. Correlation function for an off-diagonal component of stress tensor can be obtained as the results of calculation. Shear viscosity is calculated by integration of the correlation function based on the Kubo-type formula. Shear viscosities for a molten KCl ranging in temperature from 1047K to 1273K were calculated using the program. Calculation of 10 5 steps (1 step corresponds to 5 x 10 -15 s) was performed for each temperature in the 216 ions system. The obtained results were in good agreement with the reported experimental values. The program has been vectorized to achieve a faster computation in supercomputer. It makes possible to calculate the viscosity using a large number of statistics amounting to several million MD steps. (author)

Fusion enhancement in the reactions of neutron-rich nuclei

International Nuclear Information System (INIS)

Bian Baoan; Zhang Fengshou; Zhou Hongyu

2009-01-01

The neutron-rich fusion reactions are investigated systematically using the improved isospin dependent quantum molecular dynamics model. By studying the systematic dependence of fusion barrier on neuron excess, we find the enhancement of the fusion cross sections for neutron-rich nuclear reactions that give the lowered static Coulomb barriers. The calculated fusion cross sections agree quantitatively with the experimental data. We further discuss the mechanism of the fusion enhancement of the cross sections for neutron-rich nuclear reactions by analyzing the dynamical lowering of the Coulomb barrier that is attributed to the enhancement of the N/Z ratio at the neck region.

Fusion-fission dynamics

International Nuclear Information System (INIS)

Blocki, J.; Planeta, R.; Brzychczyk, J.; Grotowski, K.

1992-01-01

Classical dynamical calculations of the heavy ion induced fission processes have been performed for the reactions 40 Ar+ 141 Pr, 20 Ne+ 165 Ho and 12 C+ 175 Lu leading to the iridium like nucleus. As a result prescission lifetimes were obtained and compared with the experimental values. The comparison between the calculated and experimental lifetimes indicates that the one-body dissipation picture is much more relevant in describing the fusion-fission dynamics than the two-body one. (orig.)

Dynamics of {sup 58}Ni + {sup 54}Fe → {sup 112}Xe* reaction across the Coulomb barrier

Energy Technology Data Exchange (ETDEWEB)

Kaur, Manpreet; Sharma, Manoj K. [Thapar University, School of Physics and Materials Science, Patiala (India)

2014-03-15

The dynamical cluster-decay model (DCM) has been applied to study the decay of the {sup 112}Xe* compound nucleus formed in the massive heavy-ion reaction {sup 58}Ni + {sup 54}Fe at energies across the Coulomb barrier with E{sub c.m.} ∼ 85-110 MeV. The calculations are done for spherical fragmentation as well as by including deformation and orientation degrees of freedom of the decaying fragments. DCM-based cross sections give a nice description of the experimental fusion excitation function σ{sub ER}, within one parameter fitting, the neck length parameter (ΔR), whose value remains within the range of nuclear proximity interaction. The barrier height corresponding to the neck length parameter brings into the picture the barrier modification which enables us to address the data particularly at below barrier energies. The role of excitation energy (or temperature), deformations, orientations, angular momentum and diffuseness parameter is investigated to understand the dynamics of the {sup 58}Ni + {sup 54}Fe reaction. Finally the N/Z dependence of the fragmentation structure of different compound systems formed via {sup 58}Ni beam (projectile) is explored. (orig.)

Investigation of the Three-Nucleon System Dynamics in the Deuteron-Proton Breakup Reaction

Science.gov (United States)

Ciepał, I.; Kłos, B.; Kistryn, St.; Stephan, E.; Biegun, A.; Bodek, K.; Deltuva, A.; Epelbaum, E.; Eslami-Kalantari, M.; Fonseca, A. C.; Golak, J.; Jha, V.; Kalantar-Nayestanaki, N.; Kamada, H.; Khatri, G.; Kirillov, Da.; Kirillov, Di.; Kliczewski, St.; Kozela, A.; Kravcikova, M.; Machner, H.; Magiera, A.; Martinska, G.; Messchendorp, J.; Nogga, A.; Parol, W.; Ramazani-Moghaddam-Arani, A.; Roy, B. J.; Sakai, H.; Sekiguchi, K.; Sitnik, I.; Siudak, R.; Skibiński, R.; Sworst, R.; Urban, J.; Witała, H.; Zejma, J.

2014-08-01

Precise and large sets of cross section, vector A x , A y and tensor A xx , A xy , A yy analyzing power data for the 1 H( d, pp) n breakup reactions were measured at 100 and 130 MeV deuteron beam energies with the SALAD and BINA detectors at KVI and the Germanium Wall setup at FZ-Jülich. Results are compared with various theoretical approaches which model the three-nucleon system dynamics. The cross section data reveal a sizable three-nucleon force (3NF) and Coulomb force influence. In case of the analyzing powers very low sensitivity to these effects was found and the data are well describe by 2N models only. For A xy at 130 MeV, serious disagreements were observed when 3NF models are included in the calculations.

Capturing Chemistry in Action with Electrons: Realization of Atomically Resolved Reaction Dynamics.

Science.gov (United States)

Ischenko, Anatoly A; Weber, Peter M; Miller, R J Dwayne

2017-08-23

One of the grand challenges in chemistry has been to directly observe atomic motions during chemical processes. The depiction of the nuclear configurations in space-time to understand barrier crossing events has served as a unifying intellectual theme connecting the different disciplines of chemistry. This challenge has been cast as an imaging problem in which the technical issues reduce to achieving not only sufficient simultaneous space-time resolution but also brightness for sufficient image contrast to capture the atomic motions. This objective has been met with electrons as the imaging source. The review chronicles the first use of electron structural probes to study reactive intermediates, to the development of high bunch charge electron pulses with sufficient combined spatial-temporal resolution and intensity to literally light up atomic motions, as well as the means to characterize the electron pulses in terms of temporal brightness and image reconstruction. The use of femtosecond Rydberg spectroscopy as a novel means to use internal electron scattering within the molecular reference frame to obtain similar information on reaction dynamics is also discussed. The focus is on atomically resolved chemical reaction dynamics with pertinent references to work in other areas and forms of spectroscopy that provide additional information. Effectively, we can now directly observe the far-from-equilibrium atomic motions involved in barrier crossing and categorize chemistry in terms of a power spectrum of a few dominant reaction modes. It is this reduction in dimensionality that makes chemical reaction mechanisms transferrable to seemingly arbitrarily complex (large N) systems, up to molecules as large as biological macromolecules (N > 1000 atoms). We now have a new way to reformulate reaction mechanisms using an experimentally determined dynamic mode basis that in combination with recent theoretical advances has the potential to lead to a new conceptual basis for

The Atmospherically Important Reaction of Hydroxyl Radicals with Methyl Nitrate: A Theoretical Study Involving the Calculation of Reaction Mechanisms, Enthalpies, Activation Energies, and Rate Coefficients.

Science.gov (United States)

Ng, Maggie; Mok, Daniel K W; Lee, Edmond P F; Dyke, John M

2017-09-07

A theoretical study, involving the calculation of reaction enthalpies, activation energies, mechanisms, and rate coefficients, was made of the reaction of hydroxyl radicals with methyl nitrate, an important process for methyl nitrate removal in the earth's atmosphere. Four reaction channels were considered: formation of H 2 O + CH 2 ONO 2 , CH 3 OOH + NO 2 , CH 3 OH + NO 3 , and CH 3 O + HNO 3 . For all channels, geometry optimization and frequency calculations were performed at the M06-2X/6-31+G** level, while relative energies were improved at the UCCSD(T*)-F12/CBS level. The major channel is found to be the H abstraction channel, to give the products H 2 O + CH 2 ONO 2 . The reaction enthalpy (ΔH 298 K RX ) of this channel is computed as -17.90 kcal mol -1 . Although the other reaction channels are also exothermic, their reaction barriers are high (>24 kcal mol -1 ), and therefore these reactions do not contribute to the overall rate coefficient in the temperature range considered (200-400 K). Pathways via three transition states were identified for the H abstraction channel. Rate coefficients were calculated for these pathways at various levels of variational transition state theory including tunneling. The results obtained are used to distinguish between two sets of experimental rate coefficients, measured in the temperature range of 200-400 K, one of which is approximately an order of magnitude greater than the other. This comparison, as well as the temperature dependence of the computed rate coefficients, shows that the lower experimental values are favored. The implications of the results to atmospheric chemistry are discussed.

Kowledge-based dynamic network safety calculations. Wissensbasierte dynamische Netzsicherheitsberechnungen

Energy Technology Data Exchange (ETDEWEB)

Kulicke, B [Inst. fuer Hochspannungstechnik und Starkstromanlagen, Berlin (Germany); Schlegel, S [Inst. fuer Hochspannungstechnik und Starkstromanlagen, Berlin (Germany)

1993-06-28

An important part of network operation management is the estimation and maintenance of the security of supply. So far the control personnel has only been supported by static network analyses and safety calculations. The authors describe an expert system, which is coupled to a real time simulation program on a transputer basis, for dynamic network safety calculations. They also introduce the system concept and the most important functions of the expert system. (orig.)

Coupled-channel calculation for cross section of fusion and barrier distribution of {}^{16,17,18}O + {}^{16}O reactions

Science.gov (United States)

Fereidonnejad, R.; Sadeghi, H.; Ghambari, M.

2018-03-01

In this work, the effect of multi-phonon excitation on heavy-ion fusion reactions has been studied and fusion barrier distributions of energy intervals near and below the Coulomb barrier have been studied for 16,17,18O + 16O reactions. The structure and deformation of nuclear projectiles have been studied. Given the adaptation of computations to experimental data, our calculations predict the behavior of reactions in intervals of energy in which experimental measurements are not available. In addition the S-factor for these reactions has been calculated. The results showed that the structure and deformation of a nuclear projectile are important factors. The S-factor, obtained in the coupled-channel calculations for the {}^{16}O + {}^{16}O, {}^{17}O +{}^{16}O and {}^{18}O +{}^{16}O reactions, showed good agreement with the experimental data and had a maximum value at an energy near 5, 4.5 and 4 MeV, respectively.

Modeling the Electrochemical Hydrogen Oxidation and Evolution Reactions on the Basis of Density Functional Theory Calculations

DEFF Research Database (Denmark)

Skulason, Egill; Tripkovic, Vladimir; Björketun, Mårten

2010-01-01

charged Pt(111) slab and solvated protons in up to three water bilayers is considered and reaction energies and activation barriers are determined by using a newly developed computational scheme where the potential can be kept constant during a charge transfer reaction. We determine the rate limiting...... reaction on Pt(111) to be Tafel−Volmer for HOR and Volmer−Tafel for HER. Calculated rates agree well with experimental data. Both the H adsorption energy and the energy barrier for the Tafel reaction are then calculated for a range of metal electrodes, including Au, Ag, Cu, Pt, Pd, Ni, Ir, Rh, Co, Ru, Re......, W, Mo, and Nb, different facets, and step of surfaces. We compare the results for different facets of the Pt electrode to experimental data. Our results suggest that the most important parameter for describing the HOR or the HER activity of an electrode is its binding free energy of H. We present...

Quantum mechanical calculations of state-to-state cross sections and rate constants for the F + DCl → Cl + DF reaction.

Science.gov (United States)

Bulut, Niyazi; Kłos, Jacek; Roncero, Octavio

2015-06-07

We present accurate state-to-state quantum wave packet calculations of integral cross sections and rate constants for the title reaction. Calculations are carried out on the best available ground 1(2)A' global adiabatic potential energy surface of Deskevich et al. [J. Chem. Phys. 124, 224303 (2006)]. Converged state-to-state reaction cross sections have been calculated for collision energies up to 0.5 eV and different initial rotational and vibrational excitations, DCl(v = 0, j = 0 - 1; v = 1, j = 0). Also, initial-state resolved rate constants of the title reaction have been calculated in a temperature range of 100-400 K. It is found that the initial rotational excitation of the DCl molecule does not enhance reactivity, in contract to the reaction with the isotopologue HCl in which initial rotational excitation produces an important enhancement. These differences between the isotopologue reactions are analyzed in detail and attributed to the presence of resonances for HCl(v = 0, j), absent in the case of DCl(v = 0, j). For vibrational excited DCl(v = 1, j), however, the reaction cross section increases noticeably, what is also explained by another resonance.

Calculation of particle dynamics in CI-10 cyclotron

International Nuclear Information System (INIS)

Samsonov, E.V.; Karamysheva, G.A.; Vorozhtsov, S.B.

1999-01-01

The calculations of beam dynamic characteristics of High-Intensity Cyclotron-Injector CI-10 for deuteron beam of 15 MeV energy are presented. Analytical estimations of space charge effects are given. In order to increase the intensity of the accelerator beam some ideas about the cyclotron design modification are given too. (author)

Fission cross section calculations for 209Bi target nucleus based on fission reaction models in high energy regions

Directory of Open Access Journals (Sweden)

Kaplan Abdullah

2015-01-01

Full Text Available Implementation of projects of new generation nuclear power plants requires the solving of material science and technological issues in developing of reactor materials. Melts of heavy metals (Pb, Bi and Pb-Bi due to their nuclear and thermophysical properties, are the candidate coolants for fast reactors and accelerator-driven systems (ADS. In this study, α, γ, p, n and 3He induced fission cross section calculations for 209Bi target nucleus at high-energy regions for (α,f, (γ,f, (p,f, (n,f and (3He,f reactions have been investigated using different fission reaction models. Mamdouh Table, Sierk, Rotating Liquid Drop and Fission Path models of theoretical fission barriers of TALYS 1.6 code have been used for the fission cross section calculations. The calculated results have been compared with the experimental data taken from the EXFOR database. TALYS 1.6 Sierk model calculations exhibit generally good agreement with the experimental measurements for all reactions used in this study.

Coarse-grained molecular dynamics simulations of polymerization with forward and backward reactions.

Science.gov (United States)

Krajniak, Jakub; Zhang, Zidan; Pandiyan, Sudharsan; Nies, Eric; Samaey, Giovanni

2018-06-11

We develop novel parallel algorithms that allow molecular dynamics simulations in which byproduct molecules are created and removed because of the chemical reactions during the molecular dynamics simulation. To prevent large increases in the potential energy, we introduce the byproduct molecules smoothly by changing the non-bonded interactions gradually. To simulate complete equilibrium reactions, we allow the byproduct molecules attack and destroy created bonds. Modeling of such reactions are, for instance, important to study the pore formation due to the presence of e.g. water molecules or development of polymer morphology during the process of splitting off byproduct molecules. Another concept that could be studied is the degradation of polymeric materials, a very important topic in a recycling of polymer waste. We illustrate the method by simulating the polymerization of polyethylene terephthalate (PET) at the coarse-grained level as an example of a polycondensation reaction with water as a byproduct. The algorithms are implemented in a publicly available software package and are easily accessible using a domain-specific language that describes chemical reactions in an input configuration file. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Calculations of long-lived isomer production in neutron reactions

International Nuclear Information System (INIS)

Chadwick, M.B.; Young, P.G.

1992-01-01

We present theoretical calculations for the production of the long-lived isomers 93m Nb (1/2-, 16 yr), 121m Sn (11/2-, 55 yr), 166m Ho (7-, 1200 yr), 184m Re (8+, 165 d), 186m Re (8+, 2x10 5 yr), 178 Hf (16+, 31 yr), 179m Hf (25/2-, 25 d), and 192m Ir (9+, 241 yr), all of which pose potential radiation activation problems in nuclear fusion reactors if produced in 14-MeV neutron-induced reactions. We consider (n,2n), (n,n'), and (n,γ) production modes and compare our results both with experimental data (where available) and systematics. We also investigate the dependence of the isomeric cross section ratio on incident neutron energy for the isomers under consideration. The statistical Hauser-Feshbach plus preequilibrium code GNASH was used for the calculations. Where discrete state experimental information was lacking, rotational band members above the isomeric state, which can be justified theoretically but have not been experimentally resolved, were reconstructed. (author). 16 refs, 10 figs, 4 tabs

Dynamic phase transition in diffusion-limited reactions

International Nuclear Information System (INIS)

Tauber, U.C.

2002-01-01

Many non-equilibrium systems display dynamic phase transitions from active to absorbing states, where fluctuations cease entirely. Based on a field theory representation of the master equation, the critical behavior can be analyzed by means of the renormalization group. The resulting universality classes for single-species systems are reviewed here. Generically, the critical exponents are those of directed percolation (Reggeon field theory), with critical dimension d c = 4. Yet local particle number parity conservation in even-offspring branching and annihilating random walks implies an inactive phase (emerging below d c = 4/3) that is characterized by the power laws of the pair annihilation reaction, and leads to different critical exponents at the transition. For local processes without memory, the pair contact process with diffusion represents the only other non-trivial universality class. The consistent treatment of restricted site occupations and quenched random reaction rates are important open issues (Author)

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multi-zone Reaction Kinetics: Model Derivation and Validation

Science.gov (United States)

Rout, Bapin Kumar; Brooks, Geoff; Rhamdhani, M. Akbar; Li, Zushu; Schrama, Frank N. H.; Sun, Jianjun

2018-04-01

A multi-zone kinetic model coupled with a dynamic slag generation model was developed for the simulation of hot metal and slag composition during the basic oxygen furnace (BOF) operation. The three reaction zones (i) jet impact zone, (ii) slag-bulk metal zone, (iii) slag-metal-gas emulsion zone were considered for the calculation of overall refining kinetics. In the rate equations, the transient rate parameters were mathematically described as a function of process variables. A micro and macroscopic rate calculation methodology (micro-kinetics and macro-kinetics) were developed to estimate the total refining contributed by the recirculating metal droplets through the slag-metal emulsion zone. The micro-kinetics involves developing the rate equation for individual droplets in the emulsion. The mathematical models for the size distribution of initial droplets, kinetics of simultaneous refining of elements, the residence time in the emulsion, and dynamic interfacial area change were established in the micro-kinetic model. In the macro-kinetics calculation, a droplet generation model was employed and the total amount of refining by emulsion was calculated by summing the refining from the entire population of returning droplets. A dynamic FetO generation model based on oxygen mass balance was developed and coupled with the multi-zone kinetic model. The effect of post-combustion on the evolution of slag and metal composition was investigated. The model was applied to a 200-ton top blowing converter and the simulated value of metal and slag was found to be in good agreement with the measured data. The post-combustion ratio was found to be an important factor in controlling FetO content in the slag and the kinetics of Mn and P in a BOF process.

A modified Gaussian integration method for thermal reaction rate calculation in U- and Pu-isotopes

International Nuclear Information System (INIS)

Bosevski, T.; Fredin, B.

1966-01-01

An advanced multi-group cell calculations a lot of data information is very often necessary, and hence the data administration will be elaborate, and the spectrum calculation will be time consuming. We think it is possible to reduce the necessary data information by using an effective reaction rate integration method well suited for U- and Pu-absorptions (author)

Chemical memory reactions induced bursting dynamics in gene expression.

Science.gov (United States)

Tian, Tianhai

2013-01-01

Memory is a ubiquitous phenomenon in biological systems in which the present system state is not entirely determined by the current conditions but also depends on the time evolutionary path of the system. Specifically, many memorial phenomena are characterized by chemical memory reactions that may fire under particular system conditions. These conditional chemical reactions contradict to the extant stochastic approaches for modeling chemical kinetics and have increasingly posed significant challenges to mathematical modeling and computer simulation. To tackle the challenge, I proposed a novel theory consisting of the memory chemical master equations and memory stochastic simulation algorithm. A stochastic model for single-gene expression was proposed to illustrate the key function of memory reactions in inducing bursting dynamics of gene expression that has been observed in experiments recently. The importance of memory reactions has been further validated by the stochastic model of the p53-MDM2 core module. Simulations showed that memory reactions is a major mechanism for realizing both sustained oscillations of p53 protein numbers in single cells and damped oscillations over a population of cells. These successful applications of the memory modeling framework suggested that this innovative theory is an effective and powerful tool to study memory process and conditional chemical reactions in a wide range of complex biological systems.

Direct dynamics trajectory study of the reaction of formaldehyde cation with D2: vibrational and zero-point energy effects on quasiclassical trajectories.

Science.gov (United States)

Liu, Jianbo; Song, Kihyung; Hase, William L; Anderson, Scott L

2005-12-22

Quasiclassical, direct dynamics trajectories have been used to study the reaction of formaldehyde cation with molecular hydrogen, simulating the conditions in an experimental study of H2CO+ vibrational effects on this reaction. Effects of five different H2CO+ modes were probed, and we also examined different approaches to treating zero-point energy in quasiclassical trajectories. The calculated absolute cross-sections are in excellent agreement with experiments, and the results provide insight into the reaction mechanism, product scattering behavior, and energy disposal, and how they vary with impact parameter and reactant state. The reaction is sharply orientation-dependent, even at high collision energies, and both trajectories and experiment find that H2CO+ vibration inhibits reaction. On the other hand, the trajectories do not reproduce the anomalously strong effect of nu2(+) (the CO stretch). The origin of the discrepancy and approaches for minimizing such problems in quasiclassical trajectories are discussed.

Dynamically biased statistical model for the ortho/para conversion in the H2+H3+ --> H3++ H2 reaction

Science.gov (United States)

Gómez-Carrasco, Susana; González-Sánchez, Lola; Aguado, Alfredo; Sanz-Sanz, Cristina; Zanchet, Alexandre; Roncero, Octavio

2012-09-01

In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007), 10.1063/1.2430711]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H_5^+ complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasi-classical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H_5^+ complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, α(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011), 10.1063/1.3587246] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.

Calculation of reaction energies and adiabatic temperatures for waste tank reactions

International Nuclear Information System (INIS)

Burger, L.L.

1995-10-01

Continual concern has been expressed over potentially hazardous exothermic reactions that might occur in Hanford Site underground waste storage tanks. These tanks contain many different oxidizable compounds covering a wide range of concentrations. The chemical hazards are a function of several interrelated factors, including the amount of energy (heat) produced, how fast it is produced, and the thermal absorption and heat transfer properties of the system. The reaction path(s) will determine the amount of energy produced and kinetics will determine the rate that it is produced. The tanks also contain many inorganic compounds inert to oxidation. These compounds act as diluents and can inhibit exothermic reactions because of their heat capacity and thus, in contrast to the oxidizable compounds, provide mitigation of hazardous reactions. In this report the energy that may be released when various organic and inorganic compounds react is computed as a function of the reaction-mix composition and the temperature. The enthalpy, or integrated heat capacity, of these compounds and various reaction products is presented as a function of temperature; the enthalpy of a given mixture can then be equated to the energy release from various reactions to predict the maximum temperature which may be reached. This is estimated for several different compositions. Alternatively, the amounts of various diluents required to prevent the temperature from reaching a critical value can be estimated. Reactions taking different paths, forming different products such as N 2 O in place of N 2 are also considered, as are reactions where an excess of caustic is present. Oxidants other than nitrate and nitrite are considered briefly

Calculation of reaction energies and adiabatic temperatures for waste tank reactions

Energy Technology Data Exchange (ETDEWEB)

Burger, L.L.

1995-10-01

Continual concern has been expressed over potentially hazardous exothermic reactions that might occur in Hanford Site underground waste storage tanks. These tanks contain many different oxidizable compounds covering a wide range of concentrations. The chemical hazards are a function of several interrelated factors, including the amount of energy (heat) produced, how fast it is produced, and the thermal absorption and heat transfer properties of the system. The reaction path(s) will determine the amount of energy produced and kinetics will determine the rate that it is produced. The tanks also contain many inorganic compounds inert to oxidation. These compounds act as diluents and can inhibit exothermic reactions because of their heat capacity and thus, in contrast to the oxidizable compounds, provide mitigation of hazardous reactions. In this report the energy that may be released when various organic and inorganic compounds react is computed as a function of the reaction-mix composition and the temperature. The enthalpy, or integrated heat capacity, of these compounds and various reaction products is presented as a function of temperature; the enthalpy of a given mixture can then be equated to the energy release from various reactions to predict the maximum temperature which may be reached. This is estimated for several different compositions. Alternatively, the amounts of various diluents required to prevent the temperature from reaching a critical value can be estimated. Reactions taking different paths, forming different products such as N{sub 2}O in place of N{sub 2} are also considered, as are reactions where an excess of caustic is present. Oxidants other than nitrate and nitrite are considered briefly.

Calculation of the fifth atomic energy research dynamic benchmark with APROS

International Nuclear Information System (INIS)

Puska Eija Karita; Kontio Harii

1998-01-01

The band-out presents the model used for calculation of the fifth atomic energy research dynamic benchmark with APROS code. In the calculation of the fifth atomic energy research dynamic benchmark the three-dimensional neutronics model of APROS was used. The core was divided axially into 20 nodes according to the specifications of the benchmark and each six identical fuel assemblies were placed into one one-dimensional thermal hydraulic channel. The five-equation thermal hydraulic model was used in the benchmark. The plant process and automation was described with a generic WWER-440 plant model created by IVO Power Engineering Ltd. - Finland. (Author)

The oxygen reduction reaction mechanism on Pt(111) from density functional theory calculations

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Skulason, Egill; Siahrostami, Samira

2010-01-01

We study the oxygen reduction reaction (ORR) mechanism on a Pt(1 1 1) surface using density functional theory calculations We find that at low overpotentials the surface is covered with a half dissociated water layer We estimate the barrier for proton transfer to this surface and the barrier...

The hydrogen abstraction reaction O(3P) + CH4: A new analytical potential energy surface based on fit to ab initio calculations

International Nuclear Information System (INIS)

González-Lavado, Eloisa; Corchado, Jose C.; Espinosa-Garcia, Joaquin

2014-01-01

Based exclusively on high-level ab initio calculations, a new full-dimensional analytical potential energy surface (PES-2014) for the gas-phase reaction of hydrogen abstraction from methane by an oxygen atom is developed. The ab initio information employed in the fit includes properties (equilibrium geometries, relative energies, and vibrational frequencies) of the reactants, products, saddle point, points on the reaction path, and points on the reaction swath, taking especial caution respecting the location and characterization of the intermediate complexes in the entrance and exit channels. By comparing with the reference results we show that the resulting PES-2014 reproduces reasonably well the whole set of ab initio data used in the fitting, obtained at the CCSD(T) = FULL/aug-cc-pVQZ//CCSD(T) = FC/cc-pVTZ single point level, which represents a severe test of the new surface. As a first application, on this analytical surface we perform an extensive dynamics study using quasi-classical trajectory calculations, comparing the results with recent experimental and theoretical data. The excitation function increases with energy (concave-up) reproducing experimental and theoretical information, although our values are somewhat larger. The OH rotovibrational distribution is cold in agreement with experiment. Finally, our results reproduce experimental backward scattering distribution, associated to a rebound mechanism. These results lend confidence to the accuracy of the new surface, which substantially improves the results obtained with our previous surface (PES-2000) for the same system

Dynamical isospin effects in nucleon-induced reactions

International Nuclear Information System (INIS)

Ou Li; Li Zhuxia; Wu Xizhen

2008-01-01

The isospin effects in proton-induced reactions on isotopes of 112-132 Sn and the corresponding β-stable isobars are studied by means of the improved quantum molecular dynamics model and some sensitive probes for the density dependence of the symmetry energy at subnormal densities are proposed. The beam energy range is chosen to be 100-300 MeV. Our study shows that the system size dependence of the reaction cross sections for p+ 112-132 Sn deviates from the Carlson's empirical expression obtained by fitting the reaction cross sections for proton on nuclei along the β-stability line and sensitively depends on the stiffness of the symmetry energy. We also find that the angular distribution of elastic scattering for p+ 132 Sn at large impact parameters is very sensitive to the density dependence of the symmetry energy, which is uniquely due to the effect of the symmetry potential with no mixture of the effect from the isospin dependence of the nucleon-nucleon cross sections. The isospin effects in neutron-induced reactions are also studied and it is found that the effects are just opposite to that in proton-induced reactions. We find that the difference between the peaks of the angular distributions of elastic scattering for p+ 132 Sn and n+ 132 Sn at E p,n =100 MeV and b=7.5 fm is positive for soft symmetry energy U sym sf and negative for super-stiff symmetry energy U sym nlin and close to zero for linear density dependent symmetry energy U sym lin , which seems very useful for constraining the density dependence of the symmetry energy at subnormal densities

Low energy ion-molecule reaction dynamics and chemiionization kinetics: Progress report, February 1, 1985-January 31, 1988

International Nuclear Information System (INIS)

Farrar, J.M.

1988-01-01

The research program at Rochester is devoted to an understanding of the dynamics of elementary gas phase ionic reactions by using the molecular beam methods. We seek to elucidate pathways for energy disposal in elementary reactions, with the goal of using this information to understand the topology of the potential surfaces which govern the reaction, applying the results to ionic channels in combustion systems. We have made significant accomplishments in several distinct areas of research in crossed beam studies of ion-neutral reaction dynamics in the past three years. Our research has focused on the following topics and has resulted in 15 publications and submissions to major journals, with several additional manuscripts in preparation: dynamics of gas phase proton transfer reactions, gas phase carbon and methyl cation chemistry, reactive scattering from double minimum potentials, reactions of highly vibrationally excited ions: NH 3 + + D 2 , and electron and proton transfer reactions of anions. 9 refs

Comparison of measured and calculated reaction rate distributions in an scwr-like test lattice

Energy Technology Data Exchange (ETDEWEB)

Raetz, Dominik, E-mail: dominik.raetz@psi.ch [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Jordan, Kelly A., E-mail: kelly.jordan@psi.ch [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Murphy, Michael F., E-mail: mike.murphy@psi.ch [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Perret, Gregory, E-mail: gregory.perret@psi.ch [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Chawla, Rakesh, E-mail: rakesh.chawla@psi.ch [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, EPFL (Switzerland)

2011-04-15

High resolution gamma-ray spectroscopy measurements were performed on 61 rods of an SCWR-like fuel lattice, after irradiation in the central test zone of the PROTEUS zero-power research reactor at the Paul Scherrer Institute in Switzerland. The derived reaction rates are the capture rate in {sup 238}U (C{sub 8}) and the total fission rate (F{sub tot}), and also the reaction rate ratio C{sub 8}/F{sub tot}. Each of these has been mapped rod-wise on the lattice and compared to calculated results from whole-reactor Monte Carlo simulations with MCNPX. Ratios of calculated to experimental values (C/E's) have been assessed for the C{sub 8}, F{sub tot} and C{sub 8}/F{sub tot} distributions across the lattice. These C/E's show excellent agreement between the calculations and the measurements. For the {sup 238}U capture rate distribution, the 1{sigma} level in the comparisons corresponds to an uncertainty of {+-}0.8%, while for the total fission rate the corresponding value is {+-}0.4%. The uncertainty for C{sub 8}/F{sub tot}, assessed as a reaction rate ratio characterizing each individual rod position in the test lattice, is significantly higher at {+-}2.2%. To determine the reproducibility of these results, the measurements were performed twice, once in 2006 and again in 2009. The agreement between these two measurement sets is within the respective statistical uncertainties.

Dynamical gluon masses in perturbative calculations at the loop level

International Nuclear Information System (INIS)

Machado, Fatima A.; Natale, Adriano A.

2013-01-01

Full text: In the phenomenology of strong interactions one always has to deal at some extent with the interplay between perturbative and non-perturbative QCD. On one hand, the former has quite developed tools, yielded by asymptotic freedom. On the other, concerning the latter, we nowadays envisage the following scenario: 1) There are strong evidences for a dynamically massive gluon propagator and infrared finite coupling constant; 2) There is an extensive and successful use of an infrared finite coupling constant in phenomenological calculations at tree level; 3) The infrared finite coupling improves the perturbative series convergence; 4) The dynamical gluon mass provides a natural infrared cutoff in the physical processes at the tree level. Considering this scenario it is natural to ask how these non-perturbative results can be used in perturbative calculations of physical observables at the loop level. Recent papers discuss how off-shell gauge and renormalization group invariant Green functions can be computed with the use of the Pinch Technique (PT), with IR divergences removed by the dynamical gluon mass, and using a well defined effective charge. In this work we improve the former results by the authors, which evaluate 1-loop corrections to some two- and three-point functions of SU(3) pure Yang-Mills, investigating the dressing of quantities that could account for an extension of loop calculations to the infrared domain of the theory, in a way applicable to phenomenological calculations. One of these improvements is maintaining the gluon propagator transverse in such a scheme. (author)

Zero-point Energy is Needed in Molecular Dynamics Calculations to Access the Saddle Point for H+HCN→H2CN* and cis/trans-HCNH* on a New Potential Energy Surface.

Science.gov (United States)

Wang, Xiaohong; Bowman, Joel M

2013-02-12

We calculate the probabilities for the association reactions H+HCN→H2CN* and cis/trans-HCNH*, using quasiclassical trajectory (QCT) and classical trajectory (CT) calculations, on a new global ab initio potential energy surface (PES) for H2CN including the reaction channels. The surface is a linear least-squares fit of roughly 60 000 CCSD(T)-F12b/aug-cc-pVDZ electronic energies, using a permutationally invariant basis with Morse-type variables. The reaction probabilities are obtained at a variety of collision energies and impact parameters. Large differences in the threshold energies in the two types of dynamics calculations are traced to the absence of zero-point energy in the CT calculations. We argue that the QCT threshold energy is the realistic one. In addition, trajectories find a direct pathway to trans-HCNH, even though there is no obvious transition state (TS) for this pathway. Instead the saddle point (SP) for the addition to cis-HCNH is evidently also the TS for direct formation of trans-HCNH.

Calculations of Excitation Functions of Some Structural Fusion Materials for ( n, t) Reactions up to 50 MeV Energy

Science.gov (United States)

Tel, E.; Durgu, C.; Aktı, N. N.; Okuducu, Ş.

2010-06-01

Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So, the working out the systematics of ( n, t) reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. In this study, ( n, t) reactions for some structural fusion materials such as 27Al, 51V, 52Cr, 55Mn, and 56Fe have been investigated. The new calculations on the excitation functions of 27Al( n, t)25Mg, 51V( n, t)49Ti, 52Cr( n, t)50V, 55Mn( n, t)53Cr and 56Fe( n, t)54Mn reactions have been carried out up to 50 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve the new evaluated the geometry dependent hybrid model, hybrid model and the cascade exciton model. Equilibrium effects are calculated according to the Weisskopf-Ewing model. Also in the present work, we have calculated ( n, t) reaction cross-sections by using new evaluated semi-empirical formulas developed by Tel et al. at 14-15 MeV energy. The calculated results are discussed and compared with the experimental data taken from the literature.

The calculation of turbulence phenomena in plasma focus dynamics using REDUCE

International Nuclear Information System (INIS)

Hayd, A.; Maurer, M.; Meinke, P.; Kaeppeler, H.J.

1982-05-01

Based on previous calculations of the development of highly turbulent plasma states resulting from m=0 instabilities and the application to the turbulent development in the late stage of a plasma focus experiment, using REDUE, the treatment of plasma focus dynamics is extended to the compression stage and 'intermediate' stage between maximum density and m = o onset. For this, a two-fluid model of the magneto-fluid dynamic equations is employed. The non-linear development is again treated in ω, k-space and transformed back into r, t-space to obtain local dynamic variables as functions of time. The calculation is applied to the Stuttgart plasma focus experiment POSEIDON. It is shown that for relatively high pinch currents, neutron production also appears in the 'intermediate' phase, the life-time of which increases with increasing pinch current. (orig.)

Are Nonadiabatic Reaction Dynamics the Key to Novel Organosilicon Molecules? The Silicon (Si(3P))-Dimethylacetylene (C4H6(X1A1g)) System as a Case Study.

Science.gov (United States)

Thomas, Aaron M; Dangi, Beni B; Yang, Tao; Kaiser, Ralf I; Lin, Lin; Chou, Tzu-Jung; Chang, Agnes H H

2018-06-06

The bimolecular gas phase reaction of ground-state silicon (Si; 3 P) with dimethylacetylene (C 4 H 6 ; X 1 A 1g ) was investigated under single collision conditions in a crossed molecular beams machine. Merged with electronic structure calculations, the data propose nonadiabatic reaction dynamics leading to the formation of singlet SiC 4 H 4 isomer(s) and molecular hydrogen (H 2 ) via indirect scattering dynamics along with intersystem crossing (ISC) from the triplet to the singlet surface. The reaction may lead to distinct energetically accessible singlet SiC 4 H 4 isomers ( 1 p8- 1 p24) in overall exoergic reaction(s) (-107 -20 +12 kJ mol -1 ). All feasible reaction products are either cyclic, carry carbene analogous silylene moieties, or carry C-Si-H or C-Si-C bonds that would require extensive isomerization from the initial collision complex(es) to the fragmenting singlet intermediate(s). The present study demonstrates the first successful crossed beams study of an exoergic reaction channel arising from bimolecular collisions of silicon, Si( 3 P), with a hydrocarbon molecule.

Pattern dynamics of the reaction-diffusion immune system.

Science.gov (United States)

Zheng, Qianqian; Shen, Jianwei; Wang, Zhijie

2018-01-01

In this paper, we will investigate the effect of diffusion, which is ubiquitous in nature, on the immune system using a reaction-diffusion model in order to understand the dynamical behavior of complex patterns and control the dynamics of different patterns. Through control theory and linear stability analysis of local equilibrium, we obtain the optimal condition under which the system loses stability and a Turing pattern occurs. By combining mathematical analysis and numerical simulation, we show the possible patterns and how these patterns evolve. In addition, we establish a bridge between the complex patterns and the biological mechanism using the results from a previous study in Nature Cell Biology. The results in this paper can help us better understand the biological significance of the immune system.

Photonuclear reactions in the GNASH code: Benchmarking model calculations for reactions on lead up to 140 MeV

International Nuclear Information System (INIS)

Chadwick, M.B.; Young, P.G.

1994-08-01

The authors have developed the GNASH code to include photonuclear reactions for incident energies up to 140 MeV. Photoabsorption is modeled through the giant resonance at the lower energies, and the quasideuteron mechanism at the higher energies, and the angular momentum coupling of the incident photon to the target is properly accounted for. After the initial interaction, primary and multiple preequilibrium emission of fast particles can occur before compound nucleus decay from the equilibrated compound nucleus. The angular distributions from compound nucleus decay are taken as isotropic, and those from preequilibrium emission (which they obtain from a phase-space model which conserves momentum) are forward-peaked. To test the new modeling they apply the code to calculate photonuclear reactions on 208 Pb for incident energies up to 140 MeV

Reaction dynamics of electronically excited alkali atoms with simpler molecules

International Nuclear Information System (INIS)

Weiss, P.S.; Mestdagh, J.M.; Schmidt, H.; Vernon, M.F.; Covinsky, M.H.; Balko, B.A.; Lee, Y.T.

1985-05-01

The reactions of electronically excited sodium atoms with simple molecules have been studied in crossed molecular beams experiments. Electronically excited Na(3 2 P/sub 3/2/, 4 2 D/sub 5/2/, and 5 2 S/sub 1/2/) were produced by optical pumping using single frequency dye lasers. The effects of the symmetry, and the orientation and alignment of the excited orbital on the chemical reactivity, and detailed information on the reaction dynamics were derived from measurements of the product angular and velocity distributions. 12 refs., 9 figs

Dynamical Dipole and Equation of State in N/Z Asymmetric Fusion Reactions

Directory of Open Access Journals (Sweden)

Giaz Agnese

2014-03-01

Full Text Available In heavy ion reactions, in the case of N/Z asymmetry between projectile and target, the process leading to complete fusion is expected to produce pre-equilibrium dipole γ-ray emission. It is generated during the charge equilibration process and it is known as Dynamical Dipole. A new measurement of the dynamical dipole emission was performed by studying 16O + 116Sn at 12 MeV/u. These data, together with those measured at 8.1 MeV/u and 15.6 MeV/u for the same reaction, provide the dependence on the Dynamical Dipole total emission yield with beam energy and they can be compared with theoretical expectations. The experimental results show a weak increase of the Dynamical Dipole total yield with beam energies and are in agreement with the prediction of a theoretical model based on the Boltzmann–Nordheim–Vlasov (BNV approach. The measured trend with beam energy does not confirm the rise and fall behavior previously reported for the same fused compound but with a much higher dipole moment.

Variational RRKM calculation of thermal rate constant for C–H bond fission reaction of nitro methane

Directory of Open Access Journals (Sweden)

Afshin Taghva Manesh

2017-02-01

Full Text Available The present work provides quantitative results for the rate constants of unimolecular C–H bond fission reactions in the nitro methane at elevated temperatures up to 2000 K. In fact, there are three different hydrogen atoms in the nitro methane. The potential energy surface for each C–H bond fission reaction of nitro methane was investigated by ab initio calculations. The geometry and vibrational frequencies of the species involved in this process were optimized at the MP2 level of theory, using the cc-pvdz basis set. Since C–H bond fission channel is a barrierless reaction, we have used variational RRKM theory to predict rate coefficients. By means of calculated rate coefficients at different temperatures, the Arrhenius expression of the channel over the temperature range of 100–2000 K is k(T = 5.9E19∗exp(−56274.6/T.

ORBIT : BEAM DYNAMICS CALCULATIONS FOR HIGH - INTENSITY RINGS

International Nuclear Information System (INIS)

HOLMES, J.A.; DANILOV, V.; GALAMBOS, J.; SHISHLO, A.; COUSINEAU, S.; CHOU, W.; MICHELOTTI, L.; OSTIGUY, F.; WEI, J.

2002-01-01

We are developing a computer code, ORBIT, specifically for beam dynamics calculations in high-intensity rings. Our approach allows detailed simulation of realistic accelerator problems. ORBIT is a particle-in-cell tracking code that transports bunches of interacting particles through a series of nodes representing elements, effects, or diagnostics that occur in the accelerator lattice. At present, ORBIT contains detailed models for strip-foil injection including painting and foil scattering; rf focusing and acceleration; transport through various magnetic elements; longitudinal and transverse impedances; longitudinal, transverse, and three-dimensional space charge forces; collimation and limiting apertures; and the calculation of many useful diagnostic quantities. ORBIT is an object-oriented code, written in C++ and utilizing a scripting interface for the convenience of the user. Ongoing improvements include the addition of a library of accelerator maps, BEAMLINE/MXYZPTLK the introduction of a treatment magnet errors and fringe fields; the conversion of the scripting interface to the standard scripting language, Python; and the parallelization of the computations using MPI. The ORBIT code is an open source, powerful, and convenient tool for studying beam dynamics in high-intensity rings

Dynamics of ion–molecule reactions from beam experiments: A historical survey

Czech Academy of Sciences Publication Activity Database

Herman, Zdeněk; Futrell, J. H.

2015-01-01

Roč. 377, FEB 2015 (2015), s. 84-92 ISSN 1387-3806 Institutional support: RVO:61388955 Keywords : Ion–molecule reactions * Dynamics * Beam scattering Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.183, year: 2015

Dynamically biased statistical model for the ortho/para conversion in the H2 + H3+ → H3+ + H2 reaction.

Science.gov (United States)

Gómez-Carrasco, Susana; González-Sánchez, Lola; Aguado, Alfredo; Sanz-Sanz, Cristina; Zanchet, Alexandre; Roncero, Octavio

2012-09-07

In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H(5)(+) complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasi-classical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H(5)(+) complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, α(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011)] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.

Mining chemical reactions using neighborhood behavior and condensed graphs of reactions approaches.

Science.gov (United States)

de Luca, Aurélie; Horvath, Dragos; Marcou, Gilles; Solov'ev, Vitaly; Varnek, Alexandre

2012-09-24

This work addresses the problem of similarity search and classification of chemical reactions using Neighborhood Behavior (NB) and Condensed Graphs of Reaction (CGR) approaches. The CGR formalism represents chemical reactions as a classical molecular graph with dynamic bonds, enabling descriptor calculations on this graph. Different types of the ISIDA fragment descriptors generated for CGRs in combination with two metrics--Tanimoto and Euclidean--were considered as chemical spaces, to serve for reaction dissimilarity scoring. The NB method has been used to select an optimal combination of descriptors which distinguish different types of chemical reactions in a database containing 8544 reactions of 9 classes. Relevance of NB analysis has been validated in generic (multiclass) similarity search and in clustering with Self-Organizing Maps (SOM). NB-compliant sets of descriptors were shown to display enhanced mapping propensities, allowing the construction of better Self-Organizing Maps and similarity searches (NB and classical similarity search criteria--AUC ROC--correlate at a level of 0.7). The analysis of the SOM clusters proved chemically meaningful CGR substructures representing specific reaction signatures.

Development of a new molecular dynamics method for tribochemical reaction and its application to formation dynamics of MoS2 tribofilm

International Nuclear Information System (INIS)

Morita, Yusuke; Onodera, Tasuku; Suzuki, Ai; Sahnoun, Riadh; Koyama, Michihisa; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Del Carpio, Carlos A.; Shin-yoshi, Takatoshi; Nishino, Noriaki; Suzuki, Atsushi; Miyamoto, Akira

2008-01-01

Recently we have developed a novel molecular dynamics program NEW-RYUDO-CR, which can deal with chemical reactions. The developed method has been applied to the study of tribochemical reaction dynamics of MoS 2 tribofilm on iron surface. The initially amorphous MoS 2 layer self-organized its structure as result of the tribochemical reactions and formed layered MoS 2 tribofilm. The friction coefficient significantly decreased as the MoS 2 tribofilm was formed. Besides, sliding was observed between sulfur layers of MoS 2 tribofilms which occurred due to repulsive Coulombic interaction forces between sulfur atoms. This indicates that the formation of the layered MoS 2 tribofilm is important to achieve better lubrication properties

Calculation for fission decay from heavy ion reactions at intermediate energies

International Nuclear Information System (INIS)

Blaich, T.; Begemann-Blaich, M.; Fowler, M.M.; Wilhelmy, J.B.; Britt, H.C.; Fields, D.J.; Hansen, L.F.; Namboodiri, M.N.; Sangster, T.C.; Fraenkel, Z.

1992-01-01

A detailed deexcitation calculation is presented for target residues resulting from intermediate-energy heavy ion reactions. The model involves an intranuclear cascade, subsequent fast nucleon emission, and final decay by statistical evaporation including fission. Results are compared to data from bombardments with Fe and Nb projectiles on targets of Ta, Au, and Th at 100 MeV/nucleon. The majority of observable features are reproduced with this simple approach, making obvious the need for involving new physical phenomena associated with multifragmentation or other collective dissipation mechanisms

Microscopic calculation of friction coefficients for use in heavy-ion reaction

International Nuclear Information System (INIS)

Iwamoto, A.; Harada, K.; Yoshida, S.

1981-01-01

A microscopic calculation has been done for the friction coefficient for use in the deep-inelastic collision of heavy nuclei. We adopted the formalism of the linear response theory as a basis and used the adiabatic base of the two-center shell model. Several reaction channels with the total mass numbers of 236 and 260 systems were investigated. The friction coefficients for the radial and deforming motions including the coupling term were calculated as a function of the distance between two nuclei and deformation of the two nuclei for each channel. The general feature of the friction coefficient, its strength and form factor, was clarified in this model and comparison with the results of other models were done. It was found that our model gives a physically plausible value for the friction coefficient as a whole. (orig.)

Calculation of reaction energies and adiabatic temperatures for waste tank reactions

International Nuclear Information System (INIS)

Burger, L.L.

1993-03-01

Continual concern has been expressed over potentially hazardous exothermic reactions that might occur in underground Hanford waste tanks. These tanks contain many different oxidizable compounds covering a wide range of concentrations. Several may be in concentrations and quantities great enough to be considered a hazard in that they could undergo rapid and energetic chemical reactions with nitrate and nitrite salts that are present. The tanks also contain many inorganic compounds inert to oxidation. In this report the computed energy that may be released when various organic and inorganic compounds react is computed as a function of the reaction mix composition and the temperature. The enthalpy, or integrated heat capacity, of these compounds and various reaction products is presented as a function of temperature, and the enthalpy of a given mixture can then be equated to the energy release from various reactions to predict the maximum temperature that may be reached. This is estimated for several different compositions. Alternatively, the amounts of various diluents required to prevent the temperature from reaching a critical value can be estimated

Structure-dynamic model verification calculation of PWR 5 tests

International Nuclear Information System (INIS)

Engel, R.

1980-02-01

Within reactor safety research project RS 16 B of the German Federal Ministry of Research and Technology (BMFT), blowdown experiments are conducted at Battelle Institut e.V. Frankfurt/Main using a model reactor pressure vessel with a height of 11,2 m and internals corresponding to those in a PWR. In the present report the dynamic loading on the pressure vessel internals (upper perforated plate and barrel suspension) during the DWR 5 experiment are calculated by means of a vertical and horizontal dynamic model using the CESHOCK code. The equations of motion are resolved by direct integration. (orig./RW) [de

Dynamical constraints and adiabatic invariants in chemical reactions.

Science.gov (United States)

Lorquet, J C

2007-08-23

For long-range electrostatic potentials and, more generally, when the topography of the potential energy surface is locally simple, the reaction path coordinate is adiabatically separable from the perpendicular degrees of freedom. For the ion-permanent dipole and ion-quadrupole interactions, the Poisson bracket of the adiabatic invariant decreases with the interfragment distance more rapidly than the electrostatic potential. The smaller the translational momentum, the moment of inertia of the neutral fragment, and the dipole or quadrupole moments are, the more reliable the adiabatic approximation is, as expected from the usual argumentation. Closed-form expressions for an effective one-dimensional potential in an adiabatic Hamiltonian are given. Connection with a model where the decoupling is exact is obtained in the limit of an infinitely heavy dipole. The dynamics is also constrained by adiabatic invariance for a harmonic valley about a curved reaction path, as shown by the reaction path Hamiltonian method. The maximum entropy method reveals that, as a result of the invariance properties of the entropy, constraints whose validity has been demonstrated locally only subsist in all parts of phase space. However, their form varies continuously, and they are not necessarily expressed in simple terms as they are in the asymptotic region. Therefore, although the influence of adiabatic invariance has been demonstrated at asymptotically large values of the reaction coordinate only, it persists in more interesting ranges.

Role of rotational energy and deformations in the dynamics of {sup 6}Li+{sup 90}Zr reaction

Energy Technology Data Exchange (ETDEWEB)

Kaur, Gurvinder; Grover, Neha; Sandhu, Kirandeep; Sharma, Manoj K., E-mail: msharma@thapar.edu

2014-07-15

In reference to recent experimental data, the dynamical cluster-decay model (DCM) has been applied to study the neutron evaporation residue (ER) cross sections of intermediate mass nucleus {sup 96}Tc{sup ⁎} spread over a wide range of incident energy across the Coulomb barrier. In order to analyze the effect of rotational energy in the dynamics of {sup 6}Li+{sup 90}Zr reaction, the cross sections have been calculated using the sticking (I{sub S}) and the non-sticking (I{sub NS}) limits of moment of inertia with inclusion of quadrupole (β{sub 2}) deformation within optimum orientation approach. The effect of either of the two approaches on the angular momentum, and hence the rotational energy associated with it, is assessed through the fragment mass distribution, preformation factor and the barrier penetrability. Also, the role of deformations is studied through a comparative analysis of decay path for spherical and β{sub 2} deformed fragmentation. The calculated evaporation residue cross sections show excellent agreement with the reported data at all incident energies for both spherical and β{sub 2}-deformed approach. Finally, the incomplete fusion (ICF) process observed due to loosely bound projectile {sup 6}Li is addressed within the framework of DCM.

Molecular dynamics simulation of sodium aluminosilicate glass structures and glass surface-water reactions using the reactive force field (ReaxFF)

Science.gov (United States)

Dongol, R.; Wang, L.; Cormack, A. N.; Sundaram, S. K.

2018-05-01

Reactive potentials are increasingly used to study the properties of glasses and glass water reactions in a reactive molecular dynamics (MD) framework. In this study, we have simulated a ternary sodium aluminosilicate glass and investigated the initial stages of the glass surface-water reactions at 300 K using reactive force field (ReaxFF). On comparison of the simulated glass structures generated using ReaxFF and classical Buckingham potentials, our results show that the atomic density profiles calculated for the surface glass structures indicate a bond-angle distribution dependency. The atomic density profiles also show higher concentrations of non-bridging oxygens (NBOs) and sodium ions at the glass surface. Additionally, we present our results of formation of silanol species and the diffusion of water molecules at the glass surface using ReaxFF.

Lipid Dynamics Studied by Calculation of 31P Solid-State NMR Spectra Using Ensembles from Molecular Dynamics Simulations

DEFF Research Database (Denmark)

Hansen, Sara Krogh; Vestergaard, Mikkel; Thøgersen, Lea

2014-01-01

, for example, order parameters. Therefore, valuable insight into the dynamics of biomolecules may be achieved by the present method. We have applied this method to study the dynamics of lipid bilayers containing the antimicrobial peptide alamethicin, and we show that the calculated 31P spectra obtained...

Dynamics of GeV light-ion-induced reactions

International Nuclear Information System (INIS)

Kwiatkowski, K.; Bracken, D.S.; Foxford, E.R.; Ginger, D.S.; Hsi, W.C.; Morley, K.B.; Viola, V.E.; Wang, G.; Korteling, R.G.; Legrain, R.

1996-09-01

Recent results from studies of the 1.8 - 4.8 GeV 3 He + nat Ag, 197 Au reactions at LNS with the ISiS detector array have shown evidence for a saturation in deposition energy and multifragmentation from a low-density source. The collision dynamics have been examined in the context of intranuclear cascade and BUU models, while breakup phenomena have been compared with EES and SMM models. Fragment-fragment correlations and isotope ratios are also investigated. (K.A.)

Quantum Dynamics Study of the Isotopic Effect on Capture Reactions: HD, D2 + CH3

Science.gov (United States)

Wang, Dunyou; Kwak, Dochan (Technical Monitor)

2002-01-01

Time-dependent wave-packet-propagation calculations are reported for the isotopic reactions, HD + CH3 and D2 + CH3, in six degrees of freedom and for zero total angular momentum. Initial state selected reaction probabilities for different initial rotational-vibrational states are presented in this study. This study shows that excitations of the HD(D2) enhances the reactivities; whereas the excitations of the CH3 umbrella mode have the opposite effects. This is consistent with the reaction of H2 + CH3. The comparison of these three isotopic reactions also shows the isotopic effects in the initial-state-selected reaction probabilities. The cumulative reaction probabilities (CRP) are obtained by summing over initial-state-selected reaction probabilities. The energy-shift approximation to account for the contribution of degrees of freedom missing in the six dimensionality calculation is employed to obtain approximate full-dimensional CRPs. The rate constant comparison shows H2 + CH3 reaction has the biggest reactivity, then HD + CH3, and D2 + CH3 has the smallest.

Theory of the reaction dynamics of small molecules on metal surfaces

Energy Technology Data Exchange (ETDEWEB)

Jackson, Bret [Univ. of Massachusetts, Amherst, MA (United States)

2016-09-09

The objective of this project has been to develop realistic theoretical models for gas-surface interactions, with a focus on processes important in heterogeneous catalysis. The dissociative chemisorption of a molecule on a metal is a key step in many catalyzed reactions, and is often the rate-limiting step. We have explored the dissociative chemisorption of H₂, H₂O and CH₄ on a variety of metal surfaces. Most recently, our extensive studies of methane dissociation on Ni and Pt surfaces have fully elucidated its dependence on translational energy, vibrational state and surface temperature, providing the first accurate comparisons with experimental data. We have explored Eley-Rideal and hot atom reactions of H atoms with H- and C-covered metal surfaces. H atom interactions with graphite have also been explored, including both sticking and Eley-Rideal recombination processes. Again, our methods made it possible to explain several experiments studying these reactions. The sticking of atoms on metal surfaces has also been studied. To help elucidate the experiments that study these processes, we examine how the reaction dynamics depend upon the nature of the molecule-metal interaction, as well as experimental variables such as substrate temperature, beam energy, angle of impact, and the internal states of the molecules. Electronic structure methods based on Density Functional Theory are used to compute each molecule-metal potential energy surface. Both time-dependent quantum scattering techniques and quasi-classical methods are used to examine the reaction or scattering dynamics. Much of our effort has been directed towards developing improved quantum methods that can accurately describe reactions, as well as include the effects of substrate temperature (lattice vibration).

Study of Cold Fusion Reactions Using Collective Clusterization Approach

Science.gov (United States)

Kaur, Gurjit; Sandhu, Kirandeep; Sharma, Manoj K.

2017-10-01

Within the framework of the dynamical cluster decay model (DCM), the 1n evaporation cross-sections ({σ }1n) of cold fusion reactions (Pb and Bi targets) are calculated for {Z}{CN}=104-113 superheavy nuclei. The calculations are carried out in the fixed range of excitation energy {E}{CN}* =15+/- 1 {MeV}, so that the comparative analysis of reaction dynamics can be worked out. First of all, the fission barriers (B f ) and neutron separation energies ({S}1n) are estimated to account the decreasing cross-sections of cold fusion reactions. In addition to this, the importance of hot optimum orientations of β 2i-deformed nuclei over cold one is explored at fixed angular momentum and neck-length parameters. The hot optimum orientations support all the target-projectile (t,p) combinations, which are explored experimentally in the cold fusion reactions. Some new target-projectile combinations are also predicted for future exploration. Further, the 1n cross-sections are addressed for {Z}{CN}=104-113 superheavy nuclei at comparable excitation energies which show the decent agrement with experimental data upto {Z}{CN}=109 nuclei. Finally, to understand the dynamics of higher-Z superheavy nuclei, the cross-sections are also calculated at maximum available energies around the Coulomb barrier and the effect of non-sticking moment of inertia ({I}{NS}) is also investigated at these energies. Supported by the Council of Scientific and Industrial Research (CSIR), in the Form of Research Project Grant No. 03(1341)/15/EMR-II, and to DST, New Delhi, for INSPIRE-Fellowship Grant No. DST/INSPIRE/03/2015/000199

Dynamic Characteristics and Model for Centralization Reaction of Acidic Tailings From Heap Leaching of Uranium Ore

International Nuclear Information System (INIS)

Ding Dexin; Liu Yulong; Li Guangyue; Wang Youtuan

2010-01-01

Centralization tests were carried out on acidic tailings from heap leaching of uranium ore by using CaO, NaOH and NH 4 OH. The variations of pH with time were measured for the three centralization systems and the dynamic models for the systems were set up by regressing the measured data. The centralization process consists of the fast reaction phase representing the reaction between the centralization agent and the acid on the surface of the tailing's particles and the slow diffusion-reaction phase representing the diffusion-reaction between the centralization agent and the acid within the tailing's particles. The non-linear coupling and feedback function model for the diffusion-reaction of the centralization agent can reflect the process and mode of the centralization reaction. There is a non-linear oscillation in the variation of pH within the centralization systems. The dynamic model for the tailing's centralization reaction can fit the pH variation within the centralization systems. (authors)

Dynamics of interface in three-dimensional anisotropic bistable reaction-diffusion system

International Nuclear Information System (INIS)

He Zhizhu; Liu, Jing

2010-01-01

This paper presents a theoretical investigation of dynamics of interface (wave front) in three-dimensional (3D) reaction-diffusion (RD) system for bistable media with anisotropy constructed by means of anisotropic surface tension. An equation of motion for the wave front is derived to carry out stability analysis of transverse perturbations, which discloses mechanism of pattern formation such as labyrinthine in 3D bistable media. Particularly, the effects of anisotropy on wave propagation are studied. It was found that, sufficiently strong anisotropy can induce dynamical instabilities and lead to breakup of the wave front. With the fast-inhibitor limit, the bistable system can further be described by a variational dynamics so that the boundary integral method is adopted to study the dynamics of wave fronts.

Reaction dynamics of molecular hydrogen on silicon surfaces

DEFF Research Database (Denmark)

Bratu, P.; Brenig, W.; Gross, A.

1996-01-01

of the preexponential factor by about one order of magnitude per lateral degree of freedom. Molecular vibrations have practically no effect on the adsorption/desorption dynamics itself, but lead to vibrational heating in desorption with a strong isotope effect. Ab initio calculations for the H-2 interaction...... between the two surfaces. These results indicate that tunneling, molecular vibrations, and the structural details of the surface play only a minor role for the adsorption dynamics. Instead, they appear to be governed by the localized H-Si bonding and Si-Si lattice vibrations. Theoretically, an effective......Experimental and theoretical results on the dynamics of dissociative adsorption and recombinative desorption of hydrogen on silicon are presented. Using optical second-harmonic generation, extremely small sticking probabilities in the range 10(-9)-10(-5) could be measured for H-2 and D-2 on Si(111...

Dynamical optimization techniques for the calculation of electronic structure in solids

International Nuclear Information System (INIS)

Benedek, R.; Min, B.I.; Garner, J.

1989-01-01

The method of dynamical simulated annealing, recently introduced by Car and Parrinello, provides a new tool for electronic structure computation as well as for molecular dynamics simulation. In this paper, we explore an optimization technique that is complementary to dynamical simulated annealing, the method of steepest descents (SD). As an illustration, SD is applied to calculate the total energy of diamond-Si, a system previously treated by Car and Parrinello. The adaptation of SD to treat metallic systems is discussed and a numerical application is presented. (author) 18 refs., 3 figs

Nuclear structure effects on heavy-ion reactions with microscopic theory

Directory of Open Access Journals (Sweden)

Vo-Phuoc K.

2016-01-01

Full Text Available The self-consistent mean-field Hartree–Fock (HF theory, both static and time-dependent (TDHF versions, is used to study static and dynamic properties of fusion reactions between even 40–54Ca isotopes and 116Sn. The bare nucleus-nucleus potential, calculated with the frozen HF approach, is affected by the groundstate density of the nuclei. However, once dynamical effects are included, as in TDHF, the static effects on the barrier are essentially washed out. Dynamic properties of the nuclei, including low-lying vibrational modes, are calculated with TDHF and selectively used in coupled-channels calculations to identify which modes have the most effect on the TDHF fusion threshold. Vibrations cannot fully explain the difference between the static HF and TDHF fusion barriers trend so other dynamical effects such as transfer are considered.

Calculation of dynamic hydraulic forces in nuclear plant piping systems

International Nuclear Information System (INIS)

Choi, D.K.

1982-01-01

A computer code was developed as one of the tools needed for analysis of piping dynamic loading on nuclear power plant high energy piping systems, including reactor safety and relief value upstream and discharge piping systems. The code calculates the transient hydraulic data and dynamic forces within the one-dimensional system, caused by a pipe rupture or sudden value motion, using a fixed space and varying time grid-method of characteristics. Subcooled, superheated, homogeneous two-phase and transition flow regimes are considered. A non-equilibrium effect is also considered in computing the fluid specific volume and fluid local sonic velocity in the two-phase mixture. Various hydraulic components such as a spring loaded or power operated value, enlarger, orifice, pressurized tank, multiple pipe junction (tee), etc. are considered as boundary conditions. Comparisons of calculated results with available experimental data shows a good agreement. (Author)

CRSEC: a general purpose Hauser--Feshbach code for the calculation of nuclear cross-sections and thermonuclear reaction rates

International Nuclear Information System (INIS)

Woosley, S.; Fowler, W.A.

1977-09-01

CRSEC is a FORTRAN IV computer code designed for the efficient calculation of average nuclear cross sections in situations where a statistical theory of nuclear reactions is applicable and where compound nuclear formation is the dominant reaction mechanism. This code generates cross sections of roughly factor of 2 accuracy for incident particle energies in the range of 10 keV to 10 MeV for most target nuclei from magnesium to bismuth. Exceptions usually involve reactions that enter the compound nucleus at such a low energy that fewer than 10 levels are present in the ''energy window of interest.'' The incident particle must be a neutron, proton, or alpha particle, and only binary reactions resulting in the emission of a single n, p, α, or γ (cascade) are calculated. CRSEC is quite fast, a complete calculation of 12 different reactions over a grid of roughly 150 energy points and the generation of Maxwellian averaged rates taking about 30 seconds of CDC7600 time. Also the semi-empirical parameterization of nuclear properties contained in CRSEC is very general. Greater accuracy may be obtained, however, by furnishing specific low-lying excited states, level density parameterization, and nuclear strength functions. A more general version of CRSEC, called CRSECI, is available that conserves isospin properly in all reactions and allows the user to specify a given degree of isospin mixing in the highly excited states of the compound nucleus. Besides the cross section as a function of center-of-mass energy, CRSEC also generates the Maxwell--Boltzmann averaged thermonuclear reaction rate and temperature dependent nuclear partition function for a grid of temperatures from 10 8 to 10 10 0 K. Sections of this report describe in greater detail the physics employed in CRSEC and how to use the code. 2 tables

New Systematic CFD Methods to Calculate Static and Single Dynamic Stability Derivatives of Aircraft

Directory of Open Access Journals (Sweden)

Bai-gang Mi

2017-01-01

Full Text Available Several new systematic methods for high fidelity and reliability calculation of static and single dynamic derivatives are proposed in this paper. Angle of attack step response is used to obtain static derivative directly; then translation acceleration dynamic derivative and rotary dynamic derivative can be calculated by employing the step response motion of rate of the angle of attack and unsteady motion of pitching angular velocity step response, respectively. Longitudinal stability derivative calculations of SACCON UCAV are taken as test cases for validation. Numerical results of all cases achieve good agreement with reference values or experiments data from wind tunnel, which indicate that the proposed methods can be considered as new tools in the process of design and production of advanced aircrafts for their high efficiency and precision.

Photonuclear reactions at intermediate energy

International Nuclear Information System (INIS)

Koch, J.H.

1982-01-01

The dominant feature of photonuclear reactions at intermediate energies is the excitation of the δ resonance and one can therefore use such reactions to study the dynamics of δ propagation in a nucleus. Following an introductory section the author comments on photoabsorption on a single nucleon in Section II. A review of the δ-n Greens function and of the photonuclear amplitude is given in Section III. Results for photoabsorption on 4 He are shown in Section IV and compared with the data. Coherent π 0 photoproduction is discussed in Section V and calculations for 12 C are compared to recent measurements. (Auth.)

A Practical Quantum Mechanics Molecular Mechanics Method for the Dynamical Study of Reactions in Biomolecules.

Science.gov (United States)

Mendieta-Moreno, Jesús I; Marcos-Alcalde, Iñigo; Trabada, Daniel G; Gómez-Puertas, Paulino; Ortega, José; Mendieta, Jesús

2015-01-01

Quantum mechanics/molecular mechanics (QM/MM) methods are excellent tools for the modeling of biomolecular reactions. Recently, we have implemented a new QM/MM method (Fireball/Amber), which combines an efficient density functional theory method (Fireball) and a well-recognized molecular dynamics package (Amber), offering an excellent balance between accuracy and sampling capabilities. Here, we present a detailed explanation of the Fireball method and Fireball/Amber implementation. We also discuss how this tool can be used to analyze reactions in biomolecules using steered molecular dynamics simulations. The potential of this approach is shown by the analysis of a reaction catalyzed by the enzyme triose-phosphate isomerase (TIM). The conformational space and energetic landscape for this reaction are analyzed without a priori assumptions about the protonation states of the different residues during the reaction. The results offer a detailed description of the reaction and reveal some new features of the catalytic mechanism. In particular, we find a new reaction mechanism that is characterized by the intramolecular proton transfer from O1 to O2 and the simultaneous proton transfer from Glu 165 to C2. Copyright © 2015 Elsevier Inc. All rights reserved.

Mechanism and kinetics in reactions of caffeic acid with radicals by pulse radiolysis and calculation

International Nuclear Information System (INIS)

Li, Xifeng; Cai, Zhongli; Katsumura, Yosuke

2000-01-01

The interaction of caffeic acid with e aq - , (CH 3 ) 2 (OH) CCH 2 · , CO 2 ·- , H · , ·OH and N 3 · radicals were studied by γ-, pulse radiolysis and molecular orbital calculation. UV-visible spectra of electron/·OH adducts, semi-quinone radicals of caffeic ions, and the stable products from the reactions were derived. The rate constants were determined. The attacked sites and the most favorable structures of the transient radicals were predicted. Reaction mechanisms were proposed. (author)

Quantum chemical and thermodynamic calculations of fulvic and humic copper complexes in reactions of malachite and azurite formation

International Nuclear Information System (INIS)

Fomin, Vitaliy N.; Gogol, Daniil B.; Rozhkovoy, Ivan E.; Ponomarev, Dmitriy L.

2017-01-01

This article provides a thermodynamic evaluation of the reactions of humic and fulvic acids in the process of malachite and azurite mineralogenesis. Semi-empirical methods AM/1, MNDO, PM3, PM5, PM6 and PM7 were used to compute the heat of formation, enthalpy and entropy for thermodynamic calculations of the reactions performed on the basis of Hess's law. It is shown that methods PM6 and PM7 in the MOPAC software package provide good compliance with experimental and calculated heats of formation for copper complexes and alkaline earth metal complexes with organic acids. It is found that the malachite and azurite formation processes involving humus complexing substances are thermodynamically possible. - Highlights: • Copper and alkali-earth metal complexes with humic and fulvic acids are considered. • Quantum chemical calculation of thermodynamics for the structures was performed. • Semi-empirical methods PM6 and PM7 provide best correlation for the properties. • Parameters of basic copper carbonate formation reactions were obtained by Hess's law. • Processes of malachite and azurite formation from humus complexes are possible.

The Role of Electronic Excitations on Chemical Reaction Dynamics at Metal, Semiconductor and Nanoparticle Surfaces

Energy Technology Data Exchange (ETDEWEB)

Tully, John C. [Yale Univ., New Haven, CT (United States)

2017-06-10

Chemical reactions are often facilitated and steered when carried out on solid surfaces, essential for applications such as heterogeneous catalysis, solar energy conversion, corrosion, materials processing, and many others. A critical factor that can determine the rates and pathways of chemical reactions at surfaces is the efficiency and specificity of energy transfer; how fast does energy move around and where does it go? For reactions on insulator surfaces energy transfer generally moves in and out of vibrations of the adsorbed molecule and the underlying substrate. By contrast, on metal surfaces, metallic nanoparticles and semiconductors, another pathway for energy flow opens up, excitation and de-excitation of electrons. This so-called “nonadiabatic” mechanism often dominates the transfer of energy and can directly impact the course of a chemical reaction. Conventional computational methods such as molecular dynamics simulation do not account for this nonadiabatic behavior. The current DOE-BES funded project has focused on developing the underlying theoretical foundation and the computational methodology for the prediction of nonadiabatic chemical reaction dynamics at surfaces. The research has successfully opened up new methodology and new applications for molecular simulation. In particular, over the last three years, the “Electronic Friction” theory, pioneered by the PI, has now been developed into a stable and accurate computational method that is sufficiently practical to allow first principles “on-the-fly” simulation of chemical reaction dynamics at metal surfaces.

A New Calculation Method of Dynamic Kill Fluid Density Variation during Deep Water Drilling

Directory of Open Access Journals (Sweden)

Honghai Fan

2017-01-01

Full Text Available There are plenty of uncertainties and enormous challenges in deep water drilling due to complicated shallow flow and deep strata of high temperature and pressure. This paper investigates density of dynamic kill fluid and optimum density during the kill operation process in which dynamic kill process can be divided into two stages, that is, dynamic stable stage and static stable stage. The dynamic kill fluid consists of a single liquid phase and different solid phases. In addition, liquid phase is a mixture of water and oil. Therefore, a new method in calculating the temperature and pressure field of deep water wellbore is proposed. The paper calculates the changing trend of kill fluid density under different temperature and pressure by means of superposition method, nonlinear regression, and segment processing technique. By employing the improved model of kill fluid density, deep water kill operation in a well is investigated. By comparison, the calculated density results are in line with the field data. The model proposed in this paper proves to be satisfactory in optimizing dynamic kill operations to ensure the safety in deep water.

NATO Advanced Research Workshop on The Theory of Chemical Reaction Dynamics

CERN Document Server

1986-01-01

The calculation of cross sections and rate constants for chemical reactions in the gas phase has long been a major problem in theoretical chemistry. The need for reliable and applicable theories in this field is evident when one considers the significant recent advances that have been made in developing experimental techniques, such as lasers and molecular beams, to probe the microscopic details of chemical reactions. For example, it is now becoming possible to measure cross sections for chemical reactions state selected in the vibrational­ rotational states of both reactants and products. Furthermore, in areas such as atmospheric, combustion and interstellar chemistry, there is an urgent need for reliable reaction rate constant data over a range of temperatures, and this information is often difficult to obtain in experiments. The classical trajectory method can be applied routinely to simple reactions, but this approach neglects important quantum mechanical effects such as tunnelling and resonances. For al...

Calculation of proton and neutron emission spectra from proton reactions with 90Zr and 208Pb to 160 MeV with the GNASH code

International Nuclear Information System (INIS)

Young, P.G.; Chadwick, M.B.

1994-01-01

A number of modifications have been made to the reaction theory code GNASH in order the accuracy of calculations at incident particle energies up to 200 MeV. Direct reaction a level density models appropriate for higher energy calculations are now used in the code, and most importantly, improved preequilibrium models have been incorporated into the code system. The code has been used to calculate proton-induced reactions on 90 Zr and 208 Pb for the International Code and Model Intercomparison for Intermediate Energy Reactions organized by the NEA. Calculations were performed with GNASH at incident proton energies of 25, 45, 80, and 160 mev using both the exciton model and Feshbach-Kerman-Koonin theory for the preequilibrium component. The models and procedures used in the GNASH calculations with the exciton model are described here. The results are compared to experimental data and to results from the GNASH calculations with Feshbach-Kerman-Koonin preequilibrium theory

Development of Dynamic Environmental Effect Calculation Model

International Nuclear Information System (INIS)

Jeong, Chang Joon; Ko, Won Il

2010-01-01

The short-term, long-term decay heat, and radioactivity are considered as main environmental parameters of SF and HLA. In this study, the dynamic calculation models for radioactivity, short-term decay heat, and long-term heat load of the SF are developed and incorporated into the Doneness code. The spent fuel accumulation has become a major issue for sustainable operation of nuclear power plants. If a once-through fuel cycle is selected, the SF will be disposed into the repository. Otherwise, in case of fast reactor or reuse cycle, the SF will be reprocessed and the high level waste will be disposed

Crossed-beam studies of the dynamics of radical reactions

Energy Technology Data Exchange (ETDEWEB)

Liu, K. [Argonne National Laboratory, IL (United States)

1993-12-01

The objective of this program is to characterize the detailed dynamics of elementary radical reactions and to provide a better understanding of radical reactivity in general. The radical beam is typically generated by a laser photolysis method. After colliding with the reacting molecule in a crossed-beam apparatus, the reaction product state distribution is interrogated by laser spectroscopic techniques. Several radicals of combustion significance, such as O, CH, OH, CN and NCO have been successfully generated and their collisional behavior at the state-to-state integral cross section level of detail has been studied in this manner. During the past year, the detection system has been converted from LIF to REMPI schemes, and the emphasis of this program shifted to investigate the product angular distributions. Both inelastic and reactive processes have been studied.

The effect of walking speed on local dynamic stability is sensitive to calculation methods

DEFF Research Database (Denmark)

Stenum, Jan; Bruijn, Sjoerd M; Jensen, Bente Rona

2014-01-01

Local dynamic stability has been assessed by the short-term local divergence exponent (λS), which quantifies the average rate of logarithmic divergence of infinitesimally close trajectories in state space. Both increased and decreased local dynamic stability at faster walking speeds have been...... reported. This might pertain to methodological differences in calculating λS. Therefore, the aim was to test if different calculation methods would induce different effects of walking speed on local dynamic stability. Ten young healthy participants walked on a treadmill at five speeds (60%, 80%, 100%, 120......% and 140% of preferred walking speed) for 3min each, while upper body accelerations in three directions were sampled. From these time-series, λS was calculated by three different methods using: (a) a fixed time interval and expressed as logarithmic divergence per stride-time (λS-a), (b) a fixed number...

The rate of the reaction between C2H and C2H2 at interstellar temperatures

Science.gov (United States)

Herbst, E.; Woon, D. E.

1997-01-01

The reaction between the radical C2H and the stable hydrocarbon C2H2 is one of the simplest neutral-neutral hydrocarbon reactions in chemical models of dense interstellar clouds and carbon-rich circumstellar shells. Although known to be rapid at temperatures > or = 300 K, the reaction has yet to be studied at lower temperatures. We present here ab initio calculations of the potential surface for this reaction and dynamical calculations to determine its rate at low temperature. Despite a small potential barrier in the exit channel, the calculated rate is large, showing that this reaction and, most probably, more complex analogs contribute to the formation of complex organic molecules in low-temperature sources.

Molecular dynamics calculations of defect energetics in β-SiC

International Nuclear Information System (INIS)

Huang, H.; El-Azab, A.; Ghoniem, N.

1993-01-01

The Molecular Dynamics (MD) method is used to calculate defect energetics in β-silicon carbide. Many-body interaction effects in this covalent material are accounted for by using a hybrid of two-body and three-body potentials. Calculated bulk properties of β-SiC based on this potential are in agreement with experimental data to within 17%. A micro-crystal is constructed to represent the computational cell and external forces are applied to the micro-crystal so that it behaves as a part of an infinite medium. The potential energy for the unperturbed computational cell is first calculated. The cell is then set at a defect configuration and relaxed, and the potential energy of the relaxed cell is calculated. The difference between the potential energy of the unperturbed cell and that of the defect-containing cell is used to calculate the formation and binding energies of point defects, defect clusters and helium-vacancy clusters in SiC

Analysis of kinetic reaction mechanisms

CERN Document Server

Turányi, Tamás

2014-01-01

Chemical processes in many fields of science and technology, including combustion, atmospheric chemistry, environmental modelling, process engineering, and systems biology, can be described by detailed reaction mechanisms consisting of numerous reaction steps. This book describes methods for the analysis of reaction mechanisms that are applicable in all these fields. Topics addressed include: how sensitivity and uncertainty analyses allow the calculation of the overall uncertainty of simulation results and the identification of the most important input parameters, the ways in which mechanisms can be reduced without losing important kinetic and dynamic detail, and the application of reduced models for more accurate engineering optimizations. This monograph is invaluable for researchers and engineers dealing with detailed reaction mechanisms, but is also useful for graduate students of related courses in chemistry, mechanical engineering, energy and environmental science and biology.

Thermodynamic calculation of simultaneous reactions of n-butane isomerization and isobutane alkylation with ethylene

Energy Technology Data Exchange (ETDEWEB)

Batyrshin, N.N.; Beresneva, L.D.; Sidorov, V.A.

1981-08-01

Industrial production of ethylene alkylate has gained further development in connection with worldwide ecological problems and the planned changeover of automobile transport to unleaded gasolines, but the scale of production is still substantially less than that of sulfuric acid or hydrogen fluoride alkylates. This is due both to the instability of market prices for ethylene and the shortage of isobutane - a raw material for these large-tonnage production processes and for the synthetic rubber industry. The latter difficulty can be overcome by combining processes of isomerization of n-butane and alkylation of the resultant isobutane with ethylene in a single reaction unit. The possibility of combining these reactions using AlCl/sub 3/-based catalysts has been pointed out previously but in the literature there are no theoretical developments of technology or thermodynamic substantiation of a combined process. We have made a thermodynamic calculation of the consecutive (series-parallel) reactions of isomerization and alkylation with the goal of determining suitable technological conditions for carrying them out simultaneously and establishing the expected equilibrium yields of target products and the compositions of the reaction mixture.

Advanced Dynamics Analytical and Numerical Calculations with MATLAB

CERN Document Server

Marghitu, Dan B

2012-01-01

Advanced Dynamics: Analytical and Numerical Calculations with MATLAB provides a thorough, rigorous presentation of kinematics and dynamics while using MATLAB as an integrated tool to solve problems. Topics presented are explained thoroughly and directly, allowing fundamental principles to emerge through applications from areas such as multibody systems, robotics, spacecraft and design of complex mechanical devices. This book differs from others in that it uses symbolic MATLAB for both theory and applications. Special attention is given to solutions that are solved analytically and numerically using MATLAB. The illustrations and figures generated with MATLAB reinforce visual learning while an abundance of examples offer additional support. This book also: Provides solutions analytically and numerically using MATLAB Illustrations and graphs generated with MATLAB reinforce visual learning for students as they study Covers modern technical advancements in areas like multibody systems, robotics, spacecraft and des...

Density-functional molecular-dynamics study of the redox reactions of two anionic, aqueous transition-metal complexes

International Nuclear Information System (INIS)

Tateyama, Yoshitaka; Blumberger, Jochen; Sprik, Michiel; Tavernelli, Ivano

2005-01-01

The thermochemistry of the RuO 4 2- +MnO 4 - →RuO 4 - +MnO 4 2- redox reaction in aqueous solution is studied by separate density-functional-based ab initio molecular-dynamics simulations of the component half reactions RuO 4 2- →RuO 4 - +e - and MnO 4 2- →MnO 4 - +e - . We compare the results of a recently developed grand-canonical method for the computation of oxidation free energies to the predictions by the energy-gap relations of the Marcus theory that can be assumed to apply to these reactions. The calculated redox potentials are in good agreement. The subtraction of the half-reaction free energies gives an estimate of the free energy of the full reaction. The result obtained from the grand-canonical method is -0.4 eV, while the application of the Marcus theory gives -0.3 eV. These should be compared to the experimental value of 0.0 eV. Size effects, in response to increasing the number of water molecules in the periodic model system from 30 to 48, are found to be small (≅0.1 eV). The link to the Marcus theory also has enabled us to compute reorganization free energies for oxidation. For both the MnO 4 2- and RuO 4 2- redox reactions we find the same reorganization free energy of 0.8 eV (1.0 eV in the larger system). The results for the free energies and further analysis of solvation and electronic structure confirm that these two tetrahedral oxoanions show very similar behavior in solution in spite of the central transition-metal atoms occupying a different row and column in the periodic table

Application of optimization numerical methods in calculation of the two-particle nuclear reactions

International Nuclear Information System (INIS)

Titarenko, N.N.

1987-01-01

An optimization packet of PEAK-OPT applied programs intended for solution of problems of absolute minimization of functions of many variables in calculations of cross sections of binary nuclear reactions is described. The main algorithms of computerized numerical solution of systems of nonlinear equations for the least square method are presented. Principles for plotting and functioning the optimization software as well as results of its practical application are given

Influence of inverse dynamics methods on the calculation of inter-segmental moments in vertical jumping and weightlifting

Directory of Open Access Journals (Sweden)

Cleather Daniel J

2010-11-01

Full Text Available Abstract Background A vast number of biomechanical studies have employed inverse dynamics methods to calculate inter-segmental moments during movement. Although all inverse dynamics methods are rooted in classical mechanics and thus theoretically the same, there exist a number of distinct computational methods. Recent research has demonstrated a key influence of the dynamics computation of the inverse dynamics method on the calculated moments, despite the theoretical equivalence of the methods. The purpose of this study was therefore to explore the influence of the choice of inverse dynamics on the calculation of inter-segmental moments. Methods An inverse dynamics analysis was performed to analyse vertical jumping and weightlifting movements using two distinct methods. The first method was the traditional inverse dynamics approach, in this study characterized as the 3 step method, where inter-segmental moments were calculated in the local coordinate system of each segment, thus requiring multiple coordinate system transformations. The second method (the 1 step method was the recently proposed approach based on wrench notation that allows all calculations to be performed in the global coordinate system. In order to best compare the effect of the inverse dynamics computation a number of the key assumptions and methods were harmonized, in particular unit quaternions were used to parameterize rotation in both methods in order to standardize the kinematics. Results Mean peak inter-segmental moments calculated by the two methods were found to agree to 2 decimal places in all cases and were not significantly different (p > 0.05. Equally the normalized dispersions of the two methods were small. Conclusions In contrast to previously documented research the difference between the two methods was found to be negligible. This study demonstrates that the 1 and 3 step method are computationally equivalent and can thus be used interchangeably in

Theoretical studies of the reaction dynamics of the matrix-isolated F2+cis-d2 -ethylene system

Science.gov (United States)

Raff, Lionel M.

1991-12-01

The molecular dynamics of the F2+cis-d2 -ethylene addition reaction and the subsequent decomposition dynamics of the vibrationally excited 1,2-difluoroethane-d2 product isolated in Ar or Xe matrices at 12 K are investigated using trajectory methods that incorporate nonstatistical sampling to enhance the reaction probabilities. The matrix is represented by a face-centered-cubic crystal containing 125 unit cells with 666 lattice atoms in a cubic (5×5×5) arrangement. Both interstitial and substitutional sites for the F2/cis-d2 -ethylene pair are examined. Transport effects of the bulk are simulated using the velocity reset method introduced by Riley, Coltrin, and Diestler [J. Chem. Phys. 88, 5934 (1988)]. The potential-energy hypersurface for the system is written as the separable sum of a lattice potential, a lattice-substrate interaction, and a gas-phase potential for 1,2-difluoroethane-d2. The first two of these have pairwise form, while the 1,2-difluoroethane-d2 potential is identical to that employed previously to study the unimolecular reaction dynamics of matrix-isolated 1,2-difluoroethane-d4 [J. Chem. Phys. 93, 3160 (1990)]. The major F2+cis-d2 -ethylene reaction mechanism involves a four-center, concerted αβ addition across the C=C double bond. A small contribution from an atomic addition mechanism that initially forms fluoroethyl and fluorine radicals is observed in a xenon matrix, but not in argon. Subsequent to the formation of 1,2-difluoroethane-d2, the observed dynamic processes are vibrational relaxation to the lattice phonon modes, orientational exchange, and HF or DF elimination reactions. Vibrational relaxation is found to be very similar to that observed previously for 1,2-difluoroethane-d4. The process is well described by a first-order rate law with rate coefficients in the range 0.046-0.069 ps-1. The distribution of rate coefficients, as well as the averages, are nearly identical for Ar and Xe lattices. Very little difference is found between

New calculations of cyclotron production cross sections of some positron emitting radioisotopes in proton induced reactions

International Nuclear Information System (INIS)

Tel, E.; Aydin, E.G.; Kaplan, A.; Aydin, A.

2009-01-01

In this study, new calculations on the excitation functions of 13 C(p, n) 13 N, 14 N (p, α) 11 C, 15 N(p, n) 15 O, 16 O(p, α) 13 N, 18 O(p, n) 18 F, 62 Ni(p, n) 62 Cu, 68 Zn(p, n) 68 Ga and 72 Ge(p, n) 72 As reactions have been carried out in the 5-40 MeV incident proton energy range. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve hybrid model, geometry dependent hybrid model, the cascade exciton model and full exciton model. Equilibrium effects were calculated according to Weisskopf-Ewing model. The calculated results have been compared with experimental data taken from literature. (author)

Gibbs Sampler-Based λ-Dynamics and Rao-Blackwell Estimator for Alchemical Free Energy Calculation.

Science.gov (United States)

Ding, Xinqiang; Vilseck, Jonah Z; Hayes, Ryan L; Brooks, Charles L

2017-06-13

λ-dynamics is a generalized ensemble method for alchemical free energy calculations. In traditional λ-dynamics, the alchemical switch variable λ is treated as a continuous variable ranging from 0 to 1 and an empirical estimator is utilized to approximate the free energy. In the present article, we describe an alternative formulation of λ-dynamics that utilizes the Gibbs sampler framework, which we call Gibbs sampler-based λ-dynamics (GSLD). GSLD, like traditional λ-dynamics, can be readily extended to calculate free energy differences between multiple ligands in one simulation. We also introduce a new free energy estimator, the Rao-Blackwell estimator (RBE), for use in conjunction with GSLD. Compared with the current empirical estimator, the advantage of RBE is that RBE is an unbiased estimator and its variance is usually smaller than the current empirical estimator. We also show that the multistate Bennett acceptance ratio equation or the unbinned weighted histogram analysis method equation can be derived using the RBE. We illustrate the use and performance of this new free energy computational framework by application to a simple harmonic system as well as relevant calculations of small molecule relative free energies of solvation and binding to a protein receptor. Our findings demonstrate consistent and improved performance compared with conventional alchemical free energy methods.

Effect of loading rate on dynamic fracture of reaction bonded silicon nitride

Science.gov (United States)

Liaw, B. M.; Kobayashi, A. S.; Emery, A. F.

1986-01-01

Wedge-loaded, modified tapered double cantilever beam (WL-MTDCB) specimens under impact loading were used to determine the room temperature dynamic fracture response of reaction bonded silicon nitride (RBSN). The crack extension history, with the exception of the terminal phase, was similar to that obtained under static loading. Like its static counterpart, a distinct crack acceleration phase, which was not observed in dynamic fracture of steel and brittle polymers, was noted. Unlike its static counterpart, the crack continued to propagate at nearly its terminal velocity under a low dynamic stress intensity factor during the terminal phase of crack propagation. These and previously obtained results for glass and RBSN show that dynamic crack arrest under a positive dynamic stress intensity factor is unlikely in static and impact loaded structural ceramics.

Possible reaction pathways of the lincomycin molecule according to the DFT calculation method

Directory of Open Access Journals (Sweden)

Eren Bahar

2017-01-01

Full Text Available Human-used antibiotics are eliminated from the body with little or no transformation at all. Traces of eliminated antibiotics enter the receiving environment directly since they cannot be treated in prevalent wastewater treatment facilities. Thus, wastewaters containing traces of antibiotics have to be treated accordingly. Lincomycin is subsequently isolated from Streptomyces lincolnensis. Lincomycin and its derivatives are antibiotics exhibiting biological activity against Gram-positive bacteria, and are natural antibiotics in the environment as pollutants. This study aims to predict the degradation mechanism of lincomycin molecule in the gaseous phase and aqueous media. Probable reaction path of lincomycin molecule with OH radicals was analyzed. Optimized geometry was calculated via Gauss View 5. Subsequently, the lowest energy status was determined through geometric optimization via Gaussian 09 program. Aiming to determine the intermediates in photocatalytic degradation mechanism of lincomycin, geometric optimization of the molecule was realized through DFT method. Activation energy for the probable reaction path was calculated, and their most stable state from the thermodynamic perspective determined for the gaseous phase and aqueous media. Impact of water solvent was investigated using the conductor-like screening solvation model (COSMO. The predicted mechanism was confirmed by comparison with experimental results on simple structures reported in literature.

The fifth Atomic Energy Research dynamic benchmark calculation with HEXTRAN-SMABRE

International Nuclear Information System (INIS)

Haenaelaeinen, Anitta

1998-01-01

The fifth Atomic Energy Research dynamic benchmark is the first Atomic Energy Research benchmark for coupling of the thermohydraulic codes and three-dimensional reactor dynamic core models. In VTT HEXTRAN 2.7 is used for the core dynamics and SMABRE 4.6 as a thermohydraulic model for the primary and secondary loops. The plant model for SMABRE is based mainly on two input models. the Loviisa model and standard WWER-440/213 plant model. The primary circuit includes six separate loops, totally 505 nodes and 652 junctions. The reactor pressure vessel is divided into six parallel channels. In HEXTRAN calculation 176 symmetry is used in the core. In the sequence of main steam header break at the hot standby state, the liquid temperature is decreased symmetrically in the core inlet which leads to return to power. In the benchmark, no isolations of the steam generators are assumed and the maximum core power is about 38 % of the nominal power at four minutes after the break opening in the HEXTRAN-SMABRE calculation. Due to boric acid in the high pressure safety injection water, the power finally starts to decrease. The break flow is pure steam in the HEXTRAN-SMABRE calculation during the whole transient even in the swell levels in the steam generators are very high due to flashing. Because of sudden peaks in the preliminary results of the steam generator heat transfer, the SMABRE drift-flux model was modified. The new model is a simplified version of the EPRI correlation based on test data. The modified correlation behaves smoothly. In the calculations nuclear data is based on the ENDF/B-IV library and it has been evaluated with the CASMO-HEX code. The importance of the nuclear data was illustrated by repeating the benchmark calculation with using three different data sets. Optimal extensive data valid from hot to cold conditions were not available for all types of fuel enrichments needed in this benchmark.(Author)

Mechanism and kinetics in reactions of caffeic acid with radicals by pulse radiolysis and calculation

Energy Technology Data Exchange (ETDEWEB)

Li, Xifeng; Cai, Zhongli; Katsumura, Yosuke [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab

2000-03-01

The interaction of caffeic acid with e{sub aq}{sup -}, (CH{sub 3}){sub 2}(OH) CCH{sub 2}{sup {center_dot}}, CO{sub 2}{sup {center_dot}}{sup -}, H{sup {center_dot}}, {center_dot}OH and N{sub 3}{sup {center_dot}} radicals were studied by {gamma}-, pulse radiolysis and molecular orbital calculation. UV-visible spectra of electron/{center_dot}OH adducts, semi-quinone radicals of caffeic ions, and the stable products from the reactions were derived. The rate constants were determined. The attacked sites and the most favorable structures of the transient radicals were predicted. Reaction mechanisms were proposed. (author)

The Lower Extremities Exoskeleton Actuator Dynamics Research Taking into Account Support Reaction

Directory of Open Access Journals (Sweden)

A. A. Vereikin

2014-01-01

Full Text Available The article shows high relevance of research, aimed at the robotic exoskeleton creation. It defines some problems related to the process of their designing; including a lack of power supply to provide enough autonomy, and difficulties of man-machine complex control. There is a review of literature on the walking robots with tree-like kinematic structure development. This work reflects the continuing investigations, currently conducted by the authors, and relies heavily on the results of previous works, devoted to this subject.The article presents the exoskeleton dynamics equation, taking into account the impact of external forces and torques, as well as external relations imposed. Using a model of lower extremities exoskeleton developed in SolidWorks software complex, baricentric parameters of the actuator links were found. The different types of movements, committed due to harmonic changes of generalized coordinates in exoskeleton degrees of mobility, equipped with electrohydraulic actuators, were analyzed. The laws of generalized coordinate changes in time, corresponding to the worst case loading, were found. All the necessary input data for the exoskeleton dynamics equation solution were determined.The numerical values of all components of the dynamics equation were obtained as result of the dynamics equation simulation. In this case, the exoskeleton actuator load capacity was assumed to be 50 kg. The article shows dependences of torque and power in the actuator degrees of mobility on the time, as well as a curve of total capacity of all drives both, ignoring and taking into consideration the support surface reactions. Obtained dependences are the initial data for the calculation of the drive system.The proposed method for determination of exoskeleton energy parameters allows developer to perform a prompt evaluation of various options for the actuator design in accordance with the selected criteria. As a main evaluation criterion, a minimum

Implementation of random set-up errors in Monte Carlo calculated dynamic IMRT treatment plans

International Nuclear Information System (INIS)

Stapleton, S; Zavgorodni, S; Popescu, I A; Beckham, W A

2005-01-01

The fluence-convolution method for incorporating random set-up errors (RSE) into the Monte Carlo treatment planning dose calculations was previously proposed by Beckham et al, and it was validated for open field radiotherapy treatments. This study confirms the applicability of the fluence-convolution method for dynamic intensity modulated radiotherapy (IMRT) dose calculations and evaluates the impact of set-up uncertainties on a clinical IMRT dose distribution. BEAMnrc and DOSXYZnrc codes were used for Monte Carlo calculations. A sliding window IMRT delivery was simulated using a dynamic multi-leaf collimator (DMLC) transport model developed by Keall et al. The dose distributions were benchmarked for dynamic IMRT fields using extended dose range (EDR) film, accumulating the dose from 16 subsequent fractions shifted randomly. Agreement of calculated and measured relative dose values was well within statistical uncertainty. A clinical seven field sliding window IMRT head and neck treatment was then simulated and the effects of random set-up errors (standard deviation of 2 mm) were evaluated. The dose-volume histograms calculated in the PTV with and without corrections for RSE showed only small differences indicating a reduction of the volume of high dose region due to set-up errors. As well, it showed that adequate coverage of the PTV was maintained when RSE was incorporated. Slice-by-slice comparison of the dose distributions revealed differences of up to 5.6%. The incorporation of set-up errors altered the position of the hot spot in the plan. This work demonstrated validity of implementation of the fluence-convolution method to dynamic IMRT Monte Carlo dose calculations. It also showed that accounting for the set-up errors could be essential for correct identification of the value and position of the hot spot

Implementation of random set-up errors in Monte Carlo calculated dynamic IMRT treatment plans

Science.gov (United States)

Stapleton, S.; Zavgorodni, S.; Popescu, I. A.; Beckham, W. A.

2005-02-01

The fluence-convolution method for incorporating random set-up errors (RSE) into the Monte Carlo treatment planning dose calculations was previously proposed by Beckham et al, and it was validated for open field radiotherapy treatments. This study confirms the applicability of the fluence-convolution method for dynamic intensity modulated radiotherapy (IMRT) dose calculations and evaluates the impact of set-up uncertainties on a clinical IMRT dose distribution. BEAMnrc and DOSXYZnrc codes were used for Monte Carlo calculations. A sliding window IMRT delivery was simulated using a dynamic multi-leaf collimator (DMLC) transport model developed by Keall et al. The dose distributions were benchmarked for dynamic IMRT fields using extended dose range (EDR) film, accumulating the dose from 16 subsequent fractions shifted randomly. Agreement of calculated and measured relative dose values was well within statistical uncertainty. A clinical seven field sliding window IMRT head and neck treatment was then simulated and the effects of random set-up errors (standard deviation of 2 mm) were evaluated. The dose-volume histograms calculated in the PTV with and without corrections for RSE showed only small differences indicating a reduction of the volume of high dose region due to set-up errors. As well, it showed that adequate coverage of the PTV was maintained when RSE was incorporated. Slice-by-slice comparison of the dose distributions revealed differences of up to 5.6%. The incorporation of set-up errors altered the position of the hot spot in the plan. This work demonstrated validity of implementation of the fluence-convolution method to dynamic IMRT Monte Carlo dose calculations. It also showed that accounting for the set-up errors could be essential for correct identification of the value and position of the hot spot.

Modeling Dynamic Objects in Monte Carlo Particle Transport Calculations

International Nuclear Information System (INIS)

Yegin, G.

2008-01-01

In this study, the Multi-Geometry geometry modeling technique was improved in order to handle moving objects in a Monte Carlo particle transport calculation. In the Multi-Geometry technique, the geometry is a superposition of objects not surfaces. By using this feature, we developed a new algorithm which allows a user to make enable or disable geometry elements during particle transport. A disabled object can be ignored at a certain stage of a calculation and switching among identical copies of the same object located adjacent poins during a particle simulation corresponds to the movement of that object in space. We called this powerfull feature as Dynamic Multi-Geometry technique (DMG) which is used for the first time in Brachy Dose Monte Carlo code to simulate HDR brachytherapy treatment systems. Our results showed that having disabled objects in a geometry does not effect calculated dose values. This technique is also suitable to be used in other areas such as IMRT treatment planning systems

The fifth AER dynamic benchmark calculation with hextran-smabre

International Nuclear Information System (INIS)

Haemaelaeinen, A.; Kyrki-Rajamaeki, R.

1998-01-01

The first AER benchmark for coupling of the thermohydraulic codes and three-dimensional reactordynamic core models is discussed. HEXTRAN 2.7 is used for the core dynamics and SMABRE 4.6 as a thermohydraulic model for the primary and secondary loops. The plant model for SMABRE is based mainly on two input models, the Loviisa model and standard VVER-440/213 plant model. The primary circuit includes six separate loops, totally 505 nodes and 652 junctions. The reactor pressure vessel is divided into six parallel channels. In HEXTRAN calculation 1/6 symmetry is used in the core. In the calculations nuclear data is based on the ENDF/B-IV library and it has been evaluated with the CASMO-HEX code. The importance of the nuclear data was illustrated by repeating the benchmark calculation with using three different data sets. Optimal extensive data valid from hot to cold conditions were not available for all types of fuel enrichments needed in this benchmark. (author)

Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

Energy Technology Data Exchange (ETDEWEB)

Bradforth, S.E.

1992-11-01

The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound [yields] bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN[sup [minus

Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Chen Li [Department of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Goettingen (Germany); Ueta, Hirokazu; Beck, Rainer D. [Laboratoire de Chimie Physique Moleculaire, Ecole Polytechnique Federale de Lausanne (Switzerland); Bisson, Regis [Aix-Marseille Universite, PIIM, CNRS, UMR 7345, 13397 Marseille (France)

2013-05-15

We report the design and characterization of a new molecular-beam/surface-science apparatus for quantum state-resolved studies of gas/surface reaction dynamics combining optical state-specific reactant preparation in a molecular beam by rapid adiabatic passage with detection of surface-bound reaction products by reflection absorption infrared spectroscopy (RAIRS). RAIRS is a non-invasive infrared spectroscopic detection technique that enables online monitoring of the buildup of reaction products on the target surface during reactant deposition by a molecular beam. The product uptake rate obtained by calibrated RAIRS detection yields the coverage dependent state-resolved reaction probability S({theta}). Furthermore, the infrared absorption spectra of the adsorbed products obtained by the RAIRS technique provide structural information, which help to identify nascent reaction products, investigate reaction pathways, and determine branching ratios for different pathways of a chemisorption reaction. Measurements of the dissociative chemisorption of methane on Pt(111) with this new apparatus are presented to illustrate the utility of RAIRS detection for highly detailed studies of chemical reactions at the gas/surface interface.

Methods of neutron spectrum calculation from measured reaction rates in saips. Part 1. Review of mathematical methods

International Nuclear Information System (INIS)

Bondars, Kh.Ya.; Lapenas, A.A.

1981-01-01

We adapted or used on ES EhVM, operating under the control of OS ES, the currently most common algorithms for calculating neutron spectra from measured reaction rates. These programs, together with the neutron cross-section and spectrum libraries, are part of the computerized information system SAIPS. The present article descibes the basic mathematical concepts used in the algorithms of the SAIPS calculation programs

Macroscopic treatment of nuclear dynamics

International Nuclear Information System (INIS)

Swiatecki, W.J.

1984-05-01

A qualitative classification of nucleus-nucleus reactions into four types is described, a consequence of the existence of up to three milestone configurations that a fusing system may be faced with. These considerations lead to phenomenological formulae for fusion and compound-nucleus cross-sections that may be compared with experiments by the use of rectilinear cross section plots. Examples of more specific model calculations of nuclear reactions employing the Chaotic Regime Dynamics are described. Some misunderstandings regarding the Wall and Wall-and-Window formulae, underlying this type of dynamics, are discussed in the appendix. 23 references

Free energy from molecular dynamics with multiple constraints

NARCIS (Netherlands)

den Otter, Wouter K.; Briels, Willem J.

2000-01-01

In molecular dynamics simulations of reacting systems, the key step to determining the equilibrium constant and the reaction rate is the calculation of the free energy as a function of the reaction coordinate. Intuitively the derivative of the free energy is equal to the average force needed to

Redox reaction characteristics of riboflavin: a fluorescence spectroelectrochemical analysis and density functional theory calculation.

Science.gov (United States)

Chen, Wei; Chen, Jie-Jie; Lu, Rui; Qian, Chen; Li, Wen-Wei; Yu, Han-Qing

2014-08-01

Riboflavin (RF), the primary redox active component of flavin, is involved in many redox processes in biogeochemical systems. Despite of its wide distribution and important roles in environmental remediation, its redox behaviors and reaction mechanisms in hydrophobic sites remain unclear yet. In this study, spectroelectrochemical analysis and density functional theory (DFT) calculation were integrated to explore the redox behaviors of RF in dimethyl sulfoxide (DMSO), which was used to create a hydrophobic environment. Specifically, cyclic voltafluorometry (CVF) and derivative cyclic voltafluorometry (DCVF) were employed to track the RF concentration changing profiles. It was found that the reduction contained a series of proton-coupled electron transfers dependent of potential driving force. In addition to the electron transfer-chemical reaction-electron transfer process, a disproportionation (DISP1) process was also identified to be involved in the reduction. The redox potential and free energy of each step obtained from the DFT calculations further confirmed the mechanisms proposed based on the experimental results. The combination of experimental and theoretical approaches yields a deep insight into the characteristics of RF in environmental remediation and better understanding about the proton-coupled electron transfer mechanisms. Copyright © 2014 Elsevier B.V. All rights reserved.

Interplay between excitation kinetics and reaction-center dynamics in purple bacteria

International Nuclear Information System (INIS)

Caycedo-Soler, Felipe; RodrIguez, Ferney J; Quiroga, Luis; Johnson, Neil F

2010-01-01

Photosynthesis is arguably the fundamental process of life, since it enables energy from the Sun to enter the food chain on the Earth. It is a remarkable non-equilibrium process in which photons are converted to many-body excitations, which traverse a complex biomolecular membrane, where they are captured and fuel chemical reactions within a reaction center (RC) in order to produce nutrients. The precise nature of these dynamical processes-which lie at the interface between quantum and classical behavior and involve both noise and coordination-is still being explored. Here, we focus on a striking recent empirical finding concerning an illumination-driven transition in the biomolecular membrane architecture of the purple bacteria Rsp. photometricum. Using stochastic realizations to describe a hopping rate model for excitation transfer, we show numerically and analytically that this surprising shift in preferred architectures can be traced to the interplay between the excitation kinetics and the RC dynamics. The net effect is that the bacteria profit from efficient metabolism at low illumination intensities while using dissipation to avoid an oversupply of energy at high illumination intensities.

Standard Gibbs free energies of reactions of ozone with free radicals in aqueous solution: quantum-chemical calculations.

Science.gov (United States)

Naumov, Sergej; von Sonntag, Clemens

2011-11-01

Free radicals are common intermediates in the chemistry of ozone in aqueous solution. Their reactions with ozone have been probed by calculating the standard Gibbs free energies of such reactions using density functional theory (Jaguar 7.6 program). O(2) reacts fast and irreversibly only with simple carbon-centered radicals. In contrast, ozone also reacts irreversibly with conjugated carbon-centered radicals such as bisallylic (hydroxycylohexadienyl) radicals, with conjugated carbon/oxygen-centered radicals such as phenoxyl radicals, and even with nitrogen- oxygen-, sulfur-, and halogen-centered radicals. In these reactions, further ozone-reactive radicals are generated. Chain reactions may destroy ozone without giving rise to products other than O(2). This may be of importance when ozonation is used in pollution control, and reactions of free radicals with ozone have to be taken into account in modeling such processes.

Dynamics of {sup 40,48}Ca+{sup 238}U→{sup 278,286}112{sup ⁎} reactions across the Coulomb barrier using dynamical cluster decay model

Energy Technology Data Exchange (ETDEWEB)

Sandhu, Kirandeep; Kaur, Gurvinder; Sharma, Manoj K., E-mail: msharma@thapar.edu

2014-01-15

The role of deformations and related orientations (optimum or compact) is investigated in reference to dynamics of {sup 40,48}Ca+{sup 238}U→{sup 278,286}112{sup ⁎} reactions using dynamical cluster decay model (DCM). The use of quadrupole and hexadecapole deformations in the decay of compound system suggest that the degree of compactness changes with addition of higher order deformations. The decay cross-sections are calculated in reference to the available data, including β{sub 2}-static deformations within ‘optimum’ orientation approach. The comparative analysis of spherical, β{sub 2}-static and dynamic alongwith β{sub 4}-static deformations is investigated at comparable center of mass energy of 230 MeV for both nuclei. To address the specific role of optimized orientations in the decay of {sup 278}112{sup ⁎} and {sup 286}112{sup ⁎} nuclei, the calculations are done using equatorial compact and polar elongated orientations. Using hot equatorial collisions, symmetric fission is observed as the dominant decay mode across the barrier, which otherwise becomes asymmetric for cold elongated approach. The calculated cross-sections match nicely with experimental data using hot configuration but the same are overestimated for the use of cold (polar) orientation approach at deep sub-barrier region. This overestimation in the deep sub-barrier region may be associated with the quasi-fission decay channel. The contribution of QF in both {sup 278}112{sup ⁎} and {sup 286}112{sup ⁎} nuclei are predicted through the overestimated cross-sections being more for neutron-deficient {sup 278}112{sup ⁎} nucleus, in agreement with experimental results. Larger barrier modification ΔV{sub B} is observed at sub-barrier energies for both isotopes of Z=112 nucleus. Also the contribution of ΔV{sub B} at lower incident energies is relatively higher for cold elongated polar configuration as compared to hot compact equatorial configuration, causing overestimation of cross

A model for steady-state and transient determination of subcooled boiling for calculations coupling a thermohydraulic and a neutron physics calculation program for reactor core calculation

International Nuclear Information System (INIS)

Mueller, R.G.

1987-06-01

Due to the strong influence of vapour bubbles on the nuclear chain reaction, an exact calculation of neutron physics and thermal hydraulics in light water reactors requires consideration of subcooled boiling. To this purpose, in the present study a dynamic model is derived from the time-dependent conservation equations. It contains new methods for the time-dependent determination of evaporation and condensation heat flow and for the heat transfer coefficient in subcooled boiling. Furthermore, it enables the complete two-phase flow region to be treated in a consistent manner. The calculation model was verified using measured data of experiments covering a wide range of thermodynamic boundary conditions. In all cases very good agreement was reached. The results from the coupling of the new calculation model with a neutron kinetics program proved its suitability for the steady-state and transient calculation of reactor cores. (orig.) [de

Mixed quantum-classical studies of energy partitioning in unimolecular chemical reactions

Science.gov (United States)

Bladow, Landon Lowell

A mixed quantum-classical reaction path Hamiltonian method is utilized to study the dynamics of unimolecular reactions. The method treats motion along the reaction path classically and treats the transverse vibrations quantum mechanically. The theory leads to equations that predict the disposai of the exit-channel potential energy to product translation and vibration. In addition, vibrational state distributions are obtained for the product normal modes. Vibrational excitation results from the curvature of the minimum energy reaction path. The method is applied to six unimolecular reactions: HF elimination from fluoroethane, 1,1-difluoroethane, 1,1-difluoroethene, and trifluoromethane; and HCl elimination from chloroethane and acetyl chloride. The minimum energy paths were calculated at either the MP2 or B3LYP level of theory. In all cases, the majority of the vibrational excitation of the products occurs in the HX fragment. The results are compared to experimental data and other theoretical results, where available. The best agreement between the experimental and calculated HX vibrational distributions is found for the halogenated ethanes, and the experimental deduction that the majority of the HX vibrational excitation arises from the potential energy release is supported. It is believed that the excess energy provided in experiments contributes to the poorer agreement between experiment and theory observed for HF elimination from 1,1-difluoroethene and trifluoromethane. An attempt is described to incorporate a treatment of the excess energy into the present method. However, the sign of the curvature coupling elements is then found to affect the dynamics. Overall, the method appears to be an efficient dynamical tool for modeling the disposal of the exit-channel potential energy in unimolecular reactions.

Modeling of pollutant formation in fully premixing surface burners using a verified practice-oriented experimental reaction-kinetic calculation method. Final report

International Nuclear Information System (INIS)

Ruy, C.; Kremer, H.

1996-01-01

The intent of the present study was to simulate quantitatively pollutant formation in premixing surface burners and to describe qualitatively the share of the premixing flame in pollut emissions from atmospheric burners. For this purpose reaction-kinetic programmes for one-dimensional premixing flames were extended by a terms describing heat discharge through gas radiation. Furthermore, the calculation range for the flame was extended far into the secondary reaction zone. Temperature, CO, and NO x profiles were measured in the secondary reaction zone of premixing burners at standard pressure. The air-fuel ratio was calculated within the practically relevant range between 0.5 and 1.5, as was load behaviour. (DG) [de

Mechanism of the Glycosidic Bond Cleavage of Mismatched Thymine in Human Thymine DNA Glycosylase Revealed by Classical Molecular Dynamics and Quantum Mechanical/Molecular Mechanical Calculations.

Science.gov (United States)

Kanaan, Natalia; Crehuet, Ramon; Imhof, Petra

2015-09-24

Base excision of mismatched or damaged nucleotides catalyzed by glycosylase enzymes is the first step of the base excision repair system, a machinery preserving the integrity of DNA. Thymine DNA glycosylase recognizes and removes mismatched thymine by cleaving the C1'-N1 bond between the base and the sugar ring. Our quantum mechanical/molecular mechanical calculations of this reaction in human thymine DNA glycosylase reveal a requirement for a positive charge in the active site to facilitate C1'-N1 bond scission: protonation of His151 significantly lowers the free energy barrier for C1'-N1 bond dissociation compared to the situation with neutral His151. Shuttling a proton from His151 to the thymine base further reduces the activation free energy for glycosidic bond cleavage. Classical molecular dynamics simulations of the H151A mutant suggest that the mutation to the smaller, neutral, residue increases the water accessibility of the thymine base, rendering direct proton transfer from the bulk feasible. Quantum mechanical/molecular mechanical calculations of the glycosidic bond cleavage reaction in the H151A mutant show that the activation free energy is slightly lower than in the wild-type enzyme, explaining the experimentally observed higher reaction rates in this mutant.

Viscosity of magnetic fluids must be modified in calculations of dynamic susceptibility

Energy Technology Data Exchange (ETDEWEB)

Lebedev, A.V., E-mail: lav@icmm.ru

2017-06-01

The frequency dependences of dynamic susceptibility were measured for a series of magnetic fluid samples with the same dispersed composition at different temperatures. Coincidence of normalized dynamic susceptibility curves plotted for different concentrations was obtained only after introducing correction for the value of dynamic viscosity of the magnetic fluid. The value of the correction coefficient doesn’t depend on temperature and is the universal function of the hydrodynamic concentration of particles. - Highlights: • Dynamic susceptibility was measured at different temperatures and concentrations. • Coincidence of curves requires a correction of value of viscosity in calculations. • This correction is function of the hydrodynamic concentration of particles. • With this function the rotation of particles are described correctly.

Exploring the dynamics of hydrogen atom release from the radical-radical reaction of O(3P) with C3H5

International Nuclear Information System (INIS)

Joo, Sun-Kyu; Kwon, Lee-Kyoung; Lee, Hohjai; Choi, Jong-Ho

2004-01-01

The gas-phase radical-radical reaction dynamics of O( 3 P)+C 3 H 5 →H( 2 S)+C 3 H 4 O was studied at an average collision energy of 6.4 kcal/mol in a crossed beam configuration. The ground-state atomic oxygen [O( 3 P)] and allyl radicals (C 3 H 5 ) were generated by the photolysis of NO 2 and the supersonic flash pyrolysis of allyl iodide, respectively. Nascent hydrogen atom products were probed by the vacuum-ultraviolet-laser induced fluorescence spectroscopy in the Lyman-α region centered at 121.6 nm. With the aid of the CBS-QB3 level of ab initio theory, it has been found that the barrierless addition of O( 3 P) to C 3 H 5 forms the energy-rich addition complexes on the lowest doublet potential energy surface, which are predicted to undergo a subsequent direct decomposition step leading to the reaction products H+C 3 H 4 O. The major counterpart C 3 H 4 O of the probed hydrogen atom is calculated to be acrolein after taking into account the factors of barrier height, reaction enthalpy, and the number of intermediates involved along the reaction pathway. The nascent H-atom Doppler profile analysis shows that the average center-of-mass translational energy of the H+C 3 H 4 O products and the fraction of the total available energy released as the translational energy were determined to be 3.83 kcal/mol and 0.054, respectively. On the basis of comparison with statistical calculations, the reaction proceeds through the formation of short-lived addition complexes rather than statistical, long-lived intermediates, and the polyatomic acrolein product is significantly internally excited at the moment of the decomposition

Exploring the dynamics of hydrogen atom release from the radical-radical reaction of O(3P) with C3H5

Science.gov (United States)

Joo, Sun-Kyu; Kwon, Lee-Kyoung; Lee, Hohjai; Choi, Jong-Ho

2004-05-01

The gas-phase radical-radical reaction dynamics of O(3P)+C3H5→H(2S)+C3H4O was studied at an average collision energy of 6.4 kcal/mol in a crossed beam configuration. The ground-state atomic oxygen [O(3P)] and allyl radicals (C3H5) were generated by the photolysis of NO2 and the supersonic flash pyrolysis of allyl iodide, respectively. Nascent hydrogen atom products were probed by the vacuum-ultraviolet-laser induced fluorescence spectroscopy in the Lyman-α region centered at 121.6 nm. With the aid of the CBS-QB3 level of ab initio theory, it has been found that the barrierless addition of O(3P) to C3H5 forms the energy-rich addition complexes on the lowest doublet potential energy surface, which are predicted to undergo a subsequent direct decomposition step leading to the reaction products H+C3H4O. The major counterpart C3H4O of the probed hydrogen atom is calculated to be acrolein after taking into account the factors of barrier height, reaction enthalpy, and the number of intermediates involved along the reaction pathway. The nascent H-atom Doppler profile analysis shows that the average center-of-mass translational energy of the H+C3H4O products and the fraction of the total available energy released as the translational energy were determined to be 3.83 kcal/mol and 0.054, respectively. On the basis of comparison with statistical calculations, the reaction proceeds through the formation of short-lived addition complexes rather than statistical, long-lived intermediates, and the polyatomic acrolein product is significantly internally excited at the moment of the decomposition.

Replica Exchange Gaussian Accelerated Molecular Dynamics: Improved Enhanced Sampling and Free Energy Calculation.

Science.gov (United States)

Huang, Yu-Ming M; McCammon, J Andrew; Miao, Yinglong

2018-04-10

Through adding a harmonic boost potential to smooth the system potential energy surface, Gaussian accelerated molecular dynamics (GaMD) provides enhanced sampling and free energy calculation of biomolecules without the need of predefined reaction coordinates. This work continues to improve the acceleration power and energy reweighting of the GaMD by combining the GaMD with replica exchange algorithms. Two versions of replica exchange GaMD (rex-GaMD) are presented: force constant rex-GaMD and threshold energy rex-GaMD. During simulations of force constant rex-GaMD, the boost potential can be exchanged between replicas of different harmonic force constants with fixed threshold energy. However, the algorithm of threshold energy rex-GaMD tends to switch the threshold energy between lower and upper bounds for generating different levels of boost potential. Testing simulations on three model systems, including the alanine dipeptide, chignolin, and HIV protease, demonstrate that through continuous exchanges of the boost potential, the rex-GaMD simulations not only enhance the conformational transitions of the systems but also narrow down the distribution width of the applied boost potential for accurate energetic reweighting to recover biomolecular free energy profiles.

Rate coefficients from quantum and quasi-classical cumulative reaction probabilities for the S(1D) + H2 reaction

Science.gov (United States)

Jambrina, P. G.; Lara, Manuel; Menéndez, M.; Launay, J.-M.; Aoiz, F. J.

2012-10-01

Cumulative reaction probabilities (CRPs) at various total angular momenta have been calculated for the barrierless reaction S(1D) + H2 → SH + H at total energies up to 1.2 eV using three different theoretical approaches: time-independent quantum mechanics (QM), quasiclassical trajectories (QCT), and statistical quasiclassical trajectories (SQCT). The calculations have been carried out on the widely used potential energy surface (PES) by Ho et al. [J. Chem. Phys. 116, 4124 (2002), 10.1063/1.1431280] as well as on the recent PES developed by Song et al. [J. Phys. Chem. A 113, 9213 (2009), 10.1021/jp903790h]. The results show that the differences between these two PES are relatively minor and mostly related to the different topologies of the well. In addition, the agreement between the three theoretical methodologies is good, even for the highest total angular momenta and energies. In particular, the good accordance between the CRPs obtained with dynamical methods (QM and QCT) and the statistical model (SQCT) indicates that the reaction can be considered statistical in the whole range of energies in contrast with the findings for other prototypical barrierless reactions. In addition, total CRPs and rate coefficients in the range of 20-1000 K have been calculated using the QCT and SQCT methods and have been found somewhat smaller than the experimental total removal rates of S(1D).

Calculation of the mutual diffusion coefficient by equilibrium and nonequilibrium molecular dynamics

International Nuclear Information System (INIS)

Erpenbeck, J.J.; Kincaid, J.M.

1986-01-01

A nonequilibrium molecular dynamics method for the calculation of the mutual diffusion coefficient for a mixture of hard spheres is described. The method is applied to a 50-50 mixture of equidiameter particles having a mass ratio of 0.1 for the two species, at a volume of three times close-packing. By extrapolating the results to the limit of vanishing concentration gradient and infinite system size, we obtain a value in statistical agreement with the result obtained using a Green-Kubo molecular dynamics procedure, which is also described. The nonequilibrium calculation yields a mutual diffusion coefficient which decreases slightly with increasing concentration gradient. The Green-Kubo timecorrelation function for mutual diffusion displays a slow decay with time, qualitatively similar to the long-time tail which has been predicted by the hydrodynamic theory of Pomeau

Dynamics of chemical reactions of multiply-charged cations: Information from beam scattering experiments

Czech Academy of Sciences Publication Activity Database

Herman, Zdeněk

2015-01-01

Roč. 378, FEB 2015 (2015), s. 113-126 ISSN 1387-3806 Institutional support: RVO:61388955 Keywords : Multiply-charged ions * Dynamics of chemical reactions * Beam scattering Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.183, year: 2015

The Crossed-Beam Scattering Method in Studies of Ion-Molecule Reaction Dynamics

Czech Academy of Sciences Publication Activity Database

Herman, Zdeněk

2001-01-01

Roč. 212, - (2001), s. 413-443 ISSN 1387-3806 R&D Projects: GA ČR GA203/00/0632 Institutional research plan: CEZ:AV0Z4040901 Keywords : ion-molecule reaction dynamics * ion scattering * experimental methods Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.176, year: 2001

Meson exchange calculation of the p-barp→Lambda-barΛ reaction

International Nuclear Information System (INIS)

Tabakin, F.; Eisenstein, R.A.

1985-01-01

The process p-barp→Lambda-barΛ is studied using a one-boson t-channel strangeness exchange mechanism incorporating pseudoscalar, vector, and tensor mesons. Particular attention is paid to the spin degrees of freedom in the calculation. Initial and final state interactions, including the spin-orbit interaction and absorption, are taken into account using simple phenomenological models. The calculations are performed using density matrix ideas in the helicity basis, and the most important contributing amplitudes are identified. A reasonable fit to existing data can be obtained by allowing a smooth variation of the final state parameters with laboratory momentum. The effect of each of the exchanged mesons, and of the initial- and final-state baryon-baryon interactions on the cross sections and spin observables, is discussed. It is found that the tensor meson exchange plays an essential role even near threshold, which indicates the need for a detailed understanding of the short-range spin dynamics, perhaps as provided by future quark model studies

Experimental and theoretical studies of the O(3P) + C2H4 reaction dynamics: Collision energy dependence of branching ratios and extent of intersystem crossing

Science.gov (United States)

Fu, Bina; Han, Yong-Chang; Bowman, Joel M.; Leonori, Francesca; Balucani, Nadia; Angelucci, Luca; Occhiogrosso, Angela; Petrucci, Raffaele; Casavecchia, Piergiorgio

2012-12-01

The reaction of O(3P) with C2H4, of importance in combustion and atmospheric chemistry, stands out as paradigm reaction involving not only the indicated triplet state potential energy surface (PES) but also an interleaved singlet PES that is coupled to the triplet surface. This reaction poses great challenges for theory and experiment, owing to the ruggedness and high dimensionality of these potentials, as well as the long lifetimes of the collision complexes. Crossed molecular beam (CMB) scattering experiments with soft electron ionization detection are used to disentangle the dynamics of this polyatomic multichannel reaction at a collision energy Ec of 8.4 kcal/mol. Five different primary products have been identified and characterized, which correspond to the five exothermic competing channels leading to H + CH2CHO, H + CH3CO, CH3 + HCO, CH2 + H2CO, and H2 + CH2CO. These experiments extend our previous CMB work at higher collision energy (Ec ˜ 13 kcal/mol) and when the results are combined with the literature branching ratios from kinetics experiments at room temperature (Ec ˜ 1 kcal/mol), permit to explore the variation of the branching ratios over a wide range of collision energies. In a synergistic fashion, full-dimensional, QCT surface hopping calculations of the O(3P) + C2H4 reaction using ab initio PESs for the singlet and triplet states and their coupling, are reported at collision energies corresponding to the CMB and the kinetics ones. Both theory and experiment find almost an equal contribution from the triplet and singlet surfaces to the reaction, as seen from the collision energy dependence of branching ratios of product channels and extent of intersystem crossing (ISC). Further detailed comparisons at the level of angular distributions and translational energy distributions are made between theory and experiment for the three primary radical channel products, H + CH2CHO, CH3 + HCO, and CH2 + H2CO. The very good agreement between theory and

Studies in the reaction dynamics of beam-gas chemiluminescent reactions

International Nuclear Information System (INIS)

Prisant, M.G.

1984-01-01

This thesis develops techniques for the analysis and interpretation of data obtained from beam-gas chemiluminescence experiments. These techniques are applied to experimental studies of atom transfer reactions of the type A + BC → AB + C. A procedure is developed for determining the product rotational alignment in the center-of-mass frame from polarization measurements of chemiluminescent atom-diatom exchange reactions under beam-gas conditions. Knowledge of a vector property of a reaction, such as product alignment, provides information on the disposition of angular momentum by a chemical reaction. Fluorescence polarization and hence product alignment are measured for two prototype reactions. The reaction of metastable calcium atoms with hydrogen-chloride gas yields highly aligned calcium-chloride product which exhibits little variation of alignment with vibrational state. The reaction of ground-state calcium with fluorine gas yields moderately aligned product which shows strong variation of alignment with vibration. A multi-surface direct-interaction model is developed to interpret product alignment and population data. The predictions of this model for the reaction of calcium with fluorine show reasonable agreement with experiment

A theoretical study of the mechanism of the atmospherically relevant reaction of chlorine atoms with methyl nitrate, and calculation of the reaction rate coefficients at temperatures relevant to the troposphere.

Science.gov (United States)

Ng, Maggie; Mok, Daniel K W; Lee, Edmond P F; Dyke, John M

2015-03-21

The reaction between atomic chlorine (Cl) and methyl nitrate (CH3ONO2) is significant in the atmosphere, as Cl is a key oxidant, especially in the marine boundary layer, and alkyl nitrates are important nitrogen-containing organic compounds, which are temporary reservoirs of the reactive nitrogen oxides NO, NO2 and NO3 (NOx). Four reaction channels HCl + CH2ONO2, CH3OCl + NO2, CH3Cl + NO3 and CH3O + ClNO2 were considered. The major channel is found to be the H abstraction channel, to give the products HCl + CH2ONO2. For all channels, geometry optimization and frequency calculations were carried out at the M06-2X/6-31+G** level, while relative electronic energies were improved to the UCCSD(T*)-F12/CBS level. The reaction barrier (ΔE(‡)0K) and reaction enthalpy (ΔH(RX)298K) of the H abstraction channel were computed to be 0.61 and -2.30 kcal mol(-1), respectively, at the UCCSD(T*)-F12/CBS//M06-2X/6-31+G** level. Reaction barriers (ΔE(‡)0K) for the other channels are more positive and these pathways do not contribute to the overall reaction rate coefficient in the temperature range considered (200-400 K). Rate coefficients were calculated for the H-abstraction channel at various levels of variational transition state theory (VTST) including tunnelling. Recommended ICVT/SCT rate coefficients in the temperature range 200-400 K are presented for the first time for this reaction. The values obtained in the 200-300 K region are particularly important as they will be valuable for atmospheric modelling calculations involving reactions with methyl nitrate. The implications of the results to atmospheric chemistry are discussed. Also, the enthalpies of formation, ΔHf,298K, of CH3ONO2 and CH2ONO2 were computed to be -29.7 and 19.3 kcal mol(-1), respectively, at the UCCSD(T*)-F12/CBS level.

Calculation of homogenized Pickering NGS stainless steel adjuster rod neutron cross-sections using conservation of reaction rates

Energy Technology Data Exchange (ETDEWEB)

Robinson, R C [Atlantic Nuclear Services Ltd. (Canada); Tran, F [Ontario Hydro, Pickering, ON (Canada). Pickering Generating Station

1996-12-31

A homogenization methodology for calculation of reactivity device incremental cross-sections has been developed using reaction rate conservation (RRC). A heterogeneous transport calculation of flux was utilised to produce the homogenized cross-sections for a finite difference two group diffusion code. The RRC cross-sections have been shown to improve significantly the prediction of reactivity worth for stainless steel adjuster rods installed in Pickering NGS reactors. (author). 10 refs., 3 tabs., 6 figs.

Programming chemical kinetics: engineering dynamic reaction networks with DNA strand displacement

Science.gov (United States)

Srinivas, Niranjan

Over the last century, the silicon revolution has enabled us to build faster, smaller and more sophisticated computers. Today, these computers control phones, cars, satellites, assembly lines, and other electromechanical devices. Just as electrical wiring controls electromechanical devices, living organisms employ "chemical wiring" to make decisions about their environment and control physical processes. Currently, the big difference between these two substrates is that while we have the abstractions, design principles, verification and fabrication techniques in place for programming with silicon, we have no comparable understanding or expertise for programming chemistry. In this thesis we take a small step towards the goal of learning how to systematically engineer prescribed non-equilibrium dynamical behaviors in chemical systems. We use the formalism of chemical reaction networks (CRNs), combined with mass-action kinetics, as our programming language for specifying dynamical behaviors. Leveraging the tools of nucleic acid nanotechnology (introduced in Chapter 1), we employ synthetic DNA molecules as our molecular architecture and toehold-mediated DNA strand displacement as our reaction primitive. Abstraction, modular design and systematic fabrication can work only with well-understood and quantitatively characterized tools. Therefore, we embark on a detailed study of the "device physics" of DNA strand displacement (Chapter 2). We present a unified view of strand displacement biophysics and kinetics by studying the process at multiple levels of detail, using an intuitive model of a random walk on a 1-dimensional energy landscape, a secondary structure kinetics model with single base-pair steps, and a coarse-grained molecular model that incorporates three-dimensional geometric and steric effects. Further, we experimentally investigate the thermodynamics of three-way branch migration. Our findings are consistent with previously measured or inferred rates for

Quantum mechanical calculations of vibrational population inversion in chemical reactions - Numerically exact L-squared-amplitude-density study of the H2Br reactive system

Science.gov (United States)

Zhang, Y. C.; Zhang, J. Z. H.; Kouri, D. J.; Haug, K.; Schwenke, D. W.

1988-01-01

Numerically exact, fully three-dimensional quantum mechanicl reactive scattering calculations are reported for the H2Br system. Both the exchange (H + H-prime Br to H-prime + HBr) and abstraction (H + HBR to H2 + Br) reaction channels are included in the calculations. The present results are the first completely converged three-dimensional quantum calculations for a system involving a highly exoergic reaction channel (the abstraction process). It is found that the production of vibrationally hot H2 in the abstraction reaction, and hence the extent of population inversion in the products, is a sensitive function of initial HBr rotational state and collision energy.

Magnetic materials at finite temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations

International Nuclear Information System (INIS)

Eisenbach, Markus; Perera, Meewanage Dilina N.; Landau, David P; Nicholson, Don M.; Yin, Junqi; Brown, Greg

2015-01-01

We present a unified approach to describe the combined behavior of the atomic and magnetic degrees of freedom in magnetic materials. Using Monte Carlo simulations directly combined with first principles the Curie temperature can be obtained ab initio in good agreement with experimental values. The large scale constrained first principles calculations have been used to construct effective potentials for both the atomic and magnetic degrees of freedom that allow the unified study of influence of phonon-magnon coupling on the thermodynamics and dynamics of magnetic systems. The MC calculations predict the specific heat of iron in near perfect agreement with experimental results from 300K to above Tc and allow the identification of the importance of the magnon-phonon interaction at the phase-transition. Further Molecular Dynamics and Spin Dynamics calculations elucidate the dynamics of this coupling and open the potential for quantitative and predictive descriptions of dynamic structure factors in magnetic materials using first principles-derived simulations.

Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal.

Science.gov (United States)

Zhao, Bin; Sun, Zhigang; Guo, Hua

2015-06-28

Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H2O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H2O → H2 + OH reaction. The strong enhancement of reactivity by the H2O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal.

Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal

International Nuclear Information System (INIS)

Zhao, Bin; Guo, Hua; Sun, Zhigang

2015-01-01

Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H 2 O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H 2 O → H 2 + OH reaction. The strong enhancement of reactivity by the H 2 O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal

Generalized monitor unit calculation for the Varian enhanced dynamic wedge field

International Nuclear Information System (INIS)

Liu Chihray; Kim, Siyong; Kahler, Darren L.; Palta, Jatinder R.

2003-01-01

The generalized monitor unit (MU) calculation equation for the Varian enhanced dynamic wedge (EDW) is derived. The assumption of this MU calculation method is that the wedge factor of the EDW at the center of the field is a function of field size, the position of the center of the field in the wedge direction, and the final position of the moving jaw. The wedge factors at the center of the field in both symmetric and asymmetric fields are examined. The difference between calculated and measured wedge factors is within 1.0%. The method developed here is easy to implement. The only datum required in addition to the standard set of conventional physical wedge implementation data is the off-axis output factor for the open field in the reference condition. The off-center point calculation is also examined. For the off-center point calculation, the dose profile in the wedge direction for the largest EDW field is used to obtain the relative off-center ratio in any smaller wedge field. The accuracy of the off-center point calculation decreases when the point of calculation is too close to the field edge

Combustion kinetics and reaction pathways

Energy Technology Data Exchange (ETDEWEB)

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

1993-12-01

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

Multi-nucleon transfer: a probe to investigate the reaction mechanism around the barrier

International Nuclear Information System (INIS)

Mandal, Samit K.

2014-01-01

The investigation of multi-nucleon transfer mechanism offers valuable information on the pairing interactions that enhance the transfer of nucleon pairs across heavy ions involved in the reaction. These reactions are also a useful tool to study exotic nuclei far from the stability line, which can be explored with the new generation radioactive beam facility. In this talk, multi-nucleon transfer reaction mechanisms between heavy ions and their effect on the reaction dynamics around the coulomb barrier energies have been discussed. Experimental results will be presented with a semi classical description of multi nucleon transfer reaction calculation. One and two nucleon transfer cross sections reproduced using a quantum mechanical coupled channel calculations will also be discussed. A feasibility of investigation of multi-nucleon transfer mechanism to explore the pairing correlation at moderate spin states with radioactive beams will be discussed. (author)

Quantum dynamics of the Eley-Rideal hydrogen formation reaction on graphite at typical interstellar cloud conditions.

Science.gov (United States)

Casolo, Simone; Martinazzo, Rocco; Bonfanti, Matteo; Tantardini, Gian Franco

2009-12-31

Eley-Rideal formation of hydrogen molecules on graphite, as well as competing collision induced processes, are investigated quantum dynamically at typical interstellar cloud conditions, focusing in particular on gas-phase temperatures below 100 K, where much of the chemistry of the so-called diffuse clouds takes place on the surface of bare carbonaceous dust grains. Collisions of gas-phase hydrogen atoms with both chemisorbed and physisorbed species are considered using available potential energy surfaces (Sha et al., J. Chem. Phys.2002 116, 7158), and state-to-state, energy-resolved cross sections are computed for a number of initial vibrational states of the hydrogen atoms bound to the surface. Results show that (i) product molecules are internally hot in both cases, with vibrational distributions sharply peaked around few (one or two) vibrational levels, and (ii) cross sections for chemisorbed species are 2-3x smaller than those for physisorbed ones. In particular, we find that H(2) formation cross sections out of chemically bound species decrease steadily when the temperature drops below approximately 1000 K, and this is likely due to a quantum reflection phenomenon. This suggests that such Eley-Rideal reaction is all but efficient in the relevant gas-phase temperature range, even when gas-phase H atoms happen to chemisorb barrierless to the surface as observed, e.g., for forming so-called para dimers. Comparison with results from classical trajectory calculations highlights the need of a quantum description of the dynamics in the astrophysically relevant energy range, whereas preliminary results of an extensive first-principles investigation of the reaction energetics reveal the importance of the adopted substrate model.

Calculation of the mutual diffusion coefficient by equilibrium and nonequilibrium molecular dynamics

International Nuclear Information System (INIS)

Erpenbeck, J.J.; Kincaid, J.M.

1985-01-01

A nonequilibrium molecular dynamics method for the calculation of the mutual diffusion coefficient for a mixture of hard spheres is described. The method is applied to a 50-50 mixture of equidiameter particles having a mass ratio of 0.1 for the two species, at a volume of three times close-packing. By extrapolating the results to the limit of vanishing concentration gradient and infinite system size, we obtain a value in statistical agreement with the result obtained using a Green-Kubo molecular dynamics procedure which is also described. The nonequilibrium calculation yields a mutual diffusion coefficient which decreases slightly with increasing concentration gradient. The Green-Kubo time correlation function for mutual diffusion displays a slow decay with time, qualitatively similar to the long-time tail which has been predicted by the hydrodynamic theory of Pomeau

Biological Applications of Hybrid Quantum Mechanics/Molecular Mechanics Calculation

Directory of Open Access Journals (Sweden)

Jiyoung Kang

2012-01-01

Full Text Available Since in most cases biological macromolecular systems including solvent water molecules are remarkably large, the computational costs of performing ab initio calculations for the entire structures are prohibitive. Accordingly, QM calculations that are jointed with MM calculations are crucial to evaluate the long-range electrostatic interactions, which significantly affect the electronic structures of biological macromolecules. A UNIX-shell-based interface program connecting the quantum mechanics (QMs and molecular mechanics (MMs calculation engines, GAMESS and AMBER, was developed in our lab. The system was applied to a metalloenzyme, azurin, and PU.1-DNA complex; thereby, the significance of the environmental effects on the electronic structures of the site of interest was elucidated. Subsequently, hybrid QM/MM molecular dynamics (MD simulation using the calculation system was employed for investigation of mechanisms of hydrolysis (editing reaction in leucyl-tRNA synthetase complexed with the misaminoacylated tRNALeu, and a novel mechanism of the enzymatic reaction was revealed. Thus, our interface program can play a critical role as a powerful tool for state-of-the-art sophisticated hybrid ab initio QM/MM MD simulations of large systems, such as biological macromolecules.

Three-dimensional static and dynamic reactor calculations by the nodal expansion method

International Nuclear Information System (INIS)

Christensen, B.

1985-05-01

This report reviews various method for the calculation of the neutron-flux- and power distribution in an nuclear reactor. The nodal expansion method (NEM) is especially described in much detail. The nodal expansion method solves the diffusion equation. In this method the reactor core is divided into nodes, typically 10 to 20 cm in each direction, and the average flux in each node is calculated. To obtain the coupling between the nodes the local flux inside each node is expressed by use of a polynomial expansion. The expansion is one-dimensional, so inside each node such three expansions occur. To calculate the expansion coefficients it is necessary that the polynomial expansion is a solution to the one-dimensional diffusion equation. When the one-dimensional diffusion equation is established a term with the transversal leakage occur, and this term is expanded after the same polynomials. The resulting equation system with the expansion coefficients as the unknowns is solved with weigthed residual technique. The nodal expansion method is built into a computer program (also called NEM), which is divided into two parts, one part for steady-state calculations and one part for dynamic calculations. It is possible to take advantage of symmetry properties of the reactor core. The program is very flexible with regard to the number of energy groups, the node size, the flux expansion order and the transverse leakage expansion order. The boundary of the core is described by albedos. The program and input to it are described. The program is tested on a number of examples extending from small theoretical one up to realistic reactor cores. Many calculations are done on the wellknown IAEA benchmark case. The calculations have tested the accuracy and the computing time for various node sizes and polynomial expansions. In the dynamic examples various strategies for variation of the time step-length have been tested. (author)

Role of delta excitations in pion-, photon- and nucleon-nucleus reactions studied with microscopic models

International Nuclear Information System (INIS)

Engel, A.

1995-01-01

Delta excitation plays a prominent role in intermediate heavy reactions. In this paper, comment is made on the calculations done for pion-, photon- and nucleon-nucleus reactions using the Boltzmann-Uehling-Uhlenbeck (BUU) model and the antisymmetrized molecular dynamics (AMD) model. First, it is recalled how to include delta degrees in microscopic models in general. Then, the comparison of the microscopic calculation performed by the author with the experimental data is presented. Deltas in microscopic models are discussed. Pion-nucleus reactions have been studied since pion beams became available, especially for exploring the delta resonance in a nuclear medium. The dependence of pion absorption cross section on incident pion energy is shown. The photon-induced pion production in the resonance energy region was studied with the BUU model. The calculated results of neutral pion photo-production are shown. In both inelastic proton scattering and (p,n) charge exchange reaction, the excitation of delta resonance can be observed clearly in the experimental data. The results of the AMD calculation for 12 C(p,p') reaction are shown. (K.I.)

Error Propagation dynamics: from PIV-based pressure reconstruction to vorticity field calculation

Science.gov (United States)

Pan, Zhao; Whitehead, Jared; Richards, Geordie; Truscott, Tadd; USU Team; BYU Team

2017-11-01

Noninvasive data from velocimetry experiments (e.g., PIV) have been used to calculate vorticity and pressure fields. However, the noise, error, or uncertainties in the PIV measurements would eventually propagate to the calculated pressure or vorticity field through reconstruction schemes. Despite the vast applications of pressure and/or vorticity field calculated from PIV measurements, studies on the error propagation from the velocity field to the reconstructed fields (PIV-pressure and PIV-vorticity are few. In the current study, we break down the inherent connections between PIV-based pressure reconstruction and PIV-based vorticity calculation. The similar error propagation dynamics, which involve competition between physical properties of the flow and numerical errors from reconstruction schemes, are found in both PIV-pressure and PIV-vorticity reconstructions.

Ground Reaction Forces Generated During Rhythmical Squats as a Dynamic Loads of the Structure

Science.gov (United States)

Pantak, Marek

2017-10-01

Dynamic forces generated by moving persons can lead to excessive vibration of the long span, slender and lightweight structure such as floors, stairs, stadium stands and footbridges. These dynamic forces are generated during walking, running, jumping and rhythmical body swaying in vertical or horizontal direction etc. In the paper the mathematical models of the Ground Reaction Forces (GRFs) generated during squats have been presented. Elaborated models was compared to the GRFs measured during laboratory tests carried out by author in wide range of frequency using force platform. Moreover, the GRFs models were evaluated during dynamic numerical analyses and dynamic field tests of the exemplary structure (steel footbridge).

Dosimetric comparison of interactive planned and dynamic dose calculated prostate seed brachytherapy

International Nuclear Information System (INIS)

Meijer, Gert J.; Berg, Hetty A. van den; Hurkmans, Coen W.; Stijns, Pascal E.; Weterings, Jan H.

2006-01-01

Purpose: To compare the dosimetrical results of an interactive planning procedure and a procedure based on dynamic dose calculation for permanent prostate brachytherapy. Materials and methods: Between 6/2000 and 11/2005, 510 patients underwent 125 I implants for T1-T2 prostate cancer. Before 4/2003, 187 patients were treated using an interactive technique that included needle updating. After that period, 323 patients were treated with a more refined dynamic technique that included constant updating of the deposited seed position. The comparison is based on postimplant dose-volume parameters such as the V 100 and d 90 for the target, V 100 r for the rectum and d 10 u for the urethra. Furthermore, the target volume ratios (TVR=V 100 body /V 100 ), and the homogeneity indices (HI=[V 100 -V 150 ]/V 100 ) were calculated as additional quality parameters. Results: The dose outside the target volume was significantly reduced, the V 100 r decreased from 1.4cm 3 for the interactive technique to 0.6cm 3 for the dynamic technique. Similarly the mean TVR reduced from 1.66 to 1.44. In addition, the mean V 100 increased from 92% for the interactive procedure to 95% for the dynamic procedure. More importantly, the percentage of patients with a V 100 10 u (136% vs. 140%) and the HI (0.58 vs. 0.51). Conclusion: The dynamic implant procedure resulted in improved implants. Almost ideal dose coverage was achieved, while minimizing the dose outside the prostate

Evidence for the Active Phase of Heterogeneous Catalysts through In Situ Reaction Product Imaging and Multiscale Modeling

Energy Technology Data Exchange (ETDEWEB)

Matera, S.; Blomberg, S.; Hoffmann, M. J.; Zetterberg, J.; Gustafson, J.; Lundgren, E.; Reuter, K.

2015-06-17

We use multiscale modeling to analyze laser-induced fluorescence (LIF) measurements of the CO oxidation reaction over Pd(100) at near-ambient reaction conditions. Integrating density functional theory-based kinetic Monte Carlo simulations of the active catalyst into fluid-dynamical simulations of the mass transport inside the reactor chamber, we calculate the reaction product concentration directly above the catalyst surface. Comparing corresponding data calculated for different surface models against the measured LIF signals, we can discriminate the one that predominantly actuates the experimentally measured catalytic activity. For the probed CO oxidation reaction conditions, the experimental activity is due to pristine Pd(100) possibly coexisting with other (oxidic) domains on the surface.

One-loop calculation in time-dependent non-equilibrium thermo field dynamics

International Nuclear Information System (INIS)

Umezawa, H.; Yamanaka, Y.

1989-01-01

This paper is a review on the structure of thermo field dynamics (TFD) in which the basic concepts such as the thermal doublets, the quasi-particles and the self-consistent renormalization are presented in detail. A strong emphasis is put on the computational scheme. A detailed structure of this scheme is illustrated by the one-loop calculation in a non-equilibrium time-dependent process. A detailed account of the one-loop calculation has never been reported anywhere. The role of the self-consistent renormalization is explained. The equilibrium TFD is obtained as the long-time limit of non-equilibrium TFD. (author)

Cluster expression in fission and fusion in high-dimensional macroscopic-microscopic calculations

International Nuclear Information System (INIS)

Iwamoto, Akira; Ichikawa, Takatoshi; Moller, Peter; Sierk, Arnold J.

2004-01-01

We discuss the relation between the fission-fusion potential-energy surfaces of very heavy nuclei and the formation process of these nuclei in cold-fusion reactions. In the potential-energy surfaces, we find a pronounced valley structure, with one valley corresponding to the cold-fusion reaction, the other to fission. As the touching point is approached in the cold-fusion entrance channel, an instability towards dynamical deformation of the projectile occurs, which enhances the fusion cross section. These two 'cluster effects' enhance the production of superheavy nuclei in cold-fusion reactions, in addition to the effect of the low compound-system excitation energy in these reactions. Heavy-ion fusion reactions have been used extensively to synthesize heavy elements beyond actinide nuclei. In order to proceed further in this direction, we need to understand the formation process more precisely, not just the decay process. The dynamics of the formation process are considerably more complex than the dynamics necessary to interpret the spontaneous-fission decay of heavy elements. However, before implementing a full dynamical description it is useful to understand the basic properties of the potential-energy landscape encountered in the initial stages of the collision. The collision process and entrance-channel landscape can conveniently be separated into two parts, namely the early-stage separated system before touching and the late-stage composite system after touching. The transition between these two stages is particularly important, but not very well understood until now. To understand better the transition between the two stages we analyze here in detail the potential energy landscape or 'collision surface' of the system both outside and inside the touching configuration of the target and projectile. In Sec. 2, we discuss calculated five-dimensional potential-energy landscapes inside touching and identify major features. In Sec. 3, we present calculated

Interplay between inhibited transport and reaction in nanoporous materials

Energy Technology Data Exchange (ETDEWEB)

Ackerman, David Michael [Iowa State Univ., Ames, IA (United States)

2013-01-01

This work presents a detailed formulation of reaction and diffusion dynamics of molecules in confined pores such as mesoporous silica and zeolites. A general reaction-diffusion model and discrete Monte Carlo simulations are presented. Both transient and steady state behavior is covered. Failure of previous mean-field models for these systems is explained and discussed. A coarse-grained, generalized hydrodynamic model is developed that accurately captures the interplay between reaction and restricted transport in these systems. This method incorporates the non-uniform chemical diffusion behavior present in finite pores with multi-component diffusion. Two methods of calculating these diffusion values are developed: a random walk based approach and a driven diffusion model based on an extension of Fick's law. The effects of reaction, diffusion, pore length, and catalytic site distribution are investigated. In addition to strictly single file motion, quasi-single file diffusion is incorporated into the model to match a range of experimental systems. The connection between these experimental systems and model parameters is made through Langevin dynamics modeling of particles in confined pores.

Multilevel Quantum Mechanics Theories and Molecular Mechanics Calculations of the Cl- + CH3I Reaction in Water.

Science.gov (United States)

Liu, Peng; Li, Chen; Wang, Dunyou

2017-10-19

The Cl - + CH 3 I → CH 3 Cl + I - reaction in water was studied using combined multilevel quantum mechanism theories and molecular mechanics with an explicit water solvent model. The study shows a significant influence of aqueous solution on the structures of the stationary points along the reaction pathway. A detailed, atomic-level evolution of the reaction mechanism shows a concerted one-bond-broken and one-bond-formed mechanism, as well as a synchronized charge-transfer process. The potentials of mean force calculated with the CCSD(T) and DFT treatments of the solute produce a free activation barrier at 24.5 and 19.0 kcal/mol, respectively, which agrees with the experimental one at 22.0 kcal/mol. The solvent effects have also been quantitatively analyzed: in total, the solvent effects raise the activation energy by 20.2 kcal/mol, which shows a significant impact on this reaction in water.

Dynamical Behaviors of Stochastic Reaction-Diffusion Cohen-Grossberg Neural Networks with Delays

Directory of Open Access Journals (Sweden)

Li Wan

2012-01-01

Full Text Available This paper investigates dynamical behaviors of stochastic Cohen-Grossberg neural network with delays and reaction diffusion. By employing Lyapunov method, Poincaré inequality and matrix technique, some sufficient criteria on ultimate boundedness, weak attractor, and asymptotic stability are obtained. Finally, a numerical example is given to illustrate the correctness and effectiveness of our theoretical results.

Identifying Slow Molecular Motions in Complex Chemical Reactions.

Science.gov (United States)

Piccini, GiovanniMaria; Polino, Daniela; Parrinello, Michele

2017-09-07

We have studied the cyclization reaction of deprotonated 4-chloro-1-butanethiol to tetrahydrothiophene by means of well-tempered metadynamics. To properly select the collective variables, we used the recently proposed variational approach to conformational dynamics within the framework of metadyanmics. This allowed us to select the appropriate linear combinations from a set of collective variables representing the slow degrees of freedom that best describe the slow modes of the reaction. We performed our calculations at three different temperatures, namely, 300, 350, and 400 K. We show that the choice of such collective variables allows one to easily interpret the complex free-energy surface of such a reaction by univocal identification of the conformers belonging to reactants and product states playing a fundamental role in the reaction mechanism.

Fast and stable redox reactions of MnO2/CNT hybrid electrodes for dynamically stretchable pseudocapacitors

Science.gov (United States)

Gu, Taoli; Wei, Bingqing

2015-07-01

Pseudocapacitors, which are energy storage devices that take advantage of redox reactions to store electricity, have a different charge storage mechanism compared to lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs), and they could realize further gains if they were used as stretchable power sources. The realization of dynamically stretchable pseudocapacitors and understanding of the underlying fundamentals of their mechanical-electrochemical relationship have become indispensable. We report herein the electrochemical performance of dynamically stretchable pseudocapacitors using buckled MnO2/CNT hybrid electrodes. The extremely small relaxation time constant of less than 0.15 s indicates a fast redox reaction at the MnO2/CNT hybrid electrodes, securing a stable electrochemical performance for the dynamically stretchable pseudocapacitors. This finding and the fundamental understanding gained from the pseudo-capacitive behavior coupled with mechanical deformation under a dynamic stretching mode would provide guidance to further improve their overall performance including a higher power density than LIBs, a higher energy density than EDLCs, and a long-life cycling stability. Most importantly, these results will potentially accelerate the applications of stretchable pseudocapacitors for flexible and biomedical electronics.Pseudocapacitors, which are energy storage devices that take advantage of redox reactions to store electricity, have a different charge storage mechanism compared to lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs), and they could realize further gains if they were used as stretchable power sources. The realization of dynamically stretchable pseudocapacitors and understanding of the underlying fundamentals of their mechanical-electrochemical relationship have become indispensable. We report herein the electrochemical performance of dynamically stretchable pseudocapacitors using buckled MnO2/CNT hybrid

The decay of hot nuclei formed in La-induced reactions at E/A=45 MeV

International Nuclear Information System (INIS)

Libby, B.

1993-01-01

The decay of hot nuclei formed in the reactions 139 La + 27 Al, 51 V, nat Cu, and 139 La were studied by the coincident detection of up to four complex fragments (Z > 3) emitted in these reactions. Fragments were characterized as to their atomic number, energy and in- and out-of-plane angles. The probability of the decay by an event of a given complex fragment multiplicity as a function of excitation energy per nucleon of the source is nearly independent of the system studied. Additionally, there is no large increase in the proportion of multiple fragment events as the excitation energy of the source increases past 5 MeV/nucleon. This is at odds with many prompt multifragmentation models of nuclear decay. The reactions 139 La + 27 Al, 51 V, nat Cu were also studied by combining a dynamical model calculation that simulates the early stages of nuclear reactions with a statistical model calculation for the latter stages of the reactions. For the reaction 139 La + 27 Al, these calculations reproduced many of the experimental features, but other features were not reproduced. For the reaction 139 La + 51 V, the calculation failed to reproduce somewhat more of the experimental features. The calculation failed to reproduce any of the experimental features of the reaction 139 La + nat Cu, with the exception of the source velocity distributions

Sources and characteristics of complex fragments in La-induced reactions

International Nuclear Information System (INIS)

Roussel-Chomaz, P.; Blumenfeld, Y.; Charity, R.; Colonna, M.; Colonna, N.; Libby, B.; Hanold, K.; Moretto, L.; Peaslee, G.; Wozniak, G.

1991-01-01

Complex fragment emission has been studied for a variety of reactions at intermediate energies. Multifragment events are shown to be associated with specific sources characterized by their mass and excitation energy through the incomplete fusion model. Excitation functions for the different multifragment decay channels are found to be almost independent of the system and the incident energy. Preliminary comparisons of the data with dynamical calculations followed by statistical decay calculations are discussed. 11 refs., 7 figs

Parallel replica dynamics method for bistable stochastic reaction networks: Simulation and sensitivity analysis

Science.gov (United States)

Wang, Ting; Plecháč, Petr

2017-12-01

Stochastic reaction networks that exhibit bistable behavior are common in systems biology, materials science, and catalysis. Sampling of stationary distributions is crucial for understanding and characterizing the long-time dynamics of bistable stochastic dynamical systems. However, simulations are often hindered by the insufficient sampling of rare transitions between the two metastable regions. In this paper, we apply the parallel replica method for a continuous time Markov chain in order to improve sampling of the stationary distribution in bistable stochastic reaction networks. The proposed method uses parallel computing to accelerate the sampling of rare transitions. Furthermore, it can be combined with the path-space information bounds for parametric sensitivity analysis. With the proposed methodology, we study three bistable biological networks: the Schlögl model, the genetic switch network, and the enzymatic futile cycle network. We demonstrate the algorithmic speedup achieved in these numerical benchmarks. More significant acceleration is expected when multi-core or graphics processing unit computer architectures and programming tools such as CUDA are employed.

Parallel replica dynamics method for bistable stochastic reaction networks: Simulation and sensitivity analysis.

Science.gov (United States)

Wang, Ting; Plecháč, Petr

2017-12-21

Stochastic reaction networks that exhibit bistable behavior are common in systems biology, materials science, and catalysis. Sampling of stationary distributions is crucial for understanding and characterizing the long-time dynamics of bistable stochastic dynamical systems. However, simulations are often hindered by the insufficient sampling of rare transitions between the two metastable regions. In this paper, we apply the parallel replica method for a continuous time Markov chain in order to improve sampling of the stationary distribution in bistable stochastic reaction networks. The proposed method uses parallel computing to accelerate the sampling of rare transitions. Furthermore, it can be combined with the path-space information bounds for parametric sensitivity analysis. With the proposed methodology, we study three bistable biological networks: the Schlögl model, the genetic switch network, and the enzymatic futile cycle network. We demonstrate the algorithmic speedup achieved in these numerical benchmarks. More significant acceleration is expected when multi-core or graphics processing unit computer architectures and programming tools such as CUDA are employed.

General-purpose software for science technology calculation

International Nuclear Information System (INIS)

Aikawa, Hiroshi

1999-01-01

We have developed many general-purpose softwares for parallel processing of science technology calculation. This paper reported six softwares such as STA (Seamless Thinking Aid) basic soft, parallel numerical computation library, grid formation software for parallel computer, real-time visualizing system, parallel benchmark test system and object-oriented parallel programing method. STA is a user interface software to perform a total environment for parallel programing, a network computing environment for various parallel computers and a desktop computing environment via Web. Some examples using the above softwares are explained. One of them is a simultaneous parallel calculation of both analysis of flow and structure of supersonic transport to design of them. The other is various kinds of computer parallel calculations for nuclear fusion reaction such as a molecular dynamic calculation and a calculation of reactor structure and fluid. These softs are opened to the public by the home page {http://guide.tokai.jaeri.go.jp/ccse/}. (S.Y.)

Fission dynamics of superheavy nuclei formed in uranium induced reactions

International Nuclear Information System (INIS)

Gurjit Kaur; Sandhu, Kirandeep; Sharma, Manoj K.

2017-01-01

The compound nuclear system follows symmetric fission if the competing processes such as quasi-elastic, deep inelastic, quasi-fission etc are absent. The contribution of quasi fission events towards the fusion-fission mechanism depends on the entrance channel asymmetry of reaction partners, deformations and orientations of colliding nuclei beside the dependence on energy and angular momentum. Usually the 209 Bi and 208 Pb targets are opted for the production of superheavy nuclei with Z CN =104-113. The nuclei in same mass/charge range can also be synthesized using actinide targets + light projectiles (i.e. asymmetric reaction partners) via hot fusion interactions. These actinide targets are prolate deformed which prefer the compact configurations at above barrier energies, indicating the occurrence of symmetric fission events. Here an attempt is made to address the dynamics of light superheavy system (Z CN =104-106), formed via hot fusion interactions involving actinide targets

Hartree-Fock (HF) method and density functional theory calculations of Methanol to Gasoline (MTG) reaction

International Nuclear Information System (INIS)

Seddigi, Z.S.

2004-01-01

We found interesting results regarding some thermodynamical parameters (Delta H, Delta G and Delta S of the MTG Reaction and FTIR Spectra of methanol and dimethylether, using the Hartree-Fock method and Density Functional Theory (DFT) calculations at different computational levels. It is the aim of this paper to highlight these results. The GAUSSIAN 98 program was used to carry out the LCAO-MO-SCF calculations at the following levels: RHF/3-21g, RHF/6-31g and DFT/B3LYP/d95**. Calculations at the restricted Hartree-Fock levels (FHR/3-22 g and RHF/6-31g) were performed since they are expensive as other levels (DFT/B3LYP/d95**. In case of the HF method, working with larger basis set (6-31g) has improved the values slightly, which is as expected. We have noticed that performing calculations at higher levels (DFT/B3LY/D95**) than the Hartree-Fock method does not dramatically improve the situation. Indeed RHF is a reasonable approximation for many single gas phase molecular calculations. HF calculations at relatively small basis sets are adequate. The theoretical vibrational spectra of both methanol and dimethylether were compared with experimental results. (author)

Studies of heavy-ion reactions and transuranic nuclei

International Nuclear Information System (INIS)

Schroeder, W.U.

1993-08-01

This report contain papers on the following topics: The Cold-Fusion Saga; Decay Patterns of Dysprosium Nuclei Produced in 32 S + 118,124 Sn Fusion Reactions; Unexpected Features of Reactions Between Very Heavy Ions at Intermediate Bombarding Energies; Correlations Between Neutrons and Charged Products from the Dissipative Reaction 197 Au+ 208 Pb at E/A = 29 MeV; Dissipative Dynamics of Projectile-Like Fragment Production in the Reaction 209 Bi+ 136 Xe at E/A = 28.2 MeV; Dynamical Production of Intermediate-Mass Fragments in Peripheral 209 Bi+ 136 Xe Collisions at E lab /A = 28.2 MeV; The Rochester 960-Liter Neutron Multiplicity Meter; A Simple Pulse Processing Concept for a Low-Cost Pulse-Shape-Based Particle Identification; A One-Transistor Preamplifier for PMT Anode Signals; A Five-Channel Multistop TDC/Event Handler for the SuperBall Neutron Multiplicity Meter; Construction of the SuperBall -- a 16,000-Liter Neutron Detector for Calorimetric Studies of Intermediate-Energy Heavy-Ion Reactions; A Computer Code for Light Detection Efficiency Calculations for Photo-multipliers of a Neutron Detector; Evaluation of Gd-Loaded Liquid Scintillators for the SuperBall Neutron Calorimeter; and Measurement of the Interaction of Cosmic-Ray μ - with a Muon Telescope

Calculations for the excitation functions of the 63Cup, n63Zn, 63Cup, 2n62Zn and 65Cup, n65Zn reactions

International Nuclear Information System (INIS)

Gul, K.

2001-01-01

Calculations for the excitation functions of 63 Cup, n 63 Zn, 63 Cup, 2n 62 Zn and 65 Cup, n 65 Zn reactions have been carried out in 3-30 MeV energy range using statistical and pre-equilibrium nuclear reaction models. The calculations have been compared with reported measurements and discussed

Fission dynamics of 240Cf* formed in 34,36S induced reactions

Directory of Open Access Journals (Sweden)

Jain Deepika

2015-01-01

Full Text Available We have studied the entrance channel effects in the decay of Compound nucleus 240Cf* formed in 34S+206Pb and 36S+204Pb reactions by using energy density dependent nuclear proximity potential in the framework of dynamical cluster-decay model (DCM. At different excitation energies, the fragmentation potential and preformation probability of decaying fragments are almost identical for both the entrance channels, which seem to suggest that decay is independent of its formation and entrance channel excitation energy. It is also observed that, with inclusion of deformation effects upto quadrupole within the optimum orientation approach, the fragmentation path governing potential energy surfaces gets modified significantly. Beside this, the fission mass distribution of Cf* isotopes is also investigated. The calculated fission cross-sections using SIII force for both the channels find nice agreement with the available experimental data for deformed choice of fragments, except at higher energies. In addition to this, the comparative analysis with Blocki based nuclear attraction is also worked out. It is observed that Blocki proximity potential accounts well for the CN decay at all energies whereas the use of EDF based nuclear potential suggests the presence of some non-compound nucleus process (such as quasi-fission (qf at higher energies.

Effect of vibrational excitation on the dynamics of ion-molecule reactions

International Nuclear Information System (INIS)

Anderson, S.L.

1981-11-01

A new experimental technique for the study of vibrational effects on ion-molecule reaction cross sections is described. Vibrational and collision energy dependent cross sections are presented for proton and H atom transfer, charge transfer and collision induced dissociation reactions in various isotopic H 2 + + H 2 systems. Charge and proton transfer cross sections are presented for the reactions of H 2 + and D 2 + with Ar, N 2 , CO, and O 2 . All the reactions are shown to be highly influenced by avoided crossings between the ground and first excited potential energy surfaces. Because of the nature of the crossings, vibrational motion of the systems can cause both adiabatic and non-adiabatic behavior of the system. This makes the vibrational dependences of the various cross sections a very sensitive probe of the dynamics of the collisions particularly, their behavior in the region of the crossings. Evidence is seen for charge transfer between reagents as they approach each other, transition to and in some cases reactions on excited potential energy surfaces, competition between different channels, and strong coupling of proton and charge transfer channels which occurs only for two of the systems studied (H 2 + + Ar, N 2 ). Oscillatory structure is observed in the collision energy dependence of the endoergic H 2 + (v = 0) + Ar charge transfer reaction for the first time, and a simple model which is commonly used for atom-atom charge transfer is used to fit the peaks. Finally a simple model is used to assess the importance of energy resonance and Franck-Condon effects on molecular charge transfer

Collective flow as a probe of heavy-ion reaction dynamics

International Nuclear Information System (INIS)

Awes, T.C.

1997-01-01

Collective flow of nuclear matter probes the dynamics of heavy-ion reactions and can provide information about the nuclear-matter equation of state. In particular, the incident energy dependences of collective flow may be a sensitive means to deduce the existence of a Quark Gluon Plasma phase in the equation of state. Collective flow measurements from 30 A MeV to 200 A GeV incident energies are briefly reviewed. Preliminary results on collective flow from the WA98 experiment at the CERN SPS are presented

Explore the reaction mechanism of the Maillard reaction: a density functional theory study.

Science.gov (United States)

Ren, Ge-Rui; Zhao, Li-Jiang; Sun, Qiang; Xie, Hu-Jun; Lei, Qun-Fang; Fang, Wen-Jun

2015-05-01

The mechanism of Maillard reaction has been investigated by means of density functional theory calculations in the gaseous phase and aqueous solution. The Maillard reaction is a cascade of consecutive and parallel reaction. In the present model system study, glucose and glycine were taken as the initial reactants. On the basis of previous experimental results, the mechanisms of Maillard reaction have been proposed, and the possibility for the formation of different compounds have been evaluated through calculating the relative energy changes for different steps of reaction under different pH conditions. Our calculations reveal that the TS3 in Amadori rearrangement reaction is the rate-determining step of Maillard reaction with the activation barriers of about 66.7 and 68.8 kcal mol(-1) in the gaseous phase and aqueous solution, respectively. The calculation results are in good agreement with previous studies and could provide insights into the reaction mechanism of Maillard reaction, since experimental evaluation of the role of intermediates in the Maillard reaction is quite complicated.

Global dynamics of a nonlocal delayed reaction-diffusion equation on a half plane

Science.gov (United States)

Hu, Wenjie; Duan, Yueliang

2018-04-01

We consider a delayed reaction-diffusion equation with spatial nonlocality on a half plane that describes population dynamics of a two-stage species living in a semi-infinite environment. A Neumann boundary condition is imposed accounting for an isolated domain. To describe the global dynamics, we first establish some a priori estimate for nontrivial solutions after investigating asymptotic properties of the nonlocal delayed effect and the diffusion operator, which enables us to show the permanence of the equation with respect to the compact open topology. We then employ standard dynamical system arguments to establish the global attractivity of the nontrivial equilibrium. The main results are illustrated by the diffusive Nicholson's blowfly equation and the diffusive Mackey-Glass equation.

Calculation of dynamic and electronic properties of perfect and defect crystals by semiempirical quantum mechanical methods

International Nuclear Information System (INIS)

Zunger, A.

1975-07-01

Semiempirical all-valence-electron LCAO methods, that were previously used to study the electronic structure of molecules are applied to three problems in solid state physics: the electronic band structure of covalent crystals, point defect problems in solids and lattice dynamical study of molecular crystals. Calculation methods for the electronic band structure of regular solids are introduced and problems regarding the computation of the density matrix in solids are discussed. Three models for treating the electronic eigenvalue problem in the solid, within the proposed calculation schemes, are discussed and the proposed models and calculation schemes are applied to the calculation of the electronic structure of several solids belonging to different crystal types. The calculation models also describe electronic properties of deep defects in covalent insulating crystals. The possible usefulness of the semieipirical LCAO methods in determining the first order intermolecular interaction potential in solids and an improved model for treating the lattice dynamics and related thermodynamical properties of molecular solids are presented. The improved lattice dynamical is used to compute phonon dispersion curves, phonon density of states, stable unit cell structure, lattice heat capacity and thermal crystal parameters, in α and γ-N 2 crystals, using the N 2 -N 2 intermolecular interaction potential that has been computed from the semiempirical LCAO methods. (B.G.)

Dosimetric comparison of interactive planned and dynamic dose calculated prostate seed brachytherapy.

Science.gov (United States)

Meijer, Gert J; van den Berg, Hetty A; Hurkmans, Coen W; Stijns, Pascal E; Weterings, Jan H

2006-09-01

To compare the dosimetrical results of an interactive planning procedure and a procedure based on dynamic dose calculation for permanent prostate brachytherapy. Between 6/2000 and 11/2005, 510 patients underwent (125)I implants for T1-T2 prostate cancer. Before 4/2003, 187 patients were treated using an interactive technique that included needle updating. After that period, 323 patients were treated with a more refined dynamic technique that included constant updating of the deposited seed position. The comparison is based on postimplant dose - volume parameters such as the V(100) and d(90) for the target, V(100)(r) for the rectum and d(10)(u) for the urethra. Furthermore, the target volume ratios (TVR identical with V(100)(body)/V(100)), and the homogeneity indices (HI identical with [V(100)-V(150)]/V(100)) were calculated as additional quality parameters. The dose outside the target volume was significantly reduced, the V(100)(r) decreased from 1.4 cm(3) for the interactive technique to 0.6 cm(3) for the dynamic technique. Similarly the mean TVR reduced from 1.66 to 1.44. In addition, the mean V(100) increased from 92% for the interactive procedure to 95% for the dynamic procedure. More importantly, the percentage of patients with a V(100) < 80% reduced from 5% to 1%. A slight decline was observed with regard to the d(10)(u) (136% vs. 140%) and the HI (0.58 vs. 0.51). The dynamic implant procedure resulted in improved implants. Almost ideal dose coverage was achieved, while minimizing the dose outside the prostate.

Isothermal reaction calorimetry as a tool for kinetic analysis

International Nuclear Information System (INIS)

Zogg, Andreas; Stoessel, Francis; Fischer, Ulrich; Hungerbuehler, Konrad

2004-01-01

Reaction calorimetry has found widespread application for thermal and kinetic analysis of chemical reactions in the context of thermal process safety as well as process development. This paper reviews the most important reaction calorimetric principles (heat-flow, heat-balance, power-compensation, and Peltier principle) and their applications in commercial or scientific devices. The discussion focuses on the different dynamic behavior of the main calorimetric principles during an isothermal reaction measurement. Examples of available reaction calorimeters are further compared considering their detection limit, time constant as well as temperature range. In a second part, different evaluation methods for the isothermally measured calorimetric data are reviewed and discussed. The methods will be compared, focusing especially on the fact that reaction calorimetric data always contains additional informations not directly related to the actual chemical reaction such as heat of mixing, heat of phase-transfer/change processes or simple measurement errors. Depending on the evaluation method applied such disturbances have a significant influence on the calculated reaction enthalpies or rate constants

Alkyl hydrogen atom abstraction reactions of the CN radical with ethanol

Science.gov (United States)

Athokpam, Bijyalaxmi; Ramesh, Sai G.

2018-04-01

We present a study of the abstraction of alkyl hydrogen atoms from the β and α positions of ethanol by the CN radical in solution using the Empirical Valence Bond (EVB) method. We have built separate 2 × 2 EVB models for the Hβ and Hα reactions, where the atom transfer is parameterized using ab initio calculations. The intra- and intermolecular potentials of the reactant and product molecules were modelled with the General AMBER Force Field, with some modifications. We have carried out the dynamics in water and chloroform, which are solvents of contrasting polarity. We have computed the potential of mean force for both abstractions in each of the solvents. They are found to have a small and early barrier along the reaction coordinate with a large energy release. Analyzing the solvent structure around the reaction system, we have found two solvents to have little effect on either reaction. Simulating the dynamics from the transition state, we also study the fate of the energies in the HCN vibrational modes. The HCN molecule is born vibrationally hot in the CH stretch in both reactions and additionally in the HCN bends for the Hα abstraction reaction. In the early stage of the dynamics, we find that the CN stretch mode gains energy at the expense of the energy in CH stretch mode.

Exact quantum dynamics study of the O++H2(v=0,j=0)→OH++H ion-molecule reaction and comparison with quasiclassical trajectory calculations

International Nuclear Information System (INIS)

Martinez, Rodrigo; Lucas, Josep M.; Gimenez, Xavier; Aguilar, Antonio; Gonzalez, Miguel

2006-01-01

The close-coupling hyperspherical (CCH) exact quantum method was used to study the title barrierless reaction up to a collision energy (E T ) of 0.75 eV, and the results compared with quasiclassical trajectory (QCT) calculations to determine the importance of quantum effects. The CCH integral cross section decreased with E T and, although the QCT results were in general quite similar to the CCH ones, they presented a significant deviation from the CCH data within the 0.2-0.6 eV collision energy range, where the QCT method did not correctly describe the reaction probability. A very good accord between both methods was obtained for the OH + vibrational distribution, where no inversion of population was found. For the OH + rotational distributions, the agreement between the CCH and QCT results was not as good as in the vibrational case, but it was satisfactory in many conditions. The kk ' angular distribution showed a preferential forward character, and the CCH method produced higher forward peaks than the QCT one. All the results were interpreted considering the potential energy surface and plots of a representative sampling of reactive trajectories

Self-propagating exothermic reaction analysis in Ti/Al reactive films using experiments and computational fluid dynamics simulation

Energy Technology Data Exchange (ETDEWEB)

Sen, Seema, E-mail: seema.sen@tu-ilmenau.de [Technical University of Ilmenau, Department of Materials for Electronics, Gustav-Kirchhoff-Str. 5, 98693 Ilmenau (Germany); Niederrhein University of Applied Science, Department of Mechanical and Process Engineering, Reinarzstraße 49, 47805 Krefeld (Germany); Lake, Markus; Kroppen, Norman; Farber, Peter; Wilden, Johannes [Niederrhein University of Applied Science, Department of Mechanical and Process Engineering, Reinarzstraße 49, 47805 Krefeld (Germany); Schaaf, Peter [Technical University of Ilmenau, Department of Materials for Electronics, Gustav-Kirchhoff-Str. 5, 98693 Ilmenau (Germany)

2017-02-28

Highlights: • Development of nanoscale Ti/Al multilayer films with 1:1, 1:2 and 1:3 molar ratios. • Characterization of exothermic reaction propagation by experiments and simulation. • The reaction velocity depends on the ignition potentials and molar ratios of the films. • Only 1Ti/3Al films exhibit the unsteady reaction propagation with ripple formation. • CFD simulation shows the time dependent atom mixing and temperature flow during exothermic reaction. - Abstract: This study describes the self-propagating exothermic reaction in Ti/Al reactive multilayer foils by using experiments and computational fluid dynamics simulation. The Ti/Al foils with different molar ratios of 1Ti/1Al, 1Ti/2Al and 1Ti/3Al were fabricated by magnetron sputtering method. Microstructural characteristics of the unreacted and reacted foils were analyzed by using electronic and atomic force microscopes. After an electrical ignition, the influence of ignition potentials on reaction propagation has been experimentally investigated. The reaction front propagates with a velocity of minimum 0.68 ± 0.4 m/s and maximum 2.57 ± 0.6 m/s depending on the input ignition potentials and the chemical compositions. Here, the 1Ti/3Al reactive foil exhibits both steady state and unsteady wavelike reaction propagation. Moreover, the numerical computational fluid dynamics (CFD) simulation shows the time dependent temperature flow and atomic mixing in a nanoscale reaction zone. The CFD simulation also indicates the potentiality for simulating exothermic reaction in the nanoscale Ti/Al foil.

Dynamics of the F(-) + CH3I → HF + CH2I(-) Proton Transfer Reaction.

Science.gov (United States)

Zhang, Jiaxu; Xie, Jing; Hase, William L

2015-12-17

Direct chemical dynamics simulations, at collision energies Erel of 0.32 and 1.53 eV, were performed to obtain an atomistic understanding of the F(-) + CH3I reaction dynamics. There is only the F(-) + CH3I → CH3F + I(-) bimolecular nucleophilic substitution SN2 product channel at 0.32 eV. Increasing Erel to 1.53 eV opens the endothermic F(-) + CH3I → HF + CH2I(-) proton transfer reaction, which is less competitive than the SN2 reaction. The simulations reveal proton transfer occurs by two direct atomic-level mechanisms, rebound and stripping, and indirect mechanisms, involving formation of the F(-)···HCH2I complex and the roundabout. For the indirect trajectories all of the CH2I(-) is formed with zero-point energy (ZPE), while for the direct trajectories 50% form CH2I(-) without ZPE. Without a ZPE constraint for CH2I(-), the reaction cross sections for the rebound, stripping, and indirect mechanisms are 0.2 ± 0.1, 1.2 ± 0.4, and 0.7 ± 0.2 Å(2), respectively. Discarding trajectories that do not form CH2I(-) with ZPE reduces the rebound and stripping cross sections to 0.1 ± 0.1 and 0.7 ± 0.5 Å(2). The HF product is formed rotationally and vibrationally unexcited. The average value of J is 2.6 and with histogram binning n = 0. CH2I(-) is formed rotationally excited. The partitioning between CH2I(-) vibration and HF + CH2I(-) relative translation energy depends on the treatment of CH2I(-) ZPE. Without a CH2I(-) ZPE constraint the energy partitioning is primarily to relative translation with little CH2I(-) vibration. With a ZPE constraint, energy partitioning to CH2I(-) rotation, CH2I(-) vibration, and relative translation are statistically the same. The overall F(-) + CH3I rate constant at Erel of both 0.32 and 1.53 eV is in good agreement with experiment and negligibly affected by the treatment of CH2I(-) ZPE, since the SN2 reaction is the major contributor to the total reaction rate constant. The potential energy surface and reaction dynamics for F

Improving the accuracy of dynamic mass calculation

Directory of Open Access Journals (Sweden)

Oleksandr F. Dashchenko

2015-06-01

Full Text Available With the acceleration of goods transporting, cargo accounting plays an important role in today's global and complex environment. Weight is the most reliable indicator of the materials control. Unlike many other variables that can be measured indirectly, the weight can be measured directly and accurately. Using strain-gauge transducers, weight value can be obtained within a few milliseconds; such values correspond to the momentary load, which acts on the sensor. Determination of the weight of moving transport is only possible by appropriate processing of the sensor signal. The aim of the research is to develop a methodology for weighing freight rolling stock, which increases the accuracy of the measurement of dynamic mass, in particular wagon that moves. Apart from time-series methods, preliminary filtration for improving the accuracy of calculation is used. The results of the simulation are presented.

Calcium hydroxide silylation reaction with trimethylchlorosilane

Directory of Open Access Journals (Sweden)

Novoselnov Anatoliy A.

2016-01-01

Full Text Available The silylation reaction of a calcium hydroxide with a trimethylchlorosilane is studied as a silylation model by the gas-liquid chromatography. The silylation process is divided into three stages. A material balance of these stages is calculated. The schemes of the reactions at each stage of the process are proposed. The modified calcium hydroxide obtained at three repetitive stages of the silylation reaction has been investigated by the x-ray phase analysis, IR spectroscopy, thermal analysis, electron microscopy in a combination with the elemental analysis. It has been determined that at the first stage of the interaction the processes of the trimethylchlorosilane hydrolysis and of the hydrolysis products condensation dominate, and at the same time an adsorption process of the trimethylchlorosilane and its derivatives starts. Further, the hydrolysis of the trimethylchlorosilane by the «new» portions of a water formed in the reaction of a calcium hydroxide with a hydrogen chloride takes place, simultaneously the secondary reactions of the Si-O-Ca – ties’ formation and cleavage occur including as a silylation-desilylation dynamic equilibrium process.

Predictors of chronic ankle instability: Analysis of peroneal reaction time, dynamic balance and isokinetic strength.

Science.gov (United States)

Sierra-Guzmán, Rafael; Jiménez, Fernando; Abián-Vicén, Javier

2018-05-01

Previous studies have reported the factors contributing to chronic ankle instability, which could lead to more effective treatments. However, factors such as the reflex response and ankle muscle strength have not been taken into account in previous investigations. Fifty recreational athletes with chronic ankle instability and 55 healthy controls were recruited. Peroneal reaction time in response to sudden inversion, isokinetic evertor muscle strength and dynamic balance with the Star Excursion Balance Test and the Biodex Stability System were measured. The relationship between the Cumberland Ankle Instability Tool score and performance on each test was assessed and a backward multiple linear regression analysis was conducted. Participants with chronic ankle instability showed prolonged peroneal reaction time, poor performance in the Biodex Stability System and decreased reach distance in the Star Excursion Balance Test. No significant differences were found in eversion and inversion peak torque. Moderate correlations were found between the Cumberland Ankle Instability Tool score and the peroneal reaction time and performance on the Star Excursion Balance Test. Peroneus brevis reaction time and the posteromedial and lateral directions of the Star Excursion Balance Test accounted for 36% of the variance in the Cumberland Ankle Instability Tool. Dynamic balance deficits and delayed peroneal reaction time are present in participants with chronic ankle instability. Peroneus brevis reaction time and the posteromedial and lateral directions of the Star Excursion Balance Test were the main contributing factors to the Cumberland Ankle Instability Tool score. No clear strength impairments were reported in unstable ankles. Copyright © 2018 Elsevier Ltd. All rights reserved.

Energetic change of the primary quinone in photosynthetic reaction center. Mutation, delayed fluorescence and model calculations (Theses of the Ph.D. dissertation)

International Nuclear Information System (INIS)

Rinyu, L.

2007-01-01

intensities of prompt and delayed fluorescence emitted by the primary donor of the reaction center. By use of the values of the free energy gaps, I calculated the in situ midpoint redox potential of the Q A /Q A - redox couple in the mutants and the wild type and compared these values with each other. Based on the available data of reaction center structures I gave a possible explanation to the substantial change in E m of Q A in case of mutants. The available X-ray structures of reaction center make possible to calculate the thermo- dynamic properties of the mutants with computer simulations. Using docking simulations in wild type and mutant reaction centers, I calculated the binding free energies of the quinone and semiquinone molecules to the Q A packet and estimated the midpoint redox potential of the Q A /Q A - redox couple. Additionally, by use of the free energy perturbation method, I modeled the reductions process of the primary quinone molecule in wild-type and mutant re- action centers. With the application of cardiolipin (diphosphatide-glycerol) as a model-lipid, I investigated the interaction between the reaction center protein and the lipid environment. I described how it affects to the charge-recombination process and how it influences the free energy level of the charge couple (P + Q A - ) relative to the free energy level of the excited primary donor. With the investigation of the delayed fluorescence emission of the reaction center embedded into membrane fragment (chromatophore) I gave further information about the effects of reaction center proteins and lipid membranes on the energetic properties of Q A . In addition to these studies, I characterized the complex kinetics of the decay of delayed fluorescence emitted by chromatophore and also gave a description of the new fastest kinetic component

Optically Controlled Electron-Transfer Reaction Kinetics and Solvation Dynamics : Effect of Franck-Condon States

NARCIS (Netherlands)

Gupta, Kriti; Patra, Aniket; Dhole, Kajal; Samanta, Alok Kumar; Ghosh, Swapan K.

2017-01-01

Experimental results for optically controlled electron-transfer reaction kinetics (ETRK) and nonequilibrium solvation dynamics (NESD) of Coumarin 480 in DMPC vesicle show their dependence on excitation wavelength λex. However, the celebrated Marcus theory and linear-response-theory-based approaches

Proceedings of the Workshop on open problems in heavy ion reaction dynamics at VIVITRON energies

International Nuclear Information System (INIS)

Beck, F.A.

1993-01-01

Some problems of heavy ion reaction dynamics at the VIVITRON tandem accelerator and the experimental facilities are discussed at the meeting. Topics include light dinuclear systems, collision dynamics at low energies, fission evaporation and fusion of heavy nuclei and others. Most documents consist of transparencies presented at the workshop, texts of papers are missing. All items are indexed and abstracted for the INIS database. (K.A.)

Proceedings of the Workshop on open problems in heavy ion reaction dynamics at VIVITRON energies

Energy Technology Data Exchange (ETDEWEB)

Beck, F. A.

1993-07-01

Some problems of heavy ion reaction dynamics at the VIVITRON tandem accelerator and the experimental facilities are discussed at the meeting. Topics include light dinuclear systems, collision dynamics at low energies, fission evaporation and fusion of heavy nuclei and others. Most documents consist of transparencies presented at the workshop, texts of papers are missing. All items are indexed and abstracted for the INIS database. (K.A.).

Convection and reaction in a diffusive boundary layer in a porous medium: nonlinear dynamics.

Science.gov (United States)

Andres, Jeanne Therese H; Cardoso, Silvana S S

2012-09-01

We study numerically the nonlinear interactions between chemical reaction and convective fingering in a diffusive boundary layer in a porous medium. The reaction enhances stability by consuming a solute that is unstably distributed in a gravitational field. We show that chemical reaction profoundly changes the dynamics of the system, by introducing a steady state, shortening the evolution time, and altering the spatial patterns of velocity and concentration of solute. In the presence of weak reaction, finger growth and merger occur effectively, driving strong convective currents in a thick layer of solute. However, as the reaction becomes stronger, finger growth is inhibited, tip-splitting is enhanced and the layer of solute becomes much thinner. Convection enhances the mass flux of solute consumed by reaction in the boundary layer but has a diminishing effect as reaction strength increases. This nonlinear behavior has striking differences to the density fingering of traveling reaction fronts, for which stronger chemical kinetics result in more effective finger merger owing to an increase in the speed of the front. In a boundary layer, a strong stabilizing effect of reaction can maintain a long-term state of convection in isolated fingers of wavelength comparable to that at onset of instability.

Molecular-dynamics analysis of mobile helium cluster reactions near surfaces of plasma-exposed tungsten

Energy Technology Data Exchange (ETDEWEB)

Hu, Lin; Maroudas, Dimitrios, E-mail: maroudas@ecs.umass.edu [Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003-9303 (United States); Hammond, Karl D. [Department of Chemical Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Wirth, Brian D. [Department of Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)

2015-10-28

We report the results of a systematic atomic-scale analysis of the reactions of small mobile helium clusters (He{sub n}, 4 ≤ n ≤ 7) near low-Miller-index tungsten (W) surfaces, aiming at a fundamental understanding of the near-surface dynamics of helium-carrying species in plasma-exposed tungsten. These small mobile helium clusters are attracted to the surface and migrate to the surface by Fickian diffusion and drift due to the thermodynamic driving force for surface segregation. As the clusters migrate toward the surface, trap mutation (TM) and cluster dissociation reactions are activated at rates higher than in the bulk. TM produces W adatoms and immobile complexes of helium clusters surrounding W vacancies located within the lattice planes at a short distance from the surface. These reactions are identified and characterized in detail based on the analysis of a large number of molecular-dynamics trajectories for each such mobile cluster near W(100), W(110), and W(111) surfaces. TM is found to be the dominant cluster reaction for all cluster and surface combinations, except for the He{sub 4} and He{sub 5} clusters near W(100) where cluster partial dissociation following TM dominates. We find that there exists a critical cluster size, n = 4 near W(100) and W(111) and n = 5 near W(110), beyond which the formation of multiple W adatoms and vacancies in the TM reactions is observed. The identified cluster reactions are responsible for important structural, morphological, and compositional features in the plasma-exposed tungsten, including surface adatom populations, near-surface immobile helium-vacancy complexes, and retained helium content, which are expected to influence the amount of hydrogen re-cycling and tritium retention in fusion tokamaks.

Calculation of molecular free energies in classical potentials

International Nuclear Information System (INIS)

Farhi, Asaf; Singh, Bipin

2016-01-01

Free energies of molecules can be calculated by quantum chemistry computations or by normal mode classical calculations. However, the first can be computationally impractical for large molecules and the second is based on the assumption of harmonic dynamics. We present a novel, accurate and complete calculation of molecular free energies in standard classical potentials. In this method we transform the molecule by relaxing potential terms which depend on the coordinates of a group of atoms in that molecule and calculate the free energy difference associated with the transformation. Then, since the transformed molecule can be treated as non-interacting systems, the free energy associated with these atoms is analytically or numerically calculated. This two-step calculation can be applied to calculate free energies of molecules or free energy difference between (possibly large) molecules in a general environment. We demonstrate the method in free energy calculations for methanethiol and butane molecules in vacuum and solvent. We suggest the potential application of free energy calculation of chemical reactions in classical molecular simulations. (paper)

Parametric spatiotemporal oscillation in reaction-diffusion systems.

Science.gov (United States)

Ghosh, Shyamolina; Ray, Deb Shankar

2016-03-01

We consider a reaction-diffusion system in a homogeneous stable steady state. On perturbation by a time-dependent sinusoidal forcing of a suitable scaling parameter the system exhibits parametric spatiotemporal instability beyond a critical threshold frequency. We have formulated a general scheme to calculate the threshold condition for oscillation and the range of unstable spatial modes lying within a V-shaped region reminiscent of Arnold's tongue. Full numerical simulations show that depending on the specificity of nonlinearity of the models, the instability may result in time-periodic stationary patterns in the form of standing clusters or spatially localized breathing patterns with characteristic wavelengths. Our theoretical analysis of the parametric oscillation in reaction-diffusion system is corroborated by full numerical simulation of two well-known chemical dynamical models: chlorite-iodine-malonic acid and Briggs-Rauscher reactions.

Dynamic calculation of structures in seismic zones. 2. ed.

International Nuclear Information System (INIS)

Capra, Alain; Davidovici, Victor

1982-01-01

The aims of this book are both didactic and practical. It is therefore addressed to both experienced engineers and students. Some general information about earthquakes and their occurrence is first given. The problem of a simple oscillator is presented. In this way, the reader is provided with an insight into undestanding the dynamic phenomena taking place and is introduced to the concept of response spectra and to an intuitive comprehension of the behavior of structures during earthquakes. The next chapter is devoted to the cases most frequently encountered with multiple oscillator structures. Theoretical studies are based on the usual modal decomposition method. The various practical methods of calculation employed are then examined, emphasis being given to the various different stages involved and to which of them is the best suited for a particular type of structure. Advise is given on how to select the model whose behavior best describes the real structure, both manual and computer methods of calculation being envisaged [fr

Summary of calculations of dynamic response characteristics and design stress of the 1/5 scale PSE torus

International Nuclear Information System (INIS)

Arthur, D.

1977-01-01

The Lawrence Livermore Laboratory is currently involved in a 1/5 scale testing program on the Mark I BWR pressure suppression system. A key element of the test setup is a pressure vessel that is a 90 0 sector of a torus. Proper performance of the 90 0 torus depends on its structural integrity and structural dynamic characteristics. It must sustain the internal pressurization of the planned tests, and its dynamic response to the transient test loads should be minimal. If the structural vibrations are too great, interpretation of important load cell and pressure transducer data will be difficult. The purpose of the report is to bring together under one cover calculations pertaining to the structural dynamic characteristics and structural integrity of 90 0 torus. The report is divided into the following sections: (1) system description in which the torus and associated hardware are briefly described; (2) structural dynamics in which calculations of natural frequency and dynamic response are presented; and (3) structural integrity in which stress calculations for design purposes are presented; and an appendix which contains an LLL internal report comparing the expected load cell response for a three and four-point supported torus

Calculation of the energy of explosives with a partial reaction model. Comparison with cylinder test data

Energy Technology Data Exchange (ETDEWEB)

Sanchidrian, Jose A.; Lopez, Lina M. [Universidad Politecnica de Madrid - E.T.S.I. Minas, Rios Rosas 21, E-28003 Madrid (Spain)

2006-02-15

The energy delivered by explosives is described by means of the useful expansion work along the isentrope of the detonation products. A thermodynamic code (W-DETCOM) is used, in which a partial reaction model has been implemented. In this model, the reacted fraction of the explosive in the detonation state is used as a fitting factor so that the calculated detonation velocity meets the experimental value. Calculations based on such a model have been carried out for a number of commercial explosives of ANFO and emulsion types. The BKW (Becker-Kistiakowsky-Wilson) equation of state is used for the detonation gases with the Sandia parameter set (BKWS). The energy delivered in the expansion (useful work) is calculated, and the values obtained are compared with the Gurney energies from cylinder test data at various expansion ratios. The expansion work values obtained are much more realistic than those from an ideal detonation calculation and, in most cases, the values predicted by the calculation are in good agreement with the experimental ones. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Methods of neutron spectrum calculation from measured reaction rates in SAIPS. Part 2: Software and data input

International Nuclear Information System (INIS)

Berzonis, M.A.; Bondars, H.Ya.

1981-08-01

A brief description of the SAIPS software and the basic principles of its application is given. SAIPS contains programs needed to unfold spectra, libraries of neutron cross sections and reference spectra, and software for automatic calculation and for system maintenance. SAIPS offers the possibility of determining the reliability of an unfolded neutron spectrum and of planning measurements and calculations by varying different factors: the errors in the reaction rates, the errors in the cross sections used, the detector assembly, the unfolding programs, etc. SAIPS runs on the ES 1022 computer

Incident angle dependence of reactions between graphene and hydrogen atom by molecular dynamics simulation

International Nuclear Information System (INIS)

Saito, Seiki; Nakamura, Hiroaki; Ito, Atsushi

2010-01-01

Incident angle dependence of reactions between graphene and hydrogen atoms are obtained qualitatively by classical molecular dynamics simulation under the NVE condition with modified Brenner reactive empirical bond order (REBO) potential. Chemical reaction depends on two parameters, i.e., polar angle θ and azimuthal angle φ of the incident hydrogen. From the simulation results, it is found that the reaction rates strongly depend on polar angle θ. Reflection rate becomes larger with increasing θ, and the θ dependence of adsorption rate is also found. The θ dependence is caused by three dimensional structure of the small potential barrier which covers adsorption sites. φ dependence of penetration rate is also found for large θ. (author)

Utilizing the dynamic stark shift as a probe for dielectric relaxation in photosynthetic reaction centers during charge separation.

Science.gov (United States)

Guo, Zhi; Lin, Su; Woodbury, Neal W

2013-09-26

In photosynthetic reaction centers, the electric field generated by light-induced charge separation produces electrochromic shifts in the transitions of reaction center pigments. The extent of this Stark shift indirectly reflects the effective field strength at a particular cofactor in the complex. The dynamics of the effective field strength near the two monomeric bacteriochlorophylls (BA and BB) in purple photosynthetic bacterial reaction centers has been explored near physiological temperature by monitoring the time-dependent Stark shift during charge separation (dynamic Stark shift). This dynamic Stark shift was determined through analysis of femtosecond time-resolved absorbance change spectra recorded in wild type reaction centers and in four mutants at position M210. In both wild type and the mutants, the kinetics of the dynamic Stark shift differ from those of electron transfer, though not in the same way. In wild type, the initial electron transfer and the increase in the effective field strength near the active-side monomer bacteriochlorophyll (BA) occur in synchrony, but the two signals diverge on the time scale of electron transfer to the quinone. In contrast, when tyrosine is replaced by aspartic acid at M210, the kinetics of the BA Stark shift and the initial electron transfer differ, but transfer to the quinone coincides with the decay of the Stark shift. This is interpreted in terms of differences in the dynamics of the local dielectric environment between the mutants and the wild type. In wild type, comparison of the Stark shifts associated with BA and BB on the two quasi-symmetric halves of the reaction center structure confirm that the effective dielectric constants near these cofactors are quite different when the reaction center is in the state P(+)QA(-), as previously determined by Steffen et al. at 1.5 K (Steffen, M. A.; et al. Science 1994, 264, 810-816). However, it is not possible to determine from static, low-temperature measurments if the

National array of neutron detectors (NAND) a versatile setup for studies on reaction dynamics

International Nuclear Information System (INIS)

Golda, K.S.; Singh, R.P.; Zacharias, J.; Archunan, M.; Kothari, A.; Barua, P.; Gupta, Arti; Venkataramanan, S.; Suman, S.K.; Kumar, Rajesh; Kumar, Pankaj; Jhingan, A.; Sugathan, P.; Datta, S.K.; Chatterjee, Mihir; Bhowmik, R.K.; Singh, Hardev; Behera, B.; Kumar, A.; Singh, G.; Ranjit; Mandal, S.

2006-01-01

National Array of Neutron Detectors (NAND) is a large array of neutron detectors being setup at Inter University Accelerator Centre. The primary motive behind the development of this array, is the study of reaction dynamics in the energy domain near the Coulomb barrier

Reaction and Aggregation Dynamics of Cell Surface Receptors

Science.gov (United States)

Wang, Michelle Dong

This dissertation is composed of both theoretical and experimental studies of cell surface receptor reaction and aggregation. Project I studies the reaction rate enhancement due to surface diffusion of a bulk dissolved ligand with its membrane embedded target, using numerical calculations. The results show that the reaction rate enhancement is determined by ligand surface adsorption and desorption kinetic rates, surface and bulk diffusion coefficients, and geometry. In particular, we demonstrate that the ligand surface adsorption and desorption kinetic rates, rather than their ratio (the equilibrium constant), are important in rate enhancement. The second and third projects are studies of acetylcholine receptor clusters on cultured rat myotubes using fluorescence techniques after labeling the receptors with tetramethylrhodamine -alpha-bungarotoxin. The second project studies when and where the clusters form by making time-lapse movies. The movies are made from overlay of the pseudocolored total internal reflection fluorescence (TIRF) images of the cluster, and the schlieren images of the cell cultures. These movies are the first movies made using TIRF, and they clearly show the cluster formation from the myoblast fusion, the first appearance of clusters, and the eventual disappearance of clusters. The third project studies the fine structural features of individual clusters observed under TIRF. The features were characterized with six parameters by developing a novel fluorescence technique: spatial fluorescence autocorrelation. These parameters were then used to study the feature variations with age, and with treatments of drugs (oligomycin and carbachol). The results show little variation with age. However, drug treatment induced significant changes in some parameters. These changes were different for oligomycin and carbachol, which indicates that the two drugs may eliminate clusters through different mechanisms.

ACT-XN: Revised version of an activation calculation code for fusion reactor analysis. Supplement of the function for the sequential reaction activation by charged particles

International Nuclear Information System (INIS)

Yamauchi, Michinori; Sato, Satoshi; Nishitani, Takeo; Konno, Chikara; Hori, Jun-ichi; Kawasaki, Hiromitsu

2007-09-01

The ACT-XN is a revised version of the ACT4 code, which was developed in the Japan Atomic Energy Research Institute (JAERI) to calculate the transmutation, induced activity, decay heat, delayed gamma-ray source etc. for fusion devices. The ACT4 code cannot deal with the sequential reactions of charged particles generated by primary neutron reactions. In the design of present experimental reactors, the activation due to sequential reactions may not be of great concern as it is usually buried under the activity by primary neutron reactions. However, low activation material is one of the important factors for constructing high power fusion reactors in future, and unexpected activation may be produced through sequential reactions. Therefore, in the present work, the ACT4 code was newly supplemented with the calculation functions for the sequential reactions and renamed the ACT-XN. The ACT-XN code is equipped with functions to calculate effective cross sections for sequential reactions and input them in transmutation matrix. The FISPACT data were adopted for (x,n) reaction cross sections, charged particles emission spectra and stopping powers. The nuclear reaction chain data library were revised to cope with the (x,n) reactions. The charged particles are specified as p, d, t, 3 He(h) and α. The code was applied to the analysis of FNS experiment for LiF and Demo-reactor design with FLiBe, and confirmed that it reproduce the experimental values within 15-30% discrepancies. In addition, a notice was presented that the dose rate due to sequential reaction cannot always be neglected after a certain period cooling for some of the low activation material. (author)

Electron transfer dynamics: Zusman equation versus exact theory

International Nuclear Information System (INIS)

Shi Qiang; Chen Liping; Nan Guangjun; Xu Ruixue; Yan Yijing

2009-01-01

The Zusman equation has been widely used to study the effect of solvent dynamics on electron transfer reactions. However, application of this equation is limited by the classical treatment of the nuclear degrees of freedom. In this paper, we revisit the Zusman equation in the framework of the exact hierarchical equations of motion formalism, and show that a high temperature approximation of the hierarchical theory is equivalent to the Zusman equation in describing electron transfer dynamics. Thus the exact hierarchical formalism naturally extends the Zusman equation to include quantum nuclear dynamics at low temperatures. This new finding has also inspired us to rescale the original hierarchical equations and incorporate a filtering algorithm to efficiently propagate the hierarchical equations. Numerical exact results are also presented for the electron transfer reaction dynamics and rate constant calculations.

Multiscale Reaction-Diffusion Algorithms: PDE-Assisted Brownian Dynamics

KAUST Repository

Franz, Benjamin

2013-06-19

Two algorithms that combine Brownian dynami cs (BD) simulations with mean-field partial differential equations (PDEs) are presented. This PDE-assisted Brownian dynamics (PBD) methodology provides exact particle tracking data in parts of the domain, whilst making use of a mean-field reaction-diffusion PDE description elsewhere. The first PBD algorithm couples BD simulations with PDEs by randomly creating new particles close to the interface, which partitions the domain, and by reincorporating particles into the continuum PDE-description when they cross the interface. The second PBD algorithm introduces an overlap region, where both descriptions exist in parallel. It is shown that the overlap region is required to accurately compute variances using PBD simulations. Advantages of both PBD approaches are discussed and illustrative numerical examples are presented. © 2013 Society for Industrial and Applied Mathematics.

Dynamical calculation of nuclear temperature

International Nuclear Information System (INIS)

Zheng Yuming

1998-01-01

A new dynamical approach for measuring the temperature of a Hamiltonian dynamical system in the microcanonical ensemble of thermodynamics is presented. It shows that under the hypothesis of ergodicity the temperature can be computed as a time average of a function on the energy surface. This method not only yields an efficient computational approach for determining the temperature, but also provides an intrinsic link between dynamical system theory and the statistical mechanics of Hamiltonian system

Vibrational Mode-Specific Reaction of Methane with a Nickel Surface

Science.gov (United States)

Beck, Rainer

2004-03-01

The dissociation of methane on a nickel catalyst is a key step in steam reforming of natural gas for hydrogen production. Despite substantial effort in both experiment and theory, there is still no atomic scale description of this important gas-surface reaction. To elucidate its dynamics, we have performed quantum state resolved studies of vibrationally excited methane reacting on the Ni(100) surface using pulsed laser and molecular beam techniques. We observed up to a factor of 5 greater reaction probability for methane-d2 with two quanta of excitation in one C-H bond versus a nearly isoenergetic state with one quanta in each of two C-H bonds. The observed reactivities point to a transition state structure which has one of the C-H bonds significantly elongated. Our results also clearly exclude the possibility of statistical models correctly describing the mechanism of this process and emphasize the importance of full-dimensional calculations of the reaction dynamics.

Quantum chemistry and dynamics of the abstraction reaction of H atoms from formaldehyde

Energy Technology Data Exchange (ETDEWEB)

Siaï, A. [Faculté des Sciences de Tunis, Département de Physique, (LPMC), Université de Tunis El Manar, 2092 Tunis (Tunisia); Oueslati, I. [Faculté des Sciences de Tunis, Département de Physique, (LPMC), Université de Tunis El Manar, 2092 Tunis (Tunisia); Observatoire de Paris-Meudon, Sorbonne Universités, UPMC Univ Paris 06, UMR8112 du CNRS, LERMA, 5 Place Jules Janssen, 92195 Meudon cedex (France); Académie Militaire, Fondouk Jedid, 8012 Nabeul (Tunisia); Kerkeni, Boutheïna, E-mail: Boutheina.kerkeni@obspm.fr [Faculté des Sciences de Tunis, Département de Physique, (LPMC), Université de Tunis El Manar, 2092 Tunis (Tunisia); Observatoire de Paris-Meudon, Sorbonne Universités, UPMC Univ Paris 06, UMR8112 du CNRS, LERMA, 5 Place Jules Janssen, 92195 Meudon cedex (France); Institut Supérieur des Arts Multimédia de la Manouba, Université de la Manouba, 2010 la Manouba (Tunisia)

2016-08-02

This work reports a reduced dimensionality rate constant calculation of the H-abstraction reaction from formaldehyde. Quantum scattering calculations are performed treating explicitly the bonds being broken and formed. Geometry optimisations and frequency calculations are done at the MP2/cc-pVTZ level while energies are calculated with the CCSD(T) method. An analytical potential energy surface was developed from a relatively small number of grid points. When compared to semi-classical approaches, the quantum scattering calculations show that quantum tunnelling yields large contributions at low temperatures. At 200 K, we note a difference of about 5 orders of magnitude between transition state theory (TST) and quantum rate constants. Our predicted results show that the quantum and the CVT/SCT rate constants are in reasonable agreement with the available experiment at high temperatures, but that the last one gives better agreement to experimental results at low temperatures.

Directly calculated electrical conductivity of hot dense hydrogen from molecular dynamics simulation beyond Kubo-Greenwood formula

Science.gov (United States)

Ma, Qian; Kang, Dongdong; Zhao, Zengxiu; Dai, Jiayu

2018-01-01

Electrical conductivity of hot dense hydrogen is directly calculated by molecular dynamics simulation with a reduced electron force field method, in which the electrons are represented as Gaussian wave packets with fixed sizes. Here, the temperature is higher than electron Fermi temperature ( T > 300 eV , ρ = 40 g / cc ). The present method can avoid the Coulomb catastrophe and give the limit of electrical conductivity based on the Coulomb interaction. We investigate the effect of ion-electron coupled movements, which is lost in the static method such as density functional theory based Kubo-Greenwood framework. It is found that the ionic dynamics, which contributes to the dynamical electrical microfield and electron-ion collisions, will reduce the conductivity significantly compared with the fixed ion configuration calculations.

Structural, elastic, electronic and dynamical properties of OsB and ReB: Density functional calculations

Science.gov (United States)

Li, Yanling; Zeng, Zhi; Lin, Haiqing

2010-06-01

The structural, elastic, electronic and dynamical properties of ReB and OsB are investigated by first-principles calculations based on density functional theory. It turns out that ReB and OsB are metallic ultra-incompressible solids with small elastic anisotropy and high hardness. The change of c/ a ratio in OsB indicates that there is a structural phase transition at about 31 GPa. Phonon spectra calculations show that both OsB and ReB are stable dynamically and there are abnormal phonon dispersions along special directions in Brillouin zone. OsB and ReB do not show superconductivity due to very weak electron-phonon interactions in them.

Thermal neutron dose calculations in a brain phantom from 7Li(p,n) reaction based BNCT setup

International Nuclear Information System (INIS)

Elshahat, B.A.; Naqvi, A.A.; Maalej, N.; Abdallah, Khalid

2006-01-01

Monte Carlo simulations were carried out to calculate neutron dose in a brain phantom from a 7 Li(p,n) reaction based setup utilizing a high density polyethylene moderator with graphite reflector. The dimensions of the moderator and the reflector were optimized through optimization of epithermal /(fast +thermal) neutron intensity ratio as a function of geometric parameters of the setup. Results of our calculation showed the capability of our setup to treat the tumor within 4 cm of the head surface. The calculated Peak Therapeutic Ratio for the setup was found to be 2.15. With further improvement in the moderator design and brain phantom irradiation arrangement, the setup capabilities can be improved to reach further deep-seated tumor. (author)

Handling of impact forces in inverse dynamics

NARCIS (Netherlands)

Bisseling, Rob W.; Hof, At L.

2006-01-01

In the standard inverse dynamic method, joint moments are assessed from ground reaction force data and position data, where segmental accelerations are calculated by numerical differentiation of position data after low-pass filtering. This method falls short in analyzing the impact phase, e.g.

Temperature Dependence of the OH- + CH3I Reaction Kinetics. Experimental and Simulation Studies and Atomic-Level Dynamics (Postprint)

Science.gov (United States)

2013-11-25

reaction time, the core of the flow was sampled through a small orifice in a rounded nose cone, while the bulk of the gas was pumped by an oil free...with direct dynamics simulations,6’ 10’ 11’ 13- 17 have provided an atomistic understanding of the dynamics of gas phase x- + CH3Y reactions. In...OH- was mass selected using a quadrupole mass filter, injected into the flow tube through a Venturi inlet, and carried downstream by a helium

DYNAMIC DEUTERIUM ENRICHMENT IN COMETARY WATER VIA ELEY–RIDEAL REACTIONS

Energy Technology Data Exchange (ETDEWEB)

Yao, Yunxi; Giapis, Konstantinos P., E-mail: giapis@cheme.caltech.edu [Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States)

2017-01-20

The deuterium-to-hydrogen ratio (D/H) in water found in the coma of Jupiter family comet (JFC) 67P/Churyumov–Gerasimenko was reported to be (5.3 ± 0.7) × 10{sup −4}, the highest among comets and three times the value for other JFCs with an ocean-like ratio. This discrepancy suggests the diverse origins of JFCs and clouds the issue of the origin of Earth’s oceanic water. Here we demonstrate that Eley–Rideal reactions between accelerated water ions and deuterated cometary surface analogs can lead to instantaneous deuterium enrichment in water scattered from the surface. The reaction proceeds with H{sub 2}O{sup +} abstracting adsorbed D atoms, forming an excited H{sub 2}DO* state, which dissociates subsequently to produce energetic HDO. Hydronium ions are also produced readily by the abstraction of H atoms, consistent with H{sub 3}O{sup +} detection and abundance in various comets. Experiments with water isotopologs and kinematic analysis on deuterated platinum surfaces confirmed the dynamic abstraction mechanism. The instantaneous fractionation process is independent of the surface temperature and may operate on the surface of cometary nuclei or dust grains, composed of deuterium-rich silicates and carbonaceous chondrites. The requisite energetic water ions have been detected in the coma of 67P in two populations. This dynamic fractionation process may temporarily increase the water D/H ratio, especially as the comet gets closer to the Sun. The magnitude of the effect depends on the water ion energy-flux and the deuterium content of the exposed cometary surfaces.

SDI: Statistical dynamic interactions

International Nuclear Information System (INIS)

Blann, M.; Mustafa, M.G.; Peilert, G.; Stoecker, H.; Greiner, W.

1991-01-01

We focus on the combined statistical and dynamical aspects of heavy ion induced reactions. The overall picture is illustrated by considering the reaction 36 Ar + 238 U at a projectile energy of 35 MeV/nucleon. We illustrate the time dependent bound excitation energy due to the fusion/relaxation dynamics as calculated with the Boltzmann master equation. An estimate of the mass, charge and excitation of an equilibrated nucleus surviving the fast (dynamic) fusion-relaxation process is used as input into an evaporation calculation which includes 20 heavy fragment exit channels. The distribution of excitations between residue and clusters is explicitly calculated, as is the further deexcitation of clusters to bound nuclei. These results are compared with the exclusive cluster multiplicity measurements of Kim et al., and are found to give excellent agreement. We consider also an equilibrated residue system at 25% lower initial excitation, which gives an unsatisfactory exclusive multiplicity distribution. This illustrates that exclusive fragment multiplicity may provide a thermometer for system excitation. This analysis of data involves successive binary decay with no compressional effects nor phase transitions. Several examples of primary versus final (stable) cluster decay probabilities for an A = 100 nucleus at excitations of 100 to 800 MeV are presented. From these results a large change in multifragmentation patterns may be understood as a simple phase space consequence, invoking neither phase transitions, nor equation of state information. These results are used to illustrate physical quantities which are ambiguous to deduce from experimental fragment measurements. 14 refs., 4 figs

Internal Diffusion-Controlled Enzyme Reaction: The Acetylcholinesterase Kinetics.

Science.gov (United States)

Lee, Sangyun; Kim, Ji-Hyun; Lee, Sangyoub

2012-02-14

Acetylcholinesterase is an enzyme with a very high turnover rate; it quenches the neurotransmitter, acetylcholine, at the synapse. We have investigated the kinetics of the enzyme reaction by calculating the diffusion rate of the substrate molecule along an active site channel inside the enzyme from atomic-level molecular dynamics simulations. In contrast to the previous works, we have found that the internal substrate diffusion is the determinant of the acetylcholinesterase kinetics in the low substrate concentration limit. Our estimate of the overall bimolecular reaction rate constant for the enzyme is in good agreement with the experimental data. In addition, the present calculation provides a reasonable explanation for the effects of the ionic strength of solution and the mutation of surface residues of the enzyme. The study suggests that internal diffusion of the substrate could be a key factor in understanding the kinetics of enzymes of similar characteristics.

Investigation of the complex reaction coordinate of acid catalyzed amide hydrolysis from molecular dynamics simulations

International Nuclear Information System (INIS)

Zahn, Dirk

2004-01-01

The rate-determining step of acid catalyzed peptide hydrolysis is the nucleophilic attack of a water molecule to the carbon atom of the amide group. Therein the addition of the hydroxyl group to the amide carbon atom involves the association of a water molecule transferring one of its protons to an adjacent water molecule. The protonation of the amide nitrogen atom follows as a separate reaction step. Since the nucleophilic attack involves the breaking and formation of several bonds, the underlying reaction coordinate is rather complex. We investigate this reaction step from path sampling Car-Parrinello molecular dynamics simulations. This approach does not require the predefinition of reaction coordinates and is thus particularly suited for investigating reaction mechanisms. From our simulations the most relevant components of the reaction coordinate are elaborated. Though the C···O distance of the oxygen atom of the water molecule performing the nucleophilic attack and the corresponding amide carbon atom is a descriptor of the reaction progress, a complete picture of the reaction coordinate must include all three molecules taking part in the reaction. Moreover, the proton transfer is found to depend on favorable solvent configurations. Thus, also the arrangement of non-reacting, i.e. solvent water molecules needs to be considered in the reaction coordinate

Rate Coefficient for the (4)Heμ + CH4 Reaction at 500 K: Comparison between Theory and Experiment.

Science.gov (United States)

Arseneau, Donald J; Fleming, Donald G; Li, Yongle; Li, Jun; Suleimanov, Yury V; Guo, Hua

2016-03-03

The rate constant for the H atom abstraction reaction from methane by the muonic helium atom, Heμ + CH4 → HeμH + CH3, is reported at 500 K and compared with theory, providing an important test of both the potential energy surface (PES) and reaction rate theory for the prototypical polyatomic CH5 reaction system. The theory used to characterize this reaction includes both variational transition-state (CVT/μOMT) theory (VTST) and ring polymer molecular dynamics (RPMD) calculations on a recently developed PES, which are compared as well with earlier calculations on different PESs for the H, D, and Mu + CH4 reactions, the latter, in particular, providing for a variation in atomic mass by a factor of 36. Though rigorous quantum calculations have been carried out for the H + CH4 reaction, these have not yet been extended to the isotopologues of this reaction (in contrast to H3), so it is important to provide tests of less rigorous theories in comparison with kinetic isotope effects measured by experiment. In this regard, the agreement between the VTST and RPMD calculations and experiment for the rate constant of the Heμ + CH4 reaction at 500 K is excellent, within 10% in both cases, which overlaps with experimental error.

Quasi-Classical Trajectory Dynamics Study of the Cl(2P) + C2H6 → HCl(v,j) + C2H5 Reaction. Comparison with Experiment.

Science.gov (United States)

Espinosa-Garcia, Joaquin; Martinez-Nuñez, Emilio; Rangel, Cipriano

2018-03-15

To understand and simulate the dynamics behavior of the title reaction, QCT calculations were performed on a recently developed global analytical potential energy surface, PES-2017. These calculations combine the classical description of the dynamics with pseudoquantization in the reactants and products to perform a theoretical/experimental comparison on the same footing. Thus, in the products a series of constraints are included to analyze the HCl(v = 0,j) product, which is experimentally detected. At collision energies of 5.5 and 6.7 kcal mol -1 the largest fraction of available energy is deposited as translation, 67%, while the ethyl radical shows significant internal energy, 27%, and so it does not act as a spectator of the reaction, thus reproducing recent experimental evidence. The HCl(v=0, j) rotational distribution is cold, peaking at j = 2, only one unit hotter than experiment, which represents an error of 0.12 kcal mol -1 . At a collision energy of 5.5 kcal mol -1 product translational distribution is slightly hotter than experiment, but at 6.7 kcal mol -1 agreement with recent experiments is practically quantitative, suggesting that the first experiments should be revised. In addition, we observe that the HCl(v=0, j) scattering distribution shifts from isotropic at low values of j to backward at high values of j, which is in agreement with experimental data. Finally, no evidence was found for the "chattering" mechanism suggested to explain the low translational energy of the HCl product in the backward scattering region. In sum, agreement with experiments of a series of sensible dynamic properties permits us to be optimistic on the quality and accuracy of the theoretical tools used in the present work, QCT and PES-2017.

Automatic generation of active coordinates for quantum dynamics calculations: Application to the dynamics of benzene photochemistry

International Nuclear Information System (INIS)

Lasorne, Benjamin; Sicilia, Fabrizio; Bearpark, Michael J.; Robb, Michael A.; Worth, Graham A.; Blancafort, Lluis

2008-01-01

A new practical method to generate a subspace of active coordinates for quantum dynamics calculations is presented. These reduced coordinates are obtained as the normal modes of an analytical quadratic representation of the energy difference between excited and ground states within the complete active space self-consistent field method. At the Franck-Condon point, the largest negative eigenvalues of this Hessian correspond to the photoactive modes: those that reduce the energy difference and lead to the conical intersection; eigenvalues close to 0 correspond to bath modes, while modes with large positive eigenvalues are photoinactive vibrations, which increase the energy difference. The efficacy of quantum dynamics run in the subspace of the photoactive modes is illustrated with the photochemistry of benzene, where theoretical simulations are designed to assist optimal control experiments

VIRGIN2007, Calculates Un-collided Neutron Flux and Neutron Reactions from Transmission in ENDF Format

International Nuclear Information System (INIS)

2007-01-01

1 - Description of program or function: VIRGIN calculates un-collided flux and reactions due to transmission of a mono-directional beam of neutrons through any thickness of material. In order to simulate an experimental measurement the results are given as integrals over energy tally groups (as opposed to point-wise in energy). IAEA0932/10: This version include the updates up to January 30, 2007. Changes in ENDF/B-VII Format and procedures, as well as the evaluations themselves, make it impossible for versions of the ENDF/B pre-processing codes earlier than PREPRO 2007 (2007 Version) to accurately process current ENDF/B-VII evaluations. The present code can handle all existing ENDF/B-VI evaluations through release 8, which will be the last release of ENDF/B-VI. Modifications from previous versions: Virgin VERS. 2007-1 (Jan. 2007): checked against all ENDF/B-VII; increased in-core page size from 60,000 to 240,000. 2 - Method of solution: By taking the ratio of reactions to flux in each group an equivalent spatially dependent group averaged cross section is calculated. 3 - Restrictions on the complexity of the problem: The evaluated data must be in the ENDF/B format. However it must be linear-linear interpolable in energy-cross section between tabulated points. Since only cross sections (file 3) are used, this program will work on any version of ENDF/B

Approximate dynamic fault tree calculations for modelling water supply risks

International Nuclear Information System (INIS)

Lindhe, Andreas; Norberg, Tommy; Rosén, Lars

2012-01-01

Traditional fault tree analysis is not always sufficient when analysing complex systems. To overcome the limitations dynamic fault tree (DFT) analysis is suggested in the literature as well as different approaches for how to solve DFTs. For added value in fault tree analysis, approximate DFT calculations based on a Markovian approach are presented and evaluated here. The approximate DFT calculations are performed using standard Monte Carlo simulations and do not require simulations of the full Markov models, which simplifies model building and in particular calculations. It is shown how to extend the calculations of the traditional OR- and AND-gates, so that information is available on the failure probability, the failure rate and the mean downtime at all levels in the fault tree. Two additional logic gates are presented that make it possible to model a system's ability to compensate for failures. This work was initiated to enable correct analyses of water supply risks. Drinking water systems are typically complex with an inherent ability to compensate for failures that is not easily modelled using traditional logic gates. The approximate DFT calculations are compared to results from simulations of the corresponding Markov models for three water supply examples. For the traditional OR- and AND-gates, and one gate modelling compensation, the errors in the results are small. For the other gate modelling compensation, the error increases with the number of compensating components. The errors are, however, in most cases acceptable with respect to uncertainties in input data. The approximate DFT calculations improve the capabilities of fault tree analysis of drinking water systems since they provide additional and important information and are simple and practically applicable.

Effects of Water Molecule on CO Oxidation by OH: Reaction Pathways, Kinetic Barriers, and Rate Constants.

Science.gov (United States)

Zhang, Linyao; Yang, Li; Zhao, Yijun; Zhang, Jiaxu; Feng, Dongdong; Sun, Shaozeng

2017-07-06

The water dilute oxy-fuel combustion is a clean combustion technology for near-zero emission power; and the presence of water molecule could have both kinetic and dynamic effects on combustion reactions. The reaction OH + CO → CO 2 + H, one of the most important elementary reactions, has been investigated by extensive electronic structure calculations. And the effects of a single water molecule on CO oxidation have been studied by considering the preformed OH(H 2 O) complex reacts with CO. The results show little change in the reaction pathways, but the additional water molecule actually increases the vibrationally adiabatic energy barriers (V a G ). Further thermal rate constant calculations in the temperature range of 200 to 2000 K demonstrate that the total low-pressure limit rate constant for the water assisted OH(H 2 O) + CO → CO 2 + H 2 O + H reaction is 1-2 orders lower than that of the water unassisted one, which is consistent with the change of V a G . Therefore, the hydrated radical OH(H 2 O) would actually slow down the oxidation of CO. Meanwhile, comparisons show that the M06-2X/aug-cc-pVDZ method gives a much better estimation in energy and thus is recommended to be employed for direct dynamics simulations.

SNR-steam generator design with respect to large sodium water reactions

International Nuclear Information System (INIS)

Jong, J.J. de; Kellner, A.; Florie, C.J.L.

1984-01-01

This paper deals with the experiences gained during the licensing procedure for the steam generators for the SNR 300 LMFBR regarding large sodium-water reactions. A description is given of the different calculations executed to investigate the effects of large leaks on the 85 MW helical coiled and straight tube steam generators. The investigations on the helical coiled steam generators are divided in the formulations of fluid behaviour, dynamic force calculations, dynamic response calculation and finally stress analyses. Several results are shown. The investigations on the straight tube steam generators are performed using models describing fluid-structure interaction, coupled with stress analyses. Several results are presented. A description is given of the problems and necessary construction changes during the licensing process. Advises are given for future analyses and design concepts for second generation commercial size LMFBR steam generators with respect to large leaks; based on the experience, gained with SNR 300, and using some new calculations for SNR 2. (author)

Comparison of calculated and experimental isotope edited FTIR difference spectra for purple bacterial photosynthetic reaction centers with different quinones incorporated into the QA binding site.

Directory of Open Access Journals (Sweden)

Nan eZhao

2013-08-01

Full Text Available Previously we have shown that ONIOM type (QM/MM calculations can be used to simulate isotope edited FTIR difference spectra for neutral ubiquinone in the QA binding site in Rhodobacter sphaeroides photosynthetic reaction centers. Here we considerably extend upon this previous work by calculating isotope edited FTIR difference spectra for reaction centers with a variety of unlabeled and 18O labeled foreign quinones incorporated into the QA binding site. Isotope edited spectra were calculated for reaction centers with 2,3-dimethoxy-5,6-dimethyl-1,4-benzoquinone (MQ0, 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ, and 2,3-dimethyl-l,4-naphthoquinone (DMNQ incorporated, and compared to corresponding experimental spectra. The calculated and experimental spectra agree well, further demonstrating the utility and applicability of our ONIOM approach for calculating the vibrational properties of pigments in protein binding sites.The normal modes that contribute to the bands in the calculated spectra, their composition, frequency and intensity, and how these quantities are modified upon 18O labeling, are presented. This computed information leads to a new and more detailed understanding/interpretation of the experimental FTIR difference spectra. Hydrogen bonding to the carbonyl groups of the incorporated quinones is shown to be relatively weak. It is also shown that there is some asymmetry in hydrogen bonding, accounting for 10-13 cm-1 separation in the frequencies of the carbonyl vibrational modes of the incorporated quinones. The extent of asymmetry H-bonding could only be established by considering the spectra for various types of quinones incorporated into the QA binding site. The quinones listed above are tail-less. Spectra were also calculated for reaction centers with corresponding tail containing quinones incorporated, and it is found that replacement of the quinone methyl group by a phytyl or prenyl chain does not alter ONIOM calculated s

New results from dissipative diabatic dynamics and nuclear elastoplasticity

International Nuclear Information System (INIS)

Noerenberg, W.; Technische Hochschule Darmstadt

1986-10-01

I present new results about dissipative diabatic dynamics and nuclear elastoplasticity, in particular on a self-consistent diabatic formulation, on first numerical calculations of dissipative diabatic dynamics in two collective degrees of freedom, on quasi-elastic recoil in central nucleus-nucleus collisions, on the diabatic hindrance of fusion reactions and on the diabatic emission of nucleons in central nucleus-nucleus collisions. (orig./HSI)

Dynamically adjustable foot-ground contact model to estimate ground reaction force during walking and running.

Science.gov (United States)

Jung, Yihwan; Jung, Moonki; Ryu, Jiseon; Yoon, Sukhoon; Park, Sang-Kyoon; Koo, Seungbum

2016-03-01

Human dynamic models have been used to estimate joint kinetics during various activities. Kinetics estimation is in demand in sports and clinical applications where data on external forces, such as the ground reaction force (GRF), are not available. The purpose of this study was to estimate the GRF during gait by utilizing distance- and velocity-dependent force models between the foot and ground in an inverse-dynamics-based optimization. Ten males were tested as they walked at four different speeds on a force plate-embedded treadmill system. The full-GRF model whose foot-ground reaction elements were dynamically adjusted according to vertical displacement and anterior-posterior speed between the foot and ground was implemented in a full-body skeletal model. The model estimated the vertical and shear forces of the GRF from body kinematics. The shear-GRF model with dynamically adjustable shear reaction elements according to the input vertical force was also implemented in the foot of a full-body skeletal model. Shear forces of the GRF were estimated from body kinematics, vertical GRF, and center of pressure. The estimated full GRF had the lowest root mean square (RMS) errors at the slow walking speed (1.0m/s) with 4.2, 1.3, and 5.7% BW for anterior-posterior, medial-lateral, and vertical forces, respectively. The estimated shear forces were not significantly different between the full-GRF and shear-GRF models, but the RMS errors of the estimated knee joint kinetics were significantly lower for the shear-GRF model. Providing COP and vertical GRF with sensors, such as an insole-type pressure mat, can help estimate shear forces of the GRF and increase accuracy for estimation of joint kinetics. Copyright © 2016 Elsevier B.V. All rights reserved.