bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rate Processes in Low Dimensional Chaotic Systems with Many Attractors
Authors: Arecchi F. T. 
Published: July 2012

AbstractKramers' paper and its successive elaborations up to the last decade have considered the transition rate between two stable situations. In the language of system dynamics, we say that the process consists in the transition between the basins of attraction of two fixed point attractors. – Here I present four situations of transitions in non equilibrium systems explored experimentally, and which await a formal treatment in terms of a generalized Kramers transition rate theory.I) Since 1967, with reference to Q‐switched lasers, we have studied the decay out of an unstable state, exploring the passage time statistics in its first and higher order moments.II) In the '80s we have been exploring situations of low dimensional chaos where two or more strange attractors coexist. The jumps from one to another are either noise induced jumps, or they are induced by a change in a control parameter which lowers the energy barrier separating the two attractors (crises).III) Investigating a dynamics with competing unstable points we have shown evidence of Shil'nikov chaos. The identification is done in terms of the iteration map of the successive return times to a given surface of section. This may be considered as an extension of the passage time method to the case of multiple passages.IV) We have given experimental evidence of “chaotic itinerancy”, that is, of jump processes self triggered by the same dynamics. So far, the corresponding understanding is based only on numerical simulations. Since chaotic itinerancy has been observed in optical systems displaying space‐time chaos, a short survey of these phenomena is presented for sake of completeness.
The Kramers Problem in the Turnover Regime: The Role of the Stochastic Separatrix
Authors: Klosek M. M. , Matkowsky B. J. , Schuss Z. 
Published: July 2012

AbstractWe consider the problem of activated escape of a Brownian particle from a potential well. We find the stochastic separatrix S (the locus of starting points of the phase space trajectories which have equal probabilities of ending up inside or outside the well) for (i) the extremely anisotropic overdamped motion of a two‐dimensional Brownian particle in a bistable potential, and (ii) the damped and underdamped motion of a one‐dimensional Brownian particle in a single metastable state. The significance of S is that (1) it defines the reactant and product wells in a natural though not necessarily intuitive way, and (2) it reduces the calculation of the escape rate to the solution of the stationary Fokker‐Planck equation inside S, with absorbing boundary conditions on S. Finally, employing this approach we derive an expression for the Kramers escape rate which bridges uniformly between Kramers weak damping regime and transition state theory.
Harmonic Noise Driven Bistable Dynamics
Authors: Schimansky‐Geier L. , Hesse J. J. , Zülicke Ch. 
Published: July 2012

AbstractWe consider bistable dynamics driven externally by a noisy harmonic oscillator. For small damping we derive a Markovian approximation for the energy dynamics. In conclusion we discuss the possibility of the inversion of bistable oscillators induced by colored noise.
Soliton – Assisted Activation Processes
Authors: Ebeling Werner , Jenssen Martin 
Published: July 2012

AbstractThis paper deals with the problem of energetic activation of one or few degrees of freedom of a spatially extended system. The fusion of soliton‐like excitations is an efficient nonlinear mechanism to generate high‐energy events at soft springs which are embedded in a one‐dimensional chain of hard springs. In equilibrium there exists an optimum temperature where thermal energy is mainly partitioned to the soft springs due to the superposition of thermally generated solitons. Some of the features obtained for the one‐dimensional system also apply to a solution of soft spheres in a hard‐sphere solvent.
Proton Quantum Tunneling in Hydrated Protein Surface
Authors: Careri G. , Consolini G. 
Published: July 2012

AbstractWe measure the protonic conductivity in water clusters adsorbed on lysozyme powders, below room temperature In the low temperature region the conductivity increases with temperature as exp T6, in agreement with prediction by the theory of dissipative quantum tunneling. We detect the onset of this effect near 180 K, where a glass transition in the protein matrix is known to take place. Quantum tunneling matches smoothly with thermal hopping near 271 K.
Quantum Brownian Motion and its Classical Limit
Authors: Ambegaokar Vinay 
Published: July 2012

AbstractThe Feynman‐Vernon, Caldeira‐Leggett model for a quantum dissipative system is used, via a general kinetic equation due to Chow, Browne, and the present author, to cast light on the classical limit of quantum Brownian motion, with special attention paid to the requirement of coarse graining in time.
Dynamics of an Impurity Spin Coupled to a Spin‐Boson Dissipative System
Authors: Dattagupta Sushanta , Qureshi Tabish 
Published: July 2012

AbstractThe dynamics of an impurity spin coupled to a spin‐boson dissipative system is studied using the resolvent expansion technique. In one particular physical realization the model simulates a highly anisotropic Kondo system. The transverse correlation function of the impurity spin is calculated and the result obtained is analyzed in various limiting cases. NMR lineshapes are also calculated for various temperatures which are relevant in another physical realization of the model. Motional narrowing is observed at high temperature.
Energy Transfer in Solid Solutions and on Fractal Polymer Surfaces
Authors: Kost S. H. , Breuer H. D. 
Published: July 2012

AbstractThe electronic energy transfer from rhodamine B to several acceptor dyes in cellulose nitrate solid solution and on the surface of membrane filters of the same polymer has been investigated at room temperature. In polymer matrix the Förster theory has been confirmed and critical distances Ro have been calculated from the theoretical equation and have also been determined by energy transfer experiments measuring the fluorescence decay time of the donor. Applying new fractal concepts to energy transfer in porous membranes, the fractal dimension of the polymer surface has been determined under several conditions. The values agree with others obtained by adsorption experiments.
Temperature Dependence of the Electric Conductivity of a Triethylamine/Water Mixture of Critical Composition
Authors: Höhn F. , Woermann D. 
Published: July 2012

AbstractResults of measurements of the temperature dependence of the specific conductivity of a triethylamine (TEA)/water mixture of critical composition (xc(TEA) = 0.0777; mole fraction of TEA) as well as of mixtures of non‐critical composition are reported. They are analysed by fitting the function K = a + b · ϵ + c · ϵ2 + d · ϵthetas + e · ϵθ+Δ (ϵ = (Tc,vis – T)/Tc,vis; Tc,vis: visually determined critical temperature; θ: critical exponents; theoretical value Δ = 0.5) to the experimental data. For the analysis the critical exponent θ is fixed at values predicted by different models (θ = 0.65, θ = 0.89). Tc is fixed at the value determined visually for each mixture studied. The analysis of the data shows that in a triethylamine/water mixture of critical composition an anomalous decrease of the electrical conductivity as a function of temperature can be detected as the critical temperature is approached. The reproducibility of the conductivity data is limited by the chemical instability of the system. Therefore it is not possible to decide unequivocally which of the proposed values of the critical exponent Θ is consistent with the data.
Photochromic Characteristics of Mixed WO3 – MoO3 Thin Films in Alcohol Vapors
Authors: Yao J. N. , Loo B. H. , Hashimoto K. , Fujishima A. 
Published: July 2012

AbstractThe photochromic responses of mixed WO3 – MoO3 thin films subjecting to UV irradiation were investigated in reducing environments, and they were compared with those of WO3 and MoO3 thin films. It was found that the photochromism of mixed 92% WO8% MoO3 thin film in ethanol vapor was significantly enhanced than that of WO3 or MoO3. The associated change in the absorbance (ΔABS) of the mixed‐oxide film was about 1.5 times that of the WO3 film, and about 2.7 times that of the MoO3 film.
Dynamics of 18‐Crown‐6 Ether in Aqueous Solution Studied by Quasielastic Neutron Scattering
Authors: Pelc H. W. , Hempelmann R. , Prager M. , Zeidler M. D. 
Published: July 2012

AbstractThe dynamical behaviour of crown ether 18‐crown‐6 in water has been investigated over the whole concentration range by incoherent quasielastic neutron scattering using the high resolution backscattering spectrometer BSS1 and the time‐of‐flight instrument SV22 at the research reactor FRJ2 in Jülich. In addition we have determined the dynamic viscosities and the mass densities of this binary system. Evaluation of the neutron scattering data by use of appropriate diffusion models gives information about the temporal and spatial development of translational, rotational and conformational motion of 18‐crown‐6. The decrease of the measured dynamical quantities on addition of water up to a concentration of 50 mole‐% suggests the formation of a 1:1 crown ether‐water adduct. Addition of more water yields a rapid increase of the translational diffusion coefficient and a decrease of the viscosity.
Thermodynamic Studies on Beta‐Silver Sulfide
Authors: Mostafa S. N. 
Published: July 2012

AbstractFrom the measurement of the emf of the solid‐state galvanic cell:Pt/Ag/AgI/β‐Ag2+δS/Pt,and its temperature dependence the following results for different Ag/S ratios in the temperature range between 200 and 350°C are obtained: the partial molar thermodynamic quantities of dissolution of one mole of silver into the compound, point defect concentrations and the width of band gap were determined as a function of the metal/sulfur ratio. The change of the thermodynamic quantities with the change of the stoichiometric composition can be explained by varying contributions of electrons and electron‐holes depending on the fact whether the electrons, which are brought into the compound by the dissolution of silver, go into the conduction band (excess of metal) or, by annihilation of electron‐holes into the valence band (deficit of metal). From the electrochemical measurements besides of other quantities – the band gap energy can be calculated and is of about 0.38 eV.
Zusammensetzung, Eigenschaften und Anwendungen mesomorpher Tensidphasen
Authors: Heusch Rudolf 
Published: July 2012

AbstractPhasendiagramme, polarisations‐ und elektronenmikroskopische Untersuchungen sowie rheologische Messungen liefern eine Erklärung für in wäßrigen Tensidsystemen auftretende Phänomene. Es wird herausgestellt, daß Wasser bei dem Zustandekommen unterschiedlicher Phasen, bei ihren Übergängen, dem Auftreten von Mischungslücken und einer ablaufenden Phasenumkehr eine entscheidende Rolle spielt. Es wird die Konkurrenz zwischen Wasserstoffbrückenbindungen und hydrophoben Wechselwirkungen untersucht, sowie auf den Zusammenhang zwischen der Bildung einer mesomorphen Phase und der Oberflachenaktivität des beteiligten Tensids hingewiesen. Flüssigkristallbildung und Oberflächenaktivität sind dann eine Funktion der Löslichkeit eines Tensids.
Thermodynamics of Solution of Hydrogen in Pd  Cu and Pd  Cu  Au Solid Solution Alloys
Authors: Sakamoto Y. , Ishimaru N. , Mukai Y. 
Published: July 2012

AbstractThermodynamic quantities for absorption of hydrogen by Pd  Cu alloys with up to atom fraction of XCu = 0.2, and by Pd  Cu  Au ternary alloys with up to (XCu + XAu) = 0.2, where XCu = XAu, have been determined at temperatures between 273 K and 423 K and hydrogen pressures up to 1000 Torr by measurements of the pressure‐composition isotherms. The hydrogen absorption characteristics of these alloys have been compared with that of the previously reported Pd – Au binary alloys. The room temperature lattice parameters of hydrogen‐free Pd – Cu – Au alloys increases with the solute content, albeit by a small amount. The relative partial molar enthalpy, ΔHH0, at infinite dilution in Pd – Cu – Au alloys increases in exothermicity with increasing (Cu + Au) content, and the alloy composition dependence of the ΔHH0 value falls near the mid‐points between those of each Pd – Cu and Pd – Au binary alloy. The relative partial molar entropy, ΔSH0, at infinite dilution in Pd – Cu – Au alloys decreases with the solute content, and the ΔSH0 values at the same alloying content are larger than that of Pd – Au alloys, but are smaller than that of Pd – Cu alloys. The [H – Cu + H – Au] pair interaction energies between the dissolved hydrogen and the substitutional solute atoms in the ternary alloys have been evaluated according to a quasi‐chemical model with zeroth order approximation by taking into account the “constant pressure” to “constant volume” correction. The hydrogen solubility behaviour at low hydrogen concentration in Pd – Cu – Au ternary alloys can be described as due to the counteraction of the repulsive H – Cu pair interaction and the attractive H – Au pair one in the Pd host lattice. The stability of the β‐phase hydride at a given temperature in Pd – Cu – Au alloys decreases with the solute content, and the alloy composition dependence of the stability is also placed near the mid‐points between those for each Pd – Cu and Pd – Au binary alloy.
Representation of the Viscosity of Alkanes as a Function of Temperature and Pressure Using a Vogel Type Equation
Authors: Kanti M. , Alliez J. , Lagourette B. , Saint‐Guirons H. , Xans P. , Barnaud G. 
Published: July 2012

AbstractPrior evaluation of the viscosity of oil field fluids according to pressure‐temperature conditions is a fundamental factor in exploitation. The aim of this article is to propose a representative form of the viscosity as a function only of pressure‐temperature variables and a parameter characteristic of the fluid, namely the molecular weight. This analytical expression applies to all the members of the same chemical family. It is based on known parameters and is consequently available without any additional experimental work. – This Vogel type analytical expression: lg η = A + B/(T – T∞) has been developed from experimental results concerning the viscosity of pure linear alkanes (n – C10 to n – C18) at different temperatures (20 – 100°C) and pressures (1 – 1000 bar) corresponding to the liquid state. The isobaric set [η = f(T)] of the different alkanes considered has been reduced to a single master curve, by double translation, a technique used for polymer study. This procedure allows the dependence of parameters A,B and T∞ to be specified with respect to pressure and molar mass. Numerical verification of the proposed representation shows that the experimental values for pure substances have on average an accuracy of 3%. The method yields results which remain acceptable for binary and quaternary mixtures of these alkanes.
A Cluster Model for Tetrahedrally Coordinated Chalcogenide Phases
Authors: Leute Volkmar 
Published: July 2012

AbstractA model is described, which allows to calculate the energy dependent cluster probabilities for quasiternary systems of type AX/BX/CX, based on a concept of reactions between tetrahedral clusters. It is shown. that for the quasibinary section A3X3/B2CX3 with C standing for structural vacancies, the cluster model allows predictions concerning the occurence of ordered compounds.
Graphical Representation of Solid‐Solute Phase Equilibria in Aqueous Solution
Authors: Königsberger Erich , Gamsjäger Heinz 
Published: July 2012

AbstractSolid‐solute phase diagrams are useful tools for the depiction of stable and metastable equilibria between binary mixed crystals with common ions and aqueous solutions. Generalized Gibbs‐Duhem equations provide the common basis and suggest natural co‐ordinates for the graphical representation of thermodynamic variables. Diagrams applicable even to highly soluble electrolytes can be constructed by plotting the osmotic coefficient of the solvent times the total molality πΣmvs. the mole fractionsxof the dissolved and solid components, respectively. According to Schmalzried and Pelton's topological classification the resulting phase diagrams are of Type II. They can be used for practical purposes, e.g., to predict the separability of the components by fractional crystallization.
Kinetic and Thermodynamic Parameters of the Ferro‐Ferricyanoferrate Redox System in Glycerol‐Water Mixed Solvent
Authors: Badawy W. A. , Hilal N. H. , El‐Shazly Sh. A. 
Published: July 2012

AbstractThe electrochemical behaviour of the Au‐rotating disc electrode (rde) in the Fe(CN)3‐/4‐6 redox system in pure water and water‐glycerol mixed solvents was studied. Using standard potentiostatic technique, the kinetic parameters controlling the anodic and cathodic processes were derived. The effect of the speed of rotation of the rde, the temperature, and the scan rate on the current‐potential characteristics of the system was investigated. The thermodynamic parameters of the Fe(CN)3‐/4‐6 in glycerol‐water mixed solvent were calculated. It turns out that the electrode processes are mass transport controlled. The presence of glycerol retards the charge transfer process and enhances the mass transport effects. The calculated thermodynamic data revealed that the rate of the anodic reaction is enthalpy controlled whereas that of the cathodic one is entropy controlled.
Phase Equilibria and Transport Properties in the Systems Water/n‐Butanol/Transition Metal Perchlorates
Authors: Mahr Michael , Weil Konrad G. 
Published: July 2012

AbstractThe miscibility gap between n‐butanol and water can be closed by the addition of transition metal perchlorates. As transition metal ions we used Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, and Zn2+. All phase diagrams are of the same shape when the salt contains a divalent cation, while the equilibrium curve in the Fe3+ system encloses a one third smaller region of the phase triangle. UV/VIS‐spectra of Ni(ClO4)2 in butanol/water show that nickel ions are preferentially hydrated. These facts lead to the conclusion that the closing of the miscibility gap is only due to butanol/perchlorate interactions. The finding that the change of the transition metal does not affect the behaviour of the system is corroborated by measurements of the density and the transport properties electrical conductivity and kinematic viscosity. All three properties depend on the concentration, but not on the nature of the salt. Investigations of the phase diagrams at lower temperatures show a second region with two coexisting liquid phases at higher salt concentrations. This region becomes smaller with increasing temperature while the miscibility gap in the region with lower salt contents grows with increasing temperature.
Small Angle Neutron Scattering Measurements on Iridescent Surfactant Solutions
Authors: Baumann J. , Kalus J. , Hoffmann H. , Thunig C. , Lindner P. 
Published: July 2012

AbstractQuaternary solutions of the surfactant Tetradecyldimethylaminoxid (C14H29N(CH3)2O, TDMAO) in D2O, equimolar concentrations of Decane and some cosurfactant Hexanol show at low concentration the phenomenon of iridescence. The colour of the backscattered light changes from red to blue with increasing surfactant concentration. Small‐angle neutron diffraction (SANS) patterns were recorded for different concentrations between 27 and 584 mM TDMAO. It is shown that the iridescent colours are due to Bragg reflections of visible light from lamellar layers. By simulation based on a one‐dimensional crystal model the thickness of the bilayers and the lattice parameter of the liquid crystalline structure could be determined. At higher concentrations the samples showed a pronounced anisotropic SANS‐pattern, the origin of which is related to the procedure of filling the solution into the flat, disklike quartz cells of path length 1 mm.
Chaos and Interior Crisis in an Electrochemical Reaction
Authors: Krischer K. , Lübke M. , Wolf W. , Eiswirth M. , Ertl G. 
Published: July 2012

AbstractThe electrochemical oxidation of hydrogen on a platinum anode in the presence of copper ions exhibits under galvanostatic conditions kinetic oscillations due to periodic poisoning and activation transitions of the electrode by underpotential deposition and dissolution of a passivating Cu monolayer In the presence of chloride ions a transition to chaos from a stationary state via a Hopf bifurcation and a sequence of period doublings (Feigenbaum scenario) was observed upon increase of the current density. Further change of this control parameter caused a transition to another qualitatively different chaotic state through an interior crisis. Near the other end of the oscillatory region, this state evolved into periodic mixed‐mode behaviour.
Temperature and Pressure Dependence of Self Diffusion in Long Liquid n‐Alkanes
Authors: Vardag T. , Karger N. , Lüdemann H.‐D. 
Published: July 2012

AbstractA titanium autoclave for the determination of self diffusion coefficients by the pulsed field gradient spin‐echo method is described, that has been used in the temperature range between 200 and 500 K at pressures up to 600 MPa.—In a first series of experiments, melts of n‐alkanes with chain lengths between 16 and 154 carbon atoms were studied. The data are analyzed with modifications of the hard sphere model and tested against the Rouse‐ and reptation model.
Critical Micelle Concentration in the AOT‐Water‐Benzene System as Determined by Small‐Angle Neutron Scattering
Authors: Gorski N. , Ostanevich Yu. M. 
Published: July 2012

AbstractWe describe an approach to the experimental determination of the critical micelle concentration (CMC) in solutions of uncharged micelles by the analysis of small‐angle neutron scattering data. It is shown that, in dilute solutions, the dependence of the product of forward scattering intensity and apparent squared radius of gyration is a linear function of the total surfactant concentration. The ratio of the two parameters of this function gives the concentration of surfactant in a monomeric state, which can be used as a reliable estimate of CMC. In the case under investigation (AOT + X · H2O + C6D6) at X = 0 we found CMC = 0.80 ± 0.04 mM, which is in reasonable agreement with the values reported by the other authors. Our first experiments at X = 4.3 and X = 8.6 show CMC = 2.2 ± 1.0 mM and 1.5 ± 0.6 mM, respectively. It seems plausible that the addition of water does not cause any serious diminution of the CMC in this system.
Dielectric Relaxation of N‐Cyano Substituted Morpholine, Piperidine and Pyrrolidine
Authors: Stockhausen M. , Wilke G. 
Published: July 2012

AbstractThe dynamic dielectric properties of the title substances are measured at 20 °C at frequencies up to 72 GHz in the pure liquid state and in mixtures (x = 0.4–1) with benzene and tetrachloromethane. Rotational tumbling motion of single (non‐associated) molecules is likely to be the main relaxation process. Peculiarities are found with two out of the six systems, namely mixtures of cyanopiperidine and cyanopyrrolidine with tetrachloromethane. These are discussed as possibly due to a concentration dependent conformational equilibrium.
S1‐Lifetime of Azulene in Solution
Authors: Schwarzer D. , Troe J. , Schroeder J. 
Published: July 2012

AbstractFemtosecond two‐photon fluorescence was used to redetermine the S1‐lifetime of azulene and perdeutero‐azulene in solution. A value of 1.0 (±0.l) ps was obtained in both cases, which is a factor of two smaller than the lifetime measured previously with lower time resolution.