The coupling of electronic transitions within molecules to condensed-phase media involves a complex hierarchy of spatial and dynamical scales. Thermodynamics of activation is related to the length scale of microscopic interactions reflected in the non-Arrhenius reaction kinetics. Solvent dynamics make a particularly strong impact on the activation barrier when the time scale of the reaction is ...

nowdays, production of high quality engine oils is one of the worries of our country’s engine oil industry. in this study, the behavior of four commercial polymers used in nation motor oil industry in obtaining the best viscosity index improver was investigated. in this regard, viscometric behavior, shear stability and polymers’ performance for engine cranking were compared at low temperature. ...

We demonstrated the activation energy approach to evaluate oxygen evolution performance and probe active site reconstruction at different potentials. Activation energies are acquired following Arrhenius equation by monitoring current densities under varied hydroxide concentrations temperatures. Our complex oxide electrocatalysts (Ag- Ce-bidoped iron manganese oxyhydroxide) exhibit a much smalle...

Using forced Rayleigh scattering, the tracer diffusion of methyl red through water and eight other solvents at different temperatures is investigated and the results are compared to the Cohen-Turnbull theory of free-volume diffusion. In seven solvents the effective non-Arrhenius activation energy measured experimentally agrees with the Cohen-Turnbull energy. In water, however, the diffusion can...

Experimental data from the literature for cross sections and rate constants for dissociative electron attachment to CF(3)Br, with separately varied electron and gas temperatures, are analyzed by a kinetic modeling approach. The analysis suggests that electronic and nuclear contributions to the rate constants can be roughly separated, the former leading to a negative temperature coefficient, the...

In this study, a large number of creep tests were carried out to study the effect of stress level and testing temperature on the creep behavior of 63 Sn/37Pb solder in a systematic manner. Based on the dislocation controlled creep mechanism and Gibbs’ free-energy theory, a new creep constitutive model was proposed. The model was found to describe accurately the creep flow of the solder and to b...

The dielectric loss spectra of a series of copolyesters of poly(ethylene terephthalate) and poly(ethylene isophthalate) have been measured as a function of temperature in a broad frequency range (10(-1)-10(9) Hz). By these measurements, the merging of the two relevant relaxations alpha and beta has been studied. The beta processes exhibit a complex temperature dependence, showing a clear Arrhen...

Thermogravimetric studies of chitin and chitosan in air atmosphere were carried out at six rates of linear increase of the temperature. The kinetics and mechanism of the thermal decomposition reaction were evaluated from the TG data using recommended from ICTAC kinetics committee isoconversional calculation procedure of Kissinger-Akahira-Sunose, as well as 27 mechanism functions. The values of ...

As a part of an analysis of the nature of chilling injury to seeds, measurements were made of the initial linear rates of water entry into and solute leakage out of cotyledons of soybean at various temperatures. Arrhenius plots were approximately linear for water entry into both living and dead cotyledons, with the slope (and activation energy) for entry into living cells being insignificantly ...

A study has been made of the kinetics of condensation reactions in phosphotriester synthesis of oligonucleotides on polystyrene copolymer resin support, using monomers, dimers, and trimers as the coupling units. The condensations follow pseudo first order kinetics, with a rate constant that decreases from monomers to dimers to trimers. Arrhenius plots indicate a nearly constant activation energ...