A theoretical study of the mechanism and kinetics of the OH hydrogen abstraction from glyoxal and methylglyoxal is presented. Optimum geometries, frequencies, and gradients have been computed at the BHandHLYP/6-311++G(d,p) level of theory for all the stationary points, as well as for 12 additional points along the minimum energy path (MEP). Energies were obtained by single-point calculations at...

The principal theme of this paper is that anomalously slow, super-Arrhenius relaxations in glassy materials may be activated processes involving chains of molecular displacements. As pointed out in a preceding paper with Lemaitre, the entropy of critically long excitation chains can enable them to grow without bound, thus activating stable thermal fluctuations in the local density or molecular ...

A quantum theory on conformation-electron system is presented. Protein folding is regarded as the quantum transition between torsion states on polypeptide chain, and the folding rate is calculated by nonadiabatic operator method. The theory is used to study the temperature dependences of folding rate of 15 proteins and their non-Arrhenius behavior can all be deduced in a natural way. A general ...

While anomalous diffusion coefficients with non-Arrhenius-like temperature dependence are observed in a number of metals, conclusive comprehensive framework explanation has not been brought forward to date. Here, we use first-principles calculations based on density functional theory calculate self-diffusion the bcc metals Mo and $\ensuremath{\beta}$-Ti by coupling quasiharmonic transition stat...

the use of accelerated temperature stability studies using the arrhenius relationship is routine for estimating the stability of a drug at room temperature. therefore, the acceleration method is used to determine the expiration date of dexamethasone aqueous formulation manufactured in iran. a high-performance liquid chromatography (hplc) method utilizing ultraviolet (uv) detection for dexametha...

Thermal decomposition kinetics of calcium carbonate was studied by non-isothermal thermogravimetric analysis at different heating rates. The reaction mechanism was found to follow a two-dimensional phase boundary-controlled model by modelfree and model-fitting methods. Two non-Arrhenius equations (Harcourt–Esson equation and Berthelot–Hood equation) were used to interpret the decomposition kine...

A brief history is presented, outlining the development of rate theory during the past century. Starting from Arrhenius [Z. Phys. Chem. 4, 226 (1889)], we follow especially the formulation of transition state theory by Wigner [Z. Phys. Chem. Abt. B 19, 203 (1932)] and Eyring [J. Chem. Phys. 3, 107 (1935)]. Transition state theory (TST) made it possible to obtain quick estimates for reaction rat...