Of the many examples of oscillatory kinetic behaviour known, several are briefly reviewed, including those of glycolysis, the peroxidase-oxidase reaction and oscillations in cellular calcium concentration. It is shown that simple mathematical models employing allosteric rate laws are sufficient to explain the instability of the steady state and the appearance of sustained oscillations. The cAMP...

We introduce systematic approaches to chemical kinetics based on the use of phase-phase (log-log) representations of the rate equations. For slow processes, we obtain a corrected form of the mass-action law, where the concentrations are replaced by kinetic activities. For fast reactions, delay expressions are derived. The phase-phase expansion is, in general, applicable to kinetic and transport...

In the current study, the kinetics of asphaltene particle flocculation is investigated under a shear flow through numerical simulation. The discrete element method (DEM) is coupled with computational fluid dynamics (CFD) to model the agglomeration and fragmentation processes. In addition, a coalescence model is proposed to consider the attachment of colliding particles. The changes in mean asph...

Biodegradation kinetics of 4-nitrophenol (PNP) in aqueous solution by a gram negative soil bacterium, Ralstoniaeutropha was firstly studied in a small scale batch reactor. The degradation of PNP was evaluated at initial PNP concentrations ranging from 3 mg/L to 14 mg/L. The rate of PNP consumption by the bacterium culture was modeled using Monod and Contois kinetics in batch condition. PNP degr...

for large and complex reacting systems, computational efficiency becomes a critical issue in process simulation, optimization and model-based control. mechanism simplification is often a necessity to improve computational speed. we present a novel approach to simplification of reaction networks that formulates the model reduction problem as an optimization problem and solves it using genetic al...

it is possible to alter the permeability of ethyl cellulose membrane with certain materials such as surfactants. in this study the effect of surfactant concentration and different hlb values on the release rate of atenolol from ethyl cellulose-coated tablets was evaluated. the results showed that when the concentration of surfactant increased, the rate of drug release also increased. the kineti...

the effect of mechanical activation on structural changes and kinetics of carbothermic reduction of hematite with graphite was studied in this research. hematite powder mixture with graphite (with stoichiometry ratio c/o=1) was milled for the time periods of zero to 50 hours, and the structural changes were studied using x ray diffraction (xrd). the effect of mechanical activation on the kineti...

this study assesses the kinetics of hydration of pulverised fuel ash and metakaolin cement pastes and compares how the rate of reaction affects the pore-characteristics and resistance to ionic ingress. the degrees of hydration for the different mixtures were evaluated, both as a function of the calcium hydroxide content and with respect to the chemically combined water contents. the reaction ra...

The effect of chemical reactions on the blast initiation of detonation in gaseous media has been investigated in this paper. Analytical method is based on the numerical solution of onedimensional reactive Euler equations. So far, analyses on the blast initiation of detonation have modeled the combustion process as a one-step chemical reaction, which follows the Arrhenius rate law. Previous stud...