Degradation modelling hydrolysis rate equation

Acetyl transfer between aspirin and sulfadiazine is a bimolecular reaction in which the translational diffusion of reactant molecules becomes rate determining when molecular mobility is limited in the solid state [33]. Therefore, it can offer a useful reaction model for understanding the ways in which chemical degradation rates in lyophilized formulations are affected by molecular mobility. Figure 17A shows the temperature dependence of the rate constant of acetyl transfer in lyophilized formulations containing dextran. Figure 17B shows the pseudo rate constant of aspirin hydrolysis that occurs in parallel with acetyl transfer in the presence of water. The rate constant of acetyl transfer ( t) and the pseudo rate constant of hydrolysis ( H> pseudo) are described by following equations ... 

The article temperature must be known in order to calculate its degradation rate. Solar modules generally are nearly black, so they get hot in the sun. We were interested in applications in which the module might be attached directly to a roof, so the back can be considered to be well insulated. Several temperature models have been described in the literature at various levels of complexity [7-12]. These models generally require empirical constants that we did not have. Instead, we adapted a simple equation that was derived from a dataset of the surface temperature of a black polycarbonate roof panel attached to a closed minivan in Arizona over the course of a year [13]. This is shown as Eq. (3.1) where T od is the module surface temperature, is the ambient dry bulb temperature, and / is the global horizontal irradiance in W/m. As it turns out, the selection of the model is not critical in the case of hydrolysis reactions, as will be shown in the Sensitivity section. 

---