Experiments like this allow quick examination of TNP effects on reactivity, but when the reactivity evolves during the reaction, as obviously occurred during this experiment, it is difficult to separate the effects of TNP and reaction time on the evolving NP reactivity. To allow NP evolution over time to be seen more clearly, experiments like those in Fig. were done. Each frame shows the reaction of an individual silica NP under conditions of constant TNP and PO2, with TNP = 1200 K and 1300 K in Figs. and, respectively. Fig. compares the EEO2 values extracted from the mass loss rates as a function of time. Note that time = 0 in Fig. was taken as the start of the oxidation period, in order to facilitate the comparison.