for the non-observable reaction over the timescale T s2 . Equations (39a) and (39b) suggest that e A 2 s 0 1 over the T s2 timescale. Furthermore, since the 225 changes in s 1 and c 1 are comparatively minimal when t c1 ≤ t ≤ T s2 , the production of e A 2 is effectively constant over the T s2 timescale: