Past exam of the short options course of the University of Oxford / 2023 / 9 / a / ii / Solution

Since $d{N}_i/dt=K_i{r}_{1}d{u}_i/d\tau$, division of the equations by $K_i{r}_1$ givesThus the dimensionless parameters areEach is a ratio of quantities with matching units. In particular $\gamma$ can be negative even though every original model parameter is positive.