Have added method to define the concentration as a function, so that the concentration can be changed with time. Seems to work-sort of. Also wrote a small function that will let me produce piecewise functions from lists of conditions and functions. Currently those conditions and functions must be lambda functions (or normal functions), but I think this is easier than writing one larger function and it will eventually provide a basis for custom function definitions by users without programming experience.https://app.asana.com/0/16684320709121/18188414584568