Uptake flux (k_osmo) for volume calibration
To calibrate the VOL module we need to calculate the concentration change (total osmolarity) due to uptake in mM/(s * um2).
We can calculate this from the fluxes in the uptake reactions, a desired value would be 0.03 mM/(s * um2).
This should take into account all species (ions, metabolites,...), right @tondre?