Turns on/off (default on) checking and updating for values falling below the given threshold after a nonlinear update. Values below the threshold are replaced with either the -minConc or their previous value if -minConcIsOldConc is specified.
In Alamode the unknowns typically represent a concentration, and it is not physical to have negative concentrations. The nonlinear solution may compute negative concentrations due to overshoot. It is usually a good idea to adjust these value to avoid converging to an incorrect fixed point in the nonlinear solver.
This should have been a per-field flag.