A process for improving the stability to photo-oxidation of a polycyclic aromatic compound having at least two polymorphic forms comprises treating a first polymorph with one or more solvents to obtain the more stable second polymorph and then separating the second polymorph from the solvent. One or both of calender stack conditioning and conditioning of a measurement from a sensor for measuring caliper of the sheet, both with feedback CD control suspended, can be selectably performed. The processing device then sets a bit in the bitmap to indicate that the memory page is unused after the memory page is freed. Moreover, the command signal may be further generated in response to a key switch or a rotary switch.