In a surge absorber, a pair of protrusion electrodes is fixed to a pair of terminal electrode members at positions shifted from the center of the terminal electrode members to be point-symmetrical with the center of a ceramic insulator tube and a distance between the protrusion electrodes is adjusted so as to obtain a desired discharge starting voltage. The charging unit is configured to charge an image bearing member in a non-contact arrangement, including a charging roller provided with a core shaft, a charging member formed of electroconductive resin integrally disposed on the periphery of the core shaft, and gap holding members formed of insulating resin each disposed at respective ends of the charging member outside an image forming region. The process monitor cell thereby provides an accurate estimate of the quality of the fabrication process used to generate other functional SRAM cells within the integrated circuit design. , the rate of variation in fog density between before and after exposure is not more than 30%, based on the fog density of the photothermographic material before exposure. The dissociation is not atomic with the reference-count check, so the releasing thread checks the reference count again.