According to the present invention, there are provided a novel partial ester of a nitrogenous carboxylic acid ester with cellulose, the partial ester being useful as an antibacterial agent, a flame retardant, etc. The heat-radiating structure includes: a signal transmission unit to which an integrated circuit is attached; a chassis having a bed for supporting the signal transmission unit formed therein; and a cover plate which covers the signal transmission unit and having a heat sink formed therein. When the media requires regeneration, the media is allowed to fall to a lower portion of the media container where a regeneration fluid is passed through the media.