A distributor structured for a 360-degree rotary ceiling fan comprises a main housing with an outer shell and a pedestal, a central shaft passing through the outer shell and the pedestal, and a power distribution ring unit around the central shaft in the main housing. 5 to 10 nm dispersed in a medium containing a nitride, an oxide or both; and thereby improves controllability for a resistivity value, stability and reproducibility, and the adequate temperature characteristics of resistance. During setting of a dose the gearing arrangement is prevented from rotating along with the dose setting member about the rotational axis. The diffractive optical element is included in the first lens unit.