The invention provides a reaction product derived from an epoxy-functional acrylic monomer and an alkylaminoalkylene polyalkoxysilane or from a reaction product derived from acrylic acid and an epoxidized polyalkoxysilane. The emission output power can be enhanced when the first reflector layer has a number of such pairs which is not less than 11 and not more than 41. The cover 12 has an opening 28 adapted to permit the flow of the substance through the lid 10. A plurality of permanent magnets are disposed on an inner surface of the outer rotor element and on an outer surface of the inner rotor element. The surface stabilized, non-agglomerated silica has a size in the nanometer range.