Methods and apparatus for grouping elements of element pairs into element sets are disclosed. Thus, the present invention provides novel substituted piperidino phenyloxazolidinone derivatives, processes for making compounds as well as antimicrobial compositions containing said derivatives as active ingredients and methods of treating bacterial infections with the said derivatives. The cell is then covered with a light blocking cover during the anoxic condition to inhibit light from entering the cell. During a call setup, the recipient decodes a received call setup message and recognizes the call as a voice message. The plug head is mounted on the rotating member. The coating material can include SiO2 or various precursors thereof, which can be disposed on the porous supporting substrate by various deposition techniques.