Control of a process for producing free sulfur from hydrogen sulfide is accomplished by manipulating the flow rate of a feed stream containing oxygen to a furnace in such a manner that a desired proportion of the hydrogen sulfide fed to the furnace is converted to sulfur dioxide. A carrier composition comprising the synthetic polymer and a bioactive agent is useful for the delivery of the bioactive agent into the nuclei of the cells. a LED and a photodetector to be used as an optical microphone. A distensible opening to an enclosure inside the holder may protect the cable end from dust or contact damage with foreign objects by defining an inner space behind an inlet for the cable, but no further opening serving as an outlet for the cable.