The present invention relates to new fibers, new processes of using said fibers, and new sheath dope compositions for multi-layer spinning processes. The process utilizes an opaque coating composition containing an opaque coating agent comprising a mixture of a polyacid and a polybase. At least one PEM fuel cell assembly is mounted on the shaft and insulated therefrom, and also has a gas passageway in register with a radially-extending port in the shaft. In another described embodiment, pulsations of the heart are sensed; and in a further described embodiment, the pulsations are converted to electrical energy by a piezoelectric device. The assembly of core web and cover layers is arranged between two press plates.