A stent may comprise a helically wound ribbon of material. The polishing device includes a platen adapted to support a polishing pad and also includes a source of polishing slurry. On releasing the detention member and unloading the spring, the hammer forcibly impacts a footrest and drives a hollow metal core into soil making a hole for a fertilizer spike. The wireless identification devices each determine if the random number generated by each wireless identification device falls within the subgroup, and if so, the wireless identification device responds to the interrogator. The power loss detector is adapted to detect a power loss event and to initiate a power shutdown. A single frame supports both inner and outer fabric enclosures.