The instant invention relates generally to catheters and to introducer catheters used to help deliver catheters or other medical devices to locations within the human body. First, a wafer has at least a first portion requiring a first doping density and a second portion requiring a second doping density is provided. The abnormalities may be advantageously detected using battery temperature characteristics, where the characteristics are subject to rule-based processing to determine impending battery failure. This can be done because the area for the slots is not needed. In one embodiment, a cam follower of a cam system comprises a tappet positioned between a cylinder valve and a camshaft, the tappet configured to drive the cylinder valve, a roller, and a pin coated with a diamond-like carbon coating coupling the roller to the tappet, the pin having a depressed contour on an outer surface of the pin.