Electrical contact surfaces of a bipolar plate for a fuel cell assembly are formed of metals or metal alloys which when oxidized form highly conductive oxide passivation layers, thus maintaining high electrical conductivity and continuity through the fuel cell and forestalling corrosion failure of a cell assembly. A first inventory data is received from a first wireless mobile communication device, and a second inventory data is received from a second wireless mobile communication device. A deflector located below the gap deflects scrap sod and defective sod rolls onto the cut portion of the sod field, rater than onto the uncut portion, so that the scrap sod deflected onto the field will not interfere with the next pass of the cutting head. An actuator makes blocking engagement with the engine valve having been opened, to thereby hold the engine valve in an open state. The net value may be used to control the power consumption of the computer. Methods for their preparation are also provided.