A test key structure includes a substrate, a closed loop, a plurality of spacers, a plurality of first and second doping regions and a plurality of contacts. Significantly, in vivo application of compounds of the instant invention established, on the basis of SSEP testing, that the compounds provide longer lasting effects at lower concentrations than comparable treatment with the known agent 4-aminopyridine. A hydraulic motor is disposed in a fluid path for recovering pressurized working fluid from a lift cylinder via a control valve to a working fluid reservoir tank so that the hydraulic motor is driven by the pressurized working fluid returning from the lift cylinder. The leakage magnetic flux between the adjacent magnetic poles is reduced by making polarities of the plurality of deployed magnetic poles one and the same polarity. The heat exchanger section conveys coolant fluid. On the shell surface of the valve plug, when the valve is in a fully open position, there is an area which, relative to the outlet of the valve housing, is situated on the other side of the axis of rotation of the valve plug, which area is free from the cavity.