An apparatus for measuring relative displacement between a first shaft and a second shaft includes first and second rotor assemblies. The belt body exhibits hardness higher at the rear surface than at the front surface after heated at 350\xb0 C. A first embodiment provides a rotating ring in a recessed retaining cup that provides for maximum flexibility. The thin layer is separated from the remaining of the structure at the level of the embrittled zone. The compositions may be used to deliver living cells to a delivery point without the use of expensive refrigerants such as dry ice or liquid nitrogen. The firmware executing on the processor can be changed when desired.