A method and system are provided for adjusting a write timing in a memory device. A base-emitter voltage of the output transistor is detected by a voltage detecting circuit composed of a transistor. The separator is coupled with the impeller such that the separator and the impeller generally rotate as a single unit about the shaft axis and fluid within the separation chamber flows from the separator outlet end directly into the impeller inlet. The disclosed mobility preservation assemblies provide for dynamic stabilization of the spinal motion segment.