A phase detector generates a first output signal if a feedback clock signal leads a reference clock signal by more than a first time. The compounds inhibit serine protease activity, particularly the activity of hepatitis c virus NS3-NS4A protease. In response to receiving, for example, a read request for the data set, the memory manager batch processes the change requests by first moving the data set into a non-linear data structure. The system also includes a pair of double O-ring sealing assemblies for sealingly coupling a lubricant tube to the system. The apparatus and methods include a window which is isolated from the reactive gases by a flow of an inert gas.