This invention relates to novel allophanate-modified diphenylmethane diisocyanates, prepolymers of these allophanate-modified diphenylmethane diisocyanates, and two-component polyureas and one-component polyureaurethanes prepared from these prepolymers. Specifically, various metadata structures associated with snapshots are utilized to reduce the number of IO operations required to locate data within any specific snapshot. The PSE typically includes a controller that controls the DC power provided to the PD at the second node of the communications link. The collected input signal is processed in accordance with at least one mode of operation of the multiplexer component, the mode of operation autonomously configured by the demultiplexer component.