An engine includes an engine body and four pistons reciprocally moveable relative to the engine body. A metallic core is provided for attachment to an implant in a patient’s mouth. An insulating spacer is formed to extend along the first and second sidewalls and to also extend along at least a portion of the bottom between the conductive line and the insulating layer. The amount of non-reciprocal rotation material utilized by embodiments of the invention may be small, and the grating coupling structures may be efficiently made to couple to each other as their field profiles may be matched and their position may be precisely defined by lithographic means. The disk controller alters the angular velocity of at least one of the active disks upon detecting that the latency of one or more of the data requests differs from a specified threshold. This enables utilization circuitry to quickly capture the signal despite differences in clock domains.