A III-nitride heterojunction semiconductor device having a III-nitride heterojunction that includes a discontinuous two-dimensional electron gas under a gate thereof. The nozzle permits passage of a fluid therethrough from the first tubular string bore and deflects the first tubular string in a substantially horizontal direction. These lens elements can be positioned relative to each other to provide wide ranges of focus correction and astigmatism correction. The service gateway keeps track of client available memory and sequence numbers in messages to generate error codes when applicable.