The present invention provides a compound of general formula A, useful as potential antitumour agents against five human cancer cell lines. A DC bias circuit is used for controlling the operation of the amplifier. A surface feature is formed in the tube wall proximate the exterior. The locking assembly locks the position of the electrical contacts and restricts access to the actuating assembly. We also present algorithms to retransmit lost packets, to maintain the overhear table and to compensate for the retransmission of packets of other nodes. A game server data storage can be in communication with the game server processor.