In order to increase the pressure of the hydraulic medium in cylinders, especially those of the hydraulic longwall construction used in underground mining and tunnel construction, a control unit 21 is used which has suitably controllable, releasable check valves 29, 30 and 25, as well as a blockable check valve 31. The system includes a tissue fixation device including a catheter body member having a proximal end, a distal end, an inner lumen, and an expandable surface element disposed proximate to the distal end of the body member, the expandable surface element sized and configured to reproducibly position tissue surrounding a resected tissue cavity in a predetermined geometry upon expansion. The system includes, at least one register for storing a trigger mode value which specifies whether an interrupt is edge triggered or level sensitive, and a vector address field that specifies a priority and address for an interrupt, and a mask value which masks an interrupt source. Use of the diversity mechanism differentiates an execution or loading environment associated with the computer system from that of other computer systems by affecting operational behavior of computer programs attempting to execute on the computer system.