Abstract: Hydraulic actuators are disclosed which are useful for controlling the reflecting surface of deformable mirrors or positioning the segments a segmented reflecting mirror. In one embodiment electrodistortive actuators are used to control movement of a piston into or out of a reservoir containing a fluid. The fluid controls movement of a second, smaller piston whose movement may be coupled to a surface whose shape or position it is desired to influence. In a second preferred embodiment two sets of actuators are used to permit the disclosed mechanism to impart movement in two directions to the reflecting surface or optical element whose shape or position it is desired to control.

Abstract: A prefabricated zero clearance fireplace includes a combustion chamber having a front opening, a glass door sized and shaped for positioning over and sealing the opening and a guide system for guiding vertical movement of the door between a lowered position over the opening and a raised position. The guide system includes tracks that are inwardly offset at their lowermost ends so that the door seals the combustion chamber without friction as the door is raised and lowered. Counterweights permit the door to be easily raised and lowered. For safety, the counterweights cause the door to automatically raise if it is pushed outwardly from the inside. The door is hinged for pivoting outwardly about a vertical axis in the lowered position. An optional motor can be provided for raising and lowering the door. A convection chamber surrounding the combustion chamber permits circulation and heating of room air.