member such as upper plate 156 and a support member such as lower plate 158 in one embodiment the support member such as lower plate 158 can be deformable similarly in one embodiment the deformable member such as upper plate 156 can act as a support member each plate 156 158 can be made of any of a variety of materials including for example metal plastic or polymer perimeter 160 can separate plate 156 from plate 158 thus defining void 164 plates 156 158 and perimeter 160 can be made of a unitary material or can be individual pieces that are connected to one another compensator 152 can be constructed such that void 164 is generally sealed and thus does not permit ingress or egress of gas or liquids void 164 can contain a compressible fluid the fluid can be for example a gas such as air argon or nitrogen alternatively the fluid can be a liquid in one embodiment the liquid has a high boiling point so that it does not expand significantly when heated alternatively void 164 can contain a mixture of different types of fluids including for example multiple gases or combinations of gas and liquid in another embodiment void 164 can be evacuated such that the initial pressure is below ambient pressure plates 156 158 can be sufficiently rigid that they generally maintain their shape when void 164 is evacuated fill valve 165 can be used to evacuate fluids from void 164 and introduce.