With the shape memory strip or wire 41 in the inactive position, the bell-shaped cavity 36 and cylindrical upper portion 37 are filled with a fluid such as propylene glycol or a gas, or the gas is removed to create a partial vacuum, and the faceplate 32 and back plate 33 are sealed together to provide a fluid tight unit. [0074] As with the previous embodiments the material(s), thickness and therma