A structure having a normal position, and a deformed position in which the structure is subject to strain resulting from {HEAD ~ external application} of {TAIL ~ stress forces}, the structure being adapted to respond to the strain induced by the external stress forces and to restore itself to the normal position, the structure comprising: 
A structure having a normal position , and a deformed position in which the structure is subject to strain resulting from { HEAD ~ external application } of { TAIL ~ stress forces } , the structure being adapted to respond to the strain induced by the external stress forces and to restore itself to the normal position , the structure comprising :
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