When it is desired to improve the performance of a given shape of insulator by the incorporation of barriers in accordance with the present invention, such barriers may in some cases conveniently be incorporated initially, during {HEAD ~ the construction} of {TAIL ~ the insulator} 
When it is desired to improve the performance of a given shape of insulator by the incorporation of barriers in accordance with the present invention , such barriers may in some cases conveniently be incorporated initially , during { HEAD ~ the construction } of { TAIL ~ the insulator }
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