The presence of {TAIL ~ some gases} such as air or an inert gas, or {HEAD ~ a vacuum}, in the porous insulation material reduces the overall dielectric constant of the insulation material, thereby effectively reducing the capacitance of the structure 
The presence of { TAIL ~ some gases } such as air or an inert gas , or { HEAD ~ a vacuum } , in the porous insulation material reduces the overall dielectric constant of the insulation material , thereby effectively reducing the capacitance of the structure
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH