Abstract: A thin shell of hard plastic has a cavity within which a polyurethane foam is received. Each panel includes an upper, relatively straight-line edge, two side edges at substantially 90 degrees to the upper edge, and a lower, irregular edge having the appearance of a plurality of individual roofing shakes. The upper edge is canted upwardly for receipt within a groove in the underside of an upper overlapping panel. In addition, immediately adjacent the canted upper edge, there is a bandlike section through which roofing nails may be applied for securing the panel to the roof. The undersurface of each panel includes a stepped arrangement, not unlike that encountered in a roof constructed of individual shakes, which arrangement enables a pair of such panels to be fitted together with the top surface of one panel contacting the lower surface of another panel and forming a substantially parallel surface package for storage and shipment.

Abstract: A proportional counter neutron detector in which the neutron absorptive material is isolated from the poly-atomic fill gas by a thin film of selected metal or metal oxide, which is substantially transmissive to neutrons, and is non-reactive with the dissociation products of the poly-atomic fill gas.