Abstract: A wall assembly consisting of at least an upper, an intermediate and a lower sheet of a rigid material, each sheet being poked with a plurality of similar protuberances and cavities extending on opposite sides of the virtual plane defined by the sheet in alternating fashion, whereby each cavity is surrounded solely by protuberances and each protuberance is surrounded solely by cavities. The sheets are glued to each other in superimposed fashion. Gaps are defined between the sheets, wherein an upper and a lower layer of undulating channels are defined thicknesswisely of the wall assembly. The wall assembly may be used as a structural wall or panel or as a heat exchanger, wherein the channels are arranged in two sets for the passage of two different fluids whereby thermal exchanges therebetween may occur.

Abstract: A weapon for propelling missiles, such as arrows, quarrels and the like, which looks like a sub-machine gun and is characterized by a compact missile-propelling assembly which is co-planar with the stock, contrary to the long bow which extends transversely of the stock of a conventional cross-bow. The missile-propelling assembly includes a modified toggle lever system which is spring actuated and is arranged to constantly accelerate the missile during the propelling stroke. The lever system is braked by the spring at the end of the propelling stroke, thereby avoiding any noise.