Abstract: A new process for marking currency to permit easy and positive authentication at a later date comprising exposing a small region of the currency to bombardment by high energy neutrons for a short period, treating the exposed small region with a chemical reagent which reacts with the treated area to form tiny holes which can later be used for authentication. Also provide is a method for authentication which comprises exposing the marked currency to monochromatic X-rays, allowing the transmitted beam to impinge upon a fluorescent screen which will show shiny dots where the beam has reached the screen, said dots corresponding to the tiny holes in the marked currency.

Abstract: A process for dissolving deposits of metal oxides, and preferably iron oxides including magnetite without materially impairing the surface on which the deposits reside, which comprises contacting the solid metal oxide with a liquid medium composition comprising (1) an alkali metal borohydride, (2) a chelating agent which forms a metal complex with the metal oxide, said chelating agent being preferably a dialkali metal salt of a polyalkylene polyamine tetraalkanoic acid. The process is particularly effective for the dissolution of Fe.sub.3 O.sub.4 (magnetite) entrapped in the tube-to-tube sheet crevices of nuclear steam generators.

Abstract: Structural failures, as in metal aircraft structures, are rapidly detected and measured by use of a new detection system comprising a thin film adhesively bonded to the metal structural surface to be monitored, said film containing a plurality of thin continuous strips which are adapted to be broken when a crack appears under the strips, said strips being substantially parallel but insulated from each other and the metal structural surface and arranged in a pattern such that there is frequent change in direction of the strips as in a zig-zag or rectangular pattern, each of said strips constituting a separate circuit joined to an electric power source and a sensing and recording means capable of detecting and recording any circuit failure caused by disruption of the metal strip, said disruption being caused by the formation of a crack under the said strip.