Abstract: A method of forming optical waveguides is described in which a film of a novolac resin is deposited on a transparent substrate and a dopant material is incorporated into the film during or after the coating step. Additional quantities of the same or different dopant may be incoporated into the dried film by solvent assisted indiffusion.

Abstract: The invention describes an optical data storage medium in which the optical contrast of stored data bits is enhanced by the use, as a photosensitive material or as an additional photosensitive material, of a layer of a photochromic fulgide.

Abstract: A method of marking an article or substrate with a mark or device which is made visible or is enhanced on exposure to U.V. light which comprises printing onto the article or substrate a photochromic ink containing a photochromic compound which is reversibly converted to a colored form on exposure to U.V. light and reverts to a substantially colorless form in the absence of U.V. light and applying a superficial protective layer to said mark or device which protects the phototochromic compound against degradation by atmospheric moisture and oxygen. In addition the invention includes a security device in the form of a label, document or card which incorporates a mark or device which is partially or wholly invisible in light which does not contain a U.V.

Abstract: A chromatographic separation device comprises a body 2 of a semiconductor material which body has a longitudinal channel 1 formed in a surface thereof, the channel 1 being capable of containing a predetermined volume of a liquid or solid material for a chromatography test or separation procedure, the channel carrying at least one electrode 6 positioned intermediate the channel ends. The semiconductor body may additionally support an electronic or optical sensor 8 arranged in line with said channel 1 to provide an integrated detection system.

Abstract: An optical waveguide and method of fabricating waveguide structures is disclosed. More specifically, a method of producing an organic waveguide which comprises treating a transparent plastic substrate with a solution in a inert solvent of an organic dopant which is absorbed into the surface of the substrate, under conditions such that a surface layer is formed having a refractive index which is greater than that of the substrate. Said dopant has a higher affinity for the plastic's substrate than for the solvent.

Abstract: Photoreactive plastics lenses are disclosed which are coated or impregnated with an adamantane 2-spiro-benzo or naphthopyran and with a blue coloring photochromic benzo- or naphthopyran having a nitrogen containing substituent in the 2-position in the pyran ring. The lenses darken in sunlight and fade rapidly at ambient temperatures in the dark or in white light which does not contain a U.V. component. The combination of the yellow/orange coloring adamantane 2-spiro pyran compound with the purple/blue coloring pyran gives a desired brown/grey coloration in the sunlight-darkened lens. The invention includes novel blue-coloring pyran compounds in which the nitrogen-containing substituent in the 2-position is a phenyl group having an amino or substituted amino or nitrogen-containing heterocyclic substituent in the ortho- or para-position of the phenyl group.

Abstract: A photochromic ink composition which comprises a solution of a 1,2-dihydroquinoline (DHQ) in a polymer solution, the dihydroquinoline being sensitive or sensitized to ultra-violet light.

Abstract: The plastic encapsulation material covering an integrated circuit is impregnated with a corrosion inhibitor evenly dispensed throughout the material. This inhibits the corrosion of the metallization on the surface of the integrated circuit thus prolonging the life of the device particularly under adverse environmental conditions.

Abstract: Small lengths of conductors, cut to the appropriate size are used as radar "chaff" or passive reflectors to give spurious returns on an enemy radar and thereby act as an electronic countermeasure. Currently used chaff includes chopped aluminum foil, aluminum coated glass fibres and silver coated nylon monofilaments. Current radars operate in the 10.sup.10 Hz region and current chaff dipoles are of centimetric size, but future radar systems are likely to operate at higher frequencies requiring shorter dipoles lengths to achieve an increased packing density the dipoles also need to be thinner. Carbon fibres have advantages over existing chaff materials as they are fine, light and much stiffer than existing chaff materials. The electrical resistance is about 1000.times.higher than that of aluminum however and this invention therefore proposes the use of carbon fibres coated with a much more conductive coating. Typical coating materials can be copper, silver aluminium applied by a number of different methods.

Abstract: A conductive gasket for use in electro magnetic interference protection of electrical apparatus comprises an elastomeric material in which high aspect ratio conductive fibres are embedded to provide the conductive paths across the gasket. Preferably the fibres are carbon fibres.

Abstract: A light transmission guide comprising an anodic film of light transmitting material having a first anodised portion with a relatively high refractive index and at least a second portion with a relatively low refractive index, in which anodic film the increase in refractive index from said relatively high to said relatively low value is smooth and continuous in the vicinity of an interface between the first and second anodised portions, and in which the outer surface of said anodic film possesses a minimum amount of structural discontinuity on an atomic scale.