Abstract: A flood defense or water-retaining device 8 comprises a hollow body of an elastomeric material having formations 30, 34 at opposite ends for sealing engagement with complementary formations on adjoining flood defense devices and having complementary formations 22, 24 on upper and lower sides for sealing engagement with complementary formations on lower and upper sides respectively of any similar devices disposed respectively above and below the first-mentioned device. The device 8 has at least one filling opening 40 through which water can be passed into the interior of the device to fill the same.

Abstract: A flood defence or water-retaining device (8) comprises a hollow body of an elastomeric material having formations (30), (34) at opposite ends for sealing engagement with complementary formations on adjoining flood defence devices and having complementary formations (22), (24) on upper and lower sides for sealing engagement with complementary formations on lower and upper sides respectively of any similar devices disposed respectively above and below the first-mentioned device. The device (8) has at least one filling opening (40) through which water can be passed into the interior of the device to fill the same.

Abstract: In a system for security marking a product, a surface of the product 10 is covered by a layer 14 of light-transmitting material which exhibits variations in refractive index throughout the material such that for most angles of view the material acts as a conventional diffuser of light and thereby conceals or obscures a marking 12 applied to a surface of the product and covered by layer 14, but for a critical angle of view, or a limited range of angles close to that critical angle, the layer is effectively transparent allowing unimpeded viewing of the marking. In a variant, the marking is itself incorporated in the layer in the form of refractive index variations in the layer.

Abstract: Anti-counterfeiting marking for documents, which marking may be disguised as an incidental or artistic feature of overall marking on the documents is adapted to be read by a complementary reading device. In one embodiment the marking may be a one, two or three-dimensional statistically fractal marking and is representative of an array of digits in which the value of each digit is represented by the fractal dimensions over a corresponding region or set of regions of the document bearing the marking. Corresponding apparatus for reading the anti-corresponding marking is also provided.

Abstract: This invention relates to the application of techniques based upon the mathematics of fractals and chaos in various fields including document verification, data encryption and weather forecasting. The invention also relates, in one of its aspects, to image processing.

Abstract: A biological process is enhanced by a method and apparatus used to contact a biomass with a gas and with a nutrient liquid. A resiliently compressible porous matrix system containing the biomass is mounted in a reaction vessel containing a body of the nutrient liquid and a body of the gas above the body of the liquid. The body of liquid having an upper surface exposed to the body of gas and defining a liquid-gas interface. The resiliently compressible porous matrix system is located in a position in the reaction vessel so that compressible porous matrix system is partly immersed in the nutrient liquid and partly extends above the upper surface of the liquid into the body of gas.

Abstract: An alarm system for detecting attempted theft of an article includes means incorporated in the article itself and arranged to transmit and to continuing transmitting an alarm signal when the article is removed from its original location. An example of the alarm system provides an audible alarm, or transmitted alarm, and is arranged to be operated when a thief removes or attempts to remove a car radio, cassette player, compact disc player or the like from a car. Unauthorized removal of the unit from a car is detected by the consequent breaking of an electrical circuit which may be the power supply connections to the radio from the car electrical system or may be the connections to the loudspeakers or the radio aerial.

Abstract: A device for distributing a deodorising, fragrancing insecticidal or the like product is arranged to be activated by opening and closing a room door. In one embodiment, the device comprises a spring plastics bracket 10 clipped to the bottom of a door and carrying spring clips 16 supporting for rotation a hollow plastics roller 20 containing a solid deodorant, fragrancing compound or insecticide, and having apertures in its wall to allow vaporised deodorant or the like to escape. The dispersal of the deodorant, fragrance or the like is promoted every time the door is opened and closed and so the rate of use of the deodorant, fragrancer or insecticide is appropriately related to room use.

Abstract: A viewing device for receiving video signals and generating corresponding images for viewing comprising a frame or support, adapted to be worn on the user's head, for example, a frame similar to a spectacle frame. The frame supports a pixelated LCD screen in front of each of the wearer's eyes. Respective optical systems located between the user's eyes and the screens allow the user to view the images generated as if they were at infinity. A light-transmitting microlens screen may be located in front of each LCD screen to produce an improved subjective viewing impression by "de-pixelating" the image.

Abstract: A mask through which a sheet or layer of a photopolymerizable monomer can be exposed to polymerizing light is manufactured by placing a fiber optic plate, or a ground glass plate or the equivalent over the emulsion layer of a photographic plate and exposing the photographic emulsion, through the fiber optic plate or ground glass plate, by a laser beam scanned across the plate in a raster. By this technique, there is produced, over the photographic plate, a random speckle pattern of substantially the same density and intensity over the whole plate.