Abstract: The invention provides a liquid crystal device having an aligned and surface tilted liquid crystal layer contained between two cell walls. The cell walls carry electrodes for applying voltages across the layer thickness to provide a display. The alignment is provided by a layer of a material that undergoes optically induced ordering during cross linking. That is, a material capable of aligning liquid crystal molecules after cross linking with polarized light. One such material is polyvinylcinnamate. The aligning layer is profiled with an asymmetric grating, eg approximately sawtooth in cross section by interferometer, oblique incidence photolithography, or embossing. The shape of the grating provides the surface tilt. The liquid crystal material may be nematic, cholesteric, or smectic.

Abstract: A method of making a boron carbide article by sintering includes mixing boron carbide with an epoxidized resin in solution and drying to form a granulated homogenized mixture and a carbonization cycle in which the mixture is maintained at at least two constant temperatures for predetermined times. The rates of temperature rise are at controlled rates sufficient to allow outgassing of the gases evolved during the decomposition of the resin.

Abstract: Ammunition round comprising a primary cartridge (1) and a secondary cartridge (2) provided with mutually cooperable push fit connection means for connecting the two cartridges during loading. The cartridges (1, 2) incorporate sockets (10, 12) which contain and are connected by a connecting piece (14). Socket (12) includes a cavity (20) having sufficient longitudinal depth to allow some axial movement of the connecting piece (14) ensuring that strain on the connecting piece (14) during loading is minimized.

Abstract: A multi-functional epoxy resin with good high temperature properties allowing prolonged service at temperatures above 120.degree. C. is derived from a precursor of formula (I): ##STR1## in which R.sup.3 to R.sup.8 inclusive are independently selected from hydrogen, C.sub.1 to C.sub.3 alkyl or halo-alkyl and R.sup.9 is hydrogen, alkyl or halogen, and in which n has the value 0, 1 or 2. The precursor (I) may be self-coupled or cross-coupled with precursors of other epoxy compounds of the TGDDM type. Such cross-coupling gives rise to a complex mixture containing not only the mixed product, but also the self-coupled products of each constituent. Regardless of the precise chemical make-up of the mixture, the observed glass transition temperature is higher than for TGDDM resins formed without precursor (I). If the substituent at the R.sup.9 position is alkyl or halogen, oligomer formation is suppressed and a less complex mixture results.

Abstract: A multi-sensor flow-through system which mitigates or at least overcomes any cross field effects between different sampling conduits comprising a plurality of flow-through sample cells (2), wherein each sample cell (2) is provided in an independent and isolated sample channel (16a, 16b. . . ), whereby fluid flowing within each channel (16a, 16b, . . . ) is isolated from fluid flowing in neighboring channels (16a, 16b, . . . ). In one embodiment of the multi-sensor system, each sensor cell (2) operates as an autonomous and independent unit isolated from all other units. Ideally, each of the sample channels (16a, 16b, . . . ) are also independent and isolated from other sample channels (16a, 16b. . . ). The multi-sensor system can additionally have the exit end of the channels (16a, 16b, . . . ) feed into a well in such a way that free space is provided between the ends of the channels and the uppermost surface of fluid in the well.

Abstract: Gas detector includes structure (10) defining a gas flow passage (11), means (12) for passing an ultraviolet light beam (13) across the passage, and first and second electrodes (16, 17) downstream of the ultraviolet light means (12), at least one of the first and second electrodes (16, 17) being in the form of a series of electrically separate segments (16a, 17a) extending in a downstream direction, the electrodes (16, 17) being connectable to potential applying means (18) and to means (20) whereby the current passing through each segment (16a, 17a) of a segmented electrode (16, 17) can be measured.

Abstract: This invention relates to apparatus for adding mercury ions to a sample fluid within a flow-through sensor system comprising housing means in fluid connection with a main sample stream conduit via a semi-permeable part (2.11), a first electrode (2.8) located within the housing means preferably designed so that it would be in electrical contact with only the mercury when the mercury is located within the housing means, and a second electrode (2.12) located ideally within the main sample stream conduit, the apparatus being arranged such that when mercury is located within housing means and an electrical current is passed between the first and second electrodes, mercury ions are formed in the housing means which then are able to migrate from the housing means via the semi-permeable part into the main sample stream conduit.

Abstract: A waveguide laser (10) incorporates a guide (12) and two concave resonator mirrors (14, 16). The guide (12) is of square section with side (2a), and of length L equal to 4a.sup.2 /.lambda., where .lambda. is a laser operating wavelength. The mirrors (14, 16) are phase matched to respective Gaussian intensity profile radiation beams with beam waists at respective waveguide end apertures (20, 22). Each beam waist has a radius w.sub.0 in the range 0.1a to 0.65a to avoid waveguide edge effects and excitation of unwanted high order waveguide modes. The laser (10) has good transverse spatial mode characteristics.

Abstract: A resonant power circuit which supplies pulsed power to a load, such as a pulsed laser, from a d.c. supply by cyclically charging a capacitor. The capacitor is discharged through the load on closure of a switch which should then open to allow the capacitor to re-charge. Occasionally the switch fails to open and the circuit of the invention then develops and applies a reverse voltage to the switch to force it to become open circuit.

Abstract: A children's speech training aid compares a child's speech with models of speech, stored as sub-word acoustic models, and a general speech model to give an indication of whether or not the child has spoken correctly. An indication of how well the word has been pronounced may also be given. An adult operator enters the word to be tested into the training aid which then forms a model of that word from the stored sub-word speech models. The stored acoustic models are formed by first recording a plurality of words by a plurality of children from a given list of single words. These recordings are then processed off-line to give a basic acoustic model of an acceptable or correct sound for each phoneme in the context of the pre- and proceeding phonemes. The acoustic models are Hidden Markov Models. The limits of acceptable pronunciation applied to different words and children may be adjusted by variable penalty values applied in association with the general speech acoustic model.

Abstract: A liquid crystal polymer or copolymer is disclosed of structure (A) where X=CN, COR, CO.sub.2 R, CHO, CF.sub.3 ; R=branched chain, straight chain or chiral alkyl; .rect-hollow.=any suitable mesogenic group; Z=single covalent bond, oxygen, sulfur, CO.sub.2 or OCO; n=1 to 20; Y=H, OH, F, OCH.sub.3 ; m=3 to 200; P=a single covalent bond, oxygen, or OCO.

Abstract: A laser device incorporates a rectangular multi-mode beamsplitter waveguide connected at one end to a retro-reflecting mirror. The beamsplitter waveguide is connected at a second end to an output coupling waveguide and a reflection coupling waveguide. The reflection coupling waveguide is terminated by a second retro-reflecting mirror. Radiation produced within the device is reflected by the mirror and coupled to the two coupling waveguides in a manner such that a partially reflecting mirror is not required at an output to the device.

Abstract: A composite gas filtration system for removal of toxic or harmful agents from a breathable gas supply, wherein a compressor fed pressure swing adsorption unit is placed upstream of an adsorbent carbon filter unit in a gas supply line, characterized in that a plenum chamber is positioned in the gas supply line with one or more inlet orifices supplied by gas treated by the pressure swing adsorption unit, one or more exit orifices leading to the carbon filter unit, and one or more further inlet orifices supplied by gas from upstream of the pressure swing adsorption unit, wherein a device for drawing or propelling breathable gas through the plenum chamber and carbon filter from the further inlet orifices in the event of shut down of the pressure swing adsorption unit and/or compressor is provided.

Abstract: A muzzle brake for reducing gun recoil comprises a hollow cylindrical tube (7) having an open forward end and having at least two apertures in the cylinder wall (4) each which is provided with closure means (6) mounted on the tube so as to be movable between a closed position and a fully open position. Each closure means (6) has at least one associated biasing member (22) to bias it into the closed position, which is preferably preloaded to introduce an inertia into the movement of the closure means (6) which is of such a degree that the rapid blast pressure wave passes with little effect, but the longer exhaust wave effects opening. The brake further comprises at least one rearwardly directed gas deflecting surface (13, 30) to deflect the exhaust wave gases rearwards and produce a braking effect.

Abstract: A method for detecting the presence and/or mount of microorganisms is described by adding adenosine diphosphate (ADP) to a sample suspected of containing microorganisms and/or their intracellular material, determining the amount of adenosine triphosphate (ATP) generated by adenylate kinase present, for example using a bioluminescent assay involving luciferase and luciferin, and relating the results to the presence and/or amount of microorganism. Test kits and apparatus for use in the method are also described.

Abstract: An optical system mounted on a helmet (29) for superimposing a collimated image of a display object on the external view of the helmet's wearer comprising: display object means (1a, 1b) mounted on the helmet for generating a display; a concave collimator (6a, 6b) for collimating light from said display; an optical relay unit (3a, 3b) located in the forehead region for generating an intermediate image of said display in the focal plane of the collimator; a reflecting surface (4a, 4b) for reflecting display light from the relay unit towards the collimator; and an inclined combiner (5) essentially transparent to incoming display light and to the wearer's external view, for reflecting display light reflected from the collimator towards the viewer's eye.

Abstract: The invention provides a surface, or electric field, stabilised ferroelectric liquid crystal (SSFLC) device with an improved contrast ratio between its two switched states. The device comprises a liquid crystal cell formed by a thin layer (7), typically 1 to 5 .mu.m thick, of a smectic liquid crystal material, eg a smectic c, held between two glass walls (2, 3) coated on their inner faces with electrodes (5, 6). Polarizers (8, 9) are arranged either side the walls (2, 3). The device is switched between two bistable states by application of unidirectional voltage pulses, with or without the simultaneous application of ac bias voltages. To obtain optimum contrast ratio CR, the optical axis of the polarisers are rotated away from a crossed, or othogonal position. eg by +/-20.degree., and the cell rotated between the polarisers (8, 9); the precise optimum rotation depends upon material, and ac bias voltage.

Abstract: A color display device (10) incorporates three light sources (12) supplying red, green and blue light respectively. A spatial light modulator (20) is positioned to provide time varying selective blocking of light from the sources (12) under television signal control. Light passes from the sources (12) to a condenser lens (16), then through a liquid crystal display element (22) and a projection lens (18) before reaching a screen (30). The display element (22) is also under television signal control. Signals supplied to the display element (22) provide for successive sets of three frames to be displayed, each set incorporating frame information to be displayed as red, green and blue and combinable to form a colored frame. When the element (22) displays a frame corresponding to one of the three colors red, green and blue, the modulator (20) transmits that color and blocks the others. The screen (30) receives a color image in which red, green and blue are displayed successively for each frame.

Abstract: A novel LCP material based on forked side chain acrylates is disclosed having a general formula I; ##STR1## wherein W=H, CH.sub.3, Cl R.sub.1 and R.sub.2 may or may not be the same but have the following general structure: ##STR2## p=2 to 14; q=0 or 1;r=1 or 2;s=1 or 2;X=O, CO.sub.2, O.sub.2 C, CH.sub.2 ;Y=C.sub.2 H.sub.4, O, CO.sub.2, O.sub.2 C;Z=CN, halogen, R, CO.sub.2 R, OR, O.sub.2 CR, wherein R=chiral or achiral.

Abstract: A vehicle intruder detection system including at least one pressure operated switch which comprises a first, movable, conductive strip contact and a second, fixed, conductive strip contact. The second contact is attached to a fixed surface located within a vehicle interior so that the first contact is located in proximity, but not fixedly attached, to an internal face of a vehicle window. Each switch is connected into a circuit which incorporates an alarm, which is then triggered by application of a force to the external surface of a window sufficient to bring the first and second contacts together to close one of the switches.