Abstract: A compound of formula (I): where R1 is alkyl or alkenyl, Y1 and Y2 are independently selected from oxygen or sulphur, n is an integer of from 1 to 5, A is an optionally substituted phenyl or an optionally substituted cycloalkyl ring, X is a direct bond, a C1-4alkylene, a C2-4alkenylene, an acetylene, —CO(O)— or a group of sub-formula (i): where X1 and X2 are independently selected from a direct bond, a C1-4alkylene, a C2-4alkenylene, an acetylene, —CO(O)— and R2, R3 and R4 are independently selected from hydrogen, halo or cyano, provided that no more than one of R2, R3 and R4 is hydrogen. These compounds have a high dipole moment and may be used as dopants in liquid crystal mixtures.

Abstract: A composite element comprises:(a) a metal or metal alloy component having an elastic modulus that decreases with increasing temperature in a temperature range; and (b) sufficient amount of a shape memory alloy component having an elastic modulus that shows an increase in elastic modulus with increasing temperature in the said temperature range, such that the elastic modulus of the composite element does not fall substantially as the temperature is increased across the said temperature range. An article comprising such a composite element is suitable for use in high temperature applications, including motor vehicle components.

Abstract: A resonant magnetometer comprises a substrate having a member and circuitry for passing an alternating current (AC) through the member. The magnetometer is characterized in that a driver is also provided to impart a magnetic field independent oscillatory force to the member. Disclosed is a micro-electro mechanical systems (MEMS) implementation of a magnetometer.

Abstract: A bistable display device comprises two cell walls enclosing a sheet having a plurality of cavities each containing a rotatable bicoloured sphere within a liquid crystal material carrier (15), and electrodes for applying an electrical field. The spheres and cavities are provided with a surface alignment which imposes a substantially unidirectional director alignment on the liquid crystal material in contact with them. The elastic distortion free energy of the liquid crystal material in each cavity is arranged to be zero when the preferred direction of the suspended spheres coincides with that of the surrounding cavity, e.g. black upwards. It is also zero when the sphere is rotated through 180° to present its opposite hemisphere which has a contrasting optical appearance, e.g. black downwards. Between these two states, there is an energetic barrier determined by the elastic constants of the liquid crystal which provides both a threshold for switching and improved bistability.

Abstract: A coherent laser radar or lidar device (2;20;84;90) for measuring wind speed is described that comprises a transmitter for transmitting a beam of light to a remote probe volume (6;54), a receiver for detecting back-scattered light and an analyzer for calculating wind velocity at the remote probe volume from the Doppler shift in frequency of the detected back-scattered light. The analyzer is arranged to monitor for the presence of, and/or to ensure the calculated wind speed is corrected for, any Doppler frequency components of the detected back-scattered light that arise from back-scatter off cloud located at a range greater than the range of the remote probe volume. It is described how the lidar (2;20;84;90) may be scanned and wind velocity components calculated by fitting the scanned line of sight velocity values to a predetermined function. Furthermore, it is outlined how an initial fit may be performed to determine which points are to be used in this calculation.

Abstract: An eye tracking system includes an eye camera and a scene camera for supplying video data to interlace electronics indicative of an image of the user's eye and an image of the scene observed by the user. A frame grabber is provided for digitizing the video data and for separating the eye and scene data into two processing channels, and a spot location module determines the location of a reference spot formed on the user's eye. The module includes an adaptive threshold and spot identification sub-modules for indicating parts of the eye camera image which have higher brightness, and for selecting a valid reference spot. A pupil location module determines the user's line of gaze, and a display for indicating the user's point of regard from the user's line of gaze determined by the pupil and spot location modules.

Abstract: A microwave plasma generator including field-enhancing electrodes consisting of opposed laminae (108,109) with a gap (110) between them orthogonal to the direction of propagation through the plasma generator of microwave radiation. Gas inlet (106) and outlet (107) ports are arranged so that a gaseous medium to be excited into the plasma state passes through the gap (110).

Abstract: A fluid temperature measurement probe, particularly for total temperature measurements in high temperature unsteady gas flows, such as in gas turbine engines. A pair of thin film resistance thermometers are deposited on the probe to sense its surface temperature at respective locations and the structure of the probe is configured such that the regions into which heat diffuses from the respective locations have different thermal products. In this way the thin film elements experience different heat transfer rates when exposed to the same fluid temperature. In one embodiment this is achieved by applying one of the elements to the surface of a solid rod of glass or ceramic and the other element to a portion which has been machined to leave an air pocket under a thin cylindrical wall of the rod material. In use the probe is exposed only temporarily to the high temperature fluid and withdrawn again before reaching its softening temperature.

Abstract: A biological sensor, especially a barosensor, which can be operated using a neuronal network is described. Neuronal cultures suitable for use in such a sensor are also described.

Abstract: A long range artillery shell having a rocket motor which comprises a combustion chamber (shown filled with solid propellant 9, burn inhibitor 10, igniter material 13 and propellant support 11,12) which has at one end a plenum chamber 8 and a rocket nozzle 14 for venting the plenum chamber 8. The propellant 9 is arranged in an end-burn configuration and housed within the combustion chamber and the propellant support 11,12 is located between the propellant 9 and the plenum chamber 8 and is capable of preventing entry of unburnt propellant into the plenum chamber 8 while permitting, in use, the substantially unhindered transfer of propellant combustion products to the plenum chamber 8.

Abstract: This invention relates to optical fibres, fibre lasers, fibre laser arrays and sensor systems comprising fibre laser arrays. Conventional fibre laser sensor arrangements comprise a plurality of fibre lasers arranged in series along a length of optical fibre. A pump light source is located a one end of the fibre and supplies pump light energy to each of the fibre lasers in turn. Such sensor systems experience a number of disadvantages. Firstly, there is an uneven distribution of pump power along the length of the fibre which effectively limits the number of laser devices that can successfully be incorporated into the optical fibre array. Secondly, the manner in which existing sensor systems are constructed often results in back reflections, optical losses and mechanical weaknesses. The present invention provides a fibre laser which mitigates the above problems with fibre laser sensor arrays.

Abstract: An illumination source of predominantly non-directional and incoherent millimeter-wave radiation for illuminating an area for passive millimeter-wave imaging comprises a container with at least a partly reflective internal surface and a plurality of exit apertures and a primary source of millimeter-wave radiation for emitting millimeter-wave radiation into the container. The primary source and the container are arranged so that a proportion of the millimeter-wave radiation emitted by the source undergoes reflection within the container before being emitted through the apertures, such that the different paths lengths are at least equal to the coherence length of the radiation. This is facilitated if the bandwidth of the radiation is preferably at least 1 GHz. The container may be a box in which a waveguide is used to couple radiation from the primary source into the box. Alternatively, the container may be formed from a mesh and the plurality of holes is provided by the holes in the mesh.

Abstract: A compound of formula (I) or a dimer thereof; where R1 and R2 are independently selected from optionally substituted alkyl, optionally substitituted alkenyl, optionally substituted alkynyl, a functional group or a group of sub-formula (i) —(O)m—(CH2)p—R7??(i) where m is 0 or 1; p is an integer of from 1 to 12; R7 is a group of formula —CqX2q+1 where q is an integer of from 1 to 12 and X is halogen such as fluoro, or R7 a group of sub-formula (ii) where k is an integer of from 1 to 10, R8, R10, and R12 and each R9 and R11 are independently selected from alkyl, alkenyl or aryl, such as lower alkyl and in particular methyl; provided that at least one of R1 or R2 is a group of sub-formula (i); R3, R4, R5 and R6 are independently selected from hydrogen or halogen, and in particular fluorine, n is 0 or 1, and A is a ring structure as specified. Compounds of formula (I) may have liquid crystal properties and/or be useful in liquid crystal devices.

Abstract: Computer hard disk security comprises encrypting data on a computer's hard disk with a cryptographic key depending partly on computer memory contents, RAM and/or BIOS memory. Memory contents changing with time are excluded. The SHA-1 algorithm cryptographically hashes the memory contents giving a hash for XORing with a user password. XORing provides a result which is used as a password for an encryption unit implementing a conventional full disk encryption technique, such as XORing the password with a hard disk dock number. The key is generated with the BIOS memory configured so that the computer boots only from the hard disk. Hostile alteration of the BIOS memory contents results in failure to decrypt because the key now cannot be used to decrypt the hard disk. This defeats an attacker who alters BIOS settings in an attack with rogue computer boot media such as a floppy disk or a CD ROM.

Abstract: A method of hermetically packaging an electronic device (8), in an enclosure (2) comprising mutually inter-engageable first and second housing members (4, 6), comprising the steps of securing the electronic device (8) to the first housing member (4), engaging the first (4) and second (6) housing members such that an hermetic seal is provided there between, wherein the engagement step is performed in a controlled atmosphere. The hermetic seal may be provided by an interference fit between the first (4) and second (6) housing members or via sealing means (16) interposed between the housing members (4, 6). The second housing member (6) may comprise an optical element (20), for example a window or lens. The packaging method is particularly applicable to packaging thermal detectors, for example microbolometer arrays.

Abstract: A coherent laser radar (lidar) device is described. The device has a transmitter portion that comprises a single wavelength laser source, a conversion means (such as an electro-optic modulator) for producing a combined light beam that comprises at least two component light beams of discrete wavelength from the output of said single wavelength laser source, and transmit optics to direct the combined light beam to a remote target. Each component light beam of the combined light beam traverses the same optical path from the single wavelength laser source to the transmit optics. The device is used to make differential absorption measurements.

Abstract: A system includes a three dimensional display device configured to project computer generated controls and a target image in a three dimensional target volume; and an actuator configured to be worn by an operator. The system further includes one or more sensors configured to sense a movement of the actuator, wherein the controls are configured to be manipulated corresponding with the movement of the actuator within the target volume to alter an appearance of the target image.

Abstract: A vibration sensing device, package and system and a method of manufacturing a vibration sensing device are disclosed. The vibration sensing device comprises a body whose geometry is such that it exhibits flextensional properties.

Abstract: An optical sensor assembly including a coupler and an optical fibre coil. The coupler is attached to the central member of the cable at a position where outer layers of the cable been removed. A first terminal of the coupler is connected to an optical fibre traveling along the cable in a fibre conduit external to the central strength member. A second terminal of the coupler is connected to a first end of the coil and a third terminal of the coupler is connected to an optical fibre a mirrored end. The coil is supported about a tubular mandrel, which mandrel fits over the cable. The other end of the coil is attached to the fibre in the cable. The mandrel is located about the cable at a position covering the coupler and the part of the cable where the outer layers are removed.

Abstract: A metal object detecting apparatus comprising, a transmitter for generating a primary magnetic field having a resultant magnetic field direction which varies along any substantially linear path through a surveillance volume such that at three locations along said path the resultant magnetic field points in three mutually substantially orthogonal directions; a detector for measuring a secondary magnetic field at a plurality of positions as a function of time due to the presence of a metal object within the surveillance volume as it passes a plurality of measurement points there-through; and a processor for determining from the measured secondary magnetic fields a track through the surveillance volume comprising a plurality of locations of the metal object and a magnetic moment thereof at each location, the processor being adapted in use to derive there-from a magnetic signature that is characteristic of the metal object and independent of the orientation and track of the metal object.