Abstract: Disubstituted ethanes having a formula ##STR1## wherein R is alkyl, X is selected from hydrogen, ##STR2## wherein each R.sub.1 is selected from H, alkyl, alkoxy, halo and cyano and each of Q.sub.1, Q.sub.2, Q.sub.3 and Q.sub.4 is independently selected from H and F are useful as components of liquid crystal materials for electro-optical displays and compounds useful in the production of such components.

Abstract: Apparatus to focus light onto a given surface, having a light focusing device which has appreciable chromatic aberration; a variable wavelength light source, supplying light through the focusing device to the given surface; a focus detecting device to receive light from the source reflected from the given surface; and control and indicating devices responsive to the wavelength of the light source and to the focus detecting device to vary the wavelength of the light from the light source to maintain the light in focus on the given surface.

Abstract: A receiver for a navigation satellite system such as NAVSTAR, including an antenna for receiving an incoming coded, time-based, spread spectrum signal which includes navigational data from a plurality, P, of satellites, a circuit for deriving baseband I and Q components of each of the signals, circuitry for digitizing the I and Q components, a Fast Fourier Transform (FFT) processor for transforming the digitized I and Q components and their respective codes, and a multiplier for multiplying together the transformed components and codes derived for each of the P satellite signals and to inverse transform the signals and to then determine correlation peaks in the inverse transformed signals.

Abstract: A condenser including a condenser chamber having an extension portion extending through the base of a refrigerant storage vessel. The length of the conduction path along this portion is variable. This may be performed by partial retraction of the extension from the vessel, or by inclusion of one or more insulating shields. Both extension and shield may be threaded. The vessel may be of thin stainless steel or compliant solid insulating material, allowing fine adjustment of the conductive path length by tightening of the shield against the base of the vessel. The internal surface of the chamber may be undulated, in particular by threading, to promote turbulent flow and mixing within the chamber. The extension may be recessed and joined to a filling tube, to facilitate initial cool down. The complete condenser is encased by expanded polyurethane foam inside a box.

Abstract: The invention provides a linear beam tube which may be protected against high voltage arcs between the cathode and anode of its electron gun by connecting to ground a limiting impedance in a series path from said anode. The anode is carried upon the end of a ceramic cylinder which is co-axially within a conical metallic member. The end of the ceramic cylinder remote from the anode is attached to one end of said conical metallic member, the other end of which is flanged, with the flange passing through the tube envelope to provide an external termination which may be connected to ground. Resistive material is deposited in a groove in the inner surface of said ceramic cylinder to form a deposited impedance which extends from the anode over the end of the ceramic cylinder, to the end of the conical metallic member and constitutes said limiting impedance.

Abstract: A method of producing an adduct of an organometallic compound M(R.sup.1).sub.3 where M is either indium or gallium and (R.sup.1).sub.3 represents a plurality of organic radicals which may be the same or different, preferably methyl or ethyl groups, comprising electrolysing, using a sacrificial anode of the metal M, a solution containing components 1 and 2 as follows:component 1: one or more organomagnesium halide compounds R.sup.1 MgX where X is a halide radical selected from Cl, Br and I; where R.sup.1 represents one of the groups contained in (R.sup.1).sub.3 ;component 2: a polar aprotic liquid which is a solvent for component 1, e.g. tetrahydrofuran, diethyl ether, di-isopentyl ether, di-n-butyl ether, diphenyl ether or anisole.Preferably, the solution electrolysed additionally contains a third component, component 3, which is one or more organic halides R.sup.1 X.sub.A, where R.sup.1 is one of the groups contained in (R.sup.1).sub.3, X.sub.

Abstract: An electrochemical cell system suitable for use in a thermal battery based on a cathode incorporating an active material consisting of a mixture of LiV.sub.2 O.sub.5 and VO.sub.2, is disclosed. The cathode material is intended primarily for use in cells with lithium or lithium alloy anodes and lithium halide electrolytes.

Abstract: A liquid crystal device comprises a layer of long pitch cholesteric liquid crystal material incorporating a pleochroic dye. The layer is contained between two cell walls surface treated to align liquid crystal molecules in a tilted homogeneous structure. The surface alignment and natural pitch of the cholesteric material are matched to provide a progressive molecular twist of between .pi. and 2.pi., preferably about 3.pi./2, with a uniform tilt direction. The ratio natural pitch P divided by thickness d of the liquid crystal layer is arranged to lie between 0.5 and 1.0, with a value of d less than 20 .mu.m. Both low tilt and high tilt surface alignment may be used separately or in combination. Polarizers may be used to enhance between ON and OFF states. The device has a sharp transmission/voltage characteristic which enables it to be used in large multiplex addressed matrix displays.

Abstract: An electrometer amplifier with automatic zero-error correction in which the input current is switched periodically between two amplifier channels by twin reed switches 2,2', the channel outputs being switched in synchronism (15,15') to a common output 19. Each channel includes a current-to-voltage converter 3,4; 3',4' feeding an amplifier 8,9; 8',9', followed by an integrator and store 11,12,13; 11',12',13' whose output is continuously fed back negatively to the input of this amplifier but whose input is synchronously switched (10,10') into connection with the amplifier output only when that channel is disconnected from the input terminal 1. During the latter period capacitors 13,13' store a voltage corresponding to the zero error in the circuitry preceding amplifiers 8,8', so that the stored value (periodically updated) continues to cancel the zero error when terminal 1 is reconnected to that channel and switch 10,10' reopens.

Abstract: A thermal imager includes an infrared sensitive light valve and a light source arranged to illuminate the full responsive area of the valve. The imager also includes an optical stage having focussing optics for forming an infrared image upon the surface of the valve and a chopper for modulating infrared radiation from a scene. Modulated light from the valve is read out in parallel by a detector array, and frame signals corresponding to alternate positions of the chopper are subtracted to provide uniformity correction. The light valve may comprise an infrared sensitive optically active liquid crystal cell and an analyzer adjusted to near extinction. An optical processor comprising a lens and an apodized stop filter lies in the light path between the valve and the detector array. The light source may comprise an array of light emitting diode elements and the filter a number of corresponding off-axis stop regions.

Abstract: Novel terphenyls having a relatively high clearing point and which are suitable for use in liquid crystal materials or in the preparation of compounds for use in such material are characterised by a formula: ##STR1## wherein: R.sub.1 is selected from H, alkyl, alkoxy, alkylcarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy;R.sub.2 is selected from H, alkyl, alkoxy;X.sub.1 is selected from H and fluorine;X.sub.2 is selected from H and fluorine; and ##STR2## is selected from ##STR3## and ##STR4## provided that one of X.sub.1 and X.sub.2 is fluroine. Compounds wherein ##STR5## is ##STR6## or ##STR7## are generally useful as liquid crystal compounds.

Abstract: A remotely controllable gripper for picking up and setting down objects of various shapes and sizes, comprising a plurality of gripper arms which can be drawn together to enfold the object, by a continuous snare line attached to a support plate and engaged, via a parallel thrust plate, with each of the arms. The snare is tightened by increasing the separation of the thrust plate from the support plate by the operation of an interjacent bellows actuator.

Abstract: A liquid crystal display includes a liquid crystal cell formed by enclosing a thin layer of a cholesteric liquid crystal material between two slides. A set of electrode structures is formed on each slide so that voltages may be applied to the liquid crystal material causing an observable display effect. Voltages are supplied to the electrodes in sequence by driver electronics under the control of a logic unit which also controls a variable voltage source supplying voltages to the driver electronics. The logic unit controls the drive electronics to give an R.M.S. voltage V.sub.x at elements required to be at an OFF state and an R.M.S. voltage V.sub.c higher than V.sub.x at elements required to be in an ON state. The logic unit also controls the voltage source to reduce its voltage output to both OFF and ON elements simultaneously while maintaining the ratio of V.sub.x and V.sub.c for a period while information displayed is to be changed.

Abstract: On an aircraft having spoilers on the wing, the spoilers are converted, according to this invention, following the ACT philosophy, for use in countering gust effects. Accordingly, a sensor of gusts is arranged to transmit warning of the arrival of a significant gust to a spoiler operator which, taking into account airspeed, deploys the spoilers in a mode so that a phase of spoiler generated lift decrement is timed to coincide with effective arrival of the gust.

Abstract: The reflectance of a mirror is variable to provide a dipping car mirror. The mirror comprises a liquid crystal cell formed by two transparent slides coated on their inner surfaces with electrodes. The front electrode is transparent while the rear one is a reflector or a separate reflecting surface is provided. Between the slides is a layer 8 to 12 .mu.m thick of a cholesteric liquid crystal material. The slides are surface treated to give a high tilt homogeneous boundary condition, i.e. the liquid crystal molecules at the slide wall incline at a high (20.degree.-75.degree.) tilt to the surface. A control unit applies either a high voltage (10 volts at 1 kHz) or a low voltage (1 to 2 volts at 1 kHz). The high voltage results in the liquid crystal adopting a light transmissive state. In this state light reflects off the rear of the cell. The low voltage state is a scattering state for the liquid crystal material.

Abstract: A ceramic mould is supported on a stainless steel platform carried at the upper end of a water-cooled tube surrounded by a copper cylinder containing alumina powder of approximately 100 .mu.m particle size which is fluidized by an inert gas. Metal in the mould is melted by a furnace which surrounds the mould and the mould is progressively withdrawn into the fluidized bed by which heat is extracted and transferred to water cooled coils surrounding the copper cylinder. In a modification, the inert gas is drawn from the fluidized bed by way of a filter and vacuum pump whereby the outlet pressure is reduced to about 1 torr. This reduces the risk of contamination of the alloy and permits re-use of expensive cooling gases.

Abstract: A fiber reinforced metal is made by introducing an array of fibers into a die, charging the die with molten metal by vacuum infiltration and then applying pressure by means of an inert gas to improve the penetration of the molten metal into the fiber array. Apparatus for producing a reinforced metal cylinder comprises a cylindrical former (2) onto which a composite fiber (3) of boron, silicon and carbon is wound. The former (2) forms an inner closure member for the die defining a cylindrical die cavity (8) with an outer die body (4). A central cavity (15) within the former (2) is for insertion of a heating element to facilitate the flow of metal through the cavity (8). The die cavity is evacuated via conduit (16) and molten metal is then drawn into the cavity via the passage (7). After charging the die with molten metal the conduit (16) is connected to a source of high pressure nitrogen.

Abstract: An infra red photo detector system comprises a piece of detector material, such as Cd.sub.x Hg.sub.1-x Te, InSb, InAs, etc, carrying at least a pair of spaced electrodes. An optical arrangement directs a small spot of radiation onto the detector. The position of the small spot on the much larger detector is found by applying an electrical bias between the electrodes causing a drift of photo carriers. The bias may be of alternating polarity and the detector output measured at each polarity. Alternatively a high frequency bias may be applied and the A.C. offset from the detector used to indicate spot position. Alternatively the spot position may be modulated or swept along the detector by a mirror moving in a sawtooth scanning action.

Abstract: A fascine capable of conforming to the contours of a supporting surface, comprises a core of cylindrical pipes loosely disposed within a surrounding flexible sleeve comprised of similar pipes transversely and continuously interconnected by tensioned flexible ties. All the pipes are capable of elastic cross-sectional deformation, the sleeve pipes being held in diametral compression by the flexible ties to provide increased resistance to external compression forces acting substantially perpendicularly to the direction of diametral compression, and the core pipes being selected to have less resistance to deformation than the sleeve pipes so as to absorb external point loading forces acting on the sleeve pipes. The fascine is suitable for use by both wheeled and tracked vehicles.

Abstract: A layer of Cd.sub.x Hg.sub.1-x Te is grown on a substrate by growing layers of HgTe t.sub.1 thick, and CdTe t.sub.2 thick alternately. The thicknesses t.sub.1 and t.sub.2 combined are less than 0.5 .mu.m so that interdiffusion occurs during growth to give a single layer of Cd.sub.x Hg.sub.1-x Te. The HgTe layers are grown by flowing a Te alkyl into a vessel containing the substrate and filled with an Hg atmosphere by an Hg bath. The CdTe layers are grown by flowing of Cd alkyl into the vessel where it combines preferentially with the Te on the substrate. Varying the ratio of t.sub.1 to t.sub.2 varies the value of x. Dopants such as alkyls or hydrides of Al, Ga, As and P, or Si, Ge, As and P respectively may be introduced to dope the growing layer.