Abstract: A collimator is formed of a stack of layers (11) of different thicknesses in a way analogous to a low-pass interference filter. When illuminated by narrow-band light of a predetermined wavelength just within the pass band of the filter, the collimator preferentially transmits light incident within a predetermined angular range, usually near-normal. The collimator is especially useful with photoluminescent liquid-crystal display, having phosphor emitters (17), because the collimator layers can simply be deposited on one face of the liquid-crystal modulator (1).

Abstract: Phthalocyanines of formula (I) are described, wherein M is a metal atom, metal compound or silicon or a compound of silicon or is 2H; R.sub.1 -R.sub.25 may be the same or different, provided that at least one of R.sub.1 -R.sub.25 has the Formula (II), wherein Y groups are independently H, C.sub.1-3 alkyl, halogen or CN; k=0 or 1; l=1-10; m=0 or 1; n=1-10; p=1-10; q=1-20; r=0 or 1; X may be H, Me, etc . . . Compounds of the above formulae are useful in a broad range of applications, including electrooptical devices, and for use in optical recording media.

Abstract: Phthalocyanine of formula (I), wherein M is a metal or is 2H, bonded at 29 and 31 positions shown, R.sub.1 to R.sub.8 are the same or different and are independently selected from C.sub.1 to C.sub.20 alkyl, C.sub.1 -C.sub.20 alkenyl, --X--COO--X.sup.1, --X--O--Y, a, and --X--COZ where X is independently selected from a chemical bond, (CH.sub.2).sub.n where n-0-20 or (CH.sub.2).sub.a CH--CH (CH.sub.2).sub.b where a and b are independently selected from 0-20 and a+b is in the range 0-20, X.sup.1 is independently selected from C.sub.1 -C.sub.20 alkyl or C.sub.2 -C.sub.20 alkenyl, Y is independently selected from C.sub.1 -C.sub.20 alkyl, C.sub.2 -C.sub.20 alkenyl or H and Z is selected from OH or NR.sup.1 R.sup.11 are independently selected from H, C.sub.1 -C.sub.20 alkyl and C.sub.2 -C.sub.20 alkenyl. These phthalocyanines may exhibit discotic liquid crystal phases, absorb infra-red radiation and make good Langmuir-Blodgett films.

Abstract: A microwave connector comprises two substrates arranged in orthogonal planes. A first substrate (2) is formed as a microstrip system (8) with a microstrip component (3) connected via a quarter wavelength taper (4) to a parallel transmission line (5). This transmission line terminates in a short circuit (15) to a ground electrode (7) on the back of the microstrip. A second substrate (10) is formed as a slotline system (9) having a slotline (13) between two sheet electrodes (14). In this slotline is a slot (16) of dimensions slightly less than the slotline width and sufficient length to accommodate the microstrip. The microstrip and slotline are electrically unconnected. Energy transfer between microstrip and slotline, or vice versa, takes place by electromagnetic coupling between the transmission line and the edges of the slotline. The slotline may be formed with an additional substrate and slotline electrode in a triplate configuration. Several microstrip components (8.sub.1 to 8.sub.

Abstract: An optical beam steering device (10) incorporates a laser (12), three Brillouin shifters (22 to 26, 44 to 48, 54 to 58), a four wave mixing cell (40) and a low power beam steering device (62). The first shifter (22 to 26) and the mixing cell (40) contain TiCl.sub.4, and the other shifters (44 to 48, 54 to 58) contain 20% CCl.sub.4 /80% CS.sub.2. The first and third shifters (22 to 26, 54 to 58) frequency downshift the laser beam (16) by .delta..upsilon..sub.A and .delta..upsilon..sub.B respectively. Light (16') from the first shifter (22 to 26) is amplified and provides a first pump beam input to the mixing cell (40). It then passes to the second shifter (44 to 48), for frequency downshifting by .delta..upsilon..sub.B and returns as a second cell pump beam ( 16"). Light (18') from the third shifter (54 to 58) passes via the low power beam steering device (62) to the cell (40) as a weak input signal beam (18").

Abstract: Curable thermosetting prepolymerized imide resin compositions are prepared by chemically reacting, at a temperature below 150.degree. C., a liquid mixture of carboxy-terminated polybutadiene/acrylonitrile (CTBN) and a co-reactant comprising at least one N,N'-bisimide of an unsaturated carboxylic acid of formula (I) where B represents a divalent radical containing a carbon-carbon double bond and A represents a divalent radical having at least two carbon atoms to yield a curable thermosetting prepolymerized imide resin composition containing copolymerized CTBN and co-reactant. A resin composition prepared by this method may be cured at a temperature between 100.degree. C. and 350.degree. C. to yield a fully cross-linked polyimide matrix containing a dispersion of phase-separated solid particles of copolymerized CTBN and co-reactant, the matrix having a lapshear strength at 20.degree. C. at least 50% greater than that of a fully cross-linked polyimide cured from the co-reactant alone.

Abstract: Biphenyl egters of formula (I), ##STR1## wherein formula (II) represents formula (III) or formula (IV), R.sub.1 represents C.sub.3 -C.sub.12 alkyl, alkoxy, alkylcarbonyloxy, alkoxycarbonyl or alkoxycarbonyloxy, j is O or 1 R.sub.2 represents C.sub.3 -C.sub.12 alkyl or alkoxy, one of Q.sub.1 or Q.sub.2 is fluorine and the other is hydrogen, provided that when j is O and formula (II) is formula (III) and both R.sub.1 and R.sub.2 are n-alkyl, then the total number of carbon atoms in R.sub.1 and R.sub.2 is more than 12. These compounds may be used as constituents of liquid crystal mixtures which show a room temperature ferroelectric smectic phase, and a number of such mixtures are described.

Abstract: A method of growing an epitaxial crystalline layer on a substrate which comprises the steps of(a) providing in the reaction zone of a reaction vessel a heated substrate(b) establishing a gas stream, provided by a carrier gas which gas stream comprises at least 50% by volume of a gas which suppresses the homogeneous nucleation of particles in the vapor phase which contains, in the vapor phase, at least one alkyl of an element selected from Group 15 and Group 16 of the Periodic Table,(c) passing the gas stream through the reaction zone into contact with the heated substrate, and(d) irradiating at least a major part of the surface of the substrate with electromagnetic radiation to provide photolytic decomposition of the at least one alkyl and consequential epitaxial deposition of the layer containing the said element across at least a major part of the surface of the substrate.

Abstract: Langmuir-Blodgett(LB) films of ABAB structure in which the compounds A and B are different and contain complementary groups which result in non-centrosymmetry of the layer plane. Three types of structures are described: (1) in which A and B have similar backbones with complementary chromophore groups, (2) in which A and B have similar backbones with complementary functional groups, and (3) in which A and B have related functional groups but complementary backbones.

Abstract: New bicyclohexyls of the formula IR.sup.1 --Cy--Cy--R.sup.2wherein R.sup.1 and R.sup.2 are each alkyl which has 1-10 C atoms and in which one or two CH.sub.2 group(s) can be replaced by 0 atoms, and Cy is 1,4-cyclohexylene,are suitable for use as the coponents of liquid-crystal dielectrics.

Abstract: An adhesion pad assembly for tracked vehicles includes a resilient adhesion pad having a ground engageable face, the pad being laterally confined by an encasement having side walls of a material having greater tear strength and less abrasion resistance than the material of the pad. The encasement provides protection to the pad from tearing by stones as well as reducing deformation heating.

Abstract: A wide track vehicle with improved skid steering by having a chassis (1) supported upon two independently drivable tracks (2) by side support wheels (3) engaged with each track adjacent the outer edges only. Downwardly projecting rubbing strips (11, 12, 13) are attached to the underside of the chassis (1) to engage slideably with each track only when the track is upwardly deflected by uneven terrain. The tracks (2) each rotate upon a plurality of full width direction-changing rollers attached to the chassis and each having a rolling surface which is provided with mud-cutting, helical ridges (18).

Abstract: A diver's mask for use in contaminated water includes a shroud (12) which manifolds the demand regulator exhale port (7) with a second exhale port (9) from the diver's oral/nasal mask (2) to form a gas filled cavity (11). The shroud (12) has an outlet port (13) to the surrounding water (15). When the diver breathes out exhaled gas enters the cavity (11) and the pressure causes the non-return valve (14) of the outlet port (13) to open, allowing gas to escape from the cavity (11) into the surrounding water (15). When the diver stops exhaling, the pressure of the water (15) causes the non-re turn valve (14) to close, leaving a residue of exhaled gas in the cavity (11). When the diver inhales again, the outlet port non-return valve (14) prevents water being drawn into the cavity (11) and non-return valves (8,10) of the exhale ports (7,9) prevent the exhaled gas from being drawn back into the inhaled gas.

Abstract: A flat panel VDU or TV screen has pixel elements controlled by an array of small single crystal semiconductor bars or chips. Power and information are connected directly or capacitatively to the chips; chip surfaces have pick-up pads. X-Y address lines are provided on a VDU panel substrate, and each chip has bridging links to complete continuity of the Y-line. For data address, data lines are provided on the substrate, and decoding an address recognition circuitry is incorporated in each chip. Chips may be responsive to more than one address, and may be addressed either singly or using a single code address. Each chip may control its neighboring pixels. A single crystal wafer is processed and mounted on a support. Chips are defined by back etching the wafer and separated by stretching the support prior to transfer to a substrate. Self aligned electrodes may be produced using a mask stretched on the surface of the support.

Abstract: A vibration sensor for measuring the flow of vibrational energy through a structure comprises four accelerometers (24-27) placed in cruciform arrangement on the surface of the structure. The signals from the accelerometers are processed in pairs using sum/difference amplifiers (36-40) to give two rotational (41, 42) and one translational (43) acceleration signal. The acceleration signals are frequency modulated (46-48) by as local oscillator (53) of preselected frequency, low-pass filtered (62-64) and the rotational acceleration signals (68, 70) then multiplied (72, 73) in phase quadrature (54) with the translational acceleration signal (69). The DC components of the resulting signals (76) are proportional to the time-average vibrational power flow. Knowledge of the flow paths facilitates the design of the structure to minimize effects of unwanted vibrations.

Abstract: An apparatus for ejecting an aircrewmans helmet-mounted electro-optical equipment from an aircraft cockpit comprising an arm having a first end pivotally mounted at a position behind an aircrewmans ejection seat, a second end of the arm having on it a line reel-in apparatus and a flexible line depending therefrom, the flexible line attachable to helmet mounted electro-optical equipment, a guide and damper connecting the arm to the ejection seat, upon operation of the ejection seat the electro-optical equipment being detached from the helmet, the ejection seat rising in the cockpit and causing rotation of the arm about the pivot point, the line reel-in apparatus locking to prevent the line extending and the electro-optical equipemnt being ejected from the cockpit into the airstream by rotation of the arm prior to the ejection seat leaving the cockpit.

Abstract: A photovoltaic solar cell comprises a piece of semiconductor material incorporating a p-type region, an n-type region, a p-n junction between the two, electrodes contacting the two regions, and within its body a lattice defect denuded zone and a lattice defect gettering zone.The defect gettering zone may be a precipitate-rich zone or a region of lattice damage. The denuded zone may include the p-n junction.The semiconductor material may be Si, GaAs or InP.Methods for making the solar cell are described, involving heat treatment steps to produce a denuded zone, nucleating precipitates and generating precipitates. Alternatively precipitation may be nucleated, or a lattice damage zone may be generated, by proton bombardment.

Abstract: A thermoplastic polymeric material comprises a copolymer which is a poly(bisphenol A tere-and/or-isophthalate) copolymer having a molar ratio of phthalate to carbonate units in the inclusive range from 2 to 10, preferably 3 to 8. The material, which may be prepared by techniques which are known, may be used in applications for high temperature transparent thermoplastics, e.g. transparencies for the aerospace industry.

Abstract: A heuristic processor incorporates a digital arithmetic unit arranged to compute the squared norm of each member of a training data set with respect to each member of a set of centers, and to transform the squared norms in accordance with a nonlinear function to produce training &phgr; vectors. A systolic array arranged for QR decomposition and least mean squares processing forms combinations of the elements of each &phgr; vector to provide a fit to corresponding training answers. The form of combination is then employed with like-transformed to provide estimates of unknown result. The processor is applicable to provide estimated results for problems which are nonlinear and for which explicit mathematical formalisms are unknown.

Abstract: A method of preparing a methyl alkyl of formula (R.sub.3 M).sub.x where R.sub.3 represents three alkyl groups R which may be the same or different, M represents a Group III metallic element and x is 1 or 2, which method comprises (a) forming a trialkyl adduct of formula (R.sub.3 M).sub.y. L wherein L represents an aryl-containing Group V, preferably phosphorus, donor ligand provided by an organic Lewis base which is stable at 20.degree. C., and wherein Y is an integer equal to the number of Group V atoms presents in the ligand, and (b) heating the adduct to provide thermal dissociation thereof thereby releasing the alkyl as a gaseous product.