Abstract: A liquid crystal composition comprises a host material capable of exhibiting a smectic C phase, and a chiral dopant material which imparts or enhances chirality in the host material. The composition exhibits &tgr;-Vmin curves. The chiral dopant material comprises at least first and second chiral centers. The chiral centers individually produce, in the liquid crystal composition, different and complementary temperature coefficients of spontaneous polarization within a predetermined temperature range. The chiral centers are present in the liquid crystal composition in relative amounts such that regions of the &tgr;-Vmin curves across the predetermined temperature range are substantially coincident.

Abstract: An electoclinic device having two spaced cell walls each bearing electrode structures and treated on at least one facing surface with an alignment layer, a layer of a smectic liquid crystal material enclosed between the cell walls, where the liquid crystal material contains one or more of the compounds described by formula I as defined in the specification.

Abstract: A method and apparatus for monitoring a gaseous environment for the presence of cellular material capable of providing a measure of presence and/or numbers of cellular microorganisms, such as bacterial cells, in a large volume of air such as in a warehouse or production facility or in an open air location where bacterial presence is suspected. The method and apparatus are particularly suited for determining the likelihood of pathogenic material being present in an environment by batch or on-line measurement of cell numbers. On-line measurement provides continuous monitoring of an environment for presence of pathogens. The device includes a continuous flow luminometer preferably fed by a cyclone or high velocity virtual impactor and luminescence reagents which detect the amount of ATP or adenylate kinase present in a sample of air.

Abstract: The invention describes liquid crystal compounds of formula (I) which are suitable for use in liquid crystal devices including those devices which exploit the electroclinic effect, ##STR1## where X may be CN, NO.sub.2, CF.sub.3, CF.sub.2 H, CFH.sub.2, halogen, hydrogen, alkyl or alkoxy; X.sub.2 may be CN, NO.sub.2, CF.sub.3, CF.sub.2 H, CFH.sub.2, halogen, hydrogen, alkyl or alkoxy; X.sub.3 may be CN, NO.sub.2, CF.sub.3, CF.sub.2 H, CFH.sub.2, halogen, alkyl, alkoxy or hydrogen; X.sub.4 may be CN, NO.sub.2, CF.sub.3, CF.sub.2 H, CFH.sub.2, halogen, alkyl, alkoxy or hydrogen; provided that at lease one of X or X.sub.2 is CF.sub.3, CF.sub.2 H, CFH.sub.2, CN, NO.sub.2 or halogen; A and B are independently phenyl, mono-fluorinated phenyl, di-fluorinated phenyl or cyclohexyl; Y may be single bond, COO, OOC, C.dbd.C; q may be 0 or 1; R.sub.1 may be an end group of formula (II) wherein Z may be a single bond, O, CO.sub.2, (CH.sub.2).sub.n or (CH.sub.2).sub.

Abstract: Apparatus for the measurement of unsteady gas temperatures comprises (a) a temperature probe having a sensing element. The sensing element has an optical interferometer optically coupled to one end of a first, addressing optical fibre. The interferometer has a first partially reflective surface defined at the end of the addressing fibre and a second partially reflective surface spaced from the first partially reflective surface by an optical path length I.

Abstract: A mid-infrared emitting diode with a substrate which is transparent to radiation produced by the device by virtue of the Moss-Burstein shift which is induced in the substrate by heavy doping. Emission from the device takes place via said substrate with a significant increase in external efficiency due to avoidance of obscuration by metallic contact.

Abstract: A coreless refractory fiber is made by introducing a filament (16) of a starting material into a chemical vapor deposition (CVD) enclosure (10) and then heating the end (21) of the filament by means of a contactless heating source. The source comprises a conducting coil connected to an AC source in the frequency range HF to UHF and with a linear or strip conducting element (110) connected to it such that the ends of the element is adjacent to the end (21) of the filament. The filament (16) is then withdrawn such that refractory material is continuously built up on its end from the chemical vapors in the enclosure to form a coreless retractory fiber. Whiskers of a coreless refractory material may be made by introducing fine particles of a catalyst material to form droplets and then feeding CVD gases to the droplets (30) to thereby promote crystal growth by precipitation from the supersaturated liquid.

Abstract: A method for forming a layer of a Group II or III fluoride on a semiconductor substrate (e.g. as epitaxial insulating layer) comprising vaporizing a precursor (I), where M is Be, Ca, Sr, Ba or lanthanide, b and d are 0 or 1. A, B, C and D are independently (IIA) or (IIB), X being O, S, NR, PR where R is H, alkyl, perfluoroalkyl; Y is perfluoroalkyl, fluoroalkenyl, fluoroalkylamine or fluoroalkenylamine; Z is H, F, alkyl, perfluoroalkyl or perfluoroalkenyl; and then decomposing the precursor vapor to form M fluoride. A preferred precursor for calcium fluoride is calcium 1,1,1,5,5,5-hexafluor-2,4-pentanedione complex where b and d are 0.

Abstract: A micro pyrotechnic train is formed from a reactive laminate comprised by a plurality of thin films of an electron acceptor material (9) and an electron donor material (10) alternately layered upon a substrate layer by vacuum deposition. The thus deposited films are then removed from selected areas by etching, using standard printed circuit board techniques, to leave a desired network of reaction progression paths (2). The thickness of the films is of substantially molecular order to maximize molecular intermingling between them, and the number of films is selected to ensure a reliable burning characteristic. Ignition of the conjoint films at any selected location initiates a self-sustaining exothermic reaction which progresses laterally along the film interfaces.In further aspects the reactive laminate is applicable as an infra-red emitting coating and as a flash transmitter.

Abstract: An energy absorbing device, suitable for use in the leg structure of aircraft passenger seating for the purpose of attenuating crash forces, having first and second attachment fittings 11, 21 with a tube 10 of fiber reinforced plastics material extending between them. Tube 10 has a crush initiation band 17 at which buckling of the tube commences upon compressive overload. Long, tough fibers are used as the reinforcing material in the tube so that, when compression of the device has concluded, there is a residual tensile capability. Successful operation of the device is facilitated by providing attachment fitting 12 with a slider 15 which helps to maintain the collapsing portion of the tube in axial alignment with the uncollapsed portion. The slider also acts as a tube wall straightener to unbuckle the collapsed fibers when tensile load is applied.

Abstract: A liquid crystal material which comprises a mixture of compounds includes at least one low viscosity additive compound of Formula (I) as follows:A--CH.sub.2.CH.sub.2 --B Formula (I)wherein A is selected from: ##STR1## and B is selected from: ##STR2##where R.sub.1 is selected from alkyl, alkoxy, alkylcarbonyloxy and alkoxycarbonyloxy; and R.sub.2 is alkyl; and where ##STR3## is a benzene ring; ##STR4## is a cyclohexane ring, which is in the trans-configuration if di-substituted; and ##STR5## is a bicyclo(2,2,2)octane ring.

Abstract: A material suitable for a guest-host liquid crystal device comprises a solution of a liquid crystal material and a pleochroic dye wherein the pleochroic dye comprises at least one anthraquinone compound free from water solubilizing and ionic substituents and having the formula: ##STR1## wherein P is OH or NH.sub.2 ; each group X.sup.A is independently selected from OH, NO.sub.2, SR and NZ.sub.1 Z.sub.2 provided that one group X.sup.A is SR and the other group X.sup.A is OH, NO.sub.2 or NZ.sub.1 Z.sub.2 is 1 or 2; each group Q.sub.1 is independently alkyl having from 1 to 20 carbon atoms; each group R is independently selected from alkyl having from 1 to 20 carbon atoms, aryl having up to 15 carbon atoms and cycloalkyl having from 4 to 8 carbon atoms.

Abstract: A method of producing a composite material in which a reinforcing material (eg as fibres) is embedded in a matrix material is characterized in that the reinforcement material comprises a polymer material having a draw ratio of at least 12:1 which is plama treated, prior to incorporation in the matrix, preferably to produce pitting in its surface whereby improved adhesion is obtained between the reinforcement material and the matrix material by mechanical interlocking of the pitted surface of the reinforcement material and the complementary surface of the matrix material. Preferably, the surface pitting is effected by a plasma discharge treatment. Preferably the average pit size is from 0.1 to 4 microns.

Abstract: Plasticized cellulose polymers comprise a base polymer having a chain of .beta.-anhydroglucose units joined by ether linkages and having ether substituents, with at least one of the units being additionally substituted, by esterification of at least one hydroxyl group, by at least one ester group, which contains at least two carbon atoms and is chemically unreactive.Preferably the ester group contains four or more, most preferably five, carbon atoms. The carbon chains of the ester groups may be straight or branched.These internally plasticized celluloses may be prepared by, for example, reacting the base polymer with a carboxylic acid in xylene or with an acid chloride or anhydride in pyridine. They are useful in particular as inhibitor coatings for rocket motor propellants and in general wherever cellulose polymers are employed.

Abstract: A liquid crystal guest-host display device includes a dye dissolved in the liquid crystal material. The invention is characterized in that the dye comprises three colored dye compounds mixed together to provide gray in the absence of an applied electric field. The compounds may be Sudan Black, Sudan Red and .beta.-carotene. The liquid crystal material preferably includes at least one 4'-alkyl- or -alkoxy-4'-cyanobiphenyl compound.

Abstract: A method, device, and material for providing a fast switching liquid crystal display employs the ferro electric effect of chiral smectic liquid crystal material. To provide a uniform appearance the liquid crystal material is arranged to have a long cholesteric pitch at a temperature close to a smectic/cholesteric phase transistion temperature. This long cholesteric pitch allows liquid crystal molecules to cool from the cholesteric to smectic phase with a uniform alignment. The smectic material is contained in a cell between wells (2, 3) bearing electrodes (5, 6) and surface treated to provide homogeneous alignment of liquid crystal material (7).