Abstract: A nematic liquid crystal composition suitable for use as the liquid crystal material of a multiplexed twisted nematic electro-optical display comprising a mixture of Components A, B and C as follows:Component A: a high dielectric anisotropy component;Component B: a low dielectric anisotropy component;Component C: a high cleaning component having a clearing point greater than 80.degree. C.;wherein Component A forms from 25% to 50% inclusive by weight of the composition and consists of one or more two ringed compounds having a terminal cyano group and includes at least one compound having formula I as follows ##STR1## where R.sub.1 is an n-alkyl group having up to 7 carbon atoms and ##STR2## represents a trans-1,4 disubstituted cyclohexane ring; wherein Component B forms from 25% to 50% inclusive by weight of the composition and consists of one or more low dielectric anisotropy compounds, at least 50% of Component B being formed by one or more ester compounds having Formula II as follows: ##STR3## where R.sub.

Abstract: A portable "Ski-Jump" runway for use by Hawker Siddeley Harrier Type V/STOL aircraft and other conventional tricycle undercarriage aircraft having suitable performance characteristics. The runway comprises a main central ramp constructed on or as the chassis of a truck or trailer along which in use the main undercarriage wheels travel and secondary ramp sections of substantially lighter structural construction collapsibly mounted on support frames cantilevered from the main ramp section along which in use the secondary undercarriage wheels of the aircraft travel. The main ramp section is conveniently divided into at least two, preferably three, lengths, the foremost length being part of the truck or trailer and with the rearward length or lengths capable of being stored on top of the foremost length for transportation purposes. Component parts of the secondary ramp sections may be stored in the truck for transportation purposes.

Abstract: 1. A process for the manufacture of a nitric ester by the nitration of an alcohol by a nitrating acid wherein the alcohol and the nitrating acid are reacted together in the presence of an inert highly halogenated hydrocarbon containing fluorine and which is a solvent for and has a boiling point which is between 0.degree. and 50.degree. C and which is below that of the nitric ester product whereby the temperature of the reaction mixture is limited to that of the boiling point of the solvent by evaporation of part of the solvent, separating out the solvent containing dissolved nitric ester from the reaction mixture, and evaporating the solvent to leave the nitric ester.

Abstract: A primary explosive composition consisting of a polybasic lead salt of a di- or a tri-nitro- substituted resorcinol containing 3, 4, 5 or 6 atoms of lead per aromatic nucleus in which a minor proportion of finely-divided boron is entrained within, and dispensed throughout, individual crystals of the polybasic lead salt.