Abstract: An apparatus for detecting the presence of volatile substances in a gaseous medium, including apparatus for producing within a sensor chamber a localised electric field the energy density of which is sufficient to excite the gaseous medium to a plasma condition, and apparatus for detecting changes in a parameter of the plasma due to the presence of the volatile substances in the gaseous medium.

Abstract: Chemical treatment agents are supplied to a well or borehole extending through an earth formation by subjecting the well to a fracturing treatment with a high pressure fluid and proppant particles. The proppant particles are thereby trapped in fractures in the earth formation. Some or all of the proppant particles are of porous insoluble inorganic material, and are impregnated with a chemical treatment agent, such as a scale inhibitor or a corrosion inhibitor. The porous particles may be of a ceramic or oxide material, for example a silica and/or an alumina-based material.

Abstract: A filter which can be cleaned in situ consists of a filter membrane (33), and fluid permeable electrodes (34, 35). The membrane may be one of the electrodes, or may be electrically non-conducting but integral with or in contact with one of the electrodes (34). The electrodes (34, 35) are separated from each other only by a fluid permeable electrically insulating sheet. This sheet may be less than 1 mm thick, and may be the filter membrane (33). The filter is cleaned by periodic brief applications of electric current between the electrodes (34, 35) so that gas is generated electrolytically, and the close spacing of the electrodes (34, 35) reduces the electric power required.

Abstract: Metal matrix composite is made by assembling pre-forms of porous reinforcing material with an array of separator plates in a die in a pressure vessel, and infiltrating molten metal matrix material. Pre-evacuation followed by pressurisation when the molten metal matrix material is introduced into the die aids the infiltration. Re-introduction of gas during initial heating prior to melting speeds the heat-up process.

Abstract: A fire suppressant powder with particle sizes less than 5 .mu.m is made by a chemical reaction between a gas or vapour of a first material and a vapour or an aerosol of a second material. For example an aerosol of sodium hydroxide droplets may be reacted with carbon dioxide gas to produce sodium bicarbonate powder; or boron halide vapour may be reacted with steam to form boric acid powder The powder may be used in fire extinguishers either on its own, or combined with other ingredients such as silica and/or alumina, and calcium stearate.

Abstract: During filtration, periodic application of a potential difference between an electrically conducting filter medium and counter electrode (as anode) generates a gaseous product at the filter and cleans the filter. To minimise corrosion the counter electrode is of low chromium stainless steel, for example 9% chromium.

Abstract: An apparatus for generating a liquid spray from two jets of fluid which issue from a pair of opposing nozzles and interact, wherein the fluid is supplied to the nozzles under fully turbulent conditions such that random variations in the momentum of the fluid as it leaves the nozzles occur which results in random variations in the orientation of the resultant spray of liquid drops.

Abstract: A polymer electrolyte suitable for use in a lithium ion cell comprises polyvinylidene fluoride (PVdF) combined with a solution of a salt such as lithium perchlorate, in a compatible solvent such as an ethylene carbonate/N-methyl-pyrrolidone mixture. The PVdF is a homopolymer of high molecular weight, with a melt flow index at 230.degree. C. and 10 kg of less than 1.O g/10 min.

Abstract: A radioactive waste stream (12) is of high pH and contains a wide variety of different fission products and also organic materials which act as complexants. Technetium and/or ruthenium are removed by first electrolytically oxidising the organic materials at an anodically stable anode (26), and then electrolytically reducing the technetium and/or ruthenium at a porous fluid-permeable cathode (42). The cathode (42) might for example be of lead wool.

Abstract: Corrosion, scale-formation, or other deleterious processes are inhibited in an oil well by installing within the oil well (10) fluid-permeable elements, such as tubular filters (20), which comprises a suppressing material. Each filter (20) comprises two tubular filter screens (24) between which is a bed (26) of particles comprising suitable inhibitor material. The particles might for example be porous ceramic spheres impregnated with the inhibitor material. The inhibitor material gradually dissolves in the well fluids during operation, and may for example inhibit corrosion and/or scale formation.

Abstract: A mass-analysed ion beam generator in which the ion beam is in the form of a thin flat ribbon with its major transverse dimension aligned parallel with the direction of the mass-analysing magnetic field.

Abstract: A double lid system is provided with an electric motor (44) to actuate mechanisms to release the lid (20) from a drum (18) and simultaneously clamp the lid (20) to a door (14) of a port (or vice versa), and with an electric motor (74) to withdraw the door (14) from the port to open the port (or to close it). The system is monitored by sensors (60,62,64,82) associated with an electronic logic interlock to ensure the correct sequence of operations of the motors (44,74). The sensors (60,62,64,82) and the motors (44,74) are readily demountable for remote maintenance or replacement. The door-opening motor (74) may he a linear actuator cooperating with a part-helical slot (80) to open the door (14) and then swing it clear of the port.

Abstract: Apparatus for the on-line treatment of chemical reagents, including a flow line for a reagent flow, a vortex mixer in the flow line for combining and mixing the reagent flow with at least one further reagent flow, a pulser in the flow line for causing the pulsing of the mixed flow from the vortex mixer, and a vessel having an array of vortex cells for receiving the pulsing mixed flow to cause development and growth of precipitate under narrow residence time distribution conditions. Flow lines mix a flow of reagents to initiate precipitation. The pulser pulses the admixed reagents and causes the pulsing mixed flow to swirl with a constantly reversing rotational flow to achieve development and growth of precipitate.

Abstract: Decomposition of waste and particularly organic waste matter is carried out in an electrochemical cell (11) in which the electrolyte comprises nitric acid containing silver ions as an electrochemically regenerable primary oxidizing species. A separation plant (34) for continuously or periodically withdrawing anolyte is operated to remove or reduce contamination of the anolyte with anions of or containing phosphorus, sulphur, nitrogen or halogens.

Abstract: A corona discharge reactor which has a central electrode in the form of a metal rod with radial projections and a cylindrical outer electrode surrounding the inner electrode.

Abstract: An electromagnetic machine which is suitable for use as a direct-drive, directly-coupled, mains electricity generator (14) to be driven by a low speed device such as a wind turbine (18), consists of one or more rotor rings (30) of many permanent magnets (40) of alternating polarity, with coaxial stator rings (28) of many laminated yokes (35), each yoke defining slots to locate coils (38). The yokes (35) and coils (38) form modules which are supported by beams (32) relative to the rotor rings (30). The rotor rings (30) may also be of modular construction. Manufacture and assembly are thereby simplified, and sub-harmonic magnetic flux components are suppressed.

Abstract: The absolute values of biaxial stresses in a ferromagnetic material (16) are measured using a probe (12) which comprises an electromagnet (26), a sensor (32) for stress-induced magnetic anisotropy (SMA) and a sensor (30) for directional effective permeability (DEP). The DEP sensor (30) enables absolute values of stress to be determined; the SMA sensor (32) enables the directions of the principal stress axes to be accurately determined, and improves the accuracy of the stress measurements.

Abstract: The casing metal of, for example, a munition containing organic materials is removed or at least perforated by anodic dissolution in a chamber (16) fabricated to contain the explosion should the munition detonate. The contents are then exposed to reaction with anolyte from a plant (17), the anolyte comprising nitric acid and electrochemically regenerable silver II ions.

Abstract: An electrode for use in electrochemical ion exchange which includes a hydrolysable metal phosphate such as zirconium phosphate (Zr(HPO.sub.4).sub.2) which has been hydrolysed at least in part is regenerated. The electrode is made the anode of an electrochemical cell in which the electrolyte is an aqueous solution containing one or more phosphate ions provided, for example, by a dissolved salt (eg Na.sub.3 PO.sub.4, Na.sub.2 HPO.sub.4 or NaH.sub.2 PO.sub.4) or orthophosphoric acid, or both. Preferably, the electrolyte is acidic (eg pH 2). Operation of the cell reverses the hydrolysis reaction and enhances the performance of the electrode.

Abstract: A dry powder inhaler (10) consists of a chamber (12) into which powder is introduced from a metering system, and a mouthpiece (26) through which a patient inhales, connected by a duct (16), so that air flows through the chamber carrying the powder into the patient's lungs. Within the duct is an impactor (25) consisting of a plate (27) spaced in front of a similarly sized aperture, and between the chamber and the impactor plate is an orifice (18) narrower than the duct, so the air stream is diverted along S-shaped paths to avoid the plate. The presence of the impactor can improve the efficiency of delivery of a drug to the lungs, and decrease the unwanted dose to the mouth and throat, as the latter is principally due to agglomerates or larger particles which are intercepted or broken up by the impactor.