Abstract: A pressure breathing mask, particularly an aircrew oxygen mask, includes an exoskeleton (10), a flexible facepiece (11) with an oxygen delivery connection (15), an inflatable bladder (20) positioned between the exoskeleton (10) and a rigid intermediate member (30), the intermediate member (30) bearing on the facepiece (11), and means (21, 23) for automatically inflating the bladder (20) when oxygen is delivered under pressure to the mask.

Abstract: In a heavy structure e.g. a bridge which includes an element liable to low frequency vibration during erection, i.e. when the structure is unstable, another element which is an integral structure part after erection is used as the mass of a dynamic absorber for damping this vibration. In the example given, a launch rail (46) for erecting a bridge across a river is cantilevered out over the river, after which a support leg (50) is extended by means of an integral jack to engage the ground and form a stable structure. The support leg includes a lower part (54) which is suspended during erection from the upper part of the leg through a gas spring, with the gas spring and the mass of the lower part together constituting a dynamic absorber for the lauch rail during erection. After erection, structural loads are transmitted directly to the lower leg part via a trunnion.

Abstract: A dye laser amplifier is formed by a stimulated brillouin scattering (SBS) dye cell which receives both dye laser light to be amplified and a pump beam along a common optical path. Phase conjugation and amplification of received energy are reflected from the SBS cell. The cell comprises an SBS medium that is a solvent for the laser dye used. Typical SBS mediums are methanol, acetone, isopropyl alcohol, etc. Typical dyes are Rhodamine 6G, Rhodamine B, Rhodamine 560, Rhodamine 575, Sulphorhodamine B, Kiton Red, DCM, Courrarun 523, etc. A plurality of amplifiers may be connected in series to provide increased amplification. The action of the phase conjugation corrects optical distorsions, thereby preserving beam quality and bandwidth even after multiple amplifications. A typical dye laser beam of 590 nm wavelength, about 1 .mu.J may be amplified to about 120 mJ, with a 17 nsec pulse width, and <500 MHz bandwidth.

Abstract: An intensity dividing device (10) incorporates a rectangular multimode waveguide (20) connected to an input waveguide (18) and a set of four output waveguides (22). The input waveguide (18) provides a fundamental mode input excitation of CO.sub.2 laser radiation to the multimode waveguide (20). The input waveguide (18) is offset from the multimode waveguide longitudinal axis (24). Consequently, both symmetric and antisymmetric modes of the multimode waveguide (20) are excited. Modal dispersion along the multimode waveguide produces electric field intensity maxima of differing magnitude centred on respective output waveguides (22). This provides division of the input radiation into a range of differing intensity outputs.

Abstract: Laminated armour comprising a first part (11) situated on the side of the armor from which attack is to be resisted and a second part (12) which is coextensive with the first part wherein: (i) the first part comprises a lamination of first metal sheets (1) each having an average thickness t.sub.2 adhesively bonded by interface layers (8) having a thickness (t.sub.1) between 0.4t.sub.2 and 0.9t.sub.2 and a compressive Young's Modulus perpendicular to the layers below 4 GPa; (ii) the second part comprises material which is more ductile than the metal of the first metal sheets, and preferably comprises second metal sheets (2) which are bonded to each other and to the first part of the armor (11) with aramid fibre reinforced adhesive.

Abstract: A thermal imager testing device (10) incorporates a pattern plate (32) with patterns (P0, P1, P2 and P3) cut through it. Patterns (P0 and P1) are of like spatial frequency, whereas patterns (P2 and P3) have respective relatively higher spatial frequencies. The patterns (P0 to P3) are like structured and like oriented, and they underlie blackbodies (34, 26, 28 and 30) respectively. Temperature differentials between the blackbodies (34 and 26 to 30) are maintained at constant values by temperature control circuits. The temperature of blackbody (34) is adjustable. The pattern plate (32) and underlying blackbodies are viewed by a thermal imager under test. The temperature of the blackbody (34) is adjusted until pattern (P0) is just discernable as cold relative to the pattern plate (32). If the thermal imager performance is acceptable patterns (P1 to P3) are then just discernable as hot relative to the pattern plate (32).

Abstract: An alloy formed by rapid solidification comprising Al, 1 to 7 wt % Cr and up to 6 wt % X where X is selected from refractory metals Nb, Mo, Hf, Ta, and W, has improved thermal stability.

Abstract: Toughened epoxy resins are prepared by curing a mixture of epoxy resin, a liquid carboxyl-terminated elastomer, and, as curing agent, a non-aromatic heterocyclic amine or a salt thereof. Cure is in two stages, the first stage at a temperature of at least 135.degree. C. for less than two hours to provide a partly cured formulation comprising phase-separated rubbery particles in an epoxy resin matrix, and a second stage of completing the cure.

Abstract: A medical implant for injecting into the vascular system of animals comprises a device less than 500 .mu.m in size carrying signal processing means for providing an output in response to an input signal. The input may be acoustic, electromagnetic, temperature, pH value, or chemical. The output may be acoustic, electromagnetic, or chemical. Large numbers, e.g., 10.sup.8, of the implant devices may be mixed into a saline solution and injected into a blood vessel where they are carried around the vascular system, or the devices may be mixed with a gas and inhaled. The amount of circulation depends on the device size. For the larger device e.g., above 7 .mu.m to around 250 .mu.m, circulation will be short lived. Smaller sized e.g., <3 .mu.m devices will circulate for a considerable time. Anti-bodies may be coated onto the devices to cause them to adhere to target areas such as tumors. In one device a chemical is released when illuminated externally by an acoustic beam.