Abstract: A muzzle brake for reducing gun recoil comprises a hollow cylindrical tube (7) having an open forward end and having at least two apertures in the cylinder wall (4) each which is provided with closure means (6) mounted on the tube so as to be movable between a closed position and a fully open position. Each closure means (6) has at least one associated biasing member (22) to bias it into the closed position, which is preferably preloaded to introduce an inertia into the movement of the closure means (6) which is of such a degree that the rapid blast pressure wave passes with little effect, but the longer exhaust wave effects opening. The brake further comprises at least one rearwardly directed gas deflecting surface (13, 30) to deflect the exhaust wave gases rearwards and produce a braking effect.

Abstract: The invention provides a surface, or electric field, stabilised ferroelectric liquid crystal (SSFLC) device with an improved contrast ratio between its two switched states. The device comprises a liquid crystal cell formed by a thin layer (7), typically 1 to 5 .mu.m thick, of a smectic liquid crystal material, eg a smectic c, held between two glass walls (2, 3) coated on their inner faces with electrodes (5, 6). Polarizers (8, 9) are arranged either side the walls (2, 3). The device is switched between two bistable states by application of unidirectional voltage pulses, with or without the simultaneous application of ac bias voltages. To obtain optimum contrast ratio CR, the optical axis of the polarisers are rotated away from a crossed, or othogonal position. eg by +/-20.degree., and the cell rotated between the polarisers (8, 9); the precise optimum rotation depends upon material, and ac bias voltage.

Abstract: A calibration system includes an air system having a blower unit (10), a flow meter (16) and means (15) for controlling an airflow through a mixing manifold (17) to which a metered amount of a test gas can be added from either a mass flow controller (19) or a syringe drive unit (21).

Abstract: A device and a process for enabling an incident wide bandwidth (greater than about 1 GHz) short duration (less than about 10 microseconds) individual pulse of electromagnetic radiation to be digitally sampled at a sampling rate that is achievable by available digital sampling circuits. The incident pulse is modulated onto an optical signal to form a modulated optical signal and the whole, or successive or randomly selected parts, of the modulated optical signal are replicated using optical time delay means. The resulting plurality of modulated optical signal representations of the whole or parts of the incident pulse can then be digitally sampled at a sampling rate which is reduced in proportion to the number of replications to obtain a complete digital representation of the incident pulse.