Abstract: There is disclosed a three stage method for the preparation of ladder-like silicone polymers. The first stage comprises hydrolysis and polymerization of alkyltrialkoxylsilane-like monomers to give relatively low molecular weight prepolymers. The second stage comprises dehydrated condensation polymerization of the prepolymers to give high molecular weight polymers. The third stage comprises partial blocking of a proportion of the pendant Si—OH (silanol) groups with a pre-determined sub-stoichiometric amount of a blocking agent. Also disclosed are the prepolymers, polymers and partially blocked polymers so produced.

Abstract: Determining the angle of arrival of a signal by providing a plurality of antennae, sampling, in turn, the output from each of the antennae to obtain a set of samples, each of the samples relating to different points in time, performing a Fourier transform on the set of samples, thereby producing a sequence of spectral lines, identifying a signal impinging on the antennae from the configuration of the spectral lines, and calculating, from phase and amplitude data gathered from at least a subset of the spectral lines, the direction of arrival of the signal at the antennae.

Abstract: An apparatus for generating laser radiation, the apparatus comprising: a pumping device comprising a resonant cavity; and a laser radiation generation element that is substantially Poynting vector walk-off compensated, the laser radiation generation element being located within the resonant cavity.

Abstract: A device for producing laser radiation, the device comprising: an elongate sample of a quasi-three-level laser material; a source of pumping radiation; and a concentrator configured such that at least some of the pumping radiation emitted by the source of pumping radiation is concentrated by the concentrator and subsequently enters the sample through a side surface thereof.

Abstract: A method of determining the angle of arrival of a signal, the method comprising the steps of: providing a plurality of antennae; sampling, in turn, the output from each of the antennae, to obtain a set of samples, each of the samples relating to different points in time; performing a Fourier transform on the set of samples, thereby producing a sequence of spectral lines; identifying a signal impinging on the antennae from the configuration of the spectral lines; and calculating, from phase and amplitude data gathered from at least a subset of the spectral lines, the direction of arrival of the signal at the antennae.

Abstract: A device for producing laser radiation having a wavelength of about 2 &mgr;m, the device comprising: a solid-state sample capable of producing lasing transitions corresponding to a wavelength of about 2 &mgr;m; and a source of pumping radiation having a wavelength of about 1 &mgr;m, the source being arranged so that at least some of the radiation produced thereby is absorbed by the solid-state sample, causing the solid-state sample to emit radiation having a wavelength of about 2 &mgr;m.

Abstract: A heat sink comprising: a body having an envelope including a flexible portion for thermal contact with a heat source, the envelope being filled with a thermally conductive liquid; and a thermosyphon having one end disposed at least partly within the liquid in the body to absorb heat from the heat source and another end disposed outside the envelope to dissipate heat.