Abstract: The present invention relates to a fluid injection system comprising a tubular member (12) arranged to form part of a fluid line through which, in use, fluid flows under pressure, a venturi (14) contained within the tubular member (12), first and second volumes arranged to contain first and second fluids respectively, said first and second volumes being separated by a pressure responsive means such as a bladder (30), the tubular member (12) on a high pressure side of the venturi (14) being in fluid communication with said first volume, and a metering line (40) extending from the tubular member on a low pressure side of the venturi and being in fluid communication with said second volume, the arrangement being such that, in use a pressure differential is created across the venturi (14) so that the first volume is increased by fluid passing from the fluid line (12) into the first volume and by movement of the pressure responsive means, the second volume is correspondingly decreased by fluid passing therefrom th

Abstract: A method of manufacturing a hollow structure of uniform wall thickness comprising the steps of selecting or forming a precursor having one wall surface of desired geometry, treating a portion of the precursor consisting of the one wall surface and a uniform depth of material beneath the wall surface to increase resistance to ablation, and then removing by ablation and discarding the remaining or untreated portion of the precursor.

Abstract: A method of manufacturing gel powder suitable for use as a starting material in the manufacture of hollow glass microspheres having a high concentration of silica. The powder is manufactured from a gel containing boron in the amount of about 1% to 20% (oxide equivalent mole percent), alkali metals, specifically potassium and sodium, in an amount exceeding 8% total, and the remainder silicon. Preferably, the ratio of potassium to sodium is greater than 1.5.