Abstract: A high gain optically pumped laser device includes a mask having cut-out portions defining a given pattern disposed in the resonant optical cavity defined between end mirrors at opposite ends of the laser material. Each of the end mirrors is equivalent to an optically flat reflecting surface such that only cross-sectional portions in the laser material similar to the pattern are stimulated to emit output laser radiation. This stimulated emission has a high energy density and may be directly radiated to a target surface to alter the surface in a manner corresponding to the given pattern. The alteration may take the form of actual vaporization, heating, or oxidation of portions of the surface. Thus carefully controlled engraving type processes or other processes involving a physical alteration of a surface such as the drilling of square or unusually shaped holes as determined by the pattern can be carried out.

Abstract: Ferrocement structures and the method for producing them comprising: providing a load-bearing framework, covering the framework with a strong flexible sheet-like material and then a flexible metal reinforcing material, and applying cement mortar thereover to cover the reinforcing material. The framework can be made of easily fabricated wooden ribs.

Abstract: BOD-containing water such as sewage is mixed with active biomass and a first quantity of oxygen feed gas in a first cycle for biochemical oxidation to produce oxygenated liquid-solid and unconsumed oxygen-containing gas of lower purity than the feed gas. The unconsumed oxygen is discharged and a second quantity of oxygen feed gas is introduced for mixing in a second biochemical oxygenation cycle.