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An idea based on a feature of fish anatomy should make it easier for engineers to lay telephone or TV cables through underground ducts, says Think Tank New Zealand of Auckland (GB 2363207). TTNZ suggests moulding a cable’s outer sheath with little flaps, like fish gills. Blowing air through the duct from behind the flaps pushes the cable along it. The pressure is evenly distributed over the surface of the cable and along its full length. This puts far less local strain on the cable than pulling it through with a winch would, so it can be lighter, thinner and…