An optical logic gate comprises: first and second optical inputs for receiving respective optical signals and an optical output for outputting an optical signal which represents the result of applying a required logic function. Known devices comprise skin-removing rollers, designed to enable height adjustment via a control cam. The throttle valve has at least two variable orifices and a compensation chamber between the variable orifices. The hot pipe second end includes a generally cylindrical outside surface. The polymer can be prepared from monomers having a B1-A1-B2 structure, wherein at least one of B1 and B2 comprises a reactive group enabling polymerization.