"Additional mixtures of polymers and multi-unsaturated monomers have been prepared, irradiated and the gel content determined. The gel content determination of crosslinked polyolefins has been investigated in detail. The multi-unsaturated monomers used and radiation conditions applied up to this time have not given significant gel contents for polypropylene. the polypropylene resin used has been characterized by differential extraction."

When light propagates with the wave normal in the direction of an optic axis of a biaxial crystal, the usual ray theory breaks down. This phenomenon can be analyzed by means of an asymptotic solution of Maxwell's equations. The intensity is governed by a partial differential equation within the phase surfaces, instead of ordinary differential equations along rays. This example slows that light does not always propagate along rays. A similar phenomenon occurs in hydromagnetics.