Abstract: An optical system for direct measurement of vorticity in a flowing fluid is disclosed. Spherical particles suspended in the flow rotate with an angular velocity that is accurately equal to half the local vorticity; thus, measurements of the rotation rates of such particles indicate the vorticity. The particles are transparent, and preferably are less than 50 .mu.m diameter, and each contains embedded planar crystal mirrors. The particles are suspended in a refractive index matched liquid. Measurement of the particle rotation rate and thus the vorticity of the fluid is preferably accomplished by measuring the rotation rates of reflections of one or more light beams from the planar mirrors. The measurements may be carried out using any system of position sensitive optical detectors such as photo sensitive devices screened by suitable slits or photo diode arrays.

Abstract: A coating composition is described which is suitable for use on road surfaces, floors, driveways, and similar surfaces and comprises chlorinated rubber, a plasticizer component and an organic solvent. The composition also advantgeously may contain powdered, amorphous silica. Preferred in the present invention is about equal amounts by weight of chlorinated rubber and a mixture of solid and liquid chlorinated paraffins as plasticizers, a minor amount of powdered amorphous silica and a mixture of aromatic and chlorinated aliphatic organic solvents.

Abstract: Compositions comprising copolymers of methyl methacrylate and ethyl acrylate and of vinylidene fluoride and hexafluoropropylene may be blended to form transparent compositions of low refractive index, making them useful in retroreflective products as a layer in which glass microspheres are embedded.

Abstract: Coating compositions containing identifier particles are disclosed for the retrospective identification of articles. The compositions comprise a clear lacquer binder, visually-readable microparticles and reflective spotting particles. The reflective spotting particles facilitate location of the coating on the surface of the tagged article.

Abstract: A melt-adhesive traffic paint composition having improved low temperature stability is disclosed which comprises 20-35% by weight of a dimer acid-modified polyamide resin, 1-5% by weight of a plasticizer, 30-45% by weight of an inorganic filler, and balance a coloring pigment and a reflective agent. The composition may further comprise a thermoplastic resin such as hydrogenated rosin or a rosin-modified maleic acid resin. The resultant paint has improved low temperature stability and improved abrasion resistance and is thus highly resistant to the action of spike tires or tire chains.