PHOTOCHEMICAL DEGRADATION OF KERATINS

Abstract— Twenty-nine samples of fur, hair. wool and feathers have been irradiated with a Sunlamp (Λ max. 310 nm) and with a 2 kW mercury vapour lamp emitting mixed U.V. and visible radiation resembling sunlight. Photodegradation is accompanied by progressive yellowing when irradiated with the Sunlamp. It is accompanied by bleaching followed by yellowing, or by bleaching throughout irradiation if the initial yellowness is high, when exposed to the 2 kW lamp. A group of nine fur and hair samples, representing four different orders of mammals, are the most sensitive to yellowing, followed by a group of ten wool and hair samples from the Artiodactyla and finally by the feather keratins which are less susceptible than the α-keratins. Amino acid analysis of the keratins before and after Sunlamp irradiation shows strong correlation of yellowing both with the initial concentration of tryptophan and with its destruction during irradiation. Similar correlations of yellowing with destruction of other amino acids are less significant. Preliminary washing with non-ionic detergent increases susceptibility to u.v. yellowing.     

Painleve analysis for a semi-linear parabolic equation arising in smectic liquid crystals

This article presents a systematic method, employing a Painlevéanalysis for obtaining static and travelling wave solutionsto a semi-linear parabolic equation which frequently arisesin the smectic liquid crystal literature. The equation consideredhas sinusoidal non-linearities and shares some of the featuresof the double sine-Gordon equation; a brief discussion of therelationship of this equation to liquid crystals is also given.