Showing papers by "Glyn O. Phillips published in 1983"

Polymeric articles modified with hyaluronate

Abstract: Polymeric materials (and articles made therefrom) including polyurethanes, polyesters, polyolefins, polyamides, polysiloxanes, vinylic and acrylic polymers are rendered biocompatible by including with the polymeric material hyaluronic acid or a salt thereof. The hyaluronic acid may be coated onto the surface of the polymeric material, dispersed throughout the body of the polymeric material, or both. The hyaluronic acid on the surface of the polymeric material may optionally be cross-linked. The biocompatible polymeric materials are used in the making of various prosthetic devices including heart valves, intraocular lenses, vascular grafts, pacemaker leads and the like.

Primary processes in the laser flash photolysis and pulse radiolysis of l-ephedrine.

Abstract: — Transient absorption spectra produced by laser flash-photolysis of an aqueous solution of ephedrine have been measured under a variety of conditions. Ephedrine was found to photoionise via a biphotonic process. The apparent yield of photoionisation increases with lowering of pH, a value of 8.8 being found for the pKa associated with this change. The cation radical absorption spectrum has been determined using the techniques of both pulse radiolysis and laser flash photolysis. The extinction coefficient of the cation at 295 nm was determined to be 1.37 × 104 dm3 mol-1 cm-1 and 1.2 × 104 dm3 mol-1cm-1 by the two techniques, respectively, at pH 11. It is also shown that the rate constant for electron abstraction by the azide radical to form the ephedrine cation is controlled by protonation of the amine group in the side chain. The ephedrine anion radical spectrum and its extinction coefficient at 305 nm were also determined. The excited states responsible for photoionisation and photodegradation are discussed.

One-electron reduction of lumichrome and its methyl derivatives in aqueous solution: a pulse radiolysis study

Abstract: The one-electron reduction by CO/sub 2//sup -/. and e/sub aq//sup -/ of lumichrome and its 1-methyl,3-methyl, and dimethyl derivatives in aqueous solution has been investigated. By studying spectral changes as a function of pH, we have characterized three distinct types of radical anion. These radical anions derived from the dimethyl,1-methyl, and 3-methyl derivatives respectively exhibit differing absorption spectra in the range 280-600 nm. In addition, pK/sub a/ values for protonation of these species have been measured as 10.5-12.0, 10.5, and 7.8 for the species derived from dimethyllumichrome, 1-methyllumichrome, and 3-methyllumichrome, respectively. The neutral radicals all show similar absorption spectra and appear to be characterized by an absorption band at 450 nm (epsilon = 4000 M/sup -1/ cm/sup -1/). At low pH (2-5), protonation of the neutral species occurs with a pK/sub a/ close to 3.5 for all derivatives. The data obtained from the methyl derivatives of lumichrome is used to interpret the spectral changes which occur upon the one-electron reduction of lumichrome itself. Tentative structures have been assigned to all forms of the free radicals under investigation.