Deep continuous layers of iridophores were discovered in certain Asian Agkistrodon species. A survey of available snakes showed the banded iridophores to be present in North American Crotalus and Sistrurus also, indicating an unreported morphology to be a possible common phenomenon. Skin samples from 147 species and/or subspecies of snakes of the families Leptotyphlopidae, Boidae, Colubridae, Elapidae and Viperidae were examined and photographed by polarized light microscopy. Dermal iridophore patterns were visually identified and categorized as (1) isolated cells, (2) lightly layered, (3) moderately layered and (4) heavily layered. Selected specimens were examined and photographed by electron microscopy; isolated iridophore ultrastructure and layered iridophore ultrastructure patterns are illustrated and described. Reflectometry of four selected crotalids reveals positive correlation between iridophore quantities and albedo, but habitat adaptation and correlation of individual species/subspecies is difficult to show and only subjectively suggested. Published phylogenies of the species of the genera Agkistrodon, Calloselasma, Deinagkistrodon and Hypnale are revised to reflect taxonomic works and are correlated with iridophore pattern data. Phylogenetic relationships of Crotalus and Sistrurus are also revised with recent publications; they are neither supported nor contradicted because layered iridophores occur in all of their phylogenetic groups.

No description available.

No description available.

No description available.

Pyocyanine is a blue pigment characterized by the basic phenazine structure. Several other pigments were isolated from bacterial origins which contained the phenazine "nucleus." The similarities between these chemical compounds and their relation to phenazine are more readily observed by a comparison of structural formulae. [...]

No description available.

No description available.

A wide range of lime green/yellow to mustard/orange bismuth orthovanadate samples were prepared via solid state and precipitation techniques. The materials were characterised using thermal analysis, X-ray diffraction, evolved gas analysis, reflectance infra-red spectroscopy, electron microscopy, colour measurement, wet chemical analysis and ac impedance spectroscopy. This product characterisation identified more complex materials than previously reported, with generally non-stoichiometric compositions established. The fergusonite-type polymorph of BiVO₄ was prepared via solid state synthesis. This phase was found to be slightly V-rich in composition, of BiV_1.025O_4+x. It occurs as a line composition and melts congruently at 930°C ± 10°C. A reversible, non-quenchable phase transition from fergusonite to scheelite-type BiV_1.025O_{4 + x} was determined at 240-250°C. The zircon and scheelite-type polymorphs of BiVo₄ were produced by controlled room temperature precipitation, at pH 1-2 and 3-7 respectively, whereas the fergusonite-type polymorph was obtained at pH 1-7 on precipitation from solutions at 95°C. All three precipitated polymorphs were found to contain a proportion of foreign ions, totalling 2.0-3.0, 2.7-3.6 and 0.3-0.9 weight% for the zircon, scheelite and fergusonite-type polymorphs respectively. These foreign ions consist of adsorbed water and structural nitrate, carbonate and hydroxyl constituents. Chemical analysis identified essentially Bi-rich compositions for the precipitated polymorphs. An irreversible phase transition from zircon to scheelite-type BiVO₄ was determined at 500-520°C. BiVO₄ is studied as a possible alternative yellow pigment for the toxic cadmium and chrome-containing traditional yellow colourants. The sample colours obtained were compared with those of the commercial CdS, PbCrO₄ and BiVO₄/Bi₂MoO₆ pigments. Polycrystalline, phase pure BiV_1.025O_{4 + x} ceramics, prepared by solid state synthesis were investigated using ac impedance spectroscopy. These materials were found to exhibit mixed oxide ion/electronic conduction at both low and high temperatures, ie. <400°C and >600°C. Oxide ion conductivity dominates the temperature region between 400 and 600°C, with an activation energy of 0.80 + 0.01eV. The bulk conductivity below 400°C was found to be metastable and influenced by the presence of water. The possibility of protonic conduction below 400^OC is identified.

Graduation date: 1955

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1964. / Bibliography: leaves 175-186. / xii, 186 l illus