Thesis (Ph. D.)--University of Pittsburgh, 1922. / Vita. Bibliography: [1] p. following p. 14.

Thesis (Ph. D.)--University of Michigan, 1921.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Michigan, 1921.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references. Also available on the Internet.

No description available.

<p> The nature of the coloured solutions of selenium and tellurium in sulfuric acid has been investigated using mainly cryoscopic, conductimetric, and spectrophotometric techniques. Evidence has been obtained for the new species Se₈²⁺ and Se₄²⁺ in the green and yellow solutions of selenium respectively. Evidence on red solutions of tellurium seems consistent with the formulation Te₄²⁺. Solid compounds analysing as Se₄S₄O₁₃, Se₄(HS₂O₇)₂ and TeO(HS₂O₇)₂ have been prepared and characterised. </p> <P> Solutions of some selenium(IV) and selenium(VI) compounds have been examined. It is shown that a number of phosphates and arsenates ionise in sulfuric acid to give the P(OH)₄⁺ and As(OH)₄⁺ ions respectively. Ammonium metavanadate and vanadium pentoxide ionise to give the complex acid H[VO(HSO₄)₄]. Potassium chromate and dichromate ionise to give the compound CrO₂(HSO₄)₂ and potassium permanganate ionises to give the non-electrolyte MnO₃∙SO₄H. </p> / Thesis / Doctor of Philosophy (PhD)

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The present thesis presents new renewable, antimicrobial and biodegradable superabsorbent polymers (SAPs), produced from the cell wall of zygomycetes fungi. The cell wall was characterized and chitosan, being one of the most important ingredients, was extracted, purified, and converted to SAP for use in disposable personal care products designed for absorption of different body fluids. The cell wall of zygomycetes fungi was characterized by subsequent hydrolysis with sulfuric and nitrous acids and analyses of the products. The main ingredients of the cell wall were found to be polyphosphates (4-20%) and copolymers of glucosamine and N-acetyl glucosamine, i.e. chitin and chitosan (45-85%). The proportion of each of these components was significantly affected by the fungal strain and also the cultivation conditions. Moreover, dual functions of dilute sulfuric acid in relation to chitosan, i.e. dissolution at high temperatures and precipitation at lowered temperatures, were discovered and thus used as a basis for development of a new method for extraction and purification of the fungal chitosan. Treatment of the cell wall with dilute sulfuric acid at room temperature resulted in considerable dissolution of the cell wall polyphosphates, while chitosan and chitin remained intact in the cell wall residue. Further treatment of this cell wall residue, with fresh acid at 120°C, resulted in dissolution of chitosan and its separation from the remaining chitin/chitosan of the cell wall skeleton which was not soluble in hot acid. Finally, the purified fungal chitosan (0.34 g/g cell wall) was recovered by precipitation at lowered temperatures and pH 8-10. The purity and the yield of fungal chitosan in the new method were significantly higher than that were obtained in the traditional acetic acid extraction method. As a reference to pure chitosan, SAP from shellfish chitosan, was produced by conversion of this biopolymer into water soluble carboxymethyl chitosan (CMCS), gelation of CMCS with glutaraldehyde in aqueous solutions (1-2%), and drying the resultant gel. Effects of carboxymethylation, gelation and drying conditions on the water binding capacity (WBC) of the final products, were investigated. Finally, choosing the best condition, a biological superabsorbent was produced from zygomycetes chitosan. The CMCS-based SAPs were able to absorb up to 200 g water/g SAP. The WBC of the best SAP in urine and saline solutions was 40 and 32 g/g respectively, which is comparable to the WBC of commercially acceptable SAPs under identical conditions (34-57 and 30-37 g/g respectively). / <p>Disputationen sker fredagen den 1 oktober kl. 10.00 i KA-salen, Kemigården 4, Chalmers, Göteborg</p>

No description available.