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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

The mechanism of action of peroxygen biocides

Jackson, Natalie Diane January 1999 (has links)
No description available.
52

New methods for the synthesis of complex amino acids and carbohydrates

Norrish, Andrew Mark January 2001 (has links)
No description available.
53

Synthesis of C-3 functionalised 1-pyrroline 1-oxides

Kemp, Steven J. January 1999 (has links)
Chapter 1 introduces the phenomenon of oxygen toxicity and the central role played by oxygen free radicals, most notably the superoxide radical anion. The technique of spin trapping, whereby reactive free radicals are studied and identified, is then introduced. The synthesis of improved spin traps for superoxide by the preparation of 1-pyrroline 1-oxides bearing a C-3 ester or alkyl halide substituent is then discussed. Chapter 2 describes the preparation of 2-(prop-2-enyl)-aldehydes, 2-dimethoxymethylaldehydes and a 2-phenylthiomethylaldehyde. Bromination of 5,5-dimethyl-1-(prop-2-enyl)-1-pyrroline 1-oxide did not give rise to addition at the C=C double bond but recovery of the nitrone and a hydroxamic acid. Similarly, hydrohalogenation of the alkenyl-nitrone did not lead to addition at the C=C double bond. The preparation and utility of 3-(ethoxycarbonylprop-2-enyl)-5,5-dimethyl-1-pyrroline 1-oxide is then described. Chapter 3 details the preparation of 3-dimethoxymethyl-1-pyrroline 1-oxides. Acid-catalysed deprotection of these nitrone acetals did not result in the formation of the expected 3-aldehydo-5,5-dimethyl-1-pyrroline 1-oxides. Chapter 4 deals with the preparation of 5,5-dimethyl-3-phenylthiomethyl-1-pyrroline 1-oxide. Conversion of the phenylthiomethyl group to an iodomethyl group led to the loss of the nitrone. Chlorination of the nitrone gave 4-methyl-4-nitro-2-phenylthiomethylpentanoic acid. Oxidation of 5,5-dimethyl-3-ethoxycarbonyl-1-hydroxypyrrolidine resulted in the dimeric nitrone 3,3'-bis(ethoxycarbonyl)-5,5,5',5'-tetramethyl-3,3'-bi-1-pyrrolinyl 1,1-dioxide being isolated. Chapter 5 concerns the synthetic utility of α-bromoaldehydes. The preparation of 5,5-dimethyl-3-benzenesulphonyl-1-pyrroline 1-oxide is then described. Alkylation of the nitrone in the presence of sodium hydride with methylbromoacetate gave the C-3 disubstituted nitrone, 3-benzenesulphonyl-5,5-dimethyl-3-methoxycarbonylmethyl-1-pyrroline 1-oxide. Chapter 6 concerns the spin trapping reactions of the nitrones prepared in this thesis. The ESR spectra of the hydrogen atom adducts showed the magnetic non-equivalence of the β-hydrogens owing to the presence of the C-3 substituent. Spin trapping of the <I>t</I>-butoxy radical was found to be stereospecific. Apparent selectivity for the hydroxyl radical was found as no spin adducts were detected with the superoxide radical anion.
54

Mechanisms of haemoglobin or copper ion promoted lipid peroxidation : implications for the oxidative modification of low density lipoprotein

Patel, Rakesh P. January 1996 (has links)
No description available.
55

Studies of transient free radicals in solution by flash photolysis E.S.R

Simpson, Nigel J. K. January 1990 (has links)
An introduction is presented to the nature of polarized and non-polarized transient spin resonance signals, produced by flash-photolysis e.s.r., followed by a description of the equipment used for experimental work. Theories of Chemically Induced Dynamic Electron Spin Polarization are reviewed and various models introduced to illustrate these concepts. A description is given of the first thorough investigation into the effect of CIDEP polarization transfer down a free radical chain and expands upon the consequences of hyperfine-dependent relaxation and the relative signs of coupling constants in various radical species. It concludes with an account of two methods of kinetic analysis which are the first practical demonstrations of their kind, and employ extension of expressions developed in earlier chapters. Studies are made of the CIDEP behaviour of radicals in high viscosity paraffins. A reassessment of previous published work is made: anomalous polarization behaviour was found to have been over-compensated for. A new method of extracting values for T<sub>1</sub> and T<sub>2,/sub> is demonstrated for strong transient e.s.r. signals. A collection of experimental data relating to the previously unexplained absorptive polarization observed in the spectrum of ketyl radicals and the longer-time phase inversion of hyperfine-dependent CIDEP is given. The operation of Triplet Mechanism CIDEP in the ketyl radical systems is ruled out and a division of radicals into geminately formed and free-encounter pairs is shown to be incapable of explaining the observed phase changes. In its place a cross-relaxational mechanism, drawing upon simultaneously generated nuclear spin polarization is advanced. Conclusions are drawn that this may account for both anomalies. Lastly a photochemical application of CIDEP is demonstrated; two different reaction intermediates are identified upon photolysis of ortho phthalaldehyde, depending upon the quenching conditions. A reaction scheme consistent with all experimental data is proposed. A brief comment upon the photo-chemistry of indan 2-one concludes this work.
56

Measurement of free radicals and their effects on human spermatozoa /

Lampiao, Fanuel. January 2006 (has links)
Thesis (MSc)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.
57

Synthesis and evaluation of model initiator/reversible terminating adducts for the stable free radical polymerization process /

Moffat, Karen Ann. January 1998 (has links)
Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references. Also available via World Wide Web.
58

Advances in free radical polymerization kinetics.

Zhu, Shiping. HAMIELEC, A.E. Unknown Date (has links)
Thesis (Ph.D.)--McMaster University (Canada), 1991. / Source: Dissertation Abstracts International, Volume: 53-01, Section: B, page: 0439. Supervisor: A. E. Hamielec.
59

Internal pressure's role in the selectivity of the bromine radical /

Hulvey, Glenn A., January 1993 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaf 53). Also available via the Internet.
60

High resolution spectroscopy of free radicals /

Leung, Wan-sze. January 1998 (has links)
Thesis (Ph. D.)--University of Hong Kong, 1998. / Includes bibliographical references.

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