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"April, 2002" Includes bibliographical references and Publications list (leaves 22-30) V. 1. nos.1-50 -- v. 2. nos. 51-105 "Selected research publications submitted to the University of Adelaide for the degree of Doctor of Science."

In this thesis we make a new measurement of the primordial deuterium abundance, and analyse five other systems selected as possible D/H candidates. We also undertake an investigation of systematic errors in a system where an existing deuterium measurement has been made. We measure the number of hydrogen components and their velocity distributions in a moderate and high redshift sample of Lyman limit systems in one Angstrom resolution spectra. We present a new measurement of the deuterium-to-hydrogen ratio, D/H, at z=3.2560 in a newly-discovered low metallicity absorption system towards the quasar PG1937-1009. We attempt to account for any systematic effects that could influence the D/H measurement. We find a 1 sigma range for D/H*1e5 of 1.6 (+0.25) (-0.30). Using high resolution spectra from the Hubble Space Telescope and the Very Large Telescope, we assess the suitability of five D/H candidate absorption systems. These systems were selected as candidates using lower resolution spectra. We measure the neutral hydrogen column density, identify metal lines and analyse the velocity structure of each system, and show them to be unsuitable for measuring D/H. We also investigate the systematic errors in the absorber at z=0.701 towards quasar PG1718-4801 that was initially thought to show a high primordial D/H value. We analyse the dependence of the putative deuterium line's parameters on wavelength calibration errors in the HST spectra and present a revised deuterium measurement. We examine the velocity widths of two samples of one Angstrom resolution quasar spectra showing Lyman limit absorption systems. The first sample is at high redshifts, taken from the Sloan quasar data release 3 catalogue. The second is at intermediate redshifts, compiled from a survey for UV quasar absorption systems taken with the Hubble Space Telescope. We use a modified version of the Voigt profile fitting program, VPFIT, to estimate the number of hydrogen velocity components and column density in the Lyman limit systems. We compare the velocity distributions of the higher and lower redshift samples. We find the distributions are consistent with other measures of the velocity spread in absorption systems, and find no compelling evidence for evolution between the redshift samples.

"April, 2002" / Includes bibliographical references and Publications list (leaves 22-30) / 2 v. (various paging) : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / "Selected research publications submitted to the University of Adelaide for the degree of Doctor of Science." / Thesis (D.Sc.)--University of Adelaide, Dept. of Environmental Biology, 2003

In this study the enzymatic activity of adsorbed Thermomonospora fusca E��� and Trichoderma reesei CBHI cellulases were investigated using fluorescence techniques. In particular, cellulases were allowed to contact hydrophobic polystyrene surfaces under conditions of different solution concentrations, and adsorption times. Each of these variables is known to have a potential effect on enzyme structure and activity at an interface. Enzymatic activity was measured after partial elution of the adsorbed layer with both protein-free buffer and the surfactant, dodecyltrimethylammonium bromide. For E��� at high concentration (0.5 mg/ml), adsorbed enzyme activity decreased about 20% in increasing adsorption time from 0.25 h to 24 h. At low concentration (0.001 mg/ml), adsorbed enzyme activity decreased by one order of magnitude during a 24 h period. CBHI layers lost activity only after a sufficiently long contact time with the surface, and this effect was not strongly dependent on enzyme concentrations in solution. These findings were explained with reference to structural changes undergone by adsorbed enzyme as a function of time and available interfacial area. / Graduation date: 2000

Graduation date: 1999

Graduation date: 1999

Graduation date: 1998