[en] The first problem to be investigated in this dissertation concerns the metallicity and atmospheric structure of the super-metal-rich (SMR) stars. High dispersion coude echelle scans of the [Ca II] lambda 7323.9 A forbidden line and the Ca I lambda 6572.8 A intercombination line have been obtained for three SMR K giants and for three K giant standard stars. The SMR stars investigated are ν²C Ma, μ Aq1 and μ Leo; the standard stars' are epsilon Vir, α Cas, and α Boo. Abundances obtained from the [Ca II] line indicate that calcium is overabundant by + 0.2 to 0.4 dex in these SMR stars', relative to the sun. This supports the view that the metal enhancements reported by many observers are real, and are not a spurious consequence of some other mechanism acting in these stars atmospheres. The second problem to be investigated in this dissertation concerns the carbon, nitrogen and oxygen (CNO) abundances in the weak G-band stars. High dispersion photographic coude spectra have been obtained for the weak G-band stars HR 6791 and HR 885, and for the solar abundance standard epsilon Vir. The [O I] lambda 6300 and lambda 6363 lines, CH A²Δ - X²II system bands and CN A²Δ - X²Σ⁺ red system bands are the CNO abundance criteria. The results for HR 6791 and HR 885, respectively, are [C/H] = -0.92 and -1.57, [N/H] = + 0.76 and +0.22, [O/H] = -0.08 and -0.25 dex. The results show that the atmospheres of these stars have undergone a greater exposure to CN-cycle processing than is predicted by current stellar evolution theory

[en] Forty-two uranium and mixed uranium and thorium anomalies were selected from the analogue radiometric records generated during theBarberton-Phalaborwa airborne geophysical survey. Thirty-eight of the anomalies plotted over rocks of the Timeball Hill and Daspoort Formations, and ground follow-up work is recommended for these anomalies. Two more anomalies probably originate from rocks of the Palabora Igneous Complex, another anomaly overlies a diabase intrusive, and the remaining anomaly appears related to an outlier of Ecca Group rocks

[en] The analogue gamma-ray spectrometer records of block 12 of the Karoo airborne geophysical survey were studied and significant uranium anomalies were selected and graded. The anomalies were plotted on 1:50 000 scale maps and the co-ordinates of the anomalies were tabulated. The anomalies were transferred to 1:250 000 scale maps which are included in this report. The geological setting of the anomalies has been studied. Ground follow-up work has been recommended for anomalies which occur over mineralized pans and drainage channels, and the Lower Beaufort Stage. Other anomalies which occur over the Ecca Series, the Middle Beaufort Stage, the Upper Beaufort Stage and the Stormberg Series have also been recommended for ground investigation

No abstract available

[en] Measurements of v sin i for 74 OB stars, mostly with v sin i < 60 km s^-1, have been made on spectrograms obtained with the coude spectrographs of the 82-in. and 017-in. reflectors at McDonald Observatory. This high-resolution study enables us to define the frequency distributions of v sin i for small values of v sin i with improved accuracy. Combining the data with that from Slettebak for v sin i > 60 km s^-1 new frequency distributions of v sin i for main sequence and evolved B stars were produced. Bimodal Maxwellian distribution functions are fitted to these curves. (author)

[en] Ionoluminescence (IL) combined with particle induced X-ray emission (PIXE) imaging has been employed to identify intrinsic growth bands in the spire region, and extrinsic bands at the growth edge of Australian Black-lip abalone shell (Haliotis rubra). Previous studies using optical flood cathodoluminescence, scanning electron microscope cathodoluminescence (SEM-CL) and Raman spectroscopy on samples from the same population suggest that the visible luminescence is due to Mn²⁺ activated calcium carbonate. In this study we confirm Mn²⁺ as the activator in both the spire and growth edge regions of the shell. The sensitivity of ionoluminescence to the co-ordination environment of the Mn²⁺ activators in the shell allows for the spatial identification of the calcium carbonate polymorph responsible for the growth lines observed optically. Furthermore the detection and mapping of trace elements such as Mn and Sr with the PIXE technique enables comparisons to be made between calcite and aragonite biomineralized in the wild and under laboratory conditions

No abstract available