Faculty of Natural and Agricultural Sciences
School of Physical Sciences
Department of Physics
Selected Highlights from Research Findings
The sacred hill of Mapungubwe in the Limpopo valley is the subject of numerous myths and legends. In 1933, a stunning archaeological find catapulted these tales into the realm of historical fact. At the summit of the hill, graves were discovered that contained large numbers of golden artefacts, marking the site as the final resting place of the rulers of an ancient African trade kingdom.
Subsequent excavations also uncovered thousands of imported glass beads and shards of Chinese porcelain. These remains connect Mapungubwe to an extensive maritime trade network that linked Africa to the East from as early as the first century AD.
The age of the site has been the subject of some dispute, however. By virtue of their colour, shape and decoration, the pieces of Chinese porcelain were initially assumed to have been manufactured at the famous Longquan kilns during the late Southern Song dynasty – a period that lasted from 1127–1279 AD. According to current opinion, the latest occupation date of Mapungubwe hill was around 1280 AD.
A research project by scientists at the Geology Department under leadership of Dr SMC Verryn, the Physics Department, in collaboration with the University’s Mapungubwe Museum and Oxford University’s Research Laboratory for Archaeology and the History of Art has called these assumptions into question.
The shards were studied by means of Raman spectroscopy, x-ray fluorescence spectroscopy and x-ray diffraction. The Raman polymerisation index calculated from the spectra of the glaze on the shards indicates that its firing temperature was higher than one would expect for the relatively calcium-rich Longquan glazes of the Southern Song dynasty.
X-ray fluorescence analysis of the glaze and x-ray diffraction measurements of the bulk of the shards confirm that the porcelain may well belong to the Yuan (1279–1368 AD) or even early Ming (1368–1644 AD) dynasty.
The results of this study are extremely important for the chronological history of Sub-Saharan Africa, as they suggest that the glory of Mapungubwe may have shone for much longer than previously believed. Ms L Prinsloo
Physics
+27 (0) 12 420 2458
linda.prinsloo@up.ac.za
Biophysics is one of the fastest growing specialisation fields in physics in the world. At the University optical characterisation techniques have been applied to investigate coloration effects in biological materials such as butterfly wings and seashells.
In the past year, this work has been extended to bird feathers and insect exocuticles. A detailed knowledge of the physical processes which create colours purely by structural effects in essentially colourless materials have already produced a number of interesting new applications in nano-structured electronic materials such as photonic crystals used in the detection and control of weak optical signals.
Recent work on the iridescent colours of scarabus beetles revealed that these insects employ a unique heliciodal structure, which strongly reflects a narrow band of colours when illuminated by right-circularly polarized light, but appears dark when illuminated by left-circularly polarised light. This kind of structure has potential applications in liquid crystal display units.
The backbone of the research in the application of optical techniques and methods in biology comes from the optical characterisation of solid-state materials, where the effects of ion implantation on modern wide band gap electronic materials are investigated.
The main aim of this work is to modify the optical and electronic properties of such materials in a useful way. To this end we have developed and refined characterisation techniques such as ellipsometry, photoluminescence, Raman spectroscopy and reflectance spectroscopy. Prof JB Malherbe
Physics
+27 (0) 12 420 2896
johan.malherbe@up.ac.za
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