Of science and small things: recollections of the past twenty(-)odd years
- Authors: Botha, J. R
- Subjects: Nanoscience , Nanotechnology , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/20867 , vital:29409
- Description: I will start, therefore, with an overview of achievements in a “new” field of endeavour, a science of small things, popularly called nanoscience, and its spin-off called nanotechnology. I will present a brief history, look at the approaches that have been followed by scientists and engineers to develop and understand small things, and summarise some of the benefits to society in terms of new materials and processes, energy storage and generation, electronics, environmental applications, medicine and transportation. Since our own research focuses on the development on semiconductors, I will conclude the scientific part of the presentation by considering the contribution of semiconductors to the development of nanotechnology and highlight a few examples from our own research during the past two decades on the development of nano-scale semiconductor structures, like nanorods, quantum wells and superlattices.
- Full Text:
Primeness in near-rings of continuous maps
- Authors: Mogae, Kabelo
- Subjects: Near-rings , Topological algebras
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10512 , http://hdl.handle.net/10948/d1020597
- Description: The prototype of a near-ring is the set of all self-maps of an additively written (but not necessarily abelian) group under pointwise addition and composition of maps. Moreover, any near-ring with unity can be embedded in a near-ring (with unity) of self-maps of some group. For this reason, a lot of research has been done on near-rings of maps. In 1979, Hofer [16] gave the study of near-rings of maps a topological avour by considering the near- ring of all continuous self-maps of a topological group. In this dissertation we consider some standard constructions of near-rings of maps on a group G and investigate these when G is a topological group and our near-ring consists of continuous maps.
- Full Text:
Resource utilization and reproduction of the hermit crab Clibanarius virescens (Crustacea: Decapoda : Anomura)
- Authors: Wait, Michelle
- Subjects: Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10599 , http://hdl.handle.net/10948/1553 , Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Description: Clibanarius virescens (Krauss) is a common and abundant hermit crab along the East coast of South Africa. Despite this, its biology is poorly known, both in South Africa and throughout the rest of its range in the West Indo-Pacific region. This study focuses on the descriptive analysis of the shell resource used by C. virescens and of the effects of this resource on crab populations. The underlying hypothesis of the study is that biogeographically imposed gradients in the morphology of intertidal gastropod shells used by hermit crabs affect hermit crab population parameters. The gradient of potential change in the shell resource was captured by sampling at 12 localities, encompassing the range of C. virescens in South Africa. Seasonal changes in shell use, population structure and reproduction at a single locality (Cape Recife) were recorded over a period of 13 months. The breeding season of C. virescens at the southern extreme of its range extended from December to June. The population structure shows some seasonal change, but no clear trends emerge. The shell resource changed substantially in nature over the region studied. Based on shell use, localities clustered into separate southern and northern groups with a break occurring between Dwesa and Coffee Bay. Southern localities were characterised by use of Burnupena cincta, B. lagenaria and B. pubescens. Northern localities were characterised by the use of Morula granulata, M. nodosa and Peristernia forskalii. Intertidal shells used by C. virescens show fewer adaptations to predation in southern localities than shells from northern localities. Southern shells ii are relatively large, light and have wider apertures than those from northern localities which are generally smaller, heavier and have decreased aperture widths. Shell parameters affect population size-distributions as southern crabs were larger and heavier than northern crabs. C. virescens show sexual size dimorphism in which male crabs uniformly dominate the larger size classes at all localities. Differences in the sex ratio between males and females show more variable patterns. Most southern localities show no difference in the number of male and female crabs, but most northern localities show a skewed sex ratio in favour of females. Shell use and population size distributions of females affect reproductive output. Southern females produced significantly larger clutches than northern females. Reproductive output was related to crab mass and shell volume. Shell use patterns conform to the biogeographical regions in the range of the study and have a clear effect on both the population size distributions and reproductive output of Clibanarius virescens.
- Full Text:
Sea turtles as ocean ambassadors: opportunities and challenges
- Authors: Nel, Ronel
- Subjects: Sea turtles -- South Africa , Sea turtles -- Conservation , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/55258 , vital:51136
- Description: Sea turtles are ocean migrants that nest on the same beaches where they were born but forage on reefs and oceanic waters great distances away. Movement between these locations is sometimes years or even decades apart. Because of these broad-ranging movements and the many countries, they visit throughout their lives, effective conservation can only be achieved through international cooperation. However, wherever and whenever sea turtles come ashore, they fascinate people. Watching a sea turtle nest is like looking back through a window into deep time. This appearance and disappearing act of sea turtles create an enigma that elicits a multitude of disciplinary, inter-, and intradisciplinary teaching, research and engagement opportunities ranging from archaeology to social sciences, including tourism, biology and ecology, conservation and policy. In these different spheres, I operated over the last two decades to understand sea turtles, their biology and behaviour to affect their conservation. The biggest question I have pursued in my research career is to understand why the leatherback sea turtle population (Dermochelys coriacea) nesting in the iSimangaliso Wetland Park, South Africa, has not increased despite decades of protection. Another sea turtle species, namely loggerheads (Caretta caretta) nesting in the same area, experiencing similar conditions, has responded positively to conservation. Through two decades of research evaluating the intrinsic and extrinsic population drivers, such as reproductive output, age to maturity, natality and mortality, it seems evident that the population dynamics of sea turtles is much more complicated than what a simple population model would predict. From the literature, it is clear that other species, like the Mediterranean monk seal, red knot (a sandpiper) and other coastal species, are suffering a similar fate, i.e., lack of recovery despite conservation. These trends suggest that these species have become refugees in their own habitat. Marine habitats are transformed through human activities and may now be unsuitable to support larger populations under the current climate for these complex species. Current research is aimed to disentangle past and present distributions to assess if these species have responded by using alternative habitats over time or if there are body condition parameters (such as individual size, offspring size or survivorship, or metabolomics) that will point us in the direction to grow these endangered populations. Our research suggests that sea turtles, with their very complex life history facing multiple threats, live at the edge of success and extinction. Understanding and managing their path to success is a delicate balance with many aspects that need consideration.
- Full Text:
South African estuaries in the Anthropocene
- Authors: Perissinotto, Renzo
- Subjects: Estuaries -- South Africa , Geology, Stratigraphic -- Anthropocene , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/20977 , vital:29424
- Description: In the new geological epoch of total human dominance of the planet, already widely referred to as the “Anthropocene”, estuaries are among the most vulnerable ecosystems to the changes that man’s activities have imposed on the coastal zone. For the non-specialist, an estuary is a “semi-enclosed coastal body of water, which has a permanent or temporary connection with the open sea, and within which sea water is diluted with fresh water from land drainage”.
- Full Text:
Towards mineral beneficiation: from basic chemistry to applications
- Authors: Tshentu, Zenixole
- Subjects: Metallurgy , Ore-dressing , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/55783 , vital:53876
- Description: The role of mineral beneficiation in the survival, growth, development and sustainability of a developing economy cannot be overstated. Our development as a human species has always been involvedly linked with the use of mineral resources from the stone, bronze and iron ages through the early modern eras to the present. In the current modern era, characterized by highly technological equipment, fourth industrial revolution (4IR) and new energy technologies, the role of mineral beneficiation has been elevated. Precious metals find use in the fine chemicals and petrochemicals industry, fuel cells, electrical and electronic products, medical and dentistry applications, jewellery, autocatalysts, and glass and ceramics. The markets for precious metals keep growing and the supply does not meet demand. The development of methods for recovery of metal value from feeds of mineral ore solutions, solutions of spent secondary resources and from mining wastewaters remains of great importance. Further beneficiation strategies for utilization of mineral products in other “value-added” applications are also important for the growth of the mineral markets. The usage of platinum, palladium and rhodium in the autocatalyst industry has grown significantly and this has further elevated the importance of platinum group metals (PGMs), but other areas of application of the strategic metals need to be harnessed. The four stages of beneficiation, namely, primary, secondary, tertiary and final stage, provide an opportunity to beneficiate to greater value for domestic or export use. Our own research work is engaged in several of these stages, from hydrometallurgical recovery of base metals and platinum group metals from feeds of primary mining and solutions of waste secondary resources such as spent catalytic converters and e-waste to the use of metals in “value added” products such as metalbased catalysts for the fuel industry and in metallodrugs. Examples of “value added” products include rhodium as a promoter in molybdenum sulfide as a catalyst for hydrodesulfurization of fuel oil, vanadium as a catalyst in oxidative desulfurization of fuel oil, vanadium and palladium as therapeutic agents for diabetes and cancer, respectively. Current and future work involves (i) the development of metal-selective scavengers to recover lost metal value in mining wastewaters, and (ii) the design of metal-based catalytic materials for refinement of bio-based oils to biofuel as well as for production of green LPG through hydroprocessing. Our work centres around both basic and applied chemistry towards mineral beneficiation and with a bias towards greener production.
- Full Text:
Utilising new technology to enable sustainable chemical and drug manufacturing in Africa
- Authors: Watts, Paul
- Subjects: Drug development , Pharmacology , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/21000 , vital:29426
- Description: Over the last few decades organic chemists have developed highly sophisticated chemical reactions to prepare very complex molecules. The pharmaceutical industry uses the methodology that academics develop within research programmes to manufacture drugs to treat a plethora of medical conditions. When unwell, all citizens expect treatment, however it needs to be remembered that the pharmaceutical industry is a business in order to make a profit for its shareholders, and consequently only rich nations can afford access to the most modern treatments available.
- Full Text: