An investigation into the effect of solid particulate phase on the bioleaching performance of Sulfolobus metallicus

Includes bibliographical references.Gold-bearing refractory sulphidic ores require a pretreatment process before extraction of the valuable metal, may be carried out. Bioleaching of the mineral may be used as pretreatment. Further mineral bioleaching may be used to liberate base metals such as copper from refractory sulphidic ores. The microorganisms used in the high intensity tank-based commercial biohydrometallurgy processes are mainly mesophiles, although moderate thermophiles are currently used at Youanmi Mine in Australia (Brierley, 1997). Extreme thermophiles have been found to exhibit enhanced oxidation kinetics in terms of rate of reaction and extent of solubilisation (Duarte et al, 1993; Norris and Barr, 1988; Konishi et al., 1995). However, these thermophiles appear to be sensitive to hydrodynamic conditions (Clark and Norris, 1996) and the presence of solids (Le Roux and Wakerley, 1988; Nemati and Harrison, 2000). An understanding of this sensitivity would be useful in developing systems to utilise extreme thermophiles in commercial biohydrometallurgy processes. The main objective of this study was to determine the effect of the solid particulate phase on the bioleaching performance of the extreme thermophile Sulfolobus metallicus. The hypothesis of the thesis was as follows: Archae involved in bioleaching are susceptible to damage in agitated aerated vessels, especially with increasing pulp density

A criminological exploration of cyber stalking in South Africa

The introduction of cyber technology, accompanied by its fast developing nature, has not only resulted in numerous advantages to its user and society as a whole but has also produced harmful consequences specifically impacting on cyber crime. One of these harmful effects is cyber stalking. Cyber stalking is the use of the Internet or any electronic medium to stalk, harass and pursue victims. This unwanted perusal has various negative implications for the victim, as cyber stalking can disrupt many aspects of an individual’s lifestyle. In this study, the occurrence, nature and the impact of cyber stalking among the victims of cyber stalking were explored. Additionally, protective measures available to victims of cyber stalking were examined as a way to facilitate the operational efficiency of related legislation. This was done through determining the occurrence, nature and the impact of cyber stalking as well as the extent of the usage of social networks in the commission of cyber stalking. Legislation specific to South Africa and the effectiveness of such legislation were examined. The study implemented a qualitative approach. Twelve research participants who met the requirements of the study were selected by means of purposive and snowball sampling methods. The study was publicised on the Internet through current popular social network sites. In conjunction to the cyber theme of the study, the research participants were requested to complete an online e-mail interview to share their personal cyber stalking victimisation experiences. Within the constraints of the e-mail interview, a semi-structured interview schedule was incorporated in order to guide the research participants in sharing their cyber stalking victimisation experiences. The findings of the study were extensive; ranging from emerged patterns to unique and exclusive experiences. In brief, the study concludes that cyber stalking is occurring in South Africa, its nature and impact is complex and although there are many common themes within cyber stalking, it is uniquely situated to individual cyber stalking incident(s). Although there is no current South African legislation specifically aimed at addressing cyber stalking, South African legislation comprehensively deals with addressing the problem of cyber stalking within various related legislation. It was determined that although cyber stalking is effectively addressed in the drafting of legislation, it is ineffectively administered at grass roots level, where the police act as the gatekeepers and vital role players in the reporting and intervention of crime. Based upon the findings, as guided by the aims and objectives of the study, recommendations for the prevention and intervention of cyber stalking as well as recommendations for future research were made. As derived from the research participants’ responses as well as from current literature, recommendations focused on all victims of cyber stalking while specifically paying attention to young victims and victims who are business users. Recommendations were also made to assist in dealing with cyber stalking as well as recommendations aimed at assisting professional role players. In the final chapter of the study, emphasis is placed on awareness and educational campaigns aimed at informing the cyber community of cyber stalking.M. A. (Criminology)Criminal and Procedural La

Information technology architecture and related strategic factors supporting business advantage

Magister Commercii (Information Management) - MCom(IM)Information Technology (IT) architecture is not restricted to technology, but may also address the views of business activities; their processes; data sets and information flows; applications and software; and technology. The objective of this study is to understand the role of IT Architecture and related factors that support competitive business advantage. This study investigates the null hypothesis: IT architecture enhances the competitive advantage of business. This study sets out to explore IT architecture and strategic factorsthat support business advantage. The study findings indicated that business advantage is supported by a sound architecture, by IT and business alignmentand by the enablers of organisations.South Afric

Information technology architecture and related strategic factors supporting business advantage

Magister Commercii (Information Management) - MCom(IM)Information Technology (IT) architecture is not restricted to technology, but may also address the views of business activities; their processes; data sets and information flows; applications and software; and technology. The objective of this study is to understand the role of IT Architecture and related factors that support competitive business advantage. This study investigates the null hypothesis: IT architecture enhances the competitive advantage of business. This study sets out to explore IT architecture and strategic factorsthat support business advantage. The study findings indicated that business advantage is supported by a sound architecture, by IT and business alignmentand by the enablers of organisations.South Afric

4000 years of thinkers on education - brochure

4000 Years of Thinkers on Education is een Engelstalig boek. Het bevat honderden houtsnijdende uitspraken over het nut en de betekenis van onderwijs

lnvestigations into the cancer modulating properties of Aspalathus linearis (Rooibos), Cyclopia intermedia (Honeybush) and Sutherlandia frutescens (Cancer bush) in oesophagea! carci nogenesis

>Magister Scientiae - MScThis thesis contains scientific evidence on the anticancer properties of two unique South African herbal teas, rooibos and honeybush, and the herbal plant Sutherlandia frutescens (cancer bush) using an in vivo oesophageal cancer model in rats and a human cancer cell line in vitro. Green and black teas (Camellia srnensls), known to modulate oesophageal cancer in rats were included as references. The unfermented herbal teas reduced tumour multiplicity (number and size) by significantly (P<0.05) decreasing the total mean number and the mean sizes of papillomas. Green and black teas significantly (P<0.05) reduced the total mean number of papillomas, while the mean size was markedly reduced. The Sutherlandia frufescens infusion markedly reduced the total mean number and mean size of papillomas. Modulation of the growth kinetics of the early neoplastic oesophageal lesions by the teas, presumably the polyphenolic constituents, is likely to reduce their proliferative activity. A total polyphenol intake threshold of 7 mgi 100 g body weight is proposed for the herbal teas to effectively modulate oesophageal papilloma development in rats. Specific polyphenol subgroup ratios also appear to be important, as 'fermentation" chemically alters polyphenols and reduces the water soluble polyphenol content of rooibos and honeybush and therefore reduced their chemopreventive properties. The cytotoxicity and anti-proliferative properties of the different teas were also evaluated in a human oesophageal cancer cell line. Although the cytotoxicity could not be measured accurately when using the lactate dehydrogenase (LDH) release and tetrazolium bromide (MTT) colorimetric assays as a result of colour interference of the teas, satisfactory results were obtained when employing flow cytometry, CellTiter Gloo Luminescence and Brd incorporation cell proliferation assays. Plant matrix and media interactions effected by Sutherlandia frutescens also prevented the determination of cytotoxic parameters in the cancer cells. When utilising flow cytometry and cell viability assays, unfermented rooibos tea displayed properties comparable lo lhe Camellia smensls teas, while honeybush exhibited weaker effects. Unfermented rooibos, however, exhibited a more potent inhibitory effect on cell proliferation when compared to green and unfermented honeybush teas. lmpairment of the proliferative capacity of the papillomas and the human cancer cell line could be important in utilizing the herbal teas as chemopreventive agents against oesophageal cancer

Thermophilic mineral bioleaching performance: A compromise between maximising mineral loading and maximising microbial growth and activity

Synopsis Thermophilic bioleaching, conducted at temperatures in excess of 65°C, provides considerable benefit over mesophilic bioleaching, particularly through extending the extent of leaching of base metal minerals such as chalcopyrite. Thermophilic bioleaching is facilitated through a group of micro-organisms known as the Archae, well adapted to extreme environment. In order to maximize the space time utilization of the stirred tank reactor in the thermophilic bioleaching process, it is desirable to maximize the loading of the finely divided mineral phase present while not adversely affecting the microbial performance. In this paper, the effect of the loading of the solid particulate phase on the bioleaching performance of Sulfolobus metallicus was studied in a stirred tank reactor. Emphasis was placed on the effect of the concentration of the finely divided solid phase (35 – 75 µm). A model system comprised of 3% (w/v) pyrite in the presence of varying quantities of quartzite in the range 0 to 24% (w/v) was used to obtain the different solids concentrations. The bioleaching experiments revealed similar bioleaching performance in the presence of 3 to 18% (w/v) total solids. Above 18% (w/v) total solids (15% quartzite loading), bioleaching was impaired progressively with increasing solids concentration. At the highest solids loading studied of 27% (w/v), bioleaching was still observed. In terms of mass transfer, oxygen transfer potential was not significantly influenced in the bioleaching process over the range of solids investigated

Maintaining the legitimacy of school choice in the segregated schooling environment of Amsterdam

In 2015, Amsterdam implemented a centralised primary school admissions policy, constraining school choice after a long history of highly autonomous schools and free parental choice which has resulted, in part, in the city's segregated schooling environment. Introduced out of concerns of inequality for parents and disorganisation by schools, this policy implemented a uniform choosing procedure and a distance-based priority mechanism. Drawing on interviews with school directors and municipal education officials, this paper examines how schools seek to maintain their legitimacy in a highly segregated school choice environment undergoing constrained change. The Amsterdam case serves as a unique example of local education officials confronting the well-documented negative effects of school choice through policies controlling school choice in an era of global school choice expansion

Thermophilic mineral bioleaching performance: a compromise between maximising mineral loading and maximising microbial growth and activity

Thermophilic bioleaching, conducted at temperatures in excess of 65°C, provides considerable benefit over mesophilic bioleaching, particularly through extending the extent of leaching of base metal minerals such as chalcopyrite. Thermophilic bioleaching is facilitated through a group of micro-organisms known as the Archae, well adapted to extreme environment. In order to maximize the space time utilization of the stirred tank reactor in the thermophilic bioleaching process, it is desirable to maximize the loading of the finely divided mineral phase present while not adversely affecting the microbial performance. In this paper, the effect of the loading of the solid particulate phase on the bioleaching performance of Sulfolobus metallicus was studied in a stirred tank reactor. Emphasis was placed on the effect of the concentration of the finely divided solid phase (35 – 75 µm). A model system comprised of 3% (w/v) pyrite in the presence of varying quantities of quartzite in the range 0 to 24% (w/v) was used to obtain the different solids concentrations. The bioleaching experiments revealed similar bioleaching performance in the presence of 3 to 18% (w/v) total solids. Above 18% (w/v) total solids (15% quartzite loading), bioleaching was impaired progressively with increasing solids concentration. At the highest solids loading studied of 27% (w/v), bioleaching was still observed. In terms of mass transfer, oxygen transfer potential was not significantly influenced in the bioleaching process over the range of solids investigated