This research focuses on three elements i.e. employment equity, employee engagement and generation theory and specifically where these elements intersect. The literature found that there were different perceptions of employment equity legislation. In addition, the literature found generational differences with respect to some elements of employee engagement. Limited empirical evidence was found on whether employment equity legislation had an impact on employee engagement. Consequently, three research questions were drawn from the literature reviewed. The research is a quantitative study based on a sample drawn from South African individuals who have completed grade 12 and are currently employed or have an employment history. The sample included employees of a financial services company based in Gauteng and GIBS MBA students. The results showed that there were differing perceptions of employment equity legislation and that the majority of respondents perceived the legislation to be affirmative action. There were no differences in the perception of employment equity legislation between generations. Additional findings were that the perception of employment equity legislation did not enhance employee engagement neither did the perception of the organisations implementation of employment equity legislation enhance employee engagement. Limited generational differences were found in terms of these findings. / Dissertation (MBA)--University of Pretoria, 2014. / zkgibs2015 / Gordon Institute of Business Science (GIBS) / MBA / Unrestricted

A field in bloom: photoredox catalysis has allowed chemists access to highly reactive intermediates via the photo-mediated excitation of transition metal complexes and organic dyes for the mild generation of free radicals. These complexes and dyes are designed based on Nature’s blueprints of light-harvesting biomolecules that transform solar energy (photons) into chemical energy during photosynthesis. Light-mediated chemical activation is regarded as one of the most sustainable forms of chemical activation being that the energy provided by the sun is considered renewable and largely underutilized and presents an attractive avenue for research and development of new transformations that are mild, efficient, and waste-limiting in organic synthesis. Radical chemistry and photochemistry are united in their inherent ability to undergo single (or photoinduced) electron transfers by one-electron reaction modes. Combining these unique fields, photoredox catalysis has emerged as a mild and efficient alternative to classic alkyl radical generation using hazardous initiators and organostannanes. Photoredox catalysis has been dominated by ruthenium- and iridium-based polypyridyl complexes. These complexes are limited by their inherent redox potentials, restricting their reactivity towards relatively activated bonds. Nonactivated bromoalkanes and arenes are considered challenging substrates to engage using redox chemistry and typically only accessible in the realm of organostannane chemistry. Described herein are the efforts towards the discovery of free radical based organic transformations derived from nonactivated bromoalkanes and arenes mediated by photochemical excitation of polynuclear gold(I) complexes as photoredox catalysts. This work represents some of the first uses of a photoredox catalyst in the reduction of substrates having such high reduction potentials and offers a practical and useful alternative to classic radical reactions mediated by initiators (peroxides, persulfates, and azo compounds) and toxic organostannanes (Bu3SnH). Using gold based photoredox catalysts, the research conducted has provided many methodological advancements for the mild and efficient formation of carbon-carbon bonds using nonactivated bromoalkanes and a large collection of radical acceptors. Establishing the use of these photoexcited polynuclear gold(I) complexes in the context of classic radical reactions in organic synthesis was important for their validation as useful photocatalysts. First, the Ueno-Stork cyclization of nonactivated bromoalkanes was used to demonstrate the powerful reducing capabilities of the excited-state gold(I) complexes. Next, a photo-mediated variant of the Appel reaction was described, where the transformation of an alcohol to a bromoalkane was achieved using carbontetrabromide and N,N-dimethylformamide through the intermediacy of a Vilsmeier-Haack reagent. In combination with the hydrodebromination chemistry developed with photoexcited polynuclear gold(I) complexes, a photo-mediated one-pot formal deoxygenation reaction of alcohols was described; a useful alternative to the organostannane mediated Barton-McCombie deoxygenation reaction. Finally, in the field of medicinal chemistry, the functionalization of heteroarenes is of high interest for the discovery of drug candidates and bioactive molecules. In this respect, one of the most useful reactions for the functionalization of heteroarenes by alkyl radicals is the Minisci reaction using silver salts, carboxylic acids, and persulfates. Detailed are the efforts for the development of a photo-mediated redox-neutral improvement of the Minisci reaction, needing only gold(I) photocatalyst and nonactivated bromoalkane in the presence of heteroarenes. Overall, the work described in this thesis represents the push for mild and efficient alternatives to the relatively harsh conditions and/or toxic reagents and byproducts associated with classic radical chemistry. These studies demonstrate the ability to control highly reactive alkyl radical intermediates with the goal of their broader application in synthetic organic chemistry. The use of photoexcited polynuclear gold(I) complexes as potent reductants compared to ruthenium- and iridium-based polypyridyl complexes is illustrated through the genesis of highly reactive alkyl radicals from nonactivated bromoalkanes.

Master of Science / Department of Geology / Brice LaCroix / The Los Burros mining district (LBMD) is located within the Lucia subterrane (Underwood et al., 1995) along the Sur- San Gregorio-San Simeon-Hosgri fault system of California’s Franciscan complex. The LBMD presented an attractive gold prospecting and mining area during the late 19th and early 20th centuries. Recent interest in the area has focused on fault-offset modelling through thermochronology (Underwood et al., 1995, Chapman et al., 2016). However, the mechanism, conditions, and timing of ore formation in the area are poorly constrained due to a lack of academic interest and documentation. This research seeks to arrive at a better understanding of gold emplacement mechanisms in the LBMD through an examination of lithologic and structural controls coupled with source fluid composition and peak P/T constraints. Sampling and mapping of lithologies and structures within the vicinity of the LBMD were conducted during the summer of 2016. Samples were collected for clay-fraction and bulk-rock mineralogy via XRD analyses, petrographic inspection and interpretation, including fluid inclusion microscopy/microthermometry as well as Raman spectroscopy. These analyses were conducted in an endeavor to constrain and explain a previously identified regional thermal anomaly within the vicinity of the LBMD with the intention of characterizing and modelling the impacts of structural controls on gold deposition. The results of this study suggest gold deposition from a gas-poor, metamorphic source-fluid with approximately 300 ppm CH₄, CO₂ density of 0.15 g/cm³, and an average salinity of 1.7 wt % NaCl equivalent. These data, along with peak P/T conditions of ~285°C and 680 bars were inferred using input from illite crystallinity data, fluid inclusion microthermometry, and the application of the Raman spectroscopy of carbonaceous material (RSCM) geothermometer used by Lahfid et al. Gold mobilization from sulfide and carbonaceous-rich sediments through polyphase deformation events led to emplacement along structural and lithologic contacts likely as a syn-orogenic event. Gold emplacement occurred during the reorientation of the regional structure by transpression.

The project deals with the effect of the airflow and temperature on the gold wirebond due to possible application in hot-wire anemometry. Theoretical fundamentals of wirebonding and hot-air anemometry are included in the text. From the area of anemometry, there is also a detailed description of measurement principles, areas of application and measuring instruments. The practical part of the text deals with design of the experimental sensor for hot-wire anemometry with use of the gold wirebond, including also the verification of the sensor's properties.

Doctor Scientiae / Acid Mine Drainage (AMD) is identified as one of the contributors to environmental hazard in the gold mining region of South Africa, as caused by the mining operational activities performed by mining industries in South Africa. This effect motivates the development of AMD prediction techniques application and geochemistry modelling using gold tailing dams located in West Rand area, Witwatersrand Basin as a case study. Control strategies are devised to assess, understand and measure the acidic potential generation of waste materials in ensuring the right method required to analyse risks caused by AMD to environment. The method encompasses mineralogical and geochemical analysis of 93 samples collected, AMD prediction, test modification and geochemical modelling. This method was appropriately applied to understand the basic mechanisms involved in controlling acid generation, assessing prediction procedure and selecting the right prediction tools. Study objectives are attained by performing a series of experimental lab tests on the samples collected from the two major tailing dams (Mogale and Gold One_1 tailings). Results derived from the lab experiments (XRD and SEM-EDS) show presence of mineral phases characterised with the surface feature of samples, and unknown substances of samples were identified. Geochemical characterisation was performed by XRF and ICP-MS to determine the major oxides elements and trace elements, respectively. Leco test generate total sulphur and total carbon. Multistatistical analysis is used to interpret the data derived from geochemical characterisation process to explicate the metal and trace elements distribution and occurrence. Initial samples were screened and categorised based on paste pH and EC using kinetic tests to determine acid-forming and neutralising minerals in samples and static tests to determine acid generation potential in samples. Net Acid Producing (NAPP) was mathematically calculated from Acid Neutralising Capacity (ANC), Maximum Potential Acidity (MPA) and total Sulphur. Results obtained from the Paste pH demonstrate that samples collected from 1 meter downward the holes to 10 meters, with a few meters samples in hole T003 at Gold One_1 are non-acidic while the remaining tailing samples are acidic. ANC/MPA ratio was applied to assess the risk of acid generation from mine waste materials. Graphical illustrations of the Acid Base Account (ABA) are plotted to demonstrate the net acidic generation potential trends of samples, which were classified into non-acid forming, potential acid forming and uncertain categories. Results integration between ANC, Single Addition Net Acid Generation (NAG) test and NAPP were used to classify acid generation potential of the samples. Leachate collected from leaching column test were analysed for pH, EC and chemical element by ICP-MS. The leaching column test used to analyse samples (T004) and (T001) collected from the two major tailings was set up for a 4-month experiment. Study findings present environmental assessment report on the two investigated gold tailing dams in Witwatersrand Basin area. Other findings are improved understanding of the application and limitations of various existing AMD prediction methods for assessment of gold mine waste and conceptual geochemical modelling developed to test appropriate methodology for AMD potential at a given gold mine site.

In this work the synergy between a polymer containing chelate sites and gold ions was explored by the fabrication of a polymeric membrane with embedded gold nanoparticles inside its matrix and by developing a process to recover gold from acidic solutions. After realizing that the thiosemicarbazide groups present in the monomeric unit of poly-thiosemicarbazide (PTSC) formed strong complexes with Au ions, membrane technology was used to exploit this property to its maximum. The incorporation of metal nanoparticles into polymeric matrices with current technologies involves either expensive and complicated procedures or leads to poor results in terms of agglomeration, loading, dispersion, stability or efficient use of raw materials. The fabrication procedure described in this thesis solves these problems by fabricating a PTSC membrane containing 33.5 wt% in the form of 2.9 nm gold nanoparticles (AuNPs) by a three step simple and scalable procedure. It showed outstanding results in all of the areas mentioned above and demonstrated catalytic activity for the reduction of 4-Nitrophenol (4−NP) to 4-Aminophenol (4−AP). The current exponential demand of gold for electronics has encouraged the development of efficient processes to recycle it. Several adsorbents used to recover gold from acidic solutions can be found in the literature with outstanding maximum uptakes,yet, poor kinetics leading to an overall inefficient process. The method developed in this dissertation consisted in permeating the gold-containing solution through a PTSC membrane that will capture all the Au ions by forming a metal complex with them. Forcing the ions through the pores of the membrane eliminates the diffusion limitations and the adsorption will only depended on the fast complexation kinetics, resulting in a very efficient process. A flux as high as 1868 L/h m2 was enough to capture >90% of the precious metal present in a solution of 100 ppm Au. The maximum uptake achieved without sacrificing the mechanical stability was 5.4 mmol/g. The selectivity between gold and copper (the most common unwanted metal present along with gold) was 6.7 for 100 ppm initial concentration of both metals and 14.6 for 500 ppm.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Recently nanoparticles (NPs) have been introduced and used in combination with therapeutic approaches to develop nanotechnology-enabled medicine. These nanostructures allow for the exploitation of the physiochemical properties which may be beneficial in cancer treatment. The use of NPs in nanomedicine has proven successful in modern chemotherapeutics and has demonstrated promising potential in in vivo and in vitro radiosensitization studies. This is a baseline study aimed to determine the cytotoxic effects of AuNPs for potential radiosensitization analysis. The study analysed the effects of different AuNP sizes (30, 50 and 80nm), concentrations (5, 10 and 15 μg/ml) over various time periods in CHOK1 and A549 cells.

Philosophiae Doctor - PhD / The Sandamap gold prospect is a metaturbidite shear zone-hosted gold mineralization located in the Neoproterozoic Damara Orogen 30 km northwest of the town of Usakos in Namibia with an estimated gold content of 240 000 t at 3.6 g/t up to 40 m below surface. This research project was aimed at constraining the age, crustal level of formation, pressure-temperature conditions during formation, sources of the mineralizing fluids, and by implication, the metal sources of the Sandamap gold mineralization. Fluid inclusion, geochronological and isotopic studies were carried out on quartz veins hosting the ore. The presence of kaolinite, alunite and jarosite suggest post-hydrothermal weathering of sulfides. Various sources of data from this study, giving rise to depths of entrapment of 4 to 14 km, temperature range of entrapment of fluids of 187 – 594 °C, stable isotope data (δ13C and δ18O), δD values and a δD vs. δ18OH2O plot are all in favour of an orogenic gold deposit. Additionally, the dominant CO2-rich and CH4-rich fluids observed at Sandamap do not contradict this interpretation. The calculated depth of entrapment of mineralization covers the lower portion of the epizonal zone to the upper portion of the hypozonal zone of gold deposits. The Sandamap mineralization’s δD values of -35‰ to -49‰ fall within the range of most published data for typical orogenic gold deposits which varies from -20 to -80‰. Moreover, the calculated δ18Owater values of the ore-fluids (+6.6 to +11.3‰) of the higher temperature aqueous group from the Sandamap mineralization fall within the range observed in typical orogenic gold deposits found in Phanerozoic terrains (+7 to +13‰). The schist hosting the mineralized shear zone with a gold content of 0.05 ppm Au or its higher grade equivalent at depth, is a possible gold source candidate. Two mechanisms of deposition were possibly at play: (i) the cooling below 500 °C and possible sulfidation (resulting from fluid-rock interaction), lowered the solubility of pyrite causing S3- and Au(HS)S3- (possible main Au carriers) to breakdown resulting in decreased Au solubility and its subsequent deposition and (ii) the elevated amount of CO2 (e.g. trench 14 where CO2-rich fluid inclusions are dominant) led to a sharp decrease in the Au(HS)2- and Au(HS)S3- concentrations, causing decreased Au solubility and its subsequent deposition. The age of mineralization obtained from 40Ar/39Ar dating of the muscovite associated with the ore-hosting quartz veins is placed at 472 ± 3 Ma. The mineralization is younger than the shear zone, which acted as a conduit for ore-fluid migration and it has no age relationship with proximal plutonic bodies. The mineralization is younger than the foliated granite (FG), which exhibits a metamorphic fabric in the form of mineral segregation, but older than the non-foliated granite (GT) which hosts a mineralized xenolith.

In this paper, the electrochemical behaviors of a single gold nanoparticle attached on a nanometer sized electrode have been studied. The single nanoparticle was characterized by using electrochemical methods. Since there is only one nanoparticle on the electrode, unarguable information for that sized particle could be obtained. Our preliminary results show that it becomes more difficult to oxidize gold nanoparticle or reduce gold nanoparticle oxide as the radius of the particle becomes smaller. Also, the peak potential of the reduction of gold nanoparticle oxide is proportional to the reciprocal of the radius of the particle.

Over the past few decades, inorganic nanoparticles, which exhibit significantly distinct physical, chemical and biological properties from their bulk counterpart's, have elicited much interest. Discoveries in the past decade have demonstrated that the electromagnetic, optical and catalytic properties of noble-metal nanoparticles such as gold, silver and platinum, are strongly influenced by shape and size. This has motivated an upsurge in research on the synthesis routes that allow better control of shape and size for various nano-biotechnological applications. Biomedical applications of metal nanoparticles have been dominated by the use of nanobioconjugates that started in 1971 after the discovery of immunogold labeling by Faulk and Taylor. Currently metal-based nanoconjugates are used in various biomedical applications such as probes for electron microscopy to visualize cellular components, drug delivery (vehicle for delivering drugs, proteins, peptides, plasmids, DNAs, etc), detection, diagnosis and therapy (targeted and non-targeted). However biological properties of bare-metal (naked) nanoparticles have remained largely unexplored. Therefore, in this review we discuss the novel biological properties and applications of three most widely used metal nanoparticles, namely, the nanoparticles of gold, silver and platinum. We describe the novel properties and use of these nanoparticles in angiogenesis and cancer related disorders.