The South African gold mining sector consumes 47% of the mining industry’s electricity. On a deep level gold mine, 20% of the energy is consumed by the refrigeration system. The refrigeration system cools 67 ˚C virgin rock temperatures underground. Underground cooling demand increases significantly with deeper mining activities. Various cooling systems are available for underground cooling. This study focuses on the electricity usage of an ice storage system versus a chilled water system for underground cooling. An energy-savings approach was developed to determine possible power savings on the surface refrigeration system of Mine M. The savings approach involved converting an ice storage system to a chilled water system and varying the water flow through the system. The water flow was varied by installing variable speed drives on the evaporator and condenser water pumps. The feasibility of the energy-efficiency approach was simulated with a verified simulation model. Simulation results indicated the feasibility of converting the thermal ice storage to a chilled water system and implementing the energy-efficiency approach on Mine M. Simulated results indicated a 9% electricity saving when using a chilled water system. Various problems encountered by the mine were also a motivation to convert the thermal ice storage system. Converting an ice storage facility to a chilled water system for energy efficiency on a deep level gold mine Energy management is achieved through the monitoring, controlling and reporting of the implemented savings approach. Converting the glycol plant and recommissioning the chilled water plant gave the mine an additional chiller as backup to sufficiently meet underground demand. An annual summer power saving of 1.5 MW was achieved through the conversion and control strategy. It is concluded that conversion of the thermal ice storage system on Mine M results in an energy- and cost saving. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

Doctor of Philosophy / Department of Physics / Christopher M. Sorensen / Nano-size materials are new materials in an intermediate state between the bulk and atomic or molecular states. Nanoparticles in colloidal solution and their assemblies have the great attention of researchers to investigate the novel fundamental properties and numerous applications. In this dissertation, we investigated the solubility phase transition behavior of gold nanoparticles in colloidal solution. We used the nearly monodisperse gold nanoparticles synthesized by either the inverse micelle or the solvated metal atom dispersion methods followed by digestive ripening. The gold nanoparticles were ligated with alkyl chains, which were dodecanethiol, decanethiol, or octanethiol for individual samples. They dispersed in toluene or t-butyl toluene like large molecules at room temperature. In analogy to molecular solutions, the colloidal solution had thermally reversible phase transitions between a dissolved phase of dispersed single nanoparticles and dispersed-aggregation co-existing phase. A more polar solvent, 2-butanone, was added to the colloidal solution for changing the solubility of gold nanoparticles and adjusting the phase transition temperatures to accessible temperatures. Superclusters formed by the nanoparticles when the colloidal solutions were quenched from a one-phase regime at high temperature to a two-phase regime at low temperature. Solubility phase diagrams were obtained for gold nanoparticles with different ligands in the mixtures of different ratios of 2-butanone and toluene or t-butyl toluene. The explanation from classical ideal solution theory gave the fusion enthalpy of superclusters. Temperature quenches from the one-phase to the two-phase regime yielded superclusters of the nanoparticle solid phase with sizes that depended on the quench depth. Classical nucleation theory was used to describe these sizes using a relative small value of the surface tension for the nanoparticle solid phase. This value is consistent with molecule size scaling of the surface tension. In total these results show that the solubility behavior of nanoparticles in colloidal solution is similar to the behavior in molecular solutions.

Submitted in complete fulfillment for the Degree of Master of Technology: Biotechnology, Durban University of Technology, 2013. / The biosynthesis of NPs has many advantages over the tedious, expensive and toxic physical and chemical methods of synthesis. Plants are stocked with valuable metabolites that are capable of reducing metal salts to form NPs. In this study, aqueous leaf extracts of A. dubius, G. perpensa, C. roseus and C. triloba were reacted with AgNO3 and HAuCl4 to determine the plants reducing abilities and hence synthesis of Ag and Au NPs capabilities. The synthesis reactions were carried out at different temperatures and extract concentrations for optimization. The goal was to form NPs within the specific wavelength range. Polar solvents: methanol and ethyl acetate extractions were carried out at the optimized conditions to evaluate the best solvent for the extraction of phytochemicals from the plants. The plant leaf extracts that were successful (A. dubius, G. perpensa and C. triloba) in synthesizing NPs were then micropropagated to form callus cultures. The reducing abilities of these callus cultures extracts were determined by varying temperature and concentration parameters. Characterization of the NPs formed by the different extracts was performed using UV-vis, TEM and FTIR. UV-vis spectrophotometry was used as a confirmatory as well as characterizing tool. TEM analysis was able to provide a description on the size and shape of the NPs whereas FTIR provided information on the biomolecules responsible for synthesis and capping of NPs. The stability of the NPs was determined by UV-vis scans over a period of 30 days which allowed observation of the alteration in peak shape and absorbance and hence condition of particles. Phytochemical tests were performed on the leaf extracts of the four plants to elucidate possible phytochemicals responsible for the reduction of metal salts. Antibacterial activity of the NPs was evaluated by using the disk diffusion assay and MICs were determined by the broth dilution method against pathogenic bacteria. A. dubius, G. perpensa and C. triloba were capable of synthesizing Ag NPs and Au NPs which were indicated by yellowish orange and reddish purple colour changes respectively. G. perpensa was able to spontaneously form Ag and Au NPs without any addition of heat whereas A. dubius and C. triloba required heat to form Au NPs. As the temperature of the reactions increased, the absorbance and possibly the number of NPs produced, increased. When the concentration of the extract was doubled, the absorbance was seen to decrease. C. roseus did not produce any Ag or Au NPs with any of the leaf extracts. Only A. dubius and C. triloba callus extracts were investigated for NP synthesis and it was found that A. dubius callus extracts were unsuccessful in synthesizing NPs and C. triloba callus extracts were able to form unstable Ag and Au NPs. The spherical Ag NPs that were formed from aqueous extracts of A. dubius were slightly larger than the methanolic Ag NPs. The Ag NPs produced by G. perpensa were in the same size range for aqueous and methanolic extracts. C. triloba Ag NPs formed from the methanolic extract were closer in size to A. dubius aqueous Ag NPs but the C. triloba aqueous extract produced much larger Ag NPs than the other extracts. The Ag NPs produced from A. dubius aqueous and methanolic extracts as well as C. triloba methanolic extracts exhibited the longest stability of 30 days. Ag NPs from G. perpensa aqueous extracts had the least stability. G. perpensa did not form any hexagonal Au NPs and the spherical and triangular Au NPs were smaller unlike in A. dubius and C. triloba Au NPs. The Au NPs formed by the aqueous extracts of A. dubius and C. triloba were larger in comparison to their methanolic counterparts. The Au NPs produced from G. perpensa aqueous and methanolic extracts as well as A. dubius and C. triloba methanolic extracts exhibited the longest stability of 30 days. Au NPs were stable for longer in comparison to Ag NPs. FTIR provided evidence that Ag and Au NPs have a chemical bond with the amide group in amino acids. However the intensities of biomolecules for Au NPs are more pronounced compared to the Ag NPs. It was also found that the Ag NPs synthesized by methanolic leaf extracts have slightly higher intensities than Ag NPs synthesized from aqueous leaf extracts. Phytochemical screening showed the absence of tannins in the C. roseus leaf, A. dubius and C. triloba callus extracts and presence in the other three plants. C. triloba methanolic extract Ag NPs showed the highest activity against Gram-positive S. aureus. Aqueous and methanolic Ag NPs from G. perpensa and C. triloba as well as A. dubius methanolic Ag NPs had activity against all fourteen bacteria. A. dubius aqueous Ag NPs had no activity against Enterobacter spp. and a strain of Klebsiella pneumoniae. G. perpensa Ag NPs had better antibacterial activity and lower MICs against Gram-positive and Gram-negative pathogenic bacteria compared to A. dubius and C. triloba. There was no antibacterial activity seen with Au NPs. The size and shape of NPs are the keys to their biomedical properties. Green synthesis of NPs is a feasible way for the future. This study showed that NPs can be synthesized very easily and economically. A key finding of this study is that different plants produce varying sizes and aggregation of NPs. / National Research Foundation

The use of Au-NHC complexes in homogenous gold catalysis has become very popular during the last 10 years. The work described in this thesis represents a modest contribution towards a better understanding of the reactivity of these fascinating complexes and the intermediate species involved during gold-catalysed transformations. There are two main themes that permeate the following chapters: a) synthesis and reactivity studies of monoaurated species and b) synthesis and reactivity studies of diaurated species. The main motivation for the work presented herein was to develop more efficient synthetic routes towards a series of gold complexes, such as [Au(NHC)Cl], [Au(NHC)(OH)] and [{Au(IPr)}₂(μ-OH)][X], in order to be able to further explore their reactivity. Chapter 2 constitutes the first approach that I had with the chemistry of Au-NHC complexes, and describes our efforts to evaluate how the use of a highly sterically demanding NHC ligand affects gold-catalysed transformations. Chapters 3 and 4 explore alternative, more efficient synthetic routes towards known Au- NHC complexes. For example, a new, highly robust protocol has been developed for the synthesis of [Au(NHC)X] (X = Cl, Br, I) complexes, which are the starting materials to prepare a wide range of Au-NHC based species. Moreover, as a result of our investigations it has been possible to isolate a series of [Au(NHC)(OH)] species and to gain some insight into the stability of these complexes. Chapters 5 and 6 describe the synthesis and applications of digold hydroxide species [{Au(IPr)}₂(μ-OH)][X] in a series of catalytic and stoichiometric transformations. For example, they have been used as silver-free catalysts for water-inclusive gold-catalysed transformations or to access key intermediates in gold catalysis, such as gem-diaurated and σ,π-digold-acetylide species. Finally, Chapter 7 combines what we learned about the reactivity of [{Au(IPr)}₂(μ- OH)][X] in order to develop for the first time a gold-catalysed transformation where two gold centres independently react with two substrate molecules to catalyse the hydrophenoxylation of alkynes.

International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper presents an exciting new concept in real-time information distribution that can be easily integrated into existing and future telemetry reception and data dispersal systems. After briefly examining the evolutionary path and various perceptions of the concept “real-time”, a variety of techniques are explored in achieving the expedient movement of real-time information. Many non-telemetry application environments are now using real-time shared-memory networking techniques to obtain large, highspeed integrated sharing of common information. The phenomenal results are partially attributable to high reliability, extremely low latency, and ease of use. This paper attempts to present various telemetry applications and scenarios with descriptions of benefits achieved by simply changing existing data movement techniques to those using shared-memory networking techniques.

Gold nanoparticles can serve as an ideal radiosensitizer for radiation therapy due to the high-atomic-number nature of gold and the increased tumor specificity in nanoparticle form. The degree of radiosensitization is highly dependent on both the local gold nanoparticle concentration in the tumor and the radiation source type. Previous Monte Carlo simulations have demonstrated that the gamma-ray energy spectrum of Ytterbium-169 is a strong candidate for a high dose rate brachytherapy implementation of gold nanoparticle-aided radiation therapy. Therefore, the current study focuses on the design of a high dose rate Ytterbium-169 source that would maximize dose enhancement during gold nanoparticle-aided radiation therapy; while meeting the practical constraints for the production of a clinically relevant brachytherapy source. Different encapsulation materials are studied in order to determine its effect on the dosimetric characteristics of the source. Specifically, the photon spectra, secondary electron spectra, and dose enhancement characteristics are calculated via Monte Carlo simulations to elucidate the effects on potential radiosensitization during gold nanoparticle-aided radiation therapy. Furthermore, this project involves a study into the modification of external x-ray beams from a Philips RT-250 orthovoltage x-ray machine in an attempt to match the dosimetric characteristics of the Ytterbium-169 brachytherapy source. This investigation will enable the production of an external beam that can serve as a good surrogate of an actual brachytherapy source and facilitate the pre-clinical investigation of gold nanoparticle-aided radiation therapy with Ytterbium-169.

This thesis re-examines the suspension of the gold standard rule in Britain between 1797 and 1821 within the framework of the theory of credible and time consistent monetary policy. By combining both historical and theoretical analysis the thesis challenges the prevailing theory in which the gold standard is considered as a contingent rule and the suspension as an exogenously credible regime. Firstly, the thesis analyses what made the suspension credible in the absence of the gold standard rule. It is proposed that the suspension was a credible regime, because the resumption of the gold standard at the old par value in the future was a sustainable plan. It is shown that monetary policy during the bad state -- such as war -- can still be time consistent in the absence of the formal commitment rule, if the policy maker's plan is to resume the original commitment rule when the economy returns to the good state. The equilibrium is based on trigger strategies where private agents retaliate if a policy maker deviates from its policy plan to resume the gold standard rule. Secondly, the thesis aims to establish why the gold standard rule was suspended for twenty-four years. Both historical analysis and a dynamic general equilibrium model demonstrate that the gold standard was a shock amplifier when the shocks became persistent in the 1790s, and suspension was used to restore monetary stability during the French Wars. As the suspension of cash payments was a credible regime, it maintained the value and circulation of paper currency that in turn stabilised production and consumption. Suspension increased the degree of flexibility in the economic policy as the monetary authority had an opportunity to stimulate the economy by issuing fiat money during the war, on the understanding that the fiat money so issued would be withdrawn from circulation before the gold standard resumed. Finally, it is explained why the gold standard was resumed after the relatively successful Suspension Period. The gold standard was seen as a solution to the problem that arose from the Bank of England's ambiguous role as a public and private institution. Rules were considered to be better than discretion, and the gold convertibility was a transparent principle, which maximised the long-run welfare of the society. The thesis demonstrates how already in the eighteenth century commitment to the gold standard rule had increased the efficiency of capital markets and enabled Britain to finance its eighteenth-century wars by using deficit finance. Maintaining these abilities through the gold standard was desirable.

Heterogeneous enantioselective catalysis strives to create new successful catalysts. One of the most researched examples is the hydrogenation β-ketoesters using nickel-based catalysts. A hindrance in the industrial scale-up of this enantioselective hydrogenation reaction is the lack of exact details of how chirality is bestowed onto this achiral metal surface. While a number of mechanisms have been proposed to explain the enantioselective behaviour of this system, these are predominantly based on catalytic studies. An alternative approach is through surface science studies examining the morphology, structure and composition of this catalytic system. A range of ultrahigh vacuum based model studies investigating the structure and composition of ultrathin Ni films and Ni/Au surface alloys on Au{111} using the techniques of Scanning Tunnelling Microscopy (STM) and Medium Energy Ion Scattering (MEIS) are presented in this thesis. In addition, the adsorption of the chiral modifier (S)-glutamic acid has been studied on these surfaces using vibrational spectroscopy (Reflection Absorption Infrared Spectroscopy (RAIRS)) and Temperature Programmed Desorption (TPD). Furthermore, MEIS has been used to investigate the influence of (S)-glutamic acid on the surface composition of Au/Ni model catalysts detecting effects such as adsorbate induced segregation and de-alloying behaviour. In addition, colloidal preparative routes have been used to synthesise bimetallic Au/Ni nanoparticles supported on mesoporous silica. The catalysts are then modified by the adsorption of the chiral ligand, (R,R)-tartaric acid. Finally, the catalysts are tested for their activity and enantioselectivity with respect to methylacetoacetate hydrogenation. At each stage the catalysts are characterised by a combination of Extended X-ray Absorption Fine Structure (EXAFS); Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectrometry (EDS) and Atomic Absorption Spectroscopy (AAS).

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy