Thesis (MTech (Chemical Engineering))--Cape Technikon, 2000. / Internationally, there is an increase in the need for safer environmental processes that can be applied to mining operations, especially on a small scale, where mercury amalgamation is the main process used for the recovery of free gold. An alternative, more environmentally acceptable, process called the Coal Gold Agglomeration (CGA) process has been investigated at the Cape Technikon. This paper explains the application of flotation as a means of separation for the CGA process. The CGA process is based on the recovery of hydrophobic gold particles from ore slurries into agglomerates formed from coal and oil. The agglomerates are separated from the slurry through scraping, screening, flotation or a combination of the aforementioned. They are then ashed to release the gold particles, after which it is smelted to form gold bullion. All components were contacted for fifty minutes after which a frother was added and after three minutes of conditioning, air, at a rate of one I/min per cell volume was introduced into the system. The addition of a collector (Potassium Amyl Xanthate) at the start of each run significantly improved gold recoveries. Preliminary experiments indicated that the use of baffles decreased the gold recoveries, which was concluded to be due to agglomerate breakage. The system was also found to be frother-selective and hence only DOW-200 was used in subsequent experiments. A significant increase or decrease in the air addition rate both had a negative effect on the recoveries; therefore, the air addition rate was not altered during further tests. The use of tap water as opposed to distilled water decreased the attainable recoveries by less than five per cent. This was a very encouraging result, in terms of the practical implementation of the CGA process.

No description available.

No description available.

Bodas de oro químicas: como homenaje a la sección química por sus 50 años este ensayo muestra estampillas relacionadas con el oro / Chemical golden anniversary: as tribute to the PUCP's chemical section for its 50 years of work this essay features stamps with gold-related pictures

Submitted by Daniella Sodre (daniella.sodre@ufpe.br) on 2015-04-15T15:11:48Z No. of bitstreams: 2 TESE Gabriela Guedes.pdf: 1658990 bytes, checksum: d74ac5823949c1e44d7efd506322f238 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-04-15T15:11:48Z (GMT). No. of bitstreams: 2 TESE Gabriela Guedes.pdf: 1658990 bytes, checksum: d74ac5823949c1e44d7efd506322f238 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2013 / A imunossupressão, causada por diversos fatores tais como desnutrição, doença auto-imune, infecção pelo HIV ou uso de drogas imunossupressoras tem contribuído com o aumento da incidência da tuberculose (TB) no mundo. O requisito essencial para o controle da TB é a identificação rápida e precisa dos indivíduos infectados. Os métodos convencionais (baciloscopia, cultura, histopatológico, radiografia de tórax e teste tuberculínico-TT) para diagnóstico da TB têm as suas limitações de especificidade, rapidez e sensibilidade. Ainda é uma tarefa desafiadora diferenciar pacientes com tuberculose ativa daqueles com lesões quiescentes, vacinação prévia com BCG ou outras doenças com sintomas semelhantes ao da TB. Portanto, o trabalho teve como objetivo principal avaliar o desempenho dos testes QuantiFERON®-TB Gold (QFT-GIT) e PCR único tubo (STNPCR) no diagnóstico da TB em pacientes imunodeprimidos. Foram selecionados 100 pacientes, que foram divididos em dois grupos: imunodeprimidos (n = 88) e controle (n = 12). As amostras biológicas (sangue, urina, LCR e escarro) de todos os indivíduos envolvidos foram submetidas aos testes QFT-GIT e STNPCR. A sensibilidade e especificidade do QFT-GIT, da STNPCR e do TT foram 57,4% e 95,3%; 64,3% e 91,4%; 69,2% e 98,1%, respectivamente. Os testes QFT-GIT e TT demonstraram uma concordância moderada (κ = 0,41). Dez pacientes apresentaram resultado indeterminado ao QFT-GIT e apenas 1 foi reagente ao TT. A maior frequência de TT reatores ocorreu nos indivíduos com contagem de T CD4+ >350 céls/μL. Entre os pacientes com TT reator, 60% possuíam vacina BCG, confirmada através da cicatriz vacinal e 46,7% relataram história prévia de TB. Apenas 20% dos pacientes com TB confirmada apresentaram cultura bacteriana positiva nas amostras (urina, LCR ou escarro). Os testes QFT-GIT e STNPCR não demonstraram utilidade na rotina dignóstica em pacientes imunodeprimidos. Portanto, o TT deverá continuar a ser usado para a triagem inicial de pacientes imunodeprimidos com suspeita de TB.

Made available in DSpace on 2014-10-09T12:38:26Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:29Z (GMT). No. of bitstreams: 1 05827.pdf: 4162110 bytes, checksum: 4818bf19a034f75fcbef60b0310a8176 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

M.Phil. (Industrial Psychology) / Please refer to full text to view abstract

The Navachab Gold mine, an orogenic lode gold deposit, is located in the Karibib region of the Pan-African (ca. 550-500) Damara belt of central Namibia. Gold mineralisation is developed within the steeply NW dipping limb of the Karibib dome. Here, ore envelopes trend along three main orientations: a) trends shallowly towards the NE (the down plunge extent), b) trends sub-vertically in and along the down plunge extent and c) trends sub-horizontally across the down plunge extent. The down plunge extent represents the bulk of the gold mineralisation, hosting the only high grade ores mined at Navachab. As such, past work primarily focused on establishing the controls to the mineralisation observed here. The sub-vertical and sub–horizontal ore trends are seen as secondary, lower grade, being hosted in the footwall. By cutting pushbacks into the footwall, in an effort to regain access to high grade pit bottom, future gold production almost exclusively relies upon optimally mining these ores. This underlines the importance to investigate and outline the mineralising controls to the secondary ore trends. This study identified the following prevailing quartz vein sets developed within the footwall, set (1) dips shallowly towards the NE (conjugate vein set), (2) steeply towards the NW (bedding parallel veins) and (3) steeply towards the SE (S2 foliation parallel). The NW and SE dipping sets contain high average gold grades, occurring at an infrequent vein density. The NE dipping veins, as a result of occurrence density alone, was highlighted as the dominant gold hosting set. Veining occurred during the late stages of the NW-SE directed, sub-horizontal shortening (D2) event and is associated with top-to-the-NW thrusting and NW-verging folds. Re-Os molybdenite dating from auriferous quartz veins indicates mineralisation occurred at 525-520 Ma. As crustal shortening amplified the Karibib dome, flexural flow developed fractures along bedding planes, providing the control to bedding parallel veins (NW dipping). With continued crustal compression the dome later experienced fold lock up associated with reduced mean rock stress and sub-horizontal extension occurred along the steeply NW dipping limb. Horizontal extensional gashes sucked in fluids to form the shallowly NE dipping conjugate vein set. These features suggest the regional D2 strain as the first-order control to quartz vein development, down plunge and within the footwall ores. To further define the secondary ores, lithological and structural controls were evaluated on a more detailed local scale. With equal amounts of biotite schist and calc-silicate host rock (bulk of the footwall lithology) material analysed, the biotite schist units were found to contain a larger volume amount of quartz veins. The mineralisation incurred is also developed at higher average gold grades compared to that of the calc-silicates, demonstrating biotite schist having the optimal rheology for quartz vein emplacement. Normal faulting and thrusting occurs widespread, at all scale levels, across the footwall. These were primarily observed along bedding foliations and secondly at higher angles cutting across foliation. The study did not constrain the extent of these, but can conclude faulting plays a very prominent role in re-distributing the secondary ores parallel to bedding along sub-vertical trend planes. Great care should be placed in properly modelling these with 3D software such as Leapfrog. The Navachab gold mineralisation came about as a result of convergent and collisional tectonics activating metamorphic dehydration of the crustal metapelites. As these fluids ascended they absorbed gold from the crust, emplaced by either a magmatic or paleo-placer source. The gold enriched hydrothermal fluids amalgamated in large scale 1ste order structures (shearing of the steep NW limb of the Karibib Dome, the Mon Repos Thrust Zone) that acted as primary active fluid path ways. In the case of Navachab the gold enriched fluid fluxed along these pathways while interacting with fluid sinks related to a physical throttle (brittle schist, folding, bedding parallel shears) and/or a chemical trap (marbles). By summarising and detailing the fluid sinks and active fluid pathways identified by this and previous works, it is strongly recommended that a mineral approach system be designed and implemented as targeting model to lead future exploration endeavours.

Human interaction with gold can be traced far back in history, and throughout history, the metal has been both worshipped and fought for. People almost intuitively place a high value on this yellow metal and gold has always had a special place in the human heart. Nonetheless, the question many irresolute investors seek the answer to today is whether gold deserves a special place in their investment portfolios. The main purpose of this quantitative study was to determine whether gold is an appropriate diversifier for Swedish investors, and to find the optimal weight of gold in a Swedish equity portfolio. Corresponding properties of other precious metals silver and platinum were also investigated for comparative purposes. One of the reasons for augmented interest in investing in gold is the perceived risk in the economy. The theoretical framework for the study was Modern Portfolio Theory (MPT). The insight of MPT is that efficient diversification handles the risk better than individual assets. Risk management is especially crucial in an era of heightened economic, financial and political uncertainty as today. At the same time, rising correlation among traditional diversifiers make diversification more difficult. Gold, influenced by its history as a currency, has often taken the role as an inflation hedge and a portfolio stabilizer during turbulent financial markets. Inflation hedge assets like gold should be negatively correlated with the market and should give the best diversification benefits in a portfolio. This indicates that gold may be an appropriate diversifier in an equity portfolio. The study took the perspective of Swedish investors, and a Swedish equity index was therefore used as proxy for a well-diversified portfolio. Registry data for past prices of assets over a period of 47 years were obtained via a study published on the official website of the Swedish central bank and Thomson Reuters Datastream. Excess returns were then calculated and processed to obtain descriptive and inferential statistics. The optimal weights of gold and the other precious metals in an investment portfolio were calculated under the optimization framework of maximization of the Sharpe ratio where reward to volatility is highest. The calculations were performed for eight different holding periods. Results show near 0, or weak positive correlations between Swedish domestic equity and gold during the examined periods. On stand-alone basis, gold is superior to other precious metals in most of the studied periods, but all three precious metals have potential to function as diversifiers in an investment portfolio that is only devoted to Swedish domestic equities. Therefore, weightings of 9% gold, 12% silver and 9% platinum are preferred to improve the performance of the Swedish equity portfolio. However, the Sharpe ratio does not take into account the ethics of investing and possible environmental and social consequences. Therefore, the suggested allocation of gold in this study may not be a sustainable investment at long term.

M.Sc. / Background: The continuous emergence of drug resistant strains of HIV as a result of errors made by reverse transcriptase coupled with undesirable side effects of available drugs, latency problems, cost etc, warrants the continuous search for new drug candidates. Chrysotherapy which is the use of gold compounds for the treatment of various ailments has been practiced since 2500 BC. The use of gold compounds such as auranofin for the treatment of rheumatoid arthritis has lead to remission of this disease. Gold compounds such as auranofin not only prevented the progression of arthritis but also increased the CD4+ count of an HIV positive patient who was not on antiretrovirals. These compounds have been implicated in the treatment of cancers, autoimmune diseases and microorganism infections. Objectives: In this work, novel gold compounds were evaluated with the aim of identifying lead compound(s) that can eventually serve as anti-HIV agents. Materials and Methods: Eleven gold (I) phosphine complexes, four of their corresponding ligands (compound without gold atom), and a gold (III) complex were tested for the ability to inhibit reverse transcriptase (RT) and protease (PR) in direct enzyme assays. Uptake of the compounds by host cells was evaluated with inductively coupled plasma atomic emission spectrometry (ICP-AES). Potential toxicity of the gold compounds was screened for by viability dyes and flow cytometry assays. To determine inhibition of whole virus by other mechanisms in addition to RT or PR, p24 production by infected cells was evaluated. Prior to all these analysis, stability of compounds in solution was determined by 31P nuclear magnetic resonance (NMR) and UV-visible spectroscopy. Results: The compounds were shown to be stable in solution over a one week period and were taken up by both continuous cell lines and primary cells. Eight of the gold compounds significantly inhibited HIV-1 reverse transcriptase at concentrations of 25 and 250 μM while four compounds and the four ligands did not. In a fluorogenic assay against HIV-1 PR, four of the gold compounds demonstrated inhibitory activity. The gold compounds were toxic to cells lines but not to primary cells. One of the complexes (EK231) significantly reduced p24 (p=0.0042) production at a concentration of 25 μM. Conclusion: Data provided here suggests that the therapeutic benefits of these gold containing compounds as potential HIV-1 reverse transcriptase and protease inhibitors should be considered.