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Investigation of the effect of hydrocarbon spillages and their interaction with alteration minerals on the flotation of UG2 PGE ore
(2023) Tshinavhe, Thendo Arthur; Becker, Megan; Mcfadzean Belinda
With growing safety, low productivity and operational cost concerns in the local PGE mining industry, mechanized mining is becoming more frequent to address these challenges and offer easy access to ore bodies compared to conventional mining methods. The heavy-duty machinery used may contaminate the ore because of oil inadvertently leaking from their hydraulic components during mining. Such contaminants have been anecdotally linked to the reduction of downstream flotation performance. Anecdotal evidence suggests that such problems are further exacerbated in the presence of phyllosilicate alteration minerals (serpentine, chlorite and talc) from weathered or altered ores. The near-surface Two Rivers Platinum (TRP) UG2 ore is routinely exposed to hydrocarbon contamination when the underground ore is excavated and transported to surface, resulting in reduced PGE flotation recoveries. Therefore, this study aimed to decouple the effects of oil contaminants on the flotation performance of PGE bearing ores and further establish the interaction mechanism(s) between oil and phyllosilicate alteration minerals. Two ores of varying alteration degrees (normal and altered UG2) were utilized to assess the effects of oil. Batch flotation tests were conducted to decouple the effect of oil on the flotation performance of the two UG2 ores by varying the oil dosage from 0 to 500 g/t, followed by conducting supplementary experiments in which the key interests were on column froth stability, rheology, and oil adsorption tests. These were performed to understand the mechanism(s) leading to the reduced flotation performance. Quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) was utilized to characterize the bulk mineralogy as well as PGM. The bulk mineralogy was validated with quantitative X-ray diffraction (QXRD). The last phase on the study involved using sodium metasilicate (1500 g/t) and a degreaser (500 g/t) as a potential mitigation measure to the deleterious effect of oil on flotation performance. As was expected, the QEMSCAN bulk mineralogy recorded a higher percentage of the phyllosilicate alteration minerals (serpentine, chlorite, and talc) in the altered UG2 (9.1 wt.%) relative to the normal UG2 (6.2 wt.%), consistent with the observations of alteration during sampling. Talc contributed around half of the total phyllosilicate alteration minerals in both ores; however, it was slightly higher in the altered UG2 compared to the normal UG2 (5.8 wt.% versus 3.8 wt.%). Therefore, the altered ore was expected to experience more severe detrimental flotation effects. The results of batch flotation tests indicated a decrease in Pt (~3 g.t) and Pd (~3 g/t) concentrate grades in the normal ore with increasing oil dosage with no significant negative effects on recovery (Pt increased by 4% and Pd was constant). In contrast, the oil resulted in detrimental effects to both Pt and Pd recovery for the altered ore, where a recovery loss of 6% Pt and 12 % Pd were observed. The concentrate grades remained unaffected. The addition of oil increased the froth stability for both ores (34% in the normal ore and 47% in the altered) as well as the pulp viscosity (including pure talc). The increase in viscosity was greater in the altered ore. The oil adsorption study on the two feeds revealed that most of the iv oil coats the particles with no preferential adsorption between the two ores (nearly the same concentration). The oil adsorption study on the concentrate and the tails showed no preferential recovery to either the concentrate or tails in the normal ore whereas more selective recovery of the oil-coated particles to the tails was observed for the altered ore. The observed decrease in grade in the normal ore due to oil contamination was attributed to oil improving the froth stability which caused excess entrainment of gangue materials and thereby diluting the concentrate grade. The decrease in recovery in the altered ore was ascribed to oil forming particle agglomerates (particularly complex talc agglomerates) which increased the pulp viscosity and subsequently resulting in poor gas dispersion and reduced particle-bubble collision. After understanding the mechanisms in each ore, batch flotation with sodium metasilicate and a degreaser were conducted in the presence of oil, as a potential mitigation measure. Sodium metasilicate (SS) improved the grades in the normal ore floats and had no detrimental effect toward the recovery (constant recoveries, no loss in Pt and Pd). For the altered ore, both the grade and recovery (Pt-8% and Pd-5%) were improved by the adding of SS. The effects on the grade were most noticeable at low oil concentration (0 and 300 compared to 500 g/t). For the degreaser, only the flotation experiments with the degreaser were performed due to laboratory technical problems-new flotation cell was used. Thus, there was no comparison with the no degreaser condition. The trends (% difference between 0 g/t and 500 g/t) were compared to the no degreaser (oil only) conditions conducted in the first cell. The degreaser was shown to improve 2E grade and recovery in both ores. However, the improvement in flotation performance was unquantified. The deleterious effects were successfully mitigated when using sodium metasilicate due to its beneficial effects in reducing pulp viscosity as well as improving the froth drainage. With the degreaser, the flotation performance was not quantified. Therefore, this study demonstrated that, SS can be implemented to mitigate the viscous effects caused by oil spillages and alteration minerals (particle agglomeration) in mechanized mines. However, SS should not be implemented blindly as other downstream processes should be considered (settling in the thickener). To implement the degreaser, more tests need to be conducted.
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Open Access
Divine Madness in Plato’s Phaedrus
(2024-04-17) Shelton, Matthew
Critics often suggest that Socrates’ portrait of the philosopher’s inspired madness in his second speech in Plato’s Phaedrus is incompatible with the other types of divine madness outlined in the same speech, namely poetic, prophetic, and purificatory madness. This incompatibility is frequently taken to show that Socrates’ characterisation of philosophers as mad is disingenuous or misleading in some way. While philosophical madness and the other types of divine madness are distinguished by the non-philosophical crowd’s different interpretations of them, I aim to show that they are not, in fact, presented as incompatible. Socrates’ pair of speeches demonstrates that madness can be divided into harmful and beneficial kinds, and in Socrates’ key discussion of philosophical madness (249c4-e4), I argue that the crowd correctly recognises that the philosopher is mad on the basis of his eccentricity, but wrongly assumes that the philosopher’s madness is of the harmful type because it fails to realise that the philosopher is enthused. Socrates’ second speech provides information about human souls and gods which shows that philosophical madness belongs to the beneficial type and so falls under the heading of divine enthusiasm after all. Importantly, human souls and gods are shown in the speech to be roughly isomorphic. Both philosophical and other kinds of divine madness involve having something divine inside a human body (entheos): in the former a human soul has become godlike; in the latter a human soul has been displaced by a god. Because of this, I propose that philosophy is presented as a genuine form of divine madness alongside the other more conventional examples.
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Open Access
Outcomes of penetrating keratoplasty at a tertiary institution in South Africa.
(2023) Theron, Yolande; du Toit, Nagib
Aims: To determine corneal graft survival rates and visual outcomes of penetrating keratoplasty (PKP) in a South African setting. Methods: A retrospective review of 99 penetrating keratoplasties performed at Groote Schuur Hospital, South Africa over a 3-year period between February 2016 and February 2019. Results: The mean age of study participants was 38 years (14-85). The study included 60% females and 40% males. The main indications for surgery were keratoconus (58%), corneal scar (21%), regrafts (8%), pseudophakic bullous keratopathy (6%), corneal dystrophies (3%) and pellucid marginal degeneration (1%). The overall graft survival at 1-year follow up was 86%. A higher 1-year graft survival rate of 94% was seen in patients with keratoconus. The total number of patients diagnosed with graft failure at 1 year was 13.The Kaplan-Meier survival analysis was used to assess time to graft failure. The estimate was 11.7 months (mean time to graft failure) with a 95% CI confidence interval from 11.4 to 12 months. In our study, best corrected Snellen acuity in the category of 6/6-6/18 was found in 59.2% of patients 1-one year post-operatively, compared with 1% of patients in the same BCVA group pre-operatively. Patients with a BCVA equal to 3/60 or less reduced from 56% preoperatively to 20% postoperatively at 1 one year. Conclusion: Penetrating Keratoplasty is an effective long term treatment option to restore visual acuity in certain corneal disorders in a middle to low-income country. Our results demonstrated a comparable 1-year graft survival rate to high-income countries.
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Open Access
Copyright and Accessibility in South African Research Archives
(2023) Walker, Andrea; Tong, Lee-Ann
Research archives aim to achieve a balance between preservation and access. Copyright law aims to achieve a balance between the interests of rightsholders and users. These aims sound broadly similar at first, but there are areas where the intersection can be problematic. This dissertation examines the problem of archival accessibility through three lenses: copyright duration, preservation, and third-party and orphan works. Copyright assumes an author intends to exploit their work through some form of publication. Most of the works within a research archives are unpublished. One of the ways archives seek to make works more accessible to more people, is by placing them online. Unless the copyright has expired or been assigned to the archives, this requires permission from the rightsholder(s). In South Africa, many unpublished works have perpetual copyright. Determining when the copyright expires—if it expires—is complicated by more than publication status. Certain works require reference to otherwise repealed laws due to the transitional provisions that continue to apply to archival works long after the transition has taken place. The question of internet ‘publishing' also needs to be considered. In order to make works accessible in perpetuity, the works need to be preserved so that they continue to exist. To preserve works, archives need to reproduce them. The Copyright Regulations allow the creation of facsimile copies for preservation purposes without requiring the permission of the rightsholder(s). If the reproduction is not in facsimile form, then it is infringement without the rightsholder(s) permission. It is not clear if the format shifting that audiovisual and digital content requires is allowed when creating a facsimile. This material becomes inaccessible and is lost very quickly as format shifting is needed in order to keep the content accessible, as well as to preserve it for the long-term. Copyright and Accessibility in South African Research Archives | Andrea Walker | ii Many archival works, such as letters, are authored by third-parties—that is, someone other than the person or corporate body who created the bulk of the collection. Many of these become orphan works as identifying and locating the rightsholder(s) with limited information is very difficult. Works with perpetual copyright frequently become orphaned as tracing the author's descendants and their subsequent heirs and any licences or assignments is a lengthy and difficult process. The inability to identify and locate rightsholders does not only impact on accessibility, but also preservation. There are some simple solutions to these problems, but while suggestions for improvements are offered, most of these are not issues that can easily be dealt with.
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Open Access
The Influence of Jazz in 20th-Century Classical Clarinet Music: A performance-based investigation of Copland's Clarinet Concerto and Bernstein's Clarinet Sonata
(2023) Rotevatn, Marie; Herbst, Theo
Playing classical compositions containing stylistic elements of jazz can be a challenge for a classically trained clarinettist. This study explored how to play such compositions by investigating, learning, and performing Concerto for Clarinet and String Orchestra (with Harp and Piano) by Aaron Copland and Sonata for Clarinet and Piano by Leonard Bernstein. Considering the historical context and exploring the works practically, the stylistic influence of jazz was unpacked through practice-based research and performance practice. Upon analysis, it was found that both compositions incorporate jazz elements such as rhythm and timbre. Further, an influence of jazz in terms of context was discovered. Bernstein and Copland's other works and Benny Goodman's fame as “The King of Swing” somewhat affect the perception of jazz-influence. The original recordings of the two compositions revealed how both works were played in the classical idiom and with close attention to the markings in the sheet music. However, newer recordings of the two compositions incorporate stylistic elements of jazz that were not present in the original recordings.