The temporal evolution of neutral modes in the impulsively started flow through a circular pipe and their connection to the nonlinear stability of Hagen-Poiseuille flow

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The phytoextraction of gold and palladium from mine tailings : this thesis is presented in fulfilment of the requirements for the degree of Master of Philosophy

The extraction of gold and palladium from a South African mine tailing (Klipfontein) and artificial substrate was examined. A variety of solutions were tested and extractants observed to dissolve large quantities of metal were subsequently used in trials investigating plant uptake of gold and palladium. Extraction by thiocyanate amended with an oxidising agent dissolved large amounts of gold and palladium from the test substrates. Various combinations of thiocyanate/Fe(III) and thiocyanate/H 2 O 2 were examined. Metal extraction in the thiocyanate/Fe(III) showed dependence on redox potential and acidity of the solution; this dependence was not observed in the thiocyanate/H 2 O 2 system where production of cyanide may be an important factor. The addition of iodide to thiocyanate/Fe(III) did not affect dissolution of metals. Thiourea was also tested. This chemical was shown to be a relatively poor extractant of gold and palladium, with and without an oxidant. Two plant species, Berkheya coddii and Brassica juncea, were investigated in plant trials. Initial experiments showed uptake of metals to be independent of plant species. Greatest metal uptake was achieved using cyanide as a chemical amendment, with nearly 500 ppm gold accumulation in B. juncea planted in artificial substrate and treated with 1 gL -1 KCN every day over 6 days. Nearly 13 ppm palladium had accumulated in these plants - the highest average concentration observed with any treatment. KCN also induced the largest metal uptake from Klipfontein substrate – nearly 1600 ppb gold and 7700 ppb palladium accumulation in B. coddii. As an exercise it was shown that the value of gold and palladium that would be recovered from a phytomining operation on Klipfontein substrate would be greater than the cost of cyanide added in such an operation. Plant uptake of gold and palladium from the mine tailing after treatment with thiocyanate plus an oxidant was poor. Gold and palladium uptake by B. coddii from artificial substrate after treatment with thiocyanate + H 2 O 2 was improved, with levels of accumulation similar to that of cyanide. Metal uptake by thiocyanate + Fe(III), however, remained poor. The conclusion of this thesis is that phytomining of gold and palladium offers large potential in both practical and research terms. The relative importance of the species thiocyanate, H 2 O 2 , and cyanide remain unknown in the thiocyanate/H 2 O 2 system and further research is needed to elucidate this behaviour

Access space and digital outreach trainers case study

This paper evaluates a situation where two organisations, in the field of encouraging digital inclusion, targeted the same population with the same intent, but with different modes of engagement. This entailed reaching outward, making contacts with those to whom the benefits of the digital realm could make a significant difference to their lives. It was the aim of the Digital Outreach Trainers to enable the articulation of the tacit knowledge of that part of the population that was considered 'hard to reach'. Success would be deemed to be the number of challenged individuals who became learned as a consequence. The two ways in which this process was conducted is the subject of this paper

The obligatory passage point : abstracting the meaning in tacit knowledge

The lived experience of individuals in the workplace results in an accumulation of dispositions to act. Such dispositions have been termed knowledge [Boisot 1998]. Further, this knowledge is considered to be tacit or explicit [Baumard 1999]. Therefore tacit knowledge is one of the precursors of new knowledge. There have been a number of hypotheses as to how such knowledge is transformed into explicit knowledge [Nonaka et al 2000], and then subsequently diffused [Boisot 1998]. Moreover it is impossible to know the magnitude of tacit knowledge that is not articulated, however insightful, original or crucial it may be. The transformation to the explicit rendition can and will act as a filter in an attempt to eliminate meaningless utterances. Therefore some tacit knowledge will be lost in this process. This is an Obligatory Passage Point (OPP) a concept normally associated with Actor Network Theory [Latour 2005]. This is where the decision is made as to ‘what counts’ as legitimate knowledge and it is irreversible. This obligatory passage point is for all tacit knowledge in a community, an organization or even a nation. The case study presented comprises a small number of individuals working in a third sector environment. Although there is agreement as to what is to be achieved, the how question remains open. Despite the common concrete experiences, the tacit appreciation of the perceived action world varies significantly. A process by which an inventory of tacit knowledge can be established, abstracted and combined to act as a base to affect dispositions and expectations is described. The path to the subsequent generation of actionable knowledge is plotted which can subsequently form the basis for an intervention. The delineation between tacit knowledge and explicit knowledge in this context is explored by the application of the obligatory passage point. Utilizing the principles of language by Karl Buller the notion of legitimation is discussed. The OPP is significant because when tacit knowledge is shared, there is a process of gaining inter-subjective agreement which legitimizes the explicit representation of the tacit knowledge. The eye can see and interpret the world, but it cannot see itself. All tacit knowledge is gained through the mind’s eye. The collective minds are seeing the collective tacit knowledge of the group and agreeing

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Fiction by Lucia Walto