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Sample preparation for pesticide analysis in water and sediments a case study of the Okavango Delta, Botswana

  • Authors: Mmualefe, Lesego Cecilia
  • Date: 2010
  • Subjects: Water quality -- Botswana -- Okavango Delta Water -- Analysis Pesticides -- Environmental aspects -- Botswana -- Okavango Delta Water -- Pollution -- Botswana -- Okavango Delta DDT (Insecticide) -- Environmental aspects -- Botswana -- Okavango Delta
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4344 , http://hdl.handle.net/10962/d1005006
  • Description: This thesis presents a first ever extensive analysis of pesticides in water and sediments from the Okavango Delta, Botswana, employing green sample preparation techniques that require small volumes of organic solvents hence generating negligible volumes of organic solvent waste. Pesticides were extracted and pre-concentrated from water by solid phase extraction (SPE) and headspace solid phase microextraction (HS-SPME) while supercritical fluid extraction (SFE) and pressurized fluid extraction (PFE) were employed for sediments. Subsequent analysis was carried out on a gas chromatograph with electron capture detection and analytes were unequivocally confirmed by high resolution mass spectrometric detection. Hexachlorobenzene (HCB), trans-chlordane, 4,4′-DDD and 4,4′-DDE were detected after optimized HS-SPME in several water samples from the lower Delta at concentrations ranging from 2.4 to 61.4 μg L-1 that are much higher than the 0.1 μg L-1 maximum limit of individual organochlorine pesticides in drinking water set by the European Community Directive. The same samples were cleaned with ISOLUTE C18 SPE sorbent with an optimal acetone/n-hexane (1:1 v/v) mixture for the elution of analytes. No pesticides were detected after SPE clean-up and pre-concentration. HCB, aldrin and 4, 4‟-DDT were identified in sediments after SFE at concentration ranges of 1.1 - 30.3, 0.5 – 15.2 and 1.4 – 55.4 μg/g, respectively. There was an increase of pesticides concentrations in the direction of water flow from the Panhandle (point of entry) to the lower delta. DDE, fatty acids and phthalates were detected after PFE with optimized extraction solvent and temperature. The presence of DDT metabolites in the water and sediments from the Okavango Delta confirm historical exposure to the pesticide. However their cumulative concentration increase in the water-flow direction calls for further investigation of point sources for the long-term preservation of the Delta. The green sample preparation techniques and low toxicity solvents employed in this thesis are thus recommended for routine environmental monitoring exercises.
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  • Date Issued: 2010

Contesting boundaries: a case of municipal demarcation disputes in Vuwani Vhembe District

  • Authors: Khowa, Thandeka Promise
  • Date: 2020
  • Subjects: Geographical boundaries
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/50767 , vital:42670
  • Description: The research study in Vuwani Vhembe district sought to investigate demarcation disputes, the relationship between service delivery and demarcation disputes. The study further investigates the role of municipal demarcation board and local government adherence to sound governance principles and the causes of the demarcation dispute in Vuwani. The study additionally examines the conceptions and misconceptions, their impact on the current demarcation disputes in Vuwani. It further intended to establish the role and involvement of Vuwani stakeholders such as traditional structures/ leaders, civil unions, community members etc. in the processes of demarcating Vuwani. “What is the cause of Vuwani community member’s rejection of the re-demarcation, which is said to correct the past spatial injustices and promote municipal sizing, thus enabling better performance in service provision by municipalities?” The study employed a mixed-method involving the use of both quantitative (mini-survey) and qualitative (use of in-depth, semi structures interviews and focus group discussions). Research findings suggest that re-demarcation is a sensitive aspect/process in South Africa, mainly due to the past Apartheid era. There was forceful removal of people from their land supported by Apartheid legislation such as the Native Land Act 1913, Group Act 1950, Native Resettlement Act 1954 etc. Thus, fears of the past Apartheid system cloud any attempt to correct spatial injustices of the country. The new democratic South African government, therefore, needs to be cautious in its acts to correct the spatial injustices, thus adhering to sound governance principles. Findings reveal that several misconceptions and lack of adherence of good governance principles by the Municipal Demarcation Board and Local government have, to some extent, fueled the demarcation disputes in Vuwani. Municipal performance in the rendering of service delivery has a major impact and contributes to the community’s acceptance or rejection of demarcation/ amalgamations. The study further reveals that in Vuwani municipal performance with the establishment of the new Collins Chabane municipality has been clouded by fear of the unknown as this form of “demarcation of establishing a new municipality” altogether is relatively new. Rural land authority, the role of traditional leaders, ethnicity ties have all been found to have contributed to the disputes in Vuwani. Limpopo Province is home to three ethnic groups, namely, vaVhenda, baPedi and xiTsonga. The study findings have presented traits of tribalism as contributing to on-going demarcation disputes in Vuwani.
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  • Date Issued: 2020

Variability in and coupling of larval availability and settlement of the mussel Perna perna : a spatio-temporal approach

  • Authors: Porri, Francesca
  • Date: 2004
  • Subjects: Mussels -- South Africa Perna -- South Africa Perna -- Spawning Perna -- Larvae
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5796 , http://hdl.handle.net/10962/d1005484
  • Description: Population dynamics of many intertidal organisms are highly influenced by the abundance and distribution of planktonic larvae in the water column and their arrival on the shore. The brown mussel, Perna perna was used to investigate two of the primary processes that affect population size and dynamics, larval availability and settlement, on the south coast of South Africa. Perna perna is a dominant species on rocky shores of the southern and eastern coasts of South Africa. It creates three-dimensional beds that provide habitats for many other species and hence promotes biodiversity. Larval availability and settlement were examined at different spatial and temporal scales using a nested experimental design. To detect possible relationships between larval availability and settlement, the studies were simultaneous. Two sites, 4km apart, were chosen to investigate mussel settlement patterns. Within each site, three locations (300m from each other) were selected. At each location, five artificial settler collectors were placed at approximately 20cm intervals. Collectors were replaced at a range of time intervals, from daily to seasonal, for 16 months. Each intertidal location was paired with an offshore station, 500m from the shore, where larval availability was measured. At each offshore station, three vertical hauls were collected twice a month using a plankton net. Plankton sampling lasted for 14 months and was designed to examine variability on three temporal scales: seasonal, lunar and daily. The results showed no correlation between the distribution of larvae in the water and settlers on the shore. While larvae were abundant in the water at the start of sampling, they became very rare throughout the rest of the study at both sites and all locations. In contrast, distinct peaks of settler abundance were observed during the seasonal settlement study. In addition to the expected, strong temporal variation that emerged from both studies at all time scales, spatial patterns of variability were also observed. While no spatial effect was detected for the larvae in the water column, there was distinct spatial variation in settlement at the location level: some locations always showed higher settlement than others. These results suggest that, on scales of hundreds of meters to kilometers, larval availability and settlement are very unpredictable in time and that differential delivery of larvae occurs from nearshore waters to the shore. Although the effect of the state of the moon (new or full) was not significant in either study, more settlers seemed to arrive on the shore during new moon. Wind direction did not correlate significantly with settlement. However, the dropping of offshore winds and the prevalence of onshore winds, which are characteristic of summer, may be linked to the start of settlement. Nevertheless, further investigations on tidal or lunar cycles and on the influence of wind on surface currents are required to clarify the effects of moon and wind on settlement.
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  • Date Issued: 2004

The determination of geomorphologically effective flows for selected eastern sea-Board Rivers in South Africa

  • Authors: Dollar, E S J
  • Date: 2001
  • Subjects: Rivers--South Africa River channels Geomorphology
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4824 , http://hdl.handle.net/10962/d1005499
  • Description: In South Africa the need to protect and manage the national water resource has led to the development of the Reserve as a basic right under the National Water Act (1998). The Ecological Reserve relates to the quality and quantity of water necessary to protect the sustainable functioning of aquatic ecosystems. The geomorphological contribution to setting the Reserve has focussed on three groups of information requirements: the spatial and temporal availability of habitat, the maintenance of substratum characteristics, and the maintenance of channel form. This thesis focusses on the second and third information requirements. The thesis has attempted to achieve this by adding value to the theoretical and applied understanding of the magnitude and frequency of channel forming discharge for selected southern African rivers. Many of the eastern sea-board rivers are strongly influenced by bed rock in the channel perimeter, and by a highly variable hydrological regime. This has resulted in characteristic channel forms, with an active channel incised into a larger macro-channel being a common feature of eastern seaboard rivers. Within the active channel inset channel benches commonly occur. This alluvial architecture is used to provide clues as to the types of flows necessary to meet the Reserve. Three river basins are considered : the Mkomazi, Mhlathuze and Olifants. The Mkomazi is a relatively un-impacted perennial eastern-sea board river and forms the research component of the study. The Mhlathuze and Olifants rivers are highly regulated systems and form the application component of the study. Utilising synthesised daily hydrological data, bed material data, cross-sectional surveys, hydraulic data and relevant bed material transport equations, channel form was related to dominant discharge and effective discharge in an attempt to identify the magnitude and frequency offlows that can be considered to be ' effective'. Results from the Mkomazi River indicate that no single effective discharge exists, but rather that there is a range of effective discharges in the 5-0.1% range on the 1-day daily flow duration curves that are responsible for the bulk (>80%) of the bed material transport. Only large floods (termed 'reset'discharges) with average return periods of around 20 years generate sufficient stream power and shear stress to mobilise the entire bed. The macro-channel is thus maintained by the large ' reset' flood events, and the active channel is maintained both by the range of effective discharges and the ' reset 'discharges. These are the geomorphologically 'effective' flows. Results from the Mhlathuze River have indicated that the Goedertrouw Dam has had a considerable impact on the downstream channel morphology and bed material transport capacity and consequently the effective and dominant discharges. It has been suggested that the Mhlathuze River is now adjusting its channel geometry in sympathy with the regulated flow environment. Under present-day conditions it has been demonstrated that the total bed material load has been reduced by up to three times, but there has also been a clear change in the way in which the load has been distributed around the duration curve. Under present-day conditions, over 90% of the total bed material load is transported by the top 5% of the flows, whereas under virgin flow conditions 90% of the total bed material load was transported by the top 20% of the flows. For the Olifants River there appears to be no relationship between the estimated bankfull discharge and any hydrological statistic. The effective discharge flow class is in the 5-0.01% range on the 1-day daily flow duration curve. It has also been pointed out that even the highest flows simulated for the Olifants River do not generate sufficient energy to mobilise the entire bed. It is useful to consider the Olifants River as being adapted to a highly variable flow regime. It is erroneous to think of one ' effective' discharge, but rather a range of effective discharges are of significance. It has been argued that strong bed rock control and a highly variable flow regime in many southern African rivers accounts for the channel architecture, and that there is a need to develop an ' indigenous knowledge' in the management of southern African fluvial systems
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  • Date Issued: 2001

Comparative biogeography and ecology of freshwater fishes in the Breede and associated river systems, South Africa

  • Authors: Chakona, Albert
  • Date: 2012
  • Subjects: Freshwater fishes -- South Africa -- Breede River , Freshwater fishes -- South Africa -- Geographical distribution , Freshwater fishes -- Ecology , Feshwater fishes -- Genetics
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5372 , http://hdl.handle.net/10962/d1015694
  • Description: Distribution patterns and levels of genetic diversity in extant taxa are a product of complex palaeogeographic processes and climatic oscillations as well as the species’ intrinsic ecological adaptations. The Cape Floristic Region of South Africa presents a unique system for studying the processes that promote species diversification and distribution patterns. This region has a high degree of endemism of both terrestrial and aquatic biota and is clearly isolated from neighbouring areas by the Cape Fold Mountains and the Great Escarpment. The objective of this study was to firstly examine the ecology of freshwater fishes belonging to the genera Galaxias, Pseudobarbus and Sandelia in the south-western CFR. This was followed by an assessment of the genetic diversity of these taxa. Unique lineages were identified and their distribution was mapped. The work aimed to explore the role of the region’s complex palaeogeographic and climatic history as well as the role of the species’ ecological adaptations in driving lineage diversification and shaping contemporary distribution patterns. The four main components of the study can be summarised as follows: 1. Habitat associations of three widely distributed lineages of Galaxias zebratus Pseudobarbus burchelli and Sandelia capensis were evaluated at multiple localities in minimally disturbed mountain tributaries of the Breede, Duiwenhoks and Goukou River systems. The lineages have distinct habitat associations which were related to differences in their morphological traits. The slender-bodied Galaxias ‘nebula’ and the fusiform-shaped Pseudobarbus ‘Breede’ are capable of exploiting upper reaches with faster water velocity. By contrast, the laterally compressed Sandelia ‘eastern’ is restricted to lower reaches, making this lineage more susceptible to a wide array of impacts. 2. A recently discovered lineage of Galaxias zebratus, (Galaxias ‘nebula’), was found to be capable of tolerating emersion for a prolonged period of time. This is the first time that such capabilities have been documented in an African galaxiid. These adaptations have implications for the interpretation of Galaxias ‘nebula’s wide distribution range. 3. The phylogeography of Galaxias ‘nebula’ across its entire distribution range was investigated using two mitochondrial genes (cytochrome c oxidase subunit I (COI) and cytochrome b (cyt b)). This lineage has a complex evolutionary history that was influenced by both intrinsic and extrinsic factors. Rare events such as episodic drainage connections during Pleistocene and Holocene pluvial periods, possibly augmented by river confluences during periods of lower sea-levels and river capture events seem to be the most credible explanation for the extensive contemporary distribution and the relatively shallow genetic divergence between different river systems. 4. Mitochondrial cyt b sequences were used (i) to assess genetic diversity in G. zebratus, P. burchelli and S. capensis from the south-western CFR and (ii) to determine the roles of intrinsic ecological adaptations and extrinsic landscape and climatic changes in promoting genetic diversification and shaping present day distribution patterns of lineages in the three taxa. Marine incursions during periods of major sea-level transgressions are proposed to have isolated populations in upland refugia, thereby driving allopatric divergence in these species. Subsequent connections of rivers during wetter periods and lower sea-levels are proposed to have facilitated post-speciation dispersal of lineages to attain present day distribution patterns. While detailed morphological studies and further genetic analysis are needed to substantiate the taxonomic status of the newly discovered lineages of Galaxias zebratus, Pseudobarbus burchelli and Sandelia capensis, results of the present study indicate that the south-western CFR represents a previously unrecognised centre of freshwater fish diversity and microendemism in the broader Cape Floristic Region. Accurate identification of lineages and comprehensive mapping of their distribution is a fundamental pre-requisite for ecological studies, assessing conservation status and implementation of appropriate conservation measures.
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  • Date Issued: 2012

The FAST fabric objective measurement properties of commercial worsted apparel fabrics available in South Africa

  • Authors: Das, Sweta
  • Date: 2018
  • Subjects: Textile fabrics -- Testing , Textile fabrics -- Measurement , Textile fibers -- Testing , Textile design
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/17814 , vital:28458
  • Description: In the last few decades, there has been a shift globally towards the objective measurement of these textile fibre, yarn and fabric properties which determine processing performance and product quality. This shift is also very apparent in the objective measurement of fabric properties, particularly those relating to handle and making-up into a garment. This study was motivated by the fact that the adoption of fabric objective measurement (FOM), specifically the FAST system, will benefit the South African worsted apparel sector, as it has done in various other countries which produce high quality worsted apparel fabrics and garments. FAST is robust and portable, yet inexpensive. The main objective of the study was to develop a FAST referencing system which can be used for benchmarking by the local apparel industry and, as a basis for encouraging and persuading the industry to adopt this system of fabric quality measurement and assurance and thereby improve their product quality and international competitiveness. To achieve the main objective, involved sourcing and FAST testing a representative cross-section of commercial worsted apparel fabrics with the emphasis on wool and wool blends from the local fabric and clothing manufacturing industry, and determining how the various FAST properties were affected by factors such as fabric weave, fibre blend and weight, since this could impact on the specific nature and validity of the referencing system. A total of some 394 worsted type commercial fabrics, mainly in wool and wool blends, were sourced from, and with the inputs of, local apparel fabric and clothing manufacturers so as to ensure the local fabric and garment representative of the sample population and after which the fabrics were tested on the FAST system. ANOVA (regression analysis) was carried out on each of the FAST parameters in order to determine whether fabric weight, weave, thickness and fibre composition (pure wool and wool blends) had a statistically significant effect on them, since this is an important aspect which needs to be clarified prior to the development of a envisaged meaningful FAST system.
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  • Date Issued: 2018

The life and times of Ethel Tawse Jollie : a case study of the transference and adaptation of British social and political ideas of the Edwardian era to a colonial society

  • Authors: Lowry, Daniel William
  • Date: 1989
  • Subjects: Jollie, Ethel Tawse, 1876-1950 Zimbabwe -- History -- 1890-1965
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2525 , http://hdl.handle.net/10962/d1001854
  • Description: This is an appraisal of the career of Ethel Tawse Jollie (1876-1950), the first woman parliamentarian in Southern Rhodesia, and the British Empire overseas, prolific writer and leading intellectual of her political generation who played a key role in the achievement of responsible government in Southern Rhodesia in 1923. As the founder and principal organiser of the Responsible Government Association she imported from Britain a singular political philosophy which made a lasting impression on Rhodesia's political character and social identity. She was an influential figure in British imperialist circles and in the women's suffrage controversy. No other Rhodesian politician had achieved such prominence in the metropole, or possessed such a thoroughly formed, comprehensive ideology, and the propaganda skills necessary to give it effect. The study traces the formation of her ideas within the intellectual milieu of pre-1914 Britain and - through her - its subsequent adaptation in Rhodesia; how, through her marriage to Archibald Colquhoun - explorer, writer and Cecil Rhodes's first Administrator of Mashonaland - she became steeped in the ideology of the Edwardian Radical Right - that reaction to imperial decline denoted by the slogan 'National Efficiency'. By 1915. when she arrived in Rhodesia, she had come to believe that by 1915, when she arrived in Rhodesia, she had come to believe that the salvation of the Empire lay in its 'patriotic' periphery where it was possible to create new societies on Radical Right principles. Both in and out of parliament she gave to Rhodesian public policy and identity a distinct Radical Right hue, which she further enhanced by her involvement in various extra parliamentary pressure groups. It is a life and times study and considerable use is made of contemporary ballads and novels in the belief that immersion in the atmosphere of the period is particularly useful in an intellectual biography of this kind. Comparisons are also made with other British peripheries notably Ulster, Canada and New Zealand. The study challenges the traditional view of Rhodesia as a neo-Victorian intellectual backwater; seeing it rather as a society which continued to import selectively ideas from elsewhere in the Empire. It should interest Commonwealth and - because of its central character - women's historians.
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  • Date Issued: 1989

Causes of persistent rural poverty in Thika district of Kenya, c.1953-2000

  • Authors: Kinyanjui, Felistus Kinuna
  • Date: 2007
  • Subjects: Poverty -- Kenya -- History Rural poor -- Kenya -- History Agriculture -- Kenya -- History Kenya -- History Kenya -- Politics and government
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2547 , http://hdl.handle.net/10962/d1002399
  • Description: This study investigates the causes of poverty among the residents of Thika District in Kenya over the period 1953-2000. Using the articulation of modes of production perspective, the study traces the dynamics of poverty to the geography, history and politics of Thika District. The thrust of the argument is that livelihoods in the district changed during the period under investigation, but not necessarily for the better. Landlessness, collapse of the coffee industry, intergenerational poverty, and the ravages of diseases (particularly of HIV/AIDS) are analysed. This leads to the conclusion that causes of poverty in Thika District during the period under examination were complex as one form of deprivation led to another. The study established that poverty in Thika District during the period under review was a product of a process of exclusion from the centre of political power and appropriation. While race was the basis for allocation of public resources in colonial Kenya, ethnicity has dominated the independence period. Consequently, one would have expected the residents of Thika District, the home of Kenya’s first president, Mzee Jomo Kenyatta, to have benefited inordinately from public resources during his rule. Kenyatta’s administration, however, mainly benefited the Kikuyu elite. The study therefore demonstrates that during the period under examination, the Kikuyu, like any other Kenyan community, were a heterogeneous group whose differences were accentuated by class relations. Subaltern groups in Thika District therefore benefited minimally from state patronage, just like similar groups elsewhere in rural Kenya. By the late 1970s, the level of deprivation in rural Kenya had been contained as a result of favourable prices for the country’s agricultural exports. But in the subsequent period, poverty increased under the pressures of world economic recession and slowdowns in trade. The situation was worse for Kikuyu peasants as the Second Republic of President Daniel Moi deliberately attempted undermine the Kikuyu economically. For the majority of Thika residents, this translated into further marginalisation as the Moi regime lumped them together with the Kikuyu elite who had benefitted inordinately from public resources during the Kenyatta era. This study demonstrates that no single factor can explain the prevalence of poverty in Thika District during the period under consideration. However, the poor in the district devised survival mechanisms that could be replicated elsewhere. Indeed, the dynamics of poverty in Thika District represent a microcosm not just for the broader Kenyan situation but also of rural livelihoods elsewhere in the world. The study recommends land reform and horticulture as possible ways of reducing poverty among rural communities. Further, for a successful global war on poverty there is an urgent need to have the West go beyond rhetoric and deliver on its promises to make poverty history.
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  • Date Issued: 2007

Investigating the radical democratic potential of social media use by new social movements in South Africa

  • Authors: Zdanow, Carla
  • Date: 2015
  • Subjects: Social media -- South Africa , Social movements -- South Africa , Neoliberalism -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/4310 , vital:20583
  • Description: Since its inception, the internet ‒ and in particular Web 2.0 ‒ have been valorized as potentially revolutionary democratic spaces. Despite the emergence of concerns over the progressively neoliberal orientation and narcissistic effects of the internet, evidence of the radical democratic potential of this media has received considerable attention. This thesis is orientated around both an exploration of such evidence, and a consideration of its relevance for South Africa. In this regard, the thesis commences with an exploration of the neoliberal underpinnings of the internet and the growing translation of dominant neoliberal discourses into the online practices of mainstream liberal democratic politics. Focus then shifts toward the mounting influence of alternative radical democratic positions online, through an investigation of the virtual manifestations of deliberative, autonomous, and agonistic approaches to radical democracy. And following an examination of the online political practices of selected recent global social movements, the primacy of agonism in online expressions of radical democracy is advanced. In turn, resonances and dissonances between the online activity and practices of such global social movements, and the use of the internet and social media by well-known South African new social movements, are explored. Finally, this thesis concludes by recommending a fourfold new media approach through which the agonistic radical democratic potential of the internet can be realized more fully by the new social movements of South Africa.
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  • Date Issued: 2015

Identity, belonging and ecological crisis in South African speculative fiction

  • Authors: Steenkamp, Elzette Lorna
  • Date: 2011
  • Subjects: South African fiction -- History and criticism Identity (Philosophical concept) in literature Group identity in literature Ecology in literature Science fiction, South African -- History and criticism Fantasy fiction, South African -- History and criticism Ecofiction -- History and criticism Ecocriticism
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2219 , http://hdl.handle.net/10962/d1002262
  • Description: This study examines a range of South African speculative novels which situate their narratives in futuristic or ‘alternative’ milieus, exploring how these narratives not only address identity formation in a deeply divided and rapidly changing society, but also the ways in which human beings place themselves in relation to Nature and form notions of ‘ecological’ belonging. It offers close readings of these speculative narratives in order to investigate the ways in which they evince concerns which are rooted in the natural, social and political landscapes which inform them. Specific attention is paid to the texts’ treatment of the intertwined issues of identity, belonging and ecological crisis. This dissertation draws on the fields of Ecocriticism, Postcolonial Studies and Science Fiction Studies, and assumes a culturally specific approach to primary texts while investigating possible cross-cultural commonalities between Afrikaans and English speculative narratives, as well as the cross-fertilisation of global SF/speculative features. It is suggested that South African speculative fiction presents a socio-historically situated, rhizomatic approach to ecology – one that is attuned to the tension between humanistic- and ecological concerns.
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  • Date Issued: 2011

Comparative study of the feeding damage caused by the South African biotypes of the Russian wheat aphid (Diuraphis noxia Kurdjumov) on resistant and non-resistant lines of barley (Hordeum vulgare L.)

  • Authors: Jimoh, Mahboob Adekilekun
  • Date: 2011
  • Subjects: Aphids Russian wheat aphid -- Research -- South Africa Barley -- Diseases and pests -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4201 , http://hdl.handle.net/10962/d1003770
  • Description: Cereal crop productivity is hampered when these plants are infested by phloem feeding aphids. A great deal of research has been carried out with the direct aim of a clearer understanding of the mechanism involved in the interaction between aphids and their host plants. Research has directly or indirectly been geared towards enhanced plant productivity and achieving sustainable agriculture. Barley (Hordeum vulgare L.) is an important small grain crop in South Africa, whose crop performance is negatively affected by fluctuations in weather patterns as well as by agricultural pests. One of the insect pests infesting barley is the Russian wheat aphid, Diuraphis noxia Kurdjumov (RWA), of which the two South African biotypes, codenamed RWASA1 and RWASA2, were studied in this thesis. During dry spells, RWA infestation becomes a more serious threat to barley productivity. Resistant plants have been used to combat RWA infestation of small grains. In South Africa, 27 RWA-resistant wheat cultivars are currently used in commercial cultivation, but no resistant barley lines have, unfortunately, been developed, in spite of this grain’s significant economic importance. This informed the study in this thesis, and this interest particularly focussed on three RWA-resistant lines developed by the USDA, testing their performance against South African RWA biotypes, for possible adaptation to South Africa. The aim was thus to examine the plant-aphid interactions, aphid breeding rates, plant damage and sustainability, evidence of resistance or tolerance and finally potential performance under elevated CO2 (a very real climate change threat). Two major avenues of research were undertaken. The first aspect involved examination of structural and functional damage caused by RWASA1 and RWASA2 on the three resistant and a non-resistant line. Aphid population growth and damage symptoms (chlorosis and leaf roll) of infestation by these aphid biotypes were evaluated. This was followed by a structural and functional approach in which the effects of feeding on the transport systems (phloem and xylem) of barley were investigated. Fluorescence microscopy techniques (using aniline blue fluorochrome, a specific stain for callose and 5,6-CFDA, a phloem-mobile probe) were applied to investigate the feeding-related damage caused by the aphids, through an examination of wound callose formation and related to this, the resultant reduction in phloem transport capacity. Transmission electron microscopy (TEM) techniques provided evidence of the extent of the feeding-related cell damage. The second aspect involved a study of the effect of changing CO2 concentrations ([CO2]) on the resistant and susceptible barley cultivars to feeding by the two RWA biotypes. Leaves of plants grown at ambient and two elevated levels of [CO2] were analysed to investigate the effect of changing [CO2] on biomass, leaf nitrogen content and C:N ratio of control (uninfested) and infested plants. The population growth studies showed that the populations of the two RWA biotypes as well as bird cherry-oat aphid (BCA, Rhopalosiphum padi L.) increased substantially on the four barley lines. BCA was included here, as it had been the subject of several previous studies. RWASA2 bred faster than RWASA1 on all lines. The breeding rates of the two RWA biotypes were both suppressed and at near-equivalent levels on the three resistant lines, compared to the non-resistant PUMA. This suggests that the resistant lines possessed an antibiosis resistance mechanism against the feeding aphids. Feeding by the aphids manifested in morphological damage symptoms of chlorosis and leaf roll. The two biotypes inflicted severe chlorosis and leaf roll on the non-resistant PUMA. In the resistant plants, leaf rolling was more severe because of RWASA2 feeding compared to RWASA1 feeding. In contrast, chlorosis symptoms were more severe during RWASA1 feeding than was the case with RWASA2 feeding. Investigation of the effect of aphid feeding on the plants showed that callose was deposited within 24h and that this increased with longer feeding exposure. Wound callose distribution is more extensive in the non-resistant PUMA than in the resistant plants. RWASA2 feeding on the resistant lines caused deposition of more callose than was evident with RWASA1 feeding. During long-term feeding, it was evident that variation in the intensity and amount of wound callose was visible in the longitudinal and transverse veins of the resistant plants. Of the three STARS plants, STARS-9301B had the least callose. Interestingly, wound callose occurred in both resistant and non-resistant plants, in sharp contrast to what has been reported on resistant wheat cultivars that were developed in South Africa. The relative reduction in the wound callose deposited in the resistant line, when compared to the non-resistant lines, suggests the presence of a mechanism in the resistant lines, which may prevent excessive callose formation. Alternatively, the mechanism may stimulate callose breakdown. RWASA2 feeding on the resistant lines deposited more wound callose than RWASA1 feeding. This evidence supports the hypothesis that RWASA2 is a resistance breaking and more aggressive feeder than RWASA1 is; and further underscores the urgent need for development of RWA-resistant barley cultivars. The ultrastructural investigation of the feeding damage showed that the two biotypes caused extensive vascular damage in non-resistant plants. There was extensive and severe cell disruption and often obliteration of cell structure of the vascular parenchyma, xylem and phloem elements. In sharp contrast, among the resistant plants, feeding-related cell damage appeared to be substantially reduced compared to the non-resistant PUMA. Low frequency of damaged cells indicated that majority of the cell components of the vascular tissues were intact and presumed functional. There was evidence of salivary material lining the secondary walls of the vascular tissue, which resulted in severe damage. Within xylem vessels, saliva material impregnated half-bordered pit pairs between the vessels and adjacent xylem parenchyma. This is believed to prevent solute exchange through this interface, thereby inducing leaf stress and vi leaf roll. A notable finding is that RWASA2 effectively induced more cell damage to vascular tissues in the resistant lines than did RWASA1. In general the experimental evidence (see Chapter 5) suggests that the resistant lines are possibly more tolerant (or able to cope with) to RWA feeding. Evidence for this is the reduction of wound callose and at the TEM level, a comparatively less obvious cell damage in the resistant lines, which suggests that they possess antibiosis and tolerance capacity. The apparent reduction of feeding-related cell damage from the TEM study confirmed the disruptive action of the feeding aphids in experiments using the phloem-mobile probe, 5,6-CF. Results showed that feeding by RWASA1 and RWASA2 reducedthe transport functionality of the phloem in all cases, but that RWASA2 feeding caused a more obvious reduction in the rate and distance that 5,6-carboxyfluorescein was transported, than did RWASA1. Investigation of the effect of changing [CO2] on the barley cultivars showed that in the absence of aphids and under elevated CO2 conditions, the plants grew more vigorously. In this series of experiments, the infested plants suffered significant reduction in biomass under ambient (as was expected) and under the two elevated CO2 regimes. Biomass loss was greater at elevated CO2 than under ambient [CO2]. The infested nonresistant PUMA plants showed a more significant biomass loss than did the resistant cultivars. Clearly, the benefits derived from elevated CO2 enrichment was thus redirected to the now-advantaged aphids. Uninfested vii plants showed an increase in leaf nitrogen under the experimental conditions. However, feeding aphids depleted leaf nitrogen content and this was more apparent on plants exposed to RWASA2 than was the case with RWASA1. The end result of this was that C:N ratio of infested plants were higher than uninfested plants. Clearly, the faster breeding rates of the aphids at elevated CO2 caused depletion of N and a resultant deficiency exacerbated chlorosis as well as leaf rolling due to the higher aphid population density under elevated CO2 than at ambient. By 28 days after infestation (DAI), majority of the plants exposed to enriched CO2 treatments had died. A major finding here was thus that although this study demonstrated that elevated CO2 resulted in an increase in biomass, this was detrimentally offset in plants infested by the aphids, with a decline in biomass and loss of functionality leading to plant death at 28DAI. The overriding conclusion from this study is a clear signal that the twin effects of CO2 enrichment (a feature of current climate change) and aphid infestations may precipitate potential grain shortages. A disastrous food security threat looms.
  • Full Text:
  • Date Issued: 2011

Studies on the nutritional value of seven accessions of cocoyam growing in South Africa

  • Authors: Lewu, Muinat Nike
  • Date: 2010
  • Subjects: Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:11305 , http://hdl.handle.net/10353/d1001054 , Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
  • Description: Cocoyam [Colocasia esculenta (L.) Schott] is widely cultivated as a staple food in the tropical and subtropical regions of the world. The crop, however, remains unpopular and not well known outside KwaZulu-Natal Province of South Africa where it is cultivated mainly for subsistence. The aims of the study were to collect local landraces (accessions) of the crop from where it is found growing within the country for various studies and also to document its nutritional values as well as the safety/toxicity of the crop. The study was carried out using various methods. These included a comparative assessment of the proximate, mineral and antinutrient compositions of cooked and uncooked tubers of a typical commercially available cocoyam and potato found in South African markets. These investigations were repeated for the tubers and leaves of available landraces (seven accessions) of C. esculenta found growing in the farmers’ fields in KwaZulu-Natal Province. Also, an in vivo toxicological study on cooked accessions of the local landraces was conducted to determine possible toxicity effects after consumption using albino rats as a model. The results revealed that commercially available cocoyam and potato tubers have very close nutritional components. Analysis of the proximate composition of seven accessions (UFCe1- UFCe7) of cooked and uncooked tubers of cocoyam indicated that UFCe7 was better in ash, crude protein, crude fibre and crude lipid contents but with higher moisture which could make it more vulnerable to microbial attack. No tubers of the seven accessions appeared to be ii outstandingly better than the others based on their mineral compositions. However, in terms of antinutritional factors, UFCe1, UFCe3 and UFCe7 had the least amounts of oxalate, tannins and phytate in their cooked states. It was discovered however, that the leaves of the accessions of this vegetable contain substantial amount of minerals, and therefore, can contribute significantly to the nutrient requirements of humans and could be recommended as a cheap source of nutrients in South Africa. None of the accessions was outstandingly better than the others in terms of their mineral contents and anti-nutritional factors. Moreover, the current study has shown that boiling the leaves of cocoyam prior to consumption is an effective way of reducing the antinutrient contents of the leaves of the plant thereby making it safe for consumption. The findings also revealed that cooking C. esculenta leaves may increase the levels of protein, fibre and lipid contents while cooking may also decrease the mineral, carbohydrate and caloric contents of the leaves of the accessions. The leafy vegetable may, therefore, be recommended as a cheap source of plant protein. Cooking improved the nutritive value as a result of the reduction in antinutrient levels, thereby improving the food quality in all the tuber and leaf samples used for this study. At the same time, cooked samples also suffered loss of some nutrients with respect to the proximate and mineral compositions. However, supplementation from other food sources that are rich in these nutrients is necessary when these crops are cooked for consumption. Any of the cocoyam accessions may be recommended for consumption for improved protein and mineral nutrients while tubers of accession UFCe7 have also shown good promise in terms of protein and fibre content availability. The results of the in vivo study, using the liver and kidney functional endpoints of weanling albino rats (Rattus norvegicus) maintained on different accessions of cooked cocoyam-based iii diets (UFCe1-UFCe7) for 28 days, revealed that all the accessions produced selective alterations on the hepatorenal indices of weanling rats. The highest alterations were produced by UFCe4 while the least was from UFCe2. These alterations may have consequential effects on the normal functioning of the liver and kidney of the animals. The UFCe2 exhibited the least toxicity risk among the accessions of C. esculenta growing in KwaZulu-Natal Province of South Africa.
  • Full Text:
  • Date Issued: 2010

The precarious ‘good mother’ position: a psychosocial reading of maternal subjectivity of working mothers in scarcely-resourced South African communities

  • Authors: Kinahan-Sweeney, Siobhan
  • Date: 2020
  • Subjects: Motherhood -- Psychological aspects -- South Africa , Working mothers -- South Africa -- Attitudes , Working mothers -- South Africa -- Psychology
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/142464 , vital:38082
  • Description: This psychosocial study investigates the maternal subjectivities of mothers returning to work after maternity leave, who are living in scarcely-resourced Cape Town communities in South Africa. Engaging with interview texts and listening to mothers’ talk, I explore how and why maternal subjectivity is constructed discursively and defensively in our talk. This thesis claims that these particular mothers predominately employ instrumental mothering discourse. The traditional subject position of the intensive mother – which is typically assumed to be the ‘good mother’ – is not a position available to these mothers due to their social circumstances and working role. Subsequently, material provision, the baby’s thriving and surviving body, finding substitute carers and maternal preoccupation are constructed as qualities of ‘good mothering’ in their talk. This ‘good mother’ position, however, is a precarious position that both these mothers and I invest in to defend against feelings towards their babies and themselves as well as to deny (maternal) ambivalence in a problematic social system. In a combined analysis drawing on discursive theory and psychoanalysis, more specifically contemporary attachment theory and intersubjectivity theory, I illustrate how both these mothers and I – as emotional, social and political subjects – co-construct maternal subjectivity. Based on the findings, recommendations for parent-infant interventions are discussed. Arguing that a purely psychoanalytic reading of investment perpetuates notions of individual blame and pathology, I advocate for a psychosocial reading that does not neglect failing social systems but rather pursues an open and reflective, yet critical, mindfulness when listening to talk.
  • Full Text:
  • Date Issued: 2020

A bioinorganic study of some cobalt(II) Schiff base complexes of variously substituted hydroxybenzaldimines

  • Authors: Shaibu, Rafiu Olarewaju
  • Date: 2008
  • Subjects: Cobalt Schiff bases Artemia Spectrum analysis Ligands -- Analysis Bioinorganic chemistry Antineoplastic agents Cancer -- Chemotherapy Ligands -- Toxicity
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4394 , http://hdl.handle.net/10962/d1006009
  • Description: Syntheses of Schiff bases were carried out by reacting salicylaldyhde, ortho-vanillin, para-vanillin or vanillin with aniline, 1-aminonaphthalene, 4- and 3-aminopyridine, and also with 2- and 3-aminomethylpyridine. The various Schiff bases obtained from the condensation reaction were reacted with CoCl₂.6H₂0, triethylamine stripped CoCl₂.6H₂0 or Co(CH₃COO)₂ to form cobalt(Il) complexes of ratio 2:1. The complexes obtained from cobalt chloride designated as the "A series" are of the general formulae ML₂X₂.nH₂0 , (L = Schiff base, X = chlorine) while those obtained from cobalt acetate or triethylamine stripped cobalt chloride denoted as "B" and C" are of the general formulae ML₂. nH₂0. The few complexes that do not follow the general formulae highlighted above are: IA [M(HL)₃.Cl₂], (L = N-phenylsalicylaldimine), 4A = (MLCl₂), (L = N-phenylvanaldiminato), 7 A and 21 A (ML₂), (L = N-naphthyl-o-vanaldiminato, and N-methy-2-pyridylsalicylaldiminato respectively), 8A = MLCI, (L = N-naphthylvanaldiminato), 12A = M₂L₃Cl₂, (L = N-4-pyridylvanaldiminato), 15A (MLCI), (L = N-3-pyridyl-o-vanaldiminato). The ligands and their complexes were characterized using elemental analyses and cobalt analysis using ICP, FT-IR spectroscopy (mid and far-IR), NIR-UV/vis (diffuse reflectance), UV/vis in an aprotic and a protic solvents, while mass spectrometry, ¹HNMR and ¹³CNMR, was used to further characterized the ligands. The tautomeric nature of the Schiff bases were determined by examining the behaviour of Schiff bases and their complexes in a protic (e.g. MeOH) and non-protic (e.g. DMF) polar solvents. The effects of solvents on the electronic behaviour of the compounds were also examined. Using CDCl₃, the NMR technique was further used to confirm the structures of the Schiff bases. The tentative geometry of the complexes was determined using the spectra information obtained from the far infrared and the diffuse reflectance spectroscopy. With few exceptions, most of the "A" series are tetrahedral or distorted tetrahedral, while the "B + C" are octahedral or pseudooctahedral. A small number of complexes are assigned square-planar geometry owing to the characteristic spectral behaviour shown. In order to determine their biological activity, two biological assay methods (antimicrobial testing and brine shrimp lethality assay) were used. Using disc method, the bacteriostatic and fungicidal activities of the various Schiff bases and their respective complexes to Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa as well as Aspergillus niger, were measured and the average inhibition zones are tabulated and analysed. Both the Schiff bases and their complexes showed varying bacteriostatic and fungicidal activity against the bacteria and fungus tested. The inhibition activity is concentration dependent and potential antibiotic and fungicides are identified. To determine the toxicity of the ligands and their corresponding cobalt(II) complexes, brine shrimp lethality assay was used. The LD₅₀ of the tested compounds were calculated and the results obtained were tabulated for comparison.
  • Full Text:
  • Date Issued: 2008

Richard Charles Nicholas Branson : a psychobiographical study

  • Authors: Preston, Amanda Lorraine
  • Date: 2017
  • Subjects: Branson, Richard Charles Nicholas, -- 1950- Businessmen -- Great Britain -- Biography Success in business
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10353/5543 , vital:29318
  • Description: Unique individuals are fascinating as we all want to be successful. There is thus a need to understand, unpack and share the psychological development and traits that allow some people to become sui generis, and to learn from them. Psychobiographical research is a qualitative approach that can be utilised to uncover the story of such an individual life, resulting in greater understanding of the psychological concepts underpinning the person. This form of study is invaluable, and involves applying psychological theory to lives completed or unfinished, enabling the development and testing of developmental theories. Richard Branson (1950-present), an entrepreneur, adventurer, philanthropist and family man is the single psychological subject chosen in this study. Branson was selected based on interest value, his uniqueness and the lack of a specifically academic and psychologically focused case study on his life. The primary aim was to explore and describe Branson’s personality development across his life, to date. This was achieved by applying both Maslow’s (1954, 1970) theory of optimal development and Adler’s (1929, 1956) Individual Psychology theory to provide a comprehensive idiographic interpretation of the development of Branson. To achieve this, the case study utilised the systematic and consistent collection, analysis and interpretation of life history materials, highlighting three areas of development, namely Childhood, Adolescence and Adulthood. The theoretical frameworks were used to discern, transform and reconstruct his life into a coherent and illuminating narrative of his psychological movement through life. Alexander’s (1988; 1990) model of identifying salient themes was used to analyse data for analytical generalisation (Yin, 2009). The conceptual framework derived from the theoretical perspective was constructed to organize, integrate data, and guide the presentation and discussion of findings of the study in an integrative and comprehensive manner. The findings suggest both Maslow’s and Adler’s theories considered the biopsychosocial context in Branson’s personality development and, at least to some extent, supported concepts indicative of progression toward optimality through having met the needs of the ego actualisation of his self, toward transcending selfishness and attaining altruism and social interest. The study of Branson’s personality development has provided a positive demonstration of the value of Maslow’s (1970a) and Adler’s (1929, 1956) theories to understand the process of development. It has further highlighted the unique trajectory of an individual’s life, contextualized, as well as the possibility of being agents in our own lives and despite challenges, able to become our own idiosyncratic best. The study also highlights the need, at a macro level, for governments to assist those unable to satisfy basic needs such as food, shelter and safety, to set an imperative, to aid those who struggle if a country and its people are to be uplifted. In terms of Adlerian theory, the study highlights the importance of family and early experiences in supporting the earliest years of children to assist them to develop an identity that is healthy and socially useful. Finally, recommendations were made for future research utilising a psychobiographical research design to uncover, illuminate and reconstruct the lives of outstanding and interesting individuals.
  • Full Text:
  • Date Issued: 2017

The effects of relative market share and the rate of market growth on the strategic attributes and financial performance of selected South African companies from 1977 to 1981

  • Authors: Viljoen, John
  • Date: 1984
  • Subjects: Johannesburg Stock Exchange Boston Consulting Group Business enterprises -- Valuation -- South Africa Business enterprises -- South Africa -- Finance Business enterprises -- Economic aspects -- South Africa Stock exchanges -- South Africa Success in business Marketing research Strategic planning Business planning
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:722 , http://hdl.handle.net/10962/d1003816
  • Description: This thesis analyses the effects of relative market share and the rate of market growth on the strategic characteristics and financial performance of selected companies quoted on the Johannesburg Stock Exchange over the period 1977 to 198. It is well established that business performance is partially contingent upon relative market share position and the rate of market growth. Together these variables comprise the basis of the Boston Consulting Group approach to portfolio analysis in the form of the Boston Consulting Group Growth/Share Matrix. A methodology was designed to test the validity of this matrix in measuring and predicting corporate behaviour at the business level in South Africa. Selected companies were placed into the matrix and analysed in terms of their strategic attributes (represented by selected financial ratios) and their level of performance (represented by a wide range of financial performance measures). The research findings show that relative market share and the rate of market growth have a significant impact on the strategic attributes and financial performance of South African businesses. Also, certain attributes are closely associated with particular types of performance. Therefore, given a specific performance target, management should ultimately be able to isolate and monitor the relevant strategic attributes in ensuring that the target is achieved. The analysis of contingent models of strategy is still in its infancy, but this study indicates that the field is possessed of great potential.
  • Full Text:
  • Date Issued: 1984

Institutional change, institutional isolation and biodiversity governance in South Africa: a case study of the trout industry in alien and invasive species regulatory reforms

  • Authors: Marire, Juniours
  • Date: 2016
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/639 , vital:19977
  • Description: The world, in recent decades, has witnessed an incalculable surge in global “wicked” policy problems that have long-term, and most often irreversible, impacts, not least terrorism, climate change, biodiversity losses and desertification. Wicked problems are wicked because there is no single epistemological system that can adequately coordinate policy action for addressing them. Literature abounds with international case studies of opposition to national institutions that are designed to put into effect global and regional policies for resolving wicked problems. This raises questions about what constitutes reasonable institutions, how such institutions can be designed and why societies sometimes fail to develop such institutions despite the obvious need for them. As a point of entry into these issues, the thesis adapted and extended the Northean (2007, 2012) macro meta-theoretic framework for studying the violence-development relationship, which focuses on the role of political and economic competition in the emergence of ‘right’ institutions that promote development, while containing violence. The Northean framework conceptualises two mutually exclusive social orders – the limited access order and the open access order – which provide the socio-cultural context for the evolution of specific institutions. The macro meta-theoretic framework was transformed into a micro metatheoretic framework in such a way that the limited access order and the open access order co-existed in the evolution of specific institutions. This reconceptualisation built on Bromley’s (2004, 2006) two realms of public policy: the realm of reasons (legislative-judicial system) and the realm of rules (administrative system) as well as the feminist concept of epistemic violence, which broadened the concept of violence from being exclusively physical to including the sociocognitive. The feminist concept of epistemic oppression logically fitted into, and became a new sub-category of, Commons’ (1899, 1924, 1934) theories of sovereignty and negotiational psychology. The innovations showed that either of these realms can be a limited access order, while the other can be an open access order or both can be open access orders or both can be limited access orders. The conceptual innovations were then used as an interpretive scheme in analysing the evolution of the South African invasive alien species regulatory reforms under the National Environmental Management: Biodiversity Act of 2004, using a case study of the trout sector, which was the most opposed to the reforms. There was a general perception among socioeconomic sectors that utilise invasive alien species that the regulatory reform processes for the governance of such species had institutionally isolated the sectors. Because of this perception, the regulatory reform process was contested, and implementation of the Fifth Chapter of the Act, which deals with the governance of invasive alien species, was delayed for nearly a decade. The thesis evaluated whether institutional isolation existed and how and why it came to be since it has implications for the reasonableness of emerging regulatory institutions, economic performance of sectors and efficient allocation of fiscal resources in institutional design processes. A mixed methods methodology was used, which included data analysis techniques such as semiosis, exploratory factor analysis, econometric estimation and document analysis. Policy documents, an online survey and key informant interviews comprised the data. The findings suggested six dimensions of institutional change that a theory of institutional change might have to address: the origin and continuity of pecuniary institutions; selfreinforcing mechanisms of the limited access policymaking order; succession and disbandment of the limited access policymaking order; exclusivity of negotiations in institutional design; tiers of institutional isolation; and the role of administrative discontinuities. Findings suggested that institutional isolation existed in the regulatory process, manifesting in three forms: administrative isolation, epistemological isolation and sectoral isolation. Administrative isolation was the most complex of the three in that it also involved a less obvious process of institutional isolation in the form of administrative redefinition of opportunity sets that were already legislatively redefined. The mechanisms of institutional isolation through which administrative isolation was sustained were administrative financing of research and careerism. The two mechanisms created a revolving door-type scenario through which invasion biologists supplied the administrative agency with candidates for senior (decision making) positions and the administrative agency, in turn, demanded specific types of knowledge over which the same epistemic community had a monopoly. The revolving door-type scenario was found to ideologically and physically entrench invasion biologists into the regulatory community. The consequence of the entrenchment was institutional hegemony, which manifested itself through the mechanism of epistemic violence insofar as the invasion biologists became the epistemic arbiters about what kinds of ideas and institutions really mattered in the governance of invasive alien species. Econometric estimates suggested that the extent to which an emerging institution is perceived to be reasonable by regulated sectors depends on the extent to which the institution is designed in a participatory and inclusive manner (that is, using integrative knowledge systems), the extent to which the designers used credible evidence and contextualised international evidence as well as the extent to which the emergent biodiversity governance institution was anthropocentric. However, findings suggested that the South African regulatory reform process fell short on all these four dimensions of reasonable institutions, which is characteristic of institutional design process shaped by hegemonic social imaginaries, resulting in institutional isolation. Emerging from the findings are several theoretical insights. Bush’s (1987) concept of institutional spaces under the Veblenian Dichotomy was extended, the result of which was identification of two stable institutional equilibria – one ceremonial and another instrumental. The ceremonial equilibrium was a typical limited access policymaking order and was responsible for the historical and present emergence of regressive institutions. Findings also suggested that the entrenched invasion biologists ceremonially encapsulated the knowledge fund that had been accumulated since the 1980s, which could have facilitated the consensual design of regulatory institutions for invasive alien species without protracted controversy. Findings suggested that a limited access policymaking order could only be disbanded by the intervention of an external sovereign agent (in this case the office of the state president) since the administrative agency, and the epistemic community that advised it, adopted the solutions that were empirically tested and proposed in the 1980s only after the intervention of the external sovereign agent. The instrumental equilibrium repealed the contested prisoner’s dilemma that was characteristic of the policy process and turned it into an assurance policy game by facilitating the identification of common interests. This finding logically links the study to a recent theoretical development in institutional theory – Ordonomics – which focuses on the causality between ideas and institutions. The findings imply that it is possible to design reasonable institutions as long as integrative (transdisciplinary) knowledge systems, including the non-scientific knowledge of the resource users, are incorporated. Integrative knowledge systems facilitate semantic innovations, which create social DNA, but epistemic violence destroys social DNA. They also imply that reliance on unidisciplinary knowledge systems in institutional design induces a large and inefficient transaction cost burden of public policy on the fiscus and private agents alike because of the inevitability of controversy, especially for wicked policy problems.
  • Full Text:
  • Date Issued: 2016

Continuous-flow dynamic dialysis and its application to collagen-ligand interactions

  • Authors: Sparrow, Neil Arthur
  • Date: 1983
  • Subjects: Collagen Ligands (Biochemistry) Ligand binding (Biochemistry) Protein-protein interactions Tannins
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4297 , http://hdl.handle.net/10962/d1004617
  • Description: Studies undertaken to investigate the binding of low molecular mass analogues of polyphenolic vegetable tannins to collagen have prompted the development of a new method to investigate protein-ligand interactions. This method, the continuous-flow dynamic dialysis method (CFDD), differs from conventional dialysis procedures used for protein-ligand binding studies. In this method, the ligand concentration in the diffusate is monitored automatically at successive closely spaced time intervals while being continuously eluted from the dialysis cell. The primary data obtained by this method consists of a series of spectrophotometric absorbance measurements representing the ligand concentration in the sink compartment of a dialysis cell. This primary data is recorded by means of a data logging device onto a punched paper tape for subsequent computer processing. Two original methods are presented for analysing the primary data to extract the protein-ligand binding isotherm. The first of these is a direct analysis which relies on Fick's first law of diffusion. In this method it is necessary to establish, by means of a control experiment, a value for the ligand permeation constant. This is used in a subsequent analysis to establish a relationship between the measured rate of diffusion of the ligand from a protein-ligand mixture and the concentration of unbound ligand which is in equilibrium with the protein-ligand complex. The protein-ligand binding isotherm is obtained from parametric equations which give the quantity of ligand bound to the protein and the concentration of unbound ligand in the sample compartment as functions of time. The second method, which is more general, utilizes the same primary data but is based on establishing a system transfer function to characterise the dialysis and eluting processes. This analysis depends on the linearity of the system and utilizes numerical laplace transforms of the primary data sets obtained from control and protein-ligand dialyses. Laplace transforms are used to effect a deconvolution of the transfer function from the primary data and yield the concentration of ligand in equilibrium with the protein-ligand complex. This procedure yields, simultaneously, both the total ligand concentration and the concentration of unbound ligand in the protein compartment of the dialysis cell. These quantities are used to establish the binding isotherm for the protein ligand system. Numerical inversion of the laplace transforms in this analysis is effected by their reduction to Fourier series. The experimental reliability of the continuous-flow dynamic dialysis method, and validity of the two analytical methods used to derive a binding isotherm from dialysis data are evaluated from studies of the binding of phenol red to bovine serum albumin (BSA) at 15⁰, 20⁰ and 25⁰ C, as well as from simulated binding curves generated by the numerical solution of the differential equations used to describe the dialysis and elution process in terms of a two-site Scatchard binding model. The method is used to investigate the binding to collagen of a series of low molecular mass phenolic compounds which can be isolated from Wattle and Quebracho vegetable tannin extracts. These compounds can be considered as monomeric precursor analogues of the polymeric vegetable tannins. The binding of these ligands to collagen is shown to be characterised by high capacity, low affinity binding in which the uptake of ligand by the protein increases linearly with increasing ligand concentration. Collagen exhibits no indication of site saturation for these ligands over the experimentally accessible concentration ranges investigated.
  • Full Text:
  • Date Issued: 1983

Integrating sustainability principles in construction health and safety management practices in Zimbabwe

  • Authors: Chigara, Benviolent
  • Date: 2018
  • Subjects: Sustainable construction -- Zimbabwe , Construction industry -- Safety measures Industrial safety -- Zimbabwe -- Management
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10948/23459 , vital:30565
  • Description: The construction industry is an important industry to national development through the provision of infrastructure and creation of employment, and hence contributing to sustainable development. Nevertheless, the construction industry has a poor health and safety (H&S) and environmental record. Globally, the construction industry is a leading contributor to workplace fatalities, injuries, and disease. In Zimbabwe, the Millennium Towers accident, which resulted in 15 construction workers losing their lives, compromised the integrity of construction H&S management, and highlighted the need to improve H&S management in the sector. This study examined H&S management in Zimbabwe and developed a framework for integrating sustainability into H&S management practices. The study employed a mixed method research design involving the use of interviews and questionnaires to collect primary data from contractors, consultants, government, clients, and workers in Harare and Bulawayo. A total of 101 questionnaires were successfully completed and analysed, representing a response rate of 55.6%. The data from questionnaires were analysed with the help of the SPSS software v.23 to produce descriptive and inferential statistics. The results of the study suggest that H&S practices are inadequate as demonstrated by the extent to which workers are exposed to hazards and the occurrence of injuries, disease, and fatalities. The factors contributing to workers’ exposure to hazards and the occurrence of injuries, disease, and fatalities include, inter alia, inadequate planning for H&S, inadequate hazard identification and risk assessments (HIRAs), inadequate management of hazards, inadequate occupational health (OH) surveillance, appointment of stakeholders who do not systematically manage H&S, inadequate design HIRAs, and unsafe work practices. The problem is amplified by inadequate integration of H&S within procurement systems, which limit the extent to which contractors make financial provision for H&S. Regrettably, workplace fatalities, injuries, and disease diminish the quality of life for the injured workers, increase project cost and delays project completion. Against this background, the study investigated the integration of sustainability principles in construction H&S as a strategy to improve H&S practices in Zimbabwe. The outcome of that investigation was a strategy and interventions, and a framework for improved practices in the form of a Sustainability Framework for Construction H&S (SFCHS). The validation of the SFCHS by construction practitioners confirms the importance of the recommended practices to reducing workplace fatalities, injuries, and disease in Zimbabwe and beyond. The development of a SFCHS, as a strategy to improve H&S practices in Zimbabwe, and the validation thereof, resulted in a significant contribution to the related body of knowledge. Nevertheless, the transition to sustainable H&S practices require contractors, consultants, government, clients and workers to take a proactive role relative to the recommended practices in the SFCHS. Further studies can explore the responsiveness of sustainability factors relative to the occurrence of injuries, disease and fatalities based on selected case studies.
  • Full Text:
  • Date Issued: 2018

Design, synthesis and evaluation of silver-specific ligands

  • Authors: Daubinet, André
  • Date: 2001
  • Subjects: Ligands Ligands -- Design Ligands -- Analysis Ligands -- Evaluation Silver -- Metallurgy
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4308 , http://hdl.handle.net/10962/d1004966
  • Description: Several series of ligands, designed to chelate silver(I) specifically in the presence of base metals, have been synthesised. The ligands include: - dithiodiamide compounds, prepared by the condensation of acetanilide derivatives with 1,2-dibromoethane; propanenitrile and propanoic ester derivatives prepared from pyridine-2-carbaldehyde via the Morita-Baylis-Hillman reaction; and novel malonamide ligands from the reaction of diethyl malonate with a range of primary amines. The malonamide derivatives were prepared under both conventional thermal and microwave-assisted conditions, the latter proving to be highly efficient. The ligands were all characterised using a combination of spectroscopic and, where appropriate, elemental analysis; in one case, the structural assignment was confirmed by single-crystal X-ray analysis. The fragmentation patterns in the electron-impact mass spectra of the malonamide derivatives have been explored using high-resolution and meta-stable peak scanning techniques. Complexes of the malonamide ligands with copper(II) and silver(I) have been synthesised, and examination of these complexes has revealed distinct differences in their co-ordination preferences towards silver(I) and copper(II). Tentative, computer-modelled structures for the complexes have been proposed using the available spectroscopic and elemental analysis data. Computer modelling, at the Molecular Mechanics level, has also been used to assess the capacity of the ligand systems to adopt conformations suitable for the chelation of tetrahedral silver(I). Solvent extraction studies have been undertaken using aqueous metal ion solutions and various organic solvents. The dithiodiamide derivatives typically presented solubility problems, but one of the ligands, N,N´-bis(3-chlorophenyl)-3,6-dithiaoctanediamide, exhibited significant but slow extraction of silver(I) into toluene. The malonamide derivatives, however, proved to be readily soluble in ethyl acetate and, in some cases, exhibited good to excellent selectivity for silver(I) in the presence of the base metals copper and lead. Atomic absorption analysis revealed rapid equilibration times (<15 min) and high extraction efficiencies over a wide pH range (2.78 - 9.0). Metal selectivity has been determined by ICP-MS analysis of the residual silver, copper and lead present in the aqueous phase after 15 min, and one of the ligands, N,N´-bis(2-benzylsulfanylethyl)malonamide, exhibits excellent (≥ 96 %) silver(I) specificity.
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  • Date Issued: 2001
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