The design, synthesis and antiplasmodial activity of a series of halogenated fosmidomycin analogues and hybrid drugs
- Authors: Afolayan, Anthonia Folake
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64370 , vital:28538
- Description: Malaria continues to be a devastating disease and a major cause of death in sub-Saharan Africa. With resistance against most of the available antimalarial drugs, there is a need for ongoing research and development of antimalarial agents. Fosmidomycin and its acetyl analogue FR900098 have been identified as potent inhibitors of Plasmodium falciparum, the causative agent of the most deadly form of malaria. Clinical trials of these agents have revealed poor absorption due to their high hydrophilicity. In the present studies the effect of halogenation of the acyl chain as well as the biological effect of extending the acyl sidechain was explored. This provided the basis on which fosmidomycin hybrids were designed to investigate the feasibility of hybrid extending into NADPH binding pocket. Synthesis of a series of halogenated FR900098 analogues was carried out in three stages. This included i) The introduction of the phosphonate group by reaction with 1,3dibromopropane in an Arbuzov reaction, ii) The introduction of a hydroxamate group by reaction of the propyl phosphonate by means of a nucleophilic substitution reaction with BocNHOBn and iii) The introduction of a halogenated acyl side chain on a protected fosmidomycin backbone. The synthesis of fosmidomycin-hybrids for which chloroquinefosmidomycin hybrids were used as the prototype, involved convergence of the two separately constructed moieties i.e. fosmidomycin and the quinoline moieties in a covalent linkage. The quinoline moiety was easily synthesized from the reaction of 4,7dichloroquinoline with 1,2-diamino ethane. The aminoquinoline so formed resulted in chloroquine-fosmidomycin hybrids 3.8 and 3.9 when reacted with halogenated FR900098 analogues. Antiplasmodial assays were conducted on the chloroquine-fosmidomycin hybrids and the halogenated fosmidomycin derivatives against the chloroquine resistant Gambian FCR-3 strain of P. falciparum. The most potent iodoacetyl fosmidomycin analogues 2.21 gave an IC50 value of 5.54 µM which is eight times more potent than the known antiplasmodial FR900098 which gave an IC50 value of 41.67 µM. All the halogenated FR900098 analogues showed better antiplasmodial activity than their non-halogenated derivatives. This indicated that the presence of halogens in the FR900098 analogues contributes to their biological Chapter 1 Literature review activity. The acetyl and propyl linked hybrids 3.8 and 3.9 showed potent antiplasmodial activity with IC50 values of 0.18 and 0.82 µM respectively. These were by far the most potent hybrids synthesized and provided leads for a new class of promising antimalarial agents. Preliminary E. coli DXR enzyme inhibition assays were carried out on the halogenated fosmidomycin analogues. The results showed good inhibition of the enzyme by the phosphonic acids of the chloroacetyl and chloropropyl analogues 2.1 and 2.2 respectively. Molecular modelling of the compounds on E. coli (PDB code: 2EGH) and P. falciparum (PDB code: 3AUA) DXR showed strong binding of the halogenated fosmidomycin analogues while the hybrids in the absence of docked NADPH showed minimum binding to the enzymes.
- Full Text:
- Date Issued: 2012
Young veterans, not always social misfits: a sociological discourse of Liberian transmogrification experiences
- Authors: Agbedahin, Komlan
- Date: 2012
- Subjects: Child soldiers -- Liberia Children and war -- Liberia Liberia. Armed Forces -- Demobilization -- Social aspects Liberia -- History -- Civil War, 1989-1996 Liberia -- History -- Civil War, 1999-2003
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3316 , http://hdl.handle.net/10962/d1003104
- Description: This thesis examines the phenomenon of child-soldiering from a different perspective. It seeks to challenge, using a novel approach, earlier studies on the roles of former child-soldiers in post-war societies. It focuses on the subjectivity of young veterans, that is war veterans formerly associated with armed forces and groups as children during the 14-year gruesome civil war which bedevilled Liberia between 1989 and 2003. This civil war claimed roughly 250,000 lives, and saw the active participation of approximately 21,000 child-soldiers. This thesis departs from previous works which mostly painted an apocalyptic picture of young veterans, and explores the nexus between their self-agency, Foucauldian technologies of the self and their transformation in the post-war society. The majority of previous scholarly works which have dominated the field of child-soldiering dwelt on the impact of armed conflict on the child-soldiers, the negative consequences, the causes of child-soldiering, and the rehabilitation and reintegration of the young veterans after their disarmament and demobilization. What this thesis seeks to do however, is to establish that, rather than considering the young veterans simply as social misfits, distraught and dispirited human beings, it should be noted that young veterans through their agency, are capable of ensuring their reintegration into their war-ravaged societies. Sadly, these young former fighters’ self-agency and technologies of the self in defining their civilian trajectories have often been overshadowed by vaunted humanitarian aid and multilayered war-profiteering. This study is underpinned by interpretive constructivism, symbolic interactionism, social identity theory, sociometer theory and expectancy theory, and sheds light on how young veterans’ self-agency, instrumental coalitions, and decision-making processes, synergistically shifted the negative identities foisted on them as a result of their participation in the war.
- Full Text:
- Date Issued: 2012
Quantification of the cross-sectoral impacts of waterweeds and their control in Ghana
- Authors: Akpabey, Felix Jerry
- Date: 2012
- Subjects: Water hyacinth -- Control -- Environmental aspects -- Ghana Alien plants -- Research -- Ghana Introduced organisms Economic development -- Social aspects -- Research -- Ghana
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5748 , http://hdl.handle.net/10962/d1005435
- Description: The Akosombo Dam on the Volta River in Ghana was built in 1963 to provide cheap energy to fuel industry and to accelerate the economic growth of the country. It provides hydroelectric power, enhanced fishing and water transportation upstream, and improved opportunities for irrigated farming, especially in the lower reaches, and their attendant economic multiplier effects. A few years after the construction of this major dam, a rapid expansion of industrialization took place in Ghana. This brought about an exponential increase in demand for more electrical power. This led to the construction of a smaller dam at Akuse, downstream of the Akosomho Dam in 1981 and the formation of a headpond at Kpong. The impoundment of the river at the two sites (Akosombo and Kpong) caused an alteration in the existing ecological and biophysical processes in the river basin, including a slowing of the flow of the river, upstream and downstream. Changes in the natural processes, such as a reduction in the flow of the river and an increase in nutrient status of the water, resulted in an invasion of aquatic weeds, increasing the density of aquatic snails (intermediate hosts of schistosomiasis), silting and closure of the estuary, as well as other more subtle effects. The invasion of the river's main course and the dams by aquatic plants led to a corresponding reduction of navigable water both upstream and downstream. The aim of this thesis was to quantify the impact and control of waterweeds, especially water hyacinth, Eichhornia crassipes (Mart) Solms-Laubach (Pontederiaceae), in Ghana. A floral survey on the Kpong Headpond recorded 49 emergent, 12 free floating and I submerged aquatic plant species, many of which were indigenous, but the exotic or introduced water hyacinth was recorded at most of the sampling sites, and was the most abundant and had the biggest impact on the utilization of the water resource. Mats of water hyacinth served as substrates for other, indigenous species to grow out into the main channel of the headpond, including the intake point of the Kpong head works of the Ghana Water Company Limited (GWCL) and landing sites for boats. These mats resulted in a reduction of the fish (fin and shell) harvest, reducing the annual production to far below demand. Water hyacinth was also shown to have severe health implications. A survey of the Ministry of Health records showed that the prevalence of both urinary and intestinal schistosomiasis had risen significantly over time as the abundance of waterweeds, most notably water hyacinth, increased, and ranged between 70% and 75% but up to 100% in some lakeside communities. Based on the work done by an NGO on board the medical boat ("Onipa Nua "), losses in terms of money due to the effect on health of the aquatic weed infestations on the Volta River in 2006 amounted to US$ 620,000. Economic losses due to invasive alien aquatic weeds were also calculated on the Oti River Arm of Lake Volta. It was estimated that about US$2.3 million per annum would be lost to the Volta Lake Transport Company and individual boat transport operators if this section of the river were 100% covered by aquatic weeds (water hyacinth and Salvinia molesta D.S. Mitchell (Salviniaceae)). It was also estimated that US$327,038 was spent annually in monitoring and managing the weeds in the Oti River. Control interventions for aquatic weeds have been implemented in river systems in Ghana. The biological control agents Neochetina bruchi Hustache (Coleoptera, Curculionidae) and Neochetina eichhorniae Warner (Coleoptera, Curculionidae) have been used on water hyacinth infestations in the Oti River Arm of Lake Volta, the Tano River and the Lagoon complex in the south-western part of the country. Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) has been used to control salvinia, and Neohydronomous affinis Hustache (Coleoptera: Curculionidae) to control water lettuce, Pistia stratiotes Lilmaeus (Araceae) in the Tano River and Lagoon complex. Although these projects have been regarded as successful, they have relied on research from elsewhere in the world and no postrelease quantification has been conducted. In evaluating the impact of the biological control agents Neochetina bruchi and Neochetina eichhorniae weevils on water hyacinth infestations in the Tano River, fresh adult feeding scars were recorded as well as the numbers of adult weevils on each water hyacinth plant sampled at six sites. Despite being released in 1994, weevil numbers and resultant damage to plants in the Tano Lagoon was low in comparison to other regions of the world where these agents have been used. The main reason for this is that this lagoon floods seasonally, washing weevil-infested plants out to sea. Water hyacinth then re-infests the lagoon from seed and the weevil populations are low. To resolve this situation, two courses of action are proposed. The first is to mass rear the weevils along the shore of the lagoon and release them when the first seedlings recruit. The second proposal is that additional agents that have shorter lifecycies and are more mobile than the weevils should be released. To this end, the water hyacinth mirid, Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) was imported from South Africa and released onto the Tano Lagoon in 2009. Retrospective laboratory host specificity trials were conducted on Neachetina eichharniae and Neachetina bruchi weevils 15 years after their release into Ghana to see if any variation in their host ranges had occurred. Considerable damage was inflicted on the E. crassipes leaves by the Neachetina weevils, while little feeding damage was recorded on both Heteranthera callifalia Kunth. (Pontederiaceae) and Eichharnia natans (P.Beauv.) Solms (Pontederiaceae). All the weevils introduced on H callifalia and E. natans died after the first week. This study served to confirm the host specificity and thereby the safety of these agents. Invasive alien aquatic macrophytes have negative impacts on the environment and economy of Ghana. The control of these weeds is essential to socioeconomic development and improved human health standards in riparian communities. Biological control offers a safe and sustainable control option, but requires diligent implementation. However, aquatic weed invasion is more typically a result of the anthropogenically induced eutrophication of water bodies, and this is the main issue that has to be addressed.
- Full Text:
- Date Issued: 2012
Participatory mapping, learning and change in the context of biocultural diversity and resilience
- Authors: Ali, Million Belay
- Date: 2012
- Subjects: Biodiversity conservation -- Research -- Ethiopia Cultural pluralism -- Research -- Ethiopia Ethnopsychology -- Research -- Ethiopia Adult education -- Research -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1689 , http://hdl.handle.net/10962/d1003572
- Description: This study set out to investigate the learning and change that emerged in and through participatory mapping in the context of biocultural diversity and resilience in rural Ethiopia. It did this through examining the learning and agency emerging from three participatory mapping practices (Participatory 3 Dimensional Modelling, sketch mapping and eco-cultural calendars) using two case study sites, located in the Bale Mountains and the Foata Mountains in Ethiopia, and honing in on in-depth reflective processes in two community contexts located within the broader case study sites, namely Horo Soba, Dinsho wereda in Bale; and Telecho, in Wolmera wereda, in the Foata Mountain complex. This study tried to answer three research questions related to participatory mapping: its role in mobilizing knowledge related to biocultural landscape, its role in learning and change, and its value in building resilience. The study used qualitative case study research methodology underpinned by critical realist philosophy, and used photographic ‘cues’ to structure the reporting on the cases. It used four categories of analysis: biocultural diversity, educational processes, learning and agency, in the first instance to report on the interactions associated with the participatory mapping practices as they emerged in the two case study sites. This was followed by in-depth analysis and interpretation of participatory mapping and biocultural diversity, as well as participatory mapping and learning, with an emphasis on acquisition, meaning making and identity formation processes. The in-depth analysis drew on social and learning theory, and theory of biocultural diversity and social-ecological resilience. The study also included analysis of broader change processes that were related to and emerged from the social interactions in the mapping activities, and the resultant morphogenesis (change), showing that morphogenesis, while broadly temporal, is not linear, and involves ‘little iterative morphogenic cycles’. These insights were then used to interpret how participatory mapping may contribute to resilience building in a context where social-ecological resilience is increasingly required, such as the two case study sites, where socialecological degradation is highly visible and is occurring rapidly. The study’s contribution to new knowledge lies in relation to the role of participatory mapping in facilitating learning, agency and change which, to date, appears to be under-theorised and under-developed in the participatory mapping and environmental education literature. As such, the study findings provide in-depth insight into how participatory mapping methodologies may ‘work in the world’, in contexts such as those presented in the two cases under study. It has tried to demonstrate how participatory mapping has managed to mobilize knowledge related to biocultural diversity, facilitated the acquisition of knowledge and helped members of the community to engage in meaning making activities relevant to their biocultural landscape and renegotiate their identity within the wider community context. It has also shown that dissonance is an important dynamic in the learning process; and that morphogenesis (or change) occurs over time, but also in smaller cycles that interact at different levels; and that participatory mapping cannot, by itself mobilise significant structural change, at least in the short term. It has also shown, however, that learning and the desire for change can emerge from participatory mapping processes, and that this can be utilized to adapt to the changing socio-ecological environments, potentially contributing to longer term resilience of social-ecological systems.
- Full Text:
- Date Issued: 2012
Development of molecularly imprinted polymer based solid phase extraction sorbents for the selective cleanup of food and pharmaceutical residue samples
- Authors: Batlokwa, Bareki Shima
- Date: 2012
- Subjects: Sorbents -- Research Nanofibers -- Research Aflatoxins -- Research Electrospinning -- Research Extraction (Chemistry) -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4309 , http://hdl.handle.net/10962/d1004967
- Description: This thesis presents the development of chlorophyll, cholic acid, aflatoxin B1 molecularly imprinted polymer (MIP) particles and cholic acid MIP nanofibers for application as selective solid phase extraction (SPE) sorbents. The particles were prepared by bulk polymerization and the nanofibers by a novel approach combining molecular imprinting and electrospinning technology. The AFB1 MIP particles were compared with an aflatoxin specific immunoextraction sorbent in cleaning-up and pre-concentrating aflatoxins from nut extracts. They both recorded high extraction efficiencies (EEs) of > 97 % in selectively extracting the aflatoxins (AFB1, AFB2, AFG1 and AFG2). High reproducibility marked by the low %RSDs of < 1% and low LODs of ≤ 0.02 ng/g were calculated in all cases. The LODs were within the monitoring requirements of the European Commission. The results were validated with a peanut butter certified reference material. The chlorophyll MIP on the other hand selectively removed chlorophyll that would otherwise interfere during pesticide residue analysis (PRA) from > 0.6 to <0.09 Au in green plants extracts. The extracted chlorophyll was removed to far below the level of ≥ 0.399 Au that is usually associated with interference during PRA. Furthermore, the MIP demonstrated better selectivity by removing only chlorophyll (> 99%) in the presence of planar pesticides than the currently employed graphitized carbon black (GCB) that removed both the chlorophyll (> 88%) and planar pesticides (> 89%). For the interfering cholic acid during drug residue analysis, cholic acid MIP electrospun nanofibers demonstrated to be more sensitive and possessing higher loading capacity than the MIP particles. 100% cholic acid was removed by the nanofibers from standard solutions relative to 80% by the particles. This showed that the nanofibers have better performance than the micro particles and as such have potential to replace the particle based SPE sorbents that are currently in use. All the templates were optimally removed from the prepared MIPs by employing a novel pressurized hot water extraction template removal method that was used for the first time in this thesis. The method employed only water, an environmentally friendly solvent to remove templates to ≥ 99.6% with template residual bleeding of ≤ 0.02%.
- Full Text:
- Date Issued: 2012
Movement patterns, stock delineation and conservation of an overexploited fishery species, Lithognathus Lithognathus (Pisces: Sparidae)
- Authors: Bennett, Rhett Hamilton
- Date: 2012
- Subjects: Reef fishes -- Behavior , Endangered species -- South Africa , Fish stock assessment -- South Africa , Fishery management -- South Africa , Fish communities -- South Africa , Sparidae , Lithognathus , Lithognathus -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5374 , http://hdl.handle.net/10962/d1015709
- Description: White steenbras Lithognathus lithognathus (Pisces: Sparidae) has been a major target species of numerous fisheries in South Africa, since the late 19th century. Historically, it contributed substantially to annual catches in commercial net fisheries, and became dominant in recreational shore catches in the latter half of the 20th century. However, overexploitation in both sectors resulted in severe declines in abundance. The ultimate collapse of the stock by the end of the last century, and the failure of traditional management measures to protect the species indicate that a new management approach for this species is necessary. The species was identified as a priority for research, management and conservation in a National Linefish Status Report. Despite knowledge on aspects of its biology and life history, little is known about juvenile habitat use patterns, home range dynamics and movement behaviour in estuaries. Similarly, the movement and migration of larger juveniles and adults in the marine environment are poorly understood. Furthermore, there is a complete lack of information on its genetic stock structure. Such information is essential for effective management of a fishery species. This thesis aimed to address the gaps in the understanding of white steenbras movement patterns and genetic stock structure, and provide an assessment of its current conservation status. The study adopted a multidisciplinary approach, incorporating a range of methods and drawing on available information, including published literature, unpublished reports and data from long-term monitoring programmes. Acoustic telemetry, conducted in a range of estuaries, showed high site fidelity, restricted area use, small home ranges relative to the size of the estuary, and a high level of residency within estuaries at the early juvenile life stage. Behaviour within estuaries was dominated by station-keeping, superimposed by a strong diel behaviour, presumably based on feeding and/or predator avoidance, with individuals entering the shallow littoral zone at night to feed, and seeking refuge in the deeper channel areas during the daytime. Conventional dart tagging and recapture data from four ongoing, long-term coastal fish tagging projects, spread throughout the distribution of this species, indicated high levels of residency in the surf zone at the late juvenile and sub-adult life stages. Consequently, juvenile and sub-adult white steenbras are vulnerable to localised depletion, although they can be effectively protected by suitably positioned estuarine protected areas (EPAs) and marine protected areas (MPAs), respectively. It has been hypothesized that adult white steenbras undertake large-scale coastal migrations between summer aggregation areas and winter spawning grounds. The scale of observed coastal movements was correlated with fish size (and age), with larger fish undertaking considerably longer-distance coastal movements than smaller individuals, supporting this hypothesis. Given the migratory behaviour of adults, and indications that limited spawning habitat exists, MPAs designed to protect white steenbras during the adult life stage should encompass all known spawning aggregation sites. The fishery is plagued by problems such as low compliance and low enforcement capacity, and alternative management measures, such as seasonal closure, need to be evaluated. Despite considerable conventional dart tagging effort around the coastline (5 782 fish tagged) with 292 recaptures there remains a lack of empirical evidence of fish migrating long distances (> 600 km) between aggregation and spawning areas. This uncertainty in the level of connectivity among coastal regions was addressed using mitochondrial DNA sequencing and genotyping of microsatellite repeat loci in the nuclear genome, which showed no evidence of major geographic barriers to gene flow in this species. Samples collected throughout the white steenbras core distribution showed high genetic diversity, low genetic differentiation and no evidence of isolation by distance or localised spawning. Although historically dominant in several fisheries, analysis of long-term commercial and recreational catch data for white steenbras indicated considerable declines and ultimately stock collapse. Improved catch-per-unit-effort in two large MPAs subsequent to closure confirmed that MPAs can be effective for the protection of white steenbras. However, the current MPA network encompasses a low proportion of sandy shoreline, for which white steenbras exhibits an affinity. Many MPAs do not prohibit recreational shore angling, which currently accounts for the greatest proportion of the total annual catch. Furthermore, EPAs within the juvenile distribution protect a negligible proportion of the total available surface area of estuaries – habitat on which white steenbras is wholly dependent. Despite some evidence of recent increases in abundance in estuaries and the surf zone in certain areas, white steenbras meets the criteria for “Endangered” on the IUCN Red List of Threatened Species, and for “Protected species” status on the National Environmental Management: Biodiversity Act of South Africa. The species requires improved management, with consideration for its life-history style, estuarine dependency, surf zone residency, predictable spawning migrations and its poor conservation status. The multidisciplinary approach provides valuable information towards an improved scientific basis for the management of white steenbras and a framework for research that can be adopted for other overexploited, estuarine-associated coastal fishery species.
- Full Text:
- Date Issued: 2012
Effect of cultivar on the quality of flax and hemp grown in South Africa
- Authors: Blouw, Langa Sunshine
- Date: 2012
- Subjects: Hemp -- South Africa , Flaxseed -- South Africa , Plant varieties , Textile industry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9387 , http://hdl.handle.net/10948/d1010997 , Hemp -- South Africa , Flaxseed -- South Africa , Plant varieties , Textile industry
- Description: Bast fibrous renewable materials, as commercial crops for the manufacture of textile based and other products, have been used for thousands of years to satisfy certain human needs, such as for shelter, clothing, source of energy and tools, and to sustain the livelihood of many communities in countries, such as in Asia, Europe and Africa. Concern for the environment has led to a number of global initiatives that favour the use of natural fibres. It is forecast that the global fibre demand by 2050 will be 130 million tonnes, which the cotton and synthetic fibre production will not be able to meet. Other than the environmental concerns, the renewed global interest in natural fibres, such as flax and hemp, forms part of a strategy to satisfy the fibre demand. South Africa, notwithstanding the fact that the flax and hemp industries have long been established for thousands of years in Europe, Asia and Egypt (Africa), has no history of the breeding, growing, processing and production of these cash crops. The renewed global interest in these crops has also stimulated interest from South Africa with respect to the development of a flax and hemp fibre industry so as to address some of the socio-economic challenges confronting the country today in its attempts to bring about real development in the rural areas through the cultivation and complete beneficiation of these fibre crops. In this regard, the relevant stakeholders, namely government, research councils, tertiary education institutions, farmers and communities worked together to investigate whether South Africa has the agronomic and climatic conditions, technical expertise as well as the necessary processing and production infrastructure to support the development of a local flax and hemp agro-industry. The purpose of this study was firstly to evaluate the performance of EU flax and hemp cultivars grown under different agronomic conditions in South Africa, and their effect on straw biomass yield, fibre yield and total fibre yield per hectare as well as associated fibre properties, and secondly to undertake mechanical fibre modification trials aimed at producing flax and hemp fibres with fibre diameters close to those of cotton. The minimum fibre diameter targeted being 20μm. In accordance with the project objectives and work plan, selected dew retted flax and hemp straw samples from the various planting sites selected by the Agriculture Research Council – Institute for Industrial Crops, representing all the agronomic conditions under investigation, were taken to the CSIR for fibre extraction and testing. A relatively inexpensive and easy to operate Russian designed and manufactured machine, the CMT-200M breaker-cum-scutcher, was used for fibre extraction and the resultant extracted fibre bundles were further refined, using a steel comb, to obtain optimal fibre separation before their physical and chemical properties were evaluated. Results obtained in this research study proved that the climatic and agronomic conditions in South Africa were suitable for the cultivation of flax and hemp, notwithstanding the fact that the fibre yields achieved for hemp were lower than the minimum criteria of 23 percent, and that for flax only just exceeded the 25 percent minimum. The lack of local technical expertise on the growing and retting of flax and hemp, contributed to the low fibre yields. The planting parameters which were found to produce good results for the cultivation of hemp were the October planting date, using a row spacing of between 12.5 to 25 cm, with a seeding density of between 80 – 100kg, and the application of 50 – 100kg nitrogen fertiliser. The use of extra artificial lighting and herbicide treatment did not appear to beneficially improve the hemp fibre yields. Similar considerations for flax cultivation in the Southern Cape region, particularly Oudtshoorn and Outeniqua, indicated that May to July planting dates, using inter-row spacing of 25cm and sowing density of 63kg seed.haˉ¹, produced a fibre yield and total fibre yield per hectare above the minimum values of 25 percent and 0,8 tonnes per hectare, respectively, quoted in the literature.
- Full Text:
- Date Issued: 2012
Teaching pharmacology: issues of language and learning in a multilingual classroom setting
- Authors: Boschmans, Shirley-Anne Inez
- Date: 2012
- Subjects: English language -- Study and teaching -- South Africa , Pharmacology -- Terminology , Multicultural education , Second language acquisition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9562 , http://hdl.handle.net/10948/d1013398
- Description: The medium for teaching and learning in South African universities is not the mother tongue of the majority of students and this has been reported to be a barrier to achievement (Department of Education, 2002). Poor English language skills, as well as poor discipline specific vocabulary knowledge, can lead to poor study techniques with the students resorting to rote learning as they are unable to interpret the recommended texts (Gow, Kember, & Chow, 1991; Shembe, 2002). In 2005 at the NMMU a significant difference was reported between the marks achieved for the Pharmacology 2 (ZCL2) module by English first language (EFL) students and the English second language students (EAL) (Boschmans & McCartney, 2005). These finding provided motivation for this study which interrogates issues of language and learning in a multilingual Pharmacology classroom. A mixed methods approach, which employed a concurrent triangulation design with quantitative dominance, was used. Two parallel studies were undertaken. One consisted of a quasi-experimental, pre-test and post-test control group design using an intervention which consisted of the application of the didactical practice of exploratory talk with an experimental sample group during ZCL2 Supplementary Instruction sessions (SI). A second study involved a parallel data collection from the ZCL303 and ZCL401 Pharmacy students at the NMMU to investigate possible effects of academic progression. Purposive, homogenous sampling was used in selection of the samples. The mean ZCL2 mark for the experimental group (58.70±14.14 percent) of students who experienced the intervention (application of exploratory talk) was significantly higher (p = .0004) than the mark achieved by the ZCL2 comparison group (46.47±14.48). This Abstract difference was of high practical significance (Cohen‟s d = 0.85). This quantitative finding was supported by the qualitative data where the students expressed support for the discussion sessions (application of exploratory talk) held during SI sessions. There was a significant increase, with academic progression, of English reading comprehension amongst the EFL students (p = .025) but not in the EAL students and BPharm1 weighted average (p < .001) as well as SI attendance (p = .02) correlated significantly with achievement in ZCL2. The findings of this study provide insights into the teaching of Pharmacology in a multilingual classroom. The qualitative results in addition to strengthening the quantitative findings through triangulation have provided a rich, deep and detailed description of the lived experiences of Pharmacology students. The data will provide insights into students‟ experiences for Pharmacy academics and are a resource for understanding student perspectives.
- Full Text:
- Date Issued: 2012
Self-perceived professional identity of pharmacy educators
- Authors: Burton, Susan
- Date: 2012
- Subjects: Academic identity , Communities of practice , Identity (Philosophical concept) , Pharmacy -- Study and teaching , Pharmacy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10139 , http://hdl.handle.net/10948/d1008352 , Academic identity , Communities of practice , Identity (Philosophical concept) , Pharmacy -- Study and teaching , Pharmacy
- Description: The philosophy of pharmaceutical care, which defines a patient-centred approach to practice, has been embraced and upheld by national and international pharmaceutical organisations for two decades. However, pharmacists have been slow to change their practice and implement a pharmaceutical care approach. It has been suggested that amongst other factors, short-comings in pharmaceutical education have contributed to this reluctance of the profession to transform practice. Efforts to address these short-comings in pharmaceutical education have focused on the curriculum and pedagogic practices, and not on the pharmacy educators themselves. Palmer (1998) asserts that “good teaching cannot be reduced to technique; good teaching comes from the identity and integrity of the teacher”. In essence, "we teach who we are" and good teachers have one common trait: “a strong sense of personal identity that infuses their work”. This study identified, described and analysed the self-perceived professional identities of pharmacy educators within the South African context. This included ascertaining factors and contexts which contributed to participants’ self-perception of their professional identity. In an effort to understand the influence the educators have on practice and on changing practice and vice-versa, the attitudes, beliefs and behaviours of participants regarding the philosophy and practice of pharmaceutical care, and pharmaceutical education were also explored. Situated within a constructivist-interpretive, qualitative paradigm and making use of methodological triangulation, this study was conducted in three phases, each employing a different qualitative method to collect data. The first phase made use of narrative analysis to gain an in-depth understanding of pharmacy educators’ perceived professional identities and to explore how their experiences, across various contexts, have formed their professional identities. In-depth individual narrative interviews were used to provide a forum in which the participants could reflect upon and tell their professional life-story. This phase of the study also made use of the exploration of metaphors to further investigate the participants’ professional identity and, more particularly, their images of themselves as “teacher” and role model for students. A maximum variation, purposeful sampling approach was used to recruit eight pharmacy academics - one from each school or faculty of pharmacy in South Africa, as participants in this phase of the study. The second and third phases explored more widely, the insights gained from the first phase and the formation of professional identity, attitudes, beliefs and practices of pharmacy educators in South Africa. Two focus groups were employed during the second phase and the study sample was broadened to include a further ten pharmacy educators. In the third phase, a purpose-designed, qualitative questionnaire was used to extend the study sample to all pharmacy educators in South Africa. A convenience sampling approach was used in both the second and third phases of the study. Thematic analysis and interpretation of the narrative interview and focus group transcripts and the questionnaire responses were conducted using qualitative data analysis software – Atlas.ti®. A multiplicity of self-perceived professional identities was described. However, all of these were multi-faceted and could be situated on a continuum between pharmacist identity on one end and academic identity on the other. In addition, six key determinants were recognised as underpinning the participants’ self-perception of their professional identity. These included three structural determinants: expected role; knowledge base; and practice, and three determinants relating to the emotional dimensions and agency of professional identity: professional status; passions; and satisfiers. The professional identity of the participants had been formed through membership of multiple pharmacy-related communities of practice and continued to be sustained through a nexus of multi-membership. There was extensive support by the participants for the concept of pharmaceutical care; however, it did not impact extensively on their role as pharmacy educators. Furthermore, many expressed concern around the use of the term ‘pharmaceutical care’: its definition; its lack of penetration into, and implementation within the practice environment; and even its relevance to the South African healthcare context. Many of the participants perceived the professional development of future pharmacists to be integral to their role as educators, and was often their source of greatest professional satisfaction. However, concern was also expressed at the dissonance that students were perceived to experience, sometimes, because of the incongruities that they are taught and what they experience in practice. This study has afforded pharmacy educators in South Africa an opportunity to understand better “who” they are as professionals, and to reflect on their role as educators and as role models for future pharmacist. Moreover, the findings contribute to a collective understanding of the professional identity of pharmacy educators and socialisation of pharmacy students into the profession. The insights and recommendations emerging from the study have the potential to make academic pharmacy a more attractive career choice which may have positive implications for the future attraction and retention of pharmacists to academic posts within universities.
- Full Text:
- Date Issued: 2012
A model for automated topic spotting in a mobile chat based mathematics tutoring environment
- Authors: Butgereit, Laura Lee
- Date: 2012
- Subjects: Mobile communication systems in education , Mathematics -- Study and teaching , Tutors and tutoring -- Mathematics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9809 , http://hdl.handle.net/10948/d1013741
- Description: Systems of writing have existed for thousands of years. The history of civilisation and the history of writing are so intertwined that it is hard to separate the one from the other. These systems of writing, however, are not static. They change. One of the latest developments in systems of writing is short electronic messages such as seen on Twitter and in MXit. One novel application which uses these short electronic messages is the Dr Math® project. Dr Math is a mobile online tutoring system where pupils can use MXit on their cell phones and receive help with their mathematics homework from volunteer tutors around the world. These conversations between pupils and tutors are held in MXit lingo or MXit language – this cryptic, abbreviated system 0f ryting w1ch l0ks lyk dis. Project μ (pronounced mu and indicating MXit Understander) investigated how topics could be determined in MXit lingo and Project μ's research outputs spot mathematics topics in conversations between Dr Math tutors and pupils. Once the topics are determined, supporting documentation can be presented to the tutors to assist them in helping pupils with their mathematics homework. Project μ made the following contributions to new knowledge: a statistical and linguistic analysis of MXit lingo provides letter frequencies, word frequencies, message length statistics as well as linguistic bases for new spelling conventions seen in MXit based conversations; a post-stemmer for use with MXit lingo removes suffixes from the ends of words taking into account MXit spelling conventions allowing words such as equashun and equation to be reduced to the same root stem; a list of over ten thousand stop words for MXit lingo appropriate for the domain of mathematics; a misspelling corrector for MXit lingo which corrects words such as acount and equates it to account; and a model for spotting mathematical topics in MXit lingo. The model was instantiated and integrated into the Dr Math tutoring platform. Empirical evidence as to the effectiveness of the μ Topic Spotter and the other contributions is also presented. The empirical evidence includes specific statistical tests with MXit lingo, specific tests of the misspelling corrector, stemmer, and feedback mechanism, and an extensive exercise of content analysis with respect to mathematics topics.
- Full Text:
- Date Issued: 2012
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.
- Full Text:
- Date Issued: 2012
Systematic marine spatial planning and monitoring in a data poor environment: a case study of Algoa Bay, South Africa
- Authors: Chalmers, Russell
- Date: 2012
- Subjects: Spatial ecology -- South Africa -- Algoa Bay , Coastal zone management -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5373 , http://hdl.handle.net/10962/d1015695
- Description: Globally the failure of traditional fisheries management approaches is evident through the increasing number of overexploited or depleted marine stocks. Past sectoral management has failed to address cumulative impacts of fisheries activities on ecosystem health. Ecosystem based approaches have been advocated as a viable alternative for sustainable management of marine ecosystems as they present a holistic and precautionary approach, which integrates management of multiple activities with that of maintaining ecological health. Although conceptually advanced, implementation has been poor due to the complexities of competing ecological and socio-economic management objectives. Marine spatial planning can facilitate the implementation of ecosystem based management as it is able to address the spatial heterogeneity of biological communities and anthropogenic activities. Ecosystem based management approaches aim to address the full range of anthropogenic drivers on the marine environment, including but not limited to fisheries, tourism, coastal development, and land and marine based pollution sources amongst others. Fisheries activities have a direct impact on the local marine environment and were therefore the focus of this study which forms a starting point for implementing ecosystem based management in Algoa Bay. It is envisaged that future research will build on this foundation and include additional anthropogenic drivers into the management and monitoring strategies developed in this study in order to achieve a truly holistic ecosystem approach to management in Algoa Bay. Algoa Bay is situated centrally within the warm-temperate Agulhas bioregion along the east coast of South Africa and is the largest and best formed logarithmic spiral bay along this section of coastline. A large city, two commercial ports and several coastal settlements are located within Algoa Bay and a wide range of marine based activities occur within the area. A large section of the coastline is proclaimed as a National Park yet only two small offshore marine areas are formally protected. The development of a large marine protected area (MPA) adjoining the terrestrial section was proposed in the mid-1990s but a lack of adequate spatial data with which to quantify the fishery costs and conservation benefits led to wide scale public opposition and halted the declaration process. The primary goal of this study was to obtain and analyse baseline data to understand spatial and temporal trends in the distribution and abundance of fish populations and fisheries activities in order to develop a spatial framework for marine conservation and management in a data limited situation using Algoa Bay, South Africa as a case study. Furthermore, it aims to contribute to the development of a monitoring framework to evaluate the success of implementation and the resultant changes in biological and socio-economic environments. This information will be used to re-initiate the stakeholder engagement process in the future.
- Full Text:
- Date Issued: 2012
Electrochemistry and photophysicochemical studies of titanium, tantalum and vanadium phthalocyanines in the presence of nanomaterials
- Authors: Chauke, Vongani Portia
- Date: 2012
- Subjects: Phthalocyanines -- Synthesis Electrochemistry Titanium Tantalum Vanadium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4313 , http://hdl.handle.net/10962/d1004971
- Description: The syntheses of tetra- and octa-substituted phthalocyanine complexes of titanium (IV) oxide vanadium (IV) oxide and tantalum (V) hydroxide and their electrochemical characterisation are presented in this work. The structures and purity of these complexes were confirmed by NMR, infrared and mass spectroscopies and elemental analysis. They show good solubility in most common solvents especially non-viscous solvents such as dichloromethane and chloroform. The cyclic voltammograms (CV) showed reversible to quasi reversible behavior for all the reduction couples and the oxidation peaks were irreversible. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes. The synthesis of gold nanoparticles and their conjugation with the new phthalocyanines was carried out. Similarly, single walled carbon nanotubes were conjugated to selected tantalum complexes and the characterization of all the nanomaterials and their conjugates using different techniques that include TEM, XRD and AFM is also presented in this work. The photophysical and photochemical properties and photocatalytic oxidation of cyclohexene properties of the newly synthesised in the presence of gold nanoparticles were investigated. The compounds were stable, well within the stability range for phthalocyanines. The singlet oxygen quantum yield values increased drastically in the presence of gold nanoparticles. The photocatalytic products obtained from the reaction were cyclohexene oxide, 2-cyclohexen-1-ol, 2-cyclohexene-1-one and 1,4-cyclohexanediol. The percentage conversion values, yields and selectivity values improved significantly in the presence of AuNPs. Singlet oxygen was determined to be the main agent involved in the photocatalytic oxidation of cyclohexene. The electrocatalytic oxidation of bisphenol A and p-nitrophenol was carried out using nickel tetraamino phthalocyanine and all the newly synthesised metallophthalocyanine in the presence of gold nanoparticles and single walled carbon nanotubes. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc, TiPc and VPc complexes. The presence of single walled carbon nanotubes further improved electron transfer and minimised electrode passivation.
- Full Text:
- Date Issued: 2012
Electrospun nanofibers : an alternative sorbent material for solid phase extraction
- Authors: Chigome, Samuel , Samuel Chigome
- Date: 2012 , 2012-03-26
- Subjects: Nanofibers -- Research Electrospinning -- Research Sorbents -- Research Extraction (Chemistry) -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4314 , http://hdl.handle.net/10962/d1004972
- Description: The work described in the thesis seeks to lay a foundation for a better understanding of the use of electrospun nanofibers as a sorbent material. Three miniaturised electrospun nanofiber based solid phase extraction devices were fabricated. For the first two, 10 mg of electrospun polystyrene fibers were used as a sorbent bed for a micro column SPE device (8 mm bed height in a 200 μl pipette tip) and a disk (I) SPE device (5 mm 1 mm sorbent bed in a 1000 μl SPE barrel). While for the third, 4.6 mg of electrospun nylon nanofibers were used as a sorbent bed for a disk (II) SPE device, (sorbent bed consisting of 5 5 mm 350 μm stacked disks in a 500 μl SPE barrel). Corticosteroids were employed as model analytes for performance evaluation of the fabricated SPE devices. Quantitative recoveries (45.5-124.29 percent) were achieved for all SPE devices at a loading volume of 100 μl and analyte concentration of 500 ng ml-1. Three mathematical models; the Boltzmann, Weibull five parameter and the Sigmoid three parameter were employed to describe the break through profiles of each of the sorbent beds. The micro column SPE device exhibited a breakthrough volume of 1400 μl, and theoretical plates (7.98-9.1) while disk (I) SPE device exhibited 400-500 μl and 1.39-2.82 respectively. Disk (II) SPE device exhibited a breakthrough volume of 200 μl and theoretical plates 0.38-1.15. It was proposed that the formats of future electrospun nanofiber sorbent based SPE devices will be guided by mechanical strength of the polymer. The study classified electrospun polymer fibers into two as polystyrene type (relatively low mechanical strength) and nylon type (relatively high mechanical strength).
- Full Text:
- Date Issued: 2012
Liquidity risk management by Zimbabwean commercial banks
- Authors: Chikoko, Laurine
- Date: 2012
- Subjects: Liquidity (Economics) , Banks and banking -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9027 , http://hdl.handle.net/10948/d1020344
- Description: Macroeconomic and financial market developments in Zimbabwe since 2000 have led to an increase in many banks‟ overall exposure to liquidity risk. The thesis highlights the importance of understanding and building comprehensive liquidity frameworks as defenses against liquidity stress. This study explores liquidity and liquidity risk management practices as well as the linkages and factors that affected different types of liquidity in the Zimbabwean banking sector during the Zimbabwean dollar and multiple currency eras. The research sought to present a comprehensive analysis of Zimbabwean commercial banks‟ liquidity risk management in challenging operating environments. Two periods were selected: January 2000 to December 2008 (the Zimbabwean dollar era) and March 2009 to June 2011 (the multiple currency era). Explanatory and survey research designs were used. The study applied econometric modeling using panel regression analysis to identify the major determinants of liquidity risk for 15 commercial banks in Zimbabwe. The financing gap ratio was used as the proxy for liquidity risk. The first investigation was on liquidity risk determinants in the Zimbabwean dollar era. The econometric investigations revealed that an increase in capital adequacy reduced liquidity risk and that there was a positive relationship between size and bank illiquidity. Liquidity risk was also explained by spreads. Inflation was positively related to liquidity risk and was a significant explanatory variable. Non-performing loans were not significant in explaining commercial banks‟ illiquidity, which is contrary to expectations. The second investigation was on commercial banks‟ liquidity risk determinants in the multiple currency era by using panel monthly data. The results showed that capital adequacy had a significant negative relationship with liquidity risk. The size of the bank was significant and positively related to bank illiquidity. Unlike in the Zimbabwean dollar era, spreads were negatively related to bank liquidity risk. Again, non-performing loans were a significant explanatory variable. The reserve requirements ratio and inflation also influenced bank illiquidity in the multiple currency regime. In both investigations, robustness tests for the main findings were done with an alternative dependent variable to the financing gap ratio. To complement the econometric analysis, a survey was conducted using questionnaires and interviews for the same 15 commercial banks. Empirical analysis in this research showed that during the 2000-2008 era; (i) no liquidity risk management guidelines were issued by the Reserve Bank of Zimbabwe until 2007. Banks relied on internal efforts in managing liquidity risk (ii) Liquidity was managed daily by treasury (iii) The operating environment was challenging with high inflation rates, which led to high demand for cash withdrawals by depositors (iv) Locally owned banks were more exposed to liquidity risk as compared to the foreign owned banks (v) Major sources of funds were new deposits, retention of maturities, shareholders, interbank borrowings, offshore lines of credit and also banks relied on the Reserve Bank of Zimbabwe as the lender of last resort (vi) Financial markets were active and banks offered a wide range of products (vii) To manage liquidity from depositors, banks relied on cash reserves, calculating and analysing the withdrawal patterns. When faced with cash shortages, banks relied on the daily limits set by the Reserve Bank of Zimbabwe (viii) Banks were lending but when the challenges deepened, they lent less in advances and increased investment in government securities. (ix) Inflation had major effects on liquidity risk management as it affected demand deposit tenors, fixed term products, corporate sector deposit mobilisation, cost of funds and investment portfolios (x) The regulatory environment was not favourable with RBZ policy measures designed to arrest inflation having negative repercussions on banks` liquidity management (xi) Banks had no liquidity crisis management frameworks. During the multiple currency exchange rate system (i) Commercial banks had problems in sourcing funds. They were mainly funded by transitory deposits with little coming in from treasury activities, interbank activities and offshore lines of credit. There was no lender of last resort function by the Reserve Bank of Zimbabwe. (ii) Some banks were still struggling to raise the minimum capital requirements (iii) Commercial banks offered narrow product ranges to clients (iv) To manage liquidity demand from clients, banks relied on the cash reserve ratio, and calculated the patterns of withdrawal, while some banks communicated with corporate clients on withdrawal schedules. (v) Zimbabwe commercial banks resumed the lending activity after dollarisation. Locally owned banks were aggressive, while foreign owned banks took a passive stance. There were problems with non-performing loans, especially from corporate clients, which exposed many banks to liquidity risk. (vi) Liquidity risk management in Zimbabwe was still guided by the Reserve Bank of Zimbabwe Risk Management Guideline BSD-04, 2007. All banks had liquidity risk management policies and procedure manuals but some banks were not adhering to them. Banks also had liquidity risk limits in place but some violated them. Furthermore, some banks were not conducting stress tests. Although all banks had contingency plans in place, none were testing them. Specifically, the research study highlighted the potential sources of liquidity risk in the Zimbabwean dollar and multiple currency periods. Based on the results, the study recommends survival strategies for banks in managing liquidity risk in such environments. It proposes a comprehensive liquidity management framework that clearly identifies, measures and control liquidity risk consistent with bank-specific and the country‟s macroeconomic developments. The envisaged framework would assist banks in dealing with illiquidity in a manner that would be less disruptive and that could render any future crisis less painful. Of importance is the recommendation that the central bank might not need to be too strict or too relaxed, but be moderate in ensuring an enabling regulatory environment. This would help banks to manage liquidity risk and at the same time protect depositors in any challenging operating environment. In both the studied time periods, there were transitory deposits. Generally there is need to inculcate a savings culture in Zimbabwe.
- Full Text:
- Date Issued: 2012
Farm level institutions in emergent communities in post fast track Zimbabwe: case of Mazowe district
- Authors: Chiweshe, Manase Kudzai
- Date: 2012
- Subjects: Land reform -- Zimbabwe -- History -- 21st century Land settlement -- Social aspects -- Zimbabwe Zimbabwe -- Social conditions -- 1980- Zimbabwe -- Economic conditions Zimbabwe -- Politics and government -- 1980-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3308 , http://hdl.handle.net/10962/d1003096
- Description: The thesis seeks to understand how emerging communities borne out of the Fast Track Land Reform Programme in Zimbabwe have been able to ensure social cohesion and social service provision using farm level institutions. The Fast Track Programme brought together people from diverse backgrounds into new communities in the former commercial farming areas. The formation of new communities meant that, often, there were 'stranger households'living next to each other. Since 2000, these people have been involved in various processes aimed at turning clusters of homesteads into functioning communities through farm level institutions. Fast track land reform precipitated economic and political crisis in Zimbabwe characterised by a rapidly devaluating Zimbabwean dollar, enormous inflation and high unemployment figures. This economic crisis has impacted heavily on new farmers who find it increasingly difficult to afford inputs and access loans. They have formed social networks in response to these challenges, taking the form of farm level institutions such as farm committees, irrigation committees and health committees. The study uses case studies from small-scale 'A1 farmers‘ in Mazowe district which is in Mashonaland Central Province. It employs qualitative methodologies to enable a nuanced understanding of associational life in the new communities. Through focus group discussions, in-depth interviews, narratives, key informant interviews and institutional mapping the study outlines the formation, taxonomy, activities, roles, internal dynamics and social organisation of farm level institutions. The study also uses secondary data collected in 2007-08 by the Centre for Rural Development in the newly resettled areas in Mazowe. The major finding of the study is that farmers are organising in novel ways at grassroots levels to meet everyday challenges. These institutional forms however are internally weak, lacking leadership with a clear vision and they appear as if they are transitory in nature. They remain marginalised from national and global processes and isolated from critical connections to policy makers at all levels; thus A1 farmers remain voiceless and unable to have their interests addressed. Farm level institutions are at the forefront of the microeconomics of survival among these rural farmers. They are survivalist in nature and form, and this requires a major shift in focus if they are to be involved in developmental work. The institutions remain fragmented and compete amongst themselves for services from government without uniting as A1 farmers with similar interests and challenges.
- Full Text:
- Date Issued: 2012
Pre-concentration of heavy metals in aqueous environments using electrospun polymer nanofiber sorbents
- Authors: Darko, Godfred
- Date: 2012
- Subjects: Heavy metals -- Absorption and adsorption -- Research Nanochemistry -- Research Polystyrene -- Research Polyamides -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4337 , http://hdl.handle.net/10962/d1004998
- Description: This thesis presents an alternative approach for pre-concentrating heavy metals in aqueous environments using electro spun polymer nanofiber sorbents. The conditions for electrospinning polyethersulfone, polystyrene, polysulfone and polyamide-6 were optimized. The morphologies and porosities of the electrospun nanofibers were studied using SEM and BET nitrogen gas adsorptions. The nanofibers had mesoporous morphologies with specific surface areas up to 58 m2/g. The electro spun nanofiber sorbents were characterized in terms of their tunability for both uptake and release of heavy metals. The usability of the sorbent was also assessed. The sorbents showed fast adsorption kinetics for heavy metals « 20 min for As, Cu, Ni and Pb) in different aqueous environments. The adsorption characteristics of the sorbents best fitted the Freundlich isotherm and followed the first order kinetics. The efficiencies of adsorption and desorption of heavy metals on both imidazolyl-functionalized polystyrene and amino-functionalized polysulfone sorbents were more than 95% up to the fifth cycle of usage. Reusability improved dramatically (up to 10 runs of usage) when mechanically stable amino-functionalized nylon-6 electro spun nanofibers were used. The capacity of the amino-functionalized nylon-6 sorbent to pre-concentrate heavy metals compared very favourably with those of aqua regia and HN03+H202 digestions especially in less complex matrices. Due to their highly porous nature, the electro spun nanofibers exhibited high adsorption capacities (up to 50 mg/g) for heavy metal ions. The loading capacities achieved with the imidazolyl-functionalized sorbent were higher than those for amino-functionalized mesoporous silica and biomass-based sorbents. The electro spun nanofiber sorbents presents an efficient and cost effective alternative for preconcentrating heavy metals in aqueous environments.
- Full Text:
- Date Issued: 2012
Identification of novel marine algal compounds with differential anti-cancer activity: towards a cancer stem-cell specific chemotherapy
- Authors: De la Mare, Jo-Anne
- Date: 2012
- Subjects: Breast -- Cancer , Stem cells -- Research , Chemotherapy , Algae -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4143 , http://hdl.handle.net/10962/d1016250
- Description: Breast cancer remains the leading cause of cancer-related death in women worldwide. Furthermore, it has been demonstrated that the treatment-resistant ER-PR-HER2/neu- sub-type is more common among women of African descent, necessitating the search for novel chemotherapies for this form of the disease. The secondary metabolites produced by marine algae represent a rich source of structurally unique compounds with chemotherapeutic potential, particularly in South Africa, whose oceans allegedly host 15 % of the total number of species in the world. Indeed, a recent study reported the isolation of a range of novel compounds from South African red and brown algae of the Plocamium, Portiera and Sargassum genera which displayed cytotoxicity against oesophageal cancer cells in vitro. The molecular mechanisms mediating this toxicity were unknown, as was the effect of these and similar compounds on metastatic ER-PR-HER2/neu- breast cancer cell lines or breast cancer stem cells. The current study aimed to address these questions by screening a library of twenty-two novel marine algal compounds for the ability to inhibit MDA-MB-231 and Hs578T breast cancer cells, while having no adverse effects on non-cancerous MCF12A breast epithelial cells. While twelve of these were toxic in the micromolar range against breast cancer cells, only the polyhalogenated monoterpenes RU004 and RU007, and the tetraprenylated quinone sargaquinoic acid (SQA) were identified as hit compounds based on the criteria that their cytotoxicity was specific to breast cancer and not healthy breast cells in vitro. On the other hand, the halogenated monoterpene RU015 was found to be highly toxic to both breast cancer and non-cancerous breast cell lines, while the halogenated monoterpene stereoisomers RU017 and RU018 were non-toxic to either of these cell lines. The mode of action of RU004, RU007, RU015 and SQA, together with the previously characterized carotenoid fucoxanthin (FXN), was assessed in terms of the type of cell death induced and the effect on cell cycle distribution of these compounds. Flow cytometric analysis of the extent of Hoescht 33342 and propidium iodide staining along with PARP cleavage studies suggested that SQA induced apoptosis in MDA-MB-231 cells. On the other hand, the highly toxic compound RU015 appeared to induce necrosis as evidenced by 50 kDa PARP cleavage product in MDA-MB-231 cells. The flow cytometry profiles of MDA-MB-231 and Hst578T cells treated with the hit compounds RU004 and RU007 were suggestive of the induction of apoptosis by these compounds. Cell cycle analysis by flow cytometry with propidium iodide staining revealed that both SQA and FXN induced G0-G1 arrest together with an increase in the apoptotic sub-G0 population, which agreed with previous reports in the literature. The molecular mechanism of action of SQA and FXN were further investigated by the identification of specific signal transducer molecules involved in mediating their anti-cancer activities. SQA was found to require the activity of numerous caspases, including caspase-3, -6, -8, -9, -10 and -13, for its cytotoxicity and was demonstrated to decrease the level of the antiapoptotic protein Bcl-2. On the other hand, FXN was shown to require caspase-1, -2, -3, -9 and - 10 for its toxicity. This, together with the ability to decrease the levels of Bcl-2, pointed to the involvement of the intrinsic pathway in particular in mediating the activity of FXN. The screening of algal compounds against non-cancerous breast epithelial cells carried out in this study, together with the investigation into their mechanisms of action, represent one of the few reports in which characterization of algal metabolites goes beyond the initial cytotoxicity assays. Finally, in order to assess the potential anti-cancer stem cell activity of the marine algal compounds, a subset of these was screened using a mammosphere assay technique developed in this study. The cancer stem cell (CSC) theory proposes that cancers arise from and are maintained by a specific subpopulation of cells able to undergo asymmetric cell division and termed CSCs. These CSCs are capable of anchorage-independent growth in serum-free culture conditions, such as those in the mammosphere assay. Using this assay, the novel halogenated monoterpene stereoisomers RU017 and RU018 were demonstrated to possess putative anti- CSC activity as evidenced by their ability to completely eliminate mammosphere formation in vitro. Furthermore, since RU017 and RU018 were non-toxic to both breast cancer and healthy breast cells, it appeared that the activity of the compounds was potentially specific to the CSCs. The results require further validation, but represent the first report of selective anti-CSC activity.
- Full Text:
- Date Issued: 2012
Development of a hydraulic sub-model as part of a desktop environmental flow assessment method
- Authors: Desai, Ahmed Yacoob
- Date: 2012
- Subjects: Hydrologic models -- Research -- South Africa Hydraulic engineering -- South Africa Rivers -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6041 , http://hdl.handle.net/10962/d1006200
- Description: Countries around the world have been developing ecological policies to protect their water resources and minimise the impacts of development on their river systems. The concept of ‘minimum flows’ was initially established as a solution but it did not provide sufficient protection as all elements of a flow regime were found to be important for the protection of the river ecosystem. “Environmental flows” were developed to determine these flow regimes to maintain a river in some defined ecological condition. Rapid, initial estimates of the quantity component of environmental flows may be determined using the Desktop Reserve Model in South Africa. However, the Desktop Reserve Model is dependent upon the characteristics of the reference natural hydrology used. The advancements in hydraulic and ecological relationships from the past decade have prompted the development of a Revised Desktop Reserve Model (RDRM) that would incorporate these relationships. The research in this thesis presents the development of the hydraulic sub-model for the RDRM. The hydraulic sub-model was designed to produce a realistic representation of the hydraulic conditions using hydraulic parameters/characteristics from readily available information for any part of South Africa. Hydraulic data from past EWR studies were used to estimate the hydraulic parameters. These estimated hydraulic parameters were used to develop hydraulic estimation relationships and these relationships were developed based on a combination of regression and rule-based procedures. The estimation relationships were incorporated into the hydraulic sub-model of the integrated RDRM and assessments of the hydraulic outputs and EWR results were undertaken to assess the ‘applicability’ of the hydraulic sub-model. The hydraulic sub-model was assessed to be at a stage where it can satisfactorily be incorporated in the RDRM and that it is adequately robust in many situations. Recommendations for future work include the refinement of estimation of the channel forming discharge or the use of spatial imagery to check the maximum channel width estimation. It is also proposed that a future version of the hydraulic sub-model could include flow regime change impacts on channel geomorphology and sedimentology so that flow management scenarios can be more effectively assessed.
- Full Text:
- Date Issued: 2012
Knowledge retention strategies in selected Southern Africa public broadcasting corporations
- Authors: Dewah, Peterson
- Date: 2012
- Subjects: Knowledge management , Intellectual capital -- Management , Employee retention , Broadcasting -- South Africa , Broadcasting -- Zimbabwe , Broadcasting -- Botswana
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11572 , http://hdl.handle.net/10353/438 , Knowledge management , Intellectual capital -- Management , Employee retention , Broadcasting -- South Africa , Broadcasting -- Zimbabwe , Broadcasting -- Botswana
- Description: Knowledge is now regarded as the most important resource surpassing other resources like land and capital. It is a foregone conclusion that knowledge flows out of organizations through various ways such as resignations, retirement and death yet, it does not seem as if organizations are employing strategies to retain such a vital component of production and service delivery. This study investigated the knowledge retention strategies in three Southern Africa Development Community (SADC) public broadcasting organizations of the South African Broadcasting Corporation in South African (SABC), the Department of Broadcasting Services (DBS) in Botswana and the Zimbabwe Broadcasting Corporation (ZBC) in Zimbabwe. The aim of this study was to establish how knowledge is captured and retained at such organizations. The objectives of the study were; to find out the types of strategies the three broadcasting organizations employ to capture and retain knowledge; establish how the three broadcasting organizational cultures enable knowledge acquisition, transfer, sharing and retention; establish the role of ICTs as tools and enablers of knowledge retention, creation, transfer and sharing in the three broadcasting organizations; and to propose recommendations on the best strategies for retention of knowledge in the three public broadcasting organizations as well as suggest areas for further and future research. v The study used the survey method and employed the triangulation design for data gathering. Data were collected from three SADC public broadcasting organizations. The population sample comprised 240 professional staff including 38 managers from different sections of the broadcasting organizations. The researcher collected data by administering a questionnaire to staff, interviews with managers and observations. Documentary analysis was also conducted in order to supplement data and fill in gaps. The researcher was mainly interested in gathering data that would give a comprehensive picture about knowledge retention methods in broadcasting organizations. There were four main findings. First, knowledge management as a relatively new concept and practice has not yet been properly embraced in the public broadcasting organization system in order to capture and retain knowledge that is acquired and generated in the organizations. There are no measures put in place in the organizations to retain the knowledge to ensure that once those who hold vital tacit knowledge are gone, the knowledge may still be available and accessible. Second, the study established that the respective organizational cultures impede on organizational knowledge retention. The study established that there was no culture of knowledge sharing. It also emerged that employees were not free to share their knowledge because of government regulations, prevailing political contexts, mistrust and general lack of incentive to share knowledge. Third, the study established that the organizations have no strategies or systems in place to capture the experts‟ knowledge or the knowledge of experienced staff and vi those approaching retiring age. The Human Resources Departments hold exit interviews that cover issues purely to do with why the person is leaving the organization instead of recording the work experiences and expertise of the departing employees. Fourth, the study revealed that the public broadcasting organizations still lag behind in collaborative and communicative technologies that facilitate knowledge transfer and sharing of tacit knowledge but retention of knowledge generally. The study also found that, some of the organizations studied did not have internet connectivity and websites were not yet functional, which hampered acquisition and sharing of knowledge for retention purposes. The importance of this study is that it has made a contribution and provided literature on knowledge retention strategies for public broadcasting corporations as part of knowledge management practice. On the basis of these findings the study recommended the following: appointment of knowledge management officers, establishment of Communities of Practice, encouraging knowledge sharing between employees, introduction of joint programmes with other broadcasting organizations by managers and their supervision of mentoring programmes; organizations to facilitate acquisition of information and communication technologies that enable knowledge management
- Full Text:
- Date Issued: 2012