List of Titles

Higher order modulation formats for high speed optical communication systems with digital signal processing aided receiver

- Chabata, Tichakunda Valentine

Authors: Chabata, Tichakunda Valentine
Date: 2016
Subjects: Optical communications , Modulation (Electronics) , Signal processing
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/4775 , vital:20677
Description: The drastic increase in the number of internet users and the general convergence of all other communication systems into an optical system have brought a sharp rise in demand for bandwidth and calls for high capacity transmission networks. Large unamplified transmission reach is another contributor in reducing deployment costs of an optical communication system. Spectrally efficient modulation formats are suggested as a solution to overcome the problems associated with limited channels and bandwidth of dense wavelength division multiplexing (DWDM) optical communication systems. Higher order modulation formats which are considered to be spectrally efficient and can increase the transmission capacity by transmitting more information in the amplitude, phase, polarization or a combination of all was studied. Different detection technologies are to be implemented to suit a particular higher order modulation format. In this research multilevel modulation formats, different detection technologies and a digital signal processing aided receiver were studied in a practical optical transmission system. The work in this thesis started with the implementation of the traditional amplitude shift keying (ASK) modulation and a differential phase shift keying (DPSK) modulation systems as they form the basic building block in the design of higher order modulation formats. Results obtained from using virtual photonics instruments (VPI)simulation software, receiver sensitivity for 10Gbpsnon-return-to-zero (NRZ), amplitude phase shift keying (ASK) and DPSK signals were measured to be -22.7 dBm and -22.0 dBm respectively. Performance comparison for the two modulation formats were done over different transmission distances. ASK also known as On-Off keying (OOK) performed better for shorter lengths whereas DPSK performed better for longer lengths of up to90km.Experimental results on a 10 Gbps NRZ- ASK signal gave a receiver sensitivity of -21.1 dBm from digital signal processing (DSP) aided receiver against -19.8 dBm from the commercial bit error ratio tester (BERT) yielding a small difference of 1.3 dB hence validating the reliability and accuracy of the digital signal processing (DSP) assisted receiver. Traditional direct detection scheme and coherent detection scheme performances were evaluated again on a 10 Gbps NRZ ASK signal. Coherent detection that can achieve a large unamplified transmission reach and has a higher passive optical splitting ratio was first evaluated using the VPI simulation software. Simulation results gave a receiver sensitivity of -30.4 dBm forcoherent detection and -18.3 dBm for direct detection, yielding a gain in receiver sensitivity of 12.1 dB. The complex coherently detected signal, from the experimental setup gave a receiver sensitivity of -20.6 dBm with a gain in receiver sensitivity of 3.5 dBm with respect to direct detection. A multilevel pulse amplitude modulation (4-PAM) that doubles the data rate per channel from10 Gbps to 20 Gbps by transmitting more information in the amplitude of the carrier signal was implemented. This was achieved by modulating the optical amplitude with an electrical four level amplitude shift keyed (ASK) signal. A receiver consisting of a single photodiode, three decision circuits and a decoding logic circuit was used to receive and extract the original transmitted data. A DSP aided receiver was used to evaluate the link performance. A receiver sensitivity of -12.8 dBm is attained with a dispersion penalty of about 7.2 dB after transmission through 25 km of G.652 fibre.
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Date Issued: 2016

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A new synthetic approach for preparation of Efavirenz

- Chada, Sravanthi

Authors: Chada, Sravanthi
Date: 2017
Subjects: Antiretroviral agents , Asymmetric synthesis , Enzyme inhibitors , HIV (Viruses) -- Enzymes
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/15512 , vital:28265
Description: Efavirenz, a drug that is still inaccessible to millions of people worldwide, is potent non nucleoside reverse transcriptase inhibitor (NNRTI), is one of the preferred agents used in combination therapy for first-line treatment of the human immunodeficiency virus (HIV). NNRTIs attach to and block an HIV enzyme called reverse transcriptase, by blocking reverse transcriptase; NNRTIs prevent HIV from multiplying and can reduce the amount of HIV in the body. Efavirenz can't cure HIV/AIDS, but taken in combination with other HIV medicines (called an HIV regimen) every day helps people with HIV live longer healthier lives. Efavirenz also reduces the risk of HIV transmission and can be used by children who are suffering from HIV/AIDS. All the above therapeutic uses of efavirenz prompted us to identify the novel and hopefully cost efficient synthetic methodology for the preparation of efavirenz. In this thesis a new synthetic method for asymmetric synthesis of efavirenz is described. This route started from commercially available starting materials and it is first established in traditional batch chemistry and further the parameters transferred to a semi continuous flow protocol for optimization.
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Date Issued: 2017

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Former farm workers of foreign descent in communal areas in post-fast track Zimbabwe : the case of Shamva District

- Chadambuka, Patience

Authors: Chadambuka, Patience
Date: 2021-10-29
Subjects: Migrant agricultural laborers -- Zimbabwe -- Shamva District , Agricultural laborers, Foreign -- Zimbabwe -- Shamva District , Land reform -- Zimbabwe , Belonging (Social psychology) -- Zimbabwe -- Shamva District , Social integration-- Zimbabwe -- Shamva District , Fast Track Land Reform Programme (FTLRP)
Language: English
Type: thesis , text , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/178420 , vital:42938 , 10.21504/10962/178420
Description: Land and ethnicity continue to condition contestations in relation to belonging amongst rural Zimbabweans. The colonial era defined Zimbabwe’s land politics in a highly racialised and ethnicised manner. Racially, the colonial era gave birth to white-owned fertile farm lands, while blacks (or Africans) were resettled in agriculturally-unproductive Reserves, later referred to as communal areas in the post-colonial era. Though they were initially created with a segregatory and oppressive intent bent on disenfranchising native Africans, the Reserves became a definitive landscape embedded in ethnic and ancestral belonging for the autochthonous Natives. The Reserves were created exclusively for autochthonous Africans, and the colonial administration ensured that foreign migrant Africans recruited mainly as covenanted labour from nearby colonies would not be accommodated and consequently belong in Reserves. Migrant Africans were instead domiciled in white commercial farms, mines and urban areas, and deprived of land rights accorded to the autochthones. In the case of white farms specifically, the labourers experienced a conditional belonging (to the farm). This overall exclusionary system was later inherited and maintained by the post-colonial Zimbabwean government, up until the year 2000. Zimbabwe’s highly documented Fast Track Land Reform Programme (FTLRP) from the year 2000 did away with the entrenched racial bifurcations of land, as white commercial farms became fast track farms. However, it did not undercut the existence of communal areas. The FTLRP had a profound effect on the lives of commercial farm workers, particularly those of foreign origin who had no other home or source of livelihood to fall back on after fast track displacements. Some though sought to move into communal areas, from which they had been excluded previously. Within this context, most scholarly studies of the post fast track period ignore the plight of former farm workers especially those that moved to, and into, communal areas. This ethnographic study, specifically of former farm workers of foreign origin in Shamva communal areas, therefore seeks to contribute to Zimbabwean studies in this regard. It documents and examines the perceptions, practices and lived experiences of former farm workers of foreign origin now residing in the Bushu communal areas of Shamva, and how they interface with Bushu autochthones in seeking to belong to Bushu. This is pursued by way of qualitative research methods (including lengthy stays in the study sites) as well as through the use of a theoretical framing focusing on lifeworlds, interfaces, belonging, othering and strangerhood. Key findings reveal that belonging by the former farm workers in Bushu entails a non-linear and convoluted process characterised by a series of contestations around for instance land shortages, limited livelihood strategies and cultural difference. This project of belonging does not entail assimilation on the part of the former farm workers, as they continue to uphold certain historical practices, leading to a form of co-existence between the autochthones and allochthones in Bushu. In this way, the former farm workers seem to develop a conditional belonging in (and to) Bushu, albeit different than the one experienced on white farms in the past. , Thesis (PhD) -- Faculty of Humanities, Sociology, 2021
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Date Issued: 2021-10-29

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Metabolic effects brought about by tricyclic antidepressants and the contribution of a medicinal plant in alleviating high fat diet induced insulin resistance in male wistar rats

- Chadwick, Wayne

Authors: Chadwick, Wayne
Date: 2006
Subjects: Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:10329 , http://hdl.handle.net/10948/461 , Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
Description: Type II diabetes is becoming a growing problem in developed countries worldwide. The median age for diagnosis was around sixty, but recent surveys have shown that the entire age distribution curve shifting left. The incidence of type II diabetes is thought to be parallel with the growing rate of obesity associated with an unhealthy western diet. Type II diabetes is an expensive disease to manage, it is for this reason that cheaper medication needs to be investigated in the form of traditional plants, such as Sutherlandia frutescens. Prescription medication, such as tricyclic antidepressants, may also increase body weight thereby playing a role in obesity. The cause of weight gain in such cases may go unrecognized or lead to cessation of the medication with or without the practitioner’s knowledge or approval. It is therefore necessary to investigate the causative agents responsible for the excessive weight gain. Drinking water containing extracts of S. frutescens or metformin was administered to two groups of eleven insulin resistant male Wistar rats. The insulin resistant control group received water without any medication. Rats were sacrificed after 8 weeks allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. The effect of the medication and the diet on muscle post receptor insulin signaling proteins was determined through Western blots. Liver proteomics was also performed using 2-D electrophoresis. In a separate experiment 26 male Wistar rats were exposed to strepotozotocin toxin, 7 of these rats received intravenous insulin treatment, 7 rats received S. frutescens extract and 7 rats received a combination of both medications, the remaining 5 received no treatment and served as the control. Rats were sacrificed after 6 days allowing for fasting blood glucose, insulin and tissue glycogen content determination. Two groups of 14 male Wistar rats received amitriptyline or trimipramine (common tricyclic antidepressants) in their drinking water, the control group (30 rats) received water without any medication. The rats’ weight and food consumption was monitored throughout the trial and their oxygen consumption was also determined. Rats were sacrificed after 6 weeks or 14 weeks of medicinal compliance allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. S. frutescens treatment normalized circulating serum insulin levels and significantly increased the rate of glucose clearance. Certain post receptor insulin signaling proteins were also significantly increased relative to the insulin resistant control group. 2-D electrophoresis identified the normalization of protein levels associated with the urea cycle. S. frutescens was also able to, independently; maintain normoglycaemic levels in the strepotozotocin treated group. The tricyclic antidepressants significantly increased blood glucose levels while significantly reducing tissue glycogen levels for both sacrifice periods. Serum insulin remained unchanged while a significant increase in insulin degradation and insulin degrading enzyme levels were found for both antidepressants. S. frutescens shows promise as a low cost antidiabetic medication for future use. Although the antidepressants did not promote weight gain, the increase in blood glucose levels may be cause for concern in patients with a pre-disposition toward developing diabetes.
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Date Issued: 2006

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The use of response surface methodology and artificial neural networks for the establishment of a design space for a sustained release salbutamol sulphate formulation

- Chaibva, Faith Anesu

Authors: Chaibva, Faith Anesu
Date: 2010
Subjects: Salbutamol sulphate Artificial intelligence -- Medical applications Neural networks (Computer science) Response surfaces (Statistics) Pharmaceutical biotechnology -- Quality contro Drugs -- Design Pharmacokinetics Drugs -- Dosage forms Drugs -- Controlled release
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:3845 , http://hdl.handle.net/10962/d1010432
Description: Quality by Design (QbD) is a systematic approach that has been recommended as suitable for the development of quality pharmaceutical products. The QbD approach commences with the definition of a quality target drug profile and predetermined objectives that are then used to direct the formulation development process with an emphasis on understanding the pharmaceutical science and manufacturing principles that apply to a product. The design space is directly linked to the use of QbD for formulation development and is a multidimensional combination and interaction of input variables and process parameters that have been demonstrated to provide an assurance of quality. The objective of these studies was to apply the principles of QbD as a framework for the optimisation of a sustained release (SR) formulation of salbutamol sulphate (SBS), and for the establishment of a design space using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). SBS is a short-acting ♭₂ agonist that is used for the management of asthma and chronic obstructive pulmonary disease (COPD). The use of a SR formulation of SBS may provide clinical benefits in the management of these respiratory disorders. Ashtalin®8 ER (Cipla Ltd., Mumbai, Maharashtra, India) was selected as a reference formulation for use in these studies. An Ishikawa or Cause and Effect diagram was used to determine the impact of formulation and process factors that have the potential to affect product quality. Key areas of concern that must be monitored include the raw materials, the manufacturing equipment and processes, and the analytical and assessment methods employed. The conditions in the laboratory and manufacturing processes were carefully monitored and recorded for any deviation from protocol, and equipment for assessment of dosage form performance, including dissolution equipment, balances and hardness testers, underwent regular maintenance. Preliminary studies to assess the potential utility of Methocel® Kl OOM, alone and in combination with other matrix forming polymers, revealed that the combination of this polymer with xanthan gum and Carbopol® has the potential to modulate the release of SBS at a specific rate, for a period of 12 hr. A central composite design using Methocel® KlOOM, xanthan gum, Carbopol® 974P and Surelease® as the granulating fluid was constructed to fully evaluate the impact of these formulation variables on the rate and extent of SBS release from manufactured formulations. The results revealed that although Methocel® KlOOM and xanthan gum had the greatest retardant effect on drug release, interactions between the polymers used in the study were also important determinants of the measureable responses. An ANN model was trained for optimisation using the data generated from a central composite study. The efficiency of the network was optimised by assessing the impact of the number of nodes in the hidden layer using a three layer Multi Layer Perceptron (MLP). The results revealed that a network with nine nodes in the hidden layer had the best predictive ability, suitable for application to formulation optimisation studies. Pharmaceutical optimisation was conducted using both the RSM and the trained ANN models. The results from the two optimisation procedures yielded two different formulation compositions that were subjected to in vitro dissolution testing using USP Apparatus 3. The results revealed that, although the formulation compositions that were derived from the optimisation procedures were different, both solutions gave reproducible results for which the dissolution profiles were indeed similar to that of the reference formulation. RSM and ANN were further investigated as possible means of establishing a design space for formulation compositions that would result in dosage forms that have similar in vitro release test profiles comparable to the reference product. Constraint plots were used to determine the bounds of the formulation variables that would result in the manufacture of dosage forms with the desired release profile. ANN simulations with hypothetical formulations that were generated within a small region of the experimental domain were investigated as a means of understanding the impact of varying the composition of the formulation on resultant dissolution profiles. Although both methods were suitable for the establishment of a design space, the use of ANN may be better suited for this purpose because of the manner in which ANN handles data. As more information about the behaviour of a formulation and its processes is generated during the product Iifecycle, ANN may be used to evaluate the impact of formulation and process variables on measureable responses. It is recommended that ANN may be suitable for the optimisation of pharmaceutical formulations and establishment of a design space in line with ICH Pharmaceutical Development [1], Quality Risk Management [2] and Pharmaceutical Quality Systems [3]
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Date Issued: 2010

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

- Chakona, Albert

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

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Changes in household food security, nutrition and food waste along an agro-ecological gradient and the rural-urban continuum in mid-sized South African towns

- Chakona, Gamuchirai

Authors: Chakona, Gamuchirai
Date: 2017
Subjects: Food security -- South Africa , Women -- South Africa -- Nutritiona , Urban women -- South Africa -- Nutrition , Rural women -- South Africa -- Nutrition , Wild foods -- South Africa , Food supply -- South Africa , Malnutrition in children -- South Africa , Grants-in-aid -- South Africa , Household ecology -- South Africa
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/6484 , vital:21127
Description: The lack of dietary diversity is a severe problem experienced by most poor households globally. Most poor communities are at high risk of inadequate intake of micronutrients resulting from diets dominated by starchy staples. The present study considered the diets, dietary diversities and food security of women of reproductive age between 15-49 years, households and communities along the rural-urban continuum in three mid-sized towns situated along an agro-ecological gradient in South Africa. A 48-hour dietary recall was performed across two seasons (twice in summer and once in winter) and focus group discussions were held to gather all information including food abundance, seasons of food scarcity as well as coping strategies which households employ during periods of food shocks. Households were further asked to quantify any type of food waste that they could have generated in the previous 48 hours. Nutritional status of children under the age of five in all three towns was also measured using height-for-age (HAZ) and mid-upper arm circumference (MUAC) as indicators of stunting and wasting respectively. The household surveys were conducted with 554 women randomly selected in rural, peri-urban and urban locations of Richards Bay, Dundee and Harrismith. For nutritional status, the sample consisted of 216 children who were randomly selected from the sampled households in rural, peri-urban and urban locations of the study sites. Household Dietary Diversity Scores (HDDS) and Women’s Dietary Diversity Scores (WDDS) were calculated from the food items consumed by each household and each woman over a two-day period, respectively. Household food access was also measured for each household using Household Food Insecurity Access Scale (HFIAS). The mean WDDS and HDDS for the wettest site of Richards Bay (3.8±0.29 and 8.44±1.72, respectively) was significantly higher than at Dundee (3.4±0.30 and 7.76±1.63, respectively) and Harrismith (3.5±0.27 and 7.83±1.59, respectively) which were not different from one another. The mean HFIAS for Dundee (9.39±7.13) was significantly higher than that in Richards Bay (5.57±6.98) and Harrismith (6.43±6.59) which were not significantly different from one another. Dietary diversity scores were also significantly higher in urban locations than in peri-urban and rural ones whilst HFIAS was significantly lower in the urban locations than peri-urban and rural locations. There was lower dependence on food purchasing in Richards Bay compared to Dundee and Harrismith where the majority of the population was purchasing most of their food. The majority of Richards Bay households were involved in subsistence agriculture and also produced a surplus for sale, as well as collecting wild foods, which improved food security, unlike Dundee and Harrismith. Food insecurity was higher in rural and peri-urban areas compared to urban areas. In all towns, food was always available throughout the year but was beyond the reach of many households. In urban areas food was readily available and only limited by access, whereas rural populations have limited access to affordable food and face higher prices. The peri-urban populations were more food insecure because of high levels of poverty, unemployment and lack of access/entitlements to land. Periurban dwellers are therefore more sensitive to changes in incomes and food prices because they lack safety nets to absorb income or price shocks as they purchase more, rather than growing their own food. Household dietary diversity was significantly negatively correlated with household food access, that is households with low HDDS had higher HFIAS scores. Due to high levels of food insecurity, a greater percentage of children under the age of five years were stunted (35 %) and wasted (18 %). There were no significant differences in stunting along the agro-ecological gradient, along the rural-urban continuum and sex of child. However, significant differences were observed in child wasting along the agro-ecological gradient with Harrismith having more wasted children than the other two towns, which were not significantly different from each other. Significant differences were also observed between MUAC and sex of child where male children had higher MUAC than females. Wasting was significantly negatively associated with HDDS, with children from households with low HDDS tending to have large MUAC thus showing an inverse association among HDDS and obesity. However, further studies are needed to confirm this finding. In general food insecurity was closely associated with low wealth, food expenditure, large household size and limited access to land. The study did not find any significant role in the use of wild foods and social grants in improving food security for those households who were consuming wild foods and those receiving social grants. Although a greater percentage of households were food insecure, significant amounts of unprepared food (495±179 g per household) were wasted in Richards Bay alone in 48 hours mainly because the food had passed the best before date or had visibly gone bad. The amount of food waste was closely significantly negatively associated with household size. In general, the prevalence of food insecurity and wasting followed the agro-ecological gradient, with households in Richards Bay where the area.
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Date Issued: 2017

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A critical analysis of the dynamics of intergovernmental relations in Zimbabwe

- Chakunda, Vincent

Authors: Chakunda, Vincent
Date: 2017
Subjects: Intergovernmental fiscal relations -- Zimbabwe International relations
Language: English
Type: Thesis , Doctoral , Public Administration
Identifier: http://hdl.handle.net/10353/7979 , vital:31345
Description: The field of intergovernmental relations (IGR), both from a conceptual and practical perspective presents a contested order in Zimbabwe’s political and public administration discourse, with a fairly long and complex historical and institutional context. The advent of colonialism in Zimbabwe (then Rhodesia) gave birth to a dualised form of government with a separatist development agenda. The dualistic model of government was anchored on a segregationist centralist ideology that advanced a white supremacist agenda while entrenching underdevelopment in native areas. This was attained through the use of draconic and ingrained racially discriminatory laws, ordinances and policy enactments, inter alia, the 1910 High Commissioner’s Proclamation, the Native Councils Act, the African Councils Act, and the District Councils Act which supported the overriding philosophy of colonialist hegemony. The direct rule policy was used and in practice, administrative, political, judicial and legislative powers were under the purview of the whites. Under this political dispensation, the nature of IGR was typically a master-servant relationship as African institutions had limited policy latitude under the tentacles of race-driven white control over the socio-economic and political space with an exploitative and subservient underpinning. The demise of colonialism and the birth of independent Zimbabwe in 1980 ushered a new political dispensation. The post-independence government embarked on a number of reforms aimed at dismantling the racist undertones of government. These reforms include the expanded decentralization frameworks supported by legislative instruments and policies such as the 1984 Prime Minister’s Directive and the 1996 thirteen principles of decentralization. Other key reforms are the 1996 Urban Councils Act, Chapter 29:15 and the 1988 Rural District Councils Act, Chapter 29:13. However, it is important to note that despite this plethora of legislation and reforms purportedly meant to dismantle racist backed institutional differentiation, the new national government did not depose its excessive control on sub-national governments. It is therefore an insoluble contradiction that the legislation and institutions created in post-independence Zimbabwe promoted the autonomy of sub-national governments while broadening democracy and citizen participation. This era rather presents an aporetic discourse epitomized by the national government’s perfection of colonial dominance approaches through creating legislation and institutions to retain wide and extensive control of sub-national governments. The Global Political Agreement of 2009 culminated into the promulgation of the Constitution of Zimbabwe Amendment Number 20 of 2013 with provisions for devolution of power, Provincial and Metropolitan Councils and the enshrinement of Local Government as a tier of government with constitutionally guaranteed autonomy. However, despite these reforms with far reaching implications on the configuration of IGR, the ZANUPF led national government is lethargic in implementing them. This has sparked controversy as these constitutional reforms and their potential to promote an integrated and efficient system of governance may turn out to be a pyrrhic victory. This is so because the necessary legislation anchoring the constitutional reforms may not be created in the foreseeable future as the current national government views devolution, for instance, as tantamount to surrendering political power to sub-national institutions. The purpose of the study was to critically examine the dynamics of intergovernmental relations in Zimbabwe. The overlapping authority model of IGR and the theory of networked governance underpinned the study. A comparative study of IGR was conducted focusing on two federal nations (United States of America) and Nigeria) and two unitary nations (United Kingdom and South Africa). A qualitative phenomenological methodology was used and the sample size was 20 respondents selected using the purposive sampling technique. Data was collected using in-depth interviews and analyzed using thematic analysis and critical discourse analysis. Key findings of the study reflected on the conception and relevance of IGR in unitary nations in contrast to classical perspectives that restricted the field as a discourse of federalism. The study established that the unitary system of Zimbabwe is anchored on a strong centralist ideology that suffocates the autonomy of sub-national institutions. In the same context, there is absence of political will on the part of the ZANUPF led government to implement crucial constitutional reforms that have a bearing on the configuration of IGR. The study also revealed that political party incongruence is a threat to intergovernmental coordination, integrated planning and collaborative development. Various recommendations were made from the study and these include that national government should expedite the implementation of the Constitution, codification of IGR by way of legislation and rationalization of fiscal transfers and intergovernmental fiscal equalization.
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Date Issued: 2017

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Systematic marine spatial planning and monitoring in a data poor environment: a case study of Algoa Bay, South Africa

- Chalmers, Russell

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.
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Date Issued: 2012

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Production of Cydia pomonella granulovirus (CpGV) in a heteralogous host, Thaumatotibia Leucotreta (Meyrick) (False codling moth)

- Chambers, Craig Brian

Authors: Chambers, Craig Brian
Date: 2015
Subjects: Cryptophlebia leucotreta -- South Africa , Codling moth -- South Africa , Apples -- Diseases and pests -- South Africa , Codling moth -- Biological control -- South Africa , Insect pests -- Biological control -- South Africa , Biological pest control agents -- South Africa , Baculoviruses -- South Africa
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:5935 , http://hdl.handle.net/10962/d1017906
Description: Cydia pomonella (Linnaeus) (Family: Tortricidae), the codling moth, is considered one of the most significant pests of apples and pears worldwide, causing up to 80% crop loss in orchards if no control measures are applied. Cydia pomonella is oligophagous feeding on a number of alternate hosts including quince, walnuts, apricots, peaches, plums and nectarines. Historically the control of this pest has been achieved with the use of various chemical control strategies which have maintained pest levels below the economic threshold at a relatively low cost to the grower. However, there are serious concerns surrounding the use of chemical insecticides including the development of resistance in insect populations, the banning of various insecticides, regulations for lowering of the maximum residue level and employee and consumer safety. For this reason, alternate measures of control are slowly being adopted by growers such as mating disruption, cultural methods and the use of baculovirus biopesticides as part of integrated pest management programmes. The reluctance of growers to accept baculovirus or other biological control products in the past has been due to questionable product quality and inconsistencies in their field performance. Moreover, the development and application of biological control products is more costly than the use of chemical alternatives. Baculoviruses are arthropod specific viruses that are highly virulent to a number of lepidopteran species. Due to the virulence and host specificity of baculoviruses, Cydia pomonella granulovirus has been extensively and successfully used as part of integrated pest management systems for the control of C. pomonella in Europe and around the world, including South Africa. Commercial formulations have been typically based on the Mexican strain of CpGV. However due to long-term multiple applications of CpGV and the reliance on CpGV in organic farming practices in Europe, resistance to the CpGV-M strain has developed in a number of field populations of C. pomonella. This study aimed to identify and characterize novel isolates of CpGV in South Africa and compare their virulence with the commercial standard CpGV-M. Secondly, since C. pomonella is difficult to culture on a large scale, an alternate method of CpGV production was investigated in order to determine if CpGV could be produced more efficiently and at a reduced cost without negatively impacting the quality of the product. Several isolates of CpGV were recovered either from field collected larvae or from a laboratory-reared C. pomonella colony. Characterisation of DNA profiles using a variety of restriction enzymes revealed that only a single isolate, CpGV-SA, was genetically different from the Mexican strain of the virus used in the commercially available CpGV based products in South Africa. In dose-response bioassays using CpGV-SA, LC₅₀ and LC₉₀ values for neonate C. pomonella larvae were 3.18 x 10³ OBs/ml and 7.33 x 10⁴ respectively. A comparison of these values with those of CpGV-M indicated no significant difference in the virulence of the two isolates under laboratory conditions. This is a first report of a genetically distinct CpGV isolate in South Africa. The biological activity and novelty of CpGV-SA makes this isolate a potentially important tool for CpGV resistance management in South Africa. In order to justify production of CpGV in an alternative host, studies on the comparative biological performance of C. pomonella and T. leucotreta based on oviposition, time to hatch, larval developmental times and rearing efficiency as well as production costs were performed. Thaumatotibia leucotreta was found to be more fecund and to have significantly shorter egg and larval developmental times. In addition, larval production per unit of artificial diet was significantly higher than for C. pomonella. This resulted in T. leucotreta being more cost effective to produce with implications for reduced insectary space, sanitation practices as well as the labour component of production. Virus yield data generated by inoculation both C. pomonella and T. leucotreta with nine concentrations of CpGV resulted in comparable virus yields, justifying the continuation of the research into production of CpGV in T. leucotreta. It was important to determine the LC and LT values required for mass production of CpGV in late instar T. leucotreta larvae. Dose- and time-response bioassays with CpGV-M were conducted on artificial diet to determine these values. Fourth instar LC₅₀ and LC₉₀ values were 5.96 x 10³ OBs/ml and 1.64 x 10⁵ OBs/ml respectively. LT50 and LT90 values were 81.10 hours and 88.58 hours respectively. Fifth instar LC₅₀ and LC₉₀ values were 6.88 x 10⁴ OBs/ml and 9.78 x 10⁶ OBs/ml respectively. LT₅₀ and LT₉₀ values were 111.56 hours and 137.57 hours respectively. Virus produced in fourth instar T. leucotreta larvae was bioassayed against C. pomonella neonate larvae and compared to CpGV-M to establish if production in the heterologous host negatively affected the virulence of the isolate. No significant difference in virulence was observed between virus produced in T. leucotreta and that produced in C. pomonella. The data generated in the bioassays was used in CpGV mass production trials to evaluate production. All production methods tested produced acceptable virus yields. To examine the quality of the virus product, genomic DNA was extracted from larval cadavers and subjected to REN analysis with HindIII. The resulting DNA profiles indicated that the virus product was contaminated with the homologous virus, CrleGV. Based on the above results, the use of T. leucotreta as an alternate host for the in vivo production of CpGV on a commercial basis is not at this stage viable and requires further investigation before this production methodology can be reliable used to produce CpGV. However, this study has shown that CpGV can be produced in a homologous host, T. leucotreta and significant strides have been made towards developing a set of quality control standards that are essential for further development of successful production methodology. Finally a novel isolate of CpGV has been identified with comparable virulence to the CpGV-M. This is an important finding as it has broad reaching implications for resistance management of CpGV products in South Africa.
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Date Issued: 2015

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The conflict between adaptation and constraint : the case of the Siphonariid limpets

- Chambers, Richard Jonathan

Authors: Chambers, Richard Jonathan
Date: 1995
Subjects: Siphonaria -- Adaptation Limpets -- Adaptation Pulmonata
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:5657 , http://hdl.handle.net/10962/d1005340
Description: The reproductive strategies of marine invertebrates have been related to various aspects of both their ecology, and their phylogenetic history. It has been the purpose of this thesis to try and separate these components among Siphonaria, a group of marine pulmonates. The taxonomy of these species is revised and I conclude that nine species are valid. All species deposit benthic egg masses and development may be either direct (S. anneae, S. compressa, S. dayi, S. nigerrima, S. serrata and S. tenuicostulata) or planktonic (S. capensis, S.concinna and S. oculus). Data on distribution and life-history relating to mode of larval development is then presented for 26 species of Siphonaria worldwide. Fifteen species are direct developers, nine are planktonic developers and a further two appear to have a dual developmental capacity, retaining both the velar swimming apparatus of a planktonic developer and the crawling foot of a direct developer. Direct developing species hatch from larger egg capsules, and generally occur higher on the shore than planktonic developers. Worldwide, planktonic developers are more widespread than direct developers, and individual planktonic species may have a greater latitudinal range. In most S~honaria subgenera, mode of larval development appears to be constant, although two subgenera (Patel/opsis and Sacculosiphonaria) include both developmental types. Locally, the intertidal zonation of three sympatric species (S. capensis, S. concinna and S. serrata) does not support a model which predicts direct development on the high shore and planktonic development on the low shore. However, distributions do correspond to particular intertidal microhabitats, and while there may be no, direct relationship between mode of larval development and intertidal height, the physical structure of egg masses, and the microhabitats used for spawning appear adaptive with regards to desiccation in the intertidal. S. concinna (planktonic development) and S. serrata (direct development) occur in similar microhabitats and are likely to be under similar selection pressures. In having different modes of larval development, there appears to be more than one optimal solution in a particular selective regime. In addition, both species seem to apportion similar amounts of energy to reproduction for each spawning episode, and also annually suggesting an optimum allocation of resources to reproduction. Genetic investigations using PolyAcrylamide Gel Electrophoresis (PAGE) confirm the status of the southern African species initially described, and indicate greater genetic variability associated with planktonic developing species than direct developing species. The systematic relationships revealed by DNA fingerprinting support the current classification systems, and also have implications with regards the evolution of larval development: direct development may be the plesiomorphic condition in, and among, some Siphonaria groups. There are both phylogenetic and adaptive explanations for the distribution of reproductive mode among benthic marine invertebrates. An evolutionary question, however, is not just a matter of either adaptation or constraint, it is a combination of these. Both contribute to the distribution of developmental mode among Siphonaria.
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Date Issued: 1995

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Psychological capital, psychological empowerment and organisational citizenship behaviour among nurses in public hospitals in Eastern Cape, South Africa

- Chamisa, Shingirayi Florence

Authors: Chamisa, Shingirayi Florence
Date: 2018
Subjects: Organizational behavior--South Africa Nurses--Employment--South Africa--Eastern Cape Organizational effectiveness--South Africa
Language: English
Type: Thesis , Doctoral , Industrial Psychology
Identifier: http://hdl.handle.net/10353/15441 , vital:40408
Description: The current task environment in the South African public hospitals has reconfirmed the importance of researching on the psychological environment and its influence on individual employee performance. The motivation of this study is to examine the relationship between psychological capital and psychological empowerment on the one hand and organisational citizenship behaviour on the other hand among nurses within selected public hospitals in the Eastern Cape Province of South Africa. This contributes to the theoretical conceptual knowledge on how performance can be enhanced through the appropriate provision of psychological resources in the workplace and the promotion of competence, efficiency and sustainability of organisations. Survey questionnaires were used to collect data. Inferential analysis from SPSS was carried out to understand the antecedents and consequences of organisation citizenship behaviour. An overall model of the study was also identified through AMOS using structural equation modeling. Findings from the selected South African public hospitals indicate that there is a significant positive relationship between psychological capital and psychological empowerment on the one hand and organisational citizenship behaviour on the other hand among nurses within the selected public hospitals. The results validate certain aspects of the Conservative frame work and the Job Demands Resources Model. The study recommends that hospital managers and supervisors should determine the social networks in their hospitals as a strategy to promote performance and organisational citizenship behaviour. Individual employees who are located at the fringes of the network must be recognised and empowered. This allows for the comparison evaluation of both individual and organisational characteristics on organisational citizenship behaviour and the promotion of slack resources which are important in maintaining a steady organisational performance which further widens organisational capacity.
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Date Issued: 2018

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An assessment of the motivational value of rewards among health professionals in Malawi's Ministry of Health

- Chanza, Alfred Witness Dzanja

Authors: Chanza, Alfred Witness Dzanja
Date: 2012
Subjects: Employee motivation -- Malawi , Medical personnel -- Salaries, etc. -- Malawi , Medical personnel -- Job satisfaction -- Malawi , Public health -- Malawi
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: vital:9963 , http://hdl.handle.net/10948/d1020330
Description: The assessment of the motivational value of rewards in the world of work is interesting but difficult to understand. Variations in research reports and inadequate comprehension of the efficiency and motivational value of rewards have brought about confusions, controversies and contradictions among authors, researchers, consultants and practitioners in the field of Industrial and Organisational Psychology (Mangham, 2007; Muula, 2006; Muula & Maseko, 2005; Palmer, 2006; World Bank, 2004). As a consequence, organisations are applying theories and models of motivation selectively depending on their beliefs, ideological framework of values and assumptions (Dzimbiri, 2009). The study was therefore carried out as a positive contribution to the existing knowledge and debate on the motivational value of rewards for health professionals in the public health sectors of the developing countries. Through a systematic sampling method, 571 health professionals were sampled for the study. Data were collected through the use of a self-administered questionnaire which was composed based on the data collected from desk research/literature review, focus group discussions and interviews. The findings of the study revealed that the Malawi‟s Ministry of Health (MoH) is failing to attract, motivate and retain health professionals; there is perception of inequity of the rewards among the health professionals; health professionals develop coping strategies to supplement their monthly financial rewards; health professionals engage in corrupt practices to supplement their monthly financial rewards; and there is erosion of industrial democracy in the Malawi‟s Public Health Sector. While the statistical testing of the hypothesized model proved a lack of fit between the variables, the statistical testing of the re-specified model suggests that there is a positive relationship between financial rewards and reward-related problems being faced by health professionals in the Malawi‟s MoH. Through the Structural Equation Modeling (SEM) exercise, an inverse (negative) relationship between financial and non-financial rewards was deduced, and scientifically and graphically demonstrated. Both the re-specified and graphical models symbolize a pragmatic departure from the theoretical model whose authors (Franco, Bennett, Kanfer & Stubblebine, 2004) are largely inclined to the use of non-financial rewards and suggest that financial rewards should be used with caution. These findings also reject the Herzberg‟s two factor theory (Herzberg, 1960) which claims that financial rewards (salaries) are not a motivator. The major recommendations of the study are that the Franco et al.‟s (2004) model should be adopted and adapted in the Malawi‟s MoH with the view that the value of both financial and non-financial rewards (as motivators) varies from individual to individual due to individual differences and prevailing factors/forces in both the work environment and wider society in which the MoH operates; a hybrid reward system combining the strengths of time-based, performance-based and competence-based reward systems should be developed and implemented; the results of scientifically testing the re-specified model and the inverse (causal) relationship established between financial and non-financial rewards (as demonstrated in a graphic model) should be re-tested with other samples in the public health sectors of the developing countries; and the motivational value of non-financial rewards should be scientifically established and compared with the motivational value of financial rewards used independent of each other in business organisations to make an objective conclusion on the rewards-motivation debate.
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Date Issued: 2012

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Indigenous knowledge and climate change : insights from Muzarabani, Zimbabwe

- Chanza, Nelson

Authors: Chanza, Nelson
Date: 2014
Subjects: Indigenous peoples – Ecology – Zimbabwe -- Centenary District , Climatic changes -- Social aspects – Zimbabwe -- Centenary District , Climatic changes – Zimbabwe -- Centenary District
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: vital:10671 , http://hdl.handle.net/10948/d1020299
Description: Discourse characterising climate change has largely revolved around aspects within the realm of impact identification, mitigation and adaptation. Apparently, a burgeoning appetite to examine the role of indigenous knowledge (IK) now confronts the fronts of climate science, policy and practice. The surge in attention to localbased knowledge is attributed to growing challenges posed by change and variability in the climate system. This study argues that indigenous-based knowledge is capable of filling knowledge gaps and validating current understanding about climate change particularly at local levels. Essentially, the paucity of knowledge about local climatic events can be circumvented by engaging indigenous ‘scientists’ whose many years of direct contact with the environment have equipped them with the indispensable knowledge, skills and experiences to understand the same. Primarily, the thesis’ objectives were threefold. One, it captured useful indicators of climate change and variability from the understanding of the indigenous people, which can also be used to enhance understanding of climate change impacts.Two, it drew from the knowledge, experiences, skills and practices of the locals in order to inform appropriate community level mitigation and adaptation interventions. And, three, it highlighted the fact that knowledge of the indigenous people can be used to direct research on climate change. The study area (Muzarabani in Zimbabwe) experiences recurrent droughts and floods and its villagers rely predominantly on climate-sensitive livelihoods. As such, it was selected to provide a reliable case on IK practices and experiences of the people witnessing climatic events. The study was framed within an epistemological and methodological configuration of emancipatory pedagogy that looks at the generators of climate knowledge as ‘scientists’ in their own right. A qualitative elicitation interviewing technique involving in-depth discussions with traditional leaders and elderly knowledgeable citizens was conducted. The participants were selected through chain referrals until the level of theoretical saturation. In addition, directed field observations, document analysis and key informant interviews with other respondents selected through theoretical sampling enhanced the robustness of data acquisition methods. Group-based participatory data analysis and reflexive pragmatism also enhanced rigour and quality of research findings intended to balance between the strictures of the scientific audience and the views of the knowledge generators. Three key themes were derived from IK-climate change linkages as: indigenous based indicators of climate change, indigenous-based mitigation and indigenous based adaptation. A range of indigenous-based indicators identified pointed to a progressively drier climate with shorter growing seasons that are also punctuated by mid-season dry spells. A trend towards increased desiccation of water bodies (rivers, ponds and vleis) was further observed. There is also an upsurge in the abundance and pestiferous nature of Macrotermes spp, Quelea quelea and Acanthoplus discoidalis, which are most likely related to climate change. Some of these indicators closely match with those used in mainstream climate science and they also serve to understand climate change impacts at a finer local level of analysis. Indigenous-based mitigation is mainly driven by the notion of sacredness where the locals regard forestry, certain trees and vleis as sacrosanct. Tampering with these is believed to upset the spirits who have powers to influence climate. Opportunities associated with IK deployment in climate mitigation are understood from the viewpoint of enhancing greenhouse gas (GHG) sinks and that of reducing vulnerability to extreme climatic events. Specifically, this can be achieved through enhancing GHG sequestration through forestry and land-use management initiatives; that is, reducing emissions from deforestation and forestry related degradation (REDD+) and Land Use and Land-Use Cover and Forestry (LULUCF). These two are the dominant schemes adopted by the Intergovernmental Panel on Climate Change (IPCC) to govern climate mitigation. Indigenous disaster risk management (DRM) strategies abound in drought, famine, flood and violent storms through various forms such as Zunde raMambo, nhimbe, rain-making ceremonies and community early warning systems (EWS).The locals in Muzarabani are not passive observers of the changing climate system. Increasing environmental risks necessitates them to devise countermeasures for responding to climatic stimuli with the intention of minimising harm and/or enhancing the benefits brought about by the same. Thus, a portfolio of IK-based adaptation strategies best described as an assortment of short-term coping practices and longterm adaptive strategies were identified. These range from exploitation of ecosystem services, agricultural based interventions, riverine farming, traditional phonological knowledge (TPK) to migration. Therefore, it was revealed that community-based adaptation (CBA) can adequately leverage on IK to improve adaptive capacity and build community resilience against climate change. Clearly, the complementary role of indigenous-based knowledge cannot be disputed, given the demonstrated range of applications from identifying several indicators of change and variability in the climate system, examination of climate change impacts, to identification and assessment of mitigation and adaptation options. The study advises that exogenous climate interventions need to be congruent with indigenous based strategies to avoid maladaptation. To the climate research community therefore, it should be realised that IK is useful both as leads and as baseline knowledge for future work on the impacts of climate change, and in the assessment of climate interventions. In this regard, the remaining challenge is to formulate a framework of constructive dialogue between indigenous scientists and conventional scientists so as to make sure that the mutual benefits of the two knowledge forms are adequately harnessed. Handled well, such collaborative effort would ensure enhanced climate change knowledge for successful mitigation and adaptation strategies. Handled poorly, there is a risk that the developmental needs of communities exposed to climatic events would not be addressed.
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Date Issued: 2014

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Predators of aerial insects and riparian cross-boundary trophic dynamics: web-building spiders, dragonflies and damselflies

- Chari, Lenin Dzibakwe

Authors: Chari, Lenin Dzibakwe
Date: 2016
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/55791 , vital:26734
Description: This thesis characterises the cross-boundary trophic interactions of a relatively small model ecosystem, the Kowie River (Eastern Cape of South Africa), to explore their epistemic implications for systems ecology. Using web-building spiders and odonates (dragonflies and damselflies) as model organisms, I sought to investigate whether the diets of predators of aerial insects could be used to assess the strength of the trophic connectivity between freshwater and terrestrial systems in relation to variables such as stream width, distance from the river and aquatic insect emergence rates and abundances. Predator diet composition was determined by using a combination of diet analysis tools: direct observations of cross-subsidies, naturally-abundant stable (carbon and nitrogen) isotope analysis and fatty acid analysis. I also sought to reveal feeding niches and guilds among riparian aerial predators and investigate how the environment influenced predators’ access to aquatic prey subsidies. As emergent aquatic insect abundances decreased with an increase in distance from the river, and increased with stream width and seasonal changes from winter to summer, stable isotope and fatty acid analyses revealed distinct changes in web-building spider diet composition. Examination of the fatty acid eicosapentaenoic acid, a component commonly used as an indicator of consumer reliance on aquatic nutritional subsidies, showed that aquatic subsidies extended further inland at the wider sections of the river. Spiders and odonates at the wider sections of the Kowie River generally received more subsidies (56 – 70%) than those at the narrower sections (25 – 60%). When terrestrial insect biomass was distinctly low in winter, the benefit of aquatic subsidisation to spiders was relatively lower at the narrower sections of the Kowie River relative to the wide sections. As such, riparian areas adjacent to wide parts of the river were more likely to support larger populations of aerial predators than those at the narrow sections. Apart from the diet changes across time and space, there was evidence of inter-specific niche partitioning in both spiders and odonates, but no differences were observed between males and females of the same species. Results showed odonates of different sizes and hunting strategies had separate dietary niches, hence varied access to aquatic nutritional subsidies. The larger odonate taxa that frequently foraged mid-air had more varied diets and relied less on aquatic emergent insects than the smaller odonates that foraged from perches near the river. There was also evidence of niche partitioning amongst the spiders, as those that built horizontal webs captured more aquatic insects (40 – 78%) than the vertical orb-web builders (20 – 66%). This study showed that the nature and extent of trophic cross-boundary linkages in riparian areas largely depended on the availability of subsidies that varied seasonally and spatially. The width of the stream and seasonal variability emerged as important predictors of emergent insect abundances/biomasses that influenced predator feeding niches. The high mobility of odonates made their reliance on aquatic nutritional subsidies different from the less mobile spiders. The link between the width of the river and the extent of trophic connectivity has implications for riparian area management and definition of riparian buffer zones. However, the variation in diet niches amongst terrestrial consumers makes the results area-specific, and more studies are required that incorporate additional terrestrial predators in other fluvial systems so that we can make some generalizations on the dynamics of riparian trophic cross-boundary links.
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Date Issued: 2016

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Disasters and development nexus : theory and practice - a case of Zimbabwe

- Chatora, Gift

Authors: Chatora, Gift
Date: 2017
Subjects: Disaster relief Human beings -- Effect of environment on Political ecology
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10353/11525 , vital:39080
Description: This study is premised on the notion that disasters and development have a nexus, both theoretically and practically although the two fields have been traditionally viewed as antagonistic at face value. The principal objective was to analyze the existing theoretical and practical gaps between disasters and development in Zimbabwe. Furthermore, factors that affect achievement of disaster mitigation and development linkages in Zimbabwe were critically examined. The study conceptualizes disasters and development from multiple angles. The nested relationship between disasters and development are reinforced with the use of multiple disaster risk reduction strategies to mitigate vulnerability in both rural and urban areas. Hence, this study opted for the mixed methods approach from conceptualization throughout the research process so as to capitalize on the strengths entrenched in both qualitative and quantitative approaches. Drawing on a mixed methodology approach, this study approached the variables from multiple dimensions since disasters and development are intertwined. Evidently, the study demonstrates that disasters and development have a strong nexus, theoretically and practically. This confirms the study hypothesis that disasters and development are correlated, as disasters can both destroy development initiatives and create development opportunities, and that development schemes can both increase and decrease vulnerability. The study also found that policy practice in Zimbabwe is heavily fragmented, thereby leading to incoherent policy implementation. This results in increased vulnerability and huge disaster impacts that erode development gains therefore compromising achievement of sustainable development goals. Hence, the study recommended for the adoption of a Disaster Risk Reduction theoretical framework in cementing the disasters and development linkages theoretically and pragmatically. DRR enhances community’s resilience capacity in curtailing the progression of vulnerability and mitigate the accelerated incubation of disasters that impact on development strides.
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Date Issued: 2017

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Electrochemistry and photophysicochemical studies of titanium, tantalum and vanadium phthalocyanines in the presence of nanomaterials

- Chauke, Vongani Portia

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.
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Date Issued: 2012

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Spermiogenesis, sperm ultrastructure and reproductive tract morphology in cicadas implications for systematic relationships

- Chawanji, Abraham Simbarashe

Authors: Chawanji, Abraham Simbarashe
Date: 2007
Subjects: Cicadas Cicadas -- Reproduction Spermiogenesis in animals
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:5770 , http://hdl.handle.net/10962/d1005458
Description: Sperm structure in five species of cicadine cicadas (Albanycada albigera, Azanicada zuluensis, Platypleura capensis, P. hirtipennis and Pycna semiclara) and five species of cicadettine cicadas (Melampsalta leucoptera, Quintilia walkeri, Stagira simplex, Xosopsaltria thunbergi and Monomatapa matoposa) was investigated by light and electron microscopy. In addition, spermiogenesis in cicadas was described; the information was derived from two cicadettines (Diceroprocta biconica and M. matoposa) and three cicadines (Kongota punctigera, P. capensis and P. semiclara). Mature spermatozoa of all species investigated are elongate and filiform, consisting of three distinct regions: the head (acrosome and nucleus), mid-piece and tail. All species produce more than one discrete length of nucleated, motile sperm, a form of sperm polymorphism termed polymegaly. Polymegaly is expressed in three ways; sperm have uni-, bi- or trimodal nucleus and tail lengths. Besides the differences in length, there are also notable differences in the size of nuclei. The anterior parts of sperm heads are embedded in an elongate homogenous matrix forming spermatodesmata. The conical acrosome is deeply invaginated posteriorly, and sits on top of the nucleus. The acrosomal contents are differentiated internally with a tubular substructure and a subacrosomal space. The anterior of the nucleus intrudes into the posterior section of the subacrosomal space. Anteriorly the acrosome is laterally flattened; posteriorly it extends as two tubular processes on either side of the nucleus that gradually decrease in diameter. The homogenously electron-dense nucleus is pointed anteriorly and is generally cylindrical, although posteriorly there is a lateral invagination that extends part-way along the nucleus. This invagination houses fine granular material of the putative centriolar adjunct which does not form in close proximity to the centriole and hence may not be a true centriolar adjunct. The lamellate disposition of the centriolar adjunct material within the sperm-midpiece of cicadettine cicadas is distinct, and separates these cicadas from their cicadine counterparts in which the centriolar adjunct material is non-lamellate. Vesicle-like elements that are associated with both the posterior nucleus and the centriolar adjunct are also found within the invagination. Immediately posterior of and adjoining the centriolar adjunct is a pair of mitochondrial derivatives that are elongated and extend for almost the entire length of the tail. Except for size the architecture of short and long spermatozoa is generally similar in all species. The absence of accessory bodies in cicada sperm suggests that within the Cicadomorpha, the families Cicadidae and Cercopidae are closely related. Only long nuclei were observed in the fertilized eggs of A. zuluensis indicating that sperm with long nuclei might be favoured for fertilization. Spermiogenesis involves: (a) development of the acrosome from a proacrosomal granule; (b) development of the nucleus, characterized by elongation and streamlining with a simultaneous condensation of chromatin; (c) development of the axoneme from the centriole; (d) amalgamation of individual small mitochondria to form elongated mitochondrial derivatives in which cristae are arranged into regularly spaced lamellae; and (f) elimination of cytoplasm. The presence of a manchette, a transient microtubular organelle, which surrounds the acrosome, nucleus and mitochondrial derivatives, is a characteristic feature of spermiogenesis. The gross morphology of the reproductive tract in both male and female cicadas exhibits an organization similar to that in most oviparous insects. The non-functional spermatheca is the only exceptional feature in the female reproductive tract. Its role has been taken over by the common oviduct which, subsequently, has become modified into a swollen, differentiated structure with a dual role of receiving oocytes from the paired ovaries and storage of spermatozoa. Testis mass varies between cicada species; this variation might be linked to the intensity of sperm competition which has been found to be positively correlated with relative investment in spermatogenesis. Based on the preliminary findings of this study, K. punctigera, with its larger testis relative to body size, would be the ideal candidate to show the greatest levels of sperm competition. Accessory glands in both male and female A. zuluensis, D. biconica, P. hirtipennis and O. quadraticollis are very long; this character might be of phylogenetic significance. Despite being notoriously refractory spermiocladistics is potentially valuable in systematic and phylogenic studies of cicadas, especially at the subfamily level.
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Date Issued: 2007

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