Bridging and enriching top-down and participatory learning: The case of smallholder, organic conservation agriculture farmers in Zimbabwe
- Authors: Mukute, Mutizwa
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432967 , vital:72919 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122261"
- Description: This article discusses the combined use of top-down and participatory learning approaches during the course of a 42-month organic conservation agriculture project that is being implemented in eight districts of Mashonaland East Province in Zimbabwe. The initial 18-month project was extended by a further 24 months in order to build on what had been achieved by deepening organic conservation agriculture practices, by increasing the understanding of, and access to, markets, and by expanding farmer agency. The top-down approach involves farmer representatives, known as ‘access farmers’ in the project, undergoing training at training centres and then returning to their respective farmer associations to train other farmers in what they have learnt. Participatory learning includes farmer-to-farmer learning within and among associations, and trainers learning from, and acting on, farmer experiences. Expansive learning, which combines, and goes beyond, both approaches and allows for joint learning, innovation and agency, has been used to support the associations to learn about, practise and benefit from organic conservation agriculture. This was stimulated by change laboratory workshops being conducted with each of the 32 farmer associations formed during the first 18 months of the project. The main argument in the present article is that combining these seemingly opposite approaches to learning is feasible and is essential for accelerating practice-oriented changes in agriculture. The concept that appears to enable this linkage is dialectics.
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Building a Graphical Fuzzing Framework
- Authors: Zeisberger, Sascha , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429772 , vital:72638 , https://digifors.cs.up.ac.za/issa/2012/Proceedings/Research/59_ResearchInProgress.pdf
- Description: Fuzz testing is a robustness testing technique that sends malformed data to an application’s input. This is to test an application’s behaviour when presented with input beyond its specification. The main difference between traditional testing techniques and fuzz testing is that in most traditional techniques an application is tested according to a specification and rated on how well the application conforms to that specification. Fuzz testing tests beyond the scope of a specification by intelligently generating values that may be interpreted by an application in an unintended manner. The use of fuzz testing has been more prevalent in academic and security communities despite showing success in production environments. To measure the effectiveness of fuzz testing, an experiment was conducted where several publicly available applications were fuzzed. In some instances, fuzz testing was able to force an application into an invalid state and it was concluded that fuzz testing is a relevant testing technique that could assist in developing more robust applications. This success prompted a further investigation into fuzz testing in order to compile a list of requirements that makes an effective fuzzer. The aforementioned investigation assisted in the design of a fuzz testing framework, the goal of which is to make the process more accessible to users outside of an academic and security environment. Design methodologies and justifications of said framework are discussed, focusing on the graphical user interface components as this aspect of the framework is used to increase the usability of the framework.
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Butterfly bones
- Authors: Gowans, Elisabeth
- Date: 2012
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5986 , http://hdl.handle.net/10962/d1015723
- Description: Butterfly Bones is a lyrical sequence of poetry and prose poems organised to trace a rhythmical, emotional pattern of experience. In its subject matter, the sequence presents an implied personal narrative recording the author's grief in the ten months following her mother's death in January 2011. It presents brief, vivid scenes from the poet's daily life in a rural village outside Grahamstown, and observations of creatures and her natural surroundings, which serve as a counterpoint to her grief. It can also be read as a meditation on writing, solitude and the possibilities of poetry.
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Can contracts be both plain and precise?
- Authors: Siebörger, Ian , Adendorff, Ralph D
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123299 , vital:35425 , https://doi.org/10.2989/16073614.2011.651944
- Description: One argument against the use of plain language in legal documents is that it is impossible to convey legal meanings in plain language with the same precision as in specialist legal discourse (Hunt, 2003). We tested this claim by redrafting an extract from a lease agreement into plain English in three stages, producing three versions of the extract in progressively plainer English. We submitted these with the original lease agreement to a senior advocate to elicit his opinion on whether the plain-language versions of the extract are equivalent to the original in legal force. Various differences between the versions are analysed using lexical semantics and Systemic Functional Grammar (as described in Halliday & Matthiessen, 2004). This analysis reveals that the redrafted versions could easily be altered to eliminate the difference between them and the original extract, and that ‘plain language’ as conceived by redrafters of official documents may be easy for non-experts to read, but more difficult for experts. This demonstrates that a ‘one-size-fits-all’ approach to readability is often not tenable, and that plain-language activists can learn much from research (such as Street, 1993) which asserts the existence of a plurality of literacies.
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Can sport impact rational investor behaviour? : an evaluation of the impact of national sporting performance on stock market returns in South Africa
- Authors: De Beer, Carl Francois
- Date: 2012
- Subjects: Investments -- Psychological aspects -- Research -- South Africa Finance -- Psychological aspects -- Research -- South Africa Sports -- Economic aspects -- Research -- South Africa Sports -- Psychological aspects -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MEcon
- Identifier: vital:1013 , http://hdl.handle.net/10962/d1002748
- Description: The finance industry is an extremely fast and complex world dominated by the Efficient Markets Hypothesis (EMH). This theory contains many assumptions which include that investors are rational utility maximisers and that market prices reflect all relevant economic information available to the public. However, over the years, a new form of financial literature known as behavioural finance has been gaining momentum. Behavioural finance seeks to bridge the gap between psychology and economics in an attempt to gain a better understanding of how markets react to different situations. Behavioural finance has also gained much attention in recent years due to the EMH’s inability to explain many economic anomalies. This study first considers the differences between behavioural finance theory and EMH theory before explaining how an individual’s mood has the ability to influence one’s risk taking preferences. Mood changes were also found to be linked to changes in the way an individual reacts to different situations, the way they thinks and processes thoughts. Negative events were also found to have a greater influence on an individual’s mood than positive events did, resulting in an asymmetric relationship between positive and negative results. This study then examines numerous studies indicating how non-economic events can have a statistical and significant influence on stock market returns before analysing previous literature where sport was found to influence market prices. The aim of this study is to determine if South African national sporting performance can influence investors in such a way that it has the ability to impact on market returns. Using standard event study methodology, this study determines the constant mean return using the daily All-Share price index on the JSE for the period of 1 January 1990 to 31 December 2010. This study focuses on three of South Africa’s most popular sports, namely soccer, cricket and rugby and examine if these three sports have the ability to influence market returns. Although there is some evidence of a relationship between stock returns and sporting performance in the descriptive analysis, the regression results indicate that sporting performance in South Africa does not significantly explain abnormal market returns on the JSE. The study provides a number of possible reasons for this finding and concludes by suggesting areas for future research.
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Capturefoundry: a gpu accelerated packet capture analysis tool
- Authors: Nottingham, Alastair , Richter, John , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430112 , vital:72666 , https://doi.org/10.1145/2389836.2389877
- Description: Packet captures are used to support a variety of tasks, including network administration, fault diagnosis and security and network related research. Despite their usefulness, processing packet capture files is a slow and tedious process that impedes the analysis of large, long-term captures. This paper discusses the primary components and observed performance of CaptureFoundry, a stand-alone capture analysis support tool designed to quickly map, filter and extract packets from large capture files using a combination of indexing techniques and GPU accelerated packet classification. All results are persistent, and may be used to rapidly extract small pre-filtered captures on demand that may be analysed quickly in existing capture analysis applications. Performance results show that CaptureFoundry is capable of generating multiple indexes and classification results for large captures at hundreds of megabytes per second, with minimal CPU and memory overhead and only minor additional storage space requirements.
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Cash transfers and poverty reduction in South Africa: a case study of old age pensions
- Authors: Kasere, Gayle Farai
- Date: 2012
- Subjects: Poverty -- Economic aspects -- South Africa -- Eastern Cape Poverty -- Grahamstown -- Eastern Cape Social security -- South Africa Pensions -- South Africa
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3321 , http://hdl.handle.net/10962/d1003109
- Description: Social assistance in the form of cash grants is a large and fiscally costly component of anti-poverty policy in South Africa. A critical question arises: Are the grants effective tools for reducing poverty in South Africa and, moreover, how significant is their impact on poverty? As a measure of reducing poverty, the government has expanded the social grants system since the advent of the new democracy in 1994. The country's social grant system is quite comprehensive and it is intended to cover vulnerable individuals over their life course from childhood to adulthood and into old age. Policy discourse surrounding the grants centres on the sustainability of the system and its implications for socio-economic development and poverty alleviation. It is therefore important that the significance of grants is identified and assessed particularly in relation to very poor households. This dissertation focuses specifically on one particular grant, namely, the old age pension. It does so in the context of the sustainable livelihoods conceptual framework and the history of the social grant system in South Africa. Statistical data collected by the South African government as well as more localised evidence gathered in the Eastern Cape town of Grahamstown is used to ascertain the significance of old age pensions for poverty reduction. While there is some evidence to suggest that pensions contribute to poverty reduction, this does not translate into poverty alleviation. In fact, there is some unevenness in the impact of pensions on poverty. In this regard, the decision-making structures in poor households regularly influence the way pension money is allocated and used within households. Grant money is normally shared in extended households, such that the pension does not simply benefit the recipient but the recipient's household as a whole. Although there is cause for concern regarding the propensity of social grants to affect people's behaviour negatively, there is a case to be made for retaining grants as an important, though not the only, form of anti-poverty strategy. This highlights the need for continued research on the social grant system and pensions more specifically.
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CdTe quantum dots functionalized with 4-amino-2, 2, 6, 6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion
- Authors: Adegoke, Oluwasesan , Hosten, Eric , McCleland, Cedric , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244393 , vital:51253 , xlink:href="https://doi.org/10.1016/j.aca.2012.01.040"
- Description: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
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Challenges experienced in the first year of implementation of a teaching and learning virtual partnership at the University of Namibia
- Authors: Mufeti, K , Foster, Greg , Terzoli, Alfredo
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431234 , vital:72756 , https://rcetj.org/index.php/rcetj/article/view/178
- Description: Advances in information and communication technologies are enabling higher educa-tion institutions to build virtual partnerships with other institutions. Virtual partner-ships are defined here as collaborations between geographically dispersed institutions, where interaction between these institutions is enabled mainly by electronic modes of communication. This article reports on the participants’ experiences of the implemen-tation of one such partnership from the perspective of a partner in a developing con-text. It uses the SANTED Virtual Classroom Project (VCP), a virtual partnership initia-tive between the Departments of Computer Science at the University of Namibia (UNAM) and Rhodes University (RU), as a case study. In the VCP, the department at RU was tasked with building teaching and human resource capacity in the department at UNAM. The article focuses on the challenges experienced at UNAM during the first year of implementation of the VCP and lessons learned.
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Changing sediment yield and sediment dynamics in the Karoo uplands, South Africa : post-European impacts
- Authors: Foster, I D L , Rowntree, Kate M , Boardman, J , Mighall, T M
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6684 , http://hdl.handle.net/10962/d1006683
- Description: We provide an overview of published results and a significant body of new data from an ongoing research programme designed to reconstruct sediment yields and sources in small (<60 km2) catchments in the Eastern Cape, South Africa over the last 150 years. Our analysis of four catchments has determined that sediment yield increased significantly in the latter half of the 20th Century but that the exact timing of these increases was different in each of the four catchments. In two high altitude locations, sediment yield increases were not associated with a significant change in sediment source, although in one case areas of former cultivation appear to have made a slightly greater contribution since the 1960s. In a third catchment, increases in sediment yield appear to have been driven by the development of badlands and by an increase in connectivity between the badlands and the main channel network in the 1960s. In the fourth catchment, increased connectivity between the main catchment and dam occurred as a result of the construction of a causeway to carry a main road and by the construction of culverts beneath the road. Occasional changes in sediment source have also been identified in the sedimentary record but these were not linked directly to road construction. Research to date shows the complexity of sediment delivery in these semi-arid catchment systems and emphasises the need to combine sediment yield with source ascription in order to better understand the dynamics of these systems.
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Characterization of 2,(3)-tetra-(4-oxo-benzamide) phthalocyaninato cobalt (II)—single walled carbon nanotube conjugate platforms and their use in electrocatalysis of amitrole
- Authors: Mugadza, Tawanda , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244382 , vital:51252 , xlink:href="https://doi.org/10.1016/j.electacta.2012.02.041"
- Description: In this paper we report on the use of carboxylic acid functionalized single walled carbon nanotubes (SWCNT) in the synthesis of 2,(3)-tetra-(4-oxo-benzamide)phthalocyaninato cobalt (II)–single walled carbon nanotube conjugates (CoTOBPc–SWCNT), their characterization and application in the electrocatalytic oxidation of amitrole. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used for the detection of amitrole on the modified glassy carbon electrode. The catalytic rate constant was 1.6 × 103 M−1 s−1 and the apparent electron rate transfer constant was 1.5 × 10−5 cm s−1. The linear dynamic range was 1.0 × 10−6–3.0 × 10−5 M, with a sensitivity of ∼1.13 A mol−1 L cm−2.
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Chief executive officer compensation and the effect on company performance in a South African context
- Authors: Bradley, Samuel
- Date: 2012
- Subjects: Chief executive officers -- Salaries, etc. -- South Africa , Compensation management -- South Africa , Wage surveys -- South Africa , Organizational effectiveness -- Evaluation
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:883 , http://hdl.handle.net/10962/d1001637 , Chief executive officers -- Salaries, etc. -- South Africa , Compensation management -- South Africa , Wage surveys -- South Africa , Organizational effectiveness -- Evaluation
- Description: The goal of this research was to determine, in a South African context, whether there is any correlation between chief executive officer compensation and the performance of the company. For the purposes of the research , the compensation of chief executive officers was broken down into three components: salary, bonus and "other" remuneration, while company performance was measured on return on equity, return on assets and earnings per share figures. Studies on this topic have been carried out in other countries, most notably in the United States of America and the United Kingdom. It appears that no research of a similar nature has been carried out in South Africa. Data in respect of the forty largest listed companies in South Africa were collected over a period of five years. The econometric models used for the research were based on models identified in the literature study. The data were then analysed for evidence of a correlation between chief executive officer compensation and the performance of the company. The results of this study indicate that there is no linear relationship between chief executive officer compensation and company performance variables. The econometric models did, however, show correlations between certain variables, taking into account the other predictor variables in the model. Evidence of correlations between age and experience and compensation was also found , which may present potential avenues of research to scholars in the future.
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Chieftainship succession and gender equality in Lesotho: negotiating the right to equality in a jungle of pluralism
- Authors: Juma, Laurence
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127067 , vital:35951 , https://heinonline.org/HOL/Page?handle=hein.journals/tjwl22amp;div=11amp;g_sent=1amp;casa_token=amp;collection=journals
- Description: Women constitute about 51% of Lesotho's population 1 and enjoy a higher literacy rate than men. 2 They are also the backbone of a society that for several hundreds of years provided male labor to South Africa's farms and gold mines.3 However, Basotho women are generally excluded from mainstream politics and are discriminated against in almost all spheres of socioeconomic life. This exclusion, marginalization, and discrimination have been largely blamed on patriarchy and entrenched traditional norms, both of which are sustained by a plural legal system that has seemingly remained insular to developments around the globe. 4
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China-Africa relations: research approaches
- Authors: Simbao, Ruth K
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147503 , vital:38644 , https://doi.org/10.1162/afar.2012.45.2.1
- Description: About to board a plane in Johannesburg, I handed my temporary boarding pass to the flight attendant who exclaimed,“Simbao, you have a fong kong boarding pass!” Fong kong is a slang term used in South Africa meaning fake, cheap, or low quality and is often associated with Chinese imports. In this case, the term was used to refer to a temporary pass issued earlier on my journey that needed to be replaced with a new boarding pass in Johannesburg.
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Civil society and state-centred struggles
- Authors: Helliker, Kirk D
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71231 , vital:29821 , https://doi.org/10.1080/02589001.2012.641723
- Description: This article is about civil society and state-centred struggles in contemporary Zimbabwe. I first identify and outline three current understandings of civil society. Two understandings (one Liberal, one Radical) are state-centric and exist firmly within the logic of state discourses and state politics. A third understanding, also Radical, is society-centric and speaks about politics existing at a distance from the state and possibly beyond the boundaries of civil society. This civil society-state discussion frames the second section of the article, which looks specifically at Zimbabwe. It details civil society as contested terrain (from the late 1990s onwards) within the context of a scholarly debate about agrarian transformation and political change. This debate, which reproduces (in theoretical garb) the key political society (or party) fault-lines within Zimbabwean society, has taken place primarily within the restricted confines of state-centred discourses.
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Classifying network attack scenarios using an ontology
- Authors: Van Heerden, Renier , Irwin, Barry V W , Burke, I D
- Date: 2012
- Language: English
- Type: Conference paper
- Identifier: vital:6606 , http://hdl.handle.net/10962/d1009326
- Description: This paper presents a methodology using network attack ontology to classify computer-based attacks. Computer network attacks differ in motivation, execution and end result. Because attacks are diverse, no standard classification exists. If an attack could be classified, it could be mitigated accordingly. A taxonomy of computer network attacks forms the basis of the ontology. Most published taxonomies present an attack from either the attacker's or defender's point of view. This taxonomy presents both views. The main taxonomy classes are: Actor, Actor Location, Aggressor, Attack Goal, Attack Mechanism, Attack Scenario, Automation Level, Effects, Motivation, Phase, Scope and Target. The "Actor" class is the entity executing the attack. The "Actor Location" class is the Actor‟s country of origin. The "Aggressor" class is the group instigating an attack. The "Attack Goal" class specifies the attacker‟s goal. The "Attack Mechanism" class defines the attack methodology. The "Automation Level" class indicates the level of human interaction. The "Effects" class describes the consequences of an attack. The "Motivation" class specifies incentives for an attack. The "Scope" class describes the size and utility of the target. The "Target" class is the physical device or entity targeted by an attack. The "Vulnerability" class describes a target vulnerability used by the attacker. The "Phase" class represents an attack model that subdivides an attack into different phases. The ontology was developed using an "Attack Scenario" class, which draws from other classes and can be used to characterize and classify computer network attacks. An "Attack Scenario" consists of phases, has a scope and is attributed to an actor and aggressor which have a goal. The "Attack Scenario" thus represents different classes of attacks. High profile computer network attacks such as Stuxnet and the Estonia attacks can now be been classified through the “Attack Scenario” class.
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COIN : a customisable, incentive driven video on demand framework for low-cost IPTV services
- Authors: Musvibe, Ray
- Date: 2012 , 2012-03-02
- Subjects: Internet television , Digital television , Television broadcasting -- Technological innovations , Multicasting (Computer networks) , Video dial tone , Open source software , Telecommunication , Capital investments
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4654 , http://hdl.handle.net/10962/d1006650 , Internet television , Digital television , Television broadcasting -- Technological innovations , Multicasting (Computer networks) , Video dial tone , Open source software , Telecommunication , Capital investments
- Description: There has been a significant rise in the provision of television and video services over IP (IPTV) in recent years. Increasing network capacity and falling bandwidth costs have made it both technically and economically feasible for service providers to deliver IPTV services. Several telecommunications (telco) operators worldwide are rolling out IPTV solutions and view IPTV as a major service differentiator and alternative revenue source. The main challenge that IPTV providers currently face, however, is the increasingly congested television service provider market, which also includes Internet Television. IPTV solutions therefore need strong service differentiators to succeed. IPTV solutions can doubtlessly sell much faster if they are more affordable or low-cost. Advertising has already been used in many service sectors to help lower service costs, including traditional broadcast television. This thesis therefore explores the role that advertising can play in helping to lower the cost of IPTV services and to incentivise IPTV billing. Another approach that IPTV providers can use to help sell their product is by addressing the growing need for control by today's multimedia users. This thesis will therefore explore the varied approaches that can be used to achieve viewer focused IPTV implementations. To further lower the cost of IPTV services, telcos can also turn to low-cost, open source platforms for service delivery. The adoption of low-cost infrastructure by telcos can lead to reduced Capital Expenditure (CAPEX), which in turn can lead to lower service fees, and ultimately to higher subscriptions and revenue. Therefore, in this thesis, the author proposes a CustOmisable, INcentive (COIN) driven Video on Demand (VoD) framework to be developed and deployed using the Mobicents Communication Platform, an open source service creation and execution platform. The COIN framework aims to provide a viewer focused, economically competitive service that combines the potential cost savings of using free and open source software (FOSS), with an innovative, incentive-driven billing approach. This project will also aim to evaluate whether the Mobicents Platform is a suitable service creation and execution platform for the proposed framework. Additionally, the proposed implementation aims to be interoperable with other IPTV implementations, hence shall follow current IPTV standardisation architectures and trends. The service testbed and its implementation are described in detail and only free and open source software is used; this is to enable its easy duplication and extension for future research. , TeX output 2012.03.02:1241 , Adobe Acrobat 9.2 Paper Capture Plug-in
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Communication at the health care coalface: lessons from selected clinics in Port Elizabeth
- Authors: Mbengo, Nomatshawe
- Date: 2012
- Subjects: Communication in medicine -- Research -- South Africa Community health services -- South Africa -- Eastern Cape Social medicine -- Research -- South Africa Medical care -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3591 , http://hdl.handle.net/10962/d1002166
- Description: This thesis analyses the state of health care in South Africa with particular reference to a clinic and the Provincial Hospital in Port Elizabeth, Eastern Cape. The complexities of health care provision in a diverse sociolinguistic environment where certain languages are emphasized over others, forms the cornerstone of the research. The research focuses on health care in a complex multi-cultural environment. The goal of the research is to present a coherent and robust translation framework for the development of suitable materials to enhance communication across language and cultural barriers in the health care sector. A model (based on research completed in the USA) is presented as a possible alternative in the final chapter of the thesis.
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Comparative biogeography and ecology of freshwater fishes in the Breede and associated river systems, South Africa
- Authors: Chakona, Albert
- Date: 2012
- Subjects: Freshwater fishes -- South Africa -- Breede River , Freshwater fishes -- South Africa -- Geographical distribution , Freshwater fishes -- Ecology , Feshwater fishes -- Genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5372 , http://hdl.handle.net/10962/d1015694
- Description: Distribution patterns and levels of genetic diversity in extant taxa are a product of complex palaeogeographic processes and climatic oscillations as well as the species’ intrinsic ecological adaptations. The Cape Floristic Region of South Africa presents a unique system for studying the processes that promote species diversification and distribution patterns. This region has a high degree of endemism of both terrestrial and aquatic biota and is clearly isolated from neighbouring areas by the Cape Fold Mountains and the Great Escarpment. The objective of this study was to firstly examine the ecology of freshwater fishes belonging to the genera Galaxias, Pseudobarbus and Sandelia in the south-western CFR. This was followed by an assessment of the genetic diversity of these taxa. Unique lineages were identified and their distribution was mapped. The work aimed to explore the role of the region’s complex palaeogeographic and climatic history as well as the role of the species’ ecological adaptations in driving lineage diversification and shaping contemporary distribution patterns. The four main components of the study can be summarised as follows: 1. Habitat associations of three widely distributed lineages of Galaxias zebratus Pseudobarbus burchelli and Sandelia capensis were evaluated at multiple localities in minimally disturbed mountain tributaries of the Breede, Duiwenhoks and Goukou River systems. The lineages have distinct habitat associations which were related to differences in their morphological traits. The slender-bodied Galaxias ‘nebula’ and the fusiform-shaped Pseudobarbus ‘Breede’ are capable of exploiting upper reaches with faster water velocity. By contrast, the laterally compressed Sandelia ‘eastern’ is restricted to lower reaches, making this lineage more susceptible to a wide array of impacts. 2. A recently discovered lineage of Galaxias zebratus, (Galaxias ‘nebula’), was found to be capable of tolerating emersion for a prolonged period of time. This is the first time that such capabilities have been documented in an African galaxiid. These adaptations have implications for the interpretation of Galaxias ‘nebula’s wide distribution range. 3. The phylogeography of Galaxias ‘nebula’ across its entire distribution range was investigated using two mitochondrial genes (cytochrome c oxidase subunit I (COI) and cytochrome b (cyt b)). This lineage has a complex evolutionary history that was influenced by both intrinsic and extrinsic factors. Rare events such as episodic drainage connections during Pleistocene and Holocene pluvial periods, possibly augmented by river confluences during periods of lower sea-levels and river capture events seem to be the most credible explanation for the extensive contemporary distribution and the relatively shallow genetic divergence between different river systems. 4. Mitochondrial cyt b sequences were used (i) to assess genetic diversity in G. zebratus, P. burchelli and S. capensis from the south-western CFR and (ii) to determine the roles of intrinsic ecological adaptations and extrinsic landscape and climatic changes in promoting genetic diversification and shaping present day distribution patterns of lineages in the three taxa. Marine incursions during periods of major sea-level transgressions are proposed to have isolated populations in upland refugia, thereby driving allopatric divergence in these species. Subsequent connections of rivers during wetter periods and lower sea-levels are proposed to have facilitated post-speciation dispersal of lineages to attain present day distribution patterns. While detailed morphological studies and further genetic analysis are needed to substantiate the taxonomic status of the newly discovered lineages of Galaxias zebratus, Pseudobarbus burchelli and Sandelia capensis, results of the present study indicate that the south-western CFR represents a previously unrecognised centre of freshwater fish diversity and microendemism in the broader Cape Floristic Region. Accurate identification of lineages and comprehensive mapping of their distribution is a fundamental pre-requisite for ecological studies, assessing conservation status and implementation of appropriate conservation measures.
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Comparison of carbon screen-printed and disk electrodes in the detection of antioxidants using CoPc derivatives
- Authors: Matemadombo, Fungisai , Apetrei, Constantin , Nyokong, Tebello , Rodríguez-Méndez, María Luz , de Saja, José Antonio
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244371 , vital:51251 , xlink:href="https://doi.org/10.1016/j.snb.2012.02.088"
- Description: Cobalt phthalocyanine (CoPc) and cobalt phthalocyanine carboxylic derivatives (CoTCPc and CoOCPc) have been used as electrocatalysts for the detection of the antioxidants vanillic acid, caffeic acid, pyrogallol, and ascorbic acid on screen-printed carbon and disk electrode surfaces. The cobalt phthalocyanines were used to detect vanillic acid (with limit of detection ranging from 1.15 μM to 2.42 μM at potentials of 0.55–0.88 V vs. Ag|AgCl), caffeic acid (with limit of detection ranging from 1.17 μM to 2.20 μM at potentials of 0.30–0.81 V vs. Ag|AgCl), pyrogallol (with limit of detection ranging from 1.16 μM to 3.63 μM at potentials of 0.52–0.63 V vs. Ag|AgCl), and ascorbic acid (with limit of detection ranging from 1.16 μM to 1.58 μM at potentials of 0.34–0.46 V vs. Ag|AgCl). The kinetic studies also demonstrate diffusion-controlled processes at the electrode surface. The SPCE electrodes have better detection properties towards vanillic acid, caffeic acid, pyrogallol while the disk electrodes had better ascorbic acid detection properties as proven by kinetic studies. Both types CoPc-influenced electrodes show 100% discrimination of the antioxidants.
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