Isolation and structure elucidation of halogenated metabolites from Portieria hornemannii and Portieria tripinnata
- Authors: Adam, Mohammed
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64674 , vital:28591
- Description: The red marine algal genus, Portieria, is known to produce a number of potent cytotoxic compounds with anticancer potential. The most important anticancer lead produced by this genus is the compound halomon. Unfortunately, the lack of sufficient quantities of this compound hampered its further development. Two Portieria species, Portieria hornemannii and Portieria tripinnata, are found along the South African coastline. Recent studies, based on DNA analysis, suggest that Portieria hornemannii may in fact be divided into several cryptic species. The current project is part of a larger study designed to investigate the use of secondary metabolites to identify new marine algal species. In this study 1H NMR profiles of the organic extracts of selected Portieria spp were compared in order to identify new species. Selected compounds were then isolated and characterised as potential chemotaxonomic markers. Four halogenated monoterpenes were isolated from Portieria hornemannii. Two of these were new compounds 4-(3-bromo-4-chloro-4-methylpentyl)-3-chlorofuran-2(5H)-one, which were isomers of each other. The two known compounds had been previously isolated from Portieria hornemannii samples off the Madagascar coast. These compounds could prove to be useful as chemotaxonomic marker compounds, as they have never been isolated from any other species of marine algae. Three known halogenated monoterpenes were isolated from Portieria tripinnata. These compounds had been previously isolated from different species of marine algae and therefore, could not serve as chemotaxonomic marker compounds for this species of marine alga. Further work needs to be done on Portieria tripinnata, with regards to its chemistry, as it is a species of marine algae that has not been previously researched.
- Full Text:
- Date Issued: 2015
- Authors: Adam, Mohammed
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64674 , vital:28591
- Description: The red marine algal genus, Portieria, is known to produce a number of potent cytotoxic compounds with anticancer potential. The most important anticancer lead produced by this genus is the compound halomon. Unfortunately, the lack of sufficient quantities of this compound hampered its further development. Two Portieria species, Portieria hornemannii and Portieria tripinnata, are found along the South African coastline. Recent studies, based on DNA analysis, suggest that Portieria hornemannii may in fact be divided into several cryptic species. The current project is part of a larger study designed to investigate the use of secondary metabolites to identify new marine algal species. In this study 1H NMR profiles of the organic extracts of selected Portieria spp were compared in order to identify new species. Selected compounds were then isolated and characterised as potential chemotaxonomic markers. Four halogenated monoterpenes were isolated from Portieria hornemannii. Two of these were new compounds 4-(3-bromo-4-chloro-4-methylpentyl)-3-chlorofuran-2(5H)-one, which were isomers of each other. The two known compounds had been previously isolated from Portieria hornemannii samples off the Madagascar coast. These compounds could prove to be useful as chemotaxonomic marker compounds, as they have never been isolated from any other species of marine algae. Three known halogenated monoterpenes were isolated from Portieria tripinnata. These compounds had been previously isolated from different species of marine algae and therefore, could not serve as chemotaxonomic marker compounds for this species of marine alga. Further work needs to be done on Portieria tripinnata, with regards to its chemistry, as it is a species of marine algae that has not been previously researched.
- Full Text:
- Date Issued: 2015
Contributions to the study of a class of optimal control problems on the orthogonal groups SO(3) and SO(4)
- Authors: Adams, Ross Montague
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64826 , vital:28608
- Description: In this thesis we investigate a class of invariant optimal control problems, and their associated quadratic Hamilton-Poisson systems, on the orthogonal groups SO(3) and SO(4). Specifically, we are concerned with the class of left-invariant control affine systems. We begin by classifying all cost-extended systems on SO(3) under cost equivalence. (Cost-extended systems are closely related to optimal control problems.) A classification of all quadratic Hamilton-Poisson systems on the (minus) Lie-Poisson space so(3)*, under affine equivalence, is also obtained. For the normal forms obtained in our classification (of Hamilton-Poisson systems) we investigate the (Lyapunov) stability nature of the equilibria using spectral and energy-Casimir methods. For a subclass of these systems, we obtain analytic expressions for the integral curves of the associated Hamiltonian vector fields in terms of (basic) Jacobi elliptic functions. The explicit relationship between the classification of cost-extended systems on SO(3) and the classification of quadratic Hamilton- Poisson systems on so(3)* is provided. On SO(4), a classification of all left-invariant control affine systems under L-equivalence is obtained. We then determine which of these representatives are controllable, thus obtaining a classification under detached feedback equivalence. We also obtain a partial classification of quadratic Hamilton-Poisson systems on the Lie-Poisson space so(4)*. An investigation of the stability nature of the equilibria for a subclass of these systems is also done. Several illustrative examples of optimal control problems on the orthogonal group SO(3) are provided. More specifically, we consider an optimal control problem corresponding to a representative of our classification (of cost-extended system) for each possible number of control inputs. For each of these problems, we obtain explicit expressions for the extremal trajectories on the homogeneous space S2 by projecting the extremal trajectories on the group SO(3). The examples provided show how our classifications of cost-extended systems and Hamilton-Poisson systems can be used to obtain the optimal controls and the extremal trajectories corresponding to a large class of optimal control problems on SO(3). An example of a four-input optimal control problem on SO(4) is also provided. This example is provided to show how the solutions of certain problems on SO(4) can be related to the solutions of certain optimal control problems on SO(3).
- Full Text:
- Date Issued: 2015
- Authors: Adams, Ross Montague
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64826 , vital:28608
- Description: In this thesis we investigate a class of invariant optimal control problems, and their associated quadratic Hamilton-Poisson systems, on the orthogonal groups SO(3) and SO(4). Specifically, we are concerned with the class of left-invariant control affine systems. We begin by classifying all cost-extended systems on SO(3) under cost equivalence. (Cost-extended systems are closely related to optimal control problems.) A classification of all quadratic Hamilton-Poisson systems on the (minus) Lie-Poisson space so(3)*, under affine equivalence, is also obtained. For the normal forms obtained in our classification (of Hamilton-Poisson systems) we investigate the (Lyapunov) stability nature of the equilibria using spectral and energy-Casimir methods. For a subclass of these systems, we obtain analytic expressions for the integral curves of the associated Hamiltonian vector fields in terms of (basic) Jacobi elliptic functions. The explicit relationship between the classification of cost-extended systems on SO(3) and the classification of quadratic Hamilton- Poisson systems on so(3)* is provided. On SO(4), a classification of all left-invariant control affine systems under L-equivalence is obtained. We then determine which of these representatives are controllable, thus obtaining a classification under detached feedback equivalence. We also obtain a partial classification of quadratic Hamilton-Poisson systems on the Lie-Poisson space so(4)*. An investigation of the stability nature of the equilibria for a subclass of these systems is also done. Several illustrative examples of optimal control problems on the orthogonal group SO(3) are provided. More specifically, we consider an optimal control problem corresponding to a representative of our classification (of cost-extended system) for each possible number of control inputs. For each of these problems, we obtain explicit expressions for the extremal trajectories on the homogeneous space S2 by projecting the extremal trajectories on the group SO(3). The examples provided show how our classifications of cost-extended systems and Hamilton-Poisson systems can be used to obtain the optimal controls and the extremal trajectories corresponding to a large class of optimal control problems on SO(3). An example of a four-input optimal control problem on SO(4) is also provided. This example is provided to show how the solutions of certain problems on SO(4) can be related to the solutions of certain optimal control problems on SO(3).
- Full Text:
- Date Issued: 2015
Studies towards the development of novel antimalarial agents
- Authors: Adeyemi, Christiana Modupe
- Date: 2015
- Subjects: Antimalarials , Malaria , Drug resistance , Drug development , Enzyme inhibitors , Plasmodium
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54645 , vital:26596
- Description: Considerable efforts have been made in the modification of existing antimalarial drugs, and the support of incentive programmes have led to a drastic decrease in malaria cases reported by WHO during the past 6 years. However, the development of drug resistance threatens the eradication of this deadly disease and has prompted research on the synthesis of novel antimalarial drugs. Our research has involved the design and synthesis of novel benzylated phosphonate esters as potential 1-deoxy-D-xylose-5-phosphate reductoisomerase (DXR) inhibitors. A series of amidoalkylphosphonate esters were obtained by reacting various 3-subsituted anilines and heterocyclic amines with chloroalkanoyl chlorides and reacting the resulting chloroalkanamides with triethyl phosphite using Michaelis-Arbuzov methodology. Benzylation of the phosphonate esters afforded a series of novel N-benzylated derivatives in good yields and these compounds were fully characterised by NMR and HRMS methods. Several approaches to the introduction of a benzyl group at the C-2 position of the phosphonate ester derivatives have been explored, leading unexpectedly to the isolation of unprecedented tetrahydrofuranyl derivatives. Studies towards the preparation of potential bi-functional PfDXR / HIV-1 RT inhibitors have also been initiated. Preliminary in silico docking studies of selected non-benzylated and benzylated phosphonated derivatives into the Pf-DXR active-site has provided useful insight into the binding potential of these ligands. Bioassays have revealed a very low toxicity for all the synthesised phosphonated compounds and a number of these ligands also exhibit a promising inhibitory activity against the Plasmodium parasite.
- Full Text:
- Date Issued: 2015
- Authors: Adeyemi, Christiana Modupe
- Date: 2015
- Subjects: Antimalarials , Malaria , Drug resistance , Drug development , Enzyme inhibitors , Plasmodium
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54645 , vital:26596
- Description: Considerable efforts have been made in the modification of existing antimalarial drugs, and the support of incentive programmes have led to a drastic decrease in malaria cases reported by WHO during the past 6 years. However, the development of drug resistance threatens the eradication of this deadly disease and has prompted research on the synthesis of novel antimalarial drugs. Our research has involved the design and synthesis of novel benzylated phosphonate esters as potential 1-deoxy-D-xylose-5-phosphate reductoisomerase (DXR) inhibitors. A series of amidoalkylphosphonate esters were obtained by reacting various 3-subsituted anilines and heterocyclic amines with chloroalkanoyl chlorides and reacting the resulting chloroalkanamides with triethyl phosphite using Michaelis-Arbuzov methodology. Benzylation of the phosphonate esters afforded a series of novel N-benzylated derivatives in good yields and these compounds were fully characterised by NMR and HRMS methods. Several approaches to the introduction of a benzyl group at the C-2 position of the phosphonate ester derivatives have been explored, leading unexpectedly to the isolation of unprecedented tetrahydrofuranyl derivatives. Studies towards the preparation of potential bi-functional PfDXR / HIV-1 RT inhibitors have also been initiated. Preliminary in silico docking studies of selected non-benzylated and benzylated phosphonated derivatives into the Pf-DXR active-site has provided useful insight into the binding potential of these ligands. Bioassays have revealed a very low toxicity for all the synthesised phosphonated compounds and a number of these ligands also exhibit a promising inhibitory activity against the Plasmodium parasite.
- Full Text:
- Date Issued: 2015
E-commerce: the challenge of virtual permanent establishments
- Adlkofer, Michelle Leigh, Venter, Michelle
- Authors: Adlkofer, Michelle Leigh , Venter, Michelle
- Date: 2015
- Subjects: Organisation for Economic Co-operation and Development , Electronic commerce , Electronic commerce -- Taxation , Double taxation -- Treaties , Globalization
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:921 , http://hdl.handle.net/10962/d1020057
- Description: The continued growth of world commerce has led to the advance of the permanent establishment principles. These principles are, however, constantly challenged by the developments of e-commerce. This thesis considers the taxing of a permanent establishment and the influence of e-commerce on the concept of a permanent establishment. In 2000, the Organisation for Economic Co-operation and Development (“OECD”) developed and introduced guidelines on how to deal with e-commerce in the context of a permanent establishment. Since the OECD guidelines on e-commerce were issued, the permanent establishment principles have come under further scrutiny. The latest development came about in 2013 with the release of the Base Erosion and Profit Shifting (“BEPS”) Action Plan. This Action Plan addresses the intention of the OECD to deal with the taxing of the digital economy. With the development of e-commerce and the result of e-commerce creating intangible boundaries between countries, the concept of a virtual permanent establishment has emerged. This has resulted in the need to tax a presence of an enterprise in a jurisdiction where no actual physical connection can be established. Various authors have made suggestions on how to ensure that an economy in which business is being carried on is correctly compensated for in the form of taxes. The source of income is the driving force for the imposition of taxation today. The main goal of this thesis was to explore the alignment of the concepts of a permanent establishment and e-commerce in the digital economy. This study therefore examined the concepts of both permanent establishments and e-commerce, and explored authors’ views and suggestions on how to deal with the inter-related effects of these two concepts. The relevant Action Points in the OECD Action Plan were also considered. , Maiden name: Venter, Michelle
- Full Text:
- Date Issued: 2015
- Authors: Adlkofer, Michelle Leigh , Venter, Michelle
- Date: 2015
- Subjects: Organisation for Economic Co-operation and Development , Electronic commerce , Electronic commerce -- Taxation , Double taxation -- Treaties , Globalization
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:921 , http://hdl.handle.net/10962/d1020057
- Description: The continued growth of world commerce has led to the advance of the permanent establishment principles. These principles are, however, constantly challenged by the developments of e-commerce. This thesis considers the taxing of a permanent establishment and the influence of e-commerce on the concept of a permanent establishment. In 2000, the Organisation for Economic Co-operation and Development (“OECD”) developed and introduced guidelines on how to deal with e-commerce in the context of a permanent establishment. Since the OECD guidelines on e-commerce were issued, the permanent establishment principles have come under further scrutiny. The latest development came about in 2013 with the release of the Base Erosion and Profit Shifting (“BEPS”) Action Plan. This Action Plan addresses the intention of the OECD to deal with the taxing of the digital economy. With the development of e-commerce and the result of e-commerce creating intangible boundaries between countries, the concept of a virtual permanent establishment has emerged. This has resulted in the need to tax a presence of an enterprise in a jurisdiction where no actual physical connection can be established. Various authors have made suggestions on how to ensure that an economy in which business is being carried on is correctly compensated for in the form of taxes. The source of income is the driving force for the imposition of taxation today. The main goal of this thesis was to explore the alignment of the concepts of a permanent establishment and e-commerce in the digital economy. This study therefore examined the concepts of both permanent establishments and e-commerce, and explored authors’ views and suggestions on how to deal with the inter-related effects of these two concepts. The relevant Action Points in the OECD Action Plan were also considered. , Maiden name: Venter, Michelle
- Full Text:
- Date Issued: 2015
Exploring problematic experiences : an IPA study of 'Internet Addiction'
- Authors: Allie, Naaheeda
- Date: 2015
- Subjects: Internet addiction , Compulsive behavior , Security (Psychology)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3256 , http://hdl.handle.net/10962/d1016395
- Description: In the past two decades, a considerable amount of research has been carried out on the phenomenon of excessive Internet use, variously termed Internet addiction, Internet dependency and problematic Internet use. Despite this, there is still little agreement as to what constitutes this phenomenon, whether it should be considered a clinical disorder or not and what leads to this excessive or maladaptive use. The terminology used in this study is that of Problematic Internet Use (PIU). Several theoretical models have been proposed in the understanding of PIU including personality models, operant conditioning models, social cognitive and cognitive behavioural models (Davis, 2001; LaRose, lin & Eastin, 2003; Young, 1999). A proposed gap in the literature is the lack of studies exploring participant experiences of problematic Internet use. It is for this reason that this study aimed at exploring the experiences of a small sample of individuals with self-identified problematic Internet use. The implications of this phenomenological data for the above-mentioned theoretical models were then reviewed. This study used an Interpretative Phenomenological Analysis (IPA) approach in exploring these aims. A sample of four participants was selected through purposive sampling techniques. Four major themes emerged from the analysis namely: Escapism, Social Insecurity and Validation, Perfectionism and Control. These experiences of participants were also explored in terms of the conceptual models reviewed in order to compare how closely they related to participant experiences. A strong inter-relationship was found between the four themes mentioned above. The Internet appeared to provide a sense of control and validation to these individuals while simultaneously rendering them unable to maintain control of their Internet usage in relation to this. This sense of control was experienced through an escape from negative emotions, offline obligations and at times a dissatisfactory position in reality. Of the four models reviewed, the Social Cognitive model proposed by LaRose et al. (2003) appeared to offer the most relevant understanding of PIU to participant experiences. The presence of maladaptive cognitions also appeared to feature strongly as an underlying factor in participants' PIU, as theorised by cognitive behavioural models (Davis, 2001; Young, 1999) Finally recommendations are made for further more detailed exploration of PIU using interpretative, experiential methods.
- Full Text:
- Date Issued: 2015
- Authors: Allie, Naaheeda
- Date: 2015
- Subjects: Internet addiction , Compulsive behavior , Security (Psychology)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3256 , http://hdl.handle.net/10962/d1016395
- Description: In the past two decades, a considerable amount of research has been carried out on the phenomenon of excessive Internet use, variously termed Internet addiction, Internet dependency and problematic Internet use. Despite this, there is still little agreement as to what constitutes this phenomenon, whether it should be considered a clinical disorder or not and what leads to this excessive or maladaptive use. The terminology used in this study is that of Problematic Internet Use (PIU). Several theoretical models have been proposed in the understanding of PIU including personality models, operant conditioning models, social cognitive and cognitive behavioural models (Davis, 2001; LaRose, lin & Eastin, 2003; Young, 1999). A proposed gap in the literature is the lack of studies exploring participant experiences of problematic Internet use. It is for this reason that this study aimed at exploring the experiences of a small sample of individuals with self-identified problematic Internet use. The implications of this phenomenological data for the above-mentioned theoretical models were then reviewed. This study used an Interpretative Phenomenological Analysis (IPA) approach in exploring these aims. A sample of four participants was selected through purposive sampling techniques. Four major themes emerged from the analysis namely: Escapism, Social Insecurity and Validation, Perfectionism and Control. These experiences of participants were also explored in terms of the conceptual models reviewed in order to compare how closely they related to participant experiences. A strong inter-relationship was found between the four themes mentioned above. The Internet appeared to provide a sense of control and validation to these individuals while simultaneously rendering them unable to maintain control of their Internet usage in relation to this. This sense of control was experienced through an escape from negative emotions, offline obligations and at times a dissatisfactory position in reality. Of the four models reviewed, the Social Cognitive model proposed by LaRose et al. (2003) appeared to offer the most relevant understanding of PIU to participant experiences. The presence of maladaptive cognitions also appeared to feature strongly as an underlying factor in participants' PIU, as theorised by cognitive behavioural models (Davis, 2001; Young, 1999) Finally recommendations are made for further more detailed exploration of PIU using interpretative, experiential methods.
- Full Text:
- Date Issued: 2015
An investigation into the nature of mathematical connections selected grade 7 teachers make when teaching fractions : a Namibian case study.
- Authors: Amupolo, Loide M
- Date: 2015
- Subjects: Mathematics -- Study and teaching -- Namibia , Fractions -- Study and teaching -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2016 , http://hdl.handle.net/10962/d1016374
- Description: The general understanding of mathematics as a subject and its implications is, in reality alarmingly low. Evidence of this is evident in learners’ performance and their reaction towards the subject. Fractions as a domain of Mathematics are no exception. The majority of the learners do not learn Fractions comfortably. The causes of this may be varied. However, it is believed that one way of ensuring meaningful teaching and learning is to make use of appropriate connections. The significance and the important role of the teacher in making mathematical connections in learning for understanding are well documented in the literature. This study focuses on the nature of mathematical connections selected Grade 7 teachers make when teaching Fractions, as well as their perceptions of the importance of making such connections. This qualitative case study was conducted in three schools in the Oshana region. The purpose was to investigate how mathematics teachers make connections in fractions. Underpinned by an interpretive paradigm, the study made use of observations and interviews to generate data. The framework borrowed from Businkas’ (2008) study was used in analysing and coding the nature of connections used in the lessons observed. An individual conversation on the nature and perceptions of the connections made in the observed lessons was undertaken with each teacher followed by a focus group discussion that aimed at analysing deeper perceptions on connections. The main findings of the study revealed that teachers made use of all the different types of connections as per Businkas’s framework. The frequency of occurrence showed that Instruction-Oriented Connection and Multiple Representation connections topped the list of connections used. Teachers pointed out that connections to prior knowledge and making multiple representations were most significant, as they related to learners’ existing knowledge and pointed to different ways of solving a problem. The teachers were, however, not familiar with the other connections identified as this was their first experience of interrogating connections. They, however, agreed on the importance of making those connections. The teachers agreed that meaningful connections indeed helped with their conceptual understanding of Mathematics. They believed that connections can increase learners’ interest in school and help reduce negative views of fractions, in particular, and mathematics in general. However, they felt that the limited number of resources, poor teaching approaches and the inability of creating fraction sense may hinder them from making appropriate connections.
- Full Text:
- Date Issued: 2015
- Authors: Amupolo, Loide M
- Date: 2015
- Subjects: Mathematics -- Study and teaching -- Namibia , Fractions -- Study and teaching -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2016 , http://hdl.handle.net/10962/d1016374
- Description: The general understanding of mathematics as a subject and its implications is, in reality alarmingly low. Evidence of this is evident in learners’ performance and their reaction towards the subject. Fractions as a domain of Mathematics are no exception. The majority of the learners do not learn Fractions comfortably. The causes of this may be varied. However, it is believed that one way of ensuring meaningful teaching and learning is to make use of appropriate connections. The significance and the important role of the teacher in making mathematical connections in learning for understanding are well documented in the literature. This study focuses on the nature of mathematical connections selected Grade 7 teachers make when teaching Fractions, as well as their perceptions of the importance of making such connections. This qualitative case study was conducted in three schools in the Oshana region. The purpose was to investigate how mathematics teachers make connections in fractions. Underpinned by an interpretive paradigm, the study made use of observations and interviews to generate data. The framework borrowed from Businkas’ (2008) study was used in analysing and coding the nature of connections used in the lessons observed. An individual conversation on the nature and perceptions of the connections made in the observed lessons was undertaken with each teacher followed by a focus group discussion that aimed at analysing deeper perceptions on connections. The main findings of the study revealed that teachers made use of all the different types of connections as per Businkas’s framework. The frequency of occurrence showed that Instruction-Oriented Connection and Multiple Representation connections topped the list of connections used. Teachers pointed out that connections to prior knowledge and making multiple representations were most significant, as they related to learners’ existing knowledge and pointed to different ways of solving a problem. The teachers were, however, not familiar with the other connections identified as this was their first experience of interrogating connections. They, however, agreed on the importance of making those connections. The teachers agreed that meaningful connections indeed helped with their conceptual understanding of Mathematics. They believed that connections can increase learners’ interest in school and help reduce negative views of fractions, in particular, and mathematics in general. However, they felt that the limited number of resources, poor teaching approaches and the inability of creating fraction sense may hinder them from making appropriate connections.
- Full Text:
- Date Issued: 2015
Understanding how Grade 11 Biology teachers mediate learning of respiration: A Namibian case study
- Authors: Amutenya, Laina N
- Date: 2015
- Subjects: Biology -- Study and teaching (Secondary) -- Namibia , Respiration -- Study and teaching (Secondary) -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2020 , http://hdl.handle.net/10962/d1017331
- Description: The new curriculum in Namibia has introduced a new approach to teaching and learning requiring teachers to make use of learners’ prior everyday knowledge (PEK) including indigenous knowledge (IK) and practical work/activities. It further emphasizes some variations in teaching methods such as; the use of analogies, the use of mind maps, and so forth with the aim to actively involve learners in the learning process and develop skills to solve global challenges. The emphasis is on understanding of knowledge, skills and the will to use them appropriately throughout their lives. The main aim of this study was to understand and document how Biology teachers mediate learning of the topic respiration. Informed by an interpretive paradigm, a qualitative case study was conducted at two secondary schools in the Kunene region. The participants were selected using a convenience sampling. Data were gathered using three main sources, namely, documents, semi-structured interview questions which culminated into a questionnaire and observations. Triangulation was thus used to give credibility, objectivity and validity to the interpretation of the data. Data analysis in this case study involved a multi-stage process of organizing, coding and categorizing, synthesizing and summarizing. The audio recorded lessons were transcribed into text and I analyzed data using a colour coding technique by segmenting and labelling text to identify descriptions and broad themes in the data. Vygotsky’s Mediation of Learning and Social Constructivism in conjunction with Shulman’s Pedagogical Content Knowledge (PCK) informed the data analysis process. Teacher-learner interactions were the main theme for mediation of learning (social constructivist perspective), hence during analysis I paid more attention to moments where interactions evolved and I used PCK to gain insights in teaching and instructional strategies used by teachers. The findings of this study revealed that: 1) teachers endeavor to use a variety of teaching methods such as the use of a mind maps and question and answer method. Learners were keen to ask questions in order to understand this topic. 2) The study also revealed that a lack of practical activities is one of the challenges teachers are faced with. Based on my research findings, I therefore suggest that there is a need for continuous professional development of biology teachers and capacity building in order to improve both their content and pedagogical content knowledge.
- Full Text:
- Date Issued: 2015
- Authors: Amutenya, Laina N
- Date: 2015
- Subjects: Biology -- Study and teaching (Secondary) -- Namibia , Respiration -- Study and teaching (Secondary) -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2020 , http://hdl.handle.net/10962/d1017331
- Description: The new curriculum in Namibia has introduced a new approach to teaching and learning requiring teachers to make use of learners’ prior everyday knowledge (PEK) including indigenous knowledge (IK) and practical work/activities. It further emphasizes some variations in teaching methods such as; the use of analogies, the use of mind maps, and so forth with the aim to actively involve learners in the learning process and develop skills to solve global challenges. The emphasis is on understanding of knowledge, skills and the will to use them appropriately throughout their lives. The main aim of this study was to understand and document how Biology teachers mediate learning of the topic respiration. Informed by an interpretive paradigm, a qualitative case study was conducted at two secondary schools in the Kunene region. The participants were selected using a convenience sampling. Data were gathered using three main sources, namely, documents, semi-structured interview questions which culminated into a questionnaire and observations. Triangulation was thus used to give credibility, objectivity and validity to the interpretation of the data. Data analysis in this case study involved a multi-stage process of organizing, coding and categorizing, synthesizing and summarizing. The audio recorded lessons were transcribed into text and I analyzed data using a colour coding technique by segmenting and labelling text to identify descriptions and broad themes in the data. Vygotsky’s Mediation of Learning and Social Constructivism in conjunction with Shulman’s Pedagogical Content Knowledge (PCK) informed the data analysis process. Teacher-learner interactions were the main theme for mediation of learning (social constructivist perspective), hence during analysis I paid more attention to moments where interactions evolved and I used PCK to gain insights in teaching and instructional strategies used by teachers. The findings of this study revealed that: 1) teachers endeavor to use a variety of teaching methods such as the use of a mind maps and question and answer method. Learners were keen to ask questions in order to understand this topic. 2) The study also revealed that a lack of practical activities is one of the challenges teachers are faced with. Based on my research findings, I therefore suggest that there is a need for continuous professional development of biology teachers and capacity building in order to improve both their content and pedagogical content knowledge.
- Full Text:
- Date Issued: 2015
Regolith mapping and gold geochemical anomalies in the Siguiri Gold Mine of AngloGold Ashanti, Guinea, West Africa
- Authors: Bah, Boubacar
- Date: 2015
- Subjects: AngloGold Ashanti Ltd. , Regolith -- Guinea -- Siguiri (Region) , Gold mines and mining -- Guinea -- Siguiri (Region) , Geochemical surveys -- Guinea -- Siguiri (Region) , Soil surveys -- Geochemical methods -- Guinea -- Siguiri (Region) , Kriging
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5090 , http://hdl.handle.net/10962/d1019878
- Description: Gold exploration in the laterite terrains of the Siguiri basin (Guinea-West Africa) is discussed in this thesis. It seeks to propose and develop effective and reliable geochemical exploration techniques applied in such laterite terrains. The study is also intended to investigate and provide some geological clues as to why, in some target areas, the reconnaissance test drilling across the geochemical anomalies couldn’t intersect economic gold mineralisation. Targets were generated based on soil geochemical results, some of which were drilled without delivering economic discoveries even on areas with strong and consistent geochemical signatures. To find the failure and define the appropriate methods to be used is the core of the thesis. More importantly, the geological observation is aimed at sourcing and establishing the nature and validity of geochemical anomalies within the license area and their relationship with the underlying lithologies and structural networks. The geological field work conducted during this study is mostly based on regolith and surface geological mapping. The thick laterite cover, deep weathering, bedrock geology, gold geochemistry (the gold geochemical anomalous results are defined according to historical data before 2007), soil formations and variations in climate conditions are emphasized to illustrate the importance of mineral element mobility and dispersion in the weathering profiles. The knowledge and experience in regolith geochemistry and regolith mapping provide the advantage to exploration geologists. The depletion of ore resources and reserves in Siguiri and the continuous decline of the gold price in comparison to the complexity of exploring for gold are demanding more scientific-related thoughts and techniques to be integrated in the available geological, geochemical and geophysical information so as to reduce costs. The integration of good exploration strategy and technique may result in the possibility of making viable discoveries in this highly competitive geological environment where the mineral resources become depleted every day.
- Full Text:
- Date Issued: 2015
- Authors: Bah, Boubacar
- Date: 2015
- Subjects: AngloGold Ashanti Ltd. , Regolith -- Guinea -- Siguiri (Region) , Gold mines and mining -- Guinea -- Siguiri (Region) , Geochemical surveys -- Guinea -- Siguiri (Region) , Soil surveys -- Geochemical methods -- Guinea -- Siguiri (Region) , Kriging
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5090 , http://hdl.handle.net/10962/d1019878
- Description: Gold exploration in the laterite terrains of the Siguiri basin (Guinea-West Africa) is discussed in this thesis. It seeks to propose and develop effective and reliable geochemical exploration techniques applied in such laterite terrains. The study is also intended to investigate and provide some geological clues as to why, in some target areas, the reconnaissance test drilling across the geochemical anomalies couldn’t intersect economic gold mineralisation. Targets were generated based on soil geochemical results, some of which were drilled without delivering economic discoveries even on areas with strong and consistent geochemical signatures. To find the failure and define the appropriate methods to be used is the core of the thesis. More importantly, the geological observation is aimed at sourcing and establishing the nature and validity of geochemical anomalies within the license area and their relationship with the underlying lithologies and structural networks. The geological field work conducted during this study is mostly based on regolith and surface geological mapping. The thick laterite cover, deep weathering, bedrock geology, gold geochemistry (the gold geochemical anomalous results are defined according to historical data before 2007), soil formations and variations in climate conditions are emphasized to illustrate the importance of mineral element mobility and dispersion in the weathering profiles. The knowledge and experience in regolith geochemistry and regolith mapping provide the advantage to exploration geologists. The depletion of ore resources and reserves in Siguiri and the continuous decline of the gold price in comparison to the complexity of exploring for gold are demanding more scientific-related thoughts and techniques to be integrated in the available geological, geochemical and geophysical information so as to reduce costs. The integration of good exploration strategy and technique may result in the possibility of making viable discoveries in this highly competitive geological environment where the mineral resources become depleted every day.
- Full Text:
- Date Issued: 2015
An ergonomics intervention study into the physiological, perceptual and productivity effects of three citrus harvesting bag designs in the Eastern Cape of South Africa : a combined laboratory and field approach
- Bassey-Duke, Elizabeth Misan
- Authors: Bassey-Duke, Elizabeth Misan
- Date: 2015
- Subjects: Citrus -- Harvesting -- South Africa -- Eastern Cape , Lifting and carrying -- South Africa -- Eastern Cape , Manual work -- South Africa -- Eastern Cape , Blue collar workers -- South Africa -- Eastern Cape , Work -- Physiological aspects , Human mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5176 , http://hdl.handle.net/10962/d1018908
- Description: Background: Agriculture plays a vital role in the economy of any industrially developing country, including South Africa. In the Eastern Cape of South Africa citrus farming is a significant contributor to the local economy (Johnson et al., 2005). The harvesting phase of citrus farming is performed manually and exposes workers to physical risks, which can lead to the development of musculoskeletal disorders. In particular, the standard harvesting bag comprises of a single shoulder strap and promotes asymmetrical load carriage which results in shoulder and lower back pain complaints. The current study compared the physiological (EMG), perceptual (RPE), usability (PUEU) and productivity effects of two new harvesting bag designs (a hip belt and a backpack bag design) to the standard harvesting bag design. This was performed in a laboratory as well as a field setting. Methods (Laboratory phase): 36 participants (12 males and 24 females) were assigned to one worker group. The “tall ladder worker” group was comprised of only males and the “step ladder worker” and “ground worker” group of females. Each participant was required to simulate a citrus harvesting task while utilizing each of the bag designs on different days. On each day/test session, participants performed three harvesting cycles. Muscle activity was measured throughout the entire testing session and RPE were recorded at the end of each cycle. Results (Laboratory phase): The EMG and RPE results indicate that the backpack design was the most ideal design to reduce asymmetry, while the standard harvesting bag design was the worst. Although not significant, there was greater muscle asymmetry (p=0.109) and a significantly higher perceived exertion when using the standard bag (p=0.0004), in comparison to using the backpack. Methods (Field phase): 17 Xhosa-speaking citrus harvesters (6 females and 11 males) participated in this study. Each harvester worked with one of the three bag designs on a different day. Productivity of each worker was assessed every hour by recording the number of bags filled with fruit and at the end of the shift. A Perceived Usefulness & Ease of Use questionnaire was presented to each participant to obtain feedback on worker acceptance to the new bag designs. Results (Field phase): A general trend in support of the hip belt bag design over the other two bag designs were found, even within the different worker demographic groups (age, sex and worker experience). The workers perceived less exertion (7.98 ± 1.86) and were more productive (9.90 ± 2.11 bags/hour) when using the hip belt design; they also found this bag the most useful (1.02 ± 0.09) and easy to use (1.07 ± 0.25). In contrast, the backpack bag design had significantly poorer responses when compared to the other two bag designs and this was evident in all the dependent variables assessed (RPE, productivity and PUEU). Conclusion: The results from the laboratory phase supported the expectation that the backpack bag design reduces asymmetry and hence, is more suitable than the standard harvesting bag. However, results from the field show that the hip belt bag design was the most preferred and the backpack was the least preferred. Bao & Shahnavaz (1989) highlight the need for ergonomics researcher to convey laboratory findings into the field context. However, as shown by the current study, there are numerous challenges associated with field work, making it difficult for laboratory findings to be successfully conveyed to the field. Limitations and Recommendations: For the laboratory phase of the project, no biomechanical and cardiovascular responses were assessed. However, for a holistic approach, these variables should be considered in future studies. Due to high variability from one harvesting cycle to another, more than three harvesting cycles should also be performed to accurately replicate the harvesting process as done in the field over extended durations of time. For the field phase, data should be collected from more than one citrus farm and thus a larger sample size could be obtained. This would improve the validity of the study. In addition to this, data should be collected for a full working day, especially if environmental conditions are not a hindrance, as well as for a whole season, since workloads vary, depending on the time of the harvesting season. , Name on Graduation Programme: Bassey-Duke, Elizabeth Missan
- Full Text:
- Date Issued: 2015
- Authors: Bassey-Duke, Elizabeth Misan
- Date: 2015
- Subjects: Citrus -- Harvesting -- South Africa -- Eastern Cape , Lifting and carrying -- South Africa -- Eastern Cape , Manual work -- South Africa -- Eastern Cape , Blue collar workers -- South Africa -- Eastern Cape , Work -- Physiological aspects , Human mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5176 , http://hdl.handle.net/10962/d1018908
- Description: Background: Agriculture plays a vital role in the economy of any industrially developing country, including South Africa. In the Eastern Cape of South Africa citrus farming is a significant contributor to the local economy (Johnson et al., 2005). The harvesting phase of citrus farming is performed manually and exposes workers to physical risks, which can lead to the development of musculoskeletal disorders. In particular, the standard harvesting bag comprises of a single shoulder strap and promotes asymmetrical load carriage which results in shoulder and lower back pain complaints. The current study compared the physiological (EMG), perceptual (RPE), usability (PUEU) and productivity effects of two new harvesting bag designs (a hip belt and a backpack bag design) to the standard harvesting bag design. This was performed in a laboratory as well as a field setting. Methods (Laboratory phase): 36 participants (12 males and 24 females) were assigned to one worker group. The “tall ladder worker” group was comprised of only males and the “step ladder worker” and “ground worker” group of females. Each participant was required to simulate a citrus harvesting task while utilizing each of the bag designs on different days. On each day/test session, participants performed three harvesting cycles. Muscle activity was measured throughout the entire testing session and RPE were recorded at the end of each cycle. Results (Laboratory phase): The EMG and RPE results indicate that the backpack design was the most ideal design to reduce asymmetry, while the standard harvesting bag design was the worst. Although not significant, there was greater muscle asymmetry (p=0.109) and a significantly higher perceived exertion when using the standard bag (p=0.0004), in comparison to using the backpack. Methods (Field phase): 17 Xhosa-speaking citrus harvesters (6 females and 11 males) participated in this study. Each harvester worked with one of the three bag designs on a different day. Productivity of each worker was assessed every hour by recording the number of bags filled with fruit and at the end of the shift. A Perceived Usefulness & Ease of Use questionnaire was presented to each participant to obtain feedback on worker acceptance to the new bag designs. Results (Field phase): A general trend in support of the hip belt bag design over the other two bag designs were found, even within the different worker demographic groups (age, sex and worker experience). The workers perceived less exertion (7.98 ± 1.86) and were more productive (9.90 ± 2.11 bags/hour) when using the hip belt design; they also found this bag the most useful (1.02 ± 0.09) and easy to use (1.07 ± 0.25). In contrast, the backpack bag design had significantly poorer responses when compared to the other two bag designs and this was evident in all the dependent variables assessed (RPE, productivity and PUEU). Conclusion: The results from the laboratory phase supported the expectation that the backpack bag design reduces asymmetry and hence, is more suitable than the standard harvesting bag. However, results from the field show that the hip belt bag design was the most preferred and the backpack was the least preferred. Bao & Shahnavaz (1989) highlight the need for ergonomics researcher to convey laboratory findings into the field context. However, as shown by the current study, there are numerous challenges associated with field work, making it difficult for laboratory findings to be successfully conveyed to the field. Limitations and Recommendations: For the laboratory phase of the project, no biomechanical and cardiovascular responses were assessed. However, for a holistic approach, these variables should be considered in future studies. Due to high variability from one harvesting cycle to another, more than three harvesting cycles should also be performed to accurately replicate the harvesting process as done in the field over extended durations of time. For the field phase, data should be collected from more than one citrus farm and thus a larger sample size could be obtained. This would improve the validity of the study. In addition to this, data should be collected for a full working day, especially if environmental conditions are not a hindrance, as well as for a whole season, since workloads vary, depending on the time of the harvesting season. , Name on Graduation Programme: Bassey-Duke, Elizabeth Missan
- Full Text:
- Date Issued: 2015
The cognitive rehabilitation of a sample of children living with HIV : a specific focus on the cognitive rehabilitation of sustained attention
- Authors: Basterfield, Candice
- Date: 2015
- Subjects: HIV-positive children -- Rehabilitation , Antiretroviral agents , HIV (Viruses) -- Side effects , Brain damage -- Patients -- Rehabilitation , Cognition disorders -- Patients -- Rehabilitation
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3258 , http://hdl.handle.net/10962/d1017881
- Description: Pharmacological interventions to treat Human Immunodeficiency Virus (HIV) with antiretrovirals (ARVs), have dramatically improved the survival rates of HIV positive children maturing into adulthood. However, HIV-associated neurocognitive decline still persists in the era of ARVs. Within the framework of brain plasticity, a number of researchers have begun to assess the feasibility of cognitive rehabilitation therapy as a complement to ARVs to reverse neurocognitive decline as a result of HIV (e.g., Becker et al., 2012). Only one study has been conducted in South Africa, by Zondo & Mulder (2014), assessing the efficacy of cognitive rehabilitation in a paediatric sample. The current research builds on the above mentioned study by implementing an experimental approach to examine the effect of cognitive rehabilitation in a sample of both HIV positive and HIV negative children. Five HIV positive and six HIV negative children were assigned to either an experimental or control group. The experimental group underwent two months of cognitive rehabilitation therapy remediating sustained attention, whereas the control group took part in placebo activities. Sustained attention measures were taken before and after the intervention training sessions, using a sustained attention subtest from the Test of Everyday Attention for Children (TEA-CH). A Mann Whitney U Test revealed that the experimental group (Mdn=38.50) did not differ significantly from the control group (Mdn = 37.00) after the cognitive rehabilitation intervention, U=12.00, z= -.55, p= .66, r= -.17. But a Wilcoxon Signed Rank Test found that there was a significant improvement from pretest scores (Mdn=31.00) to posttest scores (Mdn=38.00) following the rehabilitation for HIV positive participants in the sample, T=15.00, z = -2.02, p= .04, r= -.90. This raises the possibility that cognitive rehabilitation could be used as a low cost intervention in underdeveloped contexts
- Full Text:
- Date Issued: 2015
- Authors: Basterfield, Candice
- Date: 2015
- Subjects: HIV-positive children -- Rehabilitation , Antiretroviral agents , HIV (Viruses) -- Side effects , Brain damage -- Patients -- Rehabilitation , Cognition disorders -- Patients -- Rehabilitation
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3258 , http://hdl.handle.net/10962/d1017881
- Description: Pharmacological interventions to treat Human Immunodeficiency Virus (HIV) with antiretrovirals (ARVs), have dramatically improved the survival rates of HIV positive children maturing into adulthood. However, HIV-associated neurocognitive decline still persists in the era of ARVs. Within the framework of brain plasticity, a number of researchers have begun to assess the feasibility of cognitive rehabilitation therapy as a complement to ARVs to reverse neurocognitive decline as a result of HIV (e.g., Becker et al., 2012). Only one study has been conducted in South Africa, by Zondo & Mulder (2014), assessing the efficacy of cognitive rehabilitation in a paediatric sample. The current research builds on the above mentioned study by implementing an experimental approach to examine the effect of cognitive rehabilitation in a sample of both HIV positive and HIV negative children. Five HIV positive and six HIV negative children were assigned to either an experimental or control group. The experimental group underwent two months of cognitive rehabilitation therapy remediating sustained attention, whereas the control group took part in placebo activities. Sustained attention measures were taken before and after the intervention training sessions, using a sustained attention subtest from the Test of Everyday Attention for Children (TEA-CH). A Mann Whitney U Test revealed that the experimental group (Mdn=38.50) did not differ significantly from the control group (Mdn = 37.00) after the cognitive rehabilitation intervention, U=12.00, z= -.55, p= .66, r= -.17. But a Wilcoxon Signed Rank Test found that there was a significant improvement from pretest scores (Mdn=31.00) to posttest scores (Mdn=38.00) following the rehabilitation for HIV positive participants in the sample, T=15.00, z = -2.02, p= .04, r= -.90. This raises the possibility that cognitive rehabilitation could be used as a low cost intervention in underdeveloped contexts
- Full Text:
- Date Issued: 2015
Case study : profitability drivers in the South African airline industry : a comparative analysis of SAA and Comair
- Authors: Batidzirai, Davison Herbert
- Date: 2015
- Subjects: South African Airways , Comair Limited , Airlines -- South Africa , Corporate profits -- South Africa , Organizational effectiveness -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:846 , http://hdl.handle.net/10962/d1017191
- Full Text:
- Date Issued: 2015
- Authors: Batidzirai, Davison Herbert
- Date: 2015
- Subjects: South African Airways , Comair Limited , Airlines -- South Africa , Corporate profits -- South Africa , Organizational effectiveness -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:846 , http://hdl.handle.net/10962/d1017191
- Full Text:
- Date Issued: 2015
Short-term changes to the life history of shad, Pomatomus saltatrix (Perciformes: Pomatomidae), in Southern Angola
- Authors: Bealey, Roy Steven John
- Date: 2015
- Subjects: Shad -- Angola , Bluefish -- Angola , Bluefish -- Climatic factors -- Angola , Bluefish -- Effect of temperature on -- Angola , Bluefish -- Effect of global warming on -- Angola , Bluefish -- Effect of fishing on -- Angola , Bluefish -- Life cycles , Pomatomidae -- Angola , Fishery management -- Angola , Climatic changes -- Angola
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5379 , http://hdl.handle.net/10962/d1017211
- Description: A general lack of biological information is hampering the effective management of Angola’s fisheries. While this lack of information is largely a result of the country’s extended civil war that ended in 2002, the subsequent rapid expansion of fisheries is most likely impacting fish abundance and influencing the biology of this regions fishes. Besides the influence of fisheries, the southern Angolan coastal region is considered to be a climate change “hotspot” due to rapidly (>0.8°C/decade) increasing water temperatures. These changes are thought to drive further changes to the biology of fishes. It is therefore critical to provide baseline biological information and to identify the impacts of exploitation and warming on the biology of southern Angolan fishes. Pomatomus saltatrix is a warm-temperate marine fish species that forms an important component of fisheries throughout its broad distribution. P. saltatrix is a migratory predator that displays variable growth and maturity schedules. Typically it is heavily targeted in a range of coastal fisheries of Angola and is therefore an ideal candidate to study the biological impacts of exploitation and climate change. The aim of this study was to provide the first description of P. saltatrix biology in Angola and examine recent changes of the species biological parameters in an attempt to uncouple fishery driven from climate driven changes. Samples of P. saltatrix were collected monthly using standardised biological methods from June 2005 to December 2006 (period 1) and from June 2012 to February 2013 (period 2). The average (508mm – 1st period, 462mm – 2nd period) and maximum (760mm – 1st period, 746mm – 2nd period) size of P. saltatrix was smaller during the second period to suggest selective overharvesting of large individuals by developing fisheries. Angolan P. saltatrix grew very rapidly in their first year and thereafter, relatively slowly when compared to other populations globally. However, fish grew faster (ω = 103 – 1st period, ω = 124 – 2nd period), matured at a larger size (303mm - 1st period, 336mm - 2nd period) and younger age (0.83 years - 1st period, 0.67 years – 2nd period) during the second period. Peaks in reproductive activity remained similar (November) during both periods but a temperature anomaly appears to have influenced spawning during period 2. Sardinella aurita was the dominant prey during both periods but a greater dependence upon mugilids was observed during the second period. Although the changes in life history were not statistically significant, the faster growth observed during period two could be attributed to both increasing temperature and/or exploitation. Fishes generally grow faster, mature smaller and attain a smaller maximum size in warmer temperatures. Fisheries targeting small and large specimens of a species (as observed in this study) largely have the same impacts as ocean warming. With rapidly increasing water temperatures and exploitation rates, faster growth and earlier maturation of P. saltatrix populations will mitigate the impacts of exploitation in the short-term. However, the sustainability of Angola’s P. saltatrix stock is questionable as phenotypic adaptation will have a limited thermal scope and overexploitation will, like in all fisheries, negatively influence recruitment. Ultimately, strict monitoring, regulation and control will be necessary to ensure the sustainability of the P. saltatrix resource in Angola as it continues to face increasing anthropogenic and environmental pressures. Management guidelines and future research suggestions are therefore outlined with reference to the results of analyses conducted during this study.
- Full Text:
- Date Issued: 2015
- Authors: Bealey, Roy Steven John
- Date: 2015
- Subjects: Shad -- Angola , Bluefish -- Angola , Bluefish -- Climatic factors -- Angola , Bluefish -- Effect of temperature on -- Angola , Bluefish -- Effect of global warming on -- Angola , Bluefish -- Effect of fishing on -- Angola , Bluefish -- Life cycles , Pomatomidae -- Angola , Fishery management -- Angola , Climatic changes -- Angola
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5379 , http://hdl.handle.net/10962/d1017211
- Description: A general lack of biological information is hampering the effective management of Angola’s fisheries. While this lack of information is largely a result of the country’s extended civil war that ended in 2002, the subsequent rapid expansion of fisheries is most likely impacting fish abundance and influencing the biology of this regions fishes. Besides the influence of fisheries, the southern Angolan coastal region is considered to be a climate change “hotspot” due to rapidly (>0.8°C/decade) increasing water temperatures. These changes are thought to drive further changes to the biology of fishes. It is therefore critical to provide baseline biological information and to identify the impacts of exploitation and warming on the biology of southern Angolan fishes. Pomatomus saltatrix is a warm-temperate marine fish species that forms an important component of fisheries throughout its broad distribution. P. saltatrix is a migratory predator that displays variable growth and maturity schedules. Typically it is heavily targeted in a range of coastal fisheries of Angola and is therefore an ideal candidate to study the biological impacts of exploitation and climate change. The aim of this study was to provide the first description of P. saltatrix biology in Angola and examine recent changes of the species biological parameters in an attempt to uncouple fishery driven from climate driven changes. Samples of P. saltatrix were collected monthly using standardised biological methods from June 2005 to December 2006 (period 1) and from June 2012 to February 2013 (period 2). The average (508mm – 1st period, 462mm – 2nd period) and maximum (760mm – 1st period, 746mm – 2nd period) size of P. saltatrix was smaller during the second period to suggest selective overharvesting of large individuals by developing fisheries. Angolan P. saltatrix grew very rapidly in their first year and thereafter, relatively slowly when compared to other populations globally. However, fish grew faster (ω = 103 – 1st period, ω = 124 – 2nd period), matured at a larger size (303mm - 1st period, 336mm - 2nd period) and younger age (0.83 years - 1st period, 0.67 years – 2nd period) during the second period. Peaks in reproductive activity remained similar (November) during both periods but a temperature anomaly appears to have influenced spawning during period 2. Sardinella aurita was the dominant prey during both periods but a greater dependence upon mugilids was observed during the second period. Although the changes in life history were not statistically significant, the faster growth observed during period two could be attributed to both increasing temperature and/or exploitation. Fishes generally grow faster, mature smaller and attain a smaller maximum size in warmer temperatures. Fisheries targeting small and large specimens of a species (as observed in this study) largely have the same impacts as ocean warming. With rapidly increasing water temperatures and exploitation rates, faster growth and earlier maturation of P. saltatrix populations will mitigate the impacts of exploitation in the short-term. However, the sustainability of Angola’s P. saltatrix stock is questionable as phenotypic adaptation will have a limited thermal scope and overexploitation will, like in all fisheries, negatively influence recruitment. Ultimately, strict monitoring, regulation and control will be necessary to ensure the sustainability of the P. saltatrix resource in Angola as it continues to face increasing anthropogenic and environmental pressures. Management guidelines and future research suggestions are therefore outlined with reference to the results of analyses conducted during this study.
- Full Text:
- Date Issued: 2015
Appraising the appraisal framework: evidence from Grahamstown property advertisements
- Authors: Beangstrom, Tracy
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/54744 , vital:26608
- Description: This thesis considers how interpersonal meaning choices in property advertisements are best reflected in a context of constraint in Grahamstown, South Africa, using and appraising Martin & White’s (2005) APPRAISAL Framework. The study is comparative in two senses since the data is analysed using Martin & White’s (2005) APPRAISAL Framework and a revision to it, and property advertisements from two competing estate agencies are analysed: Remax Frontier Properties and Pam Golding Properties. An initial strict application of Martin & White’s (2005) framework is followed by a second, based on analyst difficulties and framework limitations experienced in the first analysis, as well as those experienced by other researchers. Revisions to the original framework include added ‘local’, context-driven features and sub-categories: Exclusivity and Convenience in Attitude, a Scale of Intensity in Graduation, and a category ‘Invite’ in Engagement. These enable a richer, more detailed account of the alignment strategies and interpersonal micro-politics at play in the property advertisements than is possible using the original framework. Findings from the analyses reveal four facts of note. Firstly, that while the original Martin & White (2005) APPRAISAL Framework captures a general level of interpersonal meaning in the data, it does so more fully when it includes contextual and contextually-driven categories that are informed by local knowledge. Secondly, two levels of meaning are expressed in the data. One is aimed at an ‘external’ audience; the other, truer, fuller and more contentious, is aimed at what appears to be the intended audience only. Thirdly, and relatedly, specific contextual and cultural knowledge is needed by the intended audience to access the intended meaning. Fourthly, both estate agencies promote values of high prestige, exclusivity, elitism and wealth as their intended meaning to align a like-minded audience, although Remax Frontier Properties attribute these values to location and features of the home to a greater extent than Pam Golding Properties, who place greater emphasis on the size of the home. The thesis suggests further avenues for research into the discourse of property advertising, as well as into overcoming certain context-specific limitations of the APPRAISAL Framework.
- Full Text:
- Date Issued: 2015
- Authors: Beangstrom, Tracy
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/54744 , vital:26608
- Description: This thesis considers how interpersonal meaning choices in property advertisements are best reflected in a context of constraint in Grahamstown, South Africa, using and appraising Martin & White’s (2005) APPRAISAL Framework. The study is comparative in two senses since the data is analysed using Martin & White’s (2005) APPRAISAL Framework and a revision to it, and property advertisements from two competing estate agencies are analysed: Remax Frontier Properties and Pam Golding Properties. An initial strict application of Martin & White’s (2005) framework is followed by a second, based on analyst difficulties and framework limitations experienced in the first analysis, as well as those experienced by other researchers. Revisions to the original framework include added ‘local’, context-driven features and sub-categories: Exclusivity and Convenience in Attitude, a Scale of Intensity in Graduation, and a category ‘Invite’ in Engagement. These enable a richer, more detailed account of the alignment strategies and interpersonal micro-politics at play in the property advertisements than is possible using the original framework. Findings from the analyses reveal four facts of note. Firstly, that while the original Martin & White (2005) APPRAISAL Framework captures a general level of interpersonal meaning in the data, it does so more fully when it includes contextual and contextually-driven categories that are informed by local knowledge. Secondly, two levels of meaning are expressed in the data. One is aimed at an ‘external’ audience; the other, truer, fuller and more contentious, is aimed at what appears to be the intended audience only. Thirdly, and relatedly, specific contextual and cultural knowledge is needed by the intended audience to access the intended meaning. Fourthly, both estate agencies promote values of high prestige, exclusivity, elitism and wealth as their intended meaning to align a like-minded audience, although Remax Frontier Properties attribute these values to location and features of the home to a greater extent than Pam Golding Properties, who place greater emphasis on the size of the home. The thesis suggests further avenues for research into the discourse of property advertising, as well as into overcoming certain context-specific limitations of the APPRAISAL Framework.
- Full Text:
- Date Issued: 2015
Structural controls of gold mineralisation in Seguelen pit of Siguiri gold mine, Guinea
- Authors: Beavogui, Massa
- Date: 2015
- Subjects: AngloGold Ashanti Ltd. , Gold mines and mining -- Guinea -- Siguiri (Region) , Geochemical surveys -- Guinea -- Siguiri (Region) , Geology, Structural -- Guinea -- Siguiri (Region) , Faults (Geology) -- Guinea -- Siguiri (Region) , Folds (Geology) -- Guinea -- Siguiri (Region) , Turbidites -- Guinea -- Siguiri (Region) , Metamorphism (Geology) -- Guinea -- Siguiri (Region) , Hydrothermal alteration -- Guinea -- Siguiri (Region)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5091 , http://hdl.handle.net/10962/d1019879
- Description: The present study provides the results of detailed mapping and analysis of structures encountered in Seguelen pit of Siguiri gold mine, Guinea, where the Siguiri mine is geo-tectonically located in the Baoulé-Mossi domain of Man Shield in West African craton. The gold deposit is hosted in low-grade metamorphic sediments of turbidites sequences which form part of the Lower Proterozoic of Birimian Super group. Three rock formations of Balato, Fatoya and Kintinian underlay the overall pits. The Siguiri gold mine is characterized by the deep weathering profile, developed over the rocks reaching 200 m below the surface in some areas and often capped by the lateritic gravel or duricrust. The rock formations at Seguelen area are characterised by strong bedding monotonously dipping towards SW and trending NW-SE. The lithology of the host rocks has strong control on the disseminated mineralisation throughout the deposit. Two domains of rock formations are clearly distinguished at Seguelen: Fatoya Formation(Ffm) domain ; and Kintinian Formation (Kfm) domain. The two domains are separated by a contact zone of 1.7 m wide parallel to bedding and characterised by the presence of quartz fragments as well as thinly sheeted shale and black shale. This contact zone is identified as disconformity. The major tectonic deformation which has affected the region is known as D2 corresponding to the Eburnean orogeny. The major D2 related structures is the regional thrust striking N-S over an area of 12 km long and 3 km wide and within which corridors all Siguiri gold Mine open pits are located. In the N-S trending structures, there is east-northeast shortening and north-northwest extension. There is pervasive hydrothermal alteration (carbonatization and sideritization) and supergene alteration in the all pits. The hydrothermal alteration attests the intensity of hydrothermal fluid-flow over the host rocks. The hydrothermal fluids flowed along the fractures and within the wall rocks through bedding plans to form numerous auriferous quartz veins bearing disseminated sulphides through chemical reaction between fluids and wall rocks, which are remarkable at Seguelen pit. Three quartz vein sets are distinguished at Seguelen: NNE-SSW quartz vein set NE-SW quartz vein set NW-SE quartz vein set The NE-SW and NNE-SSW quartz veins are often lenticular and associated with the bulk mineralisation.
- Full Text:
- Date Issued: 2015
- Authors: Beavogui, Massa
- Date: 2015
- Subjects: AngloGold Ashanti Ltd. , Gold mines and mining -- Guinea -- Siguiri (Region) , Geochemical surveys -- Guinea -- Siguiri (Region) , Geology, Structural -- Guinea -- Siguiri (Region) , Faults (Geology) -- Guinea -- Siguiri (Region) , Folds (Geology) -- Guinea -- Siguiri (Region) , Turbidites -- Guinea -- Siguiri (Region) , Metamorphism (Geology) -- Guinea -- Siguiri (Region) , Hydrothermal alteration -- Guinea -- Siguiri (Region)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5091 , http://hdl.handle.net/10962/d1019879
- Description: The present study provides the results of detailed mapping and analysis of structures encountered in Seguelen pit of Siguiri gold mine, Guinea, where the Siguiri mine is geo-tectonically located in the Baoulé-Mossi domain of Man Shield in West African craton. The gold deposit is hosted in low-grade metamorphic sediments of turbidites sequences which form part of the Lower Proterozoic of Birimian Super group. Three rock formations of Balato, Fatoya and Kintinian underlay the overall pits. The Siguiri gold mine is characterized by the deep weathering profile, developed over the rocks reaching 200 m below the surface in some areas and often capped by the lateritic gravel or duricrust. The rock formations at Seguelen area are characterised by strong bedding monotonously dipping towards SW and trending NW-SE. The lithology of the host rocks has strong control on the disseminated mineralisation throughout the deposit. Two domains of rock formations are clearly distinguished at Seguelen: Fatoya Formation(Ffm) domain ; and Kintinian Formation (Kfm) domain. The two domains are separated by a contact zone of 1.7 m wide parallel to bedding and characterised by the presence of quartz fragments as well as thinly sheeted shale and black shale. This contact zone is identified as disconformity. The major tectonic deformation which has affected the region is known as D2 corresponding to the Eburnean orogeny. The major D2 related structures is the regional thrust striking N-S over an area of 12 km long and 3 km wide and within which corridors all Siguiri gold Mine open pits are located. In the N-S trending structures, there is east-northeast shortening and north-northwest extension. There is pervasive hydrothermal alteration (carbonatization and sideritization) and supergene alteration in the all pits. The hydrothermal alteration attests the intensity of hydrothermal fluid-flow over the host rocks. The hydrothermal fluids flowed along the fractures and within the wall rocks through bedding plans to form numerous auriferous quartz veins bearing disseminated sulphides through chemical reaction between fluids and wall rocks, which are remarkable at Seguelen pit. Three quartz vein sets are distinguished at Seguelen: NNE-SSW quartz vein set NE-SW quartz vein set NW-SE quartz vein set The NE-SW and NNE-SSW quartz veins are often lenticular and associated with the bulk mineralisation.
- Full Text:
- Date Issued: 2015
The role of Stress Inducible Protein 1 (STI1) in the regulation of actin dynamics
- Authors: Beckley, Samantha Joy
- Date: 2015
- Subjects: Heat shock proteins , Molecular chaperones , Actin , Microfilament proteins , Cell migration , Adenosine triphosphatase , Metastasis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193941 , vital:45409
- Description: Stress-inducible protein 1 (STI1) otherwise known as Hop (Hsp70/Hsp90 organising protein) is a highly conserved abundant co-chaperone of the Hsp70 and Hsp90 chaperones. STI1 acts as an adapter protein, where it regulates the transfer of protein substrates from Hsp70 to Hsp90 during the assembly of a number of chaperone-client protein complexes. The role of STI1 associating independently with non-chaperone proteins has become increasingly prominent. Recent data from colocalisation and co-sedimentation analyses in our laboratory suggested a direct interaction between STI1 and the cytoskeletal protein, actin. However, there was a lack of information on the motifs which mediated this interaction, as well as the exact role of STI1 in the regulation of cytoskeletal dynamics. Two putative actin binding motifs, DAYKKK (within the TPR2A domain) and a polyproline region (after the DP1 domain), were identified in mammalian STI1. Our data from in vitro interaction studies including surface plasmon resonance and high speed co-sedimentation assays suggested that both TPR1 and TPR2AB were required for the STI1-actin interaction, and peptides corresponding to either the DAYKKK or the polyproline motif, alone or in combination, could not block the STI1-actin interaction. Full length mSTI1 was shown to have ATPase activity and when combined with actin an increase in ATPase activity was seen. Ex vivo studies using STI1 knockdown shRNA HEK293T cells and non-targeting control shRNA HEK293T cells showed a change of F-actin morphology as well as reduction in levels of actin-binding proteins profilin, cofilin and tubulin in the STI1 knockdown cells. These data extend our understanding of the role of STI1 in regulating actin dynamics and may have implications for cell migration. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2015
- Full Text:
- Date Issued: 2015
- Authors: Beckley, Samantha Joy
- Date: 2015
- Subjects: Heat shock proteins , Molecular chaperones , Actin , Microfilament proteins , Cell migration , Adenosine triphosphatase , Metastasis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193941 , vital:45409
- Description: Stress-inducible protein 1 (STI1) otherwise known as Hop (Hsp70/Hsp90 organising protein) is a highly conserved abundant co-chaperone of the Hsp70 and Hsp90 chaperones. STI1 acts as an adapter protein, where it regulates the transfer of protein substrates from Hsp70 to Hsp90 during the assembly of a number of chaperone-client protein complexes. The role of STI1 associating independently with non-chaperone proteins has become increasingly prominent. Recent data from colocalisation and co-sedimentation analyses in our laboratory suggested a direct interaction between STI1 and the cytoskeletal protein, actin. However, there was a lack of information on the motifs which mediated this interaction, as well as the exact role of STI1 in the regulation of cytoskeletal dynamics. Two putative actin binding motifs, DAYKKK (within the TPR2A domain) and a polyproline region (after the DP1 domain), were identified in mammalian STI1. Our data from in vitro interaction studies including surface plasmon resonance and high speed co-sedimentation assays suggested that both TPR1 and TPR2AB were required for the STI1-actin interaction, and peptides corresponding to either the DAYKKK or the polyproline motif, alone or in combination, could not block the STI1-actin interaction. Full length mSTI1 was shown to have ATPase activity and when combined with actin an increase in ATPase activity was seen. Ex vivo studies using STI1 knockdown shRNA HEK293T cells and non-targeting control shRNA HEK293T cells showed a change of F-actin morphology as well as reduction in levels of actin-binding proteins profilin, cofilin and tubulin in the STI1 knockdown cells. These data extend our understanding of the role of STI1 in regulating actin dynamics and may have implications for cell migration. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2015
- Full Text:
- Date Issued: 2015
Conditions enabling or constraining the exercise of agency among new academics in higher education, conducive to the social inclusion of students
- Authors: Behari-Leak, Kasturi
- Date: 2015
- Subjects: Social integration -- South Africa , Students -- South Africa -- Social conditions , Educational change -- South Africa , College teachers -- South Africa , Education, Higher -- South Africa , Critical realism , Social realism , Agent (Philosophy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1333 , http://hdl.handle.net/10962/d1020295
- Description: This study, which is part of a National Research Foundation project on Social Inclusion in Higher Education (HE), focuses on the exercise of agency among new academics, conducive to the social inclusion of students. Transitioning from varied entry points into higher education, new academics face numerous challenges as they embed themselves in disciplinary and institutional contexts. Given the complexity and contested nature of the current higher education landscape, new academics are especially vulnerable. Using Roy Bhaskar’s critical realism as meta-theoretical framing and Margaret Archer’s social realist theory, with its methodological focus on analytical dualism and morphogenesis, this study offers a social realist account of how new academics engage with enabling and constraining conditions at institutional, faculty, departmental and classroom levels. Through an analysis of six individual narratives of mediation, this study explicates and exemplifies the range of agential choices exercised by new academics to mediate their contested spaces. A nuanced social and critical account of the material, ideational and agential conditions in HE shows that the courses of action taken by these new academics are driven through their concerns, commitments and projects in higher education. Yet, despite the university’s espousal of embracing change, the current induction and transition of new academics is inadequate to the task of transformation in higher education. Systemic conditions in HE, conducive to critical agency and social justice, are not enabling. Bhaskar’s Seven Scalar Being, used as an analytical frame and heuristic, guides the cross-case analysis of the six narratives across seven levels of ontology. The findings highlight that, despite difficult contextual influences, the positive exercise of agency is a marked feature of new participants in HE in this study. This has immediate implications for ways in which professional and academic development, and disciplinary and departmental programmes, could create and sustain conducive conditions for the professionalisation of new academics through more sensitised practices. Using alternative research methods such as photovoice to generate its data, this doctoral study proposes that new research methodologies, located in the third space, are needed now more than ever in HE sociological research, to recognise the researcher and the research participants as independent, autonomous and causally efficacious beings. To this end, this study includes a Chapter Zero, which captures the narrative of the doctoral scholar as researcher, who, shaped and influenced by established doctoral practices and traditions in the field, exercises her own doctoral agency in particular ways.
- Full Text:
- Date Issued: 2015
- Authors: Behari-Leak, Kasturi
- Date: 2015
- Subjects: Social integration -- South Africa , Students -- South Africa -- Social conditions , Educational change -- South Africa , College teachers -- South Africa , Education, Higher -- South Africa , Critical realism , Social realism , Agent (Philosophy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1333 , http://hdl.handle.net/10962/d1020295
- Description: This study, which is part of a National Research Foundation project on Social Inclusion in Higher Education (HE), focuses on the exercise of agency among new academics, conducive to the social inclusion of students. Transitioning from varied entry points into higher education, new academics face numerous challenges as they embed themselves in disciplinary and institutional contexts. Given the complexity and contested nature of the current higher education landscape, new academics are especially vulnerable. Using Roy Bhaskar’s critical realism as meta-theoretical framing and Margaret Archer’s social realist theory, with its methodological focus on analytical dualism and morphogenesis, this study offers a social realist account of how new academics engage with enabling and constraining conditions at institutional, faculty, departmental and classroom levels. Through an analysis of six individual narratives of mediation, this study explicates and exemplifies the range of agential choices exercised by new academics to mediate their contested spaces. A nuanced social and critical account of the material, ideational and agential conditions in HE shows that the courses of action taken by these new academics are driven through their concerns, commitments and projects in higher education. Yet, despite the university’s espousal of embracing change, the current induction and transition of new academics is inadequate to the task of transformation in higher education. Systemic conditions in HE, conducive to critical agency and social justice, are not enabling. Bhaskar’s Seven Scalar Being, used as an analytical frame and heuristic, guides the cross-case analysis of the six narratives across seven levels of ontology. The findings highlight that, despite difficult contextual influences, the positive exercise of agency is a marked feature of new participants in HE in this study. This has immediate implications for ways in which professional and academic development, and disciplinary and departmental programmes, could create and sustain conducive conditions for the professionalisation of new academics through more sensitised practices. Using alternative research methods such as photovoice to generate its data, this doctoral study proposes that new research methodologies, located in the third space, are needed now more than ever in HE sociological research, to recognise the researcher and the research participants as independent, autonomous and causally efficacious beings. To this end, this study includes a Chapter Zero, which captures the narrative of the doctoral scholar as researcher, who, shaped and influenced by established doctoral practices and traditions in the field, exercises her own doctoral agency in particular ways.
- Full Text:
- Date Issued: 2015
Entrepreneurial intention among Rhodes University undergraduate students
- Authors: Bell, Jonathan Andrew
- Date: 2015
- Subjects: Rhodes University -- Undergraduates , Entrepreneurship -- South Africa -- Grahamstown , Social cognitive theory , Intention , Attitude (Psychology) , Influence (Psychology) , South Africa -- Economic conditions -- 1991-
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3267 , http://hdl.handle.net/10962/d1020011
- Description: The entrepreneurial intentions of university students are important factors to consider when developing entrepreneurship offerings at tertiary level institutions. This research study reports on pertinent findings from a study which set out to determine Rhodes university undergraduate students‟ entrepreneurial intentions and their pull and push factors that have brought them to the decision to become entrepreneurs. A survey, using a 43 question structured web-based instrument was used to capture the responses from undergraduate students across different departments at Rhodes University, Grahamstown. Key findings suggest that few undergraduate students intend to enter into an entrepreneurship career immediately after completion of their studies, whereas many of the respondents were more interested in doing so five years after graduation. The vast majority of students were satisfied without having formal entrepreneurial education and factors such as previous employment in entrepreneurial activities, and family influence had a statistical significant relationship with entrepreneurial intention.
- Full Text:
- Date Issued: 2015
- Authors: Bell, Jonathan Andrew
- Date: 2015
- Subjects: Rhodes University -- Undergraduates , Entrepreneurship -- South Africa -- Grahamstown , Social cognitive theory , Intention , Attitude (Psychology) , Influence (Psychology) , South Africa -- Economic conditions -- 1991-
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3267 , http://hdl.handle.net/10962/d1020011
- Description: The entrepreneurial intentions of university students are important factors to consider when developing entrepreneurship offerings at tertiary level institutions. This research study reports on pertinent findings from a study which set out to determine Rhodes university undergraduate students‟ entrepreneurial intentions and their pull and push factors that have brought them to the decision to become entrepreneurs. A survey, using a 43 question structured web-based instrument was used to capture the responses from undergraduate students across different departments at Rhodes University, Grahamstown. Key findings suggest that few undergraduate students intend to enter into an entrepreneurship career immediately after completion of their studies, whereas many of the respondents were more interested in doing so five years after graduation. The vast majority of students were satisfied without having formal entrepreneurial education and factors such as previous employment in entrepreneurial activities, and family influence had a statistical significant relationship with entrepreneurial intention.
- Full Text:
- Date Issued: 2015
Spatial and temporal variations in trophic connectivity within an estuarine environment : benthic-pelagic and terrestrial-aquatic linkages via invertebrates and fishes
- Authors: Bergamino Roman, Leandro
- Date: 2015
- Subjects: Estuarine ecology -- South Africa , Marine invertebrates -- South Africa -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5921 , http://hdl.handle.net/10962/d1017799
- Description: Estuarine ecosystems are among the most biologically productive areas and they provide important ecosystem services such as erosion control, habitat and refugia for several species. These environments are characterized by the presence of a variety of organic matter sources due to their transitional position between rivers and the sea. The biotic compositions can undergo spatial and seasonal changes along the estuary due to the spatial and temporal fluctuations of environmental factors such as salinity, temperature and seston loads. Therefore, the different combinations of biotic and abiotic factors make each estuary a unique ecosystem. Because of this spatial and temporal complexity, the understanding of estuarine food web structure and which factors affect the trophic relationships within the ecosystem through space and time represent challenging tasks. Furthermore, estuaries are under an increasing number of anthropogenic perturbations because of the growing concentration of human populations in coastal areas. Knowledge of ecosystem structure and functioning is essential for effective conservation and management planning of coastal areas.In this dissertation, I combine the utilization of biological tracers to examine spatial and temporal variability in the food web structure within a small temperate and microtidal estuary located in South Africa. To this end, fatty acid profiles and stable isotope signatures were measured in several primary organic matter sources and consumers (including zooplankton, fishes and benthic invertebrates) during four consecutive seasons and in three different estuarine regions: upper, middle, and lower reaches. The three reaches had distinct habitat features of vegetation type and morphology, and in particular the lower reaches were colonized by the marsh grass Spartina maritima. Isotopic mixing models were used to estimate the relative contribution of each food source to the diets of invertebrates and fishes within the estuarine food web. The isotopic and fatty acid data showed similar results. In general, the lower reaches of the estuary were characterized by a higher deposition and assimilation by brachyuran crabs of carbon derived from marsh grass detritus, whiletowards the upper reaches a mixture of microphytobenthos and particulate organic matter (phytoplankton and detritus) was deposited and sustained the pelagic and benthic fauna. The highest deposition and assimilation of marsh grass detritus in the lower reaches of the estuary occurred during periods of low freshwater discharge (autumn and winter). In the upper reaches, microphytobenthos and suspended particulate organic matter were dominant basal food resources for the food web during all seasons. These results indicated that benthic consumers incorporated mainly local carbon sources from their local habitat.To clarify isotopic and fatty acid patterns I examined the trophic behaviour of the sesarmid crab Sesarma catenata through laboratory feeding experiments. Results from these experiments validated that decomposed leaves of riparian trees and the salt marsh plant S. maritima were the preferred food of the sesarmid crabs, potentially due to high bacterial loads. The remaining leaf material not assimilated by crabs, together with faecal material, are likely important subsidies for adjacent environments, hence representing an important energy pathway involving the microbial food chain. Furthermore, this dissertation showed the importance of mobile top predators as vectors energetically connecting distinct food chains within the estuary (i.e. littoral, benthic and pelagic). I concluded that a combination of physical (i.e. patterns of freshwater discharge and estuary morphology) and biological factors (i.e. organism feeding behaviour, mobility, primary productivity, the local vegetation type) influence the pattern of dominant primary organic matter sources, and therefore the food web structure along the estuarine environment. In particular, marsh grass detritus contributed substantially to the diets of estuarine fauna during periods of low freshwater discharge. Given the importance of the salt marsh habitat in providing trophic resources, it is important to preserve this environment to sustain the natural biota and ecosystem functioning.
- Full Text:
- Date Issued: 2015
- Authors: Bergamino Roman, Leandro
- Date: 2015
- Subjects: Estuarine ecology -- South Africa , Marine invertebrates -- South Africa -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5921 , http://hdl.handle.net/10962/d1017799
- Description: Estuarine ecosystems are among the most biologically productive areas and they provide important ecosystem services such as erosion control, habitat and refugia for several species. These environments are characterized by the presence of a variety of organic matter sources due to their transitional position between rivers and the sea. The biotic compositions can undergo spatial and seasonal changes along the estuary due to the spatial and temporal fluctuations of environmental factors such as salinity, temperature and seston loads. Therefore, the different combinations of biotic and abiotic factors make each estuary a unique ecosystem. Because of this spatial and temporal complexity, the understanding of estuarine food web structure and which factors affect the trophic relationships within the ecosystem through space and time represent challenging tasks. Furthermore, estuaries are under an increasing number of anthropogenic perturbations because of the growing concentration of human populations in coastal areas. Knowledge of ecosystem structure and functioning is essential for effective conservation and management planning of coastal areas.In this dissertation, I combine the utilization of biological tracers to examine spatial and temporal variability in the food web structure within a small temperate and microtidal estuary located in South Africa. To this end, fatty acid profiles and stable isotope signatures were measured in several primary organic matter sources and consumers (including zooplankton, fishes and benthic invertebrates) during four consecutive seasons and in three different estuarine regions: upper, middle, and lower reaches. The three reaches had distinct habitat features of vegetation type and morphology, and in particular the lower reaches were colonized by the marsh grass Spartina maritima. Isotopic mixing models were used to estimate the relative contribution of each food source to the diets of invertebrates and fishes within the estuarine food web. The isotopic and fatty acid data showed similar results. In general, the lower reaches of the estuary were characterized by a higher deposition and assimilation by brachyuran crabs of carbon derived from marsh grass detritus, whiletowards the upper reaches a mixture of microphytobenthos and particulate organic matter (phytoplankton and detritus) was deposited and sustained the pelagic and benthic fauna. The highest deposition and assimilation of marsh grass detritus in the lower reaches of the estuary occurred during periods of low freshwater discharge (autumn and winter). In the upper reaches, microphytobenthos and suspended particulate organic matter were dominant basal food resources for the food web during all seasons. These results indicated that benthic consumers incorporated mainly local carbon sources from their local habitat.To clarify isotopic and fatty acid patterns I examined the trophic behaviour of the sesarmid crab Sesarma catenata through laboratory feeding experiments. Results from these experiments validated that decomposed leaves of riparian trees and the salt marsh plant S. maritima were the preferred food of the sesarmid crabs, potentially due to high bacterial loads. The remaining leaf material not assimilated by crabs, together with faecal material, are likely important subsidies for adjacent environments, hence representing an important energy pathway involving the microbial food chain. Furthermore, this dissertation showed the importance of mobile top predators as vectors energetically connecting distinct food chains within the estuary (i.e. littoral, benthic and pelagic). I concluded that a combination of physical (i.e. patterns of freshwater discharge and estuary morphology) and biological factors (i.e. organism feeding behaviour, mobility, primary productivity, the local vegetation type) influence the pattern of dominant primary organic matter sources, and therefore the food web structure along the estuarine environment. In particular, marsh grass detritus contributed substantially to the diets of estuarine fauna during periods of low freshwater discharge. Given the importance of the salt marsh habitat in providing trophic resources, it is important to preserve this environment to sustain the natural biota and ecosystem functioning.
- Full Text:
- Date Issued: 2015
An analysis of the risk exposure of adopting IPV6 in enterprise networks
- Authors: Berko, Istvan Sandor
- Date: 2015
- Subjects: International Workshop on Deploying the Future Infrastructure , Computer networks , Computer networks -- Security measures , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4722 , http://hdl.handle.net/10962/d1018918
- Description: The IPv6 increased address pool presents changes in resource impact to the Enterprise that, if not adequately addressed, can change risks that are locally significant in IPv4 to risks that can impact the Enterprise in its entirety. The expected conclusion is that the IPv6 environment will impose significant changes in the Enterprise environment - which may negatively impact organisational security if the IPv6 nuances are not adequately addressed. This thesis reviews the risks related to the operation of enterprise networks with the introduction of IPv6. The global trends are discussed to provide insight and background to the IPv6 research space. Analysing the current state of readiness in enterprise networks, quantifies the value of developing this thesis. The base controls that should be deployed in enterprise networks to prevent the abuse of IPv6 through tunnelling and the protection of the enterprise access layer are discussed. A series of case studies are presented which identify and analyse the impact of certain changes in the IPv6 protocol on the enterprise networks. The case studies also identify mitigation techniques to reduce risk.
- Full Text:
- Date Issued: 2015
- Authors: Berko, Istvan Sandor
- Date: 2015
- Subjects: International Workshop on Deploying the Future Infrastructure , Computer networks , Computer networks -- Security measures , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4722 , http://hdl.handle.net/10962/d1018918
- Description: The IPv6 increased address pool presents changes in resource impact to the Enterprise that, if not adequately addressed, can change risks that are locally significant in IPv4 to risks that can impact the Enterprise in its entirety. The expected conclusion is that the IPv6 environment will impose significant changes in the Enterprise environment - which may negatively impact organisational security if the IPv6 nuances are not adequately addressed. This thesis reviews the risks related to the operation of enterprise networks with the introduction of IPv6. The global trends are discussed to provide insight and background to the IPv6 research space. Analysing the current state of readiness in enterprise networks, quantifies the value of developing this thesis. The base controls that should be deployed in enterprise networks to prevent the abuse of IPv6 through tunnelling and the protection of the enterprise access layer are discussed. A series of case studies are presented which identify and analyse the impact of certain changes in the IPv6 protocol on the enterprise networks. The case studies also identify mitigation techniques to reduce risk.
- Full Text:
- Date Issued: 2015
Exploring Grade 12 biology teachers' perceptions and experiences of the dissemination and utilization of Examiners' reports in the Khomas region of Namibia: a case study
- Authors: Bezuidenhoudt, Anthea
- Date: 2015
- Subjects: Biology -- Examinations -- Namibia , Biology -- Study and teaching -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2021 , http://hdl.handle.net/10962/d1017332
- Description: Teachers’ perceptions are that currently dissemination in schools is ineffective and must change. The tensions that surround the dissemination of the reports are late arrival of Examiners’ reports which clash with preparation of learners for the first term examinations. Furthermore, the time the Examiners’ reports get into teachers’ hands are late and thus result in teachers rushing through it to incorporate the recommendations given in it in the second term or in some instances teachers do not attend to it at all. The number of copies of the Examiners’ reports provided to schools appears to be inadequate. HODs still having to duplicate reports before disseminating them add to their work load and further delay dissemination of the reports to individual subject teachers. Although the teaching and learning approach in Namibian classrooms should be based on LCE, dissemination of the actual physical reports are currently restricted to teachers only with them only verbally communicating feedback given in the reports to their learners. Support in dissemination of Examiners’ reports from peers and superiors in the majority of the schools appear to be lacking. Changes would like to be seen in the timing the Examiners’ reports are available at schools, the number of hard copies provided to schools and exploring and embarking on alternative ways of disseminating the reports. The percentage of utilization of the Examiners’ reports is relatively high, yet still not the optimum. A reasonable number of Namibian learners are disadvantaged and not exposed to a source of information that can make their Biology learning more efficient because some of their teachers are not using Examiners’ reports in their teaching. The main reason for non-utilization of the reports by Biology teachers is a result of inefficient dissemination at individual schools. The argument being that if the reports are not given to the teachers they and especially novice teachers will not know about the existence of this useful teaching and learning resource. Examiners’ reports are an important and systematic impartial source of high quality data on learning in the Namibian education system. Therefore, effective dissemination and utilization of the reports must be advocated and strengthened. DNEA and the Khomas regional office should embark on tapping into available development in information technology by doing research into the possibility of disseminating the Examiners’ reports electronically. A pilot in this regard should be conducted in the Khomas region as a measure to ensure dissemination can become more efficient in the future. To ensure that teachers optimally utilize the Examiners’ reports, they should be provided to schools when the school first term commences. The Khomas regional office should strengthen their involvement in utilization by arranging annual workshops where the content of the reports can be discussed to ensure that the feedback given in the reports can aid in developing and strengthening Biology teachers’ subject content knowledge as well as pedagogical content knowledge. Optimal utilization of Examiners’ reports can enable mediation in learners which can ensure effective learning and mastery of Biology by learners which can ultimately lead to an improvement in pass rate in Biology. Therefore, appropriate support to aid teachers’ professional development can enhance maximum utilization. Furthermore, an area for future research could be to give the Examiners’ reports to learners to determine the impact it has on their learning.
- Full Text:
- Date Issued: 2015
- Authors: Bezuidenhoudt, Anthea
- Date: 2015
- Subjects: Biology -- Examinations -- Namibia , Biology -- Study and teaching -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2021 , http://hdl.handle.net/10962/d1017332
- Description: Teachers’ perceptions are that currently dissemination in schools is ineffective and must change. The tensions that surround the dissemination of the reports are late arrival of Examiners’ reports which clash with preparation of learners for the first term examinations. Furthermore, the time the Examiners’ reports get into teachers’ hands are late and thus result in teachers rushing through it to incorporate the recommendations given in it in the second term or in some instances teachers do not attend to it at all. The number of copies of the Examiners’ reports provided to schools appears to be inadequate. HODs still having to duplicate reports before disseminating them add to their work load and further delay dissemination of the reports to individual subject teachers. Although the teaching and learning approach in Namibian classrooms should be based on LCE, dissemination of the actual physical reports are currently restricted to teachers only with them only verbally communicating feedback given in the reports to their learners. Support in dissemination of Examiners’ reports from peers and superiors in the majority of the schools appear to be lacking. Changes would like to be seen in the timing the Examiners’ reports are available at schools, the number of hard copies provided to schools and exploring and embarking on alternative ways of disseminating the reports. The percentage of utilization of the Examiners’ reports is relatively high, yet still not the optimum. A reasonable number of Namibian learners are disadvantaged and not exposed to a source of information that can make their Biology learning more efficient because some of their teachers are not using Examiners’ reports in their teaching. The main reason for non-utilization of the reports by Biology teachers is a result of inefficient dissemination at individual schools. The argument being that if the reports are not given to the teachers they and especially novice teachers will not know about the existence of this useful teaching and learning resource. Examiners’ reports are an important and systematic impartial source of high quality data on learning in the Namibian education system. Therefore, effective dissemination and utilization of the reports must be advocated and strengthened. DNEA and the Khomas regional office should embark on tapping into available development in information technology by doing research into the possibility of disseminating the Examiners’ reports electronically. A pilot in this regard should be conducted in the Khomas region as a measure to ensure dissemination can become more efficient in the future. To ensure that teachers optimally utilize the Examiners’ reports, they should be provided to schools when the school first term commences. The Khomas regional office should strengthen their involvement in utilization by arranging annual workshops where the content of the reports can be discussed to ensure that the feedback given in the reports can aid in developing and strengthening Biology teachers’ subject content knowledge as well as pedagogical content knowledge. Optimal utilization of Examiners’ reports can enable mediation in learners which can ensure effective learning and mastery of Biology by learners which can ultimately lead to an improvement in pass rate in Biology. Therefore, appropriate support to aid teachers’ professional development can enhance maximum utilization. Furthermore, an area for future research could be to give the Examiners’ reports to learners to determine the impact it has on their learning.
- Full Text:
- Date Issued: 2015