Doing the twist: a test of Darwin's cross-pollination hypothesis for pollinarium reconfiguration
- Peter, Craig I, Johnson, Steven D
- Authors: Peter, Craig I , Johnson, Steven D
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6534 , http://hdl.handle.net/10962/d1005975
- Description: Mating success in plants depends largely on the efficiency of pollen dispersal. For hermaphrodite plants, self-pollination, either within or among flowers, can reduce mating opportunities because of pollen and ovule discounting and inbreeding depression. Self-pollination may be particularly detrimental in plants such as orchids and asclepiads that package each flower’s pollen into one or more pollinia which, together with accessory structures, comprise a pollinarium. Darwin proposed that physical reconfiguration of pollinaria serves as a mechanism for reducing the likelihood of self-pollination. To be effective, the time taken for pollinarium reconfiguration would need to exceed that spent by a pollinator on a plant. We investigated pollinarium reconfiguration (including pollinarium bending, pollinium shrinking and anther cap retention) in 19 species and found a strong positive relationship between reconfiguration time and the duration of pollinator visits. Reconfiguration times were also consistently longer than pollinator visit times. These results provide strong support for Darwin’s idea that this mechanism promotes cross-pollination. , Elsevier
- Full Text:
- Authors: Peter, Craig I , Johnson, Steven D
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6534 , http://hdl.handle.net/10962/d1005975
- Description: Mating success in plants depends largely on the efficiency of pollen dispersal. For hermaphrodite plants, self-pollination, either within or among flowers, can reduce mating opportunities because of pollen and ovule discounting and inbreeding depression. Self-pollination may be particularly detrimental in plants such as orchids and asclepiads that package each flower’s pollen into one or more pollinia which, together with accessory structures, comprise a pollinarium. Darwin proposed that physical reconfiguration of pollinaria serves as a mechanism for reducing the likelihood of self-pollination. To be effective, the time taken for pollinarium reconfiguration would need to exceed that spent by a pollinator on a plant. We investigated pollinarium reconfiguration (including pollinarium bending, pollinium shrinking and anther cap retention) in 19 species and found a strong positive relationship between reconfiguration time and the duration of pollinator visits. Reconfiguration times were also consistently longer than pollinator visit times. These results provide strong support for Darwin’s idea that this mechanism promotes cross-pollination. , Elsevier
- Full Text:
DRAPA-a flexible framework for evaluating the quality of VoIP components
- Clayton, Bradley, Terzoli, Alfredo, Irwin, Barry V W
- Authors: Clayton, Bradley , Terzoli, Alfredo , Irwin, Barry V W
- Date: 2006
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428213 , vital:72494 , https://d1wqtxts1xzle7.cloudfront.net/3456214/No_268_-_Clayton-libre.pdf?1390832682=andresponse-content-disposi-tion=inline%3B+filename%3DDRAPA_a_flexible_framework_for_evaluatin.pdfandExpires=1714742712andSignature=FTQ3UMH7w9KMXeuld-NbnboBP9kqza7jDnVI2AJMFrhV6fkW56bPgPZKVAY-bKJFqJP-jq4h4JwRhWVuCA-oIIA4ckbhKHA4OoL4X5DYtlujkhkombcp-B5fVR02AioXBazDtfnTGvZLE21wluH0BnkBL9OAQSen7YJDzDsYtNH2pFIn06Nmg9-kDaJoRmW9KWlQs8BwyaXml4-pG~FrpiGCRclANXBSpmsxYSdJyZAnHq2ZZNqx9pEHigaYHUUgllDq64dp8C8R84xAbbbRcvt-XNhuQ~fU2AkJILms4FUkJSjGI0E-TOKhh7vQiVIh5KzZX8MOiS~rEuBH6ekx8g__andKey-Pair-Id=APKAJLOHF5GGSLRBV4ZA
- Description: When adding to or altering a VoIP system, the overall performance and quality of the system is at risk. For example, adding confidentiality, in-tegrity and authentication (CIA) would incur an overhead for each addi-tional security method. A method of measuring the performance of a VoIP system after a change or addition is needed. This paper describes a framework and testbed (DRAPA) which provides a flexible base from which VoIP performance analysis systems can be built. DRAPA gener-ates and collects data from any part of a VoIP system within a real do-main. This paper also discusses the flexibility of DRAPA. While security is our primary focus, DRAPA allows the user to configure the testbed and change the type and nature of data to be collected.
- Full Text:
- Authors: Clayton, Bradley , Terzoli, Alfredo , Irwin, Barry V W
- Date: 2006
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428213 , vital:72494 , https://d1wqtxts1xzle7.cloudfront.net/3456214/No_268_-_Clayton-libre.pdf?1390832682=andresponse-content-disposi-tion=inline%3B+filename%3DDRAPA_a_flexible_framework_for_evaluatin.pdfandExpires=1714742712andSignature=FTQ3UMH7w9KMXeuld-NbnboBP9kqza7jDnVI2AJMFrhV6fkW56bPgPZKVAY-bKJFqJP-jq4h4JwRhWVuCA-oIIA4ckbhKHA4OoL4X5DYtlujkhkombcp-B5fVR02AioXBazDtfnTGvZLE21wluH0BnkBL9OAQSen7YJDzDsYtNH2pFIn06Nmg9-kDaJoRmW9KWlQs8BwyaXml4-pG~FrpiGCRclANXBSpmsxYSdJyZAnHq2ZZNqx9pEHigaYHUUgllDq64dp8C8R84xAbbbRcvt-XNhuQ~fU2AkJILms4FUkJSjGI0E-TOKhh7vQiVIh5KzZX8MOiS~rEuBH6ekx8g__andKey-Pair-Id=APKAJLOHF5GGSLRBV4ZA
- Description: When adding to or altering a VoIP system, the overall performance and quality of the system is at risk. For example, adding confidentiality, in-tegrity and authentication (CIA) would incur an overhead for each addi-tional security method. A method of measuring the performance of a VoIP system after a change or addition is needed. This paper describes a framework and testbed (DRAPA) which provides a flexible base from which VoIP performance analysis systems can be built. DRAPA gener-ates and collects data from any part of a VoIP system within a real do-main. This paper also discusses the flexibility of DRAPA. While security is our primary focus, DRAPA allows the user to configure the testbed and change the type and nature of data to be collected.
- Full Text:
Duplicating road patterns in south african informal settlements using procedural techniques
- Glass, Kevin R, Morkel, Chantelle, Bangay, Shaun D
- Authors: Glass, Kevin R , Morkel, Chantelle , Bangay, Shaun D
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432875 , vital:72909 , https://doi.org/10.1145/1108590.1108616
- Description: The formation of informal settlements in and around urban complexes has largely been ignored in the context of procedural city modeling. However, many cities in South Africa and globally can attest to the presence of such settlements. This paper analyses the phenomenon of informal settlements from a procedural modeling perspective. Aerial photography from two South African urban complexes, namely Johannesburg and Cape Town is used as a basis for the extraction of various features that distinguish different types of settlements. In particular, the road patterns which have formed within such settlements are analysed, and various procedural techniques proposed (including Voronoi diagrams, subdivision and L-systems) to replicate the identified features. A qualitative assessment of the procedural techniques is provided, and the most suitable combination of techniques identified for unstructured and structured settlements. In particular it is found that a combination of Voronoi diagrams and subdivision provides the closest match to unstructured informal settlements. A combination of L-systems, Voronoi diagrams and subdivision is found to produce the closest pattern to a structured informal settlement.
- Full Text:
- Authors: Glass, Kevin R , Morkel, Chantelle , Bangay, Shaun D
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432875 , vital:72909 , https://doi.org/10.1145/1108590.1108616
- Description: The formation of informal settlements in and around urban complexes has largely been ignored in the context of procedural city modeling. However, many cities in South Africa and globally can attest to the presence of such settlements. This paper analyses the phenomenon of informal settlements from a procedural modeling perspective. Aerial photography from two South African urban complexes, namely Johannesburg and Cape Town is used as a basis for the extraction of various features that distinguish different types of settlements. In particular, the road patterns which have formed within such settlements are analysed, and various procedural techniques proposed (including Voronoi diagrams, subdivision and L-systems) to replicate the identified features. A qualitative assessment of the procedural techniques is provided, and the most suitable combination of techniques identified for unstructured and structured settlements. In particular it is found that a combination of Voronoi diagrams and subdivision provides the closest match to unstructured informal settlements. A combination of L-systems, Voronoi diagrams and subdivision is found to produce the closest pattern to a structured informal settlement.
- Full Text:
Dyke swarms and associated lava formations in the northern Lebombo monocline, Karoo Large Igneous Province, South Africa
- Klausen, Martin B, Marsh, Julian S, Watkeys, M K
- Authors: Klausen, Martin B , Marsh, Julian S , Watkeys, M K
- Date: 2006
- Language: English
- Type: text , Abstracts
- Identifier: http://hdl.handle.net/10962/132751 , vital:36880
- Description: As one of the early classical examples of plume-generated Large Igneous Provinces (LIPs), the Karoo is characterized by a bulls-eye distribution of High-Ti basalts, picrites, and earliest nephelinites onto a conspicuous triple rift junction (i.e., Okavango dyke swarm and the two Mwenezi and Lebombo monoclines), surrounded by Low-Ti basalts. It is noted that this regional distribution between high-and low-Ti basalts within the Jurassic Karoo LIP differs from that of the Permian Emeishan LIP; thereby undermining the use of this particular feature as evidence for mantle plume involvement.
- Full Text:
- Authors: Klausen, Martin B , Marsh, Julian S , Watkeys, M K
- Date: 2006
- Language: English
- Type: text , Abstracts
- Identifier: http://hdl.handle.net/10962/132751 , vital:36880
- Description: As one of the early classical examples of plume-generated Large Igneous Provinces (LIPs), the Karoo is characterized by a bulls-eye distribution of High-Ti basalts, picrites, and earliest nephelinites onto a conspicuous triple rift junction (i.e., Okavango dyke swarm and the two Mwenezi and Lebombo monoclines), surrounded by Low-Ti basalts. It is noted that this regional distribution between high-and low-Ti basalts within the Jurassic Karoo LIP differs from that of the Permian Emeishan LIP; thereby undermining the use of this particular feature as evidence for mantle plume involvement.
- Full Text:
Early effects of a community-based marine protected area on the food security of participating households
- Weiant, Pamela, Shankar, Aswani
- Authors: Weiant, Pamela , Shankar, Aswani
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439084 , vital:73543
- Description: There is general agreement among conservation practitioners that community-based marine protected areas (CB-MPAs) can improve food security in coastal communities. However, little attention has been given to how communities respond to CB-MPAs, particularly how households try to meet their livelihood needs following the establishment of a restrictive management regime. In this paper, we explore the early effects of a CB-MPA geared toward the management of marine resources harvested by women, as measured by perceived income and food availability. We strive to better understand (1) the contribution of women’s fishing activities to livelihood needs, particularly the harvest of blood cockles (Anadara granosa) and mud clams (Polymesoda spp.)(the species under management);(2) differences in how households respond to a CB-MPA; and (3) the relationship between food security and certain aspects of reef health. To illustrate our case, we draw upon our research experience with social and biological impact assessments and our experience in establishing marine protection in the Western Solomon Islands.
- Full Text:
- Authors: Weiant, Pamela , Shankar, Aswani
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439084 , vital:73543
- Description: There is general agreement among conservation practitioners that community-based marine protected areas (CB-MPAs) can improve food security in coastal communities. However, little attention has been given to how communities respond to CB-MPAs, particularly how households try to meet their livelihood needs following the establishment of a restrictive management regime. In this paper, we explore the early effects of a CB-MPA geared toward the management of marine resources harvested by women, as measured by perceived income and food availability. We strive to better understand (1) the contribution of women’s fishing activities to livelihood needs, particularly the harvest of blood cockles (Anadara granosa) and mud clams (Polymesoda spp.)(the species under management);(2) differences in how households respond to a CB-MPA; and (3) the relationship between food security and certain aspects of reef health. To illustrate our case, we draw upon our research experience with social and biological impact assessments and our experience in establishing marine protection in the Western Solomon Islands.
- Full Text:
Ectomycorrhizal characterisation, species diversity and community dynamics in Pinus patula Schelcht. et Cham. plantations
- Authors: Hawley, Greer Leigh
- Date: 2006
- Subjects: Mycorrhizas Ectomycorrhizal fungi Pinus patula -- Irrigation -- South Africa Forests and forestry -- South Africa Forest ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3951 , http://hdl.handle.net/10962/d1004010
- Description: Ectomycorrhizal (ECM) associations are important elements of forest biomes, connecting and transferring nutrients through an intricate and complex system of hyphal networks, ensuring plants of the nutrients they require, in nutrient poor soil. ECM research and particularly investigations into the diversity of the fungal partners has not received much attention in South Africa, hindering the advance of research in this field. This has been attributed to the difficulty of identifying the mycobionts involved in the symbiosis. The objectives of this study were to examine the ECM fungal diversity associating with Pinus patula, in selected forest plantations in Mpumalanga, South Africa. Both morphological and molecular techniques were used to identify specimens of both sporocarp collections and ECM root tip morphotypes. Morphological analysis of the ECM root tips involved characterisation of root morphology such as colour, branching and texture, and anatomical analysis examined hyphal arrangement in the root mantle and rhizomorphs. Molecular analysis involved sequencing of the Internal Transcribed Spacer (ITS) region and comparative BLAST analysis. Twenty-four sporocarp species were identified from 13 genera, namely: Amanita, Boletus, Clavulina, Inocybe, Lactarius, Rhizopogon, Russula, Scleroderma, Suillus, Tricholoma, Thelephora, Tomentella and Xerocomus. ECM root tip analysis led to the characterisation of 7 wild-type morphotypes identified as an Albatrellus sp., 2 Amanita species, a Rhizopogon sp., Thelephora terrestris, a Tomentella sp. and Scleroderma citrinum. A secondary objective was to determine whether fertilisation treatments within the study sites were responsible for differences in fungal species community structure. No evidence of a change in species diversity or shift in species composition was encountered. It is envisaged that these comprehensive ECM descriptions will be used as reference material to stimulate continued research in this field in South Africa.
- Full Text:
- Authors: Hawley, Greer Leigh
- Date: 2006
- Subjects: Mycorrhizas Ectomycorrhizal fungi Pinus patula -- Irrigation -- South Africa Forests and forestry -- South Africa Forest ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3951 , http://hdl.handle.net/10962/d1004010
- Description: Ectomycorrhizal (ECM) associations are important elements of forest biomes, connecting and transferring nutrients through an intricate and complex system of hyphal networks, ensuring plants of the nutrients they require, in nutrient poor soil. ECM research and particularly investigations into the diversity of the fungal partners has not received much attention in South Africa, hindering the advance of research in this field. This has been attributed to the difficulty of identifying the mycobionts involved in the symbiosis. The objectives of this study were to examine the ECM fungal diversity associating with Pinus patula, in selected forest plantations in Mpumalanga, South Africa. Both morphological and molecular techniques were used to identify specimens of both sporocarp collections and ECM root tip morphotypes. Morphological analysis of the ECM root tips involved characterisation of root morphology such as colour, branching and texture, and anatomical analysis examined hyphal arrangement in the root mantle and rhizomorphs. Molecular analysis involved sequencing of the Internal Transcribed Spacer (ITS) region and comparative BLAST analysis. Twenty-four sporocarp species were identified from 13 genera, namely: Amanita, Boletus, Clavulina, Inocybe, Lactarius, Rhizopogon, Russula, Scleroderma, Suillus, Tricholoma, Thelephora, Tomentella and Xerocomus. ECM root tip analysis led to the characterisation of 7 wild-type morphotypes identified as an Albatrellus sp., 2 Amanita species, a Rhizopogon sp., Thelephora terrestris, a Tomentella sp. and Scleroderma citrinum. A secondary objective was to determine whether fertilisation treatments within the study sites were responsible for differences in fungal species community structure. No evidence of a change in species diversity or shift in species composition was encountered. It is envisaged that these comprehensive ECM descriptions will be used as reference material to stimulate continued research in this field in South Africa.
- Full Text:
Editorial: tracing actors, actants and relational dynamics in environmental education research
- Authors: Lotz-Sisitka, Heila
- Date: 2006
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67400 , vital:29084 , https://www.ajol.info/index.php/sajee/article/view/122719
- Description: publisher version , Introduction: This edition of the EEASA Journal provides insight into a range of relationships in the field of environmental education, and the complexities that exist around them, as reflected in the combination of papers. This Editorial picks up on the methodological ‘note’ (or is it a challenge?) provided by Godwell Nhamo in his paper in this edition of the journal. He provides a description of the possibilities that actor network theory provides for describing and explaining environmental policy processes, and recommends that environmental educators consider this methodology in their analyses. In particular, he refers environmental educators to applications of actor network theory for tracing relational dynamics between actors (i.e., environmental education practitioners) and actants which are non-human referents (e.g., the UN Decade of Education for Sustainable Development and UNESCO’s (2005) International Implementation Scheme). In response to his paper, I have chosen to ‘pick up’ on this methodological discussion in this Editorial, by considering aspects of this theoretical perspective in describing the ‘happenings’ that occur across the pages of this edition of the EEASA Journal. In doing so, I highlight (in part) the diversity of actors and actants that are influencing the field of environmental education, their subject matter and contexts, and I highlight the relational dynamics that become evident when one accepts a methodology that aims to trace such dynamics. In particular, this Editorial considers how ‘The language of actors, actants and actor/actant-networks brings to the fore the relationships and complexities that exist around them’ (Nhamo, this edition).
- Full Text:
- Authors: Lotz-Sisitka, Heila
- Date: 2006
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67400 , vital:29084 , https://www.ajol.info/index.php/sajee/article/view/122719
- Description: publisher version , Introduction: This edition of the EEASA Journal provides insight into a range of relationships in the field of environmental education, and the complexities that exist around them, as reflected in the combination of papers. This Editorial picks up on the methodological ‘note’ (or is it a challenge?) provided by Godwell Nhamo in his paper in this edition of the journal. He provides a description of the possibilities that actor network theory provides for describing and explaining environmental policy processes, and recommends that environmental educators consider this methodology in their analyses. In particular, he refers environmental educators to applications of actor network theory for tracing relational dynamics between actors (i.e., environmental education practitioners) and actants which are non-human referents (e.g., the UN Decade of Education for Sustainable Development and UNESCO’s (2005) International Implementation Scheme). In response to his paper, I have chosen to ‘pick up’ on this methodological discussion in this Editorial, by considering aspects of this theoretical perspective in describing the ‘happenings’ that occur across the pages of this edition of the EEASA Journal. In doing so, I highlight (in part) the diversity of actors and actants that are influencing the field of environmental education, their subject matter and contexts, and I highlight the relational dynamics that become evident when one accepts a methodology that aims to trace such dynamics. In particular, this Editorial considers how ‘The language of actors, actants and actor/actant-networks brings to the fore the relationships and complexities that exist around them’ (Nhamo, this edition).
- Full Text:
Effects of an agribusiness collapse on contract growers and their communities : a case study of Makeni Cooperative Society, Lusaka, Zambia
- Authors: Mfune, Elizabeth
- Date: 2006
- Subjects: Agriculture -- Economic aspects -- Zambia , Agricultural industries -- Zambia , Farmers -- Zambia -- Economic conditions , Cooperative societies -- Zambia , Contracts, Agricultural -- Zambia
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3357 , http://hdl.handle.net/10962/d1007627 , Agriculture -- Economic aspects -- Zambia , Agricultural industries -- Zambia , Farmers -- Zambia -- Economic conditions , Cooperative societies -- Zambia , Contracts, Agricultural -- Zambia
- Description: This study assesses the effects of an agribusiness collapse, on the contracted growers and their surrounding communities in Lusaka Province, Zambia. In 2004, Agriflora Limited, a Trans-Zambezi Industries Limited (TZI) agribusiness in Lusaka Zambia was sold off. Agriflora Limited was one ofthe largest fresh vegetable exporters in Africa. It had contracted almost 500 small-scale farmers with 1-4 hectares of land within 50 km radius of Lusaka to grow vegetables for export. Makeni Cooperative Society was one of the targeted groups of growers. It grew baby corn, mangetout peas, and sugar snap and fine beans for export. The case study relied on both primary and secondary data. I undertook two months of ethnographic fieldwork utilising observations, in-depth interviews and informal discussions with some community members in Makeni. I also reviewed the literature on contract farming schemes (documenting both the negative and positive effects for growers) in developing countries. The case study showed that the impact of the collapse of Agriflora on the growers has been severe indeed; there has been a significant reduction in production with only a few farmers producing for export. Those that are producing are limited to one crop, baby corn. The effect on the local labour market (farm workers) has been quite drastic with a drop in employment. A new agribusiness company, York Farm, was sourced by the government for the contract growers of Makeni. York Farm has signed a procurement contract under which only sale and purchase conditions are specified. This means that, services such as extension services are no longer provided. It was also found that despite the price for baby corn at York Farm being better than what Agriflora used to offer the farmers, farmers are not producing peas which have a higher turnover than baby corn because York farm does not buy peas from the farmers. However, the farmers are hopeful that they will soon start producing peas after they pass the Eurep gap requirements. Furthermore, the farmers are still interested in contract farming as they are convinced that it can lead to higher farm incomes. While the neoliberal critique of the pre- Structural Adjustment agricultural policies was based on the need to improve rural farming income and productivity, my study shows that the contract farmers are not the "traditional" peasant farmers but retired civil servants or former public sector employees who lost their jobs during the contraction of the sector. In conclusion, my field work revealed that the collapse of Agriflora has had negative effects on the growers of MCS in terms a significant decrease in crop production, decline in farmer income, lack of technical assistance such as extension services, transportation problems (to take produce to the new market-York Farm) and reduced contraction in employment opportunities for farm workers.
- Full Text:
- Authors: Mfune, Elizabeth
- Date: 2006
- Subjects: Agriculture -- Economic aspects -- Zambia , Agricultural industries -- Zambia , Farmers -- Zambia -- Economic conditions , Cooperative societies -- Zambia , Contracts, Agricultural -- Zambia
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3357 , http://hdl.handle.net/10962/d1007627 , Agriculture -- Economic aspects -- Zambia , Agricultural industries -- Zambia , Farmers -- Zambia -- Economic conditions , Cooperative societies -- Zambia , Contracts, Agricultural -- Zambia
- Description: This study assesses the effects of an agribusiness collapse, on the contracted growers and their surrounding communities in Lusaka Province, Zambia. In 2004, Agriflora Limited, a Trans-Zambezi Industries Limited (TZI) agribusiness in Lusaka Zambia was sold off. Agriflora Limited was one ofthe largest fresh vegetable exporters in Africa. It had contracted almost 500 small-scale farmers with 1-4 hectares of land within 50 km radius of Lusaka to grow vegetables for export. Makeni Cooperative Society was one of the targeted groups of growers. It grew baby corn, mangetout peas, and sugar snap and fine beans for export. The case study relied on both primary and secondary data. I undertook two months of ethnographic fieldwork utilising observations, in-depth interviews and informal discussions with some community members in Makeni. I also reviewed the literature on contract farming schemes (documenting both the negative and positive effects for growers) in developing countries. The case study showed that the impact of the collapse of Agriflora on the growers has been severe indeed; there has been a significant reduction in production with only a few farmers producing for export. Those that are producing are limited to one crop, baby corn. The effect on the local labour market (farm workers) has been quite drastic with a drop in employment. A new agribusiness company, York Farm, was sourced by the government for the contract growers of Makeni. York Farm has signed a procurement contract under which only sale and purchase conditions are specified. This means that, services such as extension services are no longer provided. It was also found that despite the price for baby corn at York Farm being better than what Agriflora used to offer the farmers, farmers are not producing peas which have a higher turnover than baby corn because York farm does not buy peas from the farmers. However, the farmers are hopeful that they will soon start producing peas after they pass the Eurep gap requirements. Furthermore, the farmers are still interested in contract farming as they are convinced that it can lead to higher farm incomes. While the neoliberal critique of the pre- Structural Adjustment agricultural policies was based on the need to improve rural farming income and productivity, my study shows that the contract farmers are not the "traditional" peasant farmers but retired civil servants or former public sector employees who lost their jobs during the contraction of the sector. In conclusion, my field work revealed that the collapse of Agriflora has had negative effects on the growers of MCS in terms a significant decrease in crop production, decline in farmer income, lack of technical assistance such as extension services, transportation problems (to take produce to the new market-York Farm) and reduced contraction in employment opportunities for farm workers.
- Full Text:
Effects of prophylactic progesterone in decomposing tissues on the development of Chrysomya chloropyga (Wiedeman)(Diptera Calliphoridae)
- da Silva, C, Villet, Martin H
- Authors: da Silva, C , Villet, Martin H
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442020 , vital:73950 , https://hdl.handle.net/10520/EJC32654
- Description: Medico-legal forensic entomology is often concerned with the estimation of postmortem intervals (PMI), the time elapsed since the death of a body, by estimating the age of maggots if they are found on a body. These estimates can be complicated by the presence of a variety of drugs that may be present in dead bodies, including steroids such as hydrocortisone (Musvasva et al. 2001).
- Full Text:
- Authors: da Silva, C , Villet, Martin H
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442020 , vital:73950 , https://hdl.handle.net/10520/EJC32654
- Description: Medico-legal forensic entomology is often concerned with the estimation of postmortem intervals (PMI), the time elapsed since the death of a body, by estimating the age of maggots if they are found on a body. These estimates can be complicated by the presence of a variety of drugs that may be present in dead bodies, including steroids such as hydrocortisone (Musvasva et al. 2001).
- Full Text:
Effects of ring substituents on electrocatalytic activity of manganese phthalocyanines towards the reduction of molecular oxygen
- Sehlotho, Nthapo, Nyokong, Tebello
- Authors: Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6594 , http://hdl.handle.net/10962/d1004343
- Description: Reduction of oxygen electrocatalyzed by adsorbed films of manganese phthalocyanine complexes is reported. The complexes studied were: manganese phthalocyanine (MnPc, 1); manganese tetraamino phthalocyanine (MnTAPc, 2); manganese tetrapentoxy pyrrole phthalocyanine (MnTPePyrPc, 3); manganese tetra phenoxy pyrrole phthalocyanine (MnTPPyrPc, 4); manganese tetra mercaptopyrimidine phthalocyanine (MnTMPyPc, 5) and manganese tetra ethoxy thiophene phthalocyanine (MnTETPc, 6). The reaction was conducted in buffer solutions of pH range 1–12. Rotating disk electrode voltammetry revealed two electron reduction in acidic and slightly alkaline media due to the formation of hydrogen peroxide. In highly basic media, water is the major product formed via four electron transfer. The reaction was found to be first order in the diffusing analyte oxygen.
- Full Text:
- Authors: Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6594 , http://hdl.handle.net/10962/d1004343
- Description: Reduction of oxygen electrocatalyzed by adsorbed films of manganese phthalocyanine complexes is reported. The complexes studied were: manganese phthalocyanine (MnPc, 1); manganese tetraamino phthalocyanine (MnTAPc, 2); manganese tetrapentoxy pyrrole phthalocyanine (MnTPePyrPc, 3); manganese tetra phenoxy pyrrole phthalocyanine (MnTPPyrPc, 4); manganese tetra mercaptopyrimidine phthalocyanine (MnTMPyPc, 5) and manganese tetra ethoxy thiophene phthalocyanine (MnTETPc, 6). The reaction was conducted in buffer solutions of pH range 1–12. Rotating disk electrode voltammetry revealed two electron reduction in acidic and slightly alkaline media due to the formation of hydrogen peroxide. In highly basic media, water is the major product formed via four electron transfer. The reaction was found to be first order in the diffusing analyte oxygen.
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Effects of temperature and salinity on the standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi
- Allan, Elizabeth L, Froneman, Pierre W, Hodgson, Alan N
- Authors: Allan, Elizabeth L , Froneman, Pierre W , Hodgson, Alan N
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6831 , http://hdl.handle.net/10962/d1007567
- Description: The standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi to changes in temperature (15–30 °C), salinity (0–45‰) and a combination thereof was investigated. The rate of oxygen consumption of the shrimp was determined using a YSI oxygen meter. At a constant salinity of 35‰ the respiration rate of P. peringueyi increased with an increase in temperature and ranged between 0.260 and 0.982 μl O[subscript 2] mg wwt[superscript −1] h[superscript −1]. The Q[subscript 10] value over the temperature range 15–25 °C was estimated at 3.13. At a constant temperature of 15 °C the respiration rate of P. peringueyi also increased with an increase in salinity and ranged between 0.231 and 0.860 μl O[subscript 2] mg wwt[superscript −1] h[superscript −1]. For combination experiments the absence of any significant difference in the respiration rate of P. peringueyi at the four temperatures over the salinity range 15–35‰ suggests that the shrimp is well adapted to inhabiting environments characterised by variations in salinity and temperature such as those encountered within the middle and lower reaches of permanently open estuaries with substantial freshwater inflow. On the other hand, the total mortality of the shrimp recorded at salinities < 5‰ at all four temperatures suggests that the upper distribution of the shrimp may reflect physiological constraints. Similarly, the increase in the respiration rate of the shrimp at the four temperatures at salinities > 35‰ suggests that the shrimp may experience osmotic stress in freshwater deprived permanently open and intermittently open estuaries where hypersaline conditions may develop.
- Full Text:
- Authors: Allan, Elizabeth L , Froneman, Pierre W , Hodgson, Alan N
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6831 , http://hdl.handle.net/10962/d1007567
- Description: The standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi to changes in temperature (15–30 °C), salinity (0–45‰) and a combination thereof was investigated. The rate of oxygen consumption of the shrimp was determined using a YSI oxygen meter. At a constant salinity of 35‰ the respiration rate of P. peringueyi increased with an increase in temperature and ranged between 0.260 and 0.982 μl O[subscript 2] mg wwt[superscript −1] h[superscript −1]. The Q[subscript 10] value over the temperature range 15–25 °C was estimated at 3.13. At a constant temperature of 15 °C the respiration rate of P. peringueyi also increased with an increase in salinity and ranged between 0.231 and 0.860 μl O[subscript 2] mg wwt[superscript −1] h[superscript −1]. For combination experiments the absence of any significant difference in the respiration rate of P. peringueyi at the four temperatures over the salinity range 15–35‰ suggests that the shrimp is well adapted to inhabiting environments characterised by variations in salinity and temperature such as those encountered within the middle and lower reaches of permanently open estuaries with substantial freshwater inflow. On the other hand, the total mortality of the shrimp recorded at salinities < 5‰ at all four temperatures suggests that the upper distribution of the shrimp may reflect physiological constraints. Similarly, the increase in the respiration rate of the shrimp at the four temperatures at salinities > 35‰ suggests that the shrimp may experience osmotic stress in freshwater deprived permanently open and intermittently open estuaries where hypersaline conditions may develop.
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Electrocatalysis of asulam on cobalt phthalocyanine modified multi-walled carbon nanotubes immobilized on a basal plane pyrolytic graphite electrode
- Siswana, Msimelelo P, Ozoemena, Kenneth I, Nyokong, Tebello
- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6595 , http://hdl.handle.net/10962/d1004344
- Description: This work describes the electrochemical properties of cobalt tetra-aminophthalocyanine (CoTAPc) complex electropolymerized at the surface of multi-walled carbon nanotube (MWCNT) abrasively immobilized onto a basal plane pyrolytic graphite electrode (BPPGE). The constructed electrode displayed excellent electrocatalytic behaviour towards the oxidation of the herbicide, asulam, as evidenced by the enhancement of the oxidation peak current (~6 times) and the shift in the oxidation potential to lower values (by ~120 mV) in comparison with the bare BPPGE. The chronoamperometric detection of asulam which was carried out in 0.10 M phosphate buffer (pH 7.0) at a fixed potential of 0.65 V (versus Ag|AgCl) yielded excellent analytical parameters; a linear concentration range of 4.5–20 μM, a sensitivity of 241 × 10[superscript −3] μA/μM, a detection limit of 1.15 μM asulam (using the Y[subscript B] + 3σ criterion) and a response time of ~2 s.
- Full Text:
- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6595 , http://hdl.handle.net/10962/d1004344
- Description: This work describes the electrochemical properties of cobalt tetra-aminophthalocyanine (CoTAPc) complex electropolymerized at the surface of multi-walled carbon nanotube (MWCNT) abrasively immobilized onto a basal plane pyrolytic graphite electrode (BPPGE). The constructed electrode displayed excellent electrocatalytic behaviour towards the oxidation of the herbicide, asulam, as evidenced by the enhancement of the oxidation peak current (~6 times) and the shift in the oxidation potential to lower values (by ~120 mV) in comparison with the bare BPPGE. The chronoamperometric detection of asulam which was carried out in 0.10 M phosphate buffer (pH 7.0) at a fixed potential of 0.65 V (versus Ag|AgCl) yielded excellent analytical parameters; a linear concentration range of 4.5–20 μM, a sensitivity of 241 × 10[superscript −3] μA/μM, a detection limit of 1.15 μM asulam (using the Y[subscript B] + 3σ criterion) and a response time of ~2 s.
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Electrocatalysis of oxidation of 2-mercaptoethanol, L-cysteine and reduced glutathione by adsorbed and electrodeposited cobalt tetra phenoxypyrrole and tetra ethoxythiophene substituted phthalocyanines
- Sehlotho, Nthapo, Nyokong, Tebello, Zagal, Jose H, Bedioui, Fethi
- Authors: Sehlotho, Nthapo , Nyokong, Tebello , Zagal, Jose H , Bedioui, Fethi
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6593 , http://hdl.handle.net/10962/d1004342
- Description: Catalytic activity of cobalt tetra ethoxythiophene and cobalt tetra phenoxypyrrole phthalocyanine complexes towards oxidation of 2-mercaptoethanol, L-cysteine and reduced glutathione is reported. It was found that the activity of the complexes depends on the substitution of the phthalocyanine ring, pH, film thickness and method of electrode modification. The high electrocatalytic activity obtained with adsorbed complexes in alkaline medium clearly demonstrates the necessity of modifying bare carbon electrodes to endow them with the desired behaviour.
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- Authors: Sehlotho, Nthapo , Nyokong, Tebello , Zagal, Jose H , Bedioui, Fethi
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6593 , http://hdl.handle.net/10962/d1004342
- Description: Catalytic activity of cobalt tetra ethoxythiophene and cobalt tetra phenoxypyrrole phthalocyanine complexes towards oxidation of 2-mercaptoethanol, L-cysteine and reduced glutathione is reported. It was found that the activity of the complexes depends on the substitution of the phthalocyanine ring, pH, film thickness and method of electrode modification. The high electrocatalytic activity obtained with adsorbed complexes in alkaline medium clearly demonstrates the necessity of modifying bare carbon electrodes to endow them with the desired behaviour.
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Electrocatalytic behaviour of carbon paste electrode modified with iron(II) phthalocyanine (FePc) nanoparticles towards the detection of amitrole
- Siswana, Msimelelo P, Ozoemena, Kenneth I, Nyokong, Tebello
- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6591 , http://hdl.handle.net/10962/d1004340
- Description: This paper describes the construction of a carbon paste electrode (CPE) impregnated with nanoparticles of iron(II) phthalocyanine (nanoFePc). The new electrode (nanoFePc-CPE) revealed interesting electrocatalytic behaviour towards amitrole; pure catalytic diffusion-controlled process, with high Tafel slope (235 mV/decade) suggesting strong binding of amitrole with nanoFePc catalyst. The effects of catalyst loading, varying pH and electrolytes were studied. The mechanism for the interaction of amitrole with the nanoFePc is proposed to involve the Fe[superscript (III)]Pc/Fe[superscript (II)]Pc redox process. Using chronoamperometry (E = +0.42 V versus Ag/AgCl) technique, the sensor was reliably employed for amitrole assay at pH 12.0 phosphate buffer (with sodium sulphate as the supporting electrolyte) for up to 12 nM amitrole with excellent sensitivity (ca. 3.44 μA/nM) and low detection limit (3.62 ± 0.11 nM, i.e. 0.305 μg L[superscript (−1)] using the YB + 3σB criterion and 0.85 ± 0.03 nM, i.e. 70 ng/L with the Y[subscript B] + 2[subscript σB] criterion) as well as satisfactory amperometric selectivity coefficient (K[subscript amp] ≈ 7.4 × 10[superscript (−4)] for ammonium thiocyanate, a component of many amitrole herbicides, and 3.2 × 10[superscript (−3)] for asulam pesticide). The surface of the electrode can easily be regenerated by simple polishing on an alumina paper, obtaining a fresh surface ready for use in a new assay. The proposed electrode was successfully applied in the quantification of amitrole in its commercial formulation as well as in tap water samples.
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- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6591 , http://hdl.handle.net/10962/d1004340
- Description: This paper describes the construction of a carbon paste electrode (CPE) impregnated with nanoparticles of iron(II) phthalocyanine (nanoFePc). The new electrode (nanoFePc-CPE) revealed interesting electrocatalytic behaviour towards amitrole; pure catalytic diffusion-controlled process, with high Tafel slope (235 mV/decade) suggesting strong binding of amitrole with nanoFePc catalyst. The effects of catalyst loading, varying pH and electrolytes were studied. The mechanism for the interaction of amitrole with the nanoFePc is proposed to involve the Fe[superscript (III)]Pc/Fe[superscript (II)]Pc redox process. Using chronoamperometry (E = +0.42 V versus Ag/AgCl) technique, the sensor was reliably employed for amitrole assay at pH 12.0 phosphate buffer (with sodium sulphate as the supporting electrolyte) for up to 12 nM amitrole with excellent sensitivity (ca. 3.44 μA/nM) and low detection limit (3.62 ± 0.11 nM, i.e. 0.305 μg L[superscript (−1)] using the YB + 3σB criterion and 0.85 ± 0.03 nM, i.e. 70 ng/L with the Y[subscript B] + 2[subscript σB] criterion) as well as satisfactory amperometric selectivity coefficient (K[subscript amp] ≈ 7.4 × 10[superscript (−4)] for ammonium thiocyanate, a component of many amitrole herbicides, and 3.2 × 10[superscript (−3)] for asulam pesticide). The surface of the electrode can easily be regenerated by simple polishing on an alumina paper, obtaining a fresh surface ready for use in a new assay. The proposed electrode was successfully applied in the quantification of amitrole in its commercial formulation as well as in tap water samples.
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Electrocatalytic oxidation of thiocyanate, L-cysteine and 2-mercaptoethanol by self-assembled monolayer of cobalt tetraethoxy thiophene phthalocyanine
- Sehlotho, Nthapo, Nyokong, Tebello
- Authors: Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283814 , vital:55993 , xlink:href="https://doi.org/10.1016/j.electacta.2005.12.024"
- Description: Catalytic activity of a self-assembled monolayer (SAM) of cobalt tetra ethoxythiophene phthalocyanine (CoTEThPc-SAM) complex towards oxidation of thiocyanate (SCN−), L-cysteine (CYS) and 2-mercaptoethanol (2-ME) is reported. The oxidation of thiocyanate occurs via a two electron transfer, whereas L-cysteine and 2-ME require 1 electron. The oxidation of thiocyanate is catalysed by ring based processes, while L-cysteine is catalysed by both CoIII/CoII process and by ring based processes. 2-ME is catalysed by CoIII/CoII process. The oxidation of thiocyanate on CoTEThPc was performed in acid media instead of basic media commonly employed. The reaction order was found to be unity for all the analytes, showing that only one molecule of analyte interacts with one molecule of the catalyst during the rate determining step.
- Full Text:
- Authors: Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/283814 , vital:55993 , xlink:href="https://doi.org/10.1016/j.electacta.2005.12.024"
- Description: Catalytic activity of a self-assembled monolayer (SAM) of cobalt tetra ethoxythiophene phthalocyanine (CoTEThPc-SAM) complex towards oxidation of thiocyanate (SCN−), L-cysteine (CYS) and 2-mercaptoethanol (2-ME) is reported. The oxidation of thiocyanate occurs via a two electron transfer, whereas L-cysteine and 2-ME require 1 electron. The oxidation of thiocyanate is catalysed by ring based processes, while L-cysteine is catalysed by both CoIII/CoII process and by ring based processes. 2-ME is catalysed by CoIII/CoII process. The oxidation of thiocyanate on CoTEThPc was performed in acid media instead of basic media commonly employed. The reaction order was found to be unity for all the analytes, showing that only one molecule of analyte interacts with one molecule of the catalyst during the rate determining step.
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Electrochemical properties of benzylmercapto and dodecylmercapto tetra substituted nickel phthalocyanine complexes: Electrocatalytic oxidation of nitrite
- Agboola, Bolade O, Ozoemena, Kenneth I, Nyokong, Tebello
- Authors: Agboola, Bolade O , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6562 , http://hdl.handle.net/10962/d1003826
- Description: Nickel tetrakis(benzylmercapto)phthalocyanine (NiTBMPc) and nickel tetrakis(dodecylmercapto)phthalocyanine (NiTDMPc) complexes were synthesized and their spectral and electrochemical properties reported. The CV showed four or five redox processes for NiTBMPc and NiTDMPc, respectively. For the first time, spectroelectrochemistry gave evidence for the formation of NiII/NiI process in a NiPc complex. The rest of the processes were ring based. The NiTBMPc complex was successfully deposited on both gold and glassy carbon electrodes by electropolymerisation while NiTDMPc complex was deposited on gold electrode only. The films were electro-transformed in aqueous 0.1 M NaOH solution to the O–Ni–O oxo bridged form. The modified electrodes were characterized using electrochemical impedance spectroscopy and the results showed typical behavior for modified electrodes. Electrodes with poly-Ni(OH)Pcs films exhibited higher charge transfer resistance values, Rp than their corresponding poly-NiPcs films counterparts. All the modified electrodes showed improved catalytic activities than the unmodified electrodes towards nitrite ions electrooxidation. Better catalytic activities were observed for the modified electrodes when they were transformed to O–Ni–O oxo bridge form. All the modified electrodes exhibited high resistance to electrode surface passivation.
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- Authors: Agboola, Bolade O , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6562 , http://hdl.handle.net/10962/d1003826
- Description: Nickel tetrakis(benzylmercapto)phthalocyanine (NiTBMPc) and nickel tetrakis(dodecylmercapto)phthalocyanine (NiTDMPc) complexes were synthesized and their spectral and electrochemical properties reported. The CV showed four or five redox processes for NiTBMPc and NiTDMPc, respectively. For the first time, spectroelectrochemistry gave evidence for the formation of NiII/NiI process in a NiPc complex. The rest of the processes were ring based. The NiTBMPc complex was successfully deposited on both gold and glassy carbon electrodes by electropolymerisation while NiTDMPc complex was deposited on gold electrode only. The films were electro-transformed in aqueous 0.1 M NaOH solution to the O–Ni–O oxo bridged form. The modified electrodes were characterized using electrochemical impedance spectroscopy and the results showed typical behavior for modified electrodes. Electrodes with poly-Ni(OH)Pcs films exhibited higher charge transfer resistance values, Rp than their corresponding poly-NiPcs films counterparts. All the modified electrodes showed improved catalytic activities than the unmodified electrodes towards nitrite ions electrooxidation. Better catalytic activities were observed for the modified electrodes when they were transformed to O–Ni–O oxo bridge form. All the modified electrodes exhibited high resistance to electrode surface passivation.
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Electropolymerizable iron (III) and cobalt (II) dicyanophenoxy tetraphenylporphyrin complexes
- Ozoemena, Kenneth I, Zhao, Zhixin, Nyokong, Tebello
- Authors: Ozoemena, Kenneth I , Zhao, Zhixin , Nyokong, Tebello
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/286080 , vital:56236 , xlink:href="https://doi.org/10.1016/j.inoche.2005.11.024"
- Description: Solution and solid phase electrochemical features of 5-[4-(3,4-dicyanophenoxy)phenyl],10,15,20-triphenylporphyrin complexes of iron(III) (FeCNOTPP(Cl)) and cobalt(II) (CoCNOTPP) have been described. These novel asymmetric dicyanophenoxy-derivatised cobalt and iron porphyrin complexes were electropolymerised onto glassy carbon electrodes, which in aqueous solutions, gave surface concentrations (ca. 10−10 mol cm−2) typical of monolayer coverages. The films also exhibited excellent stability and electrocatalysis towards the direct detection of important analytes as nitrite, nitric oxide, and hydrogen peroxide in aqueous solutions.
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- Authors: Ozoemena, Kenneth I , Zhao, Zhixin , Nyokong, Tebello
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/286080 , vital:56236 , xlink:href="https://doi.org/10.1016/j.inoche.2005.11.024"
- Description: Solution and solid phase electrochemical features of 5-[4-(3,4-dicyanophenoxy)phenyl],10,15,20-triphenylporphyrin complexes of iron(III) (FeCNOTPP(Cl)) and cobalt(II) (CoCNOTPP) have been described. These novel asymmetric dicyanophenoxy-derivatised cobalt and iron porphyrin complexes were electropolymerised onto glassy carbon electrodes, which in aqueous solutions, gave surface concentrations (ca. 10−10 mol cm−2) typical of monolayer coverages. The films also exhibited excellent stability and electrocatalysis towards the direct detection of important analytes as nitrite, nitric oxide, and hydrogen peroxide in aqueous solutions.
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Email meets issue-tracking: a prototype implementation
- Authors: Kwinana, Zukhanye N
- Date: 2006 , 2013-06-11
- Subjects: Microsoft Visual studio , Electronic mail systems , Computer networks , eXtreme programming , Computer software -- Development
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4614 , http://hdl.handle.net/10962/d1005644 , Microsoft Visual studio , Electronic mail systems , Computer networks , eXtreme programming , Computer software -- Development
- Description: The use of electronic mail (email) has evolved from sending simple messages to task delegation and management. Most mail clients, however, have not kept up with the evolution and as a result have limited task management features available. On the other hand, while issue tracking systems offer useful task management functionality, they are not as widespread as emails and also have a few drawbacks. This thesis reports on the exploration of the integration of the ubiquitous nature of email with the task management features of issue-tracking systems. We explore this using simple ad-hoc as well as semi-automated tasks. With these two working together, tasks can be delegated from email clients without needing to switch between the two environments. It brings some of the benefits of issue tracking systems closer to our email users.The system is developed using Microsoft VisuaI Studio.NET. with the code written in C#. The eXtreme Programming (XP) methodology was used during the development of the proof-of-concept prototype that demonstrates the integration of the two environments, as we were faced at first with vague requirements bound to change, as we better understood the problem domain through our development. XP allowed us to skip an extended and comprehensive initial design process and incrementally develop the system, making refinements and extensions as we encountered the need for them. This alleviated the need to make upfront decisions that were based on minimal knowledge of what to expect during development. This thesis describes the implementation of the prototype and the decisions made with each step taken towards developing an email-based issue tracking system. With the two environments working together, we can now easily track issues from our email clients without needing to switch to another system. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Kwinana, Zukhanye N
- Date: 2006 , 2013-06-11
- Subjects: Microsoft Visual studio , Electronic mail systems , Computer networks , eXtreme programming , Computer software -- Development
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4614 , http://hdl.handle.net/10962/d1005644 , Microsoft Visual studio , Electronic mail systems , Computer networks , eXtreme programming , Computer software -- Development
- Description: The use of electronic mail (email) has evolved from sending simple messages to task delegation and management. Most mail clients, however, have not kept up with the evolution and as a result have limited task management features available. On the other hand, while issue tracking systems offer useful task management functionality, they are not as widespread as emails and also have a few drawbacks. This thesis reports on the exploration of the integration of the ubiquitous nature of email with the task management features of issue-tracking systems. We explore this using simple ad-hoc as well as semi-automated tasks. With these two working together, tasks can be delegated from email clients without needing to switch between the two environments. It brings some of the benefits of issue tracking systems closer to our email users.The system is developed using Microsoft VisuaI Studio.NET. with the code written in C#. The eXtreme Programming (XP) methodology was used during the development of the proof-of-concept prototype that demonstrates the integration of the two environments, as we were faced at first with vague requirements bound to change, as we better understood the problem domain through our development. XP allowed us to skip an extended and comprehensive initial design process and incrementally develop the system, making refinements and extensions as we encountered the need for them. This alleviated the need to make upfront decisions that were based on minimal knowledge of what to expect during development. This thesis describes the implementation of the prototype and the decisions made with each step taken towards developing an email-based issue tracking system. With the two environments working together, we can now easily track issues from our email clients without needing to switch to another system. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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Empirical studies of fish movement behaviour and their application in spatially explicit models for marine conservation
- Authors: Kerwath, Sven Ebo
- Date: 2006
- Subjects: Fishing -- South Africa Fishes -- Behavior -- South Africa Fish tagging Marine parks and reserves -- South Africa Marine resources conservation Pomadasys -- South Africa Reef fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5277 , http://hdl.handle.net/10962/d1005121
- Description: This thesis investigates the movement behaviour of South African two coastal fish species and evaluates the effectiveness of marine protected areas (MPAs) in their protection and management. Its primary focus is on resolving the movement patterns of roman Chrysoblephus laticeps (Sparidae) in and around the Goukamma and Castle Rock MPAs in the Western Cape province of South Africa. A pilot study of the methodology investigated the movement behaviour of spotted grunter Pomadasys commersonnii (Haemulidae) in the sheltered East Kleinmonde Estuary in the Eastern Cape province. The application of different tagging methods was tested in a controlled tank experiment. Tagged roman were monitored over a 198-day period. Barbed dart, t-bar anchor and Visible Implanted Fluorescent Elastomer (VIFE) tags were compared. Application techniques and underwater visibility of VIFE tags were tested on roman and on fransmadam Boobsoidia inornata in a pilot study. Needles of gauge 25 were found to be optimal for VIFE tag application. Whereas VIFE tagging caused fin rot in fransmadam, it had no negative effect on roman. VIFE tagged fish could be identified by divers from a distance of three metres under ambient light in an observation tank in five metres water depth. There was no significant difference in growth rate between groups of roman with different tags and controls after 198 days. High tag loss rates were experienced for barbed dart and t-bar anchor tags, although barbed dart tags performed better than t-bar anchor tags. Although some of the VIFE marks had deteriorated, all VIFE tagged fish were individually recognised at the end of the study. Conventional dart and VIFE tags are feasible methods to tag roman. However, the high tag loss rate of conventional tags must be taken into account in the design of a tagging study. Previous mark and recapture studies on roman are beset with a number of problems. Poor experimental design and low precision of capture positions resulted in equivocal results of limited value. A tagging experiment was designed to eliminate ambiguity in data interpretation and to produce a dataset that could be used to model roman residency and dispersal. A combination of conventional barbed dart tags and Visible Implanted Fluorescent Elastomer tags was used to tag roman in the Goukamma Marine Protected Area (GMPA) on the temperate South African south coast. Sixty one percent of roman were recaptured within 50 m of the tagging position. A small proportion moved considerable distances of up to four kilometres. The extent of these movements was not dependent on fish size or sex. Data from this experiment and from a previous tagging study in the Tsitsikamma National Park (TNP) were used to model the resident behaviour of roman. The model suggests a probability of 91% (GMPA) and 94% (TNP) of residency within a 10000 m² cell. This result suggests that individual roman will benefit from protection in small MPAs. A different experimental approach was required to investigate the exact home range of this species. Firstly the feasibility of using acoustic telemetry to study the movement of coastal fish in South Africa was investigated. The telemetry equipment comprised two VEMCO V8 transmitters and a VEMCO VR60 receiver linked to a directional hydrophone. A tank experiment was conducted to examine the effects of the transmitter implantation. A tracking experiment was conducted on spotted grunter Pomadasys commersonnii in the East Kleinmonde Estuary. Operated fish recovered quickly and, with respect to swimming behaviour and growth rates, no differences were found between fish with implants and controls. The maximum detection range in the estuary was 400 m. Interference between different transmitter frequencies was negligible. Transmitter location recordings were found to be accurate within five metres. Two fish were tracked over a seven-day period. The fish preferred the lower reaches of the estuary where they made repeated and prolonged use of specific areas. The success of the initial experiments allowed this method to be used to investigate the spatial utilisation and activity patterns of roman Chrysoblephus laticeps. Surgically implanted VEMCO V8, V13 and V16 transmitters were used to track 13 roman inside the Castle Rock MPA in False Bay. Transmitters implanted into C. laticeps in tanks had no apparent effects on growth and physiology. Manual boatand diver-based tracking experiments covered a 17-month period. A VEMCO VRAP radio acoustic positioning system was used over two one-month periods during and after the spawning season of roman. Analysis of data using a 95% fixed kernel algorithm suggests that roman are resident throughout their adult life, occupying home ranges between 1000 and 3000 m². Activity was lower at night. During periods of cold-water upwelling, fish retreated into caves. During the spawning season, females extended their home ranges, possibly to mate with different males. These results confirm that this species is well suited for protection and management with small MPAs. The effect of two MPAs on the South African south coast on the population of C. laticeps was simulated with a spatially explicit individual based model (IBM). Life history parameters determined in recent studies and the effect of fishing on the size of sex change was taken into account. Fish densities and size frequencies were based on recent underwater visual census. The distribution of suitable habitat in the study areas was also incorporated. The results show a rapid recovery of the fish size frequency spectrum and sex ratio to pre-exploitation levels inside both MPAs. Little 'spillover' of fish into the fished areas occurred resulting in negligible improvement of catches. The results suggest that for resident species like roman, even small MPAs offer sufficient protection.
- Full Text:
- Authors: Kerwath, Sven Ebo
- Date: 2006
- Subjects: Fishing -- South Africa Fishes -- Behavior -- South Africa Fish tagging Marine parks and reserves -- South Africa Marine resources conservation Pomadasys -- South Africa Reef fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5277 , http://hdl.handle.net/10962/d1005121
- Description: This thesis investigates the movement behaviour of South African two coastal fish species and evaluates the effectiveness of marine protected areas (MPAs) in their protection and management. Its primary focus is on resolving the movement patterns of roman Chrysoblephus laticeps (Sparidae) in and around the Goukamma and Castle Rock MPAs in the Western Cape province of South Africa. A pilot study of the methodology investigated the movement behaviour of spotted grunter Pomadasys commersonnii (Haemulidae) in the sheltered East Kleinmonde Estuary in the Eastern Cape province. The application of different tagging methods was tested in a controlled tank experiment. Tagged roman were monitored over a 198-day period. Barbed dart, t-bar anchor and Visible Implanted Fluorescent Elastomer (VIFE) tags were compared. Application techniques and underwater visibility of VIFE tags were tested on roman and on fransmadam Boobsoidia inornata in a pilot study. Needles of gauge 25 were found to be optimal for VIFE tag application. Whereas VIFE tagging caused fin rot in fransmadam, it had no negative effect on roman. VIFE tagged fish could be identified by divers from a distance of three metres under ambient light in an observation tank in five metres water depth. There was no significant difference in growth rate between groups of roman with different tags and controls after 198 days. High tag loss rates were experienced for barbed dart and t-bar anchor tags, although barbed dart tags performed better than t-bar anchor tags. Although some of the VIFE marks had deteriorated, all VIFE tagged fish were individually recognised at the end of the study. Conventional dart and VIFE tags are feasible methods to tag roman. However, the high tag loss rate of conventional tags must be taken into account in the design of a tagging study. Previous mark and recapture studies on roman are beset with a number of problems. Poor experimental design and low precision of capture positions resulted in equivocal results of limited value. A tagging experiment was designed to eliminate ambiguity in data interpretation and to produce a dataset that could be used to model roman residency and dispersal. A combination of conventional barbed dart tags and Visible Implanted Fluorescent Elastomer tags was used to tag roman in the Goukamma Marine Protected Area (GMPA) on the temperate South African south coast. Sixty one percent of roman were recaptured within 50 m of the tagging position. A small proportion moved considerable distances of up to four kilometres. The extent of these movements was not dependent on fish size or sex. Data from this experiment and from a previous tagging study in the Tsitsikamma National Park (TNP) were used to model the resident behaviour of roman. The model suggests a probability of 91% (GMPA) and 94% (TNP) of residency within a 10000 m² cell. This result suggests that individual roman will benefit from protection in small MPAs. A different experimental approach was required to investigate the exact home range of this species. Firstly the feasibility of using acoustic telemetry to study the movement of coastal fish in South Africa was investigated. The telemetry equipment comprised two VEMCO V8 transmitters and a VEMCO VR60 receiver linked to a directional hydrophone. A tank experiment was conducted to examine the effects of the transmitter implantation. A tracking experiment was conducted on spotted grunter Pomadasys commersonnii in the East Kleinmonde Estuary. Operated fish recovered quickly and, with respect to swimming behaviour and growth rates, no differences were found between fish with implants and controls. The maximum detection range in the estuary was 400 m. Interference between different transmitter frequencies was negligible. Transmitter location recordings were found to be accurate within five metres. Two fish were tracked over a seven-day period. The fish preferred the lower reaches of the estuary where they made repeated and prolonged use of specific areas. The success of the initial experiments allowed this method to be used to investigate the spatial utilisation and activity patterns of roman Chrysoblephus laticeps. Surgically implanted VEMCO V8, V13 and V16 transmitters were used to track 13 roman inside the Castle Rock MPA in False Bay. Transmitters implanted into C. laticeps in tanks had no apparent effects on growth and physiology. Manual boatand diver-based tracking experiments covered a 17-month period. A VEMCO VRAP radio acoustic positioning system was used over two one-month periods during and after the spawning season of roman. Analysis of data using a 95% fixed kernel algorithm suggests that roman are resident throughout their adult life, occupying home ranges between 1000 and 3000 m². Activity was lower at night. During periods of cold-water upwelling, fish retreated into caves. During the spawning season, females extended their home ranges, possibly to mate with different males. These results confirm that this species is well suited for protection and management with small MPAs. The effect of two MPAs on the South African south coast on the population of C. laticeps was simulated with a spatially explicit individual based model (IBM). Life history parameters determined in recent studies and the effect of fishing on the size of sex change was taken into account. Fish densities and size frequencies were based on recent underwater visual census. The distribution of suitable habitat in the study areas was also incorporated. The results show a rapid recovery of the fish size frequency spectrum and sex ratio to pre-exploitation levels inside both MPAs. Little 'spillover' of fish into the fished areas occurred resulting in negligible improvement of catches. The results suggest that for resident species like roman, even small MPAs offer sufficient protection.
- Full Text:
Emthonjeni:
- Authors: Kaschula, Russell H
- Date: 2006
- Language: isiXhosa
- Type: text , book
- Identifier: http://hdl.handle.net/10962/175351 , vital:42567 , ISBN 9781869285012
- Full Text:
- Authors: Kaschula, Russell H
- Date: 2006
- Language: isiXhosa
- Type: text , book
- Identifier: http://hdl.handle.net/10962/175351 , vital:42567 , ISBN 9781869285012
- Full Text: