Detecting plant species in the field with deep learning and drone technology:
- James, Katherine, Bradshaw, Karen
- Authors: James, Katherine , Bradshaw, Karen
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160445 , vital:40446 , https://0-doi.org.wam.seals.ac.za/10.1111/2041-210X.13473
- Description: Aerial drones are providing a new source of high‐resolution imagery for mapping of plant species of interest, amongst other applications. On‐board detection algorithms could open the door to allow for applications in which drones can intelligently interact with their environment. However, the majority of plant detection studies have focused on detection in post‐flight processed orthomosaics. Greater research into developing detection algorithms robust to real‐world variations in environmental conditions is necessary, such that they are suitable for deployment in the field under variable conditions. We outline the steps necessary to develop such a system, show by example how real‐world considerations can be addressed during model training and briefly illustrate the performance of our best performing model in the field when integrated with an aerial drone.
- Full Text:
- Date Issued: 2020
- Authors: James, Katherine , Bradshaw, Karen
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160445 , vital:40446 , https://0-doi.org.wam.seals.ac.za/10.1111/2041-210X.13473
- Description: Aerial drones are providing a new source of high‐resolution imagery for mapping of plant species of interest, amongst other applications. On‐board detection algorithms could open the door to allow for applications in which drones can intelligently interact with their environment. However, the majority of plant detection studies have focused on detection in post‐flight processed orthomosaics. Greater research into developing detection algorithms robust to real‐world variations in environmental conditions is necessary, such that they are suitable for deployment in the field under variable conditions. We outline the steps necessary to develop such a system, show by example how real‐world considerations can be addressed during model training and briefly illustrate the performance of our best performing model in the field when integrated with an aerial drone.
- Full Text:
- Date Issued: 2020
African Foreign Policies: Selecting signifiers to explain agency
- Authors: Bischoff, Paul, 1954-
- Date: 2020
- Subjects: Africa Foreign relations 1960- , Africa Politics and government 1960-
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/161716 , vital:40657 , ISBN 9780367348281 , https://www.routledge.com/African-Foreign-Policies-Selecting-Signifiers-to-Explain-Agency/Bischoff/p/book/9780367348281
- Description: This book explores, at a time when several powers have become serious players on the continent, aspects of African agency, past and present, by African writers on foreign policy, representative of geography, language and state size. In the past, African foreign policy has largely been considered within the context of reactions to the international or global 'external factor'. This ground-breaking book, however, looks at how foreign policy has been crafted and used in response not just to external, but also, mainly, domestic imperatives or (theoretical) signifiers. As such, it narrates individual and changing foreign policy orientations over time - and as far back as independence - with mainly African-based scholars who present their own constructs of what is a useful theoretical narrative regarding foreign policy on the continent - how theory is adapted to local circumstance or substituted for continentally based ontologies. The book therefore contends that the African experience carries valuable import for expanding general understandings of foreign policy in general. This book will be of key interest to scholars and students of Foreign Policy Analysis, Foreign Policy Studies, African International Relations/Politics/Studies, Diplomacy and more broadly to International Relations. , Introduction / Paul-Henri Bischoff -- What Next? Past and present African foreign policy concepts and practices / Paul-Henri Bischoff -- The African Union as a Foreign Policy Player: African Agency in International Cooperation / Tshepo Gwatiwa -- Unprincipled Pragmatism and Anti-Imperialist Impulses in an Interconnected World: The Zuma Presidency, 2009-2017 / Mzukisi Qobo -- Towards A Strategic Culture Approach to Understanding and Conceptualising Ethiopia's Foreign Policy Towards Israel and the Middle Eastern Arab Countries / Makonnen Tesfaye -- Nigeria's Foreign Policy and Intervention Behaviour in Africa: What Role for Agency? / Olumuyiwa Amao -- Zimbabwe and New Signifiers: Towards a cultural political economy of Foreign Policy Making / Mike Mavura -- Realist Conceptions of Kenya's Foreign Policy and Foreign Policy Behaviour: A Theoretical and Contextual Disposition / Korwa Gombe Adar and Mercy Kathambi Kaburu -- Addressing the Conceptual Void of African Small State Foreign Policy in Orthodox Theory: A Case Study of Botswana's Principled Pragmatism / Kabelo M. Mahupela -- Tunisia's Foreign Policy Towards France Before and After an Undemanding 'Revolution': A Theoretical Explanation of the An-Nahdha-led Interim Governments' Soft Policy / Ahmed Ali Salem -- Straddling Between Convergence and Divergence: A Constructivist's View of Malawi's Foreign Policy in Post-independence Africa / Eugenio Njoloma -- Strategies of a Small State Between Realism and Liberalism: Sixty Years of Guinea's Diplomacy and Foreign Policy (1958-2018) / Issaka K. Souaré -- Rethinking SADC's Collective Policymaking Processes on External Relations and Non-state Participation for Region-building / Cecilia Lwiindi Nedziwe -- Towards an Understanding of the Interplay Between Ghana's Foreign and Defence Policies / Kwesi Aning and Kwaku Danso -- Conclusion / Paul-Henri Bischoff
- Full Text:
- Date Issued: 2020
- Authors: Bischoff, Paul, 1954-
- Date: 2020
- Subjects: Africa Foreign relations 1960- , Africa Politics and government 1960-
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/161716 , vital:40657 , ISBN 9780367348281 , https://www.routledge.com/African-Foreign-Policies-Selecting-Signifiers-to-Explain-Agency/Bischoff/p/book/9780367348281
- Description: This book explores, at a time when several powers have become serious players on the continent, aspects of African agency, past and present, by African writers on foreign policy, representative of geography, language and state size. In the past, African foreign policy has largely been considered within the context of reactions to the international or global 'external factor'. This ground-breaking book, however, looks at how foreign policy has been crafted and used in response not just to external, but also, mainly, domestic imperatives or (theoretical) signifiers. As such, it narrates individual and changing foreign policy orientations over time - and as far back as independence - with mainly African-based scholars who present their own constructs of what is a useful theoretical narrative regarding foreign policy on the continent - how theory is adapted to local circumstance or substituted for continentally based ontologies. The book therefore contends that the African experience carries valuable import for expanding general understandings of foreign policy in general. This book will be of key interest to scholars and students of Foreign Policy Analysis, Foreign Policy Studies, African International Relations/Politics/Studies, Diplomacy and more broadly to International Relations. , Introduction / Paul-Henri Bischoff -- What Next? Past and present African foreign policy concepts and practices / Paul-Henri Bischoff -- The African Union as a Foreign Policy Player: African Agency in International Cooperation / Tshepo Gwatiwa -- Unprincipled Pragmatism and Anti-Imperialist Impulses in an Interconnected World: The Zuma Presidency, 2009-2017 / Mzukisi Qobo -- Towards A Strategic Culture Approach to Understanding and Conceptualising Ethiopia's Foreign Policy Towards Israel and the Middle Eastern Arab Countries / Makonnen Tesfaye -- Nigeria's Foreign Policy and Intervention Behaviour in Africa: What Role for Agency? / Olumuyiwa Amao -- Zimbabwe and New Signifiers: Towards a cultural political economy of Foreign Policy Making / Mike Mavura -- Realist Conceptions of Kenya's Foreign Policy and Foreign Policy Behaviour: A Theoretical and Contextual Disposition / Korwa Gombe Adar and Mercy Kathambi Kaburu -- Addressing the Conceptual Void of African Small State Foreign Policy in Orthodox Theory: A Case Study of Botswana's Principled Pragmatism / Kabelo M. Mahupela -- Tunisia's Foreign Policy Towards France Before and After an Undemanding 'Revolution': A Theoretical Explanation of the An-Nahdha-led Interim Governments' Soft Policy / Ahmed Ali Salem -- Straddling Between Convergence and Divergence: A Constructivist's View of Malawi's Foreign Policy in Post-independence Africa / Eugenio Njoloma -- Strategies of a Small State Between Realism and Liberalism: Sixty Years of Guinea's Diplomacy and Foreign Policy (1958-2018) / Issaka K. Souaré -- Rethinking SADC's Collective Policymaking Processes on External Relations and Non-state Participation for Region-building / Cecilia Lwiindi Nedziwe -- Towards an Understanding of the Interplay Between Ghana's Foreign and Defence Policies / Kwesi Aning and Kwaku Danso -- Conclusion / Paul-Henri Bischoff
- Full Text:
- Date Issued: 2020
First candidates for γ vibrational bands built on the [505] 11/2− neutron orbital in odd-A Dy isotopes:
- Majola, S N T, Sithole, M A, Mdletshe, L, Hartley, D, Timár, J, Nyakó, B M, Allmond, J M, Bark, R A, Beausang, C, Bianco, L, Bucher, T D, Bvumbi, S P, Carpenter, M P, Chiara, C J, Cooper, N, Cullen, D M, Curien, D, Dinoko, T S, Gall, B J P, Garrett, P E, Greenlees, P T, Hirvonen, J, Jakobsson, U, Jones, P M, Julin, R, Juutinen, S, Ketelhut, S, Keswa, B V, Kondev, F G, Korichi, A, Kulp, W D, Lauritsen, T, Lawrie, E A, Makhathini, L, Masiteng, P L, Maqabuka, B, McCutchan, E A, Miller, D, Miller, S, Minkova, A, Msebi, L, Mthembu, S H, Ndayishmiye, J, Nieminen, P, Ngcobo, P Z, Ntshamgase, S S, Orce, J N, Peura, P, Rahkila, P, Redon, N, Riedinger, L L, Riley, M A, Roux, D G, Ruotsalainen, P, Piot, J, Saren, J, Sharpey-Schafer, J F, Scholey, C, Shirinda, O, Simpson, J, Sorri, J, Stefansecu, I, Stolze, S, Uusitalo, J, Wang, X, Werner, V, Wood, J L, Yu, C-H, Zhu, S, Zimba, G
- Authors: Majola, S N T , Sithole, M A , Mdletshe, L , Hartley, D , Timár, J , Nyakó, B M , Allmond, J M , Bark, R A , Beausang, C , Bianco, L , Bucher, T D , Bvumbi, S P , Carpenter, M P , Chiara, C J , Cooper, N , Cullen, D M , Curien, D , Dinoko, T S , Gall, B J P , Garrett, P E , Greenlees, P T , Hirvonen, J , Jakobsson, U , Jones, P M , Julin, R , Juutinen, S , Ketelhut, S , Keswa, B V , Kondev, F G , Korichi, A , Kulp, W D , Lauritsen, T , Lawrie, E A , Makhathini, L , Masiteng, P L , Maqabuka, B , McCutchan, E A , Miller, D , Miller, S , Minkova, A , Msebi, L , Mthembu, S H , Ndayishmiye, J , Nieminen, P , Ngcobo, P Z , Ntshamgase, S S , Orce, J N , Peura, P , Rahkila, P , Redon, N , Riedinger, L L , Riley, M A , Roux, D G , Ruotsalainen, P , Piot, J , Saren, J , Sharpey-Schafer, J F , Scholey, C , Shirinda, O , Simpson, J , Sorri, J , Stefansecu, I , Stolze, S , Uusitalo, J , Wang, X , Werner, V , Wood, J L , Yu, C-H , Zhu, S , Zimba, G
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148827 , vital:38777 , https://0-journals.aps.org.wam.seals.ac.za/prc/abstract/10.1103/PhysRevC.101.044312
- Description: Rotational structures have been measured using the Jurogam II and GAMMASPHERE arrays at low spin following the 155Gd(α,2n)157Dy and 148Nd(12C,5n)155Dy reactions at 25 and 65 MeV, respectively. We report high-K bands, which are conjectured to be the first candidates of a Kπ=2+γ vibrational band, built on the [505]11/2− neutron orbital, in both odd-A155,157Dy isotopes. The coupling of the first excited K=0+ states or the so-called β vibrational bands at 661 and 676 keV in 154Dy and 156Dy to the [505]11/2− orbital, to produce a Kπ=11/2− band, was not observed in both 155Dy and 157Dy, respectively. The implication of these findings on the interpretation of the first excited 0+ states in the core nuclei 154Dy and 156Dy are also discussed.
- Full Text:
- Date Issued: 2020
- Authors: Majola, S N T , Sithole, M A , Mdletshe, L , Hartley, D , Timár, J , Nyakó, B M , Allmond, J M , Bark, R A , Beausang, C , Bianco, L , Bucher, T D , Bvumbi, S P , Carpenter, M P , Chiara, C J , Cooper, N , Cullen, D M , Curien, D , Dinoko, T S , Gall, B J P , Garrett, P E , Greenlees, P T , Hirvonen, J , Jakobsson, U , Jones, P M , Julin, R , Juutinen, S , Ketelhut, S , Keswa, B V , Kondev, F G , Korichi, A , Kulp, W D , Lauritsen, T , Lawrie, E A , Makhathini, L , Masiteng, P L , Maqabuka, B , McCutchan, E A , Miller, D , Miller, S , Minkova, A , Msebi, L , Mthembu, S H , Ndayishmiye, J , Nieminen, P , Ngcobo, P Z , Ntshamgase, S S , Orce, J N , Peura, P , Rahkila, P , Redon, N , Riedinger, L L , Riley, M A , Roux, D G , Ruotsalainen, P , Piot, J , Saren, J , Sharpey-Schafer, J F , Scholey, C , Shirinda, O , Simpson, J , Sorri, J , Stefansecu, I , Stolze, S , Uusitalo, J , Wang, X , Werner, V , Wood, J L , Yu, C-H , Zhu, S , Zimba, G
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148827 , vital:38777 , https://0-journals.aps.org.wam.seals.ac.za/prc/abstract/10.1103/PhysRevC.101.044312
- Description: Rotational structures have been measured using the Jurogam II and GAMMASPHERE arrays at low spin following the 155Gd(α,2n)157Dy and 148Nd(12C,5n)155Dy reactions at 25 and 65 MeV, respectively. We report high-K bands, which are conjectured to be the first candidates of a Kπ=2+γ vibrational band, built on the [505]11/2− neutron orbital, in both odd-A155,157Dy isotopes. The coupling of the first excited K=0+ states or the so-called β vibrational bands at 661 and 676 keV in 154Dy and 156Dy to the [505]11/2− orbital, to produce a Kπ=11/2− band, was not observed in both 155Dy and 157Dy, respectively. The implication of these findings on the interpretation of the first excited 0+ states in the core nuclei 154Dy and 156Dy are also discussed.
- Full Text:
- Date Issued: 2020
Technology in conservation: towards a system for in-field drone detection of invasive vegetation
- James, Katherine Margaret Frances
- Authors: James, Katherine Margaret Frances
- Date: 2020
- Subjects: Drone aircraft in remote sensing , Neural networks (Computer science) , Drone aircraft in remote sensing -- Case studies , Machine learning , Computer vision , Environmental monitoring -- Remote sensing , Invasive plants -- Monitoring
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/143408 , vital:38244
- Description: Remote sensing can assist in monitoring the spread of invasive vegetation. The adoption of camera-carrying unmanned aerial vehicles, commonly referred to as drones, as remote sensing tools has yielded images of higher spatial resolution than traditional techniques. Drones also have the potential to interact with the environment through the delivery of bio-control or herbicide, as seen with their adoption in precision agriculture. Unlike in agricultural applications, however, invasive plants do not have a predictable position relative to each other within the environment. To facilitate the adoption of drones as an environmental monitoring and management tool, drones need to be able to intelligently distinguish between invasive and non-invasive vegetation on the fly. In this thesis, we present the augmentation of a commercially available drone with a deep machine learning model to investigate the viability of differentiating between an invasive shrub and other vegetation. As a case study, this was applied to the shrub genus Hakea, originating in Australia and invasive in several countries including South Africa. However, for this research, the methodology is important, rather than the chosen target plant. A dataset was collected using the available drone and manually annotated to facilitate the supervised training of the model. Two approaches were explored, namely, classification and semantic segmentation. For each of these, several models were trained and evaluated to find the optimal one. The chosen model was then interfaced with the drone via an Android application on a mobile device and its performance was preliminarily evaluated in the field. Based on these findings, refinements were made and thereafter a thorough field evaluation was performed to determine the best conditions for model operation. Results from the classification task show that deep learning models are capable of distinguishing between target and other shrubs in ideal candidate windows. However, classification in this manner is restricted by the proposal of such candidate windows. End-to-end image segmentation using deep learning overcomes this problem, classifying the image in a pixel-wise manner. Furthermore, the use of appropriate loss functions was found to improve model performance. Field tests show that illumination and shadow pose challenges to the model, but that good recall can be achieved when the conditions are ideal. False positive detection remains an issue that could be improved. This approach shows the potential for drones as an environmental monitoring and management tool when coupled with deep machine learning techniques and outlines potential problems that may be encountered.
- Full Text:
- Date Issued: 2020
- Authors: James, Katherine Margaret Frances
- Date: 2020
- Subjects: Drone aircraft in remote sensing , Neural networks (Computer science) , Drone aircraft in remote sensing -- Case studies , Machine learning , Computer vision , Environmental monitoring -- Remote sensing , Invasive plants -- Monitoring
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/143408 , vital:38244
- Description: Remote sensing can assist in monitoring the spread of invasive vegetation. The adoption of camera-carrying unmanned aerial vehicles, commonly referred to as drones, as remote sensing tools has yielded images of higher spatial resolution than traditional techniques. Drones also have the potential to interact with the environment through the delivery of bio-control or herbicide, as seen with their adoption in precision agriculture. Unlike in agricultural applications, however, invasive plants do not have a predictable position relative to each other within the environment. To facilitate the adoption of drones as an environmental monitoring and management tool, drones need to be able to intelligently distinguish between invasive and non-invasive vegetation on the fly. In this thesis, we present the augmentation of a commercially available drone with a deep machine learning model to investigate the viability of differentiating between an invasive shrub and other vegetation. As a case study, this was applied to the shrub genus Hakea, originating in Australia and invasive in several countries including South Africa. However, for this research, the methodology is important, rather than the chosen target plant. A dataset was collected using the available drone and manually annotated to facilitate the supervised training of the model. Two approaches were explored, namely, classification and semantic segmentation. For each of these, several models were trained and evaluated to find the optimal one. The chosen model was then interfaced with the drone via an Android application on a mobile device and its performance was preliminarily evaluated in the field. Based on these findings, refinements were made and thereafter a thorough field evaluation was performed to determine the best conditions for model operation. Results from the classification task show that deep learning models are capable of distinguishing between target and other shrubs in ideal candidate windows. However, classification in this manner is restricted by the proposal of such candidate windows. End-to-end image segmentation using deep learning overcomes this problem, classifying the image in a pixel-wise manner. Furthermore, the use of appropriate loss functions was found to improve model performance. Field tests show that illumination and shadow pose challenges to the model, but that good recall can be achieved when the conditions are ideal. False positive detection remains an issue that could be improved. This approach shows the potential for drones as an environmental monitoring and management tool when coupled with deep machine learning techniques and outlines potential problems that may be encountered.
- Full Text:
- Date Issued: 2020
Retracted COVID-19 Papers and the level of 'citation pollution': a preliminary analysis and directions for future research
- Van der Walt, Wynand, Willems, Kris A, Friedrich, Wernher, Hatsu, Sylvester, Krauss, Kirstin
- Authors: Van der Walt, Wynand , Willems, Kris A , Friedrich, Wernher , Hatsu, Sylvester , Krauss, Kirstin
- Date: 2020
- Subjects: Retraction watch , Research -- Evaluation , Bibliographical citations -- Evaluation , Science publishing -- Corrupt practices , Scholarly publishing -- Corrupt practices , Learning and scholarship -- Corrupt practices , Medical publishing -- Corrupt practices , COVID-19 (Disease) -- Publishing
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/167732 , vital:41508 , https://www.abd-bvd.be/nl/bladen-voor-documentatie/2020-3-4/
- Description: Retraction Watch maintains a "running list" of retracted papers on Covid-19 related research. By the end of September 2020, thirty-three retracted Covid-19 papers were listed. We analysed these retracted papers, focusing specifically on how they have been cited by review papers, and subsequently how they have penetrated and potentially distorted public discourse and legitimate research on Covid-19. The study demonstrates the need for more in-depth studies that focus on the phenomenon of citation pollution. We show that the "Covid-19 publication race", amplified by a pressure-to-publish research culture, distorted published science on Covid-19. We highlight the urgency to engage popular media and critical decision makers on how to distinguish between questionable and legitimate science. We also emphasise the importance of dealing with illegitimate research in a timely manner, both from a scholarly communications and research quality perspective. , Retraction Watch maintient une "liste courante" des articles rétractés sur les recherches liées au Covid-19. Fin septembre 2020, trente-trois articles rétractés sur le Covid-19 étaient répertoriés. Nous avons analysé ces articles rétractés, en nous concentrant spécifiquement sur la façon dont ils ont été cités par d'autres articles, et ensuite sur la façon dont ils ont pénétré et potentiellement faussé le discours public et la recherche légitime sur le Covid-19. L'étude démontre le besoin d'études plus approfondies qui se concentrent sur le phénomène de la pollution des citations. Nous montrons que la "course à la publication sur le Covid-19", amplifiée par une culture de la pression à la publication de la recherche, a déformé l'information scientifique publiée sur le Covid-19. Nous soulignons l'urgence d'engager les médias populaires et les décideurs critiques sur la manière de distinguer la science douteuse de la science légitime. Nous soulignons également l'importance de traiter rapidement les recherches illégitimes, tant du point de vue de la communication scientifique que de la qualité de la recherche. , Retraction Watch houdt een "lopende lijst" bij van ingetrokken papieren over Covid-19-gerelateerd onderzoek. Eind september 2020 waren drieëndertig ingetrokken Covid-19 papieren op de lijst geplaatst. We hebben deze ingetrokken papieren geanalyseerd, waarbij we ons specifiek hebben gericht op de manier waarop ze zijn geciteerd door review papers, en vervolgens op de manier waarop ze zijn doorgedrongen en mogelijk vervormd in het publieke discours en het legitieme onderzoek naar Covid-19. De studie toont aan dat er behoefte is aan meer diepgaande studies die zich richten op het fenomeen van de citatievervuiling. We tonen aan dat de "Covid-19-publicatierace", versterkt door een druk om te publiceren onderzoekscultuur, de gepubliceerde wetenschap over Covid-19 vertekend heeft. We benadrukken de urgentie om de populaire media en kritische besluitvormers te betrekken bij het maken van een onderscheid tussen twijfelachtige en legitieme wetenschap. We benadrukken ook het belang van het tijdig aanpakken van onrechtmatig onderzoek, zowel vanuit het oogpunt van wetenschappelijke communicatie als vanuit het oogpunt van de kwaliteit van het onderzoek.
- Full Text:
- Date Issued: 2020
- Authors: Van der Walt, Wynand , Willems, Kris A , Friedrich, Wernher , Hatsu, Sylvester , Krauss, Kirstin
- Date: 2020
- Subjects: Retraction watch , Research -- Evaluation , Bibliographical citations -- Evaluation , Science publishing -- Corrupt practices , Scholarly publishing -- Corrupt practices , Learning and scholarship -- Corrupt practices , Medical publishing -- Corrupt practices , COVID-19 (Disease) -- Publishing
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/167732 , vital:41508 , https://www.abd-bvd.be/nl/bladen-voor-documentatie/2020-3-4/
- Description: Retraction Watch maintains a "running list" of retracted papers on Covid-19 related research. By the end of September 2020, thirty-three retracted Covid-19 papers were listed. We analysed these retracted papers, focusing specifically on how they have been cited by review papers, and subsequently how they have penetrated and potentially distorted public discourse and legitimate research on Covid-19. The study demonstrates the need for more in-depth studies that focus on the phenomenon of citation pollution. We show that the "Covid-19 publication race", amplified by a pressure-to-publish research culture, distorted published science on Covid-19. We highlight the urgency to engage popular media and critical decision makers on how to distinguish between questionable and legitimate science. We also emphasise the importance of dealing with illegitimate research in a timely manner, both from a scholarly communications and research quality perspective. , Retraction Watch maintient une "liste courante" des articles rétractés sur les recherches liées au Covid-19. Fin septembre 2020, trente-trois articles rétractés sur le Covid-19 étaient répertoriés. Nous avons analysé ces articles rétractés, en nous concentrant spécifiquement sur la façon dont ils ont été cités par d'autres articles, et ensuite sur la façon dont ils ont pénétré et potentiellement faussé le discours public et la recherche légitime sur le Covid-19. L'étude démontre le besoin d'études plus approfondies qui se concentrent sur le phénomène de la pollution des citations. Nous montrons que la "course à la publication sur le Covid-19", amplifiée par une culture de la pression à la publication de la recherche, a déformé l'information scientifique publiée sur le Covid-19. Nous soulignons l'urgence d'engager les médias populaires et les décideurs critiques sur la manière de distinguer la science douteuse de la science légitime. Nous soulignons également l'importance de traiter rapidement les recherches illégitimes, tant du point de vue de la communication scientifique que de la qualité de la recherche. , Retraction Watch houdt een "lopende lijst" bij van ingetrokken papieren over Covid-19-gerelateerd onderzoek. Eind september 2020 waren drieëndertig ingetrokken Covid-19 papieren op de lijst geplaatst. We hebben deze ingetrokken papieren geanalyseerd, waarbij we ons specifiek hebben gericht op de manier waarop ze zijn geciteerd door review papers, en vervolgens op de manier waarop ze zijn doorgedrongen en mogelijk vervormd in het publieke discours en het legitieme onderzoek naar Covid-19. De studie toont aan dat er behoefte is aan meer diepgaande studies die zich richten op het fenomeen van de citatievervuiling. We tonen aan dat de "Covid-19-publicatierace", versterkt door een druk om te publiceren onderzoekscultuur, de gepubliceerde wetenschap over Covid-19 vertekend heeft. We benadrukken de urgentie om de populaire media en kritische besluitvormers te betrekken bij het maken van een onderscheid tussen twijfelachtige en legitieme wetenschap. We benadrukken ook het belang van het tijdig aanpakken van onrechtmatig onderzoek, zowel vanuit het oogpunt van wetenschappelijke communicatie als vanuit het oogpunt van de kwaliteit van het onderzoek.
- Full Text:
- Date Issued: 2020
Dragonfly (Odonata) community structure in the Eastern Highlands Biodiversity Hotspot of Zimbabwe: potential threats of land use changes on freshwater invertebrates
- Mafuwe, Kudzai, Moyo, Sydney
- Authors: Mafuwe, Kudzai , Moyo, Sydney
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158265 , vital:40167 , https://doi.org/10.1080/13887890.2020.1768156
- Description: We examined the diversity and potential drivers of dragonfly distribution in a biodiversity hotspot of Southern Africa (Eastern Highlands, Zimbabwe) by surveying 30 sites (13 lentic and 17 lotic habitats) located within this region. Additionally, we identified the anthropogenic factors that may threaten Odonata diversity and abundance.
- Full Text:
- Date Issued: 2020
- Authors: Mafuwe, Kudzai , Moyo, Sydney
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158265 , vital:40167 , https://doi.org/10.1080/13887890.2020.1768156
- Description: We examined the diversity and potential drivers of dragonfly distribution in a biodiversity hotspot of Southern Africa (Eastern Highlands, Zimbabwe) by surveying 30 sites (13 lentic and 17 lotic habitats) located within this region. Additionally, we identified the anthropogenic factors that may threaten Odonata diversity and abundance.
- Full Text:
- Date Issued: 2020
Hop as an anti-cancer drug target
- Vaaltyn, Michaelone Chantelle
- Authors: Vaaltyn, Michaelone Chantelle
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/164704 , vital:41156 , doi:10.21504/10962/164704
- Description: Thesis (PhD)--Rhodes University, Biochemistry and Microbiology, 2020
- Full Text:
- Date Issued: 2020
- Authors: Vaaltyn, Michaelone Chantelle
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/164704 , vital:41156 , doi:10.21504/10962/164704
- Description: Thesis (PhD)--Rhodes University, Biochemistry and Microbiology, 2020
- Full Text:
- Date Issued: 2020
Enactment of hands-on practical activities through using easily accessible resources in a Grade 10 Physical Science classroom
- Authors: Ndevahoma, Martha Kashike
- Date: 2020
- Subjects: Physical science -- Study and teaching (Secondary) -- Namibia
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/110229 , vital:33251
- Description: The Namibian National Subject Policy Guide for Physical Science Grade 8-12 (MoE, 2010) indicates that science teachers should be creative and innovative in producing their own teaching and learning support materials that are linked to practice. Practical activities play a major role in the learning of science. Due to the lack of science laboratory equipment, however, minimal practical activities are done in some schools especially under-resourced disadvantaged schools. It is against this background that this case study investigated the possibilities and challenges associated with the use of easily accessible resources to carry out hands-on practical activities. Underpinned by an interpretive paradigm, this study used a mixed-method approach by generating both quantitative and qualitative data. It was carried out in the Otjozondjupa region in Namibia at Wato Secondary School (pseudonym). It was conducted with a Grade 10 Physical Science class consisting of 30 learners. To generate data, questionnaires, focus group interviews, lesson observations, stimulated recall interviews, as well as learners’ journal reflections were used. Conceptions, dispositions, interest and sense-making were used as conceptual lenses while Vygotsky’s social constructivism was the theoretical framework that informed this study. Quantitative data were analysed using the conceptual lenses and were subsequently presented in tables and graphs. That is, a deductive approach to analysis was used. On the other hand, a thematic approach was used to analyse the qualitative data. That is, qualitative data were inductively analysed to come up with sub-themes and themes. The findings from this study revealed significant shifts in learners’ conceptions, dispositions and interest towards science after the use of easily accessible resources to do hands-on practical activities. Similarly, learners’ sense-making of science concepts improved. This study thus recommends that science teachers should, where possible, make use of easily accessible resources to carry out hands-on practical activities during their science lessons. During such hands-on practicals, however, emphasis should be on the development of scientific concepts.
- Full Text:
- Date Issued: 2020
- Authors: Ndevahoma, Martha Kashike
- Date: 2020
- Subjects: Physical science -- Study and teaching (Secondary) -- Namibia
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/110229 , vital:33251
- Description: The Namibian National Subject Policy Guide for Physical Science Grade 8-12 (MoE, 2010) indicates that science teachers should be creative and innovative in producing their own teaching and learning support materials that are linked to practice. Practical activities play a major role in the learning of science. Due to the lack of science laboratory equipment, however, minimal practical activities are done in some schools especially under-resourced disadvantaged schools. It is against this background that this case study investigated the possibilities and challenges associated with the use of easily accessible resources to carry out hands-on practical activities. Underpinned by an interpretive paradigm, this study used a mixed-method approach by generating both quantitative and qualitative data. It was carried out in the Otjozondjupa region in Namibia at Wato Secondary School (pseudonym). It was conducted with a Grade 10 Physical Science class consisting of 30 learners. To generate data, questionnaires, focus group interviews, lesson observations, stimulated recall interviews, as well as learners’ journal reflections were used. Conceptions, dispositions, interest and sense-making were used as conceptual lenses while Vygotsky’s social constructivism was the theoretical framework that informed this study. Quantitative data were analysed using the conceptual lenses and were subsequently presented in tables and graphs. That is, a deductive approach to analysis was used. On the other hand, a thematic approach was used to analyse the qualitative data. That is, qualitative data were inductively analysed to come up with sub-themes and themes. The findings from this study revealed significant shifts in learners’ conceptions, dispositions and interest towards science after the use of easily accessible resources to do hands-on practical activities. Similarly, learners’ sense-making of science concepts improved. This study thus recommends that science teachers should, where possible, make use of easily accessible resources to carry out hands-on practical activities during their science lessons. During such hands-on practicals, however, emphasis should be on the development of scientific concepts.
- Full Text:
- Date Issued: 2020
New directions in Maritime and Fisheries Anthropology:
- Authors: Aswani, Shankar
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179028 , vital:40101 , https://0-doi.org.wam.seals.ac.za/10.1111/aman.13380
- Description: Maritime and fisheries anthropology is a mixture of different themes couched under various theoretical frameworks that straddle the humanities and the sciences. In this subject survey, I explore different thematic and theoretical strands of maritime and fisheries anthropology and illustrate broader changes in this subdiscipline since around the mid‐1990s. I also review developing and future thematic and theoretical research frontiers, and discuss their potential contribution to a public and actionable anthropology/scholarship that can better inform fisheries management and conservation. This is important because in the twenty‐first century, coastal peoples are facing socioeconomic and environmental challenges that are increasingly becoming hazardous. To create a more actionable discipline, anthropology needs to be more accessible, inform innovation, and recapture a more pluralistic scholarship that champions interdisciplinary work. This will require the consilience between the humanities and natural sciences for studying human–marine interactions more broadly and for protecting the marine environment.
- Full Text:
- Date Issued: 2020
- Authors: Aswani, Shankar
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179028 , vital:40101 , https://0-doi.org.wam.seals.ac.za/10.1111/aman.13380
- Description: Maritime and fisheries anthropology is a mixture of different themes couched under various theoretical frameworks that straddle the humanities and the sciences. In this subject survey, I explore different thematic and theoretical strands of maritime and fisheries anthropology and illustrate broader changes in this subdiscipline since around the mid‐1990s. I also review developing and future thematic and theoretical research frontiers, and discuss their potential contribution to a public and actionable anthropology/scholarship that can better inform fisheries management and conservation. This is important because in the twenty‐first century, coastal peoples are facing socioeconomic and environmental challenges that are increasingly becoming hazardous. To create a more actionable discipline, anthropology needs to be more accessible, inform innovation, and recapture a more pluralistic scholarship that champions interdisciplinary work. This will require the consilience between the humanities and natural sciences for studying human–marine interactions more broadly and for protecting the marine environment.
- Full Text:
- Date Issued: 2020
Livelihood implications of a possible Ramsar declaration of the Swartkops estuary, Eastern Cape, South Africa
- Authors: Vembo, Glen Muchengeti
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164715 , vital:41157
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Environmental Science, 2020
- Full Text:
- Date Issued: 2020
- Authors: Vembo, Glen Muchengeti
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164715 , vital:41157
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Environmental Science, 2020
- Full Text:
- Date Issued: 2020
Satire in J.J. R. Jolobe's literary works : a critique in relation to contemporary South Africa
- Authors: Benayo, Xolela
- Date: 2020
- Subjects: Jolobe, James J. R. , Xhosa literature -- History and criticism , Xhosa poetry -- History and criticism , Humor in literature , Xhosa literature -- Humor , Xhosa language
- Language: English , Xhosa
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/161762 , vital:40667
- Description: J.J.R. Jolobe is regarded as one of the individuals who made a valuable contribution to the development of isiXhosa literature through his works, notably in his poetry (Ilitha, Umyezo; Jolobe 1936). His poetry ranges from abstract subjects to more philosophical matters. This study is aimed at decoding the manner in which he employs satire to conscientise African people of the then horrible situation that they were facing. With that said, poetry will not be the only work that this thesis analyses in the process of evaluating Jolobe’s satire; his essays will also be examined (Amavo; Jolobe 1940). Based on the writings of various authors specialising in the subject, satire has been deemed to be a style of literary writing, one which involves invective satire. For the researcher, that statement will be rebutted, as it will be argued that the mode of satire need not be wholly invective. Jolobe’s light-hearted satire not only showcases the amusing side of his writings, but also indicates the seriousness with which they were intended. Themes covered in Jolobe’s satire have inspired the researcher to evaluate these literary texts in relation to modern contexts, especially when it comes to the relationship between the lines of the author’s experience and the public. With that said, the social role of satire is something that one cannot deny. One could therefore say that there is an urgent need for African satirists to face the existing social and economic reality as authentically as possible. The voice of a satirist should also echo the voice of their society as a whole. Satirical study in post-colonial Africa, in South Africa in particular, is useful due to the idea that the works of the likes of Jolobe may diminish in significance due to neo-colonialism. In fact, this is the point which is considered in this study of Jolobe’s satire. This study also examines stages afforded to the development of satire in Africa, especially in the post-colonial era. The purpose is to identify the effects of satire that are related to socio-political as well as religious factors. These factors are often seen as those that play a vital role is one’s personal morals, and those that are meant to shape the whole community. Jolobe addresses imperialism and the class struggle, which speaks to the society’s loyalties regarding the mobilization toward realizing the dream of being independent. This speaks to the works analysed, revealing protests against oppression and exploitation by imperialists; such works show how inhumane people could be against those who they deem to be beneath their standards. Researchers like Mahlasela (1973), Sirayi (1985), Kwetana (2000) and Khumalo (2015) are amongst those who have made it a point to study Jolobe to ensure that these works are kept alive, along with their significance. Other prospective researchers can follow suite in researching the great Jolobe. In ensuring that the aims of this study come to light, the researcher will be using socialist realism as a way of seeing that the works of Jolobe are realistic in nature. With that said, there will be an exploration of allegoric satire. Satiric allegory will be evaluated with regard to the view that it represents a unique slant on satire, whereby it deems satire to be more than just a supportive method of literary criticism. This allows the researcher to hold the view that satire should not be a restrictive framework when dealing with African literature. Satire as a modern form of criticism can be viewed as having an element of humanism, which would result in the satirist doing all he can to make sure that what is satirized is not isolated from the struggle of the community. It is for the above-mentioned reasons that we see a big challenge in the future development of satiric discourse in African literature.
- Full Text:
- Date Issued: 2020
- Authors: Benayo, Xolela
- Date: 2020
- Subjects: Jolobe, James J. R. , Xhosa literature -- History and criticism , Xhosa poetry -- History and criticism , Humor in literature , Xhosa literature -- Humor , Xhosa language
- Language: English , Xhosa
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/161762 , vital:40667
- Description: J.J.R. Jolobe is regarded as one of the individuals who made a valuable contribution to the development of isiXhosa literature through his works, notably in his poetry (Ilitha, Umyezo; Jolobe 1936). His poetry ranges from abstract subjects to more philosophical matters. This study is aimed at decoding the manner in which he employs satire to conscientise African people of the then horrible situation that they were facing. With that said, poetry will not be the only work that this thesis analyses in the process of evaluating Jolobe’s satire; his essays will also be examined (Amavo; Jolobe 1940). Based on the writings of various authors specialising in the subject, satire has been deemed to be a style of literary writing, one which involves invective satire. For the researcher, that statement will be rebutted, as it will be argued that the mode of satire need not be wholly invective. Jolobe’s light-hearted satire not only showcases the amusing side of his writings, but also indicates the seriousness with which they were intended. Themes covered in Jolobe’s satire have inspired the researcher to evaluate these literary texts in relation to modern contexts, especially when it comes to the relationship between the lines of the author’s experience and the public. With that said, the social role of satire is something that one cannot deny. One could therefore say that there is an urgent need for African satirists to face the existing social and economic reality as authentically as possible. The voice of a satirist should also echo the voice of their society as a whole. Satirical study in post-colonial Africa, in South Africa in particular, is useful due to the idea that the works of the likes of Jolobe may diminish in significance due to neo-colonialism. In fact, this is the point which is considered in this study of Jolobe’s satire. This study also examines stages afforded to the development of satire in Africa, especially in the post-colonial era. The purpose is to identify the effects of satire that are related to socio-political as well as religious factors. These factors are often seen as those that play a vital role is one’s personal morals, and those that are meant to shape the whole community. Jolobe addresses imperialism and the class struggle, which speaks to the society’s loyalties regarding the mobilization toward realizing the dream of being independent. This speaks to the works analysed, revealing protests against oppression and exploitation by imperialists; such works show how inhumane people could be against those who they deem to be beneath their standards. Researchers like Mahlasela (1973), Sirayi (1985), Kwetana (2000) and Khumalo (2015) are amongst those who have made it a point to study Jolobe to ensure that these works are kept alive, along with their significance. Other prospective researchers can follow suite in researching the great Jolobe. In ensuring that the aims of this study come to light, the researcher will be using socialist realism as a way of seeing that the works of Jolobe are realistic in nature. With that said, there will be an exploration of allegoric satire. Satiric allegory will be evaluated with regard to the view that it represents a unique slant on satire, whereby it deems satire to be more than just a supportive method of literary criticism. This allows the researcher to hold the view that satire should not be a restrictive framework when dealing with African literature. Satire as a modern form of criticism can be viewed as having an element of humanism, which would result in the satirist doing all he can to make sure that what is satirized is not isolated from the struggle of the community. It is for the above-mentioned reasons that we see a big challenge in the future development of satiric discourse in African literature.
- Full Text:
- Date Issued: 2020
Effectiveness of private land conservation areas in maintaining natural land cover and biodiversity intactness
- Shumba, Tafadzwa, de Vos, Alta, Biggs, Reinette, Esler, Karen J, Ament, Judith M, Clements, Hayley S
- Authors: Shumba, Tafadzwa , de Vos, Alta , Biggs, Reinette , Esler, Karen J , Ament, Judith M , Clements, Hayley S
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/415852 , vital:71294 , xlink:href="https://doi.org/10.1016/j.gecco.2020.e00935"
- Description: Private land conservation areas (PLCAs) are increasingly looked to for meeting the deficit left by state-owned protected areas in reaching global conservation targets. However, despite the increasing extent and recognition of PLCAs as a complementary conservation strategy, little research has been done to quantify their effectiveness; a critical consideration if they are to be counted towards international biodiversity conservation targets. The long history of PLCAs in South Africa provides an interesting case study to address this knowledge gap. Here, we quantified the effectiveness of South African PLCAs by comparing losses in natural land cover and biodiversity intactness within PLCAs with different levels of protection to that of unprotected control points. Points within PLCAs were matched with unprotected control points to test the prediction that if PLCAs offer effective protection, losses in natural land cover and biodiversity intactness would be significantly lower within their boundaries in comparison to unprotected controls exposed to similar conditions. Consequences of natural land cover loss on biodiversity intactness were thus assessed, thus advancing standard approaches for quantifying effectiveness.
- Full Text:
- Date Issued: 2020
- Authors: Shumba, Tafadzwa , de Vos, Alta , Biggs, Reinette , Esler, Karen J , Ament, Judith M , Clements, Hayley S
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/415852 , vital:71294 , xlink:href="https://doi.org/10.1016/j.gecco.2020.e00935"
- Description: Private land conservation areas (PLCAs) are increasingly looked to for meeting the deficit left by state-owned protected areas in reaching global conservation targets. However, despite the increasing extent and recognition of PLCAs as a complementary conservation strategy, little research has been done to quantify their effectiveness; a critical consideration if they are to be counted towards international biodiversity conservation targets. The long history of PLCAs in South Africa provides an interesting case study to address this knowledge gap. Here, we quantified the effectiveness of South African PLCAs by comparing losses in natural land cover and biodiversity intactness within PLCAs with different levels of protection to that of unprotected control points. Points within PLCAs were matched with unprotected control points to test the prediction that if PLCAs offer effective protection, losses in natural land cover and biodiversity intactness would be significantly lower within their boundaries in comparison to unprotected controls exposed to similar conditions. Consequences of natural land cover loss on biodiversity intactness were thus assessed, thus advancing standard approaches for quantifying effectiveness.
- Full Text:
- Date Issued: 2020
Anti-cancer and anti-trypanosomal properties of alkaloids from the root bark of Zanthoxylum leprieurii Guill and Perr
- Eze, Fabian I, Siwe-Noundou, Xavier, Isaacs, Michelle, Patala, Srivinas, Osadebe, Patience O, Krause, Rui W M
- Authors: Eze, Fabian I , Siwe-Noundou, Xavier , Isaacs, Michelle , Patala, Srivinas , Osadebe, Patience O , Krause, Rui W M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193352 , vital:45324 , xlink:href="http://dx.doi.org/10.4314/tjpr.v19i11.19"
- Description: Purpose: To isolate the anti-cancer and anti-trypanosomal principles of Zanthoxylum leprieurii, a medicinally versatile wild tropical plant used for managing tumours, African trypanosomiasis, and inflammation in southeastern Nigeria. Methods: The pure compounds were isolated using chromatographic methods. The structural elucidation of the pure compounds was based on their NMR (1D and 2D) and mass spectral data as well as chemical test results. Structure-activity relationships were based on the structural differences among the compounds. The cytotoxicity of the extracts and compounds (1, 2, 3, and 4) was evaluated in HeLa (human cervix adenocarcinoma) cell line while the trypanocidal activities were evaluated on Trypanosoma brucei brucei. Results: Two acridone alkaloids, 1-hydroxy-3-methoxy-10-methylacridin-9 (10H)-one, named fabiocinine (1), and 1-hydroxy-2,3-dimethoxy-10-methylacridin-9 (10H)-one (arborinine, 2), together with a furoquinoline alkaloid, skimmianine (3), and a chelerythrine derivative, 6-acetonyl-5,6-dihydrochelerythrine (4) were isolated from the root bark of Zanthoxylum leprieurii. Skimmianine (3) exhibited cytotoxicity and anti-trypanosomal IC50 of 12.8 and 13.2 µg/mL respectively (p less than 0.05). Compound (1) and arborinine (2) were selectively cytotoxic to HeLa cells with cytotoxicity IC50 of 28.49 and 62.71 µg/mL, respectively, while (4) did not show significant activity (p less than 0.05). Conclusion: Zanthoxylum leprieurii root bark contains cytotoxic and trypanocidal compounds, and is thus a potential source of anti-cancer and anti-trypanosomal leads.
- Full Text:
- Date Issued: 2020
- Authors: Eze, Fabian I , Siwe-Noundou, Xavier , Isaacs, Michelle , Patala, Srivinas , Osadebe, Patience O , Krause, Rui W M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193352 , vital:45324 , xlink:href="http://dx.doi.org/10.4314/tjpr.v19i11.19"
- Description: Purpose: To isolate the anti-cancer and anti-trypanosomal principles of Zanthoxylum leprieurii, a medicinally versatile wild tropical plant used for managing tumours, African trypanosomiasis, and inflammation in southeastern Nigeria. Methods: The pure compounds were isolated using chromatographic methods. The structural elucidation of the pure compounds was based on their NMR (1D and 2D) and mass spectral data as well as chemical test results. Structure-activity relationships were based on the structural differences among the compounds. The cytotoxicity of the extracts and compounds (1, 2, 3, and 4) was evaluated in HeLa (human cervix adenocarcinoma) cell line while the trypanocidal activities were evaluated on Trypanosoma brucei brucei. Results: Two acridone alkaloids, 1-hydroxy-3-methoxy-10-methylacridin-9 (10H)-one, named fabiocinine (1), and 1-hydroxy-2,3-dimethoxy-10-methylacridin-9 (10H)-one (arborinine, 2), together with a furoquinoline alkaloid, skimmianine (3), and a chelerythrine derivative, 6-acetonyl-5,6-dihydrochelerythrine (4) were isolated from the root bark of Zanthoxylum leprieurii. Skimmianine (3) exhibited cytotoxicity and anti-trypanosomal IC50 of 12.8 and 13.2 µg/mL respectively (p less than 0.05). Compound (1) and arborinine (2) were selectively cytotoxic to HeLa cells with cytotoxicity IC50 of 28.49 and 62.71 µg/mL, respectively, while (4) did not show significant activity (p less than 0.05). Conclusion: Zanthoxylum leprieurii root bark contains cytotoxic and trypanocidal compounds, and is thus a potential source of anti-cancer and anti-trypanosomal leads.
- Full Text:
- Date Issued: 2020
A q-metholological approach to audience reception of public awareness messages on sexual violence
- Authors: Bennie, Rachel
- Date: 2020
- Subjects: Psychology -- Research -- Methodology , Psychology -- Research , Communication in social action -- South Africa , Psychology -- Research -- South Africa , Women -- Violence against -- South Africa , Women -- Violence against -- South Africa -- Prevention
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/140805 , vital:37920
- Description: Public awareness poster campaigns are an often-used method for raising awareness about, and engaging audiences on the topic of rape and other forms of sexual violence (Potter, 2012). However, poster campaigns, as social artefacts, operate in a public arena in which numerous discourses about a phenomenon are produced, reproduced and interact with each other, with sometimes unintended/unanticipated discursive consequences (Böhmke, Bennie, Minnie, Moore, Pilusa & Pollock, 2015). How messages aimed at raising awareness of sexual violence are framed has the potential to reproduce dominant social narratives and gendered subject positions in ways that reinforce notions of men as active sexual agents and potential perpetrators, and women as sexually passive and potential victims (Gavey, 2005). Other approaches, such as bystander intervention, seek to move away from a focus on victims and perpetrators to emphasise the role that community members can play in risk detection, safety promotion and the prevention of sexual violence (McMahon & Banyard, 2012). Since a range of possible messages about sexual violence can be communicated through poster campaigns, it is important to critically examine the content and orientation of campaign material. This study focused on intended audience views regarding messages about sexual violence contained in anti-sexual violence poster materials. The purpose was to collaborate with a selected audience to better understand which messages are effective and which strategies of communication are perceived to be less so. Through the use of Q-methodology, volunteer participants were invited to express their opinions in relation to messages about sexual violence from a range of posters from several international campaigns. The analysis focused on uncovering the discursive subject positions that participants’ express in their attitudinal responses to the poster messages, providing not only a description of these positions, but also illustrating the level of resonance that the poster messages may find with intended audiences. The aim of the study is to potentially inform the development of more focused campaign material, tailored to the specific context from which participants were drawn. Analysis shows clear patterns of audience resistance towards stereotypical representations of sexual violence and messages that are geared towards the simple prohibition of behaviours. The findings highlight the need for the development of alternative strategies of engagement that focus on specific engagement with understandings of sexual violence in the context of intimate and/or acquaintance relationships and which are aimed at inviting audiences to take up a position in relation to sexual violence phenomena that troubles the reproduction of received notions of gendered subjectivities and (hetero) sexuality
- Full Text:
- Date Issued: 2020
- Authors: Bennie, Rachel
- Date: 2020
- Subjects: Psychology -- Research -- Methodology , Psychology -- Research , Communication in social action -- South Africa , Psychology -- Research -- South Africa , Women -- Violence against -- South Africa , Women -- Violence against -- South Africa -- Prevention
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/140805 , vital:37920
- Description: Public awareness poster campaigns are an often-used method for raising awareness about, and engaging audiences on the topic of rape and other forms of sexual violence (Potter, 2012). However, poster campaigns, as social artefacts, operate in a public arena in which numerous discourses about a phenomenon are produced, reproduced and interact with each other, with sometimes unintended/unanticipated discursive consequences (Böhmke, Bennie, Minnie, Moore, Pilusa & Pollock, 2015). How messages aimed at raising awareness of sexual violence are framed has the potential to reproduce dominant social narratives and gendered subject positions in ways that reinforce notions of men as active sexual agents and potential perpetrators, and women as sexually passive and potential victims (Gavey, 2005). Other approaches, such as bystander intervention, seek to move away from a focus on victims and perpetrators to emphasise the role that community members can play in risk detection, safety promotion and the prevention of sexual violence (McMahon & Banyard, 2012). Since a range of possible messages about sexual violence can be communicated through poster campaigns, it is important to critically examine the content and orientation of campaign material. This study focused on intended audience views regarding messages about sexual violence contained in anti-sexual violence poster materials. The purpose was to collaborate with a selected audience to better understand which messages are effective and which strategies of communication are perceived to be less so. Through the use of Q-methodology, volunteer participants were invited to express their opinions in relation to messages about sexual violence from a range of posters from several international campaigns. The analysis focused on uncovering the discursive subject positions that participants’ express in their attitudinal responses to the poster messages, providing not only a description of these positions, but also illustrating the level of resonance that the poster messages may find with intended audiences. The aim of the study is to potentially inform the development of more focused campaign material, tailored to the specific context from which participants were drawn. Analysis shows clear patterns of audience resistance towards stereotypical representations of sexual violence and messages that are geared towards the simple prohibition of behaviours. The findings highlight the need for the development of alternative strategies of engagement that focus on specific engagement with understandings of sexual violence in the context of intimate and/or acquaintance relationships and which are aimed at inviting audiences to take up a position in relation to sexual violence phenomena that troubles the reproduction of received notions of gendered subjectivities and (hetero) sexuality
- Full Text:
- Date Issued: 2020
An investigation into the use of visualisation processes as a teaching strategy to enhance number sense
- Authors: Griqua, Ronald Max
- Date: 2020
- Subjects: Mathematics -- Study and teaching -- South Africa , Mathematics -- Study and teaching -- Psychological aspects , Visualization , Number concept , RUMEP (Rhodes University Mathematics Education Project)
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/147226 , vital:38606
- Description: The literature agrees that in order to improve learning outcomes, instruction in classrooms should be improved first. Mathematics educationists therefore advocate that schools should make extensive and deep efforts to rethink their instructional programmes. Research furthermore suggests that increasingly, indicators on school performance and teaching reveal largely unacknowledged problematic teaching of mathematics in the great majority of South African schools. This research study is therefore a contribution towards rethinking the teaching strategies within mathematics classrooms. The study examined the use of visualisation processes in order to understand how these interact with the pedagogy of selected mathematics teachers when they teach number sense after participating in an intervention programme. This study argues that the effective use of visualisation processes enhanced the teaching of number sense. The research study was framed as a case study that was grounded within the interpretive paradigm. The study was located in classrooms where the participating teachers promoted active learning after taking part in an intervention programme. A constructivist theoretical underpinning was therefore adopted. At the heart of the study was the Visualisation Intervention Programme (VIP), which involved seven Rhodes University Mathematics Education Project (RUMEP) teachers within the John Taolo Gaetsewe District of the Northern Cape Province. The content of the VIP was informed by initially working with five teachers of well-resourced schools within the Northern Cape who made interesting use of visualisation processes and manipulatives to teach number sense. With the assistance of these five teachers, the VIP was then implemented by seven selected RUMEP teachers to investigate the role of visualisation processes in the teaching of number sense understandings. The study employed a mixed method approach. Qualitative data was collected through observations and interviews, while quantitative data was collected with a series of pre- and post-tests. The analysis of the findings of this research study revealed that the effective use of visualisation processes was instrumental in enhancing the teaching of number sense understandings. Furthermore, the use of visualisation processes by the selected teachers fostered independent thought and conceptual understanding of number sense topics on the part of their learners.
- Full Text:
- Date Issued: 2020
- Authors: Griqua, Ronald Max
- Date: 2020
- Subjects: Mathematics -- Study and teaching -- South Africa , Mathematics -- Study and teaching -- Psychological aspects , Visualization , Number concept , RUMEP (Rhodes University Mathematics Education Project)
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/147226 , vital:38606
- Description: The literature agrees that in order to improve learning outcomes, instruction in classrooms should be improved first. Mathematics educationists therefore advocate that schools should make extensive and deep efforts to rethink their instructional programmes. Research furthermore suggests that increasingly, indicators on school performance and teaching reveal largely unacknowledged problematic teaching of mathematics in the great majority of South African schools. This research study is therefore a contribution towards rethinking the teaching strategies within mathematics classrooms. The study examined the use of visualisation processes in order to understand how these interact with the pedagogy of selected mathematics teachers when they teach number sense after participating in an intervention programme. This study argues that the effective use of visualisation processes enhanced the teaching of number sense. The research study was framed as a case study that was grounded within the interpretive paradigm. The study was located in classrooms where the participating teachers promoted active learning after taking part in an intervention programme. A constructivist theoretical underpinning was therefore adopted. At the heart of the study was the Visualisation Intervention Programme (VIP), which involved seven Rhodes University Mathematics Education Project (RUMEP) teachers within the John Taolo Gaetsewe District of the Northern Cape Province. The content of the VIP was informed by initially working with five teachers of well-resourced schools within the Northern Cape who made interesting use of visualisation processes and manipulatives to teach number sense. With the assistance of these five teachers, the VIP was then implemented by seven selected RUMEP teachers to investigate the role of visualisation processes in the teaching of number sense understandings. The study employed a mixed method approach. Qualitative data was collected through observations and interviews, while quantitative data was collected with a series of pre- and post-tests. The analysis of the findings of this research study revealed that the effective use of visualisation processes was instrumental in enhancing the teaching of number sense understandings. Furthermore, the use of visualisation processes by the selected teachers fostered independent thought and conceptual understanding of number sense topics on the part of their learners.
- Full Text:
- Date Issued: 2020
Initiating biological control for Nymphaea mexicana zuccarini (Nymphaeaceae) in South Africa
- Authors: Reid, Megan
- Date: 2020
- Subjects: Nymphaea mexicana zuccarini -- Biological control -- South Africa , Nymphaeaceae -- Biological control -- South Africa , Invasive plants -- Biological control -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/144510 , vital:38352
- Description: Nymphaea mexicana Zuccarini (Nymphaeaceae) is an aquatic plant originating from south-eastern USA that is becoming increasingly invasive in South Africa as other invasive aquatic plants are being managed successfully through biological control. Mechanical and chemical control of aquatic weeds is expensive, damaging to the environment, and only effective in the short term, so biological control is more desirable as a management strategy for N. mexicana. The biological control of invasive alien plants requires that agents are host specific so that non-target risks are mitigated. For success to be achieved, it is important to ensure that the genetic structure of invasive populations is clarified so that agents can be collected from populations in the native range that match genetically to populations in the invasive range. This is especially important in cases where the morphology of invasive alien plants does not reflect genetic differences between populations. A previous study of the genetic structure of the invasive populations of N. mexicana in South Africa suggests the presence of hybrid forms of the plant in South Africa, with only one of these populations matching with samples from the native range. However, the study only used samples from two sites in the native range using amplified fragment length polymorphisms (AFLPs), so it was necessary to conduct further genetic analyses using samples from more sites in the native range. Hence, the first aim of this study was to develop a better understanding of the genetic structure of N. mexicana populations in the native and invaded range. Genetic samples were collected from sites in the native range during field surveys for potential biological control agents, and inter-simple sequence repeats (ISSRs) were used to compare the genetic structure of invasive and native populations of N. mexicana in South Africa. The results from these analyses suggest that seven of the 14 investigated invasive populations of N. mexicana in South Africa are genetically similar to populations in the native range, while the remaining seven populations are likely to be hybrid forms of the plant. This knowledge will be useful to target populations for biological control and highlights the need for further genetic analyses to determine the parentage of these hybrids so that biological control efforts are more likely to be successful. The initiation of a biological control programme requires that a series of steps are taken in order to maximise the likelihood that this form of intervention will be successful. The first few steps include: identification of the target weed and its genetic structure; exploration in the native range for potential biological control agents; and prioritisation of these agents based on factors such as climatic and genetic compatibility, feeding damage, abundance, and likely host range. Hence, the second aim of this study was to conduct surveys for potential biological control agents in the native range of N. mexicana, and to prioritise these agents. Field surveys were conducted between August and October in 2018 at 17 sites in Florida, Louisiana, and Texas, USA. Sites were selected based on climatic similarity of native sites compared to invasive sites by use of MaxEnt modelling. Native N. mexicana plants were searched for natural enemies, and these were prioritised based on feeding damage, abundance, incidence, and observations of field host range. Two species were prioritised: Bagous americanus LeConte (Coleoptera: Curculionidae) and Megamelus toddi Beamer (Hemiptera: Delphacidae). These species will be imported into quarantine facilities at Rhodes University for host specificity tests to be conducted. Understanding the factors that contribute to the successful establishment of biological control agents is important to improve the efficiency and reduce the costs incurred during the initiation of biological control programmes. Acquiring knowledge of the factors that predict the efficacy of biological control agents is similarly important, and these factors are discussed in the last chapter of this study. The challenges of the biological control of hybrids are also considered, and recommendations are made for the control of N. mexicana and other plants in South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Reid, Megan
- Date: 2020
- Subjects: Nymphaea mexicana zuccarini -- Biological control -- South Africa , Nymphaeaceae -- Biological control -- South Africa , Invasive plants -- Biological control -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/144510 , vital:38352
- Description: Nymphaea mexicana Zuccarini (Nymphaeaceae) is an aquatic plant originating from south-eastern USA that is becoming increasingly invasive in South Africa as other invasive aquatic plants are being managed successfully through biological control. Mechanical and chemical control of aquatic weeds is expensive, damaging to the environment, and only effective in the short term, so biological control is more desirable as a management strategy for N. mexicana. The biological control of invasive alien plants requires that agents are host specific so that non-target risks are mitigated. For success to be achieved, it is important to ensure that the genetic structure of invasive populations is clarified so that agents can be collected from populations in the native range that match genetically to populations in the invasive range. This is especially important in cases where the morphology of invasive alien plants does not reflect genetic differences between populations. A previous study of the genetic structure of the invasive populations of N. mexicana in South Africa suggests the presence of hybrid forms of the plant in South Africa, with only one of these populations matching with samples from the native range. However, the study only used samples from two sites in the native range using amplified fragment length polymorphisms (AFLPs), so it was necessary to conduct further genetic analyses using samples from more sites in the native range. Hence, the first aim of this study was to develop a better understanding of the genetic structure of N. mexicana populations in the native and invaded range. Genetic samples were collected from sites in the native range during field surveys for potential biological control agents, and inter-simple sequence repeats (ISSRs) were used to compare the genetic structure of invasive and native populations of N. mexicana in South Africa. The results from these analyses suggest that seven of the 14 investigated invasive populations of N. mexicana in South Africa are genetically similar to populations in the native range, while the remaining seven populations are likely to be hybrid forms of the plant. This knowledge will be useful to target populations for biological control and highlights the need for further genetic analyses to determine the parentage of these hybrids so that biological control efforts are more likely to be successful. The initiation of a biological control programme requires that a series of steps are taken in order to maximise the likelihood that this form of intervention will be successful. The first few steps include: identification of the target weed and its genetic structure; exploration in the native range for potential biological control agents; and prioritisation of these agents based on factors such as climatic and genetic compatibility, feeding damage, abundance, and likely host range. Hence, the second aim of this study was to conduct surveys for potential biological control agents in the native range of N. mexicana, and to prioritise these agents. Field surveys were conducted between August and October in 2018 at 17 sites in Florida, Louisiana, and Texas, USA. Sites were selected based on climatic similarity of native sites compared to invasive sites by use of MaxEnt modelling. Native N. mexicana plants were searched for natural enemies, and these were prioritised based on feeding damage, abundance, incidence, and observations of field host range. Two species were prioritised: Bagous americanus LeConte (Coleoptera: Curculionidae) and Megamelus toddi Beamer (Hemiptera: Delphacidae). These species will be imported into quarantine facilities at Rhodes University for host specificity tests to be conducted. Understanding the factors that contribute to the successful establishment of biological control agents is important to improve the efficiency and reduce the costs incurred during the initiation of biological control programmes. Acquiring knowledge of the factors that predict the efficacy of biological control agents is similarly important, and these factors are discussed in the last chapter of this study. The challenges of the biological control of hybrids are also considered, and recommendations are made for the control of N. mexicana and other plants in South Africa.
- Full Text:
- Date Issued: 2020
PKS 2250−351: A Giant Radio Galaxy in Abell 3936
- Seymour, N, Huynh, M, Shabala, S S, Rogers, J, Davies, L J M, Turner, R J, O'Brien, A, Ishwara-Chandra, C H, Thorne, J E, Galvin, T J, Jarrett, T, Anderbach, H, Anderson, A, Bunton, J, Chow, K, Collier, J D, Driver, S, Filipovic, M D, Gurkan, G, Hopkins, A M, Kapinska, A D, Leahy, D A, Marvil, J, Manojlovic, P, Norris, R P, Phillips, C, Robotham, A, Rudnick, L, Singh, V, White, S V
- Authors: Seymour, N , Huynh, M , Shabala, S S , Rogers, J , Davies, L J M , Turner, R J , O'Brien, A , Ishwara-Chandra, C H , Thorne, J E , Galvin, T J , Jarrett, T , Anderbach, H , Anderson, A , Bunton, J , Chow, K , Collier, J D , Driver, S , Filipovic, M D , Gurkan, G , Hopkins, A M , Kapinska, A D , Leahy, D A , Marvil, J , Manojlovic, P , Norris, R P , Phillips, C , Robotham, A , Rudnick, L , Singh, V , White, S V
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150320 , vital:38967 , https://doi.org/10.1017/pasa.2019.49
- Description: We present a detailed analysis of the radio galaxy PKS , a giant of 1.2 Mpc projected size, its host galaxy, and its environment. We use radio data from the Murchison Widefield Array, the upgraded Giant Metre-wavelength Radio Telescope, the Australian Square Kilometre Array Pathfinder, and the Australia Telescope Compact Array to model the jet power and age. Optical and IR data come from the Galaxy And Mass Assembly (GAMA) survey and provide information on the host galaxy and environment.
- Full Text:
- Date Issued: 2020
- Authors: Seymour, N , Huynh, M , Shabala, S S , Rogers, J , Davies, L J M , Turner, R J , O'Brien, A , Ishwara-Chandra, C H , Thorne, J E , Galvin, T J , Jarrett, T , Anderbach, H , Anderson, A , Bunton, J , Chow, K , Collier, J D , Driver, S , Filipovic, M D , Gurkan, G , Hopkins, A M , Kapinska, A D , Leahy, D A , Marvil, J , Manojlovic, P , Norris, R P , Phillips, C , Robotham, A , Rudnick, L , Singh, V , White, S V
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150320 , vital:38967 , https://doi.org/10.1017/pasa.2019.49
- Description: We present a detailed analysis of the radio galaxy PKS , a giant of 1.2 Mpc projected size, its host galaxy, and its environment. We use radio data from the Murchison Widefield Array, the upgraded Giant Metre-wavelength Radio Telescope, the Australian Square Kilometre Array Pathfinder, and the Australia Telescope Compact Array to model the jet power and age. Optical and IR data come from the Galaxy And Mass Assembly (GAMA) survey and provide information on the host galaxy and environment.
- Full Text:
- Date Issued: 2020
The role of microhabitats within mangroves: an invertebrate and fish larval perspective
- Authors: Vorsatz, Lyle Dennis
- Date: 2020
- Subjects: Mangrove ecology -- South Africa , Mangrove forests -- South Africa , Niche (Ecology) , Rhizophora mucronata , Acanthaceae , Rhizophoraceae , Fishes -- Larvae -- South Africa , Aquatic ecology -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167644 , vital:41499
- Description: Microhabitats provided through structural complexity are central for the diversity, productivity, connectivity and niche differentiation within and among ecosystems. Mangrove forests afford juvenile fish and invertebrates with nursery and recruitment habitats, facilitated by the fine scale configuration of their specialised root systems. Although the importance of mangroves for resident and transient juveniles is well recognised, the roles that mangrove microhabitats play for larvae is not yet comprehensively understood. This study aimed to determine how microhabitats with varying degrees of complexity influence the composition, abundance and distribution of larval communities that inhabit mangrove forests and the physiological responses of larvae to acute temperature variations in relation to ontogenetic stage and microenvironment exposure. Two relatively pristine study sites were selected to represent a warm temperate and subtropical mangrove system in the Eastern Cape and KwaZulu-Natal on the east coast of South Africa, respectively. The differences in complexity among the root systems of Rhizophora mucronata, Avicennia marina and Bruguiera gymnorhiza were assessed using 3D scanning and the computed 3D models were then analysed using four complexity metrics. Results indicated that A. marina is the most complex in terms of surface-volume ratio, R. mucronata has the most interstitial space among its roots and B. gymnorhiza and R. mucronata differ in their fractal dimensions. Larvae collected in each microhabitat at each site using light traps showed that, despite temperature and salinity homogeneity across microenvironments, spatio-temporal differences occurred in both fish and invertebrate assemblages. This trend suggests that microhabitat structural complexity exerts an influence on larval community composition by acting as a microscape of available habitat, which ensures ecological linkages within and among the mangrove forest and adjacent ecosystems. In addition, the oxygen consumption rates of mangrove-associated brachyuran larvae varied according to mangrove microhabitat, whereby larvae collected at less complex environments had the highest metabolic rates at increased temperatures. Moreover, ontogenetic shifts in physiology were prevalent as older brachyuran larvae were more eurythermal than earlier stages, suggesting that thermally stressful events will have a greater impact on recently spawned larvae. Overall, the interstitial spaces within individual root systems are the most important complexity measure, as utilisation of these mangrove microhabitats is scale-dependent, and larvae will most likely occupy spaces inaccessible to large predators. Likewise, microscale variation in the environmental conditions and ontogenetic stage of brachyuran larvae within the mangrove microscape, can amplify the physiological responses to rapid temperature variations. Results suggest that early stage larvae are the most vulnerable to mass-mortality, and if thermally stressful events increase in frequency, duration and magnitude, the larval supply for the successful recruitment into adult populations could be under threat. Through linking how mangrove microhabitat complexity influences larvae in terms of community metrics and physiology, this study paves the way for further advancement of our understanding of how microscale processes emerge into meso- and macroscale patterns and influence the stability and functioning of highly productive ecosystems.
- Full Text:
- Date Issued: 2020
- Authors: Vorsatz, Lyle Dennis
- Date: 2020
- Subjects: Mangrove ecology -- South Africa , Mangrove forests -- South Africa , Niche (Ecology) , Rhizophora mucronata , Acanthaceae , Rhizophoraceae , Fishes -- Larvae -- South Africa , Aquatic ecology -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167644 , vital:41499
- Description: Microhabitats provided through structural complexity are central for the diversity, productivity, connectivity and niche differentiation within and among ecosystems. Mangrove forests afford juvenile fish and invertebrates with nursery and recruitment habitats, facilitated by the fine scale configuration of their specialised root systems. Although the importance of mangroves for resident and transient juveniles is well recognised, the roles that mangrove microhabitats play for larvae is not yet comprehensively understood. This study aimed to determine how microhabitats with varying degrees of complexity influence the composition, abundance and distribution of larval communities that inhabit mangrove forests and the physiological responses of larvae to acute temperature variations in relation to ontogenetic stage and microenvironment exposure. Two relatively pristine study sites were selected to represent a warm temperate and subtropical mangrove system in the Eastern Cape and KwaZulu-Natal on the east coast of South Africa, respectively. The differences in complexity among the root systems of Rhizophora mucronata, Avicennia marina and Bruguiera gymnorhiza were assessed using 3D scanning and the computed 3D models were then analysed using four complexity metrics. Results indicated that A. marina is the most complex in terms of surface-volume ratio, R. mucronata has the most interstitial space among its roots and B. gymnorhiza and R. mucronata differ in their fractal dimensions. Larvae collected in each microhabitat at each site using light traps showed that, despite temperature and salinity homogeneity across microenvironments, spatio-temporal differences occurred in both fish and invertebrate assemblages. This trend suggests that microhabitat structural complexity exerts an influence on larval community composition by acting as a microscape of available habitat, which ensures ecological linkages within and among the mangrove forest and adjacent ecosystems. In addition, the oxygen consumption rates of mangrove-associated brachyuran larvae varied according to mangrove microhabitat, whereby larvae collected at less complex environments had the highest metabolic rates at increased temperatures. Moreover, ontogenetic shifts in physiology were prevalent as older brachyuran larvae were more eurythermal than earlier stages, suggesting that thermally stressful events will have a greater impact on recently spawned larvae. Overall, the interstitial spaces within individual root systems are the most important complexity measure, as utilisation of these mangrove microhabitats is scale-dependent, and larvae will most likely occupy spaces inaccessible to large predators. Likewise, microscale variation in the environmental conditions and ontogenetic stage of brachyuran larvae within the mangrove microscape, can amplify the physiological responses to rapid temperature variations. Results suggest that early stage larvae are the most vulnerable to mass-mortality, and if thermally stressful events increase in frequency, duration and magnitude, the larval supply for the successful recruitment into adult populations could be under threat. Through linking how mangrove microhabitat complexity influences larvae in terms of community metrics and physiology, this study paves the way for further advancement of our understanding of how microscale processes emerge into meso- and macroscale patterns and influence the stability and functioning of highly productive ecosystems.
- Full Text:
- Date Issued: 2020
Ecological assessment of a temperate river system using biomonitoring techniques: a case study of the Bloukrans River system, South Africa
- Authors: Magadze, Tinotenda
- Date: 2020
- Subjects: Bloukrans River , Ecological assessment (Biology) -- South Africa , Stream ecology -- South Africa , Rivers -- Environmental aspects -- South Africa , Benthic animals -- Effect of human beings on -- South Africa , Water quality biological assessment -- South Africa , Diatoms -- South Africa -- Data processing
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/142933 , vital:38177
- Description: Escalating pressures from growing human populations and environmental impacts increasingly imperil freshwater ecosystems. The Bloukrans River, which drains an urbanised and agricultural catchment in the Eastern Cape province of South Africa, is no exception. Detailed knowledge of the structure and function of the aquatic ecosystems is required in order to create models and matrices that predict, guide assessment and direct intervention on ecological integrity and water quality management in these systems. The main objectives of this research were to: examine the effects of urbanization on the benthic macroinvertebrate functional feeding guild structure among different stream orders; determine if benthic diatoms can be used as effective and reliable indicators of ionic composition and conductivity in different stream order categories and finally; to evaluate the applicability of the South African Diatom Index (SADI) and other indices in the Eastern Cape region of South Africa. Field studies were carried out to explore temporal patterns in community structure (macroinvertebrates and diatoms) and ecosystem function related to land-use patterns, instream habitat availability, and water quality parameters in the Bloukrans River system across four study periods: February (summer) and July (winter) 2016 and February (summer) and May/July (winter) 2018. The study was conducted along a gradient of impacts from less impacted agricultural headwaters to highly impacted urban sites located immediately downstream of the city of Makhanda. Macroinvertebrates were separated into functional feeding groups (FFGs) (i.e. collector-gatherer, collector-filterer, scraper, shredder, and predator) which were then used to assess the effects of selected physico-chemical variables and riparian zone condition on FFG organization. Collector-gatherers were the most abundant in the Bloukrans River and represented 71.3 % of the macroinvertebrate assemblages. Stream order 1species such as Nitzschia palea, Gomphonema parvulum, Tryblionella apiculata, Diploneis vulgaris and Staurosira elliptica. Multivariate analysis (Canonical correspondence analysis (CCA)) indicated that differences in diatom community assemblages were best explained by calcium, magnesium, pH, phosphate, nitrate, dissolved oxygen, sediment nitrate, conductivity and salinity. These results indicate that diatoms can be used as bioindicators for monitoring highly impacted river systems and to also further examine pollution gradients and impacts of specific/point pollution sources. In order to further test the application of diatom indices, nine sites with contrasting water quality were sampled along the length river system in February, May and July 2018. Diatom-based indices incorporated in OMNIDIA software were applied to assess the integrity of the water quality as indicated by diatom communities. For comparative purposes, several foreign indices (e.g. the trophic diatom index (TDI), the percentage pollution-tolerant valves (%PTV), biological diatom index (BDI)) and the South African Diatom Index (SADI) were used in the study. From the results, the Percentage Pollution-Tolerant Valves (%PTV) of most urban sites in the Bloukrans River was above the 20% limit indicating the presence of organic pollutants. Although the foreign diatom indices were applicable in the study, the SADI had significant correlations with most water quality variables (p < 0.05) compared to other indices such as Watanabe Index (WAT), Biological Index of Water Quality Trophic Index (BIWQ) and Trophic Index (TI)). These results support wider use of the SADI as an indicator of water quality conditions in South African river systems. Finally, the observed variations in diatom community structure and composition as a result of changes in water quality were broadly in agreement with the results of macroinvertebrate FFG structure indicating that the two biological indicators can, and should, be used as complementary techniques in the biomonitoring of rivers and streams in South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Magadze, Tinotenda
- Date: 2020
- Subjects: Bloukrans River , Ecological assessment (Biology) -- South Africa , Stream ecology -- South Africa , Rivers -- Environmental aspects -- South Africa , Benthic animals -- Effect of human beings on -- South Africa , Water quality biological assessment -- South Africa , Diatoms -- South Africa -- Data processing
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/142933 , vital:38177
- Description: Escalating pressures from growing human populations and environmental impacts increasingly imperil freshwater ecosystems. The Bloukrans River, which drains an urbanised and agricultural catchment in the Eastern Cape province of South Africa, is no exception. Detailed knowledge of the structure and function of the aquatic ecosystems is required in order to create models and matrices that predict, guide assessment and direct intervention on ecological integrity and water quality management in these systems. The main objectives of this research were to: examine the effects of urbanization on the benthic macroinvertebrate functional feeding guild structure among different stream orders; determine if benthic diatoms can be used as effective and reliable indicators of ionic composition and conductivity in different stream order categories and finally; to evaluate the applicability of the South African Diatom Index (SADI) and other indices in the Eastern Cape region of South Africa. Field studies were carried out to explore temporal patterns in community structure (macroinvertebrates and diatoms) and ecosystem function related to land-use patterns, instream habitat availability, and water quality parameters in the Bloukrans River system across four study periods: February (summer) and July (winter) 2016 and February (summer) and May/July (winter) 2018. The study was conducted along a gradient of impacts from less impacted agricultural headwaters to highly impacted urban sites located immediately downstream of the city of Makhanda. Macroinvertebrates were separated into functional feeding groups (FFGs) (i.e. collector-gatherer, collector-filterer, scraper, shredder, and predator) which were then used to assess the effects of selected physico-chemical variables and riparian zone condition on FFG organization. Collector-gatherers were the most abundant in the Bloukrans River and represented 71.3 % of the macroinvertebrate assemblages. Stream order 1species such as Nitzschia palea, Gomphonema parvulum, Tryblionella apiculata, Diploneis vulgaris and Staurosira elliptica. Multivariate analysis (Canonical correspondence analysis (CCA)) indicated that differences in diatom community assemblages were best explained by calcium, magnesium, pH, phosphate, nitrate, dissolved oxygen, sediment nitrate, conductivity and salinity. These results indicate that diatoms can be used as bioindicators for monitoring highly impacted river systems and to also further examine pollution gradients and impacts of specific/point pollution sources. In order to further test the application of diatom indices, nine sites with contrasting water quality were sampled along the length river system in February, May and July 2018. Diatom-based indices incorporated in OMNIDIA software were applied to assess the integrity of the water quality as indicated by diatom communities. For comparative purposes, several foreign indices (e.g. the trophic diatom index (TDI), the percentage pollution-tolerant valves (%PTV), biological diatom index (BDI)) and the South African Diatom Index (SADI) were used in the study. From the results, the Percentage Pollution-Tolerant Valves (%PTV) of most urban sites in the Bloukrans River was above the 20% limit indicating the presence of organic pollutants. Although the foreign diatom indices were applicable in the study, the SADI had significant correlations with most water quality variables (p < 0.05) compared to other indices such as Watanabe Index (WAT), Biological Index of Water Quality Trophic Index (BIWQ) and Trophic Index (TI)). These results support wider use of the SADI as an indicator of water quality conditions in South African river systems. Finally, the observed variations in diatom community structure and composition as a result of changes in water quality were broadly in agreement with the results of macroinvertebrate FFG structure indicating that the two biological indicators can, and should, be used as complementary techniques in the biomonitoring of rivers and streams in South Africa.
- Full Text:
- Date Issued: 2020
Understanding climate change and rural livelihoods in Zimbabwe: adaptation by communal farmers in Ngundu, Chivi District
- Authors: Nciizah, Elinah
- Date: 2020
- Subjects: Agriculture -- Zimbabwe , Agriculture -- Climatic factors -- Chivi District (Zimbabwe) , Chivi District (Zimbabwe) -- Rural conditions
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/118765 , vital:34666
- Description: Climate change and variability is a global phenomenon which has deeply localised patterns, dynamics and effects. Amongst those people who are particularly vulnerable to climate change effects are small-scale farmers who are dependent in large part on rain-fed agriculture in pursuing their livelihoods. This is true of small-scale farmers in contemporary Zimbabwe and, more specifically, farmers in communal areas. At the same time, at international and national levels, there are attempts currently to minimise the effects of, and to adapt to, climate change. However, adaptation measures also exist at local levels amongst small-scale farmers, such as communal farmers in Zimbabwe. In this context, as its main objective, this thesis examines climate change and small-scale farmer livelihood adaptation to climate change with specific reference to communal farmers in Chivi District in Zimbabwe and, in particular, in Ward 25 which is popularly known as Ngundu. In pursuing this main objective, a number of subsidiary objectives are addressed, including a focus on the established livelihoods of Ngundu farmers, the perceptions and concerns of Ngundu farmers about climate change, the coping and adaptation measures of Ngundu farmers, and the enablements and constraints which affect attempts by Ngundu farmers to adopt such measures. The fieldwork for the thesis involved a diverse array of research methods, such as a questionnaire survey, life-history interviews, key informant interviews, focus group discussions and transect walks. In terms of theoretical framing, the thesis makes use of both middle-level theory (the Sustainable Livelihoods Framework) and macro-theory in the form of the sociological work of Margaret Archer. Combined, these two theories allow for a focus on both structure and agency when seeking to understand livelihood adaptations to climate change by communal farmers in Ngundu. The thesis concludes that there are massive constraints inhibiting adaptation measures by Ngundu farmers, but that this should not distract from the deep, often historically-embedded, concerns of Ngundu farmers about climate change and the multiple ways in which they express agency in and through adaptation and coping activities. It also highlights the need for more specifically sociological investigations of climate change and small-scale farmer adaptation, as well as the need for localised studies which are able to identify and analyse the specificities of adaptation.
- Full Text:
- Date Issued: 2020
- Authors: Nciizah, Elinah
- Date: 2020
- Subjects: Agriculture -- Zimbabwe , Agriculture -- Climatic factors -- Chivi District (Zimbabwe) , Chivi District (Zimbabwe) -- Rural conditions
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/118765 , vital:34666
- Description: Climate change and variability is a global phenomenon which has deeply localised patterns, dynamics and effects. Amongst those people who are particularly vulnerable to climate change effects are small-scale farmers who are dependent in large part on rain-fed agriculture in pursuing their livelihoods. This is true of small-scale farmers in contemporary Zimbabwe and, more specifically, farmers in communal areas. At the same time, at international and national levels, there are attempts currently to minimise the effects of, and to adapt to, climate change. However, adaptation measures also exist at local levels amongst small-scale farmers, such as communal farmers in Zimbabwe. In this context, as its main objective, this thesis examines climate change and small-scale farmer livelihood adaptation to climate change with specific reference to communal farmers in Chivi District in Zimbabwe and, in particular, in Ward 25 which is popularly known as Ngundu. In pursuing this main objective, a number of subsidiary objectives are addressed, including a focus on the established livelihoods of Ngundu farmers, the perceptions and concerns of Ngundu farmers about climate change, the coping and adaptation measures of Ngundu farmers, and the enablements and constraints which affect attempts by Ngundu farmers to adopt such measures. The fieldwork for the thesis involved a diverse array of research methods, such as a questionnaire survey, life-history interviews, key informant interviews, focus group discussions and transect walks. In terms of theoretical framing, the thesis makes use of both middle-level theory (the Sustainable Livelihoods Framework) and macro-theory in the form of the sociological work of Margaret Archer. Combined, these two theories allow for a focus on both structure and agency when seeking to understand livelihood adaptations to climate change by communal farmers in Ngundu. The thesis concludes that there are massive constraints inhibiting adaptation measures by Ngundu farmers, but that this should not distract from the deep, often historically-embedded, concerns of Ngundu farmers about climate change and the multiple ways in which they express agency in and through adaptation and coping activities. It also highlights the need for more specifically sociological investigations of climate change and small-scale farmer adaptation, as well as the need for localised studies which are able to identify and analyse the specificities of adaptation.
- Full Text:
- Date Issued: 2020