Developments and prospects for biological control of Prosopis (Leguminosae) in South Africa
- Kleinjan,Catharina, Hoffman, John H, Heystek, F, Ivey, Philip J, Kistensamy, Y
- Authors: Kleinjan,Catharina , Hoffman, John H , Heystek, F , Ivey, Philip J , Kistensamy, Y
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414360 , vital:71139 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a13"
- Description: South Africa was the first country to deploy biological control (biocontrol) against invasive Prosopis populations. Developments in this regard have been ongoing, and have been reviewed, at approximately 10-year intervals, since 1991. This review spans the period 2011-2020, a timespan globally characterised by increased awareness of the impacts of invasive Prosopis populations, and recognition of the need for improved management. Concerted international collaboration has resulted in enhanced clarity on phylogenetic relationships within the Leguminosae and the phylogenetic placement of Prosopis. These advances have improved the framework for interpreting the host range of potential agents and for evaluating risk. At the outset of the biocontrol programme, in the 1980s, only agents that consumed mature seeds were considered. The intention was to reduce the invasiveness of Prosopis while simultaneously retaining it as a usable resource. The programme was subsequently expanded to investigate agents that prevent pod set or maturation of seed. More recently, potential agents that damage the vegetative growth of the plants have been included in response to recognition in South Africa, that there is no other route to successful management of Prosopis. There is a wealth of largely unexplored potential in this regard.
- Full Text:
- Date Issued: 2021
- Authors: Kleinjan,Catharina , Hoffman, John H , Heystek, F , Ivey, Philip J , Kistensamy, Y
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414360 , vital:71139 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a13"
- Description: South Africa was the first country to deploy biological control (biocontrol) against invasive Prosopis populations. Developments in this regard have been ongoing, and have been reviewed, at approximately 10-year intervals, since 1991. This review spans the period 2011-2020, a timespan globally characterised by increased awareness of the impacts of invasive Prosopis populations, and recognition of the need for improved management. Concerted international collaboration has resulted in enhanced clarity on phylogenetic relationships within the Leguminosae and the phylogenetic placement of Prosopis. These advances have improved the framework for interpreting the host range of potential agents and for evaluating risk. At the outset of the biocontrol programme, in the 1980s, only agents that consumed mature seeds were considered. The intention was to reduce the invasiveness of Prosopis while simultaneously retaining it as a usable resource. The programme was subsequently expanded to investigate agents that prevent pod set or maturation of seed. More recently, potential agents that damage the vegetative growth of the plants have been included in response to recognition in South Africa, that there is no other route to successful management of Prosopis. There is a wealth of largely unexplored potential in this regard.
- Full Text:
- Date Issued: 2021
Disilane-bridged architectures with high optical transparency for optical limiting
- Feng, Hongjie, Zhou, Zhikuan, May, Aviwe K, Chen, Jiaying, Mack, John, Nyokong, Tebello, Gai, Lizhi, Lu, Hua
- Authors: Feng, Hongjie , Zhou, Zhikuan , May, Aviwe K , Chen, Jiaying , Mack, John , Nyokong, Tebello , Gai, Lizhi , Lu, Hua
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190623 , vital:45011 , xlink:href="https://doi.org/10.1039/D1TC01488A"
- Description: A novel tetraphenylethylene (TPE) architecture that makes use of a disilane bridge was developed to successfully prepare organic optical power limiting (OPL) materials with high transparency. The σ-bridged TPE derivatives exhibit enhanced solid-state emission efficacies up to 4 times that of TPE. Due to the unique σ-electron delocalization, the incorporated Si–Si bridge gives rise to intense nonlinear optics (NLO) properties. These compounds show favorable optical transparency in the visible region, since the σ–π interaction has a relatively minor effect on the absorption properties of TPE. The poly(bisphenol A carbonate) (PBC) thin films of disilane-bridged compounds exhibit significant reverse saturable absorbance (RSA) responses during Z-scan measurements at 532 nm. In contrast, negligible OPL properties were observed in tetrahydrofuran (THF) solution and when a PBC thin film was prepared with TPE. The disilane-bridged molecular system represents a novel and easily prepared architecture for the construction of solid-state optical limiting materials.
- Full Text:
- Date Issued: 2021
- Authors: Feng, Hongjie , Zhou, Zhikuan , May, Aviwe K , Chen, Jiaying , Mack, John , Nyokong, Tebello , Gai, Lizhi , Lu, Hua
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190623 , vital:45011 , xlink:href="https://doi.org/10.1039/D1TC01488A"
- Description: A novel tetraphenylethylene (TPE) architecture that makes use of a disilane bridge was developed to successfully prepare organic optical power limiting (OPL) materials with high transparency. The σ-bridged TPE derivatives exhibit enhanced solid-state emission efficacies up to 4 times that of TPE. Due to the unique σ-electron delocalization, the incorporated Si–Si bridge gives rise to intense nonlinear optics (NLO) properties. These compounds show favorable optical transparency in the visible region, since the σ–π interaction has a relatively minor effect on the absorption properties of TPE. The poly(bisphenol A carbonate) (PBC) thin films of disilane-bridged compounds exhibit significant reverse saturable absorbance (RSA) responses during Z-scan measurements at 532 nm. In contrast, negligible OPL properties were observed in tetrahydrofuran (THF) solution and when a PBC thin film was prepared with TPE. The disilane-bridged molecular system represents a novel and easily prepared architecture for the construction of solid-state optical limiting materials.
- Full Text:
- Date Issued: 2021
Diversity is an asset to science not a threat
- Authors: Blackie, Margaret A
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426624 , vital:72373 , xlink:href="https://www.jstor.org/stable/48687065"
- Description: In this paper, Critical Realism is used as a theoretical framework to show that diversity is an asset to science not a threat. Critical Realism situates the reliability and reproducibility of science in the realm of the real and thus relocates the notion of “objectivity” from the person of the scientist to the process of science. This means that it no longer necessary to attempt to minimise the person of the scientist in pursuit of rigorous knowledge. The implication is that diversity both in terms of intellectual training (within limits) and in terms of being multicultural, gender, sexuality, multilingual, is revealed to be an asset. This is because the construction of knowledge draws on personal experience and having people with divergent experience interrogating the same problem is more likely to provide a reliable, reproducible solution. In the latter parts of the paper, the implications for teaching are described. In addition, it is demonstrated that this argument can be extended into different knowledge areas.
- Full Text:
- Date Issued: 2021
- Authors: Blackie, Margaret A
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426624 , vital:72373 , xlink:href="https://www.jstor.org/stable/48687065"
- Description: In this paper, Critical Realism is used as a theoretical framework to show that diversity is an asset to science not a threat. Critical Realism situates the reliability and reproducibility of science in the realm of the real and thus relocates the notion of “objectivity” from the person of the scientist to the process of science. This means that it no longer necessary to attempt to minimise the person of the scientist in pursuit of rigorous knowledge. The implication is that diversity both in terms of intellectual training (within limits) and in terms of being multicultural, gender, sexuality, multilingual, is revealed to be an asset. This is because the construction of knowledge draws on personal experience and having people with divergent experience interrogating the same problem is more likely to provide a reliable, reproducible solution. In the latter parts of the paper, the implications for teaching are described. In addition, it is demonstrated that this argument can be extended into different knowledge areas.
- Full Text:
- Date Issued: 2021
Doctors’ practice and attitudes towards red blood cell transfusion at Mthatha Regional Hospital, Eastern Cape, South Africa: A mixed methods study
- O’Mahony, Don, Adedayo, Temitope, Adeleke, Olukayode
- Authors: O’Mahony, Don , Adedayo, Temitope , Adeleke, Olukayode
- Date: 2021
- Subjects: Physicians Erythrocytes--Transfusion Article
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/7989 , vital:57871 , xlink:href="https://doi.org/10.4102/phcfm.v13i1.2889"
- Description: Background: Unnecessary blood transfusion exposes recipients to potential harms. Aim: The aim of this study was to describe blood transfusion practice and explore doctors’ attitudes towards transfusion. Setting: A hospital providing level 1 and 2 services. Methods: A mixed-methods study design was used. In the cross-sectional descriptive component, a sample was taken from patients transfused over a 2-month period. Blood use was categorised as for medical anaemia or haemorrhage, and appropriate or not. The qualitative component comprised a purposeful sample for focus group and individual semistructured interviews. Results: Of 239 patients sampled, 62% were transfused for medical anaemia and 38% for haemorrhage. In the medical anaemia group, compliance with age-appropriate transfusion thresholds was 69%. In medical anaemia and haemorrhage, 114 (77%) and 85 (93.4%) of recipients had orders for ≥ 2 red blood cell (RBC) units, respectively. In adults ≥ 18 years old with medical anaemia, 47.1% of orders would have resulted in a haemoglobin (Hb) > 8 g/dL. Six doctors participated in focus group and eleven in individual interviews. There was a lack of awareness of institutional transfusion guidelines, disagreement on appropriate RBC transfusion thresholds and comments that more than one RBC unit should always be transfused. Factors informing decisions to transfuse included advice from senior colleagues, relieving symptoms of anaemia and high product costs. Conclusion: Most orders were for two or more units. In medical anaemia, doctors’ compliance with RBC transfusion thresholds was reasonable; however, almost half of the orders would have resulted in overtransfusion. The attitudes of doctors sampled suggest that their transfusion practice is influenced more by institutional values than formal guidelines. Keywords: red blood cell transfusion; doctors’ attitudes; doctors’ practice; transfusion thresholds; overtransfusion; descriptive study; qualitative study.
- Full Text:
- Date Issued: 2021
- Authors: O’Mahony, Don , Adedayo, Temitope , Adeleke, Olukayode
- Date: 2021
- Subjects: Physicians Erythrocytes--Transfusion Article
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/7989 , vital:57871 , xlink:href="https://doi.org/10.4102/phcfm.v13i1.2889"
- Description: Background: Unnecessary blood transfusion exposes recipients to potential harms. Aim: The aim of this study was to describe blood transfusion practice and explore doctors’ attitudes towards transfusion. Setting: A hospital providing level 1 and 2 services. Methods: A mixed-methods study design was used. In the cross-sectional descriptive component, a sample was taken from patients transfused over a 2-month period. Blood use was categorised as for medical anaemia or haemorrhage, and appropriate or not. The qualitative component comprised a purposeful sample for focus group and individual semistructured interviews. Results: Of 239 patients sampled, 62% were transfused for medical anaemia and 38% for haemorrhage. In the medical anaemia group, compliance with age-appropriate transfusion thresholds was 69%. In medical anaemia and haemorrhage, 114 (77%) and 85 (93.4%) of recipients had orders for ≥ 2 red blood cell (RBC) units, respectively. In adults ≥ 18 years old with medical anaemia, 47.1% of orders would have resulted in a haemoglobin (Hb) > 8 g/dL. Six doctors participated in focus group and eleven in individual interviews. There was a lack of awareness of institutional transfusion guidelines, disagreement on appropriate RBC transfusion thresholds and comments that more than one RBC unit should always be transfused. Factors informing decisions to transfuse included advice from senior colleagues, relieving symptoms of anaemia and high product costs. Conclusion: Most orders were for two or more units. In medical anaemia, doctors’ compliance with RBC transfusion thresholds was reasonable; however, almost half of the orders would have resulted in overtransfusion. The attitudes of doctors sampled suggest that their transfusion practice is influenced more by institutional values than formal guidelines. Keywords: red blood cell transfusion; doctors’ attitudes; doctors’ practice; transfusion thresholds; overtransfusion; descriptive study; qualitative study.
- Full Text:
- Date Issued: 2021
Doctors’ practice and attitudes towards red blood cell transfusion at Mthatha Regional Hospital, Eastern Cape, South Africa: A mixed methods study
- Mabunda, Sikhumbuzo A, O’Mahony, Don, Adedayo, Temitope, Adeleke, Olukayode
- Authors: Mabunda, Sikhumbuzo A , O’Mahony, Don , Adedayo, Temitope , Adeleke, Olukayode
- Date: 2021
- Subjects: Physicians Erythrocytes--Transfusion Article
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/7216 , vital:53088 , xlink:href="https://doi.org/10.4102/phcfm.v13i1.2889"
- Description: Background: Unnecessary blood transfusion exposes recipients to potential harms. Aim: The aim of this study was to describe blood transfusion practice and explore doctors’ attitudes towards transfusion. Setting: A hospital providing level 1 and 2 services. Methods: A mixed-methods study design was used. In the cross-sectional descriptive component, a sample was taken from patients transfused over a 2-month period. Blood use was categorised as for medical anaemia or haemorrhage, and appropriate or not. The qualitative component comprised a purposeful sample for focus group and individual semistructured interviews. Results: Of 239 patients sampled, 62% were transfused for medical anaemia and 38% for haemorrhage. In the medical anaemia group, compliance with age-appropriate transfusion thresholds was 69%. In medical anaemia and haemorrhage, 114 (77%) and 85 (93.4%) of recipients had orders for ≥ 2 red blood cell (RBC) units, respectively. In adults ≥ 18 years old with medical anaemia, 47.1% of orders would have resulted in a haemoglobin (Hb) > 8 g/dL. Six doctors participated in focus group and eleven in individual interviews. There was a lack of awareness of institutional transfusion guidelines, disagreement on appropriate RBC transfusion thresholds and comments that more than one RBC unit should always be transfused. Factors informing decisions to transfuse included advice from senior colleagues, relieving symptoms of anaemia and high product costs. Conclusion: Most orders were for two or more units. In medical anaemia, doctors’ compliance with RBC transfusion thresholds was reasonable; however, almost half of the orders would have resulted in overtransfusion. The attitudes of doctors sampled suggest that their transfusion practice is influenced more by institutional values than formal guidelines. Keywords: red blood cell transfusion; doctors’ attitudes; doctors’ practice; transfusion thresholds; overtransfusion; descriptive study; qualitative study.
- Full Text:
- Date Issued: 2021
- Authors: Mabunda, Sikhumbuzo A , O’Mahony, Don , Adedayo, Temitope , Adeleke, Olukayode
- Date: 2021
- Subjects: Physicians Erythrocytes--Transfusion Article
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/7216 , vital:53088 , xlink:href="https://doi.org/10.4102/phcfm.v13i1.2889"
- Description: Background: Unnecessary blood transfusion exposes recipients to potential harms. Aim: The aim of this study was to describe blood transfusion practice and explore doctors’ attitudes towards transfusion. Setting: A hospital providing level 1 and 2 services. Methods: A mixed-methods study design was used. In the cross-sectional descriptive component, a sample was taken from patients transfused over a 2-month period. Blood use was categorised as for medical anaemia or haemorrhage, and appropriate or not. The qualitative component comprised a purposeful sample for focus group and individual semistructured interviews. Results: Of 239 patients sampled, 62% were transfused for medical anaemia and 38% for haemorrhage. In the medical anaemia group, compliance with age-appropriate transfusion thresholds was 69%. In medical anaemia and haemorrhage, 114 (77%) and 85 (93.4%) of recipients had orders for ≥ 2 red blood cell (RBC) units, respectively. In adults ≥ 18 years old with medical anaemia, 47.1% of orders would have resulted in a haemoglobin (Hb) > 8 g/dL. Six doctors participated in focus group and eleven in individual interviews. There was a lack of awareness of institutional transfusion guidelines, disagreement on appropriate RBC transfusion thresholds and comments that more than one RBC unit should always be transfused. Factors informing decisions to transfuse included advice from senior colleagues, relieving symptoms of anaemia and high product costs. Conclusion: Most orders were for two or more units. In medical anaemia, doctors’ compliance with RBC transfusion thresholds was reasonable; however, almost half of the orders would have resulted in overtransfusion. The attitudes of doctors sampled suggest that their transfusion practice is influenced more by institutional values than formal guidelines. Keywords: red blood cell transfusion; doctors’ attitudes; doctors’ practice; transfusion thresholds; overtransfusion; descriptive study; qualitative study.
- Full Text:
- Date Issued: 2021
Does the absence of community involvement underpin the demise of urban neighbourhood parks in the Eastern Cape, South Africa?:
- Shackleton, Charlie M, Njwaxu, Afrika
- Authors: Shackleton, Charlie M , Njwaxu, Afrika
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/175791 , vital:42624 , https://doi.org/10.1016/j.landurbplan.2020.104006
- Description: Public urban green spaces are essential for urban sustainability and the physical and mental wellbeing of urban residents. Yet in some settings they may face a number of threats, ranging from land transformation and development, through to poor maintenance and vandalism. It has been posited that community engagement is a crucial strategy in addressing or minimising many of these threats. Here we report on the condition of 11 newly created or renovated parks in poorer neighbourhoods of six towns over a three year period, along with in-depth interviews regarding the sentiments of local residents and officials to the (re)creation of the parks and their subsequent deterioration.
- Full Text:
- Date Issued: 2021
- Authors: Shackleton, Charlie M , Njwaxu, Afrika
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/175791 , vital:42624 , https://doi.org/10.1016/j.landurbplan.2020.104006
- Description: Public urban green spaces are essential for urban sustainability and the physical and mental wellbeing of urban residents. Yet in some settings they may face a number of threats, ranging from land transformation and development, through to poor maintenance and vandalism. It has been posited that community engagement is a crucial strategy in addressing or minimising many of these threats. Here we report on the condition of 11 newly created or renovated parks in poorer neighbourhoods of six towns over a three year period, along with in-depth interviews regarding the sentiments of local residents and officials to the (re)creation of the parks and their subsequent deterioration.
- Full Text:
- Date Issued: 2021
Ecological patterns and effectiveness of protected areas in the preservation of Mimusops species’ habitats under climate change
- Sinasson, Gisèle K S, Shackleton, Charlie M, Teka, Oscar, Sinsin, Brice
- Authors: Sinasson, Gisèle K S , Shackleton, Charlie M , Teka, Oscar , Sinsin, Brice
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/175812 , vital:42626 , https://doi.org/10.1016/j.gecco.2021.e01527 , https://researchdata.ru.ac.za/search?q=:keyword: "Gap analysis"
- Description: Understanding the niche and habitat requirements of useful and threatened species, their shifts under climate change and how well protected areas (PAs) preserve these habitats is relevant for guiding sustainable management actions. Here we assessed the ecological factors underlying the distribution of two multipurpose and threatened species, Mimusops andongensis and M. kummel, in Benin, and potential changes in the suitable habitats covered by PAs, under climate change scenarios. Fifty seven occurrence points were collected for M. andongensis and 81 for M. kummel.
- Full Text:
- Date Issued: 2021
- Authors: Sinasson, Gisèle K S , Shackleton, Charlie M , Teka, Oscar , Sinsin, Brice
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/175812 , vital:42626 , https://doi.org/10.1016/j.gecco.2021.e01527 , https://researchdata.ru.ac.za/search?q=:keyword: "Gap analysis"
- Description: Understanding the niche and habitat requirements of useful and threatened species, their shifts under climate change and how well protected areas (PAs) preserve these habitats is relevant for guiding sustainable management actions. Here we assessed the ecological factors underlying the distribution of two multipurpose and threatened species, Mimusops andongensis and M. kummel, in Benin, and potential changes in the suitable habitats covered by PAs, under climate change scenarios. Fifty seven occurrence points were collected for M. andongensis and 81 for M. kummel.
- Full Text:
- Date Issued: 2021
Ecosystem provisioning services in Global South cities
- Authors: Shackleton, Charlie M
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/433764 , vital:72999 , ISBN 978-3-030-67650-6 , https://doi.org/10.1007/978-3-030-67650-6_8
- Description: All of humankind, urban and rural, rich and poor and whether living in the Global South or the Global North rely to some degree on provisioning ecosystem services such as food, water, timber, fibre and medicinal products. However, in contrast to the Global North the contextual forces shaping many urban livelihoods in the Global South necessitate that many people access the needed provisioning services themselves by directly harvesting or collecting from the immediate, local urban and peri-urban environments, or purchasing them from those who do. Thus, the need for and local availability of provisioning services has profound implications for not only the quality of urban livelihoods, but also the urban ecology in relation to extent and use of urban green infrastructure from where the provisioning services are sourced and the species within them. This chapter summarises compelling evidence from throughout the Global South regarding the extent of use of locally sourced provisioning services by urban communities. It shows that Global South contexts prompt the use of a diverse array of resource types and hundreds of different species in specific settings, much greater than found in Global North cities.
- Full Text:
- Date Issued: 2021
- Authors: Shackleton, Charlie M
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/433764 , vital:72999 , ISBN 978-3-030-67650-6 , https://doi.org/10.1007/978-3-030-67650-6_8
- Description: All of humankind, urban and rural, rich and poor and whether living in the Global South or the Global North rely to some degree on provisioning ecosystem services such as food, water, timber, fibre and medicinal products. However, in contrast to the Global North the contextual forces shaping many urban livelihoods in the Global South necessitate that many people access the needed provisioning services themselves by directly harvesting or collecting from the immediate, local urban and peri-urban environments, or purchasing them from those who do. Thus, the need for and local availability of provisioning services has profound implications for not only the quality of urban livelihoods, but also the urban ecology in relation to extent and use of urban green infrastructure from where the provisioning services are sourced and the species within them. This chapter summarises compelling evidence from throughout the Global South regarding the extent of use of locally sourced provisioning services by urban communities. It shows that Global South contexts prompt the use of a diverse array of resource types and hundreds of different species in specific settings, much greater than found in Global North cities.
- Full Text:
- Date Issued: 2021
Editorial
- Authors: Rosenberg, Eureta
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/389759 , vital:68481 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/216901"
- Description: This issue of the Southern African Journal of Environmental Education coincides with the start of the 26th United Nations Conference on Climate Change. COP26 in Glasgow is, like its predecessors, a Conference of Parties who will deliberate how to lower global greenhouse emissions and build adaptive capacity so as to reduce the risk and impacts of climate change.
- Full Text:
- Date Issued: 2021
- Authors: Rosenberg, Eureta
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/389759 , vital:68481 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/216901"
- Description: This issue of the Southern African Journal of Environmental Education coincides with the start of the 26th United Nations Conference on Climate Change. COP26 in Glasgow is, like its predecessors, a Conference of Parties who will deliberate how to lower global greenhouse emissions and build adaptive capacity so as to reduce the risk and impacts of climate change.
- Full Text:
- Date Issued: 2021
Effect of ultrasonic frequency and power on the sonodynamic therapy activity of cationic Zn (II) phthalocyanines
- Nene, Lindokuhle C, Sindelo, Azole, Britton, Jonathan, Nyokong, Tebello
- Authors: Nene, Lindokuhle C , Sindelo, Azole , Britton, Jonathan , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185737 , vital:44419 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2021.111397"
- Description: We report on the sonodynamic activity of cationic phthalocyanines (Pcs) and the effect of the variation of two parameters: ultrasound frequency and power (Par I (1 MHz, 1 W cm−2), Par II (1 MHz, 2 W cm−2), Par III (3 MHz, 1 W cm−2) and Par IV (3 MHz, 2 W cm−2)) on the efficiency of their reactive oxygen species generation and cancer eradication in vitro thereof. Where Par stands for the various combinations of these parameters. Four Pcs were investigated with substituents bearing diethylamine, ortho- and para-pyridine and morpholine groups. Overall, the para-pyridine and morpholine Pcs showed substantial sono-activity in the various ultrasound parameters with Par I and IV generally showing better singlet oxygen and hydroxyl radicals generation confirmed by electron paramagnetic resonance spectroscopy. In some cases, very high hydroxyl radicals' generation was observed at Par II. Furthermore, the fragmentation of the Pcs after Par II treatments was confirmed using UV–vis and magnetic circular dichroism spectroscopy. The reactive species generation efficacy decreased at Par III for all samples. Ultrasound assisted cytotoxicity of the Pcs was confirmed in vitro using the human (Michigan Cancer Foundation-7) breast cancer cell line.
- Full Text:
- Date Issued: 2021
- Authors: Nene, Lindokuhle C , Sindelo, Azole , Britton, Jonathan , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185737 , vital:44419 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2021.111397"
- Description: We report on the sonodynamic activity of cationic phthalocyanines (Pcs) and the effect of the variation of two parameters: ultrasound frequency and power (Par I (1 MHz, 1 W cm−2), Par II (1 MHz, 2 W cm−2), Par III (3 MHz, 1 W cm−2) and Par IV (3 MHz, 2 W cm−2)) on the efficiency of their reactive oxygen species generation and cancer eradication in vitro thereof. Where Par stands for the various combinations of these parameters. Four Pcs were investigated with substituents bearing diethylamine, ortho- and para-pyridine and morpholine groups. Overall, the para-pyridine and morpholine Pcs showed substantial sono-activity in the various ultrasound parameters with Par I and IV generally showing better singlet oxygen and hydroxyl radicals generation confirmed by electron paramagnetic resonance spectroscopy. In some cases, very high hydroxyl radicals' generation was observed at Par II. Furthermore, the fragmentation of the Pcs after Par II treatments was confirmed using UV–vis and magnetic circular dichroism spectroscopy. The reactive species generation efficacy decreased at Par III for all samples. Ultrasound assisted cytotoxicity of the Pcs was confirmed in vitro using the human (Michigan Cancer Foundation-7) breast cancer cell line.
- Full Text:
- Date Issued: 2021
Efforts towards engaging communities to promote the benefits of biological control research and implementation in South Africa
- Weaver, Kim N, Hill, Martin P, Byrne, Marcus J, Ivey, Philip J
- Authors: Weaver, Kim N , Hill, Martin P , Byrne, Marcus J , Ivey, Philip J
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414428 , vital:71146 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a23"
- Description: In the last decade, biological control in South Africa has evolved from a classical applied science, allied to an extension service, to a more community engagement-based activity. Therefore, capacity building is important for the sustainability of biological control research and its implementation. In South Africa, a broad approach has been taken to build capacity in weed biological control, starting at grass-roots level with primary and secondary school learner programmes, through to developing research capacity at the tertiary level and enhancing technical capacity through adult education. Non-specialists are empowered through access to knowledge. The dissemination of accurate information through the most appropriate outlets has become increasingly important, including non-traditional science communication through the internet and, more importantly, social media, which has the potential to reach a far wider audience. Public understanding of biological control has the potential to contribute significantly to the green and knowledge economies of South Africa, but relies on government support for the sustainability of this discipline.
- Full Text:
- Date Issued: 2021
- Authors: Weaver, Kim N , Hill, Martin P , Byrne, Marcus J , Ivey, Philip J
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414428 , vital:71146 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a23"
- Description: In the last decade, biological control in South Africa has evolved from a classical applied science, allied to an extension service, to a more community engagement-based activity. Therefore, capacity building is important for the sustainability of biological control research and its implementation. In South Africa, a broad approach has been taken to build capacity in weed biological control, starting at grass-roots level with primary and secondary school learner programmes, through to developing research capacity at the tertiary level and enhancing technical capacity through adult education. Non-specialists are empowered through access to knowledge. The dissemination of accurate information through the most appropriate outlets has become increasingly important, including non-traditional science communication through the internet and, more importantly, social media, which has the potential to reach a far wider audience. Public understanding of biological control has the potential to contribute significantly to the green and knowledge economies of South Africa, but relies on government support for the sustainability of this discipline.
- Full Text:
- Date Issued: 2021
Electrocatalytic Activity of Cobalt Phthalocyanines Revisited: Effect of the Number of Oxygen Atoms and Conjugation to Carbon Nanomaterials
- Ndebele, Nobuhle, Mgidlana, Sithi, Nyokong, Tebello
- Authors: Ndebele, Nobuhle , Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185700 , vital:44416 , xlink:href="https://doi.org/10.1007/s12678-021-00670-x"
- Description: The synthesis and characterization of tetrakis[4(4-acetlyphenoxy)phthalocyanato] cobalt (II) (1) are presented. Complex 1 together with the reported tetrakis dimethyl 5-(phenoxy)-isophthalatephthalocyaninato] cobalt (II) (2) are conjugated to carbon-based nanomaterials: graphene quantum dots (GQDs) and single-walled carbon nanotubes (SWCNTs) via π-π stacking, taking advantage of the π electrons on the graphitic structure of the nanomaterial as well as on the aromatic rings of the Co phthalocyanines (CoPcs). The electrocatalytic behaviour of the CoPcs, GQDs, SWCNTs and their respective conjugates towards the electrochemical oxidation of catechol was studied. The electrocatalytic probes were drop-dried onto the electrode surface of the glassy carbon electrode (GCE). The electrochemical oxidation of catechol was studied using cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Complex 2 when linked to GQDs gave the lowest oxidation peak potentials of 0.33 V. Low catechol detection limits (LOD) of 0.057 µM was obtained for complex 2 with SWCNT. Thus, complex 2 containing more oxygen atoms outperformed complex 1 with less oxygen atoms. The CoPcs on their own showed moderate electrocatalytic behaviour, hence showing the importance of conjugating them to the carbon nanomaterials. SWCNT-based electrodes performed better than GQDs, and an improvement in the LoDs, sensitivity and the catalytic rate was observed upon conjugation.
- Full Text:
- Date Issued: 2021
- Authors: Ndebele, Nobuhle , Mgidlana, Sithi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185700 , vital:44416 , xlink:href="https://doi.org/10.1007/s12678-021-00670-x"
- Description: The synthesis and characterization of tetrakis[4(4-acetlyphenoxy)phthalocyanato] cobalt (II) (1) are presented. Complex 1 together with the reported tetrakis dimethyl 5-(phenoxy)-isophthalatephthalocyaninato] cobalt (II) (2) are conjugated to carbon-based nanomaterials: graphene quantum dots (GQDs) and single-walled carbon nanotubes (SWCNTs) via π-π stacking, taking advantage of the π electrons on the graphitic structure of the nanomaterial as well as on the aromatic rings of the Co phthalocyanines (CoPcs). The electrocatalytic behaviour of the CoPcs, GQDs, SWCNTs and their respective conjugates towards the electrochemical oxidation of catechol was studied. The electrocatalytic probes were drop-dried onto the electrode surface of the glassy carbon electrode (GCE). The electrochemical oxidation of catechol was studied using cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Complex 2 when linked to GQDs gave the lowest oxidation peak potentials of 0.33 V. Low catechol detection limits (LOD) of 0.057 µM was obtained for complex 2 with SWCNT. Thus, complex 2 containing more oxygen atoms outperformed complex 1 with less oxygen atoms. The CoPcs on their own showed moderate electrocatalytic behaviour, hence showing the importance of conjugating them to the carbon nanomaterials. SWCNT-based electrodes performed better than GQDs, and an improvement in the LoDs, sensitivity and the catalytic rate was observed upon conjugation.
- Full Text:
- Date Issued: 2021
Electrocatalytic activity of manganese tetra 4-aminophenyl porphyrin in the presence of graphene quantum dots
- Jokzai, Mbulelo, Mpeta, Lekhetho S, Nyokong, Tebello
- Authors: Jokzai, Mbulelo , Mpeta, Lekhetho S , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231443 , vital:49888 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: A manganese tetra 4-aminophenyl porphyrin (MnTAPP) was synthesized and attached to graphene quantum dots (GQDs) via covalent and π-π interaction to give MnTAPP@GQDs and MnTAPP--GQDs, respectively. There was an increase (using dynamic light scattering and transmission electron microscopy) in size of the GQDs in the presence of the porphyrin due to aggregation. The porphyrins in the absence and presence of GQDs were then adsorbed onto a glassy carbon electrode using drop and dry method. The electrochemical behavior was tested by cyclic voltammetry and chronoamperometry towards hydrazine. Both methods of combining MnTAPP with GQDs improved the activity of the electrocatalysis compared to individual components. MnTAPP@GQDs showed better catalytic rate constant of 4.36 × 102 Ms−1 and lowest LoD of 0.0023 mM followed by MnTAPP--GQDs. Furthermore, the sensor showed good selectivity in the presence of interfering analytes. All probes showed good stability.
- Full Text:
- Date Issued: 2021
- Authors: Jokzai, Mbulelo , Mpeta, Lekhetho S , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231443 , vital:49888 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: A manganese tetra 4-aminophenyl porphyrin (MnTAPP) was synthesized and attached to graphene quantum dots (GQDs) via covalent and π-π interaction to give MnTAPP@GQDs and MnTAPP--GQDs, respectively. There was an increase (using dynamic light scattering and transmission electron microscopy) in size of the GQDs in the presence of the porphyrin due to aggregation. The porphyrins in the absence and presence of GQDs were then adsorbed onto a glassy carbon electrode using drop and dry method. The electrochemical behavior was tested by cyclic voltammetry and chronoamperometry towards hydrazine. Both methods of combining MnTAPP with GQDs improved the activity of the electrocatalysis compared to individual components. MnTAPP@GQDs showed better catalytic rate constant of 4.36 × 102 Ms−1 and lowest LoD of 0.0023 mM followed by MnTAPP--GQDs. Furthermore, the sensor showed good selectivity in the presence of interfering analytes. All probes showed good stability.
- Full Text:
- Date Issued: 2021
Electrocatalytic activity of Schiff base containing copper phthalocyanines towards the detection of catechol
- Ndebele, Nobuhle, Sen, Pinar, Nyokong, Tebello
- Authors: Ndebele, Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231410 , vital:49885 , xlink:href="https://doi.org/10.1016/j.poly.2021.115518"
- Description: In this study, four new copper phthalocyanine complexes were synthesised and studied as electrocatalysts for the detection of catechol. Two of these complexes were derived from a symmetrical benzaldehyde phthalocyanine complex via the condensation of the benzaldehyde substituents with amine reagents. The electrocatalysts proved to be highly stable towards the detection of catechol. The oxidation peaks obtained using cyclic voltammetry range from 0.20 to 0.38 V. Detection limits were obtained via chronoamperometry and are as low as 0.16 µM with fairly high sensitives being obtained. Overall all four copper complexes exhibited excellent electrocatalytic activity towards the electrooxidation of catechol.
- Full Text:
- Date Issued: 2021
- Authors: Ndebele, Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231410 , vital:49885 , xlink:href="https://doi.org/10.1016/j.poly.2021.115518"
- Description: In this study, four new copper phthalocyanine complexes were synthesised and studied as electrocatalysts for the detection of catechol. Two of these complexes were derived from a symmetrical benzaldehyde phthalocyanine complex via the condensation of the benzaldehyde substituents with amine reagents. The electrocatalysts proved to be highly stable towards the detection of catechol. The oxidation peaks obtained using cyclic voltammetry range from 0.20 to 0.38 V. Detection limits were obtained via chronoamperometry and are as low as 0.16 µM with fairly high sensitives being obtained. Overall all four copper complexes exhibited excellent electrocatalytic activity towards the electrooxidation of catechol.
- Full Text:
- Date Issued: 2021
Electrocatalytic detection of l-cysteine using molybdenum POM doped-HKUST-1 metal organic frameworks
- Murinzi, Tafadzwa W, Watkins, Gareth M, Shumba, Munyaradzi, Nyokong, Tebello
- Authors: Murinzi, Tafadzwa W , Watkins, Gareth M , Shumba, Munyaradzi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185748 , vital:44420 , xlink:href="https://doi.org/10.1080/00958972.2021.1907573"
- Description: Glass carbon electrodes (GCE) were modified with metal organic frameworks (MOFs) containing molybdenum polyoxometallates (Mo POMs) in a copper benzene tricarboxylate framework (HKUST-1). The Mo POMs were introduced via one-pot synthesis (Mo2) and post-synthetic modification (Mo1) techniques. The electrode modifiers were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal analysis. The modified electrodes’ oxidation capacity toward L-cysteine was studied. Mo POMs significantly improved electron transfer kinetics compared to the bare GCE. The best Mo POM doped electrode (Mo1-GCE) had a catalytic rate constant of 2.2 × 104 M−1 s−1 and a limit of detection of 3.07 × 10−7 M. Under the employed experimental conditions, the detection response for L-cysteine was very fast (within 0.1 s) for all the modified electrodes and selective toward L-cysteine in the presence of other amino acids.
- Full Text:
- Date Issued: 2021
Electrocatalytic detection of l-cysteine using molybdenum POM doped-HKUST-1 metal organic frameworks
- Authors: Murinzi, Tafadzwa W , Watkins, Gareth M , Shumba, Munyaradzi , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185748 , vital:44420 , xlink:href="https://doi.org/10.1080/00958972.2021.1907573"
- Description: Glass carbon electrodes (GCE) were modified with metal organic frameworks (MOFs) containing molybdenum polyoxometallates (Mo POMs) in a copper benzene tricarboxylate framework (HKUST-1). The Mo POMs were introduced via one-pot synthesis (Mo2) and post-synthetic modification (Mo1) techniques. The electrode modifiers were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal analysis. The modified electrodes’ oxidation capacity toward L-cysteine was studied. Mo POMs significantly improved electron transfer kinetics compared to the bare GCE. The best Mo POM doped electrode (Mo1-GCE) had a catalytic rate constant of 2.2 × 104 M−1 s−1 and a limit of detection of 3.07 × 10−7 M. Under the employed experimental conditions, the detection response for L-cysteine was very fast (within 0.1 s) for all the modified electrodes and selective toward L-cysteine in the presence of other amino acids.
- Full Text:
- Date Issued: 2021
Electrochemical detection of dopamine using phthalocyanine-nitrogen-doped graphene quantum dot conjugates
- Ndebele Nobuhle, Sen, Pinar, Nyokong, Tebello
- Authors: Ndebele Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185724 , vital:44418 , xlink:href="https://doi.org/10.1016/j.jelechem.2021.115111"
- Description: Two cobalt phthalocyanine molecules were synthesized, a symmetrically substituted CoPc (1) and an unsymmetrically substituted CoPc (2). These CoPcs were π-π stacked onto nitrogen-doped graphene quantum dots (NGQDs). The CoPcs, NGQDs and their respective conjugates were used as electro-catalytic probes in the electrochemical oxidation of dopamine. The molecules were adsorbed onto a glassy carbon electrode (GCE) using the drop dry method, the GCE was used to support those catalysts. The electrooxidation of dopamine was studied using cyclic voltammetry and chronoamperometry. An improvement in the sensitivity and limit of detection was observed upon conjugation.
- Full Text:
- Date Issued: 2021
- Authors: Ndebele Nobuhle , Sen, Pinar , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185724 , vital:44418 , xlink:href="https://doi.org/10.1016/j.jelechem.2021.115111"
- Description: Two cobalt phthalocyanine molecules were synthesized, a symmetrically substituted CoPc (1) and an unsymmetrically substituted CoPc (2). These CoPcs were π-π stacked onto nitrogen-doped graphene quantum dots (NGQDs). The CoPcs, NGQDs and their respective conjugates were used as electro-catalytic probes in the electrochemical oxidation of dopamine. The molecules were adsorbed onto a glassy carbon electrode (GCE) using the drop dry method, the GCE was used to support those catalysts. The electrooxidation of dopamine was studied using cyclic voltammetry and chronoamperometry. An improvement in the sensitivity and limit of detection was observed upon conjugation.
- Full Text:
- Date Issued: 2021
Electrochemical Detection of Nitrite on Electrodes Modified by Click Chemistry Using Asymmetrical Co (II) and Mn (III) Phthalocyanines Containing Push-Pull Substituents
- Nkhahle, Reitumetse, Nyokong, Tebello
- Authors: Nkhahle, Reitumetse , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231425 , vital:49886 , xlink:href="https://doi.org/10.1149/1945-7111/ac377f"
- Description: The more conventional route to synthesizing asymmetric push-pull phthalocyanines (Pcs) involves pairing electron-donating substituents with electron-withdrawing groups in either an A3B or AB3 manner. In this work, a push-pull system fashioned from a substituent bearing different functional groups was created. Symmetric and asymmetric cobalt and manganese Pcs in which acetaminophen was the dominant substituent were synthesized where the asymmetric analogues bore an alkyne-terminated substituent. These complexes were applied as sensors towards the electro-oxidation of nitrite. In addition to comparing the asymmetric Pcs to the symmetric counterparts, an assessment on the different central metals as well as the method of electrode modification was made. From the studies performed, the results showed that the manganese complexes are generally better suited (more so when clicked on to the electrode) in the electrocatalysis of nitrite with a limit of detection and a catalytic rate values of 2.15 μM and 6.91 × 106 s−1 M−1 being recorded for the asymmetric MnPc.
- Full Text:
- Date Issued: 2021
- Authors: Nkhahle, Reitumetse , Nyokong, Tebello
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231425 , vital:49886 , xlink:href="https://doi.org/10.1149/1945-7111/ac377f"
- Description: The more conventional route to synthesizing asymmetric push-pull phthalocyanines (Pcs) involves pairing electron-donating substituents with electron-withdrawing groups in either an A3B or AB3 manner. In this work, a push-pull system fashioned from a substituent bearing different functional groups was created. Symmetric and asymmetric cobalt and manganese Pcs in which acetaminophen was the dominant substituent were synthesized where the asymmetric analogues bore an alkyne-terminated substituent. These complexes were applied as sensors towards the electro-oxidation of nitrite. In addition to comparing the asymmetric Pcs to the symmetric counterparts, an assessment on the different central metals as well as the method of electrode modification was made. From the studies performed, the results showed that the manganese complexes are generally better suited (more so when clicked on to the electrode) in the electrocatalysis of nitrite with a limit of detection and a catalytic rate values of 2.15 μM and 6.91 × 106 s−1 M−1 being recorded for the asymmetric MnPc.
- Full Text:
- Date Issued: 2021
Electrografting of isophthalic acid monolayer and covalent attachment of antibody onto carbon surfaces
- Mwanza, Daniel, Phal, Sereilakhena, Nyokong, Tebello, Tesfalidet, Solomon, Mashazi, Philani N
- Authors: Mwanza, Daniel , Phal, Sereilakhena , Nyokong, Tebello , Tesfalidet, Solomon , Mashazi, Philani N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231345 , vital:49879 , xlink:href="https://doi.org/10.1016/j.electacta.2021.139360"
- Description: In this study, a 5-diazonium isophthalic acid was synthesized and electrografted onto glassy carbon (GCE) and screen-printed carbon (SPCE) electrodes. SPCE was used to demonstrate fabrication of a miniature device and to compare with conventional glassy carbon electrodes. The isophthalic acid (IPA) electrografted thin film was used for the immobilization of anti-methotrexate antibody (Ab) using carbodiimide activation chemistry to form antibody modified surfaces, GCE-IPA-Ab and SPCE-IPA-Ab. The GCE -IPA-Ab and SPCE-IPA-Ab surfaces were used as capacitive biosensors for the detection of methotrexate (MTX) in phosphate buffer (pH 7.4) using capacitive electrochemical impedance spectroscopy (EIS). The EIS data was analyzed using singular value decomposition (SVD). Principal component regression analysis gave R2 values of 0.99 for both the GCE-IPA-Ab and SPCE-IPA-Ab surfaces. The detection limit from the calibration curve of the GCE-IPA-Ab and SPCE-IPA-Ab was calculated to be 7.0 pmol.L−1 and 5.5 pmol.L−1, respectively.
- Full Text:
- Date Issued: 2021
- Authors: Mwanza, Daniel , Phal, Sereilakhena , Nyokong, Tebello , Tesfalidet, Solomon , Mashazi, Philani N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/231345 , vital:49879 , xlink:href="https://doi.org/10.1016/j.electacta.2021.139360"
- Description: In this study, a 5-diazonium isophthalic acid was synthesized and electrografted onto glassy carbon (GCE) and screen-printed carbon (SPCE) electrodes. SPCE was used to demonstrate fabrication of a miniature device and to compare with conventional glassy carbon electrodes. The isophthalic acid (IPA) electrografted thin film was used for the immobilization of anti-methotrexate antibody (Ab) using carbodiimide activation chemistry to form antibody modified surfaces, GCE-IPA-Ab and SPCE-IPA-Ab. The GCE -IPA-Ab and SPCE-IPA-Ab surfaces were used as capacitive biosensors for the detection of methotrexate (MTX) in phosphate buffer (pH 7.4) using capacitive electrochemical impedance spectroscopy (EIS). The EIS data was analyzed using singular value decomposition (SVD). Principal component regression analysis gave R2 values of 0.99 for both the GCE-IPA-Ab and SPCE-IPA-Ab surfaces. The detection limit from the calibration curve of the GCE-IPA-Ab and SPCE-IPA-Ab was calculated to be 7.0 pmol.L−1 and 5.5 pmol.L−1, respectively.
- Full Text:
- Date Issued: 2021
Elucidating Tuta absoluta (Meyrick) invasion and enhancing its management in Eastern Africa : spread, socio-ecological impacts, and potential of a newly imported larval parasitoid for classical biological control Eastern in Africa
- Aigbedion-Atalor, Pascal Osabhahiemen
- Authors: Aigbedion-Atalor, Pascal Osabhahiemen
- Date: 2021
- Subjects: Tuta absoluta -- Biological control , Tomatoes -- Diseases and pests -- Africa, East , Braconidae , Gelechiidae -- Biological control -- Africa, East , Insects as biological pest control agents -- Africa, East
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/170421 , vital:41920 , 10.21504/10962/170421
- Description: Agriculture is a fundamental source of sustainable livelihoods in sub-Saharan Africa and millions of people in the region rely solely on small-scale farming for their food security. However, the impacts of invasive alien species (IAS) on crop production are serious, and there is no sign of this abating. Among the recent IAS that have invaded Africa in the last decade, the South American tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has been one of the most damaging. Following its first record in the Maghreb region of Africa in 2008, T. absoluta rapidly spread throughout Africa with substantial impacts on tomato production, often causing 100% yield loss. Management options adopted against T. absoluta by tomato growers in Africa have been based on the use of synthetic insecticides. While chemical insecticide applications are an important component of an integrated pest management programme, misuse and over-reliance often exacerbates the impacts of T. absolutadue to the development of resistance to commonly used active substances, increasing the fitness of the pest. This thesis sought to understand the socio-economic impacts of the spread of T. absoluta in Eastern Africa and provide effective sustainable pest management strategies to reduce its impacts below economic thresholds. Mapping surveys of Tabsoluta were conducted in 226 tomato agro-ecosystems across four eastern countries (Kenya, Sudan, Tanzania, and Uganda) Eastern Africa from 2016 to 2018 to determine the spatiotemporal distribution of the pest. The impacts of T. absoluta on the livelihoods of tomato growers were also assessed. Here, 200 tomato growers in Kenya were interviewed using a semi-structured questionnaire. Although T. absoluta, a recent invader, was distributed at high infestation levels throughout the subregion (all four countries) and was considered as the most damaging invasive alien species of agriculturally sustainable livelihoods. The arrival of T. absoluta in the subregion has resulted in livelihood losses and increased the cost of tomato production and price of the fruit, and the frequency of pesticide applications. The impact of this pest and the and the absence of effective indigenous natural enemies of the pest in Eastern Africa, was the rationale for the importation of a larval parasitoid, Dolichogenidea gelechiidivoris Marsh Syn.: Apanteles gelechiidivoris Marsh) (Hymenoptera: Braconidae), of T. absoluta from Peru into the quarantine facility of the International Centre of Insect Physiology and ecologyz(icipe), in Kenya. Pre-release assessments on the parasitzation potential of D. gelechiidivoris, encompassing host larval preference and the host suitability, and its reproductive strategy, for classical biological control of T. absoluta in Africa were conducted. Dolichogenidea gelechiidivoris females preferentially oviposited in early (1st and 2nd) larval instars of T. absoluta but parasitized and completed development in all four instars of the host. Host instar did not affect D. gelechiidivoris sex-ratio but females reared on the first instar had significantly fewer eggs than when reared in late larval instars (3rd and 4th). Females of the parasitoid emerged with a high mature egg load which peaked 2 d post-eclosion. The females of D. gelechiidivoris survived 8.51±0.65 d and produced 103±8 offspring per female at 26±4°C (range: 24 to 29°C) and 50–70% relative humidity (RH) in the presence of males and fed honey-water (80% honey). Increasing maternal age decreased the proportion of female offspring. Under the aforementioned laboratory conditions, the Gross and Net reproductive rates were 72 and 39.5 respectively, while the mean generation time was 20 d. The estimated intrinsic rate of natural increase was 0.18. These findings indicate that D. gelechiidivorisis a potential biological control agent of T. absoluta and should be considered for augmentative/inundative release in Kenya and across Africa following host specificity testing and risk assessments. The nature of the interaction between D. gelechidivoris and the predatory mirid bug Nesidiocoris tenuis(Reuter) (Hemiptera: Miridae), an important and widespread natural enemy of T. absoluta in Africa was evaluated because N. tenuis, although being a voracious predator of T. absoluta eggs, it can also prey on the early host larval instars (1st and 2nd) which are the preferred oviposition host stages of D. gelechiidivoris. Here, the impact of N. tenuis feeding on T. absoluta and the effects on D. gelechiidivoris performance was tested. Regardless of the order of introductions (i.e. the sequence of combination with D. gelechiidivoris) and densities (i.e. number of N. tenuis combined with D. gelechiidivoris), there was no intraguild predation by N. tenuis on D. gelechiidivorisas there was little host larval feeding behaviour. Also, the presence of N. tenuis did not affect the oviposition performance of D. gelechiidivoris. Further investigations revealed that the combined efficacy of N. tenuis and D. gelechiidivorison T. absoluta population was significantly higher than either natural enemy alone, thus contributes to the data supporting the release of D. gelechiidivoris in Africa. In concluding, integrating D. gelechiidivoris and N. tenuis in the management of T. absolut could potentially reduce yield losses in tomato in Eastern Africa where the socio-economic impacts of the pest are very serious.
- Full Text:
- Date Issued: 2021
- Authors: Aigbedion-Atalor, Pascal Osabhahiemen
- Date: 2021
- Subjects: Tuta absoluta -- Biological control , Tomatoes -- Diseases and pests -- Africa, East , Braconidae , Gelechiidae -- Biological control -- Africa, East , Insects as biological pest control agents -- Africa, East
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/170421 , vital:41920 , 10.21504/10962/170421
- Description: Agriculture is a fundamental source of sustainable livelihoods in sub-Saharan Africa and millions of people in the region rely solely on small-scale farming for their food security. However, the impacts of invasive alien species (IAS) on crop production are serious, and there is no sign of this abating. Among the recent IAS that have invaded Africa in the last decade, the South American tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has been one of the most damaging. Following its first record in the Maghreb region of Africa in 2008, T. absoluta rapidly spread throughout Africa with substantial impacts on tomato production, often causing 100% yield loss. Management options adopted against T. absoluta by tomato growers in Africa have been based on the use of synthetic insecticides. While chemical insecticide applications are an important component of an integrated pest management programme, misuse and over-reliance often exacerbates the impacts of T. absolutadue to the development of resistance to commonly used active substances, increasing the fitness of the pest. This thesis sought to understand the socio-economic impacts of the spread of T. absoluta in Eastern Africa and provide effective sustainable pest management strategies to reduce its impacts below economic thresholds. Mapping surveys of Tabsoluta were conducted in 226 tomato agro-ecosystems across four eastern countries (Kenya, Sudan, Tanzania, and Uganda) Eastern Africa from 2016 to 2018 to determine the spatiotemporal distribution of the pest. The impacts of T. absoluta on the livelihoods of tomato growers were also assessed. Here, 200 tomato growers in Kenya were interviewed using a semi-structured questionnaire. Although T. absoluta, a recent invader, was distributed at high infestation levels throughout the subregion (all four countries) and was considered as the most damaging invasive alien species of agriculturally sustainable livelihoods. The arrival of T. absoluta in the subregion has resulted in livelihood losses and increased the cost of tomato production and price of the fruit, and the frequency of pesticide applications. The impact of this pest and the and the absence of effective indigenous natural enemies of the pest in Eastern Africa, was the rationale for the importation of a larval parasitoid, Dolichogenidea gelechiidivoris Marsh Syn.: Apanteles gelechiidivoris Marsh) (Hymenoptera: Braconidae), of T. absoluta from Peru into the quarantine facility of the International Centre of Insect Physiology and ecologyz(icipe), in Kenya. Pre-release assessments on the parasitzation potential of D. gelechiidivoris, encompassing host larval preference and the host suitability, and its reproductive strategy, for classical biological control of T. absoluta in Africa were conducted. Dolichogenidea gelechiidivoris females preferentially oviposited in early (1st and 2nd) larval instars of T. absoluta but parasitized and completed development in all four instars of the host. Host instar did not affect D. gelechiidivoris sex-ratio but females reared on the first instar had significantly fewer eggs than when reared in late larval instars (3rd and 4th). Females of the parasitoid emerged with a high mature egg load which peaked 2 d post-eclosion. The females of D. gelechiidivoris survived 8.51±0.65 d and produced 103±8 offspring per female at 26±4°C (range: 24 to 29°C) and 50–70% relative humidity (RH) in the presence of males and fed honey-water (80% honey). Increasing maternal age decreased the proportion of female offspring. Under the aforementioned laboratory conditions, the Gross and Net reproductive rates were 72 and 39.5 respectively, while the mean generation time was 20 d. The estimated intrinsic rate of natural increase was 0.18. These findings indicate that D. gelechiidivorisis a potential biological control agent of T. absoluta and should be considered for augmentative/inundative release in Kenya and across Africa following host specificity testing and risk assessments. The nature of the interaction between D. gelechidivoris and the predatory mirid bug Nesidiocoris tenuis(Reuter) (Hemiptera: Miridae), an important and widespread natural enemy of T. absoluta in Africa was evaluated because N. tenuis, although being a voracious predator of T. absoluta eggs, it can also prey on the early host larval instars (1st and 2nd) which are the preferred oviposition host stages of D. gelechiidivoris. Here, the impact of N. tenuis feeding on T. absoluta and the effects on D. gelechiidivoris performance was tested. Regardless of the order of introductions (i.e. the sequence of combination with D. gelechiidivoris) and densities (i.e. number of N. tenuis combined with D. gelechiidivoris), there was no intraguild predation by N. tenuis on D. gelechiidivorisas there was little host larval feeding behaviour. Also, the presence of N. tenuis did not affect the oviposition performance of D. gelechiidivoris. Further investigations revealed that the combined efficacy of N. tenuis and D. gelechiidivorison T. absoluta population was significantly higher than either natural enemy alone, thus contributes to the data supporting the release of D. gelechiidivoris in Africa. In concluding, integrating D. gelechiidivoris and N. tenuis in the management of T. absolut could potentially reduce yield losses in tomato in Eastern Africa where the socio-economic impacts of the pest are very serious.
- Full Text:
- Date Issued: 2021
Emergent Curriculum and Sustainability Competencies in Environmental Learning
- Mkhabela, Antonia T, Schudel, Ingrid
- Authors: Mkhabela, Antonia T , Schudel, Ingrid
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/435112 , vital:73131 , ISBN 9781928502241 , https://library.oapen.org/handle/20.500.12657/64082
- Description: This study was influenced by the South African National Diagnostic Report on Learner Performance in the 2012 final examinations, which highlighted learner struggles with ‘higher order thinking skills such as application, problem solving, critical thinking, analysis and evaluation’ (South Africa DBE 2013: 16). These are skills typically associated with essay questions in examinations. Another issue reported in the abovementioned document was poorly answered essay questions on Environmental Studies, ‘giving the impression that this topic, which is scheduled towards the end of the year, was neglected by both teachers and learners’ (p. 121). The problem of weak higher order thinking skills, compounded by difficulty with Environmental Studies, informed part of the research interest for this study: namely, how higher order thinking is engaged when reflecting on environmental issues in Life Sciences classrooms (specifically required for the Environmental Studies topic of ‘human impact’).
- Full Text:
- Date Issued: 2021
- Authors: Mkhabela, Antonia T , Schudel, Ingrid
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/435112 , vital:73131 , ISBN 9781928502241 , https://library.oapen.org/handle/20.500.12657/64082
- Description: This study was influenced by the South African National Diagnostic Report on Learner Performance in the 2012 final examinations, which highlighted learner struggles with ‘higher order thinking skills such as application, problem solving, critical thinking, analysis and evaluation’ (South Africa DBE 2013: 16). These are skills typically associated with essay questions in examinations. Another issue reported in the abovementioned document was poorly answered essay questions on Environmental Studies, ‘giving the impression that this topic, which is scheduled towards the end of the year, was neglected by both teachers and learners’ (p. 121). The problem of weak higher order thinking skills, compounded by difficulty with Environmental Studies, informed part of the research interest for this study: namely, how higher order thinking is engaged when reflecting on environmental issues in Life Sciences classrooms (specifically required for the Environmental Studies topic of ‘human impact’).
- Full Text:
- Date Issued: 2021