Photophysicochemical properties and TD-DFT calculations of a novel terminal alkyne substituted metal free phthalocyanine
- Yilmaz, Yusuf, Mack, John, Sönmez, Mehmet, Nyokong, Tebello
- Authors: Yilmaz, Yusuf , Mack, John , Sönmez, Mehmet , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241562 , vital:50950 , xlink:href="https://doi.org/10.1142/S1088424613501241"
- Description: The synthesis of a novel free base tetrakis(prop-2-ynyloxy)phthalocyanine (2) is described, along with its characterization by IR, UV-visible absorption, and 1H NMR spectroscopy and mass spectrometry. The compound exhibited good solubility in a wide range of organic solvents and no significant aggregation was observed over a wide concentration range. The values for the singlet oxygen (ΦΔ), photodegradation, fluorescence (ΦF) and triplet state quantum yields and the fluorescence and triplet state lifetimes are reported. A relatively high ΦΔ value of 0.46 was obtained in DMSO. The ability to carry out "click" chemistry at the ligand periphery enhances the potential utility of 2 for use in bioconjugates in photodynamic therapy (PDT). A moderately high ΦF value of 0.18 is observed for emission in the therapeutic window in the near-IR region, which suggests that it may also be possible to determine the level of localization of 2 in tumor cells through bioimaging.
- Full Text:
- Date Issued: 2014
- Authors: Yilmaz, Yusuf , Mack, John , Sönmez, Mehmet , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241562 , vital:50950 , xlink:href="https://doi.org/10.1142/S1088424613501241"
- Description: The synthesis of a novel free base tetrakis(prop-2-ynyloxy)phthalocyanine (2) is described, along with its characterization by IR, UV-visible absorption, and 1H NMR spectroscopy and mass spectrometry. The compound exhibited good solubility in a wide range of organic solvents and no significant aggregation was observed over a wide concentration range. The values for the singlet oxygen (ΦΔ), photodegradation, fluorescence (ΦF) and triplet state quantum yields and the fluorescence and triplet state lifetimes are reported. A relatively high ΦΔ value of 0.46 was obtained in DMSO. The ability to carry out "click" chemistry at the ligand periphery enhances the potential utility of 2 for use in bioconjugates in photodynamic therapy (PDT). A moderately high ΦF value of 0.18 is observed for emission in the therapeutic window in the near-IR region, which suggests that it may also be possible to determine the level of localization of 2 in tumor cells through bioimaging.
- Full Text:
- Date Issued: 2014
Synthesis and photophysical properties of covalent conjugates of aqua platinum (II) and octacarboxy-substituted zinc phthalocyanine
- Bulgakov, Roman A, Kuznetsova, Nina A, Dolotova, Olga V, Solovieva, Ludmila I, Mack, John, Chidawanyika, Wadzanai J U, Kaliya, Oleg L, Nyokong, Tebello
- Authors: Bulgakov, Roman A , Kuznetsova, Nina A , Dolotova, Olga V , Solovieva, Ludmila I , Mack, John , Chidawanyika, Wadzanai J U , Kaliya, Oleg L , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242726 , vital:51073 , xlink:href="https://doi.org/10.1142/S1088424612501209"
- Description: New covalent conjugates of aqua platinum(II) and octacarboxy-substituted zinc phthalocyanine, bearing one, two, three and four aqua platinum moieties on the periphery of the Pc ligand have been synthesized and characterized. The effect of the stepwise introduction of the aqua platinums on the photophysical and photochemical properties of these compounds has been investigated in dimethylsulfoxide solution. It has been found that aqua platinum moieties have only a limited effect on the dynamics of the singlet and triplet excited states, on the ability to sensitize singlet oxygen formation and on the photostability. Each conjugate has a high singlet oxygen quantum yield (ΦΔ 0.51–0.62) and thus retains potential for use as a dual action anticancer drugs by acting as a sensitizer for PDT in addition to the likely chemotherapeutic effects of the Pt(II) complexes.
- Full Text:
- Date Issued: 2012
- Authors: Bulgakov, Roman A , Kuznetsova, Nina A , Dolotova, Olga V , Solovieva, Ludmila I , Mack, John , Chidawanyika, Wadzanai J U , Kaliya, Oleg L , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242726 , vital:51073 , xlink:href="https://doi.org/10.1142/S1088424612501209"
- Description: New covalent conjugates of aqua platinum(II) and octacarboxy-substituted zinc phthalocyanine, bearing one, two, three and four aqua platinum moieties on the periphery of the Pc ligand have been synthesized and characterized. The effect of the stepwise introduction of the aqua platinums on the photophysical and photochemical properties of these compounds has been investigated in dimethylsulfoxide solution. It has been found that aqua platinum moieties have only a limited effect on the dynamics of the singlet and triplet excited states, on the ability to sensitize singlet oxygen formation and on the photostability. Each conjugate has a high singlet oxygen quantum yield (ΦΔ 0.51–0.62) and thus retains potential for use as a dual action anticancer drugs by acting as a sensitizer for PDT in addition to the likely chemotherapeutic effects of the Pt(II) complexes.
- Full Text:
- Date Issued: 2012
Synthesis and conformational studies of 5-bromo-1-[(N-substituted-carbamoyl) methyl]-7-azabenzimidazoles
- Oluwafemi, Kola A, Klein, Rosalyn, Lobb, Kevin A, Tshiwawa, Tendamudzimu, Isaacs, Michelle, Hoppe, Heinrich C, Kaye, Perry T
- Authors: Oluwafemi, Kola A , Klein, Rosalyn , Lobb, Kevin A , Tshiwawa, Tendamudzimu , Isaacs, Michelle , Hoppe, Heinrich C , Kaye, Perry T
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452800 , vital:75171 , xlink:href="https://doi.org/10.1016/j.molstruc.2022.133811"
- Description: The Cs2CO3-catalysed condensation of 5-bromo-7-azabenzimidazole with a series of bromomethyl ketones has afforded a small library of ten, novel 5-bromo-1-[(N-substututed-carbamoyl)methyl]-7-azabenzimidazoles. Rotamerism in the products, as evidenced by the splitting of 1H- and 13C-NMR signals, is attributed to hindered internal rotation about the amide N-C(=O) bond, and has been explored using dynamic NMR (DNMR) analysis and computational methods at the GIAO B3LYP/6-311+G(2d,p) level of theory. Coalescence temperatures have been obtained for representative examples and rotational barriers determined experimentally and theoretically. A detailed theoretical analysis has been undertaken to explore conformations which may contribute to the relative populations of the s-cis and s-trans rotamers. The products have also been screened for cytotoxicity and activity against two parasitic protozoan strains (Plasmodium falciparum and Trypanosoma brucei).
- Full Text:
- Date Issued: 2022
- Authors: Oluwafemi, Kola A , Klein, Rosalyn , Lobb, Kevin A , Tshiwawa, Tendamudzimu , Isaacs, Michelle , Hoppe, Heinrich C , Kaye, Perry T
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452800 , vital:75171 , xlink:href="https://doi.org/10.1016/j.molstruc.2022.133811"
- Description: The Cs2CO3-catalysed condensation of 5-bromo-7-azabenzimidazole with a series of bromomethyl ketones has afforded a small library of ten, novel 5-bromo-1-[(N-substututed-carbamoyl)methyl]-7-azabenzimidazoles. Rotamerism in the products, as evidenced by the splitting of 1H- and 13C-NMR signals, is attributed to hindered internal rotation about the amide N-C(=O) bond, and has been explored using dynamic NMR (DNMR) analysis and computational methods at the GIAO B3LYP/6-311+G(2d,p) level of theory. Coalescence temperatures have been obtained for representative examples and rotational barriers determined experimentally and theoretically. A detailed theoretical analysis has been undertaken to explore conformations which may contribute to the relative populations of the s-cis and s-trans rotamers. The products have also been screened for cytotoxicity and activity against two parasitic protozoan strains (Plasmodium falciparum and Trypanosoma brucei).
- Full Text:
- Date Issued: 2022
Synthesis, stereochemistry and in vitro STD NMR and in silico HIV-1 PR enzyme-binding potential of MBH-derived inhibitors
- Tukulula, Matshawandile, Olasupo, Idris A, Mugumbate, Grace C, Lobb, Kevin A, Klein, Rosalyn, Sayed, Yasien, Tshiwawa, Tendamudzimu, Kaye, Perry T
- Authors: Tukulula, Matshawandile , Olasupo, Idris A , Mugumbate, Grace C , Lobb, Kevin A , Klein, Rosalyn , Sayed, Yasien , Tshiwawa, Tendamudzimu , Kaye, Perry T
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452813 , vital:75172 , xlink:href="https://doi.org/10.1016/j.molstruc.2022.133716"
- Description: Aza-Michael reactions of a pyridine-3-carbaldehyde-derived Morita-Baylis-Hillman (MBH) adduct with various amines have afforded a series of 10 diastereomeric products, stereochemical analysis of which has been achieved using a combination of NMR (1D, 2D and NOESY) and computer modelling methods. Saturation Transfer Difference (STD) 1H NMR spectroscopy and in silico molecular docking studies have been used to explore the HIV-1 protease sub-type C enzyme binding potential of these compounds in five different HIV-1 PR enzyme receptors.
- Full Text:
- Date Issued: 2022
- Authors: Tukulula, Matshawandile , Olasupo, Idris A , Mugumbate, Grace C , Lobb, Kevin A , Klein, Rosalyn , Sayed, Yasien , Tshiwawa, Tendamudzimu , Kaye, Perry T
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452813 , vital:75172 , xlink:href="https://doi.org/10.1016/j.molstruc.2022.133716"
- Description: Aza-Michael reactions of a pyridine-3-carbaldehyde-derived Morita-Baylis-Hillman (MBH) adduct with various amines have afforded a series of 10 diastereomeric products, stereochemical analysis of which has been achieved using a combination of NMR (1D, 2D and NOESY) and computer modelling methods. Saturation Transfer Difference (STD) 1H NMR spectroscopy and in silico molecular docking studies have been used to explore the HIV-1 protease sub-type C enzyme binding potential of these compounds in five different HIV-1 PR enzyme receptors.
- Full Text:
- Date Issued: 2022
The case for collation to inform debate and transform practice in decolonising Psychology
- Authors: Macleod, Catriona I
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444397 , vital:74225 , xlink:href="https://doi.org/10.1177/0081246318784508"
- Description: Critiques of the ‘relevance’ of Psychology in South Africa and Africa have been raging for a number of decades now. Recent debates about decolonising Psychology and what is meant by African Psychology have been rigorous and necessary. In this commentary, I argue that in order for Psychology to move beyond Euro-American-centric epistemology and practice, these efforts need to be supplemented with the grounded praxis of research and literature collation. The epistemological, empirical, and conceptual knowledges that have been generated within the South African, African, and Global South contexts need to be brought together in coherent forms. As with other analytical processes, the grounded praxis of collating knowledges around a particular topic or approach allows for fresh insights and for the transfer of knowledges generated in context. Gaps in current research may be identified, debates on particular issues strengthened, and practice potentially improved. Drawing on two examples – textbooks and systematic literature reviews – and from my and colleagues’ work in conducting these kinds of collation work, I argue that: textbook writers should use grounded methodologies to generate texts based on South African, African, and Global South research, with reference to research conducted in the Global North being peripheral at best; and systematic reviews enable the cross-fertilisation of ideas from other social science research where psychological research is sparse. Funders should consider funding collation efforts.
- Full Text:
- Date Issued: 2018
- Authors: Macleod, Catriona I
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444397 , vital:74225 , xlink:href="https://doi.org/10.1177/0081246318784508"
- Description: Critiques of the ‘relevance’ of Psychology in South Africa and Africa have been raging for a number of decades now. Recent debates about decolonising Psychology and what is meant by African Psychology have been rigorous and necessary. In this commentary, I argue that in order for Psychology to move beyond Euro-American-centric epistemology and practice, these efforts need to be supplemented with the grounded praxis of research and literature collation. The epistemological, empirical, and conceptual knowledges that have been generated within the South African, African, and Global South contexts need to be brought together in coherent forms. As with other analytical processes, the grounded praxis of collating knowledges around a particular topic or approach allows for fresh insights and for the transfer of knowledges generated in context. Gaps in current research may be identified, debates on particular issues strengthened, and practice potentially improved. Drawing on two examples – textbooks and systematic literature reviews – and from my and colleagues’ work in conducting these kinds of collation work, I argue that: textbook writers should use grounded methodologies to generate texts based on South African, African, and Global South research, with reference to research conducted in the Global North being peripheral at best; and systematic reviews enable the cross-fertilisation of ideas from other social science research where psychological research is sparse. Funders should consider funding collation efforts.
- Full Text:
- Date Issued: 2018
How people foraging in urban greenspace can mobilize social–ecological resilience during Covid-19 and beyond
- Sardeshpande, Mallika, Hurley, Patrick T, Mollee, Eefke, Garekae, Hesekia, Dahlberg, Annika C, Emery, Marla R, Shackleton, Charlie M
- Authors: Sardeshpande, Mallika , Hurley, Patrick T , Mollee, Eefke , Garekae, Hesekia , Dahlberg, Annika C , Emery, Marla R , Shackleton, Charlie M
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/402313 , vital:69841 , xlink:href="https://doi.org/10.3389/frsc.2021.686254"
- Description: Informal foraging for food and other natural materials in urban greenspaces is an activity undertaken by many across the world. For some, foraging is a necessary means of survival and livelihood, while for others, it provides cultural and recreational opportunities. In the socioeconomic crises induced by Covid-19, foraging can help communities, especially (but not exclusively) vulnerable people, cope with the impacts of lockdowns, and associated economic decline. In the long run, foraging can help improve social–ecological resilience in urban systems, particularly in response to climate, economic, and disease disruptions. First, we elaborate the ways in which urban foraging can provide immediate relief from the shocks to natural, human, social, physical, and financial capital. We then describe how over time, the livelihood, food, and income diversification brought about by foraging can contribute to preparedness for future uncertainties and gradual change. Cities are increasingly becoming home to the majority of humanity, and urban foraging can be one of the pathways that makes cities more liveable, for humans as well as other species we coexist with. Through the capitals framework, we explore the role foraging could play in addressing issues of biodiversity conservation, culture, and education, good governance and social justice, multifunctional greenspace, and sustainable nature-based livelihoods in urban areas.
- Full Text:
- Date Issued: 2021
- Authors: Sardeshpande, Mallika , Hurley, Patrick T , Mollee, Eefke , Garekae, Hesekia , Dahlberg, Annika C , Emery, Marla R , Shackleton, Charlie M
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/402313 , vital:69841 , xlink:href="https://doi.org/10.3389/frsc.2021.686254"
- Description: Informal foraging for food and other natural materials in urban greenspaces is an activity undertaken by many across the world. For some, foraging is a necessary means of survival and livelihood, while for others, it provides cultural and recreational opportunities. In the socioeconomic crises induced by Covid-19, foraging can help communities, especially (but not exclusively) vulnerable people, cope with the impacts of lockdowns, and associated economic decline. In the long run, foraging can help improve social–ecological resilience in urban systems, particularly in response to climate, economic, and disease disruptions. First, we elaborate the ways in which urban foraging can provide immediate relief from the shocks to natural, human, social, physical, and financial capital. We then describe how over time, the livelihood, food, and income diversification brought about by foraging can contribute to preparedness for future uncertainties and gradual change. Cities are increasingly becoming home to the majority of humanity, and urban foraging can be one of the pathways that makes cities more liveable, for humans as well as other species we coexist with. Through the capitals framework, we explore the role foraging could play in addressing issues of biodiversity conservation, culture, and education, good governance and social justice, multifunctional greenspace, and sustainable nature-based livelihoods in urban areas.
- Full Text:
- Date Issued: 2021
ISSRs indicate that Chromolaena odorata invading southern Africa originates in Jamaica or Cuba
- Paterson, Iain D, Zachariades, Costas
- Authors: Paterson, Iain D , Zachariades, Costas
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406105 , vital:70239 , xlink:href="https://doi.org/10.1016/j.biocontrol.2013.04.005"
- Description: Two biotypes of the invasive alien plant, Chromolaena odorata (L.) R.M. King and Rob. (Asteraceae: Eupatorieae), are recognized in the plant’s introduced distribution. The Asian/West African (A/WA) biotype is present in West and Central Africa, India, Southeast Asia and Oceania, while the southern African (SA) biotype is only present in southern Africa. Biological control using insect natural enemies has been significantly more successful against the A/WA biotype than the SA biotype, suggesting that host plant incompatibility may have resulted in reduced efficacy of biological control agents in southern Africa. Inter-Simple Sequence Repeats (ISSR) were used to identify the origin of the SA biotype as Jamaica or Cuba. The data also confirm that the SA biotype is genetically distinct from the A/WA biotype and that the SA biotype is the result of a separate introduction. Biological control agents for C. odorata in southern Africa should be sourced from Jamaica and Cuba in order to avoid host plant incompatibility problems.
- Full Text:
- Date Issued: 2014
- Authors: Paterson, Iain D , Zachariades, Costas
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406105 , vital:70239 , xlink:href="https://doi.org/10.1016/j.biocontrol.2013.04.005"
- Description: Two biotypes of the invasive alien plant, Chromolaena odorata (L.) R.M. King and Rob. (Asteraceae: Eupatorieae), are recognized in the plant’s introduced distribution. The Asian/West African (A/WA) biotype is present in West and Central Africa, India, Southeast Asia and Oceania, while the southern African (SA) biotype is only present in southern Africa. Biological control using insect natural enemies has been significantly more successful against the A/WA biotype than the SA biotype, suggesting that host plant incompatibility may have resulted in reduced efficacy of biological control agents in southern Africa. Inter-Simple Sequence Repeats (ISSR) were used to identify the origin of the SA biotype as Jamaica or Cuba. The data also confirm that the SA biotype is genetically distinct from the A/WA biotype and that the SA biotype is the result of a separate introduction. Biological control agents for C. odorata in southern Africa should be sourced from Jamaica and Cuba in order to avoid host plant incompatibility problems.
- Full Text:
- Date Issued: 2014
In vitro antimalarial, antitrypanosomal and HIV-1 integrase inhibitory activities of two Cameroonian medicinal plants
- Fouokeng, Yannick, Feumo Feusso, H M, Mbosso Teinkela, Jean E, Siwe-Noundou, Xavier, Wintjens, René T, Isaacs, Michelle, Hoppe, Heinrich C, Krause, Rui W M, Azébazé, Anatole G B, Vardamides, Juliette C
- Authors: Fouokeng, Yannick , Feumo Feusso, H M , Mbosso Teinkela, Jean E , Siwe-Noundou, Xavier , Wintjens, René T , Isaacs, Michelle , Hoppe, Heinrich C , Krause, Rui W M , Azébazé, Anatole G B , Vardamides, Juliette C
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/195014 , vital:45519 , xlink:href="https://doi.org/10.1016/j.sajb.2018.10.008"
- Description: Antiplasmodial, antitrypanosomal and anti-HIV-1 activities of crude extracts, fractions and some isolated compounds from two Cameroonian medicinal plants: Antrocaryon klaineanum Pierre (Anacardiaceae) and Diospyros conocarpa Gürke ex K. Schum. (Ebenaceae) were assessed. The phytochemical studies led to the isolation of eight compounds (1–8) from Diospyros conocarpa and six compounds (6, 9–13) from Antrocaryon klaineanum. These compounds were identified as mangiferolic acid (1), 3β, 22(S)-dihydroxycycloart-24E-en-26-oic acid (2), lupeol (3), aridanin (4), betulin (5), betulinic acid (6), bergenin (7), D-quercitol(8), entilin C(9), entilin A(10), antrocarine A(11), 7R,20(S)-dihydroxy-4,24(28)-ergostadien-3-one(12) and stigmasterol glucoside (13). The criteria for activity were set as follows: an IC50 value more than 10 μg/mL for crude extracts and more than 1 μg/mL for pure compounds. The hexane/ethyl acetate (1:1) fraction of A.klaineanum root bark (AKERF1) and the hexane/ethyl acetate (1:1) fraction of A.klaineanum trunk bark (AKETF1) presented the strongest antiplasmodial activities with IC50 values of 0.4 and 4.4 μg/mL, respectively. Aridanin (4) and antrocarine A(11), as well as the crude extract of D.conocarpa roots (EDCR), AKERF1 and AKETF1 showed moderate trypanocidal effects. The crude extract of A.klaineanum root bark (AKER) and AKETF1 exhibited attractive activities on HIV-1 integrase with IC50 values of 1.96 and 24.04 μg/mL, respectively. The results provide baseline information on the use of A.klaineanum and D.conocarpa extracts, as well as certain components, as sources of new antiplasmodial, antitrypanosomal and anti-HIV drugs.
- Full Text:
- Date Issued: 2019
- Authors: Fouokeng, Yannick , Feumo Feusso, H M , Mbosso Teinkela, Jean E , Siwe-Noundou, Xavier , Wintjens, René T , Isaacs, Michelle , Hoppe, Heinrich C , Krause, Rui W M , Azébazé, Anatole G B , Vardamides, Juliette C
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/195014 , vital:45519 , xlink:href="https://doi.org/10.1016/j.sajb.2018.10.008"
- Description: Antiplasmodial, antitrypanosomal and anti-HIV-1 activities of crude extracts, fractions and some isolated compounds from two Cameroonian medicinal plants: Antrocaryon klaineanum Pierre (Anacardiaceae) and Diospyros conocarpa Gürke ex K. Schum. (Ebenaceae) were assessed. The phytochemical studies led to the isolation of eight compounds (1–8) from Diospyros conocarpa and six compounds (6, 9–13) from Antrocaryon klaineanum. These compounds were identified as mangiferolic acid (1), 3β, 22(S)-dihydroxycycloart-24E-en-26-oic acid (2), lupeol (3), aridanin (4), betulin (5), betulinic acid (6), bergenin (7), D-quercitol(8), entilin C(9), entilin A(10), antrocarine A(11), 7R,20(S)-dihydroxy-4,24(28)-ergostadien-3-one(12) and stigmasterol glucoside (13). The criteria for activity were set as follows: an IC50 value more than 10 μg/mL for crude extracts and more than 1 μg/mL for pure compounds. The hexane/ethyl acetate (1:1) fraction of A.klaineanum root bark (AKERF1) and the hexane/ethyl acetate (1:1) fraction of A.klaineanum trunk bark (AKETF1) presented the strongest antiplasmodial activities with IC50 values of 0.4 and 4.4 μg/mL, respectively. Aridanin (4) and antrocarine A(11), as well as the crude extract of D.conocarpa roots (EDCR), AKERF1 and AKETF1 showed moderate trypanocidal effects. The crude extract of A.klaineanum root bark (AKER) and AKETF1 exhibited attractive activities on HIV-1 integrase with IC50 values of 1.96 and 24.04 μg/mL, respectively. The results provide baseline information on the use of A.klaineanum and D.conocarpa extracts, as well as certain components, as sources of new antiplasmodial, antitrypanosomal and anti-HIV drugs.
- Full Text:
- Date Issued: 2019
An Exploration of Flow Control Using Machine Learning and Computational Fluid Dynamics
- Bradshaw, Karen L, Cornfield Matthew
- Authors: Bradshaw, Karen L , Cornfield Matthew
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440211 , vital:73757 , xlink:href="https://doi.org/10.59200/ICARTI.2023.017"
- Description: Although numerous studies relating to computational fluid dynamics and machine learning have been conducted in relation to automotive development, the majority focus on either early development using completed 3D models, or the final testing stages of development, or machine learning accelerated computational fluid dynamic simulations. While this approach is helpful in software development and simulation, it is not easily adaptable to automotive design where the final model is constantly changing and being modified. Consequently, the aim of this study is to propose a method for conducting computational fluid dynamics and machine learning concurrently to accelerate the development process. The proposed method is used to design and improve the aerodynamic efficiency of an object. The approach focuses on developing, implementing, and comparing machine learning models capable of generating optimised three-dimensional objects with the required geometry to direct airflow paths required in applications such as pressure generation, as needed for both active and passive flow control. The study concludes that both decision tree regression and long short-term memory (LSTM) autoencoder models could be used to optimise the aerodynamic efficiency of solid bodies, but that the LSTM autoencoder performs better overall. An undesirable effect of the shape optimisation is an overall reduction in shape size as optimization increases.
- Full Text:
- Date Issued: 2023
- Authors: Bradshaw, Karen L , Cornfield Matthew
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440211 , vital:73757 , xlink:href="https://doi.org/10.59200/ICARTI.2023.017"
- Description: Although numerous studies relating to computational fluid dynamics and machine learning have been conducted in relation to automotive development, the majority focus on either early development using completed 3D models, or the final testing stages of development, or machine learning accelerated computational fluid dynamic simulations. While this approach is helpful in software development and simulation, it is not easily adaptable to automotive design where the final model is constantly changing and being modified. Consequently, the aim of this study is to propose a method for conducting computational fluid dynamics and machine learning concurrently to accelerate the development process. The proposed method is used to design and improve the aerodynamic efficiency of an object. The approach focuses on developing, implementing, and comparing machine learning models capable of generating optimised three-dimensional objects with the required geometry to direct airflow paths required in applications such as pressure generation, as needed for both active and passive flow control. The study concludes that both decision tree regression and long short-term memory (LSTM) autoencoder models could be used to optimise the aerodynamic efficiency of solid bodies, but that the LSTM autoencoder performs better overall. An undesirable effect of the shape optimisation is an overall reduction in shape size as optimization increases.
- Full Text:
- Date Issued: 2023
A new indole alkaloid and other constituents from Monodora minor and Uvaria tanzaniae: their antitrypanosomal and antiplasmodial evaluation
- Christopher, Robert, Mgani, Quintino A, Nyandoro, Stephen S, Rousseau, Amanda L, Isaacs, Michelle, Hoppe, Heinrich C
- Authors: Christopher, Robert , Mgani, Quintino A , Nyandoro, Stephen S , Rousseau, Amanda L , Isaacs, Michelle , Hoppe, Heinrich C
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429347 , vital:72603 , xlink:href="https://doi.org/10.1080/14786419.2019.1710705"
- Description: Phytochemical investigation of the methanolic extract of Monodora minor Engl. and Diels (Annonaceae) stem bark yielded a new indole (E)-4-(1H-indol-5-yl)-but-3-en-2-one (1), a known indole 5-formyl-1H-indole (2) and an ubiquitous steroid sitosterol (3). The investigations of the methanolic extract of Uvaria tanzaniae Verdc. (Annonaceae) root bark yielded two previously reported C-benzylated dihydrochalcones namely uvaretin (4) and diuvaretin (5). Structures of the isolated compounds were elucidated based on NMR spectroscopy and high resolution electron ionization mass spectrometry (HR-EI-MS) data. All compounds were tested against Trypanosoma brucei brucei and Plasmodium falciparum. At a single concentration (20 μM) in the antitrypanosomal and antiplasmodial assays, compound 4 exhibited remarkable activities against T. brucei brucei and P. falciparum with percentage inhibition of 97.3% and 83.0% respectively, whereas compounds 1, 2, 3 and 5 were inactive. In a dose response antiplasmodial assay compound 4 exhibited moderate activity against P. falciparum with an IC50 value of 7.20 μM.
- Full Text:
- Date Issued: 2020
- Authors: Christopher, Robert , Mgani, Quintino A , Nyandoro, Stephen S , Rousseau, Amanda L , Isaacs, Michelle , Hoppe, Heinrich C
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429347 , vital:72603 , xlink:href="https://doi.org/10.1080/14786419.2019.1710705"
- Description: Phytochemical investigation of the methanolic extract of Monodora minor Engl. and Diels (Annonaceae) stem bark yielded a new indole (E)-4-(1H-indol-5-yl)-but-3-en-2-one (1), a known indole 5-formyl-1H-indole (2) and an ubiquitous steroid sitosterol (3). The investigations of the methanolic extract of Uvaria tanzaniae Verdc. (Annonaceae) root bark yielded two previously reported C-benzylated dihydrochalcones namely uvaretin (4) and diuvaretin (5). Structures of the isolated compounds were elucidated based on NMR spectroscopy and high resolution electron ionization mass spectrometry (HR-EI-MS) data. All compounds were tested against Trypanosoma brucei brucei and Plasmodium falciparum. At a single concentration (20 μM) in the antitrypanosomal and antiplasmodial assays, compound 4 exhibited remarkable activities against T. brucei brucei and P. falciparum with percentage inhibition of 97.3% and 83.0% respectively, whereas compounds 1, 2, 3 and 5 were inactive. In a dose response antiplasmodial assay compound 4 exhibited moderate activity against P. falciparum with an IC50 value of 7.20 μM.
- Full Text:
- Date Issued: 2020
Delineating functional properties of a cello-oligosaccharide and Bglucan specific cellobiohydrolase (GH5_38): Its synergism with Cel6A and Cel7A for B-(1,3)-(1,4)-glucan degradation
- Mafa, Mpho S, Malgas, Samkelo, Rashamuse, Konanani, Pletschke, Brett I
- Authors: Mafa, Mpho S , Malgas, Samkelo , Rashamuse, Konanani , Pletschke, Brett I
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429425 , vital:72609 , xlink:href="https://doi.org/10.1016/j.carres.2020.108081"
- Description: Cellulase cocktails formulated to degrade crystalline cellulose generally contain cellobiohydrolases (CBHs), referred to as CBHI (Cel7A) and CBHII (Cel6A), as the major constituents. The combined hydrolytic activities of CBHI and CBHII improve the release of fermentable sugars (β-1,4-cellobiose as the main product) from crystalline cellulose. In this study, a novel cellobiohydrolase (Exg-D) sourced from a metagenome of hindgut bacterial symbionts of a termite was heterologouly expressed, purified, and functionally characterised. Exg-D specific activity was higher on insoluble barley β-glucan (38.94 U/mg protein), soluble wheat flour β-glucan (12.71 U/mg protein) and oat β-glucan (8.89 U/mg protein) compared to cellulosic substrates; Avicel and CMC. We further explored Exg-D activity on the unpretreated or NaOH-pretreated (mercerised) Avicel and compared its activity to commercially available CBHI and CBHII on these celluloses. CBHI displayed the highest activity of 4.74 U/mg protein on mercerised cellulose followed by CBHII (2.14 U/mg protein), while Exg-D activity on untreated and mercerised cellulose was 1.66 and 1.67 U/mg protein, respectively. The high activity of CBHI was supported by binding assays, which revealed that CBHI has a higher binding capacity towards crystalline cellulose compared to Exg-D and CBHII. Only CBHI and CBHII showed synergism during the hydrolysis of mercerised Avicel, showing a degree of synergy (DS) of about 1.299 and yielded about 1.43 μmol/ml of reducing sugars higher than control. In contrast, Exg-D and CBHII displayed synergism during β-glucan degradation, displaying a DS of about 1.22. Thus, we propose that Exg-D should only be used synergistically with other CBHs to degrade mixed linked-β-(1,3)-(1,4)-glucan.
- Full Text:
- Date Issued: 2020
- Authors: Mafa, Mpho S , Malgas, Samkelo , Rashamuse, Konanani , Pletschke, Brett I
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429425 , vital:72609 , xlink:href="https://doi.org/10.1016/j.carres.2020.108081"
- Description: Cellulase cocktails formulated to degrade crystalline cellulose generally contain cellobiohydrolases (CBHs), referred to as CBHI (Cel7A) and CBHII (Cel6A), as the major constituents. The combined hydrolytic activities of CBHI and CBHII improve the release of fermentable sugars (β-1,4-cellobiose as the main product) from crystalline cellulose. In this study, a novel cellobiohydrolase (Exg-D) sourced from a metagenome of hindgut bacterial symbionts of a termite was heterologouly expressed, purified, and functionally characterised. Exg-D specific activity was higher on insoluble barley β-glucan (38.94 U/mg protein), soluble wheat flour β-glucan (12.71 U/mg protein) and oat β-glucan (8.89 U/mg protein) compared to cellulosic substrates; Avicel and CMC. We further explored Exg-D activity on the unpretreated or NaOH-pretreated (mercerised) Avicel and compared its activity to commercially available CBHI and CBHII on these celluloses. CBHI displayed the highest activity of 4.74 U/mg protein on mercerised cellulose followed by CBHII (2.14 U/mg protein), while Exg-D activity on untreated and mercerised cellulose was 1.66 and 1.67 U/mg protein, respectively. The high activity of CBHI was supported by binding assays, which revealed that CBHI has a higher binding capacity towards crystalline cellulose compared to Exg-D and CBHII. Only CBHI and CBHII showed synergism during the hydrolysis of mercerised Avicel, showing a degree of synergy (DS) of about 1.299 and yielded about 1.43 μmol/ml of reducing sugars higher than control. In contrast, Exg-D and CBHII displayed synergism during β-glucan degradation, displaying a DS of about 1.22. Thus, we propose that Exg-D should only be used synergistically with other CBHs to degrade mixed linked-β-(1,3)-(1,4)-glucan.
- Full Text:
- Date Issued: 2020
Combination of CTec2 and GH5 or GH26 Endo-Mannanases for Effective Lignocellulosic Biomass Degradation
- Malgas, Samkelo, Pletschke, Brett I
- Authors: Malgas, Samkelo , Pletschke, Brett I
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429397 , vital:72607 , xlink:href="https://doi.org/10.3390/catal10101193"
- Description: Among endo-mannanases, glycoside hydrolase (GH) family 26 enzymes have been shown to be more catalytically active than GH5 enzymes on mannans. However, only GH5 endo-mannanases have been used for the formulation of enzyme cocktails. In this study, Bacillus sp.-derived GH5 and GH26 endo-mannanases were comparatively analysed biochemically for their synergistic action with a commercial cellulase blend, CTec2, during pre-treated lignocellulose degradation. Substrate specificity and thermo-stability studies on mannan substrates showed that GH26 endo-mannanase was more catalytically active and stable than GH5. GH26 also exhibited higher binding affinity for mannan than GH5, while GH5 showed more affinity for lignocellulosic substrates than GH26. Applying the endo-mannanases in combination with CTec2 for lignocellulose degradation led to synergism with a 1.3-fold increase in reducing sugar release compared to when CTec2 was used alone. This study showed that using the activity of endo-mannanases displayed with model substrates is a poor predictor of their activity and synergism on complex lignocelluloses.
- Full Text:
- Date Issued: 2020
- Authors: Malgas, Samkelo , Pletschke, Brett I
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429397 , vital:72607 , xlink:href="https://doi.org/10.3390/catal10101193"
- Description: Among endo-mannanases, glycoside hydrolase (GH) family 26 enzymes have been shown to be more catalytically active than GH5 enzymes on mannans. However, only GH5 endo-mannanases have been used for the formulation of enzyme cocktails. In this study, Bacillus sp.-derived GH5 and GH26 endo-mannanases were comparatively analysed biochemically for their synergistic action with a commercial cellulase blend, CTec2, during pre-treated lignocellulose degradation. Substrate specificity and thermo-stability studies on mannan substrates showed that GH26 endo-mannanase was more catalytically active and stable than GH5. GH26 also exhibited higher binding affinity for mannan than GH5, while GH5 showed more affinity for lignocellulosic substrates than GH26. Applying the endo-mannanases in combination with CTec2 for lignocellulose degradation led to synergism with a 1.3-fold increase in reducing sugar release compared to when CTec2 was used alone. This study showed that using the activity of endo-mannanases displayed with model substrates is a poor predictor of their activity and synergism on complex lignocelluloses.
- Full Text:
- Date Issued: 2020
Towards transformative social learning on the path to 1.5 degrees
- Macintyre, Thomas, Lotz-Sisitka, Heila, Wals, Arjen E, Vogel, Coleen, Tassone, Valenina
- Authors: Macintyre, Thomas , Lotz-Sisitka, Heila , Wals, Arjen E , Vogel, Coleen , Tassone, Valenina
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182461 , vital:43832 , xlink:href="https://doi.org/10.1016/j.cosust.2017.12.003"
- Description: This paper provides insights into learning orientations and approaches that encourage change and transformation on the path to achieving the 1.5 degree C target. This literature review of the climate change and education/learning interface positions relevant literature in a heuristic tool, and reveals different learning approaches to addressing climate change. We highlight that although traditional lines of departure for achieving climate targets are usually technocratic in nature, especially if a zero emissions pathway is aimed for, there is an increasing realisation that climate issues are complex, deeply intertwined with unsustainable development and cultural change, and require collective engagement. Through considering the 1.5 degree C target as a metaphor for the fundamental changes needed in society, we argue that a wide range of learning orientations, including more inclusive and transformative social learning approaches, are needed to address the colossal challenges facing society.
- Full Text:
- Date Issued: 2018
- Authors: Macintyre, Thomas , Lotz-Sisitka, Heila , Wals, Arjen E , Vogel, Coleen , Tassone, Valenina
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182461 , vital:43832 , xlink:href="https://doi.org/10.1016/j.cosust.2017.12.003"
- Description: This paper provides insights into learning orientations and approaches that encourage change and transformation on the path to achieving the 1.5 degree C target. This literature review of the climate change and education/learning interface positions relevant literature in a heuristic tool, and reveals different learning approaches to addressing climate change. We highlight that although traditional lines of departure for achieving climate targets are usually technocratic in nature, especially if a zero emissions pathway is aimed for, there is an increasing realisation that climate issues are complex, deeply intertwined with unsustainable development and cultural change, and require collective engagement. Through considering the 1.5 degree C target as a metaphor for the fundamental changes needed in society, we argue that a wide range of learning orientations, including more inclusive and transformative social learning approaches, are needed to address the colossal challenges facing society.
- Full Text:
- Date Issued: 2018
The Scope of Teaching and Learning in Environmental Education
- Authors: Lotz-Sisitka, Heila
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183037 , vital:43906 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/172809"
- Description: Environmental Education involves a variety of teaching and learning processes which are diversely situated in a range of social and educational contexts. The diversity of scope is an interesting 'contour' of a field like environmental education. Contemporary environmental sciences and complexity studies draw our attention to an ever-changing world and to increasingly complex social-ecological issues, patterns and risks that require our attention. These too influence the scope of environmental education teaching and learning processes. This edition of the Southern African Journal of Environmental Education provides a window through which we may see some of the scope of environmental education activities, research questions, learning and teaching settings, and educational activity. It provides insight into the range of research methodologies that are being deployed to investigate the educational processes that are needed for re-orientation towards sustainability, equity, adaptability and transformation at the people-environment interface.
- Full Text: false
- Date Issued: 2010
- Authors: Lotz-Sisitka, Heila
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183037 , vital:43906 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/172809"
- Description: Environmental Education involves a variety of teaching and learning processes which are diversely situated in a range of social and educational contexts. The diversity of scope is an interesting 'contour' of a field like environmental education. Contemporary environmental sciences and complexity studies draw our attention to an ever-changing world and to increasingly complex social-ecological issues, patterns and risks that require our attention. These too influence the scope of environmental education teaching and learning processes. This edition of the Southern African Journal of Environmental Education provides a window through which we may see some of the scope of environmental education activities, research questions, learning and teaching settings, and educational activity. It provides insight into the range of research methodologies that are being deployed to investigate the educational processes that are needed for re-orientation towards sustainability, equity, adaptability and transformation at the people-environment interface.
- Full Text: false
- Date Issued: 2010
Nutrient-mediated effects on Cornops aquaticum Brüner (Orthoptera: Acrididae), a potential biological control agent of water hyacinth, Eichhornia crassipes (Mart.) Solms (Pontederiaceae)
- Bownes, Angela, Hill, Martin P, Byrne, Marcus J
- Authors: Bownes, Angela , Hill, Martin P , Byrne, Marcus J
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406131 , vital:70241 , xlink:href="https://doi.org/10.1016/j.biocontrol.2013.07.023"
- Description: Environmental nutrient availability can drive and modify both plant responses to herbivory by phytophagous insects and insect feeding patterns which, in insect-weed systems, may ultimately determine whether biological control succeeds or fails. The impacts of insect biological control agents on the invasive aquatic weed, water hyacinth (Eichhornia crassipes) vary with nutrient levels in the environment. It was therefore considered important to evaluate nutrient-specific responses of E. crassipes to a grasshopper herbivore, Cornops aquaticum, prior to its release in South Africa. Both plant productivity and the response of E. crassipes to herbivory by C. aquaticum were nutrient dependent. Increases in plant biomass and leaf and ramet production were correlated with increases in nutrients in the water and plant biomass accumulation was reduced by herbivory at all three nutrient levels tested (high = 67%; medium = 100%; low = 400%). C. aquaticum nymphs fed E. crassipes leaves with the lowest nitrogen levels produced the highest biomass of frass during their development, indicating compensatory consumption. The results suggest that environmental nutrient availability will influence efficacy of C. aquaticum. They also provide further evidence that E. crassipes problems are exacerbated by an over-abundance of nutrients in aquatic environments, and that biological control would be a highly effective management tool if aquatic systems in South Africa were less polluted. Additionally, the results also show how an understanding of the fundamental responses of E. crassipes and its insect biocontrol agents to their environment can assist in determining specific management strategies or interventions according to prevailing site-specific conditions.
- Full Text:
- Date Issued: 2013
- Authors: Bownes, Angela , Hill, Martin P , Byrne, Marcus J
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406131 , vital:70241 , xlink:href="https://doi.org/10.1016/j.biocontrol.2013.07.023"
- Description: Environmental nutrient availability can drive and modify both plant responses to herbivory by phytophagous insects and insect feeding patterns which, in insect-weed systems, may ultimately determine whether biological control succeeds or fails. The impacts of insect biological control agents on the invasive aquatic weed, water hyacinth (Eichhornia crassipes) vary with nutrient levels in the environment. It was therefore considered important to evaluate nutrient-specific responses of E. crassipes to a grasshopper herbivore, Cornops aquaticum, prior to its release in South Africa. Both plant productivity and the response of E. crassipes to herbivory by C. aquaticum were nutrient dependent. Increases in plant biomass and leaf and ramet production were correlated with increases in nutrients in the water and plant biomass accumulation was reduced by herbivory at all three nutrient levels tested (high = 67%; medium = 100%; low = 400%). C. aquaticum nymphs fed E. crassipes leaves with the lowest nitrogen levels produced the highest biomass of frass during their development, indicating compensatory consumption. The results suggest that environmental nutrient availability will influence efficacy of C. aquaticum. They also provide further evidence that E. crassipes problems are exacerbated by an over-abundance of nutrients in aquatic environments, and that biological control would be a highly effective management tool if aquatic systems in South Africa were less polluted. Additionally, the results also show how an understanding of the fundamental responses of E. crassipes and its insect biocontrol agents to their environment can assist in determining specific management strategies or interventions according to prevailing site-specific conditions.
- Full Text:
- Date Issued: 2013
Comparison of the biology of geographically distinct populations of the citrus pest, Thaumatotibia leucotreta (Meyrick)(Lepidoptera: Tortricidae)
- Opoku-Debrah, John K, Hill, Martin P, Knox, Caroline M, Moore, Sean D
- Authors: Opoku-Debrah, John K , Hill, Martin P , Knox, Caroline M , Moore, Sean D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/405769 , vital:70204 , xlink:href="https://hdl.handle.net/10520/EJC160246"
- Description: Baculovirus biopesticides are an important component of integrated pest management programmes worldwide. One such example is the Cryptophlebia leucotreta granulovirus (CrleGV) which is used for the control of false codling moth, Thaumatotibia (= Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae), a pest of citrus and other crops in South Africa. A potential problem associated with constant application of viral biopesticides is the differing susceptibility to the virus observed between different geographic populations of the insect host. This could be related to a number of factors, including biological performance and fitness of the target insect population. This study compared a variety of phenotypic traits between geographically distinct T. leucotreta populations collected from the Addo, Marble Hall, Citrusdal and Nelspruit regions of South Africa, and reared under laboratory conditions for several generations. Traits including pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and developmental time were used as parameters to measure biological performance and fitness. Insects from the Citrusdal region of the Western Cape exhibited significantly lower pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and the longest duration in larval and pupal development compared to the other colonies investigated. This is the first study to report differences in the performance of laboratory reared T. leucotreta from different geographic locations, and the findings may have important implications for the application of viral biopesticides for the control of this pest in South Africa.
- Full Text:
- Date Issued: 2014
- Authors: Opoku-Debrah, John K , Hill, Martin P , Knox, Caroline M , Moore, Sean D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/405769 , vital:70204 , xlink:href="https://hdl.handle.net/10520/EJC160246"
- Description: Baculovirus biopesticides are an important component of integrated pest management programmes worldwide. One such example is the Cryptophlebia leucotreta granulovirus (CrleGV) which is used for the control of false codling moth, Thaumatotibia (= Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae), a pest of citrus and other crops in South Africa. A potential problem associated with constant application of viral biopesticides is the differing susceptibility to the virus observed between different geographic populations of the insect host. This could be related to a number of factors, including biological performance and fitness of the target insect population. This study compared a variety of phenotypic traits between geographically distinct T. leucotreta populations collected from the Addo, Marble Hall, Citrusdal and Nelspruit regions of South Africa, and reared under laboratory conditions for several generations. Traits including pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and developmental time were used as parameters to measure biological performance and fitness. Insects from the Citrusdal region of the Western Cape exhibited significantly lower pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and the longest duration in larval and pupal development compared to the other colonies investigated. This is the first study to report differences in the performance of laboratory reared T. leucotreta from different geographic locations, and the findings may have important implications for the application of viral biopesticides for the control of this pest in South Africa.
- Full Text:
- Date Issued: 2014
AMADAR: a python-based package for large scale prediction of Diels–Alder transition state geometries and IRC path analysis
- Isamura, Bienfait K, Lobb, Kevin A
- Authors: Isamura, Bienfait K , Lobb, Kevin A
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453143 , vital:75226 , xlink:href="https://link.springer.com/article/10.1186/s13321-022-00618-3"
- Description: Predicting transition state geometries is one of the most challenging tasks in computational chemistry, which often requires expert-based knowledge and permanent human intervention. This short communication reports technical details and preliminary results of a python-based tool (AMADAR) designed to generate any Diels–Alder (DA) transition state geometry (TS) and analyze determined IRC paths in a (quasi-)automated fashion, given the product SMILES. Two modules of the package are devoted to performing, from IRC paths, reaction force analyses (RFA) and atomic (fragment) decompositions of the reaction force F and reaction force constant κ. The performance of the protocol has been assessed using a dataset of 2000 DA cycloadducts retrieved from the ZINC database. The sequential location of the corresponding TSs was achieved with a success rate of 95%. RFA plots confrmed the reaction force constant κ to be a good indicator of the (non)synchronicity of the associated DA reactions. Moreover, the atomic decomposition of κ allows for the rationalization of the (a)synchronicity of each DA reaction in terms of contributions stemming from pairs of interacting atoms. The source code of the AMADAR tool is available on GitHub [CMCDD/AMADAR(github. com)] and can be used directly with minor customizations, mostly regarding the local working environment of the user.
- Full Text:
- Date Issued: 2022
- Authors: Isamura, Bienfait K , Lobb, Kevin A
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453143 , vital:75226 , xlink:href="https://link.springer.com/article/10.1186/s13321-022-00618-3"
- Description: Predicting transition state geometries is one of the most challenging tasks in computational chemistry, which often requires expert-based knowledge and permanent human intervention. This short communication reports technical details and preliminary results of a python-based tool (AMADAR) designed to generate any Diels–Alder (DA) transition state geometry (TS) and analyze determined IRC paths in a (quasi-)automated fashion, given the product SMILES. Two modules of the package are devoted to performing, from IRC paths, reaction force analyses (RFA) and atomic (fragment) decompositions of the reaction force F and reaction force constant κ. The performance of the protocol has been assessed using a dataset of 2000 DA cycloadducts retrieved from the ZINC database. The sequential location of the corresponding TSs was achieved with a success rate of 95%. RFA plots confrmed the reaction force constant κ to be a good indicator of the (non)synchronicity of the associated DA reactions. Moreover, the atomic decomposition of κ allows for the rationalization of the (a)synchronicity of each DA reaction in terms of contributions stemming from pairs of interacting atoms. The source code of the AMADAR tool is available on GitHub [CMCDD/AMADAR(github. com)] and can be used directly with minor customizations, mostly regarding the local working environment of the user.
- Full Text:
- Date Issued: 2022
Land claims and the pursuit of co-management on four protected areas in South Africa
- Cundill, Georgina, Thondhlana, Gladman, Sisitka, Lawrence, Shackleton, Sheona E, Blorea, M
- Authors: Cundill, Georgina , Thondhlana, Gladman , Sisitka, Lawrence , Shackleton, Sheona E , Blorea, M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/391223 , vital:68632 , xlink:href="https://doi.org/10.1016/j.landusepol.2013.05.016"
- Description: Successful land claims on protected areas by previously disenfranchised communities often result in co-management agreements between claimant communities and state conservation agencies. South Africa, in particular, has pursued co-management as the desired outcome of land claims on its protected areas. We review four cases of co-management on protected areas in South Africa, and reflect on the appropriateness of the pursuit of co-management as the preferred outcome of land claims. Despite promises of pro-poor, democratically informed management, the practical experience of co-management has seen the continuation of the status quo in terms of conservation, with very few material benefits for claimant communities and limited sharing of responsibilities and decision-making functions. The findings underscore two deep challenges facing co-management in cases of land claims worldwide. First, during land claims negotiations in cases involving protected areas, the state cannot be expected to represent the best interests of its citizens (the land claimants), while simultaneously seeking to meet national and international obligations for protected area coverage. Second, the concept of democratic co-management may sit uncomfortably beside the realities of managing loss-making protected areas with ever-shrinking conservation budgets. Where co-management agreements have already been signed, ensuring that new landowners do indeed have a say in management should form the driving focus for co-management practice going forward.
- Full Text:
- Date Issued: 2013
- Authors: Cundill, Georgina , Thondhlana, Gladman , Sisitka, Lawrence , Shackleton, Sheona E , Blorea, M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/391223 , vital:68632 , xlink:href="https://doi.org/10.1016/j.landusepol.2013.05.016"
- Description: Successful land claims on protected areas by previously disenfranchised communities often result in co-management agreements between claimant communities and state conservation agencies. South Africa, in particular, has pursued co-management as the desired outcome of land claims on its protected areas. We review four cases of co-management on protected areas in South Africa, and reflect on the appropriateness of the pursuit of co-management as the preferred outcome of land claims. Despite promises of pro-poor, democratically informed management, the practical experience of co-management has seen the continuation of the status quo in terms of conservation, with very few material benefits for claimant communities and limited sharing of responsibilities and decision-making functions. The findings underscore two deep challenges facing co-management in cases of land claims worldwide. First, during land claims negotiations in cases involving protected areas, the state cannot be expected to represent the best interests of its citizens (the land claimants), while simultaneously seeking to meet national and international obligations for protected area coverage. Second, the concept of democratic co-management may sit uncomfortably beside the realities of managing loss-making protected areas with ever-shrinking conservation budgets. Where co-management agreements have already been signed, ensuring that new landowners do indeed have a say in management should form the driving focus for co-management practice going forward.
- Full Text:
- Date Issued: 2013
Comparative avifaunal richness and diversity in invasive Acacia dealbata patches and adjacent montane grasslands
- Seath, Jessica, Shackleton, Charlie M
- Authors: Seath, Jessica , Shackleton, Charlie M
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406585 , vital:70287 , xlink:href="https://hdl.handle.net/10520/ejc-afzoo_v57_i1_a12"
- Description: Abstract Invasive alien species are regarded as the second greatest threat to biodiversity globally. Yet, at a local scale their effects may vary, underlying the requirement for more local-scale studies across taxa and settings. Here we consider the effects of an alien invasive tree (Acacia dealbata, 5–8 m tall) on avifaunal numbers, richness and diversity in A. dealbata patches of three sizes relative to adjacent montane grasslands. Analysis of historical aerial photographs showed that A. dealbata first occurred in the area in the late 1930s/early 1940s and has continued to spread, despite some efforts by the landowner to keep it in check. It now covers approximately 11% of the site. This has provided habitat for a number of bird species more characteristic of wooded vegetation types. The number, richness and diversity of birds were greater in A. dealbata patches than the adjacent grasslands of equivalent size. These measures increased with increasing patch size, but more rapidly for A. dealbata patches than grassland ones. Only six of the 48 species of birds recorded were common between the two vegetation types. The most common feeding guild in the A. dealbata patches was insectivores, whereas in the grasslands it was omnivores. Although the invasion of A. dealbata has added to the habitat diversity of the area, thereby facilitating increased avifaunal diversity, if it continues to spread, then the populations and perhaps richness of grassland birds are likely to be negatively affected.
- Full Text:
- Date Issued: 2022
- Authors: Seath, Jessica , Shackleton, Charlie M
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406585 , vital:70287 , xlink:href="https://hdl.handle.net/10520/ejc-afzoo_v57_i1_a12"
- Description: Abstract Invasive alien species are regarded as the second greatest threat to biodiversity globally. Yet, at a local scale their effects may vary, underlying the requirement for more local-scale studies across taxa and settings. Here we consider the effects of an alien invasive tree (Acacia dealbata, 5–8 m tall) on avifaunal numbers, richness and diversity in A. dealbata patches of three sizes relative to adjacent montane grasslands. Analysis of historical aerial photographs showed that A. dealbata first occurred in the area in the late 1930s/early 1940s and has continued to spread, despite some efforts by the landowner to keep it in check. It now covers approximately 11% of the site. This has provided habitat for a number of bird species more characteristic of wooded vegetation types. The number, richness and diversity of birds were greater in A. dealbata patches than the adjacent grasslands of equivalent size. These measures increased with increasing patch size, but more rapidly for A. dealbata patches than grassland ones. Only six of the 48 species of birds recorded were common between the two vegetation types. The most common feeding guild in the A. dealbata patches was insectivores, whereas in the grasslands it was omnivores. Although the invasion of A. dealbata has added to the habitat diversity of the area, thereby facilitating increased avifaunal diversity, if it continues to spread, then the populations and perhaps richness of grassland birds are likely to be negatively affected.
- Full Text:
- Date Issued: 2022
Photodegradation of Orange-G using zinc octacarboxyphthalocyanine supported on Fe3O4 nanoparticles
- Modisha, Phillimon, Nyokong, Tebello, Antunes, Edith M
- Authors: Modisha, Phillimon , Nyokong, Tebello , Antunes, Edith M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241653 , vital:50958 , xlink:href="https://doi.org/10.1016/j.molcata.2013.09.030"
- Description: Zinc octacarboxy phthalocyanine (ZnOCPc) was covalently immobilized on the surface of magnetite nanoparticles (MNPs) for the photocatalytic degradation of Orange G (OG) under visible light irradiation. It is noteworthy that the catalyst can be easily recovered using an external magnet and that it is reusable. The ZnOCPc remained bound to the MNP surface even after 25 min of photolysis as confirmed by the FT-IR and X-ray diffraction spectra. Kinetic analysis shows that the photodegradation rates of OG can be approximated to be pseudo-first order, according to the Langmuir–Hinshelwood kinetics model.
- Full Text:
- Date Issued: 2013
- Authors: Modisha, Phillimon , Nyokong, Tebello , Antunes, Edith M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241653 , vital:50958 , xlink:href="https://doi.org/10.1016/j.molcata.2013.09.030"
- Description: Zinc octacarboxy phthalocyanine (ZnOCPc) was covalently immobilized on the surface of magnetite nanoparticles (MNPs) for the photocatalytic degradation of Orange G (OG) under visible light irradiation. It is noteworthy that the catalyst can be easily recovered using an external magnet and that it is reusable. The ZnOCPc remained bound to the MNP surface even after 25 min of photolysis as confirmed by the FT-IR and X-ray diffraction spectra. Kinetic analysis shows that the photodegradation rates of OG can be approximated to be pseudo-first order, according to the Langmuir–Hinshelwood kinetics model.
- Full Text:
- Date Issued: 2013