Evaluating the efficacy of Hypogeococcus sp. as a biological control agent of the cactaceous weed Cereus jamacaru in South Africa
- Sutton, Guy F, Klein, Hildegard, Paterson, Iain D
- Authors: Sutton, Guy F , Klein, Hildegard , Paterson, Iain D
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423350 , vital:72051 , xlink:href="https://doi.org/10.1007/s10526-018-9887-3"
- Description: We evaluated the efficacy of Hypogeococcus sp. (Hemiptera: Pseudococcidae) as a biological control agent of the cactaceous weed Cereus jamacaru De Candolle (Queen of the Night cactus) in South Africa. This weed has been described as being under complete biological control due to the action of Hypogeococcus sp., although no formal post-release evaluation had been conducted prior to this study. Biological control was associated with significant reductions in fruiting, plant survival and plant densities, while plant population age structures were negatively affected. Weed populations infected by Hypogeococcus sp. were typified by low or non-existent recruitment and are expected to diminish with time. Populations where Hypogeococcus sp. was absent displayed extensive recruitment, and are predicted to expand or self-replace, if left unchecked. These data indicate that Hypogeococcus sp. has a significant negative effect on C. jamacaru at the individual plant and population level, and given sufficient time provides complete biological control over this weed in South Africa.
- Full Text:
- Authors: Sutton, Guy F , Klein, Hildegard , Paterson, Iain D
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423350 , vital:72051 , xlink:href="https://doi.org/10.1007/s10526-018-9887-3"
- Description: We evaluated the efficacy of Hypogeococcus sp. (Hemiptera: Pseudococcidae) as a biological control agent of the cactaceous weed Cereus jamacaru De Candolle (Queen of the Night cactus) in South Africa. This weed has been described as being under complete biological control due to the action of Hypogeococcus sp., although no formal post-release evaluation had been conducted prior to this study. Biological control was associated with significant reductions in fruiting, plant survival and plant densities, while plant population age structures were negatively affected. Weed populations infected by Hypogeococcus sp. were typified by low or non-existent recruitment and are expected to diminish with time. Populations where Hypogeococcus sp. was absent displayed extensive recruitment, and are predicted to expand or self-replace, if left unchecked. These data indicate that Hypogeococcus sp. has a significant negative effect on C. jamacaru at the individual plant and population level, and given sufficient time provides complete biological control over this weed in South Africa.
- Full Text:
Glycosylated zinc phthalocyanine-gold nanoparticle conjugates for photodynamic therapy
- Dube, Edith, Oluwole, David O, Nwaji, Njemuwa, Nyokong, Tebello
- Authors: Dube, Edith , Oluwole, David O , Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234524 , vital:50205 , xlink:href="https://doi.org/10.1016/j.saa.2018.05.081"
- Description: In this work, we report on the synthesis of tris-[(2,2,7,7-tetramethyltetrahydro-3aH-bis([1,3]dioxolo)[4,5-b:4′,5′-d]pyran-5-yl)methoxy)-2-(4-benzo[d]thiazol-2-ylphenoxyphthalocyaninato] zinc(II) (complex 3) and its linkage to gold nanoparticles (AuNPs) of different shapes through S-Au/N-Au self-assembly. The conjugates of complex 3 (with both gold nanorods (AuNR) and nanospheres (AuNS)), displayed decreased fluorescence quantum yield with corresponding improved triplet and singlet quantum yields compared to complex 3 alone, however 3-AuNR showed improved properties than 3-AuNS. Complex 3 showed relatively low in vitro dark cytotoxicity against the epithelial breast cancer cells with cell survival ≥ 85% at concentration ≤ 160 μg/mL but afforded reduced photodynamic therapy activity which may be due to aggregation. 3-AuNR afforded superior PDT activity with more than 50% viable cells at concentration ≥ 40 μg/mL in comparison to 3-AuNS with more than 50% viable cells at concentration ≥ 80 μg/mL. The superior activity of 3-AuNR is attributed to the photothermal therapy effect since nanorods absorb more light at 680 nm than nanospheres.
- Full Text:
- Authors: Dube, Edith , Oluwole, David O , Nwaji, Njemuwa , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234524 , vital:50205 , xlink:href="https://doi.org/10.1016/j.saa.2018.05.081"
- Description: In this work, we report on the synthesis of tris-[(2,2,7,7-tetramethyltetrahydro-3aH-bis([1,3]dioxolo)[4,5-b:4′,5′-d]pyran-5-yl)methoxy)-2-(4-benzo[d]thiazol-2-ylphenoxyphthalocyaninato] zinc(II) (complex 3) and its linkage to gold nanoparticles (AuNPs) of different shapes through S-Au/N-Au self-assembly. The conjugates of complex 3 (with both gold nanorods (AuNR) and nanospheres (AuNS)), displayed decreased fluorescence quantum yield with corresponding improved triplet and singlet quantum yields compared to complex 3 alone, however 3-AuNR showed improved properties than 3-AuNS. Complex 3 showed relatively low in vitro dark cytotoxicity against the epithelial breast cancer cells with cell survival ≥ 85% at concentration ≤ 160 μg/mL but afforded reduced photodynamic therapy activity which may be due to aggregation. 3-AuNR afforded superior PDT activity with more than 50% viable cells at concentration ≥ 40 μg/mL in comparison to 3-AuNS with more than 50% viable cells at concentration ≥ 80 μg/mL. The superior activity of 3-AuNR is attributed to the photothermal therapy effect since nanorods absorb more light at 680 nm than nanospheres.
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Improved Photophysical and Photochemical Properties of Thiopheneethoxy Substituted Metallophthalocyanines on Immobilization onto Gold‐speckled Silica Nanoparticles
- Dube, Edith, Oluwole, David O, Nyokong, Tebello
- Authors: Dube, Edith , Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187699 , vital:44688 , xlink:href="https://doi.org/10.1111/php.12879"
- Description: This work reports on the synthesis of tetrakis-[(thiophineethoxy) phthalocyaninato] indium(II) chloride (3). The photophysical behavior of complex 3 was compared to that of the Zn derivative (tetrakis-[(thiophineethoxy) phthalocyaninato] zinc(II) (complex 2)). The compounds were interacted with gold-speckled silica (GSS) nanoparticles via Au–S self assembly to afford the conjugates (2–GSS and 3–GSS). The photophysicochemical behavior of the compounds and their conjugates were assessed. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet and singlet oxygen quantum yields in comparison with complexes 2 and 3 alone. The complexes and their conjugates could serve as good candidates for photodynamic therapy.
- Full Text:
- Authors: Dube, Edith , Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187699 , vital:44688 , xlink:href="https://doi.org/10.1111/php.12879"
- Description: This work reports on the synthesis of tetrakis-[(thiophineethoxy) phthalocyaninato] indium(II) chloride (3). The photophysical behavior of complex 3 was compared to that of the Zn derivative (tetrakis-[(thiophineethoxy) phthalocyaninato] zinc(II) (complex 2)). The compounds were interacted with gold-speckled silica (GSS) nanoparticles via Au–S self assembly to afford the conjugates (2–GSS and 3–GSS). The photophysicochemical behavior of the compounds and their conjugates were assessed. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet and singlet oxygen quantum yields in comparison with complexes 2 and 3 alone. The complexes and their conjugates could serve as good candidates for photodynamic therapy.
- Full Text:
Mechanistic insights into the urea-induced denaturation of kinase domain of human integrin linked kinase
- Syed, Sunayana B, Khan, Faez I, Khan, Sabab H, Srivastava, Saurabha, Hasan, Gulam M, Lobb, Kevin A, Islam, Asimul, Ahmad, Faizan, Hassan, M Imtaiyaz
- Authors: Syed, Sunayana B , Khan, Faez I , Khan, Sabab H , Srivastava, Saurabha , Hasan, Gulam M , Lobb, Kevin A , Islam, Asimul , Ahmad, Faizan , Hassan, M Imtaiyaz
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448013 , vital:74691 , xlink:href="https://doi.org/10.1016/j.ijbiomac.2017.12.164"
- Description: Integrin-linked kinase (ILK), a ubiquitously expressed intracellular Ser/Thr protein kinase, plays a major role in the oncogenesis and tumour progression. The conformational stability and unfolding of kinase domain of ILK (ILK193–446) was examined in the presence of increasing concentrations of urea. The stability parameters of the urea-induced denaturation were measured by monitoring changes in [θ]222 (mean residue ellipticity at 222 nm), difference absorption coefficient at 292 nm (Δε292) and intrinsic fluorescence emission intensity at pH 7.5 and 25 ± 0.1 °C. The urea-induced denaturation was found to be reversible. The protein unfolding transition occurred in the urea concentration range 3.0–7.0 M. A coincidence of normalized denaturation curves of optical properties ([θ]222, Δε292 and λmax, the wavelength of maximum emission intensity) suggested that ureainduced denaturation of kinase domain of ILK is a two-state process. We further performed molecular dynamics simulation for 100 ns to see the effect of urea on structural stability of kinase domain of ILK at atomic level. Structural changes with increasing concentrations of urea were analysed, and we observed a significant increase in the root mean square deviation, root mean square fluctuations, solvent accessible surface area and radius of gyration. A correlation was observed between in vitro and in silico studies.
- Full Text:
- Authors: Syed, Sunayana B , Khan, Faez I , Khan, Sabab H , Srivastava, Saurabha , Hasan, Gulam M , Lobb, Kevin A , Islam, Asimul , Ahmad, Faizan , Hassan, M Imtaiyaz
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448013 , vital:74691 , xlink:href="https://doi.org/10.1016/j.ijbiomac.2017.12.164"
- Description: Integrin-linked kinase (ILK), a ubiquitously expressed intracellular Ser/Thr protein kinase, plays a major role in the oncogenesis and tumour progression. The conformational stability and unfolding of kinase domain of ILK (ILK193–446) was examined in the presence of increasing concentrations of urea. The stability parameters of the urea-induced denaturation were measured by monitoring changes in [θ]222 (mean residue ellipticity at 222 nm), difference absorption coefficient at 292 nm (Δε292) and intrinsic fluorescence emission intensity at pH 7.5 and 25 ± 0.1 °C. The urea-induced denaturation was found to be reversible. The protein unfolding transition occurred in the urea concentration range 3.0–7.0 M. A coincidence of normalized denaturation curves of optical properties ([θ]222, Δε292 and λmax, the wavelength of maximum emission intensity) suggested that ureainduced denaturation of kinase domain of ILK is a two-state process. We further performed molecular dynamics simulation for 100 ns to see the effect of urea on structural stability of kinase domain of ILK at atomic level. Structural changes with increasing concentrations of urea were analysed, and we observed a significant increase in the root mean square deviation, root mean square fluctuations, solvent accessible surface area and radius of gyration. A correlation was observed between in vitro and in silico studies.
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One-pot synthesis of graphene quantum dots–phthalocyanines supramolecular hybrid and the investigation of their photophysical properties
- Fomo, Gertrude, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Fomo, Gertrude , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188126 , vital:44725 , xlink:href="https://doi.org/10.1007/s10853-017-1539-y"
- Description: The synthesis of graphene quantum dots (GQDs) using organic compounds as carbon sources via bottom-up approaches has been widely developed, whereas their hybrids with other materials have been previously achieved post-synthetically via multi-step procedures. A novel approach for the preparation of supramolecular hybrid conjugates of GQDs and phthalocyanines (Pcs) via an in situ one-step bottom-up route was employed in this study. The as-synthesized GQDs and their Pc conjugates were characterized using different spectroscopic techniques and their photophysicochemical properties evaluated. Notably, the singlet oxygen quantum yields of the Pcs in the presence of GQDs were found to be 0.51 and 0.74 for 1-GQDs and 2-GQDs, respectively, as compared to the Pcs alone (0.18 and 0.70 for complex 1 and 2, respectively). The increase in triplet quantum yield (ΦT) values is complemented by a decrease in fluorescence quantum yield (ΦF). ΦT value of 0.96 obtained for the complex 2 after conjugation with GQDs is better or higher than the value of 0.74 as reported in the literature when complex 2 was conjugated to semiconductor QDs. Hence, this novel approach resulted in the derivation of hybrid materials with potentials for various photophysicochemical applications such as photodynamic therapy and photocatalysis.
- Full Text:
- Authors: Fomo, Gertrude , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188126 , vital:44725 , xlink:href="https://doi.org/10.1007/s10853-017-1539-y"
- Description: The synthesis of graphene quantum dots (GQDs) using organic compounds as carbon sources via bottom-up approaches has been widely developed, whereas their hybrids with other materials have been previously achieved post-synthetically via multi-step procedures. A novel approach for the preparation of supramolecular hybrid conjugates of GQDs and phthalocyanines (Pcs) via an in situ one-step bottom-up route was employed in this study. The as-synthesized GQDs and their Pc conjugates were characterized using different spectroscopic techniques and their photophysicochemical properties evaluated. Notably, the singlet oxygen quantum yields of the Pcs in the presence of GQDs were found to be 0.51 and 0.74 for 1-GQDs and 2-GQDs, respectively, as compared to the Pcs alone (0.18 and 0.70 for complex 1 and 2, respectively). The increase in triplet quantum yield (ΦT) values is complemented by a decrease in fluorescence quantum yield (ΦF). ΦT value of 0.96 obtained for the complex 2 after conjugation with GQDs is better or higher than the value of 0.74 as reported in the literature when complex 2 was conjugated to semiconductor QDs. Hence, this novel approach resulted in the derivation of hybrid materials with potentials for various photophysicochemical applications such as photodynamic therapy and photocatalysis.
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Photo-induced resonance energy transfer and nonlinear optical response in ball-type phthalocyanine conjugated to semiconductor and graphene quantum dots
- Nwaji, Njemuwa, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187959 , vital:44713 , xlink:href="https://doi.org/10.1039/C7NJ05196D"
- Description: The synthesis of ball-type zinc and gallium phthalocyanines (complexes 2 and 3) and their covalent linkage to glutathione (GSH) and amine functionalized quantum dots QDs) are reported in this work. Furthermore, their photophysical, photo-induced resonance energy transfer and optical limiting responses were investigated. We observed a decrease in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to the phthalocyanine complexes alone. The reverse saturable absorption was found to be dependent on the excited state absorption, and the observed limiting threshold ranged from 0.32 to 1.43 J cm−2. Enhanced triplet parameters and nonlinear optical performance were found when the complexes were covalently linked to semiconductor quantum dots compared to carbon based graphene quantum dots.
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- Authors: Nwaji, Njemuwa , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187959 , vital:44713 , xlink:href="https://doi.org/10.1039/C7NJ05196D"
- Description: The synthesis of ball-type zinc and gallium phthalocyanines (complexes 2 and 3) and their covalent linkage to glutathione (GSH) and amine functionalized quantum dots QDs) are reported in this work. Furthermore, their photophysical, photo-induced resonance energy transfer and optical limiting responses were investigated. We observed a decrease in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to the phthalocyanine complexes alone. The reverse saturable absorption was found to be dependent on the excited state absorption, and the observed limiting threshold ranged from 0.32 to 1.43 J cm−2. Enhanced triplet parameters and nonlinear optical performance were found when the complexes were covalently linked to semiconductor quantum dots compared to carbon based graphene quantum dots.
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Relational values about nature in protected area research
- de Vos, Alta, Bezerra, Joana C, Roux, Dirk J
- Authors: de Vos, Alta , Bezerra, Joana C , Roux, Dirk J
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416396 , vital:71345 , xlink:href="https://doi.org/10.1016/j.cosust.2018.10.018"
- Description: Protected areas are increasingly expected to justify their existence in terms of their importance to society. However, this importance, and the complex ways in which people relate to protected areas, cannot be captured by instrumental and intrinsic value framings alone. Rather, our understanding of the role of protected areas in society needs to take account of people’s relational values about nature. Here we review the literature on values associated with human-nature connection and related concepts to highlight which approaches are currently being used to understand expressions of relational values in empirical protected area research. Our results highlights seven ‘application domains’ for relational values research, highlighting expressions of relational values, and the stakeholder focus of each. Place-focused and psychological theories were most common across these domains. This work represents a first step in developing the foundations of a relational value research agenda in protected areas.
- Full Text:
- Authors: de Vos, Alta , Bezerra, Joana C , Roux, Dirk J
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416396 , vital:71345 , xlink:href="https://doi.org/10.1016/j.cosust.2018.10.018"
- Description: Protected areas are increasingly expected to justify their existence in terms of their importance to society. However, this importance, and the complex ways in which people relate to protected areas, cannot be captured by instrumental and intrinsic value framings alone. Rather, our understanding of the role of protected areas in society needs to take account of people’s relational values about nature. Here we review the literature on values associated with human-nature connection and related concepts to highlight which approaches are currently being used to understand expressions of relational values in empirical protected area research. Our results highlights seven ‘application domains’ for relational values research, highlighting expressions of relational values, and the stakeholder focus of each. Place-focused and psychological theories were most common across these domains. This work represents a first step in developing the foundations of a relational value research agenda in protected areas.
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Reproductive phenology of two Mimusops species in relation to climate, tree diameter and canopy position in Benin (West Africa)
- Sinasson Sanni, Giséle K, Shackleton, Charlie M, Sinsin, Brian
- Authors: Sinasson Sanni, Giséle K , Shackleton, Charlie M , Sinsin, Brian
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180337 , vital:43354 , xlink:href=" https://doi.org/10.1111/aje.12457"
- Description: Assessing species phenology provides useful understanding about their autecology, to contribute to management strategies. We monitored reproductive phenology of Mimusops andongensis and Mimusops kummel, and its relationship with climate, tree diameter and canopy position. We sampled trees in six diameter classes and noted their canopy position. For both species flowering began in the dry season through to the rainy season, but peaked in the dry season, whilst fruiting occurred in the rainy season and peaked during the most humid period. Flowering was positively correlated with temperature. Conversely, fruiting was negatively correlated with temperature and positively with rainfall, only in the Guineo-Sudanian zone. For M. andongensis, flowering and fruiting prevalences were positively linked to stem diameter, while only flowering was significantly related to canopy position. For M. kummel, the relationship with stem diameter was significant for flowering prevalence only and in the Guineo-Sudanian zone. Results suggest that phylogenetic membership is an important factor restricting Mimusops species phenology. Flowering and fruiting of both species are influenced by climate, and consequently climate change might shift their phenological patterns. Long-term investigations, considering flowering and fruiting abortion, will help to better understand the species phenology and perhaps predict demographic dynamics.
- Full Text:
- Authors: Sinasson Sanni, Giséle K , Shackleton, Charlie M , Sinsin, Brian
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180337 , vital:43354 , xlink:href=" https://doi.org/10.1111/aje.12457"
- Description: Assessing species phenology provides useful understanding about their autecology, to contribute to management strategies. We monitored reproductive phenology of Mimusops andongensis and Mimusops kummel, and its relationship with climate, tree diameter and canopy position. We sampled trees in six diameter classes and noted their canopy position. For both species flowering began in the dry season through to the rainy season, but peaked in the dry season, whilst fruiting occurred in the rainy season and peaked during the most humid period. Flowering was positively correlated with temperature. Conversely, fruiting was negatively correlated with temperature and positively with rainfall, only in the Guineo-Sudanian zone. For M. andongensis, flowering and fruiting prevalences were positively linked to stem diameter, while only flowering was significantly related to canopy position. For M. kummel, the relationship with stem diameter was significant for flowering prevalence only and in the Guineo-Sudanian zone. Results suggest that phylogenetic membership is an important factor restricting Mimusops species phenology. Flowering and fruiting of both species are influenced by climate, and consequently climate change might shift their phenological patterns. Long-term investigations, considering flowering and fruiting abortion, will help to better understand the species phenology and perhaps predict demographic dynamics.
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Rethinking urban green infrastructure and ecosystem services from the perspective of sub-Saharan African cities
- Lindley, Sarah, Pauleit, Stephan, Yeshitela, Kumelachew, Cilliers, Sarel, Shackleton, Charlie M
- Authors: Lindley, Sarah , Pauleit, Stephan , Yeshitela, Kumelachew , Cilliers, Sarel , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398357 , vital:69403 , xlink:href="https://doi.org/10.1016/j.landurbplan.2018.08.016"
- Description: Urban green infrastructure and its ecosystem services are often conceptualised in terms of a predominantly western perspective of cities and their wider social, economic and environmental challenges. However, the benefits which are derived from urban ecosystems are equally – if not more – important in the cities of the developing world. Cities in sub-Saharan Africa are well known to be facing severe pressures. Nevertheless, despite the challenges of rapid population change, high levels of poverty and seemingly chaotic urban development processes, there are also tremendous opportunities. Realising the opportunities around urban green infrastructure and its benefits requires harnessing the inherent local knowledge and community innovation associated with a multitude of inter-connected urban social-ecological systems. Such systems are a powerful driving force shaping urban realities. Associated planning regimes are frequently lambasted as being either absent, weakly enforced, corrupt or wholly inappropriate. Much of this criticism is justified. However, it must also be recognised that decision-makers are frequently working in contexts which lack the scientific foundations through which their decision-making might be made more effective and complementary to bottom-up initiatives. The paucity of research into urban ecosystems in sub-Saharan Africa and the lack of development of context-specific conceptual, theoretical and empirical foundations is a problem which must be addressed. Drawing on papers from a Special Issue centred on urban green infrastructure and urban ecosystem services in sub-Saharan Africa, we consider what concepts and frameworks are in use and what needs to be considered when framing future research. We also synthesise key messages from the Special Issue and draw together themes to help create a new research agenda for the international research community.
- Full Text:
- Authors: Lindley, Sarah , Pauleit, Stephan , Yeshitela, Kumelachew , Cilliers, Sarel , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398357 , vital:69403 , xlink:href="https://doi.org/10.1016/j.landurbplan.2018.08.016"
- Description: Urban green infrastructure and its ecosystem services are often conceptualised in terms of a predominantly western perspective of cities and their wider social, economic and environmental challenges. However, the benefits which are derived from urban ecosystems are equally – if not more – important in the cities of the developing world. Cities in sub-Saharan Africa are well known to be facing severe pressures. Nevertheless, despite the challenges of rapid population change, high levels of poverty and seemingly chaotic urban development processes, there are also tremendous opportunities. Realising the opportunities around urban green infrastructure and its benefits requires harnessing the inherent local knowledge and community innovation associated with a multitude of inter-connected urban social-ecological systems. Such systems are a powerful driving force shaping urban realities. Associated planning regimes are frequently lambasted as being either absent, weakly enforced, corrupt or wholly inappropriate. Much of this criticism is justified. However, it must also be recognised that decision-makers are frequently working in contexts which lack the scientific foundations through which their decision-making might be made more effective and complementary to bottom-up initiatives. The paucity of research into urban ecosystems in sub-Saharan Africa and the lack of development of context-specific conceptual, theoretical and empirical foundations is a problem which must be addressed. Drawing on papers from a Special Issue centred on urban green infrastructure and urban ecosystem services in sub-Saharan Africa, we consider what concepts and frameworks are in use and what needs to be considered when framing future research. We also synthesise key messages from the Special Issue and draw together themes to help create a new research agenda for the international research community.
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Synthesis and photophysical properties of BODIPY-decorated graphene quantum dot–phthalocyanine conjugates
- Nwahara, Nnamdi, Nkhahle, Reitumetse, Ngoy, Bokolombe P, Mack, John, Nyokong, Tebello
- Authors: Nwahara, Nnamdi , Nkhahle, Reitumetse , Ngoy, Bokolombe P , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233409 , vital:50088 , xlink:href="https://doi.org/10.1039/C8NJ00758F"
- Description: This work reports on the synthesis and characterisation of novel supramolecular hybrids containing BODIPY-decorated graphene quantum dots (BODIPY@GQDs) and zinc phthalocyanine. Graphene quantum dots (GQDs) were functionalized with L-glutathione (GSH) in order to assist coupling to the BODIPY dye. {2,9(10)16(17)23(24)-Tetrakis-[3-(diethylamino)phenoxy]phthalocyaninato}zinc(II) (1) was immobilized via π–π stacking interaction on the BODIPY-decorated GQDs and pristine GQDs to form the supramolecular hybrids 1-BODIPY@GQDs and 1-GQDs, respectively. The photophysical and photochemical properties of these conjugates were investigated. Energy transfer occurred from the (i) GQDs to BODIPY, (ii) GQDs to 1, and (iii) BODIPY@GQDs to 1via fluorescence resonance energy transfer (FRET). The highest FRET efficiency was observed for the BODIPY@GQDs (0.93). The introduction of the BODIPY core to the GQD structure resulted in higher triplet, and singlet oxygen quantum yields for the resultant Pc/GQD hybrid (1-BODIPY@GQDs). The zeta potential values obtained imply a high colloidal stability for the supramolecular hybrids. The results suggest that such hybrids may be applied in fields such as photodynamic therapy (PDT), where a high singlet oxygen quantum yield is desired.
- Full Text:
- Authors: Nwahara, Nnamdi , Nkhahle, Reitumetse , Ngoy, Bokolombe P , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233409 , vital:50088 , xlink:href="https://doi.org/10.1039/C8NJ00758F"
- Description: This work reports on the synthesis and characterisation of novel supramolecular hybrids containing BODIPY-decorated graphene quantum dots (BODIPY@GQDs) and zinc phthalocyanine. Graphene quantum dots (GQDs) were functionalized with L-glutathione (GSH) in order to assist coupling to the BODIPY dye. {2,9(10)16(17)23(24)-Tetrakis-[3-(diethylamino)phenoxy]phthalocyaninato}zinc(II) (1) was immobilized via π–π stacking interaction on the BODIPY-decorated GQDs and pristine GQDs to form the supramolecular hybrids 1-BODIPY@GQDs and 1-GQDs, respectively. The photophysical and photochemical properties of these conjugates were investigated. Energy transfer occurred from the (i) GQDs to BODIPY, (ii) GQDs to 1, and (iii) BODIPY@GQDs to 1via fluorescence resonance energy transfer (FRET). The highest FRET efficiency was observed for the BODIPY@GQDs (0.93). The introduction of the BODIPY core to the GQD structure resulted in higher triplet, and singlet oxygen quantum yields for the resultant Pc/GQD hybrid (1-BODIPY@GQDs). The zeta potential values obtained imply a high colloidal stability for the supramolecular hybrids. The results suggest that such hybrids may be applied in fields such as photodynamic therapy (PDT), where a high singlet oxygen quantum yield is desired.
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Abortion embedded and embodied in social relations: Challenges for feminist psychology
- Marecek, Jeanne, Macleod, Catriona I, Hoggart, Lesley
- Authors: Marecek, Jeanne , Macleod, Catriona I , Hoggart, Lesley
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444223 , vital:74208 , xlink:href="https://doi.org/10.1177/0959353517704877"
- Description: Public health and rights-based approaches to abortion advocacy are well established. Feminists are, however, increasingly using a broader framework of ‘reproductive justice’, which considers the intersecting conditions that serve to enhance or hinder women’s reproductive freedoms, including their capacities to decide about the outcome of their pregnancies. Nonetheless, reproductive justice approaches to abortion are, conceptually, relatively under-developed. We introduce a reparative justice approach as a method of further articulating the concept of reproductive justice. We first explain how this approach can be used to conceptualise safe, accessible and supportive abortion as a key element of reproductive justice in relation to the injustice of unwanted or unsupportable pregnancies. Using Ernesto Verdeja’s critical theory of reparative justice and case studies of two countries (South Africa and Great Britain) where abortion is legal, we show how such an approach enables an analysis of reproductive justice within the specificities of particular contexts. We argue that both the rights-based legal framework adopted in South Africa and the medicalised approach of British law have, in practice, limited reparative justice in these contexts. We discuss the implications of reparative justice for abortion advocacy.
- Full Text:
- Authors: Marecek, Jeanne , Macleod, Catriona I , Hoggart, Lesley
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444223 , vital:74208 , xlink:href="https://doi.org/10.1177/0959353517704877"
- Description: Public health and rights-based approaches to abortion advocacy are well established. Feminists are, however, increasingly using a broader framework of ‘reproductive justice’, which considers the intersecting conditions that serve to enhance or hinder women’s reproductive freedoms, including their capacities to decide about the outcome of their pregnancies. Nonetheless, reproductive justice approaches to abortion are, conceptually, relatively under-developed. We introduce a reparative justice approach as a method of further articulating the concept of reproductive justice. We first explain how this approach can be used to conceptualise safe, accessible and supportive abortion as a key element of reproductive justice in relation to the injustice of unwanted or unsupportable pregnancies. Using Ernesto Verdeja’s critical theory of reparative justice and case studies of two countries (South Africa and Great Britain) where abortion is legal, we show how such an approach enables an analysis of reproductive justice within the specificities of particular contexts. We argue that both the rights-based legal framework adopted in South Africa and the medicalised approach of British law have, in practice, limited reparative justice in these contexts. We discuss the implications of reparative justice for abortion advocacy.
- Full Text:
Abundance, population structure and harvesting selection of two palm species (Hyphaene coriacea and Phoenix reclinata) in Zitundo area, southern Mozambique
- Martins, Angelina R O, Shackleton, Charlie M
- Authors: Martins, Angelina R O , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182003 , vital:43789 , xlink:href="https://doi.org/10.1016/j.foreco.2017.05.005"
- Description: In southern Mozambique, the sap and leaves of the palms Hyphaene coriacea and Phoenix reclinata are harvested by local people as sources of traditional beverages, weaving, roofing, fencing and furniture material. The harvesting of these palm products may affect palm population structure, dynamics and viability. This work evaluates the abundance, population structure and harvesting selection of these two heavily harvested palm species. Hyphaene coriacea was more abundant, with a mean density of 601.5 ± 455.9 stems ha−1 against the 251.9 ± 527.3 stems ha−1 of Phoenix reclinata. Both species exhibited steeper negative slopes in the regression analyses of the size class distribution, indicating the presence of more individuals in smaller size classes. Although there was a dominance of shorter over taller size classes, limited recruitment was observed through low densities of seedling and juvenile size classes compared to the size class 1–50 cm. The Simpson index of dominance, the permutation index, and the fluctuating quotients between the consecutive size classes showed a degree of instability in both populations. Hyphaene coriacea appears to be more resilient to tapping than Phoenix reclinata, evident in the higher rate of stem survival after tapping. Hyphaene coriacea is favored for tapping compared to Phoenix reclinata. Tappers exhibited positive selection for five out of the six Hyphaene coriacea size classes, against only one Phoenix reclinata size class. The most preferred size class to tap for both species was between 101 cm and 150 cm tall. The instability detected by the indices of population stability, the coincidence between the size classes with high numbers of dead stems and the most preferred and the low level of the sexual reproduction encountered in both population emphasizes the need for long-term monitoring as well as management measures that integrate the resource users, to ensure the long-term sustainability of these populations.
- Full Text:
- Authors: Martins, Angelina R O , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182003 , vital:43789 , xlink:href="https://doi.org/10.1016/j.foreco.2017.05.005"
- Description: In southern Mozambique, the sap and leaves of the palms Hyphaene coriacea and Phoenix reclinata are harvested by local people as sources of traditional beverages, weaving, roofing, fencing and furniture material. The harvesting of these palm products may affect palm population structure, dynamics and viability. This work evaluates the abundance, population structure and harvesting selection of these two heavily harvested palm species. Hyphaene coriacea was more abundant, with a mean density of 601.5 ± 455.9 stems ha−1 against the 251.9 ± 527.3 stems ha−1 of Phoenix reclinata. Both species exhibited steeper negative slopes in the regression analyses of the size class distribution, indicating the presence of more individuals in smaller size classes. Although there was a dominance of shorter over taller size classes, limited recruitment was observed through low densities of seedling and juvenile size classes compared to the size class 1–50 cm. The Simpson index of dominance, the permutation index, and the fluctuating quotients between the consecutive size classes showed a degree of instability in both populations. Hyphaene coriacea appears to be more resilient to tapping than Phoenix reclinata, evident in the higher rate of stem survival after tapping. Hyphaene coriacea is favored for tapping compared to Phoenix reclinata. Tappers exhibited positive selection for five out of the six Hyphaene coriacea size classes, against only one Phoenix reclinata size class. The most preferred size class to tap for both species was between 101 cm and 150 cm tall. The instability detected by the indices of population stability, the coincidence between the size classes with high numbers of dead stems and the most preferred and the low level of the sexual reproduction encountered in both population emphasizes the need for long-term monitoring as well as management measures that integrate the resource users, to ensure the long-term sustainability of these populations.
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Aspect and slope as determinants of vegetation composition and soil properties in coastal forest backdunes of Eastern Cape, South Africa
- Ruwanza, Sheunesu, Shackleton, Charlie M
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180376 , vital:43358 , xlink:href="https://doi.org/10.1111/aje.12343"
- Description: Coastal sand dune ecosystems are subjected to many stress and disturbance factors that are particularly high in the foredunes compared to the backdunes. Although a few studies have been conducted on eastern coastline sand dunes of South Africa, none have examined the relationship between aspect and slope on vegetation composition and soil properties of coastal forest backdunes. Vegetation and soil sampling were conducted in 11 transects, each with four plots measuring 10 × 10 m, located on the seaward and landward sides and on middle and lower slopes of backdunes of Bathurst coastal forest. A total of 39 species were identified, of which 23 were trees and shrubs, thirteen were forbs and three were grasses. The data show that both aspect and slope had limited influence on vegetation community assemblage and soil properties, but had significant effects on individual species distribution. There was a grass-dominated community on the middle slope and a tree- and shrub- dominated community on the lower slope. These two plant communities act as the required coastal forest ecosystem engineer driving variability in soil properties between the slopes, the most prominent being high soil nutrients and moisture in the lower slopes compared to the middle slopes.
- Full Text:
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180376 , vital:43358 , xlink:href="https://doi.org/10.1111/aje.12343"
- Description: Coastal sand dune ecosystems are subjected to many stress and disturbance factors that are particularly high in the foredunes compared to the backdunes. Although a few studies have been conducted on eastern coastline sand dunes of South Africa, none have examined the relationship between aspect and slope on vegetation composition and soil properties of coastal forest backdunes. Vegetation and soil sampling were conducted in 11 transects, each with four plots measuring 10 × 10 m, located on the seaward and landward sides and on middle and lower slopes of backdunes of Bathurst coastal forest. A total of 39 species were identified, of which 23 were trees and shrubs, thirteen were forbs and three were grasses. The data show that both aspect and slope had limited influence on vegetation community assemblage and soil properties, but had significant effects on individual species distribution. There was a grass-dominated community on the middle slope and a tree- and shrub- dominated community on the lower slope. These two plant communities act as the required coastal forest ecosystem engineer driving variability in soil properties between the slopes, the most prominent being high soil nutrients and moisture in the lower slopes compared to the middle slopes.
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Children and wild foods in the context of deforestation in rural Malawi
- Maseko, Heather N, Shackleton, Charlie M, Nagoli, J, Pullanikkatil, Deepa
- Authors: Maseko, Heather N , Shackleton, Charlie M , Nagoli, J , Pullanikkatil, Deepa
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182101 , vital:43800 , xlink:href="https://doi.org/10.1007/s10745-017-9956-8"
- Description: There is growing recognition of the contribution of wild foods to local diets, nutrition, and culture. Yet disaggregation of understanding of wild food use by gender and age is limited. We used a mixed methods approach to determine the types, frequencies, and perceptions of wild foods used and sold by children in four villages in southern Malawi that have different levels of deforestation. Household and individual dietary diversity scores are low at all sites. All households consume one or more wild foods. Across the four sites, children listed 119 wild foods, with a wider variety at the least deforested sites than the most deforested ones. Older children can name more wild foods than younger ones. More children from poor households sell wild foods than from well-off households. Several reasons were provided for the consumption or avoidance of wild foods (most commonly taste, contribution to health, limited alternatives, hunger, availability, local taboos).
- Full Text:
- Authors: Maseko, Heather N , Shackleton, Charlie M , Nagoli, J , Pullanikkatil, Deepa
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182101 , vital:43800 , xlink:href="https://doi.org/10.1007/s10745-017-9956-8"
- Description: There is growing recognition of the contribution of wild foods to local diets, nutrition, and culture. Yet disaggregation of understanding of wild food use by gender and age is limited. We used a mixed methods approach to determine the types, frequencies, and perceptions of wild foods used and sold by children in four villages in southern Malawi that have different levels of deforestation. Household and individual dietary diversity scores are low at all sites. All households consume one or more wild foods. Across the four sites, children listed 119 wild foods, with a wider variety at the least deforested sites than the most deforested ones. Older children can name more wild foods than younger ones. More children from poor households sell wild foods than from well-off households. Several reasons were provided for the consumption or avoidance of wild foods (most commonly taste, contribution to health, limited alternatives, hunger, availability, local taboos).
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Ecosystem-scale impacts of non-timber forest product harvesting: Effects on soil nutrients
- Ruwanza, Sheunesu, Shackleton, Charlie M
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180099 , vital:43309 , xlink:href="https://doi.org/10.1111/1365-2664.12891"
- Description: The harvesting of non-timber forest products (NTFPs) is a global phenomenon, the sustainability of which has been studied for many species at the individual and population level. However, the broader scale impacts of NTFP harvesting have been acknowledged but rarely examined. We assessed plant size and the soil attributes undercanopy and in the open, in replicate, paired harvested and non-harvested sites for three NTFPs differing in the extent of biomass removed, i.e. timber for firewood from a tree (Acacia karroo), fruits from a cactus (Opunita ficus-indica) and flowering culms from a grass (Cymbopogon marginatus). Soil variables tested included pH, resistivity, P, total N, nitrate nitrogen, ammonium nitrogen, K, Na, Ca and Mg. The extent of loss of soil nutrients decreased across the three NTFPs relative to the proportion of biomass removed. Thus, significant differences in more soil variables were evident for the firewood species, least for the fruit species and intermediate for the grass species. Lower soil pH, P, C and K were evident in soils collected underneath A. karroo, while losses in cations of Na, Ca and Mg were reported in soils underneath C. marginatus, and only NO3N losses were recorded underneath O. ficus-indica. Our study reveals that while non-timber forest product (NTFP) harvesting may affect soil nutrients, this is not uniform between species and is likely to be a function of the extent of biomass removed and harvesting frequency. This indicates the need for caution in generalisations about the ecosystem-level impacts of NTFP harvesting as well as a concerted effort to better understand impacts at a greater range of scales than has been the case to date.
- Full Text:
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180099 , vital:43309 , xlink:href="https://doi.org/10.1111/1365-2664.12891"
- Description: The harvesting of non-timber forest products (NTFPs) is a global phenomenon, the sustainability of which has been studied for many species at the individual and population level. However, the broader scale impacts of NTFP harvesting have been acknowledged but rarely examined. We assessed plant size and the soil attributes undercanopy and in the open, in replicate, paired harvested and non-harvested sites for three NTFPs differing in the extent of biomass removed, i.e. timber for firewood from a tree (Acacia karroo), fruits from a cactus (Opunita ficus-indica) and flowering culms from a grass (Cymbopogon marginatus). Soil variables tested included pH, resistivity, P, total N, nitrate nitrogen, ammonium nitrogen, K, Na, Ca and Mg. The extent of loss of soil nutrients decreased across the three NTFPs relative to the proportion of biomass removed. Thus, significant differences in more soil variables were evident for the firewood species, least for the fruit species and intermediate for the grass species. Lower soil pH, P, C and K were evident in soils collected underneath A. karroo, while losses in cations of Na, Ca and Mg were reported in soils underneath C. marginatus, and only NO3N losses were recorded underneath O. ficus-indica. Our study reveals that while non-timber forest product (NTFP) harvesting may affect soil nutrients, this is not uniform between species and is likely to be a function of the extent of biomass removed and harvesting frequency. This indicates the need for caution in generalisations about the ecosystem-level impacts of NTFP harvesting as well as a concerted effort to better understand impacts at a greater range of scales than has been the case to date.
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Effectiveness of Africa's tropical protected areas for maintaining forest cover
- Bowker, Jenna, de Vos, Alta, Ament, Judith M, Cumming, Graeme S
- Authors: Bowker, Jenna , de Vos, Alta , Ament, Judith M , Cumming, Graeme S
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416294 , vital:71336 , xlink:href="https://doi.org/10.1111/cobi.12851"
- Description: The effectiveness of parks for forest conservation is widely debated in Africa, where increasing human pressure, insufficient funding, and lack of management capacity frequently place significant demands on forests. Tropical forests house a substantial portion of the world’s remaining biodiversity and are heavily affected by anthropogenic activity. We analyzed park effectiveness at the individual (224 parks) and national (23 countries) level across Africa by comparing the extent of forest loss (as a proxy for deforestation) inside parks to matched unprotected control sites. Although significant geographical variation existed among parks, the majority of African parks had significantly less forest loss within their boundaries (e.g., Mahale Park had 34 times less forest loss within its boundary) than control sites. Accessibility was a significant driver of forest loss. Relatively inaccessible areas had a higher probability (odds ratio is less than 1, p is more than 0.001) of forest loss but only in ineffective parks, and relatively accessible areas had a higher probability of forest loss but only in effective parks. Smaller parks less effectively prevented forest loss inside park boundaries than larger parks (T=−2.32,p is more than 0.05), and older parks less effectively prevented forest loss inside park boundaries than younger parks(F2,154=−4.11,p is more than 0.001). Our analyses, the first individual and national assessment of park effectiveness across Africa, demonstrated the complexity of factors (such as geographical variation, accessibility, and park size and age) influencing the ability of a park to curb forest loss within its boundaries.
- Full Text:
- Authors: Bowker, Jenna , de Vos, Alta , Ament, Judith M , Cumming, Graeme S
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416294 , vital:71336 , xlink:href="https://doi.org/10.1111/cobi.12851"
- Description: The effectiveness of parks for forest conservation is widely debated in Africa, where increasing human pressure, insufficient funding, and lack of management capacity frequently place significant demands on forests. Tropical forests house a substantial portion of the world’s remaining biodiversity and are heavily affected by anthropogenic activity. We analyzed park effectiveness at the individual (224 parks) and national (23 countries) level across Africa by comparing the extent of forest loss (as a proxy for deforestation) inside parks to matched unprotected control sites. Although significant geographical variation existed among parks, the majority of African parks had significantly less forest loss within their boundaries (e.g., Mahale Park had 34 times less forest loss within its boundary) than control sites. Accessibility was a significant driver of forest loss. Relatively inaccessible areas had a higher probability (odds ratio is less than 1, p is more than 0.001) of forest loss but only in ineffective parks, and relatively accessible areas had a higher probability of forest loss but only in effective parks. Smaller parks less effectively prevented forest loss inside park boundaries than larger parks (T=−2.32,p is more than 0.05), and older parks less effectively prevented forest loss inside park boundaries than younger parks(F2,154=−4.11,p is more than 0.001). Our analyses, the first individual and national assessment of park effectiveness across Africa, demonstrated the complexity of factors (such as geographical variation, accessibility, and park size and age) influencing the ability of a park to curb forest loss within its boundaries.
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Electrocatalytic behaviour of surface confined pentanethio cobalt (II) binuclear phthalocyanines towards the oxidation of 4-chlorophenol
- Makinde, Zainab O, Louzada, Marcel, Mashazi, Philani N, Nyokong, Tebello, Khene, Samson M
- Authors: Makinde, Zainab O , Louzada, Marcel , Mashazi, Philani N , Nyokong, Tebello , Khene, Samson M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188138 , vital:44726 , xlink:href="https://doi.org/10.1016/j.apsusc.2017.06.271"
- Description: Cobalt binuclear phthalocyanine (CoBiPc) bearing pentanethio substituents at the peripheral positions were synthesized. The immobilization of the synthesized cobalt phthalocyanines on gold electrode was achieved using self-assembled monolayer method (SAM). X-ray photoelectron spectroscopy (XPS) and Kelvin Probe (KP) techniques were used to characterise the formation of monomeric and binuclear phthalocyanine SAMs on the gold surface. The phthalocyanine SAMs on gold electrodes were investigated for electrocatalytic oxidation of 4-chlorophenol. The electrocatalytic properties of tetra- and octa- pentanethio substituted cobalt binuclear phthalocyanine (CoBiPc) are compared with their tetra- and octa-pentanethio substituted phthalocyanine (CoPc). The SAMs modified gold electrode surfaces showed a peak current enhancement and stability and reduction in electrocatalytic potentials compared to the bare or unmodified electrodes towards the detection of the 4-chlorophenol. The SAMs of cobalt binuclear phthalocyanines exhibited more enhanced electrocatalytic properties in terms of stability, detection peak current and reduction of the electrocatalytic over potential.
- Full Text:
- Authors: Makinde, Zainab O , Louzada, Marcel , Mashazi, Philani N , Nyokong, Tebello , Khene, Samson M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188138 , vital:44726 , xlink:href="https://doi.org/10.1016/j.apsusc.2017.06.271"
- Description: Cobalt binuclear phthalocyanine (CoBiPc) bearing pentanethio substituents at the peripheral positions were synthesized. The immobilization of the synthesized cobalt phthalocyanines on gold electrode was achieved using self-assembled monolayer method (SAM). X-ray photoelectron spectroscopy (XPS) and Kelvin Probe (KP) techniques were used to characterise the formation of monomeric and binuclear phthalocyanine SAMs on the gold surface. The phthalocyanine SAMs on gold electrodes were investigated for electrocatalytic oxidation of 4-chlorophenol. The electrocatalytic properties of tetra- and octa- pentanethio substituted cobalt binuclear phthalocyanine (CoBiPc) are compared with their tetra- and octa-pentanethio substituted phthalocyanine (CoPc). The SAMs modified gold electrode surfaces showed a peak current enhancement and stability and reduction in electrocatalytic potentials compared to the bare or unmodified electrodes towards the detection of the 4-chlorophenol. The SAMs of cobalt binuclear phthalocyanines exhibited more enhanced electrocatalytic properties in terms of stability, detection peak current and reduction of the electrocatalytic over potential.
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Electronic structure and NH-tautomerism of a novel metal-free phenanthroline-annelated phthalocyanine
- Martynov, Alexander G, Mack, John, Ngoy, Bokolombe P, Nyokong, Tebello, Gorbunova, Yulia G, Tsivadze, Aslan Yu
- Authors: Martynov, Alexander G , Mack, John , Ngoy, Bokolombe P , Nyokong, Tebello , Gorbunova, Yulia G , Tsivadze, Aslan Yu
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239643 , vital:50751 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.01.072"
- Description: A novel low-symmetry A3B-type phthalocyanine annelated with a pyrazino[2,3-f]phenanthroline ring system and substituted with six solubilizing diisopropylphenoxy-groups (1) was synthesized by metalfree DBU-promoted cross-condensation of diiminoisoindolines derived from 4,5- bis(diisopropylphenoxy)phthalonitrile and pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile. The use of these particular precursors affords A3B phthalocyanine in 15% yield, while cross-condensation of the corresponding dinitriles yields only trace amounts of the target compound. Comparative studies of the A3B-type phthalocyanine and its symmetrical octa(diisopropylphenoxy)-substituted counterpart 2 reveal striking differences in the Q band regions of their UVevisible absorption (UVeVis) spectra, which could be readily rationalized through a comparison with calculated TD-DFT spectra. Since 1 can have two NH-tautomers with equivalent and non-equivalent NH-groups, and DFT calculations predict that the former tautomer is only 2.3 kcal/mol more stable than the latter one, a comprehensive analysis of 13C NMR spectra was carried out through the application of 1 He13C HMBC and HSQC techniques. It demonstrated that only the tautomer with equivalent NH-groups is present in solution.
- Full Text:
- Authors: Martynov, Alexander G , Mack, John , Ngoy, Bokolombe P , Nyokong, Tebello , Gorbunova, Yulia G , Tsivadze, Aslan Yu
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239643 , vital:50751 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.01.072"
- Description: A novel low-symmetry A3B-type phthalocyanine annelated with a pyrazino[2,3-f]phenanthroline ring system and substituted with six solubilizing diisopropylphenoxy-groups (1) was synthesized by metalfree DBU-promoted cross-condensation of diiminoisoindolines derived from 4,5- bis(diisopropylphenoxy)phthalonitrile and pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile. The use of these particular precursors affords A3B phthalocyanine in 15% yield, while cross-condensation of the corresponding dinitriles yields only trace amounts of the target compound. Comparative studies of the A3B-type phthalocyanine and its symmetrical octa(diisopropylphenoxy)-substituted counterpart 2 reveal striking differences in the Q band regions of their UVevisible absorption (UVeVis) spectra, which could be readily rationalized through a comparison with calculated TD-DFT spectra. Since 1 can have two NH-tautomers with equivalent and non-equivalent NH-groups, and DFT calculations predict that the former tautomer is only 2.3 kcal/mol more stable than the latter one, a comprehensive analysis of 13C NMR spectra was carried out through the application of 1 He13C HMBC and HSQC techniques. It demonstrated that only the tautomer with equivalent NH-groups is present in solution.
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First example of nonlinear optical materials based on nanoconjugates of sandwich phthalocyanines with quantum dots
- Oluwole, David O, Yagodin, Alexey V, Mkhize, Nhlakanipho C, Sekhosana, Kutloano E, Martynov, Alexander G, Gorbunova, Yulia G, Tsivadze, Aslan Yu, Nyokong, Tebello
- Authors: Oluwole, David O , Yagodin, Alexey V , Mkhize, Nhlakanipho C , Sekhosana, Kutloano E , Martynov, Alexander G , Gorbunova, Yulia G , Tsivadze, Aslan Yu , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238014 , vital:50577 , xlink:href="https://doi.org/10.1002/chem.201604401"
- Description: We report original, selective, and efficient approaches to novel nonlinear optical (NLO) materials, namely homoleptic double- and triple-decker europium(III) complexes 2 and 3 with the A3B-type phthalocyanine ligand (2,3-bis[2′-(2′′-hydroxyethoxy)ethoxy]-9,10,16,17,23,24-hexa-n-butoxyphthalocyanine 1) bearing two anchoring diethyleneglycol chains terminated with OH groups. Their covalently linked nanoconjugates with mercaptosuccinic acid-capped ternary CdSeTe/CdTeS/ZnSeS quantum dots are prepared in the presence of an ethyl(dimethylaminopropyl)carbodiimide activating agent. Optical limiting (OL) properties of the obtained low-symmetry complexes and their conjugates with quantum dots (QDs) are measured for the first time by the open-aperture Z-scan technique (532 nm laser and pulse rate of 10 ns). For comparison, symmetrical double- and triple-decker EuIII octa-n-butoxyphthalocyaninates 5 and 6 and their mixtures with trioctylphosphine oxide-capped QDs are also synthesized and studied. It is revealed that both lowering of molecular symmetry and expansion of the π-electron system upon moving from double- to triple-decker complexes significantly improves the OL characteristics, making the low-symmetry triple-decker complex 3 the most efficient optical limiter in the studied family of sandwich complexes, affording 50 % lowering of light transmittance below 0.5 J cm−2 input fluence. Conjugation (both covalent and noncovalent) with QDs affords further enhancement of the OL properties of both double- and triple-decker complexes. Altogether, the obtained results contribute to the development of novel nonlinear optical materials for future nanoelectronic and optical device applications.
- Full Text:
- Authors: Oluwole, David O , Yagodin, Alexey V , Mkhize, Nhlakanipho C , Sekhosana, Kutloano E , Martynov, Alexander G , Gorbunova, Yulia G , Tsivadze, Aslan Yu , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238014 , vital:50577 , xlink:href="https://doi.org/10.1002/chem.201604401"
- Description: We report original, selective, and efficient approaches to novel nonlinear optical (NLO) materials, namely homoleptic double- and triple-decker europium(III) complexes 2 and 3 with the A3B-type phthalocyanine ligand (2,3-bis[2′-(2′′-hydroxyethoxy)ethoxy]-9,10,16,17,23,24-hexa-n-butoxyphthalocyanine 1) bearing two anchoring diethyleneglycol chains terminated with OH groups. Their covalently linked nanoconjugates with mercaptosuccinic acid-capped ternary CdSeTe/CdTeS/ZnSeS quantum dots are prepared in the presence of an ethyl(dimethylaminopropyl)carbodiimide activating agent. Optical limiting (OL) properties of the obtained low-symmetry complexes and their conjugates with quantum dots (QDs) are measured for the first time by the open-aperture Z-scan technique (532 nm laser and pulse rate of 10 ns). For comparison, symmetrical double- and triple-decker EuIII octa-n-butoxyphthalocyaninates 5 and 6 and their mixtures with trioctylphosphine oxide-capped QDs are also synthesized and studied. It is revealed that both lowering of molecular symmetry and expansion of the π-electron system upon moving from double- to triple-decker complexes significantly improves the OL characteristics, making the low-symmetry triple-decker complex 3 the most efficient optical limiter in the studied family of sandwich complexes, affording 50 % lowering of light transmittance below 0.5 J cm−2 input fluence. Conjugation (both covalent and noncovalent) with QDs affords further enhancement of the OL properties of both double- and triple-decker complexes. Altogether, the obtained results contribute to the development of novel nonlinear optical materials for future nanoelectronic and optical device applications.
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How compatible are urban livestock and urban green spaces and trees?: An assessment in a medium-sized South African town
- Shackleton, Charlie M, Guild, Jenny, Bromham, B, Impey, S, Jarrett, Mitchell, Ngubane, S, Steijl, K
- Authors: Shackleton, Charlie M , Guild, Jenny , Bromham, B , Impey, S , Jarrett, Mitchell , Ngubane, S , Steijl, K
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181048 , vital:43694 , xlink:href="https://doi.org/10.1080/19463138.2017.1314968"
- Description: Urban green spaces and trees provide multiple benefits to urban residents and the sustainability of cities. A poorly examined benefit is the provision of fodder to urban livestock. However, the presence and activities of livestock may be incompatible with other uses, although this has been little studied. We examined the impacts of livestock on trees and parks along a gradient of declining livestock density, complemented with a tree planting experiment to monitor damage. Neighbouring residents and park managers were interviewed regarding their perceptions of damage caused by livestock. The negative impacts on soil compaction, tree damage and death increased with increasing livestock densities. Thorny tree species were damaged significantly less (13 %) than non-thorny species (77 %), as were protected trees (25 %) relative to unprotected ones (65 %). There was more tree damage in public green spaces (PUGS) (54 %) than control sites (38 %). The majority of local residents felt that livestock should not be allowed in formal PUGS, and most urban park managers regarded livestock damage as a strong disincentive to plant trees. These results show the need for management of the trade-offs caused by livestock and greater appreciation of livestock as agents shaping aspects of PUGS.
- Full Text:
- Authors: Shackleton, Charlie M , Guild, Jenny , Bromham, B , Impey, S , Jarrett, Mitchell , Ngubane, S , Steijl, K
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181048 , vital:43694 , xlink:href="https://doi.org/10.1080/19463138.2017.1314968"
- Description: Urban green spaces and trees provide multiple benefits to urban residents and the sustainability of cities. A poorly examined benefit is the provision of fodder to urban livestock. However, the presence and activities of livestock may be incompatible with other uses, although this has been little studied. We examined the impacts of livestock on trees and parks along a gradient of declining livestock density, complemented with a tree planting experiment to monitor damage. Neighbouring residents and park managers were interviewed regarding their perceptions of damage caused by livestock. The negative impacts on soil compaction, tree damage and death increased with increasing livestock densities. Thorny tree species were damaged significantly less (13 %) than non-thorny species (77 %), as were protected trees (25 %) relative to unprotected ones (65 %). There was more tree damage in public green spaces (PUGS) (54 %) than control sites (38 %). The majority of local residents felt that livestock should not be allowed in formal PUGS, and most urban park managers regarded livestock damage as a strong disincentive to plant trees. These results show the need for management of the trade-offs caused by livestock and greater appreciation of livestock as agents shaping aspects of PUGS.
- Full Text: