Enhanced Optical Limiting Behavior of an Indium Phthalocyanine–Single-Walled Carbon Nanotube Composite
- Sanusi, Kayode, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Sanusi, Kayode , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193871 , vital:45401 , xlink:href="https://doi.org/10.1021/jp501469e "
- Description: The nonlinear optical behavior of 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy) phthalocyaninato indium (III) chloride (2) and its carbon nanotube composite in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions is described. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. A large nonlinear absorption that increased on covalent linking with single-walled carbon nanotubes (SWCNTs) was observed for the compound in DMSO. The nanosecond nonlinear absorption and the optical limiting behavior of this complex are shown to be dominated by a strong excited state absorption from a two-photon pumped state. The optical limiter using the new nanocomposite material (SWCNT-2) in the appropriate solvent showed a much lower threshold for optical limiting together with a much lower transmission at high fluences than previously reported nanocomposite limiters. The optical properties of the phthalocyanine and its conjugate were found to show high sensitivity toward the change of solvent matrix.
- Full Text:
- Authors: Sanusi, Kayode , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193871 , vital:45401 , xlink:href="https://doi.org/10.1021/jp501469e "
- Description: The nonlinear optical behavior of 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy) phthalocyaninato indium (III) chloride (2) and its carbon nanotube composite in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions is described. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. A large nonlinear absorption that increased on covalent linking with single-walled carbon nanotubes (SWCNTs) was observed for the compound in DMSO. The nanosecond nonlinear absorption and the optical limiting behavior of this complex are shown to be dominated by a strong excited state absorption from a two-photon pumped state. The optical limiter using the new nanocomposite material (SWCNT-2) in the appropriate solvent showed a much lower threshold for optical limiting together with a much lower transmission at high fluences than previously reported nanocomposite limiters. The optical properties of the phthalocyanine and its conjugate were found to show high sensitivity toward the change of solvent matrix.
- Full Text:
Evidence of spatial and temporal changes in sources of organic matter in estuarine sediments
- Bergamino, Leandro, Dalu, Tatenda, Richoux, Nicole B
- Authors: Bergamino, Leandro , Dalu, Tatenda , Richoux, Nicole B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457242 , vital:75619 , xlink:href="https://doi.org/10.1007/s10750-014-1853-1"
- Description: We investigated spatial and temporal changes in sources of organic matter in sediments within an estuarine environment in South Africa using fatty acids (FA) and stable isotopes (SI). Samples of sediments and sources of organic matter [i.e., particulate organic matter, microphytobenthos (MPB), macrophytes, salt marsh plants, and terrestrial leaves] were collected during spring and summer 2012, and autumn and winter 2013 from the upper, middle, and lower reaches. A Stable Isotope Analysis in R (SIAR) mixing model was used to identify the organic matter sources contributing to sediments in each estuarine reach and season. We found that diatom-associated fatty acids (20:5ω3; 16:1ω7) increased toward the upper reaches, while long-chained terrigenous fatty acids (24:0) tended to be more prevalent in lower reach sediments. In support of the FA results, the SI mixing model showed a substantial contribution from the marsh grass Spartina maritima in sediments of the lower estuary during periods of low-freshwater discharge (autumn and winter), while MPB was the main component in sediments from the upper and middle reaches during all seasons. Our results have implications for evaluating estuarine food webs since the spatial and seasonal variability in the organic matter deposited can influence estuarine community structure.
- Full Text:
- Authors: Bergamino, Leandro , Dalu, Tatenda , Richoux, Nicole B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457242 , vital:75619 , xlink:href="https://doi.org/10.1007/s10750-014-1853-1"
- Description: We investigated spatial and temporal changes in sources of organic matter in sediments within an estuarine environment in South Africa using fatty acids (FA) and stable isotopes (SI). Samples of sediments and sources of organic matter [i.e., particulate organic matter, microphytobenthos (MPB), macrophytes, salt marsh plants, and terrestrial leaves] were collected during spring and summer 2012, and autumn and winter 2013 from the upper, middle, and lower reaches. A Stable Isotope Analysis in R (SIAR) mixing model was used to identify the organic matter sources contributing to sediments in each estuarine reach and season. We found that diatom-associated fatty acids (20:5ω3; 16:1ω7) increased toward the upper reaches, while long-chained terrigenous fatty acids (24:0) tended to be more prevalent in lower reach sediments. In support of the FA results, the SI mixing model showed a substantial contribution from the marsh grass Spartina maritima in sediments of the lower estuary during periods of low-freshwater discharge (autumn and winter), while MPB was the main component in sediments from the upper and middle reaches during all seasons. Our results have implications for evaluating estuarine food webs since the spatial and seasonal variability in the organic matter deposited can influence estuarine community structure.
- Full Text:
Investigating the chaperone properties of a novel heat shock protein, Hsp70. c, from Trypanosoma brucei
- Burger, Adélle, Ludewig, Michael H, Boshoff, Aileen
- Authors: Burger, Adélle , Ludewig, Michael H , Boshoff, Aileen
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431155 , vital:72749 , xlink:href="https://doi.org/10.1155/2014/172582"
- Description: The neglected tropical disease, African Trypanosomiasis, is fatal and has a crippling impact on economic development. Heat shock protein 70 (Hsp70) is an important molecular chaperone that is expressed in response to stress and Hsp40 acts as its co-chaperone. These proteins play a wide range of roles in the cell and they are required to assist the parasite as it moves from a cold blooded insect vector to a warm blooded mammalian host. A novel cytosolic Hsp70, from Trypanosoma brucei, TbHsp70.c, contains an acidic substrate binding domain and lacks the C-terminal EEVD motif.The ability of a cytosolic Hsp40 from Trypanosoma brucei J protein 2, Tbj2, to function as a co-chaperone of TbHsp70.c was investigated.The main objective was to functionally characterize TbHsp70.c to further expand our knowledge of parasite biology. TbHsp70.c and Tbj2 were heterologously expressed and purified and both proteins displayed the ability to suppress aggregation of thermolabile MDH and chemically denatured rhodanese. ATPase assays revealed a 2.8-fold stimulation of the ATPase activity of TbHsp70.c by Tbj2. TbHsp70.c and Tbj2 both demonstrated chaperone activity and Tbj2 functions as a co-chaperone of TbHsp70.c.In vivo heat stress experiments indicated upregulation of the expression levels of TbHsp70.c.
- Full Text:
- Authors: Burger, Adélle , Ludewig, Michael H , Boshoff, Aileen
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431155 , vital:72749 , xlink:href="https://doi.org/10.1155/2014/172582"
- Description: The neglected tropical disease, African Trypanosomiasis, is fatal and has a crippling impact on economic development. Heat shock protein 70 (Hsp70) is an important molecular chaperone that is expressed in response to stress and Hsp40 acts as its co-chaperone. These proteins play a wide range of roles in the cell and they are required to assist the parasite as it moves from a cold blooded insect vector to a warm blooded mammalian host. A novel cytosolic Hsp70, from Trypanosoma brucei, TbHsp70.c, contains an acidic substrate binding domain and lacks the C-terminal EEVD motif.The ability of a cytosolic Hsp40 from Trypanosoma brucei J protein 2, Tbj2, to function as a co-chaperone of TbHsp70.c was investigated.The main objective was to functionally characterize TbHsp70.c to further expand our knowledge of parasite biology. TbHsp70.c and Tbj2 were heterologously expressed and purified and both proteins displayed the ability to suppress aggregation of thermolabile MDH and chemically denatured rhodanese. ATPase assays revealed a 2.8-fold stimulation of the ATPase activity of TbHsp70.c by Tbj2. TbHsp70.c and Tbj2 both demonstrated chaperone activity and Tbj2 functions as a co-chaperone of TbHsp70.c.In vivo heat stress experiments indicated upregulation of the expression levels of TbHsp70.c.
- Full Text:
Spectral properties and photophysical behaviour of water soluble cationic Mg (II) and Al (III) phthalocyanines
- Idowu, Mopelola A I, Arslanoğlu, Yasin, Nyokong, Tebello
- Authors: Idowu, Mopelola A I , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241549 , vital:50949 , xlink:href="https://doi.org/10.2478/s11532-013-0388-z"
- Description: Peripherally and non-peripherally tetrasubstituted-[(N-methyl-2-pyridylthio)]phthalocyaninato magnesium (II) (5 and 6) and chloro aluminium (III) (7 and 8) tetraiodide have been synthesized and characterized. The photophysical properties of the complexes in dimethyl sulfoxide (DMSO) and aqueous medium in the presence and absence of cremophore EL have been studied. These complexes show high solubility in aqueous medium though they were aggregated. The triplet state quantum yields (FT) and the triplet lifetimes (tT) were found to be higher in DMSO with ΦT ranging from 0.32 to 0.51, while tT ranged from 282 to 622 ms in DMSO, compared to aqueous medium (pH 7.4 buffer) where ΦT ranged from 0.15 to 0.19 and tT from 26 to 35 ms. Addition of cremophore EL in aqueous solution resulted in partial disaggregation and increased photoactivity. The fluorescence lifetimes of the complexes showed strong dependence on their immediate environment. The ionic magnesium(II) and aluminium(III) phthalocyanines strongly bind to bovine serum albumin (BSA).
- Full Text:
- Authors: Idowu, Mopelola A I , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241549 , vital:50949 , xlink:href="https://doi.org/10.2478/s11532-013-0388-z"
- Description: Peripherally and non-peripherally tetrasubstituted-[(N-methyl-2-pyridylthio)]phthalocyaninato magnesium (II) (5 and 6) and chloro aluminium (III) (7 and 8) tetraiodide have been synthesized and characterized. The photophysical properties of the complexes in dimethyl sulfoxide (DMSO) and aqueous medium in the presence and absence of cremophore EL have been studied. These complexes show high solubility in aqueous medium though they were aggregated. The triplet state quantum yields (FT) and the triplet lifetimes (tT) were found to be higher in DMSO with ΦT ranging from 0.32 to 0.51, while tT ranged from 282 to 622 ms in DMSO, compared to aqueous medium (pH 7.4 buffer) where ΦT ranged from 0.15 to 0.19 and tT from 26 to 35 ms. Addition of cremophore EL in aqueous solution resulted in partial disaggregation and increased photoactivity. The fluorescence lifetimes of the complexes showed strong dependence on their immediate environment. The ionic magnesium(II) and aluminium(III) phthalocyanines strongly bind to bovine serum albumin (BSA).
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Temporal shifts in the fatty acid profiles of rocky intertidal invertebrates
- Richoux, Nicole B, Ndhlovu, Rachel T
- Authors: Richoux, Nicole B , Ndhlovu, Rachel T
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457336 , vital:75626 , xlink:href="https://doi.org/10.1007/s00227-014-2481-z"
- Description: Fatty acid profiles were determined in rocky intertidal suspension-feeders (mussels and polychaetes) and grazers (limpets and sea urchins) on a monthly basis over 1 year to assess potential dietary overlap between consumers occupying the same trophic guild, and any temporal shifts in diets. Both reproductive and non-reproductive tissues were assessed in an attempt to separate influences of food quality with those of life cycle. Relative variability in fatty acids over time could not be predicted from the feeding guild occupied by a consumer, and influential factors of the temporal shifts included both dietary and reproductive dynamics (even in muscle tissues). Species in the same trophic guild occupied separate trophic niches throughout the year, hence minimising competitive interactions regarding food acquisition. Based on overall variation in fatty acid profiles of muscle tissues, the suspension-feeders Perna perna and Gunnarea gaimardi and the grazing limpet Cymbula oculus occupied narrower feeding niches relative to the grazing sea urchin Parechinus angulosus. Our results provide compelling evidence for potentially large changes in the lipid composition of intertidal invertebrate populations over relatively small temporal scales (i.e. month to month), and these have important implications for short-term field collections intended for assessing invertebrate diets.
- Full Text:
- Authors: Richoux, Nicole B , Ndhlovu, Rachel T
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457336 , vital:75626 , xlink:href="https://doi.org/10.1007/s00227-014-2481-z"
- Description: Fatty acid profiles were determined in rocky intertidal suspension-feeders (mussels and polychaetes) and grazers (limpets and sea urchins) on a monthly basis over 1 year to assess potential dietary overlap between consumers occupying the same trophic guild, and any temporal shifts in diets. Both reproductive and non-reproductive tissues were assessed in an attempt to separate influences of food quality with those of life cycle. Relative variability in fatty acids over time could not be predicted from the feeding guild occupied by a consumer, and influential factors of the temporal shifts included both dietary and reproductive dynamics (even in muscle tissues). Species in the same trophic guild occupied separate trophic niches throughout the year, hence minimising competitive interactions regarding food acquisition. Based on overall variation in fatty acid profiles of muscle tissues, the suspension-feeders Perna perna and Gunnarea gaimardi and the grazing limpet Cymbula oculus occupied narrower feeding niches relative to the grazing sea urchin Parechinus angulosus. Our results provide compelling evidence for potentially large changes in the lipid composition of intertidal invertebrate populations over relatively small temporal scales (i.e. month to month), and these have important implications for short-term field collections intended for assessing invertebrate diets.
- Full Text:
Understanding food security in a perfect storm: an ecosystem services approach
- Poppy, G M, Chiotha, S, Eigenbrod, Felix, Harvey, Celia A, Honza´k, M, Hudson, Malcolm D, Jarvis, A, Madise, Nyovani J, Schreckenberg, Kate, Shackleton, Charlie M, Villa, Ferdinando, Dawson, Terence P
- Authors: Poppy, G M , Chiotha, S , Eigenbrod, Felix , Harvey, Celia A , Honza´k, M , Hudson, Malcolm D , Jarvis, A , Madise, Nyovani J , Schreckenberg, Kate , Shackleton, Charlie M , Villa, Ferdinando , Dawson, Terence P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398423 , vital:69410 , xlink:href="https://doi.org/10.1098/rstb.2012.0288"
- Description: Achieving food security in a ‘perfect storm’ scenario is a grand challenge for society. Climate change and an expanding global population act in concert to make global food security even more complex and demanding. As achieving food security and the millennium development goal (MDG) to eradicate hunger influences the attainment of other MDGs, it is imperative that we offer solutions which are complementary and do not oppose one another. Sustainable intensification of agriculture has been proposed as a way to address hunger while also minimizing further environmental impact. However, the desire to raise productivity and yields has historically led to a degraded environment, reduced biodiversity and a reduction in ecosystem services (ES), with the greatest impacts affecting the poor. This paper proposes that the ES framework coupled with a policy response framework, for example Driver-Pressure-State-Impact-Response (DPSIR), can allow food security to be delivered alongside healthy ecosystems, which provide many other valuable services to humankind. Too often, agro-ecosystems have been considered as separate from other natural ecosystems and insufficient attention has been paid to the way in which services can flow to and from the agro-ecosystem to surrounding ecosystems. Highlighting recent research in a large multi-disciplinary project (ASSETS), we illustrate the ES approach to food security using a case study from the Zomba district of Malawi.
- Full Text:
- Authors: Poppy, G M , Chiotha, S , Eigenbrod, Felix , Harvey, Celia A , Honza´k, M , Hudson, Malcolm D , Jarvis, A , Madise, Nyovani J , Schreckenberg, Kate , Shackleton, Charlie M , Villa, Ferdinando , Dawson, Terence P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398423 , vital:69410 , xlink:href="https://doi.org/10.1098/rstb.2012.0288"
- Description: Achieving food security in a ‘perfect storm’ scenario is a grand challenge for society. Climate change and an expanding global population act in concert to make global food security even more complex and demanding. As achieving food security and the millennium development goal (MDG) to eradicate hunger influences the attainment of other MDGs, it is imperative that we offer solutions which are complementary and do not oppose one another. Sustainable intensification of agriculture has been proposed as a way to address hunger while also minimizing further environmental impact. However, the desire to raise productivity and yields has historically led to a degraded environment, reduced biodiversity and a reduction in ecosystem services (ES), with the greatest impacts affecting the poor. This paper proposes that the ES framework coupled with a policy response framework, for example Driver-Pressure-State-Impact-Response (DPSIR), can allow food security to be delivered alongside healthy ecosystems, which provide many other valuable services to humankind. Too often, agro-ecosystems have been considered as separate from other natural ecosystems and insufficient attention has been paid to the way in which services can flow to and from the agro-ecosystem to surrounding ecosystems. Highlighting recent research in a large multi-disciplinary project (ASSETS), we illustrate the ES approach to food security using a case study from the Zomba district of Malawi.
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Gazing at Exhibit A
- Authors: Krueger, Anton
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229643 , vital:49696 , xlink:href="http://liminalities.net/9-1/exhibit.pdf"
- Description: Brett Bailey recently toured a new work in Europe and South Africa, called The Exhibit Series (2010-2013). In different countries the work has appeared under different titles—Exhibit A and Exhibit B, while Exhibit C will be produced in 2014. These productions replicate and parody ethnographic spectacles of the nineteenth century, interrogating European colonial atrocities in Africa, as well as contemporary xenophobia. They consist of a series of installations housed in individual rooms that audience members enter one by one. Inside these rooms one is confronted by beautifully arranged spectacles referencing historical atrocities committed in Namibia by German speaking peoples, as well as atrocities under the Belgian and French colonial regimes in the two Congos. The “exhibits” also include references to more recent incidents of European racism against migrants from Africa. The work has been both applauded and derided. In Berlin, for example, activists called it “a human zoo” and protested that this was “the wrong way to discuss a violent colonial history,”1 while others have called the work “haunting”, praising the production for its “dignity” and “beauty.”2
- Full Text:
- Authors: Krueger, Anton
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229643 , vital:49696 , xlink:href="http://liminalities.net/9-1/exhibit.pdf"
- Description: Brett Bailey recently toured a new work in Europe and South Africa, called The Exhibit Series (2010-2013). In different countries the work has appeared under different titles—Exhibit A and Exhibit B, while Exhibit C will be produced in 2014. These productions replicate and parody ethnographic spectacles of the nineteenth century, interrogating European colonial atrocities in Africa, as well as contemporary xenophobia. They consist of a series of installations housed in individual rooms that audience members enter one by one. Inside these rooms one is confronted by beautifully arranged spectacles referencing historical atrocities committed in Namibia by German speaking peoples, as well as atrocities under the Belgian and French colonial regimes in the two Congos. The “exhibits” also include references to more recent incidents of European racism against migrants from Africa. The work has been both applauded and derided. In Berlin, for example, activists called it “a human zoo” and protested that this was “the wrong way to discuss a violent colonial history,”1 while others have called the work “haunting”, praising the production for its “dignity” and “beauty.”2
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Influence of an intermittent food supply on energy storage by the subpolar deposit feeder Yoldia hyperborea (Bivalvia: Nuculanidae)
- Stead, R A, Richoux, Nicole B, Pereda, S V, Thompson, R J
- Authors: Stead, R A , Richoux, Nicole B , Pereda, S V , Thompson, R J
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457271 , vital:75621 , xlink:href="https://doi.org/10.1007/s00300-013-1353-1"
- Description: Food supply for deposit feeders varies from highly seasonal phytodetritus to a steady source of older organic matter, resulting in contrasting patterns of nutrient uptake and storage. To identify patterns in energy storage and feeding behaviour driven by different food conditions for the circumpolar deposit-feeding protobranch bivalve Yoldia hyperborea, we measured variations in cytological (digestive cell height) and biochemical (lipid class, fatty acid, glycogen, and protein content) components during controlled experiments. Three treatments with organisms in sediment with high refractory organic matter (12 % OM) were exposed to different feeding regimes resembling (a) the annual spring bloom settlement, (b) low food availability during winter, and (c) sporadic resuspension events. Yoldia exposed to a diatom-supplemented diet showed significantly higher mean values for digestive cell height (28.44 μm), glycogen (30.4 mg g−1 dry mass, DM), diatom-specific fatty acids, and total lipid (TL) levels (14.4 mg g−1 DM), but lower protein concentrations, than in non-supplemented treatments (digestive cell height 20.34 μm; glycogen 9.23 mg g−1 DM; TL 6.7 mg g−1 DM). All analyses showed no effect of resuspension events; thus, it was unlikely that resuspension improved sediment nutritional value. In the absence of recently deposited diatoms, Y. hyperborea did not increase nutrient storage, suggesting that significant amounts of older refractory OM are not used for growth or reproduction. The rapid storage of nutrients derived from diatoms demonstrates the role of seasonal episodic events of settling algae in the nutrition of subpolar Y. hyperborea and in the transfer of energy from the water column to the benthos.
- Full Text:
- Authors: Stead, R A , Richoux, Nicole B , Pereda, S V , Thompson, R J
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457271 , vital:75621 , xlink:href="https://doi.org/10.1007/s00300-013-1353-1"
- Description: Food supply for deposit feeders varies from highly seasonal phytodetritus to a steady source of older organic matter, resulting in contrasting patterns of nutrient uptake and storage. To identify patterns in energy storage and feeding behaviour driven by different food conditions for the circumpolar deposit-feeding protobranch bivalve Yoldia hyperborea, we measured variations in cytological (digestive cell height) and biochemical (lipid class, fatty acid, glycogen, and protein content) components during controlled experiments. Three treatments with organisms in sediment with high refractory organic matter (12 % OM) were exposed to different feeding regimes resembling (a) the annual spring bloom settlement, (b) low food availability during winter, and (c) sporadic resuspension events. Yoldia exposed to a diatom-supplemented diet showed significantly higher mean values for digestive cell height (28.44 μm), glycogen (30.4 mg g−1 dry mass, DM), diatom-specific fatty acids, and total lipid (TL) levels (14.4 mg g−1 DM), but lower protein concentrations, than in non-supplemented treatments (digestive cell height 20.34 μm; glycogen 9.23 mg g−1 DM; TL 6.7 mg g−1 DM). All analyses showed no effect of resuspension events; thus, it was unlikely that resuspension improved sediment nutritional value. In the absence of recently deposited diatoms, Y. hyperborea did not increase nutrient storage, suggesting that significant amounts of older refractory OM are not used for growth or reproduction. The rapid storage of nutrients derived from diatoms demonstrates the role of seasonal episodic events of settling algae in the nutrition of subpolar Y. hyperborea and in the transfer of energy from the water column to the benthos.
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Linking poverty, HIV/AIDS and climate change to human and ecosystem vulnerability in southern Africa: Consequences for livelihoods and sustainable ecosystem management
- Shackleton, Sheona E, Shackleton, Charlie M
- Authors: Shackleton, Sheona E , Shackleton, Charlie M
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181081 , vital:43697 , xlink:href="https://doi.org/10.1080/13504509.2011.641039"
- Description: People in southern Africa are facing escalating levels of risk, uncertainty and consequently vulnerability as a result of multiple interacting stressors, including HIV/AIDS, poverty, food insecurity, weak governance, climate change and land degradation, to name but a few. Vulnerability or livelihood insecurity emerges when poor people as individuals or social units have to face harmful threats or shocks with inadequate capacity to respond effectively. In such situations, people often have no choice but to turn to their immediate environment for support. Evidence suggests that rising levels of human vulnerability are driving increased dependency on biodiversity and ecosystem services, which in turn, and along with other threats, is rendering ecosystems more vulnerable. This paper explores the dynamic and complex linkages and feedbacks between human vulnerability and ecosystem vulnerability, drawing on data from the southern African region. Human vulnerability is conceptualized as a threat to ecosystem health, as driven by the interplay between a number of current and emerging factors. We focus on poverty, HIV/AIDS and more intense climate extremes as examples of stressors on livelihoods and direct and indirect drivers of ecosystem change. We discuss how some of the responses to increased vulnerability may pose threats to biodiversity conservation, ecosystem management and sustainable development, whilst considering potential solutions that rely on a thorough understanding of coupled social–ecological systems and the interplay between multiple stressors and responses at different scales.
- Full Text:
- Authors: Shackleton, Sheona E , Shackleton, Charlie M
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181081 , vital:43697 , xlink:href="https://doi.org/10.1080/13504509.2011.641039"
- Description: People in southern Africa are facing escalating levels of risk, uncertainty and consequently vulnerability as a result of multiple interacting stressors, including HIV/AIDS, poverty, food insecurity, weak governance, climate change and land degradation, to name but a few. Vulnerability or livelihood insecurity emerges when poor people as individuals or social units have to face harmful threats or shocks with inadequate capacity to respond effectively. In such situations, people often have no choice but to turn to their immediate environment for support. Evidence suggests that rising levels of human vulnerability are driving increased dependency on biodiversity and ecosystem services, which in turn, and along with other threats, is rendering ecosystems more vulnerable. This paper explores the dynamic and complex linkages and feedbacks between human vulnerability and ecosystem vulnerability, drawing on data from the southern African region. Human vulnerability is conceptualized as a threat to ecosystem health, as driven by the interplay between a number of current and emerging factors. We focus on poverty, HIV/AIDS and more intense climate extremes as examples of stressors on livelihoods and direct and indirect drivers of ecosystem change. We discuss how some of the responses to increased vulnerability may pose threats to biodiversity conservation, ecosystem management and sustainable development, whilst considering potential solutions that rely on a thorough understanding of coupled social–ecological systems and the interplay between multiple stressors and responses at different scales.
- Full Text:
A research tool for analysing and monitoring the Extent to which Environmental issues are integrated into teachers’ lessons
- Authors: Nsubuga, Yvonne
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386447 , vital:68142 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122246"
- Description: South Africa enjoys strong policy support for the integration of environmental issues into school curricula. However, much doubt exists over the extent to which this has been converted into appropriate classroom practice at the majority of under-resourced rural schools in the country. This article reports on a study which piloted a research tool which can be used to analyse teachers’ lessons, with the aim of gaining insight into the extent to which they integrate natural resource management issues. The research tool was based on Bernstein’s concept of classification and consisted of five indicators of natural resource management integration into Life Sciences lessons. The study contributes to the design of research tools that can be used to analyse and monitor the integration of environmental issues into teachers’ lessons. It also provides some insight into the environmental content of a sample of Grade 10 Life Sciences lessons at four rural underresourced schools in the Eastern Cape.
- Full Text:
- Authors: Nsubuga, Yvonne
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386447 , vital:68142 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122246"
- Description: South Africa enjoys strong policy support for the integration of environmental issues into school curricula. However, much doubt exists over the extent to which this has been converted into appropriate classroom practice at the majority of under-resourced rural schools in the country. This article reports on a study which piloted a research tool which can be used to analyse teachers’ lessons, with the aim of gaining insight into the extent to which they integrate natural resource management issues. The research tool was based on Bernstein’s concept of classification and consisted of five indicators of natural resource management integration into Life Sciences lessons. The study contributes to the design of research tools that can be used to analyse and monitor the integration of environmental issues into teachers’ lessons. It also provides some insight into the environmental content of a sample of Grade 10 Life Sciences lessons at four rural underresourced schools in the Eastern Cape.
- Full Text:
Formation, surface characterization, and electrocatalytic application of self-assembled monolayer films of tetra-substituted manganese, iron, and cobalt benzylthio phthalocyanine complexes
- Akinbulu, Isaac Adebayo, Ozoemena, Kenneth Iyke, Nyokong, Tebello
- Authors: Akinbulu, Isaac Adebayo , Ozoemena, Kenneth Iyke , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247163 , vital:51552 , xlink:href="https://doi.org/10.1007/s10008-010-1243-1"
- Description: Molecular thin films of manganese (SAM-2), iron (SAM-3), and cobalt (SAM-4) phthalocyanine complexes, non-peripherally tetra-substituted with benzylmercapto, were formed on polycrystalline gold disc electrode by self-assembly technique. Surface characteristics of the films were interrogated by cyclic voltammetry. Significant passivation of voltammetry processes associated with bare gold surface (gold oxidation and underpotential deposition of copper) confirmed formation of the films. Electrocatalytic property of the films was evidenced from better voltammetry responses (less positive oxidation potential and better current signal) of the insecticide, carbofuran, on these films, relative to that on bare gold electrode. In terms of less positive oxidation potential, the FePc derivative (3) gave the best response, while the best current signal was observed on SAM-2-modified gold electrode. The average heterogeneous rate constant, k, for the oxidation of carbofuran was 3.6 × 10−2 cm s−1 on the SAM film with the best current signal (SAM-2).
- Full Text:
- Authors: Akinbulu, Isaac Adebayo , Ozoemena, Kenneth Iyke , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247163 , vital:51552 , xlink:href="https://doi.org/10.1007/s10008-010-1243-1"
- Description: Molecular thin films of manganese (SAM-2), iron (SAM-3), and cobalt (SAM-4) phthalocyanine complexes, non-peripherally tetra-substituted with benzylmercapto, were formed on polycrystalline gold disc electrode by self-assembly technique. Surface characteristics of the films were interrogated by cyclic voltammetry. Significant passivation of voltammetry processes associated with bare gold surface (gold oxidation and underpotential deposition of copper) confirmed formation of the films. Electrocatalytic property of the films was evidenced from better voltammetry responses (less positive oxidation potential and better current signal) of the insecticide, carbofuran, on these films, relative to that on bare gold electrode. In terms of less positive oxidation potential, the FePc derivative (3) gave the best response, while the best current signal was observed on SAM-2-modified gold electrode. The average heterogeneous rate constant, k, for the oxidation of carbofuran was 3.6 × 10−2 cm s−1 on the SAM film with the best current signal (SAM-2).
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Formulation development and in vitro evaluation of didanosine-loaded nanostructured lipid carriers for the potential treatment of AIDS dementia complex
- Wa Kasongo, Kasongo, Shegokar, Ranjita, Müller, Rainer H, Walker, Roderick B
- Authors: Wa Kasongo, Kasongo , Shegokar, Ranjita , Müller, Rainer H , Walker, Roderick B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184210 , vital:44190 , xlink:href="https://doi.org/10.3109/03639045.2010.516264"
- Description: The purpose of this article was to investigate the feasibility of incorporating didanosine (DDI) into nanostructured lipid carriers (NLC) for potential treatment of AIDS dementia complex. Aqueous DDI-free and DDI-loaded NLC were manufactured using hot high-pressure homogenization. The lipid matrix contained a mixture of Precirol ® ATO 5 and Transcutol ® HP. Photon correlation spectroscopy revealed that the mean particle size for all formulations was below 250 nm with narrow polydispersity indices. In addition, the d99% values for all formulations determined using laser diffractometry were below 400 nm with the span values ranging from 0.84 to 1.0. The zeta potential values ranged from −18.4 to −11.4 mV and the encapsulation efficiency of NLC for DDI ranged from 33.02% to 78.34%. These parameters remained relatively constant for all formulations tested following storage for 2 months at 25°C indicating that all the formulations were relatively stable. Differential scanning calorimetry revealed a decrease in the degree of crystallinity of NLC in all formulations developed relative to the bulk lipid material. In addition, wide-angle X-ray scattering showed that NLC in all formulations tested existed in a single β-modification form and that DDI that had been incorporated into the NLC appeared to be molecularly dispersed in the lipid matrices. Images of the NLC formulations obtained using transmission electron microscopy revealed that all formulations contained a mixture of spherical and nonspherical particles irrespective of the amount of DDI that was added during the manufacture of the formulations.
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- Authors: Wa Kasongo, Kasongo , Shegokar, Ranjita , Müller, Rainer H , Walker, Roderick B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184210 , vital:44190 , xlink:href="https://doi.org/10.3109/03639045.2010.516264"
- Description: The purpose of this article was to investigate the feasibility of incorporating didanosine (DDI) into nanostructured lipid carriers (NLC) for potential treatment of AIDS dementia complex. Aqueous DDI-free and DDI-loaded NLC were manufactured using hot high-pressure homogenization. The lipid matrix contained a mixture of Precirol ® ATO 5 and Transcutol ® HP. Photon correlation spectroscopy revealed that the mean particle size for all formulations was below 250 nm with narrow polydispersity indices. In addition, the d99% values for all formulations determined using laser diffractometry were below 400 nm with the span values ranging from 0.84 to 1.0. The zeta potential values ranged from −18.4 to −11.4 mV and the encapsulation efficiency of NLC for DDI ranged from 33.02% to 78.34%. These parameters remained relatively constant for all formulations tested following storage for 2 months at 25°C indicating that all the formulations were relatively stable. Differential scanning calorimetry revealed a decrease in the degree of crystallinity of NLC in all formulations developed relative to the bulk lipid material. In addition, wide-angle X-ray scattering showed that NLC in all formulations tested existed in a single β-modification form and that DDI that had been incorporated into the NLC appeared to be molecularly dispersed in the lipid matrices. Images of the NLC formulations obtained using transmission electron microscopy revealed that all formulations contained a mixture of spherical and nonspherical particles irrespective of the amount of DDI that was added during the manufacture of the formulations.
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The use of experimental design in the development of an HPLC–ECD method for the analysis of captopril
- Khamanga, Sandile M, Walker, Roderick B
- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184056 , vital:44163 , xlink:href="https://doi.org/10.1016/j.talanta.2010.11.025"
- Description: An accurate, sensitive and specific high performance liquid chromatography–electrochemical detection (HPLC–ECD) method that was developed and validated for captopril (CPT) is presented. Separation was achieved using a Phenomenex® Luna 5 μm (C18) column and a mobile phase comprised of phosphate buffer (adjusted to pH 3.0): acetonitrile in a ratio of 70:30 (v/v). Detection was accomplished using a full scan multi channel ESA Coulometric detector in the “oxidative-screen” mode with the upstream electrode (E1) set at +600 mV and the downstream (analytical) electrode (E2) set at +950 mV, while the potential of the guard cell was maintained at +1050 mV. The detector gain was set at 300. Experimental design using central composite design (CCD) was used to facilitate method development. Mobile phase pH, molarity and concentration of acetonitrile (ACN) were considered the critical factors to be studied to establish the retention time of CPT and cyclizine (CYC) that was used as the internal standard. Twenty experiments including centre points were undertaken and a quadratic model was derived for the retention time for CPT using the experimental data. The method was validated for linearity, accuracy, precision, limits of quantitation and detection, as per the ICH guidelines. The system was found to produce sharp and well-resolved peaks for CPT and CYC with retention times of 3.08 and 7.56 min, respectively. Linear regression analysis for the calibration curve showed a good linear relationship with a regression coefficient of 0.978 in the concentration range of 2–70 μg/mL. The linear regression equation was y = 0.0131x + 0.0275. The limits of detection (LOQ) and quantitation (LOD) were found to be 2.27 and 0.6 μg/mL, respectively. The method was used to analyze CPT in tablets. The wide range for linearity, accuracy, sensitivity, short retention time and composition of the mobile phase indicated that this method is better for the quantification of CPT than the pharmacopoeial methods.
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- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184056 , vital:44163 , xlink:href="https://doi.org/10.1016/j.talanta.2010.11.025"
- Description: An accurate, sensitive and specific high performance liquid chromatography–electrochemical detection (HPLC–ECD) method that was developed and validated for captopril (CPT) is presented. Separation was achieved using a Phenomenex® Luna 5 μm (C18) column and a mobile phase comprised of phosphate buffer (adjusted to pH 3.0): acetonitrile in a ratio of 70:30 (v/v). Detection was accomplished using a full scan multi channel ESA Coulometric detector in the “oxidative-screen” mode with the upstream electrode (E1) set at +600 mV and the downstream (analytical) electrode (E2) set at +950 mV, while the potential of the guard cell was maintained at +1050 mV. The detector gain was set at 300. Experimental design using central composite design (CCD) was used to facilitate method development. Mobile phase pH, molarity and concentration of acetonitrile (ACN) were considered the critical factors to be studied to establish the retention time of CPT and cyclizine (CYC) that was used as the internal standard. Twenty experiments including centre points were undertaken and a quadratic model was derived for the retention time for CPT using the experimental data. The method was validated for linearity, accuracy, precision, limits of quantitation and detection, as per the ICH guidelines. The system was found to produce sharp and well-resolved peaks for CPT and CYC with retention times of 3.08 and 7.56 min, respectively. Linear regression analysis for the calibration curve showed a good linear relationship with a regression coefficient of 0.978 in the concentration range of 2–70 μg/mL. The linear regression equation was y = 0.0131x + 0.0275. The limits of detection (LOQ) and quantitation (LOD) were found to be 2.27 and 0.6 μg/mL, respectively. The method was used to analyze CPT in tablets. The wide range for linearity, accuracy, sensitivity, short retention time and composition of the mobile phase indicated that this method is better for the quantification of CPT than the pharmacopoeial methods.
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Applications of polymerized metal tetra-amino phthalocyanines towards hydrogen peroxide detection
- Mashazi, Philani N, Togo, Chumunorwa, Limson, Janice L, Nyokong, Tebello
- Authors: Mashazi, Philani N , Togo, Chumunorwa , Limson, Janice L , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261840 , vital:53451 , xlink:href="https://doi.org/10.1142/S1088424610001994"
- Description: This work reports the use of metallo tetra-amino phthalocyanines (MTAPc, M = Co and Mn) polymer thin films on gold and glassy carbon electrode surfaces for the detection and monitoring of hydrogen peroxide (H2O2). The polymer-modified electrodes were characterized using electrochemical and microscopic-based methods. Atomic force microscopy (AFM) was used to study the bare and polymer-modified ITO surfaces. The electrocatalytic reduction of H2O2 with glassy carbon polymer-modified electrodes gave higher current densities compared to their gold counterparts. The electroanalytical properties of H2O2 were obtained using a real-time calibration curve of the amperometric determination in pH 7.4 aqueous solution. The limits of detection (LoD) of the polymer-modified electrodes towards electroreduction of H2O2 were of the order of 10–7 M, with high sensitivity ranging from 6.0–15.4 mA.mM-1.cm-2.
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- Authors: Mashazi, Philani N , Togo, Chumunorwa , Limson, Janice L , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261840 , vital:53451 , xlink:href="https://doi.org/10.1142/S1088424610001994"
- Description: This work reports the use of metallo tetra-amino phthalocyanines (MTAPc, M = Co and Mn) polymer thin films on gold and glassy carbon electrode surfaces for the detection and monitoring of hydrogen peroxide (H2O2). The polymer-modified electrodes were characterized using electrochemical and microscopic-based methods. Atomic force microscopy (AFM) was used to study the bare and polymer-modified ITO surfaces. The electrocatalytic reduction of H2O2 with glassy carbon polymer-modified electrodes gave higher current densities compared to their gold counterparts. The electroanalytical properties of H2O2 were obtained using a real-time calibration curve of the amperometric determination in pH 7.4 aqueous solution. The limits of detection (LoD) of the polymer-modified electrodes towards electroreduction of H2O2 were of the order of 10–7 M, with high sensitivity ranging from 6.0–15.4 mA.mM-1.cm-2.
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Effects of the number of ring substituents of cobalt carboxyphthalocyanines on the electrocatalytic detection of nitrite, cysteine and melatonin
- Matemadombo, Fungisai, Sehlotho, Nthapo, Nyokong, Tebello
- Authors: Matemadombo, Fungisai , Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263408 , vital:53625 , xlink:href="https://doi.org/10.1142/S108842460900125X"
- Description: Cobalt phthalocyanine (CoPc), cobalt tetracarboxy phthalocyanine (CoTCPc) and cobalt octacarboxy phthalocyanine (CoOCPc), adsorbed onto glassy carbon electrodes, have been used for the electrocatalytic detection of nitrite, L-cysteine and melatonin. The modified electrodes electrocatalytically detected nitrite around 800 mV vs.Ag|AgCl, a value less positive compared to that of an unmodified glassy carbon electrode (at 950 mV vs.Ag|AgCl) and also gave detection limits in the 10-7 M range for nitrite detection. L-cysteine was detected by the modified electrodes at potentials between 0.50 to 0.65 V vs.Ag|AgCl, with L-cysteine detection limits also in the 10-7 M range. The detection limits for melatonin ranged from 10-7 to 10-6 M. CoPc-modified electrodes displayed good separation of interferents (tryptophan and ascorbic acid) in the presence of melatonin. Analyses of commercial melatonin tablets using modified electrodes gave excellent agreement with manufacturer's value for all modified electrodes of this work.
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- Authors: Matemadombo, Fungisai , Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263408 , vital:53625 , xlink:href="https://doi.org/10.1142/S108842460900125X"
- Description: Cobalt phthalocyanine (CoPc), cobalt tetracarboxy phthalocyanine (CoTCPc) and cobalt octacarboxy phthalocyanine (CoOCPc), adsorbed onto glassy carbon electrodes, have been used for the electrocatalytic detection of nitrite, L-cysteine and melatonin. The modified electrodes electrocatalytically detected nitrite around 800 mV vs.Ag|AgCl, a value less positive compared to that of an unmodified glassy carbon electrode (at 950 mV vs.Ag|AgCl) and also gave detection limits in the 10-7 M range for nitrite detection. L-cysteine was detected by the modified electrodes at potentials between 0.50 to 0.65 V vs.Ag|AgCl, with L-cysteine detection limits also in the 10-7 M range. The detection limits for melatonin ranged from 10-7 to 10-6 M. CoPc-modified electrodes displayed good separation of interferents (tryptophan and ascorbic acid) in the presence of melatonin. Analyses of commercial melatonin tablets using modified electrodes gave excellent agreement with manufacturer's value for all modified electrodes of this work.
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Photocatalytic transformation of 4-nitrophenol in aqueous media using suspended, water-insoluble metallophthalocyanine complexes
- Marais, Eloïse A, Antunes, Edith M, Nyokong, Tebello
- Authors: Marais, Eloïse A , Antunes, Edith M , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265986 , vital:53907 , xlink:href="https://doi.org/10.1080/00958970802146056"
- Description: Unsubstituted magnesium (MgPc), zinc (ZnPc) and chloroaluminium (ClAlPc) phthalocyanine complexes and the ring substituted zinc tetranitro (ZnPc(NO2)4), zinc tetraamino (ZnPc(NH2)4), zinc hexadecafluoro (ZnPcF16) and zinc hexadecachloro (ZnPcCl16), phthalocyanine complexes are employed as photocatalysts for the heterogeneous transformation of 4-nitrophenol (4-Np) to fumaric acid and 4-nitrocatechol. ClAlPc is the best catalyst, with 89 ± 8% degradation of 4-Np after 100 min. The least effective catalysts were ZnPcCl16 and MgPc.
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- Authors: Marais, Eloïse A , Antunes, Edith M , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265986 , vital:53907 , xlink:href="https://doi.org/10.1080/00958970802146056"
- Description: Unsubstituted magnesium (MgPc), zinc (ZnPc) and chloroaluminium (ClAlPc) phthalocyanine complexes and the ring substituted zinc tetranitro (ZnPc(NO2)4), zinc tetraamino (ZnPc(NH2)4), zinc hexadecafluoro (ZnPcF16) and zinc hexadecachloro (ZnPcCl16), phthalocyanine complexes are employed as photocatalysts for the heterogeneous transformation of 4-nitrophenol (4-Np) to fumaric acid and 4-nitrocatechol. ClAlPc is the best catalyst, with 89 ± 8% degradation of 4-Np after 100 min. The least effective catalysts were ZnPcCl16 and MgPc.
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Synthesis, photophysical and photochemical properties of tetra-and octa-substituted gallium and indium phthalocyanines
- Durmus, Mahmut, Nyokong, Tebello
- Authors: Durmus, Mahmut , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271276 , vital:54529 , xlink:href="https://doi.org/10.1016/j.poly.2007.03.007"
- Description: The synthesis, photophysical and photochemical properties of the tetra- and octa-[4-(benzyloxyphenoxy)] substituted gallium(III) and indium(III) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H NMR spectroscopy and electronic spectroscopy. General trends are described for quantum yields of photodegredation, fluorescence quantum yields and lifetimes, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds in dimethylsulfoxide (DMSO). Substituted indium phthalocyanine complexes (7b–9b) showed much higher quantum yields of triplet state and shorter triplet lifetimes, compared to the substituted GaPc derivatives due to enhanced intersystem crossing (ISC) in the former. The gallium and indium phthalocyanine complexes showed phototransformation during laser irradiation due to ring reduction. The singlet oxygen quantum yields (ΦΔ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.51 to 0.94. Thus, these complexes show potential as photodynamic therapy of cancer.
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- Authors: Durmus, Mahmut , Nyokong, Tebello
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/271276 , vital:54529 , xlink:href="https://doi.org/10.1016/j.poly.2007.03.007"
- Description: The synthesis, photophysical and photochemical properties of the tetra- and octa-[4-(benzyloxyphenoxy)] substituted gallium(III) and indium(III) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H NMR spectroscopy and electronic spectroscopy. General trends are described for quantum yields of photodegredation, fluorescence quantum yields and lifetimes, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds in dimethylsulfoxide (DMSO). Substituted indium phthalocyanine complexes (7b–9b) showed much higher quantum yields of triplet state and shorter triplet lifetimes, compared to the substituted GaPc derivatives due to enhanced intersystem crossing (ISC) in the former. The gallium and indium phthalocyanine complexes showed phototransformation during laser irradiation due to ring reduction. The singlet oxygen quantum yields (ΦΔ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.51 to 0.94. Thus, these complexes show potential as photodynamic therapy of cancer.
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Langarm in and around Grahamstown: the dance, the social history and the music
- Authors: McConnachie, Boudina E
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/480685 , vital:78466 , xlink:href="https://doi.org/10.2989/18121000509486702"
- Description: Langarm is a popular dance form in South Africa and appeals to people from diverse cultural backgrounds. This paper reports on Langarm music and dance as it is practised by members of the coloured community in Grahamstown in the Eastern Cape. Documenting the performances of the band Coysan, it looks at the social aspects of the dance and music style, and recalls local community members’ memories of the development of Langarm in and around Grahamstown.
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- Authors: McConnachie, Boudina E
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/480685 , vital:78466 , xlink:href="https://doi.org/10.2989/18121000509486702"
- Description: Langarm is a popular dance form in South Africa and appeals to people from diverse cultural backgrounds. This paper reports on Langarm music and dance as it is practised by members of the coloured community in Grahamstown in the Eastern Cape. Documenting the performances of the band Coysan, it looks at the social aspects of the dance and music style, and recalls local community members’ memories of the development of Langarm in and around Grahamstown.
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Methodological Decisions in Context: The dilemmas and challenges of novice African scholars
- Lupele, Justin, Mwingi, Mweru P, Kinyanjui, Felistus, Kimani, Joyce, Kisamba, Christine
- Authors: Lupele, Justin , Mwingi, Mweru P , Kinyanjui, Felistus , Kimani, Joyce , Kisamba, Christine
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/373734 , vital:66717 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122698"
- Description: This paper emerges out of a panel discussion during a PhD week and subsequent 8th International Environmental Education Invitation Seminar held at Rhodes University in 2004 and 2005 respectively. It illuminates some insights into our struggles (as novice African researchers) in trying to respond to contextual realities as we research education and social change in African contexts, seeking insight into what counts as legitimate research in this context. The paper considers our struggles at conceptual, methodological, analytical and data generation levels, and in a politics of research. This is done by means of examples drawn from five current doctoral research projects being undertaken in east and southern African regions, using a review framework that represents fairly common dimensions of PhD research. We conclude that research, when defined rigidly within research disciplines/paradigms (as have been defined in some – primarily Western – research trajectories) may fail to take into account African social and contextual realities when applied uncritically. We argue that there is need for researchers in Africa to consider a multiplicity of approaches if research is to be meaningful in, and responsive to, social and contextual realities. In particular, we argue for taking account of socio historical and socio-cultural contexts in creating African epistemology in and through research.
- Full Text:
- Authors: Lupele, Justin , Mwingi, Mweru P , Kinyanjui, Felistus , Kimani, Joyce , Kisamba, Christine
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/373734 , vital:66717 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122698"
- Description: This paper emerges out of a panel discussion during a PhD week and subsequent 8th International Environmental Education Invitation Seminar held at Rhodes University in 2004 and 2005 respectively. It illuminates some insights into our struggles (as novice African researchers) in trying to respond to contextual realities as we research education and social change in African contexts, seeking insight into what counts as legitimate research in this context. The paper considers our struggles at conceptual, methodological, analytical and data generation levels, and in a politics of research. This is done by means of examples drawn from five current doctoral research projects being undertaken in east and southern African regions, using a review framework that represents fairly common dimensions of PhD research. We conclude that research, when defined rigidly within research disciplines/paradigms (as have been defined in some – primarily Western – research trajectories) may fail to take into account African social and contextual realities when applied uncritically. We argue that there is need for researchers in Africa to consider a multiplicity of approaches if research is to be meaningful in, and responsive to, social and contextual realities. In particular, we argue for taking account of socio historical and socio-cultural contexts in creating African epistemology in and through research.
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Modelling the sustainable harvest of Sclerocarya birrea subsp. caffra fruits in the South African lowveld
- Emanuel, P L, Shackleton, Charlie M, Baxter, Jeremy
- Authors: Emanuel, P L , Shackleton, Charlie M , Baxter, Jeremy
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181312 , vital:43718 , xlink:href="https://doi.org/10.1016/j.foreco.2005.03.066"
- Description: Levels of commercialization, size class profile and fruit production of Sclerocarya birrea (marula) trees were studied in the Bushbuckridge region of South Africa. A stage-based population matrix model was used to estimate the sustainable yield for S. birrea fruit. The trees begin to bear fruit at an average size of 42.8 cm in circumference and this relates to an approximate age of 19 years. For a stable size class profile, the population growth rate, λ, was 1.1828758. The observed size class profile did not conform to the stable stage size class profile, obtained from the model. Thus, it was not possible to predict the state of the observed population. Using the model, it was estimated that 92% of fruit could be removed without impacting the current population profile. The management of other more destructive forms of S. birrea resource use (such as bark or firewood harvesting), however, do need to be monitored to limit negative impacts on the population that may reduce fruit availability for regeneration or cropping.
- Full Text:
- Authors: Emanuel, P L , Shackleton, Charlie M , Baxter, Jeremy
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181312 , vital:43718 , xlink:href="https://doi.org/10.1016/j.foreco.2005.03.066"
- Description: Levels of commercialization, size class profile and fruit production of Sclerocarya birrea (marula) trees were studied in the Bushbuckridge region of South Africa. A stage-based population matrix model was used to estimate the sustainable yield for S. birrea fruit. The trees begin to bear fruit at an average size of 42.8 cm in circumference and this relates to an approximate age of 19 years. For a stable size class profile, the population growth rate, λ, was 1.1828758. The observed size class profile did not conform to the stable stage size class profile, obtained from the model. Thus, it was not possible to predict the state of the observed population. Using the model, it was estimated that 92% of fruit could be removed without impacting the current population profile. The management of other more destructive forms of S. birrea resource use (such as bark or firewood harvesting), however, do need to be monitored to limit negative impacts on the population that may reduce fruit availability for regeneration or cropping.
- Full Text: