Earnings quality and equity returns : evidence of the accrual anomaly from the South African equity market
- Authors: Lutchmun, Thashveen
- Date: 2015
- Subjects: Earnings management -- South Africa , Accounting -- Standards
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:915 , http://hdl.handle.net/10962/d1017537
- Description: A key incentive for accounting research is to provide evidence on the usefulness of earnings in making economic decisions. Of particular interest over the last two decades is the issue of the quality of financial reporting, specifically the quality of earnings, given the number of global financial scandals reported during that period. The quality of earnings is driven by the choices, estimates and judgments that the accounting standards make available to managers in order to portray the firm’s economic position and performance in a timely and credible manner. However, this leeway in financial reporting also creates opportunities for earnings management. The objective of this thesis is firstly to establish whether earnings manipulation has had the ability to predict cross-sectional returns in South Africa during the 2007-2014 period. In other words, the purpose of this thesis is to find evidence whether the market reacts to earnings management practices, as measured by accruals, and rewards high earnings quality companies with higher equity returns (a process known as the accrual anomaly). The timeframe selected for the research encompasses the global financial crisis, a period in which accounting manipulation incentives are likely to be strong. Secondly, this study attempts to establish the presence of the accrual anomaly amongst growth and value firms. The motivations for earnings management of the former are expected to be strong. Securities are allocated to portfolios according to accruals and the subsequent equity returns are analysed cross-sectionally to establish the existence of the accrual anomaly and hence assessing the usefulness of earnings manipulation in predicting equity returns. To provide evidence for the presence of the accrual anomaly amongst growth and value shares, securities are independently allocated to portfolios according to their book-to-market ratio and accruals and a cross-sectional analysis is performed on their subsequent equity returns. In order to increase the robustness of the tests, two measures of accruals are used: a balance sheet approach and a cash flow measure. Evidence is provided for the presence of the accrual anomaly among South African listed companies for the balance sheet measure of accruals but not the cash flow approach. Whilst the accrual anomaly is significantly present in a growth-neutral-value construct, statistical significance is not established when growth and value shares are considered individually.
- Full Text:
- Authors: Lutchmun, Thashveen
- Date: 2015
- Subjects: Earnings management -- South Africa , Accounting -- Standards
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:915 , http://hdl.handle.net/10962/d1017537
- Description: A key incentive for accounting research is to provide evidence on the usefulness of earnings in making economic decisions. Of particular interest over the last two decades is the issue of the quality of financial reporting, specifically the quality of earnings, given the number of global financial scandals reported during that period. The quality of earnings is driven by the choices, estimates and judgments that the accounting standards make available to managers in order to portray the firm’s economic position and performance in a timely and credible manner. However, this leeway in financial reporting also creates opportunities for earnings management. The objective of this thesis is firstly to establish whether earnings manipulation has had the ability to predict cross-sectional returns in South Africa during the 2007-2014 period. In other words, the purpose of this thesis is to find evidence whether the market reacts to earnings management practices, as measured by accruals, and rewards high earnings quality companies with higher equity returns (a process known as the accrual anomaly). The timeframe selected for the research encompasses the global financial crisis, a period in which accounting manipulation incentives are likely to be strong. Secondly, this study attempts to establish the presence of the accrual anomaly amongst growth and value firms. The motivations for earnings management of the former are expected to be strong. Securities are allocated to portfolios according to accruals and the subsequent equity returns are analysed cross-sectionally to establish the existence of the accrual anomaly and hence assessing the usefulness of earnings manipulation in predicting equity returns. To provide evidence for the presence of the accrual anomaly amongst growth and value shares, securities are independently allocated to portfolios according to their book-to-market ratio and accruals and a cross-sectional analysis is performed on their subsequent equity returns. In order to increase the robustness of the tests, two measures of accruals are used: a balance sheet approach and a cash flow measure. Evidence is provided for the presence of the accrual anomaly among South African listed companies for the balance sheet measure of accruals but not the cash flow approach. Whilst the accrual anomaly is significantly present in a growth-neutral-value construct, statistical significance is not established when growth and value shares are considered individually.
- Full Text:
Ecological sustainability for non-timber forest products: dynamics and case studies of harvesting
- Shackleton, Charlie M, Pandey, Ashok K, Ticktin, Tamara
- Authors: Shackleton, Charlie M , Pandey, Ashok K , Ticktin, Tamara
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/433656 , vital:72992 , ISBN 9781317916130 , https://www.routledge.com/Ecological-Sustainability-for-Non-timber-Forest-Products-Dynamics-and-Case/Shackleton-Pandey-Ticktin/p/book/9781138618251
- Description: There is growing knowledge about and appreciation of the im-portance of Non-timber Forest Products (NTFPs) to rural liveli-hoods in developing countries, and to a lesser extent, devel-oped countries. However, there is also an assumption on the part of policy-makers that any harvesting of wild animal or plant products from the forests and other natural and modi-fied ecosystems must be detrimental to the long-term viability of target populations and species. This book challenges this idea and shows that while examples of such negative impacts certainly exist, there are also many examples of sustainable harvesting systems for NTFPs. The chapters review and pre-sent coherent and scientifically sound information and case studies on the ecologically sustainable use of NTFPs. They also outline a general interdisciplinary approach for assessing the sustainability of NTFP harvesting systems at different scales. A wide range of case studies is included from Africa, Asia and South America, using plant and animal products for food, crafts, textiles, medicines and cosmetics.
- Full Text:
- Authors: Shackleton, Charlie M , Pandey, Ashok K , Ticktin, Tamara
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/433656 , vital:72992 , ISBN 9781317916130 , https://www.routledge.com/Ecological-Sustainability-for-Non-timber-Forest-Products-Dynamics-and-Case/Shackleton-Pandey-Ticktin/p/book/9781138618251
- Description: There is growing knowledge about and appreciation of the im-portance of Non-timber Forest Products (NTFPs) to rural liveli-hoods in developing countries, and to a lesser extent, devel-oped countries. However, there is also an assumption on the part of policy-makers that any harvesting of wild animal or plant products from the forests and other natural and modi-fied ecosystems must be detrimental to the long-term viability of target populations and species. This book challenges this idea and shows that while examples of such negative impacts certainly exist, there are also many examples of sustainable harvesting systems for NTFPs. The chapters review and pre-sent coherent and scientifically sound information and case studies on the ecologically sustainable use of NTFPs. They also outline a general interdisciplinary approach for assessing the sustainability of NTFP harvesting systems at different scales. A wide range of case studies is included from Africa, Asia and South America, using plant and animal products for food, crafts, textiles, medicines and cosmetics.
- Full Text:
Ecologically sustainable harvesting of non-timber forest products: Disarming the narrative and the complexity
- Shackleton, Charlie M, Pandey, Ashok K, Ticktin, Tamara
- Authors: Shackleton, Charlie M , Pandey, Ashok K , Ticktin, Tamara
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/433670 , vital:72993 , ISBN 9781317916130 , https://www.routledge.com/Ecological-Sustainability-for-Non-timber-Forest-Products-Dynamics-and-Case/Shackleton-Pandey-Ticktin/p/book/9781138618251
- Description: As introduced at the outset of this book, the need for ecologically sustainable harvesting systems for tens of thousands of non-timber forest products (NTFPs) around the world is a requirement for the conservation of the species concerned, and the lives, livelihoods and economies that depend on those species. Ecological sustainability is not simply a ‘nice to have’, a marketing ploy or a conservation fad. Unsustainable harvesting leads to the decline, sooner or later, of NTFP gene pools, populations and species and hence the livelihoods, and species and ecosystem services dependent upon them. Often the negative impacts on peoples’ lives and incomes are not immediately apparent because they may substitute the diminishing returns from one species by harvesting another species, such as favoured firewood species for less preferred species (Madubansi and Shackleton 2007). However, the second, third or more substitute yields lower returns in quality or quantity (or both) than the most preferred species and so a trajectory of dwindling returns looms, either of the benefits obtained, or increased costs to access the benefits. On the other hand, the concept of an ecologically sustainable yield is relatively easy to grasp (Ticktin Chapter 3). All biological resources are renewable. If the rate of harvest is less than the rate of renewal, then the NTFP species or population should persist in the long term. This simplistic picture needs to be fine-tuned to ensure that there are no exacerbatory or synergistic impacts associated with the direct effects of harvesting (such as changes in browsing patterns or fire behaviour)(Ticktin and Shackleton 2011, Ticktin Chapter 3). Additionally, the effects at broader scales, ie beyond just the target species, need to be also taken into account, such as on pollinators, decomposers, nutrient cycles and the like (Ticktin 2004). But in principle, the definition and measurement of an ecologically sustainable yield is well within the means of modern science for the majority of plant and animal NTFP species.
- Full Text:
- Authors: Shackleton, Charlie M , Pandey, Ashok K , Ticktin, Tamara
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/433670 , vital:72993 , ISBN 9781317916130 , https://www.routledge.com/Ecological-Sustainability-for-Non-timber-Forest-Products-Dynamics-and-Case/Shackleton-Pandey-Ticktin/p/book/9781138618251
- Description: As introduced at the outset of this book, the need for ecologically sustainable harvesting systems for tens of thousands of non-timber forest products (NTFPs) around the world is a requirement for the conservation of the species concerned, and the lives, livelihoods and economies that depend on those species. Ecological sustainability is not simply a ‘nice to have’, a marketing ploy or a conservation fad. Unsustainable harvesting leads to the decline, sooner or later, of NTFP gene pools, populations and species and hence the livelihoods, and species and ecosystem services dependent upon them. Often the negative impacts on peoples’ lives and incomes are not immediately apparent because they may substitute the diminishing returns from one species by harvesting another species, such as favoured firewood species for less preferred species (Madubansi and Shackleton 2007). However, the second, third or more substitute yields lower returns in quality or quantity (or both) than the most preferred species and so a trajectory of dwindling returns looms, either of the benefits obtained, or increased costs to access the benefits. On the other hand, the concept of an ecologically sustainable yield is relatively easy to grasp (Ticktin Chapter 3). All biological resources are renewable. If the rate of harvest is less than the rate of renewal, then the NTFP species or population should persist in the long term. This simplistic picture needs to be fine-tuned to ensure that there are no exacerbatory or synergistic impacts associated with the direct effects of harvesting (such as changes in browsing patterns or fire behaviour)(Ticktin and Shackleton 2011, Ticktin Chapter 3). Additionally, the effects at broader scales, ie beyond just the target species, need to be also taken into account, such as on pollinators, decomposers, nutrient cycles and the like (Ticktin 2004). But in principle, the definition and measurement of an ecologically sustainable yield is well within the means of modern science for the majority of plant and animal NTFP species.
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Editorial. Perspectives on transformations in learning and education
- Authors: Lotz-Sisitka, Heila
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/387277 , vital:68221 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/137656"
- Description: Perspectives on transformations in learning and education
- Full Text:
- Authors: Lotz-Sisitka, Heila
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/387277 , vital:68221 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/137656"
- Description: Perspectives on transformations in learning and education
- Full Text:
Effect of conventional and organic orchard floor management practices on arbuscular mycorrhizal fungi in a ‘Cripp’s Pink’/M7 apple orchard soil
- Meyer, André H, Wooldridge, John, Dames, Joanna F
- Authors: Meyer, André H , Wooldridge, John , Dames, Joanna F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444012 , vital:74178 , https://doi.org/10.1016/j.agee.2015.07.026
- Description: Arbuscular mycorrhizal (AM) fungi are key components of agricultural soil–plant systems, which may be affected by agricultural practices. In organically managed (ORG) orchards, nutrients are supplied in the form of compost, and weeds are suppressed with mulches, whereas synthetic fertilizers and herbicides are used for these respective purposes in conventional (CON) orchards. The effects of ORG and CON orchard floor management practices on native AM fungi in apple orchards were investigated in a randomized field trial. AM root colonization, spore abundance, infectivity potentials and soil glomalin contents were determined in the 0–30 cm soil depth interval, in tree rows, over consecutive seasons. Root colonization was higher in the ORG than the CON treatments, but intermediate where straw mulch was substituted for green work-row covers. Glomalin levels were not affected by the treatments. Root colonization by AM fungi increased with increasing soil pH, P, C, K, Zn, and Mn concentrations, but were suppressed by Cu. Colonization correlated positively with leaf P, Ca and Mg, and with stem circumference, but negatively with leaf N and yield. ORG orchard floor management practices therefore, promoted functional AM associations more effectively than CON practices.
- Full Text:
- Authors: Meyer, André H , Wooldridge, John , Dames, Joanna F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444012 , vital:74178 , https://doi.org/10.1016/j.agee.2015.07.026
- Description: Arbuscular mycorrhizal (AM) fungi are key components of agricultural soil–plant systems, which may be affected by agricultural practices. In organically managed (ORG) orchards, nutrients are supplied in the form of compost, and weeds are suppressed with mulches, whereas synthetic fertilizers and herbicides are used for these respective purposes in conventional (CON) orchards. The effects of ORG and CON orchard floor management practices on native AM fungi in apple orchards were investigated in a randomized field trial. AM root colonization, spore abundance, infectivity potentials and soil glomalin contents were determined in the 0–30 cm soil depth interval, in tree rows, over consecutive seasons. Root colonization was higher in the ORG than the CON treatments, but intermediate where straw mulch was substituted for green work-row covers. Glomalin levels were not affected by the treatments. Root colonization by AM fungi increased with increasing soil pH, P, C, K, Zn, and Mn concentrations, but were suppressed by Cu. Colonization correlated positively with leaf P, Ca and Mg, and with stem circumference, but negatively with leaf N and yield. ORG orchard floor management practices therefore, promoted functional AM associations more effectively than CON practices.
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Effect of temperature on development of the blowfly, Lucilia cuprina (Wiedemann)(Diptera: Calliphoridae)
- Kotzé, Zanthé, Villet, Martin H, Weldon, Christopher W
- Authors: Kotzé, Zanthé , Villet, Martin H , Weldon, Christopher W
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442116 , vital:73960 , https://doi.org/10.1007/s00414-015-1153-y
- Description: The blowfly Lucilia cuprina is a primary colonizer of decaying vertebrate carrion, and its development provides a temperature-dependent clock that may be used to estimate the post-mortem interval of corpses and carcasses in medicolegal forensic investigations. This study uses the development of L. cuprina raised on a substrate of chicken liver at six constant temperatures from 18 to 33 °C to calibrate a thermal accumulation model of development for forensic applications. Development was optimal near 24 °C; above this temperature, survival of post-feeding life stages was increasingly compromised, while below it, development was increasingly retarded. The lower developmental threshold (~12 °C) and thermal summation constants of L. cuprina are distinct from those reported for Lucilia sericata, verifying that it is essential to identify African Lucilia specimens accurately when using them to estimate post-mortem intervals.
- Full Text:
- Authors: Kotzé, Zanthé , Villet, Martin H , Weldon, Christopher W
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442116 , vital:73960 , https://doi.org/10.1007/s00414-015-1153-y
- Description: The blowfly Lucilia cuprina is a primary colonizer of decaying vertebrate carrion, and its development provides a temperature-dependent clock that may be used to estimate the post-mortem interval of corpses and carcasses in medicolegal forensic investigations. This study uses the development of L. cuprina raised on a substrate of chicken liver at six constant temperatures from 18 to 33 °C to calibrate a thermal accumulation model of development for forensic applications. Development was optimal near 24 °C; above this temperature, survival of post-feeding life stages was increasingly compromised, while below it, development was increasingly retarded. The lower developmental threshold (~12 °C) and thermal summation constants of L. cuprina are distinct from those reported for Lucilia sericata, verifying that it is essential to identify African Lucilia specimens accurately when using them to estimate post-mortem intervals.
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Effects of differently shaped silver nanoparticles on the photophysics of pyridylsulfanyl-substituted phthalocyanines
- D'Souza, Sarah, Mashazi, Philani N, Britton, Jonathan, Nyokong, Tebello
- Authors: D'Souza, Sarah , Mashazi, Philani N , Britton, Jonathan , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193564 , vital:45348 , xlink:href="https://doi.org/10.1016/j.poly.2015.06.038"
- Description: This paper reports on the photophysical behavior of (2-pyridylsulfanyl)phthalocyaninato zinc(II) and 2,9(10),16(17),23(24)-tetra-(2-pyridylsulfanyl)phthalocyaninato zinc(II) in the presence of differently shaped silver nanoparticles (nanospheres, nanotriangles and nanoflowers). The presence of shaped nanoparticles increased both triplet quantum yields and lifetimes of the tetra-substituted mercaptopyridine zinc phthalocyanine in DMSO. It is apparent from this work that the shape of the silver nanoparticle used is of little consequence in influencing photophysical behavior of the phthalocyanines.
- Full Text:
- Authors: D'Souza, Sarah , Mashazi, Philani N , Britton, Jonathan , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193564 , vital:45348 , xlink:href="https://doi.org/10.1016/j.poly.2015.06.038"
- Description: This paper reports on the photophysical behavior of (2-pyridylsulfanyl)phthalocyaninato zinc(II) and 2,9(10),16(17),23(24)-tetra-(2-pyridylsulfanyl)phthalocyaninato zinc(II) in the presence of differently shaped silver nanoparticles (nanospheres, nanotriangles and nanoflowers). The presence of shaped nanoparticles increased both triplet quantum yields and lifetimes of the tetra-substituted mercaptopyridine zinc phthalocyanine in DMSO. It is apparent from this work that the shape of the silver nanoparticle used is of little consequence in influencing photophysical behavior of the phthalocyanines.
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Effects of inoculating Lachnum and Cadophora isolates on the growth of Vaccinium corymbosum
- Mbizabani, Christine, Dames, Joanna F
- Authors: Mbizabani, Christine , Dames, Joanna F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444024 , vital:74179 , https://doi.org/10.1016/j.micres.2015.08.005
- Description: The roots of ericaceous plants harbour a diversity of fungal taxa, which confer eco-physiological benefits to the host. Some of the fungi have been established to form ericoid mycorrhizal (ERM) associations and enhance plant growth in certain ericaceous genera. Although, Lachnum and Cadophora isolates have frequently been identified from the roots of this family, the status of their association and functional roles is still vague. The aims of this study were to identify Lachnum and Cadophora isolates; determine the root-fungal interactive structures formed in associations with Vaccinium corymbosum L. (blueberry) hosts and to examine inoculation effects of the fungal associates using several varieties of the blueberry. Lachnum and Cadophora were isolated and identified from Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth using morphological and molecular techniques. Micropropagated blueberry varieties (Bluecrop, Elliott, Spartan, Chandler and Brightwell) were inoculated with respective fungi and plant growth evaluated. Both fungi colonised the roots and did not have any pathogenic effect.
- Full Text:
- Authors: Mbizabani, Christine , Dames, Joanna F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444024 , vital:74179 , https://doi.org/10.1016/j.micres.2015.08.005
- Description: The roots of ericaceous plants harbour a diversity of fungal taxa, which confer eco-physiological benefits to the host. Some of the fungi have been established to form ericoid mycorrhizal (ERM) associations and enhance plant growth in certain ericaceous genera. Although, Lachnum and Cadophora isolates have frequently been identified from the roots of this family, the status of their association and functional roles is still vague. The aims of this study were to identify Lachnum and Cadophora isolates; determine the root-fungal interactive structures formed in associations with Vaccinium corymbosum L. (blueberry) hosts and to examine inoculation effects of the fungal associates using several varieties of the blueberry. Lachnum and Cadophora were isolated and identified from Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth using morphological and molecular techniques. Micropropagated blueberry varieties (Bluecrop, Elliott, Spartan, Chandler and Brightwell) were inoculated with respective fungi and plant growth evaluated. Both fungi colonised the roots and did not have any pathogenic effect.
- Full Text:
Effects of ZnO nanohexagons and nanorods on the fluorescence behavior of metallophthalocyanines
- D'Souza, Sarah, Moeno, Sharon, Nyokong, Tebello
- Authors: D'Souza, Sarah , Moeno, Sharon , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189741 , vital:44927 , xlink:href="https://doi.org/10.1016/j.poly.2014.09.012"
- Description: This paper looks at the fluorescence behavior of zinc phthalocyanines: 2,(3),9(10),16(17),23(24)-tetrakis- (mercaptoacetic acid phthalocyaninato) zinc(II) (ZnTMAAPc), 2,(3),9(10),16(17),23(24)-tetrakis-(mercaptopropanoic acid phthalocyaninato) zinc(II) (ZnTMPAPc) and (OH)AlPcSmix (the latter contains a mixture of the di-, tri- and tetra-sulfonated derivatives with an average of three sulfonated groups per molecule) in the presence of ZnO nanoparticles. Fluorescence lifetimes of Pc complexes generally decreased in the presence of ZnO nanoparticles, with generally longer lifetimes for ZnO nanohexagons compared to ZnO nanorods.
- Full Text:
- Authors: D'Souza, Sarah , Moeno, Sharon , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189741 , vital:44927 , xlink:href="https://doi.org/10.1016/j.poly.2014.09.012"
- Description: This paper looks at the fluorescence behavior of zinc phthalocyanines: 2,(3),9(10),16(17),23(24)-tetrakis- (mercaptoacetic acid phthalocyaninato) zinc(II) (ZnTMAAPc), 2,(3),9(10),16(17),23(24)-tetrakis-(mercaptopropanoic acid phthalocyaninato) zinc(II) (ZnTMPAPc) and (OH)AlPcSmix (the latter contains a mixture of the di-, tri- and tetra-sulfonated derivatives with an average of three sulfonated groups per molecule) in the presence of ZnO nanoparticles. Fluorescence lifetimes of Pc complexes generally decreased in the presence of ZnO nanoparticles, with generally longer lifetimes for ZnO nanohexagons compared to ZnO nanorods.
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Electrocatalytic activity of bimetallic Au–Pd nanoparticles in the presence of cobalt tetraaminophthalocyanine
- Maringa, Audacity, Mashazi, Philani N, Nyokong, Tebello
- Authors: Maringa, Audacity , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189719 , vital:44925 , xlink:href="https://doi.org/10.1016/j.jcis.2014.10.056"
- Description: Au and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 lA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 lA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 lM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.
- Full Text:
- Authors: Maringa, Audacity , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189719 , vital:44925 , xlink:href="https://doi.org/10.1016/j.jcis.2014.10.056"
- Description: Au and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 lA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 lA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 lM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.
- Full Text:
Electrocatalytic studies of covalently immobilized metal tetra-amino phthalocyanines onto derivatized screen-printed gold electrodes
- Mashazi, Philani N, Nyokong, Tebello
- Authors: Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249059 , vital:51774 , xlink:href="https://doi.org/10.1007/s00604-010-0438-6"
- Description: Metal tetra-amino phthalocyanine complexes (MTAPc; where M is Co or Mn) were immobilized on screen-printed gold electrodes pre-modified with monolayers of benzylamino groups. The functionalized electrodes were then activated using benzene-1,4-dicarbaldehyde as a linker before MTAPc complexes were immobilized. The surface coverages for the modified electrodes confirmed the perpendicular orientation of the MTAPcs. The apparent electron transfer constant (kapp) for the electrodes is 2.2 × 10−5 cm.s−1 for both CoTAPc and MnTAPc modified electrodes as calculated with data from impedance measurements. The kapp values for the bare and benzylamino modified electrodes were found to be 1.2 × 10−4 cm.s−1 and 4.9 × 10−6 cm.s−1, respectively. The electrocatalysis of the modified electrodes towards detection of H2O2 gave significant peak current densities and electrocatalytic potentials at −0.28 V and −0.31 V for the MnTAPc and CoTAPc modified electrodes, respectively.
- Full Text:
- Authors: Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249059 , vital:51774 , xlink:href="https://doi.org/10.1007/s00604-010-0438-6"
- Description: Metal tetra-amino phthalocyanine complexes (MTAPc; where M is Co or Mn) were immobilized on screen-printed gold electrodes pre-modified with monolayers of benzylamino groups. The functionalized electrodes were then activated using benzene-1,4-dicarbaldehyde as a linker before MTAPc complexes were immobilized. The surface coverages for the modified electrodes confirmed the perpendicular orientation of the MTAPcs. The apparent electron transfer constant (kapp) for the electrodes is 2.2 × 10−5 cm.s−1 for both CoTAPc and MnTAPc modified electrodes as calculated with data from impedance measurements. The kapp values for the bare and benzylamino modified electrodes were found to be 1.2 × 10−4 cm.s−1 and 4.9 × 10−6 cm.s−1, respectively. The electrocatalysis of the modified electrodes towards detection of H2O2 gave significant peak current densities and electrocatalytic potentials at −0.28 V and −0.31 V for the MnTAPc and CoTAPc modified electrodes, respectively.
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Electrode modification using alkynyl substituted Fe (II) phthalocyanine via electrografting and click chemistry for electrocatalysis
- Nxele, Siphesihle R, Mashazi, Philani N, Nyokong, Tebello
- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189296 , vital:44835 , xlink:href="https://doi.org/10.1002/elan.201500212"
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM.
- Full Text:
- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189296 , vital:44835 , xlink:href="https://doi.org/10.1002/elan.201500212"
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM.
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Electrode surface modification using metallophthalocyanines and metal nanoparticles : electrocatalytic activity
- Authors: Maringa, Audacity
- Date: 2015
- Subjects: Phthalocyanines , Nanoparticles , Electrocatalysis , Scanning electron microscopy , X-ray photoelectron spectroscopy , Electrochemistry , Scanning electrochemical microscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4541 , http://hdl.handle.net/10962/d1017921
- Description: Metallophthalocyanines and metal nanoparticles were successfully synthesized and applied for the electrooxidation of amitrole, nitrite and hydrazine individually or when employed together. The synthesized materials were characterized using the following techniques: predominantly scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning electrochemical microscopy (SECM). Different electrode modification methods were used to modify the glassy carbon substrates. The methods include adsorption, electrodeposition, electropolymerization and click chemistry. Modifying the glassy carbon substrate with MPc (electropolymerization) followed by metal nanoparticles (electrodeposition) or vice versa, made a hybrid modified surface that had efficient electron transfer. This was confirmed by electrochemical impedance studies with voltammetry measurements having lower detection potentials for the analytes. This work also describes for the first time the micropatterning of the glassy carbon substrate using the SECM tip. The substrate was electrografted with 4-azidobenzenediazonium salt and then the click reaction was performed using ethynylferrocene facilitated by Cu⁺ produced at the SECM tip. The SECM imaging was then used to show the clicked spot.
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- Authors: Maringa, Audacity
- Date: 2015
- Subjects: Phthalocyanines , Nanoparticles , Electrocatalysis , Scanning electron microscopy , X-ray photoelectron spectroscopy , Electrochemistry , Scanning electrochemical microscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4541 , http://hdl.handle.net/10962/d1017921
- Description: Metallophthalocyanines and metal nanoparticles were successfully synthesized and applied for the electrooxidation of amitrole, nitrite and hydrazine individually or when employed together. The synthesized materials were characterized using the following techniques: predominantly scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning electrochemical microscopy (SECM). Different electrode modification methods were used to modify the glassy carbon substrates. The methods include adsorption, electrodeposition, electropolymerization and click chemistry. Modifying the glassy carbon substrate with MPc (electropolymerization) followed by metal nanoparticles (electrodeposition) or vice versa, made a hybrid modified surface that had efficient electron transfer. This was confirmed by electrochemical impedance studies with voltammetry measurements having lower detection potentials for the analytes. This work also describes for the first time the micropatterning of the glassy carbon substrate using the SECM tip. The substrate was electrografted with 4-azidobenzenediazonium salt and then the click reaction was performed using ethynylferrocene facilitated by Cu⁺ produced at the SECM tip. The SECM imaging was then used to show the clicked spot.
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Eliciting and combining expert opinion : an overview and comparison of methods
- Authors: Chinyamakobvu, Mutsa Carole
- Date: 2015
- Subjects: Decision making -- Statistical methods , Expertise , Bayesian statistical decision theory , Statistical decision , Delphi method , Paired comparisons (Statistics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5579 , http://hdl.handle.net/10962/d1017827
- Description: Decision makers have long relied on experts to inform their decision making. Expert judgment analysis is a way to elicit and combine the opinions of a group of experts to facilitate decision making. The use of expert judgment is most appropriate when there is a lack of data for obtaining reasonable statistical results. The experts are asked for advice by one or more decision makers who face a specific real decision problem. The decision makers are outside the group of experts and are jointly responsible and accountable for the decision and committed to finding solutions that everyone can live with. The emphasis is on the decision makers learning from the experts. The focus of this thesis is an overview and comparison of the various elicitation and combination methods available. These include the traditional committee method, the Delphi method, the paired comparisons method, the negative exponential model, Cooke’s classical model, the histogram technique, using the Dirichlet distribution in the case of a set of uncertain proportions which must sum to one, and the employment of overfitting. The supra Bayes approach, the determination of weights for the experts, and combining the opinions of experts where each opinion is associated with a confidence level that represents the expert’s conviction of his own judgment are also considered.
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- Authors: Chinyamakobvu, Mutsa Carole
- Date: 2015
- Subjects: Decision making -- Statistical methods , Expertise , Bayesian statistical decision theory , Statistical decision , Delphi method , Paired comparisons (Statistics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5579 , http://hdl.handle.net/10962/d1017827
- Description: Decision makers have long relied on experts to inform their decision making. Expert judgment analysis is a way to elicit and combine the opinions of a group of experts to facilitate decision making. The use of expert judgment is most appropriate when there is a lack of data for obtaining reasonable statistical results. The experts are asked for advice by one or more decision makers who face a specific real decision problem. The decision makers are outside the group of experts and are jointly responsible and accountable for the decision and committed to finding solutions that everyone can live with. The emphasis is on the decision makers learning from the experts. The focus of this thesis is an overview and comparison of the various elicitation and combination methods available. These include the traditional committee method, the Delphi method, the paired comparisons method, the negative exponential model, Cooke’s classical model, the histogram technique, using the Dirichlet distribution in the case of a set of uncertain proportions which must sum to one, and the employment of overfitting. The supra Bayes approach, the determination of weights for the experts, and combining the opinions of experts where each opinion is associated with a confidence level that represents the expert’s conviction of his own judgment are also considered.
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Employing safe bets: reflections on attracting, developing and retaining the next generation of academics
- Authors: Hlengwa, Amanda I
- Date: 2015
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/142145 , vital:38053 , ISBN 9781869142902 , https://books.google.co.za/books?id=49o8rgEACAAJanddq=Being+at+home:+Race,+institutional+culture+and+transformation+at+South+African+higher+education+institutionandhl=enandsa=Xandved=0ahUKEwiPgsa6mpjjAhXNN8AKHbNwAtoQ6AEIKDAA
- Description: This edited work has gathered together contributions on how to transform universities in South Africa; as many are struggling to shift their institutional culture. In a South African context, transformation means to attempt to change higher education institutions such that they no longer reflect the values promoted by apartheid but rather reflect the values embodied in South Africa's 1996 Constitution. Institutional culture is the main subject for discussion in this book. In order to transform South Africa's universities, the contributors begin by analyzing the idea of what a university is, and relatedly, what its ideal aims are. A second theme is to understand what institutional culture is and how it functions. Moreover, transformation cannot occur without transforming the broader cultures of which they are a part. Related to this theme is a general concern about how contemporary moves towards the instrumentalization of higher education affect the ability to transform institutions. These institutions are being pushed to conform to goals that are outside the traditional idea of a university, such as concerns that universities are being 'bureaucratized' and becoming corporations, instead of a place of learning open to all. In conclusion it can be said that the contemporary South African academic community has an opportunity to recreate itself as the end of apartheid created space for engaging in transformative epistemic projects. The transformation of the tertiary sector entails a transformation of institutional cultures.
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- Authors: Hlengwa, Amanda I
- Date: 2015
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/142145 , vital:38053 , ISBN 9781869142902 , https://books.google.co.za/books?id=49o8rgEACAAJanddq=Being+at+home:+Race,+institutional+culture+and+transformation+at+South+African+higher+education+institutionandhl=enandsa=Xandved=0ahUKEwiPgsa6mpjjAhXNN8AKHbNwAtoQ6AEIKDAA
- Description: This edited work has gathered together contributions on how to transform universities in South Africa; as many are struggling to shift their institutional culture. In a South African context, transformation means to attempt to change higher education institutions such that they no longer reflect the values promoted by apartheid but rather reflect the values embodied in South Africa's 1996 Constitution. Institutional culture is the main subject for discussion in this book. In order to transform South Africa's universities, the contributors begin by analyzing the idea of what a university is, and relatedly, what its ideal aims are. A second theme is to understand what institutional culture is and how it functions. Moreover, transformation cannot occur without transforming the broader cultures of which they are a part. Related to this theme is a general concern about how contemporary moves towards the instrumentalization of higher education affect the ability to transform institutions. These institutions are being pushed to conform to goals that are outside the traditional idea of a university, such as concerns that universities are being 'bureaucratized' and becoming corporations, instead of a place of learning open to all. In conclusion it can be said that the contemporary South African academic community has an opportunity to recreate itself as the end of apartheid created space for engaging in transformative epistemic projects. The transformation of the tertiary sector entails a transformation of institutional cultures.
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Encouraging individual retirement savings in South Africa
- Authors: Hirschbeck, Lisa
- Date: 2015
- Subjects: Retirement income -- Planning-- South Africa , Retirement income -- Government policy -- South Africa , Pension trusts -- South Africa -- Management , Pension trusts -- Termination -- Law and legislation -- South Africa , Income tax deductions for retirement contributions -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:913 , http://hdl.handle.net/10962/d1017535
- Description: Many South Africans may not have adequate retirement savings when they retire and this has the effect of a low income replacement ratio on retirement that may lead to a decrease in the standard of living of the retiree and in extreme cases the retiree becoming dependent on their family and the government. Owing to this trend of no or inadequate retirement savings, South Africa embarked on a retirement reform journey in 2004. The goal of this research is to determine whether the retirement reform mechanisms outlined by National Treasury would encourage individual retirement savings that should assist South Africans to achieve stability of income in their retirement. This research analysed the current retirement savings options and vehicles available for South Africans, the current tax incentives and disincentives and reviewed the proposed changes to tax incentives and disincentives during the accumulation phase of retirement savings and explained how these proposed tax incentives are harmonised for the accumulation phase of retirement. The research explained how National Treasury aims to limit pre-retirement withdrawals and how it intends to encourage the annuitisation of post-retirement benefits. The penultimate chapter of this research measured the effect (by making certain assumptions) of the changes proposed by National Treasury on the income replacement ratio of the retiree. Throughout the research comparisons were made between The OECD Roadmap for the good design of defined contribution pension plans and National Treasury’s proposals. This research did not directly address the effect of increased life expectancies on retirement savings or increases in youth unemployment and the effect that this may have on retirement savings. The effect of financial charges levied on retirement savings on the income replacement ratio of a retiree was also not explored. Furthermore, not all pension funds are regulated by the Pension Funds Act and how these pension funds can be brought within the purview of the Pension Funds Act was not investigated. Automatic enrolment of retirement savings for all employees in South Africa in retirement vehicles is a further research area that could be addressed.
- Full Text:
- Authors: Hirschbeck, Lisa
- Date: 2015
- Subjects: Retirement income -- Planning-- South Africa , Retirement income -- Government policy -- South Africa , Pension trusts -- South Africa -- Management , Pension trusts -- Termination -- Law and legislation -- South Africa , Income tax deductions for retirement contributions -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:913 , http://hdl.handle.net/10962/d1017535
- Description: Many South Africans may not have adequate retirement savings when they retire and this has the effect of a low income replacement ratio on retirement that may lead to a decrease in the standard of living of the retiree and in extreme cases the retiree becoming dependent on their family and the government. Owing to this trend of no or inadequate retirement savings, South Africa embarked on a retirement reform journey in 2004. The goal of this research is to determine whether the retirement reform mechanisms outlined by National Treasury would encourage individual retirement savings that should assist South Africans to achieve stability of income in their retirement. This research analysed the current retirement savings options and vehicles available for South Africans, the current tax incentives and disincentives and reviewed the proposed changes to tax incentives and disincentives during the accumulation phase of retirement savings and explained how these proposed tax incentives are harmonised for the accumulation phase of retirement. The research explained how National Treasury aims to limit pre-retirement withdrawals and how it intends to encourage the annuitisation of post-retirement benefits. The penultimate chapter of this research measured the effect (by making certain assumptions) of the changes proposed by National Treasury on the income replacement ratio of the retiree. Throughout the research comparisons were made between The OECD Roadmap for the good design of defined contribution pension plans and National Treasury’s proposals. This research did not directly address the effect of increased life expectancies on retirement savings or increases in youth unemployment and the effect that this may have on retirement savings. The effect of financial charges levied on retirement savings on the income replacement ratio of a retiree was also not explored. Furthermore, not all pension funds are regulated by the Pension Funds Act and how these pension funds can be brought within the purview of the Pension Funds Act was not investigated. Automatic enrolment of retirement savings for all employees in South Africa in retirement vehicles is a further research area that could be addressed.
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End of the march
- Authors: Thomas, Cornelius
- Date: 2015
- Language: English
- Type: still image
- Identifier: vital:7981 , http://hdl.handle.net/10962/d1020456
- Description: On Wednesday, 21 October 2015, Rhodes University closed in solidarity with the higher education sector as students and staff embarked on nationwide protest action against the shortage of funding in the South African higher education sector. #FeesMustFall is a national student led protest movement that began in mid-October 2015 in response to proposed increases in fees at South African universities. These images depict the peaceful march and illustrate the extent of solidarity among staff, students and community members who joined in support of the protest.
- Full Text: false
- Authors: Thomas, Cornelius
- Date: 2015
- Language: English
- Type: still image
- Identifier: vital:7981 , http://hdl.handle.net/10962/d1020456
- Description: On Wednesday, 21 October 2015, Rhodes University closed in solidarity with the higher education sector as students and staff embarked on nationwide protest action against the shortage of funding in the South African higher education sector. #FeesMustFall is a national student led protest movement that began in mid-October 2015 in response to proposed increases in fees at South African universities. These images depict the peaceful march and illustrate the extent of solidarity among staff, students and community members who joined in support of the protest.
- Full Text: false
Engaging within zones of proximal development on Facebook : the case of using Facebook to support learning and mentoring on a NQF Level 5 environmental education, training and development practices learnership
- Authors: Chetty, Preven
- Date: 2015
- Subjects: Social media -- Study and teaching (Higher) -- South Africa , Internet in education , Online social networks , Organizational learning , Employees -- Training of , Group work in education
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2024 , http://hdl.handle.net/10962/d1017335
- Description: This study focuses on two roll-outs of a, year-long National Qualification Framework (NQF) level 5, environmental education learnership in South Africa and attempts at enhancing collaborative learning at workplaces using a familiar social networking site called Facebook. This study uses the Facebook group sites created for the workplace course component of the course as one of the means of data collection. Additional interviews and focus groups with learners and administrators on both Environmental Education Training and Development Practices (EETDP) courses also informed the study. The study is located within the context of the rise of the information age, its effects on socio-ecological landscape at large and ways of using social networking sites in order to facilitate scaffolding and meaning making within zones of proximal development for environmental education learnerships. It also looks at the model of apprenticeship and workplace based learning as it is broadly located at the nexus of the SAQA-led academic inquiry into workplace based learning and professional development. It was found that the use of Facebook on the EETDP learnership allowed for collaborative learning to take place between peer to peer interactions as well as between tutors and learners. It was also noted that scaffolding processes requires both technical assistance and strong instructional input from course tutors. One of the most important findings in terms of collaborative learning and engaging within the Zone of Proximal Development (ZPD) was that learners were able to communicate more effectively and freely with both fellow learners and tutors on course after participating on the Facebook group sites. The study offers recommendations on how a social networking platform like Facebook can be utilised effectively for environmental education. The study recommends that scaffolding of workplace based tasks and concepts needs to be better integrated with the course and in both online and offline interactions between learners. It also illustrates how social networking sites can become powerful tools for creating meaning making when combined with course work.
- Full Text:
- Authors: Chetty, Preven
- Date: 2015
- Subjects: Social media -- Study and teaching (Higher) -- South Africa , Internet in education , Online social networks , Organizational learning , Employees -- Training of , Group work in education
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2024 , http://hdl.handle.net/10962/d1017335
- Description: This study focuses on two roll-outs of a, year-long National Qualification Framework (NQF) level 5, environmental education learnership in South Africa and attempts at enhancing collaborative learning at workplaces using a familiar social networking site called Facebook. This study uses the Facebook group sites created for the workplace course component of the course as one of the means of data collection. Additional interviews and focus groups with learners and administrators on both Environmental Education Training and Development Practices (EETDP) courses also informed the study. The study is located within the context of the rise of the information age, its effects on socio-ecological landscape at large and ways of using social networking sites in order to facilitate scaffolding and meaning making within zones of proximal development for environmental education learnerships. It also looks at the model of apprenticeship and workplace based learning as it is broadly located at the nexus of the SAQA-led academic inquiry into workplace based learning and professional development. It was found that the use of Facebook on the EETDP learnership allowed for collaborative learning to take place between peer to peer interactions as well as between tutors and learners. It was also noted that scaffolding processes requires both technical assistance and strong instructional input from course tutors. One of the most important findings in terms of collaborative learning and engaging within the Zone of Proximal Development (ZPD) was that learners were able to communicate more effectively and freely with both fellow learners and tutors on course after participating on the Facebook group sites. The study offers recommendations on how a social networking platform like Facebook can be utilised effectively for environmental education. The study recommends that scaffolding of workplace based tasks and concepts needs to be better integrated with the course and in both online and offline interactions between learners. It also illustrates how social networking sites can become powerful tools for creating meaning making when combined with course work.
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Enhanced optical limiting behaviour of indium phthalocyanine derivatives when in solution or embedded in poly (acrylic acid) or poly (methyl methacrylate) polymers
- Sanusi, Kayode, Nyokong, Tebello
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189445 , vital:44847 , xlink:href="https://doi.org/10.1016/j.jphotochem.2015.02.003"
- Description: The optical limiting performance of indium phthalocyanine-based polymer thin-films with large nonlinear absorption coefficients (βeff) and low limiting threshold intensity (Ilim) are described. The absorption cross-sections and the population dynamics of the excited states are also reported. The excited state absorption cross-sections (σexc) are shown to depend on the transition moment between the T1 and T2 states. βeff values have been shown to be related to the population density of the molecules in the T1 state. The improved optical limiting performance recorded for the investigated phthalocyanine complexes in the presence of polymer matrices has been attributed to the aggregation effects of the complexes in the polymer thin-films. The optical properties of the indium phthalocyanine moieties were found to possess robust sensitivity to a change of the polymer materials.
- Full Text:
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189445 , vital:44847 , xlink:href="https://doi.org/10.1016/j.jphotochem.2015.02.003"
- Description: The optical limiting performance of indium phthalocyanine-based polymer thin-films with large nonlinear absorption coefficients (βeff) and low limiting threshold intensity (Ilim) are described. The absorption cross-sections and the population dynamics of the excited states are also reported. The excited state absorption cross-sections (σexc) are shown to depend on the transition moment between the T1 and T2 states. βeff values have been shown to be related to the population density of the molecules in the T1 state. The improved optical limiting performance recorded for the investigated phthalocyanine complexes in the presence of polymer matrices has been attributed to the aggregation effects of the complexes in the polymer thin-films. The optical properties of the indium phthalocyanine moieties were found to possess robust sensitivity to a change of the polymer materials.
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Enhanced triplet state parameters for zinc carboxy phenoxy phthalocyanine following conjugation to ascorbic acid
- Ogbodu, Racheal O, Nyokong, Tebello
- Authors: Ogbodu, Racheal O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189348 , vital:44839 , xlink:href="https://doi.org/10.1016/j.poly.2015.01.032"
- Description: Zinc phthalocyanine bearing four ascorbic acid units (formed via ester bond between zinc carboxy phenoxy phthalocyanines and ascorbic acid) was synthesized and characterized using different spectroscopic methods. The complex (with or without ascorbic acid) was further adsorbed onto single walled carbon nanotubes (SWCNTs) and further characterized using Raman spectroscopy, X-ray diffractometry, transmission electron microscopy and thermogravimetric analysis. The photophysical properties of the complexes were studied. The synthesized complex showed better photophysical properties when compared to the carboxy phenoxy phthalocyanines alone, this is evident in the increase of the triplet quantum yields (ΦT), triplet life-times (τT) and singlet oxygen quantum yields (ΦΔ). The zinc phthalocyanines bearing ascorbic acid showed improved triplet life-times even in the presence of SWCNTs.
- Full Text:
- Authors: Ogbodu, Racheal O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189348 , vital:44839 , xlink:href="https://doi.org/10.1016/j.poly.2015.01.032"
- Description: Zinc phthalocyanine bearing four ascorbic acid units (formed via ester bond between zinc carboxy phenoxy phthalocyanines and ascorbic acid) was synthesized and characterized using different spectroscopic methods. The complex (with or without ascorbic acid) was further adsorbed onto single walled carbon nanotubes (SWCNTs) and further characterized using Raman spectroscopy, X-ray diffractometry, transmission electron microscopy and thermogravimetric analysis. The photophysical properties of the complexes were studied. The synthesized complex showed better photophysical properties when compared to the carboxy phenoxy phthalocyanines alone, this is evident in the increase of the triplet quantum yields (ΦT), triplet life-times (τT) and singlet oxygen quantum yields (ΦΔ). The zinc phthalocyanines bearing ascorbic acid showed improved triplet life-times even in the presence of SWCNTs.
- Full Text: