Synthesis, density functional theory, molecular dynamics and electrochemical studies of 3-thiopheneacetic acid-capped gold nanoparticles
- Sosibo, Ndabenhle M, Mdluli, Phumlane S, Mashazi, Philani N, Dyan, Busiswa, Revaprasadu, Neerish, Nyokong, Tebello, Tshikhudo, Robert T, Skepu, Amanda, Van Der Lingen, Elma
- Authors: Sosibo, Ndabenhle M , Mdluli, Phumlane S , Mashazi, Philani N , Dyan, Busiswa , Revaprasadu, Neerish , Nyokong, Tebello , Tshikhudo, Robert T , Skepu, Amanda , Van Der Lingen, Elma
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246446 , vital:51477 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.09.057"
- Description: Gold nanoparticles capped with a bifunctional ligand, 3-thiopheneacetic acid (3-TAA) were synthesised by borohydride reduction at room temperature. The transmission electron microscopy (TEM) analysis showed that the particle aggregates and had semi-linear partial linkages that could be attributed to multi-modal binding of the ligand with various gold nanoparticles through the terminal thiolether (–S–) group and oxygen of the carboxylic (–COOH) group. This bimodal interaction led to limited stability of the resultant nanoparticles when tested using highly electrolytic media. To investigate further, density functional theory (DFT) quantum chemical and molecular dynamic calculations were conducted. The energetically favorable binding modes of the ligand to gold nanoparticle surfaces using the Gaussian program were studied. The DFT results showed kinetic stability of Au–3-TAA–Au interactions leading to inter-particle coupling or aggregation. Electrochemical analysis of the resultant nature of the capping agent revealed that 3-thiopheneacetic acid did not form a polymer during the preparation of Au–3-TAA. The cyclic voltammograms of Au–3-TAA nanoparticles coated glassy carbon electrode showed a typical gold character with the oxidation and reduction peaks at 1.4 V and 0.9 V, respectively.
- Full Text:
- Date Issued: 2012
- Authors: Sosibo, Ndabenhle M , Mdluli, Phumlane S , Mashazi, Philani N , Dyan, Busiswa , Revaprasadu, Neerish , Nyokong, Tebello , Tshikhudo, Robert T , Skepu, Amanda , Van Der Lingen, Elma
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246446 , vital:51477 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.09.057"
- Description: Gold nanoparticles capped with a bifunctional ligand, 3-thiopheneacetic acid (3-TAA) were synthesised by borohydride reduction at room temperature. The transmission electron microscopy (TEM) analysis showed that the particle aggregates and had semi-linear partial linkages that could be attributed to multi-modal binding of the ligand with various gold nanoparticles through the terminal thiolether (–S–) group and oxygen of the carboxylic (–COOH) group. This bimodal interaction led to limited stability of the resultant nanoparticles when tested using highly electrolytic media. To investigate further, density functional theory (DFT) quantum chemical and molecular dynamic calculations were conducted. The energetically favorable binding modes of the ligand to gold nanoparticle surfaces using the Gaussian program were studied. The DFT results showed kinetic stability of Au–3-TAA–Au interactions leading to inter-particle coupling or aggregation. Electrochemical analysis of the resultant nature of the capping agent revealed that 3-thiopheneacetic acid did not form a polymer during the preparation of Au–3-TAA. The cyclic voltammograms of Au–3-TAA nanoparticles coated glassy carbon electrode showed a typical gold character with the oxidation and reduction peaks at 1.4 V and 0.9 V, respectively.
- Full Text:
- Date Issued: 2012
Tetra and octa (2, 6-di-iso-propylphenoxy)-substituted phthalocyanines
- Tuhl, Ahmad, Chidawanayika, Wadzanai, Ibrahim, Hamada Mohamed, Al-Awadi, Nouria, Litwinski, Christian, Nyokong, Tebello, Behbehani, Haider, Manaa, Hacene, Makhseed, Saad
- Authors: Tuhl, Ahmad , Chidawanayika, Wadzanai , Ibrahim, Hamada Mohamed , Al-Awadi, Nouria , Litwinski, Christian , Nyokong, Tebello , Behbehani, Haider , Manaa, Hacene , Makhseed, Saad
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245855 , vital:51411 , xlink:href="https://doi.org/10.1142/S1088424612004495"
- Description: This work reports on the synthesis of novel metal free, zinc, aluminum, gallium and indium tetra and octa (2,6-di-iso-propylphenoxy)-substituted phthalocyanine derivatives. UV-visible and 1H NMR analyses confirm that a non-planar conformation, adapted by the phenoxy substituents due to steric interaction in both derivative series, perfectly discourage cofacial aggregation. Fluorescence quantum yields vary as a function of the number of substituents on the ring periphery, while the fluorescence lifetimes display no distinct trend. Triplet quantum yields are significantly larger for the tetra 2,6-di-iso-propylphenoxy- substituted derivatives relative to their corresponding octa-substituted species. However there was no overall trend in the triplet lifetime values. For almost all of the phthalocyanine derivatives, singlet oxygen was produced with relatively good quantum yields. This study explores the possibility of fine-tuning their physicochemical properties by simple structural modification.
- Full Text:
- Date Issued: 2012
- Authors: Tuhl, Ahmad , Chidawanayika, Wadzanai , Ibrahim, Hamada Mohamed , Al-Awadi, Nouria , Litwinski, Christian , Nyokong, Tebello , Behbehani, Haider , Manaa, Hacene , Makhseed, Saad
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245855 , vital:51411 , xlink:href="https://doi.org/10.1142/S1088424612004495"
- Description: This work reports on the synthesis of novel metal free, zinc, aluminum, gallium and indium tetra and octa (2,6-di-iso-propylphenoxy)-substituted phthalocyanine derivatives. UV-visible and 1H NMR analyses confirm that a non-planar conformation, adapted by the phenoxy substituents due to steric interaction in both derivative series, perfectly discourage cofacial aggregation. Fluorescence quantum yields vary as a function of the number of substituents on the ring periphery, while the fluorescence lifetimes display no distinct trend. Triplet quantum yields are significantly larger for the tetra 2,6-di-iso-propylphenoxy- substituted derivatives relative to their corresponding octa-substituted species. However there was no overall trend in the triplet lifetime values. For almost all of the phthalocyanine derivatives, singlet oxygen was produced with relatively good quantum yields. This study explores the possibility of fine-tuning their physicochemical properties by simple structural modification.
- Full Text:
- Date Issued: 2012
The art of dying
- Authors: Jones, Ward E
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275722 , vital:55073 , xlink:href="https://doi.org/10.1080/05568641.2012.743217"
- Description: In this paper, I explore what Jean Améry calls the ‘aesthetic view of death’. I address the following three questions. To what extent, and how, do we take an aesthetic view of death? Why do we take an aesthetic view of death? Third, for those whose deaths are impending and have some choice over how they die—most prominently the elderly and the terminally ill—what would it mean for them to take an aesthetic view of their own impending deaths, and, in particular, what would it mean for them to act in the light of such a view?
- Full Text:
- Date Issued: 2012
- Authors: Jones, Ward E
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275722 , vital:55073 , xlink:href="https://doi.org/10.1080/05568641.2012.743217"
- Description: In this paper, I explore what Jean Améry calls the ‘aesthetic view of death’. I address the following three questions. To what extent, and how, do we take an aesthetic view of death? Why do we take an aesthetic view of death? Third, for those whose deaths are impending and have some choice over how they die—most prominently the elderly and the terminally ill—what would it mean for them to take an aesthetic view of their own impending deaths, and, in particular, what would it mean for them to act in the light of such a view?
- Full Text:
- Date Issued: 2012
The direct use value of municipal commonage goods and services to urban households in the Eastern Cape, South Africa
- Davenport, Nicholas A, Shackleton, Charlie M, Gambiza, James
- Authors: Davenport, Nicholas A , Shackleton, Charlie M , Gambiza, James
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181071 , vital:43696 , xlink:href="https://doi.org/10.1016/j.landusepol.2011.09.008"
- Description: To redress past racial discrepancies in ownership and tenure, the ANC government of South Africa initiated programmes to make land accessible to the previously disadvantaged. A key component of the national land reform programme was the provision of commonage lands to urban municipalities for use by the urban poor. However, there has been no assessment of the contribution that urban commonage makes to previously disadvantaged households. This study assessed the economic benefits of the commonage programme to local households, through an in-depth survey of 90 households across three small towns in the Eastern Cape of South Africa. We examined the marketed and non-marketed consumptive direct-use values of land-based livelihoods on commonage, calculated via the ‘own reported values’ approach. The results indicate that a proportion of South Africa's urban population rely to some degree on municipal commonage for part of their livelihoods. Commonage contributions to total livelihood incomes ranged between 14 and 20%. If the contributions from commonage were excluded, the incomes of over 10% of households in each study town would drop below the poverty line. Overall, the value of harvests from commonage was worth over R1 000 (US$ 142) per hectare per year and over R4.7 million (US$ 0.68 million) per commonage per year. However, the extent and nature of use and reliance was not uniform among households, so that we developed a typology of commonage users, with four types being identified. However, rapidly growing urban populations and high levels of poverty potentially threaten the sustainability of commonage resource use. Yet the national land reform programme focuses largely on the transfer of land to municipalities and not on sustainable management. Municipalities, in turn, invest relatively little in commonage management, and the little they do is focussed on livestock production. Non-timber forest products are not considered at all, even though this study shows that they are a vital resource for the urban poor, notably for energy and construction materials.
- Full Text:
- Date Issued: 2012
- Authors: Davenport, Nicholas A , Shackleton, Charlie M , Gambiza, James
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181071 , vital:43696 , xlink:href="https://doi.org/10.1016/j.landusepol.2011.09.008"
- Description: To redress past racial discrepancies in ownership and tenure, the ANC government of South Africa initiated programmes to make land accessible to the previously disadvantaged. A key component of the national land reform programme was the provision of commonage lands to urban municipalities for use by the urban poor. However, there has been no assessment of the contribution that urban commonage makes to previously disadvantaged households. This study assessed the economic benefits of the commonage programme to local households, through an in-depth survey of 90 households across three small towns in the Eastern Cape of South Africa. We examined the marketed and non-marketed consumptive direct-use values of land-based livelihoods on commonage, calculated via the ‘own reported values’ approach. The results indicate that a proportion of South Africa's urban population rely to some degree on municipal commonage for part of their livelihoods. Commonage contributions to total livelihood incomes ranged between 14 and 20%. If the contributions from commonage were excluded, the incomes of over 10% of households in each study town would drop below the poverty line. Overall, the value of harvests from commonage was worth over R1 000 (US$ 142) per hectare per year and over R4.7 million (US$ 0.68 million) per commonage per year. However, the extent and nature of use and reliance was not uniform among households, so that we developed a typology of commonage users, with four types being identified. However, rapidly growing urban populations and high levels of poverty potentially threaten the sustainability of commonage resource use. Yet the national land reform programme focuses largely on the transfer of land to municipalities and not on sustainable management. Municipalities, in turn, invest relatively little in commonage management, and the little they do is focussed on livestock production. Non-timber forest products are not considered at all, even though this study shows that they are a vital resource for the urban poor, notably for energy and construction materials.
- Full Text:
- Date Issued: 2012
The economics of suicide in South Africa
- Authors: Botha, Ferdi
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396168 , vital:69155 , xlink:href="https://doi.org/10.1111/j.1813-6982.2012.01336.x"
- Description: This study investigates the economics of suicide in South Africa using the Mortality and Causes of Death data from death notification as well as regional economic data for the 2006-2008 period. Using an inflation rate that varies by month and across province of residence as a proxy for economic performance, the results indicate a negative relationship between inflation and suicide, suggesting that suicides are countercyclical. When controlling for month and province fixed effects, however, the inflation coefficient, albeit remaining negative, is no longer significant, except in the female sample. Suicide is more prevalent among younger individuals, while the greatest proportion of suicide is seen among men. Suicides also exhibit a strong seasonal variation, with peaks in spring and summer, with December having the highest suicide prevalence. The overall results indicate a negative but insignificant relationship between economic performance and suicide in South Africa, with socio-economic differences and individual characteristics accounting for most of the variation in suicide.
- Full Text:
- Date Issued: 2012
- Authors: Botha, Ferdi
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396168 , vital:69155 , xlink:href="https://doi.org/10.1111/j.1813-6982.2012.01336.x"
- Description: This study investigates the economics of suicide in South Africa using the Mortality and Causes of Death data from death notification as well as regional economic data for the 2006-2008 period. Using an inflation rate that varies by month and across province of residence as a proxy for economic performance, the results indicate a negative relationship between inflation and suicide, suggesting that suicides are countercyclical. When controlling for month and province fixed effects, however, the inflation coefficient, albeit remaining negative, is no longer significant, except in the female sample. Suicide is more prevalent among younger individuals, while the greatest proportion of suicide is seen among men. Suicides also exhibit a strong seasonal variation, with peaks in spring and summer, with December having the highest suicide prevalence. The overall results indicate a negative but insignificant relationship between economic performance and suicide in South Africa, with socio-economic differences and individual characteristics accounting for most of the variation in suicide.
- Full Text:
- Date Issued: 2012
The effect of harvesting approaches on fruit yield, embelin concentration and regrowth dynamics of the forest shrub, Embelia tsjeriam-cottam, in central India
- Pandey, Ashok K, Shackleton, Charlie M
- Authors: Pandey, Ashok K , Shackleton, Charlie M
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181094 , vital:43698 , xlink:href="https://doi.org/10.1016/j.foreco.2011.11.015"
- Description: Embelia tsjeriam-cottam Roem and Schult A. DC. (Myrsinaceae), popularly known as Vaividang, is a vulnerable forest species because of the high demand of fruits for medicinal purposes. It is in great demand in ayurveda and the pharmaceutical industry (>100 t/yr), which has imposed tremendous pressure on some natural populations. The fruits contain embelin (a benzoquinone derivative), which has wide clinical applications. Considering the importance, growing use and decreasing populations in some areas of its natural habitat, a study on development of sustainable harvesting practices of E. tsjeriam-cottam fruits was conducted in Chhattisgarh, in central India. Experiments were laid out in Dhamtari, Marvahi and Bilaspur forest divisions of the state covering both protected and open forests in a randomized design with three replications. At each site, quadrats of 40 × 20 m were laid out to study the effect of two fruit harvesting methods and four harvesting intensities on fruit yield, and regeneration of the species. Fruits were analyzed for their embelin content by HPLC method. This study is the first to experimentally assess the consequences of harvesting of E. tsjeriam-cottam fruits from India. It was found that up to 70% fruits could be hand plucked at the right time of maturity (December) to obtain quality produce without impacting the current population size. Since every year is not a good fruiting year, it is difficult to develop universal harvest regime for sustainable management of E. tsjeriam-cottam. The embelin content increased as fruits ripened, ranging from 1.01% to 5.63%. The adoption of sustainable harvesting practices will be helpful in sustainable management of E. tsjeriam-cottam and also provide income and livelihood opportunities to rural people on a sustainable basis.
- Full Text:
- Date Issued: 2012
- Authors: Pandey, Ashok K , Shackleton, Charlie M
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181094 , vital:43698 , xlink:href="https://doi.org/10.1016/j.foreco.2011.11.015"
- Description: Embelia tsjeriam-cottam Roem and Schult A. DC. (Myrsinaceae), popularly known as Vaividang, is a vulnerable forest species because of the high demand of fruits for medicinal purposes. It is in great demand in ayurveda and the pharmaceutical industry (>100 t/yr), which has imposed tremendous pressure on some natural populations. The fruits contain embelin (a benzoquinone derivative), which has wide clinical applications. Considering the importance, growing use and decreasing populations in some areas of its natural habitat, a study on development of sustainable harvesting practices of E. tsjeriam-cottam fruits was conducted in Chhattisgarh, in central India. Experiments were laid out in Dhamtari, Marvahi and Bilaspur forest divisions of the state covering both protected and open forests in a randomized design with three replications. At each site, quadrats of 40 × 20 m were laid out to study the effect of two fruit harvesting methods and four harvesting intensities on fruit yield, and regeneration of the species. Fruits were analyzed for their embelin content by HPLC method. This study is the first to experimentally assess the consequences of harvesting of E. tsjeriam-cottam fruits from India. It was found that up to 70% fruits could be hand plucked at the right time of maturity (December) to obtain quality produce without impacting the current population size. Since every year is not a good fruiting year, it is difficult to develop universal harvest regime for sustainable management of E. tsjeriam-cottam. The embelin content increased as fruits ripened, ranging from 1.01% to 5.63%. The adoption of sustainable harvesting practices will be helpful in sustainable management of E. tsjeriam-cottam and also provide income and livelihood opportunities to rural people on a sustainable basis.
- Full Text:
- Date Issued: 2012
The implacable grandeur of the stranger
- Authors: Krueger, Anton
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229430 , vital:49673 , xlink:href="https://doi.org/10.1080/10137548.2013.799798"
- Description: South Africa is a nation of strangers, an uneasy mishmash of heterogeneous economic groupings, cultures and languages, a nation of marginalised minorities awkwardly pasted together. Numerous attempts have been made by its government to define and bolster a sense of nationalism and to create a sense of cohesion; however, a shadow side of this appeal for national identity has been the rise in xenophobic violence precipitated by the steady influx of refugees into the country. The title of this article is drawn from Albert Camus’s introduction to his disarming novella of dislocation, L’Etranger (1942), and I would like to explore some of the philosophical implications of representing strangers in different ways. Drawing on works by Zygmunt Bauman, Georg Simmel and Julia Kristeva, I will consider ambivalences towards the stranger represented in Magnet Theatre’s production (2010) of Die Vreemdeling [The Stranger], and pose a few questions about our relationship with the unknown. Attempts to familiarise the constituents of various communities with aspects of each other’s strangeness is a project which has typified much South African theatre in the past; and yet this is an approach which stands in sharp contrast to the importance granted processes of defamiliarisation first proposed so succinctly by Victor Shklovsky in 1917. Instead of attempts to harness and explain the unfamiliarity of others in order to communicate diversity, a celebration of the grandeur of the stranger may provide a more enriching alternative.
- Full Text:
- Date Issued: 2012
- Authors: Krueger, Anton
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229430 , vital:49673 , xlink:href="https://doi.org/10.1080/10137548.2013.799798"
- Description: South Africa is a nation of strangers, an uneasy mishmash of heterogeneous economic groupings, cultures and languages, a nation of marginalised minorities awkwardly pasted together. Numerous attempts have been made by its government to define and bolster a sense of nationalism and to create a sense of cohesion; however, a shadow side of this appeal for national identity has been the rise in xenophobic violence precipitated by the steady influx of refugees into the country. The title of this article is drawn from Albert Camus’s introduction to his disarming novella of dislocation, L’Etranger (1942), and I would like to explore some of the philosophical implications of representing strangers in different ways. Drawing on works by Zygmunt Bauman, Georg Simmel and Julia Kristeva, I will consider ambivalences towards the stranger represented in Magnet Theatre’s production (2010) of Die Vreemdeling [The Stranger], and pose a few questions about our relationship with the unknown. Attempts to familiarise the constituents of various communities with aspects of each other’s strangeness is a project which has typified much South African theatre in the past; and yet this is an approach which stands in sharp contrast to the importance granted processes of defamiliarisation first proposed so succinctly by Victor Shklovsky in 1917. Instead of attempts to harness and explain the unfamiliarity of others in order to communicate diversity, a celebration of the grandeur of the stranger may provide a more enriching alternative.
- Full Text:
- Date Issued: 2012
The photophysical and energy transfer behaviour of low symmetry phthalocyanine complexes conjugated to coreshell quantum dots
- Masilela, Nkosiphile, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243051 , vital:51111 , xlink:href="https://doi.org/10.1016/j.jphotochem.2012.07.016"
- Description: This work reports on the synthesis of new coreshell quantum dots (QDs)-low symmetry phthalocyanines conjugates. The energy transfer from QDs (donor) to phthalocyanines (acceptor) was investigated when the two are mixed together or chemically linked to each other. Ti monocarboxy phthalocyanine QDs-linked and Sn monocarboxy phthalocyanine QDs-linked gave the smallest centre-to-centre separation distance (r) corresponding to their higher Förster resonance energy transfer efficiencies which are estimated at 0.76 and 0.85 respectively. Higher energy transfer behaviour was achieved for all the covalently linked conjugates compared to their corresponding mixed counterparts. An improvement in triplet quantum yields and lifetimes was achieved for all the complexes in the presence of quantum dots, with the linked counterparts displaying excellent triplet state behaviour.
- Full Text:
- Date Issued: 2012
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243051 , vital:51111 , xlink:href="https://doi.org/10.1016/j.jphotochem.2012.07.016"
- Description: This work reports on the synthesis of new coreshell quantum dots (QDs)-low symmetry phthalocyanines conjugates. The energy transfer from QDs (donor) to phthalocyanines (acceptor) was investigated when the two are mixed together or chemically linked to each other. Ti monocarboxy phthalocyanine QDs-linked and Sn monocarboxy phthalocyanine QDs-linked gave the smallest centre-to-centre separation distance (r) corresponding to their higher Förster resonance energy transfer efficiencies which are estimated at 0.76 and 0.85 respectively. Higher energy transfer behaviour was achieved for all the covalently linked conjugates compared to their corresponding mixed counterparts. An improvement in triplet quantum yields and lifetimes was achieved for all the complexes in the presence of quantum dots, with the linked counterparts displaying excellent triplet state behaviour.
- Full Text:
- Date Issued: 2012
The pump room
- Authors: Krueger, Anton
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225764 , vital:49256 , xlink:href="https://doi.org/10.1080/10137548.2012.754084"
- Description: I like Allan Kolski Horwitz. He’s done great things for independent publishing in South Africa. Through his company, Botsotso, he’s probably responsible for publishing more poetry, prose and drama than any single person in the country today. The industriousness of his one-man operation has generously sponsored and nurtured thousands of pages of local literature over the course of many years. This is why it makes me so uncomfortable to say that I really don’t like this play. It gives me no pleasure to write a negative review, and especially not about books written by people I like. If I hadn’t already committed myself to writing this review, I would have avoided it. Nevertheless, I had, so I won’t.
- Full Text:
- Date Issued: 2012
- Authors: Krueger, Anton
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225764 , vital:49256 , xlink:href="https://doi.org/10.1080/10137548.2012.754084"
- Description: I like Allan Kolski Horwitz. He’s done great things for independent publishing in South Africa. Through his company, Botsotso, he’s probably responsible for publishing more poetry, prose and drama than any single person in the country today. The industriousness of his one-man operation has generously sponsored and nurtured thousands of pages of local literature over the course of many years. This is why it makes me so uncomfortable to say that I really don’t like this play. It gives me no pleasure to write a negative review, and especially not about books written by people I like. If I hadn’t already committed myself to writing this review, I would have avoided it. Nevertheless, I had, so I won’t.
- Full Text:
- Date Issued: 2012
The syntheses and photophysical properties of 4, 4′-isopropylidendioxydiphenyl substituted ball-type dinuclear Mg (II) and Zn (II) phthalocyanines
- Canlıca, Mevlüde, Nyokong, Tebello
- Authors: Canlıca, Mevlüde , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243554 , vital:51163 , xlink:href="https://doi.org/10.1016/j.poly.2011.10.024"
- Description: The syntheses of ball-type dinuclear Zn(II) and Mg(II) phthalocyanines containing four 4,4′-isopropylidendioxydiphenyl substituents at the peripheral and non-peripheral positions are presented. The structures of the synthesized compounds were characterized using elemental analyses, and UV–Vis, FT-IR, 1H NMR and mass spectroscopies. The ΦF values were 0.14, 0.11, 0.22, 0.15 and ΦT values were 0.84, 0.88, 0.62, 0.74, for 6–9, respectively. The largest triplet yields were observed for the non-peripherally substituted complexes 6 and 7, showing that non-peripheral substitution favors increased population of the triplet state. All complexes showed reasonably long triplet lifetimes with τT 510, 310, 910 and 350 μs in DMSO, respectively.
- Full Text:
- Date Issued: 2012
- Authors: Canlıca, Mevlüde , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243554 , vital:51163 , xlink:href="https://doi.org/10.1016/j.poly.2011.10.024"
- Description: The syntheses of ball-type dinuclear Zn(II) and Mg(II) phthalocyanines containing four 4,4′-isopropylidendioxydiphenyl substituents at the peripheral and non-peripheral positions are presented. The structures of the synthesized compounds were characterized using elemental analyses, and UV–Vis, FT-IR, 1H NMR and mass spectroscopies. The ΦF values were 0.14, 0.11, 0.22, 0.15 and ΦT values were 0.84, 0.88, 0.62, 0.74, for 6–9, respectively. The largest triplet yields were observed for the non-peripherally substituted complexes 6 and 7, showing that non-peripheral substitution favors increased population of the triplet state. All complexes showed reasonably long triplet lifetimes with τT 510, 310, 910 and 350 μs in DMSO, respectively.
- Full Text:
- Date Issued: 2012
The synthesis, photophysical and dielectric properties of ball-type dinuclear zinc phthalocyanine
- Canlıca, Mevlüde, Altındal, Ahmet, Nyokong, Tebello
- Authors: Canlıca, Mevlüde , Altındal, Ahmet , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243532 , vital:51161 , xlink:href="https://doi.org/10.1142/S1088424612500836"
- Description: The synthesis of ball-type dinuclear Zn(II) phthalocyanine containing four 4,4′-(9H-fluorene-9,9-diyl)diphenol substituents at the non-peripheral position is presented. The structure of the synthesized compound was characterized using elemental analyzes, and UV-vis, FT-IR, 1H NMR and mass spectroscopies. The ΦF value was 0.16 and ΦT value was 0.72. The complex showed reasonably long triplet lifetimes with τT 7210 μs in DMSO. The frequency and temperature dependence of the dielectric properties of ZnPc were also investigated in the frequency range of 40–105 Hz and in the temperature range of 300–440 °K. It has been observed that both dielectric constant ε′ and dielectric loss ε″ decrease with the rise in frequency as they increase with the rise in temperature. The decrease in ε′ with increasing frequency is attributed to the fact that as the frequency increases, the polarizability contribution from orientation sources decreases and finally disappears.
- Full Text:
- Date Issued: 2012
- Authors: Canlıca, Mevlüde , Altındal, Ahmet , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243532 , vital:51161 , xlink:href="https://doi.org/10.1142/S1088424612500836"
- Description: The synthesis of ball-type dinuclear Zn(II) phthalocyanine containing four 4,4′-(9H-fluorene-9,9-diyl)diphenol substituents at the non-peripheral position is presented. The structure of the synthesized compound was characterized using elemental analyzes, and UV-vis, FT-IR, 1H NMR and mass spectroscopies. The ΦF value was 0.16 and ΦT value was 0.72. The complex showed reasonably long triplet lifetimes with τT 7210 μs in DMSO. The frequency and temperature dependence of the dielectric properties of ZnPc were also investigated in the frequency range of 40–105 Hz and in the temperature range of 300–440 °K. It has been observed that both dielectric constant ε′ and dielectric loss ε″ decrease with the rise in frequency as they increase with the rise in temperature. The decrease in ε′ with increasing frequency is attributed to the fact that as the frequency increases, the polarizability contribution from orientation sources decreases and finally disappears.
- Full Text:
- Date Issued: 2012
The use of hot and cold high pressure homogenization to enhance the loading capacity and encapsulation efficiency of nanostructured lipid carriers for the hydrophilic antiretroviral drug, didanosine for potential administration to paediatric patients
- Kasongo, Kasongo W, Müller, Rainer H, Walker, Roderick B
- Authors: Kasongo, Kasongo W , Müller, Rainer H , Walker, Roderick B
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184087 , vital:44170 , xlink:href="https://doi.org/10.3109/10837450.2010.542163"
- Description: A major obstacle to the application of nanostructured lipid carriers (NLCs) as carriers for hydrophilic drugs is the limited loading capacity (LC) and encapsulation efficiency (EE) of NLCs for these molecules. The purpose of this research was to design and implement a strategy to enhance the LC and EE of NLCs for the hydrophilic drug, didanosine (DDI). DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid was reduced gradually using hot high pressure homogenization (HPH). The product obtained thereafter was added to Precirol® ATO 5 and the hot mixture was immediately dried using liquid nitrogen. The dried materials were then ground and passed through a 200 μm sieve and the solid lipid particles were dispersed in a surfactant solution and subsequently used to manufacture DDI-loaded NLCs using cold HPH. The LC and EE of NLCs for DDI manufactured using the new strategy were 3.39 ± 0.63% and 51.58 ± 1.31%, respectively, compared to 0.079 ± 0.001% and 32.45 ± 0.08%, respectively, obtained when DDI-loaded NLCs were produced using conventional hot HPH. The enhanced LC and EE for DDI make NLCs a potential technology for the oral administration of DDI to paediatric patients.
- Full Text:
- Date Issued: 2012
- Authors: Kasongo, Kasongo W , Müller, Rainer H , Walker, Roderick B
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184087 , vital:44170 , xlink:href="https://doi.org/10.3109/10837450.2010.542163"
- Description: A major obstacle to the application of nanostructured lipid carriers (NLCs) as carriers for hydrophilic drugs is the limited loading capacity (LC) and encapsulation efficiency (EE) of NLCs for these molecules. The purpose of this research was to design and implement a strategy to enhance the LC and EE of NLCs for the hydrophilic drug, didanosine (DDI). DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid was reduced gradually using hot high pressure homogenization (HPH). The product obtained thereafter was added to Precirol® ATO 5 and the hot mixture was immediately dried using liquid nitrogen. The dried materials were then ground and passed through a 200 μm sieve and the solid lipid particles were dispersed in a surfactant solution and subsequently used to manufacture DDI-loaded NLCs using cold HPH. The LC and EE of NLCs for DDI manufactured using the new strategy were 3.39 ± 0.63% and 51.58 ± 1.31%, respectively, compared to 0.079 ± 0.001% and 32.45 ± 0.08%, respectively, obtained when DDI-loaded NLCs were produced using conventional hot HPH. The enhanced LC and EE for DDI make NLCs a potential technology for the oral administration of DDI to paediatric patients.
- Full Text:
- Date Issued: 2012
The use of response surface methodology in the evaluation of captopril microparticles manufactured using an oil in oil solvent evaporation technique
- Khamanga, Sandile M, Walker, Roderick B
- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184221 , vital:44191 , xlink:href="https://doi.org/10.3109/02652048.2011.629744"
- Description: Captopril (CPT) microparticles were manufactured by solvent evaporation using acetone (dispersion phase) and liquid paraffin (manufacturing phase) with Eudragit® and Methocel® as coat materials. Design of experiments and response surface methodology (RSM) approaches were used to optimize the process. The microparticles were characterized based on the percent of drug released and yield, microcapsule size, entrapment efficiency and Hausner ratio. Differential scanning calorimetry (DSC), Infrared (IR) spectroscopy, scanning electron microscopy (SEM) and in vitro dissolution studies were conducted. The microcapsules were spherical, free-flowing and IR and DSC thermograms revealed that CPT was stable. The percent drug released was investigated with respect to Eudragit® RS and Methocel® K100M, Methocel® K15M concentrations and homogenizing speed. The optimal conditions for microencapsulation were 1.12 g Eudragit® RS, 0.67 g Methocel® K100M and 0.39 g Methocel® K15M at a homogenizing speed of 1643 rpm and 89% CPT was released. The value of RSM-mediated microencapsulation of CPT was elucidated.
- Full Text:
- Date Issued: 2012
- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184221 , vital:44191 , xlink:href="https://doi.org/10.3109/02652048.2011.629744"
- Description: Captopril (CPT) microparticles were manufactured by solvent evaporation using acetone (dispersion phase) and liquid paraffin (manufacturing phase) with Eudragit® and Methocel® as coat materials. Design of experiments and response surface methodology (RSM) approaches were used to optimize the process. The microparticles were characterized based on the percent of drug released and yield, microcapsule size, entrapment efficiency and Hausner ratio. Differential scanning calorimetry (DSC), Infrared (IR) spectroscopy, scanning electron microscopy (SEM) and in vitro dissolution studies were conducted. The microcapsules were spherical, free-flowing and IR and DSC thermograms revealed that CPT was stable. The percent drug released was investigated with respect to Eudragit® RS and Methocel® K100M, Methocel® K15M concentrations and homogenizing speed. The optimal conditions for microencapsulation were 1.12 g Eudragit® RS, 0.67 g Methocel® K100M and 0.39 g Methocel® K15M at a homogenizing speed of 1643 rpm and 89% CPT was released. The value of RSM-mediated microencapsulation of CPT was elucidated.
- Full Text:
- Date Issued: 2012
Trends in the optical and redox properties of tetraphenyltetraphenanthroporphyrins
- Mack, John, Lobb, Kevin, Nyokong, Tebello, Shen, Zhen, Kobayashi, Nagao
- Authors: Mack, John , Lobb, Kevin , Nyokong, Tebello , Shen, Zhen , Kobayashi, Nagao
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245809 , vital:51407 , xlink:href="https://doi.org/10.1142/S1088424612500885"
- Description: The results of TD-DFT calculations for a series of tetraaryltetraphenanthroporphyrins containing para-substituents with differing electron donating and accepting properties are compared to the observed optical and redox properties and Michl's perimeter model is used as a conceptual framework for analyzing the results.
- Full Text:
- Date Issued: 2012
- Authors: Mack, John , Lobb, Kevin , Nyokong, Tebello , Shen, Zhen , Kobayashi, Nagao
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245809 , vital:51407 , xlink:href="https://doi.org/10.1142/S1088424612500885"
- Description: The results of TD-DFT calculations for a series of tetraaryltetraphenanthroporphyrins containing para-substituents with differing electron donating and accepting properties are compared to the observed optical and redox properties and Michl's perimeter model is used as a conceptual framework for analyzing the results.
- Full Text:
- Date Issued: 2012
Unquenched fluorescence lifetime for β-phenylthio substituted zinc phthalocyanine upon conjugation to gold nanoparticles
- Forteath, Shaun, Antunes, Edith M, Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Forteath, Shaun , Antunes, Edith M , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245774 , vital:51404 , xlink:href="https://doi.org/10.1016/j.poly.2011.12.015"
- Description: Photoinduced processes in phthalocyanine-functionalized gold nanoparticles have been investigated by spectroscopic measurements. The zinc phthalocyanine used contained four phenylthio peripheral substituents (ZnPc(SPh)4). The conjugates formed are represented as ZnPc(SPh)4–AuNP. The absorption spectrum of the ZnPc(SPh)4–AuNP shows a broadening of the phthalocyanine Q-band absorption, probably due to a tight packing of the phthalocyanines on the gold nanoparticle surface. For the attached phthalocyanines, the two fluorescence lifetimes obtained by time-correlated single photon counting (TCSPC) were determined to be both longer and shorter than that of the free Pc. The fluorescence lifetimes were resolved using time resolved fluorescence spectroscopy (TRES).
- Full Text:
- Date Issued: 2012
- Authors: Forteath, Shaun , Antunes, Edith M , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245774 , vital:51404 , xlink:href="https://doi.org/10.1016/j.poly.2011.12.015"
- Description: Photoinduced processes in phthalocyanine-functionalized gold nanoparticles have been investigated by spectroscopic measurements. The zinc phthalocyanine used contained four phenylthio peripheral substituents (ZnPc(SPh)4). The conjugates formed are represented as ZnPc(SPh)4–AuNP. The absorption spectrum of the ZnPc(SPh)4–AuNP shows a broadening of the phthalocyanine Q-band absorption, probably due to a tight packing of the phthalocyanines on the gold nanoparticle surface. For the attached phthalocyanines, the two fluorescence lifetimes obtained by time-correlated single photon counting (TCSPC) were determined to be both longer and shorter than that of the free Pc. The fluorescence lifetimes were resolved using time resolved fluorescence spectroscopy (TRES).
- Full Text:
- Date Issued: 2012
Working with cultural-historical activity theory and critical realism to investigate and expand farmer learning in Southern Africa
- Mukute, Mutizwa, Lotz-Sisitka, Heila
- Authors: Mukute, Mutizwa , Lotz-Sisitka, Heila
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182494 , vital:43835 , xlink:href="https://doi.org/10.1080/10749039.2012.656173"
- Description: This article uses the theoretical and methodological tools of cultural historical activity theory and critical realism to examine three case studies of the introduction and expansion of sustainable agricultural practices in southern Africa. The article addresses relevant issues in the field of agricultural extension, which lacks a theoretical “bridge” between top-down knowledge transfer and bottom-up participatory approaches to learning. Further, the article considers the learning environments necessary for sustainable agriculture. Such environments provided research participants with encounters with “postnormal” scientific practices that recognise and engage plural ways of knowing. Our research explored why farmers learn and practise sustainable agriculture, how they learn and practise it, the contradictions they are facing, and how these contradictions can be overcome in a context of change-oriented learning.
- Full Text:
- Date Issued: 2012
- Authors: Mukute, Mutizwa , Lotz-Sisitka, Heila
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182494 , vital:43835 , xlink:href="https://doi.org/10.1080/10749039.2012.656173"
- Description: This article uses the theoretical and methodological tools of cultural historical activity theory and critical realism to examine three case studies of the introduction and expansion of sustainable agricultural practices in southern Africa. The article addresses relevant issues in the field of agricultural extension, which lacks a theoretical “bridge” between top-down knowledge transfer and bottom-up participatory approaches to learning. Further, the article considers the learning environments necessary for sustainable agriculture. Such environments provided research participants with encounters with “postnormal” scientific practices that recognise and engage plural ways of knowing. Our research explored why farmers learn and practise sustainable agriculture, how they learn and practise it, the contradictions they are facing, and how these contradictions can be overcome in a context of change-oriented learning.
- Full Text:
- Date Issued: 2012