Synthesis, photophysics and photochemistry of novel tetra (quinoxalinyl) phthalocyaninato zinc (II) complexes
- Erdoğmuş, Ali, Ogunsipe, Abimbola, Nyokong, Tebello
- Authors: Erdoğmuş, Ali , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263441 , vital:53628 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.04.007"
- Description: The syntheses and spectral, photophysical and photochemical properties of some zinc phthalocyanine derivatives – {2, (3)-tetra(quinoxalinyl)phthalocyaninato zinc(II), (β-ZnPc) and 1, (4)-tetra(quinoxalinyl)phthalocyaninato zinc(II), (α-ZnPc)} – are presented. The β-substituted complex is more fluorescent and exhibits lower tendencies to undergo intersystem crossing than its α-substituted counterpart, as judged by the former's higher fluorescence quantum yield (ΦF) and lower triplet quantum yield (ΦT) than the latter's in three solvents (DMSO, DMF and toluene). Singlet oxygen quantum yield (ΦΔ) values show the same trends as ΦT values. The differences in the spectral and photophysical properties of α-ZnPc and β-ZnPc are partly attributed to greater molecular distortions in the former. Studies of the interaction of the triplet states of α-ZnPc and β-ZnPc with triplet oxygen showed that α-ZnPc is more vulnerable to oxygen quenching than β-ZnPc. Also, the smallest quenching rate constants were observed in DMSO, which is attributed to the higher viscosity of DMSO than DMF and toluene.
- Full Text:
- Date Issued: 2009
- Authors: Erdoğmuş, Ali , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263441 , vital:53628 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.04.007"
- Description: The syntheses and spectral, photophysical and photochemical properties of some zinc phthalocyanine derivatives – {2, (3)-tetra(quinoxalinyl)phthalocyaninato zinc(II), (β-ZnPc) and 1, (4)-tetra(quinoxalinyl)phthalocyaninato zinc(II), (α-ZnPc)} – are presented. The β-substituted complex is more fluorescent and exhibits lower tendencies to undergo intersystem crossing than its α-substituted counterpart, as judged by the former's higher fluorescence quantum yield (ΦF) and lower triplet quantum yield (ΦT) than the latter's in three solvents (DMSO, DMF and toluene). Singlet oxygen quantum yield (ΦΔ) values show the same trends as ΦT values. The differences in the spectral and photophysical properties of α-ZnPc and β-ZnPc are partly attributed to greater molecular distortions in the former. Studies of the interaction of the triplet states of α-ZnPc and β-ZnPc with triplet oxygen showed that α-ZnPc is more vulnerable to oxygen quenching than β-ZnPc. Also, the smallest quenching rate constants were observed in DMSO, which is attributed to the higher viscosity of DMSO than DMF and toluene.
- Full Text:
- Date Issued: 2009
The formation of self-assembled monolayers of thiophthalocyanine complexes of titanium, vanadium and manganese and their use in l-cysteine electrocatalysis
- Mbambisa, Gcineka, Nombona, Nolwazi, Nyokong, Tebello
- Authors: Mbambisa, Gcineka , Nombona, Nolwazi , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263375 , vital:53622 , xlink:href="https://doi.org/10.1016/j.microc.2009.04.009"
- Description: Self-assembled monolayers (SAMs) based on octapentylthiophthalocyanine complexes of oxovanadium (IV) (OVOPThPc), titanium(IV) (OTiOPThPc), and manganese (III) acetate (AcMnOPThPc), and of tetraphenylthiophthalocyanine complexes of hydroxo manganese(III) (OHMnTPPc) and oxotitanium(IV) (OTiTPPc) are described. The oxidation of l-cysteine was observed at potentials which ranged from 0.52 V to 0.67 V. The detection limits for l-cysteine analysis were of the order of 10− 7 to 10− 6 M.
- Full Text:
- Date Issued: 2009
- Authors: Mbambisa, Gcineka , Nombona, Nolwazi , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263375 , vital:53622 , xlink:href="https://doi.org/10.1016/j.microc.2009.04.009"
- Description: Self-assembled monolayers (SAMs) based on octapentylthiophthalocyanine complexes of oxovanadium (IV) (OVOPThPc), titanium(IV) (OTiOPThPc), and manganese (III) acetate (AcMnOPThPc), and of tetraphenylthiophthalocyanine complexes of hydroxo manganese(III) (OHMnTPPc) and oxotitanium(IV) (OTiTPPc) are described. The oxidation of l-cysteine was observed at potentials which ranged from 0.52 V to 0.67 V. The detection limits for l-cysteine analysis were of the order of 10− 7 to 10− 6 M.
- Full Text:
- Date Issued: 2009
The syntheses, characterization and fluorescence spectra of novel, octakis (alkylthiophthalocyanato) nickel (II) and palladium (II) complexes
- Ogunbayo, Taofeek Babatunde, Ogunsipe, Abimbola, Nyokong, Tebello
- Authors: Ogunbayo, Taofeek Babatunde , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263386 , vital:53623 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.03.009"
- Description: The syntheses, characterization and fluorescence studies of several {octakis(alkylthio)phthalocyanato} palladium(II) and nickel(II) complexes are presented. The absorption spectra of some of the complexes showed extra peaks which are attributable to non-planar distortion, the extent of which, was found to dependent on alkyl chain length. The fluorescence excitation spectra of the nickel(II) derivatives were not in agreement with their absorption spectra, owing to structural changes upon excitation. Fluorescence quantum yields were very low (more than 1%) for all complexes as a consequence of the open-shell electronic structures of nickel(II) and palladium(II).
- Full Text:
- Date Issued: 2009
- Authors: Ogunbayo, Taofeek Babatunde , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263386 , vital:53623 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.03.009"
- Description: The syntheses, characterization and fluorescence studies of several {octakis(alkylthio)phthalocyanato} palladium(II) and nickel(II) complexes are presented. The absorption spectra of some of the complexes showed extra peaks which are attributable to non-planar distortion, the extent of which, was found to dependent on alkyl chain length. The fluorescence excitation spectra of the nickel(II) derivatives were not in agreement with their absorption spectra, owing to structural changes upon excitation. Fluorescence quantum yields were very low (more than 1%) for all complexes as a consequence of the open-shell electronic structures of nickel(II) and palladium(II).
- Full Text:
- Date Issued: 2009
The synthesis and photophysicochemical behaviour of novel water-soluble cationic indium (III) phthalocyanine
- Durmus, Mahmut, Erdoğmuş, Ali, Ogunsipe, Abimbola, Nyokong, Tebello
- Authors: Durmus, Mahmut , Erdoğmuş, Ali , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263419 , vital:53626 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.01.008"
- Description: The syntheses and characterization of 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) and quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) are described. The ground state electronic absorption spectra, photophysics and photochemistry of both dyes in DMSO as well as that of the quaternized compound in aqueous solution are also presented. A comparison of the photophysical and photochemical parameters of the two dyes revealed that quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) was a better photosensitizer than its unquaternized counterpart. The quantum yield values of fluorescence (ΦF), triplet state formation (ΦT) and singlet oxygen formation (ΦΔ) for the cationic dye were found to be 0.03, 0.68 and 0.66 respectively in DMSO; these values were higher than those for 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III), which exhibited values of 0.02, 0.66 and 0.63, respectively in DMSO. The values for the cationic dye in aq. solution were 0.02, 0.59 and 0.56 respectively, suggesting that the water-soluble quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) offers potential as a photosensitizer in photodynamic therapy treatment.
- Full Text:
- Date Issued: 2009
- Authors: Durmus, Mahmut , Erdoğmuş, Ali , Ogunsipe, Abimbola , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263419 , vital:53626 , xlink:href="https://doi.org/10.1016/j.dyepig.2009.01.008"
- Description: The syntheses and characterization of 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) and quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) are described. The ground state electronic absorption spectra, photophysics and photochemistry of both dyes in DMSO as well as that of the quaternized compound in aqueous solution are also presented. A comparison of the photophysical and photochemical parameters of the two dyes revealed that quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) was a better photosensitizer than its unquaternized counterpart. The quantum yield values of fluorescence (ΦF), triplet state formation (ΦT) and singlet oxygen formation (ΦΔ) for the cationic dye were found to be 0.03, 0.68 and 0.66 respectively in DMSO; these values were higher than those for 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III), which exhibited values of 0.02, 0.66 and 0.63, respectively in DMSO. The values for the cationic dye in aq. solution were 0.02, 0.59 and 0.56 respectively, suggesting that the water-soluble quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) offers potential as a photosensitizer in photodynamic therapy treatment.
- Full Text:
- Date Issued: 2009
The synthesis and photophysicochemical properties of low-symmetry zinc phthalocyanine analogues
- Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263397 , vital:53624 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.06.005"
- Description: The synthesis of a low-symmetry derivative, zinc mono-carboxy substituted phthalocyanine, ZnPc-COOH (4) has been reported. The photochemical and photophysical properties of ZnPc-COOH (4), ZnTMPyPc (5), ZnttbPc (6) and a previously synthesized low-symmetry derivative, ZnttbIPc (7), in various organic solvents are reported. The red-shifting of the spectra of 4 and 5 (relative to that of unsubstituted zinc phthalocyanine, ZnPc) is a function of the electron-donating sulfur-containing substituents attached to the periphery of the molecule. High triplet quantum yields (ФT) generally occur in response to substitution on the zinc phthalocyanine ring periphery. The highest ФT values and triplet lifetimes (τT) occur in DMSO for all derivatives as a result of the solvent's high viscosity. The strongly electron-withdrawing imido fused ring of ZnttbIPc (7) stabilizes it against photo-oxidative degradation relative to the other derivatives.
- Full Text:
- Date Issued: 2009
- Authors: Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263397 , vital:53624 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.06.005"
- Description: The synthesis of a low-symmetry derivative, zinc mono-carboxy substituted phthalocyanine, ZnPc-COOH (4) has been reported. The photochemical and photophysical properties of ZnPc-COOH (4), ZnTMPyPc (5), ZnttbPc (6) and a previously synthesized low-symmetry derivative, ZnttbIPc (7), in various organic solvents are reported. The red-shifting of the spectra of 4 and 5 (relative to that of unsubstituted zinc phthalocyanine, ZnPc) is a function of the electron-donating sulfur-containing substituents attached to the periphery of the molecule. High triplet quantum yields (ФT) generally occur in response to substitution on the zinc phthalocyanine ring periphery. The highest ФT values and triplet lifetimes (τT) occur in DMSO for all derivatives as a result of the solvent's high viscosity. The strongly electron-withdrawing imido fused ring of ZnttbIPc (7) stabilizes it against photo-oxidative degradation relative to the other derivatives.
- Full Text:
- Date Issued: 2009
The synthesis, cyclic voltammetry and spectroelectrochemical studies of Co (II) phthalocyanines tetra-substituted at the α and β positions with phenylthio groups
- Nombona, Nolwazi, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264529 , vital:53742 , xlink:href="https://doi.org/10.1016/j.dyepig.2008.06.002"
- Description: Non-peripherally substituted cobalt 1,(4)-(tetraphenylthiophthalocyaninato) and peripherally substituted cobalt 2,(3)-(tetraphenylthiophthalocyaninato) complexes were synthesized. Redox processes were observed at E1/2 = −1.44 V (I), −0.39 V (II), +0.37 V (III), +0.78 V (IV) and 1.15 V (V) for the non-peripherally substituted and at E1/2 = −1.42 V (I), −0.57, −0.39 V (II), +0.27 V (III), +0.79 V (IV) and +1.10 V (V) for the peripherally substituted complexes, respectively. The couples were assigned to CoIPc−2/CoIPc−3 (I), CoIIPc−2/CoIPc−2 (II), CoIIIPc−2/CoIIPc−2 (III), and CoIIIPc−1/CoIIIPc−2 (IV) using spectroelectrochemistry. The last process (V) could not be ascertained by spectroelectrochemistry but is associated with ring oxidation. Upon reduction or oxidation, the Q band of the non-peripherally substituted complex became less red shifted compared to that of its peripherally substituted counterpart.
- Full Text:
- Date Issued: 2009
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264529 , vital:53742 , xlink:href="https://doi.org/10.1016/j.dyepig.2008.06.002"
- Description: Non-peripherally substituted cobalt 1,(4)-(tetraphenylthiophthalocyaninato) and peripherally substituted cobalt 2,(3)-(tetraphenylthiophthalocyaninato) complexes were synthesized. Redox processes were observed at E1/2 = −1.44 V (I), −0.39 V (II), +0.37 V (III), +0.78 V (IV) and 1.15 V (V) for the non-peripherally substituted and at E1/2 = −1.42 V (I), −0.57, −0.39 V (II), +0.27 V (III), +0.79 V (IV) and +1.10 V (V) for the peripherally substituted complexes, respectively. The couples were assigned to CoIPc−2/CoIPc−3 (I), CoIIPc−2/CoIPc−2 (II), CoIIIPc−2/CoIIPc−2 (III), and CoIIIPc−1/CoIIIPc−2 (IV) using spectroelectrochemistry. The last process (V) could not be ascertained by spectroelectrochemistry but is associated with ring oxidation. Upon reduction or oxidation, the Q band of the non-peripherally substituted complex became less red shifted compared to that of its peripherally substituted counterpart.
- Full Text:
- Date Issued: 2009
Thermal ecophysiology of seven carrion‐feeding blowflies in Southern Africa
- Richards, Cameron S, Price, Benjamin W, Villet, Martin H
- Authors: Richards, Cameron S , Price, Benjamin W , Villet, Martin H
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442384 , vital:73980 , https://doi.org/10.1111/j.1570-7458.2009.00824.x
- Description: A variety of temperature thresholds for larvae, pupae, and adults of seven African species of carrion‐feeding blowflies (Diptera: Calliphoridae) was measured and compared to understand their basic thermal biology and the influence of temperature on their behaviour. Calliphoraácroceipalpis (Jaennicke) had consistently lower temperature thresholds than all other species tested for all larval (42.9á░C), pupal (16.6á░C), and adult (45.6á░C) stages. Larvae (50.1á░C) and adults (53.4á░C) of Chrysomyaámarginalis (Robineau‐Desvoidy) had higher upper lethal temperature thresholds than all other species and weighed more than all other species. Pupae and adults of both Chrysomyaáalbiceps (Wiedemann) and Luciliaásericata (Meigen) had similar temperature thresholds, whereas Chrysomyaáputoria (Wiedemann), Chrysomyaáchloropyga (Wiedemann), and Chrysomyaámegacephala (Fabricius) had inconsistent rank temperature thresholds between the larval, pupal, and adult stages. With a few minor exceptions, the nervous activity, muscle activity, and death thresholds in female adult flies responded at higher temperatures than conspecific male flies for all species tested. Similarly, female adult flies weighed consistently more than conspecific male flies for all species tested, except Ca.ácroceipalpis. These data suggest that there is a phylogenetic component to the thermal biology of blowflies, because Ca.ácroceipalpis belongs to a primarily Holarctic genus and shows adaptation to that climate even though it inhabits Africa. Comparisons between these temperature thresholds and the distributions of blowfly species present on three rhinoceros carcasses suggest that blowfly larvae with high upper lethal temperature thresholds (particularly C.ámarginalis) dominate in interspecific competition on the carcass by raising the temperature of the amassed maggots above the thresholds of other carrion‐feeding blowflies, through metabolically generated heat.
- Full Text:
- Date Issued: 2009
- Authors: Richards, Cameron S , Price, Benjamin W , Villet, Martin H
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442384 , vital:73980 , https://doi.org/10.1111/j.1570-7458.2009.00824.x
- Description: A variety of temperature thresholds for larvae, pupae, and adults of seven African species of carrion‐feeding blowflies (Diptera: Calliphoridae) was measured and compared to understand their basic thermal biology and the influence of temperature on their behaviour. Calliphoraácroceipalpis (Jaennicke) had consistently lower temperature thresholds than all other species tested for all larval (42.9á░C), pupal (16.6á░C), and adult (45.6á░C) stages. Larvae (50.1á░C) and adults (53.4á░C) of Chrysomyaámarginalis (Robineau‐Desvoidy) had higher upper lethal temperature thresholds than all other species and weighed more than all other species. Pupae and adults of both Chrysomyaáalbiceps (Wiedemann) and Luciliaásericata (Meigen) had similar temperature thresholds, whereas Chrysomyaáputoria (Wiedemann), Chrysomyaáchloropyga (Wiedemann), and Chrysomyaámegacephala (Fabricius) had inconsistent rank temperature thresholds between the larval, pupal, and adult stages. With a few minor exceptions, the nervous activity, muscle activity, and death thresholds in female adult flies responded at higher temperatures than conspecific male flies for all species tested. Similarly, female adult flies weighed consistently more than conspecific male flies for all species tested, except Ca.ácroceipalpis. These data suggest that there is a phylogenetic component to the thermal biology of blowflies, because Ca.ácroceipalpis belongs to a primarily Holarctic genus and shows adaptation to that climate even though it inhabits Africa. Comparisons between these temperature thresholds and the distributions of blowfly species present on three rhinoceros carcasses suggest that blowfly larvae with high upper lethal temperature thresholds (particularly C.ámarginalis) dominate in interspecific competition on the carcass by raising the temperature of the amassed maggots above the thresholds of other carrion‐feeding blowflies, through metabolically generated heat.
- Full Text:
- Date Issued: 2009
Traditional food crops as a source of community resilience in Zimbabwe
- Shava, Soul, O'Donoghue, Rob B, Krasny, Marianne E, Zazu, Clayton
- Authors: Shava, Soul , O'Donoghue, Rob B , Krasny, Marianne E , Zazu, Clayton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/438804 , vital:73501 , xlink:href="https://doi.org/10.1080/18186870903101982"
- Description: This article draws on local narratives and observations of food sustenance practices in relocated farming communities in Sebakwe, Zimbabwe. Local knowledge on traditional food crops and related agricultural practices was proven to be a source of local community resilience, enabling residents to sustain their livelihoods. Local community agency in maintaining, cultivating and processing traditional food crops was found to sustain their culture and livelihoods, thereby providing community resilience in a changing environment.
- Full Text:
- Date Issued: 2009
- Authors: Shava, Soul , O'Donoghue, Rob B , Krasny, Marianne E , Zazu, Clayton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/438804 , vital:73501 , xlink:href="https://doi.org/10.1080/18186870903101982"
- Description: This article draws on local narratives and observations of food sustenance practices in relocated farming communities in Sebakwe, Zimbabwe. Local knowledge on traditional food crops and related agricultural practices was proven to be a source of local community resilience, enabling residents to sustain their livelihoods. Local community agency in maintaining, cultivating and processing traditional food crops was found to sustain their culture and livelihoods, thereby providing community resilience in a changing environment.
- Full Text:
- Date Issued: 2009
Understanding social learning processes in a citrus farming community of practice
- Authors: Downsborough, Linda
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386949 , vital:68191 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122819"
- Description: This paper focuses on what would traditionally be termed ‘non-formal’ learning processes in the context of a case study examining how citrus farming communities in the Patensie Valley in the Eastern Cape in South Africa were learning conservation practices. Communities of Practice theory was used to provide a conceptual framework for researching these learning interactions. Through historical and other qualitative research methods, I was able to establish that farmers in this community of practice learned mainly through responding to change and uncertainty, through forming and drawing on networks and community structures, through intergenerational learning, and through various interactions with each other. The historical research also pointed to the significance of policy and market-based changes in farmer learning, and their attachment to the land, which is shaped through historical associations with the land, and through embedded relations in farming practice cultures. The paper provides an example of how Communities of Practice theory, complemented by historical research, can be used to understand non-formal learning.
- Full Text:
- Date Issued: 2009
- Authors: Downsborough, Linda
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386949 , vital:68191 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122819"
- Description: This paper focuses on what would traditionally be termed ‘non-formal’ learning processes in the context of a case study examining how citrus farming communities in the Patensie Valley in the Eastern Cape in South Africa were learning conservation practices. Communities of Practice theory was used to provide a conceptual framework for researching these learning interactions. Through historical and other qualitative research methods, I was able to establish that farmers in this community of practice learned mainly through responding to change and uncertainty, through forming and drawing on networks and community structures, through intergenerational learning, and through various interactions with each other. The historical research also pointed to the significance of policy and market-based changes in farmer learning, and their attachment to the land, which is shaped through historical associations with the land, and through embedded relations in farming practice cultures. The paper provides an example of how Communities of Practice theory, complemented by historical research, can be used to understand non-formal learning.
- Full Text:
- Date Issued: 2009
Universal digital inclusion: Beyond connectivity, affordability and capability
- Thinyane, Mamello, Terzoli, Alfredo
- Authors: Thinyane, Mamello , Terzoli, Alfredo
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430876 , vital:72724 , https://ieeexplore.ieee.org/abstract/document/5338911
- Description: Traditionally digital marginalization and exclusion were understood to be a factor of connectivity to the Internet, affordability of the technology, and the capability of the communities to utilize the technology. ICT for development (ICT4D) interventions have been undertaken that address these specific factors of marginalization, however, it remains that com-munities are still excluded from the global knowledge society. In this paper we argue that key factors towards reaching greater inclusion and participation of the digitally marginalized communities, are the knowledge-centricity and context-sensitivity of the undertaken interven-tions. The solutions developed, and the services deployed, must intrin-sically encapsulate the local knowledge within the community of de-ployment. Based on this premise we have developed an architectural framework, named PIASK, that formalizes the contextualization of the developed applications within the socio-technical environment and po-sitions them within the local knowledge system of the community. We highlight the components of this architecture and discuss its implemen-tation through a knowledge platform for a community in South Africa.
- Full Text:
- Date Issued: 2009
- Authors: Thinyane, Mamello , Terzoli, Alfredo
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430876 , vital:72724 , https://ieeexplore.ieee.org/abstract/document/5338911
- Description: Traditionally digital marginalization and exclusion were understood to be a factor of connectivity to the Internet, affordability of the technology, and the capability of the communities to utilize the technology. ICT for development (ICT4D) interventions have been undertaken that address these specific factors of marginalization, however, it remains that com-munities are still excluded from the global knowledge society. In this paper we argue that key factors towards reaching greater inclusion and participation of the digitally marginalized communities, are the knowledge-centricity and context-sensitivity of the undertaken interven-tions. The solutions developed, and the services deployed, must intrin-sically encapsulate the local knowledge within the community of de-ployment. Based on this premise we have developed an architectural framework, named PIASK, that formalizes the contextualization of the developed applications within the socio-technical environment and po-sitions them within the local knowledge system of the community. We highlight the components of this architecture and discuss its implemen-tation through a knowledge platform for a community in South Africa.
- Full Text:
- Date Issued: 2009
Utopianism and educational processes in the United Nations Decade of Education for Sustainable Development
- Authors: Lotz-Sisitka, Heila
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184756 , vital:44269 , xlink:href="https://cjee.lakeheadu.ca/article/view/866"
- Description: Recent international policy literature on Education for Sustainable Development puts forward utopian concepts of sustainable development and transformed learning as objects for educational thinking and practice. This paper, drawing on three illustrative educational investigations with youth in a South African context, critically examines how we might engage with utopian concepts such as those put forward in the United Nations Decade of Education for Sustainable Development. It incorporates an engagement with other related utopian concepts such as democracy and social justice, which feature strongly in post-apartheid societal reconstruction in South Africa. The paper argues that if we are to avoid valuable utopian concepts such as democracy, sustainability, and social justice from becoming doxic knowledge, a reflexive realist orientation might best guide our educational engagements with such concepts. Such an approach to utopianism would take account of contextual realities and situated learning processes, and foster a creativity of action that is constructivist in nature, but not relativist.
- Full Text:
- Date Issued: 2009
- Authors: Lotz-Sisitka, Heila
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184756 , vital:44269 , xlink:href="https://cjee.lakeheadu.ca/article/view/866"
- Description: Recent international policy literature on Education for Sustainable Development puts forward utopian concepts of sustainable development and transformed learning as objects for educational thinking and practice. This paper, drawing on three illustrative educational investigations with youth in a South African context, critically examines how we might engage with utopian concepts such as those put forward in the United Nations Decade of Education for Sustainable Development. It incorporates an engagement with other related utopian concepts such as democracy and social justice, which feature strongly in post-apartheid societal reconstruction in South Africa. The paper argues that if we are to avoid valuable utopian concepts such as democracy, sustainability, and social justice from becoming doxic knowledge, a reflexive realist orientation might best guide our educational engagements with such concepts. Such an approach to utopianism would take account of contextual realities and situated learning processes, and foster a creativity of action that is constructivist in nature, but not relativist.
- Full Text:
- Date Issued: 2009
Variability in the fractionation of stable isotopes during degradation of two intertidal red algae
- Hill, Jaclyn M, McQuaid, Christopher D
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444649 , vital:74257 , https://doi.org/10.1016/j.ecss.2009.02.001
- Description: Macroalgae contribute to intertidal food webs primarily as detritus, with unclear implications for food web studies using stable isotope analysis. We examined differences in the thallus parts of two South African rhodophytes (Gelidium pristoides and Hypnea spicifera) and changes in overall δ13C, δ15N signatures and C:N ratios during degradation in both the field and laboratory. We hypothesized that both degrading macroalgal tissue and macroalgal-derived suspended particulate material (SPM) would show negligible changes in δ13C, but enriched δ15N signatures and lower C:N ratios relative to healthy plants. Only C:N laboratory ratios conformed to predictions, with both species of macroalgae showing decomposition related changes in δ13C and significant depletions in δ15N in both the field and laboratory. In the laboratory, algal tissue and SPM from each species behaved similarly (though some effects were non-significant) but with differing strengths. Gelidium pristoides δ13C increased and C:N ratios decreased over time in tissue and SPM; δ15N became depleted only in SPM. Hypnea spicifera, δ13C, δ15N and C:N ratios all decreased during degradation in both SPM and algae.
- Full Text:
- Date Issued: 2009
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444649 , vital:74257 , https://doi.org/10.1016/j.ecss.2009.02.001
- Description: Macroalgae contribute to intertidal food webs primarily as detritus, with unclear implications for food web studies using stable isotope analysis. We examined differences in the thallus parts of two South African rhodophytes (Gelidium pristoides and Hypnea spicifera) and changes in overall δ13C, δ15N signatures and C:N ratios during degradation in both the field and laboratory. We hypothesized that both degrading macroalgal tissue and macroalgal-derived suspended particulate material (SPM) would show negligible changes in δ13C, but enriched δ15N signatures and lower C:N ratios relative to healthy plants. Only C:N laboratory ratios conformed to predictions, with both species of macroalgae showing decomposition related changes in δ13C and significant depletions in δ15N in both the field and laboratory. In the laboratory, algal tissue and SPM from each species behaved similarly (though some effects were non-significant) but with differing strengths. Gelidium pristoides δ13C increased and C:N ratios decreased over time in tissue and SPM; δ15N became depleted only in SPM. Hypnea spicifera, δ13C, δ15N and C:N ratios all decreased during degradation in both SPM and algae.
- Full Text:
- Date Issued: 2009
Water-soluble phthalocyanines mediated photodynamic effect on mesothelioma cells
- Saydan, Nil, Durmus, Mahmut, Dizge, Meltem G, Yaman, Hanif, Gürek, Ayşe G, Antunes, Edith M, Nyokong, Tebello, Ahsen, Vefa
- Authors: Saydan, Nil , Durmus, Mahmut , Dizge, Meltem G , Yaman, Hanif , Gürek, Ayşe G , Antunes, Edith M , Nyokong, Tebello , Ahsen, Vefa
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263480 , vital:53631 , xlink:href="https://doi.org/10.1142/S1088424609000863"
- Description: The new peripherally 2-mercaptopyridine tetrasubstituted zinc phthalocyanine (2) and its quaternized derivative (3) have been synthesized and characterized by elemental analysis, IR, 1H NMR spectroscopy, electronic spectroscopy and mass spectra. The quaternized compound (3) shows excellent solubility in water, which makes it a potential photosensitizer for use in photodynamic therapy (PDT) of cancer. Fluorescence and singlet oxygen quantum yield measurements were conducted on 2-mercaptopyridine appended zinc phthalocyanines in dimethylsulphoxide (DMSO) for both the non-ionic (2) and quaternized (3) derivatives, and in aqueous media for the water-soluble complex 3. General trends are described for fluorescence and singlet oxygen quantum yields of these compounds. In this study, the cells were incubated with a novel water-soluble zinc phthalocyanine derivative (3) and thereafter the cells were illuminated using broad-band incoherent light source of various energy levels. Cytotoxicity of PDT on two pleural malign mesothelioma cell lines was determined by colorimetric proliferation assay. In addition, after PDT treatment, determination of activity matrix metalloproteinases (MMPs) were evaluated using gelatine zymography.
- Full Text:
- Date Issued: 2009
- Authors: Saydan, Nil , Durmus, Mahmut , Dizge, Meltem G , Yaman, Hanif , Gürek, Ayşe G , Antunes, Edith M , Nyokong, Tebello , Ahsen, Vefa
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263480 , vital:53631 , xlink:href="https://doi.org/10.1142/S1088424609000863"
- Description: The new peripherally 2-mercaptopyridine tetrasubstituted zinc phthalocyanine (2) and its quaternized derivative (3) have been synthesized and characterized by elemental analysis, IR, 1H NMR spectroscopy, electronic spectroscopy and mass spectra. The quaternized compound (3) shows excellent solubility in water, which makes it a potential photosensitizer for use in photodynamic therapy (PDT) of cancer. Fluorescence and singlet oxygen quantum yield measurements were conducted on 2-mercaptopyridine appended zinc phthalocyanines in dimethylsulphoxide (DMSO) for both the non-ionic (2) and quaternized (3) derivatives, and in aqueous media for the water-soluble complex 3. General trends are described for fluorescence and singlet oxygen quantum yields of these compounds. In this study, the cells were incubated with a novel water-soluble zinc phthalocyanine derivative (3) and thereafter the cells were illuminated using broad-band incoherent light source of various energy levels. Cytotoxicity of PDT on two pleural malign mesothelioma cell lines was determined by colorimetric proliferation assay. In addition, after PDT treatment, determination of activity matrix metalloproteinases (MMPs) were evaluated using gelatine zymography.
- Full Text:
- Date Issued: 2009
Wax discrimination in the Lesser Honeyguide Indicator minor
- Authors: Hepburn, H Randall
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448440 , vital:74730 , https://doi.org/10.2989/OSTRICH.2009.80.2.11.838
- Description: Beeswaxes consist of complex mixtures of homologous neutral lipids that vary among species of honeybees but share many compounds in common (Aichholz and Lorbeer 1999). However, the beeswaxes of subspecies of the honeybee, Apis mellifera, can only be distinguished after careful calculation of the peak elution pattern area ratios of selected compounds (Brand-Garnys and Sprenger 1988). This is of interest in an ornithological context because honeyguides (Indicatoridae) subsist in large measure on the pillage of the combs of honeybees (Friedman 1955) and their enzymic capacity to digest beeswax has been demonstrated experimentally (Friedmann and Kern 1956, Diamond and Place 1988, Downs et al. 2002). Honeyguides can utilise olfactory orientation to find beeswax (Stager 1967, Archer and Glen 1969) and can even detect and seek out the combs of honeybees stored in hives devoid of bees in darkened out-buildings (HRH pers. obs.).
- Full Text:
- Date Issued: 2009
- Authors: Hepburn, H Randall
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448440 , vital:74730 , https://doi.org/10.2989/OSTRICH.2009.80.2.11.838
- Description: Beeswaxes consist of complex mixtures of homologous neutral lipids that vary among species of honeybees but share many compounds in common (Aichholz and Lorbeer 1999). However, the beeswaxes of subspecies of the honeybee, Apis mellifera, can only be distinguished after careful calculation of the peak elution pattern area ratios of selected compounds (Brand-Garnys and Sprenger 1988). This is of interest in an ornithological context because honeyguides (Indicatoridae) subsist in large measure on the pillage of the combs of honeybees (Friedman 1955) and their enzymic capacity to digest beeswax has been demonstrated experimentally (Friedmann and Kern 1956, Diamond and Place 1988, Downs et al. 2002). Honeyguides can utilise olfactory orientation to find beeswax (Stager 1967, Archer and Glen 1969) and can even detect and seek out the combs of honeybees stored in hives devoid of bees in darkened out-buildings (HRH pers. obs.).
- Full Text:
- Date Issued: 2009
What's wrong with Walden Two?
- Authors: Tabensky, Pedro
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305791 , vital:58612 , xlink:href="https://hdl.handle.net/10520/EJC96066"
- Description: Despite being eminently forgettable from the literary point of view, B. F. Skinner's novel, Walden Two, provides us with an excellent opportunity, not so much to show what is wrong with mainstream accounts of free will, as Robert Kane thinks, but rather to explore another key and importantly neglected condition for genuine agency; namely, that properly lived human lives are those that are and must continue to be vulnerable to unforseable reversals, as Aldous Huxley speculates in his Brave New World. In short, I argue, perhaps scandalously, that one of the central conditions for genuine agency is that our lives are and must continue to be, to a large extent, out of our personal control. The promise of too much personal control, not too little (as Kane thinks), is what is wrong with Skinner's social utopia.
- Full Text:
- Date Issued: 2009
- Authors: Tabensky, Pedro
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305791 , vital:58612 , xlink:href="https://hdl.handle.net/10520/EJC96066"
- Description: Despite being eminently forgettable from the literary point of view, B. F. Skinner's novel, Walden Two, provides us with an excellent opportunity, not so much to show what is wrong with mainstream accounts of free will, as Robert Kane thinks, but rather to explore another key and importantly neglected condition for genuine agency; namely, that properly lived human lives are those that are and must continue to be vulnerable to unforseable reversals, as Aldous Huxley speculates in his Brave New World. In short, I argue, perhaps scandalously, that one of the central conditions for genuine agency is that our lives are and must continue to be, to a large extent, out of our personal control. The promise of too much personal control, not too little (as Kane thinks), is what is wrong with Skinner's social utopia.
- Full Text:
- Date Issued: 2009
White Guys Can't Beg
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229796 , vital:49711 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
- Date Issued: 2009
- Authors: Krueger, Anton
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229796 , vital:49711 , xlink:href="https://hdl.handle.net/10520/EJC47812"
- Full Text:
- Date Issued: 2009
Why ontology matters to reviewing environmental education
- Authors: Lotz-Sisitka, Heila
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182646 , vital:43850 , xlink:href="https://doi.org/10.1080/13504620902807550"
- Description: This paper responds to a keynote paper presented by William Scott at the 2007 World Environmental Education Congress held in Durban, South Africa. The keynote address reviewed 30 years of environmental education research. In this response to William Scott's paper I contemplate the way in which environmental education research may enable reflexivity in modernity and develop knowledge that can serve as cultural mediator between individual and society. Through emphasizing ontology, I consider the reality of global knowledge production in relation to the way in which ontology may influence the reasons how and why we come to do particular forms of research, providing an ontological reference for the ever‐expanding pluralism that characterizes the field of environmental education research. The paper comments on various aspects of the Scott paper, but presents an argument for not only valuing pluralism, methodological experimentation and ‘reaching out’, but for embracing the cosmopolitan implications of wider ontological referents of environmental concerns in environmental education research. The paper argues that research in environmental education ought to become ontologically defensible at both local and global scales.
- Full Text:
- Date Issued: 2009
- Authors: Lotz-Sisitka, Heila
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182646 , vital:43850 , xlink:href="https://doi.org/10.1080/13504620902807550"
- Description: This paper responds to a keynote paper presented by William Scott at the 2007 World Environmental Education Congress held in Durban, South Africa. The keynote address reviewed 30 years of environmental education research. In this response to William Scott's paper I contemplate the way in which environmental education research may enable reflexivity in modernity and develop knowledge that can serve as cultural mediator between individual and society. Through emphasizing ontology, I consider the reality of global knowledge production in relation to the way in which ontology may influence the reasons how and why we come to do particular forms of research, providing an ontological reference for the ever‐expanding pluralism that characterizes the field of environmental education research. The paper comments on various aspects of the Scott paper, but presents an argument for not only valuing pluralism, methodological experimentation and ‘reaching out’, but for embracing the cosmopolitan implications of wider ontological referents of environmental concerns in environmental education research. The paper argues that research in environmental education ought to become ontologically defensible at both local and global scales.
- Full Text:
- Date Issued: 2009