Rock magnetic stratigraphy of a mafic layered sill: a key to the Karoo volcanics plumbing system
- Maes, S M, Ferré, E E, Tikoff, B, Brown, P E, Marsh, Julian S
- Authors: Maes, S M , Ferré, E E , Tikoff, B , Brown, P E , Marsh, Julian S
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144901 , vital:38389 , https://doi.org/10.1016/j.jvolgeores.2005.07.038
- Description: The Insizwa sill is an 1 km-thick subhorizontal layered mafic intrusion and part of the Karoo Large Igneous Province in South Africa. This well-exposed intrusion consists of several superimposed petrologically and geochemically distinct units. Magnetic methods were used to study the intrusion in order to constrain the physical processes active in these types of bodies during crystallization. Rock magnetism studies indicate that within different petrologic units bulk susceptibility is controlled by primary magnetite (with minor pyrrhotite) and/or paramagnetic minerals (olivine, pyroxene). New magnetic data based on 659 specimens obtained from 3 vertical borehole cores, each spaced 5 km apart, confirm the prominent vertical zonation in low field magnetic susceptibility (Klf), degree of anisotropy (Pj) and orientation of the anisotropy of magnetic susceptibility (AMS) axes.
- Full Text:
- Authors: Maes, S M , Ferré, E E , Tikoff, B , Brown, P E , Marsh, Julian S
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144901 , vital:38389 , https://doi.org/10.1016/j.jvolgeores.2005.07.038
- Description: The Insizwa sill is an 1 km-thick subhorizontal layered mafic intrusion and part of the Karoo Large Igneous Province in South Africa. This well-exposed intrusion consists of several superimposed petrologically and geochemically distinct units. Magnetic methods were used to study the intrusion in order to constrain the physical processes active in these types of bodies during crystallization. Rock magnetism studies indicate that within different petrologic units bulk susceptibility is controlled by primary magnetite (with minor pyrrhotite) and/or paramagnetic minerals (olivine, pyroxene). New magnetic data based on 659 specimens obtained from 3 vertical borehole cores, each spaced 5 km apart, confirm the prominent vertical zonation in low field magnetic susceptibility (Klf), degree of anisotropy (Pj) and orientation of the anisotropy of magnetic susceptibility (AMS) axes.
- Full Text:
SA scientist one of the top five female physical scientists
- Authors: Limson, Janice L
- Date: 2008
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7189 , http://hdl.handle.net/10962/d1006283 , http://www.scienceinafrica.co.za/2008/october/nyokong.htm
- Description: South African scientist Professor Tebello Nyokong scoops 2009 L’ORÉAL-UNESCO For Women in Science Award. Announced on November 10, South African scientist Professor Tebello Nyokong has become the first South African scientist to win the L’ORÉALUNESCO award for women in science for research in physical sciences.
- Full Text:
- Authors: Limson, Janice L
- Date: 2008
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7189 , http://hdl.handle.net/10962/d1006283 , http://www.scienceinafrica.co.za/2008/october/nyokong.htm
- Description: South African scientist Professor Tebello Nyokong scoops 2009 L’ORÉAL-UNESCO For Women in Science Award. Announced on November 10, South African scientist Professor Tebello Nyokong has become the first South African scientist to win the L’ORÉALUNESCO award for women in science for research in physical sciences.
- Full Text:
Sing a swansong for the SABC as we know it : keep public broadcasting, redistribute the broadcaster
- Authors: Berger, Guy
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159326 , vital:40288 , https://hdl.handle.net/10520/EJC140098
- Description: Behind the dragged-out confrontations around the SABC are a politics of paralysis. That's not necessarily a bad thing if the alternative is the broadcaster being a tool of a single particular force. But it's also not exactly first prize for South Africans. Power is divided across so many centres that no single force has been able to easily prevail on SABC during the year.
- Full Text:
- Authors: Berger, Guy
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159326 , vital:40288 , https://hdl.handle.net/10520/EJC140098
- Description: Behind the dragged-out confrontations around the SABC are a politics of paralysis. That's not necessarily a bad thing if the alternative is the broadcaster being a tool of a single particular force. But it's also not exactly first prize for South Africans. Power is divided across so many centres that no single force has been able to easily prevail on SABC during the year.
- Full Text:
Social and ecological trade offs in combating land degradation: The case of invasion by a woody shrub (Euryops floribundus) at Macubeni, South Africa
- Shackleton, Charlie M, Gambiza, James
- Authors: Shackleton, Charlie M , Gambiza, James
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181235 , vital:43711 , xlink:href="https://doi.org/10.1002/ldr.849"
- Description: Woody plant invasions, either of alien or indigenous species, are deemed to result in loss of ecosystem goods and services in many areas throughout the world, resulting in significant degradation and economic costs. Invasion of Euryops floribundus, a species indigenous to South Africa, is perceived to have reduced the grazing available for domestic livestock. Consequently, a programme of manual eradication has been implemented to improve the grazing resource and provide jobs for poverty alleviation. However, there is potential for a conflict of interest as our study shows that almost all households rely on Euryops for fuel and at times fencing material, whereas only a minority of households own livestock. Moreover, comparison of invaded and non-invaded sites indicated that the invaded sites harbour greater plant species richness and higher grass culm density per unit area of grass cover, as well as higher forb and litter cover. While invaded sites had lower grass cover, overall plant cover was no different between invaded and non-invaded sites. Multivariate analysis indicated no obvious differentiation in community composition between invaded and non-invaded areas, suggesting stronger drivers of community composition other than Euryops invasion presumed to be facilitated by the effects of high livestock densities. Overall, our study suggests that the clearing operation may well benefit from a better understanding of the social needs, perceptions of degradation by the various stakeholders and ecological dynamics of the area, especially local reliance on the resources, and the dynamics of the invasion, particularly its extent, rate of spread and susceptibility for re-invasion in the cleared areas.
- Full Text:
- Authors: Shackleton, Charlie M , Gambiza, James
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181235 , vital:43711 , xlink:href="https://doi.org/10.1002/ldr.849"
- Description: Woody plant invasions, either of alien or indigenous species, are deemed to result in loss of ecosystem goods and services in many areas throughout the world, resulting in significant degradation and economic costs. Invasion of Euryops floribundus, a species indigenous to South Africa, is perceived to have reduced the grazing available for domestic livestock. Consequently, a programme of manual eradication has been implemented to improve the grazing resource and provide jobs for poverty alleviation. However, there is potential for a conflict of interest as our study shows that almost all households rely on Euryops for fuel and at times fencing material, whereas only a minority of households own livestock. Moreover, comparison of invaded and non-invaded sites indicated that the invaded sites harbour greater plant species richness and higher grass culm density per unit area of grass cover, as well as higher forb and litter cover. While invaded sites had lower grass cover, overall plant cover was no different between invaded and non-invaded sites. Multivariate analysis indicated no obvious differentiation in community composition between invaded and non-invaded areas, suggesting stronger drivers of community composition other than Euryops invasion presumed to be facilitated by the effects of high livestock densities. Overall, our study suggests that the clearing operation may well benefit from a better understanding of the social needs, perceptions of degradation by the various stakeholders and ecological dynamics of the area, especially local reliance on the resources, and the dynamics of the invasion, particularly its extent, rate of spread and susceptibility for re-invasion in the cleared areas.
- Full Text:
Social Services and Benefits
- Authors: Kruuse, Helen
- Date: 2008
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/54211 , vital:26405 , https://store.lexisnexis.co.za/products/family-law-service-skuZASKUPG642
- Description: Family Law Service is a subscription based product including both the printed loose-leaf and LexisMobile publications. Updates for 12 months (print and mobile) are included in the price. Family Law Service covers aspects of law pertaining to the family, including domestic violence, the Law of Islam, same- sex life partnerships, the effects of the Children's Act, 2008 and anti-trafficking law in South Africa. Family Law Service is maintained in three volumes with commentary and legislation, and with two service issues published a year.
- Full Text: false
- Authors: Kruuse, Helen
- Date: 2008
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/54211 , vital:26405 , https://store.lexisnexis.co.za/products/family-law-service-skuZASKUPG642
- Description: Family Law Service is a subscription based product including both the printed loose-leaf and LexisMobile publications. Updates for 12 months (print and mobile) are included in the price. Family Law Service covers aspects of law pertaining to the family, including domestic violence, the Law of Islam, same- sex life partnerships, the effects of the Children's Act, 2008 and anti-trafficking law in South Africa. Family Law Service is maintained in three volumes with commentary and legislation, and with two service issues published a year.
- Full Text: false
Spam Construction Trends
- Irwin, Barry V W, Friedman, Blake
- Authors: Irwin, Barry V W , Friedman, Blake
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428762 , vital:72534 , https://www.researchgate.net/profile/Barry-Ir-win/publication/220803159_Spam_Construction_Trends/links/53fc76bd0cf2dca8ffff22fb/Spam-Construction-Trends.pdf
- Description: This paper replicates and extends Observed Trends in Spam Construction Tech-niques: A Case Study of Spam Evolution. A corpus of 169,274 spam email was col-lected over a period of five years. Each spam email was tested for construction techniques using SpamAssassin’s spamicity tests. The results of these tests were col-lected in a database. Formal definitions of Pu and Webb’s co-existence, extinction and complex trends were developed and applied to the results within the database. A comparison of the Spam Evolution Study and this paper’s results took place to de-termine the relevance of the trends. A geolocation analysis was conducted on the corpus, as an extension, to determine the major geographic sources of the corpus.
- Full Text:
- Authors: Irwin, Barry V W , Friedman, Blake
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428762 , vital:72534 , https://www.researchgate.net/profile/Barry-Ir-win/publication/220803159_Spam_Construction_Trends/links/53fc76bd0cf2dca8ffff22fb/Spam-Construction-Trends.pdf
- Description: This paper replicates and extends Observed Trends in Spam Construction Tech-niques: A Case Study of Spam Evolution. A corpus of 169,274 spam email was col-lected over a period of five years. Each spam email was tested for construction techniques using SpamAssassin’s spamicity tests. The results of these tests were col-lected in a database. Formal definitions of Pu and Webb’s co-existence, extinction and complex trends were developed and applied to the results within the database. A comparison of the Spam Evolution Study and this paper’s results took place to de-termine the relevance of the trends. A geolocation analysis was conducted on the corpus, as an extension, to determine the major geographic sources of the corpus.
- Full Text:
Spontaneous charge transfer between zinc tetramethyl-tetra-2, 3-pyridinoporphyrazine and CdTe and ZnS quantum dots
- Moeno, Sharon, Idowu, Mopelola, Nyokong, Tebello
- Authors: Moeno, Sharon , Idowu, Mopelola , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265997 , vital:53908 , xlink:href="https://doi.org/10.1016/j.ica.2008.02.048"
- Description: Zinc tetramethyl-tetra-2,3-pyridinoporphyrazine (ZnTmtppa(-2)) gets reduced to the ZnTmtppa(-3) species on interaction with CdTe QDs capped with 2-mercaptoethanol (2-ME) or thioglycolic acid (TGA) and ZnS QDs capped with 2-ME. The interaction occurs without photolysis. The fluorescence of the QDs is quenched by ZnTmtppa resulting in large quenching constants. Binding of ZnTmtppa to QDs occurs with two molecules of the former binding to the latter.
- Full Text:
- Authors: Moeno, Sharon , Idowu, Mopelola , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265997 , vital:53908 , xlink:href="https://doi.org/10.1016/j.ica.2008.02.048"
- Description: Zinc tetramethyl-tetra-2,3-pyridinoporphyrazine (ZnTmtppa(-2)) gets reduced to the ZnTmtppa(-3) species on interaction with CdTe QDs capped with 2-mercaptoethanol (2-ME) or thioglycolic acid (TGA) and ZnS QDs capped with 2-ME. The interaction occurs without photolysis. The fluorescence of the QDs is quenched by ZnTmtppa resulting in large quenching constants. Binding of ZnTmtppa to QDs occurs with two molecules of the former binding to the latter.
- Full Text:
Sterols and sterolins in Hypoxis hemerocallidea (African potato)
- Nair, V D P, Kanfer, Isadore
- Authors: Nair, V D P , Kanfer, Isadore
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6417 , http://hdl.handle.net/10962/d1006535
- Description: Commercially available health supplements and herbal remedies containing sterols and sterolins, either from African potato (Hypoxis hemerocallidea) alone, or whether enriched with sterols and sterolins, are claimed to be efficacious in the treatment of a variety of ailments. Sterols and sterolins in African potato are purported to be the relevant constituents that are required for the therapeutic claims of such products. A patent describing the extraction of sterolins from African potato plant material has claimed that approximately 9 mg sterolins can be isolated from 100 g of an enriched aqueous African potato extract. Our analysis of African potato plant material and its sterol and sterolin content, when similarly prepared, shows that the measureable content of sterols and sterolins in African potato is far less than the amounts of these compounds that have been claimed to be necessary for therapeutic benefit. We conclude that therapeutic claims relating to sterol and sterolin content in African potato are unsubstantiated, in view of the extremely low content of such compounds that we have isolated from our plant material, and in products containing African potato, or extracts thereof.
- Full Text:
- Authors: Nair, V D P , Kanfer, Isadore
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6417 , http://hdl.handle.net/10962/d1006535
- Description: Commercially available health supplements and herbal remedies containing sterols and sterolins, either from African potato (Hypoxis hemerocallidea) alone, or whether enriched with sterols and sterolins, are claimed to be efficacious in the treatment of a variety of ailments. Sterols and sterolins in African potato are purported to be the relevant constituents that are required for the therapeutic claims of such products. A patent describing the extraction of sterolins from African potato plant material has claimed that approximately 9 mg sterolins can be isolated from 100 g of an enriched aqueous African potato extract. Our analysis of African potato plant material and its sterol and sterolin content, when similarly prepared, shows that the measureable content of sterols and sterolins in African potato is far less than the amounts of these compounds that have been claimed to be necessary for therapeutic benefit. We conclude that therapeutic claims relating to sterol and sterolin content in African potato are unsubstantiated, in view of the extremely low content of such compounds that we have isolated from our plant material, and in products containing African potato, or extracts thereof.
- Full Text:
Study South Africa
- International Education Association of South Africa (IEASA), Higher Education South Africa (Organization), Kishun, Roshen
- Authors: International Education Association of South Africa (IEASA) , Higher Education South Africa (Organization) , Kishun, Roshen
- Date: 2008
- Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/65010 , vital:28653 , ISBN 9780620415521
- Description: [Extract from message from Minister of Higher Education, Hon. Naledi Pandor]: The International Education Association of South Africa (IEASA) has produced yet another magnificent publication on higher education in South Africa It is an excellent source of information for everyone interested in universities and research in this country. It is especially useful for international students who plan to study in South Africa, and for people involved in developing international programmes. The theme of this edition, “The role of internationalisation in South Africa’s knowledge environment, is opportune at this juncture. It provides role-players in higher education with the opportunity to examine critical issues such as the place, purposes, benefits and limitations of internationalisation in the sector and the contribution internationalisation makes to the knowledge economy of our country. To participate effectively in the knowledge economy, South Africa has to grow its research base. For this, we need a pool of vibrant young researchers. South Africa is able to provide opportunities for groundbreaking research, and internationalisation provides students, academics and researchers with prospects to broaden the scope of their research. Exchange programmes, bilateral research connections, collaborative partnerships and other international links lend themselves to pathways through which local and international staff and students can expand their horizons and skills. In this way internationalisation can assist South Africa in realising its objectives. The South African higher education sector has identified priority areas in which it needs to develop human capital. They include science, technology and engineering. We can use international programmes to accelerate our capacity building plans and in particular the training and development of postgraduate students. Through research collaborations, for example, postgraduate students can be jointly trained and co-supervised with partners. This has beneficial outcomes for students, research partners and academics, as well as for the system as a whole. Aside from benefiting from sending our students abroad, South Africa also gains by receiving foreign students. International students bring with them different viewpoints, technologies and skills, which assist in developing new perspectives and techniques in South Africa Furthermore, cultural interaction enhances our own students' experiences. By studying together students come to understand and accept cultural differences and are enriched. These interactions, in turn, build positive relations which have positive long term benefits in developing economic and social links between people and countries, and which will help overcome newly surfaced problems of xenophobia in South Africa South Africa is currently host to more than 60,000 international students and many academics. The greatest proportion of international students and academics are from Africa particularly from the Southern African Development Community. As a host country we ensure high quality courses at universities, in order for our qualifications to be recognisable worldwide. South African institutions produce professionals who are highly sought- after around the world. This publication supports South Africa's education sector by providing information and by publicising our institutions and the sector as a whole. I would like to thank IEASA for the important role it plays in higher education. , 8th Edition
- Full Text:
- Authors: International Education Association of South Africa (IEASA) , Higher Education South Africa (Organization) , Kishun, Roshen
- Date: 2008
- Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/65010 , vital:28653 , ISBN 9780620415521
- Description: [Extract from message from Minister of Higher Education, Hon. Naledi Pandor]: The International Education Association of South Africa (IEASA) has produced yet another magnificent publication on higher education in South Africa It is an excellent source of information for everyone interested in universities and research in this country. It is especially useful for international students who plan to study in South Africa, and for people involved in developing international programmes. The theme of this edition, “The role of internationalisation in South Africa’s knowledge environment, is opportune at this juncture. It provides role-players in higher education with the opportunity to examine critical issues such as the place, purposes, benefits and limitations of internationalisation in the sector and the contribution internationalisation makes to the knowledge economy of our country. To participate effectively in the knowledge economy, South Africa has to grow its research base. For this, we need a pool of vibrant young researchers. South Africa is able to provide opportunities for groundbreaking research, and internationalisation provides students, academics and researchers with prospects to broaden the scope of their research. Exchange programmes, bilateral research connections, collaborative partnerships and other international links lend themselves to pathways through which local and international staff and students can expand their horizons and skills. In this way internationalisation can assist South Africa in realising its objectives. The South African higher education sector has identified priority areas in which it needs to develop human capital. They include science, technology and engineering. We can use international programmes to accelerate our capacity building plans and in particular the training and development of postgraduate students. Through research collaborations, for example, postgraduate students can be jointly trained and co-supervised with partners. This has beneficial outcomes for students, research partners and academics, as well as for the system as a whole. Aside from benefiting from sending our students abroad, South Africa also gains by receiving foreign students. International students bring with them different viewpoints, technologies and skills, which assist in developing new perspectives and techniques in South Africa Furthermore, cultural interaction enhances our own students' experiences. By studying together students come to understand and accept cultural differences and are enriched. These interactions, in turn, build positive relations which have positive long term benefits in developing economic and social links between people and countries, and which will help overcome newly surfaced problems of xenophobia in South Africa South Africa is currently host to more than 60,000 international students and many academics. The greatest proportion of international students and academics are from Africa particularly from the Southern African Development Community. As a host country we ensure high quality courses at universities, in order for our qualifications to be recognisable worldwide. South African institutions produce professionals who are highly sought- after around the world. This publication supports South Africa's education sector by providing information and by publicising our institutions and the sector as a whole. I would like to thank IEASA for the important role it plays in higher education. , 8th Edition
- Full Text:
Sustainability assessment using a unit-based sustainability assessment tool: The case of three teaching departments at Rhodes University, South Africa
- Authors: Togo, Muchaiteyi
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386863 , vital:68182 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122776"
- Description: A sustainability assessment study was performed with three teaching departments at Rhodes University – Ichthyology and Fisheries Science, Anthropology, and Accounting. The assessment used a Unit-based Sustainability Assessment Tool (USAT) and was guided by systems thinking and the ontological framework provided by critical realism. Results of the study showed that the Department of Ichthyology and Fisheries Science had a higher integration of sustainability issues in its activities than the other departments sampled, with Accounting having the lowest integration. Interviews conducted with departmental heads and content analyses of documents revealed differences in sustainability issues addressed and in approaches used in tackling them among these departments. The study is intended to inform the Mainstreaming of Environment and Sustainability in African (MESA) Universities Partnership, which promotes mainstreaming environment and sustainability in universities during the United Nations Decade of Education for Sustainable Development. The study does not provide answers to mainstreaming activities, but opens up space to debate and deliberate how to deal with the mainstreaming of sustainability in universities. It identified some of the challenges to be addressed in university-wide mainstreaming work, and affirmed the need for systems thinking in bringing about change at institutional level to extend changes taking place in individual teaching contexts.
- Full Text:
- Authors: Togo, Muchaiteyi
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386863 , vital:68182 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122776"
- Description: A sustainability assessment study was performed with three teaching departments at Rhodes University – Ichthyology and Fisheries Science, Anthropology, and Accounting. The assessment used a Unit-based Sustainability Assessment Tool (USAT) and was guided by systems thinking and the ontological framework provided by critical realism. Results of the study showed that the Department of Ichthyology and Fisheries Science had a higher integration of sustainability issues in its activities than the other departments sampled, with Accounting having the lowest integration. Interviews conducted with departmental heads and content analyses of documents revealed differences in sustainability issues addressed and in approaches used in tackling them among these departments. The study is intended to inform the Mainstreaming of Environment and Sustainability in African (MESA) Universities Partnership, which promotes mainstreaming environment and sustainability in universities during the United Nations Decade of Education for Sustainable Development. The study does not provide answers to mainstreaming activities, but opens up space to debate and deliberate how to deal with the mainstreaming of sustainability in universities. It identified some of the challenges to be addressed in university-wide mainstreaming work, and affirmed the need for systems thinking in bringing about change at institutional level to extend changes taking place in individual teaching contexts.
- Full Text:
Synthesis and electrochemical characterisation of a near infrared absorbing oxo vanadium (IV) octapentylthio-phthalocyanine
- Mbambisa, Gcineka, Nyokong, Tebello
- Authors: Mbambisa, Gcineka , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/266008 , vital:53909 , xlink:href="https://doi.org/10.1016/j.poly.2008.06.004"
- Description: The synthesis of an α-substituted phthalocyanine oxo vanadium(IV) 1,4,8,11,15,18,22,25-octapentathiophthalocyanine (4) which absorbs at 850 nm in dichloromethane is reported. The complex is purple in colour and becomes green on reduction. The cyclic and square wave voltammetries of the complex show five redox couples. The spectroelectrochemical data showed only ring based processes. The ring reduced species is observed at wavelengths greater than 680 nm rather than the usual 500–600 nm range typical of ring reduced phthalocyanine complexes.
- Full Text:
- Authors: Mbambisa, Gcineka , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/266008 , vital:53909 , xlink:href="https://doi.org/10.1016/j.poly.2008.06.004"
- Description: The synthesis of an α-substituted phthalocyanine oxo vanadium(IV) 1,4,8,11,15,18,22,25-octapentathiophthalocyanine (4) which absorbs at 850 nm in dichloromethane is reported. The complex is purple in colour and becomes green on reduction. The cyclic and square wave voltammetries of the complex show five redox couples. The spectroelectrochemical data showed only ring based processes. The ring reduced species is observed at wavelengths greater than 680 nm rather than the usual 500–600 nm range typical of ring reduced phthalocyanine complexes.
- Full Text:
Synthesis and photophysical properties of lead phthalocyanines
- Modibane, D.K., Nyokong, Tebello
- Authors: Modibane, D.K. , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268636 , vital:54216 , xlink:href="https://doi.org/10.1016/j.poly.2007.12.004"
- Description: This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.70 to 0.88 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom.
- Full Text:
- Authors: Modibane, D.K. , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268636 , vital:54216 , xlink:href="https://doi.org/10.1016/j.poly.2007.12.004"
- Description: This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.70 to 0.88 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom.
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Synthesis and solvent effects on the photophysicochemical properties of novel cadmium phenoxy phthalocyanines
- Chidawanyika, Wadzanai J U, Antunes, Edith M, Nyokong, Tebello
- Authors: Chidawanyika, Wadzanai J U , Antunes, Edith M , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268649 , vital:54217 , xlink:href="https://doi.org/10.1016/j.jphotochem.2007.09.020"
- Description: The syntheses of novel cadmium phenoxy complexes; tetrakis{1,(4)-tert-butylphenoxyphthalocyaninato}cadmium(II) (5a), tetrakis{1,(4)-phenoxyphthalocyaninato}cadmium(II) (5b), tetrakis{2,(3)-tert-butylphenoxyphthalocyaninato}cadmium(II) (6a) and tetrakis{2,(3)-phenoxyphthalocyaninato}cadmium(II) (6b) are presented herein. The spectroscopic and photophysicochemical properties have also been carried out and discussed together with the influence of various organic solvents on these properties. Spectroscopic properties, i.e. ground state electronic absorption and fluorescence spectra have been found to vary as a function of substituent position on the phthalocyanine macrocycle, i.e. α-substitution versus β-substitution. The photophysical parameters are reported as well as the photodegradation and singlet oxygen quantum yields, where the complexes were found to exhibit good photostability with the production of appreciable amounts of singlet oxygen.
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- Authors: Chidawanyika, Wadzanai J U , Antunes, Edith M , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268649 , vital:54217 , xlink:href="https://doi.org/10.1016/j.jphotochem.2007.09.020"
- Description: The syntheses of novel cadmium phenoxy complexes; tetrakis{1,(4)-tert-butylphenoxyphthalocyaninato}cadmium(II) (5a), tetrakis{1,(4)-phenoxyphthalocyaninato}cadmium(II) (5b), tetrakis{2,(3)-tert-butylphenoxyphthalocyaninato}cadmium(II) (6a) and tetrakis{2,(3)-phenoxyphthalocyaninato}cadmium(II) (6b) are presented herein. The spectroscopic and photophysicochemical properties have also been carried out and discussed together with the influence of various organic solvents on these properties. Spectroscopic properties, i.e. ground state electronic absorption and fluorescence spectra have been found to vary as a function of substituent position on the phthalocyanine macrocycle, i.e. α-substitution versus β-substitution. The photophysical parameters are reported as well as the photodegradation and singlet oxygen quantum yields, where the complexes were found to exhibit good photostability with the production of appreciable amounts of singlet oxygen.
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Synthesis, electrochemical characterization of tetra-and octa-substituted dodecyl-mercapto tin phthalocyanines in solution and as self-assembled monolayers
- Khene, Samson M, Geraldo, Daniela A, Togo, Chamunorwa A, Limson, Janice L, Nyokong, Tebello
- Authors: Khene, Samson M , Geraldo, Daniela A , Togo, Chamunorwa A , Limson, Janice L , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264541 , vital:53743 , xlink:href="https://doi.org/10.1016/j.electacta.2008.08.018"
- Description: Non-peripherally (α) tetra- (9) and octa-(7) substituted dodecyl-mercapto tin(IV) phthalocyanines were synthesized and their electrochemical behavior studied. Cyclic voltammetry and spectroelectrochemistry show ring-based reductions for 7 and 9, the former shows two ring oxidations, while the latter shows only one ring-based oxidation. The adsorption kinetics of (7) and (9) on gold electrode were investigated by electrochemical impedance spectroscopy (EIS). The equilibrium constant (K) for the adsorption and the Gibbs free energy (ΔGads) of the SAMs were evaluated based on the Frumkin isotherm.
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- Authors: Khene, Samson M , Geraldo, Daniela A , Togo, Chamunorwa A , Limson, Janice L , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264541 , vital:53743 , xlink:href="https://doi.org/10.1016/j.electacta.2008.08.018"
- Description: Non-peripherally (α) tetra- (9) and octa-(7) substituted dodecyl-mercapto tin(IV) phthalocyanines were synthesized and their electrochemical behavior studied. Cyclic voltammetry and spectroelectrochemistry show ring-based reductions for 7 and 9, the former shows two ring oxidations, while the latter shows only one ring-based oxidation. The adsorption kinetics of (7) and (9) on gold electrode were investigated by electrochemical impedance spectroscopy (EIS). The equilibrium constant (K) for the adsorption and the Gibbs free energy (ΔGads) of the SAMs were evaluated based on the Frumkin isotherm.
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Synthesis, photophysical and photochemical studies on long chain zinc phthalocyanine derivatives
- Ogunsipe, Abimbola, Durmus, Mahmut, Atilla, Devrim, Gürek, Ayşe Gül, Ahsen, Vefa, Nyokong, Tebello
- Authors: Ogunsipe, Abimbola , Durmus, Mahmut , Atilla, Devrim , Gürek, Ayşe Gül , Ahsen, Vefa , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/266019 , vital:53910 , xlink:href="https://doi.org/10.1016/j.synthmet.2008.06.007"
- Description: The synthesis and characterization of 2,9,16,23-chloro-3,10,17,24-triethyleneoxysulphanylphthalocyaninato zinc(II) (CTESZnPc) is described. The photophysics and photochemistry of CTESZnPc and those of tetrakis(triethyleneoxysulphanyl)zinc phthalocyanine (TTESZnPc) and octakis(triethyleneoxysulphanyl)zinc phthalocyanine (OTESZnPc), are presented and compared with those of unsubstituted zinc phthalocyanine (ZnPc). The presence of triethyleneoxysulphanyl substituents on the ZnPc ring gave rise to higher values of singlet oxygen (ΦΔ) and photodegradation (ΦPd) quantum yields in DMF. However, TTESZnPc, OTESZnPc and CTESZnPc are less fluorescent than ZnPc, judging from their fluorescence quantum yield (ΦF) values. Fluorescence was lower in toluene than in DMF due to aggregation in the former solvent. Triplet quantum yield (ΦT) values were found to increase with the presence of substituents on the ZnPc ring, while triplet lifetimes (τT) were found to vary linearly with the logarithms of solvent viscosities. The fluorescences of the substituted ZnPc complexes were effectively quenched by benzoquinone (BQ), and the quenching data analyzed by the Stern–Volmer equation. The Stern–Volmer constants and the diffusion-controlled bimolecular rate constants were calculated.
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- Authors: Ogunsipe, Abimbola , Durmus, Mahmut , Atilla, Devrim , Gürek, Ayşe Gül , Ahsen, Vefa , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/266019 , vital:53910 , xlink:href="https://doi.org/10.1016/j.synthmet.2008.06.007"
- Description: The synthesis and characterization of 2,9,16,23-chloro-3,10,17,24-triethyleneoxysulphanylphthalocyaninato zinc(II) (CTESZnPc) is described. The photophysics and photochemistry of CTESZnPc and those of tetrakis(triethyleneoxysulphanyl)zinc phthalocyanine (TTESZnPc) and octakis(triethyleneoxysulphanyl)zinc phthalocyanine (OTESZnPc), are presented and compared with those of unsubstituted zinc phthalocyanine (ZnPc). The presence of triethyleneoxysulphanyl substituents on the ZnPc ring gave rise to higher values of singlet oxygen (ΦΔ) and photodegradation (ΦPd) quantum yields in DMF. However, TTESZnPc, OTESZnPc and CTESZnPc are less fluorescent than ZnPc, judging from their fluorescence quantum yield (ΦF) values. Fluorescence was lower in toluene than in DMF due to aggregation in the former solvent. Triplet quantum yield (ΦT) values were found to increase with the presence of substituents on the ZnPc ring, while triplet lifetimes (τT) were found to vary linearly with the logarithms of solvent viscosities. The fluorescences of the substituted ZnPc complexes were effectively quenched by benzoquinone (BQ), and the quenching data analyzed by the Stern–Volmer equation. The Stern–Volmer constants and the diffusion-controlled bimolecular rate constants were calculated.
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Temporal and spatial variability in stable isotope ratios of SPM link to local hydrography and longer term SPM averages suggest heavy dependence of mussels on nearshore production
- Hill, Jaclyn M, McQuaid, Christopher D, Kaehler, Sven
- Authors: Hill, Jaclyn M , McQuaid, Christopher D , Kaehler, Sven
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6969 , http://hdl.handle.net/10962/d1012034
- Description: Temporal changes in hydrography affect suspended particulate matter (SPM) composition and distribution in coastal systems, potentially influencing the diets of suspension feeders. Temporal variation in SPM and in the diet of the mussel Perna perna, were investigated using stable isotope analysis. The δ13C and δ15 N ratios of SPM, mussels and macroalgae were determined monthly, with SPM samples collected along a 10 km onshore–offshore transect, over 14 months at Kenton-on-Sea, on the south coast of South Africa. Clear nearshore (0 km) to offshore (10 km) carbon depletion gradients were seen in SPM during all months and extended for 50 km offshore on one occasion. Carbon enrichment of coastal SPM in winter (June–August 2004 and May 2005) indicated temporal changes in the nearshore detrital pool, presumably reflecting changes in macroalgal detritus, linked to local changes in coastal hydrography and algal seasonality. Nitrogen patterns were less clear, with SPM enrichment seen between July and October 2004 from 0 to 10 km. Nearshore SPM demonstrated cyclical patterns in carbon over 24-h periods that correlated closely with tidal cycles and mussel carbon signatures, sampled monthly, demonstrated fluctuations that could not be correlated to seasonal or monthly changes in SPM. Macroalgae showed extreme variability in isotopic signatures, with no discernable patterns. IsoSource mixing models indicated over 50% reliance of mussel tissue on nearshore carbon, highlighting the importance of nearshore SPM in mussel diet. Overall, carbon variation in SPM at both large and small temporal scales can be related to hydrographic processes, but is masked in mussels by long-term isotope integration.
- Full Text:
- Authors: Hill, Jaclyn M , McQuaid, Christopher D , Kaehler, Sven
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6969 , http://hdl.handle.net/10962/d1012034
- Description: Temporal changes in hydrography affect suspended particulate matter (SPM) composition and distribution in coastal systems, potentially influencing the diets of suspension feeders. Temporal variation in SPM and in the diet of the mussel Perna perna, were investigated using stable isotope analysis. The δ13C and δ15 N ratios of SPM, mussels and macroalgae were determined monthly, with SPM samples collected along a 10 km onshore–offshore transect, over 14 months at Kenton-on-Sea, on the south coast of South Africa. Clear nearshore (0 km) to offshore (10 km) carbon depletion gradients were seen in SPM during all months and extended for 50 km offshore on one occasion. Carbon enrichment of coastal SPM in winter (June–August 2004 and May 2005) indicated temporal changes in the nearshore detrital pool, presumably reflecting changes in macroalgal detritus, linked to local changes in coastal hydrography and algal seasonality. Nitrogen patterns were less clear, with SPM enrichment seen between July and October 2004 from 0 to 10 km. Nearshore SPM demonstrated cyclical patterns in carbon over 24-h periods that correlated closely with tidal cycles and mussel carbon signatures, sampled monthly, demonstrated fluctuations that could not be correlated to seasonal or monthly changes in SPM. Macroalgae showed extreme variability in isotopic signatures, with no discernable patterns. IsoSource mixing models indicated over 50% reliance of mussel tissue on nearshore carbon, highlighting the importance of nearshore SPM in mussel diet. Overall, carbon variation in SPM at both large and small temporal scales can be related to hydrographic processes, but is masked in mussels by long-term isotope integration.
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The African reception of global media:
- Strelitz, Larry N, Boshoff, Priscilla A
- Authors: Strelitz, Larry N , Boshoff, Priscilla A
- Date: 2008
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/143527 , vital:38254 , ISBN 9781473971752 , https://books.google.co.za/books?id=pfRcCwAAQBAJanddq=The+African+Reception+of+Global+Mediaandlr=andsource=gbs_navlinks_s
- Description: This chapter engages debates concerning the impact of global media on local youth audiences in Africa. Recognizing the profound rootedness of media consumption in everyday life, the chapter specifically examines the way selected South African youth audiences, differentially embedded in their particular economic and ideological formations, use local and global media texts as part of their ongoing attempts to make sense of their lives.
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- Authors: Strelitz, Larry N , Boshoff, Priscilla A
- Date: 2008
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/143527 , vital:38254 , ISBN 9781473971752 , https://books.google.co.za/books?id=pfRcCwAAQBAJanddq=The+African+Reception+of+Global+Mediaandlr=andsource=gbs_navlinks_s
- Description: This chapter engages debates concerning the impact of global media on local youth audiences in Africa. Recognizing the profound rootedness of media consumption in everyday life, the chapter specifically examines the way selected South African youth audiences, differentially embedded in their particular economic and ideological formations, use local and global media texts as part of their ongoing attempts to make sense of their lives.
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The Cultural Use of the Wild Olive Tree by the amaXhosa People in the Eastern Cape Province of South Africa:
- Cocks, Michelle L, Dold, Anthony P
- Authors: Cocks, Michelle L , Dold, Anthony P
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141314 , vital:37961 , DOI: 10.1558/jsrnc.v2i3.292
- Description: The cultural meanings of harvested plants have for the most part been ignored in academic research on non-timber forest products (NTFPs) in southern Africa. Historically scientists have tended to ignore the complex relationships between nature and culture. Given the country's unique political and economic past and the current search for sustainable use of natural resources, a focus on the convergence of natural science and cultural diversity is important at this time. Empirical data on cultural practices is being collected in order to develop fresh and relevant insights into the complex relationships between culture and bítKÜversity. The purpose of this paper is to demonstrate that the concept of culture needs to be brought into our understanding of the role of NTFPs. We dtxrument the use and value of a specific tree, Olea europaea L. subsp. africana (Mill.) P,S. Green, called Umiicjuma in the Xhosa language, for cultural purposes, by both rural and urban households.
- Full Text:
- Authors: Cocks, Michelle L , Dold, Anthony P
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141314 , vital:37961 , DOI: 10.1558/jsrnc.v2i3.292
- Description: The cultural meanings of harvested plants have for the most part been ignored in academic research on non-timber forest products (NTFPs) in southern Africa. Historically scientists have tended to ignore the complex relationships between nature and culture. Given the country's unique political and economic past and the current search for sustainable use of natural resources, a focus on the convergence of natural science and cultural diversity is important at this time. Empirical data on cultural practices is being collected in order to develop fresh and relevant insights into the complex relationships between culture and bítKÜversity. The purpose of this paper is to demonstrate that the concept of culture needs to be brought into our understanding of the role of NTFPs. We dtxrument the use and value of a specific tree, Olea europaea L. subsp. africana (Mill.) P,S. Green, called Umiicjuma in the Xhosa language, for cultural purposes, by both rural and urban households.
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The development of ICT networks for South African schools: Two pilot studies in disadvantaged areas
- Siebörger, Ingrid, Terzoli, Alfredo, Hodgkinson-Williams, Cheryl
- Authors: Siebörger, Ingrid , Terzoli, Alfredo , Hodgkinson-Williams, Cheryl
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431018 , vital:72737 , https://doi.org/10.1007/978-0-387-09729-9_25
- Description: Information and Communication Technologies (ICTs) are increasingly considered valuable tools in educa-tion, promoting the development of higher cognitive processes and allowing teachers and learners access to a plethora of information. This paper reports on two pilot studies conducted in South Africa in proto-typical previously disadvantaged schools and their surrounding communities. Each pilot study deployed a local loop network within impoverished communi-ties, connecting schools to one another and central services such as email and voice communications. The benefits of these networks were that teachers, learners and the local community had access to in-formation, and communication and collaboration channels, providing potential test beds for investigat-ing the use of computers as mind tools.
- Full Text:
- Authors: Siebörger, Ingrid , Terzoli, Alfredo , Hodgkinson-Williams, Cheryl
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431018 , vital:72737 , https://doi.org/10.1007/978-0-387-09729-9_25
- Description: Information and Communication Technologies (ICTs) are increasingly considered valuable tools in educa-tion, promoting the development of higher cognitive processes and allowing teachers and learners access to a plethora of information. This paper reports on two pilot studies conducted in South Africa in proto-typical previously disadvantaged schools and their surrounding communities. Each pilot study deployed a local loop network within impoverished communi-ties, connecting schools to one another and central services such as email and voice communications. The benefits of these networks were that teachers, learners and the local community had access to in-formation, and communication and collaboration channels, providing potential test beds for investigat-ing the use of computers as mind tools.
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The Internet in rural communities: unrestricted and contextualized
- Thinyane, Mamello, Dalvit, Lorenzo, Terzoli, Alfredo, Clayton, Peter G
- Authors: Thinyane, Mamello , Dalvit, Lorenzo , Terzoli, Alfredo , Clayton, Peter G
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431344 , vital:72766 , https://www.researchgate.net/profile/Alfredo-Ter-zoli/publication/262259378_The_Internet_in_rural_communities_unrestricted_and_contextualized/links/6597ec140bb2c7472b35fcac/The-Internet-in-rural-communities-unrestricted-and-contextualized.pdf
- Description: The benefits of the Internet are still not available to many marginalized communities because of lack of connectivity, costs of infrastructure and scarcity of skills. Many ICTforDevelopment (ICT4D) projects offer piecemeal interventions relying either on restricted (and often decontex-tualised) access to the Internet or on isolated Local Area Networks (LANs). In this paper we argue that marginalized rural communities should have unrestricted access to the Internet in order to exploit its full potential. We also believe that the Internet could be contextualized through an optional adaptation layer which would facilitate access. We discuss an ICT4D project which was shaped from the very beginning according to these principles. It involves the deployment of an eCom-merce platform (soon to be integrated with eHealth, eLearning and eGovernment capabilities) in a rural community in South Africa. We re-port on how the various components of this intervention fit into the model, and the benefits for the community.
- Full Text:
- Authors: Thinyane, Mamello , Dalvit, Lorenzo , Terzoli, Alfredo , Clayton, Peter G
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431344 , vital:72766 , https://www.researchgate.net/profile/Alfredo-Ter-zoli/publication/262259378_The_Internet_in_rural_communities_unrestricted_and_contextualized/links/6597ec140bb2c7472b35fcac/The-Internet-in-rural-communities-unrestricted-and-contextualized.pdf
- Description: The benefits of the Internet are still not available to many marginalized communities because of lack of connectivity, costs of infrastructure and scarcity of skills. Many ICTforDevelopment (ICT4D) projects offer piecemeal interventions relying either on restricted (and often decontex-tualised) access to the Internet or on isolated Local Area Networks (LANs). In this paper we argue that marginalized rural communities should have unrestricted access to the Internet in order to exploit its full potential. We also believe that the Internet could be contextualized through an optional adaptation layer which would facilitate access. We discuss an ICT4D project which was shaped from the very beginning according to these principles. It involves the deployment of an eCom-merce platform (soon to be integrated with eHealth, eLearning and eGovernment capabilities) in a rural community in South Africa. We re-port on how the various components of this intervention fit into the model, and the benefits for the community.
- Full Text: