My First Book of Southern African Insects, C. Uys: book review
- Authors: Villet, Martin H
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451749 , vital:75074 , https://hdl.handle.net/10520/EJC32855
- Description: I concur with Antoine de Saint-Exupéry (1943): we are born with a strong appreciation of the world around us that most of us lose as we grow up. While few adults have much empathy with insects, they are a source of fascination for most children, at least until they start school. The problem facing professional entomology is how to sustain and encourage that early attitude so that we recruit passionate and well-prepared people into the profession, and sensitise the remainder of the population to the value of insects.
- Full Text:
- Authors: Villet, Martin H
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451749 , vital:75074 , https://hdl.handle.net/10520/EJC32855
- Description: I concur with Antoine de Saint-Exupéry (1943): we are born with a strong appreciation of the world around us that most of us lose as we grow up. While few adults have much empathy with insects, they are a source of fascination for most children, at least until they start school. The problem facing professional entomology is how to sustain and encourage that early attitude so that we recruit passionate and well-prepared people into the profession, and sensitise the remainder of the population to the value of insects.
- Full Text:
Natural enemies from South Africa for biological control of Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae) in Europe
- Baars, Jan-Robert, Coetzee, Julie A, Martin, Grant D, Hill, Martin P, Caffrey, J M
- Authors: Baars, Jan-Robert , Coetzee, Julie A , Martin, Grant D , Hill, Martin P , Caffrey, J M
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76914 , vital:30637 , https://doi.org/10.1007/s10750-010-0427-0
- Description: The non-native invasive plant, Lagarosiphon major (Hydrocharitaceae) is a submersed aquatic macrophyte that poses a significant threat to water bodies in Europe. Dense infestations prove difficult to manage using traditional methods. In order to initiate a biocontrol programme, a survey for natural enemies of Lagarosiphon was conducted in South Africa. Several phytophagous species were recorded for the first time, with at least three showing notable promise as candidate agents. Amongst these, a leaf-mining fly, Hydrellia sp. (Ephydridae) that occurred over a wide distribution causes significant leaf damage despite high levels of parasitism by braconid wasps. Another yet unidentified fly was recorded mining the stem of L. major. Two leaf-feeding and shoot boring weevils, cf. Bagous sp. (Curculionidae) were recorded damaging the shoot tips and stunting the growth of the stem. Several leaf-feeding lepidopteran species (Nymphulinae) were frequently recorded, but are expected to feed on a wide range of plant species and are not considered for importation before other candidates are assessed. The discovery of several natural enemies in the country of origin improves the biological control prospects of L. major in Europe.
- Full Text:
- Authors: Baars, Jan-Robert , Coetzee, Julie A , Martin, Grant D , Hill, Martin P , Caffrey, J M
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76914 , vital:30637 , https://doi.org/10.1007/s10750-010-0427-0
- Description: The non-native invasive plant, Lagarosiphon major (Hydrocharitaceae) is a submersed aquatic macrophyte that poses a significant threat to water bodies in Europe. Dense infestations prove difficult to manage using traditional methods. In order to initiate a biocontrol programme, a survey for natural enemies of Lagarosiphon was conducted in South Africa. Several phytophagous species were recorded for the first time, with at least three showing notable promise as candidate agents. Amongst these, a leaf-mining fly, Hydrellia sp. (Ephydridae) that occurred over a wide distribution causes significant leaf damage despite high levels of parasitism by braconid wasps. Another yet unidentified fly was recorded mining the stem of L. major. Two leaf-feeding and shoot boring weevils, cf. Bagous sp. (Curculionidae) were recorded damaging the shoot tips and stunting the growth of the stem. Several leaf-feeding lepidopteran species (Nymphulinae) were frequently recorded, but are expected to feed on a wide range of plant species and are not considered for importation before other candidates are assessed. The discovery of several natural enemies in the country of origin improves the biological control prospects of L. major in Europe.
- Full Text:
Negotiating sexuality in Grahamstown East: young black women's experiences of relationships in the context of HIV risk
- Authors: Clüver, Frances Rose Mannix
- Date: 2010
- Subjects: HIV infections -- South Africa -- Grahamstown Man-woman relationships -- South Africa -- Grahamstown Intimacy -- South Africa -- Grahamstown Sex -- South Africa -- Grahamstown Youth, Black -- South Africa -- Grahamstown -- Sexual behavior HIV infections -- Social aspects -- South Africa -- Grahamstown Youth, Black -- South Africa -- Grahamstown -- Attitudes Reproductive health -- South Africa -- Grahamstown Health education -- South Africa -- Grahamstown Youth, Black -- South Africa -- Grahamstown -- Health and hygiene Phenomenological psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2951 , http://hdl.handle.net/10962/d1002460
- Description: Adolescent sexual health has been identified as a significant health and development problem facing South Africa. Limited amounts of research on sexual interactions have been undertaken, with information on adolescents’ romantic relationships being particularly scarce. Qualitative research needs to foster an understanding of the dynamics of sexual interactions in specific settings, and with emphasis in the past on cognitive health psychology models, very little is thus known about how adolescents negotiate and make sense of their sexual experiences. This highlights the need to investigate the complexities of human sexuality in a contextual manner. In response, this study explores the lived experiences of four young black women as they negotiate their agency and sexuality in a local context. By way of in-depth qualitative interviews, which were analysed for recurrent themes using interpretative phenomenological analysis, this project examines the participants’ experiences regarding sex, relationships, communication, sexual health care, as well as HIV and pregnancy prevention. The results reveal that communication about sexuality in the participants’ homes was limited if not absent altogether. When seeking sexual health care, they found clinic nurses to be judgemental and rude. Regarding sexuality and HIV education, the participants stressed the need for outside educators to teach in more practical ways to increase efficacy. In their dating relationships, most participants revealed their boyfriends had a great deal of influence over their sexual initiation. Unwanted pregnancy surfaced as a greater fear than HIV in their accounts due to pressure to finish their education and attain well-paying jobs in the future. The participants felt unable to stop their boyfriends’ infidelity and had limited agency when facing sexual demands. Their accounts revealed that they negotiate their agency in an atmosphere of coercion and the threat of rape. However, areas of agency included their consistent condom use even when facing pressure to have unprotected sex, and their active accessing of sexual health services for hormonal contraception. These insights serve to better inform sexual and reproductive health education and intervention programmes for young women. Moreover, educators, researchers and programme developers alike may gain useful insights from the personalised accounts derived from this study.
- Full Text:
- Authors: Clüver, Frances Rose Mannix
- Date: 2010
- Subjects: HIV infections -- South Africa -- Grahamstown Man-woman relationships -- South Africa -- Grahamstown Intimacy -- South Africa -- Grahamstown Sex -- South Africa -- Grahamstown Youth, Black -- South Africa -- Grahamstown -- Sexual behavior HIV infections -- Social aspects -- South Africa -- Grahamstown Youth, Black -- South Africa -- Grahamstown -- Attitudes Reproductive health -- South Africa -- Grahamstown Health education -- South Africa -- Grahamstown Youth, Black -- South Africa -- Grahamstown -- Health and hygiene Phenomenological psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2951 , http://hdl.handle.net/10962/d1002460
- Description: Adolescent sexual health has been identified as a significant health and development problem facing South Africa. Limited amounts of research on sexual interactions have been undertaken, with information on adolescents’ romantic relationships being particularly scarce. Qualitative research needs to foster an understanding of the dynamics of sexual interactions in specific settings, and with emphasis in the past on cognitive health psychology models, very little is thus known about how adolescents negotiate and make sense of their sexual experiences. This highlights the need to investigate the complexities of human sexuality in a contextual manner. In response, this study explores the lived experiences of four young black women as they negotiate their agency and sexuality in a local context. By way of in-depth qualitative interviews, which were analysed for recurrent themes using interpretative phenomenological analysis, this project examines the participants’ experiences regarding sex, relationships, communication, sexual health care, as well as HIV and pregnancy prevention. The results reveal that communication about sexuality in the participants’ homes was limited if not absent altogether. When seeking sexual health care, they found clinic nurses to be judgemental and rude. Regarding sexuality and HIV education, the participants stressed the need for outside educators to teach in more practical ways to increase efficacy. In their dating relationships, most participants revealed their boyfriends had a great deal of influence over their sexual initiation. Unwanted pregnancy surfaced as a greater fear than HIV in their accounts due to pressure to finish their education and attain well-paying jobs in the future. The participants felt unable to stop their boyfriends’ infidelity and had limited agency when facing sexual demands. Their accounts revealed that they negotiate their agency in an atmosphere of coercion and the threat of rape. However, areas of agency included their consistent condom use even when facing pressure to have unprotected sex, and their active accessing of sexual health services for hormonal contraception. These insights serve to better inform sexual and reproductive health education and intervention programmes for young women. Moreover, educators, researchers and programme developers alike may gain useful insights from the personalised accounts derived from this study.
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Network management for community networks
- Authors: Wells, Daniel David
- Date: 2010 , 2010-03-26
- Subjects: Computer networks -- Management , Internet -- South Africa , Internet -- Management , Broadband communication systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4643 , http://hdl.handle.net/10962/d1006587
- Description: Community networks (in South Africa and Africa) are often serviced by limited bandwidth network backhauls. Relative to the basic needs of the community, this is an expensive ongoing concern. In many cases the Internet connection is shared among multiple sites. Community networks may also have a lack of technical personnel to maintain a network of this nature. Hence, there is a demand for a system which will monitor and manage bandwidth use, as well as network use. The proposed solution for community networks and the focus within this dissertation, is a system of two parts. A Community Access Point (CAP) is located at each site within the community network. This provides the hosts and servers at that site with access to services on the community network and the Internet, it is the site's router. The CAP provides a web based interface (CAPgui) which allows configuration of the device and viewing of simple monitoring statistics. The Access Concentrator (AC) is the default router for the CAPs and the gateway to the Internet. It provides authenticated and encrypted communication between the network sites. The AC performs several monitoring functions, both for the individual sites and for the upstream Internet connection. The AC provides a means for centrally managing and effectively allocating Internet bandwidth by using the web based interface (ACgui). Bandwidth use can be allocated per user, per host and per site. The system is maintainable, extendable and customisable for different network architectures. The system was deployed successfully to two community networks. The Centre of Excellence (CoE) testbed network is a peri-urban network deployment whereas the Siyakhula Living Lab (SLL) network is a rural deployment. The results gathered conclude that the project was successful as the deployed system is more robust and more manageable than the previous systems.
- Full Text:
- Authors: Wells, Daniel David
- Date: 2010 , 2010-03-26
- Subjects: Computer networks -- Management , Internet -- South Africa , Internet -- Management , Broadband communication systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4643 , http://hdl.handle.net/10962/d1006587
- Description: Community networks (in South Africa and Africa) are often serviced by limited bandwidth network backhauls. Relative to the basic needs of the community, this is an expensive ongoing concern. In many cases the Internet connection is shared among multiple sites. Community networks may also have a lack of technical personnel to maintain a network of this nature. Hence, there is a demand for a system which will monitor and manage bandwidth use, as well as network use. The proposed solution for community networks and the focus within this dissertation, is a system of two parts. A Community Access Point (CAP) is located at each site within the community network. This provides the hosts and servers at that site with access to services on the community network and the Internet, it is the site's router. The CAP provides a web based interface (CAPgui) which allows configuration of the device and viewing of simple monitoring statistics. The Access Concentrator (AC) is the default router for the CAPs and the gateway to the Internet. It provides authenticated and encrypted communication between the network sites. The AC performs several monitoring functions, both for the individual sites and for the upstream Internet connection. The AC provides a means for centrally managing and effectively allocating Internet bandwidth by using the web based interface (ACgui). Bandwidth use can be allocated per user, per host and per site. The system is maintainable, extendable and customisable for different network architectures. The system was deployed successfully to two community networks. The Centre of Excellence (CoE) testbed network is a peri-urban network deployment whereas the Siyakhula Living Lab (SLL) network is a rural deployment. The results gathered conclude that the project was successful as the deployed system is more robust and more manageable than the previous systems.
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Neurocognitive and symptom profiles of concussed and nonconcussed provincial rugby players over one season
- Authors: Clark, Susan Beverley
- Date: 2010
- Subjects: Rugby football injuries Brain -- Concussion -- Complications Head -- Wounds and injuries -- Complications Sports injuries -- Psychological aspects Brain damage Neuropsychological tests Rugby Union football players
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2950 , http://hdl.handle.net/10962/d1002459
- Description: Neurocognitive and symptom profiles of concussed and nonconcussed adult provincial rugby union players were investigated over one rugby season, including early season (baseline), intermittent postconcussion, and end of season testing. In a non-equivalent quasi-experimental design, nonconcussed (n = 54) and concussed (n = 17) rugby groups were compared with demographically equivalent noncontact sport controls (n = 37, and n = 17, respectively). Measures included the ImPACT cognitive and symptom composites, and the WMS-III Visual Reproduction and Verbal Paired Associates subtests. The independent and dependent comparative analyses in respect of both nonconcussed and concussed groups, provided cross-validation of poorer acute and/or chronic neuropsychological outcomes for the rugby groups on the ImPACT Reaction Time, Visual Motor Speed, Impulse Control and Symptom composites, and the WMS-III Verbal Paired Associates. The finding of significantly poorer scores on Verbal Paired Associates up to 24 days post concussion for the rugby players versus controls, was longer than the 7 – 10 day recovery period frequently cited in the literature. The overall implication of the study is that even in a group with high cognitive reserve such as these provincial level athletes, there may be prolonged acute recovery, as well as permanent deleterious neuropsychological consequences of cumulative concussive injury in association with a sport such as rugby. Accordingly, the move towards careful individualised postconcussion monitoring of neurocognitive functioning is endorsed, including early identification of any significant permanent reductions in cognitive reserve. Sensitivity of the ImPACT test might be enhanced via inclusion of a verbal associate learning task.
- Full Text:
- Authors: Clark, Susan Beverley
- Date: 2010
- Subjects: Rugby football injuries Brain -- Concussion -- Complications Head -- Wounds and injuries -- Complications Sports injuries -- Psychological aspects Brain damage Neuropsychological tests Rugby Union football players
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2950 , http://hdl.handle.net/10962/d1002459
- Description: Neurocognitive and symptom profiles of concussed and nonconcussed adult provincial rugby union players were investigated over one rugby season, including early season (baseline), intermittent postconcussion, and end of season testing. In a non-equivalent quasi-experimental design, nonconcussed (n = 54) and concussed (n = 17) rugby groups were compared with demographically equivalent noncontact sport controls (n = 37, and n = 17, respectively). Measures included the ImPACT cognitive and symptom composites, and the WMS-III Visual Reproduction and Verbal Paired Associates subtests. The independent and dependent comparative analyses in respect of both nonconcussed and concussed groups, provided cross-validation of poorer acute and/or chronic neuropsychological outcomes for the rugby groups on the ImPACT Reaction Time, Visual Motor Speed, Impulse Control and Symptom composites, and the WMS-III Verbal Paired Associates. The finding of significantly poorer scores on Verbal Paired Associates up to 24 days post concussion for the rugby players versus controls, was longer than the 7 – 10 day recovery period frequently cited in the literature. The overall implication of the study is that even in a group with high cognitive reserve such as these provincial level athletes, there may be prolonged acute recovery, as well as permanent deleterious neuropsychological consequences of cumulative concussive injury in association with a sport such as rugby. Accordingly, the move towards careful individualised postconcussion monitoring of neurocognitive functioning is endorsed, including early identification of any significant permanent reductions in cognitive reserve. Sensitivity of the ImPACT test might be enhanced via inclusion of a verbal associate learning task.
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New Possibilities for Mediation in Society: How is Environmental Education Research Responding?
- O’Donoghue, Rob B, Lotz-Sisitka, Heila
- Authors: O’Donoghue, Rob B , Lotz-Sisitka, Heila
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/437354 , vital:73372 , ISBN 978-9460911590 , https://brill.com/display/title/36964?rskey=xymnmAandresult=1
- Description: African universities have, since their inception in the colonial era, been governed by a colonial framing of research agendas and modernist trajectories. Keeley and Scoones (2003), for example, explain how agronomy in the French colonies in Afri-ca was shaped by the ‘particular form of science’that arrived in Mali as the French set about expanding the production of cot-ton. French scientific research, at the time (in the post World War 1 period) emphasized the economic development of the colonies, which introduced scientific ways of improving the par-ticular production of cash crops, dealing with pests and improv-ing varieties, locating early university-based research in pat-terns of bureaucratic and state formation. Expatriate research-ers from universities in France, England and Belgium were brought to the colonies to set the agenda for research, as most of the colonial universities offered research and teaching pro-grammes that were accredited by universities in the ‘mother country’. While the number of expatriate researchers working in African universities may have declined in recent years, with the emphasis now on short-term consultancies (from the ‘donor country’), funding and technical inputs from mother and donor countries continues to shape research. What is of note here is how research agendas are coupled with particular research conventions and processes of administrative and social organ-ization1 that are seldom explicit..
- Full Text:
- Authors: O’Donoghue, Rob B , Lotz-Sisitka, Heila
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/437354 , vital:73372 , ISBN 978-9460911590 , https://brill.com/display/title/36964?rskey=xymnmAandresult=1
- Description: African universities have, since their inception in the colonial era, been governed by a colonial framing of research agendas and modernist trajectories. Keeley and Scoones (2003), for example, explain how agronomy in the French colonies in Afri-ca was shaped by the ‘particular form of science’that arrived in Mali as the French set about expanding the production of cot-ton. French scientific research, at the time (in the post World War 1 period) emphasized the economic development of the colonies, which introduced scientific ways of improving the par-ticular production of cash crops, dealing with pests and improv-ing varieties, locating early university-based research in pat-terns of bureaucratic and state formation. Expatriate research-ers from universities in France, England and Belgium were brought to the colonies to set the agenda for research, as most of the colonial universities offered research and teaching pro-grammes that were accredited by universities in the ‘mother country’. While the number of expatriate researchers working in African universities may have declined in recent years, with the emphasis now on short-term consultancies (from the ‘donor country’), funding and technical inputs from mother and donor countries continues to shape research. What is of note here is how research agendas are coupled with particular research conventions and processes of administrative and social organ-ization1 that are seldom explicit..
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Newspaper literacy and communication for democracy: is there a crisis in South African journalism?
- Siebörger, Ian, Adendorff, Ralph D
- Authors: Siebörger, Ian , Adendorff, Ralph D
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125304 , vital:35770 , https://doi.org/10.2989/SALALS.2009.27.4.4.1024
- Description: Media theorists such as Barnett (2002), Buckingham (1997 & 2000) and Sampson (1999) describe a perceived crisis hindering the media’s ability to inform citizens for participation in democracy. One of the symptoms and causes of this crisis, they argue, is that the media use language that many citizens cannot understand. This article draws on theories and methodologies from linguistics to investigate whether this claim holds true for South African newspapers. The concept of the crisis in journalism is deconstructed in the light of Street’s (1984) ideological model of literacy. In a pilot study, multiple readability tests were conducted on one article from each of three newspapers, Business Day, The Herald and Daily Sun. The findings of these tests, and a systemic functional grammar analysis of cohesion and lexical density in the three articles, show that all three newspapers tailor their language to fit their target markets. This, triangulated with the rapid growth in readership of the Daily Sun and the more modest growth of The Herald, suggests that many South Africans are better informed for participation in democracy than in the past, although newspapers can do more to help readers learn a plurality of literacy practices.
- Full Text:
- Authors: Siebörger, Ian , Adendorff, Ralph D
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125304 , vital:35770 , https://doi.org/10.2989/SALALS.2009.27.4.4.1024
- Description: Media theorists such as Barnett (2002), Buckingham (1997 & 2000) and Sampson (1999) describe a perceived crisis hindering the media’s ability to inform citizens for participation in democracy. One of the symptoms and causes of this crisis, they argue, is that the media use language that many citizens cannot understand. This article draws on theories and methodologies from linguistics to investigate whether this claim holds true for South African newspapers. The concept of the crisis in journalism is deconstructed in the light of Street’s (1984) ideological model of literacy. In a pilot study, multiple readability tests were conducted on one article from each of three newspapers, Business Day, The Herald and Daily Sun. The findings of these tests, and a systemic functional grammar analysis of cohesion and lexical density in the three articles, show that all three newspapers tailor their language to fit their target markets. This, triangulated with the rapid growth in readership of the Daily Sun and the more modest growth of The Herald, suggests that many South Africans are better informed for participation in democracy than in the past, although newspapers can do more to help readers learn a plurality of literacy practices.
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Novel, soluble, FluXoro functional substituted zinc phthalocyanines; synthesis, characterization and photophysicochemical properties
- Erdoğmuş, Ali, Nyokong, Tebello
- Authors: Erdoğmuş, Ali , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261258 , vital:53378 , xlink:href="https://doi.org/10.1016/j.dyepig.2010.01.001"
- Description: Three novel phthalonitriles and the respective, peripheral tetrakis zinc phthalocyanines were synthesized and characterized using elemental analysis, IR, 1H NMR, mass spectra and electronic spectroscopy. The phthalocyanines displayed good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene. The presence of a long chain fluorine substitituent was found to result in reduced aggregation. The singlet oxygen, photodegradation, fluorescence quantum yield, triplet quantum yield and triplet life time of the complexes in toluene were determined. The effect of fluoro-functional groups on the photophysical and photochemical parameters of the zinc(II) phthalocyanines are also reported. Fluorescence quantum yields for the complexes ranged from 0.021 to 0.041.
- Full Text:
- Authors: Erdoğmuş, Ali , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261258 , vital:53378 , xlink:href="https://doi.org/10.1016/j.dyepig.2010.01.001"
- Description: Three novel phthalonitriles and the respective, peripheral tetrakis zinc phthalocyanines were synthesized and characterized using elemental analysis, IR, 1H NMR, mass spectra and electronic spectroscopy. The phthalocyanines displayed good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene. The presence of a long chain fluorine substitituent was found to result in reduced aggregation. The singlet oxygen, photodegradation, fluorescence quantum yield, triplet quantum yield and triplet life time of the complexes in toluene were determined. The effect of fluoro-functional groups on the photophysical and photochemical parameters of the zinc(II) phthalocyanines are also reported. Fluorescence quantum yields for the complexes ranged from 0.021 to 0.041.
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Optical limiting properties of zinc phthalocyanines in solution and solid PMMA composite films
- Tekin, Sezen, Kürüm, Ulaş, Durmus, Mahmut, Yaglioglu, H Gul, Nyokong, Tebello, Elmali, Ayhan
- Authors: Tekin, Sezen , Kürüm, Ulaş , Durmus, Mahmut , Yaglioglu, H Gul , Nyokong, Tebello , Elmali, Ayhan
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249071 , vital:51775 , xlink:href="https://doi.org/10.1016/j.optcom.2010.07.003"
- Description: The nonlinear absorption and optical limiting (OL) performance of tetra- and octasubstituted zinc phthalocyanine complexes were described in solution and in the solid state using the open-aperture Z-scan technique. The measurements were performed using collimated 4 ns pulses generated from a frequency-doubled Nd:YAG laser at 532 nm wavelength. The polymeric films exhibit a much larger effective nonlinear absorption coefficient in comparison with solution. However, the parameters of the ratio of the excited to ground state absorption cross section and energy-dependent saturation in solution are much better compared to properties in the polymeric film. In terms of the ratio of the excited to ground state absorption cross section, the peripherally substituted complexes show better OL performance than the non-peripherally substituted derivative.
- Full Text:
- Authors: Tekin, Sezen , Kürüm, Ulaş , Durmus, Mahmut , Yaglioglu, H Gul , Nyokong, Tebello , Elmali, Ayhan
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249071 , vital:51775 , xlink:href="https://doi.org/10.1016/j.optcom.2010.07.003"
- Description: The nonlinear absorption and optical limiting (OL) performance of tetra- and octasubstituted zinc phthalocyanine complexes were described in solution and in the solid state using the open-aperture Z-scan technique. The measurements were performed using collimated 4 ns pulses generated from a frequency-doubled Nd:YAG laser at 532 nm wavelength. The polymeric films exhibit a much larger effective nonlinear absorption coefficient in comparison with solution. However, the parameters of the ratio of the excited to ground state absorption cross section and energy-dependent saturation in solution are much better compared to properties in the polymeric film. In terms of the ratio of the excited to ground state absorption cross section, the peripherally substituted complexes show better OL performance than the non-peripherally substituted derivative.
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Optimization of salbutamol sulfate dissolution from sustained release matrix formulations using an artificial neural network
- Chaibva, Faith A, Burton, Michael H, Walker, Roderick B
- Authors: Chaibva, Faith A , Burton, Michael H , Walker, Roderick B
- Date: 2010
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Article
- Identifier: vital:6352 , http://hdl.handle.net/10962/d1006034
- Description: An artificial neural network was used to optimize the release of salbutamol sulfate from hydrophilic matrix formulations. Model formulations to be used for training, testing and validating the neural network were manufactured with the aid of a central composite design with varying the levels of Methocel® K100M, xanthan gum, Carbopol® 974P and Surelease® as the input factors. In vitro dissolution time profiles at six different sampling times were used as target data in training the neural network for formulation optimization. A multi layer perceptron with one hidden layer was constructed using Matlab®, and the number of nodes in the hidden layer was optimized by trial and error to develop a model with the best predictive ability. The results revealed that a neural network with nine nodes was optimal for developing and optimizing formulations. Simulations undertaken with the training data revealed that the constructed model was useable. The optimized neural network was used for optimization of formulation with desirable release characteristics and the results indicated that there was agreement between the predicted formulation and the manufactured formulation. This work illustrates the possible utility of artificial neural networks for the optimization of pharmaceutical formulations with desirable performance characteristics.
- Full Text:
- Authors: Chaibva, Faith A , Burton, Michael H , Walker, Roderick B
- Date: 2010
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Article
- Identifier: vital:6352 , http://hdl.handle.net/10962/d1006034
- Description: An artificial neural network was used to optimize the release of salbutamol sulfate from hydrophilic matrix formulations. Model formulations to be used for training, testing and validating the neural network were manufactured with the aid of a central composite design with varying the levels of Methocel® K100M, xanthan gum, Carbopol® 974P and Surelease® as the input factors. In vitro dissolution time profiles at six different sampling times were used as target data in training the neural network for formulation optimization. A multi layer perceptron with one hidden layer was constructed using Matlab®, and the number of nodes in the hidden layer was optimized by trial and error to develop a model with the best predictive ability. The results revealed that a neural network with nine nodes was optimal for developing and optimizing formulations. Simulations undertaken with the training data revealed that the constructed model was useable. The optimized neural network was used for optimization of formulation with desirable release characteristics and the results indicated that there was agreement between the predicted formulation and the manufactured formulation. This work illustrates the possible utility of artificial neural networks for the optimization of pharmaceutical formulations with desirable performance characteristics.
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Osmoregulation in freshwater invertebrates in response to exposure to salt pollution
- Holland, Alexandra J, Gordon, Andrew K, Muller, Nikite W J
- Authors: Holland, Alexandra J , Gordon, Andrew K , Muller, Nikite W J
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/437700 , vital:73403 , ISBN 978-1-4312-0075-7 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/1585.pdf
- Description: The South African National Water Act (No. 36 of 1998) provides for an ecological Reserve which is intended to protect fresh water ecosystems and resources from degradation as a result of misuse, and to maintain vital ecological functions within these systems (Palmer et al., 2004). Water quality guidelines are an important tool in the management of these water resources, aiming to adequately balance protec-tion of aquatic ecological systems with sustainable human use needs. Jooste and Rossouw (2002) proposed guidelines or boundary values for inorganic salts to be included in the ecological Reserve. These boundary values for inorganic salts were derived as follows, acute lethality data (LC50s) from the ECOTOX database main-tained by the USEPA were projected to 336 h and the 5th percentile determined as a lethality benchmark, analogous to the Fair/Poor boundary. Similarly, the 5th percen-tile of available sublethal data was determined as the sublethality benchmark and analogous with the Natural/Good boundary value. The Good/Fair boundary was the mean value between Natural/Good and Fair/Poor values. It has been suggested however, that these guidelines might not be entirely appropriate as they were de-rived without including tolerances of South African biota. Furthermore, the accuracy for some salt boundary values have been questioned (Scherman, 2009; Scherman, 2010).
- Full Text:
- Authors: Holland, Alexandra J , Gordon, Andrew K , Muller, Nikite W J
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/437700 , vital:73403 , ISBN 978-1-4312-0075-7 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/1585.pdf
- Description: The South African National Water Act (No. 36 of 1998) provides for an ecological Reserve which is intended to protect fresh water ecosystems and resources from degradation as a result of misuse, and to maintain vital ecological functions within these systems (Palmer et al., 2004). Water quality guidelines are an important tool in the management of these water resources, aiming to adequately balance protec-tion of aquatic ecological systems with sustainable human use needs. Jooste and Rossouw (2002) proposed guidelines or boundary values for inorganic salts to be included in the ecological Reserve. These boundary values for inorganic salts were derived as follows, acute lethality data (LC50s) from the ECOTOX database main-tained by the USEPA were projected to 336 h and the 5th percentile determined as a lethality benchmark, analogous to the Fair/Poor boundary. Similarly, the 5th percen-tile of available sublethal data was determined as the sublethality benchmark and analogous with the Natural/Good boundary value. The Good/Fair boundary was the mean value between Natural/Good and Fair/Poor values. It has been suggested however, that these guidelines might not be entirely appropriate as they were de-rived without including tolerances of South African biota. Furthermore, the accuracy for some salt boundary values have been questioned (Scherman, 2009; Scherman, 2010).
- Full Text:
Parallel packet classification using GPU co-processors
- Nottingham, Alistair, Irwin, Barry V W
- Authors: Nottingham, Alistair , Irwin, Barry V W
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430250 , vital:72677 , https://doi.org/10.1145/1899503.1899529
- Description: In the domain of network security, packet filtering for classification pur-poses is of significant interest. Packet classification provides a mecha-nism for understanding the composition of packet streams arriving at distinct network interfaces, and is useful in diagnosing threats and un-covering vulnerabilities so as to maximise data integrity and system se-curity. Traditional packet classifiers, such as PCAP, have utilised Con-trol Flow Graphs (CFGs) in representing filter sets, due to both their amenability to optimisation, and their inherent structural applicability to the metaphor of decision-based classification. Unfortunately, CFGs do not map well to cooperative processing implementations, and single-threaded CPU-based implementations have proven too slow for real-time classification against multiple arbitrary filters on next generation networks. In this paper, we consider a novel multithreaded classification algorithm, optimised for execution on GPU co-processors, intended to accelerate classification throughput and maximise processing efficien-cy in a highly parallel execution context.
- Full Text:
- Authors: Nottingham, Alistair , Irwin, Barry V W
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430250 , vital:72677 , https://doi.org/10.1145/1899503.1899529
- Description: In the domain of network security, packet filtering for classification pur-poses is of significant interest. Packet classification provides a mecha-nism for understanding the composition of packet streams arriving at distinct network interfaces, and is useful in diagnosing threats and un-covering vulnerabilities so as to maximise data integrity and system se-curity. Traditional packet classifiers, such as PCAP, have utilised Con-trol Flow Graphs (CFGs) in representing filter sets, due to both their amenability to optimisation, and their inherent structural applicability to the metaphor of decision-based classification. Unfortunately, CFGs do not map well to cooperative processing implementations, and single-threaded CPU-based implementations have proven too slow for real-time classification against multiple arbitrary filters on next generation networks. In this paper, we consider a novel multithreaded classification algorithm, optimised for execution on GPU co-processors, intended to accelerate classification throughput and maximise processing efficien-cy in a highly parallel execution context.
- Full Text:
Participatory human development in post-apartheid South Africa: a discussion of the 2006/7 Tantyi Youth Empowerment Project
- Authors: Kulundu, Injairu M
- Date: 2010
- Subjects: Spirals Trust (South Africa) Community development -- South Africa -- Citizen participation Economic development projects -- South Africa -- Citizen participation Youth in development -- South Africa Non-governmental organizations -- South Africa Post-apartheid era -- South Africa South Africa -- Politics and government -- 1994-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2791 , http://hdl.handle.net/10962/d1003001
- Description: This thesis relates the work of a non-governmental organisation, The Spirals Trust, to discussions on human and participatory development. The focus of the study is one of The Spirals Trust’s projects, the 2006/7 Tantyi Youth Empowerment Project, which is discussed in relation to theoretical material on human development and participatory development. Collectively these perspectives are defined in this thesis as ‘participatory human development’. The 2006/7 Tantyi Youth Empowerment Project illustrates some of the challenges that face the practice of participatory human development. Workshops and focus group interviews were conducted with participants who were part of the 2006/7 Tantyi Youth Empowerment Project in order to draw out their experiences of the project. Questions were created from themes that emerged from the participants’ discussion of their experiences and these questions were then posed to members of staff of The Spirals Trust. The experiences of both the participants and the staff members are discussed in order to explore issues that emerge in the practice of participatory human development in the 2006/7 Tantyi Youth Empowerment Project. The results highlight the challenges of putting into action the tenets of participatory human development. Feedback showed that a focus on personal development can help cultivate the ethic of participation. The effort that this entailed on the part of facilitators is discussed. The importance of exposing and continually working with power dynamics that may emerge in projects of this nature is revealed and the eroding influence of bureaucratic compliance in projects like this one is explored. The study also suggests that there is a need to promote development initiatives that challenge the political status quo rather than just finding ways to incorporate the marginalised more effectively into current systems. New questions that the research poses to the practice of participatory human development are considered in conjunction with suggestions for further research.
- Full Text:
- Authors: Kulundu, Injairu M
- Date: 2010
- Subjects: Spirals Trust (South Africa) Community development -- South Africa -- Citizen participation Economic development projects -- South Africa -- Citizen participation Youth in development -- South Africa Non-governmental organizations -- South Africa Post-apartheid era -- South Africa South Africa -- Politics and government -- 1994-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2791 , http://hdl.handle.net/10962/d1003001
- Description: This thesis relates the work of a non-governmental organisation, The Spirals Trust, to discussions on human and participatory development. The focus of the study is one of The Spirals Trust’s projects, the 2006/7 Tantyi Youth Empowerment Project, which is discussed in relation to theoretical material on human development and participatory development. Collectively these perspectives are defined in this thesis as ‘participatory human development’. The 2006/7 Tantyi Youth Empowerment Project illustrates some of the challenges that face the practice of participatory human development. Workshops and focus group interviews were conducted with participants who were part of the 2006/7 Tantyi Youth Empowerment Project in order to draw out their experiences of the project. Questions were created from themes that emerged from the participants’ discussion of their experiences and these questions were then posed to members of staff of The Spirals Trust. The experiences of both the participants and the staff members are discussed in order to explore issues that emerge in the practice of participatory human development in the 2006/7 Tantyi Youth Empowerment Project. The results highlight the challenges of putting into action the tenets of participatory human development. Feedback showed that a focus on personal development can help cultivate the ethic of participation. The effort that this entailed on the part of facilitators is discussed. The importance of exposing and continually working with power dynamics that may emerge in projects of this nature is revealed and the eroding influence of bureaucratic compliance in projects like this one is explored. The study also suggests that there is a need to promote development initiatives that challenge the political status quo rather than just finding ways to incorporate the marginalised more effectively into current systems. New questions that the research poses to the practice of participatory human development are considered in conjunction with suggestions for further research.
- Full Text:
Philosophers and the Poor
- Authors: Jones, Ward E
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275671 , vital:55068 , xlink:href="https://doi.org/10.3167/th.2010.5712506"
- Description: This is a programmatic paper, calling for the renewal andmodernisation of the therapeutic approach to philosophy found inEpicureans, Stoics, and Skeptics; and, in particular, for an applicationof the therapeutic approach to the life of poverty. The general assump-tion behind a therapeutic approach to philosophy is that it is possiblefor someone to be exposed to philosophical work which leads her toan improved understanding of herself and her situation, and for herlife to be improved by this understanding. After offering a sketch ofhow, given the current nature of academic philosophy, such work willbe carried out and disseminated, I suggest three areas in which philo-sophical discourse could have a therapeutic affect on the poor.
- Full Text:
- Authors: Jones, Ward E
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275671 , vital:55068 , xlink:href="https://doi.org/10.3167/th.2010.5712506"
- Description: This is a programmatic paper, calling for the renewal andmodernisation of the therapeutic approach to philosophy found inEpicureans, Stoics, and Skeptics; and, in particular, for an applicationof the therapeutic approach to the life of poverty. The general assump-tion behind a therapeutic approach to philosophy is that it is possiblefor someone to be exposed to philosophical work which leads her toan improved understanding of herself and her situation, and for herlife to be improved by this understanding. After offering a sketch ofhow, given the current nature of academic philosophy, such work willbe carried out and disseminated, I suggest three areas in which philo-sophical discourse could have a therapeutic affect on the poor.
- Full Text:
Photoelectrochemical characterization of electrodeposited ZnO thin films sensitized by octacarboxymetallophthalocyanine derivatives
- Idowu, Mopelola, Loewenstein, Thomas, Hastall, Andreas, Nyokong, Tebello, Schlettwein, Derck
- Authors: Idowu, Mopelola , Loewenstein, Thomas , Hastall, Andreas , Nyokong, Tebello , Schlettwein, Derck
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262655 , vital:53541 , xlink:href="https://doi.org/10.1142/S1088424610001854"
- Description: Hybrid thin films of crystalline zinc oxide (ZnO) modified by different octacarboxymetallophthalocyanines (MOCPc) were prepared by the readsorption method. Homogeneously blue or green thin films were formed. The photoelectrochemical characteristics of the electrodes were studied by time-resolved photocurrent measurements. Zinc(II) 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine (ZnOCPc) showed considerably large quantum efficiency in sensitization of ZnO, one of the highest quantum efficiencies obtained so far with phthalocyanine-type sensitizers on nanocrystalline ZnO films.
- Full Text:
- Authors: Idowu, Mopelola , Loewenstein, Thomas , Hastall, Andreas , Nyokong, Tebello , Schlettwein, Derck
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262655 , vital:53541 , xlink:href="https://doi.org/10.1142/S1088424610001854"
- Description: Hybrid thin films of crystalline zinc oxide (ZnO) modified by different octacarboxymetallophthalocyanines (MOCPc) were prepared by the readsorption method. Homogeneously blue or green thin films were formed. The photoelectrochemical characteristics of the electrodes were studied by time-resolved photocurrent measurements. Zinc(II) 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine (ZnOCPc) showed considerably large quantum efficiency in sensitization of ZnO, one of the highest quantum efficiencies obtained so far with phthalocyanine-type sensitizers on nanocrystalline ZnO films.
- Full Text:
Photophysical and photochemical parameters of octakis (benzylthio) phthalocyaninato zinc, aluminium and tin
- Akpe, Victor, Brismar, Hjalmar, Nyokong, Tebello, Osadebe, Patience Ogoamak
- Authors: Akpe, Victor , Brismar, Hjalmar , Nyokong, Tebello , Osadebe, Patience Ogoamak
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/248472 , vital:51689 , xlink:href="https://doi.org/10.1016/j.molstruc.2010.08.033"
- Description: This paper addresses the synthesis of octa-substituted benzylthio metallophthalocyanines (OBTMPcs) that contain the central metal ions of Zn2+, Al3+ and Sn4+. The ground state absorption of ZnPc(SR)8 (OBTZnPc) along with the ZnPc derivatives, well documented in literature were used to study a new concept called the red shift index (RsI). The concept is based on the empirical values of RsI of the different complexes in solvent media. Unequivocally, parameters used in this paper show strong correlations that are consistent with the results obtained. For instance, RsI of the complexes tend to increase as the refractive index, nD, and solvent donor, DN, of solvent increases. Photodegradation (photobleaching) quantum yield, ϕd measurements of these compounds show that they are highly photostable, ϕd (0.03–0.33 × 10−5). The triplet quantum yield, ϕT (0.40–0.53) and the triplet lifetime, τT (610–810 μs) are within the typical range for metallophthalocyanines in DMSO. The photosensitisation efficiency, SΔ, is relatively high for all the molecules (0.74–0.90).
- Full Text:
- Authors: Akpe, Victor , Brismar, Hjalmar , Nyokong, Tebello , Osadebe, Patience Ogoamak
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/248472 , vital:51689 , xlink:href="https://doi.org/10.1016/j.molstruc.2010.08.033"
- Description: This paper addresses the synthesis of octa-substituted benzylthio metallophthalocyanines (OBTMPcs) that contain the central metal ions of Zn2+, Al3+ and Sn4+. The ground state absorption of ZnPc(SR)8 (OBTZnPc) along with the ZnPc derivatives, well documented in literature were used to study a new concept called the red shift index (RsI). The concept is based on the empirical values of RsI of the different complexes in solvent media. Unequivocally, parameters used in this paper show strong correlations that are consistent with the results obtained. For instance, RsI of the complexes tend to increase as the refractive index, nD, and solvent donor, DN, of solvent increases. Photodegradation (photobleaching) quantum yield, ϕd measurements of these compounds show that they are highly photostable, ϕd (0.03–0.33 × 10−5). The triplet quantum yield, ϕT (0.40–0.53) and the triplet lifetime, τT (610–810 μs) are within the typical range for metallophthalocyanines in DMSO. The photosensitisation efficiency, SΔ, is relatively high for all the molecules (0.74–0.90).
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Photophysical and photochemical properties of Ni (II), Pd (II) and Pt (II) aryloxo and alkylthio derivatised phthalocyanine
- Ogunbayo, Taofeek B, Nyokong, Tebello
- Authors: Ogunbayo, Taofeek B , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261511 , vital:53416 , xlink:href="https://doi.org/10.1016/j.molstruc.2010.03.047"
- Description: Several aryloxo (3a–6a and 3b–6b) and alkylthio (3d and 3e) derivatised phthalocyanines were synthesized, characterized and the photochemical and photophysical properties investigated along with those of the previously reported (3c–5c, 4d, 5d, 4e and 5e) complexes. The effects of open-shell metals (Ni(II), Pd(II) and Pt(II)) on the photophysical and photochemical properties of the phthalocyanine ligands were investigated. Palladium and platinum improved the triplet quantum yield and singlet oxygen generation capacities of the unmetalated phthalocyanines (3a–3e) making their complexes candidates for further investigation in photocatalysis. Ni(II)Pc analogues gave poor results compared with their Pd(II)Pc and Pt(II)Pc counterparts.
- Full Text:
- Authors: Ogunbayo, Taofeek B , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/261511 , vital:53416 , xlink:href="https://doi.org/10.1016/j.molstruc.2010.03.047"
- Description: Several aryloxo (3a–6a and 3b–6b) and alkylthio (3d and 3e) derivatised phthalocyanines were synthesized, characterized and the photochemical and photophysical properties investigated along with those of the previously reported (3c–5c, 4d, 5d, 4e and 5e) complexes. The effects of open-shell metals (Ni(II), Pd(II) and Pt(II)) on the photophysical and photochemical properties of the phthalocyanine ligands were investigated. Palladium and platinum improved the triplet quantum yield and singlet oxygen generation capacities of the unmetalated phthalocyanines (3a–3e) making their complexes candidates for further investigation in photocatalysis. Ni(II)Pc analogues gave poor results compared with their Pd(II)Pc and Pt(II)Pc counterparts.
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Photophysical and photoelectrochemical properties of water soluble metallophthalocyanines
- Authors: Masilela, Nkosiphile
- Date: 2010
- Subjects: Phthalocyanines , Electrochemistry , Photoelectrochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4330 , http://hdl.handle.net/10962/d1004991 , Phthalocyanines , Electrochemistry , Photoelectrochemistry
- Description: This work presents the synthesis, characterization, photophysicochemical and photoelectrochemical properties of anionic octa-caboxylated (MOCPcs), tetra-sulfonated (MTSPcs) and quaternized cationic (Q(T-2-Py)MPcs) water soluble aluminium, gallium, silicon, titanium and zinc phthalocynines. The peripherally tetra-substituted cationic (Q(T-2-Py)MPcs) and anionic (MTSPcs) were found to be aggregated in aqueous media, yet the octa-carboxylated (MOCPcs) counterparts were monomeric in solution. Cremophor EL (CEL) was used as a disaggregating agent, all the aggregated complexes disaggregated partially or completely in the presence of CEL. The photophysicochemical properties of aggregated complexes were investigated both in the presence of CEL and in aqueous media of pH 11 alone. Low triplet, singlet oxygen and fluorescence quantum yield were obtained in aqueous media (especially for the aggregated complexes) but a high improvement was achieved upon addition of CEL. The gallium complexes ((OH)GaOCPc and (OH)GaTSPc) showed good photophysicochemical properties with higher triplet and singlet oxygen quantum yields. For photoelectrochemistry the (MPcs) dyes were adsorbed to nanoporous ZnO, electrodeposited in the presence of eosin Y as structure directing agent (SDA) on FTO substrates by refluxing or soaking the films in a solution containing the dye of interest such that a full surface coverage was achieved. Quaternized cationic (Q(T-2-Py)MPc) and tetrasulfonated (MTSPcs) phthalocyanines formed strong aggregates when deposited on the surface of FTO/ZnO substrate leading. High external (IPCE) and internal (APCE) quantum efficiencies of up to 50.6% and 96.7% were achieved for the OTiOCPc complex. There was a lower overall cell efficiency for quaternized and tetrasulfonated metallophthalocyanines because of the strong aggregates when they were on the surface of the electrodes. Among the studied materials, OTiOCPc gave the highest overall cell efficiency of phthalocyanine electrodeposited on ZnO of so far = 0.48%.
- Full Text:
- Authors: Masilela, Nkosiphile
- Date: 2010
- Subjects: Phthalocyanines , Electrochemistry , Photoelectrochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4330 , http://hdl.handle.net/10962/d1004991 , Phthalocyanines , Electrochemistry , Photoelectrochemistry
- Description: This work presents the synthesis, characterization, photophysicochemical and photoelectrochemical properties of anionic octa-caboxylated (MOCPcs), tetra-sulfonated (MTSPcs) and quaternized cationic (Q(T-2-Py)MPcs) water soluble aluminium, gallium, silicon, titanium and zinc phthalocynines. The peripherally tetra-substituted cationic (Q(T-2-Py)MPcs) and anionic (MTSPcs) were found to be aggregated in aqueous media, yet the octa-carboxylated (MOCPcs) counterparts were monomeric in solution. Cremophor EL (CEL) was used as a disaggregating agent, all the aggregated complexes disaggregated partially or completely in the presence of CEL. The photophysicochemical properties of aggregated complexes were investigated both in the presence of CEL and in aqueous media of pH 11 alone. Low triplet, singlet oxygen and fluorescence quantum yield were obtained in aqueous media (especially for the aggregated complexes) but a high improvement was achieved upon addition of CEL. The gallium complexes ((OH)GaOCPc and (OH)GaTSPc) showed good photophysicochemical properties with higher triplet and singlet oxygen quantum yields. For photoelectrochemistry the (MPcs) dyes were adsorbed to nanoporous ZnO, electrodeposited in the presence of eosin Y as structure directing agent (SDA) on FTO substrates by refluxing or soaking the films in a solution containing the dye of interest such that a full surface coverage was achieved. Quaternized cationic (Q(T-2-Py)MPc) and tetrasulfonated (MTSPcs) phthalocyanines formed strong aggregates when deposited on the surface of FTO/ZnO substrate leading. High external (IPCE) and internal (APCE) quantum efficiencies of up to 50.6% and 96.7% were achieved for the OTiOCPc complex. There was a lower overall cell efficiency for quaternized and tetrasulfonated metallophthalocyanines because of the strong aggregates when they were on the surface of the electrodes. Among the studied materials, OTiOCPc gave the highest overall cell efficiency of phthalocyanine electrodeposited on ZnO of so far = 0.48%.
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Photophysical properties of newly synthesized fluorinated zinc phthalocyanines in the presence of CdTe quantum dots and the accompanying energy transfer processes
- Erdoğmuş, Ali, Moeno, Sharon, Litwinski, Christian, Nyokong, Tebello
- Authors: Erdoğmuş, Ali , Moeno, Sharon , Litwinski, Christian , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262671 , vital:53543 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.12.014"
- Description: The photophysical properties of two newly synthesized phthalocyanines (Pcs) were studied in the presence and the absence of 3-mercaptopropionic acid (MPA) capped quantum dots (QDs). Energy transfer processes resulting from the combination of QDs and the Pcs: 4-(tetrakis-5-(trifluoromethyl)-2-mercaptopyridinephthalocyaninato)zinc(II) (TtfmMPyZnPc, 3) and 4-(tetrakis-5-(trifluoromethyl)-2-pyridyloxyphthalocyaninato) zinc(II) (TtfmPyZnPc, 4) were also studied. The photophysical properties of the Pcs in the presence of QDs were enhanced and Förster resonance energy transfer (FRET) was observed with the phthalocyanines used. The efficiency of FRET between the QDs and TtfmMPyZnPc and TtfmPyZnPc was found to be 0.31% and 0.45% in DMSO and 0.24% and 0.32% in pyridine, respectively. The triplet state quantum yields for TtfmMPyZnPc and TtfmPyZnPc were found to be 0.86 and 0.74 in DMSO and 0.83 and 0.76 in pyridine.
- Full Text:
- Authors: Erdoğmuş, Ali , Moeno, Sharon , Litwinski, Christian , Nyokong, Tebello
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/262671 , vital:53543 , xlink:href="https://doi.org/10.1016/j.jphotochem.2009.12.014"
- Description: The photophysical properties of two newly synthesized phthalocyanines (Pcs) were studied in the presence and the absence of 3-mercaptopropionic acid (MPA) capped quantum dots (QDs). Energy transfer processes resulting from the combination of QDs and the Pcs: 4-(tetrakis-5-(trifluoromethyl)-2-mercaptopyridinephthalocyaninato)zinc(II) (TtfmMPyZnPc, 3) and 4-(tetrakis-5-(trifluoromethyl)-2-pyridyloxyphthalocyaninato) zinc(II) (TtfmPyZnPc, 4) were also studied. The photophysical properties of the Pcs in the presence of QDs were enhanced and Förster resonance energy transfer (FRET) was observed with the phthalocyanines used. The efficiency of FRET between the QDs and TtfmMPyZnPc and TtfmPyZnPc was found to be 0.31% and 0.45% in DMSO and 0.24% and 0.32% in pyridine, respectively. The triplet state quantum yields for TtfmMPyZnPc and TtfmPyZnPc were found to be 0.86 and 0.74 in DMSO and 0.83 and 0.76 in pyridine.
- Full Text:
Photophysical studies of zinc and indium tetraaminophthalocyanines in the presence of CdTe quantum dots
- Authors: Britton, Jonathan
- Date: 2010
- Subjects: Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4332 , http://hdl.handle.net/10962/d1004993 , Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Description: CdTe QDs capped with mercaptopropionic acid (MPA) and thioglycolic acid (TGA) were covalently linked to zinc and indium tetraaminophthalocyanines (TAPcs) using N-ethyl-N(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) as the coupling agents. The results presented give evidence in favour of formation of an amide bond between the MTAPc and CdTe QDs. Both the linked ZnTAPc–QD complexes and the mixture of QDs and ZnTAPc (without chemical linking) showed Förster resonance energy transfer (FRET), though the linked showed less FRET, whereas the QD interactions with InTAPc yielded no evidence of FRET. Both MTAPcs quenched the QDs emission, with quenching constants of the order of 103–104M−1, binding constants of the order of 108-1010M-1 and the number of binding sites for the MTAPc upon the QD being 2. High energy transfer efficiencies were obtained (in some cases as high as 93%), due to the low donor to acceptor distances. Lastly, both MTAPc were shown to be poor optical limiters because their imaginary third-order susceptibility (Im[χ(3)]) was of the order of 10-17-10-16 (optimal range is 10-9-10-11), the hyperpolarizability (γ) of the order of 10-37-10-36 (optimal range is 10-29-10-34) and the k values were above one but below ten.
- Full Text:
- Authors: Britton, Jonathan
- Date: 2010
- Subjects: Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4332 , http://hdl.handle.net/10962/d1004993 , Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Description: CdTe QDs capped with mercaptopropionic acid (MPA) and thioglycolic acid (TGA) were covalently linked to zinc and indium tetraaminophthalocyanines (TAPcs) using N-ethyl-N(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) as the coupling agents. The results presented give evidence in favour of formation of an amide bond between the MTAPc and CdTe QDs. Both the linked ZnTAPc–QD complexes and the mixture of QDs and ZnTAPc (without chemical linking) showed Förster resonance energy transfer (FRET), though the linked showed less FRET, whereas the QD interactions with InTAPc yielded no evidence of FRET. Both MTAPcs quenched the QDs emission, with quenching constants of the order of 103–104M−1, binding constants of the order of 108-1010M-1 and the number of binding sites for the MTAPc upon the QD being 2. High energy transfer efficiencies were obtained (in some cases as high as 93%), due to the low donor to acceptor distances. Lastly, both MTAPc were shown to be poor optical limiters because their imaginary third-order susceptibility (Im[χ(3)]) was of the order of 10-17-10-16 (optimal range is 10-9-10-11), the hyperpolarizability (γ) of the order of 10-37-10-36 (optimal range is 10-29-10-34) and the k values were above one but below ten.
- Full Text: