Comparison of carbon screen-printed and disk electrodes in the detection of antioxidants using CoPc derivatives
- Matemadombo, Fungisai, Apetrei, Constantin, Nyokong, Tebello, Rodríguez-Méndez, María Luz, de Saja, José Antonio
- Authors: Matemadombo, Fungisai , Apetrei, Constantin , Nyokong, Tebello , Rodríguez-Méndez, María Luz , de Saja, José Antonio
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244371 , vital:51251 , xlink:href="https://doi.org/10.1016/j.snb.2012.02.088"
- Description: Cobalt phthalocyanine (CoPc) and cobalt phthalocyanine carboxylic derivatives (CoTCPc and CoOCPc) have been used as electrocatalysts for the detection of the antioxidants vanillic acid, caffeic acid, pyrogallol, and ascorbic acid on screen-printed carbon and disk electrode surfaces. The cobalt phthalocyanines were used to detect vanillic acid (with limit of detection ranging from 1.15 μM to 2.42 μM at potentials of 0.55–0.88 V vs. Ag|AgCl), caffeic acid (with limit of detection ranging from 1.17 μM to 2.20 μM at potentials of 0.30–0.81 V vs. Ag|AgCl), pyrogallol (with limit of detection ranging from 1.16 μM to 3.63 μM at potentials of 0.52–0.63 V vs. Ag|AgCl), and ascorbic acid (with limit of detection ranging from 1.16 μM to 1.58 μM at potentials of 0.34–0.46 V vs. Ag|AgCl). The kinetic studies also demonstrate diffusion-controlled processes at the electrode surface. The SPCE electrodes have better detection properties towards vanillic acid, caffeic acid, pyrogallol while the disk electrodes had better ascorbic acid detection properties as proven by kinetic studies. Both types CoPc-influenced electrodes show 100% discrimination of the antioxidants.
- Full Text:
- Date Issued: 2012
- Authors: Matemadombo, Fungisai , Apetrei, Constantin , Nyokong, Tebello , Rodríguez-Méndez, María Luz , de Saja, José Antonio
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244371 , vital:51251 , xlink:href="https://doi.org/10.1016/j.snb.2012.02.088"
- Description: Cobalt phthalocyanine (CoPc) and cobalt phthalocyanine carboxylic derivatives (CoTCPc and CoOCPc) have been used as electrocatalysts for the detection of the antioxidants vanillic acid, caffeic acid, pyrogallol, and ascorbic acid on screen-printed carbon and disk electrode surfaces. The cobalt phthalocyanines were used to detect vanillic acid (with limit of detection ranging from 1.15 μM to 2.42 μM at potentials of 0.55–0.88 V vs. Ag|AgCl), caffeic acid (with limit of detection ranging from 1.17 μM to 2.20 μM at potentials of 0.30–0.81 V vs. Ag|AgCl), pyrogallol (with limit of detection ranging from 1.16 μM to 3.63 μM at potentials of 0.52–0.63 V vs. Ag|AgCl), and ascorbic acid (with limit of detection ranging from 1.16 μM to 1.58 μM at potentials of 0.34–0.46 V vs. Ag|AgCl). The kinetic studies also demonstrate diffusion-controlled processes at the electrode surface. The SPCE electrodes have better detection properties towards vanillic acid, caffeic acid, pyrogallol while the disk electrodes had better ascorbic acid detection properties as proven by kinetic studies. Both types CoPc-influenced electrodes show 100% discrimination of the antioxidants.
- Full Text:
- Date Issued: 2012
Comprehension and production of figurative language by Afrikaans-speaking children with and without specific language impairment
- van der Merwe, Kristin, Adendorff, Ralph
- Authors: van der Merwe, Kristin , Adendorff, Ralph
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123442 , vital:35438 , https://doi.org/10.2989/16073614.2012.693708
- Description: This article reports on the comprehension and production of figurative language, namely idioms and similes, in first language Afrikaans-speaking (AFR) boys, ages eight to 10 years, and first language Afrikaans-speaking boys with specific language impairment (SLI), also ages eight to 10. It draws on a larger study by Van der Merwe (2007; see also Van der Merwe & Southwood, 2008). Testing of the comprehension and production abilities of the children was conducted verbally and individually and elicited their understanding of 25 idioms and 25 similes. The idioms were first presented without context; if the child gave an incorrect interpretation, the idiom was placed in context. Raw scores show that the SLI group performed marginally more poorly than the AFR group, but there was no statistically significant difference between the comprehension of idioms by the two groups. The same can be said for the number of literal interpretations provided by the groups. Placing the idioms in context was beneficial to both groups. The simile completion task required the children to provide the last word of each simile. For both groups, the similes task proved to be easier than the idioms task but there was again no statistically significant difference found between the two groups. The results seem to imply that children at this developmental phase, aged eight to 10, whether language impaired or not, have not yet fully grasped figurative language as a concept and need explicit instructions on figurative language. The article ends with a reflection on the suitability of idioms and similes as particular categories of figurative language in studies of this nature.
- Full Text:
- Date Issued: 2012
- Authors: van der Merwe, Kristin , Adendorff, Ralph
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123442 , vital:35438 , https://doi.org/10.2989/16073614.2012.693708
- Description: This article reports on the comprehension and production of figurative language, namely idioms and similes, in first language Afrikaans-speaking (AFR) boys, ages eight to 10 years, and first language Afrikaans-speaking boys with specific language impairment (SLI), also ages eight to 10. It draws on a larger study by Van der Merwe (2007; see also Van der Merwe & Southwood, 2008). Testing of the comprehension and production abilities of the children was conducted verbally and individually and elicited their understanding of 25 idioms and 25 similes. The idioms were first presented without context; if the child gave an incorrect interpretation, the idiom was placed in context. Raw scores show that the SLI group performed marginally more poorly than the AFR group, but there was no statistically significant difference between the comprehension of idioms by the two groups. The same can be said for the number of literal interpretations provided by the groups. Placing the idioms in context was beneficial to both groups. The simile completion task required the children to provide the last word of each simile. For both groups, the similes task proved to be easier than the idioms task but there was again no statistically significant difference found between the two groups. The results seem to imply that children at this developmental phase, aged eight to 10, whether language impaired or not, have not yet fully grasped figurative language as a concept and need explicit instructions on figurative language. The article ends with a reflection on the suitability of idioms and similes as particular categories of figurative language in studies of this nature.
- Full Text:
- Date Issued: 2012
Computer-aided identification of coelacanths, latimeria chalumnae, using scale patterns
- Thornycroft, Rosanne E, Booth, Anthony J
- Authors: Thornycroft, Rosanne E , Booth, Anthony J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124013 , vital:35526 , https://doi.10.1080/17451000.2011.628679
- Description: Despite coelacanths, Latimeria chalumnae, being listed as either endangered by CITES or critically endangered by the IUCN, their population size within South Africa is unknown and still needs to be estimated. Their conservation status unfortunately excludes the use of conventional tagging to mark individual animals for a possible mark-recapture experiment. This study shows that because coelacanths have a unique spot patterning it is possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator, the software accurately identified between 56 and 92% of the individuals. Indentification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60˚ could be accurately identified in photographs, although the percentage of fish correctly identified without operator-intervention decreased rapidly with increasing yaw angle. Computer-aided identification should therefore facilitate future coelacanth research as it is both efficient and accurate while also reducing potential stress on the animals observed.
- Full Text:
- Date Issued: 2012
- Authors: Thornycroft, Rosanne E , Booth, Anthony J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124013 , vital:35526 , https://doi.10.1080/17451000.2011.628679
- Description: Despite coelacanths, Latimeria chalumnae, being listed as either endangered by CITES or critically endangered by the IUCN, their population size within South Africa is unknown and still needs to be estimated. Their conservation status unfortunately excludes the use of conventional tagging to mark individual animals for a possible mark-recapture experiment. This study shows that because coelacanths have a unique spot patterning it is possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator, the software accurately identified between 56 and 92% of the individuals. Indentification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60˚ could be accurately identified in photographs, although the percentage of fish correctly identified without operator-intervention decreased rapidly with increasing yaw angle. Computer-aided identification should therefore facilitate future coelacanth research as it is both efficient and accurate while also reducing potential stress on the animals observed.
- Full Text:
- Date Issued: 2012
Cost-effective realisation of the Internet of Things
- Andersen, Michael, Irwin, Barry V W
- Authors: Andersen, Michael , Irwin, Barry V W
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427930 , vital:72474 , https://www.researchgate.net/profile/Barry-Irwin/publication/326225063_Cost-effec-tive_realisation_of_the_Internet_of_Things/links/5b3f2262a6fdcc8506ffe75e/Cost-effective-realisation-of-the-Internet-of-Things.pdf
- Description: A hardware and software platform, created to facilitate power usage and power quality measurements along with direct power line actuation is under development. Additional general purpose control and sensing interfaces have been integrated. Measurements are persistently stored on each node to allow asynchronous retrieval of data without the need for a central server. The device communicates using an IEEE 802.15. 4 radio transceiver to create a self-configuring mesh network. Users can interface with the mesh network by connecting to any node via USB and utilising the developed high level API and interactive environment.
- Full Text:
- Date Issued: 2012
- Authors: Andersen, Michael , Irwin, Barry V W
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427930 , vital:72474 , https://www.researchgate.net/profile/Barry-Irwin/publication/326225063_Cost-effec-tive_realisation_of_the_Internet_of_Things/links/5b3f2262a6fdcc8506ffe75e/Cost-effective-realisation-of-the-Internet-of-Things.pdf
- Description: A hardware and software platform, created to facilitate power usage and power quality measurements along with direct power line actuation is under development. Additional general purpose control and sensing interfaces have been integrated. Measurements are persistently stored on each node to allow asynchronous retrieval of data without the need for a central server. The device communicates using an IEEE 802.15. 4 radio transceiver to create a self-configuring mesh network. Users can interface with the mesh network by connecting to any node via USB and utilising the developed high level API and interactive environment.
- Full Text:
- Date Issued: 2012
Design of realistic hybrid marine resource management programs in Oceania
- Aswani, Shankar, Ruddle, Kenneth
- Authors: Aswani, Shankar , Ruddle, Kenneth
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70615 , vital:29681 , https://doi.org/10.2984/67.3.11
- Description: This review article synthesizes the authors' several decades of multidisciplinary natural and social science and applied marine resource management experience in the Asia-Pacific region to examine the strengthening of coastal and marine resource management and conservation using alliances between local communities and external institutions. The objective is to assist the design of resource management and conservation programs that enhance the capacity of coastal communities in Oceania to confront both diminishing marine resources and the effects of climate change by providing guidelines for protecting marine biodiversity and vulnerable ecosystem functions. This article describes a management framework that hybridizes local beliefs and institutions expressed in customary management (CM) with such modern management concepts as marine protected areas (MPAs) and ecosystem-based management (EBM). Hybrid management accommodates the social, political, economic, and cultural contexts of Oceanic communities and, compared with recent or conventional management approaches, can therefore better address fundamental local concerns such as coastal degradation, climate change, sea level rise, weak governance, corruption, limited resources and staff to manage and monitor marine resources, and increasing poverty. Research on the hybridization of management systems demonstrates opportunities to establish context-appropriate EBM and/or other managerial arrangements that include terrestrial and adjacent coastal-marine ecosystems. Formal and informal CM systems are widespread in Oceania and in some parts of Southeast Asia, and if appropriate strategies are employed rapid progress toward hybrid CM-EBM could be enabled.
- Full Text:
- Date Issued: 2012
- Authors: Aswani, Shankar , Ruddle, Kenneth
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70615 , vital:29681 , https://doi.org/10.2984/67.3.11
- Description: This review article synthesizes the authors' several decades of multidisciplinary natural and social science and applied marine resource management experience in the Asia-Pacific region to examine the strengthening of coastal and marine resource management and conservation using alliances between local communities and external institutions. The objective is to assist the design of resource management and conservation programs that enhance the capacity of coastal communities in Oceania to confront both diminishing marine resources and the effects of climate change by providing guidelines for protecting marine biodiversity and vulnerable ecosystem functions. This article describes a management framework that hybridizes local beliefs and institutions expressed in customary management (CM) with such modern management concepts as marine protected areas (MPAs) and ecosystem-based management (EBM). Hybrid management accommodates the social, political, economic, and cultural contexts of Oceanic communities and, compared with recent or conventional management approaches, can therefore better address fundamental local concerns such as coastal degradation, climate change, sea level rise, weak governance, corruption, limited resources and staff to manage and monitor marine resources, and increasing poverty. Research on the hybridization of management systems demonstrates opportunities to establish context-appropriate EBM and/or other managerial arrangements that include terrestrial and adjacent coastal-marine ecosystems. Formal and informal CM systems are widespread in Oceania and in some parts of Southeast Asia, and if appropriate strategies are employed rapid progress toward hybrid CM-EBM could be enabled.
- Full Text:
- Date Issued: 2012
Detecting impacts of invasive non-native sharptooth catfish, Clarias gariepinus, within invaded and non-invaded rivers.
- Kadye, Wilbert T, Booth, Anthony J
- Authors: Kadye, Wilbert T , Booth, Anthony J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124100 , vital:35539 , https://doi.10.1007/s10531-012-0291-5
- Description: In aquatic ecosystems, impacts by invasive introduced fish can be likened to press disturbances that persistently influence communities. This study examined invasion disturbances by determining the relationship between non-native sharptooth catfish Clarias gariepinus and aquatic macroinvertebrates in the Eastern Cape, South Africa. A Multiple Before–After Control–Impact (MBACI) experimental design was used to examine macroinvertebrate communities within two rivers: one with catfish and another one without catfish. Within the invaded river, macroinvertebrates showed little response to catfish presence, whereas predator exclusion appeared to benefit community structure. This suggests that the macroinvertebrate community within the invaded river was adapted to predation impact because of the dominance of resilient taxa, such as Hirudinea, Oligochaeta and Chironomidae that were abundant in the Impact treatment relative to the Control treatment. High macroinvertebrate diversity and richness that was observed in the Control treatment, which excluded the predator, relative to the Impact treatment suggests predator avoidance behaviour within the invaded river. By comparison, within the uninvaded river, catfish introduction into the Impact treatment plots indicated negative effects on macroinvertebrate community that was reflected by decrease in diversity, richness and biomass. A community level impact was also reflected in the multivariate analysis that indicated more variation in macroinvertebrate composition within the Impact treatment relative to the Control in the uninvaded river. Catfish impact within the uninvaded river suggests the dominance of vulnerable taxa, such as odonates that were less abundant in the Impact treatment plots after catfish introduction. From a disturbance perspective, this study revealed different macroinvertebrate responses to catfish impact, and suggests that within invaded habitats, macroinvertebrates were less responsive to catfish presence, whereas catfish introduction within uninvaded habitats demonstrated invasion impact that was shown by a decrease in the abundance of vulnerable taxa. The occurrence of non-native sharptooth catfish within many Eastern Cape rivers is a concern because of its predation impact and potential to influence trophic interrelationships, and efforts should be taken to protect uninvaded rivers, and, where possible, eradicate the invader.
- Full Text:
- Date Issued: 2012
- Authors: Kadye, Wilbert T , Booth, Anthony J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124100 , vital:35539 , https://doi.10.1007/s10531-012-0291-5
- Description: In aquatic ecosystems, impacts by invasive introduced fish can be likened to press disturbances that persistently influence communities. This study examined invasion disturbances by determining the relationship between non-native sharptooth catfish Clarias gariepinus and aquatic macroinvertebrates in the Eastern Cape, South Africa. A Multiple Before–After Control–Impact (MBACI) experimental design was used to examine macroinvertebrate communities within two rivers: one with catfish and another one without catfish. Within the invaded river, macroinvertebrates showed little response to catfish presence, whereas predator exclusion appeared to benefit community structure. This suggests that the macroinvertebrate community within the invaded river was adapted to predation impact because of the dominance of resilient taxa, such as Hirudinea, Oligochaeta and Chironomidae that were abundant in the Impact treatment relative to the Control treatment. High macroinvertebrate diversity and richness that was observed in the Control treatment, which excluded the predator, relative to the Impact treatment suggests predator avoidance behaviour within the invaded river. By comparison, within the uninvaded river, catfish introduction into the Impact treatment plots indicated negative effects on macroinvertebrate community that was reflected by decrease in diversity, richness and biomass. A community level impact was also reflected in the multivariate analysis that indicated more variation in macroinvertebrate composition within the Impact treatment relative to the Control in the uninvaded river. Catfish impact within the uninvaded river suggests the dominance of vulnerable taxa, such as odonates that were less abundant in the Impact treatment plots after catfish introduction. From a disturbance perspective, this study revealed different macroinvertebrate responses to catfish impact, and suggests that within invaded habitats, macroinvertebrates were less responsive to catfish presence, whereas catfish introduction within uninvaded habitats demonstrated invasion impact that was shown by a decrease in the abundance of vulnerable taxa. The occurrence of non-native sharptooth catfish within many Eastern Cape rivers is a concern because of its predation impact and potential to influence trophic interrelationships, and efforts should be taken to protect uninvaded rivers, and, where possible, eradicate the invader.
- Full Text:
- Date Issued: 2012
Developing images of self: childhood, youth and family photographs in works by three South African women artists
- Authors: Schmahmann, Brenda
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147571 , vital:38650 , https://doi.org/10.1162/AFAR_a_00024
- Description: In 1996, South African artist Bridget Baker (b. 1971), completed So It Goes (Fig. 1), a work comprising four Vicks Vapour Rub containers which each feature the same photograph. A representation of the artist being taught to swim by her father, who died when she was a child, this is the only shot she possesses that shows them together. The photograph is overlaid with progressively increased amounts of the Vapour Rub until, in the last of the four tins, the image is almost entirely obliterated.
- Full Text:
- Date Issued: 2012
- Authors: Schmahmann, Brenda
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147571 , vital:38650 , https://doi.org/10.1162/AFAR_a_00024
- Description: In 1996, South African artist Bridget Baker (b. 1971), completed So It Goes (Fig. 1), a work comprising four Vicks Vapour Rub containers which each feature the same photograph. A representation of the artist being taught to swim by her father, who died when she was a child, this is the only shot she possesses that shows them together. The photograph is overlaid with progressively increased amounts of the Vapour Rub until, in the last of the four tins, the image is almost entirely obliterated.
- Full Text:
- Date Issued: 2012
Differential regulation of monocyte cytokine release by αV and β2 integrins that bind CD23:
- Edkins, Adrienne L, Borland, Gillian, Acharya, Mridu, Cogdell, Richard, Ozanne, Bradford W, Cushley, William
- Authors: Edkins, Adrienne L , Borland, Gillian , Acharya, Mridu , Cogdell, Richard , Ozanne, Bradford W , Cushley, William
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165153 , vital:41213 , DOI: 10.1111/j.1365-2567.2012.03576.x
- Description: The human soluble CD23 (sCD23) protein displays highly pleiotropic cytokine‐like activity. Monocytic cells express the sCD23‐binding integrins αVβ3, αVβ5, αMβ2 and αXβ2, but it is unclear which of these four integrins most acutely regulates sCD23‐driven cytokine release. The hypothesis that ligation of different sCD23‐binding integrins promoted release of distinct subsets of cytokines was tested. Lipopolysaccharide (LPS) and sCD23 promoted release of distinct groups of cytokines from the THP‐1 model cell line.
- Full Text:
- Date Issued: 2012
- Authors: Edkins, Adrienne L , Borland, Gillian , Acharya, Mridu , Cogdell, Richard , Ozanne, Bradford W , Cushley, William
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165153 , vital:41213 , DOI: 10.1111/j.1365-2567.2012.03576.x
- Description: The human soluble CD23 (sCD23) protein displays highly pleiotropic cytokine‐like activity. Monocytic cells express the sCD23‐binding integrins αVβ3, αVβ5, αMβ2 and αXβ2, but it is unclear which of these four integrins most acutely regulates sCD23‐driven cytokine release. The hypothesis that ligation of different sCD23‐binding integrins promoted release of distinct subsets of cytokines was tested. Lipopolysaccharide (LPS) and sCD23 promoted release of distinct groups of cytokines from the THP‐1 model cell line.
- Full Text:
- Date Issued: 2012
Dragging young people down the drain: the mobile phone, gossip mobile website Outoilet and the creation of a mobile ghetto
- Authors: Schoon, Alette
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147858 , vital:38679 , DOI: 10.1080/02560046.2012.744723
- Description: This qualitative study uses the domestication model to describe how a geographically based gossip mobile website, Outoilet (old toilet), helped to shape the meanings of everyday life for young adults in Hooggenoeg, a poor black low-income urban settlement in Grahamstown, South Africa. All the residents here know one another and there is very little privacy, and the mobile phone, during the period of this research, reinforced the lack of privacy through gossip. Such gossip promoted an inward-looking collective sociability. As this article demonstrates, subjects of gossip avoided the streets to escape collective surveillance. Outoilet's explicit sexual language seemed to target those who attempted social mobility by replicating local discourses of respectability and shame. Contrary to findings from other contexts, the mobile phone here thus promoted a collective sociability and may have discouraged mobility as well as economic development.
- Full Text:
- Date Issued: 2012
- Authors: Schoon, Alette
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147858 , vital:38679 , DOI: 10.1080/02560046.2012.744723
- Description: This qualitative study uses the domestication model to describe how a geographically based gossip mobile website, Outoilet (old toilet), helped to shape the meanings of everyday life for young adults in Hooggenoeg, a poor black low-income urban settlement in Grahamstown, South Africa. All the residents here know one another and there is very little privacy, and the mobile phone, during the period of this research, reinforced the lack of privacy through gossip. Such gossip promoted an inward-looking collective sociability. As this article demonstrates, subjects of gossip avoided the streets to escape collective surveillance. Outoilet's explicit sexual language seemed to target those who attempted social mobility by replicating local discourses of respectability and shame. Contrary to findings from other contexts, the mobile phone here thus promoted a collective sociability and may have discouraged mobility as well as economic development.
- Full Text:
- Date Issued: 2012
Electrocatalytic behavior of cobalt phthalocyanine complexes immobilized on glassy carbon electrode towards the reduction of dicrotophos pesticide
- Vilakazi, Sibulelo, Nyokong, Tebello, Fukuda, Takamitsu, Kobayashi, Nagao
- Authors: Vilakazi, Sibulelo , Nyokong, Tebello , Fukuda, Takamitsu , Kobayashi, Nagao
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245832 , vital:51409 , xlink:href="https://doi.org/10.1142/S1088424612501040"
- Description: Electrocatalytic properties of cobalt phthalocyanine (CoPc), cobalt tetra-carboxy phthalocyanine (CoTCPc) and cobalt octa-carboxy (CoOCPc), towards the detection of dicrotophos have been studied. Catalytic behavior towards the reduction of dicrotophos was found to be dependent on the pH, as well as the substitution on the phthalocyanine ring. Strong electron withdrawing groups on the phthalocyanine ring yielded best catalysis as evidenced by the enhancement of the reduction peak current, (~5 fold) compared to the bare glassy carbon electrode. The analysis gave a good detection limit of 1.25 × 10-7 M, and good linearity for the studied concentration range. A high Tafel slope value was obtained, indicating a strong interaction between dicrotophos and the cobalt phthalocyanine complex.
- Full Text:
- Date Issued: 2012
- Authors: Vilakazi, Sibulelo , Nyokong, Tebello , Fukuda, Takamitsu , Kobayashi, Nagao
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245832 , vital:51409 , xlink:href="https://doi.org/10.1142/S1088424612501040"
- Description: Electrocatalytic properties of cobalt phthalocyanine (CoPc), cobalt tetra-carboxy phthalocyanine (CoTCPc) and cobalt octa-carboxy (CoOCPc), towards the detection of dicrotophos have been studied. Catalytic behavior towards the reduction of dicrotophos was found to be dependent on the pH, as well as the substitution on the phthalocyanine ring. Strong electron withdrawing groups on the phthalocyanine ring yielded best catalysis as evidenced by the enhancement of the reduction peak current, (~5 fold) compared to the bare glassy carbon electrode. The analysis gave a good detection limit of 1.25 × 10-7 M, and good linearity for the studied concentration range. A high Tafel slope value was obtained, indicating a strong interaction between dicrotophos and the cobalt phthalocyanine complex.
- Full Text:
- Date Issued: 2012
Electrospun polyacrylic acid polymer fibers functionalized with metallophthalocyanines for photosensitizing and gas sensing applications
- Zugle, Ruphino, Nyokong, Tebello
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243543 , vital:51162 , xlink:href="https://doi.org/10.1080/10601325.2012.662006"
- Description: The photophysical and photochemical properties of tetraaminophthalocyanine complexes of lutetium and zinc covalently linked to polyacrylic acid were studied alongside those of unsubstituted zinc phthalocyanine within the same polymeric fiber matrix. All three phthalocyanines within the solid fiber matrices showed photoactivity by the generation of singlet oxygen as was observed in solution. The fluorescence behaviors of the composite fibers equally parallel those in solution. For the unsubstituted zinc phthalocyanine composite, the fiber showed fluorescence quenching on interaction with gaseous nitrogen dioxide similar to that in DMF and, thus could be a promising nanofabric material in developing optoelectronic devices that are responsive to the gas.
- Full Text:
- Date Issued: 2012
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243543 , vital:51162 , xlink:href="https://doi.org/10.1080/10601325.2012.662006"
- Description: The photophysical and photochemical properties of tetraaminophthalocyanine complexes of lutetium and zinc covalently linked to polyacrylic acid were studied alongside those of unsubstituted zinc phthalocyanine within the same polymeric fiber matrix. All three phthalocyanines within the solid fiber matrices showed photoactivity by the generation of singlet oxygen as was observed in solution. The fluorescence behaviors of the composite fibers equally parallel those in solution. For the unsubstituted zinc phthalocyanine composite, the fiber showed fluorescence quenching on interaction with gaseous nitrogen dioxide similar to that in DMF and, thus could be a promising nanofabric material in developing optoelectronic devices that are responsive to the gas.
- Full Text:
- Date Issued: 2012
Embrace! Invest! Flourish!: Africa rising
- Authors: Malila, Vanessa
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159539 , vital:40306 , https://hdl.handle.net/10520/EJC134110
- Description: Currently the trend across Africa within the media landscape is growth - compared with its European and American counterparts who are feeling the full weight of the current financial crisis which has seen many newspapers downsize, cut jobs and suffer massive cost cutting strategies.
- Full Text:
- Date Issued: 2012
- Authors: Malila, Vanessa
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159539 , vital:40306 , https://hdl.handle.net/10520/EJC134110
- Description: Currently the trend across Africa within the media landscape is growth - compared with its European and American counterparts who are feeling the full weight of the current financial crisis which has seen many newspapers downsize, cut jobs and suffer massive cost cutting strategies.
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- Date Issued: 2012
Exploring relationship between value-and life-orientation and job satisfaction:
- Louw, Lynette, Mayer, Claude-Hélène, Baxter, Jeremy
- Authors: Louw, Lynette , Mayer, Claude-Hélène , Baxter, Jeremy
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142782 , vital:38116 , DOI: 10.4102/ac.v12i1.131
- Description: The purpose of this article is to investigate the relationship between value- and life-orientation and job satisfaction, as well as determining the influence of gender, age and cultural group within the selected South African organisational context.
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- Date Issued: 2012
- Authors: Louw, Lynette , Mayer, Claude-Hélène , Baxter, Jeremy
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142782 , vital:38116 , DOI: 10.4102/ac.v12i1.131
- Description: The purpose of this article is to investigate the relationship between value- and life-orientation and job satisfaction, as well as determining the influence of gender, age and cultural group within the selected South African organisational context.
- Full Text:
- Date Issued: 2012
Facile deposition of gold nanoparticle thin films on semi-permeable cellulose substrate
- Sosibo, Ndabenhle, Mdluli, Phumlani, Mashazi, Philani N, Tshikhudo, Robert, Skepu, Amanda, Vilakazi, Sibulelo, Nyokong, Tebello
- Authors: Sosibo, Ndabenhle , Mdluli, Phumlani , Mashazi, Philani N , Tshikhudo, Robert , Skepu, Amanda , Vilakazi, Sibulelo , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242638 , vital:51063 , xlink:href="https://doi.org/10.1016/j.matlet.2012.08.043"
- Description: This study reports the facile method for the deposition of gold nanoparticle thin film onto a monoporous semi-permeable cellulose membrane through the diffusion of borohydride ions leading to the reduction of AuCl4− ions. The synthesis of gold nanoparticle thin film was deposited on one side of the membrane that was exposed to AuCl4− ions while the other side containing a reducing agent remained clear. The gold nanoparticle thin film exhibited a broad surface plasmon resonance (SPR) peak at 529 nm. Various characterization techniques were employed and all demonstrated the presence of gold thin film. The reported method represents a simplistic method for the deposition of gold nanoparticle thin films and various other metal nanoparticles may be deposited following this method.
- Full Text:
- Date Issued: 2012
- Authors: Sosibo, Ndabenhle , Mdluli, Phumlani , Mashazi, Philani N , Tshikhudo, Robert , Skepu, Amanda , Vilakazi, Sibulelo , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242638 , vital:51063 , xlink:href="https://doi.org/10.1016/j.matlet.2012.08.043"
- Description: This study reports the facile method for the deposition of gold nanoparticle thin film onto a monoporous semi-permeable cellulose membrane through the diffusion of borohydride ions leading to the reduction of AuCl4− ions. The synthesis of gold nanoparticle thin film was deposited on one side of the membrane that was exposed to AuCl4− ions while the other side containing a reducing agent remained clear. The gold nanoparticle thin film exhibited a broad surface plasmon resonance (SPR) peak at 529 nm. Various characterization techniques were employed and all demonstrated the presence of gold thin film. The reported method represents a simplistic method for the deposition of gold nanoparticle thin films and various other metal nanoparticles may be deposited following this method.
- Full Text:
- Date Issued: 2012
Firm age, collateral value, and access to debt financing in an emerging economy: evidence from South Africa
- Authors: Ezeoha,Abel , Botha, Ferdi
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396060 , vital:69147 , xlink:href="https://hdl.handle.net/10520/EJC31367"
- Description: This paper applies the Blundell and Bond system generalised method of moments (GMM) two-step estimator to examine the impact of age and collateral value on debt financing, using a panel of 177 non-financial companies listed on the Johannesburg Stock Exchange over the period 1999 to 2009. The results show that South African firms have target leverage ratios and adjust their capital structures from time to time to achieve their respective targets, that the relationship between firm age and debt financing is non-monotonic, and that firms with higher collateral value are likely to face fewer constraints on borrowing and therefore have greater access to medium-term and long-term debts. Robustness tests also reveal that during start-up and maturity stages, a firm's access to debt markets is significantly influenced by investments in assets that are acceptable to external creditors as collateral. These findings suggest that debt financing policies could be more critical for firms in the start-up and maturity stages.
- Full Text:
- Date Issued: 2012
- Authors: Ezeoha,Abel , Botha, Ferdi
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396060 , vital:69147 , xlink:href="https://hdl.handle.net/10520/EJC31367"
- Description: This paper applies the Blundell and Bond system generalised method of moments (GMM) two-step estimator to examine the impact of age and collateral value on debt financing, using a panel of 177 non-financial companies listed on the Johannesburg Stock Exchange over the period 1999 to 2009. The results show that South African firms have target leverage ratios and adjust their capital structures from time to time to achieve their respective targets, that the relationship between firm age and debt financing is non-monotonic, and that firms with higher collateral value are likely to face fewer constraints on borrowing and therefore have greater access to medium-term and long-term debts. Robustness tests also reveal that during start-up and maturity stages, a firm's access to debt markets is significantly influenced by investments in assets that are acceptable to external creditors as collateral. These findings suggest that debt financing policies could be more critical for firms in the start-up and maturity stages.
- Full Text:
- Date Issued: 2012
Five unpublished coins of Alexander the Great and his successors in the Rhodes University Collection
- Snowball, Jeanette D, Snowball, Warren D
- Authors: Snowball, Jeanette D , Snowball, Warren D
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68489 , vital:29267 , http://dx.doi.org/10.7445/50-0-73
- Description: Publisher version , The article briefly discusses the economic and political significance of the Alexander III (“the Great”) type silver tetradrachm and publishes three of his coins currently held by the Rhodes University Classics Museum. Based on stylistic elements, they are classified as from the Amphipolis and Arados mints and were probably minted during his lifetime. Two further tetradrachms from the empires of Alexander’s successors, Ptolemy II and Seleucus IV, are also published.
- Full Text:
- Date Issued: 2012
Five unpublished coins of Alexander the Great and his successors in the Rhodes University Collection
- Authors: Snowball, Jeanette D , Snowball, Warren D
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68489 , vital:29267 , http://dx.doi.org/10.7445/50-0-73
- Description: Publisher version , The article briefly discusses the economic and political significance of the Alexander III (“the Great”) type silver tetradrachm and publishes three of his coins currently held by the Rhodes University Classics Museum. Based on stylistic elements, they are classified as from the Amphipolis and Arados mints and were probably minted during his lifetime. Two further tetradrachms from the empires of Alexander’s successors, Ptolemy II and Seleucus IV, are also published.
- Full Text:
- Date Issued: 2012
Functional programming and security
- Authors: Motara, Yusuf, M
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428985 , vital:72551 , https://doi.org/10.48550/arXiv.1201.5728
- Description: This paper analyses the security contribution of typical functional-language features by examining them in the light of accepted information security principles. Imperative and functional code are compared to illustrate various cases. In conclusion, there may be an excellent case for the use of functional languages on the grounds of better security; however, empirical research should be done to validate this possibility.
- Full Text:
- Date Issued: 2012
- Authors: Motara, Yusuf, M
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428985 , vital:72551 , https://doi.org/10.48550/arXiv.1201.5728
- Description: This paper analyses the security contribution of typical functional-language features by examining them in the light of accepted information security principles. Imperative and functional code are compared to illustrate various cases. In conclusion, there may be an excellent case for the use of functional languages on the grounds of better security; however, empirical research should be done to validate this possibility.
- Full Text:
- Date Issued: 2012
Geo-spatial autocorrelation as a metric for the detection of fast-flux botnet domains
- Stalmans, Etienne, Hunter, Samuel O, Irwin, Barry V W
- Authors: Stalmans, Etienne , Hunter, Samuel O , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429799 , vital:72640 , 10.1109/ISSA.2012.6320433
- Description: Botnets consist of thousands of hosts infected with malware. Botnet owners communicate with these hosts using Command and Control (C2) servers. These C2 servers are usually infected hosts which the botnet owners do not have physical access to. For this reason botnets can be shut down by taking over or blocking the C2 servers. Botnet owners have employed numerous shutdown avoidance techniques. One of these techniques, DNS Fast-Flux, relies on rapidly changing address records. The addresses returned by the Fast-Flux DNS servers consist of geographically widely distributed hosts. The distributed nature of Fast-Flux botnets differs from legitimate domains, which tend to have geographically clustered server locations. This paper examines the use of spatial autocorrelation techniques based on the geographic distribution of domain servers to detect Fast-Flux domains. Moran's I and Geary's C are used to produce classifiers using multiple geographic co-ordinate systems to produce efficient and accurate results. It is shown how Fast-Flux domains can be detected reliably while only a small percentage of false positives are produced.
- Full Text:
- Date Issued: 2012
- Authors: Stalmans, Etienne , Hunter, Samuel O , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429799 , vital:72640 , 10.1109/ISSA.2012.6320433
- Description: Botnets consist of thousands of hosts infected with malware. Botnet owners communicate with these hosts using Command and Control (C2) servers. These C2 servers are usually infected hosts which the botnet owners do not have physical access to. For this reason botnets can be shut down by taking over or blocking the C2 servers. Botnet owners have employed numerous shutdown avoidance techniques. One of these techniques, DNS Fast-Flux, relies on rapidly changing address records. The addresses returned by the Fast-Flux DNS servers consist of geographically widely distributed hosts. The distributed nature of Fast-Flux botnets differs from legitimate domains, which tend to have geographically clustered server locations. This paper examines the use of spatial autocorrelation techniques based on the geographic distribution of domain servers to detect Fast-Flux domains. Moran's I and Geary's C are used to produce classifiers using multiple geographic co-ordinate systems to produce efficient and accurate results. It is shown how Fast-Flux domains can be detected reliably while only a small percentage of false positives are produced.
- Full Text:
- Date Issued: 2012
Guy Butler’s South Africanism: ‘Being present where you are’
- Authors: Wright, Laurence
- Date: 2012
- Language: English
- Type: text , article
- Identifier: vital:7069 , http://hdl.handle.net/10962/d1007460 , https://doi.org/10.1080/10131752.2012.730182
- Description: preprint , A peer-reviewed lecture delivered at Rhodes University on the occasion of the presentation to Professor Wright of the English Academy's Gold Medal, 16 November 2011. Guy Butler (1918-2001) has been gone some ten years. This lecture sets out to illuminate the thinking behind his important role in South Africa's national life. The institutions he created continue to make vital cultural contributions in South Africa's efforts to make sense of its own complex historical make-up, working towards a happier, richer, and more equal future. However, despite what he achieved, there is little surety that today the rationale informing his massive effort to foster processes of artistic and cultural endeavour has been appreciated or accurately understood.
- Full Text:
- Date Issued: 2012
- Authors: Wright, Laurence
- Date: 2012
- Language: English
- Type: text , article
- Identifier: vital:7069 , http://hdl.handle.net/10962/d1007460 , https://doi.org/10.1080/10131752.2012.730182
- Description: preprint , A peer-reviewed lecture delivered at Rhodes University on the occasion of the presentation to Professor Wright of the English Academy's Gold Medal, 16 November 2011. Guy Butler (1918-2001) has been gone some ten years. This lecture sets out to illuminate the thinking behind his important role in South Africa's national life. The institutions he created continue to make vital cultural contributions in South Africa's efforts to make sense of its own complex historical make-up, working towards a happier, richer, and more equal future. However, despite what he achieved, there is little surety that today the rationale informing his massive effort to foster processes of artistic and cultural endeavour has been appreciated or accurately understood.
- Full Text:
- Date Issued: 2012
Having a phone, having style:
- Authors: Schoon, Alette
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159506 , vital:40303 , https://hdl.handle.net/10520/EJC135828
- Description: It was dusk, and a group of young men with a dog trailing behind them, were walking past on a dusty township road in Hooggenoeg, an RDP village on the rim of the Grahamstown bowl. While they ambled along, one was holding up a mobile phone on which music was playing, dancing while he walked. This was exactly the kind of thing I was hoping to observe in my new identity as researcher and participant observer, and was why I had agreed to judge the Hooggenoeg fashion show which turned out to be more of a beauty competition. While I'm not generally fond of these kind of shows and the way they essentialise beauty, I agreed because I wanted to get more of a sense of how mobile phones are integrated into the everyday lives of these young adults.
- Full Text:
- Date Issued: 2012
- Authors: Schoon, Alette
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159506 , vital:40303 , https://hdl.handle.net/10520/EJC135828
- Description: It was dusk, and a group of young men with a dog trailing behind them, were walking past on a dusty township road in Hooggenoeg, an RDP village on the rim of the Grahamstown bowl. While they ambled along, one was holding up a mobile phone on which music was playing, dancing while he walked. This was exactly the kind of thing I was hoping to observe in my new identity as researcher and participant observer, and was why I had agreed to judge the Hooggenoeg fashion show which turned out to be more of a beauty competition. While I'm not generally fond of these kind of shows and the way they essentialise beauty, I agreed because I wanted to get more of a sense of how mobile phones are integrated into the everyday lives of these young adults.
- Full Text:
- Date Issued: 2012