A qualitative analysis to determine the readiness of rural communities to adopt ICTs: A Siyakhula Living Lab Case Study
- Gumbo, Sibukelo, Jere, Norbert, Terzoli, Alfredo
- Authors: Gumbo, Sibukelo , Jere, Norbert , Terzoli, Alfredo
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431396 , vital:72771
- Description: Rural schools have a pressing need for ICT and Internet services, for them-selves and the surrounding communities. Educators can play a crucial role of fulfilling this need. But how ready are schools, educators and communi-ties to engage with ICT and use it for their empowerment? This paper re-ports the findings of an e-readiness assessment and promotion drive by re-searchers from the Siyakhula Living Lab in parts of the Mbashe Municipali-ty, in South Africa. The Siyakhula Living Lab is a multi-disciplinary, multi-year initiative to foster grassroots innovation in marginalized communities with the aim of improving their lives and economies. The drive was con-ducted to support the expansion of the network of Digital Access Nodes, ie ICT points-of-presence of the Living Lab in the community: this network rep-resents the structural backbone on which all other activities rest. The as-sessment shows that, while the practical difficulties are many, the communi-ties are very eager to engage with ICT and understand fairly well the con-nection between ICT availability and the possibility of improvement in their life conditions.
- Full Text:
- Date Issued: 2012
- Authors: Gumbo, Sibukelo , Jere, Norbert , Terzoli, Alfredo
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431396 , vital:72771
- Description: Rural schools have a pressing need for ICT and Internet services, for them-selves and the surrounding communities. Educators can play a crucial role of fulfilling this need. But how ready are schools, educators and communi-ties to engage with ICT and use it for their empowerment? This paper re-ports the findings of an e-readiness assessment and promotion drive by re-searchers from the Siyakhula Living Lab in parts of the Mbashe Municipali-ty, in South Africa. The Siyakhula Living Lab is a multi-disciplinary, multi-year initiative to foster grassroots innovation in marginalized communities with the aim of improving their lives and economies. The drive was con-ducted to support the expansion of the network of Digital Access Nodes, ie ICT points-of-presence of the Living Lab in the community: this network rep-resents the structural backbone on which all other activities rest. The as-sessment shows that, while the practical difficulties are many, the communi-ties are very eager to engage with ICT and understand fairly well the con-nection between ICT availability and the possibility of improvement in their life conditions.
- Full Text:
- Date Issued: 2012
A study on the morphology of thin copper films on para-aramid yarns and their influence on the yarn’s electro-conductive and mechanical properties
- Schwarz, Anne, Hakuzimana, Jean, Westbroek, Philippe, Mey, Gilbert De, Priniotakis, Georgios, Nyokong, Tebello, Langenhove, Lieva Van
- Authors: Schwarz, Anne , Hakuzimana, Jean , Westbroek, Philippe , Mey, Gilbert De , Priniotakis, Georgios , Nyokong, Tebello , Langenhove, Lieva Van
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243487 , vital:51157 , xlink:href="https://doi.org/10.1177/0040517511431291"
- Description: The latest technological advances in new materials and devices enabled wearable systems to be created by utilizing textile solutions. These solutions require electro-conductive yarns as a basic component. Although the production of electroconductive yarn is widely reported, research is still necessary to characterize them to advance their electro-conductive and mechanical properties. Hence, we served this need and characterized copper-coated para-aramid yarns produced by an in-house developed electroless deposition method. In this paper we present our investigation on the yarn’s copper layer characteristics after deposition. Furthermore, we looked, in depth, at the yarn’s electro-conductive properties before and after washing as well as their mechanical properties before and after copper deposition. We found a dependency of the copper layer morphology on its deposition time. This is directly correlated to the resulting layer thickness and hence to the yarn’s electro-conductive properties, demonstrating the autocatalytic nature of the coating process. Above that, the electro-conductive properties of the coated yarn linearly decrease with washing cycles. Furthermore, the copper coating impairs the yarn’s mechanical properties decreasing its specific stress at break by 30%.
- Full Text:
- Date Issued: 2012
- Authors: Schwarz, Anne , Hakuzimana, Jean , Westbroek, Philippe , Mey, Gilbert De , Priniotakis, Georgios , Nyokong, Tebello , Langenhove, Lieva Van
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243487 , vital:51157 , xlink:href="https://doi.org/10.1177/0040517511431291"
- Description: The latest technological advances in new materials and devices enabled wearable systems to be created by utilizing textile solutions. These solutions require electro-conductive yarns as a basic component. Although the production of electroconductive yarn is widely reported, research is still necessary to characterize them to advance their electro-conductive and mechanical properties. Hence, we served this need and characterized copper-coated para-aramid yarns produced by an in-house developed electroless deposition method. In this paper we present our investigation on the yarn’s copper layer characteristics after deposition. Furthermore, we looked, in depth, at the yarn’s electro-conductive properties before and after washing as well as their mechanical properties before and after copper deposition. We found a dependency of the copper layer morphology on its deposition time. This is directly correlated to the resulting layer thickness and hence to the yarn’s electro-conductive properties, demonstrating the autocatalytic nature of the coating process. Above that, the electro-conductive properties of the coated yarn linearly decrease with washing cycles. Furthermore, the copper coating impairs the yarn’s mechanical properties decreasing its specific stress at break by 30%.
- Full Text:
- Date Issued: 2012
An Analysis and Implementation of Methods for High Speed Lexical Classification of Malicious URLs
- Egan, Shaun P, Irwin, Barry V W
- Authors: Egan, Shaun P , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429757 , vital:72637 , https://digifors.cs.up.ac.za/issa/2012/Proceedings/Research/58_ResearchInProgress.pdf
- Description: Several authors have put forward methods of using Artificial Neural Networks (ANN) to classify URLs as malicious or benign by using lexical features of those URLs. These methods have been compared to other methods of classification, such as blacklisting and spam filtering, and have been found to be as accurate. Early attempts proved to be as highly accurate. Fully featured classifications use lexical features as well as lookups to classify URLs and include (but are not limited to) blacklists, spam filters and reputation services. These classifiers are based on the Online Perceptron Model, using a single neuron as a linear combiner and used lexical features that rely on the presence (or lack thereof) of words belonging to a bag-of-words. Several obfuscation resistant features are also used to increase the positive classification rate of these perceptrons. Examples of these include URL length, number of directory traversals and length of arguments passed to the file within the URL. In this paper we describe how we implement the online perceptron model and methods that we used to try to increase the accuracy of this model through the use of hidden layers and training cost validation. We discuss our results in relation to those of other papers, as well as other analysis performed on the training data and the neural networks themselves to best understand why they are so effective. Also described will be the proposed model for developing these Neural Networks, how to implement them in the real world through the use of browser extensions, proxy plugins and spam filters for mail servers, and our current implementation. Finally, work that is still in progress will be described. This work includes other methods of increasing accuracy through the use of modern training techniques and testing in a real world environment.
- Full Text:
- Date Issued: 2012
- Authors: Egan, Shaun P , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429757 , vital:72637 , https://digifors.cs.up.ac.za/issa/2012/Proceedings/Research/58_ResearchInProgress.pdf
- Description: Several authors have put forward methods of using Artificial Neural Networks (ANN) to classify URLs as malicious or benign by using lexical features of those URLs. These methods have been compared to other methods of classification, such as blacklisting and spam filtering, and have been found to be as accurate. Early attempts proved to be as highly accurate. Fully featured classifications use lexical features as well as lookups to classify URLs and include (but are not limited to) blacklists, spam filters and reputation services. These classifiers are based on the Online Perceptron Model, using a single neuron as a linear combiner and used lexical features that rely on the presence (or lack thereof) of words belonging to a bag-of-words. Several obfuscation resistant features are also used to increase the positive classification rate of these perceptrons. Examples of these include URL length, number of directory traversals and length of arguments passed to the file within the URL. In this paper we describe how we implement the online perceptron model and methods that we used to try to increase the accuracy of this model through the use of hidden layers and training cost validation. We discuss our results in relation to those of other papers, as well as other analysis performed on the training data and the neural networks themselves to best understand why they are so effective. Also described will be the proposed model for developing these Neural Networks, how to implement them in the real world through the use of browser extensions, proxy plugins and spam filters for mail servers, and our current implementation. Finally, work that is still in progress will be described. This work includes other methods of increasing accuracy through the use of modern training techniques and testing in a real world environment.
- Full Text:
- Date Issued: 2012
Bridging and enriching top-down and participatory learning: The case of smallholder, organic conservation agriculture farmers in Zimbabwe
- Authors: Mukute, Mutizwa
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432967 , vital:72919 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122261"
- Description: This article discusses the combined use of top-down and participatory learning approaches during the course of a 42-month organic conservation agriculture project that is being implemented in eight districts of Mashonaland East Province in Zimbabwe. The initial 18-month project was extended by a further 24 months in order to build on what had been achieved by deepening organic conservation agriculture practices, by increasing the understanding of, and access to, markets, and by expanding farmer agency. The top-down approach involves farmer representatives, known as ‘access farmers’ in the project, undergoing training at training centres and then returning to their respective farmer associations to train other farmers in what they have learnt. Participatory learning includes farmer-to-farmer learning within and among associations, and trainers learning from, and acting on, farmer experiences. Expansive learning, which combines, and goes beyond, both approaches and allows for joint learning, innovation and agency, has been used to support the associations to learn about, practise and benefit from organic conservation agriculture. This was stimulated by change laboratory workshops being conducted with each of the 32 farmer associations formed during the first 18 months of the project. The main argument in the present article is that combining these seemingly opposite approaches to learning is feasible and is essential for accelerating practice-oriented changes in agriculture. The concept that appears to enable this linkage is dialectics.
- Full Text:
- Date Issued: 2012
- Authors: Mukute, Mutizwa
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432967 , vital:72919 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122261"
- Description: This article discusses the combined use of top-down and participatory learning approaches during the course of a 42-month organic conservation agriculture project that is being implemented in eight districts of Mashonaland East Province in Zimbabwe. The initial 18-month project was extended by a further 24 months in order to build on what had been achieved by deepening organic conservation agriculture practices, by increasing the understanding of, and access to, markets, and by expanding farmer agency. The top-down approach involves farmer representatives, known as ‘access farmers’ in the project, undergoing training at training centres and then returning to their respective farmer associations to train other farmers in what they have learnt. Participatory learning includes farmer-to-farmer learning within and among associations, and trainers learning from, and acting on, farmer experiences. Expansive learning, which combines, and goes beyond, both approaches and allows for joint learning, innovation and agency, has been used to support the associations to learn about, practise and benefit from organic conservation agriculture. This was stimulated by change laboratory workshops being conducted with each of the 32 farmer associations formed during the first 18 months of the project. The main argument in the present article is that combining these seemingly opposite approaches to learning is feasible and is essential for accelerating practice-oriented changes in agriculture. The concept that appears to enable this linkage is dialectics.
- Full Text:
- Date Issued: 2012
Building a Graphical Fuzzing Framework
- Zeisberger, Sascha, Irwin, Barry V W
- Authors: Zeisberger, Sascha , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429772 , vital:72638 , https://digifors.cs.up.ac.za/issa/2012/Proceedings/Research/59_ResearchInProgress.pdf
- Description: Fuzz testing is a robustness testing technique that sends malformed data to an application’s input. This is to test an application’s behaviour when presented with input beyond its specification. The main difference between traditional testing techniques and fuzz testing is that in most traditional techniques an application is tested according to a specification and rated on how well the application conforms to that specification. Fuzz testing tests beyond the scope of a specification by intelligently generating values that may be interpreted by an application in an unintended manner. The use of fuzz testing has been more prevalent in academic and security communities despite showing success in production environments. To measure the effectiveness of fuzz testing, an experiment was conducted where several publicly available applications were fuzzed. In some instances, fuzz testing was able to force an application into an invalid state and it was concluded that fuzz testing is a relevant testing technique that could assist in developing more robust applications. This success prompted a further investigation into fuzz testing in order to compile a list of requirements that makes an effective fuzzer. The aforementioned investigation assisted in the design of a fuzz testing framework, the goal of which is to make the process more accessible to users outside of an academic and security environment. Design methodologies and justifications of said framework are discussed, focusing on the graphical user interface components as this aspect of the framework is used to increase the usability of the framework.
- Full Text:
- Date Issued: 2012
- Authors: Zeisberger, Sascha , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429772 , vital:72638 , https://digifors.cs.up.ac.za/issa/2012/Proceedings/Research/59_ResearchInProgress.pdf
- Description: Fuzz testing is a robustness testing technique that sends malformed data to an application’s input. This is to test an application’s behaviour when presented with input beyond its specification. The main difference between traditional testing techniques and fuzz testing is that in most traditional techniques an application is tested according to a specification and rated on how well the application conforms to that specification. Fuzz testing tests beyond the scope of a specification by intelligently generating values that may be interpreted by an application in an unintended manner. The use of fuzz testing has been more prevalent in academic and security communities despite showing success in production environments. To measure the effectiveness of fuzz testing, an experiment was conducted where several publicly available applications were fuzzed. In some instances, fuzz testing was able to force an application into an invalid state and it was concluded that fuzz testing is a relevant testing technique that could assist in developing more robust applications. This success prompted a further investigation into fuzz testing in order to compile a list of requirements that makes an effective fuzzer. The aforementioned investigation assisted in the design of a fuzz testing framework, the goal of which is to make the process more accessible to users outside of an academic and security environment. Design methodologies and justifications of said framework are discussed, focusing on the graphical user interface components as this aspect of the framework is used to increase the usability of the framework.
- Full Text:
- Date Issued: 2012
Capturefoundry: a gpu accelerated packet capture analysis tool
- Nottingham, Alastair, Richter, John, Irwin, Barry V W
- Authors: Nottingham, Alastair , Richter, John , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430112 , vital:72666 , https://doi.org/10.1145/2389836.2389877
- Description: Packet captures are used to support a variety of tasks, including network administration, fault diagnosis and security and network related research. Despite their usefulness, processing packet capture files is a slow and tedious process that impedes the analysis of large, long-term captures. This paper discusses the primary components and observed performance of CaptureFoundry, a stand-alone capture analysis support tool designed to quickly map, filter and extract packets from large capture files using a combination of indexing techniques and GPU accelerated packet classification. All results are persistent, and may be used to rapidly extract small pre-filtered captures on demand that may be analysed quickly in existing capture analysis applications. Performance results show that CaptureFoundry is capable of generating multiple indexes and classification results for large captures at hundreds of megabytes per second, with minimal CPU and memory overhead and only minor additional storage space requirements.
- Full Text:
- Date Issued: 2012
- Authors: Nottingham, Alastair , Richter, John , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430112 , vital:72666 , https://doi.org/10.1145/2389836.2389877
- Description: Packet captures are used to support a variety of tasks, including network administration, fault diagnosis and security and network related research. Despite their usefulness, processing packet capture files is a slow and tedious process that impedes the analysis of large, long-term captures. This paper discusses the primary components and observed performance of CaptureFoundry, a stand-alone capture analysis support tool designed to quickly map, filter and extract packets from large capture files using a combination of indexing techniques and GPU accelerated packet classification. All results are persistent, and may be used to rapidly extract small pre-filtered captures on demand that may be analysed quickly in existing capture analysis applications. Performance results show that CaptureFoundry is capable of generating multiple indexes and classification results for large captures at hundreds of megabytes per second, with minimal CPU and memory overhead and only minor additional storage space requirements.
- Full Text:
- Date Issued: 2012
CdTe quantum dots functionalized with 4-amino-2, 2, 6, 6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion
- Adegoke, Oluwasesan, Hosten, Eric, McCleland, Cedric, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Hosten, Eric , McCleland, Cedric , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244393 , vital:51253 , xlink:href="https://doi.org/10.1016/j.aca.2012.01.040"
- Description: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
- Full Text:
- Date Issued: 2012
- Authors: Adegoke, Oluwasesan , Hosten, Eric , McCleland, Cedric , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244393 , vital:51253 , xlink:href="https://doi.org/10.1016/j.aca.2012.01.040"
- Description: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
- Full Text:
- Date Issued: 2012
Challenges experienced in the first year of implementation of a teaching and learning virtual partnership at the University of Namibia
- Mufeti, K, Foster, Greg, Terzoli, Alfredo
- Authors: Mufeti, K , Foster, Greg , Terzoli, Alfredo
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431234 , vital:72756 , https://rcetj.org/index.php/rcetj/article/view/178
- Description: Advances in information and communication technologies are enabling higher educa-tion institutions to build virtual partnerships with other institutions. Virtual partner-ships are defined here as collaborations between geographically dispersed institutions, where interaction between these institutions is enabled mainly by electronic modes of communication. This article reports on the participants’ experiences of the implemen-tation of one such partnership from the perspective of a partner in a developing con-text. It uses the SANTED Virtual Classroom Project (VCP), a virtual partnership initia-tive between the Departments of Computer Science at the University of Namibia (UNAM) and Rhodes University (RU), as a case study. In the VCP, the department at RU was tasked with building teaching and human resource capacity in the department at UNAM. The article focuses on the challenges experienced at UNAM during the first year of implementation of the VCP and lessons learned.
- Full Text:
- Date Issued: 2012
- Authors: Mufeti, K , Foster, Greg , Terzoli, Alfredo
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431234 , vital:72756 , https://rcetj.org/index.php/rcetj/article/view/178
- Description: Advances in information and communication technologies are enabling higher educa-tion institutions to build virtual partnerships with other institutions. Virtual partner-ships are defined here as collaborations between geographically dispersed institutions, where interaction between these institutions is enabled mainly by electronic modes of communication. This article reports on the participants’ experiences of the implemen-tation of one such partnership from the perspective of a partner in a developing con-text. It uses the SANTED Virtual Classroom Project (VCP), a virtual partnership initia-tive between the Departments of Computer Science at the University of Namibia (UNAM) and Rhodes University (RU), as a case study. In the VCP, the department at RU was tasked with building teaching and human resource capacity in the department at UNAM. The article focuses on the challenges experienced at UNAM during the first year of implementation of the VCP and lessons learned.
- Full Text:
- Date Issued: 2012
Characterization of 2,(3)-tetra-(4-oxo-benzamide) phthalocyaninato cobalt (II)—single walled carbon nanotube conjugate platforms and their use in electrocatalysis of amitrole
- Mugadza, Tawanda, Arslanoğlu, Yasin, Nyokong, Tebello
- Authors: Mugadza, Tawanda , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244382 , vital:51252 , xlink:href="https://doi.org/10.1016/j.electacta.2012.02.041"
- Description: In this paper we report on the use of carboxylic acid functionalized single walled carbon nanotubes (SWCNT) in the synthesis of 2,(3)-tetra-(4-oxo-benzamide)phthalocyaninato cobalt (II)–single walled carbon nanotube conjugates (CoTOBPc–SWCNT), their characterization and application in the electrocatalytic oxidation of amitrole. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used for the detection of amitrole on the modified glassy carbon electrode. The catalytic rate constant was 1.6 × 103 M−1 s−1 and the apparent electron rate transfer constant was 1.5 × 10−5 cm s−1. The linear dynamic range was 1.0 × 10−6–3.0 × 10−5 M, with a sensitivity of ∼1.13 A mol−1 L cm−2.
- Full Text:
- Date Issued: 2012
- Authors: Mugadza, Tawanda , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244382 , vital:51252 , xlink:href="https://doi.org/10.1016/j.electacta.2012.02.041"
- Description: In this paper we report on the use of carboxylic acid functionalized single walled carbon nanotubes (SWCNT) in the synthesis of 2,(3)-tetra-(4-oxo-benzamide)phthalocyaninato cobalt (II)–single walled carbon nanotube conjugates (CoTOBPc–SWCNT), their characterization and application in the electrocatalytic oxidation of amitrole. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used for the detection of amitrole on the modified glassy carbon electrode. The catalytic rate constant was 1.6 × 103 M−1 s−1 and the apparent electron rate transfer constant was 1.5 × 10−5 cm s−1. The linear dynamic range was 1.0 × 10−6–3.0 × 10−5 M, with a sensitivity of ∼1.13 A mol−1 L cm−2.
- Full Text:
- Date Issued: 2012
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
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
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
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
Higher education, academic communities, and the intellectual virtues
- Authors: Jones, Ward E
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275647 , vital:55066 , xlink:href="https://doi.org/10.1111/edth.12005"
- Description: Because higher education brings members of academic communities in direct contact with students, the reflective higher education student is in an excellent position for developing two important intellectual virtues: confidence and humility. However, academic communities differ as to whether their members reach consensus, and their teaching practices reflect this difference. In this essay, Ward Jones argues that both consensus-reaching and non-consensus-reaching communities can encourage the development of intellectual confidence and humility in their students, although each will do so in very different ways.
- Full Text:
- Date Issued: 2012
- Authors: Jones, Ward E
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275647 , vital:55066 , xlink:href="https://doi.org/10.1111/edth.12005"
- Description: Because higher education brings members of academic communities in direct contact with students, the reflective higher education student is in an excellent position for developing two important intellectual virtues: confidence and humility. However, academic communities differ as to whether their members reach consensus, and their teaching practices reflect this difference. In this essay, Ward Jones argues that both consensus-reaching and non-consensus-reaching communities can encourage the development of intellectual confidence and humility in their students, although each will do so in very different ways.
- Full Text:
- Date Issued: 2012
How do HIV and AIDS impact the use of natural resources by poor rural populations?: The case of wild animal products
- Kaschula, Sarah, Shackleton, Charlie M
- Authors: Kaschula, Sarah , Shackleton, Charlie M
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182344 , vital:43822 , xlink:href="https://hdl.handle.net/10520/EJC97203"
- Description: As a result of heightened financial and food insecurity, populations adversely affected by HIV and/or AIDS may be more likely to utilise wild natural resources to supplement their diet and livelihoods. Should this effect be pronounced, HIV and AIDS may pose a serious environmental threat. We explored the hypothesis that the presence of factors in the household, such as chronic illness in and recent mortality of individuals in a high HIV-risk age group, as well as the fostering of orphans, are associated with increased utilisation of wild animal products (WAPs) at the household level. We randomly surveyed 519 households from four sites in rural South Africa, recording household socio-economic status, the utilisation of wild animal products and health and demographic factors attributed to HIV or AIDS. Binary logistic regressions were used to test if households with markers of HIV and/or AIDS affliction were more likely to have a higher incidence and frequency of WAP utilisation relative to non-afflicted households, after adjusting for socio-economic and demographic variables. We found that, although households with markers of HIV and/or AIDS were generally poorer and had higher dependency ratios, there was no evidence to support the hypothesis that WAP harvesting was associated with either poverty, or markers of HIV and/or AIDS affliction. Our findings suggest that generalisations about a possible interaction between HIV and/or AIDS and the environment may not uniformly apply to all categories of natural resources or to all user groups.
- Full Text:
- Date Issued: 2012
- Authors: Kaschula, Sarah , Shackleton, Charlie M
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182344 , vital:43822 , xlink:href="https://hdl.handle.net/10520/EJC97203"
- Description: As a result of heightened financial and food insecurity, populations adversely affected by HIV and/or AIDS may be more likely to utilise wild natural resources to supplement their diet and livelihoods. Should this effect be pronounced, HIV and AIDS may pose a serious environmental threat. We explored the hypothesis that the presence of factors in the household, such as chronic illness in and recent mortality of individuals in a high HIV-risk age group, as well as the fostering of orphans, are associated with increased utilisation of wild animal products (WAPs) at the household level. We randomly surveyed 519 households from four sites in rural South Africa, recording household socio-economic status, the utilisation of wild animal products and health and demographic factors attributed to HIV or AIDS. Binary logistic regressions were used to test if households with markers of HIV and/or AIDS affliction were more likely to have a higher incidence and frequency of WAP utilisation relative to non-afflicted households, after adjusting for socio-economic and demographic variables. We found that, although households with markers of HIV and/or AIDS were generally poorer and had higher dependency ratios, there was no evidence to support the hypothesis that WAP harvesting was associated with either poverty, or markers of HIV and/or AIDS affliction. Our findings suggest that generalisations about a possible interaction between HIV and/or AIDS and the environment may not uniformly apply to all categories of natural resources or to all user groups.
- Full Text:
- Date Issued: 2012
Imidazole-functionalized polymer microspheres and fibers–useful materials for immobilization of oxovanadium (IV) catalysts
- Walmsley, Ryan S, Ogunlaja, Adeniyi S, Coombes, Matthew J, Chidawanyika, Wadzanai J U, Litwinski, Christian, Torto, Nelson, Nyokong, Tebello, Tshentu, Zenixole R
- Authors: Walmsley, Ryan S , Ogunlaja, Adeniyi S , Coombes, Matthew J , Chidawanyika, Wadzanai J U , Litwinski, Christian , Torto, Nelson , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246041 , vital:51431 , xlink:href="https://doi.org/10.1039/C2JM15485D"
- Description: Both polymer microspheres and microfibers containing the imidazole functionality have been prepared and used to immobilize oxovanadium(IV). The average diameters and BET surface areas of the microspheres were 322 μm and 155 m2 g−1 while the fibers were 1.85 μm and 52 m2 g−1, respectively. XPS and microanalysis confirmed the incorporation of imidazole and vanadium in the polymeric materials. The catalytic activity of both materials was evaluated using the hydrogen peroxide facilitated oxidation of thioanisole. The microspheres were applied in a typical laboratory batch reactor set-up and quantitative conversions (>99%) were obtained in under 240 min with turn-over frequencies ranging from 21.89 to 265.53 h−1, depending on the quantity of catalyst and temperature. The microspherical catalysts also proved to be recyclable with no drop in activity being observed after three successive reactions. The vanadium functionalized fibers were applied in a pseudo continuous flow set-up. Factors influencing the overall conversion and product selectivity, including flow rate and catalyst quantity, were investigated. At flow rates of 1–4 mL h−1 near quantitative conversion was maintained over an extended period. Keeping the mass of catalyst constant (0.025 g) and varying the flow rate from 1–6 mL h−1 resulted in a shift in the formation of the oxidation product methyl phenyl sulfone from 60.1 to 18.6%.
- Full Text:
- Date Issued: 2012
- Authors: Walmsley, Ryan S , Ogunlaja, Adeniyi S , Coombes, Matthew J , Chidawanyika, Wadzanai J U , Litwinski, Christian , Torto, Nelson , Nyokong, Tebello , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246041 , vital:51431 , xlink:href="https://doi.org/10.1039/C2JM15485D"
- Description: Both polymer microspheres and microfibers containing the imidazole functionality have been prepared and used to immobilize oxovanadium(IV). The average diameters and BET surface areas of the microspheres were 322 μm and 155 m2 g−1 while the fibers were 1.85 μm and 52 m2 g−1, respectively. XPS and microanalysis confirmed the incorporation of imidazole and vanadium in the polymeric materials. The catalytic activity of both materials was evaluated using the hydrogen peroxide facilitated oxidation of thioanisole. The microspheres were applied in a typical laboratory batch reactor set-up and quantitative conversions (>99%) were obtained in under 240 min with turn-over frequencies ranging from 21.89 to 265.53 h−1, depending on the quantity of catalyst and temperature. The microspherical catalysts also proved to be recyclable with no drop in activity being observed after three successive reactions. The vanadium functionalized fibers were applied in a pseudo continuous flow set-up. Factors influencing the overall conversion and product selectivity, including flow rate and catalyst quantity, were investigated. At flow rates of 1–4 mL h−1 near quantitative conversion was maintained over an extended period. Keeping the mass of catalyst constant (0.025 g) and varying the flow rate from 1–6 mL h−1 resulted in a shift in the formation of the oxidation product methyl phenyl sulfone from 60.1 to 18.6%.
- Full Text:
- Date Issued: 2012
In vitro photodynamic effect of aluminum tetrasulfophthalocyanines on melanoma skin cancer and healthy normal skin cells
- Maduray, Kaminee, Odhay, Bharti, Nyokong, Tebello
- Authors: Maduray, Kaminee , Odhay, Bharti , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245762 , vital:51403 , xlink:href="https://doi.org/10.1016/j.pdpdt.2011.07.001"
- Description: Photodynamic therapy is a medical treatment that uses an inactive dye/drug and lasers as a light source to activate the dye/drug to produce a toxic form of oxygen that destroys the cancer cells. This study aimed at investigating the cytotoxic effects of different concentrations of aluminum tetrasulfophthalocyanines in its inactive and active state (laser induced) on melanoma skin cancer cells, healthy normal skin fibroblast and keratinocyte cells. Experimentally, 3 x 10(4) cells/ml were seeded in 24-well plates before treatment with different concentrations of aluminum tetrasulfophthalocyanines. After 2 h, cells were irradiated with a light dose of 4.5 J/cm(2). Post-irradiated cells were incubated for 24 h before cell viability was measured using the CellTiter-Blue Viability Assay. Results showed that aluminum tetrasulfophthalocyanines at high concentrations were cytotoxic to melanoma cells in the absence of laser activation. In the presence of laser activation of aluminum tetrasulfophthalocyanines at a concentration of 40 mu g/ml decreased cell viability of melanoma cells to 45%, fibroblasts to 78% and keratinocytes to 73%. At this photosensitizing concentration of aluminum tetrasulfophthalocyanines the efficacy of the treatment light dose 4.5 J/cm(2) and the cell death mechanism induced by photoactivated aluminum tetrasulfophthalocyanines was evaluated. A light dose of 4.5 J/cm(2) was more efficient in killing a higher number of melanoma cells and a lower number of fibroblast and keratinocyte cells than the other light doses of 2.5 J/cm(2), 7.5 J/cm(2) and 10.5 J/cm(2). Apoptosis features such as blebbing, nucleus condensation, nucleus fragmentation and the formation of apoptotic bodies were seen in the photodynamic therapy treated melanoma skin cancer cells. This in vitro photodynamic therapy study concludes that using aluminum tetrasulfophthalocyanines at a photosensitizing concentration of 40 mu g/ml in combination with a laser dose of 4.5 J/cm(2) was potentially lethal for melanoma skin cancer cells and less harmful for the normal healthy skin cells. (c) 2011 Elsevier B.V. All rights reserved.
- Full Text:
- Date Issued: 2012
- Authors: Maduray, Kaminee , Odhay, Bharti , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245762 , vital:51403 , xlink:href="https://doi.org/10.1016/j.pdpdt.2011.07.001"
- Description: Photodynamic therapy is a medical treatment that uses an inactive dye/drug and lasers as a light source to activate the dye/drug to produce a toxic form of oxygen that destroys the cancer cells. This study aimed at investigating the cytotoxic effects of different concentrations of aluminum tetrasulfophthalocyanines in its inactive and active state (laser induced) on melanoma skin cancer cells, healthy normal skin fibroblast and keratinocyte cells. Experimentally, 3 x 10(4) cells/ml were seeded in 24-well plates before treatment with different concentrations of aluminum tetrasulfophthalocyanines. After 2 h, cells were irradiated with a light dose of 4.5 J/cm(2). Post-irradiated cells were incubated for 24 h before cell viability was measured using the CellTiter-Blue Viability Assay. Results showed that aluminum tetrasulfophthalocyanines at high concentrations were cytotoxic to melanoma cells in the absence of laser activation. In the presence of laser activation of aluminum tetrasulfophthalocyanines at a concentration of 40 mu g/ml decreased cell viability of melanoma cells to 45%, fibroblasts to 78% and keratinocytes to 73%. At this photosensitizing concentration of aluminum tetrasulfophthalocyanines the efficacy of the treatment light dose 4.5 J/cm(2) and the cell death mechanism induced by photoactivated aluminum tetrasulfophthalocyanines was evaluated. A light dose of 4.5 J/cm(2) was more efficient in killing a higher number of melanoma cells and a lower number of fibroblast and keratinocyte cells than the other light doses of 2.5 J/cm(2), 7.5 J/cm(2) and 10.5 J/cm(2). Apoptosis features such as blebbing, nucleus condensation, nucleus fragmentation and the formation of apoptotic bodies were seen in the photodynamic therapy treated melanoma skin cancer cells. This in vitro photodynamic therapy study concludes that using aluminum tetrasulfophthalocyanines at a photosensitizing concentration of 40 mu g/ml in combination with a laser dose of 4.5 J/cm(2) was potentially lethal for melanoma skin cancer cells and less harmful for the normal healthy skin cells. (c) 2011 Elsevier B.V. All rights reserved.
- Full Text:
- Date Issued: 2012
Interaction of CdTe quantum dots with 2, 2-diphenyl-1-picrylhydrazyl free radical
- Adegoke, Oluwasesan, Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245751 , vital:51402 , xlink:href="https://doi.org/10.1007/s10895-011-1012-2"
- Description: The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH●) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV–vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH● radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH● may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH● is proposed.
- Full Text:
- Date Issued: 2012
- Authors: Adegoke, Oluwasesan , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245751 , vital:51402 , xlink:href="https://doi.org/10.1007/s10895-011-1012-2"
- Description: The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH●) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV–vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH● radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH● may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH● is proposed.
- Full Text:
- Date Issued: 2012