Catalytic oxidation of thioanisole using oxovanadium (IV)‐functionalized electrospun polybenzimidazole nanofibers
- Walmsley, Ryan S, Hlangothi, Percy, Litwinski, Christian, Nyokong, Tebello, Torto, Nelson, Tshentu, Zenixole R
- Authors: Walmsley, Ryan S , Hlangothi, Percy , Litwinski, Christian , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242083 , vital:51000 , xlink:href="https://doi.org/10.1002/app.38067"
- Description: Polybenzimidazole fibers, with an average diameter of 262 nm, were produced by the process of electrospinning. These fibers were used as a solid support material for the immobilization of oxovanadium(IV) which was achieved via a reaction with vanadyl sulfate. The oxovanadium(IV)-functionalized nanofibers were used as heterogeneous catalysts for the oxidation of thioanisole under both batch and pseudo-continuous flow conditions with great success. Under batch conditions near quantitative oxidation of thioanisole was achieved in under 90 min, even after four successive catalytic reactions. Under continuous conditions, excellent conversion of thioanisole was maintained throughout the period studied at flow rates of up to 2 mLh−1. This study, therefore, proposes that electrospun polybenzimidazole nanofibers, with their small diameters, impressive chemical and thermal stability, as well as coordinating benzimidazole group, may be a desirable support material for immobilization of homogeneous catalysts.
- Full Text:
- Date Issued: 2013
- Authors: Walmsley, Ryan S , Hlangothi, Percy , Litwinski, Christian , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242083 , vital:51000 , xlink:href="https://doi.org/10.1002/app.38067"
- Description: Polybenzimidazole fibers, with an average diameter of 262 nm, were produced by the process of electrospinning. These fibers were used as a solid support material for the immobilization of oxovanadium(IV) which was achieved via a reaction with vanadyl sulfate. The oxovanadium(IV)-functionalized nanofibers were used as heterogeneous catalysts for the oxidation of thioanisole under both batch and pseudo-continuous flow conditions with great success. Under batch conditions near quantitative oxidation of thioanisole was achieved in under 90 min, even after four successive catalytic reactions. Under continuous conditions, excellent conversion of thioanisole was maintained throughout the period studied at flow rates of up to 2 mLh−1. This study, therefore, proposes that electrospun polybenzimidazole nanofibers, with their small diameters, impressive chemical and thermal stability, as well as coordinating benzimidazole group, may be a desirable support material for immobilization of homogeneous catalysts.
- Full Text:
- Date Issued: 2013
Characterisation of novel CrleGV isolates for false codling moth control-lessons learnt from codling moth resistance to CpGV.
- Opoku-Debrah, John, Moore, Sean, Hill, Martin P, Knox, Caroline
- Authors: Opoku-Debrah, John , Moore, Sean , Hill, Martin P , Knox, Caroline
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/425414 , vital:72237 , xlink:href="https://www.cabdirect.org/cabdirect/abstract/20133257674"
- Description: Recently some codling moth, Cydia pomonella, populations in Europe developed resistance to CpGV. In order to prepare for the possibility of a similar occurrence with the false codling moth, Thaumatotibia leucotreta, in South Africa, a search was conducted for novel CrleGV isolates. Through overcrowding, outbreaks of novel isolates were recorded from laboratory populations of five geographically distinct host populations. The genetic novelty of these and two commercially available isolates was confirmed through restriction enzyme analysis and sequence analysis of the granulin and egt genes. Phylogenetic analysis showed the existence of two CrleGV-SA genome types. Significant differences in virulence were also shown between certain isolates against certain host populations.
- Full Text:
- Date Issued: 2013
- Authors: Opoku-Debrah, John , Moore, Sean , Hill, Martin P , Knox, Caroline
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/425414 , vital:72237 , xlink:href="https://www.cabdirect.org/cabdirect/abstract/20133257674"
- Description: Recently some codling moth, Cydia pomonella, populations in Europe developed resistance to CpGV. In order to prepare for the possibility of a similar occurrence with the false codling moth, Thaumatotibia leucotreta, in South Africa, a search was conducted for novel CrleGV isolates. Through overcrowding, outbreaks of novel isolates were recorded from laboratory populations of five geographically distinct host populations. The genetic novelty of these and two commercially available isolates was confirmed through restriction enzyme analysis and sequence analysis of the granulin and egt genes. Phylogenetic analysis showed the existence of two CrleGV-SA genome types. Significant differences in virulence were also shown between certain isolates against certain host populations.
- Full Text:
- Date Issued: 2013
Characterization and electrocatalytic behaviour of glassy carbon electrode modified with nickel nanoparticles towards amitrole detection
- Maringa, Audacity, Mugadza, Tawanda, Antunes, Edith M, Nyokong, Tebello
- Authors: Maringa, Audacity , Mugadza, Tawanda , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241793 , vital:50970 , xlink:href="https://doi.org/10.1016/j.jelechem.2013.04.022"
- Description: We report on the synthesis of Ni nanoparticles (NiNPs) and their application in electrocatalysis in comparison with nickel phthalocyanine (NiPc). UV–vis spectroscopy, powder X-ray diffraction, transmission electron microscopy and electron paramagnetic resonance were used in the characterization of NiNPs. Cyclic voltammetry and electrochemical impedance spectroscopy were used in electrocatalytic studies of amitrole on the glassy carbon electrode modified with NiNPs. The apparent and catalytic rate constants for amitrole on the NiNP-GCE were found to be 2.58 × 10−5 cm s−1 and 1.11 × 103 M−1 s−1, respectively.
- Full Text:
- Date Issued: 2013
- Authors: Maringa, Audacity , Mugadza, Tawanda , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241793 , vital:50970 , xlink:href="https://doi.org/10.1016/j.jelechem.2013.04.022"
- Description: We report on the synthesis of Ni nanoparticles (NiNPs) and their application in electrocatalysis in comparison with nickel phthalocyanine (NiPc). UV–vis spectroscopy, powder X-ray diffraction, transmission electron microscopy and electron paramagnetic resonance were used in the characterization of NiNPs. Cyclic voltammetry and electrochemical impedance spectroscopy were used in electrocatalytic studies of amitrole on the glassy carbon electrode modified with NiNPs. The apparent and catalytic rate constants for amitrole on the NiNP-GCE were found to be 2.58 × 10−5 cm s−1 and 1.11 × 103 M−1 s−1, respectively.
- Full Text:
- Date Issued: 2013
Characterization and photophysical behavior of phthalocyanines when grafted onto silica nanoparticles
- Fashina, Adedayo, Antunes, Edith M, Nyokong, Tebello
- Authors: Fashina, Adedayo , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241981 , vital:50989 , xlink:href="https://doi.org/10.1016/j.poly.2013.01.037"
- Description: This work reports on the functionalization of silica nanoparticles with zinc phthalocyanine complexes tetra-substituted non-peripherally with 4-carboxyphenoxyl and 3-carboxyphenoxyl groups. The phthalocyanine dyes have a free carboxyl group, facilitating the covalent attachment of the dyes on the silica surface via amide bond formation. The phthalocyanine functionalized silica nanoparticles showed higher fluorescence and triplet quantum yields as well as longer triplet lifetimes compared to the free phthalocyanines.
- Full Text:
- Date Issued: 2013
- Authors: Fashina, Adedayo , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241981 , vital:50989 , xlink:href="https://doi.org/10.1016/j.poly.2013.01.037"
- Description: This work reports on the functionalization of silica nanoparticles with zinc phthalocyanine complexes tetra-substituted non-peripherally with 4-carboxyphenoxyl and 3-carboxyphenoxyl groups. The phthalocyanine dyes have a free carboxyl group, facilitating the covalent attachment of the dyes on the silica surface via amide bond formation. The phthalocyanine functionalized silica nanoparticles showed higher fluorescence and triplet quantum yields as well as longer triplet lifetimes compared to the free phthalocyanines.
- Full Text:
- Date Issued: 2013
Characterization of glassy carbon electrodes modified with carbon nanotubes and iron phthalocyanine through grafting and click chemistry
- Coates, Megan, Nyokong, Tebello
- Authors: Coates, Megan , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193746 , vital:45392 , xlink:href="https://doi.org/10.1016/j.electacta.2012.12.112"
- Description: A glassy carbon electrode was modified by adsorption of single-walled carbon nanotubes, followed by electrochemical grafting of 4-azidobenzenediazonium salt, which was in turn reacted with ethynylpyridine through the Sharpless “click chemistry” reaction. Thereafter, iron phthalocyanine was attached to the electrode through axial ligation to the pyridine group. The modified electrode was characterised using X-ray photoelectron spectroscopy and scanning electrochemical microscopy, and well as electrochemistry. The electrocatalytic ability of the modified electrode was tested using hydrazine as a sample analyte, and showed a significant 10-fold improvement in the detection of hydrazine compared to the surface without nanotubes, and comparable stability. The linear range for this surface was over 1.0 × 10−5 to 1.0 × 10−4 mol dm−3, with a limit of detection of 1.10 ± 0.06 μmol dm−3 and sensitivity of 15.61 μA mM−1.
- Full Text:
- Date Issued: 2013
- Authors: Coates, Megan , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193746 , vital:45392 , xlink:href="https://doi.org/10.1016/j.electacta.2012.12.112"
- Description: A glassy carbon electrode was modified by adsorption of single-walled carbon nanotubes, followed by electrochemical grafting of 4-azidobenzenediazonium salt, which was in turn reacted with ethynylpyridine through the Sharpless “click chemistry” reaction. Thereafter, iron phthalocyanine was attached to the electrode through axial ligation to the pyridine group. The modified electrode was characterised using X-ray photoelectron spectroscopy and scanning electrochemical microscopy, and well as electrochemistry. The electrocatalytic ability of the modified electrode was tested using hydrazine as a sample analyte, and showed a significant 10-fold improvement in the detection of hydrazine compared to the surface without nanotubes, and comparable stability. The linear range for this surface was over 1.0 × 10−5 to 1.0 × 10−4 mol dm−3, with a limit of detection of 1.10 ± 0.06 μmol dm−3 and sensitivity of 15.61 μA mM−1.
- Full Text:
- Date Issued: 2013
Classification of security operation centers
- Jacobs, Pierre, Arnab, Alapan, Irwin, Barry V W
- Authors: Jacobs, Pierre , Arnab, Alapan , Irwin, Barry V W
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429635 , vital:72628 , 10.1109/ISSA.2013.6641054
- Description: Security Operation Centers (SOCs) are a necessary service for organisations that want to address compliance and threat management. While there are frameworks in existence that addresses the technology aspects of these services, a holistic framework addressing processes, staffing and technology currently do not exist. Additionally, it would be useful for organizations and constituents considering building, buying or selling these services to measure the effectiveness and maturity of the provided services. In this paper, we propose a classification and rating scheme for SOC services, evaluating both the capabilities and the maturity of the services offered.
- Full Text:
- Date Issued: 2013
- Authors: Jacobs, Pierre , Arnab, Alapan , Irwin, Barry V W
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429635 , vital:72628 , 10.1109/ISSA.2013.6641054
- Description: Security Operation Centers (SOCs) are a necessary service for organisations that want to address compliance and threat management. While there are frameworks in existence that addresses the technology aspects of these services, a holistic framework addressing processes, staffing and technology currently do not exist. Additionally, it would be useful for organizations and constituents considering building, buying or selling these services to measure the effectiveness and maturity of the provided services. In this paper, we propose a classification and rating scheme for SOC services, evaluating both the capabilities and the maturity of the services offered.
- Full Text:
- Date Issued: 2013
Classification of security operation centers
- Jacobs, Pierre, Arnab, Alapan, Irwin, Barry V W
- Authors: Jacobs, Pierre , Arnab, Alapan , Irwin, Barry V W
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429785 , vital:72639 , 10.1109/ISSA.2013.6641054
- Description: Security Operation Centers (SOCs) are a necessary service for organisations that want to address compliance and threat management. While there are frameworks in existence that addresses the technology aspects of these services, a holistic framework addressing processes, staffing and technology currently do not exist. Additionally, it would be useful for organizations and constituents considering building, buying or selling these services to measure the effectiveness and maturity of the provided services. In this paper, we propose a classification and rating scheme for SOC services, evaluating both the capabilities and the maturity of the services offered.
- Full Text:
- Date Issued: 2013
- Authors: Jacobs, Pierre , Arnab, Alapan , Irwin, Barry V W
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429785 , vital:72639 , 10.1109/ISSA.2013.6641054
- Description: Security Operation Centers (SOCs) are a necessary service for organisations that want to address compliance and threat management. While there are frameworks in existence that addresses the technology aspects of these services, a holistic framework addressing processes, staffing and technology currently do not exist. Additionally, it would be useful for organizations and constituents considering building, buying or selling these services to measure the effectiveness and maturity of the provided services. In this paper, we propose a classification and rating scheme for SOC services, evaluating both the capabilities and the maturity of the services offered.
- Full Text:
- Date Issued: 2013
Comparative phototransformation of environmental pollutants using metallophthalocyanines supported on electrospun polymer fibers
- Zugle, Ruphino, Nyokong, Tebello
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190509 , vital:45001 , xlink:href="https://doi.org/10.1002/app.38381"
- Description: The fluorescence and photoactivity of a series of Zn and Lu phthalocyanine complexes incorporated in various polymer fibers were investigated for the phototransformation of 4-chlorophenol, 4-nitrophenol, and methyl orange. The phthalocyanine complexes functionalized on polystyrene and polysulfone polymer fibers could be applied in the degradation of 4-chlorophenol, 4-nitrophenol, and methyl orange with 4-chlorophenol being much more susceptible to degradation while methyl orange was the least. Also polymer fibers of polystyrene were found to be reusable.
- Full Text:
- Date Issued: 2013
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190509 , vital:45001 , xlink:href="https://doi.org/10.1002/app.38381"
- Description: The fluorescence and photoactivity of a series of Zn and Lu phthalocyanine complexes incorporated in various polymer fibers were investigated for the phototransformation of 4-chlorophenol, 4-nitrophenol, and methyl orange. The phthalocyanine complexes functionalized on polystyrene and polysulfone polymer fibers could be applied in the degradation of 4-chlorophenol, 4-nitrophenol, and methyl orange with 4-chlorophenol being much more susceptible to degradation while methyl orange was the least. Also polymer fibers of polystyrene were found to be reusable.
- Full Text:
- Date Issued: 2013
Comparisons of the thermal physiology of water hyacinth biological control agents: predicting establishment and distribution pre-and post-release
- May, Bronwen, Coetzee, Julie A
- Authors: May, Bronwen , Coetzee, Julie A
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123476 , vital:35446 , https://doi.10.1111/eea.120628
- Description: Investigations into the thermal physiology of weed biological control agents may elucidate reasons for establishment failure following release. Such studies have shown that the success of water hyacinth biological control in South Africa remains variable in the high-lying interior Highveld region, because the control agents are restricted to establishment and development due to extreme winter conditions. To determine the importance of thermal physiology studies, both pre- and post-release, this study compared the known thermal requirements of Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) released in 1996, with those of an agent released in 1990, Niphograpta albiguttalis (Warren) (Lepidoptera: Pyralidae) and a candidate agent, Megamelus scutellaris Berg (Hemiptera: Delphacidae), which is currently under consideration for release. The lower developmental threshold (to) and rate of development (K) were determined for N. albiguttalis and M. scutellaris, using a reduced axis regression, and incorporated into a degree-day model which compared the number of generations that E. catarinensis, N. albiguttalis, and M. scutellaris are capable of producing annually at any given site in South Africa. The degree-day models predicted that N. albiguttalis (K = 439.43, to = 9.866) can complete 4–11 generations per year, whereas M. scutellaris (K = 502.96, to = 11.458) can only complete 0–10 generations per year, compared with E. catarinensis (K = 342, to = 10.3) which is predicted to complete 3–14 generations per year. This suggests that the candidate agent, M. scutellaris, will not fare better in establishment than the other two agents that have been released in the Highveld, and that it may not be worth releasing an agent with higher thermal requirements than the agents that already occur in these high-lying areas. Thermal physiology studies conducted prior to release are important tools in biological control programmes, particularly those in resource-limited countries, to prevent wasting efforts in getting an agent established.
- Full Text:
- Date Issued: 2013
- Authors: May, Bronwen , Coetzee, Julie A
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123476 , vital:35446 , https://doi.10.1111/eea.120628
- Description: Investigations into the thermal physiology of weed biological control agents may elucidate reasons for establishment failure following release. Such studies have shown that the success of water hyacinth biological control in South Africa remains variable in the high-lying interior Highveld region, because the control agents are restricted to establishment and development due to extreme winter conditions. To determine the importance of thermal physiology studies, both pre- and post-release, this study compared the known thermal requirements of Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) released in 1996, with those of an agent released in 1990, Niphograpta albiguttalis (Warren) (Lepidoptera: Pyralidae) and a candidate agent, Megamelus scutellaris Berg (Hemiptera: Delphacidae), which is currently under consideration for release. The lower developmental threshold (to) and rate of development (K) were determined for N. albiguttalis and M. scutellaris, using a reduced axis regression, and incorporated into a degree-day model which compared the number of generations that E. catarinensis, N. albiguttalis, and M. scutellaris are capable of producing annually at any given site in South Africa. The degree-day models predicted that N. albiguttalis (K = 439.43, to = 9.866) can complete 4–11 generations per year, whereas M. scutellaris (K = 502.96, to = 11.458) can only complete 0–10 generations per year, compared with E. catarinensis (K = 342, to = 10.3) which is predicted to complete 3–14 generations per year. This suggests that the candidate agent, M. scutellaris, will not fare better in establishment than the other two agents that have been released in the Highveld, and that it may not be worth releasing an agent with higher thermal requirements than the agents that already occur in these high-lying areas. Thermal physiology studies conducted prior to release are important tools in biological control programmes, particularly those in resource-limited countries, to prevent wasting efforts in getting an agent established.
- Full Text:
- Date Issued: 2013
Composite polyester membranes with embedded dendrimer hosts and bimetallic Fe/Ni nanoparticles: synthesis, characterisation and application to water treatment
- Malinga, S P, Arotiba, O A, Mapolie, S F, Krause, Rui W M, Mamba, Bhekie B, Diallo, M S
- Authors: Malinga, S P , Arotiba, O A , Mapolie, S F , Krause, Rui W M , Mamba, Bhekie B , Diallo, M S
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125086 , vital:35727 , https://doi.org/10.1007/s11051-013-1698-y
- Description: This study describes the preparation, characterization and evaluation of new composite membranes with embedded dendrimer hosts and Fe/Ni nanoparticles. These new reactive membranes consist of films of cyclodextrin–poly(propyleneimine) dendrimers (β-CD–PPI) that are deposited onto commercial polysulfone microporous supports and crosslinked with trimesoyl chloride (TMC). The membranes were subsequently loaded with Fe/Ni nanoparticles and evaluated as separation/reactive media in aqueous solutions using 2,4,6-trichlorophenol as model pollutant. The morphology and physicochemical properties of the composite membranes were characterised using high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy and measurements of contact angle, water intake, porosity and water permeability. The sorption capacity and catalytic activity of the membranes were evaluated using ion chromatography, atmospheric pressure chemical ionisation-mass spectrometry and UV–Vis spectroscopy (UV–Vis). The sizes of the embedded Fe/Ni nanoparticles in the membranes ranged from 40 to 66 nm as confirmed by HR-TEM. The reaction rates for the dechlorination of 2,4,6-trichlorophenol ranged from 0.00148 to 0.00250 min−1. In all cases, we found that the reaction by-products consisted of chloride ions and mixtures of compounds including phenol (m/z = 93), 2,4-dichlorophenol (m/z = 163) and 4-chlorophenol (m/z = 128). The overall results of this study suggest that β-CD–PPI dendrimers are promising building blocks for the synthesis of composite and reactive membranes for the efficient removal of chlorinated organic pollutants from water.
- Full Text:
- Date Issued: 2013
- Authors: Malinga, S P , Arotiba, O A , Mapolie, S F , Krause, Rui W M , Mamba, Bhekie B , Diallo, M S
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125086 , vital:35727 , https://doi.org/10.1007/s11051-013-1698-y
- Description: This study describes the preparation, characterization and evaluation of new composite membranes with embedded dendrimer hosts and Fe/Ni nanoparticles. These new reactive membranes consist of films of cyclodextrin–poly(propyleneimine) dendrimers (β-CD–PPI) that are deposited onto commercial polysulfone microporous supports and crosslinked with trimesoyl chloride (TMC). The membranes were subsequently loaded with Fe/Ni nanoparticles and evaluated as separation/reactive media in aqueous solutions using 2,4,6-trichlorophenol as model pollutant. The morphology and physicochemical properties of the composite membranes were characterised using high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy and measurements of contact angle, water intake, porosity and water permeability. The sorption capacity and catalytic activity of the membranes were evaluated using ion chromatography, atmospheric pressure chemical ionisation-mass spectrometry and UV–Vis spectroscopy (UV–Vis). The sizes of the embedded Fe/Ni nanoparticles in the membranes ranged from 40 to 66 nm as confirmed by HR-TEM. The reaction rates for the dechlorination of 2,4,6-trichlorophenol ranged from 0.00148 to 0.00250 min−1. In all cases, we found that the reaction by-products consisted of chloride ions and mixtures of compounds including phenol (m/z = 93), 2,4-dichlorophenol (m/z = 163) and 4-chlorophenol (m/z = 128). The overall results of this study suggest that β-CD–PPI dendrimers are promising building blocks for the synthesis of composite and reactive membranes for the efficient removal of chlorinated organic pollutants from water.
- Full Text:
- Date Issued: 2013
Consistencies far beyond chance: an analysis of learner preconceptions of reflective symmetry
- Mhlolo, Michael K, Schäfer, Marc
- Authors: Mhlolo, Michael K , Schäfer, Marc
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141139 , vital:37947 , DOI: 10.15700/saje.v33n2a686
- Description: This article reports on regularities observed in learners’ preconceptions of reflective symmetry. Literature suggests that the very existence of such regularities indicates a gap between what learners know and what they need to know. Such a gap inhibits further understanding and application, and hence needed to be investigated. A total of 235 Grade 11 learners, from 13 high schools that participate in the First Rand Foundation-funded Mathematics Education project in the Eastern Cape, responded to a task on reflective symmetry. Our framework for analysing the responses was based on the taxonomy of structure of the observed learning outcome. The results indicated that 85% of learner responses reflect a motion understanding of reflections, where learners considered geometric figures as physical motions on top of the plane. While this understanding is useful in some cases, it is not an essential aspect of mapping understanding, which is critical for application in function notations and other analytical geometry contexts. We suggest that if this gap is to be closed, learners need to construct these reflections physically so that they may think of reflections beyond motion.
- Full Text:
- Date Issued: 2013
- Authors: Mhlolo, Michael K , Schäfer, Marc
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141139 , vital:37947 , DOI: 10.15700/saje.v33n2a686
- Description: This article reports on regularities observed in learners’ preconceptions of reflective symmetry. Literature suggests that the very existence of such regularities indicates a gap between what learners know and what they need to know. Such a gap inhibits further understanding and application, and hence needed to be investigated. A total of 235 Grade 11 learners, from 13 high schools that participate in the First Rand Foundation-funded Mathematics Education project in the Eastern Cape, responded to a task on reflective symmetry. Our framework for analysing the responses was based on the taxonomy of structure of the observed learning outcome. The results indicated that 85% of learner responses reflect a motion understanding of reflections, where learners considered geometric figures as physical motions on top of the plane. While this understanding is useful in some cases, it is not an essential aspect of mapping understanding, which is critical for application in function notations and other analytical geometry contexts. We suggest that if this gap is to be closed, learners need to construct these reflections physically so that they may think of reflections beyond motion.
- Full Text:
- Date Issued: 2013
Control protocol command translation for device interoperability on ethernet AVB networks
- Foss, Richard, Igumbor, Osedum P
- Authors: Foss, Richard , Igumbor, Osedum P
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426978 , vital:72405 , https://www.aes.org/e-lib/browse.cfm?elib=16707
- Description: Audio/Video Bridging (AVB) on Ethernet refers to a suite of standards that allows for deterministic and guaranteed delivery of audio and video content on Virtual Local Area Networks (VLAN). A requirement for the networking of audio devices is to allow for remote establishment and destruction of audio stream connections. There are a number of sound control protocols that utilize AVB transport, and this paper describes an approach for common control and interoperability among them. To demonstrate this approach, this paper describes the design and implementation of a command translator that enables communication between AES64 and OSC-networked AVB devices. Results from a quantitative analysis reveal that when a proxy is used for connection management, noticeable delays are not added to a user’s visual and auditory perception.
- Full Text:
- Date Issued: 2013
- Authors: Foss, Richard , Igumbor, Osedum P
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426978 , vital:72405 , https://www.aes.org/e-lib/browse.cfm?elib=16707
- Description: Audio/Video Bridging (AVB) on Ethernet refers to a suite of standards that allows for deterministic and guaranteed delivery of audio and video content on Virtual Local Area Networks (VLAN). A requirement for the networking of audio devices is to allow for remote establishment and destruction of audio stream connections. There are a number of sound control protocols that utilize AVB transport, and this paper describes an approach for common control and interoperability among them. To demonstrate this approach, this paper describes the design and implementation of a command translator that enables communication between AES64 and OSC-networked AVB devices. Results from a quantitative analysis reveal that when a proxy is used for connection management, noticeable delays are not added to a user’s visual and auditory perception.
- Full Text:
- Date Issued: 2013
Controls on the formation of Wakkerstroom Vlei, Mpumalanga province, South Africa:
- Joubert, R, Ellery, William F N
- Authors: Joubert, R , Ellery, William F N
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144421 , vital:38344 , DOI: 10.2989/16085914.2012.762897
- Description: The present study investigated controls on the formation of Wakkerstroom Vlei, an 1 000 ha unchannelled valley-bottom wetland on the South African Highveld. Along the uppermost and lowermost reaches of the wetland, where dolerite outcrops occur along the main valley, hydrogeomorphic features typical of geological control on wetland formation are present, including a meandering river channel, oxbow lakes and greater than 3 m deep organic-poor alluvial fill. Along the main body of the wetland, however, floodplain features are absent, alluvial fill is up to 4.5 m deep and contains up to 2 m deep accumulations of peat. These characteristics deviate from the traditional model of dolerite control on wetland formation described by several other studies on Highveld wetland systems.
- Full Text:
- Date Issued: 2013
- Authors: Joubert, R , Ellery, William F N
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144421 , vital:38344 , DOI: 10.2989/16085914.2012.762897
- Description: The present study investigated controls on the formation of Wakkerstroom Vlei, an 1 000 ha unchannelled valley-bottom wetland on the South African Highveld. Along the uppermost and lowermost reaches of the wetland, where dolerite outcrops occur along the main valley, hydrogeomorphic features typical of geological control on wetland formation are present, including a meandering river channel, oxbow lakes and greater than 3 m deep organic-poor alluvial fill. Along the main body of the wetland, however, floodplain features are absent, alluvial fill is up to 4.5 m deep and contains up to 2 m deep accumulations of peat. These characteristics deviate from the traditional model of dolerite control on wetland formation described by several other studies on Highveld wetland systems.
- Full Text:
- Date Issued: 2013
Could a regulated market approach for rhinoceros horns work in South Africa? Some practical issues and concerns
- Collins, Alan, Fraser, Gavin C G, Snowball, Jeanette D
- Authors: Collins, Alan , Fraser, Gavin C G , Snowball, Jeanette D
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68600 , vital:29292 , http://www.essa2013.org.za/fullpaper/essa2013_2708.pdf
- Description: Publisher version , One of the proposals for fighting rhinoceros poaching is to legalise the trade in rhino horn and adopt a regulated market approach (RMA), which would require a vote at the 2016 CITES meeting in order to overturn the ban on the trade in rhino horn. The legal trade in rhino horn would enable the auctioning of stockpiles of horn and encourage captive breeding programmes. The aim of increasing the supply of horn is to reduce incentives to poach by driving down the price. This paper uses a conceptual/theoretical approach to consider the practical implications of the adoption of an RMA, drawing on demand, supply and production theory. The intention is explicitly to set out some practical concerns and issues that seem to have been underplayed or neglected in most published economic discourse on the subject. To secure a stockpile for some species needs biological success in captive breeding programs (CBPs) but this varies across species and habitats. Rhinoceros herds in a CBP would need relatively spatially extensive terrain and costly permanent security measures, and only appear feasible for the less aggressive “white” rhino. Thus, market price would actually need to be sustained at a high level to cover the start-up and security costs of such a programme that are unlikely to fall significantly. This is a double-edged sword in that the persistent high price of rhino horn provides an incentive for continued poaching activities. Supplementary policy measures that differentiate among consumer groups may also prove necessary.
- Full Text:
- Date Issued: 2013
- Authors: Collins, Alan , Fraser, Gavin C G , Snowball, Jeanette D
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68600 , vital:29292 , http://www.essa2013.org.za/fullpaper/essa2013_2708.pdf
- Description: Publisher version , One of the proposals for fighting rhinoceros poaching is to legalise the trade in rhino horn and adopt a regulated market approach (RMA), which would require a vote at the 2016 CITES meeting in order to overturn the ban on the trade in rhino horn. The legal trade in rhino horn would enable the auctioning of stockpiles of horn and encourage captive breeding programmes. The aim of increasing the supply of horn is to reduce incentives to poach by driving down the price. This paper uses a conceptual/theoretical approach to consider the practical implications of the adoption of an RMA, drawing on demand, supply and production theory. The intention is explicitly to set out some practical concerns and issues that seem to have been underplayed or neglected in most published economic discourse on the subject. To secure a stockpile for some species needs biological success in captive breeding programs (CBPs) but this varies across species and habitats. Rhinoceros herds in a CBP would need relatively spatially extensive terrain and costly permanent security measures, and only appear feasible for the less aggressive “white” rhino. Thus, market price would actually need to be sustained at a high level to cover the start-up and security costs of such a programme that are unlikely to fall significantly. This is a double-edged sword in that the persistent high price of rhino horn provides an incentive for continued poaching activities. Supplementary policy measures that differentiate among consumer groups may also prove necessary.
- Full Text:
- Date Issued: 2013
Current and potential carbon stocks of trees in urban parking lots in towns of the Eastern Cape, South Africa
- O'Donoghue, Alexandra, Shackleton, Charlie M
- Authors: O'Donoghue, Alexandra , Shackleton, Charlie M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181037 , vital:43689 , xlink:href="https://doi.org/10.1016/j.ufug.2013.07.001"
- Description: Greening of shopping centre parking lots is a potentially important strategy that can contribute to urban carbon mitigation efforts, improve aesthetics and the shopping experience of consumers, whilst adding to urban biodiversity. Twenty-eight shopping centre parking lots in six Eastern Cape urban centres, South Africa, were sampled to determine tree species composition, density and annual carbon sequestration potential. The best case parking lot found during the study was used as a benchmark to display the difference between current tree density and above-ground carbon stocks relative to the potential optimum. The highest tree density was 66 trees ha−1, whereas the average density across all sampled parking lots was less than half that (27.2 ± 22.6 trees ha−1). The average annual carbon sequestration potential per parking lot was 1390 ± 2503 kg ha−1. Planting density was positively related to annual sequestration rates, whilst parking lot age and the mean annual rainfall of the town had no influence. Mean tree species richness per parking lot was 2.3 ± 1.8 species, with a positive relationship to parking lot size, but not to mean annual rainfall of the site. The majority of trees (62.5%) in parking lots were alien species, although newer parking lots had significantly greater proportions of indigenous species. There was no difference in mean annual carbon sequestration rate per tree between indigenous and alien trees species. Low tree densities and small parking lot areas constrained the potential for earning carbon credits from trees in parking lots. Nonetheless, planners and designers need to be more aware of the potential contribution of trees towards urban sustainability.
- Full Text:
- Date Issued: 2013
- Authors: O'Donoghue, Alexandra , Shackleton, Charlie M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181037 , vital:43689 , xlink:href="https://doi.org/10.1016/j.ufug.2013.07.001"
- Description: Greening of shopping centre parking lots is a potentially important strategy that can contribute to urban carbon mitigation efforts, improve aesthetics and the shopping experience of consumers, whilst adding to urban biodiversity. Twenty-eight shopping centre parking lots in six Eastern Cape urban centres, South Africa, were sampled to determine tree species composition, density and annual carbon sequestration potential. The best case parking lot found during the study was used as a benchmark to display the difference between current tree density and above-ground carbon stocks relative to the potential optimum. The highest tree density was 66 trees ha−1, whereas the average density across all sampled parking lots was less than half that (27.2 ± 22.6 trees ha−1). The average annual carbon sequestration potential per parking lot was 1390 ± 2503 kg ha−1. Planting density was positively related to annual sequestration rates, whilst parking lot age and the mean annual rainfall of the town had no influence. Mean tree species richness per parking lot was 2.3 ± 1.8 species, with a positive relationship to parking lot size, but not to mean annual rainfall of the site. The majority of trees (62.5%) in parking lots were alien species, although newer parking lots had significantly greater proportions of indigenous species. There was no difference in mean annual carbon sequestration rate per tree between indigenous and alien trees species. Low tree densities and small parking lot areas constrained the potential for earning carbon credits from trees in parking lots. Nonetheless, planners and designers need to be more aware of the potential contribution of trees towards urban sustainability.
- Full Text:
- Date Issued: 2013
Customising a BBVC for Asterisk VoIP Services
- Oyedele, Y, Terzoli, Alfredo, Mufeti, K
- Authors: Oyedele, Y , Terzoli, Alfredo , Mufeti, K
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430942 , vital:72730 , https://doi.org/10.1007/978-1-4614-3558-7_62
- Description: Browser-based Voice over Internet Protocol Clients (BBVC) are used to access pre-determined VoIP services from VoIP service providers through Internet connections. For nomadic users within an organisa-tion’s Intranet, connections are made to the Internet to utilise these BBVC. An Intranet with an Asterisk Private Branch Exchange (PBX) as a VoIP provider however can be linked with any form of VoIP client to improve service accessibility for its users. This study aims to find a BBVC that can be customised to provide such accessibility within an Intranet. The study revealed that three BBVC are compatible. One of three BBVC was selected for customisation to provide nomadic acces-sibility to Asterisk. The functionality of the customised BBVC depended on the web technologies used and the available VoIP services.
- Full Text:
- Date Issued: 2013
- Authors: Oyedele, Y , Terzoli, Alfredo , Mufeti, K
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430942 , vital:72730 , https://doi.org/10.1007/978-1-4614-3558-7_62
- Description: Browser-based Voice over Internet Protocol Clients (BBVC) are used to access pre-determined VoIP services from VoIP service providers through Internet connections. For nomadic users within an organisa-tion’s Intranet, connections are made to the Internet to utilise these BBVC. An Intranet with an Asterisk Private Branch Exchange (PBX) as a VoIP provider however can be linked with any form of VoIP client to improve service accessibility for its users. This study aims to find a BBVC that can be customised to provide such accessibility within an Intranet. The study revealed that three BBVC are compatible. One of three BBVC was selected for customisation to provide nomadic acces-sibility to Asterisk. The functionality of the customised BBVC depended on the web technologies used and the available VoIP services.
- Full Text:
- Date Issued: 2013
Cytotoxicity of lapachol, β-lapachone and related synthetic 1, 4-naphthoquinones against oesophageal cancer cells:
- Sunassee, Suthananda N, Veale, Clinton G L, Shunmoogam-Gounden, Nelusha, Osoniyi, Omalaja, Hendricks, Denver T, Caira, Mino R, de la Mare, Jo-Anne, Edkins, Adrienne L, Pinto, Antônio V, da Silva Junior, Eufrânio N, Davies-Coleman, Michael T
- Authors: Sunassee, Suthananda N , Veale, Clinton G L , Shunmoogam-Gounden, Nelusha , Osoniyi, Omalaja , Hendricks, Denver T , Caira, Mino R , de la Mare, Jo-Anne , Edkins, Adrienne L , Pinto, Antônio V , da Silva Junior, Eufrânio N , Davies-Coleman, Michael T
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165207 , vital:41218 , DOI: 10.1016/j.ejmech.2012.12.048
- Description: Naphthoquinones have been found to have a wide range of biological activities, including cytotoxicity to cancer cells. The secondary metabolites lapachol, α- and β-lapachone and a series of 25 related synthetic 1,4-naphthoquinones were screened against the oesophageal cancer cell line (WHCO1). Most of the compounds exhibited enhanced cytotoxicity (IC50 1.6–11.7 μM) compared to the current drug of choice cisplatin (IC50 = 16.5 μM).
- Full Text:
- Date Issued: 2013
- Authors: Sunassee, Suthananda N , Veale, Clinton G L , Shunmoogam-Gounden, Nelusha , Osoniyi, Omalaja , Hendricks, Denver T , Caira, Mino R , de la Mare, Jo-Anne , Edkins, Adrienne L , Pinto, Antônio V , da Silva Junior, Eufrânio N , Davies-Coleman, Michael T
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165207 , vital:41218 , DOI: 10.1016/j.ejmech.2012.12.048
- Description: Naphthoquinones have been found to have a wide range of biological activities, including cytotoxicity to cancer cells. The secondary metabolites lapachol, α- and β-lapachone and a series of 25 related synthetic 1,4-naphthoquinones were screened against the oesophageal cancer cell line (WHCO1). Most of the compounds exhibited enhanced cytotoxicity (IC50 1.6–11.7 μM) compared to the current drug of choice cisplatin (IC50 = 16.5 μM).
- Full Text:
- Date Issued: 2013
Dancing with the devil: formative peer assessment and academic performance
- Mostert, Markus, Snowball, Jeanette D
- Authors: Mostert, Markus , Snowball, Jeanette D
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69301 , vital:29483 , https://doi.org/10.1080/07294360.2012.705262
- Description: Peer assessment can be important in developing active and independent learners, as well as providing more and faster feedback in large classes, compared to marking done by tutors. In addition, the evaluative, critical stance required by students in order to assess their peers' work encourages the development of higher-order cognitive skills. Changing roles from being assessed to being an assessor can also improve students' ability to judge and improve on their own work. However, peer assessment does have potential problems and there is some debate as to the appropriate academic level at which to implement it, the kinds of feedback that are given and the ways in which students respond. In addition, there is little evidence that peer assessment has an impact on academic performance. This research reports the results of an online peer assessment exercise for a macroeconomics essay conducted in a large Economics 1 class at Rhodes University. Of the 800 students, about half participated in the peer assessment exercise. Data were collected from students via a formal course evaluation. In addition, a sample of 50 essays was evaluated in terms of the relationship between peer marks and final (tutor) marks received and the impact that peer assessment had on the quality of the final essay submitted. An Ordinary Least Squares regression was used to investigate the impact of peer assessment participation on marks. Results showed that peer marks tended to ‘bunch’ in the 60–68% range, indicating the reluctance of peers to give very high or low marks. In general, peers gave more useful feedback on technical aspects, such as presentation and referencing (which were also the categories in which students most often made improvements), than on content. Regression analysis showed that peer assessment participation was not a significant determinant of final essay mark, but that economics ability and English language proficiency were.
- Full Text: false
- Date Issued: 2013
- Authors: Mostert, Markus , Snowball, Jeanette D
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69301 , vital:29483 , https://doi.org/10.1080/07294360.2012.705262
- Description: Peer assessment can be important in developing active and independent learners, as well as providing more and faster feedback in large classes, compared to marking done by tutors. In addition, the evaluative, critical stance required by students in order to assess their peers' work encourages the development of higher-order cognitive skills. Changing roles from being assessed to being an assessor can also improve students' ability to judge and improve on their own work. However, peer assessment does have potential problems and there is some debate as to the appropriate academic level at which to implement it, the kinds of feedback that are given and the ways in which students respond. In addition, there is little evidence that peer assessment has an impact on academic performance. This research reports the results of an online peer assessment exercise for a macroeconomics essay conducted in a large Economics 1 class at Rhodes University. Of the 800 students, about half participated in the peer assessment exercise. Data were collected from students via a formal course evaluation. In addition, a sample of 50 essays was evaluated in terms of the relationship between peer marks and final (tutor) marks received and the impact that peer assessment had on the quality of the final essay submitted. An Ordinary Least Squares regression was used to investigate the impact of peer assessment participation on marks. Results showed that peer marks tended to ‘bunch’ in the 60–68% range, indicating the reluctance of peers to give very high or low marks. In general, peers gave more useful feedback on technical aspects, such as presentation and referencing (which were also the categories in which students most often made improvements), than on content. Regression analysis showed that peer assessment participation was not a significant determinant of final essay mark, but that economics ability and English language proficiency were.
- Full Text: false
- Date Issued: 2013
Deagrarianisation and forest revegetation in a biodiversity hotspot on the Wild Coast, South Africa
- Shackleton, Ross T, Shackleton, Charlie M, Shackleton, Sheona E, Gambiza, James
- Authors: Shackleton, Ross T , Shackleton, Charlie M , Shackleton, Sheona E , Gambiza, James
- Date: 2013
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/60984 , vital:27905 , doi:10.1371/journal.pone.0076939
- Description: Deagraianisation is a worldwide phenomenon with widespread social, ecological and economic effects yet with little consensus on the local or higher level causes. There have been contested views on the causes and consequences of deagrarianisation on South Africa’s Wild Coast, which is an international biodiversity hotspot. Using GIS, household interviews and ecological sampling, we compared the perspectives of current and former cultivators as to why some have abandoned farming, whilst also tracking the uses and woody plant cover and composition of fields abandoned at different periods. The GIS analysis showed that field abandonment had been ongoing over several decades, with a decline from 12.5 % field cover in 1961 to 2.7 % in 2009. The area of forests and woodlands almost doubled in the corresponding period. There was a distinct peak in field abandonment during the time of political transition at the national level in the early 1990s. This political change led to a decrease in government support for livestock farming, which in turn resulted in reduced animal draught power at the household and community level, and hence reduced cropping. The study showed it is largely the wealthier households that have remained in arable agriculture and that the poorer households have abandoned farming. The abandoned fields show a distinct trend of increasing woody biomass and species richness with length of time since abandonment, with approximately three woody plant species added per decade. Most local respondents dislike the increases in forest and woodland extent and density because of anxiety about wild animals causing harm to crops and even humans, and the loss of an agricultural identity to livelihoods and the landscape.
- Full Text:
- Date Issued: 2013
- Authors: Shackleton, Ross T , Shackleton, Charlie M , Shackleton, Sheona E , Gambiza, James
- Date: 2013
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/60984 , vital:27905 , doi:10.1371/journal.pone.0076939
- Description: Deagraianisation is a worldwide phenomenon with widespread social, ecological and economic effects yet with little consensus on the local or higher level causes. There have been contested views on the causes and consequences of deagrarianisation on South Africa’s Wild Coast, which is an international biodiversity hotspot. Using GIS, household interviews and ecological sampling, we compared the perspectives of current and former cultivators as to why some have abandoned farming, whilst also tracking the uses and woody plant cover and composition of fields abandoned at different periods. The GIS analysis showed that field abandonment had been ongoing over several decades, with a decline from 12.5 % field cover in 1961 to 2.7 % in 2009. The area of forests and woodlands almost doubled in the corresponding period. There was a distinct peak in field abandonment during the time of political transition at the national level in the early 1990s. This political change led to a decrease in government support for livestock farming, which in turn resulted in reduced animal draught power at the household and community level, and hence reduced cropping. The study showed it is largely the wealthier households that have remained in arable agriculture and that the poorer households have abandoned farming. The abandoned fields show a distinct trend of increasing woody biomass and species richness with length of time since abandonment, with approximately three woody plant species added per decade. Most local respondents dislike the increases in forest and woodland extent and density because of anxiety about wild animals causing harm to crops and even humans, and the loss of an agricultural identity to livelihoods and the landscape.
- Full Text:
- Date Issued: 2013
Deep Routing Simulation
- Irwin, Barry V W, Herbert, Alan
- Authors: Irwin, Barry V W , Herbert, Alan
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430353 , vital:72685 , https://www.academic-bookshop.com/ourshop/prod_2546879-ICIW-2013-8th-International-Conference-on-Information-Warfare-and-Security.html
- Description: This paper discusses a dataset of some 16 million packets targeting port 445/tcp collected by a network telescope utilising a /24 netblock in South African IP address space. An initial overview of the collected data is provided. This is followed by a detailed analysis of the packet characteristics observed, including size and TTL. The peculiarities of the observed target selection and the results of the flaw in the Conficker worm's propagation algorithm are presented. An analysis of the 4 million observed source hosts is reported, grouped by both packet counts and the number of distinct hosts per network address block. Address blocks of size /8, 16 and 24 are used for groupings. The localisation, by geographic region and numerical proximity, of high ranking aggregate netblocks is highlighted. The observed shift in geopolitical origins observed during the evolution of the Conficker worm is also discussed. The paper concludes with some overall analyses, and consideration of the application of network telescopes to the monitoring of such outbreaks in the future.
- Full Text:
- Date Issued: 2013
- Authors: Irwin, Barry V W , Herbert, Alan
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430353 , vital:72685 , https://www.academic-bookshop.com/ourshop/prod_2546879-ICIW-2013-8th-International-Conference-on-Information-Warfare-and-Security.html
- Description: This paper discusses a dataset of some 16 million packets targeting port 445/tcp collected by a network telescope utilising a /24 netblock in South African IP address space. An initial overview of the collected data is provided. This is followed by a detailed analysis of the packet characteristics observed, including size and TTL. The peculiarities of the observed target selection and the results of the flaw in the Conficker worm's propagation algorithm are presented. An analysis of the 4 million observed source hosts is reported, grouped by both packet counts and the number of distinct hosts per network address block. Address blocks of size /8, 16 and 24 are used for groupings. The localisation, by geographic region and numerical proximity, of high ranking aggregate netblocks is highlighted. The observed shift in geopolitical origins observed during the evolution of the Conficker worm is also discussed. The paper concludes with some overall analyses, and consideration of the application of network telescopes to the monitoring of such outbreaks in the future.
- Full Text:
- Date Issued: 2013