Conceptualising the more knowledgeable other within a multi-directional ZPD:
- Authors: Graven, Mellony
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69519 , vital:29545 , https://doi.org/10.1007/s10649-017-9768-1
- Description: From a Marxian/Vygotskian perspective, learning is social in origin and it happens in the presence of others that are more knowledgeable. Extending this view to the learning of mathematics, such learning also becomes inseparable from the presence of others (people and artefacts). Researchers over decades have studied different interactions to see how such learning with others occurs, what is the role of the (more knowledgeable) other, and if at all this role alternates between the participants. In this paper, we looked at a 5-year-old’s (Lila) interaction with her mother (Mellony) and a television remote control as Lila attempted to count in threes using the three by three physical layout of the numbered buttons 1–9 on the remote control. We specifically looked at the emergence of the Zone of Proximal Development (ZPD) as Lila’s attention was caught by the properties of the remote control and by her mother’s questions. We also pay attention to how the role of the more knowledgeable other alternates among the participants. Our findings suggest that Lila, at times, used resources provided by the physical properties of the remote control and sometimes, used resources provided by Mellony to think about the task of counting in threes. In Lila’s interaction, we interpreted a multi-directional ZPD as the role of the more knowledgeable other alternated between Mellony, Lila and the remote control.
- Full Text:
- Authors: Graven, Mellony
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69519 , vital:29545 , https://doi.org/10.1007/s10649-017-9768-1
- Description: From a Marxian/Vygotskian perspective, learning is social in origin and it happens in the presence of others that are more knowledgeable. Extending this view to the learning of mathematics, such learning also becomes inseparable from the presence of others (people and artefacts). Researchers over decades have studied different interactions to see how such learning with others occurs, what is the role of the (more knowledgeable) other, and if at all this role alternates between the participants. In this paper, we looked at a 5-year-old’s (Lila) interaction with her mother (Mellony) and a television remote control as Lila attempted to count in threes using the three by three physical layout of the numbered buttons 1–9 on the remote control. We specifically looked at the emergence of the Zone of Proximal Development (ZPD) as Lila’s attention was caught by the properties of the remote control and by her mother’s questions. We also pay attention to how the role of the more knowledgeable other alternates among the participants. Our findings suggest that Lila, at times, used resources provided by the physical properties of the remote control and sometimes, used resources provided by Mellony to think about the task of counting in threes. In Lila’s interaction, we interpreted a multi-directional ZPD as the role of the more knowledgeable other alternated between Mellony, Lila and the remote control.
- Full Text:
Conservation, commercialisation and confusion: Harvesting of Ischyrolepis in a coastal forest, South Africa
- Shackleton, Charlie M, Parkin, Fiona, Chauke, Maphambe I, Downsborough, Linda, Olsen, Ashleigh, Brill, Greg, Weideman, Craig I
- Authors: Shackleton, Charlie M , Parkin, Fiona , Chauke, Maphambe I , Downsborough, Linda , Olsen, Ashleigh , Brill, Greg , Weideman, Craig I
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181169 , vital:43704 , xlink:href="https://doi.org/10.1007/s10668-007-9106-3"
- Description: Harvesting of non-timber forest products is an integral component of rural livelihoods throughout the developing world. At times this is at odds with conservation objectives. Reconciliation of the two requires examination of local level contexts and needs. This paper reports on the harvesting needs for Ischyrolepis by a rural community in South Africa, against the setting that they had recently been prohibited from harvesting by the local conservation officials. Interviews were conducted with conservation officials to understand the reasoning for the prohibition. Local demand for Ischyrolepis was assessed by household surveys, as well as in-depth interviews with traders. The density and size class distribution of Ischyrolepis was determined using transects. The total annual demand for Ischyrolepis was determined to be approximately only 2.7% of the standing crop. The bulk of the annual demand was for small-scale trade, the income from which was a primary source of income for the few harvesters. Very little evidence could be found indicating that harvesting was damaging the resource or its habitat, and local knowledge suggested that the abundance of the species was stimulated by harvesting. Even if market demand were to increase, the size of the shoots required means that less than 20% of the standing crop could be harvested annually. Current regulations around harvesting are in a state of revision, and hence confusion prevails regarding if harvesting is permissible, and if so, under what conditions, which is detrimental to both conservation and livelihoods.
- Full Text:
- Authors: Shackleton, Charlie M , Parkin, Fiona , Chauke, Maphambe I , Downsborough, Linda , Olsen, Ashleigh , Brill, Greg , Weideman, Craig I
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181169 , vital:43704 , xlink:href="https://doi.org/10.1007/s10668-007-9106-3"
- Description: Harvesting of non-timber forest products is an integral component of rural livelihoods throughout the developing world. At times this is at odds with conservation objectives. Reconciliation of the two requires examination of local level contexts and needs. This paper reports on the harvesting needs for Ischyrolepis by a rural community in South Africa, against the setting that they had recently been prohibited from harvesting by the local conservation officials. Interviews were conducted with conservation officials to understand the reasoning for the prohibition. Local demand for Ischyrolepis was assessed by household surveys, as well as in-depth interviews with traders. The density and size class distribution of Ischyrolepis was determined using transects. The total annual demand for Ischyrolepis was determined to be approximately only 2.7% of the standing crop. The bulk of the annual demand was for small-scale trade, the income from which was a primary source of income for the few harvesters. Very little evidence could be found indicating that harvesting was damaging the resource or its habitat, and local knowledge suggested that the abundance of the species was stimulated by harvesting. Even if market demand were to increase, the size of the shoots required means that less than 20% of the standing crop could be harvested annually. Current regulations around harvesting are in a state of revision, and hence confusion prevails regarding if harvesting is permissible, and if so, under what conditions, which is detrimental to both conservation and livelihoods.
- Full Text:
Cretaceous erosion in central South Africa: evidence from upper-crustal xenoliths in kimberlite diatremes
- Hanson, E Kelsey, Moore, John M, Bordy, Emese M, Marsh, Julian S, Howarth, Geoffrey H, Robey, Julian van Aardt
- Authors: Hanson, E Kelsey , Moore, John M , Bordy, Emese M , Marsh, Julian S , Howarth, Geoffrey H , Robey, Julian van Aardt
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144978 , vital:38397 , https://doi.org/10.2113/gssajg.112.2.125
- Description: Twelve Group II and fourteen Group I kimberlite diatremes in central South Africa were examined for upper crustal xenoliths in order to estimate the extent of various lithological units of the Karoo Supergroup in the main Karoo basin at times of kimberlite eruption, the Cretaceous erosional history of the area, and the approximate vertical extent of the kimberlite diatremes prior to erosion. Sandstone and amygdaloidal basaltic lava xenoliths from the Karoo Supergroup were specifically selected as their modal mineralogies and geochemical compositions respectively can be attributed to specific stratigraphic positions within the Karoo Supergroup. Results indicated that, at the time of Group II kimberlite eruption (120 Ma), basaltic lavas of the Drakensberg Group covered the entire area, but by the time of Group I kimberlite eruption (85 Ma), they were restricted to the south-eastern half of the study area.
- Full Text:
- Authors: Hanson, E Kelsey , Moore, John M , Bordy, Emese M , Marsh, Julian S , Howarth, Geoffrey H , Robey, Julian van Aardt
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144978 , vital:38397 , https://doi.org/10.2113/gssajg.112.2.125
- Description: Twelve Group II and fourteen Group I kimberlite diatremes in central South Africa were examined for upper crustal xenoliths in order to estimate the extent of various lithological units of the Karoo Supergroup in the main Karoo basin at times of kimberlite eruption, the Cretaceous erosional history of the area, and the approximate vertical extent of the kimberlite diatremes prior to erosion. Sandstone and amygdaloidal basaltic lava xenoliths from the Karoo Supergroup were specifically selected as their modal mineralogies and geochemical compositions respectively can be attributed to specific stratigraphic positions within the Karoo Supergroup. Results indicated that, at the time of Group II kimberlite eruption (120 Ma), basaltic lavas of the Drakensberg Group covered the entire area, but by the time of Group I kimberlite eruption (85 Ma), they were restricted to the south-eastern half of the study area.
- Full Text:
Cultural historical activity theory, expansive learning and agency in permaculture workplaces
- Authors: Mukute, Mutizwa
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386474 , vital:68145 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122818"
- Description: This paper reports on how Cultural Historical Activity Theory was used to identify and analyse contradictions; model and implement solutions in the learning and practice of permaculture at one school and its community in Zimbabwe. This is one of three sustainable agriculture workplace learning sites being examined in a wider study on change-oriented learning and sustainability practices (Mukute, 2009). It gives a brief background to permaculture and the School and Colleges Permaculture Programme (SCOPE) in Zimbabwe. The paper focuses on how contradictions were used as sources of learning and development leading to ‘real life expansions’. This demonstrates and reflects on the value of an interventionist research theory and methodology employed in the study to enhance participants’ agency in sustainable agriculture workplaces.
- Full Text:
- Authors: Mukute, Mutizwa
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386474 , vital:68145 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122818"
- Description: This paper reports on how Cultural Historical Activity Theory was used to identify and analyse contradictions; model and implement solutions in the learning and practice of permaculture at one school and its community in Zimbabwe. This is one of three sustainable agriculture workplace learning sites being examined in a wider study on change-oriented learning and sustainability practices (Mukute, 2009). It gives a brief background to permaculture and the School and Colleges Permaculture Programme (SCOPE) in Zimbabwe. The paper focuses on how contradictions were used as sources of learning and development leading to ‘real life expansions’. This demonstrates and reflects on the value of an interventionist research theory and methodology employed in the study to enhance participants’ agency in sustainable agriculture workplaces.
- Full Text:
Dancing around the same spot? land reform and Ngos in Zimbabwe: the case of SOS Children’s Villages
- Authors: Helliker, Kirk D
- Date: 2009
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/61006 , vital:27910 , http://dx.doi.org/10.4314/asr.v13i2.60408
- Description: This paper discusses the rural-based operations of an international NGO in Mashonaland Central province, Zimbabwe. The aim is to highlight the contingent variation of NGO practices within defined limits. It does this through 'thick description’ of the NGO of focus, the SOS Children’s Village, and compares its 'handling' of the transforming countryside with the response of two other NGOs. It concludes by suggesting some conceptual points in understanding organizational dispositions of NGOs.
- Full Text:
- Authors: Helliker, Kirk D
- Date: 2009
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/61006 , vital:27910 , http://dx.doi.org/10.4314/asr.v13i2.60408
- Description: This paper discusses the rural-based operations of an international NGO in Mashonaland Central province, Zimbabwe. The aim is to highlight the contingent variation of NGO practices within defined limits. It does this through 'thick description’ of the NGO of focus, the SOS Children’s Village, and compares its 'handling' of the transforming countryside with the response of two other NGOs. It concludes by suggesting some conceptual points in understanding organizational dispositions of NGOs.
- Full Text:
Data quality in thermal summation development models for forensically important blowflies
- Richards, Cameron S, Villet, Martin H
- Authors: Richards, Cameron S , Villet, Martin H
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441889 , vital:73932 , https://doi.org/10.1111/j.1365-2915.2009.00819.x
- Description: To highlight some issues regarding data quality that are significant in estimating post‐mortem intervals (PMI) from maggots, the developmental constants of thermal summation models for development of Chrysomya megacephala Fabricius (Diptera: Calliphoridae) were calculated from incidental data gathered from 12 published studies, and from data generated specifically for the purpose in a single experiment. The focused experiment involved measuring the timing of five developmental landmarks at nine constant temperatures with a sampling resolution of 6–12 h, which is characteristic of other published studies. Combining data from different studies produced inconsistent results because of statistical noise introduced by (at least) disparities in temporal precision, descriptive statistics, geographical location and rearing diets. A robust experimental design to estimate a developmental model should involve at least six constant temperatures, starting at about 7°C above the relevant developmental zero (D0) and going almost to the upper critical temperature, and a temporal sampling interval with a relative precision of about 10%, which requires sampling about every 2 h until hatching, about every 3 h until first ecdysis and about every 6 h until second ecdysis.
- Full Text:
- Authors: Richards, Cameron S , Villet, Martin H
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441889 , vital:73932 , https://doi.org/10.1111/j.1365-2915.2009.00819.x
- Description: To highlight some issues regarding data quality that are significant in estimating post‐mortem intervals (PMI) from maggots, the developmental constants of thermal summation models for development of Chrysomya megacephala Fabricius (Diptera: Calliphoridae) were calculated from incidental data gathered from 12 published studies, and from data generated specifically for the purpose in a single experiment. The focused experiment involved measuring the timing of five developmental landmarks at nine constant temperatures with a sampling resolution of 6–12 h, which is characteristic of other published studies. Combining data from different studies produced inconsistent results because of statistical noise introduced by (at least) disparities in temporal precision, descriptive statistics, geographical location and rearing diets. A robust experimental design to estimate a developmental model should involve at least six constant temperatures, starting at about 7°C above the relevant developmental zero (D0) and going almost to the upper critical temperature, and a temporal sampling interval with a relative precision of about 10%, which requires sampling about every 2 h until hatching, about every 3 h until first ecdysis and about every 6 h until second ecdysis.
- Full Text:
Deconstructing language myths: which languages of learning and teaching in South Africa
- Dalvit, Lorenzo, Murray, Sarah, Terzoli, Alfredo
- Authors: Dalvit, Lorenzo , Murray, Sarah , Terzoli, Alfredo
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431260 , vital:72759 , https://d1wqtxts1xzle7.cloudfront.net/91537059/Deconstructing_language_myths_which_languages_of_learning_and_teaching_in_South_Africa.sflb-libre.pdf?1664136385=response-content-disposi-tion=inline%3B+filename%3DDeconstructing_language_myths_which_lang.pdfExpires=1714984902Signature=dj35y~SObsQq0TnqD-oDUj3CX7lgNnKJcMAchC7rarU74xqfrMlVfOwi-MZrNZvWvpxyzquBsmr1veH-ggRVXQP7TX4eKQq3tXV-gJZg3xyo7QJoGwrGPTjC4btF2kNrVJc6TQulzuPFEz47GtjQ6Nint4SmE7A30EMUMd8j25KgCUdtzqwx9kjBs-niKu~z-pk-Xon5YOolMTepbOwNr9wKGj8JafblTdnFs-H8CZ-Et4BD2mYV3GxnR0QLfgawFgDYkOSZnYhkl6wFsXG~Euwlhcvtp0EgUOfP4id~Ov9hhA-rSQxl81X2Dh1BdMuT3GSsK6VNmO7TikSC7NeGlQ__Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA
- Description: In this article we argue for the use of African languages as Languages of Learning and Teaching (LoLT) for native speakers of such language in South Africa. We believe that both public and academic debate is in-fluenced by a set of ‘language myths’: 1) only one language should be used; 2) the earlier one starts using English as LoLT, the better; 3) us-ing English as LoLT improves English proficiency. These myths be seen as a direct manifestation of Western hegemony, and English-functional arguments are often the terms of reference. We will try a dif-ferent approach by highlighting the advantages of using an African lan-guage (ie isiXhosa) as LoLT and, whenever possible, we will try to put English on the ‘defence stand’. The purpose of this paper is not to ad-vocate the substitution of English with an African language. We believe that bilingual education is the appropriate choice for South Africa, but in order to achieve full equality between English and the African lan-guages in education, arguments in support of the latter must be put forward proactively. With our paper, we hope to contribute to this new perspective.
- Full Text:
- Authors: Dalvit, Lorenzo , Murray, Sarah , Terzoli, Alfredo
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431260 , vital:72759 , https://d1wqtxts1xzle7.cloudfront.net/91537059/Deconstructing_language_myths_which_languages_of_learning_and_teaching_in_South_Africa.sflb-libre.pdf?1664136385=response-content-disposi-tion=inline%3B+filename%3DDeconstructing_language_myths_which_lang.pdfExpires=1714984902Signature=dj35y~SObsQq0TnqD-oDUj3CX7lgNnKJcMAchC7rarU74xqfrMlVfOwi-MZrNZvWvpxyzquBsmr1veH-ggRVXQP7TX4eKQq3tXV-gJZg3xyo7QJoGwrGPTjC4btF2kNrVJc6TQulzuPFEz47GtjQ6Nint4SmE7A30EMUMd8j25KgCUdtzqwx9kjBs-niKu~z-pk-Xon5YOolMTepbOwNr9wKGj8JafblTdnFs-H8CZ-Et4BD2mYV3GxnR0QLfgawFgDYkOSZnYhkl6wFsXG~Euwlhcvtp0EgUOfP4id~Ov9hhA-rSQxl81X2Dh1BdMuT3GSsK6VNmO7TikSC7NeGlQ__Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA
- Description: In this article we argue for the use of African languages as Languages of Learning and Teaching (LoLT) for native speakers of such language in South Africa. We believe that both public and academic debate is in-fluenced by a set of ‘language myths’: 1) only one language should be used; 2) the earlier one starts using English as LoLT, the better; 3) us-ing English as LoLT improves English proficiency. These myths be seen as a direct manifestation of Western hegemony, and English-functional arguments are often the terms of reference. We will try a dif-ferent approach by highlighting the advantages of using an African lan-guage (ie isiXhosa) as LoLT and, whenever possible, we will try to put English on the ‘defence stand’. The purpose of this paper is not to ad-vocate the substitution of English with an African language. We believe that bilingual education is the appropriate choice for South Africa, but in order to achieve full equality between English and the African lan-guages in education, arguments in support of the latter must be put forward proactively. With our paper, we hope to contribute to this new perspective.
- Full Text:
Deployment and Extension of a Converged WiMAX/WiFi Network for Dwesa Community Area South Africa
- Ndlovu, N, Terzoli, Alfredo, Thinyane, Mamello
- Authors: Ndlovu, N , Terzoli, Alfredo , Thinyane, Mamello
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428479 , vital:72514 , https://citeseerx.ist.psu.edu/document?repid=rep1andtype=pdfanddoi=22468be0252776eabb9e015b51e8e5cf2855ca5f
- Description: As demand for new, reliable, flexible and relatively inexpensive internet access in marginalized rural areas in developing countries increases, there is a need to amalgamate broadband technologies such as WiMAX and WiFi so as to extend the coverage area. Consequently, this will en-able provision of high-speed mobile data and telecommunications ser-vices. This paper describes how WiMAX and WiFi can be merged to-gether, with VSAT technology offering backhaul internet connectivity to provide ever present broadband access. We also look at their respective network applications and how there are going to be used to help support ICT4D activities in these marginalized areas.
- Full Text:
- Authors: Ndlovu, N , Terzoli, Alfredo , Thinyane, Mamello
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428479 , vital:72514 , https://citeseerx.ist.psu.edu/document?repid=rep1andtype=pdfanddoi=22468be0252776eabb9e015b51e8e5cf2855ca5f
- Description: As demand for new, reliable, flexible and relatively inexpensive internet access in marginalized rural areas in developing countries increases, there is a need to amalgamate broadband technologies such as WiMAX and WiFi so as to extend the coverage area. Consequently, this will en-able provision of high-speed mobile data and telecommunications ser-vices. This paper describes how WiMAX and WiFi can be merged to-gether, with VSAT technology offering backhaul internet connectivity to provide ever present broadband access. We also look at their respective network applications and how there are going to be used to help support ICT4D activities in these marginalized areas.
- Full Text:
Development and validation of a stability-indicating method for the quantitation of paclitaxel in pharmaceutical dosage forms
- Mohammadi, Ali, Esimaeili, Farnaz, Dinarvand, Rasoul, Atyabi, Fatemeh, Walker, Roderick B
- Authors: Mohammadi, Ali , Esimaeili, Farnaz , Dinarvand, Rasoul , Atyabi, Fatemeh , Walker, Roderick B
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184278 , vital:44196 , xlink:href="https://doi.org/10.1093/chromsci/47.7.599"
- Description: A simple, rapid stability-indicating isocratic assay has been developed and validated for the determination of Paclitaxel (PTX) in commercial injection formulations. The assay is performed using a Nucleosil RP-18 (5 µm, 250 × 4.0 mm i.d) column protected by a Nucleosil C18 precolumn (5 µm, 4.0 × 4.0 mm i.d.) with a mobile phase of methanol–water (80:20) and UV detection at 230 nm. The method was found to be specific for PTX in the presence of degradation products with an overall analytical run time of ~ 9 min. Accuracy reported as % bias was found to be 0.1–2.5% bias for all samples tested. Intra-assay precision (repeatability) was found to be 0.22–2.65% RSD, while inter-day precision (intermediate precision) was found to be 1.0–3.0% RSD for the samples studied. The calibration curve was found to be linear with the equation y = 29.78x + 7.65, and a linear regression coefficient of 0.9994 over the concentration range 0.05–20 µg/mL. The limits of quantitation and detection were 0.05 and 0.02 µg/mL, respectively. Taxol (30 mg/5 mL), a commercially available dosage form of PTX, was assayed and 100.6–103.6% of the label claim was recovered.
- Full Text:
- Authors: Mohammadi, Ali , Esimaeili, Farnaz , Dinarvand, Rasoul , Atyabi, Fatemeh , Walker, Roderick B
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184278 , vital:44196 , xlink:href="https://doi.org/10.1093/chromsci/47.7.599"
- Description: A simple, rapid stability-indicating isocratic assay has been developed and validated for the determination of Paclitaxel (PTX) in commercial injection formulations. The assay is performed using a Nucleosil RP-18 (5 µm, 250 × 4.0 mm i.d) column protected by a Nucleosil C18 precolumn (5 µm, 4.0 × 4.0 mm i.d.) with a mobile phase of methanol–water (80:20) and UV detection at 230 nm. The method was found to be specific for PTX in the presence of degradation products with an overall analytical run time of ~ 9 min. Accuracy reported as % bias was found to be 0.1–2.5% bias for all samples tested. Intra-assay precision (repeatability) was found to be 0.22–2.65% RSD, while inter-day precision (intermediate precision) was found to be 1.0–3.0% RSD for the samples studied. The calibration curve was found to be linear with the equation y = 29.78x + 7.65, and a linear regression coefficient of 0.9994 over the concentration range 0.05–20 µg/mL. The limits of quantitation and detection were 0.05 and 0.02 µg/mL, respectively. Taxol (30 mg/5 mL), a commercially available dosage form of PTX, was assayed and 100.6–103.6% of the label claim was recovered.
- Full Text:
Development of Thanatophilus micans (Fabricius 1794)(Coleoptera: Silphidae) at constant temperatures
- Midgley, John M, Villet, Martin H
- Authors: Midgley, John M , Villet, Martin H
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441904 , vital:73933 , https://doi.org/10.1007/s00414-008-0280-0
- Description: Thanatophilus micans is capable of finding corpses at least as quickly as most fly species and, as the most widespread species of the Silphidae in Africa, offers a useful model for estimating post-mortem interval. Larvae were reared at ten constant temperatures from 15°C to 35°C and their length measured at 4, 8, or 12-h intervals depending on their instar. Length generally increased with increased rearing temperature, but decreased at extremely high temperatures. Note was made of the age at which individuals progressed past developmental milestones. Development took longer at lower temperatures. These results are presented as a combined isomegalen and isomorphen diagram. Developmental constants were generated for each milestone using major axis regression. Developmental threshold values did not differ significantly between milestones. Development took longer than in blow flies, but was faster than in Dermestidae. The three models presented here, therefore, cover an important time frame in estimating minimum PMI once fly larvae have matured to the point of leaving a corpse, and, therefore, provide a tool that was not previously available to forensic entomologists.
- Full Text:
Development of Thanatophilus micans (Fabricius 1794)(Coleoptera: Silphidae) at constant temperatures
- Authors: Midgley, John M , Villet, Martin H
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441904 , vital:73933 , https://doi.org/10.1007/s00414-008-0280-0
- Description: Thanatophilus micans is capable of finding corpses at least as quickly as most fly species and, as the most widespread species of the Silphidae in Africa, offers a useful model for estimating post-mortem interval. Larvae were reared at ten constant temperatures from 15°C to 35°C and their length measured at 4, 8, or 12-h intervals depending on their instar. Length generally increased with increased rearing temperature, but decreased at extremely high temperatures. Note was made of the age at which individuals progressed past developmental milestones. Development took longer at lower temperatures. These results are presented as a combined isomegalen and isomorphen diagram. Developmental constants were generated for each milestone using major axis regression. Developmental threshold values did not differ significantly between milestones. Development took longer than in blow flies, but was faster than in Dermestidae. The three models presented here, therefore, cover an important time frame in estimating minimum PMI once fly larvae have matured to the point of leaving a corpse, and, therefore, provide a tool that was not previously available to forensic entomologists.
- Full Text:
Diffraction efficiency and I–V characteristics of metal-free phthalocyanine doped nematic liquid crystals
- Köysal, Oguz, Okutan, Mustafa, San, S Eren, Nyokong, Tebello, Durmus, Mahmut
- Authors: Köysal, Oguz , Okutan, Mustafa , San, S Eren , Nyokong, Tebello , Durmus, Mahmut
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263511 , vital:53634 , xlink:href="https://doi.org/10.1016/j.matchemphys.2008.10.056"
- Description: The synthesis and characterization of the tetra-4-benzyloxyphenoxy substituted metal-free phthalocyanine (H2Pc) is reported for the first time. Formation of the photoinduced gratings has been experienced in a metal-free phthalocyanine doped nematic liquid crystal (LC) system and its I–V properties are characterized by electrical measurements. Four samples are prepared at different doping percentages and in homogenously aligned sandwiched geometry. We report the results of two set of experiments on these samples. One of them is the grating diffraction experiment for the analysis of optically induced reorientation process which is a basis for possible holographic applications. Accessible diffraction efficiency is found to be linearly increasing as the amount of the phthalocyanine doping rises. In the scope of the other set of measurements I–V peculiarity of the system is also found to be enhanced and linearly dependent on doping.
- Full Text:
- Authors: Köysal, Oguz , Okutan, Mustafa , San, S Eren , Nyokong, Tebello , Durmus, Mahmut
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263511 , vital:53634 , xlink:href="https://doi.org/10.1016/j.matchemphys.2008.10.056"
- Description: The synthesis and characterization of the tetra-4-benzyloxyphenoxy substituted metal-free phthalocyanine (H2Pc) is reported for the first time. Formation of the photoinduced gratings has been experienced in a metal-free phthalocyanine doped nematic liquid crystal (LC) system and its I–V properties are characterized by electrical measurements. Four samples are prepared at different doping percentages and in homogenously aligned sandwiched geometry. We report the results of two set of experiments on these samples. One of them is the grating diffraction experiment for the analysis of optically induced reorientation process which is a basis for possible holographic applications. Accessible diffraction efficiency is found to be linearly increasing as the amount of the phthalocyanine doping rises. In the scope of the other set of measurements I–V peculiarity of the system is also found to be enhanced and linearly dependent on doping.
- Full Text:
Editorial: environmental-education research in the year of COP 15
- Lotz-Sisitka, Heila, Kronlid, David O
- Authors: Lotz-Sisitka, Heila , Kronlid, David O
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67356 , vital:29080 , https://www.ajol.info/index.php/sajee/article/view/122784
- Description: publisher version , Introduction: This year there has literally been a cacophony surrounding the implications of climate change, as the world geared up for the 15th Conference of the Parties (COP 15) in Copenhagen, where it was expected that the largest ever gathering of world leaders would sign binding agreements to reduce carbon emissions to keep global temperatures from rising by more than 2⁰C. As we make the final contributions to the refinement of this editorial, late in December 2009, it is concerning to note that this did not happen, that civil society voices were marginalised at the COP 15 and that there has been little progress on a socially just and ecologically sound global climate change deal. The stark reality remains that developing countries – southern African countries in particular – remain most vulnerable to the risks associated with global climate change. Havnevik (2007) stated a while ago that: The ways in which poverty, consumption and climate change are addressed, tend to blur historical, structural and power features underlying global inequalities. This makes possible the focus on market forces, such as carbon trading, to resolve the problems. However, these market solutions will not suffice, and may only delay a real solution, which will then have to be developed in a situation of more acute global social injustice and possibly deeper conflicts … Issues related to inequality, energy and climate are of a global character: there is no longer one solution for the South and one for the North. (18,19) So where does the current state of climate change and the political failures surrounding responses to climate change leave education research in developing and developed nations? What are the implications for environmental education researchers in southern Africa and elsewhere? These are some of the questions pondered in this edition of the Southern African Journal of Environmental Education (SAJEE). As one of us (Kronlid) reflects in a Think Piece in this journal: ‘the world is one and many and … the complexities associated with climate change means that we have a shared global systematic problem manifested in a myriad different concrete ways in people’s everyday life throughout the globe. We need many different kinds and modes of climate change education research’ (Kronlid, this edition).
- Full Text:
- Authors: Lotz-Sisitka, Heila , Kronlid, David O
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67356 , vital:29080 , https://www.ajol.info/index.php/sajee/article/view/122784
- Description: publisher version , Introduction: This year there has literally been a cacophony surrounding the implications of climate change, as the world geared up for the 15th Conference of the Parties (COP 15) in Copenhagen, where it was expected that the largest ever gathering of world leaders would sign binding agreements to reduce carbon emissions to keep global temperatures from rising by more than 2⁰C. As we make the final contributions to the refinement of this editorial, late in December 2009, it is concerning to note that this did not happen, that civil society voices were marginalised at the COP 15 and that there has been little progress on a socially just and ecologically sound global climate change deal. The stark reality remains that developing countries – southern African countries in particular – remain most vulnerable to the risks associated with global climate change. Havnevik (2007) stated a while ago that: The ways in which poverty, consumption and climate change are addressed, tend to blur historical, structural and power features underlying global inequalities. This makes possible the focus on market forces, such as carbon trading, to resolve the problems. However, these market solutions will not suffice, and may only delay a real solution, which will then have to be developed in a situation of more acute global social injustice and possibly deeper conflicts … Issues related to inequality, energy and climate are of a global character: there is no longer one solution for the South and one for the North. (18,19) So where does the current state of climate change and the political failures surrounding responses to climate change leave education research in developing and developed nations? What are the implications for environmental education researchers in southern Africa and elsewhere? These are some of the questions pondered in this edition of the Southern African Journal of Environmental Education (SAJEE). As one of us (Kronlid) reflects in a Think Piece in this journal: ‘the world is one and many and … the complexities associated with climate change means that we have a shared global systematic problem manifested in a myriad different concrete ways in people’s everyday life throughout the globe. We need many different kinds and modes of climate change education research’ (Kronlid, this edition).
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Effect of peripheral fused ring substitution on the optical spectroscopy and electronic structure of metal phthalocyanine complexes
- Chidawanyika, Wadzanai J U, Mack, John, Shimizu, Soji, Kobayashi, Nagao, Nyokong, Tebello
- Authors: Chidawanyika, Wadzanai J U , Mack, John , Shimizu, Soji , Kobayashi, Nagao , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263353 , vital:53620 , xlink:href="https://doi.org/10.1142/S1088424609001339"
- Description: In this paper the impact of peripheral substitution with a strongly withdrawing fused ring group on the optical spectroscopy of a metal phthalocyanine complex is analyzed. We report the synthesis of [9 (or 10), 16 (or 17), 23 (or 24)-tri-tert-butylimidophthalocyaninato]zinc(II) (ZnttbIPc), which should eventually prove to be a useful precursor for forming dimeric compounds. The electronic structure is analyzed through a detailed analysis of the UV-visible absorption and magnetic circular dichroism spectra and time-dependent density functional theory calculations. Other than a marked splitting of the Q band, the spectrum is broadly similar to that of ZnPc in terms of the main π → π* electronic bands. The vibrational bands differ markedly in the Q band region when an imido group is added to ligand periphery, relative to what is observed in the case of zinc mononaphthotribenzotetraazaporphyrin (Zn3B1N) with an additional fused benzene ring. The absorption and emission spectra lack mirror symmetry as is the case with ZnPc and thus provide possible evidence for a second set of electronic origins in the Q band region arising from n → π* rather then π → π* transitions.
- Full Text:
- Authors: Chidawanyika, Wadzanai J U , Mack, John , Shimizu, Soji , Kobayashi, Nagao , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263353 , vital:53620 , xlink:href="https://doi.org/10.1142/S1088424609001339"
- Description: In this paper the impact of peripheral substitution with a strongly withdrawing fused ring group on the optical spectroscopy of a metal phthalocyanine complex is analyzed. We report the synthesis of [9 (or 10), 16 (or 17), 23 (or 24)-tri-tert-butylimidophthalocyaninato]zinc(II) (ZnttbIPc), which should eventually prove to be a useful precursor for forming dimeric compounds. The electronic structure is analyzed through a detailed analysis of the UV-visible absorption and magnetic circular dichroism spectra and time-dependent density functional theory calculations. Other than a marked splitting of the Q band, the spectrum is broadly similar to that of ZnPc in terms of the main π → π* electronic bands. The vibrational bands differ markedly in the Q band region when an imido group is added to ligand periphery, relative to what is observed in the case of zinc mononaphthotribenzotetraazaporphyrin (Zn3B1N) with an additional fused benzene ring. The absorption and emission spectra lack mirror symmetry as is the case with ZnPc and thus provide possible evidence for a second set of electronic origins in the Q band region arising from n → π* rather then π → π* transitions.
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Effects of food quality on tissue-specific isotope ratios in the mussel Perna perna
- Hill, Jaclyn M, McQuaid, Christopher D
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444563 , vital:74251 , https://doi.org/10.1007/s10750-009-9865-y
- Description: Investigations into trophic ecology and aquatic food web resolution are increasingly accomplished through stable isotope analysis. The incorporation of dietary and metabolic changes over time results in variations in isotope signatures and turnover rates of producers and consumers at tissue, individual, population and species levels. Consequently, the elucidation of trophic relationships in aquatic systems depends on establishing standard isotope values and tissue turnover rates for the level in question. This study investigated the effect of diet and food quality on isotopic signatures of four mussel tissues: adductor muscle, gonad, gill and mantle tissue from the brown mussel Perna perna. In the laboratory, mussels were fed one of the two isotopically distinct diets for 3 months.
- Full Text:
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444563 , vital:74251 , https://doi.org/10.1007/s10750-009-9865-y
- Description: Investigations into trophic ecology and aquatic food web resolution are increasingly accomplished through stable isotope analysis. The incorporation of dietary and metabolic changes over time results in variations in isotope signatures and turnover rates of producers and consumers at tissue, individual, population and species levels. Consequently, the elucidation of trophic relationships in aquatic systems depends on establishing standard isotope values and tissue turnover rates for the level in question. This study investigated the effect of diet and food quality on isotopic signatures of four mussel tissues: adductor muscle, gonad, gill and mantle tissue from the brown mussel Perna perna. In the laboratory, mussels were fed one of the two isotopically distinct diets for 3 months.
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Effects of the number of ring substituents of cobalt carboxyphthalocyanines on the electrocatalytic detection of nitrite, cysteine and melatonin
- Matemadombo, Fungisai, Sehlotho, Nthapo, Nyokong, Tebello
- Authors: Matemadombo, Fungisai , Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263408 , vital:53625 , xlink:href="https://doi.org/10.1142/S108842460900125X"
- Description: Cobalt phthalocyanine (CoPc), cobalt tetracarboxy phthalocyanine (CoTCPc) and cobalt octacarboxy phthalocyanine (CoOCPc), adsorbed onto glassy carbon electrodes, have been used for the electrocatalytic detection of nitrite, L-cysteine and melatonin. The modified electrodes electrocatalytically detected nitrite around 800 mV vs.Ag|AgCl, a value less positive compared to that of an unmodified glassy carbon electrode (at 950 mV vs.Ag|AgCl) and also gave detection limits in the 10-7 M range for nitrite detection. L-cysteine was detected by the modified electrodes at potentials between 0.50 to 0.65 V vs.Ag|AgCl, with L-cysteine detection limits also in the 10-7 M range. The detection limits for melatonin ranged from 10-7 to 10-6 M. CoPc-modified electrodes displayed good separation of interferents (tryptophan and ascorbic acid) in the presence of melatonin. Analyses of commercial melatonin tablets using modified electrodes gave excellent agreement with manufacturer's value for all modified electrodes of this work.
- Full Text:
- Authors: Matemadombo, Fungisai , Sehlotho, Nthapo , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263408 , vital:53625 , xlink:href="https://doi.org/10.1142/S108842460900125X"
- Description: Cobalt phthalocyanine (CoPc), cobalt tetracarboxy phthalocyanine (CoTCPc) and cobalt octacarboxy phthalocyanine (CoOCPc), adsorbed onto glassy carbon electrodes, have been used for the electrocatalytic detection of nitrite, L-cysteine and melatonin. The modified electrodes electrocatalytically detected nitrite around 800 mV vs.Ag|AgCl, a value less positive compared to that of an unmodified glassy carbon electrode (at 950 mV vs.Ag|AgCl) and also gave detection limits in the 10-7 M range for nitrite detection. L-cysteine was detected by the modified electrodes at potentials between 0.50 to 0.65 V vs.Ag|AgCl, with L-cysteine detection limits also in the 10-7 M range. The detection limits for melatonin ranged from 10-7 to 10-6 M. CoPc-modified electrodes displayed good separation of interferents (tryptophan and ascorbic acid) in the presence of melatonin. Analyses of commercial melatonin tablets using modified electrodes gave excellent agreement with manufacturer's value for all modified electrodes of this work.
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Electrostatic self-assembly of quaternized 2,(3)-tetra (oxo-pyridine) phthalocyaninato chloroindium (III) with a series of tetrasulfonated phthalocyanines
- George, Reama C, Durmus, Mahmut, Egharevba, Gabriel O, Nyokong, Tebello
- Authors: George, Reama C , Durmus, Mahmut , Egharevba, Gabriel O , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263330 , vital:53618 , xlink:href="https://doi.org/10.1016/j.poly.2009.07.035"
- Description: The self-assembly of oppositely charged phthalocyanines, fabricated using quaternized 2,(3)-tetra(oxo-pyridine) phthalocyaninato chloroindium (III) (QInPyPc) as the positively charge molecule and a series of tetrasulfonate phthalocyanine (MTSPc), M = 2H, Mn, Fe, Co and Ni as negatively charged molecules are reported. The self-assembly results in the formation of heteroaggregates. The metallated sulfonated phthalocyanines form nanorod and nanoleaf shaped structures as evidenced by transmission electron microscopy (TEM). The UV–Vis spectra showed blue shifted Q bands, suggesting that these structures were in a face-to-face arrangement. The Raman spectra of the heteroaggregates showed shifting compared to the spectra of the precursors.
- Full Text:
- Authors: George, Reama C , Durmus, Mahmut , Egharevba, Gabriel O , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263330 , vital:53618 , xlink:href="https://doi.org/10.1016/j.poly.2009.07.035"
- Description: The self-assembly of oppositely charged phthalocyanines, fabricated using quaternized 2,(3)-tetra(oxo-pyridine) phthalocyaninato chloroindium (III) (QInPyPc) as the positively charge molecule and a series of tetrasulfonate phthalocyanine (MTSPc), M = 2H, Mn, Fe, Co and Ni as negatively charged molecules are reported. The self-assembly results in the formation of heteroaggregates. The metallated sulfonated phthalocyanines form nanorod and nanoleaf shaped structures as evidenced by transmission electron microscopy (TEM). The UV–Vis spectra showed blue shifted Q bands, suggesting that these structures were in a face-to-face arrangement. The Raman spectra of the heteroaggregates showed shifting compared to the spectra of the precursors.
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eServices provisioning in a community development context through a JADE MAS platform
- Thinyane, Mamello, Terzoli, Alfredo, Clayton, Peter G
- Authors: Thinyane, Mamello , Terzoli, Alfredo , Clayton, Peter G
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430836 , vital:72720 , 10.1109/ICTD.2009.5426697
- Description: A growing proliferation of ICT4D interventions has necessitated the ex-ploration of innovative solutions for the provisioning of eServices in ru-ral, marginalized communities. The challenges currently faced in these interventions include: situating the developed applications within the cultural and ethnographic context of the target communities, integrating greater levels of granularity and flexibility within the applications for in-creased context sensitivity, handling the intermittence and instability of supporting infrastructural services. These are the challenges that we address in the context of ICT4D intervention undertaken in a rural community in the Eastern Cape province of South Africa. We explore the design and implementation of a Multi-Agent System (MAS) for this community as a platform for provisioning of context-sensitive eServ-ices, and highlight some observations with regards to the applicability and adequacy of the solution.
- Full Text:
- Authors: Thinyane, Mamello , Terzoli, Alfredo , Clayton, Peter G
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430836 , vital:72720 , 10.1109/ICTD.2009.5426697
- Description: A growing proliferation of ICT4D interventions has necessitated the ex-ploration of innovative solutions for the provisioning of eServices in ru-ral, marginalized communities. The challenges currently faced in these interventions include: situating the developed applications within the cultural and ethnographic context of the target communities, integrating greater levels of granularity and flexibility within the applications for in-creased context sensitivity, handling the intermittence and instability of supporting infrastructural services. These are the challenges that we address in the context of ICT4D intervention undertaken in a rural community in the Eastern Cape province of South Africa. We explore the design and implementation of a Multi-Agent System (MAS) for this community as a platform for provisioning of context-sensitive eServ-ices, and highlight some observations with regards to the applicability and adequacy of the solution.
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Establishment of translocated populations of smallmouth yellowfish, Labeobarbus aeneus (Pisces: Cyprinidae), in lentic and lotic habitats in the Great Fish River system, South Africa
- Weyl, Olaf L F, Stadtlander, Timo, Booth, Anthony J
- Authors: Weyl, Olaf L F , Stadtlander, Timo , Booth, Anthony J
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124418 , vital:35607 , https://doi.org/10.3377/004.044.0109
- Description: As a result of numerous introductions and translocations of fishes, South Africa has recently been identified as a fish invasion hotspot (Leprieur et al. 2008). In freshwater ecosystems invasion by alien species is considered a leading mechanism driving environmental change (Clavero & Garcia- Berthou 2005; Garcia-Berthou et al. 2005). In South Africa, documented effects of fish invasions include the extirpation of indigenous fishes through predation (Cambray 2003), changes in invertebrate community structure (Lowe et al. 2008) and hybridization (Canonico et al. 2005). As a result, the management of alien species is a high national priority (National Environmental Management: Biodiversity Act 2004). Such management requires an understanding of the biology, ecology and establishment success of fishes outside their native range.
- Full Text:
- Authors: Weyl, Olaf L F , Stadtlander, Timo , Booth, Anthony J
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124418 , vital:35607 , https://doi.org/10.3377/004.044.0109
- Description: As a result of numerous introductions and translocations of fishes, South Africa has recently been identified as a fish invasion hotspot (Leprieur et al. 2008). In freshwater ecosystems invasion by alien species is considered a leading mechanism driving environmental change (Clavero & Garcia- Berthou 2005; Garcia-Berthou et al. 2005). In South Africa, documented effects of fish invasions include the extirpation of indigenous fishes through predation (Cambray 2003), changes in invertebrate community structure (Lowe et al. 2008) and hybridization (Canonico et al. 2005). As a result, the management of alien species is a high national priority (National Environmental Management: Biodiversity Act 2004). Such management requires an understanding of the biology, ecology and establishment success of fishes outside their native range.
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Evaluating text preprocessing to improve compression on maillogs
- Otten, Fred, Irwin, Barry V W, Thinyane, Hannah
- Authors: Otten, Fred , Irwin, Barry V W , Thinyane, Hannah
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430138 , vital:72668 , https://doi.org/10.1145/1632149.1632157
- Description: Maillogs contain important information about mail which has been sent or received. This information can be used for statistical purposes, to help prevent viruses or to help prevent SPAM. In order to satisfy regula-tions and follow good security practices, maillogs need to be monitored and archived. Since there is a large quantity of data, some form of data reduction is necessary. Data compression programs such as gzip and bzip2 are commonly used to reduce the quantity of data. Text preprocessing can be used to aid the compression of English text files. This paper evaluates whether text preprocessing, particularly word replacement, can be used to improve the compression of maillogs. It presents an algorithm for constructing a dictionary for word replacement and provides the results of experiments conducted using the ppmd, gzip, bzip2 and 7zip programs. These tests show that text prepro-cessing improves data compression on maillogs. Improvements of up to 56 percent in compression time and up to 32 percent in compression ratio are achieved. It also shows that a dictionary may be generated and used on other maillogs to yield reductions within half a percent of the results achieved for the maillog used to generate the dictionary.
- Full Text:
- Authors: Otten, Fred , Irwin, Barry V W , Thinyane, Hannah
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430138 , vital:72668 , https://doi.org/10.1145/1632149.1632157
- Description: Maillogs contain important information about mail which has been sent or received. This information can be used for statistical purposes, to help prevent viruses or to help prevent SPAM. In order to satisfy regula-tions and follow good security practices, maillogs need to be monitored and archived. Since there is a large quantity of data, some form of data reduction is necessary. Data compression programs such as gzip and bzip2 are commonly used to reduce the quantity of data. Text preprocessing can be used to aid the compression of English text files. This paper evaluates whether text preprocessing, particularly word replacement, can be used to improve the compression of maillogs. It presents an algorithm for constructing a dictionary for word replacement and provides the results of experiments conducted using the ppmd, gzip, bzip2 and 7zip programs. These tests show that text prepro-cessing improves data compression on maillogs. Improvements of up to 56 percent in compression time and up to 32 percent in compression ratio are achieved. It also shows that a dictionary may be generated and used on other maillogs to yield reductions within half a percent of the results achieved for the maillog used to generate the dictionary.
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Exploratory mathematics talk in a second language: a sociolinguistic perspective:
- Graven, Mellony, Robertson, Sally-Ann
- Authors: Graven, Mellony , Robertson, Sally-Ann
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69907 , vital:29594 , https://doi.org/10.1007/s11858-018-0952-2
- Description: This paper illuminates challenges confronting teachers and students at the literacy/numeracy interface in contexts where students have not developed sufficient English language proficiency to be learning mathematics through English but, due to socio-politically and economically driven perceptions are being taught in English. We analyse transcript data of classroom talk in a South African grade 4 mathematics lesson on fractions. Together with interview data, the lesson data highlight some of the consequences students’ diminished access to their home language appear to have on their access to mathematical meaning-making.
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- Authors: Graven, Mellony , Robertson, Sally-Ann
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69907 , vital:29594 , https://doi.org/10.1007/s11858-018-0952-2
- Description: This paper illuminates challenges confronting teachers and students at the literacy/numeracy interface in contexts where students have not developed sufficient English language proficiency to be learning mathematics through English but, due to socio-politically and economically driven perceptions are being taught in English. We analyse transcript data of classroom talk in a South African grade 4 mathematics lesson on fractions. Together with interview data, the lesson data highlight some of the consequences students’ diminished access to their home language appear to have on their access to mathematical meaning-making.
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