The synthesis and photophysical properties of water soluble tetrasulfonated, octacarboxylated and quaternised 2,(3)-tetra-(2 pyridiloxy) Ga phthalocyanines
- Masilela, Nkosiphile, Nyokong, Tebello
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6579 , http://hdl.handle.net/10962/d1004142
- Description: The photophysical behaviour of chlorogallium 2,(3)-tetra-(2 pyridiloxy) phthalocyanine (ClGaT-2-PyPc) and its quaternised derivative were compared with that of the water soluble anionic tetrasulfonated gallium phthalocyanine ((OH)GaTSPc) and hydoxy gallium octacarboxy phthalocyanine ((OH)GaOCPc). Although both the quaternised compound and the tetrasulfonated gallium phthalocyanine aggregated in aq. solution at pH 11, resulting in low fluorescence and triplet yields, the presence of the surfactant Cremophore EL improved yields. Triplet quantum yields ranged from 0.52 to 0.70 and fluorescence quantum yields ranged from <0.01 to 0.21. The nature of substituent (sulfonate, carboxy and pyridiloxy) did not influence photophysical properties. Chlorogallium 2,(3)-tetra-(2 pyridiloxy) phthalocyanine and its quaternised derivative displayed longer triplet lifetime than both the tetrasulfonated gallium phthalocyanine ((OH)GaTSPc) and hydroxy gallium octacarboxy phthalocyanine in DMSO and in aq. media in both the presence and absence of surfactant.
- Full Text:
- Date Issued: 2010
- Authors: Masilela, Nkosiphile , Nyokong, Tebello
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6579 , http://hdl.handle.net/10962/d1004142
- Description: The photophysical behaviour of chlorogallium 2,(3)-tetra-(2 pyridiloxy) phthalocyanine (ClGaT-2-PyPc) and its quaternised derivative were compared with that of the water soluble anionic tetrasulfonated gallium phthalocyanine ((OH)GaTSPc) and hydoxy gallium octacarboxy phthalocyanine ((OH)GaOCPc). Although both the quaternised compound and the tetrasulfonated gallium phthalocyanine aggregated in aq. solution at pH 11, resulting in low fluorescence and triplet yields, the presence of the surfactant Cremophore EL improved yields. Triplet quantum yields ranged from 0.52 to 0.70 and fluorescence quantum yields ranged from <0.01 to 0.21. The nature of substituent (sulfonate, carboxy and pyridiloxy) did not influence photophysical properties. Chlorogallium 2,(3)-tetra-(2 pyridiloxy) phthalocyanine and its quaternised derivative displayed longer triplet lifetime than both the tetrasulfonated gallium phthalocyanine ((OH)GaTSPc) and hydroxy gallium octacarboxy phthalocyanine in DMSO and in aq. media in both the presence and absence of surfactant.
- Full Text:
- Date Issued: 2010
Compactification of lattice-valued convergence spaces
- Authors: Jäger, Gunter
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:6828 , http://hdl.handle.net/10962/d1012339
- Description: We define compactness for stratified lattice-valued convergence spaces and show that a Tychonoff theorem is true. Further a generalization of the classical Richardson compactification is given. This compactification has a universal property.
- Full Text:
- Date Issued: 2010
- Authors: Jäger, Gunter
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:6828 , http://hdl.handle.net/10962/d1012339
- Description: We define compactness for stratified lattice-valued convergence spaces and show that a Tychonoff theorem is true. Further a generalization of the classical Richardson compactification is given. This compactification has a universal property.
- Full Text:
- Date Issued: 2010
A decade later: follow-up review of South African research on the consequences of and contributory factors in teen-aged pregnancy
- Macleod, Catriona I, Tracey, Tiffany
- Authors: Macleod, Catriona I , Tracey, Tiffany
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6276 , http://hdl.handle.net/10962/d1008276 , http://journals.sagepub.com/doi/abs/10.1177/008124631004000103
- Description: In this paper, we review South African research conducted in the last 10 years on the consequences of and contributory factors in teen-aged pregnancy. We discuss research into the rates of teen-aged pregnancy, the intentionality and wantedness of pregnancy, the disruption of schooling, health issues, consequences for the children, welfare concerns, knowledge and use of contraception, timing of sexual debut, age of partner, coercive sexual relations, cultural factors and health service provision. We compare this discussion to the reviews on the same topic appearing in the South African Journal of Psychology a decade ago. We find that there are several changes in focus in the research on pregnancy amongst young women. We conclude that, in general, there has been an improvement in the breadth of data available, mostly as a result of representative national and local surveys. A better teasing out of nuances around particular issues and a grappling with theoretical issues are also evident in recent research.
- Full Text:
- Date Issued: 2010
- Authors: Macleod, Catriona I , Tracey, Tiffany
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6276 , http://hdl.handle.net/10962/d1008276 , http://journals.sagepub.com/doi/abs/10.1177/008124631004000103
- Description: In this paper, we review South African research conducted in the last 10 years on the consequences of and contributory factors in teen-aged pregnancy. We discuss research into the rates of teen-aged pregnancy, the intentionality and wantedness of pregnancy, the disruption of schooling, health issues, consequences for the children, welfare concerns, knowledge and use of contraception, timing of sexual debut, age of partner, coercive sexual relations, cultural factors and health service provision. We compare this discussion to the reviews on the same topic appearing in the South African Journal of Psychology a decade ago. We find that there are several changes in focus in the research on pregnancy amongst young women. We conclude that, in general, there has been an improvement in the breadth of data available, mostly as a result of representative national and local surveys. A better teasing out of nuances around particular issues and a grappling with theoretical issues are also evident in recent research.
- Full Text:
- Date Issued: 2010
Characterization of amine-functionalized single-walled carbon nanotube-low symmetry phthalocyanine conjugates
- Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7237 , http://hdl.handle.net/10962/d1019688
- Description: Functionalization of single-walled carbon nanotubes (SWCNTs) with amine groups using a previously developed diazonium approach, followed by reaction with a carboxylic acid moiety allows direct attachment by an amide bond. We have developed a new SWCNT-low symmetry phthalocyanine conjugate using this approach, using dicyclohexylcarbodiimide as an activating agent to facilitate formation of an amide bond to give a covalently linked conjugate. A conjugate formed by non-covalent attachment has been used for a comparative investigation by FT-IR, Raman, and UV–Vis spectroscopies, and thermal gravimetric analysis. The fluorescence of the phthalocyanine is quenched in the conjugate. , Original publication is available at http://dx.doi.org/10.1016/j.carbon.2010.04.015
- Full Text: false
- Authors: Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7237 , http://hdl.handle.net/10962/d1019688
- Description: Functionalization of single-walled carbon nanotubes (SWCNTs) with amine groups using a previously developed diazonium approach, followed by reaction with a carboxylic acid moiety allows direct attachment by an amide bond. We have developed a new SWCNT-low symmetry phthalocyanine conjugate using this approach, using dicyclohexylcarbodiimide as an activating agent to facilitate formation of an amide bond to give a covalently linked conjugate. A conjugate formed by non-covalent attachment has been used for a comparative investigation by FT-IR, Raman, and UV–Vis spectroscopies, and thermal gravimetric analysis. The fluorescence of the phthalocyanine is quenched in the conjugate. , Original publication is available at http://dx.doi.org/10.1016/j.carbon.2010.04.015
- Full Text: false
Reflecting on the next generation of models for community-based natural resources management
- Shackleton, Charlie M, Willis, T V, Brown, K, Polunin, N
- Authors: Shackleton, Charlie M , Willis, T V , Brown, K , Polunin, N
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6659 , http://hdl.handle.net/10962/d1007083
- Description: Community-based natural resource management (CBNRM) has been a pervasive paradigm in conservation circles for three decades. Despite many potentially attractive attributes it has been extensively critiqued from both ecological and sociological perspectives with respect to theory and practice (for example Leach et al. 1999; Berkes 2004; Fabricius et al. 2004; Blaikie 2006). Nonetheless, many successful examples exist, although an equal number have seemingly not met expectations. Is this because of poor implementation or rather a generally flawed model? If the criteria and conditions for success are so onerous that relatively few projects or situations are likely to qualify, what then is the value of the model? The questions thus become: how and what can we learn from the past theory and practice to develop a new generation of flexible, locally responsive and implementable CBNRM models, and what are likely to be the attributes of such models?
- Full Text:
- Date Issued: 2010
- Authors: Shackleton, Charlie M , Willis, T V , Brown, K , Polunin, N
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6659 , http://hdl.handle.net/10962/d1007083
- Description: Community-based natural resource management (CBNRM) has been a pervasive paradigm in conservation circles for three decades. Despite many potentially attractive attributes it has been extensively critiqued from both ecological and sociological perspectives with respect to theory and practice (for example Leach et al. 1999; Berkes 2004; Fabricius et al. 2004; Blaikie 2006). Nonetheless, many successful examples exist, although an equal number have seemingly not met expectations. Is this because of poor implementation or rather a generally flawed model? If the criteria and conditions for success are so onerous that relatively few projects or situations are likely to qualify, what then is the value of the model? The questions thus become: how and what can we learn from the past theory and practice to develop a new generation of flexible, locally responsive and implementable CBNRM models, and what are likely to be the attributes of such models?
- Full Text:
- Date Issued: 2010
Using local experts as benchmarks for household local ecological knowledge: scoring in South African savannas
- Steele, Melita Z, Shackleton, Charlie M
- Authors: Steele, Melita Z , Shackleton, Charlie M
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6660 , http://hdl.handle.net/10962/d1007084
- Description: It is well recognised that local ecological knowledge is an important facet of natural resource management in rural regions of the developing world. However, techniques to assess levels and to integrate it into formal or informal management approaches require further development. In particular, quantitative tools are missing, which would allow more robust analysis of the factors that positively or negatively affect local ecological knowledge and vice versa. This paper reports on a quick assessment approach that provides a quantitative score of generalist local ecological knowledge at the household level. It does so by comparing responses to the knowledge of local people identified as experts within the community. In this way it is both locally constructed and contextualized, and thereby avoids pitfalls of trying to score local ecological knowledge relative to conventional scientific knowledge which frequently cannot account for local constructs. The approach is applied at eight villages throughout the savanna biome in South Africa.
- Full Text:
- Date Issued: 2010
- Authors: Steele, Melita Z , Shackleton, Charlie M
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6660 , http://hdl.handle.net/10962/d1007084
- Description: It is well recognised that local ecological knowledge is an important facet of natural resource management in rural regions of the developing world. However, techniques to assess levels and to integrate it into formal or informal management approaches require further development. In particular, quantitative tools are missing, which would allow more robust analysis of the factors that positively or negatively affect local ecological knowledge and vice versa. This paper reports on a quick assessment approach that provides a quantitative score of generalist local ecological knowledge at the household level. It does so by comparing responses to the knowledge of local people identified as experts within the community. In this way it is both locally constructed and contextualized, and thereby avoids pitfalls of trying to score local ecological knowledge relative to conventional scientific knowledge which frequently cannot account for local constructs. The approach is applied at eight villages throughout the savanna biome in South Africa.
- Full Text:
- Date Issued: 2010
Public green space inequality in small towns in South Africa
- McConnachie, Matthew M, Shackleton, Charlie M
- Authors: McConnachie, Matthew M , Shackleton, Charlie M
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6644 , http://hdl.handle.net/10962/d1006874
- Description: The distribution of public green space within towns is frequently uneven, and influenced by attributes such as its location relative to the commercial core, as well as the ethnicity and relative wealth and education of the residents. Yet most studies are from large cities in developed countries. In contrast, this study reports on the distribution of public green space across 9 small towns in a developing country, namely South Africa, which offers a unique case study because of its former racially defined settlement patterns. We do so using GIS analysis of aerial photographs focusing on 3 types of suburbs in each town, defined on the basis of wealth as well as race-based history under the previous apartheid regime. The more affluent suburbs, inhabited mainly by whites, have the lowest density of housing and the highest area of green space per capita. Proportionally, they have a similar area under public green space as to the previously racially defined townships, but because of the lower housing density, they have a greater area per person. The newly built low-cost housing areas (termed RDP suburbs), occupied largely by poor black South Africans, are poorly endowed with public green space, and fare worse than the other 2 suburb types on all attributes measured. This needs to be addressed in further low-cost housing developments.
- Full Text:
- Date Issued: 2010
- Authors: McConnachie, Matthew M , Shackleton, Charlie M
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6644 , http://hdl.handle.net/10962/d1006874
- Description: The distribution of public green space within towns is frequently uneven, and influenced by attributes such as its location relative to the commercial core, as well as the ethnicity and relative wealth and education of the residents. Yet most studies are from large cities in developed countries. In contrast, this study reports on the distribution of public green space across 9 small towns in a developing country, namely South Africa, which offers a unique case study because of its former racially defined settlement patterns. We do so using GIS analysis of aerial photographs focusing on 3 types of suburbs in each town, defined on the basis of wealth as well as race-based history under the previous apartheid regime. The more affluent suburbs, inhabited mainly by whites, have the lowest density of housing and the highest area of green space per capita. Proportionally, they have a similar area under public green space as to the previously racially defined townships, but because of the lower housing density, they have a greater area per person. The newly built low-cost housing areas (termed RDP suburbs), occupied largely by poor black South Africans, are poorly endowed with public green space, and fare worse than the other 2 suburb types on all attributes measured. This needs to be addressed in further low-cost housing developments.
- Full Text:
- Date Issued: 2010
The use and appreciation of urban green spaces: the case of selected botanical gardens in South Africa
- Ward, Catherine D, Parker, Caitlin M, Shackleton, Charlie M
- Authors: Ward, Catherine D , Parker, Caitlin M , Shackleton, Charlie M
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6662 , http://hdl.handle.net/10962/d1007086
- Description: There are few formal studies on the contribution of botanical gardens as urban green spaces, particularly within developing countries. Therefore, this paper reports on an assessment of the use and appreciation of botanical gardens as urban green spaces in South Africa. Users and staff were surveyed in six national botanical gardens. The gardens provided numerous benefits in terms of conservation, education and recreation. However, the people using the gardens were not demographically representative of the general population of the surrounding city or town. Generally, most of the visitors were middle- to old-aged, well-educated professionals with medium to high incomes. Most were white and English was their home language. There was an even gender representation. Most visited only a few times per year. The majority of users visited the gardens for recreation and psychological reasons rather than educational ones. However, the staff of each garden placed emphasis on education in the gardens and amongst surrounding schools. Most visitors appreciated the conservation dimensions of botanical gardens, and felt that there was insufficient public green space in their town or city. Understanding how people perceive and use the botanical gardens of South Africa is important to inform future research and strategies regarding the conservation of urban green space within a developing country.
- Full Text:
- Date Issued: 2010
- Authors: Ward, Catherine D , Parker, Caitlin M , Shackleton, Charlie M
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6662 , http://hdl.handle.net/10962/d1007086
- Description: There are few formal studies on the contribution of botanical gardens as urban green spaces, particularly within developing countries. Therefore, this paper reports on an assessment of the use and appreciation of botanical gardens as urban green spaces in South Africa. Users and staff were surveyed in six national botanical gardens. The gardens provided numerous benefits in terms of conservation, education and recreation. However, the people using the gardens were not demographically representative of the general population of the surrounding city or town. Generally, most of the visitors were middle- to old-aged, well-educated professionals with medium to high incomes. Most were white and English was their home language. There was an even gender representation. Most visited only a few times per year. The majority of users visited the gardens for recreation and psychological reasons rather than educational ones. However, the staff of each garden placed emphasis on education in the gardens and amongst surrounding schools. Most visitors appreciated the conservation dimensions of botanical gardens, and felt that there was insufficient public green space in their town or city. Understanding how people perceive and use the botanical gardens of South Africa is important to inform future research and strategies regarding the conservation of urban green space within a developing country.
- Full Text:
- Date Issued: 2010
Quantifying the annual fish harvest from South Africa’s largest freshwater reservoir
- Ellender, Bruce R, Weyl, Olaf L F, Winker, A Henning, Booth, Anthony J
- Authors: Ellender, Bruce R , Weyl, Olaf L F , Winker, A Henning , Booth, Anthony J
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:7149 , http://hdl.handle.net/10962/d1011852
- Description: South African inland fisheries are poorly developed and their contribution to near-shore communities is poorly understood. This study is the first comprehensive assessment of recreational and subsistence angling undertaken in an inland fishery in South Africa. The study was conducted on the 360 km2 Lake Gariep, South Africa’s largest freshwater reservoir. A total of 508 anglers were interviewed between February 2007 and January 2008. Of those interviewed, 67% were subsistence anglers and 33% recreational anglers. Catch per unit effort (CPUE) did not differ significantly between sectors. CPUE fluctuated seasonally, ranging between 0.37 (95% CI= 0.26 to 0.51) kg·angler-1·h-1 in winter and 0.88 (0.67 to 1.17) kg·angler- 1·h-1 in summer. The duration of a fishing day ranged from 5.99 (5.24 to 6.74) h in mid-winter to 7.26 (6.88 to 7.63) h in early summer. Expected end-of-day catch (CPUE × fishing-trip duration) ranged from 2.2 to 6.4 kg·angler-1·d-1 depending on the season. The number of anglers ranged from 22 (8 to 53) anglers·d-1 in June/July to 74 (25 to 176) anglers·d-1 in April. Total annual catch from the roving creel survey was estimated at 71.4 (57.4 to 91.4) t·yr-1. Another 7.5 t∙yr-1 were landed during recreational angling competitions. The resultant total catch divided by the lakeshore population equated to a per capita fish supply of 11.1 kg·yr-1. More than 70% of the catch was the alien invasive carp Cyprinus carpio and there was no evidence of overfishing. The fish resource of Lake Gariep is of significant recreational and subsistence value. As a result of the low fish price (ZAR5.72 ± 2.60·kg-1) subsistence fishing was considered a low-revenue activity that mainly augmented food security in lakeshore communities. The relatively high CPUE indicated that the fishery may be an important safety-net during periods when alternate sources of livelihoods are limited. Consequently, we recommend that the importance of angling to local communities needs to be taken into account when planning fisheries development and developing an inland fisheries policy
- Full Text:
- Date Issued: 2010
- Authors: Ellender, Bruce R , Weyl, Olaf L F , Winker, A Henning , Booth, Anthony J
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:7149 , http://hdl.handle.net/10962/d1011852
- Description: South African inland fisheries are poorly developed and their contribution to near-shore communities is poorly understood. This study is the first comprehensive assessment of recreational and subsistence angling undertaken in an inland fishery in South Africa. The study was conducted on the 360 km2 Lake Gariep, South Africa’s largest freshwater reservoir. A total of 508 anglers were interviewed between February 2007 and January 2008. Of those interviewed, 67% were subsistence anglers and 33% recreational anglers. Catch per unit effort (CPUE) did not differ significantly between sectors. CPUE fluctuated seasonally, ranging between 0.37 (95% CI= 0.26 to 0.51) kg·angler-1·h-1 in winter and 0.88 (0.67 to 1.17) kg·angler- 1·h-1 in summer. The duration of a fishing day ranged from 5.99 (5.24 to 6.74) h in mid-winter to 7.26 (6.88 to 7.63) h in early summer. Expected end-of-day catch (CPUE × fishing-trip duration) ranged from 2.2 to 6.4 kg·angler-1·d-1 depending on the season. The number of anglers ranged from 22 (8 to 53) anglers·d-1 in June/July to 74 (25 to 176) anglers·d-1 in April. Total annual catch from the roving creel survey was estimated at 71.4 (57.4 to 91.4) t·yr-1. Another 7.5 t∙yr-1 were landed during recreational angling competitions. The resultant total catch divided by the lakeshore population equated to a per capita fish supply of 11.1 kg·yr-1. More than 70% of the catch was the alien invasive carp Cyprinus carpio and there was no evidence of overfishing. The fish resource of Lake Gariep is of significant recreational and subsistence value. As a result of the low fish price (ZAR5.72 ± 2.60·kg-1) subsistence fishing was considered a low-revenue activity that mainly augmented food security in lakeshore communities. The relatively high CPUE indicated that the fishery may be an important safety-net during periods when alternate sources of livelihoods are limited. Consequently, we recommend that the importance of angling to local communities needs to be taken into account when planning fisheries development and developing an inland fisheries policy
- Full Text:
- Date Issued: 2010
Connectivity between marine reserves and exploited areas in the philopatric reef fish Chrysoblephus laticeps (Teleostei: Sparidae)
- Teske, Peter R, Forget, F R G, Cowley, Paul D, Von der Heyden, S, Beheregaray, L B
- Authors: Teske, Peter R , Forget, F R G , Cowley, Paul D , Von der Heyden, S , Beheregaray, L B
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6776 , http://hdl.handle.net/10962/d1008086
- Description: "No-take‟ Marine Protected Areas (MPAs) are successful in protecting populations of many exploited fish species, but it is often unclear whether networks of MPAs are adequately spaced to ensure connectivity among reserves, and whether spillover occurs into adjacent exploited areas. Such issues are particularly important in species with low dispersal potential, many of which exist as genetically distinct regional stocks.The roman, Chrysoblephus laticeps, is an overexploited, commercially important fishery species endemic to South Africa. Post-recruits display resident behavior and occupy small home ranges, making C. laticeps a suitable model species to investigate connectivity in marine teleosts with potentially low dispersal ability. We used multilocus data from two types of highly variable genetic markers (mitochondrial DNA control region and microsatellites) to clarify patterns of genetic connectivity and population structure in C. laticeps using samples from two MPAs and several moderately or severely exploited regions. Despite using analytical tools that are sensitive to detect even subtle genetic structure, we found that this species exists as a single, well-mixed stock throughout its core distribution. This finding lends supports to the status of MPAs as an adequate tool for managing overexploited marine teleosts. Even though adult dispersal out of MPAs is limited, the fact that the large adults in these reserves produce exponentially more offspring than their smaller counterparts in exploited areas makes MPAs a rich source of recruits. We nonetheless caution against concluding that the lack of structure identified in C. laticeps and several other southern African teleosts can be considered to be representative of marine teleosts in this region in general. Many such species are represented in more than one marine biogeographic province and may be comprised of regionally-adapted stocks that need to be managed individually.
- Full Text:
- Date Issued: 2010
- Authors: Teske, Peter R , Forget, F R G , Cowley, Paul D , Von der Heyden, S , Beheregaray, L B
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6776 , http://hdl.handle.net/10962/d1008086
- Description: "No-take‟ Marine Protected Areas (MPAs) are successful in protecting populations of many exploited fish species, but it is often unclear whether networks of MPAs are adequately spaced to ensure connectivity among reserves, and whether spillover occurs into adjacent exploited areas. Such issues are particularly important in species with low dispersal potential, many of which exist as genetically distinct regional stocks.The roman, Chrysoblephus laticeps, is an overexploited, commercially important fishery species endemic to South Africa. Post-recruits display resident behavior and occupy small home ranges, making C. laticeps a suitable model species to investigate connectivity in marine teleosts with potentially low dispersal ability. We used multilocus data from two types of highly variable genetic markers (mitochondrial DNA control region and microsatellites) to clarify patterns of genetic connectivity and population structure in C. laticeps using samples from two MPAs and several moderately or severely exploited regions. Despite using analytical tools that are sensitive to detect even subtle genetic structure, we found that this species exists as a single, well-mixed stock throughout its core distribution. This finding lends supports to the status of MPAs as an adequate tool for managing overexploited marine teleosts. Even though adult dispersal out of MPAs is limited, the fact that the large adults in these reserves produce exponentially more offspring than their smaller counterparts in exploited areas makes MPAs a rich source of recruits. We nonetheless caution against concluding that the lack of structure identified in C. laticeps and several other southern African teleosts can be considered to be representative of marine teleosts in this region in general. Many such species are represented in more than one marine biogeographic province and may be comprised of regionally-adapted stocks that need to be managed individually.
- Full Text:
- Date Issued: 2010
A comparison of two sampling methods for surveying mammalian herbivore impacts on beetle communities in the canopy of Acacia drepanolobium in Kenya
- Kuria, K S, Villet, Martin H, Palmer, T, Stanton, M
- Authors: Kuria, K S , Villet, Martin H , Palmer, T , Stanton, M
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6860 , http://hdl.handle.net/10962/d1011150
- Description: Even though several methods are used to sample and monitor canopy arthropods, there are no studies to indicate which of these methods is more effective.We compared the efficacy of the beating and canopy fogging methods in collecting beetles that inhabit Acacia drepanolobium (Harms) tree canopies at Mpala Research Centre in Laikipia district, Kenya. These trees grow naturally on the black cotton soils of the Laikipia ecosystem, accounting for more than 98%of the overstorey at the study site, and are important for local cattle and wildlife production. The ultimate objective of this study was to determine the effect of differential grazing and browsing pressure from large mammalian herbivores on the beetle communities of A. drepanolobium. Seven hundred and twenty trees 1.0–2.5 m tall were sampled using each method, making a total of 1440 trees. Sampling using the two methods was done concurrently and repeated quarterly over a period of 14 months. In total, 4320 individuals were collected, 1456 by beating and 2864 by fogging. The methods jointly yielded beetle specimens from 13 families and 55 morphospecies. Fogging collected significantly more beetle morphospecies than beating, and there was a significant interaction effect between method and sampling date. We found that numerically Anthicidae and Curculionidae responded positively to the presence of cattle.We also found that Anthicidae sp. A and Myllocerus sp. A numbers significantly increased in plots where livestock were grazed.
- Full Text:
- Date Issued: 2010
- Authors: Kuria, K S , Villet, Martin H , Palmer, T , Stanton, M
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6860 , http://hdl.handle.net/10962/d1011150
- Description: Even though several methods are used to sample and monitor canopy arthropods, there are no studies to indicate which of these methods is more effective.We compared the efficacy of the beating and canopy fogging methods in collecting beetles that inhabit Acacia drepanolobium (Harms) tree canopies at Mpala Research Centre in Laikipia district, Kenya. These trees grow naturally on the black cotton soils of the Laikipia ecosystem, accounting for more than 98%of the overstorey at the study site, and are important for local cattle and wildlife production. The ultimate objective of this study was to determine the effect of differential grazing and browsing pressure from large mammalian herbivores on the beetle communities of A. drepanolobium. Seven hundred and twenty trees 1.0–2.5 m tall were sampled using each method, making a total of 1440 trees. Sampling using the two methods was done concurrently and repeated quarterly over a period of 14 months. In total, 4320 individuals were collected, 1456 by beating and 2864 by fogging. The methods jointly yielded beetle specimens from 13 families and 55 morphospecies. Fogging collected significantly more beetle morphospecies than beating, and there was a significant interaction effect between method and sampling date. We found that numerically Anthicidae and Curculionidae responded positively to the presence of cattle.We also found that Anthicidae sp. A and Myllocerus sp. A numbers significantly increased in plots where livestock were grazed.
- Full Text:
- Date Issued: 2010
Mechanisms of habitat segregation between an invasive (Mytilus galloprovincialis) and an indigenous (Perna perna) mussel: adult growth and mortality
- Bownes, Sarah J, McQuaid, Christopher D
- Authors: Bownes, Sarah J , McQuaid, Christopher D
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6868 , http://hdl.handle.net/10962/d1011500
- Description: The invasive mussel Mytilus galloprovincialis and the indigenous mussel Perna perna coexist intertidally on the south coast of South Africa through partial vertical habitat segregation: M. galloprovincialis dominates the upper shore and P. perna the lower shore. Recruitment patterns can explain the zonation of P. perna, but not the invasive species. We examined the role of post-recruitment interactions by measuring spatial and temporal differences in adult growth and mortality rates of the two species. Specifically, we tested the hypothesis that interspecific differences in growth and mortality reflect adult distribution patterns. The two study locations, Plettenberg Bay and Tsitsikamma, are 70 km apart with two sites (separated by 300–400 m) per location, each divided into three vertical zones. Growth was measured seasonally using different marking methods in 2001 and 2003. Cumulative adult mortality was measured through summer in 2003/2004. Both species generally grew more slowly upshore, but they showed different effects of season. For P. perna, growth was significantly reduced in winter in the low zone, but unaffected by season in the high zone. For M. galloprovincialis, growth was either unaffected by season or increased in winter, even in the high zone. Thus, growth of P. perna and M. galloprovincialis was reduced under cool winter and warm summer temperatures, respectively; and while growth was more similar between species in summer, M. galloprovincialis grew much faster than P. perna in winter. Mortality of P. perna increased upshore. For M. galloprovincialis, mortality was not zone-dependent and was significantly greater than for P. perna on the low-shore and (generally) across the shore in Tsitsikamma. Both species had higher growth and mortality rates in Plettenberg Bay than in Tsitsikamma. Thus, P. perna seems able to maintain spatial dominance on the low-shore and at certain sites because of higher mortality of M. galloprovincialis. We conclude that seasonality in growth of the two species reflects their biogeographic affinities and that coexistence is possible through pre-recruitment effects that limit the vertical distribution of P. perna and post-recruitment effects that limit M. galloprovincialis.
- Full Text:
- Date Issued: 2010
- Authors: Bownes, Sarah J , McQuaid, Christopher D
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6868 , http://hdl.handle.net/10962/d1011500
- Description: The invasive mussel Mytilus galloprovincialis and the indigenous mussel Perna perna coexist intertidally on the south coast of South Africa through partial vertical habitat segregation: M. galloprovincialis dominates the upper shore and P. perna the lower shore. Recruitment patterns can explain the zonation of P. perna, but not the invasive species. We examined the role of post-recruitment interactions by measuring spatial and temporal differences in adult growth and mortality rates of the two species. Specifically, we tested the hypothesis that interspecific differences in growth and mortality reflect adult distribution patterns. The two study locations, Plettenberg Bay and Tsitsikamma, are 70 km apart with two sites (separated by 300–400 m) per location, each divided into three vertical zones. Growth was measured seasonally using different marking methods in 2001 and 2003. Cumulative adult mortality was measured through summer in 2003/2004. Both species generally grew more slowly upshore, but they showed different effects of season. For P. perna, growth was significantly reduced in winter in the low zone, but unaffected by season in the high zone. For M. galloprovincialis, growth was either unaffected by season or increased in winter, even in the high zone. Thus, growth of P. perna and M. galloprovincialis was reduced under cool winter and warm summer temperatures, respectively; and while growth was more similar between species in summer, M. galloprovincialis grew much faster than P. perna in winter. Mortality of P. perna increased upshore. For M. galloprovincialis, mortality was not zone-dependent and was significantly greater than for P. perna on the low-shore and (generally) across the shore in Tsitsikamma. Both species had higher growth and mortality rates in Plettenberg Bay than in Tsitsikamma. Thus, P. perna seems able to maintain spatial dominance on the low-shore and at certain sites because of higher mortality of M. galloprovincialis. We conclude that seasonality in growth of the two species reflects their biogeographic affinities and that coexistence is possible through pre-recruitment effects that limit the vertical distribution of P. perna and post-recruitment effects that limit M. galloprovincialis.
- Full Text:
- Date Issued: 2010
First oceanographic survey of the entire continental shelf adjacent to the northern Agulhas Current
- Lutjeharms, Johan R E, Durgadoo, Jonathan V, Schapira, Mathilde, McQuaid, Christopher D
- Authors: Lutjeharms, Johan R E , Durgadoo, Jonathan V , Schapira, Mathilde , McQuaid, Christopher D
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6867 , http://hdl.handle.net/10962/d1011499 , http://www.sajs.co.za/index.php/SAJS/article/view/410
- Description: [from introduction] The Agulhas Current is by far the largest western boundary current of the southern hemisphere1 and carries about 70 × 106 m3/s of seawater past the eastern shores of South Africa.2 Being more than 2000 m deep, it follows the continental shelf edge quite closely. Its northern part, all the way downstream to Algoa Bay, has a very stable trajectory whereas the southern part meanders widely to either side of a mean geographical location,3 in the process creating shear edge eddies and attendant plumes of warm surface water over the shelf.4 However, the direct influence of the Agulhas Current on the waters and ecosystems of the adjacent shelf of South Africa remains largely unknown.
- Full Text:
- Date Issued: 2010
- Authors: Lutjeharms, Johan R E , Durgadoo, Jonathan V , Schapira, Mathilde , McQuaid, Christopher D
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6867 , http://hdl.handle.net/10962/d1011499 , http://www.sajs.co.za/index.php/SAJS/article/view/410
- Description: [from introduction] The Agulhas Current is by far the largest western boundary current of the southern hemisphere1 and carries about 70 × 106 m3/s of seawater past the eastern shores of South Africa.2 Being more than 2000 m deep, it follows the continental shelf edge quite closely. Its northern part, all the way downstream to Algoa Bay, has a very stable trajectory whereas the southern part meanders widely to either side of a mean geographical location,3 in the process creating shear edge eddies and attendant plumes of warm surface water over the shelf.4 However, the direct influence of the Agulhas Current on the waters and ecosystems of the adjacent shelf of South Africa remains largely unknown.
- Full Text:
- Date Issued: 2010
The invasive ‘mothcatcher’ (Araujia sericifera Brot.; Asclepiadoideae) co-opts native honeybees as its primary pollinator in South Africa
- Coombs, Gareth, Peter, Craig I
- Authors: Coombs, Gareth , Peter, Craig I
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6510 , http://hdl.handle.net/10962/d1005937
- Description: Background and aims: Successful invasive plants such as Araujia sericifera usually either are capable of automatic self-pollination or maintain pollinator services by having generalized pollination systems to make use of local pollinators in the invaded range. Alternatively, plants must co-opt new pollinators with similar morphology to native pollinators or reproduce asexually. We aimed to document the pollination biology of A. sericifera in South Africa. Given the success of this species as an invader, we predicted that sexual reproduction occurs either through self-pollination or because A. sericifera has successfully co-opted native insect pollinators. Methodology: We examined the pollination biology of the South American A. sericifera in South Africa. We documented the effective pollinators including a comparison of the efficacy of nocturnal versus diurnal pollinators as well as the breeding system and long-term natural levels of the pollination success of this species. Principal results: We found that native honeybees (Apis mellifera) were the main pollinators of A. sericifera in South Africa. Visiting moths are unimportant pollinators despite being attracted by the pale colour and nocturnal scent of the flowers. Plants from the Grahamstown population were incapable of autonomous self-pollination but pollinator-mediated self-pollination does occur. However, the highest fruit initiation resulted from out-crossed pollination treatments. The high pollen transfer efficiency of this species was comparable to other hymenopteranpollinated exotic and native milkweeds, suggesting that A. sericifera maintains pollinator services at levels experienced by indigenous asclepiad species. Conclusions: Araujia sericifera reproduces successfully in South Africa due to a combined ability of this species to attract and exploit native honeybees as its pollinators and of individual plants to set fruit from pollinator-mediated self-pollination.
- Full Text:
- Date Issued: 2010
- Authors: Coombs, Gareth , Peter, Craig I
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6510 , http://hdl.handle.net/10962/d1005937
- Description: Background and aims: Successful invasive plants such as Araujia sericifera usually either are capable of automatic self-pollination or maintain pollinator services by having generalized pollination systems to make use of local pollinators in the invaded range. Alternatively, plants must co-opt new pollinators with similar morphology to native pollinators or reproduce asexually. We aimed to document the pollination biology of A. sericifera in South Africa. Given the success of this species as an invader, we predicted that sexual reproduction occurs either through self-pollination or because A. sericifera has successfully co-opted native insect pollinators. Methodology: We examined the pollination biology of the South American A. sericifera in South Africa. We documented the effective pollinators including a comparison of the efficacy of nocturnal versus diurnal pollinators as well as the breeding system and long-term natural levels of the pollination success of this species. Principal results: We found that native honeybees (Apis mellifera) were the main pollinators of A. sericifera in South Africa. Visiting moths are unimportant pollinators despite being attracted by the pale colour and nocturnal scent of the flowers. Plants from the Grahamstown population were incapable of autonomous self-pollination but pollinator-mediated self-pollination does occur. However, the highest fruit initiation resulted from out-crossed pollination treatments. The high pollen transfer efficiency of this species was comparable to other hymenopteranpollinated exotic and native milkweeds, suggesting that A. sericifera maintains pollinator services at levels experienced by indigenous asclepiad species. Conclusions: Araujia sericifera reproduces successfully in South Africa due to a combined ability of this species to attract and exploit native honeybees as its pollinators and of individual plants to set fruit from pollinator-mediated self-pollination.
- Full Text:
- Date Issued: 2010
Simultaneous determination of irinotecan hydrochloride and its related compounds by high performance liquid chromatography using ultraviolet detection
- Mohammadi, Ali, Esmaeili, Farnaz, Dinarvand, Rassoul, Atyabi, Fatemeh, Walker, Roderick B
- Authors: Mohammadi, Ali , Esmaeili, Farnaz , Dinarvand, Rassoul , Atyabi, Fatemeh , Walker, Roderick B
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6413 , http://hdl.handle.net/10962/d1006508
- Description: A new simple, precise and accurate high performance liquid chromatography (HPLC) method was developed and validated for the simultaneous determination of irinotecan (CPT-11) and two related compounds viz., 7-ethyl-10 hydroxycamptothecin (SN-38) and camptothecin (CPT) in pharmaceutical dosage forms. Chromatography was accomplished using a reversed-phase C18 column and ultraviolet (UV)detection and an isocratic mobile phase consisting of 3 % v/v triethylammonium acetate buffer (pH 3) and acetonitrile (70:30 v/v). The linear range of quantitation for all the compounds was 0.1-10 μg/mL. The limit of quantitation for all the compounds ranged between 0.01-0.05 μg/mL. The method has the requisite accuracy, selectivity, sensitivity and precision to assay of CPT-11 and related compounds in pharmaceutical dosage forms and bulk API.
- Full Text:
- Date Issued: 2010
- Authors: Mohammadi, Ali , Esmaeili, Farnaz , Dinarvand, Rassoul , Atyabi, Fatemeh , Walker, Roderick B
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6413 , http://hdl.handle.net/10962/d1006508
- Description: A new simple, precise and accurate high performance liquid chromatography (HPLC) method was developed and validated for the simultaneous determination of irinotecan (CPT-11) and two related compounds viz., 7-ethyl-10 hydroxycamptothecin (SN-38) and camptothecin (CPT) in pharmaceutical dosage forms. Chromatography was accomplished using a reversed-phase C18 column and ultraviolet (UV)detection and an isocratic mobile phase consisting of 3 % v/v triethylammonium acetate buffer (pH 3) and acetonitrile (70:30 v/v). The linear range of quantitation for all the compounds was 0.1-10 μg/mL. The limit of quantitation for all the compounds ranged between 0.01-0.05 μg/mL. The method has the requisite accuracy, selectivity, sensitivity and precision to assay of CPT-11 and related compounds in pharmaceutical dosage forms and bulk API.
- Full Text:
- Date Issued: 2010
Development of a stability-indicating high performance liquid chromatographic method for the analysis of topiramate and dissolution rate testing in topiramate tablets
- Mohammadi, Ali, Rezanour, Nasrin, Ansari Dogaheh, M, Walker, Roderick B
- Authors: Mohammadi, Ali , Rezanour, Nasrin , Ansari Dogaheh, M , Walker, Roderick B
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:6412 , http://hdl.handle.net/10962/d1006507
- Description: A stability-indicating high performance liquid chromatographic(HPLC) method was developed and validated for the quantitation and dissolution determination of topiramate in tablet dosage forms. An isocratic separation was achieved using a phenyl column with a flow rate of 1 mL/min using UV detection at 264 nm. Topiramate has low UV absorbtivity and was subjected to derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl). The mobile phase for the separation consisted of acetonitrile: 50 mM sodium dihydrogen phosphate(NaH2PO4) containing 3 % v/v triethylamine (pH 2.8) in a 48:52 v/v ratio. Topiramate was subjected to oxidation, hydrolysis, photolysis and heat for the purposes of stress testing. Separation was achieved for the parent compound and all the degradation products in an overall analytical run time of approximately 15 min with the parent compound topiramate eluting at approximately 9.2 min. The method was linear over the concentration range of 1-100 μg/mL (r = 0.9996) with limits of quantitation and detection of 1 and 0.3 μg/mL, respectively.
- Full Text:
- Date Issued: 2010
- Authors: Mohammadi, Ali , Rezanour, Nasrin , Ansari Dogaheh, M , Walker, Roderick B
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:6412 , http://hdl.handle.net/10962/d1006507
- Description: A stability-indicating high performance liquid chromatographic(HPLC) method was developed and validated for the quantitation and dissolution determination of topiramate in tablet dosage forms. An isocratic separation was achieved using a phenyl column with a flow rate of 1 mL/min using UV detection at 264 nm. Topiramate has low UV absorbtivity and was subjected to derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl). The mobile phase for the separation consisted of acetonitrile: 50 mM sodium dihydrogen phosphate(NaH2PO4) containing 3 % v/v triethylamine (pH 2.8) in a 48:52 v/v ratio. Topiramate was subjected to oxidation, hydrolysis, photolysis and heat for the purposes of stress testing. Separation was achieved for the parent compound and all the degradation products in an overall analytical run time of approximately 15 min with the parent compound topiramate eluting at approximately 9.2 min. The method was linear over the concentration range of 1-100 μg/mL (r = 0.9996) with limits of quantitation and detection of 1 and 0.3 μg/mL, respectively.
- Full Text:
- Date Issued: 2010
Analytical methods for the quantitative determination of oxytocin
- Chaibva, Faith A, Walker, Roderick B
- Authors: Chaibva, Faith A , Walker, Roderick B
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6353 , http://hdl.handle.net/10962/d1006037
- Description: Oxytocin is a clinically important nonapeptide that is used for the induction and/or augmentation of labor and is normally administered as a slow intravenous infusion diluted with normal saline or Ringer’s lactate solution. Oxytocin is also indicated for use in the prevention and treatment of post partum hemorrhage and may be administered via either the intramuscular or intravenous routes in order to increase uterine tone and/or reduce bleeding. The analysis of oxytocin in different media has evolved over the past 30 years with the result that more sophisticated, selective and sensitive techniques are used for the determination of the compound. A variety of techniques have been applied to the determination of oxytocin in different matrices ranging from simple paper chromatography to hyphenated liquid chromatographic such as liquid chromatography coupled with mass-spectrometry. Additionally enzyme linked immuno-sorbent assays (ELISA) and radio immuno-assays (RIA) are used for the determination of low concentrations of oxytocin in biological matrices. This manuscript provides a systematic survey of the analytical methods that have been reported for isolation and quantitation of oxytocin in different matrices.
- Full Text:
- Date Issued: 2010
- Authors: Chaibva, Faith A , Walker, Roderick B
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6353 , http://hdl.handle.net/10962/d1006037
- Description: Oxytocin is a clinically important nonapeptide that is used for the induction and/or augmentation of labor and is normally administered as a slow intravenous infusion diluted with normal saline or Ringer’s lactate solution. Oxytocin is also indicated for use in the prevention and treatment of post partum hemorrhage and may be administered via either the intramuscular or intravenous routes in order to increase uterine tone and/or reduce bleeding. The analysis of oxytocin in different media has evolved over the past 30 years with the result that more sophisticated, selective and sensitive techniques are used for the determination of the compound. A variety of techniques have been applied to the determination of oxytocin in different matrices ranging from simple paper chromatography to hyphenated liquid chromatographic such as liquid chromatography coupled with mass-spectrometry. Additionally enzyme linked immuno-sorbent assays (ELISA) and radio immuno-assays (RIA) are used for the determination of low concentrations of oxytocin in biological matrices. This manuscript provides a systematic survey of the analytical methods that have been reported for isolation and quantitation of oxytocin in different matrices.
- Full Text:
- Date Issued: 2010
The determination of acetaminophen using a carbon nanotube: graphite-based electrode
- Moghaddam, Abdolmajid B, Mohammadi, Ali, Mohammadi, Somaye, Rayeji, Danyal, Dinarvand, Rassoul, Baghi, Mansoureh, Walker, Roderick B
- Authors: Moghaddam, Abdolmajid B , Mohammadi, Ali , Mohammadi, Somaye , Rayeji, Danyal , Dinarvand, Rassoul , Baghi, Mansoureh , Walker, Roderick B
- Date: 2010
- Language: English
- Type: Article , text
- Identifier: vital:6414 , http://hdl.handle.net/10962/d1006509
- Description: The oxidation of acetaminophen was studied at a glassy carbon electrode modified with multi-walled carbon nanotubes and a graphite paste. Cyclic voltammety, differential pulse voltammetry and square wave voltammetry at various pH values, scan rates, and the effect of the ratio of nanotubes to graphite were investigated in order to optimize the parameters for the determination of acetaminophen. Square wave voltammetry is the most appropriate technique in giving a characteristic peak at 0.52 V at pH 5. The porous nanostructure of the electrode improves the surface area which results in an increase in the peak current. The voltammetric response is linear in the range between 75 and 2000 ng.mL−1, with standard deviations between 0.25 and 7.8%, and a limit of detection of 25 ng.mL−1. The method has been successfully applied to the analysis of acetaminophen in tablets and biological fluids.
- Full Text:
- Date Issued: 2010
- Authors: Moghaddam, Abdolmajid B , Mohammadi, Ali , Mohammadi, Somaye , Rayeji, Danyal , Dinarvand, Rassoul , Baghi, Mansoureh , Walker, Roderick B
- Date: 2010
- Language: English
- Type: Article , text
- Identifier: vital:6414 , http://hdl.handle.net/10962/d1006509
- Description: The oxidation of acetaminophen was studied at a glassy carbon electrode modified with multi-walled carbon nanotubes and a graphite paste. Cyclic voltammety, differential pulse voltammetry and square wave voltammetry at various pH values, scan rates, and the effect of the ratio of nanotubes to graphite were investigated in order to optimize the parameters for the determination of acetaminophen. Square wave voltammetry is the most appropriate technique in giving a characteristic peak at 0.52 V at pH 5. The porous nanostructure of the electrode improves the surface area which results in an increase in the peak current. The voltammetric response is linear in the range between 75 and 2000 ng.mL−1, with standard deviations between 0.25 and 7.8%, and a limit of detection of 25 ng.mL−1. The method has been successfully applied to the analysis of acetaminophen in tablets and biological fluids.
- Full Text:
- Date Issued: 2010
Optimization of salbutamol sulfate dissolution from sustained release matrix formulations using an artificial neural network
- Chaibva, Faith A, Burton, Michael, Walker, Roderick B
- Authors: Chaibva, Faith A , Burton, Michael , Walker, Roderick B
- Date: 2010
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Article
- Identifier: vital:6352 , http://hdl.handle.net/10962/d1006034
- Description: An artificial neural network was used to optimize the release of salbutamol sulfate from hydrophilic matrix formulations. Model formulations to be used for training, testing and validating the neural network were manufactured with the aid of a central composite design with varying the levels of Methocel® K100M, xanthan gum, Carbopol® 974P and Surelease® as the input factors. In vitro dissolution time profiles at six different sampling times were used as target data in training the neural network for formulation optimization. A multi layer perceptron with one hidden layer was constructed using Matlab®, and the number of nodes in the hidden layer was optimized by trial and error to develop a model with the best predictive ability. The results revealed that a neural network with nine nodes was optimal for developing and optimizing formulations. Simulations undertaken with the training data revealed that the constructed model was useable. The optimized neural network was used for optimization of formulation with desirable release characteristics and the results indicated that there was agreement between the predicted formulation and the manufactured formulation. This work illustrates the possible utility of artificial neural networks for the optimization of pharmaceutical formulations with desirable performance characteristics.
- Full Text:
- Date Issued: 2010
- Authors: Chaibva, Faith A , Burton, Michael , Walker, Roderick B
- Date: 2010
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Article
- Identifier: vital:6352 , http://hdl.handle.net/10962/d1006034
- Description: An artificial neural network was used to optimize the release of salbutamol sulfate from hydrophilic matrix formulations. Model formulations to be used for training, testing and validating the neural network were manufactured with the aid of a central composite design with varying the levels of Methocel® K100M, xanthan gum, Carbopol® 974P and Surelease® as the input factors. In vitro dissolution time profiles at six different sampling times were used as target data in training the neural network for formulation optimization. A multi layer perceptron with one hidden layer was constructed using Matlab®, and the number of nodes in the hidden layer was optimized by trial and error to develop a model with the best predictive ability. The results revealed that a neural network with nine nodes was optimal for developing and optimizing formulations. Simulations undertaken with the training data revealed that the constructed model was useable. The optimized neural network was used for optimization of formulation with desirable release characteristics and the results indicated that there was agreement between the predicted formulation and the manufactured formulation. This work illustrates the possible utility of artificial neural networks for the optimization of pharmaceutical formulations with desirable performance characteristics.
- Full Text:
- Date Issued: 2010
Present day challenges in understanding the geomagnetic hazard to national power grids
- Thompson, A W P, Kotze, P, Ngwira, C M, Lotz, Stefanus I, Gaunt, C T, Cilliers, P, Wild, J A, Opperman, Ben D L, McKinnell, Lee-Anne, Lotz, S I
- Authors: Thompson, A W P , Kotze, P , Ngwira, C M , Lotz, Stefanus I , Gaunt, C T , Cilliers, P , Wild, J A , Opperman, Ben D L , McKinnell, Lee-Anne , Lotz, S I
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6812 , http://hdl.handle.net/10962/d1004305
- Description: Power grids and pipeline networks at all latitudes are known to be at risk from the natural hazard of geomagnetically induced currents. At a recent workshop in South Africa, UK and South African scientists and engineers discussed the current understanding of this hazard, as it affects major power systems in Europe and Africa. They also summarised, to better inform the public and industry, what can be said with some certainty about the hazard and what research is yet required to develop useful tools for geomagnetic hazard mitigation.
- Full Text:
- Date Issued: 2010
- Authors: Thompson, A W P , Kotze, P , Ngwira, C M , Lotz, Stefanus I , Gaunt, C T , Cilliers, P , Wild, J A , Opperman, Ben D L , McKinnell, Lee-Anne , Lotz, S I
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6812 , http://hdl.handle.net/10962/d1004305
- Description: Power grids and pipeline networks at all latitudes are known to be at risk from the natural hazard of geomagnetically induced currents. At a recent workshop in South Africa, UK and South African scientists and engineers discussed the current understanding of this hazard, as it affects major power systems in Europe and Africa. They also summarised, to better inform the public and industry, what can be said with some certainty about the hazard and what research is yet required to develop useful tools for geomagnetic hazard mitigation.
- Full Text:
- Date Issued: 2010