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
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
Politics in the slum: a view from South Africa
- Authors: Pithouse, Richard, 1970-
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6209 , http://hdl.handle.net/10962/d1008579
- Description: [From introduction]The modern state, and its civil society, have always been comfortable with workers in their allotted place – be it formed around the immediate needs of industrial production, like the migrant workers hostels in apartheid South Africa or contemporary Dubai, or an attempt at creating a haven, like the suburban home which has its roots in the gendered and raced class compromise reached in North America after the Second World War. When there has been a part of the population rendered or considered superfluous to the immediate needs of production there has been a degree of comfort with the inevitably bounded spaces into which these people have been abandoned or contained – prisons, ghettos, Bantustans etc. But both the modern state and civil society have always been acutely uncomfortable with that part of the ‘dangerous class’ - vagabonds or squatters - that are, by virtue of their occupation of space outside of state regulation, by definition out of place and threatening to domination constructed, along with other lines of force, on the ordering of space.
- Full Text:
- Date Issued: 2010
- Authors: Pithouse, Richard, 1970-
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6209 , http://hdl.handle.net/10962/d1008579
- Description: [From introduction]The modern state, and its civil society, have always been comfortable with workers in their allotted place – be it formed around the immediate needs of industrial production, like the migrant workers hostels in apartheid South Africa or contemporary Dubai, or an attempt at creating a haven, like the suburban home which has its roots in the gendered and raced class compromise reached in North America after the Second World War. When there has been a part of the population rendered or considered superfluous to the immediate needs of production there has been a degree of comfort with the inevitably bounded spaces into which these people have been abandoned or contained – prisons, ghettos, Bantustans etc. But both the modern state and civil society have always been acutely uncomfortable with that part of the ‘dangerous class’ - vagabonds or squatters - that are, by virtue of their occupation of space outside of state regulation, by definition out of place and threatening to domination constructed, along with other lines of force, on the ordering of space.
- 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
Sunday Times: Celebrating Women
- Authors: Sunday Times
- Date: 2010
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7187 , http://hdl.handle.net/10962/d1006279 , Nyokong, Tebello
- Description: A passion for light drove Professor Tebello Nyokong of Rhodes University into her photodynamic therapy research, harnessing light for cancer therapy and environmental clean-up using special dyes. And with this groundbreaking work she won the Africa-Arab State 2009 L'Oreal UNESCO Award for Women in Science.
- Full Text:
- Date Issued: 2010
- Authors: Sunday Times
- Date: 2010
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7187 , http://hdl.handle.net/10962/d1006279 , Nyokong, Tebello
- Description: A passion for light drove Professor Tebello Nyokong of Rhodes University into her photodynamic therapy research, harnessing light for cancer therapy and environmental clean-up using special dyes. And with this groundbreaking work she won the Africa-Arab State 2009 L'Oreal UNESCO Award for Women in Science.
- Full Text:
- Date Issued: 2010
Developing an ionospheric map for South Africa
- McKinnell, Lee-Anne, Okoh, D I, Cilliers, P J
- Authors: McKinnell, Lee-Anne , Okoh, D I , Cilliers, P J
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6822 , http://hdl.handle.net/10962/d1004438 , http://dx.doi.org/10.5194/angeo-28-1431-2010
- Description: The development of a map of the ionosphere over South Africa is presented in this paper. The International Reference Ionosphere (IRI) model, South African Bottomside Ionospheric Model (SABIM), and measurements from ionosondes in the South African Ionosonde Network, were combined within their own limitations to develop an accurate representation of the South African ionosphere. The map is essentially in the form of a computer program that shows spatial and temporal representations of the South African ionosphere for a given set of geophysical parameters. A validation of the map is attempted using a comparison of Total Electron Content (TEC) values derived from the map, from the IRI model, and from Global Positioning System (GPS) measurements. It is foreseen that the final South African ionospheric map will be implemented as a Space Weather product of the African Space Weather Regional Warning Centre.
- Full Text:
- Date Issued: 2010
- Authors: McKinnell, Lee-Anne , Okoh, D I , Cilliers, P J
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6822 , http://hdl.handle.net/10962/d1004438 , http://dx.doi.org/10.5194/angeo-28-1431-2010
- Description: The development of a map of the ionosphere over South Africa is presented in this paper. The International Reference Ionosphere (IRI) model, South African Bottomside Ionospheric Model (SABIM), and measurements from ionosondes in the South African Ionosonde Network, were combined within their own limitations to develop an accurate representation of the South African ionosphere. The map is essentially in the form of a computer program that shows spatial and temporal representations of the South African ionosphere for a given set of geophysical parameters. A validation of the map is attempted using a comparison of Total Electron Content (TEC) values derived from the map, from the IRI model, and from Global Positioning System (GPS) measurements. It is foreseen that the final South African ionospheric map will be implemented as a Space Weather product of the African Space Weather Regional Warning Centre.
- Full Text:
- Date Issued: 2010
Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity
- Pineda, Jesus, Porri, Francesca, Starczak, Victroria, Blythe, Jonathan
- Authors: Pineda, Jesus , Porri, Francesca , Starczak, Victroria , Blythe, Jonathan
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6869 , http://hdl.handle.net/10962/d1011501
- Description: Marine broadcast spawners have two-phase life cycles, with pelagic larvae and benthic adults. Larval supply and settlement link these two phases and are crucial for the persistence of marine populations. Mainly due to the complexity in sampling larval supply accurately, many researchers use settlement as a proxy for larval supply. Larval supply is a constraining variable for settlement because, without larval supply, there is no settlement. Larval supply and settlement may not be well correlated, however, and settlement may not consistently estimate larval supply. This paper explores the argument that larval supply (i.e., larval abundance near settlement sites) may not relate linearly to settlement. We review the relationship between larval supply and settlement, from estimates and biases in larval supply sampling, to non-behavioral and behavioral components, including small-scale hydrodynamics, competency, gregarious behavior, intensification of settlement, lunar periodicity, predation and cannibalism. Physical and structural processes coupled with behavior, such as small-scale hydrodynamics and intensification of settlement, sometimes result in under- or overestimation of larval supply, where it is predicted from a linear relationship with settlement. Although settlement is a function of larval supply, spatial and temporal processes interact with larval behavior to distort the relationship between larval supply and settlement, and when these distortions act consistently in time and space, they cause biased estimates of larval supply from settlement data. Most of the examples discussed here suggest that behavior is the main source of the decoupling between larval supply and settlement because larval behavior affects the vertical distribution of larvae, the response of larvae to hydrodynamics, intensification of settlement, gregariousness, predation and cannibalism. Thus, larval behavior seems to limit broad generalizations on the regulation of settlement by larval supply. Knowledge of the relationship is further hindered by the lack of a well founded theoretical relationship between the two variables. The larval supply–settlement transition may have strong general consequences for population connectivity, since larval supply is a result of larval transport, and settlement constrains recruitment. Thus, measuring larval supply and settlement effectively allows more accurate quantification and understanding of larval transport, recruitment and population connectivity.
- Full Text:
- Date Issued: 2010
- Authors: Pineda, Jesus , Porri, Francesca , Starczak, Victroria , Blythe, Jonathan
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6869 , http://hdl.handle.net/10962/d1011501
- Description: Marine broadcast spawners have two-phase life cycles, with pelagic larvae and benthic adults. Larval supply and settlement link these two phases and are crucial for the persistence of marine populations. Mainly due to the complexity in sampling larval supply accurately, many researchers use settlement as a proxy for larval supply. Larval supply is a constraining variable for settlement because, without larval supply, there is no settlement. Larval supply and settlement may not be well correlated, however, and settlement may not consistently estimate larval supply. This paper explores the argument that larval supply (i.e., larval abundance near settlement sites) may not relate linearly to settlement. We review the relationship between larval supply and settlement, from estimates and biases in larval supply sampling, to non-behavioral and behavioral components, including small-scale hydrodynamics, competency, gregarious behavior, intensification of settlement, lunar periodicity, predation and cannibalism. Physical and structural processes coupled with behavior, such as small-scale hydrodynamics and intensification of settlement, sometimes result in under- or overestimation of larval supply, where it is predicted from a linear relationship with settlement. Although settlement is a function of larval supply, spatial and temporal processes interact with larval behavior to distort the relationship between larval supply and settlement, and when these distortions act consistently in time and space, they cause biased estimates of larval supply from settlement data. Most of the examples discussed here suggest that behavior is the main source of the decoupling between larval supply and settlement because larval behavior affects the vertical distribution of larvae, the response of larvae to hydrodynamics, intensification of settlement, gregariousness, predation and cannibalism. Thus, larval behavior seems to limit broad generalizations on the regulation of settlement by larval supply. Knowledge of the relationship is further hindered by the lack of a well founded theoretical relationship between the two variables. The larval supply–settlement transition may have strong general consequences for population connectivity, since larval supply is a result of larval transport, and settlement constrains recruitment. Thus, measuring larval supply and settlement effectively allows more accurate quantification and understanding of larval transport, recruitment and population connectivity.
- 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
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
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
TB treatment initiation and adherence in a South African community influenced more by perceptions than by knowledge of tuberculosis
- Cramm, Jane M, Finkenflügel, Harry J M, Moller, Valerie, Nieboer, Anna P
- Authors: Cramm, Jane M , Finkenflügel, Harry J M , Moller, Valerie , Nieboer, Anna P
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:7101 , http://hdl.handle.net/10962/d1010657
- Description: Background Tuberculosis (TB) is a global health concern. Inadequate case finding and case holding has been cited as major barrier to the control of TB. The TB literature is written almost entirely from a biomedical perspective, while recent studies show that it is imperative to understand lay perception to determine why people seek treatment and may stop taking treatment. The Eastern Cape is known as a province with high TB incidence, prevalence and with one of the worst cure rates of South Africa. Its inhabitants can be considered lay experts when it comes to TB. Therefore, we investigated knowledge, perceptions of (access to) TB treatment and adherence to treatment among an Eastern Cape population. Methods An area-stratified sampling design was applied. A total of 1020 households were selected randomly in proportion to the total number of households in each neighbourhood. Results TB knowledge can be considered fairly good among this community. Respondents' perceptions suggest that stigma may influence TB patients' decision in health seeking behavior and adherence to TB treatment. A full 95 percent of those interviewed believe people with TB tend to hide their TB status out of fear of what others may say. Regression analyses revealed that in this population young and old, men and women and the lower and higher educated share the same attitudes and perceptions. Our findings are therefore likely to reflect the actual situation of TB patients in this population. Conclusions The lay experts' perceptions suggests that stigma appears to effect case holding and case finding. Future interventions should be directed at improving attitudes and perceptions to potentially reduce stigma. This requires a patient-centered approach to empower TB patients and active involvement in the development and implementation of stigma reduction programs.
- Full Text:
- Date Issued: 2010
- Authors: Cramm, Jane M , Finkenflügel, Harry J M , Moller, Valerie , Nieboer, Anna P
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:7101 , http://hdl.handle.net/10962/d1010657
- Description: Background Tuberculosis (TB) is a global health concern. Inadequate case finding and case holding has been cited as major barrier to the control of TB. The TB literature is written almost entirely from a biomedical perspective, while recent studies show that it is imperative to understand lay perception to determine why people seek treatment and may stop taking treatment. The Eastern Cape is known as a province with high TB incidence, prevalence and with one of the worst cure rates of South Africa. Its inhabitants can be considered lay experts when it comes to TB. Therefore, we investigated knowledge, perceptions of (access to) TB treatment and adherence to treatment among an Eastern Cape population. Methods An area-stratified sampling design was applied. A total of 1020 households were selected randomly in proportion to the total number of households in each neighbourhood. Results TB knowledge can be considered fairly good among this community. Respondents' perceptions suggest that stigma may influence TB patients' decision in health seeking behavior and adherence to TB treatment. A full 95 percent of those interviewed believe people with TB tend to hide their TB status out of fear of what others may say. Regression analyses revealed that in this population young and old, men and women and the lower and higher educated share the same attitudes and perceptions. Our findings are therefore likely to reflect the actual situation of TB patients in this population. Conclusions The lay experts' perceptions suggests that stigma appears to effect case holding and case finding. Future interventions should be directed at improving attitudes and perceptions to potentially reduce stigma. This requires a patient-centered approach to empower TB patients and active involvement in the development and implementation of stigma reduction programs.
- 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
Ecological impacts of small dams on South African rivers Part 2: Biotic response – abundance and composition of macroinvertebrate communities
- Mantel, Sukhmani K, Muller, N W J, Hughes, Denis A
- Authors: Mantel, Sukhmani K , Muller, N W J , Hughes, Denis A
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:7095 , http://hdl.handle.net/10962/d1012437
- Description: This paper investigates the cumulative impacts of small dams on invertebrate communities in 2 regions of South Africa – the Western Cape and Mpumalanga. Previous research found reduced discharge, increased total dissolved salts, and a decrease in average score per taxon (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigated using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catchment in foothill-gravel streams (in both Western Cape and Mpumalanga) and in foothill-cobble streams (in Western Cape only). Opportunistic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and seasons) and detailed (at species level) collection of data to verify the results of cumulative effects of small dams. This can further the development of a framework for small-dam construction and management that will limit their impact on river catchments.
- Full Text:
- Date Issued: 2010
- Authors: Mantel, Sukhmani K , Muller, N W J , Hughes, Denis A
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:7095 , http://hdl.handle.net/10962/d1012437
- Description: This paper investigates the cumulative impacts of small dams on invertebrate communities in 2 regions of South Africa – the Western Cape and Mpumalanga. Previous research found reduced discharge, increased total dissolved salts, and a decrease in average score per taxon (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigated using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catchment in foothill-gravel streams (in both Western Cape and Mpumalanga) and in foothill-cobble streams (in Western Cape only). Opportunistic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and seasons) and detailed (at species level) collection of data to verify the results of cumulative effects of small dams. This can further the development of a framework for small-dam construction and management that will limit their impact on river catchments.
- Full Text:
- Date Issued: 2010
An in-service development programme for potential information services staff in the Rhodes Library
- Authors: Shepherd, Eileen
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6986 , http://hdl.handle.net/10962/d1011602
- Description: This paper discusses the need for continuing professional development for librarians in academic libraries in general and at Rhodes University Library, South Africa in particular. It describes the planning, design, implementation and evaluation of a staff-development and training pilot programme for professional librarians at Rhodes Library. A group of 15 librarians, drawn from the library staff complement, participated in an 8-session training course developed by Information Services librarians. The course, which covered basic information-finding skills using a variety of research databases and offered an introduction to concepts in 21st century academic librarianship, was presented using course management software in a face-to-face environment and required homework exercises and the completion of a 2-hour final test. The results of the project demonstrated the urgent need for such development programmes for professional library staff. 80% of the participants completed the course. The final test results indicated below average database search skills and an inability to think laterally. An unexpected finding was a lack of IT competencies. Important lessons were learned with regard to course-construction, content and timing.
- Full Text:
- Date Issued: 2010
- Authors: Shepherd, Eileen
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6986 , http://hdl.handle.net/10962/d1011602
- Description: This paper discusses the need for continuing professional development for librarians in academic libraries in general and at Rhodes University Library, South Africa in particular. It describes the planning, design, implementation and evaluation of a staff-development and training pilot programme for professional librarians at Rhodes Library. A group of 15 librarians, drawn from the library staff complement, participated in an 8-session training course developed by Information Services librarians. The course, which covered basic information-finding skills using a variety of research databases and offered an introduction to concepts in 21st century academic librarianship, was presented using course management software in a face-to-face environment and required homework exercises and the completion of a 2-hour final test. The results of the project demonstrated the urgent need for such development programmes for professional library staff. 80% of the participants completed the course. The final test results indicated below average database search skills and an inability to think laterally. An unexpected finding was a lack of IT competencies. Important lessons were learned with regard to course-construction, content and timing.
- Full Text:
- Date Issued: 2010
Change ringing in eastern Breconshire before the First World War, with especial reference to peal ringing at Glasbury
- Authors: Lewis, Colin A
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6191 , http://hdl.handle.net/10962/d1012397 , http://www.brecknocksociety.co.uk/society.htm
- Description: This paper discusses the development of change ringing in eastern Breconshire before the start of the First World War in 19 14, with special reference to peal ringing at Glasbury. Since the men who rang peals there, prior to that war, came from other towers as well as from Glasbury, brief mention is made of ringing at those towers and of members of those towers who rang peals at Glasbury. The towers discussed include Talgarth, Bronllys, Brecon, Llanelli (named Llanelly on Ordnance Survey maps) and Builth Wells, which were in the Diocese of St David's at that time, and centres in Herefordshire which were in the Diocese of Hereford. Attention is also paid to the role of the Hereford Diocesan Guild of Bellringers and of the peripatetic instructors employed by that Guild. An excellent introduction toringing is provided by R. J. Johnston's Bell-Ringing; the English Art of Change-Ringing (Viking, 1986), while the web-site of the Central Council of Church Bell Ringers (www.cccbr.org.uk) is also informative. , Colin Lewis was Professor of Geography at Rhodes University, Grahamstown, South Africa from 1989 until his retirement at the end of 2007. In 1990, with the strong support of the incumbent Vice-Chancellor, Dr Derek Henderson, he instigated the Certificate in Change Ringing (Church Bell Ringing) in the Rhodes University Department of Music and Musicology - the first such course to be offered in Africa. Since that date he has lectured in the basic theory, and taught the practice of change ringing. He was the Ringing Master of the Cathedral of St Michael and St George, Grahamstown, South Africa for 20 years.
- Full Text:
- Date Issued: 2010
- Authors: Lewis, Colin A
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6191 , http://hdl.handle.net/10962/d1012397 , http://www.brecknocksociety.co.uk/society.htm
- Description: This paper discusses the development of change ringing in eastern Breconshire before the start of the First World War in 19 14, with special reference to peal ringing at Glasbury. Since the men who rang peals there, prior to that war, came from other towers as well as from Glasbury, brief mention is made of ringing at those towers and of members of those towers who rang peals at Glasbury. The towers discussed include Talgarth, Bronllys, Brecon, Llanelli (named Llanelly on Ordnance Survey maps) and Builth Wells, which were in the Diocese of St David's at that time, and centres in Herefordshire which were in the Diocese of Hereford. Attention is also paid to the role of the Hereford Diocesan Guild of Bellringers and of the peripatetic instructors employed by that Guild. An excellent introduction toringing is provided by R. J. Johnston's Bell-Ringing; the English Art of Change-Ringing (Viking, 1986), while the web-site of the Central Council of Church Bell Ringers (www.cccbr.org.uk) is also informative. , Colin Lewis was Professor of Geography at Rhodes University, Grahamstown, South Africa from 1989 until his retirement at the end of 2007. In 1990, with the strong support of the incumbent Vice-Chancellor, Dr Derek Henderson, he instigated the Certificate in Change Ringing (Church Bell Ringing) in the Rhodes University Department of Music and Musicology - the first such course to be offered in Africa. Since that date he has lectured in the basic theory, and taught the practice of change ringing. He was the Ringing Master of the Cathedral of St Michael and St George, Grahamstown, South Africa for 20 years.
- 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
The devastation of Haiti
- Authors: Pithouse, Richard, 1970-
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6207 , http://hdl.handle.net/10962/d1008577
- Description: [From introduction] The devastation of Haiti is not a simple matter of bad luck. Earthquakes, like storms and epidemics, hit the poor with vastly more force than the rich. Much of the press coverage of the catastrophe in Haiti has wilfully disregarded the history of how Haiti was made poor and kept poor by, above all, the same American elites that are now dispensing charity, soldiers and advice. Racism has often been close to the surface or even grinning hideously far above it
- Full Text:
- Date Issued: 2010
- Authors: Pithouse, Richard, 1970-
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6207 , http://hdl.handle.net/10962/d1008577
- Description: [From introduction] The devastation of Haiti is not a simple matter of bad luck. Earthquakes, like storms and epidemics, hit the poor with vastly more force than the rich. Much of the press coverage of the catastrophe in Haiti has wilfully disregarded the history of how Haiti was made poor and kept poor by, above all, the same American elites that are now dispensing charity, soldiers and advice. Racism has often been close to the surface or even grinning hideously far above it
- 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
Empirically modelled Pc3 activity based on solar wind parameters
- Heilig, B, Lotz, S I, Verő, J, Sutcliffe, P, Reda, J, Pajunpää, G, Raita, T
- Authors: Heilig, B , Lotz, S I , Verő, J , Sutcliffe, P , Reda, J , Pajunpää, G , Raita, T
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:6814 , http://hdl.handle.net/10962/d1004324
- Description: It is known that under certain solar wind (SW)/interplanetary magnetic field (IMF) conditions (e.g. high SW speed, low cone angle) the occurrence of ground-level Pc3–4 pulsations is more likely. In this paper we demonstrate that in the event of anomalously low SW particle density, Pc3 activity is extremely low regardless of otherwise favourable SW speed and cone angle. We re-investigate the SW control of Pc3 pulsation activity through a statistical analysis and two empirical models with emphasis on the influence of SW density on Pc3 activity. We utilise SW and IMF measurements from the OMNI project and ground-based magnetometer measurements from the MM100 array to relate SW and IMF measurements to the occurrence of Pc3 activity. Multiple linear regression and artificial neural network models are used in iterative processes in order to identify sets of SW-based input parameters, which optimally reproduce a set of Pc3 activity data. The inclusion of SW density in the parameter set significantly improves the models. Not only the density itself, but other density related parameters, such as the dynamic pressure of the SW, or the standoff distance of the magnetopause work equally well in the model. The disappearance of Pc3s during low-density events can have at least four reasons according to the existing upstream wave theory: 1. Pausing the ion-cyclotron resonance that generates the upstream ultra low frequency waves in the absence of protons, 2. Weakening of the bow shock that implies less efficient reflection, 3. The SW becomes sub-Alfvénic and hence it is not able to sweep back the waves propagating upstream with the Alfvén-speed, and 4. The increase of the standoff distance of the magnetopause (and of the bow shock). Although the models cannot account for the lack of Pc3s during intervals when the SW density is extremely low, the resulting sets of optimal model inputs support the generation of mid latitude Pc3 activity predominantly through upstream waves.
- Full Text:
- Date Issued: 2010
- Authors: Heilig, B , Lotz, S I , Verő, J , Sutcliffe, P , Reda, J , Pajunpää, G , Raita, T
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:6814 , http://hdl.handle.net/10962/d1004324
- Description: It is known that under certain solar wind (SW)/interplanetary magnetic field (IMF) conditions (e.g. high SW speed, low cone angle) the occurrence of ground-level Pc3–4 pulsations is more likely. In this paper we demonstrate that in the event of anomalously low SW particle density, Pc3 activity is extremely low regardless of otherwise favourable SW speed and cone angle. We re-investigate the SW control of Pc3 pulsation activity through a statistical analysis and two empirical models with emphasis on the influence of SW density on Pc3 activity. We utilise SW and IMF measurements from the OMNI project and ground-based magnetometer measurements from the MM100 array to relate SW and IMF measurements to the occurrence of Pc3 activity. Multiple linear regression and artificial neural network models are used in iterative processes in order to identify sets of SW-based input parameters, which optimally reproduce a set of Pc3 activity data. The inclusion of SW density in the parameter set significantly improves the models. Not only the density itself, but other density related parameters, such as the dynamic pressure of the SW, or the standoff distance of the magnetopause work equally well in the model. The disappearance of Pc3s during low-density events can have at least four reasons according to the existing upstream wave theory: 1. Pausing the ion-cyclotron resonance that generates the upstream ultra low frequency waves in the absence of protons, 2. Weakening of the bow shock that implies less efficient reflection, 3. The SW becomes sub-Alfvénic and hence it is not able to sweep back the waves propagating upstream with the Alfvén-speed, and 4. The increase of the standoff distance of the magnetopause (and of the bow shock). Although the models cannot account for the lack of Pc3s during intervals when the SW density is extremely low, the resulting sets of optimal model inputs support the generation of mid latitude Pc3 activity predominantly through upstream waves.
- Full Text:
- Date Issued: 2010
Physical and biological coupling in eddies in the lee of the South-West Indian Ridge
- Ansorge, Isabelle J, Pakhomov, E A, Kaehler, Sven, Lutjeharms, Johan R E, Durgadoo, J V
- Authors: Ansorge, Isabelle J , Pakhomov, E A , Kaehler, Sven , Lutjeharms, Johan R E , Durgadoo, J V
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6493 , http://hdl.handle.net/10962/d1004477
- Description: Eddies have some decisive functions in the dynamics of the Southern Ocean ecosystems. This is particularly true in the Indian sector of the Southern Ocean, where a region of unusually high-mesoscale variability has been observed in the vicinity of the South-West Indian Ridge. In April 2003, three eddies were studied: eddy A, a recently spawned anticyclone south of the Antarctic Polar Front (APF),; eddy B, an anticyclone north of lying between the Subantarctic Front and the APF; and eddy C, a cyclone north of the APF west of the ridge. Elevated concentrations of total Chl-a coincided with the edges of the cyclonic eddy, whereas both anticyclonic eddies A and B were characterised by low total Chl-a concentrations. Biologically, the two anticyclonic eddies A and B were distinctly different in their biogeographic origin. The zooplankton community in the larger anticyclonic eddy A was similar in composition to the Antarctic Polar Frontal Zone (APFZ) community with an addition of some Antarctic species suggesting an origin just north of the APF. In contrast, the species composition within the second anticyclonic eddy B appeared to be more typical of the transitional nature of the APFZ, comprising species of both subantarctic and subtropical origin and thus influenced by intrusions of water masses from both north and south of the Subantarctic Front. Back-tracking of these features shows that the biological composition clearly demarcates the hydrographic origin of these features.
- Full Text:
- Date Issued: 2010
- Authors: Ansorge, Isabelle J , Pakhomov, E A , Kaehler, Sven , Lutjeharms, Johan R E , Durgadoo, J V
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6493 , http://hdl.handle.net/10962/d1004477
- Description: Eddies have some decisive functions in the dynamics of the Southern Ocean ecosystems. This is particularly true in the Indian sector of the Southern Ocean, where a region of unusually high-mesoscale variability has been observed in the vicinity of the South-West Indian Ridge. In April 2003, three eddies were studied: eddy A, a recently spawned anticyclone south of the Antarctic Polar Front (APF),; eddy B, an anticyclone north of lying between the Subantarctic Front and the APF; and eddy C, a cyclone north of the APF west of the ridge. Elevated concentrations of total Chl-a coincided with the edges of the cyclonic eddy, whereas both anticyclonic eddies A and B were characterised by low total Chl-a concentrations. Biologically, the two anticyclonic eddies A and B were distinctly different in their biogeographic origin. The zooplankton community in the larger anticyclonic eddy A was similar in composition to the Antarctic Polar Frontal Zone (APFZ) community with an addition of some Antarctic species suggesting an origin just north of the APF. In contrast, the species composition within the second anticyclonic eddy B appeared to be more typical of the transitional nature of the APFZ, comprising species of both subantarctic and subtropical origin and thus influenced by intrusions of water masses from both north and south of the Subantarctic Front. Back-tracking of these features shows that the biological composition clearly demarcates the hydrographic origin of these features.
- Full Text:
- Date Issued: 2010